空调变流量水系统设计技术发展(之三)——全变速离心冷水机组 装置设计与等临界性能原理

阐述了全变速离心冷水机组装置的组成、性能特征、设计与运行以及与定速装置的初投资对比。提出了基于需求控制的方法,并结合具体实例进行了分析。介绍了等临界性能原理,并将其应用于系统设计以使系统运行最佳化。

Ba-122铁基超导带材扭转下临界性能研究

为推动铁基超导带材实用化发展,本文研制出一种在铁基超导带材纯扭转测试装置,分析了7芯Ba_(1-x)K_(x)Fe_(2)As_(2)(Ba-122)带材在扭转应变下临界性能变化。带材临界电流在扭转应变下会出现衰退行为,并且随扭转应变增大而减小。四对电压信号测量结果一致,表明扭转变形均匀。以95%的初始临界电流为临界扭转标准,带材临界扭转角为120°,相应的临界剪切应变为0.86%和临界扭转螺距为240 mm。扭转应力会损伤超导芯,导致带材临界载流性能降低。

5 MW级超临界二氧化碳燃气锅炉性能评价研究及程序集成

以超临界二氧化碳(S-CO_(2))布雷顿循环发电机组中主设备S-CO_(2)锅炉作为研究目标,以5MW试验机组作为研究对象,开展S-CO_(2)锅炉性能指标评价体系研究。S-CO_(2)锅炉的核心性能指标为锅炉燃料效率、换热面吸热量占比、空气预热器性能、工质系统压降和锅炉NOx排放浓度等。燃料效率计算中,通过计算尾部烟气含氧量进行过量空气系数推算燃料消耗量和风量,并改进排烟热损失的计算方法。引入了换热面吸热量占总吸热量比值作为SCO_(2)锅炉工质侧性能考核指标。建立了5 MW S-CO_(2)燃气锅炉性能指标评价体系并集成程序且完成案例分析。实际工况与研究对象的设计参数(设计效率93.53%)基本相当,最终计算获得锅炉燃料效率未经修正为92.05%,锅炉燃料效率修正为93.79%。

用于沥青路面抗滑表层的石灰岩碎石筛选技术

为了探索用于沥青路面抗滑表层的石灰岩集料筛选技术,研究了不同岩性集料及其互掺集料的压碎值、磨耗值、磨光值、矿物组成及动态抗滑性能。结果表明:不同岩性互掺集料的压碎值、磨耗值、磨光值均与其互掺比例间存在较好的线性相关性,在已知单一集料的压碎值、磨耗值与磨光值的前提下,能够预测出不同比例下不同岩性互掺集料的压碎值、磨耗值与磨光值。确定了利用矿物组成筛选石灰岩的原则:首先选择白云石和石英含量较多的石灰岩,其次选择方解石含量相对较少的石灰岩,再次选择黏土矿物含量要少,甚至为0的石灰岩。基于自研仪器,提出了集料的抗滑性能控制指标Dμ集-临值。

钢筋混凝土梁疲劳临界剩余承载性能尺寸效应试验研究

对3组不同尺寸钢筋混凝土简支梁分别进行静载试验和等幅疲劳加载试验,以研究钢筋混凝土简支梁受弯疲劳临界剩余承载性能、疲劳临界剩余变形性能的尺寸效应.试验结果表明:疲劳临界状态下,小尺寸试件的刚度、剩余承载力较大尺寸试件而言有着更明显的下降且裂缝发展速度更快,试件尺寸越大构变形性能越强.依据试件在疲劳过程中的性能退化情况,分析了不同尺寸构件的疲劳破坏机理,基于极限状态下的破坏特征,拟合了考虑尺寸效应的极限承载力特征参数,建立了疲劳临界状态下受弯构件极限承载力特征参数计算公式.

Supercritical-hydrothermal accelerated solid state reaction route for synthesis of LiMn_2O_4 cathode material for high-power Li-ion batteries

Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.

Mechanism analysis on pillar instability induced by micro-disturbance under critical condition

A simplified mechanical model of ultra-high pillar was established and its potential energy expression was derived under axial load on the basis of energy theory. Under critical conditions according to the nonlinear theory, the critical behaviors and the forming mechanism of pillar instability were discussed by external disturbance , such as stresses waves by blasting , axial force eccentricity ratherish and imperfections in pillar. The results show that the micro-disturbances attenuate with time and they are independence each other when pillar is in the stability state. Their effects on the stability of system are inessential. The correlation degree of disturbances increases sharply and various micro-disturbances are relative and nested reciprocally when the system is in critical state and they also cooperate with each other, which induces system to reach a new state.

医用设备用各向同性导电胶的研究

在粘接固化过程中,在界面处出现原子能级现象和器件老化过程是文章的主要焦点之一。讨论了组装过程的基本原子和分子水平机理以及材料化学对电阻稳定性的影响。该机制包括在粘合剂固化过程中导电路径形成在粘合剂和金垫界面上以及界面在老化过程中是如何演变的。还讨论了可能影响电阻不稳定性的粘合剂配方中的成分,以及稳定电阻的溶液空间。

Long term performance of warm mix asphalt versus hot mix asphalt

The fatigue behavior, indirect tensile strength （ITS） and resilient modulus test results for warm mix asphalt （WMA） as well as hot mix asphalt （HMA） at different ageing levels were evaluated. Laboratory-prepared samples were aged artificially in the oven to simulate short-term and long term ageing in accordance with AASHTO R30 and then compared with unaged specimens. Beam fatigue testing was performed using beam specimens at 25 ℃ based on AASHTO T321 standard. Fatigue life, bending stiffness and dissipated energy for both unaged and aged mixtures were calculated using four-point beam fatigue test results. Three-point bending tests were performed using semi-circular bend （SCB） specimens at -10 ℃ and the critical mode I stress intensity factor K1 was then calculated using the peak load obtained from the load-displacement curve. It is observed that Sasobit and Rheofalt warm mix asphalt additives have a significant effect on indirect tensile strength, resilient modulus, fatigue behavior and stress intensity factor of aged and unaged mixtures.

Performance analysis of a zeotropic mixture(R290/CO_2) for trans-critical power cycle

Low critical temperature limits the application of CO_2 trans-critical power cycle.The binary mixture of R290/CO_2has higher critical temperature.Using mixture fluid may solve the problem that subcritical CO_2 is hardly condensed by conventional cooling water.In this article,theoretical analysis is executed to study the performance of the zeotropic mixture for trans-critical power cycle using low-grade liquid heat source with temperature of200℃.The results indicated that the problem that CO_2 can't be condensed in power cycle by conventional cooling water can be solved by mixing R290 to CO_2.Variation trend of outlet temperature of thermal oil in supercritical heater with heating pressure is determined by the composition of the mixture fluid.Gliding temperature causes the maximum outlet temperature of cooling water with the increase of mass fraction of R290.There are the maximum values for cycle thermal efficiency and net power output with the increase of supercritical heating pressure.

Modeling Topology and Nonlinear Dynamical Behavior of the Weighted Scale-Free Networks

An improved weighted scale-free network, which has two evolution mechanisms： topological growth and strength dynamics, has been introduced. The topology structure of the model will be explored in details in this work. The evolution driven mechanism of Olami-Feder Christensen （OFC） model is added to our model to study the self-organlzed criticality and the dynamical behavior. We also.consider attack mechanism and the study of the model with attack is also investigated in this paper. We tlnd there are differences between the model with attack and without attack.

Influence of Inhomogeneity on Critical Behavior of Earthquake Model on Random Graph

We consider the earthquake model on a random graph. A detailed analysis of the probability distribution of the size of the avalanches will be given. The model with different inhomogeneities is studied in order to compare the critical behavior of different systems. The results indicate that with the increase of the inhomogeneities, the avalanche exponents reduce, i.e., the different numbers of defects cause different critical behaviors of the system. This is virtually ascribed to the dynamical perturbation.

Hydrodynamics and Mass Transfer Performance in Supercritical Fluid Extraction Columns

New models for describing hydrodynamics and mass transfer performance in supercritical fluid extraction columns were proposed. Those models were proved by experimental data, which were obtained in supercritical fluid extraction packed column, spray column and sieve tray column respectively. The inner diameter of those columns areФ25 mm. These experimental systems include supercritical carbon diox-ide-isopropanol-water and supercritical carbon dioxide-ethanol-water, in which supercritical carbon dioxide was dispersed phase, and another was continuous phase. The extraction processes were operated with continuous countercurrent flow. The predicted values are agreed well with experimental data.

Statistical damage model for quasi-brittle materials under uniaxial tension

Based on the parallel bar system, combining with the synergetic method, the catastrophe theory and the acoustic emission test, a new motivated statistical damage model for quasi-brittle solid was developed. Taking concrete for instances, the rationality and the flexibility of this model and its parameters-determining method were identified by the comparative analyses between theoretical and experimental curves. The results show that the model can simulate the whole damage and fracture process in the fracture process zone of material when the materials arc exposed to quasi-static uniaxial tensile traction. The influence of the mesoscopic damage mechanism on the macroscopic mechanical properties of quasi-brittle materials is summarized into two aspects, rupture damage and yield damage. The whole damage course is divided into the statistical even damage phase and the local breach phase, corresponding to the two stages described by the catastrophe theory. The two characteristic states, the peak nominal stress state and the critical state are distinguished, and the critical state plays a key role during the whole damage evolution course.

Performance Analysis and Retrofit on 350-MW China-Made Supercritical Steam Turbines

In this paper the development status and background of 350-MW China-made supercritical steam turbines are introduced.Through the study on the eight turbines that are put into operation,their technical performances are compared and summarized.The major factors affecting the heat consumption rate are analyzed in details and the technical measures to reduce the heat consumption rate are put forward.These measures have been applied to several such units with significant improvements,which can provide important references for the maintenance and retrofit of 350-MW super critical steam turbines.

Investigation on adsorption and regeneration performances of multi-walled carbon nanotubes by supercritical water technique

In this paper, adsorption and regeneration characteristics of multi-walled carbon nanotubes （MWNTs） used as adsorbent were investigated for the removal of 1,3-beuzenediol （BDO） from water by the supercritieal water （SCW） technique. FFIR, XPS, SEM and dispersion stability tests were used to characterize the structure and surface morphology of CNTs. The results showed that CNTs surfaces were slightly activated and strongly etched in supercritieal water system. The adsorption capacity of SCW-treated CNTs was higher than that of raw CNTs. The adsorbed amounts for treated CNTs and raw CNTs samples at the same initial concentration of 60 mg/L were ca. 16.42 and 7.30 mg/g, respectively. The BDO adsorption of treated CNTs was due to the physical adsorption. The experimental data fit Freundlich isotherm model better than Langmuir one. The loaded adsorbent could be efficiently desorbed and regenerated by SCW technique. Therefore, SCW is a promising and environmentally friendly technique for the improvement of adsorption and regeneration of CNTs.

Technological Properties of Yeast Produced Surface Active Compounds in Connection with Their Application in Clean-Up Technologies

Biologically produced surfactants （SACs） can mobilize and solubilize non-aqueous phase liquids （NAPL） adsorbed onto soil constituents. The interest in microbial surfactants has increased during recent years due to their lower toxicity, higher biodegradability, selectivity and specific activity under extreme conditions than synthetic SACs. Main output of the project represents preparation of this yeast biosurfactant intended for washing of matrices contaminated by NAPL. The influence of cultivation media composition on biosurfactant production was studied and basic properties （critical micelle concentration （CMC）, minimum surface tension） of isolated biosurfactants were compared with properties of synthetic surfactant with surface tension measurement. The interracial tension of the systems containing aqueous solutions of different concentrations and non-polar substances was measured with petroleum compounds （kerosene Jet A-l）, aromatic and aliphatic hydrocarbons （represented by toluene and hexane）. The solution of biosurfactant Yarrowia lipolytica （YAR） in the concentration range of 0-500 mg/L reduced interracial tension by 80% in all representative systems with model contaminants; biosurfactant Candida bombicola （CAN） was less efficient. Solubilization properties were proved with toluene and hexachlorocyclohexane （HCH） isomers alpha and gamma, and effective concentration of biosurfactants was determined as 100 mg/L for toluene and HCH. SACs produced by lipophilic yeast with non-toxic and non-pathogenic status （Yarrowia lipolytica, Candida sp., etc.） seem to be very promising. The results obtained will be used for the application of biosurfactants in the clean-up technologies as agents for the mobilization of non-polar contaminants as well as for stimulation of bioremediation processes.

Study on the Structural Performance of Steel Plate Shear Wall with Slits on Both Sides

This paper presents a new type of two sides slotted steel plate shear wall, and carries on the analysis to the finite element elastic buckling, respectively discusses the critical buckling load and the buckling mode. For the steel plate shear wall without stiffening ribs on both sides, the paper given the buckling coefficient formula, and give design proposal and reference value of steel plate shear wall with stiffened on both sides.

Seismic Hazard Assessment for Selected Real Locality in Central Europe-Critical Points of Assessment

The seismic hazard value is a fundamental quantity for the seismic risk assessment and for the determination of terms of references of seismic design of important facilities as dams, chemical plants, nuclear power plants, etc.. In real sites, the seismic hazard value is influenced by both, the earthquake sizes, the impacts of which in a given site may be expected, and the properties of geological structure through which seismic waves spread from earthquake loci to a given site. The seismic risk is predetermined by hazard value, distribution of assets in the given site and asset numbers and vulnerabilities. The paper describes the used procedure of hazard assessment of important sites. The attention is especially paid to the basic steps as the data collection （homogeneity level, uncertainty and vagueness）, the focal region boundaries （their uncertainties and vagueness）, and the maximum expected earthquake size in each focal region that must be taken into account （its uncertainty and vagueness）, because they substantially influence the hazard value. Discussion is also concentrated to the attenuation that Central Europe substantially depends on the azimuth between earthquake focus and the given site. The attenuation differences are shown in seismic scenarios for individual focal regions. They are caused by focal mechanisms in near focal zone and differences in structure properties in distant zone; the boundary between near and distant zone in Central Europe is ca 2.5 h, where h is the focal depth in km. The real results are given for a real locality in Central Europe. It is shown than that great influence on hazard value is caused by great differences in azimuth attenuation curves. It is the reality that the Bohemian Massif is characterised with very low seismic attenuation in comparison with its vicinity. The following real results are presented： geological structure of near site vicinity, earthquake catalogue for Central Europe, focal regions in Central Europe, attenuation curves in Central Europe, typical earthquake isoseismals for individual focal regions, frequency graph, recurrence probability curve, etc.. The approaches used for nuclear facilities were recommended by the IAEA （International Atomic Energy Agency）.