• Title/Summary/Keyword: Optical propagation

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Realization of Object Detection Algorithm and Eight-channel LiDAR sensor for Autonomous Vehicles (자율주행자동차를 위한 8채널 LiDAR 센서 및 객체 검출 알고리즘의 구현)

  • Kim, Ju-Young;Woo, Seong Tak;Yoo, Jong-Ho;Park, Young-Bin;Lee, Joong-Hee;Cho, Hyun-Chang;Choi, Hyun-Yong
    • Journal of Sensor Science and Technology
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    • v.28 no.3
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    • pp.157-163
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    • 2019
  • The LiDAR sensor, which is widely regarded as one of the most important sensors, has recently undergone active commercialization owing to the significant growth in the production of ADAS and autonomous vehicle components. The LiDAR sensor technology involves radiating a laser beam at a particular angle and acquiring a three-dimensional image by measuring the lapsed time of the laser beam that has returned after being reflected. The LiDAR sensor has been incorporated and utilized in various devices such as drones and robots. This study focuses on object detection and recognition by employing sensor fusion. Object detection and recognition can be executed as a single function by incorporating sensors capable of recognition, such as image sensors, optical sensors, and propagation sensors. However, a single sensor has limitations with respect to object detection and recognition, and such limitations can be overcome by employing multiple sensors. In this paper, the performance of an eight-channel scanning LiDAR was evaluated and an object detection algorithm based on it was implemented. Furthermore, object detection characteristics during daytime and nighttime in a real road environment were verified. Obtained experimental results corroborate that an excellent detection performance of 92.87% can be achieved.

Dedicated preparation for in situ transmission electron microscope tensile testing of exfoliated graphene

  • Kim, Kangsik;Yoon, Jong Chan;Kim, Jaemin;Kim, Jung Hwa;Lee, Suk Woo;Yoon, Aram;Lee, Zonghoon
    • Applied Microscopy
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    • v.49
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    • pp.3.1-3.7
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    • 2019
  • Graphene, which is one of the most promising materials for its state-of-the-art applications, has received extensive attention because of its superior mechanical properties. However, there is little experimental evidence related to the mechanical properties of graphene at the atomic level because of the challenges associated with transferring atomically-thin two-dimensional (2D) materials onto microelectromechanical systems (MEMS) devices. In this study, we show successful dry transfer with a gel material of a stable, clean, and free-standing exfoliated graphene film onto a push-to-pull (PTP) device, which is a MEMS device used for uniaxial tensile testing in in situ transmission electron microscopy (TEM). Through the results of optical microscopy, Raman spectroscopy, and TEM, we demonstrate high quality exfoliated graphene on the PTP device. Finally, the stress-strain results corresponding to propagating cracks in folded graphene were simultaneously obtained during the tensile tests in TEM. The zigzag and armchair edges of graphene confirmed that the fracture occurred in association with the hexagonal lattice structure of graphene while the tensile testing. In the wake of the results, we envision the dedicated preparation and in situ TEM tensile experiments advance the understanding of the relationship between the mechanical properties and structural characteristics of 2D materials.

Seed Morphological Characteristics and Dormancy type of Eranthis stellata Maxim., Korea Rare Plant. (희귀식물 너도바람꽃(Eranthis stellata Maxim.) 종자의 형태특성 및 휴면유형 분석)

  • Inhwan Chae;Geon Hui Ryu;Se-kyu Song;Jin-Woo Kim;Gi Ho Kang;Hayan Lee
    • Proceedings of the Plant Resources Society of Korea Conference
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    • 2020.08a
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    • pp.20-20
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    • 2020
  • Eranthis stellata Maxim. is a perennial plant that grows around the valley. E. stellata is concerned about the decline in natural habitats due to climate change in KOREA, continues to be observed and protected as an endangered species (Least Concrned, LC). Nevertheless, studies on the characteristics of the seeds of E. stellata are insufficient. So, this study analyzed the morphological characteristics and dormancy types of seeds. Seeds of E. stellata was collected in April at Gyeongsangbuk-do Arboretum and kept at 5 ℃ until using. To investigate the morphology of seeds, an optical microscope and a scanning electron microscope (SEM) were used. GA3 treated or untreated seeds (4 replicates of 25 seeds each) were observed germination and embryo growth for 1 month at 5 ℃ and 25/15 ℃ (12h day/12h night). The seed surface of E. stellata, light brown, was observed as a common characteristic of Eranthis genus, reticulate. The short axis of seeds was 1.11~1.77mm (average 1.44mm), and the long axis was 1.27~1.91mm (average 1.63mm), which was investigated in a slightly round shape (subglose). While no germination was observed at all conditions, Embryo growth was observed at 5 ℃ both in the control group and with GA3treated groups. Thus, seeds of E. stellata are classified as morphological physiological dormancy (MDP), which requires embryonic development and dormant break at the same time. These results can be useful information for determining morphological physiological seed dormancy and germination, and will be an important basic data for seed propagation of E. stellata as a resource.

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Performance Analysis of Spiral Axicon Wavefront Coding Imaging System for Laser Protection

  • Haoqi Luo;Yangliang Li;Junyu Zhang;Hao Zhang;Yunlong Wu;Qing Ye
    • Current Optics and Photonics
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    • v.8 no.4
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    • pp.355-365
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    • 2024
  • Wavefront coding (WFC) imaging systems can redistribute the energy of an interference laser spot on an image plane sensor by wavefront phase modulation and reduce the peak intensity, realizing laser protection while maintaining imaging functionality by leveraging algorithmic post-processing. In this paper, a spiral axicon WFC imaging system is proposed, and the performance for laser protection is investigated by constructing a laser transmission model. An Airy disk on an image plane sensor is refactored into a symmetrical hollow ring by a spiral axicon phase mask, and the maximum intensity can be reduced to lower than 1% and single-pixel power to 1.2%. The spiral axicon phase mask exhibits strong robustness to the position of the interference laser source and can effectively reduce the risk of sensor damage for an almost arbitrary lase propagation distance. Moreover, we revealed that there is a sensor hazard distance for both conventional and WFC imaging systems where the maximum single-pixel power reaches a peak value under irradiation of a power-fixed laser source. Our findings can offer guidance for the anti-laser reinforcement design of photoelectric imaging systems, thereby enhancing the adaptability of imaging systems in a complex laser environment. The laser blinding-resistant imaging system has potential applications in security monitoring, autonomous driving, and intense-laser-pulse experiments.

Identification of primary input parameters affecting evacuation in ventilated main control room through CFAST simulations and application of a machine learning algorithm to replace CFAST model

  • Sumit Kumar Singh;Jinsoo Bae;Yu Zhang;Saerin Lim;Jongkook Heo;Seoung Bum Kim;Weon Gyu Shin
    • Nuclear Engineering and Technology
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    • v.56 no.9
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    • pp.3717-3729
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    • 2024
  • Accurately predicting evacuation time in a ventilated main control room (MCR) during fire emergencies is crucial for ensuring the safety of personnel at nuclear power plants. This study proposes to use neural networks alongside consolidated fire and smoke transport (CFAST) simulations to serve as a surrogate model for physics-based simulation tools. Our neural networks can promptly predict the evacuation time in MCRs, proving to be a valuable asset in fire emergencies and eliminating the need for time-consuming rollouts of the CFAST simulations. The CFAST model simulates fire and evacuation scenarios in a ventilated MCR with variations in input parameters such as door conditions, ventilation flow rate, leakage area, and fire propagation time. Target output parameters, such as hot gas layer temperature (HGLT), heat flux (HF), and optical density (OD), are used alongside standardized evacuation variables to train a machine learning model for predicting evacuation time. The findings suggest that high ventilation flow rates help to dilute smoke and discharge hot gas, leading to lower target output parameters and quicker evacuation. Standardized evacuation variables exceed the required abandonment criteria for all door conditions, indicating the importance of proper evacuation procedures. The results show that neural networks can generate evacuation times close to those obtained from CFAST simulations.

EFFECT OF $CEO_2$ ADDITION IN GLASS COMPOSITION ON THE STRENGTH OF ALUMINA-GLASS COMPOSITES (알루미나-유리 복합체용 글래스의 조성에서 $CeO_2$의 함량변화가 강도에 미치는 영향)

  • Lee, Hwa-Jin;Song, Kwang-Yeob;Kang, Jeong-Kil
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.5
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    • pp.595-605
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    • 2000
  • Dental ceramics have good aesthetics, biocompatibility, low thermal conductivity, abrasion resistance, and color stability. However poor resistance to fracture and shrinkage during firing process have been limiting factors in their use, particularly in multiunit ceramic restorations. A new method for making all-ceramic crowns that have high strength and low processing shrinkage has been developed and is referred to as the Vita In-Ceram method. This study was performed to investigate the effect of $CeO_2$ addition in borosilicate glasses on the strength of alumina-glass composites. Porous alumina compacts were prepared by slip casting and sintered at $1,100^{\circ}C$ for 2 hours. Dense composites were made by infiltration of molten glass into partially sintered alumina at $1,140^{\circ}C$ for 4 hours. Specimens were polished sequentially from #800 to #2000 diamond disk. and the final surface finishing on the tensile side was received an additional polishing sequence through $1{\mu}m$ diamond paste. Biaxial flexure test was conducted by using ball-on-three-ball method at a crosshead speed of 0.5mm/min. To examine the microstructural aspect of crack propagation in the alumina-glass composites, Vickers-produced indentation crack was made on the tensile surface at a load of 98.0 N and dwell time of 15 sec, and the radial crack patterns were examined by an optical microscope and a scanning electron microscope. The results obtained were summarized as follows; 1. The porosity rates of partially sintered alumina decreased with the rising of firing temperature. 2. The maximum biaxial flexure strength of 423.5MPa in alumina-glass composites was obtained with an addition of 3 mol% $CeO_2$ in glass composition and strength values showed the aspect of decrease with the increase of $CeO_2$ content. 3 The biaxial flexure strength values of alumina-glass composites were decreased with rising the firing temperature. 4. Observation of the fracture surfaces of alumina-glass composites indicated that the enhancement of strength in alumina-glass composites was due to the frictional or geometrical inter-locking of rough fracture surfaces and ligamentary bridging by intact islands of materials left behind the fracture front.

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A Study of Skin Reflectance Using Kubelka-Munk Model (Kubelka-Munk 모델을 이용한 피부 분광반사율 연구)

  • Cho, A Ra;Kim, Su Ji;Lee, Jun Bae;Sim, Geon Young;Back, Min;Cho, Eun Seul;Jang, Ji Hui;Jang, Eunseon;Kim, Youn Joon;Yoo, Kweon Jong;Han, Jeong Woo
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.42 no.1
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    • pp.45-55
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    • 2016
  • Light shows various optical behaviors such as reflection, absorption, and scattering on skin for individuals. In particular, reflection of light from the skin has been widely used as the brightness index of the skin of individuals through the measurement of the physical quantity of spectral reflectance. Therefore, the study of light behavior on skin would be useful for the preparation of new evaluation method in the development stage of make-up products. In this study, multi-dimensional analysis for spectral reflectance behavior of light on individual skin was performed using Kubelka-Munk model. Also, we analyzed the contribution of skin parameters such as skin thickness and hemoglobin, which could affect the spectral reflectance, using above model and literature information. Base on this, we calculated the theoretical reflectance of normal women for visual light, which showed good agreement with the measured reflectance. Our study of light propagation in skin based on Kubelka-Munk model provides useful insight for the development of personalized cosmetic in the near future.

Refractometric Glucose Biosensor Incorporating a Vertically Coupled Microring Resonator in Polymeric Waveguides (수직형 폴리머 마이크로링 공진기 기반의 글루코스 바이오 센서)

  • Kim, Gun-Duk;Son, Keun-Sik;Lee, Hak-Soon;Kim, Ki-Do;Lee, Sang-Shin
    • Korean Journal of Optics and Photonics
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    • v.19 no.2
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    • pp.127-131
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    • 2008
  • A refractometric glucose biosensor incorporating a vertically coupled microring resonator in polymers was proposed and realized. The ring was covered with a target analyte of glucose solution with a certain concentration, so that its effective refractive index could be altered and, as a result, the resonance wavelength of the sensor was shifted. Therefore the concentration of the glucose solution can be estimated by observing the shift in the resonance wavelength. Two schemes were exploited for enhancing the sensitivity of the sensor. First, the effective refractive index of the polymeric waveguide used for the resonator sensor was adjusted to approach that of the target analyte as best as possible. Second, the ring waveguide, which serves as a crucial sensing part, was appropriately over-etched to enlarge its contact area with the analyte. The proposed resonator sensor was designed with the beam propagation method. The refractive indices of the core and cladding polymer involved were 1.430 and 1.375 respectively, leading to the waveguide's effective refractive index of ${\sim}1.390$, which is faiirly close to that of the glucose solution of ${\sim}1.333$. The prepared ring resonator with the $400-{\mu}m$ radius exhibited the free spectral range of 0.66 nm, the bandwidth of 0.15 nm, and the quality factor of 10,000. For the sensor operating at 1,550 nm wavelength, the achieved sensitivity was as great as 0.28 pm/(mg/dL), which is equivalent to 200 nm/RIU.

Characterization of Interfacial Adhesion of Cu-Cu Bonding Fabricated by Thermo-Compression Bonding Process (열가압 접합 공정으로 제조된 Cu-Cu 접합의 계면 접합 특성 평가)

  • Kim, Kwang-Seop;Lee, Hee-Jung;Kim, Hee-Yeoun;Kim, Jae-Hyun;Hyun, Seung-Min;Lee, Hak-Joo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.7
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    • pp.929-933
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    • 2010
  • Four-point bending tests were performed to investigate the interfacial adhesion of Cu-Cu bonding fabricated by thermo-compression process for three dimensional packaging. A pair of Cu-coated Si wafers was bonded under a pressure of 15 kN at $350^{\circ}C$ for 1 h, followed by post annealing at $350^{\circ}C$ for 1 h. The bonded wafers were diced into $30\;mm\;{\times}\;3\;mm$ pieces for the test. Each specimen had a $400-{\mu}m$-deep notch along the center. An optical inspection module was installed in the testing apparatus to observe crack initiation at the notch and crack propagation over the weak interface. The tests were performed under a fixed loading speed, and the corresponding load was measured. The measured interfacial adhesion energy of the Cu-to-Cu bonding was $9.75\;J/m^2$, and the delaminated interfaces were analyzed after the test. The surface analysis shows that the delamination occurred in the interface between $SiO_2$ and Ti.

Compact Design and Fabrication of 'Improved QS-MMI' Demultiplexer (Improved QS-MMI' 1.31/1.55μm 파장분리기의 최적화 설계 및 제작)

  • Kim, Nam-Kook;Kim, Jang-Kyum;Choi, Chul-Hyun;O, Beom-Hoan;Lee, Seung-Gol;Park, Se-Gun;Lee, El-Hang
    • Korean Journal of Optics and Photonics
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    • v.16 no.3
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    • pp.248-253
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    • 2005
  • We designed and fabricated a compact multi-mode interference (MMI) wavelength demultiplexer using the concept of 'Improved Quasi-State' modes. The output power and extinction ratio were improved by utilizing modal phase error which is specially occurred in low-index contrast. For a designed demultiplexer, the mode propagation analysis with effective index approximation shows significant improvement of extinction ratio to -25 dB for both $1.31{\mu}m\;and\;1.51{\mu}m$ wavelength region and the split-length was reduced about 1/5 of other MMI devices. The fabricated device shows successful characteristics for both 1.31 and $1.55{\mu}m$ wavelengths. These results demonstrate the potential of low-index materials system and the embossing process for photonic integrated circuits.