Effect of Ti-ion non-stoichiometry on microstructure and microwave dielectric characteristic of Li<Subscript>2</Subscript>ZnTi<Subscript>3</Subscript>O<Subscript>8</Subscript> ceramics

This paper studies the microwave dielectric properties, microstructure, vibration and densification of Li₂ZnTi_3+xO_8+2x (\(- 0.04 \le {\text{x}} \le +0.06\)) ceramics, manufactured via a conventional mixed oxide route. The X-ray diffraction and Raman spectroscopy revealed the unit cell parameter and cation ordering in LZT non-stoichiometry in their vibrational modes. The densification and phase composition were characterized by the EDX and SEM methods. It was found that a slight Ti vacancy can improve the relative density to the maximum value (96.2%). The XRD results showed that the second phase of TiO₂ in the Li₂ZnTi_3.06O_8.12 composition is formed. The sintered samples were detected in the microwave frequency range by using the resonance technique. The \({\text{~}}{\tau _f}\) values of the ceramics within Ti excess adjusted to near zero. The Li₂ZnTi_2.96O_7.92 ceramic showed the best relative density, single phase and best microwave dielectric \({\varepsilon _r}~={\text{ }}25.98\), Q?×?f?=?61,000 GHz, \({\tau _f}={\text{ }} - 17.4{\text{ ppm/}}^\circ {\text{C}}\) sintered at 1100 °C for 4 h.     

An effective hybrid multi-objective genetic algorithm for bi-criteria scheduling on a single batch processing machine with non-identical job sizes

This paper addresses the problem of scheduling jobs with non-identical sizes on a single batch processing machine. A batch processing machine is one which can process multiple jobs simultaneously as a batch as long as the total size of jobs being processed does not exceed the machine capacity. The batch processing time is equal to the longest processing time among all jobs in the batch. For the simultaneous minimization of the bi-criteria of makespan and maximum tardiness, we propose two different multi-objective genetic algorithms based on different representation schemes. While the first algorithm do search via generating sequences of jobs using genetic operators and then batching jobs keeping their order in the sequence, the second algorithm uses the idea of generating batches of jobs directly using genetic operators and ensures feasibility through using heuristic procedures. The type of representation used in the second algorithm allows introducing heuristics with the ability of biasing the search towards each objective and also allows hybridization with a local search heuristic that gives the ability of finding Pareto-optimal or locally efficient Pareto-solutions. Computational results show that the non-dominated solutions obtained by the latter algorithm are very superior in closeness to the true Pareto-optimal solutions and to keep diversity in the obtained Pareto-set, as the problem size increases.     

A Simulated Annealing algorithm for a mixed model assembly U-line balancing type-I problem considering human efficiency and Just-In-Time approach

This research deals with balancing a mixed-model U-line in a Just-In-Time (JIT) production system. The research intends to reduce the number of stations via balancing the workload and maximizing the weighted efficiency, which both are considered as the objectives of this research paper.After balancing the line and determining the number of stations, the labor assignment policy should be set. In this study, it was assumed that there are two types of operators: permanent and temporary. Both types can work in regular and overtime periods. Based on their skill levels, workers are classified into four types. The sign at each work station indicates types of workers allowed to work at that station. An alert system using the hybrid kanban systems was also considered. To solve this problem, a Simulated Annealing algorithm was applied in the following three stages. First, the balancing problem was solved and the number of stations was determined. Second, workers were assigned to the workstations in which they are qualified to work. Following that, an alert system based on the kanban system was designed to balance the work in the process inventory. This was achieved by defining control points based on the processing time and making control decisions to minimize the number of kanban cards. In the proposed SA algorithm, two methods for the temperature cooling schedule were considered and two methods were defined for determining the number of neighborhood search. The initial temperature was considered equal to the cost of the initial solution to reach the convergence situation as soon as possible. Five problems were solved in small size using the GAMS software. The results obtained from the GAMS software were compared with those obtained from the SA algorithm to determine the performance difference. The computational results demonstrated that the SA algorithm is more consistent with the answers obtained. Also seven large scale problems were solved. The results showed that the SA algorithm still have better reliability. To show the efficiency of the proposed SA algorithm, an axel assembly company was studied. To satisfy demands and reduce backlogging, a mixed model assembly line was designed for this case study. The results showed that the mixed model assembly line designed using the SA algorithm had good efficiency.     

A hybrid multi-objective approach based on the genetic algorithm and neural network to design an incremental cellular manufacturing system

One important issue related to the implementation of cellular manufacturing systems (CMSs) is to decide whether to convert an existing job shop into a CMS comprehensively in a single run, or in stages incrementally by forming cells one after the other, taking the advantage of the experiences of implementation. This paper presents a new multi-objective nonlinear programming model in a dynamic environment. Furthermore, a novel hybrid multi-objective approach based on the genetic algorithm and artificial neural network is proposed to solve the presented model. From the computational analyses, the proposed algorithm is found much more efficient than the fast non-dominated sorting genetic algorithm (NSGA-II) in generating Pareto optimal fronts.     

A Management Perspective on Risk of Security Threats to Information Systems

Electronic commerce and the Internet have enabled businesses to reduce costs, attain greater market reach, and develop closer partner and customer relationships. However, using the Internet has led to new risks and concerns. This paper provides a management perspective on the issues confronting CIOs and IT managers: it outlines the current state of the art for security in e-commerce, the important issues confronting managers, security enforcement measure/techniques, and potential threats and attacks. It develops a scheme for probabilistic evaluation of the impact of security threats with some illustrative examples. This methodology may be used to assess the probability of success of attacks on information assets in organizations, and to evaluate the expected damages of these attacks. The paper also outlines some possible remedies, suggested controls and countermeasures. Finally, it proposes the development of cost models which quantify damages of these attacks and the effort of confronting these attacks. The construction of one such cost model for security risk assessment is also outlined. It helps decision makers to select the appropriate choice of countermeasure(s) to minimize damages/losses due to security incidents. Finally, some recommendations for future work are provided to improve the management of security in organizations on the whole.     

Mathematical modeling of onset of convection in a porous layer with viscosity variation

IntroduthenIn a novel EOR (Enhanced Oil Recovery) method,diffusion-convechon may be employed as a drive toforce heavy, viscous oil to move. A ~ of gas isexpanded beneath oil, and gas is allowed tO diffuseupward. As oil dissolves gas, it becomes lighter.Therefore, an inverse density gradient is develOPed in oillayer gradually. When this density gradient exceeds acritical value, convechon is started. It may be concjudedthat develOPing a theory, which predictS the onset ofconvection, should…     

Water—ethanol—gasoline blends as spark ignition engine fuels

The miscibility characteristics of hydrated ethanol with gasoline is investigated as a means of reducing the cost of ethanol/gasoline blends for use as a spark ignition engine fuel. For a given percentage of water in the ethanol, the experimental data shows that a limited volume of gasoline can be added to form a stable mixture. Engine experiments indicate that, at normal ambient temperatures, a water/ethanol/gasoline mixture containing up to 6 vol% of water in the ethanol constitutes a desirable motor fuel with power characteristics similar to those of the base gasoline. As a means of reducing the smog causing components of the exhaust gases, such as the oxides of nitrogen and the unburnt hydrocarbons, the water/ethanol/gasoline mixture is superior to the base gasoline.     

能源、环境与空调制冷

１９９７年,世界上１６０多个国家在日本京都签订了有关减少温室气体排放的协议（京都协议）。该协议对缔约国的能源政策甚至经济的发展都有巨大的影响。作为能源消耗量很大的空调制冷行业,有必要对此予以充分的关注和深入研究。本研究了国内外能源环境现状和空调制冷系统与能源环境的关系,给出了对空调制系统适应新的能源结构和环境政策进行适当调整的建议。     

The effect of normal stress on hydro-mechanical deep drawing process

Normal stress has some role in the deformation analysis of hydroforming processes. In this study, analytical modeling is pursued to evaluate the effect of normal stress on the hydro-mechanical deep drawing (HDD) process. Analyses are carried out for axisymmetric elements of the formed cup-shaped part for increments of the punch travel. The formulations are obtained using mechanical and geometrical relations and the finite difference method, thereby being solved by proper numerical algorithms. Furthermore, in the present work, part thickness is variable, the loading and straining are non-proportional, and bending/unbending effects over the part curvature are considered. The results show that there are some differences between thickness values, radial and circumferential strains and stresses, and punch force under plane stress and three-dimensional stress conditions. Thus, the normal stress should be considered in the design of HDD processes in order to improve accuracy.