熟化红薯热风干燥特性及数学模型适用性

为了为红薯干热风干燥工业化提供理论基础,该文研究了不同温度（60、70、80℃）、风速（0.8、1.2、1.6 m/s）和厚度（0.6、0.9、1.2 cm）条件下红薯的热风干燥特性。比较了12种数学模型在熟化红薯热风干燥中的适用性,结果表明Wang and Singh模型的拟合程度最高,R2值、χ2和RMSE值分别为0.998、0.000168和0.0117。计算了不同干燥条件下的有效水分扩散系数Deff和活化能Ea,有效水分扩散系数Deff随着干燥温度、风速和物料厚度的增加而变大,干燥活化能Ea为40.103 kJ/mol,可为其干燥工艺的控制提供技术依据。     

污泥低温干燥动力学特性及干燥参数优化

为了研究污泥的低温干燥动力学特性,以薄层污泥为研究对象进行了低温干燥试验,探讨了温度、薄层厚度以及风速对污泥水分比和干燥速率的影响,并对低温干燥参数进行了优化.结果表明:污泥低温干燥过程主要由升速和降速段组成,其中降速阶段存在第一、第二降速阶段;不同低温干燥条件下的第二临界含水率变化不大,大致在0.5g/g(干基)附近.使用决定系数R2、卡方χ2及均方根误差RMSE对6种常用干燥模型进行评价,结果表明Midilli模型的平均R2最大、平均χ2及RMSE最小,分别为0.9998、2.46×10-5、0.0042,是描述污泥低温热风干燥的最优模型.根据Fick第二定律和Arrhenius方程,得到5、10和15mm厚度污泥在50~90℃热风干燥的水分有效扩散系数和活化能.正交试验得到相对单位能耗最优干燥工艺为:温度90℃、风速0.8m/s、厚度10mm,平均干燥强度最优工艺为干燥温度90℃、风速0.8m/s、厚度5mm.试验结果可为后续研究污泥热泵干燥及太阳能-热泵联合干燥提供参考.     

哈密瓜片气体射流冲击干燥特性和干燥模型

为了提高哈密瓜制干品质、缩短干燥时间,该文将气体射流冲击干燥技术应用于哈密瓜片的干燥,研究了其在不同干燥温度（60、65、70、75和80℃）和风速（5、10、15和20 m/s）下的干燥曲线、水分有效扩散系数以及干燥活化能,并建立了气体射流冲击干燥哈密瓜片的数学模型。研究结果表明：哈密瓜片的整个干燥过程属于降速干燥,水分有效扩散系数在2.38～4.55×10-9 m2/s的范围内随着干燥温度和风速的升高而升高;通过阿伦尼乌斯公式计算出了哈密瓜片的干燥活化能为29.44 kJ/mol。通过决定系数R2、均方误差的根（RMSE）和卡方检验值（2）等拟合优度评价指标对各种干燥模型进行评价,结果表明：Modified Page模型能很好的预测哈密瓜片气体射流冲击干燥过程中的水分比变化规律。该研究为使用气体射流冲击技术工业化干燥哈密瓜提供了技术依据。     

基于Weibull分布函数的马铃薯丁薄层热风干燥特性

为了实现马铃薯的规模化热风干燥,提高脱水制品的品质、降低生产能耗和成本,该文以薄层干燥试验为基础,研究了鲜切马铃薯丁在不同热风温度（40、50、60、70、80、90℃）、风速（0.5、1.0、1.5、2.5、3.5 m/s）和切丁长度（2.5、5、10、15 mm）条件下的干燥曲线、水分有效扩散系数和干燥活化能。利用Weibull分布函数拟合了干燥曲线,并建立了风温、风速和切丁长度与模型参数的定量关系。研究表明：鲜切马铃薯丁的热风干燥过程服从 Weibull 分布函数（R2=0.991～0.999）,是典型的降速干燥过程,模型的尺度参数与热风温度、风速和切丁长度有关;模型的形状参数与风速和切丁长度有关,而温度对其影响不显著（P＞0.05）;水分有效平均扩散系数在1.859～12.509×10-9 m2/s之间,与热风温度和风速显著相关（P＜0.05）,而物料切丁长度对其影响不显著（P＞0.05）;几何尺寸值与干燥物料的切丁长度和风速有关;马铃薯丁热风干燥的活化能为19.107 kJ/mol。该研究可为马铃薯热风干燥提供理论和技术基础。     

鱼膨化饲料热风干燥动力学模型及湿热特性

热风干燥是水产膨化饲料加工过程中极为重要的工序。为了探究水产膨化饲料在热风干燥过程中的湿热特性变化规律,该研究以草鱼（成鱼）膨化饲料为对象,设置热风温度（60～100 ℃）和风速（0.5～1.5 m/s）2个试验因素,在自行设计的热风干燥机上进行干燥试验。结果表明,在同一风速条件下,饲料的干燥速率随着热风温度的升高而显著增大（P<0.01）。同样的,在同一热风温度条件下,增大风速可以提高干燥速率。使用Verma模型拟合上述试验数据,决定系数（R2）、离差平方和（χ2）、均方根误差（RMSE）和平均相对误差（e）的计算结果表明该模型对草鱼膨化饲料在不同干燥条件下的试验数据具有较高的预测精度。同时分别建立了Verma模型参数关于热风温度和风速的回归模型,且回归模型R2均大于0.979。低场核磁共振（Low-Field Nuclear Magnetic Resonance analysis,LF-NMR）的横向弛豫时间（T2）谱显示,随着干燥过程的进行,T21峰面积逐渐减小,即不易流动水占比显著减少（P<0.01）;而且弛豫曲线有整体向左偏移的趋势,说明水分与底物的结合更加紧密,自由度降低。红外热像图显示,在干燥时间为5 min时,饲料出现了边角效应;在干燥时间为15 min和20 min时,部分中心处饲料出现了过热效应。上述研究可为草鱼膨化饲料干燥工艺参数的选择提供参考,并为其他种类水产饲料热风干燥湿热特性的研究提供新思路。     

红外联合热风干燥白萝卜片的耦合建模与热质传递分析

为寻求红外联合热风干燥过程中物料内部热量传递的物理解释,克服水分输运现象不能直观获取的问题,该研究建立白萝卜片红外联合热风干燥过程中水分和温度分布的数值模型。考虑到干燥过程中物料扩散系数动态变化,对实现精准模拟产生干扰,该研究对比考虑温度、收缩相关扩散系数两种方式下单独热风干燥及红外联合热风干燥过程中的热质传递情况并进行试验验证。考虑到二维轴对称几何结构,采用COMSOL Multiphysics 5.2a对该系统的传热传质模型进行求解。结果表明：基于收缩相关有效扩散系数能够准确描述白萝卜片在单独热风及联合干燥过程中的热质传递情况, 单独热风和红外联合热风干燥模拟值与试验值的决定系数（R2）分别为0.893和0.911。红外辐射是影响传热传质速率的主导因素。具体表现为恒定干燥温度60 ℃条件下,红外联合热风干燥比单独热风干燥物料至安全含水率（10%）有效缩短21.4%时间（90 min）,红外联合热风干燥样品比单独热风干燥物料达到设定温度值（60 ℃）缩短36.0%时间。进一步研究表明有效水分扩散系数随红外辐射温度的升高而升高,传热、传质系数对物料升温及水分脱除影响显著。该模型为其他物料在联合干燥技术的模拟研究提供有益借鉴。     

污泥干燥模型选择及Weibull分布模型求解与分析

为了研究污泥薄层干燥的动力学模型、明确薄层干燥模型选取原则、分析模型参数影响因素及在干燥中应用,该研究搭建了污泥干燥试验台,对不同干燥温度（50、75、100、125 ℃）、不同风速（0.5、1.0、1.5、2.0 m/s）与不同污泥厚度（5、10、15、20 mm）的污泥进行干燥试验,利用Weibull分布模型对其干燥动力学曲线进行模拟并分析,建立了风温、风速和污泥厚度与模型参数的定量关系。从原模型与改进模型、因变量与自变量转换、多参数模型及初始条件等4个角度分析,选择Lewis、Page、Two-term exponential和Weibull分布模型进行拟合分析,发现污泥的热风干燥过程服从 Weibull 分布模型（R2=0.994～0.997）,是典型的降速干燥过程,降速阶段存在第一、第二降速段,模型的尺度参数（α）和形状参数（β）均与热风温度、风速和污泥厚度有关;第二降速段扩散系数大于第一降速段扩散系数,第一降速段活化能变化范围为12.91～17.12kJ/mol,第二降速段活化能变化范围9.56～15.05 kJ/mol。研究结果可为污泥干燥工艺参数优化及干燥设备研制提供参考。     

枸杞分段式变温热风干燥特性及干燥品质

为了提高枸杞干燥品质、缩短干燥时间和降低能耗,该文对枸杞分段式变温热风干燥加工工艺进行试验研究。试验表明:恒温恒湿干燥条件下,随热风温度升高,枸杞干燥时间缩短,但枸杞多糖、色泽、复水率等干燥品质变差;采用阶段变温干燥方式可较好地缩短干燥时间,同时防止干燥品质变差。通过试验确定最佳的分段变温干燥工艺条件为40℃(6 h)-50℃(6 h)-60℃,干燥湿度40%,料层厚度3层(单层8 mm),在此条件下,枸杞干制品营养色泽俱佳,复水性良好。另外,碱液(3%Na CO3溶液)浸泡预处理可提高枸杞干燥速率、保留其鲜红色泽。     

曲拉热风干燥工艺参数筛选及色泽品质评价

为了降低曲拉因干燥过程引起的褐变,保证产品干燥后色泽良好,同时为曲拉干燥设备及工艺提供理论依据,该研究选择热风干燥的方式,以干燥后产品的亮度值L*、红度值a*和黄度值b*为目标,利用数据标准化的综合评分方法对3个目标评分。根据响应面中心组合设计理论,探讨了热风温度、物料厚度和风速对曲拉热风干燥工艺的影响,建立二次多项回归模型,并对干燥工艺进行了优化。结果表明,3个因素对综合评分的影响大小依次为：热风温度、风速、物料厚度;曲拉热风干燥最佳工艺参数为：热风温度41℃,物料厚度10 mm,风速60 m/min,此时得到最大综合分为0.9012;工艺优化后曲拉的亮度值L*比牧区自然暴晒干燥方式提高了7.18（P<0.05）,红度值a*和黄度值b*分别极显著的降低了1.41和10.29（P<0.01）,过氧化氢值（peroxide value, POV）、硫代苯巴比妥酸反应底物值（thiobarbituric acid reactive substances, TBARS）及5-羟甲基糠醛（5-hydroxymethylfurfural, 5-HMF）值分别极显著降低了1.15 g/100 g、0.84 mg/kg和1.973 mg/L（P<0.01）。表明该干燥工艺可有效降低曲拉干燥过程中脂肪的氧化程度与美拉德反应的发生,改善产品色泽品质。研究结果为曲拉热风干燥设备及工艺提供了理论依据。     

板栗气体射流冲击干燥特性和工艺优化

为了解决板栗深加工中的干燥问题,将气体射流冲击干燥技术应用于板栗干燥,研究了板栗仁在不同风温（70、75、80和85℃）和风速（10、12、14和16 m/s）下的干燥特性;根据单因素试验结果进行了风温、风速和预处理（不烫漂、100℃热水烫漂和100℃蒸汽烫漂）的正交试验。试验结果表明：板栗的整个干燥过程属于降速干燥,风温和风速对板栗的干燥速率均有显著影响,但风温对其的影响比风速更为突出;正交试验各因素对明亮度、蓝黄值和感官评分的影响顺序为：预处理＞风温＞风速,对缩短板栗干燥时间的影响顺序为：风温＞风速＞     

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.     

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.     

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,     

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.