MgO 개질 칼슘 알루미네이트 시멘트의 미세구조 발달 및 내구특성

학위논문(박사) - 한국과학기술원 : 건설및환경공학과, 2024.2,[x, 115 p. :]Calcium aluminate cement (CAC) has been used as an alternative for Portland cement (PC) under some extreme conditions and for specific purpose such as rapid strength gain, even at temperatures approaching 0°C, the ability to customize fresh property characteristics, high abrasion resistance, and resistance to chemical corrosion. Despite various advantages, CAC is vulnerable to phase conversion and strength loss over a period of time or exposure to elevated temperature and humidity. Due to phase conversion, CAC also becomes vulnerable against extreme condition. However, this dissertation mainly focuses on the features of CAC incorporated with reactive MgO in order to cater/minimize the microstructure instability and strength loss due to phase conversion along with durability against extreme conditions.This dissertation investigates the fundamentals of phase conversion and strength loss of CAC along with the effect of MgO on phase conversion, microstructure modification, and strength loss mitigation before and after exposure to expedited curing. Furthermore, MgO-modified CAC was exposed to extreme conditions involving CO$_2$, high temperature, and acid rich environment. The structural evolution of binder phases in MgO-modified CAC exposed to extreme conditions was investigated using multi analytical tools. The obtained results will provide new insights into the phase conversion, microstructural alteration, and durability of MgO-modified CAC. The thesis is concluded by summarizing implications of the results.한국과학기술원 :건설및환경공학과

연산을 완전히 중첩하여 수행하는 저밀도 패러티 검사 코드의 복호 방식

학위논문(석사) - 한국과학기술원 : 전기및전자공학전공, 2009.2, [ v, 54 p. ]A new scheduling scheme to improve the resource utilization of a low-density parity-check decoder has been proposed in this thesis. In the proposed scheme, a completely overlapped processing of check nodes and variable nodes is ensured to achieve full utilization of resources, increasing the throughput of the decoder and reducing the overall decoding latency. Moreover, no restriction is posed on the formation of the parity check matrix and any preprocessing is also not required prior to the decoding. The effectiveness of the proposed scheme is measured through a series of simulations using WiMax802.16e codes with considering an additive white Gaussian noise channel. Furthermore, the proposed scheme is used to implement a decoder for a (576, 7, 6) irregular code. Altera’s CycloneII FPGA is used to verify the working of the developed decoder.한국과학기술원 : 전기및전자공학전공

영상 센서를 활용한 비협조적 위성의 딥러닝 기반 상대 위치 추정

학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2024.2,[vi, 67 p. :]The objective of the proposed work is to perform monocular vision based relative 6DOF pose estimation of the non-cooperative spacecraft autonomously during proximity operations in the orbit. This area of research has gained importance in recent years due to the increase of interest in the fields of Active Debris Removal (ADR) and On-Orbit Servicing (OOS). The aim is to provide an integrated robust solution to estimate the pose of the non-cooperative target spacecraft with respect to the chaser satellite in Rendezvous operations by using only monocular camera. The relative pose estimation has been performed using Convolutional Neural Networks (CNNs) and has outperformed the conventional image processing methods in achieving better accuracy and more availability of the pose solutions in harsh space environment. In this work, CNNs are replaced by the High-Resolution Transformer network to further improve the pose estimation accuracy by using less computation resources and low-resolution image. Moreover, the Transformers have inherited advantage to overcome the shortcomings of the translation equivariance and 2D neighborhood awareness in CNNs. Transformers also perform better for long range dependencies and does not generalize to just local features of the target objects. First, the 3D model of the target satellite is reconstructed using corresponding 2D keypoints among different images of the dataset with the help of Inverse Direct Linear Transform (IDLT) method. Then, the pose estimation pipeline is developed with deep learning-based image processing subsystem and geometric optimization of the pose solver. The image processing subsystem perform target localization and draw a bounded box around the satellite body using CNN based architectures. Then, Keypoints Detection network perform regression to predict the 2D keypoints using Transformer based network architecture. Afterwards, the predicted keypoints based on their confidence scores are projected onto the corresponding 3D points of the known reconstructed 3D model, then the pose value is computed by reducing the reprojection error between 3D-2D points using PnP method. The pose is further refined between 3D model points and predicted keypoints using the Gauss Newton method. The proposed architecture is trained and tested on Spacecraft Pose Estimation Dataset (SPEED) dataset and it shows the superior accuracy both in translation and rotation values. The architecture shows robustness against the drastically changing clutter background and light conditions in the images. Moreover, this method is using less floating-point operations and trainable parameters with low image resolution that make it one step closer for implementation on a space hardware. The resource efficient architecture is feasible for small satellites with low mass and power budget.한국과학기술원 :항공우주공학과

A CUTTER FOR SUBSTRATE USING MICROWAVES LASER BEAM AND METHOD THEREOF

본 발명은 초단파 레이저 빔을 이용한 기판 절단장치 및 그 절단방법에 관한 것으로, 초단파 레이저 빔을 발생하기 위한 레이저 발생수단과, 상기 초단파 레이저 빔의 초점이 절단하고자 하는 기판의 내부에 맞춰지도록 조절하기 위한 초점조절수단을 포함하며, 상기 초단파 레이저 빔을 상기 기판의 내부에 초점을 맞추어 원하는 절단 경로를 따라 조사함으로써, 내부 필라멘테이션(filamentation) 현상을 유도하여 상기 기판의 내부에 절단홈이 형성되도록 한다. 이에 따라, 각종 디스플레이에 사용되는 기판을 크랙(crack)이나 손상 없이 간단한 공정으로 신속하고 정밀하게 절단할 수 있는 효과가 있다.초단파 레이저 빔, 펨토초, 피코초, 초점, 기판, 절단, 플라즈마, 필라멘테이

Failure recovery method in non revertive mode of ethernet ring netwrok

이더넷 링 네트워크의 비환원 모드에서의 장애 복구 방법이 개시된다. 이더넷 링 네트워크에서 각 노드의 맥 주소를 기반으로 각 노드 사이의 링크 우선순위 값을 설정하거나 노드의 우선 순위를 설정하여, 그 우선순위 값을 기준으로 장애 복구 후 폐색 포트를 가지는 노드를 결정함으로써, 폐색 포트 선정의 분산이 가능하다