马占相思树皮中原花色素提取工艺及其生物活性的研究

通过正交试验优化了马占相思树皮中原花色素的3种提取方法的最佳提取工艺条件。结果显示,传统溶剂提取法的最佳工艺为：60%乙醇、70℃、70 min、料液比1∶18（g∶mL,下同）,原花色素得率为7.42%;微波辅助提取法的最佳工艺条件为：60%乙醇、微波功率200 W、微波时间8 min、料液比1∶18,得率为7.05%;超声波辅助提取法的最佳工艺为：70%乙醇、超声波温度50℃、超声波时间50 min、料液比为1∶16,得率为8.57%。超声波辅助提取法效果最好,浸提温度低,得率高。进一步对超声波提取物不同溶剂萃取物的体外抗氧化活性和抗肿瘤活性进行了研究。结果表明,乙酸乙酯萃取物对DPPH·清除效果最好,其半数抑制浓度（IC₅₀）为17.94 mg/L,低于对照样维生素C（Vc）的IC₅₀值;乙酸乙酯萃取物对人肝癌细胞Bel-7404具有明显的抑制效果,IC₅₀值为4.86 mg/L,与抗肿瘤药依托泊苷效果相当。     

马占相思栲胶浓胶波美度与浓度换算关系及浸提、磺化工艺研究

研究了马占相思栲胶主要生产工序的工艺参数。结果得出：马占相思栲胶浓胶在20 ℃时的波美度（y,°Bé）与浓度（x,kg/L）的关系式为： y=1.2+40x。不同温度（T,℃）下,实测波美度（y’）换算为20 ℃时的波美度（y,°Bé）与温度的关系式为： y=y’+（T-20）/15;浸提工艺：马占相思树皮400 g,吸水率210%,头步加水1 200 mL,以后每步加水800 mL,浸提首罐温度100 ℃,尾罐温度128 ℃,浸提时间12 h,添加焦亚硫酸钠量助浸为气干原料质量的1.8%,栲胶得率为 81.9%,单宁得率为90.6%。磺化工艺：在 85 ℃下,添加焦亚硫酸钠（Na₂S₂O₅）量为栲胶绝干质量的6%,反应时间为 2 h,磺化后得栲胶产品的单宁含量为67.8%,不溶物为3.2%,pH值为4.5,总色度为9.6。其他工艺同杨梅栲胶生产工艺。     

Kiln Drying of Acacia mangium Willd Wood: Considerations of Moisture Content before and after Drying and Presence of Wet Pockets

Acacia mangium is an important plantation species cultivated in Costa Rica and other tropical countries worldwide. However, wood uses have been limited due to drying-related problems such as high initial moisture content (MC_i) and high variability in final moisture content (MC_f). The objective of this study was to investigate the causes of these problems. Climatic conditions where trees grow, tree height, grain pattern, drying schedules, distance from pith, and sapwood or heartwood presence were considered. Results showed an average MC_i of 127% ranging from 58 to 186%. MC_i variation was influenced by climatic conditions, tree height, and grain pattern. Average MC_f was 19%, ranging from 9 to 52%. Lack of MC_f uniformity after drying is influenced by tree height, drying schedule, and the interaction of both factors. Wet pockets were also found to develop during drying. Lumber from trees growing in humid tropical climates subjected to a low relative humidity drying schedule as well as rift-sawn or double rift-sawn lumber was likely to develop wet pockets.     

城市污泥与木屑混合薄层干燥实验及动力学分析

角度研究了比,添加木通过对纯污泥和添加木屑的污泥进行薄层干燥对比实验,分别从混合比例、薄层厚度、干燥温度、风速木屑添加对污泥干燥特性的影响,并引入薄层模型对其干燥过程进行模拟。结果表明：与纯污泥干燥相屑后污泥干燥速率明显加快,且木屑添加比例越大、薄层越薄、干燥温度越高干燥速率越快,风速对干燥速率的影响不大;Wang—singh模型能很好的描述两种污泥薄层干燥,利用费克第二扩散定律导出的无限平板公式求出纯污泥和添加木屑的污泥在温度120℃～170℃时的有效扩散系数分别为6．13×10-6m／s～1．11×10-5m／s、1．07×10-5m／s～1．67×10-5m／s;由阿伦尼乌斯方程分别求得活化能为Es=16．67kJ／mol、Es=12．97kJ／mol。     

Convective Drying Kinetics of Red Chillies

The drying kinetics of four varieties of chillies (Pb-Lal, Pb-Guchhedar, Pb-Surkh, and CH-1) was studied. The chillies (pricked and unpricked) were pretreated in the dip sol solution. The treated chillies were dried in an automatic weighing experimental dryer at selected temperatures (45°, 50°, 55°, 60°, and 65°C). The results indicated that drying took place in the falling rate period. Out of three models considered, Page's model was found to be the most suitable for describing the drying behavior of chillies. The dependence of drying constant on temperature was analyzed using an Arrhenius equation. The variety Pb-Lal has the maximum value of activation energy (42.59 kJ/mol), which is also reflected in the reduced drying time for this variety. The results of quality studies of dried chillies in terms of capsaicin content and coloring matter indicated that the Pb-Lal variety had acceptable capsaicin content of 532.08 µg and coloring matter of 73.8 ASTA.     

Convective Drying Kinetics of Red Chillies

The drying kinetics of four varieties of chillies (Pb-Lal, Pb-Guchhedar, Pb-Surkh, and CH-1) was studied. The chillies (pricked and unpricked) were pretreated in the dip sol solution. The treated chillies were dried in an automatic weighing experimental dryer at selected temperatures (45°, 50°, 55°, 60°, and 65°C). The results indicated that drying took place in the falling rate period. Out of three models considered, Page's model was found to be the most suitable for describing the drying behavior of chillies. The dependence of drying constant on temperature was analyzed using an Arrhenius equation. The variety Pb-Lal has the maximum value of activation energy (42.59 kJ/mol), which is also reflected in the reduced drying time for this variety. The results of quality studies of dried chillies in terms of capsaicin content and coloring matter indicated that the Pb-Lal variety had acceptable capsaicin content of 532.08 µg and coloring matter of 73.8 ASTA.     

Drying Kinetics of Pinus Rqdiata Boards at Elevated Temperatures

ABSTRACT

From the numerical results of a rigorous, mathematical model, the rate–o–drying curves for high–temperature seasoning of Pinus radiata board show that the drying process can be divided into three periods. Based on the mechanistic picture of moisture movement and differences in the movement in each period, this paper simplifies the model by using the concept of the haracteristic drying curve.

In heartwood drying, the first period is very short (5–15 minutes), hence it can be neglected, whereas for sapwood, the first period is substantial with the drying rate being taken as constant in the analysis. Since the physical characteristics of the second and third drying periods are different, separate characteristic drying curves have been developed for each period. It has been found that common normalised drying curves are able to describe the results generated from the earlier model for normal range of kiln conditions over the examined ranges in dry–bulb temperatures of 1 10–140°C, wet–bulb temperatures of 70–90°C and air velocity of 3–7 m s^-1. Therefore. the derived simplified model can directly be used to calculate kiln–wide variations in moisture content and drying rate.     

亚硝酸钠与氯化铵反应动力学研究

研究了在盐酸催化的亚硝酸钠(NaNO2)与氯化铵(NH4C1)反应动力学,结果显示:亚硝酸钠与氯化铵在水中的反应为二级反应;其速率常数与该体系中氢离子的浓度成正比;活化能为50.26 kJ/mol;亚硝酸钠与氯化铵反应的动力学方程为dC/dt=-2.066×107CH+e-6045/TC2.     

三种木材的裂解动力学研究

在氮气氛和不同的加热速率下对三种木材(马尾松、棉杆和杉木)进行了热重分析.同时研究了碳酸钠对这三种木材热解的催化效应.运用Popescu法从22种动力学机理函数中寻求裂解的最概然机理函数并计算裂解的动力学参数.结果表明,Zhuralev,Lesokin and Tempelmen(Z-L-T)方程为最概然机理函数.根据Z-L-T方程计算的动力学参数表明,在裂解的低转化率范围,碳酸钠可以降低表观裂解活化能,而在裂解的高转化率范围,碳酸钠可以增加表观裂解活化能.根据木材的结构成分对碳酸钠的催化行为进行了分析.     

Multiphase Thermo-Hydro-Mechanical Model for Concrete Under Drying at High Temperatures

This article presents a numerical study for the analysis of the thermo-hydro-mechanical behavior of concrete subjected to high temperatures. Concrete is considered as a multiphase porous medium. The model, describing the strong coupling between mass, heat, and momentum transfers, takes into account the dehydration of the solid skeleton caused by a temperature increase. Simulations of the governing equations are presented in a two-dimensional configuration using the finite element method. Drying kinetics and mechanical behavior of concrete are presented and discussed in terms of moisture content, temperature, gas pressure, porosity, saturation, normal and shear stresses, and volumetric shrinkage evolutions. The model is validated in comparison with numerical and experimental results taken from the literature.     

Pyrolysis Kinetics of Wood and Wood Components

The kinetics of pyrolysis decomposition reactions of wood and its components are described employing mathematical modeling tools for first and n^th order reactions, autocatalytic reactions, and parallel first order and autocatalytic reactions. Secondary reactions may accelerate the reaction rate and a new autocatalytic reaction model was developed to describe this specific behavior.     

Kinetics Analysis on Mixing Calcination Process of Fly Ash and Ammonium Sulfate

abstract The further development of the extraction of alumina that is produced in the calcination process of ammonium sulfate mixed with fly ash was limited because of the lack of systematic theoretica...     

Effect of Wall Surface Properties at Different Drying Kinetics on the Deposition Problem in Spray Drying

Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.     

Hydrolysis Kinetics of 2-Pyridinecarboxamide, 3-Pyridinecarboxamide and 4-Pyridinecarboxamide in High-Temperature Water

abstract A kinetic study is reported here on hydrolysis of three pyridinecarboxamides in high-temperature water in the temperature range of 190-250 °C at 8 MPa. 2-Pyridinecarboxamide, 3-pyridinecarboxa...     

不同温度条件下HTPB推进剂干燥恢复研究

以在30℃、RH为100%条件下湿老化5 d的丁羟(HTPB)推进剂试样为研究对象,分别进行了在10、30、50℃3种温度下的干燥恢复试验,测试了干燥恢复过程中推进剂试样的失水率和力学性能。综合分析了试验数据,得到了不同温度下干燥时初始阶段推进剂试样的失水率、抗拉强度恢复速率,以及各力学性能参量恢复度90%且伸长率比值1.2的恢复时间。对抗拉强度测试中得到的断面照片进行了对比和分析,将样品30℃干燥恢复1、4、9 d后的单向拉伸曲线绘制在一张图上进行比较寻找规律,在对试验数据和试验现象分析总结的基础上探讨了HTPB推进剂干燥恢复过程中氢键的作用规律。     

太阳能-除湿-常规分段组合木材干燥工艺优化

为降低木材干燥能耗,通过对杨木进行太阳能-除湿-常规分段组合干燥,即含水率40%以上采用太阳能进行预干,25%—40%采用除湿干燥,25%以下采用常规干燥,并与常规干燥进行干燥能耗和木材质量的对比。结果表明,分段组合干燥比常规干燥节能19%左右,而且干燥质量和常规干燥基本一致。分段组合干燥充分利用了三者各自的优势,从而达到节能的目的。     

A Comparison of the Drying Simulation Codes Transpore and Wood2D which are used for the Modelling of Two-Dimensional Wood Drying Processes

ABSTRACT

This study is devoted to investigating the heat and mass transfer phenomena that occur during the convective drying of wood at high temperatures. A comparison will be made between an existing two-dimensional computer code known as Transpore. which was developed by Perre in France, and another two-dimensional code which was developed independently by Turner in Australia. Both numerical codes use a comprehensive set of macroscopic equations to describe the drying process, and most importantly treat the anisotropic behaviour of the wood. The porous medium is defined by three state variables: temperature, moisture content and gaseous pressure and the numerical simulation codes allow the evolution of the distributions of these state variables to be analysed throughout the drying process. The numerical investigation presented in this research work will compare the results obtained from both simulation codes and comments will be made on their consistencies. The influence that the drying air characteristics (moist air and super-heated stream) have on the overall drying kinetics, together with the effect that varying the mesh structure or changing the relative permeability curves have on the results will be throughly scrutinised.     

Drying Stress and Strain in Tension Wood: A Conventional Kiln Schedule to Efficiently Dry Mixed Tension/Normal Wood Boards in Poplar

Orthotropic drying stresses of tension and normal wood in poplar were evaluated. The degree of residual stresses was interpreted by prong and slice cutting tests. A strain gauge was employed to determine longitudinal drying stresses. Mixed tension/normal wood boards were also dried using three different schedules, T₈ F₄, T₈ F₅, and T₉ F₄ to find the best schedule. Results revealed more intense drying stress in the longitudinal and radial directions of tension wood. Despite a high susceptibility of the mixed tension/normal wood boards to drying defects, the quality of the boards dried by the schedule of T₉ F₄ was satisfactory.     

Microwave Heat Treatment of Spinach: Drying Kinetics and Effective Moisture Diffusivity

The effect of microwave drying technique on moisture content, moisture ratio, drying rate, drying time, effective moisture diffusivity, and porosity of spinach (Spinacia oleracea L.) were investigated. By increasing the microwave output powers (180–900 W) and the sample amounts (25–100 g), the drying time decreased from 18 to 3.5 min and increased from 7.7 to 25 min, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among of the models proposed, Page's model gave a better fit for all drying conditions applied. The activation energy was calculated using an exponential expression based on Arrhenius equation. The relationship between the drying rate constant and effective moisture diffusivity was also estimated and gave a linear relationship.     

Microwave Heat Treatment of Spinach: Drying Kinetics and Effective Moisture Diffusivity

The effect of microwave drying technique on moisture content, moisture ratio, drying rate, drying time, effective moisture diffusivity, and porosity of spinach (Spinacia oleracea L.) were investigated. By increasing the microwave output powers (180-900 W) and the sample amounts (25-100 g), the drying time decreased from 18 to 3.5 min and increased from 7.7 to 25 min, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among of the models proposed, Page's model gave a better fit for all drying conditions applied. The activation energy was calculated using an exponential expression based on Arrhenius equation. The relationship between the drying rate constant and effective moisture diffusivity was also estimated and gave a linear relationship.