Starting Characteristics of Motor in Inverter-Motor Drive System

When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, based on the steady state equivalent circuit of the induction motor.The corresponding expressions are derived, and the corresponding curves are also drawn, from which the initial starting frequency range can be determined properly and easily. The initial starting frequency range is the common range, in which the starting torque should be high enough and the starting current low enough.Some other useful formulas are also derived.These results are significant for electrical drive designers to make the starting schemes. The effects of the increase of the stator and the rotor resistances on the starting torque and the initial starting frequency range are also discussed, which is caused by the skin effects of the high order harmonics present in the PWM inverter output voltage.

Improved electrochemical performance of ternary Sn-Sb-Cu nanospheres as anode materials for lithium-ion batteries

Ternary Sn-Sb-Cu alloy nanoparticles were successfully synthesized via co-reduction of metal chlorides in aqueous alkaline solution.The results of the transmission electron microscopy(TEM)show that the as prepared Sn-Sb-Cu nanoparticles have a specific hollow structure with a uniform particle size of 10-20 nm.As there are not any hard templates in the synthesis system,a galvanic displacement reaction mechanism is proposed to account for the formation of the hollow nanostructures.When the alloy powders are used as anode materials for lithium-ion batteries,they exhibit relatively high electrochemical capacity and good cyclic retention.The good electrochemical performance can be attributed to the inactive Cu species.During electrochemical reactions,the inactive copper phase in the hollow structure serves as a soft and ductile matrix,which alleviates the mechanical stresses caused by the severe volume change during lithium insertion and extraction.With their high reversible capacities,the Sn-Sb-Cu alloys are a promising candidate as the anode material of rechargeable lithium-ion batteries.

Effects of Al contents on microstructure and properties of hot-dip Zn-Al alloy coatings on hydrogen reduced hot-rolled steel without acid pickling

A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigated.Phase composition,microstructure and element distribution in Zn-Al alloy coatings were analyzed using X-ray diffraction（XRD）and electron probe micro analysis（EPMA）,respectively.It is found that Al content（0.6-6.0 wt.%）in galvanizing zinc affects surface quality and adhesion between coatings and matrix in the newly developed method.In addition,with increasing Al content,micro-hardness significantly increased due to the increase in Zn-Al eutectoid phases.Potentiodynamic polarization and electrochemical impedance spectroscopy（EIS）also revealed that increase in Al plays a noticeable role in improving the corrosion resistance of Zn-Al alloy coatings.

Crystallinity dependence of electrochemical properties for LiFePO_4

LiFePOa composites were prepared by solid state reactions at different temperatures and time. The crystalline structure and morphology of the composites were analyzed by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, while X-ray absorption spectroscopy （XAS） was employed to characterize the crystallinity. Experimental results show that the electrochemical properties do not monotonously get better with the decrease of particle size and the traditional long reaction time is needless. Moreover, XAS is an effective technique to discover the change in crystallinity.

Total alkaloids of Sophora alopecuroides-and matrine-induced reactive oxygen species impair biofilm formation of Staphylococcus epidermidis and increase bacterial susceptibility to ciprofloxacin

Objective:To investigate the mechanism by which total alkaloids of Sophora alopecuroides(TASA)and matrine(MT)impair biofilm to increase the susceptibility of Staphylococcus epidermidis(S.epidermidis)to ciprofloxacin.Methods:The minimum biofilm inhibitory concentration(mBIC)was determined using a 2-fold dilution method.Structure of biofilm of S.epidermidis was examined by Confocal Laser Scanning Microscope(CLSM).The cellular reactive oxygen species(ROS)was determined using a DCFH-DA assay.The key factors related to the regulation of ROS were accessed using respective kits.Results:TASA and MT were more beneficial to impair biofilm of S.epidermidis than ciprofloxacin(CIP)(P<0.05).TASA and MT were not easily developed resistance to biofilm-producing S.epidermidis.The mBIC of CIP decreased by 2-6-fold following the treatment of sub-biofilm inhibitory concentration(sub-BIC)TASA and MT,whereas the mBIC of CIP increased by 2-fold following a treatment of sub-BIC CIP from the first to sixth generations.TASA and MT can improve the production of ROS in biofilmproducing S.epidermidis.The ROS content was decreased 23%-33%following the treatment of submBIC CIP,whereas ROS content increased 7%-24%following treatment with TASA+CIP and MT+CIP combination from the first to sixth generations.Nitric oxide(NO)as a ROS,which was consistent with the previously confirmed relationship between ROS and drug resistance.Related regulatory factorssuperoxide dismutase(SOD)and glutathione peroxidase(GSH)could synergistically maintain the redox balance in vivo.Conclusion:TASA and MT enhanced reactive oxygen species to restore the susceptibility of S.epidermidis to ciprofloxacin.

TiO_(2)-coated LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)cathode materials with enhanced cycle performance for Li-ion batteries

Ni-rich cathode material is one of the most promising materials for Li-ion batteries in electric vehicles.However,fading capacity,poor cyclic stability and high p H value are still major challenges,which suppress its practical application.In this study,spherical LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)powders with 0.4 wt%TiO_(2)coating layer were prepared by impregnation-hydrolysis method.Scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM)and X-ray diffraction(XRD)results show that TiO_(2)is uniformly coated on the surface of LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)particle and slightly embedded into LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)particles.After 100 cycles at 2.0 C,0.4 wt%TiO_(2)-coated LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)electrode delivers much higher discharge capacity retention(77.0%)than the pristine LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)electrode(63.3%).The excellent cycling performance of 0.4 wt%Ti O_(2)-coated LiNi_(0.)9Co_(0.08)Al_(0.02)O_(2)electrode at a high discharge ratio is due to a TiO_(2)coating layer which can effectively reduce the direct contact between cathode material and electrolyte,suppress the oxidation of electrolyte,improve electrical conductivity of the electrode and increase the stability of the structure.

Effect of Sn on Corrosion Behavior of Ultra-pure 17 mass% Cr Ferritic Stainless Steels in Sulphuric Acid

The effect of Sn on corrosion behavior of ferritic stainless steels in 20mass% H2SO4 was investigated by alternating current and direct current electrochemical methods and gravimetric tests at 25 ℃.The results show that Sn can effectively improve general corrosion resistance of ferritic stainless steels in H2SO4,mainly due to highly raised hydrogen evolution overpotential which is in favour of strong suppression of hydrogen evolution reaction,and inhibitive effect of dissolved Sn^2＋ on elementary anodic reactions.With increasing Sn content,the better corrosion resistance can be reached.The Electrochemical Impedance Spectroscopy（EIS）includes four time constants and can be perfectly fitted by equivalent circuit：Rs（CdlRct）（QadsRads（RL1（L1（RL2L2））））.

Corrosion Behavior of High Performance Offshore Platform Steel with Chromium and Nickel Addition in the Environment Containing Chloride Ions

The characterization of corrosion products formed on a high performance offshore platform steel in the en- vironment containing chloride ions has been investigated by scanning electron microscopy （SEM）, X ray diffraction （XRD）, electron probe microanalysis （EPMA） and electrochemical impedance spectroscopy （EIS）. The results re- veal that the corrosion process can be divided into the initial stage and the later stage. The main constituents of rust layers are c~ FeOOH, 13-FeOOH, y-FeOOH, Fe：^（）~ and large amounts of amorphous compounds. With increasing corrosion time, the mass fraction of a-FeOOH and Fe：~ O,, increased, while that of y-FeOOH and ^-FeOOH changed slightly. The enrichment of Cr and Ni at the inner/outer interface, especially the side of inner rust, can be observed in the later corrosion stage of Cr Ni steel, which can promote the formation of compact inner rust layer, impeding the transmission of corrosion mediums and slowing down the electrochemical reaction process.

Phase formation and crystallization of LiMn_(x)Fe_(1-x)PO_(4)-C olivine material with different Mn^(2+)contents fabricated at lower calcination temperatures

LiMn_(x)Fe_(1-x)PO_(4)-C cathode materials for lithium ion batteries were synthesized via solid-state method using Li_(2)CO_(3),MnCO_(3),NH_(4)H_(2)PO_(4),FePO_(4) and sucrose as starting raw materials,followed by high-temperature reduction-annealing.A series of calcination experiments at different temperatures reveal that Mn^(2+)-containing materials exhibit a lower temperature for olivine phase formation,for example LiMn_(0.5)Fe_(0.5)PO_(4) olivine phase forms at 275℃,while manganese-free crystalline LiFePO_(4) generally forms at the required temperature of 350℃.Increasing Mn^(2+) content is found to enhance crystallization degree of LiMn_(x)Fe_(1-x)PO_(4) material prepared at lower calcination temperatures.X-ray photoelectron spectroscopy(XPS)results confirm that Mn valence state(+2)remains unchanged up to~250℃ when calcined in ambient atmosphere.The above-mentioned beneficial effect of manganese on phase formation and crystallization of olivine can be well attributed to the stable nature of Mn^(2+)and its strong propensity to form olivine phases.