Multiple Breakdowns Research Articles

Method of assessment and prediction of overvoltage caused by single-phase arc ground short circuits in the 6–10 kV mains, as a way of increasing the electrical safety level in mining facilities

Introduction. Overvoltage caused by single-phase ground short circuits are the main reason of multiple breakdowns of insulation. Assessment and forecast of overvoltage in SPGSC in the 6–10 kV mains is therefore a relevant task, and the solution to this problem will make it possible to select effective methods and means of limiting overvoltage and improve the conditions of electrical safety. Research aim is to improve the methods of assessing and forecasting overvoltage of arch SPGSC in the 6–10 kV mains of mining facilities. Methodology. This article provides analysis of current hypothesis and methods for the assessment of overvoltages in the single-phase ground short circuit (SPGSC) mode. Currently the hypothesis of Peterson, Peters–Slepyan, Belyakov–Djuvarl does not fully reflect the factors that affect the maximum overvoltage emergence of the single-phase arc ground short circuits in the 6–10 kV mains, because they don’t take into account the capacitive current value of SPGSC, arc combustion conditions, lifetime of SPGSC, inductance of engines and transformers. Results. There have been obtained dependences that show the dependences of frequency with which overvoltage happens from the factors that were mentioned above. The shown dependences can be used for calculation and assessment of overvoltage in the 6–10 kV mains with different neutral modes to justify the need for activities that will protect electrical systems, transformers, electrical engines from overvoltage in the SPGSC mode and considering its lifecycle. Summary. It was established that from the electrical safety positions of 6–10 kV mains with resistive or combined modes of neutrals on mining and extractive facilities create conditions for the safer exploitation of technological complexes, facilities and electrical equipment, because it can reduce maximum overvoltage ratios by half and thus reduce the number of repeated breakdown of insulation in the SPGSC mode.

Rotation of small diatomics in water-ethanol mixture: Multiple breakdowns of hydrodynamic predictions.

We study the rotational and translational dynamics of three small important linear molecules, namely, carbon monoxide (CO), nitric oxide (NO), and cyanide ion (CN-) in water-ethanol mixtures, at different compositions. Here, we report a detailed study of the dynamics of these diatomics in water-ethanol binary mixtures for the first time. We find multiple anomalous results, namely, (i) faster rotational motion of CO and NO than CN-, (ii) larger translational diffusion of CO and NO in pure ethanol than in water but the reverse for CN-, (iii) a pronounced anomaly in the composition dependence of translational-rotational dynamics at low ethanol composition, and (iv) a re-entrant type behavior in the viscosity dependence of orientational relaxation. We compare our simulation result-based observations with the existing experimental results wherever available and find that the simulation results are in reasonably good agreement with the experiments. We implement, for the first time, a calculation of the rotational binary friction following the sophisticated scheme of Evans and co-workers. We also calculate the hydrodynamic predictions for the solute molecules. On comparison with the simulation and experimental results, we find that neither the rotational binary friction nor the hydrodynamic expressions (both stick and slip) can reproduce the results. To rectify the situation, we develop a detailed mode-coupling theory and suggest that such an approach if completely implemented can provide a more reliable description than the hydrodynamic approach. Many of our results could be tested in experimental studies because these linear molecules are amenable to spectroscopic studies, such as 2D-IR.

No Other Safe Care Option: Nursing Home Admission as a Last Resort Strategy.

Background and ObjectivesNursing homes are intended for older adults with the highest care needs. However, approximately 12% of all nursing home residents have similar care needs as older adults who live in the community and the reasons they are admitted to nursing homes is largely unstudied. The purpose of this study was to explore the reasons why lower-care nursing home residents are living in nursing homes.Research Design and MethodsA qualitative interpretive description methodology was used to gather and analyze data describing lower-care nursing home resident and family member perspectives regarding factors influencing nursing home admission, including the facilitators and barriers to living in a community setting. Data were collected via semistructured interviews and field notes. Data were coded and sorted, and patterns were identified. This resulted in themes describing this experience.ResultsThe main problem experienced by lower-care residents was living alone in the community. Residents and family members used many strategies to avoid safety crises in the community but experienced multiple care breakdowns in both community and health care settings. Nursing home admission was a strategy used to avoid a crisis when residents did not receive the needed support to remain in the community.Discussion and ImplicationsTo successfully remain in the community, older adults require specialized supports targeting mental health and substance use needs, as well as enhanced hospital discharge plans and improved information about community-based care options. Implications involve reforming policies and practices in both hospital and community-based care settings.

Field emission microscopy of carbon nanotube fibers: Evaluating and interpreting spatial emission

In this work, the authors quantify field emission properties of cathodes made from carbon nanotube (CNT) fibers. The cathodes were arranged in different configurations to determine the effect of cathode geometry on the emission properties. Various geometries were investigated including (1) flat cut fiber tip, (2) folded fiber, (3) looped fiber, and (4) fibers wound around a cylinder. The authors employ a custom field emission microscope to quantify I-V characteristics in combination with laterally resolved field-dependent electron emission area. Additionally, they look at the very early emission stages, first when a CNT fiber is turned on for the first time, which is then followed by multiple ramp-up/down runs. Upon the first turn on, all fibers demonstrated limited and discrete emission area. During ramping runs, all CNT fibers underwent multiple (minor and/or major) breakdowns, which improved emission properties in that turn-on field decreased and field enhancement factor and emission area both increased. It is proposed that breakdowns are responsible for removing initially undesirable emission sites caused by stray fibers higher than average. This initial breakdown process gives way to a larger emission area that is created when the CNT fiber subcomponents unfold and align with the electric field. The authors' results form the basis for careful evaluation of CNT fiber cathodes for dc or low frequency pulsed power systems in which large uniform area emission is required or for narrow beam high frequency applications in which high brightness is a must.

Optimum Volume of Freeway Corridors

Conventional methods to assess the quality of service on freeways are based on the comparison of a specific peak hour traffic demand to the capacity of the facility, which is usually measured at a single uniform bottleneck section. However, estimating the quality of service of one bottleneck section may not be sufficient to assess the performance of an entire freeway facility. A driver traveling along a freeway corridor may actually encounter multiple flow breakdowns at independent bottleneck sections, which affect the overall quality of service. This paper introduces a comprehensive approach that considers an entire freeway corridor as a system consisting of successive independent bottlenecks with different characteristics, and can be used to estimate the optimum sustainable volume. The methodology is based on the sustained flow index, which is defined as the product of traffic volume and the probability of survival at this volume. Optimum volumes of two real-world corridors are estimated based on the new derivations. The empirical results reveal that the optimum volume and the capacity of an entire corridor is less than those of its most restrictive bottleneck.

A Technique for Fast Reroute on Data Transmission with Data Protection

It is always viewed that data transmission get break down which is unique in all the IP sector in networks thus there many ideas which are given for fast rerouting in local areas by giving a high range of speed in data transferring insipte of the break downs. The overall ideas are only used for managing and preventing the single break downs only these ideas can only be used for single where as in multiple break downs they reflect as loops and even drop the data because of multiple non-partisan break downs are not handled by using such idea’s. To safeguard the flow of data even in multiple breaks down we scheme LOLS (Localized On-demand Link State). In LOLS the block list are converted into packets where sets are small in number in which links are failed and come across its path and next node is determined by omitting the block list. A ascendable LOLS is used for protecting and routing the data transmission in multiple break downs. Degrade is used to determine the links in LOLS. In this the world widely used and famous state greater than the current state. In LOLS block lists are in packets and next node is mentioned by running the block list links. This research gives a solution for the path break down occurring in data transmission and also gives protection to the data while they are transferred. Grade diffusion and direct diffusion are the two algorithms which are used in this paper

Decomposition characteristics of C4F7N/CO2 mixture under AC discharge breakdown

Recently, the C4F7N/CO2 mixture has been highly considered as a promising SF6 alternative due to its low greenhouse effect and excellent electrical performance. Apart from its dielectric strength and arc-quenching capability, the decomposition characteristics of C4F7N/CO2 also play an important role in its future applications in gas-insulated electrical equipment. Therefore, decomposition experiments of the C4F7N/CO2 mixture were carried out under multiple AC discharge breakdowns by using a needle-to-plate electrode configuration. The compositions of the gas mixture before and after breakdowns were detected by using a gas chromatography-mass spectrometer. The results show that a trace amount of C3HF7 exists in the C4F7N product; the decomposition of the C4F7N/CO2 mixture mainly produces CO, CF4, CO2, C2F4, C2F6, C3F8, CF3CN, C3F6, C4F6, C4F10, C2F5CN, C2N2, HCN, C2F3CN, and HF. As the number of breakdowns increases, the content of most decomposition products increases significantly, while the content of C3HF7 decreases. The possible formation pathways of the decomposition products were determined, and the corresponding reaction enthalpies were calculated by quantum chemistry calculation. Relevant results not only reveal the decomposition characteristics of C4F7N/CO2 under AC breakdowns but also help us to better understand the corresponding physicochemical mechanisms, which will provide a good reference for stable operation and safe maintenance in applications.

Association of a Lean Surgical Plan of the Day With Reduced Operating Room Time for Head and Neck Free Flap Reconstruction

Inefficiency in the operating room (OR) is detrimental to the patient, the hospital, and the surgeon. Head and neck procedures requiring microvascular reconstruction are complex, lengthy operations in which prolonged operative time is associated with higher complication rates and increased costs. To use Lean methodology to identify potential OR efficiency improvement opportunities for head and neck surgical cases involving free tissue transfer, to implement an intervention, the free flap plan of the day, and to evaluate OR times after implementation. Phase 1: In 2015, with the assistance of the Lean Promotion Office at our institution, a tertiary academic medical center, we identified efficiency-improvement opportunities for 10 patients undergoing free flap reconstruction. Phase 2: A single intervention, the free flap plan of the day, was implemented on February 1, 2016. A retrospective medical record review of head and neck free flap reconstructions beginning 2 years before the implementation of the intervention and ending 2 years after the intervention was performed from February 1, 2014 until February 1, 2018 to analyze OR times, cost, and complications. Mean OR times were compared using the t test. In-room-to-incision time and total OR time. Phase 1: The surgical procedures of 10 patients undergoing free flap reconstruction were observed by Lean specialists, and a time study with a process map was completed. Using this framework, major opportunities for decreasing intraoperative time waste were identified. Multiple communication breakdowns were seen to drive intraoperative time waste; therefore, a free flap plan of the day was created to improve communication between team members. Phase 2: 200 patients were included in the study and were categorized into 2 groups, no plan group (n = 104) and plan group (n = 96), based on whether the plan of the day was used or not. The age and sex distributions of the study participants were not collected. Mean in-room-to-incision time was 54.3 minutes for the no plan group and 47.2 minutes for the plan group (difference, 7.1 minutes; 95% CI, 3.8-10.4 minutes). Mean total OR time was 524.1 minutes for the no plan group and 467.4 minutes for the plan group (difference, 56.7 minutes; 95% CI, 23.6-89.6 minutes). Lean methodology was used to identify efficiency-improvement opportunities for head and neck free flap reconstruction procedures and to design a focused intervention. A free flap plan of the day was used in this study to improve communication between the OR team and was found to improve efficiency and be associated with reduced OR times.

No-Load Dielectric Recovery of the Ultra-Fast Vacuum Switch in Hybrid DC Circuit Breaker

The no-load curve of the dielectric recovery strength of the ultra-fast mechanical vacuum switch (MVS) changing with time is the theoretical foundation to optimize the turn-off strategy of the hybrid direct current circuit breaker with load commutation switch. To avoid the shortcomings of the classic synthetic circuit, a novel test circuit is proposed to measure the no-load dielectric recovery curve of the MVS in this paper. In the test circuit, a succession of pulse voltages is automatically applied on the MVS, and multiple breakdowns of the MVS occur in one test. Therefore, the dielectric strength of the MVS at multiple time points is obtained, and the envelope of the applied voltage on the MVS during one test can describe the dielectric recovery curve of the MVS; as a result, the test workload could be reduced dramatically and the measurement is more authentic. By changing test conditions, including the rate of rise of the test voltage and the operating speed of the MVS, no-load dielectric recovery characteristics are studied. The research has shown that the dielectric recovery speed of the MVS is irrelative with the rate of rise of the test voltage and it is directly proportional to the opening speed of the MVS.

Destructive mechanisms in laser induced forward transfer

Laser Induced Forward Transfer (LIFT) is an additive direct-writing technique, in which a piece of material (ink) is transferred from a donor to a receiver surface, utilizing a laser impulse. In practice, the process of jet formation can suffer from irreproducibility. We identify two possible destructive mechanisms due to multiple optical breakdowns (originating from imperfections of the optical system) and rarefaction waves (originating from impurities), both with harmful consequences caused by cavitation. Based on experiments in a model system that allows for visualization and numerical simulations employing the boundary integral method, we reveal the underlying fluid dynamics of both mechanisms. Finally, to overcome the irreproducibility, we provide recommendations for the industrial use of LIFT.

Experimental investigation on multiple breakdown in water induced by focused nanosecond laser.

Multiple breakdowns in liquids still remains obscure for its complex, non-equilibrium and transient dynamic process. We introduced three methods, namely, plasma imaging, light-scattering technique, and acoustic detection, to measure the multiple breakdown in water induced by focused nanosecond laser pulses simultaneously. Our results showed that linear dependence existed among the cavitation-bubble lifetime, the far-field peak pressure of the initial shock wave, and the corresponding plasma volume. Such a relationship can be used to evaluate the ideal size and energy of each bubble during multiple breakdown. The major bubble lifetime was hardly affected by the inevitable coalescence of cavitation bubbles, thereby confirming the availability of light-scattering technique on the estimation of bubble size during multiple breakdown. Whereas, the strength of collapse-shock-wave and the subsequent rebound of bubbles was strongly influenced, i.e., the occurrence of multiple breakdown suppressed the cavitation-bubble energy being converted into collapse-shock-wave energy but enhanced conversion into rebound-bubble energy. This study is a valuable contribution to research on the rapid mixing of microfluidics, damage control of microsurgery, and photoacoustic applications.

Effect of Film Thickness and Electrode Area on the Dielectric Breakdown Characteristics of Metallized Capacitor Films

An alternative approach for measuring breakdown characteristics of metallized and non-metallized polymer films has been previously developed at TUT. The method enables measurement of multiple breakdowns beyond the weakest point of each sample film by utilizing low-energy self-healing breakdown of metallized film. The method yields a large amount of breakdown data even from a relatively small sample area which enables the formation of detailed material-specific breakdown fingerprints. In this paper, some preliminary results of an ongoing further research on the area and thickness dependence of the breakdown characteristics of various polymer films are presented.

Suspended liquid particle disturbance on laser-induced blast wave and low density distribution

The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in all cases. The shock wave front that propagates toward the opposite laser focal spot impinges on one another, and thereafter a transmitted shock wave (TSW) appears. The TSW interacts with the low density core called a kernel; the kernel then longitudinally expands quickly due to a Richtmyer-Meshkov-like instability. The laser-particle interaction causes an increase in the kernel volume which is approximately five times as large as that in the gas breakdown without particles. In addition, the laser-particle interaction can improve the laser energy efficiency.

Leadership: Convergence and Divergence in Leadership Relations

The article argues for theorizing and studying the significance of how so-called leaders and followers converge or diverge in their views and understandings of the leadership/followership relations they may be part of. Divergence or misfits may be common yet missed by the researcher who takes only one party’s view of leadership into account and/or assumes that people involved define the relationship in a similar way. The article identifies and illustrates four typical forms of shared/diverse meanings regarding leadership: high-alignment leadership (shared meanings), value misfit (diverse assessment), construction misfit (different views of what goes on), and multiple breakdowns (high level of confusion of what goes on and how to assess it). Given variations in views of leadership, this article makes a case for considering “divergent relationalities”—in some opposition to common ideas about “smooth” leadership/followership relations based on convergent meanings.

Implications of heavy neutralino dark matter: The underlying structure in the hidden sector

The possibility of heavy neutralino dark matter (DM) in the gravity-mediation mechanism is explored. The appearance of the heavy lightest supersymmetric particle is seemingly suggested by Large Hadron Collider runs, which have not provided evidence of superparticles around the TeV region. On the basis of the so-called WIMPZILLA scenario, it is understood that the nonthermally produced DM has the larger mass than the reheating temperature. Hence, the expected DM mass should be more than 109 GeV so that thermal leptogenesis successfully occurs. In this paper, we first examine the generation of the Higgsino mass parameter [Formula: see text] in the context of gravity mediation, postulating that the resolution of the strong CP problem should be the criterion for arriving at a valid hypothesis for heavy neutralino DM. Accordingly, we address how the Peccei–Quinn (PQ) symmetry could influence dynamical supersymmetry breaking (DSB) models. It is found that as long as [Formula: see text] (the SUSY-breaking scale) approximately coincides with [Formula: see text] (the PQ-breaking scale), no DSB models can naturally account for the existence of the heavy neutralino DM, based upon the supersymmetric Dine–Fischler–Srednicki–Zhitinitski (DFSZ)-like mechanism. Thus, we attempt to construct a new model wherein hierarchical SUSY breakings occur. For this purpose, we propose gauge coupling unification in the hidden-sector dynamics at some high-energy scale, and we show that such a class of models can achieve [Formula: see text] through renormalization flow. As a consequence, the nonthermal neutralino, practically the wino-like one in our model, is shown to be a rather natural and viable DM candidate. Moreover, we argue that on the basis of Kac–Moody algebra, multiple breakdowns of supersymmetry may entail unified gauge dynamics. We also present a possible unified model. Finally, the heavy wino-like neutralino may be a DM candidate that will favor future direct DM detection experiments, mainly because its scattering on nuclei well conserves isospin symmetry.

Multiple Rock Breakdown in Electrodischarge Technology

The article covers the research of the electric strength and fracture of rocks that are undergone multiple breakdowns generated by electric discharge rock fracture and drilling technologies. The research outcomes allow proposing an experimental technology able to determine operating high voltage pulse values in the electric discharge drilling process where one should take into account such factors as the rock re-crushing and the drill bit shift cyclicity.

Multiple electrical breakdowns and electrical annealing using high current approximating breakdown current of silver nanowire network

The failure of a silver nanowire (AgNW) random network due to high electric current density is described. The AgNW network breaks down as result of electromigration and Joule heating at junctions, which leads to destroyed interconnections between AgNWs. The AgNW network is not completely destroyed after breakdown, but instead is able to undergo multiple breakdowns after being cooled down, with increased resistance and reduced breakdown current density. The breakdown current density of AgNW network is for a network with outperforming a CuNW network. An effective electrical annealing method is demonstrated to decrease network resistance by 18% by periodically applying high current that is slightly lower than breakdown current with a period of 1 min for a few cycles.

Farmers' beliefs about bovine tuberculosis control in Northern Ireland

Beliefs can play an important role in farmer behaviour and willingness to adopt new policies. In Northern Ireland, bovine tuberculosis (bTB) is one of the most important endemic diseases facing the cattle industry. An observational study was conducted on 192 farms in a high bTB incidence area during 2010–2011 in order to obtain a better understanding of farmers' beliefs in relation to bTB control. The views of farmers who had experienced a recent confirmed or multiple reactor bTB breakdowns (cases) were compared to those of farmers who had no recent reactors or restricted herd tests (controls). Data were obtained from a face-to-face questionnaire assessing farmers' agreement to 22 statements.All participating farmers found bTB control important and most were keen to learn more about bTB biosecurity measures and were in favour of the cattle-related bTB control measures as presented in the questionnaire (isolation of skin test inconclusive animals, use of the gamma-interferon test and pre-movement testing). The majority of farmers would allow badger vaccination and culling on their own land with an overall preference for vaccination. Highest disagreement was shown for the statements querying a willingness to pay for bTB control measures. There was agreement on most issues between case and control farmers and between different age groups of farmers although case farmers showed more support for additional advice on bTB biosecurity measures (P = 0.042). Case farmers were also more in favour of allowing badger vaccination (P = 0.008) and culling (P = 0.043) on their land and showed less concern for public opposition (P = 0.048).

Observation of temporal evolution following laser triggered rf breakdown in vacuum

Radio frequency breakdown is one of the fundamental phenomena that limits the operational performance of most of high power and high gradient vacuum rf devices. We report on experimental results of rf breakdown in an $S$-band photocathode gun triggered by an intensity controlled laser. Through measurement and analysis of the time dependence of the collected current at the gun exit and the stored rf energy in the cavity, one can gain insight into the time evolution of the rf breakdown process. Multiple breakdowns were observed within one rf pulse due to power flow between cells after the initial emission. Similarities of the laser-triggered breakdowns to those occurring in the course of cavity conditioning and normal operation are found by comparing the postbreakdown signals in both cases. It is shown that an intense laser can offer a more controllable and flexible method for rf breakdown studies.

Why are there cattle in the conservation area? Social barriers to biofuel governance in Brazil

Amid a rapid expansion of global investments in biofuels there has been an equally rapid proliferation of concerns about the inadequacies of current governance schemes to mitigate the environmental impacts of growing agroenergy production. Managing the land use practices of small producers in a way that ensures their activities are financially and environmentally sustainable is a particularly pressing issue that has been overlooked in research on biofuel governance. I illuminate these challenges through an ethnographic study on the multiple breakdowns of environmental governance in the Southern Goiás region of Brazil, a major expansion region for sugarcane ethanol production. I focus on one of the most pressing compliance issues among small and medium size sugarcane farmers; their persistent use of federally mandated conservation areas for cattle production. I find that while these transgressions are often perceived by administrators and officials as being the result of a lack of “environmental awareness” among rural farmers, they are better understood as a safety net to protect landowners against perceived risks of sugarcane production. These violations are further enabled by continuing ambiguity in the enforcement structure for conservation legislation in the region. Recalibrating regulatory systems to better address these issues of accountability and risk is a critical step toward improving environmental governance of global biofuel commodity chains.