Production and inventory policies for an integrated manufacturing firm

The coordination of production and inventory decisions for raw materials, intermediate products and finished goods is important. We compare some decision rules for a ‘firm that uses a single raw material to manufacture n different parts which are then assembled into the final product. Demand for the final product is probabilistic and there are costs of holding inventory and of ordering, manufacture and assembly. These characteristics are an idealization of the problem faced by a manufacturer of scaffolds in which the major processes are the manufacture of different sheet metal parts and their assembly.

We develop production rules that use system-wide information. We use simulation to evaluate the performance of these rules and compare system behaviour to that under production rules that are derived separately for each item and use only local information about that item's status.     

Application of multivariate statistical analyses in the differentiation between two phosphate ores from the Nuba Mountains,Sudan

In previously published research, uranium abundance and major and trace element content were determined in phosphate ore samples from the Kurun and Uro areas of the Nuba Mountains in Sudan. The current work aims to characterise and differentiate between the phosphate ores from these two areas by subjecting the obtained geochemical data to quantitative and qualitative statistical analyses. Multivariate statistical analyses and correlation studies show several geochemical differences in the occurrence of uranium in Kurun and Uro phosphate ores. Uranium in Uro phosphate ore shows a higher degree of mobility coefficient of variability (CV%?=?91) than that in Kurun phosphate ore (CV%?=?48). Kurun and Uro phosphate ores are found to be good sources of titanium and strontium. The average concentrations of Ti and Sr in Uro phosphate ore are 4880 and 2780?mg?kg^–1, respectively. The corresponding values in Kurun phosphate ore are 7300 and 2630?mg?kg^–1, respectively. A cluster analysis of trace elements demonstrates that both Ti and Sr, which are the most abundant trace elements, appear in individual groups or in sub-groups. Uranium behaves in the same manner in both phosphate ores in that it associates in groups containing all the transition metals except for the most abundant trace element, titanium.     

ANALYSIS OF COAL DISSOLUTION REACTION ENGINEERING

A phenomenological approach was developed for conversion of coal to pyridine soluble materials with the object of shedding additional light on the reactions taking place during short contact times. The approach was based on a theoretical analysis of many parallel reactions in a complex reacting mixture. The analysis used the concept of lumped species and weighted activation energies to improve on coal liquefaction models. i.e. to remove insensitivity problems for parameters in coal liquefaction models and to answer questions about behaviour of liquefaction reactions in different vessels.     

The Ontolingua Server: a tool for collaborative ontology construction

Reusable ontologies are becoming increasingly important for tasks such as information integration, knowledge-level interoperation and knowledge-base development. We have developed a set of tools and services to support the process of achieving consensus on commonly shared ontologies by geographically distributed groups. These tools make use of the World Wide Web to enable wide access and provide users with the ability to publish, browse, create and edit ontologies stored on anontology server. Users can quickly assemble a new ontology from a library of modules. We discuss how our system was constructed, how it exploits existing protocols and browsing tools, and our experience supporting hundreds of users. We describe applications using our tools to achieve consensus on ontologies and to integrate information.The Ontolingua Server may be accessed through the URLhttp://ontolingua.stanford.edu     

Force and pressure measuring by means of TCNQ-complex thin films

Sandwich samples of organic polycrystalline TCNQ-complex thin films with a TTF derivative as donor exhibit a significant current (I) dependence on a force F acting perpendicularly to the film plane, of the form I～F. The current dependence on temperature can be influenced by the deposition conditions and mostly it is weak for temperatures up to 70°C. Hysteresis effects are small.     

Multiparadigm distributed computing with TPVM

Distributed concurrent computing based on lightweight processes can potentially address performance and functionality limits in heterogeneous systems. The TPVM framework, based on the notion of ‘exportable services’, is an extension to the PVM message-passing system, but uses threads as units of computing, scheduling, and parallelism. TPVM facilitates and supports three different distributed concurrent programming paradigms: (a) the traditional, task based, explicit message-passing model; (b) a data-driven instantiation model that enables straightforward specification of computation based on data dependencies; and (c) a partial shared-address space model via remote memory access, with naming and typing of distributed data areas. The latter models offer significantly different computing paradigms for network-based computing, while maintaining a close resemblance to, and building upon, the conventional PVM infrastructure in the interest of compatibility and ease of transition. The TPVM system comprises three basic modules: a library interface that provides access to thread-based distributed concurrent computing facilities, a portable thread interface module which abstracts the required thread-related services, and a thread server module which performs scheduling and system data management. System implementation as well as applications experiences have been very encouraging, indicating the viability of the proposed models, the feasibility of portable and efficient threads systems for distributed computing, and the performance improvements that result from multithreaded concurrent computing. © 1998 John Wiley & Sons, Ltd.     

RELATIONSHIP BETWEEN CERTAIN PHYSICAL-CHEMICAL MEASUREMENTS AND SENSORY APPRAISALS OF APPLE TEXTURE

Apples were selected as the test medium to provide information about the relative value of physical-chemical measurements as predictors of sensory appraisal of texture. Sensory, shear force, moisture, pH and protopectin/total pectin measurements of textural parameters for five variety-lots, after various storage periods, were treated by multiple regression, analysis of variance, and covariance and path analyses. Statistical treatments revealed relationships that were clearcut and certain trends that appear to be meaningful. Panel scores were not well predicted by objective measurements with one exception. Shear force was an excellent predictor for crispness of Colorado Red Delicious. Tenderness of Golden Delicious increased as storage increased and protopectin/total pectin decreased, whereas losses of crispness and juiciness were small and inconsistent. Overall results of sensory and physical-chemical tests for Winesap and Red Delicious were rather consistent in that tenderness increased and juiciness decreased linearly with the length of storage.