Interactive optimization of mechanical systems with multiple performance requirements

In the design of mechanical systems, the designer is often faced with the problem of satisfying a number of competing requirements, including light weight and limits on displacements, stresses, and natural frequencies. This usually leads to an optimization problem with weight as the objective and the performance requirements as constraints. It may be desirable, in addition to minimizing weight, to minimize or maximize other performance measures rather than enforcing performance limits;This thesis recast the optimization problem as the minimization of multiple objectives, including performance indices and weight, subject to restrictions placed on the size of the design variables. The thesis also developed an interactive optimization procedure to enable design engineers to bring their skill into play during the optimization process;The procedure transforms the multi-objective problem into a single objective problem by taking the weighted sum of the performance indices and the structure\u27s weight. The weighting factors reflect the relative importance to the designer of the various conflicting objectives. The choice of the weighting factors best suited for the problem is not generally obvious and may require several adjustments before leading to an acceptable design. Thus the procedure is set up so that the designer can choose the weighting factors interactively;Optimization software was developed to provide designers with a decision making tool which is easy to use and provides useful information from which designer can confidently proceed. Since the method uses the NASTRAN for the response and sensitivity calculations, it is applicable to almost any structure which can be modelled using finite elements;Two examples illustrate the power of the technique. The first considers the redesign of an automotive engine block where the challenge was to find a low-weight design which has no natural frequencies in undesirable frequency bands. This problem illustrated the trade-offs between the weight and the natural frequencies, and it demonstrated the interactive process wherein the designer found a combination of the twelve design variables that met performance requirements with a very low weight structure. The second example concerned the redesign of the mounting structure of a heavy-duty truck\u27s exhaust pipe. The structural optimization was stated as finding a low weight structure which satisfied limits on maximum displacements and stresses, and shifted the natural frequencies out of an undesirable band. Again, the design engineer interactively found a very nice solution

Application of state-of-the-art FEM techniques to magnetostatic NDE

A typical example of the complexities involved in the numerical modeling of electromagnetic phenomena is that of modeling the magnetic flux leakage inspection of gas transmission pipelines. The problem calls for three-dimensional modeling of motionally induced currents (using transient analysis), modeling nonlinearity of the ferromagnetic parts, and accurate modeling of the permanent magnet used in the magnetizer. Researchers, have thus far simplified the problem using several assumptions, including that of axisymmetry, and modeling velocity effects using steady-state analysis. However, there has been no attempt to quantify the errors introduced by these assumptions. Also, due to the unavailability of commercial codes to solve three-dimensional motion-related problems using transient analysis, a detailed study of the true nature of velocity effects has not been possible;This dissertation implements and evaluates state-of-the-art finite element modeling techniques applied to the specific problem of modeling magnetic flux leakage inspection of gas pipelines. This provides the basis from which conclusions can be drawn on the general problem of modeling magnetostatic phenomena. Axisymmetric and three-dimensional models are developed capable of modeling velocity effects. A detailed analysis of the differences between axisymmetric and three-dimensional geometries, based on a study of permeability variations in the vicinity of defects is presented. Also, the need for transient analysis is argued based on results generated. As part of this study, serious problems (including spurious solutions and corner singularities) associated with the traditional node-based finite-element techniques, when applied to the three-dimensional modeling, are discussed. In this work, new and efficient numerical modeling concepts, using the edge-based finite-element technique are employed to overcome these problems;This study demonstrates the need for accurate modeling of the full three-dimensional geometry, incorporating velocity effects and nonlinear permeability, for realistic predictions of flux leakage inspection tools. Major contributions of this work include: (1) detailed analysis of the physical processes associated with the magnetic flux leakage tool, (2) design ideas to improve the performance of the tool, and (3) development of an edge-based finite element code for modeling magnetostatic nondestructive testing applications in three-dimensions incorporating velocity effects. This is the first study of this nature, applied to pipeline inspection, and, many of the conclusions presented can be applied to nondestructive testing techniques in general

An Approach to Select Cluster Head in Wireless Sensor Networks

Recent advancement in mobile network and wireless technologies has resulted in improvements in sensor networks. But there are various challenges and security threats that disturb the Wireless communication. This paper proposes a technique called cluster head selection, which is used for selecting the cluster head. The longevity of a network can be enhanced by using a group of mobile sensor network. The role of the head of this group is collecting data and forwarding it. This data is transferred to the head by the other nodes in the group. We are using fuzzy logic scheme for selecting cluster head. AOMDV protocol is used for path identification in sensor network

Providing Query Suggestions and Ranking for User Search History

The investigation analysis explored in this paper concentrates on the blueprint of the record that helps to retrieve information. Customers are undergoing more sophisticated tasks with the help of internet. Such as running plans ,building travel plans or purchase plans. Searchers produce and use exterior reports of actions and consequent outcomes by using copy and paste capabilities, typing notes, and making printouts. The superior helps users within their extended period information quests around the net, web searchers keep tabs on their query and click on looking on-line. Within this paper, the trouble of managing a user�s history inquiries in to groups in a automated and dynamic manner. In the case of different search-engines, it can be identify the query group automatic programs and their components. That is query alterations, result positions, query suggestions and two-way search experimentally analyze the presentation of view their possible, practically joined goals

A Generic Review on Effective Intrusion Detection in Ad hoc Networks

Ad hoc network is specifically designed for the establishment of a network anywhere and anytime, which does not have any fixed infrastructure in order to support the mobility of the users in the network. The network is established without using any access points or base stations for communication implemented in multi hop schemes. Hence we call an Ad hoc network as a collection of nodes which are mobile in nature with a dynamic network infrastructure and forms a temporary network. Because of dynamic topological changes, these networks are vulnerable at the physical link, and they can easily be manipulated. An intruder can easily attack the Ad hoc network by loading the network resources which are available, such as wireless links and energy (battery) levels of other users, and then starts disturbing all the users. This paper provides a comparative survey on the various existing intrusion detection systems for Ad hoc networks based on the various approaches applied in the intrusion detection systems for providing security to the Ad hoc network

Current trends in renal cell carcinoma

Kidney cancer is one of the most lethal urological malignancies and surgery was the only treatment of modality a decade ago. Open radical nephrectomy was the procedure of choice for long time for all malignant masses. The increase use of imaging modalities has led to diagnose small renal masses and most of the tumors are incidentally detected now a day[1]. Depending on tumor size, age and associated co-morbidities, various management options has evolved like AS, minimal invasive ablation, nephron sparing surgery, laparoscopic and robotic nephrectomy, open radical nephrectomy. Role of renal biopsy has become proven in many circumstances. Targeted systemic chemotherapy has shown improved progression free survival in metastatic RCC