工程车辆翻车事故中司机头部伤害与保护仿真

为了研究司机的头部在碰撞中的机械响应特性,该文采用有限元三维实体建模技术,建立了成人头部碰撞模型。通过虚拟试验方法使用成人头部模型对驾驶室内饰进行冲击分析,比较不同厚度和密度的聚氨酯泡沫对人体头部损伤评价指标的影响。结果表明：头部损伤值（HIC(d)）随着泡沫厚度的增加而减小,随着密度的增大,呈现先减后增的二次抛物线趋势。在驾驶室内壁覆盖18 mm厚的聚氨酯泡沫材料可以降低翻车事故中二次碰撞对司机头部的损伤。     

玉米农田行尺度土壤热特性变异特征及其对土壤含水量和温度的响应

农田土壤热特性受地表能量平衡、土壤特性和作物生长的影响,存在显著的时空变异性,而目前缺乏关于作物行尺度土壤热特性变异特征的研究。本研究采用定位试验,利用热脉冲技术监测了玉米农田行尺度四个位置处（1/2行间、1/4行间、棵下和棵间）两个深度（2 cm和4.5 cm）土壤热特性的时空变异规律,并分析了土壤温度和含水量对土壤热特性的影响。结果表明,在试验期间,热导率、热容量和热扩散率的变化范围分别为0.66—2.22 W/(m?K),1.46—4.49 MJ/(m3?K)和4.07×10-7—6.88×10-7 m2/s。降雨之后,热导率和热容量增加,且随着时间推移逐渐降低。2 cm深度的土壤热特性的波动较大,棵下位置土壤热导率和热容量值最大,波动最为明显;土壤热扩散率在1/2行间位置最大。在4.5 cm深度,各位置土壤热特性变化趋势基本一致,土壤热导率和热容量值在1/2行间位置最大,土壤热扩散率在棵间位置最大。综合两个土层数据得出1/4行间位置的热导率和热容量更具代表性。本研究中土壤热特性对土壤含水量的响应规律较为明显,随着土壤含水量增加,热导率和热容量线性增加,热扩散率则表现出先增加后降低的规律。在测定的土壤温度范围内,热扩散率随土壤温度增加呈上升趋势。该研究可以为农田水热管理提供理论依据。     

膨化干燥灰枣粉玻璃化转变及贮藏稳定性

为了综合水分活度及玻璃化转变理论构建状态图,获得灰枣粉的较佳贮藏条件,该文采用静态称量法和差示扫描量热法测定灰枣粉的吸附特性及玻璃化转变温度。结果表明,膨化干燥灰枣粉水分吸附的平衡干基含水率随水分活度的增加而增加,水分吸附等温线呈J型,描述灰枣粉水分吸附特性的适宜模型为GAB模型（R2=0.9968）;灰枣粉的玻璃化转变温度随含水率升高而降低,湿基含水率由0.064 g/g增加到0.175 g/g时,玻璃化转变温度由29.90℃降低到?35.02℃;灰枣粉干基含水率≤0.1223 g/g、贮藏温度≤?0.062°C时其稳定性较好,研究结果为灰枣粉加工、运输等过程中的贮藏条件提供理论参考。     

2种高分子保水材料对土壤持水能力的影响

采用离心机法,研究聚丙烯酸钠与聚丙烯酰胺2种高分子化合物在5种使用浓度（占干土质量0、0．01％、0．08％、0．2％与1％）的条件下对3种土壤（砂土、壤土、黏土）持水能力的影响。结果表明：3种土壤在0．01—1．5MPa水吸力时,持水能力随着2种高分子材料用量的增加而增加,砂土的作用效果较壤土、黏土更显著;2种高分子材料与土壤质量比控制在8／10000～2／1000范围内其作用效果较好,该用量条件下高分子吸持水分平均可释放83．7％供植物吸收利用。2种高分子材料对土壤持水能力的作用效果基本相同。     

反应温度和停留时间对纤维素水热解产物理化特性的影响

为了解纤维素在水热降解过程中产物的理化特性及其形成机制,该文对生物质主要组分—纤维素的水热降解特性进行了系统地研究,全面分析了反应温度和停留时间对纤维素水热产物分布的影响,并从产物的化学结构入手,对纤维素水热解机理进行了探索。随着温度的升高,重质油产率在250℃时达到最大,重质油组分变得复杂,焦炭产率逐渐降低。随着停留时间的延长重质油产率呈现先增加后降低的趋势,焦炭产率变化趋势较小,然而通过对焦炭的热重、红外、元素、电子扫描显微镜和X射线光电子能谱仪分析表明停留时间的延长可以提高焦炭的化学官能性,这为生物质水热机理的研究提供了依据。     

灌浆结实期高温对水稻剑叶生理特性和稻米品质的影响

以水稻耐热品系996和热敏感品系4628为材料,在灌浆结实期利用人工气候室进行高温处理（9：00-17：00,37℃,17：00-翌日9：00,30℃）和适温处理（CK,9：00-17：00,30℃,17：00-翌日9：00,25℃）22d,研究高温胁迫对水稻剑叶光合特性、膜透性、抗氧化酶活性及稻米品质的影响,并进行对比分析.结果表明：（1）灌浆结实期高温胁迫下水稻剑叶叶绿素含量、叶绿素a/b和净光合速率均降低,超氧化物歧化酶（SOD）、过氧化物酶（POD）活性表现出胁迫初期升高,高温处理5d后,随胁迫时间延长呈降低趋势,热敏感品系4628剑叶中叶绿素含量、净光合速率和抗氧化酶活性下降幅度大于耐热品系996;（2）高温下剑叶丙二醛（MDA）含量上升,相对电导率增加,热敏感品系4628增加幅度大于耐热品系996;（3）高温胁迫下垩白粒率和垩白度显著增加,精米率和整精米率显著降低,直链淀粉含量降低,蛋白质含量增加.灌浆结实期高温胁迫下,水稻功能叶抗氧化酶活性降低,膜透性增加,光合能力及光合产物的运输与卸载能力下降,可能是稻米品质降低的重要原因.     

生物降解聚氨酯包膜尿素化肥的研究

以天然吸水剂魔芋为掺杂料,参与合成生物降解型聚氨酯泡沫材料,用作为尿素化肥缓释包膜材料,研究结果表明通过调整魔芋粉的数量、水的份量及控制包膜的厚度,可控制尿素氮的缓释速度及包膜材料的降解速度。用水溶解方法测定试样缓释速率,用埋入法测定包膜材料的降解情况,结果表明该材料能够自然降解。     

纳米SiO2对聚乙烯醇基复合涂膜包装材料成膜透湿性能的影响

聚乙烯醇（PVA）由于其亲水性能而影响其在食品包装上的应用。本研究采用添加纳米SiO2对聚乙烯醇基复合涂膜包装材料进行改性,利用响应曲面方法研究SiO2、硬脂酸、戊二醛对三元复合涂膜材料成膜效能特性的影响及交互作用。结果表明：加入纳米SiO2可有效提高聚乙烯醇基复合涂膜包装材料的阻水阻湿性能,优化组成膜透湿率（8.18 g•m-2•d-1）比对照组（不添加纳米SiO2的PVA复合膜）降低26.61%（p<0.05）。硬脂酸、戊二醛对复合涂膜材料成膜的透湿率的影响与纳米SiO2存在显著的交互作用,每100 mL 5%（W/VH2O）的PVA溶液中纳米SiO2添加量在小于0.05 g范围内随着其含量增大,复合涂膜材料成膜透湿率随硬脂酸、戊二醛的比例增加而降低,阻水阻湿性能提高。     

高密度CO2对羊肉糜凝胶特性的影响

以羊肉糜为材料,以常压下热处理产生的热诱导凝胶为对照,通过测定凝胶色泽、pH值、持水力、质构特性以及微观结构,研究高密度CO2对羊肉糜凝胶特性的影响。结果表明,与热诱导凝胶（对照）相比,高密度CO2处理能使羊肉糜形成更加致密的凝胶结构,显著增加羊肉糜凝胶的L*值、硬度、弹性、内聚性和咀嚼性,但pH值变化不明显,持水力略有降低。表明高密度CO2作为一种新型的非热技术,可用于蛋白凝胶制品的制备。     

拔节期追氮对鲜食糯玉米粉糊化和热力学特性的影响

以苏玉糯1号、苏玉糯5号和渝糯7号为材料,研究了拔节期追氮量（N 0、150和300 kg/hm2）对鲜食糯玉米粉糊化和热力学特性的影响。结果表明,随着拔节期追氮量的增加,峰值黏度和崩解值下降,糊化温度升高,而谷值黏度、终值黏度和回复值呈先降后升趋势; 热力学特征参数中,回生值、终值温度、糊化范围和峰值指数受拔节期追氮量影响较小。原样品热焓值和回生后样品热焓值均表现为随着拔节期追氮量的增加呈先降后升趋势。糊化和热力学特征值对拔节期追氮量的响应不同品种间存在差异。鲜食糯玉米粉的理化特性存在显著的基因型差异,峰值黏度以苏玉糯5号最高,苏玉糯1号最低; 峰值温度苏玉糯1号和苏玉糯5号无显著差异,但均高于渝糯7号; 热焓值、回生值、糊化范围和峰值指数不同品种间相对稳定。相关分析表明,峰值黏度与原样品热焓值和峰值指数呈显著正相关; 崩解值与糊化温度及转变温度,回生值与淀粉的终值黏度和回复值呈显著负相关。在本试验条件下,拔节期追氮总体上使糯玉米食用品质降低,其中以苏玉糯5号在不追氮处理下的糊化和热力学特性较优,即峰值黏度、崩解值和热焓值较高,回生值较低。     

Corn Gluten Meal as a Thermoplastic Resin: Effect of Plasticizers and Water Content

Corn gluten meal (CGM) was studied to investigate the effect plasticizers and water have on its melt processing, and how this melting affects its mechanical properties. GCM containing varying amounts of water were mixed with 23% (w/w) plasticizers; (glycerol, triethylene glycol (TEG), dibutyl tartrate, and octanoic acid in a Haake bowl mixer at 80°C. The amount of water in the CGM affected the amount of torque produced in the Haake mixer. This increase in torque was correlated with how well the CGM melted in the mixer. SEM images of CGM melted in the mixer showed a more uniform homogenous structure when processed at its optimum moisture content. Glycerol, TEG, and dibutyl tartrate produced the greatest torque when the CGM contained <1% water. Octanoic acid produced the greatest torque when the CGM was processed at 8% moisture. CGM plasticized with TEG and octanoic acid were mixed at either their optimum moisture or at 9.6% moisture and then compression molded into tensile bars. The tensile strengths of the bars that were mixed at their optimum moisture content were significantly greater than the bars mixed at 9.6% moisture. The tensile properties of the CGM samples were affected by relative humidity (rh). The tensile strength decreased and elongation increased as relative humidity increased. CGM plasticized with TEG saw a greater changes in its tensile properties due to relative humidity than did octanoic acid plasticized CGM.     

Impact of Thiocyanate Salts on Physical,Thermal, and Rheological Properties of Zein Films

A new class of zein additives was investigated, thiocyanate salts. Ammonium, potassium, guanidine (GTC), and magnesium thiocyanate salts were added to solutions of zein in with various amounts of tri(ethylene glycol) (TEG), cast as films, and then tested to determine the impact that each salt had on properties. The presence of these salts affected solution rheology and intrinsic viscosity, demonstrating that the salts interacted with the protein. It was found that these salts acted as plasticizers, as they lowered the glass transition temperature of zein when evaluated with differential scanning calorimetry. In zein films in which TEG was present, these salts increased elongation and reduced tensile strength. However, unlike traditional plasticizers (such as TEG), when the salts were used as the only additive, elongation was not increased and tensile strength was not decreased. Of the salts tested, GTC in combination with TEG was found to increase elongation the most. The impact of salts on elongation was greatly affected by the relative humidity in which the samples were stored.     

三重耦合改性防止水基聚合物包膜肥料粘连并延缓释放

  【目的】  水基聚丙烯酸酯价格低廉、成膜性好,具有作为控释肥料包膜材料的潜力,但其玻璃转化温度低和耐水性差,导致用其制备的包膜控释肥料颗粒容易相互粘连并且养分释放过快。本研究旨在通过改性措施防止水基聚丙烯酸酯包膜控释肥料的粘连,并提升其控释性能。  【方法】  选用易获取且价格低廉的3种改性剂纳米二氧化硅、FeⅢ-单宁酸配合物和十六烷,通过简单的物理混合方式对水基聚丙烯酸酯进行耦合改性。采用动态热机械性能测定了改性前后包膜材料的玻璃转化温度和储能模量,采用接触角仪和水蒸气渗透装置分别测定了包膜的水接触角和水蒸气渗透率,采用静水溶出法测定了控释肥料的养分释放特征。为了更好地比较耦合改性的效果,将未改性的丙烯酸酯 (PA)、纳米二氧化硅单独改性的丙烯酸酯 (PA+Silica)、FeⅢ-单宁酸配合物单独改性的丙烯酸酯 (PA+Fe) 和十六烷单独改性的丙烯酸酯 (PA+HD)作为对照,分析了包膜材料性质改变对控释肥料养分释放特征的影响。  【结果】  耦合改性后包膜的玻璃转化温度提升了4.4℃,?70°C的储能模量提升了72.2%,水接触角提高了22°,水蒸气渗透率降低了13.6%。以上包膜材料性质的改变不但有效防止了控释肥料的粘连,也将其初期溶出率从未改性的38.29%降低到2.04%,控释期从未改性的8天延长到52天,释放模式也从和作物养分需求不匹配的“倒L”型变为和作物养分需求相匹配的“S”型。耦合改性改善包膜肥料粘连现象的原因为耦合改性将包膜材料的玻璃转化温度从20.40℃提升到了24.80℃。相关分析表明,包膜肥料初期溶出率的显著降低主要是因为FeⅢ-单宁酸配合物所降低的水蒸气渗透率和纳米二氧化硅所提高的玻璃转化温度和储能模量,而控释期的延长主要是由于十六烷所带来的水接触角的上升。  【结论】  采用纳米二氧化硅、FeⅢ-单宁酸配合物和十六烷耦合改性水基聚丙烯酸酯后,有效防止了控释肥料的粘连,显著提升了控释性能,并且该改性方式易于应用到工业生产中,是一种可行的水基聚合物包膜材料的改性方法。     

用于生物降解膜的聚己内酯与聚乳酸共混物制备及性能分析

聚乳酸农用薄膜在自然条件下能够降解为CO2和H2O,可以有效地避免传统农用薄膜废弃后造成的土壤和环境污染。将聚己内酯与聚乳酸共混可以改善聚乳酸脆性强和韧性差的特点。该文将不同质量比例的聚己内酯(polycaprolactone,PCL)和聚乳酸(polylactic acid,PLA)熔融共混后通过注射成型工艺制备了农业薄膜用PCL/PLA共混物,研究了PCL与PLA配比对共混物力学性能、热稳定性、结晶熔融行为以及表面润湿性的影响。结果表明:随着PCL含量增加,共混物的拉伸强度逐渐下降,而拉伸断裂伸长率和冲击强度则先增大后减小。PCL质量分数为50%时,共混物拉伸断裂伸长率和冲击强度分别达到最大值11.2%和6.4 KJ/m2;扫描电镜分析显示,PCL与PLA相容差,聚酯连续相种类及优势共同主导力学性能走向;热重分析表明,PCL的引入有效减缓了共混物热解速率,PLA质量分数增加共混物燃烧成炭率增大;差示扫描量热法分析表明,相对于PCL和PLA,PCL/PLA共混物玻璃化转化温度、熔融温度和结晶温度均产生了变化,但二者配料比对3种温度影响不明显;接触角分析表明,PCL/PLA共混物接触角相比于PCL和PLA均有所增大,水润湿性能不同程度的降低。综合考虑,PCL与PLA最佳质量比为50∶50。研究可为农业薄膜用聚己内酯与聚乳酸共混物的制备提供依据。     

Plasticizers for Zein: Their Effect on Tensile Properties and Water Absorption of Zein Films

Cast zein films are brittle at room conditions, so plasticizers are added to make them more flexible. The tensile properties of these films are known to be affected by the relative humidity (RH) of the ambient air. However, little is known about how the plasticizers are affected by RH. Cast zein films were plasticized with either glycerol (GLY), triethylene glycol (TEG), dibutyl tartrate (DBT), levulinic acid (LA), polyethylene glycol 300 (PEG), or oleic acid (OA). Mechanical properties and moisture content (MC) of the films were measured after one week of storage at 3, 20, 50, 70, 81, and 93% RH. The relative humidity of the films' storage had a great effect on the films' tensile properties. All the films' tensile strength and Young's modulus values decreased as RH increased. Films containing DBT, TEG, LA, or PEG showed an increase in the percent elongation with increasing RH. Films containing GLY, OA, or no plasticizer did not show any increase in percent elongation as RH increased. The changes seen in tensile properties with increasing RH are because of zein's hygroscopic nature. The absorbed water will further plasticize the zein. The type of plasticizer used determined the extent of the changes seen in the tensile properties of films stored at different RH values. Depending on the plasticizers used in the film, there were large differences in the amount of water absorbed. Films increasingly absorbed water depending on the plasticizer they contained in the order GLY > TEG > LA > PEG > NONE > DBT > OA. Films containing hygroscopic plasticizers like TEG absorbed too much water at high RH and became weak, but they absorbed enough water at lower RH values to not be brittle. While films containing the more hydrophobic plasticizer DBT were brittle at intermediate RH values, they had good mechanical properties at high RH values.     

Effect of water activity on the release characteristics and oxidative stability of D-limonene encapsulated by spray drying

The stability of encapsulated D-limonene, which was prepared by spray drying, was studied in view of the release characteristics and oxidation stability. Gum arabic, soybean water-soluble polysaccharide, or modified starch, blended with maltodextrin were used as the wall materials. The powders were stored under the conditions of 23-96% relative humidity at 50 degrees C. The release rate and the oxidation rate were closely related to the relative humidity. The relationship was not simple. Initially, the release rate and the oxidation rate increased with increasing water activity, but around the glass transition temperature, the rates decreased sharply to increase again at a further increase of water activity. The results could be explained by a change in the powder structure, where a glass capsule matrix was changed into rubbery state during storage.     

Aging of whey protein films and the effect on mechanical and barrier properties

This work focuses on the aging of whey protein isolate (WPI) films plasticized with glycerol (G) and sorbitol (S). The films were cast from heated aqueous solutions at pH 7 and dried at 23 degrees C and 50% relative humidity (RH) for 16 h. They were stored in a climate room (23 degrees C, 50% RH) for 120 days, and the film properties were measured at regular intervals. The moisture content (MC) of the WPI/G films decreased from 22% (2 days) to 15% (45 days) and was thereafter constant at 15% (up to 120 days). This affected the mechanical properties and caused an increased stress at break (from 2.7 to 8.3 MPa), a decreased strain at break (from 33 to 4%), and an increased glass transition temperature (T(g)) (from -56 to -45 degrees C). The barrier properties were, however, unaffected, with constant water vapor permeability and a uniform film thickness. The MC of the WPI/S films was constant at approximately 9%, which gave no change in film properties.     

聚氨酯/蒙脱土复合控释肥膜材的制备与性能

【目的】蒙脱土 (MMT) 是一种由纳米硅酸盐片层堆积的粘土矿物，具有优良的力学、热学及气体阻隔性能。本研究尝试了不同离子交换剂，以使其能在聚氨酯 (PU) 基体中充分剥层分散，制成力学性能与控释性能优良的复合控释肥膜材。【方法】试验选用3种有机离子交换剂十八烷基三甲基氯化铵 (SA1)、十二烷基双羟乙基甲基氯化铵 (SA2)、二甲基双十八烷基氯化铵 (SA3) 对MMT进行插层改性，然后通过原位聚合制备蓖麻油基聚氨酯/蒙脱土 (PU/MMT) 复合缓释肥膜材。纳米粒子及复合膜材的形态与结构用电镜扫描、傅里叶红外光谱、X射线衍射等方法进行了表征。采用吸水法和浸泡法测试了PU/MMT复合膜材的动态力学性能和热稳定性能及缓释性能。【结果】3种有机插层改性的MMT纳米粒子在PU基质中具有良好的分散性和相容性，纳米粒子的加入也明显改进了PU基质的动态力学性能、热稳定性能以及缓释性能，其中SA2改性MMT对复合膜材的动态力学性能和热稳定性影响最为明显，使基质PU的玻璃化转变温度 (Tg) 从30℃增加到80℃，热分解温度从300℃增加到330℃，因为SA2结构中的双羟乙基能使MMT与PU结合更加紧密；而SA3改性MMT制备的复合膜材缓释性能最佳，使尿素释放时间从30天增加到75天，因为SA3含有双长链有机结构。【结论】采用十二烷基双羟乙基甲基氯化铵或者二甲基双十八烷基氯化铵对MMT进行插层改性，可制备结构疏松、在聚合物中分散性良好的纳米粒子。添加改性蒙脱石纳米粒子可大大提高聚合物包膜材料的吸水性和稳定性，从而制备出阻隔性能优良、释放期理想且价廉质高的PU/MMT复合控释肥膜材。     

Effect of sodicity and salinity on disaggregation and tensile strength of an Alfisol under different cropping systems

The influence of electrolyte concentration (EC) and sodium adsorption ratio (SAR) on the tensile strength and aggregate stability via flocculation and dispersion behaviour of an Alfisol varying in organic carbon content due to different cropping systems was assessed using a split-split plot experiment involving eight soils, three levels of EC and seven levels of SAR.

Generally, at a given SAR value, mean weight diameter (MWD) increased with organic matter status of the soil in the following order: virgin pasture>wheat>wheat-fallow. As MWD decreased, the amount of dispersible clay increased at a given SAR indicating that more surfaces exposed due to slaking of aggregates led to more clay dispersion. Statistical analysis of changes in tensile strength with various factors showed that an increase in organic matter decreased the magnitude of changes in strength induced by sodicity because organic matter tends to increase aggregate stability (higher MWD). While individual soils had significant relationships between the tensile strength of the aggregates and the amount of spontaneously dispersible clay, this relationship was poor when the results of all soils were pooled together. The amounts of dispersible clay from dry aggregates were higher than from wet aggregates and dispersive breakdown of the aggregates of sodic soils occured irrespective of the mode of wetting. The most important factor in determining the soil strength was the amount of clay dispersed during wet-sieving analysis followed by MWD.     

Differential Scanning Calorimetric Study on the Effects of Frozen Storage on Gluten and Dough

Water transport from the gluten to the starch paste during frozen storage of a dough was studied by analysis of the differential scanning calorimetry (DSC) peak shape for gluten and dough. The results indicate that in gluten stored at ‐15°C, the water content in the gluten phase decreased by ≈1% over the first three weeks. An apparent steady state was attained over this period and the amount of ice did not increase further. Such changes were not observed for samples stored at ‐25°C. Qualitatively similar observations were made for dough stored at either ‐15 or ‐25°C. The greater sensitivity of dough to frozen storage is tentatively attributed to a slightly lower glass transition temperature in dough.