固井供水车自吸系统的设计

为了改善固井供水车离心式水泵的自吸性能 ,研制了供水车自吸系统。系统由空压泵、溢流阀、单向阀、贮气筒、控制阀、喷射器和输气管线等组成。喷射器是系统的执行元件 ,分别安装在 2台水泵的排水口上方。高速气流通过喷射器喷嘴后 ,在喷射器空腔内形成负压区 ,从而实现水位提升。这种自吸系统结构简单 ,所需零部件易于加工和购买 ,系统自吸高度可以达到 4m。

一种自吸离心泵装置系统研制

针对一些特殊自吸工况,其安装环境、使用条件、输送介质特性等不能够采用真空泵,又不能直接采用离心泵的情况,研制了一种特殊配置的自吸离心泵装置系统,来满足现场自吸应急给水工况的使用要求。自吸离心泵系统由离心泵、驱动电机、主水箱、辅助水箱、阀门、管道、流量计和压力传感器等组成。同时,针对现场运行时出现的超低水池水位,研制了一种特殊结构的防旋涡装置来满足自吸离心泵装置系统的进水要求。通过主水箱和辅助水箱之间的阀门,辅助水箱上部的进水和排气阀门,排除装置系统运行过程中内部的空气,确保离心泵运行时水箱具备有安全水位。通过水池吸入口防漩涡试验、自吸高度和运转试验,验证了整个装置系统能够安全可靠运行。

大型自吸离心泵设计及试验研究

基于大流量自吸离心泵在结构上创新的设计了自吸系统,该系统主要由射流和排气装置组成,实现了大流量离心泵的自吸性能。对大流量自吸离心泵的性能进行了检测,结果表明,泵的各项指标都满足设计要求,扬程45.22 m,效率72.79%,自吸高度5.3 m时,自吸时间为62 s;自吸高度8.1 m时,自吸时间为173 s,自吸时间小于国家标准规定值。该泵设计合理,效率高,性能曲线平坦,高效率区宽。该泵的研制成功对于城市排涝、矿山排水、农业大型排灌具有重要现实意义。

Compound structure analysis of a new chaotic system

This paper analyzes the compound attractor structure of a new three-dimensional autonomous chaotic system. First, it is found that there exist five equilibria in the chaotic system, and the stabilities of these equilibria are discussed under a constant scalar control input parameter m. Secondly, the trajectories of the attractors on a y-z plane are examined, the reasons why these trajectories can exist or disappear are also described. Finally, the forming procedure of the different scrolls chaotic attractor is explored by computer simulations when the parameter m is varied. It is shown that the new chaotic attractor has a compound structure, it can evolve to other three-dimensional autonomous chaotic systems. The results of theoretical analysis and simulation are helpful for better understanding of other similar chaotic systems.

COMPOUND STRUCTURE OF NEW FOUR-SCROLLS CHAOTIC SYSTEM

The finding of the compound structure of a new four-scrolls chaotic system is reported, which is obtained by merging together two symmetrical attractors. And the two symmetrical attractors are generated only by adding a constant gain to the original system. Also, the forming procedure of the new four-scrolls chaotic attractor is explored and the relation between the constant gain and the properties of the system is given.

离心泵优化设计理论与方法分析

大型自吸离心泵是一种无需灌水,通过自吸系统将进口管内空气排净,实现快速自吸,从而使离心泵正常工作的水利机械,具有结构紧凑、效率高、运行稳定以及自吸能力强等特点,广泛应用于大面积喷灌供水系统、城市排水以及抗洪抗涝等,应用前景十分广阔。文章首先分析了大型自吸离心泵存在的问题,然后介绍了自吸离心泵结构、参数设计以及工作原理,最后对大型自吸离心泵进行了试验研究。

An Air-Breathing Micro Direct Methanol Fuel Cell with 3D KOH-Etched Cathode Structure

A micro direct methanol fuel cell （μDMFC） using MEMS technology is reported. The prototype features a unique 3D air-breathing cathode structure fabricated using KOH etching and double-side lithography. The optimization of the MEMS fabrication process is analyzed. The experimental results show the prototype generates a maximum power density of 2.52mW/cm^2 at room temperature. This performance is better than the published resuits of other silicon-based passive μDMFCs. Moreover,it is comparable with that of our previous active μDMFCs which require an external pump, certificating the feasibility of this new configuration.

Video-assisted thoracoscopic surgery (VATS) for bilateral primary spontaneous pneumothorax

Objective： To review our experience of the treatment of bilateral primary spontaneous pneumothorax （PSP） by video-assisted thoracoscopic surgery （VATS）. Materials and methods： Retrospective chart review was followed by an on-clinic or telephone interview. Patients were cared for by one thoracic surgeon in four medical centers or community hospitals in Northern and Central Taiwan. Thirteen patients with bilateral PSP underwent bilateral VATS simultaneously or sequentially from July 1994 to December 2005. Results： Twelve males and one female, with age ranging from 15 to 36 years （mean 23.1 years）, were treated with VATS for bilateral PSP, under the indications of bilateral pneumothoracis simultaneously （n=4） or sequentially （n=9）. The interval between the first and second contra-lateral VATS procedure for non-simultaneous PSP patients ranged from 7 d to 6 years. Eleven of 13 patients （84.6%） had prominent pulmonary bullae/blebs, and underwent bullae resection with mechanical or chemical pleurodesis. The mean operative time was （45.6±18.3） min （range 25-96 min） and （120.6±28.7） min （range 84-166 min） respectively for the non-simultaneous （second VATS for the recurrence of contralateral side after first VATS） and simultaneous （bilateral VATS in one operation） procedures. There was no postoperative mortality. However, prolonged air leakage （〉7 d） occurred in one patient （7.7%） who recovered after conservative treatment. The mean duration of chest tube drainage was 3.1 d and the median follow up period was 3.4 years. Conclusions： VATS is a safe and effective procedure in the treatment of bilateral PSP. Bilateral VATS is only recommended for patients with simultaneously bilateral PSP, because the incidence of recurrence, even with visible bullae, was not so high in my group and in some previous literature. Bilateral VATS in a supine position should only be used in selective cases, because of possible pleural adhesion or hidden bullae on the posterior side.

Investigation of Influence of Magnetic Nanoparticles on the Quality-Factor of the Oscillatory Circuit

In this study, author investigated the spectral response of EM （electromagnetic） energy absorption in a colloidal system of Fe3O4 nanoparticles with an average size of 9.50 nm immersed in a 2% aqueous solution of SDS （sodium dodeci[ sulfate）. The temperature of the nanoparticles and the SDS solution was evaluated by a novel method based on measuring the Q-factor （quality-factor） of a resonant circuit. The Q-factor of the investigated system as a function of the frequency of the EM field was obtained. The nanoparticles-SDS liquid system exhibited a resonance-like behavior of the absorption, where the resonance frequency was about 170 MHz, and the absorption rise up to the resonance frequency was rather slow. The observed absorption of EM energy was accompanied by a small temperature increasing of the system. Measurements of the ESR （electron spin resonance） spectrum of the Fe3O4 nanoparticles have presented a slightly asymmetric singlet with the proportionality factor g = 2 and a line-width of the magnetic field strength △H = 0.1 mT. It was shown that the observed absorption spectrum corresponds to paramagnetic behavior of the investigated nanoparticles.

UNIFORM PERSISTENCE AND GLOBAL ATTRACTIVITY FOR NONAUTONOMOUS COMPETITIVE SYSTEMS WITH DISPERSION

In this paper, we consider a nonautonomous competitive model with dispersion and a finite number of discrete delays. The system, which consists of two Lotka-Volterra patches, has two competitors: one can disperse between the two patches, but the other is confined to one patch and cannot disperse. Our purpose is to demonstrate that the dispersion rates have no effect on the uniform persistence of the solutions of the system. Furthermore, we establish the conditions under which the system admits a positive periodic solution which attracts all solutions.

Seasonal and diurnal variation in ecosystem respiration and environmental controls from an alpine wetland in arid northwest China

Wetlands store large amounts of carbon stocks and are essential in both global carbon cycling and regional ecosystem services.Understanding the dynamics of wetland carbon exchange is crucial for assessing carbon budgets and predicting their future evolution.Although many studies have been conducted on the effects of climate change on the ecosystem carbon cycle,little is known regarding carbon emissions from the alpine wetlands in arid northwest China.In this study,we used an automatic chamber system(LI-8100A)to measure ecosystem respiration(ER)in the Bayinbuluk alpine wetland in northwest China.The ER showed a significant bimodal diurnal variation,with peak values appearing at 16:30 and 23:30(Beijing time,UTC+8).A clear seasonal pattern in ER was observed,with the highest value(19.38μmol m-2 s-l)occurring in August and the lowest value(0.11μmol m-2 s-1)occurring in late December.The annual ER in 2018 was 678 g C m-2 and respiration during the non-growing season accounted for 13%of the annual sum.Nonlinear regression revealed that soil temperature at 5 cm depth and soil water content(SwC)were the main factors controlling the seasonal variation in ER.The diurnal variation in ER was mainly controlled by air temperature and solar radiation.Higher temperature sensitivity(Qio)occurred under conditions of lower soil temperatures and medium SWC(25%≤SWC≤40%).The present study deepens our understanding of CO,emissions in alpine wetland ecosystems and helps evaluate the carbon budget in alpine wetlands in arid regions.