• 천문학회보
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• 제41권1호
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• pp.45.3-46
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• 2016

Solar activity shows a self-similarity as it has many periods of activity cycle in the time series of long-term observation, such as 13.5, 51, 150, 300 days, and 11, 88 years and so on. Since fractal dimension is a quantitative parameter for this kind of an irregular time series, we applied this method to long-term observations including sunspot number, total solar irradiance, and 3.75 GHz solar radio flux to predict the start and maximum times as well as expected maximum sunspot number for the next solar cycle. As a result, we found that the radio flux data tend to have lower fractal dimensions than the sunspot number data, which means that the radio emission from the sun is more regular than the solar activity expressed by sunspot number. Based on the relation between radio flux of 3.75 GHz and sunspot number, we could calculate the expected maximum sunspot number of solar cycle 24 as 156, while the observed value is 146. For the maximum time, estimated mean values from 7 different observations are January 2013 and this is quite different to observed value of February 2014. We speculate this is from extraordinary extended properties of solar cycle 24. As the cycle length of solar cycle 24, 10.1 to 12.8 years are expected, and the mean value is 11.0. This implies that the next solar cycle will be started at December 2019.

• 천문학회보
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• 제40권1호
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• pp.56.3-57
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• 2015

As of early 2015, more than 12,000 Near-Earth Objects (NEOs) have been catalogued by the Minor Planet Center, however their observational properties such as broadband colors and rotational periods are known only for a small fraction of the population. Thanks to time series observations with the KMTNet, orbits, optical sizes (and albedo), spin states and three dimensional shapes of asteroids and comets including NEOs will be systematically investigated and archived for the first time. Based on SDSS and BVRI colors, their approximate surface mineralogy will also be characterized. This so-called DEEP-South (Deep Ecliptic Patrol of the Southern Sky) project will provide a prompt solution to the demand from the scientific community to bridge the gaps in global sky coverage with a coordinated use of the network of ground-based telescopes in the southern hemisphere. We will soon finish implementing dedicated software subsystem consisted of automated observation scheduler and data pipeline for the sake of increased discovery rate, rapid follow-up, timely phase coverage, and efficient data analysis. We will give a brief introduction to test runs conducted at CTIO with the first KMTNet telescope in February and March 2015 and experimental data processing. Preliminary scientific results will also be presented.

• 지역연구
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• 제37권2호
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• pp.17-33
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• 2021

이 연구는 코로나바이러스감염증-19(이하 COVID-19) 확산 및 이에 따른 사회적 거리두기의 시행이 공원 이용자 수에 미치는 효과를 실증적으로 분석하였다. 이를 위해 서울시 송파구에 소재한 대규모 종합도시공원인 올림픽공원과 동일 자치구 내 근린공원 4 곳의 이용자 수와 COVID-19 발생에 관한 시계열 자료를 분석하고, 이를 서울의 대표적 실내 복합여가공간인 잠실 롯데월드 일대 이용자 수 변화 효과와 비교하였다. 분석결과는 다음과 같다. 먼저, 주거지역 내 위치한 소규모 근린공원은 COVID-19 확산과 이에 따른 사회적 거리두기 시행으로 발생 이전에 비해 평균적으로 3~6% 정도 이용자 수가 증가하였다. 특히 사회적 거리두기 강도 상향에 따라 공원 이용변화가 민감한 것으로 나타났다. 반면 잠실 롯데월드 일대 이용자 수가 평균적으로 38%가량 감소하였고, 올림픽공원의 경우에는 COVID-19 확산에 따라 평균적으로 1.9% 정도 이용자 수가 감소하였다. 올림픽공원의 원거리 이용자를 나타내는 차량 이용자 수가 평균적으로 23%가량 감소한 것을 고려하면, 주변지역 이용자 수는 거의 변화가 없는 것으로 추정된다. 이는 COVID-19와 같은 전염병 재난 시 도시공원, 특히 주거지역 내 근린공원은 도시인들에게 주요한 피난처이자 여가공간으로서 역할을 수행하므로 이의 적절한 공급과 유지관리가 필요하다는 것을 시사한다.

• ETRI Journal
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• 제43권6호
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• pp.1058-1080
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• 2021

Crime is not a completely random event but rather shows a pattern in space and time. Capturing the dynamic nature of crime patterns is a challenging task. Crime prediction models that rely only on neighborhood influence and demographic features might not be able to capture the dynamics of crime patterns, as demographic data collection does not occur frequently and is static. This work proposes a novel approach for crime count and hotspot prediction to capture the dynamic nature of crime patterns using taxi data along with historical crime and demographic data. The proposed approach predicts crime events in spatial units and classifies each of them into a hotspot category based on the number of crime events. Four models are proposed, which consider different covariates to select a set of independent variables. The experimental results show that the proposed combined subset model (CSM), in which static and dynamic aspects of crime are combined by employing the taxi dataset, is more accurate than the other models presented in this study.

• 천문학회보
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• 제42권2호
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• pp.70.2-70.2
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• 2017

Transit event of exoplanet is a good example of observational studies with youth, because the event is geometrically simple and its analysis is essential to astronomical observation. Therefore, we developed the package of data reduction and aperture photometry in Python for educational purpose. In 27 July, we observed the transit event of TrES-3b with the students of "NYSC Space Science Club" program, and presented the Python package, PyPhotW for data reduction and aperture photometry. PyPhotW consists of simple functions for youth to understand the processes easier. Nonetheless, the photometric results of PyPhotW show a good agreement with those of Source Extractor, ${\Delta}m{\sim}-0.01{\pm}0.03$ and $-0.04{\pm}0.08$ for TrES-3b and TrES-5b time-series observations in 27 - 28 July.

• 천문학회보
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• 제46권2호
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• pp.52.4-52.4
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• 2021

The 7-dimensional Telescope (7DT) is an innovative multiple telescope system that can perform a rapid identification of optical counterparts of gravitational-wave (GW) sources and a wide variety of other astronomical projects. This telescope is being developed as a part of the recently approved National Challenge program, the GW Universe project, with a full operation planned at the end of 2023. The word 7-dimension stands for x, y, z positions, the radial velocity, the time, the wavelength, and the flux of astronomical sources, implying the telescope's capability of performing time-series wide-field, IFU-type spectroscopic observations. The 7DT is composed of about twenty 0.5-m wide-field telescopes, and it can obtain spectral-imaging data at 40 different wavelengths to the depth of 20 AB mag with 3 min exposure for a given epoch. In this talk, we will introduce the telescope system, and outline its scientific capabilities with an emphasis on multi-messenger astronomy and a few other key science topics.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(I)
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• pp.27-40
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• 2002

Developed at Colorado State University, CASC2D-SED is a physically-based model simulating the hydrologic response of a watershed to a distributed rainfall field. The time-dependent processes include: precipitation, interception, infiltration, surface runoff and channel routing, upland erosion, transport and sedimentation. CASC2D-SED is applied to Goodwin Creek, Mississippi. The watershed covers 21 $\textrm{km}^2$ and has been extensively monitored both at the outlet and at several internal locations by the ARS-NSL at Oxford, MS. The model has been calibrated and validated using rainfall data from 16 meteorological stations,6 stream gaging stations and 6 sediment gaging stations. Sediment erosion/deposition rates by size fraction are predicted both in space and time. Geovisualization, a powerful data exploration technique based on GIS technology, is used to analyze and display the dynamic output time series generated by the CASC2D-SED model.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1024-1026
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• 2003

The purpose of establishing GPS networks of continuously operating reference stations (CORS) is aimed to assist land surveying or crustal deformation in the early stage. However, with a fast evolving and improving path the GPS technique has been extended to accurately measure atmospheric precip itable water vapor as a core objective of many projects developed in many countries and regions such as the SuomiNet (U.S., UNAVCO), COST716 (European, COST), GEONET (Japan, GSI), ...etc. In this paper, we present the current progress of the being-set-up GPS network in Taiwan whose atmospheric profile observations mainly count on the traditional radiosonde soundings as typically seen in any other part of the world. The GPS data collected from the Taiwan dense GPS network primarily supported by Central Weather Bureau are processed using the Bernese software version 4.2. Precipitable water vapor is then derived with the auxiliary surface meteorological measurements. Time series of precipitable water are examined and analyzed. A focus on the extreme weather cases is shown as an example.

• 한국지능시스템학회논문지
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• 제10권4호
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• pp.315-323
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• 2000

본 논문에서는 생명창발과 진화에 기반한 신경망 구성방법을 제안한다. 이 방법은 생뭉의 DNA 구조의 특성과 식물의 생장에 기반을 둔 방법이다. 본 논문에서 제안한 방법은 DNA 코딩 방법과 L-system의 생장 구칙을 이용하여 신경망을 구성하는 방법이닫. L-system은 병렬적인 제조합 규칙을 이용하여, DNA 코딩 방법은 표현의 제약이 없는 표기법이다. 또한 진화 알고리듬은 다윈의 자연도태를 모방한 탐색법으로 다양한 해공간의 표현과 높은 효율로 탐색이 가능하다. 본 논문에서는 이러한 방법들을 이용햐 신경망을 구성하고, 신경망의 Mackey-Glass, Sunspot, KOSPI 같은 시계열 예측분제에 적용하여 유효성을 입증하고자 한다.

• 산업기술연구
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• 제21권A호
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• pp.167-179
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• 2001

This paper discusses an index-based subsequence matching that supports time warping in large sequence databases. Time warping enables finding sequences with similar patterns even when they are of different lengths. In earlier work, we suggested an efficient method for whole matching under time warping. This method constructs a multidimensional index on a set of feature vectors, which are invariant to time warping, from data sequences. For filtering at feature space, it also applies a lower-bound function, which consistently underestimates the time warping distance as well as satisfies the triangular inequality. In this paper, we incorporate the prefix-querying approach based on sliding windows into the earlier approach. For indexing, we extract a feature vector from every subsequence inside a sliding window and construct a multi-dimensional index using a feature vector as indexing attributes. For query precessing, we perform a series of index searches using the feature vectors of qualifying query prefixes. Our approach provides effective and scalable subsequence matching even with a large volume of a database. We also prove that our approach does not incur false dismissal. To verily the superiority of our method, we perform extensive experiments. The results reseal that our method achieves significant speedup with real-world S&P 500 stock data and with very large synthetic data.