• Steel and Composite Structures
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• 제2권1호
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• pp.35-50
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• 2002

A series of tests on simple-welded plate specimens (SWPS) and T-stub tension specimens simulating some of the joint details in moment frame connections were conducted in this investigation. The effects of weld strength mismatch and weld metal toughness on structural behavior of these specimens were considered under both static and dynamic loading conditions. Finite element analyses were performed by taking into account typical weld residual stress distributions and weld metal strength mismatch conditions to facilitate the interpretation of the test results. The major findings are as follows: (a) Sufficient specimen size requirements are essential in simulating both load transfer and constraint conditions that are relevant to moment frame connections, (b) Weld residual stresses can significantly elevate stress triaxiality in addition to structural constraint effects, both of which can significantly reduce the plastic deformation capacity in moment frame connections, (c) Based on the test results, dynamic loading within a loading rate of 0.02 in/in/sec, as used in this study, premature brittle fractures were not seen, although a significant elevation of the yield strength can be clearly observed. However, brittle fracture features can be clearly identified in T-stub specimens in which severe constraint effects (stress triaxiality) are considered as the primary cause, (d) Based on both the test and FEA results, T-stub specimens provide a reasonable representation of the joint conditions in moment frame connections in simulating both complex load transfer mode and constraint conditions.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.752-759
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• 2017

The fatigue crack growth behavior of Type 347 (S347) and Type 347N (S347N) stainless steel was evaluated under the operating conditions of a pressurized water reactor (PWR). These two materials showed different fatigue crack growth rates (FCGRs) according to the changes in dissolved oxygen content and frequency. Under the simulated PWR conditions for normal operation, the FCGR of S347N was lower than that of S347 and insensitive to the changes in PWR water conditions. The higher yield strength and better corrosion resistance of the nitrogen-alloyed Type 347 stainless steel might be a main cause of slower FCGR and more stable properties against changes in environmental conditions.

• 한국정밀공학회지
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• 제25권6호
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• pp.159-167
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• 2008

Cooling lubricants are used in machining operations in order to reduce friction at the tool-chip and tool-workpiece interfaces, cool both chip and tool, and remove chip. Furthermore, they influence a strong effect on the shearing mechanisms and, consequently, on the machined surface quality and tool wear. However, several researchers state that the costs related to cutting fluids is frequently higher than those related to cutting tools. Moreover, the cooling lubricants cause an increase in both worker's health and social problems related to their use and correct disposal. Therefore, many researchers have focused on the environmentally conscious machining technologies. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. In this paper, an experimental model to obtain the optimal cutting conditions in MQL turning was suggested, and the effects of cutting conditions on surface roughness and cutting force were analyzed. For these purposes, FFD (Fractional Factorial Design) and RSM (Response Surface Methods) were used for the experiment. Cutting force and surface roughness with different cutting conditions were measured through the external cylindrical turning of Al 6061 based on the experiment plan. The measured data were analyzed by regression analysis and verification experiments with random conditions were conducted to confirm the suggested experimental model.

• Journal of Microbiology and Biotechnology
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• 제29권7호
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• pp.1053-1060
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• 2019

Thermal drying is a common process used in the food industry for the modification of agricultural products. However, while various studies have investigated the alteration in physiochemical properties and chemical composition after drying, research focusing on the relationship between different dehydration conditions and bioactivity is scarce. In the current study, we prepared dried ginger under nine different conditions by varying the processing time and temperature and compared their immunomodulatory effects. Interestingly, depending on the drying condition, there were significant differences in the immunestimulating activity of the dried ginger samples. Gingers processed at $50^{\circ}C$ 1h displayed the strongest activation of macrophages measured by $TNF-{\alpha}$ and IL-6 levels, whereas, freezedried or $70^{\circ}C$- and $90^{\circ}C$-dried ginger showed little effect. Similar results were recapitulated in primary bone marrow-derived macrophages, further confirming that different dehydration conditions can cause significant differences in the immune-stimulating activity of ginger. Induction of ERK, p38, and JNK signaling was found to be the major underlying molecular mechanism responsible for the immunomodulatory effect of ginger. These results highlight the potential to improve the bioactivity of functional foods by selectively controlling processing conditions.

• 한국기계가공학회지
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• 제21권2호
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• pp.123-129
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• 2022

Quartz (SiO2) has high abrasion and heat resistances and excellent chemical and mechanical properties; therefore, it is used in various industries, such as machinery, chemistry, optics, and medicine. Quartz is a high-hardness and brittle material and is classified as the topmost difficult-to-cut material, which is because of the cracking or chipping at the edge during processing. Corner wear, such as cracks and chippings that occur during cutting, is a major cause for the deterioration in the machining quality. Therefore, many researchers are investigating various techniques to process quartz effectively. However, owing to the mechanical properties of quartz, most studies have been conducted on grinding, micromachining, and microdrilling. Few studies have been conducted on quartz processing. The purpose of this study was to analyze the machining characteristics according to the machining factors during the slot machining of quartz using a cubic boron nitride (CBN) tool and to select the optimal machining conditions using the Taguchi method. The machining experiment was performed considering three process variables: the spindle speed, feed rate, and depth of cut. The cutting force and surface roughness were analyzed according to the processing conditions.

• Geomechanics and Engineering
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• 제28권4호
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• pp.421-435
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• 2022

The necessity of estimating the time and cost required for tunnel construction has led to extensive research in this regard. Since geological conditions are significant factors in terms of time and cost of road tunnels, considering these conditions is crucial. Uncertainties about the geological conditions of a tunnel alignment cause difficulties in planning ahead of the required construction time and costs. In this paper, the continuous-space, discrete-state Markov process has been used to predict geological conditions. The Monte-Carlo (MC) simulation (MCS) method is employed to estimate the construction time and costs of a road tunnel project using the input data obtained from six tunneling expert questionnaires. In the first case, the input data obtained from each expert are individually considered and in the second case, they are simultaneously considered. Finally, a comparison of these two modes based on the technique presented in this article suggests considering views of several experts simultaneously to reduce uncertainties and ensure the results obtained for geological conditions and the construction time and costs.

• International Journal of Human Ecology
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• 제9권1호
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• pp.17-27
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• 2008

Black garments can lose color, image, and be the main cause of color staining when washed with other laundry that can cause color contamination from interaction with other garments. To know the fiber-based dye fastness for colored garments, 4-5 pieces of various fibers of different fabrics were selected; cotton, linen, wool, silk, rayon, acetate, polyester, and nylon. To determine the colorfastness to washing and crocking, the black fabrics were washed with alkali and neutral detergents under the Laund-O-Meter method under the Crockmeter method. In an alkali detergent laundering conditions, most colored samples did not undergo color or light fastness. However, most of the stained fabrics slightly changed in K/S values while other samples underwent severe changes. With neutral detergent laundering, sample fabrics underwent less shrinking, and had less naps. The stained fabrics also underwent less change in K/S values. With time-repeatedly-washing the original sample went through colorfastness to lose color. In crocking fastness, most samples produced good to excellent results under dry conditions but produced relatively low crocking fastness under wet conditions. Natural fibers especially showed lower crocking fastness than artificial fibers. In conclusion, garments of the same color should be laundered together. The black garments that are washed using neutral detergents can decrease the amount of damage from color change. While it is the responsibility of garment producers to provide appropriate quality indications they should also provide adequate instructions for consumers to understand and appropriately cope with the quality indications in order to contribute to establishing a correct laundering method.

• 한국결정성장학회지
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• 제14권4호
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• pp.174-186
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• 2004

Striations are growth-induced inhomogeneities which hamper the applications of solid-solution crystals and of doped crystals in numerous technologies. Thus the optimized performance of solid solutions often can not be exploited. The inhomogeneity problem can be solved in specific cases by achieving a distribution coefficient one in growth from melts and from solutions. Macrostep-induced striations can be suppressed by controlling the growth mode, by achieving growth on facets thereby preventing step bunching. Thermal striations are commonly assumed to be caused by convective instabilities so that reduced convection by microgravity or by damping magnetic fields was and is widely attempted to reduce such inhomogeneities. Here it will be shown that temperature fluctuations at the growth interface cause striations, and that hydrodynamic fluctuations in a quasi-isothermal growth system do not cause striations. The theoretically derived conditions were experimentally established and allowed the growth of striation-free crystals of $KTa_{1-x}Nb_xO_3$"KTN" solid solutions. Hydrodynamic variations from the accelerated crucible rotation technique ACRT did not cause striations as long as the temperature was controlled within $0.03^{\circ}$ at $1200^{\circ}C$ growth temperature. Alternative approaches to solve or reduce the segregation and striation problems in growth from melts and from solutions are discussed as well.

• 한국안전학회지
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• 제28권5호
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• pp.35-40
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• 2013

Recently reclamation land is largely developed to utilize the land according to economic growth. The soil of landfill is soft, low shear strength, which makes it difficult to use the equipment. A large movement is occurred on the utility tunnel under construction. The inclined land with high water level and underground facilities are widely distributed and the excess pore water pressure may occur under construction similarly to this study. Some different conditions are made to design result, such as 4m of soil piling near the construction area, heavy rainfall during 2nd excavation that may cause flow liquefaction. To analyze the cause of transverse lateral movement, Three dimensional analysis are performed to four load cases, which is original design condition, flow liquefaction by heavy rainfall, unsymmetric lateral soil pressure, and both of them simultaneously. Ten steps of full construction stage, 1st excavation for utility tunnel, construction of utility tunnel, 1st refill, piling soil from 1m to 4 m, 2nd excavation for drainage culvert, liquefaction around the utility tunnel, construction of drainage culvert and 2nd refill, are take into account to investigate the cause of movement.

• 수면정신생리
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• 제11권1호
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• pp.17-21
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• 2004

Nasal congestion is one of the most common symptoms of medical complaints. Snoring is caused by vibration of the uvula and the soft palate. Nasal obstruction may contribute not only to snoring and obstructive sleep apnea (OSA) but also impair application of continuous nasal positive airway pressure (CPAP), which is the most widely employed treatment for OSA. Total or near-total nasal obstruction leads to mouth breathing and has been shown to cause increased airway resistance. However, the exact role of the nasal airway in the pathogenesis of OSA is not clear and there is no consensus about the role of nasal obstruction in snoring and sleep apnea. Some reports have failed to demonstrate any correlation between snoring and nasal obstruction. On the other hand, opposing reports suggest that nasal disease may cause sleep disorders and that snoring can be improved after nasoseptal surgery. Reduced cross-sectional area causes increased nasal resistance and predisposes the patient to inspiratory collapse of the oropharynx, hypopharynx, or both. Discrete abnormalities of the nasal airway, such as septal deformities, nasal polyps, and choanal atresia and with certain mucosal conditions such as sinusitis, allergic rhinitis and inferior turbinate hypertrophy can cause snoring or OSA. Thus, these sources of nasal obstruction should be corrected medically or surgically for the effective management of OSA and adjunctive for CPAP.