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The microwave window breakdown due to the plasma formation greatly limits the power handling capability of high-power microwave systems. However, the experimentally-observed fast plasma propagation cannot be explained using previous theory or simulation results. In this paper, the photoionization is considered to investigate the mechanism of microwave window breakdown at the air/dielectric interface by particle-in-cell simulation. The results show that photoelectrons produced by high-speed photons can profoundly promote discharge above the air/dielectric interface. Then a fast plasma formation and propagation occurs. The speed of plasma propagation can reach 1 × 106 m s−1, which agrees well with experiments. As a result, the transmitting power is attenuated more seriously than the case without the photoionization. Furthermore, the effects of size of microwave window, gas pressure, strength of microwave electric field and distribution of microwave electric field on the plasma propagation are investigated. The results show that the total number of electrons is nonlinearly increasing with the size of microwave window when a uniform microwave electric field is applied. The speed of the plasma propagation exponentially increases with the strength of microwave electric field. Therefore, the photoionization is an indispensable process in the microwave window breakdown with high-strength microwave electric field. [ABSTRACT FROM AUTHOR]

This paper investigates the external circuit effect in corona discharge by means of numerical simulation, while the effect is usually disregarded in previous plasma simulations. A general numerical solution method of serial external circuit, which can compute surface charges on any shape of electrodes adaptively and solve electrode potential and circuit current simultaneously, is developed to support the investigation, due to lack of theoretical solution in irregular electrode systems. Brief description and validation of the scheme are presented in section 2. In general, the accuracy of numerical solution improves with mesh refinement in orthogonal mesh, due to stair step approximation. Simulations are performed in our self-developed 3D PIC-MCC (particle-in-cell, Monte Carlo collision) code with photoionization and external circuit. The simulation model including recently developed photoionization model is described briefly in section 3. Then the simulation results in a needle-plate electrode in air, such as spatiotemporal evolution of corona discharge and waveforms of electrode voltage and circuit current, are presented. Physical mechanisms of formation of branched corona discharge and self-consistent adjustment of electrode voltage and circuit current are discussed. The waveforms of voltage and current in this simulation are generally consistent with experimental result. The external circuit has negative feedback effect on the discharge, and can adjusts electrode voltage self-consistently. The application of external circuit improves the applicability of particle simulation method to the simulation of discharge phenomenon in actual devices. [ABSTRACT FROM AUTHOR]

To suppress microwave window breakdown, an external parallel dc bias electric field is applied to sweep out the electrons from the discharge zone. The development of microwave window breakdown under an external dc electric field is investigated using particle-in-cell and Monte Carlo collision simulation. The results show that the number of multipactor electrons decreases with the strength of the external unidirectional dc electric field when the size of the microwave window is finite. In addition, the threshold of breakdown is strongly influenced by the direction of the external bidirectional dc electric field. When the electric field is directed from the center to the edge of the microwave window, breakdown occurs more readily than in the absence of the electric field. However, when the electric field is directed toward the center of the microwave window, the discharge process starts at the edge of the window and develops to the center of the window. This is because a smaller density of electrons at the window edge results in a smaller gas pressure and the low gas pressure above the dielectric surface thus makes formation of the plasma more difficult. As a result, the early stage of breakdown is suppressed and the maximum transmitting power is enhanced. [ABSTRACT FROM AUTHOR]

The interaction of an electromagnetic wave with a relativistic ionization front with frequency up-conversion has been demonstrated by the particle-in-cell (PIC) method. In the PIC simulation, the plasma ionization front is formed by using an electron beam ionizing the background gas. The PIC results are in good agreement with the basic analytic theory. In addition, the charged particles are modulated in the interaction area observed in the PIC simulation, which is hardly obtained by other methods. Based on the verified PIC methods, a relativistic hollow ionization front for frequency up-conversion of microwave to terahertz radiation is proposed for increasing the reflection cross section. Finally, the reflected energy can be increased by at least 3 orders of magnitude compared to the traditional methods. [ABSTRACT FROM AUTHOR]

Self-organization of periodic, streamer-like ionization waves in planar microplasma devices having a dielectric barrier discharge structure is observed. In contrast to plasma propagation in arrays of microchannels or microcavities, the ionization waves originate from a single point but rapidly sub-divide into as many as 10 'branch' plasma wave packets that eventually recombine. In less than 70 ns, the self-organization of the spatially-periodic array of co-propagating branches is complete and two successive sets of waves, separated in distance and time by ∼1.8 mm and ∼50 ns, respectively, are generated. The mean propagation velocity of each plasma packet is greater than 70 km s−1 but values as large as 150 km s−1 have been measured. Because the propagation path for all subsequent streamers is established by the first set of plasma packets, the intensity of the second set is noticeably enhanced. The average length of the primary branches is ∼1.5 mm but reaches a maximum of ∼4.5 mm as the wave packets travel an overall distance of 1 cm. These phenomena are interpreted in terms of photoelectron emission from the floor and walls of the shallow dielectric microcavity, induced by radiation from the advancing packets, and the rapid collapse of the sheath of each microplasma owing to the accumulation of charge on the underlying dielectric. The spatial profiles of the propagating plasmas suggest that generating and probing plasma solitons may now be feasible. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a focused detection system for X-ray pulsar-based Navigation (XNAV) is designed based on Silicon Drift Detector (SDD). The detector electronics mainly adopts the digital trapezoidal shaping method to measure the Times-Of-Arrival (TOAs) and energy of photons. The time measurement accuracy is better than 500ns. The energy resolution is 191eV at 8.05keV, and the maximum count rate is 500kcps between 1 and 12keV. In the semi-physical simulation experiment, the filtering of noise photons by energy discrimination significantly improves the correlation degree between the cumulative pulse profile and the standard profile. [ABSTRACT FROM AUTHOR]

Bone cancer pain (BCP) causes troubles and burdens to patients globally. Increasing evidence proved that neuromedin U receptor 2 (NMUR2) was involved in pains. Our study was performed to investigate the role of NMUR2 on BCP and the underlying mechanism. The rats were raised and BCP rat model was established by injection with Walker 256 cells. The RNA and protein expression levels of NMUR2 in rat neurons-dorsal spinal cord cells, RNdsc cells were detected by qRT-PCR and western blot. The administration with NMUR2 was via intrathecal injection with siRNA to silence NMUR2. The tolerance of rat to pain was measured by mechanical allodynia test and presented by paw withdrawal threshold (PWT) value. The effects on protein kinase C (PKC)/extracellular regulated protein kinases (ERK) and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signal pathways were examined by western blot. The expression of NMUR2 in both mRNA and protein levels was upregulated in BCP rat model. In addition, siRNA injection significantly decreased the expression of NMUR2 on the 3rd, 7th and 14th day. BCP group revealed lower PWT value compared with control while NMUR2 silence increased the PWT value compared with negative control. The phosphorylation of PKC, ERK, PI3K and AKT was increased in BCP model while was decreased by si-NMUR2. PKC/ERK and PI3K/AKT inhibitor administration increased the PWT value compared with BCP group. si-NMUR2 alleviates BCP via inactivation of PKC/ERK and PI3K/AKT signal pathways. • NMUR2 is upregulated in BCP rat model. • si-NMUR2 alleviates nociception in BCP rat model. • si-NMUR2 relieves nociception by inactivating PKC/ERK and PI3K/AKT pathways. [ABSTRACT FROM AUTHOR]

Passive intermodulation (PIM) interference that occurs in communication systems could limit the communication capacity and increase the manufacturing and maintenance costs. In this letter, a composite exponential model is developed to characterize the weak nonlinearity of passive components that causes PIM generation accurately. This proposed model fully considers the correlation between the PIM products on each order and the relation of PIM products with variation of carrier powers. For verification, a microwave filter is given to demonstrate the effectiveness of this composite model, and the reliability of this model is proved by the sensitivity analysis due to measurement uncertainty. Besides, the good agreement between the calculated powers of PIM products and the measured data shows that it can provide a theoretical guidance for PIM performance assessment in engineering application, thereby evaluating the influence of PIM interference on communication quality effectively. [ABSTRACT FROM AUTHOR]

A micro-channel plate detector with wedge and strip anode can be used for visible and ultraviolet light imaging. In this paper, the imager electronics are designed in order to process specific output charge characteristics. The original signal output from the detector is shaped into a Gaussian pulse signal, and a digital Constant Fraction Discriminator is used to judge the arrival time of the pulse. The resolution of the electronic output image is 1024 × 1024, and the position decoding accuracy is 1 pixel. The experimental imaging resolving power of the detector is as high as 70 µm. [ABSTRACT FROM AUTHOR]

Plasma pattern transition in a symmetric hybrid structure cavity device at micrometer scale is researched through microplasma interaction in intervening microchannel between adjacent cavities while manipulating electric field strength. Plasma distribution reconfiguration in central (objective) cavity is observed when sidearm (donor) cavities are ignited. As long as coupling effect occurred by modulating the electric field strength in the sidearm cavities, stable plasma pattern transition in objective cavity is obtained, exhibiting plasma pattern split from one circular spot (initial pattern) to two small circular spots (transited pattern), along with plasma peak emission intensity displacement over 100 μm to its equilibrium position. The shape of transited plasma patterns are depending on the coupling effect from sidearm cavities. The two circular spots unsymmetrically distributed if either donor cavity is ignited, and the ratio of average emission intensity between the two plasma spots is over 30%, however, which is less than 4% if coupling symmetrically occurred. The electrical and optical properties of central microplasma are also modulated, that the breakthrough voltage is decreased by 22% and emission intensity is improved by ∼30%, by means of plasma coupling. The microplasma pattern formation at micrometre scale and manipulation of the electrical properties in microscale cavity implies significant value in the application of plasma transistor and signal processing. [ABSTRACT FROM AUTHOR]

In this paper, emphasis is put on passive intermodulation (PIM) caused by multipaction. The results are calculated by particle-in-cell simulation under the conditions of 2-tone and 4-tone carriers. A temporal evolution of the number of particles with different carrier powers is presented. The input and output signals in the time domain and the power spectrum densities of these signals in the frequency domain under different conditions are compared. The relationship between multipaction and PIM interference is discussed. It shows that the appearance of the PIM phenomenon follows the occurrence of saturation of multipactor discharge and the powers of PIM products basically increase as the carrier powers grow. In addition, to suppress the occurrence of PIM interference, an external magnetic field is added in the direction perpendicular to the electric field, which is a practical way to inhibit multipaction, and the effectiveness and the reliability of this method are also verified by simulation. [ABSTRACT FROM AUTHOR]

With the introduction of an external circuit model and a gas desorption model, the surface flashover on the plane insulator-vacuum interface perpendicular to parallel electrodes is simulated by a Particle-In-Cell method. It can be seen from simulations that when the secondary electron emission avalanche (SEEA) occurs, the current sharply increases because of the influence of the insulator surface charge on the cathode field emission. With the introduction of the gas desorption model, the current keeps on increasing after SEEA, and then the feedback of the external circuit causes the voltage between the two electrodes to decrease. The cathode emission current decreases, while the anode current keeps growing. With the definition that flashover occurs when the diode voltage drops by more than 20%, we obtained the simulated flashover voltage which agrees with the experimental value with the use of the field enhancement factor β = 145 and the gas molecule desorption coefficient γ = 0.25. From the simulation results, we can also see that the time delay of flashover decreases exponentially with voltage. In addition, from the gas desorption model, the gas density on the insulator surface is found to be proportional to the square of the gas desorption rate and linear with time. [ABSTRACT FROM AUTHOR]

The excitation dynamics and self-oriented plasma coupling of a micro-structure plasma device with a rectangular cross-section are investigated. The device consists of 7 × 7 microcavity arrays, which are blended into a unity by a 50 μm-thick bulk area above them. The device is operated in argon with a pressure of 200 Torr, driven by a bipolar pulse waveform of 20 kHz. The discharge evolution is characterized by means of electrical measurements and optical emission profiles. It has been found that different emission patterns are observed within microcavities. The formation of these patterns induced by the combined action between the applied electric field and surface deactivation is discussed. The microplasma distribution in some specific regions along the diagonal direction of cavities in the bulk area is observed, and self-oriented microplasma coupling is explored, while the plasma interaction occurred between cross adjacent cavities, contributed by the ionization wave propagation. The velocity of ionization wave propagation is measured to be 1.2 km/s to 3.5 km/s. The exploration of this plasma interaction in the bulk area is of value to applications in electromagnetics and signal processing. [ABSTRACT FROM AUTHOR]

Aberrant DNA methylation is a recognized feature in various types of human cancer, and folate has a vital role in the epigenetics of mammalian cells by supplying methyl groups for DNA methylation reactions. Fragile histidine triad (FHIT) is a tumor suppressor gene that is frequently silenced in cervical cancer (CC) and preneoplastic lesions. Promoter hypermethylation was previously observed in CC, and its epigenetic silencing has been observed at mRNA or protein levels. Changes in folate intake to modulate DNA methylation may be a mechanistic link to cancer, but this remains to be elucidated. The aim of the present study was to evaluate the influences of folate on FHIT gene methylation and expression in the progression of cervical cancerization. In the present study, red blood cell (RBC) folate levels, FHIT gene methylation status, and mRNA and protein expression levels were detected in 254 women, including normal cervix (NC, n=80), cervical intraepithelial neoplasm grade 1 (CIN1, n=55; CIN2/3, n=55) and cervical squamous cell carcinoma (SCC, n=64) samples. The methylation status of FHIT gene and its mRNA and protein expression levels were measured in CaSki (HPV16 positive) and C33A (HPV16 negative) CC cells treated with different concentrations of folate. The results indicated that FHIT gene methylation rate increased with the severity of cervix lesions, however, RBC folate levels, FHIT mRNA and protein expression levels were reduced. The proliferation inhibition rate, apoptosis rate, and FHIT protein and mRNA expression levels increased along with rising concentrations of folate, whereas the degree of FHIT gene methylation gradually weakened in CaSki or C33A cell lines. The present findings indicated that folate deficiency, FHIT gene promoter hypermethylation and reduced expression were significantly associated with cervical carcinogenesis. The results indicated that folate was able to enhance apoptosis and inhibit the cervical cell proliferation while regulating FHIT gene methylation and expression. Adequate intake of folate to maintain normal DNA methylation status is an effective way for cervical lesions prevention, and demethylation treatment may offer a new strategy for therapy of CC. [ABSTRACT FROM AUTHOR]

Many radio frequency measurement systems require multicarrier signals with coherent phases between carriers with different frequencies. A typical example is the signal generator which is used in multicarrier multipactor (MM) testing systems. In this paper, we propose a new approach for the generation of coherent multicarrier signals based on a state-of-the-art phase-locked loops technique. Different from existing systems that rely on a heavy use of commercial microwave instruments, this generator can be implemented with on-shelf chips and devices. As an example, an ultrahigh frequency band generator is implemented and how to implement the in-system calibration of this generator in an experimental multipactor testing system is demonstrated. Based on the proposed approach, performing a quantitative experimental research on MM becomes affordable for an ordinary microwave laboratory, which may promote the in-depth experimental study in this area. It can also be used in a wide range of applications such as MIMO and phased array systems. [ABSTRACT FROM AUTHOR]

The newly discovered “long-term” multicarrier multipactors that can be induced by low-energy electric fields potentially threatens the reliability of spaceborne microwave systems. It also causes a new technical challenge to the prediction of the global occurrence threshold of multicarrier multipactors. In this paper, we propose efficient approaches to rapidly compute the fluctuation of space electrons in the evolving process of a multicarrier multipactor, based on which Monte Carlo approaches are developed to efficiently find the global “worst case” waveforms and the occurrence thresholds for both “single-event” and “long-term” multipactors. The proposed approaches can be used for wideband devices, providing an efficient integrated solution for the multicarrier multipactor analysis for practical high-power microwave devices with inhomogeneous field distribution. [ABSTRACT FROM PUBLISHER]

Microchannel plates (MCPs) are widely used as electron, ion, and X-ray detectors. The gain factor and time resolution of the MCP are strongly dependent on its operating and geometry parameters (applied voltage, length-to-diameter ratio, bias angle, and electrode penetration depth). Measurements about this dependence are sparse and do not cover the full range of the parameters. In this paper, 3-D single channel models are developed in computer simulation technology studio suit to systematically and comprehensively calculate the MCP gain and time resolution for various operating and geometry parameters. Furman secondaries electron emission model is employed in our simulation. Simulated result of the gain versus bias voltage is validated by the available experimental data. Finally, geometry parameters of L = 373.6~\mu \textm , D =10~\mu \textm , $h_{{{\text {in}}}}=h_{{{\text {out}}}}= 5~\mu \text{m}$ , and \theta =12^{\circ } are proposed to optimize the MCP performances. Simulation results show that the gain, mean transit time, and transit time spread of the optimized MCP are expected to reach 128 012, 128 ps and 19 ps at the applied voltage of 1000 V. [ABSTRACT FROM AUTHOR]

To obtain a high spatial resolution of a image intensifier based on microchannel plate (MCP), the long tail in the exit energy distribution of the output electrons (EDOE) is undesirable. The existing solution is increasing the penetration depth of the MCP output electrode, which will result in a serious gain reduction. Coating the MCP output electrode with efficient secondary electron yield (SEY) materials is supposed to be an effective approach to suppress the unfavorable tail component in the EDOE without negative effects on the gain. In our work, a three-dimensional MCP single channel model is developed in CST STUDIO SUITE to systematically investigate the dependences of the EDOE and the gain on the SEY property of the coated material, based on the Finite Integral Technique and Monte Carlo method. The results show that besides the high SEY of the coated material, the low incident energy corresponding to the peak SEY is another essential element affecting the electron yield in the final stage of multiplication and suppressing the output energy spread. [ABSTRACT FROM AUTHOR]

Owning to the serious loss of photoelectrons striking at the input electrode of traditional microchannel plate (MCP), photoelectron collection efficiency (CE) of photomultiplier tubes based on MCP (MCP-PMTs) fluctuates around the MCP open area fraction and cannot make a breakthrough. Depositing a thin film of high secondary electron yield material on the MCP is proposed as an effective approach to improve the CE. The available simulation and experimental data to validate it, however, is sparse. In our work, a three-dimensional small area MCP model is developed in CST Studio Suite to evaluate the collection efficiencies of PMTs based on the traditional MCP and the coated one, respectively. Results predict that CE of the PMT based on the coated MCP has a significant increase and a better uniformity, which is expected to reach 100%. [ABSTRACT FROM AUTHOR]

In this paper, the light images of addressing discharge by plasma in subpixel cells of plasma display panel are presented. The evolution of plasma discharge was recorded using an intensified charge-coupled device digital camera with nanosecond exposure time. The discharge images using a new ramp setup waveform show an improvement of addressing discharge speed. [ABSTRACT FROM AUTHOR]

Nanosecond pulsed plasma has an enormous potential in many applications. In this paper, the characteristics of barrier free nanosecond pulsed surface discharge are investigated by the use of an actuator with a strip-strip film electrode configuration, including the effect of electrode width and the gap distance on the plasma morphology and electrical characteristics at atmospheric pressure. It was found that it is relative easier to generate a quasi uniform discharge with a thinner electrode width and a smaller gap distance. The underlying physical mechanism was also discussed. Besides that, the influence of airflow on repetitive pulsed surface discharge was examined. By comparing to the discharge produced by two different pulse waveforms in airflows, we found that the discharge driven by a faster pulse behaves more stable. Finally, a model was developed to analyze the interaction of the airflow and the discharge channels. [ABSTRACT FROM AUTHOR]

The particle-in-cell (PIC) simulation of an A6 magnetron with diffraction output (MDO) in our earlier work shows the peak output power (especially the short power pulse with several nanoseconds duration) is lowered when electrons with high energy strike the anode block, which leads to the emission of secondary and backscattered electrons. In addition, the PIC simulation for a 12-cavity MDO also shows when secondary electron emission occurs, the boundary for neighboring modes becomes more complicated than before. Replacing tapered cavities by single-stepped cavities in a relativistic MDO increases the interaction space where the charged particles interact with the induced RF waves. The electronic efficiency of the A6 relativistic MDO as well as the 12-cavity MDO with single-stepped cavities driven by the transparent cathode can be over 70% with gigawatts output power level. And with single-stepped cavities, the distance between the cathode and the wall of relativistic MDO is increased such that the possibility for electrons with high energy striking on the wall is decreased, which results in less emission of secondary and backscattered electrons under the same applied voltage. The PIC simulation demonstrated that in the 12-cavity MDO with single-stepped cavities driven by the transparent cathode with 400-kV applied voltage, the electrons with above 500 eV from cathode under the crossed electromagnetic field can strike on the anode block of MDO, resulting in a secondary and backscattered electron current that can cause different modes to be prevalent or stop the designed mechanism from working. Especially when applied with short voltage pulse with 10-ns duration, the output power pulse is shorted with peak power lowered. The simulation results presented in this paper possibly provide references for multicavity resonator when considering mode selection or mode switching experiments. [ABSTRACT FROM PUBLISHER]

This paper deals with the theory of plasma development in the nanosecond high-power microwave breakdown at the dielectric/air interface. Utilizing the Poisson and Boltzmann equations, the basic physics are explored and investigated. Corresponding to the incident electric field, electrons moving back and forth bring about the negative charge accumulation at the interface. This process generates an extra electric field, strengthening the total amplitude. Simultaneously, deviations of electrons and ions lead to a sheath region providing a space charge field. Secondary electrons are strongly accelerated in the sheath region, eventually leading to an ionization avalanche in a very short time. Both the densities and energies of particles reach the maximums near the sheath region, and that is why the illumination is most significant near the interface. The theory is in good accordance with an experiment conducted under the same conditions. [ABSTRACT FROM PUBLISHER]

We report the performance of an A6 relativistic magnetron with single-stepped cavities output. Particle-in-cell simulation shows the electronic efficiency of an A6 relativistic magnetron with an anode block made of six single-stepped cavities can be up to 78% with an output power of one gigawatt for an applied voltage of 400 kV. When the A6 relativistic magnetron with axial extraction using six single-stepped cavities is applied with a voltage of \(V \sim 400~{\rm kV}\pm 50\) kV the electronic efficiency can be as high as 60%, while the output power can be as high as 1 GW. And, when a 10-ns voltage pulse of 400 kV is applied on this magnetrons with diffraction output using single-stepped cavities, the output power pulse can be as high 1.2 GW. The results in this paper will provide a reference for choosing a cavity that is easily manufactured, so that a physical experiment is more feasible. [ABSTRACT FROM PUBLISHER]

Parasitic nematodes are responsible for devastating illnesses that plague many of the world's poorest populations indigenous to the tropical areas of developing nations. Among these diseases is lymphatic filariasis, a major cause of permanent and long-term disability. Proteins essential to nematodes that do not have mammalian counterparts represent targets for therapeutic inhibitor discovery. One promising target is trehalose-6-phosphate phosphatase (T6PP) from Brugia malayi. In the model nematode Caenorhabditis elegans, T6PP is essential for survival due to the toxic effect(s) of the accumulation of trehalose 6-phosphate. T6PP has also been shown to be essential in Mycobacterium tuberculosis. We determined the X-ray crystal structure of T6PP from B. malayi. The protein structure revealed a stabilizing N-terminal MIT-like domain and a catalytic C-terminal C2B-type HAD phosphatase fold. Structure-guided mutagenesis, combined with kinetic analyses using a designed competitive inhibitor, trehalose 6-sulfate, identified five residues important for binding and catalysis. This structure-function analysis along with computational mapping provided the basis for the proposed model of the T6PP-trehalose 6-phosphate complex. The model indicates a substrate-binding mode wherein shape complementarity and van der Waals interactions drive recognition. The mode of binding is in sharp contrast to the homolog sucrose-6-phosphate phosphatase where extensive hydrogen-bond interactions are made to the substrate. Together these results suggest that high-affinity inhibitors will be bi-dentate, taking advantage of substrate-like binding to the phosphoryl-binding pocket while simultaneously utilizing non-native binding to the trehalose pocket. The conservation of the key residues that enforce the shape of the substrate pocket in T6PP enzymes suggest that development of broad-range anthelmintic and antibacterial therapeutics employing this platform may be possible. [ABSTRACT FROM AUTHOR]

The corona discharge process in a point-plane structure has been simulated using the 3-D particle-in-cell code VORPAL. The motivation behind these simulations was to understand how the corona needle worked in the gas switch, and to look for the methods to improve the stability of the gas switch by achieving a steady corona discharge. The influences of three parameters on ionization region were investigated, the needle size, the gas pressure, and the voltage applied across the electrodes. The needle size varied from 0.05 to 0.25 mm, the air pressure varied from 1.0 to 3.0 atm and the applied voltage varied from 1.2 to 2.3 kV. The voltage polarity was also changed. From the simulations, we obtained the electric field distribution, the distribution of the ionization region, and the current–voltage characteristic. All these parameters have an effect on the corona. Different voltage polarity would result in a different corona shape. Unlike the voltage polarity, the needle size, the air pressure, and the applied voltage have no effect on the shape of the corona. However, with an increase in needle size, or applied voltage, the corona size will also increase, while the corona size will decrease when the air pressure increases. The degree of influence is different; that of the applied voltage is the highest followed by the needle size, while that of the air pressure is the lowest. [ABSTRACT FROM AUTHOR]

A fundamental T-branch in one-dimensional photonic crystal waveguides based on the omnidirectional reflection is constructed. Numerical simulations of this T-branch indicate that without any structural optimization, four high reflectance peaks and three high transmittance peaks appear alternately within a wide enough frequency band. The T-branch with the unique transmission characteristics can be used as a wavelength splitter. Combining the fundamental T-branch with flexible bends of one-dimensional photonic crystal waveguides, we construct simple and compact wavelength splitters with arbitrary branching angles. Those wavelength splitters are expected to be applied to high density photonic integrated circuits. [ABSTRACT FROM PUBLISHER]

Abstract: Mg–Zr–O protective films for plasma display panels (PDPs) were deposited on soda-lime glass substrates by magnetron sputtering method. The effects of Zr doping on both the discharge properties (firing voltage, V f and the minimum sustaining voltage, V s) and the microstructure of the Mg–Zr–O films were investigated. The results show that the deposited Mg–Zr–O films retain the NaCl-type structure as the pure MgO crystal. The doped Zr exists in the form of Zr4+ substitution solution in MgO crystal and an appropriate amount of Zr can improve the surface characteristics of the Mg–Zr–O films effectively. When the Zr atomic concentration is about 2%, the Mg–Zr–O films have the strongest (200) preferred orientation and the minimum surface roughness. The firing voltage and the minimum sustaining voltage of Mg–Zr–O protective layer are reduced at most by about 25V and 15V, respectively, compared with those of the pure MgO film. Mg–Zr–O protective layers with an appropriate amount of Zr are promising to meet the demands of advanced high-vision PDPs. [Copyright &y& Elsevier]

Abstract: The striation phenomenon in large-gap coplanar plasma display panel (PDP) has been investigated experimentally in macroscopic cells. The results show that the striations can generate either above anode accompanying the development of discharge or in the weak-field plasma channel near the dielectric surface after the discharge having developed. The surface state of the dielectric layer and the pre-accumulated wall charge play non-important role on the generation of striation. It is supposed that the physical process in the gas volume govern the formation of striation in PDP cells. [Copyright &y& Elsevier]

Influences of wall-charge accumulation on gas dielectric barrier discharge (DBD) breakdown threshold and sustaining voltage margin of alternating current plasma display panel (AC-PDP) were investigated. It is observed that wall-charge accumulation results in a remarkable increase of gas DBD breakdown threshold during sustaining discharge period. Sustaining voltage margin is reduced by the threshold increase. A larger margin can be obtained when the threshold is decreased by removing unfavorable influence of wall-charge accumulation. Compared with normal margin, improved margin has a larger value and a faster linear increase with increasing wall-charge voltage. That indicates a way to improve AC-PDP performances remarkably. [ABSTRACT FROM AUTHOR]

In this paper, we provided a Gaussian fitting method for fast periodic search to improve the accuracy of chi-square method. And this method can be used for the pulse periodic search of X-ray Pulsar. Firstly, we built the fast search model based on the epoch folding procedure by employing the basic principle of the chi-square evaluation. Secondly, we simulated the distribution of chi-square value by applying the pulsar profile to the fast search model, and it is fitting well with the Gaussian function. Finally, the designed experiments indicated that applying Gaussian fitting to chi - square method can significantly improve period search accuracy. [ABSTRACT FROM AUTHOR]

To improve the performance of amorphous InGaZnOx (a-IGZO) thin film transistors (TFTs), in this thesis, Cs+ ions adsorbed IGZO (Cs-IGZO) films were prepared through a solution immersion method at low temperature. Under the modification of surface structure and oxygen vacancies concentrations of a-IGZO film, with the effective introduction of Cs+ ions into the surface of a-IGZO films, the transfer properties and stability of a-IGZO TFTs are greatly improved. Different parameters of Cs+ ion concentrations were investigated in our work. When the Cs+ ions concentration reached 2% mol/L, the optimized performance Cs-IGZO TFT was obtained, showing the carrier mobility of 18.7 cm2 V−1 s−1, the OFF current of 0.8 × 10−10 A, and the threshold voltage of 0.2 V, accompanied by the threshold voltage shifts of 1.3 V under positive bias stress for 5000 s. [ABSTRACT FROM AUTHOR]

Statistical multipactor theories are critical prediction approaches for multipactor breakdown determination. However, these approaches still require a negotiation between the calculation efficiency and accuracy. This paper presents an improved stationary statistical theory for efficient threshold analysis of two-surface multipactor. A general integral equation over the distribution function of the electron emission phase with both the single-sided and double-sided impacts considered is formulated. The modeling results indicate that the improved stationary statistical theory can not only obtain equally good accuracy of multipactor threshold calculation as the nonstationary statistical theory, but also achieve high calculation efficiency concurrently. By using this improved stationary statistical theory, the total time consumption in calculating full multipactor susceptibility zones of parallel plates can be decreased by as much as a factor of four relative to the nonstationary statistical theory. It also shows that the effect of single-sided impacts is indispensable for accurate multipactor prediction of coaxial lines and also more significant for the high order multipactor. Finally, the influence of secondary emission yield (SEY) properties on the multipactor threshold is further investigated. It is observed that the first cross energy and the energy range between the first cross and the SEY maximum both play a significant role in determining the multipactor threshold, which agrees with the numerical simulation results in the literature. [ABSTRACT FROM AUTHOR]

Photoionization plays an important role in the mechanism of positive streamer discharges in air. The photoelectron production rate at high pressures is significantly overestimated in the widely used quantitative photoionization model in nitrogen-oxygen mixtures. A new photoionization model is proposed to surmount this disadvantage approximately by tracking the generation and deactivation of high excited states of N2. Implementation, validation, and discussion of the new photoionization model are presented in this paper. The photoionization coefficient, the fraction of nitrogen ionization events that leads to oxygen photoionization events without quenching, is computed in the new model. It decreases with the increasing pressure when E/p is constant, which agrees with the early experimental results and corrects the overestimation of the photoionization coefficients at high pressures to some extent. Simulations of positive streamers show that the generation and deactivation of high excited states of N2 weaken the discharge of nitrogen and enhance the nonlocal discharge of oxygen with a time delay in the new model. The time delay slows down the positive streamer discharges in our simulations. [ABSTRACT FROM AUTHOR]

By introducing a compensated Monte Carlo collision (MCC) model into the particle-in-cell/MCC method, the streamer initiation process in a laser-triggered gas switch is simulated with a large time step. The spatial distributions of electron density at various pressures and voltages are obtained. [ABSTRACT FROM AUTHOR]

A positive streamer in a strong electric field in air at 1-atm pressure is investigated with particle-in-cell/Monte Carlo collision method including a photoionization model. The simulation results of streamer discharge in parallel plate air gap with and without the photoionization model are compared. It is shown that the seed electrons produced by photoionization generate secondary avalanches which lead to the formation of the streamer. No streamer is observed without photoionization model. [ABSTRACT FROM AUTHOR]