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Search Results: 1 - 10 of 6819 matches for " Cheol Ho Yeum "
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Effects of prostaglandin F on small intestinal interstitial cells of Cajal
Chan Guk Park, Young Dae Kim, Man Yoo Kim, Jae Woong Koh, Jae Yeoul Jun, Cheol Ho Yeum, Insuk So, Seok Choi
World Journal of Gastroenterology , 2011,
Abstract: AIM: To explore the role of prostaglandin F2α (PGF2α)) on pacemaker activity in interstitial cells of Cajal (ICC) from mouse small intestine.METHODS: In this study, effects of PGF2α in the cultured ICC cells were investigated with patch clamp technology combined with Ca2+ image analysis.RESULTS: Externally applied PGF2α (10 μmol/L) produced membrane depolarization in current-clamp mode and increased tonic inward pacemaker currents in voltage-clamp mode. The application of flufenamic acid (a non-selective cation channel inhibitor) or niflumic acid (a Cl- channel inhibitor) abolished the generation of pacemaker currents but only flufenamic acid inhibited the PGF2α-induced tonic inward currents. In addition, the tonic inward currents induced by PGF2α were not inhibited by intracellular application of 5’-[-thio]diphosphate trilithium salt. Pretreatment with Ca2+ free solution, U-73122, an active phospholipase C inhibitor, and thapsigargin, a Ca2+-ATPase inhibitor in endoplasmic reticulum, abolished the generation of pacemaker currents and suppressed the PGF2α-induced tonic inward currents. However, chelerythrine or calphostin C, protein kinase C inhibitors, did not block the PGF2α-induced effects on pacemaker currents. When recording intracellular Ca2+ ([Ca2+]i) concentration using fluo-3/AM, PGF2α broadly increased the spontaneous [Ca2+]i oscillations.CONCLUSION: These results suggest that PGF2α can modulate pacemaker activity of ICC by acting non-selective action channels through phospholipase C-dependent pathway via [Ca2+]i regulation
Degrees of Freedom of Interference Channels with Hybrid Beam-forming
Sung Ho Chae,Cheol Jeong
Mathematics , 2015,
Abstract: We study the sum degrees of freedom (DoF) of interference channels with hybrid beam-forming in which hybrid beam-forming composed of analog and digital precodings is employed at each node. For the two-user case, we completely characterize the sum DoF for an arbitrary number of antennas and RF chains by developing an achievable scheme optimized for the hybrid beam-forming structure and deriving its matching upper bound. For a general K-user case, we focus on a symmetric case and obtain lower and upper bounds on the sum DoF, which are tight for certain cases. The results show that hybrid beam-forming can increase the sum DoF of interference channel under certain conditions while it cannot improve the sum DoFs of point-to-point channel, multiple access channel, and broadcast channel. The key insights on this gain is that hybrid beam-forming enables users to manage inter user interference better, and thus each user can increase the dimension of interference-free signal space for its own desired signals.
Influence of Bed Temperature on Heat Shrinkage Shape Error in FDM Additive Manufacturing of the ABS-Engineering Plastic  [PDF]
Young-Hyu Choi, Cheol-Min Kim, Hwan-Seock Jeong, Jeong-Ho Youn
World Journal of Engineering and Technology (WJET) , 2016, DOI: 10.4236/wjet.2016.43D022
Abstract:
In case of manufacturing hexahedral ABS (Acrylonitrile Butadiene Styrene) plastic components using a FDM (Fused Deposition Modeling)-based 3D printer, undesirable shape errors occur in the product due to heat shrinkage. This paper experimentally ob-served the influence of the bed temperature change on the deformed shape errors of a hexahedral specimen of 100 × 50 × 50 mm3 produced by using a 3D printer. During printing work, the head nozzle temperature was kept at 240?C and the head speed was set at 50 mm/s. The chamber was enclosed with a PC-plate. 3D printing was conducted at four different bed temperatures; 50?C, 70?C, 90?C, and 110?C. After the produced specimens naturally cooled down to room temperature, their deformed shape errors were measured. As a result, the higher the bed temperature, the lower the deformed shape errors of the specimens were. However, if the bed temperature had exceeded 120?C, laminating adhesion became poor. That seems to occur because of the material phase change and can make 3D printing work very hard as a consequence. Results of this study can be helpful to set optimum bed temperature condition in FDM additive manufacturing.
Self-knowledge of Reason as a vital phenomenon in Kant’s transcendental dialectic (translated by A. G. Zhavoronkov)
Yeum S. J.
Kantovskij Sbornik , 2012,
Abstract: This study attempts to interpret the process of self-knowledge of reason in the transcendental dialectic as a vital phenomena. In the transcendental dialectic, a thesis and antithesis arises from the division of reason, which can not happen in the death of reason. Dogmatism and skepticism, which had been derived from a division of reason, have formed the history of philosophy. The disputes between the thesis and the antithesis, or the dogmatism and skepticism could be regarded as a battlefields or a war in the history of philosophy. Nevertheless, the aims of these disputes or wars is to cultivate the reason, which in other words is the process of self-knowledge of reason.
A Hybrid Structure of Dual Stators and a Pneumatic Spring for Resonance Control in an Air Mount  [PDF]
Hyung-Tae Kim, Cheol-Ho Kim, Sung-Bok Kang, Seok-Jun Moon, Gyu-Seop Lee
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.53019
Abstract:

An active device using electromagnetic forces was constructed and examined for the purpose of minimizing the resonance in air mounts of clean rooms. The air mounts are vulnerable to low-frequency resonance due to heavy weight and low stiffness. A hybrid structure of the active device, composed of pneumatic and electromagnetic parts, was developed and tested. The pneumatic parts in the device support heavy weights under the air mounts, and the electromagnetic parts reduce the resonance. The electromagnetic parts are composed of dual stators and an armature, which surround the pneumatic parts. The resonance can decrease when electromagnetic forces are generated in the gaps between the stators and the armature. Four active devices were installed under a 3-ton surface plate for a vibration test apparatus. The vibration was detected by eddy-current sensors. Discrete P Control logic was based on displacement, and embedded in a C6713 DSP. The results from impact tests show that the peak magnitude in the resonance frequency can be reduced to 10 dB.

Localization between Curved Shell Plate and Its Unfolded Shape in Different Coordinate Systems for Ship-Hull Plate Forming
Se Yun Hwang,Cheol Ho Ryu,Jang Hyun Lee
Mathematical Problems in Engineering , 2011, DOI: 10.1155/2011/257804
Abstract: This paper describes a mathematical formulation for the efficient localization of 3D surfaces including free-form surfaces and flat surfaces. An important application of this paper is to register flat surface calculated from unfolding process with a curved surface extracted from ship CAD prior to the multipoint press forming works. The mathematical formulation handles the registration and comparison of two free surfaces represented by sparse points based on the iterative closest point (ICP) algorithm and localization that can be applicable to ship-hull plate forming. The ICP algorithm gives an adequate set of initial translation and rotation for surface objects with little correspondence through the minimization of mean square distance metric. Comparison of surfaces is explained in order to determine a corresponding set which gives the optimized press stroke between unfold surface and referential object surface. It thereby allows the optimized press works in ship-hull forming. The combination of registration and comparison is applied to decide the shape equivalence of correspondent surfaces as well as to estimate the transform matrix between point sets where similarity is low. Experimental results show the capabilities of the registration on unfolding surface and curved surface.
Skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease
Ho Cheol Kim,Mahroo Mofarrahi,Sabah NA Hussain
International Journal of COPD , 2009,
Abstract: Ho Cheol Kim1, Mahroo Mofarrahi2, Sabah NA Hussain21Department of Internal Medicine, College of Medicine, Gyeongsang National University, Gyeongsang University Hospital, Jinju, Korea; 2Critical Care and Respiratory Divisions, Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, CanadaAbstract: Chronic obstructive pulmonary disease (COPD) is a debilitating disease characterized by inflammation-induced airflow limitation and parenchymal destruction. In addition to pulmonary manifestations, patients with COPD develop systemic problems, including skeletal muscle and other organ-specific dysfunctions, nutritional abnormalities, weight loss, and adverse psychological responses. Patients with COPD often complain of dyspnea on exertion, reduced exercise capacity, and develop a progressive decline in lung function with increasing age. These symptoms have been attributed to increases in the work of breathing and in impairments in gas exchange that result from airflow limitation and dynamic hyperinflation. However, there is mounting evidence to suggest that skeletal muscle dysfunction, independent of lung function, contributes significantly to reduced exercise capacity and poor quality of life in these patients. Limb and ventilatory skeletal muscle dysfunction in COPD patients has been attributed to a myriad of factors, including the presence of low grade systemic inflammatory processes, nutritional depletion, corticosteroid medications, chronic inactivity, age, hypoxemia, smoking, oxidative and nitrosative stresses, protein degradation and changes in vascular density. This review briefly summarizes the contribution of these factors to overall skeletal muscle dysfunction in patients with COPD, with particular attention paid to the latest advances in the field.Keywords: skeletal muscles, chronic obstructive pulmonary disease, diaphragm, quadriceps, fatigue, disuse, atrophy, smoking, exercise
Recurrent symptomatic intraocular pressure spikes during hemodialysis in a patient with unilateral anterior uveitis
Lim Su-Ho,Son Junhyuk,Cha Soon Cheol
BMC Ophthalmology , 2013, DOI: 10.1186/1471-2415-13-3
Abstract: Background The relationship between intraocular pressure (IOP) changes and hemodialysis has been evaluated for several decades. However, no report on an IOP rise in uveitis patients during hemodialysis has been previously documented. This report describes the case of an uveitis patient with repetitive IOP spikes associated with severe ocular pain during hemodialysis sessions, which resolved after glaucoma filtering surgery. Case presentation A 47-year-old male with diabetes and hypertension had complained of recurrent ocular pain in the left eye during hemodialysis sessions. A slit-lamp examination showed diffuse corneal epithelial edema with several white keratic precipitates and inflammatory cells (Grade 3+) in the anterior chamber of the left eye. No visible neovascularization or synechiae were visible on the iris or angle. Topical glaucoma eye-drops and intravenous mannitol before hemodialysis did not prevent subsequent painful IOP spikes in the left eye. At the end of hemodialysis, IOP averaged ~40 mmHg. After trabeculectomy with mitomycin C in the left eye, his IOP stabilized in the low-teens (range, 10–14 mmHg) and no painful IOP spikes occurred during hemodialysis over the first postoperative year. Conclusion We present a case of recurrent painful IOP spikes during hemodialysis in a patient with unilateral anterior uveitis unresponsive to conventional medical treatment prior to hemodialysis. To our knowledge, this is the first case report of repetitive symptomatic IOP rise during hemodialysis in an uveitic glaucoma patient. This case highlights the importance of the awareness of the possibility that IOP may rise intolerably during hemodialysis in uveitis patients with a compromised outflow facility.
Removal of primary iron rich phase from aluminum-silicon melt by centrifugal separation
Seong Woo Kim,Un Ho Im,Hyeong Cheol Cha
China Foundry , 2013,
Abstract: Recycling is a major consideration in continued aluminum use due to the enormous demand for high quality products. Some impurity elements gradually accumulate through the repetitive reuse of aluminum alloy scrap. Of them, the iron content should be suppressed under the allowed limit. In the present research, a novel separation method was introduced to remove primary iron-rich intermetallic compounds by centrifugation during solidification of Al-Si-Fe alloys. This method does not use the density difference between two phases as in other centrifugal methods, but uses the order of solidification in Al-Si-Fe alloys, because iron promotes the formation of intermetallic compounds with other alloying elements as a primary phase. Two Al-Si-Fe alloys which have different iron contents were chosen as the starting materials. The iron-rich phase could be efficiently removed by centrifuging under a centrifugal force of 40 g. Coarse intermetallic compounds were found in the sample inside the crucible, while rather fine intermetallic compounds were found in the sample outside the crucible. Primary intermetallic compounds were linked to each other via aluminum-rich matrix, and formed like a network. The highest iron removal fraction is 67% and the lowest one is 7% for Al-12Si-1.7Fe alloy. And they are 82% and 18% for Al-12Si-3.4Fe alloy, respectively.
How frequently is a system of 2-linear Boolean equations solvable?
Boris Pittel,Ji-A Yeum
Computer Science , 2010,
Abstract: We consider a random system of equations $x_i+x_j=b_{(i,j)} (\text{mod }2)$, $(x_u\in \{0,1\},\, b_{(u,v)}=b_{(v,u)}\in\{0,1\})$, with the pairs $(i,j)$ from $E$, a symmetric subset of $[n]\times [n]$. $E$ is chosen uniformly at random among all such subsets of a given cardinality $m$; alternatively $(i,j)\in E$ with a given probability $p$, independently of all other pairs. Also, given $E$, $\pr\{b_{e}=0\}=\pr\{b_e=1\}$ for each $e\in E$, independently of all other $b_{e^\prime}$. It is well known that, as $m$ passes through $n/2$ ($p$ passes through $1/n$, resp.), the underlying random graph $G(n,\#\text{edges}=m)$, ($G(n,\pr(\text{edge})=p)$, resp.) undergoes a rapid transition, from essentially a forest of many small trees to a graph with one large, multicyclic, component in a sea of small tree components. We should expect then that the solvability probability decreases precipitously in the vicinity of $m\sim n/2$ ($p\sim 1/n$), and indeed this probability is of order $(1-2m/n)^{1/4}$, for $m0$. Mike Molloy noticed that the Boolean system with $b_e\equiv 1$ is solvable iff the underlying graph is $2$-colorable, and asked whether this connection might be used to determine an order of probability of $2$-colorability in the near-critical case. We answer Mike's question affirmatively and show that probability of $2$-colorability is $\lesssim 2^{-1/4}e^{1/8}c(\lambda)n^{-1/12}$, and asymptotic to $2^{-1/4}e^{1/8}c(\la)n^{-1/12}$ at a critical phase $\la=O(1)$, and for $\la\to -\infty$. (Submitted to Electronic Journal of Combinatorics on September 7, 2009.)
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