An improved approach to application-specific power electronicseducation-switch characterization and modeling

An integrated power electronics curriculum has been implemented in the Department of Electrical and Computer Engineering at the University of Illinois, Chicago. This paper describes the development of a set of hands-on laboratory experiments to accompany classroom lectures. Content is based on switching converter topologies and commercial power semiconductor devices. Unlike most experiments, which focus on circuit- or control-level characteristics, our approach emphasizes the circuit-device-load interactions. The concept presented is innovative in that it creates a 3×3 matrix of experiment variation-devices, circuits-control, and machines-loads-with one set of hardware. The lab development is ongoing with future experiments to address three-phase converters and motor control applications. Experiment content is described, as well as the means by which the material has been integrated within the course sequence. Lab station construction and safety issues are also addressed. The experiments require hands-on measurement and circuit connection and complement the established course elements of theory and computer-based circuit modeling. Laboratory experiments and computer simulations collectively provide quantitative evidence of mixed circuit and device optimization     

核电厂环保应急计算机系统的设计

以核电厂环保与应急计算机系统为例,建立了一个具有实时监测数据的收集、评价与可靠传输、日常办公事务处理等主要功能的计算机系统。介绍了该系统的架构、设计原理、思想与方法,给出了相应的总体设计方案与应用软件功能。该系统亦适用于同类电厂。     

A rare and little known variant of hypospadias

Hypospadia is a congenital defect presenting as different variants of dysplasia of the distal urethra with ectopy of the urethral external orifice and distortion of the penis. A variant of hypospadia not yet described in Russian medical literature was observed in a newborn boy. He had normal penis and scrotum, but on the under-side of the penis there was a site of thin skin protruding as a resonance bag in urination. At the site of the thin skin the back urethral wall was absent with a cavity covered by the thin skin. In urination urine filled the cavity blowing up the skin above it to the form of the resonance bag. This variant of hypospadia was designated as segmental urethral hypoplasia.     

A prospective 12-year study of subsyndromal and syndromal depressive symptoms in unipolar major depressive disorders

BACKGROUND: Investigations of unipolar major depressive disorder (MDD) have focused primarily on major depressive episode remission/recovery and relapse/recurrence. This is the first prospective, naturalistic, long-term study of the weekly symptomatic course of MDD. METHODS: The weekly depressive symptoms of 431 patients with MDD seeking treatment at 5 academic centers were divided into 4 levels of severity: (1) depressive symptoms at the threshold for MDD; (2) depressive symptoms at the threshold for minor depressive or dysthymic disorder (MinD); (3) subsyndromal or subthreshold depressive symptoms (SSDs), below the thresholds for MinD and MDD; and (4) no depressive symptoms. The percentage of weeks at each level, number of changes in symptom level, and medication status were analyzed overall and for 3 subgroups defined by mood disorder history. RESULTS: Patients were symptomatically ill in 59% of weeks. Symptom levels changed frequently (1.8/y), and 9 of 10 patients spent weeks at 3 or 4 different levels during follow-up. The MinD (27%) and SSD (17%) symptom levels were more common than the MDD (15%) symptom level. Patients with double depression and recurrent depression had more chronic symptoms than patients with their first lifetime major depressive episode (72% and 65%, respectively, vs 46% of follow-up weeks). CONCLUSION: The long-term weekly course of unipolar MDD is dominated by prolonged symptomatic chronicity. Combined MinD and SSD level symptoms were about 3 times more common (43%) than MDD level symptoms (15%). The symptomatic course is dynamic and changeable, and MDD, MinD, and SSD symptom levels commonly alternate over time in the same patients as a symptomatic continuum of illness activity of a single clinical disease.     

Routine intraoperative laparoscopic cholangiography

BACKGROUND: Whether intraoperative laparoscopic cholangiography should be routine is debatable. METHODS: We reviewed the cholangiography experience in 669 consecutive laparoscopic cholecystectomies. RESULTS: Mean age of the patients was 39 years, 78% were female, and 29% had acute cholecystitis. Cholecystectomy was completed laparoscopically in 606 (91%). Laparoscopic cholangiography was completed in 562 (93%) and 348 (62%) were routine (no preoperative indication). The mean operating time in 1996 was 61 minutes. Out of the 348 routine cholangiograms, 17 demonstrated evidence of unsuspected choledocholithiasis. Five patients had choledocholithiasis documented by laparoscopic common bile duct exploration and/or endoscopic retrograde cholangiopancreatography. Two patients had normal postoperative cholangiopancreatography. One of 10 patients managed expectantly was readmitted postoperatively with obstructive jaundice. In 4 patients, routine cholangiography revealed unexpected anatomy, and in 2, this prevented misidentification and transection of the common bile duct. CONCLUSION: Laparoscopic cholangiography is safe, quick, detects unsuspected choledocholithiasis, and can prevent common bile duct transection. It should be routine.     

Low pressure hydrogenation of castor oil

Castor Oil was hydrogenated at low pressure (2.0–2.5 kg/cm²) and low temperature (125–135 C) using nickel catalyst to obtain a saturated waxy product rich in hydroxy stearic acid. High catalyst concentration was required to obtain good results. However, the catalyst could be recycled. The final product had iodine value below 3.0, hydroxyl value 155, and slip point of 84 C.     

Presence of genomes of phage PBV-1 in the mycelia of the fungus Penicillium brevi-compactum

Progressive systemic sclerosis may be associated with focal myocardial fibrosis. Electrocardiographic abnormalities including conduction block are common in progressive systemic sclerosis but whether they are due to direct destruction of the specialized conduction tissue of the heart is uncertain. The conduction systems of 35 patients with progressive systemic sclerosis were studied. Of these 35 patients, 17 (50 per cent) had myocardial fibrosis of the type seen in progressive systemic sclerosis. In 10 of the 17, it was severe. Sinus node fibrosis was present in 13 patients and was nearly as frequent in those with as in those without the progressive systemic sclerosis myocardial lesion. Overlying pericarditis may have contributed to the fibrotic changes within the sinoatrial nodes in seven of the 13 patients. The atrioventricular node and main His bundles were normal. However, fibrotic changes were found in the proximal bundle systems in six patients. In three of the six, severe myocardial progressive systemic sclerosis was present, two had focal fibrous atrophy of the left bundle, and one had complete interruption of the right bundle. In only the latter patient was this reflected in the electrocardiogram which showed a right bundle branch block. Three patients without progressive systemic sclerosis myocardial lesions also had fibrous atrophy of a portion of the proximal left bundle branch, and in one the electrocardiogram showed an isolated left anterior hemiblock. Thus, morphologic abnormalities within the conduction system in our patients are difficult to attribute to progressive systemic sclerosis per se. Furthermore, although conduction abnormalities were more frequent in patients with myocardial disease, specific conduction system disease was not the cause in most patients. As has been noted in ischemic heart disease, the conduction system appears to be relatively spared from the myocardial changes of progressive systemic sclerosis, and the high incidence of conduction disturbances in this condition may be a consequence, rather, of damage to working myocardium.