Creep Behavior and Grain-Boundary Sliding in Polycrystalline A12O3

The creep properties of polycrystalline A1₂O₃ (grain size 14 to 65 μm) were examined under compressive stresses of between 4,000 and 18,000 psi (27.6 and 124 MPa) in the range 1600° to 1700°C. Two distinct types of behavior were observed. The creep rate of medium-grained specimens (14 to 30 μm) could be described by ασ^1.2 / d² where σ is the applied stress and d is the grain size. These results are consistent with the Nabarro-Herring creep mechanism. For the coarse-grained (65 μm) specimens, the creep rate was related to the stress by ασ^2.6. This behavior was not related to cracking; instead, a dislocation mechanism was thought to be rate-controlling. Considerable evidence for grain-boundary sliding was seen, and measurements showed that grain-boundary sliding contributed between 46 and 77% of the total strain in the 3 medium-grained specimens examined and between 38 and 50% in the 3 coarsegrained specimens examined.     

SEQUENTIAL PARTITION DETECTORS WITH DEPENDENT SAMPLING

In this paper, the theory of sequential partition detectors with dependent sampling is introduced. A new formulation is given which predicts the thresholds under q-dependent sampling in order to maintain the same error probabilities as in the independent sampling case. A comparison is made between independent and dependent sequential partition detectors based on the average time to detection. Under stated conditions dependent sequential partition detectors show improved efficiency for both Lehmann and shift of the mean alternatives.     

Object-oriented simulation to support research in manufacturing systems

Simulation is a popular tool for modelling and analysing modern manufacturing systems. Choosing an appropriate simulation approach for a long-term research activity is not an easy task. This report discusses the issues involved in selecting a simulation approach to support research in real-time resource allocation decisions in manufacturing. A review of current directions in simulation software is presented. Specialized simulation needs of university-based research are described. After evaluating our needs with respect to the available options, we found that an object-oriented programming paradigm suits our needs best.     

Manufacturing evaluation using resource-based, template-free features

This paper addresses the theory and tools that promote rapid product and process development of machined products. A foundation of this approach is the application of a new definition of manufacturing features called resource-based free-form features. Using free-form features we demonstrate how cost, time and quality predictions, based on available equipment, are computed. We also introduce the concept of intelligently clustering alternative features to achieve better process alternatives. The approach presented herein is appropriate throughout the product design life-cycle as an aid to faster product realization by evaluating the parochial manufacturability of a completed design. In particular, this approach will provide the design team with cost, time and quality predictions, based on available equipment, that can be used to guide the design process. It also provides the manufacturing team with an approach to evaluating producibility and generating a production plan for a product model using available equipment in terms of cost, time and quality.     

ITERATIVE AND RECURSIVE ALGORITHMS FOR TREE SEARCH AND PARTITION SEARCH OF THE LATTICE OF STRUCTURE MODELS

An important problem in reconstructability analysis, and modelling in general, is determination of the set of simplest models, all of which acceptably represent the information contained in a given overall system. Evaluation of these models depends on acceptability (semantic) criteria and structural criteria. Structural criteria determine whether one model is simpler than another. In this paper we assume the existence of acceptability criteria and mechanisms to determine if given models meet them. The general problem we solve is how to most efficiently generate the set of all models. We use these results to determine the set of simplest models that satisfy the acceptability criteria

The main results of the paper are: a procedural definition of a recursive Boolean lattice that is based on recursive partitioning of the set of models, a definition of a spanning tree of the lattice of models, and algorithms for non-duplicating generation and search of the lattice of models. The generation and search algorithms fall into two categories: (i) iterative and recursive algorithms that implement the definition of the spanning tree and use it to determine the set of simplest models; (ii) algorithms that implement recursive partition search of the lattice of models. Two algorithms for recursive partition search are given, one that applies the procedural definition of a recursive Boolean lattice to the full set of models, and one that first partitions the full set into C-Structure equivalence classes, and then applies the definition of the recursive Boolean lattice to the equivalence classes.     

FUNCTION-BASED MODELING AND TROUBLESHOOTING

Abstract

This report describes an ongoing effort to apply the functional modeling (FM) approach to the representation of and reasoning about engineered artifacts. The application domain is the external active thermal control system (EATCS) of space station Freedom. The intuitions behind FM are threefold. First, knowing the purposes of a device allows organization of the causal understanding of how a device works. Second, causality may be represented in modular chunks, which are indexed by the purposes of the device and its interrelated subsystems. Finally, the global behavior of a device in a given situation can be understood by composition of the relevant causal net fragments. These starting intuitions provide a framework for organizing calculations about a device and for performing a limited type of simulation with the organized ensemble. Parallel to the FM modeling effort for EATCS is the development of a methodology that generates diagnostic knowledge for a device directly from its FM representation. This knowledge compilation strategy takes the FM representation of the target device and compiles organized knowledge structures for troubleshooting. The knowledge structures are utilized in two ways for diagnosis: (1) efficient hypothesis generation and (2) hypothesis evaluation. The central result of the research reported here is that an FM representation of a device can be used to generate knowledge for diagnostic troubleshooting.     

Asset prices and the fundamentals: a Q test

A test of the relationship between financial asset values and the fundamentals is presented. The test is an indirect test based on Tobin's (1969) q model of investment. The advantage of this test is that it avoids conditioning on a specific model of equilibrium returns by substituting an observable proxy, capital, for the unobservable fundamental value of the firm. It is shown that under mild restrictions, the value of capital and the financial value of the firm should move together even if marginal or average q does not accurately describe the actual investment decision rule. Average q is a mean reverting process. The results of tests for violations of the mean reversion restriction are presented. The tests cannot reject the unit root null hypothesis for a long annual sample from 1926 to 1988 or a quarterly post-World War II sample. The power of the tests is examined with Monte Carlo simulations. The simulations show that the tests have good power until the serial correlation in the series gets quite high. The tests cannot distinguish between no mean reversion and very slow mean reversion. The empirical evidence presented in this paper provides fairly strong evidence against the hypothesis that the financial and real values are closely linked in the short run or even in the medium run.     

核磁共振及成像技术在食品工业中的应用

核磁共振技术以快速、无损伤、无侵入检测等优点使其在食品中得到广泛的应用,本文综述了其在食品工业中五大方面的应用,分别为测量食品和生物体系中的含水量、研究食品中水分的分布和水分的流动性、研究果蔬的成熟度和损伤程度、研究食品中的油脂、研究食品的玻璃态转变温度。     

Approaches to the Batchwise Dyeing of Polyester—Cellulose Blends in Woven and Knitted Piece Goods

One- and two-bath dyeing procedures for polyester-cellulosic fabrics are compared, mainly from the practical dyers' viewpoint. Particular attention is paid to the ease of control of dyeing, coupled with economic factors. Dye selection and laboratory control are also discussed.     

A Rapid Method for the Determination of Soluble and Insoluble Dietary Fiber: Comparison with AOAC Total Dietary Fiber Procedure and Englyst's Method

Total dietary fiber (TDF) was measured in 16 foods by three methods: a rapid enzyme-NDF (neutral detergent fiber) procedure supplemented with a separate procedure for soluble (SOL) fiber, the AOAC TDF method and the comprehensive Englyst's procedure. The NDF+SOL method needed less operator time than the AOAC method and its TDF values were in agreement with the AOAC method (y = 0.98 -0.39; r = 0.997) and with the Englyst's method (y = 1.17 -0.19; r = 0.996). The constituent sugars of polysaccharides in NDF+SOL residues were similar to those by the Englyst's method, indicating an adequate estimation of dietary fiber in foods and food products.