Key Technical Problems Research Articles

A Flexible Reactive Power Injection Method for DC-Link Capacitors Voltage Balancing in Back-to-Back Multilevel Converters

The dc-link capacitor voltage drift is the key technical problem of the converters with multi-intermediate nodes. The back-to-back (BTB) configuration with voltage balancing control can achieve a certain operation range. Nevertheless, the challenge of voltage drift still remains, especially when both sides operate at high but different modulation indexes and high power factors. This article focuses on a BTB seven-level V-clamp multilevel converter (VMC). The balanced operation limits are presented, and the effect of the power factor on balancing capability is analyzed. To maintain the voltage balancing of the dc-link capacitor under different operation conditions of the load (inverter side), a reactive power injection control is proposed in this article. Suitable reactive power is injected into the rectifier according to the balancing situation. The proposed control method can actively adjust the power factor of the rectifier to provide the required balancing capability. In this way, the dc-link capacitor voltage balancing is maintained within a larger operation range. In this article, a 10-kVA laboratory prototype of BTB seven-level VMC is set up to verify the effectiveness of the proposed control.

Research Progress of High-Speed Wheel–Rail Relationship

The research on wheel–rail relationship includes the basic theoretical models and corresponding numerical methods of wheel–rail in rolling contact, geometric parameter matching and material matching of them, friction and wear, wheel–rail rolling contact fatigue, wheel–rail adhesion and noise. They are also key theoretical and technical problems of the high-speed train/track coupling system. The basic theoretical models of wheel–rail in rolling contact and the corresponding numerical methods are the basis and one of the basic means for solving other wheel–rail relationship problems. The other is the experimental means. Moreover, the modeling and analysis of coupling behavior of the train and track can only be realized by means of the wheel–rail rolling contact mechanics model and its corresponding numerical method. This paper mainly discusses some research work and achievements on high-speed wheel–rail relationship problems since China opened a high-speed railway system on a large scale. The discussions in this paper include the classic wheel–rail rolling contact theoretical models (analytical forms) and the modern wheel–rail rolling contact theories (numerical methods), their advantages and disadvantages, their application and future development direction of them. The reviewed research progress on the other wheel–rail relationships mainly expounds the thorny problems of the wheel–rail relationship encountered in the operation of China’s high-speed railway, how to adopt new theoretical analysis methods, test means and take effective measures to solve these problems. It also includes research results of similar important reference values performed by international peer experts in related fields. Challenging and unsolved problems in high-speed wheel–rail relationship research are also reviewed in the full text.

Home Care System for Mobility Disabilities Based on Intelligent Perception.

In order to explore how to realize home care for the elderly with mobility difficulties, this paper proposes a home care system for the elderly with mobility difficulties based on intelligent perception. This method explores the research of home care for mobility disabilities by recommending key technical problems and solutions based on information represented by intelligent perception. The research shows that the home care system based on intelligent perception can effectively solve the nursing problems of the elderly, which is about 60% more efficient than the traditional methods. The combination of intelligent perception and reasonable home care mode will improve the social and economic benefits of health services and promote the balance between supply and demand of the whole health services.

Rare earth doped double perovskite nanocrystals with controllable emission wavelength and model for high-level anti-counterfeiting

Fluorescent anti-counterfeiting technology has become one of the most commonly used anti-counterfeiting technologies because of its simple preparation, low cost and high safety. However, there are still some key technical problems to be solved in developing multi-mode and polychromatic fluorescent materials for high-level anti-counterfeiting. Herein, Yb3+/Er3+ codoped Cs2AgIn0.99Bi0.01Cl6 double perovskite nanocrystals (DPNCs) with dual-mode polychromatic emission were developed. Under the irradiation of 365 nm ultraviolet (UV) light, the DPNCs emitted a bright downshifting (DS) yellow light, which comes from the self-trapping excitons (STEs) recombination. While the DPNCs produced upconversion (UC) green fluorescence under the 980 nm laser excitation, which is attributed to the transitions of 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 of Er3+ ions. In view of its dual-mode and polychromatic fluorescence characteristics, a high-level anti-counterfeiting based on this fluorescent material is designed. Moreover, the brightness of the anti-counterfeiting pattern based on this material decreases very little after three months. These results indicated that the dual-mode and polychromatic DPNCs reported have potential application in information encryption and identity recognition.

Optimization Design of Short Life Cycle Product Logistics Supply Chain Scheme Based on Support Vector Machine.

In order to better solve the problem of product logistics supply chains with short life cycles, a solution optimization of short life cycle product logistics supply chains based on support vector machines is proposed. This method recommends key technical problems and solutions through information represented by support vector machines and explore the research of short life cycle products to realize logistics supply chains. The research shows that, whether it is a retail channel or a network channel, the RMSE value of the effect index predicted by SVM is smaller than the RMSE value of the improved Bass. It can be seen that the SVM demand forecasting model constructed by considering multiple input factors can obtain a more accurate forecasting effect. The accuracy of the demand forecasting model based on SVM is verified.

Secure Internet of Things Gateway Technology Based on Multicommunication Methods

In order to explore how the Internet of Things implements a secure Internet of Things gateway technology, the author proposes a research on a secure Internet of Things gateway technology based on multicommunication methods. This method recommends key technical problems and solutions based on information represented by multiple communication methods and explores how the Internet of Things can realize the research of Internet of Things gateway technology. Research has shown that the security IoT gateway based on multiple communication methods is about 40% more efficient than the traditional method. By studying some exploratory guidance and suggestions for the development of the Internet of Things, it is found that there are still many problems to be solved before realizing the real Internet of Things environment.

Research on English Vocabulary and Speech Corpus Recognition Based on Deep Learning

In order to investigate how to recognize English words and speech corpus, an English vocabulary and English speech recognition model based on deep learning algorithm was proposed. Through recommending key technical problems and solutions based on deep learning algorithm, how to realize the recognition of English vocabulary and speech corpus was investigated. In the research, the accuracy of the method on the English vocabulary and speech corpus recognition based on the deep learning algorithm increased 79% over the previous methods. Combined with the principle of the deep automatic encoder and deep learning algorithm, the research emphasis was on the effects of speech recognition framework for speech corpus. The speech recognition research based on the theory of deep learning not only had a theoretical guidance meaning but also had the use value in the practical application.

Prediction of Higher Education Cost and Analysis of Sharing Ability Based on Artificial Neural Network

In order to explore how to realize the cost prediction and sharing ability of higher education, this paper proposes an analysis of the cost prediction and sharing ability of higher education based on artificial neural network. This method explores how to realize the cost prediction of higher education through the key technical problems and solutions of information recommendation based on artificial neural network. The research shows that the ability of college education cost prediction and sharing based on artificial neural network is 61% higher than that of traditional cost prediction and sharing. With the help of BP neural network algorithm, the accuracy of cost prediction can be maintained above 90%. It is proved that the artificial neural network algorithm can effectively improve the cost forecasting, financial system, and cost management system of colleges and universities.

Digital Image Restoration Based on Multicontour Batch Scanning.

In order to explore the problem of digital image restoration, the authors propose a research on digital image restoration based on multicontour batch scanning. This method recommends key technical problems and solutions based on information represented by multicontour batch scans, exploring research in digital image restoration. Research has shown that the research on digital image restoration based on multicontour batch scanning is about 40% more efficient than traditional methods. Aiming at the new application of digital image inpainting, the application of image inpainting in image compression is studied in depth, and the technical principles of image inpainting and image compression are complemented.

Dynamic resource allocation of UAV swarms based on cooperative and competitive public goods game

The dynamic resource allocation of unmanned aerial vehicle (UAV) swarms is a challenging key technical problem in mission planning. In this paper, a dynamic resource allocation method based on a cooperative and competitive mechanism is proposed. The average income of the system is improved by designing regulation rules for special individuals. Finally, the feasibility and effectiveness of the proposed method for UAV dynamic resource allocation are verified according to the network structure, model parameters, and steady-state results of the system under different excitation mechanisms through simulation experiments of the UAV game model.

Image Effect Observation of Acanthopanax senticosus on Antifatigue Activity after Exercise.

In order to explore the effect of Acanthopanax senticosus on antifatigue activity after exercise, this paper proposes an image effect observation based on the effect of Acanthopanax senticosus on antifatigue activity after exercise. This method recommends key technical problems and solutions based on the information represented by image effect observation and explores the influence of Acanthopanax senticosus on antifatigue after exercise. Through the retrospective analysis of certain personnel, it is shown that the image effect observation based on the influence of Acanthopanax senticosus on the antifatigue activity after exercise is about 25% more accurate than the traditional method. Most of the active ingredients of Acanthopanax senticosus have phenolic hydroxyl groups, which can resist oxidation, fatigue, focus attention, and reduce work mistakes. This experiment shows that after sleep deprivation, the antioxidant capacity of the body decreases with time. Acanthopanax senticosus extract can significantly improve the above symptoms and fight fatigue.

Reconstruction and Utilization of Energy Economy Information Resources against Humanistic Background

In order to explore the problem of reconstruction of energy economic information resources, the author proposes a reconstruction of energy economic information resources based on the background of digital humanities. This method recommends key technical problems and solutions based on information represented by the digital humanities background and explores research on the reconstruction of economic information resources. The research has shown that the reconstruction of energy and economic information resources based on the background of digital humanities is about 30% more efficient than traditional methods. The concept of sustainable energy development is a continuation of the concept of “sustainable development,” emphasizing the improvement of energy efficiency and using it as a way to improve overall economic efficiency and reduce energy-related environmental costs, so that economic development will not harm the environment, and future generations have equal opportunities for development.

Research on two-step advanced treatment of old landfill leachate by sequential electrochemical peroxidation-electro-Fenton process

Electrochemical technology is an alternative method for the removal of high concentration ammonium-N (NH4+-N) and refractory organics from old landfill leachate (OLL). However, the limited performance of a single electrochemical process and the subsequent long tertiary treatment time to meet the water quality standards are the key technical problems that hinder its practical application. This study demonstrates that the sequential ECP-EF process can realize two-step advanced treatment of OLL. Under the optimal conditions (ECP: j = 30 mA cm−2, initial pH = 9.0; EF: j = 30 mA cm−2, initial pH = 3.5), the removals of COD, TOC, NH4+-N, and TN can be achieved 95.9 ± 0.4 %, 85.1 ± 0.8 %, 99.4 ± 0.1 %, and 99.2 ± 0.1 %, respectively, to meet the first-class standard of integrated wastewater discharge standard of China. The organics in OLL are mainly removed by ECP process and further mineralized or converted to small molecular hydrophobic components in EF process. The sequential ECP-EF process can reduce the aromaticity and complexity of organics, as well as can decrease the acute cytotoxicity (ACT) and hydrophilicity. A proper electrolysis time can effectively avoid the rise of ACT, energy consumption, and cost. The treatment cost ($0.0134 L−1) is approximately 32 % less than the previously reported electrochemical processes of electrocoagulation/electro-Fenton. These findings obtained with real OLL provide a basis for scaling up this new sequential electrochemical treatment approach.

Data Transmission and Processing Analysis of Power Economic Management Terminal Based on the Internet of Things

In order to explore how the power economy can realize the data transmission and processing of the management terminal, this paper presents a data transmission and processing analysis of the power economy management terminal based on the Internet of Things. This method explores the research on how to realize the data transmission and processing of management terminal in power economy through the key technical problems and solutions of information recommendation based on the Internet of Things. The research shows that the efficiency of data transmission and processing analysis of power economic management terminal based on the Internet of Things is about 65% higher than that of traditional data analysis. Improve the overall quality of employees in power enterprises and inject new vitality into the development of power economy.

A hydrostatic test study on the waterproofing of an underground ecological granary using a plastic-concrete system

Underground granaries can store grains at low and quasi-low temperatures due to the existing shallow geothermal energy, which can ensure long-term quality and grain preservation. However, water and moisture resistance of groundwater is a key technical problem which restricts its wide application. Consequently, a polypropylene plastic-concrete wall was proposed in this study to solve these problems. First, a hydraulic test was performed on three plastic-concrete specimens using polypropylene plastic (PP) plates of different thicknesses including 10, 15, and 20 mm to investigate the mechanical performance under water pressure loading. The displacement, deformation, interior force, failure mode, and mechanism of the plastic-concrete specimens were comprehensively analysed. Second, a lining waterproof component model was established based on the ABAQUS software. Finally, the interior force adjustment coefficient calculation formulas and interior force analysis method are presented according to the experimental results and direct design method for column-supported slabs. Consequently, the ultimate bearing capacities of the specimens with different PP plate thicknesses were 120, 180, and 170 kPa, respectively, and the failure modes of the specimens varied with the thickness of the PP plate. Moreover, for thicknesses greater than 15 mm, the ultimate bearing capacity of the specimen was mainly dependent on the strength of the nodes. The numerical simulation results correlated with the experimental data, where the stress and displacement of the plastic waterproof components increased gradually with increasing water pressure. The experimental and simulation results of this study can provide a reference for the waterproof design of underground granaries and widen their practical applications.

Effects of Sports Drinks on Weight Loss Control and Lipid Metabolism in Overweight Students

In order to explore how sports drinks can achieve weight loss control and lipid metabolism in college students, the author proposes an experiment based on weight loss control and lipid metabolism in college students. This experiment recommends key technical problems and solutions based on information represented by college students’ weight loss control, a study exploring how sports drinks can achieve weight loss control in college students. Research has shown that Jupu sports drink is more suitable than 87% of sports drinks on the market for college students to lose weight. Sports drinks have a positive effect on maintaining a high blood sugar level during exercise and have a certain antifatigue effect in mass fitness. Jupu sports drink not only has the effect of other sports drinks but also has a certain effect on weight loss control.

Evaluation of the effect and investment benefit of Marine ecosystem protection and restoration

In order to explore the effectiveness of Marine ecosystem conservation and restoration, an evaluation method based on the effectiveness and investment benefit of Marine ecosystem conservation and restoration was proposed. This method recommends key technical problems and solutions based on the information represented by Marine ecosystem protection to explore the effectiveness of Marine ecosystem protection and restoration. The results show that the evaluation efficiency of Marine ecosystem protection and restoration and investment benefit is about 30% higher than that of traditional methods. Due to the uncertainty of Marine ecological restoration, the role of adaptive management in Marine ecological restoration has been paid more and more attention, and the systematic process of improved management adapted to new knowledge and information has been explored.

Epoxy resin-hydrated halt shaped composite thermal control packaging material for thermal management of electronic components

With the rapid increase of the thermal power of electronic devices, phase change material(PCM) have shown great application prospects in the field of electronic thermal management . However, due to the irregular surface of the electronic device, PCM can only act on the back of the component or the outside of the package, which leads to the occurrence of heat transfer hysteresis . In order to reduce the heat transfer distance between the heat source and PCM, a new type of ER/SAT/DSP composite functional material with thermal control function was prepared in this paper to solve the key technical problem of fluid seamless packaging thermal control. The composite material is encapsulated in a fluid state and will no longer melt after solidification. Through thermophysical experiments and morphological characterization, the results show that when the mass fraction of PCM is 35%, the composite material has the best physical properties and application performance. And after 200 thermal cycles, the leakage rate is only 3.7%. Through the PTC thermal control experiment, the results show that the maximum temperature at different positions of the device for pouring the new composite was reduced by 7.4 °C and 8.1 °C, respectively, and the operation time corresponding to different temperatures was increased by 5.76 times, 5.80 times and 6.98 times, respectively. Therefore, the composite material shows a good thermal control ability for electronic components of any surface shape.

Optimal Design Method for Vessel-Bridge Collision Based on Life-Cycle Theory

As structures crossing waterways, bridges are obstacles to vessels. Vessel-bridge collisions are inevitable. They not only involve the safety of vessel passage but also seriously affect the safe operation of bridges. Vessel-bridge collisions cause not only huge economic losses and casualties but also severe political and environmental losses. Vessel collision safety of existing and new bridges is one of the key technical problems that engineers and bridge managers must solve. Comprehensive consideration of vessel-bridge collision risk loss and structural performance in the design stage to achieve optimal cost over the life cycle is an important aspect of bridge design. Based on the current life-cycle design theory of engineering structures, this paper proposes a theoretical framework for vessel-bridge collision optimization design based on the life cycle, which includes three parts: vessel-bridge collision probability analysis, vessel-bridge collision vulnerability analysis, and vessel-bridge collision hazard. Taking the minimum cost of the bridge structure in the design service life period as the objective function, the optimization design model and design process of vessel-bridge collision based on whole life are established, and the key problems to be solved in each part are expounded.

Study on Subjective Evaluation of Acoustic Environment in Urban Open Space Based on "Effective Characteristics".

With the continuous expansion of urban scale with dense population and traffic and the gradual improvement of residents’ requirements for environmental quality, the traditional evaluation method relying on acoustic energy is not enough to reflect the feelings of urban crowds about acoustic environment quality. The acoustic environment quality evaluation method based on human subjective perception has gradually become one of the research focuses in the field of environmental noise control. In recent years, various subjective and objective acoustic characteristic parameters have been introduced into the study of acoustic environment assessment in the global literature. However, the extraction of “effective characteristics” from a large number of physical and psychoacoustic characteristics contained in acoustic signals and the creation of a scientific and efficient subjective evaluation model have always been key technical problems in the field of acoustic environment evaluation. Based on subjective human perceptions, the overall acoustic environment quality evaluation of urban open spaces is studied in this paper. Based on the “effective characteristic” parameters and the subjective characteristic proposed in the previous research, including equivalent continuous A-weighted sound pressure level (LA), the difference between median noise and ambient background noise (L50 − L90), Sharpness (Sh), as well as satisfaction (Sat), the multivariable linear regression algorithm is used to further study the intrinsic correlation between the proposed “effective characteristics” and subjective perception. Then, a satisfaction evaluation model of the acoustic environment based on “effective characteristics” is built in this paper. Furthermore, the soundwalk evaluation experiment and the MATLAB numerical simulation experiment are carried out, which verify that the prediction accuracy of the proposed model is more than 92%, the consistency of satisfaction level is more than 88%, as well as the changes in the values of Sh and L50 − L90 have a significant impact on the satisfaction prediction of the proposed model. It shows that the proposed “effective characteristics” more comprehensively describe the quality level of the regional acoustic environment in urban open space compared with a single LA index, and the proposed acoustic environment satisfaction evaluation model based on “effective characteristics” has significant accuracy superiority and regional applicability.