• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.33 no.6
• /
• pp.308-320
• /
• 2021

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.

• Korean Journal of Environmental Agriculture
• /
• v.38 no.4
• /
• pp.332-337
• /
• 2019

BACKGROUND: From year 2005, landfill for food waste has been prohibited. Also, according to London agreement in year 2013, ocean discharge for livestock manure, sewage sludge, and food waste has been regulated. Alternative way for food waste disposal is incineration. However, due to high moisture content, additional input for energy is needed. Therefore, effective way for food waste disposal such as application of food waste compost is needed. METHODS AND RESULTS: Seven different treatments (livestock compost, food waste compost, food waste + livestock compost, livestock compost + chemical fertilizer, food waste compost + chemical fertilizer, food waste + livestock compost + chemical fertilizer and control) were applied to tomato crop. All treatments were replicated with completely randomized design. Tomato growth treated with LC+NPK showed the highest values at 6 weeks for all parameters such as leaf length (11.80 cm), leaf width (6.88 cm), and chlorophyll (61.12 O.D.), compared to other treatments. Subsequently the FWC+LC+NPK treatment was followed (11.51 cm, 6.40 cm, 59.50 O.D. for leaf length, leaf width, and chlorophyll, respectably). EC, OM contents, and CEC in the soil treated with the composts significantly increased. CONCLUSION: To evaluate the effect of food waste compost application on tomato growth and soil chemical properties, we carried out field experiment treated with 7 treatments with 3 replicates. The LC+NPK treatment showed highest values for all parameters. Some parameters such as shoot length and total length for tomato were not significantly different between the LC+NPK and the FWC+LC+NPK treatments.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.7
• /
• pp.589-594
• /
• 2014

Recently, higher capacity and energy density of lithium ion batteries are increasingly demanded for enhancing their performance in view of the rise in the commercial distribution of electric and hybrid vehicles. Computational analysis of a porous structure of vanadium pentoxide cathode was performed, employing a phase field model. The incipient model was designed as a spherical structure with cylindrical-shaped pores. Modifying the diameters and lengths of the pore cylinder and the number of pores, we considered different conditions for the porous vanadium pentoxide cathodes for analyzing their effect on the amount of lithium ion intercalated to them. Subsequently, we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.4
• /
• pp.447-458
• /
• 2009

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban areas. Therefore, it is necessary to analyze head loss at manholes, especially in case of surcharged flow. Hydraulic experiments were conducted with three cases. Case A is to test whether the shapes of the manholes influence head loss coefficients. Case B and C were proposed to further reduce head losses by improving the manhole hydraulic efficiency. In case B, the joining part of the pipe at both shapes of manholes is shifted from central part to side part. The test in case C is to check the average head loss coefficient by installing the side benching in square manhole, based on shifted joining part model. The average head loss coefficient for circular and square manhole on case A was 1.6. This did not show much difference of the head loss coefficients in spite of the discharge variation in this case. However, case B and C show large difference between head loss coefficients due to the strong oscillation of water surface and the horizontal swirl motion. The circular and square manholes in case B reduced the head loss by 30% and 6% than ones in case A, respectively. The average head loss coefficient for circular manhole in case B was 1.1. Case C reduced average loss coefficients of the square manhole in case A from 1.6 to 1.1. Accordingly, the circular manhole in case B and the square manhole in case C showed the effective way to reduce the head loss. These head loss coefficients could be available to apply to the urban sewer system with surcharged flow.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.2
• /
• pp.165-171
• /
• 2009

We developed a 'multi-point vibration acceleration method' for accurately predicting the cavitation intensity in pumps. Pressure wave generated by cavitation bubble collapse propagates and causes pump vibration. We measured vibration accelerations at several points on a casing, suction and discharge pipes of centrifugal and mixed-flow pumps. The measured vibration accelerations scattered because the pressure wave damped differently between the bubble collapse location and each sensor. In a conventional method, experimental constants are proposed without evaluating pressure propagation paths, then, the scattered vibration accelerations cause the inaccurate cavitation intensity. In our method, we formulated damping rate, transmittance of the pressure wave, and energy conversion from the pressure wave to the vibration along assumed pressure propagation paths. In the formulation, we theoretically defined a 'pressure propagation coefficient,' which is a correlation coefficient between the vibration acceleration and the bubble collapse pressure. With the pressure propagation coefficient, we can predict the cavitation intensity without experimental constants as proposed in a conventional method. The prediction accuracy of cavitation intensity is improved based on a statistical analysis of the multi-point vibration accelerations. The predicted cavitation intensity was verified with the plastic deformation rate of an aluminum sheet in the cavitation erosion area of the impeller blade. The cavitation intensities were proportional to the measured plastic deformation rates for three kinds of pumps. This suggests that our method is effective for estimating the cavitation intensity in pumps. We can make a cavitation intensity map by conducting this method and varying the flow rate and the net positive suction head (NPSH). The map is useful for avoiding the operating conditions having high risk of cavitation erosion.

• Nano
• /
• v.13 no.12
• /
• pp.1850141.1-1850141.11
• /
• 2018

Sodium ion batteries based on the more sodium source reserve than that of lithium have been designed as promising alternatives to lithium ion batteries. However, several problems including unsatisfied specific capacity and serious cyclic stability must be solved before the reality. One of the effective approaches to solve the abovementioned problems is to search for suitable anode materials. In this work, we designed and prepared $FeSe_2$ nanoflakes via a simple hydrothermal method which can be adjusted in composition by Fe precursor. As a potential anode for sodium storage, the optimized $FeSe_2$ electrode was further evaluated in different electrolytes of $NaClO_4$ in propylene carbonate/fluoroethylene carbonate and $NaCF_3SO_3$ in diethylene glycol dimethyl ether. The capacity was about $470mAh\;g^{-1}$ and $535mAh\;g^{-1}$ at $0.5A\;g^{-1}$, respectively, in the voltage between 0.5 V and 2.9 V in the cycle of stabilization phase. Superior performance both in capacity and in stability was obtained in ether-based electrolyte, which affords the property without plugging the intermediates of transition metal dichalcogenides during charge/discharge processes.

• Tribology and Lubricants
• /
• v.37 no.6
• /
• pp.246-252
• /
• 2021

Among the engine components of an internal combustion engine, the valve train is a series of systems that supply intake gas to the combustion chamber and operate intake and exhaust valves that discharge exhaust gas. If excessive wear occurs in the valve train system, the suction and exhaust valves do not open and close on time, which leads to abnormal combustion and exhaust gas. In this study, we conduct experiments and analyses on friction and wear characteristics of the valve train system. Moreover, we experimentally study the correlation between the pinball and pinball cap on engine oil lubrication, friction experiment, wear amount analysis, and surface analysis. Specifically, we experiment using Ball on reciprocating tribo-tester and apply commercial engine oil sold on the market engine oil. We construct the experimental conditions for each new oil and oil. Accordingly, the completed specimen was subjected to a confocal microscope to check the wear volume, observe the surface of the specimen, and confirm the elemental components using a scanning microscope (SEM) and an energy dispersion X-ray spectrometer (EDS). Through this experiment, we analyze the friction and wear characteristics of valve train components according to engine oil grade, and the obtained data serve as an effective engine oil management method.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.16 no.1
• /
• pp.42-62
• /
• 2003

Subjects : We tried to analysis dermatosurgical prescriptions including 477 WonBang(元方) prescriptions for SangJungHaTong(上中下統) introduced by HwangDoYeon(黃道淵). Methods : Prescriptions in BangYakHapPyun(方藥合編) is generally categorized into SangTong(上統), JungTong(中統), HaTong(下統) which are called PoJe(補劑), HwaJe(和劑), KongJe(功劑) respectively. This study classified and analyzed major diseases and symptoms appeared in dermatosurgical prescription and composition of medicine, as well as in BangYakHapPyun(方藥合編). Results and conclusions : The results of examining dermatosurgical prescriptions in WonBang(元方) of SangJungHaTong(上中下統) in BangYakHapPyun(方藥合編) are as follows; 1. The proportion of dematosurgical prescriptions was SangTong(上統) $\frac{10}{126}$(7.9$\%$). JungTong(中統) $\frac{22}{181}$(12.1$\%$), and HaTong(下統) $\frac{16}{163}$(9.8$\%$), which means that JungTong(中統)(HwaJe 和劑) takes up relatively the largest portion. 2. As for SangTong(上統), upper level herbs used in medicine are Glycyrrhiza uralensis(甘草), Paeonia japonica(白芍藥), Angelica gigas(當歸). Astragalus membranaceus(황기). Ginseng(人蔘), Poria cocos(복령), Atractylodis macrocephalae rhizoma(白朮). Cinnamon(肉桂), Rehmaniniae radix preparat(熱地黃). And these herbs are the components of Sipjundaebo-tang(十全大補湯), one of the most well-known medicine for weak energy and blood(補氣血). 3. As for JungTong(中統), in addition to medicine for weak energy and blood. Ledebouriella seseloides(防風) that removes ill elements on skin surface and Pung(風) called "wind". Limonium tetragonum(桔梗) that eliminates discharges and sputum, Angelica dahurica(白芷) that removes discharge and suppress tumor are applied. Other herbs are Ostericum koreanum(羌活). Skullcap(황령),Schizonepeta tenuifolia(荊芥), Aurantii fructus(地殼), Cimicifuga heracleifolia(升麻), Bupleurum falcatum(柴胡), Lonicerae flos(金銀花). These herbs are more effective for wind-calming treatment. cooling down fever, clearing skin irritation, detoxication. removal of tumor and discharge than replenishing energy and blood. 4. As for HaTong(下統), Angelica gigas(當歸) and Ledebouriella seseloides(防風), the two major herbs for SangTong(上統) and JungTong(中統), are mostly used. In addition, Skullcap(黃芩), Gardenia jasminoides(梔子), Eisenia bicyclis(大黃) are other major components and their key efficacy is to lower fever and KongHa(功下). 5. Herbs applied for SangTong(上統), JungTong(中統), and HaTong(下統) in large quantity are Glycyrrhiza uralensis(甘草) that harmoniously combine different herbal elements and Poria cocos(복령) that discharges humidity and watery elements out of body, removes humid and hot elements, and strengthen gastrointestinal system. Based on this, it is inferred that prescriptions for this study focus largely on treatment of humid and hot elements. In the composition of this prescription, Angelica gigas(當歸), Paeonia japonica(白芍藥), and Cnidium officinale(川芎) are taking up relatively large proportion, which are basic herbs for Samul-tang(四物湯). Therefore, it is incurred here that the concept of "replenishing blood" bears importance in dermatosurgical treatment. 6. As for herb medicines used for more than two types of prescriptions of SangTong(上統), JungTong(中統), and HaTong(下統), most of them are simultaneously used for SangTong(上統) and JungTong(中統), or for JungTong(中統), and HaTong(下統) except for Atractylodis macrocephalae rhizoma(白朮) and Gleditsia sinensis(조각자). This finding implies that prescription or treatment that are simultaneously applied are replenishing and harmonizing, or harmonizing and attacking while replenishing and attacking never go together.

• Journal of the Korean Institute of Gas
• /
• v.20 no.2
• /
• pp.1-9
• /
• 2016

Combined removal of n-heptane and carbon monoxide (CO) using a plasma-catalytic process was investigated. The performance of the plasma-catalytic process was compared with that of the catalyst-alone process to characterize the decomposition of n-heptane and CO with the operation parameters such as the type of catalyst, reaction temperature, and discharge power. From several sets of experiments, it was found that the decomposition efficiency of n-heptane mainly depended on the specific input energy rather than the reactor temperature, whereas the oxidation of CO on both the energy density and the reaction temperature. The results conducted over several metal oxide catalysts exhibited that the decomposition efficiency of n-heptane was in the order: $Pd/{\gamma}-Al_2O_3$ > $Ru/{\gamma}-Al_2O_3{\approx}Ag/{\gamma}-Al_2O_3$. Especially, $Pd/{\gamma}-Al_2O_3$ catalyst did hardly generate CO as a byproduct during the decomposition of n-heptane under an appropriate condition, revealing $CO_2$ selectivity of nearly 100%. The CO oxidation efficiency was largely affected by the type of catalyst ($Pd/{\gamma}-Al_2O_3$ > $Ru/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$). At temperatures below $180^{\circ}C$, the plasma-catalytic process was more effective in the oxidation of CO, while above $180^{\circ}C$, the catalytic process resulted in slightly higher CO oxidation efficiency.

• Nuclear Engineering and Technology
• /
• v.14 no.4
• /
• pp.186-195
• /
• 1982

The steam line break accident for Kori Unit 1 is analyzed by a code SYSRAN which calculates nuclear power and heat flux using the point kinetics equation and the lumped-parameter model and calculates system transient using the mass and energy balance equation with the assumption of uniform reactor coolant system pressure. The 1.4 f $t^2$ steam line break accident is analyzed at EOL (End of Life), hot shutdown condition in which case the accident would be most severe. The steam discharge rate is assumed to follow the Moody critical flow model. The results reveal the peak heat flux of 38% of nominal full power value at 60 second after the accident initiates, which is higher than the FSAR result of 26%. Trends for the transient are in good agreement with FSAR results. A sensitivity study shows that this accident is most sensitive to the moderator density coefficient and the lower plenum mixing factor. The DNBR calculation under the assumption of $F_{{\Delta}H}$=3.66, which is used in the FSAR with all the control and the shutdown assemblies inserted except one B bank assembly and of Fz=1.55 shows that minimum DNBR reaches 1.62 at 60 second, indicating that the fuel failure is not anticipated to occur. The point kinetics equation, the lumped-parameter model and the system transient model which uses the mass and energy balance equation are verified to be effective to follow the system transient phenomena of the nuclear power plants.lear power plants.