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Search Results: 1 - 10 of 105656 matches for " ZHANG Biao "
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MDCT Angiography Imaging Presentation of ALCAPA in Adults  [PDF]
Qinyi Dai, Biao Lv, Zhaoqi Zhang
Advances in Computed Tomography (ACT) , 2013, DOI: 10.4236/act.2013.21005
Abstract: Objective: To make a pictorial presentation of the anomalous origin of left coronary artery arising from the pulmonary artery (ALCAPA) appearances in adults on MDCT angiography. Methods: A retrospective evaluation was performed between 2005 and 2011 by ECG-gated coronary MDCT angiography. Total 8 patients included (9-51 years, mean age 29 years, 7 female). Image quality was evaluated firstly. Multi planar reformations (MPRs), maximum intensity projections (MIPs) and 3D volume-rendering techniques were used to evaluate image features. In addition, right and left coronary artery orifices were measured for each case. Results: Total 8/70,000 cases diagnosed ALCAPA by MDCT exam, all image qualities were acceptable. As the diagnose key point, all left coronary artery origin were clearly described, and indirect signs such as dilated and tortuous right/left arteries and collateral vessels between them, enlarged left ventricle were also well showed, the dilated degree of both the RCA and the LCA were marked with ages, the diameter of RCA for each case were a mild wider than that of left one. Other combined signs like papillary muscle calcification, bronchial arteries from aorta to the cardiac and coronary artery degeneration change were also included by MDCT angiography findings in a single data acquisition. No combined inter cardiac malformations in our group. Conclusion: ECG-gated MDCT an-giography plays an important role as a first-line modality in assessment of ALCAPA.
Combined 18F-FDG PET/CT with Enhanced CT Perform One-Stop Shop Imaging for Assessing Pancreatic Carcinoma  [PDF]
Miao Zhang, Min Zhang, Lihua Wang, Jiajia Hu, Biao Li
Journal of Cancer Therapy (JCT) , 2012, DOI: 10.4236/jct.2012.35070
Abstract: Objective: To evaluate the role of PET/CT with contrast enhanced CT in diagnosing and staging for pancreatic diseases and optimize the use of enhanced PET/CT as one-stop imaging modality. Methods: Fifty-six patients who presented with suspected pancreatic carcinoma underwent whole-body 18F-FDG PET/CT and enhanced CT imaging. Images were interpreted and compared with the histopathology findings. The sensitivity, specificity and accuracy of enhanced CT, PET/CT and combined PET/CT with contrast enhanced CT diagnosis were analyzed. The vascular invasion and distant metastases of pancreatic lesions on different imaging modality were analyzed and compared. Results: Among the fifty-six patients evaluated for primary tumor, thirty-nine patients had malignant diseases and seventeen had benign lesions. Sensitivity, specificity and accuracy of enhanced CT were 87.5%, 75% and 83.9%, those of non-enhanced PET/CT were 89.7%, 88.2% and 89.2%, of PET/CT with enhanced CT were 100%, 94.1% and 98.2%. Combined PET/CT with enhanced CT had highest sensitivity, specificity and accuracy in diagnosing pancreatic carcinoma. Average SUVmax of malignant lesions was 6.72 ± 3.84, compared with 2.56 ± 1.22 for patients with benign disease (P < 0.01). Combined PET/CT with enhanced CT can help to make accurate staging especially in assessing metastases and vascular invasion. Seven patients deemed surgical candidates were changed to non-surgical treatment. SUVmax didn’t correlate with distant metastases and survival time (Pearson = –0.243, P = 0.136). Distant metastases correlate with survival time (Pearson = –0.447, P = 0.004). Conclusion: PET/CT with contrast enhanced CT is of greater value in the diagnosis of pancreatic lesions as well as preoperative staging especially in assessing vascular invasion and distant metastasis. It is feasible to perform one-stop shop imaging by combining PET/CT with enhanced CT, supplying more accurate assessment before operation and help to select optimal therapeutic plan.
Spatial Profile of the Dead Core for the Fast Diffusion Equation with Dependent Coefficient
Zhengce Zhang,Biao Wang
International Journal of Differential Equations , 2011, DOI: 10.1155/2011/751969
Abstract: We consider the dead-core problem for the fast diffusion equation with spatially dependent coefficient and obtain precise estimates on the single-point final dead-core profile. The proofs rely on maximum principle and require much delicate computation. 1. Introduction In this paper, we study the porous medium equation with the following initial boundary condition: where and . Assume and that the initial data satisfies Moreover, we denote Here we are mainly interested in the asymptotic behavior of nonnegative and global classical solutions. However, Problem (1.1) is singular at for . In fact, the solutions can be approximated, if necessary, by the ones satisfying the following equation with the same initial-boundary value conditions and taking the limit . We set and denote For suitable initial data, we will show that (see Theorem 1.1). We say that the solution develops a dead core in finite time, and is called the dead-core time. In the past few years, much attentions have been taken to the dead-core problems. For the semilinear case of and , the temporal dead-core profile was investigated in [1] by Guo and Souplet. For the quasilinear case of and , Guo et al. [2] firstly investigated the solution which develops a dead core in finite time; then they obtained the spatial profile of the dead core and also studied the non-self-similar dead-core rate of the solution. Numerous related works have been devoted to some of the regularity and the corresponding problems such as blowup, quenching, and gradient blowup; we refer the interested reader to [3–11] and the references therein. Our aim of this paper is to study the dead-core problem for the fast diffusion with strong absorption. In view of the observation concerning the interaction of diffusion and absorption, this question is of interest since the effect of fast diffusion, as compared with linear diffusion, is much stronger near the level . Although our strategy of proof is close to that in [2], the proof is technically much more difficult due to the presence of a nonlinear operator and spatially dependent absorption coefficient. The paper is organized as follows. In Section 2, we prove that the solution of the porous medium equation develops a dead core in finite time. In Section 3, firstly, we obtain the spatial profile of the dead-core upper bound estimate by the initial monotone assumption; then we construct auxiliary function and derive the lower bound estimate by maximum principle. Our first result gives sufficient conditions under which the solution of Problem (1.1) develops a dead core in finite
Vector Potential and Berry phase-induced Force
Qi Zhang,Biao Wu
Physics , 2006, DOI: 10.1103/PhysRevLett.97.190401
Abstract: We present a general theoretical framework for the exact treatment of a hybrid system that is composed of a quantum subsystem and a classical subsystem. When the quantum subsystem is dynamically fast and the classical subsystem is slow, a vector potential is generated with a simple canonical transformation. This vector potential, on one hand, gives rise to the familiar Berry phase in the fast quantum dynamics; on the other hand, it yields a Lorentz-like force in the slow classical dynamics. In this way, the pure phase (Berry phase) of a wavefunction is linked to a physical force.
The Characteristics of the Evaporator/Evaporator for Direct Expansion Solar Assisted Heat Pump System  [PDF]
Mingyan Zhu, Huanrong Xie, Biao Zhang, Xin Guan
Journal of Power and Energy Engineering (JPEE) , 2013, DOI: 10.4236/jpee.2013.15012
Abstract:

Direct expansion solar assisted heat pump (DX-SAHP) technology is developed by combining solar energy heat utilization with heat pump energy saving technology. The experimental researches of the DX-SAHP hot water system are conducted in this paper, and overall performance of DX-SAHP is analyzed with three different structures of collectors/evaporators, namely a bare-plate collector, a glass-plate collector and double collectors/evaporators (a bare-plate collector and a glass-plate collector). The influence factors and overall performance are studied, which show that the overall performance of the system is mainly influenced by solar irradiation intensity and the collector area. Comparing with glass-plate collector in similar conditions, bare-plate collector system COP is higher. While increasing collector area is conducive to improve the system COP, but will reduce the collector efficiency and increase the workload of the compressor by comparing the bare-plate collector with double-plate collectors.

Study on Co-combustion Characteristics of Superfine Coal with Conventional Size Coal in O2/CO2 Atmosphere  [PDF]
Yuhang Zhang, Mingyan Gu, Biao Ma, Huaqiang Chu
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B007
Abstract: The pulverized coal combustion in O2/CO2 atmosphere is one of the promising new technologies which can reduce the emission of carbon dioxide and NOx. In this study, the combustion behaviors of different mixing ratio of Shenhua coal with 20 μm and 74 μm particle size in the O2/CO2 atmosphere and air atmosphere were studied by using a thermal-gravimetric analyzer. The combustion characteristics such as ignition and burnout behavior were investigated in the temperature from 20 to 850. The influence of mixing ratio on combustion characteristics was conduced. The results obtained showed that the ignition temperature of the two kinds of particle size in O2/CO2 atmosphere is higher than in the air, while the activation energy in O2/CO2 atmosphere is lower. With the increasing ratio of 20 μm superfine pulverized coals, the ignition temperature and the activation energy decreased, while the DTG peak value increased, the maximum burning rate position advanced. There were three trends for the ignition temperature curve with the increasing of superfine coal ratio: the ignition of the mixed coal decreased rapidly, then changed less, at last reduced quickly.
Opportunities and Challenges of Robotics and Automation in Offshore Oil & Gas Industry  [PDF]
Heping Chen, Samuel Stavinoha, Michael Walker, Biao Zhang, Thomas Fuhlbrigge
Intelligent Control and Automation (ICA) , 2014, DOI: 10.4236/ica.2014.53016
Abstract:

The oil and gas industry will continue to boom in the coming few decades. Obtaining oil and gas from conventional and non-conventional resources will become more and more challenging. This intensifying need will impose very considerable demands on work force, financial and technology capabilities. Since the future supplies of oil and gas are to expand, advanced technology will become increasingly necessary to obtain access to more challenging conventional and non-conventional resources. Therefore oil and gas technologies will be very costly to operate in the coming future due to hostile, hard-to-reach environments. The offshore oil industry will become a complicated myriad of advanced equipment, structures, and work force. Our objectives are to identify potential applications and research directions of robotics and automation in the oil & gas field and explore the obstacles and challenges of robotic and automation applications to this area. This study performs the necessary survey and investigation about the work conditions of robotics and automation equipment in the oil and gas industry, especially offshore oil rigs. The oil & gas industry processes are first investigated. The personals and tasks are then explored. Furthermore, this paper reviews the current robotic automation technology. The challenges and requirements are identified for robotics and automation equipment in the oil and gas industry. The requirements of robotics and automation in the oil & gas industry are presented. Future research opportunities are discussed from a technical perspective.

Inference of time-varying regression models
Ting Zhang,Wei Biao Wu
Statistics , 2012, DOI: 10.1214/12-AOS1010
Abstract: We consider parameter estimation, hypothesis testing and variable selection for partially time-varying coefficient models. Our asymptotic theory has the useful feature that it can allow dependent, nonstationary error and covariate processes. With a two-stage method, the parametric component can be estimated with a $n^{1/2}$-convergence rate. A simulation-assisted hypothesis testing procedure is proposed for testing significance and parameter constancy. We further propose an information criterion that can consistently select the true set of significant predictors. Our method is applied to autoregressive models with time-varying coefficients. Simulation results and a real data application are provided.
Time-varying nonlinear regression models: Nonparametric estimation and model selection
Ting Zhang,Wei Biao Wu
Statistics , 2015, DOI: 10.1214/14-AOS1299
Abstract: This paper considers a general class of nonparametric time series regression models where the regression function can be time-dependent. We establish an asymptotic theory for estimates of the time-varying regression functions. For this general class of models, an important issue in practice is to address the necessity of modeling the regression function as nonlinear and time-varying. To tackle this, we propose an information criterion and prove its selection consistency property. The results are applied to the U.S. Treasury interest rate data.
Gaussian Approximation for High Dimensional Time Series
Danna Zhang,Wei Biao Wu
Statistics , 2015,
Abstract: We consider the problem of approximating sums of high-dimensional stationary time series by Gaussian vectors, using the framework of functional dependence measure. The validity of the Gaussian approximation depends on the sample size $n$, the dimension $p$, the moment condition and the dependence of the underlying processes. We also consider an estimator for long-run covariance matrices and study its convergence properties. Our results allow constructing simultaneous confidence intervals for mean vectors of high-dimensional time series with asymptotically correct coverage probabilities. A Gaussian multiplier bootstrap method is proposed. A simulation study indicates the quality of Gaussian approximation with different $n$, $p$ under different moment and dependence conditions.
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