• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.35-41
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• 2011

In this study, the interface soaking effect in InAs/GaAs strained-layer superlattice (SLS) on crystalline phase modulation has been analyzed by the x-ray diffraction (XRD) curve. The strain variation induced by As and/or Sb soaking was determined by the separation angle between the substrate peak and the 0th-order superlattice satellite peak in the XRD spectra. Contrated that the As/InAs soaking arises minor GaAs-like interfacial layer, the Sb/GaSb soaking induces InSb-like one. The Fourier-transformed curves of the Pendellosung interference oscillation shows that the optimum soaking times of As/InAs and Sb/GaSb are 2 sec and 12 sec, at which the highest crystallineity has, respectively. An anomalous twin-peak phenomenon that a satellite peak splits into two peaks was observed in the SLS structure co-soaked by As and Sb at InAs${\rightarrow}$GaSb interfaces. We suggest that it may be resulted from coexistence of two kinds crystalline phases of InAsSb and GaAsSb due to intermixing of In${\leftrightarrow}$Ga and Sb${\leftrightarrow}$As.

• Current Photovoltaic Research
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• v.9 no.4
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• pp.145-159
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• 2021

Light soaking (LS) stability in polymer solar cells (PSCs) has always been a challenge to achieve due to unstable photoactive layer-electrode interface. Especially, the electron transport layer (ETL) and photoactive layer interface limits the LS stability of PSCs. Herein, we have modified the most commonly used and robust zinc oxide (ZnO) ETL-interface using an organic dye molecule and a co-adsorbent. Power conversion efficiencies have been slightly improved but when these PSCs were subjected to long term LS stability chamber, equipped with heat and humidity (45℃ and 85% relative humidity), an outstanding stability in the case of ZnO/dye+co-adsorbent ETL containing devices have been achieved. The enhanced LS stability occurred due to the suppressed interfacial defects and robust contact between the ZnO and photoactive layer. Current density as well as fill factors have been retained after LS with the modified ETL as compared to un-modified ETL, owing to their higher charge collection efficiencies which originated from higher electron mobilities. Moreover, the existence of less traps (as observed from light intensity-open circuit voltage measurements and dark currents at -2V) are also found to be one of the reasons for enhanced LS stability in the current study. We conclude that the mitigation ETL-surface traps using an organic dye with a co-adsorbent is an effective and robust approach to enhance the LS stability in PSCs.

• Journal of Adhesion and Interface
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• v.20 no.3
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• pp.87-95
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• 2019

In the present study, the effect of alkali treatment of rice straw on the flexural properties and impact strength of rice straw/recycled polyethylene composite was investigated. Alkali treatments were performed by means of two different methods at various sodium hydroxide (NaOH) concentrations. One is static soaking method and the other is dynamic shaking method. The composites were made by compression molding technique using rice straw/recycled polyethylene pellets produced by twin-screw extrusion process. The result strongly depends on the alkali treatment method and concentration. The shaking method done with a low concentration of 1 wt% NaOH exhibits the highest flexural and impact properties whereas the soaking method done with a high concentration of 10 wt% NaOH exhibits the highest properties, being supported qualitatively by the fiber-matrix interfacial bonding of the composites. The properties between the two highest property cases above-described are comparable each other. The study suggests that such a low concentration of 1 wt% NaOH may be used for alkali treatment of natural fibers to improve the flexural and impact properties of resulting composites, rather than using high concentrations of NaOH, 10 wt% or higher. Considering of environmental concerns of alkali treatment, the shaking method is preferable to use.

• Journal of Adhesion and Interface
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• v.9 no.4
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• pp.1-11
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• 2008

In the present study, kenaf fibers were treated with sodium hydroxide using soaking and ultrasonic methods prior to biocomposite processing, respectively. The effect of alkali treatment on the kenaf-PLA interfacial adhesion and mechanical and thermal characteristics of kenaf/poly(lactic acid) biocomposites was investigated in terms of their interfacial shear strength, flexural properties, dynamic mechanical properties and thermal stability and also microscopic observations of kenaf fibers and the composite fracture surfaces. As a result, use of both soaking and ultrasonic methods for treating kenaf fiber surfaces played a role in increasing the fiber-matrix adhesion and the mechanical properties of the biocomposites. Their characteristics depended not only on the fiber surface treatment method but also on the treatment condition like alkali concentration and treatment time.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.446-451
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• 2018

In this study, different formulations of magnesium oxide and various modifiers (phosphoric acid, ferrous sulfate, pure acrylic emulsion, silicone acrylic emulsion, glass fiber, and polypropylene fiber) were used to prepare magnesium oxychloride cement composites. The compressive strength of the magnesium oxychloride cement was tested, and the softening coefficients of the composites after soaking in water were also calculated. The results showed that a magnesium oxychloride cement sample could not be coagulated when the MgO activity was 24.3%, but the coagulation effect of the magnesium oxide cement sample was excellent when the MgO activity was 69.5%. While pure acrylic emulsion, silicon-acrylic emulsion, and glass fiber showed insignificant modification effects on the magnesium oxychloride cement, ferrous sulfate heptahydrate, phosphoric acid, and polypropylene fiber could effectively improve its water resistance and compressive strength. When the phosphoric acid, ferrous sulfate heptahydrate, and polypropylene fiber contents were 0.47%, 0.73%, and 0.25%, respectively, the softening coefficient of a composite soaked in water reached 0.93 after 7 days, and the compressive strength reached 64.3 MPa.

• Journal of Powder Materials
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• v.26 no.5
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• pp.369-374
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• 2019

The properties of powder metallurgy products are related to their densities. In the present work, we demonstrate a method to apply artificial neural networks (ANNs) trained on experimental data to predict the bulk density of barium titanates. The density is modeled as a function of pressure, press rate, heating rate, sintering temperature, and soaking time using the ANN method. The model predictions with the training and testing data result in a high coefficient of correlation (R2 = 0.95 and Pearson's r = 0.97) and low average error. Moreover, a graphical user interface for the model is developed on the basis of the transformed weights of the optimally trained model. It facilitates the prediction of an infinite combination of process parameters with reasonable accuracy. Sensitivity analysis performed on the ANN model aids the identification of the impact of process parameters on the density of barium titanates.

• Korean Journal of Food Science and Technology
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• v.10 no.1
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• pp.52-56
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• 1978

The mechanism of cooking rice was investigated using a japonica type rice variety, Akibare, of 50%, 70% and 90% polishing degrees. The hardness of rice cooked at various cooking temperatures ($90^{\circ}-120^{\circ}C$) was measured with a Texturometer. The cooking rate followed the equation of a first-order reaction. The reaction rate constants were in the increasing order of 50%, 70% and 90% polished rice. The temperature coefficient of the reaction rate constant at cooking temperatures of ($90^{\circ}-100^{\circ}C$) was about 2 in all rice samples. The activation energies of cooking at temperatures below $100^{\circ}C$ and above $100^{\circ}C$ were about 17,000 and 9,000 cal/mole, respectively. The polishing degrees and water soaking time of rice did not affect the activation energy of cooking; however, the lower polishing degrees and shorter soaking increased the cooking time The experimental results suggested that the cooking process of rice comprises two mechanisms: At temperatures below $100^{\circ}C$ the cooking rate is controlled by the reaction rate of rice constituents with water, and at temperatures above $100^{\circ}C$, it is controlled by the rate of diffusion of water through the cooked portion (or layer) toward the interface of uncooked core in which the reaction is occurring.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.23-32
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• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.