bluuebunny/crossref_metadata_2025 huggingface dataset:
A Pipeline-based Low Complexity Dual Thresholds and Multiresolution Mouth Detection Method
Authors: Lin Jingli , Li Changwei , Lan Xi , Li Jinge
Published: March 2022

Mouth detection is a basic step in the automatic diagnosis of buccal diseases. This paper proposes a method of using FPGA(Field Prog ram mable Gate Array) to detect the human mouth region in images, which adopts a pipelined design for high-speed operating. Thus, it can be applied to mouth motion detection as well. After an original image is processed regularly by median filtering, color conversion is performed to obtain its corresponding H component, which is used to create a partitioned binary image. Each constituent region of the binary image uses two thresholds for regional processing separately, which results in two binary images: one comprises the mouth and some other regions with a color close to that of the mouth, and the other indicates the position of the mouth. A logical AND is performed on these two binary images to calculate the border of mouth region with reduced resolution, which is then superimposed on the buffered original image to confirm the mouth region eventually. An FPGA-based scheme is presented, which shows the method could detect the whole mouth properly, with a maximum clock speed of 150MHz. In addition, processing an image of 200*200 only consumes 2178 Slice LUTs(Look Up Table), which is a relatively low resource consumption.
Research on Network Routing Control Algorithm Based on OpenFlow and IGP
Authors: Tian Xuejun , Wen Lizi , Yang Xingyan , Chen Liangzhe , Min Gang , Shu Zhong
Published: March 2022

Given the coexistence of heterogeneous hybrid networks such as IP network, 4G network and Software Defined Network (SDN) in the application of digital news media system, this paper designs a routing control algorithm based on SDN network architecture, which can realize the compatibility of internal gateway protocol and OpenFlow communication strategies. Through the analysis of OpenFlow communication protocol in SDN network architecture, the relationship between Interior Gateway Protocol (IGP) and OpenFlow routing rules is found out. Based on the existing hardware structure of the OpenFlow router, the configuration parameters of a port table, port address table and routing table are improved, and the adjacent routing relation table and information transmission port are used to realize the connection between routers are designed. The attention of users is considered It can reduce the burden of system operation and is compatible with the forwarding control of route forwarding and routing filtering. The adjacent routing relation table is designed to control the process of data collection, storage and forwarding, and the input and output ports between adjacent routers are defined. The open router designed in this paper integrates Simple Network Management Protocol (SNMP) agent and SDN agent mechanism organically to achieve the goal of SDN network management; the routing control module focuses on the management of key data flow, realizes the control of routing state and data flow at the same time, and provides the visualization function of routing state and routing state data flow. By constructing the experimental platform of routing transmission and control functions based on routing control and interior gateway protocol, the effect of routing state control of the two methods is compared and analysed from three aspects of packet transmission state, packet processing state and packet receiving delay in routing control process. The experimental results verify the correctness of the design results.
The Echo Model and Simulation Method of Impulse Radar Fuze Based on Attribute Scattering Center Model
Authors: Kong Ming , Li Yuzhao , Chen Jichi , Wang Xu , Wei Guohua
Published: March 2022

This article focuses on solving the problem of performance evaluation and algorithm verification of ultra-bandwidth impulse radar fuze. A modeling and simulation method for the scattering echo of an impulse radar target is proposed. We distinguish the scattering center of the extended target and construct its echo based on the attribute scattering center model. Besides, the position variation characteristics of the scattering center, and the azimuth dependence of the scattering amplitude are fully considered. At the same time, the motion information of the target is modulated to obtain the target scattering echo of the impulse radar. We generate the scattering echo of the typical streamlined moving target at different observation angles by calculation. The changes of the echo position and amplitude of each scattering center are consistent with the scattering echo model. We use the generated echo data to image, and the imaging results are basically consistent with the shape of the target, which verifies the effectiveness of the proposed method.
A Blockchain-based Security Framework for Secure and Resilient Smart Grid
Authors: Luo Bin , Xu Guibin , Xie Jinglong , Wang Yufei
Published: March 2022

Smart grid integrates the information and communication technologies with the physical grid. It can not only improve security and efficiency of traditional power grids, but also has advantages in promoting environmental protection and sustainable development. However, the existing smart grid systems suffer some security concerns such as privacy leakage and data tampering. In order to address these security issues, we propose a security framework for smart grid using Blockchain. It protects data privacy through cryptographic tools, and it applies Blockchain technologies to prevent data tampering. Compared with the existing smart grid systems, our proposed system enjoys better security and resilience.
Model of Information System for Application of Blockchain Technologies
Authors: Ishchukova Evgeniya , Romanenko Kirill , Salmanov Vyacheslav
Published: March 2022

This article describes the current security problems of blockchain networks, identifying the least explored area. The concept of an information system for investigating blockchain incidents is presented. An example of stealing bitcoins from a cryptocurrency wallet was taken as input. This example contains a fairly large number of blocks and transactions, and everything needs to be studied. An overview of the existing vulnerabilities in the Ethereum blockchain platform is presented. A brief description of the basic principles of operation of two largest cryptocurrency platforms - Bitcoin and Ether - is given. Examples of possible incidents that are widespread among users of blockchain systems are considered. The architecture of the designed solutions is described. The first experimental results obtained on the basis of the implementation of the designed algorithms are presented. It is concluded that iterating over a large number of transactions takes a lot of time; in the future, it is planned to apply machine learning methods to analyze such a large data array.
A Hand Gesture Recognition Algorithm Based on Multi-scale Hybrid Features
Authors: Tu Pu , Huang Chen , Zhu Jinxia
Published: March 2022

A human hand gesture recognition algorithm based on multi-scale hybrid features is pro-posed. A large number of gesture data images are organized and annotated by automatic im-age annotation algorithm. Based on dense sampling, the multi-scale Gaussian pyramid is taken into account for enhancing the image details; it can realize the recognition of both large and small target gestures. Meanwhile, according to the aggregation and distribution of gestures, statistical analysis is used to optimize the size and aspect ratio of anchors, which can further improve the accuracy of recognition. The experiment results show that the mean average precisions of this algorithm can be improved to 99.7% and 93.3% for the simple gesture and complex gesture, respectively, which are higher than that obtained by these traditional methods, such as faster region-convolution neural network (Faster R-CNN), You Only Look Once (YOLO), and SSD.
Permanent Magnet Synchronous Motor Control Method Based on Fuzzy PI and Sliding Mode Observer
Authors: Sha Linlin , Song Yi , Li Zijin
Published: March 2022

In order to solve the many shortcomings of the current servo system using mechanical position sensors, this article combines the traditional fuzzy PI control and sliding mode observer, and proposes a control method of PMSM based on fuzzy PI and sliding mode observer. Simulink is used for simulation analysis, and the results are compared. It can be seen from the simulation results that the designed control method can efficiently control the permanent magnet synchronous speed control system, so that the system has excellent starting characteristics and dynamic stability.
Permanent Magnet Synchronous Motor Control Based on New Sliding Mode Observer
Authors: Song Yi , Song Zehang , Yao Xiaodong
Published: March 2022

Aiming at the problems of large chattering and slow response time existing in the preexisting sliding mode observer permanent magnet synchronous motor control, this paper proposes a new sliding mode observer control way. The model of the permanent magnet synchronous motor was established, and design a new function to take the place of the preexisting transforming function. And use Lyapunov stability criterion to analyse the system stability. At the same time, Use Matlab/Simulink simulation software to carry out simulation experiments, build simulation experiment models, and obtain the control result waveforms of the integrated sliding mode observer control system and the newly designed sliding mode observer control system. Compared to pre-existing sliding mode observers, it can be known that, constrasted with the pre-existing sliding film observer, better performance and stronger stability are possessed by the new sliding mode observer proposed in this artical.
Statistical Method of Low Efficiency Wind Turbine Generating Wind Power Curve Based on Operating Data
Authors: Chen Zhannan , Wang Jiechang , Guo Jianfei , Dong Yan , Yu Jinglong , Zhou Runan , Xiao Huanxiu
Published: March 2022

Aiming at the low efficiency of wind turbines in service, this paper proposes a statistical method of low efficiency turbines based on wind power curve generated from operating data. According to the data distribution characteristics of the wind-power data scatter diagram, a data preprocessing model was established based on the quartile method and quadratic clustering method, which can effectively mark the data of shutdown, invalidity, undergeneration, overgeneration and power limit, and draw the wind power curve which can accurately represent the fan’s performance. On this basis, a mining method for low efficiency units based on the difference rate of lost electric quantity and power consistency coefficient is established, which can make statistics of high loss electric quantity units, units deviating from the designed power curve and units with degraded performance regularly, and evaluate the generation improvement before and after maintenance. Through the actual operation and maintenance data of all 814 wind turbines of a certain company, the effectiveness of the method is verified.
Electromechanical Actuator Design and Control Strategy for UAV Landing Gear
Authors: Yang Tao , Wu Jiufeng , Cao Xinlei
Published: March 2022

UAV is becoming more and more prevalent not only in the military field but also in the civilian field, whose flight safety and performance is of top concern. The landing gear system is undoubtedly a determining factor in UAV taking off and landing. In recent days, the all-electric trend in UAV design is not irreversible. As a result, the hydraulic actuator is replaced by EMA in the landing system. The electromechanical actuator for UAV landing system is designed in this paper. The detailed actuator system design is introduced in the beginning. And then communication protocol between the actuator system and the flight control computer is presented, serving as the basis of control strategy, which is the main content to study. The control strategy mainly deals with normal landing and emergency landing process. At last, the conclusion part summarizes its applications. The EMA devised in this paper and its corresponding control strategy provide a new idea in the landing system design of UAV.
Experiment and Modelling of Triangular Holes Array by Non-traditional Machining Process
Authors: Wang Panpan , He Yafeng , Yang Tao , Xu Bo , Long Bing
Published: March 2022

Triangular holes array is a common structure of the specially shaped holes that can be used for various products in aerospace vehicles. These are commonly produced in the electrochemical machining (ECM) process. The high-quality and accuracy of a triangular grid are closely related to the processing parameters of cathode structure and sidewall insulation sleeve, power supply, electrolyte flow rate, feed speed, and machining gap. Simulations have been carried out to consider the influence of parameters including structure and dimension of the cathode, initial machining gap, feed speed, and current on the homogeneity of the flow field in the machining gap. Consequently, the modeling can support the design of the cathode. The paper is divided into two parts. Firstly, the tool cathode is simulated and fabricated. Secondly, the triangular holes array is produced by using the designed cathode tool. It was found that higher feed speed and lower machining gap increase the stability, accuracy, and efficiency of the machining process and the quality of the triangular holes array.
Realization of Control System of Automatic Welding Machine for Air Conditioning Flange Based on CANopen
Authors: Ren Kailang , Yan Liangwen , Huang Shan , Dong Xudong , Wei Mingsen , Chen Jiajian
Published: March 2022

The principle of automatic welding machine (AWM) for air conditioning flange is introduced. The architecture of the control system of AWM realizes the multi spindle linkage control. The communication between PLC and servo driver is built based on CANopen protocol, and the communication between PLC and touch screen is set up based on Modbus RTU protocol. To meet the welding machine spindle coordination control requirements, the PLC program is designed by Delta ISPsoft programming software, and simplified by the application of sequential function chart (SFC) and function block. The human machine interaction (HMI) is developed by Xinjie Touchwin. Linear interpolation algorithm (LIA) is used to prevent the welding defects on the air conditioning flange corner thus it improves the welding quality and realizes the straight path of welding torch from the original to starting welding point and from the end welding point to the original simultaneously. The AWM for air conditioning flange can replace the manual welding and has a broad application prospect in many areas.
Research on Thermal Analysis and Thermal Design of a Space Inertial Sensor Using Laser Measurement
Authors: Chen Haowen , Li Zongfeng , Wang Yi
Published: March 2022

In this paper, a new space inertial sensor based on laser interferometry developed by the experimental team is used for temperature simulation analysis of multi-physics coupling. Through the analysis of the noise influence of the inertial sensor, it is calculated that under the index of the acceleration noise level of 1×10−10g/Hz1/2, the temperature fluctuation of the Test Mass (TM) needs to be controlled ≯0.1 °C. The finite element analysis method is used to simulate and calculate the temperature change inside the inertial sensor within 36 hours. In the case of no heat insulation component, the temperature difference between the six surfaces of the TM is maintained within 10−5K, and the temperature of the Electrode Housing (EH) only fluctuates ±0.1K in the stable fluctuation section when the external environment fluctuates ±1K. After 36h, the temperature of the TM decreased by 0.007K compared with the initial value. With the addition of heat insulation components, the fluctuation range of internal temperature decreases, and the temperature of the EH fluctuates within the range of ±0.015K.
Research on high-temperature resistant resin matrix composites of hypersonic aircraft structure
Authors: Fu Xinwei , Wang Jiafu , Ren Yiru
Published: March 2022

The aircraft structure would be suffered high temperature during the hypersonic flight. To solve the problem of high temperature resistance of hypersonic aircraft, the mechanical properties of different structural materials at different temperatures are studied. The tensile strength and tensile modulus of structural steel, aluminum alloy, titanium alloy, resin matrix composites and polyimide composites are analyzed, and the performance of the materials at high temperature is compared. The results show that the properties of typical materials will decrease with the increase of temperature. The high-temperature mechanical properties of structural steel and aluminum alloy are poor, and the titanium alloy can withstand higher temperature. Polyimide resin composites can work at higher temperature for a long time compared with epoxy resin and bismaleimide resin composites, and it has more obvious advantages than titanium alloy at 400 °C. Polyimide resin composite has great potential to replace traditional materials as load-bearing structural material of hypersonic aircraft.
Numerical simulation of a two-dimensional S-shaped inlet
Authors: Zhan Haoran
Published: March 2022

In order to solve the problem that different operation conditions affect the performance of S-shaped inlet, we have carried out a numerical study on a two-dimensional S-shaped inlet and analysed the influences of incoming Mach number, attack of angle α and the outlet pressure on the performance parameters of the inlet, such as the total pressure recovery coefficient, total compression ratio and the steady-state total pressure distortion index at the exit of inlet. The results show that Ma number and the outlet pressure are the main factors affecting inlet performance. With the increase of Ma number, the total pressure recovery coefficient of inlet decreases from 0.975 to 0.793, the total compression ratio decreases from 1.212 to 1.146, and the steady-state total pressure distortion index increases from 0.0536 to 0.377. The flow energy loss in the inlet increases, the flow uniformity decreases, and the inlet performance becomes worse. With the increase of the outlet pressure, the total pressure recovery coefficient of inlet rises from 0.875 to 0.931, the total compression ratio rises from 1.101 to 1.216, and the steady-state total pressure distortion index decreases from 0.219 to 0.123. The mass flow rate of inlet and airflow loss decrease, and the performance of the inlet improves. We study the influence of different operation conditions on the inlet performance, which provides a certain reference for the performance evaluation of S-shaped inlet.
Research on parallel output method of DC regulated power supply
Authors: Yan Xu , Li Meng , Wang QiYue , Liu He , Zhang XiaoMing , Zhang Yue
Published: March 2022

This paper describes the output characteristics of DC regulated power supply in spacecraft ground test system and proposes a scheme of DC regulated power supply parallel output with remote sampling. Then the power-on and power-off procedure as well as the characteristics of normal operation in space vehicle using ground power supply are analyzed.The transient characteristics of parallel power supply are summarized. This method with simple circuit connection is able to meet the power supply requirements of spacecraft as well as improve the reliability and security of power supply system. Experimental verification demonstrates the effectiveness of the proposed method. It solves the problem of heavy load energy requirement of spacecraft in ground test and verification stage.
Design and Verification of an Electro Hydrostatic Brake System
Authors: Zhao Jia , Chang Kai , Ru Fen , Xie Yan , Li Wei
Published: March 2022

Electro-Hydraulic Actuation is a distributed power telex technology which integrates machine, electricity and liquid as one. A miniaturized Electro-Hydraulic Brake System is designed by introducing Electro-Hydraulic Actuation Technology into aircraft Anti-skid Brake System. It can transmit power by electricity in brake system. Firstly, the mathematical model of the Electro-Hydraulic Braking System is established. Secondly, the semi physical simulation of the hardware in the loop is completed in the real-time simulation platform to verify the anti-skid braking control function of the system, realize the parameter optimization process, and determine the important parameters, so as to provide guidance for the production of the sample. Finally, the correctness and function of the Electro-Hydraulic Brake System are verified by the test on the inertial platform. The results show that the system can achieve the expected anti-skid braking function, and can provide support for subsequent engineering.
Application of aluminum alloy in aircraft
Authors: Wu Yue
Published: March 2022

From the perspective of aircraft manufacturing industry, aluminum alloy is a material with high practicability. It has the advantages of simple process, convenient processing, good forming performance, high durability and reliability, convenient maintenance, taking into account a series of advantages such as corrosion resistance, high strength, high stiffness and low cost. Applying it to the aircraft manufacturing industry can not only effectively control the cost of aircraft manufacturing, but also give full play to the material properties, improve the service performance of various aircraft components, improve the aircraft manufacturing level, and meet the development needs of the aircraft manufacturing industry. Based on the application case of aluminum alloy in aircraft, this paper studies the application of aluminum alloy in aircraft, and then puts forward the existing problems and solutions of aluminum alloy in aircraft, in order to provide valuable reference for the development of material field and aircraft manufacturing field in China.
Research on interference fit of high-lock bolts based on finite element simulation
Authors: Feng Yu
Published: March 2022

Firstly, the finite element simulation of high-lock bolt pressing into single-layer plate is carried out based on ABAQUS,and compared with the theoretical calculation results which are derived from the elastic-plastic mechanics.It illustrates that the validity of the finite element model.Finally, the life-death unit technology of ABAQUS is used to analyze and compare the stress state of hole wall, the HST10AG6 high-lock bolt hole is wrongly installed by HST110AG6 high-lock bolt. It is considered that it is appropriate to expand the hole and install the HST10AG8 high-lock bolt.
Study on plasma combustion process in aero engine combustor
Authors: Wang Tianyu , Yu Jinlu , Zhao Bingbing , Cheng Weida , Zhang Lei , Sun Yongkun
Published: March 2022

In order to explore the effect of plasma combustion on the performance of aeroengine combustion chamber, a simplified 9-Step plasma reaction mechanism was added to the 16 component 25 step reaction mechanism of aviation kerosene, and a kerosene combustion chemical reaction process model considering the excited state relaxation reaction of plasma electron collision reaction and the chemical reaction involved in excited state was established, The numerical calculation of combustion process in combustion chamber was carried out, and the numerical calculation results of combustion process with and without plasma combustion support were compared and analyzed. The results showed that after adding plasma in the combustion chamber, the active particles produced by plasma reaction made kerosene burn more fully in the main combustion zone. Under the appropriate chemical ratio, the average temperature of the outlet section of the combustion chamber increases from 2208.5K to 2543.5K, and the combustion efficiency increases by 11% to 95.6% on the basis of 84.6%; The outlet temperature field was more uniform, and the temperature distribution coefficient (OTDF) was reduced from 0.131 to 0.111, which improved the performance of the combustion chamber.
Research on the Scheme of Variable Thrust Solid Rocket Motor
Authors: Yin Yongqi , Zhou Wei , Ma Peiyang , Ma Qingzhuang , Shi Xueqian
Published: March 2022

The solid rocket motor is extremely widely used due to its many advantages, but the solid rocket motor also has the disadvantage that the thrust cannot be changed. To solve this problem, there are generally two solutions to this problem. One is to use a mechanical pintle structure to change the effective cross-sectional area of the nozzle, and then to change the size of the thrust. The other is to change the effective cross-sectional area through the secondary jet method. These two methods all can change the size of the thrust, but they also have their drawbacks. The domestic team proposed a plan that combines the two methods to make up for each other’s shortcomings.
Numerical Simulation of Wind-induced Swing Angle of 1000kV Transmission Line Suspension Insulator Strings Considering Dynamic Response
Authors: Feng Zhihui , Li Tao , Zheng Lei , Li Jian
Published: March 2022

The wind-induced swing angle of insulator strings directly affects the electrical insulation performance and the construction cost of the UHV transmission project. However, due to not considering the fluctuating wind pressure, the calculation results of wind-induced swing tend to be conservative when adopting the recommended guidelines of standard especially in the face of severe weather. This paper simulates the transient wind field of strong winds based on time-space correlation characteristics and constructs the fluctuating wind load distribution model exerting on the UHV transmission line. Then a refined finite element model of the multi-span transmission line including the entire tensile section is established. And the swing angle of the insulator strings calculation formula is fitted based on the calculation results of the wind-induced swing response. The calculation result shows the swing angle decreases with the increase of ice thickness, and the magnified coefficient of the wind-induced swing angle at the target tower under the basic wind speed of 15m/s is 1.03.
Spatial Load Prediction of Urban Distribution Grid under the Low-carbon Concept
Authors: Zheng Zhen , Jiang Chen , Zhang Guanhua , Han Wanli , Liu Jiale
Published: March 2022

Under the goal of “dual carbon”, distribution grid is the basic platform serving the country to achieve carbon peak and carbon neutral goals, and spatial load prediction is of great significance to the planning and construction of distribution grid. To improve the accuracy of the spatial load prediction of the distribution grid, this paper proposes an algorithm based on the ELM (Extreme Learning Machine), using the parameters of the particle group optimization model. Through the simulation experiment of the searched data, the relative error of the FCM algorithm, the PSO optimization algorithm has high accuracy and meets the requirements of practical engineering.
Design and Application of Intelligent Patrol System in Substation
Authors: Zhang Shun , Zhang Yankai , Cao Shibao , Li Biao , Qi Xiangmeng , Li Shengpeng
Published: March 2022

With the continuous development and improvement of power grid technology, intelligence has become the development goal of power grid technology. By designing an intelligent substation inspection system, simplifies the operational tasks of inspectors, and makes inspection of power equipment more accurate, efficient, and traceable. In the implementation of the system, the mobile terminal is responsible for the collection, input, and upload of inspection data, and the server completes the data reception and statistics and displays it visually. And the application of the case proves that the intelligent patrol system is convenient and quick to operate, the social and economic benefits produced are significant, and it has strong practicability.
Research on Frequent Failures of Pilot Solenoid Valve of Emergency Diesel Engine in Nuclear Power Plant
Authors: Fu Jiang , Pan Weiwei , Qin Qiang , An Kang , Wang Meng
Published: March 2022

The working pressure of the start-up compressed air pilot solenoid valve is 40bar when it starts, it is an important part of the emergency diesel air start system of nuclear power plants. Since the operation of the nuclear power plant, it has been found that the start-up compressed air pilot solenoid valve has more frequent failures, the failure modes are air leaks and jams. The start-up compressed air pilot solenoid valve are all solenoid valves of the same type, the manufacturer is MABO, the model is MV320V DN20 G34 NC. Once the start-up compressed air pilot solenoid valve fails, it will affect the reliability and availability of the diesel engine’s start-up air system, directly cause the diesel engine to fail to start. Through a series of tests, the jamming and air leakage failures in the use of the start-up compressed air pilot solenoid valve are tested and analyzed. The reasons for the frequent air leakage and jamming of the starting compressed air pilot solenoid valve are determined, effective improvement plans are proposed, such as changing to another type of grease, adding the solenoid spool guide ring and return spring, improving the spool structure, increasing the diameter of the pilot valve and coil power, etc.. After analysis and demonstration, it is further clarified that the reasons for the leakage and jamming of the pilot solenoid valve are clear, the improvement plan is effective. The results show that the improved program obtained through research has laid a foundation for solving the problem of frequent leakage and jamming of the pilot solenoid valve.
Research on open source platform of digital power grid based on CEPH open source distributed storage technology
Authors: Liang Jinzhao , Chen Haomin
Published: March 2022

In order to ensure the operational quality of open source platform and improve the security of power grid information management, a research method of digital power grid open source platform based on CEPH open source distributed storage technology is proposed. The open source platform structure of digital power grid is optimized by using the operation of object to block mapping and human-computer interaction function of CEPH platform. CEPH open source distributed storage is used to optimize the information management function of digital grid open source platform and improve the effect of grid data and information sharing. An adaptive quantization strategy is designed to dynamically determine the load factor weightthe weighty of load factor of the digital grid open source platform and improve the resource storage performance of the platform. The test results show that the digital grid open source platform based on CEPH open source distributed storage technology has low memory occupancy, data processing of high efficiency and good system load balancing ability, which meets the needs of information security and data processing of the digital grid open source platform.
Three-dimensional culture and chondrogenic differentiation of mesenchymal stem cells in interconnected collagen scaffolds
Authors: Xie Yan , Sutrisno Linawati , Yoshitomi Toru , Kawazoe Naoki , Yang Yingnan , Chen Guoping
Published: March 2022

Interconnected scaffolds are useful for promoting the chondrogenic differentiation of stem cells. Collagen scaffolds with interconnected pore structures were fabricated with poly(lactic acid-co-glycolic acid) (PLGA) sponge templates. The PLGA-templated collagen scaffolds were used to culture human bone marrow-derived mesenchymal stem cells (hMSCs) to investigate their promotive effect on the chondrogenic differentiation of hMSCs. The cells adhered to the scaffolds with a homogeneous distribution and proliferated with culture time. The expression of chondrogenesis-related genes was upregulated, and abundant cartilaginous matrices were detected. After subcutaneous implantation, the PLGA-templated collagen scaffolds further enhanced the production of cartilaginous matrices and the mechanical properties of the implants. The good interconnectivity of the PLGA-templated collagen scaffolds promoted chondrogenic differentiation. In particular, the collagen scaffolds prepared with large pore-bearing PLGA sponge templates showed the highest promotive effect.
Bioinspired TiO2/chitosan/HA coatings on Ti surfaces: biomedical improvement by intermediate hierarchical films
Authors: Rahnamaee Seyed Yahya , Ahmadi Seyedkhani Shahab , Eslami Saed Aylar , Sadrnezhaad Sayed Khatiboleslam , Seza Ashkan
Published: March 2022

The most common reasons for hard-tissue implant failure are structural loosening and prosthetic infections. Hence, in this study, to overcome the first problem, different bioinspired coatings, including dual acid-etched, anodic TiO2 nanotubes array, anodic hierarchical titanium oxide (HO), micro- and nanostructured hydroxyapatite (HA) layers, and HA/chitosan (HA/CS) nanocomposite, were applied to the titanium alloy surfaces. X-ray diffraction and FTIR analysis demonstrated that the in situ HA/CS nanocomposite formed successfully. The MTT assay showed that all samples had excellent cell viability, with cell proliferation rates ranging from 120% to 150% after 10 days. The HO coating demonstrated superhydrophilicity (θ ≈ 0°) and increased the wettability of the metallic Ti surface by more than 120%. The friction coefficient of all fabricated surfaces was within the range of natural bone’s mechanical behavior. The intermediate HO layer increased the adhesion strength of the HA/CS coating by more than 60%. The HO layer caused the mechanical stability of HA/CS during the 1000 m of friction test. The microhardness of HA/CS (22.5 HV) and micro-HA (25.5 HV) coatings was comparable to that of human bone. A mechanism for improved adhesion strength of HA/CS coatings by intermediate oxide layer was proposed.
Discrete Hamilton–Jacobi theory for systems with external forces
Authors: de León Manuel , Lainz Manuel , López-Gordón Asier
Published: March 2022

This paper is devoted to discrete mechanical systems subject to external forces. We introduce a discrete version of systems with Rayleigh-type forces, obtain the equations of motion and characterize the equivalence for these systems. Additionally, we obtain a Noether’s theorem and other theorem characterizing the Lie subalgebra of symmetries of a forced discrete Lagrangian system. Moreover, we develop a Hamilton–Jacobi theory for forced discrete Hamiltonian systems. These results are useful for the construction of so-called variational integrators, which, as we illustrate with some examples, are remarkably superior to the usual numerical integrators such as the Runge–Kutta method.
Environmentally sustainable socio-economic welfare and agricultural employment: evidence from ECOWAS
Authors: Umehruo C.H. , Owolabi O.A. , Aderounmu B. , Rotimi M.O. , Osabuohien E.S.
Published: March 2022

Environmental sustainability considerations in socio-economic welfare has been argued in recent welfare literature. With an emphasis on the role of agricultural employment, this present study explores environmentally sustainable socio-economic welfare in ECOWAS, which features countries abundant in agriculture resources, although with low levels of socio-economic welfare and low carbon emissions. The study utilises a balanced panel data set of observations in respect of all fifteen ECOWAS countries over the period of 2010 to 2019. The Human Sustainable Development Index (HSDI) was used to measure environmentally sustainable socio-economic welfare. On the other hand, agricultural employment was measured using the percentage of the employed population earning their livelihoods from agricultural employment. Panel data fixed effects estimation was used to estimate the model for the study, and the findings were that agricultural employment had a significant adverse influence on environmentally sustainable socio-economic welfare as measured by HSDI, while a further comparison of the findings with that of welfare measured using HDI indicated that agricultural employment also adversely affected HDI. The study recommends that socio-economic welfare be assessed from the view point of environmental sustainability, and the governments of ECOWAS member countries provide strong governance including strong laws and policies to ensure that socio-economic welfare that is environmentally sustainable is realised as abundant agricultural resources as well as agricultural employment are well managed.
Nitrous oxide variability and predictability in the tropics using statistical analysis
Authors: Ogunsola O.E.
Published: March 2022

Among the three most powerful long-lived greenhouse gases (CO2, CH4, and N2O) present in the atmosphere and affected by human activities, N2O has the longest atmospheric lifetime than the rest and a large global warming potential. Its impact is about 300 times that of CO2 which also has a life time next to it amongst these three long-lived gases. The presence of N2O has the potential effect of raising global temperature because of its ability to trap heat. Hence, it is necessary to predict its future concentration so as to know its possible trend. The analyses of these concentrations were carried out using descriptive statistics. The moving average was used in smoothening out its fluctuations in order for the trend to become apparent and the regression analysis was utilized in fitting the appropriate equations for predicting its concentration. The mean annual concentration value of this gas for the period 1998 – 2012 at the various stations consideredwas 319.09±0.63ppb with an average range of 11.98±0.23ppb.The comparison of the actual data with the modeled data showed high correlation coefficients and the polynomial function of order 1 (linear equation) is sufficient in predicting the concentrations of this gas if the current trend should continue.
Suitability and hydrogeochemical imprints of groundwater in residential location around Abeokuta, southwestern Nigeria
Authors: Academe S.O. , Emenike P.C. , Unokiwedi P. , Nnaji C.C. , Etim M.A.
Published: March 2022

Water quality evaluations of domestic wells are required to monitor its consumption suitability since its dependence is on an increasing rate in the study region. Therefore, the rationale for the study is to obtain the hydrogeochemical characteristics of water from domestic wells and their level of potability. In the current study, the hydrogeochemical footprints of twenty water samples obtained from deep wells located in residential buildings were analyzed for TDS, Turbidity, TSS, TH, Acidity, Alka, HCO3
−, CO3
2-, DO, NO2
−, NO3
−, SiO2, PO4
3-, SO4
2-, Br−, Cl−, F−, Ca2+, Fe2+, Mg2+, K+, Na+, EC and ranked using the entropy-based water quality index (EBWQI) to determine its drinking suitability.Water classification was achieved using hydrogeochemical facies and the ion exchange was obtained using biplots of important water quality parameters. The mean concentration of the water quality parameters mentioned above were 717.69, 46.11, 157.20, 224.81, 72.91, 64.06, 78.07, 0.01, 3.89, 0.89, 51.56, 16.50, 0.73, 32.87, 0.01, 174.41, 1.89, 58.91, 0.03, 19.41, 3.05, 72.82 mg/L and 1009.63 μS/cm, respectively. Benchmarking the results with the WHO 2017 standard, 10%, 85%, 10%, 45%, 20%, and 45% of the water samples surpassed the threshold for TDS, EC, DO, NO3
−, Cl−, and F−, respectively. The groundwater classification derived from the piper plot revealed 40% mixed type, 15% Na-Ca-Cl water type, 15% Na-Ca-Mg-Cl water type, 20% Ca-Na-Cl water type, and 10% Ca-Na-Mg-Cl water type, with Na and Cl dominating the hydrogeochemical facies. The geochemical activity governing the groundwater chemistry obtained from the plot of [Ca2+ + Mg2+] vs [HCO3
− + SO4
2−] showed silicate weathering and carbonate weathering in 5% and 95% of the water samples, respectively. Furthermore, the ion exchange activity based on [Na+ + K+ – Cl−] vs [(Ca2+ + Mg2+) – (HCO3
− + SO4
2–)], CAI-1 and CAI-2 plots supports reverse ion exchange. Generally, the chemical activities support rock-water and evaporation dominance within the sample location. The EBWQI ranking showed that 10% of the water samples are excellent, 20% are good, 40% are moderate, 10% are poor, and 20% of the water samples are abysmal for consumption. Therefore, the water situation in the study region requires adequate treatment strategies to foster healthy living for residents.
Electrical resistivity application for road failure assessment at an industrial hub in Ogun State, Nigeria
Authors: Okeniyi Elizabeth Toyin , Adagunodo Theophilus Aanuoluwa , Okeniyi Joshua Olusegun
Published: March 2022

This paper employs the geophysical surveying technique of two-dimensional electrical resistivity imaging (2D ERI) for gaining insights into the causes of incessant road failures being encountered at an industrial hub, along Idiroko Road, in Ota, Ogun State, Nigeria. These utilises occupation of three traverses, each of 100 m for the 2D ERI, constituting a control of a stable road portion, and a stable and unstable portions of a crucial turning along the dual carriage highway of Idiroko Road in Ota. The obtained 2D ERI measurements were rendered to the processing of the RES2DINV software for the derivation of the 2D resistivity inverse model. Results show that the portions of the roads that are stable exhibited higher values of apparent resistivity compared to portions exhibiting frequent road failures. Ensuing sub-surface layer characterisations by the 2D ERI revealed geo-electrical layers exhibiting permeable soil formations that allow water to percolate in the stable portion of the road while the unstable portion depicted presence of water in an impermeable soil formation. These engender recommendations for road construction durability issues that can culminate into system of sustainable road network at the studied industrial hub location in Ogun State, Nigeria.
An image classification based approach for islanding detection in a sustainable distributed generation system using convolutional neural network
Authors: Adenugba F.T. , Orovwode H.E. , Ademola O.F.
Published: March 2022

In today’s power system, distributed generation (DG) penetration level has increased to match the ever-increasing demand for energy. DG integration introduces peculiar challenges to the entire power system. Due to the increased DG penetration, these challenges have become technically and economically very important. Effective and fast islanding detection is necessary to prevent power quality degradation, equipment loss, and human life loss. In this study, an islanding detection model based on convolutional neural network (CNN) is proposed. The method utilizes the ability of CNN to perform accurate image classification. It identifies islanding by classifying scalogram images obtained by applying wavelet transform to the concatenated voltage waveforms for each event. The islanding detection model is trained with well-processed images to improve classification accuracy. Noise is incorporated into the data to investigate the susceptibility of the method to noise. The results obtained prove that the proposed islanding detection model can handle the problem of islanding detection.
Predictions of cloud attenuation models for uplink and downlink margins at ku, ka and v bands in tropical regions
Authors: Adewusi O.M. , Akinwumi S.A. , Ometan O.O. , Omotosho T.V. , Akinyemi M.L.
Published: March 2022

To achieve effective wireless transmission margin and larger bandwidth at lower cost, hydrometeor models roles are of primary importance. The almost perpetual existence of clouds in tropical climates makes cloud models all the more fundamental. Details of four years station spectrum analyzer data, five years climatological data and fifty – eight years radiosonde data used in this research were earlier published. The radiosonde data was used to obtain existing primary cloud models’ predicted cloud attenuation cumulative distributions for the station and it was also used to deduce the new algorithm’s parameters for the station. The every minute measured and logged station cloud attenuation data using spectrum analyzer was used to deduce the station cloud attenuation cumulative distribution for comparison with that of other existing cloud models. The simulation program was run to generate the new cloud attenuation algorithm’s parameters, which defines the cloud attenuation model for the station. Thus the new model only fundamentally requires station radiosonde data. The cloud cover data and all others are needed only for graphical comparisons and corroboration. Thus the new tropical cloud attenuation algorithm can be used to develop the cloud attenuation model for any station climatic zone by using the methodology earlier published. Collected spectrum analyzer data, climatological data and acquired radiosonde data were used to compute projected attenuation values for each cloud attenuation model at propagation signal frequencies between 12 GHz to 50 GHz. The predicted values were extracted and analysed statistically. With respect to frequency, the new cloud attenuation model’s cumulative distribution proportionally averaged the characteristics of the cumulative distributions deduced from the station radiosonde data and that of the spectrum analyzer data as shown by the graphical figures. The results show that convergence of the range of predicted attenuation values by each of the cloud models increases directly with frequency.
Forecasting tropospheric wet delay using LSTM neural network
Authors: Ogunjo S.T. , Dada J.B. , Ajayi O.J.
Published: March 2022

Tropospheric wet delay is a critical factor in radio communication. Accurate estimation of the wet delay is difficult due to the variability in water vapour. In this study, we aim to model and predict tropospheric wet delay over four tropical locations using Long Short-Term Memory (LSTM) neural network. Results obtained in this study showed RMSE and MAE within the range 18.96–21.16 and 14.08–16.38 respectively. LSTM model was able to capture the different regimes of wet delays in each of the locations under consideration. This approach can significantly improve link budget and planning within tropical regions.
Divertor detachment operation in helium plasmas with ITER-like tungsten divertor in EAST
Authors: LIU Jianbin , MENG Lingyi , GUO Houyang , LI Kedong , XU Jichan , WANG Huiqian , XU Guosheng , DING Fang , ZHANG Ling , DUAN Yanmin , ZHANG Bin , YU Lin , WANG Ping , LI Ang , WU Donggui , DING Rui , WANG Liang
Published: March 2022

Detachment in helium (He) discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor. This paper presents the experimental observations of divertor detachment achieved by increasing the plasma density in He discharges. During density ramp-up, the particle flux shows a clear rollover, while the electron temperature around the outer strike point is decreasing simultaneously. The divertor detachment also exhibits a significant difference from that observed in comparable deuterium (D) discharges. The density threshold of detachment in the He plasma is higher than that in the D plasma for the same heating power, and increases with the heating power. Moreover, detachment assisted with neon (Ne) seeding was also performed in L- and H-mode plasmas, pointing to the direction for reducing the density threshold of detachment in He operation. However, excessive Ne seeding causes confinement degradation during the divertor detachment phase. The precise feedback control of impurity seeding will be performed in EAST to improve the compatibility of core plasma performance with divertor detachment for future high heating power operations.