Novel multi-center concave bottom for hydrogen storage cylinder

Hydrogen storage steel cylinders are the earliest and widely used hydrogen storage vessels. Fatigue cracks are easy to initiate and grow under hydrogen pressure, which threatens the safety of users. Although hydrogen has an effect on the initiation and growth of fatigue cracks, a reasonable structure of cylinder will make the stress distribution more reasonable and reduce the probability of crack initiation from the source. This paper researched the multi-center concave bottom for hydrogen storage cylinder. The geometric design parameters of the new base end are determined by the orthogonal design method. We analyze the effects of various parameters on the multi-center concave base end by using the finite element method. Based on the finite element analysis (FEA) of different structure, the results show that the stress concentration of new base end can be greatly reduced, and the minimum stress concentration factor is close to 1.1. The results provide valuable insights for designing and manufacturing the new type of seamless gas cylinder. The corresponding gas cylinder that we processed according to the simulation had successfully passed a series of tests.     

徐楼闸深厚粉细砂闸基防渗防冲方法及处理效果

鉴于徐楼闸老闸因闸基渗透、上下游冲刷而损坏,移址改建的徐楼闸新闸必须解决闸基深厚粉细砂层渗透能力强、不耐冲刷的问题,采用闸基换填水泥土、闸基设置截渗墙、下游消力池末端设置防冲墙等加固补强措施,就可有效减弱粉细砂的渗透问题,并可有效提高闸基的抗冲能力,从而确保闸基稳定安全运行。     

热环工作特性的理论分析与实验研究

热环是用于非相邻冷热源间热量传递或余热回收的节能装置。本文对热环的基本原理、特点进行了简要介绍 ,在此基础上 ,分析建立了热环的输热能力、输热系数、工作温度等性能指标的计算方程 ,并进行了较系统的实验研究     

Performance of different structured surfaces in nucleate pool boiling

Several structured surfaces have been developed in-house for the augmentation of boiling heat transfer using distilled water as test fluid under atmospheric pressure. These surfaces have either a number of parallel tunnels or orthogonally intersecting tunnels. Effect of design parameters like tunnel inclination and different cavity structure at the tunnel base on the boiling heat transfer has been investigated. Three different structures namely circular groove, rectangular groove and rounded base have been used at the end of the tunnels. Heat flux is varied in the range of 0–250 kW/m². Experimental results showed tunnels inclined at an angle 60° with the horizontal provide better augmentation compared to straight vertical tunnels. Amongst different base geometry the circular pocket produced most conducive condition for the boiling heat transfer. The use of tunnels also increases the degree of augmentation. The highest augmentation was obtained from the surface having intersecting inclined tunnels with a circular base.     

Alternative transportation vehicles for military-base operations

With an increasing emphasis on improving the defense capabilities of our nation, the demand for petroleum by the military services will remain high. Now is the time to specifically address programs that will reduce the gasoline and diesel requirements for base transportation vehicles; such programs might be integrated from the onset into military construction projects planned for the 1980s.

In the context of Fig. 1, the base technology for non-petroleum-based, low-polluting fuels exists today. Relatively low cost entry demonstration programs at the use end could begin immediately without commitment to any particular supply-path option.     

Heat transfer from a horizontal fin array by natural convection and radiation—A conjugate analysis

The problem of natural convection heat transfer from a horizontal fin array is theoretically formulated by treating the adjacent internal fins as two-fin enclosures. A conjugate analysis is carried out in which the mass, momentum and energy balance equations for the fluid in the two-fin enclosure are solved together with the heat conduction equations in both the fins. The numerical solutions by using alternating direction implicit (ADI) method yield steady state temperature and velocity fields in the fluid, and temperatures along the fins. Each end fin of the array is exposed to limited enclosure on one side and to infinite fluid medium on the other side. Hence a separate analysis is carried out for the problem of end fin exposed to infinite fluid medium with appropriate boundary conditions. From the numerical results, the heat fluxes from the fins and the base of the two-fin enclosure, and the heat flux from the end fin are calculated. Making use of the heat fluxes the total heat transfer rate and average heat transfer coefficient for a fin array are estimated. Heat transfer by radiation is also considered in the analysis. The results obtained for a four-fin array are compared with the experimental data available in literature, which show good agreement. Numerical results are obtained to study the effectiveness for different values of fin heights, emissivities, number of fins in a fixed base, fin base temperature and fin spacing. The numerical results are subjected to non-linear regression and equations are obtained for heat fluxes from the two-fin enclosure and single fin as functions of Rayleigh number, aspect ratio and fin emissivity. Also regression equations are obtained to readily calculate the average Nusselt number, heat transfer rate and effectiveness for a fin array.     

Futures pricing in electricity markets based on stable CARMA spot models

We present a new model for the electricity spot price dynamics, which is able to capture seasonality, low-frequency dynamics and extreme spikes in the market. Instead of the usual purely deterministic trend we introduce a non-stationary independent increment process for the low-frequency dynamics, and model the large fluctuations by a non-Gaussian stable CARMA process. The model allows for analytic futures prices, and we apply these to model and estimate the whole market consistently. Besides standard parameter estimation, an estimation procedure is suggested, where we fit the non-stationary trend using futures data with long time until delivery, and a robust L¹-filter to find the states of the CARMA process. The procedure also involves the empirical and theoretical risk premia which – as a by-product – are also estimated. We apply this procedure to data from the German electricity exchange EEX, where we split the empirical analysis into base load and peak load prices. We find an overall negative risk premium for the base load futures contracts, except for contracts close to delivery, where a small positive risk premium is detected. Peak load contracts, on the other hand, show a clear positive risk premium, when they are close to delivery, while contracts in the longer end also have a negative premium.     

Experimental investigation of the performance of a solar‐assisted ground‐source heat pump system for greenhouse heating

The main objective of the present study is to investigate the performance characteristics of a solar‐assisted ground‐source heat pump system (SAGSHPS) for greenhouse heating with a 50 m vertical 1¼ in nominal diameter U‐bend ground heat exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22°C, 1226 degree days heating, base: 18°C), Turkey. Based upon the measurements made in the heating mode, the heat extraction rate from the soil is found to be, on average, 54.08 Wm^?1 of bore depth, while the required borehole length in meter per kW of heating capacity is obtained as 12.57. The entering water temperature to the unit ranges from 8.2 to 16.2°C, with an average value of 9.1°C. The greenhouse air is at a maximum day temperature of 25°C and night temperature of 14°C with a relative humidity of 40%. The heating coefficient of performance of the heat pump (COP_HP) is about 2.13 at the end of a cloudy day, while it is about 2.84 at the end of sunny day and fluctuates between these values in other times. The COP values for the whole system are also obtained to be 5–15% lower than COP_HP. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of copper surface wettability on the evaporation performance: Tests in a flat-plate heat pipe with visualization

The effects of copper surface wettability on the evaporation performance of a copper mesh wick were experimentally studied in an operating flat-plate heat pipe. Different degrees of wettability were obtained by varying the exposure times in air after the wicked plates were taken out of the sintering furnace. Three different working fluids: water, methanol and acetone, which possess different figures of merit, were investigated at the same volumetric liquid charge. The surface wettability was quantified by the static contact angle of sessile water drops on a flat copper surface. While the static contact angles of water drops varied from 10° to 40° for different degrees of wettability, the methanol and acetone drops still fully wetted the copper surface. A two-layer 100 + 200 mesh copper wick, 0.26 mm in thickness, was sintered on a 3 mm-thick copper base plate. A glass plate was adopted as the top wall of the heat pipe for visualization. Uniform heating was applied to the base plate near one end, and a cooling water jacket was connected at the other end. With increasing heat load, the evaporative resistance decreased with liquid film recession until a critical heat load showing the minimum evaporative resistance. Afterwards, partial dryout began from the front end of the evaporator. With decreasing wettability, the evaporating water film receded faster with increasing heat load and the critical heat loads were significantly reduced. In contrast, the critical heat loads for methanol and acetone seemed hardly affected by different wettability conditions. The minimum evaporative resistances, however, remained unaffected by surface wettability for all the three working fluids.     

Boundary Feedback Stabilization of a Variant of the SCOLE Model

This paper deals with the boundary feedback stabilization of a variant of the SCOLE model, namely, a flexible beam clamped at one end, and free at the other end where a rigid body is attached. Using the frequency domain method, we first prove that the considered system is uniformly stabilizable if the control force and control moment are simultaneously applied at the free end of the beam. Secondly, if only a control force is applied, we give a sufficient condition on the physical parameters of the system to guarantee the uniform stabilization. Finally, it is shown that the presence of boundary control force is necessary to achieve the uniform stabilization. To verify these theoretical developments, an asymptotic analysis and numerical study of the spectrum are performed.     

大坝背管混凝土裂缝前馈网络的预测研究

基于人工神经网络的BP网络方法和全局优化方法的基本理论,对坝后背管外包混凝土结构裂缝预测进行了研究,提出了基于神经网络的管道混凝土裂缝预测模型,并重点研究了水头的变化对压力管道混凝土最大裂缝宽度的影响,最后对三峡电站压力管道混凝土结构裂缝进行了预测。     

Evaluation of alternative methods of preparing hydrogen producing seeds from digested wastewater sludge

Six digested sludges, pre-treated by different methods (heat-shock, aeration, acid and base treatments, 2-bromoethanesulfonic acid (BESA) inhibition and iodopropane inhibition) as well as an untreated sample were compared for their suitability in the preparation of hydrogen producing seeds by cultivations in a sucrose medium. The heat-shock and acid treatment methods completely repressed methanogenic activity; however, they also partially repressed hydrogen production. The base treatment option did not completely repress methanogenic activity and also significantly impacted hydrogen production. The aeration method was unsuccessful at completely repressing methanogenic activity; however, it did not significantly affect the hydrogen production activity. The BESA and iodopropane pre-treatment methods specifically inhibited the methanogens, and there were no significant effects found on hydrogen production. Similar to the aeration pre-treated digested sludge sample, the untreated sludge showed high hydrogen production activity and a small amount of methanogenic activity (lower than the activity detected in the base treatment sample). In the subsequent second-step batch cultivations with the same sucrose medium and the diluted media, methanogenic activity was not detected in any of the test bottles. The microbial seed prepared from base treatment exhibited the highest hydrogen production activity, whereas those prepared from acid treatment did not exhibit any activity. Again, the microbial seed prepared from untreated sludge also exhibited relatively high hydrogen producing activity. A lower pH was detected at the end of the cultivation in all the test bottles. Interestingly, the variations in pH in the different tests bottles indicate that pH is an important parameter in the control of methanogenic activity.     

电控单体泵电液延迟特性标定

在EFS油泵试验台上,结合电磁阀供油脉冲、泵端压力和喷油速率信号,研究了不同工况下电控单体泵燃油喷射系统的电液延迟特性。试验结果表明:电力延迟时间在任何工况下基本为常量;喷油及停喷液力延迟时间受供油量的影响较小,而与转速及供油提前角有较大的相关性。电液延迟特性的标定为单体泵喷射过程的精确控制提供了依据。     

Improvement of the cycleability of nano-crystalline lithium manganate cathodes by cation co-doping

Lithium manganate spinel is extensively studied as a positive electrode in lithium ion rechargeable batteries. Growth of nano-size cathode particles is proposed to improve the rate capabilities of these cathode materials. It remains controversial if the particle size in the nano-range (as compared to the conventional micrometer size particles of these materials) has any appreciable influence on the discharge capacity, rate capabilities, and cycleability of these materials. In the 4 V range, especially at slightly elevated temperature, lithium manganate exhibits capacity fading though the underlying mechanism for such fading is not yet clear. In the present work, we have successfully prepared nano-crystalline lithium manganate spinel powder by an acetate base solution route. Though the discharge capacity of these nano-crystalline cathodes was equivalent to their microcrystalline counterpart, these exhibited capacity fading in the 4 V range. Through a combined X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses, we correlated the observed capacity fading with the onset of Jahn–Teller (J–T) distortion toward the end of the discharge in the cut-off limit between 4.2 and 3.4 V. It was postulated that if J–T distortion is the dominant fading mechanism of these nano-crystalline cathodes then by increasing the average oxidation state of the Mn ions in a virgin lithium manganate cathode, the onset of such distortion towards the end of the discharge could be delayed, and therefore, the cycleability of these cathodes could be improved. By synthesizing lithium and aluminum ion co-doped lithium manganate particles, we could increase the average oxidation state of the Mn ions in the virgin electrodes. Indeed, the cycleability of these co-doped cathodes was dramatically improved which supports our postulation. The doping contents of lithium and aluminum, however, should be further optimized to further increase the discharge capacity of these modified cathodes.     

Spatial Behavior in the Strongly Elliptic Anisotropic Thermoelastic Materials

In the present article we consider a prismatic semi-infinite cylinder occupied by an anisotropic homogeneous compressible linear thermoelastic material having an elasticity tensor that is strongly elliptic. The cylinder is subjected to zero body force and heat supply, zero displacement–temperature variation on the lateral boundary and pointwise specified displacement–temperature variation over the base. The main purpose of this contribution is to examine how certain measures of the displacement–temperature variation evolve with respect to the axial variable, provided that the strong ellipticity of the elasticity tensor is assumed. To this end, some appropriate measures are associated with the displacement–temperature variation and then an appropriate second-order differential inequality is established under the strong ellipticity condition on the elasticity tensor. The results are specialized for transversely isotropic and rhombic systems of elastic materials.     

北方农村"四位一体"模式调查研究

"四位一体"模式的推广运用促进了农村社会、经济的发展和能源、生态环境状况的改善.通过对北方典型农村的调查,发现"四位一体"的迅速推广在创造为人熟知的效益同时,仍然存在制约该模式持续健康发展的诸多问题,主要表现在:沼气池配套服务技术缺乏,农户自身管理水平落后,农(畜)产品的生产、销售,居住模式和猪舍卫生,劳动力的竞争以及土地资源、投资、信贷、基础设施等方面问题.文章并就存在的问题提出了适当的对策.     

Role of Melt Convection on Optimization of PCM-Based Heat Sink Under Cyclic Heat Load

In this article, we study the thermal performance of phase-change material (PCM)-based heat sinks under cyclic heat load and subjected to melt convection. Plate fin type heat sinks made of aluminum and filled with PCM are considered in this study. The heat sink is heated from the bottom. For a prescribed value of heat flux, design of such a heat sink can be optimized with respect to its geometry, with the objective of minimizing the temperature rise during heating and ensuring complete solidification of PCM at the end of the cooling period for a given cycle. For given length and base plate thickness of a heat sink, a genetic algorithm (GA)-based optimization is carried out with respect to geometrical variables such as fin thickness, fin height, and the number of fins. The thermal performance of the heat sink for a given set of parameters is evaluated using an enthalpy-based heat transfer model, which provides the necessary data for the optimization algorithm. The effect of melt convection is studied by taking two cases, one without melt convection (conduction regime) and the other with convection. The results show that melt convection alters the results of geometrical optimization.     

Understanding of Interactions for Bubbles Generated at Neighboring Nucleation Sites

Bubble dynamics and site interaction are studied numerically by solving conservation of mass, momentum, and energy equations for the liquid and vapor phases. The liquid-vapor interface is tracked by a volume of fluid method. The effects of applied mean heat flux, site-site interactions, orientation of the boiling surface, inclination of nucleating tunnels, and reentrant cavity shape on the bubble dynamics are investigated. With the increase of mean heat flux three separate regimes namely surface tension driven interaction, no interaction and instability driven interaction between the bubbles were shown. Closer nucleation sites fascilitates bubble merging whereas sites away from each other behaves like individual bubble release. Critical spacing between the sites are predicted bifurcating interaction and no interaction zones separately. Site-site interaction patterns are also tested on inclined planes and critical inclination angle has been reported beyond which columnar bubble formation is observed as a result of merging. Using numerical simulation efforts have been also made to check suitability of site inclination and base pocket at the end of the tunnel to generate high heat transfer coefficient. Proposal of reentrant cavity base geometry matches well with literature.     

煤炭企业的非煤产业研究

本文讲述了我国煤炭工业非煤产业在不同发展阶段的国家政策、经营特色及取得的成果等。在此基础上指出非煤产业发展中存在的问题,并从战略的角度提出了解决问题的对策。     

Analysis of Russia's biofuel knowledge base: A comparison with Germany and China

This study assesses the evolutionary trajectory of the knowledge base of Russian biofuel technology compared to that of Germany, one of the successful leaders in adopting renewable energy, and China, an aggressive latecomer at promoting renewable energy. A total of 1797 patents filed in Russia, 8282 in Germany and 20,549 in China were retrieved from the European Patent Office database through 2012. We identify four collectively representative measures of a knowledge base (size, growth, cumulativeness, and interdependence), which are observable from biofuel patent citations. Furthermore, we define the exploratory–exploitative index, which enables us to identify the nature of learning embedded in the knowledge base structure. Our citation network analysis of the biofuel knowledge base trajectory by country, in conjunction with policy milestones, shows that Russia's biofuel knowledge base lacks both the increasing technological specialization of that in Germany and the accelerated growth rate of that in China. The German biofuel citation network shows a well-established knowledge base with increasing connectivity, while China's has grown exceptionally fast but with a sparseness of citations reflecting limited connections to preceding, foundational technologies. We conclude by addressing policy implications as well as limitations of the study and potential topics to explore in future research.