Territorial contestation and repressive violence in civil war

This study models the structural sources of variation in the use of selective (discriminate) repression within 89 civil wars fought between 1981 and 2005. The severity of repressive violence is modeled as a function of the amount of territory being contested by the insurgents. This idea is operationalized using measures of the location, size, and density of insurgency violence. The analysis finds evidence that the repressive behavior of both governments and rebel groups is linked to conflict geography. Governments violate physical integrity rights more frequently and kill more civilians the greater the overall amount of territory under contestation. Rebels kill more civilians in highly dispersed insurgencies that lack a clear epicenter.     

Performance measurement in military operations: information versus incentives

We explore the impact of strategic assessment efforts on military organizations at war. To do so, we construct a model to explore the impact of a principal’s choice among imperfect performance metrics for a military operation. In doing so, the principal must consider both the incentivizing and informational properties of the metric. We show the conditions under which uncertainty regarding the nature of the agent, as well as uncertainty regarding the operational environment, drives a metric choice that induces pathological behavior from the agent. More specifically, a poor metric choice can create an overly optimistic assessment and end up prolonging the conflict. We illustrate the model’s insights in the cases of World War II and the Vietnam War.     

ADVANCED US CONVENTIONAL WEAPONS AND NUCLEAR DISARMAMENT

The Obama administration has made a great effort to increase the role of advanced conventional weaponry in US national security thinking and practice, in part to help reinvigorate the global nuclear disarmament agenda by reducing the role played by nuclear weapons in the US defense posture. However, such a strategy is fundamentally flawed because increases in US conventional superiority will exacerbate US relative strength vis-à-vis other powers, and therefore make the prospect of a nuclear weapon-free world seem less attractive to Washington's current and potential nuclear rivals. Consequently, it is highly likely that the impact of efforts to increase US advanced conventional superiority through ballistic missile defense and a conventional “prompt global strike” program will ensure that the Obama administration is adopting a pathway to nuclear abolition on which it is the sole traveler for the foreseeable future.     

The asymptotic joint distribution of the state occupancy times in an alternating renewal process

An alternating renewal process starts at time zero and visits states 1,2,…,r, 1,2, …,r 1,2, …,r, … in sucession. The time spent in state i during any cycle has cumulative distribution function F_i, and the sojourn times in each state are mutually independent, positive and nondegenerate random variables. In the fixed time interval [0,T], let U_i(T) denote the total amount of time spent in state i. In this note, a central limit theorem is proved for the random vector (U_i(T), 1 ≤ i ≤ r) (properly normed and centered) as T → ∞.     

A (Q,R) inventory model with lost sales and erlang-distributed lead times

The exact expression is derived for the average stationary cost of a (Q,R) inventory system with lost sales, unit Poisson demands, Erlang-distributed lead times, fixed order cost, fixed cost per unit lost sale, linear holding cost per unit time, and a maximum of one order outstanding. Explicit expressions for the state probabilities and a fast method of calculating them are obtained for the case of Q greater than R. Exponential lead times are analyzed as a special case. A simple cyclic coordinate search procedure is used to locate the minimum cost policy. Examples of the effect of lead time variability on costs are given.     

Estimating a survival curve when new is better than used in expectation

Let X be a positive random variable. The distribution F of X is said to be “new better than used in expectation,” or “NBUE,” if E(X) ⩾ E(X – t|X > t) for all t ⩾ 0. Suppose X₁, …, X_n, is a random sample from an NBUE distribution F. The problem of estimating F by a distribution which is itself NBUE is considered. The estimator G_n, defined as the NBUE distribution supported on the sample which minimizes the (sup norm) distance between the NBUE class and the empirical distribution function, is studied. The strong uniform consistency of G_n, is proven, and a numerical algorithm for obtaining G_n, is given. Our approach is applied to provide an estimate of the distribution of lifetime following the diagnosis of chronic granulocytic leukemia based on data from a National Cancer Institute study.     

Periodic replacement when minimal repair costs vary with time

A policy of periodic replacement with minimal repair at failure is considered for a complex system. Under such a policy the system is replaced at multiples of some period T while minimal repair is performed at any intervening system failures. The cost of a minimal repair to the system is assumed to be a nonde-creasing function of its age. A simple expression is derived for the expected minimal repair cost in an interval in terms of the cost function and the failure rate of the system. Necessary and sufficient conditions for the existence of an optimal replacement interval are exhibited in the case where the system life distribution is strictly increasing failure rate (IFR).