Monte-Carlo model for the hydrogenation of alkenes on metal catalyst

A Monte-Carlo model for the simulation of alkene hydrogenation on metallic catalysts has been developed and implemented in Fortran language. We describe the model employed for ethylene hydrogenation on platinum and show the flow chart of the program. Computational characteristics such as number of necessary calculations to reach steady state, running times on different platforms, and effect of the size of the catalyst matrix, are presented. Good correlation between simulated and experimental data was observed. A subroutine allows for visual observation of the reaction. This approach is very useful for obtaining a personal impression of the important factors governing the reaction. By using this example the advantages of Monte-Carlo simulation to test the level of understanding of catalytic phenomena are discussed. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 396–403, 1998     

休哈特单值-移动极差控制图与精密度试验方法在入境澳洲铁矿质量波动跟踪中的应用

以澳洲某两个公司的块铁矿和粉铁矿为例,分析了近年来由澳洲进口的铁矿的质量变化情况。采用单值-移动极差控制图考察了2004年和2005年块铁矿的品质波动情况。用ISO 5725-2中的公式计算纯粉铁矿及混合粉铁矿中铁含量测量的精密度。分析结果显示,块铁矿品质从2004年以来呈现下降趋势,2005年品质波动较2004年大。混合粉铁矿的品质不如纯粉铁矿稳定,波动性较大。     

Researches on the Structure and Properties of Mullite Solid Solution Made from Industrial Waste

1 INTRODUCTION The mullite has excellent properties of high tem- perature thermodynamics and mechanics, such as corrosion resistance, creep resistance, thermal shock resistance and high hot strength at high temperature. So it can be used as the inner lining of industrial furnace, thermal insulator material, crucible, protec- ting tube and electronic packaging material, which are widely used in such industries as metallurgy, ceramics, cement, and fireproof materials[1]. So far there has no …     

Meta-Learning-Based Physics-Informed Neural Network: Numerical Simulations of Initial Value Problems of Nonlinear Dynamical Systems without Labeled Data and Correlation Analyses

There are several main challenges in solving nonlinear differential equations with artificial neural networks (ANNs), such as a nonlinear system''s sensitivity to its initial values, discretization, and strategies for incorporating physics-based information into ANNs. As for the first issue, this paper addresses the initial value problems of nonlinear dynamical systems (a Duffing oscillator and a Burger''s equation), which cause large global truncation errors in sub-domains with a significant reduction in the influence of initial constraints, using meta-learning-based physics-informed neural networks (MPINNs). The MPINNs with dual learners outperform physics-informed neural networks with a single learner (no fine reinitialization capability). As a result, the former approach improves solution convergence by 98.83\% in the sub-time domain (III) of a Duffing oscillator, and by 85.89\% at $t = 45$ in a Burger''s equation problem, compared to the latter one. Model accuracy is highly dependent on the adaptability of the initial parameters in the first hidden layers of the meta-models. From correlation analyses, it is obvious that the parameters become less (the Duffing oscillator) or more (the Burger''s equation) correlated during fine reinitialization, as the update manner differs or is similar to the one used in pre-initialization. In the first example, the MPINN achieves both the mitigation of model sensitivity to its output and the improvement of model accuracy. Conversely, the second example shows that the proposed approach is not enough to solve both issues simultaneously, as increased model sensitivity to its output leads to higher model accuracy. The application of transfer learning reduces the number of iterative pre-meta-trainings.     

Novel method to characterize the hydrolytic decomposition of biopolymer surfaces

Present pharmaceutical research is focused on the development, modification and characterisation of new drug delivery systems. Among the many different substances, biodegradable polymers and copolymers are of practical importance, especially if their degradation byproducts are non-toxic. The polymeric drug carriers are not easily wettable by water or aqueous solutions, i.e. they are hydrophobic. This surface hydrophobicity is unfavourable for keeping drug carriers circulating in the blood long enough to release the drug so that it reaches its target. Therefore, copolymers with components of different hydrophobicity were introduced, to make them less hydrophobic and hence more suitable for drug delivery in the human body. Exploratory experiments with one homopolymer, , -poly(lactic acid), , -PLA and two of its copolymers, , -poly(lactic/glycolic acid), and , -PLGA with 85/15 and 50/50 copolymer ratios were carried out. Films of these substances were prepared by dip coating onto hydrophobic and hydrophilic substrates. The changes in wettability of the polymer layers, caused by the direct contact with an aqueous environment (soaking the samples in distilled water), have been studied to model the hydrolytic decomposition of polymer surfaces and to follow the changes in their wettability by dynamic contact angle measurements in a non-destructive manner. It was found that each polymer film became less hydrophobic (dynamic contact angles decreased) and more heterogeneous as the decomposition progressed with time. Increasingly significant decreases in contact angles were observed for the copolymer films containing 15 and 50% glycolic acid, during the 50–80-day-long study. These findings were supported by gel chromatographic analysis of the soaking liquids. It was concluded that the homopolymer layer of , -PLA was the most resistant to hydrolysis and the stability of copolymer films decreased with increasing glycolic acid ratio in the copolymers. This is accordance with the fact that the less crystalline poly(glycolic acid) is more hydrophilic and hence less resistant to hydrolytic decomposition, than the poly(lactic acid). The effect of pH on the rate of hydrolysis of polymer films was also established; the influence of pH on the decomposition was best demonstrated, again, for the copolymer with 50/50 component ratio. The outcome of these experiments showed that the contact angle measuring method enables us to detect, follow and interpret the hydrolytic decomposition of biopolymer substances in a non-invasive manner.     

Ultra-Hydrophilic Transition Metals as Histophilic Biomaterials

Extremely hydrophilic surfaces have been prepared on titanium, stainless steel and cobalt chromium alloys after treatment by a chromosulfuric acid method at 200-240 °C. In spite of a ca. 300-500-fold higher surface roughness (Ra ∼ 880-1100 nm) in comparison to the quartz glass controls (Ra ∼ 2-3 nm), surfaces with contact angles close to 0° in the absence of contact angle hysteresis (ultra-hydrophilic surfaces) were obtained. We have called this phenomenon “Inverse Lotus Effect” . Metal surface layers exhibiting such properties form excellent priming coats with bioadhesive properties (histophilic surfaces) for the attachment of biocoats consisting of BMP-2 with bioactive properties in bone. Direct immobilization of BMP-2 on implant surfaces eliminates the need for a separate BMP-2 carrier or delivery system such as collagen, as is widely employed by others. A fundamental problem in such surfaces is that it is not at all certain that a protein immobilized in such a manner will retain its biological activity. In the case of BMP-2 it can be shown in vitro that the novel surfaces are biologically active. Similarly in vivo studies indicate an accelerated and improved osseointegration.     

Yang–Lee zeros of the Ising model on random graphs of non planar topology

We obtain in a closed form the 1/N² contribution to the free energy of the two Hermitian N×N random matrix model with nonsymmetric quartic potential. From this result, we calculate numerically the Yang–Lee zeros of the 2D Ising model on dynamical random graphs with the topology of a torus up to n=16 vertices. They are found to be located on the unit circle on the complex fugacity plane. In order to include contributions of even higher topologies we calculated analytically the nonperturbative (sum over all genus) partition function of the model for the special cases of N=1,2 and graphs with n≤20 vertices. Once again the Yang–Lee zeros are shown numerically to lie on the unit circle on the complex fugacity plane. Our results thus generalize previous numerical results on random graphs by going beyond the planar approximation and strongly indicate that there might be a generalization of the Lee–Yang circle theorem for dynamical random graphs.     

Adsorption of a Gaussian random copolymer chain at an interface

We consider the adsorption of an isolated, Gaussian, random, and quenched copolymer chain at an interface. We first propose a simple analytical method to obtain the adsorption/depletion transition, by averaging over the disorder the partition function instead of the free energy. The adsorption thresholds obtained by previous authors at a solid/liquid and at a liquid/liquid interface for multicopolymer chains can be rederived using this method. We also compare the adsorption thresholds obtained for bimodal and for Gaussian disorder; they only agree for small disorder. We focus on the specific case of an ideally flat asymmetric liquid/liquid interface, and consider the situation where the chain is composed of monomers of two different chemical species A and B. The replica method is developed for this case. We show that the Hartree approximation, coupled to a replica symmetry assumption, leads to the same adsorption thresholds as obtained from our general method. In order to describe the properties of the adsorbed (or depleted) chain, we develop a new approximation for long chains, within the framework of the replica theory. In most cases, the behavior of a random copolymer chain can be mapped onto that of a homopolymer chain at an asymmetric attractive interface. The values of the effective adsorption energy are different for a random and a periodic copolymer chain. Finally, we consider the case of uncorrelated annealed disorder. The behavior of an annealed chain can be mapped onto that of a homopolymer chain at an asymmetric non attractive interface; hence, an annealed chain cannot adsorb at an asymmetric interface. Received 21 January 1999     

Weakly charged lamellar bilayer system: Interplay between thermal undulations and electrostatic repulsion

We study the interplay between thermal undulations and electrostatic interactions for weakly charged surfactant bilayers by measuring the backscattering of light from very dilute lamellar phases of the non-ionic surfactant triethylene glycol monodecyl ether (C₁₀E₃) doped with small amounts of the anionic surfactant sodium dodecyl sulphate (SDS), both with and without added electrolyte. Upon charging, the lamellar phases show a transition from undulation to electrostatic stabilization. Non-lamellar structures develop if the molar mixing ratio exceeds . Deviations from ideal swelling, , where is the lamellar repeating distance and the membrane volume fraction, were detected for all lamellar phases. Salt-free lamellar phases with charge densities below , as well as more highly charged lamellar phases at high ionic strength show a universal logarithmic deviation from ideal swelling that was analyzed using theories for undulation stabilized lamellar phases. Deviations from ideal swelling for electrostatically stabilized lamellar phases were analyzed using theories recently developed for undulations in charged lamellar phases. The fits to the various theories yield a value of for the bending modulus of the C₁₀E₃ bilayers. Received 21 June 1999 and Received in final form 25 August 1999