A Consideration of the Similarity Solution for Laminar Forced-Convection Condensation of Saturated Vapors

The similarity solution of the two-phase boundary layer equations of laminar forced-convection condensation of saturated vapors on a flat surface is obtained by combining the series expansion method with Runge-Kutta-Verner method, and new correlation equations are presented as follows: Eq. (46) with Fig. 3 and Eq. (48) for the local heat transfer coefficient and the local condensation mass flux, respectively, in the ranges of R=5, 10, 100, PrL=1~100 and RH/PrL=0.01~10, Eq. (49) for the local heat transfer coefficient in the ranges of R=1000, PrL=0.003~0.03, H/PrL=0.01~1, and．Eps. (59) and (60) for the shear stress at the vapor-1iquid interface and the cooling surface, respectively. The convection term in the condensate film affects remarkably upon the decrease of condensation mass flux rather than the increase of heat transfer coefficient

Biogenetic temperament and character profiles and attention deficit hyperactivity disorder symptoms in Korean adolescents with problematic Internet use

The objective of this study was to evaluate the biogenetic temperament and character profiles in Korean adolescents with problematic Internet use. Six hundred eighty-six high school students completed the Internet Addiction Test (IAT), Junior Temperament and Character Inventory (JTCI), and Conners/Wells Adolescent Self-Report Scale: Short Form (CASS: Short). The problematic Internet use group showed higher scores in the Self-Directedness and Cooperativeness profiles and lower scores in the Novelty Seeking and Self-Transcendence profiles of the JTCI, compared with the nonproblematic Internet use group, after controlling for the ADHD symptoms. The results of this study suggest that temperament/character patterns should be considered in accounts of the etiology of problematic Internet use

Reference Temperature for Evaluating Physical Properties of Condensate Film in the case of Free-Convection Laminar Film Condensation

The boundary layer equations for free-convection laminar film condensation of pure vapors of water, ethanol and propane on a vertical surface are numerically solved for the cases of constant properties, variable viscosity and variable relevant physical properties. The conclusions are as follows: (1) The ratio of the heat flux at the vapor-liquid interface to that at the cooling surface is expressed by [numerical formula] (2) The correction for Nusselt\u27s equation due to the thermal convection effect is roughly estimated by [numerical formula] (3) The dimensionless reference temperature r_T derived from Fujii\u27s aproximate analysis has been confirmed by the numerical results for the case of variable viscosity. (4) The Nusselt\u27s equation evaluated by the physical properties at r_T=1/4 predicts heat flux at the cooling surface within an error of two per cent

Associations between symptoms of attention deficit hyperactivity disorder, depression, and suicide in Korean female adolescents

The objective of this study was to examine the associations between symptoms of attention-deficit/hyperactivity disorder (ADHD), depression, and suicide in Korean female adolescents. It was hypothesized that the relationship between ADHD symptoms and suicidal ideation would be mediated by the level of depressive symptoms. Seven hundred and eighty-eight high school girls completed the Conners/Wells Adolescent Self-Report Scale: Short Form, Children's Depression Inventory, and Reynolds Suicidal Ideation Questionnaire. Path analyses were conducted using the statistical program, AMOS version 4.0, to determine the best fitting model. The conduct, cognitive, and hyperactivity problems of the ADHD symptoms in each domain were associated positively with the depressive symptoms, with the depressive symptoms being associated with suicidal ideation. This initially proposed model represented an acceptable fit to the data (root mean square error of approximation, RMSEA=0.077; normed fit index, NFI=0.998; non-NFI, NNFI=0.990; comparative fit index, CFI=0.998). The inclusion of a direct path from the conduct problems of ADHD symptoms to suicidal ideation significantly improved the model fit (RMSEA=0, NFI=1, NNFI=1, CFI=1). The results of our study suggest that depressive symptoms partially mediate the relationship between ADHD symptoms and suicidal ideation, and that the conduct problems of ADHD symptoms are associated with suicidal ideation both directly and indirectly via the depressive symptoms in Korean female adolescents

High-Performance Graphene-Based Transparent Flexible Heaters

We demonstrate high-performance, flexible, transparent heaters based on large-scale graphene films synthesized by chemical vapor deposition on Cu foils. After multiple transfers and chemical doping processes, the graphene films show sheet resistance as low as similar to 43 Olun/sq with similar to 89% optical transmittance, which are ideal as low-voltage transparent heaters. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional transparent heaters based on indium tin oxide. In addition, we confirmed that mechanical strain as high as similar to 4% did not substantially affect heater performance. Therefore, graphene-based, flexible, transparent heaters are expected to find uses in a broad range of applications, including automobile defogging/deicing systems and heatable smart windows

Representative Physical Properties for the Vapor Boundary Layer in the Case of Laminar Film Condensation of Binary Vapor Mixtures : (I) Forced-Convection Condensation

The two-phase boundary layer equations for forced-convection condensation of binary vapor mixtures air-water and ethanol-water are numerically solved under the assumption that the physical properties in the vapor phase depend on mass concentration and temperature and those in the condensate film are constant. The results for wall heat flux and concentration mass flux agree well with the solutions of the author\u27s algebraic equations when the physical properties are evaluated at the arithmetic mean of the mass concentration at the vapor-liquid interface and the bulk and the corresponding saturation temperature, or evaluated at the arithmetic means of the mass concentration and temperature at the vapor-liquid interface and the bulk, and agree with the arithmetic mean values of the wall heat flux and concentration mass flux which are solved by using the physical properties evaluated at the vapor-liquid interface and the bulk