bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Diverse Differential Plating Methods to Enrich Bovine Spermatogonial Cells
Authors: Giassetti MI , Goissis MD , de Barros FRO , Bruno AH , Assumpção MEOA , Visintin JA
Published: November 2015

Contents

Spermatogonial stem cells (SSC) have important applications in domestic animal reproduction and advanced biotechnologies. Because differential plating is one of the most common methods used for SSC enrichment, the goal of this study was to compare three differential plating methods for the enrichment of bovine SSC. To achieve this goal, testicular parenchyma from pre‐pubertal calves was minced and single cells were obtained after two enzymatic digestions. We compared three coating methods for differential plating: laminin (20 ng/ml), BSA (0.05 mg/ml) and PBS. Cells were incubated at 37°C, 5% CO2 in air for 15 min onto laminin‐coated dishes or 2 h onto BSA‐ or PBS‐coated dishes. Cell viability was assessed by trypan blue exclusion method. Recovered cells were analysed for the expression of SSC molecular markers by quantitative RT‐PCR (GFRA1, CXCR4, ITGA6, THY1) and flow cytometry (GFRA1, CXCR4 and ITGA6). Cells at time 0, adherent cells on laminin and non‐adherent cells from BSA and PBS groups had the same cell viability (p = 0.0655). GFRA1, CXCR4 and THY1 relative gene expression was higher (p = 0.0402, p = 0.0007, p = 0.0117, respectively) for non‐adherent cells selected in PBS group. Flow cytometry analysis revealed that the presence of GFRA‐positive (GFRA+) cells was higher in non‐adherent cells from BSA and PBS groups (p < 0.001). However, laminin‐adherent cells had higher number of ITGA6+ cells (p < 0.001) and lower presence of CXCR4+ cells (p = 0.0012). In conclusion, differential plating is an effective method for the enrichment of bovine undifferentiated spermatogonia and higher expression of SSC markers is obtained without laminin or BSA coating.
Risk factors associated with Chagas disease in pregnant women in Santander, a highly endemic Colombian area
Authors: Castellanos‐Domínguez Yeny Z. , Cucunubá Zulma M. , Orozco Luis C. , Valencia‐Hernández Carlos A. , León Cielo M. , Florez Astrid C. , Muñoz Lyda , Pavía Paula , Montilla Marleny , Uribe Luz Marina , García Carlos , Ardila William , Nicholls Rubén Santiago , Puerta Concepción J.
Published: November 2015

Objective

To determine the prevalence and risk factors associated with Chagas disease in pregnant women in an endemic area of Santander, Colombia.

Methods

Cross‐sectional study included 23 municipalities of Santander, Colombia. Serological IFAT and ELISA tests were undertaken to detect IgG anti‐ Trypanosoma cruzi. A questionnaire was conducted for assessing the risk factors of each participant. Newborns were evaluated at birth and followed up to 1 year of age to determine congenital infection.

Results

An overall prevalence of 3.2% (95% CI 2.4–4.2) among 1518 pregnant women was detected. Prevalences by provinces were as follows: Guanentina: 6.0% (95% CI 4.1–8.5), García Rovira: 2.9% (95% CI: 1.5–4.8) and Comunera: 0.4% (0.4–2.3). The main risk factors identified were age >32 years old (OR: 2.1; 95% CI: 1.1–3.9); currently having a thatched roof (OR: 11.8; CI95% 2.2–63.2) and a thatched roof during childhood (OR: 3.0; 95% CI: 1.4–6.6); having below primary school education level (OR: 4.6; 95% CI: 2.2–9.5); and a history of a close contact with the vector (triatomine bugs) at least once during their lifetime (OR: 6.9; 95% CI: 3.7–12.9). No congenital cases were detected by parasitological or serological techniques.

Conclusions

Prevalence of Chagas disease in pregnant women is a potential source of infection in this Colombian endemic area. The main risk factors associated with seropositivity were related to conditions favouring the contact with the vector. The results show that it is necessary to continue an active surveillance in order to offer diagnosis and treatment to mothers and their newborns in addition to screening to pregnant women from endemic areas.
Urinary di‐(2‐ethylhexyl) phthalate metabolites for detecting transfusion of autologous blood stored in plasticizer‐free bags
Authors: Leuenberger Nicolas , Barras Laura , Nicoli Raul , Robinson Neil , Baume Norbert , Lion Niels , Barelli Stefano , Tissot Jean‐Daniel , Saugy Martial
Published: November 2015

BACKGROUND

Autologous blood transfusion (ABT) efficiently increases sport performance and is the most challenging doping method to detect. Current methods for detecting this practice center on the plasticizer di(2‐ethlyhexyl) phthalate (DEHP), which enters the stored blood from blood bags. Quantification of this plasticizer and its metabolites in urine can detect the transfusion of autologous blood stored in these bags. However, DEHP‐free blood bags are available on the market, including n‐butyryl‐tri‐(n‐hexyl)‐citrate (BTHC) blood bags. Athletes may shift to using such bags to avoid the detection of urinary DEHP metabolites.

STUDY DESIGN AND METHODS

A clinical randomized double‐blinded two‐phase study was conducted of healthy male volunteers who underwent ABT using DEHP‐containing or BTHC blood bags. All subjects received a saline injection for the control phase and a blood donation followed by ABT 36 days later. Kinetic excretion of five urinary DEHP metabolites was quantified with liquid chromatography coupled with tandem mass spectrometry.

RESULTS

Surprisingly, considerable levels of urinary DEHP metabolites were observed up to 1 day after blood transfusion with BTHC blood bags. The long‐term metabolites mono‐(2‐ethyl‐5‐carboxypentyl) phthalate and mono‐(2‐carboxymethylhexyl) phthalate were the most sensitive biomarkers to detect ABT with BTHC blood bags. Levels of DEHP were high in BTHC bags (6.6%), the tubing in the transfusion kit (25.2%), and the white blood cell filter (22.3%).

CONCLUSIONS

The BTHC bag contained DEHP, despite being labeled DEHP‐free. Urinary DEHP metabolite measurement is a cost‐effective way to detect ABT in the antidoping field even when BTHC bags are used for blood storage.
A Molecular Dynamics Study for Stability of Thin Water Films on Nanostructured Surfaces
Authors: Sun Liyong , Zhou Jun
Published: November 2015

The stability of thin water films on a variety of gold nanostructures was simulated by molecular dynamics simulations. The critical film thickness to prevent a film break-up was investigated as a function of the characteristic length of the nanostructures. Layering of water molecules adjacent to the gold substrate was observed as a result of the strong van der Waals interactions between the water molecules and the gold atoms. A model for the critical film thickness in the presence of nanostructures is developed based on the stability analysis. The model prediction is compared with molecular dynamics simulations with good agreement.
On the 3D Structure of Elasticity-Induced Unstable Flow in the Curved Microchannel by Using Confocal Micro-PIV and Polarized Camera
Authors: Li Xiao-Bin , Oishi Masamichi , Oshima Marie , Li Feng-Chen , Li Song-Jing
Published: November 2015

In this paper, the three-dimensional (3D) structures of a micellar solution flow in the curvilinear microchannel have been investigated by means of confocal micro particle image velocimetry (PIV). The working fluid is aqueous solution of CTAC/NaSal (cetyltrimethylammonium / Sodium Salysilate). As the flow rate increases, the flow gradually gets into the irregular motion. It is found that the inside flow seems not completely chaotic, but in a manner of oscillation. To be specific, the flow nonlinearity grows as the flow rate increases, the inside flow shows different structures near the wall region and in the bulk due to the elongation of viscoelastic surfactant. Typically, two sub-streams were twisted together, and their flow directions change at the locations where the signs of geometric curvature change. The oscillation stripes represented the area of high extensional stress in the viscoelastic fluid, and were further identified by using polarized high-speed camera. Moreover, statistics shows that the viscoelastic flow field inside the curved microchannel shares the main features of elastic turbulence.
Evaporation Heat Transfer Characteristics on the Outside of Horizontal Smooth, Herringbone and Enhanced Surface 1EHT Tubes
Authors: Sun Jian-jun , Chen Jing-xiang , Kukulka David J. , Zhou Kan , Li Wei , Shi Yanping
Published: November 2015

An experiment investigation was performed using R410A in order to determine the single-phase and evaporation heat transfer coefficients on the outside of (i) a smooth tube; (ii) herringbone tube; and (iii) the newly developed Vipertex enhanced surface 1EHT tube; all with the same external diameter (12.7 mm). The nominal evaporation temperature is 279 K, with inlet and outlet qualities of 0.1 and 0.8. Mass fluxes ranged from 10 to 40 kg m−2s−1. Results suggest that the 1EHT tube has excellent heat transfer performance but a higher pressure drop when compared to a smooth tube. Evaporation heat transfer coefficient for the 1EHT is lower than the herringbone tube and the pressure drop is almost the same.
Influence of Synthesis Conditions on the Transport Properties of Graphene Oxide Laminates
Authors: Paneri Abhilash , Moghaddam Saeed
Published: November 2015

In this study, the effect of oxidation conditions during the synthesis process of graphene oxide (GO) flakes on the transport characteristics of its laminates is investigated. Transport properties of the GO laminates synthesized by different oxidation methods are characterized by determining their ionic conductivity (via proton conductivity) and mass diffusion of species (via methanol permeability). These properties are observed to be considerably different for each sample owing to the difference in their physicochemical properties. It is determined that for GO synthesized under a more aggressive environment, proliferation of surface defects plays a dominant role in determining mass transport across GO laminate. A parametric study is conducted to systematically understand the impact of changing oxidation level on transport properties of GO laminate.
Absorption Characteristics of Multilayered Thin Lithium Bromide (LiBr) Solution Film
Authors: Mortazavi Mehdi , Isfahani Rasool Nasr , Bigham Sajjad , Moghaddam Saeed
Published: November 2015

In this study, an alternative absorber design suitable for the plate-and-frame absorber configuration is introduced. The design utilizes a fin structure installed on a vertical flat plate to produce a uniform solution film and minimize its thickness and to continuously interrupt the boundary layer. Using numerical models supported by experiments employing dye visualization, the suitable fin spacing and size and wettability are determined. The solution flow thickness is measured using the laser confocal displacement measurement technique. The new surface structure is tested in an experimental absorption system. An absorption rate as high as 6×10−3 kg/m2s at a driving pressure potential of 700 Pa is achieved, which is considerably high in comparison with conventional absorption systems. The effect of water vapor pressure, solution flow rate, solution inlet concentration, cooling water inlet temperature and solution inlet temperature on the absorption rate is also investigated. The proposed design provides a potential framework for development of highly compact absorption refrigeration systems.
Visualization of Spray Structure at the Outlet of the Micro Orifices
Authors: Ghorbani Morteza , Koşar Ali
Published: November 2015

Spray formation occurring at the outlet of short microchannels/micro orifices due to the cavitation phenomenon is of great importance in biomedical and engineering applications. The spray characteristics are affected dramatically by the flow regime in the micro orifice. If properties of the flow are identified in the outlet of the nozzle, the treatment of the spray can be predicted. These properties can be used as boundary conditions. The experimental investigations show that the cavitation phenomenon occurs in the orifice and strongly affects the spray characteristics. However, visualization of the spray at the outlet of the micro orifice is a challenging task, since the phenomena related to the spray are occurred in very small scale and also the region near to the micro orifice is not clear. Therefore there is an urgent need to new and advanced visualization techniques and measurement equipments. In this study, spray formation and atomization, bubble evolution at the outlet of a short microchannel of an inner diameter of 152 μm were experimentally studied at different injection pressures with the use of a high speed visualization system. High speed visualization was performed at four different segments to cover ∼15 mm distance beginning from the microchannel outlet to understand the spray formation mechanism. It was observed that cavitating bubbly flow is strongly affected by injection pressure. Up to an injection pressure of 50 bars bigger size droplets form at the outlet, while beyond 50 bar injection pressure, cavitation erosion of intensified cavitation becomes dominant leading to smaller droplet sizes and a more conical spray. The results showed a good agreement with previous studies. This energy could be exploited in several applications, where destructive effects of bubbly cavitating flows are needed.
Numerical Modeling of Pore Fluid Flow in Reconstructed Porous Media
Authors: Liu Zhenyu , Wu Huiying
Published: November 2015

In this paper, the numerical simulation of pore fluid flow in reconstructed porous media was carried out. The 3D porous computational domain was reconstructed based on the 2D images from micro CT scanner equipment. The Shan-Chen type lattice Boltzmann method (LBM) was adopted to establish the numerical model to predict the two-phase flow in the complex porous domain. The pore space is in micro/mini scale and the surface structure will have an influence on the pore fluid flow. Different surface tension coefficients were adopted in the numerical simulation to analyze its effect on the two-phase flow in complex porous media.
Droplet Formation in a T-Junction Microfluidic Device in the Presence of an Electric Field
Authors: Ahmad Zeeshan , Singh Rattandeep , Bahga Supreet Singh , Gupta Amit
Published: November 2015

In this work, the effect of applying an electric field on droplet formation in a T-junction microfluidic device is examined by simulations based on a recent technique known as lattice Boltzmann method (LBM). The electric field is applied in the main channel just beyond the confluence of the continuous and dispersed phases. A combined electrohydrodynamics-multiphase model that can simulate the flow of immiscible fluids in the presence of an electric field is developed and validated. The same model is then applied to study the droplet formation process in a T-junction microfluidic device at a capillary number of 0.01 and at different dispersed to continuous phase flow rate ratios. Results show that there is a decrease in the droplet size and an increase in formation frequency as the electric field is increased. The interplay of the electric and interfacial forces on droplet formation is investigated.
Thermal Performance and Pressure Drop of Galinstan-Based Microchannel Heat-Sink for High Heat-Flux Thermal Management
Authors: Hayashi Yoshikazu , Saneie Navid , Kim Yoon Jo , Kim Jong-Hoon
Published: November 2015

We numerically investigated a novel galinstan-based microfluidic heat-sink. Galinstan is an eutectic alloys of gallium, indium, and tin. The thermal conductivity of galinstan is ∼27 times that of water, while the dynamic viscosity is only twice of water. Thus, heat transfer coefficient can be remarkably enhanced with a small penalty of pumping power. However, the specific heat of galinstan is significantly lower than that of water, which will inevitably undermine the cooling capability by increasing fluid outlet temperature (i.e., increase of caloric thermal management) and/or flow rate. As an alternative, therefore, galinstan/water heterogeneous mixture was proposed as a working fluid and the cooling performance was numerically explored with varying volume composition of galinstan. Effective medium theory for heterogeneous medium was used to evaluate the thermal conductivity of the mixture. The viscosity change with respect to the volume composition was also predicted considering both the viscosity of dispersed phase and interaction between the droplets. Classical models were used for the mixture density and specific heat calculations. Heat transfer and pressure drop characteristics of laminar flow through a silicon microchannel heat-sink was simulated using Fluent. The length and width of the channel array are 10 mm and 9.5 mm, respectively. The cross-sectional area of each channel is 300 μm × 300 μm and the spacing between channels is 100 μm. The heat dissipation was 50 W and the pumping power was fixed at 5 mW for the comparison between the varying galinstan/water compositions. The results showed that more than 30% of the thermal resistance enhancement was attainable using the novel working fluid. Due to the compromise between the convective thermal resistance (effect of thermal conductivity) and the caloric thermal resistance (effect of viscosity and specific heat), the lowest junction temperature was marked at the galinstan composition of ∼35% by volume.
Boiling Heat Transfer Performance in a Spiraling Radial Inflow Microchannel Cold Plate
Authors: Ruiz Maritza , Kunkle Claire M. , Padilla Jorge , Carey Van P.
Published: November 2015

This study presents an experimental exploration of flow boiling heat transfer in a spiraling radial inflow microchannel heat sink. The effect of surface wettability, fluid subcooling levels, and mass fluxes are considered in this type of heat sink for use in applications with high fluxes up to 300 W/cm2. The design of the heat sink provides an inward radial swirl flow between parallel, coaxial disks that form a microchannel of 300 μm and 1 cm radius with a single inlet and a single outlet. The channel is heated on one side through a copper conducting surface, while the opposite side is essentially adiabatic to simulate a heat sink scenario for electronics cooling. Flow boiling heat transfer and pressure drop data were obtained for this heat sink device using water at near atmospheric pressure as the working fluid for inlet subcooling levels from 20 to 81°C and mean mass flux levels ranging from 184 to 716 kg/m2s. To explore the effects of varying surface wetting, experiments were conducted with two different heated surfaces. One was a clean, machined copper surface with water equilibrium contact angles in the range of 14–40°, typical of common metal surfaces. The other was a surface coated with zinc oxide nanostructures that are superhydrophilic with equilibrium contact angles measured below 10°. During boiling, increased wettability resulted in quicker rewetting and smaller bubble departure diameter as indicated by reduced temperature oscillations during boiling and achieving higher maximum heat flux without dryout. Reducing inlet subcooling levels was also found to reduce the magnitude of oscillations in the oscillatory boiling regime. The highest heat transfer coefficients were seen in fully developed boiling with low subcooling levels as a result of heat transfer being dominated by nucleate boiling. The highest heat fluxes achieved were during partial subcooled flow boiling at 300 W/cm2 with an average surface temperature of 134 °C and requiring a pumping power to heat rate ratio of 0.01%. The hydrophilic surface retained wettability after a series of boiling tests. Recommendations for use of this heat sink design in high flux applications is also discussed.
Thermal Stability of Rare Earth Oxide Coated Superhydrophobic Microstructured Metallic Surfaces
Authors: Hassebrook Anton , Lucis Michael J. , Shield Jeffrey E. , Zuhlke Craig , Anderson Troy , Alexander Dennis , Gogos George , Ndao Sidy
Published: November 2015

In this paper, we present a method of generating nearly superhydrophobic surfaces from Femtosecond Laser Surface Processed (FLSP) metallic substrates and the study of their thermal stability at high temperatures. Using an FLSP process, hierarchical micro/nano structures were fabricated on stainless steel 316 after which a 200 nm Cerium Oxide (CeO2) film was sputtered onto the surface. Before CeO2 deposition, the contact angle of sample was measured. Post CeO2 deposition, the contact angles were measured again. As a result of the cerium oxide deposition, the contact angle of the originally hydrophilic FLSP surface turned near superhydrophobic with an equilibrium contact angle of approximately 140°. Subsequently, the coated surfaces were annealed in air. The surface maintained its high contact angle from room temperature to about 160°C, after which it lost its hydrophobicity due to hydrocarbon burn off. For each annealing temperature, we monitored the chemical composition for the cerium oxide-coated FLSP surface using energy dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD). Under a nitrogen rich annealing environment, the nearly superhydrophobic FLSP metallic surface maintained its high contact angle up to temperatures as high as 350°C. To further understand the physics behind the observed phenomenon, we investigated two additional samples of polished stainless steel 310 again coated with 200 nm of CeO2.
Heat Transfer During Evaporation and Boiling at the Three Phase Contact Line Region: A Critical Review
Authors: Raghupathi Pruthvik A. , Kandlikar Satish G.
Published: November 2015

A fundamental understanding of the various modes of heat transfer and their contributions is critical in the development of enhanced surfaces to augment boiling performance. Recently, a number of studies have highlighted the importance of contact line region in boiling-especially in applications involving thin film evaporation and wicking structures. Contact line region also plays an important role during heat transfer around a nucleating bubble, especially at higher bubble frequencies near critical heat flux (CHF). In this work, a review of the characteristics of the contact line region, the forces at play, and the associated heat transfer mechanisms is conducted. Experimental and analytical works on the contact line region are explored to develop a comprehensive picture of its physical and heat transfer behavior. Various optical and thermal measurement techniques employed by researchers to understand evaporation in the contact line region are also reviewed. The interaction of different forces in this region and the analytical models for predicting the forces is studied. Finally, the contribution of microlayer and contact line heat transfer in nucleate boiling is also presented.
Enhanced Flow Boiling of Ethanol in Open Microchannels With Tapered Manifolds in a Gravity-Driven Flow
Authors: Buchling Philipp K. , Kandlikar Satish G.
Published: November 2015

Flow boiling in microchannel heat sinks has been studied extensively in the past decade with the aim of implementation in the cooling of high-power integrated circuit chips. It has the potential to provide high-heat flux cooling at low wall superheats and a compact heater surface geometry. Prior works using water as the working fluid have shown that open microchannels with tapered manifolds deliver enhanced flow boiling performance, with substantial improvements in flow stability and a low pressure drop. The present work investigates the use of ethanol in flow boiling via a gravity-driven flow loop, eliminating the need for a pump. The flow boiling performance, critical heat flux (CHF) behavior, and pressure drop characteristics of ethanol in open microchannels with tapered gap manifolds (OMM) are studied. Several microchannel chips with different manifold gap heights and channel geometries are tested at multiple flow rates. The performance of ethanol in the present work was found to exceed all previously published results with ethanol, with a record maximum heat flux of 217 W/cm2 at a wall superheat of 34°C. Thanks to a remarkably low pressure drop, with maximal values below 9 kPa, ethanol is identified as a suitable dielectric fluid for reaching high heat flux goals in a gravity-driven configuration investigated in this study.
An Updated Two-Phase Flow Regime Map in Active PEM Fuel Cells Based on a Force Balance Approach
Authors: Zhang Lifeng , Anderson Ryan
Published: November 2015

The water balance in proton exchange membrane (PEM) fuel cells still remains a topic of much investigation in order to maintain satisfactory cell performance. One specific water management issue relates to the gas-liquid flows that occur when water enters the reactant flow field channels, which are typically microchannels or minichannels. Due to its unique water introduction, the Lockhart-Martinelli (LM) approach has been revised for its applicability in predicting the two-phase pressure drop in these channels where water emerges from a gas diffusion layer perpendicular to the direction of gas flow. In the revised LM approach, the Chisholm parameter C is found not to vary strongly as a function of key fuel cell operating variables (relative humidity, temperature, materials, gas stoichiometry), whereas it does vary as a function of flow regime and current density. A new flow regime map was proposed based on all pressure drop data collected from active fuel cells, where an accumulating flow regime is presented in addition to single-phase, film/droplet, and slug flow. The proposed accumulating regime is linked to water droplet dynamics, namely, water droplet emergence, growth, and detachment. A force balance approach shows when detachment will occur, which clarifies the bounds of the accumulating regime in terms of superficial gas velocity (gas stoichiometry ratio) and liquid velocity (current density). The balance considers different wetting scenarios in the channels and a range of superficial velocities of importance to PEM fuel cells.
Use of a Separability Parameter for the Design of a High Frequency Dielectrophoresis Cell Sorter Device
Authors: Hadady Hanieh , Hiibel Sage R. , Redelman Doug , Geiger Emil J.
Published: November 2015

We present a method to quantify and enhance separation of binary cells mixture in the microfluidic device using high frequency dielectrophoresis (>20 MHz). At these frequencies, the DEP response depends primarily on the dielectric properties of the cytoplasm. In order to achieve efficient separation, there must be a difference in the intrinsic dielectric properties of the populations to be sorted. For algae cells, the shift in high frequency dielectrophoresis response during lipid accumulation can be used as a basis of separation. We defined a separability parameter based on the expected difference in the dielectrophoresis responses of the algae cells.

Chlamydomonas reinhardtii cells were cultured in regular media and then the same cells were cultured under nitrogenfree conditions to accumulate neutral (non-polar) lipids. Separability of microalgae cells with different lipid content via high frequency dielectrophoresis were investigated by a thin needle shaped electrodes patterned by standard photolithographic and wet etching procedures. Experimental separability factors were measured by estimation of relative lipid content with BODIPY 505/515 fluorescence dye and calculating the area-weighted intensity average of fluorescent images. Theoretical separability parameter was calculated using analytical analysis of single shell model by MATLAB.

Theoretical and experimental separability parameters, as tools to determine the optimal separation method, were calculated for microalgae cells with different lipid content. This objective function was maximized in the range of 35–45 MHz for C. reinhardtii cells after 21 days of lipid accumulation in a static separation. In order to design a continuous cell sorter device, the theoretical separation factor was maximized based on differences in the magnitude or the direction of the DEP force.
Thermodynamic Analysis of the Transition Between Slug and Annular Flow in Minichannels
Authors: Khovalyg Dolaana M. , Hrnjak Predrag S. , Jacobi Anthony M.
Published: November 2015

Heat transfer mechanism during flow boiling of fluids in small channels differs significantly depending on whether two-phase flow is in slug or annular regime. Understanding of the transition conditions between homogeneous slug flow and annular two-phase flow is an important topic for mini- and microchannel heat exchangers performance optimization. The current study focuses on the analysis of thermodynamic equilibrium conditions of two neighboring two-phase flow regimes. In both flow patterns the total energy is equal at specific mass flux and vapor quality and those values can be used to mark the transition conditions.
Three-Dimensional Measurement of Near-Wall Velocity in Millimeter Channel by a Single View Imaging
Authors: Ichikawa Yoshiyasu , Nishiwake Kojiro , Wakayama Hiromu , Kameya Yuki , Yamamoto Makoto , Motosuke Masahiro
Published: November 2015

It is well known that there is a strong correlation between heat transfer and near-wall flow. It is important to obtain the detailed near-wall flow field, but it has a lot of difficulties to measure near-wall region by traditional approaches for example hot wire anemometry and particle image velocimetry (PIV). The purpose of this study is to determine the three-dimensional velocity field at near-wall area in micron resolution by the astigmatism particle tracking velocimetry (APTV). In this study, an estimation of depth location of tracer particles by applying a specialized imaging optics controlling the astigmatism [1] was employed. We have developed a measurement system to get the particle location within 15 μm from wall using a long-working-distance microscope with astigmatic optics. As a proof-of-concept, near-wall velocity field in a millimeter-ordered parallel plate channel was measured with low Reynolds numbers (Re = 1 ∼ 5) Poiseuille flow to confirm the validity of it. As a result, we can obtain the near-wall velocity within 15 μm from the wall precisely. From the velocity distribution, the standard deviation of the velocity at each location was calculated and the dispersion of velocity was evaluated. As a result, it was confirmed that the measurement was carried out more accurately in high-speed area. Comparison of the measured velocity distribution with a theoretical calculation and micro-PIV results were also done. From these velocity distributions, the wall shear stress on the wall was determined.
Design of Multiscale Nanofluidic Networks
Authors: Stephenson David , Lockerby Duncan A. , Borg Matthew K. , Reese Jason M.
Published: November 2015

We present a hybrid molecular-continuum method for the design and simulation of high-aspect-ratio nanofluidic networks. By generalising the application of constraints, we enable the geometry, i.e. channel heights and lengths, to be the output of the method, removing the need for a costly trial-and-error process.

We compare multiple constraint combinations of our hybrid method with a full molecular dynamics simulation for a network consisting of a straight channel between two reservoirs. We show that, in each case, our method converges quickly, within 3 iterations, providing a computational speed-up over a full molecular simulation of 3:9. The speed-up demonstrated is far more modest than it would be for larger networks, but our verification case is restricted by the need to perform a full molecular simulation. Excellent agreement is found between our hybrid method and the full molecular simulation, with relative errors of < 1% for all cases.
Mechanistic Considerations for Enhancing Flow Boiling Heat Transfer in Microchannels
Authors: Kandlikar Satish G.
Published: November 2015

Research efforts on flow boiling in microchannels were focused on stabilizing the flow during the early part of the last decade. After achieving that goal through inlet restrictors and distributed nucleation sites, the focus has now shifted on improving its performance for high heat flux dissipation. The recent worldwide efforts described in this paper are aimed at increasing the critical heat flux (CHF) while keeping the pressure drop low, with an implicit goal of dissipating 1 kW/cm2 for meeting the high-end target in electronics cooling application. The underlying mechanisms in these studies are identified and critically evaluated for their potential in meeting the high heat flux dissipation goals. Future need to simultaneously increase the CHF and the heat transfer coefficient (HTC) has been identified and hierarchical integration of nanoscale and microscale technologies is deemed necessary for developing integrated pathways toward meeting this objective.
Performance Characterization of a Capacitive Deionization Water Desalination System With an Intermediate Solution and Low Salinity Water
Authors: Salamat Seyedehyasamin , Rios Perez Carlos A. , Hidrovo Carlos
Published: November 2015

In recent years, more efforts have been made to improve new and more efficient non-membrane-based methods for water desalination. Capacitive deionization (CDI), a novel technique for water desalination using an electric field to adsorb ions from a solution to a high-porous media, has the capability to recover a fraction of the energy consumed for the desalination during the regeneration process, which happens to be its most prominent characteristic among other desalination methods. This paper introduces a new desalination method that aims improving the performance of traditional CDI systems. The proposed process consists of an array of CDI cells connected in series with buffer containers in between them. Each buffer, serve two purposes: 1) average the outlet solution from the preceding cell, and 2) secure a continuous water supply to the following cell. Initial evaluation of the proposed CDI system architecture was made by comparing a two-cell-one-buffer assembly with a two cascaded cells array. Concentration of the intermediate solution buffer was the minimum averaged concentration attained at the outlet of the first CDI cell, under a steady state condition. The obtained results show that proposed CDI system with intermediate solution had better performance in terms of desalination percentage. This publication opens new opportunities to improve the performance of CDI systems and implement this technology on industrial applications.
Shrinkage of Post-Cure Die Attach Adhesives During Isothermal Storage
Authors: Liu Ruiyang , Lee HoHyung , Park Seungbae , Xue Xiaojie
Published: November 2015

Polymeric die-attach adhesives have been widely utilized for attaching the sensor die to the lead-frame substrate in the packaging of micro-electro-mechanical systems (MEMS). Although much study has been performed regarding viscoelastic behaviors of packaging materials, less literature has addressed the issue of post-cure shrinkage, which occurs in isothermal storage and in accelerated tests. However, the influence of post-cure shrinkage cannot be ignored in characterizing long-term viscoelastic properties or evaluating long-term reliability for highly sensitive automotive sensors.

In this study, a non-contact digital image correlation (DIC) method was used to characterize the post-cure aging shrinkage on a commercial epoxy-based die attach adhesive. The shrinkage strain of bulk specimens was monitored over a period of isothermal aging. Analysis indicates that the process of postcure shrinkage can be expressed in terms of exponential time functions. Using hygroscopic shrinking as an analogous process, this aging was introduced into a time-dependent finite element (FE) simulation in ANSYS®15.0. FE case studies combining both stress and dimensional relaxation indicate that certain differences can occur in the long-term finite element analysis if the shrinkage strain is ignored.
Passive Thermal Management Using Phase Change Materials: Experimental Evaluation of Thermal Resistances
Authors: Ganatra Yash , Marconnet Amy
Published: November 2015

Limited heat dissipation and increasing power consumption in processors has led to a utilization wall. Specifically due to high transistor density, not all processors can be used continuously without exceeding safe operating temperatures. This is more significant in mobile electronic devices which, despite relatively large chip area, are limited by poor heat dissipation — primarily natural convection from the exposed surfaces. In the past, solid-to-liquid phase change materials (PCMs) have been employed for passive thermal control — absorbing energy during the phase change process while maintaining a relatively fixed temperature. However, the lower thermal conductivity of the liquid phase after melting often limits the heat dissipation from the PCM, and in the liquid state, the material can flow away from the desired location. Here we focus on characterization of thermal performance of PCMs with the goal of evaluating dry (gel-to-solid/amorphous-to-crystalline) phase change materials which are intended to mitigate the pumpout issue. Critical thermophysical properties include the thermal conductivity, heat capacity, and latent heat of the phase/state change. The thermal resistance throughout the phase change process is measured by in-house rig which miniaturizes the reference bar method for use with infrared temperature sensing.
Influence of Secondary Impact on Failure Modes in PWAs With High Resonant Frequency
Authors: Meng Jingshi , Dasgupta Abhijit
Published: November 2015

Thinner printed wiring assemblies (PWA) and smaller clearances are driven by the continuing increase of functionality and miniaturization in portable electronic devices. The probability of secondary impact during accidental drop and impact between a circuit card and adjacent components increases with the decrease in the size and weight of the product. In particular, compared to the initial impact, impulses caused by contact during secondary impacts are typically characterized by significant increase of amplitudes and extremely short pulse widths. As a result, stress wave transmission and reflection in printed wiring boards (PWBs) can be at a frequency range close to the resonant frequencies of PWA components with miniature internal structures, such as MEMS. This study focuses on analyzing the high frequency content of the accelerations due to stress wave propagation, reflections and dispersions in the thickness direction of multilayered PWBs, caused by secondary impact, and on the consequential effects on typical failure modes with high resonant frequencies.
Hydrogen Storage Using Carbon Nanostructures
Authors: Smith Sheriden , Park Young Ho
Published: November 2015

Carbon nanostructures were reported to be very promising materials for hydrogen storage, and a great deal of interest has been focused on adsorption of molecular hydrogen in carbon nanostructures. Although many experimental results for hydrogen storage in carbon nanostructures were reported, corresponding theoretical studies have not been developed and adsorption mechanisms have not been fully identified. Better understanding of molecular level phenomena provides clues to designing hydrogen storage that performs better. Atomic simulations are useful in the evaluation of hydrogen storage capacity of carbon nanotubes. In this paper, molecular simulations of hydrogen physisorption in carbon nanotubes were conducted. Hydrogen density distribution near carbon nanotubes was studied, and hydrogen storage capability is determined by computing hydrogen to carbon atom ratio. The peak hydrogen concentration around the nanostructures was simulated to be located relatively consistently around 3 angstroms away from each nanostructure.
Evaluation of Stress Amplitude of Bolted Joints by FE Analysis and Joint Diagram and a Simple Strategy for its Reduction
Authors: Fukuoka Toshimichi , Taniuchi Hiroyuki
Published: November 2015

Fatigue failures of bolted joints are of great concern when designing machines and structures. A joint diagram is often used to evaluate the stress amplitude of the target bolt caused by alternating external forces. It has already been pointed out by some researchers and design engineers that the diagram cannot estimate the stress amplitude with sufficient accuracy for practical use. The primary reason is that a conventional joint diagram does not take into account the effect of joint interface separation, which often occurs under high external forces. Also, Load Factor, the ratio of the bolt force increase to the applied external force, shows a non-linear behavior for varying external force, though it is usually assumed to be constant in a conventional joint diagram.
Nuclear Fatigue Analysis Codified Design Rules: Comparison of Cyclic Plasticity Effects
Authors: Faidy Claude , Wasylyk Andrew
Published: November 2015

Large uncertainties exist in fatigue life evaluation using existing elastic stress analysis.

The usage factor is obtained by comparison of strain amplitude evaluation on different points of the components and the fatigue S-N curve of the material.

This paper will review existing codified rules in major nuclear Codes that are proposed as simplified elastic-plastic analysis of strain amplitude.

The different formulas proposed by the different Codes are described with their own background document and compared on typical cases.

Methods are based on simplified elastic-plastic approach (elastic analysis plus correction factor) with associated material data.

The Code comparison includes nuclear Codes, as ASME Boiler and Pressure Vessel Code Section III, French RCC-M and RCC-MRx and German KTA; Russian PNAEG Code and JSME rules are also considered based on specific English version of the Codes for fatigue rules.

Two types of components are concerned by the comparison: vessels and piping systems.

All these Codes are proposing different Ke and Kv rules based on different assumption.

Finally, a first set of recommendation to perform reference inelastic analysis will be presented to improve existing codes on an harmonized way, associated to analytical recommendations, all material properties needed and criteria to apply this modern methods.

This review is mainly done in World Nuclear Association (WNA), Cooperation in Reactor Design Evaluation and Licensing (CORDEL) Working Group, Codes & Standards Task Force.
Effect of Conversion of Margin for Allowable Stress on NDE Flaw Detectability
Authors: Hasegawa Kunio , Oishi Yuichi , Hasegawa Tadayuki , Sato Takemitsu
Published: November 2015

Allowable stress for code is determined based on material tensile strength SU using design margin, where the design margin is normally taken to be 5.0, 4.0 or 3.5. ASME B&PV Codes Sections I, III and VIII Division 1 had improved the design margin from 4.0 to 3.5 in 1998. Japanese industrial codes such as JIS (Japanese Industrial Standards), HPI (High Pressure Institute) codes and Japanese government rules has two design margins of 4.0 and/or 3.5. One of the Japanese government rules is discussing to introduce the design margin of 3.5 for thermal power boilers. The allowable stress based on 3.5 increases to 14% larger that based on 4.0. The objective of the paper is to demonstrate that minimum flaws by NDE (non destructive examination) technologies can be well identified, and permissible flaws by NDE are harmless to cause fractures, even when the design stresses increase by 14%.
The Investigation of Significance of the Geometrical Nonlinearity for 1-D Crack Stress Intensity Factor Calculation in Slightly Distorted Thin-Walled Pressurized Pipe
Authors: Orynyak Igor , Oryniak Andrii
Published: November 2015

The consideration of a geometrical nonlinearity is a common practice for the thin-walled structures. The relevance here are two well-known cases treated in ASME codes. First one is accounting for reduction of the pipe bends flexibility due to the inner pressure. The second one is the retarded increasing (and subsequent saturation) of additional local bending stress with increasing of inner pressure in a pipe with initial cross section form distortion. In both cases the rerounding effect and decreasing of local flexibilities take place. The crack can be treated as the concentrated flexibility and it is quite natural to expect that the stress intensity factor should grow nonlinearly with applied load.

Two cases of SIF calculation for 1-D long axial surface crack in a pipe loaded by inner pressure are considered here: a) cross section has an ideal circular form: b) the form has a small distortion and crack is located in the place of maximal additional bending stresses.

The theoretical analysis is based on: a) the well known crack compliance method [1] and b) analytical linearized solution obtained for deformation of the curved beam in case of action of fixed circumferential stress due to pressure written in the form convenient for transfer matrix method application.

It was shown that for moderately deep crack (crack depth to the wall thickness ratio is 0.5 and bigger) and typical dimensions of pipes used for oil and gas transportation (radius to thickness ratio is 25–40) and loading which can reach up to 200 to 300 MPa, the effect investigated can be quite noticeable and can lead to 5–15 percent reduction of calculated SIF as compared with linear calculation.

The analytical results are supported by nonlinear FEM calculation.
The Effect of Biaxial Loading on the Limit Load of Cracked Plates
Authors: Meek Caroline , Ainsworth Robert A.
Published: November 2015

To address the issue of the lack of guidance in fitness-for-service codes [1], [2], for biaxial and triaxial effects on fracture, this paper expands on results presented at PVP 2014 [3] for a centre cracked plate by including the effect of plate length and then presents results for single edge and double edge cracked plates. The results demonstrate that load biaxiality can have a significant effect on the limit load and the crack driving force; reducing the limit load and increasing the crack driving force relative to that for uniaxial loading for negative biaxiality and high positive biaxiality but increasing the limit load and reducing the crack driving force for some intermediate levels close to equibiaxial loading.
ASME Section VIII Recertification of a 33,000 Gallon Vacuum-Jacketed LH2 Storage Vessel for Densified Hydrogen Testing at NASA Kennedy Space Center
Authors: Swanger Adam M. , Notardonato William U. , Jumper Kevin M.
Published: November 2015

The Ground Operations Demonstration Unit for Liquid Hydrogen (GODU-LH2) has been developed at NASA Kennedy Space Center in Florida. GODU-LH2 has three main objectives: zero-loss storage and transfer, liquefaction, and densification of liquid hydrogen. A cryogenic refrigerator has been integrated into an existing, previously certified, 33,000 gallon vacuum-jacketed storage vessel built by Minnesota Valley Engineering in 1991 for the Titan program. The dewar has an inner diameter of 9.5’ and a length of 71.5’; original design temperature and pressure ranges are −423°F to 100°F and 0 to 95 psig respectively. During densification operations the liquid temperature will be decreased below the normal boiling point by the refrigerator, and consequently the pressure inside the inner vessel will be sub-atmospheric. These new operational conditions rendered the original certification invalid, so an effort was undertaken to recertify the tank to the new pressure and temperature requirements (−12.7 to 95 psig and −433°F to 100°F respectively) per ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. This paper will discuss the unique design, analysis and implementation issues encountered during the vessel recertification process.