Patents by Inventor Lizheng Zhang

Lizheng Zhang has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20150168582
    Abstract: Disclosed is a downhole fluid resistivity sensor that includes a ceramic cylinder having a fluid-contacting surface, and at least four metal pins that penetrate a wall of the ceramic cylinder at axially-spaced locations. The pins are bonded to the ceramic to form a pressure seal. The sensor may include a circuit that injects current into a fluid via an outer two of the pins, and measures a resulting voltage via an inner two of the pins. The circuit may also provide an indication of fluid resistivity based at least in part on the resulting voltage. At each of the axially-spaced locations, a set of multiple pins may penetrate the wall to contact the fluid at circumferentially-spaced positions. The fluid-contacting surface may be an inner surface or an outer surface of the ceramic cylinder. A downhole fluid resistivity measurement method is also described.
    Type: Application
    Filed: March 28, 2012
    Publication date: June 18, 2015
    Applicant: HALLIBURTON ENERGY SERVICES, INC.
    Inventors: Wei Zhang, Lizheng Zhang, Li Gao, David Earl Ball
  • Publication number: 20150068736
    Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to advance a sampling and guard probe (100) with a surrounding sealing pad (108) against a borehole wall, to adjust the size of the area associated with a fluid flow inlet of the probe, where the size of the inlet area (104) is selectably and incrementally variable, and to draw fluid into the fluid flow inlet by activating at least one pump (344) coupled to at least one fluid passage (128) in the probe. Additional apparatus, systems, and methods are disclosed.
    Type: Application
    Filed: May 7, 2012
    Publication date: March 12, 2015
    Applicant: Halliburton Energy Services, Inc.
    Inventors: Ronald Johannes Dirksen, Mark A. Proett, Jim Wilson, Abbas Sami Eyuboglu, Lizheng Zhang, Wei Zhang, Abdolhamid Hadibeik
  • Publication number: 20150027216
    Abstract: Methods and systems for improving operations of a formation tester are disclosed. The formation tester (400) is placed in a wellbore at a location of interest. The formation tester comprises a first isolation pad (402) coupled to a pad carrier (410) and a second isolation pad (404). The first isolation is extendable to substantially seal a probe of the formation tester against a well bore wall. The first isolation pad is then replaced with the second isolation pad if it is determined that the first isolation pad should be replaced with the second isolation pad.
    Type: Application
    Filed: March 29, 2012
    Publication date: January 29, 2015
    Applicant: Halliburton Energy Services, Inc.
    Inventor: Lizheng Zhang
  • Patent number: 8341569
    Abstract: Statistical timing analysis methods for circuits having latches and feedback loops are described wherein the circuit yield, and/or the critical cycle mean (the largest cycle mean among all loops in the circuit), may be iteratively calculated with high speed and accuracy, thereby allowing their ready usage in the analysis and validation of proposed circuit designs.
    Type: Grant
    Filed: July 23, 2010
    Date of Patent: December 25, 2012
    Assignee: Wisconsin Alumni Research Foundation
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Patent number: 8244491
    Abstract: A method is provided to evaluate crosstalk effect of aggressor switching upon victim net signal transition time within an integrated circuit comprising: combining a first probability density function (PDF) of first aggressor switching time in response to a first input signal to an aggressor net driver and a second aggressor switching time in response to a second input signal to the aggressor net driver; determining a delay change curve that represents a relationship between delay change of arrival time of a victim net signal transition and relative alignment of the aggressor net driver switching time and a victim net driver switching time; and determining a third PDF of delay change of a transition of the victim net signal based upon the combination and the delay change curve.
    Type: Grant
    Filed: December 23, 2008
    Date of Patent: August 14, 2012
    Assignee: Cadence Design Systems, Inc.
    Inventor: Lizheng Zhang
  • Patent number: 8086978
    Abstract: A method, system, and computer program product are disclosed for performing statistical leakage power characterization to estimate yield of a circuit in terms of leakage power. According to some approaches, this is performed with consideration of state correlation.
    Type: Grant
    Filed: June 20, 2008
    Date of Patent: December 27, 2011
    Assignee: Cadence Design Systems, Inc.
    Inventors: Lizheng Zhang, Parveen Khurana, Vassilios Gerousis, Hongliang Chang, Sachin Shrivastava
  • Patent number: 8069432
    Abstract: A method, system, and computer program product are disclosed for performing statistical leakage power characterization to estimate yield of a circuit in terms of leakage power. According to some approaches, this is performed with consideration of bi-exponential modeling.
    Type: Grant
    Filed: September 30, 2008
    Date of Patent: November 29, 2011
    Assignee: Cadence Design Systems, Inc.
    Inventors: Lizheng Zhang, Hongliang Chang, Kai-Ti Huang, Vassilios Gerousis
  • Publication number: 20100313177
    Abstract: Statistical timing analysis methods for circuits having latches and feedback loops are described wherein the circuit yield, and/or the critical cycle mean (the largest cycle mean among all loops in the circuit), may be iteratively calculated with high speed and accuracy, thereby allowing their ready usage in the analysis and validation of proposed circuit designs.
    Type: Application
    Filed: July 23, 2010
    Publication date: December 9, 2010
    Applicant: Wisconsin Alumni Research Foundation
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Patent number: 7793245
    Abstract: Statistical timing analysis methods for circuits having latches and feedback loops are described wherein the circuit yield, and/or the critical cycle mean (the largest cycle mean among all loops in the circuit), may be iteratively calculated with high speed and accuracy, thereby allowing their ready usage in the analysis and validation of proposed circuit designs.
    Type: Grant
    Filed: December 28, 2007
    Date of Patent: September 7, 2010
    Assignee: Wisconsin Alumni Research Foundation
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Patent number: 7761826
    Abstract: Method and system for crosstalk analysis relating to a statistical crosstalk path delay model that fits into existing static timing framework with little overhead in performance and capacity. More realistic models or assumptions are utilized rather than the more aggressive and less likely deterministic model.
    Type: Grant
    Filed: July 24, 2007
    Date of Patent: July 20, 2010
    Assignee: Cadence Design Systems, Inc.
    Inventors: Venkat Thanvantri, Shiva Raja, Igor Keller, Lizheng Zhang
  • Publication number: 20100083198
    Abstract: A method, system, and computer program product are disclosed for performing statistical leakage power characterization to estimate yield of a circuit in terms of leakage power. According to some approaches, this is performed with consideration of bi-exponential modeling.
    Type: Application
    Filed: September 30, 2008
    Publication date: April 1, 2010
    Inventors: Lizheng Zhang, Hongliang Chang, Kai-Ti Huang, Vassilios Gerousis
  • Patent number: 7689954
    Abstract: Statistical timing analysis methods for circuits are described which compensate for circuit elements having correlated timing delays with a high degree of computational efficiency. An quadratic timing model is used to represent each delay element along a circuit path, wherein each element's delay has a first-order relationship to local variations and a second-order relationship to global variations. Propagation of the modeled delays through the circuit is efficiently done via straightforward ADD operations where an input propagates through another element in a circuit path, and via a MAX operation (or an approximation thereof) where two or more inputs merge at an intersection. The inputs to the MAX operator can be tested for gaussianity, and can be processed by the MAX operation (or its approximation) if they are substantially gaussian. Otherwise, they may be stored in a tuple for processing at later points along the circuit path.
    Type: Grant
    Filed: May 25, 2006
    Date of Patent: March 30, 2010
    Assignee: Wisconsin Alumni Research Foundation
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Publication number: 20090319969
    Abstract: A method, system, and computer program product are disclosed for performing statistical leakage power characterization to estimate yield of a circuit in terms of leakage power. According to some approaches, this is performed with consideration of state correlation.
    Type: Application
    Filed: June 20, 2008
    Publication date: December 24, 2009
    Inventors: Lizheng Zhang, Parveen Khurana, Vassilios Gerousis, Hongliang Chang, Sachin Shrivastava
  • Publication number: 20090055785
    Abstract: Statistical timing analysis methods for circuits having latches and feedback loops are described wherein the circuit yield, and/or the critical cycle mean (the largest cycle mean among all loops in the circuit), may be iteratively calculated with high speed and accuracy, thereby allowing their ready usage in the analysis and validation of proposed circuit designs.
    Type: Application
    Filed: December 28, 2007
    Publication date: February 26, 2009
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Patent number: 7492449
    Abstract: Embodiments of inspection systems and methods are disclosed. One embodiment of an inspection system, among others, comprises logic configured to receive a reference signal and a target signal, the reference signal having first surface displacement information and the target signal having second surface displacement information, said logic configured to determine a correlation coefficient between the first surface displacement information and the second surface displacement information, the correlation coefficient indicating whether an inspected object exhibits a defect.
    Type: Grant
    Filed: March 22, 2005
    Date of Patent: February 17, 2009
    Assignee: Georgia Tech Research Corporation
    Inventors: Ifeanyi Charles Ume, Lizheng Zhang
  • Patent number: 7350171
    Abstract: Statistical timing analysis methods for circuits are described which compensate for circuit elements having correlated timing delays with a high degree of computational efficiency. An extended canonical timing model is used to represent each delay element along a circuit path, wherein the model bears information regarding any correlations that each element has to any other elements in the circuit (and/or to any external global factors, e.g., global temperature variations over the circuit, etc.). The model can be represented in a vectorized format which allows enhancement of computational efficiency, wherein the coefficients of the vectors allow an objective measure of element correlation (and wherein the vectors can be “pruned” by dropping insignificant coefficients to further enhance computational efficiency). A decomposition procedure can be used to decompose correlated elements into uncorrelated elements to allow delays to me more easily propagated through the timing diagram representing the circuit.
    Type: Grant
    Filed: November 17, 2005
    Date of Patent: March 25, 2008
    Inventors: Lizheng Zhang, YuHen Hu, Chun-ping Chen
  • Publication number: 20070277134
    Abstract: Statistical timing analysis methods for circuits are described which compensate for circuit elements having correlated timing delays with a high degree of computational efficiency. An quadratic timing model is used to represent each delay element along a circuit path, wherein each element's delay has a first-order relationship to local variations and a second-order relationship to global variations. Propagation of the modeled delays through the circuit is efficiently done via straightforward ADD operations where an input propagates through another element in a circuit path, and via a MAX operation (or an approximation thereof) where two or more inputs merge at an intersection. The inputs to the MAX operator can be tested for gaussianity, and can be processed by the MAX operation (or its approximation) if they are substantially gaussian. Otherwise, they may be stored in a tuple for processing at later points along the circuit path.
    Type: Application
    Filed: May 25, 2006
    Publication date: November 29, 2007
    Inventors: Lizheng Zhang, Yuhen Hu, Chun-ping Chen
  • Publication number: 20070118331
    Abstract: The invention provides a method, system, and program product for accommodating spatially-correlated variation in a process parameter during statistical timing of a circuit. In one embodiment, the method includes dividing an area of the circuit into a plurality of grid cells; associating an independent random variable with each of the plurality of grid cells; and expressing at least one spatially-correlated parameter of a first grid cell as a function of the random variables associated with the first grid cell and at least one neighboring grid cell.
    Type: Application
    Filed: November 10, 2005
    Publication date: May 24, 2007
    Applicant: International Business Machines Corporation
    Inventors: Natesan Venkateswaran, Chandramouli Visweswariah, Lizheng Zhang, Vladimir Zolotov
  • Publication number: 20070113211
    Abstract: Statistical timing analysis methods for circuits are described which compensate for circuit elements having correlated timing delays with a high degree of computational efficiency. An extended canonical timing model is used to represent each delay element along a circuit path, wherein the model bears information regarding any correlations that each element has to any other elements in the circuit (and/or to any external global factors, e.g., global temperature variations over the circuit, etc.). The model can be represented in a vectorized format which allows enhancement of computational efficiency, wherein the coefficients of the vectors allow an objective measure of element correlation (and wherein the vectors can be “pruned” by dropping insignificant coefficients to further enhance computational efficiency). A decomposition procedure can be used to decompose correlated elements into uncorrelated elements to allow delays to me more easily propagated through the timing diagram representing the circuit.
    Type: Application
    Filed: November 17, 2005
    Publication date: May 17, 2007
    Inventors: Lizheng Zhang, YuHen Hu, Chun-ping Chen
  • Patent number: 7212946
    Abstract: The invention provides a method, system, and program product for accommodating spatially-correlated variation in a process parameter during statistical timing of a circuit. In one embodiment, the method includes dividing an area of the circuit into a plurality of grid cells; associating an independent random variable with each of the plurality of grid cells; and expressing at least one spatially-correlated parameter of a first grid cell as a function of the random variables associated with the first grid cell and at least one neighboring grid cell.
    Type: Grant
    Filed: November 10, 2005
    Date of Patent: May 1, 2007
    Assignee: International Business Machines Corporation
    Inventors: Natesan Venkateswaran, Chandramouli Visweswariah, Lizheng Zhang, Vladimir Zolotov