• 제목/요약/키워드: Physical Host

검색결과 195건 처리시간 0.025초

What Makes Red Quasars Red?

  • Kim, Dohyeong;Im, Myungshin
    • 천문학회보
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    • 제41권1호
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    • pp.66.2-66.2
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    • 2016
  • Red quasars have been suspected to be an intermediate population between merger-driven star-forming galaxies and normal quasars. In this scenario, red quasars are expected to have dusty red color coming from the dust extinction by dust and gas in their host galaxy. However, several studies have proposed different explanation of the red color of red quasars, which are i) a moderate viewing angle between type 1 and 2 quasars, ii) an unusual covering factor of dust torus, and iii) an anomalous synchrotron emission with a peak at NIR wavelength. In this study, we investigate the factor leading to the red color of red quasars by using the line luminosity ratios of the hydrogen Balmer to Paschen series of 11 red quasars. We find the Pb/Hb luminosity ratios of the red quasars are significantly higher than those of normal quasars. Moreover, we compare the Pb/Hb luminosity ratios of the red quasars to the theoretically expected line luminosity ratios computed from the CLOUDY code. We find the line luminosity ratios of the red quasars cannot be explained by the theoretical line luminosity ratios with any physical conditions. We conclude that red color of red quasars comes from dust extinction by their host galaxy. This result is consistent with the picture that red quasars are an intermediate population between the merger-driven star-forming galaxies and normal quasars.

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이동 호드트들간의 경제성있는 통신을 위한 새로운 루팅 프로토콜 (A New Routing Protocol for Cost-Effective Communication between Mobile Hosts)

  • 차영환
    • 한국정보처리학회논문지
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    • 제2권3호
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    • pp.406-416
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    • 1995
  • 본 논문은 이동 호스트(mobile hast)를 수용하는 컴퓨터 네트워크상에 있어 이동 호스트간의 경제성 있는 통신을 지원하는 메세지 루팅 프로토콜에 관한 것이다. 제안 된 루팅 프로토콜은 이동 호스트의 위치 이동에 따른 위치 정보의 등록을 담당하는 위치 등록 프로토콜과 이동 호스트로의 신뢰성있는 메세지 전달을 수행하는 메세지 전 달 프로토콜로 구성된다. 제안 프로토콜은 주요 특성과 동작 절차를 제안 하고, 기존 의 대표적인 프로토콜들과의 비교를 통해 제안된 프로토콜이 기능적인 측면에서는 물 론 메세지 루팅시 수반되는 통신 비용(메세지 수)에 있어서도 개선되었음을 보였다.

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The Chemical Composition of HD47536: A Planetary Host Halo Giant with Possible 𝛌 Bootis Features and Signs of Interstellar Matter Accretion

  • Yushchenko, Alexander;Doikov, Dmytry;Andrievsky, Sergei;Jeong, Yeuncheol;Yushchenko, Volodymyr;Rittipruk, Pakakaew;Kovtyukh, Valery;Demessinova, Aizat;Gopka, Vira;Raikov, Alexander;Jeong, Kyung Sook
    • Journal of Astronomy and Space Sciences
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    • 제39권4호
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    • pp.169-180
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    • 2022
  • We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements. We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to qualitatively explain the abundance patterns in the atmosphere of HD47536.

Site spectroscopy probing of Eu3+ incorporated into novel LiYxSryZrO3+α host matrix

  • Ahemen, I.;Dejene, F.B.
    • Current Applied Physics
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    • 제18권11호
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    • pp.1359-1367
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    • 2018
  • In this work, we investigated the spectroscopic properties of $LiY_xSr_yZrO_{3+{\alpha}:Eu^{3+}$, a red emitting nanophosphor based on $SrZrO_3$ perovskite. The synthesis process was an auto-combustion process. X-ray diffractograms show the orthorhombic structure of $SrZrO_3$. Photoluminescence (PL) excitation spectra display a split charge transfer band revealing the presence of two possible sites for the $Eu^{3+}$ ions. The emission spectra at 231 nm excitation illustrate the dominance of the $^5D_0-^7F_1$ transition, which is an indication that the smaller sized $Eu^{3+}$ ions are mostly situated at the more ordered (symmetric) $Sr^{2+}$ sites. The emission spectra at 292 nm & 397 nm excitations show the dominance of $^5D_0-^7F_2$ transition which suggests some of the $Eu^{3+}$ ions are also situated at the distorted $Zr^{4+}$ sites. Both the intensity parameters, asymmetry ratio and the decay lifetimes of the nanophosphors show dependence on $Y^{3+}$ concentration, signifying a modification in the host structure. Maximum quantum efficiency value of ${\approx}46%$ was obtained for the nanophosphors which indicate the need for improvement for practical applications. CIE coordinates show the suitability of this phosphor for both red emission in LED and as a complementary colour for white LED applications.

Satellites of Isolated Early-type Galaxies and the Missing Satellite Galaxy Problem

  • Park, Changbom;Hwang, Ho Seong;Park, Hyunbae;Lee, Jong Chul
    • 천문학회보
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    • 제42권2호
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    • pp.39.1-39.1
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    • 2017
  • The standard hierarchical galaxy formation scenario in the popular LCDM cosmogony has been very successful in explaining the large-scale distribution of galaxies. However, one of the failures of the theory is that it predicts too many satellite galaxies associated with massive galaxies compared to observations, which is called the missing satellite galaxy problem. Isolated groups of galaxies hosted by passively evolving massive early-type galaxies are ideal laboratories for finding the missing physics in the current theory. We discover through a deep spectroscopic survey of galactic satellite systems that bright isolated early-type galaxies have almost no satellite galaxies fainter than the r-band absolute magnitude of about Mr=-14. The cutoff is at somewhat brighter magnitude of about Mr=-15 when only early-type satellites are used. Such a cutoff is not observed in the luminosity function of galaxies in the field. Physical properties of the observed satellites depend sensitively on the host-centric distance. All these are strong evidence that galactic satellites can become invisible due to astrophysics of satellite-host galaxy interaction. A recent state-of-the-art hydrodynamic simulation of galaxy formation does not reproduce such a cutoff in the satellite galaxy luminosity function. But the past history of the simulated satellites shows that many satellite galaxies near or somewhat fainter than the cutoff magnitude have recently become extinct through fatal encounters with the host or other satellite galaxies. Our observation indicates that the missing satellite galaxy problem could be mitigated if the astrophysics of galaxy interaction is more elaborated in the theory.

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Adaptive Fuzzy 제어기를 이용한 Embedded 시스템 기반의 기능성 고분자 구동체 다중제어에 관한 연구 (A Study on Multi-Vehicle Control of Electro Active Polymer Actuator based on Embedded System using Adaptive Fuzzy Controller)

  • 김태형;김훈모
    • 한국정밀공학회지
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    • 제20권2호
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    • pp.94-103
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    • 2003
  • In case of environment requiring safety such as human body and requiring flexible shape, a conventional mechanical actuator system does not satisfy requirements. Therefore, in order to solve these problems. a research of various smart material such as EAP (Electro Active Polymer), EAC (Electro Active Ceramic) and SMA (Shape Memory Alloy) is in progress. Recently, the highest preferring material among various smart material is EP (Electrostictive Polymer), because it has very fast response time, powerful force and large displacement. The previous researches have been studied properties of polymer and simple control, but present researches are studied a polymer actuator. An EP (Electostrictive Polymer) actuator has properties which change variably ils shape and environmental condition. Therefore, in order to coincide with a user's purpose, it is important not only to decide a shape of actuator and mechanical design but also to investigate a efficient controller. In this paper, we constructed the control logic with an adaptive fuzzy algorithm which depends on the physical properties of EP that has a dielectric constant depending on time. It caused for a sub-actuator to operate at the same time that a sub-actuator system operation increase with a functional improvement and control efficiency improvement in each actuator, hence it becomes very important to manage it effectively and to control the sub-system which Is operated effectively. There is a limitation on the management of Main-host system which has multiple sub-system, hence it brings out the Multi-Vehicle Control process that disperse the task efficiently. Controlling the multi-dispersion system efficiently, it needs the research of Main-host system's scheduling, data interchange between sub-actuators, data interchange between Main-host system and sub-actuator system, and data communication process. Therefore in this papers, we compared the fuzzy controller with the adaptive fuzzy controller. also, we applied the scheduling method for efficient multi-control in EP Actuator and the algorithm with interchanging data, protocol design.

무선 네트워크에서의 초증가 수열을 통한 주소 은닉 기법 설계 (Design of the Covered Address Generation using the Super Increasing Sequence in Wireless Networks)

  • 천준호;김성찬;장근원;도경화;전문석
    • 정보처리학회논문지C
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    • 제14C권5호
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    • pp.411-416
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    • 2007
  • 대부분의 무선 네트워크 보안 기법은 암호학적인 안정성을 기반으로 통신 내용을 악의적인 호스트로 부터 보호하는 기밀성을 제공하지만 통신의 논리/물리적 주소를 노출시킨다. 이는 악의적인 노드에게 통신 내용은 숨길 수 있지만 대략의 전송량과 송신자와 수신자를 노출시키는 단점을 갖는다. 본 논문에서 제안하는 은닉주소 체계는 송신자와 수신자의 주소를 초증가 수열을 사용한 knapsack problem을 응용하여 생성된 은닉주소로 치환한다. 또한 은닉주소의 잦은 변환을 통해 악의적인 사용자가 공격 대상을 감시하거나 측정 호스트를 공격 대상으로 삼는 것을 원천적으로 차단한다. 이 기법은 공격 목표가 되는 호스트의 주소가 계속 변화하므로 DDoS 공격을 시도하려는 공격자가 공격 목표를 특정 할 수 없다.

OGLE-2017-BLG-1049: ANOTHER GIANT PLANET MICROLENSING EVENT

  • Kim, Yun Hak;Chung, Sun-Ju;Udalski, A.;Bond, Ian A.;Jung, Youn Kil;Gould, Andrew;Albrow, Michael D.;Han, Cheongho;Hwang, Kyu-Ha;Ryu, Yoon-Hyun;Shin, In-Gu;Shvartzvald, Yossi;Yee, Jennifer C.;Zang, Weicheng;Cha, Sang-Mok;Kim, Dong-Jin;Kim, Hyoun-Woo;Kim, Seung-Lee;Lee, Chung-Uk;Lee, Dong-Joo
    • 천문학회지
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    • 제53권6호
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    • pp.161-168
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    • 2020
  • We report the discovery of a giant exoplanet in the microlensing event OGLE-2017-BLG-1049, with a planet-host star mass ratio of q = 9.53 ± 0.39 × 10-3 and a caustic crossing feature in Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of θE = 0.52 ± 0.11 mas. However, the microlens parallax is not measured because the time scale of the event, tE ≃ 29 days, is too short. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. We find that the lens system has a star with mass Mh = 0.55+0.36-0.29 M⊙ hosting a giant planet with Mp = 5.53+3.62-2.87 MJup, at a distance of DL = 5.67+1.11-1.52 kpc. The projected star-planet separation is a⊥ = 3.92+1.10-1.32 au. This means that the planet is located beyond the snow line of the host. The relative lens-source proper motion is μrel ~ 7 mas yr-1, thus the lens and source will be separated from each other within 10 years. After this, it will be possible to measure the flux of the host star with 30 meter class telescopes and to determine its mass.

해남 대흥사 북미륵암 마애여래좌상의 암석기재적 특성과 손상도 평가 (Petrographic Characteristics and Deterioration Evaluation of the Rock-carved Seated Buddha at Bugmireugam Hermitage in Daeheungsa Temple of Haenam, Korea)

  • 조지현;이찬희
    • 자원환경지질
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    • 제52권6호
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    • pp.617-626
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    • 2019
  • 이 연구에서는 해남 대흥사 북미륵암 마애여래좌상을 구성하는 석재의 암석학적 특성과 물성을 진단하였다. 이 마애불상은 미문상화강암에 부조되어 있으며, 전체적인 암상은 장석에 포위된 작은 석영 결정들이 미문상 조직을 이루고 있다. 손상도 진단 및 평가 결과, 흑색변색(8.4%)과 균열지수(6.6)에서 높은 훼손율을 보였고, 초음파 속도는 약간 풍화단계의 풍화도지수(평균 0.18)가 산출되었다. 마애불의 표면에 나타나는 손상은 기존 보호각의 영향으로 판단되고, 물성은 자연암반의 구조적 특성과 균열의 직접적인 영향에 의한 것으로 해석된다.

A Pattern-Based Prediction Model for Dynamic Resource Provisioning in Cloud Environment

  • Kim, Hyuk-Ho;Kim, Woong-Sup;Kim, Yang-Woo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제5권10호
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    • pp.1712-1732
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    • 2011
  • Cloud provides dynamically scalable virtualized computing resources as a service over the Internet. To achieve higher resource utilization over virtualization technology, an optimized strategy that deploys virtual machines on physical machines is needed. That is, the total number of active physical host nodes should be dynamically changed to correspond to their resource usage rate, thereby maintaining optimum utilization of physical machines. In this paper, we propose a pattern-based prediction model for resource provisioning which facilitates best possible resource preparation by analyzing the resource utilization and deriving resource usage patterns. The focus of our work is on predicting future resource requests by optimized dynamic resource management strategy that is applied to a virtualized data center in a Cloud computing environment. To this end, we build a prediction model that is based on user request patterns and make a prediction of system behavior for the near future. As a result, this model can save time for predicting the needed resource amount and reduce the possibility of resource overuse. In addition, we studied the performance of our proposed model comparing with conventional resource provisioning models under various Cloud execution conditions. The experimental results showed that our pattern-based prediction model gives significant benefits over conventional models.