bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolonged treatment of fair‐skinned mice with topical forskolin causes persistent tanning and UV protection
Authors: Spry Malinda L , Vanover Jillian C , Scott Timothy , Abona‐Ama Osama , Wakamatsu Kazumasa , Ito Shosuke , D’Orazio John A
Published: December 2008

We previously reported that topical application of forskolin to the skin of fair‐skinned MC1R‐defective mice with epidermal melanocytes resulted in accumulation of eumelanin in the epidermis and was highly protective against UV‐mediated cutaneous injury. In this report, we describe the long‐term effects of chronic topical forskolin treatment in this animal model. Forskolin‐induced eumelanin production persisted through 3 months of daily applications, and forskolin‐induced eumelanin remained protective against UV damage as assessed by minimal erythematous dose (MED). No obvious toxic changes were noted in the skin or overall health of animals exposed to prolonged forskolin therapy. Body weights were maintained throughout the course of topical forskolin application. Topical application of forskolin was associated with an increase in the number of melanocytes in the epidermis and thickening of the epidermis due, at least in part, to an accumulation of nucleated keratinocytes. Together, these data suggest in this animal model, short‐term topical regular application of forskolin promotes eumelanin induction and that over time, topical forskolin treatment is associated with persistent melanization, epidermal cell accumulation, and skin thickening.
Rewetting Analysis of Hot Vertical Surfaces With Precursory Cooling by the Heat Balance Integral Method
Authors: Sahu S. K. , Das P. K. , Bhattacharyya S.
Published: December 2008

The effect of precursory cooling on conduction-controlled rewetting of both slab and solid cylinder is analyzed by the heat balance integral method. A constant heat transfer coefficient is assumed in the wet region behind the wet front, while an exponentially decaying heat flux is assumed in the dry region ahead of the wet front. The physical problem is characterized by two dimensionless constants describing the extent of precursory cooling and three dimensionless numbers, namely, Peclet number, Biot number, and the nondimensional temperature. Results of the present solution are found to be in good agreement with other analytical solutions obtained through the Weiner–Hopf technique and the separation of variables as well as with the published experimental data for different coolants over a varied range of coolant flow rate. It is seen that precursory cooling increases the rewetting velocity particularly at higher flow rates. If it is neglected, the model grossly underpredicts the quench velocities.
Study on Micropump Using Boiling Bubbles
Authors: Koizumi Yasuo , Ohtake Hiroyasu
Published: December 2008

A micropump was developed using boiling and condensation in a microchannel. The length and hydraulic diameter of the semi-half-circle cross-section microchannel having two open tanks at both ends were 26mm and 0.465mm, respectively. A 0.5×0.5mm2 electrically heated patch was located at the offset location from the center between both ends of the microchannel, at a distance of 8.5mm from one end and at a distance of 17mm from the other end. The microchannel and the two open tanks were filled with distilled water. The heating patch was heated periodically to cause cyclic formation of a boiling bubble and its condensation. By this procedure, flow from the short side (8.5mm side) to the long side was created. The flow rate increased as the heating rate was increased. The obtained maximum average flow velocity and flow rate were 10.4mm∕s and 2.16mm3∕s, respectively. The velocity of an interface between the bubble and the liquid plug during the condensing period was much faster than that during the boiling period. During the condensing period, the velocity of the interface at the short channel side (8.5mm side) was faster than that at the long channel side (17mm side). The equation of motion of liquid in the flow channel was solved in order to calculate the travel of liquid in the flow channel. The predicted velocities agreed well with the experimental results. The velocity differences between the short side and the long side, as well as those between the boiling period and the condensing period, were expressed well by the calculation. Liquid began to move from the stationary condition during both the boiling and the condensing periods. The liquid in the inlet side (short side) moved faster than that in the outlet side (long side) during the condensing period because the inertia in the short side was lower than that in the long side. Since the condensation was much faster than boiling, this effect was more prominent during the condensing period. By iterating these procedures, the net flow from the short side to the long side was created.
Thermal Transport in a Microchannel Exhibiting Ultrahydrophobic Microribs Maintained at Constant Temperature
Authors: Maynes D. , Webb B. W. , Davies J.
Published: December 2008

This paper presents numerical results exploring the periodically repeating laminar flow thermal transport in a parallel-plate microchannel with ultrahydrophobic walls maintained at constant temperature. The walls considered here exhibit alternating microribs and cavities positioned perpendicular to the flow direction. Results describing the thermally periodically repeating dynamics far from the inlet of the channel have been obtained over a range of laminar flow Reynolds numbers and relative microrib/cavity module lengths and depths in the laminar flow regime. Previously, it has been shown that significant reductions in the overall frictional pressure drop can be achieved relative to the classical smooth channel laminar flow. The present predictions reveal that the overall thermal transport is also reduced as the relative size of the cavity region is increased. The overall Nusselt number behavior is presented and discussed in conjunction with the frictional pressure drop behavior for the parameter range explored. The following conclusions can be made regarding thermal transport for a constant temperature channel exhibiting ultrahydrophobic surfaces: (1) Increases in the relative cavity length yield decreases in the Nusselt number, (2) increasing the relative rib/cavity module length yields a decrease in the Nusselt number, and (3) decreases in the Reynolds number result in smaller values of the Nusselt number.
Direct Numerical Simulation of Condensing Stratified Flow
Authors: Lakehal Djamel , Fulgosi Marco , Yadigaroglu George
Published: December 2008

The paper discusses the results of a detailed direct numerical simulation study of condensing stratified flow, involving a sheared steam-water interface under various thermal and turbulent conditions. The flow system comprises a superheated steam and subcooled water flowing in opposite directions. The transport equations for the two fluids are alternately solved in separate domains and then coupled at the interface by imposing mass, momentum, and energy jump conditions with phase change. The effects induced by changes in the interfacial shear were analyzed by comparing the relevant statistical flow properties. New scaling laws for the normalized heat transfer coefficient (HTC), K+, have been derived for both the steam and liquid phases. The steam-side law is found to compare with the passive-scalar law obtained hitherto by (Lakehal et al.(2003, “Direct Numerical Simulation of Turbulent Heat Transfer Across a Mobile, Sheared Gas-Liquid Interfaces,” ASME J. Heat Transfer, 125, pp. 1129–1139) in that HTC scales with Pr−3∕5. A close inspection of the transfer rates on the liquid side reveals a consistent relationship between K+, the local wave deformation or curvature and the interfacial shear stress. The surface divergence model of Banerjee et al. (2004, “Surface Divergence Models for Scalar Exchange Between Turbulent Streams,” Int. J. Multiphase Flow, 30(8), pp. 965–977) is found to apply in the liquid phase, too.
Thermophysical Properties of Biporous Heat Pipe Evaporators
Authors: Semenic Tadej , Lin Ying-Yu , Catton Ivan
Published: December 2008

Thirty biporous slugs with 3 different cluster diameters and 5 different particle diameters (15 combinations with 2 repetitions) and 12 monoporous slugs with 6 different particle diameters were sintered from spherical copper powder, and thermophysical properties were measured. The neck size ratio for all the particles was approximately 0.4. The porosity of monoporous samples was found to be independent of particle diameter and was equal to 0.28, and the porosity of biporous samples was found to be independent of cluster and particle diameters, and was equal to 0.64. The liquid permeability and maximum capillary pressure of small pores were found to be a linear function of the particle diameter. Similarly, vapor permeability was found to be a linear function of the cluster diameter. The thermal conductivity of monoporous samples was measured to be 142±3W∕mK at 42±2°C, and it was independent of particle diameter. The thermal conductivity of biporous samples was found to be a function of cluster to particle diameter ratio.
The Effects of Temperature Cyclic Loading on Lead-Free Solder Joints of Wafer Level Chip Scale Package by Taguchi Method
Authors: Jong Wen-Ren , Tsai Hsin-Chun , Chang Hsiu-Tao , Peng Shu-Hui
Published: December 2008

In this study, the effects of the temperature cyclic loading on three lead-free solder joints of 96.5Sn–3.5Ag, 95.5Sn–3.8Ag-0.7Cu, and 95.5Sn–3.9Ag-0.6Cu bumped wafer level chip scale package (WLCSP) on printed circuit board assemblies are investigated by Taguchi method. The orthogonal arrays of L16 is applied to examine the shear strain effects of solder joints under five temperature loading parameters of the temperature ramp rate, the high and low temperature dwells, and the dwell time of both high and low temperatures by means of three simulated analyses of creep, plastic, and plastic-creep behavior on the WLCSP assemblies. It is found that the temperature dwell is the most significant factor on the effects of shear strain range from these analyses. The effect of high temperature dwell on the shear strain range is larger than that of low temperature dwell in creep analysis, while the effect of high temperature dwell on the shear strain range is smaller than that of low temperature dwell in both plastic and plastic-creep analyses.
Investigation of Microporous Coatings and Mesoscale Evaporator Enhancements for Two-Phase Cooling of Electronic Components
Authors: Trautman Mark A. , Tirumala Murli , You S. M.
Published: December 2008

An empirical study of pool nucleate boiling enhanced with a microporous coating was conducted within the context of microprocessor cooling. A thermal test vehicle (TTV) emulated the heat load from a general purpose microprocessor and delivered a moderately nonuniform heat flux density distribution at the boiling surface that would be typical of mainstream microprocessors. The TTV was affixed to a copper test coupon that formed the bottom surface of a sealed boiling chamber containing FC-72 at atmospheric pressure. A design of experiments was conducted on multiple test coupons to identify how the microporous coating, the base thickness of the coupon, and the height of small pin fins affect the combined conduction and boiling heat transfer from the test coupon. The data revealed that the presence of the microporous coating was the most significant factor of the three tested and indicates that the presence of fins as short as 0.5mm may play a role in reducing hysteresis in the boiling curve.
Numerical and Experimental Analysis of Solder Joint Self-Alignment in Fiber Attachment Soldering
Authors: Zhang Wei , Wang Chunqing , Tian Yanhong
Published: December 2008

Fiber attachment soldering is low cost and high-precision technology in direct-coupling optoelectronic packaging. For accurate alignment, it is crucial to understand the self-alignment behavior of solder joint. In this research, the self-alignment method by using surface tension of molten solder and by adopting specific pad shape was proposed. First, the self-alignment model of solder joint in fiber attachment soldering was developed by using the public domain software called SURFACE EVOLVER and the three-dimensional geometry of solder joint with different solder volume was analyzed. Then, the self-alignment behavior of solder joint with an initial yaw misalignment was discussed and the theoretical equilibrium positions of ellipse and square pad were calculated. Next, based on the minimum potential energy theorem and data from geometry simulation, the influences of design and material parameters on the standoff height (SOH) were analyzed. Furthermore, experiments were done to examine the theoretical equilibrium positions of ellipse and square pad and the SOHs of solder joints were measured by using confocal scanning laser microscope. The numerical results show that the theoretical equilibrium positions of ellipse and square pad are the major axis of ellipse and the diagonal of square, respectively. SOH can be controlled by adopting proper solder volume, which is above the critical value for specific pad. The experimental results show that the solder joint with initial yaw angle can be self-aligned to the theoretical equilibrium position of pad and solder joint with ellipse pad substrate demonstrates smaller alignment error than those with square pad substrate. The measurement results of SOH are in agreement with the simulation results.
Analysis and Prediction of Vibration-Induced Solder Joint Failure for a Ceramic Column Grid Array Package
Authors: Perkins Andy , Sitaraman Suresh K.
Published: December 2008

Solder joint fatigue failure under vibration loading continues to be a concern in microelectronic industry. Existing literature has not adequately addressed high-cycle fatigue failure of high-lead solder joints, especially under a broad spectrum of vibration frequencies. Also, damage mapping across solder joints in an area-array package has not been effectively studied using numerical models and experimental cross sectioning. This paper aims to develop an experimental and modeling approach that can accurately determine the solder joint behavior of electronic components under vibration conditions. In particular, this paper discusses the out-of-plane sinusoidal vibration experiments at 1G, numerical modeling, and fatigue life prediction for a 42.5×42.5×4mm3 1089 input∕output ceramic column grid array (CCGA) package on a 133×56×2.8mm3 FR4 board. Detailed investigation and characterization involving dye-and-pry analysis, microstructural examination, and numerical modeling enabled the development of a high-cycle stress-based equation for lead-containing CCGA under sinusoidal loading. The developed approach has been applied to a number of cases including a CCGA package with a heat sink as well as a CCGA package subjected to frequency sweeps. It is seen that the predictions from the developed model agree well with experimental data and that the developed model can map the evolution of solder damage across all solder joints and can also provide important design recommendations in terms of solder joint location as well as heat sink attachment.
Advanced Thermal-Moisture Analogy Scheme for Anisothermal Moisture Diffusion Problem
Authors: Jang Changsoo , Park Seungbae , Han Bongtae , Yoon Samson
Published: December 2008

We propose an advanced thermal-moisture analogy scheme to cope with the inherent limitations of the existing analogy schemes. The new scheme is based on the experimentally observed unique hygroscopic behavior of polymeric materials used in microelectronics; i.e., the saturated concentration is only a function of relative humidity regardless of temperature. A new analogy formulation based on the modified solubility is presented and the scheme is implemented to investigate its accuracy and applicability. The results from a simple case study corroborate that the advanced scheme can be used effectively for package assemblies subjected to general anisothermal loading conditions.
Reliability of Fine Pitch Sn–3.8Ag–0.7Cu Flip Chip Solder Joints With Different Connection Pads on PCB
Authors: Li Dezhi , Liu Changqing , Conway Paul P.
Published: December 2008

The reliability of fine pitch Sn–3.8Ag–0.7Cu flip chip solder joints with three different pads, i.e., bare pads, pads with solder masks, and pads with microvia, on printed circuit boards (PCBs) was studied through thermal cycling. After assembly, (Au,Ni)Sn4 intermetallics (IMCs) formed both in the bulk solder and at the interfaces due to the immersion-Au finish on the PCB side. The (Au,Ni)Sn4 IMCs formed in the solder joints on the pads with microvia were more abundant than those formed in the solder joints on the pads without microvia. The results showed that the solder joints on the pads with a microvia had poor reliability due to the insufficient solder volume and the formation of large amounts of (Au,Ni)Sn4 IMCs. The main crack initiation position was the corner of solder joint at the chip side. For the pads with microvia, the main location of failure was at the (Au,Ni)Sn4/solder interface on the chip side, and for the solder joints on bare pads and pads with solder mask, the possible failure location was in the bulk solder.
Boiling of Water at Subatmospheric Conditions With Enhanced Structures: Effect of Liquid Fill Volume
Authors: Pal Aniruddha , Joshi Yogendra
Published: December 2008

Liquid cooling with phase change has been demonstrated to be a very efficient technique for thermal management of electronics because it has the potential to achieve high heat transfer coefficients compared to single phase liquid cooling. Previous studies on liquid immersion cooling with fluorocarbons have shown the effectiveness of boiling enhancement structures in lowering boiling incipience, raising the critical heat flux, and reducing evaporator size. Two-phase thermosyphons are an alternative to liquid immersion cooling, where phase change liquid cooling can be implemented within a closed-loop device. The present study involves a two-phase thermosyphon with boiling enhancement structure in the evaporator, which is subjected to subatmospheric pressures for lowering the saturation temperature of the working fluid. The objective of the present research is to provide a detailed understanding of the effect of liquid-fill level on boiling of water with enhancement structures at subatmospheric pressures. The study will take into account the influence of system pressure and enhancement structure geometry on the boiling heat transfer. Experiments were performed at three different pressures, 9.7kPa, 15kPa, and 21kPa, using a stacked enhancement structure with three different geometries (one, four, and six layers), corresponding to three different liquid-fill levels (fill ratios of 0.5, 0.7, and 0.9). The results are compared with a base line study on subatmospheric pressure boiling from a plain surface at similar liquid-fill levels.
Enhancement of Cooling Characteristics for Electronic Cooling by Modifying Substrate Under Natural Convection
Authors: Tseng Yung-Shin , Hung Tzu-Chen , Pei Bau-Shei
Published: December 2008

In this study, a computational fluid dynamics model has been developed to explain and validate the experimental results originating from the concept of a substrate with an opening. It is found that the openings will interrupt the growth of the boundary layer on substrate surfaces and hence improve the cooling ability of a module without any additional active parts. Furthermore, the concept of openings has not only so far provided at least 12% improvement in heat transfer, but also reduced some difficulties in finding thermal solution, such as the manufacturing cost and the design freedom. More importantly, this study has provided a further step in the direction of demonstrating the opening effect.
Stability Analysis of TLP Tethers Under Vortex-Induced Oscillations
Authors: Banik A. K. , Datta T. K.
Published: December 2008

The vortex-induced oscillation of TLP tether is investigated in the vicinity of lock-in condition. The vortex shedding is caused purely due to current, which may vary across the depth of the sea. The vibration of TLP is modeled as a SDOF problem by assuming that the first mode response of the tether dominates the motion. Nonlinearity in the equation of motion is produced due to the relative velocity squared drag force. In order to trace different branches of the response curve and investigate different instability phenomena that may exist, an arc-length continuation technique along with the incremental harmonic balance method (IHBC) is employed. A procedure for treating the nonlinear term using distribution theory is presented so that the equation of motion is transformed to a form amenable to the application of IHBC. The stability of the solution is investigated by the Floquet theory using Hsu’s scheme.
Application of Constrained Multi-Objective Optimization to the Design
of Offshore Structure Hulls
Authors: Birk Lothar
Published: December 2008

The paper reports on the continuous development of an automated optimization procedure for the design of offshore structure hulls. Advanced parametric design algorithms, numerical analysis of wave-body interaction, and formal multi-objective optimization are integrated into a computer aided design system that produces hull shapes with superior seakeeping qualities. By allowing multiple objectives in the procedure naval architects may pursue concurrent design objectives, e.g., minimizing heave motion while simultaneously maximizing deck load. The system develops a Pareto frontier of the best design alternatives for the user to choose from. Constraints are directly considered within the optimization algorithm, thus eliminating infeasible or unfit designs. The paper summarizes the new developments in the shape generation, illustrates the optimization procedure, and presents results of the multi-objective hull shape optimization.
A Hybrid Model to Predict the Onset of Gas Entrainment With Surface Tension Effects
Authors: Saleh W. , Bowden R. C. , Hassan I. G. , Kadem L.
Published: December 2008

The onset of gas entrainment in a single downward discharge, from a stratified gas-liquid region, was modeled. The discharge was modeled as a point-sink and Kelvin–Laplace’s equation was used to incorporate surface tension effects. Consequently, a criterion to characterize the dip radius of curvature, at the onset of gas entrainment, was required. The dip geometry was experimentally investigated and a correlation was developed relating the dip radius of curvature to the discharge Froude number. The correlation was used in conjunction with the theoretical model. It was found that the predicted critical height demonstrated good agreement with experimental data with the three-dimensional point-sink approach, while poor agreement using the two-dimensional finite-branch approach was found. The inclusion of surface tension improved the model’s capability to predict the critical height, particularly at discharge Froude numbers below 1.
The VIVACE Converter: Model Tests at High Damping and Reynolds Number Around 105
Authors: Bernitsas Michael M. , Ben-Simon Y. , Raghavan Kamaldev , Garcia E. M. H.
Published: December 2008

The vortex induced vibrations for aquatic clean energy (VIVACE) converter is a new concept to generate clean and renewable energy from fluid flows such as those abundant in oceans, rivers, or other water resources. The underlying concepts for design, scaling, and operation of VIVACE were introduced in Bernitsas et al., 2008, “VIVACE (Vortex Induced Vibration Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy From Fluid Flow,” ASME J. Offshore Mech. Arct. Eng., 130(4), p. 041101. In its simplest form, a VIVACE modulo consists of a single rigid cylinder mounted on elastic supports and connected to a power takeoff (PTO) system. The cylinder is placed in a steady unidirectional current and excited in vortex induced vibration (VIV). In this paper, the VIVACE modulo was tested in the Low Turbulence Free-Surface Water Channel of the University of Michigan to demonstrate the concept, generate electricity, measure the power out, and calculate basic benchmarking measures such as energy density. The tests performed were tailored to the particulars of the VIVACE modulo, which dictate that the cylinder operate in VIV under high damping and as high a Reynolds number as possible. At the same time, a broad range of synchronization is required to make VIVACE effective in energy generation in a realistic environment. Due to these requirements, VIV tests have not been performed before in the subspace applicable to the operation of the VIVACE modulo. In the process of extracting fluid kinetic energy and converting it to electricity in the laboratory, for a given set of cylinder-springs-transmission-generator, only the damping used for harnessing electricity was optimized. Even at this early stage of development, for the tested VIVACE modulo, the maximum peak power achieved was Ppeak=0.308×12ρDLL. The corresponding integrated power in that particular test was PVIVACE=0.22×12ρU3DL with theoretical upper limit based on measurements of PUL–VIVACE=0.3663. Such power was achieved at velocity U=0.840m∕s=1.63Kn.
Risk Based Structural Integrity Management of Marine Platforms Using Bayesian Probabilistic Nets
Authors: Montes-Iturrizaga Roberto , Heredia-Zavoni Ernesto , Vargas-Rodríguez Francisco , Faber Michael Havbro , Straub Daniel , de Dios de la O Juan
Published: December 2008

The present paper introduces a general framework for integrity management of offshore steel jacket structures allowing for the risk based planning of inspections and maintenance activities with a joint consideration of various relevant deterioration and damage processes. The suggested approach relates the relevant deterioration and damage processes to damage states, which in turn may be related to the overall integrity of the jacket structural system as measured through the reserve strength ratio. Each state of degradation, irrespective of the cause, can then be assessed in terms of their impact on the annual probability of failure for the structure. Based on data and subjective information regarding the annual probabilities of occurrence of the relevant deterioration and damage processes, together with a probabilistic modeling of the quality of condition control, it is possible to assess the structural effect of each type of deterioration and damage phenomenon. This facilitates the development of a general framework for risk based integrity management. In the present work such a framework is formulated using Bayesian probabilistic networks for evaluating the time varying global structural reliability of jackets subject to progressive deterioration of its members due to the combined effect of different sources of damage. In principle, system effects, i.e., the effect of damage in one element of the structural system on the capacity of other elements, can also be accounted for through a Bayesian probabilistic net; however, this is not considered in this work.
Time-Domain Hydroelastic Analysis of a Flexible Marine Structure Using State-Space Models
Authors: Taghipour Reza , Perez Tristan , Moan Torgeir
Published: December 2008

This article deals with time-domain hydroelastic analysis of a marine structure. The convolution terms associated with fluid memory effects are replaced by an alternative state-space representation, the parameters of which are obtained by using realization theory. The mathematical model established is validated by comparison to experimental results of a very flexible barge. Two types of time-domain simulations are performed: dynamic response of the initially inert structure to incident regular waves and transient response of the structure after it is released from a displaced condition in still water. The accuracy and the efficiency of the simulations based on the state-space model representations are compared to those that integrate the convolutions.
PIV Investigation of Flow Behind Surface Mounted Detached Square Cylinder
Authors: Panigrahi P. K.
Published: December 2008

The flow field behind surface mounted detached square ribs under the approaching flat plate turbulent boundary layer has been experimentally studied using the particle image velocimetry (PIV) (two-component and stereo) technique in both streamwise and cross stream measurement planes. An oil film visualization study has been carried out for correlating the surface flow patterns to the flow structures. The Reynolds number based on the rib height is equal to 11,075. The ratio of the gap height to the square rib size is set equal to 0.2, 0.37, 0.57, and 1.0. The ratio of approaching boundary layer thickness to rib height is equal to 0.2. The mean and rms velocity fields, streamwise and spanwise vorticity fields, velocity gradient and velocity vector fields, turbulent kinetic energy budgets, and stream trace results are reported. The second invariant of the velocity gradient tensor results are presented to distinguish between the rotational and shear contribution of the vorticity field. The recirculation bubbles with a focilike structure are observed behind the detached ribs. These structures are displaced upward, i.e., away from the wall surface with an increase in gap size of the detached cylinder. The size of the recirculation bubble also drops with an increase in the gap size. The stream traces in the cross stream plane show node-saddle patterns, whose near wall concentration is high for a lower gap size detached cylinder. The oil film visualization images show saddle patterns at the meeting point between the flow through the gap and the reattaching shear layer for the lower gap size detached cylinder. The v-velocity magnitude distribution shows greater wall-normal motion across the wake for the detached cylinder of lower gap size. There is a significant near wall velocity fluctuation for the lower gap size detached cylinder. The higher velocity fluctuation due to the near wall flow structures contributes toward an increase in the near wall mixing of a detached cylinder geometry. Overall, the present study clearly demonstrates the flow structures behind detached ribs, which are responsible for effective near wall mixing. The results from this study provide useful understanding for the design of turbulators in various practical applications.
Aero-Acoustic Coupling Inside Large Deep Cavities at Low-Subsonic Speeds
Authors: El Hassan Mouhammad , Keirsbulck Laurent , Labraga Larbi
Published: December 2008

Aero-acoustic coupling inside a deep cavity is present in many industrial processes. This investigation focuses on the pressure amplitude response, within two deep cavities characterized by their length over depth ratios (L/H=0.2 and 0.41), as a function of freestream velocities of a 2×2m2 wind tunnel. Convection velocity of instabilities was measured along the shear layer, using velocity cross-correlations. Experiments have shown that in deep cavity for low Mach numbers, oscillations of discrete frequencies can be produced. These oscillations appear when the freestream velocity becomes higher than a minimum value. Oscillations start at L/θ0=10 and 21 for L/H=0.2 and 0.41, respectively. The highest sound pressure level inside a deep cavity is localized at the cavity floor. A quite different behavior of the convection velocity was observed between oscillating and nonoscillating shear-layer modes. The hydrodynamic mode of the cavity shear layer is well predicted by the Rossiter model (1964, “Wind Tunnel Experiments on the Flow Over Rectangular Cavities at Subsonic and Transonic Speeds,” Aeronautical Research Council Reports and Memo No. 3438) when measured convection velocity is used and the empirical time delay is neglected. For L/H=0.2, only the first Rossiter mode is present. For L/H=0.41, both the first and the second modes are detected with the second mode being the strongest.
Break-Up Length and Spreading Angle of Liquid Sheets Formed by Splash Plate Nozzles
Authors: Ahmed M. , Ashgriz N. , Tran H. N.
Published: December 2008

An experimental investigation is conducted to determine the effect of liquid viscosity and density, nozzle diameter, and flow velocity on the break-up length and spreading angle of liquid sheets formed by splash plate nozzles. Various mixtures of corn syrup and water were used to obtain viscosities in the range of 1–170 mPa s. Four different splash plate nozzle diameters of 0.5 mm, 0.75 mm, 1 mm, and 2 mm, with a constant plate angle of 55 deg were tested. The liquid sheet angles and the break-up lengths were measured at various operating conditions. An empirical correlation for the sheet spreading angle and a semi-empirical correlation for the sheet break-up lengths are developed.
Liquid Taylor Bubbles Rising in a Vertical Column of a Heavier Liquid: An Approximate Analysis
Authors: Mandal T. K. , Das G. , Das P. K.
Published: December 2008

It has been noted that a volume of lighter liquid when injected into a stationary column of a heavier liquid, it rises up as a simple elongated Taylor bubble. In the present study, experimental and theoretical analyses have been performed to understand the rise of liquid Taylor bubbles. The experiments have been performed with different liquid pairs with their viscosities ranging from 0.71mPas to 1.75mPas and conduit sizes ranging from 0.012 m to 0.0461 m. The bubble shape has been predicted using a potential flow analysis and validated from photographic measurements. This analysis has been further modified to predict the rise velocity. The modified analysis accounts for the density difference between the two liquids, viscosity effects of the primary liquid, and interfacial tension of two fluids. A semi-empirical equation has been developed, which gives satisfactory results for most of the cases.
Frequency domain characterization of the vibrations of a tuning fork by vision and digital image processing
Authors: Sandoz P. , Carry É. , Friedt J.-M. , Trolard B. , Reyes J. Garzon
Published: December 2008

We demonstrate an experimental setup and associated digital image processing software for measuring the vibrational amplitude of a tuning fork with subpixel accuracy. Stroboscopic illumination allows the use of a standard video camera to explore the resonant frequencies up to the kHz range. No preliminary surface patterning is required because the image processing is based on features present in the object’s structure. Because the tuning fork is a high quality-factor resonator, it can be used for demonstrating the spectral power distribution of various excitation signals and the temperature dependence of the resonance frequency. The procedure can be generalized to the measurement of the in-plane lateral displacements of any structure.
Consequences of a generalized law of the lever
Authors: Assis A. K. T. , Ravanelli F. M. d. M.
Published: December 2008

We discuss the controversy about the demonstration of the law of the lever as given by Archimedes. One aspect of the discussion concentrates on the meaning of the postulates which he utilized. We analyze what consequences would arise if nature behaved in such a way that the lever followed a generalized power law. In particular, we consider the cases of a torque independent of the distances of the bodies to the fulcrum, proportional to these distances, and quadratic in the distances.
Construction and testing of a replica of Einstein’s “little machine”
Authors: Segers Danny , Wautier Kristel , Uyttenhove Jos
Published: December 2008

Einstein developed his “little machine” to measure small electrical charges, but there are no publications that describe measurements done with this apparatus. We report on our construction of a replica of the little machine and on our tests of its performance.
Multipole radiation fields from the Jefimenko equation for the magnetic field and the Panofsky-Phillips equation for the electric field
Authors: de Melo e Souza R. , Cougo-Pinto M. V. , Farina C. , Moriconi M.
Published: December 2008

We show how to obtain the first multipole contributions to the electromagnetic radiation emitted by an arbitrary localized source directly from the Jefimenko equation for the magnetic field and the Panofsky-Phillips equation for the electric field. This procedure avoids the unnecessary calculation of the electromagnetic potentials.
Bounds on the ground state energy: Application of the variational principle
Authors: Bhattacharyya Bibhas
Published: December 2008

The variational principle is revisited in the context of finding the upper and lower bounds to the ground state energy. It is shown how the variational principle can be employed to find the lower bound by partitioning the Hamiltonian into several parts. We demonstrate how the variational principle can be used to find the exact ground states in some special cases. We consider the harmonic oscillator and the Ising Hamiltonian on a bipartite lattice which are familiar yet instructive examples for students.
Increased frequency of chromosome translocations in airline pilots with long-term flying experience
Authors: Yong L C , Sigurdson A J , Ward E M , Waters M A , Whelan E A , Petersen M R , Bhatti P , Ramsey M J , Ron E , Tucker J D
Published: December 2008

Background:

Chromosome translocations are an established biomarker of cumulative exposure to external ionising radiation. Airline pilots are exposed to cosmic ionising radiation, but few flight crew studies have examined translocations in relation to flight experience.

Methods:

We determined the frequency of translocations in the peripheral blood lymphocytes of 83 airline pilots and 50 comparison subjects (mean age 47 and 46 years, respectively). Translocations were scored in an average of 1039 cell equivalents (CE) per subject using fluorescence in situ hybridisation (FISH) whole chromosome painting and expressed per 100 CE. Negative binomial regression models were used to assess the relationship between translocation frequency and exposure status and flight years, adjusting for age, diagnosticxray procedures, and military flying.

Results:

There was no significant difference in the adjusted mean translocation frequency of pilots and comparison subjects (0.37 (SE 0.04) vs 0.38 (SE 0.06) translocations/100 CE, respectively). However, among pilots, the adjusted translocation frequency was significantly associated with flight years (p = 0.01) with rate ratios of 1.06 (95% CI 1.01 to 1.11) and 1.81 (95% CI 1.16 to 2.82) for a 1- and 10-year incremental increase in flight years, respectively. The adjusted rate ratio for pilots in the highest compared to the lowest quartile of flight years was 2.59 (95% CI 1.26 to 5.33).

Conclusions:

Our data suggests that pilots with long-term flying experience may be exposed to biologically significant doses of ionising radiation. Epidemiological studies with longer follow-up of larger cohorts of pilots with a wide range of radiation exposure levels are needed to clarify the relationship between cosmic radiation exposure and cancer risk.
The protocontinental nature and regional variability of the Central Metasedimentary Belt of the Grenville Province: lead isotope evidence
Authors: Fletcher I. R. , Farquhar R. M.
Published: December 2008

The lead isotopic compositions of sulphide samples (mainly galenas) from a representative set of mineral deposits within the Central Metasedimentary Belt of the Grenville Province have been determined by high-precision solid-source mass spectrometry. Data for 13 sites of Proterozoic age (including Tétrault mine, which lies outside the belt) reveal an isotopic fine structure that can be correlated with the various geological and regional groupings of the deposits. In particular, sulphides in the Balmat–Edwards mining district are seen to be isotopically atypical of Central Metasedimentary Belt Pb–Zn mineralizations, and those in the Mont Laurier Basin are distinct from those in the Hastings Basin. Collectively, the data suggest that the lead in the sulphides was derived from an environment with the relatively low U/Pb characteristics of oceanic mantle, and therefore that the Central Metasedimentary Belt is a segment of "proto-crust" formed at approximately 1.3–1.0 Ga. This precludes its derivation from older segments of the Canadian Shield. Leads in ores of the Balmat–Edwards district, however, seem to be derived at least partly from sources of a more continental character.Galenas from 11 post-Ordovician fissure veins define a secondary isochron that shows the Grenville basement to be the only likely source of the vein lead. The slope of the isochron indicates that the radiogenic component of the lead in the veins could not have been derived from the uraniferous deposits dated at 970–950 Ma by Fowler and Doig (1979). The isotopic variations in the vein galenas are thought to reflect a general uniformity of Th/Pb and variability of U/Pb in the Grenville gneisses.
Zircon U–Pb ages from the Wabigoon–Manitou Lakes region, Wabigoon Subprovince, northwest Ontario
Authors: Davis D. W. , Blackburn C. E. , Krogh T. E.
Published: December 2008

Three distinct stratigraphic units have been recognized in the Crow Lake – Savant Lake belt. These are a basal unit consisting of high magnesium tholeiitic flows, a middle unit consisting mostly of tholeiitic to calc-alkaline pyroclastic rocks and flows, and an upper unit of high iron tholeiitic flows.A zircon U–Pb study has been carried out on seven rocks from the Wabigoon–Manitou Lakes region of this belt. In the Manitou Lakes area, a minimum age of 2755 Ma on a porphyry pluton intruded into the Wapageisi Volcanics gives a minimum age for the high magnesium tholeiitic sequence.A trondhjemite phase of the Atikwa batholith near Wabigoon Lake that is dated at 2732.2 ± 2.9 Ma has the same age within experimental error as a rhyolite flow from the Lower Wabigoon Volcanics in the same area that is dated at [Formula: see text]. However, a trondhjemite phase of the Atikwa batholith at Eagle Lake that is dated at [Formula: see text] is distinctly younger than a dacite flow collected nearby from the Lower Wabigoon Volcanics that is dated at [Formula: see text]. Both these volcanic rocks are from the middle mixed sequence.A rhyolite tuff from the Boyer Lake Volcanics, from the upper high iron tholeiitic sequence, gives a relatively young age of [Formula: see text]. An age of 2695 ± 3.6 Ma on the post-tectonic Taylor Lake stock gives a minimum age for the end of deformation.Several new techniques such as air abrasion with pyrite, crushing and abrasion, and high gradient magnetic separation have been employed to reduce the discordance of zircons. Of these, the air abrasion technique has proven to be the most effective.
Depositional mechanisms of deep-sea coarse clastic sediments, Cap Enragé Formation, Quebec
Authors: Hein Frances J.
Published: December 2008

Cambro-Ordovician Cap Enragé deep-sea sediments consist of six main facies: (1) coarse conglomerates; (2) graded–stratified/cross-bedded fine conglomerates; (3) dispersed pebbly sandstones; (4) liquefied pebbly sandstones; (5) ungraded cross-bedded fine conglomerate and pebbly sandstones; (6) massive sandstones.Facies 1 and coarser parts of facies 2 beds have unimodal grain orientations in bedding, with unimodal a-axis imbrications. Finer facies 2 beds have unimodal or bimodal grain orientations in bedding, with bimodal (up- and downstream) a-axis imbrications. Facies 3, 4, and 6 beds have unimodal, bimodal, or random grain orientations in bedding. The a-axis imbrications vary as follows: mainly bimodal for facies 3, bimodal or unimodal for facies 4, and dominantly unimodal for facies 6.Facies 5 beds result from fractional reworking of previous deposits by strong bottom currents (velocities 70–125 cm/s) (? dilute spillover flows). All other facies were deposited mostly from concentrated clast dispersions at bases of large turbidity currents. Calculations show basal dispersions range from 15 to 27 cm thick beneath turbidity currents 100 m thick for facies 3 and facies 1 beds. Finer facies 2 beds had fractional phases, with maximum velocities 140–146 or 71–78 cm/s (depending on friction factors) for graded trough cross-bedded types. Facies 3, 4, and 6 basal dispersions had high apparent viscosities; for facies 1 and 2, inertial effects dominated. Syn- or early post-depositional deformation or liquefaction produced bimodal imbrications for facies 3, 4, and 6, and liquefaction structures in facies 4.
Thermal diagenesis in the Swiss molasse basin: implications for oil generation
Authors: Monnier F.
Published: December 2008

Clay mineral transformations during burial are indicators of the degree of diagenesis of sediments. Diagenetic zonations in numerous wells of the Swiss molasse basin are defined by the disappearance of smectite and (or) the appearance of either corrensite or irregular 2:1 mixed layers. The maximum level attained in the thickest molasse sections corresponds to organic matter maturation suitable for hydrocarbon generation. Reconstructed on the basis of the clay mineral transformation data, a burial history of the basin is proposed.
New data on Late Silurian and Early Devonian brachiopods from the Royal Greek area, Yukon Territory
Authors: Lenz Alfred C.
Published: December 2008

Late Silurian and Early Devonian brachiopod species are listed from two new sections in the Royal Creek area, Yukon. The data from these sections fill in knowledge of the biostratigraphy of brachiopods of Late Silurian (Ludlovian and Pridolian) and, more importantly, of early Zlichovian (late Early Devonian) ages, of the northern Cordillera.Thirteen species of brachiopods are described in this study, five (none new) from the Late Silurian, and eight from the early Zlichovian (late Early Devonian), of which species of Phragmostrophia, Linguopugnoides, Vagrania, ?Salairina, and Metaplasia are probably new, but have not been given formal species names.
A field technique to directly measure river bank erosion
Authors: Hudson H. R.
Published: December 2008

Presently used techniques were found to be unsuitable in monitoring intermediate rates of river bank erosion. Sequential bank profiling from a fixed baseline using a stadia rod for vertical control and another stadia rod, Brunton compass, and metre rule for horizontal control provides a rapid, accurate representation of river bank changes, using inexpensive, readily available equipment.
Filter testing of broadly graded cohesionless tills
Authors: Lafleur Jean
Published: December 2008

Filter criteria have generally been checked experimentally with relatively uniform bases (protected soils). However, these criteria may not be applicable when nonuniform soils are used, especially broadly graded cohesionless tills with nonlinear grain size curves. Such soils were extensively used at the James Bay project as impervious core material, and a testing programme was undertaken to establish the margin of safety associated with the application of current filter criteria: the design was based on the arbitrarily defined portion of the base soil grain size curve. Also, a more general objective of the programme was to assess the role that self-filtration plays in the filtration process of such broadly graded cohesionless soils.This paper presents and discusses the factors that have been found relevant in the development of a representative laboratory simulation of the complex filtration phenomenon; namely, maximum particle size, density, saturation of the samples, direction of flow, intensity of the gradients, and development of hydraulic fracturing. Some preliminary test results are given for a till from the LG-3 dam that showed a marked bend in the grain size curve at [Formula: see text]. It is seen that particles coarser than this size do not significantly influence the self-filtration process. Finally, the test results demonstrate that the filters specified for the LG-3 project are more than adequate. Key words: earth dam, filtration, broadly graded cohesionless soils, internal erosion, laboratory tests, design.