Laser transformation hardening on rod-shaped carbon steel by Gaussian beam

Laser transformation hardening(LTH) is one of the laser surface modification processes. The surface hardening of rod-shaped carbon steel (SM45C) was performed by lathe-based laser composite processor with Gaussian-beam optical head. The LTH characteristics by dominant processes, longitudinal and depth directional hardness distributions and behaviors of phase transformation in hardened zones were examined. Especially, two concepts of circumferential speed and theoretical overlap rate were applied. When laser power increased or circumferential speed decreased, the surface hardening depth gradually increases due to the increased heat input. Moreover, the longitudinal hardness distribution particularly shows periodicity of repetitive increase and decrease, which results from tempering effect by overlap. Finally, the feasibility of laser transformation hardening is verified by using the beam with Gaussian intensity distribution.     

ANGIOTENSIN I-CONVERTING ENZYME (ACE) INHIBITORY PEPTIDES FROM WHEY FERMENTED BY LACTOBACILLUS SPECIES

From 2% (w/w) whey powder in growth media, inhibitory peptides against angiotensin I-converting enzyme (ACE) were studied with nine Lactobacillus species. Lb. brevis, Lb. helveticus and Lb. paracasei were proved to be the most effective strains in liberating ACE inhibitory peptides from whey protein. The inhibition rates of these peptides against ACE ranging from 93.3 to 100%. Several distinct peaks were eluted when the whey proteins were fractionated on a Delta Pak C₁₈ column by reversed phase-high performance liquid chromatography (RP-HPLC). Among ACE inhibitory activities of 14 peptides purified by dialysis and by fractionation using RP-HPLC, two peptide fractions (H5 and H7) of Lb. helveticus showing IC₅₀ values of 5.3 and 7.8 were the most potent ACE inhibitors.
All of these peptides including some other peptides (H1 and B1), having strong inhibitory activities against ACE were pentapeptides positioning with Ala at their N-terminal and these petapeptides had mostly hydrophobic (Pro, Val and Leu) or aromatic (Phe) amino acids at the C-terminal.

PRACTICAL APPLICATIONS

There is a significant amount of research and interest in developing and charactering the peptides that inhibit angiotensin I-converting enzyme (ACE) activity as these natural products may have a role in blood pressure control in man. This study revealed that the identification of peptides, mostly composed of pentapeptides following fermentation of whey protein in growth medium with different strains have the ACE inhibitory activities. These peptides may have antihypertensive effect as natural and safe nutraceutical/functional ingredients, though the exact potency of the pentapeptides isolated in this experiment has not been determined.     

Electrochemical characteristics of phosphorus doped Si-C composite for anode active material of lithium secondary batteries

Phosphorus doped silicon-carbon composite particles were synthesized through a DC arc plasma torch. Silane(SiH₄) and methane(CH₄) were introduced into the reaction chamber as the precursor of silicon and carbon, respectively. Phosphine(PH₃) was used as a phosphorus dopant gas. Characterization of synthesized particles were carried out by scanning electron microscopy(SEM), X-ray diffractometry(XRD), X-ray photoelectron spectroscopy(XPS) and bulk resistivity measurement. Electrochemical properties were investigated by cyclic test and electrochemical voltage spectroscopy(EVS). In the experimental range, phosphorus doped silicon-carbon composite electrode exhibits enhanced cycle performance than intrinsic silicon and phosphorus doped silicon. It can be explained that incorporation of carbon into silicon acts as a buffer matrix and phosphorus doping plays an important role to enhance the conductivity of the electrode, which leads to the improvement of the cycle performance of the cell.     

Refinement of circular-polarization based on multilayer film structure

Circular-polarization discrimination appears in many antennas' applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.     

Synthesis and behavior ofAl-stabilized α-Ni（OH）2

Nano-fibrous Al-stabilized α-Ni(OH)2 was synthesized by the urea thermal decomposition method. The grain morphology, crystal structure, thermal stability, chemical composition and electrochemical performance of the Al-stabilized α-Ni(OH)2 were investigated. It is found that the urea thermal decomposition is an appropriate way to precipitate the Al-stabilized α-Ni(OH)2 with excellent performance. The fiber cluster TEM pattern shows that the synthesized α-Ni(OH)2 powder is composed of agglomerates of much smaller primary particles. The stabilized α-Ni(OH)2 powder with a 7.67 A c-axis distance and low thermal stabilities is obtained. The FTIR spectrum shows that the materials contain absorbed water molecules, and intercalated CO32- and SO42- anions. The experimental α-Ni(OH)2 electrode exhibits excellent electrochemical redox reversibility, high special capacity, good rate discharging performance and perfect cyclic stability. Moreover, the synthesized α-Ni(OH)2 electrode also shows high discharge capacity and cyclic stability at high temperature. The electrode specific capacity remains 290 mA-h/g at 60 ℃, which is only 15 mA-h/g lower than its ambient value, and the capacity loss is 0.9 mA-h/g per charge-discharge cycle.