• Proceedings of the KSME Conference
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• 2001.06e
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• pp.386-391
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• 2001

A finite element code based on P2P1 tetra element has been developed for the large eddy simulation (LES) of turbulent flows around a complex geometry. Fractional 4-step algorithm is employed to obtain time accurate solution since it is less expensive than the integrated formulation, in which the velocity and pressure fields are solved at the same time. Crank-Nicolson method is used for second order temporal discretization and Galerkin method is adopted for spatial discretization. For very high Reynolds number flows, which would require a formidable number of nodes to resolve the flow field, SUPG (Streamline Upwind Petrov-Galerkin) method is applied to the quadratic interpolation function for velocity variables, Noting that the calculation of intrinsic time scale is very complicated when using SUPG for quadratic tetra element of velocity variables, the present study uses a unique intrinsic time scale proposed by Codina et al. since it makes the present three-dimensional unstructured code much simpler in terms of implementing SUPG. In order to see the effect of numerical diffusion caused by using an upwind scheme (SUPG), those obtained from P2P1 Galerkin method and P2P1 Petrov-Galerkin approach are compared for the flow around a sphere at some Reynolds number. Smagorinsky model is adopted as subgrid scale models in the context of P2P1 finite element method. As a benchmark problem for code validation, turbulent flows around a sphere and a MIRA model have been studied at various Reynolds numbers.

• ETRI Journal
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• v.36 no.2
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• pp.317-320
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• 2014

A balanced RF duplexer with low interference in an extremely narrow bandgap is proposed. The Long-Term Evolution band-7 duplexer should be designed to prevent the co-existence problem with the WiFi band, whose fractional bandgap corresponds to only 0.7%. By implementing a hybrid bulk acoustic wave (BAW) structure, the temperature coefficient of frequency (TCF) value of the duplexer is successfully reduced and the suppressed interference for the narrow bandgap is performed. To achieve an RF duplexer with balanced Rx output topology, we also propose a novel balanced BAW Rx topology and RF circuit block. The novel balanced Rx filter is designed with both lattice- and ladder-type configurations to ensure excellent attenuation. The RF circuit block, which is located between the antenna and the Rx filter, is developed to simultaneously function as a balance-tounbalance transformer and a phase shift network. The size of the fabricated duplexer is as small as $2.0mm{\times}1.6mm$. The maximum insertion loss of the duplexer is as low as 2.4 dB in the Tx band, and the minimum attenuation in the WiFi band is as high as 36.8 dB. The TCF value is considerably lowered to $-16.9ppm/^{\circ}C$.

• The Korean Journal of Applied Statistics
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• v.15 no.2
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• pp.395-403
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• 2002

In the third phase of the response surface methods, the first-order model is assumed and the curvature of the response surface is checked with a fractional factorial design augmented by centre runs. We further assume that a true model is a quadratic polynomial. To choose an optimal design, Box and Draper(1959) suggested the use of an average mean squared error (AMSE), an average of MSE of y(x) over the region of interest R. The AMSE can be partitioned into the average prediction variance (APV) and average squared bias (ASB). Since AMSE is a function of design moments, region moments and a standardized vector of parameters, it is not possible to select the design that minimizes AMSE. As a practical alternative, Box and Draper(1959) proposed minimum bias design which minimize ASB and showed that factorial design points are shrunk toward the origin for a minimum bias design. In this paper we propose a robust AMSE design which maximizes the minimum efficiency of the design with respect to a standardized vector of parameters.

• Toxicological Research
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• v.34 no.2
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• pp.143-150
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• 2018

It has been demonstrated that vanadate causes nephrotoxicity. Vanadate inhibits renal sodium potassium adenosine triphosphatase (Na, K-ATPase) activity and this is more pronounced in injured renal tissues. Cardiac cyclic adenosine monophosphate (cAMP) is enhanced by vanadate, while increased cAMP suppresses Na, K-ATPase action in renal tubular cells. There are no in vivo data collectively demonstrating the effect of vanadate on renal cAMP levels; on the abundance of the alpha 1 isoform (${\alpha}_1$) of the Na, K-ATPase protein or its cellular localization; or on renal tissue injury. In this study, rats received a normal saline solution or vanadate (5 mg/kg BW) by intraperitoneal injection for 10 days. Levels of vanadium, cAMP, and malondialdehyde (MDA), a marker of lipid peroxidation were measured in renal tissues. Protein abundance and the localization of renal ${\alpha}_1-Na$, K-ATPase was determined by Western blot and immunohistochemistry, respectively. Renal tissue injury was examined by histological evaluation and renal function was assessed by blood biochemical parameters. Rats treated with vanadate had markedly increased vanadium levels in their plasma, urine, and renal tissues. Vanadate significantly induced renal cAMP and MDA accumulation, whereas the protein level of ${\alpha}_1-Na$, K-ATPase was suppressed. Vanadate caused renal damage, azotemia, hypokalemia, and hypophosphatemia. Fractional excretions of all studied electrolytes were increased with vanadate administration. These in vivo findings demonstrate that vanadate might suppress renal ${\alpha}_1-Na$, K-ATPase protein functionally by enhancing cAMP and structurally by augmenting lipid peroxidation.

• Journal of the Korean Chemical Society
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• v.39 no.10
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• pp.776-782
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• 1995

A theory of the helix/coil transition for $\alpha$ helical dimer such as $\alpha$ tropomycin and paramycin is developed. The treatment differs from those formulated previously for oligopeptide dimer which is explained by the matrix method using Zimm-Bragg parameter: In the present treatement, it is explained by the zipper model which can account for the dangling H-bond. We calculate the fractional helicity in $\alpha$ helical dimer as a function of helix initiation $constant(\sigma)$, helix stability constant(${\xi}$) and hydrophobic interaction parameter(w). For $\alpha$ tropomycin, the helix stability profile is also calculated. The transitions of this oligomer due to the change of temperature and the concentration of oligopeptide involve simultaneous dissociation of the dimer. The transitions of dimers which have cross-linked S-S bonds or have long chains don't occur, because they keep always helical structures. The transitons due to the concentration of the oligopeptides are steeper than those due to the chain length or temperature.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.29-34
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• 2014

We introduce a number of antenna optimization problem for the zero-forcing beamforming (ZFBF) scheme to enhance energy-efficiency (EE) of the multiple-input-multiple-output broadcast channel. For proposed optimization problem, we assume an instantaneous channel gain of the ZFBF scheme as an average channel gain, given by $N_a-K+1$, in order to reduce a computational complexity of finding the number of active antennas $N_a$. Then, we convert a fractional-form objective function into a subtractive-form, and find a solution of $N_a$ and the maximum EE by an iterative process. Simulation results show that the maximum EE value obtained by proposed algorithm is almost identical to the optimal EE value by the exhaustive search method.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.6
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• pp.461-468
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• 2012

In this study, a Cartesian-grid method based on finite volume approach is applied to simulate the ship motions in large amplitude waves. Fractional step method is applied for pressure-velocity coupling and TVD limiter is used to interpolate the cell face value for the discretization of convective term. Water, air, and solid phases are identified by using the concept of volume-fraction function for each phase. In order to capture the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with weighed line interface calculation (WLIC) method which considers multidimensional information. The volume fraction of solid body embedded in the Cartesian grid system is calculated using a level-set based algorithm, and the body boundary condition is imposed by a volume weighted formula. Numerical simulations for the two-dimensional barge type model and Wigley hull in linear waves have been carried out to validate the newly developed code. To demonstrate the applicability for highly nonlinear wave-body interactions such as green water on the deck, numerical analysis on the large-amplitude motion of S175 containership is conducted and all computational results are compared with experimental data.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.168-172
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• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• Archives of Obesity and Metabolism
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• v.1 no.2
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• pp.78-82
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• 2022

Liraglutide (Saxenda^R) is prescribed to induce and sustain weight loss in obese patients. The starting dose of liraglutide is 0.6 mg/day for 1 week, which is increased by 0.6 mg/day every week until the full maintenance dose of 3 mg/day is achieved. Such dose titration is needed to prevent side effects, which primarily include gastrointestinal problems such as nausea, diarrhea, constipation, vomiting, dyspepsia, and abdominal pain. A 35-year-old, reportedly healthy obese man receiving liraglutide treatment for obesity visited the emergency room complaining of generalized weakness and dizziness accompanied by repeated diarrhea and vomiting. He reported over 20 episodes of diarrhea starting the day after liraglutide dose escalation from 1.2 mg/day to 1.8 mg/day. Laboratory findings suggested pre-renal acute kidney injury, including serum creatinine 4.77 mg/dl, blood urea nitrogen (BUN) 37 mg/dl, estimated glomerular filtration rate (eGFR) 15 ml/min/1.73 m², and Fractional excretion of sodium 0.08. After volume repletion therapy, his renal function recovered to a normal range with laboratory values of creatinine 1.08 mg/dl, BUN 14 mg/dl, and eGFR 88 ml/min/1.73 m². This case emphasizes the need for caution when prescribing glucagon-like peptide-1 receptor agonists, including liraglutide, given the risk of serious renal impairments induced by volume depletion and dehydration through severe-grade diarrhea and vomiting.

• Tuberculosis and Respiratory Diseases
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• v.85 no.3
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• pp.227-236
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• 2022

Background: The use of low-dose inhaled corticosteroid-formoterol as reliever monotherapy has recently been recommended in the asthma treatment guidelines. However, the efficacy of this treatment strategy has not yet been determined during the stepping-down period in moderate asthma. This study aimed to evaluate the feasibility of reducing treatment to as-needed budesonide-formoterol (BFM) in moderate asthma with complete remission. Methods: We randomly assigned 31 patients (8 males and 23 females with a mean age of 57.2 years) with complete remission of asthma by inhaled BFM (160/4.5 ㎍) twice daily to receive BFM (160/4.5 ㎍) as needed (16 patients), or budesonide (BUD) (200 ㎍) twice daily (15 patients). The study was an open-label study done for 48 weeks, with the primary outcome as the cumulative percentages of patients with treatment failure (asthma exacerbation or loss of asthma control or lack of satisfaction after using medications) in the two groups. Results: Six patients (42%) using as-needed BFM had treatment failure, as compared with three patients (21.4%) using BUD maintenance (hazards ratio for as-needed BFM, 1.77; 95% confidential interval, 0.44-7.12; p=0.41). The changes in forced expiratory volume in 1 second were -211.3 mL with as-needed BFM versus -97.8 mL with BUD maintenance (difference, 113.5 mL; p=0.75) and the change in fractional exhaled nitric oxide was significantly higher in both groups, at 8.68 parts per billion (ppb) in the as-needed BFM group and 2.5 ppb. in the BUD maintenance group (difference, 6.18 ppb; p=0.049). Conclusion: Compared with BUD maintenance, there were no significant differences in treatment failure rate in patients who received as-needed BFM during the stepping down period in moderate asthma. However, they showed reduced lung function and relapsed airway inflammation. The results are limited by imprecision, and further large RCTs are needed.