23 research outputs found
Measuring the possibilities of interfuel substitution
No full textWhat are the costs of making consumption of production activities use less-polluting fuels? The author reviews how the fuel mix used by different industries has changed over time and examines 2 techniques for estimating the responsiveness of fuel demand to fuel prices: econometric models and the engineering approach. With econometric models, the elasticity of substitution between energy and other inputs determines the costs of making activities less energy-intensive, while the elasticity of substitution between sources of energy (interfuel substitutability) determines the marginal costs of replacing one energy source with another. The engineering approach uses more detailed technical information and can draw a more complete picture, but with less ability to inform about activities with a vast number of different economic agents. Among the author's main conclusions: There are surprisingly large variations in energy and fuel use over time and between countries. Industrial output increased 62 percent in OECD countries between 1971 and 1988, for example, while energy use stayed unchanged. Also, shares of energy sources for industry and electricity vary greatly with local availablity, indicating that these sectors have some flexibility in choice of energy source. A judgment on whether this variability indicates that an economy responds cheaply if energy prices are changed selectively depends on how one reads the more detailed studies in the econometric and engineering literature. Lack of data is the biggest problem in estimating fuel and energy substitutability in non-OECD countries. Engineering studies of fuel switching in industry are rarely available. They exist, however, for the power industry and could be used to estimate the costs of alternative fuel-mixes for particular greenfield sites. The technique could not be used for assessment of economywide policies. Econometric studies are useful inasmuch as they take a sector- or economywide perspective. Econometric techniques are challenging, but often represent the state of the art in providing reliable estimates for elasticies of substitution - particularly when data are scarce and the level of aggregation is high. The issue of whether econometrically estimated structural parameters can be transferred across borders has not been thoroughly investigated.Oil Refining&Gas Industry,Transport and Environment,Energy and Poverty Alleviation,Energy and Environment,Airports and Air Services
Features of patients with laryngeal tuberculosis
No full textObjective: The aim of this study was to evaluate the clinical and radiological properties of patients with pulmonary and laryngeal tuberculosis (tbc) who were followed in our hospital. Material and Methods: Fifteen patients with laryngeal the were detected among 6229 patients who had been treated for pulmonary tbc in our hospital. They were retrospectively analyzed. Results: Fourteen patients were male and one patient was female. The mean age was 39.4 +/- 7.6 (24-51). All were snickers with an average of 28.9 (1-80) pack-years. Four patients had a family history of tbc. In addition to pulmonary symptoms, 14 (93.33%) had hoarseness, 10 (66.6%) had dysphagia, 2 (13.3%) had odynophagia and I patient (6.66%) had laryngeal strider. Mean duration of hoarseness was 86.6 + 54.9 days. Chest x-ray revealed 12 (80%) bilateral disseminated infiltrations, 5 (33.3%) cavitary lesions and 3 (20%) unilateral infiltrations. All patients (I female, 14 males) had positive smears (category 1). Thirteen patients had been examined with laryngoscope and tissue samples had been obtained from nodular lesions in 7 patients with the suspicion of larynx malignancy. Larynx tbc was diagnosed with biopsy in 10 patients and with clinical and laryngoscopic features in 5 patients. Thirteen patients were treated with isoniasid (H), rifampicin (R), morfazinamide (Z) and ethambutol (E) and two patients were treated with H,R,Z and streptomycin (S). Conclusion: Tbc of the larynx should be considered in the differential diagnosis of patients with hoarseness of long duration or nodular laryngeal lesions
Hilbert transformation of waveforms to determine shear wave velocity in concrete
No full textWOS: 000269268000009Given the density value, elastic properties of a homogeneous and isotropic material can be determined provided that primary and shear wave (P- and S-wave) velocities are known. P-waves are easier to monitor and detect compared to the S-waves. In concrete, along with P-wave velocity, shear wave velocity measurement is important in determining the elastic properties. These elastic properties could be implemented in assessing the quality of in-situ concrete. After an extensive literature survey, this study focused on the applicability of Hilbert transformation of waveforms to determine shear wave velocity in concrete material. The experimental work consisted of a set of ultrasonic measurements on the surface of a reinforced concrete deck. The recorded waveforms were then analyzed to obtain the arrival times of P- and S-waves. Hilbert transformation of the waveforms proved to yield reliable and repeatable results. (C) 2009 Elsevier Ltd. All rights reserved.Wayne State University of Detroit, MIThe author wishes to express his deep appreciation to the Civil and Environmental Engineering Department of Wayne State University of Detroit, MI for the financial support to complete this study. The author is also grateful to Prof. Haluk Aktan and Assoc. Prof. Ozgur Yaman for their constructive criticisms. Invaluable help from Mr. Jason Rutyna and Mr. Hakan Karaca are greatly appreciated in obtaining the experimental data
Tariff index theory
No full textFor a single tariff, the height of the tariff is an unambiguous measure of the policy's restrictiveness. With more than one tariff, theory has not provided an extension that captures the idea of the tariff's height, so analysts have used index numbers such as the mean and the coefficient of variation (standard deviation divided by the mean) of tariffs. By contrast, the theoretical literature on the piecemeal reform of tariffs shows that efficiency gains from tariff reform depend on complex conditions that have little relation to the mean or variance of tariffs. But in the absence of a connection between theory and empirical measures, it is difficult to know whether to discard the measures. Moreover, the piecemeal reform question of measuring the welfare gain from a tariff is not directly related to the problem of evaluating the height of restrictiveness. The problem of finding a single number analogous to the height of tariffs is the tariff index number problem. The authors have developed a solution: the Trade Restrictiveness Index, which they define as the uniform tariff factor that is equivalent in trade restrictiveness (equivalent in the balance of trade) to the actual differentiated tariff structure. Here, the author develops the Trade Restrictiveness Index in terms of mean and variance-covariance indexes of the tariff schedule. There are two payoffs. First, the Trade Restrictiveness Index can be decomposed into expressions that rescue the commonsense idea that lower mean and lower variance of tariffs are both efficient. Second, a special case is offered in which the proper weights in the mean and variance of tariffs are the observed trade weights. Thus, the Trade Restrictiveness Index is superior to traditional summary measures such as the average tariff rate and the coefficient variation for the tariff schedule. It requires only limited additional information on the structure of the economy to yield a measure that is preferable on both theoretical and practical grounds.Environmental Economics&Policies,Export Competitiveness,Trade Policy,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research
Valorization of Apple Pomace Via Single Cell Oil Production Using Oleaginous Yeast Rhodosporidium toruloides
No full text© 2022, The Author(s), under exclusive licence to Springer Nature B.V.Apple pomace was used as a sole raw material for single cell oil (SCO) production by the oleaginous yeast Rhodosporidium toruloides DSM 4444. Preliminary studies with glucose medium revealed 100 mL of working volume in 500 mL Erlenmeyer flask as the most efficient in terms of lipid content. Thus, apple pomace hydrolysate was tested in six different conditions using 100 mL medium. The detoxified hydrolysate without chemical supplement (D medium) was found to be the most viable medium by 47.5 ± 2.47% lipid on dry cell basis (w/w). Apple pomace hydrolysate was also proven effective for SCO productions in bench-top fermenter (1 L working volume) under controlled temperature (25 °C), pH (5.0), and aeration (1vvm) by 40.1 ± 5.51% (w/w) lipid content. The same medium resulted in 50.9% (w/w) lipid on a dry cell basis in 30 L industrial-type bioreactor with 10 L of working volume, without exact control of temperature and pH. The results confirm that apple pomace is a prosperous raw material for SCO production in flask and fermenter scales. Graphical Abstract: [Figure not available: see fulltext.]
Die Bestimmung der optimalen materialzusammensetzung und das mechanische verhalten des fur den bootsbau geeigneten ferrocements
No full textTez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1986Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1986Ferrosement, son yıllarda tüm Dünya'da gittikçe yay gınlaşan; sertleşmiş beton ile onu takviye eden çelik tel ve çubukların oluşturduğu bir yapı malzemesidir. Konstrüksiyon kolaylığı ve maliyetinin düşük olması; özellikle küçük tekne lerin yapımı için malzemeyi çekici hale getirmektedir. Bu çalışmada; altıgen tel ağ ile pekiştirilmiş ferro- Sementin geometrik ve mekanik özellikleri kuramsal ve deney sel olarak incelenmiş ve gemi yapımında nasıl daha efektif olarak kullanılabileceği araştırılmıştır. Çalışma beş bölümden oluşmaktadır. Birinci bölümde, ferrosement genel olarak tanıtılmakta ve gemi inşaatına uygun olan ve olmayan özellikleri belirtil mektedir. Daha sonra malzemenin mekanik özellikleri üzerinde bugüne kadar yapılan çalışmalar özetlenerek eksik yönleri tar tışılmaktadır. Harç bileşiminin etkisini de göz önüne alarak deniz koşullarına ve tekne, yapımına uygun bir malzeme oluş turmaya yönelik çalışmalar ıu^gok az ve yetersiz olduğu sapta narak, araştırmanın bu yönde geliştirilmesi amaçlanmıştır. İkinci bölümde, ferrosement tekne yapımında kullanılan, çelik boru, çubuk ve tel ağların geometrisi incelenmiştir. Boru ve çubuklar tekneye gerekli form ve rijidliği vermek amacıyla kullanılmaktadır. Bunun dışında mukavemete katkıları çok azdır. Dolayısıyla kompoziti temsil eden birim hücre sa dece sertleşmiş beton ve altıgen tel ağ göze alınarak oluştu rulmuştur. Bezukladov | 14 | ve Shah|l|'m tel ağların pekiştir me özellikleri için verdiği tanımlar altıgen tel ağ ile pe kiştirilmiş ferrosemet kompozitine uygulanmış ye birim hücre için özgül yüzey 2. 3 ; pekiştirme oranı 2.12 ve çelik içeriği 2.17 nolu denklemler ile verilmiştir. Daha sonra çelik çubuk ve boruların' etkisini de görebilmek amacıyla en genel ferro sement yapı tipi olan D-tipi yapı için bu tanımlar genelleş tirilmiştir. Özgül yüzey için 2.21, pekiştirme oranı için 2.26 ve çelik içeriği için 2.29 denklemleri elde edilmiştir. Ayrıca teller arasındaki ortalama mesafe ve ortalama» tel sa yısı için 2.32 ve 2.23 ifadeleri geliştirilmiştir. Üçüncü bölümde, kompoziti oluşturan çelik teller ve beton matris için ger ilme-bir im uzama denklemleri 3.3 ve 3.4 denklemleri ile verilmiştir. Sertleşmiş beton ve onu pekiştiren tek bir çelik teli ayrı ayrı homojen, izotrop ve lineer elastik kabul ederek or- totropik malzemenin Ex, E", Vxy, VyX ve Gxv elastik sabitleri karışım kuralları ile yazılmıştır. Kuvvet etkime yönü ile lif doğrultuları farklı olduğundan kuvvet etkime doğrultusundaki malzeme sabitleri tansörel dönüşümle bulunmuştur. Neticede bi rim hücrenin iki bileşeni seçilen yükleme durumu için seri bağ lı kabul edilerek altıgen kümes teli ile pekiştirilmiş ferro- sementin sabitleri hesaplanmıştır. Çalışmanın dördüncü bölümü, deneysel araştırmaya ay rılmıştır. Ferrosement tekne kaplaması için en kritik geril melerin çekme gerilmeleri olduğu düşünülerek, kesiti (7 cm x 2 cm) olan özel numuneler üzerinde uniform çekme deneyleri yapılmıştır. Deneylerde kullanılan çimento, agrega, tel ağ gibi malzeme bileşenlerinin hangi kriterlere göre seçildiği açık lanmış, fiziksel, kimyasal ve mekanik özellikleri diagram ve tablolarla verilmiştir. Beton karışımı hesabının nasıl yapıldığı bölüm 4.3'de açıklandıktan sonra hazırlanan çekme numunesi kalıplarını kullanarak ön deneyler yapılmış ve ferrosement harçları için (w/c) su-çimento oranına ve (c) çimento dozajına bağlı olarak hava boşluğu oranları verilmiştir. Deneyler için agrega granülometr isi sabit kalmak üzere su/çimento oranları 0,35-0,40-0,45; çimento dozajları 450 kg/m3-600 kg/m3-750 kg/m3 ve tel ağ katları 0-4-8-12-16 de ğerlerini alan 45 tip numune hazırlanmıştır. Deney sonuçla rında olası sapmaları düşünerek her tipten 5'er adet olmak üzere toplam 225 numune üretilmiştir. Üretim için tasarımı yazar tarafından yapılan özel kalıplar kullanılmıştır. Numu neler 1 gün kalıp içinde, 6 gün su içinde bırakılmış, döküm den 28 gün sonra çekme deneyine tabi tutulmuşlardır. Çekme deneyleri 20 tonluk universal çekme makinesinde yapılmıştır. Boy yönündeki uzamalar, özel olarak tasarlanan bir boyuna deformasyon çerçevesi, en yönündeki kısalmalar ise bir enine deformasyon çerçevesi kullanarak endüktif transdu- cerler yardımı ile elektronik olarak ölçülmüştür. Neticede herbir numune için ger ilme-boyuna şekil değiştirme diagramla- rı çizilmiş, ilk çatlama ve göçme gerilimleri saptanmıştır. Ferrosement kompozitinin sürekli fazını oluşturan sert leşmiş betonun mekanik özelliklerini saptamak amacıyla ayrıca 010x20 cm'lik silindirler üretilmiş ve standart basınç ve si lindir yarma deneyleri yapılmıştır. Beşinci bölüm elde edilen sonuçların değerlendirilme-^ sine ayrılmıştır. Ferrosement harçlarının klasik beton harç larından farklı olması nedeniyle yoğurma suyu miktarının çök- me ve VeBe değerlerine etkisi, koaıpozit birim ağırlığı, hava boşluk oranının tel miktarı ile değişimi, su emme, basınç mu kavemetinin çimento dozajı ye w/c oranı ile değişimi gibi normal betonlarda çok incelenmiş konular yeniden değerlendi rilmiştir. Aynı şekilde ferrosement harçları için basınç mukave meti ile silindir yarma deneyinden bulunan çekme mukavemeti arasındaki ilişki, yoğurma suyu miktarının basınç elastiklik modülüne etkisi, basınç mukavemeti ile elastiklik modülü ara sındaki ilişkiler araştırılarak diagramlarla ve analitik ifa delerle verilmiştir. - Bölüm 3* de ferrosement kompozitinin elastik sabitleri nin hesabı için verilen yöntem; deneysel sonuçlarla karşılaş- tırılmıştır. Kompozitin boyuna ve enine elastiklik modülleri pekiştirme oranı ile lineer olarak artmaktadır. Ancak tel yüz desi çok küçük değerlerde kaldığından bu artış önemli boyutla ra ulaşamamaktadır. Benzer ilişki Poisson oranları ve kayma modülünde de gözlenmektedir. Geliştirilen teorinin deneysel sonuçlar ile yeterli uyum içinde olduğu gözlenmiştir. İlk çatlama gerilmesi de pekiştirme oranı ile doğrusal olarak artmaktadır. Ayrıca beton fazının etkisi ile ilk çat lama gerilimi su/çimento oranı ve çimento dozajı ile de ilgi lidir. Maksimum ilk çatlama gerilmesine ulaşmak için pekiş tirme oranını yükseltirken çimento dozajını bir ölçüde düşür mek gerektiği bulunmuştur. Ayrıca pekiştirme oranı arttıkça ilk çatlama anındaki boyuna uzama ve enine kısalmaların da doğrusal olarak arttığı görülmüştür. İlk çatlağın oluşmasından sonra çatlak gelişme bölge sine girilmektedir. Bu bölgede de; çatlamalar sırasında olu şan çok küçük gerilme düşüşleri dışında gerilme ve birim uza maların orantılı olarak arttığı gözlenmiştir. Dolayısı ile literatüre uygun olarak | 27 | çatlaklı bölge için de deformas- yon modülü, Poisson oranı ve kayma modülü ölçülmüştür. Bu de ğerlerin pekiştirme oranı arttıkça azaldıkları görülmüştür. Gerilmenin belli bir maksimum değerinden itibaren çat lak oluşumu durmakta, uzamalar büyük değerlere çıkmakta, di ğer bir deyişle inelastik akma bölgesine girilmektedir. Bu bölgede ancak maksimum gerilme (ömax) ve kopma anındaki (ölçü b&lgesinde kalmıyorsa) maksimum boyuna uzamalar (eı max) ve maksimum enine kısalmalar (£2 max) ölçülebilmektedir. CJmax £.\ ^y ve £2 max değerlerinin pekiştirme oranına bağlı olarak arttı ğı, ayrıca aie/amax, ei/ei max. £2/^2 max oranlarının in celenmesi ile pekiştirme oranı arttıkça nihai değerler ile ilk çatlama arasındaki farkın büyüdüğü saptanmıştır. Elde edilen sonuçlara göre ilk çatlama gerilimi en yüksek ancak hafiflik, ekonomiklik ve işleme kolaylığı bakı mından en uygun ferrocement yapı bileşenleri; tel ağ sayısı : n = 16 pekiştirme oranı : Vç = 0.035 çimento dozajı : c = 570 kg/m^ - 600 kg/m^ su/çimento oranı : u/c = 0.45 olarak belirlenmiştir. Son olarak tüm çalışmanın önemli sonuçları tekrar özet lenmiş ve bunlarla ilgili olarak yazarın Ferrosement tekne ya pımı ile ilgili önerileri sunulmuştur.Ferrocement ist ein neuer Verbundwerks tof f aus Zement- mörtel als Matrix und einer Bewehrung aus Maschendraht und Stabstâhlen. In den letzten Jahren wurde er als Boot smater ial in der ganzen Welt verbreitet, weil er fiir die einfache und billige Konstruktion von Jachten, Fischereif ahrzeugen und Motorboote geeignet ist. In der vorliegenden Arbeit wurde die Geometrie und die mechanischen Eigenschaf ten des mit sechseckiggewobenem Maschen draht bewehrten Ferrocement s auf Theorie und Ver suchsbasis untersucht. Es wurde das Ziel eingesetzt, die Zusammensetzung und die Struktur des Werkstoffs so zu entwerfen, dass.es bes- sere Eigenschaf ten im Hinblick auf die Boot skons truktion ge- winnt. Die Thesis besteht auf fiinf Kapiteln. Im ersten Kapitel wurde Ferrocement allgemein inter- prâtiert und seine Vor-und Nachteile im Bootsbau diskutiert. Nachher wurde eine Literaturunter suchung über die mechanischen Eigenschaf ten des Materials durchgenommen, wodurch es sich nötig erwiess,eine fiir die dynamischen Seeverhâl tnisse geeig- nete Zusammensetzung und Struktur des Materials neu aufzubauen. Im zweiten Kapitel wurde die Geometrie der Anordnung def Bewehrungsmater ialien, untersucht. Da die Stahlröhre und die Stabstâhle ausser Formgebung keinen wichtigen Beitrag auf die Festigkeit des Verbundwerkstof f s haben, wurden sie in der Beschreibung der Einheit szel le nicht beriicksicht igt. Durch eine theoretische Untersuchung wurden fiir die Einheit szelle die Formeln "der spezifischen Oberflache" GI.2.3 "des Beweh- rungsgrades GI.2.12" und "der Stahlinhalt" GI.2.17, hergeleitet Dann wurden diese Beziehungen fiir die allgemeinste "Typ D" Struktur des Ferrocements ver algemeiner t, wodurch auch die Stahlröhre und Stabstöhle beriicksicht igt wurden. Ausserdem wurde "der mittlere Abstand der Drahte" mit GI.-2.23 und "die mittlere Anzahl der Drahte" mit GI;2£.-33 definiert uad formül iert. im dritten Kapitel wurde das Zugspannungs-Verlângerungs Verhalten der StahldrMhte und des Betonmatrix angegeben (GI. 3.3 und GI.3.4). Nachher wurde ein mit einein geraden Draht bewehrter Betonmatrix als ein Modeli für den Verbundwerkstoff vorgenom- meo. Die beiden Komponente wurden homogen isotropisch und linear elastisch angenommen. So wurden die elastischen Konstanten des orthotropischen Materials (Ex, Ey, Vxy, vyx und Gxy) mit Hilfe der Mischungsgesetze ("rules of mixtures") bestimmt. Da die Spannungs-und die Bewehrungsrichtungen unterschiedlich sind, wurden die in der Spannungsrichtung gültigen Konstanten durch eine geeignete Drehung berechnet. Naehdem für jedes der zwei Teile der Einheit szelle, die Konstanten in Spannungsrichtung bestimmt wurden, wurden diese in Serienschaltung miteinander vereinigt. Im vierten Kapitel wurde das Versuchssystem und seine Durchf ührung beschrieben. Da für ein ferrocement Boat die Zugspannungen kritisch sind, wurden Probestücke mit rechtecki- gen Querschnitt (7 cm x 2 cm) hergestellt und diese mit homo- genem Zugspannungsf eld belastet. Die Kriterien für die Wahl der Ver suchsmaterialien wie Zement, Sand und Maschendraht wurden erlâutert und ihre pyhsikalischen, chemischen und mechanischen Eigenschaf ten in Tabellen angegeben. Im Kapitel 4.3 wurde die Rechnung für die Betonzusam- mensetzung erklârt. Nach dieser Zusammensetzung wurden Probe- körper gegossen und die Vorversuche für die Bestimmung der Luftinhalte durchgef ührt. Bei der Herstellung der Probekörper wurden für Wasser/ Zement. Verhâltnisse die Werte 0.35-0.40 und 0.45 für Zement- inhalte 450 kg/m^-600 kg/m^ und 750 kg/m^ und für die Anzahl der Maschendrahtlagen die Werte 0-4-8-12 und 16 genommen. So wurden 45 Probekörper mit verschiedener Zusammensetzung aber mit Rİeicher kornver teilung produziert. Gegen die mögliche Streung den Messwerte wurden von j eder Zusammensetzung 5 gleiche Stücke hergestellt. In der Produktion wurden vom Author entworfene Formen verwendet. Die Propekörper wurden ein Tag in den Formen, sechs Tage im Wasser a-uf b'ewahr-t''Ao-nd nach 28 Tagen mit der 20 Tonnen Zugmaschine gezogen. Die VerlMngerungen in der Langs- richtung und die Verkürzungen in der Querrichtung wurden mit den original entworf enen AluH^e-tormat ionsrahmen mittels induktiver Transducer elektronisch gemessen. Für jedes Probestück wurden die Spannung-Verlangerung Diagramme auf- gezeichnet; die Spannungen" f-uF'den " e3r"sten Riss und der Bruch- last bestimmt. Um die me eh an i s eh en Eigenschaf ten des FerrocementmSr tels zu hestimmen, wurden ausserdem Betonzylinder mit den Massen 010 cm x 20 cm produz'iert und Druck und Zersplitterungs- versuche nach T. S. E. (İnstitut für Türkische Normen) dureh- gef ührt. im fünften Kapitel wurden die Versuchsergebnisge disku- tiert. Da die Zusammensetzung des FerrocementmSrtels unter- schiedlich ist, als die des klassischen Betons, wurden gewohn- liche Themen, wie die Zusammensetzung des MSrtels und ihr Einfluss auf die physikalischen und mechanischen Eigenschaf ten des Ferrocements, nochmals untersucht. Ausserdem wurden die Zusammenhânge zwischen den verschiedenen Materialeigenschaf ten und dem Bewehrungsgrad diskutiert. Wenn es möglich war, wurden theoretische Ergebnisse mit den Versuchsergebnissen verglichen. In den meisten Fallen wurde eine hinreichende Darstellung der Messwerte durch die Theorie beobachtet. Die wichtigsten Folgerungen sind am folgenden angege- ben. 1- Der wichtigste Faktör in der Flanung eines Ferro- cement Bootes, urn die nStige Festigkeit zu erreichen, ist der Bewehrungsgrad und die Anordnung des Bewehrungsmaterials. In dieser Hihsicht wurde die Geometrie des mit sechseckigem Maschendraht gewobenen Ferrocements untersucht und die Formeln für die spezifische Oberflâche, den Bewehrungsgrad, den Stahlinhalt im Text angegeben. 2- Die Dichte des FerrocementmSrtels ist ungefâhr 2.2 kg/dm^ und wird von der Zusammentzung des Möttels fast nicht beeinflusst. Aber für die mit Maschendraht bewehrten Probe- korper steigt die Dichte mit dem Bewehrungsgrad linear an. 3- Das Volumen der Hohlraume im Ferrocement nimmt mit dem Bewehrungsgrad zu. 4- Die Wasserauf nahme der Frobekörper ist so klein, dass man sie vernachlassen kann. 5- In der Thesis wurde Ferrocement als ein, mit sechseckig gewobenem Maschendraht bewehrter Verbundwerkstof f angenommen. Die elastischen Konstanten der Einheitszelle wurden mit Hilfe der Mischungsgesetze ausgedriickt, Sie zeigen eine geniigende Annâherung zu den Messwerten. Der Elastizitâtsmodul, die Poisson'sche Konstante und der Gleitmodul wachsen mit dem Bewehrungsgrad linear an. Da die elastischen Konstanten in den orthogonalen Hauptrichtungen fast gleich sind, kann man Ferro cement in praktischen Rechnungen als homogen. isotropisch annehmen. c ". - vııı - 6- Die Zugspannung für den ersten Rİ8S (üj.ç) *-st eine lineare Funktion des Bewehrungsgrades. Sie ist auch abhSngig von, der Matrixf estigkeit, also steigt an mit Zunahme der Zementmenge. Im untersuchten Bereich hat das u/c Verhâltniss keinen wichtigen Einfluss auf a.. 6 iç 7- Die Verlângerungen in der Zugrichtung und Verkür- zungen in der Querrichtung bei dem ersten Riss nehmen mit dem Bewehrungsgrad zu. 8- Der Bereich zwischen dem ersten Riss und dem Fliessen des Materials wird als Rissentwicklungsbereich definiert. Auch für diesen Bereich kann man Materialkonstanten angeben, die diesmal mit dem Bewehrungsgrad abnehmen. 9- Die maximal.e Zugspannung ist auch eine lineare Funktion des Bewehrungsgrades. 10- WShrend die unbewehrten Probekorper keine benennwerte Ver lângerungen zeigen, beobachtet man bei hochbewehrten Probe- körpern ziemlich groSe Verlângerungen. 11- Die Verkiirzungen in der Querrichtung wachsen geradlinig mit dem Bewehrungsgrad. 12- Mit Zunahme des Bewehrungsgrades verkleinert sich das Verhâltnis Oie/amax. Mit anderen Worten; je h5her das Bewehrungsgrad, desto gröSer ist der Unterschied zwischen der maximalen Zugspannung und der Spannung für den ersten Riss. Das Material für den Ferrocementbootsbau soil einen möglichst grogen Wert für die Zugspannung bei dem ersten Riss aufweisen. Ausserdem soil es leicht, ekonomisch und leicht zu verarbeiten sein. Mit diesen Überlegungen wurden die optimalen Parameter der Materialzusammensetzung wie folgt bestimmt. Macschendracht (I<2=3/4" d=0.63 mm): n=16 Lagen Bewehrungsgrad : Vf = 0.035 Zementinhalt : c = 570 kg/m3-600 kg/m3 Was ser/Zement Verhâltnis : w/c=0,45 Als Schlusswort wurden die wichtigsten Erkenntnisse der ganjen Untersuchung zusammengef asst und die Hinweise des Authors für die Zielbewusste Konstruktion eines Ferrocement- bootes angegeben.DoktoraPh.D
How effective are directed credit policies in the United States? A literature survey
No full textSchwarz surveys U.S. experience with directed credit as background for a larger study of the Asian experience. Almost half of net credit lent in the United States annually is directly affected by government policies - half of net credit covering budget deficits, and half falling under various federal credit programs. The main difference between U.S. and Asian credit policy is that U.S. credit policy is oriented more toward equity than toward growth. Different sectors are affected differently by U.S. credit policies. Few empirical studies test how U.S. credit policy affects growth - perhaps partly because of the motives behind those policies. Few enpirical studies even test whether the policies edffectively increase credit to the target group. Schwarz outlines a method for testing the effectiveness of credit policy, then examinesexisting empirical work to see how it fits that methodology. The first common empirical technique examines credit allocation in the economy. Schwarz finds that for the largest program, housing credit, the effect of credit program on credit allocation is very small and may be negative when cross-program effects are considered. The second common empirical technique examines individual sectors. Results here are mixed. In agriculture, much of the credit raises the demand for land, providing a gain for landowners rather than increasing production. In education, less than a third of the students who got government credit would not have gone to college without it. So in both cases, the credit has a positive impact but at a sizable cost. Schwarz concludes that despite its huge volume, directed credit in the United States has a limited impact in growth. The credit programs have generally succeeded in increasing credit to the targeted group, but not necessarily in increasing investment by that group.Banks&Banking Reform,Environmental Economics&Policies,Housing Finance,Financial Intermediation,Economic Theory&Research
Tariff andtax reform : do World Bank recommendations integrate revenue and protection objectives?
No full textTariff reform aimed at reducing domestic protection and the bias against exports holds the threat of widening the fiscal deficit by causing tariff revenue to decline. Because the success of an adjustment program depends critically on the correction of fiscal imbalances to achieve stabilization, tariff reforms must be coordinated with tax policy recommendations to develop alternative revenue sources. Conversely, the tariff reforms must eliminate the protective elements of domestic tax structures if they are to truly achieve their protection objectives. Rajaram reviews the extent to which the Bank's analysis and tariff recommendations in twelve countries (Bangladesh, Ghana, Indonesia, Jamaica, Malawi, Morocco, Pakistan, the Philippines, Thailand, Turkey, Zaire, and Zambia) reflected such an integrated framework. He focuses on (1) the revenue impact of tariff reform, (2) the effect of domestic indirect taxes on protection, and (3) the structure of protection. The review is admittedly selective and the attempt is to capture the reasoning behind"typical"Bank recommendations. Rajaram finds that the quality of analysis underlying Bank recommendations in this regard is highly uneven. The following broad conclusions are indicated: (1) revenue concerns are often not adequately addressed in the design of tariff proposals, (2) the protective effect of domestic indirect taxes is often not recognized and thus not incorporated into the reform of the structure of protection, and (3) although there is little consensus on a desirable tariff structure, in a few cases the Bank has recommended a uniform nominal tariff. This could be seen as the logical culmination of attempts to narrow the range of tariffs.Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Public Sector Economics&Finance,Economic Theory&Research,Export Competitiveness
Financial liberation and adjustment in Chile and New Zealand
No full textThe authors analyze macrodynamic adjustment during financial liberalization in Chile and New Zealand. During the adjustment to more open capital accounts in the late 1970s or mid-1980s, both countries experienced appreciation of the real exchange rate and a collapse of net exports, while domestic interest rates slowly converged to international levels. The authors develop and estimate a two-sector dynamic model using both current and time-varying parameters. They find the domestic interest rate to be more responsive to shocks under imperfect capital mobility, the real exchange rate more responsive under perfect capital mobility. In short, liberalization of the capital account does not eliminate volatility but rather shifts it from the domestic interest rate to the real exchange rate.Economic Theory&Research,Macroeconomic Management,Economic Stabilization,Environmental Economics&Policies,Banks&Banking Reform
An exact approach for evaluating the benefits from technological change
No full textIt is commonly believed that taxing agricultural commodities in developing countries, and subsidizing agricultural commodities in industrial countries, reduces incentives in the developing countries for both current production and longer-term investments in capital, knowledge, technology, and infrastructure. It is argued that distortions in agricultural markets have kept investments in research and development, and productivity rates low in agriculture in developing countries. Martin and Alston lay the theoretical foundation for empirical studies of how such distortions affect returns to agricultural research and development in developing countries. Earlier studies of the benefits from technological change have typically used partial equilibrium models with Marshallian welfare measures. Such models have not allowed for a general set of market distortions and market interactions. Techniques recently developed for evaluating welfare in the context of general equilibrium models better measure the implications of trade distorting policies. Martin and Alston describe how to harness these approaches to evaluate the benefits and costs of technological changes. They show that a modified trade expenditure function can be used to measure welfare changes exactly, with a model consistent with the optimizing behavior of both producers and consumers. They do so in a general setting that allows for multiple market distortions and multiple paths of general equilibrium feedback. They illustrate this approach using a quadratic form for a profit function that is a component of the trade expenditure function. They spell out, in principle, how to apply this approach with minimal requirements for additional information, using the results from a computable general equilibrium model. They provide a diagram to illustrate the application of the technique.Environmental Economics&Policies,Economic Theory&Research,Access to Markets,Markets and Market Access,Consumption
