塔克拉玛干沙漠腹地复合沙垄的流场和上覆沙丘组合及动态特征

复合沙垄是最大的沙丘地貌类型之一 ,表现为简单沙丘类型的垂直叠加和水平连接 ,在沙垄的高大地形影响下 ,沙垄不同部位形成不同的风沙环境特征。以塔克拉玛干沙漠腹地 /复合沙垄为例 ,通过野外实地观测研究其流场和上覆沙丘组合特征。研究结果表明 ,复合沙垄的流场可分为沙垄迎风坡气流加速区、沙垄背风坡气流转向减速区、垄间粗沙平地气流风速风向恢复区和气流风速稳定区。受沙垄流场和地形的控制 ,沙垄上覆新月形沙丘链 ,垄间地分布有简单新月形沙丘、沙堆、沙片、侵蚀地、简单线形沙丘。上覆沙丘分布特征表现为 :垄间地上覆新月形沙丘疏密度较小 ,沙垄迎风坡和沙垄背风坡上覆新月形沙丘疏密度较大 ,而且超过 1,说明沙垄迎背风坡上覆沙丘有叠置现象。沙垄上覆沙丘高度自沙垄迎风坡底部到顶部增高 ,背风坡上覆沙丘高度自沙垄顶部到背风坡底部减小 ,上覆沙丘在自身形态、地形和流场的共同影响下 ,存在相对运动 ,表现为分布进一步集中 ,因此沙垄有增高的趋势。

贵阳市空气污染数值预报的业务方法研究

使用地形跟踪坐标系上的三维动力学流场模式和平流扩散方程模式 ,开发了贵阳市分片区SO2 污染水平预报的业务数值预报模式。城市地形和大气污染物排放源强按实际情况输入 ,污染气象条件则使用天气学方法预报。经贵阳市实际应用 ,对城市平均SO2 污染指数的 2 4h预报准确率可达 80 %以上。

Airflow characteristics by air curtain jets in full-scale room

A new air distribution pattern,air curtain jet ventilation was presented.The ventilation or airflow patterns and the air velocity produced by air curtain jet were investigated in detail.To identify the airflow characteristics of this novel air curtain jet ventilation system,a full-scale room was used to measure the jet velocity with a slot-ventilated supply device,with regards to the airflow fields along the vertical wall as well as on the horizontal floor zones.The airflow fields under three supply air velocities,1.0,1.5 and 2.0 m/s,were carried out in the full-scale room.The experimental results show the velocity profiles of air distribution,the airflow fields along the attached vertical wall and the air lake zones on the floor,respectively.The current experimental research is helpful for heating,ventilation and air conditioning(HVAC) engineers to design better air distribution in rooms.

Process simulation and optimization of flow field in wet electrostatic precipitator

To improve the dust removal performance of the wet electrostatic precipitator(WESP), a flow field optimization scheme was proposed via CFD simulation in different scales. The simplified models of perforated and collection plates were determined firstly. Then the model parameters for the resistance of perforated and collection plates, obtained by small-scale flow simulation, were validated by medium-scale experiments. Through the comparison of the resistance and velocity distribution between simulation results and experimental data, the simplified model is proved to present the resistance characteristics of perforated and collection plates accurately. Numerical results show that after optimization, both the flow rate and the pressure drop in the upper room of electric field regions are basically equivalent to those of the lower room, and the velocity distribution in flue inlet of WESP becomes more uniform. Through the application in practice, the effectiveness and reliability of the optimization scheme are proved, which can provide valuable reference for further optimization of WESP.

ENSO hindcast skill of the IAP-DecPreS near-term climate prediction system:comparison of full-field and anomaly initialization

Model initialization is a key process of climate predictions using dynamical models. In this study, the authors evaluated the performances of two distinct initialization approaches--anomaly and full-field initializations--in ENSO predictions conducted using the IAP-DecPreS near-term climate prediction system developed by the Institute of Atmospheric Physics （lAP）. IAP-DecPreS is composed of the FGOALS-s2 coupled general circulation model and a newly developed ocean data assimilation scheme called＇ensemble optimal interpolation-incremental analysis update＇ （EnOI-IAU）. It was found that, for IAP-DecPreS, the hindcast runs using the anomaly initialization have higher predictive skills for both conventional ENSO and El Nino Modoki, as compared to using the full-field initialization. The anomaly hindcasts can predict super El Nino/La Nina 10 months in advance and have good skill for most moderate and weak ENSO events about 4-7 months in advance.The predictive skill of the anomaly hindcasts for El Nino Modoki is close to that for conventional ENSO. On the other hand, the anomaly hindcasts at 1- and 4-month lead time can reproduce the major features of large-scale patterns of sea surface temperature, precipitation and atmospheric circulation anomalies during conventional ENSO and El Nino Modoki winter.

Further Study of Typhoon Tracks and the Low-Frequency (30-60 Days) Wind-Field Pattern at 850 hPa

The association of typhoon tracks over the western Pacific with the low-frequency wind-field pattern of atmospheric intraseasonal (30-60 days) oscillation at 850 hPa is further studied by using observational data analyses. Comparative analyses of the composite wind fields at 850 hPa, contrasting the atmospheric intraseasonal oscillation (ISO) with the original circulation, show that the typhoon tracks are closely related to the wind pattern of the ISO but are not obviously related to the original wind fields. Case studies of two typhoons in 2006 also show that the low-frequency wind-field pattern, particularly the maximum-value line (belt) of low-frequency cyclonic vorticity at 850 hPa, is closely related to the typhoon track. Therefore, the lowfrequency circulation pattern and the maximum-value line (belt) of low- frequency cyclonic vorticity at 850hPa can be used to predict typhoon tracks over the northwestern Pacific.

Effect of Market Power in Electricity Markets

The main objective of this paper is to show an overview analysis of market power issues.Market power reflects the scarcity of power supply.It is the ability of a particular seller or group of sellers to maintain prices profitably above competitive levels for a significant period of time.Because the electric power system has its own characteristics that are different to other economic systems,both physical factors and economic factors of power system are key elements on this definition.We study some cases here,including different line limit levels,load levels and bid strategy through a market model based on OPF (optimal power flow) with a decommitment algorithm.

CFD simulation of high-temperature effect on EHD characteristics in a wire-plate electrostatic precipitator

A computational fluid dynamics （CFD） model is carried out to describe the wire-plate electrostatic precipitator （ESP） in high temperature conditions, aiming to study the effects of high temperature on the electro- hydrodynamic （EHD） characteristics. In the model, the complex interactions at high temperatures between the electric field, fluid dynamics and the particulate flow are taken into account. We apply different numerical methods for different fields, including an electric field model, Euler-Lagrange particle-laden flows model, and particle charging model. The effects of high temperature on ionic wind, EHD characteristics and collection effi- ciency are investigated. The numerical results show high temperature causes more significant effects of the ionic wind on the gas secondary flow. High viscosity of gas at high temperature makes particles follow the gas flow pattern more closely. High temperature reduces the surface electric strength, so that the mean electric strength weakens the space charging. On the contrary, there is an increase in the diffusion charging at high tem- perature compared with at low temperature. High temperature increases the ratio of mean drag force over mean electrostatic force actin~ on the ~atticles which mav contribute to a decline of collection efficiencv.

Subthermocline anticyclonic gyre east of Mindanao and its relationship with the Mindanao Undercurrent

The quasi-permanent anticyclonic gyre （ACG） east of Mindanao is a dominant feature of the subthermocline circulation in the southem Philippine Sea, and it is believed closely associated with the continuous northward alongshore flow of the Mindanao Undercurrent （MUC）. In this study, the structure and variability of this ACG were investigated using the 1950-2012 output of the Oceanic General Circulation Model for the Earth Simulator （OFES）, which can reproduce well the structure of the climatological intermediate-layer circulation and satellite-observed sea level variations in the southern Philippine Sea. Between 26.8-27.3 ao, the ACG covers a large area from the Mindanao coast to 131 ~E and from 3~N to 10~N. Its anticyclonic flow structure is unrelated to the surface Halmahera Eddy. The eddy-resolving simulation of the OFES revealed that the ACG consists of two components. The southern ACG （SACG） is centered at -6~N, while the northern ACG （NACG） is centered at -10~N. Seasonal and interannual variations of the ACG are linked to the variations of the northward MUC transport along the Mindanao coast, and the role of the SACG is more important than the NACG. Stronger （weaker） ACGs lead to greater （smaller） MUC transport. On the interannual timescale, the SACG shows a spectrum peak at 4-8 years, while the NACG has enhanced power within the 3-5-year band. A lead-lag correlation analysis indicates that interannual variations of the ACGs and the MUC transport are partly associated with the E1 Nifio-Southern Oscillation. Possible causes for the ACG variability are discussed.

Oscillating Propagation of Kink in Nondissipative Frenkel-Kontorova Chain Due to External DC Force

We report the oscillating propagation of kink in a nondissipative Frenkel-Kontorova （FK） chain driven by external DC force, which is different from the usual propagation of localized modes with equal speed. When the kink moves in the opposite direction of the external DC force, the kink will be accelerated and the potential of the FK chain in the external force field is transformed to be the kinetic energy of the kink. If the kink reaches the boundary of the FK chain, the kink will be bounced back and moves in the opposite direction, then the kink will be decelerated gradually and the kinetic energy of the kink ＆ transformed to be the potential of the FK chain in the external force field. If the speed of the kink reaches zero, the kink will move in the opposite direction again driven by the external DC force, and a new oscillating cycle begins. Simulation result demonstrates exactly the transformation between the kinetic energy of the kink and the potential of the FK chain in the external force field. The interesting energy exchange is induced by the special topology of kinks, and other localized modes, such as breathers and envelope solitons, have no the interesting phenomenon.

A two-dimensional subthreshold current model for strained-Si MOSFET

An analytical model for the subthreshold current of a strained-Si metal-oxide-semiconductor field-effect transistor (MOSFET) is developed by solving the two-dimensional (2D) Poisson equation and the conventional drift-diffusion theory. Model verification is carried out using the 2D device simulator ISE. Good agreement is obtained between the model's calculations and the simulated results. By analyzing the model, the dependence of current on the strained-Si layer strain, doping concentration, source/drain junction depths and substrate voltage is studied. This subthreshold current model provides valuable information for strained-Si MOSFET design.