• Smart Structures and Systems
• /
• 제29권1호
• /
• pp.153-166
• /
• 2022

Identifying fine cracks in steel bridge facilities is a challenging task of structural health monitoring (SHM). This study proposed an end-to-end crack image segmentation framework based on a one-step Convolutional Neural Network (CNN) for pixel-level object recognition with high accuracy. To particularly address the challenges arising from small object detection in complex background, efforts were made in loss function selection aiming at sample imbalance and module modification in order to improve the generalization ability on complicated images. Specifically, loss functions were compared among alternatives including the Binary Cross Entropy (BCE), Focal, Tversky and Dice loss, with the last three specialized for biased sample distribution. Structural modifications with dilated convolution, Spatial Pyramid Pooling (SPP) and Feature Pyramid Network (FPN) were also performed to form a new backbone termed CrackDet. Models of various loss functions and feature extraction modules were trained on crack images and tested on full-scale images collected on steel box girders. The CNN model incorporated the classic U-Net as its backbone, and Dice loss as its loss function achieved the highest mean Intersection-over-Union (mIoU) of 0.7571 on full-scale pictures. In contrast, the best performance on cropped crack images was achieved by integrating CrackDet with Dice loss at a mIoU of 0.7670.

• 전자공학회논문지
• /
• 제49권11호
• /
• pp.64-73
• /
• 2012

본 논문에서는 동일한 동영상을 검출하기 위한 방법을 제안한다. 제안하는 방법은 시공간 그룹특징 핑거프린팅이다. 동영상의 프레임은 고정된 비율 방법으로 추출되며, 수직그룹과 수평그룹으로 나눠진다. 서술자는 각 그룹특징을 이진화 핑거프린팅으로 추출하여 만든다. 그 다음 원본 동영상의 서술자로 두 종류의 핑거프린팅 데이터베이스를 구축하여 질의 동영상과 정합한다. 효율적이고 효과적인 동영상 복사 검색을 하기 위해 높은 강인성, 독립성, 정합 속도를 가져야 한다. 제안한 방법에선 그룹특징으로 동영상의 다양한 변형에 높은 강인성과 독립성을 가지게 된다. 구축된 원본 핑거프린팅 데이터베이스는 질의 동영상과의 고속 정합을 가능하게 해준다. 제안한 방법은 기존 방법들과 비교했을 때 다양한 변형에서 뛰어난 성능향상을 보였다. 특히, 속도 향상에 매우 뛰어난 성능을 가져온 것이 본 논문의 큰 장점이라 할 수 있다.

• 항공우주정책ㆍ법학회지
• /
• 제7권
• /
• pp.151-175
• /
• 1995

In recent years, questions have arisen under several forms with respect to the need for adapting present legal order established under the Chicago Convention and relevant customary rules into newly developed environment surrounding the international air transport industry. Major feature of such trends included in opinions for modification of the present legal order might be defined as more liberalistic approach to this industry. In this respect, many scholars and lawyers in this field agree with a view that a theoretical tie between an aircraft/air liners and a register - State lies in political and strategical concern of the State so that each aircraft/air liners has been attributed a single nationality. In the context of such concern, each aircraft/air liners has been related with each register-State in the form of "genuine connection". However, present and near future development of air transport industry and its world - wide market requires some modification of such single nationality regime. Taking into account such circumstances, States as creator of present legal order are in the process of establishing new legal order where air liners with multi - nationality are capable of satisfying to such needs. As adopting a series of liberalization package for air transport industry in european continent, European Union adopts a concept of "community air carrier", by which an air space of each member State is open to each other, especially through the grant of cabotage right. A serious concern may arise in such grant because the Article 7 of the Chicago Convention prohibits such grant on an exclusive basis. While many theoretical opinions have been put forward concerning the interpretation of that article, a case of European Union shall be a good test of the range of its application. It is anticipated that future development around this issue shaH furnish us a major feature of the liberalization of international air transportation and an adaptation process of present legal order.

• Journal of Computational Design and Engineering
• /
• 제3권2호
• /
• pp.161-177
• /
• 2016

In history based parametric CAD modeling systems, persistent identification of the topological entities after design modification is mandatory to keep the design intent by recording model creation history and modification history. Persistent identification of geometric and topological entities is necessary in the product design phase as well as in the re-evaluation stage. For the identification, entities should be named first according to the methodology which will be applicable for all the entities unconditionally. After successive feature operations on a part body, topology based persistent identification mechanism generates ambiguity problem that usually stems from topology splitting and topology merging. Solving the ambiguity problem needs a complex method which is a combination of topology and geometry. Topology is used to assign the basic name to the entities. And geometry is used for the ambiguity solving between the entities. In the macro parametrics approach of iCAD lab of KAIST a topology based persistent identification mechanism is applied which will solve the ambiguity problem arising from topology splitting and also in case of topology merging. Here, a method is proposed where no geometry comparison is necessary for topology merging. The present research is focused on the enhancement of the persistent identification schema for the support of ambiguity problem especially of topology splitting problem and topology merging problem. It also focused on basic naming of pattern features.

• Transactions on Electrical and Electronic Materials
• /
• 제10권6호
• /
• pp.193-195
• /
• 2009

This paper aims to develop a low gate source voltage ($V_{gs}$) N-LDMOS element that is fully operational at a CMOS Logic Gate voltage (3.3 or 5 V) realized using the 0.35 μm BCDMOS process. The basic structure of the N-LDMOS element presented here has a Low $V_{gs}$ LDMOS structure to which the thickness of a logic gate oxide is applied. Additional modification has been carried out in order to obtain features of an improved breakdown voltage and a specific on resistance ($R_{sp}$). A N-LDMOS element can be developed with improved features of breakdown voltage and specific on resistance, which is an important criterion for power elements by means of using a proper structure and appropriate process modification. In this paper, the structure has been made to withstand the excessive electrical field on the drain side by applying the double gate oxide structure to the channel area, to improve the specific on resistance in addition to providing a sufficient breakdown voltage margin. It is shown that the resulting modified N-LDMOS structure with the feature of the specific on resistance is improved by 31%, and so it is expected that optimized power efficiencies and the size-effectiveness can be obtained.

• The International Journal of Costume Culture
• /
• 제3권2호
• /
• pp.161-174
• /
• 2000

Today's advanced transport and mass media enables people to access easily and frequently to traditional costumes from different countries in the world. Consequently, fashion designers who are fascinated by the variety and beauty of traditional costumes, tend to adapt them to modern fashion design. The continuous study of traditional costumes at such time contains a meaning as a source of inspiration for the creation of a new fashion design. Therefore, among various costumes of the world, this study will focus on the costume of Palestine, that is situated at the crossroads of Europe, Asia and Afria and has exchanged various historical cultures with other cultural regions. It, especially, expects to provide a unique idea in the material modification field of today's fashion design by examining mainly the embroidery ornament which is the most distinctive feature of Palestinian costume. The conclusion was revealed that Palestinian women's costume largely consists of embroidered silk and cotton garments with a V-slitted square panel (gabeh) attached to the chest part. And a variety of luxurious embroidery was employed to emphasize different parts of the dress. These embroideries differ from area to area. Especially the embroidery from Bethlehem was well-known in many places and influenced those of other regions.

• Earthquakes and Structures
• /
• 제4권6호
• /
• pp.607-627
• /
• 2013

The application of shape memory alloys (SMAs) to the seismic response reduction of civil engineering structures has attracted growing interest due to their self-centering feature and excellent fatigue performance. The loading rate dependence of SMAs raises a concern in the seismic analysis of SMA-based devices. However, the implementation of micromechanics-based strain-rate-dependent constitutive models in structural analysis software is rather complicated and computationally demanding. This paper investigates the feasibility of replacing complex rate-dependent models with rate-independent constitutive models for superelastic SMA elements in seismic time-history analysis. Three uniaxial constitutive models for superelastic SMAs, including one rate-dependent thermomechanical model and two rate-independent phenomenological models, are considered in this comparative study. The pros and cons of the three nonlinear constitutive models are also discussed. A parametric study of single-degree-of-freedom systems with different initial periods and strength reduction factors is conducted to examine the effect of the three constitutive models on seismic simulations. Additionally, nonlinear time-history analyses of a three-story prototype steel frame building with special SMA-based damping braces are performed. Two suites of seismic records that correspond to frequent and design basis earthquakes are used as base excitations in the seismic analyses of steel-braced frames. The results of this study show that the rate-independent constitutive models, with their parameters properly tuned to dynamic test data, are able to predict the seismic responses of structures with SMA-based seismic response modification devices.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제34권2호
• /
• pp.140-149
• /
• 2007

본 논문에서는 한국어 의존 구문 분석을 위한 새로운 확률 모델을 제안한다. 한국어가 자유 어순 언어라 할지라도 지역적 어순은 존재하기 때문에 의존관계를 결정하기 위해 의존하는 두 어절인 의존소와 지배소 사이의 수식 거리가 유용하다는 것은 이미 많은 연구를 통해 밝혀졌다. 본 연구에서는 수식거리의 정확한 수식 거리의 추정을 위해 지배가능 경로 문맥을 이용한 수식 거리 확률 모델을 제안한다. 수식 거리를 위해 지배가능 경로를 고려함으로써, 긴 표층 문맥을 압축하는 효과를 가져다 준다. 이를 통해 구문 분석 정확률 향상과 원거리 의존 관계 향상을 보임을 설명한다. 실험 및 평가를 통해 제안하는 모델의 구문 분석 성능은 86.9%이며, 기존에 제안된 구문 분석 모델과 비교하여 높은 구문 분석 결과를 보이며, 특히 원거리 의존관계에 대하여 더욱 향상된 성능을 보인다.

• 한국통신학회논문지
• /
• 제32권1C호
• /
• pp.78-85
• /
• 2007

최근 디지털 방송의 발달과 인터넷 보급으로 인해 디지털 데이터의 저작권 보호를 위한 디지털 워터마킹에 관한 많은 연구가 이루어지고 있다. 본 논문에서는 저작권 보호 뿐만 아니라 자막이나 인물 소개, 배경 음악에 대한 정보 등 유용한 정보를 은닉하면서 화질 열화를 최소화하기 위하여 움직임벡터의 변경 최소화 기법을 제안한다. 제안한 방법은 매크로블록에서 구한 정보와 워터마크 정보를 비교하여 특성 벡터를 추출하고, 이에 따라 비트의 반전 여부를 결정함으로써 움직임 벡터의 변경을 최소화한다. 따라서 기존의 움직임벡터 기반의 비디오 워터마킹기법에 비해 화질 열화가 최소화될 수 있다. 또한 삽입 정보에 대한 무결성을 제공하며, 워터마크를 매우 간단히 검출할 수 있고, 원 영상이 필요없는 블라인드 워터마킹이 가능하다. 그리고 기존의 비디오 스트림의 형식이 변경되지 않으므로 기존의 MPEG-1, -2 표준과 호환성이 뛰어나다. 본 논문은 실험 결과 기존의 방법에 비해 $0.5{\sim}1.5dB$ 화질이 향상됨을 확인할 수 있었다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제3권5호
• /
• pp.163-172
• /
• 2014

Scale Invariant Feature Transform (SIFT)은 높은 매칭 능력과 회전이나 스케일 조정 시 안정성으로 인해 이미지 특징 매칭을 위해 많은 응용에서 사용되어지고 있으며, 이러한 특성으로 인해 카피-무브 위조 검출을 위한 핵심 알고리즘으로 각광받고 있다. 하지만 SIFT 변환은 이미지 조작의 증거를 감출 수 있는 안티포렌식의 가능성이 높음에도 불구하고 이에 대한 연구는 거의 없으므로, 본 논문에서는 의미론적으로 허용될 수 있는 왜곡을 적용하여 SIFT 기반 카피-무브 위조 검출을 방해하기 위한 타켓 카운터-포렌식 기법을 제안한다. 제안 기법은 공격자가 유사성 매칭 절차를 속일 수 있는 동시에 SIFT 키포인트의 변형을 통한 추적을 방해하여 이미지 조작의 증거를 숨길 수 있는 방안을 제공한다. 또한 제안 기법은 의미론적 제약 하에서 가공된 이미지와 원본 이미지 간의 높은 충실도를 유지하는 특성을 가진다. 한편, 다양한 조건의 테스트 이미지에 대한 실험을 통해 제안 기법의 효율성을 확인하였다.