Sensitivity of multi-product two-stage economic lotsizing models and their dependency on change-over and product cost ratio's

This study considers the production and inventory management problem of a two-stage semi-process production system. In case both production stages are physically connected it is obvious that materials are forced to flow. The economic lotsize depends on the holding cost of the end-product and the combined change-over cost of both production stages. On the other hand this 'flow shop' is forced to produce at the speed of the slowest stage. The benefit of this approach is the low amount of Work In Process inventory. When on the other hand, the involved stages are physically disconnected, a stock of intermediates acts as a decoupling point. Typically for the semi-process industry are high change-over costs for the process oriented first stage, which results in large lotsize differences for the different production stages. Using the stock of intermediates as a decoupling point avoids the complexity of synchronising operations but is an additional reason to augment the intermediate stock position. The disadvantage of this model is the high amount of Work-In-Process inventory. This paper proposes the 'synchronised planning model' realising a global optimum instead of the combination of two locally optimised settings. The mathematical model proves (for a two-stage single-product setting) that the optimal two-stage production frequency corresponds with the single EOQ solution for the first stage. A sensitivity study reveals, within these two-stage lotsizing models, the economical cost dependency on product and change-over cost ratio‟s. The purpose of this paper is to understand under which conditions the „joined setup‟ or the „two-stage individual eoq model‟ remain close to the optimal model. Numerical examples prove that the conclusions about the optimal settings remain valid when extending the model to a two-stage multi-product setting. The research reveals that two-stage individually optimized EOQ lotsizing should only be used when the end-product stage has a high added value and small change-over costs, compared to the first stage. Physically connected operations should be used when the end-product stage has a small added value and low change-over costs, or high added value and large change-over costs compared to the first production stage. The paper concludes with suggesting a practical common cycle approach to tackle a two-stage multi-product production and inventory management problem. The common cycle approach brings the benefit of a repetitive and predictable production schedule

Tacit knowledge externalization among geographically distributed small groups

University of Technology, Sydney. Faculty of Information Technology.Currently, organizations are shifting their activities and processes from information-based to knowledge-based as a result of the emergence of organizational knowledge as the main, if not the only, competitive advantage between rival organizations. Accordingly, the management of what an organization knows and the activities of knowledge externalization, which incorporates creation, articulation, capture, transformation, nurture, and retention, as well as knowledge measurement has become a field of serious research. Two main obstacles have emerged as a result. One is associated with the definition of knowledge, and the second is whether in fact knowledge in general and tacit knowledge in particular can be managed, externalized and measured. The literature does not provide a universal knowledge definition. Accordingly, knowledge is defined contextually by both researchers and organizations. As a result, researchers and organizations work to manage knowledge, externalize it and measure it dependent on how they define it or on available definitions. Fortunately, the majority of researchers agree that knowledge is a duality, namely, tacit and explicit, and that its management should encompass both. Explicit knowledge management proved to be easy and successful because of its information-like nature and also because it could be implemented using existing information-based concepts and tools. In contrast, work on managing tacit knowledge proved to be difficult and unsuccessful because of the illusive nature of this type of knowledge, and because its capture and transformation in its entirety is extremely difficult, if not impossible. In addition, the majority of the literary work on knowledge externalization and measurement is associated with face-to-face interactions between individuals. Similar work which addresses the externalization and measurement of tacit knowledge among geographically distributed individuals is very limited if not non-existent. This dissertation identifies the difficulties associated with managing tacit knowledge in its entirety among distributed individuals and proposes its categorization into types/kinds as a solution for its effective externalization and measurement. The categorization process implies the identification of those types or kinds of tacit knowledge which could be externalized and measured easier than others. This is in line with most researchers' beliefs; that there are parts of tacit knowledge which cannot be externalized and measured, such as intuitions, feelings, instincts, expertise and such. The parts which can be externalized and measured based on observations, learning, and experimentation are expertise, know-how and the like; while the parts which can be externalized and measured if articulated and nurtured are opinions, ideas and similar The thesis, drawing upon Hevner's design theory, develops an artifact for the effective capture and transformation of categorized types of tacit knowledge among distributed small groups. It proposes opinions and ideas as types of tacit knowledge which can easily be externalized and measured among distributed individuals. It introduces concepts regarding how to nurture articulated opinions and ideas among such individuals. It also proposes an externalization process, as an amendment of Nonaka and Takeouchi's 1995 face-to-face process, which identifies the stages of the externalization of the types in distributed environments. The dissertation is organized into two main tasks. Firstly, an elaborate literature review, which paves the ground for the introduced methodology, is undertaken. Secondly, an experiment was conducted on small groups of students who used a developed example tool for their distributed cooperation and opinions and ideas externalization. The dissertation's methodology identifies four essential steps for the externalization and measurement of tacit knowledge. The experiment, which was based on Sarker's (2004) experimental guidelines, encompasses the use of a developed example tool by the students

Accuracy of Ultrasound Diagnosis after Blunt Scrotal Trauma (10 Years Experience)

Objectives: To evaluate the role of ultrasonography (US) and its accuracy, sensitivity and specificity for the diagnosis of testicular rupture after blunt scrotal trauma. Moreover, tunica albuginea breach, testicular hematoma, testis avulsion, epididymal injuries and hematocele are particularly examined.Patients and Methods: Between 1998 and 2008, 24 patients presented to Suez Canal University Hospital after blunt scrotal trauma and underwent surgical exploration. All patients had an emergency scrotal US examination with the use of a 7.5-10 MHz linear transducer. US findings were compared with the surgical findings to calculate the sensitivity and specificity of US for each type of lesion.Results: Out of 24 patients, 12 were diagnosed as having testicular rupture and tunica albuginea breach was visualized on US in 6 patients. Sensitivity and specificity of US were 92% and 50% for testicular rupture, 85% and 75% for hematocele, 80% and 79% for testicular hematoma, and 100% and 96% for testicular avulsion, respectively. US diagnosis of epididymal injuries was poor as it failed to detect 3 out of 5 epididymal lesions.Conclusion: US was highly sensitive in the diagnosis of testis rupture. This can provide information on the integrity of the scrotal contents that can help the physician to determine the optimal treatment.Key Words: Ultrasonography, scrotal blunt trauma, testis ruptur

Competing interactions in semiconductor quantum dots

We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions at longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.Comment: 10 pages, 5 figures [v2: subsection and references added

Impact of moderate versus mild aerobic exercise training on inflammatory cytokines in obese type 2 diabetic patients: a randomized clinical trial

Background: Recently some plasma biomarkers of inflammation have been recognized as important cardiovascular risk factors. There is little information about the effects of aerobic exercise training on these biomarkers and the risk of metabolic complications in obese type 2 diabetes patients.Objective: To compare the impact of moderate versus mild aerobic exercise training on the inflammatory cytokines in obese type 2 diabetic patients.Methods: Fifty obese type 2 diabetic patients of both sexes with body mass index (BMI) varying from 31 to 36 kg/m2, non smokers, free from respiratory, kidney, liver, metabolic and neurological disorders, participated in this study. Their age ranged from 40 to 55 years. The subjects were included into two equal groups; the first group (A) received moderate aerobic exercise training. The second group (B) received mild aerobic exercise training, three times / week for 3 months.Results: The mean values of leptin, TNF- alpha, IL2, IL4, IL6, HOMA-IR and HBA1c were significantly decreased in group (A) and group (B). Also, there were significant differences between both groups after treatment.Conclusion: Moderate aerobic exercise training modulates inflammatory cytokines more than mild aerobic exercise training in obese type 2 diabetic patients.Keywords: Aerobic exercise, inflammatory cytokines, obesity, non-insulin dependent diabetesAfrican Health Sciences Vol 13 Issue 4 December 201