Hard Mode Research Articles

Momentum distribution and correlation due to mass difference caused by power-like distribution

The momentum distribution and the correlation due to the mass difference were studied both in the case of the conventional expectation value and in the case of [Formula: see text]-expectation value, when the momentum distribution is described by a Tsallis distribution with the entropic parameter [Formula: see text]. The magnitude of the momentum distribution for hard modes increases as [Formula: see text] increases, and the [Formula: see text]-dependence of the momentum distribution is quite weak for soft modes. The correlation at [Formula: see text] is larger than that at [Formula: see text] for soft modes, while the correlation at [Formula: see text] is smaller than that at [Formula: see text] for hard modes. The [Formula: see text]-dependences of these quantities in the case of [Formula: see text]-expectation value are weaker than those in the case of the conventional expectation value, respectively.

Multigap Superconductivity at Extremely High Temperature: A Model for the Case of Pressurized H2S

It is known that in pressurized H2S the complex electronic structure in the energy range of 200 meV near the chemical potential can be separated into two electronic components, the first characterized by steep bands with a high Fermi velocity and the second by flat bands with a vanishing Fermi velocity. Also the phonon modes interacting with electrons at the Fermi energy can be separated into two components: hard modes with high energy around 150 meV and soft modes with energies around 60 meV. Therefore we discuss here a multiband scenario in the standard BCS approximation where the effective BCS coupling coefficient is in the range 0.1- 0.32. We consider a first (second) BCS condensate in the strong (weak) coupling regime 0.32 (0.15). We discuss different scenario segregated in different portions of the material. The results show the phenomenology of unconventional superconducting phases in this two-gap superconductivity scenario where there are two electronic components in two Fermi surface spots, the pairing is mediated by either by a soft or a hard phonon branch where the inter-band exchange term, also if small, plays a key role for the emergence of high temperature superconductivity in pressurized sulfur hydride.

Deformation mechanism of kink-step distorted coherent twin boundaries in copper nanowire

In the construction of nanotwinned (NT) copper, inherent kink-like steps are formed on growth twin boundaries (TBs). Such imperfections in TBs play a crucial role in the yielding mechanism and plastic deformation of NT copper. Here, we used the molecular dynamic (MD) method to examine the influence of kink-step characteristics in depth, including kink density and kink-step height, on mechanical behavior of copper nanowire (NW) in uniaxial tension. The results showed that the kink-step, a stress-concentrated region, is preferential in nucleating and emitting stress-induced partial dislocations. Mixed dislocation of hard mode I and II and hard mode II dislocation were nucleated from kink-step and surface atoms, respectively. Kink-step height and kink density substantially affected the yielding mechanism and plastic behavior, with the yielding stress functional-related to kink-step height. However, intense kink density (1 kink per 4.4 nm) encourages dislocation nucleation at kink-steps without any significant decline in tensile stress. Defective nanowires with low kink-step height or high kink density offered minimal resistance to kink migration, which has been identified as one of the primary mechanisms of plastic deformation. Defective NWs with refined TB spacing were also studied. A strain-hardening effect due to the refined TB spacing and dislocation pinning was observed for defective NWs. This study has implications for designing NT copper to obtain optimum mechanical performance.

Analysis on the Operation Fatigue of Deepwater Drilling Riser System

Fatigue is one of main failure modes of deepwater drilling riser system. Analysis models of wave induced fatigue and vortex induced fatigue of deepwater drilling riser are established according to the riser connection, installation and hang-off operations. Characteristics of wave induced fatigue and vortex induced fatigue of riser system in different operation modes are studied. The influence of each operation fatigue on the combined fatigue is also identified. The results show that wave induced fatigue damage and vortex induced fatigue damage of upper riser are large in installation and hard hang-off modes. The fatigue damage of riser system in soft hang-off mode is less than that in hard hang-off mode. The combined fatigue damage of the upper and lower riser is large. The lower riser is under the influence of wave induced fatigue and vortex induced fatigue, while the upper riser is mainly under the influence of wave induced fatigue, especially that in installation and hang-off modes. The fatigue damages of riser in installation and hang-off modes have a great influence on the combined fatigue of riser and cannot be neglected in riser fatigue analysis.

MODEL OF QUASI-LINEAR RHEODYNAMIC MEDIUM AND ITS SOLUTION

This paper analyses the stable and unstable stress deformation states of elastic-viscous-inertial (retardation) model depending on the acting stress and rheological parameters of the medium. The introduced concepts: self-oscillatory deformation state, the soft mode of deformation, hard deformation mode, excitation coefficient of rheodynamcs system and others. For the initial conditions lying within the unstable, limit cycle the oscillatory deformation of rheodynamcs system is damping. For the initial conditions, located outside of this cycle, self-oscillatory deformation processes are set. Parameter , resulting in different values to the emergence and disappearance of self-oscillation in a medium, is called coefficient of stimulating rheodynamcs systems. However, an unlimited increase in the vibration strain requires unlimited admission of energy to the system. Therefore, in these cases, the approach taken under different  is to be enough and take into account the higher-order terms.

Relaxor ferroeletric behavior inSr1−xPrxTiO3: Cooperation between polar and antiferrodistortive instabilities

Chemical doping at the Sr and Ti sites is a feasible way to alter the quantum paraelectric state of $\mathrm{SrTi}{\mathrm{O}}_{3}$ perovskite. Doping with Pr is known to induce relaxor ferroelectricity at room temperature in the $\mathrm{S}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{r}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$ solid solution. The relationship between its dielectric properties and structural phase transition has been debated, but no definitive structural argument has been proposed. Here we present a systematic structural study of $\mathrm{S}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{r}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$ $(0.020\ensuremath{\le}x\ensuremath{\le}0.150)$. We establish the structural phase diagram using high-resolution x-ray powder diffraction by finding the antiferrodistortive structural phase transitions for all the compositions studied. By using pair distribution function analysis, we show the mismatch between local and long-range structures in terms of increased local order parameters. Finally, we propose a correlation between the local structural order parameters and the emergence of hard polar modes as found by Raman spectroscopy. Our results are quantitatively consistent with recent theoretical calculations showing that the increase of local tetragonality and local octahedral tilting above a critical value in fact underlie the polar instability. This confirms that structural orders involving both polar and antiferrodistortive characters compete and cooperate at different levels, promoting ferroelectricity in $\mathrm{S}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{r}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$.

Mechanical Properties of Natural Fibers Reinforced Polymer Composites: Palm/Low Density Polyethylene

In the work, mechanical properties of palm fibers/low density polyethylene (LDPE) composites were studied. These fibers were mixed with the polymeric matrix (LDPE) in a thermokinetic mixer, in which fibers were responsible for 5 to 20 wt% in the composition. After the mixture, composites were dried, ground in mill and placed in an injector camera according to ASTM D-638 and ASTM D-790 specifications. Specimens were tested in tensile, impact, flexural and Shore A hardness mode. Results showed the addition fibers in polymeric matrix presented increase mechanical properties when compared to pure polymer

Alterações de sistema estomatognático em indivíduos disfônicos

RESUMO: Objetivo: verificar a presença de alterações do sistema estomatognático e sua associação com o sexo, profissão, relato de alergias e diagnóstico fonoaudiológico do tipo de disfonia em indivíduos disfônicos que procuraram atendimento em uma clínica-escola fonoaudiológica. Métodos: estudo quantitativo e retrospectivo, por meio de banco de dados. Amostra de 69 prontuários de sujeitos de ambos os sexos, com idades entre 19 e 44 anos. Coletaram-se dados sobre faixa etária, sexo, profissão, relato de alergias, diagnóstico fonoaudiológico do tipo de disfonia, tipo respiratório e dados da avaliação antroposcópica do sistema estomatognático: oclusão, alterações horizontais e transversais de mordida, largura e profundidade do palato duro, modo respiratório e tensão de lábios, língua e bochechas. Resultados: 28,99% (n=20) eram profissionais da voz; 33,33% (n=23) relataram alergias; tipo respiratório misto com 75,36% (n=52), seguido pelo superior com 20,29% (n=14) e costodiafragmaticoabdominal com 4,35% (n=3); tipo de disfonia funcional (n=42; 66,67%), seguido pelo organofuncional (n=19; 23,54%) e orgânico (n=8; 11,59%). Nas associações de alterações do sistema estomatognático com tipos e modos respiratórios, tipos de disfonia, profissionais da voz e relato de alergias não houve significâncias, apenas do sexo feminino com ausência de alterações verticais de mordida. Conclusão: os pacientes estudados eram predominantemente mulheres; adultos; não profissionais da voz; com disfonia funcional; sem relato de alergias ou alterações de sistema estomatognático; com tipo e modo respiratórios adequados, havendo associação apenas do sexo feminino com ausência de alterações verticais de mordida.

Microstructural evolution and mechanical properties of linear friction welded Ti2AlNb joint during solution and aging treatment

Linear friction welded joints of Ti2AlNb-based alloy were subjected to different solution and aging treatments. Relationships among solution and aging conditions, microstructural evolution and mechanical properties were investigated. The results indicate that the microstructures are very sensitive to solution conditions. In weld zone, the lath O precipitates at the grain boundaries when the joint is solution treated in O+B2 phase region, while the formation of lath α2 phase occurs in α2+B2+O phase region. In thermo-mechanically affected zone (TMAZ), aggregation of O phase and rim O phase resulted from further decomposition of α2 phase can be found during solution treatment. And after aging treatment, both weld zone and TMAZ are comprised of secondary acicular O phase within B2 grains. Solution and aging treatments have significantly enhanced the microhardness of weld zone due to the precipitation hardening of O phase and refined grain strengthening. After aging treatment, the tensile strength of the joints is further improved because of precipitation of secondary O phase, whereas, elongation is reduced due to the suppression of the hard deformation modes in fine acicular microstructures.

Two-sided damping constraint control strategy for high-performance vibration isolation and end-stop impact protection

In this paper, a two-sided damping constraint control strategy is proposed to improve the performance of the quasi-zero stiffness isolator. The new control policy is achieved through switching the damping of isolator between the soft and hard modes that depend on a preset value of the relative displacement (PRD). This control approach can largely lower the isolation frequency while enhancing the effectiveness of isolation in high frequencies and preventing the severity of end-stop impacts. To realize such control objective, two key issues are solved including the suppressing of period-3 solutions that coexist with the desired period-1 orbits and the optimization of PRDs based upon the analysis of two-parameter bifurcations and basins of attraction. Finally, the capability of the proposed system in end-stop impact protection is studied, which shows that it can successfully prevent the impact and quickly stabilize the large-amplitude response into the ideal steady-state motion.

Open software architecture for east articulated maintenance arm

For the inside inspection and the maintenance of vacuum vessel in the EAST, an articulated maintenance arm is developed. In this article, an open software architecture developed for the EAST articulated maintenance arm (EAMA) is described, which offers a robust and proper performance and easy-going experience based on standard open robotic platform OROCOS. The paper presents a component-based model software architecture using multi-layer structure: end layer, up layer, middle, and down layer. In the end layer the components are defined off-line in the task planner manner. The components in up layer complete the function of trajectory plan. The CORBA, as a communication framework, is adopted to exchange the data between the distributed components. The contributors use Real-Time Workshop from the MATLAB/Simulink to generate the components in the middle layer. Real-time Toolkit guarantees control applications running in the hard real-time mode. Ethernets and the CAN bus are used for data transfer in the down layer, where the components implement the hardware functions. The distributed architecture of control system associates each processing node with each joint, which is mapped to a component with all functioning features of the framework.

The Missing Link in Donor Prescribed Educational Reforms: Lack of Ownership (The Case of the World Bank in Ethiopian Higher Education)

The World Bank (WB) as an international policy transfer and diffusion agent has been actively involved in orchestrating and driving Higher Education (HE) reforms globally. Such impact of the Bank has arguably, been more evident in the context of loan recipient countries. By using a hard mode of influence (financial), and more subtle or soft modes of influence (knowledge based and symbolic), the Bank has been steering the HE system of loan recipient countries, to which Ethiopia is not an exception. The Bank justifies its involvement by illuminating on the capacity deficit that is widely prevalent in borrowing countries. Notwithstanding, the solid expert base the Bank has, this paper contends that, the Bank is not creating sufficient spaces for local actors to collaborate in. Even when the Bank creates avenues to stimulate discussion on proposed reform ideas, such platforms merely serve the purpose of legitimizing the predetermined reforms ideas of the Bank rather than giving national actors a genuine opportunity to critically challenge, the purported reform ideas of the Bank. This has resulted in, among other things; failure to capitalize on the HE expertise of loan recipient countries, the crafting of reforms that do not resonate with borrowing countries context and most importantly, lack of ownership of the proposed reforms and their sustainability. In line with that, this paper argues for a shift in approach from the current strong top-down approach to a balanced approach that gives sufficient spaces and most importantly recognition for bottom up actors, ideas and initiatives .

Cost-Effective Solution of Input Voltage Stabilizer of Auxiliary Drive Converter for Traction Vehicles

This paper describes a prospective design concept of a hard switching input voltage stabilizer for the auxiliary drives converters of dc catenary fed light traction vehicles. Auxiliary drives are mostly dedicated to generate standard power grid that supplies various on-board equipment and charging on-board batteries. The input voltage stabilizer (IVS) is the first input block of auxiliary drives. This block defines the voltage level of the consequent dc/dc isolated converter (IC). The main aim of this paper is to present the reader with the design of a low-cost variant of the voltage stabilizer. The described input voltage stabilizer is designed as a buck (step-down) or boost (step-up) converter, operating with an input catenary voltage range of 400 (VDC) to 950 VDC. The new fast, discrete IGBT H3 transistors and SiC diodes allow switching frequency from 20 kHz to 30 kHz in a hard switching mode with power rated up to 22 kW. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13752

Cost-Effective Solution of Input Voltage Stabilizer of Auxiliary Drive Converter for Traction Vehicles

This paper describes a prospective design concept of a hard switching input voltage stabilizer for the auxiliary drives converters of dc catenary fed light traction vehicles. Auxiliary drives are mostly dedicated to generate standard power grid that supplies various on-board equipment and charging on-board batteries. The input voltage stabilizer (IVS) is the first input block of auxiliary drives. This block defines the voltage level of the consequent dc/dc isolated converter (IC). The main aim of this paper is to present the reader with the design of a low-cost variant of the voltage stabilizer. The described input voltage stabilizer is designed as a buck (step-down) or boost (step-up) converter, operating with an input catenary voltage range of 400 (VDC) to 950 VDC. The new fast, discrete IGBT H3 transistors and SiC diodes allow switching frequency from 20 kHz to 30 kHz in a hard switching mode with power rated up to 22 kW. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13752

Combustion of hydrogen-based mixtures in gas-fueled reciprocating engines

The research is devoted to the possibility for application of hydrogen accumulated from renewable energy sources as a fuel for a reciprocating engine, which serves as an electrical generator drive. Hydrogen combustion in the chamber of a reciprocating engine, as a rule, occurs in a detonation mode. In order to obtain less hard modes, the present research proposes the usage of steam additions to hydrogen–air mixture or lean hydrogen–air mixtures. Mathematical simulation is used for investigation of combustion of mentioned mixtures in the combustion chamber of a reciprocating engine with a spark-plug ignition. The comparison of the usage of hydrogen–steam–air mixtures and lean hydrogen–air mixtures as fuels is given. The dependence of arising combustion modes and its quantitative characteristics on hydrogen content in combustible composition is investigated. The analysis of optimal combustion is presented, which is based on the consideration of two parameters: peak pressure in one cycle and the crankshaft angle corresponding to the achievement of the peak pressure.

Injection locking of an electronic maser in the hard excitation mode

The phenomenon of hard excitation is natural for many electronic oscillators. In particular, in a gyrotron, a maximal efficiency is often attained in the hard excitation regime. In this paper, we study the injection-locking phenomena using two models of an electronic maser in the hard excitation mode. First, bifurcation analysis is performed for the quasilinear model described by ordinary differential equations for the slow amplitude and phase. Two main scenarios of transition to the injection-locked mode are described, which are generalizations of the well-known phase-locking and suppression mechanisms. The results obtained for the quasilinear model are confirmed by numerical simulations of a gyrotron with fixed Gaussian structure of the RF field.

Jets of light hadrons via AdS/CFT correspondence

Within the expanding fireball formed at heavy ion collision, jets are produced which probes the QGP. Analysis the energy loss of these energetic partons as they travel throw QGP may reveal extremely valuable information about the dynamics of the plasma and exhibit distinctive properties such as jet-quenching. The “AdS/CFT correspondence” which imposes the duality between the gauge theory and gravity is a novel tool provides valuable insight into the strongly coupled plasma. The most important result of AdS/CFT is calculating the value of shear viscosity to entropy density ratio which is in remarkable agreement with the hydrodynamics predictions. We study the energy loss rate of light quarks via AdS/CFT correspondence in both static and expanding plasma. In the hope of making contact with QGP physics, we propose a novel jet prescription based on the separation of hard and soft modes in the dual theory and test the AdS/CFT approach with the latest light hadron suppression data from CMS.

Effect of Aluminium Content on High Temperature Deformation Behavior of TiAl Intermetallic Compound

Fundamental studies of microstructural changes and high temperature deformation of titanium aluminide (TiAl) were conducted from the view point of the effect of Al content in order to develop the manufacturing process of TiAl. Microstructures in an as cast state consisted mainly of lamellar structure irrespective of Al content. By homogenization at 1473 K, the microstructures of Ti-49Al and Ti-51Al were transformed into an equiaxial structure which was composed of γ-TiAl, while the lamellar structure that was observed in Ti-46Al and Ti-47Al was much more stable. We found that the reduction of Al content suppressed the formation of equiaxial grains and resulted in a microstructure of only a lamellar structure. On Ti-49Al and Ti-51Al, dynamic recrystallization occurred during high temperature deformation, and the microstructure was transformed into a fine equiaxial one, while the microstructures of Ti-46Al and Ti-47Al contained few recrystallized grains and consisted mainly of a deformed lamellar structure. We observed that on the low-Al alloys the lamellar structure under hard mode deformation conditions deformed as kink observed B2-NiAl. High temperature deformation characteristics of TiAl were strongly affected by Al content. An increase of Al content resulted in a decrease of peak stress and activation energy for plastic deformation and an increase of the recrystallization ratio in TiAl.

Comparison of Turn-Off Strategies for SiC Thyristors

Three different turn-off strategies are presented for 6.5 kV class SiC Thyristors. A cathode current of 62 A (284 A/cm2) is successfully turned off by applying a reverse bias of ≈ 30 V to the cathode of a SiC Thyristor. The minimum turn-off time (tq) for the Thyristor using this forced commutation technique is investigated as a function of cathode current density, reverse gate current and the dV/dt of the re-applied forward (blocking) bias. The Anode Switched Thyristor (AST) turn-off mode is demonstrated at a maximum cathode voltage of 3600 V and 14.5 A (199 A/cm2) of cathode current. A cathode current of 5.5 A (75 A/cm2) is successfully turned off by the gate turn off (GTO) or hard turn-off mode at different temperatures up to 200°C. The high-level lifetime (tHL) in the thick p-layer is extracted from the hard turn-off waveforms.

A semi-holographic model for heavy-ion collisions

We develop a semi-holographic model for the out-of-equilibrium dynamics during the partonic stages of an ultrarelativistic heavy-ion collision. The model combines a weakly-coupled hard sector, involving gluon modes with energy and momenta of the order of the saturation momentum and relatively large occupation numbers, with a strongly-coupled soft sector, which physically represents the soft gluons radiated by the hard partons. The hard sector is described by perturbative QCD, more precisely, by its semi-classical approximation (the classical Yang-Mills equations) which becomes appropriate when the occupation numbers are large. The soft sector is described by a marginally deformed conformal field theory, which in turn admits a holographic description in terms of classical Einstein's equations in $AdS_5$ with a minimally coupled massless `dilaton'. The model involve two free parameters which characterize the gauge-invariant couplings between the hard and soft sectors. Via these couplings, the hard modes provide dynamical sources for the gravitational equations at the boundary of $AdS_5$ and feel the feedback of the latter as additional soft sources in the classical Yang-Mills equations. Importantly, the initial conditions for this coupled dynamics are fully determined by the hard sector alone, i.e. by perturbative QCD, and are conveniently given by the color glass condensate (CGC) effective theory. We also develop a new semi-holographic picture of jets in the QGP by attaching a non-Abelian charge to the endpoint of the trailing string in $AdS_5$ representing a heavy quark. This leads to modified Nambu-Goto equations for the string which govern the (collisional and radiative) energy loss by the heavy quark towards both hard and soft modes.