• International Journal of Precision Engineering and Manufacturing-Green Technology
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• 제5권5호
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• pp.583-591
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• 2018

Tool-chip adhesion impacts on cutting performance significantly, especially in finish cutting process. To promote cutting tools' anti-adhesion property, the concave micro-grooves texture (MGT) and convex volcano-like texture (VLT) were fabricated separately on lathe tools' rake faces by laser surface texturing (LST). Various orientations of MGT and different area densities (9% and 48%) and regions (partial and full) of VLT were considered in textured patterns designing. The following orthogonal cutting experiments, machining of aluminum alloy 5038, analyzed tools' performances including cutting force, cutting stability, chip shape, rake face adhesion and abrasion. It indicated that under dry finish cutting conditions, MGT contributed to cutting stability and low cutting forces, meanwhile friction and normal force reduced by around 15% and 10%, respectively with a weak correlation to the grooves' orientation. High density VLT tools, on the other hand, presented an obvious anti-adhesion property. A $5{\mu}m$ reduction of crater wear's depth can be observed on textured rake faces after long length cutting and textured rake faces presented half size of BUE regions comparing to the flat tool, however, once the texture morphologies were filled or worn, the anti-adhesion effect could be invalid. The bearing ratio curve was employed to analysis tool-chip contact and durability of textured surfaces contributing to a better understanding of anti-adhesion and enhanced durability of the textured tools.

• 대한정형도수물리치료학회지
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• 제27권2호
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• pp.69-76
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• 2021

Background: Degenerative arthritis accounts for a large portion of the elderly, causing a lot of inconvenience in daily life. Total knee replacement (TKR) are performed to relieve pain in the knee joint. The purpose of this study was to determine whether knee joint stabilization exercises are effective in improving balance and walking ability in degenerative arthritis patients who have undergone TKR. Methods: A total of 30 TKR patients participated in this study. They were assigned to two groups. The experimental group, the group that underwent knee stabilization exercises, joint mobilization and general physical therapy. On the other hand, and the controlled group, the group that underwent joint mobilization and general physical therapy. All exercises were conducted thrice a week, for four weeks. The main balance outcomes were evaluated using the posture balance training system, while walking ability was assessed using a wireless 3-axis accelerometer. Results: The experimental group had significantly higher scores in postural stability testing (PST), limits stability testing, and waling ability. The post-intervention evaluation, there were significant differences in all variables between the two groups. However, no significant difference was noted in the foam eyes closed test in PST. Conclusion: This study suggests that knee joint stabilization exercises effectively improve the balance and walking ability of TKR patients. Thus, it could be presented as useful in clinical practice.

• 한국전문물리치료학회지
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• 제28권3호
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• pp.194-199
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• 2021

Background: The scapulo-thoracic musculatures including serratus anterior (SA), upper trapezius and lower trapezius can provide shoulder stability and functional shoulder movement. Objects: The muscle activities of upper and lower SA were compared during three different scapular protraction exercises in healthy individuals in sitting position. Methods: Twenty-five healthy subjects were participated. Electromyography device was used to measure muscle activity of upper and lower SA and trapezius muscles. Each subject was asked to perform three different scapular protraction exercises (scapular protraction [SP], SP with self-resistance [SPSR], SPSR with hand-exerciser [SPSRH]) in random order. One-way repeated measures analysis of the variance and a Bonferroni post hoc test were used. Results: The muscle activity of lower SA muscle was significantly different among three conditions (SP vs. SPSR vs. SPSRH) (p < 0.01). The lower SA muscle activity was significantly greater during SPSRH compared to SP and SPSR, which required joint stability more than SP and SPSR (p < 0.01). Conclusion: SPSRH exercise can be recommended to facilitate the muscle activity of lower SA. In addition, the intramuscular variation in the upper and lower SA during scapular protraction exercise is required to consider the effective rehabilitation.

• 한국건설순환자원학회논문집
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• 제9권2호
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• pp.117-126
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• 2021

이 연구에서는 사면과의 부착력과 식물 생장력이 높은 식생기반재를 개발하고자, 시멘트 기반의 결합재와 기능성 첨가제를 혼합한 녹생토의 기초물성과 식물 생장에 미치는 영향을 평가하였다. 석고계 시멘트를 혼합한 녹생토(No.3)의 전단강도가 낮게 나타났으나, 식생 환경에 가장 적합한 경도 수준(23.6mm) 및 pH 값(7.4)을 나타냈다. 또한, 보습제를 첨가하여 성능을 개선한 녹생토의 초기 식생 발현은 일반 녹생토 비해 늦고 전도도값은 다소 높은 경향을 나타냈다. 반면, 성능을 개선한 녹생토는 타설면과의 부착력이 높았으며, 일정 시간 경과 후의 식물 생장 속도 및 동절기와 환절기 재생능력이 우월한 것으로 나타났다.

• Geomechanics and Engineering
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• 제27권6호
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• pp.561-571
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• 2021

Cofferdams made of teel sheet piles are commonly utilized as support structures for excavation of sea-crossing bridge foundations. As cofferdams are often subject to tide variation, it is imperative to consider potential effects of tide on stability and serviceability of sheet piles, particularly, ultralong steel sheet piles (USSPs). In this study, a real USSP cofferdam constructed using new construction technology in Nanxi River was reported. The design of key parts of USSP cofferdam in the presence of tidal action was first introduced followed by the description of entire construction technology and associated monitoring results. Subsequently, a three-dimensional finite-element model corresponding to all construction steps was established to back-analyze measured deflection of USSPs. Finally, a series of parametric studies was carried out to investigate effects of tide level, soil parameters, support stiffness and construction sequence on lateral deflection of USSPs. Monitoring results indicate that the maximum deflection during construction occurred near the riverbed. In addition, measured stress of USSPs showed that stability of USSP cofferdam strengthened as construction stages proceeded. Moreover, the numerical back-analysis demonstrated that the USSP cofferdam fulfilled the safety requirements for construction under tidal action. The maximum deflection of USSPs subject to high tide was only 13.57 mm at a depth of -4 m. Sensitivity analyses results showed that the design of USSP cofferdam system must be further improved for construction in cohesionless soils. Furthermore, the 5th strut level before concreting played an indispensable role in controlling lateral deflection of USSPs. It was also observed that pumping out water before concreting base slab could greatly simplify and benefit construction program. On the other hand, the simplification in construction procedures could induce seepage inside the cofferdam, which additionally increased the deflection of USSPs by 10 mm on average.

• Computers and Concrete
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• 제31권5호
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• pp.395-403
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• 2023

The paper investigates the effect of two parameters - sand content (SC) and grain migration during shearing - on the mechanical properties of gravel-sand mixtures. Consolidated undrained (CU) triaxial tests were carried out on eight series of mixtures containing gravel (1<d<16 mm) and sand (0.1<d<1 mm). The prepared mixtures have sand contents of 0, 10, 15, 20, 40, 54, 94 and 100%, and a relative density of 60%. The transition sand content (TSC) is experimentally defined and marks the transition from gravel-driven to sand-driven behavior. For SC<TSC, the dry density of the mixture increases with SC. This induces an increase in undrained peak strength and dilative trend. The slope and position of the critical state line (CSL) are also deeply dependent on SC. At SC=TSC, the mixtures exhibit the largest dry density and yield the highest undrained peak strength and the largest dilative trend. During shearing, large internal migration of grains was observed at the TSC, causing heterogeneity in the sample. Analysis of the CSL deduced from the final points of the triaxial tests shows that, at the TSC, failure appears to correspond to the behavior of the coarsest fraction of the soil. This fraction is located in the upper part of the sample, where the sand particles had been eliminated by suffusion. On the other hand, in the more stable materials, the CSL is consistent with the bulk grain size distribution of the soil.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.893-899
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• 2024

In a secondary cooling system of a sodium-cooled fast reactor (SFR), rapid detection of hydrogen due to sodium-water reaction (SWR) caused by water leakage from a heat exchanger tube of a steam generator (SG) is important in terms of safety and property protection of the SFR. For hydrogen detection, the hydrogen detectors using atomic transmission phenomenon of hydrogen within Ni-membrane were used in Japanese proto-type SFR "Monju". However, during the plant operation, detection signals of water leakage were observed even in the situation without SWR concerning temperature up and down in the cooling system. For this reason, the study of a new hydrogen detector has been carried out to improve stability, accuracy and reliability. In this research, the authors focus on the difference in composition of hydrogen and the difference between the background hydrogen under normal plant operation and the one generated by SWR and theoretically estimate the hydrogen behavior in liquid sodium by using ultra-accelerated quantum chemical molecular dynamics (UA-QCMD). Based on the estimation, dissolved H or NaH, rather than molecular hydrogen (H₂), is the predominant form of the background hydrogen in liquid sodium in terms of energetical stability. On the other hand, it was found that hydrogen molecules produced by the sodium-water reaction can exist stably as a form of a fine bubble concerning some confinement mechanism such as a NaH layer on their surface. At the same time, we observed experimentally that the fine H₂ bubbles exist stably in the liquid sodium, longer than previously expected. This paper describes the comparison between the theoretical estimation and experimental results based on hydrogen form in sodium in the development of the new hydrogen detector in Japan.

• Molecules and Cells
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• 제47권1호
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• pp.100001.1-100001.8
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• 2024

In eukaryotes, a primary protein quality control (PQC) process involves the destruction of conformationally misfolded proteins through the ubiquitin-proteasome system. Because approximately one-third of eukaryotic proteomes fold and assemble within the endoplasmic reticulum (ER) before being sent to their destinations, the ER plays a crucial role in PQC. The specific functions and biochemical roles of several E3 ubiquitin ligases involved in ER-associated degradation in mammals, on the other hand, are mainly unknown. We identified 2 E3 ligases, ubiquitin protein ligase E3 component N-recognin 1 (UBR1) and ubiquitin protein ligase E3 component N-recognin 2 (UBR2), which are the key N-recognins in the N-degron pathway and participate in the ER stress response in mammalian cells by modulating their stability. Cells lacking UBR1 and UBR2 are hypersensitive to ER stress-induced apoptosis. Under normal circumstances, these proteins are polyubiquitinated through Lys48-specific linkages and are then degraded by the 26S proteasome. In contrast, when cells are subjected to ER stress, UBR1 and UBR2 exhibit greater stability, potentially as a cellular adaptive response to stressful conditions. Although the precise mechanisms underlying these findings require further investigation, our findings show that cytoplasmic UBR1 and UBR2 have anti-ER stress activities and contribute to global PQC in mammals. These data also reveal an additional level of complexity within the mammalian ER-associated degradation system, implicating potential involvement of the N-degron pathway.

• Geomechanics and Engineering
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• 제36권6호
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• pp.527-543
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• 2024

In the implementation of most civil structures, especially underground, deep excavations with a vertical slope are required. Using flexible retaining walls is applied as one of the ways to stabilize vertical holes. Therefore, it is necessary to know the parameters affecting the performance of such walls in reducing their horizontal movement. In this research, by building a suitable laboratory model, the parameters of the amount of flexibility, the embedment depth of the wall, the type and number of tieback in the wall were investigated for 42 static laboratory models. The purpose of this research is to study the flexible retaining wall with helical tieback compared to simple tieback at different heights, which shows the best performance in terms of reducing horizontal displacement in proportion to increasing or decreasing flexibility. On the other hand, one of the parameters affecting the flexibility of the wall, which is its bending stiffness, was extracted by numerical software outputs and studied on the results such as relative flexibility, stiffness, safety and numerical stability of the wall.The results of this study show that among the parameters, in the first place, the effect of the type of tieback is inhibited and in the second place, the ratio of thickness to wall height is known as the most important parameter. the best performance for walls with the helical tiebacks in reducing their horizontal displacement can be economically, flexibly and stability assigned to a wall that tiebacks is in the range of H2/t to H4/t and its flexibility ratio is 2/3.

• 대한화장품학회지
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• 제39권2호
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• pp.117-125
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• 2013

본 연구에서는 한국산 감초의 50% 에탄올 추출물로부터 얻은 에틸아세테이트 분획을 함유한 크림의 안정성을 평가하였다. 감초추출물의 0.20% 에틸아세테이트 분획을 함유한 크림에 대하여 12주 동안 온도별 저장조건($4^{\circ}C$, $25^{\circ}C$, $37^{\circ}C$, $45^{\circ}C$)과 태양광선(2013년 3 평균온도 : $5.10^{\circ}C$, 4 ~ 5월 평균온도 : $14.10^{\circ}C$) 노출조건하에서 2주 간격으로 pH, 흡광도 및 점도 변화와 1주 간격으로 색도 변화를 측정하였다. 온도별 저장 조건에서 감초 추출물을 함유한 시료 크림의 pH 변화는 0.44로 추출물을 함유하지 않은 대조군 크림(0.66)보다 pH 변화 값이 작았다. 태양광선하에서는 pH 변화는 대조군과 시료군에서 큰 차이가 없었다. 온도별 저장조건에서 대조 크림의 점도는 평균 2,483 cPs 감소하였고 시료 크림은 평균 2,893 cPs 감소하였다. 시료 크림이 대조크림보다 평균 410 cP 감소를 나타내었다. 감초출물이 크림 점도에 큰 영향을 미치지는 않았다. 감초 추출물 에탄올 용액의 태양광선하에서 276 nm에서의 흡광도는 30.00% 감소하였다. 반면에 감초추출물 함유 크림의 경우는 동일 조건에서 흡광도가 12.02% 감소하였다. 감초추출물이 크림 속에서 비교적 안정함을 나타내었다. 색도 측정에서 대조 크림에서는 색차가 거의 일어나지 않았다. 시료 크림은 색차가 조금 증가하였으나 안정성에 크게 영향을 끼치지 않았다. 이상의 결과들로부터 한국산 감초 추출물 함유 크림 제형은 비교적 안정함을 확인하였다. 향후 제품에 응용 시 감초 추출물의 항산화 효과가 발휘할 수 있도록 보완 연구가 이루어진다면 화장품에의 응용이 가능할 것으로 사료된다.