عند تطبيق سياسات الصيانة تواجه المؤسسات الصناعية والخدمية على حدا سواء تحدى ألا وهو ماهى طريقة الصيانة المثلى والسياسة الأفضل الواجب إتباعها لصيانة النظام بالأخذ في الاعتبار التكاليف ؟ بكلمات أخرى ماهى السياسة المثلى للصيانة التي تحقق التوازن بين تقليل الأعطال والحفاظ على النظام في أحسن الظروف التشغيلية وبأقل تكلفة ممكنة للصيانة.لذلك تشكل تكلفة الصيانة دورا هاما قي عملية المفاضلة عند اختيار وتخطيط سياسات الصيانة. إن حساب تكاليف الصيانة لاى نظام من بداية تشغيله إلى نهاية عمره الافتراضي له أهمية كبيرة للمؤسسة الصناعية ، حيث يضمن لمتخذي القرار حسن التصرف في مصادر رؤؤس الأموال وهذا الأمر مهم جدا خصوصا للدول النامية نظرا لمحدودية توفر إمكانياتها . لذلك يقدم البحث نموذج رياضي مطور لتقدير التكاليف الإجمالية لسياسات الصيانة المتبعة أو المقترحة لنظام ما على طول العمر الافتراضي له ، تقدير عدد الأعطال التي يتعرض لها النظام، تقدير تكلفة المواد المطلوبة لعمليات الصيانة ، تقدير العدد الأمثل لمرات إجراء الصيانة الوقائية بكل فترة من فترات عمر النظام ، ومن خلال البحث نقوم بدراسة وتحليل تأثير العناصر المختلفة للصيانة على معايير الأداء . أيضا يعطى النموذج الرياضي المطور الوقت الأمثل لإجراء العمرة لمعدات النظام بدلا من السياسة التقليدية المتبعة ببعض المؤسسات الصناعية في الدول النامية والتي تعتمد فقط على إجراء عمرة لمعدات النظام بعد فترات زمنية ثابتة بغض النظر عن حالة النظام ومدى احتياجه فعليا لتجديد معداته .ويدعم البحث بدراسة تحليلية وعملية لنظام محطة نقل الطاقة الكهربائية بالشركة العامة للكهرباء كمثال للدراسة . Abstract Through implementation of the maintenance policies, companies face challenge with respect to system maintenance cost, which is how to keep the system in good working condition at low maintenance cost? Thus the tradeoff process between cost and performance of the system plays an important role in the selection of the maintenance policies.This research is intended to achieve the optimum maintenance policies, and to achieve the leverage between system performance and life cycle maintenance cost. It focused on accomplishing the following points:Developing a mathematical model to evaluate maintenance policies through life cycle of the system.Assessing the impact of maintenance parameters on system performance measures.Using the developed model to determine the appropriate overhauling times for the industrial enterprises, actually when the equipments should be overhauled, instead the traditional way, that is performed based on fixed number of years. The model works based on criteria's are set by enterprise's decision makers, such that if the system exceeds certain number of breakdowns through its life cycle, then system must be overhauled. This thing helps the companies saving money. Using appropriate performance measures to evaluate how well the system meets its goals based on the applied maintenance policy. Practical and analytical study of power transmission station's equipments in general electrical company of Libya was presented as a case study.
عماد مختار المصراتي (2009)

This paper investigates in detail the current status of the implementation levels of JIT key-factors and their sub-elements within the cement industry within Libya, and its implication for management within the said industry. A survey methodology has been applied in this detailed investigation using an intensive questionnaire and one-to-one interviews of the correspondent organizations. Based on the analysis of the survey findings, the results show that the implementation status of the JIT key-factors and their sub-elements are found to be in the modest levels across all the surveyed organisations, thereby indicating to opportunities for eliminating waste and improving the value chain. This paper has also pointed to crucial areas where the senior management body within this industry need to take immediate actions in order to achieve an effective and successful implementation of JIT systems. The paper also makes a contribution by providing an insight into what extent the JIT key-factors and their sub-elements are understood and implemented within the key Libyan manufacturing industry arabic 19 English 113
Rajab HOKOMA, Hala Mansour Amaigl(5-2019)

An efficient way to reduce the energy required for conditioning buildings and therefore to reduce CO2 emission is the use of proper thermal insulation in buildings' external walls. This measure requires data from metrological stations that can be used in the optimization of the thermal insulation. The main objectives of this study are to construct thermal climatic zones for Libya and to specify the optimum insulation thickness for external walls for the different zones. This work is comprehensive as the metrological data from all existing 33 weather stations has been collected and used for identifying thermal zones. For the optimization of the construction of external walls, the most commonly used local wall structures are investigated: hollow concrete block, limestone block and hollow brick. In addition, four thermal insulation materials: extruded polystyrene, expanded polystyrene, rock wool and foamed polyurethane are used with every wall type. Optimum insulation thickness, energy savings, energy cost and payback periods were estimated for the 33 locations using life cycle cost analysis. A map is constructed for the thermal zones based on degree-day values for the entire country. The results show that limestone blocks with expanded polystyrene insulation form the optimum wall construction as it provides the minimum total cost for all locations. Depending on the Degree-day values, the optimum insulation thickness varies between 5.4 and 15.3 cm across the country with energy saving varies between 28 and 178 $/m2. Using the optimum thickness, the average CO2 emissions can potentially be reduced by about 85%. Finally, a contour map represents the optimum thickness of expanded polystyrene is presented in this work. arabic 12 English 80
Samah Khlifa Otman Alghoul, (1-2021)