水泵特性排量与流量仪表测量值之间出现偏差的分析

从水泵铭牌“规定性能点”和制造厂提供的扬程一流量特性曲线的允差出发,对水泵特性排量和流量仪表测量值之间出现差异进行了分析,论证某些水泵用户误用水泵特性值核对运行中流量测量仪表测量值,并以实例加以说明.

液压泵变量控制两则

液压泵的变量是通过改变泵腔工作容积来实现的,以CY型柱塞泵为例,改变斜盘法线对缸体回转轴心的夹角γ,即改变各柱塞腔的工作容积,当γ角最大时,柱塞腔的工作容积最大,实现全排量供油,当γ角为0时,柱塞腔的工作容积为0,这时液压泵不供油。如果γ角为负值,则液压泵反向供油...

滚动转子式油气混输泵工作特性试验研究

滚动转子式油气混输泵正在天然气开采领域快速推广,其试验研究有助于为泵头理论分析和正向设计建立基础,对于实现高性能泵头研发和推动天然气开发具有重大价值。通过搭建宽工况、高稳定性、高精度的内循环试验平台,开展了某型滚动转子泵工作温度、压力、排量和功耗测试试验,完成了其工作特性分析,全面建立了泵头工作机制,证明了该类泵头性能的优越性。研究结果表明:在油气混输作用下,滚动转子泵的缸内气体增压过程趋于等温压缩,工作腔温升有限,排气温度能够维持在55℃左右。滚动转子泵虽然在天然气开发领域作为压缩机使用,但更多地体现了泵的工作特性:泵头实际排量与转速和进气压力呈正比,与进排气压差线性负相关;泵头容积效率与进排气压差线性负相关;泵头功耗与进排气压差线性正相关,但与进气压力无关,且随转速升高其增长幅度不断上升;滚动转子泵的出口压力脉动远低于往复式天然气压缩机,而其增压橇外输压力脉动几乎被完全削减,体现出了重大设备优势。研究结果可为油气混输泵的设计与应用提供参考。

Multi-attribute decision-making based on subjective and objective integrated eigenvector method

An integrated approach is proposed to investigate the fuzzy multi-attribute decision-making （MADM） problems, where subjective preferences are expressed by a pairwise comparison matrix on the relative weights of attributes and objective information is expressed by a decision matrix. An eigenvector method integrated the subjective fuzzy preference matrix and objective information is proposed. Two linear programming models based on subjective and objective information are introduced to assess the relative importance weights of attributes in an MADM problem. The simple additive weighting method is utilized to aggregate the decision information, and then all the alternatives are ranked. Finally, a numerical example is given to show the feasibility and effectiveness of the method. The result shows that it is easier than other methods of integrating subjective and objective information.

Biomass gasification and Polish coal-fired boilers for process of reburning in small boilers

Reburning was applied to Polish automatic coal-fired retort boiler (25 kW).The use of bio-syngas reduced NOx emissions from the boiler by over 25%,below the significant level of 200 mg/m3 .Reburning was carried out using an integrated system consisting of the boiler and a fixed-bed 60 kW (GazEla) gasification reactor.The process gas was continuously introduced above the coal burner of the boiler.The process parameters of the boiler and the gasifier were also measured and compared with the other units.Characteristic NOx emissions from automatic and manually operated boilers were also presented.

Instability characteristics of the cracked roof rock beam under shallow mining conditions

To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was analyzed. The changing criterion of the vertical displacement was established and the relationship between the deflection and the rotary motion of roof block was determined. Regarding a mining face in Shangwan Mine, the responsing laws of the deflection and horizontal thrust of the roof rock beam were obtained through FLAC3D numerical analysis. The results show that the structure instability of the cracked roof rock beam depends on the interaction between the vertical load and the horizontal thrust.For the roof rock beam, when the vertical load keeps constant, the horizontal thrust fluctuating rises with increasing deflection. The horizontal thrust increases constantly with the deeper buried depth and the smaller span.

Crown Fuel Characteristics and Carbon Emission from Japanese Red Pine Stands Burned by Crown Fire in Mt. Palgong, South Korea

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands （Pinus densiflora S. et Z.） burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 7o%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/m3 on average. The estimated amount of CO2 was 23,454 kg CO2/ha for the crown layer. These results will be useful for calculating the amount of CO2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.

The experimental study on combustion characteristics and emissions of a CMM fueled engine

In this paper, an experimental study on combustion characteristics and emissions of a single cylinder spark ignition engine fueled with coal-mine methane （CMM） is investigated under various loads. CMM is simulated by the compressed nature gas（ CNG）/nitrogen blend fuels. Based on experiment results, it is shown that under 0% - 35% nitrogen volume fraction in CNG/nitrogen blends, the maximum cylinder pressure, the maximum rate of pressure rise and the rate of heat release decrease, the flame propagation period increases, the center of heat release curve is closed to the top dead centre （TDC）markedly with the increase of nitrogen volume fraction. Meanwhile, the hydrocarbon （HC）, CO emissions increase, the NOx emission decreases apparently with the increase of nitrogen volume fraction.

Research on time structure characteristic of gas concentration sequence in the working face

In the procedure of coal industry production, the losses of the persons and economy caused by the gas explosion accidents are most serious, therefore, prevention and control of the gas explosion accident of the coal mines is an important issue needed to be solved urgently in the safety production work of our coal mines. The characteristic of time structure variation index characteristic was analyzed about gas concentration sequence of three measure points in the NO. 1I 1024 working face. It was found that the value of time variation about three measure points was mostly 1〈δ≤1.5, and gas emission presented consistently strong-clustering state twice, and the value of time variation presented continuous variation state in the active stage of gas concentration. Complex characteristics of the value indicated gas emission was continuously variable in time or space and presented the complex nonlinear characteristics. So the characteristic about gas emission system was correctly depicted and analyzed to gas emission system according to the relation of its state variation and essential of nonlinear system. The result also provided reliable warranty for its continued nonlinear research on gas emission.

Estimation of the Aircraft CO_2 Emissions of China's Civil Aviation during 1960-2009

Based on data collected by Chinese Civil Aviation Statistic Center, the annual CO2 emissions of aircrafts during 1960-2009 were calculated, and the emission intensity and its dynamic characteristics were analyzed. The results show that the total CO2 emissions of aircrafts in China increased from 120×10^3 t in 1960 to 41.44×10^6 t in 2009. The CO2 emission intensity decreased from 2.9 kg （converted t kra）-1 in 1960 to 0.96 kg （converted t km）-1 in 2009 at an average rate of 0.04 kg （converted t km）-I per year. The average share of CO2 emissions of aircrafts on the total CO2 emissions from the sector of transportation, storage and post was 6.6% during 1980-2005, and 0.25% on the total emissions from fossil fuel combustion during 1971-2008.

Emission Characteristics and Axial Flame Temperature Distribution of a Circumferential Reverse Flow Combustor

In partially premixed combustion of gas turbine, the combustion temperature should be lowed in order to reduce NOx. One solution is lean premixed combustion. However, the problem is that large excess air ratio may make the combustion unstable. A novel combustor with circumferential reverse flow of fuel gas is proposed for settling this problem. A 10 kw furnace is established to test performance of this combustor. Three factors such as primary air ratio, position of secondary air, total excess air ratio are studied. The emission characteristics and axial flame temperature distribution are studied. Basing on experimental results, the axial flame temperature and NOr emission increase with primary air ratio and axial length of second stream, and decrease with total excess air ratio. When the total excess air ratio is larger than 1.05, the combustor presents a lower temperature field and much lower NOx emission （less than 10 ppm）.

注水泵并联运行的特性

油田注水泵站配置多台泵,根据注水量需求,调整开泵台数。论文根据注水泵并联运行时的特性曲线变化的原理,分析了并联泵存在排量差异、压头差异、转速差异等情况下的总特性曲线,探讨了几种并联方式下的系统效率及并联运行优化的方法。

注水泵并联运行的特性

油田注水泵站配置多台泵,根据注水量需求,调整开泵台数。论文根据注水泵并联运行时的特性曲线变化的原理,分析了并联泵存在排量差异、压头差异、转速差异等情况下的总特性曲线,探讨了几种并联方式下的系统效率及并联运行优化的方法。

Male-driven reproductive and agonistic character displacement in darters and its implications for speciation in allopatry

Selection against hybridization can cause mating traits to diverge between species in sympatry via reproductive character displacement （RCD）. Additionally, selection against interspecific fighting can cause aggressive traits to diverge between sympatric species via agonistic character displacement （ACD）. By directly affecting conspecific recognition traits, RCD and ACD between species can also incidentally cause divergence in mating and fighting traits among populations within a species [termed cascade RCD （CRCD） and cascade ACD]. Here, we demonstrate patterns consistent with male-driven RCD and ACD in 2 groups of darters （orangethroat darter clade Ceasia and rainbow darter Etheostoma caeruleum）. In both groups, males that occur in sympatry （between Ceasia and E. caeruleum） have higher levels of preference for mating and fighting with conspecifics over heterospecifics than do males from allopatry. This is consistent with RCD and ACD. We also found patterns consistent with CRCD and cascade ACD among species of Ceasia. Ceasia males that are sympatric to E. caeruleum （but allopatric to one another） also have heightened preferences for mat- ing and fighting with conspecific versus heterospecific Ceasia. In contrast, Ceasia males that are allopatric to E. caeruleum readily mate and fight with heterospecific Ceasia. We suggest that RCD and ACD between Ceasia and E. caeruleum has incidentally led to divergence in mating and fighting traits among Ceasia species. This study is unique in that male preferences evolve via both RCD （male preference for conspecific females） and ACD （male preference to fight conspecific males） which leads to subsequent divergence among allopatric lineages.

A feature selection approach based on a similarity measure for software defect prediction

Software defect prediction is aimed to find potential defects based on historical data and software features. Software features can reflect the characteristics of software modules. However, some of these features may be more relevant to the class （defective or non-defective）, but others may be redundant or irrelevant. To fully measure the correlation between different features and the class, we present a feature selection approach based on a similarity measure （SM） for software defect prediction. First, the feature weights are updated according to the similarity of samples in different classes. Second, a feature ranking list is generated by sorting the feature weights in descending order, and all feature subsets are selected from the feature ranking list in sequence. Finally, all feature subsets are evaluated on a k-nearest neighbor （KNN） model and measured by an area under curve （AUC） metric for classification performance. The experiments are conducted on 11 National Aeronautics and Space Administration （NASA） datasets, and the results show that our approach performs better than or is comparable to the compared feature selection approaches in terms of classification performance.