• Tribology and Lubricants
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• 제30권5호
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• pp.247-255
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• 2014

Charged polymer chains, i.e., polyelectrolytes, are known to show superior aqueous lubricating properties compared to those of neutral polymer chains, especially in brush conformation. This is primarily because of the incorporation of a large amount of counterions within the polymer layers and the consequently increased osmotic pressure. However, this effect is active only when the polymer chains remain immobilized even under tribostress, which is not realistic for high-contact pressure tribological applications, especially when they are irreversibly immobilized on tribopair surfaces. In contrast, with free polymers, which can be included as surface-active additives in the base lubricant (water), long-term lubricating performance based on "self-healing" properties is readily expected. In order to assess whether the superior aqueous lubricating properties of polyelectrolyte chains are valid for free polymers too, this study reviews recent studies on the tribological properties of many charged biopolymer and synthetic copolymers at a nonpolar, hydrophobic interface. In contrast to the irreversibly immobilized polyelectrolyte chains, free polyelectrolyte chains show inferior aqueous lubricating properties compared to their neutral counterparts owing to charge accumulation and the consequently impeded surface adsorption on the nonpolar surface. Nevertheless, bovine submaxillary mucin (BSM), a representative biopolymer, shows a sufficiently effective surface adsorption and aqueous lubricating capabilities even at neutral pH without losing the polyanionic characteristics.

• 아동학회지
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• 제36권5호
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• pp.75-94
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• 2015

This study examined short-term longitudinal reciprocal relationships between maternal parenting behavior and preschoolers' compliance/noncompliance, as well as stability in both maternal parenting behavior and preschoolers' compliance/noncompliance over time. The sample which was used for this study was taken from a two-wave (one year apart) longitudinal study of preschool-aged children and their mothers (N = 53 dyads). At both times, mothers and their children were invited to a laboratory and engaged in 25 minutes of play involving three episodes of mother-child interaction. Maternal parenting behavior and preschoolers' compliance/noncompliance during play were coded using the Dyadic Parent-Child Interaction Coding System-III (DPICS-III). Maternal codes included positive, neutral, and negative parenting behaviors and child codes were comprised of compliance and noncompliance. The results revealed that during the play session, maternal neutral and negative parenting behavior and preschoolers' compliance were stable over time. In addition, T1 maternal negative parenting behavior was significantly related to T2 child compliance/noncompliance. However, T1 child compliance/noncompliance were not significantly associated with T2 maternal parenting behavior. These findings suggest that during the preschool period, there are unidirectional effects from mothers to children.

• 대한수학회보
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• 제45권1호
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• pp.23-31
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• 2008

In this paper, we investigate nonoscillatory solutions of a class of higher order neutral nonlinear difference equations with positive and negative coefficients $\Delta^m(x(n)+p(n)x(\tau(n)))+f_1(n,x(\sigma_1(n)))-f_2(n,x(\sigma_2(n)))=0,\;n{\geq}n_0$. Some sufficient conditions for the existence of nonoscillatory solutions are obtained.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.41-53
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• 1995

Forging of spur gears has been investigated by means of upper-bound method. The term forging means forging of spur gears with solid cylindrical billets, hollow billets with flat punch. Kinematically admissbile velocity field for forging of spur gears has been proposed in this study. The 1/2 pitch of spur gear has been divided into seven dieformation regions, wherein, an involute curve has been introduced to represent the shape of die profile. Especially neutral surface has been introduced intor forging of hollow gears from hollow billets. By using the kinematically admissible velocity field, the powder requirements and suitable conditions for forging fo spur gears were successfully calculated with numerical method. According to the analysis , the acceptable number of teeth for forging of spur gears is from 15 to 20.

• Structural Engineering and Mechanics
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• 제54권5호
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• pp.923-936
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• 2015

In this paper, a simple n-order refined theory based on neutral surface position is developed for bending and frees vibration analyses of functionally graded beams. The present theory is variationally consistent, uses the n-order polynomial term to represent the displacement field, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the Hamilton's principle and the physical neutral surface concept. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

• 국제물리치료학회지
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• 제7권1호
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• pp.908-914
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• 2016

The purpose of this study is to explore the effects of mobilization of C0-C1 and C7-T1 applied to asymptomatic individuals with reduced upper cervical rotation during the FRT. Design: parallel randomized controlled trial. 48 subjects(38.52 years${\pm}15.13$) with C1-C2 rotation hypomobility in TFR joined the study and were randomized into three groups(C0, C7, control group). FRT in both directions was measured before and after the intervention. C0 intervention consisted of a dorsal translatoric mobilization of C0-C1 in the cervical neutral position. C7 intervention consisted of a ventral cranial translatoric mobilization of C7-T1 in neutral position and the control group maintained a supine position. C0 group experienced a FRT ROM to the restricted side increase of $17.64^{\circ}$(SD=4.55), that was significantly greater (P<0.001) than $5.95^{\circ}$(SD=4.81) of the C7 group and $2.45^{\circ}$(SD=5.05) of the control group. The results showed that a dorsal translatoric mobilization of C0-C1 in neutral position restored the physiological FRT mobility in subjects with C1-C2 hypomobility and experienced statistical significant improvement in FRT as compared to a C7-T1 translatoric mobilization and a control group. (Level of evidence: 1b).

• Journal of applied mathematics & informatics
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• 제8권2호
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• pp.403-416
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• 2001

In this paper, we are mainly concerned with the classification of nonscillatory solutions for the higher order difference equation and some existence results for some kinds of nonoscillatory solutions.

• Communications for Statistical Applications and Methods
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• 제11권3호
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• pp.495-501
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• 2004

HJM representation of the term structure of interest rates sometimes produces the negative interest rates with positive probability. This paper shows that the condition of positive interest rates can be derived from the jump diffusion process, if a proper positive martingale process with the compensated jump process is chosen. As in Flesaker and Hughston, the condition is incorporated into the bond price process.

• 지능정보연구
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• 제22권3호
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• pp.129-142
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• 2016

전자상거래에서 소비자들의 구매 의사결정에 판매 제품을 이미 구매하여 사용한 고객의 리뷰가 중요한 영향을 미치고 있다. 전자상거래 업체들은 고객들이 제품 리뷰를 남기도록 유도하고 있으며, 구매고객들도 적극적으로 자신의 경험을 공유하고 있다. 한 제품에 대한 고객 리뷰가 너무 많아져서 구매하려는 제품의 모든 리뷰를 읽고 제품의 장단점을 파악하는 것은 무척 힘든 일이 되었다. 전자상거래 업체들과 연구자들은 텍스트 마이닝을 활용하여 리뷰들 중에서 유용한 리뷰들의 속성을 파악하거나 유용한 리뷰와 유용하지 않은 리뷰를 미리 분류하는 노력을 수행하고 있다. 고객들에게 유용한 리뷰를 필터링하여 전달하는 방안이다. 본 연구에서는 문서-단어 매트릭스에서 단어의 제거 기준으로 온라인 고객 리뷰가 유용한 지, 그렇지 않은지를 구분하는 문제에서 단어들이 유용 리뷰 집합과 유용하지 않은 리뷰집합에 중복하여 등장하는 정도를 측정한 중립도를 제시한다. 제시한 중립도를 희소성과 함께 분석에 활용하여 제거할 단어를 선정한 후에 각 분류 알고리즘의 성과를 비교하였다. 최적의 성과를 보이는 중립도를 찾았으며, 희소성과 중립도에 따라 단어를 선택적으로 제거하였다. 실험은 Amazon.com의 'Cellphones & Accessories', 'Movies & TV program', 'Automotive', 'CDs & Vinyl', 'Clothing, Shoes & Jewelry' 제품 분야 고객 리뷰와 사용자들의 리뷰에 대한 평가를 활용하였다. 전체 득표의 수가 4개 이상인 리뷰 중에서 제품 카테고리 별로 유용하다고 판단되는 1,500개의 리뷰와 유용하지 않다고 판단되는 1,500개의 리뷰를 무작위로 추출하여 연구에 사용하였다. 데이터 집합에 따라 정확도 개선 정도가 상이하며, F-measure 기준으로는 두 알고리즘에서 모두 희소성과 중립도에 기반하여 단어를 제거하는 방안이 더 성과가 높았다. 하지만 Information Gain 알고리즘에서는 Recall 기준으로는 5개 제품 카테고리 데이터에서 언제나 희소성만을 기준으로 단어를 제거하는 방안의 성과가 높았으며, SVM에서는 전체 단어를 활용하는 방안이 Precision 기준으로 성과가 더 높았다. 따라서, 활용하는 알고리즘과 분석 목적에 따라서 단어 제거 방안을 고려하는 것이 필요하다.

• 한국융합학회논문지
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• 제9권8호
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• pp.319-330
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• 2018

본 연구의 목적은 노인장기요양보험 재가보호서비스를 이용하는 노인성 치매환자 가족의 돌봄경험에 대한 평가와 가족기능과의 관계를 파악하기 위함이다. 본 연구의 대상자는 경기도 I병원 치매예방센터에서 DSM-IV기준에 의해 치매를 진단받고 노인장기요양보험 재가보호서비스를 이용하고 있는 65세 이상의 노인성 치매환자 가족구성원 121명을 대상으로 하였다. 연구결과 대상자의 평균 연령은 $53.80{\pm}10.86$세로 여성이 75.2%이었고 그 중 딸이 37.2%로 가장 많았다. 대상자의 돌봄평가는 중립적 인식의 요구감이 가장 높았고 긍정적 인식인 숙련감, 만족감이 그 다음으로 높았다. 대상자의 가족기능은 보통정도였고 영역별로 정서적 기능이 가장 높았던 반면, 의사소통이 가장 낮았다. 대상자의 돌봄평가 중 긍정적 인식의 만족감이 높고 중립적 인식의 요구감이 낮을수록 가족기능이 높았다. 추후 노인성 치매환자 가족의 돌봄에 대한 요구감을 줄이고 만족감을 향상시키며 가족의 정서적 기능과 의사소통을 증진시키기 위한 간호중재개발이 필요하다.