Ion Irradiation-induced Microstructural Change in SiC

The high temperature radiation resistance of nuclear materials has become a key issue in developing future nuclear reactors. Because of its mechanical stability under high-energy neutron irradiation and high temperature, silicon carbide (SiC) has great potential as a structural material in advanced nuclear energy systems. A newly developed nano-engineered (NE) 3C SiC with a nano-layered stacking fault (SFs) structure has been recently considered as a prospective choice due to enhanced point defect annihilation between layer-type structures, leading to outstanding radiation durability. The objective of this project was to advance the understanding of gas bubble formation mechanisms under irradiation conditions in SiC. In this work, microstructural evolution induced by helium implantation and ion irradiation was investigated in single crystal and NE SiC. Elastic recoil detection analysis confirmed that the as-implanted helium depth profile did not change under irradiation to 30 dpa at 700 °C. Helium bubbles were found in NE SiC after heavy ion irradiation at a lower temperature than in previous literature results. These results expand the current understanding of helium migration mechanism of NE SiC under high temperature irradiation environment. No obvious bubble growth was observed after ion irradiation at 700 °C, suggesting a long helium bubble incubation process under continued irradiation at this temperature and dose. As determined by electron energy loss spectroscopy measurements, only 1 % of the implanted helium atoms are trapped in bubbles. Helium redistribution and release was observed in the TEM samples under in-situ irradiation at 800 °C. In-situ TEM analysis revealed that the nano-layered SF structure is radiation tolerant below a dose of about 15 dpa at 800 °C, but continued irradiation to 20 dpa under these in-situ conditions leads to loss of the stacking fault structure, which may be a manifestation of irradiating thin TEM foils. The irradiation stability of the SF structure under bulk irradiation remains unknown. This stacking fault structure is critical since it suppresses the formation of dislocation loops normally observed under these irradiation conditions. Systematic studies towards understanding the role of defect migration under irradiation on the evolution of helium bubbles in NE SiC were performed

A Novel Indoor UWB Antenna Array Design by GA

[[abstract]]In this paper, a new ultra wideband circular antenna array (UCAA) combining genetic algorithm(GA) to minimize the bit error rate (BER) is proposed. The novelties of our approach is not only choosing BER as the object function instead of sidelobe level of the antenna pattern, but also consider the antenna feed length effect of each array element. The strong point of the genetic algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20090403~2009040

Bit error rate reduction by PSO in indoor wireless communication

[[abstract]]In this paper, a new ultra wideband (UWB) circular antenna array (UCAA) combining particle swarm optimizer (PSO) to minimize the bit error rate (BER) is proposed. The novelties of our approach is not only choosing BER as the object function, but also consider the antenna feed length effect of each array element. The strong point of the PSO is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the LOS path. As a result, the BER can be reduced substantially in indoor UWB communication system.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20101117~2010112

Novel radiation pattern by genetic algorithms, in wireless communication

[[abstract]]The genetic algorithm is used to synthesize the radiation pattern of the directional circular arc array to minimize the bit error rate (BER) performance in an indoor wireless communication system. By using the impulse response of the multipath channel, the performance of the synthesized antenna pattern on a BPSK (binary phase shift keying) system with phase and timing recovery circuits can be calculated. Based on the topography of the antenna and the BER formula, the synthesis problem can be reformulated into an optimization problem and solved by the genetic algorithm. Numerical results show that the synthesized antenna pattern is effective to combat the multipath fading and can increase the transmission rate of the indoor millimeter wave system[[conferencetype]]國際[[conferencedate]]20010506~20010509[[booktype]]紙本[[conferencelocation]]Rhodes, Greec

Channel Capacity with Channel Interference in MIMO-WLAN Systems

[[abstract]]The channel capacity of multiple-input multiple-output (MIMO) wireless local area network (MIMO-WLAN) systems with co-channel interference (CCI) is calculated in this paper. The ability to combat CCI for the MIMO-WLAN simple uniform linear array (ULA) and polarization diversity array (PDA) are investigated. The channel frequency response, which is further used to calculate the corresponding channel capacity is calculated by ray-tracing approach. Numerical results show that MIMO-PDA is better than those of MIMO-ULA when interference is present.[[conferencetype]]國際[[conferencedate]]20140714~20140718[[conferencelocation]]Arusha, Tanzani

Image reconstruction for the partially immersed conductor by dynamic differential evolution

[[abstract]]The application of one technique for the reconstruction of shape reconstruction of a metallic cylinder from scattered field measurements is studied in this paper. Considering that the microwave imaging is recast as a nonlinear optimization problem, a cost functional is defined by the norm of a difference between the measured scattered electric field and that calculated for an estimated the shape of metallic cylinder. Thus, the shape of metallic cylinder can be obtained by minimizing the cost function. In order to solve this inverse scattering problem, dynamic differential evolution (DDE) is employed. The technique has been tested in the case of simulated measurement contaminated by additive white Gaussian noise. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20110527~2011052

Synthesizing sectored antennas by the genetic algorithm

[[abstract]]The genetic algorithm is used to synthesize the directional circular arc array as a sectored antenna. Based on the desired pattern and the topography of the antennas, the synthesis problem can be reformulated into an optimization problem and solved by the genetic algorithm. The genetic algorithm will always converge to global extreme instead of local extreme and achieves a good approximation to the desired pattern. Numerical results show that the synthesized sectored antenna is good and effective to combat the multipath fading.[[conferencetype]]國際[[conferencedate]]19991101~19991101[[conferencelocation]]Beijing, Chin

Caffeine treatment disturbs the angiogenesis of zebrafish embryos

[[abstract]]Caffeine is a widely consumed substance that occurs in numerous dietary sources, but teratogenic effects of caffeine intake during embryonic development are still not clear. In the present study, we used the zebrafish as a model to assess caffeine-induced toxicity on embryonic vascular development. A green fluorescent vascular endothelium transgenic line, Tg(fli1:egfp), was utilized for the sensitive detection of vascular development, including vasculo- and angiogenesis. Caffeine-treated embryos showed no defects in vasculogenesis, but revealed dose-dependent (250-350 ppm) developmental defects in intersegmental vessels, dorsal longitudinal anastomotic vessels, and subintestinal vein sprouting. Further, real-time polymerase chain reaction analysis of caffeine-treated embryos showed an upregulation of nrp1a along with a downregulation of sema3aa and sema3c. In conclusion, caffeine treatment induces defects of angiogenesis in zebrafish embryos.[[journaltype]]國外[[incitationindex]]SCI[[ispeerreviewed]]Y[[countrycodes]]US