• 제목/요약/키워드: focal loss

검색결과 116건 처리시간 0.031초

Femtosecond Micromachining Applications for Optical Devices

  • Sohn, Ik-Bu;Lee, Man-Seop;Woo, Jeong-Sik
    • Journal of the Optical Society of Korea
    • /
    • 제8권3호
    • /
    • pp.127-131
    • /
    • 2004
  • This paper investigates applications of femtosecond lasers for the micromachining of transparent materials and fabrication of optical devices. We show commercial micromachining examples of transparent materials which have been fabricated for various applications. Near infrared femtosecond laser processing is an attractive method to fabricate three-dimensional optical waveguides into various transparent materials. Focused femtosecond laser pulses induce a permanent refractive-index change only near the focal point. We also demonstrate a Y coupler with the splitting ratio of 1:1 written by femtosecond laser pulses into a fused silica glass. The minimum propagation loss of 0.8 ㏈/㎝ awl the refractive-index change of 0.006-0.01 at the wavelength of 1550 ㎚ were achieved by optimization of the laser fluence.

당뇨 신경병증 (Diabetic Neuropathy)

  • 심정인;정진화
    • 대한족부족관절학회지
    • /
    • 제17권4호
    • /
    • pp.251-256
    • /
    • 2013
  • Neuropathy is a common complication of diabetes. It is characterized by a progressive loss of peripheral nerve fibers. The development of the neuropathy is linked to poor glycemic control, age, and the duration of diabetes. Peripheral sensory polyneuropathy is the most common type in neuropathy. Diabetic neuropathy is the most significant etiologic factor of the foot ulcer that may leads to amputation. Current treatments in diabetic neuropathy have no definitive effects on repair or reverse the damaged nerve but only to relieve of symptoms, especially on pain. When the focal compressive neuropathy is combined with diabetic neuropathy, the nerve would be more vulnerable and symptoms might get worse. Surgery is indicated for decompression of an entrapped nerve, like posterior tibial nerve in tarsal tunnel, after failure of the initial conservative treatments.

CD/DVD 겸용 광 픽업 액추에이터의 설계 (CD/DVD Compatible Optical Pickup Actuator Design)

  • 이문구;권대갑;이관철;정회원
    • 한국정밀공학회지
    • /
    • 제15권7호
    • /
    • pp.98-103
    • /
    • 1998
  • Recently, DVD/CD compatible driver is needed for DVD and CD is widely used as a new optical data restoring device. The optical systems of DVD and CD driver are different because they have different optical feature. If only one objective lens is used, the change of an aperture or a dual focal length of the lens is required. This method, however, increases the number of parts and results in loss of the power of laser light. Hence, we propose a dual lens actuator design that can read DVD and CD respectively. Albeit magnetic spring is important mechanism in the dual lens actuator design, there has not been the systematic approach to design the mechanism in the preceding researches. In this article. the guideway to design magnetic spring is presented by using the qualitative theoretical approach and the finite element analysis.

  • PDF

선모양을 한 레이저빔의 방향성 배율 확대를 이용한 정밀 형상측정 시스템 (A New Profilometry System for Precision Measurement of 3D Shape Using the Directional Magnification Control of a Laser Light Stripe)

  • 박승규;백성훈;김철중
    • 한국정밀공학회지
    • /
    • 제14권5호
    • /
    • pp.60-65
    • /
    • 1997
  • This paper proposes a profilometry system for precise surface contouring of 3D objects using a direc- tionally magnified image of a laser light stripe. The resolution of this system can be improved several times comparad with that of conventional systems without loss of spatial resolution and depth of measurement. A pair of cylindrical lens(a convex lens and a concave lens) are used for a directionally magnified image of a laser light stripe maintaining the same focal plane. Also, image processing procedures for image reconstruc- tions are described.

  • PDF

YOLO 기반 학교폭력 감지 시스템 (YOLO-based School Violence Detection System)

  • 신찬휘;문미경
    • 한국컴퓨터정보학회:학술대회논문집
    • /
    • 한국컴퓨터정보학회 2023년도 제68차 하계학술대회논문집 31권2호
    • /
    • pp.703-704
    • /
    • 2023
  • 학교폭력은 교육 환경에서 심각한 문제이다. 피해자에게 심리적 고통과 육체적 상해를 입히고 학교 내 안전과 안정성을 위협한다. 이에 많은 교육기관과 정부 기관이 학교폭력 예방과 대처를 위한 다양한 방안을 제시하고 있지만, 여전히 어려운 문제이다. 최근에는 인공지능 기술을 활용하여 학교폭력 방지와 대처에 관한 연구가 이루어지고 있다. 본 연구에서는 YOLOv5(You Only Look Once version 5) 딥러닝 알고리즘을 활용하여 학교 내부에서 발생하는 폭력 행위를 실시간으로 탐지하는 모델을 제안한다. 이 모델은 CCTV와 같은 영상 데이터를 입력으로 받아들여 학교 내부에서 발생하는 폭력 행위를 실시간으로 식별하는 것을 목표로 한다.

  • PDF

밀리미터파 수동 이미징 시스템 연구 II (Studies on the millimeter-wave Passive Imaging System II)

  • 정민규;채연식;김순구;윤진섭;미즈노 코지;이진구
    • 대한전자공학회논문지TC
    • /
    • 제44권3호
    • /
    • pp.105-110
    • /
    • 2007
  • 광학계 렌즈이론을 바탕으로 밀리미터파를 집속 시킬 수 있는 렌즈를 설계 제작하고, 이를 이용하여 밀리미터파를 집속하였다. 밀리미터파가 집속되는 초점에 안테나를 위치시키고, 안테나를 기계적으로 이동 시키면서 한점씩의 영상 화소를 취해 전체적인 영상을 얻는 밀리미터파 수동 이미징 시스템을 제작하였다 이를 기반으로 렌즈의 초점면에 2차원적인 안테나 배열이 가능한 영상시스템을 목표로 하여 안테나 배열 소자를 설계 제작하였다. 안테나는 페르미 테이퍼 슬롯 안테나(Fermi Taper Slot Antenna)를 채택하였으며, 이 안테나는 높은 이득과 낮은 부엽 특성를 갖는다. 안테나 배열소자는 안테나, 발룬(Balun), MMIC, 검파기를 하나의 기판위에 집적하여 저손실 및 저잡음 효과를 얻을 수 있을 수 있도록 설계 제작하였다. 집적화된 수동형 안테나 배열 소자는 $4\times1$형태로 제작되었다.

개화성 백악질-골 이형성증: 증례보고 (Florid cemento-osseous dysplasia: a report of two cases)

  • 김남균;김현실;김진;남웅;차인호;김형준
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
    • /
    • 제37권6호
    • /
    • pp.515-519
    • /
    • 2011
  • Cemento-osseous dysplasia occurs in the tooth bearing areas of the jaws and is probably the most common fibro-osseous manifestation. They are usually classified into three main groups according to their extent and radiographic appearance: periapical (surrounds the periapical region of teeth and are bilateral), focal (single lesion) and florid (scleroticsymmetrical masses) cemental-osseous dysplasias. Florid cemento-osseous dysplasia clearly appears to be a form of bone and cemental dysplasia that is limited to the jaws. Patients do not have laboratory or radiologic evidence of bone disease in other parts of the skeleton. For asymptomatic patients, the best management consists of regular recall examinations with prophylaxis and the reinforcement of good home hygiene care to control periodontal disease and prevent tooth loss. The treatment of symptomatic patients is more difficult. At this stage, there is an inflammatory component caused by the disease and the process is basically a chronic osteomyelitis involving dysplastic bone and cementum. Antibiotics might be suggested, but are not always effective. Two cases of florid cemento-osseous dysplasia diagnosed in two Korean females are reported with a review of the relevant literature.

브라운관 전자총 부품의 펄스 Nd:YAG레이저 용접에 관한 연구 (I) - 빔의 출력특성과 광학변수 - (A Study on Pulsed Nd:YAG Laser Welding of Electron Gun in Braun Tubes (I) - Characteristics of Beam Output Energy and Optical Parameters -)

  • 김종도;하승협;조상명
    • Journal of Welding and Joining
    • /
    • 제20권4호
    • /
    • pp.525-534
    • /
    • 2002
  • During laser spot welding of the braun tube electron gun, phenomena such as serious spattering and oxidative reaction, etc. were occurred. The spatter occurred from weld pool affects the braun tube, namely it blocks up a very small hole on the shadow mask and causes short circuit between two roles of the electron gun. We guessed that high power density and oxidative reaction are main sources of these problems. So, we studied to prevent and to reduce spatter occurring in spot welding of the braun tube electron gun using pulsed Nd:YAG laser. The characteristics of laser output power was estimated, and the loss of laser energy by optical parameter and spatter was measured by powermeter. The effects of welding parameters, laser defocused distance and incident angle, were investigated on the shape and penetration depth of the laser welded bead in flare and flange joints. From these results, the laser peak power was a major factor to control penetration depth and to occur spatter. It was found that the losses of laser energy by optic parameter and sticked spatter affect seriously laser weldability of thin sheets. The deepest penetration depth is gotten on focal position, and a "bead transition" occurred with a slight displacement of focal position relative to the workpiece surface and the absorption rate of the laser energy is affected by the shape factor of the workpiece. When we changed the incident angle of laser beam, the penetration depth was decreased a little with increasing of the incident angle, and the bead width was increased. The spattering was prevented by considering laser beam energy and incident angle.ent angle.

A grid-line suppression technique based on the nonsubsampled contourlet transform in digital radiography

  • Namwoo Kim;Taeyoung Um;Hyun Tae Leem;Bon Tack Koo;Kyuseok Kim;Kyu Bom Kim
    • Nuclear Engineering and Technology
    • /
    • 제55권2호
    • /
    • pp.655-668
    • /
    • 2023
  • In radiography, an antiscatter grid is a well-known device for eliminating unexpected x-ray scatter. We investigate a new stationary grid artifact suppression method based on a nonsubsampled contourlet transform (NSCT) incorporated with Gaussian band-pass filtering. The proposed method has an advantage that extracts the Moiré components while minimizing the loss of image information and apply the prior information of Moiré component positions in multi-decomposition sub-band images. We implemented the proposed algorithm and performed a simulation and an experiment to demonstrate its viability. We did this experiment using an x-ray tube (M-113T, Varian, focal spot size: 0.1 mm), a flat-panel detector (ROSE-M Sensor, Aspenstate, pixel dimension: 3032 × 3800 pixels, pixel size: 0.076 mm), and carbon graphite-interspaced grids (JPI Healthcare, 18 cm × 24 cm, line density: 103 LP/inch and 150 LP/inch, ratio: 5:1, focal distance: 65 cm). Our results indicate that the proposed method successfully suppressed grid artifacts by reducing them without either reducing the spatial resolution or causing negative side effects. Consequently, we anticipate that the proposed method can improve image acquisition in a stationary grid x-ray system as well as in extended x-ray imaging.

뇌졸중환자의 희망 (The Hope of the Stroke Patients)

  • 김이순
    • 대한간호학회지
    • /
    • 제27권1호
    • /
    • pp.212-227
    • /
    • 1997
  • Cerebrovascular diseases in Korea is an important health problem since mortality and mobidity have been increased rapidly. It marked the 2nd cause of specific death rates in 1993. The stroke causes physical function disorder due to hemiparalysis and emotional disorder, and stroke patients experience helplessness, powerlessness. sense of alienation and loss of hope. These feelings make the rehabilitation difficult because they lose the will of life. The subjects of the study were seven citizens who live in Pusan, are over 50 years old and belong to low income-level. The data were collected from Jan. to Sep. 1995. The researcher as a caregiver and volunteer made confidence of them and asked for their agreement on the purpose of the study. The subjects expressed their experience as openheartedly as possible. The analysis of the data was made through the phenomenological analytic method suggested by Giorgi, which is as follows ; as an unit of description which include the subject' expressions and the researcher's observation, it is examined the theme that express the hope experience with the subject's language(underlining), and the focal meanings are identified. The focal meaning is the crystalization of the theme, which is written in the language of the researcher. After intergrating the focal meaning and make the situated structural description as the meaning of the hope experience identified on each subject's point. After intergrating the situated structural description and make the general structural description as the meaning of the hope experience identified on total subject's point then the systemizing of the structure of the hope experienced phenomena and the flowing of the conciousness was researched. The conclusions of this study was as follows : The ten sources of hope which the subjects experienced were sorted as under 〈mutual relations to others : spouse, children, relatives, fellow believer. health professioner. associate patient group〉, 〈spiritual dependence〉. 〈recovery of physical function〉. 〈rumination of the past life〉, 〈expectation of the future〉. 〈economic power〉, 〈belief〉, 〈ability〉. 〈spontaneous participation〉 and 〈recovery of roles〉. Their hope was spoken out by the following two kinds of linguistics. First. the hope was expressed in the affirmative expression as follows : 〈 to be dependable〉, 〈to make efforts〉, 〈to keep under control〉, 〈to desire〉, 〈to be pleasant〉, 〈to be peaceful〉, 〈to be grateful〉, 〈to give help〉, 〈self-confidence. Courage〉, 〈to be happy〉, 〈to satisfy oneself〉, 〈to share with others〉, 〈to understand〉 and 〈to be affected, be impressed〉 Second, the hope was expressed in the negative on pression as under : 〈to be distressed〉, 〈to be uneasy〉, 〈to be sorry, be unsatisfied〉 〈despair〉, 〈to abandon〉, 〈to be fearful〉, 〈to suffer〉, 〈to bear a burden〉 〈to be confused〉, 〈to be solitary〉, 〈chest trouble〉, 〈to feel heavy〉 〈grief〉, 〈to be daunted〉, 〈to get angry〉, 〈to be uncomfortable〉, 〈to have something regretable〉 and 〈to feel guilty〉. And their hope was expressed by the following four behavioral expressions : 〈physical sphere〉, 〈psychological sphere〉, 〈social support sphere〉 and 〈spiritual sphere〉. The reaction patterns of their hope experience appeared in the following 4 coping method : 〈conquest type〉, 〈dependence type〉, 〈adaptation type〉 and 〈fate type〉. Finally, in the hope structure the sense of certainty don't always coexict with the sense of uncertainty, When the stroke patients try to search for the best quality of life, the senses of certainty and uncertainty make a continual cyclic system in the hope structure.

  • PDF