• International Journal of CAD/CAM
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• 제8권1호
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• pp.1-10
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• 2009

This paper presents a topology optimization approach using element-free Galerkin method (EFGM) for the optimal design of compliant mechanisms with geometrically non-linearity. Meshless method has an advantage over the finite element method(FEM) because it is more capable of handling large deformation resulted from geometrical nonlinearity. Therefore, in this paper, EFGM is employed to discretize the governing equations and the bulk density field. The sensitivity analysis of the optimization problem is performed by incorporating the adjoint approach with the meshless method. The Lagrange multipliers method adjusted for imposition of both the concentrated and continuous essential boundary conditions in the EFGM is proposed in details. The optimization mathematical formulation is developed to convert the multi-criteria problem to an equivalent single-objective problem. The popularly applied interpolation scheme, solid isotropic material with penalization (SIMP), is used to indicate the dependence of material property upon on pseudo densities discretized to the integration points. A well studied numerical example has been applied to demonstrate the proposed approach works very well and the non-linear EFGM can obtain the better topologies than the linear EFGM to design large-displacement compliant mechanisms.

• The Korean Journal of Ecology
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• 제21권5_1호
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• pp.435-448
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• 1998

The phytosociological investigation was carried out at 32 sites of the riparian vegetation in Musim-Chon stream passed through Choengju-City, Chungcheongbuk-Province by Braun-Blanquet's method from August to October, 1997. The flora of vascular plants in this survey was 202 species. The riparian vegetation was classified into 25 communities as follows. The submerged hydrophytes are Potomogeton malaianus var. latifolius community, Potomogeton crispus community, Myriophyllum verticillatum community-Hydrilla verticillata community and Ceratophyllum demersum community. The floating-leaved hydrophyte is Trapa japonica community. The emerged hydrophytes are Phragmites communis community, Perzicaria thunbergii community, Phragmites japonica community, Oenanthe javanica community, Zizania latifolia community and Persicaria hydropiper community. The herbaceous vegetation of floodplain are Artemisia montana community, Humulus japonicus community, Miscanthus sacchariflorus community, Erigeron anmus community, Impatiens balsamina community, Bidens frondosa community, Setaria viridis community, Ambrosia artemisiifolia var. elatior community and Eragrostis ferruginea community. The woody vegetation of floodplain are Robinia pseudo-acacia community, Stephanandra incisa community and Clematis apiifolia community. The species diversity was low in the upper and down stream, while the diversity was high in the mid stream situated at the center of Choengju-City because of frequent disturbance by citizens. These results suggested that distribution of communities and species diversity was closely related to the disturbance.

• 한국통신학회논문지
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• 제36권10B호
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• pp.1216-1221
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• 2011

본 논문은 코드 분할 다중방식을 이용하여 외부로부터 선박에 가해지는 변형 및 온도 변화를 모니터링 할 수 있는 광섬유 브라그 격자 (FBG) 기반의 센서 네트워크를 제안하였다. 선박에 변형이 발생 하거나 온도의 변화가 일어날 때 FBG는 본래 가지고 있는 중심 파장이 이동하며 이는 외부 변형 크기에 비례하여 증가된다. 중심파장의 변화량을 측정함으로써 센서에 가해지는 변형이나 온도의 크기를 알 수 있다. 제안된 센서 네트워크는 코드분할 다중방식을 이용하였으며 광원에서 발생되는 신호를 직접 변조하여, 변조된 신호를 센서로 보내고 센서로부터 돌아오는 신호를 검출하여 상태를 모니터링하게 된다. 또한 슬라이딩 자기상관 기법과, 파장-시간 변환 기법을 이용하여 빠른 센싱과 넓은 범위의 센싱이 가능하도록 하였다.

• 대한기계학회논문집B
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• 제32권8호
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• pp.636-644
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• 2008

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

• Environmental Engineering Research
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• 제18권1호
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• pp.45-53
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• 2013

Biocarrier beads with dead biomass, Bacillus drentensis, immobilized in polymer polysulfone were synthesized to remove heavy metals from wastewater. To identify the sorption mechanisms and theoretical nature of underlying processes, a series of batch experiments were carried out to quantify the biosorption of Pb(II) and Cu(II) by the biocarrier beads. The parameters obtained from the thermodynamic analysis revealed that the biosorption of Pb(II) and Cu(II) by biomass immobilized in biocarrier beads was a spontaneous, irreversible, and physically-occurring adsorption phenomenon. Comparing batch experimental data to various adsorption isotherms confirmed that Koble-Corrigan and Langmuir isotherms well represented the biosorption equilibrium and the system likely occurred through monolayer sorption onto a homogeneous surface. The maximum adsorption capacities of the biocarrier beads for Pb(II) and Cu(II) were calculated as 0.3332 and 0.5598 mg/g, respectively. For the entire biosorption process, pseudo-second-order and Ritchie second-order kinetic models were observed to provide better descriptions for the biosorption kinetic data. Application of the intra-particle diffusion model showed that the intraparticle diffusion was not the rate-limiting step for the biosorption phenomena. Overall, the dead biomass immobilized in polysulfone biocarrier beads effectively removed metal ions and could be applied as a biosorbent in wastewater treatment.

• Bulletin of the Korean Chemical Society
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• 제18권10호
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• pp.1050-1052
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• 1997

The complexes M(CO)4-1,2-(PPh2)2-1,2-C2B10H10 (M=Cr 2a, Mo 2b, W 2c) have been prepared in good yields from readily available bis-diphenylphosphino-o-carboranyl ligand, closo-1,2-(PPh2)2-1,2-C2B10H10 (1), by direct reaction with Group Ⅵ metal carbonyls. The infrared spectra of the complexes indicate that there is an octahedral disposition of chelate bis-diphenylphosphino-o-carboranyl ligand around the metal atom. The crystal structure of 2a was determined by X-ray diffraction. Complex 2a crystallizes in the monoclinic space group P21/n with cell parameters a = 12.2360(7), b = 17.156(1), c = 16.2040(6) Å, V = 3354.1(3) Å3, and Z =4. Of the reflections measured a total of 2514 unique reflections with F2 > 3σ(F2) was used during subsequent structure refinement. Refinement converged to R1 = 0.066 and R2 = 0.071. Structural studies showed that the chromium atom had a slightly distorted pseudo-octahedral configuration about the metal center with two phosphine groups of o-carborane occupying the equatorial plane cis-orientation to each other. These metal carbonyl complexes are rapidly converted to the corresponding metal carbene complexes, [(CO)3M=C(OCH3)(CH3)]-1,2-(PPh2)2-1,2-C2B10H10 (M= Cr 3a, Mo 3b, W 3c), via alkylation with methyllithium followed by O-methylation with CF3SO3CH3.

• Bulletin of the Korean Chemical Society
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• 제16권7호
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• pp.634-641
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• 1995

The metal-carbon σ-bond cluster complexes 1-Mn(CO)5-2-R-1,2-C2B10H10 (R=CH3 Ia, C6H5 Ib) have been prepared in good yields from readily available carboranyl lithium complexes, 1-Li+-2-R-1,2-C2B10H10- (R=CH3, C6H5), by direct reaction with (CO)5MnBr. These manganese metal complexes are rapidly converted to the corresponding manganese metal carbene complexes, 1-[(CO)4Mn=C(OCH3)(CH3)]-2-R-1,2-C2B10H10 (R=CH3 IIIa, C6H5 IIIb), via alkylation with methyllithium followed by O-methylation with CF3SO3CH3. The crystal structure of IIIb was determined by X-ray diffraction. Thus, complex IIIb crystallizes in the orthorhombic space group P212121 with cell parameters a=15.5537(5), b=19.0697(5), c=7.4286(3) Å, V=2203.4(1) Å3, and Z=4. Of the reflections measured a total of 3805 unique reflections with F2>3σ(F2) was used during subsequent structure refinement. Refinement converged to R1=0.053 and R2=0.091. Structural studies showed that the manganese atom had a slightly distorted pseudo-octahedral configuration about the metal center with the carbene and ortho-carborane occupying the equatorial plane cis-orientation to each other.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.113-116
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• 2008

액체추력기 인젝터로부터 발생하는 분무의 분열과 확산거동을 파악하기 위해 이중모드 위상도플러속도계(DPDA)를 사용하여 분무액적의 준3차원적 공간분포를 계측하고 도시한다. 분무는 27.6 bar의 분사압력 조건에서 길이-직경비가 1.67인 노즐 오리피스로부터 지면에 수직으로 분사된다. 분무액적의 수직 및 수평방향 평균속도, AMD, SMD, 그리고 부피플럭스는 분무의 상류/중심에서 하류/외곽으로 이동함에 따라 분무분열에 의해 그 크기가 감소한다.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.549-561
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• 2012

Many building foundations are embedded, however it is not easy to compact the backfill around the foundation especially for the deeply embedded ones. The soil condition around the embedded foundation may affect the seismic response of a building due to the weak contact between the soil and the foundation. In this paper, the response accelerations in the short-period range and at the period of 1 second (in the long-period range) for a seismic design spectrum specified in the IBC design code were compared considering perfect and poor backfills to investigate the effect of backfill compaction around the embedded foundation. An in-house finite-element software (P3DASS) which has the capability of horizontal pseudo-3D seismic analysis with linear soil layers was used to perform the seismic analyses of the structure-soil system with an embedded foundation. Seismic analyses were carried out with 7 bedrock earthquake records provided by the Pacific Earthquake Engineering Research Center (PEER), scaling the peak ground accelerations to 0.1 g. The results indicate that the poor backfill is not detrimental to the seismic response of a building, if the foundation is not embedded deeply in the soft soil. However, it is necessary to perform the seismic analysis for the structure-soil system embedded deeply in the soft soil to check the seismic resonance due to the soft soil layer beneath the foundation, and to compact the backfill as well as possible.

• 대한두개안면성형외과학회지
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• 제22권3호
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• pp.168-172
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• 2021

Posttraumatic pseudoaneurysm of the face is caused by blunt, penetrating, or surgical trauma. Although its incidence is low, pseudoaneurysm rupture can cause a life-threatening, massive hemorrhage. A 48-year-old man visited our emergency center due to a fall-down accident. Three-dimensional computed tomography (CT) showed a comminuted zygomaticomaxillary complex fracture of the left face. After open reduction and internal fixation, the surgical wound healed without any complications. However, the patient was readmitted 10 days after surgery due to pus-like discharge from the wound. Contrast-enhanced CT to find the abscess unexpectedly revealed a pseudoaneurysm in the left retromaxillary area. Massive oral bleeding occurred on the night of re-hospitalization and emergency surgery was done. The bleeding site was identified as a pseudo-aneurysmal rupture of the posterior superior alveolar artery in the retromaxillary area. Hemostasis was achieved by packing Vaseline gauze in the maxillary sinus using an endoscope. Delayed rupture and massive bleeding of posttraumatic retromaxillary pseudoaneurysm after a zygomaticomaxillary fracture is a low-probability, but high-impact event. Therefore, additional contrast-enhanced CT should be considered to evaluate the possibility of a posttraumatic pseudoaneurysm in cases of severe comminuted zygomaticomaxillary fracture.