Changes of Organic Matter, N, P and K Content of Soils in Red Soil Areas Under Long-Term Experiment

The content of organic matter （OM）, nitrogen （N）, phosphorus （P）, and potassium （K） in the three selected soils, including Calcaric Purpli-Orthic Primosols （purple sand-shale parent material）, Dystric Turbi-Anthric Primosols （quaternary red clay parent material） and Typic Udi-Sandic Primosols （granite parent material） were studied under a long-term experiment by using crop straw and inorganic fertilizers at the Hunan Red Soil Experiment Station of Chinese Academy of Agricultural Sciences. The results showed that the contents of OM, N, P and K in the three selected soils increased after 23 years application of crop straw and inorganic fertilizers, but the contents increased much less when crop straw or inorganic fertilizers was applied alone. The nutrient contents in the three soils developed from granite changed more remarkably than those in the soil derived from quaternary red clay and purple sand-shale. It was also found that the contents of OM, N, and P increased slightly in the treatments without applying fertilizers or returning the crop straw to the root bed. Combined application of inorganic fertilizers and crop straw could remarkably increase the contents of OM, alkalihydrolyzable N and available K, the positive correlation between application of organic fertilizers and increase of OM in soil did not always happened, it provided evidence for the relation between appropriate C/N ratio and accumulation of OM in soil. The increase of nutrient content was influenced by the soil properties. By comparing the contents of nutrient in 0-20 cm depth in the three different soils, it was concluded that the most increases of OM, alkali-hydrolyzable N, and available P were observed in Typic Udi-Sandic Primosols with the average increase by 3.03, 27.38, and 21.73 mg kg^-1, respectively. The available K increased in Dystric Turbi-Anthric Primosols with the average increase by 25.82 mg kg^-1, while it decreased in Calcaric Purpli-Orthic Primosols and Typic Udi-Sandic Primosols. It was concluded that the application of inorganic fertilizer and crop straw was important to improve the soil fertility for all of three selected soils. The straw return to the field had played a significant role for enhancement of the soil quality in the study areas. The application of inorganic fertilizer combined with the straw return to the fields could remarkably improve the soil fertility.

Crop yields and soil organic carbon dynamics in a long-term fertilization experiment in an extremely arid region of northern Xinjiang, China

A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control （CK） and six different combinations of phosphorus （P）, potassium （K）, nitrogen （N）, straw （S） and animal manure （M）. The balanced fertilization treatments had significantly （P〈0.05） higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate （NPK） and 1/3 N from farmyard manure （NPKM） had a higher average yield than the other treatments. The average yields （over the 23 years） in the treatments of NPK, and urea, calcium superphosphate （NP） did not differ significantly （P〉0.05） but were higher than that in the treatment with urea and potassium sulfate （NK; P〈0.05）. The results also show that the highest increases in SOC （P〈0.05） occurred in NPKM with a potential increase of 1.2 t C/（hm2.a）. The increase in SOC was only 0.31, 0.30 and 0.12 t C/（hm2.a） for NPKS （9/10 N from NPK and 1/10 N from straw）, NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.

Numerical experiment rock fragmentation by combined dynamic and static loads under dual-cutter head

This paper puts forward a new rock fragmentation loading method of dual-cutter head combined dynamic and static loads.By applying the numerical simulation software-RFPA2D,we have done numerical experiment about the siltstone's crushing effect by dynamic load on single cutter head without confining pressure,dynamic load on single cutter head with confining pressure 10MPa and different dual-cutter heads spacing by combined dynamic and static loads with confining pressure 10MPa.Experimental results show that the confining pressure can obviously affect the rock fragmentation effect.Combined dynamic and static loads can greatly improve the rock fragmentation effect.There exists an optimal spacing of dual-cutter head that can make the rock fragmentation achieve the desired effect.Through analyzing the acoustic emission accumulative energy and quantity,the authors make a conclusion that the optimum spacing is 30 mm.

Experimental study on desorption of soluble matter as influenced by cations in static water

With variation of drainage basin environments, desorption of soluble matter has become one of the significant erosion processes in rivers. It has a considerable impact on flow and sediment transport, as well as processes of river bed deformation and landform evolution throughout a watershed. In this study, considering influences on sediment movement, especially on cohesive sediment transport, Ca^2＋ and H^＋ were chosen as characteristic ions of soluble matter, and the total desorption quantity of Ca^2＋ and pH value when the desorption equilibrium is reached were employed as two indexes representing the desorption of soluble matter. By means of an indoor experiment, desorption of soluble matter as influenced by cations in static water was investigated. The results show that the total desorption quantity of soluble matter increases with the initial cation concentration until a maximum desorption quantity value is obtained and maintained. The total desorption quantity of soluble matter depends on properties of the specific cations in static water, and the stronger the affinity is between the cation and sediment surface, the higher the total desorption quantity will be. Finally, a strong approximate linear relationship between desorption quantities for different kinds of soluble matters was obtained, which means that variation of pH values can accurately reflect the desorption results of soluble matter.

The principles and guidelines for designing long-term agronomic experiments

Many of the important questions facing farming systems in the world today require long-term studies to provide meaningful information and answers. A long-term agronomic experiment (LTAE) should (1) have long-term objectives; (2) study important soil processes or ecological processes; and (3) be related to the productivity and sustainability of systems. A well established LTAE can provide both insights into how the system operates and foresight into where the system goes. The prerequisites for setting up a LTAE are the secured land, continuous funding and dedicated scientists. A number of principles must be considered carefully when establishing a LTAE, (1) the site must be representative of large areas; (2) the treatments should be simple, but focusing on the big questions; (3) the plots should be large enough to allow subsequent modification of the experiment if this becomes necessary; (4) crop rotations should minimise, wherever possible, the risk of build-up of pests and diseases, and rotational phase should be considered in a rotational experiment; (5) a clearly defined experimental protocol should be developed to ensure data collected is scientifically valid and statistically analysable, but with flexibility to allow essential changes; (6) soil samples, possibly plant samples, should be achieved to provide better answer to the original questions when new, perhaps more accurate analytical techniques are developed, or answer new research questions that were not considered in the original design. The MASTER experiment in Australia was used as a case study to demonstrate how these principles are implemented in practice.

Design and Experiment of Triangular Prism Mast with Tape-Spring Hyperelastic Hinges

Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like configuration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stiffness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The finite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the influence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stiffness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and finite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.

Centrifuge experiment on the penetration test for evaluating undrained strength of deep-sea surface soils

Rapid advances in deep-sea mining engineering have created an urgent need for the accurate evaluation of the undrained strength of marine soils,especially surface soils.Significant achievements have been made using full-flow penetration penetrometers to evaluate marine soil strength in the deep penetration;however,a method considering the effect of ambient water on the surface penetration needs to be established urgently.In this study,penetrometers with multiple probes were developed and used to conduct centrifuge experiments on South China Sea soil and kaolin clay.First,the forces on the probes throughout the penetration process were systematically analyzed and quantified.Second,the spatial influence zone was determined by capturing the resistance changes and sample crack development,and the penetration depth for a sample to reach a stable failure mode was given.Third,the vane shear strength was used to invert the penetration resistance factor of the ball and determine the range of the penetration resistance factor values.Furthermore,a methodology to determine the penetration resistance factors for surface marine soils was established.Finally,the effect of the water cavity above various probes in the surface penetration was used to formulate an internal mechanism for variations in the penetration resistance factor.

Experimental study on interaction between simulated sandstone and acidic fluid

In order to investigate the controlling mechanism of temperature, fluid and other factors on water-rock interaction in the diagenetic process, we performed a series of simulated experiments on the interaction between two kinds of fluids with different salinity and a composite mineral system （simulated sandstone）, which contains albite, K-feldspar and other minerals. The experimental results showed that acidity was the most important factor that affected the dissolution of minerals in the composite mineral system. The lower the pH value, the more easily the minerals dissolved. At the same pH value, the dissolution abilities of different acids for various mineral components were also different. Compared to hydrochloric acid （inorganic acid）, oxalic acid （organic acid） was more able to dissolve aluminosilicate minerals. However, the dissolution ability of oxalic acid for carbonate minerals was lower than that of hydrochloric acid. In the process of fluid-rock interaction, dissolution of feldspar was relatively complicated. Increase of temperature would accelerate the dissolution of feldspar. Under acidic conditions, albite had a higher dissolution rate than K-feldspar. K-feldspar could dissolve and convert into montmorillonite and kaolinite, while albite could dissolve and convert into kaolinite both at 40℃ and 80℃. Presence of organic acid, and decrease of pH value and water salinity were all favorable for the dissolution of feldspar, but weakened the ability to form clay minerals.

Flexural failure experiment on cracked PC simply supported box girders

Long-term load and flexural failure experiments are carried out on two prestressed concrete(PC) simply supported box girders. In the long-term load experiment, girder-1(G1) is in an elastic state, while girder-2(G2) is in a cracking state. To investigate the influence of cracking on the flexural behaviors of PC simply supported box beams, the experiment results are analyzed from many aspects, such as load–deflection, load–strain, and failure mode. Experiment results show the following: 1) the shrinkage and creep of concrete have considerable influences on the long-term deflection and strain of the two girders; 2) in the flexural failure experiment, the cracks and ultimate loads of the two girders are close. The rigidity degeneration of G2 is significantly faster than that of G1, and thus G2 shows nonlinear characteristics earlier; 3) to prove the validity and rationality of the current code, the cracking load and ultimate load of the two girders are calculated according to the current code.

Experimental study on rheological deformation and stress properties of limestone

The systematic experiment regarding the general uniaxial compression test and the creep deformations of the typical limestones from the surrounding rock of the highway tunnels were made.The relationship between the axial stress and the delayed deformation steady value was obtained from the creep tests under low loading stresses.By the least square method,the parameters of Nishihara creep model were calculated from the creep curves.The results indicate that the strain change always lags behind the increase of stress,and the long-term strength of the limestone is about 80.6% of the stress at the volumetric strain reversal which is obtained from the conventional uniaxial compression test.

QUICK ASSESSMENT METHODOLOGY FOR RELIABILITY OF SOLDER JOINTS IN BALL GRID ARRAY(BGA)ASSEMBLY——PART Ⅱ:RELIABILITY EXPERIMENT AND NUMERICAL SIMULATION

In the present study,a facility,i.e.,a mechanical deflection system (MDS),was established and applied to assess the long-term reliability of the solder joints in plastic ball grid array (BGA) assembly.It was found that the MDS not only quickly assesses the long-term reliability of solder joints within days,but can also mimic similar failure mechanisms in accelerated thermal cycling (ATC) tests. Based on the MDS and ATC reliability experiments,the acceleration factors (AF) were obtained for different reliability testing conditions.Furthermore,by using the creep constitutive relation and fatigue life model developed in part I,a numerical approach was established for the purpose of virtual life prediction of solder joints. The simulation results were found to be in good agreement with the test results from the MDS.As a result,a new reliability assessment methodology was established as an alternative to ATC for the evaluation of long-term reliability of plastic BGA assembly.

Long-Term Survival in Traumatic Brain Injury and Near-Death Experience Increases Suicide Risks: A Personal Experience and Related Literature

Background: Traumatic brain injury (TBI) remains a cause of lifelong disability, death, and suicide worldwide. TBI-induced near-death experience (NDE) could increase suicide risks. Objective: We investigated TBI coupled with NDE and posttraumatic stress disorder (PTSD) as a possible indicator of suicide. Methods: A 17-year-old male who sustained an acute severe TBI in a traffic collision, was comatose 14 days, had an NDE awakening from the coma, and, years after rehabilitation, suffered PTSD, clinical depression, and survived a suicide attempt. This personal experience of a TBI-induced NDE and lingering PTSD was acquired directly from the patient by interview. We discuss his case while considering relevant literature. Results: Longitudinal data from 1961 to 2021 generated from the PubMed interface revealed 4056 TBI patients committed suicide. NDE was only reported in one of those cases and, although not a suicide, in the personal experience. Neuropsychological assessment at long-term follow-ups revealed few TBI patients exhibited normal mental/physical functions compared to the general population. Unfavorable GOS scores were risk predictors for neuropsychological/physical impairments later in life, with outcomes of depression, PTSD, poor QOL, and/or suicide. Conclusions: For TBI-NDE survivors, including those with PTSD, long-term periodic neuropsychological follow-ups and psychosocial support may help decrease suicide risks.

Experiment study on RC frame retrofitted by the external structure

A new retrofitting method is proposed herein for reinforced concrete （RC） structures through attachment of an external structure. The external structure consists of a fiber concrete encased steel frame, connection slab and transverse beams. The external structure is connected to the existing structure through a connection slab and transverse beams. Pseudo- static experiments were carried out on one unretrofitted specimen and three retrofitted frame specimens. The characteristics, including failure mode, crack pattern, hysteresis loops behavior, relationship of strain and displacement of the concrete slab, are demonstrated. The results show that the load carrying capacity is obviously increased, and the extension length of the slab and the number of columns within the external frame are important influence factors on the working performance of the existing structure. In addition, the displacement difference between the existing structure and the outer structure was caused mainly by three factors： shear deformation of the slab, extraction of transverse beams, and drift of the conjunction part between the slab and the existing frame. Furthermore, the total deformation determined by the first two factors accounted for approximately 80% of the damage, therefore these factors should be carefully considered in engineering practice to enhance the effects of this new retrofitting method.

基于双层极值法的储能系统锂离子电池均衡实验设计

储能系统初始参数和运行环境的差异性,会导致电池单体荷电状态(state of charge,SOC)的不一致性,降低储能系统能量利用率。为解决上述问题,设计了基于双层极值法的锂离子电池均衡实验。采用耦合电感与Flyback变换器搭建均衡系统双层架构,建立电池组端电压、均衡电流及占空比间的关联特性;以储能电池端电压作为均衡目标,提出基于双层极值法的锂离子电池快速均衡方法;搭建电池均衡实验教学平台,设计充放电及静置均衡实验,通过仿真分析和实验数据验证所提方法的有效性。该教学实验将理论知识、实验操作及数据分析相结合,有助于提升电气工程专业相关课程实验的质量和效果。

任意静定桁架内力分析仿真实验设计

提出了描述桁架几何结构、载荷和支座约束的平衡方程,构建了桁架系统平衡方程的统一矩阵形式,基于MATLAB开发了静定桁架内力分析仿真实验软件。通过该软件,学生可以自主搭建任意静定平面桁架和空间桁架,并完成结构的内力分析实验。实践表明,将仿真实验引入理论力学课程教学,不仅激发了学生的学习兴趣,加深了学生对基本概念的理解;而且培养了学生的高阶思维,提升了学生利用计算机求解问题的能力。

叠合板式综合管廊侧墙连接节点面外抗震性能试验研究

叠合板式综合管廊属于半装配式结构,其接缝数量少,抗渗性能优越,应用前景广泛。为了研究采用灌浆套筒连接和浆锚搭接连接两种连接方式的叠合板式综合管廊侧墙在面外荷载作用下的抗震性能,该文开展了采用两类连接方式的足尺侧墙模型的面外低周反复试验,并与管廊现浇侧墙构件作对比。通过分析试件破坏模式、裂缝分布以及受力性能指标,初步揭示了不同连接方式对叠合板式侧墙面外抗震性能的影响。研究表明:叠合板式试件与现浇试件抗震性能基本一致,滞回曲线均较饱满,极限承载力与刚度退化规律基本一致,满足装配式结构等同现浇的抗震设计要求;两类叠合板式管廊侧墙试件延性系数分别为7.05和8.50,均具有良好的面外延性,满足我国抗震设计规范中变形能力要求;采用浆锚搭接连接的叠合板式试件与采用灌浆套筒连接的叠合板式试件相比,滞回曲线更加饱满,变形能力好,但峰值抗侧承载力低,相同侧向位移下损伤破坏严重;两种连接方式的均可有效传递钢筋应力直至构件破坏。

基于试验设计方法的液相孔型-迷宫密封几何参数敏感性分析

为了评估新型液相孔型-迷宫密封在转子偏心下的泄漏特性,提高其运行稳定性,提出了中心组合设计的试验设计方法。对新型液相密封中影响泄漏特性和静态转子动力特性的关键几何参数(迷宫腔室深度、宽度、孔深和孔径)进行敏感性分析;采用基于动网格技术和稳态RANS方程的数值计算方法求解25种几何参数组合的新型液相密封在2种偏心率(0.1、0.2)下的泄漏量、静态气流激振力和静态刚度系数;分别以泄漏量、静态气流激振力和静态刚度系数为响应,以4个几何参数为变量获得主效应图。结果表明:偏心率对泄漏量的大小以及其几何参数敏感性影响很小,当腔室深度、宽度、孔深和孔径分别在40%、24%、56%、44%水平时,泄漏量最小;在转子偏心下,切向力随着迷宫腔室深度与宽度的增加而单调递减,随着孔深与孔径的增加先增加后减小;径向力随着腔室深度的增加而增加,随着腔室宽度的增加先减小后增加;当偏心率增加到0.2时能找到使静态直接刚度最大的几何参数组合,此时腔室深度、宽度、孔深和孔径分别在24%、48%、40%和64%水平。在转子偏心与不偏心工况下,腔室深度与宽度的增加均会造成静态交叉刚度的单调递减;转子偏心时静态交叉刚度随着孔深与孔径的增加先增加后减小。该研究结果可为液相孔型-迷宫密封的性能分析和结构设计提供参考。

EPE网套包装皇冠梨的静力学特性及损伤研究

目的模拟皇冠梨在物流运输中受静压情况,研究发泡聚乙烯(Expandable Polyethylene,EPE)网套包装皇冠梨在横向、纵向及斜向上的静压力学特性及损伤。方法主要采用皇冠梨准静态压缩试验和有限元分析法。结果横向、纵向及斜向仿真与试验的结果相对误差分别为1.21%、5.49%和5.55%,验证了有限元模型的准确性。与皇冠梨裸果相比,在横向、纵向及斜向静压下,EPE网套包装皇冠梨出现初始损伤的位移分别提高了3.5倍、2.9倍和2.3倍;压缩位移为15 mm时,EPE网套包装皇冠梨承受的静压力分别减小了76.1%、74.4%和51.0%;梨果压缩至破裂时,EPE网套包装皇冠梨承受的静压力分别提高了17.9%、14.9%和21.5%,抵抗外界变形量分别提高了1.9倍、1.8倍和1.7倍。EPE网套包装皇冠梨损伤面积和体积百分比均保持在5%以下。结论EPE网套包装对静压下皇冠梨的缓冲效果明显,提高了其静压承载力,减小了静压损伤,可为皇冠梨缓冲包装设计及采收减损提供一定的参考。

压电纤维复合材料对悬臂结构的作动行为研究

压电纤维复合材料(macro fiber composite,MFC)是由美国NASA研发的综合性能优秀的新型压电材料,掌握MFC的力学行为有利于将其投入结构变形控制、减振降噪和健康监测等领域.目前对MFC宏观力学行为的研究中缺乏对作动力与驱动电压直接关系的研究,现有的以MFC为作动器的应用中所使用力电关系的精度有限,不利于将MFC投入更精密的使用场景.针对此问题,文章采用经典板理论,考虑了MFC与受控结构的相对尺寸,推导了MFC对悬臂结构的作动力方程.为兼顾计算的准确性和便利性,建立了考虑MFC叉指电极真实电场的精细有限元模型开展压电静力仿真,给出将MFC叉指电极的弯曲电场简化为匀强电场的修正系数.搭建MFC-悬臂梁结构的实验装置,对有限元模型和作动力公式加以验证.精细模型与简化模型的仿真结果与实验进行对比,总体误差较小,验证了模型和修正系数的可靠性.理论计算与仿真结果对比,误差在1%以内,表明所得作动力预测公式在较大的宽度比范围内均具有较好精度.建立的MFC作动力模型对MFC应用于悬臂结构的变形控制和振动抑制有一定指导意义.

深水夹层管准静态屈曲传播实验设计

针对海底管道发生整体失效破坏的主要模式之一屈曲传播,提出了以SS304不锈钢为内外管、高密度聚乙烯(HDPE)为夹层的夹层管准静态屈曲传播实验设计方案。设计并制作了夹层管缩尺模型,利用深水高压舱开展了准静态屈曲传播实验。结果表明,所设计的屈曲传播实验能够达到夹层管准静态屈曲传播压力测试要求。实验获得的屈曲传播压力数据可为夹层管基本结构设计和现场工程应用提供参考。