Effect of boundary conditions on shakedown analysis of heterogeneous materials

The determination of the ultimate load-bearing capacity of structures made of elastoplastic heterogeneous materials under varying loads is of great importance for engineering analysis and design. Therefore, it is necessary to accurately predict the shakedown domains of these materials. The static shakedown theorem, also known as Melan's theorem, is a fundamental method used to predict the shakedown domains of structures and materials. Within this method, a key aspect lies in the construction and application of an appropriate self-equilibrium stress field(SSF). In the structural shakedown analysis, the SSF is typically constructed by governing equations that satisfy no external force(NEF) boundary conditions. However, we discover that directly applying these governing equations is not suitable for the shakedown analysis of heterogeneous materials. Researchers must consider the requirements imposed by the Hill-Mandel condition for boundary conditions and the physical significance of representative volume elements(RVEs). This paper addresses this issue and demonstrates that the sizes of SSFs vary under different boundary conditions, such as uniform displacement boundary conditions(DBCs), uniform traction boundary conditions(TBCs), and periodic boundary conditions(PBCs). As a result, significant discrepancies arise in the predicted shakedown domain sizes of heterogeneous materials. Built on the demonstrated relationship between SSFs under different boundary conditions, this study explores the conservative relationships among different shakedown domains, and provides proof of the relationship between the elastic limit(EL) factors and the shakedown loading factors under the loading domain of two load vertices. By utilizing numerical examples, we highlight the conservatism present in certain results reported in the existing literature. Among the investigated boundary conditions, the obtained shakedown domain is the most conservative under TBCs.Conversely, utilizing PBCs to construct an SSF for the shakedown analysis leads to less conservative lower bounds, indicating that PBCs should be employed as the preferred boundary conditions for the shakedown analysis of heterogeneous materials.

The effects of process conditions on the plasma characteristic in radio-frequency capacitively coupled SiH_4/NH_3/N_2 plasmas: Two-dimensional simulations

A two-dimensional （2D） fluid model is presented to study the behavior of silicon plasma mixed with SiH4 , N2 , and NH3 in a radio-frequency capacitively coupled plasma （CCP） reactor. The plasma–wall interaction （including the deposition） is modeled by using surface reaction coefficients. In the present paper we try to identify, by numerical simulations, the effect of variations of the process parameters on the plasma properties. It is found from our simulations that by increasing the gas pressure and the discharge gap, the electron density profile shape changes continuously from an edge-high to a center-high, thus the thin films become more uniform. Moreover, as the N2 /NH3 ratio increases from 6/13 to 10/9, the hydrogen content can be significantly decreased, without decreasing the electron density significantly.

Effective Boundary Conditions for the Heat Equation with Interior Inclusion

Of concern is the scenario of a heat equation on a domain that contains a thin layer,on which the thermal conductivity is drastically different from that in the bulk.The multi-scales in the spatial variable and the thermal conductivity lead to computational difficulties,so we may think of the thin layer as a thickless surface,on which we impose"effective boundary conditions"(EBCs).These boundary conditions not only ease the computational burden,but also reveal the effect of the inclusion.In this paper,by considering the asymptotic behavior of the heat equation with interior inclusion subject to Dirichlet boundary condition,as the thickness of the thin layer shrinks,we derive,on a closed curve inside a two-dimensional domain,EBCs which include a Poisson equation on the curve,and a non-local one.It turns out that the EBCs depend on the magnitude of the thermal conductivity in the thin layer,compared to the reciprocal of its thickness.

EFFECTS OF PREPARATOIN CONDITIONS ON THE KINETIC PROPERTIES OF COMPLEX-RESINS

The effects of the reaction temperature, the crosslinking degree of the matrix, the pore-forming agent and the initial concentration of PVA on the kinetic properties of the complex-resins were investigated. The ion-exchange rate of the complex-resin for L-lysine chlorate was three-fold that of 001×8 resin and two-fold that of D61 resin.

Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.

土壤胶体磷环境效应及其影响因素

胶体是磷素在环境中迁移转化的重要载体,土壤胶体磷对磷素生物地球化学循环具有重要作用,其活化迁移对土壤、水环境具有十分重要的影响。本文介绍了国内外土壤胶体磷的分类、分离和分析技术。重点阐述了土壤胶体磷活化、土壤基础理化性质(矿物组成、其他胶体元素、土壤孔隙结构、pH、氧化还原电位)、肥料及土壤改良剂应用对土壤胶体磷环境效应的影响。并针对目前土壤胶体磷流失存在的问题,提出相关对策及展望,以期为后续胶体磷研究和胶体磷污染的治理提供参考。

生物炭基产品及其对土壤培肥改良效应的研究进展

生物炭疏松多孔,具有很强的吸附和抗分解能力,其在农业中的应用不仅实现了秸秆资源的有效利用,还对改良土壤、减少化肥使用、增强土壤固碳能力和降低温室气体排放具有重要意义。然而,生物炭直接用作肥料时,由于其养分含量相对较低,运输和储存成本较高,加之易引起粉尘污染等问题,限制了其在农业中的广泛应用。近年来,将生物炭作为载体或特定功能组分,开发新型土壤培肥改良产品及配套技术,成为推动可持续农业发展的重要方向。通过养分合理组配和控制释放,生物炭基产品不仅能改善土壤结构、提高养分利用率,还能缓解土壤障碍、改善作物生长条件,已成为当前本领域研究热点。本文综述了生物炭基产品的类型、制备工艺、性能评价和在土壤改良与培肥中的应用,指出其对提升土壤质量、促进作物增产和环境保护具有显著效果,未来需加强新材料和技术研发,完善检测标准,加快示范推广,并关注其长期应用的生态环境效应。

Evaluations and Suggestions about Effect of Weather in Guangxi on Rice Production

[Objective] The paper aims to study the effect of weather on rice production in Guangxi. [Method] The authors evaluated the effect of weather and weather disasters in Guangxi on rice production by comparison and analysis in terms of temperature,rain and sunlight in 2009. [Result] The study summarized the main favorable and unfavorable weather conditions of rice growth,and proposed the measures and suggestions to tend to interest and avoid harm on rice production in Guangxi. [Conclusion] This study provides references to the evaluations about effect of weather in Guangxi on rice production and suggestions on how to reduce weather disasters influence and ensure rice production security.

5种调理剂对水田土壤中镉赋存形态的影响及其钝化效果评价

本研究旨在评估5种不同调理剂——石灰(SCⅠ)、白云石粉(SCⅡ)、牡蛎壳粉(SCⅢ)、泥炭土(SCⅣ)和硅钙镁钾肥(SCⅤ)对水田土壤中镉(Cd)污染的钝化修复效果。采用受Cd污染的弱酸性水田土壤为材料,通过盆栽模拟试验,分析了这5种调理剂对土壤pH、土壤中Cd赋存形态分布特征及生物有效性的影响。试验结果显示,供试土壤分别添加SCⅠ、SCⅡ、SCⅢ、SCⅣ、SCⅤ0.6 g/盆(2.0 kg土壤)处理60 d后,土壤pH分别提高了1.81、1.49、1.17、0.48、0.60个单位;土壤中水溶态、弱酸提取态、可还原态、可氧化态、残渣态Cd分布特征发生了不同程度的变化。具体而言,水溶态Cd分布系数分别下降了0.70%、0.54%、0.63%、0.21%和0.24%,弱酸提取态Cd分布系数分别下降了17.68%、8.39%、11.52%、18.13%和15.95%,而残渣态Cd分布系数分别上升了14.27%、5.33%、11.54%、17.70%和14.34%(P<0.05)。这些变化表明,5种调理剂均能有效降低土壤中有效态Cd含量,并增加不可利用态Cd含量(P<0.05)。SCⅠ、SCⅡ、SCⅢ、SCⅣ和SCⅤ对土壤中Cd污染的钝化效果分别为38.98%、18.42%、25.33%、39.98%和35.12%。因此,这5种调理剂钝化修复酸性水田土壤中Cd污染均显示出良好的潜力,为安全利用受Cd污染的酸性水田提供了新的技术方案,并值得进一步的田间验证和示范应用。

生物质灰土壤调理剂对烟草青枯病的防控效果

为考察生物质灰土壤调理剂与微生物菌剂配施对烟草青枯病的防治效果,开展了田间小区试验。试验以不施土壤调理剂和微生物菌剂的处理为对照,土壤调理剂施用量设150、200、300 kg/亩(1亩=667 m^(2))等3个水平,测定了不同处理的土壤理化性状、烟草农艺性状、烟草青枯病发病率等指标。结果表明,生物质灰土壤调理剂施用量为300 kg/亩的效果最好,处理前后土壤pH由5.30提高至6.30,不同生育时期的烟草株高、有效叶片数、平均叶面积和叶面积系数均优于其他处理的,青枯病发病率由对照处理的45.6%降至7.4%。生物质灰土壤调理剂与微生物菌剂配施可以降低青枯病的发病率,促进烟株生长。

Mixed convective heat and mass transfer analysis for peristaltic transport in an asymmetric channel with Soret and Dufour effects

The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.

不同腐植酸土壤调理剂对西瓜生长的影响

为研究不同腐植酸土壤调理剂配方对西瓜生长的影响,以新蜜1号西瓜为试材,调查研究不同配方对西瓜生长及果实品质等各项指标的影响。结果表明,T5处理使坐果率提高了20.6个百分点,增产最为明显,增产21.7%;各土壤调理剂处理均能提高果实维生素C含量和降低总酸含量,以T6处理维生素C含量增加最多,增幅16.0%,其中仅T5处理提高了西瓜中心可溶性固形物含量。综合认为,参试腐植酸土壤调理剂配方具有提高西瓜产量和坐果率、调节生长和改善品质的作用,但是不同配方效果不同,尤以T5处理效果最好。

兰州某核心枢纽机房节能改造

对兰州某核心枢纽机房进行节能改造,改造方案为:对现有空调末端进行改造,在现有空调室外机上增加冷水氟泵模块,通过增加智能集成制冷站提供冷源。过渡季和冬季充分利用自然冷源,集成制冷站压缩机关闭,大幅降低运行能耗;夏季靠集成制冷站提供的冷源与冷水氟泵模块进行制冷循环,空调室外冷凝器关闭,避免风冷空调室外机的热岛效应。改造后机房的电能使用效率降低,装机能力提升,可为其他老旧机房的数据中心化改造提供技术参考。

河西绿洲灌区土壤调理剂改良盐碱土的效果初探

增施土壤调理剂是改良盐碱土壤的主要措施之一,但因盐碱土改良调理剂种类繁多,成分差别大,使用尚存争议,为给土壤调理剂在盐碱土改良中的应用及绿洲土壤盐碱化防治提供科学依据,选用5种不同成分土壤调理剂,在不改变河西绿洲灌区施肥水平和方式的前提下,研究了增施土壤调理剂对盐碱土的改良效果及对作物生长的影响。结果表明,增施土壤调理剂不同时期后,同土层各处理pH、EC值较不施土壤调理剂均有不同程度的降低,pH和EC值总体表现为增施硫黄粉9000 kg/hm^(2)>增施磷石膏30000 kg/hm^(2)>增施腐植酸1200 kg/hm^(2)>增施禾康土壤调理剂45 kg/hm^(2)>增施盐地宝盐碱土改良剂45 kg/hm^(2)>不施用土壤调理剂。增施磷石膏30000 kg/hm^(2)、硫黄粉9000 kg/hm^(2)、腐植酸1200 kg/hm^(2)均可降低Na^(+)、Cl^(-)含量,增加Ca^(2+)、SO_(4)^(2-)含量,对盐碱土改良效果明显。各处理对玉米折合产量的影响由高到低依次呈现为增施腐植酸1200 kg/hm^(2)、增施硫黄粉9000 kg/hm^(2)、增施磷石膏30000 kg/hm^(2)、增施禾康土壤调理剂45 kg/hm^(2)、施盐地宝盐碱土改良剂45 kg/hm^(2)、不施用土壤调理剂。综合考虑认为,在河西绿洲灌区不改变当地施肥水平和方式的前提下,增施腐植酸1200 kg/hm^(2)和增施硫黄粉9000 kg/hm^(2)对河西绿洲灌区盐碱地的改良效果较好。

不同土壤调理剂对水稻吸收重金属强度的影响

为研讨土壤调理剂对水稻吸收重金属的影响,探索适宜大田推广的耕地生产障碍修复治理方法,提高受污染耕地质量,实现“边生产、边修复”的目的,在贵州省麻江县开展不同土壤调理剂对水稻吸收重金属强度影响的试验。选用楚戈土壤调理剂、富力邦土壤调理剂、土沃宝土壤调理剂和改性天然矿物材料4种土壤调理剂,采用空白作对照。试验检测结果表明,土壤调理剂处理后,土壤pH值提升率达0.65%~12.03%,土壤中有效镉含量降低10.64%~14.83%,土壤重金属砷含量降低0.4~1.8 mg/kg;稻谷中镉含量降低7.80%~44.07%,硒含量增加0.004~0.017 mg/kg;对水稻产量影响不明显。试验表明在受污染的酸性耕地中施用碱性土壤调理剂,可以提高土壤pH值,降低土壤中重金属砷含量和重金属有效镉的含量,也能减少稻谷对重金属镉的吸收。

不同水分条件下施用调理剂对土壤铅镉的钝化效应

为结合农艺措施和土壤调理剂改善农田土壤重金属污染状况并提高耕地安全利用率,本研究以南方典型菜地土壤为研究对象,通过30 d和60 d的土壤培养实验,研究不同水分条件(75%土壤饱和持水量、淹水)下施用土壤调理剂(生物炭和果胶)对土壤理化特性和重金属铅镉的钝化效应差异。研究发现,淹水条件较75%饱和持水量条件下的pH值更高而重金属有效态含量更低;在2种水分条件下施用生物炭和果胶均能提高土壤pH值和有机质含量,但对土壤碱解氮、有效磷、速效钾的影响因水分条件不同而表现不同。75%饱和持水量条件下,施用生物炭和果胶均能明显降低土壤有效态镉含量,且其含量随2种调理剂施用量增加而降低。而淹水条件下,不同生物炭施用量下配施果胶对土壤有效态铅含量影响规律不一致,但土壤培养60 d比30 d的钝化效果更好。多因素方差分析结果显示,土壤调理剂种类较培养时间和水分等因素对土壤理化性质和重金属铅镉有效态影响更明显。因此,面对耕地资源日益紧缺和改善耕地土壤质量的需求更加迫切的现状,在中轻度重金属污染农田土壤中,通过合适的水分管理和不同栽培模式的调整,并结合适宜的土壤调理剂有望降低土壤重金属的有效性,实现耕地的安全利用。

基于康达效应的壁挂式空调器PMV指标试验研究

壁挂式空调器制热采暖舒适度日益成为用户关注的重点。基于康达效应的原理,对空调器导风板结构进行全新设计,通过试验的方式对室内房间的热舒适性进行验证,并用PMV指标进行对比分析。研究发现:仅改善导风板结构即可提升制热的热舒适性,使得房间底层PMV指标得到0.05以上的改善,在低风档位下改善更大,达到0.13的升幅。

土壤调理剂对作物种子发芽率和苗期生长的影响

为了探寻Phyto-Cat^(TM)土壤调理剂对中国本土作物的普适性,设置不同浓度梯度的Phyto-Cat^(TM)土壤调理剂稀释液,研究了Phyto-Cat^(TM)土壤调理剂对小麦(Triticum aestivum L.)、玉米(Zea mays L.)、番茄(Solanum lycopersicum L.)、辣椒(Capsicum annuum L.)、不结球白菜(Brassica chinensis L.)种子发芽率和苗期性状的改良效果。在此基础上,采用主成分分析法对试验数据降维,并建立函数关系式综合分析Phyto-Cat^(TM)土壤调理剂的作用效果。结果表明,较低浓度的Phyto-Cat^(TM)土壤调理剂可显著提高小麦、番茄、辣椒种子的发芽率,高浓度Phyto-Cat^(TM)易使培养皿杂菌滋生,降低种子发芽势和发芽率;Phyto-Cat^(TM)土壤调理剂对供试作物的苗期性状均有显著的改良效果,且8 mg/L的Phyto-Cat^(TM)土壤调理剂作用效果已经超过史丹利水溶肥。由此可知,Phyto-Cat^(TM)土壤调理剂对作物种子发芽率和苗期性状的改良效果显著,可以在改良土壤结构的同时为作物提供优于化肥的肥效,间接提高作物的产量与品质。

家用壁挂式空调器室内气流组织数值模拟分析

为了探索家用壁挂式空调器安装位置、送风角度、送风温度、风速对室内气流组织的影响,找出提高室内舒适性的方法,采用CFD数值模拟的方法,对某住宅卧室内的壁挂式空调器运行时在各种安装条件下的室内气流组织进行数值模拟。通过对模拟得到的室内温度场和速度场的分析,得出在满足室内温度要求(26℃)的前提下,当空调器的送风角度45°,送风速度4.5 m/s,安装高度2.2 m时,房间内的温度场和速度场效果最佳,且满足人体舒适性的要求。