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Background Treatment options for refractory metastatic colorectal cancer (mCRC) were limited. Anlotinib is a novel multitarget tyrosine kinase inhibitor. ALTER0703 study was conducted to assess efficacy and safety of anlotinib for patients with refractory mCRC. Materials and Methods This was a multicenter, double-blinded, placebo-controlled, randomized phase III trial involving 33 hospitals in China. Patients had taken at least two lines of therapies were 2:1 randomized to receive oral anlotinib (12 mg/day; days 1–14; 21 days per cycle) or placebo, plus best supportive care. Randomization was stratified by previous VEGF-targeting treatments and time from diagnosis to metastases. The primary endpoint was overall survival (OS). The secondary endpoints were progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), quality of life (QoL), and safety. Results A total of 419 patients (anlotinib: 282; placebo: 137) were treated from December 2014 to August 2016. The median PFS was improved in anlotinib group (4.1 months; 95% confidence interval [CI], 3.4–4.5) over placebo group (1.5 months; 95% CI, 1.4–1.5), with a hazard ratio (HR) of 0.34 (95% CI, 0.27–0.43; p < .0001). However, median OS was similar between two groups (8.6 months; 95% CI, 7.8–9.7 vs. 7.2 months; 95% CI, 6.2–8.8; HR, 1.02; p = .870). Improvements of ORR and DCR were observed in anlotinib over placebo. The most common grade ≥ 3 anlotinib related adverse events were hypertension (20.92%), increased γ-GT (7.09%), and hand-foot skin reaction (6.38%). Conclusion Anlotinib was tolerated in Chinese patients with refractory mCRC. Although OS did not reach significant difference, anlotinib still provided clinical benefits by substantially prolonged PFS in these patients. Implications for Practice In this randomized clinical trial that included 419 patients with refractory metastatic colorectal cancer, substantial prolonged in progression-free survival was noted in patients who received anlotinib compared with those given placebo. Improvements on objective response rate and disease control rate was also observed in anlotinib group. However, overall survival was similar between the two groups. In a word, in third-line or above treatment of Chinese patients with refractory metastatic colorectal cancer, anlotinib provided clinical benefit by significantly prolonged progression-free survival.

Laser induced breakdown spectroscopy (LIBS) can be used to analyze hazardous samples and samples in remotely accessible or hazardous environments without handling the sample or exposing the analyst to hazards. Thus, nuclear engineering applications became one of the fast-growing fields of LIBS 1,2 In this paper, we report the development of the LIBS systems in the nuclear power plant applications.

As a control and protection device of photovoltaic power generation system, the DC disconnecting switches are used extensively. The interruption capacity is an important index of DC disconnecting switch. The interruption capacity is effected by dynamic characteristics of arc. Therefore, the dynamic characteristics of arc is analyzed by MHD simulation. The 2-D MHD model of disconnecting switch is built and the motion process of moving contact is considered. The temperature, pressure distribution, arc voltage and arc current curves are obtained by simulation. The results show that the velocity of arc motion is slowly and the utilization rate of the splitter plate is lower. It leads to the arcing time is longer. Therefore, the permanent magnet and gassing material can be added to improve the arc extinguishing ability.

A compact laser probe of the fiber-optic laser-induced breakdown spectroscopy (FO-LIBS) system, based on a single-lens for energy focus and radiation collection, was developed in this paper. Elemental analysis of the Z3CN20-09 M steel sample, which is usually used as the structural material for main pipelines in nuclear power plants, was carried out using this laser probe. Most elements (e.g. Fe, Cr, Ni, Mn, Mo, Co, Cu, Nb, and Si) were successfully detected. The distance between the fiber output end face and the lens, which was one of the most important factors affecting the focused laser spot size and further inducing different degrees of self-absorption, was optimized. It was clear that the spectral intensities increased with the distance before decreasing. The optimal range of the distance was obtained by finding out the maximum spectral intensities and minimum spectral fluctuations. The effects of distances, which can be understood as the effects of spot sizes, were studied using plasma diagnostic methods. When the distance was shorter than the optimal range, the distinct self-absorption was observed, which was analyzed by the fast photography. Calculated changing trend of self-absorption effects was consistent with the observed spectral profiles. When the distance was longer than the optimal range, the plasma temperature and density became lower after ~1 μs. This demonstrates that it is possible for the single-lens laser probe to realize the accurate calibration and control of the focused spot size to achieve the best working conditions for a FO-LIBS system.

Power sources play an important role in the characteristics and the applications of the electrothermal (ET) plasma as an edge localized mode (ELM) heat flux simulator. A repetitive high current ET plasma source with the capability of working at a 10 Hz repetition rate and peak current 7.5 kA is presented in this paper. By controlling the sequence of discharge of ten pulse power modules, a repetitive high heat flux plasma jet can be generated. A two-stage capillary structure is presented, and its repetitive trigger driving circuit based on surface flashover ignition is designed to achieve reliable and repetitive discharge. The topology of the inductive and capacitive (LC) series resonant circuit is applied to the charging system of the pulsed power source. The charging current is limited to 500 A with a charging time of 3.5 ms, and the ratio of the charging voltage to the operating voltage is 1.85. A diode and a power resistor in series are used to suppress the negative overvoltage, which is helpful to increase the thyristors’ operating reliability. Using the designed repetitive ET plasma source, the characteristics of the ET plasma jet are investigated by measuring the voltages and currents and by obtaining images of the discharges. Experimental results show that the repetitive ET plasma generator can be used as an appropriate way to simulate the ELM-like heat flux plasma.

In this paper, the efficiency of a conventional cross-coupled gate CMOS bridge rectifier used in MEMS (microelectromechanical system) piezoelectric energy harvesters is investigated. The MOSFET threshold voltage is varied between 10 mV and 800 mV to evaluate the performance of the circuit for various threshold voltage levels. The circuit is simulated using the 130 nm CMOS technology process for each MOSFET to generate performance metrics for the rectifier. The results are evaluated for optimal load resistance, and it is confirmed that a lower threshold voltage results in significant improvements to the efficiency of the rectifier at lower input voltage amplitudes, with up to 62% at 0.5 V input amplitude when a smoothing capacitor is placed across the load.

Short-time withstanding current is a key parameter of air circuit breakers. Due to the structure of multiple parallel contacts, the outer movable conductors tilt and slide seriously when withstanding the large short-circuit current. This paper is aimed to investigate the contact behavior of the tilted contact. A new designed experimental setup to measure the minimum repulsion current and the contact resistance of the tilted contact is developed. Contact force and tilt angle can also be measured and adjusted. Based on the measured results and the impression marks of the tilted contact, it is concluded that the repulsion force and the contact resistance are increased seriously when the contact is tilted. During the contact tilting process, the contact type is changed from the line contact to the point contact and the contact center is offset to the edge of the movable contact. In addition, with the help of contact bridge model, it is also found that the contact type transition plays a dominant role on the increase of the repulsion force and contact resistance.

Paralleled high-voltage SF6 circuit breakers with a highly coupled split reactor (HCSR) could realize the function of automatic current-sharing and current-limiting. Aiming at investigating the arc characteristics of paralleled SF6 circuit breakers with an HCSR, the single-phase tests for the paralleled high-voltage SF6 circuit breakers with an HCSR were carried out, including the opening and closing–opening operations. The influence of the capacitor paralleled to one of the breaks was studied. A mathematical model was developed for the paralleled high-voltage SF6 circuit breakers with an HCSR by coupling the equivalent circuit equations into the magnetohydrodynamic (MHD) arc model through the embedded codes, laying the foundation for the further research. The variation of the short-circuit currents in the branches during the breaking process was analyzed in detail. The current-sharing and current-limiting effects are quite satisfying. The temperature distribution of both arc chambers was presented. The calculated results were in agreement with the experimental results to some extent.

CO2 attracts a lot of attention of researchers as a possible substitute for SF6. The arc interruption capabilities of SF6-CO2 mixtures for different mixed ratios are investigated in this paper by carrying out tests with a 126 kV puffer gas circuit breaker prototype and calculations. Based on the measured arc voltage and current around current zero, the post-arc current characteristics and the thermal interruption properties are investigated for SF6-CO2 mixtures under different rise rate of the recovery voltage RRRV and di/dt before current zero. It is found that the interruption performance of SF6-CO2 increases greatly with increasing SF6 concentration, and the critical RRRV and di/dt before current zero of SF6-CO2 mixtures for SF6 content of 0, 20 and 50% are about 39, 45 and 70% of that of SF6 respectively, at the short-circuit current of 10 kA. The pressure increment at current zero is found to have a great effect on the interruption of the short-circuit current. In addition, the pressure buildup in CO2 is much lower than that in SF6 for both no-load and loaded operations.

Without zero-crossings, dc series arc faults result in much more serious safety threats. As the dc voltage level rises and the system capacity increases, series arc faults appear in dc systems more frequently. To eliminate their damages, specific arc fault circuit interrupters (AFCI) should be developed. In this paper, two kinds of dc systems are considered in the designed experimental setup. Firstly, a dc simulated source with the ac-dc-dc structure is connected to a resistor. This source could act as a constant voltage or photovoltaic (PV) source by operating in different U-I output modes. Then a real PV array outputting the nonlinear U-I output curve is also conducted as a comparison. Next, a simple detection algorithm is proposed based on the established time-domain detection variable. Finally, this series arc fault detection algorithm is implemented using a digital signal processing (DSP) chip. The performance of this hardware behaves satisfying under various system transitions and multiple arc fault conditions with diverse operation points and current levels.

Short-time withstand current ( $I_{\mathrm{ cw}}$ ) is an important parameter for air circuit breakers (ACBs) and easily causes electrodynamic stability problems. This paper is aimed to investigate the influences of the closing phase angle and frequency on the electrodynamic stability of ACB. Considering the skin effect, the interphase effect, and the nonlinear B–H characteristics of ferromagnet, a calculation model of a three-phase ACB is built based on the 3-D transient finite-element method. It is found that the movable conductors A5, B1, and C1 show the worst electrodynamic stability when the closing phase angle ( $\psi $ ) is equal to $\varphi -\pi $ /2, $\varphi +\pi $ /6, and $\varphi +5\pi $ /6, respectively, where $\varphi $ is the phase angle difference between the voltage and the current. With the frequency increasing from 50 Hz to 100 and 200 Hz, the slope-shaped distribution of peak currents and repulsion forces in phases B and C is changed to the valley-shaped distribution, and the peak current of B1 is increased by 20% and 38.6% at the beginning stage of $I_{\mathrm{ cw}}$ , and by 12.5% and 26.4% at the periodic stage of $I_{\mathrm{ cw}}$ , respectively. In addition, the peak lateral forces of the movable conductors adjacent to other phase are also increased considerably by increasing frequency.

Short-time withstand current ( $I_{\mathrm{ cw}}$ ) is a crucial parameter of air circuit breakers (ACBs) due to the selective protection. Considering the skin effect, the interphase effect, and the nonlinear $ {B}$ – $ {H}$ characteristics of ferromagnet, the 3-D transient finite-element method is adopted to analyze the short-circuit dynamic stability of a three-phase ACB. The transient current, the repulsion torque, the tilting torque, and the sliding torque on each movable conductor are calculated at the beginning stage and the periodic stage of $I_{\mathrm{ cw}}$ , respectively. It is found that the electromagnetic torque tilts and slides the outer movable conductors toward the middle of each phase. The movable conductors of phase B perform the worst in the aspect of dynamic stability. The relevant experiments are also conducted to investigate the dynamic stability through observing the position, the size, and the sliding trace of the erosion marks on contact tips. Based on the proposed calculation model, it is found that installing ferromagnet plates on both the sides of movable conductor groups can enhance the dynamic stability.

The role of inter-pulse delay on plasma dynamics and spectral emission in dual-pulse fiber-delivery plasma has been investigated using fast imaging, optical emission spectroscopy, and laser shadowgraphy. The detection on the return spectrum in dual-pulse fiber-optic laser-induced breakdown spectroscopy showed that the self-reversal and self-absorption were reduced as the inter-pulse delay increased from 50 to 1000 ns. Using scanning electron microscopy, the ablation depth showed a changing trend of increasing first and then decreasing, and a maximum of ∼2.8 μm was achieved at 250-ns inter-pulse delay. Experimental results confirmed that the improvement was due to the reduction of the plasma thickness from 1.161 mm to 0.964 mm, and the calculation of electronic excitation temperature along the photon collection path showed that the excited atom densities became more spread, which both contributed to the self-absorption reduction. At a long inter-pulse delay, the plasma trailing edge would gradually separate from the target surface with a little further expansion distance of the leading edge, resulting in the reduction of plasma thickness after a time delay of several hundred nanoseconds. The heating of the peripheral cold particles by the second-generation plasma in the later expansion led to the rapid reduction of the peak temperature. Also, the early expansion trajectory of the second-generation plasma was tracked by laser shadowgraphy, which started to appear at an inter-pulse delay of 100 ns, and the average expansion velocity reached its maximum of ∼3.8 km/s.

Experiments are performed on the 'Qin-1' double pulse current generator at Xi'an Jiaotong University to study the effect of the prepulse current on the implosion dynamics of two-wire Z-pinches. An independent prepulse current with an adjustable time-delay (Tdelay) is introduced to preheat the wires before the start of the main pulse current. An estimation of the deposited energy and the areal density reconstructed from the interferogram suggest that the wires are partly vaporized with a gasification fraction of ~67%. The prepulse preconditioning has a redistribution effect on the load mass, which determines the subsequent implosion process. The planar implosion of the two-wire load with a preset Tdelay≤450 ns can be divided into the two-layer phase and the merged implosion phase. The snowplow-like implosion is the main characteristic of the shot with a 1050 ns Tdelay. The ablation streams gradually disappear with the increasing Tdelay. The proportion of the mass that participates in implosion increased as the preset Tdelay increases from 120 ns to 1050 ns.

The main factor that slows down the high-frequency response of a resistive voltage divider (RVD) is the distributed stray capacitance (Cg) between the high-voltage-arm (HVA) and the grounded conductors, due to the charging and discharging of Cg through the high resistance RH of the HVA with characteristic time RHCg. Based on a RVD consisted of ceramic tube resistors, a compensation method utilizing the distributed capacitance between a specially shaped inner conductor and the HVA was proposed in this paper, which is more compact than grading rings and can work well with grounded shielding. The method was verified by electromagnetic simulation, which indicated a bandwidth improvement from 3 MHz to more than 1 GHz for the prototype RVD with grounded shielding. Experimental results showed that the 10%–90% rise time for a step input was improved by the compensating electrode from ∼90 ns to 1.25 ns. The main drawback of the method is the possible degradation of insulation when precise compensation is required.

Accurate temperature-rise prediction in gas insulated switchgears (GIS) is necessary to reduce the number of heat-run tests during the product development process. An electromagnetic-thermal-fluid coupled model using computational fluid dynamics (CFD) is developed to predict the temperature-rise of a 110-kV three phase GIS in common tank type. The GIS includes the three-position isolation/ground switch and the circuit breaker insulated with SF 6 gas at 5 bar. In this model, the contact resistance, eddy current, skin effect, thermal flow, and thermal radiation are considered. The ohmic losses generated in the conducting components are calculated through the harmonic electromagnetic analysis with MAXWELL 3D software. Then, the predicted losses are imported to the commercial CFD software ANSYS Fluent to fulfill the thermal simulation. Based on this model, the distributions of heat generation, gas velocity, and temperature-rise are obtained. The results show that the maximum power density and temperature-rise both occur at the contact zones of the three-position isolation/ground switch. To verify the developed model, the temperature-rise tests of the GIS are carried out at 2200 A. The simulation and measurement results are close with a maximum error of 3.99 K.

Laser triggering is interesting for gap switches used in power systems and pulsed power because of its well-controllable delay and jitter time, as well as its electrically uncoupled characteristics. Despite the large attention that was paid to various parameters affect triggering characteristics, the underlying physics of laser triggering remain unclear. In this paper, the nanosecond-laser-triggered pulsed discharge was investigated in atmospheric air. Using a picosecond laser, a high-time-resolution interferometer was constructed and the laser- and discharge-produced plasmas were detected. The shockwaves formed by instantaneous release of the laser and electrical energy into the ambient air were well distinguished. Using the interferograms, phase-shift maps were extracted by a 2-D fast Fourier transform method. Finally, preliminary experiments were performed on laser-triggered discharge from a prototype gap switch, and delay and jitter results were given.

Studies of circuit breakers are of interest to high voltage direct current (HVDC) power system. The method for investigation of the switching arc characteristics of a 500 kV metallic return transfer breaker (MRTB) is presented in this paper, by coupling magneto-hydro-dynamics (MHD) arc model with the resonant circuit equations. 2-D MHD arc model taking account of important physical processes of mass flow, Ohmic heating, radiation energy transfer, momentum exchange, Lorentz force and current flow is developed, and then the influence of stray resistor is analyzed under the interrupting current of DC 4 kA. Calculation results of the distribution of temperature and gas pressure in the nozzle region are presented, where the shock wave and negative voltage-current characteristic of arc are discussed. The calculated arc current and voltage are in agreement with the experimental results to some extent, which could verify the validity of the calculation method partially.

Suppressing of the core-corona structures shows a strong potential as a new breakthrough in the X-ray power production of the wire array Z-pinches. In this letter, the demonstration of suppressing the core-corona structures and its ablation using a novel double pulse current generator "Qin-1" facility is presented. The "Qin-1" facility coupled a ~10 kA 20 ns prepulse generator to a ~ 1 MA 170 ns main current generator. Driven by the prepulse current, the two aluminum wire array were mostly heated to gaseous state rather than the core-corona structures, and the implosion of the aluminum vapors driven by the main current showed no ablation, and no trailing mass. The seeds for the MRT instability formed from the inhomogeneous ablation were suppressed, however, the magneto Rayleigh-Taylor instability during the implosion was still significant and further researches on the generation and development of the magneto Rayleigh-Taylor instabilities of this gasified wire array are needed., 7 pages, 5 figures

Experiments of the preconditioned wire array Z-pinches are carried out on a double-pulse current generator “Qin-1” facility to improve the implosion quality of the wire array Zpinch. Completely vaporization of a tungsten, aluminum, or silver wire array is achieved by preheating the wire array using the prepulse current(10 kA, 50 ns) on “Qin-1” facility, and greatly suppression of the significant asymmetrical structures, including the core-corona structure, the precursor plasma, the Magneto-Rayleigh-Taylor (MRT) instability, and etc., are observed under the main current (∼0.8 MA, 170 ns). This work is based on a newly built double-pulse current generator “Qin-I” facility. The output current of the prepulse current driver to a matched resistive load (5 Ω) has a peak value of 10 kA, a rise time of 30–50 ns, and a pulse width of 50–80 ns. The main current driver is composed by 42 capacitor-switch bricks. Each brick is composed of two 90 nF low inductance capacitors, a multigap gas switch, and electrical buses connections. The output current to a short load is 0.8 MA, 170 ns under a charging voltage of ± 50 kV. Since the prepulse current driver and the main current driver can be triggered individually, the time interval between the prepulse current and the main current is adjustable. Dynamics of the preconditioned wire array are investigated by a twoframe laser interferometry using a 30 ps laser.

An experiment platform is designed and set up recently to study the influences of the experimental parameters on the dynamics of the electrical explosion of wires(EEW) and the characteristics of nanoparticles 1. The platform consists of two 50 kA, 5 μs pulsed current generators, a gas recycling system and a nanoparticle collection system. Each of the generators can be work at the extremal-triggered single-shot mode or the repetitive shot mode with a shot frequency of 1000 times per hour.

The interruption process of the new-type selective miniature circuit breaker (SMCB) is different from the traditional low-voltage circuit breaker (LVCB). According to the operating principle of the SMCB, its interruption process can be divided into three stages; the corresponding mathematical model and calculation method are proposed as well. The calculation of the static characteristic of the magnetic release equipped with the permanent magnet shows that the influence of the current direction on the electromagnetic force cannot be ignored, which lead to the minimum tripping current of the release is equal to -315 and 490 A, respectively, when the armature is close to the permanent magnet. With the simulation and experimental results when the effective value of the prospective short-circuit current is 644 A and 1.5 kA, it indicates that the bigger the closing phase angle is, the quicker the arc ignition between the main contacts and the less arcing time will be. Moreover, the typical interruption parameters of the simulation and experimental results are comparable, and it demonstrates that the proposed method can be used for the optimization design of the SMCB.

Due to the structure of multiple movable contacts in parallel in Air circuit breakers, the outer movable contacts tilt seriously when enduring the large short-circuit current. This paper is aimed to investigate the resistance of the tilted contact. A new designed experimental setup is built. Especially, the tilt angle and the contact force are able to be adjusted. Based on the measured results, it is found that the contact resistance is increased seriously when the movable contact starts tilting. After the contact type changing from the line contact to the point contact and the contact center offsetting to the edge of the movable contact, the contact resistance is increased gently with the tilt angle. At that time, the contact resistance is about 2.8 times of that without tilting, in the case that the contact materials are AgW50 and AgNi30, and the contact force is 105N.

In recent years, increasing fire accidents in the photovoltaic (PV) system by PV series arc fault cause huge economic losses and pose great threats to its operating safety. However, increasing PV voltage and maximum power point track (MPPT) from the inverter during arc ignition make PV series arc fault complex to be detected. This paper aims at providing a joint detection method to arc fault circuit interrupters (AFCI) serving for smart micro grid. In this paper, two methods to bring PV series arc fault into the PV system have been recorded by intensified charge-coupled device (ICCD). By introducing PV series arc fault into the system in due time, normal and fault electric signals have been acquired under different imitated working conditions. Statistic method from time domain and short time Fourier transformation (STFT) from time-frequency domain are chosen to diagnose this kind of fault. A detection variable from each method has been proposed to recognize it accurately. A relatively satisfying joint algorithm based on two proposed detection variables has been put forward to prevent unwanted nuisance trips from system transient process. To fit constantly varying electric signals in PV system, this detection algorithm also adopts dynamic threshold value.

The low threshold microlaser is the fundamental component of integrated optical circuits. The fabrication method of the microcavity determines the dimension and threshold of lasers, while the doping method limits the available gain materials and emitted wavelength. Here we propose a silica nanoparticles self-assembly technique to fabricate a microlaser with a radius of ∼100 um and Q factor of 2000. The aggregation state of gain molecules is investigated to be J-type dimers with high fluorescence to support the laser generation. The laser can emit a ∼600 nm waveband multimode laser with a low threshold of ∼12 μJ. Such a laser is promising as a coherent light source integrated on the photonic microchips and opens up a new orientation in material science.

The dynamics of wire array Z pinches are greatly affected by the initial state of the wires, which can be preconditioned by a prepulse current. Recent advances in experimental research on preconditioned wire array Z pinches at Xi’an Jiaotong University are presented in this paper. Single-wire explosion experiments were carried out to check the state of the preconditioning and to obtain the current parameters needed for wire gasification. Double-wire explosion experiments were conducted to investigate the temporal evolution of the density distribution of the two gasified wires. Based on the results of these experiments, a double-pulse Z-pinch facility, Qin-1, in which a 10 kA prepulse current was coupled with the 0.8 MA main current was designed and constructed. Wire arrays of different wire materials, including silver and tungsten, can be preconditioned by the prepulse current to a gaseous state. Implosion of the two preconditioned aluminum wires exhibited no ablation and little trailing mass.

A 3-D transient finite-element method to analyze the short-time withstand current for an air circuit breaker (ACB) is presented. The cylindrical contact bridge is adopted to describe the current constriction between the movable and fixed contacts, and then considering the influence of the eddy current, the resistivity and thermal conductivity variations with the temperature, and the coupled calculation of the corresponding electromagnetic field and thermal field can be performed to evaluate the short-time withstand current capability. To verify the calculation method and results based on the ACB model, relevant experiments are also conducted through measuring the temperature of two points on the contacts with the thermocouple. It demonstrates that the proposed method can be used to optimize the design of ACBs.

A study was carried out on the characteristics of the dielectric strength of gaseous working medium in a puffer circuit breaker following current interruption. A reduced critical electric field strength (E/N)cr was defined. Its value for SF6 gas within the temperature range of 300 to 3000 K and pressure range of 1 to 32 atm was obtained by solving the Boltzmann equation with most recent atomic data, which allows the determination of the critical electric field strength Ecr at different temperature and pressure. The dielectric behavioral pattern of the breaker was then characterized by applying the Ecr data to the temperature and pressure fields obtained by a 2-D magneto-hydro- dynamics model encompassing all important mechanisms operating in the arcing process. The Ecr distribution at 80 and 110 μs after current zero was then compared to the electric-field distribution to arrive at important information regarding the weakest point or regions in the design. Using a standard rate of rise of recovery voltage profile, the critical dielectric withstand level of the breaker was also predicted.

Due to its low jitter, good repeatability and controllable delay, laser triggered discharge has been used widely in the large-scale pulsed power machines to synchronize the discharge of multiply modules. Recently, for the applications in the field of power system, such as generating the precise currents by synthetic test circuit for the testing of high voltage circuit interrupters, experiments on the laser triggering DC high voltage gap in open air have been carried out.

Laser produced plasmas (LPP) have various applications including laser induced breakdown spectroscopy, superconducting films fabrication, and nanoparticles formation. Although massive efforts have been made, Understanding dynamics of nanosecond laser produced plasma still requires a long-term effort due to the complicated interactions among the laser, the target, the ambient environment, and the plasma. New achievements are obtained due to the improvements of the plasma diagnostics, the developments of numerical codes, and expansions of the application fields.

Suppression of the core-corona structure formed from the electrical exploding wires in vacuum is the key process for the concept of the preconditioned wire-array Z-pinches. The preconditioned Al wire-array load was fulfilled on MAGPIE (1.4 MA, 240 ns) by using a two-stage wire array which can produce a specific prepulse current and a main current to the load. But the effect of precondition depends on the design of the two-stage wire array.

The balance between type 1 and type 2 T helper cells (the Th1-Th2 balance) is closely correlated with cancer, but the correlation in ovarian cancer remains unconfirmed. We investigated the Th1-Th2 balance for the diagnosis, treatment, and prognostic evaluation of ovarian cancer. Fifty healthy subjects and 50 ovarian cancer patients were recruited. The levels of various cytokines were determined in sera and ovarian cancer tissues using a Th1-Th2 human cytokine array. The usefulness of TNFα, IFNγ, TNFα/IL-4, and IFNγ/IL-4 for ovarian cancer diagnosis was assessed based on receiver operating characteristic (ROC) curves. The relationship between the TNFα/IL-4 level and survival time was investigated based on a survival curve. In the ovarian cancer patients, the levels of Th1 factors (IL-2, IFNγ, TNFα, and IL-13) increased significantly in the sera, and IFNγ and TNFα increased significantly in the ovarian cancer tissues. The levels of Th2 factors (IL-5 and IL-6) increased in the sera, but the level of IL-6 decreased significantly in the ovarian cancer tissues. Serum TNFα/IL-4 and IFNγ/IL-4 levels increased significantly in the peripheral blood of the ovarian cancer patients. ROC curve analysis revealed that TNFα, IFNγ, TNFα/IL-4, and IFNγ/IL-4 levels are useful for ovarian cancer diagnosis, with area under the curve values of 0.831, 0.753, 0.846, and 0.803, respectively. The TNFα/IL-4 level in the ovarian cancer patients was positively correlated with survival time, and the Th1-Th2 balance shifted toward Th1 in the ovarian cancer patients. The TNFα/IL-4 ratio might be useful for the diagnosis and prognosis of ovarian cancer.

As one of the key factors, the relationships of expansion volume and arcing characteristics have been treated importantly for the design and optimization of gas circuit breakers. In the paper, a simple 145kV auto-expansion circuit breaker model is adopted. With the method of MHD, arcing process under three different expansion volumes at large current 60Hz interruption is simulated. The contours of gas pressure, gas temperature and gas velocity around current zero are given. The physical quantities at the instants under the different expansion volumes are compared. Furthermore, the characteristics of arc plasma affected by the expansion volumes are discussed and the more suitable size of the volume for the interruption under the current 36kA is obtained.

Linkage transfer phenomenon, which exists in the opening process of the operating mechanism of the molded case circuit breaker MCCB, is introduced. The influence of the linkage transfer position on the behavior of the mechanism is analyzed. According to the analysis result, the linkage transfer position of an actual operating mechanism is improved with virtual prototype technology software ADAMS. Simulation and experiment results show that after improvement, the opening time of the mechanism is shortened by about 1 ms. Short-circuit tests demonstrate that the operating mechanism with its linkage transfer position improved is helpful for enhancing the interruption performance of MCCB while breaking the low-current faults.

The paper is devoted to the experimental study of the arc plasma characteristics in SF6, N2 and CO2. To one flexible model of gas circuit breaker, short circuit experiments have been carried out considering the influence of contact gap (4-12mm), gas pressure (1-5atm), short circuit current (1-5kA effective value) as well as gas species particularly. During the experiments, the arc image, arc current and arc voltage are recorded by the high speed camera, shunt and voltage transducer, respectively. It demonstrates that to the above mentioned three kinds of gases, the arc radius and arc voltage increase with the short circuit current and gas pressure normally; however, under the same experimental conditions, N2 arc holds the minimum arc radius and the maximum arc voltage, and the arc voltage of SF6 arc is the lowest.

A 2-D magnetohydrodynamic (MHD) arc model is developed to simulate the influence of the venting configuration on air arc plasma motion in a low-voltage circuit breaker. It is demonstrated that the fully closed back venting is helpful to accelerate the arc motion due to the propagation of a pressure wave. Side- and central-type front-venting configurations are also compared. It is found that the arc velocity is higher, and yet the probability of reignition is increased for the central-type front venting, as a consequence of differences in the current density distribution. Using an arc chamber with different venting configurations, short-circuit interruption experiments are carried out. These verify the arc reignition trends predicted in the simulations.

Gas flow in arc quenching chamber has an important effect on the interruption capability of low voltage circuit breakers. In this paper, based on a simplified model of arc chamber with a single break, which can be opened by the electro-dynamics repulsion force automatically, the effect of different vent configurations including middle vent and side vent on the interruption performance is investigated. First, the experiments are carried out to compare the different performance in the interruption process between middle vent type and side vent type. In addition, according to the experimental model, a 3-D magneto-hydrodynamic model was developed by adapting and modified the commercial computational fluid dynamics software FLUENT. The simulation results show the same trend in arc motion as explained in the experimental conclusions in theory.

This paper is devoted to study the influence of ferromagnetic material on arc behavior in low voltage electric apparatus. With the self-programmed interface, one 2-D magnetohydrodynamic arc model can be developed based on the commercial software FLUENT and ANSYS, to study the vapor of ferromagnetic material effects on air arc behavior. Then, the corresponding interruption experiments are performed to verify the simulation qualitatively. It demonstrates that the vapor of ferromagnetic material is disadvantageous to arc interruption characteristics. In addition, the influence of the size of the ferromagnetic splitter plate on arc motion is simulated. It shows that the bigger splitter plate may accelerate the arc motion.

This paper is concerned with the investigation of the motion of an air arc plasma in a quenching chamber, in particular with the effect of different chamber widths and outlet areas. A simplified arc chamber of a low-voltage switch device is used for the analysis. Based on a set of governing equations, a 3-D air arc plasma model is constructed and solved by a commercial code. It is found that increasing both the chamber width and the outlet area leads to an increase in the arc speed, but the strength of the dependence varies, depending on the values of the chamber width and the outlet areas. The tail of the arc column becomes shorter as the chamber width is reduced. This is shown due to the reduction in the backward flow by the squeezing of the two flow vortices that occurs.

Short-time withstand current is one of the crucial nominal parameters in air circuit breaker. A numerical method to evaluate the short-time withstand current is proposed. Cylindrical current carrying bridge is introduced to describe the contact spot between movable and fixed contacts. Taking into account the action of ferromagnetic splitter plates, the variation of the conductor properties with temperature and the variation of contact spot radius with the electro-dynamic repulsion force, a transient finite element calculation model is developed by coupling the electromagnetic field and thermal field. The loaded short circuit current is considered as the short-time withstand current once the highest temperature is near to the melting point of the contact material. It demonstrates that the method is useful to evaluate the performance of the air circuit breaker.

The gas-puffer effect has important effects on the interruption capability of a molded case circuit breaker (MCCB). In this paper, on the basis of a simplified model of an arc chamber with a single break, the effect of back-volume of an arc-quenching chamber on arc behavior in an MCCB is investigated. Firstly, using a 2-D optical-fiber arc-motion measurement system, experiments are performed to study the effect of back-volume on the arc-motion and gas pressure in an arc-quenching chamber. We demonstrate that the lower back-volume of the arc-quenching chamber is, the higher the pressure and the better the arc motion will be. Then, corresponding to the above experiments, the gas pressure inside the arc-quenching chamber is calculated using the integral conservation equation. The simulation results are consistent with the experimental results.

To predict the thermal behavior of switchgear quickly, the Thermal Network Finite Difference Analysis method (TNFDA) is adopted in thermal analysis of AC contactor in the paper. The thermal network model is built with nodes, thermal resistors and heat generators, and it is solved using finite difference method (FDM). The main circuit and the control system are connected by thermal resistors network, which solves the problem of multi-sources interaction in the application of TNFDA. The temperature of conducting wires is calculated according to the heat transfer process and the fundamental equations of thermal conduction. It provides a method to solve the problem of boundary conditions in applying the TNFDA. The comparison between the results of TNFDA and measurements shows the feasibility and practicability of the method.

A two-dimensional arc magnetohydrodynamic model is presented to study the effects of metallic vapour and gassing material on air switching arc motion based on different mixture plasma properties (pure air, 99% air–1% Cu, 99% air–1% Ag, 99% air–1% Fe, 90% air–10% PA6). It demonstrates that metallic vapours may cool the arc central region and reduce the arc motion velocity, and iron vapours have the strongest action compared with copper and silver vapours; the gassing material may improve the arc motion velocity. In addition, the effect of the net emission coefficient model and the grey body radiation model on the calculation results for pure air arc motion is compared. To verify the simulation results partially, using the integrated imaging diagnostics system, experiments are carried out to measure the average velocity of arc motion with one model chamber. (Some figures in this article are in colour only in the electronic version)

To the optimization design of molded case circuit breakers (MCCBs), it is important and necessary to simulate the interruption process and analyze the characteristics. A set of differential equations can describe the interactive coupled phenomena of electric circuit, electromagnetic field and mechanism motion system in MCCB. First, with virtual prototyping technology, the simulation model for the operation mechanism of MCCB can be built, and experiments have been carried out to verify its validity. Then, with the existence of electrodynamic repulsion force, the interruption process of the MCCB has been investigated with the influence of arc voltage, closing phase angle, prospective current, mechanism starting motion time and blow open force. It demonstrates the proposed method is effective and is capable of evaluating the new design of MCCB products.

For the optimization design of air circuit breaker (ACB), it is important and necessary to calculate the electro-dynamic repulsion force acting on the movable contact. A method based on 3-D FEM with the equations that describe the relationships among current, magnetic field and repulsion force, which takes the ferromagnet into account, is adopted to calculate the electro-dynamic repulsion force. The method enables one to analyze the factors that affect the electro-dynamic repulsion force, including the number of the movable conductor parallel branches as well as the location of the axis and the shape of the flexible connection. The discussion of the calculation results is also presented in this paper.

A two-dimensional compressible magnetohydrodynamic (MHD) computational model has been developed to study the effect of gassing material on air arc behavior in low voltage circuit breaker. The properties of arc plasma and the electric, magnetic and radiative phenomena have been taken into account in the model. Based on the model, steady state solutions have been performed to study the effect of gassing material on the arc radius and electric field in the arc column. Then, the effect of gassing material on the transient process of arc motion also has been simulated. In addition, using the two-dimensional optical fiber measurement system, experiments have been done to measure the average velocity of arc motion with one model chamber and to verify the simulation model and prediction results. It demonstrates that the action of gassing material may yield the stronger electric field, less arc radius and higher arc motion velocity.