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Search Results: 1 - 10 of 94951 matches for " Xin Chen "
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Undergraduate Curriculum Development for Digital Integrated Circuit Design  [PDF]
Xin Chen
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.326128
Abstract: This article describes the development of a Digital Integrated Circuit Design curriculum, which includes how to select the design level and how to implement the design. The curriculum is for the undergraduates in grade four, whose major is microelectronics. The development is in the background of very large scale integrated circuits. Since the popular design flow is a hierarchy of abstraction levels, the goal of the curriculum is to develop the students’ ability to design an actual circuit from scratch. Comparison is provided from two aspects. The first aspect is the contents of various published textbooks. The second aspect is the contents of similar courses in famous universities.
The Rigorous Stochastic Matrix Multiplication Scheme for the Calculations of Reduced Equilibrium Density Matrices of Open Multilevel Quantum Systems
Xin Chen
Physics , 2013, DOI: 10.1063/1.4870496
Abstract: Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, $\it{i.e.}$ how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernom influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems.
Quantum Path Interference through Incoherent Motions in Multilevel Quantum Systems
Xin Chen
Physics , 2013,
Abstract: Quantum path interferences or resonances in multilevel dissipative quantum systems play an important and intriguing role in the transport processes of nanoscale systems. Many previous minimalistic models used to describe the quantum path interference driven by incoherent fields are based on the approximations including the second order perturbation for the weak coupling limit, the ad-hoc choices of two-time correlation functions and $\it{etc}$. On the other hand, the similar model to study the non-adiabatic molecular electronic excitation have been extensively developed and many efficient quantum molecular dynamics simulation schemes, such as the Ehrenfest scheme, have been proposed. In this paper, I aim to propose an unified model, extend the Ehrenfest scheme to study the interactions of system-light and system-phonon simultaneously and gain insight into and principles of the roles of quantum path interferences in the realistic molecular systems. I discuss how to derive the time-dependent stochastic Schr$\ddot{o}$dinger equation from the Ehrenfest scheme as a foundation to discuss the detailed balance for the weak coupling limit and therefore the quantum correction in the Ehrenfest scheme. Different from the master equation technique, the Ehrenfest scheme doesn't need any specific assumptions about spectral densities and two time correlation functions. With simple open two-level and three-level quantum systems, I show the effect of the quantum path interference on the steady state populations. Currently I only focus on the role of the phonon thermal reservoir. The electromagnetic field (solar light) will be modeled as a thermal reservoir and discussed in detail in the future paper.
Approximating the Minimum Breakpoint Linearization Problem for Genetic Maps without Gene Strandedness
Xin Chen
Quantitative Biology , 2015,
Abstract: The study of genetic map linearization leads to a combinatorial hard problem, called the {\em minimum breakpoint linearization} (MBL) problem. It is aimed at finding a linearization of a partial order which attains the minimum breakpoint distance to a reference total order. The approximation algorithms previously developed for the MBL problem are only applicable to genetic maps in which genes or markers are represented as signed integers. However, current genetic mapping techniques generally do not specify gene strandedness so that genes can only be represented as unsigned integers. In this paper, we study the MBL problem in the latter more realistic case. An approximation algorithm is thus developed, which achieves a ratio of $(m^2+2m-1)$ and runs in $O(n^7)$ time, where $m$ is the number of genetic maps used to construct the input partial order and $n$ the total number of distinct genes in these maps.
Fast CR-SRAM Using New Charge-Recycling Scheme  [PDF]
Leilei Li, Xin Chen, Xu Wang
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.48064
Abstract: In this paper, a CR-SRAM using new charge recycling scheme is described, novel bit-line pre-charge voltage distribution is proposed. The SRAM pre-charge voltage level is designed by logarithm instead of linear. The new design leads to improvement in speed compared to the original CR-SRAM. Simulation results show that the new CR-SRAM using novel pre-charge voltage distribution scheme reduced the write access time by 34% with 9% power dissipation penalty.
Phase-Matching and Parametric Conversion for the Mid-Infrared in As2S3 Waveguides  [PDF]
Qi Chen, Xin Wang, Christi Madsen
Optics and Photonics Journal (OPJ) , 2012, DOI: 10.4236/opj.2012.24031

We illustrate two As2S3 waveguide designs for four-wave mixing, which can generate 3.03 μm mid-infrared light from a 1.55 μm near-infrared signal source and a 2.05 μm pump source. Through simulations, we verify that four-wave mixing phase-matching efficiencies up to 100% can be achieved using dispersion engineering to maintain the dispersion at 2.05 μm near to zero. The best conversion efficiency is –10 dB. When the waveguide length is 1 cm, the parametric conversion bandwidth is 1525 nm. We also evaluated the shift of 100% phase-matching efficiency wavelengths based upon fabrication tolerances.

A Restricted, Adaptive Threshold Segmentation Approach for Processing High-Speed Image Sequences of the Glottis  [PDF]
Mathew Blanco, Xin Chen, Yuling Yan
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.510B072

In this paper, we propose a restricted, adaptive threshold approach for the segmentation of images of the glottis acquired from high speed video-endoscopy (HSV). The approach involves first, identifying a region of interest (ROI) that encloses the vocal-fold motion extent for each image frame as estimated by the different image sequences. This procedure is then followed by threshold segmentation restricted within the identified ROI for each image frame of the original image sequences, or referred to as sub-image sequences. The threshold value is adapted for each sub-image frame and determined by respective minimum gray-scale value that typically corresponds to a spatial location within the glottis. The proposed approach is practical and highly efficient for segmenting a vast amount of image frames since simple threshold method is adapted. Results obtained from the segmentation of representative clinical image sequences are presented to verify the proposed method.

Carbohydrate-Derived Organocatalysts for the Reduction of Imines with Trichlorosilane  [PDF]
Xin Ge, Chao Qian, Xinzhi Chen
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.36008

The backbone of D-glucosamine hydrochloride was fine-tuned and modified by protecting the hydroxyl groups. In order to reduce imines with trichlorosilane, the carbohydrate-derived organocatalysts were prepared and screened. Methyl-4,6-O-benzylidene-2-amino-2-deoxy-α-D-glucopyr anoside was found as the best catalyst. The reduction was proceeded under CHCl3 as solvent at 40?C, affording 68% - 94% yield.

Research on Agricultural Products Cold Chain Logistics Safety Supervision System: Mechanism Improvement and Supervision Measures  [PDF]
Xin’gang Weng, Jiuyi An, Weifeng Chen
Journal of Service Science and Management (JSSM) , 2015, DOI: 10.4236/jssm.2015.86091
Abstract: With the widespread concern in the community and increased government supervision, Chinese cold chain logistics quality and safety of agricultural products are being constantly improved, but quality safety management work of cold chain logistics of agricultural products started lately in China. There are many constraints, and the management is difficult, so the quality and safety supervision of agricultural products cold chain logistics is still inadequate. Based on the system analysis of agricultural products, the paper proposes mechanism improvement of cold chain logistics of agricultural products and analyzes measures of safety supervision system of cold chain logistics of agricultural products.
Projective Synchronization of N-Dimensional Chaotic Fractional-Order Systems via Linear State Error Feedback Control
Baogui Xin,Tong Chen
Discrete Dynamics in Nature and Society , 2012, DOI: 10.1155/2012/191063
Abstract: Based on linear feedback control technique, a projective synchronization scheme of N-dimensional chaotic fractional-order systems is proposed, which consists of master and slave fractional-order financial systems coupled by linear state error variables. It is shown that the slave system can be projectively synchronized with the master system constructed by state transformation. Based on the stability theory of linear fractional order systems, a suitable controller for achieving synchronization is designed. The given scheme is applied to achieve projective synchronization of chaotic fractional-order financial systems. Numerical simulations are given to verify the effectiveness of the proposed projective synchronization scheme.
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