Virtual Machine Concept Research Articles

A virtualization approach to develop middleware for ubiquitous high performance computing

In ubiquitous high-performance computing (UHPC), performing concurrent services is an important task of middleware. Because a major development effort is not easily achieved, isolating a virtual machine (VM) may be a helpful solution but will likely suffer from additional overhead costs. This challenge can also be resolved by reusing the device driver. However, these solutions are difficult to implement without the VM technique. In this study, we present an alternative approach to minimizing overhead and develop a middleware called userspace virtualized middleware (Uware). Instead of bypassing the VM, the proposed approach depends on userspace transparency and contention management to shift the VM concept into middleware. We introduce two strategies to enhance the system adaptively: comprehensive restructuring by simplifying the VM memory mechanism and implementing zero-copy buffers to reuse devices. The result demonstrates that Uware is feasible and could be applied in a broad variety of UHPC.

A Virtual Synchronous Machine implementation for distributed control of power converters in SmartGrids

The ongoing evolution of the power system towards a “SmartGrid” implies a dominant role of power electronic converters, but poses strict requirements on their control strategies to preserve stability and controllability. In this perspective, the definition of decentralized control schemes for power converters that can provide grid support and allow for seamless transition between grid-connected or islanded operation is critical. Since these features can already be provided by synchronous generators, the concept of Virtual Synchronous Machines (VSMs) can be a suitable approach for controlling power electronics converters. This paper starts with a discussion of the general features offered by the VSM concept in the context of SmartGrids. A specific VSM implementation is then presented in detail together with its mathematical model. The intended emulation of the synchronous machine characteristics is illustrated by numerical simulations. Finally, stability is assessed by analysing the eigenvalues of a small-signal model and their parametric sensitivities.

TOTAL INTERPRETIVE STRUCTURAL MODELLING ON ENABLERS OF CLOUD COMPUTING

Cloud computing is the delivery of computer resources over a network through web services, while the actual physical location and organization of the equipment hosting these resources are unknown to the users. Cloud computing strategy is subjected to many enablers. Interpretive structural modeling is a well proven tool for finding the interrelationship among the enablers. Total Interpretive structural model is an essential innovative version of interpretive structural modeling technique(ISM). In Total Interpretive Structural Modeling (TISM), influence/enhancement of enablers and their interrelationship is considered. Total interpretive structural model steps are identification of elements, pair-wise comparison, level partition, interaction formation, diagraph representation and formation of total interpretive structural model. The methodology of TISM is used to delineate the hierarchical relationship of enablers of cloud computing. Cloud computing is based on the concept of virtual machines. Hardware cost can be reduced by using virtualization. Different types of virtualization are operating system –level virtualization, application virtualization, service virtualization, memory virtualization, storage virtualization, virtual file system, data virtualization etc .Lack of trust between cloud users and providers has hindered the universal acceptance of cloud as outsourced computing services. To promote Multitenency we must design the cloud ecosystem to be secure, trustworthy and dependable

Equivalence of Virtual Synchronous Machines and Frequency-Droops for Converter-Based MicroGrids

Over the last decade, frequency-droop-based control schemes have become the preferred solution in microgrids dominated by power electronic converters. More recently, the concept of virtual synchronous machines (VSMs) has emerged as an effective method for adding virtual inertia to the power system through the control of power electronic converters. These two approaches have been developed in two separate contexts, but present strong similarities. In fact, they are equivalent under certain conditions, as demonstrated in this letter. Analysis of this equivalence provides additional physics-based insight into the tuning and operation of both types of controllers.

Phasor Control of Converter Output Voltage for Frequency Regulation

The synchronizing torque of a power system may be weakened by increasing installation of static power converters accompanied by renewable energy resources because they used to trade their favorable active power by synchronizing their output voltage with the one at the point of common coupling. In the circumstances, a concept of Virtual Synchronous Machine (VSM) is proposed, where the self-commutated power converters are emulating synchronous generators. This paper describes a converter control to contribute to enhancing the synchronizing torque. The proposed control is similar to the VSM but it simply realizes active power trades among power generation units including converter-based generators by modulating phase angles of their output voltages. Therefore, it can provide an effective support to regulate the system frequency where the total rated power of the converter-based generators increases as much as the one of conventional rotating generators like a microgrid. This paper especially focuses on its robustness where the number of converter-based generators is increased or they are dispersed in the power network. The effectiveness is verified by simulation study based on instantaneous values.

Development of Multimedia Environment for Viewing the State of Stress in a Differential Element

The aim of this work is to present a tool developed in a multimedia environment of a cilitate the understanding of the state of plane stress at an infinite simal element, which is directed to lectures in Mechanics of Materials courses. This multimedia resource was developed in Java 3D API, liked an applet, as it is a simple language whose programs can run on all operating system platforms, using the virtual machineconcept. The multimedia resource determines the strains caused by forces acting in a solid body. Usingthis tool the learning process can be more efficiently, and the view of results at an differential element in the state of plane stress can be easier too.

Holistic methodology using computer simulation for optimisation of machine tools

Virtual machine concepts supporting optimisation of machine tools have been developed in earlier work. The virtual machine concept is a tool that can describe the behaviour of a machine tool while considering the interaction between mechanics of the machines and the control system. Considerable amount of work has been done proving the concept and showing the potential of such a design tool in different contexts. Several studies have shown the potential of using the virtual machine concept, although, no work has been found that is exploring the potential of a full optimisation study.The aim of this work is to show the potential of the virtual machine concept in an optimisation study of the complete machine tool, including the mechanical system, parameters in the control system, the NC-code as well as choice of servo and drive systems. An efficient optimisation strategy is presented, making it possible to solve the complex optimisation problem within a reasonable amount of time.A combination of optimisation algorithms is used to achieve a fast and accurate way of solving the complex task to optimise the complete machine tool. Genetic algorithms, gradient based algorithms and more traditional hands on engineering are used for solving the optimisation problem. Post processing and data mining is suggested as a way of extracting as much information as possible from optimisation results with the aim to increase the knowledge about the studied system. An important conclusion is that the virtual machine should support the decision making in product development, not replace the product developers as regards decision making.

A summary of virtualization techniques

Nowadays, virtualization is a technology that is applied for sharing the capabilities of physical computers by splitting the resources among OSs. The concept of Virtual Machines (VMs) started back in 1964 with a IBM project called CP/CMS system. Currently, there are several virtualization techniques that can be used for supporting the execution of entire operating systems. We classify the virtualization techniques from the OS view. First, we discuss two techniques that executes modified guest OSs: operating system-level virtualization and para-virtualization. Second, we discuss two techniques that executes unmodified guest OSs: binary translation and hardware assisted. Finally, we present a summary of resource management facilities for capacity planning and consolidation of server applications.

系統連系自励式変換器の運転位相制御方式の検討

As increasing installation of renewable energies which are accompanied by self-commutated power converters, installed capacity of the converters cannot be negligible as compared to the total generation capacity. Those self-commutated converters trade active power with adjusting their output voltage phase angle according to the voltage at the point of commoncoupling (pcc). Therefore, increasing installation of the self-commutated power converters may result in reducing a synchronizing torque of the power system. The tendency is remarkable in a microgrid where the rate of converter-based generation is high. The synchronizing torque is supplied by traditional synchronous generators inherently because, at some disturbance, their inertias make phase differences among their terminal voltages and they can trade active power by the phase differences. In order to keep the synchronizing torque under high penetration of renewables, a concept of Virtual Synchronous Machine was proposed. The VSM emulates a conventional synchronous generator and realizes the power trade among them. This paper deals with a controller of self-commutated converter like the VSM. Instead of applying the same characteristics of the conventional synchronous generator, the phase angle of the output voltage is adjusted as lead or lagged to the pcc voltage in order to trade the active power. The effectiveness of the control is verified in a microgrid system model where the rotating generator and self-commutated converter have almost same rated capacity. The effectiveness of the controller is verified from the viewpoint of frequency control through some simulation studies.

Hardware/Software Codesign Architecture for Online Testing in Chip Multiprocessors

As the semiconductor industry continues its relentless push for nano-CMOS technologies, long-term device reliability and occurrence of hard errors have emerged as a major concern. Long-term device reliability includes parametric degradation that results in loss of performance as well as hard failures that result in loss of functionality. It has been reported in the ITRS roadmap that effectiveness of traditional burn-in test in product life acceleration is eroding. Thus, to assure sufficient product reliability, fault detection and system reconfiguration must be performed in the field at runtime. Although regular memory structures are protected against hard errors using error-correcting codes, many structures within cores are left unprotected. Several proposed online testing techniques either rely on concurrent testing or periodically check for correctness. These techniques are attractive, but limited due to significant design effort and hardware cost. Furthermore, lack of observability and controllability of microarchitectural states result in long latency, long test sequences, and large storage of golden patterns. In this paper, we propose a low-cost scheme for detecting and debugging hard errors with a fine granularity within cores and keeping the faulty cores functional, with potentially reduced capability and performance. The solution includes both hardware and runtime software based on codesigned virtual machine concept. It has the ability to detect, debug, and isolate hard errors in small noncache array structures, execution units, and combinational logic within cores. Hardware signature registers are used to capture the footprint of execution at the output of functional modules within the cores. A runtime layer of software (microvisor) initiates functional tests concurrently on multiple cores to capture the signature footprints across cores to detect, debug, and isolate hard errors. Results show that using targeted set of functional test sequences, faults can be debugged to a fine-granular level within cores. The hardware cost of the scheme is less than three percent, while the software tasks are performed at a high-level, resulting in a relatively low design effort and cost.

Software reviews (virtualisation and search apps)

The concept of virtual machines (VMs) is well established on the server side, but virtualisation has been something of a mystery on the desktop. However, things are beginning to change on that front, and Microsoft has now started bundling its Virtual PC software with some versions of Windows 7. Add open-source virtualisation tools and the 'free for personal use' versions of commercial software such as VirtualBox and VMware, and Mac, Windows XP and Linux users can join the fun.

Evaluation of gang scheduling performance and cost in a cloud computing system

Cloud Computing refers to the notion of outsourcing on-site available services, computational facilities, or data storage to an off-site, location-transparent centralized facility or "Cloud." Gang Scheduling is an efficient job scheduling algorithm for time sharing, already applied in parallel and distributed systems. This paper studies the performance of a distributed Cloud Computing model, based on the Amazon Elastic Compute Cloud (EC2) architecture that implements a Gang Scheduling scheme. Our model utilizes the concept of Virtual Machines (or VMs) which act as the computational units of the system. Initially, the system includes no VMs, but depending on the computational needs of the jobs being serviced new VMs can be leased and later released dynamically. A simulation of the aforementioned model is used to study, analyze, and evaluate both the performance and the overall cost of two major gang scheduling algorithms. Results reveal that Gang Scheduling can be effectively applied in a Cloud Computing environment both performance-wise and cost-wise.

Synchronisation and application of three-phase converters utilising the power-hardware-in-the-loop concept

This paper addresses the timely issues of synchronisation and application of three-phase power converters, connected in parallel, utilising the power-hardware-in-the-loop (PHIL) concept. Without proper synchronisation, the converters are normally not able to distinguish the currents that circulate between them. This paper focuses on a control methodology for achieving precise phase synchronisation for equal load sharing, with minimum current circulation between the parallel connected power converter modules, and robust dynamic system control under various transient conditions. The possible converter applications for the configuration presented in this paper are the virtual machine (VM) concept and a conceptual virtual microgrid (VMG), which utilises the reactive power compensation ability of the static synchronous compensator (STATCOM). These concepts provide a solution for de-risking these costs as it utilises the PHIL concept in conjunction with high-fidelity models and detailed load dynamics. Selected experimental results on two, 25 kVA and 15.3 kVA, converters connected in parallel are presented.

Calibration strategies for scanning probe metrology

Within the Dutch standards laboratory (NMi Van Swinden Laboratorium) a traceable atomic force microscope (AFM) is currently being developed where we aim at a measurement uncertainty of 1 nm. As part of this development novel methods have been developed for the calibration of this instrument. The SPM has been constructed using a commercial AFM head that has been embedded in a metrology frame using an accurate 3D translation stage. The position of the AFM probe relative to the sample is determined along three orthogonal measurement axes by three individual laser interferometers. Due to the properties of the 3D translation stage the Abbe offset between the probe position and the measurement axes should remain below 0.1 mm in order to realize an overall measurement uncertainty of 1 nm. Since the laser interferometers use a four-pass optical configuration the measurement axis is defined by the virtual centre of the four positions of the laserspots onto the plane retro mirror. In order to accurately determine this virtual centre and therefore the position of the measurement axis a device has been designed to measure the four laserspot positions of each axis within the SPM. Since the AFM probe position is determined in 3D accurate calibration of the angles between the measurement axes is important if the measurement error is to be minimized to 1 nm. Different calibration setups to accurately determine these angles will be presented. Additionally, a method for the alignment of the optical axes of the laser interferometers with respect to the end mirrors of the interferometers will be discussed. In order to calculate the overall measurement uncertainty of the scanning probe microscope we decided to use the virtual measurement machine concept since a purely analytical approach for these types of measurement instruments is nearly impossible (Schwenke et al 2000 Ann. CIRP 49 395–8). The model or virtual SPM that has been developed for the simulation of the instrumental characteristics will be presented.

Protecting host-based intrusion detectors through virtual machines

Intrusion detection systems continuously watch the activity on a network or computer, looking for attack and intrusion evidences. However, host-based intrusion detectors are particularly vulnerable, as they can be disabled or tampered by successful intruders. This work proposes and implements an architecture model aimed to protect host-based intrusion detectors, through the application of the virtual machine concept. Virtual machine environments are becoming an interesting alternative for several computing systems due to their advantages in terms of cost and portability. The architecture proposed here makes use of the execution spaces separation provided by a virtual machine monitor, in order to separate the intrusion detection system from the system under monitoring. As a consequence, the intrusion detector becomes invisible and inaccessible to intruders. The prototype implementation and the tests performed show the viability of this solution.

PARALLELIZATION OF A MOLECULAR DYNAMICS SIMULATION OF AN ION-SURFACE COLLISION SYSTEM: Ar–Ni(100)

Parallel molecular dynamics simulation study of the ion-surface collision system is reported. A sequential molecular dynamics simulation program is converted into a parallel code utilizing the concept of parallel virtual machine (PVM). An effective and favorable algorithm is developed. Our parallelization of the algorithm shows that it is more efficient because of the optimal pair listing, linear scaling, and constant behavior of the internode communications. The code is tested in a distributed memory system consisting of a cluster of eight PCs that run under Linux (Debian 2.4.20 kernel). Our results on the collision system are discussed based on the speed up, efficiency and the system size. Furthermore, the code is used for a full simulation of the Ar–Ni (100) collision system and calculated physical quantities are presented.

A virtual machine concept for real-time simulation of machine tool dynamics

When designing CNC machine tools it is important to consider the dynamics of the control, the electrical components and the mechanical structure of the machine simultaneously. This paper describes the structure and implementation of a concept for real-time simulation of such machine tools using a water jet cutting machine as an application. The concept includes a real control system, simulation models of the dynamics of the machine and a virtual reality model for visualisation. The real-time capability of the concept, including the simulation of electrical and rather detailed mechanical component models is proofed. The validation process indicates good agreement between simulation and measurement, but suggests further studies on servo motor, connection and flexibility modelling. However, already from the initial simulation results presented in this paper it can be concluded that the influence of structural flexibility on manufacturing accuracy is of importance at desired feeding rates and accelerations. The fully automated implementation developed in this work is a promising base for dealing with this trade-off between productivity and accuracy of the manufacturing process through multidisciplinary optimisation.

O(N) parallel tight binding molecular dynamics simulation of carbon nanotubes

Abstract We report an O( N ) parallel tight binding molecular dynamics simulation study of (10×10) structured carbon nanotubes (CNT) at 300 K. We converted a sequential O( N 3 ) TBMD simulation program into an O( N ) parallel code, utilizing the concept of parallel virtual machines (PVM). The code is tested in a distributed memory system consisting of a cluster with 8 PC's that run under Linux (Slackware 2.2.13 kernel). Our results on the speed up, efficiency and system size are given.

An Object-Oriented Approach to an Agile Manufacturing Control System Design

Modern manufacturing control systems must respond quickly to continuous change in an agile manufacturing environment. With traditional manufacturing control system programming, it is time-consuming to make changes as a result of separate databases for the programmable logic controller (PLC), manmachine interface (MMI), and supervisory control and data acquisition (SCADA) packages. To resolve this, an object-oriented model of the control system using the unified modelling language (UML) is proposed, which then provides control and diagnostic code, enabling the network architecture, data mapping and control and diagnostic system to be designed within a single tool. The model is defined in accordance with the virtual machine concept which decomposes the complex machine into smaller elements. Based on the virtual machine concept, the model consists of the conceptual (or normal perception for the system) and control view (the control perception of a control engineer). A case study demonstrates the concept with both control and diagnostic code consistently derived from a single model.

Leaky virtual machines and the best of both worlds

The concept of virtual machine allows us to combine the dynamical and computational hypotheses in an investigation of cognition. Van Gelder explicitly rejects this approach, but not only does it allow us to use the modelling technique most appropriate to the task, it also opens up a new range of phenomena where these techniques interact.