The chemical environment and structural ordering in liquid Mg-Y-Zn system:An ab-initio molecular dynamics investigation of melt for the formation mechanism of LPSO structure

In an effort to clarify the formation mechanism of LPSO structure in Mg-Y-Zn alloy,the chemical environment and structural ordering in liquid Mg-rich Mg-Y-Zn system are investigated with the aid of ab-initio molecular dynamics simulation.In liquid Mg-rich Mg-Y alloys,the strong Mg-Y interaction is determined,which promotes the formation of fivefold symmetric local structure.For Mg-Zn alloys,the weak Mg-Zn interaction results in the fivefold symmetry weakening in the liquid structure.Due to the coexistence of Y and Zn,the strong attractive interaction is introduced in liquid Mg-Y-Zn ternary alloy,and contributes to the clustering of Mg,Y,Zn launched from Zn.What is more,the distribution of local structures becomes closer to that in pure Mg compared with that in binary Mg-Y and Mg-Zn alloys.These results should relate to the origins of the Y/Zn segregation zone and close-packed stacking mode in LPSO structure,which provides a new insight into the formation mechanism of LPSO structure at atomic level.

国外“化学平衡”主题教学课例研究——基于Journal of Chemical Education近二十年载文的分析

基于Journal of Chemical Education近二十年的载文,从教学主题与内容、教学手段与方法等方面分析研究了国外有关“化学平衡”主题教学课例的基本情况和研究重点。根据具体课例的内容分析,凝练出可以从实验创新与探究、游戏模拟与活动、信息工具支持这三个方面促进“化学平衡”主题的有效教学,介绍相应的典型课例,以期补充国内关于“化学平衡”主题教学课例的研究,为化学教学研究和实践提供有益参考。

Educational Process as Something Dynamic

If we conceive the educational process as something dynamic,which basically combines what is given with what is emerging,we will understand that there are protagonists in it who have a fundamental role in this process,or perhaps we should say that,in this process,each and every one of the agents has a leading role.So,talking about curriculum implies that the subject can be approached from different perspectives,some more legitimate than others,some broader than others and,what is even more notorious,some more dynamic than others.It is in these differences where the essence of the educational process is conjugated,namely,in the conception of the curriculum,so it is worth asking:What are the educational units understanding by“development of their own curricular projects”?What are they actually doing?What curricular decisions do they make?Not only these questions arise,but many more,not to mention that it is also legitimate to doubt the capacity and preparation of teachers and educational units to undertake a process of conscious and responsible construction of an effective curriculum.It is interesting to approach the subject critically,not to reconsider the theoretical aspects,in which we find a wide range of postulates,but rather to revitalize the pedagogical practice in the place where it actually occurs,the classroom,and from there to enable discussion,and analysis of the problem,assuming that a paradigm change is urgent at all levels,otherwise,the entire society will suffer even more marked dehumanization.There are many challenges and requirements that fall on the educational task,and there are many who express their opinion,judge,and dare to formulate lapidary sentences on the subject of education,with no more foundation than that allowed by a fragmented look at reality.Therefore,a deeper look can shed light on why it has not yet been possible to reach a more optimal level in the quality indices,nor has equity been achieved,and what is worse,it seems that all that has been said is slipping away through the window of the classrooms to end up in the realm of abstraction,from which it will not be possible to bring what is real and everyday.Thus,this work will also be a proposal for educational agents,a proposal that should not be kept together with others,but rather,hand in hand with the contingent,could give way to a better understanding of the problem.

An Educational GUI-Based Software for Dynamic Analysis of Framed Structural Models

This paper introduces a new version of the open-source educational software, LESM (Linear Elements Structure Model), developed in MATLAB for structural analysis of one-dimensional models such as frames, trusses, and grillages. The updated program includes dynamic analysis, which incorporates inertial and damping effects, time-dependent load conditions, and a transient solver with multiple time integration schemes. The software assumes small displacements and linear-elastic material behavior. The paper briefly explains the theoretical basis for these developments and the reorganization of the source code using Object-Oriented Programming (OOP). The updated Graphical User Interface (GUI) allows interactive use of dynamic analysis features and displays new results such as animations, envelope diagrams of internal forces, phase portraits, and the response of degrees-of-freedom in time and frequency domain. The new version was used in a structural dynamics course, and new assignments were elaborated to improve students’ understanding of the subject.

General dynamic model for educational assembling-type robot and its fast simulation algorithm

To realize automatic modeling and dynamic simulation of the educational assembling-type robot with open structure, a general dynamic model for the educational assembling-type robot and a fast simulation algorithm are put forward. First, the educational robot system is abstracted to a multibody system and a general dynamic model of the educational robot is constructed by the Newton-Euler method. Then the dynamic model is simplified by a combination of components with fixed connections according to the structural characteristics of the educational robot. Secondly, in order to obtain a high efficiency simulation algorithm, based on the sparse matrix technique, the augmentation algorithm and the direct projective constraint stabilization algorithm are improved. Finally, a numerical example is given. The results show that the model and the fast algorithm are valid and effective. This study lays a dynamic foundation for realizing the simulation platform of the educational robot.

A Hybrid Improved Genetic Algorithm and Its Application in Dynamic Optimization Problems of Chemical Processes

The solutions of dynamic optimization problems are usually very difficult due to their highly nonlinear and multidimensional nature. 13enetic algorithm （GA） has been proved to be a teasibte method when the gradient is difficult to calculate. Its advantage is that the control profiles at all time stages are optimized simultaneously, but its convergence is very slow in the later period of evolution and it is easily trapped in the local optimum. In this study, a hybrid improved genetic algorithm （HIGA） for solving dynamic optimization problems is proposed to overcome these defects. Simplex method （SM） is used to perform the local search in the neighborhood of the optimal solution. By using SM, the ideal searching direction of global optimal solution could be found as soon as possible and the convergence speed of the algorithm is improved. The hybrid algorithm presents some improvements, such as protecting the best individual, accepting immigrations, as well as employing adaptive crossover and Ganssian mutation operators. The efficiency of the proposed algorithm is demonstrated by solving several dynamic optimization problems. At last, HIGA is applied to the optimal production of secreted protein in a fed batch reactor and the optimal feed-rate found by HIGA is effective and relatively stable.

Novel Control Vector Parameterization Method with Differential Evolution Algorithm and Its Application in Dynamic Optimization of Chemical Processes

Two general approaches are adopted in solving dynamic optimization problems in chemical processes, namely, the analytical and numerical methods. The numerical method, which is based on heuristic algorithms, has been widely used. An approach that combines differential evolution （DE） algorithm and control vector parameteri- zation （CVP） is proposed in this paper. In the proposed CVP, control variables are approximated with polynomials based on state variables and time in the entire time interval. Region reduction strategy is used in DE to reduce the width of the search region, which improves the computing efficiency. The results of the case studies demonstrate the feasibility and efficiency of the oroposed methods.

中学化学虚拟仿真实验的研究进展--基于Journal of Chemical Education期刊的文献分析

从年份、研究主题、实验教学方法、文献内容等方面分析了2011-2021年Journal of Chemical Education中涉及中学化学“虚拟仿真实验”的发文情况。介绍了虚拟仿真实验教学、实验平台、相关理论、研究现状等多篇具有代表性的文献,以期对我国中学化学虚拟仿真实验教学带来启发。

Dynamic chemical processes on ZnO surfaces tuned by physisorption under ambient conditions

The catalytic properties of non-reducible metal oxides have intrigued continuous interest in the past decades.Often time,catalytic studies of bulk non-reducible oxides focused on their high-temperature applications owing to their weak interaction with small molecules.Hereby,combining ambient-pressure scanning tunneling microscopy(AP-STM),AP X-ray photoelectron spectroscopy(AP-XPS)and density functional theory(DFT)calculations,we studied the activation of CO and CO_(2)on ZnO,a typical nonreducible oxide and major catalytic material in the conversion of C1 molecules.By visualizing the chemical processes on ZnO surfaces at the atomic scale under AP conditions,we showed that new adsorbate structures induced by the enhanced physisorption and the concerted interaction of physisorbed molecules could facilitate the activation of CO and CO_(2)on ZnO.The reactivity of ZnO towards CO could be observed under AP conditions,where an ordered(2×1)–CO structure was observed on ZnO(1010).Meanwhile,chemisorption of CO_(2)on ZnO(1010)under AP conditions was also enhanced by physisorbed CO_(2),which minimizes the repulsion between surface dipoles and causes a(3×1)–CO_(2)structure.Our study has brought molecular insight into the fundamental chemistry and catalytic properties of ZnO surfaces under realistic reaction conditions.

Application of Chemical Dynamics Method in Solving Hydro-Geological Parameters

With the increasing of coal mining depth, the coal seam floor is threatened more and more seriously with the limestone aquifer of Taiyuan Formation. In order to make the coal seam floor water inrush accident to be effectively prevented, it is very important to ascertain the hydro-geological condition of the research area and adequately gain hydro-geological parameters. Based on the theory of chemical dynamics, the chemical dynamical equation of the mineral was obtained. The chemical dynamical equation of the mineral and the Darcy’s Law were combined to derive the expression of permeability coefficient and transmissibility coefficient that was indicated by hydro-chemistry index. Based on the data of water quality analysis in the research area, the hydro-geology parameter of the aquifer of Taiyuan Formation was calculated. And it was compared with what the hydro-geology parameter was determined by the data of pumping test. The results show that the permeability coefficient (K) of the research area is 1.7512 m/d, and transmissibility coefficient (T) is 42.0282 m2/d. The calculated results of chemical dynamics and pumping test results are little different between them. And it has certain practical significance in the mine water control. It provides an effective method for obtaining hydro-geological parameters.

Active Control of Chaotic Oscillations in Nonlinear Chemical Dynamics

Abstract: This work studies the active control of chemical oscillations governed by a forced modified Van der Pol-Duffing oscillator. We considered the dynamics of nonlinear chemical systems subjected to an external sinusoidal excitation. The approximative solution to the first order of the modified Van der Pol-Duffing oscillator is found using the Lindstedt’s perturbation method. The harmonic balance method is used to find the amplitudes of the oscillatory states of the system under control. The effects of the constraint parameter and the control parameter of the model on the amplitude of oscillations are presented. The effects of the active control on the behaviors of the model are analyzed and it appears that with the appropriate selection of the coupling parameter, the chaotic behavior of the model has given way to periodic movements. Numerical simulations are used to validate and complete the analytical results obtained.

Zooplankton Dynamics of the Kienke Estuary (Kribi, South Region of Cameroon): Importance of Physico-Chemical Parameters

All Cameroonian estuarine systems, like the Kienke estuarine system (urban area of the port city of Kribi), are considered, as everywhere in the world, as unstable and vulnerable coastal ecosystems insofar as they are influenced by anthropogenic activities (port facilities, industrial facilities), without forgetting climate change. The present work was initiated in order to assess the influence of the seasonal evolution of physico-chemical parameters on the dynamics of zooplankton in the estuarine system of the Kienke. A study to assess the influence of seasonal evolution of some physico-chemical parameters on Zooplankton population dynamics was conducted from June 2016 to August 2017 in the Kienke estuarine system (Kribi, South Cameroon Region). Samples were collected in five (05) sampling points at the lower stream, at the confluence and then at 100 meters from the bank at sea following a monthly frequency. The Kienke estuary was characterized by spatio-temporal variations of physico-chemical parameters. These parameters are high temperature, relatively high electrical conductivity and salinity, and a relatively basic hydrogen potential (pH). Nutrients (ammonia nitrogen, nitrates and orthophosphates) were relatively low in the Kienke estuary. The organic pollution index (OPI) indicated moderate to high water pollution. At the surface and at depth, during the long dry season (December to February), Zooplankton densities were very low in the Kienke estuarine system. But rather high during the main rainy season (August to October). The results show that 105 species of Zooplankton belonging to 46 families grouped into four orders were identified. At the surface, 52 species of Zooplankton belonging to 23 families and 4 orders were identified, while at depth, 53 species of Zooplankton belonging to 23 families were also identified. The most abundant group was the Copepods represented by the following species: Tropocyclops confinis Kiefer, 1930;Mesocyclops sp. Sars, 1914;Macrocyclops sp. Claus, 1893;Thermocyclops sp. Kiefer, 1929;Parvocalaus elegans Adronov, 1972 and Clausocalanus sp. Giesbrecht, 1888. Overall, there was a predominance of microcrustaceans (Cladocera and Copepoda) over rotifers. The results obtained in this work will be of capital importance for the elaboration of sustainable management policies for the estuary of the city of Kribi.

Dynamic Multi-objective Optimization of Chemical Processes Using Modified BareBones MOPSO Algorithm

Dynamic multi-objective optimization is a complex and difficult research topic of process systems engineering. In this paper,a modified multi-objective bare-bones particle swarm optimization( MOBBPSO) algorithm is proposed that takes advantage of a few parameters of bare-bones algorithm. To avoid premature convergence,Gaussian mutation is introduced; and an adaptive sampling distribution strategy is also used to improve the exploratory capability. Moreover, a circular crowded sorting approach is adopted to improve the uniformity of the population distribution.Finally, by combining the algorithm with control vector parameterization,an approach is proposed to solve the dynamic optimization problems of chemical processes. It is proved that the new algorithm performs better compared with other classic multiobjective optimization algorithms through the results of solving three dynamic optimization problems.

Calculations of Chemical Reaction Dynamics for D+ H_2(j_i,ν_i=0)→DH(j_f, ν_f=0) + H

The constant Centrifugal potential approximation is Corrected so as to apply to the reactions of rotational excited reactants for D + H2 (j,, νi = 0 ) -DH(jf, νf = 0) + H. Our results show that the contributions from ji≠0 and Ωi terms are not negligible.

Research on the Dynamic Relationships among Taiwan’s Early Childhood Education and Its Stakeholders: The System Dynamics Perspective

In Taiwan,the low birth rate has become one of the most critical problems faced by the government and educational institutions at all levels.The enrolling student number of kindergartens perhaps is the most directly affected by such trend.The purpose of this study aims at constructing a system dynamics model to depict the relationships between the preschool children and their stakeholders for deducing the evolutionary trends of,and the interactions of,governmental policies and the operations of the early childhood education institutions.Through the interpretation of policies and simulation analysis of the twenty-year growth trend related to the child population in Taiwan,this study found that governmental policies and the promotion of education and care services have a positive effect on the growth of all levels of kindergarten classes.Besides,the relationship between the education and care service staff and the kindergarten play a causal balancing role in our proposed model.We suggest that the system dynamics model proposed by this study can help to observe the dynamic relationships formed by the stakeholders in preschool education and care system based on the“joint responsibility”of Taiwan’s early childhood education.

On-line Dynamic Model Correction Based Fault Diagnosis in Chemical Processes

<Abstract>A novel fault detection and diagnosis method was proposed, using dynamic simulation to monitor chemical process and identify faults when large tracking deviations occur. It aims at parameter failures, and the parameters are updated via on-line correction. As it can predict the trend of process and determine the existence of malfunctions simultaneously, this method does not need to design problem-specific observer to estimate unmeasured state variables. Application of the proposed method is presented on one water tank and one aromatization reactor, and the results are compared with those from the traditional method.

Theoretical study of the intensity of chemically induce dynamic electron polarization of radical-triplet pairs

Considering the interaction between excited triplet molecule and doublet radical, based on the second-order perturbation theory and the motion equation of density matrix, the polarization intensity of RTPM were theoretically calculated with the overpopulated doublet spin states and quartet spin states of radical-triplet pairs as initial conditions respectively. The results of calculation indicate that the net emissive polarization and the net absorptive polarization on the radical result from the zero-field-splitting (zfs) and the multiplet A/E and E/A polarization result from hyperfine (hf) interactions of the triplet molecule. The hyperfine related A+A/E or E+E/A CIDEP on the radical were the overpopulation of the net absorptive or emissive polarization and multiplet A/E or E/A polarization..

The Dynamical Model of Chemical Oscillation in CaF_2-HCl-H_2O Solid-Liquid Reaction System

Based on the physical chemistry principle, this paper proposes that the surface adsorption catalytic mechanism of HF is the key to dissolving the oscillation of the CaF\-2\|HCl\|H\-2O solid\|liquid reaction system. Meanwhile the dynamical model of this system has been established in order to study its non\|linear dynamical genesis. Although this mathematics model is based on CSTR reaction apparatus, it is applicable to the foliate flow reaction apparatus, too.

Hydrodynamic Instabilities Driven by Acid-base Neutralization Reaction in Immiscible System

The hydrodynamic instabilities driven by an acid-base neutralization reaction, in contact along a plane interface, placed in a Hele-Shaw cell under the gravitational field are reported. The system consists of the heavier aqueous tetramethyle-ammonium hydroxide below the lighter layer of organic phase with propionic acid as reacting specie. The effect of chemical composition on hydrodynamic instabilities during interfacial mass transfer accompanied by a neutralization reaction is investigated. Depending on the initial concentration of the reacting species, Marangoni convection in the form of roll ceils or trains of waves is observed. Mach- Zehnder interferometer is used to measure the change in base concentration at the time of instability formation. The results show that the instabilities resulted from the convection flow are more efficient to the mechanism of mass transfer and can drastically alter pattern formation in the system.

Spinal Manipulation and Dynamic Neuromuscular Stabilization Care for a 4-Year-Old Patient with Agenesis of the Corpus Callosum

The purpose of this case study is to describe the chiropractic care of a 4-year-old male patient with agenesis of the corpus callosum. Methods: Chiropractic care plan consisted of weekly appointments with the inclusion of at-home exercises coupled with academic intervention of physical and occupational therapies and assistive gait devices. Functional changes were monitored via objective clinic findings, independent clinical examination, and parental observation. Results: Agitated flexion contracted non-weight bearing child with gastrointestinal dysfunction and developmentally shunted growth responds to co-managed chiropractic care. Focus on aiding structural balance helped improve the weight bearing movement and mobility, physical calmness and contentment, emotional and verbal communication, as well as gastointestinal function. Discussion: This therapeutic approach decreased aberrant posture and enhanced quality of life. Conclusion: Chiropractic care in combination with academic intervention improved this child’s postural abnormalities, attitude, and cognitive development warranting consideration in subsequent care investigation.