Heat Transfer from Plutons Undergoing Hydrothermal Cooling and Thermal Cracking

Abstract

Numerical calculations are reported for the transient cooling of a solidified intrusion embedded in a water-saturated porous layer. Heat transfer rates are increased greatly when the intrusion undergoes thermal cracking as it cools. The effects of a uniform heat flux into the porous layer from below are considered. Solutions are obtained for porous layers that are initially above or below the critical-layer Rayleigh number for thermal convection. For conditions considered in this study, the effects on the cooling intrusion of initial convection and layer aspect ratio are small. Results are correlated by scaling velocities with the intrusion Rayleigh number.     

卷扬式启闭机卷筒组的优化设计

本文对卷筒组的参数优化设计进行了详细讨论,通过实例分析,提出了设计卷筒组时参数选择的一般原则。在PC机上研制出了相应的优化设计软件,该程序使用灵活、方便,并可纳入整个启闭机的CAD系统。     

Analysis of Seidel aberration by use of the discrete wavelet transform

Seidel aberration coefficients can be expressed by Zernike coefficients. The least-squares matrix-inversion method of determining Zernike coefficients from a sampled wave front with measurement noise has been found to be numerically unstable. We present a method of estimating the Seidel aberration coefficients by using a two-dimensional discrete wavelet transform. This method is applied to analyze the wave front of an optical system, and we obtain not only more-accurate Seidel aberration coefficients, but we also speed the computation. Three simulated wave fronts are fitted, and simulation results are shown for spherical aberration, coma, astigmatism, and defocus.     

K-means method for rough classification of R&D employees' performance evaluation

This paper proposes an approach that can roughly cluster a data set with fuzzy linguistic entries as a prior data arrangement for performance evaluation of R&D employees. The extension principles of fuzzy linguistic numbers are used to modify the K‐means method for handling the linguistic data set. We define the absolute difference of fuzzy linguistic variables as their fuzzy distance. Based on this definition, the K‐means approach can be modified slightly for clustering purposes. The performance of employees engaged in designing and R&D‐oriented jobs is possibly related to some qualitative attributes and the evaluation of such attributes for each employee has a tendency toward semantic scales. In the proposed approach, the supervisor can evaluate the performance of each employee directly with a semantic scale. The modified K‐means approach can roughly cluster their performance into different classes in advance of applying some other sophisticated processes.     

High-efficiency InGaN-GaN MQW green light-emitting diodes with CARTand DBR structures

Distributed Bragg reflector (DBR) and charge asymmetric resonance tunneling (CART) structures were applied to nitride-based green light-emitting diodes (LEDs) to enhance their output efficiency It was found that we can reduce the forward voltage at 20 mA from 3.7 to 3.2 V with the inclusion of CART structure. It was also found that the electroluminescence peak wavelength of the CART LED is less sensitive to the amount of injection current. The output power and external quantum efficiency of the CART LED with DBR structure measured at 20 mA can reach 7.2 mW and 11.25%, respectively     

Characterization of Si implants in p-type GaN

Si ion implantation into p-type GaN followed by rapid thermal annealing (RTA) in N/sub 2/ has been performed. X-ray diffraction analyses indicate that ion-implanted damage remains even with 1050/spl deg/C, 60 s RTA. By varying implantation and postimplantation annealing conditions, we could convert carrier concentration from p-type 3 /spl times/ 10/sup 17/ cm/sup -3/ into n-type 2 /spl times/ 10/sup 17/ cm/sup -3/ /spl sim/2 /spl times/ 10/sup 19/ cm/sup -3/. It was found that typical activation energies of Si implants in p-GaN are lower than 10 meV. Such activation energies are smaller than those observed from epitaxially grown Si-doped GaN films. A deep donor level with activation energy of 60 meV was also found from some samples. Photoluminescence studies show that the peak appears at 372 nm might be related to implantation-induced defects. It was also found that a green emission band could be observed from Si-implanted GaN. It was shown that such a green emission is related to the yellow band observed from epitaxially grown Si-doped GaN. The transport properties of these Si-implanted samples were also studied.     

Using Cpk index with fuzzy numbers to evaluate service quality

Service quality is measured by customers' satisfaction. Traditionally, the degree of satisfaction is calculated from the data obtained from questionnaires that have been filled by customers directly. The percentile of each different level of a customer's satisfaction is employed to summarize and compare the quality of service provided by different enterprises. This approach does not consider the consistency of the customers' perceptions, thus making comparison difficult. This paper introduces the concept of a process capability index that considers both the average and the consistency of the data simultaneously. Evaluations of service quality are usually vague and linguistic. We use the fuzzy numbers of linguistic variables developed in fuzzy set theory to modify the process capability index, and then apply it to evaluate the quality of a service. The average and consistency of the data obtained from a service quality evaluation are thus considered simultaneously, making the comparison of the performance of service quality easier. Moreover, the value of the index can be applied to help to point out the direction for improving the performance of service quality whenever it is lower than some default value.     

Higher education for the information age

The new generation of engineering professionals needs to know not only the scientific and engineering principles, but also have extensive knowledge about arts, literature, and social sciences. They need far-reaching vision for the future in order to understand grand challenges on the technical-level, the system-level, and the social aspects of topics that are of importance to the modern society. One solution is to emphasize fundamental courses such as mathematics and physics with new interpretation to correlate with real-world applications. It is important to include system-oriented topics in the curriculum so that students know how to apply the basic principles, The key focus should be placed on analysis and design skills, and effective communication is essential to address any large-scale problems     

Magnetic resonance images of neuronal migration anomalies

Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies.     

Finite element analysis of vortex shedding oscillations from cylinders in the straight channel

In this paper a GCL (Geometry Conservation Law) – preserving finite element model is developed to simulate the fluid-structure interaction phenomena. The boundary locations are part of the solution procedures. Within the moving grid framework, the employed numerical method involves the operator splitting technique, balance tensor diffusivity (BTD), Runge-Kutta time-stepping method, and an element-by-element conjugate gradient iterative solver. Flows around a self-vibrating cylinder and elastically supported cylinders are investigated to validate the present method. The simulated results agree well with available data in the literature. The lock-in phenomenon that may cause the unstable motion of cylinders is also revealed. It is significant from the simulated 2×2 four cylinders result that the rear two cylinders approach to each other at a time earlier than the front two ones.