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Opportunistic Spectrum Access Based on a Constrained Multi-Armed Bandit Formulation
Ai, Jing,Abouzeid, Alhussein A. The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.2
Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.
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Jing-Ai Piao,Gang Li,Mei-Lan Piao,김남 한국광학회 2013 Current Optics and Photonics Vol.17 No.3
Full color holographic optical element fabrication using a photopolymer is proposed for a waveguide-type head mounted display. The fabricated full color holographic optical elements can be attached to the waveguide to replace the conventional couple-in and couple-out optics in the head mounted display. To implement the system, this study analyzed the optical characteristics of the photopolymer using three lasers (red, green and blue). Considering the color uniformity, a new laminated structure for a full color holographic optical element was also designed. The proposed system was confirmed experimentally.
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Opportunistic Spectrum Access Based on a Constrained Multi-Armed Bandit Formulation
Jing Ai,Alhussein A. Abouzeid 한국통신학회 2009 Journal of communications and networks Vol.11 No.2
Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.
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Jing, Yuan-Ming,Guo, Su-Xia,Zhang, Xiao-Ping,Sun, Ai-Jing,Tao, Feng,Qian, Hai-Xin Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.5
Objective: To investigate the association between the connexin 37 C1019T polymorphism and Helicobacter pylori infection in patients with gastric cancer. Methods: 388 patients with gastric cancer (GC), 204 with chronic superficial gastritis (CSG) were studied. H. pylori was detected by gastric mucosal biopsies biopsy dyeing method. Connexin 37 gene polymorphism 1019 site genotypes were determined by gene sequencing technology. Genotypes and alleles frequencies were compared. Results: (1) Connexin37 gene 1019 site distribution frequency (CC type, TC type, TT type) in the CSG group was 18.1%, 45.1% and 36.8%; in the stomach cancer group it was 35.1%, 45.9% and 19.%, conforming to the Hardy-Weinberg euilibrium. (2) In comparison with CSG group, the frequency of Connexin37 C allele was higher in the gastric cancer group (58.0% vs 40.7%, OR = 2.01, 95%CI = 1.58-2.57, P < 0.01). The prevalence of gastric cancer risk was significantly increased in the carriers of C allele (CC+TC) than in TT homozygote (OR = 2.47, 5%CI = 1.68- 3.610. (3) Gastric cancer patients complicated with Hp infection 211 cases, gastric cancer group of the male patients with HP positive patients with 187 cases, 40 cases of female patients with negative patients, 24 cases were HP positive, negative in 137 cases, control group male patients, 28 cases were Hp positive, negative in 95 patients, female patients with Hp positive 6 cases, 75 cases were negative. On hierarchical analysis, the male group OR value was 15.9 (95%CI to 9.22-27.3), and the female OR was 2.19 (95%CI 0.88-5.59), indicating a greater contribution in males (P <0.01). After elimination of gender effects, positive HP and gastric cancer were closely related (OR 8.82, 95% CI: 5.45-14.3). (4) The distribution frequency of C allele in patients with Hp infection was much higher than that in Hp negative cases in the GC group (64.5% vs 47.0%, OR = 2.05, 95%CI = 1.54-2.74, P < 0.01). Compared with TT homozygotes, (CC+TC) genotype prevalence of gastric cancer risk increased significantly (OR = 2.96, 5%CI = 1.76-2.99 ). Conclusion: The T allele in the connexin37 gene might not only be associated with gastric cancer but also with H. pylori infection.
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( Ai Jing Li ),( Mun Hong Choe ) 한국현대언어학회 2014 언어연구 Vol.29 No.4
A corpus-based analysis of the use of linking adverbials (LAs) in model essays for students of English and authentic essays composed by professional writers was conducted with a self-established model essay corpus (MEC) and the New York Times Annotated Corpus (NYTAC). Data from the two corpora were retrieved and analyzed by means of Antconc 3.2.4. It was found that the percentages of the top ten most frequently used LAs accounted for 46% and 52% of the total number of LAs used in MEC and NYTAC, respectively. The model essays contained far more instances of additive, adversative, causal/resultative, and sequential LAs, but significantly fewer types of LA than did NYTAC. Further, LAs in MEC were predominantly placed at sentence initial position whereas those in NYTAC were employed at varying positions in a sentence. (Chonnam National University)
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MR Imaging of the Spine at 3.0T with T2-Weighted IDEAL Fast Recovery Fast Spin-Echo Technique
Ai-Jun Ren,Yong Guo,Shu-Ping Tian,Li-Jing Shi,Min-Hua Huang 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.1
Objective: To compare the iterative decomposition of water and fat with echo asymmetry and the least-squares estimation (IDEAL) method with a fat-saturated T2-weighted (T2W) fast recovery fast spin-echo (FRFSE) imaging of the spine. Materials and Methods: Images acquired at 3.0 Tesla (T) in 35 patients with different spine lesions using fat-saturated T2W FRFSE imaging were compared with T2W IDEAL FRFSE images. Signal-to-noise ratio (SNR)-efficiencies measurements were made in the vertebral bodies and spinal cord in the mid-sagittal plane or nearest to the mid-sagittal plane. Images were scored with the consensus of two experienced radiologists on a four-point grading scale for fat suppression and overall image quality. Statistical analysis of SNR-efficiency, fat suppression and image quality scores was performed with a paired Student’s t test and Wilcoxon’s signed rank test. Results: Signal-to-noise ratio-efficiency for both vertebral body and spinal cord was higher with T2W IDEAL FRFSE imaging (p < 0.05) than with T2W FRFSE imaging. T2W IDEAL FRFSE demonstrated superior fat suppression (p < 0.01) and image quality (p < 0.01) compared to fat-saturated T2W FRFSE. Conclusion: As compared with fat-saturated T2W FRFSE, IDEAL can provide a higher image quality, higher SNR-efficiency, and consistent, robust and uniform fat suppression. T2W IDEAL FRFSE is a promising technique for MR imaging of the spine at 3.0T. Objective: To compare the iterative decomposition of water and fat with echo asymmetry and the least-squares estimation (IDEAL) method with a fat-saturated T2-weighted (T2W) fast recovery fast spin-echo (FRFSE) imaging of the spine. Materials and Methods: Images acquired at 3.0 Tesla (T) in 35 patients with different spine lesions using fat-saturated T2W FRFSE imaging were compared with T2W IDEAL FRFSE images. Signal-to-noise ratio (SNR)-efficiencies measurements were made in the vertebral bodies and spinal cord in the mid-sagittal plane or nearest to the mid-sagittal plane. Images were scored with the consensus of two experienced radiologists on a four-point grading scale for fat suppression and overall image quality. Statistical analysis of SNR-efficiency, fat suppression and image quality scores was performed with a paired Student’s t test and Wilcoxon’s signed rank test. Results: Signal-to-noise ratio-efficiency for both vertebral body and spinal cord was higher with T2W IDEAL FRFSE imaging (p < 0.05) than with T2W FRFSE imaging. T2W IDEAL FRFSE demonstrated superior fat suppression (p < 0.01) and image quality (p < 0.01) compared to fat-saturated T2W FRFSE. Conclusion: As compared with fat-saturated T2W FRFSE, IDEAL can provide a higher image quality, higher SNR-efficiency, and consistent, robust and uniform fat suppression. T2W IDEAL FRFSE is a promising technique for MR imaging of the spine at 3.0T.
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Jing Li,Jian Wu,Xiguo Yuan,Xiaobo Li,Liefu Ai 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1
This paper considers the problem of the global finite-time stabilization for the high-order nonlinear systemswith unknown control directions. Due to the uncertainty of control directions, the paper analyzes all possibleconditions of the directions. The Lyapunov-based logic switching rule ensures that we can find the correct controldirections. The adaptive switching controller with a switching parameter which is to be tuned online guarantees thatthe derivative of Lyapunov function is less than a negative definite function and the closed-loop system is globallyfinite-time stable. The effectiveness of the proposed method is illustrated by an example.
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