150 research outputs found
Performance improvements for unplanned high density wireless LANs
No full textChaotic unplanned IEEE 802.11 WLAN deployments are becoming the norm and such residential deployments have many nearby access points (APs) and stations on the same channel, either due to lack of coordination or insufficient available channels. Thus, inter-cell interference in these high-density settings is common but not well-understood. Our evaluations for such interfering deployments reveal that up-to two-thirds of the WLAN system capacity may be lost in a typical large-apartment building with 50 interfering WLANs In this thesis, we first report on our analysis of high-density unplanned WLANs' performance under realistic scenarios. We find that with a typical TCP-dominant workload, cumulative system throughput is characterized by the number of actively interfering APs rather than the number of clients. We verify that due to TCP flow control, the number of backlogged stations in such a network equals twice the number of active APs. Thus, a single AP network proves very robust even with over one hundred clients, while multiple interfering APs lead to a significant increase in collisions that reduces throughput and affects multimedia traffic. Based on our analysis, we suggest a practical contention window adaptation technique, WiPhi, using information on the number of nearby APs rather than clients. We also point out the need for collision-resilient rate adaptation in such a setting. Together these techniques can largely recover the loss in cumulative throughput in a setting with strongly interfering APs. We then propose an alternative ISP-level solution, HeedNet, recovering lost performance by scheduling the IP packets of the bulk traffic at the ISP edge-router towards interfering APs. It requires no changes to the MAC protocol and the APs of the network, making it a viable solution for ISPs. We evaluate HeedNet via simulations and an actual deployment to show that a significant portion of the lost system capacity can be regained (more than 2.2X improvement compared to legacy). HeedNet also increases the fairness, reducing starvation among WLANs. Additionally, we show that HeedNet improves the performance of the non-scheduled (i.e., non-bulk) traffic considerably, such as VoIP, due to the reduced-collision rate environment it creates.Ph.D.Includes bibliographical referencesIncludes vitaby Mesut Ali Ergi
Measuring the service quality of student affairs at higher education and an examplary application of it
Get PDFKumru, Mesut (Dogus Author) -- Yıldız Kumru, Pınar (Dogus Author)Due to its main characteristics of intangibility, inseparability, heterogeneity andperishability, it is quite difficult to describe and measure the service quality in general. A number of methods have been developed to measure service quality in the application areas. As one of these methods, SERVQUAL is to be used in this study to measure the service quality of student affairs at higher education and the gaps between expected service and perceived performance for the service beneficiaries are derived.Hacettepe Üniversitesi, Valör Kongre Organizasyonlar
Kurumsal performans değerlendirmenin önemi, gelişimi ve uygulama örnekleri
Get PDFKumru, Mesut (Dogus Author) -- Conference full title: Yöneylem Araştırması ve Endüstri Mühendisliği 32. Ulusal Kongresi - YAEM 2012, 20-22 Haziran, İstanbul: Doğuş Üniversitesi.Kurumsal performans yönetimi, firmaların daha başarılı ve rakiplerinin önünde olabilmek için uyguladıkları bir yönetim şeklidir. Bu yönetim şekli, stratejilerin tanımlanarak uygulanmasına ve sürekli performans iyileştirmeleri ve rekabet avantajı elde edilmesine yardımcı bütünleşik bir yaklaşımdır. Kurumsal performans yönetim sisteminin en önemli ayağı kurumsal planlama, kontrol ve değerlendirme alt sistemidir. Bu alt sistemin ana bileşeni kurumsal performans değerlendirme modeli olup, bu modelin yapısı planlama sisteminin veri tabanına dayandırılmakta; simülasyon modelleri, bütçeleme araçları ve ürün bilgi sistemleriyle uyumlu olmaktadır. Kurumsal performans değerlendirme modelleri firmaların özelliklerine göre farklılıklar göstermektedir. Bu modeller günümüze kadar çok değişik şekillerde tasarlanmış ve uygulanmıştır. Bu çalışmada, kurumsal performans yönetimi, kurumsal performans değerlendirme, kurumsal performans değerlendirmenin gelişimi, modeller (finansal bazlı modeller, dengeli modeller, mükemmeliyet modelleri, vb.), yurt içi ve yurt dışından kurumsal performans değerlendirme uygulama örnekleri yer almaktadır.Arçelik, Bosch, Pegasus, LG, Ekol, Borçelik, Ford Otosan, Casino Uzman
Research on A1 irregularity status in different spectral acceleration coefficients on reinforced concrete structures
Get PDFMurat YakarMost of the building damages in our country are caused by earthquakes. As known, the properties of the building are determinant in the magnitude of the earthquake forces that cause these damages. Thus, selection of the structural system is crucial in the design process. In case of any irregularity in the building, load transfer will not be provided safely. In the Turkish Earthquake Code, related irregularities are analysed under two groups. Group A indicates the irregularities in the plan, and Group B represents vertical irregularities. Irregularities in the plan include A1 Torsional Irregularities; A2 Floor Discontinuities; and A3 Bulges in the Plan. In this study, A1 irregularity status in the reinforced concrete structure was analysed for different spectral acceleration coefficients. The purpose of the study is to understand the change of torsional irregularity coefficient in different spectral acceleration coefficients. As a result, in a typical building with the same geometric and stiffness properties, the torsional irregularity coefficient is not changed for different earthquake zones. Also, the importance of the location of the shear wall elements in the plan was once again emphasized. © Author(s) 2021
Neural networks and search for minimum defectiveness in molding operation in ceramic industry
No full textKumru, Mesut (Dogus Author) -- Conference full title: 2011 International Symposium on Innovations in Intelligent Systems and Applications (INISTA 2011) Istanbul, Turkey, 15 - 18 June 2011This study is to be conducted in a ceramics production plant where the highest product defectiveness occurs in the molding shop of the plant. There are a number of factors that affect the amount of product defectiveness. The purpose is to search for a set of factor treatment conditions which provide the minimum defectiveness performance in the shop. Artificial Neural Network (ANN) method was used to realize the purpose. Based on the statistical analysis, the ANN approach is found to be reliable in predicting the amount of defectiveness that depends on various factors.TUBITAK, IEEE
Analysis of employee satisfaction in an automotive spare parts manufacturing company
Get PDFKumru, Mesut (Dogus Author) -- Conference full title: 37. Yöneylem araştırması ve Endüstri Mühendisliği Ulusal Kongresi; Yıldız Teknik Üniversitesi, İstanbul, 5-7 Temmuz 2017Otomotiv yan sanayiinin lider firmalarından birisinde çalışan memnuniyeti incelenmiştir. Bu maksatla bir anket düzenlenmiş, bu anketle çalışanların işyerindeki fiziksel çalışma ortamından, yaptıkları işlerden, iş arkadaşlarından, çalıştıkları şirketten, amirlerinden, genel şirket yönetimi ve eğitim programlarından memnun olup olmadıkları konusunda bilgi edinilmeye çalışılmıştır. Sözü edilen organizasyonel faktörlere ilaveten kişisel faktörler olarak yaş, cinsiyet, hizmet süresi, statü ve eğitim durumu incelenmiştir. Söz konusu değişkenlerin çalışan memnuniyeti düzeyine etkileri araştırılmıştır. Çalışanların sözü edilen faktörlerden memnuniyet düzeyleri ile demografik özelliklerinin ilişkisi parametrik olmayan ki-kare testiyle incelenmiştir. Bu çerçevede oluşturulan dokuz hipotez test edilmiştir. Ayrıca, yapılan iş ve çalışılan şirketle ilgili bazı hususlar yedi ana faktörle ilişkilendirilmeye çalışılmış, örnek regresyon bağıntıları ortaya konulmuştur
Multi-Stream Word-Based Compression Algorithm for Compressed Text Search
No full textOzturk, Emir (Trakya author)
Mesut, Altan (Trakya author)In this article, we present a novel word-based lossless compression algorithm for text files using a semi-static model. We named this method the Multi-stream word-based compression algorithm (MWCA)' because it stores the compressed forms of the words in three individual streams depending on their frequencies in the text and stores two dictionaries and a bit vector as side information. In our experiments, MWCA produces a compression ratio of 3.23 bpc on average and 2.88 bpc for files greater than 50 MB; if a variable length encoder such as Huffman coding is used after MWCA, the given ratios are reduced to 2.65 and 2.44 bpc, respectively. MWCA supports exact word matching without decompression, and its multi-stream approach reduces the search time with respect to single-stream algorithms. Additionally, the MWCA multi-stream structure supplies the reduction in network load by requesting only the necessary streams from the database. With the advantage of its fast compressed search feature and multi-stream structure, we believe that MWCA is a good solution, especially for storing and searching big text data
Frontier analysis in measuring the efficiency of mass media companies
No full textKumru, Mesut (Dogus Author) -- Conference full title: Joint International Symposium on "The Social Impacts of Developments in Information, Manufacturing and Service Systems" 44th International Conference on Computers and Industrial Engineering, CIE 2014 and 9th International Symposium on Intelligent Manufacturing and Service Systems, IMSS 2014; Adile Sultan PalaceIstanbul; Turkey; 14 October 2014 through 16 October 2014This paper employs frontier analysis to measure the efficiency of written and visual media companies in Turkey. Three leading print media companies and nine TV companies are evaluated. Personnel costs, total assets and total equities of the companies are selected as input factors while total value added, total sales, and net profits are preferred as the output factors. Data is gathered from open sources and covers the period of 2007 - 2013. Three-year moving average approach is applied to the data to get more smooth values and a five-year average. Banxia Frontier Analyst software with mixed approach is used in evaluations. The average efficiency rates are found to be 98.4 % for print media companies (national newspapers and magazines), and 93.2 % for visual media companies (national broadcasting TVs). The overall average is about 94.5 %. Multivariate regression is also applied to the data in order to establish a basis for more effective utilization of the technical efficiency of the method. Furthermore, sensitivity analysis is carried out to better understand the relationships between input and output variables in the model. The paper is unique and brings contributions to the literature
Clustering of hotel customers by K-means
No full textKumru, Mesut (Dogus Author) -- Conference full title: Joint International Symposium on "The Social Impacts of Developments in Information, Manufacturing and Service Systems" 44th International Conference on Computers and Industrial Engineering, CIE 2014 and 9th International Symposium on Intelligent Manufacturing and Service Systems, IMSS 2014; Adile Sultan Palace Istanbul; Turkey; 14 October 2014 through 16 October 2014In this study, hotel customers are clustered by using k-means partitioning technique. Eight attributes are used in clustering the customers which are gender, age, frequency of stay, length of stay, total expenditure, number of companions, season, and location / addres. Data collected for randomly selected 100 customers of a 5-star hotel in Antalya region are used in the analysis. Everett's approach is preferred in determining the preliminary number of clusters. Clustering operation is terminated with respect to the minimization of total mean squared error. A simple special software program is developed to carry out the analysis. Fuzzy k-means and expectation maximization methodologies are also used in the study in compariosn with the k-means algorithm. Cluster validation is achieved through the Dunn and Davies-Bouldin Indices. Further, the results are verified according to a target value calculated by using the given indices. Operation stages in the software developed and the graphical presentations of the data are also supplied in the paper. The research as a whole bears the distinction of being the first in the literature
Iron deficiency and heart failure
No full textHeart failure (HF) is a common and with poor prognosis disease that impairs quality of life. There are many causes of symptomatic worsening, but lately particular attention has been paid to iron deficiency and anemia as a cause. The reduced iron content in the body has turned to be a new important target for treatment in patients with HF. The aim of this study is to search for the prevalence of iron deficit in patients with HF hospitalized for exacerbation of existing or newly developed symptoms, and to establish its relationship with important prognostic parameters of patients. Patients and Methods: 209 consecutive patients with different etiology of HF were examined and hospitalized at the Cardiology Clinic of the University Hospital "St. Marina", Varna, at an average age of 68,89±12,06 (30-94 years), 58% of them male. Basic demographic variables, creatinine and eGFR were investigated, as well as an echocardiographic study, and a 6-minute walking test was performed. Iron deficit (ID) is formulated at ferritin values <100 µg/l, or if values are 100-300µg/l, then transferrin saturation should be <20%. An alternative method for determining ID was also used, correlating the two methods. Statistical methods include descriptive methods and Cohen's method of calculating the coefficient κ (Kappa) for determining agreement between two diagnostic methods. Results: There were 146 (70%) patients presenting with ID, with isolated deficiency without anemia occurring in 38% of patients. Anaemic syndrome is found in 87 (41.6%) of all patients, with 76% of anemia cases being iron deficient. Isolated ID is more common in women - 42 (48%) than in men - 38 (31%), p=0.014. There is no significant difference in age, EF, physical capacity, and glomerular filtration rate between patients with and without ID. The incidence of ID is similar in patients with different types of HF - with preserved, mid-range, or decreased EF. There is not a very good agreement between the different methods of determining ID, with coefficient κ=0.31. Conclusions: Iron deficit is common in patients with HF of various etiology and different forms, regardless of the presence of anemia. Females are more vulnerable to this disorder. Its significant presence and role in the prognosis and symptomatology of the patients require that patients be screened for ID and corrected consequently after its detection
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