Breaking Conditions Research Articles

Searching for Affective and Cognitive Restoration: Examining the Restorative Effects of Casual Video Game Play.

We investigated the effects of a passive break, relaxation activity, and casual video game on affect, stress, engagement, and cognitive performance. Reducing stress and improving cognitive performance is critical across many domains. Previous studies investigated taking a break, relaxation techniques, or playing a game; however, these methods have not been compared within a single experiment. Participants completed a baseline affective and cognitive assessment (ACA), which included the Positive and Negative Affect Schedule, shortened version of the Dundee Stress State Questionnaire, and backward digit-span. Next, participants completed a vigilance task, followed by another ACA. Participants were then assigned at random to complete a break or relaxation activity or play a casual video game, followed by a final ACA. Participants who played the casual video game exhibited greater engagement and affective restoration than the relaxation condition. The break condition slightly decreased affect and prevented cognitive restoration. Playing a casual video game even briefly can restore individuals' affective abilities, making it a suitable activity to restore mood in response to stress. However, future research is needed to find activities capable of cognitive restoration. Many activities in life require sustained cognitive demand, which are stressful and decrease performance, especially for workers in performance-critical domains. Our research suggests some leisure activities are better than others for restoring fatigued affective processes.

Heat fluctuations of Brownian oscillators in nonstationary processes: Fluctuation theorem and condensation transition.

We study analytically the probability distribution of the heat released by an ensemble of harmonic oscillators to the thermal bath, in the nonequilibrium relaxation process following a temperature quench. We focus on the asymmetry properties of the heat distribution in the nonstationary dynamics, in order to study the forms taken by the fluctuation theorem as the number of degrees of freedom is varied. After analyzing in great detail the cases of one and two oscillators, we consider the limit of a large number of oscillators, where the behavior of fluctuations is enriched by a condensation transition with a nontrivial phase diagram, characterized by reentrant behavior. Numerical simulations confirm our analytical findings. We also discuss and highlight how concepts borrowed from the study of fluctuations in equilibrium under symmetry-breaking conditions [Gaspard, J. Stat. Mech. (2012) P0802110.1088/1742-5468/2012/08/P08021] turn out to be quite useful in understanding the deviations from the standard fluctuation theorem.

The Impact of Breaks on Sustained Attention in a Simulated, Semi‐Automated Train Control Task

Summary: Sustained attention is a factor in many work environments where operators intervene on a regular basis to ensure the safety and security of a system. Different types of activity during break periods may facilitate different levels of performance following extended periods of attention in these environments. The impact of five different breaks from task activity was assessed against the performance of a no‐break control group during a simulated, high signal probability rail control task. A total of 87 university students were assigned to a no‐break control condition, or one of five break activity conditions that occurred between two, 20‐minute periods of simulated rail control. Post‐break, the analysis revealed that, in comparison to the control condition, performance was greater in all of the five break conditions. Any activity that drew operators' attention from the primary rail control task enabled improvements in performance beyond a no‐break control task.Copyright © 2017 John Wiley & Sons, Ltd.

Dynamic in-loop performance investigation and efficiency-cost analysis of dual heat sink thermal control system (DHS-TCS) with a sublimator for aerospace vehicles

Sublimator, as a highly efficient supplementary heat rejection device (SHReD), has been introduced to improve the performance of thermal control system (TCS). To evaluate the dynamic in-loop performance of sublimator, as well to reveal the potential optimal control strategies in particular scenarios, this paper proposes a sublimator-radiator dual heat sink thermal control system (DHS-TCS) configuration, of which the internal heat transfer mechanism model and the fast-prediction-oriented loop coupled model (FLCM) have been established. By these models, operation characteristics of sublimator, such as the allowed inlet temperature range of different sublimator area, heat rejection rate and expendable water consumption are discussed in details. Additionally, simulations of the dynamic in-loop performance of sublimator during on-orbit phase has also been conducted to compare temperature control efficiency (TCE) under different break condition temperature (BCT) settings. In order to evaluate the sublimator’s performance thoroughly, the efficiency-cost analysis between parameters of TCE and expendable water consumption has been simulated in the perspective of economy. Calculation results show that choosing a proper BCT, at which the efficiency-cost ratio achieves maximum and the water consumption remains at a local minimum, is of great importance for efficient utilization of sublimator. The FLCM and the efficiency-cost analysis model together provides the fast prediction capability of the sublimator’s performance for on-orbit control and decision making.

Convective wave breaking in the KdV equation

The KdV equation is a model equation for waves at the surface of an inviscid incompressible fluid, and it is well known that the equation describes the evolution of unidirectional waves of small amplitude and long wavelength fairly accurately if the waves fall into the Boussinesq regime. The KdV equation allows a balance of nonlinear steepening effects and dispersive spreading which leads to the formation of steady wave profiles in the form of solitary waves and cnoidal waves. While these wave profiles are solutions of the KdV equation for any amplitude, it is shown here that there for both the solitary and the cnoidal waves, there are critical amplitudes for which the horizontal component of the particle velocity matches the phase velocity of the wave. Solitary or cnoidal solutions of the KdV equation which surpass these amplitudes feature incipient wave breaking as the particle velocity exceeds the phase velocity near the crest of the wave, and the model breaks down due to violation of the kinematic surface boundary condition. The condition for breaking can be conveniently formulated as a convective breaking criterion based on the local Froude number at the wave crest. This breaking criterion can also be applied to time-dependent situations, and one case of interest is the development of an undular bore created by an influx at a lateral boundary. It is shown that this boundary forcing leads to wave breaking in the leading wave behind the bore if a certain threshold is surpassed.

Nonlinear relativistic plasma resonance: Renormalization group approach

An analytical solution to the nonlinear set of equations describing the electron dynamics and electric field structure in the vicinity of the critical density in a nonuniform plasma is constructed using the renormalization group approach with allowance for relativistic effects of electron motion. It is demonstrated that the obtained solution describes two regimes of plasma oscillations in the vicinity of the plasma resonance— stationary and nonstationary. For the stationary regime, the spatiotemporal and spectral characteristics of the resonantly enhanced electric field are investigated in detail and the effect of the relativistic nonlinearity on the spatial localization of the energy of the plasma relativistic field is considered. The applicability limits of the obtained solution, which are determined by the conditions of plasma wave breaking in the vicinity of the resonance, are established and analyzed in detail for typical laser and plasma parameters. The applicability limits of the earlier developed nonrelativistic theories are refined.

Dependence of scale thickness on the breaking behavior of the initial oxide on plasma spray bond coat surface during vacuum pre-treatment

The thermally grown oxide (TGO) on the thermal spray bond coat surface was one of the most important factors which would influence the lifetime of thermal barrier coatings (TBCs). Pre-diffusion treatment (high temperature vacuum treatment) plays an important role in the growth of the TGO. Results show that the initial thin oxide scale, formed during deposition process, on the as-sprayed bond coating surface has broken and shrunk to discontinuous oxide particles through the elements diffusion during the pre-diffusion. Two kinds of bond coats with different initial oxide scale thicknesses were subjected to the same pre-diffusion. The two pre-diffused bond coats show different results of the average distance between the individual oxide particles. In this study, a three dimensional model with thermal grooving theory was developed to explore the essential condition for the scale breaking and explain the differences of these results. This research can provide reference for the preparation optimization and pre-treatment optimization of bond coat towards high performance TBCs.

Advanced approaches to calculate recovery length and force redistribution in semi-parallel wire cables with broken wires

Two simplified models, including a theoretical approach and a finite element method (FEM) model, are proposed to calculate recovery length and study the force redistribution mechanism in a semi-parallel wire cable with broken wires. In the advanced theoretical model, the symmetrical construction and extrusion stress transfer characteristic of the semi-parallel wire cable are considered. The clench effect of the polyethylene sheath and the prestressed helical wire are considered in the derivation. The simplified FEM model can exhibit mechanical performance at both wire and cable levels. It uses helically placed beam elements to simulate twisted wires, divergently arranged rigid beam elements at the wire cross section to simulate extrusion effect, and nonlinear spring elements to consider the contact and friction between the helical wires. Results show that the recovery length is influenced by the compaction effect of wrapped sheath, as well as the twist angle and position of the broken wire. Under the symmetrical break condition, the recovery lengths calculated using the two methods are in a good agreement with each other, and force redistribution mainly results from the friction effect. Under the asymmetrical break condition, however, force redistribution is dominated by the induced unbalanced moment.

Weighted fast diffusion equations (Part Ⅰ): Sharp asymptotic rates without symmetry and symmetry breaking in Caffarelli-Kohn-Nirenberg inequalities

In this paper we consider a family of Caffarelli-Kohn-Nirenberg interpolation inequalities (CKN), with two radial power law weights and exponents in a subcritical range. We address the question of symmetry breaking: are the optimal functions radially symmetric, or not ? Our intuition comes from a weighted fast diffusion (WFD) flow: if symmetry holds, then an explicit entropy - entropy production inequality which governs the intermediate asymptotics is indeed equivalent to (CKN), and the self-similar profiles are optimal for (CKN). We establish an explicit symmetry breaking condition by proving the linear instability of the radial optimal functions for (CKN). Symmetry breaking in (CKN) also has consequences on entropy - entropy production inequalities and on the intermediate asymptotics for (WFD). Even when no symmetry holds in (CKN), asymptotic rates of convergence of the solutions to (WFD) are determined by a weighted Hardy-Poincar{e} inequality which is interpreted as a linearized entropy - entropy production inequality. All our results rely on the study of the bottom of the spectrum of the linearized diffusion operator around the self-similar profiles, which is equivalent to the linearization of (CKN) around the radial optimal functions, and on variational methods. Consequences for the (WFD) flow will be studied in Part II of this work.

Circuit breaker models for simulations of short-circuit current breaking and slow-front overvoltages in HV systems

Various circuit breaker models have been developed as a tool to evaluate the breaker interrupting capability and to investigate interaction between the breaker and the external circuit. This paper presents selected models of high voltage SF6 circuit breakers (Cassie–Mayr, Schwarz–Avdonin, and an ideal switch with a predefined chopping current level), followed by analysis of the models impact on the 400kV overhead line fault clearing process. Several study cases have been performed to demonstrate the impact of the circuit breaker model on the arcing time and on the transient recovery voltage (TRV) during breaking of the near-to-generator faults. The results obtained indicate that the arc voltage introduced by the circuit breaker model can force the fault current zero crossing and in consequence can significantly change the breaking conditions. It particular, in the study cases where the arc voltage has significant impact on the breaking conditions (such as the near-to-generator fault), the models applied accurately represent arc voltage during the entire current interruption process.

Converting separable conditions to entanglement-breaking conditions

We present a general method to derive entanglement breaking (EB) conditions for continuous-variable quantum gates. We start with an arbitrary entanglement witness, and reach an EB condition. The resultant EB condition is applicable not only for quantum channels but also for general quantum operations, namely, trace-non-increasing class of completely positive maps. We illustrate our method associated with a quantum benchmark based on the input ensemble of Gaussian distributed coherent states. We also exploit our idea for channels acting on finite dimensional systems and present a Schmidt-number benchmark based on input states of two mutually unbiased bases and measurements of generalized Pauli operators.

Oil slicks on water surface: Breakup, coalescence, and droplet formation under breaking waves

The ability to calculate the oil droplet size distribution (DSD) and its dynamic behavior in the water column is important in oil spill modeling. Breaking waves disperse oil from a surface slick into the water column as droplets of varying sizes. Oil droplets undergo further breakup and coalescence in the water column due to the turbulence. Available models simulate oil DSD based on empirical/equilibrium equations. However, the oil DSD evolution due to subsequent droplet breakup and coalescence in the water column can be best represented by a dynamic population model. This paper develops a phenomenological model to calculate the oil DSD in wave breaking conditions and ocean turbulence and is based on droplet breakup and coalescence. Its results are compared with data from laboratory experiments that include different oil types, different weathering times, and different breaking wave heights. The model comparisons showed a good agreement with experimental data.

Calculation method and application of loss of life caused by dam break in China

Dam failure constitutes a grave threat to human life. However, there is still a lack of systematic and comprehensive research on the loss of life (L) caused by dam break in China. From the perspective of protecting human life, a new calculation method for L occurred in dam break floods is put forward. Fourteen dam failure cases in China are selected as the basic data by three-dimensional stratified sampling, balancing spatial, vertical elevation and temporal representations, as well as considering various conditions of the dam collapse. The method includes three progressive steps: Firstly, some impact factors of loss of life (IFL) are selected by literature survey, i.e., severity of dam break flood (S F), population at risk (P R), understanding of dam break (U B), warning time (T W) and evacuation condition (E C). And the other IFL of weather during dam break (W B), dam break mode (M B), water storage (S W), building vulnerability (V B), dam break time (T B) and average distance from affected area to dam (D D) are also taken into account to get a more comprehensive consideration. According to disaster system and disaster risk, these eleven IFL are divided into four categories. Through the improved entropy method, eight key IFL are further selected out of the eleven. Secondly, four L modules are built based on four categories, which are L-causing factor module (M 1), L-prone environment module (M 2), affected body module (M 3) and rescue condition module (M 4). Eventually, by using two methods of multivariate nonlinear regression and leave-one-out cross-validation in combination with coupled four modules, the calculation method for L is established. Compared with the results of Graham method and D&M method, the result of the proposed one is much closer to the actual value and performs better in fitting effect and regional applicability. In the application, L calculation and consequence assessment are carried out in the example of Hengjiang reservoir that has already broken down. At the same time, L calculation and risk prediction are used in the analysis of Yunshan reservoir, which is under planning. The proposed method can not only be applied to estimate L and its rate (f L ) under various types of dam break conditions in China, but also provide a reliable consequence assessment and prediction approach to reduce the risk of L.

A Heuristic Approach for Phasor Measurement Units Placement in Power System

Objectives: The objective of PMU placement in power system in a cost effective way to determine a minimum set of PMU’s so that the whole system is observable. Methods/Analysis: This paper presents a simple heuristic method. The principle is based on system topology that a PMU placed at a node should not create more than one unobservable islands. In order to use this principle, a condition, defined as tree break condition is used. Findings: The results obtained with this heuristic method are placement location of PMUs, observability of system with and without zero-injections under normal operating conditions and for line outage contingency. The systems used are typical 6, 7 bus systems and IEEE 14, 30, 57 bus systems. Novelty/Improvement: The results obtained by this method are simple, optimum and efficient than the methods used previously.

Comparative Experiments to Assess the Effects of Accumulator Nitrogen Injection on Passive Core Cooling During Small Break LOCA

Abstract The accumulator is a passive safety injection device for emergency core cooling systems. As an important safety feature for providing a high-speed injection flow to the core by compressed nitrogen gas pressure during a loss-of-coolant accident (LOCA), the accumulator injects its precharged nitrogen into the system after its coolant has been emptied. Attention has been drawn to the possible negative effects caused by such a nitrogen injection in passive safety nuclear power plants. Although some experimental work on the nitrogen injection has been done, there have been no comparative tests in which the effects on the system responses and the core safety have been clearly assessed. In this study, a new thermal hydraulic integral test facility—the advanced core-cooling mechanism experiment (ACME)—was designed and constructed to support the CAP1400 safety review. The ACME test facility was used to study the nitrogen injection effects on the system responses to the small break loss-of-coolant accident LOCA (SBLOCA) transient. Two comparison test groups—a 2-inch cold leg break and a double-ended direct-vessel-injection (DEDVI) line break—were conducted. Each group consists of a nitrogen injection test and a nitrogen isolation comparison test with the same break conditions. To assess the nitrogen injection effects, the experimental data that are representative of the system responses and the core safety were compared and analyzed. The results of the comparison show that the effects of nitrogen injection on system responses and core safety are significantly different between the 2-inch and DEDVI breaks. The mechanisms of the different effects on the transient were also investigated. The amount of nitrogen injected, along with its heat absorption, was likewise evaluated in order to assess its effect on the system depressurization process. The results of the comparison and analyses in this study are important for recognizing and understanding the potential negative effects on the passive core cooling performance caused by nitrogen injection during the SBLOCA transient.

Seesaw-deflected Anomaly Mediation and the 125 GeV Higgs Boson

We investigate the phenomenology of a class of model that at the same time solves the tachyonic slepton problem of the pure anomaly mediated supersymmetry breaking (AMSB) model and generates neutrino masses. We introduce heavy fields in the seesaw mechanism that are the messengers in the deflected AMSB scenario. Various theoretical and phenomenological constraints have been taken into account, especially the Higgs mass limits. The viable parameter regions have been specified, and the properties of dark matter candidate have been studied. We point out that the type III seesaw with three generations of 24-messenger is excluded, while the type II seesaw and type III seesaw with two generations of 24-messenger are still allowed. The sparticle masses are heavy as in usual SUSY models. The spin-independent crosssection of the scattering between the lightest neutralino and proton show the possibility to see evidences of new physics from future dark matter search experiments. We find that the lepton flavor violation effects caused by the Yukawa mediation are suppressed due to the electroweak symmetry breaking condition.

부유식 파력-해상풍력 복합발전 구조물의 계류선 손상 시 과도 응답 해석

부유식 해양 구조물은 계류선을 이용하여 다양한 종류의 환경하중에 따른 표류를 방지하게 된다. 따라서 구조물의 초기 설계 단계에서 신뢰성 있는 계류선의 설계는 매우 중요한 요소라 할 수 있다. 하지만 다양한 해양의 하중 조건을 견딜 수 있도록 설계된 계류선이라 하더라도 극한 조건의 하중이나 오랜시간 반복된 피로 하중으로 인하여 파손되는 경우가 발생하기도 한다. 일부 계류선의 파손은 잔여 계류선의 장력 변화를 야기하여 경우에 따라서는 전체 구조물의 점진적인 파손을 초래한다. 본 연구에서는 10 MW급 부유식 파력-해상풍력 복합발전 구조물에 연결된 12개의 계류선 중 일부가 손상된 경우의 구조물의 과도 응답을 시간 영역의 수치 시뮬레이션을 통하여 해석하였다. 이를 통하여 일부 계류선 손상 시 전체적인 구조물의 거동 변화 및 잔여 계류선의 장력 변화를 확인하였다.

The improved model of estimating global whitecap coverage based on satellite data

The pro and con of whitecap parameterizations and a statistical wave breaking model are discussed. An improved model is derived by combining satellite-based parameterization and the wave breaking model. The appropriate constants for the general wave state are obtained by considering the breaking condition of the wave slope and fitting with the satellite-based parameterization. The result is close to the constants based on the whitecap data from Monahan. Comparing with satellite-based data and the original model’s results, the improved model's results are consistent with satellite-based data and previous studies. The global seasonal distributions of the whitecap coverage averaged from 1998 to 2008 are presented. Spatial and seasonal features of the whitecap coverage are analyzed.

Critical flow phenomena and modeling in advanced nuclear safety technology

Abstract The discharge could be non-choking or choking, depending on the break shape, length and conditions. This presents a challenge in the calculation of standard problems. A stable experiment of water was performed to study the break flow rate in nozzles of diameter of 1.41 and 2.0 mm with rounded-edge and sharp-edge. The pressure covered the ranges of 0.5 to 29.5 MPa, inlet quality 0 to 1.0 and subcooling up to 350 °C. The results exhibited a close relation of thermal non-equilibrium with pressure. For supercritical pressure a modified equilibrium model in combination with the Bernoulli equation is presented.

Rogue waves off the south/southeastern Brazilian coast

The occurrence of freak waves off the Brazilian coast was investigated through the analysis of data recorded by three buoys deployed in the south/southeast region, at a depth of 200 m. As well documented in the literature, these events are not rare, and more than 700 waves could be classified as abnormal based on the relation between the maximum wave height (H max) and the significant wave height (H s), H max ≥ 2H s. The use of other parameters suggested in the literature, as crest amplification index (crest height/H s ≥ 1.3) or a lower limit to the significant wave (H s ≥ 2 m), drastically reduced this number, resulting in a data set more representative of rogue waves. After applying these more strict criteria, only seven “true” freak waves were found. For the first time in Brazilian waters, it was possible to identify two freak waves in the same record. It was also investigated that an index analog to crest amplification, the trough amplification index (trough depth/H s), and several waves satisfied this new condition. The analyses of the asymmetry and directional spreading of measured spectra reveal no significant correlations between these parameters and freak waves. Probably due to the relative low energy of the area when compared to other regions, the longest wave period closer to a breaking condition is 10 s.