Multitasking and microtasking experience on the NA S Cray-2 and ACF Cray X-MP

The fast Fourier transform (FFT) kernel of the NAS benchmark program has been utilized to experiment with the multitasking library on the Cray-2 and Cray X-MP/48, and microtasking directives on the Cray X-MP. Some performance figures are shown, and the state of multitasking software is described

POST II Trajectory Animation Tool Using MATLAB, V1.0

A trajectory animation tool has been developed for accurately depicting position and the attitude of the bodies in flight. The movies generated from This MATLAB based tool serve as an engineering analysis aid to gain further understanding into the dynamic behavior of bodies in flight. This tool has been designed to interface with the output generated from POST II simulations, and is able to animate a single as well as multiple vehicles in flight

Effectiveness of combined magnetic field bone growth stimulation on lumbar spinal fusion outcomes: a single center retrospective analysis comparing combined magnetic field to no-stimulation

Background: The objective of this retrospective study was to assess the effect of combined magnetic field (CMF) bone growth stimulation on lumbar fusion outcomes, as compared to no-stimulation.Methods: This study reviewed fusion efficacy of a consecutive cohort of 652 patients who underwent lumbar fusion surgery at our institution between 2001 and 2018.  Fusion status was determined via radiographic analysis, with four surgeons contributing data to this study. The minimum patient follow-up time was 6 months. Previously identified risk factors (i.e. smoking status) were also collected. Statistical analysis was performed using cross-tabulation tests with chi-square analyses, one-way ANOVA’s, and Tukey’s range tests. 53% (343/652) of patients had undergone adjuvant treatment with CMF stimulation.Results: Patients treated with CMF stimulation had significantly greater fusion success of 97% compared to no stimulation at 62% (p<0.00001). Further, it was observed that smokers had a significantly higher fusion rate with CMF treatment than without electrical stimulation (94% vs 61%, p=0.000032).Conclusions: Additional studies to evaluate the effectiveness of CMF treatment in patients with risk factors are warranted

Mars Exploration Rover Heat Shield Recontact Analysis

The twin Mars Exploration Rover missions landed successfully on Mars surface in January of 2004. Both missions used a parachute system to slow the rover s descent rate from supersonic to subsonic speeds. Shortly after parachute deployment, the heat shield, which protected the rover during the hypersonic entry phase of the mission, was jettisoned using push-off springs. Mission designers were concerned about the heat shield recontacting the lander after separation, so a separation analysis was conducted to quantify risks. This analysis was used to choose a proper heat shield ballast mass to ensure successful separation with low probability of recontact. This paper presents the details of such an analysis, its assumptions, and the results. During both landings, the radar was able to lock on to the heat shield, measuring its distance, as it descended away from the lander. This data is presented and is used to validate the heat shield separation/recontact analysis

Ground Contact Model for Mars Science Laboratory Mission Simulations

The Program to Optimize Simulated Trajectories II (POST 2) has been successful in simulating the flight of launch vehicles and entry bodies on earth and other planets. POST 2 has been the primary simulation tool for the Entry Descent, and Landing (EDL) phase of numerous Mars lander missions such as Mars Pathfinder in 1997, the twin Mars Exploration Rovers (MER-A and MER-B) in 2004, Mars Phoenix lander in 2007, and it is now the main trajectory simulation tool for Mars Science Laboratory (MSL) in 2012. In all previous missions, the POST 2 simulation ended before ground impact, and a tool other than POST 2 simulated landing dynamics. It would be ideal for one tool to simulate the entire EDL sequence, thus avoiding errors that could be introduced by handing off position, velocity, or other fight parameters from one simulation to the other. The desire to have one continuous end-to-end simulation was the motivation for developing the ground interaction model in POST 2. Rover landing, including the detection of the postlanding state, is a very critical part of the MSL mission, as the EDL landing sequence continues for a few seconds after landing. The method explained in this paper illustrates how a simple ground force interaction model has been added to POST 2, which allows simulation of the entire EDL from atmospheric entry through touchdown

Validation of Multibody Program to Optimize Simulated Trajectories II Parachute Simulation with Interacting Forces

A capability to simulate trajectories of multiple interacting rigid bodies has been developed, tested and validated. This capability uses the Program to Optimize Simulated Trajectories II (POST 2). The standard version of POST 2 allows trajectory simulation of multiple bodies without force interaction. In the current implementation, the force interaction between the parachute and the suspended bodies has been modeled using flexible lines, allowing accurate trajectory simulation of the individual bodies in flight. The POST 2 multibody capability is intended to be general purpose and applicable to any parachute entry trajectory simulation. This research paper explains the motivation for multibody parachute simulation, discusses implementation methods, and presents validation of this capability

An Experimental Evaluation of the Performance of Lot Size Strategies in a Mrp System Facing Uncertain Demand Environment With Different Operating Conditions.

Most manufacturing organizations may be viewed as multi-stage production-inventory systems in which production of goods proceeds from the acquisition of raw material to the fabrication of final product through a series of production stages. Material requirements planning (MRP) has been introduced as an inventory planning technique for such systems. Different lot sizing models have been used to improve the economic efficiency of MRP systems. The objective of this research was to examine the impact of lot size strategies, degree of demand variability, and degree of component commonality on the performance of MRP systems in a stochastic demand environment. A computer simulation model of a hypothetical multi-stage, multi-product, production-inventory system was used as a vehicle for this study. Three different lot size models (EOQ, WW, LTC) were used at the end-item level and four (EOQ, POQ, LFL, TLC) at the intermediate levels producing twelve lot size strategies. Two levels of component-commonality, a measure of the degree of commonality of component parts among all parent-items, were introduced. Fifteen finished goods were incorporated into the model for each product structure set. Three levels of demand variability were introduced with coefficient of variation ranging from .2 to 1.4. System performance was evaluated according to several performance measures. Some of the findings of the study are as follows. First, the system performance was affected by the choice of lot size strategy with respect to all performance measures employed. Second, the system performance was affected by demand uncertainty according to seven of the nine performance measures. Third, both demand variability and component commonality had significant effect on the performance of the system. Fourth, lot size strategy was affected by demand uncertainty only according to carrying cost, setup cost, and number of setups criteria. Determining a single best performing lot size strategy for each of the twelve factor combinations of this research was not possible. However, it was shown that for any of the environmental conditions (factor combinations) there exists a class of best performing strategies from anong which MRP users will be able to select one which they prefer

Generic competencies development through entrepreneurship projects in the context of an operations management course.

[EN] Traditionally, subjects have focused on the development and assessment of specific competencies, leaving generic competencies in the background. However, in the context of the EHEA, both competencies should be developed. This paper aims to face the challenge of integrating specific and generic competencies in the teaching of Operations Management (OM). With that aim a pilot project was carried out. The objective was to integrate in a subject of industrial engineering studies traditionally dedicated to the development of specific competencies in the field of OM, general competencies through the development of entrepreneurship projects. The results indicate that students perceive that the development of such projects helped them to develop and optimally acquire most of the general competencies. The degree of student satisfaction with the experience was very high. This paper contributes to the literature on the teaching of OM by providing an innovative teaching method in engineering education that allows students to engage in their own learning, improving not only their interest but also increasing their perception of the relevance of OM. Furthermore, this method facilitates the acquisition of generic competencies, essential for OM[ES] Tradicionalmente, las asignaturas se han orientado al desarrollo y evaluación de las competencias específicas, dejando en un segundo plano las competencias transversales. Sin embargo, en el contexto del EEES, ambas competencias deben ser desarrolladas. En este trabajo se pretende dar respuesta al reto de integrar competencias específicas y transversales en la docencia de Dirección de Operaciones (DO). Para ello se realizó una experiencia piloto que tenía como objetivo integrar en una asignatura de Ingeniería Industrial dedicada tradicionalmente al desarrollo de competencias específicas del campo de la gestión, competencias transversales mediante el desarrollo de proyectos de emprendimiento empresarial. Los resultados señalan que los alumnos perciben que la elaboración de este tipo de proyectos les ha ayudado a desarrollar y a adquirir de manera óptima la mayoría de las competencias transversales. El grado de satisfacción de los alumnos con la experiencia ha sido muy alto. Este trabajo contribuye a la literatura sobre docencia en DO aportando un método docente innovador en los estudios de ingeniería que permite que los alumnos se involucren en su propio aprendizaje, mejorando no sólo su interés sino también incrementando su percepción de la relevancia que tiene la DO. Además, este método facilita la adquisición de competencias transversales fundamentales para la DOMartínez-Caro, E.; Cegarra-Navarro, JG. (2012). El desarrollo de competencias transversales en dirección de operaciones mediante proyectos de emprendimiento en el marco de una asignatura de dirección de operaciones. Working Papers on Operations Management. 3(2):9-13. doi:10.4995/wpom.v3i2.978SWORD91332Alfalla Luque, R., & Machuca, J. A. D. (2003). An empirical study of POM teaching in Spanish universities (II). International Journal of Operations & Production Management, 23(4), 375-400. doi:10.1108/01443570310467311Ammar, S., & Wright, R. (1999). Experiential learning activities in Operations Management. International Transactions in Operational Research, 6(2), 183-197. doi:10.1111/j.1475-3995.1999.tb00150.xArmistead, C., Johnston, R., & Voss, C. A. (1986). Introducing Service Industries in Operations Management Teaching. 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MOTIVATING STUDENTS IN THE OPERATIONS MANAGEMENT CLASS: CHALLENGES FOR THE PUBLISHING INDUSTRY. Production and Operations Management, 7(2), 188-193. doi:10.1111/j.1937-5956.1998.tb00450.xLewis, M. A., & Maylor, H. R. (2007). Game playing and operations management education. International Journal of Production Economics, 105(1), 134-149. doi:10.1016/j.ijpe.2006.02.009Marina, J. A. (2010). La competencia de emprender. Revista de Educación, Vol. 351, pp. 49-71MEC (2006). Borrador de propuesta Directrices para la Elaboración de Titulos Universitarios de Grado y Máster. Madrid/ MEC.Montiel, H. (2007). ¿Creadores de emprendedores o creadores de empleados? El modelo educativo emprendedor del Tecnológico de Monterrey. XI Congreso de Ingeniería de Organización International Conference on Industrial Engineering and Industrial Management, Madrid, Septiembre 5-7.Nicholson, A. (1996). POM as the systems which link commercial value and daily working practices. Proceedings of the Conference on Teaching POM: Visions, Topics and Pedagogies, 7th Annual Meeting of the Production and Operations Management Society, 1-2 April, Indianapolis, p. 2.Pasin, F., & Giroux, H. (2011). The impact of a simulation game on operations management education. Computers & Education, 57(1), 1240-1254. doi:10.1016/j.compedu.2010.12.006Raiszadeh, F.M.E.; Ettkin, L.P. (1989). POM in academia: some causes for concern. Production & Inventory Management Journal, Vol. 30, No. 2, pp. 37-40.Feger, A. L. R., & Thomas, G. A. (2011). Bailing Out the Once-Ler: Using Dr. Seuss to Teach Operations Management. Decision Sciences Journal of Innovative Education, 9(1), 69-73. doi:10.1111/j.1540-4609.2010.00291.xSchvaneveldt, S.J. (1996). Teaching operations management with popular film scenes: list of selected film scenes. Proceedings of the Conference on Teaching POM: Visions, Topics and Pedagogies, 7th Annual Meeting of the Production and Operations Management Society, 1-2 April, Indianapolis, p. A29.Vollmann, T.E.; Berry, W.L.; Whybark, D.C. (1997). Manufacturing Planning and Control Systems. 4th ed. Irwin / McGraw-Hill