参数调整对混合增压系统动态性能影响的研究

推出了混合涡轮增压系统的瞬态动力学方程,并对瞬态方程做小偏差线性化处理。在S imu link中,对混合涡轮增压系统的传递函数仿真,显示了增压器稳态转速和转动惯量的减小能提高增压系统的动态响应特性。仿真分析验证了对混合增压系统参数调整的合理性。     

华北地区作物生长期水氮含量变化过程模拟及其参数敏感性分析

根据中国科学院栾城农业生态系统试验站2006-2007年小麦-玉米生长季实测的作物水氮动态变化数据,进行CERES-Wheat和CERES-Maize模型在华北地区冬小麦和夏玉米作物水氮过程模拟能力的验证及参数敏感性分析。结果表明,模型模拟的冬小麦生长季土壤含水量、土壤硝态氮含量、植株含氮量与实测值的相关系数分别为0.46、0.74和0.68,夏玉米则依次为0.95、0.62和0.72。敏感性分析发现土壤含水量和土壤硝态氮含量对土壤参数变化比较敏感,植株含氮量则受遗传参数影响显著。当田间持水量相对变化+10%时,冬小麦和夏玉米的土壤含水量相对变化率分别为+7.5%和+8.8%,冬小麦和夏玉米土壤硝态氮含量的相对变化率分别为+12.0%和+17.9%。叶热间距PHINT对冬小麦植株含氮量有负效应,PHINT相对变化+10%时冬小麦植株含氮量的相对变化率为-11.5%;夏玉米植株含氮量对出苗-幼苗末期所需温时(P1)较为敏感,P1变化+10%时夏玉米植株含氮量相对变化+9.3%。     

花椒采摘机的设计与试验

针对目前花椒收获机械化程度低,损失率高的缺点,设计了一种机械式花椒采摘机。该机利用拔椒轮高速旋转时产生的梳刷作用和拨椒轮与弧形凹板问相对运动所产生的搓擦作用收获花椒。通过花椒采收试验,利用正交试验设计,探讨了不同工艺参数对采收效果的影响。试验数据分析显示,3个工艺参数对采收率影响大小顺序为为拨椒轮转速、凹板间隙和拨椒轮横杆数。该机的最优工作参数组合为,拨椒轮转速250r／min、凹板间隙3mm、拔椒轮横杆数4个,该机具采收率高,花椒及其枝叶损伤小。     

基于紊流模型的可控叶片减振器阻尼特性参数识别

通过对可控阻尼叶片减振器结构分析,建立基于紊流模型可控叶片减振器流量阻尼特性模型,模拟减振器内部流场结构,采用试验参数识别的方法确定模型参数,分析不同温度下减振器的阻尼特性。阐明了减振器在高温高速作用下,阻尼特性采用紊流模型综合流量参数研究的方法更为准确。最后通过仿真分析与试验结果的一致性对比,验证了所提方法的可行性和准确性。这种基于试验的参数识别方法具有普遍性,识别出的参数不仅具有数学理论推导的含意,还具备明确的物理意义,并且适用性强。     

基于吉布斯-马尔可夫随机场的板材表面纹理分析

详细阐述了吉布斯-马尔可夫随机场模型的基本原理,并针对板材表面纹理特征建立吉布斯-马尔可夫随机场模型。研究了吉布斯-马尔可夫随机场模型的参数估计过程,并在试验数据的基础上验证了吉布斯-马尔可夫随机场模型在纹理分析中的可行性。     

卧轴矩台平面磨床试验模态分析研究

探讨将试验模态分析技术在于精密平面磨床，分别采用脉冲激振法和随机激振法对整机进行了动态测试，识别出磨床的各阶模态参数和模态振型。确定了磨床的薄弱模态和薄弱部件。并对磨床结构设计中存在的一些问题提出了结构动力修改方案的建议，这对产品的优化和新产品的开发具有实际意义。     

低糖果脯工艺参数及设备的研究

从控制果脯含糖量、护色方法、感观质量、保存期等方面研究了低糖果脯的加工工艺参数。着重研究了真空渗糖糖液浓度、浸糖糖液浓度和浸糖时间对果脯含糖量的影响，建立了控制果脯含糖量的数学模型，确定了制作低糖果脯的工艺参数。通过对原料预处理方法的研究，确定了果脯的护色方法，使产品达到低硫。确定了用糖品种及其配制比例，并通过适当提高果脯含水率，使产品的感观质量有较大改善。通过对包装材料、添加剂、包装方法及杀菌方式等研究，确定了低糖果脯的短期保藏措施。     

Absent or undetected? Effects of non-detection of species occurrence on wildlife-habitat models

Presence-absence data are used widely in analysis of wildlife-habitat relationships. Failure to detect a species’ presence in an occupied habitat patch is a common sampling problem when the population size is small, individuals are difficult to sample, or sampling effort is limited. In this paper, the influence of non-detection of occurrence on parameter estimates of logistic regression models of wildlife-habitat relationships was assessed using analytical analysis and simulations. Two patterns of non-detection were investigated: (1) a random distribution of non-detection among occupied patches; and (2) a non-random distribution of non-detection in which the probability of detecting a species in an occupied patch covaried with measurable habitat variables. Our results showed that logistic regression models of wildlife-habitat relationships were sensitive to even low levels of non-detection in occupancy data. Both analytic and simulation studies show that non-detection yields bias in parameter estimation of logistic regression models. More importantly, the direction of bias was affected by the underlying pattern of non-detection and whether the habitat variable was positively or negatively related to occupancy. For a positive habitat coefficient, a random distribution of non-detection yielded negative bias in estimation, whereas linkage of the probability of non-detection to habitat covariates produced positive bias. For a negative habitat coefficient, the pattern was reversed, with a random distribution of non-detection leading to positive bias in estimation. A release-recapture livetrapping study of small mammals in central Indiana, USA, was used to illustrate the magnitude of non-detection in a typical field sampling protocol with varying levels of sampling intensity. Estimates of non-detection error ranged from 0 to 23% for seven species after 5 days of sampling. We suggest that for many sampling situations, relationships between probability of detection and habitat covariates need to be established to correctly interpret results of wildlife-habitat models.     

秸秆热解气化工程生态价值量估算方法研究

秸秆热解气化工程是一项高质消纳秸秆资源的生态生产工程,工程项目将秸秆资源转换产出"气、炭、油、液",实现了秸秆资源的生态价值,对我国农业领域落实国家节能减排任务具有重要实践意义。准确估算秸秆热解气化工程的生态价值量,提供系统全面的定量评价指标体系与计算方法,是有效推动农业绿色发展的重要科学依据。本研究基于生态价值理论中的二分法理论,对秸秆热解气化工程生态价值量的构成进行分析,得出秸秆热解气化利用项目主要产生的生态效益资产由减排效益资产与废弃资源商品化资产共同构成。据此,建立了秸秆热解气化工程生态价值量估算总公式,即:秸秆热解气化工程生态价值量(V_(PE))=秸秆热解气化工程减排效益货币价值(V_(EB))+秸秆资源产品经济价值(V_(RC))。在计算过程中,选取生命周期分析(LCA)法计量秸秆热解气化工程项目的净减排量,并借助二氧化碳影子价格将净减排量进行货币化,得到工程减排效益资产(V_(EB));而后,计算出通过生态生产项目实现的秸秆资源产品经济价值(V_(RC));最终,将V_(EB)与V_(RC)加总,得到秸秆热解气化工程生态价值量(V_(PE))。本研究在方法构建的同时,采用文献调研法对各个计算环节所需参数的选取进行了分析与对比,提供了计算过程所需的参数体系。本研究在方法研究与参数研究一体化研究过程中,力图在以下3个方面取得实质性的突破和创新:一是不仅局限于从减排效益视角进行分析与研究,系统全面构建秸秆热解气化工程项目生态价值量估算模型。二是明确将项目生态"潜在价值"合理转化为市场"真实价值",以货币价值形式对秸秆热解气化项目生态效益进行计价衡量。三是本研究在终端能源产品替代减排量估算研究过程中,考量了不同技术工艺水平和产品的能源转换率对温室气体排放的影响。     

A multi-step inflow method for estimating hydraulic conductivity at low pressure under the wetting process

The accurate determination of the wetting soil hydraulic properties for a wide range of water contents is essential for studying and predicting infiltration processes. We present a laboratory infiltration method for determining hydraulic conductivity function, K(θ), in the low-to-medium water content range. An initially air-dry soil core is subjected to infiltration from the bottom where the pressure head, ψ_bot, is controlled through a membrane. As soon as the wetting front arrives at the soil surface, the top 0.5-cm layer is sliced for measurement of the water content. The ψ_bot is stepwise increased as the hydraulic equilibrium is nearly attained at each step. The wetting water retention function, ψ(θ), is determined by curve-fitting the equilibrium inflow data and from the independently measured data obtained from vapor equilibrium. The parameter in the K(θ) is estimated inversely using the cumulative inflow and water content of the sliced layer. This method is verified through comparisons with K(θ) obtained by the Boltzmann transform method. Although requiring an additional operation, the slicing procedure is found to be valuable in enhancing the reliability of the optimized parameter. A sensitivity analysis shows that water vapor movement would be negligible under our experimental conditions.