bluuebunny/crossref_metadata_2025 huggingface dataset:
Approach to stabilisation of continuous‐time switched positive systems
Authors: Yu Zhandong , Zhang Zhuoran , Cheng Sheng , Gao Huijun
Published: July 2014

The problems of stability and stabilisation for continuous‐time switched positive linear systems (SPLSs) under arbitrary switching are investigated in this study. A common quadratic copositive Lyapunov function (CQCLF) is first proposed for stability analysis of SPLSs. It is shown that the proposed Lyapunov function for a given SPLS is less conservative than a traditional common vector‐parameterised copositive Lyapunov function. Then, sufficient conditions for the existence of CQCLF that guarantees the stability of SPLSs under arbitrary switching are derived. Based on the new stability conditions, a numerical design method of state‐feedback controllers is also given to stabilise the underlying system. Finally, a numerical example is given to demonstrate the advantages of the obtained theoretical findings.
Scheduled incremental and unscheduled interchange cost components of transmission tariff allocation: a novel approach for maintaining the grid discipline
Authors: Kharbas Babasaheb , Fozdar Manoj , Tiwari Harpal
Published: July 2014

A novel approach of transmission tariff allocation (TTA) is proposed in this study. TTA comprises scheduled incremental cost (SIC) and unscheduled interchange cost (UIC) components. This approach demonstrates the use of proposed SIC and UIC components of tariff in incremental revenue reconciliation along with the provision of heavy penalty to maintain the grid discipline against extreme unscheduled withdrawal. SIC has been allocated to users of transmission network for their scheduled injections or withdrawals. UIC take care of excessive unscheduled interchange (UI) in load or generation. Incremental power flow in MVA is used to asses and allocation of these components. The scheduled increment (SI) in load or generation is associated with planned load growth rate whereas the UI in load or generation may arise intermittently. All generating units are participating to generate both active and reactive power as per their generation participation factor to match the SI and UI demands. The SIC component may be added to the nominal TTA to user. The UIC component of tariff is an additional burden or penalty imposed on users because of extreme unscheduled withdrawal. The results are obtained for SIC and UIC components of TTA by using 6 bus and IEEE 14 bus systems.
Detection methods for blocking artefacts in transform coded images
Authors: Singh Jagroop , Singh Dilbag , Uddin Moin
Published: July 2014

In block discrete cosine transform‐based image compression, the blocking artefacts are the main cause of degradation, especially at higher compression ratio. It is of interest to be able to numerically assess the degree of blocking artefacts as it plays an important role in the design, optimisation and assessment of image and video coding systems. In this work, comparison of novel algorithms based on different modelling functions for blocking artefact detection in compressed images is proposed. The authors’ experiment results show that for all types of images, the proposed methods detect blocking artefacts more accurately as compared with other post‐processing methods/techniques and is very efficient and stable since the signal need not be compressed/decompressed.
Power control strategy for photovoltaic system based on the Newton quadratic interpolation
Authors: Liu Yun , Xin Huanhai , Wang Zhen , Yang Taicheng
Published: July 2014

To maximise the economic benefit, photovoltaic (PV) systems in general operate in the so‐called maximum power point tracking (MPPT) mode. However, in certain occasions (e.g. in a microgrid or in a weak system), it is beneficial for a PV system not to always operate in the MPPT mode, but occasionally in the power dispatch mode, because of the top priority of maintaining system stability. To this end, a Newton quadratic interpolation‐based power control strategy for PV system is proposed to iteratively obtain the required terminal voltage of PV system by approximating the power–voltage characteristic curve with a quadratic curve. With this control strategy, PV systems can operate in the power dispatch mode to flexibly adjust the active power output in a wide range, or adaptively switch to the MPPT mode if necessary. Details on the convergence rate and the way to achieve the fault ride‐through capability are also discussed. Simulation is performed based on a detailed PV dynamical model, illustrating that the proposed method has fast convergence rate and robust performance compared with a revised perturb and observe method which can attain the same function.
Grid‐tie inverter topology with maximum power extraction from two photovoltaic arrays
Authors: Patrao Iván , Garcerá Gabriel , Figueres Emilio , González‐Medina Raúl
Published: July 2014

This study presents a transformerless topology for a grid‐tied single‐phase inverter capable of performing the simultaneous maximum power point tracking of two independent and series connected photovoltaic sources. This topology is derived from the neutral point clamped multilevel inverter in half‐bridge configuration. The use of a half‐bridge topology reduces the leakage current to very low values, whereas the multilevel topology presents an output voltage quality similar to that of a full‐bridge inverter. To simultaneously track the maximum power of both photovoltaic sources, a generation control circuit is used. With this topology, it is possible to improve the performance of the converter under partial shadowing conditions, very common in photovoltaic facilities operating in residential areas. A 5 kW prototype of this topology has been implemented and tested in the laboratory.
New maximum power point tracker for photovoltaic systems exposed to realistic operational conditions
Authors: Di Vincenzo Maria Carla , Infield David
Published: July 2014

In the outdoor environment and under real operational conditions, photovoltaic (PV) systems are affected by several parameters which cannot be considered constant, principally PV cell temperature and incident radiation, and neither of these will in practice be uniform across a PV array or even an individual module. This last aspect results in non‐standard IV characteristics that can exhibit more than one local maximum. The challenge of the maximum power point tracker is finding the true maximum power point (MPP) in the face of all the variation and complexity the real environment imposes on the PV behaviour. It must do this quickly and effectively so the algorithm which controls the DC/DC converter that controls the PV system terminal voltage and thus its operating power point has to be fast and precise. This study proposes a new algorithm that is demonstrated to be highly effective in tracking the MPP under real operating conditions.
Adaptive neuro‐fuzzy based solar cell model
Authors: Chikh Ali , Chandra Ambrish
Published: July 2014

The modelling of photovoltaic (PV) solar cells using a hybrid adaptive neuro‐fuzzy inference system (ANFIS) algorithm is presented. It is based on the decomposition of the cell output current into photocurrent and junction current. The photocurrent is linearly dependent on solar irradiance and cell temperature; consequently, its analytical computation is done easily. However, the junction current is highly non‐linear and depends on cell voltage and temperature. Therefore, its analytical computation is complicated and the manufacturers do not supply any information about this parameter. Moreover, there is no way to measure it physically. Therefore, it is proposed to use the ANFIS algorithm as a powerful technique in order to estimate this current and reconstruct the output PV cell current using the photocurrent. The model validation is based on the gradient descent and chain rule applied to a set of data different than the one used for training process. The advantage of the proposed model is that only one climatic parameter is used as the input to the ANFIS algorithm, which makes it less sensitive to climatic variations.
Radar scan pattern analysis for reduction of false identification in electronic warfare support systems
Authors: Kim Yong‐Hee , Song Kyu‐Ha , Han Jin‐Woo , Kim Hyoung‐Nam
Published: July 2014

In a recent electronic warfare (EW), electronic support (ES) systems suffer from the ambiguity problem that multiple radar types are reported instead of picking out the specific one. Hence, a radar scan pattern has been utilised as an important feature to improve the accuracy of threat identification. However, since false identifications cause immediate danger to friendly forces, the probability of false identification should be reduced as well as the increase in identification accuracy. To cope with this necessity, a new decision category entitled ‘unidentified’ is introduced based on the variance of the difference in peak‐to‐peak intervals. Firstly, the successive received signal strength is modelled for a given scan pattern, and then the effects of the position and movement of an ES receiver onto the identification accuracy are examined to analyse the tendency of false identifications. Simulations are included to confirm the effect of the proposed new feature parameter. By introducing the new parameter, on average 82% of the false identifications are classified into the new decision category instead of incorrectly being classified as a radar scan, whereas only 4% of the correct identifications as a raster scan are classified into the new category.
Exploiting multiple a priori spectral models for adaptive radar detection
Authors: Aubry Augusto , Carotenuto Vincenzo , De Maio Antonio , Foglia Goffredo
Published: July 2014

This study deals with the problem of adaptive radar detection when a limited number of training data, due to environmental heterogeneity, is present. Suppose that some a priori spectral models for the interference in the cell under test and a lower bound on the power spectral density (PSD) of the white disturbance term are available. Hence, generalised likelihood ratio test‐based detection algorithms have been devised. At the design stage, the basic idea is to model the actual interference inverse covariance as a combination of the available a priori models and to account for the available lower bound on the PSD. At the analysis stage, the capabilities of the new techniques have been shown to detect targets when few training data are available as well as their superiority with respect to conventional adaptive techniques based on the sample covariance matrix.
Optimal sampling for fast eddy current testing inversion by utilising sensitivity data
Authors: Gyimóthy Szabolcs
Published: July 2014

An adaptive sampling method based on simplex‐mesh refinement is proposed for creating a forward database that can facilitate the inverse problem solution in non‐destructive testing. The resulting mesh‐database is used as a generic interpolator of the forward problem. The available sensitivity data are utilised for obtaining an optimal sampling with respect to the piecewise linear interpolation applied for data retrieval. The resulting database provides guaranteed quality of approximation using a relatively few number of samples. The method is illustrated by a crack reconstruction problem of eddy current testing.
Surface diffusion driven morphological instability in free-standing nickel nanorod arrays
Authors: Alrashid Ebtihaj , Ye Dexian
Published: July 2014

Metallic nanostructures are thermodynamically unstable due to the excess of energy of large numbers of surface atoms. Morphological instability, such as Rayleigh breakup, sintering, and coalescence, can be observed at a temperature much lower than the bulk melting point of the metal. We study the morphological and crystalline evolution of well-aligned free-standing nickel nanorod arrays at elevated temperatures up to 600 °C. The as-deposited nickel nanorods are faceted with sharp nanotips, which are deformed at annealing temperatures higher than 400 °C due to strong surface diffusion. A mud-crack like pattern is formed in the samples annealed above 400 °C, leading to the generation of interconnected porous structure. Meanwhile, the X-ray diffraction reveals the recrystallization of nickel nanocrystals when annealed from 300 to 600 °C.
Experimental investigation of silicon photomultipliers as compact light readout systems for gamma-ray spectroscopy applications in fusion plasmas
Authors: Nocente M. , Fazzi A. , Tardocchi M. , Cazzaniga C. , Lorenzoli M. , Pirovano C. , Rebai M. , Uboldi C. , Varoli V. , Gorini G.
Published: July 2014

A matrix of Silicon Photo Multipliers has been developed for light readout from a large area 1 in. × 1 in. LaBr3 crystal. The system has been characterized in the laboratory and its performance compared to that of a conventional photo multiplier tube. A pulse duration of 100 ns was achieved, which opens up to spectroscopy applications at high counting rates. The energy resolution measured using radioactive sources extrapolates to 3%–4% in the energy range Eγ = 3–5 MeV, enabling gamma-ray spectroscopy measurements at good energy resolution. The results reported here are of relevance in view of the development of compact gamma-ray detectors with spectroscopy capabilities, such as an enhanced gamma-ray camera for high power fusion plasmas, where the use of photomultiplier is impeded by space limitation and sensitivity to magnetic fields.
Over 50% reduction in the formation energy of Co-based Heusler alloy films by two-dimensional crystallisation
Authors: Sagar James , Fleet Luke R. , Walsh Michael , Lari Leonardo , Boyes Edward D. , Whear Oliver , Huminiuc Teodor , Vick Andrew , Hirohata Atsufumi
Published: July 2014

Crystalline formation of high magnetic-moment thin films through low-temperature annealing processes compatible with current semiconductor technologies is crucial for the development of next generation devices, which can utilise the spin degree of freedom. Utilising in-situ aberration corrected electron microscopy, we report a 235 °C crystallisation process for a Co-based ternary Heusler-alloy film whose initial nucleation is initiated by as few as 27 unit cells. The crystallisation occurs preferentially in the ⟨111⟩ crystalline directions via a two-dimensional (2D) layer-by-layer growth mode; resulting in grains with [110] surface normal and [111] plane facets. This growth process was found to reduce the crystallisation energy by more than 50% when compared to bulk samples whilst still leading to the growth of highly ordered grains expected to give a high degree of spin-polarisation. Our findings suggest that the 2D layer-by-layer growth minimises the crystallisation energy allowing for the possible implementation of highly spin-polarised alloy films into current chip and memory technologies.
Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets
Authors: Raston Paul L. , Douberly Gary E. , Jäger Wolfgang
Published: July 2014

Methanol is one of the simplest molecules that undergo torsional oscillations, and so it has been extensively studied in the gas phase by various spectroscopic techniques. At 300 K, a large number of rotational, torsional, and vibrational energy levels is populated, and this makes for a rather complicated spectrum, which is still not fully understood. It is expected that in going from 300 K to 0.4 K (the temperature of helium nanodroplets) the population distribution of methanol will mainly collapse into two states; the JK = 00 state for the A1 nuclear spin symmetry species (with ICH3 = 3/2), and the JK = 1−1 state for the E species (ICH3 = 1/2). This results in a simplified spectrum that consists of narrow a-type (ΔK = 0) lines and broader b- and c-type (ΔK = ±1) lines. We have recorded the rotovibrational spectrum of CH3OH in the OH stretching, CH3 stretching and bending, CH3 rocking, and CO stretching regions, and have firmly assigned five bands (v1, v2, v3, v7, and v8), and tentatively assigned five others (v9, 2v4, v4 + v10, 2v10, and v4 + v5). To our knowledge, the transitions we have assigned within the v4 + v10, 2v10, and v4 + v5 bands have not yet been assigned in the gas phase, and we hope that considering the very small “matrix” shift in helium nanodroplets (<1 cm−1 for most subband origins of CH3OH), those made here can aid in their gas phase identification. Microwave-infrared double resonance spectroscopy was used to confirm the initially tentative a-type infrared assignments in the OH stretching (v1) band of A1 species methanol, in addition to revealing “warm” b-type lines. From a rotovibrational analysis, the B rotational constant is found to be reduced quite significantly (56%) with respect to the gas phase, and the torsional tunneling splittings are relatively unaffected and are at most reduced by 16%. While most rovibrational peaks are Lorentzian shaped, and those which are significantly perturbed by vibrational coupling in the gas phase are additionally broadened, the narrowest ΔJ = +1 peaks are asymmetric, and a skew-type analysis suggests that the response time of the helium solvent upon excitation is of the order of 1 ns.
Determination of hydrogen/deuterium ratio with neutron measurements on MAST
Authors: Klimek I. , Cecconello M. , Sharapov S. E. , Harrison J. , Ericsson G.
Published: July 2014

On MAST, compressional Alfvén eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio nH/nD using neutron emission measurements is here described. The inferred isotopic ratio ranged from 0.0 to 0.6 and no experimental indication of changes in radial profile of nH/nD were observed. These findings are confirmed by TRANSP/NUBEAM simulations of the neutron emission.
Effect of gas velocity on the weakly nonlinear instability of a planar viscous sheet
Authors: Yang Li-Jun , Chen Pi-Min , Wang Chen
Published: July 2014

A weakly nonlinear spatial instability of a two-dimensional planar viscous sheet for sinuous disturbances in a co-flowing inviscid gas stream is investigated theoretically, with an emphasis on the effect of the surrounding gas velocity. The solutions of the second-order interface disturbances are derived and the wave deformation has been computed. The results indicate that the second-order surface disturbance of the fundamental sinuous mode is varicose, which causes the thinning and the subsequent breakup of the liquid sheet. The nonlinear behaviors of the planar sheet are quite sensitive to variations in gas-to-liquid velocity ratio. The deviation of the velocity ratio from the value of unity leads to a larger growth rate, a larger second-order initial amplitude, and a shorter breakup length, and therefore enhances the instability. The growth rates predicted by the present nonlinear analysis according to the shortest breakup length are generally smaller than the linear predictions and can better conform to the experimental measures of Barreras et al. [“Linear instability analysis of the viscous longitudinal perturbation on an air-blasted liquid sheets,” Atomization Sprays 11, 139 (2001)]. Furthermore, the wave deformations of the most unstable disturbances are presented. The nonlinear instability of the planar sheet for a fixed velocity difference is performed. An equal increase of the gas and liquid velocity reduces the spatial growth rate and increases the breakup length, but generally has no influences on the second-order initial amplitude and the wavelength of the disturbance.
X-ray tests of a two-dimensional stigmatic imaging scheme with variable magnifications
Authors: Lu J. , Bitter M. , Hill K. W. , Delgado-Aparicio L. F. , Efthimion P. C. , Pablant N. A. , Beiersdorfer P. , Caughey T. A. , Brunner J.
Published: July 2014

A two-dimensional stigmatic x-ray imaging scheme, consisting of two spherically bent crystals, one concave and one convex, was recently proposed [M. Bitter et al., Rev. Sci. Instrum. 83, 10E527 (2012)]. The Bragg angles and the radii of curvature of the two crystals of this imaging scheme are matched to eliminate the astigmatism and to satisfy the Bragg condition across both crystal surfaces for a given x-ray energy. In this paper, we consider more general configurations of this imaging scheme, which allow us to vary the magnification for a given pair of crystals and x-ray energy. The stigmatic imaging scheme has been validated for the first time by imaging x-rays generated by a micro-focus x-ray source with source size of 8.4 μm validated by knife-edge measurements. Results are presented from imaging the tungsten Lα1 emission at 8.3976 keV, using a convex Si-422 crystal and a concave Si-533 crystal with 2d-spacings of 2.21707 Å and 1.65635 Å and radii of curvature of 500 ± 1 mm and 823 ± 1 mm, respectively, showing a spatial resolution of 54.9 μm. This imaging scheme is expected to be of interest for the two-dimensional imaging of laser produced plasmas.
First measurement of time evolution of electron temperature profiles with Nd:YAG Thomson scattering system on Heliotron J
Authors: Kenmochi N. , Minami T. , Takahashi C. , Tei S. , Mizuuchi T. , Kobayashi S. , Nagasaki K. , Nakamura Y. , Okada H. , Kado S. , Yamamoto S. , Ohshima S. , Konoshima S. , Shi N. , Zang L. , Ohtani Y. , Kasajima K. , Sano F.
Published: July 2014

A Nd:YAG Thomson scattering system has been developed for Heliotron J. The system consists of two 550 mJ 50 Hz lasers, large collection optics, and 25 radial channel (∼1 cm spatial resolution) interference polychromators. This measurement system achieves a S/N ratio of ∼50 for low-density plasma (ne ∼ 0.5 × 1019 m−3). A time evolution of electron temperature profiles was measured with this system for a high-intensity gas-puff (HIGP) fueling neutral-beam-injection plasma. The peripheral temperature of the higher-density phase after HIGP recovers to the low-density pre-HIGP level, suggesting that improving particle transport in the HIGP plasma may be possible.
Organic cleanliness of the Mars Science Laboratory sample transfer chain
Authors: Blakkolb B. , Logan C. , Jandura L. , Okon A. , Anderson M. , Katz I. , Aveni G. , Brown K. , Chung S. , Ferraro N. , Limonadi D. , Melko J. , Mennella J. , Yavrouian A.
Published: July 2014

One of the primary science goals of the Mars Science Laboratory (MSL) Rover, Curiosity, is the detection of organics in Mars rock and regolith. To achieve this, the Curiosity rover includes a robotic sampling system that acquires rock and regolith samples and delivers it to the Sample Analysis at Mars (SAM) instrument on board the rover. In order to provide confidence that any significant organics detection result was Martian and not terrestrial in origin, a requirement was levied on the flight system (i.e., all sources minus the SAM instrument) to impart no more than 36 parts per billion (ppb by weight) of total reduced carbon terrestrial contamination to any sample transferred to the SAM instrument. This very clean level was achieved by a combination of a rigorous contamination control program on the project, and then using the first collected samples for a “dilution cleaning” campaign of the sample chain prior to delivering a sample to the SAM instrument. Direct cleanliness assays of the sample-contacting and other Flight System surfaces during pre-launch processing were used as inputs to determine the number of dilution cleaning samples needed once on Mars, to enable delivery of suitably clean samples to the SAM experiment. Taking into account contaminant redistribution during launch thorough landing of the MSL on Mars, the amount of residue present on the sampling hardware prior to the time of first dilution cleaning sample acquisition was estimated to be 60 ng/cm2 on exposed outer surfaces of the sampling hardware and 20 ng/cm2 on internal sample contacting surfaces; residues consisting mainly of aliphatic hydrocarbons and esters. After three dilution cleaning samples, estimated in-sample contamination level for the first regolith sample delivered to the SAM instrument at the Gale Crater “Rocknest” site was bounded at ≤10 ppb total organic carbon. A Project decision to forego ejecting the dilution cleaning sample and instead transfer the first drill-acquired sample at the “John Klein” site to SAM resulted in an estimated level of terrestrial contamination of ≤430 ppb. The estimated terrestrial contamination for portions from the second drill-acquired sample, at Cumberland, was ≤69 ppb; the estimate for a future, third, drilled sample is ≤38 ppb. These levels are comparable in magnitude to the SAM instrument blanks at the nanomole level (as chlorohydrocarbon).
Constrained multi-scale turnover Lagrangian map for anisotropic synthetic turbulence: A priori tests
Authors: Li Yi , Rosales Carlos
Published: July 2014

Synthetic turbulence has been useful in the modelling and simulation of turbulence, and as a surrogate to understand the dynamics of real hydrodynamic turbulence. In a recently proposed Multiscale Turnover Lagrangian Map (MTLM) method, an initial random field is transformed into a synthetic field after a series of simple mappings, with moderate computational cost. It has been shown that the resulted fields reproduce highly realistic statistics on many aspects of isotropic hydrodynamic turbulence, including small-scale intermittency, geometric statistics, and pressure statistics. Thus, it is of great interests to generalize the method to model inhomogeneous turbulence. In this paper, we formulate the problem as an optimization problem, where the initial random field is taken as the control variable, and the additional features presented in inhomogeneous turbulence are taken as a target function to be matched by the synthetic fields. The goal is to find the optimal control variable which minimizes the difference between the target function and the synthetic field. Using the adjoint formulation, we derive the optimality system of the problem, which formulates a procedure to generate inhomogeneous synthetic turbulence. The procedure, named the Constrained MTLM, is applied to synthesize two Kolmogorov flows where persistent large scale structures produce nontrivial mean flow statistics and local anisotropy in small scales. We compare the synthetic fields with direct numerical simulation data, and show that the former reproduces closely the mean flow statistics such as Reynolds stress distribution and mean turbulent kinetic energy balance. They also reproduce the effects of inhomogeneity on small scale structures, which is manifested in the distributions of mean subgrid-scale energy dissipation, and the alignment between the subgrid-scale stress tensor and the filtered strain rate tensor, among others. We conclude that the method is useful to further extend the applicability of synthetic turbulence.
Development of a compact in situ polarized 3He neutron spin filter at Oak Ridge National Laboratory
Authors: Jiang C. Y. , Tong X. , Brown D. R. , Chi S. , Christianson A. D. , Kadron B. J. , Robertson J. L. , Winn B. L.
Published: July 2014

We constructed a compact in situ polarized 3He neutron spin filter based on spin-exchange optical pumping which is capable of continuous pumping of the 3He gas while the system is in place in the neutron beam on an instrument. The compact size and light weight of the system simplifies its utilization on various neutron instruments. The system has been successfully tested as a neutron polarizer on the triple-axis spectrometer (HB3) and the hybrid spectrometer (HYSPEC) at Oak Ridge National Laboratory. Over 70% 3He polarization was achieved and maintained during the test experiments. Over 90% neutron polarization and an average of 25% transmission for neutrons of 14.7 meV and 15 meV was also obtained.
Progress in development of the neutron profile monitor for the large helical device
Authors: Ogawa K. , Isobe M. , Takada E. , Uchida Y. , Ochiai K. , Tomita H. , Uritani A. , Kobuchi T. , Takeiri Y.
Published: July 2014

The neutron profile monitor stably operated at a high-count-rate for deuterium operations in the Large Helical Device has been developed to enhance the research on the fast-ion confinement. It is composed of a multichannel collimator, scintillation-detectors, and a field programmable gate array circuit. The entire neutron detector system was tested using an accelerator-based neutron generator. This system stably acquires the pulse data without any data loss at high-count-rate conditions up to 8 × 105 counts per second.
Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR
Authors: Yun G. S. , Lee W. , Choi M. J. , Lee J. , Kim M. , Leem J. , Nam Y. , Choe G. H. , Park H. K. , Park H. , Woo D. S. , Kim K. W. , Domier C. W. , Luhmann N. C. , Ito N. , Mase A. , Lee S. G.
Published: July 2014

A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B0 = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.
Single-shot calibration of soft x-ray mirrors using a sinusoidal transmission grating
Authors: Shpilman Z. , Ehrlich Y. , Maman S. , Levy I. , Shussman T. , Oren G. , Zakosky Nueberger I. , Hurvitz G.
Published: July 2014

Calibration of soft x-ray diagnostics is a challenge due to the lack of laboratory-size calibrated sources. An in situ calibration method for newly developed x-ray mirrors, is presented. The x-ray source is produced by laser-matter interaction, and twin transmission gratings which create two identical dispersion lines. The gratings have a sinusoidal transmission function, which produces a highly precise high-orders free spectrum. An x-ray mirror interacts with one of the dispersion lines, and the mirror efficiency curve as a function of wavelength is extracted. Mirror efficiency shows good agreement with the literature, and evidence of water layer may justify the need of in situ calibration.
Optical system for liquid level measurements
Authors: Melchionni D. , Norgia M.
Published: July 2014

This work describes the development of a novel laser instrument for non-contact liquid level measurements. The physical principle of operation is based on the self-mixing effect induced in the laser diode by modulating the laser wavelength. The frequency main tone of the resulting fringes is proportional to the absolute target distance. A high speed FPGA (Field Programmable Gate Array) electronic performs the data acquisition and elaboration. The high elaboration/acquisition speed improves the chance of acquiring good signal also on a moving liquid target. The optical characteristics of the liquid surface have been studied in order to identify the optimal optical configuration when the surface is flat as well as when the surface is rippled. The final low-cost instrument works in real time and is able to track a filling process with 2.5 cm/s of speed, with resolution better than 1 mm for distances up to 50 cm.
Investigation of the adhesive bonding technology for the insulator structure of EAST neutral beam injector
Authors: Wei Jiang-Long , Li Jun , Hu Chun-Dong , Xie Ya-Hong , Jing Hao
Published: July 2014

A key issue on the development of EAST ion source was the junction design of insulator structure, which consists of three insulators and four supporting flanges of electrode grid. Because the ion source is installed on the vertical plane, the insulator structure has to withstand large bending and shear stress due to the gravity of whole ion source. Through a mechanical analysis, it was calculated that the maximum bending normal stress was 0.34 MPa and shear stress was 0.23 MPa on the insulator structure. Due to the advantages of simplicity and high strength, the adhesive bonding technology was applied to the junction of insulator structure. A tensile testing campaign of different junction designs between insulator and supporting flange was performed, and a junction design of stainless steel and fiber enhanced epoxy resin with epoxy adhesive was determined. The insulator structure based on the determined design can satisfy both the requirements of high-voltage holding and mechanical strength.
On the transmission of terahertz radiation through silicon-based structures
Authors: Persano Anna , Torres Jérémie , Korotyeyev Vadym V. , Lyaschuk Yu M. , Nouvel Philippe , Francioso Luca , Varani Luca , Cola Adriano
Published: July 2014

We report on the transmission of a terahertz (THz) radiation through prototype structures based on a p-type silicon substrate. In particular, the bare substrate and progressively more complicated multilayer structures were investigated, allowing to address the effect on the transmission of different factors, such as the orientation of interdigitated contacts with respect to the polarized beam, the temperature, and the current flowing through a conductive SnO2 nanorods layer. A suitable experimental set-up was developed for the direct spectral measurement of transmission in the range of 0.75–1.1 THz at room and low temperatures. A simple Drude-Lorentz model was formulated, finding a quantitative agreement with the experimental transmission spectrum of the bare substrate at room temperature. For the multilayer structures, the spectra variations observed with temperature are well accounted by the corresponding change of the mobility of holes in the silicon p-type substrate. The influence of the contact orientation is consistent with that of a polarizing metallic grating. Finally, Joule heating effects are observed in the spectra performed as a function of the current flowing through the SnO2 nanorods layer. The experimental results shown here, together with their theoretical interpretation, provide insights for the development of devices fabricated on conductive substrates aimed to absorb/modulate radiation in the THz range.
Forcing continuous reconnection in hybrid simulations
Authors: Laitinen T. V. , Jarvinen R. , Kallio E. , Janhunen P.
Published: July 2014

We have performed hybrid simulations of driven continuous reconnection with open boundary conditions. Reconnection is started by a collision of two subsonic plasma fronts with opposite magnetic fields, without any specified magnetic field configuration as initial condition. Due to continued forced plasma inflow, a current sheet co-located with a dense and hot plasma sheet develops. The translational symmetry of the current sheet is broken by applying a spatial gradient in the inflow speed. We compare runs with and without localized resistivity: reconnection is initiated in both cases, but localized resistivity stabilizes it and enhances its efficiency. The outflow speed reaches about half of Alfvén speed. We quantify the conversion of magnetic energy to kinetic energy of protons and to Joule heating and show that with localized resistivity, kinetic energy of protons is increased on average five-fold in the reconnection in our simulation case.
Mode composition analysis on experimental results of a Gigawatt-class Ka-band overmoded Cerenkov oscillator
Authors: Wu Dapeng , Shu Ting , Zhu Jun , Zhang Hua , Ju Jinchuan
Published: July 2014

In this paper, a modified numerical method is used to investigate the mode composition of a Gigawatt-class Ka-band overmoded Cerenkov oscillator, which has been proposed and studied in our previous experiment. In the experiment, the measured angular distribution of radiation did not fit a single TM01 mode. So the particle in cell code calculations and the antenna radiation calculations are carried out, which show a consistent picture: the dominant modes are the TM01 mode and the TM03 mode, and their phase relationship is constant with time; therefore, a steady radiation pattern is produced, which matches the experimental data. As a conclusion, the comprehensive analysis shows that the existing modes of the output microwave in our experiment are the first five TM0n modes (n = 1–5), with corresponding power ratios of 36.64%, 0.78%, 56.26%, 5.70%, and 0.52%, and relative phase differences of 0°, 146°, 54°, 169°, and 133°.
Tuning of optical bandgap and magnetization of CoFe2O4 thin films
Authors: Sharma Deepanshu , Khare Neeraj
Published: July 2014

Single phase CoFe2O4 thin films are deposited on quartz substrates at 400 °C using ultrasonic assisted chemical vapor deposition, and the tuning of optical bandgap and saturation magnetization of films is demonstrated by varying the post deposition annealing temperature. The optical band gap varies from 1.58 to 1.41 eV and saturation magnetization increases from 4 to 46 emu/g as the post deposition annealing temperature is increased from 500 °C to 700 °C. The observed change in optical bandgap and the magnetic properties is attributed of the shifting of Co2+ from the octahedral to the tetrahedral site with the increase in the annealing temperature. Raman studies of the films support the redistribution of Co2+ among the octahedral and tetrahedral sites in CoFe2O4 films with the increase in the annealing temperature.
Site selective substitution Pt for Ti in KTiOPO4:Ga crystals revealed by electron paramagnetic resonance
Authors: Grachev V. , Meyer M. , Jorgensen J. , Hunt A. W. , Malovichko G.
Published: July 2014

Electron Paramagnetic Resonance at low temperatures has been used to characterize potassium titanyl phosphate (KTiOPO4) single crystals grown by different techniques. Irradiation with 20 MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Platinum impurities act as electron traps in KTiOPO4 creating Pt3+ centers. Two different Pt3+ centers were observed, Pt(A) and Pt(D). The Pt(A) centers are dominant in undoped samples, whereas Pt(D)—in Ga-doped KTP crystals. Superhyperfine structure registered for Pt(D) centers was attributed to interactions of platinum electrons with 39K and two 31P nuclei in their surroundings. In both Pt(A) and Pt(D) centers, Pt3+ ions substitute for Ti4+ ions, but with a preference to one of two electrically distinct crystallographic positions. The site selective substitution can be controlled by the Ga-doping.
Low-temperature carrier dynamics in high-mobility organic transistors of alkylated dinaphtho-thienothiophene as investigated by electron spin resonance
Authors: Kinoshita Yutaro , Tanaka Hisaaki , Shimoi Yukihiro , Takimiya Kazuo , Kuroda Shin-ichi
Published: July 2014

Charge carriers in high-mobility organic thin-film transistors of alkylated dinaphtho-thienothiophene (C10-DNTT) have been directly observed by field-induced electron spin resonance (FI-ESR) down to 4 K. FI-ESR spectra of π-electron hole carriers of C10-DNTT exhibited clear anisotropy, indicating a highly organized end-on molecular orientation at the device interface. The intra-grain and inter-grain carrier motion were probed by the motional narrowing effect of the ESR spectra. The intra-grain motion was clearly observed even at 4 K, showing intrinsically high mobility of C10-DNTT crystallites. On the other hand, significantly low activation energy of ∼10 meV for inter-grain carrier hopping, compared with pristine DNTT, was observed, which shows that the alkyl substitution drastically enhances the carrier mobility of DNTT system.
Investigations of the electro-optic behavior of Cs2TeMo3O12 single crystal
Authors: Gao Zeliang , Sun Youxuan , Zhang Junjie , Wang Shanpeng , Tao Xutang
Published: July 2014

The electro-optic (EO) property of hexagonal Cs2TeMo3O12 (CTM) crystal is studied with interference technique at 632.8 nm. Both the value and sign of the EO coefficients have been obtained and confirmed. The largest EO coefficient is 10.4 pm/V for r33 due to its structure distortion along c-axis. The transverse effective EO effect of r33 and the half-wave voltage are calculated to be 11.08 pm/V and 5200 V at 1064 nm, respectively. The experimental results show that CTM can be one of promising candidates for the EO applications, especially in the mid-infrared region.
Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization
Authors: Kasiuk J. V. , Fedotova J. A. , Przewoznik J. , Zukrowski J. , Sikora M. , Kapusta Cz. , Grce A. , Milosavljević M.
Published: July 2014

The relation between nanoscale structure, local atomic order and magnetic properties of (FeCoZr)x(CaF2)100−x (29 ≤ x ≤ 73 at. %) granular films is studied as a function of metal/insulator fraction ratio. The films of a thickness of 1–6 μm were deposited on Al-foils and glass-ceramic substrates, by ion sputtering of targets of different metal/insulator contents. Structural characterization with X-ray and electron diffraction as well as transmission electron microscopy revealed that the films are composed of isolated nanocrystalline bcc α-FeCo(Zr) alloy and insulating fcc CaF2 matrix. They grow in a columnar structure, where elongated metallic nanograins are arranged on top of each other within the columns almost normal to the substrate surface. Mössbauer spectroscopy and magnetometry results indicate that their easy magnetization axes are oriented at an angle of 65°–74° to the surface in films with x between 46 and 74, above the electrical percolation threshold, which is attributed to the growth-induced shape anisotropy. Interatomic distances characteristic for metallic state of α-FeCo(Zr) nanograins were revealed by X-ray Absorption Spectroscopy. The results show a lack of surface oxidation of the alloy nanograins, so the growth-induced orientation of nanograins in the films cannot be attributed to this effect. The study is among the first to report a growth-induced non-planar magnetic anisotropy in metal/insulator granular films above the percolation threshold and to reveal the origin of it.
Perspectives on surface nanobubbles
Authors: Zhang Xuehua , Lohse Detlef
Published: July 2014

Materials of nanoscale size exhibit properties that macroscopic materials often do not have. The same holds for bubbles on the nanoscale: nanoscale gaseous domains on a solid-liquid interface have surprising properties. These include the shape, the long life time, and even superstability. Such so-called surface nanobubbles may have wide applications. This prospective article covers the basic properties of surface nanobubbles and gives several examples of potential nanobubble applications in nanomaterials and nanodevices. For example, nanobubbles can be used as templates or nanostructures in surface functionalization. The nanobubbles produced in situ in a microfluidic system can even induce an autonomous motion of the nanoparticles on which they form. Their formation also has implications for the fluid transport in narrow channels in which they form.
Superconducting inductive displacement detection of a microcantilever
Authors: Vinante A.
Published: July 2014

We demonstrate a superconducting inductive technique to measure the displacement of a micromechanical resonator. In our scheme, a type I superconducting microsphere is attached to the free end of a microcantilever and approached to the loop of a dc Superconducting Quantum Interference Device (SQUID) microsusceptometer. A local magnetic field as low as 100 μT, generated by a field coil concentric to the SQUID, enables detection of the cantilever thermomechanical noise at 4.2 K. The magnetomechanical coupling and the magnetic spring are in good agreement with image method calculations assuming pure Meissner effect. These measurements are relevant to recent proposals of quantum magnetomechanics experiments based on levitating superconducting microparticles.
Effect of annealing on the growth dynamics of ZnPc LB thin film and its surface morphology
Authors: Roy Dhrubojyoti , Das Nayan Mani , Gupta P. S.
Published: July 2014

The ZnPc molecules in the thin film prepared by Langmuir-Blodgett (LB) process in asdeposited state has been found to have an edge on orientation with average tilt angle of 64.3 ° as confirmed from the Pressure-Area (π-A) isotherm and X-ray diffraction (XRD) study. The ZnPc LB thin film has been observed to have abnormal growth mode at higher annealing temperature and it is mainly driven by minimization of surface free energy which lead to large increase in crystallinity of the film. Kinetically favored orientational and structural transitions of ZnPc thin film during annealing and their effect on the surface morphology of the thin film has been studied using scaling concepts. The scaling exponents 1) root mean square (RMS) roughness σ, 2) roughness exponent α and, 3) in plane correlation length ξ are calculated from the HDCF g(r) and ACF C(r). The RMS surface roughness σ is found to be dependent on the as defined short wavelength undulations (ρ) and long wavelength undulations (χ). Both ρ and χ are the function of all the three scaling exponents. σ has been observed to be maximum for the ZnPc thin film annealed at 290 °C, since the χ shoot to maximum value at this temperature due to the formation of small domains of ZnPc nanorods. The self affinity of the ZnPc thin film is found to decrease on annealing as obtained from both power spectral density (PSD) and HDCF g(R) & ACF C(R) study, which confirms that the dimension of surface morphology of the ZnPc LB thin film transform towards 2D with increase in annealing temperature.
Comparative growth performance of Kajli lambs suckling their dams or offered buffalo-milk, cow-milk or milk replacer during pre-weaning period
Authors: Anjum Musharraf Ahmad , Bhatti Shaukat Ali , Sarwar Muhammad , Muhammad Ghulam , Basra Muhammad Jamil
Published: July 2014

Kajli, is one of the most beautiful sheep breeds of Pakistan. Because of their beauty, Kajli lambs are sold at a higher price than those of other breeds with similar weight. With the increasing trend in commercial livestock farming, young Kajli lambs are purchased from the open market and reared up to Eid-ul-Adha (The Muslim Sacrificial Day). Information on feeding cost and growth performance on artificial rearing is important for the breed lovers and for a commercial enterprise. The present study aimed at generating basic information on feeding cost and growth performance of Kajli lambs offered milk replacer, cow-milk, and buffalo-milk, in comparison with those suckling directly from their dams. Fifty-six healthy Kajli lambs both male and female (with equal sex ratio) born at the Livestock Experimental Station, Khushab, Punjab, Pakistan during spring 2013 remained with their mothers for 1 week and were then divided into four groups of 14 animals each. Lambs in Group I were allowed to suckle their dams ad libitum, twice daily until 8 weeks and then once daily from 9 to 12 weeks. Lambs were weighed before and after suckling to calculate milk consumption. Lambs in the other three treatments were offered buffalo-milk, cow-milk or milk replacer at the rate of 10% of bodyweight until the 8th week and then gradually reduced to zero by the end of the 12th week. All lambs were offered starter ration from the 5th week of age in individual pens. The data on milk and starter intake, weekly bodyweight and blood glucose were analysed through MIXED procedures of SAS using repeated-measures analysis, and average daily gain (ADG), total weight gain, weaning weight and feeding cost were analysed using a completely randomised design. Least square means of ADG (g/day) and total weight gain (kg) were similar (P > 0.05) in direct suckling lambs and lambs offered buffalo-milk (175 and 151, and 14.5 and 12.5, respectively), and were higher (P < 0.05) than those offered cow-milk (118 and 10.4) or milk replacer (94 and 7.7). Feeding cost (per kg of liveweight) was highest (PKR 535) in lambs fed milk replacer and was lower (P > 0.05) in the other three groups. The cost of rearing lambs on buffalo-milk tended to be lower (PKR 375) than those offered cow-milk. In the absence of ewe’s milk, rearing Kajli lambs on buffalo-milk during the pre-weaning period therefore seems to be a better alternative.