皂荚籽热风干燥特性及干燥动力学模型研究

目的:为了研究皂荚籽干燥特性,为其机械化剥离应用提供理论参考。方法:研究了不同温度(70、90、110与130℃)与不同预处理方法(清水、碳酸氢钠溶液、焦磷酸二氢二钠溶液和酒石酸氢钾溶液浸泡)对皂荚籽干燥动力学的影响,使用Lewis模型、Page模型与Weibull分布函数对其干燥特性曲线进行非线性拟合并进行评价,并通过应面回归模型建立起干燥动力学模型。结果:皂荚籽干燥过程存在明显的升速降速段,且干燥温度越高,干燥速率越快,预处理方法对其干燥速率有一定影响。通过比较各模型的分别是决定系数()、卡方检验值()、残差平方和()与均方根误差(),结果显示Weibull分布函数能更好地模拟皂荚籽干燥过程,形状参数()随温度的升高而降低,尺寸参数()与预处理方法有关。计算了皂荚籽干燥过程的有效水分扩散系数()及其估算值()与活化能(),水分扩散系数及其估算值随着温度的升高而升高,经过酒石酸氢钠溶液预处理的皂荚籽的活化能低于其它预处理方法,可大大提高皂荚籽干燥效率。结论:经碳酸氢钠溶液预处理的皂荚籽干燥较容易发生,Weibull函数能较好地描述皂荚籽干燥过程中水分含量的变化规律,酒石酸氢钠溶液可以降低皂荚籽的活化能。该研究可为皂荚籽干燥提供理论和技术基础。     

Retrogradation Behavior of Wheat Starch Gels with Differing Molecular Profiles

Differing molecular profiles of starches were developed by acid treatment of native wheat starch. Molecular weight distribution, branching, and linear chain length distribution was characterized. Starches with fewer large size amylopectin fragments, increased smaller size amylopectin fragments, decreased branch points, decreased overall sizes, and narrower linear chain length distributions, had higher initial retrogradation rates. However, all aged starch gels had similar final crystalline enthalpy levels. Different retrogradation behaviors were due to smaller size amylopectin fragments, narrowed linear chain length distribution, and decreased branching. Retrogradation behavior was modeled using classical Avrami kinetics to allow comparison with other retrogradation studies.     

Oviposition decisions in the seed beetle, Callosobruchus maculatus (Coleoptera: Bruchidae): effects of seed size on superparasitism

The seed parasite Callosobruchus maculatus generally disperses eggs uniformly among seeds. We used cowpeas (Vigna unguiculata) of two class sizes (large and small) to test predictions based on a simple resource threshold model that females will distribute eggs among seeds in a manner that maximizes the amount of resources allocated to each offspring. When females were presented with multiple seeds of the same size, they tended to distribute their eggs relatively uniformly among seeds (I?0.27 where I is the variance/mean ratio, and I=1 reflects a random Poisson distribution). However, when seeds varied in size females distributed their eggs in a manner that maximized the amount of resources per offspring; females distributed eggs as predicted by seed differences in mass rather than as predicted by seed differences in surface area. Therefore, females must evaluate the relative quantity of resources available inside of a seed more accurately than if they compared the ratio of surface areas between seeds of varying size. Instead, females must either use cues other than surface area when estimating seed mass, or must have the ability to extrapolate non-linearly from surface area to seed mass. Females with higher egg loads (4-d-old females) laid more eggs when presented with seeds, but did not distribute their eggs less uniformly, than females with lower egg loads (1-d-old females), indicating that high egg load does not reduce female sensitivity to seed size and the presence of conspecific eggs.     

7种烟用添加剂对烟气气溶胶粒径分布的影响

为研究典型烟用添加剂（包括丙二醇、丙三醇、呋喃酮、香兰素、乙酰丙酸、亚麻酸和棕榈酸）对不同粒径烟气气溶胶粒相物质量分布的影响以及在气溶胶中的粒径分布,采用单通道吸烟机-电子低压撞击器（ELPI）,分12级捕集烟气气溶胶粒相物,进行重量分析研究粒相物的质量分布,并采用GC-MS和LC-MS/MS测定了7种添加剂在不同粒径气溶胶中的分布。实验结果表明,添加7种添加剂的卷烟样品,其气溶胶粒相物的质量均主要分布在中间粒径上（0.14~1.17 μm）,但添加不同添加剂对气溶胶质量粒径分布的影响不同,总体趋势如下:香兰素、乙酰丙酸、亚麻酸和呋喃酮能增加大于0.431 μm处粒相物质量,使小于0.261 μm处粒相物质量减小;丙二醇和丙三醇使0.261 μm处粒相物的质量减少;棕榈酸无明显影响。7种添加剂在不同粒径气溶胶粒相物中的释放量均随粒径增加先增加后减小,与粒相物质量分布一致,并主要分布在中等粒径0.261~0.722 μm的颗粒中,但不同添加剂在不同粒径粒相物中的浓度（释放量与粒相物质量之比）呈现不同的分布趋势:随着粒径的增加,丙二醇、乙酰丙酸、亚麻酸和棕榈酸的浓度先增加后减小,丙三醇的浓度先减小后略微增加,香兰素和呋喃酮的浓度无明显差异。添加合适的烟草添加剂可改变烟气气溶胶粒相物的分布,并在不同粒径粒相物中呈现不同的分布特征,研究结果可为卷烟配方设计及卷烟安全性研究提供理论基础和数据支持。      

Kinetic model for the inactivation of Lactobacillus plantarum by pulsed electric fields

The kinetics of Lactobacillus plantarum inactivation by pulsed electric fields (PEF) was studied in two different growth stages (exponential and stationary), but in the same reference medium (0.6% peptone water). Electric field intensity and treatment time varied from 20 to 28 kV/cm and 30 to 240 micros, respectively. The experimental data showed that cells in the exponential growth stage were more sensitive to PEF treatment than those in the stationary stage. The inactivation data were adjusted to the Bigelow and Hülsheger models and the Weibull frequency distribution function, and constants were calculated for both growth stages in each model. The models were tested and their accuracy was assessed by using the Accuracy Factor. According to this parameter, the Weibull frequency distribution function gave better fittings for the inactivation by PEF than Bigelow or Hülsheger models. On the other hand, the Bigelow model gave a good accuracy factor and is simpler.     

Sulfate aerosol as a potential transport medium of radiocesium from the Fukushima nuclear accident

To date, areas contaminated by radionuclides discharged from the Fukushima Dai-ichi nuclear power plant accident have been mapped in detail. However, size of the radionuclides and their mixing state with other aerosol components, which are critical in their removal from the atmosphere, have not yet been revealed. We measured activity size distributions of (134)Cs and (137)Cs in aerosols collected 47 days after the accident at Tsukuba, Japan, and found that the activity median aerodynamic diameters of (134)Cs and (137)Cs in the first sample (April 28-May 12) were 0.54 and 0.53 μm, respectively, and those in the second sample (May 12-26) were both 0.63 μm. The activity size distributions of these radiocesium were within the accumulation mode size range and almost overlapped with the mass size distribution of non-sea-salt sulfate aerosol. From the analysis of other aerosol components, we found that sulfate was the potential transport medium for these radionuclides, and resuspended soil particles that attached radionuclides were not the major airborne radioactive substances at the time of measurement. This explains the relatively similar activity sizes of radiocesium measured at various sites during the Chernobyl accident. Our results can serve as basic data for modeling the transport/deposition of radionuclides.     

Photocatalytic degradation of methanol using silica-titania composite pellets: effect of pore size on mass transfer and reaction kinetics

Nanostructured silica-titania composites (STC) synthesized with varying pore sizes (45, 134, and 299 angstroms) were tested for the removal of methanol from a humid air stream. The STC pellets were characterized for surface area and pore size distribution and tested in a packed-bed photocatalytic reactor for methanol removal and oxidation. While the pore size distributions for all STC were unimodal, STC with larger average pore sizes exhibited a broader pore size distribution. The efficiency of methanol oxidation was dependent on the surface area of the STC and the space time of the gas in the reactor. For all STC tested, the rate of methanol oxidation was not limited by resistances to external or internal mass transfer. For 134 and 299 angstroms STC, a lag time of 1.0 and 1.2 s, respectively, was observed before mineralization began. After this lag time, which was zero for the 45 angstroms STC, the data followed pseudo first-order reaction kinetics and the rate constant, k, was 0.40 s(-1) for all pore sizes.     

食用葵花籽尺寸分析与均齐性研究

为探索食用葵花籽清选、分级、选种、定价的理论依据,完善建立葵花籽的离散元法分析模型,对食用葵花籽的主要尺寸及均齐性进行了分析。选择内蒙古自治区主栽的3个品种食用葵花籽（1013、SH361、SH363）为研究对象,使用统计学方法,以籽粒的三轴尺寸(长度、宽度、厚度)、平均径（算术平均径、几何平均径）、百粒重为指标,分析葵花籽三轴尺寸的统计分布特性、均齐性以及平均径与百粒重的关系,并按宽度对葵花籽进行了清选分级试验。结果表明：不同品种葵花籽的三轴尺寸均服从正态分布并存在线性相关,且总体上存在显著性差异;葵花籽的均齐性存在差异且其几何平均径、算术平均径与百粒重的变化趋势一致;1013品种选用圆孔筛10 mm和8 mm规格,SH361和SH363品种选用圆孔筛10 mm和8.5 mm规格时,分级效果满足要求。     

Particle size distributions of organic aerosol constituents during the 2002 Yosemite Aerosol Characterization Study

The Yosemite Aerosol Characterization Study (YACS) was conducted in the summer of 2002 to investigate sources of regional haze in Yosemite National Park. Organic carbon and molecular source marker species size distributions were investigated during hazy and clear periods. More than 75% of the organic carbon mass was associated with submicron aerosol particles. Most molecular marker species for wood smoke, an important source of particulate matter during the study, were contained in submicron particles, although on some fire influenced days, levoglucosan shifted toward larger sizes. Various wood smoke marker species exhibited slightly different size distributions in the samples, suggesting different, size dependent emission or atmospheric processing rates of these species. Secondary biogenic compounds including pinic and pinonic acids were associated with smaller particles. Pinonaldehyde, however, exhibited a broader distribution, likely due to its higher volatility. Dicarboxylic acids were associated mainly with submicron particles. Hopanes, molecular markers for vehicle emissions, were mostly contained in smaller particles but exhibited some tailing into larger size classes.     

混合Weibull分布在棉纤维长度分布表征上的应用

利用含参数的概率密度函数来表征棉纤维的长度分布,不仅有利于纤维长度指标的计算,而且能够全面度量纤维的长度分布状态。本文基于USTER 的AFIS单纤维测试仪测得的纤维长度分布直方图,依据现有的混合Weibull分布模型,选用两组分与三组分的混合分布对其进行了拟合,并计算了相应的长度指标。结果表明：利用Weibull分布构建的混合分布模型能很好地拟合棉纤维的重量及根数加权长度分布。此外,通过指标计算值与实测值的对比,一般情况下二组分混合模型优于三组分模型。     

On the origin of the deviation from the first-order kinetics in inactivation of microbial cells by pulsed electric fields

A computer model was developed for the estimation of the kinetics of microbial inactivation by pulsed electric field (PEF). The model is based on the electroporation theory of individual membrane damage, where spherical cell geometry and distribution of cell sizes are assumed. The variation of microbial cell sizes was assumed to follow a statistical probability distribution of the Gaussian type. Surviving kinetics was approximated by Weibull equation. The dependencies of two Weibull parameters (shape n and time tau, respectively) versus electric field intensity E and width of cell diameters distribution were studied.     

Application of finite mixture model in cotton fiber length probability distribution

Based on the characteristic of histograms for fiber length, a finite mixture model has been applied in this paper to characterize cotton fiber length probability distribution, which made it possible to describe the entire fiber length distribution with a parametric continuous function. With the analysis of previous researches, a mixture of Weibull distributions was chosen to generate the parametric probability density function. In this paper, five cotton fiber samples were collected from different spinning processes: bale, card mat, carded sliver, combed sliver, and finished sliver. The fiber length frequency histograms by weight, the histograms by number and some length measures were tested by USTER AFIS Pro. Two-component and Three-component mixture distributions were adopted to fit these histograms, and some length measures were calculated. Then, comparisons have been made between the calculated values of fiber length measures and the tested ones. The results showed that both the finite mixture models based on different component Weibull distributions could fit the cotton fiber length frequency histograms very well, which would be beneficial to pursue the process-related factors in cotton mills for end products.     

Tensile strength prediction of irregular fibres using diameter-dependent Weibull analysis

A modified Weibull model incorporating the within-fibre diameter variation is applied to examine the fibre diameter effect on the strength of single fibres. Australian Superfine Merino Wool (ASFW) and Inner Mongolia Cashmere (IMC) were used in the present work, since these animal fibres tend to have relatively large diameter variations. To determine single fibre strength, tensile measurements were carried out for fibres with diameters varying between 9 and 21?μm at a constant gauge length. It was found that an increase in the diameter disparity along the fibre reduces the strength of fibres. To validate this, the accuracy of predicting weak-link scaling was evaluated; the results showed that the application of modified Weibull distribution gives a better relationship with the empirical data than the standard Weibull model. The results suggest that the modified Weibull model is more accurate in predicting the size dependence and strength of single fibres with diameter variations.     

Prediction of consumer acceptability of potato chips with various moisture contents using survival analysis

Consumer acceptability of potato chips with different moisture contents (MC) was evaluated using survival analysis. Nine different humidity conditions (30–70%) at 25°C were used. MC values of samples ranged from 2.2–9.2% after treatment. Panelists (50) were asked to rate chip acceptability. The chip MC was predicted using non-linear models. Panelist-generated data were categorized as left, interval, and right censored. A total of 18 panelists were left censored and 30 were interval censored. Weibull and lognormal distributions were used to fit the censored data. The mean MC of chips rejected by 50% of consumers were 3.54% (95% confidence interval, 3.14–3.99%) and 3.60% (CI 3.23–4.01%) for the Weibull and lognormal distribution, respectively. These values corresponded to 5.7 and 5.6 overall consumer liking values (Weibull and lognormal distributions, respectively). MC of 3.5–3.6% was necessary to attain consumer acceptability values of 5.6 and product acceptance by 50% of consumers.     

Optimum Cooking Conditions for Shrimp and Atlantic Salmon

The quality and safety of a cooked food product depends on many variables, including the cooking method and time–temperature combinations employed. The overall heating profile of the food can be useful in predicting the quality changes and microbial inactivation occurring during cooking. Mathematical modeling can be used to attain the complex heating profile of a food product during cooking. Studies were performed to monitor the product heating profile during the baking and boiling of shrimp and the baking and pan‐frying of salmon. Product color, texture, moisture content, mass loss, and pressed juice were evaluated during the cooking processes as the products reached the internal temperature recommended by the FDA. Studies were also performed on the inactivation of Salmonella cocktails in shrimp and salmon. To effectively predict inactivation during cooking, the Bigelow, Fermi distribution, and Weibull distribution models were applied to the Salmonella thermal inactivation data. Minimum cooking temperatures necessary to destroy Salmonella in shrimp and salmon were determined. The heating profiles of the 2 products were modeled using the finite difference method. Temperature data directly from the modeled heating profiles were then used in the kinetic modeling of quality change and Salmonella inactivation during cooking. The optimum cooking times for a 3‐log reduction of Salmonella and maintaining 95% of quality attributes are 100, 233, 159, 378, 1132, and 399 s for boiling extra jumbo shrimp, baking extra jumbo shrimp, boiling colossal shrimp, baking colossal shrimp, baking Atlantic salmon, and pan frying Atlantic Salmon, respectively.     

Growth Rate Dispersion Effects on Lactose Crystal Size Distributions from a Continuous Cooling Crystallizer

The continuous crystallization kinetics for lactose have been determined. Specifically, a model incorporating the effects of growth rate dispersion (GRD) on particle dynamics has been employed to determine continuous crystallization kinetics from experimentally determined size distributions. The existence of GRD was verified by the excessive number of fines (< 50 μm) observed. Crystal size distributions were successfully modeled using a two component rate distribution indicating the existence of two distinct types of nuclei. These could be classed as fast-growers (product crystals) and slow-growers (fines). Nucleation and growth kinetics of these populations were determined and compared to other methods of determining kinetics.     

Change in Moisture Distribution in Lasagna Pasta Post Cooking

ABSTRACT: The time-dependent internal moisture distributions in lasagna pasta were experimentally evaluated and mathematically modeled as a function of cooking time and holding time. During the holding time, changes in the moisture distribution were followed using a magnetic resonance imaging (MRI) spin-echo-based pulse sequence. Immediately after cooking, the moisture distribution was highly nonuniform for all samples. The moisture content was high on the surface of the pasta and low in the central plane. This gradient equilibrated over time as the moisture redistributed. The moisture redistribution was modeled using a one-dimensional Fickian diffusion equation; values of the diffusion coefficient ranged from 0.8 to 1.6 × 10⁻⁷ cm²/s.     

Stochastic control and optimization in retail distribution: an empirical study of a Korean fashion company

Considerable research has recently been conducted on improving the business performance of the fashion industry through supply-chain streamlining. In addition, the accuracy enhancement of sales forecasting by using statistical methods and machine learning algorithms to minimize inventory and improve profitability has been investigated. However, few studies have focused on solving the initial distribution problem to reduce logistical costs and loss of sales opportunities. This study solves the mathematical problems related to initial distributions of fashion products using stochastic control and optimization by conducting an empirical study using real data from a leading Korean fashion company. The initial distribution of a small quantity of items among numerous shops and the distribution of special sizes produced in small quantities were examined. Monte–Carlo simulations and Lebesgue’s convergence theorem were considered useful for determining initial distributions of stock produced in small quantities. Furthermore, optimal initial distributions can be achieved when experience-based expert judgment is combined with mathematical modeling using stochastic control and optimization.     

Particle size distribution and lipid composition of skim milk lipid material

Skim milk lipid material was characterized in terms of particle size distribution and lipid composition, and compared with other milk fat particle distributions. Whole milk, skim milk, large fat globules, small fat particles and skim milk lipid material were prepared using centrifugation and/or filtration, and the particle size distributions measured by laser diffraction. The lipid composition was determined using a combination of thin layer chromatography and gas chromatography–mass spectrometry. There were significant compositional differences between each fraction for both particle size distribution and fatty acid composition. The most distinguishing feature of the skim milk lipid material was the increased percentage of long chain sphingomyelin species compared with the other milk fat fractions.     

Effect of engine load on diesel soot particles

This study concentrates on characterization of nonvolatile fraction of diesel particles. These particles have an impact on earth's radiation balance as well as on health effects of vehicle emissions. In addition to composition and size distribution of particles, an important factor affecting their health effects and properties and lifetimes in the atmosphere is their morphology. The effect of engine parameters on soot particle size distributions and also on particle morphology has been studied. It was found that the shape of the size distribution and also the structure of diesel particles depend on engine load. The number distributions were found to obey log-normal assumption. The width of the distribution increased with increasing engine load. The geometric standard deviations of measured distributions varied from 1.7 to 2.1. Simultaneously, the fractal dimension of particles decreased with increasing engine load. The values for mass fractal dimensions based on sealing of particle mass and mobility size were between 2.6 and 2.8. Both electron microscopy and measurements of aerodynamic size versus mobility size suggest that the morphology of particles in different size regimes vary, with the large particles being less compact than the small ones.