다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquid- mixture, and for material processing.

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Industrial Applications of Pulsed Power Technology

This paper investigates the pitting corrosion behaviors in simulated body fluid of AISI 316L stainless steel treated by high current pulsed electron beam The treatment induces crater eruptions that preferentially occur at MnS inclusions and produces a surface purification effect The mixing in the melting process and the subsequent solute trapping effect during fast solidification process result in the homogenization of elements in the melted layer Both crater eruption and composition homogenization contribute to the selective surface purification effect As a result, the pitting corrosion resistance of the steel is significantly improved

Improved pitting corrosion resistance of AISI 316L stainless steel treated by high current pulsed electron beam

The surface integrity of machined metal components is critical to their in-service functionality, longevity and overall performance. Surface defects induced by machining operations vary from the nano to macro scale, which cause microstructural, mechanical and chemical effects. Hence, they require advanced evaluation and post processing techniques. While surface integrity varies significantly across the range of machining processes, this paper explores the state-of-the-art of surface integrity research with an emphasis on their governing mechanisms and emerging evaluation approaches. In this review, removal mechanisms are grouped by their primary energy transfer mechanisms; mechanical, thermal and chemical based. Accordingly, the resultant multi-scale phenomena associated with metal machining are analyzed. The contribution of these material removal mechanisms to the workpiece surfaces/subsurface characteristics is reviewed. Post-processing options for the mitigation of induced surface defects are also discussed.

Surface integrity in metal machining - Part I: Fundamentals of surface characteristics and formation mechanisms

Heat transfer—A review of 2005 literature

A magnetically insulated ion diode (MID) with an improved external-magnetic field system has been developed and installed onto a TEMP-6-type high-intensity pulsed ion source in order to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. The external-magnetic field MID is operated in unipolar mode based on dielectric high-voltage flashover, and a double coaxial pulse-forming line (PFL) powered with a Marx generator is used to form the unipolar pulse of nanosecond width. A specially designed cathode has been constructed with a forked connection to two symmetrically installed transformers to improve the effect of the magnetic field and thus increase the stability of generation and propagation of the ion beam. It was found that the efficient generation of HIPIB mainly depended on the magnetic field strength, the gas pressures in reverse and output switches of PFL, and the anode–cathode (A–K) gap of the external-magnetic field MID. A proper magnetic field strength was found with magnetic field power system at dc charging voltage of 8 kV. The proper A–K gap distance is not uniform with the value varied from 6 to 8 mm. Suitable gas pressures for reverse and output switches were about 1.2 and 2.4 atm, respectively, at a charging voltage of 40 kV to the Marx generator. The most efficient plasma generation and ion extraction led to a maximum output of HIPIB with a peak ion current density of 300 A cm−2 and a beam pulse width of 80 ns (full width at half maximum), at an accelerating pulse of 300–350 kV with a pulse width of 70 ns.

Characterization of a high-intensity unipolar-mode pulsed ion source with improved magnetically insulated diode

Surface morphology of pure Ti irradiated by high-intensity pulsed ion beam (HIPIB) with ion current density of 60–250 A/cm 2 and shot number of 1–30 at 220 kV has been investigated by using profilometer, scanning electron microscopy and atomic force microscopy to explore the interaction mechanism between HIPIB and metallic materials. Two kinds of samples were prepared with different initial surface roughness ( R a ), i.e. high-roughness and low-roughness Ti, respectively. A similar change trend of R a was found on the irradiated surfaces for both the two kinds of samples that increase of the R a was obtained with few shot number and then continuous decrease of the R a to a surface smoothing was with multi-shot irradiation. However, the increase of R a on the irradiated low-roughness Ti was greatly limited as compared to the high-roughness case. It is demonstrated that surface smoothing and roughening of irradiated Ti can be realized under optimization of the parameters by combining adjustments of ion current density and shot number. The morphology features on the irradiated high-roughness Ti were craters and waviness for roughened surfaces and some vague or apparent texture with disappearance of the craters for smoothed surfaces. For the low-roughness Ti, no distinct craters were formed except for some obvious texture. The micro-non-uniformity (micro-protrusions) on the irradiated surfaces causes the cratering on pure Ti by inducing a selective ablation under HIPIB irradiation. The locally more intense liquid evaporation and droplet ejection from the irradiated surfaces of different morphologies led to disturbance of the molten surface layer in the different scales, resulting in the surface roughening and smoothing.

Surface morphology of titanium irradiated by high-intensity pulsed ion beam

A high-intensity pulsed ion source of TEMP-type series, operating in bipolar mode, has been developed as a unique pulsed energy source to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. To generate the ion beam, a specially shaped bipolar pulse, consisting of a first negative pulse and a second delayed positive pulse both of nanosecond width, is formed by a double coaxial pulse-forming line (PFL) powered with a Marx generator and supplied to a magnetically insulated ion diode (MID) by a self-magnetic field. It is found that the efficient generation of a HIPIB is mainly dependent on the delay time of the bipolar pulse, adjusted by pressure ratio in the two gas switches of a PFL, and the anode–cathode (A–K) gap distance in the self-magnetic field MID. The delay time determines the effective area on the anode surface for plasma generation and the A–K gap distance ensures the stability of the process. A proper delay time and a proper A–K gap distance are obtained by a s...

Characterization of a high-intensity bipolar-mode pulsed ion source for surface modification of materials

Surface morphology and roughness of pure Ti irradiated by a high-intensity pulsed ion beam (HIPIB) have been investigated by using scanning electronic microscopy and profilometry in order to explore the interaction mechanism between HIPIB and metallic materials Two groups of Ti samples of different initial surface roughness (Ra) were prepared to determine the effect of original surface states on the crater formation as a result of HIPIB irradiation Particularly, the cratering behavior under various irradiation intensities was clarified by examining large Ti samples of high initial roughness with Ra of 018 μm It is noted that no obvious cratering took place on Ti of low initial roughness For high-roughness Ti, the Ra significantly increased from an initial value of 018 μm to the maximal 043 μm at 250 A/cm2 with 1 shot, and then decreased continuously to a final 006 μm with 30 shots presenting a planar ablated surface The similar trend for Ra was also found for the low-roughness Ti, but the maximal value was limited to 018 μm from the initial 007 μm The micro non-uniformity of the original surfaces resulted in the cratering on pure Ti by inducing a selective ablation and disturbance of the molten surfaces under HIPIB irradiation A more uniform ablated Ti surface without crater formation was obtained by multi-shot irradiation due to the gradually decreased non-uniformity at the repetitive ablation

Crater formation on the surface of titanium irradiated by a high-intensity pulsed ion beam

a nondestructive method for characterization of thermally sprayed coatings is developed using an ultrasonic small angle incidence scheme in coatings of four layers and three interfaces. Through wave mode conversion analysis, the longitudinal and the transverse waves at the interfaces are simultaneously derived at an incident angle of 4.1°. The ultrasonic reflection coefficient amplitude spectrum (URCAS) is used to determine the thickness and longitudinal wave velocity of specimens through a two-parameter inversion utilizing the cross-correlation algorithm. The elastic modulus and Poisson's ratio of coatings were calculated utilizing the inversion results and modified density. Ultrasonic experiments were carried out on four WC-Ni specimens sprayed using the high velocity oxygen fuel (HVOF) method at spray angles of 30°, 45°, 60°, and 90°. The thicknesses measured by the ultrasonic method were in good agreement with those observed by optical microscopy with less than 10% error. The porosities determined from cross-section SEM photographs were 4.67%, 1.76%, 0.92%, and 0.19%, respectively with increasing spray angle. The elastic moduli of the specimens measured by the ultrasonic method were in the range of 315 GPa–351 GPa, and the Poisson's ratios were during 0.221–0.245. Metallurgical analysis indicated that increasing the spray angle increases both the density and the bond strength between particles which leads to an enhancement of the elastic modulus of the coatings. The proposed ultrasonic method is valid for nondestructive characterization of the elastic modulus and Poisson's ratio of the coatings.

X.P. Zhu

Papers

Characterization of a high-intensity unipolar-mode pulsed ion source with improved magnetically insulated diode

Surface morphology of titanium irradiated by high-intensity pulsed ion beam

Characterization of a high-intensity bipolar-mode pulsed ion source for surface modification of materials

Crater formation on the surface of titanium irradiated by a high-intensity pulsed ion beam

Nondestructive measurement of elastic modulus for thermally sprayed WC-Ni coatings based on acoustic wave mode conversion by small angle incidence