基于Kriging模型的驾驶室悬置系统多目标优化

为提高某国产自卸车行驶平顺性,采用多体动力学软件Adams建立重型自卸车整车虚拟样机分析模型,并通过行驶平顺性道路试验验证模型的正确性。选取驾驶室悬置刚度和阻尼参数为设计变量,以驾驶室地板垂向和座椅支撑面俯仰加权加速度均方根为优化目标,以驾驶室前后悬置动挠度为约束条件,结合最优拉丁方试验设计拟合Kriging近似模型,利用粒子群优化算法对自卸车行驶平顺性进行多目标优化,得到Pareto最优解集,并选取一个最优解进行整车行驶平顺性实车试验。结果表明,Kriging近似模型具有较高的拟合精度,可大幅提高自卸车行驶平顺性优化效率;基于Kriging近似模型的多目标优化结果可通过权重系数对各个优化目标进行权衡,有效改善了自卸车行驶平顺性。     

不同耕作年限水稻土土壤颗粒的体积分形特征研究

应用基于土壤颗粒体积分布确定土壤颗粒大小分布分形维数的方法,对浙江慈溪耕作年限分别为50、100、500、700、1000和2000年的水稻土土壤颗粒体积分形特征进行了研究.结果表明:同基于土壤颗粒质量分布的分形维数相比,基于土壤颗粒体积分布的分形维数计算不需要密度假设,更具有合理性.不同年限水稻土的土壤颗粒大小分布能被体积分形模型显著拟合(p＜0.01).土壤颗粒体积分形维数与黏粒的体积百分含量之间呈显著正相关(p＜0.01),与粉粒和砂粒的体积百分含量之间呈显著负相关(p＜0.01),其中与黏粒含量关系最为密切.耕作年限对水稻土土壤颗粒的体积分形维数和分形模型的拟合度均有一定影响.与50 ～ 500年水稻土相比,700 ～ 2000年水稻土剖面中土壤颗粒体积分形维数的变异性和均值较高,但其拟合决定系数则较低;耕作年限会对水稻土剖面中黏粒的含量和分布产生影响,进而影响到剖面土壤的颗粒体积分形特征;对于同一质地类型的土壤,耕作年限越长,分形维数越高.     

基因枪法获得Phs-r转基因小麦植株的研究

实验以普通小麦豫麦18-64品种为供试材料,采用基因枪法对报告基因(Bar基因)和目的基因(PHS-r基因)两个重组质粒进行了共转化,获得了再生植株,并对转化植株进行了检测。结果表明:以预培养15d的幼胚愈伤组织作为受体材料其转化频率明显高于当天剥取和预培养3～4d的幼胚;在基因枪轰击前6h和轰击后18h,用0.5moL/L的甘露醇进行渗透处理,其转化频率会有明显的提高;实验通过基因枪转化与再生培养,共获得了12株再生植株,PPT检测且均表现出抗性,其中6株经PCR检测呈阳性,表明PHS-r基因已整合到小麦基因组中并正常表达。     

Microscreen effects on water quality in replicated recirculating aquaculture systems

This study investigated the effects of three microscreen mesh sizes (100, 60 and 20 μm) on water quality and rainbow trout (Oncorhynchus mykiss) performance compared to a control group without microscreens, in triplicated recirculating aquaculture systems (RAS). Operational conditions were kept constant during a 6-week period where the microscreens were manually rinsed three times a day. The effects of microscreen cleaning frequency and nitrification performance were subsequently assessed.Compared to the control group, microscreens removed particles, reduced particulate organic matter, and increased β-values. Particulate parameters reached steady-state in all treatment groups having microscreens at the end of the trial. The time to reach equilibrium seemingly increased with increasing mesh size but the three treatment groups (100, 60 and 20 μm) did not significantly differ at the end of the trial. Increased backwashing frequency over a 24-h period had no further significant effects on the parameters measured. The results demonstrated the role and importance of a microscreen, and showed that mesh size, within the range tested, is less important at long operations under constant conditions.Fish performed similarly in all treatments. Preliminary screening of trout gills did not reveal any pathological changes related to microscreen filtration and the resulting water quality. Biofilter performance was also unaffected, with 0′-order nitrification rates (k_0a) being equivalent for all twelve systems (0.148 ± 0.022 g N m⁻² d⁻¹).Mechanisms for RAS equilibrium establishment, within and between systems with different mesh sizes, are discussed.     

Analysis of the hydrodynamic characteristics of chain-link woven copper alloy nets for fish cages

Copper alloy nets have drawn attention from researchers and fishermen as an alternative to fabric nets for fish cages, due to such advantages as protection from predators, better cage volume retention, and good resistance to bio-fouling. The drag and lift coefficients of nine chain-link woven copper alloys and three knotless fabric nets were derived using a circulating water channel and structural analysis of the nets. The flow through one copper alloy net was visualized using particle image velocimetry (PIV) to understand better the hydrodynamic characteristics necessary for the use of the net in a fish cage. The trends in behavior of the drag and lift coefficients for the copper alloy nets based on various attack angles and current speeds were highly similar to those of the fabric nets. The coefficients of the copper alloy nets were larger than those of the fabric nets for attack angles less than 30°. For angles greater than 30°, the coefficients of the fabric nets were larger than those of the copper alloy nets. These results might be attributed to structural differences between the two nets, as well as the roughness of the surfaces. The hydrodynamic characteristics of the alloy nets were illustrated using PIV, and a difference in the structure of the net was observed to reduce the resistance when the net was set against the current with an attack angle of 90°.     

汽油缸内多孔直喷喷雾破碎模型建立与试验

为了建立汽油缸内多孔直喷喷雾破碎模型,对Huh Gosman模型进行分析评估,并且以喷油压力为参数,建立初始破碎粒径分布公式,从而建立了汽油缸内多孔直喷喷雾破碎模型;并通过定容喷雾试验进行了汽油自由喷雾试验,验证所建模型的合理性.研究结果发现:以经验公式估计的初始液滴直径评估Huh Gosman模型,模拟结果贯穿度偏小;通过建立初始破碎粒径分布函数,同时对Huh Gosman模型进行修正,模拟计算结果与实际结果相近.最后利用该模型对不同喷油压力下的自由喷雾进行模拟,计算与试验结果吻合较好,最大误差小于5％.     

基于IGWOPSO-SVM算法的水质监测及等级评定系统

目的 水污染监测是流域水污染防治工作的前提。为实现高精度的地表水水质监测及水体等级评定,本研究设计基于IGWOPSO-SVM(Improved grey wolf optimizer particle swarm optimization-support vector machine)模型的水质监测及等级评定系统。方法 选用传感器组、STM32F103单片机、ESP8266WIFI无线通信模块搭建水质监测系统数据处理模块,利用WIFI无线通信将数据处理模块采集到的水质数据传输至服务器,设计水质监测系统服务器交互端,同时开发水质监测小程序对水质等级进行实时监测。基于改进粒子群算法(Improved particle swarm optimization,IPSO)及灰狼算法(Grey wolf optimizer,GWO)提出了IGWOPSO算法,对SVM进行优化,据此提出了IGWOPSO-SVM水质等级评定算法。基于南京市玄武湖、金川河、江浦水源地135组水质数据对本系统水质等级评定效果进行试验验证。结果 相比于SVM,IGWOPSO-SVM水质等级评定算法的总样本分类准确率由86.67%上升至100.00%,上升了13.33个百分点;相比于粒子群算法(Particle swarm optimization,PSO),IGWOPSO算法的最佳适应度由86.80上升至99.20,提高了14.29%。结论 本研究解决了传统水体等级评定方法效率低、准确率低的问题,为地表水水质的精确监测提供了方法借鉴。     

长期施肥对红壤性水稻土颗粒有机质和矿物结合态有机质含量与化学组成的影响

以江西红壤地区双季稻田肥料定位试验为依托,研究了不施肥(CK)、单施化肥(NPK)及3种不同比例有机无机肥配施(LM、MM、HM)对红壤性水稻土全土、颗粒有机质(POM)和矿物结合态有机质(MinOM)组分碳、氮含量及其化学结构的影响.结果表明:施肥处理全土、POM和MinOM组分中有机碳、全氮含量均显著高于CK处理(...     

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratory-simulated rainfall events

Soil erosion, one of the most serious environmental concerns, might remove topsoil and essential element from terrestrial land. However, few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss. Therefore, this study investigated the effects of surface coverage rates (83%, 67%, 50%, 33%, 17% and 0%) and two positions (up- and downslope) on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls (R1-R6). These results showed that the sediment concentrations with 33% (R4) and 17% (R5) coverage downslope were significantly lower than those with coverage upslope, whereas there was no significant difference between the runoff rates of the two slopes. Thus, surface coverage at different positions induced two soil erosion regimes (deposition- and transport-dominated processes). Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff. The DON contributed to a substantial amount of soil nitrogen loss, which accounted approximately 81% of the organic form. The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes. The DOC is significantly correlated with Rr for transport-dominated processes. These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form. It is concluded that erosion/covered zones altered by surface coverage could produce transport- and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss. In addition, these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.