Forward positioning and consolidation of strategic inventories

The forward positioning of strategic inventory in the supply chain has an impact on transportation times and is important for sensitive demand profiles. Consolidation of stocks creates pooling effects and minimizes costs. This study analyzes a current military case where forward consolidation of equipment is considered using optimization, and payback periods are calculated for the cost of consolidating inventory at one of six locations. Results indicate that forward positioning and consolidation reduces time and cost, and also creates savings in reverse logistics flows. The study has implications for geographically diverse supply chains such as humanitarian aid and emergency response operations

Analytical techniques and the Air Force logistics readiness officer

The accelerated globalization of logistics activities over the last several decades has spurred a rapid expansion of port facilities all cross the world. However, the recent slowdown of international trade, coupled with a global financial crisis, has created an on-going glut of international port facilities throughout the world. Although the abundance of port facilities provides more transshipment options for carriers and shippers, it makes the port selection decision more complex and difficult. To cope with this new set of challenges, this paper proposes a hybrid data envelopment analysis (DEA)/ analytic hierarchy process (AHP) model that is designed to identify factors specifically influencing transshipment port selection, evaluates the extent of influence of those factors on a transshipment port selection decision, and then determines the most critical ones among various factors. To illustrate the usefulness of the proposed hybrid DEA/AHP model, major container hub ports in Far-East Asia were analyzed

A simple flip of an obstetrics clerkship lecture focusing on interactive learning

Abstract Objective: To determine the value of interactive learning after a low-tech flip of a traditional lecture during an obstetrics and gynecology clerkship. Design: All third-year medical students completed a flipped learning experience between May 2014 and April 2016. Central to the change was replacement of a mid-clerkship lecture ("late term and prolonged gestation") with interactive learning at seven stations by student pairs (one each on separate obstetrics and gynecology services). Before class, students electronically received a handout that described learning objectives, subject background, and interactive stations. The stations featured manipulative models, instruments, data, and images involving prenatal care, fetal growth and testing, and labor and delivery decision-making. Results: The flipped model was easily executed with proper preparation. The 178 consecutive students completed the two mandated surveys. The median score given by students about the same instructor's effectiveness increased from 4.0 (previous two years) to 4.4 (on a 5-point scale). Compared with traditional lectures by other clerkship faculty, the flipped classroom was judged by students to be easier for understanding and more interactive. Students perceived being more responsible for learning with better recall and application to practice. Conclusions: A low-tech approach to the flipped classroom was easily executed with favorable responses from students about interactive learning

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

Sanded Wheel–Rail Contacts: Experiments on Sand Crushing Behaviour

In railway operation, the sanding process is used to overcome low adhesion conditions in the wheel–rail contact. In the literature, previously conducted research has been experimental, e.g., measuring adhesion coefficients (ACs) under different contact conditions (dry, wet, …) or applying different sands. Under dry conditions, sanding can reduce measured ACs, while under wet conditions different types of rail sand can leave ACs unchanged or increase adhesion. Despite active research, the physical mechanisms causing the change in ACs under sanded conditions are still poorly understood. A possible remedy is the development of advanced models of sanding including local effects. As a basis for such a model, this study presents experimental results concerning single grain crushing behaviour of two types of rail sand under dry and wet contact conditions. Firstly, initial breakage behaviour is investigated with focus on the particle fragments’ size and spread as only fragments within the running band are available to influence the AC during roll-over. Secondly, single grain crushing tests are conducted under realistic wheel–rail load showing the formation of solidified clusters of sand fragments, as well as their size and thickness. This information is important for understanding mechanisms and for future physics-based modelling of the sanding process in wheel–rail contacts