bluuebunny/crossref_metadata_2025 huggingface dataset:
Colour combination attention for object recognition
Authors: Zhu Jie , Yu Jian , Wang Chaomurilige , Li Fan‐Zhang
Published: July 2014

Within the bag‐of‐words (BOWs) framework, the multiple cues fusion methods provide excellent results in object and scene classification. Top‐down colour attention (CA) method is developed to use colour to guide attention by means of a top‐down category‐specific attention map. In this method, more features are taken from category‐specific colour regions where objects are more likely to be contained. In CA, the colours on the object are considered separately, so the diversity of object colours and large intra‐class colour variation make the discrimination of every colour on the object different. Object could be recognised as a collection of related colours. To enhance the object recognition capability of CA, our colour combination attention method uses mutual information and the colour combination histogram to estimate and combine the colours on the object. Results are presented on three challenging data sets, and the experiments demonstrate that the proposed feature fusion method significantly outperforms the state‐of‐the‐art methods.
Corner detection using Gabor filters
Authors: Zhang Wei‐Chuan , Wang Fu‐Ping , Zhu Lei , Zhou Zuo‐Feng
Published: July 2014

This study proposes a contour‐based corner detector using the magnitude responses of the imaginary part of the Gabor filters on contours. Unlike the traditional contour‐based methods that detect corners by analysing the shape of the edge contours and searching for local curvature maxima points on planar curves, the proposed corner detector combines the pixels of the edge contours and their corresponding grey‐variation information. Firstly, edge contours are extracted from the original image using Canny edge detector. Secondly, the imaginary parts of the Gabor filters are used to smooth the pixels on the edge contours. At each edge pixel, the magnitude responses at each direction are normalised by their values and the sum of the normalised magnitude response at each direction is used to extract corners from edge contours. Thirdly, both the magnitude response threshold and the angle threshold are used to remove the weak or false corners. Finally, the proposed detector is compared with five state‐of‐the‐art detectors on some grey‐level images. The results from the experiment reveal that the proposed detector is more competitive with respect to detection accuracy, localisation accuracy, affine transforms and noise‐robustness.
Image authentication algorithm with recovery capabilities based on neural networks in the DCT domain
Authors: El'arbi Maher , Ben Amar Chokri
Published: July 2014

In this study, the authors propose an image authentication algorithm in the DCT domain based on neural networks. The watermark is constructed from the image to be watermarked. It consists of the average value of each 8 × 8 block of the image. Each average value of a block is inserted in another supporting block sufficiently distant from the protected block to prevent simultaneous deterioration of the image and the recovery data during local image tampering. Embedding is performed in the middle frequency coefficients of the DCT transform. In addition, a neural network is trained and used later to recover tampered regions of the image. Experimental results shows that the proposed method is robust to JPEG compression and can also not only localise alterations but also recover them.
New technique for online object tracking‐by‐detection in video
Authors: Azab Maha M. , Shedeed Howida A. , Hussein Ashraf S.
Published: July 2014

Object detection and tracking is an important task within the ﬁeld of computer vision, because of its promising application in many areas, such as video surveillance. The need for automated video analysis has generated a great deal of interest in the area of motion tracking. A new technique is proposed for online object tracking‐by‐detection capable of achieving high detection and tracking rates, using a stationary camera, in a particle filtering framework. The fundamental innovation is that the detection technique integrates the local binary pattern texture feature, the red green blue (RGB) colour feature and the Sobel edge feature, using ‘Choquet’ fuzzy integral to avoid uncertainty in the classification. This is performed by extracting the colour and edge grey scale confidence maps and introducing the texture confidence map. Then, the tracking technique makes use of the continuous confidence detectors, extracted from those confidence maps, along with another three introduced classifier confidence maps, extracted from an online boosting classifier. Finally, both the confidence detectors and the classifier maps are integrated in the particle filtering framework, using the Choquet integral. Experimental results for both indoor and outdoor dataset sequences confirmed the robustness of the proposed technique against illumination variation and scene motion.
Effectiveness of forward obstacles collision warning system based on deceleration for collision avoidance
Authors: Takada Shota , Hiraoka Toshihiro , Kawakami Hiroshi
Published: July 2014

In the authors previous study, the authors proposed deceleration for collision avoidance (DCA) as an index to evaluate collision risks against forward obstacles and examined the effectiveness of their forward obstacles collision warning system (FOCWS) based on DCA. In the present manuscript, they improve the visual interface of the FOCWS, and conduct driving simulator experiments to quantitatively evaluate the effectiveness of the improved FOCWS in situations where a preceding vehicle decelerates abruptly. The experimental results revealed that the FOCWS based on DCA was effective in assisting drivers to shorten the reaction time and to avoid collisions. Moreover, in the subjective assessment questionnaire, a significant number of experimental participants reported that the FOCWS based on DCA could evaluate collision risks more properly compared with the FOCWS based on a time‐to‐collision.
Empty vehicles management as a method for reducing passenger waiting time in Personal Rapid Transit networks
Authors: Daszczuk Wiktor Bohdan , Choromański Włodzimierz , Mieścicki Jerzy , Grabski Waldemar
Published: July 2014

Empty vehicles management may improve the average waiting time for vehicle delivery in the Personal Rapid Transit (PRT) network. In this study, original heuristic algorithm of empty vehicle management is presented. The algorithm is tested in several benchmark PRT structures under Feniks simulation environment. The results show that significant improvements of average waiting time may be achieved just because of the multi‐parameter analysis of the present network state alone rather than by the predictive use of forecasted demand. The algorithm does not use any central database of demand and location of free vehicles. Instead, it assumes the local exchange of data between stations on their state and expected vehicles. Therefore it seems well tailored to a distributed implementation.
Analysing the impact of weather on bus ridership using smart card data
Authors: Li Linbo , Wang Jing , Song Ziqi , Dong Zhi , Wu Bing
Published: July 2014

This study investigates the impact of weather on bus ridership using smart card data collected in Fengxian, Shanghai. The ridership data are categorised into three representative groups by the cluster analysis. The ridership data for each cluster are further divided according to the four seasons. Twelve separate multiple linear regression models with four weather variables and two dummy variables are constructed and calibrated. All four weather variables, namely humidity, wind speed, rainfall and temperature are found to have statistically significant negative effects on bus ridership. The magnitude of the impact varies depending on bus route types, seasons and mode share characteristics. Our analysis provides a valuable case study on weather's impact on bus ridership and concludes that there is no one‐size‐fits‐all conclusion about the relationships between weather attributes and bus ridership, and it is critical to investigate those relationships in different geographical contexts. The results of this study can be used not only for long‐term transit policy making but also as a decision making tool for short‐term ridership forecasting.
60 GHz optically transparent microstrip antenna made of meshed AuGL material
Authors: Hautcoeur Julien , Talbi Larbi , Hettak Khelifa , Nedil Mourad
Published: July 2014

In this study, a 60 GHz optically transparent microstrip (OTM) patch antenna array is designed, fabricated and measured. Gold meshes are implemented for the two layers of the antenna. A numerical parametric study on the positioning of the two meshed layers is performed to give design considerations and optimise both the electromagnetic and optical performances of OTM antennas at 60 GHz band. The simulation and measured results of the OTM antenna with a theoretical maximum transparency up to 74.6% are compared with a light reflecting reference antenna. Both antennas have similar reflection coefficients and radiating performances. This study provides practical design rules to fabricate high gain OTM antennas with performances similar to those of standard topologies at 60 GHz band, with the addition of high optical transparency.
High‐directivity on‐glass window antenna using a see‐through reflector
Authors: Choe Hyeonhyeong , Lim Sungjoon
Published: July 2014

A high‐directivity on‐glass window antenna with a see‐through reflector is presented. The proposed structure consists of two pieces of glass: one includes a radiating antenna and the other includes a reflector. To provide lower visual impact, a loop antenna and a loop‐type frequency‐selective surface are employed as the radiating antenna and reflector, respectively. Simulation and experimental results demonstrate the performance of the antenna. At 1.8 GHz, the measured peak gain with the see‐through reflector is 7.96 dBi, whereas the peak gain without the see‐through reflector is 0.68 dBi. Therefore the peak gain at 1.8 GHz is improved by 7.28 dB after using the see‐through reflector.
Sensitivity analysis of faceted reflector antennas and a contour beam synthesis technology
Authors: Zhang Shuxin , Duan Bao Yan , Yang Dongwu
Published: July 2014

Faceted reflectors are widely utilised in the application of satellite deployable antennas. The sensitivity analysis with respect to surface deformation is an essential part in the error evaluation for distorted reflector antennas. In this study, the sensitivity analysis of electrical radiation performance with respect to surface deformation for faceted reflectors is investigated. A contour beam pattern synthesis technology is proposed for the faceted reflector antennas based on sensitivity analysis, with considering the special characteristics of flat facets. Two faceted reflectors are simulated to show their directivity sensitivity with respect to surface nodal displacement, and a contour beam covering the continental United States (CONUS) with the desired directivity is obtained by shaping a single offset faceted reflector antenna.
Modelling of a paraboloid antenna for receiving and its equivalent circuit
Authors: Gao Xiang , Du Zhengwei
Published: July 2014

This study presents a SPICE model of a paraboloid antenna for receiving. The proposed model is converted from a receiving model based on the Thévenin's theorem and the reciprocity theory through rational approximation. The model gives the coupling voltages on the antenna load when the antenna is illuminated by plane waves. This model can be used in both frequency‐domain and time‐domain analyses, and can be a part of a system‐level model for electromagnetic compatibility simulation in circuit solvers. The proposed model has been verified by several examples.
Efficient modulation technique for optical code division multiple access networks: differential pulse position modulation
Authors: Khazraei Simin , Shoaie Mohammad Amin , Pakravan Mohammad Reza
Published: July 2014

In this study, the authors study a fibre‐optic local area network deploying optical code division multiple access technique with differential M ‐ary pulse position modulation (DPPM). The authors present the performance analysis of DPPM signalling using a double optical hardlimiter receiver structure considering the impairment caused by interference of other users. The analysis assumes a set of bit asynchronous transmitters employing generalised optical orthogonal codes for their DPPM signalling (GOOC‐DPPM). Using mathematical analysis and simulations, the authors have demonstrated that GOOC‐DPPM improves both frame error probability and the maximum achievable network throughput compared with M ‐ary PPM modulation scheme. It is also indicated that using generalised OOC codes instead of strict OOC codes in DPPM modulation can increase the number of users who can simultaneously transmit data in the network. The authors have analysed the stability of GOOC‐DPPM in a multi‐user system and demonstrated its stability. Moreover, the performance of the proposed scheme is evaluated when its important design parameters such as code length, code weight and multiplicity index of the modulation are changed. The findings led the authors to provide some guidelines for proper selection of these parameters to be used for efficient system design.
Mid‐infrared polarisation rotator based on an asymmetric Ge‐strip‐on‐si waveguide
Authors: He Wenbin , Cassan Eric
Published: July 2014

Polarisation rotators are of great importance for high‐data rate integrated photonic circuits. In this study, the authors provide the design of a polarisation rotator based on an asymmetric germanium strip on a silicon substrate operating in the mid‐infrared band which has recently received a strong interest because of its huge potential for various applications. Two different asymmetric geometries, the slant and the two‐step waveguides, are presented and theoretically investigated. Both of them can achieve single‐mode transmission and high conversion efficiency (> 90%) in short polarisation rotation lengths (−60 µm or −10λ and −120 µm or −20λ) and wide operation bandwidth (−5 µm ≤ λ ≤ −7 μm). The optimisation process and spectral analysis are provided and the properties of these two geometries are compared.
Analytical power losses model of boost rectifier
Authors: Ivanovic Zeljko , Blanusa Branko , Knezic Mladen
Published: July 2014

An analytical power losses model of boost rectifier is presented in this study. A power losses model that takes into account both continuous and discontinuous current modes is derived. The analytical expressions of conduction and dynamic losses, including losses in inductor core and winding, are given. Also, equivalent input resistance, which models single‐phase and three‐phase rectifiers’ power losses, is modelled. The model is verified through simulations and experimental measurements on single‐phase boost rectifier that is used in wind turbine with permanent‐magnet generator.
Frequency response analysis for bidirectional series‐resonant DC/DC converter in discontinuous mode
Authors: Ibanez Federico , Echeverria Jose Martín , Vadillo Javier , Fontan Luis
Published: July 2014

This study analyses the frequency response of a bidirectional series‐resonant DC/DC converter (SRC) working in a discontinuous mode (DCM). The converter can reach a voltage conversion ratio higher or lower than one, depending on whether the operation mode is step‐up or step‐down. The analysis is based on a novel mixed technique using both the state‐space average method and the Fourier method to obtain a state‐space averaged model of the converter. The study presents the model for the two operation modes. It also presents the frequency response of the output voltage as a function of the input voltage and as a function of the off‐time, which is the control parameter of the converter. The results of those transfer functions are compared with measurements in a 2000 W prototype. The model provides enough information to properly control the SRC in DCM.
Rotor eccentricity fault compensation by voltage control of brushless DC motor
Authors: Shakouhi Seyed Mohammad , Mohamadian Mustafa , Afjei Ebrahim
Published: July 2014

Rotor eccentricity is one of the common failures that can happen to a motor. In recent years, considerable amount of researches for rotor eccentricity fault diagnosis have been presented. However, no attention is given to the case of ‘eccentricity fault tolerant control’. The necessity of ‘eccentricity fault tolerant control’ is the importance of motor continuous operation during fault in sensitive industries with the best possible performance. Applying conventional control methods during eccentricity fault is not efficient. Since, these methods do not consider eccentricity fault effects such as distortion in flux linkage distribution and motor back‐electro‐motive force (EMF) waveform, as well as phase inductances changes which may lead to undesirable torque ripples. Hence, a new control strategy for improving motor performance is advantageous. In this study, a control method for brushless direct current (BLDC) motor in presence of static rotor eccentricity is proposed. On‐line estimation of phase inductances and phase‐to‐phase flux linkages during eccentricity is the basis of the proposed control method. In the proposed strategy, the controller adjusts motor terminal voltages considering changes in motor specifications because of eccentricity, without using phase current control loop. Experimental results verify performance of the proposed method in reducing electromagnetic torque pulsations during fault.
Stability analysis and performance evaluation of a single‐phase phase‐locked loop algorithm using a non‐autonomous adaptive filter
Authors: Bacon Vinícius Dario , Oliveira da Silva Sérgio Augusto , Garcia Campanhol Leonardo Bruno , Angélico Bruno Augusto
Published: July 2014

This study proposes a phase‐locked loop (PLL) algorithm employed for phase‐angle detection of single‐phase utility grid voltage. A detailed stability analysis is performed, as well as its performance is evaluated under several power quality problems. The proposed PLL structure is based on the instantaneous active power theory for three‐phase power systems (pPLL), which is investigated into the fictitious two‐phase stationary reference frame (αβ‐pPLL). A non‐autonomous adaptive filter (AF) operates in conjunction with the PLL, and its main function is to extract the fundamental component of the utility grid voltage allowing the rejection of voltage harmonics. The stability analysis of the proposed AF‐αβ‐pPLL scheme is carried out in order to provide adequate tuning procedures for choosing the parameters used in the proposed algorithm. In addition, the dynamic response and robustness of the AF‐αβ‐pPLL algorithm are evaluated by means of simulation and experimental tests, under utility grid disturbances, such as voltage harmonics, voltage sag, phase jumps and frequency variations. To emphasise the effectiveness of the algorithm, a comparative analysis with three other single‐phase PLL schemes is carried out, such as the conventional power‐based PLL (pPLL), the two‐phase stationary reference frame pPLL (αβ‐pPLL) and the well‐known enhanced PLL (EPLL).
Clutter suppression approach for non‐sidelooking airborne radar with medium pulse repetition frequency
Authors: Dai Baoquan , Wang Tong , Wu Yifeng , Wu Jianxin , Bao Zheng
Published: July 2014

For non‐sidelooking airborne radar operating in medium pulse repetition frequency mode, the space–time adaptive processing (STAP) technique suffers from a significant performance loss due to the range dependence of clutter. Here, an efficient clutter suppression approach is presented to improve STAP performance. Utilising the characteristics of clutter, the near‐range clutter, the major reason for the performance degradation, is extracted from raw returns using a specially designed oblique projector firstly, and then is mitigated by an adaptive beamformer estimated from the extracted components. Subsequently, an azimuth‐Doppler STAP beamformer is employed to further suppress the residual clutter. To enhance the robustness of the approach, a simple steering vector calibration technique is taken into account. The proposed approach can eliminate the near‐range clutter effectively, and therefore alleviate the clutter range dependence greatly. The STAP performance can be improved significantly. Simulation results demonstrate the effectiveness of the presented method.
Direct algorithm for the Pareto load‐pull optimisation of power‐added efficiency and adjacent‐channel power ratio
Authors: Fellows Matthew , Baylis Charles , Martin Joshua , Cohen Lawrence , Marks Robert J.
Published: July 2014

Adaptive radar systems will be required to operate in different frequency bands with spectrum requirements that will likely change both in time and with geographic region. A new algorithm is presented that allows direct optimisation of an amplifier's load reflection coefficient to find a Pareto optimum between the power‐added efficiency (PAE) and adjacent‐channel power ratio. Comparisons of simulation and measurement results are presented. The new algorithm's results compare well with traditionally acquired data and show consistency between the optimum values for PAE that are obtained from different starting points. Measurement comparison is performed with the previous optimisation algorithm reported by the authors, and results show that up to a 50% reduction in the number of measured experimental queries can be obtained. This translates into a significant time savings in reconfiguring a radar transmitter power amplifier.
A subspace‐based channel calibration algorithm for geosynchronous satellite‐airborne bistatic multi‐channel radars
Authors: Zhang Dandan , Qiu Xiaolan , Hu Donghui , Lv Xiaolei , Huang Lijia , Ding Chibiao
Published: July 2014

Ground moving target indication based on geosynchronous (GEO) satellite‐airborne (SA) bistatic radar can keep a certain area under continuous surveillance, and thus has important military application values. However, a channel error will affect the clutter suppression performance of the bistatic multi‐channel moving target indication radar. And it is found that the channel calibration algorithm used in the long sequence monostatic side‐looking synthetic aperture radar, is not applicable to the long sequence translational variant bistatic radar. An improved subspace‐based channel calibration algorithm is proposed in this study to deal with channel errors of the GEO SA bistatic multi‐channel radar. The algorithm utilises the clutter as calibrated sources, and estimates channel error parameters by minimising the projections of the calibrated sources onto the noise subspace. As the channel errors are estimated from the data, the proposed algorithm does not need any extra calibration sources. Also, the proposed algorithm does not have the limitation of the traditional array self‐calibration algorithms, which may have non‐unique estimations under the condition of linear arrays. Besides, it avoids finding the inversion of large‐size matrix and calculating with any iteration, and hence it is efficient. Moreover, the proposed algorithm can estimate channel errors that vary with azimuth. Simulations are performed to validate the proposed algorithm.
Spaceborne squinted multichannel synthetic aperture radar data focusing
Authors: Huang Pingping , Xu Wei , Li Shengyang
Published: July 2014

This study analyses echo properties of spaceborne squinted multichannel along the track synthetic aperture radar (SAR) data. The highly squint angle and the large transmitted pulse bandwidth lead to Doppler spectrum back folding in the spaceborne squinted case. The extended Doppler bandwidth in the squinted mode increases the processing difficulty of azimuth multichannel data reconstruction. According to echo properties of the spaceborne squinted mode, a new imaging approach for spaceborne squinted multichannel SAR data focusing is proposed. The key point of this imaging approach is azimuth multichannel data preprocessing to resolve the aliased Doppler spectrum caused by both azimuth sub‐sampling in each azimuth channel and the highly squint angle. Afterwards, a modified range migration algorithm is taken for consequent equivalent monostatic spaceborne squinted SAR data focusing. Simulation results on point targets and distributed target are given to validate the proposed imaging approach.
Analysis of non‐linear properties of digital radar range finders using statistical linearisation method
Authors: Bystrov Aleksandr , Djigan Viktor , Gashinova Marina
Published: July 2014

This study considers the influence of signal sampling and amplitude quantisation on the properties of digital radar range finding. The method of statistical linearisation of the non‐linear discrimination characteristic of time discriminator was used to analyse the accuracy of steady‐state range measurements, and mathematical relationships were obtained. The influence of input noise on the linearisation of discrimination characteristics was explored. The mathematical relationships and findings presented in this study are confirmed by the results of simulation and allow establishment of the optimal parameters of range finders.
Low power software defined incoherent scatter radar system design concept for continuous sounding the earth's ionosphere
Authors: Yao Ming , Deng Xiaohua , Lu Ziqing , Bai Bo , Li Huixia
Published: July 2014

The incoherent scatter radar (ISR) is the only ground based instrument, which can detect space plasma parameters from tens to thousands of kilometres height above the earth. ISR system usually has large radio frequency (RF) power and antenna array size. The novel ISR introduced in this study has the advantages of low power consumption and continuous operation as it uses novel technologies. It can probe real time plasma parameters in the entire altitude range of the ionosphere (80–1000 km). Successful development of such an ISR will resolve the problem of continuous detection of ionospheric parameters. This study will introduce the design concept of this low power software defined ISR.
Tracking algorithm with radar and infrared sensors using a novel adaptive grid interacting multiple model
Authors: Wu Panlong , Li Xingxiu , Zhang Lianzheng , Bo Yuming
Published: July 2014

This study presents a novel adaptive grid interacting multiple model based on modified iterated extended Kalman filter (AGIMM‐MIEKF) for tracking a manoeuvreing target using radar/infrared (IR) heterogeneous sensors. This tracking algorithm is developed by aligning observation data of radar/IR sensors in time, and fusing the synthesised data before applying to AGIMM‐MIEKF algorithm. Under the architecture of the proposed algorithm, the AGIMM deals with the model switching, whereas the MIEKF accounts for non‐linearity in the dynamic system models. A new measurement update equation and an iterated termination criterion are derived and applied to radar/IR tracking system. The simulation results show that the presented AGIMM‐MIEKF has higher tracking precision than the traditional algorithms.
Real‐time measurement of meteorological parameters for estimating low‐altitude atmospheric turbulence strength (Cn2)
Authors: Arockia Bazil Raj Anthonysamy , Selvi James Arputha Vijaya , Raghavan Singaravelu
Published: July 2014

The major factor that limits the performance of Free Space Optical Communication is atmospheric turbulence which fluctuates over time in accordance with the variations in local meteorological parameters. Estimating the atmospheric turbulence strength Cn2 with the measurement data becomes significant to find the data rate the system is capable of operating under different outdoor local environmental conditions. Hence, a low cost customised system for continuously measuring the local meteorological data is developed and presented in this study. A field test scintillometer setup is established for a link range of 0.5 km at an altitude of 15.25 m. Specialised sensors are interfaced to the digital architectures to acquire the real‐time data corresponding to atmospheric changes. The accuracy and performance of the measurement system are tested against standard instruments and the maximum correlation coefficients of 99.92, 99.63, 99.73 and 99.88% are achieved for wind speed, temperature, relative humidity and pressure, respectively. An experimental model to estimate Cn2 using measured meteorological data is developed and the atmospheric turbulence strength is estimated. The validations of the estimated results with the scintillometer measurement are also analysed. The weather profile and corresponding Cn2 variations at our test field for different seasons in 1 year period are presented and the results are analysed.
Unadvertised energy saving method for static and homogeneous wireless sensor networks
Authors: Menegazzo Cinara , Albini Luiz Carlos Pessoa
Published: July 2014

Several approaches have been proposed to increase the lifetime of a wireless sensor network (WSN) while preserving full coverage of the sensed area. Most of them employ protocols to reduce the energy consumption by switching the sensors off. To correctly decide the set of nodes to switch off without losing the full network coverage, these techniques must guarantee that all nodes have up‐to‐date information about their neighbours. Considering a static WSN, the only important information which must be regularly advertised is the energy level of the nodes. This information is exchanged between nodes in fixed time slots through one‐hop messages. Nevertheless, the energy spent to transmit one simple bit of information is as the same used to process hundreds of transactions in a typical sensor. Thus, reducing the communication between nodes leads to an increase in the energy saving. This study proposes the unadvertised round energy saving (u‐REST) algorithm which eliminates the energy level advertise messages, thus conserving a huge amount of energy. u‐REST is able to increase the energy savings by deciding the set of nodes which can be switched off while preserving full area coverage without using energy level advertise messages. Mathematical proofs demonstrate that u‐REST ensures a full coverage of the interest area while saving energy. In fact, it is mathematically demonstrated that the worst case for energy savings in u‐REST is able to preserve more energy than the best case of all synchronisation‐based methods.
Dual mechanical behaviour of hydrogen in stressed silicon nitride thin films
Authors: Volpi F. , Braccini M. , Devos A. , Raymond G. , Pasturel A. , Morin P.
Published: July 2014

In the present article, we report a study on the mechanical behaviour displayed by hydrogen atoms and pores in silicon nitride (SiN) films. A simple three-phase model is proposed to relate the physical properties (stiffness, film stress, mass density, etc.) of hydrogenated nanoporous SiN thin films to the volume fractions of hydrogen and pores. This model is then applied to experimental data extracted from films deposited by plasma enhanced chemical vapour deposition, where hydrogen content, stress, and mass densities range widely from 11% to 30%, −2.8 to 1.5 GPa, and 2.0 to 2.8 g/cm3, respectively. Starting from the conventional plotting of film's Young's modulus against film porosity, we first propose to correct the conventional calculation of porosity volume fraction with the hydrogen content, thus taking into account both hydrogen mass and concentration. The weight of this hydrogen-correction is found to evolve linearly with hydrogen concentration in tensile films (in accordance with a simple “mass correction” of the film density calculation), but a clear discontinuity is observed toward compressive stresses. Then, the effective volume occupied by hydrogen atoms is calculated taking account of the bond type (N-H or Si-H bonds), thus allowing a precise extraction of the hydrogen volume fraction. These calculations applied to tensile films show that both volume fractions of hydrogen and porosity are similar in magnitude and randomly distributed against Young's modulus. However, the expected linear dependence of the Young's modulus is clearly observed when both volume fractions are added. Finally, we show that the stiffer behaviour of compressive films cannot be only explained on the basis of this (hydrogen + porosity) volume fraction. Indeed this stiffness difference relies on a dual mechanical behaviour displayed by hydrogen atoms against the film stress state: while they participate to the stiffness in compressive films, hydrogen atoms mainly behave like pores in tensile films where they do not participate to the film stiffness.
Design of magnetized liner inertial fusion experiments using the Z facility
Authors: Sefkow A. B. , Slutz S. A. , Koning J. M. , Marinak M. M. , Peterson K. J. , Sinars D. B. , Vesey R. A.
Published: July 2014

The magnetized liner inertial fusion concept has been presented as a path toward obtaining substantial thermonuclear fusion yields using the Z accelerator [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. We present the first integrated magnetohydrodynamic simulations of the inertial fusion targets, which self-consistently include laser preheating of the fuel, the presence of electrodes, and end loss effects. These numerical simulations provided the design for the first thermonuclear fusion neutron-producing experiments on Z using capabilities that presently exist: peak currents of Imax = 18–20 MA, pre-seeded axial magnetic fields of Bz0=10 T, laser preheat energies of about Elas = 2 kJ delivered in 2 ns, DD fuel, and an aspect ratio 6 solid Be liner imploded to 70 km/s. Specific design details and observables for both near-term and future experiments are discussed, including sensitivity to laser timing and absorbed preheat energy. The initial experiments measured stagnation radii rstag<75 μm, temperatures around 3 keV, and isotropic neutron yields up to YnDD=2×1012, with inferred alpha-particle magnetization parameters around rstag/rLα=1.7 [M. R. Gomez et al., Phys. Rev. Lett. (submitted)].
A self-consistent thermodynamic model of metallic systems. Application for the description of gold
Authors: Balcerzak T. , Szałowski K. , Jaščur M.
Published: July 2014

A self-consistent thermodynamic model of metallic system is presented. The expression for the Gibbs energy is derived, which incorporates elastic (static) energy, vibrational energy within the Debye model, and electronic part in Hartee-Fock approximation. The elastic energy is introduced by a volume-dependent anharmonic potential. From the Gibbs energy all thermodynamic quantities, as well as the equation of state, are self-consistently obtained. The model is applied for the description of bulk gold in temperature range 0 ≤ T ≲ 1300 K and external pressure up to 30 GPa. The calculated thermodynamic properties are illustrated in figures and show satisfactory agreement with experimental data. The advantages and opportunities for further development of the method are discussed.
Design and energy control of stand-alone hybrid wind/photovoltaic/fuel cell power system supplying a desalination unit
Authors: Smaoui Mariem , Krichen Lotfi
Published: July 2014

Faced with increasing trend of water demand and decreasing resources of fossil fuels and their high costs, desalination units based on renewable energies have become the best solution to face this challenge. This paper aims to investigate the design and the operation strategy of stand-alone hybrid renewable power generation system supplying a desalination unit which feeds the Kerkennah islands (Tunisia) with fresh water. The sizing of all the main hybrid system components such as photovoltaic generator, wind turbine, a fuel cell, and an electrolyzer is investigated in order to obtain some technical and economic profitability. In order to ensure the optimal use of the produced energy and satisfy the fresh water needs, a novel power management algorithm that allows controlling the energy flows within the system components is developed. Simulation results were carried out over the two months of January and July, and its results are shown in our paper. These results demonstrate the feasibility and the efficiency of the used control strategy and the performance of the hybrid system.
Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress
Authors: Lagger P. , Steinschifter P. , Reiner M. , Stadtmüller M. , Denifl G. , Naumann A. , Müller J. , Wilde L. , Sundqvist J. , Pogany D. , Ostermaier C.
Published: July 2014

The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ΔVth, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness tD and barrier thickness tB, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ΔNit, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ΔNit is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.
Strong surface passivation of GaAs nanowires with ultrathin InP and GaP capping layers
Authors: Haggren Tuomas , Jiang Hua , Kakko Joona-Pekko , Huhtio Teppo , Dhaka Veer , Kauppinen Esko , Lipsanen Harri
Published: July 2014

We demonstrate efficient surface passivation of GaAs nanowires using ultrathin in-situ grown epitaxial InP and GaP capping layers, with metallo-organic vapor phase epitaxy as the growth system. The passivation increased photoluminescence intensity by three orders of magnitude compared to unpassivated nanowires, and the effect remained strong after a month of storage in air. Effective passivation was acquired over a wide range of growth temperatures, although the highest studied temperatures caused additional detrimental effects such as etching and GaAsP formation. The capping layer thickness was in the order of few monolayers. Therefore, the impact on any other properties of the nanowires besides the surface states was minuscule. As a simple and effective method the studied capping layers offer an excellent way for nanowire passivation.
Variation of Two-Photon Absorption Cross Sections and Optical Limiting of Compounds Induced by Static Electric Field
Authors: Zhang Yu-jin , Song Yu-zhi , Wang Chuan-kui
Published: July 2014

By numerically solving the Maxwell-Bloch equations using an iterative predictor-corrector finite-difference time-domain technique, we investigate propagating properties of a few-cycle laser pulse in a 4,4′-bis(di-n-butylamino) stilbene (BDBAS) molecular medium when a static electric field exists. Dynamical two-photon absorption (TPA) cross sections are obtained and optical limiting (OL) behavior is displayed. The results show that when the static electric field intensity increases, the dynamical TPA cross section is enhanced and the OL behavior is improved. Moreover, both even- and odd-order harmonic spectral components are generated with existence of the static electric field because it breaks the inversion symmetry of the BDBAS molecule. This work provides a method to modulate the nonlinear optical properties of the BDBAS compounds.
Pseudo-Bonding Interaction between Boron-doped Heterofullerene and Zinc Porphine Predicted by DFT Calculation
Authors: Weng Jun-ying , Zhou Ting-ting , Zhang Ying-hui
Published: July 2014

Theoretical study on the supramolecular complexes formed between boron-doped heterofullerene (C59B) and zinc porphine (ZnP), namely C59B-ZnP and its anion species C59B−-ZnP, was performed by density functional theory calculation at wB97XD/6-31G(d) level. Strong interaction between porphyrin and heterofullerene moiety was predicted for these complexes based on geometry and electronic structure analysis. Especially, pseudo-bonding interaction occurring between the B atom of fullerene and the N atom of porphyrin was predicted to occur in C59B-ZnP complex, but be broken in C59B−-ZnP complex. Time-dependent density functional theory calculation manifests the redshift of electron absorption for ZnP upon the interaction with heterofullerene.
Magnetism and Sound Velocities of Iron Carbide (Fe3C) under Pressure
Authors: Zeng Zhao-yi , Hu Cui-e , Liu Xun , Cai Ling-cang
Published: July 2014

The elastic property and sound velocity of Fe3C under high pressure are investigated by using the spin-polarized generalized gradient approximation within density-functional theory. It is found that the magnetic phase transition from the ground ferromagnetic (FM) state to the nonmagnetic (NM) state occurs at ∼73 GPa. Based on the predicted Hugoniot of Fe3C, we calculate the sound velocities of FM-Fe3C and NM-Fe3C from elastic constants. Compared with pure iron, NM-Fe3C provides a better match of compressional and shear sound velocities with the seismic data of the inner core, supporting carbon as one of the light elements in the inner core.
A Slippery Slope: Estimated Slant of Hills Increases with Distance
Authors: Chiu Eric M , Thomas Kyle A , Persike Malte , Quan Joshua R , Bridgeman Bruce
Published: July 2014

The slopes of hills tend to be greatly overestimated. Previous studies have found that slope estimates are significantly greater when estimated verbally than with a proprioceptive measure. It has yet to be determined whether these estimates are made for the entire extent of the slope, or whether the estimates in closest proximity are estimated using a different process. Since some parietal cortex neurons respond differently to objects within arm's reach, short-distance slope estimation may utilize these or analogous neurons. Alternatively, greater implied effort might make longer slopes seem steeper. We determined that both verbal and proprioceptive reports of slope are overestimates that increase logarithmically with distance from the observer, contradicting both theories. Consistent with previous work, proprioceptive estimates were more accurate at all ranges. Our results can be interpreted as a function of the angle between the observer's gaze and the plane of the hill, modified by depth cues available at only near distances.
Structural basis for the extended CAP-Gly domains of p150
glued
binding to microtubules and the implication for tubulin dynamics
Authors: Wang Qianmin , Crevenna Alvaro H. , Kunze Ines , Mizuno Naoko
Published: July 2014

Significance

This study presents a direct visualization of the microtubule-p150glued(CAP-Gly) complex by cryo-EM and seeks to describe the molecular mechanism of the control of tubulin dynamics by p150 CAP-Gly. It highlights the neutralization of the acidic tubulin surface by the basic extensions of CAP-Gly, resulting in the activation of tubulin polymerization. In the condition where the lateral association is impeded (i.e., at low temperature), the extended CAP-Gly domain induces tubulin dimers to connect longitudinally. The two directional modes of self-association of tubulin suggest a foundation for its dynamic behavior at the tip of microtubules and its regulation.
Language planning in Kazakhstan
Authors: Akzhigitova Assel , Zharkynbekova Sholpan
Published: July 2014

The political, economic and sociocultural changes that took place after the break-up of the USSR continue to impact the linguistic landscape of Kazakhstan. The historical linkages to the Russian Empire and then the USSR, both of which were characterized by policies of Russification, have resulted in the existence of a highly multilingual society that features widespread bilingualism in Kazakh and Russian. The on-going bilingualism in Kazakhstan continues to significantly affect the growth rate of the national consciousness and the identity of Kazakh society. The focus of the study reported in this article was to understand how the complex pattern of language planning programs is reflected in the linguistic landscape of Kazakhstan and particularly in Astana, the new capital city, by examining how visual public signs (ergonyms) indicate the heterogeneous characteristics of the society and how different agencies work on the problems of language use and attitudes in the country.
Lexical expansion and terminological planning in indigenous and planned languages
Authors: Krägeloh Chris , Neha Tia N.
Published: July 2014

The development of terminology features heavily in language planning, and here the differences between planned and ethnic languages are much less pronounced. This is especially the case in languages with smaller numbers of speakers, or in indigenous and endangered languages such as Te Reo Māori of Aotearoa New Zealand that rely on language planning for their survival, and where conscious terminology planning is therefore commonplace. The present article compares the terminological principles that are applied in the creation of new terms in Te Reo Māori and the planned language Esperanto. Different preferences for endogenous versus exogenous ways of developing new words generate conflict in both language communities as they adapt to the demands of functioning in modern and international arenas. Long-term success in terminological planning can only be achieved by more comprehensive application of principles from terminological science to maximize the adequacy of the generated terms and their acceptance within the speech communities.
Dual cell protective mechanisms activated by differing levels of oxidative stress in HT22 murine hippocampal cells
Authors: Sato Kazunori , Yamanaka Yuki , Ishii Masaya , Ishibashi Kazusa , Ogura Yurina , Ohtani-Kaneko Ritsuko , Nishihara Masugi , Nedachi Taku
Published: July 2014

Oxidative stress is recognized as one of the pathogenic mechanisms involved in neurodegenerative disease. However, recent evidence has suggested that regulation of cellular fate in response to oxidative stress appears to be dependent on the stress levels. In this study, using HT22 cells, we attempted to understand how an alteration in the oxidative stress levels would influence neuronal cell fate. HT22 cell viability was reduced with exposure to high levels of oxidative stress, whereas, low levels of oxidative stress promoted cell survival. Erk1/2 activation induced by a low level of oxidative stress played a role in this cell protective effect. Intriguingly, subtoxic level of H2O2 induced expression of a growth factor, progranulin (PGRN), and exogenous PGRN pretreatment attenuated HT22 cell death induced by high concentrations of H2O2 in Erk1/2-dependent manner. Together, our study indicates that two different cell protection mechanisms are activated by differing levels of oxidative stress in HT22 cells.
Alpha-mangostin promotes myoblast differentiation by modulating the gene-expression profile in C2C12 cells
Authors: Horiba Taro , Katsukawa Masahiro , Abe Keiko , Nakai Yuji
Published: July 2014

Alpha-mangostin, a xanthone contained mostly in mangosteen pericarp, has been reported to exert various biological functions. However, little is known about involvement of this xanthone in the muscle differentiation process. Here, we report the effect of α-mangostin on murine skeletal muscle-derived C2C12 myoblasts. α-mangostin stimulated myoblast differentiation leading to myotube formation. DNA microarray analysis revealed that genes associated with myoblast differentiation and muscle cell component formation were up-regulated in α-mangostin-treated cells. These results indicate that α-mangostin promotes myoblast differentiation through modulating the gene-expression profile in myoblasts.