Showing papers by "Philips published in 1985"

Robust pole assignment in linear state feedback

Abstract: Numerical methods are described for determining robust, or well-conditioned, solutions to the problem of pole assignment by state feedback. The solutions obtained are such that the sensitivity of the assigned poles to perturbations in the system and gain matrices is minimized. It is shown that for these solutions, upper bounds on the norm of the feedback matrix and on the transient response are also minimized and a lower bound on the stability margin is maximized. A measure is derived which indicates the optimal conditioning that may be expected for a particular system with a given set of closed-loop poles, and hence the suitability of the given poles for assignment.

Coherence collapse in single-mode semiconductor lasers due to optical feedback

Abstract: Line broadening up to 25 GHz in a single-mode semiconductor laser with relatively strong optical feedback is reported and theoretically analyzed. Measurements of the coherence function were performed using a Michelson interferometer and demonstrate that the coherence length decreases by a factor 1000 (to approximately 10 mm) due to optical feedback. A self-consistent theoretical description is given, which is based on the view that coherence collapse is maintained due to optical-feedback-delay effects, in which quantum fluctuations play no role of importance. A connection with recently suggested chaotic behavior is made. The theoretical results obtained are in good qualitative and reasonable quantitative agreement with measurements.

Nuclear Bragg diffraction of synchrotron radiation in yttrium iron garnet.

Abstract: Monochromatization of synchrotron radiation down to about ${10}^{\mathrm{\ensuremath{-}}8}$ eV at an energy of 14.4 keV has been achieved by double nuclear Bragg diffraction from $^{57}\mathrm{yttrium}$ iron garnet single-crystal films set for the electronically forbidden {200} reflection. The monochromatized \ensuremath{\gamma} quanta have been analyzed with respect to time delay and capabiltiy of resonance absorption. By setting of appropriate energy and time windows a pure beam of resonant \ensuremath{\gamma} quanta at a rate of about 1 Hz is available.

Supported Chromium Catalysts for Ethylene Polymerization

Abstract: Publisher Summary This chapter discusses supported chromium (Cr) catalysts for ethylene polymerization. The Phillips Cr/silica polymerization catalyst is prepared by impregnating a Cr compound onto wide pore silica and then calcining in oxygen to activate the catalyst. This leaves Cr in the hexavalent state, monodispersed on the silica surface. Chromium trioxide (CrO3) has been impregnated most commonly, but even a trivalent Cr salt can be used because oxidation to Cr(VI) occurs during calcining. Dichromate is the main species in CrO3 solutions. Trivalent Cr salts, notably CrCl3, impregnated onto silica and calcined under vacuum, are found to polymerize ethylene. Three processes are used commercially to make linear polyethylene—namely, solution, slurry, and gas phase. All these processes are called “low-pressure processes” to distinguish them from the free radical or high-pressure process that makes highly branched polyethylene. The slurry process is very convenient for batch polymerization studies. The diluent permits precise control of the temperature and serves to dissolve ethylene and other reactants that must contact the catalyst during polymerization.

Passive display device

Abstract: A passive display device comprising a first and a second supporting plate at least one of which is transparent, a number of display elements for controlling the reflection or transmission of light each having at least one fixed electrode and an electrode which is movable with respect to said electrode by electrostatic forces and which is kept separated from the fixed electrode by means of at least one electrically insulating oxidic layer, the insulating oxidic layer comprising a layer of a compound which comprises a polar and a non-polar group and the polar group of which is adsorbed or linked to the surface of the insulating oxidic layer.

Vertical seismic profiling

Abstract: Vertical seismic profiling is one of the rapidly developing areas of geophysical technology for exploring in mature basins. The measurement basically involves recording the total upgoing and downgoing seismic wave fields propagating through a stratigraphic section by means of geophones clamped to the wall of a drilled well.

On time and space decomposition of complex structures

Abstract: Models of large and complex systems can often be reduced to smaller sub-models, for easier analysis, by a process known as decomposition. Certain criteria for successful decompositions can be established.

Crystals for quartz resonators

Abstract: On decrit le processus de croissance hydrothermale et on discute des importants defauts dans le quartz et les correlations entre eux. On passe en revue les proprietes du quartz et on donne un tableau des proprietes intrinseques et des proprietes liees aux defauts. Theorie du resonateur et techniques de fabrication. Facteurs de conception du circuit

Mictomagnetic, ferromagnetic, and antiferromagnetic transitions in La(FexAl1-x)13 intermetallic compounds.

Abstract: Cubic La(${\mathrm{Fe}}_{\mathrm{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${)}_{13}$ intermetallic compounds can be stabilized with iron concentration x between 0.46 and 0.92 in the ${\mathrm{NaZn}}_{13}$-type structure (D${2}_{3}$) with Fm3c (${O}_{h}^{6}$) space-group symmetry. Here the Fe-Fe coordination number can increase up to 12. At low x values, a mictomagnetic regime occurs with distinct cusps in the ac susceptibility. With the increase of the iron concentration, a soft ferromagnetic phase is found which at lower temperatures shows anisotropy effects related to reentrant mictomagnetic behavior. Finally, for xg0.86, antiferromagnetic order appears along with a sharp metamagnetic transition in external fields of a few teslas. The saturation magnetic moment increases linearly with x from 1.4${\ensuremath{\mu}}_{B}$/Fe to 2.1${\ensuremath{\mu}}_{B}$/Fe throughout the ferromagnetic and antiferromagnetic regime. The breakdown of long-range ferromagnetic order at high x values can be explained by modifications of the iron moment and their coupling at a large Fe-Fe coordination number. However, with application of a magnetic field, the ferromagnetic state can be fully recovered. The room-temperature resistivity decreases with increasing x from 200 to 160 \ensuremath{\mu}\ensuremath{\Omega} cm. The low-temperature slope d\ensuremath{\rho}/dT is related to the magnetic order, being negative in the antiferromagnetic state and positive in the ferromagnetic state. The metamagnetic transition causes a decrease of the resistivity of about 20% and a sign change in d\ensuremath{\rho}/dT. This behavior is discussed in terms of the two-current model. The thermal expansion exhibits a strong Invar character and is described by a combined band and local-moment model which allows calculations of corresponding magnetovolume coupling constants. The metamagnetic transition causes a large magnetic striction.

In vivo nmr imaging of sodium-23 in the human head

Abstract: We report the first clinical nuclear magnetic resonance (NMR) images of cerebral sodium distribution in normal volunteers and in patients with a variety of pathological lesions. We have used a 1.5 T NMR magnet system. When compared with proton distribution, sodium shows a greater variation in its concentration from tissue to tissue and from normal to pathological conditions. Image contrast calculated on the basis of sodium concentration is 7 to 18 times greater than that of proton spin density. Normal images emphasize the extracellular compartments. In the clinical studies, areas of recent or old cerebral infarction and tumors show a pronounced increase of sodium content (300-400%). Actual measurements of image density values indicate that there is probably a further accentuation of the contrast by the increased "NMR visibility" of sodium in infarcted tissue. Sodium imaging may prove to be a more sensitive means for early detection of some brain disorders than other imaging methods.

High‐speed cinematographic analysis of the movement of Chlamydomonas

Abstract: Using high-speed microcinematography (100–500 f/s) the movement of Chlamydomonas reinhardtii mutant 622 E has been studied with frame-by-frame analysis. The stigma lies in the cell equator, displaced out of the flagellar plane anticlockwise by an angle of about 45°. During forward movement the cells rotate anticlockwise about their long axis with a frequency of 1.4–2 Hz (maximum 2.5 Hz). The rotation is caused by a lateral component of 3-dimensional beating of the flagella during the effective strokes. The helical swimming path is a result of an unequal flagellar beating. This is normally synchronous, but synchrony is interrupted from time to time by an additional beat of the outward directed flagellum, in our study one after about every twenty beats on average. These results are discussed and compared with the results published by other groups.

Molecular beam epitaxy

Abstract: This article reviews the major physico-chemical aspects of molecular beam epitaxy (MBE), especially as applied to the deposition of thin epitaxial films of III-V compound and alloy semiconductors. The experimental requirements to achieve the necessary levels of control, purity and uniformity are described first to establish the basic features of the technique. This is followed by a rather detailed treatment of the growth process, including thermodynamic considerations, surface reaction kinetics and film growth dynamics. Because MBE provides a unique means of preparing clean surfaces having controlled stoichiometry and reconstruction, the evaluation of their crystallographic and electronic structure is dealt with at some length. The structure and composition of semiconductor-semiconductor interfaces, together with the formation of quantum wells and periodic superlattices, are topics of increasing importance and as such also receive considerable attention. Dopant incorporation is dealt with rather more briefly by reference to specific examples and finally some mention is made of materials other than III-V semiconductors which have been prepared by MBE.

Vehicle navigation system provided with an adaptive inertial navigation system based on the measurement of the speed and lateral acceleration of the vehicle and provided with a correction unit for correcting the measured values

Abstract: A navigation system for a road vehicle comprises a route-determining unit and position-locating means. The route-determining unit works together with a mass memory which stores geographic data of a road network. The route-determining unit determines a driving route between a starting point and a destination supplied by the driver of the vehicle. The position-locating devices determine the vehicle position coordinates recurrently from the speed and acceleration of the moving vehicle provided by a measuring unit. A correction unit derives a correction vector for correcting the generated vehicle position coordinates. The correction vector is determined by performing a transposition of the generated vehicle position coordinates to an actual road position as repeated by coordinates of the road network stored in the mass memory. An acceleration operator is derived from the measured speed and lateral acceleration and from the generated vehicle position coordinates. The acceleration operator operates on the correction vector in order to derive a correction value for the measured acceleration. A receiver receives position coordinate signal from a navigation satellite. A Kalman filter mixes the vehicle position coordinates with the position coordinates originating from the navigation satellite.

Fiber optic switch

Abstract: A fiber optic switch producing optical connections with very low light losses. The switch has constant mechanical and optical properties over long periods of operation. Adjusting elements act on the end of at least one light conductor to move the end face of the light conductor in the axial and transverse directions. The end face can then be moved opposite to and into contact with the end face of another light conductor.

Combined bipolar-field effect transistor resurf devices

Abstract: A combined bipolar-field effect transistor RESURF device includes a lightly-doped epitaxial buried layer of a first conductivity type located between a semiconductor substrate of the first conductivity type and an epitaxial surface layer of a second conductivity type opposite to that of the first. The doping concentration and thickness of the epitaxial surface layer are selected in accordance with the Reduced Surface Field (RESURF) technique. A highly-doped buried region of the second conductivity type is located beneath the base region of the device and is sandwiched between the epitaxial buried layer and the epitaxial surface layer. The advantages of such a device include a substantially reduced "on" resistance, a more compact and flexible configuration, improved switching characteristics, reduced base device current requirements, and improved isolation. The device may be further enhanced by providing a buried annular region of the first conductivity type around and in contact with the buried region, and a surface-adjoining annular region of the first conductivity may be provided adjacent the base region.

Matrix of light-emitting elements and method of manufacturing same

Abstract: An electrically insulating substrate has an array of holes formed in it for accepting electrically conducting support pins, each pin having a light-emitting element mounted on the upper pin end. Each upper pin end is surrounded by an insulating ring and a conducting ring, the light emitting element being connected electrically between the conducting pin and the conducting ring. Electrical connections are made via a printed wiring pattern on each surface of the substrate. Optical collimating elements are formed in a wafer having openings that surround each of the conducting rings with a small clearance, the wafer engaging and being insulated from the substrate with the printed wiring.

Television receiver comprising a teletext decoding circuit and a page number memory

Abstract: A television receiver which is suitable for displaying teletext pages comprises a control system including a microcomputer. The microcomputer is coupled to a volatile memory which comprises a plurality of page number registers. A page number can be temporarily stored in each of these registers. With the aid of a keyboard the user makes known which page numbers he wants to have stored in the different registers and the stored page numbers represent a first series of pages. One single read key (RCL) is provided for the display of such a page. Each time this key is depressed once, a different page belonging to the first series appears on the picture screen. The sequence in which the pages appear is the same as the sequence in which the user has keyed-in the relevant page numbers. This sequence can be interrupted by the occurrence of a preselected operating instruction in response to which a number of teletext pages not associated with said first series can be displayed on the picture screen. Thereafter, the display of the teletext pages of the first series can be continued.

Calculation of Eddy currents in terms of H on hexahedra

Abstract: The eddy current equations are formulated here in terms of H [1] instead of the more usual vector potential A [2,3]. In both cases a combination with a scalar potential is necessary in the non conducting regions. In the case of A this leads to either a non symmetric or not positive definite system of equations to be solved. This is avoided by the formulation in H, but special elements have to be chosen in order to satisfy the interface conditions between the two regions. The construction of such elements on tetrahedra or rectangular blocks can be found in [4]. The construction for hexahedra, or more specifically, isoparametric bricks, is shown here. Compared to filling a hexahedron with tetrahedra, this method reduces the number of unknowns by a half. The computed approximations for the eddy currents are exactly non divergent.

Elastic scatter computed tomography

Abstract: A technique is proposed for imaging 2D sections based on measurement of elastic scatter radiation. In this new imaging method the radiation from a conventional X-ray source (Philips MCN 165 160 kVp tube operated at 140 kVp and 4.6 mA with 0.6 mm focus) is collimated by a lead diaphragm (1.0 mm) and falls on the object to be investigated. The transmitted radiation and the scatter falling within a range of half-angle 6 degrees (with reference to the object centre) are recorded by seven scintillation detectors (BGO) operated in current integration mode. Each scintillation crystal subtends an angular range of 1 degrees . The detector array comprises three scatter detectors arranged symmetrically on either side of the central transmission detector in such a way that six (partially overlapping) scatter measurements result.

Linear prediction of speech with a least absolute error criterion

Abstract: Most methods for linear prediction of speech are based on a least square error criterion (L 2 criterion). In this paper, it is shown that the robustness of a least absolute error criterion (L 1 criterion) is particularly well adapted to the analysis of voiced sounds. The well-known linear programming L 1 algorithms have two important drawbacks: the stability of the synthesis filter is not guaranteed, and the computation load is too heavy for real time analysis. All these problems are alleviated by the new L 1 algorithm proposed in this paper. Experiments show comparable efficiency with classical L 2 methods.