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Production and characterization of nano struc-tured RuO2/Ti coatings
Get PDFBu çalışmada titanyum altlık malzeme üzerine termal dekompozisyon yöntemi kullanılarak rutenyum klorür tuzlarından yüzeyde okside parçalama işlemi ile DSA® (boyutsal kararlı anot) elektrotlar üretilmiştir. Farklı dekompozisyon sıcaklıkları kullanılarak (400-450-500 °C) elde edilen elektrotların yüzey morfolojileri ve faz bileşimleri FESEM ve X-ışınları difraksiyon analizleri ve elektrotların elektrokimyasal özellikleri ise kronopotansiyometri ve doğrusal tarama voltametrisi yöntemleriyle incelenmiştir. Elde edilen elektrotların 100 nm’den küçük RuO2 nano-kristallerden oluştuğu bulunmuştur. Dekompozisyon sıcaklığının artışıyla tane büyümesi ve efektif yüzey alanı küçülmesi tespit edilmiştir. Buna paralel olarak, elektrodun elektrokimyasal özellikleri de (Tafel denkleminin a ve b katsayıları) değişmiştir. Düşük dekompozisyon sıcaklıklarında üretilen elektrotların yüksek elektroaktivite ve düşük anot potansiyel değerine sahip olduğu görülmüştür. Tüm elektrotların düşük akım yoğunluğu bölgesinde elektroaktif reaksiyonu temsil eden düşük Tafel eğimlerine (b =~59 mV/dec) sahip olduğu ancak anodik polarizasyon değerinin artışına bağlı olarak Tafel doğrularının kırılma gösterdiği ve oksijen deşarjının ~118 mV/dec eğimli reaksiyon üzerinden gerçekleştiği tespit edilmiştir. Bu temel büyüklüklerden hareketle, asidik çözeltilerde elektroaktif ve elektroaktif olmayan elektrotlar için geçerli oksijen deşarj reaksiyon mekanizması önerilmiştir. Elektrokatalitik aktiviteyi dolaylı yollardan etkileyen diğer bir parametre olan malzeme sabiti (a) ise artan dekompozisyon sıcaklığı ile artmıştır. Bu durumun, sıcaklığa bağlı morfolojik yapının değişmesiyle orantılı olduğu görülmüştür. Anahtar Kelimeler: DSA®, RuO2, oksijen deşarjı, elektroaktivite, titanyum elektrot, termal dekompozisyon.Dimensionally stable anodes (DSA®) are widely used as electrode materials in several electrochemical applications. In the production of these types of electrodes thermal decomposition method is successfully applied. This method is based on thermal decomposition of precious metal chloride precursor solutions on titanium surface to give metal oxide. Production conditions, namely; substrate treatment, type of precursor solution, application procedure of precursor solution and heat treatment have great influence on the morphological and electrochemical properties of these electrodes. Most of these pretreatment steps have been standardized: titanium substrates are generally sandblasted to obtain high roughness (high surface area); precursor solutions are prepared in aliphatic mono-alcohols to ease the evaporation of the solvents; painting, spraying or dip-withdrawal techniques are generally used. Among these parameters heat treatment is the key parameter affecting the behavior of both physical and electrochemical properties of DSA®. In this study, various decomposition temperatures (400-450-500 °C) were used to prepare RuO2 coated titanium electrodes by utilizing thermal decomposition method. The effect of decomposition temperature on morphology was examined by field emission scanning electron microscope (FESEM) and the phase determination was done by thin film-X ray diffraction analysis (XRD). Electrochemical behavior and characteristics of the coatings prepared at different decomposition temperatures were investigated by chronopotentiometry (CP), and linear sweep voltammetry (LSV). Correlation between the physical and electrochemical properties of the electrodes was scrutinized by means of morphology and electrocatalytical activity. In the morphological investigations, it was found that the surfaces obtained at all decomposition temperatures were alike with roughened heterogeneous morphology. The surfaces consisted of flat areas (sub-surfaces) and nano-crystals (particularly on the hills of the rough surface). Nano structured RuO2 crystals (< 100 nm) were formed in the shape of columnar base with a rutile type tetragonal structure. Crystallinity and the size of nano-structures were found to increase with increasing decomposition temperature and agglomeration occurred locally on the hills of the surface. It was seen that an increment of 50 °C in the decomposition temperature results in ~37% increase in particle size. Although particle coarsening was occurred by the increase of decomposition temperature, it was found that particle growth was also in nano-scale. Moreover, the flat areas were found to form of nano crystals which could only be detected at higher magnifications. Nano-structured crystals indicated that the real surface area of the electrodes was high, nevertheless higher decomposition temperature resulted in smaller real surface area. The results obtained from morphological investigations made us to examine their influence on the electrochemical properties of the electrodes. Chronopotentiometric tests showed that lower anode potentials could be obtained for the electrodes prepared at lower decomposition temperatures. This was due to the higher real surface area providing excess active sites being involved in the electrochemical reactions. When the decomposition temperature was higher, electrodes were found to possess higher anode potentials. This was caused by the better crystallinity and particle coarsening with increasing temperature that resulted in smaller real surface area. The electrocatalytical activities of the electrodes were investigated by current density - potential (j - E) curves. Results showed that higher current flow could be achieved for the electrode prepared at 400 °C. This indicates that surface active sites - being involved in the electrochemical reaction - were much higher than the others. Similarly, for a given current density value, the anode potentials were lower for the electrodes prepared at lower decomposition temperatures. Tafel plots were done in order to define the electrocatalytical activity of the electrodes. Break in the Tafel lines was occurred which indicates that the reaction mechanism was changed. It was observed that at lower current density region, all electrodes have the same Tafel slope (~59 mV/dec) which showed that the same reaction mechanism took place on the electrodes. At higher current densities, Tafel slope for oxygen depolarization was found to be 118 mV/dec. The materials coefficient, a, was found to increase with the increasing decomposition temperature. It is concluded that lower decomposition temperatures in the preparation of DSA® electrodes are beneficial. Keywords: DSA®, RuO2, oxygen depolarisation, electroactivity, titanium electrode, thermal decomposition
Treatment of surfactants by advanced oxidation processes: Process optimization and toxicity analysis
Get PDFBu çalışma kapsamında, ülkemizde ve dünyada ticari olarak önem taşıyan tekstil ve kimya başta olmak üzere pek çok endüstride yoğun olarak kullanılan ve çevrede yarattıkları olumsuz etkilerden dolayı önem taşıyan noniyonik (nonil fenol etoksilat), anyonik (dioktil sülfosuksinat) ve katyonik (kuaterner amonyum etoksilat) türü yüzey aktif maddelerin (YAM) Foto-Fenton ve H2O2/UV-C ileri oksidasyon prosesleri ile arıtılabilirlikleri incelenmiştir. Yapılan ön arıtılabilirlik deneyleri sonucunda, incelenen fotokimyasal ileri oksidasyon proseslerinin yüzey aktif maddelerin arıtımı için uygun ve etkin olduğu saptanmıştır. Yüzey aktif maddelerin fotokimyasal arıtımı için seçilen H2O2/UV-C ileri oksidasyon prosesi Cevap Yüzey Yöntemi kullanılarak ana madde, KOİ ve TOK giderimleri açısından modellenip, optimize edilmiştir. H2O2/UV-C prosesi ile yapılan arıtılabilirlik çalışmalarında giriş KOİ değerinin, reaksiyon süresinin ve H2O2 konsantrasyonunun (proses bağımsız değişkenleri) ana madde, KOİ ve TOK giderim verimleri (proses çıktıları/bağımlı değişkenleri) üzerindeki etkileri araştırılmıştır. Yapılan deneysel tasarım çalışmaları sonucunda proses çıktılarını bağımsız değişkenler cinsinden tanımlayan ikinci dereceden eşitlikler türetilip geçerlilikleri istatistiksel araçlar kullanılarak sorgulanmıştır. Yüzey aktif maddelerin H2O2/UV-C prosesi ile ileri oksidasyonunun Cevap Yüzey Yöntemi ile yeterli hassasiyetle modellenebildiği sonucuna varılmıştır. Farklı giriş KOİ değerleri için optimize edilen reaksiyon koşullarında yürütülen fotokimyasal oksidasyon deney sonuçlarının model çıktıları ile uyum gösterdiği gözlenmiştir. Çalışmanın son aşamasında ise yüzey aktif maddelerin ve fotokimyasal oksidasyon ürünlerinin toksisiteleri aktif çamur inhibisyon testi ile belirlenmiştir. Deneysel çalışma sonuçları ışığında YAM içeren çözeltilerin heterotrofik biyokütle üzerindeki inhibisyon etkilerinin fotokimyasal arıtma ile çok yüksek oranda azaltıldığı ve oksidasyon süresi boyunca oluşan oksidasyon ara ve son ürünlerin toksik etkisinin olmadığı söylenebilmektedir. Anahtar Kelimeler: Anyonik, katyonik ve noniyonik yüzey aktif maddeler, H2O2/UV-C arıtımı, cevap yüzey yöntemi, optimizasyon, aktif çamur inhibisyonu.Surfactants are widely used in household detergents, personal care products, paints, inks, polymers, pesticide formulations, pharmaceuticals, mining, oil recovery, pulp and paper, tannery and textile industries. Due to their amphiphilic characteristics, surfactants tend to sorb and hence accumulate onto sludge and soil sediments thus imparting serious ecotoxicological risks in the environment. As a consequence, more effective and at the same time economically feasible treatment processes have to be applied to alleviate the chronic problem of surfactant accumulation in the aquatic ecosystems. Among different alternative treatment options, in particular chemical and photochemical advanced oxidation processes (AOPs) have proven to be good candidates for the destructive treatment of surfactants. Response surface methodology (RSM) is a collection of statistical and mathematical techniques that are employed for the development, improvement and optimization of certain processes in which a response of interest is affected by several process variables and the objective is to optimize this response. RSM offers several advantages over classical experimental optimization methods in which a "one process variable at a time" approach. RSM provides more information from a relatively little number of experiments as compared with conventional optimization procedures, which is less expensive and time consuming. In particular, in more complex treatment systems such as photochemical advanced oxidation processes, interactive and synergistic effects are quite common making these applications ideal candidates for RSM. Considering the above mentioned facts, the present experimental study aimed at investigating the photochemical oxidation of commercially important anionic (a dioctyl sulfosuccinate), cationic (a quaternary ammonium ethoxylate) and nonionic (a nonyl phenol ethoxylate derivative) surfactant types. RSM-Central composite design (CCD) was used to analyze, model and optimize surfactant (parent compound, PC) and organic carbon (COD, TOC) removals during photochemical treatment. Two different experimental and statistical design matrices were developed for the assessment of both surfactants (parent compound) and their organic carbon content removals on the basis of treatment time. Process optimization was based on two photochemical treatment targets; (i) partial oxidation (for COD, TOC removals) to achieve complete parent pollutant abatement and (ii) full treatment for complete oxidation (mineralization) of aqueous surfactant solutions. The established polynomial regression models were validated by running separate experiments under photochemical oxidation conditions being previously optimized for different initial CODs. In the last stage of the study, separate experiments were run at the same local optima to examine the inhibitory effect of photochemical treatment of aqueous surfactant solutions on the oxygen uptake rate of activated sludge microorganisms. In the preliminary baseline experiments, rapid degradation of all studied textile surfactant solutions accompanied with high COD and TOC removals was observed. Surfactant abatements were complete within 15-20 min photochemical treatment, whereas over 90% COD and TOC removals could be achieved after prolonged oxidation periods for an initial surfactant COD of 450 mg/L and an initial pH of 10.5. The efficiency of the H2O2/UV-C process was appreciably influenced by all selected process outputs in the following decreasing order; photochemical treatment time (positive effect) > initial COD content of the surfactant formulation (negative effect) > initially added H2O2 concentration (positive effect, except for parent compound removals, that required low concentrations compared to organic carbon abatements). Analysis of variance revealed that the established factorial design models were statistically significant and described parent compound, COD and TOC removals at satisfactory levels. The highest correlation coefficients were obtained for TOC removals (surfactant mineralization rates). The established response surface models could be used to precisely optimize specific photochemical treatment targets for full and partial (pre-) treatment of different types of surfactants. The experimental design models were also capable of predicting advanced oxidation efficiencies at different photochemical treatment durations and varying initial CODs of the aqueous surfactant solutions. Activated sludge inhibition experiments conducted with heterotrophic biomass indicated that during the application of H2O2/UV-C treatment under optimized reaction conditions, no toxic oxidation products were formed. Keywords: Anionic, cationic and nonionic surfactants, H2O2/UV-C treatment, response surface methodology, optimization, activated sludge inhibition.
Membrane bioreactors in the treatment of wastewater
Get PDFMembran proseslerin biyolojik arıtımla birleştirilmesi sonucu ortaya çıkan arıtım teknolojileri membran biyoreaktörler (MBR) olarak tanımlanmakta olup, günümüzde bir çok çalışma bu proseslerin verimliliği ve optimum kullanım koşulları üzerine odaklanmıştır. Konvansiyonel arıtım metotlarının bir takım dezavantajlarını ortadan kaldıran bu sistemler geleceğin arıtım teknolojileri arasında önemli bir yere sahip olacaktır. Membran biyoreaktörler hem araştırma hem de ticari uygulamalarda hızlı bir ilerleme kaydetmektedir. Bu arıtım prosesi konvansiyonel biyolojik arıtım prosesleri ile karşılaştırıldığında daha düşük biyolojik parçalanabilirliğe sahip olan atıklar için yüksek kimyasal oksijen ihtiyacı (KOİ) giderim verimliliğine sahiptir. Bunun yanı sıra bu sistemler konvansiyonel sistemlerden çok daha az yer kaplarlar. Bu durum özellikle tesis için yeterli alanın bulunmadığı veya arazi maliyetlerinin oldukça yüksek olduğu yerlerde bu arıtma prosesinin uygulanmasını olanaklı kılmaktadır. Membran biyoreaktörler üzerine literatürde yapılmış olan birçok çalışma mevcuttur. Membran sistemlerinde toz aktif karbon kullanımı ile yüksek verimler elde edilmiştir. Çeşitli arıtım çalışmalarında atıksuların KOİ giderim değerlerinde %80 ile 98 arasında değişen verimlere ulaşılmıştır. Giderim verimi çalışmalarının yanı sıra biyokinetik katsayıların belirlenmesi amacıyla da literatürde çeşitli çalışmalar yer almaktadır. Ayrıca membran kirlenmesi MBR sistemlerinin en büyük problemlerinden biri olup bu konu üzerine yapılan çalışmalara da bu makalede yer verilmiştir. Bu çalışmada membran biyoreaktör sistemleri genel olarak incelenecek ve bu sistemlerle ilgili yapılmış olan farklı çalışmalara yer verilecektir. Anahtar Kelimeler: Membran biyoreaktör, atıksu arıtımı, biyolojik arıtım.Biological systems are the processes designed for removal of dissolved and suspended organic substances from wastewater. A membrane bioreactor system (MBR) is the combination of a biological aeration basin (suspended growth reactor) and a membrane filtration unit. In this study membrane bioreactor systems are investigated generally, and the research studies concerning MBR systems are given. MBR systems have several advantages when compared with conventional activated sludge processes. The characteristics of the sludge formed in MBRs may be different from those of conventional activated sludge. While only biomass capable of forming flocs big enough to be settled in the sedimentation units can exist in the CAS process, MBR sludge may contain even single bacteria. Especially in side-stream modules where the sludge is subject to high shear forces, the existence of single bacteria is possible and the microbial floc size is reduced. Bulking sludge, as may occur in the activated sludge process, cannot affect the quality of the MBR effluent and is no problem in MBR units. The MBR technology allows the aeration tank to be operated at higher mixed liquor suspended solids (MLSS) concentrations. While in the conventional activated sludge (CAS) process the MLSS concentration is typically limited to 3-5 g MLSS/L by the sludge sedimentation properties, membranes overcome these limitations. The area required for the installation of MBR systems are less than conventional activated sludge processes. This is very important where the area costs are too high or there is no enough spaces for the installation of treatment plants. In MBR systems a membrane filtration unit is used for removal of suspended solids in the aeration basin from effluent. MBRs have two main configurations: submerged or immersed and external or side-stream. There are also two modes of hydraulic operation: pumped and airlift. In an submerged MBR, the membrane module is submerged into the aeration tank and the permeate is withdrawn from the effluent side. The pressure across the membrane can be applied by suction through the membrane or by pressurizing the bioreactor. This process requires no circulation pumps thereby making it an energy saving system. Additionally, most of the submerged MBRs operate at sludge ages in excess of 40 days and, consequently, the operational parameters of submerged MBR would be different from those of conventional biological wastewater systems. In the case of external membrane bioreactor systems, the membrane is independent of the bioreactor. Feed solution enters the bioreactor and contacts with biomass. Mixture formed is then pumped around a recirculation loop which contains a membrane filter. Permeate is removed from the membrane and retentate containing activated sludge returned to aeration basin. The power consumption is much lower in submerged membrane modules when compared with external modules. In submerged type there is no circulation pump and the transmembrane pressure of system is lower than external type. Submerged systems are also more compact. Membrane fouling is one of the important disadvantages of membrane bioreactor systems. Fouling is the decline in the membrane permeability. Typically, transmembrane (TMP) pressure should be increased for obtaining stable flux values. Membrane fouling reduces the efficiency of membrane system by increasing TMP value. Consequently, this situation is increased operating and maintenance costs of membrane bioreactor process. Techniques of membrane fouling control can be categorized into four groups. In the first group the modification of membrane module design by optimizing hollow fibers or flat sheets packing density, the location of aerators, the orientation of fibers and diameters of fibers takes place. In the second, reduction of cake formation on membrane surfaces by controlling the filtration process below the critical flux, by air sparging in the vicinity of membranes, and by operating in intermittent mode exists. The third group is the improvement of the filtration characteristics of the mixed liquor by adding powdered activated carbon (PAC). The fourth and the last is the removal of the fouling material after its formation by back-washing, by back-pulsing and by chemical cleaning. In the light of the scientific research studies, the fouling problems in these systems will be decreased to a minimum. The other disadvantage of MBR is the high operating and membrane costs. However, the membrane costs were decreased since this technique was firstly applied to wastewaters. Nowadays, the operating costs are higher than conventional methods, but this will not be a disadvantage when the strict discharge standards will become effective. Keywords: Membrane bioreactors, wastewater treatment, biological treatment
The effect of the building façades openings on airflow in courtyards
Get PDFRüzgar, yerleşme ve bina tasarımında eski çağlardan beri önemli bir çevresel faktör olmuştur. Rüzgarın, yapıların soğutma yüküne etkisi, bu etkilerin bilimsel yöntemlerle ortaya konması, tasarım ve uygulama alanlarına zaman geçirilmeden yansıtılması enerji tasarrufuna her zamankinden daha fazla gereksinim duyulan günümüzde, çok büyük önem taşımaktadır. Bu bağlamda, avlulu binalarda rüzgar etkisi ile oluşacak hava hareketinin etkinliğini değiştirebilecek binaya ait diğer açıklıkların da göz önünde bulundurulması, dikkatlice incelenmesi gerekmektedir. Hava hareketlerine, bir pasif iklimlendirme aracı olarak özellikle sıcak ve nemli iklim kuşaklarında, bina içi havalandırmanın sağlanması açısından gereksinim duyulabilir. Sıcak-kuru iklim bölgelerinde doğal taşınım yoluyla oluşacak bina içi-avlu arası hava akımları, ılımlı-nemli ve sıcak-nemli iklim bölgelerinde rüzgar basıncı yardımı ile elde edilmektedir. Avlulu binaların özellikle sıcak kuru dışında ılımlı veya sıcak nemli iklimsel karakter gösteren bölgelerde doğal havalandırma açısından performansını arttıracak, dolaylı olarak soğutma yükünü azaltacak değişikliklerden biri avlu mekanına yatay doğrultuda rüzgarın iteceği havayı geçirecek boşlukların yaratılmasıdır. Bu çalışma avlulu yapıların mimari kütlesinde yaratılacak açıklıkların avlu mekanındaki hava hareketleri hızına etkilerini rüzgar tüneli deneyleriyle ortaya koymaktadır. Elde edilen sonuçlar; boşluksuz avlulu binaya göre farklı şekillerde düzenlenen açıklıkları olan binalarda, düşey yüzeylerdeki boşlukların alan ölçüsü ve konumlarıyla orantılı olarak avlu içerisindeki hava hareketi hızlarını arttırmakta olduğunu göstermektedir. Anahtar Kelimeler: Doğal havalandırma, bina içi hava hareketleri, rüzgar etkileri, pasif soğutma, avlulu bina iklimi.One of the modifications to increase the performance of the buildings with courtyard by means of ventilation and decrease the cooling load indirectly in the regions especially temperate or hot-humid climate except hot-dry is to create cavities to convey the air horizontally compelled in the courtyard by the wind. The air movement as a passive air-conditioning media may be required in order to provide in-building ventilation especially in the hot-humid climate zones. In hot-dry climates, the traditional courtyard building form ensures air flows to arise by themselves through natural ventilation between a building and its inner court, while in temperate-humid and hot-humid climates, such air flows are created by using the wind pressure. The courtyard building form should be improved by means of modifications designed to increase its performance of ventilation, especially for other hot climate regions than the hot-arid climate regions. In this context, the other openings pertaining to the building which may change the air movement effectiveness incurred with the wind effect in the buildings with courtyard should be taken into consider and studied carefully. Many numerical or experimental studies have been conducted on the insulation aspects of courtyard buildings. However, only a limited number of studies have been conducted on the wind effects. When a building contains openings, the air flows reach highest velocity in the openings made in the same direction as the wind. The results in question comply with a number of similar experiments. The courtyard depth in the building without opening makes an effective variable in controlling these events. However, except for the hot-arid climates, the openings to be arranged on perpendicular surfaces with the buildings with courtyards to be built especially in hot-humid and temperate-humid climate regions will be of great importance. The steps of the experimental study consist of the setting up of the experiment mechanism, designation of the reference building mass, scale model making, determination of the model building configurations, designation of measurement point positions and numbers, performing the measurement visualization of the outputs and interpreting the results in short. Consequently, the air flow in the courtyard not only circulates through up and down wind zones, but also circulates through the lateral areas. An air inlet opening located in the middle of the courtyard and an opening located in the middle of the lateral area of the courtyard cause the air flow to change direction in an abrupt way after moving into the courtyard, so that the air flow turns to the air outlet opening located on the lateral wall. Thus the air flow does not reach to high velocities in the wind direction within the courtyard. Results of the studies on the effects imposed by openings arranged in the mass of courtyard building, depending on said openings' positions towards the wind and their surface area rates, on the average velocity of the air flow occurring in the courtyard, can be summarized as follows. Contribution of the openings situated on the lateral faces extending in parallel with the wind within the courtyard to increase the velocity is less than the contribution of the openings situated on the upwind and downwind surfaces. In other words, for arrangements where the courtyard openings' areas are equal, average speeds are lower in choices where openings are situated on the lateral surfaces only. For choices with equal total opening areas, the ones having openings on their lateral surfaces and distributed on all upwind and downwind surfaces provide lower velocities than the ones having openings in the wind direction only. This study explains the effects imposed by openings, which will be created in the architectural mass of courtyard buildings, upon the velocities of air flows within such courtyards, through tests conducted in a wind tunnel. The results of this study indicate that for buildings containing openings arranged in different configurations from those of courtyard buildings, the openings located on perpendicular surfaces increase the velocities of air flows within courtyards in proportion with their dimensions and positions. Keywords: Natural ventilation, In-building air movements, Wind effects, Passive cooling, Climate of buildings with courtyard.
Land readjustment method and its efficient applicability within international framework
Get PDFArazi ve Arsa düzenlemesi, gelişmiş ve gelişmekte olan ülkeler için önemli bir tekniktir. Bu yöntem ile, kentsel alanlarda hem yeni alanların gelişimi hem de yapılaşmış alanların yeniden organizasyonu sağlanabilmektedir. Arazi birleşimi, plan uygulaması, arazi edinimi, altyapı inşaatı, arazi gelişiminin finansı, zamana bağlı arazi gelişimi, düşük-maliyetli konut için arazi sağlama yönlerinden arazi ve arsa düzenleme yöntemi önemli potansiyellere sahiptir. Bu nedenle hem gelişmiş hem de gelişmekte olan ülkeler açısından bu tekniğin uygulanması büyük bir öneme sahiptir. Kentsel alanlarda servisli kentsel arsa arzının yetersizliği, arazi piyasası içerisinde düşük gelirli hatta orta gelirli grupların barınma için arsaya girişinin yeterince sağlanamaması, kent kenar alanlarına doğru yoğun baskı ve hem varolan hem de yeni gelişen konut alanlarındaki altyapı ve servis alanlarının eksikliği gibi ortak sorunlar devlet müdehalesini gerektirmiştir. Farklı ülkelerde hükümetler, müdahalenin gereği olarak farklı politikalar üretmiş ve farklı araçlar kullanmışlardır. Kullanılan çoğu araç ya da programlar, bu sorunların çözümünde yetersiz kalmış ve bu yetersizlikler çeşitli uluslararası çalışmalarda da sık olarak ortaya konulmuştur. Bu noktada, Arazi ve Arsa düzenlemesi, uluslararası literatürde tüm bu araçlara karşı ülkelerin uygulayacağı önemli bir alternatif çözüm olarak görülmektedir. Bununla birlikte, hem ulusal hem de uluslararası planlama literatüründe Arazi ve Arsa düzenlemesinin kullanımı ile ilgili yayınlar oldukça kısıtlı sayıdadır. Bu makalenin amacı, uluslararası literatür çerçevesinde AAD yönteminin etkin ve başarılı uygulanabilirliğindeki koşulları incelemektir. AAD yöntemi etkin olarak uygulayamayan ülkelerdeki modellerin hangi açılardan geliştirilebileceğine yönelik bilgi sağlamaktadır. Anahtar Kelimeler: Arazi ve Arsa düzenlemesi (AAD), kentsel alanlar, uygulanabilirlik. The land readjustment (LR) is a method which is used for both the development of new areas and the reorganisation of the built-up areas in urban regions. The application of this method provides the conversion of agricultural or semi-urban land into urban land. LR can be thought as an important planning tool during the rural- suburban transition. Further, the urban plots may also be readjusted, if necessary. The models of land readjustment vary according to countries. While in some countries private initiative (landowner associations or cooperatives) is more efficient in the application of LR models, the public initiative (municipality, governorship, etc.) may be more efficient in other countries. However, in whatever country the method is applied, after a common share is allocated for public usage such as roads, parks, car parks, from the total of all plots that fall into LR area, the remaining areas are distributed to the landowners in proportion to either the area size or value criteria. LR not only capture the costs of providing infrastructure and services to the areas, but it also potentially recaptures additional value created for any the other public purposes. For example, a good standard subdivision layout, the production of plots with service in regular forms and sizes, the supply of service areas like roads, parks, etc. which are required for public use, and the achievement of price stability as a result of meeting the demand. The LR is one of methods and procedures for urban development focuses on the modification of existing land parcels in terms of shape, location, size other conditions together with the proper allocation and improvement of urban infrastructure. The LR method is applied efficiently and successfully in developed countries like Japan, Germany and France and in developing countries of the Far East. In some countries that have a long background and accumulation of LR (Turkey, India, etc.), the achievements from the use of the LR method are far behind the expectations. The aim of this article is to define and examine provisions in the efficient applicability of land readjustment method within the frame of international literature. The findings of this study provide knowledge as to which aspects of the models in the countries failing to apply the LR method efficiently can be improved. The efficient applicability of the land readjustment method can be examined under some headlines: One of the conditions for the efficient application of the LR method is "cost recovery". Main financial resources in LR are related to land contribution of landowners. In some country models, some part of this contribution land is sold to cover the infrastructure cost. In LR projects, transparency and fairness are principles necessary in the sharing of project costs and benefits. While infrastructure cost and construction are included within the scope of LR in some countries, the cost and construction of infrastructure is excluded from the process in other countries' models. Certain conditions arise in regards to planning in the efficient application of LR. of construction. The first condition is the ideal size of LR project areas. The second condition is the establishment of a connection between the master plan (local physical plan) and LR projects. The third condition is the completion of the development on the urban plots produced at the end of the LR projects. One of the important conditions in the efficient application of LR is the participation of the landowners in the project. Adoption and participation of landowners to the project will increase applicability of the LR. Another important component in the efficient application of the LR method is the availability of skilled and competent personnel. In land readjustments, the incoming data from the land registration system, which is one of the important inputs, should be precise. The efficient applicability of LR models in various countries can be evaluated within the frame of the availability of these conditions. This evaluation may enable an approach to be adopted on the elimination of problematic areas with respect to the use of the LR method in the country's legislation. The findings of this study provide knowledge as to which aspects of the models in the countries failing to apply the LR method efficiently can be improved. Keywords: Land readjustment, urban areas, applicability.
Using alternative instruments in the solid waste management and environmental cleaning tax
Get PDFBu çalışmada, uluslararası düzeyde katı atık yönetiminde ne tip ekonomik araç ve/veya araçların kullanıldığı incelenmiş ve Türkiye’de kullanılabilecek en uygun ekonomik araçların belirlenmesi konusunda öneriler geliştirilmiştir. Bu amaçla, öncelikle yurtiçi ve yurtdışındaki mevcut durum incelenerek, halen kullanılan çevre yönetimi araçları belirlenmiştir. Hâlihazırda Türkiye’de uygulanan sistemin etkinliği değerlendirilmiştir. Söz konusu araştırmalar sırasında geçerli mevzuatın ve yönetim sisteminin durumu göz önünde bulundurulmuştur. Türkiye’deki önemli çevre sorunlarından biri katı atıkların yönetiminde yaşanan eksikliklerdir. Katı atıklar konusunda Türkiye’de halen uygulanan Çevre Temizlik Vergisi (ÇTV) hem katı atıkların uzaklaştırma maliyetini karşılamamakta hem de atık miktarının azaltılması konusunda bir teşvik sağlamamaktadır. Bunun nedeni verginin, katı atık emisyon miktarı ile atık bertarafının marjinal maliyeti arasında teşvik edici bir ilişkinin olmadığı bir biçimde düzenlenmesidir. Mükellefleri daha az atık üretmeye zorlayacak veya teşvik edecek herhangi bir mali mekanizma yoktur. ÇTV tahsilatı tüketilen su miktarı (m3) başına yapılmaktadır ve bu da üretilen katı atık miktarıyla ilişkilendirilmediğinden hem atık bertaraf maliyetini karşılamamakta hem de çevre sorunlarını arttırmaktadır. Katı atıklarla ilgili mevcut ve olası sorunların çözümünde ÇTV ile finansman olanakları ve yapılabilirliği irdelenmiş, dışsallıkların da göz önünde bulundurulduğu vergilendirme sistemlerinin uygulanması durumunda elde edilecek avantaj ve dezavantajlar ortaya konulmuştur. Sonuç olarak ÇTV’nin zaman içinde kaldırılarak, üretilen atık bedeline göre ücret alınmasına yönelik bir sistemin oluşturulmasının uygun olacağı düşünülmektedir. Anahtar Kelimeler: Katı atık yönetimi, ekonomik araçlar, çevre vergileri, Çevre Temizlik Vergisi, dışsallık.In this study, a proposal was developed on the use of most appropriate economic instruments by solving conceptual problems emerging on the definition and use of main economic instruments for environmental management and was applied on solid waste management particularly. To this end; first of all, all available environmental management tools were determined while present situation had been investigated in national and international scale. Effectiveness of the current system in Turkey was evaluated. Legislation and management system in use were taken into consideration during aforementioned study. Economic instrument can be described as any instrument that aims to induce a change in behavior of economic agents by internalizing environmental or depletion cost through a change in the incentive structure that these agents face rather than mandating a standard or a technology. Generally accepted classification of economic instruments is made by OECD. According to this classification main economic instruments for environmental management can be classified as user fees, emission charges, product taxes, non-compliance fees, tradable permits, deposit refund systems, performance bonds, voluntary agreements and environmental subsidies. User fees, emission charges, product taxes, deposit refund systems, voluntary agreements and environmental subsidies are frequently used ones in solid waste management. They can be used individually or together to reach an efficient solid waste management system. There is some misusage of economic instruments both in definition and in practical use. Economic instruments can be used for revenue raising purposes or earmarked for environmental quality goals. Taxes and tax-like charges are the powerful tools in solid waste management if they are applied correctly. However, price elasticity of solid waste collection and disposal are found as inelastic by some researchers. This fact causes that taxes are not too successful to decrease the solid waste amount produced by individuals. Despite environmental cleaning tax is named as tax; it is a user charge according to OECD classification. One of the most important environmental problems in Turkey is the lack of appropriate solid waste management system. In solid waste management, besides a number of Ministries and institutions, more than 3000 municipalities are responsible and authorized in Turkey. Except for municipalities, number of directly responsible institutions and authorities is 36. Legislation is also very scattered. Direct and indirect law and regulations about environment are above one hundred in number. This structure is also an important obstacle and hampering the effectiveness of successful application of economic instruments and achieving the environmental quality goals. Municipalities allocate a significant portion of their budgets for solid waste management. Environmental Cleaning Tax (ECT), stipulated by the Municipal Revenues Law has been using since 1993 in Turkey to compensation of waste management financing in municipalities. However it is able to compensate only less than 30 percent of waste management costs. ECT is collected per m3 consumed water per household. It is not designed for environmental protection purpose. It is designed such as there is no relationship between solid waste emission and external marginal cost of solid waste disposal in a stimulating manner. Taxpayers have no incentive and/or enforcement for producing less solid waste. Externality can be defined as the impact of costs and benefits generated from economic activity on the people not related to this activity. In market economy, it is generally explained that the occurrence of externality caused by the activities of one person or company on other person or company beside of market prices. Environmental externalities are related to external costs that are described as the misuse of environmental resources in a harmful way to others without any financial indemnification. All alternative strategies about solid waste management cause some environmental externalities during collection, transfer and final disposal of solid wastes to some extent. These externalities create a number of local, regional and global problems. Human health effects, disturbance of ecosystem, depletion of resources and global warming can be sorted among them. Disamenities are also important problem for human welfare. When these externalities are not internalized by using some instruments, there will not be reached sustainable development goals. Therefore, it is believed that adoption of new economic instruments is necessary for municipal solid waste management by considering externalities and giving up the use of ECT in the future will be useful for sustainable solid waste management. Keywords: Solid waste management, economic instruments, environmental taxes, externalities
Determination of recent tectonic activity in the central part of the North Anatolian Fault
Get PDFDünyanın en aktif yanal atımlı fay sistemlerinden birisi olan Kuzey Anadolu Fayı (KAF), doğuda Karlıova’dan başlar batıda Kuzey Ege Denizi’nde Saros Körfezi’ne kadar uzanır. Kuzey Anadolu Fay Zonu (KAFZ) içinde ağaç dalları şeklinde birçok yan kolu vardır ve bu yan kollar Anadolu’nun içlerine doğru uzanmaktadır. Tüm fay zonu sismik olarak aktif ise de, fayın aktivitesinin önemli bir bölümü ana kol üzerindedir. Kuzey Anadolu Fayı’nın orta kesiminde yan kolların keserek birbirinden ayırdığı birçok kıtasal blok vardır. Bölgedeki nispeten en büyük yan kollar inceleme için seçilmiş ve aralarındaki hareket belirlenmeye çalışılmıştır. Fay sistemlerinin güncel metotlarla izlenmesi 1980’li yıllardan sonra uydu jeodezisinde meydana gelen önemli ilerlemeler sayesinde mümkün olmuştur. Bu bağlamda, yersel tekniklerin yerini uzay ve uydu tekniklerinin alması genel fotoğrafın görülmesinde büyük kolaylıklar sağlamıştır. Bu çalışmada, jeodezik metotlardan GPS (Küresel Konumlandırma Sistemi) ve InSAR (Yapay Açıklıklı Radar İnterferometri) kullanılmıştır. Çalışmanın amacı iki metot ile sonuçlar üreterek karşılaştırmak ve/veya metotların zayıf yönlerini birbiri ile tamamlamak ve böylece bölgenin depremselliğini ortaya koymaktır. GPS ile kurulan jeodezik ağ dört yıl boyunca periyodik olarak ölçülmüştür. InSAR tekniği ile bölgeyi kapsayan görüntülerden interferogramlar oluşturulmuş ve görüntü alım zamanları arasında yüzeyde meydana gelen uydu bakış yönündeki değişimler hesaplanmaya çalışılmıştır. InSAR metodu atmosfer ve bölge topografyasına bağlı olarak istenen sonuçlara ulaşmamıştır. GPS sonuçlarının modellenmesi ile yan kolların ana kola göre nispeten yavaş olduğu belirlenmiştir. Anahtar Kelimeler: Kuzey Anadolu Fayı, GPS, InSAR, deformasyon.One of the important fault systems all over the world is the North Anatolian Fault (NAF). The NAF is a long fault which stretches from Karlıova to Northern Aegean. Although a lot of studies exist, the central part of the NAF has not been studied in detail. In this study, the central part of NAF from Amasya to Kastamonu has been evaluated using geodetic techniques, GPS (Global Positioning System) and InSAR (Synthetic Aperture Radar Interferometry), and modeled with DEFNODE software. The geodetic techniques to determine the tectonic activity have been used since early 1900. The inertial methods were not sufficient to calculate the strain accumulation or slip rate of the fault. Especially, the interseismic studies cannot be possible. After the space geodesy development, the earth sciences started to use these techniques. The most useful techniques of them are GPS, InSAR, VLBI and SLR. In this study, we used GPS and InSAR technique because of the financial constrains, mobility and accuracy. The GPS campaigns were carried out in four years periodically at 16 force-centered stations. Every year, the measurements were done in the same week. Each station was measured at least 8 hours in three days. All stations were not measured simultaneously because of the lack of equipments. So, we had continuous stations to link measurements which were carried out in two stages. The measurements obtained from campaigns and downloaded from internet belonging to IGS sites close to study area were processed using GAMIT/GLOBK software. The process was run in three steps. First step was made with GAMIT, the all GPS data belonging to same day had put in the same day directory and the required files for process were updated from process center like SOPAC (Scripps Orbit and Permanent Array Center). The stations coordinates and its covariance matrix were calculated. In this step, the repeatabilities were checked to protect data against to blunder and systematic errors. Second step, the calculated data (called quasi-observation) were combined with the international global network data computed by center, SOPAC. Each data had different sites that the all quasi-observation should have various weights. In the third step, the combined data were transformed in the reference frame like ITRF (International Terrestrial Reference Frame) using common sites and transform parameters. After that, we calculated the sites velocities according to Eurasia plate in ITRF2000 reference frame using sites which have well known coordinates and have represented Eurasia plate very well. The GPS results are given in the text. InSAR method depends on phase information in two SAR images by calculating phase difference between each pair of corresponding image points. The new image with interference pattern of fringes due to relative phase difference is called an interferogram. Phase change in the interferogram shows differences in the range distance between image acquiring platform (aircraft, satellite) and point on the ground. One complete phase cycle (2π radians) corresponds to a relative range change by half of wavelength. Main InSAR components are three, first is the image, at least two, second is the topography removal tools, for example, other interferogram that does not contain deformation or DEM (Digital Elevation Model), third is orbital information. In this study, we used the ERS-1 and ERS-2 (European Remote Sensing satellite) data obtained from ESA (European Space Agency) with track numbers 164 and 300. All the possible combinations were processed but the expected phase gradient was not calculated as useful as it was useful to determine tectonic activity. Main results of these are the atmospheric effects on the interferogram. The topography also rises to effect because of the gradient differences. Finally, GPS results were modeled by DEFNODE software developed by Prof. Dr. Robert McCaffrey. The DEFNODE calculated strain and slip rate on the fault using velocity vectors of sites, locking depth, fault geometry and continental block definitions. The fault geometry was obtained from field work. The fault geometry described the continental block boundaries. All modeling results calculated from the software are shown in the text. According to results obtained from GPS and InSAR, the topography and atmosphere are important for InSAR to calculate interseismic strain accumulation of the hilly region. The other important result is that the main branch of the NAF has faster slip rate than splays of the NAF in the study area. Keywords: North Anatolian Fault, GPS, InSAR, deformation
The usage of granular sulfur with bitumen and its effects on the stability
Get PDFKaliteli asfalt karışımlarının elde edilebilmesi için, kaliteli malzemenin yanı sıra, katkı maddeleriyle güçlendirilmiş modifiye bağlayıcının kullanılması da büyük önem taşımaktadır. Malzemenin ve bağlayıcının seçiminin doğru yapılması, asfalt kaplamaları direncinin güçlendirilmesinde en etkin yöntemlerden biridir. Son yıllarda bozulma probleminin araştırılması ve çözüme kavuşturulması amacıyla, çok değişik modifiye katkı maddeleri kullanılmıştır. Her biri farklı özellik taşıyan, söz konusu katkıların asfalt kaplamaları üzerindeki etkileri de farklılıklar göstermektedir. Geniş ve değişik bir ürün yelpazesine sahip olan modifiye katkı maddelerinin ortak dezavantajları ise bir yandan karışımın özelliklerini iyileştirirken, diğer yandan maliyetini yükseltmeleridir. Modifiye edici katkı maddeleri arasında yer alan sülfür, maliyet yükseltme kuralını bozan ender katkı maddelerinden biridir. Sülfür, diğer modifiye edici katkı maddelerinin aksine, karışımın özelliklerini iyileştirirken maliyetini düşürmektedir. Bu çalışmada, bitümle birlikte bağlayıcı olarak kullanılan Granüler Sülfür (GSF)’ün karışım üzerindeki etkileri araştırılmıştır. Silindirik Marshall numuneleri hazırlanmış ve bu numunelere stabilite-akma deneyleri uygulanmıştır. Karışımda kullanılan malzeme, ilgili şartname ve standartlara uygun olarak test edilmiş ve uygun olduğu tespit edilmiştir. Bitümlü Sıcak Karışım (BSK)’ın optimum bağlayıcı miktarını belirlemek için Marshall tasarım metodu kullanılmıştır. Laboratuarda, %10, %20, %30, %40 ve %50 GSF malzemesi B50/70 bitüm yerine bağlayıcı olarak karışıma ilave edilmiştir. Geleneksel karışımla GSF karışımına Marshall stabilitesi deneyleri yapılmış ve karışım numuneleri arasında bir karşılaştırma yapılarak “Sonuçlar” bölümünde değerlendirilmiştir. Anahtar Kelimeler: Sülfür, granüler sülfür, sülfürlü asfalt, BSK, modifikasyon, katkı maddeleri.Permanent deformations, primarily in the form of ruts, are one of the basic asphalt pavement damages impairing its service properties. Application of appropriate asphalt mixtures and binder modification are effective methods for improving asphalt courses resistance. Many kinds of modifiers, in recent years, have been used for dealing and solving this problem. One of these modified materials is sulfur. The present cost of sulfur varies, dependent on transportation costs. Readily the sulfur cost is approximately five-six times lover than the bitumen cost. It is anticipated that the future price of sulfur will be much lower because supply will exceed demand. The excess sulfur will be obtained from desorbing natural gas, desulfurizing petroleum crude or coal, or recovering elemental sulfur from stack emissions. Granular Sulphur (GSF) is added into the hot mixture of aggregates and bitumen during the mixing process. It is not pre-blended with bitumen. The addition of GSF to the bitumen modifies the bitumen properties. Bitumen and GSF combine at a temperature above the melting point of the GSF (120°C). Part of the GSF is chemically combined with the bitumen and acts as an extender. This part of GSF is dissolved in the bitumen modifying the bitumen properties - viscosity is lowered and its ductility is increased. Above a certain quantity of GSF in the bitumen, GSF remains predominantly as free sulfur and when the blend cools, it crystallizes. Depending on the amount of GSF added, the crystallization gives different levels of strengthening. Sulphur crystallization acts as a structuring agent in the asphalt mixture. The chemical combination between sulphur and hydrocarbon during mixing requires close control of the temperature during the mixing process. The temperature must be maintained at 140°C ± 5°C. This operational temperature range is important to ensure a safe-working operation. Above 145°C hydrogen sulphide (H2S) and sulphur dioxide (SO2) will start to be emitted and these emissions will increase steeply with temperature increase. As the sulphur has a viscosity reducing effect on the bitumen it helps in achieving the ideal viscosity of the binder for coating at a lower temperature. In this study, the effects of Granular Sulfur Asphalt (GSF), which used as a binder in place of bituminous binders, on the mix were investigated. Standard tests were applied to binder and aggregate to define their properties before producing of cylindrical samples. Marshall design was used to evaluate the optimum binder in the Hot Mix Asphalt (HMA). The Marshall Stability and flow test provides the performance prediction measure for the Marshall Mix design method. Marshall samples were prepared in the laboratory by adding of 10%, 20%, 30% 40% and 50% GSF replacing with penetration grade B 50/70 to the mix. Details of the materials used, specimen grain size and procedures for the preparation of the GSF-containing asphalt mixture, is described below. The raw materials used for this study were obtained from different areas. The granular sulfur (GSF) was obtained from the Shell Canada Group. Bitumen with a penetration of 64.1, specific gravity of 1.022 g/cm3 at 25°C and softening point of 51.5°C was obtained from TÜPRAŞ İzmit Refinery. All kinds of aggregates (Coarse, fine and mineral filler) used throughout this study was obtained from a stone quarry in the Ömerli area of Istanbul. As the density of GSF is nearly twice that of bitumen, the binder content in weight of GSF containing asphalt mixtures is generally increased for achieving the same volume of binder in comparison with conventional hot mix asphalt (HMA). The gradation curve of the GSF-containing asphalt mixture is the same as for HMA. Marshall Stability test was carried out using Marshall Equipments. Comparisons were made between the conventional and GSF mixes test results. In comparison with HMA, the Marshall stability of GSF-containing asphalt mixtures is generally increased. The GSF 50 mix stability was much higher than the conventional mix. In addition GSF mixes are purported to be more resistant to water stripping and resistance to gasoline, diesel fuel and other solvents is improved. The laboratory test results of carried on the asphalt concrete samples and mix variables are presented in the “Conclusions” section. Keywords: Sulfur, granular sulphur, sulphur extended asphalt, HMA, modification, additives
Fuzzy logic approach for maximum wave runup estimation on rock armored slopes
Get PDFDökme-taş korumalı kıyı yapıları, arkasındaki alanı şiddetli dalga ve akıntılara karşı koruyan yüksek maliyetli yapılardır. Bu tür yapılarda, maksimum dalga tırmanması, tepe yüksekliğini belirleyen önemli bir parametredir. Kapsamlı literatür incelemesinden görülmüştür ki, regresyon analizleri neticesinde bulunan Van der Meer ve Stam yaklaşımı, dökme-taş korumalı kıyı yapılarının kret seviyesini hesaplamak için ilgili birçok şartnamede tavsiye edilmektedir. Oysa regresyon analizi neticesinde bulunan bu denklemin sağlaması gereken birtakım önkabuller vardır. Bu kabullerden herhangi biri sağlanmıyorsa regresyon analizi neticesinde elde etmiş olduğumuz denklem taraflı sonuç verir ve hatalıdır. Bu kabuller sırasıyla doğrusallık, normallik, şartlı dağılımın ortalamasının sıfır olması, eşit varyans, iç bağımlılık ve ölçülerin hatasız olmasıdır. Van der Meer ve Stam tarafından elde edilen laboratuar verilerinin istatistiki analizleri yukarıda verilen 6 şart için yapıldığında test sonuçları göstermiştir ki Van der Meer ve Stam denklemi, mevcut hali ile regresyon analizi yapılma şartlarını sağlayamamaktadır. Bu yüzden bu denklem taraflı ve hatalı sonuç vermektedir. Bu çalışmada içerisinde hiçbir önkabul barındırmayan Bulanık Mantık yönteminden yararlanılmıştır. Nümerik hata kriterleri ve grafik gösterimler, Bulanık Mantık yönteminin, Van der Meer ve Stam yaklaşımından daha gerçekçi ve daha pratik sonuçlar verdiğini göstermektedir. Ayrıca, Bulanık Mantık yönteminin kıyı benzerlik parametresine bağlı bir geçiş bölgesi bulunmamaktadır. Bundan dolayı, geliştirilen Bulanık Mantık modelin kullanımı kolay ve pratiktir. Bu yüzden, bu çalışmada önerilmiştir. Anahtar Kelimeler: Bulanık mantık, regresyon analizi, kret seviyesi.Extensive researches have been conducted about wave runup on smooth sloped breakwaters all over the world for a long time. Runup behavior on rough rock armored slopes are significantly different even under the same wave conditions. However, investigations on rock armored slopes are very limited. Rock armored slopes such as breakwaters and revetments are high-cost structures that defend the area behind them against severe wave attacks and strong currents. Wave runup is a crucial factor dictating the crest level of these structures. Van der Meer conducted extensive series of physical model tests under random sea states for investigating stability of rock armored slopes at Delft Hydraulics Laboratory, during which runup values are measured simultaneously. After qualitative review of various parameter influences concerning wave runup on impermeable, permeable and homogenous rock structures, Van der Meer and Stam proposed the most widely used formulae for the forecast of dimensionless 2% wave runup elevationas as function of surf similarity parameter by using regression analysis, which is also recommended by the U.S. Army Corps of Engineers, British standards. The regression model consists of two parts, namely linear and power functions.. Hence, it is necessary to consider a transition region which depends on the variable surf similarity parameter. Rock armored slopes are often designed according to the runup level exceeded by 2% of the incident waves, /Hs, on the front face of the coastal structure by using Van der Meer and Stam formulae. This parameter is defined as the vertical distance between the still-water level and the elevation exceeded by 2% percent of the runup values in the distribution. This means that, for every 100 waves running up a slope, two waves would have a runup elevation exceeding the level estimated by From the literature survey, it is seen that the two most important factors influencing runup phenomena on rock armored slopes are structure permeability and surf similarity parameter Since the relationships between wave runup and these parameters are complex, vague and uncertain in nature, it is quite difficult to adequately examine wave runup by conventional regressional approaches. Here, an attempt is made to construct various Takagi-Sugeno (TS, 1985) fuzzy models for predicting the 2% wave runup on rock armored slopes. The key task in developing a satisfactory forecasting model in the TS approach is the selection of appropriate input variables and numerical counts and types of Membership Functions of these variables, which determines the architecture of the model. Subsequently, the premise and consequent parameters are optimized by using ANFIS learning procedure. ANFIS, free of restrictive assumptions, optimizes premise and consequent parameters by gradient descent and least-squares methods, respectively, in order to best learn information about the dynamic system and does not contain any transition regions, as in the Meer and Stam equation depending on surf similarity parameter. In this study, many ANFIS models with different architectures are trained with the same 100 training data of Van der Meer and Stam. The training performance of each model is accomplished within a short time. They are compared with conventional empirical model of Van der Meer and Stam and with one another by using the 161 test data. As a result, the system with two inputs, namely structure permeability and surf similarity parameter, and each of which is assigned three trapezium MFs provides a smaller error compared to the empirical and other constructed ANFIS models and therefore is selected. In the constructed model, structure permeability and surf similarity parameter variables are initially assigned three trapezium MFs with equal base widths. Then each parameter in the membership functions in the premise part of fuzzy IF-THEN rules that changes the shapes of the membership function is set to an appropriate value to match the output data of the training data by using the back propagation algorithm. This leads Structure Permeability and Surf similarity parameter variables to different trapezium shapes. The developed fuzzy model with two inputs namely structure permeability and surf similarity parameter yielded the best result out of all constructed models and is proposed in this study. The presented model is validated by comparison with widely used empirical model of Meer and Stam recommended by the U.S. Army Corps of Engineers, using the experimental data-sets of Van der Meer and Stam. The verification process is obtained through scatter diagrams and two numerical error criterias. It was found that the Fuzzy Logic model produce better accuracy in performance than the Van der Meer and Stam's empirical model. Keywords: Fuzzy logic; regression analysis, crest level
Tüketici temelli marka değerinin finansal performans üzerine etkisi
Get PDFGerçekleştirilen çalışmada önemi artan (tüketici temelli) marka değeri konusu ve finansal performans üzerine etkileri incelenmiştir. Tüketici gözünde oluşan marka değerinin alt boyutlarıyla ortaya konularak, bu boyutların şirkete somut finansal katkıları olup olmadığı ve katkı şekilleri Türkiye menşeli firmalar için analiz edilmiştir. Yöntem olarak çalışma, Türkiye’de tüketici temelli marka değerinin (brand equity) bir anket çalışmasından elde edilecek veriler ile belirlenmesi, firmaların finansal performansının halka açık finansal tablolardan elde edilmesi ve bu iki veri grubu arasında istatistiksel olarak anlamlı bir ilişki bulunup bulunmadığının detaylı olarak analizi ve yorumlanması şeklindedir. Tüketici temelli firma gücünün (değerinin) ölçümünde pazarlama literatüründe genel kabul gören Aaker (1991)’in önerdiği boyutlar üzerine geliştirilen çok boyutlu bir model kullanılmıştır. Aaker’in önerdiği ve çalışma içerisinde kullanılan boyutlar marka farkındalığı, algılanan kalite, marka sadakati ve marka çağrışımları olarak sıralanabilir. Bu boyutların ölçümü için geçtiğimiz yıllar içerisinde uluslararası literatürde yer alan çalışmalarda kullanılarak geçerliliği test edilmiş ölçeklerden faydalanılmıştır. Bu ölçeklerde yer alan ölçüm soruları Türkçe’ye ve Türkiye şartlarına uyarlanarak, uzman görüşleri ve pilot çalışma doğrultusunda yapılan ekleme ve değişiklikler sonucunda nihai haline getirilmiştir. Firmaların finansal performanslarının karşılaştırılabilmesi için uluslararası kabul görmüş çeşitli finansal performans göstergelerinden faydalanılmıştır. Finansal performans göstergelerinin her bir firma için değerini hesap etmekte İstanbul Menkul Kıymetler Borsası vasıtasıyla elde edilen halka açık finansal tablolar kullanılmıştır. Anahtar Kelimeler: Tüketici temelli marka değeri, marka ederi, marka sermayesi, finansal performans.This study analyzes the brand and brand equity concepts and the financial performance that is expected to be improved as a result of branding activities and brand equity. This study is carried out to understand whether the consumer based brand equity affect the firms' financial performance and the degree and type of the relationship between these if there is a significant correlation is available.In the analysis stage, the consumer based brand equity's dimensions are revealed for companies from different business sectors in Turkey and these are compared with the financial performance indicators to understand whether a statistically significant relation is visible. The methodology used may be summarized as follows: the determination of the consumer based brand equity for each firm in the study by a field study (questionnaire), the acquirement of the financial data from Istanbul Stock Exchange, calculation of related variables and factors, the detailed analysis of the consumer based data and financial data together to understand the relationships between them and finally the interpretation of the results.The model used in the determination and measurement of the consumer based brand equity in this study is fundamentally based on the model proposed by Aaker (1991) and the scale developed by Yoo and Donthu (2001). The consumer based brand equity dimensions proposed by Aaker are; "Brand awareness", "Perceived quality", "Brand loyalty", and "Brand associations". The data needed for comparing the consumer based brand equity dimensions among the firms are obtained using a questionnaire, which is applied with face-to-face interview in Istanbul to 505 subjects. The scale used for measuring these dimensions is based on popular and verified scales referenced in international literature. The questions in the mentioned scales (Yoo and Donthu, 2001; Bruner and Hensel, 2001; Bearden and Netemeyer, 1999) are translated to Turkish and are modified to give the same meaning and feeling, moreover some questions were omitted and new ones are added in the light of a pilot study and expert opinions. The companies and brand that are included in this study are selected using the following criteria: publicly listed companies (to be able to have audited and comparable financial performance data), companies with a family brand (to be able to use the firm's financial data as the brand's data), not operating in the financial services sector (as the performance indicators are different in this sector). A total of 28 firms are included in the study. The questionnaire is structured to include; brand experience, category knowledge, consumer based brand equity dimensions (perceived quality, brand awareness, brand associations and brand loyalty), attitude towards brand, purchase intention, demographical and socio-economic-status questions. The internationally accepted financial ratios used in the study for comparison of financial performance between the firms may be listed as: Annual return on shares, Firm Value / Market Value, Price / Earnings, Price / Net Sales per share, EBITDA / Net Sales, Return on Assets, Operational Profit, Net Sales, Market Value, Financial Leverage Ratio, Current Ratio, and Annual Change in Net Sales. The balance sheets, income statements and related annotations that are publicly available through the Istanbul Stock Exchange for years 2007 and 2006 are used as data in calculating the aforementioned financial performance measures for the companies included in the study. The data obtained through questionnaires and from publicly available financials are processed and analyzed. An explanatory factor analysis is carried out to derive the brand equity dimensions from the questionnaire. Three different factors are obtained as a result of the factor analysis. These three factors of the brand equity are then used as the independent variables in the regression analysis with the financial performance measures, which are entered as dependent variables. As an outcome of the statistical analysis conducted, it has been seen that the consumer based brand equity positively affects most of the financial performance indicators to varying extents. Keywords: Consumer based brand equity, financial performance
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