响应曲面法优化微波干燥白炭黑研究

基于中心组合设计的响应曲面法,研究了微波干燥温度、干燥时间和白炭黑厚度及其交互作用对白炭黑相对脱水率的影响,得到了影响因素与白炭黑相对脱水率之间的二次方数学模型,获得了微波干燥白炭黑的优化工艺条件,即干燥温度90℃,干燥时间32min,物料厚度10mm,此条件下白炭黑的相对脱水率为99.68%。所得物料经粉碎,采用行业标准和激光粒度仪进行表征测试,其加热减量为1.2%,灼烧减量为49.8%,平均粒度为11μm。     

纳米TiO2固相光催化降解高密聚乙烯

在高密聚乙烯(HDPE)中加入经表面处理的纳米TiO2粒子,用共混法制备HDPE-TiO2纳米复合膜.利用失重、FT-IR、SEM对光照前后的纯膜及复合膜进行表征.实验表明复合膜在空气中能被紫外光有效降解,且其降解速度远远大于纯膜的降解速度.紫外光照780h后,二氧化钛含量为1%的复合膜失重达到了58.1%,而纯膜的光失重率仅为21.2%.     

预处理对罗非鱼片冻干特性影响的试验研究

为了获得预冻及其预处理条件对冻干罗非鱼片性能的影响规律,以新鲜罗非鱼为原料,进行了不同的预冻速度和不同的冻干预处理试剂浸渍处理对冻干罗非鱼片的干燥过程和干燥品质的影响试验,获得了不同预冻处理条件下的冻干曲线和干燥温升速率曲线,并以剩余含水率,水分活度,复水率和色泽等指标进行比较分析。结果表明:预冻速度会影响罗非鱼的升华干燥时间,且预冻速度越小,物料随着温度的变化表现越平缓。在本实验条件下,对残余含水率要求不太高的罗非鱼片来说,1.5 cm/h预冻速度获得的干品综合指标较优;其次,以蔗糖/山梨醇,柠檬酸钠和海藻糖三种预处理试剂及其不同浓度进行预处理试验的结果表明,经柠檬酸钠预处理后可以有效提高样品的冻干速率,且以10%柠檬酸钠预处理效果最好,样品含水率为5.63%,其水分活度为0.3917,复水率为46.71%,而海藻糖对冻干样品具有一定的保护作用,获得样品最高复水率为51.33%,最大白度值为79.64%。     

鲜切菠菜在不同冷藏温度下品质变化的动力模型

通过正交设计确定了菠菜鲜切处理的最佳方案为用75 mg/L二氧化氯水溶液、0.5%氯化钠溶液分别浸泡10 min后,PVDC保鲜膜包装。然后将处理后的菠菜分别储藏于0℃、4℃、7℃、10℃,并测定了鲜切菠菜的失重率、叶绿素含量及菌落总数,跟踪样品品质随时间、温度的变化关系。结果表明,随着贮藏温度的升高和贮藏时间的延长,菠菜叶绿素含量减少;失重率则随着储藏温度的升高和贮藏时间的延长而增大;菌落总数也随着储藏温度的升高和贮藏时间的延长而增大。这表明鲜切菠菜0℃贮藏效果最好。基于实验数据,建立了失重率、叶绿素和菌落总数的动力学模型,获得了模型中的活化能参数,为流通过程中的货架期预测奠定了理论基础。     

MAP下圣女果货架寿命的影响因素研究

建立了圣女果MAP模型,在货架寿命内对不同包装方式和贮藏温度下圣女果的Vc含量、可溶性固形物含量、可滴定酸含量、失重率、感官品质5个指标进行测定。利用SPSS软件对试验数据进行了方差分析,结果表明:包装方式对圣女果失重率的显著性方差值sig=0.0120.05,为显著影响;温度对圣女果失重率的显著性方差值sig=00.001,为极高显著影响;贮藏温度对圣女果可溶性固形物的显著性方差sig=0.05,为一般显著差异。试验表明,使用LDPE与CPP薄膜材料包装可以显著延长圣女果货架期;低温贮藏可以进一步提高圣女果的保鲜效果。     

两步氧化法制备ZnO薄膜及其光催化特性研究

本文采用热蒸发法在玻璃衬底上沉积Zn膜,然后在氧气中通过两步热氧化制备ZnO薄膜。利用X射线衍射（XRD）、扫描电子显微镜（SEM）和紫外透过光谱等表征技术,研究了氧化温度对ZnO薄膜结晶质量和光学性能的影响。研究结果表明,两步氧化法在400℃下氧化1 h后的样品中除含有ZnO成份外,还有少量金属Zn存在;525℃下氧化1 h可以制备出疏松多孔的ZnO薄膜,其在紫外光和可见光范围内的透过率可达85%。通过太阳光和紫外光（254 nm）催化降解苯酚实验,发现两步氧化法制备的ZnO薄膜具有良好的光催化特性：太阳光照10 h后苯酚降解率达到56%,紫外灯下苯酚降解率高达86%。此外,ZnO薄膜的光催化重复利用实验表明,经过H2O2溶液清洗干燥处理后,ZnO薄膜可以基本恢复其光催化能力,此特性为ZnO薄膜的重复利用提供了很好的实验依据。     

遗传算法结合响应面法优化番茄红素纳米结构脂质载体的制备

目的 提高脂溶性番茄红素的生物利用率和稳定性。方法 采用熔融-高速剪切法制备番茄红素纳米结构脂质载体。以包封率、平均粒径为主要评价指标，进行单因素实验，并在单因素基础上通过遗传算法结合Box-Behnken响应面法对制备工艺进行优化。结果 遗传算法和Box-Behnken响应面法优化得到的理论包封率分别为86.208 2%、86.169 5%。通过验证实验得到实际包封率为(86.267±0.44)%，平均粒径为(121.8±5.20)nm。结论 结果表明遗传算法结合Box-Behnken响应面法优化番茄红素纳米结构脂质载体模型可靠。     

扇贝真空冷冻干燥过程中变温变压工艺的研究

以栉孔扇贝闭壳肌为实验材料,在冻干过程中采用两次变温和一次变压的过程参数调节法进行冻干实验,结果表明:第一次变温时的物料中心温度对冻干样品的复水率和能耗是有影响的,当物料中心温度为1℃时进行第一次变温调节,样品的复水率和复水速度最快,品质最好,且干燥能耗也最少.     

SCR催化剂中钒钨钛含量的测定

试验首先采用6种不同酸配比的酸溶法和2种碱熔法对SCR催化剂进行前处理,采用电感耦合等离子体质谱法测定样品中钒、钨、钛含量。实验发现:需添加氢氟酸,否则钨、钛溶出率极低,钨在高温下易挥发,采用碱熔法溶出率低。试验通过对酸添加量,微波消解温度和消解时间的考察,进一步优化酸溶法,并以电感耦合等离子体质谱法测定样品中钒、钨、钛含量。结果显示:采用8 m L盐酸,2 m L硝酸和1 m L氢氟酸,在180℃下微波消解30 min,为SCR最佳前处理方案,钒钨钛的回收率分别为101.0%,100.7%,101.7%,相对标准偏差分别为1.0%,2.2%,0.3%,结果满意。     

原子荧光法测定土壤中的硒

本文应用双道原子荧光光度计测定土壤中的硒。本文对样品的消解方式,仪器工作条件,共存元素的干扰及消除等方面进行探讨。在优化的分析条件下,硒的检出浓度为0.12μg/L,相对标准偏差为4.36%,测定值在标准样品值的不确定度范围内。实验表明,该方法操作简便,有较好的精密度和准确度。     

基于纸胶体系及烘干模式的水基胶固化时间测定及影响因素研究

目的 了解水基胶固化过程中水分散失的规律。方法 建立基于纸胶体系及烘干模式的固化时间测定方法，提出水基胶“有效固化”的概念，利用皮尔模型对水基胶干燥曲线进行拟合，并研究5种水基胶在不同干燥温度下的干燥曲线。结果 结果表明，皮尔模型可以较好地拟合水基胶的干燥曲线。固化率在80%～90%存在一个拐点，具体位置与干燥温度有关。当固化率达到70%时纸胶体系已基本完成黏合，对应的有效固化时间相对于完全固化时间可缩短74.60%～83.70%。在干燥温度一定时，不同水基胶的固化时间有一定的差异，其差异性主要表现在低温干燥区域。结论 综上所述，干燥温度一定时，低玻璃化转变温度、低粒径、高固含量、高黏度的水基胶的固化时间更短。     

Influence of air dehumidification on water evaporation in a food plant

To reduce the proliferation of bacteria inside food plants, cleaning and disinfection are performed daily following production. These operations are followed by drying during which the drying rate should be as high as possible. This study shows the influence of a dehumidifier on the water mass evolution on surfaces during the drying of a food plant. The temperature, relative humidity and water mass evolution were monitored under two conditions: with and without a dehumidifier. Comparison of the results shows that the drying rate is about 1.5 times higher when a dehumidifier is used. These data were used to develop a simplified heat and mass transfer model allowing the prediction of the temperature and drying rate at different locations. The results can help the manufacturer to evaluate the benefits of a dehumidifier and consider the use of other devices to achieve better airflow distribution or greater heat supply for certain surfaces.     

邻苯二甲酸二丁酯在加工中的变化及膳食暴露评估

目的选取萝卜为研究对象,研究食用加工对萝卜中邻苯二甲酸二丁酯(DBP)残留量及膳食暴露评估的影响。方法采用盆栽种植、模拟餐前加工和液相色谱检测方法,研究漂烫、腌制和干制处理对萝卜中DBP残留及膳食暴露的影响。结果经漂烫、腌制和干制处理后均会对DBP残留量有明显的影响,溶度参数、水分散失和DBP挥发是影响萝卜中DBP含量的3个关键因子。在漂烫加工中,DBP残留量和加工因子随着时间的增加都呈逐渐减小的趋势,消除率为0.96%～45.54%;在腌制加工中,DBP残留量和加工因子随着时间的增加呈先减小后逐渐增加的趋势,消除率为1.36%～44.74%;在干制加工中,DBP残留量和加工因子随着时间的增加呈先增加后逐渐减小的趋势,考虑到干制加工中水分会流失,通过校正含水量后消除率可达82.06%。对DBP残留量进行膳食暴露评估的结果表明,对采用漂烫、腌制和干制等3种加工方式加工后的DBP残留量比用初始值评估值最高可分别降低45.54%,44.73%和24.32%。结论适当的食用加工方式可以有效降低萝卜中DBP的残留量,提高萝卜食用的安全性,而引入加工因子后膳食暴露评估结果会更接近真实值。     

Concrete protection using acrylic latex paints: Effect of the pigment volume content on water permeability

Concrete can be protected by coatings, which may reduce the ingress of aggressive agents coming from external sources. Paints have a great importance on concrete durability due to the advantage of being applied to both newly built and old structures, the latter being for maintenance and repair purposes. Five acrylic latex paint formulations were prepared in laboratory. Their relative performance in inhibiting the ingress of water and their drying behavior were evaluated on concrete substrates. The relative absorption and loss of water over a length of time were determined on medium and high porosity concretes. The results showed a correlation between the paint pigment volume content and water permeability. The viability of using acrylic resin in architectural paint formulations for concrete protection against water penetration was confirmed.     

Thoughts about drying shrinkage: Scale effects and modelling

In this article, we propose a theoretical approach based on the mechanics of porous media that can be used to determine, simply and rigorously (some decoupling assumptions are proposed and defended), the expression for the drying shrinkage of a concrete element subjected to drying. We show that the expression for this drying shrinkage reveals a double nonlinearity with respect to relative humidity, in the form φ¹ln(h), where φ¹ is the porosity occupied by the liquid phase and h is the relative humidity. In light of this model, we analyze the two hypotheses, both classical and yet different, that, as an initial approximation, treat drying shrinkage as being proportional to the change of relative humidity, Δh, or to the change of water content, ΔC, in the material. We then establish, within a general framework, the well-known scale effect on the water content versus the size of a test specimen of any shape (i.e. not just cylindrical or spherical). From this result, we can identify the scale effects that follow—both on the weight loss and on the drying shrinkage and drying-related stresses. We show that the expressions proposed to account for these scale effects remain valid for different constitutive laws of concrete, provided that time is a factor only through the diffusion of water in the concrete. This therefore rules out,de facto, all laws of the viscoelastic, viscoplastic types etc., where time appears as such in the expression of the law of mechanical behaviour. Finally, for three simple constitutive laws—perfectly elastic, brittle elastic, and perfectly plastic—we establish the expression for the drying shrinkage of a drying specimen.     

Prediction of Powder Stickiness along Spray Drying Process in Relation to Agglomeration

The spray drying process consists of a fast convective drying of liquid droplets by hot air. Initially, the water activity (a_w) of a drop is close to 1. During drying, the drop surface a_w decreases while viscosity increases until reaching a sticky rubbery state before further drying. This can be observed for products such as carbohydrates, leading to particles sticking on walls (product losses) or to adhesion between particles leading to agglomeration. In this study, particle stickiness was investigated in a cocurrent pilot spray dryer by measuring drying air properties (temperature and relative humidity) at different positions. This allowed describing the evolution of temperature and mean water content of the drying drops. Two model products (maltodextrin DE12 and DE21) were spray dried varying process parameters liquid flow rate (1.8, 3.6, and 5.4 kg/h), air temperature (144°, 174°, and 200°C), airflow rate (80–110 kg/h), and rotary atomizer speed (22,500–30,000 rpm). The two products exhibit different drying behaviors in relation to their affinity towards water (sorption isotherms) and glass transition temperature evolution with a_w (stickiness). Depending on drying conditions and product, the drop stickiness was observed very rapidly, close to the atomizer, or later, along the chamber. This approach can be used to identify conditions and positions corresponding to sticky particles.     

钢纤维对超高性能混凝土干燥收缩的影响

研究了在(20±2)℃、相对湿度为(50±5)%的环境中钢纤维体积掺量为0%、1%、2%和3%的超高性能混凝土(UHPC)的干燥收缩。结果表明:UHPC在前7d的干燥收缩发展速率较快,7d后发展速率逐渐减缓;但当钢纤维掺量超过2%后,钢纤维对干燥收缩的改善作用明显降低,相比钢纤维掺量为2%的UHPC,3%掺量UHPC的干燥收缩仅仅降低了1.5%。钢纤维高弹模及它与基体的界面粘结有效降低了混凝土的干燥收缩,但钢纤维掺量过多可导致多孔薄弱的界面区增加,从而使其对混凝土的收缩抑制作用减小。粉煤灰对超高性能混凝土干燥收缩的抑制作用大于矿粉。提出的新的数学拟合指数公式相比于文献中常用的ACI和王铁梦公式与实测结果吻合度更好。     

Etude expérimentale du couplage hydro-chimique dans les bétons en cours de maturation: incidence sur les retraits

The concrete cover has to protect the reinforcement of structures and therefore must withstand environmental damage. This resistance is clearly linked to the degree of hydration of the concrete, that is the proportion of hydrates produced from cement and mixing water. Natural drying of a structure, when forms are stripped, leads to an evaporation of free and adsorbed water and to the reduction of hydration in the external layers. The resulting hydration gradient has been determined by means of thermogravimetric analysis of samples taken from drying test bars in a controlled atmosphere (20°C, 50% relative humidity). At the same time the hydration and drying effects were measured:

- evolution of the air's relative humidity inside the cavities of the test bars at various distances from their dried surface. Hygrothermal probes were used for this purpose.

- evolution of autogenous and total shrinkage and consequently of drying shrinkage.

Drying and autogenous shrinkages have been linked to weight loss and internal relative humidity, respectively. These correlations can be justified theoretically.     

血管真空冷冻干燥过程的传热传质研究

本文采用无接触式称重法监测猪主动脉冷冻干燥过程,实时获取脱水速率,针对升华过程,通过采用准稳态传热模型结合脱水速率的变化来进行计算,获得升华温度、升华界面位移及传热量的变化规律.冻干参数分别设定为:预冻结温度-40 ℃、一次干燥-20℃、二次干燥10 ℃:、冻干箱压力10 Pa.结果显示,样品的平均含水量为74.24％...     

镭射纸印品表面油墨爆色问题研究

针对镭射纸烟包印刷,根据标准的印刷条件及过程,使用IGT印刷适性仪在镭射纸标准样张上印制UV油墨,通过实验研究镭射纸墨层干燥程度、纸张含水量与爆色之间的关系。研究结果表明:墨层干燥程度和纸张含水量对镭射纸印刷品爆色的产生影响明显,墨层干燥程度越高,爆色越容易发生,含水量也必须控制在一定范围内;对于镭射纸的印刷,在保证墨层初干性的前提下,纸张含水量为8%、墨层干燥度在80%~85%之间最好,此时,镭射纸的爆色率最低。