影响降膜蒸发器关键设计参数的因素分析

降膜蒸发器是一种高效并被广泛应用的关键设备。介绍了蒸发器的设计计算逻辑及数学模型,分别计算了系统压力、单管液体流量、强制循环量以及管径管长对蒸发器设计的影响,并对分析结果进行分析和比较,得出系统压力是影响蒸发器规模的主要因素。提高系统压力可大幅度降低蒸发器规模,降低投资成本。在保证蒸发器最低液体流量前提下,选用较低的单管液体流量和较大的强制循环比可以提高系统的稳定性能。     

Method for evaluating the reliability of compressor impeller of turbocharger for vehicle application in plateau area

As turbocharging diesel engines for vehicle application are applied in plateau area, the environmental adaptability of engines has drawn more attention. For the environmental adaptability problem of turbocharging diesel engines for vehicle application, the present studies almost focus on the optimization of performance match between turbocharger and engine, and the reliability problem of turbocharger is almost ignored. The reliability problem of compressor impeller of turbocharger for vehicle application when diesel engines operate in plateau area is studied. Firstly, the rule that the rotational speed of turbocharger changes with the altitude height is presented, and the potential failure modes of compressor impeller are analyzed. Then, the failure behavior models of compressor impeller are built, and the reliability models of compressor impeller operating in plateau area are developed. Finally, the rule that the reliability of compressor impeller changes with the altitude height is studied, the measurements for improving the reliability of the compressor impellers of turbocharger operating in plateau area are given. The results indicate that when the operating speed of diesel engine is certain, the rotational speed of turbocharger increases with the increase of altitude height, and the failure risk of compressor impeller with the failure modes of hub fatigue and blade resonance increases. The reliability of compressor impeller decreases with the increase of altitude height, and it also decreases as the increase of number of the mission profile cycle of engine. The method proposed can not only be used to evaluating the reliability of compressor impeller when diesel engines operate in plateau area but also be applied to direct the structural optimization of compressor impeller.     

Estimating the flow velocity and discharge of ADCP unmeasured area in tidal reach

Due to the ringing and side-lobe interference, acoustic Doppler current profiler (ADCP) is unable to accurately capture the complete velocity profile in open channels near the water surface and channel bottom, which are usually called unmeasured areas. At present, the flow velocities through the unmeasured areas are most commonly estimated using the power law with the power set to be the default value. However, since the flows are unsteady and nonuniform in tidal reaches, the velocity distribution model and corresponding parameters will vary with the bathymetric, tide period, etc. Therefore, the most common estimation with the power law may not be suitable in tidal reaches. In this paper, a simple determination method of the best model is proposed. Firstly, the parameters in three classical velocity distribution models, which are called power law, logarithmic law and parabolic law models, are solved by least squares based on the ADCP measured velocity cells. Then, the corresponding root-mean-square error (RMSE) of each model is used for the quantitative indicator that the model with the minimum RMSE is chosen as the best model. At last, the flow velocity and discharge of the unmeasured area are estimated by the best model. The experiments carried out in the tidal reach of Yangtze Estuary showed that vertical flow velocity distribution various with the bathymetry and tide period, and the best models averagely improved about 2.0% of the relative standard deviation (RSD) relative to the power law method in the discharge estimation, especially at some tide period the RSD of the best model was several times better than that of power law model. For Yangtze River with an annual average discharge of 3.0×10⁴ m³/s, the improvement should not be ignored. Therefore, it will be necessary to use the best model with minimum RMSE to estimate the flow velocity in tidal reach.     

Effect of microstructure on the electrochemical performance of Ni-ScSZ anodes

The effects of NiO powder morphology and sintering temperature on the microstructure and the electrochemical performance of Nickel-scandia-stabilized zirconia (Ni-ScSZ) cermet anodes for solid oxide fuel cells (SOFCs) were investigated. The particle size and agglomeration of the starting powders were found to affect both the microstructure and electrochemical performance of the Ni-ScSZ cermet anodes. The lowest polarization resistance, 0.690 Ω cm² at 700 °C, was measured for the Ni-ScSZ anode prepared with fine NiO powder (~0.5 µm grain size). This was attributed to the increase in the number of reaction sites afforded by the small grains and well-dispersed Ni and ScSZ phases. The effect of the anode sintering temperature was also found to affect the anode microstructure, adhesion with the electrolyte, and consequently anode polarization resistance. The lowest polarization resistance was observed for the anode sintered at 1400 °C and this was 3–5 times lower than the corresponding values for anodes sintered at lower temperatures.     

Transcranial Magnetic Stimulation of the Supplementary Motor Area in the Treatment of Obsessive-Compulsive Disorder: A Multi-Site Study

Recently, strategies beyond pharmacological and psychological treatments have been developed for the management of obsessive-compulsive disorder (OCD). Specifically, repetitive transcranial magnetic stimulation (rTMS) has been employed as an adjunctive treatment in cases of treatment-refractory OCD. Here, we investigate six weeks of low frequency rTMS, applied bilaterally and simultaneously over the sensory motor area, in OCD patients in a randomized, double-blind placebo-controlled clinical trial. Twenty-two participants were randomly enrolled into the treatment (ACTIVE = 10) or placebo (SHAM = 12) groups. At each of seven visits (baseline; day 1 and weeks 2, 4, and 6 of treatment; and two and six weeks after treatment) the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was administered. At the end of the six weeks of rTMS, patients in the ACTIVE group showed a clinically significant decrease in Y-BOCS scores compared to both the baseline and the SHAM group. This effect was maintained six weeks following the end of rTMS treatment. Therefore, in this sample, rTMS appeared to significantly improve the OCD symptoms of the treated patients beyond the treatment window. More studies need to be conducted to determine the generalizability of these findings and to define the duration of rTMS’ clinical effect on the Y-BOCS. Clinical Trial Registration Number (NCT) at www.clinicaltrials.gov: {"type":"clinical-trial","attrs":{"text":"NCT00616486","term_id":"NCT00616486"}}NCT00616486.     

Fourier‐Transform Rheology of Unvulcanized,Carbon Black Filled Styrene Butadiene Rubber

Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ₀ < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I_3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I_3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ₀ = 0.32). The addition of up to 70 phr CB leads to an increase of I_3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I_3/1 is pronounced for CB levels above the percolation threshold.

     

基于地域的景观温室热带雨林展示区 景观设计

通过对原生热带雨林景观特征的研究以及中国3个 以植物原生境为展示特色的植物园景观温室热带雨林展示区的 调查研究,发现景观温室设计上对雨林原生状态景观的表现存 在雨林类型呈现不完全、地域性不足、整体性不明显等问题。 在世界热带雨林各分布区地域特征分析的基础上,提出景观温 室热带雨林展示区以非洲雨林群系、美洲雨林群系以及印度- 马来雨林群系作为主题。从不同地域主题出发,从地形、土 壤、水体、文化、植物等景观要素的设置上进行景观设计,旨 在展现不同雨林群系的地域特色,为景观温室热带雨林展示区 景观设计提供参考。     

矩形钢管混凝土组合桁梁负弯矩区受力性能试验研究

矩形钢管混凝土组合桁梁由混凝土板和矩形钢管混凝土桁架组成,在竖向荷载作用下,其正弯矩区可充分发挥混凝土板和桁架的组合作用,但负弯矩区的力学性能较为薄弱且受拉混凝土板容易开裂。针对这一问题,提出了在负弯矩区混凝土板施加预应力以及布置局部释放剪切作用的剪力钉相结合的组合桁梁结构形式。采用跨中施加反向集中荷载模拟连续梁支点反力的方法,对2榀承受负弯矩的矩形钢管混凝土组合桁梁进行了静力加载试验,对其荷载-位移关系、裂缝发展规律、混凝土板应变分布、桁梁荷载-应变关系、钢与混凝土界面滑移及承载力进行了分析。还根据组合桁梁的简化力学模型对不同加载阶段的结构特征荷载进行了讨论。结果表明：采用局部释放剪切作用的剪力钉和混凝土板施加预应力的组合桁梁结构形式可有效提高其抗裂性能,但对受弯承载力影响较小;在加载过程中混凝土板的开裂和杆件的屈服导致结构塑性变形增大,最终节点处焊缝撕裂,组合桁梁丧失承载力;由简化力学模型计算得到的结构特征内力与实测值吻合较好,可为矩形钢管混凝土组合桁梁负弯矩区的设计和计算提供参考。     

人间仙境，妫汭花园——2019中国北京世界园艺博览会核心区景观规划设计

从博览会项目的本质入手,探讨作为世园会的核心景观区应如何定位。以功能兼顾、文化表达、空间主体和永续利用为4个主要方面,阐述在大事件背景下落实2019北京世园会核心区设计的困难与挑战,并着重论述了对场地信息层中各类因素的寻找和取舍。方案整体兼顾作为"设计"一体两面的"功能"与"立意",尊重并利用客观存在的场地记忆,从处理进入湖区的方式开始,建构起多种语言要素并置的叙事空间,勾勒出一幅徐徐展开在世界面前、极具中国意境的园艺画卷——人间仙境,妫汭花园。     

Investigation report of geotechnical disaster on river area due to typhoon landfall three times on Okhotsk region,Hokkaido, Japan

For one week from August 17 to 23, 2016, three consecutive typhoons made landfall in Hokkaido for the first time on record. These typhoons and the front they stimulated brought record-breaking torrential rain over the eastern part of Hokkaido. To investigate the damage to grounds and rivers resulting from this rainfall, the Japan Society of Civil Engineers (JSCE) and the Japanese Geotechnical Society (JGS) formed a disaster research group to conduct an investigation. This report provides the results of the investigation into damage to the grounds of areas along the Tokoro River of the Okhotsk region, Hokkaido, that suffered from this tremendous and diverse disaster. Specifically, the report describes the situation of the levees which were broken and eroded by the overflowing water, the shape of the levee bodies, the levee body soil properties examined by observation of the sections, as well as the occurrence of sand boiling and air blows. The washout of road embankments as well as damage to road bridge mounting fills and abutment backfills were also investigated. The investigation has demonstrated the need to clarify the resistance of the abutment backfills and levee bodies to flowing water as well as the geotechnical predominant factors in order to clarify the mechanisms behind erosion and washout, the need to review new measures that allow for the scale of sand boiling and resultant changes in levee body stability, and the fact that the existing embankments were able to temporarily suppress the flooding water which had spilled over from the river. Furthermore, although it has been identified that the findings of a study on an embankment washout associated with a tsunami can be applied to measures taken against the overflowing water, it has also been found necessary to clarify the predominant geotechnical factors using model tests and to use a more sophisticated analytical approach to establish a geotechnical stability review as soon as possible in order to prevent the levees and embankments from being eroded and washed out due to overflowing water.