• Journal of the Korea Organic Resources Recycling Association
• /
• v.26 no.2
• /
• pp.95-103
• /
• 2018

As a guideline for desulfurization and dehumidification pretreatment facility for optimizing utilization of biogas, the $H_2S$ concentration is set at 150 % which can be treated with iron salts, dehumidification is the optimum value for generator operation, and the relative humidity applied at the utilization of biogas in EU is set at 60 %. We have set up the generator facility guidelines to optimize utilization of biogas. The appropriate amount of biogas should be at least 90 % of the total gas generation, and the capacity of generator facility should be set at 20~30 %. In order to equalize the pressure of the incoming gas the generator, a gas equalization tank should be installed and the generator room average temperature should be kept at $45^{\circ}C$ or less. Since the gas is not produced at a certain methane concentration in the digester, the efficiency is lowered. Therefore, it is required to install an air fuel ratio control system according to the change in methane concentration. Therefore, it is necessary to compensate for the disadvantages of biogasification facilities of organic waste resources and optimize utilization of biogas and improve operation of facilities. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure), investigate the facilities problem and propose design, operation guidelines such as pre-treatment facilities and generators.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.3
• /
• pp.301-308
• /
• 2018

Anthropogenic radioactive noble gases formed by nuclear fission are significant indicators used to monitor the nuclear activity of neighboring countries. In particular, radioactive xenon, owing to its abundant generation and short half-life, can be used to detect nuclear testing, and radioactive krypton has been used as a tracer to monitor the reprocessing of nuclear fuels. Released radioactive noble gases are in the atmosphere at infinitesimal amounts due to their dilution in the air and their short half-life decay. Therefore, to obtain reliable and significant data when performing measurement of noble gases in the atmosphere, the minimum detectable activity (MDA) for noble gases should be defined as low as possible. In this study, the MDA values for radioactive xenon and krypton were theoretically obtained based on the BfS-IAR system by collecting both noble gases simultaneously. In addition, various MDA methods, confidence level and analysis conditions were suggested to reduce and optimize MDA with an assessment of the factors affecting MDA. The current investigation indicated that maximizing the pretreatment efficiency and performance maintenance of the counter were the most important aspects for Xe. In the case of Kr, since sample activities are much higher than those of Xe, it is possible to change the target MDA or to simplification of the analysis system.

• ALGAE
• /
• v.30 no.2
• /
• pp.121-137
• /
• 2015

Studies on carbon flux in the oceans have been highlighted in recent years due to increasing awareness about climate change, but the coastal ecosystem remains one of the unexplored fields in this regard. In this study, the dynamics of carbon flux in a vegetative coastal ecosystem were examined by an evaluation of net and gross ecosystem production (NEP and GEP) and $CO_2$ exchange rates (net ecosystem exchange, NEE). To estimate NEP and GEP, community production and respiration were measured along different habitat types (eelgrass and macroalgal beds, shallow and deep sedimentary, and deep rocky shore) at Gwangyang Bay, Korea from 20 June to 20 July 2007. Vegetative areas showed significantly higher ecosystem production than the other habitat types. Specifically, eelgrass beds had the highest daily GEP ($6.97{\pm}0.02g\;C\;m^{-2}\;d^{-1}$), with a large amount of biomass and high productivity of eelgrass, whereas the outer macroalgal vegetation had the lowest GEP ($0.97{\pm}0.04g\;C\;m^{-2}\;d^{-1}$). In addition, macroalgal vegetation showed the highest daily NEP ($3.31{\pm}0.45g\;C\;m^{-2}\;d^{-1}$) due to its highest P : R ratio (2.33). Furthermore, the eelgrass beds acted as a $CO_2$ sink through the air-seawater interface according to NEE data, with a carbon sink rate of $0.63mg\;C\;m^{-2}\;d^{-1}$. Overall, ecosystem production was found to be extremely high in the vegetated systems (eelgrass and macroalgal beds), which occupy a relatively small area compared to the unvegetated systems according to our conceptual diagram of a carbon-flux box model. These results indicate that the vegetative ecosystems showed significantly high capturing efficiency of inorganic carbon through coastal primary production.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.7
• /
• pp.953-960
• /
• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.

• Journal of The Korean Society For Urban Railway
• /
• v.6 no.4
• /
• pp.319-326
• /
• 2018

The safety interval to prevent collision between trains in a train control system is based on the braking distance according to the emergency braking of the train. The evaluation of the braking performance is based on the longitudinal train dynamics or the commissioning test in the test track, but since the conditions such as the weakening of the adhesion coefficient between the wheel and rail can not all be considered, these conventional methods are not sufficient to design of the train control systems. Therefore, in this study, the Monte Carlo Method (MCM) which can consider various environments is used to analyze braking performance and limitations. The braking model is based on the air braking used in the emergency braking and is modeled to take into account the braking pressure, efficiency, friction coefficient, adhesion condition, and vehicle mass distribution. It is confirmed that braking performance can be improved by controlling the quality of braking device. In addition, the change of the braking performance was confirmed according to the vehicle constituting the train. The results of this study are expected to be used as basic information for designing safety clearance for the train control systems and as a basis for improving the braking performance of railway vehicles.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.66 no.5
• /
• pp.51-65
• /
• 2024

With the advancement of Unmanned Aerial Vehicles (UAV) technology, aerial spraying has been rapidly increasing in the agricultural field. Drones offer many advantages compared to traditional applicators, but they pose challenges such as spray drift risk and spray uniformity. To address these issues, it is essential to understand the characteristics of complex airflow generated by drones and its consequences for the spray performance. This study aims to identify the air velocity distribution of drone downwash and the resulting spray deposition distribution on the ground, ultimately proposing optimized spraying widths and criteria. Experiments were conducted using two agricultural drones with different propeller arrangements under various flight and measurement conditions. The results showed that during hovering, the downward airflow affected the area within a distance of the radius of the blade (R) from the center of the drone. When the drone was flying, the downward airflow was effective up to a distance of 2R. Droplet deposition was concentrated at the center of the drone during hovering. However, during flying, the droplet deposition was more evenly distributed up to the distance of R. The drone downwash and droplet deposition were significantly different during flying compared to the hovering state. At an effective spray width of 3R, the coefficient of variation (CV) was generally less than 16%, indicating a significant improvement in spray uniformity. These findings help optimize effective spraying techniques in drone-based applications.

• Korean Journal of Poultry Science
• /
• v.8 no.1
• /
• pp.1-5
• /
• 1981

In trying to predict the effect of genetics on the broiler in the year 2000, this is a relatively short period of time as far as broiler genetics in concerned. Modern broiler genetics started around 1945 and tremendous gains when made in past 35 years. Futher improvements on broiler will depend on the evolution and revolution: 1. Evolution: (1) Growth rate has been made 4-5% per year. (2) Feed conversion has improved approximately 1% per year. (3) Abdominal fat is becoming a major complaint in broiler. (4) Because of the changing life-style, broiler meat sales in the future will be more and more in cut-up form. (5) Breeding for stress resistance and selection for docile temperament can be important in order to funker improve fled efficiency. (6) In female parent stock, reproduction characteristics are in many can negatively correlated with the desired broiler traits. (7) Egg production and hatchability in moot commercial parent nod m at a fairly high level. (8) In male parent stock, the heavier and mon super-meat-type male lines are desired to Product better broilers. 2. Revolution: Trying to forecast revolutionary change in broiler genetics is highly speculative, as sudden change are aften unpredictable. (1) Species hybridization, such as a turkey-chicken cross (2) Biochemical tools, such as blood typing. (3) Mutation breeding by radiation or chemical mutagentia. (4) Broiler breeding would be to change the phenotypic appearance by single gene, such as naked, wingless. (5) Changes in production techniques. such as growing in cage or growing in filtered air positive pressure houses.

• Clean Technology
• /
• v.25 no.4
• /
• pp.316-323
• /
• 2019

In order to enhance combustion efficiency and reduce atmosphere pollutants, it is essential to measure carbon monoxide (CO) concentration precisely in combustion exhaust. CO is the important gas species regarding pollutant emission and incomplete combustion because it can trade off with NOx and increase rapidly when incomplete combustion occurs. In the case of a steel annealing system, CO is generated intentionally to maintain the deoxidation atmosphere. However, it is difficult to measure the CO concentration in a combustion environment in real-time, because of unsteady combustion reactions and harsh environment. Tunable Diode Laser Absorption Spectroscopy (TDLAS), which is an optical measurement method, is highly attractive for measuring the concentration of certain gas species, temperature, velocity, and pressure in a combustion environment. TDLAS has several advantages such as sensitive, non-invasive, and fast response, and in-situ measurement capability. In this study, a combustion system is designed to control the equivalence ratio. Also, the combustion exhaust gases are produced in a Liquefied Petroleum Gas (LPG)/air flame. Measurement of CO concentration according to the change of equivalence ratio is confirmed through TDLAS method and compared with the simulation based on Voigt function. In order to measure the CO concentration without interference from other combustion products, a near-infrared laser at 4300.6 cm^-1 was selected.

• Clean Technology
• /
• v.29 no.1
• /
• pp.31-38
• /
• 2023

Due to water shortages caused by water pollution and climate change, total organic carbon (TOC) standards have been implemented for wastewater discharged from public sewage treatment facilities. Furthermore, there is a growing interest and body of research pertaining to the reuse of sewage treatment water as a secure alternative water resource. The membrane bio-reactor (MBR) method is commonly used for advanced wastewater treatment because it can remove organic and inorganic ions and it does not require or emit any chemicals. However, the MBR process uses a separation membrane (MF), which requires frequent film cleaning due to fouling caused by a high concentration of mixed liquor suspended solid (MLSS). In this study, process improvement and microbubble cleaning efficiency were evaluated to improve the differential pressure, water flow, and MF fouling, which are the biggest disadvantages of operating the MF. The existing MBR method was improved by installing a precipitation tank between the air tank and the MBR tank in which raw water was introduced. Microbubbles were injected into a separation membrane tank into which the supernatant water from the precipitation tank was introduced. The microbubble generator was operated with a 15 day on, 15 day off cycle for 5 months to collect discharged water samples (4L) and measure TOC. As the supernatant water from the precipitation tank flowed into the separation membrane tank, about 95% of the supernatant water MLSS was removed so the MF fouling from biological contamination was prevented. Due to the application of microbubbles to supernatant water from the precipitation tank, the differential pressure of the separation membrane tank decreased by 1.6 to 2.3 times and the water flow increased by 1.4 times. Applying microbubbles increased the TOC removal rate by more than 58%. This study showed that separately operating the air tank and the separation membrane tank can reduce fouling, and suggested that applying additional microbubbles could improve the differential pressure, water flow, and fouling to provide a more efficient advanced treatment method.

• Journal of Bio-Environment Control
• /
• v.19 no.4
• /
• pp.203-209
• /
• 2010

This study was performed to investigate photosynthetic responses of 4 foliage plants in relation to light intensity, carbon dioxide concentration, and media, and to select efficient plants for the indoor environment control based on the results. Four foliage plants used in this study included Syngonium podophyllum, Schefflera arboricola cv. Hong Kong, Dieffenbachia amoena, and Dracaena deremensis cv. Warneckii Compacta. The plants cultivated in two different growth media, peatmoss and hydroball, and subjected to various light intensities (0, 30, 50, 80, 100, 200, 400, and $600\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD) and $CO_2$ levels (0, 50, 100, 200, 400, 700, 1000, and $1500\;{\mu}mol{CO_2}{\cdot}mol^{-1}$). As a result of the photosynthetic rate of foliage plants according to change of light intensity and $CO_2$ levels, Schefflera arboricola and Dieffenbachia amoena showed high apparent quantum yield, which stands for the photosynthetic rate under low light intensity, and both plants also recorded higher photosynthetic rate under high $CO_2$ concentration compared to the other two indoor plants. Dracaena deremensis showed the lowest photosynthetic rate under the low light intensity or high $CO_2$ concentration. There were inconsistent results in photosynthetic rate of foliage plants grown in peatmoss or hydroball. Higher photosynthetic rate was observed in Schefflera arboricola with peatmoss rather than hydroball as light and $CO_2$ concentration increased. However, hydroball had a positive effect on Dieffenbachia amoena in terms of photosynthetic rate. In case of Syngonium podophyllum, peatmoss induced higher photosynthetic rate according to increased light intensity, but there was no effect of media on the rate under various $CO_2$ treatements. In contrast, media did not affect to photosynthetic efficiency of Dracaena deremensis subjected to various light intensities and the rate of Dracaena deremensis with peatmoss was a little high when $CO_2$ concentration increased. In conclusion, potential plants for the indoor air pulification and environmental control were Schefflera arboricola and Dieffenbachia amoena because they showed high photosynthetic rate under typical indoor conditions, low light intensity and high $CO_2$ concentration.