轧钢高压水除鳞喷射阀启闭特性分析

轧钢高压水喷射除鳞对提高钢材轧制表面质量效果明显 ,除鳞喷射阀结构特殊 ,由气压驱动 ,其启闭特性与一般水阀不同。分析了其阀芯所受水压力 ,液流力及密封的摩擦力 ,从而给出了启闭喷射阀所需气压作用力的计算式 ,并以研制的喷射阀的实际数据作为例子计算了该阀的启闭特性 ,解决了阀门流量大 ,压力高启闭难的问题。     

Effects of endotracheal intubation on normal cough performance

To assess the effects of endotracheal intubation on normal cough function, the tracheas of eight healthy volunteers were intubated with a standard 8.0-mm-I.D. tube. Measurements were made of expiratory flow, transpulmonary pressure, and expired volume during a cycle of three successive bursts of maximum voluntary coughing initiated after inspiration to total lung capacity. Results following intubation were compared with findings with subjects breathing through a 25-mm-I.D. mouthpiece (control). Maximum cough pressures (Pmax) following tracheal intubation were similar to control values, but with the tube in place, airflow began well before Pmax was reached and did not cease fully between cough bursts. Flows at Pmax declined with each successive burst of coughing during both experimental conditions, but with tracheal intubation, the flows were significantly lower than control. Resistance to flow at Pmax increased with each successive cough and increased significantly above control during the third burst of coughing while the subjects' tracheas were intubated. The total volume of the three control coughs was 76 +/- 3 per cent of vital capacity. This was similar following intubation, although cough duration was significantly longer. These findings indicate that tracheal intubation does not impair ability to develop normal cough pressures despite preventing glottic closure. The normal timing of flow and pressure is disrupted such that flow occurs early--as in a forced expiratory maneuver, and the flow is not fully interrupted during the cough sequence. Flows are submaximal as a result of the resistance of the tube and continue to decline as the lung volume decreases and airways are compressed. Because the tube is noncollapsible, high flow rates may be necessary to achieve the linear velocities requireed for normal airway cleansing through the tube. Such flows may be achieved only during the initial cough after full inspiration.     

分子筛自动切换程序的优化控制

为稳定上塔压力和塔内组分,保持再生污氮气流量的稳定,采用CS3000控制系统,实现了分子筛吸附装置自动切换程序控制、均压阀缓开、缓关等调节控制功能,保证了空分系统工况稳定,减少因控制系统故障造成的设备停机时间。     

3D CFD Predictions and Experimental Comparisons of Pressure Drop in a Ball Valve at Different Partial Openings in Turbulent Flow

A three dimensional computational fluid dynamics model, using the STAR-CD software, has been developed to simulate fluid flow in a commonly used flanged ball valve at different partially open settings. The Reynolds number (Re) range for the flow simulations was varied between 105 and 106 to simulate a variety of flow conditions. Each flow Re number is studied with three open positions for the valve, i.e., fully open, two-thirds open, and one-third open. The simulation was used to calculate two important parameters used in characterizing the flow properties in a typical valve namely the loss coefficient, K, and the flow coefficient, Cv. An attempt was also made to compare some of the simulation results with experimental data and available American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) data on valves. The simulations agree reasonably well with recently published experimental results and indicate that in most cases the K factor is independent of Re. The ASHRAE data for K factor values showed similar trends to the simulation but with lower values as it was only reported for gates valves. The Cv values show strong increases with the degree of valve opening and lesser influence by the Re number variations in the range studied     

Airway mechanics, gas exchange, and blood flow in a nonlinear model of the normal human lung

A model integrating airway/lung mechanics, pulmonary blood flow, and gas exchange for a normal human subject executing the forced vital capacity (FVC) maneuver is presented. It requires as input the intrapleural pressure measured during the maneuver. Selected model-generated output variables are compared against measured data (flow at the mouth, change in lung volume, and expired O2 and CO2 concentrations at the mouth). A nonlinear parameter-estimation algorithm is employed to vary selected sensitive model parameters to obtain reasonable least squares fits to the data. This study indicates that 1) all three components of the respiratory model are necessary to characterize the FVC maneuver; 2) changes in pulmonary blood flow rate are associated with changes in alveolar and intrapleural pressures and affect gas exchange and the time course of expired gas concentrations; and 3) a collapsible midairway segment must be included to match airflow during a forced expiration. Model simulations suggest that the resistances to airflow offered by the collapsible segment and the small airways are significant throughout forced expiration; their combined effect is needed to adequately match the inspiratory and expiratory flow-volume loops. Despite the limitations of this lumped single-compartment model, a remarkable agreement with airflow and expired gas concentration measurements is obtained for normal subjects. Furthermore, the model provides insight into the important dynamic interactions between ventilation and perfusion during the FVC maneuver.     

Electrical activation of the expiratory muscles to restore cough

Many patients with spinal cord injury have paralysis of their expiratory muscles and, consequently, lack an effective cough. The purpose of the present study was to evaluate the utility of lower thoracic spinal cord stimulation (SCS) to activate the expiratory muscles. Studies were performed on 15 anesthetized dogs. A quadripolar stimulating electrode (Medtronic Model 3586) was inserted epidurally and on the ventral surface of the lower thoracic spinal cord. Changes in airway pressure, airflow, and internal intercostal and abdominal muscle length were monitored to assess the effects of electrical stimulation. Spinal stimulation applied at the T9-T10 spinal level provided maximal changes in airway pressure generation in preliminary experiments. All subsequent studies were therefore performed with the electrode positioned at this level. The expiratory muscles were stimulated supramaximally over a wide range of lung volumes which were expressed as the corresponding change in airway pressure. The pressure-generating capacity of the expiratory muscles was evaluated by the change in airway pressure produced by SCS during airway occlusion. Peak expiratory airflow was also monitored following release of occlusion. At FRC, deflation (-10 cm H2O) and inflation (+ 30 cm H2O), SCS resulted in positive airway pressures of 44 cm H2O +/- 4 SE, 28 cm H2O +/- 3 SE, and 82 cm H2O +/- 7 SE. The relationship between airway pressure expiratory airflow generation and lung volume was linear (slope = 1.34 +/- 0.04) over the entire vital capacity range. Our results indicate that: (1) a major portion of the expiratory muscles can be activated reproducibly and in concert by electrical stimulation, and (2) this technique may be a clinically useful method of restoring cough in spinal cord injured patients.     

矿井通风热湿提取与资源化利用方法

矿井热湿风流中储存有大量低位热能和水汽,导致井下工作环境恶劣,乏风直排造成了大量资源浪费。因此,矿井通风热湿提取与资源化利用是解决深井热害和矿井低碳转型发展的重要途径之一。受地面大气状态参数和井下热湿源的影响,井巷热湿风流参数随时间变化,实时掌握井巷热湿风流转变特征是精准提取矿井风流中低位热能的关键。本文基于热湿风网实时解算,确定了矿井关键热湿节点分布规律及变化特征;建立了冷凝热湿提取计算模型,研发了热湿风流低位冷凝余热提用技术,形成了制冷–除湿联合的低位热能原位利用系统;提出了矿井乏风集中式和关键节点分布式热湿提取与资源化利用方法,并对提热收水效果进行了实例分析,为矿井低位热能提取利用和热害治理提供了理论基础和建设思路。      

Leak Detection in Pipes by Frequency Response Method

The frequency response method is used to determine the location and rate of leakage in open loop piping systems. A steady-oscillatory flow, produced by the periodic opening and closing of a valve, is analyzed in the frequency domain by using the transfer matrix method, and a frequency response diagram at the valve is developed. For a system with leaks, this diagram has additional resonant pressure amplitude peaks (herein referred to as the secondary pressure amplitude peaks) that are lower than the resonant pressure amplitude peaks (herein called primary amplitude peaks) for the system with no leaks. Several piping systems are successfully analyzed for all practical values of the friction factor to detect and locate individual leaks of up to 0.5% of the mean discharge. The method, requiring the measurement of pressure and discharge fluctuations at only one location, has the potential to detect leaks in real-life pipe systems conveying different types of fluids, such as water, petroleum, and so on.     

The occurrence of human intestinal parasites in Finland

We describe an apparatus measuring the cornealreflex stimulated pneumatically. The flow of preassurised air in the range of 0.1-1.5 bar is controlled by an electromagnetic switch. The time the valve is open, is variable. The air flow is directed to the cornea of the eye. The blink reflex is recorded by means of the surface electromyogramm and displayed on the screen of a storage scope. The device allows a clean, reproducable and simple measurement of the cornealreflex.     

Aerodynamic and acoustic characteristics of the adult African American voice

Laryngeal aerodynamic and acoustic characteristics of African American voice production were examined from vowel samples produced by ten adult female and ten adult male speakers. The data were compared with that for a control group consisting of ten adult female and ten adult male White speakers, matched for age, height, and weight. All measures were analyzed using Cspeech 4.0. Aerodynamic measurements, extracted from a glottal airflow waveform, included maximum flow declination rate, alternating glottal airflow, minimum glottal airflow, and airflow open quotient. Acoustic measures included fundamental frequency and sound pressure level. No significant mean differences between the African American and White speakers were found, except for maximum-flow declination rate. The White speakers produced significantly higher declination rates than the African American speakers. The factor of sex for the African American speakers was statistically significant for the measures of maximum-flow declination rate, alternating glottal airflow, open quotient, and fundamental frequency, consistent with the functioning of the White speakers. The results suggest that during vowel production, where the vocal tract is in a fairly static position, acoustic and aerodynamic characteristics for African American and White Speakers are comparable.     

Air Permeability of Waste in a Municipal Solid Waste Landfill

The permeability of compacted municipal solid waste in a landfill with respect to air (or gas) flow was estimated using a short-term air injection test. Air was added to 134 vertical wells installed at three different depths at flow rates in the range of 0.14?–1.4?m3?min?1 and the corresponding steady state pressures were recorded. The permeability of the waste with respect to airflow (described here as the air permeability) was estimated for different anisotropy ratios (kr/kz = 1, 10, and 100) using a steady state, two-dimensional, axisymmetric analytical fluid flow model in conjunction with the measured flow and pressure data. The air permeability of landfilled municipal solid waste modeled as an isotropic medium was found to range from 1.6×10?13 to 3.2×10?11?m2. The estimated air permeability results were on the low end of values previously applied to model landfill gas flow. Estimated air permeability decreased significantly with increasing waste depth. The lower permeability encountered in the deeper layers was primarily attributed to the lower porosity of the waste caused by higher overburden pressures and higher moisture content of waste in deeper layers of the landfill than in shallow layers. The results suggest that multiple wells screened at different depths provide greater control of air distribution within the landfill. Leachate recirculation was documented to impact the ability to add air. In addition to limitations posed by standing water in many of the deeper wells, waste exposed to leachate recirculation was found to be significantly less permeable to air when compared to original conditions.     

Experiences of the approaches to heart for a patient with a tracheostoma

The performance of open heart surgery in a patient with a tracheostoma can present difficult problems, including postoperative mediastinitis and inadequate operative exposure. Recently, we experienced two cases in which tracheostomy had been done preoperatively due to heart failure and reported the satisfactory results in this paper. Case 1; A 59-year-old woman who had mitral stenosis and massive regurgitation received mitral valve replacement and left atrial raphy. The approach to heart was performed in according to the following. A transverse submammary skin incision was made from right anterior axillar line to left mammary line and then a bilateral thoracotomy was made at the fourth intercostal space. Case 2; A 73-year-old man who had old myocardial infarction and postinfarction angina received coronary artery bypassgrafting to right coronary artery and left anterior descending branch, using saphenous vein grafts. A skin incision was placed at the second intercostal space in the fashion of "collar skin incision" and then made from the center of collar skin incision to the xiphoid process. The sternum was transected at the second intercostal space and divided longitudinally to the xiphoid process. These two approaches provided the adequate operative field. The cannulation of the ascending aorta, the superior vena cava and the inferior vena cava presented no difficulty and the operative procedure could be performed easily in a routine manner. We think that in a case of open heart surgery of a patient with a tracheostoma the approach in which the skin incision is distant from the area of a tracheostoma and no dissection near a tracheostoma is necessary have to be selected in order to decrease the risk of postoperative wound infection and mediastinitis.     

棒式文丘里除尘器气液两相流阻力特性

为了掌握棒式文丘里除尘器内气液两相流的阻力特性,基于多相流理论,建立其三维CFD模型,研究分析棒间距、除尘风量和液气比对棒式文丘里除尘器阻力特性的影响,并建立了阻力预测公式以及三者之间的关系式.结果表明：文丘里棒层与下筒体的压力损失随着棒间距的减小和风量的增大呈幂指数关系增大,随着液气比的增大呈近线性增大;上筒体的压力损失与风量呈近平方关系;通过与实验数据对比,关系式最大误差为16.88%,验证了其有效性.     

Heat-transfer enhancement using weakly ionized, atmospheric pressure plasma in metallurgical applications

Experimental measurements and computational analysis of heat transfer in atmospheric pressure, midtemperature range (1200 to 1600 K) plasma flow over an aluminum cylinder have been carried out. A comparison of transient temperature measurements for the aluminum cylinder under convective unionized air flow and those with convective plasma flow shows significantly higher heat transfer from plasma flow compared to air flow under identical temperature and flow conditions. A heattransfer problem is computationally modeled by using available experimental measurements of temperature rise in the cylinder to determine the degree of ionization in the plasma flow. The continuity, momentum, and energy conservation equations, as well as conservation equations for electrons and ions, and the Poisson’s equation for self-consistent electric field are solved in the plasma by a finite volume method. The conjugated transient heat transfer in the cylinder and in the plasma is obtained by simultaneous solution of the transient energy conservation equations. It is shown that the enhancement of heat transfer in plasma flow is due to the energy deposited by charged species during recombination reaction at the solid surface. An important finding is that even a small degree of ionization (<1 pct) provides significant enhancement in heat transfer. This enhancement in heat transfer can lead to a productivity increase in metallurgical applications.     

Meta-analysis and dose-response functions of air pollution respiratory effects

A Meta-analysis was conducted on 107 original epidemiological papers published between 1980 and 1993 on the respiratory health impact of suspended particles, sulfur dioxide, ozone and nitrogen dioxide. These are the usual air quality indicators that are monitored in urban ambient air. The range of exposures that were studied (averages and 90th percentiles are respectively up to 88, 83, 124 and 53 mu/m3 (averages) and 180, 147, 234 and 131 micrograms/m3 (90th percentile) for each of the four pollution indicators) allowed assessment of dose-response functions for irritative pulmonary conditions (cough and/or asthma episodes) and respiratory function (FEVI and peak expiratory flow). The dose-response functions seem linear in the range of observed concentrations, with nitrogen dioxide showing the least consistent association across different health indicators. When applied to exposures measured as a 100 micrograms/m3 increase of pollutant's concentrations compared to low background values, the average relative risks of airway irritation (cough and/or asthma épisodes) range, according to the pollutant, from 1.08 to 1.47; average relative decreases of respiratory function amount to 1.1 to 2.2%. The effects are most often stronger among young subjects. The results of this study, when applied to air pollution concentrations in the range of values that were observed in this study, should foster health risk assessment studies in places where population air pollution exposures are available.     

汽轮机高调门阀杆断裂故障的改造优化探索

通过对济钢燃气-蒸汽联合循环发电系统40MW汽轮机高调门阀杆疲劳损坏故障分析,提出在低负荷时阀碟处于不稳定状态,气流冲击和气流振荡加剧阀杆损坏的观点。依据故障原理有针对性的提出改造措施,在设备运行状态和高调门结构方面实施优化改造,顺利解决了故障问题。     

Respiratory function and surgical reduction of lung volume

Emphysema is characterised by an enlargement of the terminal air spaces. Destructions of alveolar walls lead to a loss of the lung elastic recoil. The driving pressure for expiration is decreased and the outward forces acting on the bronchioles are lost, leading to bronchiolar collapse and airflow limitation. Hyperinflation of the lungs and overdistension of the chest wall cause the respiratory muscles to operate in unfavourable conditions. Patients with advanced emphysema have decreased quality of live: they are dyspneic at rest and are unable to perform exercise. Surgical excision of parts of diffusely emphysematous lungs (Lung Volume Reduction Surgery, LVRS) has been proposed since many years. Expansion of the remaining lung should increase lung elastic recoil and restore the outward forces on the bronchioles. It has been demonstrated that LVRS reduces dyspnea symptoms, improves exercise tolerance and enhances the quality of live. LVRS increases lung elastic recoil, airway conductance and maximal expiratory flow, reduces dynamic hyperinflation and improves the efficiency of the respiratory muscles. These improvements are maintained for at least 12 to 18 months. Preoperative evaluation, surgical-induced modifications of pulmonary functions and postoperative exercise training are exposed.     

Levator veli palatini muscle activity in relation to intraoral air pressure variation in cleft palate subjects

A comparison of the ranges of levator veli palatini EMG activity for speech versus a nonspeech task for subjects with cleft palate was the focus of this study. EMG values are also compared with subjects without cleft palate obtained in a previous study. Hooked-wire electrodes were inserted into the levator muscle of five adult subjects with cleft palate exhibiting mild hypernasality. Intraoral air pressure was measured concurrently. A blowing task was used to determine the subject's operating range for the levator muscle. Both the nonspeech and speech tasks were designed to sample the widest possible ranges of levator EMG activity. It was found that the subjects with cleft palate used a relatively high activation level for the levator muscle during speech, in relation to their total activation range, compared with the subjects without cleft palate. Implications are discussed in relation to possible anatomic and physiologic differences for cleft palate subjects compared to normal.     

Inhomogeneity of pulmonary perfusion during sustained microgravity on SLS-1

We studied the effects of gravity on the inhomogeneity of pulmonary perfusion in humans by performing hyperventilation-breath-hold single-breath measurements before, during, and after 9 days of continuous exposure to microgravity during the Spacelab Life Sciences-1 (SLS-1) mission. In microgravity the indicators of inhomogeneity of perfusion, especially the size of cardiogenic oscillations in expired CO2 and the height of phase IV, were markedly reduced. Cardiogenic oscillations were reduced to approximately 60% of their preflight standing size, and the height of phase IV was between 0 and -8% (a terminal fall became a small terminal rise) of the preflight standing value. The terminal change in expired CO2 was nearly abolished in microgravity, indicating more uniformity of blood flow between lung units that close and those that remain open at the end of expiration. A possible explanation of this observation is the disappearance of gravity-dependent topographic inequality of blood flow. The residual cardiogenic oscillations in expired CO2 imply a persisting inhomogeneity of perfusion in the absence of gravity, probably in lung regions that are not within the same acinus.