电力设备SF_6气体现场高效回收回充技术研究

基于对SF6气体现场回收与回充过程中存在问题的分析,研究了回收回充技术,包括压缩机的选型与试验、吸附剂材料的选择与试验、抽真空系统的设计、电气设计及设备总装设计等。简要介绍了中国发明专利新型SF6气体回收回充设备及辅助回收设备、辅助回充设备。

一种小型智能割草机器人的设计与实现

针对传统割草机污染高、噪音大和需要人工长时间操作等弊端,结合市场需求,研制了一款小型的可预约工作、自主回充的智能割草机器人。硬件上,系统以STM32为核心,由控制系统、动力系统、传感系统、通信系统和人机交互系统5部分组成;算法和软件上,采用自主回充方案,实现预约模式下机器人多次工作,减少人工操作;为解决机器人在斜坡上无法直线行进问题,设计了一种坡度补偿算法;同时为提高机器人的割草效率,提出了一种自主寻草算法。系统符合国际安全设计指标,经过长时间测试,机器在预约模式、自主回充模式均能稳定可靠的工作。

提高变电站内SF_6湿度在线监测准确性的研究

为了在带电状态下监测GIS变电站设备内的SF_6湿度,目前电力行业的普遍做法是进行人工取样检测。部分变电站虽然实现了在线监测,但监测数据的准确性极低。文中涉及的技术是,对现有的在线监测装置进行改造,增加气体自动回充系统,使监测的气样具有代表性。该技术适用于变电站SF_6设备,文章对该技术的关键点进行了深入分析。

Performance of cemented coal gangue backfill

Possibility of cemented gangue backfill was studied with gangue of Suncun Coal Mine, Xinwen Coal Group, Shandong, and fly ash of nearby thermal power plant, in order to treat enormous coal gangue on a large scale and to recovery safety coal pillars. The results indicate that coal gangue is not an ideal aggregate for pipeline gravity flow backfill, but such disadvantages of gangue as bad fluidity and serious pipe wear can be overcome by addition of fly ash. It is approved that quality indexes such as strength and dewatering ratio and piping feature of slurry can satisfy requirement of cemented backfill if mass ratio of cement to fly ash to gangue is 1:4:15 and mass fraction of solid materials reaches 72%-75%. Harden mechanism suggests that the cemented gangue fill has a higher middle and long term comprehensive strength.

Investigation of the short-term stress distribution in stopes and drifts backfilled with cemented paste backfill

Cemented paste backfill(CPB) is largely used in underground mines worldwide.A key issue associated with application of CPB is to estimate the stresses in backfilled stopes and on barricades.Recent numerical and experimental results show that arching effect is absent shortly after the placement of CPB in stopes.However,stress decreases in barricade drift with increasing distance between the measurement points and drawpoint have also been observed,demonstrating arching effect shortly after the pouring of CPB.To explain these paradoxes,CPB is considered as Bingham fluid having a yield shear stress.Three dimensional analytical solutions are proposed to evaluate the short-term total stresses in backfilled stopes and on barricades,accounting for the CPB's yield shear stress-induced arching effect.Stress diminution due to such arching effect in the backfilled stopes and on barricades is indeed obtained.But the reduction becomes insignificant using typical yield shear stress and stope geometry.More analyses indicate that the typical yield shear stress values do not fully correspond to field conditions where the yield shear stress would increase exponentially due to apparent consolidation(loss of water by drainage,a phenomenon similar to the desiccation of overly saturated fine-grained materials).

Position-optimization on retained entry and backfilling wall in gob-side entry retaining techniques

This study investigates the stability problem of gob-side entry retaining （GER） and backfilling wall which located under the key block B. Based on the combined research of elastic-plastic mechanics, structure mechanics and modern theory of mining-induced pressure, the caving characteristic and roof structure over the GER were analyzed, and the vertical force and the torque on retained entry roof were also derived as the position for the retained entry varies. On the basis of the specific geology in Huainan mining area, the results indicate that a relatively more stable position for retained entry neighbors the hinge point of block A and B, and it also located at a scope ranging from this point to the one-third length of block B in horizontal direction. As to appropriate position for backfilling wall, this study recommends partial- road-in backfilling method for GER. Field trial conducted at panel face 12418 of Xieqiao Mine demonstrates that the recommended width for original entry is 3.6 m and the preferred width proportion between original retained entry and original entry is 75 % or so whereas the avoidable one is 88 % or so. These findings provide qualitative references to the mines which share similar geology as what Huainan mining area characterized.

A numerical evaluation of continuous backfilling in cemented paste backfilled stope through an application of wick drains

Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modeUings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.

Sedimentary system characteristics and depositional filling model of Upper Permian——Lower Triassic in South Yellow Sea Basin

In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.

Role of echo Doppler ultrasonography in the evaluation of postprandial hyperemia in cirrhotic patients

AIM: To assess the role of echo-Doppler ultrasonography in postprandial hyperemia in cirrhotic patients by comparing the results with the hepatic vein catheterization technique.METHODS: Patients with cirrhosis, admitted to the portal hemodynamic laboratory were included into the study. After an overnight fast, echo-Doppler ultrasonography (basal and 30 min after a standard meal) and hemodynamic studies by hepatic vein catheterization (basal, 15 min and 30 min after a standard meal) were performed. Ensure Plus (Abbot Laboratories, North Chicago, IL) was used as the standard liquid meal. Correlation analysis of the echo-Doppler and hepatic vein catheterization measurements were done for the basal and postprandial periods.RESULTS: Eleven patients with cirrhosis (5 Child A, 4 Child B, 2 Child C) were enrolled into the study. After the standard meal, 8 of the 11 patients showed postprandial hyperemia with increase in portal blood flow, portal blood velocity and hepatic venous pressure gradient. Hepatic venous pressure gradient in the postprandial period correlated positively with postprandial portal blood velocity (r = 0.8, P < 0.05) and correlated inversely with postprandial superior mesenteric artery pulsatility index (r = -1, P < 0.01).CONCLUSION: Postprandial hyperemia can be efficiently measured by echo-Doppler ultrasonography and the results are comparable to those obtained with the hemodynamic studies.

Overlying strata movement of recovering standing pillars with solid backfilling by physical simulation

To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling.Physical simulation experiments with sponge and wood as the backfilling simulation material were tested.The results show that:(i) The covering-rock mechanics of the overly strata comes from "two-arch structures + hinged girder + bend beam" to "backfilling material + hinged girder + bent beam" by increasing the fill ratio from 0%to 85%,the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value increases.The trend of "single polarization" of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable,(ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess,and the corresponding ground processing & transportation system was designed.

Performance of an R410a Filled Loop Heat Pipe Heat Exchanger

A simple theoretical model of a heat pipe heat exchanger （HPHE） based on the ε-NTU method is presented. An iterative computer program was developed to predict the overall effectiveness of a counter-flow air-air loop heat pipe heat exchanger （LHPHE）. A thermal resistance network approach for a single thermosyphon was first considered to determine the overall heat transfer coefficients and the NTU＇s for the evaporator and condenser sections. The model incorporated previously determined evaporating and condensing coefficients. The overall effectiveness of the 6, 4 and 2 row LHPHE was then predicted. The theoretical overall effectiveness was compared with experimental data obtained from a R410a filled LHPHE. The experimental overall effectiveness results compared very well with the simulated values, The results showed that the 6 row arrangement performed better than the 4 or 2 row arrangement in the experiment.

Efficacy of acupuncture on treating obesity and adipose-incurred illnesses

Being overweight and obese impacts health due to adiposity itself and illnesses it incurs,which produces individual and societal financial burdens.This urges effective interventions,including adjunct therapies.Acupuncture,a traditional Chinese medical practice,indicates positive signs for tackling these problems.Investigating 101 empirical human-based projects,this narrative review analyses their outcomes and then provides an overview of the effects of acupuncture in body weight reduction and obesity-induced diseases,either performed alone or with other approaches.It involves 15941 participants from 9-80 years old in China's Mainland,Taiwan,Turkey,Brazil,Egypt,Iran,Greece,Korea,Sudan,Thailand,and the USA.It also reveals practical implications and future research directions,benefiting the development of acupuncture in the modern medical arena for both patients and practitioners.

Evaluating returns to scale and congestion by production possibility set in intersection form

This research proposes a new method to estimate returns to scale(RTS) of decision making units(DM Us) with multiple inputs and outputs.The state of return to scale includes increasing RTS,constant RTS,decreasing RTS and evidence of congestion.The method is based on the production possibility set in the intersection form given by a set of linear inequalities.We propose and prove the necessary and sufficient conditions for the RTS estimation.With the new procedure,to estimate the RTS of a DM U is simply to check the position of the DM U on the production frontiers.We point out that the procedure is particularly important for dealing with a large number of DM U s.Therefore,it can be regarded as a complementary to the data mining.

Effects of different gap filling methods and land surface energy balance closure on annual net ecosystem exchange in a semiarid area of China

Based on eddy covariance measurements over two kinds of land surfaces(a degraded grassland and a maize cropland)in a semiarid area of China in 2005 and 2008,the effects of different gap filling methods,energy balance closure and friction velocity threshold(u*)on annual net ecosystem exchange(NEE)were analyzed.Six gap filling methods,including mean diurnal variation(MDV),marginal distribution sampling(MDS),and nonlinear regressions method,were investigated by generating secondary datasets with four different artificial gap lengths(ranging in length from single half-hours to 12 consecutive days).The MDS generally showed a good overall performance especially for long gaps,with an annual sum bias error less than 5 g C m-2 yr-1.There was a large positive annual sum bias error for nonlinear regressions,indicating an overestimate on net ecosystem respiration.The offset in the annual sum NEE for four nonlinear regressions was from 8.0 to 30.8 g C m-2 yr-1.As soil water content was a limiting factor in the semiarid area,the nonlinear regressions considering both soil temperature and soil water content as controlling variables had a better performance than others.The performance of MDV was better in daytime than in nighttime,with an annual sum bias error falling between-2.6 and-13.4 g C m-2 yr-1.Overall,the accuracy of the gap filling method was dependent on the type of the land surface,gap length,and the time of day when the data gap occurred.The energy balance ratio for the two ecosystems was nearly 80%.Turbulent intensity had a large impact on energy balance ratio.Low energy balance ratio was observed under low friction velocity during the night.When there was a large fetch distance in a wind direction,a low energy balance ratio was caused by mismatch of the footprints between the available energy and turbulent fluxes.The effect of energy balance correction on CO2 flux was evaluated by assuming the imbalance caused by the underestimation of sensible heat flux and latent heat flux.The results showed an average increase of 10 g C m-2 yr-1 for annual NEE in both ecosystems with an energy balance correction.On the other hand,the u*threshold also have a large impact on annual sum NEE.Net carbon emission increased 37.5 g C m-2 yr-1 as u*threshold increased from 0.1 to 0.2 m s-1,indicating a large impact of imposing u*threshold on net ecosystem carbon exchange.