森林资源动态预测方法的研究 Ⅳ.改善林分密度管理图预测精度的方法

在用密度管理图进行林分蓄积的动态预测时,建立在优势木平均高和每公顷株数基础上的收获密度效应式存在一定的不足,导致具体林分的预测精度偏低。本文以立木度Ｒｖ为修正系数,来反映林分内营养空间结构对蓄积的影响,从而提高密度管理图的应用精度。该方法可以使福建省杉木、马尾松人工林密度管理图对蓄积量的预测误差标准差分别从４４．３２ｍ３／ｈｍ２、２３．１１ｍ３／ｈｍ２减少到１７．４７ｍ３／ｈｍ２、５．２３ｍ３／ｈｍ２,提高密度管理图在实践中应用的准确性。     

样本量对MaxEnt模型预测物种分布精度和稳定性的影响

以实际调查的4个物种的34个不同样本量(5,6,8,10,15,20,25,30,40,50,60,70,80,90,100,120,150,180,200,220,250,300,350,400,450,500,550,600,650,700,800,900,1 000,1 200)为例,模拟计算分析不同的样本量对MaxEnt物种分布模型的精度和稳定性的影响.结果表明:总体上来看,样本量的大小对MaxEnt模型预测物种空间分布的精度影响不大,在样本量较小时,精度不稳定,随着样本量的增大(训练数据在样本量50左右,检验数据在样本量120左右),MaxEnt模型的预测精度越来越稳定.     

基于遗传程序设计的产流预报模型

产流预报模型是洪水预报的基础,为了提高产流预报精度,将遗传程序引入降水、径流关系回归模型中。遗传程序能够通过自身演化寻找因果变量之间的回归关系,自动形成函数表达式,比传统方法有很大的灵活性,不必事先选定具体的数学表达式。将该预报模型应用于陡河水库的径流预报,并同传统线性回归方法进行比较,结果表明:基于遗传程序设计的产流预报模型适应性强,拟合精度高,适合解决非线性问题,为径流预报提供了新方法。     

不同下限基点温度对积温模型模拟效果的影响

为探究不同下限基点温度对作物发育阶段积温稳定性和对发育期模拟效果的影响,本研究基于一个下限温度的线性生长假设,以1990—2015年北京密云冬小麦抽穗至成熟期为例,统计设定下限温度5.0~15.0℃不同基点温度的阶段活动积温和有效积温,分析活动积温和有效积温这2种积温模型的阶段积温及其标准偏差和变异系数随下限温度的变化情况,并以模拟均方根误差和模拟准确率为指标对比分析下限温度指标对积温模型模拟效果的影响。结果表明:阶段积温随下限温度而变化,有效积温随下限温度升高而降低的趋势和程度比活动积温更快;阶段活动积温大于有效积温,且两者差值随着下限温度的升高而增大;在一定的下限温度范围内,以标准偏差为指标时有效积温绝对稳定度优于活动积温,而以变异系数为指标时则活动积温相对较有效积温相对稳定;以均方根误差检验模拟效果,则阶段活动积温模拟效果优于有效积温;以发育期模拟误差在2d以内表征模拟准确率时,2种积温模型的模拟效果随下限温度而变化,下限温度在5.0~12.5℃时,有效积温的模拟准确率高于活动积温的,而当下限温度≥12.5℃时,活动积温的模拟准确率大于有效积温的。     

Mass-processing method for aging otoliths of walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> using black resin

ABSTRACT:   The reliability of a mass-processing aging method for walleye pollock Theragra chalcogramma was examined. The method is a half-otolith method, in which 10–20 otoliths are embedded simultaneously in black resin and the mass-processed half plane section is viewed under reflected light (black-resin method). Seasonal periodicity of otolith growth was confirmed by the monthly observations of the percent of translucent zone at the otolith edge, and interannual variation in age distribution detected the progression of dominant year-classes. These results support the assumption that the translucent zone is formed once a year. The black-resin method was compared to the break–burn method, which is the standard technique for this species. The estimated ages of these methods were not biased throughout the age range examined. The coefficient of variation in the black-resin method (4.9–5.7%) was similar to those of the break–burn method (3.5–5.5%). These results suggest that the black-resin method is reliable as an aging method for walleye pollock.     

ACCURACY OF DIAGNOSTIC ULTRASOUND FOR DETECTION OF CYSTIC LESIONS: DETERMINATION USING RECEIVER OPERATING CHARACTERISTIC CURVE ANALYSIS OF FINDINGS IN PHANTOM STUDIES

Anechoic, spherical cystic lesions are important findings on ultrasound examination. In polycystic renal disease of cats, they may be the only ultrasonographic sign of disease. This study assesses the accuracy of ultrasound, as used in a veterinary setting, for the detection of cysts. Using a spherical lesion ultrasound imaging phantom and 7.5- to 8-MHz linear array transducers, images of cysts of 2- and 4-mm diameter were created at various imaging depths from 0 to 6 cm. These were digitized and given to a panel of readers for interpretation. Area under receiver operating characteristic curves were used to evaluate test accuracy. It was shown that test accuracy was different at different imaging depths and differed with machines of differing price category. It is suggested that when setting standards for quality control in ultrasound, criteria used might be better related to imaging outcome studies rather than to aspects of machine specification.     

Solution for Distributed Model of Groundwater System with PCG2 for Naolihe Basin in Sanjiang Plain

PCG2 （Preconditioned Conjugate-Gradient Method 2）, the most popular mothod used in groundwater field, was used to solve the distributed model of large-scale groundwater system. Its principle and effect was analyzed mathematically, and verified by some specific examples. Numerical results acquired by PCG2 are accurate, it demonstrates that PCG2 is effective on methodology itself and man-ralated operation. So PCG2 is worthy of popularizing in the area of groundwater system for numerical analysis.     

玉米种子丸粒化加工技术的研究

对４种填充剂粉料膨润土、硅藻土、大白粉、粉煤灰和２种粘结剂１０７胶、羧甲基纤维素（ＣＭＣ）进行了种子丸粒化材料筛选试验。通过试验选出膨润土、１０７胶作为加工玉米丸粒化种子的丸衣材料,确定了玉米丸粒化种子的加工工艺流程,并对丸粒化种子的生物学特性进行了研究,证明经过丸粒化处理的玉米种子不影响其发芽率,为实现玉米精量播种提供了一条新途径。     

抚顺地区气温分布与乡镇温度预报订正方法研究

未来24 h预报是每个气象台的日常工作内容,随着人们对天气预报的关注日益增加,对乡镇温度预报准确率提出了更高的要求。本文结合抚顺地区87个自动气象观测站的数据及位置分布,选取一个数据最为完整的观测站作为代表站,绘制全市各观测站与本站的逐月温差图,研究全市气温分布规律,在此基础上以新宾县15个乡镇为例提出了等差值乡镇温度预报订正方法并对结果进行检验。结果表明:抚顺地区全年温度分布趋势具有明显的季节性变化;用等差值乡镇温度预报订正方法对新宾县15个乡镇进行温度预报,发现温度准确率大部分在80%以上。     

激光切削陶瓷的试验研究

A new process of laser machining ceramic material is experimentally studied. The microstructure of the cut surface is as the same as the substrate when using acousticoptical Q-switch YAG laser to remove the stock by vaporization. The cutting accuracy of t