Multiple otolith techniques aid stock discrimination of a broadly distributed deepwater fishery species, blue grenadier, Macruronus novaezelandiae

This study investigated otolith shape, elemental chemistry of otolith cores (first 1-3 months of life), and stable isotope ratios (δ¹⁸O and δ¹³C) of whole otoliths as indicators of stock structure among three important southern Australian blue grenadier Macruronus novaezelandiae fishery regions; west Tasmania - WTAS, east Bass Strait - EBS, and Great Australian Bight - GAB. Comparisons were confined to two dominant cohorts of age 4+ and 13+ years, spawned in winter 2002 and 1993 respectively. Otolith shape varied significantly between the WTAS and GAB regions for the age 4+ cohort only. Cu:Ca of otolith cores was significantly higher for both cohorts from WTAS than EBS and GAB, and Ba:Ca of otolith cores higher for WTAS and EBS than the GAB region. Stable isotopic signatures showed greater variation among regions for the age 13+ cohort. In particular, otoliths of age 13+ fish from WTAS displayed significantly higher δ¹⁸O (indicative of lower temperature history) than age 4+ fish from all regions, and the same age fish from the GAB and EBS regions. δ¹⁸O of blue grenadier otoliths accurately predicted water temperature at their main capture depths of 400-600 m. Chemistry of otolith cores combined with whole otolith isotope ratios discriminated GAB and EBS samples from those collected on the known WTAS spawning ground with moderate to high (64-86%) accuracy. The results provide support for the hypotheses that the GAB fishery is based on a separate stock for management purposes, and that the EBS fishery is likely replenished both from local spawning and the major WTAS spawning region.     

沼气池球盖曲率半径及容积速算法

沼气池球盖曲率半径和沼气池容积是沼气工程设计、施工等人员进行沼气池设计、施工、预决算的主要数据,也是沼气工程管理人员核查沼气工程施工正确与否的主要依据,数据既要正确又要快速计算,这对施工人员和工程管理人员要求较高。介绍了一种计算沼气池球盖曲率半径和沼气池容积的速算方法。     

Competition and tree crowns: A neighborhood analysis of three boreal tree species

Competition for canopy space is a fundamental structuring feature of forest ecosystems and remains an enduring focus of research attention. We used a spatial neighborhood approach to quantify the influence of local competition on the size of individual tree crowns in north-central British Columbia, where forests are dominated by subalpine fir (Abies lasiocarpa), lodgepole pine (Pinus contorta) and interior spruce (Picea glauca × engelmanii). Using maximum likelihood methods, we quantified crown radius and length as functions of tree size and competition, estimated by the species identity and spatial arrangement of neighboring trees. Tree crown size depended on tree bole size in all species. Given low levels of competition, pine displayed the widest, shortest tree crowns compared to the relatively long and narrow crowns found in spruce and fir. Sensitivity to crowding by neighbors declined with increasing tree height in all but the pine crown radius model. Five of the six selected best models included separate competition coefficients for each neighboring tree species, evidence that species generally differ in their competitive effects on neighboring tree crowns. The selected crown radius model for lodgepole pine, a shade-intolerant species, treated all neighbors as equivalent competitors. In all species, competition from neighbors exerted an important influence on crown size. Per-capita effects of competition across different sizes and species of neighbors and target trees varied, but subalpine fir generally displayed the strongest competitive effects on neighbors. Results from this study provide evidence that species differ both in their response to competition and in their competitive influence on neighbors, factors that may contribute to maintaining coexistence.     

The analysis on pre splitting blasting to improve permeability draining rate in heading excavation

Aiming at the problem of low excavation speed and high risk of coal and gas outburst because of low gas draining rate in heading excavation,and taking an excavation heading of a mine for example,the test of deep hole pre splitting blasting is processed.The amount of gas draining after pre splitting is compared with the amount of direct draining,and the effective radius of draining is surveyed.The test result shows that the draining rate of K1 coal seam reaches 37.13 %,which reduces the draining time by 60%,10 days after pre splitting,and the gas desorption index exceeds the standards until the fifth blasting.The draining rate of K4 needs 12 days to reach 34.28 %,which reduces the draining time by 60%,and the gas desorption index exceeds the standards when the third blasting processes.Obviously,the effect of gas draining is improved by pre splitting blasting.The effective draining radius of K1 and K4 are 4.5 and 5.2 m respectively after pre splitting blasting.The research can provide reference for the fieldwork of pre splitting blasting.     

蜗壳隔舌半径对离心泵性能及水力载荷特性的影响

为研究蜗壳隔舌半径对离心泵性能及水力载荷特性的影响,针对同一叶轮匹配5种不同隔舌半径的离心泵进行非定常数值计算.通过计算获得了不同泵的水力性能、压力脉动特征、叶片载荷及叶轮上的径向力分布,并且与试验结果进行对比分析,验证了采用的数值计算方法具有较高的正确性.研究结果表明:隔舌半径对扬程的影响较小,随隔舌半径的增大,各工况下效率呈先增大后减小的趋势;当隔舌与基圆半径之比TR取值为0.09~0.24时,叶片工作面与背面的载荷差值有最小值,即此时叶片受力沿进口至出口的变化最小;随着隔舌半径的增大,泵内的压力脉动水平逐渐降低,TR=0.03时,叶频处的压力脉动幅值约为TR=0.3时的2倍;隔舌半径对叶轮径向力的大小影响显著,在设计工况下,径向力随隔舌半径的增大而增大,且TR=0.3时的径向力约为TR=0.03时的2.5倍.     

基于转向半径的汽车稳态转向特性分析

汽车等速行驶时，常用稳态横摆角速度与前轮转角之比来评价其稳态响应。根据稳定性因数的数值不同，可将汽车的稳态转向特性分为三种类型：不足转向、中性转向和过多转向。本文通过几何学、车辆运动方程式，分别推导出汽车转向半径公式，在各相应的条件下，分别基于转向半径公式对汽车三种稳态转向特性进行分析。     

Validation of otolith daily increments for larval and juvenile Japanese halfbeak Hyporhamphus sajori

Daily ring formation was verified by examining the growth of the marginal increment on sagittal otoliths of larval and juvenile Japanese halfbeak Hyporhamphus sajori. The relationship between age (x) and number of increments (y) is y = 1.0x + 2.0. The first daily increment was formed during the 2 days before hatching. The relationship between the number of rings deposited after the alizarin complexone (ALC) mark (x) and the number of increments (y) is given by: y = 1.0x − 0.2. The index of completion of the marginal increment was 99 ± 4.1% (mean ± S.D.) at 04:00, and from 24 ± 4.4% at 08:00 it increased with time of day and reached 98 ± 3.6% until the next day at 04:00. Growth of the incremental zone started a few hours after sunrise prior to which the discontinuous zone seemed to be formed. Light rhythms tend to be one of the most important factors for the formation of the marginal increment on otoliths. Based on the relationships between time of day and the marginal increment on otoliths, it would be possible to estimate the predation time for specimens retrieved from stomach contents, and also clearer analysis of the growth history immediately prior to the sampling time.     

温度和元素浓度对Sr在褐牙鲆仔稚鱼耳石中的沉积影响

科学认识鱼类耳石中微量元素沉积与主要水环境因子的关系是基于耳石微化学方法重新构建鱼类生活史及反演其环境履历的重要前提。本研究以环境与耳石中重要元素Sr为例,研究在不同水温(16℃、19℃和22℃)和不同元素浓度(1×、2×和3×Sr)下Sr在褐牙鲆(Paralichthys olivaceus)仔稚鱼耳石形成生长过程中(孵化后15~93 d)的沉积(Sr∶Ca比)特征。结果显示,在不同水温下,耳石中Sr∶Ca比随水体中Sr浓度的升高呈线性增长,而元素分配系数(DSr)随元素浓度的升高先降低然后趋于稳定。在不同Sr浓度下,耳石中Sr∶Ca比及DSr均随水温升高呈增长趋势,二者在22℃时的值均显著高于在其他水温时的值。耳石中Sr沉积能够表征褐牙鲆仔稚鱼所经历的水环境中Sr浓度和水温的变化,可作为元素指纹应用于褐牙鲆早期生活史的重建和环境履历的反演。     

400m^3液化石油气球罐盘梯的制作

结合施工实际，介绍了液化石油气罐盘梯的结构，它是由柱盘梯与球盘梯两部分组成的，因此，在计算盘梯的弯曲半径时应分别进行，给出了利用实地放样求盘梯侧板展开下料实长的具体计算步骤，并论述了求盘梯侧板展开下料实长的理论推导过程，通过对此，发现两者数值非常接近，叙述了盘梯的制作方法，指出用该方法制作的盘梯，基本上满足工程的需要，并可实现现场预制整体吊装，减少空中作用，提高了生产效率。