• Carbon letters
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• v.9 no.4
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• pp.294-297
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• 2008

A CNT-$TiO_2$ nano composite was prepared from titanium chloride ($TiCl_4$) via sol-gel process using multi walled carbon nano tube (MWCNT) followed by calcination at $450^{\circ}C$. Spectral analysis revealed that the formed $TiO_2$ resided on the carbon in anatase form. The effect of adsorption was investigated using aqueous solution of methylene blue and procion blue dye. The photochemical reaction of CNT-$TiO_2$ composite in aqueous suspensions was studied under UV illumination in batch process. The reaction was investigated by monitoring the discoloration of the dyes employing UV-Visible spectro-photometeric technique as a function of irradiation time. The catalyst composites were found to be efficient for the photodegradation of the dye.

• BMB Reports
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• v.50 no.10
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• pp.522-527
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• 2017

A large number of transcriptional activation domains (TADs) are intrinsically unstructured, meaning they are devoid of a three-dimensional structure. The fact that these TADs are transcriptionally active without forming a 3-D structure raises the question of what features in these domains enable them to function. One of two TADs in human glucocorticoid receptor (hGR) is located at its N-terminus and is responsible for ~70% of the transcriptional activity of hGR. This 58-residue intrinsically-disordered TAD, named tau1c in an earlier study, was shown to form three helices under trifluoroethanol, which might be important for its activity. We carried out heteronuclear multi-dimensional NMR experiments on hGR tau1c in a more physiological aqueous buffer solution and found that it forms three helices that are ~30% pre-populated. Since pre-populated helices in several TADs were shown to be key elements for transcriptional activity, the three pre-formed helices in hGR tau1c delineated in this study should be critical determinants of the transcriptional activity of hGR. The presence of pre-structured helices in hGR tau1c strongly suggests that the existence of pre-structured motifs in target-unbound TADs is a very broad phenomenon.

• Journal of Korean Neurosurgical Society
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• v.63 no.4
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• pp.427-432
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• 2020

Three randomized control trials (RCTs), published in 2013, investigated efficacy of mechanical thrombectomy in large vessel occlusions and did not show better results compared to intravenous (IV) recombinant tissue-type plasminogen activator (tPA) alone. However, most clinicians treating stroke consider mechanical thrombectomy as the standard treatment rather than using IV tPA alone. This paradigm shift was based on five RCTs investigating efficacy of mechanical thrombectomy in acute ischemic stroke conducted from 2010 to 2015. They demonstrated that mechanical thrombectomy was effective and safe in acute ischemic stroke with anterior circulation occlusion when performed within 6 hours of stroke onset. There are four reasons underlying the different results observed between the trials conducted in 2013 and 2015. First, the three RCTs of 2013 used low-efficiency thrombectomy devices. Second, the three RCTs used insufficient image selection criteria. Third, following the initial presentation at the hospital, reperfusion treatment required a long time. Fourth, the three RCTs showed a low rate of successful recanalization. Time is the most important factor in the treatment of acute ischemic stroke. However, current trends utilize advanced imaging techniques, such as diffusion-weighted imaging and multi-channel computer tomographic perfusion, to facilitate the detection of core infarction, penumbra, and collateral flows. These efforts demonstrate that patient selection may overcome the barriers of time in specific cases.

• Journal of Power Electronics
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• v.11 no.4
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• pp.401-407
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• 2011

In order to enhance torque density of five-phase permanent magnetic synchronous motor with third harmonic injection for electric vehicles (EVs) applications, optimum seeking method for injection ratio of third harmonic was proposed adopting theoretical derivation and finite element analysis method, under the constraint of same amplitude for current and air-gap flux. By five-dimension space vector decomposition, the mathematic model in two orthogonal space plane, $d_1-q_1$ and $d_3-q_3$, was deduced. And the corresponding dual-plane vector control method was accomplished to independently control fundamental and third harmonic currents in each vector plane. A five-phase PMSM prototype with quasi-trapezoidal flux pattern and its fivephase voltage source inverter were designed. Also, the dual-plane vector control was digitized in a single XC3S1200E FPGA. Simulation and experimental results prove that using the proposed optimum seeking method, the torque density of five-phase PMSM is enhanced by 20%, without any increase of power converter capacity, machine size and iron core saturation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.923-930
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• 2003

We jointed Bi(Pb)-Sr-Ca-Cu-O multifilament tapes and evaluated their electrical and mechanical properties. In order to improve connectivity of multifilaments, one or two single-filament tape was inserted between two multifilament tapes. The critical current ratio(CCR) and n-value of the jointed tapes were evaluated as a function of uniaxial pressure. It was observed that critical current ratio and n-value were 24.8-29.0% and 2.5-2.8 for MM lap-jointed tape. On the other hand, the corresponding values were improved to 24.7-53.9% and 3.1-4.2 for MSM jointed tape, and 63.4-76.0% and 3.4-5.1 for double MS:vr lap-jointed tape, respectively. The highest electrical properties of double MSM lap-jointed tape are considered to be owing to the presence of single core, causing better interconnections of multifilaments between the two tapes. The mechanical property of jointed tape was evaluated and correlated to the microstructural evolution. The strength of jointed tapes was 44-64% less than that of the unjoined tape. The strain tolerance of jointed tape was also reduced compared to that of the unjoined tape. These lower mechanical properties of jointed tape are probably due to the induced nonuniform microstructure such as the existence of cracks and Ag-intrusion in the joined region.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.7
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• pp.354-360
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• 2008

Power-related issues have become important considerations in current generation microprocessor design. One of these issues is that of elevated on-chip temperatures. This has an adverse effect on cooling cost and, if not addressed suitably, on chip reliability. In this paper we investigate the general trade-offs between temporal and spatial hot spot mitigation schemes and thermal time constants, workload variations and microprocessor power distributions. By leveraging spatial and temporal heat slacks, our schemes enable lowering of on-chip unit temperatures by changing the workload in a timely manner with Operating System (OS) and existing hardware support.

• Ocean and Polar Research
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• v.23 no.2
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• pp.181-188
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• 2001

We describe here the Korea ocean prediction system that closely resembles operational numerical weather prediction systems. This prediction system will be served for real-time forecasts. The core of the system is a three-dimensional primitive equation numerical circulation model, based on ${\sigma}$-coordinate. Remotely sensed multi-channel sea surface temperature (MCSST) is imposed at the surface. Residual subsurface temperature is assimilated through the relationship between vertical temperature structure function and residual of sea surface height (RSSH) using an optimal interpolation scheme. A unified grid system, named as [K-E-Y], that covers the entire seas around Korea is used. We present and compare hindcasting results during 1990-1999 from a model forced by MCSST without incorporating RSSH data assimilation and the one with both MCSST and RSSH assimilated. The data assimilation is applied only in the East Sea, hence the comparison focuses principally on the mesoscale features prevalent in the East Sea. It is shown that the model with the data assimilation exhibits considerable skill in simulating both the permanent and transient mesoscale features in the East Sea.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.237-252
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• 2017

In recent years, data centers have become the core infrastructure to deal with big data processing. For these big data applications, network transmission has become one of the most important factors affecting the performance. In order to improve network utilization and reduce job completion time, in this paper, by real-time monitoring from the application layer, we propose job-aware priority scheduling. Our approach takes the correlations of flows in the same job into account, and flows in the same job are assigned the same priority. Therefore, we expect that flows in the same job finish their transmissions at about the same time, avoiding lagging flows. To achieve load balancing, two approaches (Flow-based and Spray) using ECMP (Equal-Cost multi-path routing) are presented. We implemented our scheme using NS-2 simulator. In our evaluations, we emulate real network environment by setting background traffic, scheduling delay and link failures. The experimental results show that our approach can enhance the Hadoop job execution efficiency of the shuffle stage, significantly reduce the network transmission time of the highest priority job.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.329-337
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• 2016

The demand for the eco-friendly vehicles is skyrocketing because of the increasing $CO_2$ emissions and global warming. In the industrial field, the battery process, a core part of an eco-friendly vehicle, is drawing increased attention; its weight lightening as well as high energy density are becoming increasingly important. In this study, pure Ni plates that were used as the battery pole plate were welded using the laser. The lab joint welding was conducted on ten pure Ni plates at a laser power of 1900 W and a feed speed of 2.8-3.4 m/min. As observed in the experiment, a faster feed speed reduced the bead width, but the laser did not penetrate all ten specimen plates. In addition, pores were trapped when protective gas was used, but they were not trapped when the welding was conducted in atmospheric condition.

• Steel and Composite Structures
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• v.34 no.4
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• pp.561-580
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• 2020

Buckling restrained braces (BRBs) were developed as an enhanced alternative to conventional braces by restraining their global buckling, thus allowing development of a stable quasi-symmetric hysteretic response. A wider adoption of buckling restrained braced frames is precluded due to proprietary character of most BRBs and the code requirement for experimental qualification. To overcome these problems, BRBs with capacities corresponding to typical steel multi-storey buildings in Romania were developed and experimentally tested in view of prequalification. In the second part of this paper, a complex nonlinear numerical model for the tested BRBs was developed in the finite element environment Abaqus. The calibration of the numerical model was performed at both component (material models: steel, concrete, unbonding material) and member levels (loading, geometrical imperfections). Geometrically and materially nonlinear analyses including imperfections were performed on buckling restrained braces models under cyclic loading. The calibrated models were further used to perform a parametric study aiming at assessing the influence of the strength of the buckling restraining mechanism, concrete class of the infill material, mechanical properties of steel used for the core, self-weight loading, and frame effect on the cyclic response of buckling restrained braces.