Preemptive Policy Research Articles

Permanent war? The domestic hegemony of the New American militarism*

Although there is an expanding body of excellent work on 9/11 and the War on Terror, and the changing forms of war‐making, militarism and imperialism, this literature lacks a sufficient critical synthesis of the historical and conjunctural events of 9/11 and its aftermath with the structural and systemic forms of US militarism and the military‐industrial complex. This article attempts a broad, critical‐theoretical analysis of the increased domestic hegemony of militarism in the US since 9/11. The article examines the complex social‐systemic interlocking of militarism with other historical, political, institutional, economic, cultural and psychological forces which tend to reinforce the hegemony of militarism and aggressive, preemptive foreign policy in the current period.

Analysis of the Colorado potato beetle protection system in Finland

Invasive species, including plants, insects and other pests, are a serious threat to agricultural production and to the environment in general. Finland has traditionally had a favourable situation concerning invasives, partly due to its isolated geographical location. The situation may now be changing and one of the currently increasing threats is the Colorado potato beetle (CPB). Finland has designed a CPB protection policy incorporating a protected zone, which is commonly used to deal with invasive plant pests in other European countries. Within this zone, the randomly occurring CPB invasions are collectively fended off, to prevent the establishment of a permanent pest population and to minimise potential damage. This paper evaluates the economics of the current protection programme, comparing this to a hypothetical situation in which the current pre-emptive policy is abandoned and control relies on producers’ individual reactive protection measures. The annual random pest invasions are modelled in a static stochastic framework. To date the pest has not been able to establish a permanent population in Finland. According to our analysis, the currently exercised pre-emptive policy is the cost-efficient choice at this point. The relatively low expected invasion magnitude is one of the key factors supporting the efficiency of the current system. Another reason is the fairly small damage incurred. However, when the invasions become larger and more frequent or the pest strains more cold-resistant, the future situation may change.

Quality of Service in Asynchronous Bufferless Optical Packet Switched Networks

Optical Packet Switching (OPS) is a promising technology for future core networks due to the ability to handle bursty traffic, adaptability to changes in the network infrastructure and good network utilization. In order to provide sufficient Quality of Service (QoS) to the emerging range of real-time and critical business applications, service differentiation should be present in future OPS. This paper presents the Preemptive Drop Policy (PDP), which provides service differentiation in asynchronous bufferless OPS. Based on time-continuous Markov chains, we introduce an analytical model of the PDP for switches with and without wavelength conversion. We extend the PDP into the Adaptive PDP (APDP), which provides absolute QoS guarantees in OPS. Simulations performed validate our analytical model and show that the APDP operates properly in a dynamic changing system load scenario.

Preemptive priority policy for hot lots transport services in 300mm semiconductor foundry

Highly automated material handling is one of the most concerns to foundry practitioners because efficient manual operations and coordination have been the core competence in 300mm manufacturing. Especially, one of the critical problems is how to provide an almost no-wait transport for hot lots in an automatic material handling environment. However, there is no effective method for hot lots handling in 300mm Overhead Hoist Transport (OHT) intrabay operation. This paper proposes an effective OHT dispatching method, Preemptive Priority Policy (PPP), to provide the transport services for hot lots against the normal lots transport requirements under 300mm frequently blocking transportation situation. The objective is to minimize the transport delay of hot lots and to convey our idea for hot lots transport services. Simulation experiments based on realistic data from a 300mm wafer foundry are conducted. Numerical results demonstrate that the PPP method can effective expedite the movement of the hot lots with acceptable time delay on normal lots, which is very useful to streamline the shop floor operations, like scheduling and dispatching, for eliminating time delays of hot lots in an automated environment. This can help fab managers for more precisely lots management and automated material handling system (AMHS) control.

New Preemption Policies for DiffServ-Aware Traffic Engineering to Minimize Rerouting in MPLS Networks

The preemption policy currently in use in MPLS-enabled commercial routers selects LSPs for preemption based only on their priority and holding time. This can lead to waste of resources and excessive number of rerouting decisions. In this paper, a new preemption policy is proposed and complemented with an adaptive scheme that aims to minimize rerouting. The new policy combines the three main preemption optimization criteria: number of LSPs to be preempted, priority of the LSPs, and preempted bandwidth. Weights can be configured to stress the desired criteria. The new policy is complemented by an adaptive scheme that selects lower priority LSPs that can afford to have their rate reduced. The selected LSPs will fairly reduce their rate in order to accommodate the new high-priority LSP setup request. Performance comparisons of a nonpreemptive approach, a policy currently in use by commercial routers, and our policies are also investigated.

Managing the Impact of Customer Support Disruptions on New Product Development Projects

Knowledge-worker development projects are often performed where multiple projects are always in progress, and where preemption often occurs for solving time-critical customer service projects. The following nonlinear model for learning-intense situations demonstrates that the choice of preemption policy significantly impacts project completion times. Within this model, the authors identify policies that reduce the detrimental effects of preemption. The best policy preempts the activity that has the most slack and has been in progress the shortest time, and restarts the activity quickly with qualified resources as soon as possible.

Crisis on the Korean Peninsula: How to Deal with a Nuclear North Korea

describing their comprehensive proposal for negotiations with North Korea, O'Hanlon and Mochizuki exhibit the strategic creativity and analytical depth badly needed by United States policy makers dealing with this strange, dangerous place. - Ash Carter, former Assistant Secretary of Defense and Ford Foundation Professor of Science and International Affairs, John F. Kennedy School of Government, Harvard University. In early 2002, in his fateful state of the union address, President Bush described North Korea as being a member of the Axis of Evil. Since then, the U.S. has gone to war with Iraq, and the world now wonders what the future of Bush's preemption policy will bring. Many of the nation's top experts feel that North Korea is a more imminent threat than Saddam's Iraq was. They have a nuclear program, a million-man army, and missiles to deploy and export. In Crisis on the Korean Peninsula, Michael O'Hanlon, a Senior Fellow at Brooking and visiting lecturer at Princeton, and Mike Mochizuki, endowed chair in Japan-US Relations at G.W. University, not only examine this issue in detail but also offer a comprehensive blueprint for diffusing the crisis with North Korea. Their solution comes in the form of a grand bargain with North Korea. Accords could be negotiated step-by-step, however they need to be guided by a broad and ambitious vision that addresses not only the nuclear issue but also the conventional forces on the hyper-militarized peninsula and the ongoing decline of the North Korean economy.

Formulation and optimization of the connection preemption problem

In the literature, the connection preemption policy is proposed for the resource allocation method in the prioritized multi-class networks. However, the connection preemption problem that is defined in the literature does not consider the rerouting of the preempted connections. When some connections are preempted at a connection preemption event, a part of the preempted connections will be rerouted with their own preemption priorities. Therefore, each rerouted connection setup can also trigger new connection preemption events. In this work, we propose to extend the existing connection preemption problem to include the subsequent connection preemption events (triggered by new or rerouted connections). We call the new extended problem the extended connection preemption problem. We formulate the existing connection preemption problem and the extended connection preemption problem with their decision variables and cost function. This is the first work that formulates the connection preemption problem in terms of its cost function. And we also analyze how to optimize the cost function of the extended connection preemption problem.

Minimal energy fixed-priority scheduling for variable voltage processors

To fully exploit the benefit of variable voltage processors, voltage schedules must be designed in the context of work load requirement. In this paper, we present an approach to finding the least-energy voltage schedule for executing real-time jobs on such a processor according to a fixed priority, preemptive policy. The significance of our approach is that the theoretical limit in terms of energy saving for such systems is established, which can, thus, serve as the standard to evaluate the performance of various heuristic approaches. Two algorithms for deriving the optimal voltage schedule are provided. The first one explores fundamental properties of voltage schedules while the second one builds on the first one to further reduce the computational cost. Experimental results are shown to compare the results of this paper with previous ones.

Swiss Monetary Targeting 1974-1996: The Role of Internal Policy Analysis

After the switch to a floating exchange rate in 1973, the Swiss National Bank at first adopted annual monetary targets and in the 1990s shifted to a medium-term targeting strategy. In this paper I review the SNB's internal policy analysis, an aspect of Swiss monetary targeting that has received little attention in the existing literature. I show that money played a key role in setting monetary policy and in communicating the SNB's decisions to the public. Due to the adoption of monetary targets, the SNB was able to reduce the inflation trend to low levels. However, it was less successful in preserving price stability during business-cycle expansions because the monetary targets did not call for a sufficiently preemptive policy stance. At the end of 1999, the SNB abandoned monetary targeting in favour of an approach based on inflation forecasts.

Petri Nets with Discrete Phase Type Timing: A Bridge Between Stochastic and Functional Analysis

The addition of timing specification in Petri Nets (PN) has followed two main lines: intervals for functional analysis or stochastic durations for performance and dependability analysis. The present paper proposes a novel technique to analyze time or stochastic PN models based on discretization. This technique can be seen as a bridge between the world of functional analysis and the world of stochastic analysis. The proposed discretization technique is based on the definition of a new construct called Discrete Phase Type Timing - DPT that can represent a discrete cumulative density function (cdf) over a finite support (or a deterministic cdf) as well as an interval with non-deterministic choice (or a deterministic duration). In both views, a preemption policy can be assigned and a strong (the transition must fire when the interval expires) or a weak (the transition can fire when the interval expires) firing semantics. The paper introduces the DPT construct and shows how the expanded state space can be built up resorting to a compositional approach based on Kronecker algebra. With this technique a functional model can be quantified by adding probability measures over the firing intervals without modifying the (compositional) structure of the PN model.

Parallel and Sequential Job Scheduling in Heterogeneous Clusters: A Simulation Study Using Software in the Loop

The task of designing and optimizing job scheduling algorithms for heterogeneous computing environments requires the ability to predict scheduling performance. The complexity of heterogeneous scheduling issues re quires that the experiments devised to test a scheduling paradigm to be both flexible and extensive. Experimen tally determined models for the prediction of job execu tion times on both sequential and parallel computing resources are combined with the implementation of a novel scheduling algorithm and a software-in-the-loop (SWIL) simulation. The result is a potent design and analysis approach for job scheduling algorithms and implementations intended for heterogeneous environ ments. This paper develops the concepts, mechanisms, and results of a SWIL design and analysis approach. The merits of this approach are shown in four case stud ies, which determine overhead, scheduling performance, and the impact of preemption and priority policies. These case studies illustrate the contributions of this research in the form of a new parallel job scheduling algorithm for heterogeneous computing and in the novel application of SWIL simulation to the analysis of job scheduling systems.

Transient analysis of Age-MRSPNs by the method of supplementary variables

Abstract In order to assist the performance evaluation of complex stochastic models, automatic program tools were developed since a long time. Stochastic Petri nets (SPN) are applied as an effective model description language supported by several analytical and simulation tools. The analytical description and the numerical analysis of non-Markovian stochastic Petri net models gained attention recently. There are different theoretical approaches and numerical methods considered in recent works, such as the Markov renewal theory and the supplementary variable approach, but to find the most effective way of the analysis of such models is still an open research problem. The supplementary variable approach was successfully applied to the transient and steady state analysis of Markov regenerative stochastic Petri nets (MSRPN) when the preemption policy associated with the Petri net (PN) transitions was preemptive repeat different (prd), but it was not applicable with other preemption mechanisms. In this paper we extend the applicability of the supplementary variable approach to a class of MRSPNs in which preemptive resume (prs) policy can also be assigned to the transitions of the PN.

Call admission control and resource management issues for real-time VBR traffic in ATM-satellite networks

In this paper, a novel strategy for handling ATM connections of different natures, traffic profile, and QoS requirements in enhanced satellite systems is proposed. The conducted research starts from early studies on resource management in integrated terrestrial-satellite environments and focuses on a combined connection admission control/traffic resource management strategy for QoS provisioning to both real-time and non-real-time constant and variable bit rate sources. The resulting connection handling policy is dynamic, and effectively exploits the system bandwidth through the statistical multiplexing of traffic sources and a preemptive policy over the satellite air interface. The proposed strategy is suited for a generic integrated ATM-satellite system, although its effectiveness has been assessed on a multimedia satellite platform, based on the Ka-band payload and on-board processing.

Markov regenerative stochastic Petri nets with general execution policies: supplementary variable analysis and a prototype tool

Stochastic Petri nets (SPNs) with general firing time distributions are considered. Generally timed transitions can have general execution policies: the preemption policy may be preemptive repeat different (prd) or preemptive resume (prs) and the firing time distribution can be marking-dependent. A stationary analysis method covering all possible combinations is presented by means of supplementary variables. The method is implemented in a prototype tool SPNica which is based on Mathematica. The use of the general execution policies is illustrated by a WWW server model.

A modeling framework to implement preemption policies in non-Markovian SPNs

Petri nets represent a useful tool for performance, dependability, and performability analysis of complex systems. Their modeling power can be increased even more if nonexponentially distributed events are considered. However, the inclusion of nonexponential distributions destroys the memoryless property and requires to specify how the marking process is conditioned upon its past history. We consider, in particular, the class of stochastic Petri nets whose marking process can be mapped into a Markov regenerative process. An adequate mathematical framework is developed to deal with the considered class of Markov Regenerative Stochastic Petri Nets (MRSPN). A unified approach for the solution of MRSPNs where different preemption policies can be defined in the same model is presented. The solution is provided both in steady-state and in transient condition. An example concludes the paper.

Self-Fulfilling Debt Crises

We characterize the values of government debt and the debt's maturity structure under which financial crises brought on by a loss of confidence in the government can arise within a dynamic, stochastic general equilibrium model. We also characterize the optimal policy response of the government to the threat of such a crisis. We show that when the country's fundamentals place it inside the crisis zone, the government may be motivated to reduce its debt and exit the crisis zone because this leads to an economic boom and a reduction in the interest rate on the government's debt. We show that this reduction can be gradual if debt is high or the probability of a crisis is low. We also show that, while lengthening the maturity of the debt can shrink the crisis zone, credibility-inducing policies can have perverse effects. Financial crises brought on by a loss of confidence in the government can arise suddenly and threaten countries with huge losses. We analyse the conditions that make these crises possible and what policy makers should do in the face of this kind of risk. To address these issues, we examine optimal government policy in a dynamic, stochastic general equilibrium model in which self-fulfilling crises can arise. Because of the government's need to roll over its debt, a liquidity crunch induced by the inability to sell new debt can lead to a self-fulfilling default. We show that, if fundamentals like the level of the government's debt, its maturity structure, and the private capital stock, lie within a particular range (the crisis zone), then the probability of default is determined by the beliefs of market participants. We show that a government is motivated to reduce its debt and exit the crisis zone because doing so leads to an economic boom and a reduction in the interest rate on the government's debt. The distinguishing feature of this paper is that it examines optimal policy within an environment in which not only can crises occur in the first period, but crises can occur in subsequent periods with positive probability. This is important since we show that previously proposed policies that seek to avert a crisis by reacting contemporaneously, such as pegging the interest rate on the government debt or lengthening the maturity of the debt being sold once a crisis has started, are ineffectual in our model. Instead, it is only preemptive policies, which seek to remove the conditions that make future crises possible, that can be effective. To examine optimal debt policy, we construct a time-consistent equilibrium of our model with a (relatively) easy-to-characterize Markov structure in which a crisis can occur with a positive probability whenever the level and maturity structure of the government's debt and the capital stock are in the crisis zone. We show that within the crisis zone, the

Threshold-based interventions to optimize performance in preemptive priority queues

This paper studies a single-server priority queueing model in which preemptions are allowed during the early stages of service. Once enough service effort has been rendered, however, further preemptions are blocked. The threshold where the change occurs is either a proportion of the service requirement, or time-based. The Laplace–Stieltjes transform and mean of each class sojourn time are derived for a model which employs this hybrid preemption policy. Both preemptive resume and preemptive repeat service disciplines are considered. Numerical examples show that it is frequently the case that a good combination of preemptible and nonpreemptible service performs better than both the standard preemptive and nonpreemptive queues. In a number of these cases, the thresholds that optimize performance measures such as overall average sojourn time are determined.

Scheduling strategies and long-range dependence

Consider a single server queue with unit service rate fed by an arrival process of the following form: sessions arrive at the times of a Poisson process of rate \lambda, with each session lasting for an independent integer time \tau \geq 1, where P(\tau = k ) = p_k with p_k \sim \alpha k^{-(1 +\alpha)}L(k), where 1<\alpha<2 and L(\cdot) is a slowly varying function. Each session brings in work at unit rate while it is active. Thus the work brought in by each arrival is regularly varying, and, because 1 < \alpha < 2, the arrival process of work is long-range dependent. Assume that the stability condition \lambda E[\tau] < 1 holds. By simple arguments we show that for any stationary nonpreemptive service policy at the queue, the stationary sojourn time of a typical session must stochastically dominate a regularly varying random variable having infinite means this is true even if the duration of a session is known at the time it arrives. On the other hand, we show that there exist causal stationary preemptive policies, which do not need knowledge of the session durations at the time of arrival, for which the stationary sojourn time of a typical session is stochastically dominated by a regularly varying random variable having finite mean. These results indicate that scheduling policies can have a significant influence on the extent to which long-range dependence in the arrivals influences the performance of communication networks.

Two Real-Time Flow Controls in Wormhole Networks

In this paper, we study wormhole routed networks and envision their suitability for real-time traffic in a priority-driven paradigm. A traditional blocking flow control in wormhole routing may lead to a priority inversion in the sense that high priority packets are blocked by low priority packets for unlimited time. The priority inversion causes the frequent deadline missing even at a low network load. This paper therefore proposes two preemptive flow control policies where high priority packets can preempt network resources held by low priority packets. As a result, the proposed flow controls can resolve the priority inversion. Our simulations show that preemptive flow controls significantly reduce deadline miss ratios for various real-time traffic configurations.