• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.1
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• pp.38-48
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• 2004

Tropospheric ozone data in Korea for 1998-2002 were analyzed to assess the impact on vegetation. SUM06(sum of hourly concentrations at or above 0.06 ppm) and AOT40(accumulated exposure over a threshold of 40 ppb), widely used as ozone indices in the U.S. and Europe, were calculated based on hourly ozone concentration in 612 areas during 1998-2002 in Korea. SUM06 of the highest 30 areas were 5-12 ppm/hr which were almost the same levels of the U.S. average, and a crop loss of 5% would be expected. Ozone pollution in Seoul during 1998-2002 had decreased compared to that for 1990-97 except in the Northern area; however, ozone pollution in Kyunggi during 1998-2002 had been increased twice compare to the previous 5 years. Korea was divided into four regions: Seoul Metropolitan area, Jungbu, Honam, and Youngnam. Ozone pollution in the Seoul Metropolitan area was much higher during 1998-2000 than the other areas, but ozone pollution during 2001-2002 was almost the same in all four regions. Chunnam-Kwangyang na Kyungbuk-Gumi, famous industrial complexes in southern Korea, were significant ozone pollution areas. However, other industrial complexes, such as Incheon, Ulsan, and Kyunggi-Sihwa, were not polluted compared to their neighbors. Comparing all ozone indices, SUM06(yr), SUM06(3mon), AOT40(yr), AOT40(3mon), number of hours exceeding 100 ppb, 95 percentile, 99 percentile, and maximum concentration, it was determined reasonable to use SUM06(3mon), AOT40(3mon) and number of hours exceeding 100 ppb for evaluation of the chronic impact of ozone on vegetation.

• Molecular & Cellular Toxicology
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• v.2 no.4
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• pp.279-284
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• 2006

This paper describes the fabrication methods of a carbon nanotube (CNT) filter and a microdialysis chip. A CNT filter can help perform dialysis on a microfluidic chip. In this study, a membrane type of a CNT filter is fabricated and located in a microfluidic chip. The filter plays a role of a dialysis membrane in a microfluidic chip. In the fabrication process of a CNT filter, individual CNTs are entangled each other by amide bonding that is catalyzed by 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The chemically treated CNTs are shaped to form a CNT filter using a PDMS film-mold and vacuum filtering. Then, the CNT filter is sandwiched between PDMS substrates, and they are bonded together using a thin layer of PDMS prepolymer as adhesive. The PDMS substrates are fabricated to have a microchannel by standard photo-lithography technique.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2696-2699
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• 2008

Microfluidic chips have been frequently utilized to perform biochemical analysis, like cell culture, because they reduce the consumptions of analytes and reagents and automate multi-step analysis processes. It is often critical to monitor temperature in a microchannel for the analyses in order to control a reaction condition of bio or chemical molecules. We propose a novel method to monitor temperature of a microchannel flow by using polydiacetylene (PDA), a conjugated polymer, that has a unique property to transform its color from visible blue to fluorescent red by thermal stress. We inject PDA sensor droplets generated by hydrodynamic instability into a microchannel with a microheater incorporated on the channel bottom. Also, we change the channel temperature by providing the different electric power to the microheater. The results show that the florescence intensity of PDA sensor droplets linearly increases in response to the flow temperature increase within a certain range.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1144-1145
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• 2007

This paper is investigated the sensorless drive for BLDC motor using microprocessor. Since the BLDC motor should be commutated according to a rotor position, the sensors are required to detect the position. But the sensors increase cost and volume, complicate the motor configuration, and do not operate properly in some operating environments such as high temperature conditions, so that the necessity of sensorless commutation algorithm is getting increased. This paper is proposed the method to drive BLDC motor without position-detecting sensor using Back EMF. Back EMF commutation method was implemented the sensorless drive system which could control the rotational speed and monitor the behavior of a motor.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.35-41
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• 2004

A numerical investigation has been made for flows in an axisymmetric circular cylinder with a rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is the vertex angle of the cone, otherwise Reynolds number of fluid and aspect ratio of the vessel is fixed. Main interest is in vortex breakdown of meridional circulation by rotation of the cone with respect to the longitudinal axis of the cylinder. The method to this problem is numerically to integrate momentum and continuity equations on a generalized body fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat end wall disks. Flow visualization photographs of a preceeding work are compared with the present numerical results.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.160-162
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• 2007

Switched-reluctance motor(SRM) has advantages such as simple structure, low cost and so on compared with induction motor. This paper proposes a new sensorless method that is based on the impressed voltage pulse method to estimate rotor position. Current sensors detect the SRM currents in the unenergised phases and output the voltage. The rotor position can be inferred by the above calculations when the peak values exceed a fixed threshold value.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2415-2418
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• 2008

Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.

• East Asian mathematical journal
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• v.27 no.1
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• pp.35-49
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• 2011

In this paper, we study multi-step iterative algorithm with errors and give the necessary and sufficient condition to converge to com mon fixed points for a finite family of asymptotically quasi-nonexpansive type mappings in Banach spaces. Also we have proved a strong convergence theorem to converge to common fixed points for a finite family said mappings on a nonempty compact convex subset of a uniformly convex Banach spaces. Our results extend and improve the corresponding results of [2, 4, 7, 8, 9, 10, 12, 15, 20].

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.940-941
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• 2008

Recently, there are a great many research for magnetic levitation(Maglev) system. Maglev system is eco-friendly used in a place that is not friction. But Maglev is system that inductance is changed according to air-gap, so this is unstable system. In this paper, we simulate 1 Maglev actuator Control and we do an experience on 4 Maglev actuator system control. however, we get a problem of 4 maglev actuator control, because Maglev is 3 DOF(Degree of Freedom). so we control average err of 2 Maglev actuator in the rear.

• Restorative Dentistry and Endodontics
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• v.40 no.1
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• pp.75-78
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• 2015

Presented here is a case where 8 canals were located in a mandibular first molar. A patient with continuing pain in mandibular left first molar even after completion of biomechanical preparation was referred by a dentist. Following basic laws of the pulp chamber floor anatomy, 8 canals were located in three steps with 4 canals in each root. In both of the roots, 4 separate canals commenced which joined into two canals and exited as two separate foramina. At 6 mon follow-up visit, the tooth was found to be asymptomatic and revealed normal radiographic periapical area. The case stresses on the fact that understanding the laws of pulp chamber anatomy and complying with them while attempting to locate additional canals can prevent missing canals.