• Journal of the Korean Society of Radiology
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• v.84 no.5
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• pp.1110-1122
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• 2023

Purpose This study aimed to assess the variability of transrectal shear wave elastography (SWE) using a designed phantom. Materials and Methods In a phantom, the SWE values were examined by two radiologists using agarose and emulsion silicone of different sizes (1, 2, and 3 cm) and shapes (round, cubic) at three depths (1, 2, and 3 cm), two region of interest (ROI) and locations (central, peripheral) using two ultrasound machines (A, B from different vendors). Variability was evaluated using the coefficient of variation (CV). Results The CVs decreased with increasing phantom size. Significant changes in SWE values included; agarose phantom at 3 cm depth (p < 0.001; machine A), 1 cm depth (p = 0.01; machine B), emulsion silicone at 2 cm depth (p = 0.047, p = 0.020; both machines). The CVs increased with increasing depth. Significant changes in SWE values included; 1 cm agarose (p = 0.037, p = 0.021; both machines) and 2 cm agarose phantom (p = 0.047; machine A). Significant differences in SWE values were observed between the shapes for emulsion silicone phantom (p = 0.032; machines A) and between ROI locations on machine B (p ≤ 0.001). The SWE values differed significantly between the two machines (p < 0.05). The intra-/inter-operator agreements were excellent (intraclass correlation coefficient > 0.9). Conclusion The phantom size, depth, and different machines affected the variability of transrectal SWE.

• Earthquakes and Structures
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• v.26 no.6
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• pp.417-431
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• 2024

The fundamental period of vibration is one of the most critical parameters in the analysis and design of structures, as it depends on the distribution of stiffness and mass within the structure. Therefore, building codes propose empirical equations based on the observed periods of actual buildings during seismic events and ambient vibration tests. However, despite the fact that infill walls increase the stiffness and mass of the structure, causing significant changes in the fundamental period, most of these equations do not account for the presence of infills walls in the structure. Typically, these equations are dependent on both the structural system type and building height. The different values between the empirical and analytical periods are due to the elimination of non-structural effects in the analytical methods. Therefore, the presence of non-structural elements, such as infill panels, should be carefully considered. Another critical factor influencing the fundamental period is the effect of Soil-Structure Interaction (SSI). Most seismic building design codes generally consider SSI to be beneficial to the structural system under seismic loading, as it increases the fundamental period and leads to higher damping of the system. Recent case studies and postseismic observations suggest that SSI can have detrimental effects, and neglecting its impact could lead to unsafe design, especially for structures located on soft soil. The current research focuses on investigating the effect of infill panels on the fundamental period of moment-resisting and eccentrically braced steel frames while considering the influence of soil-structure interaction. To achieve this, the effects of building height, infill wall stiffness, infill openings and soil structure interactions were studied using 3, 6, 9, 12, 15 and 18-story 3-D frames. These frames were modeled and analyzed using SeismoStruct software. The calculated values of the fundamental period were then compared with those obtained from the proposed equation in the seismic code. The results indicate that changing the number of stories and the soil type significantly affects the fundamental period of structures. Moreover, as the percentage of infill openings increases, the fundamental period of the structure increases almost linearly. Additionally, soil-structure interaction strongly affects the fundamental periods of structures, especially for more flexible soils. This effect is more pronounced when the infill wall stiffness is higher. In conclusion, new equations are proposed for predicting the fundamental periods of Moment Resisting Frame (MRF) and Eccentrically Braced Frame (EBF) buildings. These equations are functions of various parameters, including building height, modulus of elasticity, infill wall thickness, infill wall percentage, and soil types.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.89-98
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• 2007

This study investigates the deformation behavior, related to debonding failure, of adhesion and repairing-strengthening materials of RC construction. A strain-stress curve shows that when the stress of specimens reached the highest and then fails, the strain value of cement mortar is $2.0{\times}10^{-3}$, while concrete was indicated at around $1.3{\times}10^{-3}$, epoxy resins are $0.8{\times}10^{-3}$, polymer mortar is $2.5{\times}10^{-3}$, steel plate is $2.5{\times}10^{-3}$, and carbon bar was $9.1{\times}10^{-3}$, respectively. For a thermal expansion coefficient with temperature variation, those basis materials, cement mortar and concrete, exhibited around $10{\mu}{\varepsilon}/{^{\circ}C}$, but adhesive materials, such as epoxy resins and polymer mortar, were $41{\sim}54{\mu}{\varepsilon}/{^{\circ}C}$ and $-0.5{\sim}0.7{\mu}{\varepsilon}/{^{\circ}C}$, respectively. In the case of steel plate is similar to basic materials but carbon fiber is indicates at $-1.7{\mu}{\varepsilon}/{^{\circ}C}$, which is the lowest value. Especially, between basic and adhesive materials, the thermal expansion coefficient was highly different. Although the coefficient depends on the type of epoxy resins, it is clear that the epoxy resins are susceptible to be debonded in nature, when the difference of environmental temperature varies more than $20{\sim}35{^{\circ}C}$.

• Tuberculosis and Respiratory Diseases
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• v.87 no.3
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• pp.368-377
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• 2024

Background: Bronchiectasis is a chronic respiratory disease that leads to airway inflammation, destruction, and airflow limitation, which reflects its severity. Impulse oscillometry (IOS) is a non-invasive method that uses sound waves to estimate lung function and airway resistance. The aim of this study was to assess the usefulness of IOS in predicting the severity of bronchiectasis. Methods: We retrospectively reviewed the IOS parameters and clinical characteristics in 145 patients diagnosed with bronchiectasis between March 2020 and May 2021. Disease severity was evaluated using the FACED score, and patients were divided into mild and moderate/severe groups. Results: Forty-four patients (30.3%) were in the moderate/severe group, and 101 (69.7%) were in the mild group. Patients with moderate/severe bronchiectasis had a higher airway resistance at 5 Hz (R5), a higher difference between the resistance at 5 and 20 Hz (R5-R20), a higher resonant frequency (Fres), and a higher area of reactance (AX) than patients with mild bronchiectasis. R5 ≥0.43, resistance at 20 Hz (R20) ≥0.234, R5-R20 ≥28.3, AX ≥1.02, reactance at 5 Hz (X5) ≤-0.238, and Fres ≥20.88 revealed significant univariable relationships with bronchiectasis severity (p<0.05). Among these, only X5 ≤-0.238 exhibited a significant multivariable relationship with bronchiectasis severity (p=0.039). The receiver operating characteristic curve for predicting moderate-to-severe bronchiectasis of FACED score based on IOS parameters exhibited an area under the curve of 0.809. Conclusion: The IOS assessed by the disease severity of FACED score can effectively reflect airway resistance and elasticity in bronchiectasis patients and serve as valuable tools for predicting bronchiectasis severity.

• Steel and Composite Structures
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• v.53 no.2
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• pp.243-252
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• 2024

Conventional carbon mild steel is a type of steel known for its low carbon content and generally used in the construction industry. Its easily formable and weldable properties make this steel a widely preferred material for buildings, bridges and various construction projects. Other advantages of these steels are their low cost and good mechanical properties. However, high temperatures have an impact on the microstructure and mechanical characteristics of these materials. When high temperatures are present during a fire, steels show significant microstructural changes. Elevated temperatures often decrease the mechanical characteristics of steels. For this purpose, evaluating the post-fire behavior of conventional structural mild steel is an important issue in terms of safety. A combined experimental and parametric study was conducted to estimate fire damage to steel buildings, which is an important issue in the construction field. Tensile test coupons were cut from conventional structural S235JR mild steel sheets with thicknesses ranging from 6 mm to 12 mm. These samples were exposed to temperatures as high as 1200 ℃. After heat treatment, the specimens were allowed to naturally cool to ambient temperature using air cooling before being tested. A tensile test was performed on these coupons to evaluate their mechanical properties after fire, such as their elastic modulus, yield strength, and ultimate tensile strength. The mechanical behavior of conventional S235JR structural steel changed significantly when the heating temperature reached 600℃. The thickness of the steel had a negligible effect on yield strength loss, with the highest measured loss being 50% for 8 mm thickness at 1200℃. For thinner sections (6 mm), yield strength decreased by up to 40%, while thicker samples (12 mm) showed similar reductions. Ultimate tensile strength also showed minimal changes up to 600℃, but beyond this point, a notable decline occurred, with approximately 30% strength loss at 1200℃. The modulus of elasticity remained almost constant up to 800℃, but at 1200℃, the loss reached around 20% for thicker sections (10 mm and 12 mm) and up to 35% for thinner sections (6 mm and 8 mm). Overall, high temperatures led to significant deterioration in both yield and ultimate strength, with a general loss of load-bearing capacity above 600℃. A new equation was formulated from experimental results to predict changes in the mechanical properties of S235JR steels. This equation offers a precise evaluation of buildings made from conventional structural S235JR mild steel after fire exposure. Furthermore, the empirical equation is applicable to low-strength steels with yield strengths ranging from 235 MPa to 420 MPa.

• Science of Emotion and Sensibility
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• v.27 no.3
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• pp.61-70
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• 2024

This study aimed to investigate the effects of voluntary intrathoracic pressure adjustment during the Valsalva maneuver (VM) on changes in prefrontal brain function and cerebral blood flow dynamics using diagnostic ultrasound and near-infrared spectroscopy (NIRS). Sixteen healthy adults performed VM by adjusting their expiratory pressure. Their regional oxygen saturation (rSO2) and oxidized hemoglobin (HbO) levels were measured to confirm changes in prefrontal lobe function. To confirm hemodynamic changes in cerebral blood vessels, this study measured peak systolic velocity (PSV), heart rate (HR), vascular stiffness (STIFF), and pulse wave velocity (PWV) in the common carotid artery before and after the VM. Results showed significant cerebrovascular physiological changes after 30mmHg VM. In particular, PSV increased significantly following VM, whereas PWV and STIFF significantly decreased. A similar trend was observed in 40mmHg VM to 30mmHg, but no significant change was observed except for HR, which showed a significant decrease. Furthermore, rSO2 tended to increase in the prefrontal region after preforming 30 and 40mmHg VM, but it did not show a significant difference. In contrast, HbO significantly decreased after performing 30 and 40mmHg VM. This trend did not show any difference depending on intrathoracic pressure. In conclusion, VM performance at both intrathoracic pressure levels has the same effect on brain function, but induces difference changes in cerebrovascular vessels' physiological function. Thus, at 40mmHg VM, it interferes with effective vascular relaxation due to high intrathoracic pressure. However, 30mmHg VM has an effective effect on cerebrovascular function by causing a significant increase in the elasticity of arterial blood vessels. Such VM performance can effectively improve cerebrovascular function.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.133-144
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• 2006

In order to catch out such Bond Strength, the preceding researchers had ever examined the Bond Strength of FRP Plate through their experimentations by setting up of various fluent. However, since the experiment for research on such Bond Strength takes much of expenditure for equipment structure and time-consuming, also difficult to carry out, it is conducting limitedly. This Study purposes to develop the most suitable Artificial Neural Network Model by application of various Neural Network Model and Algorithm to the adhering experiment data of the preceding researchers. Output Layer of Artificial Neural Network Model, and Input Layer of Bond Strength were performed the learning by selection as the variable of the thickness, width, adhered length, the modulus of elasticity, tensile strength, and the compressive strength of concrete, tensile strength, width, respectively. The developed Artificial Neural Network Model has applied Back-Propagation, and its error was learnt to be converged within the range of 0.001. Besides, the process for generalization has dissolved the problem of Over-Fitting in the way of more generalized method by introduction of Bayesian Technique. The verification on the developed Model was executed by comparison with the resulted value of Bond Strength made by the other preceding researchers which was never been utilized to the learning as yet.

• Journal of Korean Society of Forest Science
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• v.80 no.1
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• pp.72-81
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• 1991

This study was carried out to provide necessary information for improving quarrying industry management in Korea. The results of the study are summarized as follows : 1. In aggregate and building-stone quarrying firms the managers over 40 years of age are 97% and 89.1%, the ones above education level of high school are 90% and 85% and the ones not more than 10 years of quarrying experience are 70% and 52%, respectively. Accordingly it can be pointed out that most of the managers of two types of firms are relatively old, have high educational background, while quarrying experiences of building-stone firm managers are longer than that of aggregate firm managers. 2. Most of the management forms are social corporation(60%) for aggregate quarry firms and private management(76%) for building-stone firms. Average areas of permitted stone-pits of aggregate and building-stone quarries are about 2.86ha and 1.66ha respectively. That is, aggregate quarrying firms are carried on a larger scale than building-stone quarrying firms. 3. The yearly average product of aggregate quarrying firms has increased steadily from $88.961m^3$ in 1985 to $144.028m^3$ in 1988, while, in case of building-stone quarry firms, it has significantly increased from $4.155m^3$ to $19.462m^3$ from 1985 to 1987, but reduced to $13.400m^3$ in 1988. Unstable production activities of building-stone quarrying firms may require continuous government support. 4. Major cost items are equipment rental, depreciation, salaries, repair, maintenance for aggregate quarrying firms, and salaries, depreciation, fuel, tax for building-stone quarrying firms. The yearly average rate of return is about 9.7% for aggregate quarry firms and 2.6% for building-stone quarry firms. It can be pointed out that aggregate quarrying firms is better managed than building-stone quarrying firms. 5. The production elasticity of salary for aggregate quarrying firms is 0.495, that of employees is 0.559, and that of capital service is 0.513. The sum of the elasticities is 1.257>1. Fur building-stone quarrying firms, that of employees is 0.492, that of variable costs is 0.192, and that of capital service is 0.498. The sum of elasticities is 1.172>1, thus denotes the increasing returns to scale for both types quarrying firms. 6. The ratio of marginal value product to opportunity cost of empolyees is 2.54, that of variable costs is 3.62, and that of capital service is 1.45, in aggregate quarrying firms. That of employees is 2.47, that is variable costs was 2.34, and that of capital service is 19.67 in building-stone quarrying firms. Therefore the critical factors for more expansion of management scale in aggregate quarrying firms are variable cost and employees, and are capital service in building-stone quarry ing firms. 7. The break-even points of stone sales are about 0.587 billion won and 0.22 billion won in aggregate and building-stone quarrying firms respectively. The optimum sales Level for profit maximization are about 2.0 billion and 0.5 billion in aggregate and building-stone quarry firms respectively.

• Korean Journal of Food Science and Technology
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• v.40 no.4
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• pp.436-442
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• 2008

Hydroxyproline and Pro-Hyp dipeptide are the digestive products of collagen hydrolysate called collagen peptide. Some suggested that collagen peptides could improve aged or damaged skins, however, the effects of collagen peptides on the skin have not been known. In this study, we investigated the effects of digestive products of collagen peptides, hydroxyproline and Pro-Hyp dipeptide on skin quality using the UV-damaged dorsal skin of hairless mouse as a model system. Female SKH hairless mice were pre-irradiated with UV for 7 weeks, and then hydroxyproline, Pro-Hyp dipeptide were orally administered for 7 weeks with UV irradiation. Wrinkle formation (by replica image), skin elasticity, barrier status (by TEWL, transepidermal water loss), epidermis thickness, and biophysical changes in the stratum comeum (by hematoxylin & eosin staining) were examined. With the oral peptide treatment, effects such as skin barrier maintenance, anti-skin thickening, and recovery of the stratum corneum were observed. These results indicate that oral intake of collagen peptides may have beneficial effects on damaged skin cells.

• Korean journal of food and cookery science
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• v.11 no.5
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• pp.446-455
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• 1995

The nutritional properties of the Chol-Pyon were investigated with changing the materials (mugwort and pine leaves). In proximate composition, rice powder added mugwort and pine leaves showed the lligher con-tents of crude protein, crude lipid and crude ash than in rice powder. Ihe pH of rice powder, mugwort and pine leaves was 6.4, 6.8 and 3.5, respectively. The rice powder added pine leaves showed the lowest pH value. The content of the free sugar in raw materials for ChOl-PyOn preparation was 0.9% in rice powder, 0.3% in mugwort and 2.7％ in pine leaves. Eighteen kinds of amino acids were determined in raw materials for ChOl-fyOn preparation and their contents were 4.8% in mugwort, 4.2% in rice powder and 2.8% in pine leaves. The major minerals of raw materials for ChOl-PyOn preparation was 0.9％ increased in the order of K> Na > Mg > Ca in rice powder, Mg > K > Ca > Na in mugwort, and K > Ca > Mg > Na in pine leaves. Both of mugwort and pine leaves additives showed the higher contents of 8 kinds of minerals (Ca, Mg, K, Na, Mn, Fe, Cu, Zn) than in rice powder. In relation to changes in the texture of ChOl-PyOn, hardness, fracturability and adhesiveness at 25${\pm}$1$^{\circ}C$ were measured to be highest in white ChOl-PyOn. Cohesiveness was shown to be highest at 15％ in case of mugwort and 2.5％ in case of pine leaves. Elasticity was measured to be highest at 0.99 in case that 7.5% mugwort was added to raw materials for ChOl-PyOn. As a result of estimating the sensory qualities of the ChOl-PyOn prepared to which the additives were added in differing amounts, immediately after its preparation the mugwort additive of 7.5％ showed the superior sensory qualities Chol-PyOn (p < 0,01).