bluuebunny/crossref_metadata_2025 huggingface dataset:
Online dense activity detection
Authors: Weiqi Li , Jianming Wang , Jiayu Liang , Guanghao Jin , Tae‐Sun Chung
Published: May 2021

Dense activity detection is a subtask of activity detection that aims to localise and identify multiple human activities in video clips. Existing methods adopt offline frameworks that require video frames to be available when activity detection begins. These offline methods are unable to be applied to online scenarios. An online framework is proposed for dense activity detection. The framework has two stages: warm‐up and detection. Warm‐up is the initialisation of dense activity detection, which generates a contextual model called an online aggregated‐event. After that, the method moves into the detection stage, which consists of two modules: coarse label prediction and refined label prediction. Coarse label prediction predicts activity labels by taking the online aggregated‐event as a priori; then, prediction is refined by two techniques, human–object interaction detection and online relation reasoning. The proposed method is evaluated using two dense activity datasets: Charades and AVA. The experimental results show that the proposed method has better performance than existing offline methods after the whole video input is added to the algorithm.
Matching hyperspectral absorptions by weighted hamming distance
Authors: Guo Baofeng
Published: May 2021

To analyse and compare hyperspectral signatures, features extraction and matching are two key issues. In this letter, hyperspectral absorption features and the corresponding matching algorithm are discussed. First, an absorption detection method is applied to catch all necessary spectral absorptions with improved reliability. Then, a weighted Hamming distance is proposed to match the binary absorption‐features. Next, an elastic matching scheme is designed to classify the hyperspectral data. Experiments of classification are carried out on six classes of vegetation from the Salinas data‐set. Results show that the proposed method not only increased the overall classification accuracy to 73.13% from back propagation neural network's 71.86% and support vector machine's 73.06%, but also improved the error distributions among different classes.
Image resolution and contrast enhancement with optimal brightness compensation using wavelet transforms and particle swarm optimization
Authors: Tirumani V Hyma Lakshmi , Tenneti Madhu , K Ch. Srikavya , Kotamraju Sarat Kumar
Published: May 2021

Improving the image resolution and contrast along with uniform brightness distribution over the entire image helps to retrieve the vital realistic information necessary for human perception and interpretation. A new procedure to improve these parameters is implemented and tested. Initially, the image is super resolute using discrete wavelet transform (DWT), stationary wavelet transform (SWT) image decomposition and bicubic interpolation. The resolute image is used for contrast enhancement by using SWT and contrast limited adaptive histogram equalization (CLAHE) approach. The optimized brightness compensation technique, which uses particle swarm optimization (PSO), is applied to the resolution and contrast‐enhanced image to obtain uniform brightness distribution over the entire image. The proposed approach is tested on three data sets of images and it is found that the visual results, as well as the resolution and contrast levels of the tested images, are significantly superior to subjective and objective results.
A field study investigating road safety effects of a front brake light
Authors: Monzel Merlin , Keidel Kristof , Schubert Wolfgang , Banse Rainer
Published: May 2021

Recent research shows that braking of vehicles equipped with a front brake light is identified significantly earlier than braking of vehicles without front brake lights. Moreover, the absence of front brake lights leads to more conservative road crossing decisions. These results suggest that front brake lights are able to facilitate the pedestrians’ anticipation of dangerous traffic situations, thereby increasing road safety. The present research investigated the effects of front brake lights in the real traffic of the Berlin Tegel Airport airside. A total of 102 vehicles were equipped with front brake lights and circulated in airport traffic for a period of three and a half months. Before and after this test period, 197 staff members were asked about their experiences with and their attitude towards front brake lights. The results show that front brake lights rarely led to misunderstandings, whereas they were significantly more often perceived to facilitate communication avoiding dangerous situations. The attitude towards front brake lights was already positive at the first interview and improved significantly during the measurement period. Overall, a great majority of participants stated that front brake lights improve communication between road users and thus increase road safety.
Sparsity‐based autoencoders for denoising cluttered radar signatures
Authors: Ram Shobha Sundar , Vishwakarma Shelly , Sneh Akanksha , Yasmeen Kainat
Published: May 2021

Narrowband and broadband indoor radar images significantly deteriorate in the presence of target‐dependent and target‐independent static and dynamic clutter arising from walls. A stacked and sparse denoising autoencoder (StackedSDAE) is proposed for mitigating the wall clutter in indoor radar images. The algorithm relies on the availability of clean images and the corresponding noisy images during training and requires no additional information regarding the wall characteristics. The algorithm is evaluated on simulated Doppler‐time spectrograms and high‐range resolution profiles generated for diverse radar frequencies and wall characteristics in around‐the‐corner radar (ACR) scenarios. Additional experiments are performed on range‐enhanced frontal images generated from measurements gathered from a wideband radio frequency imaging sensor. The results from the experiments show that the StackedSDAE successfully reconstructs images that closely resemble those that would be obtained in free space conditions. Furthermore, the incorporation of sparsity and depth in the hidden layer representations within the autoencoder makes the algorithm more robust to low signal‐to‐noise ratio (SNR) and label mismatch between clean and corrupt data during training than the conventional single‐layer DAE. For example, the denoised ACR signatures show a structural similarity above 0.75 to clean free space images at SNR of −10 dB and label mismatch error of 50%.
Machine learning initialization to accelerate Stokes profile inversions
Authors: Gafeira R. , Orozco Suárez D. , Milić I. , Quintero Noda C. , Ruiz Cobo B. , Uitenbroek H.
Published: May 2021

Context. At present, an exponential growth in scientific data from current and upcoming solar observatories is expected. Most of the data consist of high spatial and temporal resolution cubes of Stokes profiles taken in both local thermodynamic equilibrium (LTE) and non-LTE spectral lines. The analysis of such solar observations requires complex inversion codes. Hence, it is necessary to develop new tools to boost the speed and efficiency of inversions and reduce computation times and costs.

Aims. In this work we discuss the application of convolutional neural networks (CNNs) as a tool to advantageously initialize Stokes profile inversions.

Methods. To demonstrate the usefulness of CNNs, we concentrate in this paper on the inversion of LTE Stokes profiles. We use observations taken with the spectropolarimeter on board the Hinode spacecraft as a test bench mark. First, we carefully analyse the data with the SIR inversion code using a given initial atmospheric model. The code provides a set of atmospheric models that reproduce the observations well. These models are then used to train a CNN. Afterwards, the same data are again inverted with SIR but using the trained CNN to provide the initial guess atmospheric models for SIR.

Results. The CNNs allow us to significantly reduce the number of inversion cycles when used to compute initial guess model atmospheres (‘assisted inversions’), therefore decreasing the computational time for LTE inversions by a factor of two to four. CNNs alone are much faster than assisted inversions, but the latter are more robust and accurate. CNNs also help to automatically cluster pixels with similar physical properties, allowing the association with different solar features on the solar surface, which is useful when inverting huge datasets where completely different regimes are present. The advantages and limitations of machine learning techniques for estimating optimum initial atmospheric models for spectral line inversions are discussed. Finally, we describe a python wrapper for the SIR and DeSIRe codes that allows for the easy setup of parallel inversions. The tool implements the assisted inversion method described in this paper. The parallel wrapper can also be used to synthesize Stokes profiles with the RH code.

Conclusions. The assisted inversions can speed up the inversion process, but the efficiency and accuracy of the inversion results depend strongly on the solar scene and the data used for the CNN training. This method (assisted inversions) will not obviate the need for analysing individual events with the utmost care but will provide solar scientists with a much better opportunity to sample large amounts of inverted data, which will undoubtedly broaden the physical discovery space.
Introducing the NEWHORIZON simulation: Galaxy properties with resolved internal dynamics across cosmic time
Authors: Dubois Yohan , Beckmann Ricarda , Bournaud Frédéric , Choi Hoseung , Devriendt Julien , Jackson Ryan , Kaviraj Sugata , Kimm Taysun , Kraljic Katarina , Laigle Clotilde , Martin Garreth , Park Min-Jung , Peirani Sébastien , Pichon Christophe , Volonteri Marta , Yi Sukyoung K.
Published: May 2021

Hydrodynamical cosmological simulations are increasing their level of realism by considering more physical processes and having greater resolution or larger statistics. However, usually either the statistical power of such simulations or the resolution reached within galaxies are sacrificed. Here, we introduce the NEWHORIZONproject in which we simulate at high resolution a zoom-in region of ∼(16 Mpc)3that is larger than a standard zoom-in region around a single halo and is embedded in a larger box. A resolution of up to 34 pc, which is typical of individual zoom-in, up-to-date resimulated halos, is reached within galaxies; this allows the simulation to capture the multi-phase nature of the interstellar medium and the clumpy nature of the star formation process in galaxies. In this introductory paper, we present several key fundamental properties of galaxies and their black holes, including the galaxy mass function, cosmic star formation rate, galactic metallicities, the Kennicutt–Schmidt relation, the stellar-to-halo mass relation, galaxy sizes, stellar kinematics and morphology, gas content within galaxies and its kinematics, and the black hole mass and spin properties over time. The various scaling relations are broadly reproduced by NEWHORIZONwith some differences with the standard observables. Owing to its exquisite spatial resolution, NEWHORIZONcaptures the inefficient process of star formation in galaxies, which evolve over time from being more turbulent, gas rich, and star bursting at high redshift. These high-redshift galaxies are also more compact, and they are more elliptical and clumpier until the level of internal gas turbulence decays enough to allow for the formation of discs. The NEWHORIZONsimulation gives access to a broad range of galaxy formation and evolution physics at low-to-intermediate stellar masses, which is a regime that will become accessible in the near future through surveys such as the LSST.
Design of an in-duct micro-perforated panel absorber for axial fan noise attenuation
Authors: Floss Sebastian , Czwielong Felix , Kaltenbacher Manfred , Becker Stefan
Published: May 2021

The reduction of fan noise in ducts is a challenging task for acoustic engineers. Usually, the confined space where an absorber can be integrated is small. In addition, one has to consider the influence of the absorber on the flow field and the attenuation of noise should be as great as possible. In this contribution, we investigate the application of a micro-perforated absorber (MPA) in the direct vicinity of a low-pressure axial fan operating at low Mach number conditions. The micro-perforated plates (MPP) are modeled using the Johnson–Champoux–Allard–Lafarge (JCAL) model for porous materials. The entire geometrical setup of duct, fan and MPA is then simulated with the Finite Element (FE) method; the pre-processing effort is reduced by using non-conforming grids to discretize the different regions. The influence of the cavity length and the positioning of the fan are analyzed. The results are then applied to the construction of a full-sized MPA duct component that takes the limited space into consideration. Simulation results and overall functionality are compared to experimental results obtained in an axial-fan test rig. The Finite Element framework proved to be robust in predicting overall sound pressure level reduction in the higher volume flow rates. It is also shown that the MPP increases sound reduction in the low-frequency regime and at two resonant frequencies of the MPA setup. However, its main benefit lies in maintaining the efficiency of the fan. The location of the fan downstream or within the MPA has a significant effect on both the simulated and measured sound reduction.
Power Coordinated Control of Micro Sources of MMC Series Microgrid Based on Model Prediction
Authors: Ma Yanni , Wang Xinggui , Xue Sheng
Published: May 2021

To improve the utilization rate of micro sources of MMC series structured microgrid in a gridconnected operation mode, a prediction-based coordination control strategy of micro-source power of bridge arm is proposed in this paper. The connection between the output power and the delta carrier is determined by analyzing each generation unit’s output power. Each micro source’s output power is controlled independently by using the carrier-wave variable amplitude phase-shift modulation method. A finite control set-model predictive control algorithm is used to predict the next cycle’s power using the carrier amplitude of the current cycle as the controlled input. The optimal switching state for the next cycle is determined according to the coordination principle of “more work for more energy.” Through simulation, the coordination strategy can effectively control the maximum power output of the bridge arm and improve the micro source’s utilization rate.
Analysis of Rockfall Hazards Stopping position and Energy dissipation Based on Orthogonal experiment
Authors: Ge Yi , He Xiang-Rong , Yuan Xi-Qiang , Pu Xiao-Yu , Meng Ling-Da , Wang Hao-Kang , Huang Yuan-Yuan
Published: May 2021

Many factors affect the movement of rockfall. Thus, this study explored the influence of rockfall shape, slope angle, angular velocity, slope hardness, rockfall mass, and slope surface roughness on the stopping position and potential energy loss rate based on an orthogonal experiment. To study the key factors affecting the movement of rockfall, 2500 sets of orthogonal tests were carried out by using ROCFALL 8.0 (ROCSCIENCE) numerical simulation program. SPSS19.0 software was used to perform importance analysis and correlation analysis on the test results. The analysis results show that rockfall shape has the greatest influence on the stopping distance. There is a significant positive linear correlation between the number of rockfall edges and the stopping distance of rockfall on the asphalt road. The slope angle has the greatest influence on the potential energy loss rate, and there is a significant negative linear correlation between the slope angle and the potential energy loss rate. In the case of a low angle slope, the stopping position of rockfall is more concentrated. Therefore, in the process of mountain engineering construction, more attention should be paid to the influence of rockfall shape and slope angle on rockfall hazard protection.
Research and Application of Automatic Fault Diagnosis and Isolation Device for Distribution Line
Authors: Jia Keyin , Wang Cheng , Zheng Shiyang , Liu Junfeng , Chen Minghongtian
Published: May 2021

This paper takes the equipment of a specific project as an example to develop an automatic fault diagnosis and isolation device for 10kV overhead line or cable line when a user has grounding and shortcircuit faults, so as to realize fast fault location, isolation and recovery, reduce the power outage time of users, and thus improve the reliability of distribution network. The project takes the 10kV South and North Trunk Lines ‘hand in hand’ power supply network as the research object, and studies the solutions of the automatic fault isolation function and the restoration of power supply, hoping to further improve the level of rapid power recovery, reduce power loss, and improve the reliability, automation and information level of power supply for reference.
How can gas companies improve their profitability? ——Based on DuPont analysis method
Authors: Hao Yixin
Published: May 2021

In recent years, due to serious environmental problems—increasing global natural gas demand, notable supply growth, LNG supply capacity expansion, natural gas consumption has increased significantly, and the natural gas industry has entered a booming stage. In this paper, China Resources Gas, a leading company in gas industry, is selected as the research object. We use DuPont analysis to analyze its financial statement from 2014 to 2017 and decompose the company’s return on net assets into the multiple of several financial ratios step by step. So the relationship between several major financial ratios can be used to comprehensively analyze the company’s profitability. Taking this as an example, the key factors affecting profitability of gas companies are concluded.
Study on boiler’s comprehensive benefits optimization based on PSO optimized XGBoost algorithm
Authors: Wang Hui , Zhang Guobao , Huang Yongming , Zhang Yongchun
Published: May 2021

To predict the boiler’s combustion efficiency and NOx emissions, this paper introduced a particle swarm optimization optimized XGBoost algorithm. The results show that the MAPE can reach 0.107% and 3.732% respectively on the verification set, which is better SVM, LR and ANN. At the same time, this paper presents a comprehensive benefits evaluation function considering economic and environmental benefits to optimize the multi-objective optimization problem of boiler’s combustion efficiency and NOx emission. Based on the operation data of a 300 MW Circulating Fluidized Bed, the experimental results show that: the comprehensive benefits evaluation function can reasonably balance boiler’s combustion efficiency and NOx emissions to achieve the optimal comprehensive benefit.
Research on Navigation and Positioning Technology of Intelligent Accompanying Tool Car in Dispatching Automation Computer Room
Authors: Song Yufei , Shi Yu , Li Tianquan , Cao Xudong , Liu Xiaohang , Sun Li , Tang Manli
Published: May 2021

In view of the wide variety of equipment in the dispatch automation machine room and the dense arrangement of cabinets, a navigation technology suitable for the dispatch automation machine room is proposed on the intelligent companion tool cart. In this paper, three sensors of ultrasonic, infrared and lidar are designed to form an intelligent neural sensor, and the information received by the intelligent neural sensor is calculated to generate a vector map through a software algorithm. At the same time, a plane coordinate network is established. The grid coordinate unit accuracy is 0.1cm. At the same time, the concept of “virtual fence” was put forward to fix the workers at the working point, which increased the safety of work. Subsequently, an experimental test of positioning and navigation of the tool cart was carried out. The experimental results showed that the tool cart can accurately locate and generate a vector map with an accuracy error of less than 10cm. The navigation method has a good application effect and has a good promotion value.
Horizontal well workover technology present situation and development trend
Authors: Zhang Guohui , Wang Peng , Chen Rong , Duan Baoping , Zhang Guowen , Sun Jiewen
Published: May 2021

In the downhole operation of horizontal Wells, the pipe string is subjected to the combined action of many kinds of loads. The pipe string may bend sinusoidal or spiral under the action of axial compressive stress, which will also increase the friction between the pipe string and the wellbore wall. Because of the existence of friction, to the milling, salvage, unstuck, sand and other construction to bring adverse effects. This paper describes the characteristics of horizontal well in fishing, sand washing, unlocking and casing milling. The paper introduces the development of horizontal well application, such as drilling technology matching for complex structure wells, high-level completion of lateral Wells, radial lateral wells in low permeability reservoirs and supporting technology for completion and production of horizontal wells.
Stress Calculation and Analysis of a 600MW Supercritical Boiler’s Steam-water Separator
Authors: Xu Haichuan , Zhang Haishi , Sun Haihua
Published: May 2021

The steam-water separator of a 600MW boiler has been chosen as the research object. By theoretical analysis’s method and finite element analysis, the stress and secure research has been carried out in the steam-water separator as the thick-walled pressure vessel. For its start-up and normal operation of the working process and features and considering the internal pressure load and thermal stress loading conditions, the initiation of separation stress and security analysis have been carried out about the steam-water separator. The primary stress at the continuum of the cylinder structure can be calculated by the formula, and the calculated results are basically in agreement with the simulated graphic results. And the research work provides a theoretical basis for on-line stress monitoring and life assessment.
Research on Multi-objective Optimization of Substation Project Management Based on Resource Constraint
Authors: Zhou Xichu , Sun Li , Fan Sixia , Wu Bin
Published: May 2021

With the rapid development of China’s economy, the electricity load continues to increase, the national demand for power engineering projects is also increasing.In the context of the gradual improvement of national requirements for substation projects, decision makers no longer only consider the optimal standards of project duration, cost and quality, but also the resources consumed in the construction and the degree of impact on the environment are important criteria for judging projects.However, in order to be environment-friendly and based on resource constraints, the project management of substation projects is becoming more and more complicated.In this paper, resource factors are added on the basis of the three classical indexes, and the optimal resource allocation of the project is realized under the condition of minimizing the adverse impact on the environment. The feasibility scheme of multi-objective optimization is obtained through particle swarm optimization algorithm.
Design and calculation of sine wave permanent magnet brushless motor for electric vehicle
Authors: Wu Jiahua , Sun Fengchang , Deng Xiaochuan , Zhang Zhichao , Yu Dongyang , Wang Zheng , Li Zishuo
Published: May 2021

With the rapid development of the global automobile industry, energy and environmental problems have become increasingly prominent. In order to realize the sustainable development of new energy, automobile industry has become the direction of new energy. Due to the relatively mature energy storage technology, high efficiency of driving motor and mature control mode, electric vehicles have become the main development direction of new energy vehicles. The main work of this paper is to study the characteristics of various driving motors, design a motor which can meet the performance index of pure electric vehicle, and select an appropriate control scheme.
Research on the experimental performance of gas-fired boiler based on the total heat recovery technology of absorption heat pump
Authors: Zhai Xujing , Tian Shoutao , Zhu Kelin , Huang Pan , Yu Jin , Huang Ping
Published: May 2021

Based on an example of a gas-fired boiler for an industrial user in Tianjin, the absorption heat pump technology was used to carry out energy-saving transformation of the above boiler. The actual test was carried out on the gas flow, exhaust gas temperature and other parameters from January 2, 2018 to February 26, 2018. And then, the thermal efficiency of the boiler was analysed. The results show that after the energy-saving transformation, the exhaust gas temperature of the gas-fired boiler can be reduced from 140 °C to about 40 °C, and the overall thermal efficiency of the boiler also rises from 89.5% to 101.3%, which is 13.2% higher than that before optimization. According to the economic analysis, the energy-saving reconstruction project can achieve an energy-saving economic benefit of 1.598 million yuan throughout the year, with obvious energy-saving and emission reduction benefits.
Research on Incentive and restraint mechanism of capital operation of power grid enterprises under new development pattern
Authors: Zou Lifang , Lin Ling , Ke Meifeng , Zheng Chenhong , Zhang Shiming , Ye Minquan
Published: May 2021

Under the new development pattern of dual circulation economy, the reform of state-owned enterprises has entered the deep water area, and the operating environment of power grid enterprises has changed significantly, which has a profound impact on the capital operation strategy and effect of the enterprises. This paper analyzes the new characteristics of capital operation of power grid enterprises under the new development pattern, constructs the incentive and restriction index system of capital operation of power grid enterprises, designs the incentive and restraint mechanism of capital operation of power grid enterprises, and verifies the scientificity and applicability of the mechanism by financial evaluation and analysis. The research results enrich the theory of capital operation management based on financial evaluation, and provide theoretical basis and practical reference for grid enterprises to optimize the distribution of capital investment and improve the efficiency of capital operation.
The Analysis of Meteorological Conditions for Icing on UHV Transmission Lines in Southeast Guizhou in 2018
Authors: Zhang Hourong , Zhang Shiqi , Wang Qi , Chai Hao
Published: May 2021

Using ERA5 reanalysis data of ECMWF and the ultra-high voltage (UHV) transmission line icing observation system to analyze the meteorological conditions of conductor icing in Guizhou from January 24 to 29, 2018, Results show: The weather conditions for this icing event are that the temperature drops below 0°C, there is weak rainfall, and the humidity is generally between 95% and 100%; the direction is mainly northerly wind, with wind speed of 2~6m/s; the air pressure rises. The meteorological elements that are more relevant to icing are environmental temperature, air pressure, and precipitation. The relationship with wind speed and relative humidity is small.
Research on Oil and Gas Pipeline Operation Optimization Based on Improved Newton-Raphson Method
Authors: Duan Linjie , Zhang Lipeng , Jiao Chunfeng , Dang Rui , Li Xudong , Cao Jinggang
Published: May 2021

Oil and gas pipelines are the main channel to ensure national energy security and national economic development due to the safety and efficiency of the transportation coast. To achieve an optimal state of pipeline operation in terms of safety and efficiency is the crucial important issue throughout the life cycle of a pipeline system. However, the optimization problem of the pipeline network system is a typical Mixed Integer Non-Linear Problem (MINLP) which are extremely difficult to solve. An optimal solution to keep pipeline operated in most efficient state under the premise of safe operation is given in the paper by using the dynamical programming method. Firstly, the improved Newton-Raphson method is used to solve the discrete pipeline system, and the operating parameters such as temperature, pressure and flow of any section surface in the pipeline are obtained. The fluid parameter values of the each discrete nodes can ensure the safety of the pipeline. Based on this, the total energy consumption cost is set as the objective function, and the oil and gas pipeline operation optimization model is then established, and the dynamic programming method is used to solve it, so that it can obtain the optimal solution of the current working conditions in a reasonable computational cost. The actual example shows that the energy cost of the optimized operation scheme can be reduced by 6.8% compared with the pre-optimization scheme.
Non-contact measurement method of bridge deflection based on machine vision
Authors: Wei Zhao , YongBin Wei
Published: May 2021

Bridge deflection is a very important parameter for bridge structure. It directly reflects the vertical overall stiffness of bridge structure, and is an important basis for reflecting the linear change of bridge. It is closely related to the bearing capacity of the bridge and the ability to resist earthquake and other dynamic loads. Computer vision is to obtain image data through image acquisition device, and use special image processing software to get the shape and displacement information of the object. This method has high precision, low cost, and simple operation. In this paper, based on the industrial camera, the optical flow method and sub-pixel corner detection algorithm are used for target tracking and sub-pixel detection. Through the comparison between the laboratory data and the micro pan tilt data, the usability of this method in bridge deflection monitoring is verified and evaluated.
Design of temperature acquisition and servo debugging board
Authors: Yi Sun , Sun Quanyu , Shao Guowei
Published: May 2021

The temperature acquisition and servo debugging board is used in Flight control computer, mainly for temperature acquisition and servo debugging. Its good functional performance and reliability have a good application prospect.
Processing and properties of hollow glass microsphere particulate-filled PA2200 composites produced by selective laser sintering
Authors: Ye Dong , Yu Lihua , Hou Gaoyan , Zhu Hong
Published: May 2021

Selective laser sintering (SLS) to prepare composites by adding filler into polymer is an effective method to save costs and reinforce the sintered parts. This article investigated the fabrication of PA2200 composites filled with different volume fractions of hollow glass microsphere (HGM) by SLS. HGM was prepared by silane coupling agent surface treatment. The particle size distribution, microstructure, thermal and mechanical properties of PA2200/HGM composites were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and tensile experiment. The results indicated that the density of the composite was significantly reduced compared to the neat PA2200 and the density decreased with the HGMs content increasing. HGM improved the warping deformation in the process of sintering. The tensile modulus increased while tensile strength and elongation at break decreased as a function of HGM volume fraction in a certain range. This work indicated that thermal properties and tensile properties of polyamide-matrix composites can be reinforced by adjusting HGM content, and PA2200/HGM composite powder is a good material for SLS with less density and lower cost.
Dynamic analysis of autonomous risk avoidance of amphibious floating bridge based on discrete element method and physical engine
Authors: Zhang Wenbin , Ye Mingxin
Published: May 2021

In this paper, based on an intelligent floating bridge, by using discrete element methods and physical engines, under the action of certain missile repulsion fields, the force process and motion path in the process of autonomous evasion of missiles are studied. Firstly, the static simulation of missile repulsion fields is carried out by using the polynomial least square surface fitting method. According to the strength of repulsion field at different times and the extrusion force between the pontoons, the kinematic equation of the pontoon is established. The equation is discretised by using a discrete element method, and the kinematic equation is obtained according to the time iteration. Then, motion analysis is carried out by using a physical engine on the basis of equation Analysis. Finally, the position parameters before and after the self-evasion missile of the floating bridge are calculated, and the simulation program is written in MATLAB. The dynamic simulation experiment of the whole evasion missile process is carried out, and the results are satisfactory.
Synthesis and Performances of Hydrocinnamic Acid Derivatives Containing Alkyl Dihydrazide
Authors: Hu Jianxiang , Zhao Lisha , Liu Shuangqing , Cai Yanhua
Published: May 2021

In this work, four hydrocinnamic acid derivatives including N, N’-succinic bis(hydrocinnamic acid) dihydrazide (HASUD), N, N’-adipic bis(hydrocinnamic acid) dihydrazide (HAADD), N, N’-sebacic bis(hydrocinnamic acid) dihydrazide (HASED) and N, N’-dodecanedioic bis(hydrocinnamic acid) dihydrazide (HADOD) were synthesized via two liquid reactions. And then fourier transform infrared spectrometer and 1H nuclear magnetic resonance were used to characterize molecular structures of four hydrocinnamic acid derivatives. Additionally, the orthogonal experiment obtained the optimum synthesis process of four hydrocinnamic acid derivatives, and the maximum yield of HASUD, HAADD, HASED and HADOD were 33.3%, 43.2%, 43.5% and 51.9%, respectively. DMol3 was used to optimize geometric structure and obtain frontier orbital energy. Finally, hydrocinnamic acid derivatives and poly(L-lactide) (PLLA) were blended using the torque rheometer to investigate these role in PLLA resin. The resultant from the melt-crystallization process showed that hydrocinnamic acid derivatives as heterogeneous nucleating agents could significantly enhance PLLA’s crystallization.
Numerical analysis of thermal radiation of spacecraft on orbit based on SINDA/FLUINT
Authors: Shi Yi
Published: May 2021

Thermal stability is an important indicator to measure the reliability of aerospace equipment, and the space thermal environment is complex, and the commonly used thermal analysis software for ground equipment can no longer meet the needs. For this reason, based on the thermal design analysis software SINDA/FLUINT, taking a spacecraft as the research object, the thermal balance equation is first established. Then, use the thermal desktop software to establish a numerical model, and use the SINDA/FLUINT software to solve the heat transfer process. Finally, the thermal desktop is used to post-process the calculation results and analyse the thermal radiation of the spacecraft.
Study on Splitting Tensile Mechanical Properties of Carbon Fiber/Polymer Latex Powder Composite Modified Concrete
Authors: Meng Xin , Bai Erlei , Wang Zhihang , Huang Zhe , Xia Wei
Published: May 2021

The effects of carbon fiber and polymer latex powder on the split tensile mechanical properties of concrete in single and compound mixing conditions are studied. The results show that both carbon fiber or polymer latex powder can improve the split tensile strength and peak strain of concrete. When the carbon fiber content is 0.2%, the split tensile mechanical properties of carbon fiber reinforced concrete (CFRC) are the best. When the amount is 8%, the mechanical properties of polymer modified concrete (PMC) in split tension are the best. When the carbon fiber content is 0.3% and the polymer latex powder content is 0.8%, the splitting tensile mechanical properties of the carbon fiber/polymer latex powder composite modified concrete (CFRPMC) specimens are the best, and are better than CFRC specimens and PMC specimens.
Numerical Simulation of Flow Field Characteristics of The Cooling Water Jacket of A Marine Diesel Engine
Authors: Zhang Bo , Zhang Ping , Zhang Zhao , Yang Shaobo , Wang Chengli , Zeng Fanming
Published: May 2021

In order to evaluate the flow field characteristics of a marine diesel engine cooling water jacket, and provide a theoretical basis for further optimizing the water jacket structure. A computational fluid dynamics (CFD) method was used to calculate the three-dimensional flow field of the water jacket. Based on the CFD simulation model of the engine water jacket, the analysis of pressure field, velocity field, streamline distribution and flow uniformity of water jacket of diesel engine under rated condition were carried out. The results show that: the total pressure loss of water jacket is 30.3 kPa, in which the pressure loss of cylinder block is 8.4 kPa, and the one of cylinder head and outlet manifold is 21.9 kPa, which indicates that the flow resistance design of the cylinder block and head is reasonable; the flow rate of coolant in the nose zone of cylinder head is above 1.5 m/s, which meets the cooling demand of cylinder head; the cooling water flows circumferentially in the engine block water jacket, and the flow dead zones are easily formed by the mutual extrusion and collision of the water flows; the outlet of the cylinder head water jacket is connected with the outlet manifold at right angle, which leads to large energy loss of the flow field; the maximum non-uniformity of flow rate of water jacket of each cylinder is 5.85%, which can be further optimized by adjusting the position of water jacket inlet.
Study on the Influence of Different Carbon Sources on Nitrogen and Phosphorus Removal with Micro-pressure swirl Reactor
Authors: Tian Xi , Li Xuejiao , Lv Yanhong , Dong Penghui , Yang Longfei , Xue Luyao , Bian Dejun
Published: May 2021

To explore the suitable external carbon sources for Micro-pressure swirl Reactor (MPR), the experiment was run in parallel through two MPRs, using starch and glucose as carbon sources respectively. Research indicated that under the experimental operating conditions, using starch as the carbon source could more effectively promote the biological denitrification of the MPR system. Due to the structural characteristics of MPR and the slow degradation of starch, the demand for carbon source for denitrification was ensured during the operation cycle, so that the system obtained a better denitrification effect. The test results provided reference for the selection of the external carbon source of the MPR process.
Research on the Working Mechanism of Melt Metallurgical Effect
Authors: Liao Xiaoyang , Zhuang Jinwu , Liu Yazhou
Published: May 2021

This paper takes rectangular tinned silver flake as the research object to explore the working mechanism of melt metallurgical effect. Firstly, the paper designs and processes rectangular tinned silver flake through the electroplating technology, then conducts low-overload pre-arc experiment with the metallurgical samples. According to the experiment results, it is proposed that “Under low overload current, the formation of silver-tin alloy leads to the increase of current density of the metallic silver layer, which significantly advances the break time of the silver flake. At the same time, the silver-tin interpenetration speed is a linear function of the temperature.” Finally, the self-programming software is used to establish the transient electric heating field model of the metallurgical tinned silver flake. By comparing simulation and experiment, the results verify the accuracy of the hypothesis, and obtain the working mechanism of the melt metallurgical effect, which provides a reliable theoretical basis for the design and application of the metallurgical trigger.
Wave-induced residual pore pressure around a buried pipeline
Authors: Liao Zhou-Quan , Liu Xiao-Li
Published: May 2021

Seabed instability caused by cyclic wave loading is one of the main factors affecting the foundation instability of marine structures, and it is a key problem that needs to be paid attention in the design of marine structures. Based on Biot’s consolidation theory and a semi-empirical formula for calculating residual pore water pressure, the wave-induced residual seabed response around a buried pipeline was investigated by numerical simulation. The correctness of the numerical results is verified by comparing with experimental results. Effect of the self-weight of the buried pipeline on residual pore pressure development and the characteristics of residual pore pressure near the pipeline are discussed.
Experimental study on droplets evaporation on hydrophobic surface at different tilt angles
Authors: He Zhenhua , Wang Shuxiang , Cai Yu , Chen Chen
Published: May 2021

Droplets evaporation exists widely in industrial manufacturing and engineering applications. Optical visualization system was used to investigate the evaporation process of deionized water droplets on fresh taro leaves with different tilt angles. The evaporation time and mode of droplets were experimental studied at different tilt angles. The results show that the time for the droplet to completely evaporate decreased as the surface tilt angle increases. During the first half of droplet evaporation process on the slant hydrophobic surface, the evaporation modes were different between the two sides of the droplet. When the droplet on an inclined hydrophobic surface evaporated to a certain volume or a certain contact angle, its subsequent evaporation behavior was similar to that of a droplet on a non-tilted hydrophobic surface.
Design and application of purified water preparation device for chemical analysis
Authors: Li Yanping , Fang Jianjun , Hou Liwen
Published: May 2021

Qualified purified water is essential for all chemical analysis. Spectral analysis, trace analysis and general chemical analysis require different purity of water. This paper introduces a kind of purified water preparation device which can be widely used in all chemical analysis work. The purified water preparation device consists of two-stage reverse osmosis device and water treatment device of ion exchange system. The two-stage reverse osmosis water treatment unit can be operated in two modes: program-controlled and manual mode, and the water production rate is about 80%. The ion exchange water treatment unit consists of two cation exchangers, two cation exchangers and one mixed ion exchanger, which can prepare silicon free water and sodium free water and meet the requirements of trace analysis. The ion exchange water treatment unit is equipped with independent purified water pipeline system and regenerated liquid pipeline system to avoid the pollution of purified water. The regeneration operation of ion exchange resin is simple, and the discontinuous water production can be easily realized. This set of purified water preparation device can adapt to various water sources to complete purification treatment, and produce purified water meeting various chemical analysis.
Design method of the mix ratio of hot mix plant recycled asphalt mixture containing high mixture content
Authors: He Yunwu , Liu Tao , Wang Tao , Liang Xiayi , Wei Hanxin , Zheng Zhigang , Xiao Xin
Published: May 2021

This paper mainly used the Superpave and the Marshall design methods to design the mix ratio of the hot mix plant recycled asphalt mixture. The road performance of AC-20, SUP-20 with 30% RAP content and AC-20 with 50% RAP content was studied to evaluate the water stability and high temperature stability and low temperature crack resistance of the recycled asphalt mixture. Research shows that the road performance of AC-20 mixed with 50% RAP content meets the technical requirements of the same type of asphalt mixture. It is recommended to use the Marshall design method for hot mix plant recycled asphalt mixture design.
Structural Strength Design and Navigation Capability Analysis of Polar Cruise
Authors: Zhang Xuchen , Chi Linru , Li Ziqiang
Published: May 2021

The “Ice Silk Road” is an effective extension of China’s “One Belt, One Road” initiative. The construction of the “Ice Silk Road” and the development and utilization of polar waterways urgently need the equipment support of polar ships. Nowadays, the design and construction of polar cruise ships has gradually become a hot spot, but there is still a lot of room for development of such ships. Based on the relevant requirements of BV classification society and IACS, this article analyzes the current situation of polar cruises’ structural strength and operational capabilities, and evaluates the overall capabilities of polar cruises, which has a certain reference value for the design and construction of cruise ships that will be developed in the future.
Determination of Small-Amount Polypropylene in Imported Recycled Polyethylene/Polypropylene Blends by Fourier Transform Infrared Spectroscopy
Authors: Dai Shujun , Luo Chuan , Zhang Chao , Wang Hao , Zhang Yin , Yuan Lifeng
Published: May 2021

In the domestic production of recycled plastics, it is difficult to separate olefin polymers such as polyethylene and polypropylene. Therefore, the prerequisite for identifying the cargo-solid waste properties of recycled plastics is to determine the polymer composition. In this paper, Fourier transform infrared spectroscopy was used to detect polypropylene content in polyethylene and polypropylene blends. Under 2%-8% polypropylene content, an exponential relationship was shown in the ratio of characteristic peak area. This method features fast detection speed and accurate judgment. It can quickly determine whether the polypropylene content in the polyethylene and polypropylene blends is greater than 5% in the tariff inspection. Also, it can determine plastic solid waste attributes and identify whether polyethylene is mixed with a small amount of polypropylene content.
Analysis of abnormal expansion of pipe system and optimization of structural stress in 350MW unit
Authors: Liu Xin , Zhang Yanming , Liu Qun , Sun Xu , Wang Yu , Zhao Liye
Published: May 2021

A 350MW power plant main steam and reheat hot steam pipe subsidence occurred in part of the pipe section, through field inspection, calculation and checking analysis, combined with pipeline support and hanger adjustment, load testing and elevation measurement and other means, the settlement of the pipe system to optimize the overall stress state of the pipe system. Through the thermal displacement of the pipe system support lifting point, the selection and calculation of the pipe system support hanger and the overall design state stress check of the pipe system, the design state is basically consistent with the check state. Through to the key node load tests have shown that small spring hanger selection is the primary cause of section settling, combined with the spring adjustment space and calculation results are part of the hanger. Finally, the settlement of pipeline is realized, main steam pipe at the same time a stress and secondary stress were achieved about 15% of the decline, piping stress has been further optimized.