• 한국구조물진단유지관리공학회 논문집
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• 제27권1호
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• pp.86-94
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• 2023

본 연구에서는 강재 슬릿댐퍼를 대상으로 하여 면외 변형을 구속할 수 있는 보완상세를 제시하고, 제안상세 적용 유무와 댐퍼의 형상비를 변수로 하여 일정진폭 가력실험을 수행하였다. 실험결과에 따라 제안상세가 적용된 슬릿댐퍼의 반복이력은 설정된 변수 범위에서 모두 안정적인 방추형의 이력거동을 나타내었으며 종국거동까지 댐퍼의 면외변형은 관찰되지 않았다. 누적변형각 분석을 통해 제안상세가 적용된 댐퍼 시스템은 대조군에 비해 월등히 큰 소성변형능력을 확보할 수 있음을 확인하였다. 이러한 구조적 효과(구속패널효과)는 슬릿댐퍼의 형상비가 작을수록 크게 나타났다. 관련 국외기준을 참고하여 제안상세 적용유무에 따른 슬릿댐퍼의 피로곡선을 작성하고 예측곡선 제시를 위한 매개변수를 도출하였다. 본 연구의 결과를 토대로 향 후 다양한 종류의 제진장치의 구조성능에 대한 정량적인 비교가 가능할 것으로 판단된다.

• 자원ㆍ환경경제연구
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• 제31권4호
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• pp.887-908
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• 2022

본 연구는 경제성장과 환경개선 효과를 실증적으로 분석하기 위해 OECD 국가의 이산화황 배출량과 온실가스 배출량, 폐기물 배출량에 대해 환경쿠즈네츠 곡선이 존재하는가를 확인하였다. 패널분석결과, 환경오염물질에 따라 환경쿠즈네츠 곡선의 형태는 다르게 나타났다. 이산화황 배출량은 상대적으로 경제성장의 초기에 정점이 나타나 대부분의 국가가 정점을 지난 역U자형 곡선이 나타나는 반면 온실가스 배출량은 정점을 지나 감소하는 단계이다. 이때 제조업 비중은 온실가스 배출량을 증가시키며, 인구밀도와 연구개발은 배출량을 유의미하게 감소시키는 것으로 분석되었다. 한편, 폐기물에 대해서는 정점을 확인할 수 있는 환경쿠즈네츠 곡선이 존재하지 않았다. 분석대상인 환경오염물질은 각각 오염처리기술, 생산공정 전환, 소비구조 전환에 따라 환경개선 효과가 발생할 수 있는 사례를 대표한다고 보았다. 따라서 본 연구에서는 경제성장과 소득수준 향상이 있더라도 모든 환경오염물질에 대한 자발적인 배출량 감소는 기대하기 어려우며 정점이 지나기 위해서는 추가적인 지구 공동의 노력이 필요하다는 것을 확인하였다. 특히 폐기물은 소득수준보다 인구밀도와 산업구조의 영향이 더 크기 때문에 배출량을 줄이고 자원순환경제를 만들기 위해서는 추가적인 정책적 노력이 필요한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제86권2호
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• pp.167-180
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• 2023

This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler's and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article's findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.

• 한국컴퓨터정보학회논문지
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• 제14권12호
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• pp.55-62
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• 2009

이 논문에서는 개체를 명확하게 분류하기 어려운 곤충 발자국 영상으로부터 개체를 인식하기 위해서 추출된 특징값 성분들의 기여도를 측정하고, 서로 관계된 기여도에 따라 가중치를 조정하는 퍼지 가중치 결정 방법을 제안한다. 곤충은 몸의 크기가 작아서 발자국은 작은 점의 형태로 나타난다. 그리고 다른 생물체의 발자국과 달리, 규칙적인 형상을 정의하기 어렵고 발자국 데이터와 구분이 분명하지 않는 노이즈와 혼재하기 때문에 개체를 판단하는데 많은 어려움이 있다. 이런 이유로 추출된 곤충 발자국 특징값은 명확하게 구분되는 특징성분 영역과 그렇지 않는 성분을 함께 가지게 된다. 이중 어떤 성분이 다른 성분과 비교하여 다른 클래스와 구분하기에 충분한 변별력을 가질 경우, 개체를 분류하도록 높은 가중치를 할당한다. 산출된 가중치는 퍼지함수에 의해서 출력신호를 결정하고 우세한 출력신호에 의해서 개체를 판단할수 있다. 제안한 기여도 퍼지 가중치 결정 방법을 이용하여 발자국영상의 인식 실험을 수행하고 실험 결과를 제시하였다.

• Steel and Composite Structures
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• 제44권5호
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• pp.707-720
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• 2022

In the present work, bending and free vibration analyses of multilayered functionally graded (FG) graphene platelet (GPL) and fiber-reinforced hybrid composite beams are carried out using the parabolic function based shear deformation theory. Parabolic variation of transverse shear stress across the thickness of beam and transverse shear stress-free conditions at top and bottom surfaces of the beam are considered, and the proposed formulation incorporates a transverse displacement field. The present theory works only with four unknowns and is computationally efficient. Hamilton's principle has been employed for deriving the governing equations. Analytical solutions are obtained for both the bending and free vibration problems in the present work considering different variations of GPLs and fibers distribution, namely, FG-X, FG-U, FG-Λ, and FG-O for beams having simply-supported boundary condition. First, the matrix is assumed to be strengthened using GPLs, and then the fibers are embedded. Multiscale modeling for material properties of functionally graded graphene platelet/fiber hybrid composites (FG-GPL/FHRC) is performed using Halpin-Tsai micromechanical model. The study reveals that the distributions of GPLs and fibers have significant impacts on the stresses, deflections, and natural frequencies of the beam. The number of layers and shape factors widely affect the behavior of FG-GPL-FHRC beams. The multilayered FG-GPL-FHRC beams turn out to be a good approximation to the FG beams without exhibiting the stress-channeling effects.

• Geomechanics and Engineering
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• 제35권4호
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• pp.449-464
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• 2023

Advanced nonlinear effective stress constitutive models are started to be frequently used in one-dimensional (1D) and two-dimensional (2D) site response analysis for assessment of porewater generation and liquefaction potential in soft soil deposits. The emphasis of this research is on the assessment of the implementation of this category of models at the element stage. Initially, the performance of a coupled porewater pressure (PWP) and constitutive models were evaluated employing a catalogue of 40 unidirectional cyclic simple shear tests with a variety of relative densities between 35% and 80% and effective vertical stresses between 40 and 80 kPa. The authors evaluated three coupled constitutive models (PDMY02, PM4SAND and PDMY03) using cyclic direct simple shear tests and for decide input parameters used in the model, procedures are recommended. The ability of the coupled model to capture dilation as strength is valuable because the studied models reasonably capture the cyclic performance noted in the experiments and should be utilized to conduct effective stress-based 1D and 2D site response analysis. Sandy soils may become softer and liquefy during earthquakes as a result of pore-water pressure (PWP) development, which may have an impact on seismic design and site response. The tested constitutive models are mathematically coupled with a cyclic strain-based PWP generation model and can capture small-strain stiffness and large-strain shear strength. Results show that there are minor discrepancies between measured and computed excess PWP ratios, indicating that the tested constitutive models provide reasonable estimations of PWP increase during cyclic shear (r_u) and the banana shape is reproduced in a proper way indicating that dilation and shear- strain behavior is well captured by the models.

• Geomechanics and Engineering
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• 제37권3호
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• pp.293-306
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• 2024

Influenced by the alternating effects of dynamic and static pressure during the mining process of close range coal seams, the surrounding rock support of cross mining roadway is difficult and the deformation mechanism is complex, which has become an important problem affecting the safe and efficient production of coal mines. The paper takes the inclined longwall mining of the 10304 working face of Zhongheng coal mine as the engineering background, analyzes the key strata fracture mechanism of the large inclined right-angle trapezoidal mining field, explores the stress distribution characteristics and transmission law of the surrounding rock of the roadway affected by the mining of the inclined coal seam, and proposes a segmented and hierarchical support method for the cross mining roadway affected by the mining of the close range coal seam group. The research results indicate that based on the derived expressions for shear and tensile fracture of key strata, the ultimate pushing distance and ultimate suspended area of a right angle trapezoidal mining area can be calculated and obtained. Within the cross mining section, along the horizontal direction of the coal wall of the working face, the peak shear stress is located near the middle of the boundary. The cracks on the floor of the cross mining roadway gradually develop in an elliptical funnel shape from the shallow to the deep. The dual coupling support system composed of active anchor rod support and passive U-shaped steel shed support proposed in this article achieves effective control of the stability of cross mining roadways, which achieves effective control of floor by coupling active support and preventive passive support to improve the strength of the surrounding rock itself. The research results are of great significance for guiding the layout, support control, and safe mining of cross mining roadways, and to some extent, can further enrich and improve the relevant theories of roof movement and control.

• Animal Bioscience
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• 제37권4_spc호
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• pp.775-785
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• 2024

Pork production is a significant agricultural enterprise in the United States and Canada. The United States is the third-largest global producer of pork and Canada ranks seventh in pork production. The North American Free Trade Agreement and its successor, the U.S.-Mexico-Canada Agreement, have facilitated trade and integration between the two countries. The majority of production systems are modern and intensive, characterized by large vertically integrated farms using advanced technologies. Both nations benefit from their status as major producers of feed grains, with the United States leading in corn and soybeans, while Canada excels in canola and barley production. The regulatory frameworks for food safety, animal welfare, and environmental stewardship differ slightly, with the FDA and USDA overseeing these aspects in the United States, and Health Canada and the Canada Food Inspection Agency in Canada. The United States and Canada also have well-established distribution networks for pork products, relying on both domestic and international markets. Export markets play a crucial role, with the United States being a major importer of Canadian pigs, and both countries exploring opportunities in Asia. Despite a rise in global demand, domestic pork consumption trends differ, with per capita consumption remaining stable in the USA and declining in Canada. Changing consumer preferences, including a demand for ethically raised and locally sourced pork, may influence production practices. Future trends in pig production include a focus on consumer concerns, sustainability, disease prevention, reduction of antimicrobial use, and advancements in technology. The industry is adapting to challenges such as disease outbreaks and changing regulations, with a strong emphasis on animal welfare. Labor and workforce considerations, along with advancements in technology and automation, are expected to shape the efficiency of pork production in the future.

• Advances in nano research
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• 제16권4호
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• pp.413-426
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• 2024

This paper investigates the dynamic behavior of a simply supported viscoelastic plate made of functionally graded carbon nanotube reinforced composite under dynamic loading. Carbon nanotubes are distributed in 5 different shapes: U, V, A, O and X, depending on the shape they form through the thickness of the plate. The displacement fields are derived in the Laplace domain using a higher-order shear deformation theory. Equations of motion are obtained through the application of the energy method and Hamilton's principle. The resulting equations of motion are solved using Navier's method. Transforming the Laplace domain displacements into the time domain involves Durbin's modified inverse Laplace transform. To validate the accuracy of the developed algorithm, a free vibration analysis is conducted for simply supported plate made of functionally graded carbon nanotube reinforced composite and compared against existing literature. Subsequently, a parametric forced vibration analysis considers the influence of various parameters: volume fractions of carbon nanotubes, their distributions, and ratios of instantaneous value to retardation time in the relaxation function, using a linear standard viscoelastic model. In the forced vibration analysis, the dynamic distributed load applied to functionally graded carbon nanotube reinforced composite viscoelastic plate is obtained in terms of double trigonometric series. The study culminates in an examination of maximum displacement, exploring the effects of different carbon nanotube distributions, volume fractions, and ratios of instantaneous value to retardation times in the relaxation function on the amplitudes of maximum displacements.

• 대한치과보철학회지
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• 제57권3호
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• pp.203-210
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• 2019

목적: 본 연구는 치과용 모형 스캐너를 이용하여 단일 전장관과 3본 고정성의치 모형을 스캔하는 과정에서 지대치의 중첩 과정이 최종 가상 모형에 미치는 영향을 알아보려 하였다. 재료 및 방법: 평가를 위해 단일 전장관과 3본 고정성의치를 위한 석고 모형을 제작하였다. 그리고 Pindex system을 이용하여 핀 작업된 모형을 제작하였다. 기준 스캔 데이터(CAD Reference Model)와 실험 스캔 데이터(CAD Test Model)를 획득하기 위해서 치과용 모형 스캐너(E1, 3Shape A/S, Copenhagen, Denmark)를 이용했다. 기준 스캔 데이터는 지대치를 분할한 후 탈착하지 않고 스캔하였다. 그리고 실험 스캔 데이터는 분할된 지대치를 분리하여 스캔 후, 기준 스캔 데이터에 중첩되었다(n = 20). 마지막으로 3차원 검사 소프트웨어(release 2018.0.0; Geomagic control X; 3D Systems)를 이용하여 root mean square (RMS)를 분석하였고, 통계 분석은 Mann-Whitney U test를 사용하였다 (${\alpha}=.05$). 결과: 단일 전장관 지대치의 RMS 평균은 $10.93{\mu}m$, 3본 고정성의치 지대치의 RMS 평균은 $6.9{\mu}m$가 나왔다. 두 그룹의 RMS 평균값은 통계적으로 유의한 차이를 보여줬다 (P < .001). 또한 두 그룹의 양(positive)과 음(negative)의 오류는 단일 전장관 지대치는 $9.83{\mu}m$, $-6.79{\mu}m$, 3본 고정성의치 지대치는 $6.22{\mu}m$, $-3.3{\mu}m$의 평균값이 나왔다. 두 그룹의 양과 음의 오류 평균값은 통계적으로 모두 3본 고정성의치 지대치가 단일 전장관 지대치보다 통계적으로 유의하게 낮은 값을 보여주었다 (P < .001). 결론: 핀 작업된 모형의 스캔 과정에서 지대치의 개수가 증가하여도 지대치의 중첩에 의한 오류는 증가하지 않았다. 또한 단일 전장관 지대치에서 유의하게 높은 오류를 보였지만 임상적으로 허용 가능한 스캔 정확도의 범위에 있다.