• 기술혁신연구
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• 제20권2호
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• pp.1-28
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• 2012

그동안 출연연은 과학기술 발전을 선도하는 핵심 역할을 담당해 왔으나 최근에는 조직의 경쟁력 문제를 포함하여 그 미션과 역할까지 새롭게 정립해야 하는 시점에 있다. 본 연구는 ETRI를 결정적인 사례로 하여 현재 출연연이 직면하고 있는 구조적 한계와 어려움을 살펴보았다. 분석 결과 출연연의 자체 변화 노력도 문제이지만 출연연이 예산, 인력, 평가 등 통제가 어려운 구조적인 문제에 봉착되어 있음을 알 수 있다. ETRI의 경우 연구개발이나 특정기술 수준에서는 추격에서 탈추격으로 넘어서고 있으나 우리나라 출연(연) 연구 환경과 실제 일하는 방식은 추격형 체제에 머물러 있는 상황이다. 추격의 대상과 수단이 어느 정도 확실했던 추격기를 넘어 어디로 가야하며 무엇을 해야 할 것인가가 불확실한 탈추격 혁신 상황에서는 출연연의 미션 및 역할, 예산 인력 평가 체계, 사업기획 체계 및 프로세스 방식 등이 새롭게 변화될 필요가 있다.

• 국제초고층학회논문집
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• 제9권4호
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• pp.377-386
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• 2020

Beginning a few decades ago, Baku, the capital city of Azerbaijan, has experienced a dramatic construction boom that is revitalizing its skyline. The expansive growth looks to uphold the historic past of Baku as a focal point within the Caspian Sea Region while also evoking aspirations for a city of the future. With superstructure complete and interiors progressing, the Ministry of Taxation (MOT) tower is the latest addition to the city, with its stacked cubes twisting above a multi-level podium at the base. Each cube is separated by column-free green roof terraces, creating unique parametric reveals of the developing surroundings. Aside from MOT's stunning shape, its geolocation resulted in unusually high wind loads coupled with high seismic hazards for a tower of its height. In addition, limitations on possible structural systems required stepping away from a typical prescriptive code-based approach into one that utilized Performance-Based Design (PBD) methods. This paper presents the numerous structural challenges and innovations that allowed the design of a new icon to be realized.

• 대한치과의사협회지
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• 제54권7호
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• pp.563-574
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• 2016

A clear overlay appliance is a type of a removable appliance made from transparent thermoplastic plastic film that covers the entire dentition to move the teeth. It is one of the most favored orthodontic methods opted for by adult patients; this treatment is esthetic, does not cause discomfort and allows oral hygiene to be easily managed when compared to other conventional fixed treatment methods. However, the use of clear overlay appliances, such as invisalign or clear aligner, is associated with various clinical challenges. In particular, the appliances require longer treatment periods compared to fixed treatment, and due to the structural characteristics of the appliances, it is difficult to make proper posterior occlusion and certain type of tooth movement, including extrusion, rotation and tip. Thus, the clear overlay appliances are regarded as supplementary appliances by most orthodontists and have been used for simple orthodontic treatments, such as partial anterior alignments or orthodontic relapse cases. Owing to the remarkable advancement in the field of 3D digital technology over a period of 15 years, the accuracy and convenience of modern clear overlay appliances have continuously improved. Moreover, orthodontic outcomes have also been greatly improved by the introduction of new materials and successful application of various biomechanical methods from conventional orthodontic treatments in the design of clear overlay appliances. This study investigates the clinical limitations that should be considered during the application of clear overlay appliances and also examines the efforts and methods used to overcome these challenges.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.193-205
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• 2020

The growing need for assuring efficient and sustainable investments in civil engineering structures has determined a renovated interest in the rational design of such structures from designers, clients and authorities. As a result, risk-informed decision-making methodologies are increasingly being used as a direct decision tool or as an upper-level layer from which performance-based approaches are then calibrated against. One of the most important and challenging aspects of today's structural design is to adequately handle the system-level effects, the known unknowns and the unknown unknowns. These aspects revolve around assessing and evaluating relevant damage scenarios, namely those involving unacceptable/intolerable damage levels. Hence, the importance of risk analysis of disproportionate collapse, and along with it of robustness. However, the way robustness has been used in modern design codes varies substantially, from simple provisions of prescriptive rules to complex risk analysis of the disproportionate collapse. As a result, implementing design for robustness is still very much a grey area and more so when it comes to defining means to quantify robustness. This paper revisits the most common robustness frameworks, highlighting their merits and limitations, and identifies one among them which is very promising as a way forward to solve the still open challenges.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.75-84
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• 2020

Modular construction is a construction method whereby prefabricated volumetric units are produced in a factory and are installed on site to form a building block. The construction productivity can be substantially improved by the manufacturing and assembly of standardized modular units. 3D printing is a computer-controlled fabrication method first adopted in the manufacturing industry and was utilized for the automated construction of small-scale houses in recent years. Implementing 3D printing in the fabrication of modular units brings huge benefits to modular construction, including increased customization, lower material waste, and reduced labor work. Such implementation also benefits the large-scale and wider adoption of 3D printing in engineering practice. However, a critical issue for 3D printed modules is the loading capacity, particularly in response to horizontal forces like wind load, which requires a deeper understanding of the building structure behavior and the design of load-bearing modules. Therefore, this paper presents the state-of-the-art literature concerning recent achievement in 3D printing for buildings, followed by discussion on the opportunities and challenges for examining 3D printing in modular construction. Promising 3D printing techniques are critically reviewed and discussed with regard to their advantages and limitations in construction. The appropriate structural form needs to be determined at the design stage, taking into consideration the overall building structural behavior, site environmental conditions (e.g., wind), and load-carrying capacity of the 3D printed modules. Detailed finite element modelling of the entire modular buildings needs to be conducted to verify the structural performance, considering the code-stipulated lateral drift, strength criteria, and other design requirements. Moreover, integration of building information modelling (BIM) method is beneficial for generating the material and geometric details of the 3D printed modules, which can then be utilized for the fabrication.

• 한국전산구조공학회논문집
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• 제35권2호
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• pp.65-71
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• 2022

최근에는 경량화 문제에 대한 합리적인 솔루션을 제공하고 유용한 개념설계를 제공할 수 있는 다중 재료 구조 위상최적화가 더욱 중요해지고 있다. 기존의 MMTO(Multi-Material Topology Optimization)의 경우 후보 물질의 수가 증가할수록 설계변수의 수도 증가하고, 결과적으로 계산 시간이 크게 증가한다. 따라서 PSM(Phase Section Method)과 같은 단일 설계변수를 갖는 MMTO가 제안되었다. 본 연구는 조성비가 면적이나 부피비를 나타내지 못하고, 설계변수가 목표치에 충분히 집중되지 않고, 특정 재료가 요구량보다 적게 생성되는 PSM의 세 가지 주요 제한점을 고려하여 이를 개선하는데 중점을 둔다. 이러한 한계를 극복하기 위해 재정의된 조성비와 더 나은 수렴을 위한 조정된 매개변수를 제안한다. 제안된 수정 사항의 유효성을 2차원 및 3차원 수치 예제를 통해 검증한다.

• Computers and Concrete
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• 제33권4호
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• pp.341-348
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• 2024

Ultra-high-performance concrete (UHPC) has received remarkable attentions in civil infrastructure due to its unique mechanical characteristics and durability. UHPC gains increasingly dominant in essential structural elements, while its unique properties pose challenges for traditional inspection methods, as damage may not always manifest visibly on the surface. As such, the need for robust inspection techniques for detecting cracks in UHPC members has become imperative as traditional methods often fall short in providing comprehensive and timely evaluations. In the era of artificial intelligence, computer vision has gained considerable interest as a powerful tool to enhance infrastructure condition assessment with image and video data collected from sensors, cameras, and unmanned aerial vehicles. This paper presents a computer vision-based approach employing deep learning to detect cracks in UHPC beams, with the aim of addressing the inherent limitations of traditional inspection methods. This work leverages computer vision to discern intricate patterns and anomalies. Particularly, a convolutional neural network architecture employing transfer learning is adopted to identify the presence of cracks in the beams. The proposed approach is evaluated with image data collected from full-scale experiments conducted on UHPC beams subjected to flexural and shear loadings. The results of this study indicate the applicability of computer vision and deep learning as intelligent methods to detect major and minor cracks and recognize various damage mechanisms in UHPC members with better efficiency compared to conventional monitoring methods. Findings from this work pave the way for the development of autonomous infrastructure health monitoring and condition assessment, ensuring early detection in response to evolving structural challenges. By leveraging computer vision, this paper contributes to usher in a new era of effectiveness in autonomous crack detection, enhancing the resilience and sustainability of UHPC civil infrastructure.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.251-258
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• 2018

This work illustrates the progress of a TAS activity at exploring the challenges and the benefits of the Virtual Shaker Testing (VST) approach. The definition and the validation of new computational methodologies with respect to the state of the art were encouraged throughout this activity. The shaker Finite Element (FE) model in lateral configuration was built for the purpose and it was merged with the SpaceCraft (S/C) FE model, together with the S/C-Shaker adapter. FE matrices were reduced through the Craig-Bampton method. The VST transient analysis was performed in MATLAB(R) numerical computing environment. The closed-loop vibration control is accounted for and the solution is obtained through the fourth-order Runge Kutta method. The use of pre-existing built-in functions was limited by authors with the aim of tracing the impact of all the problems' parameters in the solution. Assumptions and limitations of the proposed methodology are detailed throughout this paper. Some preliminary results pertaining to the current progress of the activity are thus illustrated before the conclusions.

• Structural Engineering and Mechanics
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• 제90권4호
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• pp.417-428
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• 2024

Nanocomposite-reinforced concrete systems have gained increasing attention in bridge construction due to their enhanced mechanical properties and durability. Understanding the transient dynamics of these advanced materials is crucial for ensuring the structural integrity and performance of bridge infrastructure under dynamic loading conditions. This paper presents a comprehensive study of the measurement techniques employed for assessing the transient dynamics of nanocompositereinforced concrete systems in bridge construction applications. A numerical method, including modal analysis are discussed in detail, highlighting their advantages, limitations, and applications. Additionally, recent advancements in sensor technologies, data acquisition systems, and signal processing techniques for capturing and analyzing transient responses are explored. The paper also addresses challenges and opportunities in the measurement of transient dynamics, such as the characterization of nanocomposite-reinforced concrete materials, the development of accurate numerical models, and the integration of advanced sensing technologies into bridge monitoring systems. Through a critical review of existing literature and case studies, this paper aims to provide insights into best practices and future directions for the measurement of transient dynamics in nanocompositereinforced concrete systems, ultimately contributing to the design, construction, and maintenance of resilient and sustainable bridge infrastructure.

• BioChip Journal
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• 제12권4호
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• pp.268-279
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• 2018

Flower-shaped organic-inorganic hybrid nanostructures, termed nanoflowers, have received considerable recent attention as they possess greatly enhanced activity, stability, durability, and even selectivity of entrapped organic biomolecules, which are much better than those from the conventional methods. They can be synthesized simply via co-incubation of organic and inorganic components in aqueous buffer at room temperature and yield hierarchical nanostructures with large surface-to-volume ratios, allowing for low-cost production by easy scale-up, as well as the high loading capacity of biomolecules without severe mass transfer limitations. Since a pioneering study reported on hybrid nanoflowers prepared with protein and copper sulfate, many other organic and inorganic components, which endow nanoflowers with diverse functionalities, have been employed. Thanks to these features, they have been applied in a diverse range of areas, including biosensors and biocatalysis. To highlight the progress of research on organic-inorganic hybrid nanoflowers, this review discusses their synthetic methods and mechanisms, structural and biological characteristics, as well as recent representative applications. Current challenges and future directions toward the design and development of multi-functional nanoflowers for their widespread utilization in biotechnology are also discussed.