Numerical investigation on the flow and power of small-sized multi-bladed straight Darrieus wind turbine

Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.

k_(eff)uncertainty quantification and analysis due to nuclear data during the full lifetime burnup calculation for a small-sized prismatic high temperature gas-cooled reactor

To benefit from recent advances in modeling and computational algorithms,as well as the availability of new covariance data,sensitivity and uncertainty analyses are needed to quantify the impact of uncertain sources on the design parameters of small prismatic high-temperature gascooled reactors(HTGRs).In particular,the contribution of nuclear data to the k_(eff)uncertainty is an important part of the uncertainty analysis of small-sized HTGR physical calculations.In this study,a small-sized HTGR designed by China Nuclear Power Engineering Co.,Ltd.was selected for k_(eff)uncertainty analysis during full lifetime burnup calculations.Models of the cold zero power(CZP)condition and full lifetime burnup process were constructed using the Reactor Monte Carlo Code RMC for neutron transport calculation,depletion calculation,and sensitivity and uncertainty analysis.For the sensitivity analysis,the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Track length importance Characterization(CLUTCH)method was applied to obtain sensitive information,and the "sandwich" method was used to quantify the k_(eff)uncertainty.We also compared the k_(eff)uncertainties to other typical reactors.Our results show that ^(235)U is the largest contributor to k_(eff)uncertainty for both the CZP and depletion conditions,while the contribution of ^(239)Pu is not very significant because of the design of low discharge burnup.It is worth noting that the radioactive capture reaction of ^(28)Si significantly contributes to the k_(eff)uncertainty owing to its specific fuel design.However,the k_(eff)uncertainty during the full lifetime depletion process was relatively stable,only increasing by 1.12%owing to the low discharge burnup design of small-sized HTGRs.These numerical results are beneficial for neutronics design and core parameters optimization in further uncertainty propagation and quantification study for small-sized HTGR.

Assessment for Production and Operation Ability of Medium and Small-sized Enterprises Based on Neural Network

In order to improve production and operation ability of medium and small-sized enterprises, an assessment-index system of production and operation ability was proposed, and a corresponding assessment model was established based on BP neural network. The conjunction weights of the neural network were continuously modified from output layer to input layer in the process of neural network training to reduce the errors between the anticipated and actual outputs. The results from an example show that this method is reliable and feasible. The production and operation abilitv of an enterorise with assessed result of 0.833 is fairly oowerful, and that with assessed result of 0.644 is average.

Study on Contra-Rotating Small-Sized Axial Flow Hydro Turbine

It is thought that small hydropower generation is alternative energy, and the energy potential of small hydropower is large. The efficiency of small hydro turbines is lower than that of large one, and these small hydro turbine’s common problems are out of operation by foreign materials. Then, there are demands for small hydro turbines to keep high per- formance and wide flow passage. Therefore, we adopted contra-rotating rotors which can be expected to achieve high performance and low-solidity rotors with wide flow passage in order to accomplish high performance and stable opera- tion. Final goal on this study is development of an electric appliance type small hydro turbine which has high portability and makes an effective use of the unused small hydro power energy source. In the present paper, the performance and the internal flow conditions in detail of contra-rotating small-sized axial flow hydro turbine are shown as a first step of the research with the numerical flow analysis. Then, a capability adopting contra-rotating rotors to an electric appliance type small hydro turbine was discussed. Furthermore, the high performance design for it was considered by the numeri- cal analysis results.

Effect of Organic and Chemical Fertilizer Application on Growth, Yield, and Quality of Small-Sized Tomatoes

Tomatoes in Japan are generally cultivated under management systems that use chemical fertilizers and synthetic chemical pesticides. However, the continuous use of these fertilizers and pesticides damages the soil environment and reduces the number of soil microorganisms. Organic farming has a relatively low environmental impact compared to conventional farming techniques, but typically has lower and more unstable yields. In this study, we investigated the effect of organic and chemical fertilizer application on growth, yield, and quality of small-sized (cherry) tomatoes. Cherry tomatoes were cultivated using organic and chemical organic fertilizers. Average weight and lateral diameter were significantly higher under organic fertilizer than under chemical fertilizer. In addition, shoot dry weight was significantly higher under organic fertilizer than chemical fertilizer. Lycopene content was significantly higher under organic fertilizer than chemical fertilizer. The total carbon (TC), total phosphorus (TP), total potassium (TK), available phosphoric (SP) and exchangeable potassium (SK) contents, C/N ratio, and pH were significantly higher under organic fertilizer than chemical fertilizer. Bacterial biomass, nitrite (NO? 2-N) oxidation activity, nitrification (N) circulation activity, and phosphoric (P) circulation were higher under organic fertilizer than chemical fertilizer. From these results, the study indicates that appropriate controls such as TC, total nitrogen (TN), and C/N ratio of organic fertilizer increased microbial biomass and enhanced nutrient circulation such as N circulation activity and P circulation activity. These results can be used to improve current organic farming practices and promote soil conservation.

Performance and Internal Flow of Contra-Rotating Small-Sized Cooling Fan

High pressure and large flow rate small-sized cooling fans are used for servers in data centers and there is a strong demand to increase its performance because of increase of quantity of heat from servers. Contra-rotating rotors have been adopted for some of high pressure and large flow rate cooling fans to meet the demand. The performance curve of the contra-rotating small-sized cooling fan with 40 mm square casing was investigated by an experimental apparatus and its internal flow condition was clarified by the numerical analysis. The fan static pressure of the front rotor was extremely low and it increased significantly at the rear rotor. The uniform flow was achieved at the inlet of the rear rotor because of the special shape of the casing between the front and rear rotors. On the other hand, the tip leakage flow was large enough to influence on the main flow of the test cooling fan by the design specification of high pressure with compact rotor diameter.

Internal Flow Condition between Front and Rear Rotor of Contra-Rotating Small-Sized Axial Fan at Low Flow Rate

Contra-rotating small-sized fans are used as cooling fans for electric equipment. The internal flow condition between the front and rear rotors of the contra-rotating small-sized fan is not known well especially at the low flow rate. Furthermore, the blade row distance between the front and rear rotors is an important parameter for the contra-rotating small-sized fan and its influence on the internal flow condition is not clarified at the low flow rate. Therefore, the internal flow condition of the contra-rotating small-sized fan at the low flow rate is investigated by the numerical analysis in this research. The numerical analysis results are validated by comparing the fan static pressure curves of the numerical results to the experimental results. The internal flow condition at the low flow rate is clarified using the numerical models of the different blade row distance L = 10 mm and 30 mm. In the present paper, pressure fluctuations phase locked each front and rear rotor’s rotation are shown and the influences of the wake and the potential interference are discussed by the unsteady numerical analysis results at the low flow rate.

Study on Construction and Countermeasures of Technological Innovation Environment within Medium and Small-sized Enterprises in Hubei Province

Based on the application of the latest technological innovation theory and the successful experience generated by the domestic and overseas medium and small-sized enterprises, this thesis proposes a theoretical framework, strategic proposition and some secure measures for the regional technological innovation to promote the technological innovation within medium and small-sized enterprises in Hubei Province. In addition, the author also provides some tactics concerning the original motivation, technological market, innovation talents and innovation system, which aim at offering some consultation for the government decision, optimize industrial structure, implement the innovation strategy and propel to the medium and small-sized enterprises＇ development.

Space-to-Ground Quantum Key Distribution Using a Small-Sized Payload on Tiangong-2 Space Lab

Quantum technology establishes a foundation for secure communication via quantum key distribution （QKD）. In the last two decades, the rapid development of QKD makes a global quantum communication network feasible. In order to construct this network, it is economical to consider small-sized and low-cost QKD payloads, which can be assembled on satellites with different sizes, such as space stations. Here we report an experimental demonstration of space-to-ground QKD using a small-sized payload, from Tiangong-2 space lab to Nanshan ground station. The 57.9-kg payload integrates a tracking system, a QKD transmitter along with modules for synchronization, and a laser communication transmitter. In the space lab, a 50MHz vacuum＋weak decoy-state optical source is sent through a reflective telescope with an aperture of 200mm. On the ground station, a telescope with an aperture of 1200mm collects the signal photons. A stable and high-transmittance communication channel is set up with a high-precision bidirectional tracking system, a polarization compensation module, and a synchronization system. When the quantum link is successfully established, we obtain a key rate over 100bps with a communication distance up to 719km. Together with our recent development of QKD in daylight, the present demonstration paves the way towards a practical satellite-constellation-based global quantum secure network with small-sized QKD payloads.

Study on Virtual Training Management in Small-sized Enterprises

This paper firstly analyses the necessity of virtual management in small-sized enterprises, then presents two main modes to implement virtual training management in small-sized enterprises. The paper also points out the best mode for the small-sized enterprises＇ training to implement virtual management.

A Study on USA Promoting the Development of Middle and Small-sized Enterprises and Its Revelation

The middle and small-sized enterprises of USA develop very well, and they are the pillars of American economy. The long-term development of middle and small-sized enterprises lies in suitable supporting countermeasures and clear economic function of the government. The development of middle and small-sized enterprises of USA brings China many useful revelations.

Peers Small-sized Group Work-A Beneficial Form of Classroom Interaction

Classroom interaction plays a critical role in language teaching and learning process.It involves both the teacher-students,and students-students.This article is intended to explore the vital significance of classroom interaction in language learning process with the emphasis placed on the students' involvement in the classroom activities,furthermore,to discover whether the peers small-sized group work is a beneficial and irreplaceable form of classroom interaction.

Allocation of Mobile Chippers for a Concentrated Bioenergy Demand

Allocation of mobile chippers is a tactical problem of management in a bioenergy supply chain. It influences the entire supply cost of the wood chip since the transportation distance and the chipping productivity decide the transportation cost. Great and concentrated demands of woody biomass require multiple suppliers, and there should be the best allocation of mobile chippers which minimize the entire supply cost. This study aims to clarify better management of the supply chain consisting of multiple players for a great and concentrated demand for wood chip. The model was a supply chain for a typical biomass power plant with 5.8 MW capacity. Suppliers were assumed to select mobile chippers from two sizes, 140-kW and 353-kW. By the model simulation, it was clarified that the well-considered allocation of two different mobile chippers could reduce the entire supply cost less than the conventional system using a fixed chipper at the power plant. The best management was to use only the 353-kW chippers, and secondly to allocate the less productive chippers closer to the demand to prevent the incline of the transportation cost. However, the possible conflict was also specified as the increased cost of the suppliers using more productive chippers in the second best allocation strategy. This result emphasizes the necessity of resolving such conflict by making the collaborative relationship among stakeholders which has been pointed out by other researches as well to sustain the better condition of the supply chain.

Influence of Small-Size Contaminations on Thin Film Structural Properties

An approach for studying the influence of nano-particles on the structural properties of deposited thin films is proposed. It is based on the molecular dynamic modeling of the deposition process in the presence of contaminating nano-particles. The nano-particle is assumed to be immobile and its interaction with film atoms is described by a spherically symmetric potential. The approach is applied to the investigation of properties of silicon dioxide films. Visualization tools are used to investigate the porosity associated with nano-particles. The structure of the film near the nano-particle is studied using the radial distribution function. It is found that fluctuations of film density near the nano-particles are essentially different in the cases of low-energy and high-energy deposition processes.

新型盘式削片机刀盘结构设计及切削力研究

基于目前纤维板所需工艺木片的生产现状,为保证盘式削片机生产工艺木片的质量并解决盘式削片机飞刀快速更换的问题,设计一款采用差动螺旋结构实现飞刀伸出量微调,以及刀块整体更换的新型盘式削片机刀盘。对新型刀盘的削片工作原理以及切削力进行研究,对装刀块夹持力部分进行验证计算,通过Adams仿真软件对设计的新型刀盘进行了动力学分析,验证刀盘结构在额定转速下的稳定性。

林业剩余物可调式斜进料盘式削片机主轴刚柔耦合动力学分析

研究新型枝丫材、抚育间伐材等林业剩余物盘式削片机的主轴系统,该削片机刀盘与主轴安装结构的特点,与当下主流安装形式存在差异,验证其主轴系统在切削原木过程中是否符合结构设计要求。采用ADAMS软件与ANSYS软件建立柔性主轴的刚柔耦合模型,在模型中添加切削力周期变化的规律,仿真提取主轴与刀盘连接点位置处主轴轴向与径向振幅情况,得到刀盘在径向的最大振动幅度为175μm,结果按国标对比符合旋转轴长期运行条件。研究结果对新型削片机主轴系统的合理性提供了验证,为削片机主轴系统的结构改进提供了理论依据。

A low-melting-point metal doping strategy for the synthesis of small-sized intermetallic Pt_(5)Ce fuel cell catalysts

Carbon-supported platinum-lanthanum(Pt-Ln)intermetallic compound(IMC)nanoparticles with high activity and robust stability have been demonstrated as promising cathode catalysts for proton-exchange membrane fuel cells.However,the preparation of Pt-Ln IMC catalysts needs high-temperature annealing treatment that inevitably causes nanoparticle sintering,resulting in significant reduction of the electrochemical surface area and mass-based activity.Here,we prepare small-sized M-doped Pt_(5)Ce(M=Ga,Cd,and Sb)IMCs catalysts via a low-melting-point metal doping strategy.We speculate that the doping of low-melting-point metals can facilitate the generation of vacancies in the crystal lattice through thermal activation and thus reduce the kinetic barriers for the formation of intermetallic Pt_(5)Ce catalysts.The prepared Ga-doped Pt_(5)Ce catalyst exhibits a higher electrochemical active surface area(81 m^(2)·gPt^(-1))and a larger mass activity(0.45 A·mgPt^(-1)at 0.9 V)over the undoped Pt_(5)Ce and commercial Pt/C catalysts.In the membrane electrode assembly test,the Ga-doped Pt_(5)Ce cathode delivers a power density of 0.98 W·cm^(-2)at 0.67 V,along with a voltage loss of only 27 mV at 0.8 A·cm^(-2)at the end of accelerated stability test.

一种木材削片机远程监控系统开发

为实时监控并保证木材削片机稳定、高效地工作,开发了一套木材削片机远程监控系统。该系统由数据采集与监控平台两部分组成。其中,数据采集部分以STM32F103作为主控芯片,采用两线制压电集成电路传感器获取木材削片机的振动情况,单片机程序采用C语言编写,实现对木材削片机各项运行数据的采集,并将数据通过4G数据传输模块上传至云服务器Onenet平台;监控平台用于对木材削片机运行状态进行远程可视化监控,实时显示反映当前工况的各项数据,也可查询设备的历史运行状态。该系统运用聚类算法对运行数据进行识别,进行了稳定性和识别算法测试。测试结果表明,数据识别准确率在96%以上,整机测试基本达到设计要求。

削片机技术应用、创新与发展趋势

系统地探讨了削片机的类型、应用、技术创新及未来趋势。削片机主要分为鼓式、盘式和移动式,广泛应用于林业、园林绿化、生物质能源和纸浆生产等领域,各具特色并满足不同行业需求,有效提高了生产效率和资源利用率。其技术创新在自动化控制、噪音控制、能源效率提升和环保设计方面取得了显著进展。智能化、绿色环保、新材料和新工艺的应用将近一步推动削片机技术进一步发展,满足多样化市场需求。为削片机技术的发展提供了较为全面的参考和指导,展望了其在各行业中的广阔前景。

Sodium thiosulfate-assisted synthesis of high-Pt-content intermetallic electrocatalysts for fuel cells

Carbon supported Pt-based intermetallic compounds(IMCs)with high activity and durability are the most competitive cathode catalysts for the commercialization of proton exchange membrane fuel cells(PEMFCs).The synthesis of Pt-based intermetallics with a good balance between small size and high metal loading remains challenging because of the high-temperature annealing that is generally required to form intermetallic phases.We developed a sodium thiosulfate-assisted impregnation strategy to synthesize small-sized and highly ordered PtM IMCs catalysts(M=Co,Fe,Ni)with high-Pt-content(up to 44.5 wt%).During the impregnation process,thiosulfate could reduce H_(2)PtCl6 to form uniformly dispersed Pt colloid on carbon supports,which in turn prevents the aggregation of Pt at the low-temperature annealing stage.Additionally,the strong interaction between Pt and S inhibits particle sintering,ensuring the formation of small-sized and uniform PtM intermetallic catalysts at the high-temperature annealing stage.The optimized intermetallic PtCo catalyst delivered a high mass activity of 0.72 A mgPt^(–1)and a large power performance of 1.17 W·cm^(–2)at 0.65 V under H_(2)-air conditions,along with 74%mass activity retention after the accelerated stress test.