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Search Results: 1 - 10 of 7426 matches for " Sung-Man Jeon "
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Cognitive Profiles and Subtypes of Patients with Mild Cognitive Impairment: Data from a Clinical Follow-Up Study  [PDF]
Kyung Won Park, Eun-Joo Kim, Hwan Joo, Sung-Man Jeon, Seong-Ho Choi, Jay C. Kwon, Byoung Gwon Kim, Jae Woo Kim
International Journal of Clinical Medicine (IJCM) , 2012, DOI: 10.4236/ijcm.2012.35068
Abstract: Background: Mild cognitive impairment (MCI) is a heterogeneous condition with a variety of clinical outcomes, the presence of which correlates with risk of Alzheimer’s disease as well as pre-clinical stages of other dementia subtypes. The aims of this study were to assess the specific patterns of cognitive profiles and to identify changes from baseline to 24 weeks in patients with MCI using detailed neuropsychological testing. Methods: We consecutively recruited 120 MCI patients at baseline according to the Petersen’s clinical diagnostic criteria, who were admitted to the Dementia and Memory Clinics. We analyzed patients who fulfilled both inclusion and exclusion criteria for MCI and classified them into four subtypes according to deficits in major cognitive domains; amnestic MCI single domain (aMCI-s), amnestic multiple domain MCI (aMCI-m), non-amnestic single domain MCI (naMCI-s) and non-amnestic multiple domain MCI (naMCI-m). Four groups of MCI were evaluated by a detailed neuropsychological battery test. Results: 83 patients with MCI at the 24-week follow-up were classified into four subtypes. The most frequent subtype was amnestic multi-domain MCI, with the frequency of MCI subtypes as follows: aMCI-s (n = 21, 25.3%), aMCI-m (n = 53, 63.9%), naMCI-s (n = 5, 6.0%) and naMCI-m (n = 4, 4.8%). In the major cognitive items of the SNSB-D, there were significant changes between the initial and follow-up tests in the domains of language, memory and the fron-tal/executive function (p < 0.05), except for attention, in all MCI patient subtypes. At 24-weeks follow-up, the conversion rate to Alzheimer’s disease was 2.4% (n = 2) from a subtype of amnestic multi-domain MCI. Conclusions: Our study revealed the most frequent subtype of MCI to be multiple domain amnestic MCI, with this subtype having a higher tendency of conversion to Alzheimer’s disease.
Concurrent Failures and Redundant Protection Problem in Hierarchical GMPLS Networks
Sung-eok Jeon
Journal of Computers , 2006, DOI: 10.4304/jcp.1.2.1-7
Abstract: The generalized multiprotocol label switching (GMPLS) networks attain a hierarchical structure, andeach layer maintains an independent protection mechanism, resulting in redundant protection. The common pool method provides a basic approach to solve the redundant protection problem. Although the common pool method is simple and robust, however it can fail in some cases. This work first shows that none of the prior work satisfies both redundant protection and two links failure problem simultaneously. Moreover, this work also presents a new type of two links failure problem (i.e., the failure of two links at two different layers), which can happen frequently and the common poolmethod cannot cope with. To solve the proposed two links failure problem, while minimizing the cost of redundant protection problem, this work proposes a new protection scheme for hierarchical GMPLS networks.
Shape Optimization of a Regenerative Blower Used for Building Fuel Cell System  [PDF]
Choon-Man Jang, Jong-Sung Lee
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A023
Abstract: This paper describes the optimal design of a Cathode blower used for a building fuel cell system. The Cathode air blower has a regenerative blower type. Two design variables, extension angle and number of impeller blade are introduced to enhance the blower performance. Pressure and efficiency of the blower are selected as an object function, and the optimal design is performed by a response surface method. Three-dimensional Navier-Stokes equations are introduced to analyze the performance and internal flow of the blower and to find the value of object function for the training data. Throughout the design optimization, it is found that an extension angle is effective to increase blower efficiency in the blower. The pressure rise for the optimal blower is successfully increased up to 3.17% compared with that of reference one at the design flow rate. It is noted that low velocity region disturbs to make strong recirculation flow in the each blade passage, thus increases local pressure loss. Detailed flow field inside a regenerative blower is also analyzed and compared.
Characterization of the Family I inorganic pyrophosphatase from Pyrococcus horikoshii OT3
Sung-Jong Jeon,Kazuhiko Ishikawa
Archaea , 2005, DOI: 10.1155/2005/591628
Abstract: A gene encoding for a putative Family inorganic pyrophosphatase (PPase, EC 3.6.1.1) from the hyperthermophilic archaeon Pyrococcus horikoshii OT3 was cloned and the biochemical characteristics of the resulting recombinant protein were examined. The gene (Accession No. 1907) from P. horikoshii showed some identity with other Family I inorganic pyrophosphatases from archaea. The recombinant PPase from P. horikoshii (PhPPase) has a molecular mass of 24.5 kDa, determined by SDS-PAGE. This enzyme specifically catalyzed the hydrolysis of pyrophosphate and was sensitive to NaF. The optimum temperature and pH for PPase activity were 70 °C and 7.5, respectively. The half-life of heat inactivation was about 50 min at 105 °C. The heat stability of PhPPase was enhanced in the presence of Mg2
Prioritizing the Best Areas for Treated Wastewater Use Using RCP 8.5  [PDF]
Sang-Mook Jeon, Eun-Sung Chung, Yeonjoo Kim, Sang-ho Lee
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.41B011
Abstract: The goal of this study is to develop a new framework that prioritizes the best sites for treated wastewater (TWW) use considering climate change impacts. Fuzzy TOPSIS which is a kind of multi-criteria decision making techniques was introduced to reflect the uncertainty of input data and criteria weighting values. Representative concentration pathway 8.5 scenario was included into the hydrologic simulations for the climate change impact to hydrologic regimes using hydrological simulation program-Fortran (HSPF). Furthermore, all year scenarios were considered to determine the rankings, respectively. It can take into consideration the uncertainty of time periods which always exists in all climate change scenarios. This study can be a baseline to start to combine the fuzzy multi-criteria decision making techniques with robust prioritization for climate change adaptation strategies.
Power Law Exponents for Vertical Velocity Distributions in Natural Rivers  [PDF]
Hae-Eun Lee, Chanjoo Lee, Youg-Jeon Kim, Ji-Sung Kim, Won Kim
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.512114
Abstract:

While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.

Distributed Preemption Decisions: Probabilistic Graphical Model, Algorithm and Near-Optimality
Sung-eok Jeon,Chuanyi Ji
Computer Science , 2009,
Abstract: Cooperative decision making is a vision of future network management and control. Distributed connection preemption is an important example where nodes can make intelligent decisions on allocating resources and controlling traffic flows for multi-class service networks. A challenge is that nodal decisions are spatially dependent as traffic flows trespass multiple nodes in a network. Hence the performance-complexity trade-off becomes important, i.e., how accurate decisions are versus how much information is exchanged among nodes. Connection preemption is known to be NP-complete. Centralized preemption is optimal but computationally intractable. Decentralized preemption is computationally efficient but may result in a poor performance. This work investigates distributed preemption where nodes decide whether and which flows to preempt using only local information exchange with neighbors. We develop, based on the probabilistic graphical models, a near-optimal distributed algorithm. The algorithm is used by each node to make collectively near-optimal preemption decisions. We study trade-offs between near-optimal performance and complexity that corresponds to the amount of information-exchange of the distributed algorithm. The algorithm is validated by both analysis and simulation.
Randomized Distributed Configuration Management of Wireless Networks: Multi-layer Markov Random Fields and Near-Optimality
Sung-eok Jeon,Chunayi Ji
Computer Science , 2008,
Abstract: Distributed configuration management is imperative for wireless infrastructureless networks where each node adjusts locally its physical and logical configuration through information exchange with neighbors. Two issues remain open. The first is the optimality. The second is the complexity. We study these issues through modeling, analysis, and randomized distributed algorithms. Modeling defines the optimality. We first derive a global probabilistic model for a network configuration which characterizes jointly the statistical spatial dependence of a physical- and a logical-configuration. We then show that a local model which approximates the global model is a two-layer Markov Random Field or a random bond model. The complexity of the local model is the communication range among nodes. The local model is near-optimal when the approximation error to the global model is within a given error bound. We analyze the trade-off between an approximation error and complexity, and derive sufficient conditions on the near-optimality of the local model. We validate the model, the analysis and the randomized distributed algorithms also through simulation.
Joint Approximation of Information and Distributed Link-Scheduling Decisions in Wireless Networks
Sung-eok Jeon,Chuanyi Ji
Computer Science , 2012,
Abstract: For a large multi-hop wireless network, nodes are preferable to make distributed and localized link-scheduling decisions with only interactions among a small number of neighbors. However, for a slowly decaying channel and densely populated interferers, a small size neighborhood often results in nontrivial link outages and is thus insufficient for making optimal scheduling decisions. A question arises how to deal with the information outside a neighborhood in distributed link-scheduling. In this work, we develop joint approximation of information and distributed link scheduling. We first apply machine learning approaches to model distributed link-scheduling with complete information. We then characterize the information outside a neighborhood in form of residual interference as a random loss variable. The loss variable is further characterized by either a Mean Field approximation or a normal distribution based on the Lyapunov central limit theorem. The approximated information outside a neighborhood is incorporated in a factor graph. This results in joint approximation and distributed link-scheduling in an iterative fashion. Link-scheduling decisions are first made at each individual node based on the approximated loss variables. Loss variables are then updated and used for next link-scheduling decisions. The algorithm repeats between these two phases until convergence. Interactive iterations among these variables are implemented with a message-passing algorithm over a factor graph. Simulation results show that using learned information outside a neighborhood jointly with distributed link-scheduling reduces the outage probability close to zero even for a small neighborhood.
Degrees of Freedom of Full-Duplex Multiantenna Cellular Networks
Sang-Woon Jeon,Sung Ho Chae,Sung Hoon Lim
Mathematics , 2015,
Abstract: We study the degrees of freedom (DoF) of cellular networks in which a full duplex (FD) base station (BS) equipped with multiple transmit and receive antennas communicates with multiple mobile users. We consider two different scenarios. In the first scenario, we study the case when half duplex (HD) users, partitioned to either the uplink (UL) set or the downlink (DL) set, simultaneously communicate with the FD BS. In the second scenario, we study the case when FD users simultaneously communicate UL and DL data with the FD BS. Unlike conventional HD only systems, inter-user interference (within the cell) may severely limit the DoF, and must be carefully taken into account. With the goal of providing theoretical guidelines for designing such FD systems, we completely characterize the sum DoF of each of the two different FD cellular networks by developing an achievable scheme and obtaining a matching upper bound. The key idea of the proposed scheme is to carefully allocate UL and DL information streams using interference alignment and beamforming techniques. By comparing the DoFs of the considered FD systems with those of the conventional HD systems, we establish the DoF gain by enabling FD operation in various configurations. As a consequence of the result, we show that the DoF can approach the two-fold gain over the HD systems when the number of users becomes large enough as compared to the number of antennas at the BS.
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