Resource-requirements planning in flexible manufacturing systems

In this paper, we address the problem of planning the requirements of some of the important resources in flexible manufacturing systems. Specifically, we model the problem of estimating the required numbers and types of machines and tools in the context of a cellular layout. A two-stage procedure is developed which first forms the part families, using the complete-linkage clustering method based on a new similarity index defined in terms of the tooling requirements, and then subsequently estimates the resource requirements to manufacture the part families using an integer programming model. Several variations of the model are discussed and a numerical example is given.     

Lack of morphine and enkephalin tolerance in 129/SvEv mice: evidence for a NMDA receptor defect

Pregnancies in outbred mammals may be regarded as successfully developed homografts. One of the hypotheses that attempts to answer the enigma of why the fetus is not rejected (fetal-maternal relationships are based on reciprocal expressions of foreign transplantation antigens) claims for the existence of possible evolutionary links between invertebrate allorecognition and mammalian implantation, based on some cellular similarities. This essay further discusses the possible evolutionary perspectives between vertebrates and invertebrates alloimmunities from a different viewpoint. We discuss similarities between natural transplantation in colonial marine invertebrates, which are followed by chimerism and a state of tolerance, and two natural transplantation events in the mammalian systems which both have records for prolonged chimerism and tolerance: the phenomenon of dizygotic twin fusions and the situation of fetal cells implantation. Earlier comparative evolutionary perspectives are revisited.     

Information-theoretic bounds on target recognition performancebased on degraded image data

This paper derives bounds on the performance of statistical object recognition systems, wherein an image of a target is observed by a remote sensor. Detection and recognition problems are modeled as composite hypothesis testing problems involving nuisance parameters. We develop information-theoretic performance bounds on target recognition based on statistical models for sensors and data, and examine conditions under which these bounds are tight. In particular, we examine the validity of asymptotic approximations to probability of error in such imaging problems. Problems involving Gaussian, Poisson, and multiplicative noise, and random pixel deletions are considered, as well as least-favorable Gaussian clutter. A sixth application involving compressed sensor image data is considered in some detail. This study provides a systematic and computationally attractive framework for analytically characterizing target recognition performance under complicated, non-Gaussian models and optimizing system parameters     

Impact of Interruptions on Schedule Execution in Flexible Manufacturing Systems

Finite capacity scheduling software packages provide a detailed advance plan of production events. However, the execution of this advance plan is disrupted by a myriad of unanticipated interruptions, such as machine breakdowns, yield variations, and hot jobs. The alternatives available to respond to such interruptions include modifying the existing schedule, regenerating the complete schedule, or doing nothing and letting the production system gradually absorb the impact of the interruption. This article reports on a simulation study aimed at understanding the impact of an interruption on a schedule in order to build a knowledge base for intelligent selection of a response from a set of alternatives. The results of the experimental study are used to identify significant major factors and their interactions. The results are discussed to draw insights into the performance of a flexible manufacturing system following an interruption. The causes leading to particular performance anomalies are extensively discussed and mechanisms for propagation and absorption of the effect of interruptions in manufacturing systems are inferred. Practical implications for the development and implementation of schedules are deduced and areas for further research proposed. This study provides the groundwork necessary to proceed with the development of strategies for responding to interruptions.     

Outbreak of viral hepatitis B in a rural community in India linked to inadequately sterilized needles and syringes

BACKGROUND AND METHODS: Four hundred and eighty-four patients with inflammatory bowel disease underwent clinical examination, ultrasonography, and biochemical liver function tests, to estimate the prevalence of hepatobiliary alterations. The patient group included patients without a history of liver disease. Controls were recruited from patients with functional symptoms. RESULTS: More patients with ulcerative colitis than controls had liver steatosis and increased alkaline phosphatase levels. Factors increasing the probability of liver damage were long-standing disease, the presence of moderate/severe disease activity, and treatment with steroids and mesalazine. A significant association was found between biliary disease and long-standing colitis and also therapy with steroids and mesalazine. Alkaline phosphatase and aminotransferase levels were significantly higher in Crohn's disease patients than in controls. Hepatic and biliary damage was found more commonly in the 1st year after diagnosis. CONCLUSIONS: The monitoring of hepatobiliary function is suggested for patients with inflammatory bowel disease, even in the absence of symptoms and history.     

The Graphical Specification of Similarity Queries

Image databases will require a completely new organization due to the unstructured and ‘perceptual’ structure of the data they contain. We argue that similarity measures, rather than matching, will be the organizing principle of image databases. Similarity is a very elusive and complex judgment, and typical databases will have to rely on a number of different metrics to satisfy the different needs of their users. This poses the problem of how to combine different similarity measures in a coherent and intuitive way. In this paper we propose our solution, which is loosely based on ideas derived from fuzzy logic in that it uses the equivalent in the similarity domain of theand, orandnotoperations. The approach is much more general than that, however, and can be adapted to work with any operation that combines together similarity judgment.With this approach, a query can be described as a Directional Acyclic graph with certain properties. We analyse briefly the properties of this graph, and we present the interface we are developing to specify these queries.     

A caching strategy to reduce network impacts of PCS

We propose an auxiliary strategy, called per-user caching, for locating users who move from place to place while using Personal Communications Services (PCS). The caching strategy augments the basic location strategy proposed in existing standards such as GSM and IS-41, with the objective of reducing network signaling and database loads in exchange for increased CPU processing and memory costs. Since technology trends are driving the latter costs down, the auxiliary strategy will become increasingly attractive. The idea behind caching is to reuse the information about a called user's location for subsequent calls to that user, and is useful for those users who receive calls frequently relative to the rate at which they change registration areas. This idea attempts to exploit the spatial and temporal locality in calls received by users, similar to the idea of exploiting locality of file access in computer systems. We use a reference PCS architecture and the notion of a user's local call-to-mobility ratio (LCMR) to quantify the costs and benefits of using caching and classes of users for whom it would be beneficial. We also present two simple algorithms for estimating users' LCMR and the situation in which each is preferable. We show that under a variety of assumptions caching is likely to yield significant net benefits in terms of reduced signaling network traffic and database loads     

From content-based retrieval to invisible telepresence

Better tools for producing and managing data, combined with the human desire for information, have resulted in a data explosion. Indeed, data overload often leaves us confused, disoriented, and inefficient. The challenge is to find relevant data that lets us extract the information we want. Keyword-based systems cannot do this well, especially when working with images and video. It will be impossible to cope with the multimedia data explosion unless the data is organized for rapid information retrieval. Research in this field is in its infancy; nevertheless, commercial products are starting to appear that allow retrieval of images and video using query by pictorial example techniques. At present, these techniques work using only image primitives, but similar techniques based on domain knowledge should be available soon. Thus we will have additional techniques for providing navigational engines to ensure that the information highway is more than just a data network