Proper Bit Research Articles

A rate control scheme using Kalman filtering for H.263

This paper proposes a rate control framework for H.263 video coding called the low-delay Kalman filtering rate controller (LKFrc), whose main part is the adaptive Kalman filter. In LKFrc, a low-delay two-stage selector is proposed to select the representative frames of video. The first stage can rapidly pre-select the relatively significant frames. The second selection stage is embedded in the prediction model of Kalman filter. By the prediction model, LKFrc can distribute a proper bit budget to the pre-selected frame or definitely skip this frame. The measurement model of Kalman filter exploits a rate–distortion (R–D) model to meet the given bit budget by selecting an appropriate picture-level quantization parameter (QP). From the picture-level QP, the subsequent macroblock-level QPs are rapidly yielded by a rapid offset model using the relative macroblock activity. In comparison with the TMN8 model, the LKFrc framework can obtain better PSNRs, higher motion continuities and lower flickering effects with lower computation cost.

SAR raw data compression by subband coding

A technique for compressing synthetic aperture radar raw data using multiresolution representations and subband coding is considered. In particular, we present the performance of a transform coding compression method using wavelet basis, coupled with a threshold quantizer optimized for Gaussian statistics, as well as a proper subband bit allocation strategy. The performances achieved in terms of bit rate reduction and certain quality parameters computed on the images obtained by compressed data have been evaluated. These show an increased performance in the compression method with respect to conventional methods, albeit with a slightly increased complexity in the algorithm implementation.

Low-complexity receiver algorithms for the Grand-Alliance VSB HDTV system

We develop and simulate algorithms required for the front end of the baseband Grand-Alliance high-definition television (G-A HDTV) receiver. This includes noncoherent and coherent automatic gain controls, IF-FPLL polarity detection, segment synchronization and symbol timing recovery. Especially, we propose a simple polarity detection algorithm that resolves the bi-stability of the IF-FPLL unit used in the G-A, HDTV receiver and a segment synchronization algorithm that can be implemented with reduced complexity compared to that proposed by Sgrignoli, Bretl and Citta (see ibid., vol.41, no.3, p.367, 1995) and Bretl, Sgrignoli and Snopko (see ibid., vol.41, no.3, p.773, 1995). Computer simulation results show that the overall receiver design gives satisfactory performance under AWGN, multipath fading and timing drift. Finite bit precision simulations are also performed to determine the proper bit precisions required for each of the functional blocks for circuit implementation. The practical operation of the design is verified via HDL construction and simulation.

Proper nozzle location, bit profile, and cutter arrangement affect PDC-bit performance significantly : D. Garcia-Gavito & J. J. Azar, SPE Drilling & Completion, 9(3), 1994, pp 167–175

Proper nozzle location, bit profile, and cutter arrangement affect PDC-bit performance significantly : D. Garcia-Gavito & J. J. Azar, SPE Drilling & Completion, 9(3), 1994, pp 167–175

Proper Nozzle Location, Bit Profile, and Cutter Arrangement Affect PDC-Bit Performance Significantly

Summary An experimental study comparing the effects of polycrystalline-dia-mond-compact (PDC) -bit design features on the dynamic pressure distribution at the bit/rock interface was conducted on a full-scale drilling rig. Results showed that nozzle location, bit profile, and cutter arrangement are significant factors in PDC-bit performance.

Proper bit design improves penetration rate in abrasive horizontal wells : Gentger, R J Oil Gas JV91, N32, Aug 1993, P39–42

Overall drilling penetration rates nearly tripled, and drill bit life nearly doubled compared to conventional bits when specially designed natural diamond and polycrystalline diamond compact (PDC) bits were used during a seven-well horizontal drilling program. The improvement in drilling performance from better-designed bits lowered drilling costs at ANR Pipeline Co.'s Reed City gas storage field in Michigan. Laboratory tests with scaled down bits used on abrasive cores helped determine the optimum design for drilling the gas storage wells. The laboratory test results and actual field data were used to develop a matrix-body natural diamond bit, which was later modified to become a matrix-body, blade-type polycrystalline diamond compact bit. This bit had excellent penetration rates and abrasion resistance. The paper describes the background to the project, bit selection, natural diamond bits, field results, new bit designs, and field results from the new design.

Multi-rate digital voice coder apparatus

An analog to digital converter for a speech signal is implemented in modules to allow for changes in bit rate and changes in bit stream length according to requirements of the digital transmission system. A pre-emphasis circuit provides an array of pre-emphasized speech samples which are stored in memory. A linear predictive coder provides an array of reflection coefficients and an array of filter coefficients. A pulse processor receives the speech samples and filter coefficients and generates speech amplitude and location signals. These signals are multiplied to generate quantized speech samples. The quantized speech samples and reflection coefficients are provided to a buffer which provides an output signal of a proper bit stream length and bit rate for the digital transmission system.

Adaptive Delta Modulation with Delayed Decision

A class of adaptive schemes for delta modulation is considered whereby the decision about step size is a function of the present and the last k symbols. Such schemes are studied by computer simulations using speech-like signals through evaluation of SNR. Occasional large overshoots appear in the reconstructed signal after the integrater, and to avoid such events it is proposed to store a few signal samples and decide on the proper bit stream taking into account the adaptive logic. Two quadratic criteria have been tried, and improvements of a few decibels have been established with six stored signal samples and a sampling rate of 48 and 24 kHz. Results indicate that other criteria functions may achieve still higher values of SNR.

Drilling Characteristics of a Small Electrodrill

Drilling experiments are made with a 3.7kW electrodrill, using corn, blade and diamond impregnated bits, respectively. Sandstone, tuff and andesite of which compressive strengthes are from 200 to 800kg/cm2 are drilled by these bits. Rotating speeds are between 690 and 740 rpm depending upon bit weight which is ranged from 40 to 300kg. In these experiments following conclusions are obtained:1) A cone bit is the most favorable for the electrodrill, because it gives a high drilling rate and a low torque.2) The electrodrill can not give a high bit weight, and this causes a low drilling efficiency. Notwithstanding a low efficiency of the electrodrill, it can drill comparatively fast, because its rotating speed is high.3) Three means are proposed to increase the drilling efficiency of the electrodrill: 1) to increase the output of a motor in order to give a higher bit weight, 2) to reduce the rotating speed to a reasonable level, and 3) to use a proper bit specially designed for the electrodrill.

Relationship between Drilling Rate of Cone Bits and Physical Properties of Rock

By the use of a laboratory drilling equipment, the drilling rates of 33/4in tri-cone bits (3S, 3M and 3H type) were recorded at atmospheric pressure using water as circulating medium. For this test 17 kinds of rock were used, and compressive strength of these rocks was ranged from 200 to 3700kg/cm2. Other physical properties of the rocks such as density, porosity, radial compressive strength, sound velocity, Young's modulus, Poisson's ratio, and Shore's hardness were measured. Drilling rate of the bits was directly affected by the compressive strength of a rock. Results of the measurement showed that the cone bits of this ordinal type were not effective for drilling hard rock with compressive strength of more than 2500kg/cm2. Density of rock was possible to determine a proper bit weight. Shore's hardness was also used to some extent to assume a proper bit weight. In this study of limitted conditions there were no special relationships between the drilling rate and the radial compressive strength, sound velocity, Young's modulus, or Poisson's ratio.

Fluid Dynamics in a Diamond Drill Bit

Abstract The two-phase flow of a drilling fluid in a diamond drill bit is investigated by deriving and solving the steady-state continuity and momentum equations. Parameters in this analysis are rotational speed of the bit, local rate of addition of drill solids, non-Newtonian nature of the drilling fluid and drilling rate. The describing equations relate the flow and pressure drop to the design characteristics of the bit. The equations are integrated numerically yielding the flow-rate pressure drop characteristics for the bit, flow distribution in the bit and velocity and static pressure as a function of position in each flow channel of the bit. Results are presented for a particular bit design. This paper shows that under normal drilling conditions certain parameters may be neglected in the hydraulic calculations for a diamond drill bit. Therefore, shortened forms of the equations presented can be used to fit the proper diamond bit to the drilling fluid hydraulic system. Introduction Like the conventional bit, the diamond drill bit is a key component in the circulating system of a well. The conventional rock bit is fitted to the circulating system by selecting the flow nozzles which provide the system with the proper flow-rate pressure drop relationship. Fluid behavior across the face of the diamond bit must be better understood so the bit can also be fitted to the circulating system. Data from field operated diamond bits are presently available and do yield some information regarding the flow-rate pressure drop relationship. However, the number of factors affecting this relationship is quite large. Drilling parameters and conditions such as bit penetration rate, bit weight and rotational speed are important. Moreover, flow channels in the bit are part of the cutting head, and introducing drilled solids into the flow channels reduces the flow area, causes additional drag and influences the pressure drop. Many tests would have to be performed if field tests were required to study all parameters which might influence fluid behavior in the bit. A logical approach to this problem is to investigate analytically the fluid behavior in the bit, including parameters that are present under normal drilling operations. This approach, which seems to offer the best method for future studies, is presented in this paper. Following is the general procedure. - Equations describing the most general flowchannel are written and include the addition ofdrilling solids (which is related to penetration rate), rotation of the bit, design parameters of the bit andnon-Newtonian properties of the fluid. - A typical bit is designed and the bit parametersare substituted into the equations. - Parameters are assumed (penetration rate, rotational speed of the bit, mud weight, etc.). - The describing equations are numericallyintegrated to obtain the pressure drop across theface of the bit as a function of flow rate. - The pressure-drop contribution of each component(friction, acceleration, etc.) is obtained fromthe numerical solution, and those factors whichlargely influence the total pressure drop are identified. Classifying the drilling is important in establishing the friction factor relationship since the frictional pressure losses are the main contributors to the total pressure drop. High-density drilling fluid is commonly assumed to be a Bingham plastic. Govier presented a method for selecting a friction factor in the laminar flow region from the rheology properties of the mud and a modified Reynolds number. Metzners presented a criterion for selecting the friction factor in the turbulent flow region. The bit design used in conjunction with the solution of the equations has divergent flow channels. Stall, which is the backflow of fluid in the channels due to eddies that occur on the outer perimeter of the flow stream, can occur in these divergent channels (or diffusers).