• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.549-553
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• 1998

The structure and layer distribution of cadmium arachidate Langmuir-Blodgett film were analyzed by the small angle X-ray reflectivity measurements using synchrotron radiation. Y-to X type transition was ocurred during the 39th passage of deposition of cadmium arachidate. Based on the measurement of the consumed area of the monolayer, it was determined that about 27.5 layer was deposited. Using the synchrotron X-ray, the reflectivity profile of cadmium arachidate LB film over the wide range of grazing angle was obtained. The X-ray reflectivity profile was analyzed using the recursion formula. By fitting the location and dispersion of the subsidiary maxima between the Bragg peaks of the measured reflectivity profile with that of the calculated reflectivity profile, the average thickness and the distribution of layer thickness were evaluated. The genetic algorithm was adopted to the fitting of reflectivity profile to evaluate the optimum value of the number distribution of layer. Based on the morphology measurement with an atomic force microscopy (AFM), the domain structure and mean roughness of LB films were obtained. The mean roughness value calculated based on the number of layer distribution obtained from the measurement by AFM is consistent with that obtained from X-ray reflectivity analysis.

• 한국광학회지
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• 제12권2호
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• pp.91-97
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• 2001

광섬유 브래그 격자는 코어의 굴절률이 주기적으로 변하는 특성으로 인하여 브래그 조건을 만족하는 파장은 반사시키고 다른 파장은 통과시키는 소자이다. 본 논문에서는 광섬유 격자를 이용한 동적 스트레인 센서시스템을 구현하였다. 4-채널 동적 센서 시스템에 사용된 필터의 선형성을 보상하여 필터의 전 구간에서 동적 신호를 측정하였으며 실시간 동적 신호의 측정을 위하여 LabView를 이용한 신호처리 및 인터페이스를 하였다. 이러한 센서시스템의 분해능은 $5\mu$strain이며 동적 스트레인 측정 범위는 필터의 전 구간 약 $1200\mu$strain에 해당한다. 센서시스템을 이용하여 외팔보(steel-bar)의 4지점에서의 스트레인의 변화량을 측정하였으며 콘크리트 시험 보에 적용하여 하중 인가시 시험보가 받는 스트레인의 변화량을 실시간 측정하였다.

• 한국광학회지
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• 제14권3호
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• pp.327-330
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• 2003

본 논문에서는 도파로층이 1.3 $\mu\textrm{m}$ InGaAsP긴 파장 가변 BT(butt-coupled)-DBR(distributed bragg reflector)-LD(laser diode)를 제작하고, 특성을 측정하였다. Butt 결합 성장면의 성장조건을 건식식각과 선택식각 방법과 MOCVD(metal organic chemical vapor deposition)성장으로 최적화 한 후 활성층과 도파로층의 결합 효율을 측정한 결과 결합 효율이 85% 이상으로 나타났으며, 제작된 BT-DBR-LD에 연속전류를 인가 했을 때, 평균 임계전류는 약 21 ㎃, 최대 광출력이 25 ㎽ 이상으로 나타났다. 또한 위상제어 영역과 DBR영역에 각각 25㎃와 50 ㎃의 전류를 주입하여도 급격한 광출력 변화와 포화현상이 나타나지 않았다 이때 최대 파장 가변 폭은 7.4 nm, SMSR비는 40 ㏈이상으로 나타났다.

• 한국광학회지
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• 제12권2호
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• pp.129-134
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• 2001

본 논문에서는 일반적인 OTDR 기술로 WDM 전송시스템의 감시를 수행하는 새로운 방법을 제안하였다. 제안된 감시 방법은 전송로에 포함된 EDFA의 구조를 광회전기(optical circulator)와 FBG(Fiber Bragg Grating)를 이용하여 OTDR 광펄스의 파장에서만 양방향 전송이 가능하도록 변경하고, 전송 신호의 역방향으로 OTDR 광펄스를 삽입함으로써 EDFA의 교차이득변조에 의한 신호왜곡을 분산시켜 신호전송과 전송로 감시를 동시에 수행하는 것이다. 이 감시 방법의 타당성을 검증하기 위해 제안된 구조로 변경된 EDFA가 포함된 320km 길이의 8 채널 WDM 광전송 시스템을 구축하고 신호전송과 동시에 전송로 감시를 수행한 결과를 보였으며, 이때 전송로 감시로 인한 전송 신호 채널의 power penalty를 BERT로 측정하여 그 값이 0.3dB이하로 매우 작음을 보였다.

• 대한토목학회논문집
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• 제39권4호
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• pp.469-475
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• 2019

구조물의 장기적인 안전관리를 위하여 교량 장기계측시스템이 도입되어 운영 중에 있다. 그러나 일반적인 교량 장기계측시스템은 응답만 측정하고 입력하중은 측정하지 못하고 있기 때문에, 추세분석에 의한 관리기준 상회여부만을 판단하고 있어 정량적인 구조계의 상태평가가 어려운 실정이다. 이러한 단점을 극복하기 위하여 본 논문에서는 도로교 입력하중 측정을 위한 FBG 기반 입력하중 측정센서를 개발하였으며, 실내실험을 통하여 그 타당성을 검증하였다.

• 대한건축학회논문집:구조계
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• 제35권8호
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• pp.123-130
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• 2019

Recently, it is required to develop a monitoring technology that combines an FBG sensor as a means for continuously monitoring whether reinforcing effect of FRP is maintained on FRP reinforced structural members. However, most existing researches focus on the insertion of FBG sensors into bar-shaped FRPs, and there is insufficient study on the details strip-type FRPs combined with FBG sensors. Therefore, in this paper, it is studied to develop a reinforcement in which a FBG sensor is combined with a FRP strip. Especially, combination of FRP and FBG sensor. For this, a series of experiments were performed to find the adhesive strength of fiber-FRP-epoxy joints, the tensile strength of FBG sensor part with reflection-lattice, and the performance depending on the connection method of FRF and FBG sensor. As a result of the study, it was found that a minimum strength of $216.15N/mm^2$ is required for incorporating FBG sensors in FRP using epoxy. It is considered that the adhesion length of epoxy joints should be more than 50mm. When the FBG sensor is attached to the FRP strip as an epoxy, it is considered appropriate to use the complete attachment and the sensor non-attachment method.

• 대한두경부종양학회지
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• 제37권1호
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• pp.1-10
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• 2021

Intensity-modulated radiation therapy (IMRT) using X-rays is a standard technique implemented for treating head and neck cancer (HN C). Compared to 3D conformal RT, IMRT can significantly reduce the radiation dose to surrounding normal tissues by using a highly conformal dose to the tumor. Proton therapy is a type of RT that uses positively charged particles named protons. Proton therapy has a unique energy deposit (i.e., Bragg peak) and greater biological effectiveness than that of therapy using X-rays. These inherent properties of proton therapy make the technique advantageous for HNC treatment. Recently, advanced techniques such as intensity-modulated proton therapy have further decreased the dose to normal organs with a higher conformal dose to the tumor. The usage of proton therapy for HNC is becoming widespread as the number of operational proton therapy centers has increased worldwide. This paper aims to present the current clinical evidence of proton therapy utility to HNC clinicians through a literature review. It also discusses the challenges associated with proton therapy and prospective development of the technique.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권4호
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• pp.315-320
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• 2021

Carbon-ion radiotherapy (CIRT) is on the rise as a treatment choice for malignant tumor. Compared to conventional radiotherapy, particle beams have different physical and biological properties. Particle beam provides a low entry dose, deposits most of the energy at the endpoint of the flight path, and forms an asymptotic dose peak (the "Bragg peak"). Compared to protons, carbon with its larger mass decreases beam scattering, resulting in a sharper dose distribution border. We report a 50-year-old male who underwent CIRT without surgical resection on osteosarcoma of the mandible. After CIRT, the patient's pain was gone, and the malignant mass remained stable with accompanying necrosis. Nine months later, however, magnetic resonance imaging demonstrated progression of the left mandibular osteosarcoma with pulmonary metastases. After multidisciplinary discussion, concurrent chemoradiotherapy was conducted. While necrotic bone segments came out of the mandible during subsequent periodic outpatient visits, the tumor itself was stable. Thirty months after his first visit and diagnosis, the patient is waiting for chemotherapy. Although CIRT is superior in treating radioresistant hypoxic disease, CIRT is in its infancy, so care must be taken for its indications and complications.

• Composites Research
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• 제19권3호
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• pp.43-49
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• 2006

In this paper, a long gauge Fiber Bragg Grating (FBG) sensor system is described and long gauge FBGs are well-suited for measuring the upper parts of the bridge piers under the extremely severe movement conditions. In the experiments, we used more than 30m long FBG sensors to measure the movement of top part of the bridge piers which are separated from the main bridge by cutting the decks. With the actuator, the deck and girders were pushed and released. We checked the movement of the top of the pier while releasing the pressure of the actuator with the long gauge fiber sensor. In order to measure the movement of the upper part of the pier, the reference point must be outside of the pier. Using the optical fiber sensors, one end of the sensor is attached to the top of the pier and the other end is attached to the bottom of the next pier. The fiber sensors showed good response to the release loading and we could calculate the movement of the top part of the pear.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3700-3708
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• 2023

The stochastic origin ensembles method with resolution recovery (SOE-RR) has been proposed to reconstruct proton-induced prompt gammas (PGs), and the reconstructed PG image was used for range verification. However, due to low detection efficiency, the number of valid events is low. Such a low-count condition can degrade the accuracy of the SOE-RR method for proton range verification. In this study, we proposed two strategies to improve the reconstruction of the SOE-RR algorithm for low-count PG imaging. We also studied the number of iterations and repetitions required to achieve reliable range verification. We simulated a proton beam (10⁸ protons) irradiated on a water phantom and used a two-layer Compton camera to detect 4.44-MeV PGs. Our simulated results show that combining the SOE-RR algorithm with restricted volume (SOE-RR-RV) can reduce the error of the estimation of the Bragg peak position from 5.0 mm to 2.5 mm. We also found that the SOE-RR-RV algorithm initialized using a back-projection image could improve the convergence rate while maintaining accurate range verification. Finally, we observed that the improved SOE-RR algorithm set for 60,000 iterations and 25 repetitions could provide reliable PG images. Based on the proposed reconstruction strategies, the SOE-RR algorithm has the potential to achieve a positioning error of 2.5 mm for low-count PG imaging.