运输产品“位移说”质疑与铁路运输物流观初探

从实践和发展的视角，对以“位移”为运输产品的传统现点提出了异议和反思。论述了运输产品的物流本质。并就市场经济条件下，如何理顺铁路运输组织与产品营销的关系问题进行了初步探讨。

重庆观农贸农产品物流中心

重庆观农贸农产品物流中心（简称观农贸），于1987年5月建成投用,经过20年的发展,从最初单一的农副产品批发市场，成长为集蔬菜，副食．粮油．水产，水果．茶叶和冷冻制品七大专业批发市场为一体的大型农产品综合批发市场群．形成两大板块．区域范围2平方公里农产品物流中心。

我国物流业现状和经营战略选择

现代物流被广泛认为是在企业降低物耗、提高劳动生产率以外的第三利润源,在我国只是近些年才得到重视并成为关注的焦点。我国物流业的现状是:世界物流业强手纷纷抢滩中国市场;物流管理观念落后;大多数企业难以形成大规模的综合经营状态;第三方物流需求严重不足;物流企业数量多、质量差、专业化程度低,物流业局部市场混乱;专业人才缺乏;重复建设和地方割据现象并存;信息化程度低。我国物流业经营战略选择的依据是:立足于本土优势是战略选择的基础;现代物流观和现代物流的发展趋势是战略选择的指导思想。可供物流企业选择三种经营战略模式是:传统外包型;战略联盟型;综合物流。

CFD Simulation of Film Flow and Gas/Liquid Countercurrent Flow on Structured Packing

A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area.

Relationships Between River Water Quality and Landscape Factors in Haihe River Basin, China: Implications for Environmental Management

River water plays a key role in human health, and in social and economic development, and is often affected by both natural factors and human activities. An in-depth understanding of the role of these factors can help in developing an effective catchment management strategy to protect precious water resources. This study analyzed river water quality, patterns of terrestrial and riparian ecosystems, intensity of agricultural activities, industrial structure, and spatial distribution of pollutant emissions in the Haihe River Basin in China for the year of 2010, identifying the variables that have the greatest impact on river water quality. The area percentage of farmland in study area, the percentage of natural vegetation cover in the 1000-m riparian zone, rural population density, industrial Gross Domestic Product(GDP)/km^2, and industrial amino nitrogen emissions were all significantly correlated with river water quality(P < 0.05). Farming had the largest impact on river water quality, explaining 43.0% of the water quality variance, followed by the coverage of natural vegetation in the 1000-m riparian zone, which explained 36.2% of the water quality variance. Industrial amino nitrogen emissions intensity and rural population density explained 31.6% and 31.4% of the water quality variance, respectively, while industrial GDP/km^2 explained 26.6%. Together, these five indicators explained 67.3% of the total variance in water quality. Consequently, water environmental management of the Haihe River Basin should focus on adjusting agricultural activities, conserving riparian vegetation, and reducing industrial pollutant emissions by optimizing industrial structure. The results demonstrate how human activities drive the spatial pattern changes of river water quality, and they can provide reference for developing land use guidelines and for prioritizing management practices to maintain stream water quality in a large river basin.

Rheology and microstructure effects of waste spent coffee grounds in modifying asphalt binder

Herein the biowaste by-product spent coffee grounds(SCGs)from coffee industry were incorporated into asphalt binders for performance enhancement.From the analysis of Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),dynamic shear rheometer(DSR),and Brookfield viscosity rheometer,it is confirmed that SCGs have potential prospects as bio-waste modifiers in the application of sustainable pavements.Results demonstrated that the modification process was mainly based on physical reinforcement.Compared with that of the neat asphalt,the shearing stress-resistant ability and high-temperature performance of the SCGs modified binders with the appropriate addition presented a bit of improvement;whereas the binders with 1%and 3%SCGs exhibited remarkably enhanced low-temperature stability.However,notable weaknesses of practical performance were shown for the binder with excessive content of SCGs,indicating the necessity of proportion selecting before application.

Channel flow of the lower crust and its relation to large-scale tectonic geomorphology of the eastern Tibetan Plateau

The Tibetan Plateau is a large-scale tectonic geomorphologic unit formed by the interactions of plates.It has been commonly believed that convective removal of the thickened Tibetan lithosphere,or lateral flow of the lower crust beneath the Tibetan plateau plays a crucial role in the formation of the large-scale tectonic geomorphologic features.Recent geological and geo-physical observations have provided important evidence in support of the lower crustal channel flow model.However,it re-mains unclear as how the geometry of lower crustal channel and the lateral variation of crustal rheology within the lower crust channel may have affected spatio-temporal evolution of the tectonic geomorphologic unit of the Tibetan Plateau.Here,we use numerical methods to explore the mechanical relations between the lower crustal channel flow and the tectonic geomorpho-logic formation around the eastern Tibetan plateau,by deriving a series of governing equations from fluid mechanics theory.From numerous tests,our results show that the viscosity of the channeled lower crust is about(1-5)×1018 to(1-4)×1020 Pa s(Pa.s) beneath the margin of the eastern Tibetan Plateau,and increases to about 1022 Pa s beneath the Sichuan Basin and the southern region of Yunnan Province.Numerical tests also indicate that if channel flows of the lower crust exist,the horizontal propagation and the vertical uplifting rate of the eastern Tibetan Plateau margin could be accelerated with the time.Thus,the present results could be useful to constrain the rheological structure of the crust beneath the eastern Tibetan plateau,and to understand the possible mechanics of rapid uplift of the eastern Tibetan Plateau margin,especially since its occurrence at 8Ma as revealed by numerous geological observations.

Summer circulation structure and formation mechanism in the Beibu Gulf

Due to limited in situ data and diagnostic numerical models, the summer circulation structure and formation mechanism in the Beibu Gulf have always been in controversy in the past 50 years. Therefore, a new three-dimensional hindcast model was built within the northwestern South China Sea(SCS), forced with the daily averaged wind, heat flux, lateral flux, as well as tidal harmonic and eight major rivers discharges. And the east boundary was set up far away off the Qiongzhou Strait(QS). Lastly, the model results were consistent with not only the synchronous observation data from the project 908 but also the historical observed data. As a result, the summer circulation structure was revealed that the southern Gulf was occupied by an anticyclonic eddy whereas the northern Gulf was dominated by a cyclonic gyre. Although the circulation major structure was stable, its area and strength had yearly and monthly oscillation. The other three sensitive experiments indicated that the circulations in the southern and northern Gulf were driven by the SCS circulation and monsoon wind, respectively. After the theoretical analysis of the potential vorticity budget, it was further revealed the circulation in the northern Gulf was driven by the positive wind stress curl in summer. Besides, the river discharge was also significant as the vertical circulation had two layer structures outside the mouth of the Red River. Generally, this work calls for the further research on other subjects, such as ocean biogeochemical or marine fisheries.

Dependence of residual voltage ratio behavior of SnO_2-based varistors on Nb_2O_5 addition

SnO2-based varistor samples doped with Co2O3,Nb2O5 and Cr2O3 were prepared by ball-mixed oxide method.The microstructure,nonlinear I-V characteristic and surge current performances of these samples were investigated.This paper mainly focused on the dependence of the residual voltage ratio behavior of SnO2-based varistors on Nb2O5 addition,different factors influencing the residual voltage ratio in different concentration of Nb2O5 were analyzed.The Nb2O5 addition influences its residual voltage ratio by changing the grain size,forming defects(especially the free electrons) and cumulative effect.The measured results indicated that the optimally obtained sample with 0.07mol% Nb2O5 possesses the lowest residual voltage ratio of 1.86,the corresponding nonlinear coefficient and the threshold electric field are 42.6 and 364.6 V/mm,respectively.