Minimizing makespan during environmental stress screening using a genetic algorithm and an ant colony optimization

The environmental stress screening (ESS) chamber employed in a typical electronics manufacturing service (EMS) provider’s facility is used for screening products, attempting to expose defects that cannot be detected by visual inspection or electrical testing. The ESS chambers are bottleneck work centers in most of the EMS facilities. This research uses a genetic algorithm (GA) and an ant colony optimization (ACO) to solve the job-scheduling problem at the ESS chamber where the makespan of the process is minimized. The performances of the two approaches were compared against some of the first-fit (FF) techniques from the literature. Both the GA and ACO techniques produced satisfactory results up to a job size of 40. Furthermore, ACO generally requires a longer computational time, while offering more consistent solution quality.     

Distributed source coding using syndromes (DISCUS): design and construction

We address the problem of compressing correlated distributed sources, i.e., correlated sources which are not co-located or which cannot cooperate to directly exploit their correlation. We consider the related problem of compressing a source which is correlated with another source that is available only at the decoder. This problem has been studied in the information theory literature under the name of the Slepian-Wolf (1973) source coding problem for the lossless coding case, and as "rate-distortion with side information" for the lossy coding case. We provide a constructive practical framework based on algebraic trellis codes dubbed as DIstributed Source Coding Using Syndromes (DISCUS), that can be applicable in a variety of settings. Simulation results are presented for source coding of independent and identically distributed (i.i.d.) Gaussian sources with side information available at the decoder in the form of a noisy version of the source to be coded. Our results reveal the promise of this approach: using trellis-based quantization and coset construction, the performance of the proposed approach is 2-5 dB from the Wyner-Ziv (1976) bound.     

New galvanic cell designs for minimizing electrode polarization

New galvanic cell designs, incorporating one or two buffer electrodes, are developed to minimize the electrode polarization caused by electrochemical permeability of the electrolyte at high temperature. When a nonpolarizable reference electrode is employed, a cell with three-electrode compartments can be used to measure the chemical potential of oxygen in two-phase fields of ternary systems, associated with one degree of freedom at constant temperature. A buffer electrode is placed between the reference and measuring electrodes. The buffer electrode, maintained at approximately the same oxygen chemical potential as the measuring electrode, absorbs the semipermeability flux of oxygen between reference and measuring electrodes. When the reference electrode is polarizable, two buffer electrodes are required between the reference and measuring electrodes. The reference and reference-buffer electrodes have the same chemical potential of the active species. Similarly the measuring electrode and its buffer are of approximately the same chemical potential. A significant chemical potential difference exists only between the two buffers, which may become polarized due to coupled transport of ions and electronic defects through the electrolyte. Since the reference and measuring electrodes are insulated, the emf of the solid state cell is unaffected. The use of the buffer electrode designs permit more accurate thermodynamic measurements on metal and ceramic systems at high temperature.     

Yield optimization in large RAM's with hierarchical redundancy

The authors present and analyze large RAM architectures with hierarchical redundancy and determine the optimal redundancy organization for yield enhancement. A two-level redundancy scheme is used for defect tolerance, and the defect distribution is modeled using the compounded Poisson model. The tree random access memory (TRAM), which has been proposed as a design methodology for future multimegabit memories (N. Jarwala et al., 1988) is considered as an example for modeling and optimization. The results show that the two-level hierarchical redundancy approach, with spare bit and word lines within memory quadrants, and additional spare modules for global sparing, along with redundant interconnections can efficiently provide defect tolerance and viable yields for future generations of high-density dynamic random access memories     

Gradient solid electrolytes for thermodynamic measurements: System Na2CO3-Na2SO4

The thermodynamic properties of Na₂CO₃-Na₂SO₄ solid solution with hexagonal structure have been measured in the temperature range of 873 to 1073 K, using a composite-gradient solid electrolyte. The cell used can be represented as Pt, CO₂′ + O₂∥ Na₂CO₃Na₂ (CO₃)_x(SO₄)_1-x) ∥ CO₂″ + O₂″, Pt The composite-gradient solid electrolyte consisted of pure Na²CO³ at one extremity and the solid solution under study at the other, with variation in composition across the electrolyte. A CO₂ + O₂ + Ar gas mixture was used to fix the chemical potential of sodium at each electrode. The Nernstian response of the cell to changes in partial pressures of CO₂ and O₂ at the electrodes has been demonstrated. The activity of Na₂CO₃ in the solid solution was measured by two techniques. In the first method, the electromotive force (emf) of the cell was measured with the same CO₂ + O₂ + Ar mixture at both electrodes. The resultant emf is directly related to the activity of Na₂CO₃ at the solid solution electrode. By the second approach, the activity was calculated from the difference in compositions of CO₂ + O₂ + Ar mixtures at the two electrodes required to produce a null emf. Both methods gave identical results. The second method is more suitable for gradient solid electrolytes that exhibit significant electronic conduction. The activity of Na₂CO₃ exhibits positive deviation from Raoult’s law. The excess Gibbs’ energy of mixing of the solid solution can be represented using a subregular solution model such as the following: ΔG^E = X(1 - X)[6500(±200)X + 3320(±80)(l - X)] J mol^-1 whereX is the mole fraction of Na₂CO₃. By combining this information with the phase diagram, mixing properties of the liquid phase are obtained.     

The hyper-deBruijn networks: scalable versatile architecture

Both Hypercube and deBruijn networks possess desirable properties. It should be understood, though, that some of the attractive features of one are not found in the other. The architecture proposed in this paper is a combination of these architectures, providing some of the desirable properties of both the networks such as admitting many computationally important networks, flexibility in terms of connections per node as well as level of fault-tolerance. Also the network allows a simple VLSI layout, scalability as well as decomposability. Thus, these networks can be a potential candidate for VLSI multiprocessor networks. The proposed network possesses logarithmic diameter, optimal connectivity, and simple routing algorithms amendable to networks with faults. Importantly, in addition to being pancyclic, these hyper-deBruijn networks admit most computationally important subnetworks including rings, multidimensional meshes, complete binary trees, and mesh of trees with perfect dilation. Techniques for optimal one-to-all (OTA) broadcasting in these networks are presented. As an intermediate result, this technique provides the fastest OTA broadcasting in binary deBruijn networks as well. The recent renewed interest in binary deBruijn networks makes this later result valuable     

A mathematical model for industrial projects location

The location of an industrial project is one of the major decisions an entrepreneur has to take. The classical approach in locational analysis is based on cost minimization (especially the aggregate transport cost). Later investigations have dealt with profit maximization. This paper presents the method of developing a comprehensive model for determining the optimum plant location for an industry—considering both the objective (quantitative) factors and the subjective (non-quantitative) factors. The approach followed here identifies all the objective factors and the subjective factors at the micro level and optimizes the overall benefit to the entrepreneur. A method has been devised to evaluate the intangible factors and to combine them with the tangible factors to obtain the overall locational measure. This is done by converting the factors into consistent and dimensionless indices for comprehensive evaluation. Thus the model presented here can be used as a tool to determine the optimum plant location for a new industrial project and also to establish priorities among the feasible plant locations.     

Removal of nickel from aqueous solutions using crab shells

Partially converted crab shell waste, which contains chitosan, was used to remove nickel from water. The chelating ability of chitosan makes it an excellent adsorbent for removing pollutants. Advantages of chitosan in crab shells include availability, low cost, and high biocompatibility. The metal uptake by partially converted crab shell waste was successful and rapid. The sorption occurred primarily within 5 min. The sorption mechanism appears to be quite complicated and cannot be adequately described by either the Langmuir or Freundlich theories. Various anions, including chloride, bromide, fluoride, acetate, sulfate, nitrate, and phosphate, were found to have a very small effect on the capacity of the crab shells for uptake of nickel. The effect of pH was also found not to be prominent.