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Search Results: 1 - 10 of 25560 matches for " Xiaodai Dong "
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Detection of Ventricular Fibrillation Using Random Forest Classifier  [PDF]
Anurag Verma, Xiaodai Dong
Journal of Biomedical Science and Engineering (JBiSE) , 2016, DOI: 10.4236/jbise.2016.95019
Abstract: Early warning and detection of ventricular fibrillation is crucial to the successful treatment of this life-threatening condition. In this paper, a ventricular fibrillation classification algorithm using a machine learning method, random forest, is proposed. A total of 17 previously defined ECG feature metrics were extracted from fixed length segments of the echocardiogram (ECG). Three annotated public domain ECG databases (Creighton University Ventricular Tachycardia database, MIT-BIH Arrhythmia Database and MIT-BIH Malignant Ventricular Arrhythmia Database) were used for evaluation of the proposed method. Window sizes 3 s, 5 s and 8 s for overlapping and non-overlapping segmentation methodologies were tested. An accuracy (Acc) of 97.17%, sensitivity (Se) of 95.17% and specificity (Sp) of 97.32% were obtained with 8 s window size for overlapping segments. The results were benchmarked against recent reported results and were found to outper-form them with lower complexity.
Hybrid Block Diagonalization for Massive Multiuser MIMO Systems
Weiheng Ni,Xiaodai Dong
Mathematics , 2015,
Abstract: For a massive multiple-input multiple-output (MIMO) system, restricting the number of RF chains to far less than the number of antenna elements can significantly reduce the implementation cost compared to the full complexity RF chain configuration. In this paper, we consider the downlink communication of a massive multiuser MIMO (MU-MIMO) system and propose a low-complexity hybrid block diagonalization (Hy-BD) scheme to approach the capacity performance of the traditional BD processing method. We aim to harvest the large array gain through the phase-only RF precoding and combining and then digital BD processing is performed on the equivalent baseband channel. The proposed Hy-BD scheme is examined in both the large Rayleigh fading channels and millimeter wave (mmWave) channels. A performance analysis is further conducted for single-path channels and large number of transmit and receive antennas. Finally, simulation results demonstrate that our Hy-BD scheme, with a lower implementation and computational complexity, achieves a capacity performance that is close to (sometimes even higher than) that of the traditional high-dimensional BD processing.
Power Allocation for Multi-Pair Massive MIMO Two-Way AF Relaying with Robust Linear Processing
Yongyu Dai,Xiaodai Dong
Mathematics , 2015,
Abstract: In this paper, we consider a multi-pair two-way amplify-and-forward (AF) relaying system where multiple sources exchange information via a relay node equipped with large-scale arrays. Supposing that channel estimation is non-ideal, and that the relay employs either maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing reception/zero-forcing transmission (ZFR/ZFT) beamforming to process the signals, we derive two corresponding closed-form lower bound expressions for the ergodic achievable rate of each pair. The closed-form expressions enable us to design optimal power allocation (OPA) schemes by formulating different optimization problems to improve system performance, such as minimizing the total user power consumption to prolong the lifetime of battery-powered devices, considering fairness among different users by adopting the max-min achievable rate criterion, or maximizing the sum spectral efficiency, under certain practical constraints. Our proposed OPA schemes are based on either linear or geometric programming, which can be solved by optimization tools. The derived closed-form expressions for the achievable rate are verified to be accurate predictors of the system performance by Monte-Carlo simulations. Furthermore, numerical results demonstrate the effectiveness of the proposed OPAs in comparison to the equal power allocation schemes.
Low-Complexity Hybrid Precoding in Massive Multiuser MIMO Systems
Le Liang,Wei Xu,Xiaodai Dong
Mathematics , 2014,
Abstract: Massive multiple-input multiple-output (MIMO) is envisioned to offer considerable capacity improvement, but at the cost of high complexity of the hardware. In this paper, we propose a low-complexity hybrid precoding scheme to approach the performance of the traditional baseband zero-forcing (ZF) precoding (referred to as full-complexity ZF), which is considered a virtually optimal linear precoding scheme in massive MIMO systems. The proposed hybrid precoding scheme, named phased-ZF (PZF), essentially applies phase-only control at the RF domain and then performs a low-dimensional baseband ZF precoding based on the effective channel seen from baseband. Heavily quantized RF phase control up to $2$ bits of precision is also considered and shown to incur very limited degradation. The proposed scheme is simulated in both ideal Rayleigh fading channels and sparsely scattered millimeter wave (mmWave) channels, both achieving highly desirable performance.
Physical-Layer Network Coding for Wireless Cooperative Networks
Chen Wen,Dong Xiaodai,Fan Pingyi,Hausl Christoph
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract:
Physical-Layer Network Coding for Wireless Cooperative Networks
Wen Chen,Xiaodai Dong,Pingyi Fan,Christoph Hausl
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/693158
Abstract:
MIMO Relaying Broadcast Channels with Linear Precoding and Quantized Channel State Information Feedback
Wei Xu,Xiaodai Dong,Wu-Sheng Lu
Mathematics , 2012, DOI: 10.1109/TSP.2010.2056687
Abstract: Multi-antenna relaying has emerged as a promising technology to enhance the system performance in cellular networks. However, when precoding techniques are utilized to obtain multi-antenna gains, the system generally requires channel state information (CSI) at the transmitters. We consider a linear precoding scheme in a MIMO relaying broadcast channel with quantized CSI feedback from both two-hop links. With this scheme, each remote user feeds back its quantized CSI to the relay, and the relay sends back the quantized precoding information to the base station (BS). An upper bound on the rate loss due to quantized channel knowledge is first characterized. Then, in order to maintain the rate loss within a predetermined gap for growing SNRs, a strategy of scaling quantization quality of both two-hop links is proposed. It is revealed that the numbers of feedback bits of both links should scale linearly with the transmit power at the relay, while only the bit number of feedback from the relay to the BS needs to grow with the increasing transmit power at the BS. Numerical results are provided to verify the proposed strategy for feedback quality control.
Near-Optimal Hybrid Processing for Massive MIMO Systems via Matrix Decomposition
Weiheng Ni,Xiaodai Dong,Wu-Sheng Lu
Mathematics , 2015,
Abstract: For the practical implementation of massive multiple-input multiple-output (MIMO) systems, the hybrid processing (precoding/combining) structure is promising to reduce the high cost rendered by large number of RF chains of the traditional processing structure. The hybrid processing is performed through low-dimensional digital baseband processing combined with analog RF processing enabled by phase shifters. We propose to design hybrid RF and baseband precoders/combiners for multi-stream transmission in point-to-point massive MIMO systems, by directly decomposing the pre-designed unconstrained digital precoder/combiner of a large dimension. The constant amplitude constraint of analog RF processing results in the matrix decomposition problem non-convex. Based on an alternate optimization technique, the non-convex matrix decomposition problem can be decoupled into a series of convex sub-problems and effectively solved by restricting the phase increment of each entry in the RF precoder/combiner within a small vicinity of its preceding iterate. A singular value decomposition based technique is proposed to secure an initial point sufficiently close to the global solution of the original non-convex problem. Through simulation, the convergence of the alternate optimization for such a matrix decomposition based hybrid processing (MD-HP) scheme is examined, and the performance of the MD-HP scheme is demonstrated to be near-optimal.
Involvement of tryptophan hydroxylase 2 gene polymorphisms in susceptibility to tic disorder in Chinese Han population
Zheng Ping,Li Erzhen,Wang Jianhua,Cui Xiaodai
Behavioral and Brain Functions , 2013, DOI: 10.1186/1744-9081-9-6
Abstract: Background Tryptophan hydroxylase-2 (TPH2) is a potential candidate gene for screening tic disorder (TD). Methods A case–control study was performed to examine the association between the TPH2 gene and TD. The Sequenom Mass ARRAY iPLEX GOLD System was used to genotype two single nucleotide polymorphisms (SNPs) of the TPH2 gene in 149 TD children and in 125 normal controls. Results For rs4565946, individuals with the TT genotype showed a significantly higher risk of TD than those with TC plus CC genotypes [odds ratio (OR) =3.077, 95% confidence interval (CI): 1.273–7.437; P = 0.009], as did male TD children with the TT genotype (OR = 3.228, 95% CI: 1.153–9.040; P = 0.020). The G allele of rs4570625 was significantly more frequent in TD children with higher levels of tic symptoms (Yale Global Tic Severity Scale, YGTSS) than those in controls among the male children (OR = 1.684, 95%: 1.097–2.583; P = 0.017]. TD children with severe tic symptoms had significantly higher frequencies of rs4546946 TT genotype than did normal controls in boys (OR = 3.292, 95% CI: 1.139–9.513; P = 0.022). We also found that genotype distributions of both SNPs were different between the Asian and European populations. Conclusions Our results indicated that the TT genotype of rs4565946 is a potential genetic risk factor for TD, and the allele G of rs4570625 might be associated with the severity of tic symptoms in boys. These polymorphisms might be susceptibility loci for TD in the Chinese Han population. Because of the confounding of co-existing attention deficit hyperactivity disorder (ADHD),these findings need to be confirmed by studies in much larger samples.
Direct Laser Micropatterning of GeSe2 Nanostructures with Controlled Optoelectrical Properties
Bablu Mukherjee,Govinda Murali,Sharon Xiaodai Lim,Minrui Zheng,Eng Soon Tok,Chorng Haur Sow
Physics , 2013,
Abstract: We demonstrate that a direct focused laser beam irradiation is able to achieve localized modification on GeSe2 nanostructures (NSs) film. Using scanning focused laser beam setup, micropatterns on GeSe2 NSs film are created directly on the substrate. Controlled structural and chemical changes of the NSs are achieved by varying laser power and treatment environment. The laser modified GeSe2 NSs exhibit distinct optical, electrical and optoelectrical properties. Detailed characterization is carried out and the possible mechanisms for the laser induced changes are discussed. The laser modified NSs film shows superior photoconductivity properties as compared to the pristine nanostructure film. The construction of micropatterns with improved functionality could prove to be useful in miniature optoelectrical devices.
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