• 제목/요약/키워드: state space form

검색결과 290건 처리시간 0.023초

Nonlinear fluid-structure interaction of bridge deck: CFD analysis and semi-analytical modeling

  • Grinderslev, Christian;Lubek, Mikkel;Zhang, Zili
    • Wind and Structures
    • /
    • 제27권6호
    • /
    • pp.381-397
    • /
    • 2018
  • Nonlinear behavior in fluid-structure interaction (FSI) of bridge decks becomes increasingly significant for modern bridges with increasing spans, larger flexibility and new aerodynamic deck configurations. Better understanding of the nonlinear aeroelasticity of bridge decks and further development of reduced-order nonlinear models for the aeroelastic forces become necessary. In this paper, the amplitude-dependent and neutral angle dependent nonlinearities of the motion-induced loads are further highlighted by series of computational fluid dynamics (CFD) simulations. An effort has been made to investigate a semi-analytical time-domain model of the nonlinear motion induced loads on the deck, which enables nonlinear time domain simulations of the aeroelastic responses of the bridge deck. First, the computational schemes used here are validated through theoretically well-known cases. Then, static aerodynamic coefficients of the Great Belt East Bridge (GBEB) cross section are evaluated at various angles of attack, leading to the so-called nonlinear backbone curves. Flutter derivatives of the bridge are identified by CFD simulations using forced harmonic motion of the cross-section with various frequencies. By varying the amplitude of the forced motion, it is observed that the identified flutter derivatives are amplitude-dependent, especially for $A^*_2$ and $H^*_2$ parameters. Another nonlinear feature is observed from the change of hysteresis loop (between angle of attack and lift/moment) when the neutral angles of the cross-section are changed. Based on the CFD results, a semi-analytical time-domain model for describing the nonlinear motion-induced loads is proposed and calibrated. This model is based on accounting for the delay effect with respect to the nonlinear backbone curve and is established in the state-space form. Reasonable agreement between the results from the semi-analytical model and CFD demonstrates the potential application of the proposed model for nonlinear aeroelastic analysis of bridge decks.

Two-dimensional curved panel vibration and flutter analysis in the frequency and time domain under thermal and in-plane load

  • Moosazadeh, Hamid;Mohammadi, Mohammad M.
    • Advances in aircraft and spacecraft science
    • /
    • 제8권4호
    • /
    • pp.345-372
    • /
    • 2021
  • The analysis of nonlinear vibrations, buckling, post-buckling, flutter boundary determination and post-flutter behavior of a homogeneous curved plate assuming cylindrical bending is conducted in this article. Other assumptions include simply-supported boundary conditions, supersonic aerodynamic flow at the top of the plate, constant pressure conditions below the plate, non-viscous flow model (using first- and third-order piston theory), nonlinear structural model with large deformations, and application of mechanical and thermal loads on the curved plate. The analysis is performed with constant environmental indicators (flow density, heat, Reynolds number and Mach number). The material properties (i.e., coefficient of thermal expansion and modulus of elasticity) are temperature-dependent. The equations are derived using the principle of virtual displacement. Furthermore, based on the definitions of virtual work, the potential and kinetic energy of the final relations in the integral form, and the governing nonlinear differential equations are obtained after fractional integration. This problem is solved using two approaches. The frequency analysis and flutter are studied in the first approach by transferring the handle of ordinary differential equations to the state space, calculating the system Jacobin matrix and analyzing the eigenvalue to determine the instability conditions. The second approach discusses the nonlinear frequency analysis and nonlinear flutter using the semi-analytical solution of governing differential equations based on the weighted residual method. The partial differential equations are converted to ordinary differential equations, after which they are solved based on the Runge-Kutta fourth- and fifth-order methods. The comparison between the results of frequency and flutter analysis of curved plate is linearly and nonlinearly performed for the first time. The results show that the plate curvature has a profound impact on the instability boundary of the plate under supersonic aerodynamic loading. The flutter boundary decreases with growing thermal load and increases with growing curvature.

소양면 지역사회 환경기초조사 (A Basie Community Health Survey in Rural Korea (Soyang-Myun))

  • 최승렬
    • Journal of Preventive Medicine and Public Health
    • /
    • 제6권1호
    • /
    • pp.133-160
    • /
    • 1973
  • 1. Introduction Community medicine with the concept of comprehensive medical care and an ideal medical care delivery system not only for an individual or family but for the whole community has emerged. In April 1970, the Presbyterian Medical Center started a hospital based community health service project in order to improve the health of the people in rural areas. Prior to commencing a comprehensive medical care system, a family survey was needed. The major objective of this survey was to obtain information concerning the people and their environment so as to be able to plan and implement a comprehensive medical care program in Soyang-Myun. 2. Survey Method An interview using a family record form was carried out for each household. This family record form was designed to get information about demography, family planning, environmental sanitation and vital statistics. Prior to beginning, the members of the survey team were trained in interviewing techniques for three days. The team consisted of a public health nurse, four nurse-aides, a sanitarian and four health extension workers who are working in our project, The survey was carried out during the period November 1971 to March 1972. 3. Project area 1) Population of Soyang-Myun was 11,668; male, 5,962 and female, 5,706. Sex ratio: 104.5. 2) Households : 1,858 3) Family size: The average household consisted of 6.3 persons. 4) Educational level of householder a. Illiterate 13% b. No schooling but able to read 10% c. Preschool children 19% d. Primary school 47% e. Middle school 7% f. High school 3% g. College or University 1% 5) Occupational distribution of householders a. Farmer 67% b. Laborer 13% c. Office worker 4% d. Merchant 4% e. Industrial worker 2% f. Unemployed 8% g. Miscellaneous 2% 6) Religious affiliation a. No religion 74% b. Buddhist 12% c. Protestant 10% d. Catholic 4% 4. Survey results Living Environment : a. Home ownership 95% b. Kinds of roofing Straw-thatched house 84% Tile-roofed house 10% Slate-roofed house 5% Other 1% c. Floor space Less than 6 pyong 10% 6-10 pyong 53% 11-15 pyong 24% 16-20 pyong 9% More than 20 pyong 4% d. Radio ownership 80% Environmental Sanitation : a. the source of drinking water public well 49% private well 30% drainage water 9% steam water 8% well pump 3% water distribution system 1% b. Distance between well and toilet more than 16meters 38% 6-10 meter 31% 11-15 meters 14% Less than 6 meters 17% c. The status of well management Bad 72% Fair 26% Good 2% d. General sanitary state of house Bad 37% Fair 51% Good 12% e. House drainage system had no house drainage. 77% Family Planning : a. 24% of the people have used contraceptives, but 12% ceased to use them. 76% have never used contraceptives. b. used methods 1oop 68% oral pill 16% vasectomy 4% condom 1% tubal ligation 1% two or more methods 10% Maternal Health : a. The number of conceptions of housewives under 50 years of age. 11 times 26% 6 times 11% 5 times 11% 4 times 9% b. The place of delivery own house 88% hospital 1% others 11% Treatment of general sickness : a. The place of treatment Soyang Health Center 31% Hospital (private or otherwise) 26% Pharmacy 14% Herb medicine 5% Private care 5% No treatment 12% Miscellaneous 7% b. Usual causes of diseases Unknown 46% Tuberculosis 29% Neuralgia 8% CVA 3% Bronchitis 3% Others 11%

  • PDF

VAF 변분법을 이용한 전구 해양자료 동화 연구 (A Study of Global Ocean Data Assimilation using VAF)

  • 안중배;윤용훈;조익현;오혜람
    • 한국해양학회지:바다
    • /
    • 제10권1호
    • /
    • pp.69-78
    • /
    • 2005
  • 본 연구에서는 전구 해양에서 관측되는 ARGO및 TAO해양 자료를 이용하여 해양의 3차원적인 구조를 분석.동화하고 궁극적으로 해양대순환모형을 위한 초기장을 생산하였다. 초기장의 생산을 위하여 전구 해양대순환 모형인 MOM3.1을 이용하였으며 생산한 배경장에, 계산시간과 계산공간을 절약할 수 있는 공간필터를 사용한 변분법(VAF, variational analysis using filter)을 이용하여 ARGO와 TAO 수온 자료를 동화하였다. 또한 본 연구에서는 자료 동화가 미치는 지속적인 영향을 살펴보고자 실험적분을 수행하였는데, 모형의 초기입력 자료를 자료동화 기법을 적용한 경우와 적용하지 않은 두 가지로 나누어 비교 실험을 수행하였다. 본 연구에서 자료 동화된 분석장은 OISST와의 비교를 통해 적절히 생산되었음을 보여주었다. 관측자료를 동화한 분석장을 초기자료로 한 10개월간의 적분결과를 살펴보면, 자료 동화를 통해 제거된 모형의 계통적 bias가 적분이 진행되는 과정에서 관성 중력파 등의 형태로 소멸되지 않고 지속적으로 관측과 유사하게 유지되었다. 이는 본 연구에서 실행한 자료동화가 모형의 역학적인 균형을 유지하면서 적절히 이루어졌음을 의미하며, 전구 대순환 모형을 이용한 중.장기 대기.해양 예측에 이러한 해양 자료동화가 대단히 유용하다는 것을 의미한다.

카카오톡 이모티콘 선호도에 미치는 영향 요인에 관한 연구 (A Study on the Preference Factors of KakaoTalk Emoticon)

  • 이종윤;윤주현
    • 만화애니메이션 연구
    • /
    • 통권51호
    • /
    • pp.361-390
    • /
    • 2018
  • 카카오톡 이모티콘 이용자들은 가상공간에서 자신의 감정표현 커뮤니케이션 수단으로 카카오톡(Kakao Talk) 이모티콘을 이용하고 있다. 이모티콘에 담겨진 디자인적인 요소(보조, 색채, 형태, 모션)들과 스토리텔링적인 요소를 이용하여 자신의 감정상태를 표현하고 있다. 본 연구의 목적은 카카오톡 이모티콘이 지니고 있는 스토리텔링 및 디자인적인 요소들을 중심으로 어떠한 요인들로 카카오톡 이모티콘을 감정 표현 수단으로 선호하는지에 대해서 연구하고자 한다. 이모티콘의 스토리텔링적인 측면에서는 악어, 복숭아, 개, 오리, 사자, 두더지, 토끼들로 평범한 과일과 동물들로 구성하였다. 대부분의 이모티콘들은 각자 개성있는 성격의 소유자로 스토리가 구성되었으며 하나씩 콤플렉스를 가지고 있는 스토리를 지니고 있어 이용자들이 친근하게 다가가고 사용할 수 있는 요인이 되었다. 디자인적인 측면에서는 다양한 보조요소(불꽃, 땀, 눈물, 콧물, 성난 눈 등)를 사용하여 화남, 간절함, 초조함, 애원, 기쁨, 슬픔 등을 표현하였다. 색채요소는 희, 노, 애, 락의 감정에 관계없이 이모티콘 캐릭터가 지니고 있는 고유의 색채(초록, 빨강, 노랑, 분홍, 하양, 검정, 밤색 등)로 대부분의 난색 계열로 구성되었다. 형태 요소는 기쁨, 슬픔 등의 요소를 표현하는 경우 둥근형의 형태로 구성되었다. 반면에 FRODO, NEO가 슬픔과 분노를 표현하는 경우에는 사각형의 형태를 나타내고 있다. 모션요소로는 APPEACH, NEO, TUBE, JAY-G의 슬픔, 분노, 애원의 감정 표현에는 수평/수직/사선으로 표현하고 APEACH, TUBE, MUZI & CON등의 기쁨, 슬픔의 감정 표현은 수평/수직/사선과 방사/앞뒤/회전의 역동적인 느낌을 나타내고 있다. TUBE, FRODO의 분노는 수평/수직/사선과 방사 모션을 나타낸다. 본 연구결과 스토리텔링 측면에서는 감정을 차별화할 수 있는 스토리를 각 이모티콘 캐릭터에 맞게 구성하였다. 디자인적인 측면에서는 보조요소 불꽃, 땀, 눈물과 같은 감정의 대표적인 요소를 이미지로 표현하였다. 색채 요소는 감정의 차이와는 관계없이 난색 계열의 캐릭터 고유색을 사용하였다. 형태 요소는 각 감정 표현을 위해 다양한 움직임을 표현하였다. 이러한 연구결과들이 커뮤니케이션 측면, 감성디자인 측면, 산업적인 측면의 발전에 도움이 될 것이다. 위와 같은 논문의 의의에도 불구하고 스토리텔링의 분석틀과 보조요소에 대한 기호학적인 분석이 이루어지지 못한 것을 연구의 한계점으로 두고자 한다.

제한된 공간에서 반달가슴곰의 행동학적 특성 분석 (Behavioural Analysis of Asiatic Black Bear in Limited Space)

  • 정동혁;이배근;양정진;박종성;서의훈;김영기;이희천;이효종;연성찬
    • 한국임상수의학회지
    • /
    • 제26권3호
    • /
    • pp.246-258
    • /
    • 2009
  • This study was conducted for behavioral characteristic analysis of the Asiatic Black Bear in a limited space. Behaviors of eight Asiatic Black Bears were classified into 13 normal stances and locomotor activities, 15 normal maintenance behaviors, 9 locomotory compulsive behaviors, 2 non-locomotory compulsive behaviors through the 3 years of monitoring. The bears had originally been released into the Jiri National Park for Asiatic Black Bear Restoration Project and were withdrawn again because of several reasons such as habituation to humans, and apiary damage. Through the monitoring of 6 hours per day during 3 months, classified behaviors were analyzed based on sex, age, observing month, observing timing, captivity period, and captive form. The total rate of stereotypic behaviors was $26.51{\pm}13.38%$. Among these, RA(Rest_A) was rated high as $47.32{\pm}18.32%$. In addition, SP(Standard pace), HR(Head rear), EP(Extended pace) were most frequently observed behaviors. The time budget of TFS(Two feet stand), SA(Sniff_A) and SB(Sniff_B) on females and younger individuals were relatively higher than male and older individuals. So we confirmed that females and younger individuals had more wariness and curiosity. As the period of captivity took longer, the rate of stereotypic behaviors was higher and more stereotypic behaviors were observed in the afternoon. At night, behaviors related with resting like Rest-A, Rest-B, Lying down, Lying on abdomen, Sitting were more frequently observed. We concluded that the captive state could affect the behaviors of Asiatic Black Bear and long term research should be necessary.

최근국제항공보안대책(最近國際航空保安対策)의 제간제(諸間題) -특히 법적측면(法的測面)을 중심(中心)으로- (Some New Problems of International Aviation Security- Considerations Forcused on its Legal Aspects)

  • 최완식
    • 항공우주정책ㆍ법학회지
    • /
    • 제5권
    • /
    • pp.53-75
    • /
    • 1993
  • This article is concerned with the comment on "Some New Problems of International Aviation Security-Considerations Forcused on its Legal Aspects". Ever since 1970, in addition to the problem of failure to accept the Tokyo, Hague and Montreal Conventions, there has been also the problem of parties to them, failing to comply with their obligations under the respective treaties, in the form especially of nominal penalties or the lack of any effort to prosecute after blank refusals to extradite. There have also been cases of prolonged detention of aircraft, passengers and hostages. In this regard, all three conventions contain identical clauses which submit disputes between two or more contracting States concerning the interpretation or application of the respective conventions to arbitration or failing agreement on the organization of the arbitration, to the International Court of Justice. To the extent to which contracting States have not contracted out of this undertaking, as I fear they are expressly allowed to do, this promision can be used by contracting States to ensure compliance. But to date, this avenue does not appear to have been used. From this point of view, it may be worth mentioning that there appears to be an alarming trend towards the view that the defeat of terrorism is such an overriding imperative that all means of doing so become, in international law, automatically lawful. In addition, in as far as aviation security is concerned, as in fact it has long been suggested, what is required is the "application of the strictest security measures by all concerned."In this regard, mention should be made of Annex 17 to the Chicago Convention on Security-Safeguarding International Civil Aviation against Acts of Unlawful Intereference. ICAO has, moreover, compiled, for restricted distribution, a Security Manual for Safeguarding Civil Aviation Against Acts of Unlawful Interference, which is highly useful. In this regard, it may well be argued that, unless States members of ICAO notify the ICAO Council of their inability to comply with opecific standards in Annex 17 or any of the related Annexes in accordance with Article 38 of the 1944 Chicago Convention on International Civil Aviation, their failure to do so can involve State responsibility and, if damage were to insure, their liability. The same applies to breaches of any other treaty obligation. I hope to demonstrate that although modes of international violence may change, their underlying characteristics remain broadly similar, necessitating not simply the adoption of an adequate body of domestic legislation, firm in its content and fairly administered, but also an international network of communication, of cooperation and of coordination of policies. Afurther legal instrument is now being developed by the Legal Committee of ICAO with respect to unlawful acts at International airports. These instruments, however, are not very effective, because of the absence of universal acceptance and the deficiency I have already pointed out. Therefore, States, airports and international airlines have to concentrate on prevention. If the development of policies is important at the international level, it is equally important in the domestic setting. For example, the recent experiences of France have prompted many changes in the State's legislation and in its policies towards terrorism, with higher penalties for terrorist offences and incentives which encourage accused terrorists to pass informations to the authorities. And our government has to tighten furthermore security measures. Particularly, in the case an unarmed hijacker who boards having no instrument in his possession with which to promote the hoax, a plaintiff-passenger would be hard-pressed to show that the airline was negligent in screening the hijacker prior to boarding. In light of the airline's duty to exercise a high degree of care to provide for the safety of all the passengers on board, an acquiescence to a hijacker's demands on the part of the air carrier could constitute a breach of duty only when it is clearly shown that the carrier's employees knew or plainly should have known that the hijacker was unarmed. The general opinion is that the legal oystem could be sufficient, provided that the political will is there to use and apply it effectively. All agreed that the main responsibility for security has to be borne by the governments. A state that supports aviation terrorism is responsible for violation of International Aviation Law. Generally speaking, terrorism is a violation of international law. It violates the sovereign rights of states, and the human rights of the individuals. We have to contribute more to the creation of a general consensus amongst all states about the need to combat the threat of aviation terrorism. I think that aviation terrorism as becoming an ever more serious issue, has to be solved by internationally agreed and closely co - ordinated measures.

  • PDF

진주 용호정원(龍虎庭園) 무산십이봉의 경관의미와 축산효과 (A Study on the Meaning and Mount Effect of Twelve Peaks of Musan in Yongho Garden, Jinju)

  • 이현우
    • 한국전통조경학회지
    • /
    • 제29권4호
    • /
    • pp.27-39
    • /
    • 2011
  • 본 연구는 경남 진주시 용호정원에 조성된 무산십이봉이 전통적 축산(Mount)의 원형이자, 지형의 단조로움을 극복하고 변화와 흥미를 유발할 수 있는 설계요소라는 전제 아래 시작되었다. 또한 연구 결과가 축산되는 유사공간의 재현 및 현대적 변용에 필요한 자료 및 시사점을 제공할 수 있을 것이란 기대 또한 크다. 무산십이봉 축산을 통해 조영자가 추구하고자 했던 12봉우리의 상징성과 공간구성원리 그리고 시각구성상의 기능 및 효과를 조망경관적 측면에서 분석 또는 해석한 본 연구의 결과는 다음과 같다. 용호정원의 핵심인 용호지는 비보 풍수적 차원에서 만들어진 인공혈구의 전형적 사례로 풍수형국의 완결을 위한 비보(裨補)의 장치이자 용과 관련한 지명의 연계를 통해 온전함을 강화시키고자 했던 산물이다. 축산의 크기는 높이 2~3.5m, 지름 약 6~12m정도의 오성상 금성산형을 하고 있으며, 봉우리의 높이는 1.9~3.2m, 평균값은 2.5m로 밝혀졌다. 봉우리의 면적은 $35{\sim}138m^2$의 범위에 있고, 면적 평균값은 $73.4m^2$로 나타났으며 이에 비례한 체적은 $30.7{\sim}115.0m^3$, 그 평균값은 $62.5m^3$으로 추산되었다. 용호정과 소선 그리고 본채 터 및 용산재의 일치된 축에서도 알 수 있듯이 선과 속의 의미 부여를 통해 용호지를 피안의 세계로 상정하였으며, 조영자는 무산십이봉의 형상을 구현시키기 위한 의도로 호두 자리에서 대응되는 지점과 교차되도록 용의 골격을 형상화한 12개의 봉우리를 축산하고, 그 중심에 '여의주를 문 용이 욱일승천(旭日昇天)하는 형상'의 무산십이봉과 용호정을 배치한 것으로 보인다. 무산십이봉 주변 중경권역은 남북으로 금성산형의 산봉으로 둘러싸여, 용호지를 중심으로 동질감을 유지한채 다층의 층위구조를 보이는 바, 이는 유사 형태조화에 기인하며 무산십이봉의 조성 시 기획된 축산의도라 사료된다. 무산십이봉 축산에는 은폐와 노출을 통한 점진적인 경관연출과 전망-은신처이론 그리고 틀에넣기 기법 등의 공간 질서가 깊숙이 내재되어 있는데, 이는 무산십이봉 각 봉우리의 노출과 둘러싸임 정도의 다양함, 전망과 시선차단 조합의 다채로움을 통해 경관의 심도와 기대감을 높이고자한 의도가 반영된 것으로 보인다. 무산십이봉에 의해 '닫힌경관'은 흥미롭고 생기 있으며 매력적인 경관인식을 배태(胚胎)하는데, 특히 축산은 용호지와 용호정 주변에 관한 경관의 심도와 흥미를 불러일으키는 지형설계적 차원에서 매우 유용하게 작용하고 있다. 더불어 용호정에서 조망하였을 때 섬을 통해 또 다른 섬이 보이도록 하는 중층적 노출효과를 의도해 특수한 위치를 배려한 경관짜임의 결과인 12개 봉우리의 묶음이 이루어졌음을 확인하였다.

경복궁 후원 수림의 변화과정 및 주요 노거수군의 역사적 가치규명 (A Study on the Historical Values of the Changes of Forest and the Major Old Big Trees in Gyeongbokgung Palace's Back Garden)

  • 신현실
    • 한국전통조경학회지
    • /
    • 제40권2호
    • /
    • pp.1-13
    • /
    • 2022
  • 본고는 최근 74년만의 개방으로 수많은 관람객이 방문하고 있는 청와대 경복궁 후원 공간의 변화과정을 통하여 후원 경관의 역사적 가치를 규명하고자 조선일기와 조선왕조실록, 도성대지도, 북궐도형, 경복궁 복원기본계획 등의 사료와 도면 등을 근거로 경복궁 후원의 시원과 발달과정을 고찰하였고 이를 통하여 다음의 결과를 도출하였다. 첫째, 조선시대 경복궁 후원은 고려시대부터 명당으로 이름난 지역이었고 당시 남경으로 명명되며 신궁이 조성된 지역이었고 고려시대 이미 풍수도참사상과 주국의 고공기의 영향을 받아 궁성과 궁궐이 조영되었음을 확인하였다. 조선시대 전기 경복궁 후원은 궁궐의 후원으로 각광받지 못하였으나 고종 시기부터 현재까지 국가 통치권자의 생활공간으로서의 장소적 가치를 지니고 있다. 둘째, 후원의 경계는 도성지도, La Coree, 경무대일원, 일본지리풍속대계, 한국사진첩, 조선건축도집, 경성부 도시계획 조사서 등의 문헌을 통해 신무문 밖 현재의 청와대 권역이 경복궁의 경외에 조성된 후원임을 규명하였다. 임진왜란을 겪으면서 황폐화된 지역을 고종시기 중건과정을 거쳐 공사(公私)가 결합된 공간으로 사용되기도 하였다. 일제강점기에는 후원의 전각들이 이건되거나 훼철되며 법궁의 후원으로서의 장소성이 훼손되었으나 광복 후 대통령 관저로 사용되며 다시금 통치자의 장소라는 가치를 회복하게 되었다. 셋째, 경복궁 후원은 왜란과 일제강점기를 통해 공간의 변화가 크게 일어났다. 지형적 변화가 가장 큰 곳은 조선총독부관저가 건립되었던 경농재 일원으로 토지의 용도변화가 빈번하였다. 반면 현 경무대지역과 소정원 옆 수림과 백악의 수림은 전통적 수림의 형태를 계승하며 보존되었다. 이를 명확하게 규명하기 위하여 1:1200의 경무대관저경내부지배치도와 위성사진을 신무문 기준으로 중첩하였고 그 결과 백악에서 발원한 물길이 현재에도 여전히 유존하고 있음을 확인하였고 물길을 따라 오늘날까지도 수림지역이 변화하지 않고 존재하였음을 확인할 수 있었다. 넷째, 전통적 수림경관이 계승된 지역들은 지형의 기능적 변화가 미비하였고 더불어 주요 노거수군이 존치되고 있다. 이 지역에서 확인되는 노거수는 역사적 가치를 가지는 지표수종들이었다. 대표적으로 녹지원에 자리한 반송은 융문당 옆 식재된 반송 중 일부가 보존되어 온 것으로 추정되며 국가원수와 중요 귀빈들의 만찬 시 포토존으로 활용되어온 역사성을 지니고 있다. 마지막으로 청와대 내 경복궁 후원의 가치를 지속적으로 보존관리하기 위해서는 일제강점기 사료들에 대한 발굴을 통해 공간의 가치를 명확히 규명하고 시대별 정원고고학적 층위의 위계를 설정하는 것이 급선무이다. 또한 경복궁으로부터 청와대로 이어지는 조선시대부터 근현대에 이르는 역사경관을 보존하기 위한 근거는 과거부터 영속되어온 청와대 경복군 후원 노거수군의 영역대를 훼손하지 않아야하며 청와대 내 수림을 전수 조사하는 후속연구가 필요하다.

Positron Annihilation Spectroscopy of Active Galactic Nuclei

  • Doikov, Dmytry N.;Yushchenko, Alexander V.;Jeong, Yeuncheol
    • Journal of Astronomy and Space Sciences
    • /
    • 제36권1호
    • /
    • pp.21-33
    • /
    • 2019
  • This paper focuses on the interpretation of radiation fluxes from active galactic nuclei. The advantage of positron annihilation spectroscopy over other methods of spectral diagnostics of active galactic nuclei (therefore AGN) is demonstrated. A relationship between regular and random components in both bolometric and spectral composition of fluxes of quanta and particles generated in AGN is found. We consider their diffuse component separately and also detect radiative feedback after the passage of high-velocity cosmic rays and hard quanta through gas-and-dust aggregates surrounding massive black holes in AGN. The motion of relativistic positrons and electrons in such complex systems produces secondary radiation throughout the whole investigated region of active galactic nuclei in form of cylinder with radius R= 400-1000 pc and height H=200-400 pc, thus causing their visible luminescence across all spectral bands. We obtain radiation and electron energy distribution functions depending on the spatial distribution of the investigated bulk of matter in AGN. Radiation luminescence of the non-central part of AGN is a response to the effects of particles and quanta falling from its center created by atoms, molecules and dust of its diffuse component. The cross-sections for the single-photon annihilation of positrons of different energies with atoms in these active galactic nuclei are determined. For the first time we use the data on the change in chemical composition due to spallation reactions induced by high-energy particles. We establish or define more accurately how the energies of the incident positron, emitted ${\gamma}-quantum$ and recoiling nucleus correlate with the atomic number and weight of the target nucleus. For light elements, we provide detailed tables of all indicated parameters. A new criterion is proposed, based on the use of the ratio of the fluxes of ${\gamma}-quanta$ formed in one- and two-photon annihilation of positrons in a diffuse medium. It is concluded that, as is the case in young supernova remnants, the two-photon annihilation tends to occur in solid-state grains as a result of active loss of kinetic energy of positrons due to ionisation down to thermal energy of free electrons. The single-photon annihilation of positrons manifests itself in the gas component of active galactic nuclei. Such annihilation occurs as interaction between positrons and K-shell electrons; hence, it is suitable for identification of the chemical state of substances comprising the gas component of the investigated media. Specific physical media producing high fluxes of positrons are discussed; it allowed a significant reduction in the number of reaction channels generating positrons. We estimate the brightness distribution in the ${\gamma}-ray$ spectra of the gas-and-dust media through which positron fluxes travel with the energy range similar to that recorded by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) research module. Based on the results of our calculations, we analyse the reasons for such a high power of positrons to penetrate through gas-and-dust aggregates. The energy loss of positrons by ionisation is compared to the production of secondary positrons by high-energy cosmic rays in order to determine the depth of their penetration into gas-and-dust aggregations clustered in active galactic nuclei. The relationship between the energy of ${\gamma}-quanta$ emitted upon the single-photon annihilation and the energy of incident electrons is established. The obtained cross sections for positron interactions with bound electrons of the diffuse component of the non-central, peripheral AGN regions allowed us to obtain new spectroscopic characteristics of the atoms involved in single-photon annihilation.