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This book promises to change all of this. The lead author and M.I.T. educated scientist, Wilson Chin, and Yinao Su, Academician, Chinese Academy of Engineering, and other team members, have written the only book available that develops mud pulse telemetry from first principles, adapting sound acoustic principles to rigorous signal processing and efficient wind tunnel testing. In fact, the methods and telemetry principles developed in the book were recently adopted by one of the world’s largest industrial corporations in its mission to redefine the face of MWD.

The rotary valve speed control, extremely affected by nonlinear dependence of rotary valve load torque on rotation angle, affects the generation of drilling fluid pressure PSK signal and its quality. Based on load torque calculation model, the load torque feed forward compensation is used in linearized correction of rotation speed control system to enable the motor voltage to vary according to the calculation model. Additionally, the calculation model is also used in compensating the influence of serious nonlinearity in rotary valve load torque on rotation speed control. By means of closed-loop proportional-integral-derivative (PID) control which is formed by negative feedback of speed and the PID parameter values determination rule which is created by attenuating control of transient component in step response of rotary valve speed, the rapid servo control of rotary valve speed is realized. Simulink Simulation indicates that the closed-loop speed control system of rotary valve is able to track the change of control voltage pulse quickly and strongly suppress the interference influences from flow measurement error and load torque calculation model deviation.

A telemetry drill string system consists of a string of wired drill pipes, and high-frequency signals pass the adjacent drill pipes through inductive couplers. Such a system is used to upload downhole information at high data transmission rates for measurements while drilling (MWD). Since the signal energy attenuates greatly in the system, many repeaters must be provided to ensure signal transmission. A reduction in the signal transmission in a telemetry drill string can extend the relay distance and improve the reliability of the transmission system. In this study, the transmission characteristic of the rod of the wired drill pipe is studied using transmission line theory, and the transmission characteristic of the inductive coupler is studied using high-frequency circuit theory. Using impedance matching between the transmission line of the rod and the inductive coupler, external impedance compensation elements, including a capacitor and a resistor, are recommended, and the electromagnetic parameters of the wired drill pipe are determined. Based on the determined electromagnetic parameters, certain changes in the external impedance compensation capacitance and resistance can lead to impedance mismatch between the transmission line and the inductive coupler. This will generate a reflected signal at the transmission line, and the vector superposes with the transmitted signal. The terminal reflection coefficient of the transmission line is controlled by increasing the compensation resistance value to enhance the signal amplitude, which can compensate the transmission loss when passing through the inductive coupler to a certain extent. Thus, the signal transmission capability of the telemetry drill string can be improved, allowing for long-distance signal transmission or drastically extending the relay distance, while maintaining a certain channel bandwidth.

Based on the mathematical analysis of band transmission signal coherent detection theory and mud pressure DPSK signal modulation process, by establishing the coherent detection mathematical model of mud pressure DPSK signal, this paper studies the practicability of broadband mud pressure DPSK signal coherent detection. By analyzing the noise impact on input signal parameter of demodulation system, based on probabilistic statistics theory and coherent demodulation mathematical model, the bit error rate and antinoise ability of mud pressure DPSK signal is studied. Theoretical analysis and numerical simulation indicate that, by adding arc cosine and derivation segment to basic demodulation process, the coherent demodulation effect of mud pressure DPSK signal is satisfied, but the demodulation process is more complex than conventional communication system. Theoretical analysis shows that mud pressure DPSK signal has the same theatrical bit error rate as conventional communication binary phase shift keying (2PSK) signal, but due to the difference of signal demodulation means, the reconstruction of rotary valve control pulse will be affected seriously by the derivate of vertical component of the noise within frequency band, causing that the antinoise ability of mud pressure DPSK signal demodulation system is far lower than 2PSK signal system, and numerical calculation shows that the actual bit error rate is far higher than latter; so under the condition of large carrier frequency, to obtain relative small actual bit error rate and relative larger information transmission rate, the mud pressure DPSK signal input signal-to-noise ratio should be raised as far as possible.

OBJECTIVE： To investigate the association between angiotensinogen gene M235T polymorphism and ischemic stroke in East Asians. DATA RETRIEVAL： A computer-based online search was conducted in PubMed, Google scholar, China National Knowledge Infrastructure database between January 1990 and April 2012 for relevant studies. The key words were angiotensinogen or AGT, polymorphism or genetic and ischemic stroke or cerebral infarction. SELECTION CRITERIA： Case-controlled studies addressing the correlation between angiotensinogen gene M235T polymorphism and ischemic stroke in East Asians were included. The distribution of genotypes in the included studies was tested for Hardy-Weinberg equilibrium. Quality evaluation of the included studies was conducted by two physicians. Statistical analyses were carried out using Stata 12.0 software for meta-analysis. Heterogeneity tests, sensitivity analysis and publication bias were also conducted. MAIN OUTCOME MEASURES： The association between angiotensinogen gene M235T polymorphism and ischemic stroke risk in East Asians was assessed. RESULTS： Six relevant studies involving 891 patients with ischemic stroke and 727 controls were included in this meta-analysis. Results showed that there was a significant association between angiotensinogen gene M235T polymorphism and the risk of ischemic stroke in East Asians （T vs. M odds ratio （OR） = 1.54, 95% confidence interval （CI） = 1.10-2.16; TT vs. MM： OR = 2.24, 95%CI = 1.37-3.66; TT vs. MT： OR = 1.76, 95%CI = 1.41-2.20; MM ＋ MT vs. TT： OR = 0.57, 95%CI -= 0.46-0.70）. Sensitivity analysis confirmed that the study results were stable and reliable, with no publication bias. CONCLUSION： The angiotensinogen gene M235T polymorphism is associated with ischemic stroke in East Asians, and the TT genotype and T allele are risk factors for ischemic stroke.

This chapter contains sections titled: Desurger Distortion Downhole Drilling Noise Attenuation Mechanisms Drillpipe Attenuation and Mudpump Reflection Applications to Negative Pulser Design in Fluid Flows and to Elastic Wave Telemetry Analysis in Drillpipe Systems LMS Adaptive and Savitzky‐Golay Smoothing Filters Low Pass Butterworth, Low Pass FFT and Notch Filters Typical Frequency Spectra and MWD Signal Strength Properties

This chapter contains sections titled: Constant Area Drillpipe Wave Models Variable Area Collar‐Pipe Wave Models

This chapter contains sections titled: Method 5‐1. Problems with Acoustic Impedance Mismatch Due to Collar‐Drillpipe Area Discontinuity, with Drillbit Assumed as Open‐End Reflector Method 5‐2. Problems with Collar‐Drillpipe Area Discontinuity, with Drillbit Assumed as Closed End, Solid Drillbit Reflector