• 상하수도학회지
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• 제30권3호
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• pp.263-270
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• 2016

Recent Engineered nanoparticles were increasingly exposed to environmental system with the wide application and production of nanomaterials, concerns are increasing about their environmental risk to soil and groundwater system. In order to assess the transport behavior of silver nanoparticles (AgNPs), a saturated packed column experiments were examined. Inductively coupled plasma-mass spectrometry and a DLS detector was used for concentration and size measurement of AgNPs. The column experiment results showed that solution chemistry had a considerable temporal deposition of AgNPs on the porous media of solid glass beads. In column experiment, comparable mobility improvement of AgNPs were observed by changing solution chemistry conditions from salts (in both NaCl and $CaCl_2$ solutions) to DI conditions, but in much lower ionic strength (IS) with $CaCl_2$. Additionally, the fitted parameters with two-site kinetic attachment model form the experimental breakthrough curves (BTCs) were associated that the retention rates of the AgNPs aggregates were enhanced with increasing IS under both NaCl and $CaCl_2$ solutions.

• 한국전문물리치료학회지
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• 제26권2호
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• pp.49-60
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• 2019

Background: After stroke, in order to improve gait function, it is necessary to increase the muscle strength and to enhance the propriocetive function of the lower extremity. Objects: This study aimed to compare the effects of open kinetic chain (OKC) versus closed kinetic chain (CKC) isokinetic exercise of the hemiparetic knee using the isokinetic equipment on lower extremity sensorimotor function and gait ability in patients with chronic stroke. Methods: Thirty participants with chronic hemiplegia (> 6 months post-stroke) were randomly divided into 2 equal groups: CKC group and OKC group. Patients from both groups attended conventional physiotherapy sessions 3 times a week for 6 weeks. Additionally, subjects from the CKC group performed isokinetic exercise using the CKC attachment, while those from the OKC group performed isokinetic exercise using the OKC attachment. The isokinetic knee and ankle muscles strength, position sense of the knee joint, and spatiotemporal gait parameters were measured before and after interventions. Results: The knee muscles peak torque/body weight (PT/BW) and hamstring/quadriceps (H/Q) ratio significantly increased in both groups (p<.01). In particular, ankle plantarflexors PT/BW, position sense of the knee, gait velocity, and spatial gait symmetry significantly improved in the CKC group (p<.01, p<.05, p<.01, and p<.01, respectively). Conclusion: CKC isokinetic exercise can be an effective therapeutic intervention for the improvement of sensorimotor function of the lower extremity and gait functions, such as gait velocity and symmetry. CKC position in isokinetic strength training is effective to improve functional ability in patients with chronic stroke.

• 전기학회논문지P
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• 제61권1호
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• pp.13-17
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• 2012

Ionization and Attachment Coefficients in pure $CH_4$, $CF_4$ and mixtures of $CF_4$ and Ar, have been analyzed over a range of the reduced electric field strength between 0.1 and 350[Td] by the two-term approximation of the Boltzmann equation (BEq.) method and the Monte Carlo simulation (MCS). The calculations of electron swarm parameters require the knowledge of several collision cross-sections of electron beam. Thus, published momentum transfer, ionization, vibration, attachment, electronic excitation, and dissociation cross-sections of electrons for $CH_4$, $CF_4$ and Ar, were used. The results of the Boltzmann equation and the Monte Carlo simulation have been compared with the data presented by several workers. The deduced transport coefficients for electrons agree reasonably well with the experimental and simulation data obtained by Nakamura and Hayashi. The energy distribution function of electrons in $CF_4$-Ar mixtures shows the Maxwellian distribution for energy. That is, f(${\varepsilon}$) has the symmetrical shape whose axis of symmetry is a most probably energy. The proposed theoretical simulation techniques in this work will be useful to predict the fundamental process of charged particles and the breakdown properties of gas mixtures.

• 한국기계가공학회지
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• 제20권11호
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• pp.9-16
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• 2021

As the climate changes rapidly due to warming, it is becoming very important to ensure the stability of environmental structures. It is necessary to choose a material that withstands repeated external forces (wind loads) and satisfies members and joints that have energy absorbing power. Even if the strength of the traffic light attachment is sufficient, if the rigidity is insufficient, there is a limit to the displacement during strong winds. Excessive deformation may cause damage and fall, resulting in a safety accident. The author intends to study mechanical properties and resistance to external environment as a structural material capable of withstanding wind load (50m/sec) by fabricating a C/GFRP composite traffic light attachment using the pultrusion method (Pultrusion).

• 대한환경공학회지
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• 제31권7호
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• pp.515-520
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• 2009

본 연구에서는 칼럼실험을 이용하여 알루미늄 철 산화물 동시피복모래에서 박테리아(Bacillus subtilis)의 부착에 산화음 이온(질산염, 탄산염, 인산염)이 미치는 영향을 조사하였다. 실험결과, 질산염의 경우 피복모래에서의 박테리아 부착은 질산염 이온의 농도변화와 무관하였다. 질산염의 농도가 변화함에 따라(0.1, 1, 10 mM) 질량회수율은 10.9${\pm}$0.2 %로 일정하였다. 탄산염의 경우 농도가 0.1 mM에서 1 mM로 증가함에 따라 질량회수율이 25.6%에서 39.0%로 증가하였고, 인산염의 경우에도 동일한 농도조건에서 50.9%에서 78.9%로 증가하였다. 이러한 현상은 박테리아 부착에 대한 탄산염과 인산염 이온의 방해효과 때문이었다. 반면, 탄산염/인산염의 농도가 1 mM에서 10 mM로 증가함에 따라 질량회수율이 각각 39.0%에서 23.8%로 78.9%에서 52.6%로 감소하였다. 이러한 현상은 탄산염/인산염의 농도증가에 따라 피복모래표면에 흡착되지 않고 수용액상에 존재하는 탄산염이나 인산염 이온이 이온강도를 증가시킴으로써 일어나는 박테리아 부착에 대한 증진효과 때문이었다. 본 실험조건에서 피복모래에서의 박테리아 부착에 미치는 영향은 인산염, 탄산염, 그리고 질산염 중, 인산염이 가장 큰 것으로 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.537-543
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• 2003

This paper presents the improved procedure to assess static and dynamic strength of crawler type excavators. A fully integrated model including front attachment and chassis was prepared for structural analysis. In this paper, two types of loading input methods were investigated and the method imposing digging force directly on bucket tooth was more convenient than imposing cylinder reaction force on cylinder pin even if the two methods showed no discrepancy in analysis results. Static strength analysis was carried out for eight analysis scenarios based on two extreme digging positions, maximum digging reach position and maximum digging force positions. The results from static strength analysis were compared with measured stresses, cylinder pressures and digging forces and showed a good quantitative agreement with measured data. Dynamic strength analysis was carried out for simple reciprocation of boom cylinders. It was recognized that the effect of compressive stiffness of hydraulic oil was very important for dynamic structural behavior. The results from dynamic strength analysis including hydraulic oil stiffness were also compared with measured acceleration data and showed a qualitative agreement with measured data.

• International Journal of Human Ecology
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• 제13권1호
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• pp.17-28
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• 2012

This study determines what affects the academic achievement of senior high school students in the context of the individual, family, and school environment. The sample selection consisted of 1484 high school seniors in Korea. The following are the results of this study: First, female students scored higher in academic achievement than male students. Second, academic achievement by male students was related to levels of school satisfaction, academic motivation, and family strength, while academic achievement by female students was related to levels of parents' education, family income, ego-resiliency, school satisfaction, academic motivation, and family strength. Third, the most important predictor of academic achievement for male and female students is academic motivation, followed by school satisfaction. The present study highlighted the necessity to develop academic achievement improvement programs appropriate for both genders of senior high school students.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.75-76
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• 2020

In this study, in order to check whether the adhesion strength can be secured when installing concrete by mixing super-retarding agents, the splitting tensile strength of the joints of each mold was measured and then analyzed. The results of the experiment showed that the bonding performance of the joint is adversely affected if the installation delay is delayed for more than 24 hours, and that the attachment performance can be secured if the installation is delayed within about 24 hours.

• 대한치과교정학회지
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• 제27권5호
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• pp.771-779
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• 1997

본 연구의 목적은 법랑질 표면에 대한 산부식시간의 차이가 법랑질 표면의 부식형태, 교정장치의 전단접착강도 및 탈락 양상에 미치는 영향을 알아보는 것이다. 교정치료를 위해 발거된 하악 소구치의 법랑질을 $37\%$ 인산 용액을 이용하여 동일한 방법으로 각각 5, 10, 15, 30, 45, 60, 90, 120초 동안 부식시킨 후 법랑질 표면을 주사전자현미경으로 관찰하고, 교정장치를 접착한 후 Instron universal testing machine을 이용하여 전단접착강도를 측정하고 교정장치의 탈락 양상을 관찰하여 다음과 같은 결론을 얻었다. 1. 산부식시간을 5-120초 범위에서 변화시켜도 교정장치의 전단접착강도는 통계학적으로 유의성 있는 차이가 없었다(p<0.05). 2. 산부식시간에 따른 교정 장치의 탈락 양상은 15초 이하 부식군(5, 10, 15초)과 30초 이상 부식군(30, 45, 60, 60, 120초) 사이에 차이가 있었다. 즉, 15초 이하 부식군에서는 접착제/법랑질 경계부 탈락이 상대적으로 많았으나, 30초 이상 부식군에서는 접착제/교정장치 경계부 탈락이 많았다. 3. 법랑질 표면의 부식형태는 매우 다양하였으며 동일한 법랑질 표면에서도 여러 가지 형태의 부식 소견이 관찰되었다. 또한 법랑질 부식형태와 교정장치의 접착강도 사이에 연관성을 발견할 수 없었다. 4. 본 연구의 결과는 실험적 조건에서는 부식시간을 5초로 단축하여도 임상적으로 유용한 접착강도를 얻을 수 있음을 보여주고 있다. 그러나, 15초 이하 부식군에서 나타난 탈락 양상에 대해서는 더 많은 연구가 이루어져야 할 것으로 여겨진다.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.447-452
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• 2017

PURPOSE. To evaluate the sealing performance of Hybrid Coat and its influence on the shear bond strength of five dentin surface cements. MATERIALS AND METHODS. Six premolars were pretreated to expose the dentin surface prior to the application of Hybrid Coat. The microscopic characteristics of the dentinal surfaces were examined with scanning electron microscopy (SEM). Then, 40 premolars were sectioned longitudinally, and 80 semi-sections were divided into a control group (untreated) and a study group (treated by Hybrid Coat). Alloy restoration was bonded to the teeth specimen using five different cements. Shear bond strength was measured by the universal testing machine. The fracture patterns and the adhesive interface were observed using a stereomicroscope. RESULTS. SEM revealed that the lumens of dentinal tubules were completely occluded by Hybrid Coat. The Hybrid Coat significantly improved the shear bond strength of resin-modified glass ionomer cement (RMGIC) and resin cement (RC) but weakened the performance of zinc phosphate cement (ZPC), zinc polycarboxylate cement (ZPCC) and glass ionomer cement (GIC). CONCLUSION. Hybrid Coat is an effective dentinal tubule sealant, and therefore its combined use with resin or resin-modified glass ionomer cements can be applied for the prostheses attachment purpose.