A Hybrid Path Planning Method Based on Articulated Vehicle Model

Due to the unique steering mechanism and driving characteristics of the articulated vehicle,a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and searching the path back and forth of the articulated vehicle.First,Support Vector Machine(SVM)theory is used to obtain the two-dimensional optimal zero potential curve and the maximum margin,and then,several key points are selected from the optimal zero potential curves by using Longest Accessible Path(LAP)method.Next,the Cubic Bezier(CB)curve is adopted to connect the curve that satisfies the curvature constraint of the articulated vehicle between every two key points.Finally,Back and Forth Rapidly-exploring Random Tree with Course Correction(BFRRT-CC)is designed to connect paths that do not meet articulated vehicle curvature requirements.Simulation results show that the proposed hybrid path planning method can search a feasible path with a 90-degree turn,which meets the demand for obstacle avoidance and articulated vehicle back-and-forth movement.

Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

The carbon nanotube （CNT）-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method.

Path Planning Based on the Improved RRT^(∗) Algorithm for the Mining Truck

Planning a reasonable driving path for trucks in mining areas is a key point to improve mining efficiency.In this paper,a path planning method based on Rapidly-exploring Random Tree Star(RRT∗)is proposed,and several optimizations are carried out in the algorithm.Firstly,the selection process of growth target points is optimized.Secondly,the process of selecting the parent node is optimized and a Dubins curve is used to constraint it.Then,the expansion process from tree node to random point is optimized by the gravitational repulsion field method and dynamic step method.In the obstacle detection process,Dubins curve constraint is used,and the bidirectional RRT∗algorithm is adopted to speed up the iteration of the algorithm.After that,the obtained paths are smoothed by using the greedy algorithm and cubic B-spline interpolation.In addition,to verify the superiority and correctness of the algorithm,an unmanned mining vehicle kinematic model in the form of frontwheel steering is developed based on the Ackermann steering principle and simulated for CoppeliaSim.In the simulation,the Stanley algorithm is used for path tracking and Reeds-Shepp curve to adjust the final parking attitude of the truck.Finally,the experimental comparison shows that the improved bidirectional RRT∗algorithm performs well in the simulation experiment,and outperforms the common RRT∗algorithm in various aspects.

HIBADH Plays an Important Role in the Course of Liver Cell Necrosis

Objective To observe the biological function of human 3-hydroxyisobutyrate dehydrogenase(HIBADH).Methods Human 3-hydroxyisobutyrate dehydrogenase(HIBADH, 3-hydroxy-2-methyl propanoate: NAD+ oxidoreductase) recombinant protein was expressed in E. coli BL21, and purified by Ni+ column. The special antisera was obtained from rabbits immunized by this purified antigen. On the distribution of HIBADH, it was found that HIBADH over-expressed in the injured liver cells when serious hepatitis occurred. The phenomenon was confirmed in the animal models of SD rats with acute liver cell injury induced by CCl4, but this phenomenon did not exist in the models induced by endotoxin combined with galactosamine. Further more, HIBADH's overexpression in liver cells will induce cell necrosis through the pathway of oxidative stress.Results When the liver cells injured by drug or other chemical materials, HIBADH will be compensationally over-expressed for the deficiency of energy, so liver cells can make enough ATP through brand-chain amino acid catabolism. However, the overexpression of HIBADH will be harmful for liver cells through the product of much more active oxygens which will induce the cell necrosis. Conclusions HIBADH over-expression is a signal of the liver cell metabolism injury, and it can aggravate the liver cell injury through oxidative stress.

The Effect of Docetaxei Bounding to Activated Carbon Nanoparticles on

ticles （ACNP-DOC） on the cell membrane of A549 human lung cancer cells using atomic force microscope （AFM） . Methods： ACNP was prepared by grinding- suspenssion- centrifugation process and ACNP diameters were measured with Laser particle size analyzer and transmission e- lectron microscope （TEM） . The ACNP-DOC is made by ACNP adsorbing IDC： a mixture containing ACNP in a concentration of 0. 1% and DOC in a series of concentrations was kept in a ultrasound fields for 30 min to allow DOC was adsorbed in the inner surfaces of the holes

A Fine Synchronization Method for Coherent Fast Frequency Hopping

Coherent fast frequency hopping(CFFH)is attracting growing attention owing to its good antijamming performance and the coherent combining ability.However,compared with the conventional non-coherent fast frequency hopping,CFFH requires a more precise system synchronization.In this paper,we propose a new fine synchronization algorithm for CFFH.This algorithm consists two stages,namely,open-loop stage and closed-loop stage.In the openloop stage,a grid-based search parameter estimation method is proposed.In the closed-loop stage,we construct a fully coherent phase-locked loop(PLL)and a delay-locked loop(DLL)with decoding feedback structure to perform further fine estimation of the system clock skew and time delay,respectively.Moreover,we analyze the effect of the search parameter settings on the estimation error and derive the root mean squared error(RMSE)of estimates in the steady state of the closed-loop stage.Finally,through simulation,the RMSE performance are compared with the corresponding Cramer-Rao low bound(CRLB)and conventional code loop estimation to show the effectiveness of proposed algorithm.

An adaptive waveform-detection threshold joint optimization method for target tracking

The joint optimization of detection threshold and waveform parameters for target tracking which comes from the idea of cognitive radar is investigated for the modified probabilistic data association(MPDA)filter.The transmitted waveforms and detection threshold are adaptively selected to enhance the tracking performance.The modified Riccati equation is adopted to predict the error covariance which is used as the criterion function,while the optimization problem is solved through the genetic algorithm(GA).The detection probability,false alarm probability and measurement noise covariance are all considered together,which significantly improves the tracking performance of the joint detection and tracking system.Simulation results show that the proposed adaptive waveform-detection threshold joint optimization method outperforms the adaptive threshold method and the fixed parameters method,which will reduce the tracking error.The average reduction of range error between the adaptive joint method and the fixed parameters method is about 0.6 m,while that between the adaptive joint method and the adaptive threshold only method is about 0.3 m.Similar error reduction occurs for the velocity error and acceleration error.

Simulated Sensitivity of Ozone Generation to Precursors in Beijing during a High O_(3) Episode

This study uses the WRF-Chem model combined with the empirical kinetic modeling method(EKMA curve)to study the compound pollution event in Beijing that happened in 13−23 May 2017.Sensitivity tests are conducted to analyze ozone sensitivity to its precursors,and to develop emission reduction measures.The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze.When VOCs and NOx were reduced by the same proportion,the effect of O_(3)reduction at peak time was more obvious,and the effect during daytime was more significant than at night.The degree of change in ozone was peak time>daytime average.When reducing or increasing the ratio of precursors by 25%at the same time,the effect of reducing 25%VOCs on the average ozone concentration reduction was most significant.The degree of change in ozone decreased with increasing altitude,the location of the ozone maximum change shifted westward,and its range narrowed.As the altitude increases,the VOCs-limited zone decreases,VOCs sensitivity decreases,NOx sensitivity increases.The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited.Upon examining the EKMA curve,we have found that suburban and urban are sensitive to VOCs.The sensitivity tests indicate that when VOCs in suburban are reduced about 60%,the O_(3)-1h concentration could reach the standard,and when VOCs of the urban decreased by about 50%,the O_(3)-1h concentration could reach the standard.Thus,these findings could provide references for the control of compound air pollution in Beijing.

Secure and efficient multi-message and multi-receiver ID-based signcryption for rekeying in ad hoc networks

In this paper, the security technology of ad hoc networks is studied.To improve the previous multi-receiver signcryption schemes, an ID-based multi-message and multi-receiver signcryption scheme for rekeying in ad hoc networks is proposed.In this scheme, a sender can simultaneously signcrypt n messeges for n receivers, and a receiver can unsigncrypt the ciphertext to get his message with his own private key.An analysis of this scheme indicates that it achieves authenticity and confidentiality in the random oracle model while being of lower computation and communication overhead.Finally, for the application of our scheme in ad hoc, a threshold key updating protocol for ad hoc networks is given.

Relationship of distraction rate with inferior alveolar nerve degeneration-regeneration shift

Distraction osteogenesis is an important technique for the treatment of maxillofacial abnormities and defects. However, distraction osteo- genesis may cause the injury of the inferior alveolar nerve. The relationship between distraction rate and nerve degeneration-regeneration shift remains poorly understood. In this study, 24 rabbits were randomly divided into four groups. To establish the rabbit mandibular distraction osteogenesis model, the mandibles of rabbits in distraction osteogenesis groups were subjected to continuous osteogenesis dis- traction at a rate of 1.0, 1.5 and 2.0 mm/d, respectively, by controlling rounds of screwing each day in the distractors. In the sham group, mandible osteotomy was performed without distraction, Pin-prick test with a 10 g blunt pin on the labium, histological and histomorpho- metric analyses with methylene blue staining, Bodian＇s silver staining, transmission electron microscopy and myelinated fiber density of inferior alveolar nerve cross-sections were performed to assess inferior alveolar nerve conditions. At 28 days after model establishment, in the pin-prick test, the inferior alveolar nerve showed no response in the labium to a pin pricks in the 2 mm/d group, indicating a severe dysfunction. Histological and histomorphometric analyses indicated that the inferior alveolar nerve suffered more degeneration and in- juries at a high distraction rate （2 mm/d）. Importantly, the nerve regeneration, indicated by newborn Schwann cells and axons, was more abundant in 1.0 and 1.5 mm/d groups than in 2.0 mm/d group. We concluded that the distraction rate was strongly associated with the inferior alveolar nerve function, and the distraction rates of !.0 and 1.5 mm/d had regenerative effects on the inferior alveolar nerve. This study provides an experimental basis for the relationship between distraction rate and nerve degeneration-regeneration shift during dis- traction osteogenesis, and may facilitate reducing nerve complications during distraction osteogenesis.

Research on sea surface temperature retrieval by the one-dimensional synthetic aperture microwave radiometer, 1D-SAMR

Due to the low spatial resolution of sea surface temperature(T_S)retrieval by real aperture microwave radiometers,in this study,an iterative retrieval method that minimizes the differences between brightness temperature(T_B)measured and modeled was used to retrieve sea surface temperature with a one-dimensional synthetic aperture microwave radiometer,temporarily named 1 D-SAMR.Regarding the configuration of the radiometer,an angular resolution of 0.43°was reached by theoretical calculation.Experiments on sea surface temperature retrieval were carried out with ideal parameters;the results show that the main factors affecting the retrieval accuracy of sea surface temperature are the accuracy of radiometer calibration and the precision of auxiliary geophysical parameters.In the case of no auxiliary parameter errors,the greatest error in retrieved sea surface temperature is obtained at low T_S scene(i.e.,0.7106 K for the incidence angle of 35°under the radiometer calibration accuracy of0.5 K).While errors on auxiliary parameters are assumed to follow a Gaussian distribution,the greatest error on retrieved sea surface temperature was 1.3305 K at an incidence angle of 65°in poorly known sea surface wind speed(W)(the error on W of 1.0 m/s)over high W scene,for the radiometer calibration accuracy of 0.5 K.

Characteristics of the Asian–Pacific Oscillation in Boreal Summer Simulated by BCC_CSM with Different Horizontal Resolutions

The summer Asian-Pacific Oscillation （APO） is a major teleconnection pattern that reflects the zonal thermal contrast between East Asia and the North Pacific in the upper troposphere. The performance of Beijing Climate Center Climate System Models （BCC_CSMs） with different horizontal resolutions, i.e., BCC_CSM1.1 and BCC_CSM1.1 （m）, in reproducing APO interannual variability, APO-related precipitation anomalies, and associated atmospheric circulation anomalies, is evaluated. The results show that BCC_CSMI.I（m） can successfully capture the interannual variability of the summer APO index. It is also more capable in reproducing the APO＇s spatial pattern, compared to BCC_CSMI.1, due to its higher horizontal resolution. Associated with a positive APO index, the northward-shifted and intensified South Asian high, strengthened extratropical westerly jet, and tropical easterly jet in the upper troposphere, as well as the southwesterly monsoonal flow over North Africa and the Indian Ocean in the lower troposphere, are realistically represented by BCC_CSM1.1 （m）, leading to an improvement in reproducing the increased precipitation over tropical North Africa, South Asia, and East Asia, as well as the decreased precipitation over subtropical North Africa, Japan, and North America. In contrast, these features are less consistent with observations when simulated by BCC_CSM1.1. Regression analysis further indicates that surface temperature anomalies over the North Pacific and the southern and western flanks of the Tibetan Plateau are reasonably reproduced by BCC_CSM 1.1 （m）, which contributes to the substantial improvement in the simulation of the characteristics of summer APO compared to that of BCC_CSM1.1.

Flight Dynamic Analysis of Hypersonic Vehicle Considering Liquid-Solid Coupling

With the liquid propellant making up 60%—70% of the takeoff weight of the hypersonic vehicle,the dynamic load caused by great propellant sloshing interacts with the flexible structure of the aircraft.Therefore,the dynamic model displays characteristics of strong coupling with structure/control and nonlinearity.Based on the sloshing mass dynamic simplified as a spring-mass-damping model,a rigid-flexible-sloshing model is constructed.Moreover,the effect on the dynamic performance of the coupled model is analyzed with changing frequency and damping.The results show that propellant sloshing dynamics significantly affects the rigid body motion modes,especially flexible mode and short mode.The right half plane pole(RHP)moves far from the imaginary axis with the consumption of the propellant.The flexible mode attenuates with the increase of the sloshing damping,and the coupling becomes stronger when sloshing frequency is close to the short mode frequency or the flexible frequency of the beam.

NUMERICAL EXPERIMENTS ON THE IMPACTS OF SEA SPRAY ON TROPICAL CYCLONES

The latest version of sea spray flux parameterization scheme developed by Andreas is coupled with the PSU/NCAR model MM5 in this paper. A western Pacific tropical cyclone named Nabi in 2005 is simulated using this coupled air-sea spray modeling system to study the impacts of sea spray evaporation on the evolution of tropical cyclones. The results demonstrate that sea spray can lead to a significant increase of heat fluxes in the air-sea interface, especially the latent heat flux, the maximum of which can increase by up to about 35% - 80% The latent heat flux seems to be more important than the sensible heat flux for the evolution of tropical cyclones. Regardless of whether sea spray fluxes have been considered, the model can always simulate the track of Nabi well, which seems to indicate that sea spray has little impact on the movement of tropical cyclones. However, with sea spray fluxes taken into account in the model, the intensity of a simulated tropical cyclone can have significant increase. Due to the enhancement of water vapor and heat from the sea surface to the air caused by sea spray, the warm core structure is better-defined, the minimum sea level pressure decreases and the vertical speed is stronger around the eye in the experiments, which is propitious to the development and evolution of tropical cyclones.

A preliminary evaluation of high-performance advanced regional eta-coordinate model(H-AREM)

为验证高性能AREM模式(H-AREM)的并行性能,本文利用相同分辨率的AREM3.4P和H-AREM并行模式,比较了不同并行方法的影响;利用不同分辨率的H-AREM模式比较了不同剖分策略的影响。结果表明,基于并行框架的并行方法和二维剖分策略有利于并行性能的提升,HAREM在加速比和可扩展性方面都要优于原并行模式,特别是分辨率8 km的H-AREM模式能够扩展到8099核,在不显著增加计算时间的前提下具有更好的预报效果。

Sea surface temperature retrieval based on simulated microwave polarimetric measurements of a one-dimensional synthetic aperture microwave radiometer

Compared with traditional real aperture microwave radiometers,one-dimensional synthetic aperture microwave radiometers have higher spatial resolution.In this paper,we proposed to retrieve sea surface temperature using a one-dimensional synthetic aperture microwave radiometer that operates at frequencies of 6.9 GHz,10.65 GHz,18.7 GHz and 23.8 GHz at multiple incidence angles.We used the ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts and a radiation transmission forward model to calculate the model brightness temperature.The brightness temperature measured by the spaceborne one-dimensional synthetic aperture microwave radiometer was simulated by adding Gaussian noise to the model brightness temperature.Then,a backpropagation(BP)neural network algorithm,a random forest(RF)algorithm and two multiple linear regression algorithms(RE1 and RE2)were developed to retrieve sea surface temperature from the measured brightness temperature within the incidence angle range of 0°-65°.The results show that the retrieval errors of the four algorithms increase with the increasing Gaussian noise.The BP achieves the lowest retrieval errors at all incidence angles.The retrieval error of the RE1 and RE2 decrease first and then increase with the incidence angle and the retrieval error of the RF is contrary to that of RE1 and RE2.

CRB for 2-D DOA Estimation in MIMO Radar with UCA

The Cramer-Rao bound(CRB)for two-dimensional(2-D)direction of arrival(DOA)estimation in multiple-input multiple-output(MIMO)radar with uniform circular array(UCA)is studied.Compared with the uniform linear array(ULA),UCA can obtain the similar performance with fewer antennas and can achieve DOA estimation in the range of 360°.This paper investigates the signal model of the MIMO radar with UCA and 2-D DOA estimation with the multiple signal classification(MUSIC)method.The CRB expressions are derived for DOA estimation and the relationship between the CRB and several parameters of the MIMO radar system is discussed.The simulation results show that more antennas and larger radius of the UCA leads to lower CRB and more accurate DOA estimation performance for the monostatic MIMO radar.Also the interference during the 2-D DOA estimation will be well restrained when the number of the transmitting antennas is different from that of the receiving antennas.

Retrieval of Sea Surface Wind Speed by One-Dimensional Synthetic Aperture Microwave Radiometer

One-dimensional synthetic aperture microwave radiometers have higher spatial resolution and record measurements at multiple incidence angles.In this paper,we propose a multiple linear regression method to retrieve sea surface wind speed at an incidence angle between 0°65°.We assume that a one-dimensional synthetic aperture microwave radiometer operates at frequencies of 6.9,10.65,18.7,23.8 and 36.5 GHz.Then,the microwave radiative transfer forward model is used to simulate the measured brightness temperatures.The sensitivity of the brightness temperatures at 0°65°to the sea surface wind speed is calculated.Then,vertical polarization channels(VR),horizontal polarization channels(HR)and all channels(AR)are used to retrieve the sea surface wind speed via a multiple linear regression algorithm at 0°65°,and the relationship between the retrieval error and incidence angle is obtained.The results are as follows:(1)The sensitivity of the vertical polarization brightness temperature to the sea surface wind speed is smaller than that of the horizontal polarization.(2)The retrieval error increases with Gaussian noise.The retrieval error of VR first increases and then decreases with increasing incidence angle,the retrieval error of HR gradually decreases with increasing incidence angle,and the retrieval error of AR first decreases and then increases with increasing incidence angle.(3)The retrieval error of AR is the lowest and it is necessary to retrieve the sea surface wind speed at a larger incidence angle for AR.

Efficient Method for Accelerated Reliability Qualification Testing

Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coefficients of super Gauss vibration stress and temperature stress. Then, by applying these coefficients, an accelerated reliability qualification testing curve was obtained from the standard tests. Finally,the actual experiment on a digital marine control device was carried out under the proposed testing method.The experiment result shows that the proposed method can reduce the total experiment time and improve the efficiency of the reliability qualification test.

Hyperbolic Tangent Support Vector Machine

By utilizing hyperbolic tangent function,we constructed a novel hyperbolic tangent loss function to reduce the influences of outliers on support vector machine(SVM)classification problem.The new loss function not only limits the maximal loss value of outliers but also is smooth.Hyperbolic tangent SVM(HTSVM)is then proposed based on the new loss function.The experimental results show that HTSVM reduces the effects of outliers and gives better generalization performance than the classical SVM on both artificial data and UCI data sets.Therefore,the proposed hyperbolic tangent loss function and HTSVM are both effective.