A characterization of optimal base‐stock levels for a multistage serial supply chain

In this article, we present a multistage model to optimize inventory control decisions under stochastic demand and continuous review. We first formulate the general problem for continuous stages and use a decomposition solution approach: since it is never optimal to let orders cross, the general problem can be broken into a set of single‐unit subproblems that can be solved in a sequential fashion. These subproblems are optimal control problems for which a differential equation must be solved. This can be done easily by recursively identifying coefficients and performing a line search. The methodology is then extended to a discrete number of stages and allows us to compute the optimal solution in an efficient manner, with a competitive complexity. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 32–46, 2016     

Technical note: Characterization of binomial semivalues through delegation games

Semivalues are allocation rules for cooperative games that assign to each player in a given game a weighted sum of his marginal contributions to all coalitions he belongs to, where the weighting coefficients depend only on the coalition size. Binomial semivalues are a special class of semivalues whose weighting coefficients are obtained by means of a unique parameter. In particular, the Banzhaf value is a binomial semivalue. In this article, we provide an axiomatic characterization for each binomial semivalue. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Why do they serve? Changes and differences in motives of Danish soldiers deployed to peace-keeping and peace-enforcing missions

This paper investigates what motivates young people to volunteer for peace-keeping or peace-enforcing missions and how their motives change between pre- and post-deployment. Data include information about social and military background, and motives for more than 600 soldiers, 444 of whom answered the survey both before and after deployment. Soldiers are deployed to different missions under the same circumstances. To conceptualize motives among soldiers, we use factor analysis and find three factors: challenge, self-benefit, and fidelity. Challenge represents an occupational orientation; fidelity, an institutional orientation; and self-benefit, a desire for adventure. Exploiting the within-subject design of our data, we find that pre- and post-deployment motives vary significantly according to the type of mission and soldiers’ previous experiences (first-timers or experienced soldiers). Our results suggest that after the mission, peace-keepers are generally more disappointed than peace-enforcers. Our results also show that self-benefit motives are important for younger soldiers with only a high school education, and that this group usually serves as peace-enforcers during their gap year.     

Crime facilitation purposes of social networking sites: A review and analysis of the ‘cyberbanging’ phenomenon

There have been growing claims in media circles and law-enforcement settings that street gangs and criminal groups are turning to Internet-based social networking sites for various reasons ranging from the showcasing of their images and exploits to the suspected recruitment of members. The present study investigates whether such a trend is, in fact, in place. The presence of street gangs on these Internet sites is referred to as cyberbanging. While there is some anecdotal evidence suggesting that gangs are turning to social networking sites, there is little available research on exactly how street gangs and criminal groups use the Internet. Our main argument is that gang culture is in many ways an individualized phenomenon and this feature ties in directly with recent assessments of the Internet as a setting that is governed by a process of networked individualism. This theoretical link between the individualized gang setting and the presence of gang members on social networking sites helps us understand why recruitment is improbable even in a context where people are openly diffusing their image and exploits to a growing number of Internet users. The empirical segment of this research adds to this general outlook. Based on a keyword search of over 50 street gang names, the three main social networking sites (Twitter, Facebook, and MySpace) were monitored for street gang presence. Results illustrate that gang presence on social networking sites is linked primarily to promoting a general gang or street culture through individual displays. In regard to the visitors to such sites, there is no evidence that they are being tricked or manipulated in any way. They are, however, showing their curiosity in regard to such groups and, for those who share their comments and opinions, signs of support are evident. Thus, whereas criminal gangs are not proactively using the Internet to convert anyone into being gang members, social networking sites are creating a new venue for people who share or are sensitive to the values underlying street gang lifestyle to come together. These sites essentially create a new convergence setting for gang members to interact with a wider number of people who would probably never have been exposed to their lifestyles and exploits through physical interactions. The study's conclusion extends these findings toward further research in this area, as well as outlining the more relevant implications for law-enforcement monitoring of this growing phenomenon.     

COUNTRY SURVEY XX: DEFENCE SPENDING AND PEACEKEEPING IN URUGUAY

Uruguay is a country with a very unusual profile, since it has just 3.4 million inhabitants but is among the top ten troop contributors to the UN PKO (Peace Keeping Operations) and is the first contributor per capita. In 2002 and 2003 it was the seventh troop contributor to the UN, and by the end of 2005 it was eighth in the UN ranking. Uruguay has never had any imminent external threat to its security after its independence in 1828, and it has had no internal threat since the end of the urban guerrillas’ actions in the 1970s. The country has no defence industry, and has always had an all‐volunteer military service, which presently involves almost 1% of the total population, and about 2% of the labour force. The empirical evidence presented in this paper shows that, in the past decades, Uruguayan defence spending has been influenced mainly by internal factors, most of them of an economic nature. The high participation in PKO has not increased military expenditure and it has produced a positive impact on the country’s economy.     

Dielectric constant predictions for energetic materials using quantum calculations

The dielectric constant (DC) is one of the key properties for detection of threat materials such as Improvised Explosive Devices (IEDs). In the present paper, the density functional theory (DFT) as well as ab-initio approaches are used to explore effective methods to predict dielectric constants of a series of 12 energetic materials (EMs) for which experimental data needed to experimentally determine the dielectric constant (refractive indices) are available. These include military grades energetic materials, nitro and peroxide compounds, and the widely used nitroglycerin. Ab-initio and DFT calculations are conducted. In order to calculate dielectric constant values of materials, potential DFT functional combined with basis sets are considered for testing. Accuracy of the calculations are compared to experimental data listed in the scientific literature, and time required for calculations are both evaluated and discussed. The best functional/basis set combinations among those tested are CAM-B3LYP and AUG-cc-pVDZm, which provide great results, with accuracy deviations below 5% when calculated results are compared to experimental data.     

Dynamic evacuation routes for personnel on a naval ship

We propose a dynamic escape route system for emergency evacuation of a naval ship. The system employs signals that adapt to the causative contingency and the crew's physical distribution about the ship. A mixed‐integer nonlinear programming model, with underlying network structure, optimizes the evacuation process. The network's nodes represent compartments, closures (e.g., doors and hatches) and intersections, while arcs represent various types of passageways. The objective function integrates two potentially conflicting factors: average evacuation time and the watertight and airtight integrity of the ship after evacuation. A heuristic solves the model approximately using a sequence of mixed‐integer linear approximating problems. Using data for a Spanish frigate, with standard static routes specified by the ship's designers, computational tests show that the dynamic system can reduce average evacuation times, nearly 23%, and can improve a combined measure of ship integrity by up to 50%. In addition, plausible design changes to the frigate yield further, substantial improvements. Published 2008 Wiley Periodicals, Inc. Naval Research Logistics 2008