Index of Keywords to Volume 27

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Index of Keywords to Volume 27     

FINITE ELEMENT ANALYSIS OF CHIP FORMATION IN GROOVED TOOL METAL CUTTING

This paper presents the simulation of chip formation in grooved tool cutting using DYNA3D, 3D FEM software for dynamic nonlinear analysis that was used to simulate the orthogonal cutting problem. First, a flat-face cutting tool was employed in the simulation to verify the validity of the FEM model. Next, the same simulation techniques were used to study the effects of different groove geometries on the chip formation process in grooved tool cutting. In the first set of grooved tool simulations, the depth of the groove was constant while the width was decreased. In the second set, the width was constant and the depth was increased. By analyzing the chip flow, chip curl, chip thickness, stress and strain in the chip, the effects of different groove widths and depths on the chip formation process were then discussed.     

A flexible liquid‐metal alloy bandpass filter

This article presents a liquid‐metal Galinstan alloy bandpass filter (BPF) with good flexibility, which is fabricated by an improved soft lithography process. The Galinstan alloy is enclosed in the microfluidic channels of elastomeric polydimethylsiloxane (PDMS) substrates. Together with the PDMS substrates, the Galinstan alloy based filter features bending, twisting and stretching capabilities along any direction. A second‐order open‐loop resonator filter with 2.4 GHz center frequency and 15% fractional bandwidth was designed and fabricated to verify this concept. Experiments show that frequency response of the filter is almost unaffected in the case of bending of the different radii or twisting, while its center frequency slightly shifts down in the stretching condition. The proposed filter can be used for the flexible and conformal electronics.     

An Artificial Peripheral Neural System Based on Highly Stretchable and Integrated Multifunctional Sensors

Prostheses and robots have been affecting all aspects of life. Making them conscious and intelligent like humans is appealing and exciting, while there is a huge contrast between progress and strong demand. An alternative strategy is to develop an artificial peripheral neural system with high-performance bionic receptors. Here, a novel functional composite material that can serve as a key ingredient to simultaneously construct different artificial exteroceptive sensors (AE sensors) and artificial proprioceptive sensors (AP sensors) is demonstrated. Both AP sensors and AE sensors demonstrate outstandingly high stretchability; up to 200% stretching strain and possess the superior performance of fast response and high stability. An artificial peripheral neural system integrated with the highly stretchable AP sensor and AE sensor is constructed, which makes a significant breakthrough in the perception foundation of efficient proprioception and exteroception for intelligent prostheses and soft robots. Accurate feedback on the activities of body parts, music control, game manipulation, and wireless typing manifest the enormous superiority of the spatiotemporal resolution function of the artificial peripheral neural system, all of which powerfully contribute to promoting intelligent prostheses and soft robots into sophistication, and are expected to make lives more fascinating.     

Combination of Oxyanion Gln114 Mutation and Medium Engineering to Influence the Enantioselectivity of Thermophilic Lipase from Geobacillus zalihae

The substitution of the oxyanion Q114 with Met and Leu was carried out to investigate the role of Q114 in imparting enantioselectivity on T1 lipase. The mutation improved enantioselectivity in Q114M over the wild-type, while enantioselectivity in Q114L was reduced. The enantioselectivity of the thermophilic lipases, T1, Q114L and Q114M correlated better with log p as compared to the dielectric constant and dipole moment of the solvents. Enzyme activity was good in solvents with log p < 3.5, with the exception of hexane which deviated substantially. Isooctane was found to be the best solvent for the esterification of (R,S)-ibuprofen with oleyl alcohol for lipases Q114M and Q114L, to afford E values of 53.7 and 12.2, respectively. Selectivity of T1 was highest in tetradecane with E value 49.2. Solvents with low log p reduced overall lipase activity and dimethyl sulfoxide (DMSO) completely inhibited the lipases. Ester conversions, however, were still low. Molecular sieves employed as desiccant were found to adversely affect catalysis in the lipase variants, particularly in Q114M. The higher desiccant loading also increased viscosity in the reaction and further reduced the efficiency of the lipase-catalyzed esterifications.     

基于改进PSO算法的燃料电池模型优化

采用一种改进粒子群优化(PSO)算法,提出了一种优化燃料电池模型的方法,并用于质子交换膜燃料电池(PEMFC)的极化曲线模型,以得到最优参数.结果表明,这种优化模型的平均平方误差(MSE)为4.42×10-10V2,相关系数为99.87%,数学模型和实验数据之间的拟合精度高.     

Determination of energy and spatial distribution of oxide border traps in In0.53Ga0.47As MOS capacitors from capacitance–voltage characteristics measured at various temperatures

In this work, we have systematically studied the frequency dispersion of the capacitance–voltage (C–V) characteristics of In_0.53Ga_0.47As metal–oxide-semiconductor (MOS) capacitors in accumulation region at various temperatures based on a distributed border traps model. An empirical method to evaluate the frequency and temperature dependent response of the border traps distributed along the depth from the interface into the oxide is established. While the frequency dependent response results from the dependence of the time constant of the border traps on their depths, the temperature dependent response is ascribed to the thermal activated capture cross-section of the border traps due to the phonon-related inelastic capturing process. Consequently, it is revealed that the frequency dispersion behaviors of the accumulation capacitance at different temperatures actually reflect the spatial distribution of the border traps. On this basis, we propose a methodology to extract the border trap distribution in energy and space with emphasis on analyzing the C–V characteristics measured from low to high temperatures in sequence.     

质子交换膜燃料电池建模及其PID控制

针对目前质子交换膜燃料电池(PEMFC)模型难以适用于控制系统的设计,提出利用Matlab-Simulink仿真工具对PEMFC进行系统动态模型建立,并在此基础上采用比例积分微分(PID)算法控制其输出电压.仿真结果表明该模型较好地反映出PEMFC系统的动态特性,有助于改善PEMFC的设计,提高其性能,而且PID算法能够较好地实现对PEMFC系统的控制,可适用于控制系统的设计.     

Effects of dopant granularity on superhalo-channel MOSFETs according to two- and three-dimensional computer simulations

We have performed two-dimensional (2-D) and three-dimensional (3-D) computer simulations of random dopant fluctuations in 25-nm planar n-channel metal-oxide-semiconductor field effect transistor (MOSFET) with superhalo channel doping. Our study shows that 2-D simulations that neglect lateral percolation of the carriers can overestimate the impact on threshold voltage (V/sub T/) fluctuations by as much as a factor of four. Fundamental differences in the way the 2-D and 3-D models describe subthreshold and near-threshold conduction are highlighted in our study. Our models reveal that surface percolation of carriers is an effective agent for reducing V/sub T/ fluctuations. In addition, the halo only enhances the V/sub T/ fluctuations by approximately 10%. Though the influence of the superhalo in the device may be overwhelmed by atomistic granularity according to the 2-D model, 3-D simulations show that the halo continues to function coherently for the MOSFET ensemble when charge percolation is accounted.     

Improvement of Thermal Stability via Outer-Loop Ion Pair Interaction of Mutated T1 Lipase from Geobacillus zalihae Strain T1

Mutant D311E and K344R were constructed using site-directed mutagenesis to introduce an additional ion pair at the inter-loop and the intra-loop, respectively, to determine the effect of ion pairs on the stability of T1 lipase isolated from Geobacillus zalihae. A series of purification steps was applied, and the pure lipases of T1, D311E and K344R were obtained. The wild-type and mutant lipases were analyzed using circular dichroism. The T_m for T1 lipase, D311E lipase and K344R lipase were approximately 68.52 °C, 70.59 °C and 68.54 °C, respectively. Mutation at D311 increases the stability of T1 lipase and exhibited higher T_m as compared to the wild-type and K344R. Based on the above, D311E lipase was chosen for further study. D311E lipase was successfully crystallized using the sitting drop vapor diffusion method. The crystal was diffracted at 2.1 Å using an in-house X-ray beam and belonged to the monoclinic space group C2 with the unit cell parameters a = 117.32 Å, b = 81.16 Å and c = 100.14 Å. Structural analysis showed the existence of an additional ion pair around E311 in the structure of D311E. The additional ion pair in D311E may regulate the stability of this mutant lipase at high temperatures as predicted in silico and spectroscopically.