Seasonal and inter-annual variation of surface roughness length and bulk transfer coefficients in a semiarid area

Here we report a multiyear study on the surface roughness length and bulk transfer coefficients over the degraded grassland and cropland surfaces in a semiarid area of China. Eddy covariance measurement and the meteorological profile observation data were used to analyze characteristics of these parameters on the diurnal, seasonal, and annual scales. Significant seasonal and annual variations of the aerodynamic roughness length are observed over the two surfaces. A large variation of kB-1 is measured during the day. Both kB-1 and the bulk transfer coefficients exhibit significant seasonal and annual variations. During the growing season (May to October), average Cd and Ch are 3.1×10-3 and 2.5×10-3 over the degrade grassland surface, and 4.7×10-3 and 3.1×10-3 over the cropland surface respectively. During the non-growing season, average Cd and Ch are 2.3×10-3 and 2.0×10-3 over the degrade grassland surface, and 2.9×10-3 and 2.2×10-3 over the cropland surface respectively.

Bulk transfer coefficients of the atmospheric momentum and sensible heat over desert and Gobi in arid climate region of Northwest China

By utilizing the data of the intensive observation period (May-June, 2000) of Dunhuang land-surface process field experiment that belongs to 'Land-atmosphere Interactive Field Experiment over Arid Region of Northwest China', the bulk momentum transfer coefficient Cd and bulk sensible heat transfer coefficient Ch between surface and atmosphere over desert and Gobi in the arid region are determined according to three different methods. The result shows that, though these bulk transfer coefficients are different, they are in the same order. Especially, the means of Cd and Ch are close. Moreover, through analyzing the wind direction, the interference of the building near the observational station with the data is eliminated. From this, the relation between the bulk transfer coefficients and the bulk Richardson number and the range of the typical values of the bulk transfer coefficients over desert and Gobi in the typical arid region are obtained.

The bulk transfer coefficients and surface fluxes on the western Tibetan Plateau

On the gradient observational data of the atmospheric surface layer from September 1997 to December 1998 collected by two sets of Automatic Weather Station (AWS) installed in Gaize and Shiquanhe on the western Tibetan Plateau, mean surface roughness lengths at the two stations above are determined to be 2.7 and 2.9 cm, respectively. The bulk transfer coefficients each day are computed by the profile-flux method, means of the bulk transfer coefficient for momentum (i.e. drag coefficient) in 1998 are 4.83×10-3 and 4.75×103 at the two stations. The surface fluxes of momentum, sensible heat and latent heat each day are further estimated by the bulk formulas, annual mean of these fluxes is 3.4×10-2 and 1.8×102N/m2, 73.1 and 67.2 W/m2, 15.4 and 2.9 W/m2, respectively. The diurnal and seasonal variations are obtained by a composite method and the relationships among the heat transfers between land and atmosphere, plateau monsoon and plateau rain season are also discussed.

Characteristics of Momentum and Heat Transfer over Semiarid Grasslands with Different Grazing Intensities in Inner Mongolia,China

The drag coefficient （Ca） and heat transfer coefficient （Ch） with the bulk transfer scheme are usually used to calculate the momentum and heat fluxes in meteorological models. The aerodynamic roughness length （z0m） and thermal roughness length （z0h） are two crucial parameters for bulk transfer equations. To improve the meteorological models, the seasonal and interannual variations of Z0m, Z0h, coefficient kB-1, Cd, and Ch were investigated based on eddy covariance data over different grazed semiarid grasslands of Inner Mongolia during the growing seasons （May to September） from 2005 to 2008. For an ungrazed Leymus chinensis grassland （ungrazed since 1979）, Z0m and z0h had significant seasonal and in- terannual variations. Zorn was affected by the amount and distribution of rainfall, kB 1 exhibited a relatively negative variation compared with z0h, which indicates that the seasonal variation of z0h cannot be described by kB 1. To parameterize Zorn and z0h, the linear regressions between ln（z0m）, ln（z0h）, and the leaf area index （LAI） were performed with R2=0.71 and 0.83. The monthly average kB-1 was found to decrease linearly with LAI. The four-year averaged values of Ca and Ch were 4.5 × 10^-3 and 3.9× 10^-3, respectively. The monthly average Cd only varied by 8% while the variation of Ch was 18%, which reflects the dif- ferent impacts of dead vegetation on momentum and heat transfer at this natural grassland. Moreover, with the removal of vegetation cover, grazing intensities reduced Z0m, Z0h, Cd, and Ch.

Ground data transfer research in AMS-02

To increase the performance of bulk data transfer mission with ultra-long TCP （ transmission control protocol） connection in high-energy physics experiments, a series of experiments were conducted to explore the way to enhance the transmission efficiency. This paper introduces the overall structure of RC@ SEU （ regional center @ Southeast University） in AMS （alpha magnetic spectrometer）-02 ground data transfer system as well as the experiments conducted in CERNET （China Education and Research Network）/CERNET2 and global academic Internet. The effects of the number of parallel streams and TCP buffer size are tested. The test confirms that in the current circumstance of CERNET, to find the fight number of parallel TCP connections is the main method to improve the throughput. TCP buffer size tuning has little effect now, but may have good effects when the available bandwidth becomes higher.

散料仓储物流建筑优化策略研究——以满洲里钾肥厂房设计为例

仓储物流建筑在工农业生产中具有重要作用,在物流过程中承担短期储藏和初步加工的功能。然而,现阶段国内大部分仓储转运建筑还存在功能分区不合理、转运效率低等问题。为此,本文基于传统散料仓储转运流程,借鉴国内外先进口岸转运方式,以满洲里钾肥转运厂房设计为例,从转运流程、仓储空间、厂房形态三个层面提出散料仓储建筑设计优化方案,以期提高仓储转运效率、降低转运成本。

非富勒烯有机体异质结中磁光电流及相干自旋混合理论研究进展

有机非富勒烯分子受体,又称稠环电子受体,由于其优良的光电转换性质,现已成为备受关注的有机光电子材料之一。基于该类材料所发展的有机体异质结太阳能电池,其能量转换效率已逼近20%。而制备高效稳定的有机体异质结太阳能电池离不开对材料物性和光伏过程的深入探索。在众多研究体系中,非富勒烯光伏自旋动力学的发展尚处于起步阶段,其内在的光物理机理尚未明确。而光激发磁光电流技术能通过监测有机体异质结中极化子对的解离,在器件工作状态下,原位表征光伏自旋动力学过程。本文结合实验和理论研究,科学地阐述目前主流的有机磁光电流理论基础及函数模型,如低磁场下的超精细耦合效应和自旋-轨道耦合效应,高磁场下的Δg机制;探讨不同有机体异质结在不同表征条件下如偏压、温度、光强的信号差异;最后,讨论了超快光谱技术在有机体异质结体系中的应用。

OHCI简介及Bulk传输调试实例

通用串行总线(USB)是一种简单的计算机外围接口标准。它具有即插即用、扩展方便等优点,已成为计算机必备的一个接口。该文介绍了OHCI数据四种传输类型之一的Bulk传输,并对Bulk传输的IN/OUT Token进行研究。然后描述在调试MassStorage设备初始化过程中碰到的一个因OHCI Bulk传输而引起的问题,针对该问题进行分析,利用各种调试工具解决问题,文章最后总结了解决问题的心得和体会。

集约化生产条件下稻田土壤机械压实预测模型构建与验证

传统的土壤压实风险评估方法是基于土壤的先期固结压力理论,以机械的接地压力与土壤先期固结压力间关系作为判断依据,缺少针对集约化稻作“湿耕烂种”等生产场景中由定量机械压实造成的土壤结构破坏程度的评价方法和依据。为研究适合中国稻作特色,可以定量预测机械压实危害程度的压实容重预测模型,该研究基于土壤的回弹指数和压缩指数推导出土壤压实容重预测模型,以适用于集约化生产条件下稻田土壤机械压实预测。采用调控原状土含水率的单轴压缩试验法分别构建了土壤初始容重、初始含水率与弹性压缩模量、塑性压缩模量和先期固结压力之间的传递函数,然后基于典型机型的田间原位平板下陷试验验证所建模型的可靠性和实用性。结果表明,基于单轴压缩试验法构建的各传递函数拟合决定系数大于0.95。将各传递函数模型所得的弹性压缩模量、塑性压缩模量和先期固结压力输入土壤压实容重模型预测的压实后的土壤容重与实测值的相对误差小于5%。可见,该研究设计的土壤压实预测模型能够准确量化受机械压实情况下土壤容重的变化量,而土壤传递函数法能为构建和应用区域性农业土壤的压实模型提供便利。研究可为集约化生产条件下稻作“湿耕烂种”等生产场景中由定量机械压实造成的土壤结构破坏程度评价提供可靠方法和依据。

PRELIMINARY ANALYSIS OF TURBULENT TRANSFER CHARACTERISTICS IN THE SURFACE LAYER OVER GUANGZHOU REGION

On the basis of the Monin-Obukhov similarity theory, a semi-empirical expression of universal functions is fitted by means of the iteration method. using the gradient observation data of wind and temperature in the surface layer. The characteristics of bulk transfer coefficient are studied and some empirical relationships among the bulk transfer coefficient, the wind speed and temperature are obtained. The applicability of the results is investigated using observation data.

Particulate flow analysis in inclined pipes and transfer chutes using tomography imaging,discrete element simulations and continuum modeling approaches

In particulate material transfer systems,traditional shear test based steady state analysis can provide some insight into the strength of the bulk material and subsequent resistive frictional forces during flow.For fast flowing transfer points,dynamic flow conditions dominate and additional modelling techniques are required to improve design guidance.The research presented shows the evolution of a design solution which utilises two distinct processes;a continuum method and a discrete element method(DEM). Initially,the internal structure of dense granular flow,down vertical and inclined pipes was investigated using a twin sensor,12 electrode electrical capacitance tomography device.Subsequently,DEM simulations were conducted using the commercial software,PFC3D.Initially,two particle types and their flow behaviours were analysed:plastic pellets and sand.The pipe angle was varied between 0°and 45°to the vertical.For both the plastic pellets and the sand,good qualitative agreement was found with the spatial particle concentration analysis.Generally,the flow had a dense particle region at its core with the particle concentration reducing away from this core.As expected,at 0°, the core was centrally located within the pipe for both the plastic pellets and sand.At pipe angles 5°or greater,the dense core of particles was located on or near the pipe wall.Average flow velocity analysis was also conducted using the results of wall friction test analysis.The velocity comparisons also showed good agreement between the ECT image analysis and the DEM simulations. Subsequently,the DEM method was used to analyse a complex transfer system(or chute) with the continuum method providing comparative flow analysis with the DEM flow analysis.

Heat Transfer Coefficient between Ice Cover and Water in the Bohai Sea

The calculative method of heat transfer coefficient between ice cover and water is analyzed considering the heat balance at ice cover bottom firstly. The heat transfer coefficient is calculated with the meteorological, oceanographic data and sea ice conditions measured on the JZ20-2 Oil/Gas Platform in the Bohai Sea during the winter of 1997/1998. From the results, it is shown that the heat transfer coefficient is smaller in the freezing and melting periods, which is about 0.16×10-3 and 0.04×10-3 respectively. In the middle of ice season, the heat transfer coefficient has a larger value, which is about 0.5×10-3. Lastly, the influences of ice thickness and ice type on the heat transfer coefficient are discussed. With the heat transfer coefficient determined above, the oceanic heat flux in the winter of 1997～1998 is calculated, and its trend in the winter is analyzed. This study can be referenced in the sea ice numerical simulation and prediction in the Bohai Sea.

Mass and heat transfer mechanism in wood during radio frequency/vacuum drying and numerical analysis

The mass and heat transfer mechanisms during radio frequency/vacuum （RF/V） drying of square-edged timber were analyzed and discussed in detail, and a new one-dimensional mathematical model to describe the transport phenomena of mass and heat during continuous RF/V drying was derived from conservation equations based on the mass and heat transfer theory of porous materials The new model provided a relatively fast and efficient way to simulate vacuum drying behavior assisted by dielectric heating. Its advantages compared with the conventional models include： （1） Each independent vari- able has a separate control equation and is solved inde- pendently by converting the partial differential equation into a difference equation with the finite volume method; （2） The calculated data from different parts of the specimen can be displayed in the evolution curves, and the change law of the,parameters can be better described. After analyzing the calculated results, most of the important phenomena observed during RF/V drying were adequately described by this model.

初始含水量和容重对黑土压缩特性的影响

东北黑土区农业机械化水平高,农机作业压实导致的土壤结构和物理性状退化问题日益严重,压缩特性是定量分析土壤压实过程的有效手段,但目前黑土压缩特性随初始含水量和初始容重的变化规律尚不明确。为了解初始含水量和初始容重对黑土压缩特性的影响程度及其变化关系,该研究以重塑黑土为对象,设0.15、0.20、0.25、0.30、0.35、0.40 g/g共6个初始含水量水平,设1.00、1.10、1.20、1.30、1.45、1.60 g/cm3共6个初始容重水平,使用固结仪进行单轴压缩试验测定土壤压缩曲线,分析初始含水量和容重对压缩特性影响。结果表明,土壤初始含水量、容重及两者交互作用均极显著影响重塑黑土压缩特性(P<0.001),据此建立了预测压缩特性的土壤传递函数。黑土的预固结压力为10.42~1106.17 kPa,与初始含水量显著线性正相关、与初始容重显著线性负相关(P<0.05);压缩指数为0.311~0.852,与初始含水量和容重呈二元多项式方程的关系,随初始容重的增大而降低,在中等含水量时最大;回弹指数为0.007~0.321,与初始含水量正相关,与初始容重负相关。初始含水量大于70%田间持水量或初始容重小于1.20 g/cm3时,土壤预固结压力小于200 kPa且压缩指数大于0.4,压实风险高,应避免田间作业。建立的土壤传递函数可以较好地预测黑土压缩特性,还可用于土壤压实模型评估农机作业压实风险,为适耕性判断提供参考。

基于位置的服务技术在港口转运作业中的应用

传统散货码头主要依靠汽运车辆进行货物运输,需要大量的人员对车辆运输货物的种类、车辆次数等信息进行核对,以确保货物准确无误运到目的地。基于位置的服务技术在传统散货码头转运过程中,可充分利用多维度的定位信息,自动规划行驶路线,结合电子围栏,实现运输车辆作业起点、终点的系统确认,自动进行比对验证。现场应用表明,该技术可大幅减少港口的用工成本,提高作业效率。

散货码头带式输送机转载点粉尘控制措施分析

该文通过对散货码头带式输送机转载点粉尘特性及其析出原因进行分析,认为转载点扬尘主要受到输送带牵引气流、诱导气流、剪切气流的影响。同时,还探讨了各种粉尘控制措施中抑尘类措施的目的在于减少扬尘量,除尘类措施的目的在于扬尘的有效捕集,提出抑尘措施组合使用、除尘措施根据物料特点选择使用的设置建议,旨在有效防治散货码头转载点扬尘。

白于山区不同土层土壤密度的空间异质性

为了解黄土区丘陵沟壑区不同土层密度空间分布特征,以陕北白于山区为研究对象,研究不同土层土壤密度的空间分布特征及其影响因素。以灌木林地、乔木林地、宜林地、裸露地4种立地类型为例,根据坡位条件,结合气候、土壤、地形因子,揭示了不同土层土壤密度的空间异质性,并利用传递函数方程进行模拟与预测。结果表明:不同土地利用方式时,土壤密度从大到小依次为裸露地(1.376 g·cm^(-3))、乔木林地(1.373 g·cm^(-3))、宜林地(1.360 g·cm^(-3))、灌木林地(1.332 g·cm^(-3)),以及坡下(1.385)、坡上(1.378)、坡中(1.323),且(0,10]cm土层密度具有较强的变异性。土壤密度的平均值在土壤表层(0,10]cm出现最低值,其空间变异系数由土壤表层向土壤深层呈递减趋势;冗余分析(RDA)表明,蒸发量、海拔、日照时间对土壤密度的影响最大;相关性分析表明,3个土层土壤密度与孔隙度均呈极显著负相关;主成分分析表明,蒸发量、土地利用类型、黏粒体积分数(<0.002 mm)、粉粒体积分数(0.02~0.002 mm)是影响土壤密度的主要因子;从传递函数方程模拟结果可以看出,白于山区土壤密度受到土地利用方式、土壤性质(孔隙度、黏粒体积分数、砂粒体积分数)、气候(蒸发量、年均降水量)等大尺度与小尺度因子的综合影响,受地形因子(海拔、坡度)影响较小,各土层土壤密度利用传递函数方程可得到较好的拟合,可用于白于山区复杂环境条件时区域尺度土壤密度空间分布的模拟与预测。

甜高粱秸秆热物性研究

甜高粱秸秆是一种生物燃料,常采用回转筒固态发酵工艺生产乙醇,但回转式固态发酵工艺中易出现积热导致发酵效率低的问题。本文通过实验测量秸秆的热物性,分析在秸秆不同堆积密度(孔隙率)、温度和含水率条件下热导率和比热容的变化,为后续研究回转筒内杆状颗粒的运动特性提供基础数据。实验结果表明,秸秆孔隙率与堆积密度成线性关系,随着堆积密度增加,孔隙率降低;含水秸秆密度与含水率成线性关系,随着含水率增加,密度增加。随着温度、含水率和密度三个参数增加,秸秆热导率增加,且它们的影响顺序为:温度>含水率>密度。在本文中,随含水量与堆积密度的增加,秸秆的比热容几乎保持不变;随着温度增加,比热容增大。

TOGA-COARE IOP期间的海气通量观测结果

在TOGA－COAREIOP期间用涡度相关法对海气热通量进行了船载直接观测．对垂直风速、温度和湿度湍流脉动观测数据的谱分析显示它们在高频区基本满足"－2／3次方律"．对船体简谐震荡影响的讨论从理论上证明该影响在热通量计算中可被忽略．根据以此方法得到的通量求出了中性层结条件下感热和潜热的整体输送系数分别为2．25×10（－3）和1．26×10（－3）．对海气边界层特性的分析表明该海域的近海层主要呈中性或弱不稳定层结．海气通量的变化与背景环流形势密切相关，潜热通量主要受海面风场强度的影响，而感热通量变化除了风场的影响外，层结变化也是一个重要因素．用整体输送法计算TOGA－COAREIOP期间以及TOGA期间8个航次的通量结果而得到的Bowen比约为0．1，显示潜热通量是暖池大气的主要热源．

青藏高原总体输送系数的特征

利用中日亚洲季风机制合作研究计划设在西藏的 4个自动气象站（AWS）获得的5a多（199年7月～1998年12月）时次密集、观测连续的近地层梯度资料,以最小二乘法确定出相应站点各季节的地表粗糙度,并应用廓线-通量法计算了4站逐日的总体输送系数,分析了其随时间的变化特征。结果表明:青藏高原动量输送系数的多年平均值为3.53×10-3～4.99×10-3,热量输送系数为4.67×10-3～6.73×10-3,并且两种输送系数都存在明显的日变化和季节变化,部分站点还存在较明显的年际变化。另外,还讨论了总体输送系数与近地层大气层结稳定度、地表粗糙度以及地面风速等因子的关系,初步建立了可用常规气象站地面观测资料计算青藏高原总体输送系数的拟合公式。