• Journal of the Microelectronics and Packaging Society
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• v.27 no.2
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• pp.33-38
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• 2020

In the photoelectrochemical (PEC) water splitting, GaN is one of the most promising photoanode materials due to high stability in electrolytes and adjustable energy band position. However, the application of GaN is limited because of low efficiency. To improve solar to hydrogen conversion efficiency, we introduce a Cobalt Phosphate (Co-pi) catalyst by photo-electrodeposition. The Co-pi deposition GaN were characterized by SEM, EDS, and XPS, respectively, which illustrated that Co-pi was successfully decorated on the surface of GaN. PEC measurement showed that photocurrent density of GaN was 0.5 mA/㎠ and that of Co-pi deposited GaN was 0.75 mA/㎠. Impedance and Mott-Schottky measurements were performed, and as a result of the measurement, polarization resistance (R_p) and increased donor concentration (N_D) values decreased from 50.35 Ω to 34.16 Ω were confirmed. As a result of analyzing the surface components before and after the water decomposition, it was confirmed that the Co-pi catalyst is stable because Co-pi remains even after the water decomposition. Through this, it was confirmed that Co-pi is effective as a catalyst for improving GaN efficiency, and when applied as a catalyst to other photoelectrodes, it is considered that the efficiency of the PEC system can be improved.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.11-19
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• 2009

Recently, concerns relating to the maintenance of large structures have been increased. In addition, the number of large structures that need to be evaluated for their structural safety due to natural disasters and structural deterioration has been rapidly increasing. It is common for the structural characteristics of an older large structure to differ from the characteristics in the initial design stage, and changes in dynamic characteristics may result from a reduction in stiffness due to cracks on the materials. The process of deterioration of such structures enables the detection of damaged locations, as well as a quantitative evaluation. One of the typical measuring instruments used for the monitoring of bridges and buildings is the dynamic measurement system. Conventional dynamic measurement systems require considerable cabling to facilitate a direct connection between sensor and DAQ logger. For this reason, a method of measuring structural responses from a remote distance without the mounted sensors is needed. In terms of non-contact methods that are applicable to dynamic response measurement, the methods using the doppler effect of a laser or a GPS are commonly used. However, such methods could not be generally applied to bridge structures because of their costs and inaccuracies. Alternatively, a method using a visual image can be economical as well as feasible for measuring vibration signals of inaccessible bridge structures and extracting their dynamic characteristics. Many studies have been conducted using camera visual signals instead of conventional mounted sensors. However, these studies have been focused on measuring displacement response by an image processing technique after recording a position of the target mounted on the structure, in which the number of measurement targets may be limited. Therefore, in this study, a model experiment was carried out to verify the measurement algorithm for measuring multi-point displacement responses by using a DIC (Digital Image Correlation) technique.

• Tuberculosis and Respiratory Diseases
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• v.46 no.3
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• pp.386-393
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• 1999

Objective : Cardiopulmonary exercise testing in patients with heart and lung problems is used to assess functional capacity, evaluate responses to medical treatment, plan for exercise therapy, assess progression of disease process, and determine prognosis. Particularly in the patients with lung cancer, the exercise pulmonary function test gives significant physiologic assessment of the lung resection candidate. Common exercise modalities are running and cycling. Until now, the comparison of two tests mainly has been done in normal person and patients with cardiac diseases. This study is designed to compare the treadmill and bicycle exercise pulmonary function test in patients with respiratory diseases. Methods : Twenty one patients underwent a progressively incremental exercise test to the symptom-limited stage with the treadmill (Vmax29 Sensor Medics, USA) and the bicycle(model No. 2,900 Sensor Medics, USA) with 7 days apart between the two tests. Measurements were made of the metabolic, cardiorespiratory parameters, blood gases, and symptoms. Results : The results of the treadmill exercise showed significant elevation in the $VO_2$max, VEmax, and anaerobic threshold compared to those of bicycle exercise. In contrast, the results of the breathing and heart rate reserve showed the reverse. Conclusion : These results suggest that the type of exercise should be taken into consideration when interpreting exercise test in patients with respiratory diseases.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.131-149
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• 1999

It was found that surface roughness has a first-order effect on the interface shear strength and accordingly it should be accurately quantified if its role is to be properly understood. To quantify the surface topography, first of all, a variety of commonly used surface roughness parameters and profiling methods were reviewed in this study. Based on this review, the normalized roughness parameter. $R_n$(Uesugi and Kishida, 1986), the profile roughness parameter, $R_L$, and the surface roughness parameter, $R_n$(Dove and Frost, 1996), were selected to be appropriate candidates of roughness parameters and the digital image analysis based Optical Profile Microscopy(OPM) method(Dove and Frost, 1996) to be an appropriate profiling method for this study. Using a smooth and three textured HDPE geomembranes which encompass the range of textures and texture patterns commonly used, a series of roughness measurements on virgin and previously used geomembranes were performed. The results showed that both $R_L\; and\; R_S$ values appropriately reflect the degree of texturing for the geomembranes used in this study, however, $R_n$ value showed limited ranges of variation which may not be sufficient to permit distinction between roughness values for certain conditions. The results of this study will be extended to the investigation of the influence of surface roughness on interface strength in future study.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.105-127
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• 1999

Application of the soil nailing method is continuously extended in maintaining stable excavations and slopes. Occasionally, however, ground anchor support system may not be used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then, could play important roles in reducing deformations mainly in an upper part of the nailed-soil excavation system as well as improving local stability. In the present study, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the pretensioned soil nailing system. Also proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear. The predicted results are compared with the limited measurements obtained from the excavation site constructed by using the pretensioned soil nails. Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretensioning of the soil nails are examined in detail throughout an illustrative example and FLAC$^{2D}$ program analysis.s.

• Journal of dental hygiene science
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• v.20 no.1
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• pp.9-15
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• 2020

Background: Although the consumption of vitamin beverages has increased because of the recent interest in health and beauty, guidelines addressing appropriate consumption habits are lacking. Thus, the aim of this study was to investigate the erosive potential of several vitamin beverages and to propose guidelines for the appropriate intake of these drinks. Methods: Five vitamin beverages were selected after a pre-investigation of the current beverage market. Coca-Cola and mineral water were selected as the control beverages. The pH of the beverages was measured with a calibrated pH meter, and the titratable acidity (TA) was determined by using 1 M sodium hydroxide to reach pH 5.5 (TA5.5) and 7.0 (TA7.0). The screening method suggested by the International Organization for Standardization was used to measure pH variation (ΔpH) by using an under-saturated hydroxyapatite solution to determine the difference between the initial and final pH of the screening solution. All measurements were performed in triplicate. Results: All vitamin beverages tested in this study exhibited a low pH (2.53~2.99), similar to Coca-Cola, which is known to be a highly acidic beverage. The highest TA5.5 and TA7.0 values of the vitamin beverages were 7.03 ml and 8.81 ml, respectively. The largest change in pH determined by using the screening solution was found in Bacchus D (ΔpH 1.44±0.05). The mean ΔpH of the vitamin beverages was 1.12±0.29, which was higher than that of Coca-Cola (positive control, ΔpH 0.58±0.05). Conclusion: Vitamin beverages exhibited an erosive potential capable of damaging enamel surfaces. Therefore, the frequency of vitamin beverage intake should be limited, and individuals consuming these drinks should try to restore normal oral pH as quickly as possible.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.1
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• pp.51-60
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• 2018

Objectives: Currently, there is only limited knowledge regarding the hazard of low-level exposure to CMR materials in workplaces. To overcome this limitation, a reference concentration for workers($RfC_w$) from among the risk assessment tools proposed by the US EPA is widely used to set a provisional workplace exposure level(PWEL) for CMR materials for which there are no established Korea Occupational Exposure Limits(KOELs) or subjective chemicals for work environment measurements as regulated by Korea Ministry of Employment and Labor(KMOEL). A simple European calculator of derived no effect level(SECO-DNEL) as proposed by REACH can also be used in place of $RfC_w$ to set the PWEL for chemicals. This study was performed to test the acceptability of using SECO-DNEL as an alternative to $RfC_w$ when setting a PWEL for low-level exposures. Methods: The $RfC_w$ and DNEL for the five CMR materials of dinitrogen oxide, catechol, 2-phenoxy ethanol, carbitol, and carbon black were calculated using the dose-response assessments of the US EPA for $RfC_w$ and REACH guidance for SECO-DNEL, respectively. They were compared using paired t-tests to determine the statistical differences between them. Results: For the five chemicals, the $RfC_w$ were 2.53 ppm, 0.10 ppm, 1.73 ppm, 1.66 ppm, and $0.05mg/m^3$, respectively, while the SECO-DNEL were 2.01 ppm, 0.11 ppm, 1.83 ppm, 1.77 ppm, $0.14mg/m^3$, respectively. There was no statistically significant difference between $RfC_w$ and SECO-DNEL. Conclusions: This study suggests that the SECO-DNEL could be applied in place of $RfC_w$ to set a PWEL for low-level exposure to chemicals, especially CMR materials. To further ensure the reliability of SECO-DNEL as an alternative tool, more chemicals should be applied for calculation and comparison with $RfC_w$.

• Journal of the Korean Society for Library and Information Science
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• v.8
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• pp.183-207
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• 1981

Library standards have been the source of considerable controversy, whereas many problems are involved in developing stardard for university library collections. For evaluation purposes, standards should be precise, quantifiable and measurable. In the United States, however, standards for academic libraries are limited to qualitative statements and principles. Quantitative standards, when given, are ususally related to the number of population in the institution being served, or the prescribed quantitative objectives are often arbitrarily formulated by value judgements. The study in this paper attempts to explain the problems involved in developing quantitative standard for academic library collections. Two problems facing in the formulation of the optimal size of collection are identified. One is the theoretically faulty concept of adequacy of collection to meet the situations of diversity of university libraies, and the other is the difficulties in quantification and measurement, along with the lack of concept of adequacy of collection. However, quantification of adequate size of collection is proved to be useful on the pratical level, even though not valid theoretically. ACRL, Clapp/Jordan and Voigt developed formulas or models for setting the optimal size of a library collection for any particular university library. The main purpose of this study is the analysis of the above formulas. ACRL standard was drawn from obervation and analysis of statistcs in leading library collections. In academic field, this judgement appears to have been based on the assumption that a high-grade institution would be apt to have a good library collection. This study criticizes ACRL standard for its failure to include some determinants of measurements, and points out the limitations of the standard. In contrast. Clapp/Jordan developed a formula rather scientifically based upon bibliographical sources. This is similarly empirical but has the advantage of bringing into play the elements which make universities diverse in nature. Both ACRL and Clapp/Jordan formulas share two major defects. (1) the specific subject needs of the collection are not indiacted directly, and (2) percentage rate of growth is an indicator in measuring the potential utility of a collection. Thus both formulas failed to provide a basis for meaningful evaluation. Voigt further developed a model for determining acquisition rates for currently published materials based on bibliographic technique. Voigt model encourages experimentation with different programs and different allocations of input resources, designed to meet the needs of the library's particular population. Standard for university library collections can be formulated in terms of input(traditional indicator), or additionally, in terms of output(cost-effectiveness). Cost effectiveness is expressed as user satisfaction, ability to provide wanted materials within a reasonable time period. Thus simple quantitative method does not cover all the situations of diversity of university library collections, nor measures the effectiveness of collections. Valid standard could not be established without further research.

• Journal of Nutrition and Health
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• v.38 no.6
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• pp.419-431
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• 2005

The prevalence of atopic dermatitis (AD) continues to increase in the industrialized countries related to Western lifestyle and dietary patterns. The purpose of this study was to evaluate the nutritional status, dietary patterns and dietary quality of AD patients. AD patients (n=50) and gender age matched healthy control (HC) were studied in case-control clinical trail. Preference and frequencies of consumption for 98 foods were estimated by questionnaires. Dietary pattern, current nutrients intake, and dietary quality were evaluated by the 3-day food records. As a result, anthropometric measurements from HC and AD patients were not significantly different. AD patients had significantly lower preference for buckwheat, some fishes (shellfish, flatfish, salmon), egg yolk, some vegetables (onion, garlic, Chinese-cabbage, radish, pepper, mushroom), coffee, and snack than those of HC had (p<0.05). AD patients had significantly lower frequency for pea, some fishes (shellfish, herring, flatfish, salmon, codfish), egg, some vegetables (spinach, pumpkin, mushroom), margarine/butter, nuts, coffee and apple juice, fried chicken, coke than those of HC had (p<0.05). The intake of vitamin $B_1$, vitamin $B_2$ (p<0.05) and vitamin E (p<0.001) of AD patients were significantly lower than those of HC. The intake for Ca and Zn of AD patients were remarkably lower than RDA for each nutrient. Moreover, AD patients' index of nutritional quality (INQ) and nutrient adequacy ratio (NAR) of vitamin E, vitamin $B_1$, vitamin $B_2$ were lower than those of HC. AD patients' dietary quality including dietary diversity score (DDS), dietary variety score (DVS), DMGFV (dairy, meat, grain, fruit, vegetable), dietary quality index (DQI) was poor. This results indicate that atopic dermatitis patients had significantly different food preference and food frequency when these were compared with those of healthy people. The dietary diversity, dietary variety and dietary quality of atopic dermatitis patients were very limited.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.4
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• pp.743-750
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• 1997

Direct measurement of the kinetics of free fatty acid transfer between phospholipid model membrane is technically limited by the rapid nature of the transfer process. Separation of membrane-bound fatty acid by centrifugation has shown that although the equilibrium distribution of free fatty acid is determined by this method, fatty acid transfer occurs too rapidly for accurate kinetic measurements. Recently fluorescence resonance energy transfer(FRET) assay has been developed to examine transfer of fatty acids between membranes. Donor membranes which has fluorescent fatty acid, anthroyloxy fatty acid(AOFA), is mixed with acceptor membranes which has non-interchangeable fluorescent quencher, nitrobenzo-xadiazol(NBD), using stopped flow apparatus. As the fluorescent fatty acids transfer from donor membrane to acceptor membrane, fluorescence intensity would be decreased and the rate and degree of fatty acid transfer can be analyzed. Fatty acid transfer between micelles is more complicated because of bile salt. Therefore in experiments with micelles, fluorescence self quenching assay is used. At high concentrations, a fluorophore tends to quench its own fluorescence causing a reduction in fluorescence intensity. Donor micelles contained self quenching concentrations of fluorophore and acceptor micelles had no fluorophore. Upon mixing of donor and acceptor micelles, the rate of transfer of the fluorophore from the donor to the acceptor was measured by monitoring the release in self quenching when its concentration in donor decreased over time.