Sample records for breakdown

  1. Impulse breakdown of liquids

    CERN Document Server

    Ushakov, Vasily Y


    The book describes the main physical processes and phenomena in pulsed electric breakdown. The knowledge and the control of the electric breakdown of liquids is important not only for the insulation inside power systems but it is also used for the creation and information of high voltage and high current pulses. Such high-voltage micro- and nanosecond pulses find wide application in experimental physics, electro discharge technology, physics of dielectrics, radar detection and ranging, high-speed photography. The nature of charge carriers, mechanism of formation and evolution of the gas phase,

  2. Analysis of Laser Breakdown Data (United States)

    Becker, Roger


    Experiments on laser breakdown for ns pulses of 532 nm or 1064 nm light in water and dozens of simple hydrocarbon liquids are analyzed and compared to widely-used models and other laser breakdown experiments reported in the literature. Particular attention is given to the curve for the probability of breakdown as a function of the laser fluence at the beam focus. Criticism is made of the na"ive forms of both ``avalanche'' breakdown and multi-photon breakdown. It appears that the process is complex and is intimately tied to the chemical group of the material. Difficulties with developing an accurate model of laser breakdown in liquids are outlined.

  3. Beauty in the Breakdown (United States)

    Brisco, Nicole


    Most human beings look at erosion as the destruction of a surface, but artists can see that erosion often creates indefinable beauty. Where do you see beauty in the breakdown? In this article, the author presents an innovative lesson that would allow students to observe both human and physical nature. In this activity students will create a work…

  4. Modeling rf breakdown arcs

    CERN Document Server

    Insepov, Zeke; Huang, Dazhang; Mahalingam, Sudhakar; Veitzer, Seth


    We describe breakdown in 805 MHz rf accelerator cavities in terms of a number of mechanisms. We devide the breakdown process into three stages: (1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, (2) we model the ionization of neutrals responsible for plasma initiation and plasma growth using a particle in cell code, and (3) we model surface damage by assuming a process similar to unipolar arcing. Although unipolar arcs are strictly defined with equipotential boundaries, we find that the cold, dense plasma in contact with the surface produces very small Debye lengths and very high electric fields over a large area. These high fields produce strong erosion mechanisms, primarily self sputtering, compatible with the crater formation that we see. Results from the plasma simulation are included as a guide to experimental verification of this model.

  5. Space Charge Modulated Electrical Breakdown (United States)

    Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George


    Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20th century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes.

  6. VUV Radiation and Breakdown (United States)


    below about 130 nm.   This  leads to  chromatic   aberration  and smaller signal amplitude at short wavelengths as can be seen  in Figure 7.   The  second...the mirrors. It is possible to image the breakdown streamers using the VUV light since there is no chromatic aberration . Such images are shown in

  7. Breakdowns in collaborative information seeking

    DEFF Research Database (Denmark)

    Hertzum, Morten


    of the use of the electronic medication record adopted in a Danish healthcare region and of the reports of five years of medication incidents at Danish hospitals. The results show that breakdowns in collaborative information seeking is a major source of medication incidents, that most of these breakdowns......Collaborative information seeking is integral to many professional activities. In hospital work, the medication process encompasses continual seeking for information and collaborative grounding of information. This study investigates breakdowns in collaborative information seeking through analyses...... are breakdowns in collaborative grounding rather than information seeking, that the medication incidents mainly concern breakdowns in the use of records as opposed to oral communication, that the breakdowns span multiple degrees of separation between clinicians, and that the electronic medication record has...

  8. On Preliminary Breakdown (United States)

    Beasley, W. H.; Petersen, D.


    The preliminary breakdown phase of a negative cloud-to-ground lightning flash was observed in detail. Observations were made with a Photron SA1.1 high-speed video camera operating at 9,000 frames per second, fast optical sensors, a flat-plate electric field antenna covering the SLF to MF band, and VHF and UHF radio receivers with bandwidths of 20 MHz. Bright stepwise extensions of a negative leader were observed at an altitude of 8 km during the first few milliseconds of the flash, and were coincident with bipolar electric field pulses called 'characteristic pulses'. The 2-D step lengths of the preliminary processes were in excess of 100 meters, with some 2-D step lengths in excess of 200 meters. Smaller and shorter unipolar electric field pulses were superposed onto the bipolar electric field pulses, and were coincident with VHF and UHF radio pulses. After a few milliseconds, the emerging negative stepped leader system showed a marked decrease in luminosity, step length, and propagation velocity. Details of these events will be discussed, including the possibility that the preliminary breakdown phase consists not of a single developing lightning leader system, but of multiple smaller lightning leader systems that eventually join together into a single system.

  9. Delaying vortex breakdown by waves (United States)

    Yao, M. F.; Jiang, L. B.; Wu, J. Z.; Ma, H. Y.; Pan, J. Y.


    The effect of spiral waves on delaying vortex breakdown in a tube is studied experimentally and theoretically. When a harmonic oscillation was imposed on one of guiding vanes in the tube, the breakdown was observed to be postponed appreciately. According to the generalized Lagrangian mean theory, proper forcing spiral waves may produce an additional streaming momentum, of which the effect is favorable and similar to an axial suction at downstream end. The delayed breakdown position is further predicted by using nonlinear wave theory. Qualitative agreement between theory and experiment is obtained, and experimental comparison of the effects due to forcing spiral wave and axial suction is made.

  10. RF breakdown by toroidal helicons

    Indian Academy of Sciences (India)

    S K P Tripathi; D Bora; M Mishra


    Bounded whistlers are well-known for their efficient plasma production capabilities in thin cylindrical tubes. In this paper we shall present their radio frequency (RF) breakdown and discharge sustaining capabilities in toroidal systems. Pulsed RF power in the electronmagnetohydrodynamic (EMHD) frequency regime is fed to the neutral background medium. After the breakdown stage, discharge is sustained by toroidal bounded whistlers. In these pulsed experiments the behaviour of the time evolution of the discharge could be studied in four distinct phases of RF breakdown, steady state attainment, decay and afterglow. In the steady state average electron density of ≈ 1012 per cc and average electron temperature of ≈ 20 eV are obtained at 10-3 mbar of argon filling pressure. Experimental results on toroidal mode structure, background effects and time evolution of the electron distribution function will be presented and their implications in understanding the breakdown mechanism are discussed.

  11. Dielectric breakdown of cell membranes. (United States)

    Zimmermann, U; Pilwat, G; Riemann, F


    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector

  12. Probabilistic description of traffic breakdowns. (United States)

    Kühne, Reinhart; Mahnke, Reinhard; Lubashevsky, Ihor; Kaupuzs, Jevgenijs


    We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply the probabilistic model regarding the jam emergence as the formation of a large car cluster on a highway. In these terms, the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster model. We assume that, first, the growth of the car cluster is governed by attachment of cars to the cluster whose rate is mainly determined by the mean headway distance between the car in the vehicle flow and, maybe, also by the headway distance in the cluster. Second, the cluster dissolution is determined by the car escape from the cluster whose rate depends on the cluster size directly. The latter is justified using the available experimental data for the correlation properties of the synchronized mode. We write the appropriate master equation converted then into the Fokker-Planck equation for the cluster distribution function and analyze the formation of the critical car cluster due to the climb over a certain potential barrier. The further cluster growth irreversibly causes jam formation. Numerical estimates of the obtained characteristics and the experimental data of the traffic breakdown are compared. In particular, we draw a conclusion that the characteristic intrinsic time scale of the breakdown phenomenon should be about 1 min and explain the case why the traffic volume interval inside which traffic breakdown is observed is sufficiently wide.

  13. Electrical breakdown in tissue electroporation. (United States)

    Guenther, Enric; Klein, Nina; Mikus, Paul; Stehling, Michael K; Rubinsky, Boris


    Electroporation, the permeabilization of the cell membrane by brief, high electric fields, has become an important technology in medicine for diverse application ranging from gene transfection to tissue ablation. There is ample anecdotal evidence that the clinical application of electroporation is often associated with loud sounds and extremely high currents that exceed the devices design limit after which the devices cease to function. The goal of this paper is to elucidate and quantify the biophysical and biochemical basis for this phenomenon. Using an experimental design that includes clinical data, a tissue phantom, sound, optical, ultrasound and MRI measurements, we show that the phenomenon is caused by electrical breakdown across ionized electrolysis produced gases near the electrodes. The breakdown occurs primarily near the cathode. Electrical breakdown during electroporation is a biophysical phenomenon of substantial importance to the outcome of clinical applications. It was ignored, until now.

  14. Threshold criteria for undervoltage breakdown (United States)

    Cooley, James E.; Choueiri, Edgar Y.


    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap are experimentally and theoretically explored. The minimum number of injected electrons required to achieve breakdown in a parallel-plate gap is measured in argon at pd values of 3-10 Torr m using ultraviolet laser pulses to photoelectrically release electrons from the cathode. This value was found to scale inversely with voltage at constant pd and with pressure within the parameter range explored. A dimensionless theoretical description of the phenomenon is formulated and numerically solved. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low gain. It is also found that fewer electrons are required as the gain due to electron-impact ionization (α process) is increased, or as the sensitivity of the α process to electric field is enhanced by increasing the gas pressure. A predicted insensitivity to ion mobility implies that the breakdown is determined during the first electron avalanche when space-charge distortion is greatest.

  15. DC Breakdown Experiments with Iridium Cathode

    CERN Document Server

    Profatilova, Iaroslava; Korsback, Anders; Muranaka, Tomoko; Wuensch, Walter


    Electrical breakdown occurring in rf accelerating structures is one of the major disruptions of the accelerated beam in CLIC. At CERN, as complements to rf facilities, DC-spark systems have been used to study breakdown properties of many candidate materials for making rf components. In this note, measurements of conditioning speed, breakdown field and field enhancement factor of iridium are presented comparing with previously tested materials. The average breakdown field after conditioning reached 238 MV/m, which places iridium next to copper. By comparison with results and properties of other metals, the low breakdown field of iridium could be explained by its face-centred-cubic crystal structure.

  16. High Voltage Water Breakdown Studies (United States)


    E. Zein Eldine, and R. Hawley, "Influence of electrode coatings on the breakdown strength of transformer oil ," Nature, Vol. 202, pp. 687-688, 1964...longer needed . Do not return to sender. PLEASE NOTIFY THE DEFENSE SPECIAL WEAPONS AGENCY, ATTN: CSTI, 6801TELEGRAPH ROAD, ALEXANDRIA, VA 22310-3398, IF...reviewing instructions, searching existing data sources, gathering and maintaining the data needed , and completing and reviewing the collection of

  17. Individual breakdown of pension rights

    CERN Multimedia


    You should have recently received, via email, your “Individual breakdown of pension rights”.   Please note that: the calculation was based on data as at 1st July 2016, as at 1st September 2016, CERN will introduce a new career structure; the salary position will now be expressed as a percentage of a midpoint of a grade.   We would like to draw your attention to the fact that your pension rights will remain unchanged. Benefits Service CERN Pension Fund

  18. Tune in, breakdown, and reboot


    Pedersen, Michael


    Routine work‐process, lack of self‐management, and long work‐hours have traditionally been the main topics of discussion within the occupational stress literature, constituting the primary factors that make people breakdown and burn out. But within the last couple of years, this discussion has expanded its focus from issues concerning the disciplinary work‐space. Increasing attention is now being placed on the problems related to the burgeoning interest in employee empowerme...

  19. The Development of Breakdown in Transformer Oil

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik


    Full Text Available The conditions under which breakdown of composite liquid - solid insulation can be occurred, e.g. in transformer, play an important role in designing of such insulation. The initial state of breakdown development is explained based on development of streamers in cavitations. The whole breakdown development in transformer oil is represented by RLC circuit and it depends on the parameters of outer circuit.

  20. Investigation of the DC vacuum breakdown mechanism

    CERN Document Server

    Descoeudres, A; Calatroni, S; Taborelli, M; Wuensch, W


    Breakdowns occurring in rf accelerating structures will limit the ultimate performance of future linear colliders such as the Compact Linear Collider (CLIC). Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN to better understand the vacuum breakdown mechanism in a simple setup. Measurements of the field enhancement factor β show that the local breakdown field is constant and depends only on the electrode material. With copper electrodes, the local breakdown field is around 10:8 GV/m, independent of the gap distance. The β value characterizes the electrode surface state, and the next macroscopic breakdown field can be well predicted. In breakdown rate experiments, where a constant field is applied to the electrodes, clusters of consecutive breakdowns alternate with quiet periods. The occurrence and lengths of these clusters and quiet periods depend on the evolution of β. The application of a high field can even modify the electrode surface in the abse...

  1. On exponential growth [of gas breakdown

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson


    The agreement obtained between measured breakdown voltages and predicted breakdown values is frequently used as a means of assessing the validity of the theory/model in question. However, owing to the mathematical nature of exponential growth, it is easy to formulate a criterion that provides acc...... acceptable breakdown values, although the criterion may contain totally unrealistic features. An example from the work of A. Pedersen (1989) showing unrestricted exponential growth in SF 6 is used to highlight the insensitivity of breakdown voltages with respect to modeling...

  2. Work Breakdown Structure (WBS) Handbook (United States)


    The purpose of this document is to provide program/project teams necessary instruction and guidance in the best practices for Work Breakdown Structure (WBS) and WBS dictionary development and use for project implementation and management control. This handbook can be used for all types of NASA projects and work activities including research, development, construction, test and evaluation, and operations. The products of these work efforts may be hardware, software, data, or service elements (alone or in combination). The aim of this document is to assist project teams in the development of effective work breakdown structures that provide a framework of common reference for all project elements. The WBS and WBS dictionary are effective management processes for planning, organizing, and administering NASA programs and projects. The guidance contained in this document is applicable to both in-house, NASA-led effort and contracted effort. It assists management teams from both entities in fulfilling necessary responsibilities for successful accomplishment of project cost, schedule, and technical goals. Benefits resulting from the use of an effective WBS include, but are not limited to: providing a basis for assigned project responsibilities, providing a basis for project schedule development, simplifying a project by dividing the total work scope into manageable units, and providing a common reference for all project communication.

  3. Breakdown of interdependent directed networks. (United States)

    Liu, Xueming; Stanley, H Eugene; Gao, Jianxi


    Increasing evidence shows that real-world systems interact with one another via dependency connectivities. Failing connectivities are the mechanism behind the breakdown of interacting complex systems, e.g., blackouts caused by the interdependence of power grids and communication networks. Previous research analyzing the robustness of interdependent networks has been limited to undirected networks. However, most real-world networks are directed, their in-degrees and out-degrees may be correlated, and they are often coupled to one another as interdependent directed networks. To understand the breakdown and robustness of interdependent directed networks, we develop a theoretical framework based on generating functions and percolation theory. We find that for interdependent Erdős-Rényi networks the directionality within each network increases their vulnerability and exhibits hybrid phase transitions. We also find that the percolation behavior of interdependent directed scale-free networks with and without degree correlations is so complex that two criteria are needed to quantify and compare their robustness: the percolation threshold and the integrated size of the giant component during an entire attack process. Interestingly, we find that the in-degree and out-degree correlations in each network layer increase the robustness of interdependent degree heterogeneous networks that most real networks are, but decrease the robustness of interdependent networks with homogeneous degree distribution and with strong coupling strengths. Moreover, by applying our theoretical analysis to real interdependent international trade networks, we find that the robustness of these real-world systems increases with the in-degree and out-degree correlations, confirming our theoretical analysis.

  4. Breakdown characteristics of xenon HID Lamps (United States)

    Babaeva, Natalia; Sato, Ayumu; Brates, Nanu; Noro, Koji; Kushner, Mark


    The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity.

  5. Electrodynamic thermal breakdown of a capacitor insulator (United States)

    Emel'Yanov, O. A.


    A mechanism of the electrical breakdown is proposed for modern metal-field capacitors with the well-known property of self-healing of the breakdown strength. Upon an increase in the working voltage, the self-healing time increases to tens of microseconds, and the heating of adjacent insulator layers becomes significant. The propagating thermally activated conduction wave facilitates the enhancement of the electric field up to breakdown values. Analysis of the dynamics of electric field increase is carried out for capacitors based on polyethylene terephthalate (PET) dielectric.

  6. Humidity effects on wire insulation breakdown strength.

    Energy Technology Data Exchange (ETDEWEB)

    Appelhans, Leah


    Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

  7. A computational study of the topology of vortex breakdown (United States)

    Spall, Robert E.; Gatski, Thomas B.


    A fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations has been performed. Solutions to four distinct types of breakdown are identified and compared with experimental results. The computed solutions include weak helical, double helix, spiral, and bubble-type breakdowns. The topological structure of the various breakdowns as well as their interrelationship are studied. The data reveal that the asymmetric modes of breakdown may be subject to additional breakdowns as the vortex core evolves in the streamwise direction. The solutions also show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown.

  8. dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum

    CERN Document Server

    Descoeudres, A; Calatroni, S; Taborelli, M; Wuensch, W


    RF accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of DC and RF breakdown, a DC breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultra-high vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from 100 MV/m for Al to 850 MV/m for stainless steel, and is around 170 MV/m for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at t...

  9. Fractal properties of LED avalanche breakdown

    Directory of Open Access Journals (Sweden)

    Antonina S. Shashkina


    Full Text Available The conventional model of the processes occurring in the course of a p–n-junction's partial avalanche breakdown has been analyzed in this paper. Microplasma noise spectra of industrially produced LEDs were compared with those predicted by the model. It was established that the data obtained experimentally on reverse-biased LEDs could not be described in terms of this model. The degree to which the fractal properties were pronounced was shown to be variable by changing the reverse voltage. The discovered fractal properties of microplasma noise can serve as the basis for further studies which are bound to explain the breakdown characteristics of real LEDs and to correct the conventional model of p–n-junction's avalanche breakdown.

  10. Impact of Machine Breakdowns on Productivity

    Directory of Open Access Journals (Sweden)

    Anwaruddin Tanwari


    Full Text Available This paper reports the machine breakdowns and their impact on the total productivity for the FMCGs (Fast Moving Consumer Goods industry because higher productivity rate is important factor on which the customer services largely depend in this competitive business world. This paper also suggests that the machine breakdowns and other related problems within the plant are due to improper care, keeping the plant operative for twenty four hours a day, seven days a week without any break and lack of management\\'s concentration towards these issues. These break-downs results in un-timely closure of the plant and very poor production performance is achieved in the plant that affects the service level at great level. Realising the importance of maintenance in improving productivity and service, an attempt has been made in this paper to study the scope of maintenance with the help of a case study.

  11. The Electrical Breakdown of Thin Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed;


    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

  12. Spectrometers for RF breakdown studies for CLIC (United States)

    Jacewicz, M.; Ziemann, V.; Ekelöf, T.; Dubrovskiy, A.; Ruber, R.


    An e+e- collider of several TeV energy will be needed for the precision studies of any new physics discovered at the LHC collider at CERN. One promising candidate is CLIC, a linear collider which is based on a two-beam acceleration scheme that efficiently solves the problem of power distribution to the acceleration structures. The phenomenon that currently prevents achieving high accelerating gradients in high energy accelerators such as the CLIC is the electrical breakdown at very high electrical field. The ongoing experimental work within the CLIC collaboration is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. In order to validate the feasibility of accelerating structures and observe the characteristics of the vacuum discharges and their eroding effects on the structure two dedicated spectrometers are now commissioned at the high-power test-stands at CERN. First, the so called Flashbox has opened up a possibility for non-invasive studies of the emitted breakdown currents during two-beam acceleration experiments. It gives a unique possibility to measure the energy of electrons and ions in combination with the arrival time spectra and to put that in context with accelerated beam, which is not possible at any of the other existing test-stands. The second instrument, a spectrometer for detection of the dark and breakdown currents, is operated at one of the 12 GHz stand-alone test-stands at CERN. Built for high repetition rate operation it can measure the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. Two new analysis tools: discharge impedance tracking and tomographic image reconstruction, applied to the data from the spectrometer make possible for the first time to obtain the location of the breakdown inside the structure both in the transversal and longitudinal direction thus giving a more complete picture of the

  13. Project management strategies for prototyping breakdowns

    DEFF Research Database (Denmark)

    Granlien, Maren Sander; Pries-Heje, Jan; Baskerville, Richard


    of strategies for coping with escalation in troubled prototyping projects; the framework is based on project management triangle theory and is useful when considering how to manage prototype breakdown and escalation. All strategies were applied in the project case at different points in time. The strategies led......, managing the explorative and iterative aspects of prototyping projects is not a trivial task. We examine the managerial challenges in a small scale prototyping project in the Danish healthcare sector where a prototype breakdown and project escalation occurs. From this study we derive a framework...... to partial recovery of the project but not until several coping strategies had been tried....

  14. The Resistance of Breakdown in Transformer Oil

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik


    Full Text Available The conditions under which breakdown of composite liquid - solid insulation can be occurred, e.g., in transformer,play an important role in designing of such insulation. The initial state of breakdown development is explained on the basisof bubble theory and formation of a plasma channel between the electrodes. The electrical resistance of plasma channel iscalculated using several theories and its changes from a few ohms to a few hundred milliohms due to Joule heating caused byhigh arc current which flows through the plasma. The dynamics of the arc current depends on the parameters of outer circuitand is represented by RLC circuit.

  15. Numerical Borehole Breakdown Investigations using XFEM (United States)

    Beckhuis, Sven; Leonhart, Dirk; Meschke, Günther


    During pressurization of a wellbore a typical downhole pressure record shows the following regimes: first the applied wellbore pressure balances the reservoir pressure, then after the compressive circumferential hole stresses are overcome, tensile stresses are induced on the inside surface of the hole. When the magnitude of these stresses reach the tensile failure stress of the surrounding rock medium, a fracture is initiated and propagates into the reservoir. [1] In standard theories this pressure, the so called breakdown pressure, is the peak pressure in the down-hole pressure record. However experimental investigations [2] show that the breakdown did not occur even if a fracture was initiated at the borehole wall. Drilling muds had the tendency to seal and stabilize fractures and prevent fracture propagation. Also fracture mechanics analysis of breakdown process in mini-frac or leak off tests [3] show that the breakdown pressure could be either equal or larger than the fracture initiation pressure. In order to gain a deeper understanding of the breakdown process in reservoir rock, numerical investigations using the extended finite element method (XFEM) for hydraulic fracturing of porous materials [4] are discussed. The reservoir rock is assumed to be pre-fractured. During pressurization of the borehole, the injection pressure, the pressure distribution and the position of the highest flux along the fracture for different fracturing fluid viscosities are recorded and the influence of the aforementioned values on the stability of fracture propagation is discussed. [1] YEW, C. H. (1997), "Mechanics of Hydraulic Fracturing", Gulf Publishing Company [2] MORITA, N.; BLACK, A. D.; FUH, G.-F. (1996), "Borehole Breakdown Pressure with Drilling Fluids". International Journal of Rock Mechanics and Mining Sciences 33, pp. 39-51 [3] DETOURNAY, E.; CARBONELL, R. (1996), "Fracture Mechanics Analysis of the Breakdown Process in Minifrac or Leakoff Test", Society of Petroleum

  16. Electrical breakdown of carbon nanotube devices and the predictability of breakdown position

    Directory of Open Access Journals (Sweden)

    Gopal Krishna Goswami


    Full Text Available We have investigated electrical transport properties of long (>10 μm multiwalled carbon nanotubes (NTs by dividing individuals into several segments of identical length. Each segment has different resistance because of the random distribution of defect density in an NT and is corroborated by Raman studies. Higher is the resistance, lower is the current required to break the segments indicating that breakdown occurs at the highly resistive segment/site and not necessarily at the middle. This is consistent with the one-dimensional thermal transport model. We have demonstrated the healing of defects by annealing at moderate temperatures or by current annealing. To strengthen our mechanism, we have carried out electrical breakdown of nitrogen doped NTs (NNTs with diameter variation from one end to the other. It reveals that the electrical breakdown occurs selectively at the narrower diameter region. Overall, we believe that our results will help to predict the breakdown position of both semiconducting and metallic NTs.

  17. High-voltage breakdown studies on Si microstrip detectors

    CERN Document Server

    Albergo, S; Azzi, P; Babucci, E; Bacchetta, N; Bader, A J; Bagliesi, G; Basti, A; Biggeri, U; Bilei, G M; Bisello, D; Boemi, D; Bosi, F; Borrello, L; Bozzi, C; Braibant, S; Breuker, Horst; Bruzzi, Mara; Buffini, A; Busoni, S; Calefato, G; Candelori, A; Caner, A; Castaldi, R; Castro, A; Catacchini, E; Checcucci, B; Ciampolini, P; Civinini, C; Creanza, D; D'Alessandro, R; Da Rold, M; Demaria, N; De Palma, M; Dell'Orso, R; Marina, R D; Dutta, S; Eklund, C; Peisert, Anna; Feld, L; Fiore, L; Focardi, E; French, M; Freudenreich, Klaus; Fürtjes, A; Giassi, A; Giorgi, M A; Giraldo, A; Glessing, B; Gu, W H; Hall, G; Hammarström, R; Hebbeker, T; Hrubec, Josef; Muhtinen, M; Kaminski, A; Karimäki, V; Saint-Koenig, M; Krammer, Manfred; Lariccia, P; Lenzi, M; Loreti, M; Lübelsmeyer, K; Lustermann, W; Mättig, P; Maggi, G; Mannelli, M; Mantovani, G C; Marchioro, A; Mariotti, C; Martignon, G; McEvoy, B; Meschini, M; Messineo, A; My, S; Paccagnella, A; Palla, Fabrizio; Pandoulas, D; Papi, A; Parrini, G; Passeri, D; Pieri, M; Piperov, S; Potenza, R; Radicci, V; Raffaelli, F; Raymond, M; Santocchia, A; Schmitt, B; Selvaggi, G; Servoli, L; Sguazzoni, G; Siedling, R; Silvestris, L; Skog, K; Starodumov, Andrei; Stavitski, I; Stefanini, G; Tempesta, P; Tonelli, G; Tricomi, A; Tuuva, T; Vannini, C; Verdini, P G; Viertel, Gert M; Zie, Z; Li Ya Hong; Watts, S; Wittmer, B


    The breakdown performance of CMS barrel module prototype detectors and test devices with single and multi-guard structures were studied before and after neutron irradiation up to 2-10/sup 14/ 1 MeV equivalent neutrons. Before irradiation avalanche breakdown occurred at the guard ring implant edges. We measured 100-300 V higher breakdown voltage values for the devices with multi-guard than for devices with single-guard ring, After irradiation and type inversion the breakdown was smoother than before irradiation and the breakdown voltage value increased to 500-600 V for most of the devices. (9 refs).

  18. Laser induced breakdown spectroscopy on meteorites

    Energy Technology Data Exchange (ETDEWEB)

    De Giacomo, A. [Department of Chemistry, University of Bari (Italy); MIP-CNR sec Bari (Italy)], E-mail:; Dell' Aglio, M.; De Pascale, O. [MIP-CNR sec Bari (Italy); Longo, S.; Capitelli, M. [Department of Chemistry, University of Bari (Italy); MIP-CNR sec Bari (Italy)


    The classification of meteorites when geological analysis is unfeasible is generally made by the spectral line emission ratio of some characteristic elements. Indeed when a meteorite impacts Earth's atmosphere, hot plasma is generated, as a consequence of the braking effect of air, with the consequent ablation of the falling body. Usually, by the plasma emission spectrum, the meteorite composition is determined, assuming the Boltzmann equilibrium. The plasma generated during Laser Induced Breakdown Spectroscopy (LIBS) experiment shows similar characteristics and allows one to verify the mentioned method with higher accuracy. On the other hand the study of Laser Induced Breakdown Spectroscopy on meteorite can be useful for both improving meteorite classification methods and developing on-flight techniques for asteroid investigation. In this paper certified meteorites belonging to different typologies have been investigated by LIBS: Dofhar 461 (lunar meteorite), Chondrite L6 (stony meteorite), Dofhar 019 (Mars meteorite) and Sikhote Alin (irony meteorite)

  19. Breakdown and partial discharges in magnetic liquids (United States)

    Herchl, F.; Marton, K.; Tomčo, L.; Kopčanský, P.; Timko, M.; Koneracká, M.; Kolcunová, I.


    The dielectric properties (permittivity, loss factor, dielectric breakdown strength) of magnetic liquids were investigated. The magnetic liquids were composed of magnetite particles coated with oleic acid as surfactant and dispersed in transformer oil. To determine their dielectric properties they were subjected to a uniform magnetic field at high alternating electric fields up to 14 MV m-1. Nearly constant permittivity of magnetic liquid with particle volume concentration Φ = 0.0019 as a function of electric field was observed. Magnetic liquids with concentrations Φ = 0.019 and 0.032 showed significant changes of permittivity and loss factor dependent on electric and magnetic fields. The best concentration of magnetic fluid was found at which partial current impulse magnitudes were the lowest. The breakdown strength distribution of the magnetic liquid with Φ = 0.0025 was fitted with the Duxbury-Leath, Weibull and Gauss distribution functions.

  20. Initiation stage of nanosecond breakdown in liquid

    CERN Document Server

    Pekker, Mikhail; Shneider, Mikhail; Fridman, Alexander; Dobrynin, Danil


    In this paper, based on a theoretical model [1], it has been shown experimentally that the initial stage of development of a nanosecond breakdown in liquids is associated with the appearance of discontinuities in the liquid (cavitation) under the influence of electrostriction forces. Comparison of experimentally measured area dimensions and its temporal development were found to be in a good agreement with the theoretical calculations.

  1. Dielectric breakdown induced by picosecond laser pulses (United States)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.


    The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

  2. Kinetic Simulations of Dense Plasma Focus Breakdown (United States)

    Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.


    A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

  3. Runaway breakdown and electrical discharges in thunderstorms (United States)

    Milikh, Gennady; Roussel-Dupré, Robert


    This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.


    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland


    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  5. On streak breakdown in bypass transition (United States)

    Schlatter, Philipp; Brandt, Luca; de Lange, H. C.; Henningson, Dan S.


    Recent theoretical, numerical, and experimental investigations performed at the Department of Mechanics, KTH Stockholm, and the Department of Mechanical Engineering, Eindhoven University of Technology, are reviewed, and new material is presented to clarify the role of the boundary-layer streaks and their instability with respect to turbulent breakdown in bypass transition in a boundary layer subject to free-stream turbulence. The importance of the streak secondary-instability process for the generation of turbulent spots is clearly shown. The secondary instability manifests itself as a growing wave packet located on the low-speed streak, increasing in amplitude as it is dispersing in the streamwise direction. In particular, qualitative and quantitative data pertaining to temporal sinuous secondary instability of a steady streak, impulse responses both on a parallel and a spatially developing streak, a model problem of bypass transition, and full simulations and experiments of bypass transition itself are collected and compared. In all the flow cases considered, similar characteristics in terms of not only growth rates, group velocity, and wavelengths but also three-dimensional visualizations of the streak breakdown have been found. The wavelength of the instability is about an order of magnitude larger than the local boundary-layer displacement thickness δ∗, the group velocity about 0.8 of the free-stream velocity U∞, and the growth rate on the order of a few percent of U∞/δ∗. The characteristic structures at the breakdown are quasistreamwise vortices, located on the flanks of the low-speed region arranged in a staggered pattern.

  6. Nanolaminates: increasing dielectric breakdown strength of composites. (United States)

    Fillery, Scott P; Koerner, Hilmar; Drummy, Lawrence; Dunkerley, Erik; Durstock, Michael F; Schmidt, Daniel F; Vaia, Richard A


    Processable, low-cost, high-performance hybrid dielectrics are enablers for a vast array of green technologies, including high-temperature electrical insulation and pulsed power capacitors for all-electric transportation vehicles. Maximizing the dielectric breakdown field (E(BD)), in conjunction with minimization of leakage current, directly impacts system performance because of the field's quadratic relationship with electrostatic energy storage density. On the basis of the extreme internal interfacial area and ultrafine morphology, polymer-inorganic nanocomposites (PNCs) have demonstrated modest increases in E(BD) at very low inorganic loadings, but because of insufficient control of the hierarchal morphology of the blend, have yielded a precipitous decline in E(BD) at intermediate and high inorganic volume fractions. Here in, we demonstrate that E(BD) can be increased up to these intermediate inorganic volume fractions by creating uniform one-dimensional nanocomposites (nanolaminates) rather than blends of spherical inorganic nanoparticles and polymers. Free standing nanolaminates of highly aligned and dispersed montmorillonite in polyvinyl butyral exhibited enhancements in E(BD) up to 30 vol % inorganic (70 wt % organically modified montmorillonite). These relative enhancements extend up to five times the inorganic fraction observed for random nanoparticle dispersions, and are anywhere from two to four times greater than observed at comparable volume fraction of nanoparticles. The breakdown characteristics of this model system suggested a trade-off between increased path tortuosity and polymer-deficient structural defects. This implies that an idealized PNC morphology to retard the breakdown cascade perpendicular to the electrodes will occur at intermediate volume fractions and resemble a discotic nematic phase where highly aligned, high-aspect ratio nanometer thick plates are uniformly surrounded by nanoscopic regions of polymer.

  7. Cosmological aspects of gauge mediated supersymmetry breakdown

    CERN Document Server

    Dalianis, Ioannis


    In this thesis, we study the details of some fundamental cosmological problems of the gauge mediated supersymmetry breakdown and we probe the supersymmetry breaking sector by cosmological arguments. We manifest that problems like the metastable vacuum selection and the gravitino overproduction in the reheated early universe are naturally absent in the most general class of gauge mediation models without including additional ingredients or assumptions. We also find that the gravitino can generically account for the bulk dark matter of the universe. Cosmological implications of a stringy UV-completion of the supersymmetry breaking sector have been also considered.

  8. Ergodicity breakdown and scaling from single sequences

    Energy Technology Data Exchange (ETDEWEB)

    Kalashyan, Armen K. [Center for Nonlinear Science, University of North Texas, P.O. Box 311427, Denton, TX 76203-1427 (United States); Buiatti, Marco [Laboratoire de Neurophysique et Physiologie, CNRS UMR 8119 Universite Rene Descartes - Paris 5 45, rue des Saints Peres, 75270 Paris Cedex 06 (France); Cognitive Neuroimaging Unit - INSERM U562, Service Hospitalier Frederic Joliot, CEA/DRM/DSV, 4 Place du general Leclerc, 91401 Orsay Cedex (France); Grigolini, Paolo [Center for Nonlinear Science, University of North Texas, P.O. Box 311427, Denton, TX 76203-1427 (United States); Dipartimento di Fisica ' E.Fermi' - Universita di Pisa and INFM, Largo Pontecorvo 3, 56127 Pisa (Italy); Istituto dei Processi Chimico, Fisici del CNR Area della Ricerca di Pisa, Via G. Moruzzi 1, 56124 Pisa (Italy)], E-mail:


    In the ergodic regime, several methods efficiently estimate the temporal scaling of time series characterized by long-range power-law correlations by converting them into diffusion processes. However, in the condition of ergodicity breakdown, the same methods give ambiguous results. We show that in such regime, two different scaling behaviors emerge depending on the age of the windows used for the estimation. We explain the ambiguity of the estimation methods by the different influence of the two scaling behaviors on each method. Our results suggest that aging drastically alters the scaling properties of non-ergodic processes.

  9. QCD emergent from spontaneous breakdown of relativity

    CERN Document Server

    Nishimura, Kimihide


    Spontaneous violation of relativistic invariance of the vacuum can derive quantum chromodynamics from an U(1) Higgs model including fermions, if the emergent theory is Lorentz invariant. In this model, the vacuum becomes anisotropic, and a fermion created on a triplet of spin-one vacua acquires degeneracy analogous to the color degrees of freedom. The Nambu-Goldstone bosons originating from the breakdown of rotational symmetry provide the quasi fermions with SU(3)$\\times$U(1) effective interactions, which are interpretable as mediated by gluons and photons. The confinement of quasi quarks as well as that of Nambu-Goldstone gluons follow from the Lorentz invariance of the emergent theory.

  10. Laser-induced breakdown spectroscopy in Asia (United States)

    Wang, Zhen-Zhen; Deguchi, Yoshihiro; Zhang, Zhen-Zhen; Wang, Zhe; Zeng, Xiao-Yan; Yan, Jun-Jie


    Laser-induced breakdown spectroscopy (LIBS) is an analytical detection technique based on atomic emission spectroscopy to measure the elemental composition. LIBS has been extensively studied and developed due to the non-contact, fast response, high sensitivity, real-time and multi-elemental detection features. The development and applications of LIBS technique in Asia are summarized and discussed in this review paper. The researchers in Asia work on different aspects of the LIBS study in fundamentals, data processing and modeling, applications and instrumentations. According to the current research status, the challenges, opportunities and further development of LIBS technique in Asia are also evaluated to promote LIBS research and its applications.

  11. RF Breakdown in Drift Tube Linacs

    CERN Document Server

    Stovall, J; Lown, R


    The highest RF electric field in drift-tube linacs (DTLs) often occurs on the face of the first drift tube. Typically this drift tube contains a quadrupole focusing magnet whose fringing fields penetrate the face of the drift tube parallel to the RF electric fields in the accelerating gap. It has been shown that the threshold for RF breakdown in RF cavities may be reduced in the presence of a static magnetic field. This note offers a “rule of thumb” for picking the maximum “safe” surface electric field in DTLs based on these measurements.

  12. Bioavailability of glucosinolates and their breakdown products

    DEFF Research Database (Denmark)

    Barba Orellana, Francisco Jose; Nikmaram, Nooshin; Roohinejad, Shahin


    Glucosinolates are a large group of plant secondary metabolites with nutritional effects, and are mainly found in cruciferous plants. After ingestion, glucosinolates could be partially absorbed in their intact form through the gastrointestinal mucosa. However, the largest fraction is metabolized ...... the bioavailability of glucosinolates and their breakdown products. This review paper summarizes the assimilation, absorption, and elimination of these molecules, as well as the impact of processing on their bioavailability.......Glucosinolates are a large group of plant secondary metabolites with nutritional effects, and are mainly found in cruciferous plants. After ingestion, glucosinolates could be partially absorbed in their intact form through the gastrointestinal mucosa. However, the largest fraction is metabolized...

  13. Measurement of skeletal muscle collagen breakdown by microdialysis

    DEFF Research Database (Denmark)

    Miller, B F; Ellis, D; Robinson, M M;


    Exercise increases the synthesis of collagen in the extracellular matrix of skeletal muscle. Breakdown of skeletal muscle collagen has not yet been determined because of technical limitations. The purpose of the present study was to use local sampling to determine skeletal muscle collagen breakdown...... collagen breakdown 17–21 h post-exercise, and our measurement of OHP using GC–MS was in agreement with traditional assays....

  14. Numerical Study on Atmospheric Pressure DBD in Helium: Single-breakdown and Multi-breakdown Discharges%Numerical Study on Atmospheric Pressure DBD in Helium: Single-breakdown and Multi-breakdown Discharges

    Institute of Scientific and Technical Information of China (English)

    王小华; 杨爱军; 荣命哲; 刘定新


    A 1-D fluid model for homogeneous dielectric barrier discharge (DBD) in helium is presented, aimed at unraveling the spatial-temporal characteristics of two basic discharge regimes: single-breakdown and multi-breakdown discharges. Discharge currents, gap voltages, charge densities, electron temperature and electric field profiles of the two regimes make it clear that these two regimes are qualitatively different. It is found that the multi-breakdown discharge has a more homogeneous flux on dielectrics compared to the single-breakdown discharge.

  15. Vortex ring breakdown induced by topographic forcing

    Energy Technology Data Exchange (ETDEWEB)

    Geiser, J; Kiger, K T, E-mail: [Department of Mechanical Engineering, University of Maryland, College Park, MD 20910 (United States)


    Detailed measurements of the vortex breakdown within a strongly forced impinging jet are presented, with the goal of studying the effects of a small topographic disturbance on the breakdown and turbulence structure. This work is related to an ongoing effort to understand the dynamics of sediment suspension within a landing rotorcraft where a mobile boundary is subject to rapid erosion and deposition. The current work compares the results of a uniform surface to that of a small radial fence placed upstream of the vortex impingement location. The result is a dramatic increase in the coherence of the three-dimensional looping exhibited by the secondary vortex, leading to a more organized and strongly perturbed mean flow. Specifically, a triple decomposition of the velocity fluctuations indicates a very intense periodic stress in the vicinity of the impingement site, followed by a significant decay. Conversely, the random component of the fluctuating stresses gradually increases to modest levels as the coherent contributions decrease, eventually becoming greater than the coherent stress. The fence produces a bifurcation in the flow through the perturbation of the secondary vortex, which in turn creates a high-and low-speed streak on either side of the fence. The subsequent dynamics leads to increased fluctuating stress in the high-speed region, and a dramatically lower stress in the low-speed region, favoring preferential erosion on either side of the topographic disturbance.

  16. Symmetry breakdown and coupling constants of leptons

    Directory of Open Access Journals (Sweden)

    Gil C. Marques


    Full Text Available Based on a new approach to symmetries of the fundamental interactions we deal, in this paper, with the electroweak interactions of leptons. We show that the coupling constants, arising in the way leptons are coupled to intermediate bosons, can be understood as parameters associated to the breakdown of SU(2 and parity symmetries. The breakdown of both symmetries is characterized by a new parameter (the asymetry parameter of the electroweak interactions. This parameter gives a measure of the strength of breakdown of symmetries. We analyse the behaviour of the theory for three values of this parameter. The most relevant value is the one for which only the electromagnetic interactions do not break parity (the maximally allowed left-right asymetric theory. Maximamally allowed parity asymmetry is a requirement that is met for a value of Weinberg's theta-angle that is quite close to the experimental value of this parameter.Com base em uma formulação nova para simetrias das interações fundamentais nós lidamos, neste trabalho, com interações eletrofracas de leptons. Mostramos que as constantes do acoplamento, associadas aos acoplamentos de bósons intermediários, podem ser entendidas como parâmetros associados à quebra de simetrias SU(2 e paridade. A quebra de ambas as simetrias é caracterizada por um parâmetro novo (o parâmetro de assimetria das interações eletrofracas. Este parâmetro dá uma medida da intensidade com que a simetria é quebrada. Analisamos o comportamento da teoria para três valores deste parâmetro. O valor mais relevante é aquele para o qual apenas as interações eletromagnéticas não quebram a paridade (a teoria assimétrica esquerda-direita permitida da maneira máxima. A assimetria máxima permitida é uma exigência que leva a um ângulo de Weinberg cujo valor é próximo daquele observado experimentalmente.

  17. Streamer parameters and breakdown in CO2 (United States)

    Seeger, M.; Avaheden, J.; Pancheshnyi, S.; Votteler, T.


    CO2 is a promising gas for the replacement of SF6 in high-voltage transmission and distribution networks due to its lower environmental impact. The insulation properties of CO2 are, therefore, of great interest. For this, the properties of streamers are important, since they determine the initial discharge propagation and possibly the transition to a leader. The present experimental investigation addresses the streamer inception and propagation at ambient temperature in the pressure range 0.05-0.5 MPa at both polarities. Streamer parameters, namely the stability field, radius and velocity, were deduced in uniform and in strongly non-uniform background fields. The measured breakdown fields can then be understood by streamer propagation and streamer-to-leader transition.

  18. Runaway breakdown and hydrometeors in lightning initiation. (United States)

    Gurevich, A V; Karashtin, A N


    The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. A detailed analysis reveals that the shape of the pulses is determined by the runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of the pulse electric current is due to the multiple microdischarges at hydrometeors stimulated and synchronized by the low-energy electrons generated in the RB-EAS process. The series of specific pulse discharges leads to charge reset from hydrometeors to the free ions and creates numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning.

  19. Vortex breakdown in a truncated conical bioreactor (United States)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.; Shtern, Vladimir N.


    This numerical study explains the eddy formation and disappearance in a slow steady axisymmetric air-water flow in a vertical truncated conical container, driven by the rotating top disk. Numerous topological metamorphoses occur as the water height, Hw, and the bottom-sidewall angle, α, vary. It is found that the sidewall convergence (divergence) from the top to the bottom stimulates (suppresses) the development of vortex breakdown (VB) in both water and air. At α = 60°, the flow topology changes eighteen times as Hw varies. The changes are due to (a) competing effects of AMF (the air meridional flow) and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow on AMF. For small Hw, the AMF effect dominates. As Hw increases, the swirl effect dominates and causes VB. The water flow feedback produces and modifies air eddies. The results are of fundamental interest and can be relevant for aerial bioreactors.

  20. Development of Electrical Breakdown in Transformer Oil

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik


    Full Text Available Power transformers are key equipment for transfer and distribution of the electric power. Considering the significance of the power transformers in the electric system, their price and possible damages occurred by accidents, it is necessary to pay attention to their higher prevention. To prevent failure states of transformers, we perform different types ofmeasurements. They shall illustrate a momentary state of the measured equipment and if necessary to draw attention in advance to changes of parameters, which have specific relationship to no-failure operation of the equipment. The conditions under which breakdown of composite liquid/ solid insulation can occur, e.g. in transformer, play an important role in designing such insulation. The liquid, mainly mineral oil, generally constitutes the weakest part of insulation and a great amount of work has been devoted to the study of streamers, which appear in the gaseous phase, and most often are triggering the failure of insulation.

  1. Enzymatic Breakdown of Type II Collagen in the Human Vitreous

    NARCIS (Netherlands)

    van Deemter, Marielle; Pas, Hendri H.; Kuijer, Roel; van der Worp, Roelofje J.; Hooymans, Johanna M. M.; Los, Leonoor I.


    PURPOSE. To investigate whether enzymatic collagen breakdown is an active process in the human vitreous. METHODS. Human donor eyes were used for immunohistochemistry to detect the possible presence of the matrix metalloproteinase (MMP)-induced type II collagen breakdown product col2-3/4C-short in th

  2. Breakdown Phenomenon Study in the Bidirectional Pedestrian Flow

    NARCIS (Netherlands)

    Yang, X.; Daamen, W.; Hoogendoorn, S.P.; Chen, Y.; Dong, H.


    Pedestrian dynamics has been being a popular research area. In this paper, breakdown probability in the bidirectional flow that includes pedestrians with heterogeneities is investigated. Reaction time appears to have the most pronounced breakdown proba- bility, followed by desired velocity and then

  3. 7 CFR 51.1009 - Stylar end breakdown. (United States)


    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Stylar end breakdown. 51.1009 Section 51.1009... STANDARDS) United States Standards for Persian (Tahiti) Limes Definitions § 51.1009 Stylar end breakdown... affected area becomes darker and usually sinks below the healthy surface, but the area remains firm...

  4. Breakdown voltage of metal-oxide resistors in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Bagby, L. F. [Fermilab; Gollapinni, S. [Kansas State U.; James, C. C. [Fermilab; Jones, B. J.P. [MIT; Jostlein, H. [Fermilab; Lockwitz, S. [Fermilab; Naples, D. [Pittsburgh U.; Raaf, J. L. [Fermilab; Rameika, R. [Fermilab; Schukraft, A. [Fermilab; Strauss, T. [Bern U., LHEP; Weber, M. S. [Bern U., LHEP; Wolbers, S. A. [Fermilab


    We characterized a sample of metal-oxide resistors and measured their breakdown voltage in liquid argon by applying high voltage (HV) pulses over a 3 second period. This test mimics the situation in a HV-divider chain when a breakdown occurs and the voltage across resistors rapidly rise from the static value to much higher values. All resistors had higher breakdown voltages in liquid argon than their vendor ratings in air at room temperature. Failure modes range from full destruction to coating damage. In cases where breakdown was not catastrophic, subsequent breakdown voltages were lower in subsequent measuring runs. One resistor type withstands 131 kV pulses, the limit of the test setup.

  5. Electrical Breakdown and Mechanical Ageing in Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin

    the mechanisms behind the electrical breakdown of DEs and the second strategy is to investigate the long-term electromechanical reliability of DEs. In the first strategy, the electrothermal breakdown in polydimethylsiloxane (PDMS) elastomers was modelled in order to evaluate the thermal mechanisms behind...... the electrical failures. From the modelling based on the fitting of experimental data, it showed that the electrothermal breakdown of the PDMS elastomers was strongly influenced by the increase in both relative permittivity and conductivity. In addition to that, a methodology in determining the parameters...... that affect the breakdown strength of the pre-stretched DEs was developed. Breakdown strength was determined for samples with and without volume conservation and was found to depend strongly on the strain and the thickness of the samples. In order for DEs to be fully implementable in commercial products...

  6. Development of Hybrid Product Breakdown Structure for NASA Ground Systems (United States)

    Monaghan, Mark W.; Henry, Robert J.


    The Product Breakdown Structure is traditionally a method of identification of the products of a project in a tree structure. It is a tool used to assess, plan, document, and display the equipment requirements for a project. It is part of a product based planning technique, and attempts to break down all components of a project in as much detail as possible, so that nothing is overlooked. The PBS for ground systems at the Kennedy Space Center is being developed to encompass the traditional requirements including the alignment of facility, systems, and components to the organizational hierarchy. The Ground Operations Product Breakdown Structure is a hybrid in nature in that some aspects of a work breakdown structure will be incorporated and merged with the Architecture Concept of Operations, Master Subsystem List, customer interface, and assigned management responsibility. The Ground Operations Product Breakdown Structure needs to be able to identify the flexibility of support differing customers (internal and external) usage of ground support equipment within the Kennedy Space Center launch and processing complex. The development of the Product Breakdown Structure is an iterative activity Initially documenting the organization hierarchy structure and relationships. The Product Breakdown Structure identifies the linkage between the customer program requirements, allocation of system resources, development of design goals, and identification logistics products. As the Product Breakdown Structure progresses the incorporation of the results of requirement planning for the customer occurs identifying facility needs and systems. The mature Product Breakdown Structure is baselined with a hierarchical drawing, the Product Breakdown Structure database, and an associated document identifying the verification of the data through the life cycle of the program/product line. This paper will document, demonstrate, and identify key aspects of the life cycle of a Hybrid Product

  7. Experimental Study on High Electrical Breakdown of Water Dielectric

    Institute of Scientific and Technical Information of China (English)

    Zhang Zicheng; Zhang Jiande; Yang Jianhua


    By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561MA-1/10t-1eff/NP1/8; (2)the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing,ethylene glycol additive, and pressurization, of which pressurization is the most effective method;(4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface pohshing,the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.

  8. Work Breakdown Structures The Foundation for Project Management Excellence

    CERN Document Server

    Norman, Eric S; Fried, Robert T


    Understand and apply new concepts regarding Work Breakdown Structures The Work Breakdown Structure (WBS) has emerged as a foundational concept and tool in Project Management. It is an enabler that ensures clear definition and communication of project scope while performing a critical role as a monitoring and controlling tool. Created by the three experts who led the development of PMI's Practice Standard for Work Breakdown Structures, Second Edition, this much-needed text expands on what the standard covers and describes how to go about successfully implementing the WBS within the project life

  9. The statistics of the dielectric breakdown of thin films

    CERN Document Server

    Rowland, S M


    The statistics of the dielectric breakdown of thin films of silicon monoxide and aluminium oxide have been studied. The self healing technique which allows numerous breakdowns to be observed on one sample was employed. Ramp and steady state voltage experiments are reported and the limitations of these techniques are discussed. It is shown that the experimental data on breakdown can be fitted to two-parameter Weibull distributions using mixed distribution models. Methods have been developed to facilitate the evaluation of the associated parameters from results taken over limited time periods by graphical means. The significance of these parameters and the relationship between ramp and steady state testing techniques are discussed.

  10. Fire Whirls, Vortex Breakdown(?), and Blue Whirls (United States)

    Oran, Elaine; Xiao, Huahua; Gollner, Michael


    As we were investigating the efficiency of fire-whirl burning on water, we observed the usual transformation of a pool fire to a fire whirl, and then suddenly, we saw the fire undergo a third transition. A blue cup appeared around the base of the fire whirl, surrounding the yellow flame, the yellow flame receded into the cup and finally disappeared. What remained was a small, rapidly spinning blue flame that burned until the fuel on the water was consumed. The blue whirl was shaped like a spinning cup, closed at the bottom near the water surface, and spreading in radius moving upwards towards the rim. Above the blue cup lip, there was a purple cone-shaped mist. The fuel was usually n-heptane, but at one point it was crude oil, and still the blue whirl formed naturally. The height of the fire whirl on the laboratory pan was larger than a half meter, and this evolved into a blue whirl about 4-8 cm high. Occasionally the blue whirl would become "unstable" and revert to a transitional state of blue cup holding a yellow flame. When the blue whirl formed, turbulence seemed to disappear, and the flame became quiet. We will show videos of how this happened and discuss the evolution of the fire whirl to the blue whirl in vortex-breakdown concepts. This work was supported by and EAGER award from NSF and Minta Martin Endowment Funds in the Department of Aerospace Engineering at the University of Maryland.

  11. Multiphoton processes in KrF-laser induced gas breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Poprawe, R.; Herziger, G.


    Ionization by multiphoton processes is the dominant generation mechanism of first electrons in the UV-laser-induced gas breakdown. A strongly simplified analytical model for the ion generation rate is used to give an estimate of the threshold intensity I/sub TH/. The result is compared to descriptions by Keldish and Bebb to check its limits of applicability. Solving the kinetic conservation equations for the focus volume gives an estimation of the breakdown intensity where the Debye criterion has been used in the sense of a plasma definition. As an example, breakdown experiments with a KrF-escimer laser have been carried out at different pressures in an argon atmosphere. The pressure dependency of the breakdown threshold intensity and its order of magnitude are predicted by the model.

  12. Compact High Sensitive Laser-Induced Breakdown Spectroscopy Instrument Project (United States)

    National Aeronautics and Space Administration — Laser induced breakdown spectroscopy (LIBS) is a versatile tool for in situ substance characterization. Existing LIBS instruments are not compact enough for space...

  13. Surface of Alumina Films after Prolonged Breakdowns in Galvanostatic Anodization

    Directory of Open Access Journals (Sweden)

    Christian Girginov


    Full Text Available Breakdown phenomena are investigated at continuous isothermal (20∘C and galvanostatic (0.2–5 mA cm−2 anodizing of aluminum in ammonium salicylate in dimethylformamide (1 M AS/DMF electrolyte. From the kinetic (-curves, the breakdown voltage ( values are estimated, as well as the frequency and amplitude of oscillations of formation voltage ( at different current densities. The surface of the aluminum specimens was studied using atomic force microscopy (AFM. Data on topography and surface roughness parameters of the electrode after electric breakdowns are obtained as a function of anodization time. The electrode surface of anodic films, formed with different current densities until the same charge density has passed (2.5 C cm−2, was assessed. Results are discussed on the basis of perceptions of avalanche mechanism of the breakdown phenomena, due to the injection of electrons and their multiplication in the volume of the film.

  14. Priliminary Modeling of Air Breakdown with the ICEPIC code

    CERN Document Server

    Schulz, A E; Cartwright, K L; Mardahl, P J; Peterkin, R E; Bruner, N; Genoni, T; Hughes, T P; Welch, D


    Interest in air breakdown phenomena has recently been re-kindled with the advent of advanced virtual prototyping of radio frequency (RF) sources for use in high power microwave (HPM) weapons technology. Air breakdown phenomena are of interest because the formation of a plasma layer at the aperture of an RF source decreases the transmitted power to the target, and in some cases can cause significant reflection of RF radiation. Understanding the mechanisms behind the formation of such plasma layers will aid in the development of maximally effective sources. This paper begins with some of the basic theory behind air breakdown, and describes two independent approaches to modeling the formation of plasmas, the dielectric fluid model and the Particle in Cell (PIC) approach. Finally we present the results of preliminary studies in numerical modeling and simulation of breakdown.

  15. Optimal Rules for Single Machine Scheduling with Stochastic Breakdowns

    Directory of Open Access Journals (Sweden)

    Jinwei Gu


    Full Text Available This paper studies the problem of scheduling a set of jobs on a single machine subject to stochastic breakdowns, where jobs have to be restarted if preemptions occur because of breakdowns. The breakdown process of the machine is independent of the jobs processed on the machine. The processing times required to complete the jobs are constants if no breakdown occurs. The machine uptimes are independently and identically distributed (i.i.d. and are subject to a uniform distribution. It is proved that the Longest Processing Time first (LPT rule minimizes the expected makespan. For the large-scale problem, it is also showed that the Shortest Processing Time first (SPT rule is optimal to minimize the expected total completion times of all jobs.

  16. Laser-Induced Breakdown Spectroscopy: Capabilities and Applications (United States)


    sample preparation. 14 6. References 1. Cremers D.A.; Radziemski, L. J. Handbook of Laser-Induced Breakdown Spectroscopy; West Sussex, England...30 (21), 2882–2884. 17. Salle, B.; Lacour, J. L.; Vors, E.; Fichet, P.; Maurice, S.; Cremers , D. A.; et al. Laser- Induced Breakdown Spectroscopy...90. Martin , M. Z.; Labbe, N.; Andre, N.; Harris, R.; Ebinger, M.; Wullschleger, S. D.; et al. High Resolution Applications of Laser-Induced

  17. Ionizing potential waves and high-voltage breakdown streamers. (United States)

    Albright, N. W.; Tidman, D. A.


    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  18. Breakdown behavior of electronics at variable pulse repetition rates


    Korte, S.; H. Garbe


    The breakdown behavior of electronics exposed to single transient electromagnetic pulses is subject of investigations for several years. State-of-the-art pulse generators additionally provide the possibility to generate pulse sequences with variable pulse repetition rate. In this article the influence of this repetition rate variation on the breakdown behavior of electronic systems is described. For this purpose microcontroller systems are examined during line-led exposure to pulses with repe...

  19. Influence of ambient gases on the dc saturated breakdown field of molybdenum, tungsten, and copper during intense breakdown conditioning

    CERN Document Server

    Ramsvik, T; Reginelli, A; Taborelli, M


    A comprehensive investigation of the effect of Ar, H2, air, and CO on the saturated breakdown field (Esat) of molybdenum, tungsten, and copper has been performed at intensive breakdown conditioning. A significant decrease in Esat is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of ∼10-5   mbar, the decrease in Esat is found to be up to 50% and ∼30% compared to UHV conditions for molybdenum and tungsten, respectively. In addition, a ∼30% decrease is found when molybdenum is conditioned with a ∼10-5   mbar CO pressure. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the electrode surfaces. Ex situ heat treatment of molybdenum is shown to improve the breakdown characteristics drastically.

  20. On the assessment of extremely low breakdown probabilities by an inverse sampling procedure [gaseous insulation

    DEFF Research Database (Denmark)

    Thyregod, Poul; Vibholm, Svend


    a breakdown occurs. Following a breakdown, the procedure is restarted at the initial level. The procedure is repeated until a predetermined number of breakdowns have occurred, and the average and standard deviation of the observed first breakdown levels are recorded. The authors derive the relation between...

  1. Top predator absence enhances leaf breakdown in an intermittent stream. (United States)

    Rodríguez-Lozano, Pablo; Rieradevall, Maria; Prat, Narcís


    Current biodiversity loss is characterized by the extinction of top predators, but small-bodied freshwater fish are often overlooked in research and conservation management even when threatened because they usually lack commercial value. Therefore, the ecosystem impacts of their possible loss remain mostly unknown. We assessed whether the presence/absence of an endangered predatory fish (Barbus meridionalis (A. Risso, 1827)) in an intermittent stream affects leaf fungal biomass and leaf quality (i.e. leaf carbon:nitrogen ratio and leaf toughness), macroinvertebrate assemblages colonizing leaf packs, and leaf breakdown rates. We conducted a leaf bag experiment comparing a control reach with a population of B. meridionalis with an adjacent upstream fishless reach. In the fishless reach, leaf fungal biomass and microbially mediated breakdown rate were lower compared to the control reach. This was probably caused by the lack of the bottom-up stimulation through nutrient recycling by fish. Shredders and scrapers were found at higher abundance and biomass in the fishless compared to the control reach, and the whole macroinvertebrate community composition changed with fish absence. Consequently, macroinvertebrate mediated leaf breakdown was faster in the fishless than in the control reach, not only compensating for the lower microbially mediated leaf breakdown in the fishless reach, but accelerating the overall leaf breakdown rate. Our study contributes to understand the potential cascading effects produced by the extirpation of endangered small-bodied fish.

  2. Investigation of mechanism of breakdown in XLPE cables. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McKean, A.L.


    The basic hypothesis that microporosity plays a significant role in the mechanism of breakdown of XLPE cable is explored. The potential improvement achieved by impregnating the microporous regions of the cable core with a neutral liquid is evaluated, with relation to ac voltage life and impulse strength. The effect at higher frequency is also demonstrated. A similar test program is pursued on model cables, designed to explore the effects of gas pressure and gas type on breakdown and life, since it is reasonable to expect that only the microporous regions of the insulation should be sensitive to the gas-pressure environment. Comparison of gas-pressurized model breakdown stress (and related microvoid size) with basic Paschen curves demonstrates reasonably good agreement, indicating that partial discharge is the basic mechanism of fatigue and breakdown. The form of the voltage life curve above and below the discharge inception level is proposed, and evidence is presented indicating breakdown originates in the bulk insulation as well as at the shield interface. It is also shown that model cable discharge energies are below 0.1 pC, even at very high stress, and cannot be measured with modern detectors. Results with liquid or gas impregnation suggest a possible approach to dielectric improvement.

  3. Pulsed electrical breakdown of a void-filled dielectric (United States)

    Anderson, R. A.; Lagasse, R. R.; Schroeder, J. L.


    We report breakdown strengths in a void-filled dielectric material, epoxy containing 48 vol % hollow glass microballoon filler, which is stressed with unipolar voltage pulses of the order of 10 μs duration. The microballoon voids had mean diameters of approximately 40 μm and contained SO2 gas at roughly 30% atmospheric pressure. This void-filled material displays good dielectric strength (of the order of 100 kV mm-1) under these short-pulse test conditions. Results from a variety of electrode geometries are reported, including arrangements in which the electric stress is highly nonuniform. Conventional breakdown criteria based on mean or peak electric stress do not account for these data. A statistics-based predictive breakdown model is developed, in which the dielectric is divided into independent, microballoon-sized "discharge cells" and the spontaneous discharge of a single cell is presumed to launch full breakdown of the composite. We obtain two empirical parameters, the mean and standard deviation of the spontaneous discharge field, by fitting breakdown data from two electrode geometries having roughly uniform fields but with greatly differing volumes of electrically stressed material. This model accounts for many aspects of our data, including the inherent statistical scatter and the dependence on the stressed volume, and it provides informative predictions with electrode geometries giving highly nonuniform fields. Issues related to computational spatial resolution and cutoff distance are also discussed.

  4. Study of the breakdown voltage of SiPMs

    CERN Document Server

    Chmill, V; Klanner, R; Nitschke, M; Schwandt, J


    The breakdown behaviour of SiPMs (Silicon PhotoMultiplier) with pixel sizes of 15$\\times $15, 25$\\times $25, 50$\\times $50, and 100$\\times $100 $\\mu $m$^2$, manufactured by KETEK, has been investigated. From the current-voltage characteristics measured with and without illumination by LED light of 470 nm wavelength, the current-breakdown voltage, $V_I$, and from linear fits of the voltage dependence of the SiPM gain, measured by recording pulse-area spectra, the gain-breakdown voltage, $V_G$, have been obtained. The voltage dependence of the Geiger-breakdown probability was determined from the fraction of zero photoelectron events with LED illumination. By comparing the results to a model calculation, the photodetection-breakdown voltage, $V_{PD}$, has been determined. Within experimental uncertainties, $V_I$ and $V_{PD}$ are equal and independent of pixel size. For $V_G$, a dependence on pixel size is observed. The difference $V_I - V_G$ is about 1 V for the SiPM with 15 $\\mu $m pixels, decreases with pixel ...

  5. Dramatically enhanced electrical breakdown strength in cellulose nanopaper (United States)

    Huang, Jianwen; Zhou, Yuanxiang; Zhou, Zhongliu; Liu, Rui


    Electrical breakdown behaviors of nanopaper prepared from nanofibrillated cellulose (NFC) were investigated. Compared to conventional insulating paper made from micro softwood fibers, nanopaper has a dramatically enhanced breakdown strength. Breakdown field of nanopaper is 67.7 kV/mm, whereas that of conventional paper is only 20 kV/mm. Air voids in the surface of conventional paper are observed by scanning electron microscope (SEM). Further analyses using mercury intrusion show that pore diameter of conventional paper is around 1.7 μ m , while that of nanopaper is below 3 nm. Specific pore size of nanopaper is determined to be approximately 2.8 nm by the gas adsorption technique. In addition, theoretical breakdown strengths of nanopaper and conventional paper are also calculated to evaluate the effect of pore size. It turns out that theoretical values agree well with experimental data, indicating that the improved strength in nanopaper is mainly attributed to the decreased pore size. Due to its outstanding breakdown strength, this study indicates the suitability of nanopaper for electrical insulation in ultra-high voltage convert transformers and other electrical devices.

  6. Dramatically enhanced electrical breakdown strength in cellulose nanopaper

    Directory of Open Access Journals (Sweden)

    Jianwen Huang


    Full Text Available Electrical breakdown behaviors of nanopaper prepared from nanofibrillated cellulose (NFC were investigated. Compared to conventional insulating paper made from micro softwood fibers, nanopaper has a dramatically enhanced breakdown strength. Breakdown field of nanopaper is 67.7 kV/mm, whereas that of conventional paper is only 20 kV/mm. Air voids in the surface of conventional paper are observed by scanning electron microscope (SEM. Further analyses using mercury intrusion show that pore diameter of conventional paper is around 1.7 μm, while that of nanopaper is below 3 nm. Specific pore size of nanopaper is determined to be approximately 2.8 nm by the gas adsorption technique. In addition, theoretical breakdown strengths of nanopaper and conventional paper are also calculated to evaluate the effect of pore size. It turns out that theoretical values agree well with experimental data, indicating that the improved strength in nanopaper is mainly attributed to the decreased pore size. Due to its outstanding breakdown strength, this study indicates the suitability of nanopaper for electrical insulation in ultra-high voltage convert transformers and other electrical devices.

  7. Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Peter Gwin [IIT, Chicago


    Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

  8. Muscle breakdown and repair in polymyositis: a case study. (United States)

    Edwards, R H; Wiles, C M; Round, J M; Jackson, M J; Young, A


    Muscle breakdown and repair were measured by metabolic balance techniques in a patient with polymyositis who was being treated with prednisolone and azathioprine. Changes in body muscle mass that had been estimated from nitrogen and phosphorus balances correlated with antropometric assessments of thigh muscle mass and quadriceps strength. Decline in muscle strength was associated with a net rate of muscle breakdown of 148 g/day. Recovery was associated with a net rate of muscle repair of up to 100 g/day. Early reduction in corticosteroid treatment appeared to enhance the rate of repair. Changes in the isometric contraction force of the quadriceps muscle (but not in clinical symptoms, plasma creatine kinase [CK] or erythrocyte sedimentation rate [ESR] were found to reliably indicate whether the muscle was in a state of breakdown or repair. Treatment of the individual patient may be quantitatively monitored by metabolic balance studies or, more simply, by measurement of muscle strength.

  9. Fundamentals of undervoltage breakdown through the Townsend mechanism (United States)

    Cooley, James E.

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain, DC discharge gap are experimentally and theoretically explored. The phenomenon is relevant to fundamental understanding of breakdown physics, to switching applications such as triggered spark gaps and discharge initiation in pulsed-plasma thrusters, and to gas-avalanche particle counters. A dimensionless theoretical description of the phenomenon is formulated and solved numerically. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low avalanche-ionization gain, when an electron undergoes fewer than approximately 10 ionizing collisions during one gap transit. It is also found that fewer injected electrons are required as the gain due to electron-impact ionization (alpha process) is increased, or as the sensitivity of the alpha process to electric field is enhanced by decreasing the reduced electric field (electric field divided by pressure, E/p). A predicted insensitivity to ion mobility implies that breakdown is determined during the first electron avalanche when space charge distortion is greatest. A dimensionless, theoretical study of the development of this avalanche reveals a critical value of the reduced electric field to be the value at the Paschen curve minimum divided by 1.6. Below this value, the net result of the electric field distortion is to increase ionization for subsequent avalanches, making undervoltage breakdown possible. Above this value, ionization for subsequent avalanches will be suppressed and undervoltage breakdown is not possible. Using an experimental apparatus in which ultraviolet laser pulses are directed onto a photo-emissive cathode of a parallel-plate discharge gap, it is found that undervoltage breakdown can occur through a Townsend-like mechanism through the buildup of successively larger avalanche generations. The minimum number of injected

  10. High-voltage atmospheric breakdown across intervening rutile dielectrics.

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Kenneth Martin; Simpson, Sean; Coats, Rebecca Sue; Jorgenson, Roy Eberhardt; Hjalmarson, Harold Paul; Pasik, Michael Francis


    This report documents work conducted in FY13 on electrical discharge experiments performed to develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Further, experiments were conducted to determine if free carrier electrons could be excited into the conduction band thus lowering the effective breakdown voltage when UV photons (4.66 eV) from a high energy pulsed laser were incident on the rutile sample. This report documents the numerical approach, the experimental setup, and summarizes the data and simulations. Lastly, it describes the path forward and challenges that must be overcome in order to improve future experiments for characterizing the breakdown behavior for rutile.

  11. On sample preparation and dielectric breakdown in nanostructured epoxy resins

    Energy Technology Data Exchange (ETDEWEB)

    Reading, M; Xu, Z; Lewin, P L; Vaughan, A S, E-mail: [Tony Davies High Voltage Laboratory, University of Southampton (United Kingdom)


    There are many methods available to achieve a good dispersion of fillers within a polymeric matrix. This investigation considered several methods of dispersing three chosen fillers within an epoxy resin; the same processes were also performed on unfilled materials to investigate any effects they may have on the host material. For this investigation, the epoxy system (EP) was combined with sodium montmorillonite (MMT), micrometric silicon dioxide (SD) or nanometric silicon dioxide (NSD) as fillers. The effect of the different sample preparation routes on breakdown behaviour was then evaluated. While more thorough mixing protocols were found to lead to improved breakdown behaviour in the case of the various filled systems, surprisingly, an entirely equivalent form of behaviour was also seen in the unfilled epoxy. The influence of changes in sample geometry on the breakdown strength was established.

  12. Experimental results of breakdown in "Dena" plasma focus device (United States)

    Goudarzi, Shervin; Hoseinian, S. M.; Raeisdana, A.


    In spite of the intense research activities on Plasma Focus devices, the physics of the initial breakdown and surface discharge phase has not been realized completely. In this paper we have analyzed the surface discharge and initial breakdown phase in Filippov-type Plasma Focus Facility "Dena" (90 kJ, 25 kV) on the base of the current and current derivative measured signals by using Argon, Neon and Krypton as working gases at different discharge voltages and gas pressures, and the effects of working conditions (atomic weight, discharge voltage and gas pressure) on the breakdown and surface discharge phase have expressed. Also, on the base of these results, we have investigated about the relation of this phase with final pinch phase.

  13. Electron cyclotron resonance breakdown studies in a linear plasma system

    Indian Academy of Sciences (India)

    Vipin K Yadav; K Sathyanarayana; D Bora


    Electron cyclotron resonance (ECR) plasma breakdown is studied in a small linear cylindrical system with four different gases - hydrogen, helium, argon and nitrogen. Microwave power in the experimental system is delivered by a magnetron at 2.45 ± 0.02 GHz in TE10 mode and launched radially to have extra-ordinary (X) wave in plasma. The axial magnetic field required for ECR in the system is such that the fundamental ECR surface ( = 875.0 G) resides at the geometrical centre of the plasma system. ECR breakdown parameters such as plasma delay time and plasma decay time from plasma density measurements are carried out at the centre using a Langmuir probe. The operating parameters such as working gas pressure (1 × 10-5 -1 × 10-2 mbar) and input microwave power (160{800 W) are varied and the corresponding effect on the breakdown parameters is studied. The experimental results obtained are presented in this paper.

  14. New phenomenology of gas breakdown in DC and RF fields (United States)

    Petrović, Zoran Lj; Sivoš, Jelena; Savić, Marija; Škoro, Nikola; Radmilović Radenović, Marija; Malović, Gordana; Gocić, Saša; Marić, Dragana


    This paper follows a review lecture on the new developments in the field of gas breakdown and low current discharges, usually covered by a form of Townsend's theory and phenomenology. It gives an overview of a new approach to identifying which feedback agents provide breakdown, how to model gas discharge conditions and reconcile the results with binary experiments and how to employ that knowledge in modelling gas discharges. The next step is an illustration on how to record volt-ampere characteristics and use them on one hand to obtain the breakdown voltage and, on the other, to identify the regime of operation and model the secondary electron yields. The second aspect of this section concerns understanding the different regimes, their anatomy, how those are generated and how free running oscillations occur. While temporal development is the most useful and interesting part of the new developments, the difficulty of presenting the data in a written form precludes an easy publication and discussion. Thus, we shall only mention some of the results that stem from these measurements. Most micro discharges operate in DC albeit with complex geometries. Thus, parallel plate micro discharge measurements were needed to establish that Townsend's theory, with all its recent extensions, is still valid until some very small gaps. We have shown, for example, how a long-path breakdown puts in jeopardy many experimental observations and why a flat left-hand side of the Paschen curve often does not represent good physics. We will also summarize a kinetic representation of the RF breakdown revealing a somewhat more complex picture than the standard model. Finally, we will address briefly the breakdown in radially inhomogeneous conditions and how that affects the measured properties of the discharge. This review has the goal of summarizing (rather than developing details of) the current status of the low-current DC discharges formation and operation as a discipline which, in spite of

  15. Breakdown voltage of discrete capacitors under single-pulse conditions (United States)

    Domingos, H.; Scaturro, J.; Hayes, L.


    For electrostatic capacitors the breakdown voltage is inherently related to the properties of the dielectric, with the important parameters being the dielectric field strength which is related to the dielectric constant and the dielectric thickness. These are not necessarily related to the capacitance value and the rated voltage, but generally the larger values of capacitance have lower breakdown voltages. Foil and wet slug electrolytics can withstand conduction currents pulses without apparent damage (in either direction for foil types). For solid tantalums, damage occurs whenever the capacitor charges to the forming voltage.

  16. Modeling the Conductivity of a Subnanosecond Breakdown Gas Switch (United States)

    Chen, Jinhui; Scott Tyo, J.; Jerald Buchenauer, C.

    We present two different modeling methods for understanding subnanosecond breakdown processes in gas plasma switches. The first method uses a finite element time domain method in order to understand experimental measurements of the remote electromagnetic (EM) fields. This method only models the EM fields and is good for analysis, but lacks a predictive capability for the full nonlinear plasma system. The second modeling method uses a PIC code, and is fully self consistent. We make comparisons with experimental measurements and conclude that the PIC model may provide a good understanding of the subnanosecond breakdown phenomena.

  17. A relationship between statistical time to breakdown distributions and pre-breakdown negative differential resistance at nanometric scale

    Energy Technology Data Exchange (ETDEWEB)

    Foissac, R. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France); Univ. Grenoble Alpes, LTM, F-38000 Grenoble, France and CNRS, LTM, F-38000 Grenoble (France); Blonkowski, S.; Delcroix, P. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France); Kogelschatz, M. [Univ. Grenoble Alpes, LTM, F-38000 Grenoble, France and CNRS, LTM, F-38000 Grenoble (France)


    Using an ultra-high vacuum Conductive atomic force microscopy (C-AFM) current voltage, pre-breakdown negative differential resistance (NDR) characteristics are measured together with the time dependent dielectric breakdown (TDDB) distributions of Si/SiON (1.4 and 2.6 nm thick). Those experimental characteristics are systematically compared. The NDR effect is modelled by a conductive filament growth. It is showed that the Weibull TDDB statistic distribution scale factor is proportional to the growth rate of an individual filament and then has the same dependence on the electric field. The proportionality factor is a power law of the ratio between the surfaces of the CAFM tip and the filament's top. Moreover, it was found that, for the high fields used in those experiments, the TDDB acceleration factor as the growth rate characteristic is proportional to the Zener tunnelling probability. Those observations are discussed in the framework of possible breakdown or forming mechanism.

  18. Laser-Induced Breakdown Spectroscopy and Chlorophyll a Flourescence Transients

    DEFF Research Database (Denmark)

    Frydenvang, Jens

    of a sufficient quality; something that remains a problem for many in-situ methods. In my PhD, I present my work with two such in-situ methods, Laser-Induced Breakdown Spectroscopy (LIBS) and OJIP transients, the rising part of chlorophyll a fluorescence transients from dark-adapted leaves....

  19. RF breakdown of 805 MHz cavities in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Bowring, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Stratakis, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kochemirovskiy, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Leonova, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Moretti, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Palmer, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Peterson, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Yonehara, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Freemire, B. [Illinois Inst. of Technology, Chicago, IL (United States); Lane, P. [Illinois Inst. of Technology, Chicago, IL (United States); Torun, Y. [Illinois Inst. of Technology, Chicago, IL (United States); Haase, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States)


    Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

  20. Multiple paths to subharmonic laminar breakdown in a boundary layer (United States)

    Zang, Thomas A.; Hussaini, M. Yousuff


    Numerical simulations demonstrate that laminar breakdown in a boundary layer induced by the secondary instability of two-dimensional Tollmien-Schlichting waves to three-dimensional subharmonic disturbancews need not take the conventional lambda vortex/high-shear layer path.

  1. High Voltage Coaxial Vacuum Gap Breakdown for Pulsed Power Liners (United States)

    Cordaro, Samuel; Bott-Suzuki, Simon; Caballero Bendixsen, Luis Sebastian


    The dynamics of Magnetized Liner Inertial Fusion (MagLIF)1, are presently under detailed study at Sandia National Laboratories. Alongside this, a comprehensive analysis of the influence of the specific liner design geometry in the MagLIF system on liner initiation is underway in the academic community. Recent work at UC San Diego utilizes a high voltage pulsed system (25kV, 150ns) to analyze the vacuum breakdown stage of liner implosion. Such experimental analyses are geared towards determining how the azimuthal symmetry of coaxial gap breakdown affect plasma initiation within the liner. The final aim of the experimental analysis is to assess to what scale symmetry remains important at high (MV) voltages. An analysis of the above will utilize plasma self-emission via optical MCP, current measurements, voltage measurements near the gap, exact location of breakdown via 2D b-dot probe triangulation, as well as measuring the evolution of the B-field along the length of the liner via b-dot array. Results will be discussed along with analytical calculations of breakdown mechanisms

  2. Direct relationship between breakdown strength and tracking index of composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Henriksen, Mogens; Holbøll, Joachim


    The following paper shows a clear correlation between the measured tracking index and the breakdown field strength for noncoated glass fibre reinforced polymers (GFRP) with either a polyester or an epoxy based resin. 17 types of specimens have been tested according to IEC Publication 60587...

  3. Hyperammonemic encephalopathy due to suture line breakdown after bladder operation. (United States)

    Boogerd, W; Zoetmulder, F A; Moffie, D


    A patient is described with a severe encephalopathy and hyperammonemia in absence of liver dysfunction, attributed to urine absorption into the systemic circulation due to suture line breakdown after bladder dome resection. At autopsy characteristic Alzheimer type II astrocytes were found in the basal ganglia.

  4. Pulsed and streamer discharges in air above breakdown electric field

    NARCIS (Netherlands)

    Sun, A.B.; Teunissen, H.J.; Ebert, U.


    A 3D particle model is developed to investigate the streamer formation in electric fields above the breakdown threshold, in atmospheric air (1bar, 300 Kelvin). Adaptive particle management, adaptive mesh refinement and parallel computing techniques are used in the code. Photoionization and electron

  5. Blood-Brain Barrier Breakdown in the Aging Human Hippocampus (United States)

    Montagne, Axel; Barnes, Samuel R.; Sweeney, Melanie D.; Halliday, Matthew R.; Sagare, Abhay P.; Zhao, Zhen; Toga, Arthur W.; Jacobs, Russell E.; Liu, Collin Y.; Amezcua, Lilyana; Harrington, Michael G.; Chui, Helena C.; Law, Meng; Zlokovic, Berislav V.


    Summary The blood-brain barrier (BBB) limits entry of blood-derived products, pathogens and cells into the brain that is essential for normal neuronal functioning and information processing. Post-mortem tissue analysis indicates BBB damage in Alzheimer’s disease (AD). The timing of BBB breakdown remains, however, elusive. Using an advanced dynamic contrast-enhanced magnetic resonance imaging protocol with high spatial and temporal resolutions to quantify regional BBB permeability in the living human brain, we show an age-dependent BBB breakdown in the hippocampus, a region critical for learning and memory that is affected early in AD. The BBB breakdown in the hippocampus and its CA1 and dentate gyrus subdivisions worsened with mild cognitive impairment that correlated with injury to BBB-associated pericytes, as shown by the cerebrospinal fluid analysis. Our data suggest that BBB breakdown is an early event in the aging human brain that begins in the hippocampus and may contribute to cognitive impairment. PMID:25611508

  6. Novel dielectric reduces corona breakdown in ac capacitors (United States)

    Loehner, J. L.


    Dielectric system was developed which consists of two layers of 25-gage paper separated by one layer of 50-gage polypropylene to reduce corona breakdown in ac capacitors. System can be used in any alternating current application where constant voltage does not exceed 400 V rms. With a little research it could probably be increased to 700 to 800 V rms.

  7. Effects of streamwise vortex breakdown on supersonic combustion. (United States)

    Hiejima, Toshihiko


    This paper presents a numerical simulation study of the combustion structure of streamwise vortex breakdown at Mach number 2.48. Hydrogen fuel is injected into a combustor at sonic speed from the rear of a hypermixer strut that can generate streamwise vortices. The results show that the burning behavior is enhanced at the points of the shock waves that are incident on the vortex and therefore the vortex breakdown in the subsonic region occurs due to combustion. The breakdown domain in the mainstream is found to form a flame-holding region suited to combustion and to lead to a stable combustion field with detached flames. In this way, streamwise vortex breakdown has an essential role in combustion enhancement and the formation of flames that hold under supersonic inflow conditions. Finally, the combustion property defined here is shown to coincide with the produced-water mass flow. This property shows that the amount of combustion is saturated at equivalence ratios over 0.4, although there is a slight increase beyond 1.

  8. Generalizing Microdischarge Breakdown Scaling Laws for Pressure and Gas (United States)

    Loveless, Amanda; Garner, Allen


    Shrinking device dimensions for micro- and nanoelectromechanical systems necessitates accurate breakdown voltage predictions for reliable operation. Additionally, one must accurately predict breakdown voltage to optimize system geometry for applications in microplasmas and micropropulsion. Traditional approaches use Paschen's law (PL) to predict breakdown, but PL fails at small gap distances ( 15 μm) where field emission dominates. Subsequent work derived scaling laws and analytic expressions for breakdown voltage in argon at atmospheric pressure. Applications at high (e.g. combustion) and low (e.g. vacuum nanoelectronics) pressures for various gases motivate the generalization of these models for pressure and gas. This work addresses these concerns by deriving scaling laws generalized for gap distance, pressure, and gas, while also specifically incorporating and exploring the impact of field enhancement and work function. We compare these analytic scaling laws to experimental data and particle-in-cell simulations. Funded by a U.S. Nuclear Regulatory Commission Nuclear Education Program Faculty Development Grant Program at Purdue University.

  9. Differential saliva-induced breakdown of starch filled protein gels in relation to sensory perception

    NARCIS (Netherlands)

    Janssen, A.M.; Pijpekamp, van de A.M.; Labiausse, D.


    In this study, the differential breakdown of protein gels containing four types of high and low cross-linked starch granules were studied. Susceptibility to saliva-induced breakdown of starch granules and the consequences of these for overall breakdown of the gel matrix were captured using a multipl

  10. Calculation of Spark Breakdown or Corona Starting Voltages in Nonuniform Fields

    DEFF Research Database (Denmark)

    Pedersen, A.


    The processes leading to a spark breakdown or corona discharge are discussed very briefly. A quantitative breakdown criterion for use in high-voltage design is derived by which spark breakdown or corona starting voltages in nonuniform fields can be calculated. The criterion is applied to the sphere...

  11. Effects of polarization and absorption on laser induced optical breakdown threshold for skin rejuvenation (United States)

    Varghese, Babu; Bonito, Valentina; Turco, Simona; Verhagen, Rieko


    Laser induced optical breakdown (LIOB) is a non-linear absorption process leading to plasma formation at locations where the threshold irradiance for breakdown is surpassed. In this paper we experimentally demonstrate the influence of polarization and absorption on laser induced breakdown threshold in transparent, absorbing and scattering phantoms made from water suspensions of polystyrene microspheres. We demonstrate that radially polarized light yields a lower irradiance threshold for creating optical breakdown compared to linearly polarized light. We also demonstrate that the thermal initiation pathway used for generating seed electrons results in a lower irradiance threshold compared to multiphoton initiation pathway used for optical breakdown.

  12. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)


    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  13. Interpopulation hybrid breakdown maps to the mitochondrial genome. (United States)

    Ellison, Christopher K; Burton, Ronald S


    Hybrid breakdown, or outbreeding depression, is the loss of fitness observed in crosses between genetically divergent populations. The role of maternally inherited mitochondrial genomes in hybrid breakdown has not been widely examined. Using laboratory crosses of the marine copepod Tigriopus californicus, we report that the low fitness of F(3) hybrids is completely restored in the offspring of maternal backcrosses, where parental mitochondrial and nuclear genomic combinations are reassembled. Paternal backcrosses, which result in mismatched mitochondrial and nuclear genomes, fail to restore hybrid fitness. These results suggest that fitness loss in T. californicus hybrids is completely attributable to nuclear-mitochondrial genomic interactions. Analyses of ATP synthetic capacity in isolated mitochondria from hybrid and backcross animals found that reduced ATP synthesis in hybrids was also largely restored in backcrosses, again with maternal backcrosses outperforming paternal backcrosses. The strong fitness consequences of nuclear-mitochondrial interactions have important, and often overlooked, implications for evolutionary and conservation biology.

  14. Effects of Breakdown, Backlog and Rework on Replenishment Lot Size

    Directory of Open Access Journals (Sweden)

    Tsu-Ming Yeh


    Full Text Available This study studies the effects of machine breakdown, backlog and rework on the replenishment lot size. In real-life manufacturing systems, random defective rate and breakdown of equipment are inevitable. When backlogging is permitted during a production run, a random machine failure may take place either in backlog filling stage or in inventory piling time; this study focuses on the former situation and considers all defective items produced are repairable through a rework process. The objective of this study is to determine the optimal run time that minimizes the long-run average production-inventory costs. The result can be directly applied to the practical production planning and control field to assist practitioner in production management cost reduction.

  15. Gas breakdown and plasma impedance in split-ring resonators (United States)

    Hoskinson, Alan R.; Parsons, Stephen; Hopwood, Jeffrey


    The appearance of resonant structures in metamaterials coupled to plasmas motivates the systematic investigation of gas breakdown and plasma impedance in split-ring resonators over a frequency range of 0.5-9 GHz. In co-planar electrode gaps of 100 μm, the breakdown voltage amplitude decreases from 280 V to 225 V over this frequency range in atmospheric argon. At the highest frequency, a microplasma can be sustained using only 2 mW of power. At 20 mW, we measure a central electron density of 2 × 1020 m-3. The plasma-electrode overlap plays a key role in the microplasma impedance and causes the sheath impedance to dominate the plasma resistance at very low power levels. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

  16. Breakdown of an Inhomogeneous Scale- Free Network Under Intentional Attack

    Institute of Scientific and Technical Information of China (English)

    LIN Guo-Ji; CHENG Xiang; OU-YANG Qi


    Using a recently introduced network model with node and connection diversity, we study the breakdown of different scale-free networks under intentional attacks. Our simulation results show that inhomogeneous networks are more sensitive to intentional attack than the homogeneous ones and that the centralization of the networks is an important variable, reflecting the characteristics of the network under intentional attack. Using a recently introduced method we can theoretically develop the critical point of the inhomogeneous networks.

  17. Laser-Induced Breakdown Spectroscopy: Fundamentals, Applications, and Challenges


    Anabitarte, F.; Cobo, A.; J. M. Lopez-Higuera


    Laser-induced breakdown spectroscopy (LIBS) is a technique that provides an accurate in situ quantitative chemical analysis and, thanks to the developments in new spectral processing algorithms in the last decade, has achieved a promising performance as a quantitative chemical analyzer at the atomic level. These possibilities along with the fact that little or no sample preparation is necessary have expanded the application fields of LIBS. In this paper, we review the state of the ar...

  18. Ionizing gas breakdown waves in strong electric fields. (United States)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.


    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  19. Time-resolved laser-induced breakdown spectroscopy of aluminum

    Institute of Scientific and Technical Information of China (English)

    LIU Xian-yun; ZHANG Wei-jun; WANG Zhen-ya; HAO Li-qing; HUANG Ming-qiang; ZHAO Wen-wu; LONG Bo; Zhao Wei


    We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spectroscopy (LIBS) in our laboratory, which can be used for the determination of elements in solids, liquids and aerosols. A description of the instrumentation, including laser, sample chamber and detection, is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end, the possibilities and later uses of this technique are briefly discussed.

  20. Preliminary Studies on Pulsed Electric Field Breakdown of Lead Azide (United States)


    1/2 OS CO ton NO. S3L TECHNICAL REPORT 4991 PRELIMINARY SUJDfES ON PULSED ELECTRIC FIELD BREAKDOWN OF LEAD AZIDE L AVRAMI M. BUMS D. DOWNS...Introduction Background A. Contact Effects B. Pulsed Electric Field Measurements Experimental A. Contact Effects B. Pulsed Electric Fields Discussion...B. Pulsed Electric Field Measurements The application of pulsed electric fields to lead azide does not exactly simulate the conditions experienced

  1. Breakdown of Leaf Litter in a Neotropical Stream


    Mathuriau, Catherine; Chauvet, Eric


    International audience; We investigated the breakdown of 2 leaf species, Croton gossypifolius (Euphorbiaceae) and Clidemia sp. (Melastomataceae), in a 4th-order neotropical stream (Andean Mountains, southwestern Colombia) using leaf bags over a 6-wk period. We determined the initial leaf chemical composition and followed the change in content of organic matter, C, N, and ergosterol, the sporulation activity of aquatic hyphomy cetes, and the structure and composition of leaf-associated aquatic...

  2. Breakdown of Gallavotti-Cohen symmetry for stochastic dynamics (United States)

    Harris, R. J.; Rákos, A.; Schütz, G. M.


    We consider the behaviour of current fluctuations in the one-dimensional partially asymmetric zero-range process with open boundaries. Significantly, we find that the distribution of large current fluctuations does not satisfy the Gallavotti-Cohen symmetry and that such a breakdown can generally occur in systems with unbounded state space. We also discuss the dependence of the asymptotic current distribution on the initial state of the system.

  3. Modeling of High-voltage Breakdown in Helium (United States)

    Xu, Liang; Khrabrov, Alexander; Kaganovich, Igor; Sommerer, Timothy


    We investigate the breakdown in extremely high reduced electric fields (E/N) between parallel-plate electrodes in helium. The left branch of the Paschen curve in the voltage range of 20-350kV and inter-electrode gap range of 0.5-3.5cm is studied analytically and with Monte-Carlo/PIC simulations. The model incorporates electron, ion, and fast neutral species whose energy-dependent anisotropic scattering, as well as backscattering at the electrodes, is carefully taken into account. Our model demonstrates that (1) anisotropic scattering is indispensable for producing reliable results at such high voltage and (2) due to the heavy species backscattered at cathode, breakdown can occur even without electron- and ion-induced ionization of the background gas. Fast atoms dominate in the breakdown process more and more as the applied voltage is increased, due to their increasing ionization cross-section and to the copious flux of energetic fast atoms generated in charge-exchange collisions.

  4. Passive protections against breakdowns between accelerating grids in SPIDER experiment

    Energy Technology Data Exchange (ETDEWEB)

    Pesce, Alberto, E-mail: [Consorzio RFX - Associazione EURATOM-ENEA per la fusione, Corso Stati Uniti 4, 35127, Padova (Italy); De Lorenzi, Antonio; Boldrin, Marco [Consorzio RFX - Associazione EURATOM-ENEA per la fusione, Corso Stati Uniti 4, 35127, Padova (Italy)


    In the SPIDER experiment a ITER-like full size plasma source will be realized with the target to extract a D{sup -} beam of 70 A and then to accelerate it to 100 keV energy. The reduction of the effects due to the frequent breakdowns between the accelerating grids is needed, because of grids damage due to energy deposition by arcing and strong electromagnetic noise (EMI) emission. The solution proposed is a comprehensive design of the circuit. Two passive components are installed: a Damping Resistor and an Output Filter in series to the Power Supplies. Then a doubled screened structure will be adopted for the 30 m long - 100 kV Transmission Line TL, which connects the Ion Source and Acceleration Power Supplies to their loads: the Inner Screen will be connected to the reference ground (the vessel) by a resistive link, the Outer Screen acting as a low-impedance ground. Finally, a Distributed Core Snubber DCS (magnetic snubber) will be installed onto the TL, aimed to increase the damping of the oscillations due to the stray inductances and capacitances. The DCS is composed of 10 magnetic alloy cores and is equipped by a biasing circuit to enhance the flux swing in unsaturated condition during the breakdown. A detailed model of the circuit is developed to evaluate the passive components parameters for protection against breakdown, in which all the magnetic and capacitive couplings between components are modeled as well as the magnetic core snubber saturation.

  5. Relativistic runaway breakdown in low-frequency radio (United States)

    Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten


    The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

  6. [Galactomannan breakdown in germinating carob seeds (Ceratonia siliqua L.)]. (United States)

    Seiler, A


    In the first days of germination of carob seeds (Ceratonia siliqua L., Leguminosae) (until penetration of the seed coat by the radicle) oligosaccharides of the raffinose series present in the endosperm and embryo are hydrolysed. The mobilisation of the reserve galactomannan of the endosperm begins after the emergence of the radicle. Its degradation is effected by hydrolytic enzymes (α-galactosidase [EC], β-mannanase, [EC] and β-mannosidase [EC]) and the breakdown products-galactose and mannose-are continuously metabolised by the embryo. At the same time starch synthesis is observed in the embryo.In the germination of Ceratonia siliqua seeds the embryo does not have a direct effect on the mobilisation of the reserve polysaccharide as it does in the case of barley. The endosperm consists of living cells which, independently of the embryo, synthesise the enzymes used for galactomannan breakdown. A weak α-galactosidase activity is already present in the endosperm of mature dry seeds. This activity cannot be suppressed by inhibitors of transcription or translation, so that their presence does not prevent degradation of oligosaccharides of the raffinose series.A high proportion of the α-galactosidase responsible for the breakdown of the galactomannan is synthesised de novo during germination. Such synthesis could be demonstrated by the incorporation of [U-(14)C]serine and could be inhibited by actinomycin D or cycloheximide.

  7. Dielectric breakdown of MXB-71 phenolic and Sylgard 184/GMB silicone at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, R.T. Jr.; Beeson, P.M.


    High temperature electrical breakdown characteristics have been determined for MXB-71 phenolic and Sylgard 184/GMB silicone in air and nitrogen environments. The phenolic material is used for electronic case housings whereas the silicone is an encapsulant. The experiments were performed with constant electric fields (values ranging from 3 x 10/sup 3/ to 2.5 x 10/sup 4/ V/cm) applied to the samples while the temperature was increased at a rate of 10/sup 0/C/minute. The sample current until breakdown was determined. Results showed that breakdown occurred between 470 to 725/sup 0/C, and was principally dependent upon the material conductivity at time breakdown and the electric field. The breakdown temperature decreased with increasing electric field and decreased in an oxygen-containing environment. Materials postcured at 580 to 600/sup 0/C prior to electrical testing exhibited considerably lower breakdown temperatures at higher electric fields. Results suggest that breakdown occurred via thermal runaway.

  8. Thermal Reversible Breakdown and Resistivity Switching in Hafnium Dioxide

    Directory of Open Access Journals (Sweden)

    N. Raghavan


    Full Text Available We present a model of thermal reversible breakdown via conductive filaments (CFs in hafnium dioxide (HfO2. These CFs appear as a result of electrical pretreatment of a metal/HfO2/metal (semiconductor nanostructure (MIM(S. The model is based on an assumption that the thermal reversible breakdown of a CF is due to of Joule heating displaying an exponential dependence of conductivity on temperature. The corresponding current-voltage characteristic and temperature of a CF in its middle and at the interface with an electrode are calculated taking into account the heat conduction equation and boundary conditions with heat dissipation via electrodes. It is found that the current-voltage characteristic of a CF has three specific regions. The initial and final regions have turned out to be linear with respect to the current and display different slopes, while the middle region is characterized by both the S-shaped and ultralinear dependences which are affected by the ambient temperature and nanostructure parameters. The switching potential from the high resistivity state (HRS to the low resistivity state (LRS was shown to decrease with the ambient temperature and with worsening of heat dissipation conditions. We present a model of thermal reversible breakdown via conductive filaments (CFs in hafnium dioxide (HfO2. These CFs appear as a result of electrical pretreatment of a metal/HfO2/metal (semiconductor nanostructure (MIM(S. The model is based on an assumption that the thermal reversible breakdown of a CF is due to of Joule heating displaying an exponential dependence of conductivity on temperature. The corresponding current-voltage characteristic and temperature of a CF in its middle and at the interface with an electrode are calculated taking into account the heat conduction equation and boundary conditions with heat dissipation via electrodes. It is found that the current-voltage characteristic of a CF has three specific regions. The initial and

  9. PHENIX Work Breakdown Structure. Cost and schedule review copy

    Energy Technology Data Exchange (ETDEWEB)


    The Work Breakdown Structure (WBS) Book begins with this Overview section, which contains the high-level summary cost estimate, the cost profile, and the global construction schedule. The summary cost estimate shows the total US cost and the cost in terms of PHENIX construction funds for building the PHENIX detector. All costs in the WBS book are shown in FY 1993 dollars. Also shown are the institutional and foreign contributions, the level of pre-operations funding, and the cost of deferred items. Pie charts are presented at PHENIX WBS level 1 and 2 that show this information. The PHENIX construction funds are shown broken down to PHENIX WBS level 3 items per fiscal year, and the resulting profile is compared to the RHIC target profile. An accumulated difference of the two profiles is also shown. The PHENIX global construction schedule is presented at the end of the Overview section. Following the Overview are sections for each subsystem. Each subsystem section begins with a summary cost estimate, cost profile, and critical path. The total level 3 cost is broken down into fixed costs (M&S), engineering costs (EDIA) and labor costs. Costs are further broken down in terms of PHENIX construction funds, institutional and foreign contributions, pre-operations funding, and deferred items. Also shown is the contingency at level 3 and the level 4 breakdown of the total cost. The cost profile in fiscal years is shown at level 3. The subsystem summaries are followed by the full cost estimate and schedule sheets for that subsystem. These detailed sheets are typically carried down to level 7 or 8. The cost estimate shows Total, M&S, EDIA, and Labor breakdowns, as well as contingency, for each WBS entry.

  10. Leaf breakdown in a natural open tropical stream

    Directory of Open Access Journals (Sweden)

    Elisa A.C.C. Alvim


    Full Text Available Leaf breakdown is a primary process of nutrient cycling and energy flow, contributing to the functioning of aquatic ecosystems. In the present study, leaves of Baccharis platypoda and Coccoloba cereifera were incubated in a high-altitude stream in a rupestrian field. Two hypotheses were tested: i intrinsic factors (quality of detritus are more important than extrinsic factors (decomposer communities in decomposition; and ii low detritus quality hinders microbial colonization, thereby altering the composition and structure of the associated invertebrate community and slowing leaf breakdown. The breakdown coefficients of B. platypoda and C. cereifera leaves were low (k = -0.0019 day-1 and k = -0.0008 day-1, respectively and the proportions of structural compounds were high, delaying the remobilization of energy and nutrients into the aquatic ecosystem. Fungal biomass was higher at the end of the experiment, suggesting favorable conditions for colonization. The densities of invertebrates associated with the detritus increased coincident with the peak concentration of ergosterol, with the trophic groups collector-gatherer and scraper having the highest densities. The distribution of these groups was likely related to the growth of biofilm on the surface of the litters. As described for tropical streams, shredders had the lowest densities of any invertebrate group, suggesting a reduced participation of these invertebrates in leaf processing. The results suggest that slow decomposing species are important to both invertebrates and microorganisms as substrates and sources of particulate organic matter. The low palatability and nutritional quality of the detritus in the present study, associated with low dissolved nutrient concentrations in water, delayed the leaf conditioning process by microorganisms. Decomposition rates and invertebrate participation were reduced as a result, leading to major physical decomposition. Headwater tropical streams have

  11. Individual breakdown of pension rights and end of contract

    CERN Multimedia


    As in previous years, members of the CERN Pension Fund will shortly receive their “Individual breakdown of pension rights” by e-mail.   In this respect, we would like to remind members that according to Articles II 1.11 - II 1.12 (calculation and payment of the transfer value) and II 2.02 (retirement pension), several options are possible at the end of their contract (depending on their length of service in the Fund): payment of the transfer value into a personal bank account, payment of the transfer value into a new pension scheme, pension (deferred, anticipated or retirement). Benefits Service CERN Pension Fund

  12. Continuous breakdown of Purcell's scallop theorem with inertia

    CERN Document Server

    Lauga, Eric


    Purcell's scallop theorem defines the type of motions of a solid body - reciprocal motions - which cannot propel the body in a viscous fluid with zero Reynolds number. For example, the flapping of a wing is reciprocal and, as was recently shown, can lead to directed motion only if its frequency Reynolds number, Re_f, is above a critical value of order one. Using elementary examples, we show the existence of oscillatory reciprocal motions which are effective for all arbitrarily small values of the frequency Reynolds number and induce net velocities scaling as (Re_f)^\\alpha (alpha > 0). This demonstrates a continuous breakdown of the scallop theorem with inertia.

  13. Kinetic modeling of the Townsend breakdown in argon (United States)

    Macheret, S. O.; Shneider, M. N.


    Kinetic modeling of the Townsend breakdown in argon was performed in the "forward-back" approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

  14. Plasma temperature clamping in filamentation laser induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; Yeak, J.; Phillips, Mark C.


    Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filamentation channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also partly explains the reason for the occurrence of atomic plume during fs LIBS in air compared to long-pulse ns LIBS.

  15. Global Franck-Condon breakdown resulting from Cooper minima

    Energy Technology Data Exchange (ETDEWEB)

    Rao, R.M.; Poliakoff, E.D. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)]|[Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Wang, K.; McKoy, V. [Arthur Amos Noyes Laboratory of Chemical Physics, Californian Institute of Technology, Pasadena, California 91125 (United States)


    Using N{sub 2} 2{sigma}{sub {ital u}}{sup {minus}1} photoionization as an example, we present the first measurements and calculations of photoion vibrational distributions for an extended energy range (5{le}{ital E}{sub {ital k}}{le}230 eV). The results show a striking breakdown of the Franck-Condon approximation over a 100 eV range. We show that this coupling between vibrational and electronic motion arises from a dependence of Cooper minima on molecular bond length. Based on this mechanism, the effect is expected to be common for molecular systems. {copyright} {ital 1996 The American Physical Society.}

  16. Trace metal mapping by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Jozef [ORNL; Novotny, Dr. Karel [Masaryk University; Hrdlicka, A [Brno University of Technology, Czech Republic; Malina, R [Brno University of Technology, Czech Republic; Hartl, M [Brno University of Technology, Czech Republic; Kizek, R [Mendel University of Brno; Adam, V [Mendel University of Brno


    Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) is a sensitive optical technique capable of fast multi-elemental analysis of solid, gaseous and liquid samples. The potential applications of lasers for spectrochemical analysis were developed shortly after its invention; however the massive development of LIBS is connected with the availability of powerful pulsed laser sources. Since the late 80s of 20th century LIBS dominated the analytical atomic spectroscopy scene and its application are developed continuously. Here we review the utilization of LIBS for trace elements mapping in different matrices. The main emphasis is on trace metal mapping in biological samples.

  17. Controlled calibration method for laser induced breakdown spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Li Wang; Chijian Zhang; Yuan Feng


    Laser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration and calibration-free (CF) methods, this new method overcomes "matrix effect", and demonstrates a better ability to cope with the spectra. It is used to analyze natural soil, and errors of the concentration are decreased about 5%. The result shows that the new method is feasible and accurate.

  18. Ionization coefficient approach to modeling breakdown in nonuniform geometries.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Nicolaysen, Scott D.


    This report summarizes the work on breakdown modeling in nonuniform geometries by the ionization coefficient approach. Included are: (1) fits to primary and secondary ionization coefficients used in the modeling; (2) analytical test cases for sphere-to-sphere, wire-to-wire, corner, coaxial, and rod-to-plane geometries; a compilation of experimental data with source references; comparisons between code results, test case results, and experimental data. A simple criterion is proposed to differentiate between corona and spark. The effect of a dielectric surface on avalanche growth is examined by means of Monte Carlo simulations. The presence of a clean dry surface does not appear to enhance growth.

  19. Breakdown of the Dipole Approximation in Strong-Field Ionization

    CERN Document Server

    Ludwig, A; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U


    We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10$^{13}$ W/cm$^2$. Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semi-classical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as origin of our observations.

  20. Biomedical and environmental applications of laser-induced breakdown spectroscopy

    Indian Academy of Sciences (India)

    V K Unnikrishnan; K S Choudhari; Suresh D Kulkarni; Rajesh Nayak; V B Kartha; C Santhosh; B M Suri


    Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical technique with numerous advantages such as rapidity, multi-elemental analysis, minimal sample preparation, minimal destruction, low cost and versatility of being applied to a wide range of materials. In this paper, we report the preliminary observations we obtained using LIBS for clinical and environmental samples. Elemental analysis has been done qualitatively in human teeth samples which show encouraging results. It has also been demonstrated in this paper that LIBS can be very well utilized in field applications such as plastic waste sorting and recycling.

  1. Dielectric breakdown in nano-porous thin films (United States)

    Borja, Juan Pablo

    Unknown to most computer users and mobile device enthusiasts, we have finally entered into a critical age of chip manufacturing. January of 2014 marks the official start of the quest by the semiconductor industry to successfully integrate sub 14nm process technology nodes in accordance to the International Technology Roadmap for Semiconductors (ITRS). The manufacturing of nano-scale features represents a major bottleneck of its own. However, a bigger challenge lies in reliably isolating the massive chip interconnect network. The present work is aimed at generating a theoretical and experimental framework to predict dielectric breakdown for thin films used in computer chip components. Here, a set of experimental techniques are presented to assess and study dielectric failure in novel thin films. A theory of dielectric breakdown in thin nano-porous films is proposed to describe combined intrinsic and metal ion catalyzed failure. This theory draws on experimental evidence as well as fundamental concepts from mass and electronic charge transport. The drift of metal species was found to accelerate intrinsic dielectric failure. The solubility of metals species such as Cu was found to range from 7.0x1025 ions/m3 to 1.86x1026 ions/m3 in 7% porous SiCOH films. The diffusion coefficient for Cu species was found to span from 4.2x10-19 m2/s to 1.86x10-21 m2/s. Ramped voltage stress experiments were used to identify intrinsic failure from metal catalyzed failure. Intrinsic breakdown is defined when time to failure against applied field ramp rate results in ∂(ln(TTF))/∂(ln(R)) ≈ -1. Intrinsic failure was studied using Au. Here, ∂(ln(TTF))/∂(ln(R)) ≈ -0.95, which is an experimental best case scenario for intrinsic failure. Au is commonly reluctant to ionize which means that failure occurs in the absence of ionic species. Metal catalyzed failure was investigated using reactive electrodes such as Cu, and Ag. Here, trends for ∂(ln(TTF))/∂(ln(R)) significantly

  2. Electrical Breakdown Characteristic of Nanostructured W-Cu Contacts Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Junbo; CHEN Wen'ge; DING Bingjun


    Nanostructured (NS) W- Cu composite powder was prepared by mechanical alloying ( MA ), and nanostructured bulk of W- Cu contact material was fabricated by hot press sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness and break down voltage of NS W-Cu alloys were measured and compared to those of conventional W- Cu alloys prepared by powder metallurgy. The experimental results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of nanostructured W- Cu contacts materials. Also, the nanostructured W- Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

  3. Progress in fieldable laser-induced breakdown spectroscopy (LIBS) (United States)

    Miziolek, Andrzej W.


    In recent years there has been great progress in the Laser Induced Breakdown Spectroscopy (LIBS) technology field. Significant advances have been made both in fundamental and applied research as well as in data processing/chemometrics. Improvements in components, most notably lasers/optics and spectrometers are enabling the development of new devices that are suitable for field use. These new commercial devices recently released to the marketplace, as well as ones currently under development, are bringing the potential of LIBS for CBRNE threat analysis into real-world applications.

  4. Breakdown of 1D water wires inside Charged Carbon Nanotubes

    CERN Document Server

    Pant, Shashank


    Using Molecular Dynamics approach we investigated the structure, dynamics of water confined inside pristine and charged 6,6 carbon nanotubes (CNTs). This study reports the breakdown of 1D water wires and the emergence of triangular faced water on incorporating charges in 6,6 CNTs. Incorporation of charges results in high potential barriers to the flipping of water molecules due to the formation of a large number of hydrogen bonds. The PMF analyses show the presence of ~2 kcal/mol barrier for the movement of water inside pristine CNT and almost negligible barrier in charged CNTs.

  5. Experimental study of vortex breakdown in swirling jets (United States)

    Billant, Paul; Chomaz, Jean-Marc; Huerre, Patrick


    The goal of this study is to characterize the various breakdown states taking place in a swirling water jet as the swirl ratio S and Reynolds number Re are varied. A pressure-driven water jet discharges into a large tank, swirl being imparted by means of a motor which sets into rotation a honeycomb within a settling chamber. The experiments are conducted for two distinct jet diameters by varying the swirl ratio S while maintaining the Reynolds number Re fixed in the range 300secondary recirculating motions that are independent of confinement effects.

  6. Reconfigurable photonic crystal using self-initiated gas breakdown (United States)

    Gregório, José; Parsons, Stephen; Hopwood, Jeffrey


    We present a resonant photonic crystal for which transmission is time-modulated by a self-initiated gaseous plasma. A resonant cavity in the photonic crystal is used to amplify an incoming microwave field to intensities where gas breakdown is possible. The presence of the plasma in the resonant cavity alters the transmission spectrum of the device. We investigate both transient and steady-state operation with computational simulations using a time-domain model that couples Maxwell’s equations and plasma fluid equations. The predicted plasma ignition and stability are then experimentally verified.

  7. Influence of absorption induced thermal initiation pathway on irradiance threshold for laser induced breakdown (United States)

    Varghese, Babu; Bonito, Valentina; Jurna, Martin; Palero, Jonathan; Verhagen, Margaret Hortonand Rieko


    We investigated the influence of thermal initiation pathway on the irradiance threshold for laser induced breakdown in transparent, absorbing and scattering phantoms. We observed a transition from laser-induced optical breakdown to laser-induced thermal breakdown as the absorption coefficient of the medium is increased. We found that the irradiance threshold after correction for the path length dependent absorption and scattering losses in the medium is lower due to the thermal pathway for the generation of seed electrons compared to the laser-induced optical breakdown. Furthermore, irradiance threshold gradually decreases with the increase in the absorption properties of the medium. Creating breakdown with lower irradiance threshold that is specific at the target chromophore can provide intrinsic target selectivity and improve safety and efficacy of skin treatment methods that use laser induced breakdown. PMID:25909007

  8. DC high voltage to drive helium plasma jet comprised of repetitive streamer breakdowns

    CERN Document Server

    Wang, Xingxing


    This paper demonstrates and studies helium atmospheric pressure plasma jet comprised of series of repetitive streamer breakdowns, which is driven by a pure DC high voltage (auto-oscillations). Repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV/cm. Repetition frequency of the streamer breakdowns excited using this principle can be simply tuned by reconfiguring the discharge electrode geometry. This custom-designed type of the helium plasma jet, which operates on the DC high voltage and is comprised of the series of the repetitive streamer breakdowns at frequency about 13 kHz, is demonstrated.

  9. Experimental study of DC vacuum breakdown and application to high-gradient accelerating structures for CLIC

    CERN Document Server

    Shipman, Nicholas; Jones, Roger


    The compact linear collider (CLIC) is a leading candidate for the next generation high energy linear collider. As any breakdown would result in a partial or full loss of luminosity for the pulse in which it occurs, obtaining a low breakdown rate in CLIC accelerating structures is a critical requirement for the successful operation of the proposed collider. This thesis presents investigations into the breakdown phenomenon primarily in the low breakdown rate regime of interest to CLIC, performed using the CERN DC spark systems between 2011 and 2014. The design, construction and commissioning of several new pieces of hardware, as well as the development of improved techniques to measuring the inter-electrode gap distance are detailed. These hardware improvements were fundamental in enabling the exciting new experiments mentioned below, which in turn have provided significant additional insight into the phenomenon of breakdown. Experiments were performed to measure fundamental parameters of individual breakdowns...

  10. The Nature of Emission from Optical Breakdown Induced by Pulses of fs and ns Duration

    Energy Technology Data Exchange (ETDEWEB)

    Carr, C W; Feit, M D; Rubenchik, A M; Demange, P; Kucheyev, S; Shirk, M D; Radousky, H B; Demos, S G


    Spectral emission from optical breakdown in the bulk of a transparent dielectric contains information about the nature of the breakdown medium. We have made time resolved measurements of the breakdown induced emission caused by nanosecond and femtosecond infrared laser pulses. We previously demonstrated that the emission due to ns pulses is blackbody in nature allowing determination of the fireball temperature and pressure during and after the damage event. The emission due to femtosecond pulse breakdown is not blackbody in nature; two different spectral distributions being noted. In one case, the peak spectral distribution occurs at the second harmonic of the incident radiation, in the other the distribution is broader and flatter and presumably due to continuum generation. The differences between ns and fs breakdown emission can be explained by the differing breakdown region geometries for the two pulse durations. The possibility to use spectral emission as a diagnostic of the emission region morphology will be discussed.

  11. Noise Parameter Analysis of SiGe HBTs for Different Sizes in the Breakdown Region

    Directory of Open Access Journals (Sweden)

    Chie-In Lee


    Full Text Available Noise parameters of silicon germanium (SiGe heterojunction bipolar transistors (HBTs for different sizes are investigated in the breakdown region for the first time. When the emitter length of SiGe HBTs shortens, minimum noise figure at breakdown decreases. In addition, narrower emitter width also decreases noise figure of SiGe HBTs in the avalanche region. Reduction of noise performance for smaller emitter length and width of SiGe HBTs at breakdown resulted from the lower noise spectral density resulting from the breakdown mechanism. Good agreement between experimental and simulated noise performance at breakdown is achieved for different sized SiGe HBTs. The presented analysis can benefit the RF circuits operating in the breakdown region.

  12. Evolutionary genetics of hybrid breakdown in the marine copepod Tigriopus californicus


    Ellison, Christopher K


    Populations of the supra-littoral marine copepod Tigriopus californicus are known to be highly divergent and to exhibit a pattern of hybrid breakdown when crossed under laboratory conditions. This dissertation examines the genetic mechanisms involved in hybrid breakdown in T. californicus, particularly those involving integration of the nuclear and mitochondrial genomes. In Chapter I, I summarize some of the relevant literature concerning the importance of hybrid breakdown to evolutionary bio...

  13. Breakdown characteristics in DC spark experiments of copper focusing on purity and hardness

    CERN Document Server

    Yokoyama, Kazue; Higashi, Yasuo; Higo, Toshi; Matsumoto, Shuji; Santiago-Kern, Ana Rocia; Pasquino, Chiara; Calatroni, Sergio; Wuensch, Walter


    The breakdown characteristics related to the differences in purity and hardness were investigated for several types of copper using a DC spark test system. Three types of oxygen-free copper (OFC) materials, usual class 1 OFC 7-nine large-grain copper and 6-nine hot-isotropic-pressed (HIP) copper with/without diamond finish, were tested with the DC spark test system. The measurements of the beta, breakdown fields, and breakdown probability are presented and discussed in this paper.

  14. Fully kinetic model of breakdown during sheath expansion after interruption of vacuum arcs (United States)

    Wang, Zhenxing; Wang, Haoran; Zhou, Zhipeng; Tian, Yunbo; Geng, Yingsan; Wang, Jianhua; Liu, Zhiyuan


    Research on sheath expansion is critical to the understanding of the dielectric recovery process in a vacuum interrupter after interruption of vacuum arcs. In this paper, we investigated how residual plasma affects breakdown in the sheath expansion period after the current zero. To simulate sheath expansion and breakdown, we developed a fully kinetic particle-in-cell Monte Carlo collision model with one spatial dimension and three velocity dimensions. The model accounted for various collisions, including ionization, excitation, elastic collisions, charge exchange, and momentum exchange, and we added an external circuit to the model to make the calculations self-consistent. The existence of metal vapor slowed the sheath expansion in the gap and caused high electric field formation in front of the cathode surface. The initial residual plasma, which was at sufficiently low density, seemed to have a limited impact on breakdown, and the metal vapor dominated the breakdown in this case. Additionally, the breakdown probability was sensitive to the initial plasma density if the value exceeded a specific threshold, and plasma at sufficiently high density could mean that breakdown would occur more easily. We found that if the simulation does not take the residual plasma into account, it could overestimate the critical value of the metal vapor density, which is always used to describe the boundary of breakdown after interruption of vacuum arcs. We discussed the breakdown mechanism in sheath expansion, and the breakdown is determined by a combination of metal vapor, residual plasma, and the electric field in front of the cathode surface.

  15. A theoretical estimation of the pre-breakdown-heating time in the underwater discharge acoustic source

    Institute of Scientific and Technical Information of China (English)

    Wang Yi-Bo; Wang Shang-Wu; Zeng Xin-Wu


    One of the common characteristics of the electrothermal breakdown in an underwater discharge acoustic source(UDAS)is the existence of a pre-breakdown-heating phase.In our experiment,two phenomena were observed:(1)the breakdown time that takes on high randomicity and obeys a "double-peak" stochastic distribution;(2)the higher salt concentration that reduces the residual voltage and causes 100% non-breakdown.The mechanism of electrothermal breakdown is analysed.To specify the end of the pre-breakdown-heating phase,a "border boiling" assumption is proposed,in which the breakdown time is assumed to be the time needed to heat the border water around the initial arc to 773 K.Based on this ‘border boiling' assumption,the numerical simulation is performed to evaluate the effects of two heating mechanisms:the Joule heating from the ionic current,and the radiation heating from the initial arc.The simulation results verify the theoretical explanations to these two experiment phenomena:(1)the stochastic distribution of the radius of the initial arc results in the randomicity of the breakdown time;(2)the difference in efficiency between the radiation heating and the Joule heating determines that,in the case of higher salt concentration,more energy will be consumed in the pre-breakdown-heating phase.

  16. The research of breakdown structure and coding system for construction project

    Institute of Scientific and Technical Information of China (English)

    丁大勇; 金维兴; 李培


    Whether the breakdown structure and coding system of construction projects are reasonable or not determines to a large degree the pepfofmance level of the entire project management. We analyze in detail the similarities and differences of two kinds of decomposing methods classified by type of work and construction elements based on the discussion of international typical coding standards system designing. We then deduce the differential coefficient relation between project breakdown strueture(PBS) and work breakdown structure (WBS). At the same time we constitute a comprehensive construction project breakdown system including element code and type of work code and make a further schematic presentation of the implementation of the sysrem' s functions.

  17. Breakdown in hydrogen and deuterium gases in static and radio-frequency fields

    CERN Document Server

    Korolov, I


    We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF, 13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics.

  18. A simple mechanism for controlling vortex breakdown in a closed flow

    CERN Document Server

    Cabeza, C; Martí, A C; Sarasua, G; Bove, Italo; Marti, Arturo C.; Sarasua, Gustavo


    Vortex breakdown can be described as a change in vortex core structures in which a recirculation flux induces the formation of bubbles in the rotation axis. The development and control of a laminar vortex breakdown of a flow enclosed in a cylinder is studied both theoretical and experimentally. We show that the vortex breakdown can be controlled by the introduction of a small fixed rod in the axis of the cylinder. This method is simpler than those previously proposed, since it does not require any auxiliary device system. The experimental observations are consistent with the results of a simple model to predict the onset of vortex breakdown.

  19. Ac breakdown in near-atmospheric pressure noble gases: I. Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Sobota, A; Kanters, J H M; Van Veldhuizen, E M; Haverlag, M [Eindhoven University of Technology, Department of Applied Physics, Postbus 513, 5600MB Eindhoven (Netherlands); Manders, F; Gendre, M F; Hendriks, J, E-mail: [Philips Lighting, LightLabs, Mathildelaan 1, 5600JM Eindhoven (Netherlands)


    Ac-driven breakdown processes have been explored much less than the pulsed or dc breakdown, even though they have possible applications in industry. This paper focuses on the frequency range between 60 kHz and 1 MHz, at a pin-pin electrode geometry and gap lengths of 4 or 7 mm. The breakdown process was examined in argon and xenon at 0.3 and 0.7 bar. We used electrical and optical measurements to characterize the breakdown process, to observe the influence of frequency change and the effect of ignition enhancers-UV irradiation and radioactive material.

  20. Time domain simulations of preliminary breakdown pulses in natural lightning (United States)

    Carlson, B E; Liang, C; Bitzer, P; Christian, H


    Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mechanism. Key Points Preliminary breakdown pulses can be reproduced by simulated channel extension Channel heating and corona sheath formation are crucial to proper pulse shape Extension processes and channel orientation significantly affect observations PMID:26664815

  1. Preliminary Breakdown: Physical Mechanisms and Potential for Energetic Emissions (United States)

    Petersen, D.; Beasley, W. H.


    Observations and analysis of the preliminary breakdown phase of virgin negative cloud-to-ground (-CG) lightning strokes will be presented. Of primary interest are the physical processes responsible for the fast electric field "characteristic" pulses that are often observed during this phase. The pulse widths of characteristic pulses are shown to occur as a superposed bimodal distribution, with the short and long modes having characteristic timescales on the order of 1 microsecond and 10 microseconds, respectively. Analysis of these pulses is based on comparison with laboratory observations of long spark discharge processes and with recently acquired high-speed video observations of a single -CG event. It will be argued that the fast electric field bimodal distribution is the result of conventional discharge processes operating in an extensive strong ambient electric field environment. An important related topic will also be discussed, where it will be argued that preliminary breakdown discharges are capable of generating energetic electrons and may therefore seed relativistic electron avalanches that go on to produce pulsed energetic photon emissions.

  2. Experimental breakdown of selected anodized aluminum samples in dilute plasmas (United States)

    Grier, Norman T.; Domitz, Stanley


    Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

  3. Dielectric breakdown during Cs+ sputtering of polyvinyl chloride (United States)

    Wahoud, F.; Guillot, J.; Audinot, J. N.; Bertrand, P.; Delcorte, A.; Migeon, H. N.


    Thin films of insulating polymers are sometimes analyzed by secondary ion mass spectrometry (SIMS) or by X-ray photoelectron spectroscopy (XPS) without the use of an electron gun. In this work, both SIMS and XPS have been used to study the chemical and structural modifications due to the charge effect during Cs+ sputtering of a thin film of polyvinyl chloride (PVC). The kinetic energy distribution study shows that at a small primary fluence ˜1015 Cs+ ions/cm2, the dielectric breakdown voltage of the PVC film is reached, i.e. the minimum voltage that causes a portion of an insulator to become electrically conductive. XPS study indicates that the conducting phase created in the PVC film after energetic Cs+ bombardment consists of graphitized carbon and metallic cesium clusters. After the dielectric breakdown of the film, the positive charge, previously accumulated on the surface, is neutralized through the conductive regions, which are created in the insulating film. During Cs+ sputtering of a PVC film, the chemical structure of the analyzed surface is completely modified and some ionic bonds such as CsC and CsCl are also created.

  4. A Photographic Atlas of Rock Breakdown Features in Geomorphic Environments (United States)

    Bourke, Mary C. (Editor); Brearley, J. Alexander; Haas, Randall; Viles, Heather A.


    A primary goal of geomorphological enquiry is to make genetic associations between process and form. In rock breakdown studies, the links between process, inheritance and lithology are not well constrained. In particular, there is a need to establish an understanding of feature persistence. That is, to determine the extent to which in situ rock breakdown (e.g., aeolian abrasion or salt weathering) masks signatures of earlier geomorphic transport processes (e.g., fluvial transport or crater ejecta). Equally important is the extent to which breakdown during geomorphic transport masks the imprint of past weathering. The use of rock features in this way raises the important question: Can features on the surface of a rock reliably indicate its geomorphic history? This has not been determined for rock surfaces on Earth or other planets. A first step towards constraining the links between process, inheritance, and morphology is to identify pristine features produced by different process regimes. The purpose of this atlas is to provide a comprehensive image collection of breakdown features commonly observed on boulders in different geomorphic environments. The atlas is intended as a tool for planetary geoscientists and their students to assist in identifying features found on rocks on planetary surfaces. In compiling this atlas, we have attempted to include features that have formed 'recently' and where the potential for modification by another geomorphic process is low. However, we acknowledge that this is, in fact, difficult to achieve when selecting rocks in their natural environment. We group breakdown features according to their formative environment and process. In selecting images for inclusion in the atlas we were mindful to cover a wide range of climatic zones. For example, in the weathering chapter, clast features are shown from locations such as the hyper-arid polar desert of Antarctica and the semi-arid canyons of central Australia. This is important as some

  5. Comparison of laser induced breakdown spectroscopy and spark induced breakdown spectroscopy for determination of mercury in soils

    Energy Technology Data Exchange (ETDEWEB)

    Srungaram, Pavan K.; Ayyalasomayajula, Krishna K.; Yu-Yueh, Fang; Singh, Jagdish P., E-mail:


    Mercury is a toxic element found throughout the environment. Elevated concentrations of mercury in soils are quite hazardous to plants growing in these soils and also the runoff of soils to nearby water bodies contaminates the water, endangering the flora and fauna of that region. This makes continuous monitoring of mercury very essential. This work compares two potential spectroscopic methods (laser induced breakdown spectroscopy (LIBS) and spark induced breakdown spectroscopy (SIBS)) at their optimum experimental conditions for mercury monitoring. For LIBS, pellets were prepared from soil samples of known concentration for generating a calibration curve while for SIBS, soil samples of known concentration were used in the powder form. The limits of detection (LODs) of Hg in soil were calculated from the Hg calibration curves. The LOD for mercury in soil calculated using LIBS and SIBS is 483 ppm and 20 ppm, respectively. The detection range for LIBS and SIBS is discussed. - Highlights: • We compared SIBS and LIBS for mercury (Hg) measurements in soil. • Hg 546.07 nm line was selected for both LIBS and SIBS measurements. • Limit of detection for Hg was found to be 20 ppm with SIBS and 483 ppm with LIBS.

  6. Laser-induced breakdown spectroscopy fundamentals and applications

    CERN Document Server

    Noll, Reinhard


    This book is a comprehensive source of the fundamentals, process parameters, instrumental components and applications of laser-induced breakdown spectroscopy (LIBS). The effect of multiple pulses on material ablation, plasma dynamics and plasma emission is presented. A heuristic plasma modeling allows to simulate complex experimental plasma spectra. These methods and findings form the basis for a variety of applications to perform quantitative multi-element analysis with LIBS. These application potentials of LIBS have really boosted in the last years ranging from bulk analysis of metallic alloys and non-conducting materials, via spatially resolved analysis and depth profiling covering measuring objects in all physical states: gaseous, liquid and solid. Dedicated chapters present LIBS investigations for these tasks with special emphasis on the methodical and instrumental concepts as well as the optimization strategies for a quantitative analysis. Requirements, concepts, design and characteristic features of LI...

  7. Laser-induced breakdown spectroscopy theory and applications

    CERN Document Server

    Perini, Umberto


    This book deals with the Laser-Induced Breakdown Spectroscopy (LIBS), a widely used atomic emission spectroscopy technique for elemental analysis of materials. It is based on the use of a high-power, short pulse laser excitation. The book is divided into two main sections: the first one concerning theoretical aspects of the technique, the second one describing the state of the art in applications of the technique in different scientific/technological areas. Numerous examples of state of the art applications provide the readers an almost complete scenario of the LIBS technique. The LIBS theoretical aspects are reviewed. The book helps the readers who are less familiar with the technique to understand the basic principles. Numerous examples of state of the art applications give an almost complete scenario of the LIBS technique potentiality. These examples of applications may have a strong impact on future industrial utilization. The authors made important contributions to the development of this field.

  8. Kinetic modeling of the Townsend breakdown in argon

    Energy Technology Data Exchange (ETDEWEB)

    Macheret, S. O.; Shneider, M. N. [Department of Mechanical and Aerospace Engineering, Princeton University, D-414 Engineering Quadrangle, Princeton, New Jersey 08544 (United States)


    Kinetic modeling of the Townsend breakdown in argon was performed in the “forward-back” approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

  9. Analysis of fresco by laser induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Caneve, L., E-mail: luisa.caneve@enea.i [ENEA, CR Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Diamanti, A. [Universita ' Tor Vergata' , Dipartimento di Scienze e Tecnologie Chimiche, via della Ricerca Scientifica 1, 00133 Roma (Italy); Grimaldi, F. [ENEA, CR Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Palleschi, G. [Universita ' Tor Vergata' , Dipartimento di Scienze e Tecnologie Chimiche, via della Ricerca Scientifica 1, 00133 Roma (Italy); Spizzichino, V. [ENEA, CR Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Valentini, F. [Universita ' Tor Vergata' , Dipartimento di Scienze e Tecnologie Chimiche, via della Ricerca Scientifica 1, 00133 Roma (Italy)


    The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition. The depth profiling permitted to put in evidence the presence of successive paint layers with different compositions. A comparison with the results obtained by the microscopy inspection of the sample has been done.

  10. Analysis of fresco by laser induced breakdown spectroscopy (United States)

    Caneve, L.; Diamanti, A.; Grimaldi, F.; Palleschi, G.; Spizzichino, V.; Valentini, F.


    The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition. The depth profiling permitted to put in evidence the presence of successive paint layers with different compositions. A comparison with the results obtained by the microscopy inspection of the sample has been done.

  11. The Role of Sphingomyelin Breakdown in Measles Virus Immunmodulation

    Directory of Open Access Journals (Sweden)

    Elita Avota


    Full Text Available Measles virus (MV efficiently causes generalized immunosuppression which accounts to a major extent for cases of measles-asscociated severe morbidity and mortality. MV infections alter many functions of antigen presenting cells (APC (dendritic cells (DCs and lymphocytes, yet many molecular targets of the virus remain poorly defined. Cellular interactions and effector functions of DCs and lymphocytes are regulated by surface receptors. Associating with other proteins involved in cell signaling, receptors form part of receptosomes that respond to and transmit external signals through dynamic interctions with the cytoskeleton. Alterations in the composition and metabolism of membrane sphingolipids have a substantial impact on both processes. In this review we focus on the regulation of sphingomyelinase activity and ceramide release in cells exposed to MV and discuss the immunosuppressive role of sphingomyelin breakdown induced by MV.

  12. Elemental Analysis of Soils by Laser Induced Breakdown Spectroscopy (United States)

    Gondal, Mohammed Ashraf; Dastageer, Mohamed A.

    The chemical and elemental composition of soil is very complex as it contains many constituents like minerals, organic matters, living organisms, fossils, air and water. Considering the diversity of soil contents, quality and usability, a systematic scientific study on the elemental and chemical composition of soil is very important. In order to study the chemical composition of soil, Laser induced breakdown spectroscopy (LIBS) has been applied recently. The important features of LIBS system and its applications for the measurement of nutrients in green house soil, on-line monitoring of remediation process of chromium polluted soil, determination of trace elements in volcanic erupted soil samples collected from ancient cenozoic lava eruption sites and detection of toxic metals in Gulf war oil spill contaminated soil using LIBS are described in this chapter.

  13. Complex Quantum Networks: From Universal Breakdown to Optimal Transport

    CERN Document Server

    Muelken, Oliver; Galiceanu, Mircea


    We show that all sequentially growing networks yield the same universal behavior at the breakdown of single-particle quantum transport. For this, we study the global time-averaged transport efficiency of excitations on complex quantum networks. Further, we observe the transition to optimal transport by starting from a network with complete-graph-like sequential subgraphs and systematically reducing the number of loops. These effects are explained on the basis of the spectral properties of the network's Hamiltonian. Our theoretical considerations are supported by numerical Monte-Carlo simulations for complex quantum networks with a scale-free size distribution of sequential subgraphs and a small-world-type transition to optimal transport.

  14. Design Flaws and Service System Breakdowns: Learning from Systems Thinking

    Directory of Open Access Journals (Sweden)

    David Ing


    Full Text Available In what ways might systems thinking be helpful to designers?  In the 21st century, the types of project with which designers have become engaged has expanded to include service systems.  Service systems are typically composites of mechanisms, organisms, human beings and ecologies.  Systems thinking is a perspective with theories, methods and practices that enables transcending disciplinary boundaries.  Application of systems thinking in designing a service system can aid in surfacing potential flaws and/or anticipating future breakdowns in functions, structures and/or processes. Designers and systems thinkers should work together to improve the nature of service systems.  As a starter set into these conversations, seven conditions are proposed as a starting context.  These conditions are presented neither as rigourously defined nor as exhaustive, but as an entry point into future joint engagement.

  15. Relativistic runaway breakdown in low-frequency radio

    DEFF Research Database (Denmark)

    Fullekrug, M.; Roussel-Dupre, R.; Symbalisty, E.M.D.


    is characterized by consecutive broadband pulses in the low-frequency radio range from similar to 10 to 300 kHz at a distance of similar to 800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges...... at a distance of similar to 550 km. The measured broadband pulses occur similar to 4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from similar to 50 to 350 kHz, and they exhibit complex waveforms without the typical...... ionospheric reflection of the first hop sky wave. Two consecutive pulses occur similar to 4.5 ms and similar to 3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband...

  16. Spectrum standardization for laser-induced breakdown spectroscopy measurements

    CERN Document Server

    Wang, Zhe; West, Logan; Li, Zheng; Ni, Weidou


    This paper presents a spectra normalization method for laser-induced breakdown spectroscopy (LIBS) measurements by converting the recorded characteristic line intensity at varying conditions to the intensity under a standard condition with standard plasma temperature, degree of ionization, and total number density of the interested species to reduce the measurement uncertainty. The characteristic line intensities of the interested species are first converted to the intensity at a fixed temperature and standard degree of ionization but varying total number density for each laser pulse analysis. Under this state, if the influence of the variation of plasma morphology is neglected, the sum of multiple spectral line intensities for the measured element can be regarded proportional to the total number density of the specific element, and the fluctuation of the total number density, or the variation of ablation mass, was compensated for by the application of this relationship. In the experiments with 29 brass alloy...

  17. Mitochondrial endonuclease G mediates breakdown of paternal mitochondria upon fertilization. (United States)

    Zhou, Qinghua; Li, Haimin; Li, Hanzeng; Nakagawa, Akihisa; Lin, Jason L J; Lee, Eui-Seung; Harry, Brian L; Skeen-Gaar, Riley Robert; Suehiro, Yuji; William, Donna; Mitani, Shohei; Yuan, Hanna S; Kang, Byung-Ho; Xue, Ding


    Mitochondria are inherited maternally in most animals, but the mechanisms of selective paternal mitochondrial elimination (PME) are unknown. While examining fertilization in Caenorhabditis elegans, we observed that paternal mitochondria rapidly lose their inner membrane integrity. CPS-6, a mitochondrial endonuclease G, serves as a paternal mitochondrial factor that is critical for PME. We found that CPS-6 relocates from the intermembrane space of paternal mitochondria to the matrix after fertilization to degrade mitochondrial DNA. It acts with maternal autophagy and proteasome machineries to promote PME. Loss of cps-6 delays breakdown of mitochondrial inner membranes, autophagosome enclosure of paternal mitochondria, and PME. Delayed removal of paternal mitochondria causes increased embryonic lethality, demonstrating that PME is important for normal animal development. Thus, CPS-6 functions as a paternal mitochondrial degradation factor during animal development.

  18. Radiation Effects on Breakdown Characteristics of Multi Guarded Devices

    CERN Document Server

    Da Rold, M; Bisello, D; Candelori, A; Da Re, A; Dalla Betta, Gian Franco; Paccagnella, A; Soncini, G; Verzellesi, G; Wheadon, R


    Multiguard structures are used in order to enhance the breakdown voltage of microstrip detectors. In this work we studied the electrical properties of devices designed in four different layouts on n-Si substrates, based on a central diode surrounded by various p+ and/or n+ floating rings. In particular we measured the main DC characteristics and we compared the experimental results with those simulated by a two-dimensional drift-diffusion computer model. Device noise was also measured for the central diode as a function of the applied voltage. We repeated all measurements after neutron and gamma irradiation, in view of the application of these devices to silicon microstrip detectors for future high energy physics experiments. For example at the LHC the level of radiation damage expected during the detector lifetime implies very high bias voltages for the detector operation. Multiguards can offer a solution, provided the optimisation of the design takes into account the radiation effects.

  19. Bioavailability of Glucosinolates and Their Breakdown Products: Impact of Processing (United States)

    Barba, Francisco J.; Nikmaram, Nooshin; Roohinejad, Shahin; Khelfa, Anissa; Zhu, Zhenzhou; Koubaa, Mohamed


    Glucosinolates are a large group of plant secondary metabolites with nutritional effects, and are mainly found in cruciferous plants. After ingestion, glucosinolates could be partially absorbed in their intact form through the gastrointestinal mucosa. However, the largest fraction is metabolized in the gut lumen. When cruciferous are consumed without processing, myrosinase enzyme present in these plants hydrolyzes the glucosinolates in the proximal part of the gastrointestinal tract to various metabolites, such as isothiocyanates, nitriles, oxazolidine-2-thiones, and indole-3-carbinols. When cruciferous are cooked before consumption, myrosinase is inactivated and glucosinolates transit to the colon where they are hydrolyzed by the intestinal microbiota. Numerous factors, such as storage time, temperature, and atmosphere packaging, along with inactivation processes of myrosinase are influencing the bioavailability of glucosinolates and their breakdown products. This review paper summarizes the assimilation, absorption, and elimination of these molecules, as well as the impact of processing on their bioavailability. PMID:27579302

  20. Detection of early caries by laser-induced breakdown spectroscopy (United States)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji


    To improve sensitivity of dental caries detection by laser-induced breakdown spectroscopy (LIBS) analysis, it is proposed to utilize emission peaks in the ultraviolet. We newly focused on zinc whose emission peaks exist in ultraviolet because zinc exists at high concentration in the outer layer of enamel. It was shown that by using ratios between heights of an emission peak of Zn and that of Ca, the detection sensitivity and stability are largely improved. It was also shown that early caries are differentiated from healthy part by properly setting a threshold in the detected ratios. The proposed caries detection system can be applied to dental laser systems such as ones based on Er:YAG-lasers. When ablating early caries part by laser light, the system notices the dentist that the ablation of caries part is finished. We also show the intensity of emission peaks of zinc decreased with ablation with Er:YAG laser light.

  1. Breakdown of chiral symmetry during saturation of the Tayler instability

    CERN Document Server

    Bonanno, Alfio; Del Sordo, Fabio; Mitra, Dhrubaditya


    We study spontaneous breakdown of chiral symmetry during the nonlinear evolution of the Tayler instability. We start with an initial stationary state of zero helicity. Within linearized perturbation calculations, helical perturbations of this initial state have the same growth rate for either sign of helicity. Direct numerical simulations (DNS) of the fully nonlinear equations however shows that an infinitesimal excess of one sign of helicity in the initial perturbation gives rise to a saturated helical state. We further show that this symmetry-breaking can be described by weakly nonlinear finite amplitude equations with undetermined coefficients which can be deduced solely from symmetry consideration. By fitting solutions of the amplitude equations to data from DNS we further determine the coefficients of the amplitude equations.

  2. Degeneracy breakdown as a source of supernovae Ia

    CERN Document Server

    Clavelli, L


    We pursue the investigation of a model for sub-Chandrasekhar supernovae Ia explosions (SNIa) in which the energy stored in the Pauli tower is released to trigger a nuclear deflagration. The simplest physical model for such a degeneracy breakdown is a phase transition to an exactly supersymmetric state in which the scalar partners of protons, neutrons, and leptons become degenerate with the familiar fermions of our world as in the supersymmetric standard model with susy breaking parameters relaxed to zero. We focus on the ability of the susy phase transition model to fit the total SNIa rate as well as the delay time distribution of SNIa after the birth of a progenitor white dwarf. We also study the ejected mass distribution and its correlation with delay time. Finally, we discuss the expected SNIa remnant in the form of a black hole of Jupiter mass or lower and the prospects for detecting such remnants.

  3. Apparatus, system, and method for laser-induced breakdown spectroscopy (United States)

    Effenberger, Jr., Andrew J; Scott, Jill R; McJunkin, Timothy R


    In laser-induced breakdown spectroscopy (LIBS), an apparatus includes a pulsed laser configured to generate a pulsed laser signal toward a sample, a constructive interference object and an optical element, each located in a path of light from the sample. The constructive interference object is configured to generate constructive interference patterns of the light. The optical element is configured to disperse the light. A LIBS system includes a first and a second optical element, and a data acquisition module. The data acquisition module is configured to determine an isotope measurement based, at least in part, on light received by an image sensor from the first and second optical elements. A method for performing LIBS includes generating a pulsed laser on a sample to generate light from a plasma, generating constructive interference patterns of the light, and dispersing the light into a plurality of wavelengths.

  4. Kertész line of thermally activated breakdown phenomena

    KAUST Repository

    Yoshioka, Naoki


    Based on a fiber bundle model we substantially extend the phase-transition analogy of thermally activated breakdown of homogeneous materials. We show that the competition of breaking due to stress enhancement and due to thermal fluctuations leads to an astonishing complexity of the phase space of the system: varying the load and the temperature a phase boundary emerges, separating a Griffith-type regime of abrupt failure analogous to first-order phase transitions from disorder dominated fracture where a spanning cluster of cracks emerges. We demonstrate that the phase boundary is the Kertész line of the system along which thermally activated fracture appears as a continuous phase transition analogous to percolation. The Kertész line has technological relevance setting the boundary of safe operation for construction components under high thermal loads. © 2010 The American Physical Society.

  5. Breakdown of the classical description of a local system

    DEFF Research Database (Denmark)

    Eran, Kot; Grønbech-Jensen, Niels; Nielsen, Bo Melholt


    We provide a straightforward demonstration of a fundamental difference between classical and quantum mechanics for a single local system: namely, the absence of a joint probability distribution of the position x and momentum p. Elaborating on a recently reported criterion by Bednorz and Belzig...... of the breakdown of a classical description of the underlying state. Most importantly, the criterion used does not rely on quantum mechanics and can thus be used to demonstrate nonclassicality of systems not immediately apparent to exhibit quantum behavior. The criterion is directly applicable to any system...... [ Phys. Rev. A 83 052113 (2011)] we derive a simple criterion that must be fulfilled for any joint probability distribution in classical physics. We demonstrate the violation of this criterion using the homodyne measurement of a single photon state, thus proving a straightforward signature...

  6. Time domain simulations of preliminary breakdown pulses in natural lightning

    CERN Document Server

    Carlson, B E; Bitzer, P; Christian, H


    Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mecha...

  7. Drell-Yan diffraction: breakdown of QCD factorization

    Energy Technology Data Exchange (ETDEWEB)

    Pasechnik, R.S. [Lund University, Theoretical High Energy Physics, Department of Astronomy and Theoretical Physics, Lund (Sweden); Kopeliovich, B.Z. [Universidad Tecnica Federico Santa Maria, Departamento de Fisica, Valparaiso (Chile); Instituto de Estudios Avanzados en Ciencias e Ingenieria, Valparaiso (Chile); Centro Cientifico-Tecnologico de Valparaiso, Valparaiso (Chile)


    We consider the diffractive Drell-Yan process in proton-(anti)proton collisions at high energies in the color dipole approach. The calculations are performed at forward rapidities of the leptonic pair. The effect of eikonalization of the universal ''bare'' dipole-target elastic amplitude in the saturation regime takes into account the principal part of the gap survival probability. We present predictions for the total and differential cross sections of the single-diffractive lepton-pair production at RHIC and LHC energies. We analyze implications of the QCD factorization breakdown in the diffractive Drell-Yan process, which is caused by a specific interplay of the soft and hard interactions, resulting in rather unusual properties of the corresponding observables. (orig.)

  8. Analytical study of seashell using laser-induced breakdown spectroscopy (United States)

    Ying, LI; Yanhong, GU; Ying, Zhang; Yuandong, LI; Yuan, LU


    Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy (LIBS) was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was related to the shell growth. A similar variation was also found when using a direct LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium (Ca) is qualified as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

  9. The electrical breakdown strength of pre-stretched elastomers, with and without sample volume conservation

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed;


    strength of polydimethylsiloxane (PDMS) elastomers. Breakdown strength was determined for samples with and without volume conservation and was found to depend strongly on the stretch ratio and the thickness of thesamples. PDMS elastomers are shown to increase breakdown strength by a factor of ∼3 when...


    Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

  11. Investigation of the current break-down phenomena in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, S.K.; Srinivasamurthy, N.; Agrawal, B.L. [Power Systems Group, ISRO Satellite Centre, Bangalore (India)


    Observed reverse current-voltage characteristics of the single crystal silicon and gallium arsenide solar cells have been analyzed. Physical mechanisms behind the junction break-down in silicon cells and current break-down in gallium arsenide cells have been identified. Preliminary estimates of the diffusion capacitance in GaAs cells have been presented

  12. The Analysis of Insulation Breakdown Probabilities by the Up-And-Down Method

    DEFF Research Database (Denmark)

    Vibholm (fratrådt), Svend; Thyregod, Poul


    This paper discusses the assessment of breakdown probability by means of the up-and-down method. The Dixon and Mood approximation to the maximum-likelihood estimate is compared with the exact maximum-likelihood estimate for a number of response patterns. Estimates of the 50D probability breakdown...

  13. Vortex Breakdown Generated by off-axis Bifurcation in a cylinder with rotating covers

    DEFF Research Database (Denmark)

    Bisgaard, Anders; Brøns, Morten; Sørensen, Jens Nørkær


    Vortex breakdown of bubble type is studied for the flow in a cylinder with rotating top and bottom covers. For large ratios of the angular velocities of the covers, we observe numerically that the vortex breakdown bubble in the steady regime may occur through the creation of an off-axis vortex ring...

  14. Electronic individual breakdown of pension rights and/or transfer value

    CERN Multimedia

    Pension Fund


    Commencing this year, members of the personnel will be notified by e-mail of their annual breakdown of pension rights and/or transfer value. Each person receiving the e-mail notification will be invited to consult this breakdown by clicking on a link protected by AISlogin and a password. Benefits Service of the Pension Fund  

  15. Electrical conduction mechanism in bulk ceramic insulators at high voltages until dielectric breakdown (United States)

    Neusel, C.; Jelitto, H.; Schneider, G. A.


    In order to develop and verify a dielectric breakdown model for bulk insulators thicker than 100 μm, the knowledge of the dominating conduction mechanism at high electric fields, or respectively voltages, is necessary. The dielectric breakdown is the electrical failure of an insulator. In some existing breakdown models, ohmic conduction is assumed as dominating conduction mechanism. For verification, the dominating dc conduction mechanism of bulk insulators at room temperature was investigated by applying high voltages up to 70 kV to the insulator until dielectric breakdown occurs. Four conduction models, namely, ohmic, space charge limited, Schottky, and Poole-Frenkel conduction, were employed to identify the dominating conduction mechanism. Comparing the calculated permittivities from the Schottky and Poole-Frenkel coefficients with experimentally measured permittivity, Schottky and Poole-Frenkel conduction can be excluded as dominating conduction mechanism. Based on the current density voltage characteristics (J-V-curve) and the thickness-dependence of the current density, space charge limited conduction (SCLC) was identified to be the dominating conduction mechanism at high voltages leading to dielectric breakdown. As a consequence, breakdown models based on ohmic conduction are not appropriate to explain the breakdown of the investigated bulk insulators. Furthermore, the electrical failure of the examined bulk insulators can only be described correctly by a breakdown model which includes SCLC as conduction mechanism.

  16. Microwave cavity diagnostics of microwave breakdown plasmas. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Eckstrom, D.J.; Williams, M.S. [SRI International, Menlo Park, CA (United States)


    We have performed microwave cavity perturbation measurements in the LLNL AIM facility using a 329-MHz cavity that allow us to examine in detail the plasma formation and decay processes for electron densities between approximately 10{sup 5} and 10{sup 7}/cm{sup 3}. We believe these to be the lowest density plasmas ever studied in microwave breakdown experiments, and as such they allow us to determine the power and energy required to produce plasmas suitable for HF radar reflection as well as the effective lifetimes of these plasmas before re-ionization is required. Analyses of these results leads to the following conclusions. (1) For microwave breakdown pulses varying from 0.6 to 2.4 {mu}s, the threshold power required to produce measurable plasmas is 30 to 12 MW/m{sup 2} at 0.01 torr, decreasing to 3.5 to 1.8 MW/m{sup 2} at 1 to 3 torr, and then increasing to 5 to 3.5 MW/m{sup 2} at 30 torr. The threshold power in each case decreases with increasing pulse length, but the required pulse energy increases with decreasing power or increasing pulse length. (2) The effective electron density decay rates are approximately 100/s for 0.1 to 1 torr, after which they increase linearly with pressure. Thus, the useful plasma lifetimes are in the range of 20 to 40 ms at the lower pressures and decrease to about 1 ms at 30 torr. These decay rates and lifetimes are comparable to those that would exist for artificially ionized regions in the upper atmosphere. (3) The collision frequencies measured at pressures of 1 torr and above correspond to electron temperatures of 800 K or less. In fact, the inferred temperatures for p > 3 torr are below room temperature. This may be due to a contribution to the measured conductivity by negative ions.

  17. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Mahdieh, Mohammad Hossein, E-mail:; Akbari Jafarabadi, Marzieh [Department of Physics, Iran University of Science and Technology, Narmak, Tehran 1684613114 (Iran, Islamic Republic of)


    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  18. Picosecond laser-induced breakdown at 5321 and 5347 A - Observation of frequency-dependent behavior (United States)

    Smith, W. L.; Bechtel, J. H.; Bloembergen, N.


    A study is presented of picosecond laser-induced breakdown at 3547 and 5321 A of several materials. The thresholds obtained for breakdown at 5321 A are compared to previous results obtained at 1.064 microns using the same laser system. This comparison illustrates the transition of bulk laser-induced breakdown as it becomes increasingly frequency dependent. UV picosecond pulses are obtained by mixing 5321 A and 1.064 micron pulses in a KH2PO4 crystal. Upper and lower bounds on the 3547 A breakdown threshold are defined, although some effects of walk-off distortion and self-focusing are observed. The results are discussed with reference to models for the intrinsic processes involved in the breakdown, i.e., avalanche and multiphoton ionization.

  19. Breakdown of accommodation in nerve: a possible role for persistent sodium current

    Directory of Open Access Journals (Sweden)

    Andersen Ole K


    Full Text Available Abstract Background Accommodation and breakdown of accommodation are important elements of information processing in nerve fibers, as they determine how nerve fibers react to natural slowly changing stimuli or electrical stimulation. The aim of the present study was to elucidate the biophysical mechanism of breakdown of accommodation, which at present is unknown. Results A model of a space-clamped motor nerve fiber was developed. It was found that this new model could reproduce breakdown of accommodation when it included a low-threshold, rapidly activating, persistent sodium current. However, the phenomenon was not reproduced when the persistent sodium current did not have fast activation kinetics or a low activation threshold. Conclusion The present modeling study suggests that persistent, low-threshold, rapidly activating sodium currents have a key role in breakdown of accommodation, and that breakdown of accommodation can be used as a tool for studying persistent sodium current under normal and pathological conditions.

  20. Study of predicting breakdown voltage of stator insulation in generator based on BP neural network

    Institute of Scientific and Technical Information of China (English)

    Jiang Yuao; Zhang Aide; Liu Libing; Du Yu; Gao Naikui; Peng Zongren


    The breakdown voltage plays an important role in evaluating residual life of stator insulation in generator. In this paper, we discussed BP neural network that was used to predict the breakdown voltage of stator insulation in generator of 300 MW/18 kV. At first the neural network has been trained by the samples that include the varieties of dielectric loss factor tanδ, the partial discharge parameters and breakdown voltage. Then we tried to predict the breakdown voltage of samples and stator insulations subjected to multi-stress aging by the trained neural network. We found that it's feasible and accurate to predict the voltage. This method can be applied to predict breakdown voltage of other generators which have the same insulation structure and material.

  1. Fatigue in patients with lung cancer is related with accelerated tryptophan breakdown.

    Directory of Open Access Journals (Sweden)

    Katharina Kurz

    Full Text Available BACKGROUND: Patients with cancer often suffer from fatigue and decreased quality of life which might be related to the breakdown of essential amino acid tryptophan. METHODS: In 50 patients with lung cancer we examined fatigue and the deterioration of quality of life in patients using the Functional Assessment of Cancer Therapy Anemia (FACT-An and -Fatigue (FACT-F subscales of FACT-General and the Mental adjustment to Cancer (MAC questionnaires. Results were compared with tryptophan breakdown as well as serum concentrations of immune activation markers. RESULTS: Scores of psychological tests correlated significantly with tryptophan breakdown and with circulatory markers of inflammation. However, immune activation and tryptophan breakdown were not related to MAC scores. CONCLUSIONS: Tryptophan breakdown relates with fatigue and impaired quality of life in patients with lung cancer, while declining tryptophan levels are not associated with patients'coping strategies.

  2. Investigation of efficient termination structure for improved breakdown properties of semiconductor radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Krizaj, D.; Resnik, D.; Vrtacnik, D.; Amon, S. [Univ. of Ljubljana (Slovenia). Faculty of Electrical Engineering; Cindro, V. [Jozef Stefan Inst., Ljubljana (Slovenia)


    Efficiency of a new junction termination structure for improvement of breakdown properties of semiconductor radiation detectors is investigated. The structure consists of a diffused resistor winding around the active junction in a spiral fashion. The current flow through the spiral enables controlled potential distribution along the spiral turns and thus controlled depletion spreading from the main junction, efficiently preventing premature avalanche breakdown. Both multiple guard-ring structures and spiral junction termination structures have shown good breakdown properties typically three to five times higher than breakdown voltages of diodes without junction termination. The breakdown voltages of spiral junction termination structures are only weakly influenced by changes in substrate doping concentration caused by neutron irradiation. They can thus be considered for termination of future semiconductor radiation detectors.

  3. Variables associated with family breakdown in healthy and obese/ overweigh adolescents

    Directory of Open Access Journals (Sweden)

    Carla Cristina J. N. de Almeida


    Full Text Available Objective: To evaluate the presence of family breakdown factors among eutrophic and overweight/obese adolescents. Methods: Cross-sectional study of 242 students aged between 14 and 19 years old, from a public school. Each student was weighed, measured and answered a questionnaire with closed questions addressing the presence of family breakdown factors. The adolescents were divided in two groups: euthophic and overweight/obese. The answers of both groups were compared by Fisher's exact and Mann-Whitney tests. Results: There was no statistically significant difference in the prevalence of the studied factors between the two groups. Comparing the number of positive answers (presence of family breakdown factors and negative ones (absence of family breakdown factors, no difference was observed between the groups. Conclusions: The inclusion of a control group showed that factors of family breakdown, usually identified as associated with obesity in adolescents, may also be present in eutrophic adolescents.

  4. Quantitative statistical analysis of dielectric breakdown in zirconia-based self-assembled nanodielectrics. (United States)

    Schlitz, Ruth A; Ha, Young-geun; Marks, Tobin J; Lauhon, Lincoln J


    Uniformity of the dielectric breakdown voltage distribution for several thicknesses of a zirconia-based self-assembled nanodielectric was characterized using the Weibull distribution. Two regimes of breakdown behavior are observed: self-assembled multilayers >5 nm thick are well described by a single two-parameter Weibull distribution, with β ≈ 11. Multilayers ≤5 nm thick exhibit kinks on the Weibull plot of dielectric breakdown voltage, suggesting that multiple characteristic mechanisms for dielectric breakdown are present. Both the degree of uniformity and the effective dielectric breakdown field are observed to be greater for one layer than for two layers of Zr-SAND, suggesting that this multilayer is more promising for device applications.

  5. Communication breakdowns in normal and language learning-disabled children's conversation and narration. (United States)

    MacLachlan, B G; Chapman, R S


    The frequency and type of communication breakdowns occurring in the speech of 7 language learning-disabled children (LLD), aged 9:10-11:1 (years:months), were examined in two conditions, conversation and narration, and compared to a group of 7 normal peers matched for chronological age and 7 peers matched for mean length of communication unit in conversation. Types of communication breakdowns examined included stalls, repairs, and abandoned utterances. The LLD group incurred a significantly greater rate of communication breakdowns per communication unit in narration than conversation compared to control group differences. Mean length of communication unit was also significantly greater in narration than conversation for the LLD group compared to controls. For all groups, across both speech sample conditions, longer communication units contained more breakdowns than shorter ones. The groups did not differ in the types of breakdowns. Communication unit length and the nature of the narrative task may account for the increased dysfluencies in LLD children's speech.


    Institute of Scientific and Technical Information of China (English)



    The Galerkin and least-squares methods are two classes of the most popular Krylovsubspace methOds for solving large linear systems of equations. Unfortunately, both the methodsmay suffer from serious breakdowns of the same type: In a breakdown situation the Galerkinmethod is unable to calculate an approximate solution, while the least-squares method, althoughdoes not really break down, is unsucessful in reducing the norm of its residual. In this paper wefrst establish a unified theorem which gives a relationship between breakdowns in the two meth-ods. We further illustrate theoretically and experimentally that if the coefficient matrix of alienar system is of high defectiveness with the associated eigenvalues less than 1, then the restart-ed Galerkin and least-squares methods will be in great risks of complete breakdowns. It appearsthat our findings may help to understand phenomena observed practically and to derive treat-ments for breakdowns of this type.

  7. Effect of air breakdown with a focusing lens on ultrashort laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hu Wenqian; Shin, Yung C.; King, Galen [School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)


    The effect of air breakdown on ultrashort laser ablation is investigated in this letter using an integrated simulation method on atomistic level. The generation of air breakdown with different laser peak power densities in the range from 10{sup 13} to 10{sup 16} W/cm{sup 2} and various focusing conditions is analyzed. Air breakdown is generated directly from laser energy absorption through avalanche ionization at a high power density (over 10{sup 14} W/cm{sup 2}), while at a lower power density, air breakdown is assisted by a metal target near the focal region. The laser energy loss due to air breakdown and its effect on laser ablation are studied.

  8. DC breakdown characteristics of silicone polymer composites for HVDC insulator applications (United States)

    Han, Byung-Jo; Seo, In-Jin; Seong, Jae-Kyu; Hwang, Young-Ho; Yang, Hai-Won


    Critical components for HVDC transmission systems are polymer insulators, which have stricter requirements that are more difficult to achieve compared to those of HVAC insulators. In this study, we investigated the optimal design of HVDC polymer insulators by using a DC electric field analysis and experiments. The physical properties of the polymer specimens were analyzed to develop an optimal HVDC polymer material, and four polymer specimens were prepared for DC breakdown experiments. Single and reverse polarity breakdown tests were conducted to analyze the effect of temperature on the breakdown strength of the polymer. In addition, electric fields were analyzed via simulations, in which a small-scale polymer insulator model was applied to prevent dielectric breakdown due to electric field concentration, with four DC operating conditions taken into consideration. The experimental results show that the electrical breakdown strength and the electric field distribution exhibit significant differences in relation to different DC polarity transition procedures.

  9. Validation of an Academic Listening Test: Effects of "Breakdown" Tests and Test Takers' Cognitive Awareness of Listening Processes (United States)

    Chi, Youngshin


    This study investigated the breakdown effect of a listening comprehension test, whether test takers are affected in comprehending lectures by impediments, and collected test takers' cognitive awareness on test tasks which contain listening breakdown factors how they perceived these impediments. In this context of the study, a "Breakdown" is a test…

  10. Breakdown in the Organ Donation Process and Its Effect on Organ Availability

    Directory of Open Access Journals (Sweden)

    Manik Razdan


    Full Text Available Background. This study examines the effect of breakdown in the organ donation process on the availability of transplantable organs. A process breakdown is defined as a deviation from the organ donation protocol that may jeopardize organ recovery. Methods. A retrospective analysis of donation-eligible decedents was conducted using data from an independent organ procurement organization. Adjusted effect of process breakdown on organs transplanted from an eligible decedent was examined using multivariable zero-inflated Poisson regression. Results. An eligible decedent is four times more likely to become an organ donor when there is no process breakdown (adjusted OR: 4.01; 95% CI: 1.6838, 9.6414; P<0.01 even after controlling for the decedent’s age, gender, race, and whether or not a decedent had joined the state donor registry. However once the eligible decedent becomes a donor, whether or not there was a process breakdown does not affect the number of transplantable organs yielded. Overall, for every process breakdown occurring in the care of an eligible decedent, one less organ is available for transplant. Decedent’s age is a strong predictor of likelihood of donation and the number of organs transplanted from a donor. Conclusion. Eliminating breakdowns in the donation process can potentially increase the number of organs available for transplant but some organs will still be lost.

  11. Breakdown and space charge formation in polyimide film under DC high stress at various temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kishi, Y; Hashimoto, T; Miyake, H; Tanaka, Y; Takada, T, E-mail: [Tokyo City University, 1-28-1, Tamatsutsumi, Setagaya-ku, Tokyo (Japan)


    Relationship between breakdown strength and space charge formation in polyimide film under dc high stress at various temperatures is investigated using pulsed electro-acoustic (PEA) method. Some typical results of the space charge observations show that hetero space charges are always found before breakdown. The amount of the hetero charges increase with increase of temperature or increase of applied electric field. Since the enhancement of the internal electric field in the sample by the accumulation of the hetero charges is not so large, the accumulation doesn't seem to be an immediate cause of breakdown. However since it is always observed before breakdown, it may be predictive information for breakdown. In a certain case, the breakdown occurs after voltage application for few hours. However, while we give an interval of short circuit condition after observing the hetero space charge under dc stress, the total voltage application time to breakdown is almost the same to the case without the interval. It means that the hetero space charge generation may show a kind of degradation of the material.

  12. Breakdown Voltage Research of Penning Gas Mixture in Plasma Display Panel

    Institute of Scientific and Technical Information of China (English)

    Guo Bingang; Liu Chunliang; Song Zhongxiao; Fan Yufeng; Xia Xing; Liu Liu; Fan Duowang


    Paschen law and equations, which ignore the influence of the Penning ionization on the electron ionization coefficient (α), are always used as the approximation of the breakdown voltage criterion of the Penning gas mixture in current researches of discharge characteristics of the plasma display panel (PDP). It is doubtful that whether their results match the facts. Based on the Townsend gas self-sustaining discharge condition and the chemical kinetics analysis of the Penning gas mixture discharging in PDP, the empirical equation to describe the breakdown of the Penning gas mixture is given. It is used to calculate the breakdown voltage curves of Ne-Xe/MgO and Ne-Ar/MgO in a testing macroscopic discharge cell of AC-PDP. The effective secondary electron emission coefficients (γeff) of the MgO protective layers are derived by comparing the breakdown voltage curves obtained from the empirical equation with the experimental data of breakdown voltages. In comparison with the results calculated by the Paschen law and the equation which ignore the influence of the Penning ionization on α , the results calculated by the empirical equation have better conformity with experimental data. The empirical equation characterizes the breakdown of the Penning gas mixture in PDP effectively, and gives a convenient way to study its breakdown characteristics and the secondary electron emission behaviors.

  13. Mask characterization for CDU budget breakdown in advanced EUV lithography (United States)

    Nikolsky, Peter; Strolenberg, Chris; Nielsen, Rasmus; Nooitgedacht, Tjitte; Davydova, Natalia; Yang, Greg; Lee, Shawn; Park, Chang-Min; Kim, Insung; Yeo, Jeong-Ho


    As the ITRS Critical Dimension Uniformity (CDU) specification shrinks, semiconductor companies need to maintain a high yield of good wafers per day and a high performance (and hence market value) of finished products. This cannot be achieved without continuous analysis and improvement of on-product CDU as one of the main drivers for process control and optimization with better understanding of main contributors from the litho cluster: mask, process, metrology and scanner. In this paper we will demonstrate a study of mask CDU characterization and its impact on CDU Budget Breakdown (CDU BB) performed for an advanced EUV lithography with 1D and 2D feature cases. We will show that this CDU contributor is one of the main differentiators between well-known ArFi and new EUV CDU budgeting principles. We found that reticle contribution to intrafield CDU should be characterized in a specific way: mask absorber thickness fingerprints play a role comparable with reticle CDU in the total reticle part of the CDU budget. Wafer CD fingerprints, introduced by this contributor, may or may not compensate variations of mask CD's and hence influence on total mask impact on intrafield CDU at the wafer level. This will be shown on 1D and 2D feature examples in this paper. Also mask stack reflectivity variations should be taken into account: these fingerprints have visible impact on intrafield CDs at the wafer level and should be considered as another contributor to the reticle part of EUV CDU budget. We observed also MEEF-through-field fingerprints in the studied EUV cases. Variations of MEEF may also play a role for the total intrafield CDU and may be taken into account for EUV Lithography. We characterized MEEF-through-field for the reviewed features, the results to be discussed in our paper, but further analysis of this phenomenon is required. This comprehensive approach to characterization of the mask part of EUV CDU characterization delivers an accurate and integral CDU Budget

  14. Anomalous memory effect in the breakdown of low-pressure argon in a long discharge tube

    Energy Technology Data Exchange (ETDEWEB)

    Meshchanov, A. V.; Korshunov, A. N.; Ionikh, Yu. Z., E-mail: [St. Petersburg State University (Russian Federation); Dyatko, N. A. [Troitsk Institute for Innovation and Fusion Research (Russian Federation)


    The characteristics of breakdown of argon in a long tube (with a gap length of 75 cm and diameter of 2.8 cm) at pressures of 1 and 5 Torr and stationary discharge currents of 5–40 mA were studied experimentally. The breakdown was initiated by paired positive voltage pulses with a rise rate of ∼10{sup 8}–10{sup 9} V/s and duration of ∼1–10 ms. The time interval between pairs was varied in the range of Τ ∼ 0.1–1 s, and that between pulses in a pair was varied from τ = 0.4 ms to ≈Τ/2. The aim of this work was to detect and study the so-called “anomalous memory effect” earlier observed in breakdown in nitrogen. The effect consists in the dynamic breakdown voltage in the second pulse in a pair being higher than in the first pulse (in contrast to the “normal” memory effect, in which the relation between the breakdown voltages is opposite). It is found that this effect is observed when the time interval between pairs of pulses is such that the first pulse in a pair is in the range of the normal memory effect of the preceding pair (under the given conditions, Τ ≈ 0.1–0.4 s). In this case, at τ ∼ 10 ms, the breakdown voltage of the second pulse is higher than the reduced breakdown voltage of the first pulse. Optical observations of the ionization wave preceding breakdown in a long tube show that, in the range of the anomalous memory effect and at smaller values of τ, no ionization wave is detected before breakdown in the second pulse. A qualitative interpretation of the experimental results is given.

  15. Convergence of detrital stoichiometry predicts thresholds of nutrient-stimulated breakdown in streams. (United States)

    Manning, David W P; Rosemond, Amy D; Gulis, Vladislav; Benstead, Jonathan P; Kominoski, John S; Maerz, John C


    Nutrient enrichment of detritus-based streams increases detrital resource quality for consumers and stimulates breakdown rates of particulate organic carbon (C). The relative importance of dissolved inorganic nitrogen (N) vs. phosphorus (P) for detrital quality and their effects on microbial- vs. detritivore-mediated detrital breakdown are poorly understood. We tested effects of experimental N and P additions on detrital stoichiometry (C:N, C:P) and total and microbial breakdown (i.e., with and without detritivorous shredders, respectively) of five detritus types (four leaf litter species and wood) with different initial C : nutrient content. We enriched five headwater streams continuously for two years at different relative availabilities of N and P and compared breakdown rates and detrital stoichiometry to pretreatment conditions. Total breakdown rates increased with nutrient enrichment and were predicted by altered detrital stoichiometry. Streamwater N and P, fungal biomass, and their interactions affected stoichiometry of detritus. Streamwater N and P decreased detrital C:N, whereas streamwater P had stronger negative effects on detrital C:P. Nutrient addition and fungal biomass reduced C:N by 70% and C:P by 83% on average after conditioning, compared to only 26% for C:N and 10% for C:P under pretreatment conditions. Detritus with lowest initial nutrient content changed the most and had greatest increases in total breakdown rates. Detrital stoichiometry was reduced and differences among detritus types were homogenized by nutrient enrichment. With enrichment, detrital nutrient content approached detritivore nutritional requirements and stimulated greater detritivore vs. microbial litter breakdown. We used breakpoint regression to estimate values of detrital stoichiometry that can potentially be used to indicate elevated breakdown rates. Breakpoint ratios for total breakdown were 41 (C:N) and 1518 (C:P), coinciding with total breakdown rates that were ~1.9

  16. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)


    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  17. Measurements of electron avalanche formation time in W-band microwave air breakdown (United States)

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.


    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  18. Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility

    CERN Document Server

    Paramonov, V V


    The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.

  19. Measurement of Irradiated Pyroprocessing Samples via Laser Induced Breakdown Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Phongikaroon, Supathorn [Virginia Commonwealth Univ., Richmond, VA (United States)


    The primary objective of this research is to develop an applied technology and provide an assessment to remotely measure and analyze the real time or near real time concentrations of used nuclear fuel (UNF) dissolute in electrorefiners. Here, Laser-Induced Breakdown Spectroscopy (LIBS), in UNF pyroprocessing facilities will be investigated. LIBS is an elemental analysis method, which is based on the emission from plasma generated by focusing a laser beam into the medium. This technology has been reported to be applicable in the media of solids, liquids (includes molten metals), and gases for detecting elements of special nuclear materials. The advantages of applying the technology for pyroprocessing facilities are: (i) Rapid real-time elemental analysis|one measurement/laser pulse, or average spectra from multiple laser pulses for greater accuracy in < 2 minutes; (ii) Direct detection of elements and impurities in the system with low detection limits|element specific, ranging from 2-1000 ppm for most elements; and (iii) Near non-destructive elemental analysis method (about 1 g material). One important challenge to overcome is achieving high-resolution spectral analysis to quantitatively analyze all important fission products and actinides. Another important challenge is related to accessibility of molten salt, which is heated in a heavily insulated, remotely operated furnace in a high radiation environment with an argon atmosphere.

  20. Unsupervised verification of laser-induced breakdown spectroscopy dataset clustering (United States)

    Wójcik, Michał R.; Zdunek, Rafał; Antończak, Arkadiusz J.


    Laser-induced breakdown spectroscopy is a versatile, optical technique used in a wide range of qualitative and quantitative analyses conducted with the use of various chemometric techniques. The aim of this research is to demonstrate the possibility of unsupervised clustering of an unknown dataset using K-means clustering algorithm, and verifying its input parameters through investigating generalized eigenvalues derived with linear discriminant analysis. In all the cases, principal component analyses have been applied to reduce data dimensionality and shorten computation time of the whole operation. The experiment was conducted on a dataset collected from twenty four different materials divided into six groups: metals, semiconductors, ceramics, rocks, metal alloys and others with the use of a three-channel spectrometer (298.02-628.73nm overall spectral range) and a UV (248nm) excimer laser. Additionally, two more complex groups containing all specimens and all specimens excluding rocks were created. The resulting spaces of eigenvalues were calculated for every group and three different distances in the multidimensional space (cosine, square Euclidean and L1). As expected, the correct numbers of specimens within groups with small deviations were obtained, and the validity of the unsupervised method has thus been proven.

  1. Behavioral and spermatogenic hybrid male breakdown in Nasonia. (United States)

    Clark, M E; O'Hara, F P; Chawla, A; Werren, J H


    Several reproductive barriers exist within the Nasonia species complex, including allopatry, premating behavioral isolation, postzygotic inviability and Wolbachia-induced cytoplasmic incompatibility. Here we show that hybrid males suffer two additional reproductive disadvantages, an inability to properly court females and decreased sperm production. Hybrid behavioral sterility, characterized by a reduced ability of hybrids to perform necessary courtship behaviors, occurs in hybrids between two species of Nasonia. Hybrid males produced in crosses between N. vitripennis and N. giraulti courted females at a reduced frequency (23-69%), compared with wild-type N. vitripennis and N. giraulti males (>93%). Reduced courtship frequency was not a simple function of inactivity among hybrids. A strong effect of cytoplasmic (mitochondrial) background was also found in N. vitripennis and N. giraulti crosses; F2 hybrids with giraulti cytoplasm showing reduced ability at most stages of courtship. Hybrids produced between a younger species pair, N. giraulti and N. longicornis, were behaviorally fertile. All males possessed motile sperm, but sperm production is greatly reduced in hybrids between the older species pair, N. vitripennis and N. giraulti. This effect on hybrid males, lowered sperm counts rather than nonfunctional sperm, is different from most described cases of hybrid male sterility, and may represent an earlier stage of hybrid sperm breakdown. The results add to previous studies of F2 hybrid inviability and behavioral sterility, and indicate that Wolbachia-induced hybrid incompatibility has arisen early in species divergence, relative to behavioral sterility and spermatogenic infertility.

  2. Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy (United States)

    W, A. Farooq; M, Atif; W, Tawfik; M, S. Alsalhi; Z, A. Alahmed; M, Sarfraz; J, P. Singh


    Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

  3. Laser-induced breakdown spectroscopy for polymer identification. (United States)

    Grégoire, Sylvain; Boudinet, Marjorie; Pelascini, Frédéric; Surma, Fabrice; Detalle, Vincent; Holl, Yves


    This study aims at differentiating several organic materials, particularly polymers, by laser induced breakdown spectroscopy. The goal is to apply this technique to the fields of polymer recycling and cultural heritage conservation. We worked with some usual polymers families: polyethylene (PE), polypropylene (PP), polyoxymethylene, (POM), poly(vinyl chloride), polytetrafluoroethylene, polyoxyethylene (POE), and polyamide for the aliphatic ones, and poly(butylene terephthalate), acrylonitrile-butadiene-styrene, polystyrene, and polycarbonate for the aromatic ones. The fourth harmonic of a Nd:YAG laser (266 nm) in ambient air at atmospheric pressure was used. A careful analysis of the C(2) Swan system (0,0) band in polymers containing no C-C (POM), few C-C (POE), or aromatic C-C linkages led us to the conclusion that the C(2) signal might be native, i.e., the result of direct ablation from the sample. With use of these results, aliphatic and aromatic polymers could be differentiated. Further data treatments, such as properly chosen line ratios, principal component analysis, and partial least squares regression, were evaluated. It was shown that many polymers could be separated, including PE and PP, despite their similar chemical structures.

  4. Flux-freezing breakdown in high-conductivity magnetohydrodynamic turbulence. (United States)

    Eyink, Gregory; Vishniac, Ethan; Lalescu, Cristian; Aluie, Hussein; Kanov, Kalin; Bürger, Kai; Burns, Randal; Meneveau, Charles; Szalay, Alexander


    The idea of 'frozen-in' magnetic field lines for ideal plasmas is useful to explain diverse astrophysical phenomena, for example the shedding of excess angular momentum from protostars by twisting of field lines frozen into the interstellar medium. Frozen-in field lines, however, preclude the rapid changes in magnetic topology observed at high conductivities, as in solar flares. Microphysical plasma processes are a proposed explanation of the observed high rates, but it is an open question whether such processes can rapidly reconnect astrophysical flux structures much greater in extent than several thousand ion gyroradii. An alternative explanation is that turbulent Richardson advection brings field lines implosively together from distances far apart to separations of the order of gyroradii. Here we report an analysis of a simulation of magnetohydrodynamic turbulence at high conductivity that exhibits Richardson dispersion. This effect of advection in rough velocity fields, which appear non-differentiable in space, leads to line motions that are completely indeterministic or 'spontaneously stochastic', as predicted in analytical studies. The turbulent breakdown of standard flux freezing at scales greater than the ion gyroradius can explain fast reconnection of very large-scale flux structures, both observed (solar flares and coronal mass ejections) and predicted (the inner heliosheath, accretion disks, γ-ray bursts and so on). For laminar plasma flows with smooth velocity fields or for low turbulence intensity, stochastic flux freezing reduces to the usual frozen-in condition.

  5. Analysis of Pulverized Coal by Laser-Induced Breakdown Spectroscopy

    Institute of Scientific and Technical Information of China (English)


    Laser-induced breakdown spectroscopy (LIBS) has been used to detect atomic species in various environments. The quantitative analysis (C, H, O, N and S) of representative coal samples are being carried out with LIBS, and the effects of particle size are analyzed.A powerful pulse Nd:YAG laser is focused on the coal sample at atmosphere pressure, and the emission spectra from laser-induced plasmas are measured by time-resolved spectroscopy, and the intensity of analyzed spectral lines is obtained through observing the laser plasma with a delay time of 0.4μs. The experimental results show that the slope of calibration curve is nearly 1 when the concentration of the analyzed element is relatively low, and the slope of curve is nearly 0.5 when the concentration of C is higher than other elements. In addition, using the calibration-free model without self-absorption effect, the results show that the decreasing of particle size leads to an increase of the plasma temperature.

  6. Analysis Code for High Gradient Dielectric Insulator Surface Breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ives, Robert Lawrence [Calabazas Creek Research, Inc.; Verboncoeur, John [University of California - Berkeley; Aldan, Manuel [University of California, Berkeley


    High voltage (HV) insulators are critical components in high-energy, accelerator and pulsed power systems that drive diverse applications in the national security, nuclear weapons science, defense and industrial arenas. In these systems, the insulator may separate vacuum/non-vacuum regions or conductors with high electrical field gradients. These insulators will often fail at electric fields over an order of magnitude lower than their intrinsic dielectric strength due to flashover at the dielectric interface. Decades of studies have produced a wealth of information on fundamental processes and mechanisms important for flashover initiation, but only for relatively simple insulator configurations in controlled environments. Accelerator and pulsed power system designers are faced with applying the fundamental knowledge to complex, operational devices with escalating HV requirements. Designers are forced to rely on “best practices” and expensive prototype testing, providing boundaries for successful operation. However, the safety margin is difficult to estimate, and system design must be very conservative for situations where testing is not practicable, or replacement of failed parts is disruptive or expensive. The Phase I program demonstrated the feasibility of developing an advanced code for modeling insulator breakdown. Such a code would be of great interest for a number of applications, including high energy physics, microwave source development, fusion sciences, and other research and industrial applications using high voltage devices.

  7. Single machine stochastic JIT scheduling problem subject to machine breakdowns

    Institute of Scientific and Technical Information of China (English)


    In this paper we research the single machine stochastic JIT scheduling problem subject to the machine breakdowns for preemptive-resume and preemptive-repeat.The objective function of the problem is the sum of squared deviations of the job-expected completion times from the due date.For preemptive-resume,we show that the optimal sequence of the SSDE problem is V-shaped with respect to expected processing times.And a dynamic programming algorithm with the pseudopolynomial time complexity is given.We discuss the difference between the SSDE problem and the ESSD problem and show that the optimal solution of the SSDE problem is a good approximate optimal solution of the ESSD problem,and the optimal solution of the SSDE problem is an optimal solution of the ESSD problem under some conditions.For preemptive-repeat,the stochastic JIT scheduling problem has not been solved since the variances of the completion times cannot be computed.We replace the ESSD problem by the SSDE problem.We show that the optimal sequence of the SSDE problem is V-shaped with respect to the expected occupying times.And a dynamic programming algorithm with the pseudopolynomial time complexity is given.A new thought is advanced for the research of the preemptive-repeat stochastic JIT scheduling problem.

  8. Laser induced breakdown spectroscopy with picosecond pulse train (United States)

    Lednev, Vasily N.; Pershin, Sergey M.; Sdvizhenskii, Pavel A.; Grishin, Mikhail Ya; Davydov, Mikhail A.; Stavertiy, Anton Ya; Tretyakov, Roman S.


    Picosecond pulse train and nanosecond pulse were compared for laser ablation and laser induced breakdown spectroscopy (LIBS) measurements. A detailed study revealed that the picosecond pulse train ablation improved the quality of laser craters (symmetric crater walls and the absence of large redeposited droplets), which was explained by a smaller heat affected zone and suppression of melt splash. Greater plasma dimensions and brighter plasma emission were observed by gated imaging for picosecond pulse train compared to nanosecond pulse ablation. Increased intensity of atomic and ionic lines in gated and time integrated spectra provided better signal-to-noise ratio for picosecond pulse train sampling. Higher temperature and electron density were detected during first microsecond for the plasma induced by the picosecond pulse train. Improved shot-to-shot reproducibility for atomic/ionic line intensity in the case of picosecond pulse train LIBS was explained by more effective atomization of target material in plasma and better quality of laser craters. Improved precision and limits of detections were determined for picosecond pulse train LIBS due to better reproducibility of laser sampling and increased signal-to-noise ratio.

  9. Fast restoration of large area breakdown for power distribution systems

    Institute of Scientific and Technical Information of China (English)

    LIU Jian; XU Jing-qiu; CHENG Hong-li


    An adjacent table-based simplified model of distribution networks containing medium voltage buses of a substation is established.Identification of bus outage and the condition to start fast restoration procedure are discussed.A complex load shading parameter is set up to describe various load shading schemes.The imaginary part of the load shading parameter describes the states of switches of load shading schemes while the real part is the corresponding amount of shaded load.A new concept of independent tripping operation is also put forward.The procedure to search the operation with the least amount of shaded load for a feeder and a connected domain are detailed.The procedure for fast restoration of a large area breakdown of the whole distribution network under emergency states is dealt with using a typical grid distribution network as an example.Results of analysis show that the direct load shading scheme under the most balanced topology is not always the optimal scheme.The proposed method can obtain the optimal operating mode with the least amount of shaded load thus showing its feasibility.

  10. High Voltage Breakdown Levels in Various EPC Potting Materials (United States)

    Komm, David S.


    This viewgraph presentation reviews exploration activities at JPL into various potting materials. Since high power space-borne microwave transmitters invariably use a vacuum tube as a final power amplifier, and this tube requires high electrode voltages for operation. The associated high voltage insulation typically represents a significant fraction of the mass of the transmitter. Since mass is always a premium resource on board spacecraft, we have been investigating materials with the potential to reduce the mass required for our applications here at JPL. This paper describes electrical breakdown results obtained with various potting materials. Conathane EN-11 (polyurethane) is the traditional HVPS encapsulant at JPL, but due to temperature limitations and durability issues it was deemed inappropriate for the particular application (i.e., CloudSat radar). The choices for the best available materials were epoxies, or silicones. Epoxies are too rigid, and were deemed inadvisable. Two silicones were further investigated (i.e.,ASTM E595- 93e2: GE RTV566(R) and Dow Corning 93-500X(R), another compound was considered (i.e., DC material, Sylgard 184(R)). "Loading" (adding filler materials) the potting compound will frequently alter the final material properties. Powdered alumina and borosilicate glass known as "microballoons" were investigated as possible loading materials. The testing of the materials is described. Each of the two loading materials offers advantages and disadvantages. The advantages and disadvantages are described.

  11. Laser-induced breakdown spectroscopy of tantalum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan)


    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  12. Analysis of bakery products by laser-induced breakdown spectroscopy. (United States)

    Bilge, Gonca; Boyacı, İsmail Hakkı; Eseller, Kemal Efe; Tamer, Uğur; Çakır, Serhat


    In this study, we focused on the detection of Na in bakery products by using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method. LIBS experiments were performed to examine the Na at 589 nm to quantify NaCl. A series of standard bread sample pellets containing various concentrations of NaCl (0.025-3.5%) were used to construct the calibration curves and to determine the detection limits of the measurements. Calibration graphs were drawn to indicate functions of NaCl and Na concentrations, which showed good linearity in the range of 0.025-3.5% NaCl and 0.01-1.4% Na concentrations with correlation coefficients (R(2)) values greater than 0.98 and 0.96. The obtained detection limits for NaCl and Na were 175 and 69 ppm, respectively. Performed experimental studies showed that LIBS is a convenient method for commercial bakery products to quantify NaCl concentrations as a rapid and in situ technique.

  13. Fast analysis of wood preservers using laser induced breakdown spectroscopy (United States)

    Uhl, A.; Loebe, K.; Kreuchwig, L.


    Laser-induced breakdown spectroscopy (LIBS) is used for the investigation of wood preservers in timber and in furniture. Both experiments in laboratory and practical applications in recycling facilities and on a building site prove the new possibilities for the fast detection of harmful agents in wood. A commercial system was developed for mobile laser-plasma-analysis as well as for industrial use in sorting plants. The universal measuring principle in combination with an Echelle optics permits real simultaneous multi-element-analysis in the range of 200-780 nm with a resolution of a few picometers. It enables the user to detect main and trace elements in wood within a few seconds, nearly independent of the matrix, knowing that different kinds of wood show an equal elemental composition. Sample preparation is not required. The quantitative analysis of inorganic wood preservers (containing, e.g. Cu, Cr, B, As, Pb, Hg) has been performed exactly using carbon as reference element. It can be shown that the detection limits for heavy metals in wood are in the ppm-range. Additional information is given concerning the quantitative analysis. Statistical data, e.g. the standard deviation (S.D.), were determined and calibration curves were used for each particular element. A comparison between ICP-AES and LIBS is given using depth profile correction factors regarding the different penetration depths with respect to the different volumes in wood analyzed by both analytical methods.

  14. Enhancing the analytical performance of laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cremers, D.A.; Chinni, R.C.; Pichahchy, A.E.; Thornquist, H.K.


    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this work is to enhance the analytical capabilities of laser-induced breakdown spectroscopy (LIBS). LIBS is a method of elemental analysis in which powerful laser pulses are focused on a sample to form a microplasma. LIBS is perhaps the most versatile elemental analysis method, applicable to a variety of different real-world analysis problems. Therefore, it is important to enhance the capabilities of the method as much as possible. Accomplishments include: (1) demonstration of signal enhancements of 5--30 times from soils and metals using a double pulse method; (2) development of a model of the observed enhancement obtained using double pulses; (3) demonstration that the analytical performance achievable using low laser-pulse energies (10 and 25 mJ) can match that achievable using an energy of 100 mJ; and (4) demonstration that time-gated detection is not necessary with LIBS.

  15. Altitude Correction for Breakdown Voltages of Long Air-Gaps

    Institute of Scientific and Technical Information of China (English)

    Wang Xuan; Li Yunge; Cao Xiaolong; Su Zhiyi; Liu Ying


    The breakdown voltage of long air-gaps in high-voltage transmission systems depends on not only the waveform of the applied voltage, but also the atmospheric conditions. Based on the results of the research project on the minimum air clearance for 800-Kv HVDC substations at high altitudes, and also on the monthly and yearly statistics of the atmospheric data of last ten years and the altitude correction of the atmospheric data of last ten years, the altitude correction of the air-gaps for the 800-Kv DC system under plan, 500-Kv AC system to be built, and 1000-Kv AC system under plan in the Inner Mongolia Plateau and the Yungui Plateau in China were studied with parameter G method. Correction factors for switching and lightning impulses were calculated and then compared with those achieved according to IEC 71. It is shown that IEC 71 is appropriate for damp regions, and correction factors differ between plateau regions in China because of different atmospheric conditions.

  16. Communication and pragmatic breakdowns in amyotrophic lateral sclerosis patients. (United States)

    Bambini, Valentina; Arcara, Giorgio; Martinelli, Ilaria; Bernini, Sara; Alvisi, Elena; Moro, Andrea; Cappa, Stefano F; Ceroni, Mauro


    While there is increasing attention toward cognitive changes in amyotrophic lateral sclerosis (ALS), the domain of pragmatics, defined as the ability to integrate language and context to engage in successful communication, remains unexplored. Here we tested pragmatic abilities in 33 non-demented ALS patients and 33 healthy controls matched for age and education through 6 different tasks, ranging from discourse organization to the comprehension of figurative language, further grouped in three composite measures for pragmatic production, pragmatic comprehension and global pragmatic abilities. For a subgroup of patients, assessment included executive functions and social cognition skills. ALS patients were impaired on all pragmatic tasks relative to controls, with 45% of the patients performing below cut-off in at least one pragmatic task, and 36% impaired on the global pragmatic score. Pragmatic breakdowns were more common than executive deficit as defined by the consensus criteria, and approximately as prevalent as deficits in social cognition. Multiple regression analyses support the idea of an interplay of executive and social cognition abilities in determining the pragmatic performance, although all these domains show some degree of independence. These findings shed light on pragmatic impairment as a relevant dimension of ALS, which deserves further consideration in defining the cognitive profile of the disease, given its vital role for communication and social interaction in daily life.

  17. Hawking radiation with dispersion versus breakdown of WKB

    CERN Document Server

    Schützhold, R


    Inspired by the condensed matter analogues of black holes (a.k.a. dumb holes), we study Hawking radiation in the presence of a modified dispersion relation which becomes super-luminal at large wave-numbers. In the usual stationary coordinates $(t,x)$, one can describe the asymptotic evolution of the wave-packets in WKB, but this WKB approximation breaks down in the vicinity of the horizon, thereby allowing for a mixing between initial and final creation and annihilation operators. Thus, one might be tempted to identify this point where WKB breaks down with the moment of particle creation. However, using different coordinates $(\\tau,U)$, we find that one can evolve the waves so that WKB in these coordinates is valid throughout this transition region -- which contradicts the above identification of the breakdown of WKB as the cause of the radiation. Instead, our analysis suggests that the tearing apart of the waves into two different asymptotic regions (inside and outside the horizon) is the major ingredient of...

  18. Laser-induced breakdown plasma-based sensors (United States)

    Griffin, Steven T.


    Laser Induced Breakdown Spectroscopy (LIBS) is dependent on the interaction between the initiating Laser sequence, the sampled material and the intermediate plasma states. Pulse shaping and timing have been empirically demonstrated to have significant impact on the signal available for active/passive detection and identification. The transient nature of empirical LIBS work makes data collection for optimization an expensive process. Guidance from effective computer simulation represents an alternative. This computational method for CBRNE sensing applications models the Laser, material and plasma interaction for the purpose of performance prediction and enhancement. This paper emphasizes the aspects of light, plasma, and material interaction relevant to portable sensor development for LIBS. The modeling structure emphasizes energy balances and empirical fit descriptions with limited detailed-balance and finite element approaches where required. Dusty plasma from partially decomposed material sample interaction with pulse dynamics is considered. This heuristic is used to reduce run times and computer loads. Computer simulations and some data for validation are presented. A new University of Memphis HPC/super-computer (~15 TFLOPS) is used to enhance simulation. Results coordinated with related effort at Arkansas State University. Implications for ongoing empirical work are presented with special attention paid to the application of compressive sensing for signal processing, feature extraction, and classification.

  19. Saccharide breakdown and fermentation by the honey bee gut microbiome. (United States)

    Lee, Fredrick J; Rusch, Douglas B; Stewart, Frank J; Mattila, Heather R; Newton, Irene L G


    The honey bee, the world's most important agricultural pollinator, relies exclusively on plant-derived foods for nutrition. Nectar and pollen collected by honey bees are processed and matured within the nest through the activities of honey bee-derived microbes and enzymes. In order to better understand the contribution of the microbial community to food processing in the honey bee, we generated a metatranscriptome of the honey bee gut microbiome. The function of the microbial community in the honey bee, as revealed by metatranscriptome sequencing, resembles that of other animal guts and food-processing environments. We identified three major bacterial classes that are active in the gut (γ-Proteobacteria, Bacilli and Actinobacteria), all of which are predicted to participate in the breakdown of complex macromolecules (e.g. polysaccharides and polypeptides), the fermentation of component parts of these macromolecules, and the generation of various fermentation products, such as short-chain fatty acids and alcohol. The ability of the microbial community to metabolize these carbon-rich food sources was confirmed through the use of community-level physiological profiling. Collectively, these findings suggest that the gut microflora of the honey bee harbours bacterial members with unique roles, which ultimately can contribute to the processing of plant-derived food for colonies.

  20. Single machine stochastic JIT scheduling problem subject to machine breakdowns

    Institute of Scientific and Technical Information of China (English)

    TANG HengYong; ZHAO ChuanLi; CHENG CongDian


    In this paper we research the single machine stochastic JIT scheduling problem subject to the machine breakdowns for preemptive-resume and preemptive-repeat. The objective function of the problem is the sum of squared deviations of the job-expected completion times from the due date. For preemptive-resume, we show that the optimal sequence of the SSDE problem is V-shaped with respect to expected processing times. And a dynamic programming algorithm with the pseudopolynomial time complexity is, given. We discuss the difference between the SSDE problem and the ESSD problem and show that the optimal solution of the SSDE problem is a good approximate optimal solution of the ESSD problem, and the optimal solution of the SSDE problem is an optimal solution of the ESSD problem under some conditions. For preemptive-repeat, the stochastic JIT scheduling problem has not been solved since the variances of the completion times cannot be computed. We replace the ESSD problem by the SSDE problem. We show that the optimal sequence of the SSDE problem is V-shaped with respect to the expected occupying times. And a dynamic programming algorithm with the pseudopolynomial time complexity is given. A new thought is advanced for the research of the preemptive-repeat stochastic JIT scheduling problem.

  1. Studying the Dynamics of Breakdown of Thin Horizontal Liquid Layers with Local Heating

    Directory of Open Access Journals (Sweden)

    Spesivtsev Serafim


    Full Text Available Experimental study of liquid layers breakdown when heated locally from the substrate side was made. Water and ethanol were used as working liquids with a layer thickness of 300 μm. Basic steps of the breakdown process were found and mean velocities of the dry spot formation were determined; the values are 0.06 mm/sec for ethanol and 5.15 mm/sec for water. The formation of residual layer over the hot-spot before the breakdown has been found for both liquids. The creation of a droplet cluster near the heating region is observed when using water as a working fluid. It was shown that evaporation is one of the general factors influencing the process of layer breakdown and dry spot formation as well as thermocapillary effect.

  2. Can surface cracks and unipolar arcs explain breakdown and gradient limits?

    CERN Document Server

    Norem, Jim


    We argue that the physics of unipolar arcs and surface cracks can help understand rf breakdown, and vacuum arc data. We outline a model of the basic mechanisms involved in breakdown and explore how the physics of unipolar arcs and cracks can simplify the picture of breakdown and gradient limits in accelerators, tokamaks as well as laser ablation, micrometeorites and other applications. Cracks are commonly seen in SEM images of arc damage and they are produced as the liquid metal cools, they produce the required field enhancements to explain field emission data data and can produce fractures that would trigger breakdown events. Unipolar arcs can produce currents sufficient to short out rf structures, should cause the sort of damage seen in SEM images, should be unstable and possibly self-quenching as seen in optical fluctuations and surface damage.

  3. The inception of pulsed discharges in air: simulations in background fields above and below breakdown

    CERN Document Server

    Sun, Anbang; Ebert, Ute


    We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and O$_{2}^-$ ions. When the electric field rises above the breakdown and the detachment threshold, which are similar in air, electrons can detach from O$_{2}^-$ and start ionization avalanches. These avalanches together create one large discharge, in contrast to the `double-headed' streamers found in many fluid simulations. On the other hand, in background fields below breakdown, something must enhance the field sufficiently for a streamer to form. We use a strongly ionized seed of electrons and positive ions for this, with which we observe the growth of positive streamers. Negative streamers were not observed. Below breakdown, the inclusion of electron detachment does not change the results much, and we observe similar discharge development as in fluid simulations.

  4. Impact of field limiting ring technique on breakdown voltage of irradiated Si sensors

    CERN Document Server

    Bhardwaj, A; Namrata, S; Chatterji, S; Srivastava-Ajay, K; Kumar, A; Jha, Manoj Kumar; Shivpuri, R K


    The very intense radiation environment of high luminosity future colliding beam experiments (like LHC) makes radiation hardness the most important issue for Si detectors. One of the central issues concerning all LHC experiments is the breakdown performance of these detectors. The major macroscopic effect of radiation damage in determining the viability of long-term operation of Si sensors is the change in effective charge carrier concentration (N/sub eff/), leading to type-inversion. Floating field limiting guard rings have been established as means of improving the breakdown performance of Si detectors. In this work the usefulness of the guard rings in improving the breakdown performance of detectors after type-inversion has been studied. Simulations are carried out to study the effect of change in N/sub eff/ on the breakdown performance of optimized guard ring structure using two dimensional device simulation program, TMA- MEDICI. Detailed calculations using Hamburg Model have allowed the parameterization o...

  5. Fabrication of 4H-SiC Schottky barrier diodes with high breakdown voltages

    CERN Document Server

    Kum, B H; Shin, M W; Park, J D


    This paper discusses the fabrication and the breakdown characteristics of 4H-SiC Schottky barrier diodes (SBDs). Optimal processing conditions for the ohmic contacts were extracted using the transmission-line method (TLM) and were applied to the device fabrication. The Ti/4H-SiC SBDs with Si sub x B sub y passivation showed a maximum reverse breakdown voltage of 268 V with a forward current density as high as 70 mA/cm sup 2 at a forward voltage of 2 V. The breakdown of the Pt. 4H-SiC SBDs without any passivation occurred at near 110 V. It is concluded that the breakdown enhancement in the Ti/4H-SiC SBDs can be attributed to the passivation; otherwise, excess surface charge near the edge of the Schottky contact would lead to electric fields of sufficient magnitude to cause field emission.

  6. Subnanosecond processes in the stage of breakdown formation in gas at a high pressure (United States)

    Korolev, Yu. D.; Bykov, N. M.; Ivanov, S. N.


    Results are presented from experimental studies of the prebreakdown stage of a discharge in nitrogen at pressures of a few tens of atmospheres, gap voltages higher than 140 kV, and a voltage rise time of about 1 ns. Breakdown occurs at the front of the voltage pulse; i.e., the time of breakdown formation is shorter than the front duration. It is shown that, in gaps with a nonuniform electric field, the breakdown formation time is mainly determined by the time of avalanche development to the critical number of charge carriers. The subsequent stages of breakdown (the development of the ionization wave and the buildup of the conductivity in the weakly conducting channel bridging the gap) turn out to be shorter than this time or comparable to it.

  7. A model based DC analysis of SiPM breakdown voltages

    CERN Document Server

    Nagy, Ferenc; Kalinka, Gabor; Molnar, Jozsef


    A new method to determine the breakdown voltage of SiPMs is presented. It is backed up by a DC model which describes the breakdown phenomenon by distinct avalanche turn-on ($V_{01}$) and turn off ($V_{10}$) voltages. It is shown that $V_{01}$ is related to the 'breakdown voltage' that previous DC methods derive from simple reverse current-voltage measurements, while $V_{10}$ is the 'real' breakdown voltage commonly obtained from complex gain-voltage measurements. The proposed method reveals how the microcell population distributes around $V_{01}$ and $V_{10}$. It is found that if this distribution is assumed to be normal, then both voltages and even their standard deviation can readily be extracted from current-voltage curves. Measurements are in good agreement with the theoretical model.

  8. Characteristics and Breakdown Behaviors of Polysilicon Resistors for High Voltage Applications

    Directory of Open Access Journals (Sweden)

    Xiao-Yu Tang


    Full Text Available With the rapid development of the power integrated circuit technology, polysilicon resistors have been widely used not only in traditional CMOS circuits, but also in the high voltage applications. However, there have been few detailed reports about the polysilicon resistors’ characteristics, like voltage and temperature coefficients and breakdown behaviors which are critical parameters of high voltage applications. In this study, we experimentally find that the resistance of the polysilicon resistor with a relatively low doping concentration shows negative voltage and temperature coefficients, while that of the polysilicon resistor with a high doping concentration has positive voltage and temperature coefficients. Moreover, from the experimental results of breakdown voltages of the polysilicon resistors, it could be deduced that the breakdown of polysilicon resistors is thermally rather than electrically induced. We also proposed to add an N-type well underneath the oxide to increase the breakdown voltage in the vertical direction when the substrate is P-type doped.

  9. The effect of gas bubbles on electrical breakdown in transformer oil (United States)

    Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Akimov, P. L.; Demirov, N. A.


    To study the breakdown of transformer oil with gas bubbles an experimental setup was created that allows to determine electrical and optical properties of the discharge. Oil was sparged with air and sulfur hexafluoride gas. It was found that sparging oil with gas lowers the breakdown voltage of the oil. When a gas bubble is present between the electrodes at a considerable distance from the electrodes at first there is a spherically shape flash observed, resulting in the discharge gap overlapping by a conductive channel. These leads to discharges forming in the discharge gap with the frequency of hundreds Hz and higher. Despite the slightly lower breakdown voltage of oil sparged with sulfur hexafluoride the advantage of this medium to clean oil can serve as a two-phase medium damping properties, which may be sufficient to prevent the destruction of the body in the breakdown of oil-filled equipment.

  10. Interaction Of CO2 Laser Nanosecond Pulse Train With The Metallic Targets In Optical Breakdown Regime (United States)

    Apollonov, V. V.; Firsov, K. N.; Konov, V. I.; Nikitin, P. I.; Prokhorov, A. M.; Silenok, A. S.; Sorochenko, V. R.


    In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

  11. Probabilistic Description of Traffic Breakdowns Caused by On-ramp Flow


    Kuhne, Reinhart; Lubashevsky, Ihor; Mahnke, Reinhard; Kaupush, Jevgenijs


    The characteristic features of traffic breakdown near on-ramp are analyzed. To describe this phenomenon the probabilistic description regarding the jam emergence as the formation of a large car cluster on highway inside the synchronized traffic is constructed. In these terms the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which is located near the on-ramp. The strong cooperative car interaction in the synchronized traffic enables us to ...

  12. Electrical breakdown strength characteristics of palm kernel oil ester-based dielectric fluids


    Abdelmalik, A. A.; Fothergill, J; Dodd, S.J.


    Natural ester fluids have been synthesized from crude palm kernel oil for consideration as an alternative to mineral oil based insulating fluid. Chemical modification of the oil enhanced the physico-chemical properties of the fluid. This paper presents the statistical analysis of the AC electrical breakdown strength of the synthesized esters in comparison with the crude palm kernel oil sample. The breakdown test was carried out in accordance with ASTM 1816 test method using a bespoke test cel...

  13. Gas Breakdown in the Sub-Nanosecond Regime with Voltages Below 15 KV (United States)


    here gas breakdown during nanosecond pulses occurs mainly as corona discharges on wire antennas, and represents an unwanted effect - General...switching for pulsed power applications Published data [2,3,4,5] for subnanosecond breakdown are mainly related to discharges in gases with...pressures at or above one atmosphere , or for liquids, and for quasi- homogeneous electric fields which are at least on the order of several 100 kV/cm. For

  14. The Nanophysics of Electron Emission and Breakdown for High Power Microwave Source (United States)


    coaxial anode/collector. 3.1.2. Formation of  plasma  filaments during w‐band microwave breakdown  Regular, two-dimensional plasma ...Injection Gun ," IEEE Trans. Elec. Devices (May, 2005). 2. Booske, John H., “ Plasma physics and related challenges of millimeter-to-terahertz and...high power microwave (HPM) device technologies by establishing new physical understanding of electron emission/absorption and plasma breakdown

  15. White Paper on Multicarrier Excitation of Multipactor Breakdown: A Survey of Current Methods and Research Opportunities (United States)


    Executive Summary Multipactor breakdown is a failure mode that occurs in RF systems and system components that operate in a vacuum. For component and...However, for RF components exposed to multiple distinct signals simultaneously, there are a variety of methods used to address multipactor breakdown...and method for carrier combination )? • Consistency of results obtained • Ability to understand and interpret results obtained • Are results too

  16. Standard/Handbook for RF Ionization Breakdown Prevention in Spacecraft Components (United States)


    based on much faster rise time and overall amplitude in the change of the phase null signal from a breakdown event. 37 Near-Carrier Noise ...meant for component designers and satellite system engineers, as well as the customer community. It provides worst-case conditions, margin requirements...all satellite and spacecraft RF components susceptible to ionization breakdown. As RF component power levels increase, the processes and risk

  17. Factors contributing to the breakdown of sodium beta-alumina

    Energy Technology Data Exchange (ETDEWEB)

    Buechele, A.C.


    Clarification of the breakdown process occurring during charge transfer in sodium beta alumina solid electrolytes was derived from: (1) studying the effects of molten sodium contact at 350/sup 0/C on single crystal sodium beta alumina and polycrystalline sodium beta alumina; (2) determination of critical current density by monitoring acoustic emissions accompanying crack growth in sodium/sodium beta alumina/sodium cells subjected to linear current ramping at 1 mA cm/sup -2/ sec/sup -1/; (3) failure analysis conducted on cycled electrolytes, some from commercial sodium/sulfur cells, which had been subjected to up to 703 Ahr cm/sup -2/ of charge transfer. Gray coloration developing in beta aluminas in contact with molten sodium was found to be a consequence of formation, through reduction by sodium, of oxygen vacancies charge compensated by electrons. Electronic conductivity of the electrolyte increases as a result. No second phase formation was detected. Colored electrolytes from sodium/sulfur cells show evidence of a newly recognized degradation mechanism in which fracture occurs when sodium is reduced and deposited internally under pressure as metal in regions where an electronic conductivity gradient exists. Heating colored beta aluminas in air produces reoxidation and bleaching. Kinetics and other properties of the coloration and bleaching processes were determined. Critical current density was found to bear an inverse relation to average electrolyte grain size. Evidence was found in the cycled electrolytes for a slow crack growth mechanism and a progressive mode of degradation advancing from the sulfur electrode interface. Implications of the findings for the construction and operation of sodium/sulfur battery systems are discussed.

  18. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    Energy Technology Data Exchange (ETDEWEB)

    Forni, Olivier, E-mail: [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Maurice, Sylvestre, E-mail: [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Gasnault, Olivier, E-mail: [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Wiens, Roger C., E-mail: [Space Remote Sensing, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Cousin, Agnès, E-mail: [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Chemical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Clegg, Samuel M., E-mail: [Chemical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Sirven, Jean-Baptiste, E-mail: jean-baptiste.sirven@cea.f [CEA Saclay, DEN/DPC/SCP, 91191 Cedex, Gif sur Yvette (France); Lasue, Jérémie, E-mail: [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France)


    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches. - Highlights: • We use a novel independent component analysis method to classify LIBS spectra. • We demonstrate the usefulness of ICA. • We report the performances of the ICA classification. • We compare it to other classical classification schemes.

  19. Microbial conversion of selected azo dyes and their breakdown products. (United States)

    Yemashova, N; Kalyuzhnyi, S


    Four selected azo dyes (acid orange 6, acid orange 7, methyl orange and methyl red) were completely decolourised in the presence of anaerobic granular sludge, while only methyl red was degraded in aerobic conditions using a conventional activated sludge. Additional experiments with culture broth devoid of cells showed that anaerobic decolourisation of azo dyes was performed by extracellular reducing agents produced by anaerobic bacteria. This was further confirmed by abiotic experiments with sulphide and NADH. The presence of redox mediators such as riboflavin led to dramatic acceleration of the anaerobic biodecolourisation process. The azo dye reduction products were found to be sulphanilic acid and 4-aminoresorcinol for acid orange 6; sulphanilic acid and 1-amino-2-naphthol for acid orange 7; N,N-dimethyl-1,4-phenylenediamine and sulphanilic acid for methyl orange; and N,N-dimethyl-1,4-phenylenediamine and anthranilic acid for methyl red. Anaerobic toxicity assays showed that the azo dyes were more toxic than their breakdown products (aromatic amines), except 1-amino-2-naphthol. In the presence of activated sludge, only anthranilic acid was completely mineralised while sulphanilic acid was persistent. 4-aminoresorcinol, 1-amino-2-naphthol and N,N-dimethyl-1,4-phenylenediamine underwent autooxidation in aerobic conditions yielding coloured polymeric products. On the contrary, in the presence of granular methanogenic sludge, 4-aminoresorcinol, 1-amino-2-naphthol and anthranilic acid were quantitatively methanised, sulphanilic acid was partially (70%) mineralised while N,N-dimethyl-1,4-phenylenediamine was only demethylated producing 1,4-phenylenediamine as an end product.

  20. Priming the Dissolved Organic Matter Breakdown in Urban Streams (United States)

    Parr, T.; Cronan, C. S.; Ohno, T.; Simon, K. S.


    Land use and land cover change in the Anthropocene have altered the source, composition, and reactivity of dissolved organic matter (DOM) in aquatic ecosystems around the world. In particular, urbanization increases the abundance of bioavailable DOM in streams. This bioavailable DOM may increase the utilization of less bioavailable pools of DOM via the "priming effect." The priming effect is a phenomenon whereby the addition of a small amount of labile DOM can increase or decrease the breakdown rate of less bioavailable DOM - positive and negative priming respectively. Our research tests priming as one potential mechanism altering DOM composition and increasing its bioavailability in urban streams. We measured DOM degradation during 30-day incubations in samples from a small urban stream and two microbial DOM sources mixed with DOM from a small stream dominated by less microbial allochthonous sources. We assessed priming by looking at observed percent biodegradable dissolved organic carbon (BDOC) vs. endmember predicted BDOC. We also investigated the molecular dynamics of priming using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Using bulk DOC concentration we found evidence that adding small amounts of DOM from an urban stream could increase BDOC by a factor of two to three. At the molecular level, FT-ICR/MS showed that addition of labile DOM may increase the bioavailability of a variety of compound classes including proteins, lipids, and "black carbon." Furthermore, we observed that what is frequently reported as positive or negative priming may be more accurately understood as the net balance of simultaneous positive and negative priming operating on different DOM pools. Our results highlight an important global mechanism by which human activities may alter the composition and reactivity of DOM in fresh waters. Priming the degradation of allochthonous DOM with autochthonous or novel anthropogenic DOM may alter the organic energy

  1. Application of Laser Induced Breakdown Spectroscopy under Polar Conditions (United States)

    Clausen, J. L.; Hark, R.; Bol'shakov, A.; Plumer, J.


    Over the past decade our research team has evaluated the use of commercial-off-the-shelf laser-induced breakdown spectroscopy (LIBS) for chemical analysis of snow and ice samples under polar conditions. One avenue of research explored LIBS suitability as a detector of paleo-climate proxy indicators (Ca, K, Mg, and Na) in ice as it relates to atmospheric circulation. LIBS results revealed detection of peaks for C and N, consistent with the presence of organic material, as well as major ions (Ca, K, Mg, and Na) and trace metals (Al, Cu, Fe, Mn, Ti). The detection of Ca, K, Mg, and Na confirmed that LIBS has sufficient sensitivity to be used as a tool for characterization of paleo-climate proxy indicators in ice-core samples. Techniques were developed for direct analysis of ice as well as indirect measurements of ice via melting and filtering. Pitfalls and issues of direct ice analysis using several cooling techniques to maintain ice integrity will be discussed. In addition, a new technique, laser ablation molecular isotopic spectroscopy (LAMIS) was applied to detection of hydrogen and oxygen isotopes in ice as isotopic analysis of ice is the main tool in paleoclimatology and glaciology studies. Our results demonstrated that spectra of hydroxyl isotopologues 16OH, 18OH, and 16OD can be recorded with a compact spectrograph to determine hydrogen and oxygen isotopes simultaneously. Quantitative isotopic calibration for ice analysis can be accomplished using multivariate chemometric regression as previously realized for water vapor. Analysis with LIBS and LAMIS required no special sample preparation and was about ten times faster than analysis using ICP-MS. Combination of the two techniques in one portable instrument for in-field analysis appears possible and would eliminate the logistical and cost issues associated with ice core management.

  2. Electromagnetic activity before initial breakdown pulses of lightning (United States)

    Marshall, T.; Stolzenburg, M.; Karunarathna, N.; Karunarathne, S.


    Lightning flash initiation is studied using electric field change (E-change) measurements made in Florida. An initial E-change (IEC) was found immediately before the first initial breakdown (IB) pulse in both cloud-to-ground (CG) and intracloud (IC) flashes if the E-change sensor was within 80% of the reversal distance of the IEC. For 18 CG flashes, the IECs had an average point dipole moment of 23 C m and an average duration of 0.18 ms; these parameters for 18 IC flashes were -170 C m and 1.53 ms. The IECs of CG flashes began with a change in the slope of the E-change (with respect to time) from zero slope to a positive slope, consistent with downward motion of negative charge and/or upward motion of positive charge. For IECs of IC flashes, the beginning slope change was from zero to negative slope, consistent with upward motion of negative charge and/or downward motion of positive charge. During an IEC, the E-change monotonically increased for CG flashes and monotonically decreased for IC flashes. In 14 of 36 cases, the IEC beginning was coincident with a discrete, impulsive source of VHF radiation; another 13 cases had at least one VHF source during the IEC or the first IB pulse. Before the IECs, there were no preliminary variations detected in the 36 flashes. It is hypothesized that lightning initiation begins with an ionizing event that causes the IEC and that the IEC enhances the ambient electric field to produce the first IB pulse.

  3. Biotic and abiotic variables influencing plant litter breakdown in streams: a global study. (United States)

    Boyero, Luz; Pearson, Richard G; Hui, Cang; Gessner, Mark O; Pérez, Javier; Alexandrou, Markos A; Graça, Manuel A S; Cardinale, Bradley J; Albariño, Ricardo J; Arunachalam, Muthukumarasamy; Barmuta, Leon A; Boulton, Andrew J; Bruder, Andreas; Callisto, Marcos; Chauvet, Eric; Death, Russell G; Dudgeon, David; Encalada, Andrea C; Ferreira, Verónica; Figueroa, Ricardo; Flecker, Alexander S; Gonçalves, José F; Helson, Julie; Iwata, Tomoya; Jinggut, Tajang; Mathooko, Jude; Mathuriau, Catherine; M'Erimba, Charles; Moretti, Marcelo S; Pringle, Catherine M; Ramírez, Alonso; Ratnarajah, Lavenia; Rincon, José; Yule, Catherine M


    Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.8° N to 42.8° S, using litter mixtures of local species differing in quality and phylogenetic diversity (PD), and alder (Alnus glutinosa) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD. Effects of litter quality and PD and stream pH were more positive at higher temperatures, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons.

  4. Ac and Impulse Breakdown of Liquid Nitrogen at 77 K for Quasi-Uniform Field Gaps (United States)

    James, D. R.; Sauers, I.; Ellis, A. R.; Schwenterly, S. W.; Tuncer, E.; Pleva, E.


    Liquid nitrogen (LN2) is commonly used both as a coolant and electrical insulation in high temperature superconductor (HTS) equipment for power applications. Hence it is necessary to know the electrical breakdown characteristics of LN2 under a variety of practical conditions. The ac breakdown and positive and negative polarity breakdown results for lightning impulse (1.2 microsecond rise time/50 microsecond fall time) are presented for LN2 using sphere to plane electrode geometry for sphere diameters of 50.8 and 101.6 mm over a gap range of 1 to 15 mm. Voltages up to 110 kVrms were studied for ac breakdown and up to 500-kV peak for impulse. In this work both the ac and impulse breakdown voltages scale approximately with distance over the limited gaps studied which is indicative of a quasi-uniform (near-uniform) electric field between sphere and plane. These measurements were conducted in a dewar which could be pressurized from 1 to 2 bar absolute which greatly reduces the spontaneous formation of bubbles that can occur in open LN2 bath experiments and thus potentially reduce the breakdown strength. Results from the pressurized system and near atmospheric pressure similar to an open bath are compared.

  5. Breakdown of the Stokes-Einstein relation in two, three, and four dimensions (United States)

    Sengupta, Shiladitya; Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth


    The breakdown of the Stokes-Einstein (SE) relation between diffusivity and viscosity at low temperatures is considered to be one of the hallmarks of glassy dynamics in liquids. Theoretical analyses relate this breakdown with the presence of heterogeneous dynamics, and by extension, with the fragility of glass formers. We perform an investigation of the breakdown of the SE relation in 2, 3, and 4 dimensions in order to understand these interrelations. Results from simulations of model glass formers show that the degree of the breakdown of the SE relation decreases with increasing spatial dimensionality. The breakdown itself can be rationalized via the difference between the activation free energies for diffusivity and viscosity (or relaxation times) in the Adam-Gibbs relation in three and four dimensions. The behavior in two dimensions also can be understood in terms of a generalized Adam-Gibbs relation that is observed in previous work. We calculate various measures of heterogeneity of dynamics and find that the degree of the SE breakdown and measures of heterogeneity of dynamics are generally well correlated but with some exceptions. The two-dimensional systems we study show deviations from the pattern of behavior of the three- and four-dimensional systems both at high and low temperatures. The fragility of the studied liquids is found to increase with spatial dimensionality, contrary to the expectation based on the association of fragility with heterogeneous dynamics.

  6. The breakdown and glow phases during the initiation of discharges for lamps

    Energy Technology Data Exchange (ETDEWEB)

    Pitchford, L.C.; Peres, I.; Liland, K.B.; Boeuf, J.P. [Centre de Physique des Plasmas et Applications, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse (France); Gielen, H. [Central Development Laboratories, Philips Lighting, Eindhoven (The Netherlands)


    High intensity discharge (HID) lamps are often initiated by the application of one or more short, high-voltage, breakdown pulses superimposed on a 50 or 60 Hz generator voltage. A successful transition from the breakdown event to steady-state operating conditions in HID lamps requires that the lamp-circuit system be adequate to sustain the plasma created during breakdown until the electrodes are heated to thermionic temperatures. In this article, we use a one-dimensional (in the axial direction) transient discharge model to study the conditions needed to sustain the cold-cathode discharge after a breakdown event has occurred. While the application of our one-dimensional model to real lamps is approximate, we find that the model predictions are consistent with experimental results in HID lamps, a few of which are presented here. The main conclusion from this work is that, after breakdown, the voltage necessary to sustain a glow discharge is dependent on the source impedance, the gas composition, and on the plasma density created by the breakdown event. {copyright} {ital 1997 American Institute of Physics.}

  7. Experimental study of polarity dependence in repetitive nanosecond-pulse breakdown

    Institute of Scientific and Technical Information of China (English)

    Shao Tao; Sun Guang-Sheng; Yan Ping; Wang Jue; Yuan Wei-Qun; Zhang Shi-Chang


    Pulsed breakdown of dry air at ambient pressure has been investigated in the point-plane geometry,using repetitive nanosecond pulses with 10 ns risetime,20-30 as duration,and up to 100 kV amplitude.A major concern in this paper is to study the dependence of breakdown strength on the point-electrode polarity.Applied voltage,breakdown current and repetitive stressing time are measured under the experimental conditions of some variables including pulse voltage peak,gap spacing and repetition rate.The results show that increasing the E-field strength can decrease breakdown time lag,repetitive stressing time and the number of applied pulses as expected.However,compared with the traditional polarity dependence it is weakened and not significant in the repetitive nanosecond-pulse breakdown.The ambiguous polaxity dependence in the experimental study is involved with an accumulation effect of residual charges and metastable states.Moreover,it is suggested that the reactions associated with the detachment of negative ions and impact deactivation of metastable specms could provide a source of primary initiating electrons for breakdown.

  8. Multivariate Analysis of Laser-Induced Breakdown Spectroscopy for Discrimination between Explosives and Plastics

    Institute of Scientific and Technical Information of China (English)

    WANG Qian-Qian; LIU Kai; ZHAO Hua


    A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed. A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method. Seven types of plastics and one explosive are used as samples to test the model. The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods. The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials.%A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed.A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method.Seven types of plastics and one explosive are used as samples to test the model.The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods.The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials.

  9. Time Dependent Dielectric Breakdown in Copper Low-k Interconnects: Mechanisms and Reliability Models

    Directory of Open Access Journals (Sweden)

    Terence K.S. Wong


    Full Text Available The time dependent dielectric breakdown phenomenon in copper low-k damascene interconnects for ultra large-scale integration is reviewed. The loss of insulation between neighboring interconnects represents an emerging back end-of-the-line reliability issue that is not fully understood. After describing the main dielectric leakage mechanisms in low-k materials (Poole-Frenkel and Schottky emission, the major dielectric reliability models that had appeared in the literature are discussed, namely: the Lloyd model, 1/E model, thermochemical E model, E1/2 models, E2 model and the Haase model. These models can be broadly categorized into those that consider only intrinsic breakdown (Lloyd, 1/E, E and Haase and those that take into account copper migration in low-k materials (E1/2, E2. For each model, the physical assumptions and the proposed breakdown mechanism will be discussed, together with the quantitative relationship predicting the time to breakdown and supporting experimental data. Experimental attempts on validation of dielectric reliability models using data obtained from low field stressing are briefly discussed. The phenomenon of soft breakdown, which often precedes hard breakdown in porous ultra low-k materials, is highlighted for future research.

  10. Detection of Operator Performance Breakdown as an Automation Triggering Mechanism (United States)

    Yoo, Hyo-Sang; Lee, Paul U.; Landry, Steven J.


    Performance breakdown (PB) has been anecdotally described as a state where the human operator "loses control of context" and "cannot maintain required task performance." Preventing such a decline in performance is critical to assure the safety and reliability of human-integrated systems, and therefore PB could be useful as a point at which automation can be applied to support human performance. However, PB has never been scientifically defined or empirically demonstrated. Moreover, there is no validated objective way of detecting such a state or the transition to that state. The purpose of this work is: 1) to empirically demonstrate a PB state, and 2) to develop an objective way of detecting such a state. This paper defines PB and proposes an objective method for its detection. A human-in-the-loop study was conducted: 1) to demonstrate PB by increasing workload until the subject reported being in a state of PB, and 2) to identify possible parameters of a detection method for objectively identifying the subjectively-reported PB point, and 3) to determine if the parameters are idiosyncratic to an individual/context or are more generally applicable. In the experiment, fifteen participants were asked to manage three concurrent tasks (one primary and two secondary) for 18 minutes. The difficulty of the primary task was manipulated over time to induce PB while the difficulty of the secondary tasks remained static. The participants' task performance data was collected. Three hypotheses were constructed: 1) increasing workload will induce subjectively-identified PB, 2) there exists criteria that identifies the threshold parameters that best matches the subjectively-identified PB point, and 3) the criteria for choosing the threshold parameters is consistent across individuals. The results show that increasing workload can induce subjectively-identified PB, although it might not be generalizable-only 12 out of 15 participants declared PB. The PB detection method based on

  11. Improved polymer nanocomposite dielectric breakdown performance through barium titanate to epoxy interface control

    Energy Technology Data Exchange (ETDEWEB)

    Siddabattuni, Sasidhar [Missouri University of Science and Technology (formerly the University of Missouri-Rolla), Chemistry Department, 400W. 11th Street, Rolla, MO 65409 (United States); Schuman, Thomas P., E-mail: [Missouri University of Science and Technology (formerly the University of Missouri-Rolla), Chemistry Department, 400W. 11th Street, Rolla, MO 65409 (United States); Dogan, Fatih [Missouri University of Science and Technology, Materials Science and Engineering Department, 1400N. Bishop Avenue, Rolla, MO 65409 (United States)


    Highlights: > A covalent filler-matrix interface improves the dielectric properties of a polymer-particle nanocomposite dielectric. > A covalent interface reduced the polymer free volume around the nanoparticles as assessed through T{sub g} measurements. > Composite T{sub g} was raised and breakdown strength improved for nanocomposites with a covalent polymer-particle interface. > A larger Maxwell-Wagner (MW) relaxation correlated with reduced breakdown strengths and energy storage densities. > The MW relaxation could be considered a dielectric defect regarding breakdown strength and energy storage density. - Abstract: A composite approach to dielectric design has the potential to provide improved permittivity as well as high breakdown strength and thus afford greater electrical energy storage density. Interfacial coupling is an effective approach to improve the polymer-particle composite dielectric film resistance to charge flow and dielectric breakdown. A bi-functional interfacial coupling agent added to the inorganic oxide particles' surface assists dispersion into the thermosetting epoxy polymer matrix and upon composite cure reacts covalently with the polymer matrix. The composite then retains the glass transition temperature of pure polymer, provides a reduced Maxwell-Wagner relaxation of the polymer-particle composite, and attains a reduced sensitivity to dielectric breakdown compared to particle epoxy composites that lack interfacial coupling between the composite filler and polymer matrix. Besides an improved permittivity, the breakdown strength and thus energy density of a covalent interface nanoparticle barium titanate in epoxy composite dielectric film, at a 5 vol.% particle concentration, was significantly improved compared to a pure polymer dielectric film. The interfacially bonded, dielectric composite film had a permittivity {approx}6.3 and at a 30 {mu}m thickness achieved a calculated energy density of 4.6 J/cm{sup 3}.

  12. Effects of salinity on leaf breakdown: Dryland salinity versus salinity from a coalmine. (United States)

    Sauer, Felix G; Bundschuh, Mirco; Zubrod, Jochen P; Schäfer, Ralf B; Thompson, Kristie; Kefford, Ben J


    Salinization of freshwater ecosystems as a result of human activities represents a global threat for ecosystems' integrity. Whether different sources of salinity with their differing ionic compositions lead to variable effects in ecosystem functioning is unknown. Therefore, the present study assessed the impact of dryland- (50μS/cm to 11,000μS/cm) and coalmine-induced (100μS/cm to 2400μS/cm) salinization on the leaf litter breakdown, with focus on microorganisms as main decomposer, in two catchments in New South Wales, Australia. The breakdown of Eucalyptus camaldulensis leaves decreased with increasing salinity by up to a factor of three. Coalmine salinity, which is characterised by a higher share of bicarbonates, had a slightly but consistently higher breakdown rate at a given salinity relative to dryland salinity, which is characterised by ionic proportions similar to sea water. Complementary laboratory experiments supported the stimulatory impact of sodium bicarbonates on leaf breakdown when compared to sodium chloride or artificial sea salt. Furthermore, microbial inoculum from a high salinity site (11,000μS/cm) yielded lower leaf breakdown at lower salinity relative to inoculum from a low salinity site (50μS/cm). Conversely, inoculum from the high salinity site was less sensitive towards increasing salinity levels relative to inoculum from the low salinity site. The effects of the different inoculum were the same regardless of salt source (sodium bicarbonate, sodium chloride and artificial sea salt). Finally, the microorganism-mediated leaf litter breakdown was most efficient at intermediate salinity levels (≈500μS/cm). The present study thus points to severe implications of increasing salinity intensities on the ecosystem function of leaf litter breakdown, while the underlying processes need further scrutiny.

  13. Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins. (United States)

    Maric, Martina; Haugo, Alison C; Dauer, William; Johnson, David; Roller, Richard J


    Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway.

  14. The influence of Ac parameters in the process of micro-arc oxidation film electric breakdown

    Directory of Open Access Journals (Sweden)

    Ma Jin


    Full Text Available This paper studies the electric breakdown discharge process of micro-arc oxidation film on the surface of aluminum alloy. Based on the analysis of the AC parameters variation in the micro-arc oxidation process, the following conclusions can be drawn: The growth of oxide film can be divided into three stages, and Oxide film breakdown discharge occurs twice in the micro-arc oxidation process. The first stage is the formation and disruptive discharge of amorphous oxide film, producing the ceramic oxide granules, which belong to solid dielectric breakdown. In this stage the membrane voltage of the oxide film plays a key role; the second stage is the formation of ceramic oxide film, the ceramic oxide granules turns into porous structure oxide film in this stage; the third stage is the growth of ceramic oxide film, the gas film that forms in the oxide film’s porous structure is electric broken-down, which is the second breakdown discharge process, the current density on the oxide film surface could affect the breakdown process significantly.

  15. Field emission driven direct current argon discharges and electrical breakdown mechanism across micron scale gaps (United States)

    Matejčik, Štefan; Radjenović, Branislav; Klas, Matej; Radmilović-Radjenović, Marija


    In this paper results of the experimental and theoretical studies of the field emission driven direct current argon microdischarges for the gaps between 1 μm and 100 μm are presented and discussed. The breakdown voltage curves and Volt-Ampere characteristics proved to be a fertile basis providing better understanding of the breakdown phenomena in microgaps. Based on the measured breakdown voltage curves, the effective yields have been estimated confirming that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field leading directly to the violation of the Paschen's law. Experimental data are supported by the theoretical predictions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures confirming that Townsend phenomenology breaks down when field emission becomes the key mechanism leading to the breakdown. Field emission of electrons from the cathode, the space charge effects in the breakdown and distinction between the Fowler-Nordheim field emission and the space charge limited current density are also analyzed. Images and Volt-Ampere characteristics recorded at the electrode gap size of 20 μm indicate the existence of a discharge region similar to arc at the pressure of around 200 Torr has been observed. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

  16. Two dimensional triangulation of breakdown in a high voltage coaxial gap. (United States)

    Cordaro, S W; Bott-Suzuki, S C; Bendixsen, L S Caballero; Atoyan, Levon; Byvank, Tom; Potter, William; Kusse, B R; Greenly, J B


    We describe a technique by which magnetic field probes are used to triangulate the exact position of breakdown in a high voltage coaxial vacuum gap. An array of three probes is placed near the plane of the gap with each probe at 90° intervals around the outer (anode) electrode. These probes measure the azimuthal component of the magnetic field and are all at the same radial distance from the cylindrical axis. Using the peak magnetic field values measured by each probe, the current carried by the breakdown channel, and Ampères law we can calculate the distance away from each probe that the breakdown occurred. These calculated distances are then used to draw three circles each centered at the centers of the corresponding magnetic probes. The common intersection of these three circles then gives the predicted azimuthal location of the center of the breakdown channel. Test results first gathered on the coaxial gap breakdown device (240 A, 25 kV, 150 ns) at the University of California San Diego and then on COBRA (1 MA, 1 MV, 100 ns) at Cornell University indicate that this technique is relatively accurate and scales between these two devices.

  17. Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins

    Energy Technology Data Exchange (ETDEWEB)

    Maric, Martina; Haugo, Alison C. [Department of Microbiology, University of Iowa, Iowa City, IA 52242 (United States); Dauer, William [Department of Neurology, University of Michigan, Ann Arbor, MI 48109 (United States); Johnson, David [Department of Microbiology and Immunology, Oregon Health Sciences University, Portland, OR 97201 (United States); Roller, Richard J., E-mail: [Department of Microbiology, University of Iowa, Iowa City, IA 52242 (United States)


    Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway. - Highlights: • We show that wild-type HSV can induce breakdown of the nuclear envelope in a specific cell system. • The viral fusion proteins gB and gH are required for induction of nuclear envelope breakdown. • Nuclear envelope breakdown cannot compensate for deletion of the HSV UL34 gene.

  18. Electrical Breakdown Physics in Photoconductive Semiconductor Switches (PCSS).

    Energy Technology Data Exchange (ETDEWEB)

    Mar, Alan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zutavern, Fred J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vawter, Gregory A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hjalmarson, Harold P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gallegos, Richard Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bigman, Verle Howard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    of 200kV (DC) and 5kA current that can be stacked in parallel to achieve 100's of kA with 10e5 shot lifetime. The new vertical switch design configuration generates parallel filaments in the bulk GaAs (as opposed to just beneath the surface as in previous designs) to achieve breakdown fields close to the maximum for the bulk GaAs while operating in air, and with 2-D scalability of the number of current-sharing filaments. This design also may be highly compatible with 2-D VCSEL arrays for optical triggering. The demonstration of this design in this LDRD utilized standard thickness wafers to trigger 0.4kA at 35kV/cm (limited by 0.6mm wafer thickness), tested to 1e5 shots with no detectable degradation of switch performance. Higher fields, total current, and switching voltages would be achievable with thicker GaAs wafers. Another important application pursued in this LDRD is the use of PCSS for trigger generator applications. Conventional in-plane PCSS have achieved triggering of a 100kV sparkgap (Kinetech-type) switch of the type similar to switches being considered for accelerator upgrades. The trigger is also being developed for pulsed power for HPM applications that require miniaturization and robust performance in noisy compact environments. This has spawned new programs for developing this technology, including an STTR for VCSEL trigger laser integration, also pursuing other follow-on applications.

  19. In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Boon Yeap, Kong, E-mail: [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Gall, Martin; Liao, Zhongquan; Sander, Christoph; Muehle, Uwe; Zschech, Ehrenfried [Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Justison, Patrick [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Aubel, Oliver; Hauschildt, Meike; Beyer, Armand; Vogel, Norman [GLOBALFOUNDRIES Dresden Module One LLC and Co. KG, Wilschdorfer Landstr. 101, D-01109 Dresden (Germany)


    An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a “tip-to-tip” structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 °C to the “tip-to-tip” structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 °C and above.

  20. Follistatin288 Regulates Germ Cell Cyst Breakdown and Primordial Follicle Assembly in the Mouse Ovary.

    Directory of Open Access Journals (Sweden)

    Zhengpin Wang

    Full Text Available In mammals, the primordial follicle pool represents the entire reproductive potential of a female. The transforming growth factor-β (TGF-β family member activin (ACT contributes to folliculogenesis, although the exact mechanism is not known. The role of FST288, the strongest ACT-neutralizing isoform of follistatin (FST, during cyst breakdown and primordial follicle formation in the fetal mice ovary was assessed using an in vitro culture system. FST was continuously expressed in the oocytes as well as the cuboidal granulosa cells of growing follicles in perinatal mouse ovaries. Treatment with FST288 delayed germ cell nest breakdown, particularly near the periphery of the ovary, and dramatically decreased the percentage of primordial follicles. In addition, there was a dramatic decrease in proliferation of granulosa cells and somatic cell expression of Notch signaling was impaired. In conclusion, FST288 impacts germ cell nest breakdown and primordial follicle assembly by inhibiting somatic cell proliferation.

  1. Breakdown of Atomic Hyperfine Coupling in a Deep Optical-Dipole Trap

    CERN Document Server

    Neuzner, Andreas; Dürr, Stephan; Rempe, Gerhard; Ritter, Stephan


    We experimentally study the breakdown of hyperfine coupling for an atom in a deep optical-dipole trap. One-color laser spectroscopy is performed at the resonance lines of a single $^{87}$Rb atom for a trap wavelength of 1064 nm. Evidence of hyperfine breakdown comes from three observations, namely a nonlinear dependence of the transition frequencies on the trap intensity, a splitting of lines which are degenerate for small intensities, and the ability to drive transitions which would be forbidden by selection rules in the absence of hyperfine breakdown. From the data, we infer the hyperfine interval of the $5P_{1/2}$ state and the scalar and tensor polarizabilities for the $5P_{3/2}$ state.

  2. The role of morphology and coupling of gold nanoparticles in optical breakdown during picosecond pulse exposures

    Directory of Open Access Journals (Sweden)

    Yevgeniy R. Davletshin


    Full Text Available This paper presents a theoretical study of the interaction of a 6 ps laser pulse with uncoupled and plasmon-coupled gold nanoparticles. We show how the one-dimensional assembly of particles affects the optical breakdown threshold of its surroundings. For this purpose we used a fully coupled electromagnetic, thermodynamic and plasma dynamics model for a laser pulse interaction with gold nanospheres, nanorods and assemblies, which was solved using the finite element method. The thresholds of optical breakdown for off- and on-resonance irradiated gold nanosphere monomers were compared against nanosphere dimers, trimers, and gold nanorods with the same overall size and aspect ratio. The optical breakdown thresholds had a stronger dependence on the optical near-field enhancement than on the mass or absorption cross-section of the nanostructure. These findings can be used to advance the nanoparticle-based nanoscale manipulation of matter.

  3. Puddle-Induced Resistance Oscillations in the Breakdown of the Graphene Quantum Hall Effect (United States)

    Yang, M.; Couturaud, O.; Desrat, W.; Consejo, C.; Kazazis, D.; Yakimova, R.; Syväjärvi, M.; Goiran, M.; Béard, J.; Frings, P.; Pierre, M.; Cresti, A.; Escoffier, W.; Jouault, B.


    We report on the stability of the quantum Hall plateau in wide Hall bars made from a chemically gated graphene film grown on SiC. The ν =2 quantized plateau appears from fields B ≃5 T and persists up to B ≃80 T . At high current density, in the breakdown regime, the longitudinal resistance oscillates with a 1 /B periodicity and an anomalous phase, which we relate to the presence of additional electron reservoirs. The high field experimental data suggest that these reservoirs induce a continuous increase of the carrier density up to the highest available magnetic field, thus enlarging the quantum plateaus. These in-plane inhomogeneities, in the form of high carrier density graphene pockets, modulate the quantum Hall effect breakdown and decrease the breakdown current.

  4. On the electrical breakdown of gaseous dielectrics-an engineering approach

    DEFF Research Database (Denmark)

    Pedersen, Aage


    Quantitative criteria are derived for the onset of breakdown in atmospheric air and similar weakly electronegative gases. A comparable criterion is then formulated for strongly electronegative gases such as SF6. These criteria contain no quantities other than those which can be obtained directly ...... approximation to the field distribution can render an extensive calculation of the electrostatic field unnecessary. The discussion deals exclusively with situations in which the onset of breakdown in the system is synonymous with the onset of a corona discharge......Quantitative criteria are derived for the onset of breakdown in atmospheric air and similar weakly electronegative gases. A comparable criterion is then formulated for strongly electronegative gases such as SF6. These criteria contain no quantities other than those which can be obtained directly...

  5. Analysis of plutonium oxide surrogate residue using laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Hongbo [Department of Applied Physics, College of Science, Nanjing University of Technology, Nanjing (China); Yueh, F.Y.; Miller, Tracy [Institute for Clean Energy Technology (ICET), Mississippi State University, Starkville, MS 39759-7704 (United States); Singh, Jagdish P. [Institute for Clean Energy Technology (ICET), Mississippi State University, Starkville, MS 39759-7704 (United States)], E-mail:; Zeigler, Kristine E.; Marra, James C. [Savannah River National Laboratory (SRNL), Aiken, SC 29808 (United States)


    Laser-induced breakdown spectroscopy was used to determine the elemental composition of a CeO{sub 2} composite powder for process control verification during lanthanide borosilicate glass fabrication. Cerium oxide is used as a surrogate for plutonium oxide, which along with other canister contents will be combined with frit to make glass. Laser-induced breakdown spectroscopy data for the composition of the CeO{sub 2} batch containing concentrations of Ce, Cr, Si, Fe, Ta, Ni, Zn, Al Mg, Gd, and W were quantitatively determined from laser-induced breakdown spectroscopy spectra of both pellet and powder samples. The results of both forms were compared and it was determined that the pellet data gave slightly better precision than the powder sample.

  6. Reduce of Threshold of Laser Inducing Breakdown in Atmosphere by Introducing an Electric Spark

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xian-Bin; SHI Wei; LI Hua


    @@ We report laser-generated plasmas in atmosphere with electrical spark generated by a synchronization circuit.The breakdown thresholds under the conditions that the electrical spark is used and not used are compared.The breakdown threshold has a distinct decrease after the electrical spark is used. Breakdown thresholds as afunction of atmosphere pressure have also been measured at laser wavelengths 532nm and 1064 nm for the laserpulse width of 15ns. We also discuss the principle and performances of the ionized atmosphere by Nd:YAGlaser under the condition of electrical spark introduction. Multiphoton ionization and cascade ionization playimportant roles in the whole process of atmosphere ionization. The free electron induced by electrical spark cansupply the initialization free electron number for multiphoton ionization and cascade ionization. A model forbreakdown in atmosphere, which is in good agreement with the experimental results, is described.

  7. The inception of pulsed discharges in air: simulations in background fields above and below breakdown (United States)

    Sun, Anbang; Teunissen, Jannis; Ebert, Ute


    We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and \\text{O}2- ions. In background fields below breakdown, we use a strongly ionized seed of electrons and positive ions to enhance the field locally. In the region of enhanced field, we observe the growth of positive streamers, as in previous simulations with 2D plasma fluid models. The inclusion of background ionization has little effect in this case. When the background field is above the breakdown threshold, the situation is very different. Electrons can then detach from \\text{O}2- and start ionization avalanches in the whole volume. These avalanches together create one extended discharge, in contrast to the ‘double-headed’ streamers found in many fluid simulations.

  8. Breakdown Limits on Gigavolt-per-Meter Electron-Beam-Driven Wakefields in Dielectric Structures (United States)

    Thompson, M. C.; Badakov, H.; Cook, A. M.; Rosenzweig, J. B.; Tikhoplav, R.; Travish, G.; Blumenfeld, I.; Hogan, M. J.; Ischebeck, R.; Kirby, N.; Siemann, R.; Walz, D.; Muggli, P.; Scott, A.; Yoder, R. B.


    First measurements of the breakdown threshold in a dielectric subjected to GV/m wakefields produced by short (30 330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100μm inner diameter were exposed to a range of bunch lengths, allowing surface dielectric fields up to 27GV/m to be generated. The onset of breakdown, detected through light emission from the tube ends, is observed to occur when the peak electric field at the dielectric surface reaches 13.8±0.7GV/m. The correlation of structure damage to beam-induced breakdown is established using an array of postexposure inspection techniques.

  9. High glycogen levels enhance glycogen breakdown in isolated contracting skeletal muscle

    DEFF Research Database (Denmark)

    Richter, Erik; Galbo, H


    The influence of supranormal muscle glycogen levels on glycogen breakdown in contracting muscle was investigated. Rats either rested or swam for 3 h and subsequently had their isolated hindquarters perfused after 21 h with access to food. Muscle glycogen concentrations were measured before...... and after 15 min of intermittent electrical muscle stimulation. Before stimulation, glycogen was higher in rats that swam on the preceding day (supercompensated rats) compared with controls. During muscle contractions, glycogen breakdown in fast-twitch red and white fibers was larger in supercompensated...... hindquarters compared with controls. O2 uptake, release of tyrosine and glycerol, and tension development were similar in the two groups. In conclusion, during muscle contractions, increased muscle glycogen levels lead to increased breakdown of glycogen and release of lactate and decreased uptake of glucose...

  10. Note: A novel technique for analysis of aqueous solutions by laser-induced breakdown spectroscopy. (United States)

    Rusak, D A; Anthony, T P; Bell, Z T


    Surface-enhanced Raman spectroscopy (SERS) substrates typically consist of gold or silver nanoparticles deposited on a non-conductive substrate. In Raman spectroscopy, the nanoparticles produce an enhancement of the electromagnetic field which, in turn, leads to greater electronic excitation of molecules in the local environment. Here, we show that these same surfaces can be used to enhance the signal-to-noise ratio obtained in laser-induced breakdown spectroscopy of aqueous solutions. In this case, the SERS substrates not only lower breakdown thresholds and lead to more efficient plasma initiation but also provide an appropriately wettable surface for the deposition of the liquid. We refer to this technique as surface-enhanced laser-induced breakdown spectroscopy.

  11. Experimental studies on electrical breakdown field strength of electrode with water mist containing MC additives

    Institute of Scientific and Technical Information of China (English)

    FANG Yudong; LIU Jianghong; LIAO Guangxuan; XU Qiang; ZHOU Xiaomeng


    Water mist is one of the effective candidates for halon replacement used in electrical environment fire protection. Water mist additives may greatly enhance fire suppression effectiveness. In electrical environment, electrical breakdown field strength (E) is one of the important factors that control the performance of electrical equipment. In this study the variation principles of electrical breakdown field strength and the electrical characteristics of MC additives were investigated by electrode discharging experiments. Experimental results showed that electrical breakdown field strength was impacted obviously by the conductive metal ions and insulated fluorocarbon surfactants in MC additives. The attenuation percentages of E in different experimental cases were described, thus providing scientific guidance for the use of water mist and MC additives in electrical fire suppression.

  12. Laser-induced breakdown spectroscopy detection of heavy metal in water based on graphite conch method (United States)

    Wang, Chunlong; Liu, Jianguo; Zhao, Nanjing; Shi, Huan; Liu, Lituo; Ma, Mingjun; Zhang, Wei; Chen, Dong; Liu, Jing; Zhang, Yujun; Liu, Wenqing


    The laser-induced breakdown spectroscopy emission characteristics of trace heavy metal lead in water is studied based on graphite conch method, with a 1064nm wavelength Nd: YAG laser as excitation source, the echelle spectrometer and ICCD detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The delay time 900ns and gate time 1600ns are determined in the experiment. The calibration curve of Pb is plotted based on the different concentration measurement results, and a limit of detection of 0.0138mg / L is obtained for Pb in water. Graphite conch method effectively overcomes the current problems on laser-induced breakdown spectroscopy detection of heavy metal in water. The detection limits and stability are improved. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique.


    Institute of Scientific and Technical Information of China (English)


    A 3-D velocity measurement was carried out via LDV for vortex breakdown of swirling flow in a closed cylindrical container with a rotating disk. The experimental results of swirling flow at Ar=1.78 and Re=648-2527 are presented. At the axis, the axial velocity variation with Re describes the formation, development and disappearance of the vortex breakdown, which agrees with Escudiers’s conclusion. In the meridional plane, the velocity vectors show that the bubble type vortex breakdown region is a closed and low velocity circulating flow, which is fully isolated from the main flow thrown out by the rotating disk. For the peripheral velocity in the central region of the container, the maximum does not appear near the rotating top disk but near the stationary bottom disk and it varies sharply there. Numerical simulation results under the same conditions are also given in this paper.

  14. An integral breakdown criterion for Einstein vacuum equations in the case of asymptotically flat spacetimes

    CERN Document Server

    Parlongue, David


    We will give in this paper the proof of an integral breakdown criterion for Einstein vacuum equations. In a recent article of S.Klainerman and I.Rodnianski a new breakdown criterion was proved as a result of a sequence of articles involving new techniques. However, in this article, the authors mentioned that it was likely possible to prove a sharper result involving an integral condition instead of a pointwise one. This paper is concerned with giving the proof of this improvement. Moreover the proof of this breakdown criterion was written in the original article for a foliation of constant mean curvature, we will present it here for a maximal foliation which leads to some difficulties due to the non-compacity of the leaves of such a foliation and the use of weighted Sobolev norms.

  15. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices. (United States)

    Pejović, Milić M; Denić, Dragan B; Pejović, Momčilo M; Nešić, Nikola T; Vasović, Nikola


    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  16. Shifts in leaf litter breakdown along a forest-pasture-urban gradient in Andean streams. (United States)

    Iñiguez-Armijos, Carlos; Rausche, Sirkka; Cueva, Augusta; Sánchez-Rodríguez, Aminael; Espinosa, Carlos; Breuer, Lutz


    Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest-pasture-urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of

  17. X-Band Photonic Band-Gap Accelerator Structure Breakdown Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, Roark A.; /MIT /MIT /NIFS, Gifu /JAERI, Kyoto /LLNL, Livermore; Shapiro, Michael A.; Temkin, Richard J.; /MIT; Dolgashev, Valery A.; Laurent, Lisa L.; Lewandowski, James R.; Yeremian, A.Dian; Tantawi, Sami G.; /SLAC


    In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.

  18. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    Energy Technology Data Exchange (ETDEWEB)

    Pejovic, Milic M.; Denic, Dragan B.; Pejovic, Momcilo M.; Nesic, Nikola T.; Vasovic, Nikola [Faculty of Electronic Engineering, University of Nis, Aleksandra Medvedeva 14, 18000 Nis (Serbia)


    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  19. Thermal poling of alkaline earth boroaluminosilicate glasses with intrinsically high dielectric breakdown strength (United States)

    Smith, Nicholas J.; Lanagan, Michael T.; Pantano, Carlo G.


    Per the rectification model of thermal poling, it has been proposed that intrinsic breakdown strength plays a strong limiting role in the internal DC fields supported by the glass from the poling process. One might therefore hypothesize proportionately larger second-order nonlinearity (SON) in glasses with intrinsically high dielectric breakdown strength. We test these ideas by thermal poling of two different commercial alkali-free alkaline-earth boroaluminosilicate display glasses—one with barium only (AF45 from Schott), and the other with a mixture of alkaline-earth ions (OA-10 G from NEG). Not only are such compositions relevant from a commercial standpoint, they are also interesting in that they have been recently shown to exhibit remarkably high intrinsic dielectric breakdown strengths of 11-14 MV/cm. Quantitative Maker fringe and stack Maker-fringe measurements provide an accurate evaluation of the poling-induced SON susceptibilities, and indicate maximum χ(2) values of 0.44 and 0.26 pm/V in these glasses. These values are comparable to those reported for silica and other multicomponent glasses. Thus, the hypothesis that higher χ(2) would be observed in high intrinsic breakdown strength glasses was not validated. Based on our application of the rectification model, internal fields of the order 2-4 MV/cm were calculated, which are well below the measured intrinsic breakdown strengths at room temperature. The most plausible explanation for these observations is nonlinear electronic conduction effects taking place within the depletion region at the poling temperature, limiting internal fields to a fraction of the breakdown field.

  20. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices (United States)

    Pejović, Milić M.; Denić, Dragan B.; Pejović, Momčilo M.; Nešić, Nikola T.; Vasović, Nikola


    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  1. Experimental vortex breakdown topology in a cylinder with a free surface

    DEFF Research Database (Denmark)

    Lo Jacono, D.; Nazarinia, M.; Brøns, Morten


    to the surface, which has previously only been found numerically. We employ a technique by Brons et al ["Topology of vortex breakdown bubbles in I cylinder with rotating bottom and free surface J. Fluid Mech 428. 133 (2001)] to find the corresponding bifurcation curve in the parameter plane, which has hitherto...... only been used on numerical data The bifurcation Curve located here agrees well with previous numerical simulations. For low values of the Reynolds number We find a regime with vortex breakdown that has not been previously identified. Experiments deviate substantially from computations, indicating...

  2. Investigation of leakage current and breakdown voltage in irradiated double-sided 3D silicon sensors (United States)

    Dalla Betta, G.-F.; Ayllon, N.; Boscardin, M.; Hoeferkamp, M.; Mattiazzo, S.; McDuff, H.; Mendicino, R.; Povoli, M.; Seidel, S.; Sultan, D. M. S.; Zorzi, N.


    We report on an experimental study aimed at gaining deeper insight into the leakage current and breakdown voltage of irradiated double-sided 3D silicon sensors from FBK, so as to improve both the design and the fabrication technology for use at future hadron colliders such as the High Luminosity LHC. Several 3D diode samples of different technologies and layout are considered, as well as several irradiations with different particle types. While the leakage current follows the expected linear trend with radiation fluence, the breakdown voltage is found to depend on both the bulk damage and the surface damage, and its values can vary significantly with sensor geometry and process details.

  3. Breakdown transient study of plasma distributions in a 2.45 GHz hydrogen discharge

    Energy Technology Data Exchange (ETDEWEB)

    Cortázar, O.D., E-mail: [Universidad de Castilla-La Mancha, ETSII-INEI, Applied Mechanics and Projects Department, C.J. Cela s/n, 13170 Ciudad Real (Spain); Megía-Macías, A. [ESS Bilbao Consortium, Polígono Ugaldeguren-III Pol. A 7B, 48170-Zamudio, Vizcaya (Spain); Tarvainen, O.; Koivisto, H. [University of Jyväskylä, Department of Physics, PO Box 35 (YFL), 40500 Jyväskylä (Finland)


    Plasma distribution transients associated with the breakdown of a 2.45 GHz hydrogen discharge similar to high current microwave ion sources are studied by means of an ultra-fast frame image acquisition system in visible light range. Eight different plasma distributions have been studied by photographing the 2D projections of the discharge through a transparent plasma electrode. The temporal evolution of images in Balmer-alpha and Fulcher band wavelengths have been recorded associated to atomic and molecular excitation and ionization processes. Some unexpected plasma distributions transient behaviors during breakdown are reported.

  4. Study of Edge Effects in the Breakdown Process of p+ on n-bulk Silicon Diodes

    CERN Document Server

    Borrello, L; Da Rold, M; Dell'Orso, R; Dutta, S; Messineo, A; Mihul, A; Militaru, O; Tonelli, G; Verdini, P G; Wheadon, R; Xie, Z


    The paper describes the role of the n+ edge implants in the breakdown process of p+ on n-bulk silicon diodes. Laboratory measurements and simulation studies are presented on a series of test structures aimed at an optimisation of the design in the edge region. The dependence of the breakdown voltage on the geometrical parameters of the devices is discussed in detail. Design rules are extracted for the use of n-wells along the scribe line to avoid surface conduction of current generated by the exposed edges. The effect of neutron irradiation has been studied up to a fluence 1.8*10^15 n/cm2.

  5. SEMICONDUCTOR DEVICES: Off-state avalanche breakdown induced degradation in 20 V NLDMOS devices (United States)

    Shifeng, Zhang; Koubao, Ding; Yan, Han; Chenggong, Han; Jiaxian, Hu; Bin, Zhang


    Degradation behaviors of 20 V NLDMOS operated under off-state avalanche breakdown conditions are presented. A constant current pulse stressing test is applied to the device. Two different degradation mechanisms are identified by analysis of electrical data, technology computer-aided design (TCAD) simulations and charge pumping measurements. The first mechanism is attributed to positive oxide-trapped charges in the N-type drift region, and the second one is due to decreased electron mobility upon interface state formation in the drift region. Both of the mechanisms are enhanced with increasing avalanche breakdown current.

  6. Dielectric-breakdown and conduction-mechanism in a thinned alkali-free glass

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hoikwan; Lanagan, Michael T. [The Pennsylvania State University, University Park, PA (United States)


    The leakage current in alkali-free glass was analyzed to understand the dielectric breakdown behavior and the potential conduction mechanism. The dielectric breakdown strength and the leakage current were increased after the thickness of the glass had been recuded. To identify the predominant conduction mechanism, we carefully interpreted the dc voltage-current curves via fitting with various conduction mechanisms, e.g., Poole-Frenkel emission, Schottky emission, space charge-limited current, and hopping conduction. The result suggested that the space-charge-limited current and the hopping conduction of thermally-excited carriers were the most likely mechanisms of conduction in alkali-free glass.

  7. Breakdown characteristics in pulsed-driven dielectric barrier discharges: influence of the pre-breakdown phase due to volume memory effects (United States)

    Höft, H.; Kettlitz, M.; Becker, M. M.; Hoder, T.; Loffhagen, D.; Brandenburg, R.; Weltmann, K.-D.


    The pre-phase of the breakdown of pulsed-driven dielectric barrier discharges (DBDs) was investigated by fast optical and electrical measurements on double-sided DBDs with a 1 mm gap in a gas mixture of 0.1 vol% O2 in N2 at atmospheric pressure. Depending on the pulse width (the pause time between subsequent DBDs), four different breakdown regimes of the following discharge were observed. By systematically reducing the pulse width, the breakdown characteristics could be changed from a single cathode-directed propagation (positive streamer) to simultaneous cathode- and anode-directed propagations (positive and negative streamer) and no propagation at all for sub-μs pulse times. For all cases, different spatio-temporal emission structures in the pre-phase were observed. The experimental results were compared with time-dependent, spatially one-dimensional fluid model calculations. The modelling results confirmed that different pre-ionisation conditions, i.e. considerably high space charges in the volume created by the residual electrons and ions from the previous discharge, are the reason for the observed phenomena.

  8. Electrical breakdown of an acrylic dielectric elastomer: effects of hemispherical probing electrode’s size and force

    Directory of Open Access Journals (Sweden)

    Bin Chen


    Full Text Available Dielectric elastomers are widely investigated as soft electromechanically active polymers (EAPs for actuators, stretch/force sensors, and mechanical energy harvesters to generate electricity. Although the performance of such devices is limited by the dielectric strength of the constitutive material, the electrical breakdown of soft elastomers for electromechanical transduction is still scarcely studied. Here, we describe a custom-made setup to measure electrical breakdown of soft EAPs, and we present data for a widely studied acrylic elastomer (VHB 4905 from 3M. The elastomer was electrically stimulated via a planar and a hemispherical metal electrode. The breakdown was characterized under different conditions to investigate the effects of the radius of curvature and applied force of the hemispherical electrode. With a given radius of curvature, the breakdown field increased by about 50% for a nearly 10-fold increase of the applied mechanical stress, while with a given mechanical stress the breakdown field increased by about 20% for an approximately twofold increase of the radius of curvature. These results indicate that the breakdown field is highly dependent on the boundary conditions, suggesting the need for reporting breakdown data always in close association with the measurement conditions. These findings might help future investigations in elucidating the ultimate breakdown mechanism/s of soft elastomers.

  9. 7 CFR Exhibit A to Subpart A of... - Estimated Breakdown of Dwelling Costs for Estimating Partial Payments (United States)


    ... 7 Agriculture 12 2010-01-01 2010-01-01 false Estimated Breakdown of Dwelling Costs for Estimating Partial Payments A Exhibit A to Subpart A of Part 1924 Agriculture Regulations of the Department of... A of Part 1924—Estimated Breakdown of Dwelling Costs for Estimating Partial Payments With slab...

  10. Breakdown conditioning of copper, CuZr and GlidCop® : effect of mechanical surface treatments

    CERN Document Server

    Ramsvik, T; Calatroni, S; Taborelli, M; CERN. Geneva. TS Department


    Motivated by the need of novel materials for the CLIC accelerating structures to resist mechanical fatigue, the copper based metals Copper Zirconium C15000 (CuZr) and GlidCop® Al-15 C15715 have been investigated by DC breakdown measurements, and compared with commercially pure Oxygen-free Copper C10100 (Cu-OFE). In all three cases the saturated breakdown fields (Esat) are similar, despite significant differences in their tensile strengths. In addition, the choice of mechanical surface preparation techniques influences the final breakdown characteristics. For both CuZr and GlidCop® immediate conditioning takes place when the surfaces are prepared by milling. For electro discharge machined (EDM) surfaces, however, several breakdown events are needed to obtain saturation. Specifically, for EDM treated CuZr and GlidCop®, ~50 and ~200 breakdown events are required to reach Esat.

  11. Computational studies of suppression of microwave gas breakdown by crossed dc magnetic field using electron fluid model (United States)

    Zhao, Pengcheng; Guo, Lixin; Shu, Panpan


    The gas breakdown induced by a square microwave pulse with a crossed dc magnetic field is investigated using the electron fluid model, in which the accurate electron energy distribution functions are adopted. Simulation results show that at low gas pressures the dc magnetic field of a few tenths of a tesla can prolong the breakdown formation time by reducing the mean electron energy. With the gas pressure increasing, the higher dc magnetic field is required to suppress the microwave breakdown. The electric field along the microwave propagation direction generated due to the motion of electrons obviously increases with the dc magnetic field, but it is much less than the incident electric field. The breakdown predictions of the electron fluid model agree very well with the particle-in-cell-Monte Carlo collision simulations as well as the scaling law for the microwave gas breakdown.

  12. The leaf breakdown of Picramnia sellowii (Picramniales: Picramniaceae as index of anthropic disturbances in tropical streams

    Directory of Open Access Journals (Sweden)

    M. P. Lopes

    Full Text Available Abstract There are few studies in tropical regions exploring the use of leaf breakdown process as a functional tool to assess anthropic disturbance on aquatic ecosystems. We assessed the effects of water pollution due to human activities on the leaf breakdown rate of Picramnia sellowii in streams of the southeastern Brazil. The experiment was carried out for 60 days in three reference streams and three streams impaired by organic pollution and absence of riparian vegetation. Three litter bags were incubated in each stream containing 3 ± 0.05 g of P. sellowii leaves. The reference streams presented higher values of dissolved oxygen and lower values of nutrients, turbidity, electrical conductivity, total impermeable area and water temperature. The leaf breakdown rate (k differed significantly between the reference (k = 0.014 ± 0.003 d–1 and impaired streams (k = 0.005 ± 0.001 d–1. The leaves incubated in the reference streams contained greater fungal biomass (measured as ergosterol concentration and abundance of invertebrates, as well as greater presence of shredders, with k values being related to the biomass of these organisms. Overall, there were clear differences between the leaf mass loss in the reference and impaired streams. These results reinforce the negative effect of urbanization on leaf breakdown and fungal and shredder biomass.

  13. The leaf breakdown of Picramnia sellowii (Picramniales: Picramniaceae) as index of anthropic disturbances in tropical streams. (United States)

    Lopes, M P; Martins, R T; Silveira, L S; Alves, R G


    There are few studies in tropical regions exploring the use of leaf breakdown process as a functional tool to assess anthropic disturbance on aquatic ecosystems. We assessed the effects of water pollution due to human activities on the leaf breakdown rate of Picramnia sellowii in streams of the southeastern Brazil. The experiment was carried out for 60 days in three reference streams and three streams impaired by organic pollution and absence of riparian vegetation. Three litter bags were incubated in each stream containing 3 ± 0.05 g of P. sellowii leaves. The reference streams presented higher values of dissolved oxygen and lower values of nutrients, turbidity, electrical conductivity, total impermeable area and water temperature. The leaf breakdown rate (k) differed significantly between the reference (k = 0.014 ± 0.003 d-1) and impaired streams (k = 0.005 ± 0.001 d-1). The leaves incubated in the reference streams contained greater fungal biomass (measured as ergosterol concentration) and abundance of invertebrates, as well as greater presence of shredders, with k values being related to the biomass of these organisms. Overall, there were clear differences between the leaf mass loss in the reference and impaired streams. These results reinforce the negative effect of urbanization on leaf breakdown and fungal and shredder biomass.

  14. Tensile stress generation by optical breakdown in tissue: Experimental investigations and numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, A. [Medizinisches Laserzentrum Luebeck (Germany); Scammon, R.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States)


    Biological tissue is more susceptible to damage from tensile stress than to compressive stress. Tensile stress may arise through the thermoelastic response of laser-irradiated media. Optical breakdown, however, has to date been exclusively associated with compressive stress. The authors show that this is appropriate for water, but not for tissues for which the elastic-plastic material response needs to be considered. The acoustic transients following optical breakdown in water and cornea were measured with a fast hydrophone and the cavitation bubble dynamics, which is closely linked to the stress wave generation, was documented by flash photography. Breakdown in water produced a monopolar acoustic signal and a bubble oscillation in which the expansion and collapse phases were symmetric. Breakdown in cornea produced a bipolar acoustic signal coupled with a pronounced shortening of the bubble expansion phase and a considerable prolongation of its collapse phase. The tensile stress wave is related to the abrupt end of the bubble expansion. Numerical simulations using the MESA-2D code were performed assuming elastic-plastic material behavior in a wide range of values for the shear modulus and yield strength. The calculations revealed that consideration of the elastic-plastic material response is essential to reproduce the experimentally observed bipolar stress waves. The tensile stress evolves during the outward propagation of the acoustic transient and reaches an amplitude of 30--40% of the compressive pulse.

  15. Diamond-shaped body contact for on-state breakdown voltage improvement of SOI LDMOSFET (United States)

    Daghighi, Arash; Hematian, Hadi


    In this paper, we report a diamond-shaped body contact (DSBC) for silicon-on-insulator (SOI) LDMOSFET. Several DSBC devices along with conventional body contact (CBC) structures are laid out using 0.35 μm SOI MOSFET foundry process. The DSBC device is designed using the same standard layers as in the CBC structure and the contact layout is adapted to process design rules. Experimental characterization of the CBC and DSBC devices in terms of off-state breakdown voltage (BVoff), on-state breakdown voltage (BVon), on-resistance (Ron) and device foot print showed 19% improvement in BVon compared DSBC device with that of the CBC structure. BVoff and Ron of both of the devices are identical. The device foot print is smaller in DSBC device by 11% compared with that of the CBC structure leading to enhanced "On-resistance × Area" figure of merit where smaller high voltage SOI LDMOSEFT reduces the area and cost of power integrated circuits. In order to explain BVon improvement of DSBC structures, three-dimensional (3-D) device simulation is carried out to clarify the lateral BJT action and breakdown mechanism. It is demonstrated that the number of P+ diffusions in DSBC device can be increased to improve BVon without increasing "On-resistance × Area". The on-state breakdown voltage improvement and area efficiency of the diamond-shaped body contact proposes it as a promising candidate for reliable operation of SOI LDMOSFET.

  16. Improvement in breakdown characteristics with multiguard structures in microstrip silicon detectors for CMS

    CERN Document Server

    Bacchetta, N; Candelori, A; Da Rold, M; Descovich, M; Kaminski, A; Messineo, A; Rizzo, F; Verzellesi, G


    To obtain full charge collection the CMS silicon detectors should be able to operate at high bias voltage. We observed that multiguard structures enhance the breakdown performance of the devices on several tens of baby detectors designed for CMS. The beneficial effects of the multiguard structures still remains after the strong neutron irradiation performed to simulate the operation at the LHC. (3 refs).

  17. Effect of surface-breakdown plasma on metal drilling by pulsed CO2-laser radiation (United States)

    Arutiunian, P. V.; Baranov, V. Iu.; Bobkov, I. V.; Bol'Shakov, L. A.; Dolgov, V. A.


    The effect of low-threshold surface breakdown produced by short (5-microsec) CO2-laser pulses on the metal drilling process is investigated. Data on the interaction of metals with laser pulses having the same duration but different shape are shown to be different. The effect of the ambient atmospheric pressure on the laser drilling process is investigated.

  18. Nanoparticle detection in aqueous solutions using Raman and Laser Induced Breakdown Spectroscopy

    NARCIS (Netherlands)

    Sovago, M.; Buis, E.-J.; Sandtke, M.


    We show the chemical identification and quantification of the concentration and size of nanoparticle (NP) dispersions in aqueous solutions by using a combination of Raman Spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS). The two spectroscopic techniques are applied to demonstrate the NP

  19. Roles of Tunneling, Multiphoton Ionization, and Cascade Ionization for Femtosecond Optical Breakdown in Aqueous Media (United States)


    Appl Phys B 76:215-229 [Mao04] Mao S S, Quéré F, Guizard S. Mao X, Russo E, Petite G, Martin P (2004) Dynamics of femtosecond laser interactions...Wey89] Weyl G M (1989) Physics of laser-induced breakdown: An update. In Radziemski LJ, Cremers DA (eds) Laser-induced plasmas and applications. Marcel

  20. Quantifying lycopene synthesis and chlorophyll breakdown in tomato fruit using remittance VIS spectroscopy

    NARCIS (Netherlands)

    Schouten, R.E.; Farneti, B.; Tijskens, L.M.M.; Algarra Alarcon, A.; Woltering, E.J.


    The aim of this study was to increase the understanding of chlorophyll breakdown and lycopene synthesis at a quantitative level in Solanum lycopersicum fruit. To accomplish this, a kinetic model is proposed describing the transition from chloro- to chromoplast. Remittance VIS spectroscopy was used t

  1. A one-dimensional study of the evolution of the microwave breakdown in air

    Energy Technology Data Exchange (ETDEWEB)

    Semenov, V. E.; Rakova, E. I.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation); Tarakanov, V. P. [JIHT RAS, Moscow (Russian Federation); National Research Nuclear University MEPhI, Moscow (Russian Federation); Nusinovich, G. S. [IREAP, University of Maryland, College Park, Maryland 20742-3511 (United States)


    The microwave breakdown in air is simulated numerically within a simple 1D model taking into account a perturbation of electromagnetic field by plasma. The simulations were performed using two qualitatively different codes. One of these codes is based on computation of Maxwell equations, whereas the other one utilizes an approximation of quasi-monochromatic electromagnetic field. There is a good agreement between simulation results obtained by using both codes. Calculations have been carried out in a wide range of air pressures and field frequencies; also varied were initial spatial distributions of plasma density. The results reveal strong dependence of the breakdown evolution on the relation between the field frequency and the gas pressure as well as on the presence of extended rarefied background plasma. At relatively low gas pressures (or high field frequencies), the breakdown process is accompanied by the stationary ionization wave propagating towards the incident electromagnetic wave. In the case of a high gas pressure (or a relatively low field frequency), the peculiarities of the breakdown are associated with a formation of plasma filament array. The extended background plasma can suppress formation of the plasma filament array completely even at high pressures (or low frequencies)

  2. Regulation of glycogen breakdown and its consequences for skeletal muscle function after training. (United States)

    Katz, Abram; Westerblad, Håkan


    Repeated bouts of physical exercise, i.e., training, induce mitochondrial biogenesis and result in improved physical performance and attenuation of glycogen breakdown during submaximal exercise. It has been suggested that as a consequence of the increased mitochondrial volume, a smaller degree of metabolic stress (e.g., smaller increases in ADP and Pi) is required to maintain mitochondrial respiration in the trained state during exercise at the same absolute intensity. The lower degree of Pi accumulation is believed to account for the diminished glycogen breakdown, since Pi is a substrate for glycogen phosphorylase, the rate-limiting enzyme for glycogenolysis. However, in this review, we present an alternative explanation for the diminished glycogen breakdown. Thus, the lower degree of metabolic stress after training is also associated with smaller increases in AMP (free concentration during contraction at specific intracellular sites) and this results in less activation of phosphorylase b (the non-phosphorylated form of phosphorylase), resulting in diminished glycogen breakdown. Concomitantly, the smaller accumulation of Pi, which interferes with cross-bridge function and intracellular Ca(2+) handling, contributes to the increased fatigue resistance. The delay in glycogen depletion also contributes to enhanced performance during prolonged exercise by functioning as an energy reserve.

  3. Minimally invasive non-thermal laser technology using laser-induced optical breakdown for skin rejuvenation

    NARCIS (Netherlands)

    Habbema, L.; Verhagen, R.; Van Hal, R.; Liu, Y.; Varghese, B.


    We describe a novel, minimally invasive laser technology for skin rejuvenation by creating isolated microscopic lesions within tissue below the epidermis using laser induced optical breakdown. Using an in-house built prototype device, tightly focused near-infrared laser pulses are used to create opt

  4. A model for foam formation, stability, and breakdown in glass-melting furnaces

    NARCIS (Netherlands)

    Schaaf, J. van der; Beerkens, R.G.C.


    A dynamic model for describing the build-up and breakdown of a glass-melt foam is presented. The foam height is determined by the gas flux to the glass-melt surface and the drainage rate of the liquid lamellae between the gas bubbles. The drainage rate is determined by the average gas bubble radius

  5. Identification of the breakdown and analysis of transformer 22/0.4 kV

    Directory of Open Access Journals (Sweden)

    Martin Brandt


    Full Text Available The paper deals with the identification of the breakdown of the transformer withdrawn from operation because of repeated reaction of transformer protections. Successively the transformer was put of operation, removed from the distribution and put to diagnostic measurements. The analysis SFRA contributed to the interturn short circuit.

  6. Experimental results with an optimized magnetic field configuration for JET breakdown

    NARCIS (Netherlands)

    Albanese, R.; Maviglia, F.; Lomas, P. J.; Manzanares, A.; Mattei, M.; Neto, A.; Rimini, F. G.; de Vries, P. C.; JET-EFDA Contributors,


    Experiments and modelling have been carried out to optimize the magnetic field null during breakdown at JET. Such optimization may prove to be essential for reliable plasma initiation at low voltages, e.g. in ITER where the value of the electric field available will be limited to 0.33 V&

  7. An assessment of cellulose filters as a standardized material for measuring litter breakdown in headwater streams (United States)

    The decay rate of cellulose filters and associated chemical and biological characteristics were compared to those of white oak (Quercus alba) leaves to determine if cellulose filters could be a suitable standardized material for measuring deciduous leaf breakdown in headwater str...

  8. Experimental Investigation of the Relationship between Breakdown Strength and Tracking Characteristics of Composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Holbøll, Joachim; Henriksen, Mogens;


    The following paper shows possible correlations between results obtained by tracking tests and breakdown field strengths for non coated Glass Fibre Reinforced Polymers (GFRP) with either a polyester or an epoxy based resin. 15 specimens have been tested according to IEC Publication 60587 [4...

  9. Myelin Breakdown Mediates Age-Related Slowing in Cognitive Processing Speed in Healthy Elderly Men (United States)

    Lu, Po H.; Lee, Grace J.; Tishler, Todd A.; Meghpara, Michael; Thompson, Paul M.; Bartzokis, George


    Background: To assess the hypothesis that in a sample of very healthy elderly men selected to minimize risk for Alzheimer's disease (AD) and cerebrovascular disease, myelin breakdown in late-myelinating regions mediates age-related slowing in cognitive processing speed (CPS). Materials and methods: The prefrontal lobe white matter and the genu of…

  10. A breakdown voltage model for implanted resurf p-LDMOS device on n+ buried layer

    NARCIS (Netherlands)

    Zhou, Ming-Jiang; Van Calster, A.


    This paper presents an analytical expression of the breakdown voltage of a high voltage implanted RESURF p-LDMOS device which uses the n+ buried layer as an effective device substrate. In this model, the doping profile of the buried layer is considered and discussed. The implant dose for the drift r

  11. Children Increase Their Sensitivity to a Speaker's Nonlinguistic Cues Following a Communicative Breakdown (United States)

    Yow, W. Quin; Markman, Ellen M.


    Bilingual children regularly face communicative challenges when speakers switch languages. To cope with such challenges, children may attempt to discern a speaker's communicative intent, thereby heightening their sensitivity to nonverbal communicative cues. Two studies examined whether such communication breakdowns increase sensitivity to…

  12. Bifurcation of Vortex Breakdown Patterns in a Circular Cylinder with two Rotating Covers

    DEFF Research Database (Denmark)

    Brøns, Morten; Bisgaard, Anders


    We analyse the topology of vortex breakdown in a closed cylindrical container in the steady domain under variation of three parameters, the aspect ratio of the cylinder, the Reynolds number, and the ratio of the angular velocities of the covers. We develop a general post-processing method to obtain...

  13. New models and distributions of the electrical breakdown time delay in neon

    Energy Technology Data Exchange (ETDEWEB)

    Stamenkovic, S N, E-mail: [Department of Physics, University of Nis, P.O. BOX 224, 18001 Nis (Serbia)


    The measurements of the electrical breakdown time delay t{sub d} for a wide range of working voltages and at different preionization levels are presented. The statistical breakdown time delay t{sub s} and the discharge formative time t{sub f} are experimentally separated and theoretical models of their dependencies on the overvoltage and number densities of residual charges during relaxation are suggested. Several empirical and semiempirical models are used to describe the formative time delay dependence on working voltages t{sub f} (U). The empirical and theoretical models from the literature are also applied to the experimental data, without and with empirical corrections. Moreover, several new distributions are experimentally obtained: Gauss-exponential, Gaussian and double Gaussian ones for the statistical time delay, as well as Gaussian and double Gaussian distributions for the formative time. The measurements of the breakdown time delay at different preionization levels (afterglow periods) t{sub d} ({tau}) obtained with a galvanic layer of gold and a sub-layer of nickel on the copper cathode are compared to the measurements with a vacuum deposited gold layer on the cathode surface. It was found that the surface charges retaining on a galvanic layer of gold influence the breakdown time delay which leads to double Gaussian distributions of the formative and statistical time delay.

  14. On the electrical breakdown of gaseous dielectrics-an engineering approach

    DEFF Research Database (Denmark)

    Pedersen, Aage


    Following an examination of the basic gas-discharge concepts, the Townsend breakdown criterion is derived for nonuniform fields and a reformulation of the streamer criterion is undertaken. A direct application of the Townsend criterion to a practical situation is hardly possible, whereas the stre...

  15. Breakdown pathways during oral processing of different breads: impact of crumb and crust structures. (United States)

    Jourdren, S; Panouillé, M; Saint-Eve, A; Déléris, I; Forest, D; Lejeune, P; Souchon, I


    Oral processing during bread consumption is a key process related to the dynamics of texture perceptions, sensory stimuli release and starch digestion. The aim of this study was to determine the respective contribution of bread properties (composition and structure of crumb and crust) and of the oral physiology of subjects to the breakdown pathways in the mouth. The properties of the in vivo bread bolus obtained from eight healthy subjects were studied at three key points in time during their oral processing. The progressive lubrication and breakdown of bread were observed, as well as the beginning of the enzymatic degradation of starch. The study showed that "time" was the factor responsible for the greatest variability in bolus properties. Breakdown pathways were established for crumbs with and without crust. The presence of crust modified the oral processing, increasing, for instance, the heterogeneity of particle size at the middle of the oral processing sequence. Moreover, the hydration capacity of crust contributed to high starch degradation at swallowing time, in comparison with crumb alone. The main subject characteristics impacting bolus properties were the in-mouth duration, the individual masticatory index and the mouth volume, while the main bread properties explaining the bolus properties were the initial composition and the water-absorbing capacity. We concluded that both crumb and crust structures had an impact on the oral processing, affecting the capacity of hydration, the rheology and the breakdown degree of the bolus.

  16. The influence of titanium dioxide additive on the short-term DC breakdown strength of polyethylene

    DEFF Research Database (Denmark)

    Khalil, M. S; Henk, Peter O; Henriksen, Mogens


    The effect of the addition of 1% by weight of titanium dioxide fine particles to low-density polyethylene (LDPE) on the short-term DC breakdown strength of the LDPE was investigated using direct and reverse polarity voltages. The samples used were cylinders of both plain and doped materials...

  17. Combined raman/laser-induced breakdown spectrometer: space and non-space applications

    NARCIS (Netherlands)

    Sandtke, M.; Laan, E.C.; Ahlers, B.


    TNO has developed the combination of two spectroscopic analysis methods in one instrument. Raman spectroscopy and Laser-induced Breakdown Spectroscopy (LIBS) were brought together for an instrument to be flown on the ExoMars mission from the European Space Agency (ESA) to investigate the Martian (su

  18. Dielectric breakdown strength of magnetic nanofluid based on insulation oil after impulse test (United States)

    Nazari, M.; Rasoulifard, M. H.; Hosseini, H.


    In this study, the dielectric breakdown strength of magnetic nanofluids based on transformer mineral oil for use in power systems is reviewed. Nano oil samples are obtained from dispersion of the magnetic nanofluid within uninhibited transformer mineral oil NYTRO LIBRA as the base fluid. AC dielectric breakdown voltage measurement was carried out according to IEC 60156 standard and the lightning impulse breakdown voltage was obtained by using the sphere-sphere electrodes in an experimental setup for nano oil in volume concentration of 0.1-0.6%. Results indicate improved AC and lightning impulse breakdown voltage of nano oil compared to the base oil. AC test was performed again after applying impulse current and result showed that nano oil unlike the base oil retains its dielectric properties. Increase the dielectric strength of the nano oil is mainly due to dielectric and magnetic properties of Fe3O4 nanoparticles that act as free electrons snapper, and reduce the rate of free electrons in the ionization process.

  19. Adaptive build-up and breakdown of trust : An agent based computational approach

    NARCIS (Netherlands)

    Gorobets, A.; Nooteboom, B.


    This article employs Agent-Based Computational Economics (ACE) to investigate whether, and under what conditions, trust is viable in markets. The emergence and breakdown of trust is modeled in a context of multiple buyers and suppliers. Agents develop trust in a partner as a function of observed loy

  20. Vortex breakdown and control experiments in the Ames-Dryden water tunnel (United States)

    Owen, F. K.; Peake, D. J.


    Flow-field measurements have been made to determine the effects of core blowing on vortex breakdown and control. The results of these proof-of-concept experiments clearly demonstrate the usefulness of water tunnels as test platforms for advanced flow-field simulation and measurement.

  1. Three-dimensional vortex analysis and aeroacoustic source characterization of jet core breakdown

    NARCIS (Netherlands)

    Violato, D.; Scarano, F.


    The three-dimensional behavior of jet core breakdown is investigated with experiments conducted on a free water jet at Re = 5000 by time-resolved tomographic particle image velocimetry (TR-TOMO PIV). The investigated domain encompasses the range between 0 and 10 jet diameters. The characteristic pul

  2. Corticosteroids increase protein breakdown and loss in newly diagnosed pediatric Crohn disease. (United States)

    Steiner, Steven J; Noe, Joshua D; Denne, Scott C


    Children with Crohn disease have altered growth and body composition. Previous studies have demonstrated decreased protein breakdown after either corticosteroid or anti-TNF-α therapy. The aim of this study was to evaluate whole body protein metabolism during corticosteroid therapy in children with newly diagnosed Crohn disease. Children with suspected Crohn disease and children with abdominal symptoms not consistent with Crohn disease underwent outpatient metabolic assessment. Patients diagnosed with Crohn disease and prescribed corticosteroid therapy returned in 2 wk for repeat metabolic assessment. Using the stable isotopes [d5] phenylalanine, [1-(13)C] leucine, and [(15)N(2)] urea, protein kinetics were determined in the fasting state. Thirty-one children (18 controls and 13 newly diagnosed with Crohn disease) completed the study. There were no significant differences in protein breakdown or loss between patients with Crohn disease at diagnosis and controls. After corticosteroid therapy in patients with Crohn disease, the rates of appearance of phenylalanine (32%) and leucine (26%) increased significantly, reflecting increased protein breakdown, and the rate of appearance of urea also increased significantly (273%), reflecting increased protein loss. Whole body protein breakdown and loss increased significantly after 2 wk of corticosteroid therapy in children with newly diagnosed Crohn disease, which may have profound effects on body composition.

  3. Control of vortex breakdown in a closed cylinder with a small rotating rod

    DEFF Research Database (Denmark)

    Lo Jacono, D.; Sørensen, Jens Nørkær; Thompson, M.C.


    Effective control of vortex breakdown in a cylinder with a rotating lid was achieved with small rotating rods positioned on the stationary lid. After validation with accurate measurements using a novel stereoscopic particle image velocimetry (SPIV) technique, analysis of numerical simulations using...

  4. Simple cellular automaton model for traffic breakdown, highway capacity, and synchronized flow. (United States)

    Kerner, Boris S; Klenov, Sergey L; Schreckenberg, Michael


    We present a simple cellular automaton (CA) model for two-lane roads explaining the physics of traffic breakdown, highway capacity, and synchronized flow. The model consists of the rules "acceleration," "deceleration," "randomization," and "motion" of the Nagel-Schreckenberg CA model as well as "overacceleration through lane changing to the faster lane," "comparison of vehicle gap with the synchronization gap," and "speed adaptation within the synchronization gap" of Kerner's three-phase traffic theory. We show that these few rules of the CA model can appropriately simulate fundamental empirical features of traffic breakdown and highway capacity found in traffic data measured over years in different countries, like characteristics of synchronized flow, the existence of the spontaneous and induced breakdowns at the same bottleneck, and associated probabilistic features of traffic breakdown and highway capacity. Single-vehicle data derived in model simulations show that synchronized flow first occurs and then self-maintains due to a spatiotemporal competition between speed adaptation to a slower speed of the preceding vehicle and passing of this slower vehicle. We find that the application of simple dependences of randomization probability and synchronization gap on driving situation allows us to explain the physics of moving synchronized flow patterns and the pinch effect in synchronized flow as observed in real traffic data.

  5. Empirical Features of Spontaneous and Induced Traffic Breakdowns in Free Flow at Highway Bottlenecks

    CERN Document Server

    Kerner, Boris S; Klenov, Sergey L; Rehborn, Hubert; Leibel, Michael


    Based on an empirical study of real field traffic data measured in 1996--2014 through road detectors installed on German freeways, we reveal physical features of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks. It is shown that the source of a nucleus for traffic breakdown is the solely difference between empirical spontaneous and induced traffic breakdowns at a highway bottleneck. Microscopic traffic simulations with a stochastic traffic flow model in the framework of three-phase theory explain the empirical findings. It turns out that in the most cases, a nucleus for empirical spontaneous traffic breakdown occurs through an interaction of one of waves in free flow with an empirical permanent speed disturbance localized at a highway bottleneck. The wave is a localized structure in free flow, in which the total flow rate is larger and the speed averaged across the highway is smaller than outside the wave. The waves in free flow appear due to oscilations in the percentage...

  6. Standard/Handbook for RF Ionization Breakdown Prevention in Spacecraft Components (United States)


    Boeing Company Steven Gold Naval Research Lab Timothy Graves The Aerospace Corporation Eric Holzman Northrop Grumman Kurt Ketola Raytheon Space and...and T. Lewin . "Generalized criteria for microwave breakdown in airfilled waveguides," J. Appl. Phys., vol. 65, no. 8, p. 2935, 1989. [3] Jordan, U

  7. Placement breakdown in foster care: Reducing risks by a foster parent training program?

    NARCIS (Netherlands)

    Maaskant, A.M.


    This thesis started by focusing on Dutch foster children’s well-being, emotional and behavioral functioning and placement stability. Subsequently, we attempted to identify how foster families who are considered to be at a high risk of placement breakdown could be given effective support. The finding

  8. Experiments and Computational Theory for Electrical Breakdown in Critical Components: THz Imaging of Electronic Plasmas.

    Energy Technology Data Exchange (ETDEWEB)

    Zutavern, Fred J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hjalmarson, Harold P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bigman, Verle Howard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gallegos, Richard Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    This report describes the development of ultra-short pulse laser (USPL) induced terahertz (THz) radiation to image electronic plasmas during electrical breakdown. The technique uses three pulses from two USPLs to (1) trigger the breakdown, (2) create a 2 picosecond (ps, 10 -12 s), THz pulse to illuminate the breakdown, and (3) record the THz image of the breakdown. During this three year internal research program, sub-picosecond jitter timing for the lasers, THz generation, high bandwidth (BW) diagnostics, and THz image acquisition was demonstrated. High intensity THz radiation was optically-induced in a pulse-charged gallium arsenide photoconductive switch. The radiation was collected, transported, concentrated, and co-propagated through an electro-optic crystal with an 800 nm USPL pulse whose polarization was rotated due to the spatially varying electric field of the THz image. The polarization modulated USPL pulse was then passed through a polarizer and the resulting spatially varying intensity was detected in a high resolution digital camera. Single shot images had a signal to noise of %7E3:1. Signal to noise was improved to %7E30:1 with several experimental techniques and by averaging the THz images from %7E4000 laser pulses internally and externally with the camera and the acquisition system (40 pulses per readout). THz shadows of metallic films and objects were also recorded with this system to demonstrate free-carrier absorption of the THz radiation and improve image contrast and resolution. These 2 ps THz pulses were created and resolved with 100 femtosecond (fs, 10 -15 s) long USPL pulses. Thus this technology has the capability to time-resolve extremely fast repetitive or single shot phenomena, such as those that occur during the initiation of electrical breakdown. The goal of imaging electrical breakdown was not reached during this three year project. However, plans to achieve this goal as part of a follow-on project are described in this document

  9. Epidemiological Investigation of Bovine Tuberculosis Herd Breakdowns in Spain 2009/2011 (United States)

    Guta, Sintayehu; Casal, Jordi; Napp, Sebastian; Saez, Jose Luis; Garcia-Saenz, Ariadna; Perez de Val, Bernat; Romero, Beatriz; Alvarez, Julio; Allepuz, Alberto


    We analyzed the most likely cause of 687 bovine tuberculosis (bTB) breakdowns detected in Spain between 2009 and 2011 (i.e., 22% of the total number of breakdowns detected during this period). Seven possible causes were considered: i) residual infection; ii) introduction of infected cattle from other herds; iii) sharing of pastures with infected herds; iv) contiguous spread from infected neighbor herds; v) presence of infected goats in the farm; vi) interaction with wildlife reservoirs and vii) contact with an infected human. For each possible cause a decision tree was developed and key questions were included in each of them. Answers to these key questions lead to different events within each decision tree. In order to assess the likelihood of occurrence of the different events a qualitative risk assessment approach was used. For this purpose, an expert opinion workshop was organized and ordinal values, ranging from 0 to 9 (i.e., null to very high likelihood of occurrence) were assigned. The analysis identified residual infection as the most frequent cause of bTB breakdowns (22.3%; 95%CI: 19.4–25.6), followed by interaction with wildlife reservoirs (13.1%; 95%CI: 10.8–15.8). The introduction of infected cattle, sharing of pastures and contiguous spread from infected neighbour herds were also identified as relevant causes. In 41.6% (95%CI: 38.0–45.4) of the breakdowns the origin of infection remained unknown. Veterinary officers conducting bTB breakdown investigations have to state their opinion about the possible cause of each breakdown. Comparison between the results of our analysis and the opinion from veterinary officers revealed a slight concordance. This slight agreement might reflect a lack of harmonized criteria to assess the most likely cause of bTB breakdowns as well as different perceptions about the importance of the possible causes. This is especially relevant in the case of the role of wildlife reservoirs. PMID:25127254

  10. Calcium ion requirement for acetylcholine-stimulated breakdown of triphosphoinositide in rabbit iris smooth muscle. (United States)

    Akhtar, R A; Abdel-Latif, A A


    Previous studies from this laboratory have established that addition of acetylcholine (ACh) or norepinephrine to 32P-labeled rabbit iris smooth muscle increases significantly the breakdown of triphosphoinositide (TPI) and that these stimulatory effects are blocked by atropine and phentolamine, respectively. The present studies were undertaken in order to show the effect of Ca++ on the ACh-stimulated breakdown of TPI ("TPI effect") in this tissue. Paired iris smooth muscles were prelabeled with 32Pi for 30 minutes at 37 degrees C in Ca++-free iso-osmotic salt medium. The prelabeled irises were then washed and incubated for 10 minutes in nonradioactive Ca++-free medium which contained 10 mM 2-deoxyglucose under various conditions. The phospholipids were isolated by means of two-dimensional thin-layer chromatography and their radioactivities were determined. In the absence of Ca++, 50 micrometer ACh increased TPI breakdown and phosphatidic acid (PA) labeling by 16 and 38%, respectively. In the absence of ACh, 0.75 micrometer Ca++ increased TPI breakdown and PA labeling by 11 and 20%, respectively. When both ACh and Ca++ were added, the increase in TPI breakdown and PA labeling rose to 32 and 74%, respectively. The labeling of phosphatidylinositol was found to be insensitive to the presence of Ca++. Ca++ was determined in the iris smooth muscle and it was found to contain 3.13 mumol of Ca++ per g of tissue. This was reduced by 80% after the muscle was washed and incubated in a medium which contained 0.25 micrometer ethyleneglycol bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA). The TPI effect was abolished by 0.25 micrometer EGTA and restored when excess Ca++ (1.25 micrometer) was added. Concentrations of Ca++ as low as 50 micrometer provoked a TPI effect. Sr++ (2 micrometer), but not Ba++ or Mn++, was found to substitute partially for Ca++. Ionophore A-23187 (20 micrometer) was found to increase the breakdown of TPI and labeling of PA by 11 and 24

  11. Drought, Mutualism Breakdown, and Landscape-Scale Degradation of Seagrass Beds. (United States)

    de Fouw, Jimmy; Govers, Laura L; van de Koppel, Johan; van Belzen, Jim; Dorigo, Wouter; Sidi Cheikh, Mohammed A; Christianen, Marjolijn J A; van der Reijden, Karin J; van der Geest, Matthijs; Piersma, Theunis; Smolders, Alfons J P; Olff, Han; Lamers, Leon P M; van Gils, Jan A; van der Heide, Tjisse


    In many marine ecosystems, biodiversity critically depends on foundation species such as corals and seagrasses that engage in mutualistic interactions [1-3]. Concerns grow that environmental disruption of marine mutualisms exacerbates ecosystem degradation, with breakdown of the obligate coral mutualism ("coral bleaching") being an iconic example [2, 4, 5]. However, as these mutualisms are mostly facultative rather than obligate, it remains unclear whether mutualism breakdown is a common risk in marine ecosystems, and thus a potential accelerator of ecosystem degradation. Here, we provide evidence that drought triggered landscape-scale seagrass degradation and show the consequent failure of a facultative mutualistic feedback between seagrass and sulfide-consuming lucinid bivalves that in turn appeared to exacerbate the observed collapse. Local climate and remote sensing analyses revealed seagrass collapse after a summer with intense low-tide drought stress. Potential analysis-a novel approach to detect feedback-mediated state shifts-revealed two attractors (healthy and degraded states) during the collapse, suggesting that the drought disrupted internal feedbacks to cause abrupt, patch-wise degradation. Field measurements comparing degraded patches that were healthy before the collapse with patches that remained healthy demonstrated that bivalves declined dramatically in degrading patches with associated high sediment sulfide concentrations, confirming the breakdown of the mutualistic seagrass-lucinid feedback. Our findings indicate that drought triggered mutualism breakdown, resulting in toxic sulfide concentrations that aggravated seagrass degradation. We conclude that external disturbances can cause sudden breakdown of facultative marine mutualistic feedbacks. As this may amplify ecosystem degradation, we suggest including mutualisms in marine conservation and restoration approaches.

  12. Direct numerical simulation and stability analyses of three-dimensional swirling jets and wakes exhibiting vortex breakdown (United States)

    Ruith, Michael Rudolf

    Vortex breakdown of nominally axisymmetric, swirling incompressible jets and wakes issuing into a semi-infinite domain is studied by means of direct numerical simulations, as well as local and global linear stability analyses. From the point of view of specifying conditions at the open boundaries, this class of flows is particularly challenging due to its ability to support traveling waves. Several boundary conditions, ranging from free-slip and various homogeneous Neumann conditions to radiation conditions, are implemented in a staggered grid, finite difference algorithm that solves the unsteady Navier-Stokes equations in cylindrical coordinates by means of a fractional step method. Their advantages and shortcomings are evaluated in detail, and the question of the proper implementation of intermediate step boundary conditions is addressed. The data obtained from a large variety of test simulations points to the radiation condition as the most suitable lateral and outflow boundary condition for both high and low entrainment jets and wakes. A two-parameterc low entrainment velocity profile for which the steady, axisymmetric breakdown is well studied is selected for further investigation. Hence, issues regarding the role of three-dimensionality and unsteadiness with respect to the existence, mode selection, and internal structure of vortex breakdown can be addressed in terms of the two governing parameters and the Reynolds number. Low Reynolds numbers are found to yield flow fields lacking breakdown bubbles or helical breakdown modes even for high swirl. In contrast, highly swirling flows at large Reynolds numbers exhibit bubble, helical or double helical breakdown modes, where the axisymmetric mode is promoted by a jet-like axial velocity profile, while a wake-like profile renders the flow helically unstable and ultimately yields non-axisymmetric breakdown modes. It is shown that a transition from super- to subcritical flow, accurately predicts the parameter

  13. Imaging the Effect of Electrical Breakdown in Multilayer Polymer Capacitor Films (United States)

    Wolak, Mason


    Multilayer polymer films show great promise as the dielectric material in high energy density capacitors. Such films show enhancement in both dielectric strength (EB) and energy density (Ud) relative to monolithic films of either source polymer. Composites are typically comprised of alternating layers of a high EB polymer and a high permittivity polymer. Here, we discuss a multilayer system based on polycarbonate (PC) interleaved with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The dielectric properties of the PC/PVDF-HFP films are influenced by both composition and individual layer thickness. Optimized films show EB = 750 kV/mm and Ud = 13 J/cm3. Further enhancements in EB and Ud are expected through optimization of the component polymers, composition, and layer structure. To guide next generation design, it is important to understand the breakdown mechanism, as it directly influences EB. To elucidate the role of the layer structure during electrical breakdown, we use a tandem focused ion beam (FIB) / scanning electron microscope (SEM) imaging technique. The technique allows us to image the internal layer structure of both `as fabricated' control films, and those subjected to high electric fields. It is therefore a powerful tool to assess film quality and analyze failure mechanisms. Specifically, the FIB is used to mill site-specific holes in a film and the resulting cross-sections are imaged via SEM. Individual layers are easily resolved down to 50 nm. For films subjected to electrical breakdown, the location and propagation of damage is tracked with sequential FIB milling and SEM imaging. Spatially resolved FIB/SEM imaging allows preparation of quasi-3D maps displaying the evolution of internal voids in areas adjacent to the breakdown location (pinhole of d = 30-80 microns). A majority of the voids are localized at the interfaces between layers and may propagate as far as 30-50 microns from the pinhole. The data suggest that the enhancement in

  14. Do secondary compounds inhibit microbial- and insect-mediated leaf breakdown in a tropical rainforest stream, Costa Rica? (United States)

    Ardón, Marcelo; Pringle, Catherine M


    We examined the hypothesis that high concentrations of secondary compounds in leaf litter of some tropical riparian tree species decrease leaf breakdown by inhibiting microbial and insect colonization. We measured leaf breakdown rates, chemical changes, bacterial, fungal, and insect biomass on litterbags of eight species of common riparian trees incubated in a lowland stream in Costa Rica. The eight species spanned a wide range of litter quality due to varying concentrations of nutrients, structural and secondary compounds. Leaf breakdown rates were fast, ranging from 0.198 d(-1 )(Trema integerrima) to 0.011 d(-1) (Zygia longifolia). Processing of individual chemical constituents was also rapid: cellulose was processed threefold faster and hemicellulose was processed fourfold faster compared to similar studies in temperate streams. Leaf toughness (r = -0.86, P = 0.01) and cellulose (r = -0.78, P = 0.02) were the physicochemical parameters most strongly correlated with breakdown rate. Contrary to our initial hypothesis, secondary compounds were rapidly leached (threefold faster than in temperate studies), with all species losing all secondary compounds within the first week of incubation. Cellulose was more important than secondary compounds in inhibiting breakdown. Levels of fungal and bacterial biomass were strongly correlated with breakdown rate (fungi r = 0.64, P = 0.05; bacteria r = 0.93, P shredders dominate. Insect biomass was negatively correlated with breakdown rate (r = -0.70, P = 0.02), suggesting that insects did not play an important role in breakdown. Despite a wide range of initial concentrations of secondary compounds among the eight species used, we found that secondary compounds were rapidly leached and were less important than structural compounds in determining breakdown rates.

  15. A novel high-voltage device structure with an N+ ring in substrate and the breakdown voltage model

    Institute of Scientific and Technical Information of China (English)

    Li Qi; Zhu Jinluan; Wang Weidong; Yue Hongwei; Jin Liangnian


    A novel high-voltage device structure with a floating heavily doped N+ ring embedded in the substrate is reported,which is called FR LDMOS.When the N+ ring is introduced in the device substrate,the electric field peak of the main junction is reduced due to the transfer of the voltage from the main junction to the N+ ring junction,and the vertical breakdown characteristic is improved significantly.Based on the Poisson equation of cylindrical coordinates,a breakdown voltage model is developed.The numerical results indicate that the breakdown voltage of the proposed device is increased by 56% in comparison to conventional LDMOS.

  16. Comparison of the detection characteristics of trace species using laser-induced breakdown spectroscopy and laser breakdown time-of-flight mass spectrometry. (United States)

    Wang, Zhenzhen; Deguchi, Yoshihiro; Yan, Junjie; Liu, Jiping


    The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS) and laser breakdown time-of-flight mass spectrometry (LB-TOFMS). Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application.

  17. Meiosis, egg activation, and nuclear envelope breakdown are differentially reliant on Ca2+, whereas germinal vesicle breakdown is Ca2+ independent in the mouse oocyte (United States)

    Tombes, R. M.; Simerly, C.; Borisy, G. G.; Schatten, G.


    During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activation and during first mitosis in a single species using the same methodologies. Cumulus-free metaphase II mouse oocytes immediately resumed anaphase upon the induction of a large, transient Ca2+ elevation. This resumption of meiosis and associated events, such as cortical granule discharge, were not sensitive to extracellular Ca2+ removal, but were blocked by intracellular Ca2+ chelators. In contrast, meiosis I was dependent on external Ca2+; in its absence, the formation and function of the first meiotic spindle was delayed, the first polar body did not form and an interphase-like state was induced. GVBD was not dependent on external Ca2+ and showed no associated Ca2+ changes. NEBD at first mitosis in fertilized eggs, on the other hand, was frequently, but not always associated with a brief Ca2+ transient and was dependent on Ca2+ mobilization. We conclude that GVBD is Ca2+ independent, but that the dependence of NEBD on Ca2+ suggests regulation by more than one pathway. As cells develop from Ca(2+)-independent germinal vesicle oocytes to internal Ca(2+)-dependent pronuclear eggs, internal Ca2+ pools increase by approximately fourfold.

  18. Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Zhenzhen Wang


    Full Text Available The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS and laser breakdown time-of-flight mass spectrometry (LB-TOFMS. Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application.


    Institute of Scientific and Technical Information of China (English)

    Liu Ying-zheng; Chen Han-ping; Koyama Hide S.


    Bubble-type vortex breakdown of the swirling flow inside a closed cylindrical container with a rotating upper endwall was experimentally investigated via LDV.3D measurement of the steady bubble at H/R=1.5 was firstly carried out with very fine grid arrangement.Flow details inside the bubble and its Re-dependent structure were made clear.Abrupt waves of the azimuthal velocity component were always found to be between the bottom stationary endwall and the upstream stagnation point, which might be the reason of bubble formation.Variation of bubble structure and bubble center with the increasing Re gives the explanation for the disappearance of the breakdown region.

  20. The Graphene Oxide Polymer Composites with High Breakdown Field Strength and Energy Storage Ability (United States)

    Li, Yang; Hu, Jun; He, Jinliang; Gao, Lei

    The crystalline structure of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is strongly related with its breakdown characteristic and energy storage capability. A graphene oxide (GO) polymer composite, making use of the specific interaction between GO and PVDF-HFP that can induce the formation of β-phase when crystallizing from solution, was developed. The results indicate that the breakdown field strength of the composites with GO nanosheets can reach more than 350 MV/m with small variance. And the composites exhibit a moderate dielectric constant (>13) which can obtain a maximum energy storage density of near 10 J/cm3 and discharged 5 J/cm3. Besides GO can alter the crystalline structure of PVDF-HFP from the non-polar phase to the polar phase. As a result, the composites with GO can achieve the similar results by mechanical stretching and avoid the necking effect in stretching.

  1. Universally Spatial-Temporal Dynamics of Spontaneous Superfluidity Breakdown within Synthetic Gauge Fields

    CERN Document Server

    Wu, Shuyuan; Xu, Jun; Lee, Chaohong


    According to the famous Kibble-Zurek mechanism (KZM), the universality of spontaneous defect generation in continuous phase transitions (CPTs) can be understood by the critical slowing down. In most CPTs of atomic Bose-Einstein condensates (BECs), the universality of spontaneous defect generations has been explained by the divergent relaxation time associated with the nontrivial gapless Bogoliubov excitations. However, for atomic BECs in synthetic gauge fields, their spontaneous superfluidity breakdown is resulted from the divergent correlation length associated with the zero Landau critical velocity. Here, by considering an atomic BEC ladder subjected to a synthetic magnetic field, we reveal that the spontaneous superfluidity breakdown obeys the KZM. The Kibble-Zurek scalings are derived from the Landau critical velocity which determines the correlation length. In further, the critical exponents are numerically extracted from the critical spatial-temporal dynamics of the bifurcation delay and the spontaneous...

  2. High-Voltage Breakdown Penalties for the Beam-Breakup Instability

    Energy Technology Data Exchange (ETDEWEB)

    Ekdahl, Carl August [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    The strength of the dangerous beam breakup (BBU) instability in linear induction accelerators (LIAs) is determined by the transverse coupling impedance Z of the induction cell cavity. For accelerating gap width w less than the beam pipe radius b, the transverse impedance is theoretically proportional to w/b, favoring narrow gaps to suppress BBU. On the other hand, cells with narrow gaps cannot support high accelerating gradients, because of electrical breakdown and shorting of the gap. Thus, there is an engineering trade-off between BBU growth and accelerating gradient, which must be considered for next generation LIAs now being designed. In this article this tradeoff is explored, using a simple pillbox cavity as an illustrative example. For this model, widening the gap to reduce the probability of breakdown increases BBU growth, unless higher magnetic focusing fields are used to further suppress the instability.

  3. CFD simulations of a wind turbine for analysis of tip vortex breakdown (United States)

    Kimura, K.; Tanabe, Y.; Aoyama, T.; Matsuo, Y.; Arakawa, C.; Iida, M.


    This paper discusses about the wake structure of wind turbine via the use of URANS and Quasi-DNS, focussing on the tip vortex breakdown. The moving overlapped structured grids CFD Solver based on a fourth-order reconstruction and an all-speed scheme, rFlow3D is used for capturing the characteristics of tip vortices. The results from the Model Experiments in Controlled Conditions project (MEXICO) was accordingly selected for executing wake simulations through the variation of tip speed ratio (TSR); in an operational wind turbine, TSR often changes in value. Therefore, it is important to assess the potential effects of TSR on wake characteristics. The results obtained by changing TSR show the variations of the position of wake breakdown and wake expansion. The correspondence between vortices and radial/rotational flow is also confirmed.

  4. Study of electrical breakdown and secondary pull-in failure modes for NEM relays (United States)

    Ramezani, M.; Severi, S.; Tilmans, H. A. C.; De Meyer, K.


    In this work, two common failure modes of nano-electro-mechanical (NEM) relays: (1) electrical breakdown and (2) stiction due to secondary pull-in were analyzed. These effects are dominant when dimensions of the device are scaled to the sub-micrometer scale. Like MEMS devices, design adjustments, such as introduction of dimples, cannot provide a solution. The geometrical parameters and working environment drive directly the occurrence of these failure modes. The beam length is the key parameter in driving the electrical breakdown while the distance of the gate to the drain, the beam thickness, and the actuation gap set the limits for secondary pull-in voltage. The analysis shows that these failure modes could be mitigated and a physical parameters design space could be identified to achieve NEM devices for high speed operation.

  5. Interaction of high-power microwave with air breakdown plasma at low pressure (United States)

    Zhao, Pengcheng; Guo, Lixin; Shu, Panpan


    The high-power microwave breakdown at the low air pressure (about 0.01 atm) is simulated numerically using the one-dimensional model coupling Maxwell's equations with plasma fluid equations. The accuracy of the model is validated by comparing the breakdown prediction with the experimental data. We find that a diffuse plasma with a stationary front profile forms due to the large electron diffusion. Most of the incident wave energy is absorbed and reflected by the plasma when the plasma front achieves a stationary profile. The front propagation velocity remains almost unchanged with time and increases when the incident wave amplitude increases or the incident wave frequency decreases. With the incident wave frequency increasing, the maximum density of the stationary plasma front increases, while the ratio of the reflected wave power to the incident wave power remains almost unchanged. At a higher incident wave amplitude, the maximum density and reflectance become large.

  6. Phase Space for the Breakdown of the Quantum Hall Effect in Epitaxial Graphene (United States)

    Alexander-Webber, J. A.; Baker, A. M. R.; Janssen, T. J. B. M.; Tzalenchuk, A.; Lara-Avila, S.; Kubatkin, S.; Yakimova, R.; Piot, B. A.; Maude, D. K.; Nicholas, R. J.


    We report the phase space defined by the quantum Hall effect breakdown in polymer gated epitaxial graphene on SiC (SiC/G) as a function of temperature, current, carrier density, and magnetic fields up to 30 T. At 2 K, breakdown currents (Ic) almost 2 orders of magnitude greater than in GaAs devices are observed. The phase boundary of the dissipationless state (ρxx=0) shows a [1-(T/Tc)2] dependence and persists up to Tc>45K at 29 T. With magnetic field Ic was found to increase ∝B3/2 and Tc∝B2. As the Fermi energy approaches the Dirac point, the ν=2 quantized Hall plateau appears continuously from fields as low as 1 T up to at least 19 T due to a strong magnetic field dependence of the carrier density.

  7. Characterization of breakdown behavior of diamond Schottky barrier diodes using impact ionization coefficients (United States)

    Driche, Khaled; Umezawa, Hitoshi; Rouger, Nicolas; Chicot, Gauthier; Gheeraert, Etienne


    Diamond has the advantage of having an exceptionally high critical electric field owing to its large band gap, which implies its high ability to withstand high voltages. At this maximum electric field, the operation of Schottky barrier diodes (SBDs), as well as FETs, may be limited by impact ionization, leading to avalanche multiplication, and hence the devices may breakdown. In this study, three of the reported impact ionization coefficients for electrons, αn, and holes, αp, in diamond at room temperature (300 K) are analyzed. Experimental data on reverse operation characteristics obtained from two different diamond SBDs are compared with those obtained from their corresponding simulated structures. Owing to the crucial role played by the impact ionization rate in determining the carrier transport, the three reported avalanche parameters implemented affect the behavior not only of the breakdown voltage but also of the leakage current for the same structure.

  8. Origin of anomalous magnetic breakdown frequencies in quasi-two-dimensional organic conductors (United States)

    Sandhu, P. S.; Kim, Ju H.; Brooks, J. S.


    We investigate the origin of anomalous magnetic breakdown frequencies in the de Haas-van Alphen (dHvA) effect in quasi-two-dimensional organic conductors such as α-(BEDT-TTF)2KHg(SCN)4 and κ-(BEDT-TTF)2Cu(NCS)2. A tight-binding model based on their realistic band structure is constructed and solved numerically to compute the field dependence of the magnetization. The present model provides a natural description for the phenomenon of magnetic breakdown between coexisting closed and open Fermi surfaces and accounts for the experimentally observed frequencies that are forbidden in the semiclassical picture. We find that the appearance of these anomalous frequencies in the dHvA signal is a quantum-mechanical effect which arises from differences in field dependence of the states in the two partially occupied bands near the Fermi level.

  9. Growth by random walker sampling and scaling of the dielectric breakdown model (United States)

    Somfai, Ellák; Goold, Nicholas R.; Ball, Robin C.; Devita, Jason P.; Sander, Leonard M.


    Random walkers absorbing on a boundary sample the harmonic measure linearly and independently: we discuss how the recurrence times between impacts enable nonlinear moments of the measure to be estimated. From this we derive a technique to simulate dielectric breakdown model growth, which is governed nonlinearly by the harmonic measure. For diffusion-limited aggregation, recurrence times are shown to be accurate and effective in probing the multifractal growth measure in its active region. For the dielectric breakdown model our technique grows large clusters efficiently and we are led to significantly revise earlier exponent estimates. Previous results by two conformal mapping techniques were less converged than expected, and in particular a recent theoretical suggestion of superuniversality is firmly refuted.

  10. Investigation of laser induced breakdown in liquid nitromethane using nanosecond shadowgraphy (United States)

    Guo, Wencan; Zheng, Xianxu; Yu, Guoyang; Zhao, Jun; Zeng, Yangyang; Liu, Cangli


    A nanosecond time-resolved shadowgraphy is performed to observe a laser-induced breakdown in nitromethane. The digital delays are introduced between a pump beam and an illumination light to achieve a measuring range from 40 ns to 100 ms, which enable us to study the shock wave propagation, bubble dynamics, and other process of the laser-induced breakdown. Compared with distilled water, there are two obvious differences observed in nitromethane: (1) the production of a non-evaporative gas at the final stage, and (2) an absence of the secondary shock wave after the first collapse of the bubble. We also calculated the bubble energy in nitromethane and distilled water under a different incident energy. The results indicate that the bubble energy in nitromethane is more than twice as large as that in water. It is suggested that chemical reactions contribute to the releasing of energy.

  11. Prediction of the breakdown voltage of transformer oil based on a backpropagation network

    Energy Technology Data Exchange (ETDEWEB)

    Cao Shun' an; Li Rui; Sheng Kai [Wuhan Univ., Hubei Province (China). Dept. of Water Quality Engineering


    Prediction of the breakdown voltage of transformer oil facilitates the early fault diagnosis of transformers, and provides a scientific basis for the prevention of faults in transformer oil. In this paper, based on the correlation between performance parameters of transformer oil, along with the excellent fault-tolerant ability, prominent non-linear approximation capability and self-learning capacity of backpropagation (BP) networks, a BP network with a BP algorithm and a BP network with an improved BP algorithm are developed to simulate the correlation between breakdown voltage and four relevant parameters, using the monitoring data of transformer oil. The results show that the latter algorithm gives more accurate predicted values, which proves to be of high application value. (orig.)

  12. Reverse flow and vortex breakdown in a shear-thinning fluid

    Energy Technology Data Exchange (ETDEWEB)

    Cabeza, C; Sarasua, G; Barrere, N; Marti, A C, E-mail: [Instituto de Fisica, Facultad de Ciencias, UDELAR (Uruguay)


    The effect of polymer concentration on the development of reverse secondary flow and vortex breakdown was studied using a viscoelastic solution of polyacrlylamide in water. The fluid was contained in cylindrical containers of two different radii, the top end wall of which rotated at a varying speed, thus, imparting a circulating motion to the fluid. Whereas using a newtonian fluid, streamlines will occupy the entire container, the flow of a shear-thinning fluid may divide into two cells of opposite circulating motion. The curve of critical Reynolds and elasticity numbers (Re, E) values corresponding to the development of reverse flow was obtained over a wide range of Re values. Vortex breakdown was found to occur at extremely low Re values.

  13. Anisotropic breakdown of Fermi liquid quasiparticle excitations in overdoped La₂-xSrxCuO₄. (United States)

    Chang, J; Månsson, M; Pailhès, S; Claesson, T; Lipscombe, O J; Hayden, S M; Patthey, L; Tjernberg, O; Mesot, J


    High-temperature superconductivity emerges from an un-conventional metallic state. This has stimulated strong efforts to understand exactly how Fermi liquids breakdown and evolve into an un-conventional metal. A fundamental question is how Fermi liquid quasiparticle excitations break down in momentum space. Here we show, using angle-resolved photoemission spectroscopy, that the Fermi liquid quasiparticle excitations of the overdoped superconducting cuprate La1.77Sr0.23CuO4 is highly anisotropic in momentum space. The quasiparticle scattering and residue behave differently along the Fermi surface and hence the Kadowaki-Wood's relation is not obeyed. This kind of Fermi liquid breakdown may apply to a wide range of strongly correlated metal systems where spin fluctuations are present.

  14. Identification of inks and structural characterization of contemporary artistic prints by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Oujja, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Vila, A. [Departament de Pintura, Conservacio-Restauracio, Facultat de Belles Arts, Universitat de Barcelona, Pau Gargallo 4, 08028 Barcelona (Spain); Rebollar, E. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Garcia, J.F. [Departament de Pintura, Conservacio-Restauracio, Facultat de Belles Arts, Universitat de Barcelona, Pau Gargallo 4, 08028 Barcelona (Spain); Castillejo, M. [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain)]. E-mail:


    Identification of the inks used in artistic prints and the order in which different ink layers have been applied on a paper substrate are important factors to complement the classical stylistic aspects for the authentication of this type of objects. Laser-induced breakdown spectroscopy (LIBS) is investigated to determine the chemical composition and structural distribution of the constituent materials of model prints made by applying one or two layers of several blue and black inks on an Arches paper substrate. By using suitable laser excitation conditions, identification of the inks was possible by virtue of emissions from key elements present in their composition. Analysis of successive spectra on the same spot allowed the identification of the order in which the inks were applied on the paper. The results show the potential of laser-induced breakdown spectroscopy for the chemical and structural characterization of artistic prints.

  15. Exciton photoluminescence from ZnO layers produced by laser-induced gas breakdown processing

    Energy Technology Data Exchange (ETDEWEB)

    Kabashin, A.V.; Trudeau, A.; Meunier, M. [Laser Processing Laboratory, Ecole Polytechnique de Montreal, Departement de Genie Physique, Case Postale 6079, Montreal, Quebec (Canada); Marine, W. [CRMCN UPR CNRS 7251, Departement de Physique, Case 901, Faculte des Sciences de Luminy, Marseille Cedex 9 (France)


    The plasma of optically-excited gas breakdown has been used to treat a Zn target in atmospheric pressure gases (air, O{sub 2}, N{sub 2}, Ar). The breakdown is produced near the target by a pulsed CO{sub 2} laser radiation, yielding to a local erosion of the target under the irradiation spot and the formation of a porous nanostructured layer, consisting of ZnO nanoscale spheres. We show that the produced nanostructured layers exhibit an intense exciton emission band in the ultraviolet range (380-385 nm), while defect-related photoluminescent bands were weak and could be completely removed by varying the fabrication parameters. Properties of the produced layers were found to be very promising for the development of optoelectronic devices. (orig.)

  16. Extension of the dielectric breakdown model for simulation of viscous fingering at finite viscosity ratios. (United States)

    Doorwar, Shashvat; Mohanty, Kishore K


    Immiscible displacement of viscous oil by water in a petroleum reservoir is often hydrodynamically unstable. Due to similarities between the physics of dielectric breakdown and immiscible flow in porous media, we extend the existing dielectric breakdown model to simulate viscous fingering patterns for a wide range of viscosity ratios (μ(r)). At low values of power-law index η, the system behaves like a stable Eden growth model and as the value of η is increased to unity, diffusion limited aggregation-like fractals appear. This model is compared with our two-dimensional (2D) experiments to develop a correlation between the viscosity ratio and the power index, i.e., η = 10(-5)μ(r)(0.8775). The 2D and three-dimensional (3D) simulation data appear scalable. The fingering pattern in 3D simulations at finite viscosity ratios appear qualitatively similar to the few experimental results published in the literature.

  17. Impact of gas flow rate on breakdown of filamentary dielectric barrier discharges (United States)

    Höft, H.; Becker, M. M.; Kettlitz, M.


    The influence of gas flow rate on breakdown properties and stability of pulsed dielectric barrier discharges (DBDs) in a single filament arrangement using a gas mixture of 0.1 vol. % O2 in N2 at atmospheric pressure was investigated by means of electrical and optical diagnostics, accompanied by fluid dynamics and electrostatics simulations. A higher flow rate perpendicular to the electrode symmetry axis resulted in an increased breakdown voltage and DBD current maximum, a higher discharge inception jitter, and a larger emission diameter of the discharge channel. In addition, a shift of the filament position for low gas flow rates with respect to the electrode symmetry axis was observed. These effects can be explained by the change of the residence time of charge carriers in the discharge region—i.e., the volume pre-ionization—for changed flow conditions due to the convective transport of particles out of the center of the gap.

  18. Effect of Induced Charge on the Passivity and Passivity Breakdown of 304LN Stainless Steels

    Directory of Open Access Journals (Sweden)

    Gargi Roy Chowdhury


    Full Text Available Passivity breakdown of stainless steel by pitting in chloride environment is believed to occur at point at zero charge (pzc. So, the nature and quantity of charge on the surface plays a very important role on the breakdown of passivity, as chloride ion adsorption depends on that. In this work a DC potential was maintained between aluminium and graphite electrodes, and the aluminium electrode, in turn, was kept in the vicinity of the working electrode in the potentiostatic circuit. Both positive and negative polarity was applied on aluminium to attract or repel chloride ions in the vicinity of the working electrode. Chloride adsorption pattern on the stainless steel electrode got drastically altered due to application of DC potential on the aluminium-graphite circuit.

  19. Electron radiation effects on time-dependent dielectric breakdown in SiO2 films (United States)

    Li, S. P.; Maserjian, J.


    An experiment testing the effect of ionizing radiation on breakdown characteristics of SiO2 films is presented. Silicon wafers were oxidized and metallized, and a capacitor array was etched into a control sample while the rest were first irradiated with 1 MeV electrons and then etched. Time-dependent dielectric tests were made on all the capacitors, and the average characteristics of 96 capacitors are illustrated graphically. The curves are consistent with the model of holes trapped in the SiO2 film during irradiation leading to a retarding field for positive ion emission and drift toward the interface. It is shown how an externally applied field is reduced by the trapped charge, and that changes in the dielectric breakdown properties of the SiO2 film after irradiation depend on the positive trapped charge near the metal interface.

  20. Investigation Of Breakdown Induced Surface Damage On 805 Mhz Pillbox Cavity Interior Surfaces

    CERN Document Server

    Jana, M R; Leonova, M; Moretti, A; Tollestrup, A; Yonehara, K; Freemire, B; Torun, Y; Bowring, D; Flanagan, G


    The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, we have tested two 805 MHz vacuum RF cavities in a multi-Tesla magnetic field to study the effects of the static magnetic field on the cavity operation. This study gives useful information on field emitters in the cavity, dark current, surface conditioning, breakdown mechanisms and material properties of the cavity. All these factors determine the maximum accelerating gradient in the cavity. This paper discusses the image processing technique for quantitative estimation of spark damage spot distribution on cavity interior surfaces. The distribution is compared with the electric field distribution predicted by a computer code calculation. The local spark density is proportional to probability of surface breakdown and shows a power law dependence on the maximum electric field (E). This E dependence is consistent with ...

  1. Innovative Applications of Laser Scanning and Rapid Prototype Printing to Rock Breakdown Experiments (United States)

    Bourke, Mary; Viles, Heather; Nicoll, Joe; Lyew-Ayee, Parris; Ghent, Rebecca; Holmlund, James


    We present the novel application of two technologies for use in rock breakdown experiments, i.e. close-range, ground-based 3D triangulation scanning and rapid prototype printing. These techniques aid analyses of form-process interactions across the range of scales relevant to breakdown (micron-m). This is achieved through (a) the creation of DEMs (which permit quantitative description and analysis of rock surface morphology and morphological change) and (b) the production of more realistically-shaped experimental blocks. We illustrate the use of these techniques, alongside appropriate data analysis routines, in experiments designed to investigate the persistence of fluvially-derived features in the face of subsequent wind abrasion and weathering. These techniques have a range of potential applications in experimental field and lab-based geomorphic studies beyond those specifically outlined here.

  2. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Meng; Zhao, Yuning; Yan, Xiaodong; Li, Guowang; Verma, Jai; Fay, Patrick [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Nomoto, Kazuki; Zhu, Mingda; Hu, Zongyang; Protasenko, Vladimir; Song, Bo; Xing, Huili Grace; Jena, Debdeep, E-mail: [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Departments of ECE and MSE, Cornell University, Ithaca, New York 14853 (United States); Bader, Samuel [Departments of ECE and MSE, Cornell University, Ithaca, New York 14853 (United States)


    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm{sup 2} is obtained with reverse bias voltage up to −20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm{sup 2} is achieved, with a breakdown voltage corresponding to a peak electric field of ∼3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low.

  3. The Influence of the Magnetic Field on the Electrical Breakdown Phenomena

    Institute of Scientific and Technical Information of China (English)



    A simple phenomenological model and detailed simulation studies of the breakdown phenomena in argon and nitrogen under the simultaneous action of electric and magnetic fields are presented in this paper. Expressions for the breakdown voltage have been derived taking into account variations of both the ionization coefficient and the secondary electron yield in a magnetic field. Calculations were performed by using XOOPIC code, an Object Oriented Particle in Cell code, with both the original and the improved secondary emission model with inclusion of the influence of the magnetic field on the secondary electron production. The simulation results presented here clearly show that the inclusion of the dependence of the secondary electron yield on the magnetic field leads to better agreement with existing experimental results.

  4. Electric field strength of charged conducting balls and the breakdown of the air gap between them

    Energy Technology Data Exchange (ETDEWEB)

    Saranin, Vladimir A [Department of Physics, V.G. Korolenko Glazov State Pedagogical Institute, Glazov (Russian Federation)


    Field amplification factors at the surfaces of two charged conducting balls are calculated numerically. It is shown that as the balls are brought closer together, except when their potentials are equal, the amplification factors go to infinity, and in the case of like-charged balls the field at the surface of one of them changes sign. Breakdown field strengths for the air gap between balls of a different diameter are calculated using the experimental data of other authors as the base. The results suggest that the minimum breakdown field strength is 26 kV cm{sup -1} . The author's earlier results on the interaction force between the balls are revised. (methodological notes)

  5. Robustness of complex networks with an improved breakdown probability against cascading failures (United States)

    Liu, Jun; Xiong, Qingyu; Shi, Xin; Wang, Kai; Shi, Weiren


    The robustness of complex network is a core issue in complex network research. We agree that not all overload nodes will be removed from the network in real networks because some effective measures can be taken to protect them. But only a few researches consider this issue. Based on previous researches, we propose a cascading model with an improved breakdown probability. Different from previous breakdown probability model, the current model brings in some parameters to explore the optimal distribution strategy of the protection resources. Furthermore, we quantify the allocation of the protection resources. We explore the relationship between the parameters of our cascading model and the robustness of three networks (two typical networks and one real network), based on which we find out the optimal value of the parameter. It in turn helps us to quantify the allocation of protection resources and form an optimal protection strategy. Our work may be helpful for improving the robustness of complex networks.

  6. Pre-breakdown cavitation development in the dielectric fluid in the inhomogeneous, pulsed electric fields

    CERN Document Server

    Shneider, Mikhail N


    We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the ...

  7. Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

    Institute of Scientific and Technical Information of China (English)

    Wenge CHEN; Zhanying KANG; Bingjun DING


    Nanostructured (NS) W-Cu composite powder was prepared by mechanical alloying (MA), and nanostructured bulk of W-Cu contact material was fabricated by hot pressed sintering in an electrical vacuum furnace. The microstructure,electric conductivity, hardness, breakdown voltage and arcing time of NS W-Cu alloys were measured and compared to conventional W-Cu alloys prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior, the electric arc stability and the arc extinction ability of nanostructured W-Cu contacts materials. Also, the nanostructured W-Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

  8. Applying the Different Statistical Tests in Analysis of Electrical Breakdown Mechanisms in Nitrogen Filled Gas Diode (United States)

    Čedomir, A. Maluckov; Saša, A. Rančev; Miodrag, K. Radović


    This paper presents the results of our investigations of breakdown mechanisms, as well as a description of their influence on the distributions of time delay distributions, for a gas tube filled with nitrogen at 4 mbar. The values of the time delay are measured for different voltages, and the values of the relaxation times and their distributions and probability plots are analyzed. The obtained density distributions have Gaussian distributions and exponential distributions for different values of relaxation times (Gaussian for small values and exponential for large values of relaxation time). It is shown that for middle values of relaxation time the delay distributions have a shape between Gaussian and exponential distributions, which is a result of the different influences of electrical breakdown.

  9. Loss of Myelin Basic Protein Function Triggers Myelin Breakdown in Models of Demyelinating Diseases

    Directory of Open Access Journals (Sweden)

    Marie-Theres Weil


    Full Text Available Breakdown of myelin sheaths is a pathological hallmark of several autoimmune diseases of the nervous system. We employed autoantibody-mediated animal models of demyelinating diseases, including a rat model of neuromyelitis optica (NMO, to target myelin and found that myelin lamellae are broken down into vesicular structures at the innermost region of the myelin sheath. We demonstrated that myelin basic proteins (MBP, which form a polymer in between the myelin membrane layers, are targeted in these models. Elevation of intracellular Ca2+ levels resulted in MBP network disassembly and myelin vesiculation. We propose that the aberrant phase transition of MBP molecules from their cohesive to soluble and non-adhesive state is a mechanism triggering myelin breakdown in NMO and possibly in other demyelinating diseases.

  10. Loss of Myelin Basic Protein Function Triggers Myelin Breakdown in Models of Demyelinating Diseases. (United States)

    Weil, Marie-Theres; Möbius, Wiebke; Winkler, Anne; Ruhwedel, Torben; Wrzos, Claudia; Romanelli, Elisa; Bennett, Jeffrey L; Enz, Lukas; Goebels, Norbert; Nave, Klaus-Armin; Kerschensteiner, Martin; Schaeren-Wiemers, Nicole; Stadelmann, Christine; Simons, Mikael


    Breakdown of myelin sheaths is a pathological hallmark of several autoimmune diseases of the nervous system. We employed autoantibody-mediated animal models of demyelinating diseases, including a rat model of neuromyelitis optica (NMO), to target myelin and found that myelin lamellae are broken down into vesicular structures at the innermost region of the myelin sheath. We demonstrated that myelin basic proteins (MBP), which form a polymer in between the myelin membrane layers, are targeted in these models. Elevation of intracellular Ca(2+) levels resulted in MBP network disassembly and myelin vesiculation. We propose that the aberrant phase transition of MBP molecules from their cohesive to soluble and non-adhesive state is a mechanism triggering myelin breakdown in NMO and possibly in other demyelinating diseases.

  11. Influence of coaxial cylinders on vortex breakdown in a closed flow

    CERN Document Server

    Cabeza, Cecilia; Marti, Arturo C; Bove, Italo; Varela, Sylvana; Usera, Gabriel; Vernet, Anton


    The effect of fixed cylindrical rods located at the centerline axis on vortex breakdown (VB) is studied experimentally and numerically. We find that the VB is enhanced for very small values of the rod radius $d$, while it is suppressed for values of $d$ beyond a critical value. In order to characterize this effect, the critical Reynolds number for the appearance of vortex breakdown as a function of the radius of the fixed rods and the different aspect ratios was accurately determined, using digital particle image velocimetry. The numerical and experimental results are compared showing an excellent agreement. In addition, a simple model in order to show that this effect also appears in open pipe flows is presented in the appendix.


    Institute of Scientific and Technical Information of China (English)

    Liu Ying-zheng; Koyama Hide S.; Chen Han-ping


    The whole field measurements of swirling flow in spin-up and spin-down processes via PIV are presented in the paper. Investigation of the flow patterns at H/R=1.50 was experimentally carried out for the first time in both processes. By means of symmetry analysis, it is found that the overall flow structure in the spin-up process still keep axisymmetric to a great extent, but deteriorated very fast in the spin-down process. The time to settle to the state of rest in the spin-down process is found to be greatly shorter than the time to achieve the steady state in the spin-up process. Temporarily oscillatory vortex breakdown was discovered during the spin-up process, although no breakdown in the steady state at the same Reynolds number is found in precious researches.

  13. Electric field breakdown of lateral-type Schottky diodes formed on lightly doped homoepitaxial diamond (United States)

    Teraji, Tokuyuki; Koizumi, Satoshi; Koide, Yasuo; Ito, Toshimichi


    The reverse current of lateral-type Schottky diodes fabricated on p-type homoepitaxial diamond was analyzed by changing the distance between Schottky and Ohmic electrodes and the metal materials in the Schottky electrodes. The maximum electric field at breakdown was 0.56 MV cm -1 for the Au Schottky contact and less than 0.26 MV cm -1 for the Al Schottky contact. The breakdown voltage depended on the electrode distance when the diamond surface was revealed in vacuum, whereas the Schottky diodes sustained the applied voltage of 500 V, corresponding to 0.69 MV cm -1, after covering of the diamond surface with an insulating liquid. Diamond surface protection is an indispensable technique for fabrication of high-voltage Schottky diodes based on diamond.

  14. Cu-Induced Dielectric Breakdown of Porous Low-Dielectric-Constant Film (United States)

    Cheng, Yi-Lung; Lee, Chih-Yen; Huang, Yao-Liang; Sun, Chung-Ren; Lee, Wen-Hsi; Chen, Giin-Shan; Fang, Jau-Shiung; Phan, Bach Thang


    Dielectric breakdown induced by Cu ion migration in porous low-k dielectric films has been investigated in alternating-polarity bias conditions using a metal-insulator-metal capacitor with Cu top metal electrode. The experimental results indicated that Cu ions migrated into the dielectric film under stress with positive polarity, leading to weaker dielectric strength and shorter time to failure (TTF). In the alternating-polarity test, the measured TTFs increased with decreasing stressing frequency, implying backward migration of Cu ions during reverse-bias stress. Additionally, compared with a direct-current stress condition, the measured TTFs were higher as the frequency was decreased to 10-2 Hz. The electric-field acceleration factor for porous low-k dielectric film breakdown in the alternating-polarity test was also found to increase. This Cu backward migration effect is effective when the stressing time under negative polarity is longer than 0.1 s.

  15. Performance evaluation of self-breakdown-based single-gap plasma cathode electron gun

    Indian Academy of Sciences (India)

    Niraj Kumar; Nalini Pareek; Udit Narayan Pal; Deepak Kumar Verma; Jitendra Prajapati; Mahesh Kumar; Bharat Lal Meena; Ram Prakash


    This paper presents the experimental studies on self-breakdown-based single-gap plasma cathode electron (PCE) gun (5–20 kV/50–160 A) in argon, gas atmosphere and its performance evaluation based on particle-in-cell (PIC) simulation code `OOPIC-Pro’.The PCE-Gun works in conducting phase (low energy, high current) of pseudospark discharge. It produces an intense electron beam, which can propagate more than 200 mm in the drift space region without external magnetic field. The profile of this beam in the drift space region at different breakdown conditions (i.e., gas pressures and applied voltages) has been studied and the experimental results are compared with simulated values. It is demonstrated that ∼30% beam current is lost during the propagation possibly due to space charge neutralization and collisions with neutral particles and walls.

  16. Comparison of Simulations of Preliminary Breakdown to Observations from the Huntsville Alabama Marx Meter Array (United States)

    Carlson, B. E.; Liang, C.; Bitzer, P. M.; Christian, H. J., Jr.


    Preliminary breakdown pulses in electric field change records are thought to be produced by sudden extensions of the lightning channel. We present detailed time domain electrodynamic simulations of extension of an existing lightning leader channel due to heating processes and compare the results to observations of a natural cloud-to-ground lightning discharge made with the Huntsville Alabama Marx Meter Array (HAMMA) at a variety of locations near the discharge. Varying the geometry and parameters of the simulations in an attempt to reproduce the data allows us to constrain the directionality and physical properties of the channel. We simulate a variety of leader step phenomena, including uniform heating over the entire step, connection with a space leader, and dart leader propagation onto a preconditioned channel. Results support the notion of impulsive channel extension as the mechanism for preliminary breakdown and shed light on the mechanics of the process.

  17. Time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water

    Institute of Scientific and Technical Information of China (English)

    WU Jiang-lai; LU Yuan; Li Ying; CHENG Kai; GUO Jin-jia; ZHENG Rong-er


    @@ The laser induced breakdown spectroscopy (LIBS) is an element analysis technique with the advantages of real time detection, simultaneous multi-element identification, and in-situ and stand-off capacities.To evaluate its potential of ocean applications, in this paper, the time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water is investigated.With the optimum experimental parameters, the plasma emission lifetime is determined to be about 500 ns with 532 nm laser excitation, and 1000 ns with 1064 nm laser excitation.The lowest detection concentration of 50ppm is achieved for calcium detection in CaC12 water solution using the 532 nm LIBS.Even better detection sensitivity is achieved using the 1064 nm LIBS, and the resulted lowest detection concentration of calcium is 25 ppm.The results suggest that it is feasible to develop LIBS as an on-line sensor for metal element monitoring in the sea.

  18. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on dipolar copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede;


    Dielectric elastomers (DES) are a promising new transducer technology, but high driving voltages limit their current commercial potential. One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric permi......-4-nitrobenzene. Here, a high increase in dielectric permittivity (similar to 70%) was obtained without compromising other favourable DE properties such as elastic modulus, gel fraction, dielectric loss and electrical breakdown strength. © 2014 Elsevier Ltd. All rights reserved....

  19. Impact of water abstraction on storage and breakdown of coarse organic matter in mountain streams. (United States)

    Arroita, Maite; Aristi, Ibon; Díez, Joserra; Martinez, Miren; Oyarzun, Gorka; Elosegi, Arturo


    Water abstraction is a prevalent impact in streams and rivers, which is likely to increase in the near future. Because abstraction reduces discharge, the dimensions of the wetted channel and water depth and velocity, it can have strong influence on stream ecosystem functioning. Although the impacts of large dams on stream and river ecosystems are pretty well known, the effects of diversion schemes associated with low dams are still poorly understood. Furthermore, the remote location of many diversion schemes and the lack of collaboration by power companies often make it difficult to know the volume of water diverted and its environmental consequences. To assess the impact of water abstraction on the storage and breakdown of coarse particulate organic matter in streams we compared reaches upstream and downstream from five low dams that divert water to hydropower plants in mountain streams in N Spain. We measured the storage of organic matter and the breakdown of alder leaves in winter and spring, and calculated the results at the patch (i.e., per square meter of bed) and at the reach scale (i.e., per lineal meter of channel). Water diversion significantly reduced discharge, and the width and depth of the wetted channel, but did not affect water quality. Diversion significantly reduced the storage and breakdown of organic matter in winter but not in spring. The number of shredders colonizing litter bags was also significantly reduced. The results point to an important effect of water abstraction on the storage and breakdown of organic matter in streams at least in some periods, which could affect downstream reaches, global carbon fluxes, and associated ecosystem services.

  20. Leaf litter breakdown, microbial respiration and shredder production in metal-polluted streams (United States)

    Carlisle, D.M.; Clements, W.H.


    1. If species disproportionately influence ecosystem functioning and also differ in their sensitivities to environmental conditions, the selective removal of species by anthropogenic stressors may lead to strong effects on ecosystem processes. We evaluated whether these circumstances held for several Colorado, U.S.A. streams stressed by Zn. 2. Benthic invertebrates and chemistry were sampled in five second-third order streams for 1 year. Study streams differed in dissolved metal concentrations, but were otherwise similar in chemical and physical characteristics. Secondary production of leaf-shredding insects was estimated using the increment summation and size-frequency methods. Leaf litter breakdown rates were estimated by retrieving litter-bags over a 171 day period. Microbial activity on leaf litter was measured in the laboratory using changes in oxygen concentration over a 48 h incubation period. 3. Dissolved Zn concentrations varied eightfold among two reference and three polluted streams. Total secondary production of shredders was negatively associated with metal contamination. Secondary production in reference streams was dominated by Taenionema pallidum. Results of previous studies and the current investigation demonstrate that this shredder is highly sensitive to metals in Colorado headwater streams. Leaf litter breakdown rates were similar between reference streams and declined significantly in the polluted streams. Microbial respiration at the most contaminated site was significantly lower than at reference sites. 4. Our results supported the hypothesis that some shredder species contribute disproportionately to leaf litter breakdown. Furthermore, the functionally dominant taxon was also the most sensitive to metal contamination. We conclude that leaf litter breakdown in our study streams lacked functional redundancy and was therefore highly sensitive to contaminant-induced alterations in community structure. We argue for the necessity of simultaneously

  1. Impulse Breakdown Characteristics In Air In The Presence Of A Local Spark


    Settaouti, Abdelrahmane [عبد الرحمن ساتوتو


    In this paper, we study the flashover phenomena in air gaps containing floating metallic objects. The effect of a local spark on the impulse breakdown characteristics of a model gap arrangement which simulating a gas insulated switch (GIS) has been experimentally investigated. The three electrode gap consists of two conical rods facing each other together with a ground plane (or conical rod with the angle of the tip being varied). One of the horizontal rods is energized and one is left floati...

  2. Ion density and dielectric breakdown in the afterglow of a high-current arc discharge

    Energy Technology Data Exchange (ETDEWEB)

    Rutgers, W.R.; Verhagen, F.C.M.; De Zeeuw, W.A.


    The ion density in the afterglow of a high-current atmospheric arc-discharge and electrical breakdown have been investigated in atomic (argon), molecular (nitrogen) and electronegative (carbon dioxide) media. From the decay with time of the ion density, effective recombination coefficients can be calculated. When the ion density is reduced to values below 2 x 10/sup 17/m/sup -3/, the afterglow plasma changes from a resistive into a dielectric medium. (J.C.R.)

  3. Determining spatial sodium distribution in fresh and aged bread using laser-induced breakdown spectroscopy

    NARCIS (Netherlands)

    Scholtes-Timmerman, M.; Heddes, C.; Noort, M.W.J.; Veen, S. van


    A fast and easy-to-use method using laser-induced breakdown spectroscopy (LIBS) was set up to determine Na (sodium) distribution in baked bread. Standard bread was made using a standard recipe and the amount of salt added was 0, 0.5, 1, 2, 4, 10, 15 and 20g corresponding to 0, 0.25, 0.5, 1.0, 2.0, 5

  4. White Paper on Multicarrier Excitation of Multipactor Breakdown: A Survey of Current Methods and Research Opportunities (United States)


    AEROSPACE REPORT NO. TOR-2015-02548 White Paper on Multicarrier Excitation of Multipactor Breakdown: A Survey of Current Methods and...voltage phenomena where the verification power level is chosen such that the maximum instantaneous operational voltage in the component is excited . In...analysis methods under investigation for multicarrier excitation threshold prediction based on a survey of the research literature. In general, this

  5. Coal gasification systems engineering and analysis. Appendix H: Work breakdown structure (United States)


    A work breakdown structure (WBS) is presented which encompasses the multiple facets (hardware, software, services, and other tasks) of the coal gasification program. The WBS is shown to provide the basis for the following: management and control; cost estimating; budgeting and reporting; scheduling activities; organizational structuring; specification tree generation; weight allocation and control; procurement and contracting activities; and serves as a tool for program evaluation.

  6. rf breakdown measurements in electron beam driven 200 GHz copper and copper-silver accelerating structures (United States)

    Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; Clarke, Christine; Hogan, Mark; McCormick, Doug; Novokhatski, Alexander; O'Shea, Brendan; Spataro, Bruno; Weathersby, Stephen; Tantawi, Sami G.


    This paper explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present the experimental results of rf tests of 200 GHz metallic accelerating structures, made of copper and copper-silver. These experiments were carried out at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. The traveling-wave structure is an open geometry, 10 cm long, composed of two halves separated by a gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 160 to 235 GHz. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measure the deflecting forces by observing the displacement of the electron bunch and use this measurement to verify the expected accelerating gradient. Furthermore, we present the first quantitative measurement of rf breakdown rates in 200 GHz metallic accelerating structures. The breakdown rate of the copper structure is 10-2 per pulse, with a peak surface electric field of 500 MV /m and a rf pulse length of 0.3 ns, which at a relatively large gap of 1.5 mm, or one wavelength, corresponds to an accelerating gradient of 56 MV /m . For the same breakdown rate, the copper-silver structure has a peak electric field of 320 MV /m at a pulse length of 0.5 ns. For a gap of 1.1 mm, or 0.74 wavelengths, this corresponds to an accelerating gradient of 50 MV /m .

  7. Numerical analysis of excimer laser-induced breakdown of Kr gas (United States)

    Hamam, Kholoud A.; Elsayed, Khaled A.; Gamal, Yosr E. E.


    The present paper displays a numerical study on the role of electron dynamics in relation to the dependence of the threshold intensity on the pressure in the breakdown of gases by laser radiation. The analysis aimed to find out the origin of the steep slope observed in the measurements of threshold intensity against gas pressure in the breakdown of Kr induced by an excimer laser source (Opt. Commun. 13:66-68, 1). The experiment was carried out using wavelength 248 nm and pulse width of 18 ns for a gas pressure range 4.5-300 torr. The investigation centered on an adaptation of our previously developed electron cascade model given in Evans and Gamal (J. Phys. D Appl. Phys. 13:1447-1458, 2). This model solves numerically a time-dependent energy equation simultaneously with a set of rate equations that describe the change of the population of the formed excited states. The modifications introduced into the model the realistic structure of the krypton gas atom as well as electron diffusion as a loss process to inspect the experimentally tested low-pressure regime. A computer program is undertaken to determine the breakdown threshold intensity as a function of gas pressure. Reasonable agreement is obtained between the calculated thresholds and measured ones, corresponding to the examined pressure range. This agreement validates the applicability of the model. The relationship between the role of the physical mechanisms and gas pressure is studied by analyzing the EEDF and its parameters at selected pressure values that cover the experimentally tested range. The result of this study clarified that electron diffusion out of the focal region is responsible for the steep slope of the threshold intensities for pressures values showed non-Maxwellian distribution as well as determined the time and energy region at which breakdown is formed.

  8. Break-down of a planar liquid-solid interface during directional solidification - Influence of convection (United States)

    Tewari, S. N.; Chopra, M. A.


    The influence of convection on the development of morphological instability at the liquid-solid interface during directional solidification in a positive thermal gradient has been examined in Pb-10 wt pct Sn and succinonitrile-1.9 wt pct acetone. The onset of interfacial breakdown occurs at higher growth speeds in the presence of convection. The linear stability analysis due to Favier and Rouzaud which uses the 'deformable' mass flow boundary layer concept shows a good agreement with the experimentally observed behavior.

  9. Collision and Diffusion in Microwave Breakdown of Nitrogen Gas in and around Microgaps

    CERN Document Server

    Campbell, J D; Bowman, A; Remillard, S K


    The microwave induced breakdown of N2 gas in microgaps was modeled using the collision frequency between electrons and neutrals and the effective electric field concept. The threshold electric field at low pressures occurs outside the gap, but at high pressures with a mean free path shorter than the effective diffusion length, it is found to occur inside the microgap. Two very clear pressure regimes are seen, divided by a sharp transition, and each separately fitting the collision frequency model.

  10. Analysis of breakdown on thermal and electrical measurements for SPIDER accelerating grids

    Energy Technology Data Exchange (ETDEWEB)

    Pesce, Alberto, E-mail: [Consorzio RFX - Associazione EURATOM-ENEA per la fusione, Corso Stati Uniti 4, 35127 Padova (Italy); Pomaro, Nicola [Consorzio RFX - Associazione EURATOM-ENEA per la fusione, Corso Stati Uniti 4, 35127 Padova (Italy)


    The PRIMA test facility, under realization in Padova, includes a full size plasma source prototype for ITER, called SPIDER (Source for the Production of Ions of Deuterium Extracted from Radio Frequency plasma). The effects of breakdown in the electrical insulation inside the ion source are analyzed with particular care to the embedded diagnostic system, i.e. the thermal and electrical measurements installed on the grids and ion source case and transferred by multipolar cables to the acquisition system, located inside the 100 kV insulated deck and hosting the ion source power supply, the signal conditioning and the acquisition cubicles. The breakdown affects strongly the measurements, so it has to be mitigated in order to guarantee adequate reliability of the whole measurement set. A parametric study has been carried out on a detailed circuital model for fast transients, implemented using SimPowerSystems{sup TM} tool of Matlab Simulink code. The model includes all the relevant conductors of the subsystems downstream the insulating transformer of the Accelerating Grids Power Supply (AGPS), i.e. the AGPS rectifier, the multipolar transmission line, the 100 kV High Voltage Deck, the ion source power supply and the ion source itself. In particular all the magnetic and capacitive couplings have been computed by a proper 2D fem model. The optimization of the cabling layout, of the wire screening and of the protection devices, like surge arresters and resistors, has been carried out through the accurate modeling of the circuit. The energy dissipated on each ion source surge arrester is estimated and adequate TSD (transient suppression devices) are selected. A peculiar and difficult to satisfy requirement is the high number of surges that the TSD has to withstand. Breakdowns between components polarized at different voltages have been considered, in order to inspect the worst condition during a breakdown.

  11. Analysis Si/Al ratio in zeolites type FAU by laser induced breakdown spectroscopy (LIBS) (United States)

    Contreras, W. A.; Cabanzo, R.; Mejía-Ospino, E.


    In this work, Laser Induced Breakdown Spectroscopy (LIBS) is used to determine the Si/Al ratio of Zeolite type Y. The catalytic activity of zeolite is strongly dependent of the Si/Al ratio. We have used Si lines in the spectral region between 245-265 nm to determine temperature of the plasma generated on pelletized sample of zeolite, and stoichiometry relation between Si and Al.

  12. Search for the Missing L-mode Edge Transport and Possible Breakdown of Gyrokinetics (United States)

    Waltz, R. E.


    While GYRO simulations of typical core (0 theory of 6D drift-cyclotron kinetics following the fast time scale of the gyrophase to test the breakdown of 5D gyrokinetics with reduced model simulations is presented. 6pt [1] C. Holland, A.E. White, et al., Phys. Plasmas 16, 052301 (2009). [2] R.E. Waltz, J. Candy, C.C. Petty, Phys. Plasmas 13, 072304 (2006).


    Institute of Scientific and Technical Information of China (English)

    YUAN Xueming; LI Wei


    In the existing literature of Repairable Queueing Systems (RQS), i.e., queueing systems with server breakdowns, it is almost all assumed that interarrival times of successive customers are independent, identically exponentially distributed. In this paper, we deal with more generic system GI/PH/1 with server's exponential uptime and phase-type repair time. With matrix analysis theory, we establish the equilibrium condition and the characteristics of the system, derive the transient and stationary availability behavior of the system.


    Directory of Open Access Journals (Sweden)

    Djeison Cesar Batista


    Full Text Available aim of this work was to analyze the operational performance of chainsaw log breakdown of Eucalyptus grandis W.Hill, taking into account small scale use, e.g., in small farms, using yield and efficiency as evaluation tools. The specific aim was to analyze the behavior of yield and efficiency in five diametric classes: 20.0-25.9cm, 26.0-28.9 cm, 29.0-31.9 cm, 32.0-34.9 cm and 35.0-41.0 cm. According to the results obtained, the chainsaw log breakdown had a satisfactory operational behavior, with average yield and efficiency of 58,5% and 0.55m³/operator/h, respectively. However, the feasibility of such technique is restricted to small scale use. Diametric class 3 (29.0-31.9 cm presented the best yield (66.6% because it was the one that presented the best adequacy between log diameter and products. It is suggested for further researches the development of specific sawing diagrams per diametric class, in addition to the reduction of class ranges, aiming the yield increase. The average breakdown time spent per log was the same for classes 3, 4 and 5, resulting that the latter presented the best efficiency, 0.82 m³/operator/h.

  15. Liquid argon dielectric breakdown studies with the MicroBooNE purification system

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R.; Carls, B.; James, C.; Johnson, B.; Jostlein, H.; Lockwitz, S.; Lundberg, B.; Raaf, J. L.; Rameika, R.; Rebel, B.; Zeller, G. P.; Zuckerbrot, M.


    The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per-trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

  16. X-ray spectromicroscopy investigation of soft and hard breakdown in RRAM devices (United States)

    Carta, D.; Guttmann, P.; Regoutz, A.; Khiat, A.; Serb, A.; Gupta, I.; Mehonic, A.; Buckwell, M.; Hudziak, S.; Kenyon, A. J.; Prodromakis, T.


    Resistive random access memory (RRAM) is considered an attractive candidate for next generation memory devices due to its competitive scalability, low-power operation and high switching speed. The technology however, still faces several challenges that overall prohibit its industrial translation, such as low yields, large switching variability and ultimately hard breakdown due to long-term operation or high-voltage biasing. The latter issue is of particular interest, because it ultimately leads to device failure. In this work, we have investigated the physicochemical changes that occur within RRAM devices as a consequence of soft and hard breakdown by combining full-field transmission x-ray microscopy with soft x-ray spectroscopic analysis performed on lamella samples. The high lateral resolution of this technique (down to 25 nm) allows the investigation of localized nanometric areas underneath permanent damage of the metal top electrode. Results show that devices after hard breakdown present discontinuity in the active layer, Pt inclusions and the formation of crystalline phases such as rutile, which indicates that the temperature increased locally up to 1000 K.

  17. Time-Resolved Spectroscopy Diagnostic of Laser-Induced Optical Breakdown

    Directory of Open Access Journals (Sweden)

    Christian G. Parigger


    Full Text Available Transient laser plasma is generated in laser-induced optical breakdown (LIOB. Here we report experiments conducted with 10.6-micron CO2 laser radiation, and with 1.064-micron fundamental, 0.532-micron frequency-doubled, 0.355-micron frequency-tripled Nd:YAG laser radiation. Characterization of laser induced plasma utilizes laser-induced breakdown spectroscopy (LIBS techniques. Atomic hydrogen Balmer series emissions show electron number density of 1017 cm−3 measured approximately 10 μs and 1 μs after optical breakdown for CO2 and Nd:YAG laser radiation, respectively. Recorded molecular recombination emission spectra of CN and C2 Swan bands indicate an equilibrium temperature in excess of 7000 Kelvin, inferred for these diatomic molecules. Reported are also graphite ablation experiments where we use unfocused laser radiation that is favorable for observation of neutral C3 emission due to reduced C3 cation formation. Our analysis is based on computation of diatomic molecular spectra that includes accurate determination of rotational line strengths, or Hönl-London factors.

  18. Investigation of multipactor breakdown in communication satellite microwave co-axial systems

    Indian Academy of Sciences (India)

    S K Nagesh; D Revannasiddiah; S V K Shastry


    Multipactor breakdown or multipactor discharge is a form of high frequency discharge that may occur in microwave components operating at very low pressures. Some RF components of multi-channel communication satellites have co-axial geometry and handle high RF power under near-vacuum conditions. The breakdown occurs due to secondary electron resonance, wherein electrons move back and forth in synchronism with the RF voltage across the gap between the inner and outer conductors of the co-axial structure. If the yield of secondary electrons from the walls of the co-axial structure is greater than unity, then the electron density increases with time and eventually leads to the breakdown. In this paper, the current due to the oscillating electrons in the co-axial geometry has been treated as a radially oriented Hertzian dipole. The electric field, due to this dipole, at any point in the coaxial structure, may then be determined by employing the dyadic Green’s function technique. This field has been compared with the field that would exist in the absence of multipactor.

  19. Extended scaling and Paschen law for micro-sized radiofrequency plasma breakdown (United States)

    Lee, Min Uk; Lee, Jimo; Lee, Jae Koo; Yun, Gunsu S.


    The single particle motion analysis and particle-in-cell merged with Monte Carlo collision (PIC/MCC) simulations are compared to explain substantial breakdown voltage reduction for helium microwave discharge above a critical frequency corresponding to the transition from the drift-dominant to the diffusion-dominant electron loss regime. The single particle analysis suggests that the transition frequency is proportional to the product of {p}-{m} and {d}-({m+1)} where p is the neutral gas pressure, d is the gap distance, and m is a numerical parameter, which is confirmed by the PIC simulation. In the low-frequency or drift-dominant regime, i.e., γ - {{r}}{{e}}{{g}}{{i}}{{m}}{{e}}, the secondary electron emission induced by ion drift motion is the key parameter for determining the breakdown voltage. The fluid analysis including the secondary emission coefficient, γ , induces the extended Paschen law that implies the breakdown voltage is determined by pd, f/p, γ , and d/R where f is the frequency of the radio or microwave frequency source, and R is the diameter of electrode. The extended Paschen law reproduces the same scaling law for the transition frequency and is confirmed by the independent PIC and fluid simulations.

  20. Development and Breakdown of Goertler Vortices in High Speed Boundary Layers (United States)

    Li, Fei; Choudhari, Meelan; Chang, Chau-Lyan; Wu, Minwei; Greene, Ptrick T.


    The nonlinear development of G rtler instability over a concave surface gives rise to a highly distorted stationary flow in the boundary layer that has strong velocity gradients in both spanwise and wall-normal directions. This distorted flow is susceptible to strong, high frequency secondary instability that leads to the onset of transition. For high Mach number flows, the boundary layer is also subject to the second mode instability. The nonlinear development of G rtler vortices and the ensuing growth and breakdown of secondary instability, the G rtler vortex interactions with second mode instabilities as well as oblique second mode interactions are examined in the context of both internal and external hypersonic configurations using nonlinear parabolized stability equations, 2-D eigenvalue analysis and direct numerical simulation. For G rtler vortex development inside the Purdue Mach 6 Ludwieg tube wind tunnel, multiple families of unstable secondary eigenmodes are identified and their linear and nonlinear evolution is examined. The computation of secondary instability is continued past the onset of transition to elucidate the physical mechanisms underlying the laminar breakdown process. Nonlinear breakdown scenarios associated with transition over a Mach 6 compression cone configuration are also explored.

  1. Liquid Argon Dielectric Breakdown Studies with the MicroBooNE Purification System

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R. [Fermilab; Carls, B. [Fermilab; James, C. [Fermilab; Johnson, B. [Fermilab; Jostlein, H. [Fermilab; Lockwitz, S. [Fermilab; Lundberg, B. [Fermilab; Raaf, J. L. [Fermilab; Rameika, R. [Fermilab; Rebel, B. [Fermilab; Zeller, G. P. [Fermilab; Zuckerbrot, M. [Fermilab


    The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per-trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

  2. Liquid Argon Dielectric Breakdown Studies with the MicroBooNE Purification System

    CERN Document Server

    Acciarri, R; James, C; Johnson, B; Jostlein, H; Lockwitz, S; Lundberg, B; Raaf, J L; Rameika, R; Rebel, B; Zeller, G P; Zuckerbrot, M


    The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per- trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

  3. Instrumental Developments for In-situ Breakdown Experiments inside a Scanning Electron Microscope

    CERN Document Server

    Muranaka, T; Leifer, K; Ziemann, V


    Electrical discharges in accelerating structures are one of the key issues limiting the performance of future high energy accelerators such as the Compact Linear Collider (CLIC). Fundamental understanding of breakdown phenomena is an indispensable part of the CLIC feasibility study. The present work concerns the experimental study of breakdown using Scanning Electron Microscopes (SEMs). A SEM gives us the opportunity to achieve high electrical gradients of 1\\,kV/$\\mu$m which corresponds to 1\\,GV/m by exciting a probe needle with a high voltage power supply and controlling the positioning of the needle with a linear piezo motor. The gap between the needle tip and the surface is controlled with sub-micron precision. A second electron microscope equipped with a Focused Ion Beam (FIB) is used to create surface corrugations and to sharpen the probe needle to a tip radius of about 50\\,nm. Moreover it is used to prepare cross sections of a voltage breakdown area in order to study the geometrical surface damages as w...

  4. Numerical modeling of tokamak breakdown phase driven by pure Ohmic heating under ideal conditions (United States)

    Jiang, Wei; Peng, Yanli; Zhang, Ya; Lapenta, Giovanni


    We have simulated tokamak breakdown phase driven by pure Ohmic heating with implicit particle in cell/Monte Carlo collision (PIC/MCC) method. We have found two modes can be differentiated. When performing breakdown at low initial gas pressure, we find that it works at lower density and current, but higher temperature, and requires lower heating power, compared to when having a high initial pressure. Further, two stages can be distinguished during the avalanche process. One is the fast avalanche stage, in which the plasma is heated by induced toroidal electric field. The other is the slow avalanche stage, which begins when the plasma density reaches 1015 m-3. It has been shown that ions are mainly heated by ambipolar field and become stochastic in the velocity distribution. However, when the induced electric field is low, there exists a transition phase between the two stages. Our model simulates the breakdown and early hydrogen burn-through under ideal conditions during tokamak start-up. It adopted fewer assumptions, and can give an idealized range of operative parameters for Ohmic start-up. Qualitatively, the results agree well with certain experimental observations.

  5. The physics of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks (United States)

    Kerner, Boris S.; Koller, Micha; Klenov, Sergey L.; Rehborn, Hubert; Leibel, Michael


    Based on an empirical study of real field traffic data measured in 1996-2014 through road detectors installed on German freeways, we reveal physical features of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks. A microscopic stochastic three-phase traffic model of the nucleation of spontaneous traffic breakdown presented in the article explains the empirical findings. It turns out that in the most cases a nucleus for the breakdown occurs through an interaction of one of waves in free flow with an empirical permanent speed disturbance localized at a highway bottleneck. The wave is a localized structure in free flow, in which the total flow rate is larger and the speed averaged across the highway is smaller than outside the wave. The waves in free flow appear due to oscillations in the percentage of slow vehicles; these waves propagate with the average speed of slow vehicles in free flow. Any of the empirical waves exhibits a two-dimensional asymmetric spatiotemporal structure: Wave's characteristics are different in different highway lanes.

  6. LASER PLASMA: Experimental confirmation of the erosion origin of pulsed low-threshold surface optical breakdown of air (United States)

    Min'ko, L. Ya; Chumakou, A. N.; Chivel', Yu A.


    Nanosecond kinetic spectroscopy techniques were used to identify the erosion origin of pulsed low-threshold surface optical breakdown of air as a result of interaction of microsecond neodymium and CO2 laser pulses with some metals (indium, lead).

  7. On the effect of impurities introduced during the breakdown on the performance of a magnetically driven shock tube

    DEFF Research Database (Denmark)

    Chang, C.T.; Mondrup, K.


    Through a proper transformation of variables it is shown that, when the amount of impurities introduced during the break-down is constant, the main result of the previous work of Chang and Kofoed-Hansen remains unaltered....

  8. Wavelength Dependence of Nanosecond IR Laser-Induced Breakdown in Water: Evidence for Multiphoton Initiation via an Intermediate State (United States)


    breakdown threshold in water for nanosecond (ns) IR laser pulses . Avalanche ionization (AI) is the most powerful mechanism driving IR ns laser-induced...acknowledged that femtosecond (fs) and picosecond (ps) IR breakdown is initiated by photoionization because ultrashort pulses are sufficiently...formation depends critically on the density of pre-existing traps, χtrap. An estimate of χtrap can be obtained by relating the initial quantum efficiency

  9. Thickness-dependent dielectric breakdown and nanopore creation on sub-10-nm-thick SiN membranes in solution (United States)

    Yanagi, Itaru; Fujisaki, Koji; Hamamura, Hirotaka; Takeda, Ken-ichi


    Recently, dielectric breakdown of solid-state membranes in solution has come to be known as a powerful method for fabricating nanopore sensors. This method has enabled a stable fabrication of nanopores down to sub-2 nm in diameter, which can be used to detect the sizes and structures of small molecules. Until now, the behavior of dielectric breakdown for nanopore creation in SiN membranes with thicknesses of less than 10 nm has not been studied, while the thinner nanopore membranes are preferable for nanopore sensors in terms of spatial resolution. In the present study, the thickness dependence of the dielectric breakdown of sub-10-nm-thick SiN membranes in solution was investigated using gradually increased voltage pulses. The increment in leakage current through the membrane at the breakdown was found to become smaller with a decrease in the thickness of the membrane, which resulted in the creation of smaller nanopores. In addition, the electric field for dielectric breakdown drastically decreased when the thickness of the membrane was less than 5 nm. These breakdown behaviors are quite similar to those observed in gate insulators of metal-oxide-semiconductor devices. Finally, stable ionic-current blockades were observed when single-stranded DNA passed through the nanopores created on the membranes with thicknesses of 3-7 nm.

  10. Cellulose Breakdown (United States)

    Greenler, John; Nye, Leith; Tangen, Travis


    Production of liquid fuels such as ethanol from fibrous plant biomass could potentially be a significant sustainable component of the U.S. energy portfolio. Engineers and scientists are actively researching this area, and high school students can engage in this contemporary inquiry process by experimenting with different types of biomass, varying…

  11. Detrital stoichiometry as a critical nexus for the effects of streamwater nutrients on leaf litter breakdown rates. (United States)

    Manning, David W P; Rosemond, Amy D; Kominoski, John S; Gulis, Vladislav; Benstead, Jonathan P; Maerz, John C


    Nitrogen (N) and phosphorus (P) concentrations are elevated in many freshwater systems, stimulating breakdown rates of terrestrially derived plant litter; however, the relative importance of N and P in driving litter breakdown via microbial and detritivore processing are not fully understood. Here, we determined breakdown rates of two litter species, Acer rubrum (maple) and Rhododendron maximum (rhododendron), before (PRE) and during two years (YR1, YR2) of experimental N and P additions to five streams, and quantified the relative importance of hypothesized factors contributing to breakdown. Treatment streams received a gradient of P additions (low to high soluble reactive phosphorus [SRP]; ~10-85 µg/L) crossed with a gradient of N additions (high to low dissolved inorganic nitrogen [DIN]; ~472-96 µg/L) to achieve target molar N:P ratios ranging from 128 to 2. Litter breakdown rates increased above pre-treatment levels by an average of 1.1-2.2x for maple, and 2.7-4.9x for rhododendron in YR1 and YR2. We used path analysis to compare fungal biomass, shredder biomass, litter stoichiometry (nutrient content as C:N or C:P), discharge, and streamwater temperature as predictors of breakdown rates and compared models containing streamwater N, P or N + P and litter C:N or C:P using model selection criteria. Litter breakdown rates were predicted equally with either streamwater N or P (R2 = 0.57). In models with N or P, fungal biomass, litter stoichiometry, discharge, and shredder biomass predicted breakdown rates; litter stoichiometry and fungal biomass were most important for model fit. However, N and P effects may have occurred via subtly different pathways. Litter N content increased with fungal biomass (N-driven effects) and litter P content increased with streamwater P availability (P-driven effects), presumably via P storage in fungal biomass. In either case, the effects of N and P through these pathways were associated with higher shredder biomass and breakdown

  12. Effects of void size and gas content on electrical breakdown in lightweight, mechanically compliant, void-filled dielectrics (United States)

    Anderson, R. A.; Lagasse, R. R.; Russick, E. M.; Schroeder, J. L.


    Dielectric potting materials (encapsulants) are used to prevent air breakdown in high-voltage electrical devices. We report breakdown strengths in void-filled encapsulants, stressed with unipolar voltage pulses of the order of 10 μs duration. High strengths, on the order of 100 kV mm-1, are measured under these test conditions. The materials studied include low-density open celled gel-derived foams with cell sizes of 4 μm or less, closed celled CO2-blown polystyrene and urethane foams, and epoxies containing 48 vol % of hollow glass microballoon (GMB) fillers. These last specimens varied the void gas (N2 or SO2) and also the void diameters (tens to hundreds of μm). Our measurements are thought to be directly sensitive to the rate of field-induced ionization events in the void gas; however, the breakdown strengths of the materials tested appeared to vary in direct proportion with the conventional Paschen-law gas-discharge inception threshold, the electric stress at which gas-ionization avalanches become possible. The GMB-epoxy specimens displayed this type of dependence of breakdown strength on the void-gas density and void size, but the measurements were an order of magnitude above the conventional predictions. Small-celled foams also showed increased breakdown strengths with decreased cell size, although their irregular void geometry prevented a direct comparison with the more uniformly structured microballoon-filled encapsulants. The experimental observations are consistent with a breakdown mechanism in which the discharge of a few voids can launch a full breakdown in the composite material.

  13. Topological invariants for interacting topological insulators. II. Breakdown of single-particle Green's function formalism (United States)

    He, Yuan-Yao; Wu, Han-Qing; Meng, Zi Yang; Lu, Zhong-Yi


    Topological phase transitions in free fermion systems can be characterized by the closing of single-particle gap and the change in topological invariants. However, in the presence of electronic interactions, topological phase transitions can be more complicated. In paper I of this series [Phys. Rev. B 93, 195163 (2016), 10.1103/PhysRevB.93.195163], we have proposed an efficient scheme to evaluate the topological invariants based on the single-particle Green's function formalism. Here, in paper II, we demonstrate several interaction-driven topological phase transitions (TPTs) in two-dimensional (2D) interacting topological insulators (TIs) via large-scale quantum Monte Carlo (QMC) simulations, based on the scheme of evaluating topological invariants presented in paper I. Across these transitions, the defining symmetries of the TIs have been neither explicitly nor spontaneously broken. In the first two models, the topological invariants calculated from the Green's function formalism succeed in characterizing the topologically distinct phases and identifying interaction-driven TPTs. However, in the other two models, we find that the single-particle gap does not close and the topological invariants constructed from the single-particle Green's function acquire no change across the TPTs. Unexpected breakdown of the Green's function formalism in constructing the topological invariants is thus discovered. We thence classify the topological phase transitions in interacting TIs into two categories in practical computation: Those that have noninteracting correspondence can be characterized successfully by the topological invariants constructed from the Green's functions, while for the others that do not have noninteracting correspondence, the Green's function formalism experiences a breakdown, but more interesting and exciting phenomena, such as emergent collective critical modes at the transition, arise. Discussion on the success and breakdown of topological invariants

  14. Comparative study of electrical breakdown properties of deionized water and heavy water under pulsed power conditions

    Energy Technology Data Exchange (ETDEWEB)

    Veda Prakash, G.; Kumar, R.; Saurabh, K.; Nasir,; Anitha, V. P.; Chowdhuri, M. B.; Shyam, A. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)


    A comparative study of electrical breakdown properties of deionized water (H{sub 2}O) and heavy water (D{sub 2}O) is presented with two different electrode materials (stainless steel (SS) and brass) and polarity (positive and negative) combinations. The pulsed (∼a few tens of nanoseconds) discharges are conducted by applying high voltage (∼a few hundred kV) pulse between two hemisphere electrodes of the same material, spaced 3 mm apart, at room temperature (∼26-28 °C) with the help of Tesla based pulse generator. It is observed that breakdown occurred in heavy water at lesser voltage and in short duration compared to deionized water irrespective of the electrode material and applied voltage polarity chosen. SS electrodes are seen to perform better in terms of the voltage withstanding capacity of the liquid dielectric as compared to brass electrodes. Further, discharges with negative polarity are found to give slightly enhanced discharge breakdown voltage when compared with those with positive polarity. The observations corroborate well with conductivity measurements carried out on original and post-treated liquid samples. An interpretation of the observations is attempted using Fourier transform infrared measurements on original and post-treated liquids as well as in situ emission spectra studies. A yet another important observation from the emission spectra has been that even short (nanosecond) duration discharges result in the formation of a considerable amount of ions injected into the liquid from the electrodes in a similar manner as reported for long (microseconds) discharges. The experimental observations show that deionised water is better suited for high voltage applications and also offer a comparison of the discharge behaviour with different electrodes and polarities.

  15. Fertility, birth timing and marital breakdown: a reinterpretation of the evidence. (United States)

    Murphy, M J


    The conventional view that childlessness was associated with higher than average risk of marital breakdown was questioned on the basis of analysis of divorce records. The General Household Survey (GHS) is a large scale multipurpose continuous household survey in Great Britain. Since 1979, it has contained an expanded family information section addressed to women under 50 which, for ever-married women, collects information about numbers and dates of marriages, births (both inside and outside marriage) and, in the case of marriages which have ended, the reason for ending (death, divorce or separation), the date when cohabitation ceased and the date of absolute decree if available. In 1980, there were 5017 ever-married women aged 16-49 for whom marriage and fertility histories were obtained. Some results are shown for the interval between separation and divorce based on life table methods for women aged 50 and under. The marriage duration data suggest that, apart from very short and very long durations, the proportion of separation not followed by divorce by 10 years is reasonably constant, about 13%. The median interval is around 2.5 years, with short and long duration marriages having above-average intervals, partly due to restictions on divorce in the early years of marriage. The proportion of marriages breaking down at various marriage durations by the fertility status at the start of the year in question is shown. The proportion is calculated as the number of marriages which were intact at various specified marriage durations, but which had broken down in 1, 5 or 10 years and which could have experienced the full period in the absence of breakdown. At short durations, early childbearing (including premarital births) is associated with higher than average probabilities of breakdown. The impression given by these results is different from other studies. Retrospective multipurpose surveys such as the GHS appear to have many advantages over administrative records.

  16. Dielectric breakdown properties of hot SF6/He mixtures predicted from basic data (United States)

    Wang, Weizong; Tu, Xin; Mei, Danhua; Rong, Mingzhe


    Sulfur hexafluoride (SF6) gas has a quite high global warming potential and hence it is required that applying any substitute for SF6 gas. Much interest in the use of a mixture of helium and SF6 as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF6. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF6/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF6 and pure hot He and experimental results and previous calculations. The addition of He to SF6 was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF6/He mixtures.

  17. Optical-fiber-based laser-induced breakdown spectroscopy for detection of early caries (United States)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji


    A laser-induced breakdown spectroscopy (LIBS) system targeting for the in vivo analysis of tooth enamel is described. The system is planned to enable real-time analysis of teeth during laser dental treatment by utilizing a hollow optical fiber that transmits both Q-switched Nd:YAG laser light for LIBS and infrared Er:YAG laser light for tooth ablation. The sensitivity of caries detection was substantially improved by expanding the spectral region under analysis to ultraviolet (UV) light and by focusing on emission peaks of Zn in the UV region. Subsequently, early caries were distinguished from healthy teeth with accuracy rates above 80% in vitro.

  18. Forming-free and hard-breakdown depressed resistive switching based on natural conductive path (United States)

    Duan, W. J.; Wang, J. B.; Zhong, X. L.; Song, H. J.; Li, B.


    A forming-free, compliance-current needless and hard-breakdown depressed resistive switching is demonstrated in Cu2O film. Different from the conventional resistive switching behaviors, this reversible switch is free from the forming process, and does not dependent on the direction of the initial electric field. The resistive switching effect may be triggered by the break and recovery of natural conductive path, and a dynamic model is proposed to explain the switching process. Meanwhile, the influence of degradation in local region is also discussed, which is important for switching mechanism understanding. These results are an important step towards the development of resistive switching devices and their applications.

  19. Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field (United States)

    Shalygin, V. A.; Vorobjev, L. E.; Firsov, D. A.; Panevin, V. Yu.; Sofronov, A. N.; Melentyev, G. A.; Antonov, A. V.; Gavrilenko, V. I.; Andrianov, A. V.; Zakharyin, A. O.; Suihkonen, S.; Törma, P. T.; Ali, M.; Lipsanen, H.


    We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×1016 to 3.4×1018 cm-3). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.

  20. Laser-induced breakdown spectroscopy for real time and online elemental analysis

    CERN Document Server

    Rai, V N; Yueh, Fang-Yu; Singh, J P


    Laser-induced breakdown spectroscopy (LIBS) is a laser based diagnostics used to study atomic emission from the expanding plasma plume formed during the laser-matter interaction. It provides valuable information about the composition of the target material. LIBS has proved its potential application in the analysis of impurities, pollutants and toxic elements in various types of matrices of different samples (solid, liquid and gases), even those present under difficult and harsh environmental conditions. This article reviews some recent developments in the field, and its wide application in various fields of research and analysis.

  1. Rapid Analysis of Energetic and Geo-Materials Using Laser Induced Breakdown Spectroscopy (United States)


    Anal (2005) 5, 21. 20. Anzano, J. M., et al., Anal Chim Acta (2006) 575, 230. 21. Rusak, D. A., et al., TrAC Trend Anal Chem (1998) 17, 453. 22. Martin ...Spectrosc Reviews (2004) 39, 27. 25. Winefordner, J. D., et al., J Anal Atom Spectrom (2004) 19, 1061. 26. Cremers , D. A., and Radziemski, L. J., Handbook...29. Singh, J. P. and Thakur, S. N., Eds., Laser-Induced Breakdown Spectroscopy, Elsevier: Amsterdam, The Netherlands, 2007. 30. Cremers , D. A., and

  2. Single microchannel high-temperature fiber sensor by femtosecond laser-induced water breakdown. (United States)

    Liu, Yi; Qu, Shiliang; Li, Yan


    Single microchannel high-temperature fiber sensors were fabricated by drilling a microchannel across the fiber core near the end of the common single-mode fiber using femtosecond laser-induced water breakdown. Then the microchannel was annealed by the arc discharge to smooth its inwall. The two sides of microchannel and the end surface of the fiber constitute three reflective mirrors, which form a three-wave Fabry-Pérot interferometer (FPI). The fabricated FPI can be used as a high-temperature sensor in harsh environments due to its large temperature range (up to 1000°C), high linearity, miniaturized size, and perfect mechanical property.

  3. New Fundamental Light Particle and Breakdown of Stefan-Boltzmann's Law

    Directory of Open Access Journals (Sweden)

    Samoilov V.


    Full Text Available Recently, we predicted the existence of fundamental particles in Nature, neutral Light Particles with spin 1 and rest mass m = 1.8 x 10^{-4} m_e, in addition to electrons, neutrons and protons. We call these particles Light Bosons because they create electromagnetic field which represents Planck's gas of massless photons together with a gas of Light Particles in the condensate. Such reasoning leads to a breakdown of Stefan-Boltzmann's law at low temperature. On the other hand, the existence of new fundamental neutral Light Particles leads to correction of such physical concepts as Bose-Einstein condensation of photons, polaritons and exciton polaritons.

  4. New Fundamental Light Particle and Breakdown of Stefan-Boltzmann's Law

    Directory of Open Access Journals (Sweden)

    Minasyan V.


    Full Text Available Recently, we predicted the existence of fundamental particles in Nature, neutral Light Particles with spin 1 and rest mass m = 1 : 8 10E-4 me, in addition to electrons, neutrons and protons. We call these particles Light Bosons because they create electromagnetic field which represents Planck’s gas of massless photons together with a gas of Light Par- ticles in the condensate. Such reasoning leads to a breakdown of Stefan–Boltzmann’s law at low temperature. On the other hand, the existence of new fundamental neutral Light Particles leads to correction of such physical concepts as Bose-Einstein conden- sation of photons, polaritons and exciton polaritons.

  5. The Functional Breakdown Structure (FBS) and Its Relationship to Life Cycle Cost (United States)

    DeHoff, Bryan; Levack, Danie J. H.; Rhodes, Russell E.


    The Functional Breakdown Structure (FBS) is a structured, modular breakdown of every function that must be addressed to perform a generic mission. It is also usable for any subset of the mission. Unlike a Work Breakdown Structure (WBS), the FBS is a function-oriented tree, not a product-oriented tree. The FBS details not products, but operations or activities that should be performed. The FBS is not tied to any particular architectural implementation because it is a listing of the needed functions, not the elements, of the architecture. The FBS for Space Transportation Systems provides a universal hierarchy of required functions, which include ground and space operations as well as infrastructure - it provides total visibility of the entire mission. By approaching the systems engineering problem from the functional view, instead of the element or hardware view, the SPST has created an exhaustive list of potential requirements which the architecture designers can use to evaluate the completeness of their designs. This is a new approach that will provide full accountability of all functions required to perform the planned mission. It serves as a giant check list to be sure that no functions are omitted, especially in the early architectural design phase. A significant characteristic of a FBS is that if architecture options are compared using this approach, then any missing or redundant elements of each option will be ' identified. Consequently, valid Life Cycle Costs (LCC) comparisons can be made. For example, one architecture option might not need a particular function while another option does. One option may have individual elements to perform each of three functions while another option needs only one element to perform the three functions. Once an architecture has been selected, the FBS will serve as a guide in development of the work breakdown structure, provide visibility of those technologies that need to be further developed to perform required functions

  6. Influence of external magnetic field on laser breakdown plasma in aqueous Au nanoparticles colloidal solutions

    CERN Document Server

    Serkov, A A; Simakin, A V; Kuzmin, P G; Mikhailova, G N; Antonova, L Kh; Troitskii, A V; Kuzmin, G P; Shafeev, G A


    Influence of permanent magnetic field up to 7.5 T on plasma emission and laser-assisted Au nanoparticles fragmentation in water is experimentally studied. It is found that presence of magnetic field causes the breakdown plasma emission to start earlier regarding to laser pulse. Field presence also accelerates the fragmentation of nanoparticles down to a few nanometers. Dependence of Au NPs fragmentation rate in water on magnetic field intensity is investigated. The results are discussed on the basis of laser-induced plasma interaction with magnetic field.

  7. Application of Handheld Laser-Induced Breakdown Spectroscopy (LIBS) to Geochemical Analysis. (United States)

    Connors, Brendan; Somers, Andrew; Day, David


    While laser-induced breakdown spectroscopy (LIBS) has been in use for decades, only within the last two years has technology progressed to the point of enabling true handheld, self-contained instruments. Several instruments are now commercially available with a range of capabilities and features. In this paper, the SciAps Z-500 handheld LIBS instrument functionality and sub-systems are reviewed. Several assayed geochemical sample sets, including igneous rocks and soils, are investigated. Calibration data are presented for multiple elements of interest along with examples of elemental mapping in heterogeneous samples. Sample preparation and the data collection method from multiple locations and data analysis are discussed.

  8. Non-gated laser-induced breakdown spectroscopy in bulk water by position-selective detection

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Ye; Xue, Boyang; Song, Jiaojian; Lu, Yuan; Zheng, Ronger, E-mail: [Optics and Optoelectronics Laboratory, Ocean University of China, Qingdao 266100 (China)


    Temporal and spatial evolutions of the laser-induced plasma in bulk water are investigated using fast imaging and emission spectroscopic techniques. By tightly focusing a single-pulse nanosecond Nd: YAG laser beam into the bulk water, we generate a strongly expanded plasma with high reproducibility. Such a strong expanding plasma enables us to obtain well-resolved spectral lines by means of position-selective detection; hence, the time-gated detector becomes abdicable. The present results suggest not only a possible non-gated approach for underwater laser-induced breakdown spectroscopy but also give an insight into the plasma generation and expansion in bulk water.

  9. Effect of microwave frequency on plasma formation in air breakdown at atmospheric pressure

    Institute of Scientific and Technical Information of China (English)

    赵朋程; 郭立新; 李慧敏


    Microwave breakdown at atmospheric pressure causes the formation of a discrete plasma structure. The one-dimensional fluid model coupling Maxwell equations with plasma fluid equations is used to study the effect of the mi-crowave frequency on the formation of air plasma. Simulation results show that, the filamentary plasma array propagating toward the microwave source is formed at different microwave frequencies. As the microwave frequency decreases, the ratio of the distance between two adjacent plasma filaments to the corresponding wavelength remains almost unchanged (on the order of 1/4), while the plasma front propagates more slowly due to the increase in the formation time of the new plasma filament.

  10. Double-pulse standoff laser-induced breakdown spectroscopy for versatile hazardous materials detection

    Energy Technology Data Exchange (ETDEWEB)

    Gottfried, Jennifer L. [U.S. Army Research Laboratory, AMSRD-ARL-WM-BD, Aberdeen Proving Ground, MD, 21005-5069 (United States)], E-mail:; De Lucia, Frank C.; Munson, Chase A.; Miziolek, Andrzej W. [U.S. Army Research Laboratory, AMSRD-ARL-WM-BD, Aberdeen Proving Ground, MD, 21005-5069 (United States)


    We have developed a double-pulse standoff laser-induced breakdown spectroscopy (ST-LIBS) system capable of detecting a variety of hazardous materials at tens of meters. The use of a double-pulse laser improves the sensitivity and selectivity of ST-LIBS, especially for the detection of energetic materials. In addition to various metallic and plastic materials, the system has been used to detect bulk explosives RDX and Composition-B, explosive residues, biological species such as the anthrax surrogate Bacillus subtilis, and chemical warfare simulants at 20 m. We have also demonstrated the discrimination of explosive residues from various interferents on an aluminum substrate.

  11. Breakdown and tracking properties of rubber materials for wind turbine blades

    DEFF Research Database (Denmark)

    Garolera, Anna Candela; Holboell, Joachim; Henriksen, Mogens


    The use of rubber materials in wind turbine blades, for example in controllable trailing edge flaps, requires research on their behavior under heavy exposure to electric fields and electrical discharges. Since the complex construction of blades usually involves several and often inhomogeneous...... materials, the testing methods selected should reflect the realistic conditions. In this paper the applicability of rubber materials to thunderstorm environments is studied by performing electric breakdown tests and tracking resistance tests on selected samples, and the findings are related to the possible...... future application of rubber materials to wind turbine blades....

  12. Electrical breakdown strength results from the EU testing program for potential ITER insulation

    Energy Technology Data Exchange (ETDEWEB)

    Broadbent, A.J.; Crozier, J.; Smith, K.D. [Oxford Instruments, Oxon (United Kingdom)] [and others


    Insulation systems will be a key element in the future construction and impregnation of the coils for the ITER device. Electrical barrier layers have been specified to improve the electrical reliability, and this program includes ceramic plasma sprayed coatings, Kapton, Nomex and Mica in conjunction with various Epoxy resins. The electrical breakdown strengths in liquid nitrogen of twenty-two different insulation systems are reported. The final results of this program are presented and compared with the results from a benchmark testing program (insulation system based on anhydride cured DGEBA resin and S2 glass).

  13. Laser-induced breakdown spectroscopy at high temperatures in industrial boilers and furnaces. (United States)

    Blevins, Linda G; Shaddix, Christopher R; Sickafoose, Shane M; Walsh, Peter M


    Laser-induced breakdown spectroscopy (LIBS) was applied (1) near the superheater of an electric power generation boiler burning biomass, coal, or both; (2) at the exit of a glass-melting furnace burning natural gas and oxygen; and (3) near the nose arches of two paper mill recovery boilers burning black liquor. Difficulties associated with the high temperatures and high particle loadings in these environments were surmounted by use of novel LIBS probes. Echelle and linear spectrometers coupled to intensified CCD cameras were used individually and sometimes simultaneously. Elements detected include Na, K, Ca, Mg, C, B, Si, Mn, Al, Fe, Rb, Cl, and Ti.

  14. Pulse Compression Based on Laser-Induced Optical Breakdown in Suspension

    Institute of Scientific and Technical Information of China (English)

    HASI Wu-Li-Ji; FU Mei-Ling; LU Huan-Huan; GONG Sheng; LU Zhi-Wei; LIN Dian-Yang; HE Wei-Ming


    Pulse compression based on laser-induced optical breakdown in suspension is investigated.The physical mechanism behind it is analyzed theoretically and validated in the Q-switched Nd:YAG laser system.A 12-ns pump pulse is suppressed to 5 ns with good fidelity in the front edge and sharp steepness in the trailing edge.The HT-270,which has a small gain coemcient and absorption coefficient,is used as a solvent,and therefore the disturbance induced by stimulated Brillouin scattering and absorption are minimized and the transmittivity is enhanced.

  15. Activated protein synthesis and suppressed protein breakdown signaling in skeletal muscle of critically ill patients

    DEFF Research Database (Denmark)

    Jespersen, Jakob G; Nedergaard, Anders; Reitelseder, Søren


    involved in muscle mass regulation, we investigated the phosphorylation and expression of key factors in these protein synthesis and breakdown signaling pathways in thigh skeletal muscle of critically ill intensive care unit (ICU) patients compared with healthy controls.......Skeletal muscle mass is controlled by myostatin and Akt-dependent signaling on mammalian target of rapamycin (mTOR), glycogen synthase kinase 3β (GSK3β) and forkhead box O (FoxO) pathways, but it is unknown how these pathways are regulated in critically ill human muscle. To describe factors...

  16. Activated protein synthesis and suppressed protein breakdown signaling in skeletal muscle of critically ill patients

    DEFF Research Database (Denmark)

    Jespersen, Jakob G; Nedergaard, Anders; Reitelseder, Søren


    involved in muscle mass regulation, we investigated the phosphorylation and expression of key factors in these protein synthesis and breakdown signaling pathways in thigh skeletal muscle of critically ill intensive care unit (ICU) patients compared with healthy controls.......Skeletal muscle mass is controlled by myostatin and Akt-dependent signaling on mammalian target of rapamycin (mTOR), glycogen synthase kinase 3ß (GSK3ß) and forkhead box O (FoxO) pathways, but it is unknown how these pathways are regulated in critically ill human muscle. To describe factors...

  17. Femtosecond Laser-Induced Breakdown Spectroscopy for Detection of Trace Elements in Sophora Leaves

    Institute of Scientific and Technical Information of China (English)

    Myriam Bossu; HAO Zuo-Qiang; Matthieu Baudelet; YU Jia; ZHANG Zhe; ZHANG Jie


    Sophora leaves from several areas in Beijing are analysed by femtoeecond laser-induced breakdown spectroscopy (femto-LIBS).AIthough the used spectral detection systemis not time-resolved,thespectral lines of trace mineral elements are detected and anallyed.It is proven that the femto-LIBS can be an effcient method to detect mineral trace elements contained in tree leaves which is a biomonitor for atmospheric pollution assessment or botanic studies.An interesting case of correlation between trace elements detected in tree leaves and the pollution of the concerned area is presented,for the first time to our knowledge.

  18. Electric-field-controlled suppression of Walker breakdown and chirality switching in magnetic domain wall motion (United States)

    Chen, Hong-Bo; Li, You-Quan


    We theoretically study the dynamics of a magnetic domain wall controlled by an electric field in the presence of the spin flexoelectric interaction. We reveal that this interaction generates an effective spin torque and results in significant changes in the current-driven domain wall motion. In particular, the electric field can stabilize the domain wall motion, leading to strong suppression of the current-induced Walker breakdown and thus allowing a higher maximum wall velocity. We can furthermore use this electric-field control to efficiently switch the chirality of a moving domain wall in the steady regime.

  19. Suppressing RF breakdown of powerful backward wave oscillator by field redistribution

    Directory of Open Access Journals (Sweden)

    W. Song


    Full Text Available An over mode method for suppressing the RF breakdown on metal surface of resonant reflector cavity in powerful backward wave oscillator is investigated. It is found that the electric field is redistributed and electron emission is restrained with an over longitudinal mode cavity. Compared with the general device, a frequency band of about 5 times wider and a power capacity of at least 1.7 times greater are obtained. The results were verified in an X-band high power microwave generation experiment with the output power near 4 gigawatt.

  20. Fast and efficient silicon thermo-optic switching based on reverse breakdown of pn junction. (United States)

    Li, Xianyao; Xu, Hao; Xiao, Xi; Li, Zhiyong; Yu, Yude; Yu, Jinzhong


    We propose and demonstrate a fast and efficient silicon thermo-optic switch based on reverse breakdown of the pn junction. Benefiting from the direct heating of silicon waveguide by embedding the pn junction into the waveguide center, fast switching with on/off time of 330 and 450 ns and efficient thermal tuning of 0.12  nm/mW for a 20 μm radius microring resonator are achieved, indicating a high figure of merit of only 8.8  mW·μs. The results here show great potential for application in the future optical interconnects.

  1. Connection between full-lifetime and breakdown of puffs in transitional pipe flows (United States)

    Nishi, Mina; Ertunç, Özgür; Delgado, Antonio

    Puff splitting was studied by direct measurement of the full-lifetime (LT full ) of transitional structures (puffs) in low Reynolds number pipe flows. During the investigations, a fully developed laminar pipe flow was triggered by an iris diaphragm with pre-defined amplitude and lapse time and the evolution of puffs was monitored by the transients of pressure drop along the pipe and the hot wire anemometry at the pipe exit. Those complementary measurements showed that a single puff favors to breakdown into two or more (splitting) puffs and later into slug-like puffs at Re ≈ 2300, where they are expected to have infinite LT full .

  2. Effect of gate length on breakdown voltage in AlGaN/GaN high-electron-mobility transistor (United States)

    Jun, Luo; Sheng-Lei, Zhao; Min-Han, Mi; Wei-Wei, Chen; Bin, Hou; Jin-Cheng, Zhang; Xiao-Hua, Ma; Yue, Hao


    The effects of gate length LG on breakdown voltage VBR are investigated in AlGaN/GaN high-electron-mobility transistors (HEMTs) with LG = 1 μm˜ 20 μm. With the increase of LG, VBR is first increased, and then saturated at LG = 3 μm. For the HEMT with LG = 1 μm, breakdown voltage VBR is 117 V, and it can be enhanced to 148 V for the HEMT with LG = 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage. A similar suppression of the impact ionization exists in the HEMTs with LG > 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with LG = 3 μm˜20 μm, and their breakdown voltages are in a range of 140 V-156 V. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61204085).

  3. A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes (United States)

    Kumar, Niraj; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Pal, Udit Narayan; Rahaman, Hasibur; Prakash, Ram


    In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ˜50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

  4. Adaptive optics for reduced threshold energy in femtosecond laser induced optical breakdown in water based eye model (United States)

    Hansen, Anja; Krueger, Alexander; Ripken, Tammo


    In ophthalmic microsurgery tissue dissection is achieved using femtosecond laser pulses to create an optical breakdown. For vitreo-retinal applications the irradiance distribution in the focal volume is distorted by the anterior components of the eye causing a raised threshold energy for breakdown. In this work, an adaptive optics system enables spatial beam shaping for compensation of aberrations and investigation of wave front influence on optical breakdown. An eye model was designed to allow for aberration correction as well as detection of optical breakdown. The eye model consists of an achromatic lens for modeling the eye's refractive power, a water chamber for modeling the tissue properties, and a PTFE sample for modeling the retina's scattering properties. Aberration correction was performed using a deformable mirror in combination with a Hartmann-Shack-sensor. The influence of an adaptive optics aberration correction on the pulse energy required for photodisruption was investigated using transmission measurements for determination of the breakdown threshold and video imaging of the focal region for study of the gas bubble dynamics. The threshold energy is considerably reduced when correcting for the aberrations of the system and the model eye. Also, a raise in irradiance at constant pulse energy was shown for the aberration corrected case. The reduced pulse energy lowers the potential risk of collateral damage which is especially important for retinal safety. This offers new possibilities for vitreo-retinal surgery using femtosecond laser pulses.

  5. STUDENT AWARD FINALIST: Study of Self-Absorbed Vacuum Ultraviolet Radiation during Pulsed Atmospheric Breakdown in Air (United States)

    Laity, George; Fierro, Andrew; Hatfield, Lynn; Neuber, Andreas


    This paper describes recent experiments to investigate the role of self-produced vacuum ultraviolet (VUV) radiation in the physics of pulsed atmospheric breakdown. A unique apparatus was constructed which enables the detailed exploration of VUV light in the range 115-135 nm, which is emitted from breakdown between two point-point electrodes in an air environment at atmospheric pressure. Time-resolved diagnostics include VUV sensitive photomultipliers, intensified CCD imaging, optically isolated high voltage probes, and fast rise-time Rogowski current monitors. Temporally resolved spectroscopy from air breakdowns revealed VUV emission is released during the initial streamer phase before voltage collapse, with the majority of the emission lines identified from various atmospheric gases or surface impurities. Imaging of VUV radiation was performed which conserved the spatial emission profile, and distinct differences between nitrogen and oxygen VUV emission during onset of breakdown have been observed. Specifically, the self-absorption of HI, OI, and NI lines is addressed which elucidates the role of radiation transport during the photon-dominated streamer breakdown process. Supported by AFOSR, NASA / TSGC, DEPS, and IEEE DEIS.

  6. Electrical-breakdown and electronic current of tantalum-tantalum oxide-aqueous electrolyte systems. [Ta sub 2 O sub 5

    Energy Technology Data Exchange (ETDEWEB)

    Kalra, K.C.; Katyal, P. (Dept. of Chemistry, Maharshi Dayanand Univ., Rohtak (India))


    Breakdown voltage and electronic current data for barrier anodic tantalum oxide films in contact with aqueous electrolytes of various concentrations and compositions at 298 K have been obtained. The influence of electrolyte concentration on breakdown characteristics can be broadly explained in terms of the Ikonopisov electron avalanche breakdown model. Albella and coworkers' theory explains the effect of electrolyte concentration for our results more explicitly. Various parameters of the Albella theory have been evaluated, and their dependence on electrolyte concentration has been studied. The dependence of breakdown voltage on electrolyte concentration has also been discussed in the light of the theory of Di Quarto and coworkers. (orig.).

  7. Loss of caveolin-1 causes blood-retinal barrier breakdown, venous enlargement, and mural cell alteration. (United States)

    Gu, Xiaowu; Fliesler, Steven J; Zhao, You-Yang; Stallcup, William B; Cohen, Alex W; Elliott, Michael H


    Blood-retinal barrier (BRB) breakdown and related vascular changes are implicated in several ocular diseases. The molecules and mechanisms regulating BRB integrity and pathophysiology are not fully elucidated. Caveolin-1 (Cav-1) ablation results in loss of caveolae and microvascular pathologies, but the role of Cav-1 in the retina is largely unknown. We examined BRB integrity and vasculature in Cav-1 knockout mice and found a significant increase in BRB permeability, compared with wild-type controls, with branch veins being frequent sites of breakdown. Vascular hyperpermeability occurred without apparent alteration in junctional proteins. Such hyperpermeability was not rescued by inhibiting eNOS activity. Veins of Cav-1 knockout retinas exhibited additional pathological features, including i) eNOS-independent enlargement, ii) altered expression of mural cell markers (eg, down-regulation of NG2 and up-regulation of αSMA), and iii) dramatic alterations in mural cell phenotype near the optic nerve head. We observed a significant NO-dependent increase in retinal artery diameter in Cav-1 knockout mice, suggesting that Cav-1 plays a role in autoregulation of resistance vessels in the retina. These findings implicate Cav-1 in maintaining BRB integrity in retinal vasculature and suggest a previously undefined role in the retinal venous system and associated mural cells. Our results are relevant to clinically significant retinal disorders with vascular pathologies, including diabetic retinopathy, uveoretinitis, and primary open-angle glaucoma.

  8. Stationary Crossflow Breakdown due to Mixed Mode Spectra of Secondary Instabilities (United States)

    Li, Fei; Choudhari, Meelan M.; Duan, Lian


    Numerical simulations are used to study laminar breakdown characteristics associated with stationary crossflow instability in the boundary-layer flow over a subsonic swept-wing configuration. Previous work involving the linear and nonlinear development of individual, fundamental modes of secondary instability waves is extended by considering the role of more complex, yet controlled, spectra of the secondary instability modes. Direct numerical simulations target a mixed mode transition scenario involving the simultaneous presence of Y and Z modes of secondary instability. For the initial amplitudes investigated in this paper, the Y modes are found to play an insignificant role during the onset of transition, in spite of achieving rather large, O(5%), amplitudes of RMS velocity fluctuation prior to transition. Analysis of the numerical simulations shows that this rather surprising finding can be attributed to the fact that the Y modes are concentrated near the top of the crossflow vortex and exert relatively small influence on the Z modes that reside closer to the surface and can lead to transition via nonlinear spreading that does not involve interactions with the Y mode. Finally, secondary instability calculations reveal that subharmonic modes of secondary instability have substantially lower growth rates than those of the fundamental modes, and hence, are less likely to play an important role during the breakdown process involving complex initial spectra.

  9. Modeling and analysis of breakdown EMI protection for MITICA insulation and embedded diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Pesce, A., E-mail: [Consorzio RFX – Associazione EURATOM-ENEA sulla Fusione, Corso Stati Uniti 4, 35127 Padova (Italy); Pomaro, N.; Zamengo, A.; Bigi, M.; Toigo, V. [Consorzio RFX – Associazione EURATOM-ENEA sulla Fusione, Corso Stati Uniti 4, 35127 Padova (Italy)


    Highlights: ► A fast transient model of MITICA electrical system with all relevant conductors has been developed. ► MITICA insulations on Source and main Bushing are at high risk due to electrical breakdowns. ► The introduction of capacitances in some critical points is effective to reduce overvoltages. ► Signal cables must be screened at both ends to and follow the route of reference potential conductors. -- Abstract: On the Padova PRIMA facility the prototype of the ITER HNBs will be tested in the device called MITICA (Megavolt ITER Injector and Concept Advancement). During Beam operation breakdowns will occur across the accelerator grids and Source components causing transient high voltages between parts normally at low voltages, so stressing the electrical insulation of sensor cables, connectors and feedthroughs. The MITICA electrical model implemented to estimate the characteristics of the voltage transients is here described, with particular emphasis on the feedthroughs, on the source insulation and on the embedded diagnostic system. As severe stresses result with the present design mitigating measures are necessary to avoid damage and maintain proper operation. The solution proposed and supported by the analyses to introduce concentrated capacitances in some critical points turns out to be suitable in terms of electrical effects and of technical compatibility with the main requirements of MITICA environment.

  10. Ultrafast Breakdown of dielectrics: Energy absorption mechanisms investigated by double pulse experiments

    Energy Technology Data Exchange (ETDEWEB)

    Guizard, Stéphane, E-mail: [Laboratoire des Solides Irradiés, CEA-IRAMIS, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Klimentov, Sergey [General Physics Institute of the Russian Academy of Sciences, Vavilova St 38, 11991 Moscow (Russian Federation); Mouskeftaras, Alexandros [Laboratoire des Solides Irradiés, CEA-IRAMIS, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Fedorov, Nikita; Geoffroy, Ghita [Laboratoire CELIA, CNRS-CEA-Université de Bordeaux, Cours de La Libération, Talence (France); Vilmart, Gautier [Laboratoire des Solides Irradiés, CEA-IRAMIS, CNRS, Ecole Polytechnique, 91128 Palaiseau (France)


    We investigate the mechanisms involved in the modification of dielectric materials by ultrashort laser pulses. We show that the use of a double pulse (fundamental and second harmonic of a Ti–Sa laser) excitation allows getting new insight in the fundamental processes that occur during the interaction. We first measure the optical breakdown (OB) threshold map (intensity of first pulse versus intensity of second pulse) in various materials (Al{sub 2}O{sub 3}, MgO, α-SiO{sub 2}). Using a simple model that includes multiphoton excitation followed by carrier heating in the conduction band, and assuming that OB occurs when a critical amount of energy is deposited in the material, we can satisfactorily reproduce this evolution of optical breakdown thresholds. The results demonstrate the dominant role of carrier heating in the energy transfer from the laser pulse to the solid. This important phenomenon is also highlighted by the kinetic energy distribution of photoelectrons observed in a photoemission experiment performed under similar conditions of double pulse excitation. Finally we show, in the case of α-SiO{sub 2}, that the initial electronic excitation plays a key role in the formation of surface ripples and that their characteristics are determined by the first pulse, even at intensities well below OB threshold.

  11. Evidence for the origins and breakdown of 1/f noise in heart rate (United States)

    Struzik, Zbigniew R.; Hayano, Junichiro; Sakata, Seiichiro; Kwak, Shin; Yamamoto, Yoshiharu


    We present the first systematic evidence for the origins and breakdown of 1/f scaling in human heart rate. We confirm a previously posed conjecture that 1/f scaling in heart rate is caused by the intricate balance between antagonistic activity of sympathetic (SNS) and parasympathetic (PNS) nervous systems. We demonstrate that modifying the relative importance of either of the two branches leads to a substantial decrease of 1/f scaling. In particular, the relative PNS suppression both by congestive heart failure (CHF) and by the parasympathetic blocker atropine results in a substantial increase in the Hurst exponent H and a shift of the multifractal spectrum f(α) from 1/f towards random walk scaling 1/f2. Surprisingly, we observe a similar breakdown in the case of relative and neurogenic SNS suppression by primary autonomic failure (PAF). Further, we observe an intriguing interaction between multifractality of heart rate and absolute variability. While it is generally believed that lower absolute variability results in monofractal behaviour, as has been demonstrated both for CHF and the parasympathetic blockade, in PAF patients we observe conservation of multifractal properties at substantially reduced absolute variability to levels closer to CHF. This novel and intriguing result leads us to the conjecture that the multifractality of the heart rate can be traced back to the intrinsic dynamics of the parasympathetic nervous system.

  12. Mathematical models for process commonality under quality and resources breakdown in multistage production

    Institute of Scientific and Technical Information of China (English)

    Mohammed Abdul WAZED; Shamsuddin AHMED; Yusoff Bin NUKMANt


    It is essential to manage customers' diverse desires and to keep manufacturing costs as low as possible for survival in competition and eventually in production.Sharing resources in manufacturing for different products is a vital method of accomplishing this goal.The advantages of using a common process in production are stated in the literature.However,the mathematical models as well as simulation or conceptual models are not sufficient.The main objective of this paper is to develop mathematical models for multiproduct and multistage production under quality and breakdown uncertainties.The idea of the process commonality is incorporated in the proposed models.The models are validated by primary data collected from a Malaysian company and comparison of the timely requirement schedules of earlier MRP Ⅱ and the proposed models under stable and perfect production environments.An appreciable convergence of the outcomes is observed.However,the proposed models are carrying additional information about the available locations of the parts in a time frame.After validation,the effects of process commonality on cost,capacity and the requirement schedule under uncertainties are examined.It is observed that the use of common processes in manufacturing is always better than the non-commonality scenario in terms of production cost.However,the increase in capacity requirement for commonality designs is higher for an ideal system,while it is less when the system suffers from breakdowns and a quality problem.

  13. Hybrid breakdown weakens under thermal stress in population crosses of the copepod Tigriopus californicus. (United States)

    Willett, Christopher S


    The outcome of hybridization can be impacted by environmental conditions, which themselves can contribute to reproductive isolation between taxa. In crosses of genetically divergent populations, hybridization can have both negative and positive impacts on fitness, the balance between which might be tipped by changes in the environment. Genetically divergent populations of the intertidal copepod Tigriopus californicus have been shown to differ in thermal tolerance at high temperatures along a latitudinal gradient. In this study, a series of crosses were made between pairs of genetically divergent populations of T. californicus, and the thermal tolerance of these hybrids was tested. In most cases, the first-generation hybrids had relatively high thermal tolerance and the second-generation hybrids were not generally reduced below the less-tolerant parental population for high temperature tolerance. This pattern contrasts with previous studies from crosses of genetically divergent populations of this copepod, which often shows hybrid breakdown in these second-generation hybrids for other measures of fitness. These results suggest that high temperature stress could either increase the positive impacts of hybridization or decrease the negative impacts of hybridization resulting in lowered hybrid breakdown in these population crosses.

  14. Characterization of hard coatings produced by laser cladding using laser-induced breakdown spectroscopy technique

    Energy Technology Data Exchange (ETDEWEB)

    Varela, J.A.; Amado, J.M.; Tobar, M.J.; Mateo, M.P.; Yañez, A.; Nicolas, G., E-mail:


    Highlights: • Chemical mapping and profiling by laser-induced breakdown spectroscopy (LIBS) of coatings produced by laser cladding. • Production of laser clads using tungsten carbide (WC) and nickel based matrix (NiCrBSi) powders. • Calibration by LIBS of hardfacing alloys with different WC concentrations. - Abstract: Protective coatings with a high abrasive wear resistance can be obtained from powders by laser cladding technique, in order to extend the service life of some industrial components. In this work, laser clad layers of self-fluxing NiCrBSi alloy powder mixed with WC powder have been produced on stainless steel substrates of austenitic type (AISI 304) in a first step and then chemically characterized by laser-induced breakdown spectroscopy (LIBS) technique. With the suitable laser processing parameters (mainly output power, beam scan speed and flow rate) and powders mixture proportions between WC ceramics and NiCrBSi alloys, dense pore free layers have been obtained on single tracks and on large areas with overlapped tracks. The results achieved by LIBS technique and applied for the first time to the analysis of laser clads provided the chemical composition of the tungsten carbides in metal alloy matrix. Different measurement modes (multiple point analyses, depth profiles and chemical maps) have been employed, demonstrating the usefulness of LIBS technique for the characterization of laser clads based on hardfacing alloys. The behavior of hardness can be explained by LIBS maps which evidenced the partial dilution of some WC spheres in the coating.

  15. Geographical analysis of 'conflict minerals' utilizing laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hark, Richard R., E-mail: [Department of Chemistry, Juniata College, Huntingdon, PA 16652 (United States); Remus, Jeremiah J. [Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY 13699 (United States); East, Lucille J. [Applied Spectra, Inc., Fremont, CA 94538 (United States); Harmon, Russell S. [Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695 (United States); Wise, Michael A. [Department of Mineral Sciences, Smithsonian Institution, Washington, DC 20013 (United States); Tansi, Benjamin M.; Shughrue, Katrina M. [Department of Chemistry, Juniata College, Huntingdon, PA 16652 (United States); Dunsin, Kehinde S. [Department of Electrical and Computer Engineering, Clarkson University, Potsdam, NY 13699 (United States); Liu, Chunyi [Applied Spectra, Inc., Fremont, CA 94538 (United States)


    Laser-induced breakdown spectroscopy (LIBS) offers a means of rapidly distinguishing different geographic sources for a mineral because the LIBS plasma emission spectrum provides information on the chemical composition (i.e. geochemical fingerprint) of a geomaterial. An application of this approach with potentially significant commercial and political importance is the spectral fingerprinting of 'conflict minerals' such as columbite-tantalite ('coltan'). Following a successful pilot study of a columbite-tantalite suite from North America, a more geographically diverse set of 57 samples from 37 locations around the world was analyzed using a commercially available LIBS system. The LIBS spectra were analyzed using advanced multivariate statistical signal processing techniques. Partial least squares discriminant analysis (PLSDA) resulted in a correct place-level geographic classification at success rates above 90%. The possible role of rare-earth elements (REEs) as a factor contributing to the high levels of sample discrimination was explored. These results provide additional evidence that LIBS has the potential to be utilized in the field as a real-time screening tool to discriminate between columbite-tantalite ores of different provenance. - Highlights: Black-Right-Pointing-Pointer Analysis of columbite-tantalite using laser-induced breakdown spectroscopy (LIBS) Black-Right-Pointing-Pointer Chemometric analysis (PLSDA) affords 90-100% correct sample classification. Black-Right-Pointing-Pointer Possible role of rare-earth elements in the high level of sample discrimination.

  16. Gonad morphogenesis defects drive hybrid male sterility in asymmetric hybrid breakdown of Caenorhabditis nematodes. (United States)

    Dey, Alivia; Jin, Qi; Chen, Yen-Chu; Cutter, Asher D


    Determining the causes and evolution of reproductive barriers to gene flow between populations, speciation, is the key to understanding the origin of diversity in nature. Many species manifest hybrid breakdown when they intercross, characterized by increasingly exacerbated problems in later generations of hybrids. Recently, Caenorhabditis nematodes have emerged as a genetic model for studying speciation, and here we investigate the nature and causes of hybrid breakdown between Caenorhabditis remanei and C. latens. We quantify partial F1 hybrid inviability and extensive F2 hybrid inviability; the ~75% F2 embryonic arrest occurs primarily during gastrulation or embryonic elongation. Moreover, F1 hybrid males exhibit Haldane's rule asymmetrically for both sterility and inviability, being strongest when C. remanei serves as maternal parent. We show that the mechanism by which sterile hybrid males are incapable of transferring sperm or a copulatory plug involves defective gonad morphogenesis, which we hypothesize results from linker cell defects in migration and/or cell death during development. This first documented case of partial hybrid male sterility in Caenorhabditis follows expectations of Darwin's corollary to Haldane's rule for asymmetric male fitness, providing a powerful foundation for molecular dissection of intrinsic reproductive barriers and divergence of genetic pathways controlling organ morphogenesis.

  17. Remote monostatic detection of radioactive material by laser-induced breakdown (United States)

    Isaacs, Joshua; Miao, Chenlong; Sprangle, Phillip


    This paper analyzes and evaluates a concept for remotely detecting the presence of radioactivity using electromagnetic signatures. The detection concept is based on the use of laser beams and the resulting electromagnetic signatures near the radioactive material. Free electrons, generated from ionizing radiation associated with the radioactive material, cascade down to low energies and attach to molecular oxygen. The resulting ion density depends on the level of radioactivity and can be readily photo-ionized by a low-intensity laser beam. This process provides a controllable source of seed electrons for the further collisional ionization (breakdown) of the air using a high-power, focused, CO2 laser pulse. When the air breakdown process saturates, the ionizing CO2 radiation reflects off the plasma region and can be detected. The time required for this to occur is a function of the level of radioactivity. This monostatic detection arrangement has the advantage that both the photo-ionizing and avalanche laser beams and the detector can be co-located.

  18. An ultrastructural study of spermatogenesis and sperm morula breakdown in Arenicola marina (L.) (Annelida: Polychaeta) (United States)

    Pacey, A. A.; Bentley, M. G.


    Spermatogenesis in the lugworm Arenicola marina, in common with other members of Arenicolidae, occurs in the coelomic fluid and results in the formation of discs of mature spermatozoa known as a morulae. Within a morula, individual spermatozoa are connected by a common mass of cytoplasm called the cytophore and therefore make up a syncitium. Immediately prior to spawning, and in response to an endocrine substance known as “Sperm Maturation Factor” (SMF), the structure of the sperm morulae breaks down and free spermatozoa are liberated. These are subsequently spawned from the body cavity. The investigation described here uses transmission electron microscopy to investigate the ultrastructural changes, which accompany spermatogenesis and the breakdown of sperm morulae in response to SMF in vitro. The study demonstrates that the cytophore appears to have a key role both during spermatogenesis and during sperm morula breakdown. The ultrastructure of sperm morulae and of mature spermatozoa is described. The structure of spermatozoa is shown to be primitive with a single flagellum which appears to be coiled at its distal end. The phagocytosis of free spermatozoa by coelomocytes is also described and it is suggested that these may play a role in the resorption of unspawned gametes in vivo.

  19. Quantitative analysis of metformin in antidiabetic tablets by laser-induced breakdown spectroscopy (United States)

    Contreras, U.; Ornelas-Soto, N.; Meneses-Nava, M. A.; Barbosa-García, O.; López-de-Alba, P. L.; López-Martínez, L.


    Nowadays the production of counterfeit and low quality drugs affects human health and generates losses to pharmaceutical industries and tax revenue losses to government. Currently there are several methods for pharmaceutical product analysis; nevertheless, most of them depend on complex and time consuming steps such as sample preparation. In contrast to conventional methods, Laser-induced breakdown spectroscopy (LIBS) is evaluated as a potential analytical technique for the rapid screening and quality control of anti-diabetic solid formulations. In this paper authors propose a simple method to analyze qualitatively and quantitatively Active Pharmaceutical Ingredients (APIs) such as Metformin hydrochloride. The authors used ten nanosecond duration pulses (FWHM) from a Nd:YAG laser produces the induced breakdown for the analysis. Light is collected and focused into a Cerny-Turner spectrograph and dispersed into an ICCD camera for its detection. We used atomic emissions from Chlorine atoms present only in APIs as analyte signal. The analysis was improved using Bromine as internal standard. Linear calibration curves from synthetic samples were prepared achieving linearity higher than 99%. Our results were compared with HPLC results and validation was performed by statistical methods. The validation analysis suggests that both methods have no significant differences i.e., the proposed method can be implemented for monitoring the pharmaceutical production process in-situ in real time or for inspection and recognition of authenticity.

  20. Extracting coal ash content from laser-induced breakdown spectroscopy (LIBS) spectra by multivariate analysis. (United States)

    Yao, Shunchun; Lu, Jidong; Dong, Meirong; Chen, Kai; Li, Junyan; Li, Jun


    Laser-induced breakdown spectroscopy (LIBS) combined with partial least squares (PLS) analysis has been applied for the quantitative analysis of the ash content of coal in this paper. The multivariate analysis method was employed to extract coal ash content information from LIBS spectra rather than from the concentrations of the main ash-forming elements. In order to construct a rigorous partial least squares regression model and reduce the calculation time, different spectral range data were used to construct partial least squares regression models, and then the performances of these models were compared in terms of the correlation coefficients of calibration and validation and the root mean square errors of calibration and cross-validation. Afterwards, the prediction accuracy, reproducibility, and the limit of detection of the partial least squares regression model were validated with independent laser-induced breakdown spectroscopy measurements of four unknown samples. The results show that a good agreement is observed between the ash content provided by thermo-gravimetric analyzer and the LIBS measurements coupled to the PLS regression model for the unknown samples. The feasibility of extracting coal ash content from LIBS spectra is approved. It is also confirmed that this technique has good potential for quantitative analysis of the ash content of coal.

  1. Fast-imaging and spectroscopic analysis of atmospheric argon streamers for large gap arc breakdown (United States)

    Pachuilo, Michael; Stefani, Francis; Bengtson, Roger; Raja, Laxminarayan


    A non-equilibrium plasma source has been developed to assist in the low-voltage arc breakdown of large electrode gaps. The source consists of a dielectric embedded wire helically wound around a confining cylindrical quartz chamber. Annular electrodes cap the ends of the quartz chamber. An argon feed gas is used to provide a uniform environment and exhausts to ambient atmospheric conditions. A negative polarity 50 kV trigger pulse is applied to the embedded trigger wire to initiate the arc breakdown. Application of the trigger pulse produces a localized coronal discharges along the inner surface of the quartz tube. The corona provides seed electrons through which streamers propagate from one of the main discharge electrode along the quartz surface until it reaches the opposite electrode to bridge the gap. Once the gap is bridged a spark over occurs and robust arc discharge is formed in the chamber volume. Fast imaging of the streamer propagation establishes its velocity in the range of ~ 100 km/s. Spectroscopy of the streamer discharge in atmospheric argon has been conducted and electron temperature and number density estimated from a collision radiative model. Argon spectrum is dominated by neutral argon lines in the 650--950 nm range, and singly ionized argon lines are observed in the ultra-violet to near UV (300--400 nm). Research was performed in connection with AFOSR Contract FA9550-11-1-0062.

  2. [Quantitative analysis of alloy steel based on laser induced breakdown spectroscopy with partial least squares method]. (United States)

    Cong, Zhi-Bo; Sun, Lan-Xiang; Xin, Yong; Li, Yang; Qi, Li-Feng; Yang, Zhi-Jia


    In the present paper both the partial least squares (PLS) method and the calibration curve (CC) method are used to quantitatively analyze the laser induced breakdown spectroscopy data obtained from the standard alloy steel samples. Both the major and trace elements were quantitatively analyzed. By comparing the results of two different calibration methods some useful results were obtained: for major elements, the PLS method is better than the CC method in quantitative analysis; more importantly, for the trace elements, the CC method can not give the quantitative results due to the extremely weak characteristic spectral lines, but the PLS method still has a good ability of quantitative analysis. And the regression coefficient of PLS method is compared with the original spectral data with background interference to explain the advantage of the PLS method in the LIBS quantitative analysis. Results proved that the PLS method used in laser induced breakdown spectroscopy is suitable for quantitative analysis of trace elements such as C in the metallurgical industry.

  3. Sustained inflammation after pericyte depletion induces irreversible blood-retina barrier breakdown (United States)

    Ogura, Shuntaro; Kurata, Kaori; Hattori, Yuki; Takase, Hiroshi; Ishiguro-Oonuma, Toshina; Hwang, Yoonha; Ahn, Soyeon; Ikeda, Wataru; Kusuhara, Sentaro; Fukushima, Yoko; Nara, Hiromi; Sakai, Hideto; Fujiwara, Takashi; Matsushita, Jun; Ema, Masatsugu; Hirashima, Masanori; Shibuya, Masabumi; Takakura, Nobuyuki; Kim, Pilhan; Miyata, Takaki; Ogura, Yuichiro


    In the central nervous system, endothelial cells (ECs) and pericytes (PCs) of blood vessel walls cooperatively form a physical and chemical barrier to maintain neural homeostasis. However, in diabetic retinopathy (DR), the loss of PCs from vessel walls is assumed to cause breakdown of the blood-retina barrier (BRB) and subsequent vision-threatening vascular dysfunctions. Nonetheless, the lack of adequate DR animal models has precluded disease understanding and drug discovery. Here, by using an anti-PDGFRβ antibody, we show that transient inhibition of the PC recruitment to developing retinal vessels sustained EC-PC dissociations and BRB breakdown in adult mouse retinas, reproducing characteristic features of DR such as hyperpermeability, hypoperfusion, and neoangiogenesis. Notably, PC depletion directly induced inflammatory responses in ECs and perivascular infiltration of macrophages, whereby macrophage-derived VEGF and placental growth factor (PlGF) activated VEGFR1 in macrophages and VEGFR2 in ECs. Moreover, angiopoietin-2 (Angpt2) upregulation and Tie1 downregulation activated FOXO1 in PC-free ECs locally at the leaky aneurysms. This cycle of vessel damage was shut down by simultaneously blocking VEGF, PlGF, and Angpt2, thus restoring the BRB integrity. Together, our model provides new opportunities for identifying the sequential events triggered by PC deficiency, not only in DR, but also in various neurological disorders. PMID:28194443

  4. Collegial relationship breakdown: a qualitative exploration of nurses in acute care settings. (United States)

    Cowin, Leanne S


    Poor collegial relations can cause communication breakdown, staff attrition and difficulties attracting new nursing staff. Underestimating the potential power of nursing team relationships means that opportunities to create better working environments and increase the quality of nursing care can be missed. Previous research on improving collegiality indicates that professionalism and work satisfaction increases and that staff attrition decreases. This study explores challenges, strengths and strategies used in nursing team communication in order to build collegial relationships. A qualitative approach was employed to gather nurses experiences and discussion of communication within their nursing teams and a constant comparison method was utilised for data analysis. A convenience sampling technique was employed to access both Registered Nurses and Enrolled Nurses to partake in six focus groups. Thirty mostly female nurses (ratio of 5:1) participated in the study. Inclusion criteria consisted of being a nurse currently working in acute care settings and the exclusion criteria included nursing staff currently working in closed specialty units (i.e. intensive care units). Results revealed three main themes: (1) externalisation and internalisation of nursing team communication breakdown, (2) the importance of collegiality for retention of nurses and (3) loss of respect, and civility across the healthcare workplace. A clear division between hierarchies of nurses was apparent in how nursing team communication was delivered and managed. Open, respectful and collegial communication is essential in today's dynamic and complex health environments. The nurses in this study highlighted how important nursing communication can be to work motivation and how leadership fosters teamwork.

  5. Detection of Anomalies in Citrus Leaves Using Laser-Induced Breakdown Spectroscopy (LIBS). (United States)

    Sankaran, Sindhuja; Ehsani, Reza; Morgan, Kelly T


    Nutrient assessment and management are important to maintain productivity in citrus orchards. In this study, laser-induced breakdown spectroscopy (LIBS) was applied for rapid and real-time detection of citrus anomalies. Laser-induced breakdown spectroscopy spectra were collected from citrus leaves with anomalies such as diseases (Huanglongbing, citrus canker) and nutrient deficiencies (iron, manganese, magnesium, zinc), and compared with those of healthy leaves. Baseline correction, wavelet multivariate denoising, and normalization techniques were applied to the LIBS spectra before analysis. After spectral pre-processing, features were extracted using principal component analysis and classified using two models, quadratic discriminant analysis and support vector machine (SVM). The SVM resulted in a high average classification accuracy of 97.5%, with high average canker classification accuracy (96.5%). LIBS peak analysis indicated that high intensities at 229.7, 247.9, 280.3, 393.5, 397.0, and 769.8 nm were observed of 11 peaks found in all the samples. Future studies using controlled experiments with variable nutrient applications are required for quantification of foliar nutrients by using LIBS-based sensing.

  6. Improving breakdown voltage performance of SOI power device with folded drift region

    Institute of Scientific and Technical Information of China (English)

    李琦; 李海鸥; 黄平奖; 肖功利; 杨年炯


    A novel silicon-on-insulator (SOI) high breakdown voltage (BV) power device with interlaced dielectric trenches (IDT) and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedded in the active layer, which results in an increase of length of ionization integral remarkably. The crowding phenomenon of electric field in the corner of IDT is relieved by the N/P pillars. Both traits improve two key factors of BV, the ionization integral length and electric field magnitude, and thus BV is significantly enhanced. The electric field in the dielectric layer is enhanced and a major portion of bias is borne by the oxide layer due to the accumulation of inverse charges (holes) at the corner of IDT. The average value of the lateral electric field of the proposed device reaches 60 V/µm with a 10 µm drift length, which increases by 200%in comparison to the conventional SOI LDMOS, resulting in a breakdown voltage of 607 V.

  7. Application of laser-induced breakdown spectroscopy to the analysis of algal biomass for industrial biotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Porizka, P.; Prochazka, D. [X-ray micro CT and nano CT research group, CEITEC-Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, 616 00 Brno (Czech Republic); Pilat, Z. [Institute of Scientific Instruments of the ASCR v.v.i., Academy of Sciences of the Czech Republic, Kralovopolska 147, Brno 61669 (Czech Republic); Krajcarova, L. [Department of Chemistry, Faculty of Sciences, Masaryk University, Kotlarska 2, Brno 611 37 (Czech Republic); Kaiser, J., E-mail: [X-ray micro CT and nano CT research group, CEITEC-Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, 616 00 Brno (Czech Republic); Malina, R.; Novotny, J. [X-ray micro CT and nano CT research group, CEITEC-Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, 616 00 Brno (Czech Republic); Zemanek, P.; Jezek, J.; Sery, M.; Bernatova, S.; Krzyzanek, V.; Dobranska, K. [Institute of Scientific Instruments of the ASCR v.v.i., Academy of Sciences of the Czech Republic, Kralovopolska 147, Brno 61669 (Czech Republic); Novotny, K. [Department of Chemistry, Faculty of Sciences, Masaryk University, Kotlarska 2, Brno 611 37 (Czech Republic); Trtilek, M. [Photon Systems Instruments, Drasov 470, 664 24 Drasov (Czech Republic); Samek, O. [Institute of Scientific Instruments of the ASCR v.v.i., Academy of Sciences of the Czech Republic, Kralovopolska 147, Brno 61669 (Czech Republic)


    We report on the application of laser-induced breakdown spectroscopy (LIBS) to the determination of elements distinctive in terms of their biological significance (such as potassium, magnesium, calcium, and sodium) and to the monitoring of accumulation of potentially toxic heavy metal ions in living microorganisms (algae), in order to trace e.g. the influence of environmental exposure and other cultivation and biological factors having an impact on them. Algae cells were suspended in liquid media or presented in a form of adherent cell mass on a surface (biofilm) and, consequently, characterized using their spectra. In our feasibility study we used three different experimental arrangements employing double-pulse LIBS technique in order to improve on analytical selectivity and sensitivity for potential industrial biotechnology applications, e.g. for monitoring of mass production of commercial biofuels, utilization in the food industry and control of the removal of heavy metal ions from industrial waste waters. - Highlights: Black-Right-Pointing-Pointer We realized laser-induced breakdown spectroscopy (LIBS) analysis of algal biomass. Black-Right-Pointing-Pointer We used water jet setup, bulk liquid arrangement and algal biofilms. Black-Right-Pointing-Pointer LIBS analysis of macro- and micro-element concentrations in algae was shown. Black-Right-Pointing-Pointer LIBS can be of assistance in research of sustainable biofuel generation. Black-Right-Pointing-Pointer LIBS can be used in research of algal food applications and bioremediation.

  8. Analytical modeling of Schottky tunneling source impact ionization MOSFET with reduced breakdown voltage

    Directory of Open Access Journals (Sweden)

    Sangeeta Singh


    Full Text Available In this paper, we have investigated a novel Schottky tunneling source impact ionization MOSFET (STS-IMOS to lower the breakdown voltage of conventional impact ionization MOS (IMOS and developed an analytical model for the same. In STS-IMOS there is an accumulative effect of both impact ionization and source induced barrier tunneling. The silicide source offers very low parasitic resistance, the outcome of which is an increment in voltage drop across the intrinsic region for the same applied bias. This reduces operating voltage and hence, it exhibits a significant reduction in both breakdown and threshold voltage. STS-IMOS shows high immunity against hot electron damage. As a result of this the device reliability increases magnificently. The analytical model for impact ionization current (Iii is developed based on the integration of ionization integral (M. Similarly, to get Schottky tunneling current (ITun expression, Wentzel–Kramers–Brillouin (WKB approximation is employed. Analytical models for threshold voltage and subthreshold slope is optimized against Schottky barrier height (ϕB variation. The expression for the drain current is computed as a function of gate-to-drain bias via integral expression. It is validated by comparing it with the technology computer-aided design (TCAD simulation results as well. In essence, this analytical framework provides the physical background for better understanding of STS-IMOS and its performance estimation.

  9. Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown (United States)

    Vaughan, Alun S.; Swingler, Steven G.; Zhang, Yudong

    A range of nanocomposites containing polyethylene and montmorillonite (MMT) clay was prepared using different procedures, such that the extent of MMT dispersion varied. The interactions that occur were then studied, together with the effect of MMT dispersion on structure and short-term dielectric breakdown. When the MMT is poorly dispersed, the AC ramp breakdown strength is reduced. When the MMT is well dispersed, quenched samples with and without MMT appear to behave in an equivalent manner. However, while isothermal crystallization at 117 °C results in a significant increase in performance in the absence of MMT, no equivalent change was seen when the MMT was present. The crystallization behaviour of the polyethylene indicates that while well-dispersed MMT serves to enhance nucleation, it can also serve to inhibit crystallization. These results suggest that short-range thermodynamic interactions occur between the clay platelets and the polymer during the initial crystallization phase. The interaction zone can, however, be thought to extent throughout the material.

  10. Validity of 3-methylhistidine excretion as an indicator of skeletal muscle protein breakdown in humans. (United States)

    Long, C L; Dillard, D R; Bodzin, J H; Geiger, J W; Blakemore, W S


    The urinary excretion of 3-methylhistidine (3MEH) in humans and animals has been used as a biologic marker for skeletal muscle protein breakdown. In rats, it has been recently suggested that there is a significant contribution of 3MEH in urine from the gastrointestinal tract due to the rapid turnover of protein in that tissue. To evaluate this point in humans, six patients with short bowel were evaluated. They were placed on three-day meat-free diets while 24-hour urine collections were obtained. The mean +/- SEM 3MEH in the short-bowel group was 3.27 +/- 0.34 mumol/kg/d and the mean +/- SEM molar ratio of 3MEH to creatinine was 0.0212 +/- 0.0012. These data were not significantly different from the control group at 95% confidence level. The results suggest that the contribution of the small intestine appears to be negligible, therefore urinary 3MEH should continue to be a valid index of skeletal muscle breakdown in man.

  11. Reduced probability of smoking cessation in men with increasing number of job losses and partnership breakdowns

    DEFF Research Database (Denmark)

    Kriegbaum, Margit; Larsen, Anne Mette; Christensen, Ulla


    Background Unemployment and partnership breakdowns are common stressful life events, but their association with smoking cessation has been investigated in only a few studies. Objective To investigate how history of employment and cohabitation affects the probability of smoking cessation and to st......Background Unemployment and partnership breakdowns are common stressful life events, but their association with smoking cessation has been investigated in only a few studies. Objective To investigate how history of employment and cohabitation affects the probability of smoking cessation...... by a questionnaire. Results The probability of smoking cessation decreased with the number of job losses (ranging from 1 OR 0.54 (95% CI 0.46 to 0.64) to 3+ OR 0.41 (95% CI 0.30 to 0.55)) and of broken partnerships (ranging from 1 OR 0.74 (95% CI 0.63 to 0.85) to 3+ OR 0.50 (95% CI 0.39 to 0.63)). Furthermore......, smoking cessation was associated with the duration of the periods of unemployment (ranging from 1–5 years (OR 0.75, 95% CI 0.65 to 0.85) to 10–23 years (OR 0.29, 95% CI 0.22 to 0.38)) and with living without a partner for >5 years (ranging from 6–9 years to 10–23 years (OR 0.80, 95% CI 0.66 to 0.97) to 10...

  12. Induction cell breakdown experiments for the Dual-Axis Radiographic Hydrotest (DARHT) Facility

    Energy Technology Data Exchange (ETDEWEB)

    Earley, L.M.; Barnes, G.A.; Eversole, S.A.; Kauppila, T.J.; Keel, G.; Liska, D.J.; Moir, D.C.; Parsons, W.M.; Rader, D.C.


    Linear induction cells for the Dual-Axis Radiographic Hydrotest (DARHT) Facility have been tested to determine their high-voltage breakdown characteristics. A variety of full scale insulators were tested both in actual cells and in fixtures simulating induction cells. All insulators were constructed using cross-linked polystyrene (Rexolite). High-voltage pulses up to 550 kV were applied to the insulators using both a 60-ns pulse Blumlein and a 200-ns pulse cable Marx. Two different vacuum gaps were used in these tests, 1.46 and 1.91 cm. The tests were performed at various vacuum levels ranging from 1 {times} 10{sup {minus}6} to 5 {times} 10{sup {minus}8} torr. Breakdown tests of the insulators were also performed with an electron beam generated in the vacuum gap through the use of a velvet emitter. The gap voltage and current were measured using calibrated E-dot and B-dot probes. 15 refs., 7 figs.

  13. A Single-server Discrete-time Retrial G-queue with Server Breakdowns and Repairs

    Institute of Scientific and Technical Information of China (English)

    Jin-ting Wang; Peng Zhang


    This paper concerns a discrete-time Geo/Geo/1 retrial queue with both positive and negative customers where the server is subject to breakdowns and repairs due to negative arrivals.The arrival of a negative customer causes one positive customer to be killed if any is present,and simultaneously breaks the server down.The server is sent to repair immediately and after repair it is as good as new.The negative customer also causes the server breakdown if the server is found idle,but has no effect on the system if the server is under repair.We analyze the Markov chain underlying the queueing system and obtain its ergodicity condition.The generating function of the number of customers in the orbit and in the system are also obtained,along with the marginal distributions of the orbit size when the server is idle,busy or down.Finally,we present some numerical examples to illustrate the influence of the parameters on several performance characteristics of the system.

  14. Techniques of surface optical breakdown prevention for low-depths femtosecond waveguides writing (United States)

    Bukharin, M. A.; Skryabin, N. N.; Ganin, D. V.; Khudyakov, D. V.; Vartapetov, S. K.


    We demonstrated technique of direct femtosecond waveguide writing at record low depth (2-15 μm) under surface of lithium niobate, that play a key role in design of electrooptical modulators with low operating voltage. To prevent optical breakdown of crystal surface we used high numerical aperture objectives for focusing of light and non-thermal regime of inscription in contrast to widespread femtosecond writing technique at depths of tens micrometers or higher. Surface optical breakdown threshold was measured for both x- and z- cut crystals. Inscribed waveguides were examined for intrinsic microstructure. It also reported sharp narrowing of operating pulses energy range with writing depth under the surface of crystal, that should be taken in account when near-surface waveguides design. Novelty of the results consists in reduction of inscription depth under the surface of crystals that broadens applications of direct femtosecond writing technique to full formation of near-surface waveguides and postproduction precise geometry correction of near-surfaces optical integrated circuits produced with proton-exchanged technique.

  15. Virtual nuclear envelope breakdown and its regulators in fission yeast meiosis

    Directory of Open Access Journals (Sweden)

    Haruhiko eAsakawa


    Full Text Available Ran, a small GTPase, is required for the spindle formation and nuclear envelope (NE formation. After NE breakdown (NEBD during mitosis in metazoan cells, the Ran-GTP gradient across the NE is lost and Ran-GTP becomes concentrated around chromatin, thus affecting the stability of microtubules and promoting the assembly of spindle microtubules and segregation of chromosomes. Mitosis in which chromosomes are segregated subsequent to NEBD is called open mitosis. In contrast, many fungi undergo a process termed closed mitosis in which chromosome segregation and spindle formation occur without NEBD. Although the fission yeast Schizosaccharomyces pombe undergoes a closed mitosis, it exhibits a short period during meiosis (anaphase of the second meiosis; called anaphase II when nuclear and cytoplasmic proteins are mixed in the presence of intact NE and nuclear pore complexes (NPC. This virtual nuclear envelope breakdown (vNEBD involves changes in the localization of RanGAP1, an activator of Ran-GTP hydrolysis. Recently, Nup132, a component of the structural core Nup107-160 subcomplex of the NPC, has been shown to be involved in the maintenance of the nuclear cytoplasmic barrier in yeast meiosis. In this review, we highlight the possible roles of RanGAP1 and Nup132 in vNEBD and discuss the biological significance of vNEBD in S. pombe meiosis.

  16. Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Shneider, Mikhail N., E-mail: [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Pekker, Mikhail [MMSolution, 6808 Walker Street, Philadelphia, Pennsylvania 19135 (United States)


    We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.

  17. Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields (United States)

    Shneider, Mikhail N.; Pekker, Mikhail


    We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.

  18. A comparison of push and pull production controls under machine breakdown

    Directory of Open Access Journals (Sweden)

    Prakash, J.


    Full Text Available Production control for high-mix production remains a complex issue. Common pull system replenishment generates large works-in-process (WIPs for each part type, especially under breakdown. This paper attempts to solve this by presenting a production control that classifies parts into two categories. The performances of three production control mechanisms under breakdown are compared. The production control mechanisms in consideration are push, shared constant WIP (CONWIP, and parallel CONWIP. A full-factorial simulation experiment was conducted. ANOVA was performed to determine the significant effects of input factors. Response surface methodology was used to demonstrate the behavior of performance measures in terms of these significant input factors. The results prove that parallel CONWIP is superior over shared CONWIP in terms of the average flow time per part. If categorical dispatch rules are employed, parallel CONWIP outperforms shared CONWIP in terms of service level. With high card count, parallel CONWIP generally produces lower bottleneck utilizations while maintaining a low average flow time per part than shared CONWIP.

  19. Flow visualization of the trapping induced by vortex breakdown at a junction (United States)

    Vigolo, Daniele; Riccomi, Marco; Alberini, Federico; Brunazzi, Elisabetta; Ault, Jesse; Stone, Howard


    Here we present experimental investigations of the vortex breakdown happening at a T-, Y- or "arrow" shaped junction responsible for the trapping of light material suspended in solution. Considering the ubiquitous nature of T-junctions and bifurcation in general, in industrial as well as biological environments, it is extremely interesting to better understand how this trapping phenomenon happens. In particular, we observed the flow profiles at different sections in order to perform a three-dimensional study of complex structures, such as vortices and recirculation zones, that develop at a bifurcation. We explored Reynolds number ranging from 50 to about 500 for different milli-fluidic devices. Thus we compared standard micro-PIV and a novel optical technique, the Ghost Particle Velocimetry (GPV), that was recently introduced, to investigate the onset of vortex breakdown. Moreover, the experimental results were compared with single-phase OpenFoam numerical simulations performed in the same flow conditions. Finally, we studied the mutual influence of a trapped particle on the flow field inside the recirculation zone by fully exploiting the capability of GPV to produce 3D flow field with a spatial resolution of few tens of microns. This work was partially supported by the Wellcome Trust [1516ISSFFIRA23].

  20. The effect of substrate wettability on the breakdown of a locally heated fluid film (United States)

    Zaitsev, D. V.; Kirichenko, D. P.; Kabov, O. A.


    The effect of the equilibrium contact angle of wetting on the dynamics of the dry patch propagation and on the critical heat flux upon the breakdown of a water film that is heated locally from the substrate side is studied experimentally. The equilibrium contact angle is varied from 27° ± 6° to 74° ± 9° (with no changes in the thermophysical properties of the system) through the use of different types of surface grinding. The studies are performed for three flow modes: (a) a fluid film that freely flows down along a substrate with an inclination of 5° to the horizon, (b) a film that moves along a horizontal substrate under the influence of hydrostatic pressure, and (c) a static film on a horizontal substrate. It is found that the substrate wettability has a significant effect on the dry patch propagation rate and its final size in all these cases, but has almost no effect on the threshold heat flux at which the breakdown of a film occurs.