bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of High-lightweight Space Mirror Component Based on Automatic Optimization
Authors: Wu Jianfu
Published: August 2020

Aiming at the problems of high weight, low cost and extremely short development cycle faced by commercial aerospace space remote sensing cameras, a mathematical model with modal fundamental frequency as the objective function under the constraints of weight and size has been established. Through the automatic optimization method, the lightening rate of the mirror can reach 71.8%. Using the “2 + 2 + 2” quasi-static constraint as the criterion, the flexible support structure of the mirror is optimally designed to realize the high rigidity of the component and ensure the high bearing capacity of the force and thermal environment. Static simulation analysis of the design results of the mirror assembly using hypermesh shows that under the combined influence of gravity field and temperature field, the change of the mirror surface shape (RMS) is within 0.0056λ. At the same time, the modal analysis of the design results shows that the first-order natural frequency of the component can reach 146.52 Hz, which has extremely high dynamic stiffness. It can effectively adapt to the dynamic environment, and the design of the mirror assembly can fully meet the needs of commercial aerospace space remote sensing cameras.
Efficiency Evaluation of Air-defense Early-warning Detection Based on Communication Support
Authors: Zhou Zheshuai , Li Yuntao , Tang Yubo , Li Yan
Published: August 2020

In order to quantitatively analyze the impact of communication support capability on early-warning detection efficiency under electronic jamming condition, based on the study of the air-raid targets searching process, this paper build the detection probability calculating model of target indicating radar by evaluating the jamming efficiency of the air intelligence informing communication. Combined with the typical combat scenario, analysis of examples simulation is done and the results show that the jamming effect of using airborne jamming is better than using subgrade jamming on communication and the target indicating error which is caused by early-warning information does not affect the improvement of early warning detection capability.
State algorithm and double optimization design of safety cable retractor for gecko climbing robot
Authors: Gu Lizhi , Gao Shanping , Song Jinling , Xu Jianmin , Xiao Junyan , Chen Helu , Liang Chenglong
Published: August 2020

Gecko climbing robot cable is the core part of the robot system, which plays an important role in the basic life support of the operator. Based on the analysis of the function and performance requirements of the safety cable in the climbing process, the modular design scheme of the retractor is proposed according to the system engineering principle and optimization method, and the system is divided into retractor module, guidance and control module and mechanical structure module. Based on the analysis of the characteristics of the operator’s safety state during the climbing operation, the operator’s safety state set, the operator’s safety state set and the operator’s safety state set are formed. The whole process/full state algorithm is proposed. In the structural design, the basic functions of the retractor are divided into retractor module, guidance and control module and mechanical structure module. Considering the limited space and bearing capacity of the robot vehicle, on the premise of ensuring the safety and reliability, the lightweight optimization design is carried out to realize the function module and the double-pawl-bidirectional backstop-double-optimization retraction and release system with the most concise connection of each function module.
New Curve Fitting Based Roller Modification Method for Spherical Roller Bearing
Authors: Songyang Jia
Published: August 2020

In the field of roller modification affecting the service life of rolling bearings, Different from point contact of ball bearing and line contact of cylindrical or tapered roller bearing, Spherical roller bearing is very special because it has the characteristics of point contact and line contact at the same time. To solve the problem that the spherical roller cannot be modified by line contact type roller modification method, this paper provides a new modification method of spherical roller. The spherical roller profile is divided into two parts: non modification profile and modification profile. The concept of gap space is put forward. Curve fitting is carried out in the non modified part, and then the fitting logarithmic curve is used in the modified part of the spherical roller. This method can provide reference for engineering application.
Feasibility Analysis of Cross Wedge Rolling (CWR) of Hexahedral Billet
Authors: Chang Y , Shu X D , Chen T Z
Published: August 2020

In order to expand the product range of cross wedge rolling (CWR) and realize the CWR of hexahedral billet, the hexahedral CWR is studied. In this paper, a three-dimensional finite element model (FEM) of hexahedral cross wedge rolling is established by using DEFORM software. In this paper, a three-dimensional FEM of hexahedral CWR is established by using DEFORM finite element software. The change and distribution of equivalent stress and strain in the rolling process of hexahedral billets are analyzed. By tracking the strain in the rolling core of hexahedral billet, the change law of strain in each stage of forming process is obtained. The equivalent strain during the manufacturing process, the obtained CWR of hexahedral billet and round billet are basically the same. The feasibility of CWR of hexahedral billet is further verified by experiments. The research results provide theoretical guidance for realizing CWR of hexahedral billet.
Sound Quality Prediction of Fuel Cell Vehicles Based on Regression Analysis
Authors: Liu Zeyu , Liu Hai , Zhang Yanyi , Hao Dong , Sun Xiuxiu , Ji Xiang
Published: August 2020

The typical fuel cell vehicle(FCV)was taken as the research object. The noise test of the FCV was carried out in the environment of the semi-anechoic room of the vehicle. The noise samples in the vehicle were collected under the condition of constant speed, which was intercepted and processed with equal time. Noise was subjectively evaluated using a pairwise comparison method. The objective evaluation parameters suitable for evaluating the sound quality of FCV were selected. The objective evaluation parameters were calculated and solved. According to the subjective and objective evaluation results of sound quality, run multiple linear regression analysis to quantitatively solve the correlation between the subjective and objective evaluation results. MAPE results showed that the accuracy of the multiple linear regression prediction model was low, in order to further improve the accuracy of the prediction model of the sound quality of FCVs, The GA-BP neural network prediction model was used to establish the evaluation prediction model between the subjective and objective evaluation results. The weight of the influence of objective parameters on the subjective evaluation results was calculated. The MAPE calculation results showed that the neural network model was more suitable for the establishment of FCV sound quality prediction According to the model, A-weighting and roughness were the most influential to the subjective evaluation results. The two algorithms had the same results.
Progressive stamping process and die design of high strength steel automobile structural parts
Authors: Gen Yang , Yunong Wu
Published: August 2020

High strength steel has high strength and poor plasticity. When it is used in parts with large material thickness, complex shape and many working procedures, higher requirements are put forward for mold design. This paper introduced the forming characteristics, layout scheme, overall structure design of multi-station progressive die and design key points of important parts of a high-strength steel plate car mounting part. The progressive die including blanking, drawing, local forming and bending and other 13 processes was designed. The preforming and secondary forming were adopted to form the reinforcing ribs. The double-row with center carrier layout pattern was adopted to reduce the bending side force, and made the material utilization higher. The sub-die and insert structure’s using was convenient for die machining and debugging. The practice has proved that the die structure is reasonable and reliable, which can guarantee the quality of the products. It can be used as a reference for the design of similar products.
Variant design of typical aircraft parts based on CATIA technology
Authors: Hao B , Liu F , Liu M
Published: August 2020

In order to improve the efficiency of product design, the component framework technology was studied. With the help of CATIA secondary development platform, the variant design of typical aircraft parts was realized on the basis of parametric modeling technology, the feature information was extracted quickly, and the intelligent operation was realized. By using object-oriented programming language, a variant design module integrated with CATIA system is developed to improve the design efficiency of typical aircraft parts. Taking the tie rod in the typical aircraft parts as an example, the verification of the variation design method shows that using CATIA secondary development technology and CAA programming tools, the parametric modeling of typical aircraft parts can be achieved to achieve the variation design.
Design of A New Differential Scanning Calorimeter
Authors: Zhong Xiaoqin , Niu Xiaojian , Lu Baokang , Shen Xiuguo
Published: August 2020

The core component of DSC is a temperature difference sensor used to measure the temperature change of sample and reference material during reaction. Taking temperature difference sensor as the research object, a new DSC is designed, which uses many pairs of thermocouples in series to form a radiating thermocouple stack to improve the calorimetric sensitivity of the temperature difference sensor and reduce the measurement error caused by the uneven temperature distribution on the sensor. Through theoretical analysis, it can be seen that the original signal acquisition volume of the temperature difference sensor with multiple pairs of thermocouples has increased greatly, the calorimetric sensitivity is higher, and the error is smaller. Based on the finite element analysis software ANSYS, the steady state thermal analysis is performed on the high-sensitivity temperature difference sensor and the dumbbell-type temperature difference sensor respectively. The results show that the temperature difference of the high-sensitivity temperature difference sensor is 40.8% ∼ 52.3% lower than that of the dumbbell-type temperature difference sensor under different working temperatures, which greatly reduces the measurement error caused by the uneven temperature distribution.
An Experiment Method of Choosing Structure of shrouded power turbine blade
Authors: Tiancai Guo , Youliang Xu , Yanong Chen , Yunqiu Zhang
Published: August 2020

The turbine blade presents various failure modes in service. The stress concentration located near the shroud can result in fracture failure, thus the structural optimization of the shroud is the main focus for mechanical engineers. Stress concentration is difficult to accurately evaluate by calculation and needs to be verified by experiment. Three-dimensional photoelastic test is an important method of program preference. This paper conducts three-dimensional photoelastic tests on shrouded turbine blades with different structures to select structures with minimum concentrated stress. It is shown in the experiment results that the stress fringe pattern clearly shows the stress distribution trend and stress concentration area of the blades, which shows the quality of design intuitively. It shows that photoelastic test can provide a reliable test basis for the design and model selection of small aeroengine shrouded turbine blades. The advantage of this method is that it is a fast, economical and intuitive method of program preference. The method has been successfully applied in a self-developed small aeroengine shrouded turbine blades.
Effects of strain paths on the fracture forming limit of high strength structural steel sheets
Authors: Xu Teng , Xia Qin-xiang , Qi Zhen-jie , Wu Xiao-yu , Ran Jia-qi , Gong Feng
Published: August 2020

The cruciform two-axial tensile specimen was designed and the two-axial tensile test scheme for different strain paths was developed. The effect of strain paths on the forming limit of high strength structural steel plates was obtained by the DIC method. The results show that for the unidirectional alternating loading test scheme, the equivalent strain of the ultimate strain is less than the sum of the equivalent strains from each step. When the main strain direction of the specimen pre-strain is perpendicular to the final strain path, the forming limit decreases with the increase of the pre-strain.
Study on the design of internal flash cleaning device in long diameter drill pipe used in coal mine
Authors: Fei Lan
Published: August 2020

This paper takes the long diameter geological drill pipe used in coal mine as the research object. The internal flash cleaning technology which remains in the drill pipe hole after the internal flash turning is studied. A hand - held pneumatic internal flash cleaning device was designed to replace the original manual way of removing iron filings. It greatly reduces the labor intensity of workers, improves the working environment, and shortens the cleaning time of flash inside a single drill pipe. This device greatly improves the work efficiency and makes it safer and more reliable to use.
Mechanics model and optimum design of PE pellet shell for anti-water-seepage with ease in open
Authors: Gu Lizhi , Huang Ehui , Song Jinling , Liang Fengshun , Huang Lihong , Fang Yongying , Chen Suhang
Published: August 2020

Polyethylene capsule shells are a kind of container for pills with low cost and long-term preservation, after paraffin-sealed. This kind of pellet shell is composed of two hemispheric shells with the seal convex and concave allowances, at which they connect, locate and unify together as a whole by local elastic deformation. However, the water seepage occurs in certain percentage of the pills during paraffin-seal operation. In order to solve the problem of water seepage and further improve the process, the current study presents the tension model under the action of ideal gas in paraffin-sealing, the enhanced cantilever beam model under water cooling, and the simply supported beam model for investigation of the cause of the water seepage. The criterion of impervious water was put forward and developed with anti-inference method. The case analysis shows that the seepage is caused by the unreasonable structure of the seal of PE pellet. On the basis of this, the seal allowance of the shell is improved and optimized in the current design. And the overlap amount of the half shells was increased from 0.15mm to 0.30mm, at least, with protruding and half shot shell with concave is increased and the small Angle of the double V structure is adopted. The results of calculation and test show that the new design is of rational and reliability, and it met the requirements of small force and ease in opening the shell.
A novel test rig development for experimental study of fluid mechanics of hydraulic orifice and/or gaps under high or low temperature conditions
Authors: Wang Wenlin , Xu Jiabing , Kong Xin , Wu Yongming
Published: August 2020

To meet the demand of ever operating in extreme environments of modern high-end vehicles or machineries, it is meaningful to perform basic research on fluid mechanics of hydraulic orifices and/or gaps under high or low temperature conditions. In this study, a novel compact experimental module which integrates the oil, the oil supply mechanism, the testing damping valve with orifices and/or gaps and several sensors was proposed, the experimental module has avoided the bulky method of using a full hydraulic system for oil supply and can be wholly placed into a high/low temperature chamber to undertake experiments; Based on the integrated experimental module, a test rig employing a variable-frequency-motor-driven ball screw driver to excite the testing module was developed. By using the virtual instrument technology, the hardware and software of automatic measurement and control system was further developed, so the automatic control and data collection of the test rig was realized. Final results show that the test rig can conveniently perform fluid mechanics experiments for various hydraulic orifices and/or gaps under high or low temperature conditions with high efficiency, so the test rig can be a very good platform for pertinent basic research works.
An experimental study on the discharge coefficient of a sharped-edged hydraulic orifice
Authors: Wang Wenlin , Cao Xiaochang , Kong Xin , Wu Yongming
Published: August 2020

Aiming at performing basic research on fluid mechanics of hydraulic orifices under high or low temperature conditions, in this study, a novel compact experimental module, which integrates the oil, the oil supply mechanism, the test valve with orifice and several sensors, was firstly developed, the experimental module can be wholly placed into a high/low temperature chamber to undertake experiments; Based on the integrated experimental module, an automatic measurement test rig was further developed. By using the test rig, experiments on flow characteristics of a sharp-edged hydraulic orifice, which uses the anti-wear hydraulic oil HM46 as the working fluid, were conducted in a temperature range of -10°C∼+80°C, the Flow-Pressure Characteristics and Discharge Coefficient of the hydraulic orifice were obtained by curve fitting, the effects of different temperatures on the Discharge Coefficient and damping force were finally investigated. The results show that in the temperature range up to room temperature of 20°C, the Flow-Pressure characteristics, the Discharge Coefficient and damping force of the sharp-edged orifice are not sensitive to temperature changes, but when the temperature is below room temperatures, the discharge coefficient drops linearly, and the damping force increases with the decreasing of temperatures.
Study on the characteristics of metal magnetic memory signal of X70 pipeline steel
Authors: Zhang Xiyong , Chen Yun , Chen Yonghong
Published: August 2020

In view of the zero crossing phenomenon of the normal component of the magnetic memory signal on the surface of the ferromagnetic component in the crack or stress concentration, many scholars have disputes about it. In this paper, through the simulation of the crack by wire cutting, the normal component of the magnetic leakage signal on the surface of the pipeline component is stretched on the tensile testing machine, and the normal component of the magnetic memory signal on the surface of the pipeline component is analyzed. It is found that the zero crossing phenomenon does exist in the normal component of the crack, but the zero crossing occurs with the pulling when the load increases to a certain extent, it will not drift after passing the zero point. The results show that the normal component cannot be used to judge the crack or stress concentration simply.
Simulation Analysis of Installation Process of Long stern Shaft of Large Ship
Authors: Zhou J H , Shi H
Published: August 2020

Due to the large journal and long length, the installation of the stern shaft on the large ship is very difficult. In view of this situation, the numerical method based on three bending moments is used to analyze the number and arrangement position of temporary support during the installation of the stern shaft, to solve the change of the deflection and stress of the stern shaft and the reaction force of temporary support, and to obtain the influence law of the number and arrangement position of temporary support on the deflection and stress of the stern shaft. The calculation results show that when the stern shaft is pushed into the rear end face of the fore stern bearing, the deflection of the front end of the stern shaft is too large to pass the fore stern shaft tube bearing smoothly, so that a new technology of the guide shaft fixing at the front of the stern shaft was adopted, the structure, size and hoisting mode of the guide shaft were optimized, and the smooth installation of the long stern shaft was realized. The research results can provide a theoretical reference for the installation analysis and calculation of stern shaft section of large ships.

Chinese library classification no. : U662.2
DEKA VII Multipoint Fuel Injector Application Study
Authors: Li Fu , Suli Feng , Weidong Xiang
Published: August 2020

Injectors must be capable of metering and delivering the fuel in the form of an optimized spray into the engine. That is to meet increasing requirements of emission related legislations and better engine running conditions. Every engine has unique requirements, technical background, parameters, etc. In order to determine the optimized injector characteristics, communications and joint efforts are necessary between the customer system engineering and the DEKA VII injector application. The study will provide general technical guidance.
A Thermal Conductivity Predictive Method of Graphene Epoxy Nanocomposites
Authors: Wang Danyong , Zhang Haiyun , Wei Huazhen , Li Shuhu
Published: August 2020

Interfacial interaction between flaked graphene and epoxy was the key element of effecting whether graphene as nanofillers could improve some of the properties of epoxy. Based on really materials and applied manufacturing process, a new kind of a thermal conductivity predictive method for graphene epoxy nanocomposites which could compute and analyze thermal conductivity of any content ratio of graphene in the epoxy with only one content ratio was built in order to provide theoretical foundations for design and property of graphene epoxy nanocomposites. According to practically different materials system and corresponding manufacturing processes, few experiments which only needed thermal conductivity of one random content-ratio graphene epoxy nanocomposites were made to predict effective thermal conductivity of any other content ratio of graphene epoxy nanocomposites under the same manufacturing processes by obtaining experimental constants based on numerical progressive iterative approximation method and compute the above experimental constants as basic materials parameters so as to build the whole analysis model in the next step. An excellent agreement was found between data obtained from this study and the experiment.
Effect of cold rolling process on microstructure and properties of T1 Copper sheet
Authors: Sun Shuo , Li Ting-qu
Published: August 2020

The 8mm thick T1 state copper plate was cold rolled into 3mm, 2mm and 1mm thin plate sections, and its microstructure and texture were analyzed by optical metallographic microscope and X-ray diffraction (XRD). The mechanical properties were tested by cupping machine and micro-hardness tester. The results show that with the increase of cold rolling deformation, the grain size decreases and a strong (220) diffraction surface texture appears. The highest tensile strength is 421.76MPa, and the microhardness is 129.9HV, all of which are greatly improved, but the elongation decreases from 40% to 5%, and the fracture morphology changes from ductile fracture to quasi cleavage fracture.
A Study on the Microstructure Strengthening Phase of the TC4 strengthened Layer by powder-mixed near-dry EDM
Authors: Junling Zhao , Lanrong Cai , Min Li
Published: August 2020

The surface of TC4 titanium alloy was strengthened by powder-mixed near-dry EDM. In the research, the experimental investigation analyzed the influence of pulse on time and electrode polarity on strengthened layer microstructure of TC4 titanium alloy. The wear of the substrate surface and the strengthened layer was measured. The results showed that the number of corrosion pits and petal-like tissues of the strengthening layer increases first and then decreases with the increase of pulse on time. The more petals and pit tissues were obtained by negative electrode than positive electrode. When the pulse on time is 100μs and the electrode polarity is negative, it is beneficial to produce the petal-like and pit-like tissues. The petal-like strengthening phase is the key factor affecting the wear resistance of the strengthened layer. The experimental revealed that the wear resistance of the strengthened layer is about 3.5 times as much as that of the substrate.
The effect of laser surface treatment on the adhesive bonding performance of aluminum alloy
Authors: Wang W , Xu J W , Chen X , Liang Y J , Zhu L Z
Published: August 2020

For the purpose of convenient treatment before gluing and improving the adhesive bonding performance, we compared the tensile shear strengths of epoxy adhesive bonding to 2A12 aluminum with preferred pre-treatments. Taking advantages on both convenience and pre-treatment quality, we investigated the influences of duration of laser treatment on the adhesive bonding strength to obtain the optimized extents of laser treatment. With the analysis of scanning electron microscopy, laser confocal scanning microscopy and contact angle measurements adopted to characterize the surface morphology, roughness and wettability, respectively, we discussed the effects of pre-treatments on the surface status and adhesive bonding. As a result, we proposed a pre-treatment with laser treatment on aluminum to improve adhesive bonding performance, by which the removal of oxide layer, surface roughening and cleaning were easily accomplished before gluing.
Effect of polypropylene fiber content on compressive and flexural performance of recycled concrete
Authors: Hongbing Zhu , Bei Han , Na Zhang
Published: August 2020

Recycled concrete was a kind of green, environmental protection and energy-saving building material, and its mechanical properties can be improved by adding polypropylene fiber. Taking the polypropylene fiber content as a parameter, experiment of cube compressive strength and bending strength on polypropylene fiber recycled aggregate concrete (PFRAC) and natural aggregate concrete were done, among which the PFRAC has 50% replacement rate of recycled aggregate. Through the comparison of strength and fracture mode of specimens, the influence of polypropylene fiber content on the pressure resistance and fracture resistance of recycled concrete were studied, and the recycled concrete’s appropriate amount of polypropylene fiber which strength can reach to natural aggregate concrete were obtained. The results were as follows: the compressive strength and bending strength of recycled concrete with polypropylene fiber were obviously intensified and the strength continuously intensifies along with the adding of fiber content. The compressive strength and bending strength of PFARC exceed that of natural aggregate concrete when fiber content was up to 1.0kg/m3. The recycled concrete with polypropylene fiber can still maintain the property of crack without breaking after damage, and the britttle fracture morphology wouldn’t occur in it.
Electrochemical Synthesis of Al-Sm Metal by Coreduction of Sm(III) and Al(III) in a K3A1F6 Melt
Authors: Zhang Zhen , Zhang Xiao-Lian
Published: August 2020

The electrochemical behaviors of Sm(III) in the molten K3A1F6 system were investigated with a tungsten electrode at 1024 K. By electrochemical tests, including cyclic voltammetry and square wave voltammetry, Sm(III) was reduced to Sm(0) in two steps. The diffusion coefficient of Sm(III) was 1.90*10−5 cm2/s when examined by using cyclic voltammetry in the molten salts. The electrochemical signal of the Al-Sm intermetallic compound was detected at -1.71 V and -2.22 V. AlSm2 and Al3Sm were obtained by potentiostatic electrolysis at -2.3 V for 10 h. These intermetallic compounds were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy with energy.
Preparation and characterization of Salix Psammophila cellulose and Mic-cellulose under the pretreatment of two kinds of acid
Authors: Yuan ZHONG , Ke-bing WANG , Yu-ling LIU , Xue WANG
Published: August 2020

The pretreatment of salix psammophila (SP) with HNO3-ethanol and HC1-ethanol, followed by the treatment with sodium chlorite and KOH, were investigated to obtain SP cellulose. Microcrystalline cellulose was prepared by hydrochloric acid hydrolysis from cellulose treated with nitric acid. The cellulose was characterized by FTIR, XRD, TG, SEM and DSC. The yield of cellulose pretreated with nitric acid and hydrochloric acid were 38.89% and 35.14%, respectively. Infrared spectroscopy showed that lignin and hemicellulose were separated from the extracted cellulose. The SEM photos showed that the width of the extracted cellulose was 5.71 μm and 6.92 μm respectively. XRD analysis showed that the crystallinity of the two groups was 54.13% and 60.86%, respectively. TG analysis showed that the amount of residue showed an increasing trend, and the residual amount extracted from cellulose was 6.67% and 7.90% respectively. In the SEM image of microcrystalline cellulose, a slender structure with a crystallinity of 59.32% was proposed, which had better thermal stability than cellulose.
The characterization and application of chip topside bonding materials for power modules packaging: a review
Authors: Liu Keming , Yang Jinlong , Luo Jian , Wang Li , Huang Quanquan , Chen Fei
Published: August 2020

Bonding material is one weak point in power modules packaging, and can limit the lifetime of power modules. Multiple bonding materials have been manufactured and applied in the power modules such as aluminum wire, copper wire, aluminum ribbon, copper ribbon, Al-clad-Cu wire, direct-bonding-lead. For bonded power modules packging, bonding ability, electrical and thermal conductivity, current carrying capacity, working reliability are the main applying properties of bonding materials. This paper demonstrates the characterization, failure mode & failure mechanism, life-time calculation model of the normal used bonding materials and estimates the developing tendency.
Preparation and properties of polystyrene composites modified by macromolecular antioxidant
Authors: Chen Qi , Xie Zhiwei , Xu Xu , Xu Wei , Huang Yufan , Zhang Yingqiang
Published: August 2020

A macromolecular antioxidant was prepared by copolymerization with styrene and modified A1010-co-PS. Its chemical structure was confirmed by Fourier transform infrared (FTIR). It was added into the formula of PS composite material and the thermal and oxygen aging experiment was carried out on the material. The tensile strength is stable at about 27MPa, the bending strength is stable at about 33MPa, and the impact strength is stable at about 2.3kJ/m2. The results show that it has a more significant effect than antioxidant 1010 and has higher performance stability.
Research Progress of the Preparation and Properties Graphene Cement Composite
Authors: Huang Z L , Qin X T , Mao Z X , Lan H , Tong W H , Zhu S Y
Published: August 2020

Graphehe has extremely great mechanical, electrical and thermal properties that make them ideal reinforcing materials in cement by mixing them homogenously. In this paper, firstly, the dispersion methods of graphene, including physical stirring, surfactant treating and ultrasonication, are presented to obtain stable dispersed surfactant aqueous solution. Then, the mechanical properties of graphene cement composite are studied, such as Young’s modulus, shear modulus, compressive strength, flexural strength and toughness. Moreover, the piezoresistivity of graphene cement composite is researched in comparison with plain cement. At last, the durabilities, especially the resistance to chloride ion permeability, freezing-thawing and carbonization, are summarized and compared.
Smooth and slipless walking mechanism inspired by the open–close cycle of a beetle claw
Authors: Shima Daiki , Gan Jia Hui , Umezu Shinjiro , Sato Hirotaka
Published: August 2020

This study investigated the function of the beetle’s claw for its smooth and slipless walking and designed an artificial claw open–close cycle mechanism to mimic the beetle’s walking. First, the effects of claw opening and closing on beetles’ ability to attach to surfaces were examined. A beetle does not have an attachment pad, and only its claws work to grip the ground; its claw opens and closes and attaches with two sharp hooks. With their claws, beetles can smoothly walk, neither slipping on nor having their claws stuck in the surface. How do they perform smooth walking with sharp claws? In this study, we observed that beetles close their claws when they raise and swung their legs forward, while they open their claws when they lowered their legs to the ground. We then conducted non-destructive tests: their claws were forced open or closed. There was a significant difference in the trajectories of forced-closed claws compared to intact claws and forced-open claws. When their claws were forced-closed, this caused slippage in walking. On the other hand, when a claw was forced-open and its rotation was also inhibited, the claw stuck heavily in the surface, and the beetle could not walk. Based on these findings, we designed an artificial claw to open and close in the same cyclic manner as in the case of natural beetles. The performance of the artificial claw was consistent with the conclusions drawn from natural beetles: the locomotive robot with the artificial claw smoothly moved without slippage. Through these observations, non-destructive tests and performance of the bio-inspired artificial claws, this study confirmed the function of the open–close cycle of beetle claws and demonstrated and successfully adopted it for a locomotive robot.
Extreme event impacts on CO2 fluxes across a range of high latitude, shrub-dominated ecosystems
Authors: Treharne Rachael , Bjerke Jarle W , Tømmervik Hans , Phoenix Gareth K
Published: August 2020

The Arctic is experiencing an increased frequency of extreme events which can cause landscape-scale vegetation damage. Extreme event-driven damage is an important driver of the decline in vegetation productivity (termed ‘Arctic browning’) which has become an increasingly important component of pan-Arctic vegetation change in recent years. A limited number of studies have demonstrated that event-driven damage can have major impacts on ecosystem CO2 balance, reducing ecosystem carbon sink strength. However, although there are many different extreme events that cause Arctic browning and different ecosystem types that are affected, there is no understanding of how impacts on CO2 fluxes might vary between these, or of whether commonalities in response exist that would simplify incorporation of extreme event-driven Arctic browning into models.

To address this, the impacts of different extreme events (frost-drought, extreme winter warming, ground icing and a herbivore insect outbreak) on growing season CO2 fluxes of Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and ecosystem respiration (Reco) were assessed at five sites from the boreal to High Arctic (64°N-79°N) in mainland Norway and Svalbard. Event-driven browning had consistent, major impacts across contrasting sites and event drivers, causing site-level reductions of up to 81% of NEE, 51% of GPP and 37% of Reco. Furthermore, at sites where plot-level NDVI (greenness) data were obtained, strong linear relationships between NDVI and NEE were identified, indicating clear potential for impacts of browning on CO2 balance to be consistently, predictably related to loss of greenness across contrasting types of events and heathland ecosystems.

This represents the first attempt to compare the consequences of browning driven by different extreme events on ecosystem CO2 balance, and provides an important step towards a better understanding of how ecosystem CO2 balance will respond to continuing climate change at high latitudes.
High-efficiency photoelectrochemical cathodic protection performance of the iron-nitrogen-sulfur-doped TiO2 nanotube as new efficient photoanodes
Authors: Momeni Mohamad Mohsen , Taghinejad Mohammad , Ghayeb Yousef , Bagheri Robabeh , Song Zhenlun
Published: August 2020

Novel iron-nitrogen-sulfur-tridoped titanium dioxide nanotubes (Fe-N-S-TiO2 NTs) have been synthesized via single step anodization of titanium using potassium ferricyanide, as a suitable additive, in dimethyl sulfoxide (DMSO) electrolyte and applied as photoanodes in the photocathodic protection of stainless steel 403 (SS403). Photocurrent density, open circuit potential and Tafel polarization curves have been used to study the photocathodic protection effect of the samples prepared. Upon the addition of potassium ferricyanide to the anodizing electrolyte and titanium dioxide nanotube doping, the light absorption of the Fe-N-S-TiO2 NTs were increased to the visible region, comparable with pure TiO2 NTs, according to the results obtained. Enhanced photoelectro-response activity and photocathodic protection performance for 403 stainless steel are exhibited by Fe-N-S-TiO2 NTs under light illumination. In addition, the optimal sample electrode (FT4) potentials shifted negatively to −683 mV under illumination.
Effects of ageing on low-cycle fatigue (LCF) properties of AZ80 magnesium alloy wheel hub
Authors: Wang Jun , Yang Fulai , Ma Jin , zhang Tingyan , Cao Hui , Che Xin , Geng Liye , Zhang Zhimin , Wang Qiang , Yang Yongbiao
Published: August 2020

A hollow billet Expanding-Reducing Extrusion (ERE) wheel hub forming process was carried out with AZ80 magnesium alloy. The effects of ageing on Low-cycle fatigue (LCF) properties were investigated, and the microstructure was characterized with scanning electronic microscopy (SEM). The LCF testing results exhibited that the stress amplitude increased with increasing ageing time, while the plastic strain decreased with increasing ageing time. Cyclic softening followed by hardening was observed for 0 h and 16 h aged samples; however, there was no obvious cyclic softening or hardening for 36 h aged sample. The tension-compression asymmetry were not obvious due to the low strain, precipitation and the non typical basal texture. Fracture observations indicated that the fatigue cracks were initiated on the surface, and the crack propagation area decreased with increasing ageing time. Thus, it can be concluded that ageing has strong effects on the fatigue life for the studied magnesium alloy.
Fabrication of amorphous Al2O3 optical film with various refractive index and low surface roughness
Authors: Lan Yunping , Zou Yonggang , Ma Xiaohui , Xu Li , Shi Linlin , Zhang Jiabin
Published: August 2020

Alumina(Al2O3) thin film has been widely used in many applications due to its excellent properties, especially in optical films and semiconductor industries. Refractive index, amorphous property and surface roughness are essential parameters related to its applications. In this study, the fabrication method of preparing various refractive index Al2O3 optical films was proposed. The Al2O3 optical films were deposited at room temperature by electron beam evaporation(EBE) technique. The effects of deposition rate and post-annealed temperature on refractive index, vibration peak of molecular and atom, amorphous property and surface roughness were investigated. Refractive index ranging from 1.519 to 1.627 was realized by EBE method at different deposition rates and different post-annealed temperatures. The variable refractive index was very important in adjusting half-width of reflector band. Meanwhile, analysis showed that the suitable post-annealed temperature could not exceed 400 °C. In short, this work provided an effective approach to fabricate amorphous Al2O3 optical film, which was pretty important in its applications in UV antireflection films and blue light reflection films.
A numerical toolkit for multiprojective varieties
Authors: Hauenstein Jonathan , Leykin Anton , Rodriguez Jose , Sottile Frank
Published: August 2020

A numerical description of an algebraic subvariety of projective space is given by a general linear section, called a witness set. For a subvariety of a product of projective spaces (a multiprojective variety), the corresponding numerical description is given by a witness collection, whose structure is more involved. We build on recent work to develop a toolkit for the numerical manipulation of multiprojective varieties that operates on witness collections and to use this toolkit in an algorithm for numerical irreducible decomposition of multiprojective varieties. The toolkit and decomposition algorithm are illustrated throughout in a series of examples.
On groups having a 𝑝-constant character
Authors: Dolfi Silvio , Pacifici Emanuele , Sanus Lucía
Published: August 2020

Let

G
G

be a finite group, and

p
p

a prime number; a character of

G
G

is called

p
p

-constant if it takes a constant value on all the elements of

G
G

whose order is divisible by

p
p

. This is a generalization of the very important concept of characters of

p
p

-defect zero. In this paper, we characterize the finite

p
p

-solvable groups having a faithful irreducible character that is

p
p

-constant and not of

p
p

-defect zero, and we will show that a non-

p
p

-solvable group with this property is an almost-simple group.
On Lusztig’s asymptotic Hecke algebra for 𝑆𝐿₂
Authors: Dawydiak Stefan
Published: August 2020

Let

G
G

be a split connected reductive algebraic group, let

H
H

be the corresponding affine Hecke algebra, and let

J
J

be the corresponding asymptotic Hecke algebra in the sense of Lusztig. When

G
=

S
L

2

G=\mathrm {SL}_2

, and the parameter

q
q

is specialized to a prime power, Braverman and Kazhdan showed recently that for generic values of

q
q

,

H
H

has codimension two as a subalgebra of

J
J

, and described a basis for the quotient in spectral terms. In this note we write these functions explicitly in terms of the basis

{

t
w

}

\{t_w\}

of

J
J

, and further invert the canonical isomorphism between the completions of

H
H

and

J
J

, obtaining explicit formulas for each basis element

t
w

t_w

in terms of the basis

{

T
w

}

\{T_w\}

of

H
H

. We conjecture some properties of this expansion for more general groups. We conclude by using our formulas to prove that

J
J

acts on the Schwartz space of the basic affine space of

S
L

2

\mathrm {SL}_2

, and produce some formulas for this action.
Short retractions of CAT(1) spaces
Authors: Lytchak Alexander , Petrunin Anton
Published: August 2020

We construct short retractions of a CAT(1) space to its small convex subsets. This construction provides an alternative geometric description of an analytic tool introduced by Wilfrid Kendall.

Our construction uses a tractrix flow which can be defined as a gradient flow for a family of functions of certain type. In an appendix we prove a general existence result for gradient flows of time-dependent locally Lipschitz semiconcave functions, which is of independent interest.
Cohomological dimension of ideals defining Veronese subrings
Authors: Pandey Vaibhav
Published: August 2020

Given a standard graded polynomial ring over a commutative Noetherian ring

A
A

, we prove that the cohomological dimension and the height of the ideals defining any of its Veronese subrings are equal. This result is due to Ogus when

A
A

is a field of characteristic zero, and follows from a result of Peskine and Szpiro when

A
A

is a field of positive characteristic; our result applies, for example, when

A
A

is the ring of integers.
Primary decomposition of knot concordance and von Neumann rho-invariants
Authors: Kim Min Hoon , Kim Se-Goo , Kim Taehee
Published: August 2020

We address the primary decomposition of the knot concordance group in terms of the solvable filtration and higher order von Neumann

ρ
\rho

-invariants by Cochran, Orr, and Teichner. We show that for a non-negative integer

n
n

, if the connected sum of two

n
n

-solvable knots with coprime Alexander polynomials is slice, then each of the knots has vanishing von Neumann

ρ
\rho

-invariants of order

n
n

. This gives positive evidence for the conjecture that nonslice knots with coprime Alexander polynomials are not concordant. As an application, we show that if

K
K

is one of Cochran–Orr–Teichner’s knots which are the first examples of nonslice knots with vanishing Casson–Gordon invariants, then

K
K

is not concordant to any knot with Alexander polynomial coprime to that of

K
K

.
Hyperbolic metrics on open subsets of Ptolemaic spaces with sharp parameter bounds
Authors: Katz Neil
Published: August 2020

It is shown that a construction of Z. Zhang and Y. Xiao on open subsets of Ptolemaic spaces yields, when the subset has boundary containing at least two points, metrics that are Gromov hyperbolic with parameter

log
⁡
2

\log 2

and strongly hyperbolic with parameter

1
1

with no further conditions on the open set. A class of examples is constructed on Hadamard manifolds showing that these estimates of the parameters are sharp.
Optimal estimates for far field asymptotics of solutions to the quasi-geostrophic equation
Authors: Yamamoto Masakazu , Sugiyama Yuusuke
Published: August 2020

The initial value problem for the two dimensional dissipative quasi-geostrophic equation of the critical and the supercritical cases is considered. Anomalous diffusion on this equation provides slow decay of solutions as the spatial parameter tends to infinity. In this paper, uniform estimates for far field asymptotics of solutions are given.
Zeros of Dirichlet polynomials
Authors: Roy Arindam , Vatwani Akshaa
Published: August 2020

We consider a certain class of multiplicative functions

f
:

N

→

C

f: \mathbb N \rightarrow \mathbb C

and study the distribution of zeros of Dirichlet polynomials

F
N

(
s
)
=

∑

n
≤
N

f
(
n
)

n

−
s

F_N(s)= \sum _{n\le N} f(n)n^{-s}

corresponding to these functions. We prove that the known nontrivial zero-free half-plane for Dirichlet polynomials associated to this class of multiplicative functions is optimal. We also introduce a characterization of elements in this class based on a new parameter depending on the Dirichlet series

F
(
s
)
=

∑

n
=
1

∞

f
(
n
)

n

−
s

F(s) = \sum _{n=1}^\infty f(n) n^{-s}

. In this context, we obtain nontrivial regions in which the associated Dirichlet polynomials do have zeros.
On quadratic forms in multivariate generalized hyperbolic random vectors
Authors: Broda Simon A , Zambrano Juan Arismendi
Published: August 2020

This article presents exact and approximate expressions for tail probabilities and partial moments of quadratic forms in multivariate generalized hyperbolic random vectors. The derivations involve a generalization of the classic inversion formula for distribution functions (Gil-Pelaez, 1951). Two numerical applications are considered: the distribution of the two-stage least squares estimator and the expected shortfall of a quadratic portfolio.
Easing diagnosis and pushing the detection limits of SARS-CoV-2
Authors: Kiran Uday , Gokulan C G , Kuncha Santosh Kumar , Vedagiri Dhiviya , Chander Bingi Thrilok , Sekhar Aedula Vinaya , Dontamala Suchitra , Reddy Arakatla Lohith , Tallapaka Karthik Bharadwaj , Mishra Rakesh K , Harshan Krishnan Harinivas
Published: August 2020

Rigorous testing is the way forward to fight the coronavirus disease 2019 pandemic. Here we show that the currently used and most reliable reverse transcription-polymerase chain reaction-based severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) procedure can be further simplified to make it faster, safer, and economical by eliminating the RNA isolation step. The modified method is not only fast and convenient but also at par with the traditional method in terms of accuracy, and therefore can be used for mass screening. Our method takes about half the time and is cheaper by ∼40% compared to the currently used method. We also provide a variant of the new method that increases the efficiency of detection by ∼30% compared to the existing procedure. Taken together, we demonstrate a more effective and reliable method of SARS-CoV-2 detection.