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Search Results: 1 - 10 of 57280 matches for " Jin FENG "
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Large deviation for diffusions and Hamilton--Jacobi equation in Hilbert spaces
Jin Feng
Mathematics , 2006, DOI: 10.1214/009117905000000567
Abstract: Large deviation for Markov processes can be studied by Hamilton--Jacobi equation techniques. The method of proof involves three steps: First, we apply a nonlinear transform to generators of the Markov processes, and verify that limit of the transformed generators exists. Such limit induces a Hamilton--Jacobi equation. Second, we show that a strong form of uniqueness (the comparison principle) holds for the limit equation. Finally, we verify an exponential compact containment estimate. The large deviation principle then follows from the above three verifications. This paper illustrates such a method applied to a class of Hilbert-space-valued small diffusion processes. The examples include stochastically perturbed Allen--Cahn, Cahn--Hilliard PDEs and a one-dimensional quasilinear PDE with a viscosity term. We prove the comparison principle using a variant of the Tataru method. We also discuss different notions of viscosity solution in infinite dimensions in such context.
Image Registration Algorithm Using Mexican Hat Function-Based Operator and Grouped Feature Matching Strategy
Feng Jin, Dazheng Feng
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095576
Abstract: Feature detection and matching are crucial for robust and reliable image registration. Although many methods have been developed, they commonly focus on only one class of image features. The methods that combine two or more classes of features are still novel and significant. In this work, methods for feature detection and matching are proposed. A Mexican hat function-based operator is used for image feature detection, including the local area detection and the feature point detection. For the local area detection, we use the Mexican hat operator for image filtering, and then the zero-crossing points are extracted and merged into the area borders. For the feature point detection, the Mexican hat operator is performed in scale space to get the key points. After the feature detection, an image registration is achieved by using the two classes of image features. The feature points are grouped according to a standardized region that contains correspondence to the local area, precise registration is achieved eventually by the grouped points. An image transformation matrix is estimated by the feature points in a region and then the best one is chosen through competition of a set of the transformation matrices. This strategy has been named the Grouped Sample Consensus (GCS). The GCS has also ability for removing the outliers effectively. The experimental results show that the proposed algorithm has high registration accuracy and small computational volume.
Potential and Flux Decomposition for Dynamical Systems and Non-Equilibrium Thermodynamics: Curvature, Gauge Field and Generalized Fluctuation-Dissipation Theorem
Haidong Feng,Jin Wang
Physics , 2011, DOI: 10.1063/1.3669448
Abstract: The driving force of the dynamical system can be decomposed into the gradient of a potential landscape and curl flux (current). The fluctuation-dissipation theorem (FDT) is often applied to near equilibrium systems with detailed balance. The response due to a small perturbation can be expressed by a spontaneous fluctuation. For non-equilibrium systems, we derived a generalized FDT that the response function is composed of two parts: (1) a spontaneous correlation representing the relaxation which is present in the near equilibrium systems with detailed balance; (2) a correlation related to the persistence of the curl flux in steady state, which is also in part linked to a internal curvature of a gauge field. The generalized FDT is also related to the fluctuation theorem. In the equal time limit, the generalized FDT naturally leads to non-equilibrium thermodynamics where the entropy production rate can be decomposed into spontaneous relaxation driven by gradient force and house keeping contribution driven by the non-zero flux that sustains the non-equilibrium environment and breaks the detailed balance.
A new mechanism of development and differentiation through slow binding/unbinding of regulatory proteins to the genes
Haidong Feng,Jin Wang
Quantitative Biology , 2012,
Abstract: Understanding the differentiation, a biological process from a multipotent stem or progenitor state to a mature cell is critically important. We develop a theoretical framework to quantify the underlying potential landscape and biological paths for cell development and differentiation. We propose a new mechanism of differentiation and development through binding/unbinding of regulatory proteins to the gene promoters. We found indeed the differentiated states can emerge from the slow promoter binding/unbinding processes. Furthermore, under slow promoter binding/unbinding, we found multiple meta-stable differentiated states. This can explain the origin of multiple states observed in the recent experiments. In addition, the kinetic time quantified by mean first passage transition time for the differentiation and reprogramming strongly depends on the time scale of the promoter binding/unbinding processes. We discovered an optimal speed for differentiation for certain binding/unbinding rates of regulatory proteins to promoters. More experiments in the future might be able to tell if cells differentiate at at that optimal speed. In addition, we quantify kinetic pathways for the differentiation and reprogramming. We found that they are irreversible. This captures the non-equilibrium dynamics in multipotent stem or progenitor cells. Such inherent time-asymmetry as a result of irreversibility of state transition pathways as shown may provide the origin of time arrow for cell development.
Case report of gastric antral vascular ectasia (GAVE)  [PDF]
Fengli Liu, Feng Ji, Xi Jin, Yechun Du
Open Journal of Internal Medicine (OJIM) , 2013, DOI: 10.4236/ojim.2013.32020
Abstract:

Gastric antral vascular ectasia (GAVE) is a rare clinical disease which can cause recurrent upper gastrointestinal (GI) tract bleeding. It is responsible for about 4% of non-variceal upper GI haemorrhages. As one of the vascular diseases that happened in stomach, GAVE was also named as watermelon stomach (WS) for its characteristic endoscopic performance. Compared with portal hypertensive gastropathy (PHG) which with similar performances under endoscopy but often appeared as the result of portal hypertension, the etiology of GAVE is unknown. Recent years with further research it received several presumptions according to its histopathological features. Here we will introduce the disease systematically through two cases.

Radar Imaging of Sidelobe Suppression Based on Sparse Regularization  [PDF]
Xiaoxiang Zhu, Guanghu Jin, Feng He, Zhen Dong
Journal of Computer and Communications (JCC) , 2016, DOI: 10.4236/jcc.2016.43017
Abstract:

Synthetic aperture radar based on the matched filter theory has the ability of obtaining two-di- mensional image of the scattering areas. Nevertheless, the resolution and sidelobe level of SAR imaging is limited by the antenna length and bandwidth of transmitted signal. However, for sparse signals (direct or indirect), sparse imaging methods can break through limitations of the conventional SAR methods. In this paper, we introduce the basic theory of sparse representation and reconstruction, and then analyze several common sparse imaging algorithms: the greed algorithm, the convex optimization algorithm. We apply some of these algorithms into SAR imaging using RadBasedata. The results show the presented method based on sparse construction theory outperforms the conventional SAR method based on MF theory.

Gradual Clamping Reduced Ischemia-Reperfusion Injury in an Isolated Rat Heart Model  [PDF]
Hongbin Feng, Hongli Wang, Yang Zhao, Zhinan Zheng, Sanqing Jin
World Journal of Cardiovascular Surgery (WJCS) , 2016, DOI: 10.4236/wjcs.2016.66013
Abstract: Objectives: We hypothesized that the organisms and their organs or tissues could adapt themselves to the gradual changes of environment for surviving or reducing damage. This study explored whether gradual clamping (GC) could reduce myocardial ischemia-reperfusion (IR) injury in rat heart. Methods: Twelve rats were randomized to IR group and GC group, then the hearts were isolated and perfused with Langendorff apparatus. Before cardioplegia, the perfusion was stopped abruptly in IR group while slowly with 5-minute in GC group. The hearts were subjected to 30-minute ischemia and 60-minute reperfusion. The left ventricular develop pressure (LVDP) and systolic pressure (LVSP), the maximal rate of the increase and decrease of left ventricular pressure (+dp/dtmax, ﹣dp/dtmax) were measured by polygraph system at different time points. The recovery of the variables was expressed as the ratio of these values at individual time point after reperfusion to the baseline respectively. Results: The recovery of LVDP after reperfusion was better than that in IR group (P = 0.034). No significant difference in the recovery of LVSP, +dp/dtmax and ﹣dp/dtmax between groups was observed. Conclusions: Gradual clamping could improve the recovery of LVDP after IR, suggesting that gradual clamping could reduce myocardial IR injury.
Ocean Wave Model and Wave Drift Caused by the Asymmetry of Crest and Trough  [PDF]
Jin-Liang Wang, Hui-Feng Li
Open Journal of Marine Science (OJMS) , 2017, DOI: 10.4236/ojms.2017.73025
Abstract: It follows from the review on classical wave models that the asymmetry of crest and trough is the direct cause for wave drift. Based on this, a new model of Lagrangian form is constructed. Relative to the Gerstner model, its improvement is reflected in the horizontal motion which includes an explicit drift term. On the one hand, the depth-decay factor for the new drift accords well with that of the particle’s horizontal velocity. It is more rational than that of Stokes drift. On the other hand, the new formula needs no Taylor expansion as for Stokes drift and is applicable for the waves with big slopes. In addition, the new formula can also yield a more rational magnitude for the surface drift than that of Stokes.
Techno-Economic Study on an Energy System in Northwest China  [PDF]
Jie-yuan Yang, Jin-ping Li, Rong Feng
Open Journal of Energy Efficiency (OJEE) , 2018, DOI: 10.4236/ojee.2018.71001
Abstract: A combined system of heating, power and biogas (CHPB) system has been developed and tested in a single building in MinQin County, Gansu Province, China. The proposed system satisfies the user’s demand of power, heat, and gas. The CHPB system can effectively overcome seasonal, climate and many other factors which affect the production of the renewable energy. For this purpose, experiments were conducted extensively during the winter period from November 2014 to March 2015. Compared with conventional energy supply systems meets the test household indoor temperature level, the system can reduce the consumption of standard coal 5819.30 kg/year, and save energy costs 11,046.20 yuan/year, the system’s payback period of 4.37 years, also can save 27.03 tons of carbon dioxide emissions. As a result, the CHPB system have been successfully tested for single building, use solar energy and biomass as input and produce power, heat, and gas steadily. These results contributed to the construction of energy supply systems.
Massive Storage Systems
Dan Feng,Hai Jin,
Dan
,Feng,and,Hai,Jin

计算机科学技术学报 , 2006,
Abstract: To accommodate the explosively increasing amount of data in many areas such as scientific computing and e-Business, physical storage devices and control components have been separated from traditional computing systems to become a scalable, intelligent storage subsystem that, when appropriately designed, should provide transparent storage interface, effective data allocation, flexible and efficient storage management, and other impressive features. The design goals and desirable features of such a storage subsystem include high performance, high scalability, high availability, high reliability and high security. Extensive research has been conducted in this field by researchers all over the world, yet many issues still remain open and challenging. This paper studies five different online massive storage systems and one offline storage system that we have developed with the research grant support from China. The storage pool with multiple network-attached RAIDs avoids expensive store-and-forward data copying between the server and storage system, improving data transfer rate by a factor of 2-3 over a traditional disk array. Two types of high performance distributed storage systems for local-area network storage are introduced in the paper. One of them is the Virtual Interface Storage Architecture (VISA) where VI as a communication protocol replaces the TCP/IP protocol in the system. VISA's performance is shown to achieve better than that of IP SAN by designing and implementing the vSCSI (Vl-attached SCSI) protocol to support SCSI commands in the VI network. The other is a fault-tolerant parallel virtual file system that is designed and implemented to provide high I/O performance and high reliability. A global distributed storage system for wide-area network storage is discussed in detail in the paper, where a Storage Service Provider is added to provide storage service and plays the role of user agent for the storage system. Object based Storage Systems not only store data but also adopt the attributes and methods of objects that encapsulate the data. The adaptive policy triggering mechanism (APTM), which borrows proven machine learning techniques to improve the scalability of object storage systems, is the embodiment of the idea about smart storage device and facilitates the self-management of massive storage systems. A typical offline massive storage system is used to backup data or store documents, for which the tape virtualization technology is discussed. Finally, a domain-based storage management framework for different types of storage systems is presented in the paper.
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