1,341,674 research outputs found

    Weak measurement of cotunneling time

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    Quantum mechanics allows the existence of "virtual states" that have no classical analogue. Such virtual states defy direct observation through strong measurement, which would destroy the volatile virtual state. Here we show how a virtual state of an interacting many-body system can be detected employing a weak measurement protocol with postselection. We employ this protocol for the measurement of the time it takes an electron to tunnel through a virtual state of a quantum dot (cotunneling). Contrary to classical intuition, this cotunneling time is independent of the strength of the dot-lead coupling and may deviate from that predicted by time-energy uncertainty relation. Our approach, amenable to experimental verification, may elucidate an important facet of quantum mechanics which hitherto was not accessible by direct measurements.Comment: 13 pages, 5 figures, 1 tabl

    Virtual teams: A literature review

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    In the competitive market, virtual teams represent a growing response to the need for fasting time-to-market, low-cost and rapid solutions to complex organizational problems. Virtual teams enable organizations to pool the talents and expertise of employees and non-employees by eliminating time and space barriers. Nowadays, companies are heavily investing in virtual team to enhance their performance and competitiveness. Despite virtual teams growing prevalence, relatively little is known about this new form of team. Hence the study offers an extensive literature review with definitions of virtual teams and a structured analysis of the present body of knowledge of virtual teams. First, we distinguish virtual teams from conventional teams, different types of virtual teams to identify where current knowledge applies. Second, we distinguish what is needed for effective virtual team considering the people, process and technology point of view and underlying characteristics of virtual teams and challenges they entail. Finally, we have identified and extended 12 key factors that need to be considered, and describes a methodology focused on supporting virtual team working, with a new approach that has not been specifically addressed in the existing literature and some guide line for future research extracted

    A Call to Action to Improve the Quality of Full-Time Virtual Charter Public Schools

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    Currently, more than 180,000 students attend 135 full-time virtual charter schools in 23 states and the District of Columbia. While some students do well in a full-time virtual charter school environment, too many of these schools are not providing a quality educational program to the vast majority of their students, while enrolling too many who are simply not a good fit for attending a fully online school.In this report,  A Call to Action to Improve the Quality of Full-Time Virtual Charter Public Schools, the National Alliance for Public Charter Schools, the 50-State Campaign for Achievement Now (50CAN) and the National Association of Charter School Authorizers (NACSA) propose specific policy recommendations to help states better hold full-time virtual charter schools accountable for student results

    Wait-Free Global Virtual Time Computation in Shared Memory Time-Warp Systems

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    Global Virtual Time (GVT) is a powerful abstraction used to discriminate what events belong (and what do not belong) to the past history of a parallel/distributed computation. For high performance simulation systems based on the Time Warp synchronization protocol, where concurrent simulation objects are allowed to process their events speculatively and causal consistency is achieved via rollback/recovery techniques, GVT is used to determine which portion of the simulation can be considered as committed. Hence it is the base for actuating memory recovery (e.g. of obsolete logs that were taken in order to support state recoverability) and nonrevocable operations (e.g. I/O). For shared memory implementations of simulation platforms based on the Time Warp protocol, the reference GVT algorithm is the one presented by Fujimoto and Hybinette [1]. However, this algorithm relies on critical sections that make it non-wait-free, and which can hamper scalability. In this article we present a waitfree shared memory GVT algorithm that requires no critical section. Rather, correct coordination across the processes while computing the GVT value is achieved via memory atomic operations, namely compare-and-swap. The price paid by our proposal is an increase in the number of GVT computation phases, as opposed to the single phase required by the proposal in [1]. However, as we show via the results of an experimental study, the wait-free nature of the phases carried out in our GVT algorithm pays-off in reducing the actual cost incurred by the proposal in [1]

    Real time integration of user preferences into virtual prototypes

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    Within new product development (NPD), both virtual prototypes and physical prototypes play important roles in creating, testing and modifying designs. However, in the current design process, these two forms of prototyping methods are normally used independently and converted from one to the other during different design phases. This conversion process is time consuming and expensive and also introduces potential information loss/corruption problems. If the design process requires many iterations, it may simply be impractical to generate all the conversions that are theoretically required. Therefore, the integration of virtual and physical prototyping may offer a possible solution where the design definition is maintained simultaneously in both the virtual and physical environment. The overall aim of this research was to develop an interface or a tool that achieves real time integration of physical and virtual prototyping. “Real time integration” here means changes to the virtual prototypes will reflect any changes that have been made contemporaneously to the physical prototypes, and vice versa. Thus, conversion of the prototype from physical to virtual (or vice versa) will be achieved immediately, hence saving time and cost. A review of the literature was undertaken to determine what previous research has been conducted in this area. The result of the review shows the research in this area is still in its infancy. The research hypothesis was developed through the use of a questionnaire survey. Totally 102 questionnaires were sent to designers, design directors or design managers to address the issue: will industrial designers want to make use of real time integration and if so, how? The outcome from the literature review drove further development of the research hypothesis and an initial pilot experiment to test this. The pilot trial was designed to address the research questions: • Can real time physical and virtual prototyping integration be conveniently demonstrated? • Will designers and users be comfortable using the integration method? • Will users recognise the benefits of the integration? The results showed that real time integration between physical and virtual prototyping is necessary in helping designers develop new products and for getting users more closely involved. The future research suggested is that more investigations and experiments are needed to explore a proper method that simultaneously employing these two types of prototyping in product development process. Keywords: Physical Prototyping; Virtual Prototyping; Integration; Real Time.</p
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