Search

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Physics. Please check back later for the full article. The conditions for the Sokolov-Ternov effect to occur are approximately satisfied by electrons (or positrons) circulating on the design orbit of a planar storage ring. Indeed, self-polarization was first observed in the electron/positron colliders Anneau de Collisions d’Orsay (ACO) and VEPP-2. Beam polarization offers an additional tool for understanding the physics events. The possibility of having polarized electron/positron beams for free is therefore appealing. However, the Sokolov-Ternov polarization time constant, proportional to 1/γ5 and to the third power of the bending radius, restricts the region of interest for self-polarization. For the about 100 km Future Circular Collider (FCC) under study at CERN, the polarization constant is about 10 days at 45 GeV beam energy. At high energy the randomization of the particle trajectory due to photon emission in a storage ring with finite alignment precision of the magnets introduces spin diffusion and limits the attainable polarization. In addition, in a collider the force exerted by the counter-rotating particles impact the beam polarization. This force increases with beam intensity and experiments are reluctant to pass up luminosity for polarization. To this day the electron(positron)/proton collider HERA has been the only high energy collider where electron (and positron) self-polarization was an integral part of the physics program.

In this paper, a uniform magnetic field coil with a magnetic shield is presented and designed to cancel the geomagnetic field and the surrounding magnetic noises. First, an analytical model of the uniform magnetic field coil with the magnetic shield is developed, based on the Biot-Savart law and the traditional images method. Second, in order to improve the model accuracy, the influence of the non-infinite shield thickness on the magnetic field produced by the uniform magnetic coil is considered using the multi-reflection theory, and an improved analytical model is obtained. The improved analytical model is verified by the 3D finite element method (FEM), and its accuracy is significantly improved compared to the previous analysis model. Then, the characteristic analysis of the uniform magnetic field coil is carried out using the improved analytical model, and design criteria of the uniform magnetic field coils are given to obtain a large uniform field area. Finally, the uniform magnetic field coil with the magnetic shield was constructed and the resulting magnetic field was tested. The test results show that the improved analytical model can accurately predict the performance of such magnetic field coils with magnetic shields, and can be used for its preliminary design.

With the aid of conformal mapping and analytic continuation, we prove that within the framework of anti-plane elasticity, a non-parabolic open elastic inhomogeneity can still admit an internal uniform stress field despite the presence of a nearby non-circular Eshelby inclusion undergoing uniform anti-plane eigenstrains when the surrounding elastic matrix is subjected to uniform remote stresses. The non-circular inclusion can take the form of a Booth’s lemniscate inclusion, a generalized Booth’s lemniscate inclusion or a cardioid inclusion. Our analysis indicates that the uniform stress field within the non-parabolic inhomogeneity is independent of the specific open shape of the inhomogeneity and is also unaffected by the existence of the nearby non-circular inclusion. On the other hand, the non-parabolic shape of the inhomogeneity is caused solely by the presence of the non-circular inclusion.

The theory analysis and particle-in-cell (PIC) simulation results of a 140-GHz double confocal waveguide gyrotron traveling-wave amplifier (gyro-TWA) are presented. The mode density in a double confocal waveguide is relatively sparse, and its intrinsic diffraction loss can be against the parasitic oscillation. A high-performance input coupler is designed, and simulation results show that a wave is efficiently converted from TE01 rectangular waveguide mode into the antiphase superposition TE06 double confocal waveguide mode. From theoretical analysis and PIC simulation, when the double confocal gyro-TWA and single confocal gyro-TWA operate under the same parameters, the interaction efficiency of double confocal gyro-TWA is significantly higher than the single confocal gyro-TWA. The calculated results from the nonlinear theory agree well with those from PIC simulation. The performance of the double confocal gyro-TWA is much better than that in the single confocal gyro-TWA due to a more uniform field distribution in the double confocal gyro-TWA.

The VVER-TOI reactor plant has for the first time been furnished with a new layout of steam generators in the NPP reactor building, according to which the steam produced in the steam generator is removed from it through one steam nozzle. The shift for using one steam-offtake nozzle results in that a nonuniform steam velocity field is produced in the separation volume between the evaporation surface and steam-receiving perforated sheets (SRPSs), which is caused by steam motion along the path with the lowest friction, and this can entail excessive carryover of moisture from the steam generator (SG). To obtain the necessary moisture-separation performance of a horizontal steam generator equipped with one steam nozzle, it is necessary to set up a uniform field of the steam velocity vector’s vertical component in the separation volume with limiting the pressure loss in the SG steam path down to the design value. Therefore, it is proposed to arrange nonuniform flow friction along the steam motion path from the evaporation surface to the steam line by using a variable SRPS perforation ratio. In this study, a set of optimization numerical analyses of the SRPS design for the PGV-1000MKO steam generator performed using the CFD methods was carried out for determining the perforation ratio. In carrying out the optimization numerical analyzes, the performance characteristics of the steam-receiving device equipped with one steam nozzle located in the steam generator’s upper part and consisting of more than 50 perforated sheets had to be made maximally close to the performance characteristics of the steam-receiving device equipped with ten steam nozzles. By using an elaborated computer model, a set of optimization numerical analyses of the SRPS design was carried out, and an optimized design version of the steam-receiving device with a variable perforation ratio for the PGV-1000MKO steam generator has been obtained.

Understanding the evolution events defining silicon (Si) uptake in plant species is important for the efficient exploration of Si-derived benefits. In the present study, Si accumulation was studied in 456 diverse plant species grown in uniform field conditions, and in a subset of 151 species grown under greenhouse conditions, allowing efficient comparison among the species. In addition, a systematic analysis of nodulin 26-like intrinsic proteins III (NIP-III), which form Si channels, was performed in >1000 species to trace their evolutionary path and link with Si accumulation. Significant variations in Si accumulation were observed among the plant species studied. For their part, species lacking NIP-IIIs systematically showed low Si accumulation. Interestingly, seven NIP-IIIs were identified in three moss species, namely Physcomitrella patens, Andreaea rupestris, and Scouleria aquatica, indicating that the evolution of NIP-IIIs dates back as early as 515 million years ago. These results were further supported from previous reports of Si deposition in moss fossils estimated to be from around the Ordovician era. The taxonomical distribution provided in the present study will be helpful for several other disciplines, such as palaeoecology and geology, that define the biogeochemical cycling of Si. In addition to the prediction of Si uptake potential of plant species based on sequence information and taxonomical positioning, the evolutionary path of the Si uptake mechanism described here will be helpful to understand the Si environment over the different eras of land plant evolution.

In total, 52 uniform field experiments were conducted in Illinois, Indiana, Iowa, Michigan, South Dakota, and Wisconsin in the United States and Ontario, Canada from 2013 to 2017 comparing crop protection products against sudden death syndrome (SDS) of soybean. Data were analyzed using meta-analytic models to summarize the relationship between foliar disease index (FDX) and yield. For each study, correlation and regression analyses were performed separately to determine three effect sizes: Fisher’s transformation of correlation coefficients (Z r ), intercept (β0), and slope (β1). Random- and mixed-effect meta-analyses were used to summarize the effect sizes. Study- and location-specific moderator variables FDX (low < 10% and high ≥ 10%), date of planting (early = prior to 7 May, conventional = 7 to 21 May, and late = after 21 May) cultivar (susceptible and partially resistant to SDS), study location, and growing season were used as fixed effects. The overall mean effect sizes of transformed correlation coefficient [Formula: see text] r was −0.41 and different from zero (P < 0.001), indicating that yield was negatively correlated with FDX. The [Formula: see text] r was affected by disease level (P < 0.01) and cultivar (P = 0.02), with a greater effect at higher disease levels and with susceptible cultivars. The mean [Formula: see text] 0 was 4,121 kg/ha and mean [Formula: see text] 1 was −21 kg/ha/% FDX and were different from zero (P < 0.01). Results from these data indicate that, for every unit of FDX increase, yield was decreased by 0.5%. Study locations and year affected the [Formula: see text] 0 , whereas none of the moderator variables significantly affected [Formula: see text] 1.

SF 6 /N 2 mixtures is considered as a practical alternative proposal of SF 6 in GIS and GIL. Simulating particle transportations and chemical reactions during the positive streamer propagation in SF 6 /N 2 mixtures assists in the insulation performance optimization of SF 6 /N 2 mixtures. This paper presents a fluid dynamic model coupled with the chemical reaction system for the positive streamer propagation in SF 6 /N 2 mixtures. The Townsend coefficients of the 20%SF 6 /80%N 2 mixture derived from the proposed chemical reaction system are in accordance with the measurement results. Based on this model, the propagation of the positive streamer in a 1 mm needle-plate gap in the 20%SF 6 /80%N 2 mixture is simulated. Simulated results indicate that there exists a negative space charge region in the streamer channel. It can be attributed to the increasing attachment rates of SF 6 yielding SF 5 − and SF 6 −, and the reduction of the ionization rates of N 2 and SF 6 in the streamer channel. Besides, it is noted that the ionization activities of N 2 and SF 6 at the streamer head are equally important to support the continuous propagation of the positive streamer. The ionization of N 2 in the streamer channel serves as an important factor to supply electrons and avoid the accumulation of the negative space charge.

The C 4 F 7 N/CO 2 gas mixture has attracted much attention due to its excellent insulation property and eco-friendly character. In order to evaluate the feasibility of its application in DC GIL, this paper focuses on the surface charging characteristics of spacers under DC stress in the C 4 F 7 N/CO 2 mixture. First, the DC insulation strength was tested under uniform field. The results show that the critical dielectric strength of pure C 4 F 7 N is more than twice that of SF 6 and the dielectric strength of 15%∼20% C 4 F 7 N/CO 2 mixture is equivalent to that of SF 6 . Next, the surface charge measurement of spacers was performed in C 4 F 7 N/CO 2 mixtures, which reveals that the surface charge density decreases slightly with the increase of C 4 F 7 N content. However, the surface charging level in 25% C 4 F 7 N/CO 2 mixture is still much higher than that in SF 6 . It is found that most of the surface charge stems from partial discharges (PDs) near the flange. The PD measurement shows that in SF 6 , there are more PDs with low magnitude, but much less PDs with high magnitude compared to that in the 15%∼25% C 4 F 7 N/CO 2 mixtures. It is the different PD behaviors between C 4 F 7 N/CO 2 mixtures and SF 6 that lead to their different surface charging characteristics.

The article provides a comparative analysis of multi-element sensors of an electric field of a flat shape differing in various configurations of sensitive elements, each of which is determined by its design parameters. For this, a generalized mathematical model of the sensor is compiled taking into account its design parameters which affect the error from field inhomogeneity and the spatial range of measurement. Using a generalized mathematical model, graphs of the sensor error are constructed depending on the spatial measurement range and various design parameters of its sensitive elements. The change in design parameters allowed us to model sensitive elements in the form of quadrants and truncated quadrants of a circle. According to the error graphs, it is established that sensitive elements made in the form of quadrants of a circle provide the sensor with a lower error and a larger spatial range of measurement, therefore their use is more appropriate. The studies performed allowed us to obtain the following technical results. Sensors with sensitive elements in the form of a quadrant of a circle have a minimum of an error and a maximum of a spatial range of measurement at design parameters: b = 0 and b0 = 0,2; b = 0 and b0 = 0.4, for which, with a maximum spatial range of measurement equal to unity (a = 1), the errors are respectively minus 3 % and minus 10 %.

A combined superconducting magnetic system with a uniform field of up to 20 T has been developed. The system contains several solenoidal sections and a magnetic flux concentrator consisting of hydroextruded dysprosium. The sections are wound from NbTi, Nb3Sn wires and Nb3Sn ribbon. A magnetic shield made out of Nb3Sn ribbon is applied in order to increase the uniformity of the magnetic field. The magnetic field achieved in the gap between the ends of the concentrator has a high spatial uniformity ΔН/Н ∼ 5 × 10−5.

During 2012–2015, the seed vigour of 54 commercial sugar beet varieties was evaluated. In addition, correlations among different methods of determining seed vigour and the potential impact of low vigour on the quality traits of seeds and root yield were investigated. The chosen seed vigour indicators were field emergence (early and final count), emergence course in a phytotron under controlled conditions (early and final count, mean time of emergence, emergence uniformity) and germination ability under stress conditions regarding substrate moisture and air temperature. The most effective vigour indicators were field and phytotron emergence (early count), mean time of emergence and germination ability under stress conditions. Final field and phytotron emergence constituted weak indicators of seed vigour. Low seed vigour decreased root yield by 3.2 t/ha (4.8%) compared to high seed vigour. Lower yields were caused by slower and less uniform field emergence.

Let f : P N → P N be an endomorphism of degree d ≥ 2 defined over Q ‾ or Q ‾ p , and let K be the field of moduli of f. We prove that there is a field of definition L for f whose degree [ L : K ] is bounded solely in terms of N and d.

ABA/GA4 ratio, stress resistance, carbon and nitrogen metabolism, and chromatin structure play important roles in vigour differences of seeds located at different maize ear positions. Seed vigour, which ensures rapid and uniform field emergence across diverse environments, differs at different maize ear positions. However, little is known regarding the associated mechanisms. In this study, we determined that seed vigour, stress resistance, and carbon and nitrogen metabolism were higher in seeds from middle and bottom section of the ear, while the ABA/GA4 ratio in the embryos was significantly lower. Compared with the seeds subjected to repeated pollination during silking, less variation in seed vigour and the ABA/GA4 ratio in the embryos was observed in seeds at different ear positions subjected to single pollination after complete silking. This indicated that single pollination can reduce, but not eliminate, the differences in seed vigour at different ear positions. RNA-seq analysis indicated that the seed vigour differences at the different locations of the maize ears of the single pollinated treatment were related to carbon and nitrogen metabolism. In contrast, the differences in seed vigour under repeated pollination were related to chromatin structure. The present study contributes to our understanding of the mechanisms underlying differences in seed vigour at different positions on the maize ear.

In the framework of three-dimensional nonlinear elasticity we consider linear instability of a composite plate made of functionally graded material and having initial stresses. The plae consists of two layers which were obtained as a result of flattening of an annual sector of an elastic cylinder. This deformation results in appearance of internal stresses. Thus, the plate becomes initially stressed. The initial stresses depend on the thickness coordinate, so we get inhomogeneous stress field. We have two types of inhomogeneities, the first is the inhomogeneity of the initial stresses whereas the second is the material inhomogeneity.We use the incompressible neo-Hookean material model as a constitutive relation. Despite of relatively simple form this model describes properly severe deformations of some rubber-like materials. For incompressible materials the flattening constitutes one of the so-called universal deformations, that is such deformation which is independent on the choice of constitutive relation. The material inhomogeneity is described through a dependence of the shear modulus on the thickness coordinate. Such inhomogeneity could be related to the manufacturing of the material or to further treatment. The stability was analysed using the linearization approach. We superimpose infinitesimal deformations on the finite initial one. The linearized boundary-value problem was derived and its nontrivial solutions were obtained. The solution was obtained in series of trigonometric functions. This helps to automatically satisfy a part of boundary conditions. We consider the influence of the inhomogeneity and initial stresses. We show that the initial stresses may significantly change critical deformations. For example, the loss of stability is possible due to initial stresses only.

Upon insertion of an inclusion into a medium with the uniform field, if the field is not perturbed at all outside the inclusion, then it is called a neutral inclusion. It is called a weakly neutral inclusion if the field is perturbed weakly. The inclusions neutral to multiple uniform fields are of circular shape if the medium is isotropic, and any other shape cannot be neutral. We consider in this paper the problem of constructing inclusions of general shape which are weakly neutral to multiple fields in two dimensions. We show that a simply connected domain satisfying a certain geometric condition can be realized as a weakly neutral inclusion to multiple fields by introducing an imperfect interface parameter on the boundary. The geometric condition on the domain and the imperfect interface parameter are determined by the first coefficient of the conformal mapping from the exterior of the unit disk onto the exterior of the domain. We provide some numerical examples to compare field perturbations by weakly neutral inclusions and perfectly bonding interfaces. They clearly show that the field perturbation by weakly neutral inclusions is much weaker., 19 pages, 8 figures

An inclusion is said to be neutral to uniform fields if upon insertion into a homogenous medium with a uniform field it does not perturb the uniform field at all. It is said to be weakly neutral if it perturbs the uniform field mildly. Such inclusions are of interest in relation to invisibility cloaking and effective medium theory. There have been some attempts lately to construct or to show existence of such inclusions in the form of core-shell structure or a single inclusion with the imperfect bonding parameter attached to its boundary. The purpose of this paper is to review recent progress in such attempts. We also discuss about the over-determined problem for confocal ellipsoids which is closely related with the neutral inclusion, and its equivalent formulation in terms of Newtonian potentials. The main body of this paper consists of reviews on known results, but some new results are also included.

High sub-soil strength is one of the major constraints to reduce plant root growth and crop yield and to test this hypothesis a total of 39 plot experiments consisting of 13 treatments with three replications were conducted using a factorial randomized block design (FRBD) in a uniform field conditions for a period of two years from 2006-07 and 2007-08. Triticum aestivum L. was grown after tilling the soil up to a depth of 15 cm and crop growth, yield parameters root length density was measured. The variation of soil strength with soil compaction was developed using three levels of normal loads: 4.40, 6.40 and 8.40 kN; and 1, 6, 11 and 16 numbers of passes. A maximum of 12.53% and minimum of 1.26% decrease in plant height was observed at the time of harvesting due to application of maximum and minimum sub-surface soil strength of 43.25 and 26.8 J/cm, respectively. For all combinations of normal loads and no. of passes (i.e., sub soil strength), nearly 51-61 % of wheat roots were confined in surface layer (i.e., 0-15 cm of upper soil layer) followed by nearly 17-20 % in 15-30 cm and the rest 22-28% below 30 cm of soil layer. The root length density (RLD) at 15-30 cm of soil layer was significantly higher under high level of sub-surface soil penetration as compared with control. The higher sub-soil strength reduces the crop yield upto 121 kg/ha i.e. 23.62 per cent and root length density of 0.69 cm/cm3.

The nearfield antenna with well-distributed field is required in radio frequency identification (RFID) system. In this paper, a nearfield antenna, with planar quadrifilar spiral antenna and feeding network is presented. The proposed antenna exhibits uniform field distribution with maximum variation of 10dB for both E and H fields in simulation, and field difference between inside and outside the range of antenna is 30dB.

The theory of “visual stress” holds that visual discomfort results from overactivation of the visual cortex. Despite general acceptance, there is a paucity of empirical data that confirm this relationship, particularly for discomfort from visual flicker. We examined the association between neural response and visual discomfort using flickering light of different temporal frequencies that separately targeted the magnocellular, parvocellular, and koniocellular post-receptoral pathways. Given prior work that has shown larger cortical responses to flickering light in people with migraine, we examined 10 headache free people and 10 migraineurs with visual aura. The stimulus was a uniform field, 50 degrees in diameter, that modulated with high-contrast flicker between 1.625 and 30 Hz. We asked subjects to rate their visual discomfort while we recorded steady state visually evoked potentials (ssVEP) from primary visual cortex. The peak temporal sensitivity ssVEP amplitude varied by post-receptoral pathway, and was consistent with the known properties of these visual channels. Notably, there was a direct, linear relationship between the amplitude of neural response to a stimulus and the degree of visual discomfort it evoked. No substantive differences between the migraine and control groups was found. These data link increased visual cortical activation with the experience of visual discomfort.

Rotationally invariant space with noncommutativity of coordinates and noncommutativity of momenta of canonical type is considered. A system of N interacting harmonic oscillators in uniform field and a system of N particles with harmonic oscillator interaction are studied. We analyze effect of noncommutativity on the energy levels of these systems. It is found that influence of coordinates noncommutativity on the energy levels of the systems increases with increasing of the number of particles. The spectrum of N free particles in uniform field in rotationally invariant noncommutative phase space is also analyzed. It is shown that the spectrum corresponds to the spectrum of a system of N harmonic oscillators with frequency determined by the parameter of momentum noncommutativity.

Due to the plethora of possible applicative fallouts, in the recent years several efforts have been made to develop three-dimensional (3-D) field intensity shaping methods. While many approaches able to focus a wave-field into a target point are available, few strategies have been instead developed to generate a field having a given intensity spatial distribution. This is probably due to the higher challenging nature of such a problem. In this letter, with reference to scalar fields, we present an innovative 3-D shaping procedure, which casts the problem as the solution of a finite number of convex programming problems. An example of the performance of the proposed procedure in a 3-D inhomogeneous scenario is given to show the capability of ensuring uniform field intensity within a target area while keeping it arbitrarily bounded elsewhere.

We study the dynamics of dust particles in a stratified glow discharge in inhomogeneous magnetic fields. Dust structures are formed in standing striations, in which traps for dust particles arise. When a magnetic field is applied, these structures begin to rotate. The observations were carried out in striations near the end of the solenoid, where the region of an inhomogeneous magnetic field begins. With an increase in the magnetic field, the dusty structure can be deformed. The rotation of a dusty structure in an inhomogeneous magnetic field has been studied in detail, it has its own peculiarities in comparison with rotation in a uniform field. We have considered the mechanisms of such rotation and estimated its velocity.

Although extensive work has been performed to quantify field aging of asphalt pavements and to evaluate its effect on asphalt mixture properties, little effort has been devoted towards characterizing the non-uniform field aging of asphalt pavements through laboratory testing. Due to the non-uniform air void and temperature distribution in the pavement structure, the surface of the pavement ages faster than the bottom; thus a field aging gradient exists. In this study, field cores obtained from four field projects at various in-service times were tested in the non-destructive Viscoelastic Characterization Direct Tension test to determine their mixture stiffness gradient with pavement depth. In addition, asphalt binders were extracted and recovered from the field cores at different pavement depths and then tested with the Dynamic Shear Rheometer and Fourier Transform Infrared Spectroscopy to differentiate their rheological and chemical properties. Test results obtained in this study provided a better understanding of the non-uniform field aging in asphalt pavements and its effect on asphalt binder and mixture properties.

Insulation integrity of supporting insulator plays a vital role for determining the continuity of service of the gas insulated substation which depends upon the electric field stress distribution on the surface of the spacer. Triple junction formed by the conductor, SF 6 gas and support insulator is another critical area where the field stress is to be maintained at minimum value. Shape control is a technique employed for obtaining uniform field stress along the surface of the spacer but this technique may sometimes leads to very uneven shapes. In this study, a functional graded material is designed for the standard cone type spacer to obtain uniform field stress along the surface of spacer to overcome the above problem. The grading of spacer is done with different permittivities. Electric field is computed for three cases namely grading to high, grading to low and U Shape. The metal inserts were tuned and stress is obtained in account of lower fields at the triple point junction and an improved uniform field distribution along the surface is obtained.

Natural ester oil is one of the alternative materials that can be used to increase the supply of transformer oil. This research discloses the investigation of breakdown voltage of mixed oil virgin coconut oil (VCO) with refined, bleached and deodorized palm kernel oil (RBDPKO) under the effect of different temperature and different gap distance. The test was organized based on the guideline in IEC 60156 standard for AC supply under uniform field (sphere-sphere). The ratio of mixed oils in this experiment are 0% VCO, 20% VCO, 40% VCO, 60% VCO, 80% VCO and 100% VCO. The result indicates that, the ratio of 20% VCO was the highest breakdown voltage for mixed oil at different temperature which was 48.7 kV (40°C) and 57.9 kV (80°C). The increasing of the temperature and the distance gap gave impact on the breakdown strength.

In this paper, an analytical expression has been exploited for computing the discharge inception voltage of polluted insulators under a high voltage AC system. This expression was established for DC high voltage. The present contribution is inspired from the modified Peek’s law used for calculating the inception voltage of a typical streamer discharge. An experimental investigation of the electric arc initiation on laboratory physical model using a photomultiplier has been also reported. It was observed that, the threshold voltage rises with increasing inter-electrodes gap and high voltage electrode radius. It decreases with increasing conductivity.

© 2019 IEEE. Near field phase transformation lattice structure is presented to correct the electric field phase variation above a source antenna. A high gain resonant cavity antenna (RCA) is used as a source, which operates at 12 GHz. The 3D printed phase transformation structure, with two different arrangements of the unit cells, is designed above the RCA at the one-eighth of wavelength. The rectangular arrangement exhibits a more uniform field distribution than that of the circular arrangement. Additionally, in the rectangular arrangement, the gain of the antenna is enhanced by 2.11dB from 21.98 to 24.09 dBi, whereas in the circular arrangement, this value increased by 2.08 dB from 21.98 to 24.06 dBi. For both the cases, the aperture efficiency and bandwidth aperture efficiency product (BAEP) increased from 34.24 to 55.78% and 55.024 to 109.33%2, respectively.

This paper presents a study on the influence of electric field uniformity on the streamer characteristics of a synthetic ester under positive lightning impulse. Streamers were experimentally investigated under both needle-plane (NP) nonuniform field and plane-needle-plane (PNP) semi-uniform field. At the same gap distance, streamers under PNP semi-uniform field showed less branched structure and restrained more in the axial direction compared to those under NP non-uniform field. In this paper, field inhomogeneity factor (field factor) was used to describe the degree of the non-uniformity of various field geometries. It was found that as the field factor decreases indicating more uniform field, the streamer propagation is greatly facilitated. At the same stopping length, streamers under fields with higher degrees of non-uniformity have larger areas, which quantitatively indicate a more branched structure. As a consequence, a transition from propagation-dominated process to initiation-dominated process of streamer development as field factor decreases was well evidenced.

To compare the electroretinal response associated with the uniform-field electroretinogram (UF-ERG) to that of the pattern electroretinogram (PERG) to checkerboard and bar-grating stimuli. UF-ERG and PERG to bars and checkerboard were recorded for 18 visually normal subjects (36 eyes) of mean age 45 years (range 20–75). UF-ERG was recorded to the increment and decrement of a 200-ms duration luminance modulation. Luminance onset and offset UF-ERG responses were averaged to produce a simulation of the PERG response. The mean amplitude and implicit time for the P50 and N95 potentials of actual and simulated PERG responses were recorded for each eye in the cohort. The simulated PERG waveform resulting from arithmetic averaging of the UF-ERG to luminance increment and decrement was characterized by prominent positive and negative components resembling those of the P50 and N95 PERG potentials. Implicit timing of the P50 potential was lengthened in the actual PERG to bars and checks relative to that of the simulation (P

Particle initiated partial discharge (PD) in oil is one of the significant problem associated with transformer. Among particles, conductive particles play very detrimental role. The existence of conducting particles is very difficult to avoid completely during the manufacturing process and also it can be developed during service period of the transformer. These free conductive particles can adhere to paper or pressboard insulation barrier or freely move in the bulk oil. In transformers divergent (non-uniform) fields are often present due to the geometry of the internal parts and may be due to sharp points. Therefore to understand and characterize the effect of conducting particle in oil with pressboard barrier under divergent fields are very critical for the life assessment of transformer. Sphere-plane and needle-plane electrodes are used to generate different non-uniform fields. The discharge measurements are carried out using partial discharge measurement technique according to IEC 60270. Phase resolved partial discharge (PRPD) pattern, discharge characteristics such as average and peak discharge magnitude, number of discharges per cycle, discharge power, rise and duration time of PD pulse due to conducting particle in oil with pressboard barrier under divergent fields are analyzed. The observed PRPD pattern were relatively similar regardless of applied divergent fields. The observed PD inception is much earlier in quasi uniform field compare to non-uniform filed, the PD inception voltage (PDIV) in non-uniform field is three times higher than that occur at quasi-uniform field.

This paper presents a study of the lightning breakdown voltages of Palm Oil (PO) and Coconut Oil (CO) under a non-uniform field with consideration on the polarity effect at various gap distances. All tests were carried based on a needle-sphere electrode configuration and various gap distances ranging from 2 to 25 mm under positive and negative voltage polarities. Three different testing techniques were used in this study including rising-voltage, up-and-down and multiple-voltage methods. The PO used in this study was Refined, Bleached and Deodorised Palm Oil (RBDPO) Olein. Three different samples of RBDPO and one sample of CO were tested. The Weibull distribution was used as a statistical approach to determine the withstand voltages of all samples at 1% and 50% probabilities for each type of oil. Under positive voltage polarity, it was found that the 50% breakdown voltages of RBDPO and CO were comparable with Mineral Oil (MO) whereby the highest percentage of difference among all gap distances was less than 15%. RBDPO and CO have lower 50% breakdown voltages than MO under a negative lightning impulse for which the highest percentage of difference can be up to 40%.

In this paper, experiments on breakdown voltages of helium gas in a uniform field have been carried out at a separation from 0.25 to 3.02 mm. The pressure and temperature respectively vary from 1 to 7 MPa, 25 °C to 180 °C, which is the working condition for the main helium blower and its Active Magnetic Bearings (AMBs) in the High Temperature Reactor-Pebble-bed Module (HTR-PM). COMSOL Multiphysics and a self-programmed FD-FCT (Finite Difference-Flux Corrected Transport) code with a two-dimensional drift–diffusion plasma model have been used to simulate the breakdown process and the results agree well with the experimental data. This kind of theoretical and experimental work provides valuable references for helium insulation design of electric devices in HTR-PM and other helium gas-cooled reactors. It also helps understand the mechanisms in helium discharge at high temperature and pressure which is quite different from its low counterpart.

A new diffraction field expression is proposed for a wedge with different face impedances. The modified theory of physical optics based diffraction coefficient is taken into account. The reflection coefficients are expressed in terms of the split functions that occur in the double integral solution of the resistive half-plane problem. The effects of wedge’s each faces are represented separately. The uniform field expression is obtained and compared with the literature for a right-angled impedance wedge numerically.

non uniform field TTDB stress have been performed on 28nm FDSOI MOSfet devices. After analysis of thermal effects under increasing drain voltage, as well as potential TDDB-HCI interactions, a complete TTDB model, taking into account non uniform field and self-heating is confronted to experimental data.

Quantum analogue of stabilised forced oscillations around an unstable equilibrium position is explored by solving the non-stationary Schrodinger equation (NSE) of the inverted harmonic oscillator (IHO) driven periodically by spatial uniform field of frequency $$\Omega $$ , amplitude $$F_{0}$$ and phase $$\phi $$ , i.e. the system with the Hamiltonian of $$\hat{{H}}=(\hat{{p}}^{2}/2m)-(m\omega ^{2}x^{2}/2)-F_0 x\sin $$ $$\left( {\Omega t+\phi } \right) $$ . The NSE has been solved both analytically and numerically by Maple 15 in dimensionless variables $$\xi = x\sqrt{m\omega /\hbar }\hbox {, }f_0 =F_0 /\omega \sqrt{\hbar m\omega }$$ and $$\tau =\omega t$$ . The initial condition (IC) has been specified by the wave function (w.f.) of a generalised Gaussian type which suits well the corresponding quantum IC operator. The solution obtained demonstrates the non-monotonous behaviour of the coordinate spreading $$\sigma \left( \tau \right) \hbox { =}\sqrt{\big ( {\overline{\Delta \xi ^{2}\big ( \tau \big )} } \big )}$$ which decreases first from quite macroscopic values of $$\sigma _{0} =2^{12,\ldots ,25}$$ to minimal one of $$\sim \!(1/\sqrt{2})$$ at times $$\tau

A half-plane, formed of anomalously reflecting metasurface, is taken into account. The layer is modeled by an impedance half-screen. In order to obtain the diffracted fields, the geometrical optics waves are evaluated as a sum of equivalent soft, hard and impedance surfaces. The diffracted waves are derived by the superposition of the diffracted fields from the equivalent surfaces. The uniform field expressions are obtained by the method of uniform theory of diffraction. The behaviors of the fields are studied numerically.

Helium now commonly serves as the coolant in high temperature gas-cooled reactor (HTGR). Some electrical facilities work in helium gas at certain temperature and pressure, such as the helium blower, magnetic bearings and the electrical penetration assemblies. Because the insulation property of helium is much poorer than that of air, especially at high pressure, the insulation design of these electrical facilities is rather important and challenging. So far, national standards of insulation design is only for the air while there exists almost no industrial standard for helium gas. In addition, not many scientific researches on insulation property of helium have been conducted yet and most efforts were made to deal with liquid helium. In this paper, uniform field breakdown strength in millimeter-scale gaps of helium was studied with a streamer model analysis, at from 15°C to 180°C and 0.01MPa to 7MPa. Coefficients of Paschen law are modified to better fit the experimental data under specific conditions and some analysis or explanation was given. The experimental data and rules obtained will be useful for the design of insulation structure in helium gas and promote the study of HTGR.

Both numerical simulation and experimental investigations revealed that the arsenic concentration in the nano-apex of Si tip can reach a saturated high level (i.e., $\sim6.7$$\times$ 1021 /cm3) through a controllable oxidation process. We take the thermal-induced dopant re-diffusion and self-limitation by the solubility of arsenic in Si into account for the findings. The forming of saturated arsenic concentration at tip-apex could improve the tip-to-tip uniformity of the dopant concentration in an array, and thus enhance the electron emission. Highly reliable gated emitters array (40×40) with typical current density of $\sim254.53$ mA/cm2 (229.08 μ A@118.40 V) was demonstrated using Si-tips with saturated dopant concentration.

G3 is a promising dielectric gas which consists of C4F7N and CO 2 . It shows great potential to replace SF 6 in electric system due to its low GWP and comparable dielectric strength to SF6. 145kV GIS1 and the 420kV GIL using g3 as insulating gas has been put into use in England.

Insulator surface flashover in vacuum due to pulsed and DC voltages has been thoroughly investigated, however the characteristics of surface flashover under multiple, short duration, high-voltage pulses are not well understood. A test stand has been developed at Los Alamos National Lab to further understand the effects of these conditions on the surface flashover strength of various insulators. The test stand is designed to apply voltages of up to −350 kV across a variable spacing, uniform field, electrode gap. Models indicate the electric field varies by less than 2 percent over a 4 cm cylindrical radius at up to 4 cm gap spacing. The electrodes are designed to accommodate insulator test samples ranging in axial length from 1 - 4.5 cm, and up to 8 cm diameter. Measurements of the flashover electric field and current will be made with an E-dot probe and Pearson current transformer respectively. This paper details the design, modeling, and testing plan for this multi-pulse test-bed.

Oil insulation is one of the insulation medium types commonly used in high voltage apparatus. This insulation is to separate between the conductive part and non-conductive part. However, oil insulation can experience decreasing of dielectric strength. It may be caused by the presence of solid particles. Therefore, the testing was conducted to obtain the effect of solid particles to characteristics of partial discharge and breakdown voltage of oil insulation. The results generally proved that the existence of solid particles can reduce the breakdown voltage value of oil insulation. In addition, the solid particles led to two types of corona on oil insulation, namely positive and negative corona.

This paper presents an immunity test method using a correction factor to improve an uniformity of an E-field strength in a reverberation chamber. Based on a method in the IEC 61000-4-21, input powers are varied according to stirrer steps to create a uniform field.

Using the extended ADM-phase space formulation in the canonical framework we analyze the relationship between various gauge choices made in cosmological perturbation theory and the choice of geometrical clocks in the relational formalism. We show that various gauge invariant variables obtained in the conventional analysis of cosmological perturbation theory correspond to Dirac observables tied to a specific choice of geometrical clocks. As examples, we show that the Bardeen potentials and the Mukhanov-Sasaki variable emerge naturally in our analysis as observables when gauge fixing conditions are determined via clocks in the Hamiltonian framework. Similarly other gauge invariant variables for various gauges can be systematically obtained. We demonstrate this by analyzing five common gauge choices: longitudinal, spatially flat, uniform field, synchronous and comoving gauge. For all these, we apply the observable map in the context of the relational formalism and obtain the corresponding Dirac observables associated with these choices of clocks. At the linear order, our analysis generalizes the existing results in canonical cosmological perturbation theory twofold. On the one hand we can include also gauges that can only be analyzed in the context of the extended ADM-phase space and furthermore, we obtain a set of natural gauge invariant variables, namely the Dirac observables, for each considered choice of gauge conditions. Our analysis provides insights on which clocks should be used to extract the relevant natural physical observables both at the classical and quantum level. We also discuss how to generalize our analysis in a straightforward way to higher orders in the perturbation theory to understand gauge conditions and the construction of gauge invariant quantities beyond linear order., Comment: Discussion expanded, references added. To appear in Classical and Quantum Gravity