Experimental and numerical investigations on the interactions of volatile flame and char combustion of a coal particle

The model that takes chemical reactions, heat and mass transfers in the boundary layer of the particle into account simultaneously, is developed for simulating the combustion of a pulverized coal particle. The FTIR in situ temperature-measurements and the comparison between numerical simulations for the pulverized coal and the devolatilized char show that the volatile flame induces the combustion of the primary product of surface oxidation CO. Due to the influence of volatile flame, the char particle can be ignited at temperature lower than its heterogeneous ignition temperature, which elucidates the physical essence of joint hetero-homogeneous ignition mode discovered by Jüntgen.     

Multi-scale modeling of hemodynamics in the cardiovascular system

The human cardiovascular system is a closedloop and complex vascular network with multi-scaled heterogeneous hemodynamic phenomena. Here, we give a selective review of recent progress in macro-hemodynamic modeling, with a focus on geometrical multi-scale modeling of the vascular network, micro-hemodynamic modeling of microcirculation, as well as blood cellular, subcellular,endothelial biomechanics, and their interaction with arterial vessel mechanics. We describe in detail the methodology of hemodynamic modeling and its potential applications in cardiovascular research and clinical practice. In addition,we present major topics for future study: recent progress of patient-specifi hemodynamic modeling in clinical applications, micro-hemodynamic modeling in capillaries and blood cells, and the importance and potential of the multi-scale hemodynamic modeling.     

A new aminopeptidase inhibitor from Streptomyces strain HCCB10043 found by UPLC-MS

The diversity of microbial metabolites has been of interest and concern for a long time, yet a suitable method for discovering these is still unavailable. In the work discussed in this report, ultra-performance liquid chromatography coupled with tandem quadrupole and time of flight high-resolution mass spectrometry (UPLC–Q–TOF-HRMS), with MS data analysis, was set up to study the metabolites of Streptomyces strain HCCB10043. It was found that besides antibacterial substances (A21978C complex) and two anti-aminopeptidase compounds (valistatin and bestatin), this strain can produce a new aminopeptidase inhibitor, identified as 3-amino-2-hydroxy-4-phenylbutanoylvalylisoleucine. This new compound had greater activity than valistatin or bestatin in aminopeptidase N (APN) inhibition assay. The results proved that combination of UPLC–Q–TOF-MS analysis and classic purification and identification steps as complementary strategies can provide a method with high reliability for research on microbial secondary metabolites. Furthermore, it has shown that the study of secondary metabolic profiling might be the key to discovering new drugs.     

Experimental and modeling study on centimeter pine char combustion in fast-heating Macro TGA

Biomass energy is an important renewable resource, and thermochemical conversion, including pyrolysis and combustion, is one of the main methods of biomass energy utilization. In industrial reactors, the biomass particles will experience a fast heating (∼1000 °C/min) process during pyrolysis. The particle size of biomass applied in industry has a wide range (from millimeter to centimeter scale). The study of the reaction characteristics of biomass pyrolysis and combustion is helpful for optimizing furnace design and working condition selection. In this research, the combustion of centimeter-scale pine char was studied with a newly built fast-heating Macro Thermal Gravimetric Analyzer (Macro TGA). This Macro TGA is able to conduct the pyrolysis and combustion of large biomass samples (up to 40 mm) with a fast heating rate (∼1000 °C/min), which is able to reflect the working conditions in industrial-scale reactors such as grate furnaces and dual fluidized beds. This Macro TGA can measure the online sample weight, temperature and sample size simultaneously during pyrolysis and combustion experiments. The combustion characteristics of different sizes of pine chars were investigated at various temperatures and oxygen concentrations. A zero-dimensional model was established to predict the sample weight loss, temperature change and sample shrinkage during the pine char combustion process. Three kinetic parameters α, A and E were applied in the model, and the values of the kinetic parameters were optimized by a genetic algorithm. The model prediction and experimental results are consistent with each other. Compared with previous studies, this study developed a new experimental method to measure the reaction characteristics (including sample weight, temperature and size) of centimeter-scale biomass under similar pyrolysis and combustion reaction conditions compared to industrial reactors, and a zero-dimensional model was established to describe the pine char combustion process.     

The effect of T-stress on crack–inclusion interaction under mode I loading

A closed-form solution has been developed to predict the effect of T-stress on the crack–inclusion interaction. As validated by several numerical examples, the approximate solution has satisfactory accuracy for different inclusion shapes and modulus ratios between inclusion and matrix under different T-stress levels. Thus the role of T-stress in crack–inclusion interaction can be predicted quantitatively.     

Diffusive shrinkage of a void within a grian of a stressed polycrystal

A method to predict the shrinkage rate of a void centered at an equiaxial grain under hydrostatic pressure is developed. The rate process is controlled by lattice diffusion under the combined influence of void surface energy, grain boundary interface energy and elastic energy stored in the solid. A dimensionless loading parameter that controls the void evolving is introduced. Below a certain value of this parameter the void will be rounded and is stable. Then the shrinkage behavior of the voids is described by the parameters controlling the lattice diffusion. It is found that only gas-free voids could be totally eliminated through lattice diffusion; for a gas-filled void, the internal pressure produced by the gas firstly retards the rate of the shrinkage and eventually stops the shrinkage process as it becomes high enough.     

4-(嘧啶-2-氨基)苯甲酰胺衍生物的设计、合成及Hedgehog信号通路抑制研究

Hedgehog信号通路是近年来抗肿瘤靶向治疗药物研究的一个新热点.本研究以4-(嘧啶-2-氨基)苯甲酰胺为母核,基于先导化合物1的构效关系,设计并合成了14个未见文献报道的4-(嘧啶-2-氨基)苯甲酰胺类Hedgehog信号通路抑制剂,并进行了初步的抗Hedgehog信号通路活性筛选.结果表明:所合成的化合物均表现出较好的Hedgehog信号通路抑制活性,其中化合物8e的活性最好,IC50为5.0 nmol?L-1,高于阳性药GDC-0449;同时在体内药代性质研究中,8e相比化合物1,药代性质均有所改善.     

Parameters optimization of laser brazing in crimping butt using Taguchi and BPNN-GA

The laser brazing (LB) is widely used in the automotive industry due to the advantages of high speed, small heat affected zone, high quality of welding seam, and low heat input. Welding parameters play a significant role in determining the bead geometry and hence quality of the weld joint. This paper addresses the optimization of the seam shape in LB process with welding crimping butt of 0.8 mm thickness using back propagation neural network (BPNN) and genetic algorithm (GA). A 3-factor, 5-level welding experiment is conducted by Taguchi L₂₅ orthogonal array through the statistical design method. Then, the input parameters are considered here including welding speed, wire speed rate, and gap with 5 levels. The output results are efficient connection length of left side and right side, top width (WT) and bottom width (WB) of the weld bead. The experiment results are embed into the BPNN network to establish relationship between the input and output variables. The predicted results of the BPNN are fed to GA algorithm that optimizes the process parameters subjected to the objectives. Then, the effects of welding speed (WS), wire feed rate (WF), and gap (GAP) on the sum values of bead geometry is discussed. Eventually, the confirmation experiments are carried out to demonstrate the optimal values were effective and reliable. On the whole, the proposed hybrid method, BPNN-GA, can be used to guide the actual work and improve the efficiency and stability of LB process.