Effects of Nd2O3 and TiO2 Addition on the Microstructures and Microwave Dielectric Properties of BaO-Nd2O3-TiO2 System

The effects of Nd₂O₃ and TiO₂ addition on the microstructures and microwave dielectic properties of BaO-Nd₂O₃-TiO₂ system were investigated. BaNd₂Ti₄O₁₂ or BaNd₂Ti₅O₁₄ phases were observed for compositions based on BaO/Nd₂O₃ = 1 ratio. The compositions deviated from BaO/Nd₂O₃ = 1 ratio were composed of major phases of BaNd₂Ti₄O₁₂ or BaNd₂Ti₅O₁₄, and the compound of Nd₂O₃ and TiO₂ (Nd₂Ti₂O₇) or that of BaO and TiO₂ (BaTi₄O₉). The microstructure of ceramic with BaO·Nd₂O₃ ·4TiO₂ composition varied from spherical grains to needlelike grains with increasing sintering temperature. With increasing Nd₂O₃, the optimum sintering temperature with maximum density increased, and the dielectric constant( · _r) and quality factor(Q) decreased due to the formation of secondary phases. With increasing TiO_2/ the optimum sintering temperature and the dielectric constant decreased with increased Q value. And the temperature coefficient of resonant frequency, ·_f shifted toward positive direction. The dielectric ceramics with BaO/Nd₂O₃ = 1 showed Q values of above 2000 and dielectric constants of above 80 at 3GHz.     

Liquid injection molding II. Mechanical design and characterization of a RIM machine

A unique liquid injection molding machine for polyurethane was designed and built to process a large quantity of polyurethane in a short period of time. This machine has a continuously variable flow rate. Using inexpensive, low capacity gear pumps, 5 gallon hydraulic accumulators were charged with fluid components. The fluid can be pumped into the accumulators at low pressure followed by nitrogen gas addition to the bladders to raise the fluid pressure, or the charging pumps can pump up the accumulators against an existing pressure. The two components were then discharged under pressure through linkage activated ball valves and mixed together in a mixing chamber. The system provided for a very low pressure loss during discharge, resulting in high fluid velocity. Extremely high flow rates were possible: approximately 1440 lb/min at 2500 psi, a pressure less than the maximum possible system pressure. This system delivers large flow rates of high quality urethane while still maintaining its simplicity, light weight, and relative low cost.     

Analysis of fade margins for soft and hard handoffs in cellular CDMA systems

The effect of handoff techniques on fade margin is investigated. We provide an accurate comparison for soft and hard handoffs in a two-cell system. An upper bound on the fade margin for hard-handoff systems is derived and an approximation formula is obtained empirically. Simulation results show that this approximation is very accurate over reasonable ranges of system parameters. Extension of our analysis to multiple-cell systems are illustrated using a three-cell system as an example.     

Spatially adaptive high-resolution image reconstruction of DCT-based compressed images

The problem of recovering a high-resolution image from a sequence of low-resolution DCT-based compressed observations is considered in this paper. The introduction of compression complicates the recovery problem. We analyze the DCT quantization noise and propose to model it in the spatial domain as a colored Gaussian process. This allows us to estimate the quantization noise at low bit-rates without explicit knowledge of the original image frame, and we propose a method that simultaneously estimates the quantization noise along with the high-resolution data. We also incorporate a nonstationary image prior model to address blocking and ringing artifacts while still preserving edges. To facilitate the simultaneous estimate, we employ a regularization functional to determine the regularization parameter without any prior knowledge of the reconstruction procedure. The smoothing functional to be minimized is then formulated to have a global minimizer in spite of its nonlinearity by enforcing convergence and convexity requirements. Experiments illustrate the benefit of the proposed method when compared to traditional high-resolution image reconstruction methods. Quantitative and qualitative comparisons are provided.     

PAMS: A Domain-specific Knowledge-based Parallel Machine Scheduling System

Abstract: To overcome the inefficiency of domain independent tools, a domain-specific knowledge-based shell for parallel machine scheduling problems, PAMS (PArallel Machine Scheduling System), is proposed. PAMS has the following features; mixed knowledge representation, two-stage status-driven control strategy, conflict resolution using domain theory, domain-specific syntax and primitive operators, interface with database, domain-specific input/output interface, interactive scheduling capability, built-in heuristic knowledge, multiple levels of schedule, and expansibility of the domain. A prototype of PAMS, PAMS-1, is developed using C-language on a supermicrocomputer, and the performance of PAMS-1 is evaluated. The results show that the PAMS-1 performs very well from various perspectives.     

Multiprocessor implementation of digital filtering algorithms usinga parallel block processing method

An efficient real-time implementation of digital filtering algorithms using a multiprocessor system in a ring network is investigated. This method is based on a parallel block processing approach, where a continuously supplied input data is divided into blocks, and the blocks are processed concurrently by being assigned to each processor in the system. This approach requires only a simple interconnection network and reduces significantly the number of communications among the processors, making the system easily expandable and highly efficient. In addition, various digital signal processing algorithms can be implemented on the same multiprocessor system. The data dependency of the blocks to be processed concurrently brings on dependency problems between the processors. A systematic scheduling method has been developed by using a precedence graph for the analysis of the dependency relation. Methods for solving the dependency problems between the processors are also investigated. Implementation procedures and results for FIR, recursive, and adaptive filtering algorithms are illustrated     

Establishment of a hereditary nonpolyposis colorectal cancer registry

INTRODUCTION: Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant condition characterized by early age of onset colorectal cancer, right-sided predominance, excess of synchronous and metachronous colonic neoplasms, and extracolonic cancers. The purpose of this study is to report clinical characteristics of HNPCC families in our registry. METHODS: This is a retrospective review of medical records of patients with a significant history of colorectal cancer and interviews with their families. RESULTS: Three hundred one people with cancer in 40 HNPCC families were identified. In 284 of 301 (94 percent) people, 363 cancers were identified. Colorectal cancer only was identified in 182 people (64 percent) and, in conjunction with extracolonic tumors, in another 31 people (11 percent). Extracolonic cancer alone was noted in 71 people (25 percent). Median age at diagnosis of colorectal cancer was 48 (range, 17-92) years. In patients with documented pathology, right-sided tumors predominated (55 percent), synchronous and metachronous tumors were noted in 53 percent, and synchronous of metachronous adenomas were documented in 51 percent of people. Generational anticipation was also noted. CONCLUSION: This study demonstrates and confirms characteristics that have been described in HNPCC. Namely, early age of onset of colorectal cancer, right-sided predominance, multiple synchronous and metachronous neoplasms, increased extracolonic cancers, and generational anticipation.     

Incremental feature generation and modification during design evolution

The concept of feature was introduced because of need to integrate the design and the manufacturing activities. Therefore, the generation of features usually occurs after design completion. However, in recent product development approaches such as concurrent engineering (CE), features need to be generated during design evolution. This paper presents an incremental feature generation (IFG) and feature modification (FM) approach applicable during design evolution, defined by constructive solid geometry (CSG) and boundary representation (B-rep). In IFG, a classified boundary component, obtained from boundary evaluation, is defined as a protrusion or depression (P/D) according to Boolean operation and convexity analysis. The existing features are then updated in accordance with feature interactions in the FM. The FM involves feature existence analysis and modification procedures. The modification procedures are; 1) decide whether the remaining part of an existing feature is valid for a feature definition, 2) update it as a new feature and 3) define the feature relationship. In the IFG approach, the geometry of the current design step is automatically isolated by Boolean operation and defined as a protrusion or depression (P/D) without convexity calculation of topological entities such as edges or face sets. The above procedures are performed through tracing Boolean operations and convexity checking of an intersection edge loop generated during design evolution.     

Temperature and frequency effects on fatigue crack growth in acrylonitrile–butadiene–styrene (ABS)

Fatigue crack growth (FCG) in a commercial-grade acrylonitrile–butadiene–styrene (ABS) over the temperature and frequency ranges of 10–70°C and 0.01–10 Hz was studied. A model for the effects of temperature and frequency on the FCG rate was refined. The refined model is shown to accurately predict FCG rates in ABS. Three different types of fatigue fracture surfaces have been found. The first type is characterized by discontinuous growth bands; the second, by a rather smooth surface; and the last, by a rough surface relative to the second. The transition between the first and second types was found to be dependent on temperature and frequency as well, whereas the transition between the second and last types was found to be only dependent on temperature. These findings are discussed in relation to crazing. The apparent activation energy (ΔH_th) was evaluated for both the first and second types to be 19.22 kJ/mol. © 1995 John Wiley & Sons, Inc.