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Study in Hydrogen Ion Irradiation of N+-Ion-Implanted SiC-C Films
L. Jia-Rong,N. K. Huang 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
70 % SiC-C ¯lms were deposited by r.f. magnetron sputtering on stainless steel or NaCl substrates, followed by argon ion beam bombardment or nitrogen ion implantation. These 70 % SiC-C ¯lms were irradiated with a hydrogen-ion beam at 5 keV and a dose of 1£1018 ions/cm2. Microanalyses of secondary-ion mass spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy were used to study hydrogen behaviors in these 70 % SiC-C ¯lms, in order to study the eect of nitrogen on hydrogen behaviors of the carbon-carbide ¯lms. It is found that hydrogen concentration in the nitrogen ion implanted 70 % SiC-C ¯lms is higher than that in the argon ion bombarded 70 % SiC-C ¯lms. Related mechanism is discussed in this paper.
Hui, C. Y.,Seo, K. A.,Huang, R. H. H.,Trepl, L.,Woo, Y. J.,Lu, T.-N.,Kong, A. K. H.,Walter, F. M. IOP Publishing 2012 The Astrophysical journal Vol.750 No.1
<P>ROSAT all-sky survey data have provided another window in which to search for supernova remnants (SNRs). In re-examining this data archive, a list of unidentified extended X-ray objects have been suggested as promising SNR candidates. However, most of these targets have not yet been fully explored by state-of-the-art X-ray observatories. To select a pilot target for a long-term identification campaign, we observed the brightest candidate, G308.3-1.4, with the Chandra X-ray Observatory. An incomplete shell-like X-ray structure that is well correlated with the radio shell emission at 843 MHz has been revealed. The X-ray spectrum suggests the presence of a shock-heated plasma. All these evidences confirm G308.3-1.4 as an SNR. The brightest X-ray point source detected in this field of view is also the one located closest to the geometrical center of G308.3-1.4, which has a soft spectrum. The intriguing temporal variability and the identification of the optical/infrared counterpart rule out the possibility of an isolated neutron star. On the other hand, the spectral energy distribution from the K-s band to the R band suggests a late-type star. Together with a putative periodicity of similar to 1.4 hr, the interesting excesses in the V and B bands and in H alpha suggest that this source is a promising candidate for a compact binary that survived a supernova explosion.</P>
Hydrogen Behaviors with different introduction methods in SiC - C Films
N. K. Huang,P. Zou,J. R. Liu,L. Zhang 한국진공학회(ASCT) 2003 Applied Science and Convergence Technology Vol.12 No.S1
SiC-C films were deposited with r. f. magnetron sputtering on substrates followed by argon ion bombardment. These films were then permeated by hydrogen gas under the pressure of 3.23×10^7 ㎩ for 3 hours at temperature of 500K or bombarded with hydrogen ion beam at 5 keV and a dose of 1×10^(18) ions/㎠. SIMS, AES and XPS were used to analyze hydrogen related species, chemical bonding states of C, Si as well as contamination oxygen due to hydrogen participation in the SiC-C films in order to study the different behaviors of hydrogen in carbon-carbide films due to different hydrogen introduction. Related mechanism about the effects of hydrogen on the element of the SiC-C films was discussed in this paper.
Hydrogen Behaviors with different introduction methods in SiC-C Films
Huang, N.K.,Zou, P.,Liu, J.R.,Zhang, L. The Korean Vacuum Society 2003 Applied Science and Convergence Technology Vol.12 No.1
SiC-C films were deposited with r. f. magnetron sputtering on substrates followed by argon ion bombardment. These films were then permeated by hydrogen gas under the pressure of $3.23\times10^{7}$ Pa for 3 hours at temperature of 500K or bombarded with hydrogen ion beam at 5 keV and a dose of $1\times10^{18}$ ions/$\textrm{cm}^2$. SIMS, AES and XPS were used to analyze hydrogen related species, chemical bonding states of C, Si as well as contamination oxygen due to hydrogen participation in the SiC-C films in order to study the different behaviors of hydrogen in carbon-carbide films due to different hydrogen introduction. Related mechanism about the effects of hydrogen on the element of the SiC-C films was discussed in this paper.
Study in Mechanism of Hydrogen Retention by C - SiC Films with IR
N. K. Huang,Q. Xiong,V. G. Liu,B. Yang,D. Z. Wang 한국진공학회(ASCT) 2002 Journal of Korean Vacuum Science & Technology Vol.6 No.1
C-SiC films with different content of SiC on stainless steel substrate were prepared with ion beam mixing. It was found that hydrogen concentrations in C-SiC coatings was higher than that in stainless steel after H^+ ion implantation followed by thermal annealing. Infrared (IR) transmission measurement was used to study the mechanism of hydrogen retention by C-SiC films. The vibrational features in the range between 400 and 3200 ㎝-¹ in IR transmission spectra show the Si-CH₃, Si-CH₂, Si-H, CH₂, and CH₃ bonds, which are responsible for retaining hydrogen.
Feedback-Topology Designs for Interference Alignment in MIMO Interference Channels
Sungyoon Cho,Kaibin Huang,Dong Ku Kim,Lau, V. K. N.,Hyukjin Chae,Hanbyul Seo,Byoung-Hoon Kim IEEE 2012 IEEE transactions on signal processing Vol.60 No.12
<P>Interference alignment (IA) is a joint-transmission technique for the interference channel that achieves the maximum degrees-of-freedom and provides linear scaling of the capacity with the number of users for high signal-to-noise ratios (SNRs). Most prior work on IA is based on the impractical assumption that perfect and global channel-state information (CSI) is available at all transmitters. However, to implement IA, each receiver has to feed back CSI to all interferers, resulting in overwhelming feedback overhead. In particular, the sum feedback rate of each receiver scales quadratically with the number of users even if the feedback CSI is quantized. To substantially suppress feedback overhead, this paper focuses on designing efficient arrangements of feedback links, called feedback topologies, under the IA constraint. For the multiple-input multiple-output (MIMO) <I>K</I>-user interference channel, we propose the feedback topology that supports sequential CSI exchange (feedback and feedforward) between transmitters and receivers so as to achieve IA progressively. This feedback topology is shown to reduce the network feedback overhead from a quadratic function of <I>K</I> to a linear one. To reduce the delay in the sequential CSI exchange, an alternative feedback topology is designed for supporting two-hop feedback via a control station, which also achieves the linear feedback scaling with <I>K</I>. Next, given the proposed feedback topologies, the feedback-bit allocation algorithm is designed for allocating feedback bits by each receiver to different feedback links so as to regulate the residual interference caused by finite-rate feedback. Simulation results demonstrate that the proposed bit allocation leads to significant throughput gains especially in strong interference environments.</P>
Event-Driven Optimal Feedback Control for Multiantenna Beamforming
Kaibin Huang,Lau, Vincent K N,Dongku Kim IEEE 2010 IEEE transactions on signal processing Vol.58 No.6
<P>Transmit beamforming is a simple multiantenna technique for increasing throughput and the transmission range of a wireless communication system. The required feedback of channel state information (CSI) can potentially result in excessive overhead especially for high mobility or many antennas. This work concerns efficient feedback for transmit beamforming and establishes a new approach of controlling feedback for maximizing throughput under a constraint on the average feedback rate. The feedback controller using a stationary policy turns CSI feedback on/off according to the system state that comprises the channel state and transmit beamformer. Assuming channel isotropy and Markovity, the controller's state reduces to two scalars. This allows the optimal control policy to be efficiently computed using dynamic programming. Consider the unquantized feedback channel free of error, where each feedback instant pays a fixed price. The corresponding optimal feedback control policy is proved to be of the threshold type. This result holds regardless of whether the controller's state space is discretized or continuous. Under the threshold-type policy, feedback is performed whenever a state variable indicating the accuracy of transmit CSI is below a threshold, which varies with channel power. The practical quantized feedback channel is also considered. The optimal policy for quantized feedback is proved to be also of the threshold type. The effect of CSI quantization is shown to be equivalent to an increment on the feedback price. Moreover, the increment is upper bounded by the expected logarithm of one minus the quantization error. Finally, simulation shows that feedback control increases throughput of the conventional periodic feedback by up to 0.5 bit/s/Hz without requiring additional bandwidth or antennas.</P>