bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated wideband and low phase‐noise signal source using two voltage‐controlled oscillators and a mixer
Authors: Lai Szhau , Bao Mingquan , Kuylenstierna Dan , Zirath Herbert
Published: May 2013

This study presents a method to design a wideband signal source based on two voltage‐controlled oscillators (VCOs) with different centre frequencies and a mixer. The principle is to combine three frequency bands to form one wide frequency range. The three bands consist of second harmonic bands from two VCOs and a mixer band that is generated by mixing the two fundamental signals of VCOs to bridge the frequency gap. Apart from the wide tuning range, an additional benefit of a mixer‐based signal source is that the phase‐noise increases ∼3 dB/octave, which is less than the theoretical limit (6 dB/octave) for a fundamental frequency VCO followed by a frequency multiplier or extraction of second harmonic signal from a VCO. A prototype of the proposed signal source implemented in indium gallium phosphide hetero junction bipolar transistor monolithic microwave integrated circuit technology demonstrates both wide frequency tuning range and a very low phase noise. It exhibits a tuning bandwidth extending from 11.8 to 16.7 GHz and the signal's phase noise varies between −91 and −103 dBc/Hz at 100 kHz offset frequency.
New approach for mobile ad‐hoc networks unity issue in a suspicious environment
Authors: Khosravi Adle , Kavian Yousef Seifi
Published: May 2013

This study investigates the problem of unity in a mobile ad‐hoc network (MANET) when the members are suspected of having malicious faults. This study has reexamined the related Byzantine agreement (BA) problem for the new territory of MANET. The authors provide a new fault modelling approach followed by a new algorithm for the BA problem considering the limited connectivity of MANET. The proposed protocol results in a significant save in packet transmission counts for a fault‐free member to reach an agreement in comparison with previous studies. Also, the minimum required network connectivity is reduced in this study to cover more network topologies. The proposed protocol also distinguishes faulty transmission media from a faulty processor which increases the maximum number of allowable faulty units in the network. Simulation results are provided to depict the applicability of the proposed protocol in mobile networks.
Link capacity design for shared protection with limited traffic information
Authors: Matsumura Ryutaro , Hasegawa Haruhisa
Published: May 2013

Link capacity for primary and backup paths in a telecommunication carrier network can be computed if the authors are able to use end‐to‐end traffic volume information between source and destination nodes in a network. However, this information is not easily obtained because traffic measurement puts a heavy load on network equipment, and measuring devices are not installed on all the links in the network. Network carriers must estimate the link capacity under limited traffic information. The authors explain a link capacity design problem for shared protection to work within this limitation. Shared protection is effective for economical network design; however, it requires time‐consuming computation. Therefore the authors propose a faster formulation for shared protection that takes the form of a maximum flow problem. The authors evaluated our formulation in terms of the solution's error and showed the advantage of using shared protection.
Adaptive time‐ and location‐aware routing in telecom mesh networks
Authors: Dikbiyik Ferhat , Mukherjee Biswanath , Tornatore Massimo
Published: May 2013

In telecom mesh networks, connections can be provisioned considering their availability requirements. A connection's availability can be estimated based on the links' statistical availability (e.g., depending on historical failure occurrences and repair times).The authors remark that the actual failure statistics depend on (i) when and (ii) where a connection is routed (as failure rates throughout the year and in different locations may be different). Moreover, the failure rate is not homogeneous along a link and a detailed time‐ and location‐aware availability calculation is required. Most link failures are caused by dig‐ups, thus there is a direct relationship between construction works, which require excavations, and link failures. So, the probability of a link failure at a certain location depends on (i) the time/day when dig‐up works are performed and (ii) population of the location (assuming that the more crowded the location is, the more constructions occur). By exploiting the time‐ and location‐dependent failure information, the authors investigate a novel adaptive time‐ and location‐aware routing scheme, which provisions connections on highly available paths depending on a connection's duration and availability requirements. The authors' approach shows significant upgrade‐cost savings, while satisfying the service requirements, compared with traditional approaches.
Differential fault analysis on PRINTcipher
Authors: Bagheri Nasour , Ebrahimpour Reza , Ghaedi Navid
Published: May 2013

The new block cipher PRINTcipher was introduced in CHES 2010 as a lightweight block cipher for ‘integrated circuit’ or IC‐‘printing’ technology. The key of PRINTcipher consist of two sub‐key components where the first sub‐key is ‘XORed’ to the state in each round, whereas the second sub‐key is used to generate the key‐dependent permutations. In this study, the authors describe a new differential fault analysis on the lightweight block cipher PRINTcipher. The authors present two different fault models for obtaining each sub‐key. The first fault model is used to obtain the second sub‐key, which induces a fault on the key‐dependent permutation layer so, on average, key search space is reduced from 232 to 214, given 36 faulty cipher texts. To obtain the first sub‐key, the authors induce a fault on an intermediate results then they obtain, on average, 42 bits of the first sub‐key with less than 24 faulty cipher texts. In total, on average, they reduce key search space of PRINTcipher from 280 to 220, given 60 faulty cipher texts. They also simulated their attack on a 1.8 GHz Celeron PC.
Pre‐sizing methodology of DC–AC converters using a virtual prototyping tool applied to sequential multi‐load systems
Authors: Ledoux Christophe , Lefranc Pierre , Larouci Cherif
Published: May 2013

The increasing need for higher efficiency, weight and volume reduction in embedded applications is a starting point of this study which focuses on a pre‐sizing methodology of power converters based on virtual prototyping tools to avoid physical prototypes. From a general point of view, the mutualisation of a three‐phase inverter with the help of a power sharing system is introduced. The proposed design approach optimises N inverters and a {one inverter + N‐power sharing system} topologies based on a generalised modelling and a virtual prototyping tool. The presented results based on a 3 kW–270 V DC bus application show that in addition to the switching frequency and the ambient temperature, the number of sequential loads is also a key of the optimisation parameters. Therefore the proposed methodology based on an optimisation process allows the power designers to compare N inverters and {one inverter + N‐power sharing system} as a function of the load number N.
Single‐phase 9‐level hybridised cascaded multilevel inverter
Authors: Odeh Charles I. , Nnadi Damian B.N.
Published: May 2013

This study proposes a single‐phase, 9‐level, cascade multilevel inverter topology. The multicarrier, phase disposition pulse width modulation scheme is employed to generate the gating signals for the power switches. Operational principles with switching functions are given. By controlling the modulation index, the desired number of levels: 3, 5, 7 and 9, of the inverter's output voltage can be achieved. For modulation indices of: 0.24, 0.4, 0.6 and 0.8, the proposed inverter configuration was subjected to an R–L load and the respective numbers of output voltage level were synthesized. Fast Fourier transform analyses of the output voltage waveforms were carried out and the corresponding THD values were obtained. For a modulation index of 0.8, a THD value of 10.12% has been achieved in the output voltage waveform of the proposed inverter configuration. Comparison of the proposed inverter configuration and the classical single‐phase topologies is given based on the power circuit component count. Moreover, analysis of the conduction power losses in the power semiconductor switches of the proposed inverter topology is given. To verify the performance of the proposed inverter architecture, simulations and experiments are carried out on a 2.12 kW rated prototype of the proposed inverter for an R–L load; and adequate results are presented.
Modular space‐vector pulse‐width modulation for nine‐switch converters
Authors: Dehghan Seyed Mohammad , Amiri Arash , Mohamadian Mustafa , Andersen Michael A.E.
Published: May 2013

Recently, nine‐switch inverter (NSI) has been presented as a dual‐output inverter with constant frequency (CF) or different frequency (DF) operation modes. However, the CF mode is more interesting because of its lower switching device rating. This study proposes a new space‐vector modulation (SVM) method for the NSI that supports both the CF and DF modes, whereas conventional SVM of NSI can be used only in the DF mode. The proposed SVM can be easily implemented based on the conventional six‐switch inverter SVM modules. The performance of the proposed SVM is verified by the simulation and experimental results.
Fast closed‐form solution of line‐to‐line voltage total harmonic distortion for three‐level inverters
Authors: Farokhnia Naeem , Ehsani Mehrdad , Vadizadeh Hadi , Toodeji Hamidreza , Mohammad Muneer
Published: May 2013

Harmonic emission to the network must be restricted below the predefined limits, avoiding power quality problems. Total harmonic distortion (THD) is a well‐known criterion, which is used to determine harmonic content of each waveform, and extracting its exact value is very important. Three‐level inverters produce a significant amount of harmonics and the exact closed‐form expression for their line‐to‐line voltage THD has not yet been derived. All presented methods in this regard are based on an approximate approach. This study calculates line‐to‐line voltage THD of a three‐level inverter by two different methods and presents their relevant formulas. The first method is usable for any number of controlled PWM switching angles, but the second method is limited to low number of switching angles. By the presented mathematical formulas in this study, the THD is computed simply, accurately and rapidly. The proposed methods are compared with the conventional methods and their advantages are verified by simulation and experimental results.
Sliding‐mode variable structure controller for cascade STATic var COMpensator
Authors: Wu Junyong , Chen Qichao , Du Mingjun , Yu Shuqin
Published: May 2013

The authors propose a novel sliding‐mode variable structure controller for cascade STATic var COMpensator (STATCOM), which integrates the direct feedback linearisation control for the balanced system and the individual phase instantaneous current tracking control for the unbalanced system, to achieve a versatile STATCOM controller. It can adapt automatically to various distribution system conditions. Based on the degree of system unbalance, the authors design a switching function to make the STATCOM work reliably with satisfactory performance, when the serious voltage sag occurs or the distribution system enters serious asymmetrical condition. The authors also propose a hierarchical DC‐link voltages balance control strategy. The authors build a detailed ± 10 MVar STATCOM model with power system CAD and electro magnetic transient in DC system (PSCAD/EMTDC) and validate the effectiveness and advantage of the proposed control strategy with the simulation study.
Verification of battery system model for environmentally friendly vehicles using a battery hardware‐in‐the‐loop simulation
Authors: Song Hyun‐Sik , Kim Tae‐Hoon , Jeong Jin‐Beom , Kim Byoung‐Hoon , Shin Dong‐Hyun , Lee Baek‐Haeng , Heo Hoon
Published: May 2013

Owing to high oil prices and the efforts to reduce greenhouse gases according to the United Nations Framework Convention on Climate Change, there has been active research and development on environmentally friendly, high‐efficiency vehicles. In developing the system design and specifications of an environmentally friendly vehicle, various simulations have been performed on the different components and the overall system. Although a precise modelling of each part and the system as a whole is necessary for an accurate simulation, detailed modelling of a high‐capacity battery system – which directly affects the performance of an environmentally friendly vehicle – is difficult to achieve owing to the non‐linear electrochemical properties of the battery. In this study, an electrochemical impedance measurement technique is used to implement a battery cell model, upon which a battery system model for environmentally friendly vehicles that takes into account the ancillary components of the battery pack is developed. And we used an actual battery system that requires complex and difficult modelling owing to non‐linear and irreversible properties of the battery. In addition, to verify the developed battery system model, we used models implemented for other vehicle components and systems to construct a hardware‐in‐the‐loop simulation of a battery reflecting an actual driving environment.
Control and design of a current source united power quality conditioner with fault current limiting ability
Authors: Guo Wenyong , Xiao Liye , Dai Shaotao
Published: May 2013

This study proposes control and design methods for a current source united power‐quality conditioner (CS‐UPQC). Unipolar modulation and parameter design methods are proposed for the series CS converter. The proposed modulation method doubles the equivalent switching frequency, which makes it possible to reduce the filter size and improve the control dynamics. Modified repetitive control schemes are presented for the voltage and current compensation strategies, which provide large open‐loop control gains at the integral multiple of the fundamental frequency and guarantee good harmonics compensation performance. A fault current limiting scheme is also presented, which limits the fault current effectively by utilising the large DC link inductor of the CS‐UPQC. Simulation results in Matlab/Simulink are presented to clarify the theory and feasibility of the proposed approaches.
Primary side feedforward control for TRIAC dimmable light emitting diode driver with Constant Power
Authors: Zhang Junming , Jiang Ting , Zeng Hulong , Wu Xinke
Published: May 2013

This study proposes a primary side feedforward control scheme for low‐power Triode AC semiconductor switch dimmable light emitting diode (LED) driver. The LED driver is a Flyback converter operated in constant frequency (CF) discontinuous current mode (DCM). With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by the AC input voltage. That is to say, the input power is constant with certain dimming angle. Besides, the output power is determined by the input power with a given conversion efficiency. For LED load, since the output voltage is almost constant, the output current can be regulated by TRIAC dimming angle without any secondary side feedback circuit. Almost linear dimming curve can be achieved. Also, the input current automatically follows the input voltage because of CF DCM operation, resistive input characteristic can be achieved and no dummy load is required for TRIAC dimming angle detection. Considering the LED forward voltage drop tolerance existed in the practical application, the related compensation method is also discussed in this study, which can further improve the performance of the proposed control scheme. A prototype with 27 V/0.5 A output and 180–265 V AC input has been built. Moreover, the experimental results from the prototype are presented to verify the theoretical analysis.
Single‐stage multi‐port DC–DC converter topology
Authors: Behjati Hamid , Davoudi Ali
Published: May 2013

A single‐stage multi‐port DC–DC converter topology is proposed. It can accommodate arbitrary number of input sources and output loads, and employs a single inductor. The voltage of each output port can be less than the minimum input voltage or exceed the maximum input voltage. Power regulation can be provided for the input ports in addition to providing voltage regulation for the output ports. The steady‐state and dynamic characteristics of the converter are analysed and a control scheme is proposed. Hardware measurements and numerical switch‐level simulations verify the analytical results.
Research on fast transient and 6n±1 harmonics suppressing repetitive control scheme for three‐phase grid‐connected inverters
Authors: Chen Dong , Zhang Junming , Qian Zhaoming
Published: May 2013

The repetitive control technique is widely adopted in ac systems, because of its excellent steady‐state tracking performance and low total harmonic distortion. The repetitive control method with one‐sixth of the system fundamental period T0 as the delay time has been proposed to achieve fast transient response. In this study, an improved control scheme based on the T0/6 repetitive control is proposed for three‐phase grid‐connected inverters. The proposed scheme adopts T0/6 as the delay time in the positive‐rotating and negative‐rotating synchronous reference frames to suppress the 6n ± 1 harmonics. Meanwhile, the proportional‐integral regulator and the plug‐in repetitive controller are combined to reinforce the system performance. A new auxiliary function based on the linear interpolation is proposed to maintain the ideal repetitive control performance when one‐sixth of the ratio of the sampling frequency to the grid fundamental frequency is non‐integer. The effectiveness of the proposed scheme on improving the T0/6 repetitive control is confirmed by simulation and experimental results finally.
Modulation strategies based on mathematical construction method for matrix converter under unbalanced input voltages
Authors: Li Xing , Su Mei , Sun Yao , Dan Hanbing , Xiong Wenjing
Published: May 2013

Owing to the direct coupling between the input and output of matrix converter, the abnormal power supply could disturb the output voltage easily. In this study, three modulation strategies for matrix converter based on mathematical construction are proposed under unbalanced input voltage conditions. The strategies are developed based on the construction of the rectifier and inverter modulation vectors in three different ways. By regulating appropriately the modulation index of inverter vector, the output voltages of matrix converter can maintain sinusoidal and balanced. The different rectifier vectors result in different input currents. Moreover, the analytical solutions for input currents with the three methods are presented, and the approximated solutions are derived to estimate their low‐order spectrums. Comprehensive comparisons among the three methods are made in the aspects of the complexity of realisation, voltage‐transfer capability and input current quality. Simulation and experimental results verify the correctness and effectiveness of the proposed methods.
Efficiency analysis of a sliding‐mode controlled quadratic boost converter
Authors: López‐Santos Oswaldo , Martínez‐Salamero Luis , García Germain , Valderrama‐Blavi Hugo , Mercuri Daniel O.
Published: May 2013

A quadratic boost converter with high DC gain to step up the voltage of a standard photovoltaic panel up to 400 V is analysed. First of all, a comparative analysis among boost, quadratic boost and cubic boost reveals that the quadratic boost exhibits the best trade‐off between duty ratio range and converter efficiency. A hysteretic comparator is employed as a modulator to ensure the converter operation with high values of the duty ratio without risk of modulation saturation. A two‐loop sliding‐mode control is used to regulate the output voltage. An internal loop controls cycle by cycle the input current whose reference is established by an outer loop that processes the output voltage error by means of a proportional‐integral compensating network. The measured results in a 100 W prototype operating in continuous conduction mode of average values, ripples, frequency and efficiency for different equilibrium points are in good agreement with the theoretical predictions.
Zero‐voltage switching full‐bridge DC/DC converter with parallel‐connected output and without output inductor
Authors: Lin Bor‐Ren , Shiau Tung‐Yuan
Published: May 2013

This study presents a soft‐switching converter without output inductor. The features of the proposed converter are zero‐voltage switching (ZVS) for all power switches, load current sharing and high circuit efficiency. Full‐bridge converter with phase‐shift pulse‐width modulation (PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The voltage stress of power switches is clamped to DC bus voltage. Four transformers are connected in series in the primary side. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve electric isolation and power transfer from input side to output side. Therefore no output inductor is needed in the secondary side. Two centre‐tapped rectifiers connected in parallel are used in the secondary side to achieve load current sharing. Finally, experiments based on a 960 W (48 V/20 A) laboratory prototype are provided to demonstrate the performance of proposed converter.
Asymmetrical transformer‐based embedded Z‐source inverters
Authors: Wei Mo , Chiang Loh Poh , Blaabjerg Frede
Published: May 2013

Z‐source inverters are inverters with buck–boost capability that traditional inverters cannot match. Despite this ability, present Z‐source topologies are burdened by some limitations such as chopping input current, high‐voltage stress and poor spectral performance at high gain. To improve their performances, a number of asymmetrical transformer‐based embedded Z‐source inverters are proposed. Through theoretical derivation and experiments, the proposed inverters have been shown to draw a smooth input current and produce a high gain by varying the transformer turns ratio n. The range of variation for n depends on the inverter topology chosen, which in turn depends on the application under consideration.
Boost‐type inverter‐less shunt active power filter for VAR and harmonic compensation
Authors: Liu Quanwei , Deng Yan , He Xiangning
Published: May 2013

Harmonics in power system caused by non‐linear loads degrade the power quality. As a result, shunt active power filters are widely applied to deal with current harmonics and poor power factor. However, the traditional voltage‐source inverter‐based active filters, which usually employ large electrolytic capacitors as the energy‐storage elements, cannot get much market penetration. An emerging technique that adopts the direct AC–AC conversion and even harmonic modulation can help to eliminate the bulky energy‐storage elements while realising the harmonic compensation and power factor correction functions. A three‐phase three‐wire boost‐type inverter‐less active power filter for power factor correction and harmonic compensation is presented. The proposed solution eliminates the bulky electrolytic capacitors. Meanwhile, smaller amount of AC capacitors are needed compared with the buck‐type AC–AC converters. Furthermore, continuous grid‐side current is obtained, which implies that no extra grid‐side filters are needed. Numerical calculation is applied to build the model, and the closed‐loop control algorithm employing the synchronous reference frame for power factor correction and multi‐harmonics compensation is also developed. The proposed topology and control algorithm is simulated in MATLAB/Simulink and validated with a 15 kVA experimental prototype.
Optimised active harmonic elimination technique for three‐level T‐type inverters
Authors: Hosseini Aghdam Ghasem
Published: May 2013

This study develops a pulse‐width modulation (PWM) method that is referred the optimised active harmonic elimination (AHE) technique to eliminate more harmonics with minimum switching frequency for three‐level T‐type converter (3 L‐T2C) based on the fundamental frequency switching control method. First, Homotopy algorithm is applied to non‐linear transcendental equations to eliminate low‐order harmonics and to determine switching angle sets for selective harmonic elimination PWM in 3 L‐T2C. The characteristics of the multiple solutions in terms of harmonic distribution, and total harmonic distortion (THD) are investigated. Then a detailed analysis of optimised AHE‐PWM technique is presented to cancel more harmonics in 3 L‐T2C using harmonic compensation strategy. A switching angle solution set that gives the lowest THD for optimised AHE‐PWM is derived and the effectiveness of the control method is verified through extensive simulation studies. Finally, selected experimental results are reported to verify and validate the theoretical and simulation findings.
Variable parameter pulse width modulation‐based current tracking technology applied to four‐switch three‐phase shunt active power filter
Authors: Tan Xingguo , Li Qingmin , Wang Hui , Cao Lei , Han Shuai
Published: May 2013

A novel configuration is proposed with a y/y step‐up transformer adding to AC side of the four‐switch three‐phase (FSTP) active power filter (APF), so as to improve the utilisation of DC voltage and further widen the voltage range of FSTP APF. To ameliorate the current tracking performance of the FSTP inverter, a variable parameter pulse width modulation (VPPWM) approach is presented. In the proposed VPPWM method, the triangular wave is not fixed but derived by integration of reference current error signals. A pulse width coefficient T is also adopted in VPPWM together with the parameter k, so as to make the APF current tracking width adjustable and the resultant over‐high switch frequency issue is effectively compromised. The principle and implementation of the VPPWM approach are elucidated in detail, and the validity is demonstrated by simulation studies. The simulation results are compared with that of the proportional‐integral control triangular wave comparison approach and the current hysteresis tracking approach, which indicates that the VPPWM methodology shows superior performance in response speed and accuracy to the other ones.
Simple control technique for interleaved inverters with magnetically coupled legs
Authors: Contreras Sergio Alejandro Díaz , Cortizo Porfirio Cabaleiro , Mendes Marcos Antônio Severo
Published: May 2013

Recent works of different authors have shown that the use of intercell transformers in interleaved inverters bring many improvements to this kind of parallelism. However, even though a balanced current distribution is necessary and not guaranteed by the converter itself; just a few of those studies are focused on the modelling and control of the inverter. Moreover, the fact that the paralleled modules are coupled and that the control signals are not updated simultaneously have not been considered yet. In this way, the current paper takes those facts into account and proposes a simple procedure for modelling and control a single‐phase interleaved inverter. A mathematical analysis, some simulation and experimental results are shown in order to prove the simplicity and effectiveness of the proposed procedure.
A Redundancy‐based scheme for balancing DC‐link voltages in cascaded H‐bridge rectifiers
Authors: Keshavarzian Ali , Iman‐Eini Hossein
Published: May 2013

A new voltage balancing algorithm is introduced for cascaded H‐bridge rectifiers. This kind of converter is made of a series connection of H‐bridge cells with separate dc‐links. The proposed balancing algorithm will regulate the voltage of all dc‐links to the desired reference value, even if the attached loads are very different. The input current is also programmed to be sinusoidal and has low distortion, while the switching frequency is kept low at 1 kHz. In addition, the input power factor can be controlled. The simulation and experimental results are presented to confirm the validity of the proposed algorithm.
Analysis and experimental investigation of a current controller for a full‐bridge boost rectifier
Authors: Chan Chok You
Published: May 2013

The development of a current controller with inherent integral action for a full‐bridge boost rectifier is presented. The main control objectives are to achieve dc output voltage regulation and near‐unity power factor in the presence of unknown load. The stability analysis of the current‐controlled rectifier system is carried out using Floquet theory. Some experimental results are also presented to verify the effectiveness of the control method.
Hardware implementation of series hybrid active power filter using a novel control strategy based on generalised instantaneous power theory
Authors: Mulla Mahmadasraf Abdulhamid , Rajagopalan Chudamani , Chowdhury Anandita
Published: May 2013

In the area of power quality conditioners, the series hybrid active power filter (SHAPF) has been focused more in recent times because of its multi‐functionality and lower inverter rating requirement. Existing control strategies for SHAPF are based on extracting either source current harmonics or load voltage harmonics. In this study, a novel control scheme based on decomposing multiphase voltage vector into different vectors that represent different components of power is proposed for SHAPF. The mathematical formulation of the proposed control scheme with its applications to SHAPF is presented. The validity of the proposed control scheme is verified by simulation as well as experimental study.
Non‐linear voltage regulator design for DC/DC boost converters used in photovoltaic applications: analysis and experimental results
Authors: Konstantopoulos George C. , Alexandridis Antonio T.
Published: May 2013

In this study, a new non‐linear dynamic controller is proposed for regulating the output voltage of a DC/DC boost power converter in a stand‐alone photovoltaic (PV) system. The controller provides directly the duty‐ratio input of the converter, bounded in the permitted range, and as it is proven it achieves the desired voltage regulation independently from the PV source voltage, the converter parameters and the kind of the load. An appropriate mathematical analysis is used to indicate that the proposed control scheme guarantees closed‐loop system stability with the state trajectories converging to the desired equilibrium. Particularly, using as generic concept the fundamental property of passivity of the original system, the proposed controller scheme results in a closed‐loop system wherein (i) the passivity and damping properties are maintained and (ii) the conditions which exploit these properties in a manner that guarantees stability are met. Extended simulation and experimental results verify effectiveness of the controller for the case of a DC/DC boost converter with resistance‐inductance load. The system performance, operating with the proposed non‐linear (voltage) controller is compared with that obtained by implementing conventional cascaded (voltage–current) controllers under input voltage step disturbances or load variations. Finally, some experimental resuts for the case of a non‐linear load consisted of a three‐phase voltage source inverter and a three‐phase resistance–inductance load are illustrated.
Design and control of a wind energy conversion system based on a resonant dc/dc converter
Authors: Fan Shixiong , Ma Weiwei , Lim Tee Chong , Williams Barry Wayne
Published: May 2013

Recent wind energy harvesting technology development has focused on using dc collection and a possible smaller passive grid because of high energy efficient components in the converter system. This study evaluates and compares the hard‐switched full bridge converter and the series–parallel LCC resonant converter, both with transformer coupling, and suitable for wind energy conversion system (WECS). Experimental results substantiate their merits and drawbacks in variable wind speed conditions. The unique, previously unexploited feature of the LCC resonant converter is increased gain at low output power, low speed and low input voltage. A hardware wind turbine simulator emulating an actual wind turbine is used, with its design and control briefly highlighted. This study demonstrates the feasibility of utilising an LCC resonant converter for WECS through simulation and experimental results, both at the same power level.
Direct‐drive low‐speed wind energy conversion system incorporating axial‐type permanent magnet generator and Z‐source inverter with sensorless maximum power point tracking controller
Authors: Ramasamy Bharani Kumar , Palaniappan Aravindan , Mohamed Yakoh Sanavullah
Published: May 2013

With the ever increasing concern on environmental pollution and energy crisis, generation of power from wind is developing very fast. In the proposed wind energy conversion system (WECS), a variable‐speed wind turbine, axial‐type permanent magnet generator (PMG), Z‐source inverter (ZSI) and sensorless maximum power point tracking (MPPT) controller are included. Although the conventional‐type induction generator has the advantage of robust construction and maintenance‐free operation, it has drawbacks like low‐power factor and need for an ac excitation source which is overcome by the PMG. To obtain fixed voltage and frequency, PMG‐generated voltage is fed to power converters. Conventionally the three stages of power conversion consist of rectifier, boost chopper and pulse‐width‐modulated inverter which reduce the efficiency, power quality and reliability of the overall WECS. To overcome these barriers of conventional system a two‐stage‐based direct‐drive WECS is proposed. The maximum power point for each speed is traced using sensorless MPPT controller, which estimates the rotor speed, by using a simple sensorless speed estimator which is given as the input to the MPPT controller. The proposed sensorless MPPT controller for direct‐drive WECS along with the ZSI is simulated in MATLAB/SIMULINK and the results are compared with experimental setup.
Grid‐tied photovoltaic system with series Z‐source inverter
Authors: Tang Yu , Wei Jukui , Xie Shaojun
Published: May 2013

This study presents a grid‐tied photovoltaic (PV) system based on the series Z‐source inverter. The grid‐tied current control strategy, the dc‐link voltage control, as well as the maximum power point tracking scheme is realised in the single‐stage system. The current control strategy is performed based on dq rotating frame. Indirect dc‐link control is adopted to achieve constant peak dc‐link voltage and thus can simplify the controller design in inversion stage. The overall control strategy is given and analysed in detail. Simulation and experimental results demonstrate that the proposed system can be applied in PV system with a wide input voltage range, which verify the correctness and validity of the analysis.
Pose measurement for fighter empennage based on string sensors
Authors: Qu Zhiyong , Han Jun Wei
Published: May 2013

A follow‐up control system is designed to fulfil the fatigue test experiment of fighter empennage. To measure the distortion of empennage, a cost‐effective simple rapid measurement method is put forward to permit precise pose measurement on the basis of string sensors. Two sets of string sensor measurement systems are mounted on the base and the vibration table, respectively. The joint coordinates of the measure system composed of six string sensors are determined by a coordinate measurement machine (CMM). Using the forward kinematics, inverse kinematics of Stewart table and quaternion, the string sensor measurement system gets the pose of empennage after the high‐frequency component arising from vibration table is filtered by a low‐pass filter. Compared with the computation data obtained from CMM, it is demonstrated that the measurement method on pose measurement by string sensor is valid and convenient. All two string sensor measurement systems can run effectively in the fatigue test experiment of fighter empennage.
Simplified computational routine to correct the modal decoupling in transmission lines and power systems modelling
Authors: da Costa Eduardo Coelho Marques , Kurokawa Sérgio , Gomes Pinto André Jinno , Kordi Behzad , Pissolato José
Published: May 2013

Modal analysis is widely approached in the classic theory of power systems modelling. This technique is also applied to model multiconductor transmission lines and their self and mutual electrical parameters. However, this methodology has some particularities and inaccuracies for specific applications, which are not clearly described in the technical literature. This study provides a brief review on modal decoupling applied in transmission line digital models and thereafter a novel and simplified computational routine is proposed to overcome the possible errors embedded by the modal decoupling in the simulation/modelling computational algorithm.
Developing an in silico model of the modulation of base excision repair using methoxyamine for more targeted cancer therapeutics
Authors: Gurkan‐Cavusoglu Evren , Avadhani Sriya , Liu Lili , Kinsella Timothy J. , Loparo Kenneth A.
Published: May 2013

Base excision repair (BER) is a major DNA repair pathway involved in the processing of exogenous non‐bulky base damages from certain classes of cancer chemotherapy drugs as well as ionising radiation (IR). Methoxyamine (MX) is a small molecule chemical inhibitor of BER that is shown to enhance chemotherapy and/or IR cytotoxicity in human cancers. In this study, the authors have analysed the inhibitory effect of MX on the BER pathway kinetics using a computational model of the repair pathway. The inhibitory effect of MX depends on the BER efficiency. The authors have generated variable efficiency groups using different sets of protein concentrations generated by Latin hypercube sampling, and they have clustered simulation results into high, medium and low efficiency repair groups. From analysis of the inhibitory effect of MX on each of the three groups, it is found that the inhibition is most effective for high efficiency BER, and least effective for low efficiency repair.
In vivo measurement of blood flow in a micro‐scale stenosis model generated by laser photothermal blood coagulation
Authors: Lee Sang Joon , Ha Ho Jin
Published: May 2013

Blood flow in a stenosed vessel is one of the most important issues, because it is closely related to the outbreak of circulatory diseases. To overcome the technological limitations encountered in the haemodynamic studies using in vitro stenosis models, the authors induced a stenosed flow model in the extraembryonic vessels of a chicken embryo. Blood was coagulated by laser irradiation to artificially form a stenosis on the designated spot in a straight blood vessel. Owing to photothermal coagulation of red blood cells (RBCs), the blood is denatured and a stable blood coagulum is induced in the vessel. The blood coagulum adheres firmly and stably on the vessel wall without any size variation. It disturbs the on‐coming blood flow significantly. To investigate the haemodynamic characteristics of the blood flow in the stenosed vessel, a micro particle image velocimetry technique was employed using RBCs as tracers to measure the spatial distributions of velocity vectors, streamlines and shear rate. The present simple modelling of in vivo stenosis would be useful for investigating the basic haemodynamic mechanisms underlying circulatory vascular diseases.
Systems approach to developmental biology – designs for robust patterning
Authors: Morishita Yoshihiro , Hironaka Ken‐ichi
Published: May 2013

Patterning is an important step in animal development that generates spatially non‐uniform gene expression patterns or spatially heterogeneous cellular responses. Patterning is realised by the generation and reading of positional information provided by spatial gradients of morphogens, diffusive chemicals in the extracellular environment. To achieve normal development, accurate patterning that is robust against noise is necessary. Here the authors describe how morphogen gradient formation and gradient interpretation processes are designed to achieve highly reproducible patterning. Furthermore, recent advancements in measurement and imaging techniques have enabled researchers to obtain quantitative dynamic and multi‐physical data, not only for chemical events, but also for the geometrical and mechanical properties of cells in vivo. The authors briefly review some recent studies on the effects of such non‐chemical events on patterning.
SU‐8 piezoresistive microcantilever with high gauge factor
Authors: Kok Siong Lee , Abdul Azid Ishak , Sidek Othman , Ibrahim Kamarulazizi , Devarajan Mutharasu
Published: May 2013

Presented is an SU‐8 microcantilever sensor with integrated piezoresistors made of a mixture of SU‐8 polymer and silver nanoparticles. The resulting composite is a spin‐coatable and ultraviolet patternable conductive polymer, which can be easily incorporated with any SU‐8‐based microdevice. The microfabrication technique used in this work is based on adhesive bonding of the cantilever layers with the thick support base to obtain a three‐dimensional structures device, which is a cost‐effective and fast fabrication process. Based on the current–voltage (I –V) test, the fabricated piezoresistors exhibit a linear resistance characteristic with good conductivity. The gauge factor calculated from the deflection test was obtained to be as high as 26.3, demonstrating the capability for embedded SU‐8/Ag piezoresistors to improve sensitivity when using polymeric material as a sensor platform.
Synthesis of BiOI nanobelt and its visible‐light photocatalytic activity
Authors: Wang Ping‐Quan , Bai Yang , Liu Jian‐Yi , Fan Zhou , Hu Ya‐Qin
Published: May 2013

BiOI nanobelts were synthesised by a one‐pot solvothermal process in the presence of [Bmim]I. As‐synthesised BiOI nanobelts showed higher photocatalytic activity in the aqueous RhB photodegradation system than BiOI nanosheets under visible‐light irradiation. It could be widely used for the environmental purification of organic pollutants in an aqueous solution.
Surfactant‐assisted hydrothermal synthesis and tribological properties of flower‐like MoS2 nanostructures
Authors: Tang Guogang , Sun Jianrong , Chen Wei , Tang Hua , Wang Yijiang , Li Changsheng
Published: May 2013

Flower‐like molybdenum disulfide (MoS2) nanostructures with high purity were successfully synthesised via a facile surfactant‐assisted hydrothermal route. The structure and morphology of the as‐prepared products were characterised by X‐ray powder diffraction, energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. The influence of the surfactant and the pH value of the initial mixture on the formation of the MoS2 nanostructures was investigated. A possible evolutionary process of the flower‐like MoS2 nanostructures is proposed to explain the formation of various MoS2 nanostructures on the basis of the experimental results. In addition, the tribological properties of the as‐prepared MoS2 powders as additives in HVI500 base oil were investigated on an UMT‐2 multispecimen tribo‐tester. The topography of worn scars was obtained using a common SEM. It is found that the addition of MoS2 nanoflowers can improve the tribological properties of the base oil.
Differential piezoresistive sensing in a bulk‐mode micromechanical resonator
Authors: Wei Xueyong , Seshia Ashwin A.
Published: May 2013

A report is presented on a differential piezoresistive sensing approach for transducing the motional response of bulk‐mode micromechanical resonators. High‐frequency bulk‐mode micoresonators have inherently high stiffness and demonstrate limited range of motion, which in turn presents challenges for the capacitive sensing method in the presence of large parasitic feedthrough. A differential piezoresistive sensing approach is implemented in this Letter to substantially reject the effects of parasitic capacitive feedthrough, leaving the response recovered directly from the measurement. With differential pick‐up, a 33 dB drop of feedthrough has been achieved and a resonant peak magnitude of 14 dB is obtained for a drain current of 1 mA, which is shown to be approximately 20 times higher than that obtained for the conventional piezoresistive sensing scheme. This method also enables a low DC voltage for capacitively driving the bulk‐mode resonator. As an example, a resonant peak magnitude of 5 dB is demonstrated using 3.55 mA drain current and 5 V DC driving voltage.
Graphene‐like nanocarbides and nanonitrides of d metals (MXenes): synthesis, properties and simulation
Authors: Shein Igor R. , Ivanovskii Alexander L.
Published: May 2013

Very recently (2011, Advanced Materials, 23, 4248), an elegant exfoliation approach was proposed to prepare a new family of two‐dimensional (2D)‐like transition metal carbides and nitrides from layered MAX phases. This discovery has provided the next stage in the design of new graphene‐like inorganic materials with intriguing functionalities and applications. This overview is intended as an introduction to this newest family of graphene‐like quasi‐2D nanocarbides and nanonitrides of d metals, which are known today also as MXenes. Here the authors discuss the available results achieved for MXenes (2011–2012), when a group of various MXenes (2D‐Ta4C3, Ti3(C0.5N0.5)2, TiNbC and some others) have been successfully synthesised, a set of their properties (conductivity, mechanical behaviour etc.) were measured and systematical theoretical studies of structural, electronic properties, chemical bonding and the stability of MXenes were initiated. Besides, possible applications of MXenes as promising materials for Li ion batteries, sensors or 2D electronics etc. are noted.
Synthesis and properties of multiple shell hollow SiO2@CeO2 microspheres
Authors: Zhang Li‐Xin , Sun Yi‐Xin , Fu Yue‐Hua , Jiu Hong‐Fang , Han Tao , Wang Yuan‐Zhong , Liu Jianwei
Published: May 2013

The preparation and properties of multiple shell hollow SiO2@CeO2 hybrid microspheres through a novel and facile method of layer‐by‐layer sol–gel carbon templating is presented. The whole process involves three key strategies: the loading of silica precursor into the carbon templates, the coating of cerium precursor nanocrystals upon the template, and formation of the final product after calcination. The presented approach may suggest a novel general route towards the preparation of a series of multiple shell hollow hybrid microspheres, which would show great potential for applications in drug delivery systems, catalysis, gas‐sensing and so on.
Design and characterisation of a three‐forked micropump on a fluid circulation channel
Authors: Mun Byung‐Phil , Park Chang‐Ju , Yoo Sung‐Keun , Lee Jong‐Hyun
Published: May 2013

A fluid circulation micropump that has three control channels activated by a single pressure source is reported. The proposed micropump can rotate a fluid in one direction because the control channels have widths that decrease in the fluid flow direction, thereby squeezing a fluid channel with different deflections under an identical pressure. The response time and deflection of the control channels are also investigated to demonstrate the effect of width differences on the flow rate of the micropump. In this reported work, several micropumps with different channel width ratios are fabricated, and their flow rates are experimentally analysed; the maximum flow rate of the proposed micropump was 10.8 nl/min at 3 Hz and 350 kPa for control channel widths of 300, 200 and 100 μm.