Oxidation process of polysulfides in charge process for lithium�Csulfur batteries

The oxidation of polysulfides to element sulfur in charge process was studied by solution thermodynamic analysis and means of cyclic voltammetry (CV), X-ray diffraction (XRD), and charge?Cdischarge test. Basing on the solution thermodynamic analysis, the oxidation process of polysulfides to element sulfur would arise only if the charge voltage exceeds 3.36 V in a lithium?Csulfur cell employing 1.0 M LiN(CF₃SO₂)₂ in 1,2-dimethoxy ethane. Furthermore, the minimum of charge voltage which can push the oxidation would fall down with the increasing solubility of elemental sulfur in electrolyte solution. These analyses were confirmed by practical measurements. One new anodic peak corresponding to the oxidation process of polysulfides to solid sulfur was observed by CV. Both XRD patterns and charge?Cdischarge test showed that the element sulfur appeared in the cathode after the battery was charged over 3.4 V. Hence, the lithium?Csulfur cell charged over 3.4 V exhibited an improved cycle life since the capacity degradation between the first cycle and the second was depressed. In order to improve the energy efficiency, carbon disulfide was added in the electrolyte solution of lithium?Csulfur cell to increase the solubility of sulfur.     

Influence of pH on the phototransformation process of Photogem®

Photogem® is a hematoporphyrin derivative that has been used as a photosensitizer in experimental and clinical Photodynamic Therapy (PDT) in Brazil. Photosensitizers are degraded under illumination. This process, usually called photobleaching, can be monitored by decreasing in fluorescence intensities and includes the following photoprocesses: photodegradation, phototransformation, and photorelocalization. Photobleaching of hematoporphyrin-type sensitizers during illumination in aqueous solution is related not only to photodegradation but is also followed by the formation of photoproducts with a new fluorescence band at around 640–650 nm and with increased light absorption in the red spectral region at 640 nm. In this study, the influence of pH on the phototransformation process was investigated. Photogem® solutions, 40 μg/ml, were irradiated at 514 nm with intensity of 100 mW/cm² for 20 min with different pH environments. The controls were performed with the samples in the absence of light. The Photogem® photodegradation is dependent on the pH. The behavior of photodegradation and photoproducts formation (monitored at 640 nm) is distinct and depends on the photosensitizer concentration. The processes of degradation and photoproducts formation were monitored with Photogemin the concentration of 40 μg/mL since that demonstrated the best visualization of both processes. While below pH 5 the photodegradation occurred, there was no detectable presence of photoproducts. The increase of pH led to increase of photoproducts formation rate with photodegradation reaching the highest value at pH 10. The increase of photoproducts formation and instability of Photogem® from pH 6 to pH 10 are in agreement with the desired properties of an ideal photosensitizer since there are significant differences in pH between normal (7.0 < pH < 8.6) and tumor (5.8 < pH < 7.9) tissues. It is important to know the effect of pH in the process of phototransformation (degradation and photoproduct formation) of the molecule since low pH values promotes increase in the proportion of aggregates species in solution and high pH values promotes increase in the proportion of monomeric species. There must be an ideal pH interval which favors the phototransformation process that is correlated with the singlet oxygen formation responsible by the photodynamic effect. These differences in pH between normal and tumor cells can explain the presence of photosensitizers in target tumor cells, making PDT a selective therapy.     

Effect of cutting process on machine tool noise

Based on the principle of Statistical Energy Analysis(SEA)for non-conservatively coupled systems under general excitations,relation-ship between noise radiated from and excitations on coupled complexstructures is studied,which lays a foundation for the determination ofnoise/vibration energy by evaluation of exciting forces,and from that thequantitative analysis of the effects of an excitation on sound power froma sub-structure can be done.With extending of the relationship to thestudy of cutting noise,regression analysis method for evaluating the effectsof cutting process on machine tool noise is established.Results show thatcutting process has generally negligible effects on machine tool noise,andthere is no apparent difference between machine tool noise in cutting condi-tion and in idle one.     

Influence of substrate process tolerances on transmission characteristics of frequency-selective surface

Frequency-selective surface(FSS)is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units(or apertures)arranged periodically on it.When manufacturing the substrate,its thickness and dielectric constant suffer process tolerances.This may induce the center frequency of the FSS to shift,and consequently influence its characteristics.In this paper,a bandpass FSS structure is designed.The units are the Jerusalem crosses arranged squarely.The mode-matching technique is used for simulation.The influence of the tolerances of the substrate's thickness and dielectric constant on the center frequency is analyzed.Results show that the tolerances of thickness and dielectric constant have different influences on the center frequency of the FSS.It is necessary to ensure the process tolerance of the dielectric constant in the design and manufacturing of the substrate in order to stabilize the center frequency.     

Optimization of corona discharge process using Box–Behnken design of experiments

The corona discharge process was studied using Box–Behnken design of experiments in conjunction with response surface methodology of analysis. The single as well as interaction effects of process factors namely applied voltage, time of charging, and distance between electrodes on the surface potential of meltblown nonwoven electret media were examined. The response surface model predicting the surface potential of the electrets displayed a very good correspondence with the experimental results. The optimized corona discharge process run by keeping the predicted levels of process factors yielded surface potential of the electret media very close to that predicted from the model.     

Study of laser fragmentation process of silver nanoparticles in aqueous media

Laser fragmentation of Ag nanoparticles in Ag hydrosol was studied by simultaneous measurements of the transmitted fluence of the incident laser beam and the time evolution of the surface plasmon extinction (SPE) spectra. The experiments showed that the laser fragmentation in a small volume of hydrosol proceeds during first 20 pulses and then reaches saturation. The value of the transmitted fluence corresponding to saturation increases with incident pulse fluence, but the impact of the first pulse applied to the hydrosols shows an optical limitation. Fluences above 303 mJ/cm² cause the formation of less stable, aggregating nanoparticles, while fluences below 90 mJ/cm² do not provide sufficient energy for efficient fragmentation. The interval of fluences between 90–303 mJ/cm² is optimal for fragmentation, since stable hydrosols constituted by small, non-aggregated nanoparticles are formed.     

Dynamics of aggregation－annihilation process with cluster removals

We have studied the kinetic behaviours of irreversible aggregation－annihilation models with cluster removals. In the models, an irreversible aggregation reaction occurs between any two clusters of the same species and an irreversible annihilation reaction occurs simultaneously between two different species; meanwhile, the clusters of large size are gradually removed from the system. In a mean-field limit, we obtain the general solutions of the cluster-mass distributions for the cases with an arbitrary removal probability. We found that the cluster-mass distribution of either species satisfies a generalized or modified scaling form. The results also indicate that the evolution behaviours of the systems depend strongly on the details of the reaction events.     

One-loop chiral amplitudes of Møller scattering process

The high energy amplitudes of the large angles Møller scattering are calculated in the frame of chiral basis in Born and 1-loop QED level. Taking into account as well the contribution from emission of soft real photons the compact relations free from infrared divergences are obtained. The expressions for the contributions to the cross section of individual chiral amplitudes are in agreement with renormalization group predictions.     

Study on cooling process of cryogenic system for superconducting magnets of BEPCⅡ

In the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), three superconducting magnets are employed to realize the goal of two orders of magnitude higher luminosity. A cryogenic system with a total capacity of 0.5~kW at 4.5~K was built at the Institute of High Energy Physics (IHEP) to support the operations of these superconducting devices. For preparing the commissioning of the system, the refrigeration process was simulated and analyzed numerically. The numerical model was based on the latest engineering progress and focused on the normal operation mode. The pressure and temperature profiles of the cryogenic system are achieved with the simulation. The influence of the helium mass flow rates to cool superconducting magnets on the thermodynamic parameters of their normal operation is also studied and discussed in this paper.     

Mössbauer spectroscopy study of the disordering process of Fe-rich FeAlSi alloys

In this work we study systematically the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe₇₅Al_25?x Si _x , Fe₇₀Al_30?x Si _x and Fe₆₀Al_40?x Si _x alloys by means of Mössbauer spectroscopy and X-ray diffraction measurements. In order to obtain different stages of disorder the alloys were deformed by ball milling annealed (ordered) alloys during different number of hours. X-ray and Mössbauer data show that mechanical deformation induces the disordered A2 structure in these alloys. The results indicate that addition of Si to binary Fe–Al alloys makes the disordering more difficult. The study of the hyperfine fields indicates that depending on the Fe content the magnetic behaviour of these ternary alloys varies. For Fe₇₅Al_25?x Si _x series, the alloys have different magnetic behaviours with deformation depending on the Si content. The magnetization of the alloys with high Si content decreases with deformation, as it happens to binary Fe₇₅Si₂₅ and the magnetization of the alloys with low Si content increases with deformation, as it happens to binary Fe₇₅Al₂₅. For Fe₇₀Al_30?x Si _x series the mean hyperfine fields show that there are two different stages with the disordering, in a first stage the mean hyperfine fields decrease and in the second stage they increase. Finally, for Fe₆₀Al_40?x Si _x alloys there is a magnetic transition, from a paramagnetic ordered state to a magneticdisordered state.     

Atomic mechanism of vitrification process in simple monatomic nanoparticles *

Glass formation in simple monatomic nanoparticles has been studied by molecular dynamics simulations in spherical model with a free surface. Models have been obtained by cooling from the melt toward glassy state. Atomic mechanism of glass formation was monitored via spatio-temporal arrangement of solid-like and liquid-like atoms in nanoparticles. We use Lindemann freezing-like criterion for identification of solid-like atoms which occur randomly in supercooled region. Their number grows intensively with decreasing temperature and they form clusters. Subsequently, single percolation solid-like cluster occurs at temperature above the glass transition. Glass transition occurs when atoms aggregated into this single percolation cluster are in majority in the system to form relatively rigid glassy state. Solid-like domain is forming in the center of nanoparticles and grows outward to the surface. We found temperature dependence of potential energy, mean-squared displacement (MSD) of atoms, diffusion constant, incoherent intermediate scattering function, radial distribution function (RDF), local bond-pair orders detected by Honeycutt-Andersen analysis, radial density profile and radial atomic displacement distributions in nanoparticles. We found that liquid-like atoms in models obtained below glass transition have a tendency to concentrate in the surface layer of nanoparticles. However, they do not form a purely liquid-like surface layer coated nanoparticles.     

The triple-α process and the origin of the elements

The triple-α process is the nuclear fusion of helium to carbon. Two ⁴He nuclei collide and form an unstable state of ⁸Be. Before this can decay back a third α-particle collides with it to form a ¹²C nucleus. The reaction rate is probably the most temperature sensitive known to physics because there is a resonant state of the ¹²C nucleus at just the energy of the ⁸Be? and the ⁴He that have the greatest chance of penetrating the Coulomb barrier. The reaction takes place in stars that have exhausted their central hydrogen fuel. Most interesting are the asymptotic giants that can dredge the carbon produced to the surface and return it, perhaps first processing it to nitrogen, to the interstellar medium. The fortuitous energy of the resonant state of ¹²C and its consequences are crucial to the way stars evolve and the abundance of carbon on the Earth.     

Diagnosis of phasma in CCD damage process induced by laser

In this paper, the shapes of plasma produced by a Q-switched YAG laser acted repeatedly upon a CCD with MOS structure are used, to investigate the destroying process of the optoelectronic device. The experimental results of CCD destroyed by a 1.06μm laser beam with a pulse width of 15 ns are given.     

Formation and evolution mechanisms of large-clusters during rapid solidification process of liquid metal Al

A molecular dynamics simulation study has been performed for the formation and evolution characteristics of nano-clusters in a large-scale system consisting of 400000 atoms of liquid metal Al. The center-atom method combined with pair-bond analysis technique and cluster-type index method (CTIM) has been applied here to describe the structural configurations of various basic clusters. It is demonstrated that both the 1551 bond-type and the icosahedral cluster (12 0 12 0) constructed by 1551 bond-types are dominant among all the bond-types and cluster-types, respectively, in the system and play a critical role in the microstructure transitions of liquid metal Al. The nano-clusters (containing up to 150 atoms) are formed by the combination of some middle and small clusters with distinctly different sizes, through mutual competition by unceasing annex and evolution in a seesaw manner (in turn of obtaining and losing), which do not occur as the multi-shell structures accumulated with an atom as the center and     

Chaos and Monte Carlo Approximations of the Flip-Annihilation process

The flip-annihilation process is a random particle process with one-dimensional local interaction in discrete time, initially presented by one of us, namely Toom in 2004. Its components are enumerated by integer numbers and every component has two states, “minus” and “plus”. At every time step two transformations occur. The first one, called “flip”, independently turns every minus into plus with probability β. The second one, called “annihilation”, acts thus: whenever a plus is a left neighbor of a minus, both disappear with probability α independently from other components. What is interesting about this process is that it is ergodic for β>α/2 and non-ergodic for β<α ²/250. It is natural to conjecture that there is some transition curve, which we call the true curve and denote by , which separates the areas of ergodicity and non-ergodicity of this process from each other. The estimates, mentioned above, albeit rigorous, leave a large gap between them and the present article’s purpose is to obtain some closer, albeit non-rigorous, approximations of the true curve. We do it in two ways, one of which is a chaos approximation and the other is a Monte Carlo simulation. Thus we obtain two curves, which are much closer to each other than the rigorous estimations. Also we fill in, albeit only numerically, another shortcoming of the rigorous estimation β<α ²/250, namely that it leaves us uncertain whether the true curve has a zero or positive slope at the point α=β=0. Both approximate curves have a positive slope at α=0, as we hoped.     

Numerical study of laser-induced collision process in Eu-Sr in strong field

Theoretically based on the four-level model, one LICET process in Eu-Sr system in both weak and strong fields was calculated by immediate numerical integrations. Numerical results in weak field are in fair to good agreement with analytical ones. Numerical results in strong field show that: (a) the peak of the LICET profiles moves to the violet side and the tuning range of the profiles obviously becomes narrower when the laser field intensity increases; and (b) numerical results in strong field differ a lot from analytical ones, which indicates that in strong field, the analytical expressions are not applicable any longer.     

Simulation of the graphite–diamond transition in an isentropic process

An equation of state for graphite and diamond has been derived in wide density and temperature ranges. A set of equations for the graphite–diamond phase transition has been presented. Hugoniots for graphite and diamond have been calculated. Numerical simulation data for the graphite–diamond transition in the isentropic compression process using a metallic z-pinch with diamond saving have been reported.     

Influences of laser in low power YAG laser-MAG hybrid welding process

The influences of laser defocusing amount△z,laser power P,space distance D_(LA)between laser and arc on weld penetration,arc modality and stability are investigated in low power YAG laser and metal active gas(laser-MAG)hybrid welding process.The experimental results indicate that the effects of laser- induced attraction and contraction of MAG arc are emerged in hybrid welding process,which result in the augmentation of hybrid welding energy.When D_(LA)=-0.5-2 mm,△z=-2-2 mm and P≥73 W,the synergic efficiency between laser and MAG arc is obvious,the cross section at the root of hybrid arc is contracted and the hybrid weld penetration is increased.The maximal ratio of hybrid/MAG weld penetration is 1.5 and the lowest YAG laser power that augments MAG arc is 73 W.The input of YAG laser makes the stabilities of arc ignition and combustion prominent in hybrid welding process.     

Multifractal properties of denaturation process based on Peyrard–Bishop model

DNA has attracted the interest of physicists for a long time. One interesting theoretical question is its melting behavior. The Rényi dimension spectrum of the melting transition of DNA, reveals the multifractal nature of the dynamics of the Peyrard–Bishop model. In this Letter, the effects of different parameters involved in the Peyrard–Bishop model on the multifractal nature of the melting dynamics of a DNA chain are investigated in details. As a result, it can be concluded that not only the best multifractality nature of the model arises from the Morse potential term which is taken in the model but also the multifractal nature of the model is independent of the homogeneity, the length of chain, stacking terms, the thermal bath simulation methods and even the potentials which describe the interaction between the two bases in a pair. Furthermore, our results confirm that, the best potential to describe the interactions between the bases in pairs in the PB and PBD models is the Morse potential.     

Nonlinear optical properties of stimulated Brillouin scattering process in submerged object detection

Nonlinear optical properties of stimulated Brillouin scattering(SBS)to signal detection in water are analyzed.With the threshold characteristics,SBS only occurs when the high power laser is focused in the SBS cell.When there is an object present in front of the focus,it leads to lower incident intensity and then SBS does not occur.The backward SBS signal depends on the focusing location.The nonlinear optical properties of SBS process in the focusing regime are analyzed theoretically.With the object coming near to the focusing center,the backward Stokes signal rises up from zero to a maximum,and then grows to saturation.The delay time of the echo signal to pump signal can give the object location.In experiment, the peak position of varying rate of energy can give object location.