An experimental study was carried out on a s peciall y designed horizontal axis wind turbine . The wind turbine model is 800 mm wheel diameter, and is mounted on a stand located 500 mm from the exit of a subsonic wind tunnel . The objectives of the study is to investigate the effects of some design parameters on the perfonnance of the turbine . These parameters are : the blade setting angle , the blade chord ratio and fmally the number of blades . The model was provided with facilities to make easy the changes of any or all the previous parameters . The measuring instruments used include a special torque­ meter for measuring the torque exerted on the turbine by the wind, a digital tachometer for measuring the turbine rotational speed and protractors to be able to measure the blade setting angles . The obtained data of almost s ty five combination cases of those parameters was used to plot curves of the turbine perfonnance .These curves were analyzed and studied to illustrate the variation of the turbine power coefficient as well as the exerted torque with the tip speed ratio at different combination of the investigated parameters . The blade setting angle varied from 10° to 55° . As the blade setting angle decreases the maximum power coefficient increases and the best power coefficient was obtained when the blade setting angle ranges from 13° to 23° . As for the exerted torque, higher values are obtained when the blade setting angle was ranging from 30° to 45° . The tests were carried out using blade chord ratios in the range from 0.0625 to 0.1125 . An increasing rate of the power coefficient and exerted torque was noticed as the blade chord ratio mcreases .

Abstract

. The diagnosis of gastrointestinal bleeding is not always an easy task for the physician or the surgeon thus our aim of work is to review and assess the recent literature about the diagnosis and management of obscure gastrointestinal bleeding. The common causes of gastrointestinal bleeding such as; peptic ulcer, oesophageal varices, angiodysplasia, small bowel vascular lesions or tumors, inflammatory bowel disease and diverticulosis are usually diagnosed by endoscopy, sometimes these lesions are overlooked by the unexperienced endocopist especially if they are difficult to locate or if at the time of endoscopy no bleeding is present. Those with recurrent gastrointestinal bleeding that is difficult to diagnose should undergo a sequence of investigations ranging from panendoscopy through small and large bowel, radiological contrast studies, radio-isotope scan and selective visceral angiography to peroperative enteroscopy.

By definition, an obscure source of haemorrhage has not been discovered by routine, standard investigations. The first rule is such patients, however, is that one must not hesitate to repeat previously normal investigations.