• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.409-414
• /
• 2001

The hydration of cement paste occurs when the cement is mixed with water. During the hydration, hydration heat causes the thermal stress depending on the size of concrete and the cement content. Especially in the high-strength concrete, we must give care to the concrete due to its large cement content. In this study, conduction calorimeter and concrete insulation hydration heat meter were used to investigate the hydration heat characteristics of cement and concrete. To reduce hydration heat of high-strength concrete, several types of replacement of fly-ash and blast-furnace slag powder were used in this experiment.

• Computers and Concrete
• /
• 제5권5호
• /
• pp.475-490
• /
• 2008

The paper explores the potential of applicability of Genetic programming approach (GP), adopted in this investigation, to model the combined effects of five independent variables to predict the mini-slump, the plate cohesion meter, the induced bleeding test, the J-fiber penetration value, and the compressive strength at 7 and 28 days of self-compacting slurry infiltrated fiber concrete (SIFCON). The variables investigated were the proportions of limestone powder (LSP) and sand, the dosage rates of superplasticiser (SP) and viscosity modifying agent (VMA), and water-to-binder ratio (W/B). Twenty eight mixtures were made with 10-50% LSP as replacement of cement, 0.02-0.06% VMA by mass of cement, 0.6-1.2% SP and 50-150% sand (% mass of binder) and 0.42-0.48 W/B. The proposed genetic models of the self-compacting SIFCON offer useful modelling approach regarding the mix optimisation in predicting the fluidity, the cohesion, the bleeding, the penetration, and the compressive strength.

• 한국노년학
• /
• 제28권4호
• /
• pp.941-952
• /
• 2008

이 연구는 여성 농촌노인을 대상으로 레크리에이션 복합운동 프로그램을 적용하여 체력을 향상시키는데 그 목적이 있다. 이 연구 대상자는 규칙적으로 운동을 하지 않는 경기도 지역 Y시에 소재한 경로당 75세 이상의 여성 노인 20명을 대상으로 하였으며, 대상자의 연령은 75세 ~ 88세 범위(M=80.75, SD=3.22)였다. 레크리에이션 복합운동 프로그램은 1회 50분, 주 3회, 8주간 실시하였다. 연구결과 악력, 의자 앉았다 일어서기, 2.45m 돌아오기, 눈뜨고 한발서기, 앉아서 윗몸 앞으로 굽히기, 4.6m속보에서 유의하게 향상되었다. 따라서 레크리에이션 복합운동 프로그램이 여성 농촌노인의 체력을 향상시킬 수 있는 것으로 생각된다.

• Physical Therapy Rehabilitation Science
• /
• 제11권1호
• /
• pp.58-65
• /
• 2022

Objective: The purpose of this study was to investigate the effect of visual feedback bicycle training on running performance, maximal oxygen uptake and quadriceps muscle strength. Design: A randomized controlled trial. Methods: Fifteen healthy adult men with no musculoskeletal or nervous system disease and capable of bicycle training were included. After the pretest, subjects were randomly assigned to visual feedback bicycle training group and general fixed bicycle training group. Both groups were trained two times a week for three weeks, each week for a fixed time and number of repetitions, followed by a six week washout period and then crossing the training method. visual feedback bicycle training provides visual feedback of heart rate in real time using a monitor and a heart rate meter during bicycle training, and general fixed bicycle training performed general bicycle training without visual feedback. After training, each item was measured using a wearable technology, gas analyzer, isokinetic equipment. Results: The results of this study was significant differences in running performance, maximal oxygen uptake and quadriceps muscle strength in visual feedback bicycle training group (p<0.05). The differential effect was found between visual feedback bicycle training group and general fixed bicycle training group in running performance, maximal oxygen uptake, and quadriceps muscle strength (p<0.05). Conclusions: This study suggested that that visual feedback bicycle training can be applied as a useful training method to improve running performance, maximal oxygen uptake and quadriceps muscle strength.

• 대한소아치과학회지
• /
• 제35권3호
• /
• pp.469-476
• /
• 2008

본 연구는 새로 개발된 레진 강화형 글래스 아이오노머인 $Ketac^{TM}$ N 100과 Fuji Fil LC의 개선된 점을 보기 위해 불소 유리량과 압축 강도를 Fuji II LC와 비교 평가해 보았다. 불소 유리량 측정을 위해 각 재료 별로 시편을 15개씩 제작하여 탈이온수에 보관하였고, 31일 동안 pH/ISE meter(750P, Istek, Korea)를 이용하여 불소 유리량을 측정하였다. 압축 강도 측정을 위해 각 재료별로 15개씩 시편을 제작하여 만능 경성 시험기(Kyung-sung Testing Machine Co., Korea)를 이용하여 시편이 파절된 시점의 최대 강도를 측정하였다. 연구 결과 얻은 결론은 다음과 같다. 1. 전반적인 불소 유리량은 Fuji Fil LC, Fuji II LC, $Ketac^{TM}$ N 100 순으로 높았다(p<0.05). 2. 압축 강도는 Fuji II LC와 $Ketac^{TM}$ N 100은 유의한 차이가 없었고(p>0.05), Fuji Fil LC는 두 재료보다 낮은 압축 강도 값을 보였다(p<0.05). 이상의 결과를 종합해보면 $Ketac^{TM}$ N 100은 대조군인 Fuji II LC와 비교 시 불소 유리량은 적었으나 압축 강도는 유사했고 Fuji Fil LC는 불소 유리량은 높았고 압축 강도는 낮았다. 이런 재료의 특성에 맞게 임상 적용을 하는 것이 중요할 것이다.

• 천문학회보
• /
• 제38권1호
• /
• pp.61.2-61.2
• /
• 2013

We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot using scanning spectroscopy in H-alpha and Ca II 8542A, with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler velocity maps. Temporal sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands.

• 한국전기전자재료학회논문지
• /
• 제16권8호
• /
• pp.700-704
• /
• 2003

This paper describes on characteristics of 2" 3C-SiC wafer bonding using PECVD (plasma enhanced chemical vapor deposition) oxide and HF (hydrofluoride acid) for SiCOI (SiC-on-Insulator) structures and MEMS (micro-electro-mechanical system) applications. In this work, insulator layers were formed on a heteroepitaxial 3C-SiC film grown on a Si (001) wafer by thermal wet oxidation and PECVD process, successively. The pre-bonding of two polished PECVD oxide layers made the surface activation in HF and bonded under applied pressure. The bonding characteristics were evaluated by the effect of HF concentration used in the surface treatment on the roughness of the oxide and pre-bonding strength. Hydrophilic character of the oxidized 3C-SiC film surface was investigated by ATR-FTIR (attenuated total reflection Fourier transformed infrared spectroscopy). The root-mean-square suface roughness of the oxidized SiC layers was measured by AFM (atomic force microscope). The strength of the bond was measured by tensile strength meter. The bonded interface was also analyzed by IR camera and SEM (scanning electron microscope), and there are no bubbles or cavities in the bonding interface. The bonding strength initially increases with increasing HF concentration and reaches the maximum value at 2.0 ％ and then decreases. These results indicate that the 3C-SiC wafer direct bonding technique will offers significant advantages in the harsh MEMS applications.ions.

• Steel and Composite Structures
• /
• 제39권3호
• /
• pp.307-318
• /
• 2021

Utilizing fibers is an effective way to avoid the brittle behavior of the conventional concrete and can enhance its ductility. In particular, propylene fibers can improve concrete properties, including energy absorption, physical and mechanical properties, controlling shrinkage cracks. The increase of fiber density leads to an increase of the overlapping surface of the fiber of concrete and, in turn, a decrease of cracks developed in the concrete. However, the workability of fiber reinforced concrete tends to be lower than the conventional concrete owing mainly to the hairline thickness and excessive concentration of fibers. The low slump of concrete impedes the construction of reinforced concrete members. In this research, we study if the utilization of magnetic water can alleviate the workability issue of young fiber reinforced concrete. To this end, the compressive and flexural strength of four types of concrete (conventional concrete, fiber reinforced concrete, magnetic concrete, magnetic fiber-reinforced concrete) is studied and compared at three different ages of 7, 14, and 28 days. In order to study the influence of the fiber density and length, a study on specimens with three different fiber density (1, 2, 5 kg of fiber in each cubic meter of concrete) and fiber length (6, 12, 18 mm) is undertaken. The result shows the magnetic fiber concrete can result in an increase of the flexural and compressive strength of concrete at higher ages.

• 한국재료학회지
• /
• 제29권6호
• /
• pp.378-384
• /
• 2019

Ice accumulation on Aluminum Conductor Steel Reinforced(ACSR) cable during winter is an important matter in terms of safety, economy, and efficient power supply. In this work, the ice adhesion strengths of ACSR cable oxidized during different periods(7 years oxidized and 15 years oxidized) are evaluated. At first, a plate type dry oxidation standard specimen, whose surface characteristics are similar to those of ACSR cable, is prepared. Dry oxidation standard specimens are heat-treated at $500^{\circ}C$ for 20, 60, and 120 minutes in order to obtain different degrees of oxidation. After the dry oxidation, surface properties are analyzed using contact angle analyzer, atomic force microscopy, spectrophotometer, and gloss meter. The ice adhesion strengths are measured using an ice pull-off tester. Correlations between the surface properties and the ice adhesion strength are obtained through a regression analysis indicating a Boltzmann equation. It is revealed that the ice adhesion strength of 15-year oxidized ACSR cable is approximately 8 times higher than that of ACSR-bare.

• Journal of Korean Biological Nursing Science
• /
• 제21권3호
• /
• pp.199-206
• /
• 2019

Purpose: The purpose of this paper was to verify effects of the team approach rehabilitation program on balance, gait, and muscle strength of lower extremities of elderly people with Parkinson's disease. Method: Subjects of this paper were 40 elderly people with Parkinson's disease, 20 control and experimental groups respectively, who could walk independently and were less than the 2.5 Hoehn &Yahr stage. The team approach rehabilitation program was applied to the experimental group for 12 weeks. Results: There was significant decrease in second at timed up &go test (p= .008), but no significant difference in reach length at functional reach test (p= .201) with partial improvement of balance. There was no significant difference in second at 10-meter walk test (p= .070), but showed tendency of improvement of gait. And number of times at 30s-chair stand test, indicating muscle strength on lower extremities, increased significantly (p= .029), Conclusion: The team approach rehabilitation program has demonstrated its effectiveness on improving balance, and muscle strength of lower extremities for the elderly with Parkinson's disease.