bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure Analysis of Miniature Solder Specimen
Authors: Wei Y. , Chow C. L. , Fang H. E. , Neilsen M. K. , Lim T. J. , Lu W.
Published: November 2021

The effects of specimen geometry size on the behavior of 63Sn-37Pb solder are investigated both experimentally in the laboratory and analytically with finite-element simulations. The simulations are achieved by developing a constitutive model for solder which couples viscoplasticity with a unified damage theory. The unified damage theory is characterized by a damage surface in strain space which separates fatigue damage from inelastic damage. The damage evolution equations are derived within the framework of irreversible thermodynamics. A series of uniaxial tension, tensile creep, and strain-controlled fatigue experiments are performed to obtain material parameters for the solder damage model. The solder damage model is then implemented into a finite element code and used to simulate a uniaxial tension test on a miniature specimen and on a standard ASTM specimen (ASTM standards, 1999). Predictions from these simulations are then compared with each other and with experimental results in order to examine specimen size effects.
High Digital Speed Level-2 Interconnections via a New Microcontact Design
Authors: Pryputniewicz Dariusz R. , Grabbe Dimitry G. , Pryputniewicz Ryszard J.
Published: November 2021

Requirements for high digital speed, high density, level-2 interconnections have led to development of a new microcontact. Design of this microcontact allows for separable and reusable interconnections. In this paper, we discuss methodology used to develop the microcontact, allowing 100% material utilization, present its design, including analysis and process optimization, and summarize its characteristics as they relate to electronic packaging.
Selection of Method for Fatigue Life Prediction Under Random Loading
Authors: Awasthi Amit , Mckeown Stephen , Sahay C. , Sammakia Bahgat
Published: November 2021

Solder fatigue continues to be one the primary reliability concerns in electronic packages. Three basic factors are necessary to cause fatigue failure. These are (i) a stress of sufficiently high value, (ii) varying amplitude stress, and (iii) a number of cycles of applied stress. Fatigue failure of a solder joint may also occur under cyclic thermal loading. The goal of this project is to compare the experimental results of fatigue testing with the various theoretical approaches (Rainflow counting method, Steinberg’s 3 band approach, and Rayleigh’s method) and come up with a formulation that would predict solder fatigue failure under random vibration loading.

Experiments have been performed to collect data. Initially various components having frequency range from 20–2000Hz were combined at random phase to produce a random profile. Rainflow cycle counting was done on 125 random profiles using an algorithm developed by downing (1982). The basic assumption made in this algorithm is that the strain-time history starts with either the maximum peak or the minimum valley. Further each cycle was segregated into one of the three bands depending on the value of the range of the cycle. It was found that the results matched very closely with Gaussian distribution curve.

The first phase of testing was to observe the behavior of aluminum and soldered copper (forming a lap joint) specimens under completely reversed sinusoidal loading in order to evaluate S-N curve. Three different stress levels were chosen and all experiments were carried out at a frequency of 20Hz. The second phase of testing consisted of observing the behavior of both the samples under semi-random loading. Random waveform was generated through a waveform function generator and was externally fed to the MTS machine.

The present paper presents the result of experiments along with the applicability to the three approaches to prediction.
Power Consumption of Polymer Solutions in a Stirred Vessel Powered by an Hyperboloid Impeller
Authors: Cavadas Adélio S. , Pinho Fernando T.
Published: November 2021

Measurements of power consumption in stirred vessel flows powered by a Rushton and an hyperboloid impeller were carried out. The fluids were aqueous solutions of tylose, CMC and xanthan gum at weight concentrations ranging from 0.1% to 0.6% and also included Newtonian fluids.

For the Rushton turbine flows the addition of polymer increased the Newton number by about 13–20% at Reynolds numbers in the range 1,000–3,000, whereas with the hyperboloid impeller the Newton number decreased about 13%. This decrease was especially noticeable for the CMC solutions and was absent from the 0.2% tylose solution flow.

Concentrated aqueous solutions of CMC (5.2%) and XG (3.6%) were also produced to determine the characteristic impeller parameter k for the hyperboloid, following the procedure of Metzner and Otto (1957) which was found to be 48 ±16.
Validation of Rheological Equations for Lubrication by Dynamic Experiments
Authors: Harnoy Avraham
Published: November 2021

Steady state experiments for determining the rheological characteristics of various non-Newtonian fluids. In particular, shear flow experiments, between cone and plate, are widely used for this purpose. In this study, it is shown that steady state experiments are not sufficient and dynamic (time dependent) experiments must be also conducted to uncover all the rheological characteristics. A squeeze-film flow between two parallel disks is shown to be a simple dynamic experiment that is suitable for viscoelastic fluids. This experiment can be used for validating of rheological constitutive equations of non-Newtonian fluids.
Decomposed EPS Gases Pressure Measurements in Iron Lost Foam Casting Process
Authors: Liu Ying , Bakhtiyarov Sayavur I. , Overfelt Ruel A.
Published: November 2021

A computer-aided temperature and pressure measurement technique has been built to study the thermal and pressure related processes during lost foam casting. The behavior of the gas pressure from the decomposed styrofoam pattern by-products inside both the mold and pattern during casting of ductile iron was investigated experimentally for coated and non-coated patterns. A transient history of temperature and pressure fluctuations is presented during the filling and freezing of the casting. The size of the pattern decomposition zone at the liquid metal/foam interface is estimated using the experimental data.
Experimental Study of EPS Decomposition in Lost Foam Casting Process
Authors: Liu Ying , Bakhtiyarov Sayavur I. , Overfelt Ruel A.
Published: November 2021

The thermal degradation of bulk and miniature samples of expanded polystyrene (EPS) has been investigated in a neutral atmosphere at 800°C and by differential scanning calorimetry over a range of temperatures. The differential scanning calorimetry experiments showed that the foam volatilization temperature is significantly affected by heating rate and varies from 380°C to 470°C at heating rates from 10–60°C/min. Bulk degradation due to the 800°C heat source appeared to occur instantly as the foam pattern approached the close proximity of the heat source. The chamber pressure increased and the heat source temperature dropped during degradation. The gas yield at 800°C was determined to be about 610 cm3 (STP)/g of EPS.
Gas Displacement of Non Newtonian Fluids in a Tube
Authors: Soares Edson J. , Mendes Paulo R. Souza , Carvalho Marcio S.
Published: November 2021

The displacement of a fluid in a capillary tube by gas injection occurs in many practical applications like enhanced oil recovery, coating of catalytic converters and gas-assisted injection molding. This situation has been extensively studied both by theory and experiments in the case of Newtonian fluids. However, the complete understanding of the effects of the rheological properties of the displaced fluid in this type of flow is still under investigation. Recent work has shown that, at a given Capillary number, the amount of shear thinning liquid deposited on the tube wall falls with decreasing power-law exponent, but a singular perturbation method was not able to capture this effect. The flow of viscoelastic liquids has also been analyzed experimentally by measuring the fractional coverage of the tube wall and by Particle Tracking Velocimetry. The main conclusion was that the flow near the interface presents strong extensional deformation and that the viscoelastic behavior of the liquid leads to larger deposited liquid layer on the wall. Flow simulation with non Newtonian liquids for this situation is rare. The presence of the free surface and the non linearities of the constitutive model make the problem extremely complex. In this work, the complete two dimensional solution of the free surface flow is obtained using the Galerkin finite element method. The rheological character of the liquid is modelled by two different constitutive equations: a simple Generalized Newtonian Liquid model, to analyze the effect of shear sensitive liquids; and a new algebraic constitutive relation that is capable of describing variable shear and extensional viscosity, first normal stress coefficient and second normal stress coefficient. This equation is used to analyze the effect of the viscoelastic properties of the liquid on the flow field.
Non-Linear Lubricant Behavior in Concentrated Contacts
Authors: Szeri Andras Z.
Published: November 2021

Elastohydrodynamic lubrication (EHL) is the name given to hydrodynamic lubrication when it is applied to solid surfaces of low geometric conformity (counterformal contacts) that are capable of, and are subject to, elastic deformation. In bearings relying on EHL principles, the residence time of the fluid is less than 1 ms, the pressures are up to 4 GP, the film is thin, down to 0.1 μm, and shear rates are up to 108 s−1 — under such conditions lubricants exhibit material behavior that is distinctly different from their behavior in bulk at normal temperature and pressure. In fact, without taking into account the viscosity-pressure characteristics of the liquid lubricant and the elastic deformation of the bounding solids, hydrodynamic theory is unable to explain the existence of continuous lubricant films in highly loaded gears and rolling contact bearings.
Pressure Drop of Liquid Crystal Flowing Between Two Parallel-Plate Electrodes
Authors: Tsukiji Tetsuhiro , Tanabe Shinsuke
Published: November 2021

Liquid crystal is one of homogeneous ER (Electrorheological) fluids in some range of temperature. Transient responses of pressure drop are examined when liquid crystal flows between two parallel-plate electrodes for constant flow rates. When voltages are applied on the liquid crystal and removed, the pressure responses of the inlet of electrodes are measured with the pressure transducer. At the same time, liquid crystal between the transparent electrodes made of glass is visualized with the high-speed video camera to investigate the time history of the director of the liquid crystal. Outlet of the flow channel with two parallel-plate electrodes is atmosphere. Relation between the flow visualization results and changes of pressure drop is investigated especially for transient period. In the present experiment the flow rates change from 0.001cc/sec (velocity is 1mm/sec) to 0.003cc/sec and the electric field intensity is from 0.2kV/mm to 1kV/mm. The gap of the electrodes is 0.2mm. The isotropic-nematic transition is 35.5°C and smectic-nematic transition is 23.1°C. The open-loop test facility with the liquid crystal is set in a pyrostat to keep the temperature constant.
The Yield Stress for an Electrorheological Fluid in Squeeze
Authors: El Wahed Ali K. , Sproston John L.
Published: November 2021

This paper is concerned with an experimental and theoretical determination of the rheological performance of an electrorhcological (ER) fluid when subjected to time-dependent applied loads. The experimental facility was built as a squeeze cell in which the fluid is sandwiched between two electrodes, one fixed and the other moving, which permits the instantaneous measurement of the mechanical and electrical responses of the fluid. The transient rheological characteristics of the fluid were assessed for various mechanical force levels and for constant voltage excitation of the fluid. Input and output stress levels across the fluid were monitored enabling the dynamic response of the fluid to be determined using a combination of displacement, force, velocity and acceleration transducers. The experimental results were compared with the results from a modified theoretical analysis, which employs a bi-viscous shear stress/shear strain characteristic of the electrically stressed fluid together with a fluid yield stress, which has a strain-direction dependence on the electrical field.
A Topological Study of the Genesis of a Horseshoe Vortex in the Symmetry Plane Due to an Adverse Pressure Gradient
Authors: van den Berg Martijn A. , Proot Michael M. J. , Bakker Peter G.
Published: November 2021

The present paper describes the genesis of a horseshoe vortex in the symmetry plane in front of a juncture. In contrast to a previous topological investigation, the presence of the obstacle is no longer physically modelled. Instead, the pressure gradient, induced by the obstacle, has been used to represent its influence. Consequently, the results of this investigation can be applied to any symmetrical flow above a flat plate.

The genesis of the vortical structure is analysed by using the theory of nonlinear differential equations and the bifurcation theory. In particular, the genesis of a horseshoe vortex can be described by the unfolding of the degenerate singularity resulting from a Jordan Normal Form with three vanishing eigenvalues and one linear term which is related to the adverse pressure gradient. The examination of this nonlinear dynamical system reveals that a horseshoe vortex emanates from a non-separating flow through two subsequent saddle-node bifurcations in different directions and the transition of a node into a focus located in the flow field.
Flow Through a Realistic Arterial Geometry With Two Aneurysms: Mixing Characteristics and Residence Times
Authors: Butty V. D. , Gudjonsson K. , Buchel P. , Makhijani V. B. , Ventikos Y. , Poulikakos D.
Published: November 2021

In the present work, we are presenting computational simulation results for the flow in a human right internal carotid artery, exhibiting two saccular aneurysms close to each other. We utilize computer tomography data in order to extract a realistic geometric description of the region of interest. Aspects of the flow inside the aneurysms are discussed in connection to secondary motion patterns and inflow-outflow regimes. We construct residence time maps that exhibit strong non-uniformity, connected to the existence of fluid entering only the first, only the second, or both aneurysms. Preliminary evidence that the inflow-outflow patterns of the two aneurysms may be leading to particularly complex flow and to chaotic mixing is discussed, based on the apparent properties of both the residence time map iso-contours and the basins of attraction of the two aneurysms. Particular attention is paid in establishing grid independence for the computed results and for this reason a second order spatial discretization scheme is utilized, with resolutions ranging from approximately 110,000 to 1,070,000 tetrahedra.
Computational Fluid Dynamics (CFD) Analysis to Study the Flow Phenomena Inside the Hydraulic Tank of an Earthmoving Vehicle
Authors: Barman Priyatosh
Published: November 2021

This paper summarizes the successful application of Computational Fluid Dynamics (CFD) analysis to study the flow phenomena inside the hydraulic tank of an earthmoving vehicle. The main purpose of this CFD analysis is to reduce the aeration inside the tank suction lines to avoid any cavitation damages to the suction pumps. The main source of aeration is suspected due to the strong fluid circulation inside the partially filled hydraulic tank. The CFD analysis predicts qualitatively as well as quantitatively the fluid circulation in the tank. Also, the CFD analysis is used to find the fluid pressure and velocity distribution in the tank.
Experimental Investigation of Rotating Instabilities in a Two-Stage Centrifugal Compressor With Vaneless Diffuser
Authors: Golubev Vladimir V.
Published: November 2021

This paper examines unsteady response of an experimental two-stage centrifugal compressor with vaneless diffusers. A thorough investigation of pressure fluctuations along the compressor channel is carried out in order to examine the onset of unstable flow conditions. Rotating stall structures are localized, with special attention paid to identifying the most sensitive area of the multi-stage compressor channel which may serve as a precursor to unstable compressor operation. It is shown that both stages may develop rotating stall structures simultaneously, however the 2nd stage tends to destabilize first and reveals higher magnitudes of the unsteady response.
Numerical Simulation of Particle Flow, Mixing and Chemical Reaction in the Circulating Fluidized Bed Absorbers
Authors: Mao D. , Edwards J. R. , Kuznetsov A. V. , Srivastava R.
Published: November 2021

A mixing model has been developed to simulate particle’s residence time distribution (RTD) in the circulating fluidized bed absorbers (CFBAs), also, a gas-solid reaction model for Sulfur Oxide removal by limestone has been developed. For the reaction model that considers RTD distribution inside the core and annulus regions of CFBA, macrochemical reaction can be simulated based on microchemical reaction dynamics. The presented model can predict Sulfur Oxide and limestone distributions inside the CFBA and give the amount of limestone needed to remove a given percentage of Sulfur Oxide. It is found that Sulfur Oxide concentration at the outlet from CFBA decreases with the increase of CFBA distance from the bottom in the core region. However, limestone concentration exhibits a very slight variation in the core region. This means that in CFBAs limestone is efficiently utilized to remove Sulfur Oxide. Sulfur Oxide partial pressure at the exit of CFBA decreases with the increase of the percentage of fresh limestone in the inlet to CFBA.
A Nonsymmetrical Uncertainty Analysis Method
Authors: Xu C. , Amano R. S.
Published: November 2021

An uncertainty evaluation method was proposed to reasonably consider the measurement uncertainty for measured variables which have nonsymmetric uncertainty components. The present method considers the nonsymmetrical uncertainty as one of the important parts of the uncertainty evaluation of measurements, which has not been dealt with in detail in previous uncertainty evaluation method. The present method provides more reasonable way to evaluate measurement uncertainty than other existing methods. The method is applied to report the uncertainty of a dynamic pressure measurement system.
Analysis of the Flow Past a Pivoting Plate
Authors: Veber Pascal
Published: November 2021

The increase of the water level in a room due to a pipe break is a common problem for many nuclear power plants. To avoid the submerging of safety components, flaps for load relieving are installed at the door. The increase of the water pressure will result in the opening of the flap. The plate weight counteracts the pressure force. In order to determine the water flow past the plate, a simple method is presented. Using the steady state balance of the forces moments, a rough estimation of the flow can be performed. A study case is discussed.
Calibration and Measurements of Low Speed Wind Tunnel Using Hot Wire
Authors: Shan Choo Voon
Published: November 2021

As technology advances, the principle of low air velocity plays an important part in high tech industries. The concept of measuring low speed in a confined area is a challenging one as the normal calibration method is not suitable. This paper study the method of calibrating and measuring low speed air using hot wire which focus on the effect of the overheat ratio on the calibration of a single hot wire and the design of a probe to be used for studying free convection effect.
Thermal Hydrodynamic Model of Oil-Immersed Power Transformers
Authors: Mufuta Jean-Michel
Published: November 2021

A lower hierarchy model of an oil-immersed – transformer was used to calculate the heat transfer in transformer windings. Contrary to the approach of other investigators, who considered a global network, this approach has the merit of focusing on the main body of the transformer. Further, it allows taking into account the geometric aspect of the problem. Consequently, the correlations found in this study include not only the Reynolds and the Prandtl numbers, but also the pitch ratio and the number of discs in the transformer.

The geometric model consists of an array of rectangular blocks with an in-line arrangement. It represents a part of the whole transformer. An array of 10 blocks with sufficient grid refinement was found to be relevant to study the heat transfer process.

Two different flow regimes were considered: the pure forced convection-regime and the mixed convection regime.

For the first regime, the Reynolds number spans over the range [60...450]. For the second regime, the mass flow was defined as function of a parameter, which is the ratio of the Reynolds number and the Grashof number Re/Gr1/2. This parameter range spans over [0.1...1.0] and expresses the interaction between the inertia forces and the buoyancy forces.
Parallelization of the Pseudo-Spectral Code for DNS of Channel Flow on a Shared Memory Architecture
Authors: Tiselj Iztok , Hetsroni Gad
Published: November 2021

The present paper describes our experience with the parallelization of the pseudo-spectral computer code FLOWH, which is used for DNS simulations of the channel and flume flows. The original version of the FLOWH code was developed by Gavrilakis et al. 1986 [11] and was optimized for vector computers (Cray...). In 1999 and 2000 we started the parallelization of the code for the shared memory type of parallel computers SGI Origin and Sun for turbulent heat transfer calculations (Tiselj et. al. [1,2]). OpenMP parallelization directives were used and very similar performances were obtained on both types of computers. The efficiency of the parallelization on 32 CPUs is approximately 50%. The main reason for the relatively low efficiency of the parallelization (comparing to the efficiency of finite volume codes) is in the nature of the pseudo-spectral codes, which does not allow permanent allocation of the nodes onto the particular CPU like finite volume or finite element codes.
Dynamic Analysis of Diesel Engine Common Rail Injection System: Part I — Injector Dynamics
Authors: Borghi M. , Milani M. , Piraccini M.
Published: November 2021

The aim of the paper is to analyze the dynamic behavior of an actual electro-hydraulic injector, included into a high-pressure accumulator injection system (Common Rail).

Firstly, a brief introduction of the hypotheses adopted for a lumped parameter description of each part of an industrial version of the injector (BOSCH) is outlined, together with the definition of the hypotheses assumed to treat the fuel efflux through the injection holes, through the internal mechanical couplings and the damping orifices, or to descript of the cavitations.

Then, the dynamic behavior of the injector is analyzed adopting some of the command signals imposed to the pilot stage by the Electronic Central Unit (ECU), as actually implemented into the standard map of an on board ECU of a industrial diesel engine. Among others, the paper presents the results coming from the injector handling for medium values of the crank-shaft regime (1800 and 2400 rpm), for different pressure levels in the Rail and involving also the pilot injection.

The reliability of the numerical results is stated through a wide numerical vs. experimental comparison, made up on the basis of the fuel mass injected for each cycle.

Finally, the discharge characteristics characterizing the injection are determined, such as the effective mean velocity and the effective area of the liquid core at the holes exit, or injection holes discharge coefficient.
The Specific Flowrate of Deviation Function Based Lobe Compressors
Authors: Yang Daniel C. H. , Tong Shih-Hsi
Published: November 2021

In this paper a general flowrate formula for lobe pumps is derived in terms of the pitch and deviation functions of the pump rotor. This formula applies to both circular and noncircular rotor pitch profiles. In order to relate the pump flowrate only to rotor geometry, a dimensionless flowrate expression, called “specific flowrate”, is adopted. This enables the flowrate analysis of lobe pumps without the ad-hoc effects of individual pump size and rotor speed. It is found that pump rotors can be grouped by the similarity of their deviation functions. The specific flowrates of a given group of pump rotors can be expressed solely in terms of their corresponding lobe noncircularities. This formulation enables a systematic and efficient design process of new lobe pumps. Classes of new lobe rotors based on some typical deviation functions are designed, and their corresponding specific flowrate functions are also provided.
Modeling and Simulation of a Balanced Vane Pump
Authors: Giuffrida A. , Lanzafame R.
Published: November 2021

Literature concerning balanced vane pumps is fairly rich but covers solutions usually for power steering applications.

The pump considered and modelled in this work presents fixed displacement, pressure balanced rotor like in the ones used for power steering but is different from them since the pumping effect of the chambers under each vane is not wasted as if the pump had a higher displacement under the same conditions.

Beginning from the real geometry of the pump, this work presents the mathematical model and its simulation developed in AMESim.
A Novel Approach to Active Vibration Isolation With Electrohydraulic Actuators
Authors: Zhang Yisheng , Alleyne Andrew
Published: November 2021

This paper presents a novel reformulation of the standard active vibration control problem for large systems to take advantage of the natural dynamics of a particular type of actuator: the electrohydraulic actuator. The standard linear vibration control problem set-up is followed by details of the limitations to this standard approach for electrohydraulic systems. This root of the problems lies in the attempt to utilize the electrohydraulic actuation system to provide a particular force. Previous work (Alleyne & Liu, 1999) has shown the inherent limitations to force tracking for these systems. To circumvent the limitations, the problem is reformulated as a velocity tracking one, which lends itself naturally to the dynamics of electrohydraulic systems. Subsequently, a SISO controller can be readily designed for the velocity tracking problem using standard controller design tools. Although the controller design is relatively standard, experimental results are given which demonstrate the efficacy of the problem reformulation.
Hydraulic Emulation of Injection Moulding
Authors: Guerrier Paul K. , Edge Kevin A.
Published: November 2021

The control of injection moulding is an active area for research. The inject phase of the moulding process which includes filling and packing is of particular importance. New control strategies have traditionally been evaluated either in simulation or through full scale testing. Both methods have advantages and disadvantages. This paper details the hydraulic load emulation of the filling and packing phases using the hardware-in-the-loop technique which is a compromise between these two methods. With suitable controller design successful load emulation is demonstrated.
Robust Nonlinear Control of a Novel Indexing Valve Plate Pump
Authors: Zhang X. , Nair S. S. , Manring N. D.
Published: November 2021

A robust adaptive pressure control strategy is proposed for a novel indexing variable-displacement pump. In the proposed approach, parametric uncertainties and unmodeled dynamics are identified to the extent possible using a model free learning network and used to de-couple the dynamics using physical insights derived from careful reduced order modeling. The swash plate motion control is then carefully designed to provide the desired pressure response characteristics showing improved performance with learning. The proposed control framework and designs are validated using a detailed nonlinear simulation model.
New Type of Hydraulic Rotary Actuator; Development and Application in a Large Telerobotic Manipulator System
Authors: Haas John R.
Published: November 2021

This paper describes a new type of hydraulic rotary actuator specifically developed to provide precision motion control in a very large, man rated, underwater telerobotic manipulator system. The high pressure, high torque rotary actuators are hydrostatically balanced, provide continuous rotation, constant torque output, exhibit minimal “stick-slip” and zero backlash. It is believed that the combination of features and the performance exhibited by these actuators represent an improvement in actuator technology to such an extent as to make projects previously determined unfeasible, now practical. Features of particular design value are a very large diameter through bore, and a truly modular design permitting use as an integral structural member. This paper will address design rationale, operating principles, key design features, product development highlights, an astronaut trainer case study, future development and potential applications.
Heating Effect of Pulsating Flow in Hydraulic Hoses
Authors: Ijas Mika J. , Ellman Asko U.
Published: November 2021

Some hydraulic actuators operate periodically. The periodic motion led to pulsating pressure in a hose. Pulsating pressure in the hoses led to problems with reliability of hoses and fittings. When there is high pressure oscillation in the hose, the whole hose arrangement vibrates and strains structure of the hose. If the moving hose touches somewhere the friction of abrasion warms the hose. On the other hand the hose bloats periodically all the time because of the pressure oscillation. When the hose bloats deformation of the rubber and the hose structure rises temperature. There are longitudinal and radial motions between hose linings and hose reinforcements so the friction rises temperature of the hose. The static pressure loss and the oscillation of the hose increase the temperature of the hose.

This paper concentrates to study how pressure oscillation and the hose bloating rise temperature of the hoses. The examinee hoses were measured by three different measurement ways. By means of a servo valve the pressure oscillation was produced to the examinee hoses. The all hoses (steel pipe, thermoplastic hose, heavy-duty with 2 reinforcement and extra heavy-duty with 3 reinforcement) were measured in the same time. The warming effect of abrasion was studied by help of a thermograph camera. The main result was that the warming was caused by the abrasion of the moving hoses.
A Novel Cooling Enhancement in Microelectronic Devices and Systems Using Oscillatory Impinging Air Jets
Authors: Chiriac Victor Adrian , Lee Tien -Yu Tom , Rosales Jorge Luis
Published: November 2021

A new cooling technique is proposed to simultaneously enhance the heat transfer and significantly reduce the prohibitive high temperatures usually reached by high-powered chips embedded in the last generation of packages. A comparison between flow and heat transfer characteristics for several types of microelectronic cooling arrangements was conducted using a numerical investigation. The maximum temperature and local heat transfer coefficient were determined on a single heated chip cooled by a channel flow, a steady impinging jet, and an oscillatory impinging jet at a Reynolds number of 600. A uniform inlet velocity was used for the channel flow calculation, and the upper and lower channel walls confined the jets. The calculation domain for the three simulations was identical; the steady jet configuration had an inlet jet width twice that of the unsteady jet.

The results indicate that the unsteady nature of the confined impinging jet greatly enhances the removal of heat transfer and reduces the high temperatures on the heated chip. The jet core becomes distorted and buckles beyond a critical Reynolds number of 600, which leads to a sweeping motion of its tip (stagnation point). As a result of the combined buckling/sweeping jet motion, the cooled area is significantly enhanced. A comparison between the unsteady impinging jet and the stationary impinging jet reveals that the heat transfer enhancement provided by the unsteady jet is at least two times better. A 25% cooling enhancement is observed when compared with the channel flow technique, yet the jet uses a flow rate 6.3 times lower, therefore a smaller pumping power.

The new cooling method does not require the incorporation of costly heat sinks and heat spreaders, or the unnecessary increase of pumping power/blower work, yet provides effective cooling at significantly reduced manufacturing/operating costs.
Computation of Natural Convection in Channels With Staggered Pin Fins
Authors: Boyalakuntla Dhanunjay S. , Murthy Jayathi Y. , Amon Cristina H.
Published: November 2021

In this paper we numerically analyze the possibility of using buoyant flow in the display panel of a laptop for electronics cooling. A three-dimensional channel with a staggered pin fin array is analyzed using an unstructured finite volume method. A uniform heat flux is applied on the inner wall; the outer wall is exposed to the ambient. A single periodic module is selected in the lateral direction. In the axial direction, however, the entire height of the display channel is considered. A range of Rayleigh numbers, panel inclinations and staggering arrangements are considered, and local and global flow and heat transfer results are obtained. The results are useful in designing augmented cooling schemes in portable electronics.
Thermal Design Analysis of Free Space Optical Interconnect (FSOI) Package Module
Authors: Chiriac Victor Adrian , Lee Tien-Yu Tom
Published: November 2021

A detailed thermal analysis for the FSOI (Free Space Optical Interconnect) technology incorporating VCSEL (Vertical Cavity Surface Emitting Laser) devices is performed using commercially available software. FSOI is one of the latest technologies used to transmit information at high-speed to/from a microprocessor to memory device via photons. Due to large heat dissipation and compact packaging design, temperature and associated thermal strain/stress could reach high values in the FSOI assembly, causing serious reliability and quality problems. Several design options are investigated in order to provide optimal thermal management for the FSOI module, and maintain VCSEL temperatures within reasonable limits. Convective cooling results for both organic and ceramic boards are investigated.

For designs with organic boards and without any thermal enhancement, the VCSEL temperature is well above the acceptable limit of 85°C at an ambient temperature of 30°C. The sequential inclusion of pedestals, board thermal vias, conductive rings between the optical modules, and metallic (Al) rods will significantly enhance the module thermal performance and reduce VCSEL temperature to 46°C. The presence of thermal vias in the organic board is critical; however, if the copper area percentage in the via block vs. the die area is above 3%, the VCSEL temperatures will remain constant.

The ceramic boards provide a good thermal solution, as VCSEL temperatures remain below the upper limit without including any thermal vias in the board. The comparison between the effect of convective air speed on FSOI with ceramic versus organic boards reveals that the VCSEL temperature is slightly higher (less than 2°C) for the case incorporating a ceramic board. However, the ceramic board has no thermal vias, compared to the 100% copper via block in the organic board. Hence, the same results are accomplished with much less complexity in the ceramic substrate design alternative. This option is suggested for manufacturing purposes, with improved thermal performances.
Design of Generator Acoustic Blanket and its Impact on Generator Cooling Performance
Authors: Tong Wei
Published: November 2021

Generator noise is one of the primary concerns in generator designs. The most cost-effective way to deal with the noise issue is to incorporate the reduction of sound pressure level in an early design stage. Once a generator is manufactured, it is often expensive to modify the design for reducing noise levels. For old generators with high sound pressure levels, an effective method to lower the generator noise exposure is to employ acoustic blankets wrapped on the generator external surfaces. However, with the application of acoustic blankets, heat transfer through generator walls can be greatly reduced, leading to the higher generator core temperature and higher generator cooling load.

This paper has addressed the design of generator acoustic blankets and its impact on generator cooling performance. The analysis has shown that the influence of acoustic blankets on the generator thermal performance is low or moderate. This suggests that the current acoustic blanket design is feasible. Results from this study have been used to optimize the blanket design.
A Natural Circulation Model of the Closed Loop, Two-Phase Thermosyphon for Electronics Cooling
Authors: Haider S. I. , Joshi Yogendra K. , Nakayama Wataru
Published: November 2021

The study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. Most available models deal with two-phase thermosyphons with counter-current circulation within a closed, vertical, wickless heat pipe. The present research focuses on CLTPTs for electronics cooling that face more complex two-phase flow patterns than the vertical heat pipes, due to closed loop geometry and smaller tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the chip temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.
Thermal Conductivity of Si/SiGe Superlattices
Authors: Huxtable Scott T. , Abramson Alexis R. , Majumdar Arun , Tien Chang-Lin , LaBounty Chris , Fan Xiaofeng , Zeng Gehong , Bowers John E. , Shakouri Ali , Croke Edward T.
Published: November 2021

The cross-plane and in-plane thermal conductivity of four Si/Si0.7Ge0.3 superlattice structures with periods from 45 Å to 300 Å are experimentally investigated using the 3-ω measurement technique. The experiment is conducted over a temperature range from 70 to 340 K. Results indicate that the cross-plane thermal conductivity decreases with decreasing period thickness (i.e. increasing number of interfaces per unit length). The superlattice with the shortest period exhibits a cross-plane thermal conductivity similar to that of a SiGe alloy. The in-plane thermal conductivity follows a similar decreasing trend with period thickness for the three larger period superlattices, but jumps to higher values for the shortest period superlattice. Additionally, the in-plane conductivity can be 3–4 times higher than the cross-plane value.
Real Time Sub-Micron Thermal Imaging Using Thermoreflectance
Authors: Christofferson James , Vashaee Daryoosh , Shakouri Ali , Melese Philip
Published: November 2021

Thermal measurements on a sub-micron scale are non-trivial, but are important for the characterization of modern semiconductor and opto-electronic devices. In this paper we will discuss the application of the thermoreflectance method for real time sub-micron thermal imaging. By using light in the visible spectrum, the diffraction limit, and thus spatial resolution is improved over a traditional infrared camera based on blackbody emission. With active excitation of the sample and frequency domain filtering, thermal images with 100mK temperature resolution are obtained. Experiments performed on semiconductor micro-coolers and micro-heaters are presented.
Scanning Thermal Microscopy Study of Dissipation in Current-Carrying Carbon Nanotubes
Authors: Shi L. , Kim P. , Plyasunov S. , Bachtold A. , McEuen P. L. , Majumdar A.
Published: November 2021

The temperature distribution of current-carrying carbon nanotubes (CNs) have been measured by scanning thermal microscopy. The thermal imaging results support that multiwall (MW) CNs and semiconducting single wall (SW) CNs are diffusive and dissipative, while metallic SWCNs change from non dissipative at low electric fields to dissipative at high fields due to optical phonon emission. The temperature rise in a 4.5 μm long MWCN was of order 40 K for a power input of 22 μW and increased linearly with power input. There existed a large temperature drop at the tube-substrate interface due to a weak contact thermal conductance about 0.1 W/m-K. For the MWCN, comparable amount of Joule heat was lost from the tube bulk to the substrate and from the tube to the metal contacts.
Visualization of Supercritical Carbondioxide Pseudo-Boiling Inside a Rectangular Channel
Authors: Sakurai K. , Ko H. S. , Okamoto K. , Madarame H.
Published: November 2021

The characteristics of the supercritical fluids should be precisely investigated for the next generation nuclear power reactor, i.e., Super-critical water Cooled Reactor (SCR). There are few experiments for visual observation especially in forced convection, because of the difficulty of the experiment.
A Model for the Structural Mechanisms in the Regulation of Microvessel Permeability by cAMP
Authors: Fu Bingmei M. , Chen Bin
Published: November 2021

To investigate the microstructural mechanisms of decreasing microvascular permeability induced by the enhancement of intraendothelial adenosine 3’,5’-cyclic monophosphate (cAMP) levels, we extended the previous analytical model developed by Fu et al. (J. Biomech. Eng., 1994) for the interendothelial cleft to include multiple junction strands in the cleft and an interface between the surface glycocalyx layer and the cleft entrance. Based on the electron microscopic observation by Adamson et al. (Am. J. Physiol., 1998), that elevation of intracellular cAMP levels would increase number of tight junction strands, numerical method was applied to test the case in which there are two junction strands in the cleft and there are large discontinuous breaks and a small continuous slit in each strand. Results from this two-junction-strand and two-pore model can successfully account for the experimental data for the decreased permeability to water (Adamson et al. Am. J. Physiol., 1998), small and intermediate-sized solutes (Fu et al., Am. J. Physiol., 1998) by cAMP.
Flow Dynamics During Machine Perfusion Preservation of Livers
Authors: Purohit Saurin P. , Nelson Joshua , Zhang Jian , Clemens Mark G. , Lee Charles Y.
Published: November 2021

Hypothermic machine perfusion preservation (MPP) has the potential to relieve the current donor shortage problem by providing superior preserved tissue and viable non-heart-beating donor tissue. For the liver, MPP has not improved preservation. Currently, the major cause of damage associated with MPP of livers is unknown. An intravital microscopy study was conducted to investigate the state of sinusoidal perfusion during 24-hour MPP. Fluorescein isothiocynate (FITC)-labeled albumin was utilized to mark the microvascular space while FITC-labeled red blood cells were used to determine the fluid velocity. The results showed that there was an increase in vascular resistance (> 275%) when the liver was perfused with a UW solution for 24 hours at 5°C and with a flow rate of 5 ml/min. This vascular resistance further increased (> 425%) during rewarming (for 1 hour, at 37°C and 15 ml/min). The mean flow velocities increased during initial MPP from 236 ±16 μm/s (mean ± standard error) to 434 ± 20 μm/s and the mean shear stress values increased from 5.3 ± 0.8 dynes/cm2 to 6.5 ± 0.8 dynes/cm2, after 24 hours of MPP the mean flow velocity values and shear stress values decreased (223 ± 13 μm/s and 3.3 ± 0.8 dynes/cm2) respectively. The reason for this was detected by the FITC-labeled albumin, in the tissue. It was evident that these areas (after 24 hours of MPP) also displayed increased blockage. It also appeared from the micrographs and the histology study that the blockage occurred as a result of endothelial cells rounding after 24 hours of MPP. The cells remained rounded even after rewarming the tissue. This could be a mechanism of damage to the liver during 24-hour of MPP.
In Vitro Assessment of the Efficacy of Thermal Therapy in Human Benign Prostatic Hyperplasia Tissue
Authors: Bhowmick Sankha , Bhowmick Pragati , Coad James E. , Bischof John C.
Published: November 2021

Correlation between thermal history and tissue destruction is of considerable importance for successful management of BPH using minimally invasive thermal therapies such as radiofrequency or microwave probes. In order to accomplish this goal, the present in vitro study assesses the cellular viability of BPH tissue subjected to different temperature-times in an experimental matrix. Hyperplastic prostatic tissue was obtained from 8 patients after the surgical removal of the glands for other reasons (typically cancer). A piece of tissue was taken from the lateral lobe of the gland and was then sectioned into multiple thin strips (1mm thick), placed on a coverslip and heated on a thermally controlled copper block to various temperatures (45°C-70°C) for various times (1 minute–60 minutes). After heat treatment, the tissue slices were cultured for 72 hours and viability data was obtained using two independent assays: histology and dye uptake. Results indicate that the hyperplastic prostate tissue showed a progressive histologic increase in irreversible stromal tissue injury with increasing temperature-time severity. A small amount (∼5% or less) of stromal apoptosis was found in the control and mildly treated tissue. Dye uptake studies for stromal viability paralleled the histologic findings for the temperature-time combinations explored in the present study. In vitro thermal injury thresholds for 90% destruction of human BPH tissue were identified at 45°C-60min, 55°C-20min, 60°C-5min and 70°C-2 min. The Arrhenius model of injury was fit to the viability data after controlled heating to obtain parameters that will allow the prediction of injury under variable heating conditions. Arrhenius analysis of both assays showed a break point at 60°C based on 90% normalized survival. The activation energy (E) values for temperatures below and above the break point were 199.05 and 66.04 kJ/mole for the dye uptake study and 162.6 and 62.99 kJ/mole for histology. The corresponding frequency factor (A) values below and above the break point were 1.81 × 1030 and 1.82 × 109 s−1 for dye uptake study and 2.84 × 1024 and 6.64 × 108 s−1 for histology. This study is the first to report Arrhenius parameters for human BPH tissue for supraphysiological thermal therapy and will be useful for prediction of tissue destruction during thermal therapy of BPH in the clinic.