• Journal of Environmental Health Sciences
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• v.42 no.1
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• pp.53-60
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• 2016

Objectives: Preservatives are commonly used in pharmaceuticals, cosmetics and other products to extend the expiration date and prevent the growth of microorganisms. Preservatives are generally effective in controlling mold and inhibiting yeast growth, and against a wide range of bacterial attacks as well. They also adversely affect the quality of sperm and cause precocious puberty in children. This study was performed to analyze seven preservatives used in pharmaceuticals and personal care products. Methods: Five kinds of pharmaceuticals and personal care products (PPCPs) were examined for analysis with a high performance liquid chromatography-diode array detector. Each sample was homogenized and the targeted compounds were extracted with methanol. The suspended particulate was removed by syringe filter. Next, the sample was injected into an HPLC system. The separation of the seven preservatives was achieved with a C18 column and gradient mode. The accuracies were between 73% and 120% and precision was lower than 11.58% (RSD). Results: All of the calibration curves showed good linearity with a coefficient of determination ($r^2$) over 0.999. Among the PPCP samples, the detection rate of preservatives was 32.5% for pharmaceuticals, 44.8% for toothpaste, 76.9% for mouthwash, 40.0% for body lotion and 56.0% for wet tissues. The average concentrations of the preservatives in PPCPs were BA 1141.0 mg/kg, MP 709.8 mg/kg, EP 624.9 mg/kg, PP 216.9 mg/kg, BP 167.8 mg/kg, and TCS 538.2 mg/kg. The most frequently detected preservatives in pharmaceuticals and personal care products were BA, MP and PP. The concentrations of preservatives exceeded Korean regulatory standards in 11 samples of medicines, three of mouthwash and two of body lotion. Conclusion: We found that most of the PPCP samples contained various preservatives. It is necessary to identify which preservatives were used and to determine the level of preservatives in PPCPs and to assess the health risk to susceptible populations such as children.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.275-285
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• 2015

This experimental study presents the fatigue evaluation of a precast deck connected using Ultra-High Performance, Fiber Reinforced Concrete (UHPFRC). Four types of two identical large-scale specimens were fabricated with simplified splice rebar details which had a short splice length of ten times rebar diameter. The flexural behavior of each type of specimens until failure was investigated and fatigue behavior of the same type of specimens was then evaluated using two-million cyclic loading. In the flexural tests, tensile rebars exhibited the deformation exceeding yielding strain but failure mode related to the splice details was not observed in spite of such a short splice length. In the fatigue tests, damage was not appreciably accumulated by the cyclic loading except initial flexural cracks and the stress variations in tensile rebars was less than the allowable stress range. These experimental results demonstrate that all types of specimens exhibited acceptable fatigue performance and indicate that enhanced mechanical properties of ultra-high performance material permits to use a simplified splice details along with short joint width.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.451-458
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• 2006

Automotive exhaust is suspected to be one of the major reasons of the rapid increase in greenhouse effect gases in ambient air. As the concerns regarding global worming were increased, the pressure on mobile source greenhouse gas (GHG) emission were also increased. Carbon Dioxides contribute over 90% of total GHG emission and the mobile source occupies about 20% of this $CO_2$ emission. In this study, in order to investigate $CO_2$ emission characteristics from gasoline and LPG passenger cars (PC), which is the most dominant vehicle type in Korea, 53 vehicles were tested on the chassis dynamometer. $CO_2$ emissions and fuel consumption efficiency were measured. The emission characteristics by fuel type, model year, mileage, vehicle speed and transmission type were also discussed. Test modes used in this study were NIER 10 modes and CVS-75 mode, which have been used for developing emission factors and testing new vehicles respectively. The results of this study showed that the main factors which have significant influences on the $CO_2$ emissions are fuel type, transmission type, displacement of vehicle and mileage. The correlation between $CO_2$ emission and FE was also determined by comparing $CO_2$ emission and fuel consumption efficiency. The overall results of this study will greatly contribute to domestic greenhouse gas emissions calculation and designing national strategies for climate change.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.148-154
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• 2009

With respect to the durability of large scale ($150cm^2$) membrane electrode assembly (MEA) of direct methanol fuel cell (DMFC), degradation phenomena at cathode is monitored and analyzed according to the position on the cathode surface. After constant current mode operation of large scale MEA for 500 hr, the MEA is divided into three parts along the cathode channel; (close to) inlet, middle, and (close to) outlet. The performance of each MEA is tested and it is revealed that the MEA from the cathode outlet of large MEA shows the worst performance. This is due to the catalyst degradation and GDL delamination caused by flooding at cathode outlet of large MEA during the 500 hr operation. Particularly on the catalyst degradation, the loss of electrochemically active surface area (ECSA) of catalyst gets worse along the cathode channel from inlet to outlet, of which the reason is believed to be loss of catalysts by dissolution and migration rather than their agglomeration. The extent of loss in the performance and catalyst degradation has strong relation to the cathode flooding and it is required to develop proper water management techniques and separator channel design to control the flooding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.391-399
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• 2006

We propose a novel low complexity video encoder, at the expense of a complex decoder, where video frames are intra-coded periodically and frames in between successive intra-coded frames are coded efficiently using a proposed irregular binning technique. We investigate a method of forming an irregular binning which is capable of quantizing any value effectively with only small number of bins, by exploiting the correlation between successive frames. This correlation is additionally exploited at the decoder, where the quality of reconstructed frames is enhanced gradually by applying POCS(projection on the convex sets). After an image frame is reconstructed with the irregular binning information at the proposed decoder, we can further improve the resulting quality by modifying the reconstructed image with motion-compensated image components from the neighboring frames which are considered to contain image details. In the proposed decoder, several iterations of these modification and re-projection steps can be invoked. Experimental results show that the performance of the proposed coding scheme is comparable to that of H.264/AVC coding in m mode. Since the proposed video coding does not require motion estimation at the encoder, it can be considered as an alternative for some versions of H.264/AVC in applications requiring a simple encoder.

• Journal of Life Science
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• v.22 no.8
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• pp.1018-1023
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• 2012

Snail is a zinc finger transcription factor that induces epithelial-to-mesenchymal transition (EMT), which promotes tumor invasion and metastasis by repressing E-cadherin expression. In addition, Snail restricts the cellular apoptotic response to apoptotic stimuli or survival factor withdrawal; however, its molecular mechanism remains largely unknown. In this study, we have investigated the mechanism underlying Snail-mediated chemoresistance to 5-fluorouracil (5-FU), one of the most widely used anti-cancer drugs. When Snail was overexpressed by doxycycline (DOX) in MCF-7 #5 cells, it inhibited 5-FU-induced apoptotic cell death and switched the cell death mode to necrosis. Snail expression, either by DOX treatment in MCF-7 #5 cells or by the transfection of Snail expression vectors pCR3.1-Snail-Flg, phosphorylation-resistant pCR3.1-S104, and 107A Snail-Flg in MCF-7 cells specifically induced PTEN down-regulation/inactivation and Akt/PKB activation, without affecting ERK1/2 activity. In addition, Snail prominently suppressed 5-FU-induced increases in p53 levels. These findings demonstrate that Snail switches 5-FU-induced apoptosis to necrosis through the activation of Akt/PKB and the down-regulation of p53 levels.

• Education of Primary School Mathematics
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• v.23 no.3
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• pp.135-156
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• 2020

The purpose of this study is to analyze the effect of average unit learning on the knowledge of the representative value of 5th grade elementary school students. In the information-oriented society, the ability to organize and summarize the data has become an essential resource. In the process of correctly analyzing statistical data and making reasonable decisions, the summary of the data plays an important role, and it is necessary to learn the concept of representative values in order to describe the center of the data in a series of numbers. For research, an informal knowledge type possessed by a fifth grade elementary school student with respect to a representative value before learning an average unit is examined and compared with the representative value after learning the average unit. A suggestion point for representative value guidance in school mathematics is provided while examining the change in knowledge with respect to the representative value. Seeing the informal types of elementary school students' representative values will help them learn how to formalize the concept of representative values in middle and high schools. It will give suggestions about the concept of representative values and the method of instruction that should be dealt with in elementary schools. The informal knowledge about the representative value can help with formal representative value that will be learned later. Therefore, This study's discussions on statistical learning of elementary school students are expected to present meaningful implications for statistical education.

• Membrane Journal
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• v.28 no.3
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• pp.214-219
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• 2018

In the present study, superflux nickel capillary supports for gas and vapor separation membranes were prepared by a combined process of NIPS and sintering. Nickel capillary precursors were prepared by NIPS process from PSf-Ni-DMAC-PEG400 dope solution and was sintered at various temperatures in $H_2$ atmosphere to reliably produce Ni capillary support. The optimized Ni capillary support has an outer and inner diameters of 722 and $550{\mu}m$, and its thickness was $94{\mu}m$. It has 3-dimensional pore channel network and its porosity and mean pore diameter was 26% and $4{\mu}m$, respectively. Also, its mechanical strength was tested in tensile mode: its fracture load was 2.84 kgf and the fracture elongation was 13%. Finally, its single gas permeance was measured: He, $N_2$, $O_2$, and $CO_2$ permeance was 432,327, 281,119, 264,259, and 193,143 GPU, respectively. The superflux behavior could be explained from viscous flow through the macropores having a diameter of $4{\mu}m$ and narrow thickness. It could be concluded that the superflux behavior of the Ni capillary support was from the 3-D pore channel network and the small thickness.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.732-743
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• 2008

In H.264/AVC, 4$\times$4 block transform is used for intra and inter prediction instead of 8$\times$8 block transform. Using small block size coding, H.264/AVC obtains high temporal prediction efficiency, however, it has limitation in utilizing spatial redundancy. Motivated on these points, we propose a multi-dimensional transform which achieves both the accuracy of temporal prediction as well as effective use of spatial redundancy. From preliminary experiments, the proposed multi-dimensional transform achieves higher energy compaction than 2-D DCT used in H.264. We designed an integer-based transform and quantization coder for multi-dimensional coder. Moreover, several additional methods for multi-dimensional coder are proposed, which are cube forming, scan order, mode decision and updating parameters. The Context-based Adaptive Variable-Length Coding (CAVLC) used in H.264 was employed for the entropy coder. Simulation results show that the performance of the multi-dimensional codec appears similar to that of H.264 in lower bit rates although the rate-distortion curves of the multi-dimensional DCT measured by entropy and the number of non-zero coefficients show remarkably higher performance than those of H.264/AVC. This implies that more efficient entropy coder optimized to the statistics of multi-dimensional DCT coefficients and rate-distortion operation are needed to take full advantage of the multi-dimensional DCT. There remains many issues and future works about multi-dimensional coder to improve coding efficiency over H.264/AVC.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.469-474
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• 2004

We have fabricated and designed wavelength-tunable sampled grating distributed Bragg reflector laser diodes(SGDBR-LD) by using, for the first time, planar buried heterostructures(PBH). The diodes have low threshold current values and high-performance of laser operation. Growth condition using metal organic chemical vapor deposition(MOCVD) was optimized for the formation of a good butt-coupling at the interface. A maximum output power of the fabricated device was 20 mW under 200 mA continuous wave(CW) operation at $25^{\circ}C$. Average threshold current and voltage were 12 mA and 0.8 V, approximately. This output power is higher than those of ridge waveguide(RWG) and buried ridge stripe(BRS) structures by amounts of 9 mW and 13 mW, respectively. We obtained a tuning range of 44.4nm which is well matched with the target value of our design. The side mode suppression ratio of more than 35 dB was obtained for the whole tuning range. Optical output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structures.