Earticle

Single-phase grid-connected inverters play an important role in small distributed generation (DG) systems. This paper illustrates the circuit configuration and operation principle of a novel single-phase, single-stage, three-switch, fly-back, buck-boost inverter. The equivalent circuits associated with the four operation modes are established for the charging and discharging process. The inverter can operate in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Most importantly, a new pulse generation method called pulse energy modulation (PEM) is proposed and applied to the three-switch buck-boost inverter in this paper. PEM signals for controlling the power switches are generated by meeting the output energy demand in each switching period with the stored energy in the coupled fly-back inductors. The duty ratio of PEM is thus determined by the energy demand and dc input voltage. The efficiency of the inverter used PEM is analyzed. A 400W experimental prototype is built in the laboratory to verify the operation of the proposed pulse energy modulation method. The inverter controller employs DSP dsPIC33FJ64MC506 for controlling, detecting and protecting functions. Experimental results have shown that PEM provides a new modulation mechanism for controlling the three-switch buck-boost inverter to inject a sinusoidal current into the grid under a wide range of operating conditions.

In the present work, an investigation has been made to study the effect of cutting parameters (speed, feed and depth of cut) on the multi-responses, Material Removal Rate (MRR) and Surface Roughness (Ra). The experiments were done on a conventional lathe using a tungsten carbide tool under dry environment. Twenty seven alternative combinations of speed, feed and depth of cut were considered (as per Taguchi’s standard L27 Orthogonal Array) for the machining of medium carbon steel EN8. For the optimization of multi-responses, the Multi-criteria decision making (MCDM) method, TOPSIS has been employed. Main effect plot for the Signal-to-Noise (S/N) ratios of the relative closeness coefficient (Ci+) was drawn using the MINITAB-16 software. From the TOPSIS and the main effect plot drawn for the relative closeness coefficient (Ci+), the optimal combination of the multi-responses were found at 27th alternative i.e. speed at 760 rpm, feed at 0.3 mm/rev and depth of cut at 1.5 mm respectively. The analysis of variance (ANOVA) has been done to know the influence of cutting parameters on the multi-responses. From the ANOVA results of the relative closeness coefficient (Ci+), it is found that the feed has high influence (F =41.08) followed by the depth of cut (F =25.78) and speed (F = 22.55).

In the photovoltaic micro-grid control system, delay and filter inductance change can influence system response speed, stability and grid-connected current distortion rate. Therefore, a power feed-forward dead-beat grid-connection control method for robustness prediction is proposed in this paper. The power feed-forward control is introduced therein to accelerate the system response speed, and the dead-beat control method for robustness prediction is proposed for the grid-connected current control in order to strengthen system robustness and reduce the grid-connected current distortion caused by control delay and inductance deviation. Specifically, Z-domain dead-beat control model with delay link is analyzed in this paper in order to discuss the influence of delay and inductance on system stability and accordingly provide the dead-beat control design method for robustness prediction as well as analyze the stability thereof according to the transfer function in Z-domain, thus to determine the control parameter scope. Moreover, the simulation experiment results have verified the effectiveness of the proposed control method.

With the development of network and storage technology, providing a shareable and convenient cloud storage service has become a major new application mode and development trend of internet, however, the system scale is huge and storage content is variable, so traditional performance evaluation and testing method are no suitable for cloud storage platform. This paper provides the thinking of performance evaluation of cloud storage system, sets up multiple-index 3D evaluation system facing different users and adaptable to different stages. It applies cloud testing with cloud scheme to test node visiting performance in different physical positions.

The most common problem associated with LED displays arises from reprogramming it. Most of off-the-shelf ones are somewhat inflexible in terms of updating the message instantly as well as having to re-update messages periodically through wired connection where the user is required to use a computer to change the displayed messages. In this article, an Android operating system controlled wireless dictated dot matrix display is designed and implemented. The proposed display eliminates the need to have a wired connection and requires only a smart phone to reprogram it.

Fingerprint-based recognition systems have been widely deployed in numerous civilian and government applications. However, the fingerprint recognition systems can be deceived by using an accurate imitation of a real fingerprint such as an artificially made fingerprint. In this paper, we propose a novel software-based fingerprint liveness detection algorithm based on gray level co-occurrence matrix (GLCM), from which we can calculate the texture features of fingerprint images and obtain satisfactory results. For the first time, we extract texture features by constructing four-direction GLCMs in an image, and then quantization operation and normalization operation are adopted. After these, we detected whether a fingerprint image belongs to a real fingerprint or an artificial replica of it. A trained RBF SVM (support vector machine) classifiers scheme is used to make the final live/spoof decision via training and testing feature vectors. The experimental results reveal that our proposed method can discriminate between live fingerprints and fake ones with high classification accuracy.

A structural vulnerability analysis of China mine power grid, which considering the particular of topological structure and the increase gas power generation nodes, is proposed based on complex network theory. According to transmission capacity of weighted network model, this paper analyses the network characteristics, including degree distribution, clustering coefficient and average path length, to prove that the mine power grid is a scale -free network. The node importance, node betweenness, edge weight and edge betweenness are regarded as the index of identification and the remaining load capacity after attack is chosen as evaluation index to analyze the structural vulnerability of mine power grid to have a fault simulation of the mine power grid before and after adding gas power generation nodes. The results of fault simulation show that the model is in line with the actual situation of the China mine power grid, and can better identify and assess the vulnerability of the mine power grid.

In recent years, cloud platforms have been widely applied in various areas to provide flexible service for users. However, how to evaluate the reliability of cloud platforms still remains a challenging issue because of its complexity and dynamical characteristic. In this paper, we present a novel reliability evaluation model which is aiming at providing a technique to accurately evaluate the reliability of virtualized cloud platforms. The proposed model is deprived from the classical tree-structure based reliability model and incorporates some new mechanisms to overcome the shortcomings of previous models. Extensive experiments are conducted to investigate the effectiveness of the proposed model. The results shown that, comparing with the existing approaches, the proposed model can significantly improve the accuracy of reliability evaluation, especially when the target cloud platform is in presence of intensive workloads.

GPU is the suitable equipment for accelerating computing-intensive applications in order to get the higher throughput for High Performance Computing (HPC). Sparse Matrix-Vector Multiplication (SpMV) is the core algorithm of HPC, so the SpMV’s throughput on GPU may affect the throughput on HPC platform. In the paper, we focus on the latency of reduction routine in SpMV included in CUSP, such as accessing shared memory and bank conflicting while multiple threads simultaneously accessing the same bank. We provide shuffle method to reduce the partial results instead of reducing in the shared memory in order to improve the throughput of SpMV on Kepler GPU. Experiments show that shuffle method can improve the throughput up to 9% of the original routine of SpMV in CUSP on average.

Computed Tomography (CT) has remained an important component of medical imaging since its inception. In general, it is preferred to keep the radiation dose as low as possible during the CT examinations to prevent patients as well as operators from the dangerous side effects of these radiations, which in an extreme case may lead to cancer. However, reducing the radiation dose leads to undesirable degradations which not only reduce the visual quality of CT images, but also make such images difficult to interpret in clinical routines. The most common degradations in low-dose CT images include blur, noise and low-contrast. Over the recent years, considerable research has been made to process these degradations. However, they still remain open for research due to the wide variety of challenges they offer. In this article, the causing factors of such degradations are addressed adequately. Furthermore, the challenges that face the processing of these degradations are mentioned in detail. Finally, this article is intended for researchers who are approaching this topic to understand the aforesaid issues extensively.

A SVD-Krylov method for large scale MIMO(multi-input multi-output) system model-order reduction is proposed in this paper. Its aim is to combined the singular value decomposition(SVD)and Krylov methods by retaining the best feature that can be applied for solving some problems for the large scale system model-order reduction. The method matches the first r Markov parameters and minimizes the error in the remaining ones in the least-squares sense. The reduced model is asymptotically stable, matches a certain number of moments, and minimizes a weighted error in the discrete time case. The effectiveness of the proposed approaches is tested by the Iss (international space station)model that in the SLICOT library, getting the frequency-response, the error and the error bounds of different order reduced model. The result shows that the proposed method is efficiently.

To reveal the mechanism of information platform service innovation in cloud computing environment, the hypothesis of the interactive relationship among cloud computing, service innovation middle variables, and service innovation performances was put forward in this thesis based on the investigation of relevant domestic and foreign literatures. The research chooses the information platform of logistics industry as an example, which was proceeded by constructing the structural equation model of the maximum likelihood estimate method with questionnaires about the logistics information platform in all provinces and municipalities. The result suggested that cloud computing can affect the service innovation performance of information platforms through its significant positive impacts on service concept innovation, service interface innovation and service delivery innovation, which can act as the theoretical foundation for the operation and development of the information platform.

With the widespread use of cloud platforms, their performance evaluation tools also have become the research hot spot of academic circle. So far, many performance evaluation tools of the cloud platform have been designed in their corresponding application scenarios, which have brought much convenience on the performance evaluation and management of the cloud platform. In order to predict the maximum number of virtual machines that can be opened by the cloud platform, this paper integrates the current tools of performance evaluation and proposes a performance evaluation tool based on IaaS cloud platform. The key of the performance evaluation tool is that it not only can evaluate the performance of the cloud platform, but also can predict the maximum number of virtual machines that can be opened by the cloud platform when the configuration of the virtual machine and the workload of each virtual machine have been known. This special performance evaluation tool has not been put forward now. And, the prediction model has been introduced into this tool in this paper that is the most important and core part. Lastly, to test the effectiveness of cloud platform performance evaluation tool proposed in this paper, some tests have been done on the IaaS cloud platform. According to the contrast results of the forecast error among models, establishing support vector machine and neural network as single forecasting model. The results show combined model can be chosen as the prediction model of cloud platform performance evaluation tool.

Data registration is a common operation in object digitalization. This paper proposes an algorithm for registering point cloud data with such quadratic surfaces as planes and cylinders. In the proposed algorithm, the variation of neighboring points’ normal vectors are utilized to detect data that is located at the intersection of different quadratic surfaces, which is then deleted from the point clouds. Next, region segmentation is done on remaining point clouds through the growth algorithm, and feature descriptors are created for each detected quadratic surface. Finally, rough registration of data is achieved via matching of feature descriptors, and then fine registration is achieved by optimizing rough registration results through the ICP algorithm. Experimental results show that the algorithm is insensitive to outliers, has low requirements on the original poses of data and that its registration success rate is higher than that of the original ICP algorithm.

We are in a society where availability of open courseware and countless internet-based online programmes are run by universities across the globe. The world is moving from the traditional face-to-face classroom teaching to a virtual classroom. There are concerns however; that this paradigm shift is limited by the understanding on what quality/standard is needed for a good e-learning resource. This concern has prompted the need to compare e-learning experiences in United States, South Africa and Nigeria so as to encourage developing countries to improve on this innovative approach to learning.

Building Information Modeling (BIM) is mainly being promoted and applied in civil and public building cost management, but it is seldom used in power construction industry. Electric power construction project involves many professionals and different types of buildings and structures. Coupled with Chinese specialized quantity calculation rules, these factors led to some obstacles encountered when it comes to the application of BIM. In this paper, a substation is used as the object of the study, Revit software is used to explore 5D modeling method and other problems related to cost. Especially, quantity statistics according to 2013 edition’s power quota rules is the most difficult, three solutions were provided and one particularly detailed. It can be concluded that as long as it achieves data transfer, BIM 5D technology can be used in the power construction industry and it will bring huge impact on power engineering cost.

Aiming at the reasonable configuration of virtual cluster and physical host, a new virtual machine cluster scheduling method is proposed. First of all, according to the resource requirements of the task, select the resource conditions similar to the virtual machine cluster. In the clustering process, the CPU, memory, communication bandwidth and other parameters are integrated in a measure under. Secondly, with the help of minimum flow and maximum cut theory, the virtual machine cluster is divided and configured to complete the scheduling process of virtual machine to the corresponding physical host. Experimental results show that the virtual machine cluster scheduling based on this new method makes the resource utilization of the physical host higher.

There are so many security risks for the users of cloud computing, but still the organizations are switching towards the cloud. The cloud provides data protection and a huge amount of memory usage remotely or virtually. The organization has not adopted the cloud computing completely due to some security issues. The research in cloud computing has more focus on privacy and security in the new categorization attack surface. User authentication is the additional overhead for the companies besides the management of availability of cloud services. This paper is based on the proposed model to provide central authentication technique so that secured access of resources can be provided to users instead of adopting some unordered user authentication techniques. The model is also implemented as a prototype.

Aiming at minimizing the total transmit power of relay nodes in the multiple peer-to-peer relay network in the presence of channel estimation error, a relay beamforming method based on Lorentz positive matrix is proposed. Firstly, assuming the channel state information of the second hop in the relay network is uncertain and the signal to noise ratios of the destination nodes are given, the expression of total relay nodes transmit power minimization optimization problem is deduced. Secondly, some real valued variables are defined and the concept of Lorentz cone is used to transform the optimization problem into a real valued problem. Finally, using the equivalent linear matrix inequality description of Lorentz positive matrices, the relay transmit power minimization problem is transformed into a real valued convex optimization problem. The proposed method overcomes the problem existing in the conventional robust relay beamforming methods based on semi definite relaxation technique, which sometimes yield solution matrix of with a rank greater than 1. Simulation results show that in the case of different relay nodes and channel error coefficients, the proposed method yields minimum relay transmit power in line with the results of the robust relay beamforming method based on semi definite relaxation technique, which validates the effectiveness of the proposed method.

A new task scheduling algorithm based on Hadoop is proposed to optimize scheduling of resources problems under the Distributed cloud-computing platforms. The core idea of the algorithm is full reference to the current network conditions and treat it as an important reference for system task scheduling, with the bandwidth management ability ,SDN architecture allows us to allocate bandwidth according to a time slot strategy, then according to the operation completed sooner or later the time to decide whether the task assigned to the local node or low load of non-local node .In this way, we will not only ensure the locality of the task from a global perspective , but also assign tasks in an optimal way to efficiently. In the end, we do experiments based on the scheduler to verify the quality of scheduling algorithm.

Global software development (GSD) has become a customary way of developing software whereas distributed agile software development is now gaining popularity. However, effectiveness of agile practices in GSD is a contradictory issue that needs to be explored in detail. The paper intends to investigate the effectiveness of agile practices in GSD. The research is conducted in two phases. Firstly, literature is explored to extract benefits and challenges of agile practices in GSD. Supporting practices, tools, and modifications to agile practices are also unearthed. Secondly, we have performed a survey to validate the outcome of literature review. We have identified 19 benefits and 14 challenges of distributed agile practices, and also discovered 16 supporting practices and various tools. The results of the literature review and survey both indicate that most of the agile practices can be adapted for distributed projects. Supplementary practices and tools further alleviate the incongruity between GSD and agile methods.

With Hadoop been widely used, job scheduling technology, as a key technology in Hadoop, has been developed rapidly. However, Hadoop's default scheduling algorithm Fair Scheduler when performing the task scheduler does not consider load balancing status of each node cluster system, leading to low efficiency great job. For defect fair share scheduling algorithm, and combined LATE scheduling algorithm, load balancing scheduling algorithm based on a fair share. Experimental results show that the fair share scheduling algorithm can be improved in the scheduling task when taking into account the situation of each node load balancing, improve the efficiency of large jobs.

To study the influence of woods on electric field distribution of 500kV EHV Transmission lines, the Solidworks software was applied to create the simplified model of 500kV transmission lines, and the ANSYS software based on finite-element method was applied to calculate space electric field intensity of transmission lines. This paper chooses the electric field intensity of transmission lines and span central cross section as the research object. The calculation result shows that the maximum electric field intensity is about 1808v/m without woods and 1916v/m with 12m high woods and 2055v/m with 16m high woods in the middle of the span cross section 20 meters high above the ground. Woods around transmission lines can distort the space electric field of lines, and the higher of woods, the larger of the maximum of electric field over the woods. And using the method of unmanned aerial vehicle (uav) carrying measuring instruments to measure the cases with woods and without wood, respectively, and compare which with the calculation results to find that results of analysis are in agreement with the experimental datas basicly.This paper studies the space electric field intensity distribution of transmission lines under different height and location of woods, such can provide preference for reasonable erection of 500kV EHV transmission lines.

Mobile wireless has detonated in popularity just of its simplicity, revolution in communication and Mobile computing has become very famous now days in reward of the services offered during the mobile communication and. Mobile computing has become the reality not the luxury. Mobile wireless market is increasing by leaps and bounds as Cell phones, mobile computing and communication devices have become very trendy because of their ease and portability. However, the use of such devices in this platform is accompanied by new security risks that must be recognized and addressed to protect the physical devices, the communication medium, and the information used. Security is key issue that needs to be considered. For this security protocols are proposed for different applications like Wireless Application Protocol, 802.11a etc. Most of them are based on the public and private key cryptography. The challenge for mobile network is in providing very large footprint of mobile services with high speed and security. In this paper, we have discussed security issues arising due to wireless networking of mobile computing in distributed systems. We discussed the operational model of mobile computing environment, and try to demonstrate proposed solutions. We also discuss security problems and mechanisms that can be applied one of three main components of mobile computing. The goal of paper is to point out some of the limitations, characteristics, applications and issues on security of mobile computing.

Group decision-making is a situation faced when individuals collectively make a choice from the alternatives before them. Aiming to the drawback that not all plans can be evaluated by a single expert during group decision-making process, a group decision-making method for dynamic cloud distribution is proposed in this paper based on cumulative prospect theory. First, experts and plans were divided into groups according to the classification rule, and plans were described with the cloud model. The expectation, the entropy and the super entropy decision matrix were structured respectively. Then, the maximum and minimum values in decision matrix were set as positive and negative reference points. The parameter values of cumulative cloud prospect were calculated and the synthesis prospect values of every group were obtained. Finally, the plans were sorted based on the mean of synthesis prospect values for every group, and illustrated by specific examples. The ranking results show that the proposed method is rationality and practicability. So the proposed method can be widely used in group decision-making of grouping scheme or grouping expert.

In view of traditional collaborative filtering recommendation does not take into account differences of dimension of user vector and value of evaluation, this paper proposed a collaborative filtering recommendation model based on normalization method. Before calculating the user’s or item’s similarity, the value of evaluation will be normalized to a range of specifications. Then the similarity of user vector will be calculated, and predictions and recommend will be made. The experimental results show that this model could accurately find similar neighbor users or items, and performances of prediction and recommendation have been largely improved.

In spite of the fact that it has been with us in some structure and under various names for a long time, the Internet of Things (IoT) is all of a sudden a thing. The capacity to associate, speak with, what's more, remotely deal with an endless number of arranged, mechanized gadgets through the Web is getting to be pervasive, from the manufacturing plant floor to the doctor's facility working space to the private storm cellar. The move from shut systems to big business IT systems to people in general Internet is quickening at a disturbing pace—and legitimately raising alerts about security. As we get to be progressively dependent on clever, interconnected gadgets in each part of our lives, how do we shield possibly billions of them from interruptions and obstruction that could trade off individual protection or undermine open security? There are numerous issues in security of Internet of Things (IOT) shouting out for arrangements, for example, RFID label security, remote security, system transmission security, protection assurance, data handling security. So in this paper we are covering the various security concerns that are cursing the IoT in different ways.

Eliminating noisy information and extracting information content from web pages are increasing to become an important research issue in information retrieval field. In this paper, we present an approach of information extraction based on Dom tree and weight value calculation, which contains the following steps, parse the web page to construct the Dom tree, extract the title and keywords, calculate the weight value and obtain the content. The experimental result shows that this method has the higher accuracy ratio by the various themes content extraction.

With the continuous expansion of the scale of distributed power generation，multi grid connected converters often prone to oscillation problems when parallel operation.In this paper,we study the equivalent circuit of parallel connection of multi grid connected converters , system response characteristics of voltage source and in-depth analysis of the causes of the parallel oscillation of the converters.This paper analyzes converter’s parallel complex vector model by complex vector and comes to a conclusion that power grid voltage feed-forward will produce strong coupling between converter so that cause oscillation parallel converters. In view of the above problems and the flow of the converter starting or the voltage fluctuation of the grid, we design a low feed forward method, that is to make the fundamental and the main sub components of the grid voltage forward without delay and for the relative high frequency components, the filter technology is used to attenuate, so as to achieve the maximum elimination of the feed-forward coupling between the converter, to prevent the occurrence of system oscillation. In order to verify the use of this paper, the theory of the parallel converter is applied in the field of MW level wind field. The experimental results prove the correctness of the theory.

This paper describes the different types of networks and standards used by cell phones. Here I discuss the evolution of cell network generations and the technical aspects attributed to each. On cell phone and mobile technology a brief background use in public, private and government health is reviewed. Main focus of this paper is how to use and introduction of different mobile networks. This paper is a research about the wireless network generation and technologies associated with each as well as standards of different cellular network. It is found that the necessary precautions equipment and related actions required to properly and safely seizing different phone equipment. It demonstrates the proper use the important safety equipment that assists investigators to safely and clearly seize mobile phone equipment. This paper also discuss the different imaging methodologies that exist using the latest cell phone forensic software and the pros and cons to each one as well as performs hands-on imaging scenarios utilizing several different tools.