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In a recent BAMS article, it is argued that community-based Open Source Software (OSS) could foster scientific progress in weather radar research, and make weather radar software more affordable, flexible, [...]

Virtual machine monitors are becoming popular tools for the deployment of database management systems and other enterprise software. In this article, we consider a common resource consolidation scenario in which several database management system instances, each running in a separate virtual machine, are sharing a common pool of physical computing resources. We address the problem of optimizing the performance of these database management systems by controlling the configurations of the virtual machines in which they run. These virtual machine configurations determine how the shared physical resources will be allocated to the different database system instances. We introduce a virtualization design advisor that uses information about the anticipated workloads of each of the database systems to recommend workload-specific configurations offline. Furthermore, runtime information collected after the deployment of the recommended configurations can be used to refine the recommendation and to handle changes in the workload. To estimate the effect of a particular resource allocation on workload performance, we use the query optimizer in a new what-if mode. We have implemented our approach using both PostgreSQL and DB2, and we have experimentally evaluated its effectiveness using DSS and OLTP workloads. Categories and Subject Descriptors: H.2.2 [Database Management]: Physical Design General Terms: Algorithms, Design, Experimentation, Performance Additional Key Words and Phrases: Virtualization, virtual machine configuration ACM Reference Format: Soror, A. A., Minhas, U. F., Aboulnaga, A., Salem, K., Kokosielis, P., and Kamath, S. 2010. Automatic virtual machine configuration for database workloads. ACM Trans. Datab. Syst. 35, 1, Article 7 (February 2010), 47 pages. DOI = 10.1145/1670243.1670250 http://doi.acm.org/10.1145/1670243.1670250

To address a major technical challenge in simulating geometric models of machined sculptured surfaces in three-axis virtual machining, this paper presents an efficient, accurate approach to representing the 3D envelopes of a cutter sweeping sequentially through cutter locations; these envelopes embody the furrow patches of the machined surfaces. In our research, the basic mechanism of removing stock material in three-axis computer numerically controlled (CNC) milling of sculptured surfaces is investigated, and, consequently, an effective model is proposed to represent the 3D envelopes (or furrow patches). Our main contribution is that a new directrix (or swept profile) of the furrow patches (mathematically, ruled surfaces) is identified as a simple 2D envelope of cutting circles and is formulated with a closed-form equation. Therefore, the 3D cutter-swept envelopes can be represented more accurately and quickly than the existing sweptvolume methods. With this innovative approach, a method of accurate prediction of the machining errors along tool paths in three-axis finish machining is provided, which is then applied to the optimization of tool-path discretization in two examples. Their results demonstrate the advantages of our approach and verify that the current machining-error-prediction methods can cause gouging in three-axis sculptured surface milling. [DOI: 10.1115/1.2823218] Keywords: cutter-swept envelope, machining-error prediction, sculptured surface machining, 3-axis CNC milling, virtual machining

The objective of this study was to investigate whether the appearance of virtual human models influences observers when judging a working posture. A task in which a manikin is manually assembling a car battery was used in the experiment. In total, 16 different pictures were presented to the subjects. All pictures had the same background, but included a unique posture and manikin appearance combination. 24 subjects consisting of manufacturing managers, simulation engineers and ergonomists were asked to rate and rank the pictures. The results showed that the virtual human model appearance influenced subjects when they rated pictures one by one: a more realistic manikin was rated higher than the identical posture visualized with a less natural appearance. This appearance effect was not seen when subjects ranked the pictures while looking at all of them at the same time. The study demonstrates that the human modelling tool used when showing and visually evaluating results makes a difference. To minimize subjective effects, a combination of visualizations and objective ergonomic assessment methods is recommended. Keywords: Manikin appearance; Ergonomics visualization; Virtual manufacturing

Advances on the modeling of nonlinear rotor-bearing models for prediction of the dynamic shaft response of automotive turbochargers (TCs) supported on floating ring bearings (FRBs) are presented. Comprehensive test data for a TC unit operating at a top speed of 65 krpm serves to validate the model predictions. The static forced performance of the support FRBs considers lubricant thermal effects, thermal expansion of the shaft and bearings, and entrance pressure losses due to centrifugal flow effects. The bearing analysis also yields linearized rotordynamic force coefficients for the inner and outer lubricant films. These coefficients are used with the rotor model to predict the synchronous response to imbalance and the system natural frequencies and stability. A method renders an accurate estimation of the test rotor imbalance by using the actual vibration measurements and influence coefficients derived from predictions using linearized bearing force coefficients. Predicted ring rotational speeds, operating radial clearances, and lubricant viscosities for the inner and outer films are the main input to the nonlinear time transient analysis. The nonlinear response model predicts the total shaft motion, with fast Fourier transforms showing the synchronous response, and amplitudes and whirl frequencies of subsynchronous motions. The predicted synchronous amplitudes are in good agreement with the measurements, in particular at high shaft speeds. The nonlinear analysis predicts multiple frequency subsynchronous motions for speeds ranging from 10 krpm to 55 krpm (maximum speed 70 krpm), with amplitudes and frequencies that correlate well with the test data. The comparisons validate the comprehensive rotorbearings model whose ultimate aim is to save TC design time and accelerate product development. [DOI: 10.1115/1.2436573]

The article presents the partitioning method for providing latency to users in distributed virtual environment systems. The system throughput is maximized and receives satisfactory latency for providing quality service.

Real-time human-computer interaction plays an important role in virtual-environment (VE) applications. Such interaction can be improved by detecting and reacting to the user's head motion. Today's VE systems use head-mounted inertial sensors to update and spatially stabilize the image displayed to a user through a head-mounted display. Since motion can only be detected after it has already occurred, latencies in the stabilization scheme can only be reduced but never eliminated. Such latencies slow down manual control, cause inaccuracies in matching real and virtual objects through a half-transparent display, and reduce the sense of presence. This paper presents novel methods for reducing VE latencies by anticipating future head motion based on electromyographic (EMG) signals originating from the major neck muscles and head kinematics; it also reports results for anticipation of 17.5 and 35 ms. Features extracted from the EMG signals are used to train a neural network in mapping EMG data, given present head kinematics, into future head motion. The trained network is then used in real time for head-motion anticipation, which gives the VE system the time advantage necessary to compensate for the inherent latencies. The main contribution of this work is the use of EMG energy and bounded head acceleration as the key input/output information, which results in improved performance compared to the previous work. Index Terms--Electromyogram, head-mounted display, neural networks, pattern recognition, virtual environment.

Byline: M. Emin Aydin (1), Terence C. Fogarty (1) Keywords: Parallel simulated annealing; multi-agent systems; job-shop scheduling; distributed resource machine Abstract: In this paper, a parallel implementation of the modular simulated annealing algorithm for classical job-shop scheduling is presented. The implementation is for a multi agent system running on the distributed resource machine, which is a novel, scalable, distributed virtual machine based on Java technology. The problems tackled are well known, difficult benchmarks, widely used to measure the efficiency of metaheuristics with respect to both the quality of the solutions and the central processing unit time. The empirical results obtained show that the method proposed is successful in comparison with a sequential version of modular simulated annealing algorithm and other methods described in the literature. Author Affiliation: (1) School of Computing, Information Systems and Mathematics, South Bank University, 103 Borough Road, London, SE1 0AA, UK Article History: Registration Date: 29/12/2004

Two continuously variable transmissions are examined, one that relates a pair of linear speeds and another that relates a pair of angular speeds. These devices are elemental in the design of cobots, a new class of robot that creates virtual guiding surfaces to aid a human operator in assembly tasks. Both of these transmissions are traction drive mechanisms that rely on the support of either lateral or longitudinal forces across rolling contacts with spin. When a rolling contact between elastic bodies or even between rigid bodies in spin is called upon to transmit a tractive force, kinematic creep develops, expressing a departure from the intended rolling constraint. Creep in turn gives rise to nonideal properties in a cobot's virtual guiding surfaces. This paper develops simple models of the two transmissions by expressing the relative velocity field in the contact patch between rolling bodies in terms of creep and spin. Coulomb friction laws are applied in a quasi-static analysis to produce complete force-motion models. These models may be used to evaluate a cobot's ability to support forces against its virtual guiding surfaces. [DOI: 10.1115/1.1517560]

We describe a mechanically checked proof of a property of a small system of Java programs involving an unbounded number of threads and synchronization, via monitors. We adopt the output of the javac compiler as the semantics and verify the system at the bytecode level under an operational semantics for the JVM. We assume a sequentially consistent memory model and atomicity at the bytecode level. Our operational semantics is expressed in ACL2, a Lisp-based logic of recursive functions. Our proofs are checked with the ACL2 theorem prover. The proof involves reasoning about arithmetic; infinite loops; the creation and modification of instance objects in the heap, including threads; the inheritance of fields from superclasses; pointer chasing and smashing; the invocation of instance methods (and the concomitant dynamic method resolution); use of the start method on thread objects; the use of monitors to attain synchronization between threads; and consideration of all possible interleavings (at the bytecode level) over an unbounded number of threads. Readers familiar with monitor-based proofs of mutual exclusion will recognize our proof as fairly classical. The novelty here comes from (i) the complexity of the individual operations on the abstract machine; (ii) the dependencies between Java threads, heap objects, and synchronization; (iii) the bytecode-level interleaving; (iv) the unbounded number of threads; (v) the presence in the heap of incompletely initialized threads and other objects; and (vi) the proof engineering permitting automatic mechanical verification of code-level theorems. We discuss these issues. The problem posed here is also put forth as a benchmark against which to measure other approaches to formally proving properties of multithreaded Java programs. Categories and Subject Descriptors: D.2.4 [Software Engineering]: Software/Program Verification; D.3.0 [Programming Languages]: General; F.4.0 [Mathematical Logic and Formal Languages]: General General Terms: Languages, Verification Additional Key Words and Phrases: Java, Java Virtual Machine, parallel and distributed computation, mutual exclusion, operational semantics, theorem proving

Virtual reality techniques are now more and more widely used in the field of surgical training. However, the realism of the simulation devices requires a good knowledge of the mechanical behavior of the living organs. To provide perioperative measurement of laparoscopic surgical operations, we equipped a conventional operating grasper with a force sensor and a position sensor. The entire apparatus was connected to a PC that controlled the real-time data acquisition. After calibrating the sensors, we conducted three series of in vivo measurements on animals under video control. A standardized protocol was set up to perform various surgical gestures in a reproducible manner. Under these conditions, we can assess an original tool for a quantitative approach of surgical gestures' mechanics. The preliminary results will be extended by measurements during other operations and with other surgical instruments. The in vivo quantification of the mechanical interactions between operating instruments and anatomical structures is of great interest for the introduction of the force feedback in virtual surgery, for the modeling of the mechanical behavior of living organs, and for the design of new surgical instruments. This quantification of manipulations opens new prospects in the evaluation of surgical practices. Index Terms--Biomechanics, in vivo measurements, surgical gestures.

Byline: CHELL A. ROBERTS (1), MAGED M. DESSOUKY (2), YASSER M. DESSOUKY (1) Keywords: Virtual factory; real-time control; batch-chemical manufacturing; object-oriented Abstract: This paper presents a virtual plant modeller (VPMOD), which formally characterizes and integrates chemical product designs, batch-chemical equipment (plants), the real-time scheduling of chemical batches, and the control of chemical transport through the plant. These models provide a framework for agile batch-chemical manufacturing that has the ability to reroute and control chemical product flow automatically in a flexible plant subject to unexpected events, such as changes in demand patterns and equipment failure. A formal logic model is generated to control the actual system events, which are non-deterministic. A simulation environment in VPMOD is used to validate schedules and control logic based on plant models supplied by industry. The formal models have been implemented in an object-oriented language. Author Affiliation: (1) Department of Industrial and Management Systems Engineering, Arizona State University, Tempe, Arizona, 85287-5906 (2) Department of Industrial and Systems Engineering, University Southern California, Los Angeles, CA, 90089-0193 Article History: Registration Date: 29/09/2004

This paper presents preliminary results of the development of a virtual flight data recorder (VFDR) for commercial airliners. Federal Aviation Administration (FAA) regulations, currently being revised, mandate the recording of 11 dynamic parameters, not including the control surface deflections. The absence of these data can be critical for crash investigation purposes. This paper proposed the introduction of a VFDR based on a neural network simulator (NNS) and a neural network reconstructor (NNR). The NNS is trained, using flight data for the particular aircraft, to simulate any desired control surface deflections (or any other parameter of interest not recorded by the FDR), minimizing a cost function based on the differences between the available data from the FDR and the output from the NNS. The VFDR scheme has been introduced, tested, and validated with flight data from a Boeing 737-300 with an FDR with extended recording capabilities showing accurate reconstruction of the control surface deflections' time histories. The VFDR can be considered a tool for crash investigations where control surface failures are believed to be a factor.

In the new and emerging agile manufacturing paradigm, where multiple firms cooperate under flexible virtual enterprise structures, there exists a great need for a mechanism to manage and control information flow among collaborating partners. In response to this pressing need, this paper addresses the design and implementation of an agile manufacturing information system integrating manufacturing databases dispersed at various partner sites. We propose a framework in which: (1) information is modeled in a hierarchical fashion using object-oriented methodology (OOM); (2) information transactions are specified by the workflow hierarchy consisting of partner workflows; (3) information flow between partners is controlled by a set of distributed workflow managers (WM) interacting with partner knowledge bases, which reflect partner specific information control rules on internal data exchange, as well as inter-partner mutual protocols for joint partner communications; (4) the prototype system is accomplished using the World Wide Web based on a client-server architecture. The overall approach and system provides within a dynamic environment, where virtual partnerships are synthesized in response to specific business initiatives, a dynamic and flexible mechanism to support partner information exchange and to keep the dispersed information consistent., 1. Introduction Facing a competitive market, industrial manufacturers are hard pressed to adopt novel strategies and technologies to enhance product quality, to cut manufacturing cost and to reduce product lead [...]

A Virtual Runoff Hydrograph System (VROHS) based on artificial neural network technology was designed and developed to generate runoff hydrograph. Data from 45 lab experiment sets were used to develop the VROHS. A recurrent back-propagation neural network was trained to generate runoff hydrograph. Twenty-nine of the 45 lab experiment sets were randomly selected to train the network, while 16 experiment sets were selected to test the VROHS. It was found that the VROHS could predict the runoff hydrograph system very accurately for sets of input data (experimental conditions) that it had never seen before. The values of the correlation coefficients and coefficient of determination for the testing sets ranged from 0.96 to 0.99 and 0.92 to 0.99, respectively. These high coefficient values demonstrated the good correlation between the observed data and the predicted data and also the high performance of the VROHS.

The challenge of virtual libraries is to make access of information readily available to all users. Special librarians have the responsibility to continually improve their skills and be knowledgeable in their field to be able to perform their functions., Or Plus ca Change, Plus C'est La Meme Chose In this issue of Special Libraries, we examine the concept of the library without walls or the virtual library from the [...]