Appointment scheduling at a multidisciplinary outpatient clinic using stochastic programming

The purpose of this paper is to investigate the problem of constructing an appointment template for scheduling patients at a specific type of multidisciplinary outpatient clinic called an integrated practice unit (IPU). The focus is on developing and solving a stochastic optimization model for a back pain IPU in the face of random arrivals, an uncertain patient mix, and variable service times. The deterministic version of the problem is modeled as a mixed integer program with the objective of minimizing a weighted combination of clinic closing time (duration) and total patient waiting time (length of stay). A two‐stage stochastic program is then derived to account for the randomness and the sequential nature of the decisions. Although it was not possible to solve the two‐stage problem for even a limited number of scenarios, the wait‐and‐see (WS) problem was sufficiently tractable to provide a lower bound on the stochastic solution. The introduction of valid inequalities, limiting indices, and the use of special ordered sets helped to speed up the computations. A greedy heuristic was also developed to obtain solutions much more quickly. Out of practical considerations, it was necessary to develop appointment templates with time slots at fixed intervals, which are not available from the WS solution. The first to be derived was the expected value (EV) template that is used to find the expected value of the EV solution (EEV). This solution provides an upper bound on the objective function value of the two‐stage stochastic program. The average gap between the EEV and WS solutions was 18%. Results from extensive computational testing are presented for the EV template and for our adaptation of three other templates found in the literature. Depending on the relative importance of the two objective function metrics, the results demonstrate the trade‐off that exists between them. For the templates investigated, the “closing time” ranged from an average of 235 to 275 minutes for a 300‐minute session, while the corresponding “total patient time in clinic” ranged from 80 to 71 minutes.     

Cutting,Running, or Otherwise? The US Decision to withdraw from Somalia

Although President Bill Clinton made the decision to withdraw U.S. combat troops from Somalia within three days of the disastrous Mogadishu raid that resulted in the deaths of 18 U.S. servicemen, casualties were not the only consideration. Many other factors were at play. Waning Congressional and public enthusiasm for a new “nation-building” mandate, the strategic insignificance of Somalia in the post-Cold War era, and a host of other foreign policy issues had been eroding U.S. support for the mission in Somalia for months. The “Black Hawk Down” incident merely accelerated the final rupture in public and Congressional support, forcing the president to bring the troops home. It was not a simple case of casualty aversion.     

‘Like going to a fiesta’ – the role of female fighters in Colombia's FARC-EP

Traditionally women and children have been seen as victims rather than protagonists in conflict. However, since the 1970s, women and children have assumed an active role as combatants in Colombian insurgencies. This is especially true of the FARC-EP, which integrates women into its political and military structure in ways that give them a sense of participation, accomplishment and satisfaction. Without their contributions, including sexual services, the FARC could probably not survive. However, despite their favourable experiences, many women ultimately become disillusioned with the FARC's masculine culture and value system that fails to accommodate their aspirations as women.