利用相对电导率和茎尖水势预报落叶松苗木生活力的研究

本文对落叶松在不同晾晒时间中茎尖水势，相对电导率及苗木生活力的动态变化过程进行了测定。结果表明：茎尖水势，相对电导率确实能反映苗木遇到逆境后对其生活力的影响，用于预报造林成活率和初期生长量具有极强的可靠性。     

超高分子量聚乙烯渔网线捻回角与强力的初探

本文叙述了采用 8种网线复捻捻回角的超高分子量聚乙烯渔网线强力性能的试验结果。经分析可见 ,网线的断裂强力、单线结强力均与捻回角的余弦呈回归关系。以网线的断裂强力性能为主 ,兼顾网线的单线结强力、断裂伸长率等性能参数 ,比较UHMWPE、普通聚乙烯和聚酰胺三种纤维制成网线后 ,它们的强力利用率均应 >6 5 % ,由此得出制作超高分子量聚乙烯渔网线合理的捻回角区间为 18°～ 2 1°     

Verification of mean volume backscattering strength obtained from acoustic Doppler current profiler by using sound scattering layer

ABSTRACT:   Acoustic Doppler current profilers (ADCPs) have recently been used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs) or swimming speed of fish schools and to analyze SSL spatial distribution or various behavior patterns. This paper shows that it is necessary to verify mean volume backscattering strength (MVBS, dB) values acquired from each beam for quantitative analysis of the spatial distribution or the biomass estimates of such specific targets as SSL or a fish school when using an ADCP. In this study, the SSL was selected to be a homogeneous density layer over a large area and two methods were used to verify the MVBS values from each beam of the ADCP. First, a mutual comparison among four beams was conducted after calculating MVBS from the measured echo intensity. Second, the MVBS values were verified using comparison between the calculated MVBS from the 153.6 kHz ADCP and MVBS from three frequencies of a well-calibrated scientific echosounder. Moreover, the dominant scatterers (euphausiids) were collected by a framed midwater trawl. From these samples, biological data were used to identify the different frequency characteristics between two systems, using a distorted-wave Born approximation (DWBA) theoretical backscattering model in order to assess the averaged target strength and target strength TS differences for the three frequencies.     

Differences in swimbladder volume between Baltic and Norwegian spring-spawning herring: Consequences for mean target strength

Fish swimbladders, where present, contribute most to the scattering of sound by fish, as measured by the target strength (TS). The volumes of the swimbladders of two different European stocks of Atlantic herring were compared to consider the effect on estimates of TS. Swimbladder volumes of Baltic and Norwegian spring-spawning herring (Clupea harengus) were measured, together with individual herring fat content. Swimbladder volumes were found to differ significantly between the two herring stocks. Baltic herring have a larger swimbladder volume, which is suggested to be associated with the fish's low fat content, which in turn may be linked to its specific energy budget and the low salinity of the Baltic Sea. A buoyancy model that considered the different salinity conditions and fat proportions was used to evaluate the observed differences in swimbladder volume. The swimbladder volume data were subsequently used to model the mean target strength as a function of depth and growth pattern. Backscattering of the swimbladder was modelled using the modal-series-based deformed-cylinder model (MSB-DCM), describing the swimbladder as a gas-filled, elongated prolate spheroid. The fish body component was modelled as a fluid-filled ellipsoid using the distorted wave Born approximation (DWBA). Modelling results support a different TS-to-size relationship for Baltic herring, with a stronger echo, due to the larger swimbladder. Depth- and length-dependent TS relationships based on the model results are suggested.     

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture: a production scale assessment

In previous proof-of-concept work, it was shown that the use of treated coal mine water for rainbow trout (Oncorhynchus mykiss) culture in a cage was technically feasible, though only a 50-fish bioassay was grown and no work on production-related issues was conducted. To further advance the use of treated mine water, an under-utilized water resource throughout Mid Appalachia, work was conducted to assess the effects of using treated coal mine water for the intensive production of rainbow trout in a flow-through system. During this study, comprehensive water quality data were collected to supplement fish weight and length data taken during routine monthly sampling events. The 8000 fish grew well in the raceway system over the 9 months of production, where a feed conversion ratio of 1.4 and a condition factor of 5.1 × 10⁻⁴ were measured with stocking and harvest densities of 26.4 and 50.2 kg/m³, respectively. Further, total net production was 3275 kg (7220 lb) with 98.6% survival. Throughout the study, dissolved ion concentrations (Fe, Al, Mg, Ca, and SO₄) often exceeded recommended tolerance limits. Further, elevated ammonia nitrogen concentrations generated from a component of the mine water-treatment process were identified as a potential limiting factor for aquaculture development. However, when the non-ideal effects of high ionic strength and the speciation of dissolved metal–ligand complexes were taken into account, the concentrations of free metal ions were within recommended tolerance limits.     

某汽车转向纵拉杆设计分析

转向纵拉杆是汽车转向传动机构中重要的零部件,通过转向纵拉杆受力分析,对转向纵拉杆的强度、稳定性进行了校核,提供了纵拉杆设计分析的参考.     

西瓜蔓枯病研究 Ⅰ.症状及病原

本文详细报道了西瓜蔓枯病的症状和病原菌的形态特点,并鉴定其有性阶段为Mycosphaerellamelonis(Pass)Chiu et Walker,无性阶段为Ascochyta-cucumis Fautr et Roum.此外,还在其他瓜类作物上作了病原菌的致病性试验.     

无砂大孔绿化混凝土在河涌整治护

无砂大孔绿化混凝土多孔透水，其上可种植水生植物，用于河涌整治护岸工程，具有护岸、绿化造景、美化环境、改善水体生态平衡和净化水质等功能，是一种建造生态水工的绿色混凝土。试验发现无砂大孔绿化混凝土的最佳水灰比与水泥用量呈线性关系，随水泥用量增大而减小；强度随水泥用量增大而增大，呈线性关系；强度也随水灰比减小、龄期延长而增大。     

两种常温固化木材胶粘剂胶接强度分析

对两种木材用常温固化胶粘剂--单宁-甲醛胶粘剂和聚氨酯胶粘剂胶接的速生杨木的静态剪切强度进行了测试与分析.研究结果表明,以速生杨I-72为被胶接对象,自制的双组分型单宁胶压缩剪切强度范围为8.08～8.92MPa,但木破率较低,要满足日本集成材JAS标准中用胶规定,需进一步研究改进.相比较而言,聚氨酯胶粘剂的胶接强度较高,其压缩剪切强度值均在9.8MPa以上,木破率在75%以上,能够满足日本集成材JAS标准中用胶的规定.     

漆酶处理对未漂硫酸盐浆抗张强度和纤维表面的影响

探讨了漆酶处理对未漂硫酸盐浆抗张强度的影响,研究了漆酶处理的主要工艺参数对纸页湿抗张强度的影响;并采用扫描电镜(SEM)对漆酶处理前后纤维表面微细结构的变化进行了研究。结果表明,漆酶可以改善纸浆的湿抗张强度,但对于抗张强度不起作用;提高纸浆湿强度的最佳酶促反应条件为:酶用量16U(以每克绝干浆计),温度45℃,pH值4.5,处理时间2h。扫描电镜分析表明,漆酶处理使得纤维表面变得粗糙,纤维之间产生了黏结性,湿强度得以提高。