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During the coVID-19 epidemic, online teaching has become an attempt to break the traditional offline teaching mode and break the temporal and spatial boundaries of knowledge dissemination. The introduction of new technology and its combination with new teaching models can meet the needs of knowledge dissemination. Students’ autonomy, the application of new technologies and teachers’ teaching methods have become important factors affecting teaching effect. This study investigated the online and offline teaching effect of university students in Zhejiang province, and explored the influence of the introduction of new technology on the knowledge dissemination effect, as well as the weight relation of each element in it. It is found that the free environment after leaving the fixed classroom, rich teaching resources and diversified teaching tools have a positive impact on the effect of knowledge dissemination. On the other hand, the lack of interpersonal communication in teaching, interactive question-answering and the group atmosphere of classroom teaching lead to the decline in teaching effect for some students with poor autonomy. Furthermore, the research believes that technology solves the temporal and spatial problem of knowledge dissemination, but the discipline and constraints from groups are also reduced due to the intervention of technology. An autonomous learning without monitoring requires more proactive initiative and competitive incentives from the group.

As the phenomenon of empty nest elderly becomes increasingly obvious, how to protect the health of the elderly living alone has attracted researchers' attention. Among all the researches, fall as the most common accident of the elderly, its corresponding vision-based detection system design is the most important. However, directly using image-clear traditional cameras to monitor the daily lives of the elderly at home will bring the risk of privacy disclosure. Therefore, this paper proposes a fall detection system under privacy protection. Firstly, multi-layer compressed sensing (CS) model is introduced to process the video frames, so that the video can reach visual shielding effect. Then, for the compressed video, we improve the local binary pattern on three orthogonal planes (LBP-TOP) feature to represent the object behavior effectively. Finally, the fall detection problem is transformed into a behavioral binary classification problem. The experimental results on two public datasets show that the specificity, sensitivity and accuracy of the algorithm proposed in this paper have maintained at a good level.

In order to effectively remove the magnetocardiography (MCG) signal noise and improve the accuracy of heart disease diagnosis, a cardiac Fourier-wavelet denoising method based on sparse representation is used to process the cardiac magnetic signal. The noise reduction method combines the advantages of Fourier and wavelet. The initial denoising process is performed in Fourier domain, and then the residual noise is removed in the wavelet domain. Based on the theory of sparse representation, the wavelet denoising is transformed into an optimization problem, and a denoising model based on sparse representation is established. By eliminating the sparsity of wavelet coefficients, the purpose of noise removal is achieved. The experimental results verify that the method of the paper can effectively improve the denoising effect of the cardiac magnetic signal.

We report a feasible opto-electrokinetic approach to realize rapidly controllable single cell screening and isolating culture in the extracellular environment. A nonuniform AC electric filed makes cells separate and sort by size, shape and viability. The DC electric fields-based dynamically forms the alginate hydrogel in 3D on the top of the organic photoconductive material titanium oxide phthalocyanine. The trapped cells can be cultured in the 3D alginate hydrogel pattern.

A novel broadband concave paper antenna is proposed for low cost and conformal applications. The new design is a three-dimensional monopole antenna. Owing to the concave flexible paper substrate, the proposed antenna is easy to integrate with the packing case or the communication product. The broadband antenna can be used in the applications covering the 0.903–2.63 GHz band, such as 2G, 3G, and WLAN. Its gain is 3.8 dBi at 0.915 GHz, 3.5 dBi at 1.0 GHz, 2.8 dBi at 1.8 GHz, and 4.8 dBi at 2.45 GHz. Experiments validate the simulated results of our antenna.

Clustering plays an essential role in large-volume data analysis areas such as bioinformatics, statistic, pattern recognition and so on. K-means is one of most effective clustering algorithms, which is relatively easy to implement. Most real world applications usually involve a huge amount of data. Thus, how to improve applications' efficiency while maintaining accuracy becomes a significant and considerable issue. In this paper, a K-means clustering algorithm, which uses heterogeneous parallel computing technology on Computing processing elements and distributed computing technology, is proposed. This algorithm is applied in unique Sunway architecture based on "Sunway TaihuLight" Supercomputer---the world's fastest supercomputer with peak performance over 100PFLOPS. The testing results suggest that this improved algorithm is stable, fast and efficient. Conclusively, it has a great improvement in computation performance, especially with large volumes of data.

Compared with single-server authentication scheme, the authentication scheme for multi-server environment has a lot of advantages. Such as users needn't to remember various passwords or register for every application server. In 2016, Irshad et al. proposed a three-factor scheme based on chaotic map for multi-server environment. Irshad's scheme has high efficiency and strong robustness. However, after careful analysis, this paper shows that Irshad's scheme still has many disadvantages. In order to solve these problems, a new three-factor authentication scheme based on secure sketch and Chebyshev chaotic map has been proposed in this paper. From the analysis, we can see that the proposed scheme has higher security level and deals with biometric more appropriately in spite of slight higher computation cost than Irshad's scheme. What's more, an access control method has been introduced for the purpose of making different users enjoy different access privileges with regard to the data. At the same time, the proposed scheme can achieve key agreement.

The advancement of wireless communication technology and sensor technology, as well as the popularity of portable devices has promoted the location-based services (LBS) to a new stage, while new spatial-temporal query techniques and scenarios have emerged continuously. One of the interesting scenarios is the spatial skyline query that retrieves those points of P not dominated by any other point in P with respect to their derived spatial attributes. However, being point-based, the former query method is not suitable for privacy protection. In this article, we propose a range-based spatial skyline query solution, including two algorithms, namely VRSSA for static query points, and DDOAA and DDODA for the dynamic change of the data points queried.

A novel method of reconfigurable substrate integrated waveguide (SIW) antenna is proposed. By loading ferrite slabs and applying DC magnetic bias, we realize the reconfiguration of operating frequency and polarization of the SIW antenna. The experiments demonstrate the reconfigurable SIW antenna could have broadband frequency tunable range which is up to 14.9% in microwave X-band, and the radiation can transform between circular and linear polarizations. The fabricated antennas have gain over 5 dBi and radiation patterns changes little in tuning.

A new type of frequency reconfigurable antenna, the ferrite slab loaded substrate integrated waveguide (SIW) antenna, is proposed. Due to the loaded ferrite, the operating frequency of the antenna can be tuned in a wide frequency range by bias magnetic field and the position of ferrite slab in the antenna. Three example reconfigurable SIW antennas are designed, fabricated and measured. The experimental results prove the frequency tunablity of the antennas and show the tunable range could be much larger than that of electronic reconfigurable antennas. The radiation pattern and gain of the antenna characterize their good radiation performance which may be promising in wireless communication systems.

Because of the unconstrained environment of scene text, traditional Optical Character Recognition (OCR) engines fail to achieve satisfactory results. In this paper, we propose a new technique which employs first order Histogram of Oriented Gradient (HOG) through a spatial pyramid. The spatial pyramid can encode the relative spatial layout of the character parts while HOG can only include the local image shape without spatial relation. A feature descriptor combining these two can extracts more useful information from the image for text recognition. Chi-square kernel based Support Vector Machine is employed for classification based on the proposed feature descriptors. The method is tested on three public datasets, namely ICDAR2003 robust reading dataset, Street View Text (SVT) dataset and IIIT 5K-word dataset. The results on these dataset are comparable with the state-of-the-art methods.

To obtain the attitude of spacecraft by a large field of view CCD system is not an unachievable task. The principal aim of this paper is to research the accuracy of spacecraft's attitude by shooting stars with the large field of view CCD system on the ground. In this paper, the quadrilateral algorithm model and an algorithm of data fusion from a set of real images, are given. The experimental results show that it is feasible to calculate the attitude of spacecraft by the quadrilateral model and the data fusion algorithm.

This work proposes a design of novel magnetically tunable substrate integrated waveguide (SIW) slot antenna with one ferrite slab loaded in the antenna. The operation frequency of the antenna can be tuned more than 380 MHz in the X-band from 9.32 to 9.70 GHz when the bias magnetic field changes from 0 to 0.12 tesla. Within the tunable frequency range, antenna gain is more than 6 dBi. The radiation patterns and the gain are almost not affected by the changing of applied magnetic field, showing a good high gain antenna with frequency tunable feature.

Metamaterial antenna involving a shell of left-handed materials (LHM) and a line source could be a directional antenna with lower RCS. To optimize the performance of the antenna, we studied the effects of the line source position and the properties of LHM shell on the directional radiation. The results show that these factors can greatly change the directional emission of the antenna. To maximize directive emission, one needs to optimize the source position and the size of LHM shell, and to balance the directivity and side-lobe peak levels of the antenna.

This paper investigates the link prediction problem in location-based social networking services (LBSNS) with protected location history. While former approaches mainly utilize the accurate locations, the relevant data we analyzed are modeled by a location privacy protection model called k-anonymous spatial-temporal cloaking model (KSTCM) which perturbs the location-related records on both temporal and spatial dimensions. We also propose a KSTCM-based co-located relationship model based on which various contextual features are extracted to help building the prediction model. Furthermore, we study the extent to which link between two users can be inferred from the co-located situation in space, time and degree of privacy protection. The experimental results show that our link prediction model can obtain a very high accuracy.

Smart home is widely used and has been an important part in everyday life. There are some problems to establish gateway for smart home. As we know, standards in the systems are different which makes it hard to exchange information between the consumer electronics and home appliances. To solve these problems, we investigate a new type gateway which can adapted to different standards and make it easy to exchange data.

The insulation system of superconducting power equipment often works under cryogenic vacuum environment. However, due to special cases such as material gas releasing and helium leakage, local low pressure environment is prone to be formed and this will lead to damage the insulation system so as to influence the normal operation of power equipment. Polyimide (PI) has been widely used as insulation material in various superconducting power equipments for its excellent dielectric performance and mechanical properties. In this paper, by using the home-made test system which is developed for testing cryogenic electrical characteristics of dielectrics, a series of tests for studying polyimide films' DC surface flashover characteristics have been done at temperature range from 78 K to 300 K under low pressure environment. The test results show that the surface flashover times under low pressure environment have little influence on the DC surface flashover strength of polyimide films. In the pressure range of 10 to 2000 Pa, the flashover strength decreases with the pressure increasing, but the decrement becomes slow gradually. However, the flashover strength increases to a certain extent in the range of 2000 to 3000 Pa.

In this paper, a kind of automatic hot-dip galvanizing device for small components is design in order to solve the problem of highly dependence on complex artificial operations with labor intensive and difficult control of the coating often encountered during the production process of the hot-dip galvanizing in the past. By comparing and analyzing two different design schemes of mechanisms, a better scheme is obtained. A three dimensional model was made and the corresponding motion was simulated in the design of automatic hot galvanizing device with assistance of the software Solid Edge. It is found that the device can make a continuous hot-dip galvanizing for the varieties of small components.

Sensor plays an important role in context-aware computing. While sensor modeling is usually isolated from former researches on context modeling and sensor type is always restricted to physical ones, this paper aims to provide a more comprehensive insight into the relationships between sensor and context. Based on a more generic definition of sensor and a corresponding sensor category in context-aware computing, main characteristics of sensor and the relations between sensor and context are analyzed in details. In particular, a multi-sensor oriented context model based on ontology approach is proposed. The model which has been applied to a middleware supporting for rapid context-aware applications development is proved to be effective.

SF 6 gas is used as the insulating medium in cubicle gas insulated switchgear (C-GIS) in low pressure (below 0.25 MPa). SF 6 gas has several shortcomings, such as expensive price, significant greenhouse effect, therefore, exploring alternative media of SF 6 gas is of important theoretical value and practical application significance. This paper focuses on the C-GIS switchgear which uses SF 6 gas as insulating medium and works below 0.25 MPa pressure, and by using self-designed GIS test platform, the negative lightning impulse surface flashover characteristics of insulator models in SF 6 with N 2 , air binary mixed gases have been tested under various mixing ratios and various pressures. The test results show that: in the test gas pressure range, the insulators' surface flashover strengths always increase with the increasing of air pressure in all kinds of gas mixtures, and the specific variation trends are related to the gas pressure and mixing ratio of gas mixtures; the content of SF 6 in gas mixture has a great impact on the surface flashover strength, when a little SF 6 is added to pure N 2 or pure air, the insulators' surface flashover strength can be obviously improved, however, with the increase of the content of SF 6 , the rise of insulators' surface flashover strength has a saturated trend; SF 6 /N 2 or SF 6 /air gas mixtures with higher pressure can be used as insulating medium to replace pure SF 6 gas with lower pressure.

With the development of the electric power and railway industry, more and more SF 6 gas-insulated equipments have been applied. However the greenhouse effect and environmental pollution that caused by SF 6 gas has been paid attention in recent years. Therefore looking for the SF 6 alternative gas without reducing its insulation performance becomes one of the research hotspots. Epoxy resin has been widely used as the preferred material of post insulator in cubicle type gas insulated switchgear (C-GIS) for its excellent dielectric performance and mechanical properties. In this paper, the power frequency surface flashover characteristics tests are done on the epoxy resin insulator which is in the SF 6 -N 2 and SF 6 -air gas mixtures with lower pressure range, nonuniform electric field. The test results show that the insulator's power frequency surface flashover voltage increases linearly with the increasing pressure, the proportion of SF 6 in the gas mixture influences the insulator's power frequency surface flashover voltage greatly, and adding a small amount of SF 6 to the pure N2 or the pure Air can significantly improve the insulator's power frequency surface flashover voltage. With the proportion of SF 6 in the gas mixture increasing, the insulator's power frequency surface flashover voltage increases with a saturation trend.

In this paper, simulation and analysis of the movement and energy of glass balls is carried out in the different mechanical plating bucket by using PFC3D software. In four kinds of different mechanical plating bucket, the influence of the bucket structure, rotation rate and mixed small glass balls on the effect of the coating of good quality, their characteristics and application conditions are studied and analyzed. Some results have better guidance significance for understanding the movement and energy of small glass balls and designing mechanical plating bucket. The results show that the quadrate and circular mechanical plating bucket are not perfect structure, hexagonal structure is better, octagonal structure is best. In order to obtain coating of good quality, it is best perfect to use octagonal mechanical plating bucket and mixed small glass balls at 30 rpm rotation rate. These simulation results compared with the practical application results is very consistent.

With the rapid development of superconducting technology, the electrical characteristics of insulating materials at cryogenic temperature has become an important factor which influences the operating performance and reliability and has attracted extensive attention. This paper mainly deals with a new test system which is used to produce a vacuum cryogenic environment for studying the DC insulation characteristics of polyimide from cryogenic temperature to room temperature. Meanwhile, as the wrap structure is primarily used in superconductive electrical equipment insulation, the DC breakdown characteristics of single-layer and double-layer polyimide films were studied in this paper.

Polyimide (PI) is widely used as insulation in various superconducting power equipments for its excellent dielectric performance and mechanical properties. The cryogenic vacuum is the actual work environment of the insulation systems of superconducting power equipments. Therefore, the study of polyimide film's DC surface flashover characteristics at low temperature in vacuum is of great significance. In this paper, a series of tests for studying polyimide film's DC surface flashover characteristics have been done at temperatures from 78K to 300K in vacuum by using the home-made test system which is developed for testing cryogenic electrical characteristics of dielectrics. The test results show that the surface flashover times and temperature both have some influence on the DC surface flashover strength of polyimide films.

In this paper, numerical simulation and analysis of the exhaust gas flow pattern above the hot galvanizing bath have been carried out in different collection methods, using FLUENT software. In three kinds of different collection methods, the influence of some parameters on the effect of the gas collection, their characteristics and application conditions are studied and analysed. Some results have better guidance significance for understanding the exhaust gas flow rule and designing rational recovery device.

With the further development of intelligent transportation systems and artificial intelligence techniques, the related bus scheduling method also in-depth study. In order to obtain a better plan of public transit in a bus line, we make a multi-object genetic algorithm optimizing model, including the passengers and bus companies, according to the given preconditions and passenger data. Using the genetic algorithm's global optimization search to deal with the operate buses on one bus line, obtaining the optimal solution of bus departure interval.

Nowadays, numerous applications involving spatial data are emerging. While efficient management of tremendous spatial-temporal objects is a challenge due to the highly dynamic nature of the data, the demand for fast getting query results and minimum update cost. However, the query performance optimizations and the update cost minimizations cannot be achieved at the same time. In this paper, a novel approach is presented to get a tradeoff between those two. A spatial-temporal index mechanism named as Hybrid Spatial-Temporal Index (HSTI), which satisfies the time slice, time interval, event, and trajectory queries is introduced. The effectiveness and efficiency of the proposed index is validated through extensive experiments.

Presently, cycloid gears are widely applied in horologes, apparatuses and the meters. This paper makes double-circular-arc modified cycloid gears apply to power transmission system which has the high contact strength and the high lifetime. This paper starts from the transmission characteristics of cycloid gears, then double-circular-arc modified cycloid gears are proposed and whose mathematical model is built. Based on the UG/NX operating platform, 3D models of double-circular-arc modified cycloid gears are established and which is directly carried out the FEM model analysis under the circumstance of UG/NASTRAN. The first six natural frequencies and mode shapes are extracted, which provide the reference for this gear dynamic design. Based on the CAD/CAE integration feature of the UG, the parametric modeling and the modal analysis are implemented, which are contributed to gear optimum design and manufacture.

This work proposes a new broadband ultra-high frequency tag antenna with a pair of interconnected Split Ring Resonators. By using a pair of interconnected Split Ring Resonators, a new resonant mode adjacent to the origin mode is excited and a broadband characteristic is achieved. The bandwidth (VSWR

The emergence of location-aware mobile social networking applications (SNAs) has gained considerable prominence in ubiquitous computing. However, the weak designs of privacy protection result in more potential risks that users have to face. This paper presents a deep insight into the designs of privacy protection, especially from the perspective of location privacy. Three main potential risks and some necessary privacy-related functionality in current applications are analyzed and summarized. And with respect to the risks and weak protection methods, we propose the designs of privacy protection in LaMOC which is a location-aware mobile cooperation system developed by us. The designs include both the policy-based mechanisms and computational approaches to protect users' location privacy. Policy-based mechanisms enable users to fully control their locations disclosure while computational approaches can protect users' real locations from malicious attackers. The designs provide a reasonable level of privacy protection in location-aware mobile SNAs to some extent.

Photobiomodulation (PBM) is a modulation of monochromatic light or laser irradiation (LI) on biosystems, which stimulates or inhibits biological functions but does not result in irreducible damage. As photonic methods that could potentially initiate regeneration or cell proliferation in articular disease, the PBM of low intensity LI (LIL), ~10 mW/cm2, moderate intensity LI (MIL), 102~3 mW/cm2, and photodynamic effect (PDE) on articular cartilage repair have been reviewed in vitro and in vivo from the viewpoints of homeostatic regulation, respectively.

The random shape generation method is put forward based on adaptive neural networks. The adaptive neural network is trained from an arbitrary regular geometric shape during the random deformation process. Thus, the regular shape can be changed to an irregular one with the adaptive learning method, and the global and local controllability can both be enhanced. With an improvement on the traditional adaptive neural network algorithm, certainty and randomness can be fully combined, so that fuzzy controllability and adjustability can be dominated easily and concisely.