bluuebunny/crossref_metadata_2025 huggingface dataset:
Time and frequency synchronisation scheme for orthogonal frequency division multiplexing‐based cooperative systems
Authors: Guo Yi , Liu Gang , Ge Jianhua , Ding Haiyang
Published: October 2013

In the cooperative relay system, different frames from different relays are not aligned in the time domain, and have different carrier frequency offsets (CFOs). Estimation of these timing offsets and CFOs is a crucial and challenging task. In this study, a new training structure is proposed, and a novel time and frequency synchronisation scheme is presented for orthogonal frequency division multiplexing‐based (OFDM‐based) cooperative systems. The coarse time synchronisation is accomplished by using the symmetric conjugate of the training symbol and the fine time synchronisation is accomplished by segment‐moving correlation. The fractional frequency offset is estimated by using the phase difference of the received signal and the integral frequency offset is estimated by utilising the good autocorrelation of the training symbol in frequency domain. The analysis and the simulation results show that, compared with the traditional scheme, the proposed scheme has better timing and frequency offset estimation performance and lower complexity for OFDM‐based cooperative systems.
Robust algorithm for high‐dynamic and low‐signal‐to‐noise ratio signal reception in deep space communications
Authors: Ruyuan Zhang , Yafeng Zhan , Xiaojie Dai , Yukui Pei , Jianhua Lu
Published: October 2013

In deep space communications, the received signals are always highly dynamic and very weak, which makes it quite challenging to achieve reliable data reception. To tackle these problems, a robust algorithm which joins tracking and code‐aided synchronisation is proposed in this study. The frequency lock loop‐assisted phase lock loop is used as the tracking loop, which integrates the characteristics of both outstanding dynamic performance and precise measurement. The code‐aided synchronisation is adopted as the demodulation and decoding loop, which utilises the relationship among the coded symbols to assist signal demodulation under the low signal‐to‐noise ratio condition. It is worth pointing out that the power tradeoff between the main carrier and subcarrier signals which operate in the two loops mentioned above is also optimised to minimise the total transmitting power. Simulation results showed that the proposed scheme with code rate 1/5 low‐density parity‐check codes could almost eliminate the effect of these factors, with the excellent performance, which closely approximates the ideal decoder in additive white Gaussian noise channel.
Capacity of generalised network multiple‐input–multiple‐output systems with multicell cooperation
Authors: Pan Peng , Zhang Youguang , Ju Xiaojie , Yang Lie‐Liang
Published: October 2013

In network multiple‐input–multiple‐output (MIMO) systems, cooperative base stations (BSs) and mobile terminals (MTs) are in general at different geographic locations. Correspondingly, the channel gains with respect to different BSs and/or MTs may obey different distributions, which resulted from, different pathlosses, different strength of line‐of‐sight (LOS) components and so on. Furthermore, future wireless communication systems are expected to be equipped with multiple antennas for transmission/receiving. In these multiantenna systems, signals received by the antennas of one BS from one MT may be correlated. Against the above‐mentioned scenarios, in this contribution, the authors study the capacity of the generalised uplink network MIMO systems with multicell cooperation (MCoP), when propagation pathlosses, fast Rician fading with various LOS components and spatial correlation are simultaneously considered. Specifically, the theory of operator‐valued free probability is introduced to derive the approximate eigenvalue distribution (AED) of the correlation matrix of the equivalent channels. Based on the AED, the approximate capacity of uplink network MIMO systems is then studied. Furthermore, a range of special cases are analysed by specialise the authors model and modifying their results. Finally, both numerical and simulation results are provided for characterising the capacity of network MIMO systems with MCoP.
Energy‐efficient adaptive power allocation in orthogonal frequency division multiplexing‐based amplify‐and‐forward relay link
Authors: Chen Yu , Fang Xuming , Zhao Yue
Published: October 2013

Recently, improving energy efficiency has been a new tendency in wireless relay communication. However, the introduction of relay technology may increase the system capacity, but is often followed by a more severe energy‐efficiency problem when compared with traditional single‐hop system. In this study, based on orthogonal frequency division multiplexing‐based frequency‐selective channel of amplify‐and‐forward relay link, a suboptimal two‐step power allocation algorithm of subcarriers is proposed to maximise the energy efficiency. The proposal includes two steps. First, a suboptimal subcarrier matching is achieved for introducing a virtual direct link, which may reduce the dimensionality of the power allocation. Second, the allocation problem of relay network is simplified as that in traditional cellular network. Thus, the optimal power allocation of virtual direct link can be obtained by one‐dimensional search method. Furthermore, the effects of rate and power constraints on the energy‐efficiency problem are analysed. Simulation shows that the suboptimal solution of the proposed algorithm is very close to the optimal solution, and the proposed energy efficient power allocation method can achieve the highest energy efficiency, compared with the rate adaptive and margin adaptive optimisations.
Indirect iterative learning control for robot manipulator with non‐Gaussian disturbances
Authors: Chen Haiyong , Xing Guansheng , Sun Hexu , Wang Hong
Published: October 2013

In this study, a novel indirect iterative learning control (ILC) strategy is presented for a robotic manipulator that performs repeat operation and is also subjected to non‐Gaussian disturbances. The performance index about the entropy of tracking error and the related optimisation method are used to update the local parameters of controller between any two adjacent batches. Moreover, the entropy is employed as it is a unified probabilistic measure of uncertainty quantification regardless whether the random disturbances are Gaussian distribution or not. Thus, an innovative performance index about tracking error entropy that represents the relationship between the entropy of error and controller gains is proposed in order to obtain the controller which can drive the uncertainty of output error as small as possible with the increase of the batch number. Then the non‐linear stochastic optimal method is presented so as to obtain updated gains for the next batch. Stability of closed‐loop system is analysed. Finally, a comparison between a classic ILC and the proposed approach is given. Moreover, the effectiveness and feasibility of the proposed control schemes is verified by some simulation results of robotic trajectory tracking.
Output‐feedback model predictive controller for voltage regulation of a DC/DC converter
Authors: Kim Seok‐Kyoon , Kim Jung‐Su , Park Chang Reung , Lee Young Il
Published: October 2013

In this study, an output‐feedback model predictive controller (MPC) is presented for capacitor voltage regulation on the basis of a non‐linear DC/DC converter. The proposed output‐feedback MPC scheme is constructed by combining a state‐feedback MPC scheme with a Luenberger‐type observer. The proposed MPC does not carry out any online optimisation. Although the converter model is non‐linear, the proposed observer gain ensures global exponential convergence of the state estimation errors. On the basis of this observer, an output‐feedback MPC scheme is designed by certainty equivalence. It is also shown that the capacitor voltage globally converges to its reference while fulfilling input constraints. In order to eliminate the capacitor voltage offset error, a PI controller is employed in the outer loop. The experiment results demonstrate that the closed‐loop performance is satisfactory despite the load resistance variations.
Finite‐time fault tolerant attitude control for over‐activated spacecraft subject to actuator misalignment and faults
Authors: Zhang Aihua , Hu Qinglei , Friswell Michael I.
Published: October 2013

A finite‐time attitude compensation control scheme is developed for an over‐activated rigid spacecraft subject to actuator faults, misalignment, external disturbances and uncertain inertia parameters. The controller is synthesised based on the sliding mode control theory, and guarantees the finite‐time reachability of the system states. A sufficient condition for the controller to accommodate misalignment and faults of actuator is presented. An optimised control allocation algorithm based on the Karush–Kuhn–Tucker condition is then applied to distribute the commanded control to each actuator, and optimise the consumption of energy. Numerical simulation results are presented that highlight the performance benefits of the control law.
LMI‐based H∞ control for linear singular discrete systems: a novel method
Authors: Dong Xin‐Zhuang
Published: October 2013

This study investigates the problem of state feedback H∞ control for linear singular discrete systems. First, a novel admissibility condition and then a new bounded real lemma are proposed for linear singular discrete systems. Then, the existence condition and explicit expression of a desirable state feedback H∞ controller are obtained based on the above results. It should be pointed out that all the conditions in this study are necessary and sufficient and in the form of strict linear matrix inequalities that can be solved easily. Finally, some numerical examples are provided to illustrate the effectiveness of the theoretical results in this study.
Asynchronous stabilisation of impulsive switched systems
Authors: Wang Bo , Zhang Hongbin , Xie Dehua , Wang Gang , Dang Chuangyin
Published: October 2013

In this study, the authors mainly deal with the asynchronous stabilisation problem for a class of continuous‐time impulsive switched systems. By using multiple Lyapunov functions combined with mode‐dependent average dwell time, the exponential stability sufficient condition of closed‐loop systems is derived. Based on the stability result, the problem of asynchronous stabilisation is solved under a proper control law. Moreover, the stability and stabilisation results are formulated in the form of linear matrix inequalities that are numerical feasible. Finally, an illustrative numerical example is presented to show the effectiveness of the obtained results.
Fault diagnosis for non‐linear single output systems based on adaptive high‐gain observer
Authors: Li Xiao‐Jian , Yang Guang‐Hong
Published: October 2013

This study deals with the fault diagnosis (FD) problem for affine non‐linear systems with single output. Under a well‐defined persistent excitation condition including m time delays, m parallel coupled adaptive high‐gain FD observers have been designed in some existing literature based on Lyapunov function approach. By employing Lyapunov–Krasovskiii functional approach, this study presents an alternative algorithm to design a simplified FD observer with global exponential convergence, which drastically reduces the complexity of the existing FD systems. A simulation example about a single‐link robot arm is provided to illustrate the proposed theoretical results.
Asynchronous algorithms for distributed optimisation and application to distributed regression with robustness to outliers
Authors: Liu Weikai , Hua Zeng
Published: October 2013

This study presents an asynchronous algorithm for distributed constrained optimisation problems in networks of agents. The iterative optimisation algorithm maintains a local estimate at each node and depends on local gradient or gradient‐like updates in combination with a consensus policy, where an agent averages its own value with a current or outdated value of another. This asynchronous scheme does not require that agents exchange state information frequently, so it is more energy‐efficient and more realistic than the synchronous one. Moreover, the proposed algorithm is fully distributed, that is, all agents only share data with their neighbours through local broadcasts. The proposed algorithm is applied to a distributed regression problem with robustness to outliers in sensor networks. Simulation results are provided to demonstrate the validity and superiority of the proposed scheme.
Single colour one‐shot scan using modified Penrose tiling pattern
Authors: Kawasaki Hiroshi , Masuyama Hitoshi , Sagawa Ryusuke , Furukawa Ryo
Published: October 2013

In this study, the authors propose a new technique to achieve one‐shot scan using single colour and static pattern projector; such a method is ideal for acquisition of moving objects. Since projector–camera systems generally have uncertainties on retrieving correspondences between the captured image and the projected pattern, many solutions have been proposed. Especially for one‐shot scan, which means that only a single image is required for shape reconstruction, positional information of a pixel of the projected pattern should be encoded by spatial and/or colour information. Although colour information is frequently used for encoding, it is severely affected by texture and material of the object and leads unstable reconstruction. In this study, the authors propose a technique to solve the problem by using geometrically unique pattern only with black and white colour that further considers the shape distortion by surface orientation of the shape. The authors technique successfully acquires high‐precision one‐shot scan with an actual system.
Multi‐objective optimal thyristor controlled series compensator installation strategy for transmission system loadability enhancement
Authors: Chang Ya‐Chin
Published: October 2013

Owing to the continuously increased electricity demands and power transactions, power systems are becoming more vulnerable to insecurity, generally incurred by overutilised transmission facilities or any contingency. In order for existing transmission networks to accommodate more power transfers with less network expansion cost, proper installation of thyristor controlled series compensator (TCSC) is validated to be one of the most ‘promising options’. The multi‐objective optimal TCSC installation strategy proposed in the study first applies the performance index sensitivity factor technique to investigate which lines are most necessary for TCSC installation and with the lines specified for TCSC installation and the multi‐objective function consisting of maximum system loadability and minimum TCSC installation cost, the problem to determine the capacity for each TCSC installation is then formulated as a multi‐objective optimisation problem and solved by using the fitness sharing multi‐objective particle swarm optimisation method. Finally, in the Pareto front set obtained, the solution with the TCSC installations that can make the power system provide the required loadability with biggest utilisation index value is recommended. The modified IEEE‐14 buses, IEEE‐118 buses systems and a practical power system are used to validate the performance of the proposed method.
DC corrective optimal power flow based on generator and branch outages modelled as fictitious nodal injections
Authors: Martínez‐Lacañina Pedro Jose , Martínez‐Ramos José Luis , de la Villa‐Jaén Antonio , Marano‐Marcolini Alejandro
Published: October 2013

This study deals with a new formulation for the direct current corrective optimal power flow. The formulation is based on the outage of generators and/or branches modelled as fictitious injections of active power. By including that fictitious injections in the optimisation problem, the injections are adjusted to the post‐contingency state as a consequence of the corrective actions carried out to bring the system back to its normal state. So, when the analysis of contingencies is performed, the classical topological analysis and the subsequent analyses are avoided with this approach. This new formulation uses the sensitivity matrix between branch power flows and powers injected in a power system. An important feature of this matrix is to remain constant during the contingency analysis performed for the generation‐load scenario (base case) of each period of time to be analysed. The approach proposed is illustrated in the IEEE‐RTS of 24 buses. The results obtained in this distribution network demonstrate that the proposed methodology can assess the impact of contingencies with an acceptable accuracy and a short computation time.
Comparison of fractal coding methods for medical image compression
Authors: Bhavani Sridharan , Thanushkodi Kepanna Gowder
Published: October 2013

In this study, the performance of fractal‐based coding algorithms such as standard fractal coding, quasi‐lossless fractal coding and improved quasi‐lossless fractal coding are evaluated by investigating their ability to compress magnetic resonance images (MRIs) based on compression ratio, peak signal‐to‐noise ratio and encoding time. For this purpose, MRI head scan test sets of 512 × 512 pixels have been used. A novel quasi‐lossless fractal coding scheme, which preserves important feature‐rich portions of the medical image, such as domain blocks and generates the remaining part of the image from it, has been proposed using fractal transformations. One of the biggest tasks in fractal image compression is reduction of encoding computation time. A machine learning‐based model is used for reducing the encoding time and also for improving the performance of the quasi‐lossless fractal coding scheme. The results show a better performance of improved quasi‐lossless fractal compression method. The quasi‐lossless and improved quasi‐lossless fractal coding algorithms are found to outperform standard fractal coding thereby proving the possibility of using fractal‐based image compression algorithms for medical image compression. The proposed algorithm allows significant reduction of encoding time and also improvement in the compression ratio.
Reversible data hiding based on two‐dimensional prediction errors
Authors: Wang Shyh‐Yih , Li Chun‐Yi , Kuo Wen‐Chung
Published: October 2013

The conventional histogram‐based reversible data‐hiding scheme is one‐dimensional (1D). In this article, a novel framework that can be used to design 2D reversible data‐hiding schemes is presented. Through the flexibility of selecting peaks for each channel, this 2D technique offers higher embedding performance than the conventional 1D techniques. For illustration, the framework is applied to develop two new schemes, C‐2D and S‐2D. Compared with the 1D schemes that use the predictions individually, the experimental results show that C‐2D and S‐2D have apparent performance advantages. This framework can be applied to any architecture. Furthermore, it can be easily extended into a multi‐dimensional framework. By combining appropriate prediction methods, more reversible data‐hiding schemes can be derived.
Performance analysis of hierarchical transform coding with a large kernel for video codecs
Authors: Lee Bumshik , Kim Munchurl , Kim Hui Yong , Choi Jin Soo
Published: October 2013

In this study, the performance of hierarchical transform coding is analysed with design of an order‐16 integer transform kernel. The proposed hierarchical transform‐coding structure is constructed with a set of 4 × 4, 8 × 8 and 16 × 16 integer transforms of variable transform block sizes, which takes the advantages of both lower and higher transform kernels by flexibly adapting to varying image characteristics of video sequences with homogeneous and complex regions. The proposed hierarchical transform‐coding structure is implemented as an extension to H.264/advanced video coding joint model. The authors show the effectiveness of the hierarchical variable‐sized block transform scheme by analysing the quantisation effects and the correlation among neighbouring pixels in video sequences of different spatial resolutions. The experimental results show that: (i) the variable‐sized block transform scheme with the hierarchical structure is advantageous to the texture regions with strong local edges and (ii) the higher‐order‐16 integer transform kernel itself is more effective for the homogeneous texture regions, which are often encountered in higher resolution sequences. Therefore these two features can complementarily work in an rate‐distortion (RD) optimised manner for various characteristics of the input signals.
Fine logarithmic adaptive soft morphological algorithm for synthetic aperture radar image segmentation
Authors: Koosha Mohaddeseh , Hajsadeghi Khosrow , Koosha Mohammad
Published: October 2013

Synthetic aperture radar (SAR) appropriate image processing in conjunction with noise reduction is crucial in proper image segmentation. The authors present a new algorithm, logarithmic adaptive soft morphological (LASM) filter, utilising collectivity and flexibility of order‐statistic soft morphological filters. This method not only reduces the speckle noise of the single‐look SAR imagery considerably, but it significantly enhances the segmentation results. To verify the performance, a simulated SAR image is first created by applying an imagery method to an original noiseless image. The resulting image has characteristics identical to a real SAR image. The LASM method, as well as several well‐known and state‐of‐the‐art filtering algorithms, is then applied to the image to filter out the speckles. The LASM filtered results are then compared with other results by evaluating them against the original image. Some of these methods are also applied to a real SAR image and the results are also compared. Segmentation is then applied to the filtered images and the results are used as a deterministic evaluation metric. The results show marked improvement using the LASM processing the amplitude images compared with well‐known methods, whereas the superiority of LASM algorithm is even more pronounced in processing the intensity images.
Colour edge detection based on the fusion of hue component and principal component analysis
Authors: Lei Tao , Fan Yangyu , Wang Yi
Published: October 2013

Hue component is generally denoted by angle value, so the conventional edge detection operators are incapable to accurately detect edges of hue component. As a result, the popular methods of colour image edge detection usually omit the role of hue component, thus missing some edges caused by hue changes. The authors propose a novel colour edge detection method based on the fusion of hue component and principal component analysis to solve the above problems. First, a novel computational method of hue difference is defined, and then it is applied to classical gradient operators to obtain accurate edges for hue component. Moreover, complete object edges can be obtained by using the edge fusion of the first principal component and hue component of colour image with low‐computational complexity. Experimental results show that the proposed approach not only can act on hue component directly and obtain accurate edges caused by hue changes, but also is effective and easy to implement.
Saliency‐based localising active contour for automatic natural object segmentation
Authors: Gao Shangbing , Yang Jian , Yan Yunyang , Bo Zhou Jing
Published: October 2013

In this study, a novel method named saliency‐seeded active contour is presented for automatic natural object extraction. Since approximately the location of the desired object can easily be obtained by saliency regions or pixels in the map, we propose the maximum saliency density method to detect salient object pixels in spite of the cluttered background at first. Then, the salient object pixels are employed as the seeds of convex hull to generate the initial contour for our automatic object segmentation system. It is most important that the method proposed by the authors does not require considerable user interaction in contrast with localising region‐based active contours (LRACs), that is, the segmentation task is fulfiled in a fully automatic manner. Extensive experiments results on a large variety of natural images confirm that the framework can reliably and automatically extract the object from the complex background.
AnnularCut: a graph‐cut design for left ventricle segmentation from magnetic resonance images
Authors: Dakua Sarada Prasad
Published: October 2013

Clinician‐friendly methods for cardiac image segmentation in clinical practice remain a tough challenge. Larger standard deviation in segmentation accuracy may be expected for automatic methods when the input dataset is varied; also at some instances the radiologists find them hard in case any correction is desired. In this context, this study presents a semi‐automatic algorithm that uses anisotropic diffusion for smoothing the image and enhancing the edges followed by a new graph‐cut method, ‘AnnularCut’, for three‐dimensional left ventricle (LV) segmentation from some selected slices. Unlike the conventional cellular automata, where the performance depends solely on the image features, this method simultaneously considers the minimal energy between two adjacent regions thus mitigating the convergence problem. The two main contributions in this study can be summarised as (i) a dynamic cellular automation approach to integrate the minimal energy between two distinct labels, and (ii) generation of missing contours of the subject from the selected slices using a level set method to construct the volumetric LV. Both qualitative and quantitative evaluation performed on publicly available databases reflect the potential of the proposed method.
One‐third probability embedding: a new ±1 histogram compensating image least significant bit steganography scheme
Authors: Sarreshtedari Saeed , Akhaee Mohammad Ali
Published: October 2013

A new method is introduced for the least significant bit (LSB) image steganography in spatial domain providing the capacity of one bit per pixel. Compared to the recently proposed image steganography techniques, the new method called one‐third LSB embedding reduces the probability of change per pixel to one‐third without sacrificing the embedding capacity. This improvement results in a better imperceptibility and also higher robustness against well‐known LSB detectors. Bits of the message are carried using a function of three adjacent cover pixels. It is shown that no significant improvement is achieved by increasing the length of the pixel sequence employed. A closed‐form expression for the probability of change per pixel in terms of the number of pixels used in the pixel groups has been derived. Another advantage of the proposed algorithm is to compensate, as much as possible, for any changes in the image histogram. It has been demonstrated that one‐third probability embedding outperforms histogram compensating version of the LSB matching in terms of keeping the image histogram unchanged.
Timer‐based greedy forwarding algorithm in vehicular ad hoc networks
Authors: Huang Chung‐Ming , Lin Shih‐Yang
Published: October 2013

Vehicular ad hoc networks bring new applications and services for wireless networks, such as information sharing among vehicles. These applications need data dissemination strategies or routing protocols to transmit data among vehicles efficiently. In order to reduce the transmission delay between the source vehicle and the destination vehicle, an efficient forwarding algorithm called timer‐based greedy forwarding (TGF) is proposed in this study. TGF can find forwarding paths with fewer hop counts, lower transmission delay and fewer control packets. The proposed TGF chooses the farthest vehicle from a sender to be a packet forwarder, which is decided by receivers themselves. Although the concept of the TGF is similar to the greedy forwarding algorithm, the message exchanging for neighbouring information maintenance in the proposed TGF is unnecessary. To achieve this goal, three challenges that need to be tackled in the TGF are (i) the farthest node selection, (ii) timer error at an intersection and (iii) processing of redundant forwarded packets. Comparing with other methods, the simulation results show that the proposed TGF reduces the number of control packets, transmission delay and hop counts between a source vehicle and a destination vehicle significantly.
Method for designing low‐pass filters with a sharp cut‐off
Authors: Mallahzadeh Ali Reza , Bod Mohammad
Published: October 2013

A novel method for designing a compact low‐pass filter (LPF) with a sharp cut‐off and wide stop‐band is presented. In this technique, a simple open‐stub microstrip line is printed on top of a substrate and the desired performance is obtained by optimising the shape of the defected ground structure using the genetic algorithm. Details of the design procedure are presented and evaluated through designing two different LPFs. The first LPF is optimised for a 3.5 GHz cut‐off frequency and a stop‐band up to 10 GHz, whereas the second one is optimised for a 5 GHz cut‐off frequency and the stop‐band is extended to 16 GHz. Both filters are fabricated and good agreement between simulation and measurement result is obtained. The designed filters have a sharp transition along with a compact size of 25 × 20 × 0.787 mm3.
Wide frequency independently controlled dual‐band inkjet‐printed antenna
Authors: Abutarboush Hattan F. , Shamim Atif
Published: October 2013

A low‐cost inkjet‐printed multiband monopole antenna is presented. The unique advantage of the proposed antenna is the freedom to adjust and set the dual‐band of the antenna independently over a wide range (148.83%). To demonstrate the independent control feature, the 2.4 and 3.4 GHz bands for the wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications are selected as an example. The measured impedance bandwidths for the 2.4 and 3.4 GHz are 15.2 and 23.7%, respectively. These dual‐bands have the ability to be controlled independently between 1.1 and 7.5 GHz without affecting the other band. In addition, the proposed antenna can be assigned for different mobile and wireless applications such as GPS, PCS, GSM 1800, 1900, UMTS, and up to 5‐GHz WLAN and WiMAX applications. The mechanism of independent control of each radiator through dimensional variation is discussed in detail. The antenna has a compact size of 10 × 37.3 × 0.44 mm3, leaving enough space for the driving electronics on the paper substrate. The measured results from the prototype are in good agreement with the simulated results. Owing to inkjet printing on an ordinary paper, the design is extremely light weight and highly suitable for low cost and large volume manufacturing.
Spectral occupancy rate of cognitive radio networks in queueing with adaptive modulation and coding over multiple‐input and multiple‐output transmit antenna selection/maximal ratio combining in Nakagami‐m fading
Authors: Jang Won Mee , Chang Woan Sun
Published: October 2013

Cognitive radio is successfully overlayed on the single user cross‐layer design and implementation with adaptive modulation and coding (AMC) over frame‐slotted transmission. The authors analyse the spectral occupancy rate of cognitive radio networks with AMC and queueing effect. They employ multiple‐input and multiple‐output with single transmit antenna selection and maximal ratio combining in Nakagami‐m fading channel. The average spectral efficiency and packet dropping rate are also obtained. The analytical result shows that significant cognitive radio traffic can be accommodated without compromising the primary user network quality.
Approach for channel reservation and allocation to improve quality of service in vehicular communications
Authors: Saritha Vankadara , Madhu Viswanatham Vankadara
Published: October 2013

Channel allocation plays an important role in next generation of wireless networks that require huge bandwidth support for various applications. It became very interesting and important research area in vehicular ad hoc network (VANET) as the channel allocation procedure needs to be efficient as the frequency of handoff is high because of the high mobility of the nodes. So, the authors propose a channel allocation algorithm that utilises channel reuse technique, channel borrowing process and the speed of the vehicle to reserve the channel for handoff calls to improve quality of service (QoS) in VANET. The calls are categorised as real‐time originating calls, real‐time handoff calls, non‐real‐time originating calls, non‐real‐time handoff calls and non‐real‐time transfer calls, and queue is maintained for non‐real‐time originating calls, which leads to non‐real‐time transfer calls. The channel borrowing process is incorporated only for real‐time originating calls and real‐time handoff calls. The proposed system is modelled using two‐dimensional Markov model. The proposed algorithm is simulated and evaluated in terms of QoS parameters as blocking probability, dropping probability and handoff latency. The performance is tested with varying system load, varying number of channels and is compared with legacy systems like cooperative reservation of service channels, CRaSCH, and a new dynamic channel allocation strategy which combines channel reservation with new call queuing, RQS.
Multi‐input voltage‐summation converter based on switched‐capacitor
Authors: Yuan‐mao Ye , Cheng Ka Wai Eric
Published: October 2013

This study is to propose a multi‐input converter which is designed based on switched‐capacitor instead of magnetic components. The number of its inputs can be any figure. The output voltage level of the converter is the summation of its multiple input levels which share with a common neutral. There is no need to have any level‐shift or boost‐strap for adjusting the inputs. The number of active switches and capacitors required both are equal to the number of input sources. Only a pair of complementary pulse signals is needed to control all of these switches. The converter is operated under high frequency. Non‐resonant version does not require resonant inductors and therefore they are of small size and simple structure. Small resonant inductor is also added in the resonant version to realise soft‐switching and improve the conversion efficiency. The circuit analysis, design method and experimental verification are shown.
Five‐level diode‐clamped active power filter using voltage space vector‐based indirect current and predictive harmonic control
Authors: Zhu Haifeng , Shu Zeliang , Gao Fenghua , Qin Bin , Gao Shibin
Published: October 2013

This study presents an active power filter (APF) based on diode‐clamped multilevel circuits with auxiliary dc‐link voltage balancing circuits and harmonic compensation control. The control algorithm is composed of indirect current loop for active and reactive power control, predictive current loop for harmonic filtering control and independent control for auxiliary balancing circuits. Among these modules, the indirect current along with the predictive current control will generate a combined voltage reference to the module of space vector pulse‐width modulation, which could output optimal modulation signals to the voltage control of a diode‐clamped multilevel converter. Comparing with traditional dc control for two‐level APF, this system takes advantages of indirect current control and multilevel circuits, including improvement in waveform quality, increase in system power rate and reduction in voltage stress and switching frequency on power semiconductors. Simulation and experimental results validate the effective control of the presented system.
Novel topology for DC/DC unidirectional converter for fuel cell
Authors: Ortega Manuel , Jurado Francisco , Valverde Manuel
Published: October 2013

This study presents a new isolated DC/DC converter of full‐bridge to connect a fuel cell to DC bus in a hybrid distribution generation system. This converter consists of a high‐frequency transformer and a voltage booster circuit. The circuit has been designed and each isolated‐gate bipolar transistor (IGBT) presents soft‐switching during the whole power range of the converter. The switching losses of the IGBTs, the reverse‐recovery losses of all of the diodes, and the core losses have almost been eliminated. To improve the efficiency, transformer cores and inductors have been built with material nanocrystalline. The efficiency is improved if this is compared with that of a conventional zero‐voltage switching converter. Also, this converter can obtain a high‐voltage gain and medium and high DC power can be converted. The analysis and switching techniques have been reported. Finally, to verify the principle of operation, a laboratory prototype of 2 kW has been performed.
New hybrid structure for multilevel inverter with fewer number of components for high‐voltage levels
Authors: Alishah Rasoul Shalchi , Nazarpour Daryoosh , Hosseini Seyyed Hossein , Sabahi Mehran
Published: October 2013

Application of multilevel inverters for higher voltage goals in industries has become more popular. In this study, new structures for symmetric, asymmetric and hybrid multilevel inverter are recommended. The proposed hybrid structure is used in high‐voltage levels. The proposed structures can generate a great number of output voltage levels with minimum number of power electronic components such as insulated gate bipolar transistors (IGBTs) and gate drivers. For proposed asymmetric and hybrid inverter, new methods for determination of dc voltage sources values are presented. Comparison of the results of various multilevel inverters is presented to reflect the merits of the recommended structures. The operations of the proposed multilevel inverter structures are verified with the experimental and simulation results of an asymmetric 15‐level prototype and a 19‐level hybrid inverter. Fundamental frequency‐switching method is applied to the new topologies to trigger the power switches for controlling the voltage levels generated on the output. Verification of the analytical results is performed using MATLAB/SIMULINK software.
High‐voltage‐boosting converter with charge pump capacitor and coupling inductor combined with buck–boost converter
Authors: Hwu Kuo‐Ing , Peng Tso‐Jen
Published: October 2013

A novel high‐voltage‐boosting converter is presented herein, which combines the traditional buck–boost converter, the charge pump capacitor and the coupling inductor. By doing so, the proposed converter possesses a high‐voltage conversion ratio, which can be obtained based on not only the duty cycle, but also the turn ratio so as to increase design feasibility. Above all, the used switch is driven without isolation and hence the gate driving circuit is relatively simple, thereby upgrading the industrial application capability of this converter. In this study, the basic operating principles and the associated mathematical deductions are firstly described in detail, and finally some experimental results are provided to demonstrate the effectiveness of the proposed high‐voltage‐boosting converter.
Space vector pulse‐width modulation scheme for multilevel voltage inverters with duty cycle calculation based on relative vector distances
Authors: Ovalle Andres , Ramos Gustavo
Published: October 2013

In this study, a control scheme for multilevel inverters is formulated employing space vector pulse‐width modulation. The notable formulation bases the duty cycle calculation on relative distances among constructive vectors provided by the line‐neutral voltage levels of the converter topology. Furthermore, in order to locate the control vector (or reference vector) properly, Clarke transformation of instantaneous line‐neutral voltages is employed. In this way, calculations of duty cycles are simplified, closed‐ and open‐loop operations have similar approaches and linear and over modulation operations are performed with minimal variations. Also, this approach eliminates the use of trigonometric functions in order to reduce memory demands and computational capacity. The scheme is tested on a 7seven‐level inverter with cascaded H‐bridge topology using real‐time simulation.
Research on a permanent magnet tubular linear generator for direct drive wave energy conversion
Authors: Liu Chunyuan , Yu Haitao , Hu Minqiang , Liu Qiang , Zhou Shigui , Huang Lei
Published: October 2013

An external tubular linear permanent magnet generator (ETLPMG) is proposed for direct drive wave energy conversion. ETLPMG with quasi‐Halbach array is larger in the air gap magnetic flux density than the internal and radial magnetisation one. An assistant tooth and fractional slot are implemented to decrease the detent force. The power density of ETLPMG is about 7–8 times for that of the internal one and the efficiency reached 90.03% at 18 Ω condition. The characteristics of the ETLPMG are analysed with a finite element analysis. Finally, a prototype is manufactured to verify the simulation results by some experiment tests.
Spatio‐temporal analysis of possible wind generation output reductions for the Irish transmission system with a high penetration of renewables
Authors: Ging John A. , Glavin Margaret E. , Crilly Damien J. , Kennedy Eoin P. , O'Donnell Philip A. , Sustman James E.
Published: October 2013

This study outlines a modelling methodology utilised by EirGrid, the Irish Transmission System Operator, to apportion reductions in electricity output from wind powered generators because of a variety of security of supply issues and localised transmission congestion. A set of production cost simulations compiled to account for hypothetical dispatches on the Irish transmission system extending over the period 2011–2022 are reported using actual application data. Studies addressing security of supply set a limit for non‐synchronous generation such as wind to be between 50 and 75% of the total system generation (demand plus exports) over the interval. The potential impact of the 75% maximum instantaneous wind penetration limit possible on the small, synchronous and relatively‐isolated Irish transmission system by 2020 is assessed. Ireland is expected to achieve the majority of its 40% renewable target in electricity from wind and there will invariably be instances when the amount of wind generation will be greater than demand. This should also be seen in the context of transmission congestion where wind generation connects on a non‐firm basis prior to completion of their deep assets. The description of the advanced and novel methodology used to determine these reductions is presented here.
Dynamic resampling for alleviating sample impoverishment of particle filter
Authors: Zuo Junyi
Published: October 2013

In particle filter, the use of resampling technique solves the problem of particle degeneracy to some extent, but introduces a new problem of particle impoverishment. To reconcile this dilemma, a dynamic resampling strategy is proposed, where the resampling operation is only performed on part of the particles in a step‐by‐step manner and the number of resampled particles is determined dynamically by a termination criterion based on the effective sample size. The new‐born particles produced by resampling operations are helpful in alleviating particle degeneracy, whereas particles free from being resampled is conducive to improving the diversity of particles. Thus, a tradeoff between these two problems can be achieved. Also, two techniques, that is, recursive computation of the effective sample size and improved bisection method, for improving the computational efficiency are proposed. Simulation results conducted on two typical examples show the improved performance of the proposed method.
Evaluating treatment of osteoporosis using particle swarm on a bone remodelling mathematical model
Authors: Chen Andy B. , Zhang Ping , Yokota Hiroki
Published: October 2013

Bone loss in osteoporosis, commonly observed in postmenopausal women and the elderly, is caused by an imbalance in activities of bone‐forming osteoblasts and bone‐resorbing osteoclasts. To treat osteoporosis and increase bone mineral density (BMD), physical activities and drugs are often recommended. Complex systems dynamics prevent an intuitive prediction of treatment strategies, and little is known about an optimal sequence for the combinatorial use of available treatments. In this study, the authors built a mathematical model of bone remodelling and developed a treatment strategy for mechanical loading and salubrinal, a synthetic chemical agent that enhances bone formation and prevents bone resorption. The model formulated a temporal BMD change of a mouse's whole skeleton in response to ovariectomy, mechanical loading and administration of salubrinal. Particle swarm optimisation was employed to maximise a performance index (a function of BMD and treatment cost) to find an ideal sequence of treatment. The best treatment was found to start with mechanical loading followed by salubrinal. As treatment costs increased, the sequence started with no treatment and usage of salubrinal became scarce. The treatment strategy will depend on individual needs and costs, and the proposed model is expected to contribute to the development of personalised treatment strategies.
Microfluidic device for super‐fast evaluation of membrane protein nanoparticle formation
Authors: Wu H.‐J. , Basta T. , Morphew M. , Rees D.C. , Stowell M.H.B. , Lee Y.C.
Published: October 2013

Membrane proteins embedded in bilayer lipids of cell membrane have unique functions including inter‐cell communication and ionic/molecular transport. To understand the structure and function of the membrane protein embedded in a native biological bilayer lipid environment is a major research area in biology. A reconstitution/crystallisation process of membrane proteins and lipids can form virus‐like nanoparticles, and have important potential applications in drug design and drug delivery. Earlier studies used a standard dialysis process that is inherently low‐throughput, time consuming (days to weeks) and costly in protein materials. In this reported work a new microfluidic device is demonstrated to rapidly form membrane protein lipid nanoparticles in an extremely short period (seconds). The reconstitution process occurs using a continuous flow dominated by convection‐diffusion phenomena in the microfluidic channel, which can form protein/lipid nanoparticles using only nanolitres or picolitres of protein sample. Moreover, a controllable syringe pump is used to test a combination of conditions, rather than using inefficient hand pipetting. Therefore this novel microfluidic device has an ability to rapidly form uniform membrane protein/lipid nanoparticles, and the authors believe that this new method will make a transformative impact on commercial applications in a variety of areas from biology to pharmacology.
Droplet‐based protein chip with Ni–Co coated surface
Authors: Zhang Chun‐ping , Chang Yaw‐Jen , Ding Zi‐Huan , Chang Cheng‐Hao
Published: October 2013

This Letter describes the implementation of a droplet‐based protein chip with an Ni–Co alloy layer for conducting immunoassays. The proposed chip consists of a substrate of a printed circuit board and a microchannel layer. On the substrate surface, an Ni–Co coating was fabricated by electrodeposition to immobilise the histidine‐tagged protein. Through droplet fusion and mixing, the fused droplets aligned at the downstream position of the microchannel and were immobilised by the Ni–Co layer for further incubation and fluorescence detection. The experimental results showed that the sample which is encapsulated by the carrier fluid does not have evaporation and contamination problems. Therefore strong fluorescence intensity proportional to the sample concentration can be obtained. The fluorescence intensity is also related to the droplet size. An extremely low concentration of encapsulated content in a smaller droplet might result in arduous fluorescence detection. This proposed droplet‐based protein chip allows the operation sequence of the immunoassay to be conducted automatically through the manipulation of droplets. Moreover, the fabrication process is simple and the chip can be implemented to immobilise any functional proteins with His‐tag attached.