• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
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• pp.122-126
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• 2002

Contaminant transport in porous media is characterized by solving an advection-dispersion equation(ADE). The ADE can cover equilibrium phenomena of interest, which include sorption, decay, and chemical reactions. Among these phenomena, sorption mechanism is described by several types of sorption isotherm. If we assume the sorption isotherm as linear, the solution of ADE can be easily procured. However, if we consider the sorption isotherm as non-linear isotherm like a Dual Reactive Domain Model (DRDM), the resulting differential equation becomes non-linear. In this case, the solution of ADE cannot be easily acquired by an analytic method. In this paper, we present the numerical analysis of ADE using a DRDM. The results reveal that even if sorption data may be fitted well using linear or non-linear isotherm, the characteristics of contaminant transport of the two cases are different from each other. To be concrete, the retardation of linear isotherm has stronger effect than that of the DRDM. As the non-linearity of sorption isotherm increases, the difference of retardation effects of the two cases becomes larger. For a pulse source, the maximum concentration of the linear model is higher than that of the DRDM, but the plume of the DRDM moves faster than that of the linear model. Behaviors of contaminant transport using the DRDM are consistent with common features of a linear model. For instance, biodegradation effect becomes larger as time goes by The faster the seepage velocity is, the faster the plume of contaminant moves. The plume of the contaminant is distributed evenly over overall domain in the event of high dispersion coefficient.

• 접착 및 계면
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• 제7권2호
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• pp.19-25
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• 2006

미생물 합성 고분자인 poly(hydroxylalkanoate)s (PHAs)의 초기효소분해는 표면침식의 메커니즘으로 진행하므로 이들의 분해거동은 표면특성을 개질로서 조절할 수 있다. 본 연구에서는 효소분해속도를 조절하기 위하여 플라즈마 기법을 PHAs 표면특성의 개질에 적용하였다. $CF_3H$와 $O_2$ 플라즈마를 사용하여 재료 표면에 각각 소수성 및 친수성을 부여하였다. 효소분해 실험은 pH 7.4의 0.1 M potassium phosphate 완충용액에서 Alcaligenes facalis T1에서 정제된 poly(hydroxybutyrate) 분해효소를 첨가하여 행하였다. $CF_3H$ 플라즈마 처리된 시편의 경우 표면 층의 불소화에 따른 소수성의 증가와 분해 효소에 대한 비활성으로 초기분해 속도가 상당히 지연됨을 관찰하였으나 $O_2$ 플라즈마 처리에 의한 표면 친수성은 분해속도의 촉진 등에 큰 영향을 미치지 않았다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.239-239
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• 2006

In the present study, we synthesized CBDA-FDA and its analogue, poly(4,4' -(9,9-fluorenyl)diphenylene pyromellitimide) (PMDA-FDA), and then investigated quantitatively the orientational distributions of the polymer chain segments in the surfaces of their films by using linearly polarized Fourier transform infrared (FTIR) spectroscopy and optical retardation analysis. We also examined the films' surface topographies using high spatial resolution atomic force microscopy (AFM). Further, rubbed films were used to assemble antiparallel and $90^{\circ}-twisted$ nematic (TN) LC cells, and the alignment behaviors, pretilt angles and anchoring energies of the LC molecules in the cells were determined. The films were found to have very interesting surface morphologies and LC alignment behaviors, which have not previously been reported. The observed LC alignments, pretilt angles and anchoring energies are discussed by taking into account the interactions of the LC molecules with the oriented polymer chain segments and the surface morphologies.

• Macromolecular Research
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• 제17권12호
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• pp.976-986
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• 2009

With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

• 대한소아치과학회지
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• 제38권3호
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• pp.284-289
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• 2011

Lesch-Nyhan syndrome은 purine 대사장애로 인해 나타나는 질환이다. 유아기부터 전신근육의 강직, 발육 저하가 나타나고 손발의 불수의적 운동이나 불규칙적인 운동이 보이며 정신지체, 강박적 자해행위가 나타난다. 자해행위는 대개 1세 전후에 나타나지만 간혹 10대 후반에 나타나기도 한다. 입술, 특히 아랫입술과 혀, 협점막, 손, 손가락 등을 깨물고 입술, 혀, 협점막 등이 손상되거나 심할 경우 절단되기도 한다. 나이가 들면서 자해 행위가 점점 심해지고 상처 부위를 통한 2차 감염 가능성이 있다. 자해행위로 인한 주기적인 연조직 손상은 심할 경우 구강암으로 이행되기도 한다. 이와 같은 자해행위를 억제하기 위해 약물치료, 장치치료, 발치, 외과적 수술 등 여러 가지 방법이 시도되고 있다. 본 증례는 자해행위로 인한 입술손상을 주소로 내원한 Lesch-Nyhan syndrome 환자들을 대상으로 발치 대신 보존적 치료를 위해 가철성, 고정성 장치를 사용한 결과 입술외상의 빈도를 줄이고 심미적으로 양호한 결과를 얻을 수 있었기에 보고하는 바이다.

• Biomolecules & Therapeutics
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• 제20권2호
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• pp.226-233
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• 2012

Ethanol exposure during gestational period is related to growth retardation, morphological abnormality, and even in neurological abnormalities including attention deficit/hyperactivity disorder (ADHD)-like behaviors on offspring. However, relatively little is known about the effects of maternal ethanol consumption prior to conception on their offspring. In this study, we investigated whether maternal ethanol administration during preconceptional phase produces ADHD-like behaviors in the rat offspring. Sprague-Dawley (SD) female rats were administrated ethanol via intragastric intubation with dosing regimen of 6 g/kg daily for 10 consecutive days and treated female rats then mated with non-treated male SD rats after 8 weeks. Another group subjected to the same procedure as those conducted on ethanol treated group except the saline administration instead of ethanol. Offspring was tested for their ADHD-like behaviors using open field test, Y maze test and impulsivity test that is performed in the aversive electronic foot shock paradigm. Offspring of preconceptional ethanol treated (EtOH) group showed hyperlocomotive activity, attention deficit and impulsivity. And reduction of striatal dopamine transporter (DAT) level was observed by Western blot in the EtOH group, compared to control (Con) group, while the immunohistochemical analysis exhibited increased expression of norepinephrine transporter (NET) in the frontal cortex. These results suggest that maternal ethanol consumption in the preconceptional phase induces ADHD-like behaviors in offspring that might be related to the abnormal expression of DAT and NET in rat.

• 대한간호학회지
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• 제35권1호
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• pp.5-15
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• 2005

Purpose: This study was conducted to develop a behavioral checklist to predict an autistic disorder and to identify the earliest detecting time. Method: One hundred and fifty eight children including normal, autistic, institutionalized normal, and retarded were assessed using critical interaction behavioral markers from literature review. Data was collected by semi-structured mother-child interaction by videotape recording and analyzed byfactor analysis, Cronbach a, Kappa, $x^2$, and Duncan. Result: Ten behavioral markers were sorted into 2 factors; joint-attention and synchronized behavior. Autistic children were impaired in pretend play, odeclarative pointing, proimperative pointing, gaze-monitoring, referential looking, showing, joint-attention, rhythmical vocal exchange, and synchronized laughing. The sychronized behavior was also a critical marker to predict the autistic disorder. However, it was difficult to differentiate autistic disorder from mental retardation. In addition, the appropriate detecting time was around 18 months after birth. Conclusion: This checklist should be behavior markers to predict autistic disorder and could be useful as educational material at children's clinics, parents class, and for caregivers in the health center. In addition, early detection should lead to treatment being started as soon after 18 months of age as possible.

• 한국안전학회지
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• 제9권3호
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• pp.13-21
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• 1994

Effects of tensile and compression residual stresses in the welded SS41 and A17075-76 on fatigue crack propagation behavior are investigated when a crack propagates from residual stresses region. We propose the fatigue crack growth equation on tensile and compression residual stresses in welded metal. The results obtained in this experimental study are summarized as follows . 1 ) A fatigue crack growth equation which applied fatigue fracture behavior of the welded metal is proposed. (equation omitted) where, $\alpha$, $\beta$, ${\gamma}$ and $\delta$ are constants, and R$_{eff}$ is effective stress ratio [R$_{eff}$=(Kmin+Kres)/(Kmax+Kres)], Kcf is critical fatigue stress intensity factor. The constants are obtained from nonlinear least square method. The relation between crack length and number of cycles obtained by integrating the fatigue crack growth rate equation is in agreement with the experimental data. 2) The experimental results confirmed that the cause of crack extension and retardation by residual stresses has relation to the phenomenon of crack closure. 3) The relaxing trend of residual stresses by the crack propagation was greater In case of compressive residual stress than that of tensile residual stress in the welded metal.tal.

• 한국정밀공학회지
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• 제9권3호
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• pp.140-148
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• 1992

The effect of mechanical, properties in the plastic zone near the crack-tip was investigated, under various controlled loading conditions, i.e., ${\Delta}K$ increasing, ${\Delta}K$ decreasing, and single overload test. For both ${\Delta}K$ decreasing test and ${\Delta}K$ increasing test with constant stress ratio, it is found that the ratio of material constant m'( ${\Delta}K$ decreasing test) to material constant m( ${\Delta}K$ increasing test) is larger than 1 for n<0.1, and it is equal to 1 for 0.10.2. A modified crack growth rate equation based on Forman's equation which applied stable region of fatigue crack propagation in ${\Delta}K$ decreasing test is proposed. Within the limit of this single overload test, an empirical relation between among the retardation ratio (Nd/ $N^{*}$), the strain hardening exponent (n) and the percent peak load (%PL) has been established.established.

• Journal of Nuclear Fuel Cycle and Waste Technology
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• 제1권1호
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• pp.57-63
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• 2013

Natural green rust (GR) can retard the migration of anions through geological media because it has a Layer Double Hydroxyl (LDH) structure with a positive charge. In this study, the sorption behaviors of anions such as selenite ($Se(IV)O{_3}^{2-}$), selenate ($Se(VI)O{_4}^{2-}$), and iodide ($I^-$) onto green rusts with different structures, i.e., GR($Cl^-$) and GR($CO{_3}^{2-}$), were investigated by conducting batch sorption experiments in an anoxic condition. Experimental results showed that selenite was mostly sorbed onto GR($CO{_3}^{2-}$) and then partly reduced to metal selenium, Se(0). However, little selenate and iodide was sorbed onto GR($CO{_3}^{2-}$) while some iodide was sorbed onto GR($Cl^-$). It is presumed from the experimental results that the major sorption mechanism of $SeO{_3}^{2-}$ and $I^-$ onto green rusts is the anion exchange reaction with the anions existing in the interlayer of the rusts. Green rust, therefore, can play an important role in the retardation of anions migrating through deep geological environments owing to its LDH structure with a high anion exchange capacity.