A New Method of Construction of Robust Second Order Rotatable Designs Using Balanced Incomplete Block Designs

The following article has been retracted due to the investigation of complaints received against it. Title: A New Method of Construction of Robust Second Order Rotatable Designs Using Balanced Incomplete Block Designs Authors: Bejjam Re. Victorbabu, Kottapalli Rajyalakshmi. The above paper is a copy of Dr. Rabindra Nath Das’s former article, entitled '“Robust second order rotatable designs (Part I)”. The scientific community takes a very strong view on this matter and we solemnly withdrawn?the paper from the journal OJS. This paper published in OJS Vol.2 No.1, 39-47, 2012, has been retracted.

A Novel Square-wave Pulse Rotation Modulation Strategy for Modular Multilevel Converters

悬浮直流电容电压的均衡问题是模块组合多电平变换器（modular multilevel converter,MMC）的关键问题之一。提出一种可实现MMC直流电容电压平衡的方波脉冲循环调制（square-wave pulse rotation modulation,SWPRM）策略,在保证合成的阶梯波输出波形不变的前提下,根据MMC的拓扑结构和工作原理,对传统方波脉冲列进行脉冲优化,并按照一定的次序和切换周期进行循环和判断反相调整,获得的循环方波脉冲列作为最终驱动脉冲用于实现对MMC的控制。实验结果表明,采用提出的方波脉冲循环调制策略无需任何电容电压控制措施,在较低开关频率下,实现了MMC各功率单元间有功能量的平均分配和直流电容电压的均衡。

Land and Water Use in Rice-upland Crop Rotation Areas in Lower Ili River Basin, Kazakhstan

The lower Ili River Basin is located in semi-arid area, and the annual rainfall is 177 mm. Therefore, the irrigation is inevitable for agriculture. Large-scale irrigated agriculture had been developed since 1960's in the lower parts of the river and the total irrigated area is about 32 000 hm2. In the project area, the paddy rice-upland crop rotation has been practiced. Due to the domestic water use for hydropower and agriculture as well as water use among riparian countries, the deficit of water for agriculture in the lower part has been concerned. The authors, therefore, conducted the field survey and water balance analysis of the Akdara irrigation project in the lower Ili River Basin in order to assess the land and water uses. Moreover, the impact of the water use on water environment to the basin was analyzed. The following results were obtained as following (1) the groundwater level in the irrigated district varied from 1.5 m to 3.5 m through year. (2) 1970's groundwater level was drastically raised from 8 m to 3 m and the groundwater had been recharged in this period. (3) Water use efficiency of agriculture, which is the ratio of total evapotranspiration to the total water withdrawal was as low as 0.23.

Dynamic Balancing Structure Optimal Design for the Rotating Arc Sensor

Rotating arc sensor is a key device for automation welding. The vibration has a big influence on signal's correct collection and reliable automatic welding. In order to solve the vibration problem and the dynamic balancing design with the restricted space,a bearing force analysis based dynamic balancing structure optimal design is proposed and implemented with the help of Pro/Engineer( PROE) and automatic dynamic analysis of mechanical systems( ADAMS) virtual prototype technology, in which three parameters of the counterbalance are considered. The method is suitable for the practical online adjustment. The simulation result shows that optimal design based counterbalance structure and parameters can satisfy the space requirement with lower vibration. The methodology provides a new idea for dynamic balancing design and adjustment of rotating arc sensor with adjustable rotation radius.

Period-One Rotating Solutions of Horizontally Excited Pendulum Based on Iterative Harmonic Balance

In this study, the iterative harmonic balance method was used to develop analytical solutions of period-one rotations of a pendulum driven horizontally by harmonic excitations. The performance of the method was evaluated by two criteria, one based on the system energy error and the other based on the global residual error. As a comparison, analytical solutions based on the multi-scale method were also considered. Numerical solutions obtained from the Dormand-Prince method (ODE45 in MATLAB&#169) were used as the baseline for evaluation. It was found that under lower-level excitations, the multi-scale method performed better than the iterative method. At higher-level excitations, however, the performance of the iterative method was noticeably more accurate.

Effect of potassium on soil conservation and productivity of maize/cowpea based crop rotations in the north-west Indian Himalayas

Plots under conservation tillage may require higher amount of potassium(K) application for augmenting productivity due to its stratification in upper soil layers, thereby reducing K supplying capacity in a medium or long-term period. To test this hypothesis, a field experiment was performed in 2002-2003 and 2006-2007 to study the effect of K and several crop rotations on yield, water productivity, carbon sequestration, grain quality, soil K status and economic benefits derived in maize(Zea mays L)/cowpea(Vigna sinensis L.) based cropping system under minimum tillage(MT). All crops recorded higher grain yield with a higher dose of K(120 kg K2 O ha-1) than recommended K(40 kg K2 O ha-1). The five years' average yield data showed that higher K application(120 kg K2 O ha-1) produced 16.4%(P<0.05)more maize equivalent yield. Cowpea based rotation yielded 14.2%(P<0.05) higher production than maize based rotation. The maximum enhancement was found in cowpea-mustard rotation. Relationship between yield and sustainable indices revealed that only agronomic efficiency of fertilizer input was significantly correlated with yield. Similarly, higherdoses of K application not only increased the water use efficiency(WUE) of all crops, but also reduced runoff and soil loss by 16.5% and 15.8% under maize and 23.3% and 19.7% under cowpea cover, respectively. This study also revealed that on an average 16.5% of left over carbon input contributed to soil organic carbon(SOC). Here, cowpea based rotation with the higher K application increased carbon sequestration in soil. Potassium fertilization also significantly improved the nutritional value of harvested grain by increasing the protein content for maize(by 9.5%) and cowpea(by 10.6%). The oil content in mustard increased by 5.0% and 6.0% after maize and cowpea, respectively. Net return also increased with the application of the higher K than recommended K and the trend was similar to yield. Hence, the present study demonstrated the potential yield and profit gains along with resource conservation in the Indian Himalayas due to annual additions of higher amount of K than the recommended dose. The impact of high K application was maximum in the cowpea-mustard rotation.

A Novel Method for Type Synthesis of Parallel Mechanism Without Parasitic Motion Based on 2R1T Parallel Mechanism with Rotational Bifurcation

The parasitic motion has been widely recognized as the major drawback of the parallel mechanism.Therefore a class of 2R1T PMs(parallel mechanism)without parasitic motion has been synthesized.However,these PMs can only rotate around two axes in sequential order.It decreases the performance of the balancing adjustment of the end-efector.In this paper,a family of 2R1T PMs without parasitic motion was reconstructed by using a novel method based on the remarkable properties of rotational bifurcation mechanisms,which can rotate in sequential order.Furthermore,some PMs rotating around two continuous axes in an arbitrary order are established by adding single joints.Taking the practicability of these structures into consideration,the workspace of 3-PRPS PM was analyzed as an example.Moreover,this study explores the practical application of the PMs without parasitic motion in developing balance mechanisms in rough-terrain fre-fghting robots.During the climbing process,the tank is adjusted to be parallel to the horizontal plane in real-time.It is proved that this kind of structure realizes continuous rotation around two rotation axes on the premise of no parasitic motion.

Rotational Inertial Physics in Non-Classical Thermoviscous Fluent Continua Incorporating Internal Rotation Rates

In this paper, we derive non-classical continuum theory for physics of compressible and incompressible thermoviscous non-classical fluent continua using the conservation and balance laws (CBL) by incorporating additional physics of internal rotation rates arising from the velocity gradient tensor as well as their time varying rates and the rotational inertial effects. In this non-classical continuum theory time dependent deformation of fluent continua results in time varying rotation rates i.e., angular velocities and angular accelerations at material points. Resistance offered to these by deforming fluent continua results in additional moments, angular momenta and inertial effects due to rotation rates i.e., angular velocities and angular accelerations at the material points. Currently, this physics due to internal rotation rates and inertial effects is neither considered in classical continuum mechanics (CCM) nor in non-classical continuum mechanics (NCCM). In this paper, we present a derivation of conservation and balance laws in Eulerian description: conservation of mass (CM), balance of linear momenta (BLM), balance of angular momenta (BAM), balance of moment of moments (BMM), first and second laws of thermodynamics (FLT, SLT) that include: (i) Physics of internal rotation rates resulting from the velocity gradient tensor;(ii) New physics resulting due to angular velocities and angular accelerations due to spatially varying and time dependent rotation rates. The balance laws derived here are compared with those that only consider the rotational rates but neglect rotational inertial effects and angular accelerations to demonstrate the influence of the new physics. Constitutive variables and their argument tensors are established using conjugate pairs in the entropy inequality, additional desired physics and principle of equipresence when appropriate. Constitutive theories are derived using Helmholtz free energy density as well as representation theorem and integrity (complete basis). It is shown that the mathematical model consisting of the conservation and balance laws and constitutive theories presented in this paper has closure. Influence of new physics in the conservation and balance laws on compressible and incompressible thermoviscous fluent continua is demonstrated due to presence of angular velocities and angular accelerations arising from time varying rotation rates when the deforming fluent continua offer rotational inertial resistance. The fluent continua are considered homogeneous and isotropic. Model problem studies are considered in a follow-up paper.

小吨位转体T构临时锁定称重配重技术

常规称重配重工作量大、程序繁琐且不易保证转体结构的精度。以某立交段工程转体桥项目为依托,提出并应用了小吨位转体桥T构临时锁定称重配重技术,即在施工过程前按照单侧悬臂梁施工重量偏差2%计算转体结构偏载,设计临时锁定型钢代替砂箱,将临时锁定型钢预埋转体结构中,转体前割断型钢测定型钢应变变化值,推算出转体桥不平衡弯矩并完成配重。推导了临时锁定称重配重计算公式,并与常规称重方案对比。结果证明,对于小吨位转体桥T构临时锁定称重配重技术可准确测量T构的配重力矩,给出合理配重方案,具有技术可行、安全可靠、方便快捷的优点。

基于功率开关-二极管基本单元多电平逆变器及其功率均衡调制策略研究

针对级联H桥型多电平逆变器开关器件随逆变器输出电平数增加显著增多的问题,提出一种以功率开关器件-二极管为基本单元的新型多电平逆变器。该逆变器仅使用较少开关器件即可实现高质量电平输出,且该拓扑开关损耗低、效率高,不仅易于扩展还能有效避免级联单元间电流倒灌等问题。针对传统正负反向层叠载波调制策略调制下逆变器存在级联单元间输出功率不均衡的问题,在传统调制策略基础上推导分析区域功率,提出了一种基于部分载波循环的功率均衡调制策略,并验证了载波循环规律的普适性,所提调制策略能在保持输出电压波形质量不变的情况下,载波仅变换2(n-1)次即可在nT_(o)/2内实现级联单元输出功率均衡以及开关损耗平均分配,并提高电源利用率。最后搭建两单元七电平逆变器实验平台对所提调制策略进行了实验验证。

第三代高速摆轮分拣机设计与分析

摆轮分拣机由于其对场地的需求较小、购买和维护成本较低,已成为物流仓储配送中心常用的分拣设备。近年来,摆轮分拣机的技术不断迭代、性能不断优化,目前已发展到第三代产品。文章以自行研发的第三代高速摆轮分拣机为对象,首先阐述其技术参数及工作原理,其次详细分析输送组件和旋转组件的设计,最后结合实际项目说明第三代分拣机的应用效果。

铁路小曲线半径槽型梁转体平衡控制技术研究

为了有效解决铁路小曲线半径槽型梁转体过程中的平衡与稳定性问题,结合宜兴铁路联络线工程城东特大桥(45.5+45.5)m槽型梁,在转动球铰下方及临时固结砂箱中预埋监测元器件,通过施工过程中的参数识别,在拆除临时固结前进行预配重,在转体前通过称重试验精调配重。结果表明:通过纵向预配重5.5吨、横向配重3.0吨后,拆除临时固结时梁体线形和应力状态平稳;通过球铰转动法称重试验确定偏心距满足规程要求,无需进行配重调整,转体过程较为平稳。基于施工过程“数据监测、识别分析”的平衡控制方法,可高效准确解决小半径曲线桥平衡配重问题,为同类型转体桥提供技术参考。

基于墩梁临时固结应力差的铁路转体连续梁平衡控制

为了解决铁路转体连续梁无体外临时固结措施的施工安全及转体过程的稳定性控制问题,在充分进行检算的基础上,通过布设监测传感器,构建实时动态监测系统,根据墩梁临时固结应力数据变化调整不平衡荷载,并辅以悬臂根部应力状态监测。结果表明:通过控制箱梁悬臂根部的应力状态处在理论值附近,同时控制墩梁临时固结的应力差在1MPa以内,可保证悬臂灌注施工过程中的梁体平衡,也可以为后续转体前称重试验提供主动控制辅助,可为其他类似桥梁施工提供借鉴和参考。

Optimal Design of Novel Electromagnetic-Ring Active Balancing Actuator with Radial Excitation

Imbalance vibration is a typical failure mode of rotational machines and has significant negative effects on the efficiency,accuracy,and service life of equipment.To automatically reduce the imbalance vibration during the operational process,different types of active balancing actuators have been designed and widely applied in actual production.However,the existing electromagnetic-ring active balancing actuator is designed based on an axial excitation structure which can cause structural instability and has low electromagnetic driving efficiency.In this paper,a novel radial excitation structure and the working principle of an electromagnetic-ring active balancing actuator with a combined driving strategy are presented in detail.Then,based on a finite element model,the performance parameters of the actuator are analyzed,and reasonable design parameters are obtained.Self-locking torque measurements and comparative static and dynamic experiments are performed to validate the self-locking torque and driving efficiency of the actuator.The results indicate that this novel active balancing actuator has sufficient self-locking torque,achieves normal step rotation at 2000 r/min,and reduces the driving voltage by 12.5%.The proposed novel balancing actuator using radial excitation and a combination of permanent magnets and soft-iron blocks has improved electromagnetic efficiency and a more stable and compact structure.

Magnetic circuit optimization and experimental study of new internally excited automatic balancing

Mass imbalance-induced vibration affects the rotating machinery very large,especially the highspeed types.Off-line balancing techniques have been widely developed for rejecting unbalance-induced vibration but do not eliminate unbalanced vibration in the working state.Moreover,multiple start-stops are required in off-line balancing techniques.Therefore,research on an efficient electromagnetically-driven auto-balancer is carried out in the present work,and an internal excitation actuator is designed in this balancer.The electromagnetic characteristics of the two copper coil bobbins in the internal excitation actuator are compared and analyzed.The permanent magnets inside the actuator are simulated and analyzed with different sections of round,rectangular,and elliptical.And the results show that the elliptic type has the largest self-locking force.Finally,the dynamic balance test is performed on a test bench equipped with a designed electromagnetic balancing actuator,and the unbalance vibration is reduced from 130.23 μm to 5.98 μm.

Balance Mechanism Design of Single Cylinder Engine Based on Continuous Mass Distribution of Connecting Rod

For a single cylinder engine, the total unbalanced inertial forces occur in the engine block, which results in engine’s vibration and deteriorated noise. In order to eliminate the unbalanced forces, counterweight and primary balance shaft should be attached to the cylinder block so that engine durability and ride comfortability may be further improved. Traditionally one third of connecting rod assembly’s mass is treated as reciprocating mass, and two thirds as rotating mass when designing balance mechanism. In this paper, a new method based on the multibody dynamics simulation is introduced to separate the reciprocating mass and rotating mass of connecting rod assembly. The model consists of crankshaft, connecting rod, piston and the simulation is performed subsequently. According to the simulation results of the main bearing loads, the reciprocating mass and rotating mass are separated. Finally a new balance mechanism is designed and simulation results show that it completely balances inertial forces to improve the engine’s noise vibration and harshness performance.

DISTRIBUTION LAW OF RANDOM UNBALANCE RESPONSE OF MULTISTAGE BLOWER

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义务教育阶段教师“县管校聘”政策执行的困境与突破——基于史密斯政策执行过程模型

基于史密斯政策执行过程模型,通过实地深入调研,对河南省B县的义务教育阶段教师“县管校聘”政策执行过程进行全面审视。研究发现,B县在“县管校聘”政策执行过程中存在政策文本不够全面细致、政策执行主体推进力度不足、政策配套措施落实不力等问题,其原因在于政策目标的模糊性表达、政策执行主体的动力及能力不足、政策环境存在监管漏洞。据此提出如下建议:明确目标,完善政策供给;激发动能,提高执行主体工作能力;强化监督,完善配套保障机制等破解政策执行困境。

优化施肥对小麦-玉米轮作体系产量、养分平衡与生态环境效益的影响

小麦-玉米轮作是华北平原主要的种植模式,对保障我国粮食安全起着关键作用。本文系统研究了不施肥(CK)、优化施肥(OPT)和农户习惯施肥(FP)方式连续8年对小麦-玉米轮作体系产量、养分平衡、温室气体排放和经济效益的影响。结果表明,小麦季、玉米季和周年轮作中,OPT较FP产量分别提高4.3%、5.3%和4.8%;氮肥偏生产力分别提高39.1%、31.7%和35.9%;磷肥偏生产力分别提高39.1%、40.4%和39.8%;钾肥偏生产力分别降低47.8%、47.3%和47.6%;温室气体排放量分别降低21.7%、21.1%和21.4%;温室气体排放强度分别降低27.0%、27.5%和27.3%;净收益分别提高11.2%、11.4%和11.3%,农业生产成本分别降低3.7%、2.1%和3.1%,环境修复成本分别降低28.4%、17.3%和22.1%。周年轮作中,OPT较FP氮素盈余量降低105 kg·hm^(-2)(46.3%);磷素盈余量降低48 kg·hm^(-2)(53.3%);钾素从亏缺1 kg·hm^(-2)变为盈余59 kg·hm^(-2),满足了作物生长需求。连续8年,OPT较FP土壤有机质含量提高5.3%,速效钾提高12.3%,有效磷降低27.8%。综上所述,与农户习惯施肥(FP)相比,优化施肥(OPT)具有高产、高收益以及环境友好的优势,为华北平原小麦-玉米轮作体系高效绿色生产提供了科学依据。

义务教育教师交流轮岗政策实施的困境审视与路径优化

实现城乡教育一体化以推动义务教育的优质均衡发展,难点在于深化乡村地区的教育改革,其中城乡师资配置不均衡不充分已成为当前着重关注并亟须解决的现实问题。教师的交流轮岗,有利于促进教师的专业发展,保持组织场域的教学活力,但随着政策的纵深推进,政府、学校、教师等政策推动者之间存在着利益诉求协调困境。基于此,从中央政府——强化利益表达与协商的多维性政策设计、地方政府——借力乡村振兴为教师“留得住”的利益保障兜底、学校——营造“能动、想动、持续动”的场域生态、教师——注重自身内生韧性的培植与环境适应性的培养等4个维度,为当前教师交流轮岗的路径优化提供可能的建议与参考。