• 제목/요약/키워드: quasi-root

검색결과 29건 처리시간 0.021초

Monitoring QZSS CLAS-based VRS-RTK Positioning Performance

  • Lim, Cheolsoon;Lee, Yebin;Cha, Yunho;Park, Byungwoon;Park, Sul Gee;Park, Sang Hyun
    • Journal of Positioning, Navigation, and Timing
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    • 제11권4호
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    • pp.251-261
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    • 2022
  • The Centimeter Level Augmentation Service (CLAS) is the Precise Point Positioning (PPP) - Real Time Kinematic (RTK) correction service utilizing the Quasi-Zenith Satellite System (QZSS) L6 (1278.65 MHz) signal to broadcast the Global Navigation Satellite System (GNSS) error corrections. Compact State-Space Representation (CSSR) corrections for mitigating GNSS measurement error sources such as satellite orbit, clock, code and phase biases, tropospheric error, ionospheric error are estimated from the ground segment of QZSS CLAS using the code and carrier-phase measurements collected in the Japan's GNSS Earth Observation Network (GEONET). Since the CLAS service begun on November 1, 2018, users with dedicated receivers can perform cm-level precise positioning using CSSR corrections. In this paper, CLAS-based VRS-RTK performance evaluation was performed using Global Positioning System (GPS) observables collected from the refence station, TSK2, located in Japan. As a result of performing GPS-only RTK positioning using the open-source software CLASLIB and RTKLIB, it took about 15 minutes to resolve the carrier-phase ambiguities, and the RTK fix rate was only about 41%. Also, the Root Mean Squares (RMS) values of position errors (fixed only) are about 4cm horizontally and 7 cm vertically.

Accuracy Assessment of IGSO and GEO of BDS and QZSS Broadcast Ephemeris using MGEX Products

  • Son, Eunseong;Choi, Heonho;Joo, Jungmin;Heo, Moon Beom
    • Journal of Positioning, Navigation, and Timing
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    • 제9권4호
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    • pp.347-356
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    • 2020
  • In this study, Inclined Geosynchronous Orbit (IGSO) and Geostationary Orbit (GEO) of BeiDou System (BDS) and Quasi Zenith Satellite System (QZSS) satellites positions and clock errors calculated by broadcast ephemeris and compared with Multi-GNSS Experiment (MGEX) products provided by five Analysis Centers (ACs). Root Mean Square Errors (RMSE) calculated for satellite position error. The IGSO results showed that 1.82 m, 0.91 m, 1.28 m in BDS and 1.34 m 0.36 m 0.49 m in QZSS and the GEO results showed that 2.85 m, 6.34 m, 6.42 m in BDS and 0.47 m, 4.79 m, 5.82 m in QZSS in the direction of radial, along-track and cross-track respectively. RMS calculated for satellite clock error. The IGSO result showed that 2.08 ns and 1.24 ns and the GEO result showed that 1.28 ns and 1.12 ns in BDS and QZSS respectively.

게이트 흉부자기 공명 영상법과 함께 사용할 수 있는 의사호흡정지(QBH) 바이오 피드백 (Quasi-breath-hold (QBH) Biofeedback in Gated 3D Thoracic MRI: Feasibility Study)

  • 김태호;;;;이레나;김시용
    • 한국의학물리학회지:의학물리
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    • 제25권2호
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    • pp.72-78
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    • 2014
  • 연구의 목적은 의사호흡정지(QBH) 바이오 피드백이 의료영상획득 시간의 큰변화 없이 잔류 호흡 운동을 조절함으로써 호흡 운동에 의한 영상 오류를 줄이고, 게이트 3차 흉부 자기 공명 영상을 향상시킬 수 있다는 가설을 실험하는 것이다. 가설을 확인하기 위해 건강한 다섯 사람을 대상으로 3T 지멘스 엠알아이의 호흡 탐색기가 포함된 T2 가중 스페이스 엠알 펄스 시퀀스를 이용해 두번의 게이트 자기공명 영상 연구를 시행 하였다: 자유 호흡 상태와 의사호흡정지 바이오 피드백 호흡상태, 의사호흡정지 바이오 피드백 시스템은 알피엠(RPM) 시스템(실시간 위치 관리시스템, 베리안)을 사용하여, 복부의 외부 위치를 측정하고, 음향과 시각적으로 각각의 호흡주기의 90% 위치에서 2초 숨을 정지하도록 안내하는 방법을 사용했다. 평가방법은 의사호흡정지 바이오 피드백 시스템을 이용시 간 상부의 호흡정지모습의 재현성이 게이팅 영역 내에서 향상되는지를 지원자의 실험을 통해 평가하였다. 자유호흡상태와 의사호흡정지 바이오 피드백상태에서 3차 흉부자기공명영상내에 호흡 운동에 의한 영상 오류와 게이팅영역 내에서의 잔류 호흡 운동 조절여부도 함께 평가했다. 또한, 복부 변위의 RMSE도 (제곱근오차) 조사되었다. 의사호흡정지 바이오 피드백방법을 사용함으로 자유호흡의 경우보다 게이트 3차 흉부 엠알 영상에서 폐와 간에서 호흡운동에 의한 영상오류의 감소 결과를 획득했다(영상획득시간: ~6분). 이는 의사호흡정지 바이오 피드백사용시, 게이팅 영역에서 복부 운동 감소와 횡경막의 잔류 움직임 감소가 일치함을 의미한다. 따라서, 알피엠을 통해 얻은 복부 변위의 전체 자료에서평균 RMSE는 (제곱근오차) 자유 호흡의 2.0 mm에 비해 7 mm (67% 감소, p값=0.02)로 감소하였으며, 게이팅영역만을 고려했을때는 자유 호흡의 1.7 mm가 의사호흡정지 바이오 피드백 호흡을 사용함으로써 0.7 mm (58 % 감소, p값=0.14) 로 개선되었다. 선형 피팅을 사용하여 얻은 평균 기준 이동값은 의사호흡정지 바이오 피드백 을 사용하면 자유 호흡 5.5 mm/분보다 0.6 mm/분(89% 감소, p값=0.017)으로 감소되었다. 이 연구는 의사호흡정지 바이오 피드백을 이용해 게이트 3차 흉부 자기 공명 영상 중에 간 상부의 호흡정지 재현성이 향상되는 것을 보여 주었다. 이 시스템은 내부 해부학의 운동을 조절함으로써 게이트 의료 영상과 방사선 치료에 임상적으로 적용 할 수 있다.

Papaya: A gifted nutraceutical plant - a critical review of recent human health research

  • Karunamoorthi, Kaliyaperumal;Kim, Hyung-Min;Jegajeevanram, Kaliyaperumal;Xavier, Jerome;Vijayalakshmi, Jayaraman
    • 셀메드
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    • 제4권1호
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    • pp.2.1-2.17
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    • 2014
  • The plant kingdom is considered to be a repository of modern medicine, attributable to their rich source of bio-active molecules and secondary metabolites. It is indeed the Nutraceuticals that enhance immunity and ensure a healthier life because of their prophylactic and therapeutic values. Over centuries, papaya [Caricaceae; (Carica papaya Linn.)] is a renowned nutritious and medicinal plant. Each part of the papaya like root, stem, leaf, flower, fruit, seed, rinds, and latex has its own nutraceutical properties. It serves as food, cooking aid, and Ethnomedicine to prevent and treat wide-range of diseases and disorders. It has also been traditionally used as appetite enhancer, meat tenderizer, purgative, medicinal acne, abortifacient and vermifuge. Over decades, a series of scientific attempts were made to authenticate the nutraceutical properties of papaya. These studies validated that the papaya has antiplasmodial, antitrichochramal, antitrichomonal, antidengue, and anti-cancer activities. They have also exhibited that papaya possesses antiseptic, antiparasitic, anti-inflammatory, antidiabetic, and contraceptive features, and it helps in the management of sickle-cell anaemia, HIV, heart diseases and digestional disorders too. Nevertheless, the responsible bio-active molecules and their mode of actions remain indistinct and imprecise, and this calls for further pharmacological and clinical research on them. Conclusively, papaya is one of the naturally gifted plants; though its nutraceutical properties as a food or as a quasi-drug are poorly understood or undervalued by people. Accordingly, this scrutiny, demand for instigation of public health awareness campaigns to promote papaya consumption, so that the society shall acquire optimal benefits of papaya and in turn prevent and alleviate various diseases and illness.

기상청 기후예측시스템(GloSea6) - Part 1: 운영 체계 및 개선 사항 (The KMA Global Seasonal Forecasting System (GloSea6) - Part 1: Operational System and Improvements)

  • 김혜리;이조한;현유경;황승언
    • 대기
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    • 제31권3호
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    • pp.341-359
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    • 2021
  • This technical note introduces the new Korea Meteorological Administration (KMA) Global Seasonal forecasting system version 6 (GloSea6) to provide a reference for future scientific works on GloSea6. We describe the main areas of progress and improvements to the current GloSea5 in the scientific and technical aspects of all the GloSea6 components - atmosphere, land, ocean, and sea-ice models. Also, the operational architectures of GloSea6 installed on the new KMA supercomputer are presented. It includes (1) pre-processes for atmospheric and ocean initial conditions with the quasi-real-time land surface initialization system, (2) the configurations for model runs to produce sets of forecasts and hindcasts, (3) the ensemble statistical prediction system, and (4) the verification system. The changes of operational frameworks and computing systems are also reported, including Rose/Cylc - a new framework equipped with suite configurations and workflows for operationally managing and running Glosea6. In addition, we conduct the first-ever run with GloSea6 and evaluate the potential of GloSea6 compared to GloSea5 in terms of verification against reanalysis and observations, using a one-month case of June 2020. The GloSea6 yields improvements in model performance for some variables in some regions; for example, the root mean squared error of 500 hPa geopotential height over the tropics is reduced by about 52%. These experimental results show that GloSea6 is a promising system for improved seasonal forecasts.

골내 임플랜트의 종류에 따른 광탄성 응력 분석 (PHOTOELASTIC ANALYSIS OF STRESS INDUCED BY DIFFERENT TYPE ENDOSSEOUS IMPLANTS)

  • 정재헌;장두익
    • 대한치과보철학회지
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    • 제31권4호
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    • pp.661-678
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    • 1993
  • The purpose of this study was to analyze the stress distribution at supporting bone according to the types of endosseous implants. This investigation evaluated the stress patterns in rectangular photoelastic models produced by four different types of dental implants such as $Br\ddot{a}nemark$, screw type of Steri-Oss, blade type of Steri-Oss, IMZ with IMC and resin tooth using the techniques of quasi-three dimensional photoelasticity. All prostheses were casted in the same nonprecious alloy and were cemented or screwed on their respective implants and abutments. 20 kg of vertical load was applied on the central fossa of casted crown and 16 kg of inclined had was applied on the top third of distal surface of casted crown respectively. The results were as follows : 1. Under the vertical load, screw implants of Steri-Oss and $Br\ddot{a}nemark$ showed increasing stress condition between and around the screw threads along the implant lateral surface and cylindrical implant of IMZ showed the less stress condition along the lateral surface with concentration of stress mostly near the root apex. 2. Under the vertical load, the stress of Steri-Oss blade was distributed uniformly at the alveolar bone under the broad blade. 3. Under the inclined load, the stress concentration of Steri-Oss screw and $Br\ddot{a}nemark$ was developed highly around the mesiocervical bone area on the contralateral side to force application. The stress of $Br\ddot{a}nemark$ with flexible gold glod was more concentrated in the cervical bone area than that of Steri-Oss with stiff screw. 4. Under the inclined load, the stress of Steri-Oss blade broadly was distributed around the mesioceivical bone area and the lower and mesial bone area of the blade. 5. Under the Inclined load, IMZ implant showed the gap between c개wn and fixture due ta deformation of the IMC and IMZ was lower in stress concentration developed around the mesiocervical bone area than $Br\ddot{a}nemark$ and Steri-Oss screw. 6. Under the inclined load, the stress magnitude induced in the mesiocervical bone area of implants was in order of $Br\ddot{a}nemark$, Steri-Oss strew, IMZ and Stsri-Oss blade. 7. Tilting forces as compared to axial forces exerted greater magnitude of stress in the cervical bone area of the implant. 8. In respect of stress distribution, Steri-Oss blade was superior than any other implants and in respect of the stability by horizontal lone, IMB and $Br\ddot{a}nemark$ was inferior than any other implants.

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Orbit Determination of High-Earth-Orbit Satellites by Satellite Laser Ranging

  • Oh, Hyungjik;Park, Eunseo;Lim, Hyung-Chul;Lee, Sang-Ryool;Choi, Jae-Dong;Park, Chandeok
    • Journal of Astronomy and Space Sciences
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    • 제34권4호
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    • pp.271-280
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    • 2017
  • This study presents the application of satellite laser ranging (SLR) to orbit determination (OD) of high-Earth-orbit (HEO) satellites. Two HEO satellites are considered: the Quasi-Zenith Satellite-1 (QZS-1), a Japanese elliptical-inclinedgeosynchronous-orbit (EIGSO) satellite, and the Compass-G1, a Chinese geostationary-orbit (GEO) satellite. One week of normal point (NP) data were collected for each satellite to perform the OD based on the batch least-square process. Five SLR tracking stations successfully obtained 374 NPs for QZS-1 in eight days, whereas only two ground tracking stations could track Compass-G1, yielding 68 NPs in ten days. Two types of station bias estimation and a station data weighting strategy were utilized for the OD of QZS-1. The post-fit root-mean-square (RMS) residuals of the two week-long arcs were 11.98 cm and 10.77 cm when estimating the biases once in an arc (MBIAS). These residuals were decreased significantly to 2.40 cm and 3.60 cm by estimating the biases every pass (PBIAS). Then, the resultant OD precision was evaluated by the orbit overlap method, yielding three-dimensional errors of 55.013 m with MBIAS and 1.962 m with PBIAS for the overlap period of six days. For the OD of Compass-G1, no station weighting strategy was applied, and only MBIAS was utilized due to the lack of NPs. The post-fit RMS residuals of OD were 8.81 cm and 12.00 cm with 49 NPs and 47 NPs, respectively, and the corresponding threedimensional orbit overlap error for four days was 160.564 m. These results indicate that the amount of SLR tracking data is critical for obtaining precise OD of HEO satellites using SLR because additional parameters, such as station bias, are available for estimation with sufficient tracking data. Furthermore, the stand-alone SLR-based orbit solution is consistently attainable for HEO satellites if a target satellite is continuously trackable for a specific period.

주파수 선택성 페이딩 환경하에서 $\frac{\pi}{4}$ shift QPSK 변조방식에 대한 다중파의 시간지역 검출법 제안 (A Multipath Delay Time Detection Method For $\frac{\pi}{4}$ Shift QPSK Modulation Under The Frequency Selective Fading Environment)

  • 조병진;김대영
    • 한국통신학회논문지
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    • 제16권10호
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    • pp.941-950
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    • 1991
  • 디지털 이동통신 전송로에 있어서 고속통신을 위한 시스템의 성능은 다중파 지연분산에 의해 크게 좌우된다. 본 논문에서는 최근 디지털 자동차 전화의 변복조방식으로 채택된 $\pi/4$ shift QPSK에 대해, 간이 다중파 지연시간 검출방법으로써 직교채널간섭량 (CCI)을 이용하는 방법을 제안하였다. $\pi/4$ shift QPSK신호는 원래 직교 채널에 정보를 갖고있기 때문에 BPSK변조방식처럼 Quadrature채널에서 간섭량을 얻기 위하여 주파수 체배기와 지연전파 방식을 제안하였다. 또한 다중파 전파환경하에서, 격렬하게 변하는 직교채널 간섭량으로 부터 정보를 얻는 방법으로서 절대치평균과 실효치 평균을 취하는 방법을 제안하였으며, 아울러 자연분산과 직교채널 간섭량과의 관계도 조사하였다. 이론적인 결과를 확인하기 위하여, 준정적인 2파 모델과 Rayleigh분포 2파모델하에서 computer simulation을 수행하였다. simulation결과 좋은 결과가 얻어졌으나. 본방식은 송신 대역제한에 어느정도 민감하다는 것이 밝혀졌다. 또한 H/W실현시 주요부분인 주파수 체배기에 대한 H/W구성 방안도 제안하였다.

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지구 자전속도에 따른 해들리 순환과 제트의 반응 (The Response of Hadley Cell and Jet Stream to Earth's Rotation Rate)

  • 조종혁;김서연;손석우
    • 한국지구과학회지
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    • 제40권3호
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    • pp.203-211
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    • 2019
  • 대기 대순환을 결정하는 주요 인자로는 남북방향 온도 경도와, 지구 자전으로 인한 코리올리 힘이 있다. 남북방향 온도 경도에 따른 경압성 차이로 인한 대기 대순환의 변화는 지금까지 많이 연구되어 왔으나, 자전속도에 따른 대기 대순환의 반응은 크게 연구되어 오지 않았다. 때문에 본 연구에서는 현 지구보다 느리거나 빠른 자전속도 범위를 모두 포괄하여 이에 따른 해들리 순환과 제트의 변화를 확인하였다. 이 연구에서 우리는 지구의 자전속도가 빨라질수록 해들리 순환 경계와 제트의 위치가 적도에 가까워지고, 제트와 해들리 순환의 세기가 약해진다는 것을 발견하였다. 해들리 순환 경계와 제트의 위치는 자전속도가 매우 빠르거나 느린 경우를 제외하면 준선형적인 관계를 가졌다. 특히, 해들리 순환 경계는 자전속도가 현재보다 1/8에서 8배의 자전속도 범위에서 자전속도보다 그 제곱근에 더 잘 반비례하는 경향성을 보였다. 단, 이러한 자전속도에 따른 변화는 해들리 순환 세기와 제트의 세기에 대해서는 뚜렷하지 않았다. 이는 대기 대순환의 위치 구조 변화는 지구 자전속도와 관련이 큰 반면, 세기의 변화는 자전속도로 설명되지 않음을 의미한다.