Changes in the Angstrom Exponent during Aerosol Coagulation and Condensation

Chang H. Jung,Ji Yi Lee,Yong P. Kim,김용표 한국대기환경학회 2012 Asian Journal of Atmospheric Environment (AJAE) Vol.6 No.4

In this study, the Ångstrom exponent for polydispersed aerosol during dynamic processes was investigated. Log-normal aerosol size distribution was assumed,and a sensitivity analysis of the Ångstrom exponent with regards the coagulation and condensation process was performed. The Ångstrom exponent is expected to decrease because of the particle growth due to coagulation and condensation. However, it is difficult to quantify the degree of change. In order to understand quantitatively the change in the Ångstrom exponent during coagulation and condensation,different real and imaginary parts of the refractive index were considered. The results show that the Ångstrom exponent is sensitive to changes in size distribution and refractive index. The total number concentration decreases and the geometric mean diameter of aerosols increase during coagulation. On the while, the geometric standard deviation approaches monodispersed size distribution during the condensation process, and this change in size distribution affects the Ångstrom exponent. The degree of change in the Ångstrom exponent depends on the refractive index and initial size distribution, and the size parameter changes with the Ångstrom exponent for a given refractive index or chemical composition; this indicates that the size distribution plays an important role in determining the Ångstrom exponent as well as the chemical composition. Subsequently, this study shows how the Ångstrom exponent changes quantitatively during the aerosol dynamics processes for a log-normal aerosol size distribution for different refractive indices; the results showed good agreement with the results for simple analytic size distribution solutions.

Changes in the Ångstrom Exponent during Aerosol Coagulation and Condensation

Jung, Chang H.,Lee, Ji Yi,Kim, Yong P. Korean Society for Atmospheric Environment 2012 Asian Journal of Atmospheric Environment (AJAE) Vol.6 No.4

In this study, the ${\AA}$ngstrom exponent for polydispersed aerosol during dynamic processes was investigated. Log-normal aerosol size distribution was assumed, and a sensitivity analysis of the ${\AA}$ngstrom exponent with regards the coagulation and condensation process was performed. The ${\AA}$ngstrom exponent is expected to decrease because of the particle growth due to coagulation and condensation. However, it is difficult to quantify the degree of change. In order to understand quantitatively the change in the ${\AA}$ngstrom exponent during coagulation and condensation, different real and imaginary parts of the refractive index were considered. The results show that the ${\AA}$ngstrom exponent is sensitive to changes in size distribution and refractive index. The total number concentration decreases and the geometric mean diameter of aerosols increase during coagulation. On the while, the geometric standard deviation approaches monodispersed size distribution during the condensation process, and this change in size distribution affects the ${\AA}$ngstrom exponent. The degree of change in the ${\AA}$ngstrom exponent depends on the refractive index and initial size distribution, and the size parameter changes with the ${\AA}$ngstrom exponent for a given refractive index or chemical composition; this indicates that the size distribution plays an important role in determining the ${\AA}$ngstrom exponent as well as the chemical composition. Subsequently, this study shows how the ${\AA}$ngstrom exponent changes quantitatively during the aerosol dynamics processes for a log-normal aerosol size distribution for different refractive indices; the results showed good agreement with the results for simple analytic size distribution solutions.

Path Loss Exponent Autocalibration Using UWB and ZigBee in Indoor Environment

Adriansyah Dwi Rendragraha,Lia Suci Waliani,Fussy Mentari Dirgantara,신수용 한국통신학회 2024 韓國通信學會論文誌 Vol.49 No.2

The path loss exponent, whose value is dependent on the particular propagation environment, is a parameter that indicates the rate at which the received signal strength indicator (RSSI) weakens with distance. Path loss exponent calculation is crucial in distance-based wireless sensor network localization, where distance is inferred from the RSS data. Estimating the path loss exponent is helpful for various tasks, such as distance measurement. Current methods for path loss exponent estimation use distance and RSSI measurements from the same environment to calibrate the path loss exponent. However, in certain circumstances, obtaining a distance measurement can be expensive and complicated. In this study, a novel method for the autocalibration of the path loss exponent in ZigBee is proposed. The combination of Zigbee and UWB is introduced to improve accuracy and a comprehensive path loss exponent calculation. This paper’s main contribution is to show that the path loss exponent may be estimated using a joint ultrawideband (UWB) and ZigBee in the designated area and also create the logarithm function from scratch due to the limitation of the application used. The result indicates the measurements and calculations on the error in the distance are improved.

Sensitivity Analysis of the Ångstrom Exponent for Multimodal Aerosol Size Distributions

Chang H. Jung,엄준식,이지이,김용표 한국기상학회 2013 Asia-Pacific Journal of Atmospheric Sciences Vol.49 No.5

This study characterizes the Ångstrom exponent for polydispersed aerosol size distributions. Under the assumption of a lognormal size distribution, the dependence of Ångstrom exponent on the size distribution and the refractive index with varying real and imaginary parts are determined. Further, the influence of coarse mode particles on the Ångstrom exponent is investigated quantitatively. The results show that the nuclei mode has less influence under the simulation conditions considered in this study. It is also shown that the refractive index is an important factor influencing the Ångstrom exponent. The effect of the coarse mode on the Ångstrom exponent computed with different aerosol number concentrations and as a function of a geometric standard deviation and a geometric mean diameter is tested. It is shown that the coarse mode is crucial for determining the Ångstrom exponent.

공매도와 주식시장의 효율성에 관한 연구: Multifractal 접근

윤병조 한국금융공학회 2022 금융공학연구 Vol.21 No.1

In this study, in order to understand the effect of short selling regulations on the efficiency of the stock market, changes in hurst exponent were analyzed by applying mfdfa (multifractal detended flexible analysis) to KOSPI and KOSDAQ indexes from October 1, 2008 to December 24, 2021. First, it was confirmed that multifractal characteristics existed in the time series of the stock index, and volatility differed by period, and there was also a difference between KOSPI and KOSDAQ. In addition, as the volatility of the KOSDAQ market was greater than that of the KOSPI, it was found that volatility decreased in both markets when short selling transactions were allowed. Second, it was found that the efficiency of the stock market based on changes in Hurst exchange improved after short selling transactions resumed, and in particular, the securities market improved relatively significantly. Third, external factors have increased since the 2008 short selling ban period, and in the 2011 short selling ban period, it was observed that the securities market was quite sensitive to the government's policy to ban short selling transactions. In particular, since the end of the ban on short selling in May 2021, the impact of coronavirus infections and related policies has strongly dominated the stock market. 본 연구에서는 공매도 규제가 주식시장의 효율성에 미치는 영향을 파악하기 위해 2008년 10월 1일부터 2021년 12월 24일까지 KOSPI와 KOSDAQ 지수를 대상으로 MFDFA(Multifractal detrended fluctuation analysis)를 실행해 Hurst exponent의 변화를 분석하였다. 표본기간 동안의 연구결과는 다음과 같다. 첫째 주가지수의 시계열에 multifractal 특성이 존재하고, exponent의 변화로 측정한 변동성이 기간별로 다르면서 주가지수 간에도 차이가 있는 것으로 확인되었다. 또한 KOSDAQ 시장의 변동성이 유가증권 시장(KOSPI)의 변동성보다 크면서, 공매도 거래가 재개되었을 때 두 시장 모두 변동성이 감소하는 현상이 발견되었다. 둘째 공매도 금지기간과 허용기간을 비교했을 때, Hurst exponent의 변화에 근거한 주식시장의 효율성은 공매도 거래가 재개된 이후 개선되었고, 특히 유가증권 시장이 상대적으로 크게 향상된 것으로 나타났다. 셋째 2008년 공매도 금지기간 이후부터 외부 요인의 작용이 커졌으며, 2011년 공매도 금지기간의 경우 유가증권시장이 정부의 공매도 거래 금지정책에 상당히 민감하게 반응하는 것으로 관찰되었다. 특히 2021년 5월 공매도 금지가 해제된 이후 코로나바이러스 감염증 및 관련 정책의 영향이 주식시장을 강하게 지배하는 것으로 나타났다. 주가지수에서 발견되는 multifractal 특성을 기초로 Hurst exponent와 exponent의 변화를 측정했을 때, 공매도 금지기간에서 시장의 변동성이 증가하고, 효율성이 감소한다는 연구결과는 공매도의 순기능을 강화하는 방향으로 제도개선이 필요하다는 점을 시사한다.

학교수학에서 지수, 로그 도입과 전개에 관한 연구

이정민(Lee Jung Min),조민식(Cho Min shik) 학습자중심교과교육학회 2017 학습자중심교과교육연구 Vol.17 No.4

우리나라 학교수학은 거듭제곱의 원리에 따라 지수를 확장하고 ‘지수의 역’으로 로그를 도입하는 교수-학습 방법이 중심을 이루었다. 그 결과 많은 학생들이 학습에서 오개념과 오류를 범하게 되었다. 이에 본 연구에서는 지수와 로그의 다양한 접근을 모색하기 위해 우리나라, 프랑스, 미국의 교육과정에서 지수와 로그가 도입되고 전개되는 과정을 대수적, 함수적 사고의 관점을 통해 분석하고 비교하였다. 연구 결과 거듭제곱의 원리나 상용로그를 강조하는 우리나라와 달리 미국의 CMP와 프랑스 교육과정은 함수의 구성을 위한 지수와 로그와 자연로그를 중심으로 함수적 사고를 강조하는 관점 등이 나타나고 있음을 확인할 수 있었다. 이러한 분석의 결과는 지수와 로그에 대한 우리나라 교수-학습의 방향과 방법 개선에 새로운 시사점을 제공할 수 있을 것으로 기대한다. In Korean school curriculum, the standard learning-teaching method of exponent and logarithm is based on algebraic approach. The exponent is extended by the ‘repeated multiplication approach’ and logarithm is introduced as ‘inverse of exponent’. In this study, a new approach from advanced studies is attempted by comparing the introduction and development of exponent and logarithm in the curriculum, including Korea, France and USA. we find that in CMP and France curriculum, the functional approach which contains functional thinking is appearing and the natural logarithms is emphasized in contrast with Korea developed by algebraic approach for exponent and logarithm. This result imply that exponent and logarithm could be taught functional perspective and thinking. Also, the result of this study help improving learning-teaching method for exponent and logarithm.

함수적 사고에 따른 지수와 로그의 학습 과정에 대한 교수실험

이정민(Lee, Jung Min),조민식(Cho, Minshik) 학습자중심교과교육학회 2018 학습자중심교과교육연구 Vol.18 No.22

본 연구의 목적은 함수적 사고에 따라 지수와 로그를 학습하는 과정에서 학생들의 사고가 진행되는 과정과 변화를 탐색하는 것이다. 이를 위해 지수와 로그의 학습 경험이 없는 17세 학생 2명(고등학교 1학년)을 대상으로 4주간 교수실험과 회귀분석을 진행하였다. 이를 통해 학생들이 지수현상으로부터 함수 구성, 지수 확장, 지수현상의 가역적 사고와 로그 인식, 로그함수의 그래프 표현을 어떻게 사고하는지 살펴보았다. 연구에서 학생들은 지수함수를 구성하는 경험으로부터 직관적으로 확장된 지수의 대수적 구조를 추론하고, 지수현상을 가역적으로 사고함으로서 지수적 표현으로 로그 개념을 사고해 나가는 모습을 보였다. 그 결과 함수적 사고를 통한 지수와 로그의 접근은 지수 확장과 로그의 도입에 직관적인 통찰을 제공하며, 나아가 지수현상을 함수로 사고하는 기반이 되는 것을 확인하였다. 본 연구결과는 지수와 로그를 함수적 사고에 따라 학습하는데 구체적인 도움을 줄 수 있을 것으로 기대한다. The purpose of this study is to investigate how learning of exponent and logarithms according to functional thinking occurs to students. For this purpose, we conducted teaching experiments with two students of 10-th grader who had no pre-knwledges about exponent and logarithms. Activites of students as a functional constitution of exponential phenomena were analyzed in terms of rate of change. Constituting activities as a functional approach were ascertained how to connect and think in the process of mathematically expanding the exponent. Also, we analyze how the thinking of logarithmic exponential representation from the viewpoint of function affects the covariant approach of logarithmic functions. Results show that the understanding of the exponent and logarithms through functional thinking provides an intuitive insight into the expansion of the exponent and the understanding of the logarithms. Moreover, it is confirmed that it is the basis of thinking by connecting exponent and logarithms function.

급등주식의 급락시점에 대한 선행지수로서의 국소 허스트 지수

백인수 ( In Soo Bae ) 한국금융공학회 2010 금융공학연구 Vol.9 No.3

본 연구는 급등 후 급락하는 주식의 급락시점을 대체로 예측하는 선행지수로서 국소 허스트 지수를 제시하고 그 이론적 배경을 설명한다. 허스트 지수는 이미 잘 알려진 장기기억성에 관한 이론이다. 그러나 이러한 장기기억성을 엑셀을 이용하여 단기거래에 응용하려는 시도는 지금까지 이루어지지 않았다. 국소 허스트지수 방법의 핵심 내용은 주어진 기간에 대한 두 시점에 대한 가우스의 최소자승법을 활용한 R/S(rescaled range)분석의 방법을 이용하는 것이다. 이 연구에서는 엑셀을 이용한 국소 허스트 선행지수 방법을 실증적으로 적용한다. 한편, 2000년 바른손 주가의 급등과 급작스러운 폭락은 주식시장에 큰 영향을 미쳤다. 본 연구는 그 당시 바른손 주가의 시계열에 따른 변화와 그 원인을 국소 허스트지수 방법을 이용하여 중점적으로 분석한다. 또한 코스피 지수에 대해서도 급등하는 구간에 대한 급락시점에 대한 예측을 실증적으로 적용한다. 이와 더불어 최근 급등주식에 대한 국소 허스트 선행지수 방법을 비교 분석한다. 또한 DFA 방법을 이용한 기존 국소 Hurst지수와 우리의 국소 허스트 지수의 차별성을 논한다. 엑셀을 이용한 우리의 국소 허스트 선행지수 방법을 사용한다면, 이러한 예측기능 이외에도, 주식시장을 교란하려는 세력을 미리 탐지하는 기능 또한 제공한다. We give an approximately prospective moment when to sell the abruptly rising stock using the local Hurst exponent. It is an application of the well-known Hurst exponent persistence and anti-persistence properties. The value greater than 0.5 usually gives the persistence of the stock prices while the value less than 0.5 usually gives the anti-persistence of the stock prices. The value 0.5 gives no information of the future value of the stock prices, which means the randomness of its future price. It is not an arbitrage method since it happens in the probabilistic sense. However we get the meaningfulness from the local Hurst exponent method to expect the moment when to sell the rising stocks. Barunson stock in 2000 summer is a typical example for such a method to be applied. The moment for the stock price to drop catastrophically is exactly consistent with that of the time series which our theorem points out. Finally we compare the old local Hurst exponent from DFA(detrended fluctuation analysis) with our new local Hurst exponent from R/S(rescaled range) analysis.

파킨슨병 환자의 정량적 뇌파분석 -비선형분석을 이용한 정상인 및 본태성 진전 환자와의 비교

조은경,최병옥,김용재,박기덕,김응수,최경규,Cho, Eun-Kyoung,Choi, Byung-Ok,Kim, Yong-Jae,Park, Ki-Duck,Kim, Eung-Su,Choi, Kyoung-Gyu 대한임상신경생리학회 2006 Annals of Clinical Neurophysiology Vol.8 No.2

Background: Parkinson's disease is movement disorder due to dopaminergic deficiency. It has been noted that cognitive dysfunction also presented on Parkinson's disease patients. But, it is not clear whether such a cognitive dysfunction was a dopaminergic dysfunction or cholinergic dysfunction. Using linear and non-linear analyses, we analysed the effect of cognitive and motor symptom on EEG change. Methods: EEGs were recorded from patients with Parkinson's disease and essential tremor, and normal controls during rest. We calculated the power spectrum, correlation dimension and Lyapunov exponent by using 'Complexity'program. The power spectrum, correlation dimension, and Lyapunov exponent were compared between Parkinson's disease patients and essential tremor patients. Results: Theta power was increased in Parkinson's disease patient group. Correlation dimension was increased in Parkinson's disease patients. Positive correlation was noted between MMSE and correlation dimension, and negative correlation was noted between MMSE and Lyapunov exponent. Lyapunov exponent was decreased in Parkinson's disease patient. Conclusions: We conclude that the state of Parkinson's disease patient is characterized by increased correlation dimension and decreased Lyapunov exponent.

Primary user localization using Bayesian compressive sensing and path-loss exponent estimation for cognitive radio networks

( Hoang Anh ),( Insoo Koo ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.10

In cognitive radio networks, acquiring the position information of the primary user is critical to the communication of the secondary user. Localization of primary users can help improve the efficiency with which the spectrum is reused, because the information can be used to avoid harmful interference to the network while simultaneity is exploited to improve the spectrum utilization. Despite its inherent inaccuracy, received signal strength based on range has been used as the standard tool for distance measurements in the location detection process. Most previous works have employed the path-loss propagation model with a fixed value of the path loss exponent. However, in actual environments, the path loss exponent for each channel is different. Moreover, due to the complexity of the radio channel, when the number of channel increases, a larger number of RSS measurements are needed, and this results in additional energy consumption. In this paper, to overcome this problem, we propose using the Bayesian compressive sensing method with a calibrated path loss exponent to improve the performance of the PU localization method.