Plakların Sayısal Bir Yöntemle Elasto-plastik Dinamik Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Bu çalışmada amaç, dört kenarı ankastre dikdörtgen ince plakların elastik ve elasto-plastik dinamik deplasmanlarının, değişik yükler altında Newmark Doğrusal İvme Metodu ile hesaplamaktır. İlk olarak, dikdörtgen plakların genel hareket denklemi Kirchhoff Plak Teorisi uygulanarak elde edildi ve plakın özdeğerleri ve özvektörleri sonlu farklar metodu kullanılarak hesaplandı. Daha sonra, plakın rijitlik matrisi ve kütle matrisi direkt rijitlik metoduyla oluşturuldu. Sonuçta, plakın rijitlik matrisi, kütle matrisi ve yük vektöründen oluşan sistemin hareket denklemi Newmark doğrusal ivme metodu ile çözüldü.The aim of this study is to examine the elastic and elasto-plastic deflections of rectangular thin plates with clambed supported under various dynamic loads by Newmark’s linear acceleration method. Firstly, the general equation of motion of the rectangular plate has been derived by applying Kirchhoff’s Plate Theory and the eigenvalues and eigenvectors of the plate with clambed supported have been obtained using the finite difference method. Then the stiffness matrix and mass matrix of the plate was constructed by the direct stiffness method. Finally, the equation of motion of the system which consists of the stiffness matrix, the mass matrix, and the load vector has been solved using the Newmark’s linear acceleration method

CHARACTERIZATION OF 6061 T651 ALUMINUM PLATES SUBJECTED TO HIGH-VELOCITY IMPACT LOADS

Ballistic response of single or multi-layered metal armor systems subjected to kinetic energy pro-jectiles was investigated in many experimental, theoretical and numerical studies.In this study, 6061 T651 aluminum plates impacted by 9 mm bullets were investigated. Microstructural investigations have been carried out using optical microscopy. Microhardness values were used to determine the strength behavior of the plates. Influence of the plate thickness and impact velocity on the microstructure has been evaluated. It was concluded from the study that thinner plates are more prone to deformation hardening with high penetration depth values even at low impact velocities while thick plates are more susceptible to thermal softening with less penetration depths. Maximum hardness values were obtained just below the impact zone in both plate thicknesses

Almanya ve Fransa'dan çizgiler 1954-1960

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Details of ssDNA annealing revealed by an HSV-1 ICP8-ssDNA binary complex

Infected cell protein 8 (ICP8) from herpes simplex virus 1 was first identified as a single-strand (ss) DNA-binding protein. It is essential for, and abundant during, viral replication. Studies in vitro have shown that ICP8 stimulates model replication reactions, catalyzes annealing of complementary ssDNAs and, in combination with UL12 exonuclease, will catalyze ssDNA annealing homologous recombination. DNA annealing and strand transfer occurs within large oligomeric filaments of ssDNAbound ICP8. We present the first 3D reconstruction of a novel ICP8-ssDNA complex, which seems to be the basic unit of the DNA annealing machine. The reconstructed volume consists of two nonameric rings containing ssDNA stacked on top of each other, corresponding to a molecular weight of 2.3 MDa. Fitting of the ICP8 crystal structure suggests a mechanism for the annealing reaction catalyzed by ICP8, which is most likely a general mechanism for protein-driven DNA annealing

Details of ssDNA annealing revealed by an HSV-1 ICP8-ssDNA binary complex

Infected cell protein 8 (ICP8) from herpes simplex virus 1 was first identified as a single-strand (ss) DNA-binding protein. It is essential for, and abundant during, viral replication. Studies in vitro have shown that ICP8 stimulates model replication reactions, catalyzes annealing of complementary ssDNAs and, in combination with UL12 exonuclease, will catalyze ssDNA annealing homologous recombination. DNA annealing and strand transfer occurs within large oligomeric filaments of ssDNAbound ICP8. We present the first 3D reconstruction of a novel ICP8-ssDNA complex, which seems to be the basic unit of the DNA annealing machine. The reconstructed volume consists of two nonameric rings containing ssDNA stacked on top of each other, corresponding to a molecular weight of 2.3 MDa. Fitting of the ICP8 crystal structure suggests a mechanism for the annealing reaction catalyzed by ICP8, which is most likely a general mechanism for protein-driven DNA annealing

On wing life optimization of commercial turbofan aircraft engines

Bir havayolu işletmesinde, turbofan uçak motorlarından sorumlu olan mühendisliğin birincil önceliği, motorların teknik olarak uçuşa elverişliliğini sağlayacak şekilde yönetilmesi ve bununla birlikte uçak motorlarının kullanım maliyetinin, güvenilirliğinin, emniyetinin ve operasyonel esneklik açısından motor performanslarının yeterli seviyelerde olmasının temin edilmesidir. Motorların uçak üzerinden sökülmesi ve motora gereken iyileştirme işlemlerinin yapılması gereken optimum bir zaman aralığı olduğu bilinmektedir. Optimum zaman aralığından önce gerçekleştirilen sökümlerde henüz kullanılabilir durumdaki parçaların vaktinden önce tamir edilmesi nedeniyle, kullanılabilecek parça ve motor ömrü ek bir maliyet olarak ortaya çıkacaktır. Optimum zaman aralığından sonra gerçekleştirilen sökümlerde, tamir edilmesi gereken parçaların sayılarının artması, tamirlerin zor ve maliyetli olması ek bir maliyet olarak ortaya çıkmaktadır. Söz konusu optimum uçuş ömrünün belirlenebilmesi amacıyla bir operatörün motorlarına ait veriler hem analitik hem de istatiksel olarak analiz edilmiştir. Gerçek problemin özelliklerini bozmayacak yaklaşımlarla, problem matematiksel olarak modellenmiştir. Bakım maliyeti, performans, güvenilirlik ve emniyet hedefleri bir arada düşünülmesi gerektiğinden, problem çoklu amaç fonksiyonlu bir optimizasyon problemi şeklinde çözülmüştür. Söz konusu çoklu amaç fonksiyonlu problem, bir havayolu mühendisliğinin öncelikleri göz önüne alınarak dayanıklılık fonksiyonu şekline dönüştürülmüş ve optimizasyon genetik algoritma yöntemi kullanılarak gerçekleştirilmiştir. Optimizasyon sonunda elde edilen sonuçlara göre, ele alınan motor tipi için bir optimum uçuş ömrü, bir başka değişle, optimum söküm aralığı bulunmuşur. Anahtar Kelimeler: Uçak motor bakımı, uçuş ömrü, optimizasyon.The primary objective of an airline powerplant engineer responsible from turbofan aircraft engines is to technically manage the engines to be available for revenue flight, while achieving the desired goals of cost of use, reliability and safety, with adequate engine performance level for operational flexibility. For an airline, flight safety is a must. Thus, aviation authorities throughout the world strictly bound the range in which an airline could move to meet the above goals. Since, approximately 40-45% of total aircraft maintenance cost is directly arising from engine maintenance costs, meeting these objectives becomes a very important issue as far as the competitiveness of the airline business is concerned. Under these circumstances, airlines always seek to find and explore methods in order keep the powerplants running with an optimized cost versus on wing life. The engine on wing maintenance concept is known as "on-condition maintenance". In this concept, engines are continuously monitored during their on wing operation in order to prevent failures and to meet goals on reliability and safety. In other words, engines are kept on wing as long as reliability, safety and performance levels are acceptable. All of the above conditions end up with raising the following important question: What is the time on wing of an aircraft engine that will fulfill all of these goals at the required levels This question forms the basis of analyzes performed in this study. It is known that there is an optimum time at which engine should have essential restoration done, in order to meet an optimized cost for removal. In other words, at times prior to the optimum one; the opportunity costs which are arising due to repairing an engine before all its useful life is consumed result in an increase in maintenance cost. At times greater than the optimum; the number of parts which need repair, the difficulty and cost of repair and the number of parts which must be scrapped increase. As a result, the maintenance cost increases. In order to search for this optimum, available data is gathered from one airline and analyzed both analytically and statistically. The problem is mathematically modeled by making assumptions, without effecting the accuracy of the real problem. In order to achieve a better understanding, the objectives (maintenance cost, performance, reliability and safety) are studied as sub problems. The data relating these objectives to the engine on wing time are searched and analyzed. For each of these objectives, mathematical expressions are derived. As far as the integrity of the goals of maintenance cost, performance, reliability and safety is concerned, a multi objective optimization problem is proposed. The model is converted into a fitness function form by an airline engineering perspective and multi objective problem of on wing life optimization is solved by using a Genetic Algorithm based solver. Genetic Algorithm method has been selected as being a robust and reliable technique for multi objective engineering optimization problems. Since performance deterioration characteristics end up with three different types of deterioration curves, three sub problems have been solved. This ensured the diversity in terms of actual engine performance deterioration characteristics, which is a result of operational, configurational and manufacturing diversities encountered in the real operation. Performance related diversity is believed to cover the above mentioned facts of the actual problem and enables a better forecast on the optimum on wing life of commercial turbofan aircraft engines. All the results are gathered considering airline engineering priorities and the optimum on wing life of a CFM56-3C1 engine is calculated. A removal planned within this optimum removal interval will achieve all the priorities in terms of minimum maintenance cost, adequate performance, while not sacrificing from reliability and safety. The result of the optimization is compared with the actual removals and found to be in line with the actual removal time frame. This proves the proficiency of proposed method and the mathematical model. Additionally, the operational factors affecting the aircraft engine on wing life is discussed in order to derive a generalized mathematical model for adaptation to other airline engine fleets and to other engine types. Thus, a generaized model is formulated in order to find the optimum time on wing for any type of commercial turbofan engine operated in any fleet. Keywords: Aircraft engine maintenance, on wing life, optimization

Exploiting the Central Reduction in Lattice-Based Cryptography

This paper presents a novel and efficient way of exploiting side-channel leakage of masked implementations of lattice-based cryptography (LBC). The presented attack specifically targets the central reduction technique, which is widely adapted in efficient implementations of LBC. We show that the central reduction leads to a vulnerability by creating a strong dependency between the power consumption and the sign of sensitive intermediate variables. We exploit this dependency by introducing a novel hypothetical power model, the range power model, which can be employed in higher-order multi-query side-channel analysis attacks. We particularly show that our approach is valid for the prime moduli employed by Kyber and Dilithium, the lattice-based post-quantum algorithms selected by NIST, while it generalizes to other primes used in LBC as well. We practically evaluate our introduced approach by performing second-order non-profiled attacks against a masked implementation of Kyber on an Arm Cortex-M4 micro-processor. In our experiments we revealed the full secret key of the aforementioned implementation with only 2100 electro-magnetic (EM) traces without profiling, achieving a more than 14 times reduction in the number of traces compared to classical attacks