Determination and Analysis of Soil Organic Matter Content in Greenhouses around Lhasa City

The soil organic matter content in the greenhouses around Lhasa City was determined by potassium dichromate-sulfuric acid digestion method. The results showed that the soil organic matter content differed among different soil layers of the greenhouses around Lhasa City, and it was relatively low in the deep soil. The soil organic matter content also differed among greenhouses with different cultivation modes. In the same soil layer, the organic matter content in arched greenhouse was lower than that in semi-arched greenhouse. Among all the soil samples, the samples with organic matter content below the critical value （20 g/kg） accounted for 61.33%, and the samples with higher organic matter content （≥30 g/kg） accounted for 10.64%. The soil organic matter content in the greenhouses of different counties of Lhasa City ranked as Dazi County＇s〉Duilongdeqing County＇s〉Qushui County＇s. In overall, the organic matter content in the soil of greenhouses around Lhasa City was medium-low, and the fertility of the greenhouse soil was at the middle level.

Physico-Chemical Properties and Enzyme Activities of the Arable Soils in Lhasa,Tibet,China

An understanding of the physical,chemical,and biological properties of a soil provides a basis for soil use and management.This paper reports the major physico-chemical properties and enzyme activities of the soils of Lhasa's main arable lands and the factors that influence these soil properties.Composite and core samples were taken from the three main arable soil types(alluvial soil,subalpine arable steppe soil,and subalpine arable meadow soil) and were analysed using standard methods.The bulk density and the ventilation porosity ratio of the soils were close to the recommended values for arable lands,and the dominant soil texture was sandy.The soil moisture release rates were arable steppe soil > alluvial soil > arable meadow soil.Soil organic matter content,Cation-Exchange Capacity(CEC),total and available nitrogen content,and catalase activity of the arable meadow soil were higher than those of the alluvial and the arable steppe soils,while soil pH in the arable meadow was lower.Most of the measured properties did not show a significant variance among these three soils.However,the measured indices(apart from the total potassium) indicate that there are notable differences among the three types of soil.The results implied that the utilisation patterns of the arable soil or human activities,such as tillage practices and fertiliser applications,have a substantialeffect on the soil properties in this region.Our results suggest that the cultivation practices in the region have apparently positive impact on the soil organic matter,nutrient contents and bulk density probably due to the sound fertiliser management such as the applications of farmyard manure and chemical fertilisers.However,intense cultivation practices lowered the activity of most soil enzymes.The results demonstrate that the choice of soil management strategy had a significant impact on the soil physicochemical and biological properties in the region studied.

A graphic monitoring method for electric power of VVVF hydraulic system

In order to online monitor the running state of variable voltage and variable frequency(VVVF)hydraulic system,this paper presents a graphic monitoring method that fuses the information of variable frequency electric parameters.This paper first analyzes how the voltage and current of the motor stator change with the operation conditions of VVVF hydraulic system.As a result,we draw the relationship between the electric parameters(voltage and current)and power frequency.Then,the signals of the voltage and current are fused as dynamic figures based on the idea of Lissajous figures,and the values of the electric parameters are related to the features of the dynamic figures.Rigorous theoretical analysis establishes the function between the electric power of the variable frequency motor(VFM)and the features of the plotted dynamic figures including area of diagram,area of bounding rectangle,tilt angle,etc.Finally,the effectiveness of the proposed method is verified by two cases,in which the speed of VFM and the load of VVVF hydraulic system are changed.The results show that the increase of the speed of VFM enhances its three-phase electric power,but reduces the tilt angle of the plotted dynamic figures.In addition,as the load of VVVF hydraulic system is increased,the three-phase electric power of VFM and the tilt angle of the plotted dynamic figures are both increased.This paper provides a new way to online monitor the running state of VVVF hydraulic system.

From Regional to Intercontinental Trade： The Successive European Trade Empires From the 16th to the 18thCentury in Asia

For a very long time, the areas available for continuous long-distance trade were limited to territories of Braudel＇s Mediterrande （1949）. Whatever the commercial organizations （merchants in the Roman or the Fatimid Empires, the Hanseatic League, the Florentine Companies） were, their trade was not able to directly handle branches more than a month＇s sailing from their main base （in the best conditions）. During the three centuries after Vasco de Gama had reached India, European trading areas dramatically expanded to the shores of Asia, and a long period of harsh competition set the East India Companies of the main European powers of the time against one another. What were the elements that allowed these companies to maintain transactions over such vast areas？ And why were some of these companies far more successful than the others？ A large set of secondary sources focusing on one company or on a particular aspect of trade （Chauduri, 1978; Israel, 1989; Subrahmanyan, 1993; Ames, 1996） exist, however, none of them treat their successive successes and failures. The aim of this paper is to briefly review these sources, to extract information from them and to compare the economic adaptations and innovations that allowed these companies to be the greatest of their time.

Finance Sector in Eurasian Economies During and After the Global Crisis in 2008

As in the other countries around the world, banking systems in Eurasian economies, comprised of Armenia, Azerbaijan, Georgia, Kazakhstan, the Kyrgyz Republic, Tajikistan, Turkmenistan and Uzbekistan, were adversely affected by the 2008 global crisis. A common challenge across most economies is to revive private-sector credit growth. Compared with the high increases of 80 percent in the period immediately prior to the crisis, credit growth has slowed sharply and even turned negative in real terms in a number of economies. Governments in many countries have taken measures to address banking sector stress. The measures for restoring credit growth and thus a high economic growth will be discussed in a part of our work. In the short run, such measures include aiding banks to repair balance sheets and also providing liquidity. In the medium term, measures should promote de-dollarization and the development of local debt markets.