Kinetic modeling of liquid-phase esterification of acetic acid with n-butanol using heterogeneous poly(o-methylene p-toluene sulfonic acid) as catalyst

Liquid-phase esterification of acetic acid with n-butanol to n-butyl acetate is studied in the presence of a polymeric catalyst, that is, poly(o-methylene p-toluene sulfonic acid). The performance of the proposed catalyst is compared with the other commercially available homogeneous and heterogeneous catalysts in terms of its activity. Experiments are conducted in an isothermal stirred batch reactor to study the effects of speed of agitation, temperature, and catalyst loading on the rate of reaction. A concentration-based pseudo-homogeneous (PH) kinetic model and activity-based kinetic models such as PH, Eley-Rideal (ER), and Langmuir-Hinselwood-Hougen-Watson (LHHW) models are developed. All the models considered in this study resulted in similar percentage deviation close to 4%. Further, kinetic models are validated through additional experiments, and it is observed that the simple concentration-based PH model is able to predict experimental data with least deviation compared to activity-based PH, ER, and LHHW models. The developed kinetic models are also tested using the Fisher-Snedecor test (F-test) and are found to be acceptable. By incorporating both modeling data and validation data, the overall absolute average deviations of different models are found to be concentration-based PH model 4.354%, activity-based PH model 5.006%, ER I model 5.189%, ER II model 5.403%, ER III model 5.437%, and LHHW model 6.104%, illustrating the superiority of the simple concentration-based PH model.     

Experimental and numerical investigations of bi-injection moulding of PA66/LSR peel test specimens

Bi-injection moulding is a widely used process to manufacture engineering products and consumer goods. Typically, a thermoplastic is combined with rubber or another thermoplastic to create colour differences or hard and soft areas, respectively. The aim of this study was to optimise the injection parameters and processing conditions for the moulding of two-component standard peel test specimens with suitable functional properties. In this work, all parameters of thermo-rheo-kinetic behaviour were identified to predict the entire filling stage and the effect of a liquid silicone rubber cross-linking reaction during the injection moulding process. The models of Carreau-Yasuda and Isayev-Deng regarding the thermal dependence assumed by Arrhenius’ law were used. In our study, over-injection moulding is simulated and examined using finite element software (Cadmould 3D) to investigate the thermo-rheo-kinetic behaviour and the adhesion of liquid silicone rubber during the filling mould process in over-moulding. Numerical simulation results were then compared with the experimental results, and good agreement was obtained.     

Development and validation of a mechanistic model for the release of embelin from a polycaprolactone matrix

Embelin is a natural agent with antimicrobial, antifungal and analgesic activities. This work presents a mechanistic model for the release of embelin from a polycaprolactone matrix. Based on the results of embelin release experiments and Raman microscopy measurements, the model assumes a dual dispersion of the embelin: agglomerated and dispersed. Embelin release mechanism combines the effects of the liquid migration into the matrix, the drug diffusion, and the drug dissolution within the wetted matrix. The model is formulated in terms of four partial differential equations that account for the mass balances of dispersed, agglomerated, and dissolved embelin, and aqueous solution. Model predictions show that the release mechanism involves three stages: a burst stage, in which dispersed embelin is rapidly released; a transition stage, in which dispersed and agglomerated embelin are simultaneously released; and, once the dispersed embelin depletion, a stable release stage until the agglomerated embelin exhausts.     

Novel green synthesis of Boswellia serrata leaf aqueous extract conjugated gold nanoparticles with excellent anti-acute myeloid leukemia property in comparison to mitoxantrone in a leukemic mice model: Introducing a new chemotherapeutic drug

The present research confirms the capacity of aqueous extract of Boswellia serrata grown under in vitro condition for the green synthesis of gold nanoparticles (AuNPs). Also, we showed the cytotoxicity, antioxidant, and anti-acute myeloid leukemia properties of AuNPs compared to mitoxantrone in a leukemic mouse model. The synthesized AuNPs were characterized using several techniques including XRD, TEM, FE-SEM, UV–Vis, and FT-IR. From the XRD pattern, four distinct diffraction peaks at 38.2°, 44.2°, 64.7° and 77.4° are indexed as (111), (200), (220) and (311) planes of FCC metallic gold. TEM and FE-SEM images revealed an average diameters of 15–30 nm for the nanoparticles. FT-IR findings offered antioxidant compounds in the nanoparticles were the sources of reducing power, reducing gold ions to AuNPs. UV–Vis revealed an absorption band at 536 nm that is related to the surface plasmon resonance of AuNPs. In vivo design, induction of acute myeloid leukemia was done by DMBA in 75 mice. Then, the mice were randomly divided into six subgroups, including untreated, control, HAuCl₄, B. serrata, AuNPs, and mitoxantrone. AuNPs (In the dose of 1 mg/kg body weight) similar to mitoxantrone, significantly (p ≤ 0.05) increased the platelet, lymphocyte, and RBC parameters and the anti-inflammatory cytokines (IL4, IL5, IL10, IL13, and IFNα) and reduced the weights and volumes of liver and spleen and their sub-compartment, the total WBC, blast, monocyte, neutrophil, eosinophil, and basophil counts, and the pro-inflammatory cytokines (IL1, IL6, IL12, IL18, IFNY, and TNFα) as compared to the untreated mice. By quantitative Real-Time PCR, S1PR1 and S1PR5 mRNA expression in lymphocytes were significantly (p ≤ 0.05) increased by treating the leukemic mice with the AuNPs and mitoxantrone. In vitro design, AuNPs similar to mitoxantrone had low cell viability dose-dependently against Human HL-60/vcr, 32D-FLT3-ITD, and Murine C1498 cell lines without any cytotoxicity on HUVEC cell line. Besides, the DPPH assay showed similar antioxidant potentials for AuNPs and mitoxantrone. In conclusion, the results of this research indicated the excellent capacity of synthesized gold nanoparticles using B. serrata leaf aqueous extract in the treatment of acute myeloid leukemia in leukemic mice.     

基于SVM的固化土无侧限抗压强度模型

为实现较少试验次数下固化土无侧限抗压强度(qu)的准确预测, 提出了基于支持向量机(SVM)的固化土qu的预测模型. 以固化剂各组分掺入比、龄期、初始含水量、固化剂掺量等因素为输入量, 固化土的qu作为输出量, 以径向基为核函数, 采用网格搜索法和交叉验证法进行参数优化, 建立了基于SVM的固化土qu的预测模型. 算例分析表明: 该模型适用于任意条件下固化土qu的精确预测, 且在较小试验成本下实现与响应面法相当的预测精度.     

形状记忆合金椭圆孔口问题的有限单元法

基于Lagoudas形状记忆合金(SMA)三维本构模型,假设材料为各向同性,推导了SMA平面应力状态的增量型本构方程,继而编写了ABAQUS用户自定义材料(UMAT)子程序,研究了在双向拉伸情况下,外载荷、温度、椭圆孔口长短轴之比对超弹性SMA椭圆孔口板中应力诱发马氏体相变区的影响。数值结果表明:应力诱发马氏体相变首先发生在椭圆孔口长轴端点部位,在外加载荷作用下逐渐扩展到板内,并由内向外形成马氏体相区、相变混合区和奥氏体相区;SMA板内应力诱发马氏体完全相变区面积与施加外载荷成正相关,与温度成负相关;随着椭圆孔口长短轴之比增大,SMA板内应力诱发马氏体完全相变区面积呈现出先减小后增大的趋势;拉应力差值相同时,相较于拉应力沿椭圆孔口长轴方向较大的情况,当拉应力沿椭圆孔口短轴方向较大时,SMA板内完全相变区面积较大,椭圆孔口周边应力集中现象更明显。     

Global optical model potential describing 12C-nucleus elastic scattering

We construct a new global optical model potential to describe the elastic scattering of ¹²C. The experimental data of elastic-scattering angular distributions and total reaction cross sections for targets from ²⁴Mg to ²⁰⁹Bi are considered below 200 MeV within the framework of the optical model. The results calculated using the derived global optical potential are then compared with the existing experimental data. The reliability of the global optical potential is further tested by predicting the elastic scattering data out of the mass and energy ranges, within which the global potential parameters are determined, and reasonable results are also obtained.     

秋千参数自激振动的数学模型与数值模拟

将秋千视为变长度单摆,基于归一化高斯函数构造了摆球相对摆杆的速度表达式.在此基础上建立了秋千的非线性动力学微分方程,并据此数学模型对秋千运动进行了数值模拟,得到了秋千的运动规律和功能转化的机制.     

A modified model for isothermal homogeneous and heterogeneous reactions in the boundary-layer flow of a nanofluid

The homogeneous and heterogeneous reactions in the boundary-layer of a flat surface are considered. The autocatalysts are assumed to be of regular sizes, while the solution is a dilute nanofluid. The heat release due to the chemical reactions is taken into account. The Buongiorno's model is used to describe the behaviors of this reaction system. This configuration makes the current model be different from all previous publications. Multiple solutions are given numerically to the rescaled nonlinear system, whose stability is verified. The results show that the strength coefficients of the homogeneous and heterogeneous reactions are key factors to cause the appearance of the multiple solutions in the distribution of the chemical reactions. Nanofluids enhance the diffusion of heat and help maintain the stability of chemical reactions.