Search

Microwave hyperspectral instruments represent one of the main atmospheric sounders of China's next-generation Fengyun meteorological satellites. In order to better apply microwave hyperspectral observations in the fields of atmospheric parameter retrieval and data assimilation, this paper analyzes the sensitivity of trace gases to five selected bandwidth channels using a radiative transfer model based on the simulated data of microwave hyperspectral radiances at 50–60 GHz. This method uses information entropy and a weighting function to select channels and analyze the impact of this on the retrieval accuracy of atmospheric profiles before and after channel selection. The experimental results show that channel selection can reduce the number of channels by approximately 74.05% while maintaining a large amount of information content, and this retrieval effect is significantly better than that of MWTS-III. After channel selection, the 10 MHz, 30 MHz, and 50 MHz bandwidths have the best retrieval results in the stratosphere, whole atmosphere, and troposphere, respectively. When considering the number of channels, computational scale, and retrieval results comprehensively, the channel selection method is effective. [ABSTRACT FROM AUTHOR]

Based on a mathematical model and empirical test, this paper explores the incentive of income for aspirations and its channels, forging links between theory and data. Results present evidence that income significantly inspires one's aspirations, and all conclusions still hold after overcoming the interference of potential endogenous issues. In terms of channels, the "aspirations window" (a set of similar perceivable individuals) and "bandwidth load" (the mental space to think, process problems, and come up with solutions) play the mediating role in the stimulation of money; that is, low incomes will make aspirations window narrower and bandwidth load heavier, which is a momentous force behind one's aspirations failure. This paper also enlightens income distribution and the construction of internal motivation mechanisms. [ABSTRACT FROM AUTHOR]

A ±45° linear-polarized cross-dipole with enhanced gain and isolation has been designed as an example for 5G applications in this paper. By adding stepped reflector and combined director, the isolation and radiation performance of the antenna can be improved significantly. According to the experimental results, the bandwidths with reflection coefficient lower than 10 dB in the low frequency band and high frequency band are 9.5% (3.2-3.52 GHz) and 17.5% (3.86-4.6 GHz), respectively. The dual band can cover 3.3-3.6 GHz and 4.4-4.5 GHz for 5G bands proposed by China's IMT propulsion group. Therefore, the proposed antenna can be widely used in wireless detection, transmission and communication. The isolation of low frequency band and high frequency band can reach above 26 dB and above 22 dB. The average gain is approximately 10.2 dBi in the low frequency band, but the other band is around 6.37 dBi. Compared with commonly used base station antennas, the proposed antenna has been dramatically improved in terms of size, bandwidth, and other electromagnetic properties. [ABSTRACT FROM AUTHOR]

This paper presents a four‐port design for multiple‐input and multiple‐output (MIMO) dual‐loop antennas in 5G C‐band access point applications. The dimensions of the design are 90 mm × 90 mm × 15 mm. It consists of four dual‐loop antennas, four feed lines, and a reflector. The design uses a phase difference of 90° among the antennas to improve the isolation. It was observed that a dual‐loop antenna with another nearby dual‐loop antenna generates two modes to form the bandwidths WRC 5G C‐band (3.4‐3.6 GHz) and China 5G C‐band (3.3‐3.8 GHz). A rectangular parasitic element placed in the middle of the four dual‐loop antennas enhances the antenna gain. The proposed design has a compact size, good gain, low cost, and easy manufacturing, and is a suitable candidate for practical applications. [ABSTRACT FROM AUTHOR]

Node evaluation is an important topic in electric power communication network studies. In the view of the problem of single connection weights and single evaluation index for node importance evaluation, the bandwidth and the distance of the electric power communication network is used for the network's weight to compute three evaluating indicators: compactness, node degree and node spread. We use the "fast search and finding of density peaks" method to evaluate the importance of the nodes in power communication network to support the planning of grid communications, and to carry out unsupervised classification when the nodes are divided into four fragile levels. This can effectively improve the unsupervised classification method. Actual data from a province in China is tested to verify the usefulness of this method in electric power communication network. [ABSTRACT FROM AUTHOR]

A new type of S-band multibeam klystron has been developed at the Institute of Electronics, Chinese Academy of Sciences, China. The main methods for obtaining wide bandwidth include a multibeam electron gun with 18 beams, a periodic permanent magnet focusing system, a wide-band bunching system and filter-load double-gap coupling-cavity output circuit. The design methods and experimental results are given in this paper. The test results show that this device has a peak power of 120-160 kW, a bandwidth of 10%, a gain of 41 dB, a beam voltage of 16 kV, a weight of 45 kg and a length of 700 mm. [ABSTRACT FROM AUTHOR]

The Internet industry in China is in a period of rapid development. The new businesses of Internet are springing up. As a result, bandwidth users want to improve the quality of the Internet. Interconnection between backbone networks is crucial to network quality. Therefore, the Chinese government is very concerned about the interconnection of backbone networks. This paper mainly analyzes the development status of the interconnection of China’s Internet backbone networks from the interconnection way between the backbone networks, we find out the main problems of the interconnection between the Internet backbone networks, such as the regional monopoly of backbone networks, the resource distribution is not balanced, and the existing interconnection system has raised the market power of the leading backbone network.We put forward corresponding countermeasures and suggestions for the existing problems of the backbone network interconnection. It is great significance to optimize of the interconnection quality of China’s Internet backbone network, improve interconnection efficiency of backbone networks and increase social welfare. [ABSTRACT FROM AUTHOR]

This paper presents results for delay and Doppler spread characterization in high-speed railway (HSR) hilly scenario. To investigate the propagation characteristics in this specific terrain, a measurement campaign is conducted along the "Guangzhou-Shenzhen" HSR in China. A wideband channel sounder with 40 MHz bandwidth is used to collect raw data at 2.4 GHz band. The delay spread and Doppler frequency features are analyzed based on measured data. It is found that there are abundant multipath components (MPCs) in this scenario. We present the relationship between the delay spreads and the transceiver distances. The measured route can be divided into four areas with different delay and Doppler characteristics. Finally, a tapped delay line (TDL) model is proposed to parameterize the channel responses in the HSR hilly environment, which is supposed to provide criterions for evaluations of the radio interface and development of wireless communication system. [ABSTRACT FROM AUTHOR]

Abstract: A smart power system demands a strong and self-healing communication system with greater capacity. In China, as the ultra high voltage transmission lines and large scale interconnected grids are expanding throughout the nation, disaster-tolerant communication network is essential for reliable system operation and control. In this paper, we propose a hybrid communication network utilizing both terrestrial and satellite links to improve the system reliability. The adaptive link selection protocol at network layer is developed to facilitate the network integrity. A modification of transport protocol over satellite communication is also proposed to better exploit the limited bandwidth resources. The performance analysis and field trial of the proposed scheme based on the practical network configuration in Sichuan power grid is thoroughly studied. The results showed a great bandwidth saving of satellite resources without loss of network integrity. [Copyright &y& Elsevier]

With the rapid development of wireless communication networks, the fourth generation (4G) has emerged to move beyond the limitations of the third generation (3G), with increased bandwidth, enhanced quality of services, and reduced costs of resources. In this paper, we discuss the key technologies of 4G and focus on surveying the ongoing research in 4G communications in China. The 4G technologies under investigation include multicarrier transmission, multiple antenna techniques, carrier aggregation, relays, cognitive radio, distributed antenna systems, network convergence, and network self-optimization. These technologies are the building blocks of 4G and contribute largely to the requirements of International Mobile Telecommunications Advanced (IMT-Advanced). For each technology, its benefits, research topics, and some existing approaches are examined. Finally, we briefly discuss the challenges and future research issues in 4G systems. [ABSTRACT FROM AUTHOR]

The uncertainty of wind power brings many challenges to the operation and control of power systems, especially for the joint operation of multiple wind farms. Therefore, the study of the joint probability density function (JPDF) of multiple wind farms plays a significant role in the operation and control of power systems with multiple wind farms. This research was innovative in two ways. One, an adaptive bandwidth improvement strategy was proposed. It replaced the traditional fixed bandwidth of multivariate nonparametric kernel density estimation (MNKDE) with an adaptive bandwidth. Two, based on the above strategy, an adaptive multi-variable non-parametric kernel density estimation (AMNKDE) approach was proposed and applied to the JPDF modeling for multiple wind farms. The specific steps of AMNKDE were as follows: First, the model of AMNKDE was constructed using the optimal bandwidth. Second, an optimal model of bandwidth based on Euclidean distance and maximum distance was constructed, and the comprehensive minimum of these distances was used as a measure of optimal bandwidth. Finally, the ordinal optimization (OO) algorithm was used to solve this model. The scenario results indicated that the overall fitness error of the AMNKDE method was 8.81% and 11.6% lower than that of the traditional MNKDE method and the Copula-based parameter estimation method, respectively. After replacing the modeling object the overall fitness error of the comprehensive Copula method increased by as much as 1.94 times that of AMNKDE. In summary, the proposed approach not only possesses higher accuracy and better applicability but also solved the local adaptability problem of the traditional MNKDE. [ABSTRACT FROM AUTHOR]

According to the concept of ecoclimatic factor's guarantee rate, this study purposes to quantitatively analyze the interdecadal changes of the four major vegetation transition zones in Northeast China based on the warmth index first developed by Kira and the humidity index put forward by Xu during the period 1961-2007. On this basis, the responses of the interdecadal changes of vegetation transition zones to climate were analyzed. The results indicated that latitudinal vegetation transition zones had been moving laggingly to higher latitude (shifting upwards in altitude) and that longitudinal vegetation transition zones had been shifting slowly toward humid area in the whole sequence, whereas the shifts were fluctuant in stages. The changes of vegetation transition zones of Northeast China expressed in distribution and bandwidth responded to climate change, not only in the whole sequence but also in stages. [ABSTRACT FROM AUTHOR]