• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.419-426
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• 2010

This paper discusses a series of experiments including material improvement in order to ensure quality of grouting for the post-tensioned structure. In presstressed concrete, grouting refers to the construction procedure of filling empty space of duct enclosing the prestress tendons using cementitious material, To date, adequate quality control of the grouting has not been established in Korea because the relationship between the grouting and durability of post-tensioned structure is not well-recognized. The Korean standard does not consider the important material characteristic, wick effect, which is caused by tendons in the ducts, and furthermore current standard testing method does not quantify reasonable material segregation. As a result, the grout material, which satisfies the current material standards, may well exhibit excessive bleeding of water or shrinkage during construction. In this study, international codes and standards related to grouting were surveyed. The mix proportions of the constituents and novel admixtures were suggested to meet equivalently with these standards. Performance of this enhanced grout was compared with common domestic grouts using the international standard testing method. A series of mock-up specimens considering geometry of PC beam was constructed and grout flow pattern was observed as the grout was injected. It was observed that the grouting performance was highly influenced by material properties and filling characteristic can be varied depending on geometry of ducts.

• Physical Therapy Korea
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• v.4 no.2
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• pp.1-9
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• 1997

Skeletal muscle fatigue is often associated with diminished athletic performance and inability to maintain an expected force output as a function of time. The purpose of this study was to compare the effect of duration of exercise on skeletal muscle fatigue between Weight Lifters(WL) and Non-Weight Lifters(NWL). There were twelve normal healthy adult volunteers, ranging in age from 18 to 35 years. The group consisted of six NWL and six WL. Randomized cross-over design was set up and work-rest cycle was 8 minutes work and 1 minute rest based on 15% MVC. Muscle fatigue was measured by the amount of force produced by the wrist flexor muscle and EMG amplitude over time. Repeated measures ANOVAs($2{\times}4$) were used to determine two types of subjects(WL, NWL) during four different duration of exercises(16, 32, 48, 64 minutes). The force decreased over time in NWL and WL, but there was no significant difference(F=2.83, p>0.05). However, the EMG amplitude increased in WL(0.8200) and NWL(0.6348). The WL exhibited an increase in EMG at the end of the period, especially at 48 minutes of exercises than did the NWL(F=9.58, p<.05). This suggests the WL were able to adjust to prolonged effort with adaptations in neural effect over time, resulting in higher EMG amplitude. That is, WL may be able to learn to recruit more motor units with training. It is important to the degree of neuromuscular fatigue and the time needed for recovery may differ considerably between WL and NWL, there is a need to plan proper strength training or rehabilitation protocols to match with the requirements in different characteristics of groups.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.341-348
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• 2017

The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.33-33
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• 2018

농업이 기간산업이었던 고대사회에서 수리시설(水利施設)의 축조는 농업의 성패를 가늠하는 중요한 요소로 정치 경제 사회 전반에 걸쳐 큰 영향을 미치는 국가적인 대규모 사업이었다. 이에 따라 수리시설의 축조 시기와 배경, 축조 기술과 운영, 구조, 몽리(蒙利) 효과 및 보수(補修)와 수축(修築) 등에 대한 연구는 우리의 농경(農耕)문화사를 밝히는데 중요한 관건이 된다. 관개(灌漑) 수리시설의 축조와 정비는 수전(水田) 개발과 밀접한 연관이 있다. 제방(堤防)을 축조함으로써 주변의 수전 개발을 촉진하고, 가뭄과 홍수로부터 안전하게 전답을 유지할 수 있어 수확량을 높이게 된다. 농업생산력의 향상은 대내적 체제 정비는 물론 치열한 국가 간의 경쟁에서 우위를 점하는데 필요한 경제적 배경이 된다. 이처럼 고대수리시설은 개인과 집단 나아가 국가의 생존을 뒷받침하는 근본이었지만, 과연 우리는 그 역사성과 의미에 대해 제대로 평가를 했던 것일까? 또한, 고대수리시설의 관개 및 치수(治水) 능력은 구체적으로 어느 정도였으며 근대에 비하면 어느 정도였을까? 일부 수리시설에 대해 관개면적을 추정한 경우는 있으나, 그 예도 많지 않을뿐더러 시기적인 변천 양상을 제대로 반영하고 있지 못하는 것이 현실이다. 본 연구는 고대로부터 원형을 비교적 잘 간직하고 있는 수리시설 중 경북(慶北) 영천(永川)의 청제(菁堤)를 대상으로 고고학적 역사학적 입장에서 보다는 수문학적(水文學的) 농업수리학적(農業水利學的) 관점에서 저수량(貯水量) 및 관개(灌漑) 면적에 따른 농업생산력을 살펴보았다. 지형 및 GIS (Geographic Information System) 정보를 이용하여 저수지의 규모 및 관개 면적을 추정하였으며 수문학적 해석 모형(模型)인 CAT(Catchment hydrologic cycle Assessment Tool)(김현준 등, 2012)을 이용하여 저수량 및 관개 가능량을 분석하였다. CAT은 공간 단위별로 침투(浸透), 증발(蒸發), 지하수(地下水)흐름 등의 모의(模擬)가 가능하도록 개발된 모형이다. 특히, 농업용 저수지 및 홍수방재용(洪水防災用) 저류(貯留)시설 등의 저류량(貯留量) 및 방류(放流量)에 대한 모의가 가능하다(장철희 등, 2012). 고대수리시설의 저수량 및 관개 면적에 따른 농업생산력을 공학적 수문학적으로 해석하는 연구는 과거물 관리 및 생산력의 실태를 좀 더 자세히 파악할 수 있는 토대가 될 것이며, 역사학적 자료와의 비교 분석을 통해 우리나라 고대수리시설의 역사성 및 우수성을 찾을 수 있을 것으로 판단된다.

• Journal of Investigative Cosmetology
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• v.15 no.1
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• pp.49-58
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• 2019

Special makeup companies are able to overcome the difficulties resulting from increase in labor costs by enhancing work efficiency through fabrication of prosthesis using 3D printing. With accurate fabrication being enabled, a given business area can be broadened to tailor-made prosthesis such as anaplastology. In this regard, the current study attempted to investigate the possibility of digital processing through special makeup molds and silicon patches designed using a FDM 3D printer, and the results are as follows: First, when a design modeled through the 3D graphics software 'ZBrush' was printed using a FDM 3D printer, the exact shape and surface texture which were observed on the computer monitor could be exactly obtained. Second, negative molds fabricated with flexible TPU filament were easier to use and displayed a more complete silicon mold than PLA filament-based negative molds. Third, the support, which is a disadvantage of the 3D printer, it was able to align objects or split the molds in such a way so that no support was formed in the slicing program. Fourth, the shrinkage rate of the outputs acquired through PLA or TPU filament did not change the shape of the silicon molds. Fifth, the texture of the fine contours which was found in silicon molds varied depending upon the object alignment angle in the slicing program. They can also be viewed differently depending upon the angle of lighting. To use a 3D printer in the fabrication of special makeup molds, therefore, it is necessary to examine how to fabricate them easily by concealing contours as much possible. It is also necessary to analyze the images acquired after attaching the colored silicon patches and check their availability.

• Journal of Preventive Medicine and Public Health
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• v.35 no.2
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• pp.141-146
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• 2002

Objectives : This study was peformed in order to assess the incidence of hypertension based on two-years follow-up of a rural hypertension-free cohort in Korea. Methods : The study cohen comprised 2,580 subjects aged above 20 (1,107 men and 1,473 women) of Chung-Song County in Kyungpook Province judged to be hypertensive-free at the baseline examination in 1996. For each of two examinations in the two-year follow-up, those subjects free of hypertension were followed for the development of hypertension to the next examination one year (1997) and two years later (1998). The drop-out rate was 24.7% in men and 19.6% in women. Hypertension was defined as follows 1) above mild hypertension as a SBP above 140 mmHg or a DBP above 90 mmMg,2) above moderate hypertension as a SBP above 160 mmHg or a DBP above 100 mmHg or when the participant reported having used antihypertensive medication after beginning this survey. Results : The age-standardized incidence of above mild hypertension was 6 per 100 person years (PYS) in men and that of above moderate hypertension was 1.2. In women, the age-standardized rate for above mild hypertension was 5.7 and 1.5 for above mild and moderate hypertension, respectively. However, the rates of incidence as calculated by the risk method were 4.8% and 1.0% in men and 4.6%, 1.2% in women, respectively. In both genders, incidence was significantly associated with advancing age(p<0.01), In men, the incidences of above moderate hypertension by age group were 0.5 per 100 PYS aged 20-39, 0.7 aged 40-49, 1.7 aged 50-59, 3.6 aged 60-69, and 5.8 aged above 70(p<0.01). In women, those the incidence measured 0.6 per 100 PYS aged 20-39, 1.8 aged 40-49, 1.3 aged 50-59, 3.3 aged 60-69, and 5.6 aged above 70(p<0.01). After age 60, the incidence of hypertension increased rapidly. Conclusions : The incidence data of hypertension reported in this study may serve as a reference data for evaluating the impact of future public efforts in the primary prevention of hypertension in Korea.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1972.03a
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• pp.7-8
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• 1972

The effects of noise exposure are of two types: Nonauditory effects and auditory effects. Nonauditory effects of noise exposure are interference with communication by speech, sleeping and emotional behavior. The noise will cause the high blood pressure and rapid pulse, also that decrease the salivation and gastric juice. in experimentaly showed that the Corticoid hormon: Gonatotropic hormone were decrease and Thyrotropic hormoone is increase. Auditory effect of noise exposure. when the normal ear is exposed to noise at noise at hamful intensities (above 90㏈) for sufficiently long periods of time, a temoral depression of hearing results, disappearing after minutes or hours of rest. When the exposure longer or intesity greater is reached the Permanent threshold shift called noise-induced hearing loss. Hearing loss resulting from noise exposure presents legal as well as medical problems. The otologist who examines and evaluates the industrial hearing loss cases must be properly informed, not only concerning the otologic but also about the physical and legal aspects of the problems. The measurement of hearing ability is the most important part of a hearing conservation, both preplacement and periodic follow-up tests of hearing. The ideal hearing conservation program would be able to reduce or eliminate the hazardous noise at its source or by acoustic isolation of noisy working area and two ear protections (plugs and muff type) were developed for personal protection.