油脂酵母发酵动力学初步探讨

在5L发酵罐上,对产油脂隐球酵母菌株(Cryptococcus)SP-11分批发酵动力学进行了探讨,建立了菌体生长、产物生成及底物消耗的动力学模型。采用OriginPro8.0软件进行模型求解,对试验结果进行非线性拟合,确立了该产油脂酵母菌的发酵动力学方程。模型的拟合结果表明:隐球酵母菌株(Cryptococcus)SP-11产油脂与菌体生长是相偶联的,模拟值与试验值拟合良好,建立的动力学模型能够比较好的反映菌株分批发酵过程菌体生长、油脂生成和底物消耗三者之间的关系。     

pH值对固定化酵母甜高粱茎秆汁液酒精发酵的影响

以可溶性糖含量为113g/L的甜高粱茎秆汁液为试验原料,采用摇瓶发酵方法,在水浴摇床上进行发酵.试验中,pH值分别选取3.5,4,4.5,5和5.5这5个梯度,考察其对固定化酵母发酵甜高粱茎秆汁液制取酒精过程中酒精产量、CO2失重率以及残糖含量的影响.结果表明,pH值选取4.5时,可获得较高的酒精产量、CO2失重率以及较低的残糖.     

先旱后涝胁迫下水稻茎蘖及株高动态响应

为了解先旱后涝胁迫下水稻的茎蘖和株高生长动态,采用测坑试验方法研究先旱后涝胁迫对水稻分蘖数和株高的影响,根据分蘖变化拟合分析了水稻茎蘖消长动力学模型,根据株高动态变化拟合了Logistic增长模型.试验结果表明:先旱后涝胁迫过程在分蘖期和拔节孕穗期均不同程度地抑制水稻分蘖;水稻在分蘖期、拔节孕穗期及抽穗开花期受涝可促进株高增长,在分蘖期、拔节孕穗期及抽穗开花期受旱则抑制株高增长;茎蘖消长动力学模型较好地拟合了茎蘖消长的过程,具有实践意义;Logistic模型拟合株高动态变化拟合度也较高,且适用合理.研究结果可为合理制定灌溉方案和提高水稻产量提供依据.     

蓄水坑灌单坑土壤水分运动模型的有限体积法求解

基于土壤水分运动的动力学方程,建立了蓄水坑灌单坑土壤水分运动的数学模型及边界条件,利用有限体积法对模型进行了求解.为了验证所建模型的准确性,在室内进行了蓄水单坑水分入渗试验.模拟结果和试验结果的对比表明,土壤湿润锋和含水率的模拟值与实测值吻合较好,说明所建立的蓄水单坑二维土壤水分运动模型是正确的,采用有限体积法求解是可行的.该模型可作为预测蓄水坑灌条件下单坑土壤水分运动的有效工具.     

水轮机效率曲线拟合的简便方法

针对水轮机效率曲线拟合传统方法存在的不足,平等地选取单位流量与单位转速作为自变量,建立其与效率值之间的二元高次多项式拟合函数模型,采用经典的最小二乘法确定其系数项,并利用MATLAB语言编程实现数据拟合和误差分析。通过实例分析验证,该方法模型简单,求解方便,具有较高的拟合精度和较强的适用性,易于计算机程序化实现。     

甜高粱糖分积累规律及其酒精发酵的研究

以"沈农甜杂2号"甜高粱为试验品种,进行了甜高粱糖分积累规律及其茎秆汁液酒精发酵的试验研究.结果表明:甜高粱茎秆中的糖分在糖分积累阶段呈"M"型变化.在上海地区6月初种植的甜高粱其茎秆中的总糖含量平均水平比5月初种植的甜高粱高46.5%,而还原糖的含量平均水平差异不大.将种植期延迟30天左右,甜高粱糖分在茎秆中保持时间和甜高粱的可供应时间可以延长10～14天;同时,固定化技术发酵甜高粱茎秆汁液制取酒精较传统的游离态酵母发酵制取酒精可以缩短发酵时间2/3,酒精得率提高5.06%.     

富春江入库控制断面水位计算方法研究及误差分析

近年来受人类活动影响,富春江流域下垫面因子发生重大改变,传统水位流量关系无法应用。为应用水位比降法推求入库控制站有效入库流量,首先要对水位资料进行分析计算。以圣维南方程组为理论基础建立水动力学模型,考虑河道糙率的空间变异性,根据已有资料对富春江水库上游河道进行概化,模拟计算2013年女埠站洪水水位过程。同时采用经验相关法建立水位关系函数求解女埠站水位。2种方法模拟计算精度皆较高,水动力学方法在验证期洪峰模拟上优于经验相关法,而后者在洪水过程模拟上的确定性系数更高。由计算结果误差分析可知考虑水力要素时间变异性的水动力学模型能更好拟合退水过程,值得深入研究。     

乔灌篱沟蓄沟道土壤水分运动数值模

在分析乔灌篱沟蓄沟道布置和水分运动特点的基础上,建立了乔灌篱沟蓄沟道二维非饱和土壤水分运动模型,采用Galerkin有限单元法对方程进行数值求解.室内验证试验结果表明,土壤含水率和湿润锋的模型计算值与实测值吻合较好,说明乔灌篱沟蓄沟道土壤水分运动模型正确,采用有限元法求解可行.     

基于农田不平度的拖拉机机组输入谱推导与振动仿真

推导了拖拉机为两轴四轮、播种机为单轴两轮的六轮输入谱矩阵,可用于研究牵引式播种作业机组受农田不平度激励所产生振动的频域特性.用Roberson-Wittenburg(R-W)方法建立了牵引机组的22自由度动力学模型,然后根据R-W法建立了机组的动力学普遍方程,在对方程进行运动学和动力学分析的基础上,采用多步Geal-预估-校正法进行了时域求解,采用等效的统计线性化方法进行频域求解,对比分析表明动力学模型正确.     

汽车钢板弹簧柔性体建模与仿真研究

为了建立钢板弹簧的动力学分析模型,研究其在整车动力学分析方面的应用,利用HyperWorks建立板簧的有限元模型,并计算板簧的刚度.刚度模拟值与试验值能较好地吻合,验证了生成的板簧有限元模型和计算方法的正确性.在HyperWorks中通过定义模态综合法卡片CMSMETH和超单元边界自由度卡片的方法,生成板簧的模态中性文件.在ADAMS/CAR中导入板簧模态中性文件,并建立刚柔耦合的整车多体动力学模型.通过对整车模型进行平顺性脉冲输入仿真,并与试验结果对比,分析利用此方法建立的柔性体板簧在动力学方面的应用.由结果可知,建立的板簧能很好地反映动态特性,可用于整车仿真分析.     

甜橙果酒酿造工艺

以甜橙鲜果为原料,研究其果汁经酒精发酵生产甜橙果酒的工艺条件。在单因素试验的基础上,通过正交试验设计得出甜橙果酒发酵的优化工艺条件为活性干酵母用量0.15%,初始糖度23%,发酵温度30 ℃,发酵时间144 h,在此优化条件下果酒的酒精度为12.8%。所得果酒橙黄清亮,有甜橙香味和醇香。      

甜高粱联合收割机的研制

针对甜高粱收割的技术难点,提出了一种甜高粱收割机的设计方案,重点研究了割台的可伸缩茎穗兼收装置、上下输送装置、液压升降装置等关键部件的工作原理。通过试验,研究了甜高粱果穗和茎秆联合收获技术,自主创新研制的强制拨禾喂入、多组刀片分层扶持切割的收获割台,实现了果穗和茎秆的分层切断,分段长度无级可调,适应多品种、不同高度的甜高粱果穗的收获和茎秆的切割与铺放,解决了甜高粱脱粒及清选技术难题,为高秆植株作物茎穗联合收获技术的研究提供了参考依据。      

自走式甜高粱收割铺条机设计和试验

高粱具有生物产量高、营养丰富和糖分积累快等特点,是目前公认的最具有应用前景的可再生能源作物之一,而收获技术是制约甜高粱发展的关键因素之一。为了更好地解决甜高粱的机械化收获,设计了自走式甜高粱收割铺条机,介绍了设备的总体结构方案,并对其主要工作部件设计做了系统阐述,确定了主要工作部件参数和一些部件的设计思路,并通过试验进行了验证,为甜高粱机械化收获技术的研究提供了参考依据。      

小米红枣酸奶的研制

对小米红枣酸奶的工艺进行了研究,通过正交试验L9（34）确定了小米红枣酸奶的最佳配方:小米浆20%,红枣汁10%,蔗糖量8%,接种量4%,发酵时间5 h。产品具有小米、红枣特有的香气,口感细腻,酸甜适口,是一种具有保健功能的新型酸奶产品。      

Relationships between available soil water and indicators of plant water status of sweet sorghum to be applied in irrigation scheduling

Optimal crop production depends greatly on available soil water, and it is therefore important to know when and how much to irrigate in order to attain agronomic potential. In this work, plant indicators are used to assess water stress. These are compared with available soil water to find the critical point for irrigation scheduling of sweet sorghum. The experimental trial was carried out in Bečej, in the Vojvodina region, on a sweet sorghum crop, grown in moderate climatic conditions on a well-drained, deep chernozemolic meadow soil. Plant indicators tested were predawn and midday leaf water potential and crop and air temperature difference. All the methods were sensitive to water deficit in plants, but not all can be used for irrigation scheduling. The predawn leaf water potential was the most reliable parameter among those tested due to its relative independence from weather conditions and a valid indicator of plant water status. This was not the case with canopy-air temperature difference. The predawn leaf water potential corelation with available soil water indicates that the threshold value for irrigation scheduling of sweet sorghum is when the former has decreased to –0.45 MPa. This corresponds to a soil water depletion to about 10% of available water in the active root zone. The canopy-air temperature difference was sufficiently sensitive to indicate the onset of mild plant water stress, although it showed a certain threshold value when water shortage appeared, which occurred when the air and canopy temperature were the same. Received: 9 April 1996     

Evaluation of simplified water-crop yield models

Firstly theoretical considerations on three simplified water-crop yield models are given, which are subsequently used for the analysis of a large number of reported irrigation trials on alfalfa, sorghum and maize.Alfalfa (Medicago sativa L.), being a crop on which many irrigation trials have been carried out, was first selected for calibrating and testing the three models. Being the first crop for which these simplified relationships are tested, a number of alternative calculation procedures are tried out, using published data from experiments with varying water application.Sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) were next chosen for calibrating and testing. The most important difference between alfalfa on one hand and sorghum and maize on the other is that the latter crops are not used as forage crops, but for grain production, so that one is interested only in a part of the above-ground dry matter production. This leads to a new parameter in the model, the harvest index, which is the ratio between grain and above-ground dry matter production and depends on the distribution of dry matter in the plant during the growing period.Based on earlier work of De Wit (1965), the concept of standard production is presented as a reference type of potential crop production. Two available simplified water-crop yield models based on the concept of standard production are summarized.The Rijtema model treats the water-yield relationship as a diffusion process, by combining diffusion equations for transpiration and photosynthesis. The method therefore is based on functional relationships for the resistances involved. Respiratory losses are accounted for by a factor expressing photosynthetic efficiency. The original Rijtema model is amended by introducing correction factors for the effect of temperature on plant growth and a conversion factor from total dry matter production to harvestable product.The FKZ model is a Blackman-type production model in which a maximum production level is considered. The effect of the production factor water is accounted for by a simplified transpiration/photosynthesis relationship. Water use efficiency (P/E) is considered to vary only with crop-type and vapour pressure deficit. A modification is proposed in which water-use efficiency also depends on potential production conditions.A third, Linear model is derived from the Rijtema model. The Linear model is calibrated for alfalfa using 84 data from different regions all over the world. The validation is carried out using 85 data sets. Ninety-two per cent of the observed variation in yields is explained. For the model calibration for sorghum and maize, 58 and 83 data sets, respectively, from different regions were used. The validation of the model was carried out using 42 and 38 data sets, respectively.The calculation of grain production is based on different relationships with the calculated total dry matter production, depending on water stress in sensitive periods. The grain model is calibrated and tested for sorghum using 108 and 76 data sets, respectively, and for maize using 121 and 93 data sets, respectively. The model explains 81% of the observed variations in sorghum and maize grain yields in experiments under different environmental conditions.The simplified transpiration/photosynthesis used in the original FKZ model does not adequately describe the alfalfa data used. An improved version of this relationship, containing the same functional relationships as found for the Linear model, yielded significant results. The modified model explains 95, 80 and 74% of the observed variation in alfalfa, sorghum and maize yields, respectively, using the same data sets as for the Linear model.The functional relationships derived in the calibration of the Linear model are also introduced in the Rijtema model. A number of alternative relationships for photosynthetic efficiency, stomatal and mesophyll resistance are tried for alfalfa. A significant functional relationship is derived between mesophyll and stomatal resistance at a constant value (0.6) of photosynthetic efficiency. Testing the modified model reveals that 87, 72 and 69% of the observed variation in alfalfa, sorghum and maize yields, respectively, can be explained.All three modified models yield satisfactory results for estimating the effects of alternative water management strategies.     

益生菌发酵苹果汁过程中总酚酸变化与动力学研究

为了使苹果汁中结合态多酚变为游离态多酚,提高苹果汁的功能性多酚单体含量,利用嗜酸乳杆菌6005、植物乳杆菌21805和发酵乳杆菌21828混菌发酵复合苹果汁,分析苹果汁发酵过程中活菌数及理化成分变化,建立混菌生长和总酚酸变化动力学模型,并进行模型验证。结果表明：混合益生菌在复合苹果汁中生长良好,活菌数达到2.68×108CFU/mL,发酵过程中总糖含量下降,可滴定酸含量上升,总酚酸含量总体呈上升趋势,绿原酸及没食子酸等功能性酚酸类多酚单体含量增加;建立了复合益生菌发酵苹果汁的菌体生长动力学模型和总酚酸增加量变化动力学模型,模型理论值与试验值的平均误差小于10%,说明建立的动力学模型能够较好地预测混合益生菌发酵苹果汁中总酚酸的变化过程。     

两茬收割饲用甜高粱灌溉定额试验研究

为探索饲用甜高粱最佳灌溉定额和节水效果,设置了不同灌溉定额(2 400, 3 000, 3 600, 4 200, 4 800 m³/hm²)对两茬收割饲用甜高粱生长和生物产量的影响的田间试验.结果表明,甜高粱茎粗和株高的峰值分别出现在播后62 d和158 d.随灌溉定额增加甜高粱在形态上表现为株高增加、茎粗减小的趋势.在头茬收割(播后76 d)时,株高日增长率最大,为4.00~4.89 cm/d.两茬收割甜高粱鲜生物学产量为63.9~115.5 t/hm²,干生物学产量为12.7~21.4 t/hm²,全生育期耗水量为326.95~504.24 mm,鲜生物学产量WUE为15.53~24.63 kg/m³,干生物学产量WUE为3.89~4.51 kg/m³.灌溉定额为4 200 m³/hm²时,甜高粱总鲜、干生物量最大,灌溉定额为4 800 m³/hm²时,甜高粱总鲜、干生物量增幅不大.从节水和增加生物量角度而言,畦灌方式下的两茬收割饲用甜高粱全生育期灌水4次,灌水定额为1 050 m³/hm²,灌溉定额为4 200 m³/hm²的灌溉效果最佳.     

粟酒裂殖酵母发酵菊芋生产燃料乙醇试验

以菊粉为原料,研究了粟酒裂殖酵母的乙醇发酵性能,并考察了温度、初始pH值和菊粉质量浓度对乙醇发酵的影响,进而研究了粟酒裂殖酵母发酵菊芋汁和菊芋粉生产乙醇的情况.结果表明:粟酒裂殖酵母能发酵菊粉高产乙醇;该菌株最适发酵温度为30℃,最适初始pH值为4.0,在此条件下,菊粉质量浓度200 g/L时,乙醇质量浓度达到74.58 g/L,理论转化率为81.24%;直接发酵菊芋汁和菊芋粉获得更高的乙醇产率,理论转化率分别达到84.02%和86.09%.