• Ocean and Polar Research
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• 제32권3호
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• pp.291-297
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• 2010

In the summer of 2008 (August 4-14), vertical and horizontal distributions of inorganic nutrients and dissolved organic carbon (DOC) were measured in the southwestern East Sea. Concentrations of DOC were determined for the first time in the southwestern East Sea using the high-temperature combustion oxidation (HTCO) method, and results were compared with those measured by another laboratory. Concentrations of DOC ranged from 58 to 104 ${\mu}M$ in the upper 200 m, showing a typical decreasing pattern with depth. Generally, concentrations of DOC were relatively lower, with higher nutrient concentrations, in the upper layer of the coastal upwelling zone. Concentrations of DOC ranged from 54 to 64 ${\mu}M$ in the deep Ulleung Basin (200-1500 m), and were higher than those in the Pacific and Atlantic oceans. In association with rapid vertical ventilation of the euphotic, this difference indicates a larger accumulation of semi-labile DOC in the deep East Sea than in the major oceans. A correlation between apparent oxygen utilization (AOU) and DOC in the deep ocean of the East Sea revealed that only a small portion (<10%) of the sinking DOC, relative to the sinking particulate organic carbon (POC), contributes to microbial degradation. Our results present an important data set of DOC in the East Sea, which plays a critical role in carbon cycle modeling and sequestration.

• Carbon letters
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• 제16권1호
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• pp.1-10
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• 2015

In recent years, flame synthesis has absorbed a great deal of attention as a combustion method for the production of metal oxide nanoparticles, carbon nanotubes, and other related carbon nanostructures, over the existing conventional methods. Flame synthesis is an energy-efficient, scalable, cost-effective, rapid and continuous process, where flame provides the necessary chemical species for the nucleation of carbon structures (feed stock or precursor) and the energy for the production of carbon nanostructures. The production yield can be optimized by altering various parameters such as fuel profile, equivalence ratio, catalyst chemistry and structure, burner configuration and residence time. In the present report, diffusion and premixed flame synthesis methods are reviewed to develop a better understanding of factors affecting the morphology, positioning, purity, uniformity and scalability for the development of carbon nanotubes along with their correlated carbonaceous derivative nanostructures.

• 대한화학회지
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• 제14권4호
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• pp.327-332
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• 1970

A simple and convenient device for deflection-type direct reading the variations in electrolytic conductance is described and applied to the analysis of sulfur by combustion-$H_2O_2$ oxidation method. The apparatus consisted of a high resistance-ratio bridge in which the other adjacent arms are the differential cells. By adopting unusually high a-c voltage source for the bridge excitation, the a-c method for unbalanced bridge is established, decreased sensitivity owing to reduced bridge factor, 0.01, is overcome and also the absolute sensitivity and linearity are greatly improved. Over 50% variations in impedance of the balanced cell, within 1% deviation from the linearity can be attained with a volt (rms)order of output which was detected directly with VTVM without further amplification. Analysis of the bridge shows that these useful features are natural result of the constant current character of the high source impedance generator and the performance of the device agreed with the theoretical predictions. A standard procedure for the rapid analysis of sulfur using the bridge is also given, the analytical accuracy was approximately 1%. A determination takes not more than 5 minutes.

• 한국추진공학회지
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• 제4권3호
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• pp.45-54
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• 2000

Ignition transient is a. very rapid process lasting only in the order of 100 milliseconds and therefore it is difficult to measure all relevant ballistic properties. Numerical simulation is thus useful to quantify some of these hard to measure flow and ballistic properties. One-dimensional model was employed to study the effects of aging using simplified aging scenarios for both N-H sustainer and booster motors. Also the effects of newly designed igniter on the ignition of N-H sustainer was simulated. Radiation effects could be significant in terms of energy flux increase to the propellant surface and the energy exchange between the combustion gas itself. One dimension implementation of radiation showed significant effects for rear-mounted igniter. Implementation of radiation effects into 2-D axi-symmetric numerical model was completed and its effects on the N-H sustainer were examined. To have a reliable prediction of computer model on ignition transient, accurate chemical property data on the propellant and igniter gas are required. It was found that such property data on aged N-H motors are not available. Chemical aging model can be used to predict to some degree of accuracy effects of aging on chemical and mechanical properties. Such a model was developed, albeit 2-dimensional, to study migration of moisture through a representative solid rocket motor configuration.

• Environmental Analysis Health and Toxicology
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• 제17권3호
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• pp.207-217
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• 2002

This study was designed to investigate the characteristics of atmospheric concentrations of toxic volatile organic compounds (VOCs) in Korea. Target compounds included 1,3-butadiene, aromatics such as BTEX, and a number of carbonyl compounds. In this paper, as the second part of the study, the seasonal and locational concentrations of atmospheric VOCs were evaluated. Sampling was conducted seasonally at seven sampling sites. each of them representing a large urban area (commercial and residential), a small urban area (commercial and residential), an industrial area (a site within the complex and a residential), and a background place in Korea. In general, higher concentrations were found in the petro-chemical industrial site than other sites, while VOCs measured in commercial (heavy -traffic) sites were higher than residential sites. Seasonality of VOCs concentrations were not so much clear as other combustion related pollutants such as sulfur dioxide, indicating that the VOCs are emitted from a variety of sources, not only vehicle exhaust and point sources but fugitive emissions. Except the industrial site, the concentrations of VOCs measured in this study do not reveal any serious pollution status, since the levels did not exceed any existing ambient standards in the U.K. and/or Japan. However, the increasing number of petrol -powered vehicles and the rapid industrialization in Korea may result in the increased levels of VOCs concentrations in many large urban areas in the near future, if there is no appropriate programme implemented for the control of these compounds.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.453-460
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• 2005

The tumble or swirl flow is used to promote mixing of air and fuel in the cylinder and to enlarge turbulent intensity in the end of the compression stroke. Since the in-cylinder flow is a kind of transient state with rapid flow variation, which is non-steady state flow, the tumble or swirl flow has not been analyzed sufficiently whether they are applicable to combustion theoretically. In the investigation of intake turbulent characteristics using PIV method, typical flow characteristics were figured out by SCV configurations. An engine installed SCV had higher vorticity and turbulent strength by fluctuation and turbulent kinetic energy than a baseline engine, especially near the cylinder wall and lower part of the cylinder. Above all, the engine with SCV 8 was superior to the others in aspect of vorticity and turbulent strength. For energy dissipation, a baseline engine had much higher energy loss than the engine installed SCV because flow impinged on the cylinder wall. Consequently, as swirl flow was added to existing tumble flow, it was found that fluctuation increased and flow energy was conserved effectively through the experiment.

• 전력전자학회논문지
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• 제24권1호
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• pp.9-15
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• 2019

Sensorless electric superchargers have recently been actively developed to provide a large amount of oxygen to engines in order assist the combustion process for miniaturizing the engines and improving fuel efficiency. The model-based sensorless method for surface-mounted permanent magnet synchronous motors has a disadvantage in that the system may become unstable due to parameter variations in low-speed operation and the rapid-acceleration section. An electric supercharger requires fast response to improve the engine response delay, such as the turbocharger turbo-rack. Therefore, the responsiveness must be improved to use the model-based sensorless system. The position compensation algorithm designed in this study is controlled by converting the position error into the beta, which is the angle formed by the d-axis and the stator current during sudden speed change. In this study, we improved the response of the model-based sensorless system through the algorithm and verified the algorithm validity by applying the algorithm to an actual dual-motor supercharger.

• 한국표면공학회지
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• 제56권2호
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• pp.125-136
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• 2023

Recently, ammonia has emerged as an alternative energy source that can reduce carbon emissions in various industries. Ammonia is used as a fuel in internal combustion engines because it contains no carbon in its components and does not emit any carbon when burned. It is also used in various fields such as fertilizer production, refrigeration, cleaning and disinfection, and drug manufacturing due to its unique characteristics, such as high volatility and easy solubility in water. However, it is highly corrosive to metals and is a toxic gas that can pose a risk to human health, so caution must be exercised when using it. In particular, stress corrosion cracking may occur in containers or manufacturing facilities made of carbon-manganese steel or nickel steel, so special care is needed. As ammonia has emerged as an alternative fuel for reducing carbon emissions, there is a need for a rapid response. Therefore, based on a deep understanding of the causes and mechanisms of ammonia corrosion, it is important to develop new corrosion inhibitors, improve corrosion monitoring and prediction systems, and study corrosion prevention design.

• Current Optics and Photonics
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• 제8권2호
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• pp.138-150
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• 2024

This study is essential for advancing our knowledge about the interaction between long-range high-power lasers and energetic materials, with a particular emphasis on understanding the response of a 155-mm shell under various surface irradiations, taking into account external factors such as atmospheric disturbances. The analysis addresses known limitations in understanding the use of non-realistic targets and the negligence of ambient conditions. The model employs the three-dimensional level-set method, computer-aided design (CAD)-based target design, and a message-passing interface (MPI) parallelization scheme that enables rapid calculations of the complex chemical reactions of the irradiated high explosives. Important outcomes from interaction modeling include the accurate prediction of the initiation time of ignition, transient pressure, and temperature responses with the location of the initial hot spot within the shell, and the relative magnitude of noise with and without the presence of physical ambient disturbances. The initiation time of combustion was increased by approximately a factor of two with atmospheric disturbance considered, while slower heating of the target resulted in an average temperature rise of approximately 650 K and average pressure increase of approximately 1 GPa compared to the no ambient disturbance condition. The results provide an understanding of the interaction between the high-power laser and energetic target at a long distance in an atmospheric condition.

• 한국지리정보학회지
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• 제17권3호
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• pp.54-67
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• 2014

본 연구는 RapidEye 영상을 활용하여 2013년 발생한 대형산불 피해지역(울주, 포항, 봉화)을 대상으로 온실가스 배출량 추정하였다. 온실가스 배출량 추정은 2006 IPCC(Intergovernmental Panel on Climate Change) 가이드라인에서 제시하는 추정식을 이용하였다. 본 연구에서는 최대 우도법을 기반으로 한 감독분류를 실시하여, 산불피해지역의 강도등급 및 피해면적을 산출하였으며, 현장정보와 비교하여 정확도 검증을 실시하였다. 산불피해 등급별 정확도 평가 결과는 평균적으로 전체정확도 73.93%과 Kappa 계수 0.67로 나타났다. 2013년 대형산불피해지의 온실가스 배출량 추정은 울주지역 $CO_2$ 63,260, CO 5.207, $CH_4$ 360, $N_2O$ 28.0, $NO_x$ $4.4g/kg^{-1}{\cdot}ha^{-1}$, 포항지역 $CO_2$ 28,675, CO 2.359, $CH_4$ 163, $N_2O$ 12.7, $NO_x$ $1.9g/kg^{-1}{\cdot}ha^{-1}$ 그리고 봉화지역 $CO_2$ 53,086, CO 1,655, $CH_4$ 114, $N_2O$ 23.5, $NO_x$ $3.6g/kg^{-1}{\cdot}ha^{-1}$로 나타났다.