Integrating analytical aeroelastic instability analysis into design optimization of aircraft wing structures

Two analytical flutter solution approaches have been developed to optimize two and three dimensional aircraft wing structures with design criteria based on aeroelastic instabilities. The first approach uses open loop structural dynamics and stability analysis for a two dimensional wing model in order to obtain the critical speeds of flutter, divergence and control reversal for optimization process. The second approach involves a flutter solution for three dimensional wing structures by using assumed mode technique and is applied to aeroelastic optimization based on flutter criterion efficiently. This flutter solution employs energy equations and Theodorsen function for aerodynamic load calculation and is fully-parametric in terms of design variables which are taper ratio, sweep angle, elasticity and shear modulus. Since bending and torsional natural frequencies are required for flutter solution, a free vibration analysis of aircraft wing is developed analytically as well. The analytical results obtained for flutter solution of AGARD 445.6 wing model for Mach number of 0.9011 are found to be compliant with the experimental results from literature. Next, the three dimensional flutter code is coupled with optimization framework to perform flutter based optimization of AGARD 445.6 to maximize the flutter speed.Publisher's Versio

An Application of Anomie and Strain Theories to Terrorism: Suicide Attacks in Turkey

A suicide attack is an extreme modus operandi of terrorism. This research examines the application of two similar sociological theories to terrorism and specifically, to suicide terrorism. Three models are built to test if Merton‘s strain theory can explain the propensities of provinces to produce terrorists and suicide bombers in the first phase. Next, in Phase 2 one model is built on a combination of altruistic and fatalistic type variables to test if Durkheim‘s anomie theory can explain the probability of a terrorist to become suicide bomber or not. The analyses of models 1, 2, and 3 are performed in Phase 1 using aggregate secondary data and the analysis of model 4 is performed in Phase 2 using individual level secondary data. While models 1 and 2 are employing multiple regression, models 3 and 4 use logistic regression analyses. Model 1 tests the propensity of a province to produce terrorists relative to six strain variables, while model 2 develops an optimum model, testing the same associations by using only three significant independent variables. Model 3 tests the probability of a province to produce a suicide bomber(s) using the same six indicators. Model 4 tests the probability of a terrorist to become a suicide bomber relative to anomie theory driven by seven indicators. The results reflect support for the overall model 1, while only the indicators of unemployment rate and political representation in the legislative assembly significantly contribute in explaining the propensity score of a province to produce a terrorist. However, the optimum model (2) includes three statistically significant indicators of unemployment rate, political representation in the legislative assembly, and quality of life. Although model 3 also emerged significant in its overall effect, only educational opportunity significantly contributes to explaining the probability of a province to produce a suicide bomber. Model 4 is also supported. The individual effects reveal that the indicators of age group, income level, and hierarchical position in the organization statistically contribute to explaining the probability of a terrorist to become a suicide bomber. In general, the research provides partial support for the application of strain and anomie theories to terrorism and suicide attacks

Low observable uncrewed aerial vehicle wind tunnel model design, manufacturing, and aerodynamic characterization

Developing wind tunnel models is time consuming, labor intensive, and expensive. Rapid prototyping for wind tunnel tests is an effective, faster, and cheaper method to obtain aerodynamic performance results while considerably reducing acquisition time and cost for the models. Generally, the rapid prototyping models suffer from insufficient stiffness or strength to withstand the loads generated during a wind tunnel test. In the present study, a rapid prototype model reinforced with metallic inserts was produced to experimentally investigate the aerodynamic characteristics of an uncrewed aerial vehicle with various wingtip deflections. The fused deposition modeling process was used to make the outer mold, whereas the metallic parts were produced using laser cutting and the computer numerical control machining process. Then, the model was evaluated both experimentally and numerically. The test campaign presented in this work was conducted in the de Havilland low-speed wind tunnel facility at the University of Glasgow. For better characterization of flow patterns dominated by leading edge vortices, numerical simulations were run using OpenFOAM 8.0 and validated with experimental data. The experimental data obtained from the hybrid rapid-prototyped model agreed well with the numerical results. This demonstrates the efficacy of hybrid rapid-prototyped models in providing reliable results for initial baseline aerodynamic database development within a short period and at a reduced cost for wind tunnel tests

Advanced Experiments on Gaussian Process-based Multi-fidelity Methods over Diverse Mathematical Characteristics

Advanced applications of multi-fidelity surrogate modelling techniques provide significant improvements in optimization and uncertainty quantification studies in many engineering fields. Multi-fidelity surrogate modelling can efficiently save the design process from the computational time burden caused by the need for numerous computationally expensive simulations. However, no consensus exists about which multi-fidelity surrogate modelling technique usually exhibits superiority over the other methods given for certain conditions. Therefore, the present paper focuses on assessing the performances of the Gaussian Process-based multi-fidelity methods across selected benchmark problems, especially chosen to capture diverse mathematical characteristics, by experimenting with their learning processes concerning different performance criteria. In this study, a comparison of Linear-Autoregressive Gaussian Process and NonlinearAutoregressive Gaussian Process methods is presented by using benchmark problems that mimic the behaviour of real engineering problems such as localized behaviours, multi-modality, noise, discontinuous response, and different discrepancy types. Our results indicate that the considered methodologies were able to capture the behaviour of the actual function sufficiently within the limited amount of budget for 1-D cases. As the problem dimension increases, the required number of training data increases exponentially to construct an acceptable surrogate model. Especially in higher dimensions, i.e. more than 5-D, local error metrics reveal that more training data is needed to attain an efficient surrogate for Gaussian Process based strategies

Analytical Benchmark Problems for Multifidelity Optimization Methods

The paper presents a collection of analytical benchmark problems specifically selected to provide a set of stress tests for the assessment of multifidelity optimization methods. In addition, the paper discusses a comprehensive ensemble of metrics and criteria recommended for the rigorous and meaningful assessment of the performance of multifidelity strategies and algorithms

Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

A summary is provided for the Second AIAA Sonic Boom Workshop held 8-9 January 2017 in conjunction with AIAA SciTech 2017. The workshop used three required models of increasing complexity: an axisymmetric body, a wing body, and a complete configuration with flow-through nacelle. An optional complete configuration with propulsion boundary conditions is also provided. These models are designed with similar nearfield signatures to isolate geometry and shock/expansion interaction effects. Eleven international participant groups submitted nearfield signatures with forces, pitching moment, and iterative convergence norms. Statistics and grid convergence of these nearfield signatures are presented. These submissions are propagated to the ground, and noise levels are computed. This allows the grid convergence and the statistical distribution of a noise level to be computed. While progress is documented since the first workshop, improvement to the analysis methods for a possible subsequent workshop are provided. The complete configuration with flow-through nacelle showed the most dramatic improvement between the two workshops. The current workshop cases are more relevant to vehicles with lower loudness and have the potential for lower annoyance than the first workshop cases. The models for this workshop with quieter ground noise levels than the first workshop exposed weaknesses in analysis, particularly in convective discretization

AFİŞ TASARIMINDA HEDEF KİTLENİN ALGILAMA DURUMLARINA İLİŞKİN GÖRÜŞLERİN DEĞERLENDİRİLMESİ

Afiş Tasarımında Hedef Kitlenin Algılama Durumlarına İlişkin Görüşlerin Değerlendirilmesi adlı bu çalışmanın amacı, afiş tasarımının hedef kitle üzerinde bıraktığı seçici algılama durumunu ortaya koymak ve bu doğrultuda afişte bulunması gereken renk, yazı ve imge özellikleri ile hedef kitlenin yaşantısının afiş tasarımındaki yeri ve önemini, Görsel İletişim Tasarımı Bölümü ve Grafik Bölümü öğrencilerinin görüşleriyle bulgulamaktır. Araştırmada tarama modeli kullanılmıştır. Araştırmanın çalışma grubunu, Gazi Üniversitesi, Güzel Sanatlar Fakültesi, Görsel İletişim Tasarımı Bölümü 1. ve 2. sınıf öğrencileri ile Hacettepe Üniversitesi, Güzel Sanatlar Fakültesi, Grafik Bölümü 1. ve 2. sınıf öğrencileri oluşturmuştur. Bu grup 70 kişidir. Verilerin toplanması için Likert Tutum Ölçeği oluşturulmuştur. Anketin geliştirilmesi için ilgili kaynaklar taranmıştır. Konunun uzmanlarının görüşleri sonucunda hazırlanan 20 maddelik anket, çalışma grubuna yüz yüze görüşülerek uygulanmıştır. Verilerin analizinde SPSS 16.0 paket programı kullanılmıştır. Araştırmanın alt amaçlarına en uygun olan betimsel istatistik yöntemlerinden ve frekans (f) dağılımlarına göre %'si hesaplanmış, aritmetik ortalamaları alınarak tablolaştırılmıştır. Bu araştırma sonucunda; 1. Afişin hedef kitleye ulaşabilmesi için, rengin anlamsal olarak iletilmek istenen mesajı güçlendirdiği, kontrast (zıt) renk kullanımının algılamayı arttırdığı görülmektedir. 2. Tasarımda metinin, sade, süsten arındırılmış, okunaklı olmasının, sloganın uzun ve açıklayıcı cümleler yerine daha az ve birkaç kelimeyi geçmeyecek şekilde kullanılmasının algılamayı arttırdığı görülmektedir. 3. Tasarımda, imgenin, vurgulanmak istenen mesaja göre seçilmesinin, afişin algılanması açısından önemli olduğu, afişin kısa sürede algılanmasının, akılda kalıcılığı arttırması bakımından önemli olduğu görülmektedir. 4. Hedef kitlenin algılama durumu ve tasarımda iletilmek istenen mesaj arasında bağlantı kurulacak olursa, hedef kitlenin kişisel özelliklerinin, alışkanlıklarının, yaşam standartlarının tasarımcıyı yönlendirdiği ve tanıtılan ürün ya da hizmetin, hedef kitleyi harekete geçirici nitelikte olması gerektiği görülmektedir.The purpose of this study, namely Assesing The Target Audience's Views Related To The Perception Positions In The Poster Design is to put forward the selective perception position left on the target audience by the poster design and through this way to find out the color, writing and image qualifications and the position of the target audience's life in the poster design with the point of views of the students from Department of Visual Communication and Graphic. The scanning model has been used in this study. The study group of this study consists of first and second grade students from Gazi University, Faculty of Fine Arts, Department of Visual Communication and also Hacettepe University, Faculty of Fine Arts, Graphic Department. This group is totally 70 people. In order to collect data, Likert Attitude Scale has been composed. To develop the questionnaire, related recources have been scanned. The 20-questionedquestionnaire, which has been created with the help of the views of the subject experts, has been implemented to the study group face to face. The pocket program SPSS 16.0 has been used for analysing the data. The most appropriate descriptive statistical method to the sub-goals of the study and % according to the frequency (f) dispersal have been calculated, arithmetical average has been calculated to be a table. As a result of this study; 1. It has been pointed out that fort he poster to reach the target audience, the color enforces the mesagge that wants to be conveyed. 2. It has been seen that the simple and readable text in the design and the usage of the motto in a few words rather than using long and explanatory sentences promote the perception. 3. It has been indicated that selecting the image for the message to be emphasized is important for poster perception and also important for the design to be perceived immediately. 4. If a relation between the perception position of the target audience and the mesagge that is wanted to be conveyed in the design is formed, it could be seen that the personal specialities, habits and life styles of the target audience manipulate the designer and it is needed to have the product or service to be exhibited, to remove the target audience

Tedarikçi değerlendirme sistemleri ve ISO 9001:2000 belgeli aydınlatma malzemeleri imalatçılarında bir uygulama

ÖZET Türkiye’de satın alma ve ilgili konuları üzerine mevcut çalışmalar sınırlı sayıdadır. Bu çalışma, tedarikçi performansını yönetmek için etkili bir araç olan tedarikçi değerlendirme sistemlerine odaklanmaktadır. Artan pazar rekabeti ve gelişen müşteri bilinci firmaları daha hızlı ve daha iyi ürün ve hizmetler sunmaya zorlamaktadır. Bu yüzden, şirketler tedarikçilerinin işbirliğine her zamankinden daha fazla ihtiyaç duymaktadır. Kalite yönetim sistemleri alanındaki gelişmeler, tedarikçi performansına olan ilgiyi artırmıştır. Tezin uygulama bölümünde, ISO 9001:2000 belgeli aydınlatma malzemeleri imalatçılarında tedarikçi değerlendirme sistemleri araştırılmıştır. Araştırmanın sonuçlarına göre sektördeki mevcut durum, tedarikçilerden beklentilere ulaşmak için yetersizdir. ABSTRACT Existing studies on purchasing and related subjects in Turkey are limited. This study focuses on supplier evaluation sytems which is an effective tool to manage the supplier performance. The increasing market competition and the developing consumer consciousness have pushed the firms to present faster and better goods and services to their customers. Thus, companies need the collaboration of their suppliers more than ever. The improvements in the field of quality management sytems have increased the interest in supplier performance. In the application part of the thesis, supplier evaluation systems are investigated in the ISO 9001:2000 certified manufacturers of illumination materials. According to results of the research, the existing situation in the sector is insufficient to achieve the expactations from the suppliers