Investigation on the plastic work-heat conversion coefficient of 7075-T651 aluminum alloy during an impact process based on infrared temperature measurement technology

The plastic work-heat conversion coefficient is one key parameter for studying the work-heat conversion under dynamic deformation of materials. To explore this coefficient of 7075-T651 aluminum alloy under dynamic compression, dynamic compression experiments using the Hopkinson bar under four groups of strain rates were conducted, and the temperature signals were measured by constructing a transient infrared temperature measurement system. According to stress versus strain data as well as the corresponding temperature data obtained through the experiments, the influences of the strain and the strain rate on the coefficient of plastic work converted to heat were analyzed.The experimental results show that the coefficient of plastic work converted to heat of 7075-T651 aluminum alloy is not a constant at the range of 0.85–1 and is closely related to the strain and the strain rate. The change of internal structure of material under high strain rate reduces its energy storage capacity, and makes almost all plastic work convert into heat.

Study on Purchasing Power Conversion Coefficient at Par

The basic theory of the purchasing power at par refers to the rate of one country＇s currency to U.S. dollar while purchasing ＂a basket＂ goods and services in the same quantity and quality respectively in this country and U.S.A. This paper gives out calculation method of purchasing power conversion coefficient at par and how to calculate the non-base year purchasing power at par.

Reconstructed Light Extinction Coefficients Using Chemical Compositions of PM_(2.5) in Winter in Urban Guangzhou, China

The objective of this study was to reconstruct light extinction coefficients （b ext ） according to chemical composition components of particulate matter up to 2.5 μm in size （PM 2.5 ）. PM 2.5 samples were collected at the monitoring station of the South China of Institute of Environmental Science （SCIES, Guangzhou, China） during January 2010, and the online absorbing and scattering coefficients were obtained using an aethalometer and a nephelometer. The measured values of light absorption coefficient by particle （b ap ） and light scattering coefficient by particle （b sp ） significantly correlated （R 2 0.95） with values of b ap and b sp that were reconstructed using the Interagency Monitoring of Protected Visual Environments （IMPROVE） formula when RH was 70%. The measured b ext had a good correlation （R 2 0.83） with the calculated b ext under ambient RH conditions. The result of source apportionment of b ext showed that ammonium sulfate [（NH 4 ） 2 SO 4 ] was the largest contributor （35.0%） to b ext , followed by ammonium nitrate （NH 4 NO 3 , 22.9%）, organic matter （16.1%）, elemental carbon （11.8%）, sea salt （4.7%）, and nitrogen dioxide （NO 2 , 9.6%）. To improve visibility in Guangzhou, the effective control of secondary particles like sulfates, nitrates, and ammonia should be given more attention in urban environmental management.

A General Converse Comparison Theorem for Backward Stochastic Differential Equation with Non-lipschitz Coefficient

In this article, we first introduce g-expectation via the solution of backward stochastic differential equation（BSDE in short） with non-Lipschitz coefficient, and give the properties of g-expectation, then we establish a general converse comparison theorem for backward stochastic differential equation with non-Lipschitz coefficient.

Comparison of the Performance of Two Direct Wave Energy Conversion Systems: Archimedes Wave Swing and Power Buoy

Many wave energy conversion devices have not been well received. The main reasons are that they are too complicated and not economical. However, in the last two decades direct conversion systems have drawn the attention of researchers to their widely distributed energy source due to their simple structure and low cost. The most well-known direct conversion systems presently in use include the Archimedes Wave Swing (AWS) and Power Buoy (PB). In this paper, these two systems were simulated in the same conditions and their behaviors were studied in different wave conditions. In order to verify the simulations, results of the generator of the finite element computations were followed. An attempt was made to determine the merits and drawbacks of each method under different wave conditions by comparing the performance of the two systems. The wave conditions suitable for each system were specified.

Temporal and Spatial Variations of ET 0 and Sensitivity Coefficients in Spring-summer in Eastern Agricultural Areas of Qinghai,China

Reference crop evapotranspiration(ET 0) is a key parameter to calculate crop water requirements.In the paper,ET 0 during 1960-2005 was calculated with FAO-56 PM in eastern agricultural areas of Qinghai,China.Then the sensitivity coefficients of ET 0 to meteorological variables were estimated through the nondimensional partial derivative in FAO-56 PM.Results show that the mean annual ET 0 of the whole area is 904 mm,and ET 0 portrays a very significant decrease during the 46 years.In spatial,ET 0 decreases from southeast to northwest,firstly increases then decreases from southwest to northeast.Through sensitivity analysis,in spring the most sensitive variable is relative humidity,while in summer is temperature.The temperature,sunshine duration and wind speed sensitivity coefficients(S(TA),S(n),S(u)) are higher in middle areas as opposed to surrounding areas,while the relative humidity sensitivity coefficient(S(RH)) has an opposite distribution rule.

Regulation of Power Conversion in Fuel Cells

Here we report a regulation about power conversion in fuel cells. This regulation is expressed as that total power produced by fuel cells is always proportional to the square of the potential difference between the \{equilibrium\} potential and work potential. With this regulation we deduced fuel cell performance equation which can describe the potential vs.the current performance curves, namely, polarization curves of fuel cells with three power source parameters: equilibrium potential E_0; internal resistance R; and power conversion coefficient K. The concept of the power conversion coefficient is a new criterion to evaluate and compare the characteristics and capacity of different fuel cells. The calculated values obtained with this equation agree with practical performance of different types of fuel cells.

Quantum frequency up-conversion with a cavity

The quantum state transfer from subharmonic frequency to harmonic frequency based on asymmetrically pumped second harmonic generation in a cavity is investigated theoretically. The performance of noise-free frequency up- conversion is evaluated by the signal transfer coefficient and the conversion efficiency, in which both the quadrature fluctuation and the average photon number are taken into consideration. It is shown that the quantum property can be preserved during frequency up-conversion via operating the cavity far below the threshold. The dependences of the transfer coefficient and the conversion efficiency on pump parameter, analysing frequency, and cavity extra loss are also discussed.

Numerical Research of Mode Conversion in an Inhomogeneous Plasma

The linear mode conversion of electromagnetic waves in the hot, unmagnetized inhomogeneous plasma is studied numerically for different density profiles, and the dependence of the absorption coefficient on the incident angles and the wave frequencies are obtained for different electrons＇ temperature. The results show that the shapes of the density profiles and the electron＇s temperature create a certain effect on the coefficients of absorption, which reaches its peak value （about 50%） for appropriate parameters. Effective absorption occurs in a limited range of parameter q.

Study on Correlation of Angstrom Turbidity Coefficient (β) with Aerosol Optical Depth (τ) over a Period of Two Years (2004-2006) for the Special Mangrove Ecosystem of Sun-darbans

A study on the correlation of the angstrom turbidity coefficient (β) with aerosol optical depth (τ) have been studied on the basis of field measurements carried out at Kaikhali (22.022°N & 88.614°E) lying in the east coast of India inside the Sundarbans. The angstrom turbidity coefficients have been calculated with respect to the filter channels at 340 nm, 500 nm, 870 nm, 936 nm and 1020 nm of a Sunphotometer. Assessment of the possible influx of the fine particulate concentrations to the total aerosol loading in the area have been made with respect to the calculated angstrom turbidity values for the summer and winter seasons over a period of two years from 2004 to 2006. Substantially high angstrom turbidity coefficient values exceeding 0.2 and indicative of a relatively hazy atmosphere for both the summer and winter periods over these two years from 2004-2006 have been observed. Considering the importance of this fragile mangrove ecosystem of the Sundarbans and also the vulnerability of the area to severe impacts of climate changes, this is indeed a thought provoking issue as far as the policy makers of the country are concerned. In fact, the study has confirmed positive correlation of β with τ.

Study on the conversion coefficient between ACH_(50)and ACH in typical zones of public buildings

The air infiltration of buildings is closely related to its indoor and outdoor environment and energy consumption.However,measuring air infiltration of a building under natural conditions is time-consuming,easily affected and expensive,so it’s often inferred based on building airtightness in practical engineering.Empirical models can nevertheless make a rapid prediction without building parameters,which are widely applied in practical engineering.At present,most of the existing empirical models take residential buildings as objects,therefore they are difficult to be applied to public buildings.Hence,it is imperative to build an empirical model applicable to public buildings.In this study,the conversion coefficients between the airtightness(air change rate under the pressure difference of 50Pa)and the air infiltration rates under natural conditions of four typical zones of public buildings were analyzed.Firstly,the airtightness of four zones of public buildings in the cold region of China was measured.Secondly,their air infiltration rates under 1800 combined conditions of wind pressure and stack effect pressure were simulated based on the airtightness measured results.Finally,calculation and statistical analysis of the conversion coefficient were carried out based on the measured and simulated results,and the recommended value of conversion coefficient was proposed.Analysis results show that the CC of each zone is significantly affected by outdoor meteorological conditions and varies in a wide range(1#zone:3.21 to 188.44).It is advised to ignore the extreme data and take the mean value of the CC corresponding to 95%of the data volume as the recommended value(22.2).This study can provide theoretical basis for the formulation of standards for the performance evaluation of building airtightness.

沿海地区良态风和台风气候不同时距风速转换系数研究

以华南地区某海岸机场区域2012—2021年的风速实测数据为对象,根据这10 a内台风的登陆情况,将其划分为良态风气候和台风气候,研究不同风气候环境下风速时距转换系数的变化规律。研究结果表明:在良态风气候下,月、季、年极值风速的分布规律均符合极值Ⅰ型(Gumbel分布),统计发现转换系数随时距增大呈指数递减的变化规律,基于此拟合得到良态风气候下月、季、年极值风速的时距转换系数公式;在台风气候下,时距转换系数曲线的平稳程度随台风强度的减小而减弱;时距3 s与10 min的转换系数的分布规律符合极值Ⅰ型分布,30 min、1 h与10 min的转换系数的分布规律符合极值Ⅲ型分布;使用良态风转换系数公式估计台风气候时距3 s与10 min的转换系数时,会存在10%~30%的相对误差,可将转换系数乘以对应的放大系数去近似估计,或直接采用1.63的转换系数。该研究结果可为不同风气候条件的风荷载计算提供参考。

250~500 kV X射线窄谱辐射质空气比释动能测量及剂量当量转换系数研究

辐射剂量仪表的准确测量是开展辐射防护工作的重要保障,根据ICRU中规定的实用量要求,需要在特定的参考辐射场中对其进行检定或校准。参考ISO 4037-1:2019,建立250~500 kV X射线窄谱系列参考辐射质,对所建辐射场的均匀性以及相应辐射质下的能谱进行研究。将由EGSnrc模拟的X射线能谱得到所建辐射质下的平均能量、分辨率以及实验测量得到的半值层值与ISO标准推荐值进行比较,结果均满足规范要求,表明新建辐射质准确可靠。利用A5电离室对新建辐射场中的空气比释动能进行测量,再根据X射线能谱信息计算得到的空气比释动能到剂量当量的转换系数,实现空气比释动能到周围剂量当量和个人剂量当量的转换,从而为各类辐射剂量仪表在该高能段的能量响应评价提供了测量条件,保证了量值的准确与可靠。

基于矢网的行波管AM/PM转换系数的测试

分别用传统测试方法和用矢网测量S参数法测试了行波管的调幅调相转换系数,对两次测试结果进行了比较,并重点对矢网测试的误差进行了分析和讨论,确定了用矢网测量行波管AM/PM参量的方法。实际测试结果表明通过调整状态设置参量,用矢网测试行波管AM/PM参量的方法是高效可行的。

粉煤灰-矿渣再生混凝土抗压强度及尺寸效应研究

以粉煤灰和矿渣掺入方式和掺量为变量,设计24组C30再生粗骨料混凝土,对再生混凝土的抗压强度进行了研究。试验结果表明,粉煤灰或矿渣单掺时,再生混凝土的抗压强度随矿物掺料的掺量增加呈现先上升后下降趋势,同等掺量下矿渣单掺优于粉煤灰单掺;双掺时保持粉煤灰或矿渣掺量20%不变,再生混凝土立方体和轴心抗压强度随另一种微细矿物掺量的增加同样呈现先上升后下降趋势,双掺较单掺方式对再生混凝土抗压强度的提升效果更佳,且再生混凝土的抗压强度存在明显的尺寸效应。单掺粉煤灰或矿渣时再生混凝土轴心抗压强度和立方体抗压强度换算系数随其掺量增加而增大,双掺则稳定保持在0.85±0.02。此外,论文还建立了不同微细矿物掺料条件下再生混凝土抗压强度换算系数的修正公式,验证结果表明公式预测误差较小。建议实际工程再生混凝土配制采用粉煤灰和矿渣双掺方式,且掺量控制在25%以内。

电磁吸波与极化转换融合型超表面设计

针对微波信号多频带吸收与雷达通信信号兼容性的应用需求,利用人工电磁超表面极大设计自由度的特点,结合电磁吸收和极化转换2种电磁波调控机理,设计了一种多阵列单元融合型超表面结构。采用HFSS电磁仿真软件对超表面的电磁吸收性能和极化转换性能进行仿真,并分析其综合调控机理及宽带吸波特性,提出一种将“工”字开口环极化转换超表面阵列单元引入电阻加载的交叉偶极子超表面单元中的设计方法。融合偶极子超表面在低频段的电磁吸波特性以及“工”字开口环超表面在高频段的电磁极化转换特性,扩展超表面结构的电磁吸波带宽。研究结果表明:超表面结构的吸波范围可覆盖2.08~8.36 GHz和13.32~18.46 GHz双频带,多调控机理融合型电磁超表面设计方法具有可行性。

稀土永磁同步电机的K_(ad)^(pm),K_(aq)^(pm)计算方法研究

推导了不同转子结构型式的稀土永磁同步电机 (REPMSM)的电枢反应折合系数 K(pm )ad ,K(pm )aq 的计算公式 ,并对这些公式的物理意义作了详细分析讨论 ,指出受转子磁路结构的影响 ,K(pm )ad ,K(pm )aq 大于电磁式同步电机的相应系数 K(c)ad,K(c)aq;

基于铣削加工仿真和现场数据的切削力系数挖掘方法

为提高切削力系数的辨识精度,提出了一种基于铣削加工仿真和现场数据的切削力系数挖掘方法。分别利用实验法和仿真分析法获得切削加工过程数据集。建立了基于刀具旋转周期的切削力系数挖掘方法,并将仿真数据作为数据挖掘的约束条件,分析了切削力系数的分布特性。研究结果表明:周期相关性切削力系数呈正态分布,可通过正态分布估计获得其准确数值。该方法可以有效地挖掘切削力系数,实现切削数据的准确转换。数据转换平均误差仅为3%,达到了实验标定效果,有效地提高了切削力系数辨识效率。

河北省灌溉机井水电转换系数精准估算实施方案研究

“以电折水”是河北省计量农业地下水开采量的主要方法,准确估算地区机井水电转换系数对于优化水资源配置、节约能源、提高效率等具有重要意义。依据典型地区113眼农用灌溉机井相关监测资料,在确定水电转换系数主要影响因素基础上,结合全省地下水埋深与机井分布变化情况,从监测机井的空间布设和监测频次的合理选取等方面提出区域系数精准估算实施方案。结果表明:地下水位埋深对水电转换系数影响程度较大,且呈负相关关系;从地域空间尺度提出了全省不同地区出水量计量允许误差分别在1%~5%时的监测机井合理布设方案,水位降幅越大,监测机井越多,反之亦然;根据年内地下水位下降和上升期间降/增幅变化需求,通过增设监测频次等手段保证年内时间尺度上系数的准确性。从点到面,实现全省机井水电转换系数的分区、分时精准管控,进而提高农业用水量的精准计量。研究成果为河北省在计量设施不充分地区推进“以电折水”计量提供了理论和技术支撑,进一步丰富了我国关于“以电折水系数”精度研究理论。

海南霸王岭不同起源林分森林群落特征及乔木碳储量研究

热带森林因具有很高的生物多样性和强大的生态服务功能而成为全球生态学研究的热点。然而,针对不同林分起源森林群落特征和碳储量之间的差异的研究报道却比较少见。本研究以海南霸王岭林区人工促进更新次生林(PF)、天然次生林(SF)和原始林(VF)3种不同起源的林分为研究对象,针对其群落的物种组成、群落结构、生物量和碳储量进行差异性分析,结果表明:(1)物种的丰富度大小为VF>SF>PF,径级分布均呈反“J”字型,表现为更新层>演替层>主林层的稳定的群落结构;(2)3种起源的林分乔木生物量大小排序依次均为:干>根>枝>叶,各生物量在径级分布上存在差异,PF、SF和VF各径级的生物量排序分别为Ⅱ>Ⅲ>Ⅰ>Ⅳ,Ⅳ>Ⅱ>Ⅲ>Ⅰ和Ⅳ>Ⅲ>Ⅱ>Ⅰ;(3)3种林分的乔木碳储量为105.01~199.47 t.hm^(-2),其中原始林碳储量最大,人工促进更新次生林最小,人工促进更新次生林乔木碳储量主要分布在径级Ⅱ的树木中,天然次生林乔木碳储量主要分布在径级Ⅱ和Ⅳ的树木中,原始林乔木碳储量主要分布在径级Ⅳ的树木中。研究结果可为热带林业经营管理、森林碳监测和评估提供理论支撑。