Cost-based due-date assignment with the use of classical and neural-network approaches

Traditional methods of due-date assignment presented in the literature and used in practice generally assume cost-of-earliness and cost-of-tardiness functions that may bear little resemblance to true costs. For example, practitioners using ordinary least-squares (OLS) regression implicitly minimize a quadratic cost function symmetric about the due date, thereby assigning equal second-order costs to early completion and tardy behavior. In this article the consequences of such assumptions are pointed out, and a cost-based assignment scheme is suggested whereby the cost of early completion may differ in form and/or degree from the cost of tardiness. Two classical approaches (OLS regression and mathematical programming) as well as a neural-network methodology for solving this problem are developed and compared on three hypothetical shops using simulation techniques. It is found for the cases considered that: (a) implicitly ignoring cost-based assignments can be very costly; (b) simpler regression-based rules cited in the literature are very poor cost performers; (c) if the earliness and tardiness cost functions are both linear, linear programming and neural networks are the methodologies of choice; and (d) if the form of the earliness cost function differs from that of the tardiness cost function, neural networks are statistically superior performers. Finally, it is noted that neural networks can be used for a wide range of cost functions, whereas the other methodologies are significantly more restricted. © 1997 John Wiley & Sons, Inc.     

Does Terrorism Increase after a Natural Disaster? An Analysis based upon Property Damage

Does an emergency such as a natural disaster lead to a surge of terrorism? This paper contributes to the emerging literature on this issue. We consider the experience of 129 countries during the period 1998–2012 to determine the effect of a natural disaster on both domestic as well as transnational terrorism. We also control for endogeneity using expenditure on health care and land area in a country as instruments. In contrast to the existing literature, we measure the extent of terrorism by the value of property damage. The results indicate that after natural disasters, (a) transnational terrorism increases with a lag, and (b) a statistically significant impact on domestic terrorism is not observed.     

The effects of information on a queue with balking and phase‐type service times

This article generalizes the models in Guo and Zipkin, who focus on exponential service times, to systems with phase‐type service times. Each arriving customer decides whether to stay or balk based on his expected waiting cost, conditional on the information provided. We show how to compute the throughput and customers' average utility in each case. We then obtain some analytical and numerical results to assess the effect of more or less information. We also show that service‐time variability degrades the system's performance. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Changing the paradigm: Simulation,now a method of first resort

Decades ago, simulation was famously characterized as a “method of last resort,” to which analysts should turn only “when all else fails.” In those intervening decades, the technologies supporting simulation—computing hardware, simulation‐modeling paradigms, simulation software, design‐and‐analysis methods—have all advanced dramatically. We offer an updated view that simulation is now a very appealing option for modeling and analysis. When applied properly, simulation can provide fully as much insight, with as much precision as desired, as can exact analytical methods that are based on more restrictive assumptions. The fundamental advantage of simulation is that it can tolerate far less restrictive modeling assumptions, leading to an underlying model that is more reflective of reality and thus more valid, leading to better decisions. Published 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 293–303, 2015     

Damage accumulation and probability of kill for gun and target engagements

Determination of the gunfire probability of kill against a target requires two parameters to be taken into consideration: the likelihood of hitting the target (susceptibility) and the conditional probability of kill given a hit (vulnerability). Two commonly used methods for calculating the latter probability are (1) treating each hit upon the target independently, and (2) setting an exact number of hits to obtain a target kill. Each of these methods contains an implicit assumption about the probability distribution of the number of hits‐to‐kill. Method (1) assumes that the most likely kill scenario occurs with exactly one hit, whereas (2) implies that achieving a precise number of hits always results in a kill. These methods can produce significant differences in the predicted gun effectiveness, even if the mean number of hits‐to‐kill for each distribution is the same. We therefore introduce a new modeling approach with a more general distribution for the number of hits‐to‐kill. The approach is configurable to various classes of damage mechanism and is able to match both methods (1) and (2) with a suitable choice of parameter. We use this new approach to explore the influence of various damage accumulation models on the predicted effectiveness of weapon‐target engagements.     

The next step in Somalia: exploiting victory,post-Mogadishu

From 2006 to 2011, al-Qaeda's East African proxy, al-Shabaab, served as the de facto ruling party of Somalia despite the efforts of the internationally recognised Transitional Federal Government (TFG). During these five years, a violent struggle between al-Shabaab and the peacekeeping force of the African Union Mission in Somalia (AMISOM) resulted in thousands of dead civilians, hundreds of thousands of internally displaced persons and a strategic environment inhospitable to reconciliation, recovery or development. By 2012, AMISOM was able to break the deadlock and force al-Shabaab from Mogadishu and Kismayo. In order to continue the momentum, the African Union and other partner nations must support the TFG in neutralising al-Shabaab throughout Somalia and providing good governance to its constituents. Al-Shabaab's revenue streams must be shut down and its offensive capability must be degraded while the strategic environment is shaped to ensure that conditions conducive to a revival do not exist. Failure to do so will likely see Somalia continuing to produce Islamist extremists and pirates to menace international maritime traffic in the western Indian Ocean, destabilise East Africa and adversely impact millions.     

Aerial intelligence during the Algerian war

Aviation had a highly significant role in supporting French military operations in Algeria. This was particularly true of aerial reconnaissance and intelligence gathering. Initially, however, the Air Force effort was handicapped by inappropriate approaches, too few army/air liaison officers and scepticism among army officers aware of the difficulties of earlier air operations against an insurgency in Indochina (1946–54). It also lacked sufficient suitable aircraft types. Gradually, improved aircraft and photographic techniques permitted systematic and detailed aerial mapping and intelligence work, as well as rapid provision of close air support during ground battles. Better integration of air and ground forces, along with more coordinated command and control, arrived from 1959 onwards when an air force general, Maurice Challe, became inter-service commander-in-chief in Algeria. This permitted an authentic and mostly effective combined-airms and joint service approach to the locating, tracking, engagement and destruction of Algerian nationalist bands.     

Encircled by enemies: Stalin's Perceptions of the capitalist world, 1918 – 1941

The article examines Stalin's intelligence on the capitalist world, including materials from military archives, diplomatic archives, and Stalin's private papers. It explores how these materials were collected, interpreted and shaped by Stalin's prejudices. It concludes that, from the end of the Civil War to the Nazi invasion, Stalin and the Soviet leadership believed that the Soviet Union was under a nearly constant threat of invasion from shifting coalitions of capitalist powers. No such threat existed until the late 1930s, but Stalin's perceptions have important implications for our understanding of Soviet foreign and domestic politics in the interwar period.