Demand forecasting by temporal aggregation

Demand forecasting performance is subject to the uncertainty underlying the time series an organization is dealing with. There are many approaches that may be used to reduce uncertainty and thus to improve forecasting performance. One intuitively appealing such approach is to aggregate demand in lower‐frequency “time buckets.” The approach under concern is termed to as temporal aggregation, and in this article, we investigate its impact on forecasting performance. We assume that the nonaggregated demand follows either a moving average process of order one or a first‐order autoregressive process and a single exponential smoothing (SES) procedure is used to forecast demand. These demand processes are often encountered in practice and SES is one of the standard estimators used in industry. Theoretical mean‐squared error expressions are derived for the aggregated and nonaggregated demand to contrast the relevant forecasting performances. The theoretical analysis is supported by an extensive numerical investigation and experimentation with an empirical dataset. The results indicate that performance improvements achieved through the aggregation approach are a function of the aggregation level, the smoothing constant, and the process parameters. Valuable insights are offered to practitioners and the article closes with an agenda for further research in this area. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 60: 479–498, 2013     

Feeding Bread to the Luddites: The Radical Fundamentalist Islamic Revolution in Guerrilla Warfare

This study examines the war that the United States has waged since September 2001 as a global counterinsurgency. Placing the war against al-Qaeda and its allied groups and organizations in the context of a global insurgency also presents implications for doctrine, interagency coordination and military cultural change. The first part of the article offers a distilled analysis of al-Qaeda and its associated networks. The second section examines the US military in the context of the Western way of war, with the attendant military-cultural impediments to adapting to an enemy who embraces a very different approach to war. The third section aims to define and describe the nature of the war that America and its coalition partners are trying to wage. The concluding section offers the most value as it refines and distills the work of several international security and military thinkers to arrive at some imperatives for successfully prosecuting this type of war to its end.     

The Insurgency Environment in Northeast India

The northeast states of India have faced a series of insurgencies almost since independence. Most insurgent groups have been based on the competing demands of various ethnic groups, with conflicts not only between the insurgents and the government, but also between groups. The combination of anti-government and intercommunal violence shows little sign of ending. Although the Indian government has made progress in dealing with the largest groups, the continued existence of several dozen insurgent movements represents a significant security threat to internal stability in India.     

Special Air Service Books to Choose From

Barry Davies, Joining the SAS: How to Get In and What It's Like.Miami: Lewis International Inc., 1998. Pp.214, photos, index. $22.95. ISBN 0–966771–4–2.

Peter McAleese and John Avery, McAleese's Fighting Manual: The Definitive Soldier's Handbook.London: Orion, 1998. Pp.179, illus. £18.95. ISBN 0–75280–063–9.

Steve Crawford et al.The SAS Encyclopedia: The Definitive Guide to the World's Crack Regiment.Miami: Lewis International Inc., 1998. Pp.288, photos, maps, index. $29.95. ISBN 0–9666771–0–2.

Barry Davies et al.The Complete Encyclopedia of the SAS.London: Virgin Publishing Ltd, 1998. Pp.288, photos, maps, no index. $39.95. ISBN 1–85227–707–6.     

A Clash of Wills: Hizballah's Psychological Campaign Against Israel in South Lebanon

This article analyzes Hizballah's war against Israel in south Lebanon as a psychological contest where public opinion, perception, and persuasion were the real determinants of victory. Hizballah successfully mobilized popular support for its war by communicating nationalist and religious themes to different sectarian groups in Lebanon. At the same time, it used classic guerrilla warfare as a carefully calibrated psychological tool to erode the morale of Israeli forces, their Lebanese allies, and the Israeli public's support for the war. Hizballah's sophisticated media capability, particularly combat video footage aired on its satellite TV station and the Internet, played a critical role in amplifying the effects of its attrition campaign. By orchestrating information-age media and guerrilla tactics, this strategy has important implications for the future of irregular warfare.     

Comparison between constant‐stress and step‐stress accelerated life tests under Time Constraint

By running life tests at higher stress levels than normal operating conditions, accelerated life testing (ALT) quickly yields information on the lifetime distribution of a test unit. The lifetime at the design stress is then estimated through extrapolation using a regression model. In constant‐stress testing, a unit is tested at a fixed stress level until failure or the termination time point of test, whereas step‐stress testing allows the experimenter to gradually increase the stress levels at some prefixed time points during the test. In this work, the optimal k‐level constant‐stress and step‐stress ALTs are compared for the exponential failure data under complete sampling and Type‐I censoring. The objective is to quantify the advantage of using the step‐stress testing relative to the constant‐stress one. Assuming a log‐linear life–stress relationship with the cumulative exposure model for the effect of changing stress in step‐stress testing, the optimal design points are determined under C/D/A‐optimality criteria. The efficiency of step‐stress testing to constant‐stress one is then discussed in terms of the ratio of optimal objective functions based on the information matrix. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 00: 000–000, 2013     

List of contributors

This article examines Edward Lansdale's return to South Vietnam during the Johnson administration. Lansdale offered a persuasive critique of the mistakes the American policy in Vietnam, but his potential influence was severely limited by a combination of bureaucratic infighting in Saigon and a general indifference to the political aspects of the conflict in Washington. While Lansdale was unable to signiflcantly influence the policies of the Johnson administration, his experience in Saigon during 1965–68 offers historians a unique perspective on many facets of American and South Vietnamese policymaking during a crucial period of the Vietnam War.