大颗粒低填充率外热式回转窑传热系数模型的构建

为了能较精确地预测大颗粒低填充率外热式回转窑内壁与颗粒间的传热系数,该文在对外热式回转窑传热机理分析的基础上,提出了回转窑内壁与物料颗粒间换热的基本构成为:窑内壁与气体介质间的导热、气体介质与颗粒间的对流以及窑内壁与颗粒间的辐射换热。在此基础上,建立了预测窑内壁与颗粒间总传热系数的数学模型,并以6 mm直径的氧化铝球为物料,在5%填充率下,分别在回转窑转速1,2,3 r/min,窑体壁面温度在220~420℃的11种不同壁温条件下测量了窑体内壁与颗粒间的传热系数,对模型进行验证。试验结果表明,模型预测的误差小于10%,可满足工程计算的精度要求;该文所采用的试验物料及试验条件下,在窑壁温度高于220℃时,辐射传热系数所占的比例高于75%,是总传热系数的主要构成部分。研究结果可为外热式回转窑传热机理的深入研究提供参考。     

常压列管式灭菌器研究

以对流换热理论为依据,对常压列管式灭菌器的结构、传热方式、换热系的计算及其设计进行了讨论和研究。这种灭菌器中的传热热阻主要发生在列管内壁与被加热物料之间的对流中。对牛奶等含水率大于85％的流体食品物料,其部分热物性参数可参照水的相应参数的变化规律推断计算。对其它物性参数可视其随温度或其它条件变化规律推算,以便在灭菌温度下物料物性参数未知的条件下进行有关的换热计算。其结果用经验数据和实验分别进行验算和验证是可靠、可行的,可在有关食品物料的热计算中推广应用。     

惰性粒子流化干燥机的研究

惰性粒子流化干燥是流态化干燥的特殊形式，适用于溶液、悬浮液、粘性浆状物料等液相物料的干燥，其技术关键是粒子表面对物料的均匀吸附、流化效果和干燥物料的及时脱离。本研究在设有搅拌机构的流化床内装填惰性粒子，进而提高传热传质面积和速率，并将干燥与粉碎合二为一。试验设备接近于实际工况，采用当量直径为4 mm的聚四氟乙烯颗粒为惰性粒子，以浆状物料为干燥对象，着重研究惰性粒子流化干燥机的干燥机理和设备结构，以及对搅拌、雾化、投料、传热系数、开孔率等影响因子进行试验分析，并对重要的因素进行了数据回归分析，从而找出惰性粒     

发酵柑桔皮渣流化干燥传热传质分析

为了开发高效合理的柑桔皮渣发酵—干燥成套设备,需要进行发酵柑桔皮渣的干燥机理分析、传热传质的研究。该文采用流化干燥方法对发酵柑桔皮渣的干燥进行试验研究,建立了小型的流化床干燥试验台,分析了风速、颗粒粒径、初始含水率等对发酵柑桔皮渣流化干燥过程中传热传质的影响。试验表明：流化床的传热传质性能与流体的物理性质、操作参数、颗粒本身的物理性质以及流化床的特性密切相关。试验结果表明,传热系数沿流化床床高增加而减小,在床高4～6 cm之间,传热系数减小的幅度较大;在风速、颗粒粒径、初始含水率3个影响因素中,风速对传热系数的影响最大,当风速从2.06 m/s增大到2.75 m/s时,床高2～4 cm区域的平均局部传热系数增大了近92%。根据试验结果建立了传热传质数学模型并获得了传热无因次准则方程式,为强化传热传质以提高干燥效果提供了理论依据。     

基于多参数耦合的蓄冷温控箱冷板对流换热参数优化

蓄冷温控箱利用低温相变材料储存冷量,通过缓慢释放调节并保持箱内温度,目前仍存在冷量释放速率无法控制、剩余冷量预测难等问题,而蓄冷板表面对流换热系数直接影响冷量的释放速率。针对以上问题,搭建了蓄冷板表面对流换热系数测量试验平台,研究不同环境及蓄冷板参数对表面对流换热系数的影响。采用二次回归正交试验设计方案,探究了蓄冷区进口空气流速、进口空气温度、蓄冷板传热面积以及蓄冷板间距对表面对流换热系数的影响,并对结果进行分析,建立了表面对流换热系数二阶预测模型,获得影响表面对流换热系数大小较显著的因素及较优的参数组合。试验结果表明：各因素间存在明显交互作用,进口空气温度和蓄冷板传热面积的交互效应最大;通过响应曲面法建立的表面对流换热系数预测模型,得到最优参数组合为：进口空气流速4 m/s,进口空气温度25 ℃,蓄冷板传热面积0.455 m2,蓄冷板间距0.04 m,R2值为0.927 4,变异系数CV为5.78%。回归模型计算结果与试验结果吻合,最大误差为3.58%,平均相对误差为2.69%,表明该模型可以快速、准确地预测不同条件下的蓄冷板表面对流换热系数。试验结果为蓄冷温控箱冷量释放速率精准调控及剩余冷量预测提供参考。     

基于覆盖层能量平衡法的园艺设施覆盖材料传热系数理论解析与验证

该文提出了一种园艺设施覆盖材料传热分析以及传热系数的理论计算方法,即覆盖层能量平衡法。该方法通过覆盖层辐射传热和对流换热的能量平衡,建立全面反映覆盖材料传热各主要影响因素的传热模型,得出了传热系数的理论解析计算方法,可根据覆盖材料的红外辐射发射率、反射率和透过率等热物理特性和保温比、角系数等与覆盖层构造相关的参数以及设施内外气温、天空辐射温度、植物与室内地面温度、室外风速等工作环境条件,定量分析覆盖层的传热,得出传热系数的理论计算值。     

日光温室保温被传热的理论解析及验证

为掌握日光温室保温被的传热及其保温特性,该文运用传热学理论,建立了模拟辐射、对流以及导热等形式的传热方程,在此基础上构建了日光温室保温被这类厚型覆盖材料的传热理论模型,编制了计算机程序。该模型通过对保温被内、外表面与环境间的有效辐射、投射辐射的分析,来确定辐射换热量;根据能量平衡的原理,建立了保温被表面通过对流传热、辐射传热的传热量与内部传热量之间的关系。所建立的计算方法与程序可根据覆盖材料的红外辐射特性、导热系数、覆盖层的构造参数及工作环境等条件,定量分析保温被覆盖层的传热,计算其传热量及传热系数值。试验测试结果表明,保温被的传热量及传热系数的理论计算值与试验测定值较为一致,该文的方法为保温被一类厚型覆盖材料提供了保温性定量分析评价的理论手段。     

胡萝卜带式穿流干燥的均匀设计试验研究

用胡萝卜对带式穿流干燥机的主要参数：风温、层厚、穿流风速、输送带线速度进行试验研究。使用了试验设计方法中新的方法—均匀设计,其特点是试验次数少,回归方程可靠度高,预测准确度高。确定热风温度75℃、物料层厚83 mm、风速1.0 m/s和线速500 mm/min可作为胡萝卜的带式穿流干燥机最佳参数组合。     

物料颗粒在滚筒式干燥机内停留时间的确定

通过对物料颗粒在滚筒内的运动分析,不仅确立了物料在干燥机内停留时间的计算公式,而且提出了滚筒式干燥机设计的两个重要条件,为滚筒干燥机的结构设计奠定了理论基础。     

温室多层覆盖传热的数值模拟与验证

为准确地掌握温室中不同材料和不同使用条件下多层覆盖的传热和保温特性,该文在前人研究的基础上建立了温室多层覆盖传热的理论模型,并开发了模拟其传热过程与计算传热量和传热系数的计算机程序,可根据覆盖材料的红外辐射特性、覆盖层构造参数以及工作环境等条件,定量分析覆盖层的传热情况,得出传热量以及传热系数的理论计算值。实测结果表明,传热量以及传热系数的理论计算值与试验测定值较为一致,表明该多层覆盖传热的理论模型具有较高的准确性。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.