Search

Some vacuum chambers in particle accelerators perform a waveguide- or resonator-like behavior due to their unique geometries. Electron multipacting caused by such a structural property might be able to overwhelm the classical beam-induced multipacting. This article shows that the wakefields of particle beams could stimulate the resonant modes of a vacuum chamber with a near-rectangular waveguide shape and accordingly induce much stronger electron avalanche in the chamber. Especially, it has been believed that the multipacting is responsible for pressure rise in a vacuum chamber, where energetic secondary electrons with growing numbers collide with gas particles at the chamber wall. Based on numerical simulations, the electron multipacting mechanism with the mode resonance is proposed, which can explain the significant pressure variation measured in our cryogenic vacuum chamber.

In this paper, a new ride-through module for a matrix converter has been proposed. The proposed module has been shown to maintain the rotor flux and synchronization between the motor and matrix converter during momentary power interruption. The ride-through system for matrix converter consists of two parts they are conventional matrix converter module and add-on ride through module. The principle of operation and advantages of matrix converter-fed ASDs are discussed in this paper.

Simultaneous liver and kidney transplantation (SLKT) is now considered the treatment of choice for patients with concurrent end-stage liver and kidney diseases. Even though the early postoperative mortality rate following SLKT is reported to be high compared to that of liver transplantation alone, the liver graft from the same donor has been argued to induce better kidney graft acceptance as evidenced by a low rate of acute renal rejection episodes. There have been many reports of a low incidence of acute renal rejection following SLKT; however, only a few cases were proven by simultaneous biopsies. The authors experienced a case of biopsy-proven isolated acute cellular rejection of the liver graft following SLKT.

Free electron laser (FEL) is the most powerful source in the THz range. The main task is to decrease its size and cost to a laboratory scale. An inexpensive and compact THz FEL has been developed at KAERI (Y.U. Jeong et al., 2001), (Y.U. Jeong et al., 2005) and it is expected to play an important role in encouraging advanced THz applications for biomedical imaging due to its higher power and spectral brightness when compared to the table-top sources.