An improved BEM model for the power curve prediction of stall‐regulated wind turbines

Blade element momentum (BEM) theory is the standard computational technique for the prediction of power curves of wind turbines; it is based on the two‐dimensional aerodynamic properties of aerofoil blade elements and some corrections accounting for three‐dimensional wing aerodynamics. Although most BEM models yield acceptable results for low‐wind and pitch‐controlled regimes where the local angles of attack are small, no generally accepted model exists up to date that consistently predicts the power curve in the stall regime for a variety of blade properties and operating conditions. In this article we present a modified BEM model which satisfactorily reproduces the power curves of four experimental wind turbines reported in the literature, using no free fit parameters. Since these four experimental cases comprehend a great variety of conditions (wind tunnel vs field experiments, different air densities) and blade parameters (no twist and no taper, no taper but twist, both twist and taper, different aerofoil families), it is believed that our model represents a useful working tool for the aerodynamic design of stall‐regulated wind turbines. Copyright © 2004 John Wiley & Sons, Ltd.     

Second generation CIS solar modules

Multinary Cu(In,Ga)(Se,S)₂ absorbers (abrev. CIGSSe) are promising candidates for reducing the cost of photovoltaics well below the cost of crystalline silicon. Shell Solar has pioneered production of this new thin film technology and is now with the first generation at a volume of well over 1 MW/year. In a separate pilot line for second generation products we have further improved the performance of CIGSSE based solar modules. We developed a novel CIGSSE formation technique called stacked elemental layer rapid thermal processing (SEL-RTP). This process has recently been scaled up from initial laboratory sized mini-modules (10 × 10 cm²) to full sized power modules of 60 × 90 cm². The present paper concentrates on in situ and ex situ characterization techniques that were developed to control and further improve large area CIGSSE processing. The crystalline thin film formation process has been analyzed with in situ thin film calorimetry and in situ X-ray diffraction (XRD). That work has added fundamental insights and accelerates the optimization process. The depth distribution of gallium and sulfur has been determined by secondary ion mass spectroscopy (SIMS) for different selenization and sulfurization processes. Appropriate profiles of these elements allow for a deliberate bandgap profiling within the Cu(In,Ga)(S,Se)₂ absorber. In addition further quality control tools like X-ray fluorescence analysis and Raman spectroscopy for stoichiometry monitoring, photoluminescence lifetime mapping and thermographic imaging have been developed in order to improve large area uniformity and reproducibility.

Some first full sized modules from the new pilot line look very promising: Aperture area efficiencies of up to 13.1% for monolithic thin film circuits on 0.54 m² and a module power of 65 W represent an international champion value for large are thin film solar modules.     

Meeting application requirements with conductive carbon black

High structure or so‐called conductive carbon blacks (CCBs) constitute the major family of conductive additives. They enable one to make polymers permanently conductive at “low” to “very low” loadings, for technical applications involving, e.g., the transport of energy, protection against arcing or discharge. Designing conductive parts requires certain know‐how, as many parameters influence the final electrical conductivity, and many other requirements have to be fulfilled. This paper highlights the impact of the carbon black (CB) type and loading, the polymer type, and the compounding conditions on the conductive, mechanical, dispersion, and flow properties of various plastics compounds. The study especially positions a unique family of low surface area (LSA) CCBs, suggests means to make conductive parts with compounding and transformation ease, and points out that more conductive additive does not automatically give the best overall performance. J. VINYL. ADDIT. TECHNOL., 12:14–18, 2006. © 2006 Society of Plastics Engineers     

Argon laser punctal therapy versus thermal cautery for the treatment of aqueous deficiency dry eye syndrome

1. Pregnant Wistar rats were treated orally with a single dose of 100 microg 3,3',4,4'-tetrachlorobiphenyl (PCB 77)/kg b.w. or 10 microg 3,3',4,4',5 pentachlorobiphenyl (PCB 126)/kg b.w. on day 15 of pregnancy. The control rats received peanut oil at the same day. Developmental landmarks were assessed in all offspring rats and reproductive effects of PCB 77 and PCB 126 on male offspring were studied on postnatal day 65 (at puberty) and on postnatal day 140 (at adulthood). 2. The ano-genital distance as well as the ratio ano-genital distance to body length was reduced in male pups of the PCB 126 group and the age at vaginal opening was significantly delayed in the female pups. 3. Testis, brain weights and daily sperm production were permanently increased and seminal vesicle weights were decreased in male offspring of the PCB 77 group. In male rats of PCB 126 group, the brain weights were permanently increased and ventral prostate weights permanently reduced. In both PCB groups, however, serum testosterone concentration was reduced only at adulthood. Additionally, the male rats of the PCB 126 group showed alterations in sexual behavior. In these rats the number of mounts with intromissions was significantly increased. 4. The results of this study show that PCB 126 elicits some TCDD-like reproductive effects after in utero exposure, while the reproductive effects of in utero exposure to PCB 77 on male offspring may be attributed to the neonatal hypothyroidism induced by the substance during early fetal development. Further studies using multiple doses and providing thyroid hormone data will be necessary to support this hypothesis.     

Quality of corneal donor tissue in the greater-than-75-year age group

Impaired nasal breathing has been reported to cause changes in human head posture. The aim of this study was to assess whether there was any relationship between nasorespiratory function and variables of head posture in 58 young adults. The pressure flow technique was used to measure airflow rate and oral/nasal pressure and to calculate the smallest cross-sectional area of the nasal airway. A natural head position roentgenocephalogram was used to measure the craniovertical angulation (NSL/VER), craniocervical angulation (NSL/OPT), and cervical spine inclination (OPT/HOR). The results showed a trend toward enlarged craniocervical angulation and forward inclination of the cervical spine in subjects with a relatively large nasal cross-sectional area. Though the general opinion on the effects of reduced upper airway size on head posture is opposite, these results are an experimental confirmation of the theoretically expected mechanism that leads to increased head extension in obstructed subjects.     

Clinical feasibility of a free-weight strength-training program for older adults

In the present study the intergraft mRNA formation immediately before and after transplantation of human livers was investigated by semi-quantitative polymerase chain reaction. The analysis was carried out with mRNA isolated from biopsies routinely taken perioperatively and included the determination of the expression of tumour necrosis factor alpha (TNF-alpha), interleukin (IL-6), IL-8, IL-10, transforming growth factor beta (TGF-beta) and beta-actin. It was found that biopsies obtained 30-60 min after reperfusion of the liver graft contained significantly higher levels of mRNA for TNF-alpha, IL-6 and IL-8 than biopsies collected subsequently to cold preservation. No such differences were obtained for TGF-beta and IL-10 mRNA. Considerable interindivdual differences were observed concerning the degree of inducibility, in particular for IL-6 mRNA. Retrospective comparison with the clinical course of the individual patients revealed a close and statistically significant correlation between low IL-6 expression and the occurrence of acute rejection episodes within 30 postoperative days, while high IL-6 mRNA levels coincided with the absence of rejection signs. High values for TNF-alpha mRNA were associated with ensuing acute rejection episodes.     

Social intelligence deficits in autistic children and adolescents--subjective theories of psychosocial health care professionals

The paper is concerned with personal theories of health care professionals about deficiencies in social intelligence of autistic persons. In the component-model of social intelligence means the ability of individuals or groups, to interact with each other in social situations. This contains social perception, social behavior as well as social conceptions and refers to emotional, cognitive and normative aspects. 33 interviewees, working as psychologists or teachers in kindergartens, schools or therapy institutions, are questioned by a half-standardized single interview concerning their beliefs about nonverbal social abilities, social perspective taking, and construction of a theory of mind in autistic persons. The major finding is: The impairments can be found in all aspects of social intelligence. Especially emotional handicaps, which are quoted by more than 80% of the interviewees, and low cognitive preconditions of mastering social stimuli, which are quoted by nearly all interviewees, are relevant. The subjective theories of the interviewees are in accordance to the models of parents as well as the models of the leading experts. The professional relationship to autistic persons and the practical experiences of the health care professionals lead to their specific personal theories of deficiencies in social intelligence of autistic people with wide consequences in respect to the professional contact with the autistic children and young adults.     

Assessing coronary stenosis. Quantitative coronary angiography versus visual estimation from cine-film or pharmacological stress perfusion images

Visual judgment of stenosis severity from cine-film or single-photon emission computed tomographic dipyridamole perfusion images was compared to assessment of stenosis severity as measured with digital quantitative coronary angiography. Thirty patients with angiographically verified single-vessel disease underwent dipyridamole thallium stress testing within 90 days of angiography. RESULTS: A percent diameter stenosis of > or = 50%, a percent area stenosis of > or = 75%, and a stenotic flow reserve of < 3.75 measured by quantitative coronary angiography (CMS, version 1.1, Medis Inc.) corresponded to haemodynamically significant stenosis as evaluated by visual estimates from cine-film or perfusion images. Quantitative coronary angiography percent diameter stenosis (51.2% +/- 12.6%) correlated closely (r = 0.74) but underestimated significantly visual assessment of stenosis severity from cine-film (69.3% +/- 21.2%; P = 0.0001). However, quantitative coronary angiography percent area stenosis (74.7% +/- 11.7%) more closely reflected visual estimates from cine-film (P = 0.19). Quantitative coronary angiography stenotic flow reserve showed the highest positive and negative predictive value regarding visual estimates from cine-film (88%, 86%) or perfusion images (88%, 64%) followed by percent diameter stenosis (86%, 75% 86%, 56%) and percent area stenosis (87%, 80%, 87%, 60%), respectively. CONCLUSION: Evaluation of coronary lesions by quantitative coronary angiography corresponds closely with visual estimates from cine-film and haemodynamic significance as evaluated by dipyridamole perfusion images.     

Effect of alternating postures on cognitive performance for healthy people performing sedentary work

Prolonged sitting is a risk factor for several diseases and the prevalence of worksite-based interventions such as sit-to-stand workstations is increasing. Although their impact on sedentary behaviour has been regularly investigated, the effect of working in alternating body postures on cognitive performance is unclear. To address this uncertainty, 45 students participated in a two-arm, randomised controlled cross-over trial under laboratory conditions. Subjects executed validated cognitive tests (working speed, reaction time, concentration performance) either in sitting or alternating working postures on two separate days (ClinicalTrials.gov Identifier: NCT02863731). MANOVA results showed no significant difference in cognitive performance between trials executed in alternating, standing or sitting postures. Perceived workload did not differ between sitting and alternating days. Repeated measures ANOVA revealed significant learning effects regarding concentration performance and working speed for both days. These results suggest that working posture did not affect cognitive performance in the short term.

Practitioner Summary: Prior reports indicated health-related benefits based on alternated (sit/stand) body postures. Nevertheless, their effect on cognitive performance is unknown. This randomised controlled trial showed that working in alternating body postures did not influence reaction time, concentration performance, working speed or workload perception in the short term.     

Body size estimation in anorexia nervosa patients: the significance of overestimation

Using the video distortion method on a life-size screen, we have studied body size estimation in 100 female restricting anorexia nervosa patients. About half of the patients were accurate in estimating their own body dimensions and only 20% clearly showed overestimation. We then tested whether differences in accuracy of estimation were related to scores on the following questionnaires: Eating Disorder Inventory; Body Attitude Test; and Symptom Checklist (SCL-90). Overestimators reported a more negative body attitude and a more "neurotic profile" on the SCL-90. These differences might have both prognostic and therapeutic implications.