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The operability windows and coating bead dynamics for the dual-layer slot coating process with non-Newtonian coating liquids were investigated using the viscocapillary model, a two-dimensional (2D) CFD simulation, and experiments. The simplified viscocapillary model derived from the 2D equation of motion with the shear-thinning Carreau liquids bounds the uniform coating regime without defects such as leaking, bead break-up, and mid-gap invasion in dual-layer coating systems. The coating bead flows from experiments and finite-volume-based 2D simulations with the volume-of-fluid scheme demonstrate the performance of the viscocapillary model in reliably tracking the upstream meniscus position of the bottom layer in the coating bead region. The onset of leaking, bead break-up, and mid-gap invasion defects is strongly affected by the rheological properties of Carreau-type coating liquids and the flow ratio between the top and bottom layers. In particular, the relative thickness of the shear-thinning bottom layer at the onset of mid-gap invasion is smaller than the well-known 1/3 value in the Newtonian case, depending on the degree of shear thinning.

In this study, we present a new and simple method that utilizes post-processing such as thermal treatment and mechanical compression to manufacture a grid patterned silver nanowire (AgNW) flexible transparent electrode with low sheet resistance, high transmittance, and high flexibility. The effects of thermal treatment and mechanical compression on the structural, optical, and electrical properties of AgNW deposited by bar coating have been analyzed as a function of temperature and pressure. It was discovered that there is a critical thermal treatment temperature (Tc) that determined the abrupt change—decreasing, then rapidly increasing—in the sheet resistance of AgNW. When additional pressure was applied during thermal treatment, Tc was lowered. The cohesion between AgNW wires was improved by thermal treatment below Tc, and further strengthened when pressure was applied simultaneously with heat. However, when thermal treatment was performed above Tc, the unique wire structure of AgNW collapsed. It has also been found that heat treatment and mechanical compression improve the flexibility of AgNW.

The aim of this study is to establish prediction models for the non-destructive evaluation of the carbonization characteristics of lignin-derived hydrochars as a carbon material in real time. Hydrochars are produced via the hydrothermal carbonization of kraft lignins for 1–5 h in the temperature range of 175–250 °C, and as the reaction severity of hydrothermal carbonization increases, the hydrochar is converted to a more carbon-intensive structure. Principal component analysis using near-infrared spectra suggests that the spectral regions at 2132 and 2267 nm assigned to lignins and 1449 nm assigned to phenolic groups of lignins are informative bands that indicate the carbonization degree. Partial least squares regression models trained with near-infrared spectra accurately predicts the carbon content, oxygen/carbon, and hydrogen/carbon ratios with high coefficients of determination and low root mean square errors. The established models demonstrate better prediction than ordinary least squares regression models.

In our previous work [Chun et al., Phys. Fluids 29, 121605 (2017)], we studied the migration behavior of concentrated monodisperse particles in Couette–Poiseuille flows. Here, we extend this study into an investigation of concentrated ( ϕ0=0.3) bidisperse suspensions undergoing pressure-driven flows at various combinations of volume fraction ratio ( ϕS0/ϕ0=0.13−0.67) and size ratio ( aL/aS=1.4−2.4) between small ( 2aS/H=0.022) and large ( 2aL/H=0.031−0.052) particles in a planar channel of height H. The flow behavior of neutrally buoyant hard spheres suspended in a Newtonian fluid was numerically simulated using the lattice Boltzmann method. The time evolution of the distributions of small and large particles showed segregation under inhomogeneous shear flow, resulting in enrichment of large particles and depletion of small particles near the midplane. Size-dependent particle segregation was more pronounced in these simulations than what was previously observed in the experiment. In bidisperse suspensions, the concentration evolution was markedly slower than in monodisperse situations; the characteristic time to reach a steady state was 5–8 times longer in bidisperse systems. The results of lattice Boltzmann simulation were further analyzed within the framework of a reformulated polydisperse diffusive flux model [Shauly et al., J. Rheol. 42, 1329 (1998)]; four coefficients of the diffusive flux model were adjusted to match steady-state ( KL, KS) and transient ( RL, RS) predictions. The model coefficients showed strong dependence on the particle number density ratio (ϕS0/ϕL0)(aL/aS)3; both KL and RL increased almost linearly with this ratio, whereas KS decreased and RS increased with this ratio.In our previous work [Chun et al., Phys. Fluids 29, 121605 (2017)], we studied the migration behavior of concentrated monodisperse particles in Couette–Poiseuille flows. Here, we extend this study into an investigation of concentrated ( ϕ0=0.3) bidisperse suspensions undergoing pressure-driven flows at various combinations of volume fraction ratio ( ϕS0/ϕ0=0.13−0.67) and size ratio ( aL/aS=1.4−2.4) between small ( 2aS/H=0.022) and large ( 2aL/H=0.031−0.052) particles in a planar channel of height H. The flow behavior of neutrally buoyant hard spheres suspended in a Newtonian fluid was numerically simulated using the lattice Boltzmann method. The time evolution of the distributions of small and large particles showed segregation under inhomogeneous shear flow, resulting in enrichment of large particles and depletion of small particles near the midplane. Size-dependent particle segregation was more pronounced in these simulations than what was previously observed in the experiment. In bidisperse suspension...

The manufacture of eco-friendly cocoon silk-derived sericin films increases the availability of sericulture resources and the interest in expanding the range of the potential applications of sericin-based materials. However, the brittleness and weak tensile properties of sericin and its vulnerability to moist environments have limited its use. To overcome these two shortcomings of sericin, a functionalized bacterial cellulose-derived nanocrystal (average diameter: 25.4 nm) capable of physical strengthening and chemical crosslinking on existing sericin films was prepared. The improvement of the optical, physicochemical, and mechanical properties of the sericin film was observed through the dialdehyde bacterial cellulose nanocrystals (D-CNCs) incorporated into the silk sericin (SS) matrix. The physical reinforcing effect of the D-CNCs on the SS films enhances the mechanical properties of the films. Simultaneously, the chemical crosslinking reaction of D-CNCs develops the ultraviolet-blocking, water-resistant, and antioxidant properties of the films. The simultaneous fabrication, physical reinforcement, and chemical crosslinking of the SS/D-CNCs biocomposite film produced using an aqueous solution will provide information on the functionalization and performance improvement of water-soluble biopolymeric materials, especially hydrophilic protein resources.

In this study, chitin was exclusively extracted from shrimp shells (Marsupenaeus japonicas) through a green solvent called deep eutectic solvent (DES), and various types of DES were utilized to extract chitin. The physicochemical properties of the obtained chitin were compared with the conventional method. A high purity of chitin was obtained while using DES-8 (choline chloride-malonic acid) with a yield of 19.41% ± 1.35%, and purity was confirmed using 13C nuclear magnetic resonance. The DES-produced chitin was utilized to produce chitin films and was compared with standard chitin films. The obtained films were characterized by SEM, AFM, TGA, DSC, FTIR, mechanical properties, moisture sorption, swelling behavior, and biodegradation. The DES film showed similar properties to the standard film, while the mechanical properties, swelling behavior, and biodegradation of the DES chitin films proved to be similar to standard chitin film. These chitin films can be used as wound healing resources.

This study aims to demonstrate the feasibility of cylindrical interstitial laser ablation (CILA) in porcine pancreatic tissue to develop a EUS-guided PC ablation technique with enhanced safety. A diffusing applicator created a uniformly symmetrical laser ablation in pancreatic tissue. Ex vivo tests presented that both ablation thickness and volume increased linearly with the applied power (R2 = 0.96 and 0.90, respectively) without carbonization and fiber degradation. The numerical simulations matched well with the experimental results in terms of temperature development and thermal damage (deviation of ≤ 15%). In vivo tests with EUS confirmed easy insertion and high durability of the diffusing applicator. EUS-guided CILA warranted a feasible therapeutic capacity of ablating in vivo pancreatic tissue. The proposed EUS-guided CILA can be a feasible therapeutic approach to treat PC with predictable thermal ablation and enhanced safety.

In this study, we present solution-based processes for producing copper (Cu) meshes which can be utilized as transparent conductive electrodes (TCEs) for flexible film heaters. The surface modification of polyethylene terephthalate (PET) substrates was done via corona treatment at atmospheric pressure and room temperature. The Cu layer was deposited on the corona-treated PET substrate via electroless plating and then patterned via lithography to have mesh dimensions of a 200 μm line-to-line spacing and a 6 μm line width. Also, graphene was coated on the Cu mesh via electrophoretic deposition (EPD). The chemical and physical changes in the PET surfaces were characterized according to the corona treatment conditions. The measurements of contact angles and surface energies of the corona-treated PET substrates indicated that the PET surfaces changed from hydrophobic to hydrophilic after corona treatment, leading to the improvement in the adhesion between the PET substrates and the Cu meshes. The flexibility of the Cu meshes was inspected by performing bending and twisting tests and by directly measuring the adhesion strength between the Cu layers and the PET substrates through scratch tests. The effects of graphene coating on the characteristics of the Cu meshes were examined in terms of their surface morphologies, electrical sheet resistances, transmittances and reflectances in the visible-light wavelength range, and color differences. Finally, the film heaters produced by employing the graphene-coated Cu meshes yielded a temperature rise over 85 °C with a response time shorter than 20 s.

Hafnium-aluminum zinc oxide (HAZO) films as an active layer of oxide-transistors with different hafnium (Hf) contents were deposited via co-sputtering of separate targets. The effects of the sputtering power during co-sputtering on the structural, optical, electrical, and chemical properties of the HAZO films were examined. As the sputtering power increased, the structure of the HAZO films changed from polycrystalline to amorphous, and the Hf O bonds in the HAZO films increased, but the Zn O bonds decreased. Also, a bottom-gate-type thin-film transistor (TFT) using the HAZO film as its channel layer was fabricated and characterized. The TFTs using HAZO layer at room temperature as channel layer exhibited the device characteristics, such as a field effect mobility of 0.45 cm2/V·s, a threshold voltage of 17.18 V, a subthreshold swing of 0.85 V/decade, an on/off current ratio of 3.68 × 107, and a visible transmittance of 82.7%. It was discovered that the changes of the electrical characteristics of the HAZO TFTs were closely related to the changes of the Zn O/Hf O bonding ratio.

This study demonstrates the characteristics of a hybrid-type transparent electrode for touch screen panels, which was fabricated by coating carbon nanotubes (CNTs) via electrophoretic deposition (EPD) on copper (Cu)-meshes. The surface morphologies, visible-range transmittance and reflectance, and chromatic properties, such as yellowness and redness, of the fabricated CNTs-coated Cu mesh electrodes were characterized as functions of their dimensions (line-to-line spacing, line width, and electrode thickness) and compared with those of the Cu-mesh electrodes without coating of CNTs. The experimental results showed that the coating of CNTs substantially reduced the reflectance of the Cu-mesh electrodes and also improved their chromatic properties with their transmittance and sheet resistance only slightly changed, subsequently indicating that the CNTs-coated Cu-mesh electrodes possessed desirable characteristics for touch screen panels.

Antiferromagnet (AFM)/ferromagnet (FM) bilayer structures are widely used in the magnetic devices of sensor and memory applications, as AFM materials can induce unidirectional anisotropy of the FM material via exchange coupling. The strength of the exchange coupling is known to be sensitive to quality of the interface of the AFM/FM bilayers. In this study, we utilize proton irradiation to modify the interface structures and investigate its effect on the magnetic properties of AFM/FM structures, including the exchange bias and magnetic thermoelectric effect. The magnetic properties of IrMn/CoFeB structures with various IrMn thicknesses are characterized after they are exposed to a proton beam of 3 MeV and 1~5 × 10 14 ions/cm². We observe that the magnetic moment is gradually reduced as the amount of the dose is increased. On the other hand, the exchange bias field and thermoelectric voltage are not significantly affected by proton irradiation. This indicates that proton irradiation has more of an influence on the bulk property of the FM CoFeB layer and less of an effect on the IrMn/CoFeB interface.

A reactor coolant pump is subjected to various abnormal operating modes, so the pump supplier has to provide all the transient pump characteristics to a user. Complete or homologous pump characteristics are the best forms including transient hydraulic information for an abnormally operating pump. Until now, there has been no consideration in the systematic test procedures to obtain the complete or homologous pump characteristics through a hydraulic test. No further research has been done on the relationships among the constant heads in complete pump characteristics. Likewise, no additional discussion has taken place on the direct transformation of the homologous pump characteristics into the complete pump characteristics. In present paper, a mathematical model is introduced to explain how the constant head curves in the complete pump domain are connected to each other. This means that other constant head curves can be obtained without additional hydraulic testing once a constant head curve is obtained for the full flow rate and speed range. It is also shown that the complete pump characteristics can be obtained from the homologous pump characteristics by another mathematical model. For homologous pump characteristics, even though differently enveloped test matrices that consist of different level sets of flow rate and speed are applied in hydraulic testing, the same homologous pump characteristics are obtained. These results indicate that a low-enveloped test matrix is sufficient to obtain the homologous pump characteristics.

This study demonstrates hybrid-type transparent electrodes for touch screen panels. The hybrid-type electrodes were fabricated by coating silver (Ag) meshes with carbon nanotubes (CNTs). Thin Ag films were deposited on glass substrates using the sputtering method, and were then patterned via photolithography to obtain mesh structures with a 10 μm line width and 300 μm line-to-line spacing. The Ag meshes were coated with CNTs using two different methods: spray coating and electrophoretic deposition (EPD). For the samples of Ag meshes with no CNT coating as well as of CNT-coated Ag meshes, the visible-range transmittance and reflectance as well as the surface morphology were characterized and compared. The change in sheet resistance due to long-term exposure to air with an 85 °C temperature and 85% humidity was also measured. The experimental results indicated that the reflectance of the Ag mesh electrodes was substantially reduced by the CNT coating. Especially, the Ag mesh electrodes with EPD-coated CNTs showed excellent properties, such as higher than 80% transmittance, lower than 8% reflectance, and better stability.

Silicon zinc oxide (SZO) thin films were deposited via co-sputtering, while thin-film transistors (TFTfs) with the SZO film as the active layer were fabricated with a bottom gate configuration. Two kinds of post-treatment, furnace annealing and hot pressing, were carried out on the deposited SZO films. The effects of the post-treatment on the crystalline structure, chemical bond, surface roughness, and optical transmittance of the deposited SZO TFTs were analyzed as functions of the post-treatment conditions that were used. It was observed from the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results that the structure of the SZO film became amorphous and the amount of Si-O bonds in the SZO film drastically increased after low-temperature furnace annealing. The on-off current ratio was 1.35 × 108 for the TFT after furnace annealing (200 °C) and 1.93 × 108 for the TFT after hot-pressing (200 °C, 2 MPa), while that of the as-deposited SZO-TFT was 3.16 × 106. The experiment results showed that the hot pressing method would be preferable because it could improve the electrical characteristics of the SZO-TFTs, yielding similar results from the case where furnace annealing for about 60 min was carried out, in spite of the short process time (about 30 s) of the hot pressing method.

In this study, the surface of polyethylene terephthalate (PET) substrates was modified via corona treatment before the deposition of carbon nanotubes (CNTs), and the effects of such surface modification on the properties of the CNTs for flexible transparent electrodes were investigated. The changes in the surface roughness, contact angle, and surface energy of the PET substrates due to the corona treatment were characterized in terms of the applied corona energies, PET feeding directions, and treatment times. The higher corona energies, the more frequent treatment times, and the bi-directional treatment produced the larger surface roughness of the PET substrates. The results of the contact angles and the surface energies indicated that the surfaces of the PET substrates became hydrophilic from hydrophobic after the corona treatment. The analysis using X-ray photoelectron spectroscopy confirmed that oxygen polar groups appeared when the PET substrates were corona-treated. In addition, the increase in the CNTs' sheet resistance values due to their repeated outer and inner bending (up to 16,000 times) was found to have been significantly alleviated when the CNTs were deposited on the corona-treated PET substrates. This confirmed that the adhesion of the CNTs was improved after the corona pretreatment of the PET substrates.

Hybrid-type transparent electrodes, which possess the characteristics desirable for flexible touch screen panels, were fabricated by coating PEDOT:PSS [poly (3, 4-ethylene-dioxythio-phene):poly (styrenesulfonate)] films on carbon nanotubes (CNTs) via either spin-coating or electrophoretic deposition (EPD). For all the samples including the CNTs and the hybrid electrodes (i.e., PEDOT:PSS-coated CNTs), surface morphologies and cross-sections, sheet resistances, and visible transmittances were characterized as functions of their preparation conditions. Also, to identify the flexible capabilities of the hybrid electrodes, the changes in their sheet resistances due to repetitive bending (up to 30,000 times) were measured and compared with the results measured for the CNTs. In the hybrid-type electrodes, the PEDOT:PSS particles filled up the voids between the tubes in the CNTs, thereby forming a conduction bridge for electron transfer and eventually decreasing the sheet resistance. Furthermore, the PEDOT:PSS layers induced physical gripping of the CNTs to enable them to adhere better to the underlying PET substrates, indicating that the hybrid electrodes were more desirable in flexibility than were the CNTs.

Hybrid-type transparent conductive electrodes (TCEs) were fabricated by coating copper (Cu) meshes with carbon nanotube (CNT) via electrophoretic deposition, and with nickel (Ni) via electroplating. For the fabricated electrodes, the effects of the coating with CNT and Ni on their transmittance and reflectance in the visible-light range, electrical sheet resistance, and chromatic parameters (e.g., redness and yellowness) were characterized. Also, an oxidation stability test was performed by exposing the electrodes to air for 20 d at 85 °C and 85% temperature and humidity conditions, respectively. It was discovered that the CNT coating considerably reduced the reflectance of the Cu meshes, and that the Ni coating effectively protected the Cu meshes against oxidation. Furthermore, after the coating with CNT, both the redness and yellowness of the Cu mesh regardless of the Ni coating approached almost zero, indicating a natural color. The experiment results confirmed that the hybrid-type Cu meshes with combined Ni-CNT coating improved characteristics in terms of reflectance, sheet resistance, oxidation stability, and color, superior to those of the primitive Cu mesh, and also simultaneously satisfied most of the requirements for TCEs.

In this study, the effects of substrate pretreatment on the properties of carbon nanotubes (CNTs), which are used as flexible transparent electrodes, were investigated. CNTs were deposited on PET (polyethylene terephthalate) substrates using a spray coating method. Prior to the deposition of the CNTs, the PET substrates were corona-treated by varying the feeding directions of the PET substrate and the number of treatments. The variation in the surface morphology and roughness of the PET substrates due to the corona pretreatment were characterized via atomic force microscopy (AFM). The contact angles of the PET substrates were measured using polar and dispersive liquids, and the surface energies were estimated. Also, the sheet resistance of the CNTs deposited on the PET substrates was measured before and after the bending test. The experiment results provided strong evidence that the adhesive forces between the CNTs and the PET substrate can be substantially enhanced by corona pretreatment.

This study demonstrates hybrid-type transparent electrodes based on carbon nanotubes (CNTs) that possess characteristics desirable for touch screen panels. This has been accomplished by depositing CNTs via spray-coating and then depositing thin conductive polymer (such as PEDOT:PSS) films on the CNTs via spin-coating. For all of the samples such as CNTs, PEDOT:PSS, and hybrid (i.e., PEDOT:PSS-coated CNTs), their surface morphologies, sheet resistances, visible transmittances, and chromatic properties are characterized as functions of their preparation conditions. In the PEDOT:PSS-coated CNTs, the PEDOT:PSS particles fill up the voids between tubes in CNTs, forming a conduction bridge for electron transfer and eventually decreasing the sheet resistance of the hybrid electrode. Also, the hybrid electrode reveals a superior color property compared with that of CNTs or the PEDOT:PSS single electrode due to the complementary color relation between CNTs and PEDOT:PSS. Experimental results show that the fabricated hybrid-type electrodes can simultaneously satisfy the requirements necessary for transparent electrodes of touch screen panels such as the sheet resistance requiring to be lower than 100 Ω/sq, visible transmittance higher than 80%, and yellowness approaching to zero.

The co-sputtering method was used to prepare Si-incorporated ZnO (SZO) films. The changes in the electrical resistivity, crystalline structure, optical transmittance, and chemical bonding of SZO films were examined according to the sputtering power applied to the Si target. The resistivity of the SZO film strongly depended on the sputtering power of the Si target and varied in a wide range of approximately 10 − 3 –10 7 Ω cm. With an increase in the Si sputtering power, the crystalline structure of SZO films changed from polycrystalline to amorphous. The average transmittance of all the SZO films within the wavelength-range of 400–700 nm was at least 80%. X-ray photoelectron spectroscopy measurement showed that the changes in the resistivity and optical band gap of the SZO film according to the Si sputtering power were closely related to the changes in the oxygen vacancies and SiO x bonds in the film. Finally, the bottom-gate-type SZO-TFTs were fabricated and their transistor actions were presented.

Electrotransport theory is defined as mass transportation of solute such as hydrogen in metal under the influence of an electrostatic force field. In this study, electrotransport treatment was applied to remove the accumulated hydrogen inside of the high-strength low alloy steel. The effectiveness of the electrotransport treatment was evaluated by hydrogen concentration measurement, slow strain rate test, and fracture surface analysis. The efficiency of electrotransport treatment is improved with increasing applied current and time, and the highest efficiency was obtained as 88.7% at 450 A for 40 min. The ultimate tensile strength and elongation of specimen after electrotransport treatment was enhanced dramatically in comparison with that of specimen under hydrogen charging condition. The brittle fracture mode was observed on the hydrogen charged specimen, but a clear ductile fracture mode was observed on the specimen after electrotransport treatment. These results confirm that the electrotransport treatment is effective to remove the accumulated hydrogen inside of the high-strength low alloy steel.

In this paper, we analyzed the effects of doctoring process on the patterns of Ag ink in gravure off-set printing. The parameters of doctoring process were the angle and the pressure, which was represented by the depth of blade movement to the gravure roll, of doctor blade to the surface of gravure roll, and the angle of patterns engraved on the gravure roll to the doctor blade moving direction. The proper parameters were extracted for the fine patterns and they were 15 mm for the pressure, for the blade angle. And the angle of patterns with respect to the blade movement should be less than for the best results. The gravure off-set printing with the above parameters was carried out to print gate electrodes and scan bus lines of OTFT-backplane for e-paper. The line width of was successfully obtained. The thickness of electrodes was and the surface roughness was and the sheet resistance was .

In this paper, we analyzed the effects of the number of TIPS-pentacene droplets and also the substrate temperature on the performance of OTFTs. As the number of the droplets increased, the mobility increased and reached the peak value and then reduced at the all temperatures. The peak mobility was at 3 droplets and , at 4 droplets and , and at 7 droplets and . The reason of existence of peak mobility can be found in matching the evaporation of solvent with the velocity of crystal formation. When two parameters were properly matched, the mobility produced the highest.

Alloy 690 has been selected as a steam generator tubing material for SMART owing to a near immunity to primary water stress corrosion cracking. The steam generators of SMART are faced with a neutron flux due to the integrated arrangement inside a reactor vessel, and thus it is important to know the irradiation effects of the thermal conductivity of Alloy 690. Alloy 690 was irradiated at HANARO to fluences of (0.7−28) × 1019n/cm2 (E>0.1MeV) at 250°C, and its thermal conductivity was measured using the laser-flash equipment in the IMEF. The thermal conductivity of Alloy 690 was dependent on temperature, and it was a good fit to the Smith-Palmer equation, which modified the Wiedemann-Franz law. The irradiation at 250°C did not degrade the thermal conductivity of Alloy 690, and even showed a small increase (1%) at fluences of (0.7∼28) × 1019n/cm2 (E>0.1MeV).

Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/μm, and the emission current, which was generated at an applied field of 1.2 V/μm was 56 μA. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/μm and the emission current at the same applied field increased more than ten times to 618 μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs.

A scale-down SMART reactor model was constructed to evaluate flow-induced pressure variation under normal operating conditions. The flow rate and number of operating pumps were varied, and pressure fluctuations along the reactor internals surface of the model were measured by pressure transducers. The measured transient pressure was separated into the mean and fluctuating pressure, which was evaluated by analyzing the data of two distinct regions. Specifically, the pressure obtained at frequencies less than 10 Hz was analyzed separately from those obtained at frequencies greater than 10 Hz. In the present study, the mean pressure distribution was dependent on the pressure loss due to the skin friction and changes in the static pressure due to height level differences at the measuring points. The mean pressures were similar, regardless of the location of the operating pump, because the fluid was fully mixed in the upper shell. The normalized mean pressure ratio, excluding the hydrostatic pressure change, kept constant regardless of the flow rate and number of operating pumps. It was observed that the RMS of the fluctuating pressure at frequencies less than 10 Hz did not depend on the measuring points for all of the surfaces of the model. And, periodic pressure fluctuation generated by the inlet region is not reachable to the fuel assembly region because of the structural arrangement of SMART.

In this study, a simple method of fabricating a thin-film transistor (TFT) with a double-layered channel using indium–zinc-oxide (IZO) films was proposed. Two IZO films used as channel layers were consecutively deposited via sputtering without stopping the vacuum and only by changing the volumetric fraction of the additive O2 gas during the deposition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis showed a large difference in the depth profiles of the InO− and InO2− ions between the two IZO layers. Compared to the conventional single-IZO-channel TFT, the double-IZO-channel TFT that was fabricated using the proposed two-step deposition method showed greatly improved electrical characteristics: the on/off-state current ratio was increased from 1.30 × 105 to 1.03 × 106, and the field effect mobility was enhanced from 1.2 to 9.3 cm2/Vs.

The effect of adding hydrogen gas (H2) when depositing a zinc oxide (ZnO) thin film in a thin film transistor (TFT) using the ZnO as the channel layer on the electrical characteristics of the ZnO-TFTs, particularly the change in the characteristics according to long-term exposure to air, was investigated. As the amount of added H2 gas was increased, the resistivity of ZnO films was monotonously decreased and their crystallinity was weakened. Compared with the TFT using a ZnO without H2 addition, the threshold voltage (Vth) decreased and the on/off current ratio (Ion/Ioff) greatly increased, if the amount of H2 entry was small (≤ 0.3 sccm). However, when an excessive (≥ 0.5 sccm) amount of H2 was added, the TFT's properties deteriorated. In addition, the ZnO TFTs showed a positive Vth-shift with increased air exposure time. The analysis using the X-ray photoelectron spectroscopy (XPS) confirmed that this was attributed to the reduction of oxygen vacancies due to air exposure. It was noticed that the TFTs that were manufactured using ZnO films with H2 addition showed significant suppression of the Vth-shift according to air exposure.

An approach to the preparation of a tip-type of field emitter that is made up of carbon nanotubes (CNTs) coated with amorphous carbon nitride (a-CNx) films is presented for the purpose of enhancing its electron emission property. CNTs were directly grown on nano-sized conical-type tungsten tips via the inductively coupled plasma-chemical vapor deposition system, and a-CNx films were coated on the CNTs using an radio frequency magnetron sputtering system. The morphologies and microstructures of the a-CNx-coated CNTs were analyzed via field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The electron emission properties of the a-CNx/CNT hetero-structures were measured using a high-vacuum field emission measurement system. The best field emission properties, such as a very low turn-on voltage of 500 V and a maximum emission current of 176 μA were achieved for the CNT emitter coated with the 5 nm-thick a-CNx film. In addition, this emitter showed a highly stable behavior in long-term (up to 25 h) electron emission.

The effects of amorphous carbon nitride (CN) thin films that were coated on carbon nanotubes (CNTs) and their thermal treatment were investigated, in terms of the chemical bonding and morphologies of the CNTs and their field emission properties. CNTs were directly grown on conical tip-type tungsten substrates via the inductively coupled plasma-chemical vapor deposition (ICP-CVD) system, and the CNTs were coated with CN films using the RF magnetron sputtering system. The CN-coated CNTs were thermally treated using the rapid thermal annealing (RTA) system by varying the temperature (300–700 °C). The morphologies, microstructures, and chemical compositions of the CN-coated CNTs were analyzed as a function of the thickness of the CN layers and the RTA temperatures. The field emission properties of the CN/CNT hetero-structured emitters, and the fluctuation and long-term stability of the emission currents were measured and compared with those of the conventional non-coated CNT-emitter. The results showed that the electron emission capability of CNT was noticeably improved by coating a thin CN layer on the surface of the CNT. This was attributed to the low work function and negative electron affinity nature of the CN film. The CN-coated CNT-emitter had a more stable emission characteristic than that of the non-coated one. In addition, the long-term emission stability of the CN-coated emitter was further enhanced by thermal treatment, which was verified by x-ray photoelectron spectroscopy (XPS) analysis.

X-ray imaging data obtained from cold cathodes using gallium-doped zinc oxide (GZO)-coated CNT emitters are presented. Multi-walled CNTs were directly grown on conical-type (250 μm-diameter) tungsten-tip substrates at 700 °C via inductively coupled plasma-chemical vapor deposition (ICP-CVD). GZO films were deposited on the grown CNTs at room temperature using a pulsed laser deposition (PLD) technique. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were used to monitor the variations in the morphology and microstructure of the CNTs before and after GZO coating. The formation of the GZO layers on the CNTs was confirmed using energy-dispersive X-ray spectroscopy (EDX). The CNT-emitter that was coated with a 10-nm-thick GZO film displayed an excellent performance, such as a maximum emission current of 258 μA (at an applied field of 4 V/μm) and a threshold field of 2.20 V/μm (at an emission current of 1.0 μA). The electric-field emission characteristics of the GZO-coated CNT emitter and of the pristine (i.e., non-coated) CNT emitter were compared, and the images from an X-ray system were obtained by using the GZO-coated CNT emitter as the cold cathode for X-ray generation.

Presented in this study are the results of an experiment that was performed regarding the effects of plasma post-treatment on the material properties of amorphous indium zinc oxide (a-IZO) films, and on the device characteristics of the thin film transistor when an a-IZO film is used as the channel layer. Prior to the source/drain deposition, post-treatment was performed on the area that was not covered by photoresist (PR), using Ar and H2 plasma. The electrical resistivity of a-IZO films was dramatically reduced when they were plasma-treated. The creation of an oxygen vacancy and the formation of hydroxyls in the a-IZO film due to plasma treatment were identified via X-ray photoelectron spectroscopy (XPS) analysis. The change in the field effect mobility (μFE) due to the plasma post-treatment was inversely proportional to the change in the contact resistance (RC) of the plasma-treated a-IZO layer. The prolonged (> 1 min) treatment using H2 plasma caused deep electron traps and surface damages, resulting in the increased RC (or decreased μFE) of the a-IZO TFT. In addition, for the a-IZO TFT that underwent H2 plasma treatment, the VT monotonically decreased whereas the VT of the a-IZO TFT that was Ar-plasma-treated remained almost the same as that of the untreated a-IZO TFT.

A zinc oxide (ZnO) thin film as a channel layer in an oxide thin film transistor (TFT) has been characterized by investigating the effects of additive gases (such as hydrogen and oxygen) during growth and plasma treatment (using argon or hydrogen) after growth on its electrical, optical, and structural properties. By decreasing the additive gas ratio of O 2 /H 2 or by increasing the treatment time of hydrogen plasma, the electrical resistivities of ZnO films were significantly reduced, and their transmittances and optical bandgap energies were blue-shifted in wavelength. These results were considered to be closely related to the passivation of oxygen vacancies as well as the formation of shallow donors that were induced by the injection of hydrogen in ZnO via gas addition and plasma treatment. In addition, the injection of hydrogen-including additive gas resulted in a decrease in grain size and crystallinity of ZnO films, whereas the plasma treatment hardly affected their crystalline structures.

The electron emission property and long-term stability of the emission current in various field emitters based on carbon nanotubes (CNTs) with a CNT/catalyst/buffer/W-tip configuration were examined. CNT-based field emitters were fabricated by varying the buffer layers (TiN, Al/Ni/TiN) and the catalyst materials (Ni, Co). The crystalline structure, surface morphologies, and nanostructures of all the grown CNTs were analyzed using Raman spectroscopy, field emission SEM, and high-resolution TEM. X-ray photoelectron spectroscopy (XPS) was used to monitor the chemical bonds of all the buffer and catalyst layers. When measured, the field emission characteristics showed the emitter that used the Al/Ni/TiN stacked buffer and the Co catalyst exhibited the best performance: a maximum emission current of 51 μA, a threshold field of 2.52 V/μm, and no degradation of emission current after a prolonged (up to 40 h) operation.

Carbon nanotubes (CNTs) are synthesized directly on an electrically conducting cobalt (Co) tip of 1 μm in diameter, without any additional buffer or catalyst layer, through inductively coupled plasma-chemical vapor deposition (ICP-CVD). The nanostructures, morphologies, and crystalline structures of all the CNTs are analyzed through field emission SEM, high-resolution TEM, and Raman spectroscopy. Compared with the conventional emitter, which has a configuration of CNTs/Co(catalyst)/TiN(buffer)/W-tip, the CNTs/Co-tip field emitter proposed in this work show a noticeably improved performance in the electron-emission characteristics as well as in the stability of the emission current due to prolonged operation (up to 50 h).

Thin films (

Submicron-sized conical tungsten (W) field emitters based on carbon nanotubes (CNTs) are fabricated with the configuration of CNTs/catalyst/buffer/W tip by using various buffer layers such as TiN, Al, Al/TiN, and Al/Ni/TiN. This study focuses on elucidating how the buffer layers affect the structural properties of CNTs and the electron-emission characteristics of CNT emitters. Field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) are used to study the nanostructures, surface morphologies, chemical bonds of the catalysts, and grown CNTs. Further, the crystalline structure of CNTs is characterized by Raman spectroscopy. Furthermore, the measurement of field-emission characteristics of all the fabricated field emitters shows that the emitter that employs the Al/Ni/TiN stacked buffer exhibits excellent performances, e.g., a maximum emission current of 202 μA, threshold field of 2.08 V/μm, and long-term (up to 24 h) stability of the emission current.

The relationships between the material properties of piezo-electric thin films (such as ZnO and AlN) and the frequency response characteristics of film bulk acoustic resonator (FBAR) devices based on those films are examined. ZnO and AlN films are deposited by RF magnetron plasma reactive sputtering. Issues in film growth are focused on electric bias application, oxygen incorporation, and two-step deposition. The XRD spectra, AFM topographies, and SEM images measured from all the deposited films present the optimal condition for both ZnO and AlN films to have excellent piezo-electric properties. For ZnO films, excessive injection of oxygen deteriorates the crystal quality and increases the surface roughness. Applying negative d.c. bias during deposition contributes to the improvement of crystal quality of ZnO films as well as the enhancement of acoustic coupling capability of ZnO-based FBAR devices. By adopting the two-step method to deposit AlN films, the films reveal the highly (002)-preferred growth nature and the RMS surface roughness values are drastically reduced, which also leads to the remarkable improvement in the acoustic coupling coefficient of AlN-FBAR devices.

Experimental results relating to the structural properties of carbon nanotube (CNTs) and the field-emission characteristics of conical-type tungsten tips coated with the CNTs are presented. CNTs have been grown on conical W-tips by inductively coupled plasma-chemical vapor deposition (ICP-CVD) with or without coating a TiN-buffer prior to the formation of Ni catalysts. For all the CNTs grown, their nanostructures, morphologies, and crystalline structures are analyzed by FESEM, HRTEM, and Raman spectroscopy. Furthermore, the emission properties of CNT-based field-emitters are characterized to estimate the maximum current density, threshold voltage, and spatial distribution of electron beams. Prolonged stability testing for the CNT-emitters has also been performed. All the experimental results obtained in this study indicate that the emission current level, focused beam area, and emission stability are satisfactory and desirable for application of microfocus x-ray systems, particularly for the CNT-based field emitter without a TiN-buffer layer.

The multi-pass welding generates residual stress which may change fatigue crack growth rate and impair the lifetime of nuclear welded structures. In this paper, we performed fatigue test with notched specimens and evaluate the effect of residual stress on fatigue crack growth rate of welds. In order to identify the magnitude of residual stress, the residual stress was measured by HDM (hole drilling method) and residual stress analysis was performed by using FEM (finite element method). In order to review the effect of residual stress on fatigue crack growth rate, the fatigue crack growth analysis was also performed to determine the fatigue crack growth curves by using FEM and ASME B&PV Code, Sec.XI, App.A. Finally, as a result of comparison among the fatigue crack growth curves, it is found that the fatigue crack growth rate was quite different according to the crack location even if the residual stresses are considered.

An analytical method for the hydroelastic vibration of a vessel composed of an upper annular plate and a lower circular plate is developed by the Rayleigh-Ritz method. The two plates are clamped along a rigid cylindrical vessel wall. It is assumed that the fluid bounded by a rigid cylindrical vessel is incompressible and non-viscous. The wet mode shape of the plates is assumed as a combination of the dry mode shapes of the plates. The fluid motion is described by using the fluid displacement potential and determined by using the compatibility conditions along the fluid interface with the plate. Minimizing the Rayleigh quotient based on the energy conservation gives an eigenvalue problem. It is found that the theoretical results can predict well the fluid-coupled natural frequencies comparing with the finite element analysis result.

In this study, nucleate boiling heat transfer coefficients (HTCs) of HCFC22, HFC134a, HFC125, HFC32 were measured on a low fin, Turbo-B, and Thermoexcel-E tubes. All data were taken at the liquid pool temperature of 7 °C on horizontal tubes of 152 mm length and 18.6–18.8 mm outside diameter at heat fluxes of 10–80 kW m−2 with an interval of 10 kW m−2 in the decreasing order of heat flux. For a plain and low fin tubes, refrigerants with higher vapor pressures showed higher nucleate boiling HTCs consistently. This was due to the fact that the wall superheat required to activate given size cavities became smaller as pressure increased. For Turbo-B and Thermoexcel-E tubes, HFC125 showed a peculiar behavior exhibiting much reduced HTCs due to its high reduced pressure. The heat transfer enhancement ratios of the low fin, Turbo-B, and Thermoexcel-E tubes were 1.09–1.68, 1.77–5.41, 1.64–8.77 respectively in the range of heat fluxes tested.

The growth of highly oriented diamond is performed on Si (111) and 6H–SiC (0001) substrates via two-step and three-step processes using microwave plasma CVD. The two-step process involves bias-enhanced nucleation (BEN) and deposition, and the three-step process involves carburization in addition to the two-step process. The diamond films grown on the Si (111) substrate exhibit high quality and desirable (111)-orientation under the carburization condition of 5.3×10 3 Pa in pressure with no bias applied. The mechanism for the formation of conversion layer during the carburization step is investigated on both the substrates through the Raman and X-ray photoelectron spectroscopy (XPS) studies. The results indicate that the carburization mainly composed of β-SiC, which plays a crucial role for the formation of the conversion layer and which eventually promotes the diamond nucleation. It is also suggested that a highly-oriented and high-quality diamond film can be successfully achieved by carburization.

Diamond films are grown on Si substrate by microwave plasma CVD using CH 4 +H 2 (for undoped) and additive N 2 (for nitrogen-incorporated) with/without O 2 as precursors. Crystal structures for grown films, such as micro- and nano-crystalline and surface morphologies are characterized in terms of growth condition by Raman and field-emission SEM, respectively. Cathodoluminescence (CL) spectra are monitored to identify the nitrogen-incorporation in grown diamond films. Relative intensity ratios of nitrogen-related band to band-A (denoted by I N / I A ) are also estimated from the CL characteristics and the influence of additive N 2 and O 2 precursors on the I N / I A ratio is analyzed. For all-grown films, electron-emission characteristics are measured, from which threshold fields for the emission are also estimated. Observed emission properties are correlated with crystal structures and morphologies obtained from grown films by considering the structural transformation from micro- to nano-crystalline as well as the nitrogen-induced defect states.

Polycrystalline ZnO films are deposited using RF magnetron sputtering on various substrate materials including AlN/Si-(111), sapphire, DLC/Si-(100), SiO2/Si-(100) and Si-(111). The structural parameters of deposited ZnO films, such as texture coefficient (TC) value for (002)-orientation, crystallite size and full-width at half-maximum (FWHM) at ZnO (002)-peak, are compared. Surface acoustic wave (SAW) devices are also fabricated by using a lift-off method, with the configuration of IDT/ZnO/substrate. The frequency response characteristics (including S21) of the fabricated SAW devices are measured and the device parameters, such as insertion losses and side-lobe rejection level, are estimated in terms of the substrate materials. Experimental results indicate that the lattice matching as well as the structural similarity between ZnO and substrate may be essential for determining the SAW device characteristics.

Surface acoustic wave (SAW) devices with a ZnO/buffer/Si configuration have been fabricated, employing poly-AlN (deposited by RF magnetron sputtering) and epi-AlN (deposited by plasma-assisted MBE) as the buffer layer. In particular, the effects of the AlN buffers on the orientation of ZnO films as well as the performance of SAW devices are studied. Piezoelectric ZnO films are deposited using RF sputtering at a nominal condition of RF power of 300 W, O 2 /(Ar+O 2 ) ratio of 10%, and substrate temperature of 300 °C. For all the deposited AlN and ZnO films, the X-ray diffraction (XRD) spectra and full width at half maximum ( ω FWHM) of rocking curves are measured in terms of the deposition conditions, to characterize the c -axis preferred orientation and crystal quality. The frequency response characteristics (including S 21 ) of the fabricated SAW devices are also measured. The experimental results indicate that the c-axis orientation and crystal quality of ZnO films are determined mainly by the properties of AlN buffer. Furthermore, the insertion loss of ZnO-SAW devices is found to be dependent on the crystal quality and surface morphology of AlN buffer. The correlations between the properties of AlN buffers and the characteristics of ZnO-SAW devices are also discussed in detail.