糖类对南美白对虾肉玻璃化转变温度与状态图的影响

为提高南美白对虾肉(PV)的贮藏稳定性,研究了蔗糖、菊糖和海藻糖对PV玻璃化转变温度(Tg)与状态图的影响。采用静态称量法研究了25℃下PV和按虾肉质量添加10%蔗糖(PV-S)、10%菊糖(PV-I)和10%海藻糖虾肉(PV-T)的吸附等温线。采用差示扫描量热法分析了PV、PV-S、PV-I与PV-T的Tg和冻结点温度(TF)。分别采用Gordon-Taylor方程和Clausias-Clapeyron方程拟合Tg与TF数据,构建了虾肉的状态图,探讨了添加糖类对PV的Tg与状态图的影响。结果表明,PV、PV-S、PV-I与PV-T的水分吸附等温线呈III型,GAB模型为描述PV、PV-S、PV-I与PV-T水分吸附特性的最适模型。PV、PV-S、PV-I与PV-T的平衡含水率随着水分活度aw的增大而增大。aw一定时,平衡含水率随着糖类添加而降低。添加糖类降低了PV的单分子层含水率。PV、PV-S、PV-I与PV-T的Tg随着含水率增加而降低。相同aw时,Tg值高低顺序依次为PV-I、PV-T、PV-S、PV。根据状态图,PV、PV-S、PV-I和PV-T的最大冷冻浓缩溶液时的玻璃化转变温度T'g分别为-71.35、-64.76、-58.36、-59.36℃,与之对应的溶质含量分别为73.2%、73.4%、72.6%、73.4%,即非冻结含水率分别为26.8%、26.6%、27.4%、26.6%。添加糖类尤其是菊糖与海藻糖能显著提高南美白对虾肉的贮藏稳定性,延长其货架期。     

真空干燥雪莲果粉玻璃化转变温度与贮藏稳定性研究

采用差示扫描量热法测定了真空干燥雪莲果粉(YP)和按总固形物质量比为1∶1添加麦芽糊精的雪莲果粉(YP-MD)玻璃化转变温度T g,分别采用GAB模型和Gordon-Taylor方程拟合水分吸附和T g数据,构建YP和YP-MD的状态图,探讨添加麦芽糊精(MD)对雪莲果粉临界水分活度和临界含水率的影响。结果表明,雪莲果粉的T g随着含水率升高而降低,YP的湿基含水率由5.95%增加至30.88%时,T g由15.8℃降低至-72.6℃;YP-MD的湿基含水率由5.11%增加至27.66%时,T g由30.5℃降低至-53.5℃。添加MD显著增加了雪莲果粉的T g。温度25℃时,YP和YP-MD的临界干基含水率为0.0455 g/g和0.0723 g/g,临界水分活度为0.12和0.27。因此,添加MD能显著增加雪莲果粉的临界含水率和临界水分活度,从而提高雪莲果粉的贮藏稳定性。     

雪莲果吸附等温线及热力学性质研究

采用静态称量法研究了雪莲果(包括纯雪莲果粉(YP)和按总固形物含量比例为1∶1添加麦芽糊精(MD)的雪莲果粉(YP-MD))在温度15、25、35℃时的吸附等温线;采用7种常用数学模型拟合试验数据,得到用于描述雪莲果吸附特性的最适模型;探讨了雪莲果的热力学性质(如净等量吸附热、微分熵、熵焓互补和扩张压力)及添加MD对雪莲果水分吸附特性和热力学性质的影响。结果表明,雪莲果水分吸附特性为Ⅲ型等温线,GAB模型为描述雪莲果水分吸附特性的最适模型。YP和YP-MD的平衡含水率随着水分活度a w的增加而增加。添加MD降低了雪莲果的单分子含水率M0。温度15~35℃时,YP和YP-MD的M0范围分别为15.04%~9.04%和8.80%~5.91%。雪莲果的净等量吸附热q st和微分熵S d随着含水率的增加而降低,YP和YP-MD的含水率由6.33%增加至75.29%时,其q st分别由67.44 kJ/mol和66.17 kJ/mol降低至62.23 kJ/mol和62.12 kJ/mol,YP的S d总高于YP-MD。雪莲果的扩张压力随着a w的增加而升高,随着温度的升高而降低;而在相同a w和温度下,YP的扩张压力总高于YP-MD。YP和YP-MD的水分吸附过程均为熵驱动。     

芒果玻璃化转变与状态图研究

研究了25℃下芒果的吸附等温线,实验数据采用GAB模型进行非线性拟合,结果表明芒果的吸附等温线呈"J"型,其单分子层干基含水率为0.107 g/g。芒果的状态图由冻结曲线、玻璃化转变温度曲线和最大冻结浓缩状态组成,其中冻结温度和玻璃化转变温度由差示扫描量热仪(DSC)测量得到。冻结温度和玻璃化转变温度的实验数据,分别采用Clausius-Clapeyron方程和Gordon-Taylor方程进行非线性拟合。实验结果显示,最大冻结浓缩状态时的固形物湿基质量分数为84%,在此状态下的玻璃化转变温度为-52.9℃。状态图的建立能够预测芒果贮藏过程的稳定性,并且能够提供最适干燥或冷冻加工条件。     

豌豆种子吸附等温线与热力学性质研究

采用静态称量法测量30、40、50℃时豌豆种子的吸附等温线,对实验数据进行非线性拟合,并通过对净等量吸附热、微分熵、焓熵补偿、扩张压力、净积分焓和净积分熵等热力学性质参数的研究,分析种子吸附特性和进一步揭示吸附机理,为选择和优化种子干燥和贮藏条件提供理论依据。实验结果表明,温度恒定时,平衡含水率随水分活度升高而升高,吸附等温线属于类型Ⅱ且GAB模型拟合效果最佳(R2=0.998 9,误差平方和为4.52×10-5);净等量吸附热和微分熵随着平衡含水率升高而降低的规律符合焓熵补偿理论,该理论反映出吸附过程是非自发反应,属于焓驱动,而当干基含水率达到25%时,净等量吸附热值接近纯水的汽化潜热(43.30 k J/mol);种子吸附过程的扩张压力随水分活度升高而升高,随温度升高而降低,当扩张压力一定时,净积分焓和净积分熵随着平衡含水率升高而降低,净积分熵达到最小值后逐渐升高,此最小值在30、40、50℃温度条件下分别为-137.79、-140.29、-137.74 J/(mol·K),对应的水分活度和平衡含水率分别为0.017、0.045、0.062和2.7%、2.5%、2.4%,这些条件可作为豌豆种子贮藏的最稳定条件。     

热泵干燥南美白对虾品质特性与玻璃化转变关系研究

针对南美白对虾热泵干燥过程中常出现物理、化学反应导致虾肉品质下降,而其机理又尚未明确的问题,采用静态称量法研究了南美白对虾肉的解吸等温线,利用差示扫描量热仪测定了虾肉的玻璃化转变温度(Tg)。分别采用GAB模型与Gordon-Taylor方程拟合水分吸附与Tg数据。虾肉在热泵干燥温度35℃、风速1.5 m/s下进行干燥,每隔1.0 h取样,分析虾肉品质特性(色泽、收缩程度、硬度与韧性和虾青素质量比)。基于玻璃化转变理论,阐明虾肉热泵干燥品质变化机制。结果表明,虾肉热泵干燥过程中,基质处于橡胶态,体系流动性增加,导致干制品品质下降。     

北方旱作农业区蓄水保墒耕作模式研究

分析了北方旱作农业的现状,提出了适合东北垄作区的三年轮耕法和西北黄土高原区的自然降水高效利用技术,并对其进行了试验。东北耕法：秸秆还田使土壤含水率提高10%,土壤有机质3年提高0.06个百分点,土壤容积密度降低0.09g/cm^3,深松使0-100cm土层土壤含水率提高26.2%,少耕精播土壤含水率提高3个百分点;西北新耕法：冬小麦蓄水率提高18.5%,水分生产效率提高25.6%;春玉米在0-10cm土层,含水率提高30%,水分生产效率提高47.6%。2年连续秸秆还田试验,有机质质量分数增加0.05%-0.1%,全氮质量比增加0.1g/kg左右。     

不同复合磷酸盐添加量下牛肉糜理化特性研究

利用核磁共振仪(NMR)、扫描电子显微镜(SEM)、傅里叶变换红外(FITR)、旋转流变仪(DHR)等研究复合磷酸盐添加量(质量分数0～0.5%)对牛肉糜的水分分布、结构、流变学特性的影响。结果表明,随着复合磷酸盐添加量的增加,牛肉糜含水率增加、蒸煮损失减少、p H值增加,添加量在0.2%之后各指标基本保持稳定。添加量为0.2%时,与空白对照组相比,含水率增加了5.87个百分点,蒸煮损失率减少了8.58个百分点,p H值从5.7上升到6.4;复合磷酸盐可以缩短肉糜体系与结合水、不易流动水的横向弛豫时间T21、T22(p 0.05),说明复合磷酸盐的添加提高了对水的束缚能力。随着复合磷酸盐添加量的增加,蛋白网络孔洞更加密集,孔径更加细小。与热处理前相比,热处理后的牛肉糜α-螺旋、β-折叠相对含量上升,β-转角相对含量下降;热诱导凝胶形成后,随着复合磷酸盐添加量的增加,α-螺旋相对含量由34.34%降至26.76%、β-转角相对含量由17.41%增加至29.41%。添加复合磷酸盐会降低牛肉糜的储能模量、损耗模量和损耗角正切值,添加量为0.2%的处理组损耗角正切值在升温过程中变化最为剧烈。因此,复合磷酸盐使牛肉糜体系结构疏松,与结合水、不易流动水的结合程度增强,保水性提高,蛋白质二级结构趋于无序化。复合磷酸盐添加量为0.5%时,结构最为疏松;添加量为0.2%时,保水效果最显著。     

水分管理及生物质炭对稻田土壤含水率及pH值的影响

【目的】我国亚热带地区为典型的双季稻种植区,水分管理多采用长期淹水和间歇灌溉2种方式,灌溉方式的不同会影响土壤含水率的差异,势必会影响土壤酸碱性的改变。添加生物质炭可改变土壤性质。探明稻田淹水灌溉和间歇灌溉条件下添加生物质炭对双季稻田土壤水分及酸碱性的影响。【方法】采用田间小区试验,研究水分管理方式(长期淹水(CF)和间歇灌溉(IF))及生物质炭施用量(0、24 t/hm~2(LB+IF)和48 t/hm~2(HB+IF))对亚热带双季稻田土壤含水率及pH值的影响。【结果】与长期淹水相比,早稻季和晚稻季间歇灌溉的土壤含水率并没有显著降低。生物质炭添加并未显著影响早稻季和晚稻季土壤含水率,但在休闲季生物质炭处理的土壤含水率有所降低。研究期间,CF、IF、LB+IF和HB+IF处理的土壤含水率周年均值分别为47.35%、39.58%、36.81%和39.02%,与长期淹水相比,间歇灌溉降低了全年的土壤含水率,降幅达16.41%,而生物质炭对间歇灌溉稻田土壤含水率影响不大。与长期淹水相比,早稻季和晚稻季间歇灌溉处理的土壤pH值分别显著降低了0.22和0.57个单位,休闲季不同水分管理方式之间的土壤pH值差异不显著。由于生物质炭本身呈碱性,添加到土壤后可增加土壤pH值,且随着生物质炭添加量的增加而增加。与IF处理相比,早稻季和晚稻季生物质炭处理的pH值分别增加了0.23～0.68个单位和0.17～0.60个单位。【结论】水分管理可影响双季稻田土壤含水率和pH值。间歇灌溉降低了亚热带地区双季稻酸性土壤的pH值。生物质炭添加,尤其是高量生物质炭添加,可在一定程度上缓解间歇灌溉对酸性土壤pH值的降低作用。     

枸杞的平衡含水率测定试验研究

利用WS/08-01型调温调湿试验装置,测得枸杞在温度为25℃、相对湿度为10%～90%范围内的吸湿和解吸平衡含水率数据,获得在该温度下的吸湿和解吸等温线,找到了枸杞干果的安全贮藏条件.试验结果表明:在环境湿度较大和枸杞含水率较高时,出现霉变现象;当湿度下降和枸杞含水率下降时,霉变随之减弱;当枸杞总水分含量大于40%时,出现霉变现象;空气相对湿度大于70%时,霉变现象严重.     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。