Growth rates and survival of western rock lobster (Panulirus cygnus) at two temperatures (ambient and 23 °C) and two feeding frequencies

Wild caught post-pueruli, year one and year two post settlement juvenile western rock lobster, Panulirus cygnus, were held at ambient temperatures (15.6 °C to 23.1 °C; mean 19.0 ± 0.07 °C) or at 23 °C, and fed the same ration of a formulated pellet diet either once per night, or 3 times per night, over 12 months, to determine whether elevated temperatures and multiple feeds per night would stimulate growth through increased metabolism and feed utilisation without significant negative impacts on survival. Survival of post-pueruli (mean 63%) did not differ between ambient and 23 °C. Survival of year 1 and 2 juveniles was higher at ambient temperatures (p < 0.01 ambient: year 1 juveniles, 68%; year 2 juveniles, 88%; 23 °C: 57% and 74%, respectively). Feeding frequency did not affect survival of post-pueruli and year 2 juveniles (mean 63%, 81% respectively), but survival was 9% higher for year 1 juveniles fed three times per night (58% versus 67%; p < 0.01). All lobsters grew faster at 23 °C than at ambient temperatures (p < 0.05), with the growth of post-pueruli almost doubled at 23 °C (weight gain at 23 °C versus ambient: post-pueruli, 18 438 % versus 9 915 %; year 1 juveniles 259% versus 165%; year 2 juveniles 23% versus 21%). Feed frequency did not influence the growth of year 1 and 2 juveniles. However, there was an interaction effect of temperature and feed frequency on post-pueruli where weight and carapace length were significantly higher at ambient temperatures when post-pueruli were fed three times a day, whereas at 23 °C weight and carapace length were significantly greater when fed once per day (p < 0.05). Feed intake (g pellet dry matter lobster^− 1 day^− 1) of pellet was higher at 23 °C for all lobsters (p < 0.05), but was the same between lobsters fed 3 times per night versus once per night. This study has shown that increasing temperatures to 23 °C significantly improved the growth of P. cygnus post-pueruli without any adverse effects on survival. The faster growth rates exhibited by year 1 and 2 juveniles at 23 °C may potentially offset their lower survival by significantly reducing culture period. There is no benefit of feeding P. cygnus multiple times at night in terms of growth and survival. The implications for P. cygnus culture are that temperatures should be maintained close to 23 °C during the entire growout period, with due care taken to minimise mortalities through adequate provision of food and shelter. Feeding P. cygnus once daily to excess just prior to dusk to co-incide with nocturnal feeding behaviour is recommended.     

江西一季籼粳杂交稻稻曲病防治药剂及次数研究

选择合适的防治药剂和防治次数是减轻稻曲病危害的关键。本研究以籼粳杂交稻甬优12为材料,比较了6种药剂和3种喷施次数对稻曲病的防控效果和产量性状差异。结果表明,在6种药剂中,阿米妙收处理的病穗率防效和病指防效最好,分别达到91.53%和96.63%,但与其他药剂无显著性差异。在防治次数上,爱苗和拿敌稳均为防治3次的处理病指防效最好,分别为81.73%和80.15%,显著高于防治次数3次以下的处理。阿米妙收处理的产量最高,达11 719.52 kg/hm~2,显著高于其他处理。     

灌水次数和施钾量对冬小麦茎秆形态特征和抗倒性的影响

为进一步明确兼顾节水高产抗倒的最佳灌水与施钾量组合,以冬小麦品种藁优2018为材料,通过二因素随机区组试验,研究了3种灌水次数(不灌溉、灌拔节水、灌拔节水和扬花水)和4个施钾量(施K_2O0、75、150和225kg·hm~(-2))对冬小麦茎秆形态特征和抗倒性的影响。结果表明,随灌水次数和施钾量的增加,小麦株高和重心高度显著增高,茎秆基部2个节间的单位长度干重、直径、机械强度和抗倒指数显著增加。而茎秆壁仅随施钾量的增加而显著增厚。小麦产量和3个产量构成因素也随灌水次数和施钾量的增加而增加,但4个施钾量之间的千粒重差异不显著,K225与K150之间的穗数、穗粒数和籽粒产量差异不显著。茎秆抗倒指数与茎秆基部第1、2节间的单位长度干重、直径呈极显著正相关,与株高、重心高度也呈极显著正相关。综合各项指标,春季在拔节期和扬花期灌2次水,施K_2O 150kg·hm~(-2)有利于实现小麦高产和钾肥高效,且茎秆抗倒性能较好。     

轴流泵多目标优化正交试验

为了整体提高轴流泵的水力优化设计水平,找出影响轴流泵性能的主要几何参数,运用正交试验方法,以扬程、效率、轴功率和压力脉动作为试验评判指标,将综合频率分析法应用到轴流泵多目标优化设计中。基于L_9(3~4)正交表得到了9组方案,研究叶片数、翼型、轮毂比和叶片与导叶间距离对轴流泵的扬程、效率、轴功率和压力脉动的影响规律,并通过综合频率分析法确定了一组最佳试验方案。结果表明:该最佳试验方案在设计流量下,水流在叶轮及导叶段中的流态较好,水流流线顺畅,分布相对均匀;轴流泵模型在流量和扬程满足改型要求的同时,效率提高了5.7%;轴功率下降了1.21%;压力脉动系数降低了11%,验证了综合频率分析法在多目标正交优化中的可行性。     

咸水膜下滴灌频率对土壤表层水盐环境的影响

为了更好地指导干旱区农业生产,利用地下咸水进行了膜下滴灌频率试验,设3种滴灌频率,即1次/24 h(T1)、1次/48 h(T2)和1次/72 h(T3),探讨了相同灌水量下不同滴灌频率对土壤表层水盐环境的影响。结果表明,(1)T2处理浅层土壤含水率高于T1和T3处理0.5%~1.0%,且试验后期形成面积和深度均大于T1和T3处理的;(2)土壤电导率在整个试验过程中呈增加趋势,T2处理土壤电导率增长幅度相对较小,土壤返盐程度较小;(3)土壤p H值在试验中期增大,试验后期减小,表层土壤p H值达8.5左右;(4)土壤表层各盐分离子量在试验期间的增加程度远小于土壤结冻期;土壤表层重碳酸根离子量在试验后期超过120.0 mg/kg,土壤总碱度增大,土壤存在碱化趋势。因此,滴灌频率1次/48 h可为作物提供比较适宜的土壤表层水盐环境,可作为民勤绿洲咸水滴灌频率参考值;同时,使用咸水滴灌后,绿洲土壤存在明显碱化趋势,因此还需采取其他灌排措施减弱土壤次生盐渍化。     

基于TMS320VC5416的精确频率测量技术研究

频率是决定测量仪表或控制系统性能的基本参量之一,为了提高频率测量方法的精度和效能,介绍了利用DSP进行脉冲频率测量的方法,并用TMS320VC5416实现了这一方法。经过多组试验数据表明,利用DSP能够进行频率测量,并有很高的测频精度和可靠性,运算速度更能达到160/120MIPS,是一种值得推广的测频方法。     

物联网技术在食品及农产品中应用的研究进展

物联网(IOT)技术正被越来越多地应用在食品及农产品领域。首先简介了无线射频识别标签(RFID)和无线传感器网络(WSN)的原理和技术,然后较全面地分析归纳了近年来这些技术在食品、农产品的生产监控、安全监管及供应链的溯源与追踪等领域的应用研究现状,并分析了存在的问题和解决途径,最后展望了这些技术今后的发展趋势和应用前景。     

基于DDS的可变频率可控波形超声乳化发生器的设计

用于超声乳化工艺的超声波发生器是乳化设备的主要装置,传统超声乳化方式多采用单一频率、固定波形的超声波发生方式,在应用中存在操作参数不易调节、最优因素获取受限等问题。为此,运用直接数字频率合成(DDS)技术构建一种可变频率可控波形的超声波发生器,通过在试验中改变超声波的激励频率、激励波形、功率、处理时间来研究影响乳化效果的最优操作参数,对探讨各操作参数的影响规律提供可靠依据。     

樱桃番茄运输包装件振动冲击性能试验

针对目前樱桃番茄储运过程中主要包装形式以及造成破损的情况,选择典型运输包装件,进行了正弦扫频、堆码强度、堆码扫频振动传递性能、垂直冲击和跌落试验。通过对单件包装件的扫频振动试验,测出单件的固有频率为26.61Hz;通过堆码强度试验,测出了包装件的最大堆码层数为9层。通过9层堆码扫频振动传递性能试验确定了底层、中间层和顶层包装件的固有频率分别为36.61、10.76和6.44Hz,得到了各层包装件振动加速度、振动传递率随时间的变化曲线,并探讨了固有频率和振动传递率峰值与堆码高度之间的关系。在此基础上,通过垂直冲击试验,测出了产品的脆值为89.58;通过跌落试验,测出了包装件最大允许跌落高度为580mm。     

基于ANSYS Workbench的乘坐式割草机刀盘模态分析

刀盘是割草机重要部件,其工作时固有频率与振型的大小直接关系到整机的可靠性与安全性。为此,利用CAD/CAM软件Pro/E建立刀盘的三维实体模型,并将其导入有限元分析软件ANSYS Workbench,对所建模型进行模态有限元仿真分析,提取前6阶固有频率,与刀盘转速进行比较,计算出其工作时的危险转速范围。分析结果表明:刀盘最高工作转速远低于其1阶临界转速,有效地避免了共振的发生,验证了刀盘设计的合理性,可为刀盘其它的动力学分析奠定基础。