Статьи журнала - International Journal of Wireless and Microwave Technologies
Все статьи: 454
Structure and Control of Flywheel Energy Converter
Статья научная
On the basis of the flywheel energy converter’s structure in wind power turbine, we have used permanent-magnet synchronism motor as energy converter and built mathematical model. We have studied and realized control method of wind power turbine’s constant output power. By analyzing the mathematical model, we have concluded that the needed time of stored energy is three times longer than constant torque control time, and the needed motor power is one second of constant torque control. When flywheel starts from zero speed to basic speed ([(ω_max)/5]), the constant torque control method will be acquired. When flywheel speeds up between [(ω_max)/5] and ω_max , the amplitude power control will be acquired. What we have studied is very important to realize constant output power.
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Study of 2457 MHz WIFI Network Signal Strength at Indoor and Outdoor Enviroment
Статья научная
This paper presents a study of free space path loss of WIFI network using Cell Info Lite App and WIFI analyzer tool. This paper focuses on experimental tests by using WIFI router, mobile phones to measure and analyze the loss of signal strength over distance from 0 meter to 9 meter. The result of Free Space Path Loss (FSPL) for frequency 2457 MHz shows that the longer the distance, the worse the signal get. In addition, the experiment test indoor and outdoor was done analyse. The results of the comparison conclude that the signal strength becomes weak can affect by distance and obstacles such as door, wall. Signal strength also can say from colors which is when the measurement result shows green color is strong signal while orange color is weak signal and red color is bad signal. When the signal strength become weak Wi-Fi analyzer was displayed green zone to red zone. The paper purpose showed that where the area have a stronger/weaker connection in a house environment.
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Study on Quality Evaluation System for University Students
Статья научная
From the qualitative and quantitative perspectives, by use of modern educational philosophy and statistics evaluation theory, this thesis makes study on the theory for university students’ comprehensive quality evaluation. It makes careful analysis on the students’ daily life according to their characters, and makes scientific classification after picking up the main aspects, and then, combining the design principle of indictor system and hierarchic method, it establishes scientific and reasonable comprehensive quality evaluation indicator system for university students, which is easy to operate and meets the demand of the age. So the system can measure and evaluate the comprehensive quality of university students in a more scientific and objective way. Meanwhile, this thesis puts forward effective methods for university students’ comprehensive quality evaluation under new situations.
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Study on Replica Strategy in the Grid Environment
Статья научная
An effective replica management method can save bandwidth, reduce latency, balance load, and improve system reliability. A comprehensive scheme is introduced to manage replica for the grid environment. The schemes of replica creation and placement based on the frequency of visits and storage space, replica replacement based on the replica value, and replica selection based on comprehensive performance are proposed. Our scheme can achieve optimization of data distribution and replication, improve the efficiency of data visits in the grid environment.
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Study on System Architecture Design of University Students Quality Evaluation
Статья научная
In order to improve the comprehensive qualities of students in all respects, fully reflect and evaluate the achievements of students, inspire students to improve themselves unceasingly, encourage them to strive to be the best, develop their personalities and strive for truth and innovation, as well as achieve the institutionalization, standardization and scientificalness of students management work gradually, meanwhile, along with the development of university construction and students management, maintenance and management of students' data information has been exceptionally heavy, so it cries out for a set of reasonable and convenient students quality evaluation system. Students' quality evaluation system is designed to make better use of computer technology in managing and inquiring about total performance of students' qualities. Through analysis of the objective of system construction, combining design principle of the system, this thesis analyses and designs the quality evaluation system architecture from the perspectives of architecture, function module and security model.
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Study on Thickness Calculation Method for Undigraph
Статья научная
How to solve the thickness of general graph is an unsolved problem and one of many difficult problems in graph theory. This paper studies the method for calculating the thickness of undigraph and proposes formula and concrete method for calculating the thickness of undigraph G. Meanwhile, method is proposed for testing whether division of side-derived subgraphs is correct. Some instances presented in this paper aims at illustrating the actual application and correctness of calculation of this method for reference.
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Study on the Distribution of Networked Devices’ Clock Skew
Статья научная
Clock skews of devices on the Internet are viewed as one way delay noise, but their distribution is unknown. We explore the distribution of clock skews to see the conflict probability. In this paper, we introduce an accurate clock skew estimation algorithm to filter inaccurate clock skew estimation by comparing the results between linear programming method and least square fitting. Delay jitter and other noises affect the estimation result. When the difference of two methods is large, the estimation result is unstable and inaccurate, so the estimation result should be dropped. Based on this algorithm, we use traces of real Internet measurements to collect 1825 accurate clock skews of different devices to establish a fingerprint database. Furthermore, we show the distribution of clock skews and comparing conflict probability with different number of devices. The distribution shows that clock skews are diverse, and most of clock skews are in the region of [-100, 100] PPM. The results indicate that when the number of devices is small (<5), clock skews won’t be conflict with each other, so clock skews are good tools to detect faked devices or NAT; When the number of devices increases, the conflict probability increases linearly, so clock skews of different devices can not distinguish each devices effectively.
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Supporting Audio Privacy-aware Services in Emerging IoT Environment
Статья научная
The increasing exploration of smart space voice assistants and audio monitoring IoT devices leads to significant trust and privacy concerns. Among them, some of the data are sensitive and a user may not aware of when and where audio recordings are sent for processing. This provides burning questions- how do users gain knowledge of, and control the amount of data captured in the physical world. Moreover, the sending and processing of these sensitive data to the far cloud do not provide an efficient solution for sensitive data which causes serious privacy and security concerns. In this paper, a new architecture for providing audio transparency and privacy in the IoT-rich environment is proposed. The proposed privacy enforcement module is used to operate within a nearby fog node, which situated close to the data sources and enforces privacy according to the data owner's desire. To show the effectiveness of the proposed architecture, a well-known privacy threat framework is investigated.
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Survey on 5G and Future 6G Access Networks for IoT Applications
Статья научная
This paper comprehensively reviews the recent 5G and future 6G Internet of Things (IoT) protocols/standards, applications, and access networks used. First, most of the IoT protocols/standards and application scenarios are summarized in the form of tables, pictures, and diagrams to facilitate readers to understand and compare current and future Internet of Things technologies more easily and quickly. Second, the terrestrial and aerial radio access networks are analyzed and discussed in detail. The evolution of 5G terrestrial access networks is briefly described and its performance limitations are quantitatively analyzed and discussed. When the operating frequency reaches the sub-millimeter wave band, the terrestrial radio access network will deal with high path loss caused by weather factors, such as oxygen and water vapor absorption in the atmosphere, rainfall, and cloud/fog attenuation. The development of aerial radio access networks is preparing for 6G IoT to solve the coverage and path loss issues. In this survey, the aerial radio access architectures and infrastructure are also surveyed. This survey aims to guide readers to better understand the technical status of 5G IoT and the milestones as well as key performance indicators that need to be reached for 6G IoT in the future.
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TCP/IP Jumbo Frames Network Performance Evaluation on A Test-bed Infrastructure
Статья научная
Enhancing network performance has been studied by a number of researchers. The need to provide greater throughput on network infrastructure has been the key driver for these studies. The use of jumbo frames is considered one of the methodologies that can be employed to increase data throughput on networks. In this research undertaking, the authors implement jumbo frames on a test-bed implemented with Windows Server 2003/2008 networks and performance related metrics are measured for both IPv4 and IPv6 implementations. The results obtained in this empirical study shows that performance metrics values are different in various scenarios.
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The Application of Federated Kalman Filtering in SINS/GPS/CNS Intergrated Navigation System
Статья научная
Federated filter was an important method to estimate high-precision navigation parameters based on “SINS/GPS/CNS”. A no-feedback federated filter with UD_UKF algorithm was designed in the paper, a three-time amendment scheme to correct navigation parameters was designed at the same time and the mathematical model of SINS/GPS/CNS was established in launch inertial coordinate system too. The paper discussed the simulation conditions and a lot of simulations were carried out to compare 2 aspects: (1)the performance between four navigation mode, which respectively is SINS, SINS/GPS, SINS/CNS, SINS/GPS/CNS;(2)the estimate precision of federated filter and that of centralized Kalman filter. The results of simulation showed that the designed federated filter and amendment scheme based on SINS/GPS/CNS had high estimate precision and led to gain high hitting precision of ballistic missile, that is to say position errors were less than 20 meter and velocity errors were less than 0.1m/s in simulation.
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The Channels and Demands Analysis for Chinese Farmers’ Agricultural Information Acquisition
Статья научная
This paper studies the characteristics of information sources and farmers’ demand for agricultural information in the process of agricultural informationization in China. We point out that it is not common for farmers to adopt modern information technology communication tools in rural areas nowadays, and the reason for this phenomenon is that farmers still rely mainly on traditional channels for information dissemination. To change the status quo, our government should respect farmers as dominant statuses in the process of agricultural informationization and encourage households with large-scale agricultural operation to use modern IT products in order to spread agricultural information in rural areas.
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The Comparison of Machine Learning Algorithms on Online Classification of Network Flows
Статья научная
Online classification of network flows is a process that captures packets generated by network applications and identifies types of network applications (or flows) in real time. There are three key issues about online classification: observation window size, feature selection, and classification algorithms. In this paper, by collecting five types of typical network flow data as the experiment sample data, the authors found observation window size 7 is the best for the sample data and most classifiers. The authors proposed a full feature set based on the standard feature set which reflects statistical features of network flows. Using five commonly used feature selection methods, the authors identified the most effective features could be reduced from 56 original features to 11 effective features. Lastly, according to special need for online classification, the authors studied 11 different classifiers on their classification accuracy, model construction time, and classification speed. The results show that C4.5 and JRip are the two best algorithms for online classification.
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The Economic Evaluation of Lighting Energy-saving Modification Program
Статья научная
Many lighting energy-saving modification programs have the embarrassment of uneconomical. This paper takes into account economic evaluation to solve the problem. According to illuminative equipments price, life span and power consumption, the optimal program will be found under the limited investment. Firstly, the benefit ratio will be used to evaluate on the equipments modification necessity, and get the modification sequence. If the biggest benefit ratio is in different equipment simultaneously, the better one will be selected in terms of relative investment recovery period. The relative remaining time is innovatively introduced into economic evaluation for determining the equipments modification locations. Then the system operation flowchart is to prove that the scheme is workable.
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The Empirical Study on the Relationship between Knowledge Integration and IT Project Performance
Статья научная
This article examines the relationship between timely project completion and the management’s integrative capability. Measures of the integrative capability are used to predict on-time project completion, where completion is a function of the duration of IT-related project delays. In a longitudinal study of 74 enterprise application integration projects in the medical sector, integrative capability was measured from the point of view of the CIO and a facility IT manager. Accounting for several project controls, our Cox regression results indicate both integrative dimensions significantly mitigate the duration of IT-related project delays, thus promoting timely project completion. The analysis also reveals the importance of taking management structure into consideration when studying IT phenomena in networked organizations.
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The Existence of Homoclinic Solutions for Second Order Hamiltonian System
Статья научная
The research of homoclinic orbits for Hamiltonian system is a classical problem, it has valuable applications in celestial mechanics, plasma physis, and biological engineering. For example, homoclinic orbits rupture can yield chaos lead to more complex dynamics behaviour. This paper studies the existence of homoclinic solutions for a class of second order Hamiltonian system, we will prove this system exists at least one nontrivial homoclinic solution.
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Статья научная
Cyber security is of topical concern in the computing industry and in organizations that require ICT infrastructure for business-related activities. Theft or disrupting the flow of data and information can cause devastating damage to an institution’s reputation and this may lead to huge financial losses. More mayhem can be perpetrated by malicious codes such as worms to organizations that use wireless sensor networks for collecting and transmitting data and information. To tackle this issue of cyber security, researchers have used epidemiological models (such as SEIR and SEIR-V) to gain insight into malicious code propagation. However, topological concerns and its impact in worm propagation haven’t been thoroughly studied. Here, we modify older models by applying a different expression for sensor deployment area; we intend to highlight the spatial parameters that may allow for the extinction of worms in wireless sensor networks amidst countermeasures deployed by network managers.
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The Research and Application of Webpage Temper-proofing System
Статья научная
With the sharp increase of hacking attacks over the last couple of years, web application security has become a key concern. The attack to websites, especially the explosion of webpage interpolating incidents has become one of the most serious problems of it. In this paper, the system adopts Web server core embedded technology to imbed tamper detection module and application protection module into the Web server, define corresponding strategies for temper-proofing, and realize the real-time monitoring and protection of web pages and the dynamic content in databases.
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The Research of On-line Monitoring System of Power Cable Joint Temperature
Статья научная
Power cable joint is the weak link of power system’s safe operation, it is important significance to real-time master the operating temperature of power cable joint for the safety of the power system. This paper adopts wireless technology to design the temperature monitoring system of power cable joint. Monitoring terminal collection temperature data located in each power cable joint collects the measured data in the cable branch box through the near distance micro-consumption electronic wireless technology to data concentrators located at the bottom of the cable branch box, then transmits to the monitoring center through CAN bus network. The system realizes the low cost and on-line reliable monitoring of power cable point temperature of the urban cable branch box.
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The Selective Forwarding Attack in Sensor Networks: Detections and Countermeasures
Статья научная
Sensor networks are becoming closer towards wide-spread deployment so security issues become a vital concern. Selective forwarding attack is one of the harmful attacks against sensor networks and can affect the whole sensor network communication. The variety of defense approaches against selective forwarding attack is overwhelming. In this paper we have described all the existing defensive schemes according to our best knowledge against this attack along with their drawbacks, thus providing researchers a better understanding of the attack and current solution space. This paper also classifies proposed schemes according to their nature and defense. Nature of scheme classifies into Distributed and Centralized. Defense of scheme classifies into detection and prevention.
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