• Computers and Concrete
• /
• 제33권3호
• /
• pp.325-340
• /
• 2024

The growing demands for sustainable and high-performance construction materials necessitate a deep understanding of their physicochemical properties by that of these heterogeneities. This paper presents a comprehensive review of the state-of-the-art hierarchical multiscale modeling approach aimed at predicting the intricate physicochemical characteristics of construction materials. Emphasizing the heterogeneity inherent in these materials, the review briefly introduces single-scale analyses, including the ab initio method, molecular dynamics, and micromechanics, through a scale-bridging technique. Herein, the limitations of these models are also overviewed by that of effectively scale-bridging methods of length or time scales. The hierarchical multiscale model demonstrates these physicochemical properties considering chemical reactions, material defects from nano to macro scale, microscopic properties, and their influence on macroscopic events. Thereby, hierarchical multiscale modeling can facilitate the efficient design and development of next-generation construction.

• Journal of Pharmaceutical Investigation
• /
• 제35권3호
• /
• pp.143-150
• /
• 2005

Solid lipid nanoparticles(SLNs) are particulate systems for parenteral drug administration and have good biocompatibility and stability. SLNs were prepared with lauric acid, as the lipid core. Tween 20 and tween 80 were used as surfactant. 5-fluorouracil and l-benzoyl-5-fluorouracil were used as model drugs. Drug-loaded SLNs were prepared by the hot homogenization technique in order to evaluate the physical stability, entrapment efficiency of drugs as well as release profile. The particle size of SLNs was $40{\sim}600$ nm. By increasing speed, the mean particle size of SLNs was decreased. And entrapment efficiency in the case of using 1-Benzoyl-5-fluorouracil was higher than using 5-Fluorouracil. The higher surfactant concentration, the faster release rate at the range of $1.5{\sim}2.5%$.

• Structural Engineering and Mechanics
• /
• 제61권2호
• /
• pp.209-220
• /
• 2017

The purpose of this paper is to study the geometrically nonlinear free vibration of functionally graded nano/micro beams (FGNBs) based on the modified couple stress theory. For practical applications, some analytical expressions of nonlinear frequencies for FGNBs on a nonlinear Pasternak foundation are developed. Hamilton's principle is employed to obtain nonlinear governing differential equations in the context of both Euler-Bernoulli and Timoshenko beam theories for a comprehensive investigation. The modified continuum theory contains one material length scale parameter to capture the size effect. The variation of two-constituent material along the thickness is modeled using Reddy's power-law. Also, the Mori-Tanaka method as an accurate homogenization technique is implemented to estimate the effective material properties of the FGNBs. The results are presented for both hinged-hinged and clamped-clamped boundary conditions. The nonlinear partial differential equations are reduced to ordinary differential equations using Galerkin method and then the powerful method of homotopy analysis is utilized to obtain the semi-analytical solutions. Eventually, the presented analytical expressions are used to examine the influences of the length scale parameter, material gradient index, and elastic foundation on the nonlinear free vibration of FGNBs.

• 해양환경안전학회지
• /
• 제19권5호
• /
• pp.545-551
• /
• 2013

본 연구에서는 내식성이 우수한 동합금에 대하여 내구성 향상을 위해 쇼트피닝 시간을 변수로 표면 개질하여 전기화학적 특성과 조직 변화를 관찰하였다. 그 결과 쇼트피닝 후 표면에 전체적으로 요철이 발생하였으며, 시간이 증가할수록 커버리지 향상에 따른 균질화 현상이 관찰되었다. 또한 쇼트피닝된 모든 시험편에서 경도가 향상되었으며, 쇼트피닝 시간이 3.5분일 때 52 %의 경도향상을 나타냈다. 그리고 이때 전기화학적 특성은 쇼트피닝을 실시하지 않은 경우와 유사하였다.

• 농업생명과학연구
• /
• 제44권5호
• /
• pp.75-79
• /
• 2010

사과는 전 세계적으로 대표적 과수의 하나로서 우량 사과의 생산을 위하여 신속하고 경제적이며 정확한 사과바이러스 진단이 요구되고 있다. RT-PCR은 사과바이러스 진단을 위한 중요한 기술로서 우선 시료조직의 분쇄 및 균질화를 통한 양질의 RNA 추출이 필수적이다. 그러나 분쇄작업은 다량의 시료의 경우 많은 시간과 노동이 요구된다. 본 연구에서는 조직 분쇄과정이 없이 단순 가열에 의한 RNA 추출을 시도하였으며 줄기조직이 잎조직보다 약간 더 적합함을 보여주었다. 그러나 RT-PCR에 의한 사과바이러스 진단에서는 모두 동일한 결과를 나타냈다. 이로써 사과 조직에 대한 단순가열로써 매우 간편하게 양질의 RNA추출이 가능함을 제시하였다.

• Steel and Composite Structures
• /
• 제43권1호
• /
• pp.1-17
• /
• 2022

The free and forced nonlinear dynamic behaviors of Porous Functionally Graded Material (PFGM) plates are examined by means of a High-Order Implicit Algorithm (HOIA). The formulation is developed using the Third-order Shear Deformation Theory (TSDT). Unlike previous works, the formulation is written without resorting to any homogenization technique neither rule of mixture nor considering FGM as a laminated composite, and the distribution of the porosity is assumed to be gradually variable through the thickness of the PFGM plates. Using the Hamilton principle, we establish the governing equations of motion. The Finite Element Method (FEM) is used to compute approximations of the resulting equations; FEM is adopted using a four-node quadrilateral finite element with seven Degrees Of Freedom (DOF) per node. Nonlinear equations are solved by a HOIA. The accuracy and the performance of the proposed approach are verified by presenting comparisons with literature results for vibration natural frequencies and dynamic response of PFGM plates under external loading. The influences of porosity volume fraction, porosity distribution, slenderness ratio and other parameters on the vibrations of PFGM plate are explored. The results demonstrate the significant impact of different physical and geometrical parameters on the vibration behavior of the PFGM plate.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.89-104
• /
• 2023

This work presents a proposal for employing reduced numerical integration in the formulation of the 4-node quadrilateral solid finite element. The use of these low-order integration rules leads to numerical instabilities such as those producing the hourglass effect. The proposed procedure allows evaluating a given constitutive model only in one integration point, achieving an attractive computational cost reduction and, also, successfully controls the hourglass effect. A validation of the proposal is included and discussed throughout the paper. To show the efficiency of the proposal, several application examples of masonry structures are studied and discussed. To represent the non-linear mechanical behaviour of masonry a plastic-damage model is implemented within the application of this sub-integration scheme. Also, in order to have a full and computationally efficient strategy to determine the behaviour of masonry structures, involving its evolution to collapse, a homogenization technique with a macro-modeling approach is used. The methodology discussed throughout this paper demonstrates a substantial computational cost reduction and an improved approximation of the non-linear problem evidenced by a reduction of up to 85% of the computational time for some cases.

• Journal of Microbiology and Biotechnology
• /
• 제33권4호
• /
• pp.419-429
• /
• 2023

Ultraviolet C (UV-C, 200-280 nm) light has germicidal properties that inactivate a wide range of pathogenic and spoilage microorganisms. UV-C has been extensively studied as an alternative to thermal decontamination of fruit juices. Recent studies suggest that the efficacy of UV-C irradiation in reducing microorganisms in fruit juices is greatly dependent on the characteristics of the target microorganisms, juice matrices, and parameters of the UV-C treatment procedure, such as equipment and processing. Based on evidence from recent studies, this review describes how the characteristics of target microorganisms (e.g., type of microorganism/strain, acid adaptation, physiological states, single/composite inoculum, spore, etc.) and fruit juice matrices (e.g., UV absorbance, UV transmittance, turbidity, soluble solid content, pH, color, etc.) affect the efficacy of UV-C. We also discuss the influences on UV-C treatment efficacy of parameters, including UV-C light source, reactor conditions (e.g., continuous/batch, size, thickness, volume, diameter, outer case, configuration/arrangement), pumping/flow system conditions (e.g., sample flow rate and pattern, sample residence time, number of cycles), homogenization conditions (e.g., continuous flow/recirculation, stirring, mixing), and cleaning capability of the reactor. The collective facts indicate the immense potential of UV-C irradiation in the fruit juice industry. Existing drawbacks need to be addressed in future studies before the technique is applicable at the industrial scale.

• Geomechanics and Engineering
• /
• 제38권3호
• /
• pp.261-273
• /
• 2024

This study presents a groundbreaking analytical approach to find an exact solution for the bearing capacity of strip footings on reinforced slopes, utilizing the two-phase approach and slip line method. The two-phase approach is considered as a generalized homogenization technique. The slip line method is leveraged to derive the stress field as a lower bound solution and the velocity field as an upper bound solution, thereby facilitating the attainment of an exact solution. The key finding points out the variation of the bearing capacity factor N_γ with influencing factors including the backfill soil friction angle, the footing setback distance from the slope crest edge, slope angle, strength, and volumetric fraction of inclusion layers. The results are evaluated by comparing them with those of relevant studies in the literature considering analytical and experimental studies. Through the application of the two-phase approach, it becomes feasible to determine the tensile loads mobilized along the inclusion layers associated with the failure zone. It is attempted to demonstrate the results by utilizing non-dimensional graphs to clearly illustrate variable impacts on reinforced soil stability. This research contributes significantly to advancing geotechnical engineering practices, specifically in the realm of static design considerations for reinforced soil structures.

• 한국지반공학회논문집
• /
• 제19권6호
• /
• pp.245-259
• /
• 2003

본 논문은 강관 다단 그라우팅 터널 보강에 대한 메카니즘 규명에 대한 연구이다. 본 보강공법을 구성하고 있는 보강요소들의 복잡한 기하학적 특성과 각 보강요소들이 전체 보강 메카니즘에 기여하는 정도의 불명확성에 기인하여 본 공법으로 보강된 터널을 합리적으로 해석하기란 무척 어려운 문제로 여겨지고 있다. 따라서 본 연구에서는 균질화 기법을 도입하여 본 공법으로 보강된 지반매질을 하나의 복합체로써 정의하고 수치 모델화하여, 이를 기반으로 3차원 탄소성 유한요소코드를 개발하였다. 이때 균질화 기법과 연계된 굴착단계별 해석 등과 같은 터널해석을 위해 요구되는 다양한 실용적인 알고리즘들 또한 제안되었다. 이러한 과정으로 개발된 3차원 탄소성 유한요소코드를 이용하여 본 보강공법의 이방성 보강 메카니즘에 관하여 고찰되었으며, 이를 위해 다양한 주요 설계인자들에 대한 매개변수 연구가 수행되었다. 이를 통해 유도된 복합 보강 지반체의 역학적 거동특성은 각 구성 매질들의 기하학적 특성과 기여도 등을 잘 모사하고 있는 것으로 판단되었다.