External field effect on the current distribution in superconducting composites: evaluation of the degradation in adiabatic conditions

Since cooling conditions in coils are not very good it is important to develop a nearly intrinsically stable superconducting composite. The external field effect greatly improves current distribution inside the composite and therefore improves the adiabatic stability of the composite.For a typical composite with an equal proportion of copper and superconductor, subjected only to its self-field, the maximum permissible number of filaments for an expected 10% current degradation is: N_max = 800 for a 10μ diameter filament, N_max = 2 700 for a 5μ diameter filament.For the same composite subjected to an external field of up to 5 T we get: N_max = 2 000 for a 10μ diameter filament, N_max = 7 000 for a 5μ diameter filament.This suggests the leading part of a large coupling factor K equal to B_ext/l supplies a good current redistribution in the composite.Consequently degradation is expected to be more important in a massive elementary conductor than in a multi-strand cable carrying the same overall current.     

Influence of adiabatic conditions on the losses in composite superconductors

The losses in composite multifilamentary superconductors during a pulse of a transverse magnetic field under adiabatic conditions have been studied. A considerable difference in value and character of the loss dependences under adiabatic conditions, as compared to those under isothermal conditions, was found. The influence of various factors and conductor parameters on the losses was investigated.     

Co-metabolic degradation of bensulfuron-methyl in laboratory conditions

The present study deals with the degradation of bensulfuron-methyl by microorganisms cultured with different sources of carbon, nitrogen and phosphorus. Addition of carbon source accelerated the degradation of bensulfuron-methyl under co-metabolism process. Sodium lactate was the best carbon source for the degradation of bensulfuron-methyl, compared to other carbon sources studied, and the degradation ratio of bensulfuron-methyl reached 79.5%, whereas only 34.6 and 29.7% were removed in the presence of glucose and sucrose, respectively. Supplement of nitrogen source also enhanced degradation of bensulfuron-methyl. However, no significant differences were observed in the loss of bensulfuron-methyl between organic nitrogen and inorganic source. Phosphate buffer was supplemented into the media to maintain neutral conditions for the advantage of the strain growth since increase in pH value was observed. An orthogonal array design was applied to arrange main factors singled out for investigating the influence of factor and interaction between them on the degradation of bensulfuron-methyl. Statistical analysis showed that the concentration of sodium lactate, bensulfuron-methyl and inoculum size were the main effects, and the interaction of sodium lactate and bensulfuron-methyl was of statistical significance.     

The effect of the memristor electrode material on its resistance to degradation under conditions of cyclic switching

The stability of titanium oxide memristors with gold and platinum electrodes with respect to switching-induced degradation has been studied. It is established that the use of gold instead of platinum as the electrode material significantly increases the resistance of a memristor to degradation in the course of repeated resistance read-write(erase) cycles. The first Russian high-endurance memristor based on titanium oxide has been obtained, which can withstand up to 3000 resistive switching cycles.     

长期约束条件下TiNi合金超弹性衰减研究

研究了在长期约束条件下TiNi合金超弹性的衰减规律,结果表明,超弹性衰减随时间呈类抛物线规律;约束应变越大,衰减量越大,约束应变较小时不发生明显衰减;应力-应变循环处理可显著降低超弹性衰减幅度.在阐明超弹性衰减襄律的基础上,讨论了衰减机制.     

Enhanced photocatalytic degradation of pollutants in petroleum refinery wastewater under mild conditions

A circulating photocatalytic reactor was used for removing aliphatic and aromatic organic pollutants in refinery wastewater. The TiO(2) added wastewater samples, while saturating with air, were irradiated with an immersed mercury UV lamp (400 W, 200-550 nm). Optimal catalyst concentration, fluid pH and temperature were obtained at amounts of near 100 mgL(-1), 3 and 318K, respectively. A maximum reduction in chemical oxygen demand of more than 90% was achieved after about 4h irradiation and hence, 73% after about only 90 min; significant pollutant removal was also achievable in the other conditions. The identification of the organic pollutants, provided by means of a GC/MS and a GC analysis systems, equipped with headspace injection technique, showed that the major compounds were different fractions of petroleum aliphatic hydrocarbons (up to C(10)) and the well-known aromatic compounds such as benzene, toluene and ethylbenzene. The results showed a high efficiency degradation of all of these pollutants.     

市区工况车用发动机油质量衰变分析

针对车辆使用工况的多变性、发动机油的多样性、换油周期确定的复杂性,对同一台车两个换油周期内的运行状况和润滑油的理化性能同步检测,探讨市区工况下车用发动机油的性能衰变规律,以期为润滑油的合理使用和更换提供参考。结果表明:润滑油的总酸值随运行时间延长呈线性增长,矿物油总酸值增大的幅度大于半合成油;润滑油的运动粘度、起始氧化温度随运行时间延长而逐渐降低,矿物油运动粘度和起始氧化温度降低幅度小于半合成油。一台车获得的试验结果有限,要得到共性规律,还需加大试验车和试验油的数量以及拓宽运行环境,为发动机油质量衰变规律和换油周期的研究提供更为充足、科学的参考数据。     

In vitro degradation behavior of silica nanoparticles under physiological conditions

Understanding the degradability of silica nanoparticles is significant for the rational design of desired nanomaterials for various biomedical applications. However, the effect of the intrinsic properties of silica nanoparticles, such as particle shape, surface chemistry, and porosity, on kinetic degradation process under different extrinsic conditions has still received little attention. Herein, mesoporous silica nanoparticles (MSNs) with different aspect ratios (ARs, 1, 2, and 4), the corresponding PEG-functionalized MSNs, and amorphous St?ber spherical silica nanoparticles were specially designed and their degradation was evaluated in in vitro simulated physiological media. The results show that shape, surface properties and porosity of nanoparticles, as well as the component of simulated physiological media, play important roles in tuning the degradation kinetics and behaviors. Sphere-shaped MSNs have a faster degradation rate than rod-shaped counterparts. Naked MSNs are eroded from particle external surface, while PEGylated MSNs from interior of particles. And spherical MSNs display more extensive degradation than amorphous silica nanoparticles. The presence of fetal bovine serum (FBS) in Dulbecco's Modified Eagle's Medium (DMEM) can accelerate the degradation process. These results can provide useful guidelines for the rational design of silica nanoparticles for biomedical applications.     

The adiabatic anti-jitter circuit

The anti-jitter circuit (AJC) is able to reduce phase noise and spurious content of any frequency source at sideband frequencies above a defined cut-off frequency. By contrast, a phase-locked loop (PLL) can only reduce the intrinsic phase noise of its output oscillator closer to carrier lower than a defined cut-off frequency. The AJC has no output oscillator, but its phase noise performance can be assessed as if it had. This paper reports the invention of the adiabatic AJC (AAJC), giving the AJC improved power consumption, frequency range, and maximum frequency of operation. The term “adiabatic” is adopted to indicate that the core part of the new circuit does not require a power supply. It takes power from the input source directly to create the sawtooth waveform that has considerably reduced time jitter on the longer of its two ramp waveforms. Discrete models of the AJC are now operational at 30 MHz, which is twice the 15-MHz operation previously reported. The cut-off frequency of suppression has been maintained at a few kiloHertz. Noise analysis now shows performance comparable with an LC oscillator is possible. SPICE simulations show potential operation up to 5 GHz. The AAJC is also cascadable up to the intrinsic (shot) noise limit. Shot noise can be reduced by feedback     

Performance degradation of a vapor compression refrigeration system under fouled conditions

Performance degradation due to fouling in a vapor compression cycle is investigated for various applications. Considering the first set of refrigerants i.e. R134a, R410A and R407C, from a first law standpoint, the COP indicates that R134a always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R134a performs the best in all cases. Considering the second set of refrigerants i.e. R717, R404A and R290, from a first law standpoint, the COP indicates that R717 always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R717 performs the best in all cases. Volumetric efficiency of R410A and R717 remained the highest under the respective conditions studied. Furthermore, performance degradation of the evaporator often has a larger effect on compressor power requirement while that of the condenser has an overall larger effect on the COP. A new performance degradation law is presented in light of the data generated, which can reduce the amount of experimentation and help predict relevant quantities of the refrigeration system.     

Batch salicylic acid nitration by nitric acid/acetic acid mixture under isothermal, isoperibolic and adiabatic conditions

Runaway phenomena and thermal explosions can originate during the nitration of salicylic acid by means of a nitric acid/acetic acid mixture when the thermal control is lost, mainly as a result of the formation and thermal decomposition of picric acid. The prediction of the behaviour of this system is thus of great importance in view of possible industrial applications and the need to avoid the occurrence of unwanted dangerous events. During a previous investigation a model was developed to simulate its behaviour when the starting concentration of the substrate is too low, thus, preventing the precipitation of poor soluble intermediates. In this work this model is extended to deal with more concentrated systems even in case of a solid phase separating during the process. To this purpose the previously assessed dependence of the solubility of 3-nitro and 5-nitrosalicylic acids upon temperature and nitric acid concentration is included in the model. It is assumed that when 3-nitro and 5-nitrosalicylic acids are partially suspended in the reacting medium a kinetic regime of "dissolution with reaction" is established; that is, the redissolution of these species is a fast process compared to the successive nitration to give dinitroderivatives. Good results are obtained in the comparison of the experimental data with those calculated both in isoperibolic and adiabatic conditions when the revised model is used.     

Proximity effect and branching conditions in superconducting networks

The onset of superconductivity on proximity networks made of very thin wires of different materials is investigated by adapting de Gennes' one-frequency approximation for dirty superconductors to networks. Branching conditions for the order parameter in the presence of a magnetic fieldH are derived, and an equation for the global critical temperatureT _c (H) of arbitrary networks is obtained that generalizes Alexander's equation for networks made of a single material. Numerical applications to simple proximity networks are given showing phase boundariesT _c (H) and the order parameter on adjacent branches as a function of geometry and mean free path.     

On adiabatic shear bands in rigid-plastic materials

Summary An analysis is made of a solution obtained by Coleman and Hodgdon in their theory of strain localization in rigid-plastic materials that soften on deformation. It is observed that the solution implies that certain properties of the strain distribution across a shear band should be essentially independent of material parameters and stress level. Among the implications of this type is a general relation which one can use to express the strain at the center of a shear band in terms of the mean strain in the band and the strain outside the band. Theoretical temperature and displacement fields are compared with experimental observations of shear-band formation reported by Costin, Crisman, Hawley, and Duffy for torsional deformation of cold rolled mild steel at ballistic rates.With 3 Figures     

On the adiabatic theorem in quantum mechanics

The adiabatic and postadiabatic approximations, as well as the adiabatic and nonstationary perturbation theories, are constructed using a canonical averaging method under the assumptions which are more general than those used in the existing theories. An asymptotic evaluation of the proximity of rigorous and approximate solutions is performed.     

Second law implications of a magnetocaloric effect adiabatic phase transition of type I superconductor particles

Abstract

The nature of the thermodynamic behaviour of type I superconductor particles having a cross-section less than the Ginzburg-Landau temperature dependent coherence length ξ(T) is discussed for a magnetic field-induced adiabatic phase transition from the superconductive state to the normal state. The magnetocaloric effect adiabatic phase transition of a particle-dimensioned specimen is characterized by a decrease in entropy, suggesting a quantum limit to traditional formulations of the second law, evidenced by attainment of a final process temperature below that resulting from the isentropic magnetocaloric effect adiabatic phase transition of a bulk dimensioned specimen.     

Numerical Estimation of AC Loss in MgB<Subscript>2</Subscript> Wires in Self-field Condition

In order to utilize MgB₂ wires in AC electrical devices, it is very important to be able to understand the characteristics of MgB₂ materials in the AC electromagnetic conditions and give an accurate estimate of the AC loss. A numerical method is proposed in this paper to estimate the AC loss in MgB₂ wires. This method is based on solving a set of partial differential equations in which the magnetic field is used as the unknowns to get the current and electric field distributions in the cross sections of the wires, and hence the AC loss can be calculated. A commercial FEM solver is used to give an easy and fast solution for many complex geometries. This method is used to model a monocore MgB₂ wire and a multifilamentary MgB₂ wire. The results demonstrate that the multifilamentary MgB₂ wire has a lower AC loss than monocore one when carrying the same amount of current.     

Amine promoted, metal enhanced degradation of Mirex under high temperature conditions

In this study, zero-valent metal dehalogenation of mirex was conducted with amine solvents at high temperatures. Mirex was treated with excess amine in sealed glass tube reactors under nitrogen. The amines used were n-butyl amine (l), ethyl amine (l), dimethyl amine (g), diethyl amine (l), triethyl amine (l), trimethyl amine (g) and ammonia (g). The metals used were copper, zinc, magnesium, aluminum and calcium. The most suitable amine solvent and metal were selected by running a series of reactions with different amines and different zero-valent metals, in order to optimize the conditions under which complete degradation of mirex takes place. These dehalogenation reactions illustrated the role of zero-valent metals as reductants, whereas the amine solvents acted as proton donors. In this study, we report that mirex was completely degraded with diethyl amine (l) in the presence of copper at 100 degrees C and the hydrogenated products accounted for more than 94 of the degraded mirex.