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Search Results: 1 - 10 of 49891 matches for " Dong-In Lee "
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A comparative analysis of two wind velocity retrieval techniques by using a single Doppler radar
Hee-Chang Lim,Dong-In Lee
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: This study compares the theoretical basis of the two wind velocity retrieval methods, Velocity Azimuth Display (VAD) and Velocity Area Display (VARD) by using data obtained by a single Doppler radar. Two pre-assumed shapes of the wind velocity distribution with altitude are considered, uniform and parabolic. The former presents an approximation of the non-sheared or low-sheared wind flow in the upper troposphere, while the latter is a simplified representation of the Atmospheric Boundary Layer (ABL) in lower troposphere or high-sheared wind flow at the edges of the tropospheric jet streams. Both techniques for the wind velocity retrieval considered in this study are reformulated in order to get more precise information on the wind velocity components. An algorithm is proposed to decrease the uncertainty in retrieving by evaluating the coefficients of the polynomial equation and applying a transfer function with respect to the angle formed between the wind flow and the radar beam direction. It is concluded that, provided the formulated transformation functions are used, the application of the VAD and VARD techniques to the single-Doppler data may be an invaluable tool for solving various climate and wind engineering problems.
On the Dynamical Analysis in Aftershock Networks  [PDF]
Woon-Hak Baek, Kyungsik Kim, Ki-Ho Chang, Seung-Kyu Seo, Jun-Ho Lee, Dong-In Lee
Open Journal of Earthquake Research (OJER) , 2018, DOI: 10.4236/ojer.2018.71002
Abstract:
We investigate the dynamical behavior of aftershocks in earthquake networks, and the earthquake network calculated from a time series is constructed by contemplating cell resolution and temporal causality. We attempt to connect an earthquake network using relationship between one main earthquake and its aftershocks from seismic data of California. We mainly examine some topological properties of the earthquake such as the degree distribution, the characteristic path length, the clustering coefficient, and the global efficiency. Our result cannot presently determine the universal scaling exponents in statistical quantities, but the topological properties may be inferred to advance and improve by implementing the method and its technique of networks. Particularly, it may be dealt with a network issue of convenience and of importance in the case how large networks construct in time to proceed on earthquake systems.
Design and Development of a Run-Time Monitor for Multi-Core Architectures in Cloud Computing
Mikyung Kang,Dong-In Kang,Stephen P. Crago,Gyung-Leen Park,Junghoon Lee
Sensors , 2011, DOI: 10.3390/s110403595
Abstract: Cloud computing is a new information technology trend that moves computing and data away from desktops and portable PCs into large data centers. The basic principle of cloud computing is to deliver applications as services over the Internet as well as infrastructure. A cloud is a type of parallel and distributed system consisting of a collection of inter-connected and virtualized computers that are dynamically provisioned and presented as one or more unified computing resources. The large-scale distributed applications on a cloud require adaptive service-based software, which has the capability of monitoring system status changes, analyzing the monitored information, and adapting its service configuration while considering tradeoffs among multiple QoS features simultaneously. In this paper, we design and develop a Run-Time Monitor (RTM) which is a system software to monitor the application behavior at run-time, analyze the collected information, and optimize cloud computing resources for multi-core architectures. RTM monitors application software through library instrumentation as well as underlying hardware through a performance counter optimizing its computing configuration based on the analyzed data.
Estimates of Aerosol Indirect Effect from Terra MODIS over Republic of Korea
Woon-Seon Jung,A. S. Panicker,Dong-In Lee,Sung-Hwa Park
Advances in Meteorology , 2013, DOI: 10.1155/2013/976813
Abstract: Moderate resolution imaging spectroradiometer (MODIS) data have been analyzed over four different regions (Yellow sea, Korean inland, East Sea, and South Sea) in Republic of Korea to investigate the seasonal variability of aerosol-cloud properties and aerosol indirect effect during the past decade (2000–2009). Aerosol optical depth (AOD) was found to be consistently high during spring. Cloud ice radius (CIR) also showed higher values during spring, while an enhancement in cloud water radius (CWR) and fine mode fraction (FMF) was observed during summer. AOD and aerosol index (AI) were found to be higher during January to June. However, FMF and CWR showed enhancement during July to December. Aerosol indirect effect (AIE) in each year has been estimated and found to be showing positive and negative indirect effects. The AIE for fixed cloud ice path (CIP) showed positive indirect effect (Twomey effect) over Yellow sea, while the AIE for fixed cloud water path (CWP) showed a major negative indirect effect (anti-Twomey effect) over all regions. During Changma (summer monsoon) period, the AIE for both CIP and CWP showed dominant anti-Twomey effect in middle and low level clouds, indicating the growth of cloud droplet radius with changes in aerosols, enhancing the precipitation. 1. Introduction Aerosols are known to impact the formation and the life cycle of clouds by acting as cloud condensation nuclei (CCN) or ice nuclei (IN). A wide range of measurements shows that anthropogenic aerosols induce changes in clouds and their optical properties. These changes are popularly known as aerosol indirect effect (AIE) [1–3]. It is important to understand and quantify the microphysical impact of both natural and anthropogenic aerosols on clouds, in order to understand and predict climate change. The main identified AIEs include the cloud albedo effect [4] and cloud life time effect [5]. The “Twomey effect” (positive indirect effect) refers to a decrease in a cloud effective radius with increasing aerosol content for a fixed liquid water path. Contrary to this effect, an increase in the cloud droplet size with the aerosol load, or an “anti-Twomey effect” (negative indirect effect), was also reported in some parts of the world for certain environmental conditions [6]. It has also been reported that the AIE could be an important factor in modulating the response of large scale systems such as monsoons [7–9]. However, studies on AIE and its influence on precipitation are sparse across the world [10–12]. Aerosols in Asian regions are known to be an important factor in
Aerosol Modulation of Ultraviolet Radiation Dose over Four Metro Cities in India
A. S. Panicker,G. Pandithurai,G. Beig,Dongchul Kim,Dong-In Lee
Advances in Meteorology , 2014, DOI: 10.1155/2014/202868
Abstract: This paper discusses the influence of aerosols on UV erythemal dose over four metro cities in India. Tropospheric Emission Monitoring Internet Service (TEMIS), archived UV-index (UV-I), and UV daily erythemal dose obtained from SCIAMACHY satellite were used in this study during June 2004 and May 2005 periods covering four important Indian seasons. UV-Index (UV-I), an important parameter representing UV risk, was found to be in the high to extreme range in Chennai (8.1 to 15.33), moderate to extreme range in Mumbai and Kolkata (5 to 16.5), and low to extreme over Delhi (3 to 15). Average UV erythemal dose showed seasonal variation from 5.9 to 6.3?KJm?2 during summer, 2.9 to 4.4?KJm?2 during postmonsoon, 3 to 4.5?KJm?2 during winter, and 5.1 to 6.19?KJm?2 during premonsoon seasons over the four cities. To estimate the influence of aerosols on reducing UV dose, UV aerosol radiative forcing and forcing efficiency were estimated over the sites. The average aerosol forcing efficiency was found to be from to ?KJm?2 AOD?1 on different seasons. The study suggests that aerosols can reduce the incoming UV radiation dose by 30–60% during different seasons. 1. Introduction Ultraviolet radiation, in spite of its nominal presence in solar spectrum, is important in human health perspectives. The UV region of the spectrum mainly consists of UV-C (200–280?nm), UV-B (280–315?nm), and UV-A (315–400?nm). Out of these UV-B is the most important spectral range, as it directly influences the human health. Enhanced exposure to UV-B can damage both terrestrial and oceanic organisms and also results in increases in the incidences of cataracts and skin cancer in humans [1, 2]. Very high levels of UV radiation also are reported to result in the extinction of minute biological species [3]. The impact of UV irradiance on human skin is characterized with UV erythemal dose. UV-index (UV-I) serves as a primary indicator of impact of UV radiation on human health. The UV radiation reaching the earth surface is modulated by the ozone concentration, cloud cover, solar zenith angle, and aerosols. The influences of ozone on UV radiation are well documented [4]. Several studies report the influence of cloud cover on UV radiation. Reference [5] reported that, for a solar zenith angle of 50°, average UV-B transmission was observed to be 30% for overcast skies and found to be ranging between 61 and 79% according to cloud amount. The paper [6] has shown that the effect of cloud for UV wavelengths is less than that for the whole solar spectrum and less than that for the visible part of the
Tunable 0.7 conductance plateau in quantum dots
Yunchul Chung,Sanghyun Jo,Dong-In Chang,Hu-Jong Lee,M. Zaffalon,V. Umansky,M. Heiblum
Physics , 2008, DOI: 10.1103/PhysRevB.76.035316
Abstract: A consistent approach in forming the 0.7 structure by using a quantum dot rather than a quantum point contact is demonstrated. With this scheme, it was possible to tune on and off the 0.7 structure. The 0.7 structure continuously evolved into a normal integer conductance plateau by varying the tuning condition. Unlike the conventional 0.7 plateau, the new 0.7 structure was observed even at low electron temperatures down to 100 mK, with unprecedented flatness. From our results, it is concluded that electron interference should be taken into consideration to explain the 0.7 structure.
Beating of Aharonov-Bohm oscillations in a closed-loop interferometer
Sanghyun Jo,Gyong Luck Khym,Dong-In Chang,Yunchul Chung,Hu-Jong Lee,Kicheon Kang,Diana Mahalu,Vladimir Umansky
Physics , 2008, DOI: 10.1103/PhysRevB.76.035110
Abstract: One of the points at issue with closed-loop-type interferometers is beating in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the possibility that the beating results from the Berry-phase pickup by the conducting electrons in materials with the strong spin-orbit interaction (SOI). In this study, we also observed beats in the AB oscillations in a gate-defined closed-loop interferometer fabricated on a GaAs/AlGaAs two-dimensional electron-gas heterostructure. Since this heterostructure has very small SOI, the picture of the Berry-phase pickup is ruled out. The observation of beats in this study, with the controllability of forming a single transverse subband mode in both arms of our gate-defined interferometer, also rules out the often-claimed multiple transverse subband effect. It is observed that nodes of the beats with an h/2e period exhibit a parabolic distribution for varying the side gate. These results are shown to be well interpreted, without resorting to the SOI effect, by the existence of two-dimensional multiple longitudinal modes in a single transverse subband. The Fourier spectrum of measured conductance, despite showing multiple h/e peaks with the magnetic-field dependence that are very similar to that from strong-SOI materials, can also be interpreted as the two-dimensional multiple-longitudinal-modes effect.
Quantum mechanical complementarity probed in a closed-loop Aharonov-Bohm interferometer
Dong-In Chang,Gyong Luck Khym,Kicheon Kang,Yunchul Chung,Hu-Jong Lee,Minky Seo,Moty Heiblum,Diana Mahalu,Vladimir Umansky
Physics , 2008, DOI: 10.1038/nphys854
Abstract: According to Bohr's complementarity principle, a particle possesses wave-like properties only when the different paths the particle may take are indistinguishable. In a canonical example of a two-path interferometer with a which-path detector, observation of interference and obtaining which-path information are mutually exclusive. Such duality has been demonstrated in optics with a pair of correlated photons and in solid-state devices with phase-coherent electrons. In the latter case, which-path information was provided by a charge detector embedded near one path of a two-path electron interferometer. Note that suppression of interference can always be understood either as obtaining path information or as unavoidable back action by the detector. The present study reports on dephasing of an Aharonov-Bohm (AB) ring interferometer via a coupled charge detector adjacent to the ring. In contrast to the two-path interferometer, charge detection in the ring does not always provide path information. Indeed, we found that the interference was suppressed only when path information could be acquired, even if only in principle. This demonstrates that dephasing does not always take place by coupling the `environment' to the interfering particle: path information of the particle must be available too. Moreover, this is valid regardless of the strength of environment-interferometer coupling, which refutes the general notion of the effect of strong interaction with the environment. In other words, it verifies that an acquisition of which-path information is more fundamental than the back-action in understanding quantum mechanical complementarity.
Predicting Successful Pulmonary Vein Isolation In Patients With Atrial Fibrillation By Brain Natriuretic Peptide Plasma Levels
Dong-In Shin,Thomas Deneke,Eduard Gorr,Helge Anders
Indian Pacing and Electrophysiology Journal , 2009,
Abstract: Background: Catheter ablation for atrial fibrillation is a clinically established treatment by now while success rate varies between 60% and 85%. Interventional treatment of atrial fibrillation is still a challenging technique associated with a long procedure time and risk of major complications in up to 6 % of treated patients. The aim of this study was to investigate the predictive value of plasma brain natriuretic peptide (BNP) in patients undergoing pulmonary vein isolation concerning stable sinus rhythm after ablation.Methods: In 68 consecutive patients with atrial fibrillation (AF) and normal left ventricular ejection fraction, BNP was measured at baseline before pulmonary vein isolation (PVI). All patients received a 7-days-holter monitoring 3 months after radiofrequency (RF) ablation in order to detect recurrent AF episodes. Results: 48 patients with paroxysmal and 20 patients with persistent AF were enrolled. Baseline BNP was significantly higher in patients with persistent AF compared to patients with paroxysmal AF (145,5 pg/ml vs. 84,4 pg/ml; p<0,05). 3 months after PVI 38 patients (79,1%) with paroxysmal AF had a stable sinus rhythm documented on 7-days-holter monitoring, where as in 10 patients (20,9%) AF episodes were detected. Patients with a successful PVI showed significantly lower BNP plasma levels at baseline compared to patients with AF recurrrence (68,7 pg/ml vs. 144,1 pg/ml; p<0,05). In patients with persistent AF 55% (11 cases) had no recurrence of AF at 3 months 7-days holter and in 9 patients (45%) AF recurred. BNP plasma levels at baseline were lower in patients with stable sinusrhythm after 3 months compared to the group of recurrent AF (105,8 pg/ml vs. 193,3 pg/ml; p=0,11). Conclusion: Patients with AF and low preprocedural BNP plasma levels showed a better outcome after PVI. Thus BNP may be helpful in patient selection for a successful treatment of AF by PVI.
Cryptanalysis of an Enhanced Spatiotemporal Chaotic Image/Video Cryptosystem
Eun-Jun Yoon,Jeong-Woo Hong,Sang-Yoon Yoon,Dong-In Park
EURASIP Journal on Advances in Signal Processing , 2011, DOI: 10.1155/2011/461563
Abstract:
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