Ich'ŏn, South Korea
Ich'ŏn, South Korea

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Sung J.H.,Korea Conformity Laboratories | Ji J.H.,Samsung | Park J.D.,Chung - Ang University | Song M.Y.,Korea Conformity Laboratories | And 12 more authors.
Particle and Fibre Toxicology | Year: 2011

Background: Gold nanoparticles are widely used in consumer products, including cosmetics, food packaging, beverages, toothpaste, automobiles, and lubricants. With this increase in consumer products containing gold nanoparticles, the potential for worker exposure to gold nanoparticles will also increase. Only a few studies have produced data on the in vivo toxicology of gold nanoparticles, meaning that the absorption, distribution, metabolism, and excretion (ADME) of gold nanoparticles remain unclear.Results: The toxicity of gold nanoparticles was studied in Sprague Dawley rats by inhalation. Seven-week-old rats, weighing approximately 200 g (males) and 145 g (females), were divided into 4 groups (10 rats in each group): fresh-air control, low-dose (2.36 × 104particle/cm3, 0.04 μg/m3), middle-dose (2.36 × 105particle/cm3, 0.38 μg/m3), and high-dose (1.85 × 106particle/cm3, 20.02 μg/m3). The animals were exposed to gold nanoparticles (average diameter 4-5 nm) for 6 hours/day, 5 days/week, for 90-days in a whole-body inhalation chamber. In addition to mortality and clinical observations, body weight, food consumption, and lung function were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for hematology and clinical chemistry tests, and organ weights were measured. Cellular differential counts and cytotoxicity measurements, such as albumin, lactate dehydrogenase (LDH), and total protein were also monitored in a cellular bronchoalveolar lavage (BAL) fluid. Among lung function test measurements, tidal volume and minute volume showed a tendency to decrease comparing control and dose groups during the 90-days of exposure. Although no statistically significant differences were found in cellular differential counts, histopathologic examination showed minimal alveoli, an inflammatory infiltrate with a mixed cell type, and increased macrophages in the high-dose rats. Tissue distribution of gold nanoparticles showed a dose-dependent accumulation of gold in only lungs and kidneys with a gender-related difference in gold nanoparticles content in kidneys.Conclusions: Lungs were the only organ in which there were dose-related changes in both male and female rats. Changes observed in lung histopathology and function in high-dose animals indicate that the highest concentration (20 μg/m3) is a LOAEL and the middle concentration (0.38 μg/m3) is a NOAEL for this study. © 2011 Sung et al; licensee BioMed Central Ltd.


Lee J.H.,Hoseo University | Lee S.-B.,Korea Institute of Science and Technology | Bae G.N.,Korea Institute of Science and Technology | Jeon K.S.,HCT Co. | And 9 more authors.
Inhalation Toxicology | Year: 2010

Seven CNT (carbon nanotube) handling workplaces were investigated for exposure assessment. Personal sampling, area sampling, and real-time monitoring using an SMPS (scanning mobility particle sizer), dust monitor, and aethalometer were performed to characterize the mass exposure, particle size distribution, and particle number exposure. No workplace was found to exceed the current ACGIH (American Conference of Governmental Industrial Hygienists) TLVs (threshold limit values) and OELs (occupational exposure levels) set by the Korean Ministry of Labor for carbon black (3.5mg/m3), PNOS (particles not otherwise specified; 3mg/m3), and asbestos (0.1 fiber/cc). Nanoparticles and fine particles were most frequently released after opening the CVD (chemical vapor deposition) cover, followed by catalyst preparation. Other work processes that prompted nanoparticle release included spraying, CNT preparation, ultrasonic dispersion, wafer heating, and opening the water bath cover. All these operation processes could be effectively controlled with the implementation of exposure mitigation, such as engineering control, except at one workplace where only natural ventilation was used. © 2010 Informa UK Ltd.


Lee J.H.,Hoseo University | Ahn K.,Hanyang University | Kim S.M.,Hanyang University | Jeon K.S.,Hanyang University | And 3 more authors.
Journal of Nanoparticle Research | Year: 2012

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible nanoparticle exposure at a workplace that manufactures silver nanoparticles. To estimate the potential exposure of workers, personal sampling, area monitoring, and realtime monitoring were conducted over 3 days using a scanning mobility particle sizer and dust monitor at a workplace where the workers handle nanomaterials. The area sampling concentrations obtained from the injection room showed the highest concentration, ranging from 0.00501 to 0.28873 mg/m 3. However, apart from the injection room, none of the area samplings obtained from other locations showed a concentration higher than 0.0013 mg/m 3. Meanwhile, the personal sampling concentrations ranged from 0.00004 to 0.00243 mg/m 3 over the 3 days of sampling, which was much lower than the silver TLV. The particle number concentrations at the silver nanoparticle manufacturing workplace were 911,170 (1st day), 1,631,230 (2nd day), and 1,265,024 (3rd day) particles/ cm3 with a size range of 15-710.5 nm during the operation of the reactor, while the concentration decreased to 877,364.9 (1st day), 492,732 (2nd day), and 344,343 (3rd day) particles/cm 3 when the reactor was stopped. © Springer Science+Business Media B.V. 2012.


Cho J.H.,Sungkyunkwan University | Kulkarni A.,Sungkyunkwan University | Kim H.,Sungkyunkwan University | Yoon J.U.,HCT Co. | And 3 more authors.
Journal of Mechanical Science and Technology | Year: 2010

Silver nanoparticles are among the fastest growing product categories in the nanotechnology industry. Several experimental studies reported earlier for its toxicity and its associated risks. Uniform distribution of nanoparticle concentration in inhalation toxicity exposure chambers is important in the conduct of inhalation experimental evaluation. However, relatively little is known. Several factors, including nanoparticle size, degree of mixing, and chamber design, may influence the nanoparticles distribution in whole-body exposure chamber. In the present work we investigated numerically the silver nanoparticles concentration distribution and particle trajectory in the whole body inhalation toxicity test chamber. A three dimensional numerical simulation was performed using the commercially available computational fluid dynamics code Fluent with two models, discrete phase model (DPM) and fine particle model (FPM) to calculate spatial particle trajectories and concentration. The simulated results show that the silver nanoparticle trajectories and concentration distribution are dependent on inhalation toxicity chamber geometry. © 2010 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.


Kim H.,Incheon National University | Jeon J.,Incheon National University | Khattak M.K.,Incheon National University | Kahng S.,Incheon National University | And 2 more authors.
2015 International Symposium on Antennas and Propagation, ISAP 2015 | Year: 2015

In this paper, we present a new compact antenna with multi-band characteristics for mobile communication. The antenna structure has a polyhedron shape as a 3D geometry. It is a modified dipole structure to have cooperatively coupled resonant current paths printed on both the sides of an FR-4 substrate. The basic design is carried out by 3D electromagnetic simulating software and the multi-band antenna performance is verified by the fabrication and measurement. © 2015 The Institute of Electronics, Information and Comm.


Park C.-J.,Korea University | Park D.-H.,HCT Ltd. | Min K.-S.,Korea University | Kim J.-W.,Korea University | Kim I.-H.,Korea University
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2012

In recently, mobile communication technology is developing toward the 4th generation communication technology. The LTE (Long Term Evolution) is the leading candidate technology in the 4th generation mobile communication. The LTE technology is combined with the MIMO (Multiple Input Multiple Output) technology and this coupled technology has a high-quality data transfer rate and an expended channel capacity [1]. The MIMO antenna technology is applied by a mobile handy terminal for 4th generation. The 4G mobile handy terminal antenna is composed a main antenna and a sub antenna. Main antenna has to satisfy not only conventional operating frequency service such as CDMA (824∼849 MHz), GSM900 (880∼960 MHz), DCS (1,710∼1,880 MHz), USPCS (1,850∼1,990 MHz), WCDMA (1,920∼2,170 MHz), and WiFi (2,400∼2,499 MHz) but also LTE (698∼798 MHz) frequency band. In order to realize the maximum channel capacity, the 4G handy terminal antenna must employ the sub antenna operated LTE frequency band. LTE frequency band by reference [2] has from 1 to 43 channels with respect from 699 to 3,800 MHz. Authors consider only for the LTE class 13 and 14 band in this paper, because many mobile companies use these channels for 4 G mobile service. However, because the LTE class 13 and 14 band have a relatively low operating frequency band (746∼798 MHz) for the current mobile handy terminal applications, it may still be difficult to obtain a wide bandwidth and high isolation because of two closely located antennas within the limited space [3]. In order to solve the above problems, authors have been simulated for structure of main and sub antenna, and for feeding position of two antennas, iteratively. As a result, high isolation between main and sub antenna, and bandwidth satisfying for the LTE class 13 and 14 have been realized experimentally. © 2012 IEICE.


Kim D.S.,Gwangju Institute of Science and Technology | Kim Y.M.,HCT Co. | Kwon Y.T.,HCT Co. | Park K.,Gwangju Institute of Science and Technology
Journal of Nanoparticle Research | Year: 2011

Three types of unipolar chargers (parallel multi-electrodes, single electrode, and single electrode with compact size) using the soft X-ray were constructed and their charging performance was evaluated by measuring positive, negative, and neutral fractions of size-resolved ultrafine particles (20-100 nm) with the Tandem Differential Mobility Analyzer (TDMA) technique. The unipolar charger with a single electrode and compact size showed the highest charge fraction with least particle loss probably due to lower electrostatic loss of ions among tested chargers. With positive voltage applied to electrode to remove negative ions, we found that the positively charged particles were 43, 52, 62, 69, and 75% for 20, 30, 50, 70, and 100-nm particles, respectively, and a few particles were negatively charged although their fraction increased with size (1, 2, 4, 5, and 6% for 20, 30, 50, 70, and 100-nm particles, respectively). The positive charge fractions were about three times higher than the values estimated theoretically from a bipolar charger. Also, based on comparison of current data with previously reported values using corona discharge unipolar charger, the soft X-ray charger showed better performance in terms of charging efficiency and penetration for particles (NaCl) currently tested in the particle size range of 20-100 nm. © Springer Science+Business Media B.V. 2010.


Kang D.-G.,Kyonggi University | Park J.,HCT CO. | Lee S.,HCT CO. | Sung Y.,Kyonggi University
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2011

In this paper, a shorted monopole antenna for LTE/WWAN mobile handset applications is presented. The antenna consists of a monopole, a coupling strip, a feeding pad, a stub, and a shorting strip. The basic resonance of the monopole combines with the resonance formed by the coupling that occurs between the coupling strip and the feeding pad to include the LTE700, GSM850, and GSM900 bands. The resonance of the stub combines with the harmonics of the monopole to include the GSM1800, GSM1900, and UMTS bands. Therefore, the proposed antenna covers the LTE700, GSM850, GSM900, GSM1800, GSM1900, and UMTS bands. © 2011 Engineers Australia.


Trademark
Hct Llc | Date: 2017-01-25

Chemicals for the treatment of water.


Trademark
HCT Co. | Date: 2013-03-04

television transmitter; television receiver; digital set-top box; blank optical disc storage medium; optical disc player; compact disc player; compact disc player with cassette tape player; compact disc player with MP3 player; MP3 player; DVD player; HD DVD player; audio speaker, digital camera; home theater systems comprised of audio decoders, video decoders, audio amplifiers, television screens and speakers.

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