In order to determine the effect of twine thickness on the size-selectivity of the driftnet used for the yellow croaker, size-selectivity tests were conducted with three different twine thicknesses(monofi lament diame...In order to determine the effect of twine thickness on the size-selectivity of the driftnet used for the yellow croaker, size-selectivity tests were conducted with three different twine thicknesses(monofi lament diameters of 0.279 mm(number's method; No. 3), 0.321 mm(No. 4), and 0.360 mm(No. 5)) of driftnets for the yellow croaker in the seas around Chooja-do, Jeju Islands. The selectivity curve was estimated by using Kitahara's method. In order to determine the physical properties of the twine used in the experimental fi shing nets, we measured the breaking load, elongation, and stiffness under both dry and wet conditions. In terms of physical properties, the thinnest twine(No. 3) had the strongest breaking strength per unit cross-sectional area, along with good elongation and excellent fl exibility. The thickest twine(No. 5) had the lowest fl exibility. In terms of selectivity, the net of No. 3 twine showed the broadest selection range and, thus, a relatively low selectivity compared with the other nets, while the less fl exible net of No. 5 twine showed the narrowest selectivity range and high selectivity. In addition, it was found that a thicker twine resulted in a smaller haul of small fi sh. Therefore, it can be inferred that the thickness of the twine affects the size of the catch and selectivity, and thus the size composition of the catch as well.展开更多
针对香蕉秸秆富含纤维且含水率高等物理特性,现有的秸秆与根茬粉碎还田机田间作业时存在着切割阻力大,秸秆纤维易缠绕等问题。采用理论建模方法确定了秸秆滑切刀片的刀刃曲线方程;设计阐述了还田机的关键结构参数,该文研制出一种滑切防...针对香蕉秸秆富含纤维且含水率高等物理特性,现有的秸秆与根茬粉碎还田机田间作业时存在着切割阻力大,秸秆纤维易缠绕等问题。采用理论建模方法确定了秸秆滑切刀片的刀刃曲线方程;设计阐述了还田机的关键结构参数,该文研制出一种滑切防缠式香蕉秸秆还田机,并阐述了还田机械的总体机构与工作原理,同时对其秸秆粉碎率以及功耗进行田间试验。结果表明:各因素对香蕉秸秆粉碎率和功耗影响的显著性顺序从大至小依次均为秸秆粉碎刀辊转速、灭茬刀辊转速、机器前进速度。当机器前进速度为1.39 m/s、秸秆粉碎刀辊转速为1 600 r/min、灭茬刀辊转速为500 r/min时,香蕉秸秆粉碎率为95.2%,功耗为4.96 k W。在最优工作参数情况下,实际香蕉秸秆粉碎率为94.9%,实际功耗为5.1 k W,与软件分析值(95.2%、4.96 k W)间的误差分别为0.31个百分点、0.27%,验证了分析的可信性。通过与甩刀式立式香蕉秸秆粉碎还田机进行性能对比试验,得出所研制的滑切防缠式香蕉秸秆还田机秸秆粉碎率提高1.94个百分点,功耗降低11.3%。该机器的设计为中国南方热带地区香蕉秸秆还田技术的推广与应用提供了基础。展开更多
基金Supported by the National Institute of Fisheries Science(No.R2015041)
文摘In order to determine the effect of twine thickness on the size-selectivity of the driftnet used for the yellow croaker, size-selectivity tests were conducted with three different twine thicknesses(monofi lament diameters of 0.279 mm(number's method; No. 3), 0.321 mm(No. 4), and 0.360 mm(No. 5)) of driftnets for the yellow croaker in the seas around Chooja-do, Jeju Islands. The selectivity curve was estimated by using Kitahara's method. In order to determine the physical properties of the twine used in the experimental fi shing nets, we measured the breaking load, elongation, and stiffness under both dry and wet conditions. In terms of physical properties, the thinnest twine(No. 3) had the strongest breaking strength per unit cross-sectional area, along with good elongation and excellent fl exibility. The thickest twine(No. 5) had the lowest fl exibility. In terms of selectivity, the net of No. 3 twine showed the broadest selection range and, thus, a relatively low selectivity compared with the other nets, while the less fl exible net of No. 5 twine showed the narrowest selectivity range and high selectivity. In addition, it was found that a thicker twine resulted in a smaller haul of small fi sh. Therefore, it can be inferred that the thickness of the twine affects the size of the catch and selectivity, and thus the size composition of the catch as well.
基金financially supported by the Natural Science Foundation of Liaoning Province,China(No.2020-MS-004)the National Natural Science Foundation of China(Nos.51601193,51701218)+2 种基金the National Key Research and Development Program of China(No.2016YFB0301104)the State Key Program of National Natural Science of China(No.51531002)the Natural Science Foundation of Shandong Province,China(No.ZR2021ME241)。
文摘针对香蕉秸秆富含纤维且含水率高等物理特性,现有的秸秆与根茬粉碎还田机田间作业时存在着切割阻力大,秸秆纤维易缠绕等问题。采用理论建模方法确定了秸秆滑切刀片的刀刃曲线方程;设计阐述了还田机的关键结构参数,该文研制出一种滑切防缠式香蕉秸秆还田机,并阐述了还田机械的总体机构与工作原理,同时对其秸秆粉碎率以及功耗进行田间试验。结果表明:各因素对香蕉秸秆粉碎率和功耗影响的显著性顺序从大至小依次均为秸秆粉碎刀辊转速、灭茬刀辊转速、机器前进速度。当机器前进速度为1.39 m/s、秸秆粉碎刀辊转速为1 600 r/min、灭茬刀辊转速为500 r/min时,香蕉秸秆粉碎率为95.2%,功耗为4.96 k W。在最优工作参数情况下,实际香蕉秸秆粉碎率为94.9%,实际功耗为5.1 k W,与软件分析值(95.2%、4.96 k W)间的误差分别为0.31个百分点、0.27%,验证了分析的可信性。通过与甩刀式立式香蕉秸秆粉碎还田机进行性能对比试验,得出所研制的滑切防缠式香蕉秸秆还田机秸秆粉碎率提高1.94个百分点,功耗降低11.3%。该机器的设计为中国南方热带地区香蕉秸秆还田技术的推广与应用提供了基础。
