Surface Nanocrystallization of Steel 20 Induced by Fast Multiple Rotation Rolling

In order to expand the application of steel 20 in precision device,fast multiple rotation rolling( FMRR) is applied to fabricate a nanostructured layer on the surface of steel 20. The FMRR samples are then Cr-Rare earth-boronized under low-temperature. The microstructure of the top surface layer is characterized by transmission electron microscopy( TEM). Microhardness of the top surface is measured by a Vickers microhardness tester. The boride layer is characterized by using scanning electron microscopy( SEM).Experimental results show that a nanostructured layer with their grain size range from 200 to 400 nm is obtained in the top surface layer. The microhardness of FMRR sample changes gradiently along the depth from about274 HV in the top surface layer to about 159 HV in the matrix,which is nearly 1.7 times harder than that of the original sample. The penetrating rate is enhanced significantly when the FMRR samples are Cr-Rare earthboronized at 600 ℃ for 6 h. Thickness of the boride layer increases to around 20 μm,which is nearly twice thicker than that of the original sample.

Cooperative interception with fast multiple model adaptive estimation

For the case that two pursuers intercept an evasive target,the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target,which performs a bang For the case that two pursuers intercept an evasive target,the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target,which performs a bang-bang evasive maneuver with a random switching time.Combined Fast multiple model adaptive estimation(Fast MMAE)algorithm,the cooperative guidance law takes detection configuration affecting the accuracy of interception into consideration.Introduced the detection error model related to the line-of-sight(LOS)separation angle of two interceptors,an optimal cooperative guidance law solving the optimization problem is designed to modulate the LOS separation angle to reduce the estimation error and improve the interception performance.Due to the uncertainty of the target bang-bang maneuver switching time and the effective fitting of its multi-modal motion,Fast MMAE is introduced to identify its maneuver switching time and estimate the acceleration of the target to track and intercept the target accurately.The designed cooperative optimal guidance law with Fast MMAE has better estimation ability and interception performance than the traditional guidance law and estimation method via Monte Carlo simulation.

Effect of Surface Nanocrystallization Induced by Fast Multiple Rotation Rolling on Cr-Rare Earth-Boronizing for Steel 45 under Low-Temperature

In this paper, fast multiple rotation rolling （FMRR） is applied to fabricate a nanostructured layer on the surface of steel 45. The FMRR samples are then Cr-Rare earth-boronized under low-temperature. The boride layer is characterized by using Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Experimental results indicate that the thickness of the boride layer is greatly increased by surface nanocrystallization. The boride layer with relatively continuous structure instead of the zigzag teeth structure is obtained, and the penetrating rate is enhanced by 2. 5-3.7 times when the FMRR samples are Cr-Rare earth- boronized at the temperature of 570 %, 600℃ and 650℃ for 6 h. The boride layer fabricated on the FMRR sample consists of single phase Fe2B. Severe plastic deformation with the grain size of approximately 100 nm in the top surface layer of steel 45 is observed, and the thickness of the plastic deformation layer is about 30 6xm. The microstructure in the top surface layer is characterized by Transmission electron microscopy （TEM）. Grain boundaries are largely increased with high stacking fault energy after FMRR, leading to a significant enhancement of RE boron-chromizing speed.

RESEARCH OF FAST MODULAR MULTIPLIER FOR A CLASS OF FINITE FIELDS

A new structure of bit-parallel Polynomial Basis(PB)multiplier is proposed,which isbased on a fast modular reduction method.The method was recommended by the National Instituteof Standards and Technology(NIST).It takes advantage of the characteristics of irreducible polyno-mial,i.e.,the degree of the second item of irreducible polynomial is far less than the degree of thepolynomial in the finite fields GF(2m).Deductions are made for a class of finite field in which trino-mials are chosen as irreducible polynomials.Let the trinomial bex m +x k+1,where 1 ≤k≤?m/2?.??The proposed structure has shorter critical path than the best known one up to date,whilethe space requirement keeps the same.The structure is practical,especially in real time crypto-graphic applications.

Walsh Hadamard Transform Based Transceiver Design for SC-FDMA with Discrete Wavelet Transform

This article proposes a new transceiver design for Single carrier frequency division multiple access(SCFDMA)system based on discrete wavelet transform(DWT). SCFDMA offers almost same structure as Orthogonal frequency division multiple access(OFDMA)with extra advantage of low Peak to Average Power Ratio(PAPR). Moreover,this article also suggests the application of Walsh Hadamard transform(WHT)for linear precoding(LP)to improve the PAPR performance of the system. Supremacy of the proposed transceiver over conventional Fast Fourier transform(FFT)based SCFDMA is shown through simulated results in terms of PAPR,spectral efficiency(SE)and bit error rate(BER).

Effect of Fast Multiple Rotation Rolling on Microstructure and Properties of Ti6Al4V Alloy

Using fast multiple rotation rolling(FMRR),a nanostructure layer was fabricated on the surface of Ti6Al4V alloy.The microstructure of the surface layer was investigated using optical microscopy,transmission electron microscopy,scanning electron microscopy,and X-ray diffraction.The results indicated that a nanostructured layer,with an average grain size of 72—83 nm,was obtained in the top surface layer,when the FMRR duration was 15 min.And the average grain size further reduced to 24—37 nm when the treatment duration increased to 45 min.High density dislocations,twins,and stacking faults were observed in the top surface layer.The microhardness of FMRR specimen,compared with original specimen,was significantly increased.A uniform,continuous and thicker compound layer was obtained in the top surface of FMRR sample,and the diffusion speed of N atom in the top surface layer was accelerated.FMRR treatment provides corrosion improvement.

A head-related transfer function model for fast synthesizing multiple virtual sound sources

A head-related transfer function （HRTF） model for fast and real-time synthesizing multiple virtual sound sources is proposed. A head-related impulse response （HRIR, time- domain version of HRTF） is first decomposed by a two-level wavelet packet and then represented by a model composed of subband filters and reconstruction filters. The coefficients of the subband filters are the zero interpolation of the wavelet coefficients of the HRIR. The coefficients of the reconstruction filters can be calculated from the wavelet function. The model is simplified by applying a threshold method to reduce the wavelet coefficients. The calculated results indicate that for a model with 30 wavelet coefficients, the error of reconstructed HRIR is about 1%. And the result of a psychoacoustic test shows that a model with 35 wavelet coefficients is perceptually indistinguishable from the original HRIR. When multiple virtual sound sources are synthesized simultaneously, the computational cost of the proposed model is much less than the traditional HRTF filters.

VCSRA:A fast and accurate multiple sequence alignment algorithm with a high degree of parallelism

Multiple sequence alignment （MSA） is the alignment among more than two molecular biological sequences, which is a fundamental method to analyze evolutionary events such as mutations, insertions, deletions, and re-arrangements. In theory, a dynamic programming algorithm can be employed to produce the optimal MSA. However, this leads to an explosive increase in computing time and memory consumption as the number of sequences increases （Taylor, 1990）. So far, MSA is still regarded as one of the most challenging problems in bioinformatics and computational biology （Chatzou et al., 2016）.