bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct power control of wind‐turbine‐driven DFIG during transient grid voltage unbalance
Authors: Shehata E. G.
Published: June 2013

In this paper, a direct power control (DPC) of a wind‐turbine‐driven doubly fed induction generators (DFIGs) under unbalanced network voltage conditions is studied. Variations of the stator output active, reactive and electromagnetic powers are fully deduced in the presence of negative sequence supply voltage. The rotor side converter is controlled on the basis of DPC to eliminate the electromagnetic torque oscillations at double supply frequency under unbalanced stator supply. The rotor voltage references estimation requires only simple calculations without any integral operation. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. The performance of the proposed and conventional DPC schemes is compared under the same operating conditions. Simulation results using Matlab/Simulink are carried out for a 1.5 MW DFIG wind generation system to show the validity of the proposed scheme during unbalanced voltage supply. Copyright © 2013 John Wiley & Sons, Ltd.
Transmutation of high‐level nuclear waste by means of accelerator driven system
Authors: Abderrahim Hamid Aït , De Bruyn Didier , Van den Eynde Gert , Michiels Sidney
Published: June 2013

To be able to answer the worlds’ increasing demand for energy, nuclear energy must be part of the energy basket. The generation of nuclear energy produces, besides energy, also high‐level nuclear waste, which is nowadays for geological storage. Transmutation of the minor actinides and long‐lived fission products that arise from the reprocessing of the nuclear waste can reduce the radiological impact of these radioactive elements. Transmutation can be completed in an efficient way in fast neutron spectrum facilities. Both critical fast reactors and subcritical accelerator driven systems are potential candidates as dedicated transmutation systems. Nevertheless, an accelerator driven system operates in a flexible and safer manner even with a core loading containing a high amount of minor actinides leading to a high more‐efficient transmutation approach. WIREs Energy Environ 2014, 3:60–69. doi: 10.1002/wene.82

This article is categorized under:

Fossil Fuels > Science and Materials

Fossil Fuels > Systems and Infrastructure

Fossil Fuels > Climate and Environment
Dynamics and dislodgment from pore constrictions of a trapped nonwetting droplet stimulated by seismic waves
Authors: Deng Wen , Cardenas M. Bayani
Published: June 2013

Seismic waves affect fluid flow and transport processes in porous media. Therefore, quantitative understanding of the role of seismic waves in subsurface hydrodynamics is important for the development of practical applications and prediction of natural phenomena. We present a theoretical fluid dynamics model to describe how low‐frequency elastic waves mobilize isolated droplets trapped in pores by capillary resistance. The ability of the theoretical model to predict the critical mobilization amplitudes (Ac) and the displacement dynamics of the nonwetting droplet are validated against computational fluid dynamics (CFD) simulations. Our theory has the advantage of rapid calculation of Ac for various scenarios. Both theory and CFD simulations show that the Ac increases with increasing wave frequency. The theoretical and computational models agree well in the low‐frequency range both in terms of predicting the displacement history of the droplet and its eventual dislodgment, but their results begin to diverge with increasing wave frequency since the Hagen‐Poiseuille flow approximation in the model becomes invalid. Relative to a previous “viscous seismic model,” our model compares more favorably to experimental observations. The model is thus appropriate for predicting trapped nonwetting droplet dynamics in and dislodgement from pore constrictions by low‐frequency elastic waves.
A comprehensive analysis of the effects of the main component enzymes of cellulase derived from Trichoderma reesei on biomass saccharification
Authors: Kawai Tetsushi , Nakazawa Hikaru , Ida Noriko , Okada Hirofumi , Ogasawara Wataru , Morikawa Yasushi , Kobayashi Yoshinori
Published: June 2013

The aim of this study was a comprehensive analysis of the effects of the component enzymes of cellulase derived from Trichoderma reesei strain PC-3-7 on biomass saccharification. We used cellulases with deleted CBH I, CBH II, or EG I, which contain all other component enzymes, for saccharification of differently pretreated biomasses of rice straw, Erianthus, eucalyptus, and Japanese cedar. We found that CBH I was the most effective in saccharification of all pretreated cellulosic biomasses, although the effect was weaker in saccharification of sulfuric acid- and hydrothermally pretreated rice straw than of others; CBH II was more effective for rice straw than for eucalyptus, and was the most effective at the early stages of biomass degradation; EG I had little effect on pretreated biomasses, in particular, it had no effect on steam-exploded Japanese cedar. Thus, the effects of the main component enzymes depend on the biomass source and pretreatment. These findings will likely help to improve cellulase for industrial use.
Influence of Solid Supports on Acyl Migration in 2‐Monoacylglycerols: Purification of 2‐MAG via Flash Chromatography
Authors: Compton David L. , Laszlo Joseph A. , Evans Kervin O.
Published: June 2013

Soybean oil 2‐monoacylglycerol (2‐MAG) was synthesized via the Novozym 435‐catalyzed ethanolysis of triacylglycerols and purified by conventional liquid–liquid extraction. The 2‐MAG was subjected to incubation at 20 and 40 °C in the presence of five solid commercial support materials, Lewatit, Silica Gel 60, Alumina–Neutral Brockman Activity 1, Amberlyst‐15, and SBA‐15, to determine their effects on acyl migration rates. Lewatit and SBA‐15 did not catalyze acyl migration rates after 144 h, while silica gel slightly increased migration rates. The more polar alumina and the cationic Amberlyst 15 significantly increased migration rates. Flash chromatography purification of 2‐MAG using silica gel as the immobile phase developed with an acetone/hexane binary gradient proved to be a comparable purification method to liquid–liquid extraction, resulting in 60 % 2‐MAG yield, no residual triacylglycerol, diacylglycerol, or glycerol co‐products, and a 95 mol% 2‐MAG purity vs. 1‐MAG, demonstrating that flash chromatography did not catalyze acyl migration.
Community Development Credit Unions: Securing and Protecting Assets in Black Communities
Authors: Nembhard Jessica Gordon
Published: June 2013

Credit Unions, with a hundred year history, and Community Development Credit Unions (CDCUs), with a 30–40 year history of serving the under-served, have only recently begun to be recognized by some of the media and the progressive community as “safe havens” and fair lenders. There is little independent, academic research, however, that investigates and evaluates the ways that credit unions are community-rooted and responsive to local needs, and/or their achievements in this area. This paper reports on preliminary qualitative research this author has conducted to help us understand how community development credit unions in Black communities in the U.S. provide affordable financial services, and especially help their clients/members to preserve assets. Major findings include: all CDCUs note that they charge lower rates for their products, and provide higher interest or dividends when possible; both which enable members/customers to save money and build assets. CDCUs work closely with their members to personalize services, to help them avoid loans they cannot afford, and to educate them enough to make sound financial decisions and preserve their assets. Many give some direct options to their members to avoid “payday loans” with check cashing and other predatory lenders. In addition, most CDCUs are deeply involved in their communities, and the bigger ones actually provide donations, encourage their employees to volunteer in the community and are generous employees (creating jobs with benefits and job ladder opportunities). Some are able to help finance affordable housing and contribute to other community economic development projects.
The Origins of Domestic Horses in North-west Europe: new Direct Dates on the Horses of Newgrange, Ireland
Authors: Bendrey Robin , Thorpe Nick , Outram Alan , van Wijngaarden-Bakker Louise H.
Published: June 2013

This paper presents direct radiocarbon measurements on horse skeletal remains from the Beaker period settlement at the site of Newgrange in Ireland, finds which have previously been argued as the earliest domestic horses in Ireland. The new determinations date the horse remains to the Irish Iron Age and shed important new light on the introduction of domestic horses to Ireland and to north-west Europe more generally. Although the new dates undermine the idea for the introduction of horses as part of a ‘Beaker package’, the early use of horse is not well defined archaeologically or chronologically and the earliest use of domestic horses in Ireland and Britain is still uncertain. This paper also identifies evidence for heavy bitting damage on the Iron Age Newgrange horse teeth and presents some possible parallels between the evidence from Newgrange and that at Tara, which has been previously linked with kingship rituals
Effect of N-acetyl cysteine on enterocyte apoptosis and intracellular signalling pathways' response to oxidative stress in weaned piglets
Authors: Zhu Lihui , Cai Xuan , Guo Qi , Chen Xiaolian , Zhu Suwen , Xu Jianxiong
Published: June 2013

N-acetyl cysteine (NAC) has been widely used for preventing reactive oxygen species-induced damage. However, little is known as to whether dietary NAC supplementation would alleviate intestinal injury in weaned piglets. The present study evaluated the effect of NAC on enterocyte apoptosis and intracellular signalling pathways' response to weaning stress. The control piglets were normally suckling, and piglets in the weaning and NAC groups were fed the basal diet and basal+NAC diet from 14 to 25 d of age, respectively. Compared with the control piglets, weaning increased cortisol concentrations (P< 0·05), decreased superoxide dismutase and glutathione peroxidase activities (P< 0·05), increased malondialdehyde content (P< 0·05) in serum and enhanced enterocyte apoptosis index (AI) and concentrations of caspase-3, caspase-8 and caspase-9 (P< 0·05). Gene expression analyses indicated that weaning induced apoptosis via Fas signalling and mitochondrial pathways in weaned piglets. Dietary NAC supplementation decreased (P< 0·05) cortisol concentrations and the AI, increased (P< 0·05) antioxidant status in serum and alleviated histopathological changes in the intestine. It also inhibited Fas, caspase-3, caspase-8 and integrin αvβ6 (αvβ6) gene expressions in the NAC-treated piglets. However, no significant decrease (P>0·10) in caspase-3, caspase-8 and caspase-9 concentrations was observed in the NAC group compared with the weaning group. In conclusion, weaning may induce enterocyte apoptosis via the activation of Fas-dependent and mitochondria-dependent apoptosis. Although NAC had no effect on caspase concentrations, it was clearly beneficial for preserving morphological integrity in weaned piglets via the regulation of cell apoptosis and the inhibition of Fas-dependent apoptosis and αvβ6 expression.
The Fate and Power of Heroic Bones and the Politics of Bone Transfer in Ancient Israel and Greece
Authors: Doak Brian R.
Published: June 2013

Tucked away in the Hebrew Bible at the end of 1 Samuel and then resumed near the end of 2 Samuel is a provocative tale recounting the final fate of Saul, Israel's first king. At the beginning of this two-part narrative (1 Sam 31:1), we find Saul atop Mount Gilboa, badly wounded by Philistine archers and nearly dead. Fearing the Philistine armies will rush upon him and continue the humiliation—perhaps by stabbing him repeatedly while still alive, as Saul suggests in 31:4, or something worse—Saul commits suicide. As the rest of the chapter recounts, upon finding his corpse, the enemy army abuses him in a different but perhaps not less dreadful manner, i.e., by beheading the king and hanging the remainder of his body on the wall of Beth Shan (along with the bodies of his sons, who died with their father in the battle). The residents of Jabesh Gilead, however, hear of these events and abscond with the bodies, burying the bones in their own territory and thus ending this particular episode of conflict between Israel and Philistia.
The Paradox of Holy Matter in the Later Middle Ages
Authors: Oakley Francis
Published: June 2013

Via the focus on food that she had found to be the distinguishing preoccupation in the female piety of the Middle Ages and had addressed so probingly and with such independence of scholarly spirit in her Holy Feast and Holy Fast, Caroline Walker Bynum has moved on over the past two decades, and logically enough, to bring her formidable scholarly intelligence and drive to bear, first, on issues pertaining to the body and then, beyond that, to the intriguing cat's cradle of questions pertaining to late-medieval assumptions about matter and its nature in general. The first impulse came to fruition in her Resurrection of the Body in Western Christianity, 200–1336, a book in which celibacy, asceticism, fasting, and renunciation notwithstanding, she pushed back hard against the modern temptation to project onto medieval religiosity some sort of body-hating soul-body dualism. In this she was moved, as she herself has forthrightly acknowledged, by a “determination to let individual voices be individual and to let the past be different,” as well as by the adamant refusal, evinced also in the work under review, to simplify “the intricate and contradictory assumptions and practices” she was exploring. “Paradox remains paradox,” she has bluntly insisted, and “complexity remains complex” (13).
Long-term passive acoustic monitoring revealed seasonal and diel patterns of cetacean presence in the Istanbul Strait
Authors: Dede Ayhan , Öztürk Ayaka Amaha , Akamatsu Tomonari , Tonay Arda M. , Öztürk Bayram
Published: June 2013

The Istanbul Strait (Bosphorus) is a part of the Turkish Straits System, connecting the Aegean Sea and the Black Sea. There are three cetacean species in the Strait, namely the harbour porpoise (Phocoena phocoena), the common dolphin (Delphinus delphis), and the bottlenose dolphin (Tursiops truncatus). To monitor the presence of the cetaceans, a fixed stereo passive acoustic monitoring system (A-tag) was deployed in the middle of the Strait from July 2009 to September 2010. In total 26,814 click trains were detected. Presence, direction and inter-click intervals of phonating cetaceans were measured. Most click trains were detected during the night time. Diel presence pattern was prominent in March and April. In spring, the cetaceans were concentrated in one specific direction from the fixed monitoring system. In contrast, they were found in all directions for the rest of the year. Short range sonar (inter-click intervals (ICIs) less than 50 ms) was commonly detected in spring. During the rest of the year ICIs could reach up to 150 ms. All these findings suggest that they were feeding or socializing in spring and mostly travelling in the other seasons. It is well known that pelagic fish such as sprat and bluefish start their migration from the Aegean Sea to the Black Sea in spring. This study suggests that the cetaceans use the middle part of the Strait for feeding on the pelagic fish in spring when the fish migration has just started.
A locally minimal, but not globally minimal, bridge position of a knot
Authors: OZAWA MAKOTO , TAKAO KAZUTO
Published: June 2013

We give a locally minimal, but not globally minimal, bridge position of a knot, that is, an unstabilized, nonminimal bridge position of a knot. It implies that a bridge position cannot always be simplified so that the bridge number monotonically decreases to the minimal.
The use of null models and partial least squares approach path modelling (PLS-PM) for investigating risk factors influencing post-weaning mortality in indoor pig farms
Authors: SERRANO E. , LÓPEZ-SORIA S. , TRINCHERA L. , SEGALÉS J.
Published: June 2013

Although post-weaning mortality (PWM) in pig farming is mainly due to the effect of pathogens, farm type or swine management are also directly or indirectly involved. In this work, we used null models and the partial least squares approach (PLS) to structural equation modelling, also known as PLS path modelling (PLS-PM), to explore whether farm type, swine management and pathogens, including porcine circovirus type 2, swine influenza virus, porcine reproductive and respiratory syndrome virus and Aujeszky's disease virus, directly or indirectly influenced PWM in 42 Spanish indoor pig farms. The null model analysis revealed that contact with multiple combinations of viruses could occur by chance. On the other hand, PLS-PM showed that farm characteristics do not influence virus infections, and thus neither farm type nor associated management practices shaped PWM due to pathogens. Accordingly, preventive programmes aimed at controlling PWM in intensive farming should prioritize the control of major pig pathogens.
Hayfields enhance colony size of the Barn SwallowHirundo rusticain northern Italy
Authors: SICURELLA BEATRICE , CAPRIOLI MANUELA , ROMANO ANDREA , ROMANO MARIA , RUBOLINI DIEGO , SAINO NICOLA , AMBROSINI ROBERTO
Published: June 2013

The widespread decline of farmland birds is a major issue of biological conservation in European countries. The Barn SwallowHirundo rusticais a flagship species for farmland bird conservation owing to its aesthetic and cultural value and to the sharp decline observed in several populations. Based on a long-term monitoring project of a population in a protected area of Northern Italy, we documented a dramatic decline of 56.6% between 1999 and 2011, corresponding to a decrease of 6.59% each year. We also showed that colonies were on average larger in farms with livestock than those without livestock, and that colony size increased with increasing extent of hayfields within 200 m from the colony in farms without livestock, but not in those with livestock. Hayfield extent at greater distances did not influence population size or trend. Cessation of livestock farming therefore determined a decline in local colonies, but this decline may be buffered by an increase in hayfield extent within 200 m from the farm. However, variation in the ecological features of breeding sites explained only a fraction of the observed population decline, suggesting that ecological conditions during migration and wintering may be crucial in affecting population trends. Mean hatching date of first broods advanced in recent years, but less so in farms with, than without, livestock. Independently of year, mean hatching date advanced more in farms with greater extent of hayfields within 200 m of the colony. Reproductive success, measured as the mean number of fledged offspring per nest, declined significantly with hatching date, but was not affected by hayfield extent. Conversely, nestling quality, in terms of body mass and feather development, improved with increasing extent of hayfields around the colony, particularly in late-hatched first clutches. Our findings suggest that conservation strategies for this declining species should include both the maintenance of livestock farming and the enlargement of hayfields close to breeding colonies, particularly in farms where livestock farming has ceased.
Longevity insurance markets and Money's worth ratios in Korea
Authors: LEE KYONGHEE
Published: June 2013

The rare annuitization, thin immediate annuity market, and date limitation have prevented the attempts to analyze the longevity insurance market in Korea. The purpose of this paper is to examine the relative value of Korean annuity rates to theoretical ones and to provide a new evidence on the function of the voluntary annuity market in terms of the money's worth ratio (MWR). Our results show that the immediate annuity market in Korea is reasonably efficient. For example, the money's worth ratio of an immediate annuity of a 10-year guarantee period for a 65-year-old male is estimated to be about 0.8 with the general population mortality rate, while it improves to 0.9 with the annuitant mortality table. Average MWR is similar to that of other countries with thin annuity market, which show that annuitants in Korea pay a comparable cost to that in other countries.
Medical Record Validation of Maternal Recall of Pregnancy and Birth Events From a Twin Cohort
Authors: Liu Jianghong , Tuvblad Catherine , Li Linda , Raine Adrian , Baker Laura A.
Published: June 2013

This study aims to assess the validity of maternal recall for several perinatal variables 8–10 years after pregnancy in a twin sample. Retrospective information was collected 8–10 years after the delivery event in a cohort of mothers from the University of Southern California Twin Study (N= 611) and compared with medical records for validity analysis. Recall of most variables showed substantial to perfect agreement (κ = 0.60–1.00), with notable exceptions for specific medical problems during pregnancy (κ ≤ 0.40) and substance use when mothers provided continuous data (e.g., number of cigarettes per day;r≤ 0.24). With the exception of delivery method, neonatal intensive care unit admission, birth weight, neonatal information, and post-delivery complications were also recalled with low accuracy. For mothers of twins, maternal recall is generally a valid measure for perinatal variables 10 years after pregnancy. However, caution should be taken regarding variables such as substance use, medical problems, birth length, and post-delivery complications.
Perceptual Control as a Unifying Concept in Psychology
Authors: Marken Richard S. , Mansell Warren
Published: June 2013

We show how a control system model of behavior called Perceptual Control Theory (PCT) can provide a unifying framework for research in all traditional areas of psychology—as a basis for building hypotheses, working models, and applications. PCT views behavior, at all levels, as the control of perceptual inputs. This view is virtually the opposite of that of now standard models—exemplified by the General Linear Model—which view behavior as controlled by perceptual inputs. The PCT model calls for a new approach to research that is aimed at discovering the input variables that organisms control, rather than the input variables that control organisms. This new approach, called The Test for the Controlled Variable, can be applied to the study of all aspects of behavior, from motor control to cognitive neuroscience to counseling and clinical psychology.
Howyland
Authors: Jacobs Howy
Published: June 2013

A huge amount of time and money is wasted on a grants system few perceive as fair. Howy suggests a simplified approach that could produce a more satisfactory outcome.
Scattering theory for graphs isomorphic to a regular tree at infinity
Authors: Colin de Verdière Yves , Truc Françoise
Published: June 2013

We describe the spectral theory of the adjacency operator of a graph which is isomorphic to a regular tree at infinity. Using some combinatorics, we reduce the problem to a scattering problem for a finite rank perturbation of the adjacency operator on a regular tree. We develop this scattering theory using the classical recipes for Schrödinger operators in Euclidian spaces.
Development of an ion mobility spectrometer with a paper spray ionization source
Authors: Jingjing Zhang , Jie Jiang , Xiaolin Qiao
Published: June 2013

Paper spray (PS) ionization is a recently developed ion source that has been used to analyze samples in their native environments at ambient pressure without requiring sample preparation or pre-separation. The design of an ion mobility spectrometer (IMS) coupled with PS ionization can help expand IMS applications to on-site detection of complex liquid samples. We report a paper spray ionization ion mobility spectrometer prototype that consists of a PS source and an ion mobility spectrometer optimized using a numerical simulation. The performance of the design was evaluated by measuring 2, 6-di-tert-butylpyridine (2, 6-DtBP). The mobility spectra of the 2, 6-DtBP exhibited a single-product ion peak with reduced mobility calculated at 1.42 cm2/(V s) and a linear response of 0.1–10 μg/ml, with an estimated detection limit of 0.05 μg/ml. The Relative Standard Deviation for 1 μg/ml was 5.7% over 11 measurements. The highest resolving power (47) was measured for 2, 6-DtBP. Based on these preliminary results, the present PSIMS design is expected to become a tool of choice for the rapid analysis of complex liquid samples.
Coil optimization for electromagnetic levitation using a genetic like algorithm
Authors: Royer Z. L. , Tackes C. , LeSar R. , Napolitano R. E.
Published: June 2013

The technique of electromagnetic levitation (EML) provides a means for thermally processing an electrically conductive specimen in a containerless manner. For the investigation of metallic liquids and related melting or freezing transformations, the elimination of substrate-induced nucleation affords access to much higher undercooling than otherwise attainable. With heating and levitation both arising from the currents induced by the coil, the performance of any EML system depends on controlling the balance between lifting forces and heating effects, as influenced by the levitation coil geometry. In this work, a genetic algorithm is developed and utilized to optimize the design of electromagnetic levitation coils. The optimization is targeted specifically to reduce the steady-state temperature of the stably levitated metallic specimen. Reductions in temperature of nominally 70 K relative to that obtained with the initial design are achieved through coil optimization, and the results are compared with experiments for aluminum. Additionally, the optimization method is shown to be robust, generating a small range of converged results from a variety of initial starting conditions. While our optimization criterion was set to achieve the lowest possible sample temperature, the method is general and can be used to optimize for other criteria as well.
Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors
Authors: Burenkov Viacheslav , Xu He , Qi Bing , Hadfield Robert H. , Lo Hoi-Kwong
Published: June 2013

We report on the observation of a non-uniform dark count rate in Superconducting Nanowire Single Photon Detectors (SNSPDs), specifically focusing on an afterpulsing effect present when the SNSPD is operated at a high bias current regime. The afterpulsing exists for real detection events (triggered by input photons) as well as for dark counts (no laser input). In our standard set-up, the afterpulsing is most likely to occur at around 180 ns following a detection event, for both real counts and dark counts. We characterize the afterpulsing behavior and speculate that it is not due to the SNSPD itself but rather the amplifiers used to boost the electrical output signal from the SNSPD. We show that the afterpulsing indeed disappears when we use a different amplifier with a better low frequency response. We also examine the short-lived enhancement of detection efficiency during the recovery of the SNSPD due to temporary perturbation of the bias and grounding conditions.
The temperature dependent structure of liquid 1-propanol as studied by neutron diffraction and EPSR simulations
Authors: Sillrén Per , Swenson Jan , Mattsson Johan , Bowron Daniel , Matic Aleksandar
Published: June 2013

The structure of liquid 1-propanol is investigated as a function of temperature using neutron diffraction together with Empirical Potential Structure Refinement modelling. The combined diffraction and computer modelling analysis demonstrates that propanol molecules form hydrogen bonded clusters with a relatively wide size distribution, which broadens at lower temperatures. We find that the cluster size distribution is well described by a recently proposed statistical model for branched H-bonded networks [P. Sillrén, J. Bielecki, J. Mattsson, L. Börjesson, and A. Matic, J. Chem. Phys. 136, 094514 (2012)]10.1063/1.3690137. The average cluster size increases from ∼3 to 7 molecules, whilst the standard deviation of the size distribution increases from 3.3 to 8.5 as the temperature is decreased from 293 to 155 K. The clusters are slightly branched, with a higher degree of branching towards lower temperatures. An analysis of the cluster gyration tensor (Rmn) reveals an average elongated ellipsoidal shape with axes having proportions 1:1.4:1.9. We find that the average radius of gyration has a cluster size dependence consistent with that of fractal clusters, Rg ∝ n1/D, with a fractal dimension D ≈ 2.20, which is close to D = 2.00 expected for an ideal random walk or D = 2.11 expected for reaction limited aggregation. The characteristic angles between the H-bonded OH-groups that constitute the clusters show only a weak temperature dependence with O–H⋯O angles becoming more narrowly distributed around 180° at lower temperatures.
Natural time analysis of critical phenomena: The case of pre-fracture electromagnetic emissions
Authors: Potirakis S. M. , Karadimitrakis A. , Eftaxias K.
Published: June 2013

Criticality of complex systems reveals itself in various ways. One way to monitor a system at critical state is to analyze its observable manifestations using the recently introduced method of natural time. Pre-fracture electromagnetic (EM) emissions, in agreement to laboratory experiments, have been consistently detected in the MHz band prior to significant earthquakes. It has been proposed that these emissions stem from the fracture of the heterogeneous materials surrounding the strong entities (asperities) distributed along the fault, preventing the relative slipping. It has also been proposed that the fracture of heterogeneous material could be described in analogy to the critical phase transitions in statistical physics. In this work, the natural time analysis is for the first time applied to the pre-fracture MHz EM signals revealing their critical nature. Seismicity and pre-fracture EM emissions should be two sides of the same coin concerning the earthquake generation process. Therefore, we also examine the corresponding foreshock seismic activity, as another manifestation of the same complex system at critical state. We conclude that the foreshock seismicity data present criticality features as well.
Topographically induced internal solitary waves in a pycnocline: Primary generation and topographic control
Authors: Dossmann Y. , Auclair F. , Paci A.
Published: June 2013

Internal solitary waves (hereafter ISWs) are stable nonlinear waves propagating in regions of strong density gradients common in geophysical flows. The purpose of the present work is to describe the generation of internal solitary waves at the interface of a two layer fluid, by the periodic oscillation of a topography. This academic configuration is inspired by oceanic observations. Direct numerical simulations, using the numerical model Symphonie-NH, are used to give insights into the physical parameters controlling the generation of these high amplitude interfacial waves in the primary generation case. The dynamics of the propagating ISWs is successfully compared with a simple Korteweg-de Vries scheme, showing that primarily generated ISWs propagate in an unimodal manner, and confirming that their stability relies on the balance between nonlinear and dispersive effects. Finally, the role of the topography in the primary generation process is quantitatively described by varying its shape. We show the existence of a topographic control of the primary generation of ISWs. A nondimensional parameter based on the ratio of the interfacial wavelength and the typical topography width is introduced to describe this spatial selection criterion.
Amorphous InGaZnO ultraviolet phototransistors with double-stack Ga2O3/SiO2 dielectric
Authors: Chang T. H. , Chiu C. J. , Chang S. J. , Tsai T. Y. , Yang T. H. , Huang Z. D. , Weng W. Y.
Published: June 2013

This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors with Ga2O3 gate dielectric and applied on deep-ultraviolet phototransistors. To reduce the leakage current, we introduce the SiO2 interlayer dielectric, which effectively reduces the off-current. Under the illumination of 250 nm, the measured responsivity of the device was 3.2 A/W at an applied gate bias of 0 V. The photo-generated carriers were injected into the channel by the applied electric field and Fowler-Nordheim tunneling. A large photocurrent and responsivity can be obtained which is attributed to the high mobility of the a-IGZO channel.
Structure-stress-resistivity relationship in WTi alloy ultra-thin and thin films prepared by magnetron sputtering
Authors: Le Priol A. , Le Bourhis E. , Renault P.-O. , Muller P. , Sik H.
Published: June 2013

WTi thin films were prepared from an alloyed target (W:Ti ∼ 70:30 at. %) by magnetron sputtering. Body-centered cubic WxTi1−x solid solutions with a {110} fiber texture and columnar grains have been produced with 0.75<x<0.81. The sub-stoichiometry of Ti is shown to result from atom transport and, to a lesser extent, from resputtering. The stress-free lattice parameter values of the films are shown to be close to the bulk lattice parameter of α-W. The electrical resistivity of the produced WTi thin films is about 60−200 μΩ cm, depending on the film thickness and microstructure (sputtering conditions). For both ultra-thin (9.5 nm) and thin (180 nm) films, a stress transition from compressive to tensile is observed as the working pressure increases. The process-structure-property relations of the WTi ultra-thin and thin films are discussed in relation with the state of the art.
The influence of premolding load on the electrical behavior in the initial stage of electric current activated sintering of carbonyl iron powders
Authors: Ye Yongquan , Li Xiaoqiang , Hu Ke , Lai Yangen , Li Yuanyuan
Published: June 2013

This paper reports the premolding load effect on the electrical behavior in the initial stage of electric current activated sintering of carbonyl iron powders. An electrical network model is put forward to estimate the uniformity of electric current in a powder compact subjected to different premolding loads in the initial stage. The improvement in current uniformity can be reflected from a simultaneous increase in the number N and the mass fraction θ of conductive particle chains in the compact. Both N and θ are found to follow a power law with the premolding load F for different exponent values. When θ is equal to 1, a critical load is reached, at which point the current flows through all particles during sintering. Using the results of the model and the electrical contact theory, it is also found that only an increased temperature of less than 20 K across the particle contacts. The distribution of temperature is uniform in particles. This is clearly different from the general acceptance that local high temperature is created at contact during electric current activated sintering. The neck formation and growth are thought to be mainly due to heat bonding and electromigration, of which effects on mass transport are pronouncedly enhanced by increasing the bulk temperature. Because of the poor current uniformity and relatively large power dissipation, a soft thermal breakdown is observed in the sample with high initial resistance. A reduction in premolding load may cause an increase in the initial electrical resistance of the compact. Owing to the unique voltage-current characteristic of electric current activated sintering, a higher initial resistance of compact means more thermal energy is involved, consequently producing a higher bulk temperature and getting a better quality of sintering. This also provides theoretical explanation for the experimental results from Inoue and Istomina.
Collective response to alternating current in the organic conductor α-(bis(ethylenedithio)tetrathiafulvalene)2I3
Authors: Itose Fumitake , Kawamoto Tadashi , Mori Takehiko
Published: June 2013

Interference phenomena between dc fields and ac currents are investigated in the two-dimensional charge-ordered organic conductor α-(bis(ethylenedithio)tetrathiafulvalene)2I3. When alternating current is applied together with a dc electric field, steps analogous to Shapiro steps in the ac Josephson effect appear in the voltage-current characteristics at the internal frequency, where the step height follows the first-order Bessel function of the ac field. These results are discussed through an analogy with sliding charge-density waves.
Effects of nanosecond-scale prepulse on generation of high-energy protons in target normal sheath acceleration
Authors: Wang W. P. , Shen B. F. , Zhang H. , Xu Y. , Li Y. Y. , Lu X. M. , Wang C. , Liu Y. Q. , Lu J. X. , Shi Y. , Leng Y. X. , Liang X. Y. , Li R. X. , Wang N. Y. , Xu Z. Z.
Published: June 2013

A pulse cleaner based on noncollinear optical-parametric amplification and second-harmonic generation processes is used to improve the contrast of a laser of peak intensity ∼2 × 1019 W/cm2 to ∼1011 at 100 ps before the peak of the main pulse. A 7 MeV proton beam is observed when a 2.5 μm-thick Al foil is irradiated by this high-contrast laser. The maximum proton energy decreases to 2.9 MeV when a low-contrast (∼108) laser is used. Two-dimensional particle-in-cell simulations combined with MULTI simulations show that the maximum proton energy sensitively relies on the detecting direction. The ns-time-scale prepulse can bend a thin target before the main pulse arrives, which reduces maximum proton energy in the target normal sheath acceleration.
Saturated blue-violet electroluminescence from single ZnO micro/nanowire and p-GaN film hybrid light-emitting diodes
Authors: Li Xin , Qi Junjie , Zhang Qi , Wang Qi , Yi Fang , Wang Zengze , Zhang Yue
Published: June 2013

Saturated electroluminescence behavior was observed in single ZnO micro/nanowire and GaN film heterojunctions fabricated by transferring an individual ZnO micro/nanowire onto p-type GaN substrate. A strong blue emission of ∼460 nm was observed, as a result of interfacial radiative recombination of electrons from n-ZnO and holes from p-GaN. Light-output-current characteristic followed a power law of L ∼ Im, which revealed a superlinear dependence at low current (m = 1.16) and became sublinear (m = 0.72) at high current. According to theoretical analysis, the saturated electroluminescence at high current could be attributed to the saturation of nonradiative recombination and the limitation of electrical-to-optical conversion efficiency.
Lasing action in water vapor induced by ultrashort laser filamentation
Authors: Yuan Shuai , Wang Tiejun , Teranishi Yoshiaki , Sridharan Aravindan , Hsien Lin Sheng , Zeng Heping , Leang Chin See
Published: June 2013

The water vapor fluorescence in air from filaments generated by intense ultrashort Ti:sapphire laser pulses is experimentally studied. The backscattered fluorescence from OH shows an exponential increase with increasing filament length, indicating amplified spontaneous emission. By measuring the intensity inside the filament and the fluorescence intensity of OH, a high degree of nonlinearity is obtained, indicating a highly nonlinear field dissociation of H2O molecule.
Wireless power transfer in the presence of metallic plates: Experimental results
Authors: Yu Xiaofang , Skauli Torbjørn , Skauli Bjørn , Sandhu Sunil , Catrysse Peter B. , Fan Shanhui
Published: June 2013

We demonstrate efficient wireless power transfer between two high Q resonators, especially in a complex electromagnetic environment. In the close proximity of metallic plates, the transfer efficiency stays roughly the same as the free space efficiency with proper designs. The experimental data fits well with a coupled theory model. Resonance frequency matching, alignment of the magnetic field, and impedance matching are shown to be the most important factors for efficient wireless power transfer.
The Ōuchi-Spillmann Illusion Revisited
Authors: Spillmann Lothar
Published: June 2013

In a disk – ring pattern composed of horizontally oriented checks in the centre and vertically oriented checks in the surround, the centre appears to slide relative to the surround when the pattern is slowly moved about. This phenomenon has been called the Ōuchi illusion. Slow sliding movements may represent involuntary ocular drifts, while occasional jerks suggest a contribution by microsaccades. The conditions under which the illusion occurs both with free viewing and in the absence of involuntary eye movements are reviewed. Illusory sliding is most pronounced with diagonal movement of the stimulus pattern, resulting in apparent motion orthogonal to the orientation of the disk. The illusion requires checks of low spatial frequency; it persists with low luminance contrast and blur of the inducing pattern, but is absent at equiluminance. These results suggest a magnocellular neuronal mechanism. Sliding continues to be seen with an empty annular zone separating centre and surround, and is seen even when there is no concentric surround at all, just two abutting flanks. Nine hypotheses proposed to account for the illusory motion of the centre relative to the surround are reviewed. Among these the models based on an integration bias of local motion vectors (Mather 2000 Perception29 721–727) and Type II plaid motion (Ashida 2002 Vision Research 42 1413 – 1420) come closest to explaining illusory sliding in the Ōuchi figure, but open questions remain. Specifically, more research is warranted to correlate the predicted with the perceived direction of sliding motion in both check and grating patterns.
A segmentation procedure using colour features applied to images of Arabidopsis thaliana
Authors: Ispiryan Ruben , Grigoriev Igor , zu Castell Wolfgang , Schäffner Anton R.
Published: June 2013

In studies of environmental effects on plant growth, the images of plants are often used for non-destructive measurements in phenotyping. In this work, a computational procedure has been developed to segment images of plants allowing an improved separation of plants and other types of objects in the frame such as moss or soil. The proposed procedure is based on colour analysis and image morphology. The red-green-blue (RGB) values are transformed into a colour space as ratios of R, G and B vs the sum of R, G, and B channels. We introduce an approach to render the training set of pixels on a Microsoft Excel two-dimensional graph and a technique to determine the discriminant regions of pixel classes. Two approaches for the classification based on colour analysis are shown: an automatic method using support vector machines and a procedure based on visual inspection. The segmentation procedure is designed to classify more than two object types utilising flexibly curved boundaries of discriminant regions that can also be non-convex. We propose a machine-vision algorithm to detect plant features – leaf anthocyanin accumulation and trichomes. The procedures of segmentation and feature detection are applied to images of Arabidopsis thaliana (L.) Heynh. that grow under either normal or drought stress conditions.
The source of nitrogen (NH4+ or NO3–) affects the concentration of oxalate in the shoots and the growth of Atriplex nummularia (oldman saltbush)
Authors: Al Daini Hussein , Norman Hayley C. , Young Paul , Barrett-Lennard Edward G.
Published: June 2013

Atriplex nummularia Lindl. (oldman saltbush) is a halophytic shrub used widely as a forage for ruminant production in saline farming systems. However, it can contain high concentrations of oxalate in the leaves, which may cause calcium deficiency in grazing animals. We hypothesised that supplying NH4+ instead of NO3– to a clone of this species would decrease oxalate concentrations in the shoots, and also decrease plant growth. Oxalate concentrations were measured in plants in the field, and a glasshouse experiment was conducted in which plants were grown with 10 mM NO3– or NH4+, with 50, 200 or 500 mM NaCl. The field survey showed effects of site (P < 0.001), with average oxalate concentrations in shoots varying between 2.4 and 6.4% dry mass (DM). In the glasshouse, oxalate concentrations and plant growth were both affected by N-source and salinity (P < 0.001). Averaged across salinities, plants grown with NH4+ for 24 days had only 43% of the shoot DM but 25% of the oxalate concentration of plants grown with NO3–. We discuss the effects of N-source on oxalate concentrations, the implications of this for halophyte growth, and the opportunity to select halophytes with lower oxalate and higher nutritive value for livestock.
Tensor Charge of the Nucleon on a Lattice
Authors: Hatsuda Tetsuo
Published: June 2013

The tensor charge of the nucleon, which will be measured in Drell-Yan
processes in polarized proton–proton collisions at the RHIC, is studied
in a quenched lattice QCD simulation. On the 163 ×
20 lattice with β = 5·7, connected parts of the tensor
charge are determined with small statistical error, while the disconnected
parts are found to be small with relatively large error bars. The
flavour-singlet tensor charge (δΣ =
du +
δd + δs) is not
suppressed, as opposed to the flavour-singlet axial charge (ΔΣ
= Δu + Δd
+ Δs).
Nuclear Correlation Effects in the Deep Inelastic Structure Function of 4 He
Authors: Morita Hiko , Suzuki Toru
Published: June 2013

The structure function of 4He is calculated based on a
realistic spectral function which is consistent with the momentum sum rule.
The calculation reproduces the empirical suppression of the EMC ratio
R(x) =
F2(4He)/F2(D)
at x < 1. At x~ 1 the
quasielastic contribution produces a sizable effect in the ratio, but it
becomes negligible around Q2 ~ 20
(GeV/c)2.
Coherent Population Transfer among Three States: Full Algebraic Solutions and the Relevance of Non Adiabatic Processes to Transfer by Delayed Pulses
Authors: Fewell M. P. , Shore B. W. , Bergmann K.
Published: June 2013

Ongoing work aimed at developing highly efficient methods of populating a
chosen sublevel of an energy level highlights the need to understand
off-resonant effects in coherent excitation. This motivated us to re-examine
some aspects of the theory of coherent excitation in a three-state system with
a view to obtaining algebraic expressions for off-resonant eigenvalues and
eigenvectors. Earlier work gives simple closed-form expressions for the
eigenvalues this system, expressions applying even when the system is not on
two-photon resonance. We present here expressions of similar simplicity for
the components of the normalised eigenvectors. The analytic properties of
these components explain the observed sensitivity of the
stimulated-Raman-adiabatic-passage process (STIRAP) to the condition of
two-photon resonance. None of the eigenstates is ‘trapped’ or
‘dark’ unless the system is on two-photon resonance; off
resonance, all states have nonzero projections on the unperturbed intermediate
state. A simple argument shows that no dressed state can be adiabatically
connected to both the unperturbed initial and final states when the system is
off two-photon resonance. That is, adiabatic transfer from initial to final
state requires that these be degenerate before and after the STIRAP pulse
sequence, and this implies zero two-photon detuning. However, substantial
transfer probabilities are observed experimentally for very small two-photon
detunings. We show that such systems are characterised by very sharp avoided
crossings of two eigenvalues, and that the observed population transfer can be
understood as an effect of non adiabatic transitions occurring at the avoided
crossings.