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Search Results: 1 - 10 of 49650 matches for " Kwang-Jo Lee "
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Effective Location Acquisition Control Algorithms for the Location-Based Alert Services in Mobile Environments
So-Young Kang,Kwang-Jo Lee,Sung-Bong Yang
International Journal of Computer Networks & Communications , 2010,
Abstract: The location-based alert services can be regarded as the one of the most practical locationbasedservices. For the services, an alert service system for the services alerts mobile device users whenthey enter into or leave from predefined specific regions, and provides certain services previously askedby the users for special purposes such as security. For providing proper services the alert service systemshould acquire the location information of the users periodically. However, the system that handles thelocations of the users may face serious problems as the number of users increases fast. Hence it is acritical issue to properly adjust the time interval of location data acquisitions while maintaining theaccuracy of the services. In this paper we propose effective location acquisition algorithms; the speedbasedacquisition algorithm, the angle–based acquisition algorithm, and the hybrid algorithm combiningthe speed with the angle-based algorithms. We also present three grid-based acquisition algorithms inwhich a longer time interval is used when a user is not near the alert areas. The proposed algorithmscould reduce the amount of location information to be acquired based on the movement of the users. Theaverage numbers of location acquisitions of the speed-based, the angle–based, and the hybrid algorithmswere reduced by 19.2%, 35.8%, and 35.6% over the distance-based algorithm, respectively, while theymaintained the almost same level of accuracy. Among the grid-based algorithms, the grid-angleacquisition algorithm further improved the average number of acquisitions by 5.2% over the angle-basedalgorithm, which is 41.0% improvement over the distance-based algorithm. The experimental results alsoshow that all the grid-based algorithms showed almost equal accuracy.
Jin-Woo Song,Kwang-Jo Lee,Taek-Hun Kim,Sung-Bong Yang
International Journal of Wireless & Mobile Networks , 2009,
Abstract: In mobile environments, mobile device users access and transfer a great deal of data through the online servers. In order to enhance users’ access speed in a wireless network, decentralizing replicated servers appropriately in the network is required. Previous work regarding this issue had focused on the placement of replicated servers along with the moving paths of the users to maximize the hit ratio. When a miss occurs, they simply ignored the file request. Therefore, we suggest a solution to take care of such a miss by sending a file request to a replicated server nearby in the network.This paper is to propose new cost-effective wireless access algorithms incorporating a present replicated server allocation algorithm with more keen analysis of the moving patterns of mobile device users. We propose four different algorithms that allocate available replicated servers in the network so as tominimize the communication costs. The experimental results show that, among the proposed algorithms, the replicated server clustering algorithm allocated replicated servers with near optimal communicationcosts.
Is Dust Cloud around $λ$ Orionis a Ring or a Shell, or Both?
Dukhang Lee,Kwang-Il Seon,Young-Soo Jo
Physics , 2015,
Abstract: The dust cloud around $\lambda$ Orionis is observed to be circularly symmetric with a large angular extent ($\approx$ 8 degrees). However, whether the three-dimensional (3D) structure of the cloud is shell- or ring-like has not yet been fully resolved. We study the 3D structure using a new approach that combines a 3D Monte Carlo radiative transfer model for ultraviolet (UV) scattered light and an inverse Abel transform, which gives a detailed 3D radial density profile from a two-dimensional column density map of a spherically symmetric cloud. By comparing the radiative transfer models for a spherical shell cloud and that for a ring cloud, we find that only the shell model can reproduce the radial profile of the scattered UV light, observed using the S2/68 UV observation, suggesting a dust shell structure. However, the inverse Abel transform applied to the column density data from the Pan-STARRS1 dust reddening map results in negative values at a certain radius range of the density profile, indicating the existence of additional, non-spherical clouds near the nebular boundary. The additional cloud component is assumed to be of toroidal ring shape; we subtracted from the column density to obtain a positive, radial density profile using the inverse Abel transform. The resulting density structure, composed of a toroidal ring and a spherical shell, is also found to give a good fit to the UV scattered light profile. We therefore conclude that the cloud around $\lambda$ Ori is composed of both ring and shell structures.
Hepatobiliary scintigraphy for detecting biliary strictures after living donor liver transplantation
Yu Jin Kim,Kyu Taek Lee,Young Cheol Jo,Kwang Hyuck Lee
World Journal of Gastroenterology , 2011, DOI: 10.3748/wjg.v17.i21.2626
Abstract: AIM: To investigate the diagnostic accuracy of hepatobiliary scintigraphy (HBS) in detecting biliary strictures in living donor liver transplantation (LDLT) patients. METHODS: We retrospectively reviewed 104 adult LDLT recipients of the right hepatic lobe with duct-to-duct anastomosis, who underwent HBS and cholangiography. The HBS results were categorized as normal, parenchymal dysfunction, biliary obstruction, or bile leakage without re-interpretation. The presence of biliary strictures was determined by percutaneous cholangiography or endoscopic retrograde cholangiopancreatography (ERCP). RESULTS: In 89 patients with biliary strictures, HBS showed biliary obstruction in 50 and no obstruction in 39, for a sensitivity of 56.2%. Of 15 patients with no biliary strictures, HBS showed no obstruction in 11, for a specificity of 73.3%. The positive predictive value (PPV) was 92.6% (50/54) and the negative predictive value (NPV) was 22% (11/50). We also analyzed the diagnostic accuracy of the change in bile duct size. The sensitivity, NPV, specificity, and PPV were 65.2%, 27.9%, 80% and 95%, respectively. CONCLUSION: The absence of biliary obstruction on HBS is not reliable. Thus, when post-LDLT biliary strictures are suspected, early ERCP may be considered.
Developing Mobile Collaborative Learning Applications for Mobile Users
Kwang B Lee
International Journal of Interactive Mobile Technologies (iJIM) , 2011, DOI: 10.3991/ijim.v5i4.1823
Abstract: With the rapid growth wireless communication technologies, the number of mobile applications have been developing. One of them is approached for mobile learning area since it is unique in its own way and offers learning opportunities anywhere and anytime. Mobile collaborative learning (MCL) is a small group learning application based on mobile devices. MCL is a new exciting research area in which students can earn knowledge about a topic and concept via communicating with others by a mobile device. This paper introduces describes the theoretical and technical foundations for designing and developing an effective MCL environment. Also, the paper describes a new approach for building the MCL application towards mobile technology. The prototype will be constructed using Android operating system with suggesting necessary infrastructure and middleware. Finally, the paper include the result of a usability test to find valuable hidden facilitating issues to efficiently access and obtain the class contents in collaborative learning environment.
Synthesis and Control of the Shell Thickness of Polyaniline and Polypyrrole Half Hollow Spheres Using the Polystyrene Cores
Su-Ryeon Yun,Gyeong-Ok Kim,Chan Woo Lee,Nam-Ju Jo,Yongku Kang,Kwang-Sun Ryu
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/894539
Abstract: Polyaniline (Pani) and polypyrrole (Ppy) half hollow spheres with different shell thicknesses were successfully synthesized by three steps process using polystyrene (PS) as the core. The PS core was synthesized by emulsion polymerization. Aniline and pyrrole monomers were polymerized on the surface of the PS core. The shells of Pani and Ppy were fabricated by adding different amounts of aniline and pyrrole monomers. PS cores were dissolved and removed from the core shell structure by solvent extraction. The thicknesses of the Pani and Ppy half hollow spheres were observed by FE-SEM and FE-TEM. The chemical structures of the Pani and Ppy half hollow spheres were characterized by FT-IR spectroscopy and UV-Vis spectroscopy. The shell thicknesses of the Pani half hollow spheres were 30.2, 38.0, 42.2, 48.2, and 52.4 nm, while the shell thicknesses of the Ppy half hollow spheres were 16.0, 22.0, 27.0, and 34.0 nm. The shell thicknesses of Pani and Ppy half hollow spheres linearly increased as the amount of the monomer increased. Therefore, the shell thickness of the Pani and Ppy half hollow spheres can be controlled in these ranges.
Successful Conservative Management of Ruptured Ovarian Cysts with Hemoperitoneum in Healthy Women
Jee Hyun Kim, Seung Mi Lee, Ji-Hyun Lee, Yu Ri Jo, Min Hoan Moon, Jonghwan Shin, Byoung Jae Kim, Kyu Ri Hwang, Taek Sang Lee, Kwang Bum Bai, Hye Won Jeon
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0091171
Abstract: Study Objective To determine the success rate of the “intended conservative management strategy” of ruptured ovarian cysts with hemoperitoneum and the risk factors for surgical interventions in healthy women of reproductive age. Methods Patients who visited the emergency department with abdominal pain and were diagnosed with a ruptured ovarian cyst with hemoperitoneum between August 2008 and June 2013 were included in this retrospective study. The diagnosis of the ruptured ovarian cysts and hemoperitoneum was based on the clinical symptoms, physical examination and ultrasound and CT imaging. The rate of surgical interventions and the risk factors for surgical intervention were determined. Results A total of 78 women were diagnosed with a ruptured ovarian cyst with hemoperitoneum. Most patients (80.8%, 63/78) were managed conservatively, and 19.2% of the patients (15/78) required a surgical intervention. In the multiple logistic regression analysis, the diastolic blood pressure (dBP) (odds ratio [OR] of 0.921 with 95% confidence interval [CI] of 0.855–0.993) and the depth of the total pelvic fluid collection in CT (DTFC_CT) (OR 1.599 with 95% CI 1.092–2.343) were the significant determining factors of surgical intervention after adjustment. The rate of surgical intervention was 6.5% vs. 15.8% vs. 77.8% in the patients with neither dBP≤70 mmHg nor DTFC_CT≥5.6 cm, those with only one of those features, and those with both, respectively. Conclusion Most cases of ruptured ovarian cysts with hemoperitoneum can be managed conservatively. A low diastolic blood pressure and a large amount of hemoperitoneum suggest the need for surgical intervention.
Three-level anterior cervical discectomy and fusion in elderly patients with wedge shaped tricortical autologous graft: A consecutive prospective series
Lee Suk,Oh Kwang,Yoon Kwang,Lee Sung
Indian Journal of Orthopaedics , 2008,
Abstract: Background: Treatment of multilevel cervical spondylotic myelopathy/radiculopathy is a matter of debate, more so in elderly patients due to compromised physiology. We evaluated the clinical and radiological results of cervical fusion, using wedge-shaped tricortical autologous iliac graft and Orion plate for three-level anterior cervical discectomy in elderly patients. Materials and Methods: Twelve elderly patients with mean age of 69.7 years (65-76 years) were treated between April 2000 and March 2005, for three-level anterior cervical discectomy and fusion, using wedge-shaped tricortical autologous iliac graft and Orion plate. Outcome was recorded clinically according to Odom′s criteria and radiologically in terms of correction of lordosis angle and intervertebral disc height span at the time of bony union. The mean follow-up was 29.8 months (12-58 months). Results: All the patients had a complete recovery of clinical symptoms after surgery. Postoperative score according to Odom′s criteria was excellent in six patients and good in remaining six. Bony union was achieved in all the patients with average union time of 12 weeks (8-20 weeks). The mean of sum of three segment graft height collapse was 2.50 mm (SD = 2.47). The average angle of lordosis was corrected from 18.2° (SD = 2.59°) preoperatively to 24.9° (SD = 4.54°) at the final follow-up. This improvement in the radiological findings is statistically significant (P < 0.05). Conclusion: Cervical fusion with wedge-shaped tricortical autologous iliac graft and Orion plate for three-level anterior cervical discectomy is an acceptable technique in elderly patients. It gives satisfactory results in terms of clinical outcome, predictable early solid bony union, and maintenance of disc space height along with restoration of cervical lordosis.
Estimating higher order perturbative coefficients using Borel transform
Kwang Sik Jeong,Taekoon Lee
Physics , 2002, DOI: 10.1016/S0370-2693(02)02976-3
Abstract: A new method of estimating higher order perturbative coefficients is discussed. It exploits the rapid, asymptotic growth of perturbative coefficients and the information on the singularities in the complex Borel plane. A comparison with other methods is made in several Quantum Chromodynamics (QCD) expansions.
Building the process-drug–side effect network to discover the relationship between biological Processes and side effects
Lee Sejoon,Lee Kwang H,Song Min,Lee Doheon
BMC Bioinformatics , 2011, DOI: 10.1186/1471-2105-12-s2-s2
Abstract: Background Side effects are unwanted responses to drug treatment and are important resources for human phenotype information. The recent development of a database on side effects, the side effect resource (SIDER), is a first step in documenting the relationship between drugs and their side effects. It is, however, insufficient to simply find the association of drugs with biological processes; that relationship is crucial because drugs that influence biological processes can have an impact on phenotype. Therefore, knowing which processes respond to drugs that influence the phenotype will enable more effective and systematic study of the effect of drugs on phenotype. To the best of our knowledge, the relationship between biological processes and side effects of drugs has not yet been systematically researched. Methods We propose 3 steps for systematically searching relationships between drugs and biological processes: enrichment scores (ES) calculations, t-score calculation, and threshold-based filtering. Subsequently, the side effect-related biological processes are found by merging the drug-biological process network and the drug-side effect network. Evaluation is conducted in 2 ways: first, by discerning the number of biological processes discovered by our method that co-occur with Gene Ontology (GO) terms in relation to effects extracted from PubMed records using a text-mining technique and second, determining whether there is improvement in performance by limiting response processes by drugs sharing the same side effect to frequent ones alone. Results The multi-level network (the process-drug-side effect network) was built by merging the drug-biological process network and the drug-side effect network. We generated a network of 74 drugs-168 side effects-2209 biological process relation resources. The preliminary results showed that the process-drug-side effect network was able to find meaningful relationships between biological processes and side effects in an efficient manner. Conclusions We propose a novel process-drug-side effect network for discovering the relationship between biological processes and side effects. By exploring the relationship between drugs and phenotypes through a multi-level network, the mechanisms underlying the effect of specific drugs on the human body may be understood.
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