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An experimental investigation of heat and mass transfer in a horizontal-tube falling-film ammonia-water absorber, operated as part of a complete ammonia-water absorption test facility, is presented. A tube bank consisting of four columns of six 9.5 mm nominal outer diameter, 0.292 m long tubes was installed in an absorber shell that allowed flow visualization and heat and mass transfer measurements at component- and local-levels. The Falling-film mode was found to account for a major portion of the absorber. The effects of operating conditions on the heat and mass transfer coefficients were investigated. While the solution Nusselt number increased, the vapor and liquid Sherwood numbers remained relatively insensitive to the solution Reynolds number. Heat and mass transfer models were developed to predict the absorber performance over a wide range of operating conditions in air-conditioning and heat pumping modes (solution concentration: 5–40%, pressures: 150, 345, 500 kPa, and solution flow rates: 0.019–0.034 kg s−1).

Research has shown that both gender and family socioeconomic status (SES) are important determinants of adolescents' physical activity (PA). This study expands our current knowledge by exploring the moderating role of family SES on gender differences in adolescents' out-of-school PA. We also examine whether this moderating effect varies across countries with different levels of gender inequality. Based on existing empirical studies and theoretical framework, it is hypothesized that 1) gender differences in out-of-school PA would be smaller among adolescents from higher SES families due to them being more likely to share egalitarian gender norms, and 2) this SES gradient in gender differences in adolescents' out-of-school PA would be more salient in countries with lower levels of gender inequality. A total of 316,657 15-year-old adolescents in 50 countries from the 2015 Programme for International Student Assessment (PISA) survey were analyzed. Our multilevel negative binomial regression models show that the gender gap in out-of-school PA is mitigated among families with higher SES, but this moderating role of family SES is less noticeable in countries with higher levels of national gender inequality. Our findings suggest the importance of egalitarian gender culture at both individual and macro-level in understanding gender disparities in adolescents' PA.

For application to all-solid-state thin film batteries, lithium boron phosphorus oxynitride (LiBPON) thin films were fabricated by RF magnetron sputtering technique of lithium borate (Li 3 BO 3 ) and lithium phosphate (Li 3 PO 4 ) target under N 2 atmosphere. To investigate the mixed former effect upon the LiBPON thin films, we prepared various films with controlled B and P contents. The LiBPON thin film formulation with nearly equal B and P contents showed the highest room-temperature lithium ionic conductivity of 3.52 × 10 −6 S cm −1 and the lowest activation energy of 48.24 kJ mol −1 owing to the mixed former effect, the increased lithium content and nitridation. Infrared spectra of the glass thin films achieved two dominant peaks corresponding to BO 3 3− and PO 4 3− unit. N1s spectra were analyzed by X-ray photoelectron spectroscopy that the increased ionic conductivities observed were related to the formation of triply coordinated nitrogen.

Atomically smooth, single crystalline Bi 2 Se 3 thin films were grown on a Ge(1 1 1) substrate using molecular beam epitaxy. Crystallinities of both the surface and the bulk as well as the stoichiometry of the grown film were characterized by using low-energy electron diffraction, scanning tunneling microscopy, X-ray diffraction, and photoelectron spectroscopies. Hexagonal atomic structures, quintuple layer steps observed in STM images confirmed that the Bi 2 Se 3 film with a (0 0 0 1) surface was grown. Diffraction peak positions as well as the chemical composition determined from the core-level photoelectron spectra coincide well with those expected for the Bi 2 Se 3 crystal. The surface state with a Dirac cone was observed in the valence photoelectron spectra, which also support that a high-quality Bi 2 Se 3 film was grown on the Ge(1 1 1) substrate. The interface between Ge(1 1 1) and Bi 2 Se 3 (0 0 0 1) is expected to be abrupt due to the small lattice between them.

All-solid-state lithium ion batteries (ASSLIBs) are very promising next-generation lithium ion batteries with high energy density and safety. Among the solid electrolytes that can be applied to ASSLIBs, sulfide glass-ceramics electrolytes are attracting attention because of their high ionic conductivity and good mechanical deformability. However, the lack of the chemical and electrochemical stability of the sulfide electrolytes under prolonged cycle operation has become a barrier limiting their practical use and commercialization. We investigated the effects of Sn substitution on the electrochemical and chemical stability enhancement of Li2S-P2S5 glass-ceramics electrolytes. Also, we analyzed the cause of the degradation by side reactions and lithium dendrite growth. For 80Li2S-15P2S5-10SnS2 glass-ceramics electrolyte, only the redox current of the lithium deposition/dissolution was observed in cyclic voltammetry test with lithium metal. And the result of X-ray photoelectron spectroscopy analysis demonstrated a reduction in the amount of Li2S and decomposition product from the sulfide solid electrolytes. ASSLIBs using 80Li2S-15P2S5-10SnS2 as solid electrolytes with Li metal or Li-In anodes showed improved cycling performance compared to batteries employing 80Li2S-20P2S5 glass-ceramics. These results showed that Sn substitution is effective to improve the chemical and electrochemical stability of Li2S-P2S5 glass-ceramics electrolyte to lithium metal.

Many researches have been focused on internal condensation with machined microstructure patterns on internal surfaces that can improve heat transfer performance up to 400% comparing to smooth surfaces. However, microstructure patterns are not effective for all geometries such as micro-channels and other complicated shapes. This study uses a dropwise condensation (DWC) promoter that can be easily applied to different geometries to improve internal condensation heat transfer. The main objectives of this study are to investigate internal condensation heat transfer by the dropwise condensation promoter via (i) developing an internal dropwise condensation model and (ii) conducting internal condensation experiments with the dropwise condensation promoter. The dropwise condensation model was modified to the available internal condensation model. The experiments for internal steam condensation were conducted for aluminum and copper tubes with external fins and an internal coating for dropwise condensation. The experimental results are compared to the results from several correlations in the literature and the model developed in this study. It is found that most correlations in the literature overestimate internal condensation heat transfer coefficients at low mass fluxes. The dropwise condensation model shows that dropwise condensation promoters can enhance internal condensation heat transfer coefficients. This conclusion is verified by experimental results demonstrating that the hydrophobic dropwise condensation promoter used in this study can enhance internal condensation heat transfer coefficients by 50%.

A two-step annealing method with a low thermal budget is proposed for advanced surface-energy-driven secondary grain growth of Ge films without any agglomeration. In the first-step annealing, the normal grain growth from as-deposited poly-crystalline Ge films was induced to make the grain size equivalent to the film thickness at 800 °C. After the subsequent second-step annealing at 900 °C, the much larger secondary grains were obtained than those by single-step annealing at 900 °C. The possible explanation regarding the final microstructure of the two-step annealed film is proposed. The two-step annealing was able to form the microstructure of Ge thin film with very large-grained matrix without any agglomeration, resulting in higher carrier mobility. Therefore, the proposed two-step annealing is believed to be a promising process applicable for channel formation processes in the next-generation Ge thin film transistors for 3D integrated circuits and vertical NAND flash memories.

Unique micro/nano-scale porous surfaces were fabricated on the surfaces of steam condensers to promote dropwise condensation which can exhibit higher heat transfer rate than that of filmwise condensation. Steam condensation tests were conducted to evaluate heat transfer performance of the fabricated micro/nano-scale porous surfaces. The micro/nano-scale porous surfaces were prepared using a self-assembly technique, polymer based thin coatings, and a surface etchings technique. The resulting surface morphologies and the wetting characteristics were investigated using SEM and the liquid contact angle measurements to quantify important parameters for enhancing the dropwise condensation. From visual observations, it was deduced that the micro/nano-scale porous surfaces can effectively initiate dropwise condensation by generating smaller condensates and limiting the growth of ‘large’ condensate drops and by improving surface renewal rate.

In this paper, a dropwise condensation model using innovative “nano-scale, pin structured surfaces” is presented. The surfaces are porous surfaces oriented with nano- or sub micro-scale pins randomly designed or structurally arranged on extended and/or porous surfaces. These surfaces can promote a dropwise condensation showing a higher heat transfer rate than that of “filmwise” condensation by increasing the number of nucleation sites on the condenser surface and providing tunable surface properties such as surface wetting conditions. The developed model is consisted of a heat flux estimation of a single condensate drop based on thermal resistance analysis and a population theory for small and large condensate drops. The results of heat flux of a single condensate drop indicate that a smaller condensate drop with higher contact angle has a higher condensation heat flux; however, when it combined with population theory, a hemispherical shape of condensate with Wenzel surface wetting mode and a higher pin density can increase dropwise condensation heat transfer rates. In addition, a thinner nano- or sub micro-scale pins surfaces is required to increase condensation heat fluxes, when it is applied.

We investigated the deep level photoluminescence and cathodoluminescence emissions from GaInP grown on Ge and Ge-on-Si substrates by metal-organic chemical vapor deposition. Considering the interface condition after the growth of GaInP on Ge, we speculated that the P vacancies and/or Ge atoms from the underlying layer due to interdiffusion were responsible for the deep level emissions. Moreover, the anti-phase boundaries in GaInP, incompletely suppressed even when grown on off-axis Ge substrates, were also responsible for the deep level emissions.

An experimental study was conducted to investigate the effect of a micro-scale, porous-layer coating on solution wetting and heat transfer of a horizontal-tube, falling-film heat exchanger. A uniform layer of a copper powder was sintered onto plain copper tubes to create a micro-scale, porous coating on the tubes. Distilled water was used as solution and heating fluids. When the solution was dripped onto horizontal tubes, the visual observation confirmed that plain tubes were partially wetted, while the porous-layer coated tubes were completely wetted due to capillary action even at low solution flow rates. The comparison of the heat transfer results for two different tube surfaces (plain and porous-layer coated) clearly showed that the porous-layer coated tubes had twice as high evaporation heat transfer rate due to the complete solution wetting and higher heat transfer coefficient due to the thin spreading of the solution liquid.

Heat and mass transfer in a horizontal-tube falling-film ammonia-water absorber was investigated. A tube bank consisting of four columns of six 9.5 mm nominal OD, 0.292 m long tubes was installed in a shell that allowed heat and mass transfer measurements and optical access for flow visualization. This absorber was installed in a test facility consisting of all the components of a chiller, fabricated to obtain realistic operating conditions at the absorber to account for the influence of the other components in the system. Tests were conducted over desorber solution outlet concentrations of 5–40% for three nominal absorber pressures of 150, 345 and 500 kPa, for solution flow rates of 0.019–0.034 kg s−1. Measurement and analysis techniques, heat transfer rates, and solution- and vapor-side heat and mass transfer coefficients are described. Trends in heat and mass transfer coefficients are discussed, highlighting the effects of solution flow rate and concentration, and absorber pressure.

An experiment-based, two-medium thermal model was developed to evaluate the thermal response and protective performance of permeable clothing systems under hot air jet impingement conditions. The clothing systems consisted of single- or double permeable fabric(s) and air volume between the fabrics and an enclosure wall (solid surface with an embedded heat sink of constant-temperature) to mimic human skin. Two types of permeable fabrics were considered for this study: (i) NOMEX IIIA as a thermal protective fabric and (ii) Cotton/Spandex as a commodity fabric. The predicted results from the model were well compared with the experimental results from a previous work. A parametric study was conducted using various jet impingement conditions and design variables of the protective clothing such as the number of fabric layers, air leakage rate, air gap thickness, and fabric type. It was concluded from the parametric study that the permeable clothing with multiple layers of fabric, less air leakage, and thicker air gap had better thermal protective performance under hot air jet impingement conditions.

A novel miniaturization technology for binary-fluid heat and mass exchange was developed and numerous components were fabricated for demonstration as different parts of an ammonia/water absorption heat pump. Short lengths of microchannel tubes are placed in an array, with several such arrays stacked vertically. The ammonia/water solution flows in falling film/droplet mode on the outside of the tubes while coupling fluid flows through the microchannels. Coupling fluid heat transfer coefficients are extremely high due to the use of microchannel tubes. Effective vapor–solution contact on the absorption side minimizes heat and mass transfer resistances. This concept addresses all the requirements for absorber design in an extremely compact geometry. The technology is suitable for almost all absorption heat pump components (absorbers, desorbers, condensers, rectifiers, and evaporators) and for a wide range of binary-fluid processes. The development of several components for absorption and desorption at different capacities using this technology is reported here.

We investigated the effects of low temperature (LT) Ge buffer layers on the two-step Ge growth by varying the thickness of buffer layers. Whereas the two-step Ge layers using thin ( 50 nm) LT Ge buffer layers. The lowest threading dislocation density of 1.2 × 106 cm−2 was obtained when 80-nm-thick LT Ge buffer layer was used. We concluded that the minimum thickness of buffer layer was required to grow uniform two-step Ge layers on Si and its quality was subject to the thickness of buffer layer.

The deposition behavior of 300–1500 atom Au clusters was studied with molecular dynamics (MD) using a potential of the embedded atom method (EAM). This study was aimed at examining the possibility of thin-film growth by a cluster as a building unit, which had been suggested in the charged cluster model (CCM) (Hwang et al., J. Crystal Growth 162 (1996) 55). According to the CCM, most of the commercially available thin films were actually cluster- assembled ones although they have been believed to grow by the atomic unit. Small (300 and 500 atoms) and large (1000 and 1500) clusters equilibrated at 1000 K were used as the starting points for the simulation. Small clusters melted during equilibration at 1000 K, while large clusters did not. Clusters of various sizes were deposited on a Au (1 0 0) surface thermostated at 800 K. Within 50 ps, the 300-atom cluster underwent full epitaxial recrystallization with the substrate surface. In contrast, a much longer time was required for the 1000- and 1500-atom clusters to achieve full epitaxial recrystallization. The epitaxial recrystallization behavior of small and large clusters used in this simulation suggests the possibility of thin-film growth by a cluster unit as suggested in the CCM.