Numerical Analysis of Real Fluid Behavior Effects on a Sliding-Vane Compressor Comprehensive Model

This work presents a simulation model on a sliding vane compressor based on a lumped parameter model. The model is capable of predicting the performance of sliding-vane compressors. The model is divided into different sub-sections to evaluate the compressor's geometry, kinetics, thermodynamics, and rotor dynamics. The output of the tool includes the compressor unit's performance, such as volumetric flow rate, mechanical power, and process efficiency. The study examines the tool's ability to perform quick and efficient analyses using using either ideal or real fluid characterization, based on the REFPROP code. The code is validated against one experimental point. Simulations were conducted on a mid-size sliding-vane rotary compressor operating with three different types of working fluids from 20 °C and 1 bar (absolute) to 11 bar at 1500 rpm. In the ideal fluid case, simulations took 10–27 s, while real fluid assumptions took 1038–4329 s. The volumetric flow rate was influenced by the gas used, but changes among fluid models were not substantial, with a mean absolute percent difference of 0.5%. Mechanical power consumption was affected by the fluid choice and gas model, leading to a mechanical power difference between 0.4 and 1.1% in the ideal gas case. The specific mechanical work showed greater deviations among the fluids, with methane molar mass coherently increasing its value. Results show that the model developed is able to assess the major phenomena of sliding-vane compressors, and the ideal fluid model should be preferred when possible since computational times are significantly reduced with comparable results

Relationship between hypertension, diabetes and proteinuria in rural and urban households in Yemen

Little information is available on the meanings of proteinuria in low-resource settings. A population-based, cross-sectional survey was performed in Yemen on 10 242 subjects aged 15–69 years, stratified by age, gender and urban/rural residency. Hypertension is defined as systolic blood pressure (BP) of ⩾140 mm Hg and/or diastolic BP of ⩾90 mm Hg, and/or self-reported use of antihypertensive drugs; diabetes is diagnosed as fasting glucose of ⩾126 mg dl(−1) or self-reported use of hypoglycaemic medications; proteinuria is defined as ⩾+1 at dipstick urinalysis. Odds ratios (ORs) for associations were determined by multivariable logistic regression models. Prevalence (weighted to the Yemen population aged 15–69 years) of hypertension, diabetes and proteinuria were 7.5, 3.7 and 5.1% in urban, and 7.8, 2.6 and 7.3% in rural locations, respectively. Proteinuria and hypertension were more prevalent among rural dwellers (adjusted ORs 1.56; 95% confidence limit (Cl) 1.31–1.86, and 1.23; 1.08–1.41, respectively), diabetes being less prevalent in rural areas (0.70; 0.58–0.85). Differently from hypertension and diabetes, proteinuria was inversely related with age. Most importantly, 4.6 and 6.1% of urban and rural dwellers, respectively, had proteinuria in the absence of hypertension and diabetes. The approach of considering kidney damage as a consequence of hypertension and diabetes might limit the effectiveness of prevention strategies in low-income countries

Central obesity in Yemeni children: A population based cross-sectional study

AIM: To establish percentile curves and to explore prevalence and correlates of central obesity among Yemeni children in a population based cross-sectional study. METHODS: A representative sample of 3114 Yemeni children (1564 boys, 1550 girls) aged 6-19 years participating in the HYpertension and Diabetes in Yemen study was studied. Data collection was conducted at home by survey teams composed of two investigators of both genders. Study questionnaire included questions about demographics, lifestyle, and medical history. Anthropometric measurements included body weight, height, waist circumference (WC) and hip circumferences. Waist to hip ratio (WHR) and waist-to-height ratio (WHtR) were then calculated. Age and gender specific smoothed percentiles of WC, WHR, and WHtR were obtained using lambda-mu-sigma parameters (LMS method). The independent predictors of central obesity defined as (1) WC percentile ≥ 90(th); (2) WHtR ≥ 0.5; or (3) WC percentile ≥ 90(th) and WHtR ≥ 0.5, were identified at multivariate logistic regression analysis adjusted for age, gender, urban/rural location, years of school education, sedentary/active life-style. RESULTS: Percentile curves for WC, WHR and WHtR are presented. Average WC increased with age for both genders. Boys had a higher WC than girls until early adolescence and thereafter girls had higher values than boys. WHR decreased both in boys and girls until early adolescence. Thereafter while in boys it plateaued in girls it continued to decrease. Mean WHtR decreased until early adolescence with no gender related differences and thereafter increased more in girls than in boys towards adult age. Prevalence of central obesity largely varied according to the definition used which was 10.9% for WC ≥ 90(th) percentile, 18.3% for WHtR ≥ 0.5, and 8.6% when fulfilling both criteria. At adjusted logistic regression WC ≥ 90(th) percentiles and WHtR ≥ 0.5 were less prevalent in rural than in urban areas (OR = 0.52, 95%CI: 0.41-0.67 and 0.66, 0.54-0.79 respectively), being more prevalent in children with sedentary lifestyle rather than an active one (1.52, 95%CI: 1.17-1.98 and 1.42, 95%CI: 1.14-1.75, respectively). CONCLUSION: Yemeni children central obesity indices percentile curves are presented. Central obesity prevalence varied according to the definition used and was more prevalent in urban sedentary subjects

Review of liquid hydrogen tanks for short- and medium-haul aircraft

Downloa

Sleep History and Hypertension Burden in First-Generation Chinese Migrants Settled in Italy: The CHIinese in Prato Cross-Sectional Survey

Migration flows from China are largely directed towards the South of Europe, Chinese being now the third largest overseas-born population in Italy. The aim of the study was to investigate hypertension burden and self-reported sleep disorders among 1608 first-generation Chinese migrants aged 16 to 59 years settled in Prato and recruited in a cross-sectional survey. Hypertension was defined as systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg or self-reported antihypertensive treatment; potential impact of sleep disorders was analyzed by logistic regression adjusted for age, sex, marital status, education, health insurance, current smoking, parental hypertension, alcohol drinking, overweight or obesity, central obesity, diabetes, high total cholesterol, and high triglycerides. Among the 1608 participants, 21.7% were hypertensive (age-standardized prevalence 19.2%; 95% Cl: 18.5–20.0); 54% of hypertensive subjects were aware of their condition; 70% of aware hypertensive subjects received drugs, and 39% of treated subjects had blood pressure controlled. Self-reported snoring increased the risk of hypertension; when compared with no snoring, the age- and sex-adjusted OR for hypertension of snoring 3 to 6 d/week was 2.11 (95% Cl: 1.48–3.01) and 2.48 (95% Cl: 1.79–3.46) of snoring every day. When compared with a sleep duration ≤5 hours, subjects with sleep duration of 7 hours had reduced risk of high triglycerides (adjusted OR: 0.66; 95% Cl: 0.43–0.95). Despite a high level of awareness, low treatment rates for hypertension were observed among Chinese participants, independently of health insurance. Sleep history is to be considered in screening and prevention programs

Epidemiology of hypertension in Yemen: effects of urbanization and geographical area

Although globalization can contribute to increased blood pressure by spreading unhealthy behaviors, it also provides powerful means to tackle hypertension. The dissemination of information about and advice on cardiovascular prevention and facilitated contact with health services are valuable resources. To investigate the effects of urbanization, geographical area, and air temperature on hypertension burden and kidney damage, a survey was performed in 2008 with a door-to-door approach among urban and rural adult dwellers of three geographic areas (capital, inland, coast) of Yemen. Subjects (n=10 242) received two visits several days apart to confirm the diagnosis of hypertension. Proteinuria (dipstick test ⩾+1) was used as a marker of kidney damage. Prevalence rates were weighted to represent the Yemen population aged 15–69 years in 2008. Rates of hypertension and proteinuria progressively increased from the capital (6.4% 95% confidence level (CI) 5.8–7.0 and 5.1% 4.4–5.9, respectively), to inland areas (7.9% 7.0–8.7 and 6.1% 5.1–7.1), to the coastal area (10.1% 8.9–11.4 and 8.9% 7.3–10.4). When compared with urban dwellers, rural dwellers had similar hypertension prevalence (adjusted odds ratios (ORs) 1.03; 95% CI 0.91–1.17) but higher proteinuria rates (adjusted ORs 1.55; 1.31–1.85). Overall, home temperature was associated with a lower hypertension rate (adjusted OR 0.98; 0.96–0.99). This large population study reveals that the highest burden of hypertension and kidney damage is detectable in remote areas of the country