齿轮弯曲疲劳寿命有限元计算方法研究

以材料弯曲疲劳特性为基础,采用有限元技术对齿轮的齿根应力进行分析,运用多轴疲劳设计准则对齿轮的疲劳寿命进行了计算。这一方法克服了传统的齿轮疲劳寿命计算中齿轮材料疲劳特性数据不足,应力计算不准的缺点。将计算结果与试验数据进行了对比分析,疲劳寿命计算值在试验值的0．3倍至3倍以内。     

2019年肉羊产业发展概况、存在问题及对策建议

目的揭示北川白山羊的生长发育规律及其杂交改良效果。方法选取舍饲条件下北川白山羊145只(BB)、波北山羊 (波尔山羊♂×北川白山羊♀,RB) 86只、萨北山羊 (萨能奶山羊♂×北川白山羊♀,SB) 45只和波萨北山羊[ 波尔山羊♂× (萨能奶山羊×北川白山羊)♀,RSB] 58只测定其体重和体尺,计算其体质指数,并采用Gompertz和Logistic模型拟合北川白山羊及其杂交羊生长发育过程,分析比较生长参数及模型估计值。结果2月龄RSB公羔和母羔体重均显著高于BB (P<0.05),分别达到14.29和12.36 kg;6月龄RSB公羊体重和体长均显著高于BB (P<0.05);12月龄RSB公、母羊体重显著高于BB (P<0.05),且RSB公、母羊体质指数显著高于SB (P<0.05);24月龄RSB公、母羊体重均显著高于BB (P<0.05),RSB公羊体质指数显著高于BB (P<0.05)。Gompertz模型拟合效果优于Logistic模型,Gompertz模型中RSB公、母羊最大月增重分别为3.80和3.10 kg,分别比BB提高60.34%和38.39%;RSB公、母羊体重达35 kg的日龄分别为248.74和340.35 d,分别比BB提前175.36和388.34 d。结论波萨北山羊杂交改良效果显著,Gompertz模型对山羊生长发育规律拟合度高,其生长曲线参数可为品种改良和科学饲养管理提供数据支撑和依据。     

基于实测光谱的红花叶绿素含量高光谱估算模型研究

通过分析红花(Carthamus tinctorius L.)原始光谱、变换光谱以及其他25种应用最普遍的高光谱参数与其叶绿素含量的相关性,并选择每个生长期与红花叶绿素含量相关性较好的高光谱指数和波段,建立不同生长期红花叶绿素含量的线性、抛物线、指数和对数模型,并用RMSE评价模型精度。最后得出各期的最佳模型:出苗期归一化差异指数(NDI)的抛物线模型具有最大模型精度0.900和检验精度0.932;分枝期黄边幅值(Dy)的抛物线模型精度为0.850,检验模型精度为0.811;始花期444 nm处二阶导数光谱的抛物线模型精度为0.734,检验精度为0.866;终花期798 nm处二阶导数光谱的抛物线模型精度为0.929;成熟期795 nm处二阶导数光谱的指数模型精度为0.904,检验精度为0.868。     

基于计算机视觉和非参数估计的蟹苗数量估算方法研究

养殖池内蟹苗的数量估计在蟹苗养殖中有着重要意义。但现有的数量估计方法操作复杂且实用性不强,因此提出一种基于计算机视觉和非参数估计的蟹苗数量估算方法。首先在养殖池内分水层采集视频,通过背景建模得到前景图像,并使用分水岭算法和轮廓提取得到视频中的蟹苗数量,并作为样本数据,然后通过核密度估计得出概率密度函数,最后结合该函数和样本数据估算出池内蟹苗数量。结果表明,该方法对于容积约为1 000 L、蟹苗密度100~160只/L的小型蟹苗养殖池,估算蟹苗数量的平均正确率为82.14%。研究表明,采用该方法不仅可以解决采集视频过程的操作繁琐、幼苗转移的问题,而且能够避免图像处理过程中部分背景杂质的干扰。该方法还可以推广到虾苗和鱼苗等生物的幼苗估计,具有良好的通用性和可行性。     

SONOGRAPHIC EVALUATION OF CANINE TESTICULAR AND SCROTAL ABNORMALITIES: A REVIEW OF 26 CASE HISTORIES

The ultrasonographic and medical records of 26 dogs examined for testicular/scrotal abnormalities were reviewed. Fifteen dogs were diagnosed with testicular neoplasia that included one or more of the following tumor cell types: Sertoli cell, seminoma and interstitial cell. Ultrasound was highly sensitive to detection of testicular neoplasia including one nonpalpable tumor. Tumor type specificity was not readily apparent in this study, although the three nondescended Sertoli cell tumors displayed similar characteristic sonographic patterns. Six dogs were reviewed with nonneoplastic, noninfectious disorders that included: vascular compromise, atrophy, scrotal edema and intestinal hernia. Five dogs with infectious diseases were reviewed. Ultrasound was sensitive and relatively specific for the nonneoplastic conditions.     

SC切谐振器B模抑制网络参数的计算与稳定性分析

Based on the oscillating equilibrium condition, the formulas are derived for calculating the parameters of Model B oscillating inhibitory network. The influence of temperature on the frequency stability is also discussed. The results show that only if the     

Estimation of carbon losses by cultivation from soils of the Argentine Pampa using the Century Model

Abstract. The Century model was used for estimating soil carbon levels under grassland at the regional scale in the Pampean Region of Argentina. Predicted values were compared with observed soil carbon contents obtained from soil surveys and the differences considered to be the results of cropping on soil organic matter. The Pampean Region was divided into five major sub-regions and carbon in the top 20 cm of each estimated by Century using aggregated soil and climatic data. In four of the sub-regions small differences between predicted and observed carbon contents were obtained which suggested little land use effect on soils. In the Rolling Pampa, a northern portion of the Pampean Region, observed carbon content was about half of Century prediction. In this sub-region, the main agricultural area of the country, cropping intensity, rainfall and temperature are higher than in the rest of the Pampas. A degradation index constructed by a multiplicative approach, taking into account percentage of surface cropped, rainfall and temperature was 2–5 times higher in the Rolling Pampa than in the other pampean sub-region. The difference between predicted C and observed C in the Rolling Pampa was attributed to carbon losses by cropping in a warm and wet climate.     

Outcrossing Rates of Experimental Populations of Cuphea lanceolate

Outcrossing rates of Cuphea lanceolata Ait., a new Dilseed crop, have not been estimated; however, this species is known to be insect-pollinated, self-compatible, and autosterile. We used five allozyme loci and the mixed mating model to estimate the outcrossing rates of experimental populations of Cuphea lanceolata Ait. grown at Corvallis, Oregon in 1987 and 1988. Populations were grown using densities of one and 27 plants m^?2. Multilocus out-crossing rate estimates of populations grown at low and high density ranged from 0.61 to 0.85 and 0.93 to 0.94, respectively. Density caused differences may be caused by differences in pollinator movement. In open plantings, e.g., space-plant nurseries, selfing rates are increased by increased within plant pollination by bumblebees, the primary pollinators of C. lanceolata in temperate zones. The movement of pollinators between plants is enforced in dense plantings. We found C. lanceolata is predominantly al-logamous, but selfing rates as great as 39.0 % were observed among space-plants; thus, the progeny of an open-pollinated individual plant grown in this type of nursery is a mixed half-sib and S₁ family. Maximum outcrossing can be achieved by using dense plantings.     

Population assessment of sockeye salmon Oncorhynchus nerka caught by recreational angling and commercial fishery in Lake Toya, Japan

ABSTRACT: We carried out mail and access point surveys to estimate the catch numbers, angling effort of recreational angling and the population of sockeye salmon Oncorhynchus nerka in Lake Toya in 1998 and 1999. The mail survey questions in questionnaires distributed to anglers with a recreational angling license included date of angling, caught fish species and size, and catch number. In the access point survey we also asked anglers if they had a license. We measured the fork length and weight of caught fish. The catch rate (catch number in a day by each angler) from both surveys showed no significant difference, suggesting no bias for the catch rate between surveys. The estimated total angling effort was 1760 people (1998), and 1516 people (1999). The estimated recreational catch was 28 889 (1998) and 5455 (1999), that is, two or three times larger than the commercial catch. The fish population was estimated by using the DeLury method as 60 262 (1998) and 10 806 (1999). The total exploitation rate was 62% (1998) and 78% (1999). The size of caught fish was much larger in 1999 than 1998 because of the difference in age composition.