Stochastic Process Optimization Technique

The conventional optimization methods were generally based on a deterministic approach, since their purpose is to find out an accurate solution. However, when the solution space is extremely narrowed as a result of setting many inequality constraints, an ingenious scheme based on experience may be needed. Similarly, parameters must be adjusted with solution search algorithms when nonlinearity of the problem is strong, because the risk of falling into local solution is high. Thus, we here propose a new method in which the optimization problem is replaced with stochastic process based on path integral techniques used in quantum mechanics and an approximate value of optimal solution is calculated as an expected value instead of accurate value. It was checked through some optimization problems that this method using stochastic process is effective. We call this new optimization method “stochastic process optimization technique (SPOT)”. It is expected that this method will enable efficient optimization by avoiding the above difficulties. In this report, a new optimization method based on a stochastic process is formulated, and several calculation examples are shown to prove its effectiveness as a method to obtain approximate solution for optimization problems.

Insight into relationship between composition,thickness and electrochemistry behavior of oxide film formed on TA15under different potentials in 0.5 mol·L^(-1)H_(2)SO_(4)

The oxide film formed on TA15 alloy in0.5 mol·L^(-1)H_(2)SO_(4)at different applied potentials is investigated by evaluating the film formation current density,film thickness,surface film composition,valence state,and the electrochemical characteristics.The relative quantitative spectral analysis revealed by X-ray photoelectron spectroscopy(XPS)and X-ray absorption spectra(XAS)shows that the increasing applied potential promotes the formation of thick and high-valence state films.By contrasting with XAS of the reference titanium oxides,it is found that TiO_(2)within the oxide film changes from anatase type to rutile type with the potential increases to 2.00 V.The oxide film formed at passive region has better protection performance,and with the increase of applied potential,the corrosion resistance of passive film increases,whereas the ND(donor density)values obtained from the Mott-Schottky(MS)results decrease with the increasing applied potential,indicating a better uniformity and protective effect of the oxide film.Based on above facts,the model of the oxide films formed on TA15 at different applied potentials in passive region and dissolve region is proposed.Besides,the existence forms of all the TA15alloying elements under the most corrosion resistant condition are confirmed.

Structure of polyelectrolyte brushes studied by coarse grain simulations

As an example of a very low friction system,Monte Carlo Brownian dynamics simulations have been used to calculate equilibrium structures of a polyelectrolyte brush grafted onto planes.The polymers were calculated in a semi-flexible coarse-grain model that is appropriate to treat the charge density of the polyion.The effect of linear charge density on the polyionx,the surface negative charge,and added salts were studied.In salt-free solution,scaling theories predicted the structure well in the lowxregion.In the highxregion,additional shrinkage was found from the theories due to counterion condensation.The effect of surface charge showed not only the repulsion of the polyion from the surface but also the shrinkage in the highxregion due to the additional counterions required for electrical neutrality.The addition of salts led to the shrinkage of the brush heights,and in the highxregion,additional extension was found.The computational strategy for calculating the friction dynamics of the system is also discussed.