浅论电液比例阀在长机列铝材生产线纠偏控制系统中运用的优势

以西南铝1600mm彩色涂层生产线进口的纠偏对中系统为例,进行电液比例阀控制系统代替常用的电液伺服阀控制试验,达到同样精度,实现了控制系统国产化,解决了原系统高维修成本问题,取得了较好的企业经济效益,为长机列铝材生产线提供了技术改造经验。

传输机房内列柜的安装方式探讨

列柜是传输机房内最常用的供电、分路设备。随着单设备占用列柜端子数不断增多,传统列柜安装方式已无法满足需求。本文根据现有相关工程规范对于列柜安装的要求和目前列柜设备的主流配置,归纳、总结出若干种列柜安装方式,以适应各种不同机房、机列及各种类型主设备对于列柜安装、使用的需求。

Nitrogen Mineralization in Soils Along a Vegetation Chronosequence in Hong Kong

This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected,and the in situ core incubation method was used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total Kjeldahl nitrogen (TKN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 ＞ S2 ＞ S3 ＞ S4 ＞ S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper ground.In the absence of fire for 3 to 6 years, the build-up of SOM and TKN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed.

Global localization of in-pipe robot based on ultra-long wave antenna array and global position system

A global localization system of in-pipe robot is introduced in this paper.Global position system(GPS)is applied to monitor the motion of robot along the whole pipeline which is equally divided intomany segments by tracking stations.The definite segment in which robot existing can be detected and thisis long-range localization.Ultra-long wave(ULW)is adopted to solve the problem of metallic shieldingand realize effective communication between inside and outside of pipeline.ULW emitter is carried byrobot.When the plant is broken or defects on pipe-wall are inspected,the robot will stop moving.Anten-na array is presented and disposed upon the definite segment to search the accurate location of robot,andthis is short-range localization.In this paper,five-antenna array is adopted and an effective linear signalfusion algorithm is presented.The localization precision reaches R < 25cm.By tests in Shengli oil field,the whole system is verified with robust solutions.

Triangulation Approach to Costing in Higher Education Institutions

This study presents a triangulation approach to the investigation of costing possibilities in Greek higher education institutions. The historical data contained in the financial statements of universities provide the expenditures of the latter. These expenditures are then re-determined with the use of independent variables （Jacobian determinants）, as well as with activity-based costing （ABC） and interviews, in order to obtain certainty of accuracy of the calculations and an indication of the cost of educational services, which can help determine magnitudes and improve the long-term planning of university resources. The above process can be used to create cost drivers and cost pools for the new financial burden of academic departments （cost centres） and to calculate the cost per student for each department. This information does not function at variance with or as a substitute for traditional accounting systems but in parallel （or supplementally）, providing administrators with more comparative data and a clearer picture of a university＇s economic operations which will facilitate its decision planning. Thus, it can provide higher education institutions with a decision-making tool for the following tasks： （1） allocation of national and community funds to university departments; （2） financing of textbooks, food, and accommodation; and （3） determining the optimum number of new enrolments.

Two-Queue Polling Model with a Timer and a Randomly-Timed Gated Mechanism

In this paper,we consider two-queue polling model with a Timer and a Randomly-Timed Gated(RTG) mechanism.At queue Q1,we employ a Timer T(1):whenever the server polls queue Q1 and finds it empty,it activates a Timer.If a customer arrives before the Timer expires,a busy period starts in accordance with exhaustive service discipline.However,if the Timer is shorter than the interarrival time to queue Q1,the server does not wait any more and switches back to queue Q2.At queue Q2,we operate a RTG mechanism T(2),that is,whenever the server reenters queue Q2,an exponential time T(2) is activated.If the server empties the queue before T(2),it immediately leaves for queue Q1.Otherwise,the server completes all the work accumulated up to time T(2) and leaves.Under the assumption of Poisson arrivals,general service and switchover time distributions,we obtain probability generating function(PGF) of the queue lengths at polling instant and mean cycle length and Laplace Stieltjes transform(LST) of the workload.