238 research outputs found

    SIMULTANEOUS ROUTING AND LOADING METHOD FOR MILK-RUN USING HYBRID GENETIC SEARCH ALGORITHM

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    Milk-run methodology is proposed to manage the procurement of orders from suppliers. The heuristic solution methods in the literature generally apply stepwise approach to route and load the vehicles. In this study we propose a hybrid genetic local search algorithm which simultaneous solves vehicle routing and order loading problems. This is the main contribution of the study. We consider volume and weight capacities (multi capacitated) of different types of transportation vehicles (heterogeneous fleet). Because of high adaptability and easy utilization, genetic algorithms are the most preferred approach of meta-heuristics. The chromosome structure of the proposed genetic algorithm is constituted by random numbers to eliminate infeasibility. The best chromosome of each generation is improved using local search method during the algorithm runs. We applied the algorithm to a real manufacturing company that produces welding robots and other process automation equipment. The results showed the effectiveness of the algorithm

    Weight Misperception is Prevalent Among Turkish Adults and Associated with Higher Age, Body Mass Index and Lower Education Status

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    Alper Tuna Güven,1 Murat Özdede,2 Burcu Çelik Eroğlu3 1Başkent University Faculty of Medicine, Department of Internal Medicine, Division of General Internal Medicine, Ankara, Turkey; 2Hacettepe University Faculty of Medicine, Department of Internal Medicine, Division of General Internal Medicine, Ankara, Turkey; 3Hacettepe University Faculty of Medicine, Department of Internal Medicine, Ankara, TurkeyCorrespondence: Alper Tuna Güven, Email [email protected]: Weight misperception (WM) is common among adults, and it is associated with adverse health outcomes. Research has shown that various factors are associated with weight misperception. Turkish adult population data for weight misperception and related factors do not exist.Methodology: We conducted a face-to-face cross-sectional descriptive survey in the general internal medicine outpatient clinics of two academic centers. Perception was analyzed both verbally and visually. Misperception was defined for both verbal and visual scales as being thinner than reality misperceptions (TTRM), fatter than reality misperceptions (FTRM), or either of them (ETFTRM). Demographics, anthropometrics, and social determinants of health were analyzed in different misperception groups.Results: 250 patients participated in the study. The median (interquartile range) age was 55 (14), and the BMI was 28.2 (6.9) for females and 26.9 (4.4) for males. 81.2% had ETFTRM, 45.2% had TTRM, and 22.4% had FTRM. Age and BMI were higher in the ETFTRM and TTRM groups, while education level was lower in both. Multivariate logistic regression showed that higher age, higher BMI, and lower education levels were associated with higher TTRM.Discussion: WM is common among the Turkish adult population. Similar to the previous studies, aging, high BMI, and low education levels are associated with weight misperception. However, in contrast to previous studies, gender, marital status, and employment were not associated with weight misperception in our cohort.Keywords: weight perception, body mass index, educational status, obesit

    Calvarial bone defects in ovariectomised rats treated with mesenchymal stem cells and demineralised freeze-dried bone allografts

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    Background: The aim of the study was to investigate the ability of a combination of bone marrow mesenchymal stem cells (BM-MSCs) with and without demineralised freeze-dried bone allografts (DFDBAs) to induce bone regeneration incalvarial defects in ovariectomised rats.Materials and methods: Critical size defects were filled with a combination of DFDBAs and BM-MSCs or BM-MSCs alone. Eight weeks after calvarial surgery, the rats were sacrificed. The samples were analysed histologically and immunohistochemically.Results: No difference was observed in vascularisation between groups C1 (animals with cranial defect only, control group) and O1 (animals with cranial defect only, ovariectomy group). Intramembranous ossification was observed at a limited level in groups C2 (animals with cranial defect with MSCs, control group) and O2 (animals with cranial defect with MSCs, ovariectomy group) compared to C1 and O1. In group C3 (animals with DFDBAs with MSCs, control group), the fibrous structures of the matrix became compact as a result of a bone graft having been placed in the cavity, but in group O3 (animals with DFDBAs with MSCs, ovariectomy group), the fibrous tissue was poorly distributed between the bone grafts for the most parts.Conclusions: We conclude that the insertion of BM-MSCs enhances bone healing; however, the DFDBA/BM-MSC combination has little effect on overcoming impaired bone formation in ovariectomised rats

    Changes in mechanical and morphological properties of AISI 420 stainless steels welded with M42 steel wire Associated with weld cooling medium

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    Bu çalışmada, AISI 420 martenzitik paslanmaz çeliklere TIG kaynak yöntemiyle Argon gazı korumalı ortamda, 75 amper 45cm/dk kaynak ilerleme hızıyla kaynak dikişleri çekilmiştir. Bu amaç için Ø 50mm çapında ve 2, 3.5, 5 ve 6.5 mm kalınlıklarında disk şeklinde parçalar hazırlanmıştır. 50 mm boyunca kaynak dikişi oluşturulan bu parçaların kaynaktan hemen sonra farklı soğutma sıvılarına daldırılarak oda sıcaklığına kadar soğumaları sağlanmıştır. Deney numunelerinin sertlik ölçümü kaynak dikişinden esas metale doğru gerçekleştirilmiştir. Mikroyapı karakteristikleri ise optik mikroskop, taramalı elektron mikroskobu (SEM) vasıtasıyla incelenmiştir. Sonuç olarak, östenitik yapının yüksek soğuma hızından etkilenerek martenzitik yapıya dönüşmesi gerçekleşmiştir. Bu tür paslanmaz çeliklerin kritik soğuma hızının altında soğutulmaması için uygun tedbirlerin alınması gereklidir.In this study, the method AISI 420 TIG welding of martensitic stainless steels in the protected environment of Ar gas and 75 amps and with a weld speed of 45cm/min was carried out. For this purpose, specimens of Ø 50mm diameter and thickness of 2, 3.5, 5 and 6 mm was sliced. Weld bead was formed along the specimen for about 50mm long and following the welding, specimens were immersed into a different cooling fluids to cool to room temperature. Microhardness measurement was carried out mainly from the base metal towards the weld seam. Microstructural characteristics were investigated by optical microscope, scanning electron microscopy (SEM). As a result, the martensitic transformation of the austenitic structure has been influenced by the high cooling rate. This type of stainless steel must not be cooled below a critical cooling rate and it is necessary to take the appropriate measures

    An assessment in terms of mechanization of timber harvesting operations in Artvin forest regional directorate

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    Bu çalışmada Artvin Orman Bölge Müdürlüğü (OBM)’nde gerçekleştirilen odun hammaddesi üretim çalışmaları mekanizasyon açısından değerlendirilmiştir. Bu amaçla 2004-2009 yılları arasında bölge müdürlüğünde odun hammaddesi üretimi, bölge müdürlüğünün sahip olduğu üretim makineleri, odun hammaddesi üretiminde mekanizasyon kullanım oranı ve bölgedeki kış üretimi incelenmiştir. Sonuçta; Artvin OBM, odun hammaddesi üretim çalışmalarında mekanizasyon kullanımı açısından ülkemizin dikkat çeken bölge müdürlüğü olduğu, son 5 yıl dikkate alındığında bölgede üretilen odun hammaddesinin yaklaşık % 30’unun mekanizasyona dayalı yöntemlerle bölmeden çıkarıldığı belirlenmiştir. Yörede odun hammaddesi üretim çalışmalarında kullanılan üretim makinelerinin ekonomik ömürlerini tamamlaması nedeniyle eskiyen hava hatları ve orman traktörleri yeni model hava hattı ve traktörler alınarak yenilenmesi, makinelerin daha etkin ve ekonomik olarak kullanılması açısından gereklidir.In this paper, timber harvesting operations of Artvin Forest Regional Directorate (FRD) have been evaluated in terms of mechanization. For this purpose, timber harvesting at regional directorate, timber harvesting machinery owned by regional directorate, mechanization ratio in harvesting and winter harvesting in the region between 2004 and 2009 have been examined. As a result, it has been found out that Artvin FRD is one of the remarkable regional directorates of our country in terms of mechanization in timber harvesting operations, and that mechanization ratio is almost 30% on logging of wood raw material. As the harvesting machines used during timber harvesting in the area have completed their economic lives, the skylines and forest tractors worn have to replace with new model skylines and tractors, so that machines can be used more effectively and economically

    Sixty Years of Fractal Projections

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    Sixty years ago, John Marstrand published a paper which, among other things, relates the Hausdorff dimension of a plane set to the dimensions of its orthogonal projections onto lines. For many years, the paper attracted very little attention. However, over the past 30 years, Marstrand's projection theorems have become the prototype for many results in fractal geometry with numerous variants and applications and they continue to motivate leading research.Comment: Submitted to proceedings of Fractals and Stochastics

    Pre-operative Arterial Embolization of Symptomatic Giant Hemangioma of the Liver

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    Abstract: The cavernous hemangiomas of the liver are usually small sized and asymptomatic. Most of them are incidentally diagnosed and a very small portion requires therapy. Giant hemangioma can be symptomatic, and this condition is the indication for treatment. The striking complication of surgical treatment of cavernous hemangiomas is intra-operative bleeding. In this case, we aimed to demonstrate that the risk of intraoperative bleeding can be eliminated with the preoperative percutaneous trans-catheter arterial embolization technique

    Key factors impacting performance of a salinity gradient solar pond exposed to Mediterranean climate

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    Solar ponds are low cost pools of brine solutions with integrated storage zones that harvest incident solar energy and store it as thermal energy. The current study examined the performance of a salinity gradient solar pond under the Mediterranean climatic condition for ten consecutive months of operation, from October 8, 2014 to July 31, 2015. The presented results are based on the experimental data of a small-scale circular pond, 61�cm in diameter a height of 55�cm, constructed and operated at Middle East Technical University, Northern Cyprus Campus (METUNCC). The study showed the necessity of regular surface washing and having excess undissolved salt at the lower convective zone (LCZ) to maintain the pond stability. The variations in the temperature of the non-convective (NCZ) and lower convective zones (LCZ) are found to be a function of both ambient temperature and solar irradiation (insolation). The variation of the overall pond's temperature strongly follows the changes in ambient temperature while solar insolation directly affects the increase in temperature gradient by depth. During the period of this study, the pond reached the highest average temperature of 48��C in July 2015 while the average ambient temperature for this month was 30��C. � 2016 Elsevier Lt

    Design mining interacting wind turbines

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    © 2016 by the Massachusetts Institute of Technology. An initial study has recently been presented of surrogate-assisted evolutionary algorithms used to design vertical-axis wind turbines wherein candidate prototypes are evaluated under fan-generated wind conditions after being physically instantiated by a 3D printer. Unlike other approaches, such as computational fluid dynamics simulations, no mathematical formulations were used and no model assumptions weremade. This paper extends that work by exploring alternative surrogate modelling and evolutionary techniques. The accuracy of various modelling algorithms used to estimate the fitness of evaluated individuals from the initial experiments is compared. The effect of temporally windowing surrogate model training samples is explored. A surrogateassisted approach based on an enhanced local search is introduced; and alternative coevolution collaboration schemes are examined
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