Abstract Many of the concentrating solar power (CSP) systems are expected be installed in desert locations where lack of water and sand storms might be an issue. The solar reflectors are considered to be among the main effective components. The negative effects of the harsh weather conditions, including sand storms of the desert might have strong influence on the reflector properties, leading to a decrease in the thermal performance of such solar system. This thesis studies the sand storm influence on solar reflector surfaces, where two different types of Libyan sands were considered and taken from sites suitable for the installation of CSP. These sands have different shapes, sizes and chemical compositions. Sand "A" has particle sizes that vary from 0.025 to 0.355mm, while Sand "B" has particle sizes in the range of 0.124-0.479 mm. An erosion rig was designed and built at Cranfield University, UK. the tests were conducted under different simulated sand storm conditions for both sand samples. The results have shown that Sand "A" has more severe influence than Sand "B" because the smaller particles of Sand "A" help the spread out over a larger surface area of the reflector. The higher sand storm speed has more strong impact influence, while increasing the mass quantity results in less consequences. The reflectivity of the un-cleaned surface drops by 5% in case of using Sand "A" and by 7% in case of Sand "B", both at storm speed of 21m/s with specific sand mass of 18g/m3.Sand storms with the speed exceeding 6 m/s, generate sand impact on the reflector surface causing degradation to the surface, while storms with speeds less than 6 m/s, result in wakes of suspended small particles as a consequence of the transport mechanism in the atmosphere. Sealing simulation and cleaning process, using Ultrasonic Cleaner Model, show that sand "B" makes a loss of about 3% of the surface reflectivity, due to the salt-chemical composition leading to create spots and marks on the reflector surface. However, Sand "A" has recorded no chemical reaction. Sand storm history should be taken seriously, reflector surface materials should be suitable for the sites, and cleaning operations should be considered.
عصام ميلاد اندايا (2015)

This paper investigates the current status of the implementation level of Just-In-Time (JIT) within the Oil & Gas (OGI), Iron & Steel (ISI), Cement (CI) and Construction (C) Industries within Libya and its implication for management within the said industries. A survey methodology has been applied in this investigation using an intensive questionnaire and one-to-one interviews of the correspondent organizations. Based on the analysis of the survey questionnaire and the one-to-one interview responses, the results show that the management body does not have a clear strategy towards most of the areas that are considered as being crucial in any successful implementation of the JIT techniques. The implementation levels of the JIT techniques are found to be in the modest levels even in the organizations that have indicated themselves as JIT implementers. The research has identified management limitations within the investigated areas and has pointed to areas where the management body needs to take immediate actions in order to achieve an effective and successful JIT implementation within their organizations. This is an important finding for the future success of the Libyan industries and the similar ones. arabic 18 English 107
ٌRajab HOKOMA(1-2016)

This paper is designed to present an experimental study being recently conducted for investigating the effect of some fuel additives on the performance of spark ignition within a benzene engine. Three types of additives were added separately (Gasoline Additive, Gasoline Booster, and Octane Booster) to pure gasoline with a volumetric ratio 1:6, 1:7, and 1:8 respectively. Four separate laboratory experiments being conducted using an internal combustion engine at rotational speed ranges from 600 to 3000 rpm, where the three mixtures and the pure gasoline itself were used. The findings showed that there was a positive effect on the engine performance as the brake power increases by 8%, 13% and 23% at the use of Gasoline Additive, Gasoline Booster, and Octane Booster respectively as compared with using only the pure gasoline. The brake thermal efficiency (ɳth) was also affected positively showing its maximum value of about 8% for Octane Booster, and with a minimum value for using Gasoline Additive at about 4.7%. In addition, this study showed that the value changes in the brake specific fuel consumption for Gasoline Additive, Gasoline Booster, and Octane Booster was at the levels of 1%, 2%, and 5% respectively compared with using only the pure gasoline. Furthermore, the results also showed that the use of Octane Booster gave the highest level of air fuel ratio arabic 18 English 97
ٌRajab HOKOMA, Nabil M. Muhaisen(1-2017)