• 분석과학
• /
• 제32권5호
• /
• pp.173-184
• /
• 2019

As the size of semiconductors becomes smaller, it is necessary to perform high precision polishing of nanoscale. Ceria, which is generally used as an abrasive, is widely used because of its uniform quality, but its stability is not high because it has a high molecular weight and causes agglomeration and rapid precipitation. Such agglomeration and precipitation causes scratches in the polishing process. Therefore, it is important to accurately analyze the size distribution of ceria particles. In this study, a study was conducted to select dispersants useful for preventing coagulation and sedimentation of ceria. First, a dispersant was synthesized and a ceria slurry was prepared. The defoamer selection experiment was performed in order to remove the air bubbles which may occur in the production of ceria slurry. Dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) were used to determine the size distribution of ceria particles in the slurry. AsFlFFF is a technique for separating nanoparticles based on sequential elution of samples as in chromatography, and is a useful technique for determining the particle size distribution of nanoparticle samples. AsFlFFF was able to confirm the presence of a little quantities of large particles in the vicinity of 300 nm, which DLS can not detect, besides the main distribution in the range of 60-80 nm. AsFlFFF showed better accuracy and precision than DLS for particle size analysis of a little quantities of large particles such as ceria slurry treated in this study.

• Elastomers and Composites
• /
• 제40권2호
• /
• pp.112-118
• /
• 2005

실란 커플링제가 카본블랙과 점토로 보강된 천연 고무 가황물의 회복 특성에 미치는 영향에 대해 연구하였다. Bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT)를 실란 커플링제로 사용하였다. 실란 커플링제가 함유된 가황물은 실란 커플링제가 함유되지 않은 가황물에 비해 전반적으로 빠른 회복 거동을 보였다. 그러나, 점토 함량이 높은 가황물의 경우 $-20^{\circ}C$보다 낮은 온도에서는 실란 커플링제가 함유된 가황물이 실란 커플링제가 함유되지 않은 가황물에 비해 느리게 회복되었다. 실란 커플링제가 함유된 가황물과 실란 커플링제가 함유되지 않은 가황물의 회복량 차이는 점토 함량이 증가할수록 감소하였다. 실험 결과는 가교 밀도, 모둘러스, 그리고 결합 고무량으로 설명하였다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제23권2호
• /
• pp.1-14
• /
• 2018

The recent increase in demand for lithium has led to the development of new brine prospects, The brines are hosted in closed salar basin aquifers of two types that are mature halite salars and immature clastic salars. Salar brines also contain other elements of commercial interest, most notably potassium and boron. As a result, there has been a plethora of new exploration projects focused on the brines hosted in the aquifers of the intermontane-closed basins. The estimate of lithium resources and reserves in these salars depends on a detailed knowledge of aquifer geometry, porosity, and brine grade. Because the resource is in a fluid state, it has the propensity to move, mix, rearrange itself relatively rapidly during the course of a project lifetime, and lower recovery factors compared with most metalliferous and industrial mineral deposits due to reliance on pumping of the brine from wells for extraction. This is unlike any other type of metallic mineral resource and hence a different approach specially focusing on hydrogeology and brine hydrology is required for these prospects.

• 대한정형도수물리치료학회지
• /
• 제25권1호
• /
• pp.29-36
• /
• 2019

Background: This study was conducted to investigate the effect of leg lift difference on the serratus anterior muscle and the upper trapezius muscle when a subject with winged scapula performs a scapula protraction exercise in a four-leg crawling posture. Method: Twenty normal adults and 20 subjects with winged scapula participated in the experiment. Surface EMG recordings were collected from serratus anterior muscle and back trapezius muscle during scapula protraction exercises. Scapular winging is measured with the lifting distance of scapula retraction to the back using an electronic digital caliper. In two groups of four-leg crawling posture, the two legs support, the dominant leg lifting, and the non-dominant leg lifting, including the scapula protraction, were performed. To examine the difference between groups in the variance analysis, the Bonferroni correction was used (significance level ${\alpha}=.017$). Statistical significance level ${\alpha}$ was .05. Results: There was a significant difference in serratus anterior muscle and upper trapezius muscle during push-up plus exercise in leg lifting in four-leg crawling posture, but there were no significant differences in muscle activity between serratus anterior muscle and upper trapezius muscle, and there was no significant difference according to the presence or absence of scapular winging. Conclusion: For the shoulder stability of the ipsilateral side with the serratus anterior muscle, the leg-lifting posture is effective in the four-leg crawling, and also when a subject with winged scapula chooses an exercise, lifting the ipsilateral side of leg with scapula protraction exercises at the same time may have a positive effect on scapula dysfunction.

• 디지털융복합연구
• /
• 제17권7호
• /
• pp.157-165
• /
• 2019

"Aging in place" 실현을 조력하는 제론테크놀로지는 노인의 삶의 질을 높이고 사회적 돌봄 비용을 감소시킬 수 있다. 본 연구는 지역사회 노인의 제론테크놀로지의 사용 전 수용성 및 장애요인을 파악하고 사용 전 수용성의 영향요인을 탐색하는 조사연구로 2019년 3월 16일부터 23일까지 노인복지관을 이용하는 남녀 노인 129명을 대상으로 설문 조사했다. 다중회귀분석을 한 결과 28%의 설명력으로 농촌지역의 대상자와 신체적인 기능이 높을수록, 고비용이나 기술사용에 대한 가족의 지원 부족과 같은 장애요인이 낮을수록 제론테크놀로지의 사용 전 수용성이 높은 것으로 나타났다. 따라서 노인에 대한 보건복지 전략을 개발 할 때 이러한 요인에 대한 고려는 많은 수의 노인이 제론테크놀로지 사용을 촉진하여 향후 노인의 aging in place를 가능하게 할 것이다.

• 한국기계가공학회지
• /
• 제17권6호
• /
• pp.24-30
• /
• 2018

Dental implants are currently widely used as artificial teeth due to their good chewing performance and long life cycle. A dental implant consists of an abutment as the upper part and a fixture as the lower part. When chewing forces are repeatedly applied to a dental implant, gap at the interface surface between the abutment and the fixture is often occurred, and results in some deteriorations such as loosening of fastening screw, dental retraction and fixture fracture. To cope with such problems, a sealing-type abutment having a number of grooves along the conical-surface circumference was previously developed, and shows better sealing performance than the conventional one. This study carries out optimization of the groove shape by genetic algorithm(GA) as well as structural analysis in consideration of external chewing force and pretension between the abutment and the fixture. The overall optimization system consists of two subsystems; the one is the genetic algorithm with MATLAB, and the other is the structural analysis with ANSYS. Two subsystems transmit and receive the relevant data with each other throughout the optimization processes. The optimization result is then compared with that of the conventional one with respect to the contact pressure and the maximum stress. The result shows that the optimized model gives better sealing performance than the conventional sealing abutment.

• Clinics in Shoulder and Elbow
• /
• 제21권4호
• /
• pp.200-206
• /
• 2018

Background: The purpose of this study was to assess the relevance of preoperative magnetic resonance imaging (MRI) evaluation by occupation ratio (OR) at maximum diameter of supraspinatus muscle. Methods: Patients from the Inje University Sanggye Paik Hospital who received rotator cuff repair and underwent pre- and postoperative MRI were selected as subjects of this study. On T1-weighted MRIs, OR of fat and muscle at Y-shaped view, OR at a location on supraspinatus muscle where its diameter was maximum on coronal view, and pre- and postoperative Goutallier Classification and changes in the tangent sign were measured. Statistical significance of postoperative OR was assessed regarding time from symptom onset to surgery, size of rotator cuff tear, preoperative OR, and the difference between ORs measured at maximum diameter of supraspinatus muscle and Y-shaped view. Results: Preoperative OR at Y-shaped view was $52.28{\pm}8.57$ (32.5-65.3). Preoperative OR difference between maximum diameter and Y-shaped view was $13.76{\pm}10.51$ (2.38-42.04), and Pearson correlation coefficient was 0.604 (p=0.001). Postoperative OR at Y-shaped view was $63.77{\pm}9.35$ (37.3-76.1). Pearson correlation coefficient of pre- and postoperative Goutallier Classification was -0.579 (p=0.002) and Pearson correlation coefficient of the postoperative difference between ORs measured at maximum diameter of supraspinatus muscle and Y-shaped view was -0.386 (p=0.047). Conclusions: Fatty degeneration of supraspinatus muscle in rotator cuff tear patients should be evaluated not only in the conventional Y-shaped view, but also at location of maximum diameter of supraspinatus muscle to establish patients' therapeutic plan.

• Journal of Applied Biological Chemistry
• /
• 제62권1호
• /
• pp.93-100
• /
• 2019

The root of Panax ginseng is used in ethnomedicine throughout eastern Asia and various recent studies have proved that Panax ginseng has inhibitory effects on cardiovascular disease. Each factor causing cardiovascular disease is known to have a very complex process which is achieved by a diverse number of mechanisms. Among these factors, platelets are the most important because they directly participate in thrombogenesis. Therefore, inhibiting the activity of platelets is an essential element for prevention of cardiovascular diseases. Our previous study showed the antiplatelet effects of Korean red ginseng extract and two of its components, ginsenoside Rg3 and ginsenoside Ro. However, the inhibitory mechanism of other ginsenosides remains unclear. Therefore, we investigated the inhibitory mechanism of ginsenoside F4 (G-F4) from Korean red ginseng on the regulation of signaling molecules involved in human platelet aggregation. With the use of G-F4, collagen-induced human platelet aggregation was inhibited in a dose-dependent manner, and it suppressed collagen-induced elevation of $[Ca^{2+}]_i$ mobilization through elevated phosphorylation of inositol 1, 4, 5-triphosphate receptor I ($Ser^{1756}$). In addition, G-F4 inhibited fibrinogen binding to ${\alpha}IIb/{\beta}_3$ during collagen-induced human platelet aggregation. Thus, in the present study, G-F4 showed an inhibitory effect on human platelet activation, suggesting its potential use as a new natural medicine for preventing platelet-mediated cardiovascular diseases.

• Clinics in Shoulder and Elbow
• /
• 제22권2호
• /
• pp.70-78
• /
• 2019

Background: This study evaluated postoperative changes in the supraspinatus from time-zero to 6 months, using magnetic resonance imaging (MRI). We hypothesized that restoration of the musculotendinous unit of the rotator cuff by tendon repair immediately improves the rotator cuff muscle status, and maintains it months after surgery. Methods: Totally, 76 patients (29 men, 47 women) with rotator cuff tears involving the supraspinatus tendon who underwent arthroscopic rotator cuff repairs were examined. MRI evaluation showed complete repair with intact integrity of the torn tendon at both time-zero and at 6 months follow-up. All patients underwent standardized MRI at our institution preoperatively, at 1 or 2 days postoperative, and at 6 months after surgery. Supraspinatus muscular (SSP) atrophy (Thomazeau grade) and fatty infiltrations (Goutallier stage) were evaluated by MRI. The cross-sectional area of SSP in the fossa was also measured. Results: As determined by MRI, the cross-sectional area of SSP significantly decreased 11.41% from time-zero (immediate repair) to 6 months post-surgery, whereas the Goutallier stage and Thomazeau grade showed no significant changes (p<0.01). Furthermore, compared to the preoperative MRI, the postoperative MRI at 6 months showed a no statistically significant increase of 8.03% in the cross-sectional area. In addition, morphological improvements were observed in patients with high grade Goutallier and Thomazeau at time-zero, whereas morphology of patients with low grade factors were almost similar to before surgery. Conclusions: Our results indicate that cross-sectional area of the initial repair appears to decrease after a few months postoperatively, possibly due to medial retraction or strained muscle.

• 분석과학
• /
• 제32권3호
• /
• pp.77-87
• /
• 2019

High viscosity carbon black dispersions are used in various industrial fields such as color cosmetics, rubber, tire, plastic and color filter ink. However, carbon black particles are unstable to heat due to inherent characteristics, and it is very difficult to keep the quality of the product constant due to agglomeration of particles. In general, particle size analysis is performed by dynamic light scattering (DLS) during the dispersion process in order to select the optimum dispersant in the carbon black dispersion process. However, the existing low viscosity analysis provides reproducible particle distribution analysis results, but it is difficult to select the optimum dispersant because it is difficult to analyze the reproducible particle distribution at high viscosity. In this study, dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) analysis methods were compared for reproducible particle size analysis of high viscosity carbon black. First, the stability of carbon black dispersion was investigated by particle size analysis by DLS and AsFlFFF according to milling time, and the validity of analytical method for the selection of the optimum dispersant useful for carbon black dispersion was confirmed. The correlation between color and particle size of particles in high viscosity carbon black dispersion was investigated by using colorimeter. The particle size distribution from AsFlFFF was consistent with the colorimetric results. As a result, the correlation between AsFlFFF and colorimetric results confirmed the possibility of a strong analytical method for determining the appropriate dispersant and milling time in high viscosity carbon black dispersions. In addition, for nanoparticles with relatively broad particle size distributions such as carbon black, AsFlFFF has been found to provide a more accurate particle size distribution than DLS. This is because AsFlFFF, unlike DLS, can analyze each fraction by separating particles by size.