• Journal of Environmental Science International
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• v.6 no.3
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• pp.277-283
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• 1997

SPME deuce was applied to determine the THM in an aqueous solution. The 6 kinds of THM was quantitatively detenuned by using GC-ECD which has the sample eutracted on the SPME fiber from an aqueous solution for 10 min. The THM components were well separated from $CHCl_3$ to the last $CHBr_3$ UHh 13 mons at the condition. 6 kinds of the volatile halogenated organic compounds: $CHCl_3$, $CHBrCl_2$, $CHBrtCl_2$, $CHCl_3$, $C_2Cl$. and $CHBr_3$, showed well defirled calibration graph with good llnearlty from a few ppb level up to several tens of pub concentration. $CHBr_2Cl$ and $C_2C1_4$ were detected from a few samples among the 10 of river samples. CHCl3, however, was detected In 4 sea water samples with the highest of 10 ppd among the pouuted 6 positions. Trace level of $CHBr_2Cl$ and few pub level of $CHBr_3$ were also detected at the other two sample stations. Most of the 13 rain water samples collected from 6 sampling stations were contained ppd level of $CHCl_3$, and also $CHBr_2Cl$, and C_2Cl_4$ were only detected at trace level at a few rain samples among them. We could recognize the fact that our Ut and water enoronment has already been contaminated by certain volatile halogenated organic compounds through this study.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3629-3633
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• 2011

The effect of a dense $TiO_2$ blocking layer prepared using the sol-gel method on the performance of dye-sensitized solar cells was studied. The blocking layer formed directly on the working electrode, separated it from the electrolyte, and prevented the back transfer of electrons from the electrode to the electrolyte. The dyesensitized solar cells were prepared with a working electrode of fluorine-doped tin oxide glass coated with a blocking layer of dense $TiO_2$, a dye-attached mesoporous $TiO_2$ film, and a nano-gel electrolyte, and a counter electrode of Pt-deposited FTO glass. The gel processing conditions and heat treatment temperature for blocking layer formation affected the morphology and performance of the cells, and their optimal values were determined. The introduction of the blocking layer increased the conversion efficiency of the cell by 7.37% for the cell without a blocking layer to 8.55% for the cell with a dense $TiO_2$ blocking layer, under standard illumination conditions. The short-circuit current density ($J_{sc}$) and open-circuit voltage ($V_{oc}$) also were increased by the addition of a dense $TiO_2$ blocking layer.

• Journal of Bio-Environment Control
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• v.18 no.2
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• pp.87-94
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• 2009

This study was conducted to develop an automation system of inoculation processing of a lily callus. The results are summarized as followings: The end-effector was manufactured as suction and machine type. And these end-effectors can separate the callus from the mediums and divide the separated callus and then inoculate the divided callus to new mediums. Using the machine type end-effect0r, the results of the experiment showed the success rate in the division process was 100% while the separation and inoculation process was 92%. To develop the automation controller of inoculation process, the system was developed to control an external device and the manipulator. The data communication program between a robot and a personal computer was also developed using CAsyncsocket and Ethernet Interface.

• Journal of the Korean Chemical Society
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• v.37 no.6
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• pp.604-611
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• 1993

Supercritical Fluid Chromatography(SFC) has become a technique for solving problems that are difficult by other chromatographic methods. However, the most widely used fluid, is no more polar than hexane. Polar samples which are difficult to be analyzed with pure supercritical C$O_2$ because of their high polarity can be separated by adding polar modifiers to supercritical C$O_2$. In this paper, a new method for monitering the mobile phase composition in modified supercritical fluid chromatography was developed. The amount of water dissolved in supercritical C$O_2$ was measured by amperometric microsensor which is made of thin film of perfluorosulfonate ionomer (PFSI). The amount of water dissolved in supercritical C$O_2$ stayed constant for a much longer time than with a saturator column. With this new mixing device, we could do good separations for insecticides and fungicides which are difficult to separate with pure C$O_2$.

• The KIPS Transactions:PartD
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• v.18D no.3
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• pp.197-204
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• 2011

Set-top Box which receives broadcasting signal and delivers it to display device such as TV usually doesn't have low-power mode, standby power mode. On the other side, most consumer electronics support standby power mode. The main reasons come from technical barriers and operational stability. Set-top box normally consumes 80~90% power of active mode even though turning off. This is much higher compared to other consumer electronics which consume less than 1W in standby power mode. However, most developed countries including Korea are enforcing the regulations which enhance energy efficiency of set-top box. This paper describes design and development of low-power set-top box. Key technologies are SoC supporting low-power mode, system hardware and software operating in separated power mode, and middleware managing the power with broadcasting system. Finally, we show energy saving expectation through development and proliferation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.14-17
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• 2008

This paper describes the simulation of a phase splitter for the design of Chireix Outphasing power amplifier. Phase splitter separate the input signal with $0[^{\circ}]$ into the signal with $+90[^{\circ}]$ and $-90[^{\circ}]$ Chireix Outphasing power amplifier get a linearized output from the signal amplifying and combining the separated signal with the phase of $+90[^{\circ}]$ and $-90[^{\circ}]$ of the phase splitter. phase splitter is the core device when designing Chireix Outphasing power amplifier. It is very difficult to design phase splitter with the difference of $90[^{\circ}]$. This phase splitter is used to design the difference of $180[^{\circ}]((90[^{\circ}]+{\alpha}),\;-(90[^{\circ}])+{\alpha}))$ using simulation tool and a differential amplifier.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.74-79
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• 2009

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

• Restorative Dentistry and Endodontics
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• v.39 no.4
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• pp.265-269
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• 2014

Objectives: To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. Materials and Methods: The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). Results: G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (p > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (p < 0.05). Conclusions: Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.845-853
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• 2019

The aim of this study is to investigate the factors affecting the habitat characteristics of largemouth bass (Micropterus salmoides), which is one of exotic fishes in Korea. Based on field observation, the laboratory experiments were performed in order to investigate the relationship between water temperature and the habitat characteristics of largemouth bass. It was found that largemouth bass preferred a relatively high water temperature in winter and a low temperature in summer. When the small largemouth bass coexisted with large largemouth bass, the separation of habitats depending on the size of each largemouth bass are observed. In the separated habitat areas, it is also observed that the largemouth bass preferred vicinity of the obstacle such as boulder. From the experiments for preference between water temperature and obstacle, it was observed that a primary consideration in habitat selection was obstacles. It was also observed that when light device was turned on, largemouth bass formed a new habitat.

• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.107-116
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• 1986

The steady and unsteady state models were established for the performance analysis and design of heavy water distillation columns packed with corrugated wire mesh. After the steady state model was derived with pressure drops, separated D$_2$O concentration and temperature profiles and pressure gradients in the column were obtained by solving MESH equations with equation tearing method. For the analysis of unsteady state behavior, the equilibrium stage transient model deduced from modifying the Cohen's ideal cascade equation was used to predict the concentration change of heavy water with time. These models were in good agreement with the experimental results of heavy water distillation at total reflux. And the newly developed packing material turned out to be very efficient separation device for very small HETP, pressure drop and holdup.