Korea Army Academy

Yeongcheon, South Korea

Korea Army Academy

Yeongcheon, South Korea

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Jung C.,University of South Carolina | Heo J.,University of South Carolina | Han J.,Korea Army Academy | Her N.,Korea Army Academy | And 4 more authors.
Separation and Purification Technology | Year: 2013

The adsorption behavior of ppb-level aqueous solutions of hexavalent chromium [Cr(VI)] on four different adsorbents was investigated as a function of pH, contact time, initial Cr(VI) concentration, adsorbent dose, and the copresence of competing anions. The adsorbents selected were powered activated carbon (PAC), chitosan, single-walled carbon nanotubes (SWNTs), and multi-walled carbon nanotubes (MWNTs). Each adsorbent was characterized by Fourier transform infrared spectroscopy and measurements of zeta potential to determine its suitability for Cr(VI) adsorption. The adsorption of Cr(VI) was found to be favored at low pH because all adsorbents were positively charged under acidic conditions (pH 4), while a dosage of 100 mg/L resulted in efficient adsorption behavior. PAC and chitosan provided the best removal performance. The highly functionalized and porous PAC and the protonated amines on chitosan enabled a better performance and resulted in high Cr(VI) removal efficiencies of 99.4% and 94.7%, respectively, while the removal efficiencies of SWNTs and MWNTs were 72.9% and 51.9%, respectively. Isotherm and kinetic studies were undertaken to evaluate the characteristics of the Cr(VI) adsorption process. A well-fitted Langmuir isotherm model suggested that monolayer adsorption was the main process operating with an adsorption capacity (qm) of 46.9, 35.6, 20.3, and 2.48 mg/g for PAC, chitosan, SWNTs, and MWNTs, respectively. Pseudo second-order fitted models revealed the importance of kinetic parameters (apart from adsorption capacity) in understanding the transport of Cr(VI) in the solution, while an intra-particle diffusion model fitted well for μg/L levels of Cr(VI) adsorption. This indicated that both physisorption and chemisorption were dominant, particularly for SWNTs. Anions such as Cl- and SO42- in the solution competed with HCrO4- and this phenomenon resulted in negative effects on Cr(VI) adsorption. © 2013 Elsevier B.V. All rights reserved.


Suh I.,Ohio State University | Roblin P.,Ohio State University | Doo S.J.,Korea Army Academy | Cui X.,Skyworks Solutions | And 2 more authors.
IET Microwaves, Antennas and Propagation | Year: 2011

This study presents a measurement-based methodology to efficiently design a harmonic-loaded oscillator at a targeted frequency using the novel multi-harmonic real-time active load-pull (RT-ALP) technique. Owing to the speed of the RT-ALP technique the design procedure is quasi-interactive. Simulations were first used to design a stable negative resistance around 2.5 GHz using series feedback with a variable tapped capacitor to tune the negative resistance in the desired frequency band. The device lines were then measured for characterising the negative-resistance device versus input power at 2.5 GHz. Using RT-ALP the optimal second- and third-harmonic load impedances that provide the maximum output power were then determined. Two different load circuits were then designed and implemented to approach the optimal multi-harmonic load impedances and realise a stand-alone oscillator. In accordance with the Kurokawa theory, a reasonable agreement is obtained in terms of output power and frequency of oscillation between the stand-alone oscillator built and the multi-harmonic load-pull measurements demonstrating the viability of the proposed method. To our knowledge, this is the first fabricated oscillator designed with experimental active load-pull to consider third-harmonic tuning. © 2011 The Institution of Engineering and Technology.


Lee C.,Ulsan National Institute of Science and Technology | Son C.,Korea Army Academy | Yoon B.,Dongguk University | Park Y.,Seoul National University
International Journal of Mobile Communications | Year: 2013

This study proposes a systematic approach to discovering new mobile service opportunities from related documents to overcome the weaknesses of previous methods based on the judgements of experts. At the heart of the suggested approach is text mining to explicitly specify the meanings of documents and information visualisation to effectively explore critical implications. Specifically, we integrate the strengths of Principal Component Analysis (PCA) for mapping multi-dimensional data on a two-dimensional display and the merits of Formal Concept Analysis (FCA) for grouping objects with shared properties based on the lattice theory. A case study of navigation services is presented to show the feasibility of our approach. We believe that the systematic processes and visualised outcomes offered by the proposed approach can enhance the efficiency of mobile service creation and serve as a starting point for developing more general models. Copyright © 2013 Inderscience Enterprises Ltd.


Park J.-S.,Korea Army Academy | Her N.-G.,Korea Army Academy | Yoon Y.,University of South Carolina
Water, Air, and Soil Pollution | Year: 2011

This study examined a comparative degradation of various chlorinated phenolic compounds including phenol, 4-chlorophenol (4-CP), 2,6-dichlorophenol (2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP) using 28, 580, and 1,000 kHz ultrasonic reactors. The concentration of hydrogen peroxide was also determined in order to investigate the efficacy of different sonochemical reactors for hydroxyl radical production. Clearly, it was observed that the 580 kHz sonochemical reactor had maximum efficacy for hydroxyl radical production. The degradation of all the compounds followed the order; 580 kHz (91-93%) > 1,000 kHz (84-86%) > 28 kHz (17-34%) with an initial concentration of 2.5 mg L-1 at a reaction time of 40 min with ultrasonic power of 200 ± 3 W and aqueous temperature of 20 ± 1°C in each experiment. Overall, the degradation of those phenolic compounds followed the order, PCP > 2,3,4,6-TeCP > 2,4,6-TCP > 2,6-DCP > 4-CP > phenol at various frequencies in the presence/absence of a radical scavenger (tert-butyl alcohol). It was revealed that the correlations between the compound degradation rates and the physicochemical parameters, R 2 = 0.99 for octanol-water partition coefficient, R 2 = 0.95 for water solubility, R 2 = 0.94 for vapor pressure, and R 2 = 0.88 for Henry's law constant, excluding PCP, were very good in the entire range of each parameter. © 2010 Springer Science+Business Media B.V.


Geum Y.,Seoul National University | Kim J.,Seoul National University | Son C.,Korea Army Academy | Park Y.,Seoul National University
Journal of Engineering and Technology Management - JET-M | Year: 2013

Today, innovation is no longer viewed as taking place within a single firm - but opening up the innovation process is still not a simple task. In open innovation, the mechanisms of incorporating external resources into the development process need to be carefully managed. This paper suggests a dual technology roadmap (TRM) that considers both internal and external firms. First, we introduce the concept of a dual TRM that considers partner resources as well as internal resources. Second, we suggest the structure of a dual TRM that uses dual planning objects. Third, three types of dual TRM are suggested, with three case examples. © 2013 Elsevier B.V.


Bae J.M.,Armed Forces Ildong Hospital | Ha B.,Armed Forces Ildong Hospital | Lee H.,Armed Forces Yangju Hospital | Park C.K.,Armed Forces Goyang Hospital | And 2 more authors.
Journal of Korean Medical Science | Year: 2012

This study was conducted to clarify the prevalence of common skin diseases and their associated factors among military personnel in Korea. Four dermatologists visited adjacent military units and examined soldiers. A structured questionnaire that included questions about known skin diseases, demographic information, and questions for the Perceived Stress Index was completed for each participant. The soldiers that had been diagnosed with a skin disease answered one additional questionnaire (Skindex-29) which assess the influence of an individual's skin disease on daily life. Of 1,321 soldiers examined, 798 (60.4%) had one or more skin diseases. The three most common skin problems were acne (35.6%), tinea pedis (15.2%) and atopic dermatitis (5.1%). The diseases closely related to the period of military service were acne, tinea pedis, viral warts and corns. The diseases related to the amount of stress were atopic dermatitis, seborrheic dermatitis, and acne. The most troublesome skin diseases were atopic dermatitis, tinea cruris, and seborrheic dermatitis. These results demonstrated that the prevalence of skin disease among military personnel in Korea is very high, and that some of the skin disorders may have a significant influence on their daily lives. © 2012 The Korean Academy of Medical Sciences.


Lee G.,Korea Army Academy | Ding Y.,Texas A&M University | Xie L.,Texas A&M University | Genton M.G.,King Abdullah University of Science and Technology
Wind Energy | Year: 2015

Power curves are commonly estimated using the binning method recommended by the International Electrotechnical Commission, which primarily incorporates wind speed information. When such power curves are used to quantify a turbine's upgrade, the results may not be accurate because many other environmental factors in addition to wind speed, such as temperature, air pressure, turbulence intensity, wind shear and humidity, all potentially affect the turbine's power output. Wind industry practitioners are aware of the need to filter out effects from environmental conditions. Toward that objective, we developed a kernel plus method that allows incorporation of multivariate environmental factors in a power curve model, thereby controlling the effects from environmental factors while comparing power outputs. We demonstrate that the kernel plus method can serve as a useful tool for quantifying a turbine's upgrade because it is sensitive to small and moderate changes caused by certain turbine upgrades. Although we demonstrate the utility of the kernel plus method in this specific application, the resulting method is a general, multivariate model that can connect other physical factors, as long as their measurements are available, with a turbine's power output, which may allow us to explore new physical properties associated with wind turbine performance. Copyright © 2014 John Wiley & Sons, Ltd.


Kim D.,Korea Army Academy | Choi J.,Kyung Hee University
Journal of Physics Condensed Matter | Year: 2010

The photo-response of a freestanding constricted polymeric solid-state bridge of water soluble sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (SPTEBS) was studied as a function of water vapor pressure. The dark current dramatically increases with water vapor pressure higher than 12Torr. Surprisingly, under light illumination, the short-circuit current of the polymeric solid-state bridge decreases with increasing water vapor pressure so that, above 12Torr of water vapor pressure, the short-circuit current under the light illumination is even lower than the dark current. This negative photo-response of the polymeric solid-state bridge is attributed to the self-doping by hydration of the polymer and the de-doping, possibly the result of photo-induced desorption of adsorbed water molecules. © 2010 IOP Publishing Ltd.


Kim D.,Korea Army Academy | Choi J.,Kyung Hee University
Journal of Nanoscience and Nanotechnology | Year: 2011

Two symmetrical terminal electrodes made of indium tin oxide (ITO) were employed to study the current-voltage characteristics of a bulk-heterojunction consisting of water soluble polythiophene and single walled carbon nanotubes (SWCNT). However, the current-voltage curves were asymmetrical, attributed to the polarization induced by the initial bias voltage. The polymer-SWCNT heterojunction were superior to the pristine polymer in both dark conductivity and photoconductivity by two orders of magnitude. Additionally, the open-cell voltage of 0.075 V was observed from the heterojunction even though the electrodes were symmetrical. The high conductivity and photoresponse originated from the high conductivity, high interconnectivity and hole doping capability of CNT. Copyright © 2011 American Scientific Publishers. All rights reserved.


PubMed | Korea Army Academy
Type: Journal Article | Journal: Journal of nanoscience and nanotechnology | Year: 2012

Two symmetrical terminal electrodes made of indium tin oxide (ITO) were employed to study the current-voltage characteristics of a bulk-heterojunction consisting of water soluble polythiophene and single walled carbon nanotubes (SWCNT). However, the current-voltage curves were asymmetrical, attributed to the polarization induced by the initial bias voltage. The polymer-SWCNT heterojunction were superior to the pristine polymer in both dark conductivity and photoconductivity by two orders of magnitude. Additionally, the open-cell voltage of 0.075 V was observed from the heterojunction even though the electrodes were symmetrical. The high conductivity and photoresponse originated from the high conductivity, high interconnectivity and hole doping capability of CNT.

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