对矿井井筒防冻加热风量计算的看法

以往,暖通专业在设计矿井井筒防冻空气加热装置时,其加热风量均依据采矿专业提出的井筒通风量,设计者即作为入井风量按入风温度为2℃计算其重量,而机电专业在选择矿井排风机时,亦按采矿专业提出的这一风量.但排风机常年运行的风温为20℃.因此,对同一风量产生了两种温度概念,无形中两者计算的入井空气重量就不同了.

吸气罩抽风量计算综合例题精选之一

在防尘防毒局部通风系统中,吸气罩是系统的四大部件之一。如何做好罩的设计,即设计好罩的形状、位置和计算所需的抽风量,往往是初学者忽视的。28年来,我们举办过30多期有关各种通风防尘防毒的技术培训班,学员3000多人。

综采面风量计算式和顺槽断面的探讨

一、低沼气矿井综采面风量的计算式我国不少新并适合于综机开采(尤其是几个重点建设矿区),是属于低沼气矿井(Ⅰ、Ⅱ级),其综采面配风量的计算办法仍按产量配风,必然供给的风量过多,这样既增加电耗,又使风速过大煤尘飞扬,恶化工作面气象条件;若用各局、矿的经验数据配风,因标准不一,设计单位也不好普遍采用.为了寻求这类综采面合理可靠的配风方法,且能适用于设计单位使用的风量计算式,笔者从积累的综采生产面的实测通风数据中,选择出36个配风效果好的综采面来进行统计分析.由于矿井设计时。

南方中小型矿井风量计算探讨

江南煤田煤层较薄,含煤面积大,含煤系数小,煤层赋存变化较大,水文地质条件较复杂,有的矿有煤和瓦斯突出危险以及自燃倾向。因此井下工作面较短,采煤掘进量大,工作地点多而分散。工作面机械化程度低,劳动强度也比较大。

多点热线式风量测量法分析

分析GB/T1236—2000中几种典型风量测量方法的优缺点,介绍多点热线式风量测量系统的结构、原理、选型和相关计算。通过与国标方法试验结果进行比较,笔者发现,多点热线式风量测量法测量精度较高、重复性较好,可以在工程实践中广泛使用。

移动式袋装水泥装车机收尘装置的设计及使用

移动式袋装水泥汽车装车机在水泥包装过程中的广泛应用,大大提高了袋装水泥码包装车的速度,节省了装车劳动力,减少了搬运装车过程中造成的破袋现象。但水泥袋在经过装车机出料托板落入车厢内进行码包过程中,袋内残留的气体会因为碰撞而快速逸出,夹带着水泥形成扬尘。为此,我们设计安装了移动式袋装水泥装车机收尘装置。

矿井通风网路解法(下)——逐孔计算法

通风网路逐孔计算法叙述如下: 通风网路逐孔计算法与逐孔图解法相似,先将网孔编号,然后按一定顺序逐孔进行解算。但网孔的风压平衡不用图解,而用数字计算。

Turbulence regime near the forest floor of a mixed broad leaved/Korean pine forest in Changbai Mountains

The measurement and observation for this study were carried out by using a three-dimensional (u, v, w) Sonic anemometer (IAP-SA 485), at Forest Ecosystem Opened Research Station of Changbai Mountains (12828扙 and 4224?N, Jilin Province, P. R. China) in August 2001. The basic characteristics of turbulence, such as turbulence intensity, atmospheric stability, time scales, and convection state, near the forest floor were analyzed. It is concluded that the airflow near forest floor is characterized by high intermittence and asymmetry, and the active and upward movement takes the leading position. Near forest floor, the vertical turbulence is retained and its time scale and length scale are much less than that of u, v components. The eddy near forest floor shows a flat structure and look like a ’Disk’. Buoyancy plays a leading role in the generation and maintenance of local turbulence

水泥机立窑罗茨鼓风机节电技术途径

罗茨鼓风机在机立窑水泥生产中耗电量大,约占总用电量的15％。风机选型时,风量一般均有约20％的余量,实际使用全风很少。使用时根据窑情将富余风由放风管向外排放,调节不便,噪音大,电机做了大量的无用功。按全国机立窑5000台,年运转300天计算,放风调节浪费电能高达15亿kwh(对常用的250罗茨风机按20％放风量计)。我们近几年积极参与了我省水泥行业的节电工作,现结合工作实践及成功经验,讨论机立窑罗茨鼓风机的节电技术途径。 一、调换配套电机,降低电机容量 风机配套电机的“大马拉小车”现象造成了电机负载率、自然功率因数和效率偏低。许多罗茨风机选用215KW电机,额定电流420A,实际电流一般只在180～280A间,负载率偏低,这时可考虑调换电机。 浙江嘉兴水泥厂机立窑D60×78罗茨鼓风机配套电机JS127—6—185KW,平均运行功率102KW,负载率仅55％。该厂选用JS125—6-130KW电机替换185KW电机,两电机安装尺寸基本相同,替换后电机负载率提高到78.45％,功率因数由0.78提高到0.85,效率提高2％,一年内回收改造费用。 在更换电机前,应测试运行参数。

Association of the frequency of peripheral natural killer T cells with nonalcoholic fatty liver disease

AIM: To investigate whether changes in the frequencyof peripheral natural killer T (NKT) cells were correlatedwith liver disease in patients who had metabolicpredispositions to nonalcoholic fatty liver disease(NAFLD).METHODS: Peripheral blood samples were obtainedfrom 60 Chinese NAFLD patients and 60 age and gendermatched healthy controls. The frequency of peripheralNKT cells was detected by flow cytometry. Clinical andlaboratory data were collected for further analysis. RESULTS: NAFLD patients had a lower frequencyof peripheral NKT cells than healthy controls (1.21%± 0.06% vs 1.62% ± 0.07%, P < 0.001). Furtheranalysis revealed that the frequency of peripheralNKT cells was negatively correlated with body massindex, waist circumference and serum levels of alanineaminotransferase. Logistic regression analysis revealedthat elevated body mass index [hazard ratio (HR):2.991], aspartate aminotransferase levels (HR: 1.148)and fasting blood sugar (HR: 3.133) increased the riskof NAFLD, whereas an elevated frequency of peripheralNKT cells (HR: 0.107) decreased the risk. CONCLUSION: Changes in the frequency of peripheralNKT cells were correlated with NAFLD and a decreasedfrequency of peripheral NKT cells was a risk factor forNAFLD.

Effects of Precipitation on Sonic Anemometer Measurements of Turbulent Fluxes in the Atmospheric Surface Layer

Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the-2/3 and-4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

THE LEAST SQUARES COMPREHENSIVE ADJUSTMENT FOR MINE VENTILATION MEASUREMENTS

This paper systematically introduced the method of direct, indirect and free-network adjustments and their application in data process of minewide ventilation measurements. The direct adjustment is suitable for errors collating of the measurements of airflow rates. The indirect method is suitable for the adjustment of ventilation resistance. The free-net method is adapted to the combined adjustment of the measurements of both the ventilation in branches of the air network and the air pressure at nodes of the ventilation network, the partial adjustment is also introduced here to be used for saving the storage locations in computer required for the adjustment for large scale mine ventilation measurements.

Estimations of Net Primary Productivity and Evapotranspiration Based on HJ-1A/B Data in Jinggangshan City, China

Net primary productivity （NPP） and evapotranspiration （ET） are two key variables in the carbon and water cycles of terrestrial ecosystems. In this study, to test a newly developed NPP algorithm designed for H J-1 A/B data and to evaluate the usage of HJ-1 A/B data in the quantitative assessment of environments, NPP and ET in Jinggangshan city, Jiangxi province, are calculated using H J-1 A/B data. The results illustrate the following： （1） The NPP and ET in Jinggangshan city in 2olo both show obvious seasonal variation, with the highest values in summer and the lowest values in winter, and relatively higher values were observed in autumn than in spring. （2） The spatial pattern indicates that the annual NPP is high in the southern area in Jinggangshan city and low in the northern area. Additionally, high NPP is distributed in forests located in areas with high elevation, and low NPP is found in croplands at low elevations. ET has no significant north-south difference, with high values in the southeast and northwest and low values in the southwest, and high ET is distributed in forests at low elevations in contrast to low ET in forests in high-elevation areas and in cropland and shrub grassland in low-elevation areas. （3） Compared to the MODIS product, the range of H J-1 NPP is larger, and the spatial pattern is more coincident with the topography. The range of H J-1 ET is smaller than that of the MODIS product, and ET is underestimated to some extent but can reflect the effect of topography. This study suggests that the algorithm can be used to estimate NPP and ET in a subtropical monsoon climate if remotely sensed images with high spatial resolution are available.

Venting Design for Di-tert-butyl Peroxide Runaway Reaction Based on Accelerating Rate Calorimeter Test

In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic conditions the initial exothermic temperature was 102.6 ℃,the maximum self-heating rate was 3.095×107 ℃·min-1,the maximum self-heating temperature was 375.9 ℃,and the pressure produced by unit mass was 4.512 MPa·g-1.Judged by ARC test,the emergency relief system for DTBP was a hybrid system.Based on Design Institute for Emergency Relief System(DIERS) method,the releasing mass flow rate W was determined by Leung methods,and the mass velocity G was calculated by two modified Omega methods.The two relief sizes calculated by monograph Omega method and arithmetic Omega method are close,with only 0.63% relative error.The monograph Omega method is more convenient to apply.

Discussion About Nonlinear Time Series Prediction Using Least Squares Support Vector Machine

The least squares support vector machine (LS-SVM) is used to study the nonlinear time series prediction. First, the parameter gamma and multi-step prediction capabilities of the LS-SVM network are discussed. Then we employ clustering method in the model to prune the number of the support values.. The learning rate and the capabilities of filtering noise for LS-SVM are all greatly improved.

Retrieval algorithm of sea surface wind vectors for WindSat based on a simple forward model

WindSat/Coriolis is the first satellite-borne polarimetric microwave radiometer, which aims to improve the potential of polarimetric microwave radiometry for measuring sea surface wind vectors from space. In this paper, a wind vector retrieval algorithm based on a novel and simple forward model was developed for WindSat. The retrieval algorithm of sea surface wind speed was developed using multiple linear regression based on the simulation dataset of the novel forward model. Sea surface wind directions that minimize the difference between simulated and measured values of the third and fourth Stokes parameters were found using maximum likelihood estimation, by which a group of ambiguous wind directions was obtained. A median filter was then used to remove ambiguity of wind direction. Evaluated with sea surface wind speed and direction data from the U.S. National Data Buoy Center （NDBC）, root mean square errors are 1.2 rn/s and 30~ for retrieved wind speed and wind direction, respectively. The evaluation results suggest that the simple forward model and the retrieval algorithm are practicable for near-real time applications, without reducing accuracy.

Econometric Analysis of Risk Preference Patterns among Smallholder Organic Producers in South Africa

The article assesses the determinants of farmers＇ decisions to participate in organic farming, eliciting farmers risk preferences and empirically analysing farmer＇s sources of risk and risk management strategies. The ordered probit results indicate that older farmers, who are less risk averse and reside in the sub-ward Ogagwini, Ezigani and Hwayi were more likely to be certified organic. Similarly, the propensity to adopt organic farming is positively correlated to household size, livestock ownership, asset base and tenure security. At higher pay-offs, farmers were intermediate to moderately risk-averse, with little variation according to personal characteristics. In general, price, production and financial risks were perceived as important sources of risk. Seven principal components, explaining 66.13% of the variation were extracted. Socio-economic factors having a significant effect on the various sources of risk were age, gender, education, location, information access and risk taking ability. The dimensions of risk strategies were named as diversification, precautionary savings and social networks. Results provide practical insights for policy changes relevant in motivating the adoption of organic practices, increasing smallholder farmers＇ capacity to manage risk and driving growth in the organic food market.

Carbon dioxide levels and ventilation for running vehicle

Factors contributing to ventilation quantity of the vehicle are ventilation modes, cabin characteristics and vehicle speeds. CO2 levels were investigated under different speeds and ventilation modes. Four modes were selected： A： vent closed and fan shut, B： vent closed and fan started, C： vent opened and fan shut, D： vent opened and fan started. In vent closed modes, CO2 levels reached several thousands of ppm in few minutes at any speeds. For mode C, CO2 levels exceeded the guideline at low speeds 50 km/h, while it reduced below one at higher speeds 80 km/h. Fan has no significant impact on ventilation during vent closed. The ventilation efficiency in each mode increased with the speed raising. To determine the ventilation rate of running vehicle, the experiment was implemented by using CO2 emitted from driver and passengers as tracer gas. Ventilation rate for the different modes and speeds were calculated.

Connecting Wind Turbine Generator to Distribution Power Grid--A Preload Flow Calculation Stage

A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.

Design of Control Scheme for Variable Air Volume Air- conditioning System

The air quantity of variable air volume system for the rooms and the total air quantity of the system changes with the change of room load. Combined with the system composition in the laboratory, the paper determines the control scheme of the variable air volume system, that is, indoor temperature-control, indoor positive pressure control, air distribution static pressure control, air-supply temperature control and new air volume control. The dotted lines with arrows mean the output signals from the control unit to actuator, and the solid lines with arrows represent the input signals from the actuator to the control unit.