Annual net production of the five Sargassaceae species in Yoro,western Wakasa Bay,Sea of Japan

ABSTRACT:   Annual net production of the five Sargassaceae species was investigated in Yoro, western Wakasa Bay, Sea of Japan. The Sargassaceae species were collected at a depth of 2.0–2.5 m and subjected to stratified clipping for 13 months. Annual net production was estimated at 2407 g dry wt/m² for Sargassum patens , 2132 g dry wt/m² for Sargassum macrocarpum , 1458 g dry wt/m² for Sargassum siliquastrum , 1197 g dry wt/m² for Myagropsis myagroides , and 1471 g dry wt/m² for Sargassum piluliferum . The ratio of annual net production to maximum biomass (P/B_max) for these species ranged between 1.3 and 1.7, being higher than in previous studies which used the same method. Winter storms with strong wave exposure and relatively calm condition in Yoro were considered to augment P/B_max. The total losses estimated from the different units of stratified clipping were compared. If larger and less segregated units were applied, the total loss would decrease. It was suggested that a 50 cm stratum would be applicable to the larger species (3 m or longer) and a stratum of 20 cm or less would be applicable to mid-sized or smaller species (less than 3 m).     

基于遥感分层技术的平南县森林蓄积抽样调查方法研究

采用遥感数据辅助分层可解决分层抽样在大范围森林资源调查中分层面积不准确的缺点.以ALOS数据为基础,将平南县的森林资源分为A层（有林地、疏林地层）和B层（其它地类层）.在各层内机械预布设样地,比较预布样地缓冲区（角规控制检尺所能绕测到的最大范围）的SAVI值、DNN IR值及对明显地物的目视解译,确定各样地缓冲区的地类,A层样地数有578个,B层有978个.根据分层抽样各层所需样本数,在确定好地类的样地中,随机抽取各层所需样本数并调查其蓄积量.结果表明,抽样的估计精度为91.5%,全县森林蓄积量为5 900 186.7 m3.     

Using pre-classification to improve the accuracy of species-specific forest attribute estimates from airborne laser scanner data and aerial images

The aim of this study was to examine whether pre-classification (stratification) of training data according to main tree species and stand development stage could improve the accuracy of species-specific forest attribute estimates compared to estimates without stratification using k-nearest neighbors (k-NN) imputations. The study included training data of 509 training plots and 80 validation plots from a conifer forest area in southeastern Norway. The results showed that stratification carried out by interpretation of aerial images did not improve the accuracy of the species-specific estimates due to stratification errors. The training data can of course be correctly stratified using field observations, but in the application phase the stratification entirely relies on auxiliary information with complete coverage over the entire area of interest which cannot be corrected. We therefore tried to improve the stratification using canopy height information from airborne laser scanning to discriminate between young and mature stands. The results showed that this approach slightly improved the accuracy of the k-NN predictions, especially for the main tree species (2.6% for spruce volume). Furthermore, if metrics from aerial images were used to discriminate between pine and spruce dominance in the mature plots, the accuracy of volume of pine was improved by 73.2% in pine-dominated stands while for spruce an adverse effect of 12.6% was observed.     

种子重力分选机预分层喂料系统设计与试验

为了提高种子重力分选机分选性能,降低设备使用调节难度,提出了种子进入分选台面的预分层工艺,设计了配套的分层喂料系统,计算确定了结构参数。在SolidWorks中建立了系统模型,采用SolidWorks-Simulation对模型工作应力和位移进行分析。采用SolidWorks-Flow Simulation对流场进行仿真和系统结构参数优化。在5TZX-50型重力分选机上进行试验,利用Design Expert 软件进行Box-Behnken响应面分析,建立了性能指标与影响因素的数学回归模型,选出了气流速度为3.40m/s、振动频率为9.75Hz、导流板倾角为29.65°的最佳组合,该组合下除轻杂率和除重杂率试验值为95.12%和96.37%。试验表明,除杂率与目标优化预测值的误差不大于1.36%,分层喂料系统满足设计要求。     

In search of a variance estimator for systematic sampling

Seven variance estimators to be used under systematic sampling are evaluated in a simulation study with 270 artificial spatial populations with different levels and structure of autocorrelation. In settings without an auxiliary variable a proposed new spatial resampling estimator RHO is recommended. In setting with an auxiliary variable, an estimator based on post-stratification (PST), and one with a correction for spatial autocorrelation (DOR), generated estimates with less bias than the SRS estimator in the majority of studied settings. Only in populations with either a near zero autocorrelation at the interval of sampling, or a very strong correlation between the target and the auxiliary variable did the otherwise conservative SRS estimator perform as well as the alternatives.     

应用分层抽样技术估计北部湾底拖网渔业产量

传统的按行政单元逐级上报的渔业产量调查方法在数据获取过程中受人为因素的干扰,而全面普查的方法受限于时间和经费,相比而言,抽样调查是一种科学合理的方法。本研究于2007年8月对北部湾底拖网产量进行了调查,以全体底拖网渔船为抽样总体,按功率段划分了抽样层次,按比例分配了抽样单元数,分别以生产渔船总数和总功率数推算总产量,并比较了这两种方法的方差。结果表明,用每kW平均产量估计总产量的变异系数为1.13%,用单船平均产量估计总产量的变异系数为14.65%。同时由于渔业抽样调查的难点在于总体船数的掌握,建议统计推断时,采用单位渔捞努力量渔获量（CPUE）推算总体渔获量。     

低液量水平管气液分层流摩阻压降的计算

在大型多相流试验环道上进行了空气-水、空气-HVIW150基础油试验,对水平管低液量气液分层流的流动特性进行了研究.选取了ARS模型作为界面形状模型,同时以动量平衡方程为基础,求解了气液两相流的摩阻压降,并将模型预测值与试验所测的摩阻压降作了比较分析,得出了分层流摩阻压降变化的一些规律,在低液量的分层流动中推荐采用ARS界面模型.     

垂直分层种施开沟器的设计与试验研究

通过对免耕播种机开沟器要求的分析,提出了垂直分层种施开沟器的设计方案,确定了开沟器结构参数,并将其安装在小型山地免耕播种机上,对其实用性进行了试验.结果表明:该开沟器能够将种子和化肥分别施于距地表5.4 cm和11.0 cm处,种肥间层为5.6 cm,达到播种作业的农艺要求,解决了播种作业中垂直分层种施的问题,对免耕播种机的推广应用具有重要意义.