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We formulate exact expressions for the expected values of selected estimators of the variance parameter (that is, the sum of covariances at all lags) of a steady‐state simulation output process. Given in terms of the autocovariance function of the process, these expressions are derived for variance estimators based on the simulation analysis methods of nonoverlapping batch means, overlapping batch means, and standardized time series. Comparing estimator performance in a first‐order autoregressive process and the M/M/1 queue‐waiting‐time process, we find that certain standardized time series estimators outperform their competitors as the sample size becomes large. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007  相似文献   
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We consider a manufacturer (i.e., a capacitated supplier) that produces to stock and has two classes of customers. The primary customer places orders at regular intervals of time for a random quantity, while the secondary customers request a single item at random times. At a predetermined time the manufacturer receives advance demand information regarding the order size of the primary customer. If the manufacturer is not able to fill the primary customer's demand, there is a penalty. On the other hand, serving the secondary customers results in additional profit; however, the manufacturer can refuse to serve the secondary customers in order to reserve inventory for the primary customer. We characterize the manufacturer's optimal production and stock reservation policies that maximize the manufacturer's discounted profit and the average profit per unit time. We show that these policies are threshold‐type policies, and these thresholds are monotone with respect to the primary customer's order size. Using a numerical study we provide insights into how the value of information is affected by the relative demand size of the primary and secondary customers. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007  相似文献   
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What do UK policymakers mean when they say that Britain’s strategic environment is returning to “multipolarity”? In realist international theory, polarity is a specific causal concept; the number of powers capable of balancing even the most capable other state(s) in the international system (“poles”) is taken to determine the system’s stability. Does the post-2017 appearance of polarity references in British security policy documents therefore reflect some unexpected UK renaissance of realist thought? Or is something else going on, as recent work by Ben Zala suggests? This article will demonstrate that, while UK official usage of the “multip–” word has indeed flourished recently, the term is actually being used in a more elastic, less bounded way than realism prescribes in order to generate other kinds of political effect. Specifically, “polarity” (and its “multi-” prefix) is used to characterise the behaviour of those major states that oppose Western-preferred international order, to elide Britain’s own relative power/status tensions, and to capture an expansive laundry-list of perceived international dangers. The article then discusses five ways in which a shift in polarity could negatively affect Britain; important consequences that merit preparatory contemplation, yet that an imprecise, catch-all understanding of “multipolarity” too readily obscures.  相似文献   
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ABSTRACT

Despite its portrayal as something new, the concept of the ‘gray zone’ is not novel. It was the Cold War battleground in which the USA and the Soviet Union waged rival unconventional campaigns, and it was there that the newly formed Central Intelligence Agency (CIA) was given responsibility for operating. This was not the organization’s original purpose, but Cold War exigencies forced Washington to improvise and build an organization with unique capabilities. These early years shaped the CIA’s operations directorate, creating two distinct cultures within the larger agency, one focused on intelligence collection and the other focused on covert action.  相似文献   
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ABSTRACT

Cyber attack against Critical National Infrastructure is a developing capability in state arsenals. The onset of this new instrument in national security has implications for conflict thresholds and military ethics. To serve as a legitimate tool of policy, cyber attack must operate in accordance with moral concerns. To test the viability of cyber attack, this paper provides a new perspective on cyber ethics. Cyber attack is tested against the criteria of the common good. This involves identifying the four core components of the common good from a conflict perspective: respect for the person; social wellbeing; peace and security; and solidarity. The fate of these components is assessed in relation to the six key characteristics of cyber attack from a moral standpoint: security; the role or absence of violence; discrimination; proportionality; cyberharm; and the threshold of conflict. It is concluded that the common good must be incorporated into developing state cyber strategies.  相似文献   
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ABSTRACT

Since 9/11, the United States has achieved notable gains against al Qaeda, and also Islamic State (IS), all while avoiding another mass-casualty attack at home. Yet, institutionally, culturally, and in its capabilities, the US government remains seriously ill-equipped for the task of countering irregular threats. Partly as a result, Islamist extremism shows no sign of being defeated, having instead metastasized since 9/11 and spread. Why, given the importance accorded to counterterrorism, has the US approach remained inadequate? What is impeding more fundamental reforms? The article evaluates the United States’ way of irregular warfare: its troubled engagement with counterinsurgency and its problematic search for lower cost and lower risk ways of combating terrorism. It suggests needed reforms but acknowledges also the unlikelihood of change.  相似文献   
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