Among the noncontact measurement technologies used to acquire thermal property information, those that use the photothermal effect are attracting attention. However, it is difficult to perform measurements for new materials with different optical and thermal properties, owing to limitations of existing thermal conductivity measurement methods using the photothermal effect. To address this problem, this study aimed to develop a rear-side mirage deflection method capable of measuring thermal conductivity regardless of the material characteristics based on the photothermal effect. A thin copper film (of 20 mu m thickness) was formed on the surfaces of the target materials so that measurements could not be affected by the characteristics of the target materials. In addition, phase delay signals were acquired from the rear sides of the target materials to exclude the influence of the pump beam, which is a problem in existing thermal conductivity measurement methods that use the photothermal effect. To verify the feasibility of the proposed measurement technique, thermal conductivity was measured for copper, aluminum, and stainless steel samples with a 250 mu m thickness. The results were compared with literature values and showed good agreement with relative errors equal to or less than 0.2%.

A general variational formulation of the void fraction in dissipative two-phase flows is developed. In particular, the steady-state void fraction is extracted by the extremization of the entropy generation rate, based on a comprehensive non-equilibrium expression that introduces interfacial contributions due to surface tension between different phases and fluxes due to heat and mass transfer.Such formulation opens up to the possibility of obtaining different theoretical formulas by the direct application of Prigogine's theorom of minimum entropy production and it is investigated in terms of different assumptions for showing the effect of different flow conditions, flow pattern interfacial geometry, entrainment ratio, heat flux from the external environment, and thermophysical properties of the refrigerant. Consequently, the widely-accepted Zivi's expression of void fraction is obtained as a particular case of this general formulation.

Photothermal therapy can serve as an alternative to classic surgery in the treatment of patients with cancer. However, using photothermal therapy can result in local overheating and damage to normal tissues. Therefore, it is important to determine effective heating conditions based on heat transfer. In this study, we analyzed laser-tissue interactions in gold nanoparticle (GNP)-enhanced photothermal therapy based on the theory of heat transfer. The thermal behavior inside tissues during photothermal therapy was analyzed using numerical analysis. The apoptosis ratio was defined by deriving the area having a temperature distribution between 43 degrees C and 50 degrees C, which is required for inducing apoptosis. Thermal damage, caused by local heating, was defined using the thermal hazard value. Using this approach, we confirmed that apoptosis can be predicted with respect to tumor size (aspect ratio) and heating conditions (laser intensity and radius) in photothermal therapy with a continuous-wave laser. Finally, we determined the effective apoptosis ratio and thermal hazard value of normal tissue according to tumor size and heating conditions, thereby establishing conditions for inducing maximal levels of cell apoptosis with minimal damage to normal tissue. The optimization conditions proposed in this study can be a gentle and effective treatment option for photothermal therapy.

Analyzing the quality of images generated from an imaging method is essential for determining the limits and applicability of that method. This study analyzed the quality of images resulting from a photothermal imaging method by applying the line spread function and the modulation transfer function to the spatial resolution and contrast, on the basis of certain parameters of the photothermal imaging method for a copper-resin double-layered structure. The parameters are the ratio of the first-layer thickness to the thermal diffusion length ( and the ratio of the pump-beam radius to the thermal diffusion length ( ). The phase delay profile (edge response function, ERF) of the subsurface structure derived from the photothermal imaging method becomes dimensionless upon division by the thermal diffusion length; as the ratio increases, the spatial resolution and contrast increase.

The photothermal imaging technique is a nondestructive inspection technique that visualizes the inside of a metal by utilizing the photothermal effect. Although the concept of photothermal imaging techniques has been proposed, systematic research on the characteristics thereof has not been conducted. This study attempts to enhance the measurement and reconstruction process for a photothermal imaging method. To detect the edge of a subsurface pattern more accurate, low-pass FFT (fast Fourier transform) filter for noise reduction of measured data, and derivative detectors are adopted for the reconstruction of photothermal imaging. The adopted methods are applied to and visualize 20mmx25mmx1.5mm copper block including radius 5mm, height 1mm cylindrical resin as a subsurface pattern. The results show that the developed method can detect the edge of the resin subsurface 50% more accurately than the previous reconstruction method for photothermal imaging.

Transparent anisotropic materials have garnered attention along with the growth of the semiconductor and display industries. Transparent anisotropic materials have the characteristic of varying electrical, optical, and thermal properties based on their crystal orientation, and many studies are being conducted on this topic. In order to utilize transparent anisotropic materials properly, thermal properties such as thermal conductivity are essentially required. However, due to the limitations of the existing thermal property measurement methods for transparent anisotropic materials, it is difficult to provide the thermal properties of transparent anisotropic materials. To address this problem, a transparent anisotropic collinear method capable of measuring the effective thermal conductivity of a transparent anisotropic material according to its crystal orientation is proposed in this paper. To this end, the internal temperature distribution of a transparent anisotropic material and the phase delay of the probe beam were theoretically derived through a numerical analysis model that uses a three-dimensional heat conduction equation. This model was applied to anisotropic thermal conductivity with orthorhombic structure. To verify the proposed method of measuring the thermal conductivity of a transparent anisotropic material, the thermal properties of 3 mm-thick A-plane sapphire glass were measured and compared with those of the existing literature. It was confirmed that the absolute errors were less than about 4 W/mk.

Imaging techniques for internal visualization of materials have become increasingly important in a wide range of industrial fields. Imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) employing X-rays have existed for quite some time. However, such classic techniques have physical limitations (for e.g., X-rays cannot penetrate high-density materials such as metals) because they were developed as medical applications. Therefore, alternative techniques for industrial fields should be explored. Photothermal imaging was explored from the perspective of visualization of the interior of metals as photothermal effects depend on the thermal properties of the materials. To establish photothermal imaging as a reliable technique, it is important to analyze the physical limitations and noise in the measurement. Therefore, in this study, the conditions leading to a minimum level of noise were explored using aluminum 6061 specimens of five surface roughness values under conditions of different pump beam frequencies and radii. In this work, surface roughness and pump beam frequency and radius were considered important parameters affecting photothermal imaging. Finally, comprehensive criteria to reduce signal noise in photothermal imaging were proposed.

Visualization and imaging techniques have become increasingly essential in a wide range of industrial fields. A few imaging methods such as X-ray imaging, computed tomography and magnetic resonance imaging have been developed for medical applications to materials that are basically transparent or X-ray penetrable; however, reliable techniques for optically opaque materials such as semiconductors or metallic circuits have not been suggested yet. The photothermal method has been developed mainly for the measurement of thermal properties using characteristics that exhibit photothermal effects depending on the thermal properties of the materials. This study attempts to numerically investigate the feasibility of using photothermal effects to visualize or measure the material distribution of opaque substances. For this purpose, we conducted numerical analyses of various intaglio patterns with approximate sizes of 1.2-6 mm in stainless steel 0.5 mm below copper. In addition, images of the intaglio patterns in stainless steel were reconstructed by two-dimensional numerical scanning. A quantitative comparison of the reconstructed results and the original geometries showed an average difference of 0.172 mm and demonstrated the possibility of application to experimental imaging.

Recently, as the concern for new visualization techniques increase. The related researches have been carried out such as photoacoustic technique, photothermal technique and photoelectronic technique. Photothermal technique is one of the three-dimensional imaging technique candidates. The photothermal effect has different result depending on the thermal property of materials. That characteristic was widely used for thermal property measurement. To prove the feasibility for technique using phtothermal effect, this study was numerically carried out to visualize an invisible shape inside the materials. The numerical investigation showed that the intaglio stainless-steel pattern can be imaged. The pattern which is approximately 5000 μm size of square shaped existed in 500 μm depth of copper was visualized.

Reverse electrodialysis(RED) is energy conversion phenomena which generates electricity from concentration gradient energy by mixing the ions in sea water with fresh water through ion-selective nanochannel. When nanochannels are filled with an aqueous solution, the surface of nanochannels is charged by ionization, ion adsorption, and ion dissolution. Therefore, co-ions are repelled from the nanochannels and only counter-ions can be transported through the nanochannels. As a result, the electric current can be generated by selective ion transport through the nanochannels from sea water to fresh water. Recently, solid-state nanochannels or nanopores have received attention because they have potential to replace polymer ion-selective membranes. Especially, anodic aluminum oxide (AAO) nanochannel array has advantage of easiness of pore size control and high pore density. In the present study, to collect electric current generated by the nanochannels, we deposited the porous silver layer on both front and rear surface of the AAO nanochannel array by using e-beam evaporation and changed the silver layer to the silver / silver chloride layer by chemical oxidation with aqueous FeCl3. Finally, we conduct an experimental investigation for the power generation from the AAO nanochannel arrays placed between two potassium chloride solutions with various combinations of concentrations.

The heat sinks are used to dissipate heat from electronic and industrial systems. In the present study, in order to overcome limitation of traditional heat sink, we suggest and experimentally investigate new concept of heat sink which use evaporation of water. The heat sink is made from sintered copper plate and absorbs supplied water like sponges by capillarity-driven wetting. The absorbed water evaporates at the surface of heat sink and the surface temperature is dropped due to the latent heat of water evaporation. In this study, we experimentally compare the heat dissipation performance of the suggested heat sink with traditional heat sink. And we investigate the performance of heat sink made from the sintered copper plate with various particle radius and porosities. Finally, we find the fin spacing, at which the thermal performance is maximized. Copyright © 2013 by ASME.

Recently, study of transparent materials, such as thin film form, have an important field for the development of advanced electronic devices. Therefore, the need for the precision thermal property measurement techniques of transparent thin film materials becomes increasing according to the development of these material. The ideal methods for optically measurements of these properties are noncontact method. However, optically measurements are often difficult due to the transparency. So, transparent materials have not enough temperature gradient in the air layer above thin films. To solve this problem, we used the collinear deflection method which is one of the photothermal deflection methods. In the measurement process, both of the pump beam and probe beam are irradiated vertically on the transparent sample. And the probe beam is deflected by refractive index variation of samples due to the temperature gradient inside samples. The purpose of this study is to analyze the effect of thermal and optical properties analytically on the collinear deflection method for variable materials. © (2013) Trans Tech Publications, Switzerland.