• Korean Chemical Engineering Research
• /
• 제47권1호
• /
• pp.31-37
• /
• 2009

양쪽성 계면활성제는 등전점 이하의 pH 조건에서 양이온 계면활성제로 작용함으로써 유연력을 나타낼 수 있으며, 등전점 이상의 pH 조건에서는 음이온 혹은 비이온 계면활성제로 작용하여 세정력을 나타낼 수 있다. 따라서 pH에 따른 양쪽성 계면활성제의 특성을 활용하면 한 종류의 계면활성제 분자로 세정력과 유연력을 동시에 발휘할 수 있다. 본 연구에서는 betaine 양쪽성 계면활성제에 대하여 계면활성제의 기본적인 물성(CMC, 표면장력, 계면장력, 접촉각, 점도, 계면활성제 시스템의 상거동 등)을 측정하였으며, 또한 계면활성제 수용액에 대하여 QCM(quartz crystal microbalance) 실험과 zeta potential 측정을 통하여 양쪽성 계면활성제가 양이온 계면활성제에서 음이온 계면활성제로 작용이 전환되는 등전점을 결정하였다. Betaine 계면활성제의 CMC는 약 $10^{-4}mol/L$ 이며, CMC에서의 표면장력은 약 32 mN/m이었다. Spinning drop tensiometer를 사용하여 1 wt% 계면활성제 수용액과 n-decane 오일 사이의 계면장력을 pH 2~10의 조건에서 측정한 결과, 계면장력은 pH 5까지 증가하다가 그 이후 감소하는 경향을 보였으며, 평형에 도달하는 시간도 유사한 경향을 나타내었다. 본 연구에서 사용한 betaine 양쪽성 계면활성제의 등전점을 QCM 실험을 통하여 측정한 결과, 등전점은 pH 3.0~3.3에 존재하였으며, 이 결과는 zeta potential 측정 결과와 동일함을 확인하였다.

• 대한한방내과학회지
• /
• 제32권2호
• /
• pp.259-277
• /
• 2011

Objectives : The purpose of this study was to investigate two subjects: the diagnostic value of bilateral lowering of electrical activity at point H4,5,6 of Ryodoraku and the mechanism for Ryodoraku phenomena. Methods : Electrical activities of Ryodoraku test and electrogastrography recorded simultaneously and monitored continuously from 16 cases of functional dyspeptic patients were collected and their variations were grouped by the topics of discussion which were peculiarity, stability, lagging, alterability, and anomaly. Ryodoraku recordings obtained from 6 patients with different gastrointestinal diseases and 1 normal healthy person were used as control. The results are discussed with Nakatani's suggestion, theory of sympathetic nerve and Meridian Principle, respectively. Finely, coincidence of stomach arrangement between anatomy and meridian system in Ryodoraku was also evaluated. Results : Time-course variation showed a regular relationship between the typical pattern of Ryodoraku at point H4,5,6 and gastric myoelectrical activity. However, an irregular relationship and atypical pattern of Ryodoraku occasionally appeared. A literature search suggested that electrical response at the Ryodoraku point H4,5,6 may be dependent on an afferent sympathetic spinal reflex transmitted from the stomach. However, there was no evidence for making clear whether bilateral lowering of electrical activity at this point was induced by hypofunction of local sympathetic nerve in the skin itself or of signals transmitted from the gastric sympathetic nerve or not. The coincidence of 19% could not provide a visceral arrangement of the stomach between anatomy and meridian systems. Conclusions : Bilateral lowering of electrical activity at Ryodoraku point H4,5,6 has value as a diagnostic index for gastric dysmotility of functional dyspepsia. This phenomenon is associated with spinal reflex transmitted from the afferent sympathetic nerve in the stomach but not that of meridian function.

• Progress in Superconductivity
• /
• 제3권2호
• /
• pp.146-150
• /
• 2002

We performed the point contact spectroscopy on newly discovered superconductor $MgB_2$ thin films with Au tip. In the point contact spectroscopy of the metallic Sharvin limit, the differential conductance below the gap is twice as that above the gap by virtue of Andreev Reflection. After some surface cleaning processes of sample preparation such as ion-milling and wet etching, the obtained dI/dV versus voltage curves are relatively well fitted to the Blonder-Tinkham-Klapwijk (BTK) formalism. Gaps determined by this technique were distributed in the range of 3meV~ 8meV with the BCS value of 5.9meV in the weak coupling limit. We attribute these discrepancies to the symmetry of the gap parameter and the degradation of the surface of the sample. We also present the temperature dependence of the conductance vs voltage curve and thereby the temperature dependence of the gap.

• Nonlinear Functional Analysis and Applications
• /
• 제29권2호
• /
• pp.559-580
• /
• 2024

In this paper, we aim to prove coupled and common coupled fixed point theorems for contractive type conditions in the context of partial metric spaces by means of a control function, and to provide some corollaries of the established results. This paper presents a number of results that generalize and extend previous work in the field. In order to better illustrate the process, we provide examples.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2005년도 추계 학술대회논문집
• /
• pp.99-104
• /
• 2005

For the efficient reliability analysis, Bi-direction two-point approximation(BTPA) method is developed which solves shortcomings of conventional two-point approximation(TPA) methods that generate an approximate surface with low accuracy or sometimes do an unstable approximate surface. The conventional reliability based design optimization(RBDO) methods require high computational cost compared with the deterministic design optimization(DO) methods. To overcome the computational inefficiency of RBDO, the approximate reliability analysis approaches on the TPA surface are proposed. Using these FORM and SORM analysis strategies, multi-point aerodynamic-structure interacted shape design optimizations with uncertainty are performed very efficiently.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
• /
• pp.1058-1060
• /
• 2003

A ground control point (GCP) is a point on the surface of Earth where image coord inates and map coordinates can be identified. The GCP is useful for the geometric correction of systematic and unsystematic errors usually contained in a remotely sensed data. Especially in case of synthetic aperture radar (SAR) data, it has serious geometric distortions caused by inherent side looking geometry. In addition, SAR images are usually severely corrupted by speckle noises so that it is difficult to identify ground control points. We developed a ground point extraction algorithm that has an improved capability. An application of radargrammetry to Daejon area in Korea was studied to acquire the geometric information. For the ground control point extraction algorithm, an ERS SAR data with precise Delft orbit information and rough digital elevation model (DEM) were used. We analyze the accuracy of the results from our algorithm by using digital map and GPS survey data.

• 한국통신학회논문지
• /
• 제31권7C호
• /
• pp.735-742
• /
• 2006

본 논문에서는 IEEE 802.16e OFDMA(Orthogonal Frequency Division Multiplexing-FDMA) TDD(Time Division Duplexing) 시스템 단말 수신기의 입력 신호에 대하여 DC 오프셋 보상, 자동 주파수 조정, 자동 이득 조정을 수행하는 DFE(Digital Front End)의 동작 원리와 Fixed-point 설계 방법에 대하여 설명하고, DFE의 성능을 ITU-R M. 1225 Veh-A 60km/h 채널 환경에서 시뮬레이션 결과를 통해 분석한다. DFE의 Fixed-point 설계시, 시스템의 성능에 영향을 주지 않는 범위 내에서 연산을 통해 출력되는 bit의 크기를 줄임으로서때 H/W 동작의 복잡도를 줄이고, Acquisition time과 안정도 간의 Trade-off를 고려하여 Loop Filter를 설계함으로서 DFE 의 Fixed-point 설계를 최적화 한다.

• 대한수학회보
• /
• 제36권4호
• /
• pp.755-762
• /
• 1999

Let X be a p-compace groyp, Y -> X bd a p-compact-subgroup of X and G -> X be a p-compact toral subgroup of X with $(X/Y)^{hG} \neq 0$. In this paper we show that the homotopy fixed point set of the homotopy fibre $(X/Y)^{hG}$ is $F_p$-finite.

• 호남수학학술지
• /
• 제29권1호
• /
• pp.19-40
• /
• 2007

Let L be the differential operator, Lu = $u_{tt}+u_{xxxx}$. We consider nonlinear beam equations, Lu + $bu^+$ = j, in H, where H is the Hilbert space spanned by eigenfunctions of L. We reveal the existence of multiple solutions of the nonlinear beam problems by critical point theorems.

• 대한수학회보
• /
• 제38권1호
• /
• pp.143-148
• /
• 2001

First, we show the finiteness property of the homotopy fixed point set of p-discrete toral group. Let $G_\infty$ be a p-discrete toral group and X be a finite complex with an action of $G_\infty such that X^K$ is nilpotent for each finit p-subgroup K of $G_\infty$. Assume X is $F_\rho-complete$. Then X(sup)hG$\infty$ is F(sub)p-finite. Using this result, we give the condition so that X$^{hG}$ is $F_\rho-finite for \rho-compact$ toral group G.