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- 저자 : Ho Ming Ng (검색결과 7 건)
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Artificial Noise Assisted Secure Transmission for Distributed Antenna Systems
Wang, Hui-Ming,Wang, Chao,Ng, Derrick Wing Kwan,Lee, Moon Ho,Xiao, Jia Institute of Electrical and Electronics Engineers 2016 IEEE transactions on signal processing Vol.64 No.15
<P>This paper studies the artificial noise (AN) assisted secure transmission for a distributed antenna systems (DAS). To avoid a significant overhead caused by full legitimate channel state information (CSI) acquisition, tracking and collection in the central processor, we propose a distributed AN scheme utilizing the large-scale CSI of the legitimate receiver and eavesdropper. Our objective is to maximize the ergodic secrecy rate (ESR) via optimizing the power allocation between the confidential signal and AN for each remote antenna (RA) under the per-antenna power constraint. Specifically, exploiting random matrix theory, we first establish an analytical expression of the achievable ESR, which leads to a non-convex optimization problem with multiple non-convex constraints in the form of high-order fixed-point equations. To handle the intractable constraints, we recast it into a max-min optimization problem, and propose an iterative block coordinate descent (BCD) algorithm to provide a stationary solution. The BCD algorithm is composed of three subproblems, where the first two subproblems are convex with closed-form solutions, and the last one is a convex-concave game whose saddle-point is located by a tailored barrier algorithm. Simulation results validate the effectiveness of the proposed iterative algorithm and show that our scheme not only reduces the system overhead greatly but also maintains a good secrecy performance.</P>
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Xiao Feng Zhang,Ho Ming Ng 서울대학교 교육연구소 2011 Asia Pacific Education Review Vol.12 No.4
Literature has confirmed that teacher appraisal can and should facilitate the professional development of teachers. In the past, teacher appraisal in China has been conducted mainly for administrative purposes; nowadays, it is increasingly being viewed as a means of teacher professional development. However, the way in which teacher appraisal affects teacher professional development has not been fully recognized. This case study, of a junior secondary school in Shanghai, China, explores how teacher appraisal has been carried out and how teachers and administrators have perceived it in relation to teacher professional development. The research findings identify the mechanism by which the teacher appraisal system in question facilitates professional development. The system creates pressure and extrinsic incentives that 'push and pull' teachers to improve, and supports their growth through guidance and directions. In addition, environmental factors such as school culture contribute to the positive impacts that teacher appraisal has on professional development.
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NOMA in Downlink SDMA With Limited Feedback: Performance Analysis and Optimization
Qian Yang,Hui-Ming Wang,Ng, Derrick Wing Kwan,Lee, Moon Ho IEEE 2017 IEEE journal on selected areas in communications Vol.35 No.10
<P>In this paper, the performance of non-orthogonal multiple access (NOMA) is investigated and optimized in a downlink space division multiple access network with a multi-antenna base station and randomly deployed users, under a general channel state information (CSI) limited feedback framework. We first propose a dynamic user scheduling and grouping strategy by leveraging limited feedback. Based on that, an analytical framework is proposed to obtain the outage probability of the network in closed form. The diversity order and the impacts of the number of feedback bits on the outage performance of NOMA are analyzed. Furthermore, the net throughput, which captures the network-wide throughput with the uplink feedback cost considered, is maximized by optimizing the number of feedback bits. Numerical results are demonstrated to verify our analytical findings and show that different from the perfect CSI case, there always exists a performance floor of outage probability in the considered network due to limited feedback. Moreover, the optimal number of feedback bits for net throughput maximization increases as the channel coherence time becomes longer.</P>
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CT-Guided Core Needle Biopsy of Deep Suprahyoid Head and Neck Lesions
En-Haw Wu,Yao-Liang Chen,Yi-Ming Wu,Yu-Ting Huang,Ho-Fai Wong,Shu-Hang Ng 대한영상의학회 2013 Korean Journal of Radiology Vol.14 No.2
Objective: To evaluate the efficacy of computer tomography (CT)-guided core needle biopsy (CNB) in the diagnosis of deep suprahyoid lesions in patients with treated head and neck cancers. Materials and Methods: Between December, 2003 and May, 2011, 28 CT-guided CNBs were performed in 28 patients with deep suprahyoid head and neck lesions. All patients had undergone treatment for head and neck cancers. Subzygomatic, paramaxillary, and retromandibular approaches were used. The surgical results, response to treatment, and clinical follow-up were used as the diagnostic reference standards. Results: All biopsies yielded adequate specimens for definitive histological diagnoses. A specimen from a right parapharyngeal lesion showed atypia, which was deemed a false negative diagnosis. Diagnostic accuracy was 27/28 (96.4%). Two minor complications were encountered: a local hematoma and transient facial palsy. Between the 18 or 20 gauge biopsy needles, there was no statistical difference in the diagnostic results. Conclusion: CT-guided core needle biopsy, with infrequent and minor complications, is an accurate and efficient method for the histological diagnosis of deep suprahyoid lesions in post-treated head and neck cancer patients. This procedure can preclude an unnecessary surgical intervention, especially in patients with head and neck cancers.
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Vin Cent Tai,Hui Xin Che,Xin Ying Kong,Kah Chun Ho,Wei Ming Ng 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-
Over the past decade, incessant research efforts have been devoted to the development of iron oxidenanoparticles (IONPs) for wastewater industry. Past research has witnessed the potential of non-toxicand abundant IONPs to serve as powerful nanosorbents and nanocatalysts, which has become an innovativeresearch point to provide adequate, safe, sustainable, and affordable wastewater treatment for preservingthe environment. To improve the efficiency of wastewater treatment process, worldwideresearchers have made substantial efforts in tuning the size, morphology, chemical composition, and surfacechemistry of IONPs. This review provides an up-to-date overview of the synthesis strategies, limitationsand transformation of IONPs for wastewater treatment. Special mentions on the varioustransformations of IONPs such as functionalization, homogenous-heterogenous catalyst, multifunctionalcatalyst, and green synthesis routes of IONPs. Finally, the constraints that hinder the real-life applicationsof IONPs, including the challenges in the development of IONPs with ideal properties, the long-term stabilitythat allows their repeated usage in wastewater treatment, and understanding their potential environmentalimpacts are outlined. Future research should focus on developing highly efficient andenvironmental friendly synthesis approaches, optimizing the stability and reusability of IONPs, and conductingthorough assessments of their potential environmental impacts to fully realize the potential ofIONPs in the wastewater industry.
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