bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Thermal Conduction Through Polymeric Nanowires With the Dual Cantilever Technique
Authors: Canetta Carlo , Narayanaswamy Arvind 
Published: August 2016

Bi–material microcantilevers, with their high sensitivity to thermal stimuli, are ideally suited sensors for investigating nanoscale heat transfer. We have designed and fabricated low thermal conductance bi–material microcantilevers by minimizing their width and thickness. Using such cantilevers, we have demonstrated heat flux resolution of less than 1 picowatt. A pair of such cantilevers is proposed as a configuration for measuring thermal conductance of a nanostructure suspended between the two. In this technique, two lasers are focused, one on each cantilever. One laser is modulated to vary the temperature at the end of one cantilever, while the second laser senses variation in heat flow through the second cantilever due to thermal conduction along the nanowire. We have determined the resolution of such a conductance measurement by measuring the background conductance between the two cantilevers in the absence of a nanostructure suspended between them. The background conductance is due to other pathways for heat transfer between the cantilevers besides nanostructure conductance. We have measured the background conductance to be as low as 0.05 nWK−1.
We present measurements of thermal conductance of polystyrene nanowires performed using the dual cantilever technique. The nanowires are fabricated via electrospinning technique with diameters varying in the range of 150–300 nm. While the polystyrene nanowires present a demonstration of the cantilever technique for measuring thermal conductance, the technique we have developed can be extended to other types of nanostructures so long as they can be suspended between two cantilever ends.
Experimental Study of Buckling Behavior of Octagonal Thin-Walled Silicon Tube Grown by Edge-Defined Film-Fed Method
Authors: Wei Guanghua , Ma Ronghui , Zhang Hui , Zheng Lili 
Published: August 2016

Edge-defined Film-fed Growth (EFG) is a promising technology for production of silicon wafers with minimum loss of silicon material for photovoltaic applications. The growth of the hollow tubes by the EFG method is a very high temperature gradient along the direction of tube growth at the melt-solid interface. As this high temperature gradient is necessary to sustain the high speed of silicon growth through dissipating latent heat at the melt-solid interface, it generates substantial amount of thermal stresses that are associated with defect generation and deformation of the structure. With increase of the tube diameter and reduction of wall thickness, the large thermal stresses lead to significant buckling of the tube.
In this study, the buckling behavior of the growing silicon tube is studied experimentally by monitoring deflection of two pairs of opposite faces of an octagonal tube during the growth. Four capacitance sensors were placed on a fixed plane normal to the translation of the tube to measure the varying thickness of the air between the sensor and the tube surface throughout the tube growth. The recorded data reveal the buckling behavior of tubes for several growth runs. Despite the different growth conditions in the EFG systems, similar patterns of buckling behavior have been observed in octagonal silicon tubes with face width of 12.5 cm. A typical buckling pattern observed can be divided into three distinctively different stages, namely seed holder-influenced stage, tube growth stage, and a random fluctuation stage. Each stage has different amplitude of deflection and covers different length of the tube. More interestingly, the recorded surface deflection reveals the displacement of the center of the tube, suggesting off-centered growth and possible instability of the meniscus. It is considered that these mechanisms may contribute to the special buckling pattern observed during growth.
Transient Heat Conduction and Thermal Coefficient of Ceramic Coated Fabrics
Authors: Teimoori Khashayar , Sadegh Ali M. 
Published: August 2016

Ceramic coated fabrics have been employed for heat resistant clothing such as fire-fighters gears, fire-proof insulators, and heating and cooling insulators. Thus, transient heat conduction and thermal properties of such fabrics are needed for the design of the clothing. The goal of this study is to measure the transient heat conduction and the coefficient of thermal expansion of ceramic coated fabrics with different woven morphologies. This has been accomplished through an experimental setup consists of a hotplate assembly, applying a uniform temperature, with the accuracy of +/− 1 °C in less than 500 msec, a ceramic coated fabric and an infra-red thermometer assembly. This set up has been validated by using a known material such as aluminum and copper for the coefficient of thermal expansion measurement. The hot plate temperature was varied between 30 to 400°C within 300 seconds.
The transient heat conduction and the thermal coefficient of the woven ceramic coated fabrics were compared with ceramic nonwoven fabrics materials. Finally, upon comparing different samples and measuring the coefficients of thermal expansion, K’s, the level of delay in heat transfer with respect to time has been determined.
Jet Interaction in Cross Flow: Experimental and Numerical Model
Authors: Almeida Celso , Nunes António A. , Teixeira Senhorinha , Teixeira José Carlos , Lobarinhas Pedro 
Published: August 2016

Ventilation of wide spaces often requires a correct mixing of a jet in a cross flow. The present paper describes the application of Computational Fluid Dynamics (CFD) to model the interaction of a free stream jet with a cross flow, taking into account temperature gradients between the two streams. The model uses the finite volume technique for solving the conservation equations of fluid: mass, momentum and energy. Buoyancy is described by the Boussinesq approximation. The convergence of the solution required a high mesh refinement in the region of flow interaction.
The data were compared with experimental results obtained in a subsonic wind tunnel. The experiments were carried out along the 4.0 m long test section of a 1.4×0.8 low speed wind tunnel. The jets were injected at 90° through orifices 25 mm in diameter drawn from a plenum either at the same or higher temperature the free stream. The jet velocity to the free stream velocity ratio was set at 8 for a single jet and between 4 and 16 for multiple injections. Data include velocity, pressure and temperature.
The results show that the injection of relatively small cross-flow rates can cause the development of large regions of interaction with the main flux, accompanied by the creation of large scale flow structures, which contribute effectively to rapid mixing of the two streams.
A CFD simulation of temperature showed that a jet 30 diameters downstream (30D) is an extension of the plume covering almost half of the cross section and a good homogeneity, then the extension of the plume 120D which covers almost the entire cross section and an optimum mixing occurs.
The CFD simulation temperature of 13 jets showed that a toroidal extension of the plume and a good homogenization as early as 30D downstream of the injection point, occurs.
Velocity Based Defrost and Frost Inhibition of Evaporator Coils of Heat Pump
Authors: Muthusubramanian Kamalakkannan , Dessiatoun Serguei V. , Shooshtari Amir H. , Ohadi Michael M. 
Published: August 2016

Researchers in the past have reported various methods to either retard frost formation or minimize energy expenditure during defrosting, but the methods reported in this paper is novel. Use of air flow during heating and defrosting cycles has not been studied and reported so far.
The effect of using air flow during heating and defrosting cycles of heat pump were investigated experimentally.
In the heating cycle, it is found that at higher air flow velocities, it is possible to retard the rate at which frost grows on the evaporator coils of the heat pump. Changing the air velocity from 0.8 m/s to 2 m/s caused a significant reduction in the frost growth rate. The ΔT of the working fluid for the 2 m/s experiment stayed at least 0.5 ∼ 1.0 °C more than the corresponding value of the 0.8 m/s experiment for the entire 90 minute duration of the heating cycle.
In the defrost cycle, it is found that using air flow in the direction opposite to the normal air flow on the evaporator coil provides an energy saving opportunity by increasing the time interval between subsequent defrosting. It was seen that a reduction of 1 ∼ 2 defrost cycle was possible in 1 hour of operation, depending on the level of frost formation.
Heavy Duty Vehicle Cooling System Auxiliary Load Management Control: An Application of Linear Control Strategy (MIMO and SISO)
Authors: Sermeno Salvador , Bideaux Eric , Brun Xavier , Ameur Omar 
Published: August 2016

Vehicle Thermal Management covers the engineering field of solutions that maintain the complete vehicle in acceptable operating conditions regarding components and fluid temperatures in an engine. The maximum efficiency rating of a Diesel engine reaches up to 45%; a vast amount of the energy produced is transformed into heat. This heat is partly rejected in the exhaust gases and partly transmitted to the engine cooling circuit. The latter can be seen in two different ways, on the one hand, cooling is necessary to regulate the fluids and component temperature to an optimum operating point for fuel efficiency and maintain engine performance. On the other hand it constitutes a loss since the coolant system actuators are engine driven (pump, fan, etc.).
In order to improve the fuel efficiency of the vehicle one can reduce the losses generated by the cooling system. Ideally, the full motive force of the engine should be used for propulsion, and new and more efficient energy sources have to be explored to power the secondary systems (cooling, compressed air…). The electrification of some components in the cooling system can limit losses and improve component energy efficiency but it is not the only answer and in many cases this approach might be a limited. Recent studies have shown that by improving the control strategy of the cooling system the fuel consumption can be improved, however no real data is available since its implementation has been limited.
In keeping with latter approach, this paper introduces a novel control which aims at a more efficient regulation of the cooling system operation of a Heavy Duty Truck cooling system. The main complexity in such a system remains the interactions between actuators. In this paper we propose a way to solve this using a control based on model inversion and decoupling strategy. It needs to be noted that any new approach requires the current control specifications to be modified. This enables also a better understanding of the system. However, other goals can be exploited through the use of an advanced control and the new control specifications such as a reduction of thermal shock, reduction of thermal fatigue, minimization of system overcooling (directly impacts fuel consumption but also the noise levels).
Finally, the controller has been tested on a Simulation Platform using a Matlab/Simulink (Controller) and compared to the existing system control using a reference driving cycle.
Visual and Numerical Study for Dropwise Condensation Heat Transfer Mechanism of Steam-Air Mixture Vapor
Authors: Ma Xuehu , Rongfu Wen , Lan Zhong , Zhou Xingdong 
Published: August 2016

Non-condensable gas (NCG) is well known for degrading condensation heat transfer due to the accumulation of NCG near the gas-liquid interface. It has been found that a small amount of NCG results in a significant reduction of heat transfer performance. In the present work, dropwise condensation heat and mass transfer mechanism of steam-air mixture were studied on a vertical plate experimentally and theoretically. Considering the dynamic interaction of condensate and gas-vapor diffusion layer, the study focused on the interfacial effect on heat and mass transfer of condensation in the presence of NCG. Comparison of growth rates of new nucleated droplets in different regions showed the enhancement of mass transfer by the gas phase perturbation. Taking advantage of visualization, the influences of droplet curvature, departure movement and transversal suction effect on mass transfer in the interfacial mass diffusion layer were investigated. The numerical simulation subsequently revealed the mixing characteristic of steam and air in the mass diffusion layer which was corroborated by the visual results inspected by PIV technology. Due to the relative motion of condensed droplet and steam-air mixture vapor, eddy flow occurred in the gas phase resulting in a perpendicular velocity of the bulk vapor to the condensing surface and a perpendicular velocity of the accumulated NCG to the vapor bulk which enhanced the heat and mass transfer in dropwise condensation.
The study provides an insight into the disturbance of the diffusion boundary layer by droplet departure movement, as well as the need to design specific surface to promote the droplet departure movement and achieve enhanced heat and mass transfer during dropwise condensation in the presence of NCG.
Numerical Investigation on Thermal and Fluid Dynamic Behavior of Laminar Slot-Jet Impinging on a Surface at Uniform Heat Flux in a Confined Porous Medium in Local Thermal Non-Equilibrium Conditions
Authors: Buonomo Bernardo , Manca Oronzio , Nardini Sergio , Lauriat Guy 
Published: August 2016

A numerical investigation on a single slot jet impinging in a porous parallel-plate channel containing an air-saturated high permeability porous medium is accomplished. The wall opposite the slot jet is partially heated at uniform heat flux and the buoyancy effects are taken into account. The fluid flow is assumed two dimensional, laminar and steady. The porous medium is modeled using the Brinkman–Forchheimer-extended Darcy model and the Boussinesq approximation. The local thermal non-equilibrium (LTNE) hypothesis is invoked. The results are discussed in terms of streamlines, fluid and solid phase temperature fields, wall temperature profiles and local and average Nusselt numbers.
The porous medium allows a more significant heat transfer close to the end of the heated part of the plate. For low Peclet numbers, forced flow and natural convection are opposite and the mean Nusselt number shows a decrease in heat transfer, whereas they are aiding for high Peclet numbers. Porosity effects on the mean Nusselt numbers were found weak.
An Experimental Study of Marangoni Convection in Confined and Volatile Binary Liquids: The Effect of Noncondensables
Authors: Li Yaofa , Yoda Minami 
Published: August 2016

Marangoni convection in a liquid layer subject to a horizontal temperature gradient due to variations in the surface tension at the liquid-vapor interface and confined in a rectangular enclosure is a basic problem of heat transfer and fluid mechanics, with applications in evaporative cooling. In general, surface tension increases as temperature decreases, giving rise to thermocapillary stresses that drive liquid coolant away from hot regions. In a volatile binary-fluid mixture, however, the two components can be chosen so that the surface tension of the mixture increases as temperature increases due to differential evaporation, giving rise to solutocapillary stresses that can drive liquid instead towards hot regions, and hence oppose the thermocapillary stresses.
It is of course well-known that noncondensables suppress phase change. Yet there have been few, if any studies of how noncondensables affect the Marangoni convection of volatile binary fluids in a confined geometry, where evaporation and condensation must balance. An experimental study was therefore performed of Marangoni convection in a layer of methanol-water (MeOH-H2O) mixture confined in a sealed rectangular cuvette. The cuvette was symmetrically heated on one end and cooled on the other end using Peltier devices, giving temperature differences of ∼6 °C over a horizontal distance of 4.9 cm, and two-dimensional, two-component particle-image velocimetry (2D-2C PIV) was used to measure the velocity fields in this steady flow. The study focuses on convection in liquid layers with a depth of ∼0.3 cm (vs. a test cell height of 1 cm), and how this flow is affected by changes in the relative concentration of noncondensables (i.e., air) in the gas space above the liquid. The results suggest that changing the concentration of noncondensables, which also has a marked effect on the pressure, in the gas space, can be used to “adjust” the relative importance of solutocapillary and thermocapillary stresses.
3D Examination of the Thermal Properties of Carbon-Carbon Composites
Authors: Patrick Melanie , Saad Messiha 
Published: August 2016

Thermal characterization of composites is essential for their proper assignment to a specific application. Specific heat, thermal diffusivity, and thermal conductivity of carbon-carbon composites are essential in the engineering design process and in the analysis of aerospace vehicles, space systems and other high temperature thermal systems. Specifically, thermal conductivity determines the working temperature levels of a material and is influential in its performance in high temperature applications.
There is insufficient thermal property data for carbon-carbon composites over a range of temperatures. The purpose of this research is to develop a thermal properties database for carbon-carbon composites that will contain in-plane (i-p) and through-the-thickness (t-t-t) thermal data at different temperatures as well as display the effects of graphitization on the composite material. The carbon-carbon composites tested were fabricated by the Resin Transfer Molding (RTM) technique, utilizing T300 2-D carbon fabric and Primaset PT-30 cyanate ester resin.
Experimental methods were employed to measure the thermal properties. Following the ASTM standard E-1461, the flash method enabled the direct measurement of thermal diffusivity. Additionally, differential scanning calorimetry was performed in accordance with the ASTM E-1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density data were used to compute the thermal conductivity of the carbon-carbon composites. The measured through-the-thickness thermal conductivity values of all the materials tested range from 1.0 to 17 W/m·K, while in-plane values range from 3.8 to 4.6 W/m·K due to the effect of fiber orientation. Additionally, the graphitized samples exhibit a higher thermal conductivity because of the nature of the ordered graphite structure.
Genomic Analysis of the Evolution of Fluoroquinolone Resistance in Mycobacterium tuberculosis Prior to Tuberculosis Diagnosis
Authors: Zhang Danfeng , Gomez James E. , Chien Jung-Yien , Haseley Nathan , Desjardins Christopher A. , Earl Ashlee M. , Hsueh Po-Ren , Hung Deborah T. 
Published: August 2016

ABSTRACT

Fluoroquinolones (FQs) are effective second-line drugs for treating antibiotic-resistant tuberculosis (TB) and are being considered for use as first-line agents. Because FQs are used to treat a range of infections, in a setting of undiagnosed TB, there is potential to select for drug-resistant
Mycobacterium tuberculosis
mutants during FQ-based treatment of other infections, including pneumonia. Here we present a detailed characterization of ofloxacin-resistant
M. tuberculosis
samples isolated directly from patients in Taiwan, which demonstrates that selection for FQ resistance can occur within patients who have not received FQs for the treatment of TB. Several of these samples showed no mutations in
gyrA
or
gyrB
based on PCR-based molecular assays, but genome-wide next-generation sequencing (NGS) revealed minority populations of
gyrA
and/or
gyrB
mutants. In other samples with PCR-detectable
gyrA
mutations, NGS revealed subpopulations containing alternative resistance-associated genotypes. Isolation of individual clones from these apparently heterogeneous samples confirmed the presence of the minority drug-resistant variants suggested by the NGS data. Further NGS of these purified clones established evolutionary links between FQ-sensitive and -resistant clones derived from the same patient, suggesting
de novo
emergence of FQ-resistant TB. Importantly, most of these samples were isolated from patients without a history of FQ treatment for TB. Thus, selective pressure applied by FQ monotherapy in the setting of undiagnosed TB infection appears to be able to drive the full or partial emergence of FQ-resistant
M. tuberculosis
, which has the potential to confound diagnostic tests for antibiotic susceptibility and limit the effectiveness of FQs in TB treatment.
Streptococcus pneumoniae Serotypes 9 and 14 Circulating in Brazil over a 23-Year Period Prior to Introduction of the 10-Valent Pneumococcal Conjugate Vaccine: Role of International Clones in the Evolution of Antimicrobial Resistance and Description of a Novel Genotype
Authors: Pinto Tatiana C. A. , Kegele Fabíola C. O. , Dias Cícero A. G. , Barros Rosana R. , Peralta José M. , Merquior Vânia L. C. , Carvalho Maria da Gloria , Chochua Sopio , Hawkins Paulina , McGee Lesley , Teixeira Lucia M. 
Published: August 2016

ABSTRACT

Antimicrobial-resistant pneumococcal strains have been detected worldwide since the 1960s. In Brazil, the first penicillin-nonsusceptible pneumococci (PNSP) were reported in the 1980s, and their emergence and dissemination have been mainly attributed to serogroup 9 and serotype 14 strains, especially those highly related to recognized international clones. In the present study, antimicrobial susceptibility testing and multilocus sequence typing were performed on 315 pneumococcal isolates belonging to serogroup 9 (
n
= 99) or serotype 14 (
n
= 216), recovered from patients or asymptomatic carriers between 1988 and 2011 in Brazil, in order to trace changes in antimicrobial resistance and genotypes prior to the full introduction of the pneumococcal conjugate vaccine in the country. Over the 23-year study period, the PNSP levels increased, and four clonal complexes (CC156, CC66, CC15, and CC5401) have played important roles in the evolution and dissemination of pneumococcal isolates belonging to serogroup 9 and serotype 14, as well as in the emergence of antimicrobial resistance, in the pre-pneumococcal-vaccination era. The earliest PNSP strains detected in this study belonged to serotype 9N/ST66 and were single locus variants of the international clone Tennessee
14
-18 ST67 (CC66). The first serotype 14 PNSP isolates were identified in 1990 and were related to the England
14
-9 ST9 (CC15) clone. Serotype 14 PNSP variants of the Spain
9V
-3 ST156 clone with elevated penicillin MICs and nonsusceptibility to other beta-lactams were detected in 1995 and showed an increasing trend over the years. The results also indicated that introduction of ST156 in our region was preceded by the emergence of trimethoprim-sulfamethoxazole resistance and by the dissemination of ST162. In addition to the presence of successful international clones, a novel regional serotype 14 genotype (CC5401) has emerged in 1996.