Horizontal Side Research Articles

Knee-Chest vs. Horizontal Side Position During Induction of Spinal Anaesthesia in Patients Undergoing Lumbar Disc Surgery

Knee-Chest vs. Horizontal Side Position During Induction of Spinal Anaesthesia in Patients Undergoing Lumbar Disc Surgery

98/01564 Hydronic heating systems: transient modelling, validation and load matching control: Zaheer-Uddin, M. and Monastiriakos, P. Int. J. Energy Res., 1998, 22, (1), 33–46

This paper deals with the heat transfer characteristics of horizontal steam generators, particularly under natural circulation (decay heat removal) conditions on the primary side. Special emphasis is on the inherent features of horizontal steam generator behaviour. A mathematical model of the horizontal steam generator primary side is developed and qualitative results are obtained analytically. A computer code, called HSG, is developed to solve the model numerically, and its predictions are compared with experimental data. The code is employed to obtain for VVER 440 steam generators quantitative results concerning the dependence of primary-to-secondary heat transfer efficiency on the primary side flow rate, temperature and secondary level. It turns out that the depletion of the secondary inventory leads to an inherent limitation of the decay energy removal in VVER steam generators. The limitation arises as a consequence of the steam generator tube bundle geometry. As an example, it is shown that the grace period associated with pressurizer safety valve opening during a station black-out is 2212−3 hours instead of the 5–6 hours reported in several earlier studies. (However, the change in core heat-up timing is much less—about 1 h at most.) The heat transfer limitation explains the fact that, in the Greifswald VVER 440 station black-out accident in 1975, the steam generators never boiled dry. In addition, the stability of single-phase natural circulation is discussed and insights on the modelling of horizontal steam generators with general-purpose thermal-hydraulic system codes are also presented.

Thermal Convection in a Vertical Slot with Lateral Heating

Thermal convection of a fluid contained in a two-dimensional vertical rectangle under a uniform horizontal temperature gradient is studied with the aid of numerical simulations of the governing equations of motion. The velocity is assumed to satisfy the rigid boundary conditions (b.c.) on all the boundary walls whereas the temperature satisfies the isothermal and the adiabatic b.c. on the vertical and the horizontal side walls respectively. The Prandtl number P r of the fluid is P r = 0.71 and the aspect ratio A of the rectangle is taken as A =6. With increase of the Grashof number G characterizing the intensity of the thermal gradient, the motion successively exhibits different temporal behavior: steady → periodic → quasi-periodic with two fundamental frequencies → chaotic where the transition to chaos is caused by the disruption of the T 2 -torus due to the phase-locking. The spatial patterns associated with the above temporal oscillations are also given using the contour plots of the temperature field ...

Knee-chest vs horizontal side position during induction of spinal anaesthesia in patients undergoing lumbar disc surgery

In the prone knee-chest position the spread of plain 0.5% bupivacaine in the cerebrospinal fluid and associated haemodynamic changes may be different compared with the horizontal position. A randomized comparison was performed in 40 ASA I-II patients, aged 24-61 yr, undergoing lumbar disc surgery. Subarachnoid injection (27-gauge needle) at the L2-3 interspace with 3 ml of 0.5% bupivacaine was performed with the patient in the operative knee-chest position (prone knee-chest group, n = 20) or in the horizontal side position (supine side horizontal group, n = 20). Patients in the supine side horizontal group were turned into the horizontal supine position for 20 min, and subsequently they were placed in the operative knee-chest position. In three patients in the prone knee-chest group, the spinal needle was replaced by a larger needle (25-gauge). The final cephalad extension of sensory analgesia on skin tested by pinprick was T5 (median) in the prone knee-chest group and T6 in the supine side horizontal group. Recovery was also similar, on average 210 min from injection in both groups. The mean decrease in systolic arterial pressure was somewhat greater in the prone knee-chest group (30 mm Hg) than in the supine side horizontal group (13 mm Hg). The need for ephedrine occurred earlier in the supine side horizontal group (three patients, all within 10 min from local anaesthetic injection) than in the prone knee-chest group (six patients, all after 15 min). Four of the latter patients also required administration of an anticholinergic for bradycardia compared with two patients in the supine side horizontal group. Light sedation was given to five patients in the prone knee-chest group and to four in the supine side horizontal group because of numbness and aching in the shoulders. We conclude that spinal block was similar in the two groups but there was a tendency to more frequent episodes of haemodynamic deterioration in the knee-chest position.

Analysis of OH-6A Helicopter Flight Test Data Using Lissajous Figures

Lissajous Figures for Flight Test Data Analysis In Lissajous Ž gures, when a point executes two motions simultaneously at right angles to one another in a plane, it traces out a two-dimensional trajectory that lies within a rectangle. If there is no relation between the two motions, the point does not return to its original position, and its trajectory Ž lls up the rectangle by its repeated passages. However, recognizable stationary patterns emerge whenever the two motions are either of the same frequency or are commensurate. Two motions are commensurate with each other if the ratio of their frequencies is a rational number and the initial phases are a simple fraction of 2p. Commensurateness does not require that either motion be absolutely periodic (constant frequency). These stationary patterns are Lissajous Ž gures named after J. A. Lissajous, who made an extensive study of such motions. Figure 1 shows commensurate motions at two different combining frequencies and Ž ve different initial phases. The motions combined at right angles to each other are both simple harmonics, and their frequencies ratio is a rational number. Different initial phase differences are readily apparent by inspection. Further, the trajectory is tangential to the boundary lines of the rectangle enclosing the Lissajous Ž gure. Inspection of the ratio of the number of tangencies made by the trajectories with the vertical and horizontal adjacent sides of the rectangle gives the ratio of the combining frequencies. For example, at v1/v2 = 4 and f = 90, inspection reveals four tangencies on either vertical side and one tangency on either horizontal side of the rectangle, which means the frequencies are at a ratio of 4. The only exception to this rule is when the initial phase is either 0 or 180 deg. Historically, Lissajous Ž gures have been used extensively in electrical and mechanical engineering. A signal generator generates one signal of known frequency, and an oscilloscope compares the known signal with an unknown by combining them at right angles to each other. If there is a small difference

Discharge from a smooth stratified two-phase region through two horizontal side branches located in the same vertical plane

Experimental data are presented for the mass flow rate and quality of two-phase (air-water) discharge from a stratified region through two side branches (6.35 mm W.) with their parallel centrelines located in a vertical plane. These data correspond to different values of the interface level between the onset of gas entrainment at the upper branch to the onset of liquid entrainment at the lower branch for test-section pressures of 316 and 517 kPa, test-section-to-separators pressure difference ranging from 40 to 235 kPa, branch separating distance to diameter ratio ranging from 1.5 to 8 and different hydraulic resistances of the lines connecting the test section to the separators. Normalized plots are shown to be capable of absorbing the effects of some independent variables within the tested range of operating conditions. Empirical relations were developed for the prediction of the two-phase mass flow rate and quality in terms of normalized parameters. These relations represent the data with a high degree of correlation.

Heat transfer characteristics of horizontal steam generators under natural circulation conditions

This paper deals with the heat transfer characteristics of horizontal steam generators, particularly under natural circulation (decay heat removal) conditions on the primary side. Special emphasis is on the inherent features of horizontal steam generator behaviour. A mathematical model of the horizontal steam generator primary side is developed and qualitative results are obtained analytically. A computer code, called HSG, is developed to solve the model numerically, and its predictions are compared with experimental data. The code is employed to obtain for VVER 440 steam generators quantitative results concerning the dependence of primary-to-secondary heat transfer efficiency on the primary side flow rate, temperature and secondary level. It turns out that the depletion of the secondary inventory leads to an inherent limitation of the decay energy removal in VVER steam generators. The limitation arises as a consequence of the steam generator tube bundle geometry. As an example, it is shown that the grace period associated with pressurizer safety valve opening during a station black-out is 2 21 2 −3 hours instead of the 5–6 hours reported in several earlier studies. (However, the change in core heat-up timing is much less—about 1 h at most.) The heat transfer limitation explains the fact that, in the Greifswald VVER 440 station black-out accident in 1975, the steam generators never boiled dry. In addition, the stability of single-phase natural circulation is discussed and insights on the modelling of horizontal steam generators with general-purpose thermal-hydraulic system codes are also presented.

Binocularly Perceived Direction and Outline Shape

Suppose there is a square Julesz random-dot pattern located in front of a background pattern and suppose there is a binocularly visible slider in the background. If subjects align the slider with the rims of the square, the outline of the occlusion in the background pattern has a vertically elongated rectangular shape (Erkelens, Muijs, and van Ee Vision Research in press). The cyclopean-eye concept predicts the outline shape of occluder and occlusion to be the same. However, subjects had the impression that the occluder had the shape of a square. We investigated this impression psychophysically. We measured perceived outline shape of stereoscopically defined rectangles presented in front of a random-dot pattern. In a series of 2AFC tasks subjects decided whether they perceived a horizontally or a vertically elongated rectangle. The horizontal side subtended 8 deg and the vertical side varied between 86% and 114% of 8 deg. The disparity between foreground and background was varied and all trials were presented either in the presence or the absence of monocularly visible contours. We repeated the experiment also during monocular viewing with the left and the right eye. We used exposure durations of 0.5 and 3.0 s. In all circumstances we found that the outline shape of the occluder was veridically perceived; it was not vertically elongated in accordance with the elongation found in the alignment tasks. Apparently information from the binocular alignment of objects in different depth planes is not used for extracting the outline shape of an object.

Natural Convection and Conduction in Massive Wall Solar Collectors With Honeycomb and Without Vents

Steady heat transfer by natural convection and conduction is numerically studied in passive solar collector systems consisting of a massive wall with honeycomb structure and without vents. The boundary conditions are constant heat flux on the wall and fins, isothermal on the vertical bounding sides, and adiabatic on the horizontal sides. The governing parameters are the Rayleigh number (106 ≤ Ra ≤ 5 × 109), the aspect ratio of the enclosures (0.4 ≤ A = H′/L′ ≤ 1.4), the dimensionless lengths of the fins (0 ≤ B = l′/Ll′ ≤ 1), the aspect ratio of the microcavities (0.05 ≤ C = h′/L′ ≤ 1), the wall thickness (0.008 ≤ w = w′/L′ ≤ 0.033). The fin thickness (e = e′/H′ = 0.06) and the Prandtl number (Pr = 0.72) were constant, and the conductivity ratio was variable (10−4 ≤ kr ≤ 5 × 106). Local and average Nusselt numbers along the long sides are calculated as a function of various parameters. Streamlines and isotherms are produced. Effects of various parameters on the heat transfer are examined and heat transfer correlations are derived.

EFFICIENT ENUMERATION OF GRID POINTS IN A CONVEX POLYGON AND ITS APPLICATION TO INTEGER PROGRAMMING

This paper first presents an algorithm for enumerating all the integer-grid points in a given convex m-gon in O(K + m + log n) time where K is the number of such grid points and n is the dimension of the m-gon, i.e., the shorter length of the horizontal and vertical sides of an axis-parallel rectangle enclosing the m-gon. The paper next gives a simple algorithm which solves a two-variable integer programming problem with m constraints in O(m log m + log n) time where n is the dimension of a convex polygon corresponding to the feasible solution space. This improves the best known algorithm in complexity and simplicity. The paper finally presents algorithms for counting the number of grid points in a triangle or a simple polygon.

Natural Convection From L-Shaped Corners With Adiabatic and Cold Isothermal Horizontal Walls

A numerical study of two-dimensional fluid flow and heat transfer by natural convection from L-shaped corners is reported. The vertical side is hot isothermal, and the horizontal side is either adiabatic or cold isothermal at the ambient temperature. The effect of changing the aspect ratio (length of the horizontal side/height of the vertical side) on the transport from the vertical side is studied in detail. It is shown that when the length of the horizontal wall is of the order of the boundary layer thickness on the vertical side, the entrainment flow as well as the boundary layer flow are influenced significantly by a change in the length of the horizontal surface. The heat transfer rate from the vertical side also decreases with increasing length. For values of the aspect ratio > 0.3 (Pr = 0.7), the Nusselt number for the vertical side of the L-shaped body is about 10 percent less than that for the vertical plate. As the length of the horizontal plate increases further, the flow in the outer region undergoes a significant change, but the heat transfer from the vertical heated leg remains unaffected. As the aspect ratio approaches = 2.0, increasing the length of the horizontal side ceases to have any further influence on the entire flow field. Comparison of Nusselt number with past experimental data for air shows good agreement. Finally, Nusselt number correlations in the range of Rayleigh number from 105 to 109 are presented.

Porous silicon pore filling by metal electroplating

Porous silicon can be used as an insulating material in Si devices and as a membrane for ion or molecule separation. Its recently demonstrated photo- and electro-luminescence properties may find novel applications in optoelectronics. Porous silicon has a large internal surface, and, with its pores filled with conducting materials, can form a capacitor with a high charge storage capacity. Recently, thin metal films have been electroplated on porous silicon substrates. These films were then detached and used as condenser microphone diaphragms. Electroplated metal films can also provide electrical contacts to an electro-luminescent porous silicon structure. In this paper, we report our TEM study of a copper electroplating process. We found that in such a process copper preferentially deposits from the bottom of the pore tips upward and fills the entire length of each pore as well as the horizontal side branches.Anodization of silicon was performed in an aqueous HF solution to form a porous layer. Silicon substrates used in this experiment were n-type, (l00)-oriented wafers with a doping concentration of 1017 cm−3 and p-type, (l00)-oriented wafers with a doping concentration of 1019 cm-3.

Rayleigh-Bénard convection in a small box: spatial features and thermal dependence of the velocity field

An experimental study of the spatial features of Rayleigh-Benard convection in a sall box is presented. Experiments are carried out in a rectangular cell (aspect ratios Γx = 2.03, Γy = 1.19) filled with silicone oil (Prandtl number, Pr = 130) for different Rayleigh numbers, Ra (up to Ra = 75Rac, Rac1707). The basic structure of the flow field for this range of Ra consists of two rolls with their axes parallel to the shorter horizontal side. Both senses of rotation for the rolls are observed, corresponding to the two branches of the bifurcation. Particle image velocimetry, with a 5 mW He-Ne laser as the illuminating source, is used to measure the velocity field in the midplane of the cell. From it the vorticity field (out of plane component) and two-dimensional streamlines are calculated. The flow has been measured to be three-dimensional, even for very low Ra, owing to the sidewall influence. The spatial features of the flow are shown to be dependent on both Ra and the sense of rotation of the rolls. Finally, a Fourier analysis of the velocity field is presented. The spatial and thermal dependences of the different Fourier terms are reported. The velocity field, in a first-order approximation, is quantitatively described.

Ｌａｕｒｅｎｃｅ‐Ｍｏｏｎ‐Ｂｉｅｄｌ症候群の神経耳科学的検討

Two siblings of Laurence-Moon-Biedl (L-M-B) syndrome with nystagmus and/or sensorineural hearing loss were reported. One sibling had a slight hearing impairment as well as gaze and rebound nystagmus. The auditory brainstem responses (ABR) showed increased latencies of wave V on both ears. The optokinetic nystagmus (OKN) was limited toward the both horizontal sides. Nystagmus was superimposed on the eye tracking movement. Ocular hypermetria was observed, with bilateral weakness of caloric responses and even a failure of visual fixation suppression. Another sibling had a left-beating spontaneous nystagmus. The latencies of wave V of ABR were prolonged in both ears. The leftward OKN was limited and bilateral saccadic pursuits observed on eye tracking test. These results suggest that cerebellar of brain-stem lesions may be involved in L-M-B syndrome.

A SIMD parallel trapezoid rasterization algorithm

An algorithm for the rasterization of trapezoids on the Connection Machine TM (CM) is described. The input consists of an array of trapezoids, with two horizontal sides, arranged with one trapezoid per processor. (Unless otherwise indicated, “processor” should be taken to mean virtual processor.) Each trapezoid is converted to an edge record and the edge records are then distributed to enough processors so that each processor is responsible for one scanline of one trapezoid. Each processor computes a scan record for its scanline, and the scan records are then distributed to enough processors so that one processor is responsible for a single pixel. Final interpolation of position, and possibly shading information, is performed in parallel for all pixels thus created, and the pixels are then broadcast into a frame buffer array, with depth comparisons being performed at the receiving end to ensure that the nearest pixel appears in the array. The Connection Machine-specific features used by the algorithm are logarithmic time cumulative summing, general communication with comparisons for collision arbitration, and virtual processor sets. Performance is similar to that of good graphics workstations. The intended application is to display data already resident in the machine as the result of some previous computation, when a high-performance graphics workstation is not available.

The development and deployment of an ultrasonic under-sodium viewing system in the fast breeder test reactor

A personal-computer (PC-) controlled under-sodium viewing (USV) system developed and deployed in a fast breeder test reactor (FBTR) is reported. The system is used as a sweep-arm to scan the space below the core cover plate mechanism (CCPM) of the reactor to find any obstacle, and is also used to image the CCPM to demonstrate its horizontal (side) viewing capability. The 6-m long and 900-mm diameter viewer uses an indigenously developed sodium-immersible ultrasonic transducer mounted horizontally at its bottom end whose full movements of complete rotation and 350-mm long vertical travel are controlled by two stepper motors in the drive assembly connected to its top. During the deployment of the under-sodium viewer at 180 degrees C in the FBTR reactor vessel, an Apple-II PC compatible run by a BASIC program is used. It controlled the stepper motors' rotations through one of its parallel ports, monitored an echo detector output through its single-bit game input port, and displayed the CCPM image online on a monochrome monitor. Reprocessing of the data yields pseudo-three-dimensional color images. The quality of the images obtained is discussed. >

Analysis of an annular-mist flow model in a T-junction

Gas-liquid two-phase flow in a T-junction with a horizontal side tube was analysed. Gravity effects were neglected. An annular mist flow pattern was assumed at the inlet to the T-junction. Based on the simple models of film- and gas-droplet core flow the relations for the liquid mass flowrate in the side tube, as a function of the gas flowrate, were derived. The results of the calculations were compared with previous experimental data.

Partitioning a polygonal region into trapezoids

The problem of partitioning a polygonal region into a minimum number of trapezoids with two horizontal sides is discussed. A triangle with a horizontal side is considered to be a trapezoid with two horizontal sides one of which is degenerate. First, a method of achieving a minimum partition is presented. The number M * of the trapezoids in the minimum partition of a polygonal region P is shown to be M * = n + w - h - d - 1, where n , w , and h are the number of vertices, windows (holes), and horizontal edges of P , respectively, and d is the cardinality of a maximum independent set of the straight-lines-in-the-plane graph associated with P . Next, this problem is shown to be polynomially equivalent to the problem of finding a maximum independent set of a straight-lines-in-the-plane graph, and consequently, it is shown to be NP-complete. However, for a polygonal region without windows, an O ( n 2 )-time algorithm for partitioning it into a minimum number of trapezoids is presented. Finally, an O ( n log n )-time approximation algorithm with the performance bound 3 is presented.

Leachate Composition at an Experimental Test Cell of Coal Combustion Fly Ash

ABSTRACTIn an effort to characterize the waste streams at a typical utility fly ash landfill, a large outdoor test cell of compacted fly ash was constructed in 1984 at the Pennsylvania Power & Light Company's Montour Steam Electric Station. The test cell is a scaled-down version of the active dry fly ash disposal facility at the plant and includes a liner, a leachate collection system, and surface water runoff perimeter drains. It is 100 feet by 100 feet at the base and 10 feet high with 2:1 vertical:horizontal side slopes, giving a top area of 60 feet by 60 feet. The test cell is instrumented to measure precipitation, infiltration, surface runoff, unsaturated flow, evapotranspiration and leachate drainage. This paper presents a preliminary evaluation of the chemical composition of leachate generated from the test cell during the first year of leachate production. Leachate samples are periodically collected from a concrete sump to which the leachate collection system drains. Leachate first appeared in the sump in October 1985, approximately one year after the test cell was constructed. Samples are analyzed for pH, specific conductance, 22 metals, and 10 ions. The concentrations of parameters present in the test cell leachate are compared to drinking water standards and to standard laboratory extraction results. Parameters not detected in the leachate are also identified. The preliminary findings of the leachate monitoring effort are providing valuable information on the initial quality of leachate generated under field conditions. This data will be useful in the design of leachate control systems, wastewater treatment facilities and ground water monitoring programs for future ash disposal operations.

A minimax theorem on intervals

A problem of V. Chvátal is solved. It is proved that if P is a vertically convex lattice polygon with vertical and horizontal sides then the minimum number of the rectangles in P which cover P is equal to the maximum cardinality of the point sets such that any two elements induce a rectangle (with vertical and horizontal sides) not contained by the polygon P. This result is the best possible in some sense. Actually the following conjecture of A. Frank is proved which implies this theorem. A sequence of intervals I 1,…, I m is U-increasing if − u j=1 k−1 I j ≠ ∪ j=1 k I j for k = 2, 3,…, m. The set of intervals G is a generating set for the set of intervals J if every element of J is a union of members of G . We prove the conjecture that for any set of intervals J , the minimum size of a generating set G for J is equal to the maximum size of a U-increasing sequence of intervals with members from J .