• 접착 및 계면
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• 제6권2호
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• pp.13-20
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• 2005

환경 친화적인 자연섬유 강화 고분자 복합재료의 계면 전단강도는 총체적인 기계적 물성을 조절하는데 매우 중요한 역할을 수행한다. Ramie와 Kenaf 섬유 강화 에폭시 복합재료의 계면 전단강도는 최종 물성을 위한 최적 조건을 찾아내기 위해 미세역학시험법과 비파괴 음향방출시험을 이용하여 평가했다. Ramie와 Kenaf 섬유의 동적 접촉각을 측정했고, 계면 접착에서 젖음성과 상호 관련시켜서 해석하였다. Ramie와 Kenaf 섬유의 기계적 물성은 단섬유 인장시험을 통해 조사했고, 통계학적으로 uni-와 bimodal Weibull 분포를 통해서 분석하였다. Ramie와 Kenaf 섬유에 대한 실제 신장율의 clamping 효과의 영향도 평가할 수 있었다. 두 가지의 다른 미세파괴 형상은 섬유다발과 단섬유 복합재료로부터 오는 축방향의 debonding과 섬유상의 fracture는 인장과 압축하중하에서 관찰할 수 있었다.

• BMB Reports
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• 제36권2호
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• pp.230-236
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• 2003

Hot water-soluble crude polysaccharide (HCAP-0) that was obtained from the fruits of Capsicum annuum showed potent anti-complementary activity. The activity was unchanged by pronase digestion, but decreased by periodate oxidation. The HCAP-0 was fractionated by DEAE ion-exchange chromatography to give two major fractions, HCAP-II and III. These two fractions were finally purified by gel filtration to give HCAP-IIa, HCAP-IIIa1, and IIIa2 fractions that had high anti-complementary activities. The HCAP-IIIa1 and IIIa2 consisted of homogeneous polysaccharides. The anti-complementary activities were unaffected by treatment with polymyxin B, indicating that the modes of complement activation were not due to preexisting lipopolysaccharide. The molecular weight and sugar content of HCAP-IIIa2 had potent anti-complementary activity. The highest yields were 55 kDa and 75.9%, and the molar ratio of galactose (Ara:Gal, 1.0:4.6) was higher than other sugars. The crossed immuno-electrophoresis showed that both classical and alternative pathways were activated by HCAP-IIIa2.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Geomechanics and Engineering
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• 제19권5호
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• pp.463-472
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• 2019

The mode perturbation method (MPM) is suitable and efficient for solving the eigenvalue problem of a nonuniform soil deposit whose property varies with depth. However, results of the MPM do not always converge to the exact solution, when the variation of soil deposit property is discontinuous. This discontinuity is typical because soil is usually made up of sedimentary layers of different geologic materials. Based on the energy integral of the variational principle, a new mode perturbation method, the energy-based mode perturbation method (EMPM), is proposed to address the convergence of the perturbation solution on the natural frequencies and the corresponding mode shapes and is able to find solution whether the soil properties are continuous or not. First, the variational principle is used to transform the variable coefficient differential equation into an equivalent energy integral equation. Then, the natural mode shapes of the uniform shear beam with same height and boundary conditions are used as Ritz function. The EMPM transforms the energy integral equation into a set of nonlinear algebraic equations which significantly simplifies the eigenvalue solution of the soil layer with variable properties. Finally, the accuracy and convergence of this new method are illustrated with two case study examples. Numerical results show that the EMPM is more accurate and convergent than the MPM. As for the mode shapes of the uniform shear beam included in the EMPM, the additional 8 modes of vibration are sufficient in engineering applications.

• 대한조선학회논문집
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• 제55권1호
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• pp.37-44
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• 2018

To understand the dynamic characteristics of the vessel with hydroelastic response, it is very important to estimate the dynamic modal parameters such as mode shapes, natural frequency, and damping ratio. These dynamic modal parameters of full scale ship are a priori unknowns, hence to be estimated directly based upon the full scale measurement data. In this paper, dynamic modal parameters were extracted by signal processing of acceleration and strain data measured from a large container ship whose loading capacity is 9400TEU. The mode shapes of the vibrating hull were identified using the proper orthogonal decomposition and the vibration response of hull was decomposed into its modal magnitudes. Natural frequencies of specific modes were derived via Fourier transform of these modal magnitude. Also, the free decay signal of the vibrating hull was obtained through the random decrement technique and the damping ratio was estimated with accuracy.

• 한국지진공학회논문집
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• 제11권2호
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• pp.27-38
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• 2007

노스리지 지진에 의해 손상을 받은4층 철근콘크리트조 골조건물을 대상으로 선형가진기 및 대용량의 편심가진기를 이용한 강제진동실험과 상시미진동 측정을 실시하였다. 미진동 가속도데이터 및 선형가진기에 의한 백색잡음 실험시의 가속도데이터로부터 구조물식별을 수행하여 7차모드까지의 고유진동수 및 모드감쇠비를 얻었다. 두대의 대용량 편심가진기를 사용하여 얻은 큰 진폭의 조화 진동하에서는 가속도데이터를 사용하여 각 방향 1차모드를 식별하였으며 변위계와 변형게이지를 이용하여 층간변위각, 기둥과 슬래브와 같은 구조부재의 곡률분포를 측정하였다. 각 경우 고유진동수는 진동의 크기가 클수록 낮아졌다. 즉, 편심가진기가력시 고유진동수는 상시미진동시에 비해 $70{\sim}75%$, 선형가진시가력시에 비해 $92{\sim}93%$ 정도로 낮게 나타났다. 이러한 진동수의 감소폭은 지진에 의해 큰 손상을 받았던 건물의 남북방향에서 크게 나타났다.

• 한국작물학회지
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• 제40권4호
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• pp.473-480
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• 1995

냉수처리답에서 적고현상, 간장, 수장 그리고 수수 등 각 형질에 대하여 내냉성이 강한 품종과 약한 품종을 교배하고, 그 후대에 대하여 각 형질의 유전분석을 실시하였던 바, 그 결과를 요약하면 다음과 같다. 1. 적고현상에 대하여 강한 품종과 약한 품종의 교배조합에서 강한 개체와 약한 개체의 F$_2$의 분리비가 7개 조합 중 4개 조합에서 저항성 쪽이 우성으로 3 : 1의 단성잡종분리비를 나타냈다. 2. F$_1$세대와 F$_2$집단에서 간장과 수장은 긴 쪽이 우성이고, 단축이 적게 되는 쪽으로 초우성 또는 불완전우성을 나타냈고, 수수는 많은 쪽이 우성이고, 냉수처리하에서 수수가 오히려 많아지는 쪽으로 초우성을 나타냈다. 3. 냉수답에서 간장, 수장 및 수수의 유전력은 형질 및 교배조합에 따라 다소 차이는 있으나 대체로 높았으며, 자연답보다는 냉수처리답에서 유전력이 높게 나타났다. 4. 각 형질의 잡종강세정도는 간장에서 매우 높았으며, 수장과 수수에서는 대체로 낮게 나타났다. 특히 인디카 /통일형품종의 교배조합에서, 자연답보다는 냉수처리답에서 잡종강세가 높게 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• 한국화재소방학회논문지
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• 제30권1호
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• pp.6-11
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• 2016

본 연구에서는 연기로부터 재실자의 안전을 확보하기 위해 설치되는 배연창의 개방층 설정방식에 따른 배연성능을 바람이 강한 제주지역을 대상으로 CONTAM 모델링 분석하였다. 본 연구에서 분석되어진 결과는 육지와 큰 차이를 보이는 제주도의 지형과 특정 외기온도 및 외기풍속 등, 대표적인 변수에 대한 배연창의 배연성능에 대한 평가연구로 경향성을 판단하는데 한정되어야 한다. 분석결과, 배연창의 개방이나 외부 바람의 영향은 건축물의 중성면을 상승시켜 배연창의 배연성능에 많은 영향을 초래하는 것으로 나타났다. 배연창의 개방층 설정방식에 따른 배연성능은 화재층 개방방식이 가장 우수하게 나타났으며 화재층 및 직상층 개방방식은 화재층 개방방식보다 조금 성능이 낮은 것으로 나타났다. 그러나 전 층 개방방식의 경우 배연성능이 아주 떨어져 외기의 다량 유입으로 배연성능을 전혀 기대할 수 없는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.587-596
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• 2014

A new ${\pi}$-stacked donor-acceptor (D-A) system, [Ru(1-([2,2'-bipyridine]-6-yl-methyl)-3-(2-cyclohexa-2',5'-diene-1,4-dionyl)-1H-imidazole)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (ImQ_T), has been synthesized and characterized. Similar to its precedent, [Ru(6-(2-cyclohexa-2',5'-diene-1,4-dione)-2,2':6',2"-terpyridine)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (TQ_T), this system has a cofacial alignment of terpyridine (tpy) ligand and quinonyl (Q) group, which facilitates an electron transfer through ${\pi}$-stacked manifold. Despite the presence of lowest-energy charge transfer transition from the Ru-based-HOMO-to-Q-based-LUMO (MQCT) predicted by theoretical calculations by using time-dependent density functional theory (TD-DFT), the experimental steady-state absorption spectrum does not exhibit such a band. The selective excitation to the Ru-based occupied orbitals-to-tpy-based virtual orbital MLCT state was thus possible, from which charge separation (CS) reaction occurred. The photo-induced CS and thermal charge recombination (CR) reactions were probed by using ultrafast visible-pump/mid-IR-probe (TrIR) spectroscopic method. Analysis of decay kinetics of Q and $Q^-$ state CO stretching modes as well as aromatic C=C stretching mode of tpy ligand gave time constants of <1 ps for CS, 1-3 ps for CR, and 10-20 ps for vibrational cooling processes. The electron transfer pathway was revealed to be Ru-tpy-Q rather than Ru-bpy-imidazol-Q.