OPTIMUM OF PRESSURE RATIOS OF MULTI-STAGE RECIPROCATING COMPRESSOR WITH PRACTICAL INTER-COOLING

The optimum pressure ratio distribution of a multistage reciprocating compressor is presented based on the assumption, i.e. the inter stage cooling is perfect and there are no pressure losses. The optimization of the two or three stage pressure ratio is analyzed in two cases of constant heat transfer rate for the inter cooler or constant inter stage inlet temperature, based on the minimum of the sum of theoretical compression power at each stage about a multi stage reciprocating compressor. Furthermore, with an example of two stage compressor the influence on the sum of the power of each stage is analyzed when practical pressure ratio deviates from the optimum value. It is obtained that under different cooling conditions the optimum pressure ratio distribution of the multi stage compression is various, and the change of the optimum pressure ratio within a small range has little influence on the sum of the power each stage. For the two stage compression, this range can be represented as ε 1=(0 96～1 06)ε 1j .

Optimum Determination of Partial Transmission Ratios of Three-Step Helical Gearboxes for Getting Minimum Cross Section Dimension

This paper presents a new study on optimum calculation of partial ratios of three-step helical gearboxes. The chosen objective function is the cross section dimension of the gearbox. In solving the optimization problem, the design equation for pitting resistance of a gear set was investigated and equations on moment equilibrium condition of a mechanic system including three gear units and their regular resistance condition are analyses. From the results of the study, effective formula for determination of the partial ratios of three-step helical gearboxes is introduced. As the formulas are explicit, the partial ratios can be calculated accurately and simply.

Optimum Determination of Partial Transmission Ratios of Coupled Planetary Gearboxes

This paper presents a new study on optimum determination of the partial ratios of coupled planetary gear sets for getting minimum radial size of the gear sets. In this paper, based on moment equilibrium condition of a mechanic system including two-row planetary gear sets and their regular resistance conditions, an explicit model for calculating the partial ratios of coupled planetary gear sets was proposed. In addition, by giving this effective model, the partial ratios can be calculated simply and accurately.

Optimum Calculation of Partial Transmission Ratios of Mechanical Driven Systems Using a V-belt and a Two-Step Bevel Helical Gearbox

This paper introduces a new study on the optimum calculation of partial transmission ratios of mechanical drive system using a V-belt and two-step bevel helical gearbox for getting minimum size of the system. In the paper, based on moment equilibrium condition of a mechanic system including V-belt and a two-gear-unit of the gearbox, models for optimum calculation of the partial ratios of the V-belt and the gearbox were proposed. As the models are explicit, the partial ratios can be calculated accurately and simply.

Optimum Determination of Partial Transmission Ratios of Mechanical Driven Systems Using a V-belt and a Helical Gearbox with Second-Step Double Gear-Sets

This paper presents a study on the optimum determination of partial transmission ratios of a mechanical drive system using a V-belt and a helical gearbox with second-step double gear-sets in order to get the minimum size of the system. The chosen objective function was the cross section dimension of the system. In the optimization problem, the design equation for pitting resistance of a gear set was investigated and equations on moment equilibrium condition of a mechanic system including a V-belt and a helical gearbox with second-step double gear-sets and their regular resistance condition were analysed. Based on the results of the study, effective formulas for calculation of the partial ratios of the V-belt and a helical gearbox with second-step double gear-sets were proposed. By using explicit models, the partial ratios can be determined accurately and simply.

Optimum Determination of Partial Transmission Ratios of Mechanical Driven Systems Using a Chain Drive and a Two-step Helical Gearbox

This paper presents a study on optimum determination of partial ratios of mechanical drive systems using a chain drive and two-step helical gearbox for getting minimum size of the system. The chosen objective function was the cross section dimension of the system. In solving the optimization problem, the design equation for pitting resistance of a gear set was investigated and equations on moment equilibrium condition of a mechanic system including a chain drive and two helical gear units and their regular resistance condition were analyses. From the results of the study, effective formulas for determination of the partial ratios of the chain drive and two-step helical gearboxes were introduced. As the formulas are explicit, the partial ratios can be calculated accurately and simply.

Optimum Determination of Partial Transmission Ratios of Mechanical Driven Systems Using a V-belt and a Three-Step Helical Gearbox

This paper introduces a new study on the optimum calculation of partial transmission ratios of a mechanical drive system using a V-belt and a three-step helical gearbox in order to get the minimum size of the system. The chosen objective function was the cross section dimension of the system. In solving the optimization problem, the design equation for pitting resistance of a gear set was investigated and equations on moment equilibrium condition of a mechanic system including a V-belt and three helical gear units and their regular resistance condition were analysed. From the results of the study, effective formulas for determination of the partial ratios of the V-belt and three-step helical gearboxes were introduced. As using explicit models, the partial ratios can be determined accurately and simply.

铁尾矿-钢纤维双掺混凝土制备及性能研究

铁尾矿长期堆积在尾矿库造成资源浪费和环境破坏,研究铁尾矿-钢纤维混凝土力学性能对开发利用铁尾矿具有重要意义。在混凝土中掺入铁尾矿和钢纤维,研究不同材料配比下混凝土的抗压强度变化。结果表明:铁尾矿掺量过低,生成的胶状聚合物较少,黏结作用较弱,铁尾矿掺量过高会导致混凝土含水量过高,均会降低混凝土抗压强度;钢纤维对混凝土抗压强度具有提升作用;氢氧化钠掺量与水胶比主要影响胶状聚合物的形成,分布均匀、充足的胶状聚合物可有效连接水泥基体和钢纤维,增强混凝土抗压强度;铁尾矿-钢纤维混凝土最优配比为铁尾矿掺量40%、45 mm长度钢纤维体积掺量2%、氢氧化钠掺量40%、水胶比0.2。

适宜氮磷钾用量和配比协同促进盆栽牡丹营养和生殖生长

【目的】牡丹是我国著名的木本观赏植物,施肥不平衡严重影响盆栽牡丹的生长和观赏效果。研究开花前后氮、磷、钾不同施用量和配施比例对盆栽牡丹生长的影响,确定适宜的氮、磷、钾施用量及配比,为盆栽牡丹精准施肥提供理论依据。【方法】本研究以5年生牡丹‘紫二乔’为供试材料,采用“3414”不完全正交回归设计进行盆栽试验,结合隶属函数法评价牡丹的生长状况,利用肥料效应模型拟合牡丹植株的综合隶属函数值与施肥量之间的数学关系,得出牡丹最佳生长的氮、磷、钾肥推荐施肥量。【结果】牡丹开花前后施用氮磷钾肥显著影响植株株高、茎粗、冠幅、花径和单株花数(P<0.05),适宜氮磷钾用量和配比促进盆栽牡丹营养和生殖生长的协同提高。氮、磷、钾三因素配合处理的牡丹综合隶属函数值均大于缺素处理,缺素处理又大于无肥处理,N_(2)P_(2)K_(2)处理的综合隶属函数值(0.73)是N_(0)P_(0)K_(0)的3.17倍。氮磷钾对牡丹综合生长的影响表现为氮>磷>钾。氮、磷、钾肥对牡丹营养和生殖生长存在明显交互作用,任一肥料水平的过量或不足均会抑制牡丹植株生长,降低观赏效果。采用一元二次、二元二次、三元二次肥料效应函数方程拟合牡丹的综合隶属函数值和施肥量,二者相关性均达显著水平,综合各肥料效应函数方程的推荐用量及相应的综合隶属函数值,得出牡丹开花前后氮(N)、磷(P_(2)O_(5))、钾(K_(2)O)的最优推荐施肥量分别为4.21、2.07、2.52 g/株,适宜的氮、磷、钾施肥比例为1∶0.49∶0.60。【结论】开花前后施用适量的氮、磷、钾肥可提高牡丹的农艺性状,促进牡丹的营养和生殖生长协同提高。氮、磷、钾的最优推荐施肥量为4.21、2.07、2.52 g/株,适宜的氮、磷、钾施肥比例为1∶0.49∶0.60。

Analysis and Optimum Design of Differential Inductors Using Distributed Capacitance Model

A distributed capacitance model for monolithic inductors is developed to predict the equivalently parasitical capacitances of the inductor.The ratio of the self-resonant frequency (f SR) of the differential-driven symmetric inductor to the f SR of the single-ended driven inductor is firstly predicted and explained.Compared with a single-ended configuration,experimental data demonstrate that the differential inductor offers a 127% greater maximum quality factor and a broader range of operating frequencies.Two differential inductors with low parasitical capacitance are developed and validated.

土石混合填料工程力学性能试验研究

土石混合填料力学性能是影响路堤设计和施工的重要参数,相关研究一直是热点问题。为分析不同含水率、土石混合比例、击实功、土料厚度条件下土石混合体工程力学性能,开展了不同组合下土石混合体击实试验和大型直剪试验,揭示了上述因素对混合料最优含水率和力学指标的影响,并建立了土石混合填料力学指标计算方法。研究表明:总击实功、含水率和含石量对试样干密度影响较大,且随着含石量的增大,土石混合料最大干密度逐渐增大但最优含水率逐渐降低;干密度随着每层击实次数的增加而增加;随着法向应力的增大,土石混合料应力-应变曲线由应变硬化型逐渐变为应变软化型;随着含石量的增大,其内摩擦角随之减小但黏聚力随之增大,但增大幅度较小。成果可为土石混合填料路堤施工和设计提供理论参考。

AC-13C沥青混合料配比设计及性能试验研究

文中基于马歇尔试验的AC-13C设计方法和基于Superpave系统的Sup-13(即Superpave 13 mm)设计方法,对两种不同的沥青混合料配合比设计进行研究,对比各自的特点、优势以及适用性。研究表明,对于两种设计方法所得到的油石比设计指标来说,Superpave法的空隙率和毛体积相对密度表现较好,马歇尔法的矿料间隙率和沥青饱和度表现较好;对于沥青混合料的路用性能来说,Superpave法的高温和水稳定性更好,马歇尔法的低温性能更好。

不同Pt与Ni质量比的Pt-Ni复合电极析氢性能实验

为降低PEM制氢Pt电极成本,采用电化学沉积法制备以泡沫镍为基材微量Pt沉积的Pt-Ni复合电极。采用扫描电子显微镜、X射线衍射仪、X射线光谱仪对制备的Pt-Ni复合电极进行表征,采用电化学工作站和PEM电解池对Pt与Ni质量比分别为1∶7、1∶11、1∶12、1∶14和1∶23的5种不同复合电极及泡沫镍电极的析氢性能进行电化学对比分析实验和PEM制氢对比实验。结果表明:以泡沫镍为基材,采用电化学沉积法制备的Pt-Ni复合电极性能稳定,沉积Pt质量的多少对Pt-Ni复合电极的析氢性能有较大影响;存在一个最佳Pt与Ni质量比,实验条件下的最佳Pt与Ni质量比为1∶12,沉积Pt量过多和过少都会使其析氢性能降低,过多造成的Pt沉积堆叠相比较少对析氢性能的影响更加明显。在制备微量Pt沉积的Pt-Ni复合电极时,要坚持以最佳Pt与Ni质量比为基准和沉积Pt量“宁少毋多”的原则,实际工程应用中应避免“沉积Pt量越多电极性能越好”的误区。

对沥青混合料配合比设计规范的解读与实践

为更好地掌握与运用《公路沥青路面施工技术规范》(JTG F40—2004)附录B“热拌沥青混合料配合比设计方法”,对规范相关条款进行了研究解读,阐述了沥青混合料体积设计方法的原理,分析了各体积参数的意义以及各参数之间的内在逻辑关系,着重探讨了最小矿料间隙率与空隙率的变化规律,并通过举例验证了计算法确定最佳沥青用量的可行性。结果表明:1)最小矿料间隙率的作用是保证沥青混合料具有最小的沥青膜厚度;2)当矿料组成和沥青含量已定时,采用不同压实功,试件的矿料间隙率随其空隙率的增减而增减;3)采用理论计算方法,有利于更准确快捷地确定最佳沥青用量,缩短目标配合比设计的周期。

太阳能光伏阵列的运行方式优化设计

光伏阵列的运行方式直接关系到太阳能光伏组件的发电效率和运行成本,因此开展了基于小羊窝光伏电站光伏阵列运行方式的研究。采用SolarGIS软件拟合数据计算结果,基于不同倾角倾斜面上辐射量、不同倾角度电成本投资变化、不同容配比度电成本投资变化,计算光伏阵列最佳倾角,选择光伏方阵容配比。

基于正交设计方法的塑性混凝土优化配合比试验研究

笔者利用正交试验法进行塑性混凝土试验方案设计,并结合SPSS软件对试验结果进行变异数分析和Duncan多重比较,以此探讨了引气剂掺量、膨润土用量、水胶比三种因素对其性能评价指标的影响,找出满足各设计要求的最佳配合比。结果表明:对静力抗压弹模和抗压强度而言,因素的主次顺序是膨润土掺量、水胶比、引气剂掺量;膨润土用量、水胶比及引气剂掺量的提高对弹性有利,对抗压强度不利。对渗透系数来说,主次排序是水胶比、引气剂掺量、膨润土掺量;膨润土用量及水胶比的增加对抗渗性不利,引气剂掺量的增加对抗渗性有利。该方法找出引气剂掺量0.02%、膨润土用量60%、水胶比0.95的相对最佳配比,并通过了验证。

Equivalence of Ratio and Residual Approaches in the Homotopy Analysis Method and Some Applications in Nonlinear Science and Engineering

A ratio approach based on the simple ratio test associated with the terms of homotopy series was proposed by the author in the previous publications.It was shown in the latter through various comparative physical models that the ratio approach of identifying the range of the convergence control parameter and also an optimal value for it in the homotopy analysis method is a promising alternative to the classically used h-level curves or to the minimizing the residual(squared)error.A mathematical analysis is targeted here to prove the equivalence of both the ratio approach and the traditional residual approach,especially regarding the root-finding problems via the homotopy analysis method.Examples are provided to further justify this.Moreover,it is conjectured that every nonlinear differential equation can be considered as a root-finding problem by plugging a parameter in it from a physical viewpoint.Two examples from the boundary and initial and value problems are provided to verify this assertion.Hence,besides the advantages as deciphered in the previous publications,the feasibility of the ratio approach over the traditional residual approach is made clearer in this paper.

Study on optimum arrangement of hysteretic dampers in frame structure

The earthquake mitigation effect of hysteretic dampers is not only related to the number, stiffness, strength, deformation ability of dampers but also to the strength and stiffness of the structure. This paper studied the condition that structures should be in when the hysteretic dampers mitigated seismic action most effectively and made appropriate numerical analysis to verify the effectiveness of theory derivation. The inelastic seismic responses were analyzed for the SDOF system that the shear strength ratio of the damper system was taken differently and the result showed that when the ratio was in the vicinity of the optimum strength ratio of the damper system, the displacement of the structure was minimum and the energy dissipation of dampers was maximum, which indicated that the dampers mitigated seismic action most effectively. The result also indicated that the hysteretic dampers had significant earthquake mitigation effect when the strength ratio β changed in a relatively wide range.

Separate-Type Estimators for Estimating Population Ratio in Post-Stratified Sampling Using Variable Transformation

The study proposes, along the line of [1], six separate-type estimators for estimating the population ratio of two variables in post-stratified sampling, using variable transformation. Properties of the proposed estimators were obtained up to first order approximations, both for achieved sample configurations (conditional argument) and over repeated samples of fixed size n (unconditional argument). Efficiency conditions, under which the proposed separate-type estimators would perform better than the associated customary separate-type estimators in terms of having smaller mean squared errors, were obtained. Furthermore, conditions under which some of the proposed separate-type estimators would perform better than other proposed separate-type estimators were also obtained. The optimum estimators among the proposed separate-type estimators were obtained and an empirical illustration confirmed the theoretical results.

Study on the Relationships between Utilization Ratios and Conversion Rates of Nitrogen,Phosphorus and Potassium for Maize

This paper studied the relationships between utilization ratios and conversion rates of nitrogen,phosphorus and potassium for maize by data mining method based on data of"3414 fertilizer field trials"of maize by published papers from national soil testing and recommendation since 2005.The results and conclusions were as follows:①the conceptual model of fertilizer utilization ratio of maize for plot was that,Y N≈a+b×optimum yield,Y P≈a+b×optimum yield-c×optimum nitrogen application amount-d×optimum potassium application amount,Y K≈a-b×optimum nitrogen application amount-c×temperature in growth season-d×rainfall in growth season,respectively.②Fertilizer utilization ratio and nutrient conversion rate had 4 kinds of relationships.No significant relationships:22,of which 16 were soil nutrients and 5 were environmental factors,the results showed that soil nutrients and environmental factors had little effect on nutrient conversion rate and fertilizer utilization ratio;consistent significant relationships:14,illustrating that conversion rate and utilization ratio of maize were consistent in most cases,and it was because that maize was planted for a long term,and its fertilizer absorption law was basically stable;contrary significant relationships:0,illustrating that there was no reverse relationship between conversion rate and utilization ratio of maize;complementary significant relationships:18,the cause of the complementary phenomenon was that the fertilizer utilization ratio was the measuring index of fertilizer efficiency in one season,while the nutrient conversion rate was the measuring index of fertilizer efficiency in more seasons.It showed that the fertilizer utilization ratio was significantly correlated,or the nutrient conversion rate was significantly correlated.