Showing papers by "Mobil published in 2007"

Asymptotic SER and Outage Probability of MIMO MRC in Correlated Fading

Abstract: This letter derives the asymptotic symbol error rate (SER) and outage probability of multiple-input multiple-output (MIMO) maximum ratio-combining (MRC) systems. We consider Rayleigh fading channels with both transmit and receive spatial correlation. Our results are based on new asymptotic expressions that we derive for the p.d.f. and c.d.f. of the maximum eigenvalue of positive-definite quadratic forms in complex Gaussian matrices. We prove that spatial correlation does not affect the diversity order but that it reduces the array gain and hence increases the SER in the high SNR regime

Transmission Effects in the Continuous One-dimensional Seismic Model

Abstract: Summary It is common in petroleum exploration to lower a variety of instruments down a well to record rock properties as a function of depth. These recordings are called well logs and are of many different types. One which was developed in the early fifties is called the sonic log or continuous velocity log (CVL). This log is a recording of the compressional velocity in the vertical direction as a function of depth. With the availability of this log the question arose of its connection with data obtained from seismic surveys. This subject was addressed in a very influential paper by Peterson, Fillipone & Coker. The treatment was highly simplified mathematically. It was based on a layered earth approximation, and only treated the leading term in a decomposition of the seismogram by order of reflection. This leading term has come to be known as the primary reflection synthetic seismogram. Subsequent to this paper, higher order terms were calculated, so-called multiple reflection terms. All these calculations were based upon a layered approximation to the CVL. These layered approximations were physically realizable in the sense that they could actually be constructed from suitable materials and real physical experiments conducted with them. It is, of course, true in such models that there is both a reflection coefficient and transmission coefficient associated with each interface. In the mathematical approximations there has always been a question of whether and how to treat the transmission effects. In order to shed light on this problem we here start with the continuous formulation, rather than with a layered model. We then consider a physically realizable layered approximation. A related layered model without transmission losses is then formulated and by a limiting process converted to a continuous model. This latter model is then compared to the original continuous model to reveal explicitly the effects of transmission losses. It should be emphasized that the interest in mathematical approximations derives from their connection with the inverse problem: that of obtaining the rock properties from seismic data. In these days of fast digital computers there is no longer any problem in computing synthetic seismograms based upon one-dimensional wave propagation theory. For the inverse problem, which is basically a problem in statistical estimation theory, a decomposition of the exact solution by order of reflection remains important, and the effect of transmission losses is a key issue.

A 5 GHz, 192.6 dBc/Hz/mW FOM, LC–VCO System With Amplitude Control Loop and LDO Voltage Regulator in 0.18 $\mu$ m CMOS

Abstract: To reduce phase noise degradation from oscillator tail current sources, this letter presents an inductor-capacitor voltage-controlled oscillator (LC-VCO) biased by triode metal-oxide-semiconductor transistors. The VCO system also includes an amplitude control loop and a voltage regulator to endure process, voltage, and temperature variations and to enhance power supply rejection ratio. Fabricated in a 0.18 mum CMOS process, the measured results show the adopted topology achieves a better phase noise than the conventional saturation current source. At 5.181 GHz, the VCO system demonstrates a phase noise of -104.8 dBc/Hz at 100-kHz offset, and -127.1 dBc/Hz at 1 MHz offset, while dissipating 4.2 mA from a 1.8 V supply voltage. The corresponding figures of merit at 100 kHz and 1 MHz offset are 190.3 and 192.6 dBc/Hz/mW, respectively.

The geological interpretation of gravity and magnetic surveys over the exposed southern margin of the Galway Granite, Ireland

Abstract: Gravity measurements across the southern margin of the Galway granite, on the Islands of Gorumna and Lettermullen, reveal small positive Bouguer anomalies of amplitudes less than 40 g.u. associated with the denser country rock. These anomalies suggest that the ‘country rock’ is no more than a thin wedge, thickening southwards. Such a structure may form part of a large roof pendant or roof section with the true granite margin lying further south. Magnetic anomaly profiles across the granite contact reveal that the rock groups, making up the country rock, have distinct magnetic character which may provide a means of mapping their southern extent beneath Galway Bay.

Form III to form II phase transition of polybutene‐1

Abstract: The Form III to Form II transition of crystalline potybutene-1 at elevated temperature has been observed by differential thermal analysis (DTA), dilatometry, x-ray diffraction, and photomicrography. DTA thermograma of polybutene-1 in Form III were found to exhibit endotherms at 94°C., and 110°C, corresponding to the transformation of Form III and melting of Form II, respectively. The origin of an exothermic peak observed at 90°C, is not entirely resolved at the present time. The transition of poly-biitene-1 in the Form III modification was also studied by x-ray diffraction methods. It was shown that the intensity of the peak at 2θ = 12.1°, corresponding to the Form III crystalline phase, begins to decrease in sine at 88°C, while simultaneously the peak at 2θ = 11.7°, corresponding to the Form II modification, starts to grow. The transformation is complete at 98°C. The nature of the Form III to Form II transition of polybutene-1 is discussed in the paper; two alternative mechanisms are deemed possible: a solid-solid transition or a transition involving a short-lived intermediate molten state.

Multiple phase transitions of polybutene‐1

Abstract: Multiple phase transitions of polybutene-1 in the form III modification have recently been the subject of discussion by a number of authors. The exact nature of the observed phenomena has remained in doubt, leading to the proposal of divergent theories. Differential thermal analyses and x-ray diffraction studies of polybutene-1 in the form III modifications have shown that the nature of the phase transformations is a function of the heating rate. At very slow heating rates (1°C./day), an apparent form III to form I' crystal-crystal transformation, believed to be related to a thermodynamic “selection” process, has been observed. At faster heating rates (0.2–0.3°C./min.), only part of the form III modification is able to undergo the transformation to form I' the remainder undergoes a melting transition at 96°C, followed by immediate recrystallization to form II. The form I' generated in this process melts at 100°C, and also recrystallizes to the form II modification. At very fast heating rates (20–50°C./min.), form III melts at 96°C, failing to recrystallize.

Performance Improvement of CDMA Hierarchical Cellular System with DAS Embedment in Macrocell

Abstract: In this paper, a two-layer code division multiple access (CDMA) hierarchical cellular network structure is presented, which made up underlaid distributed antenna system (DAS) and overlaid macrocells. The analysis of coverage characteristic shows that embedding DAS instead of microcells in the macrocell makes network control and site engineering easier to be performed. Signal to interference ratio (SIR) of the macrocell/DAS is studied and compared with that of the macrocell/microcell system. Remote access unit (RAU) selection is employed to reduce the interference from the forward link in DAS. Simulation results show that performance of macrocell/DAS is superior to that of macrocell/microcell in the CDMA hierarchical system.

A Tristate Approach Based on Weighted Mean and Backward Iteration

Abstract: A tristate approach (TA) for image denoising processing is presented; the noise is aimed at the presence of pepper-and-salt noise. The newness of this method is that it develops a new route in the field of image restoration. The tristate approach algorithm focuses on the removal and restoration of the noisy speckles and avoids blurring and averaging edges and non-noise pixels in a way different from other known algorithms. Any noisy pixel is replaced by an estimated value. This value is the weighted mean of the pixels neighboring to the noisy pixel or the four iteration pixels got before it. This paper describes, analyzes and compares several methods and results of removing noise from an image. We have performed the experiments by adding Salt-and-Pepper in an original image.

Chlorination of preformed polyethylene film

Abstract: Substantial chlorination of polyethylene (PE) films has been accomplished, making available films having wide varieties of physical properties. The reaction of thin PE films of 0.918 to 0.935 g./cm.3 density was investigated in an atmosphere of Cl2 and in a liquid medium saturated with Cl2. Chlorine contents from 10 to 30% in low-density films and up to 45% in medium-density films were obtained by reaction in the gaseous phase. By the use of various light sources in conjunction with peroxydic catalysts chlorine contents of up to 70% were achieved in glacial acetic acid. In the gaseous atmosphere the tendency of the reaction rate to decrease after light chlorination suggests that diffusion may be the limiting factor here. In the liquid medium the barrier to substitution above 65 to 70% appears to have a thermodynamic basis. The tensile strength and stiffness of the films pass through a minimum below 40% chlorine content and are affected by the reaction temperature. Mildly chlorinated films that have reacted at 40°C. do not exhibit a marked change in tensile properties, suggesting possible chain scission or a decrease in crystallinity on chlorination at elevated temperatures. Significant increases in the fusion point of PE are realized even with low substitutions of chlorine.

Large-Scale Acid Gas Injection Facilities for Gas Disposal

Abstract: Acid Gas Injection (AGI) has commenced at both Ras Laffan LNG Company Limited's RasGas complex (RasGas AGI) within the Ras Lafan Industrial City, Qatar and at ExxonMobil Production Company's LaBarge Treating Facility (LaBarge AGI) in southwestern Wyoming, United States. Acid gases, nominally consisting of hydrogen sulfide (H2S) and carbon dioxide (CO2), are naturally occurring, nonhydrocarbon gases that can be associated with oil and gas production. The successful commissioning, startup, and operation of these facilities demonstrate feasibility and safe operability of AGI technology to dispose of waste gases on a large scale.

Method and device for the wireless transmission of signals, and use of such a method

Abstract: The invention relates to a method and a device for the wireless transmission of at least one measured value as well as the use of such a method. A measuring device comprises a receiver (12), a transmitter (10), and a reverberating resonator (19). The frequency characteristics of said resonator are influenced by the value that is to be measured. A control and evaluation unit is provided with two independent generators (16, 17) to generate signals having a first or second high frequency from which the resonator frequency is derived by forming the difference therebetween.