Matrix substitution method for power bus analysis with isolated power island in high-speed packages and PCBs

We propose a matrix substitution method for analyzing a power bus containing a power island in high-speed packages and printed circuit boards (PCBs). The method is based on a segmentation method and a resonant cavity model for a rectangular cavity, and the impedance of the power bus containing the power island can be calculated analytically. Finally, the proposed method is verified by means of impedance measurements in the frequency domain.     

Thermodynamics of titanium and nitrogen in an Fe-Ni melt

The equilibrium solubility of titanium and nitrogen in Fe-Ni melts was measured in the presence of pure solid TiN under various nitrogen pressures in the temperature range of 1843 to 1923 K. The activity coefficients of titanium and nitrogen relative to a 1 mass pct standard state in liquid iron were calculated from the experimental results for Fe-Ni alloys of nickel contents up to 30 mass pct. Nickel decreases the activity coefficient of titanium, but it increases the activity coefficient of nitrogen in an Fe-Ni-Ti-N melt. Therefore, the effect of nickel on the solubility product of TiN is not significant. The first- and second-order interaction parameters of nickel on titanium (e _Ti ^Ni and r _Ti ^Ni , respectively) were determined to be −0.0115 and 0 at 1873 K, respectively. Similarly, the interaction parameters of nickel on nitrogen (e _N ^Ni and r _N ^Ni , respectively) were determined to be 0.012 and 0, respectively, at 1873 K. The temperature dependence of these interaction parameters was also determined.     

Material Control System for the Manufactured Housing Industry

A manufactured home is a factory-built house constructed in a controlled factory environment according to federal standards known as the Department of Housing and Urban Development (HUD) code. The manufactured home shares approximately 20% of the total housing units in the United States and plays an important role in providing affordable housing. However, in terms of material engineering, advanced techniques are scarcely used in the manufactured housing (MH) industry. The current material flow and control systems are characterized as independent demand systems that are based on the personal experience of the material managers. Although independent inventory control systems are widely used in many manufacturing industries, these systems lead to a large amount of inventory and have many drawbacks for the MH industry. On the other hand, dependent inventory systems can reduce unfavorable inventory levels using new techniques and present substantial benefits for the MH industry. This paper applies lean inventory control systems and supply chain management techniques to the current systems of the MH industry and proposes a new framework of material control systems as one of the system management tools.     

A self-organizing genetic algorithm for multimodal function optimization

A genetic algorithm (GA) has control parameters that must be determined before execution. We propose a self-organizing genetic algorithm (SOGA) as a multimodal function optimizer which sets GA parameters such as population size, crossover probability, and mutation probability adaptively during the execution of a genetic algorithm. In SOGA, GA parameters change according to the fitnesses of individuals. SOGA and other approaches for adapting operator probabilities in GAs are discussed. The validity of the proposed algorithm is verified in simulation examples, including system identification. This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996     

Combined extended and superimposed finite element method for cracks

A combination of the extended finite element method (XFEM) and the mesh superposition method (s‐version FEM) for modelling of stationary and growing cracks is presented. The near‐tip field is modelled by superimposed quarter point elements on an overlaid mesh and the rest of the discontinuity is implicitly described by a step function on partition of unity. The two displacement fields are matched through a transition region. The method can robustly deal with stationary crack and crack growth. It simplifies the numerical integration of the weak form in the Galerkin method as compared to the s‐version FEM. Numerical experiments are provided to demonstrate the effectiveness and robustness of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.     

Boiling hysteresis at low temperature on enhanced tubes

The boiling hysteresis phenomenon is studied for a real scale enhanced evaporator tube (2 m long Turbo-B type) with R134a refrigerant used in the flooded evaporator of a centrifugal brine chiller for the ice-making facility. Unlike previous studies of the boiling heat transfer with uniform heat flux and uniform wall temperature, the wall temperature varies along the tube in the present experiment. To see if the similar hysteresis occurs as in the case of uniform wall temperature, a careful control of refrigerant temperature and heat flux is made. We have found hysteresis of the temperature overshoot (TOS) at the onset of nucleate boiling initially at the inlet section of the tube, before it gradually moved downstream section of the tube until the nucleate boiling occupied the whole section of the tube as the inlet temperature increased. The hysteresis became stronger at low refrigerant temperatures. The decreasing trend of heat flux after the contents of the whole tube boiled was different from the increasing trend. This paper provides a guideline how to design the evaporator in order to avoid the abnormal operation of the chillers.     

A novel SET/MOSFET hybrid static memory cell design

In this paper, a single electron transistor (SET)/metal-oxide-semiconductor field effect transistor (MOSFET)-based static memory cell is proposed. The negative differential conductance (NDC) characteristics of the SET block help us establish the static memory cell circuits more compactly than those in conventional technologies. The proposed memory cell consists of one MOSFET and two back-to-back connected SET blocks exhibiting the NDC. The peak-to-valley current ratio of the SET block is above four with C/sub G/=5.4C/sub T/ (C/sub T/=0.1 aF) at T=77K. The read and write operations of the proposed memory cell were validated with SET/MOSFET hybrid simulations at T=77 K. Even though the fabrication process that integrates MOSFET devices and SET blocks with NDC is not yet available, these results suggest that the proposed SET/MOSFET hybrid static memory cell is suitable for a high-density memory system.     

Estimation of break location and size for loss of coolant accidents using neural networks

In this work, a probabilistic neural network (PNN) that has been applied well to the classification problems is used in order to identify the break locations of loss of coolant accidents (LOCA) such as hot-leg, cold-leg and steam generator tubes. Also, a fuzzy neural network (FNN) is designed to estimate the break size. The inputs to PNN and FNN are time-integrated values obtained by integrating measurement signals during a short time interval after reactor scram. An automatic structure constructor for the fuzzy neural network automatically selects the input variables from the time-integrated values of many measured signals, and optimizes the number of rules and its related parameters. It is verified that the proposed algorithm identifies very well the break locations of LOCAs and also, estimate their break size accurately.     

Preparation of AZ91D Slurries for Semi-Solid Forming Using Al8 ( Mn, Fe) 5 Precipitates

During the solidification of the AZ91D-alloys, the Al8(Mn, Fe)5 phase is generally precipitated in the melt in advance of the precipitation of the primary α-Mg. The basic principle for manufacturing AZ91D-alloy slurries for semi solid forming is to use the Al8(Mn, Fe)5 precipitates as the heterogeneous nucleation sites for primary α-Mg phases. Microscopic analysis for the location of the Al8(Mn, Fe)5 precipitate explains that the Al8(Mn, Fe)5 precipitate is the effective heterogeneous nucleation site for the primary α-Mg phase. It was also observed that increase of the Mn content in the melt and the cooling rate below to the solid/liquid two-phase region resulted in smaller and more globular primary α-Mg due to the increase of heterogeneous nucleation sites. It was found that the average α-Mg diameter grew as a function of t0.278, where t is the holding time at the solid/liquid two-phase region. This would be attributed to the Ostwald type ripening and coalescence between primary α-Mg phases. The cooling rate below to the solid/liquid two-phase region, Mn content in AZ91D alloy, and the holding time and temperature affected on the quality of slurry.