• Korean Journal of Construction Engineering and Management
• /
• v.10 no.5
• /
• pp.95-103
• /
• 2009

The case of rivers facilities works, expense the standard unit cost for the quality and a rough public corporation expense estimating of the rivers public corporation which is fixed form with the information available which it follows basic design phase absently and possibility of fluctuation. It exists many difficulties in rough public corporation expense estimating. The rivers public corporation expense rough estimating method of existing produces does not exist the amount of material of representative section of the rivers dike and the rough public corporation expense estimating method which is systematic with the method which multiples the seniority (M). The research sees the rough public corporation expense predictive model from the planning stage which is not basic design to consider the quality of the rivers facility public corporation. From this study, it can prevent the waste of national budget from the general public corporation and is more accurate and public corporation expense production possibly.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.3
• /
• pp.1096-1103
• /
• 2014

This paper proposes a novel strategy for attenuating the output power fluctuation of the wind farm (WF) in a range of tens of seconds delivered to the grid, where the kinetic energy caused by the large inertia of the wind turbine systems is utilized. A control scheme of the two-level structure is applied to control the wind farm, which consists of a supervisory control of the wind farm and individual wind turbine controls. The supervisory control generates the output power reference of the wind farm, which is filtered out from the available power extracted from the wind by a low-pass filter (LPF). A lead-lag compensator is used for compensating for the phase delay of the output power reference compared with the available power. By this control strategy, when the reference power is lower than the maximum available power, some of individual wind turbines are operated in the storing mode of the kinetic energy by increasing the turbine speeds. Then, these individual wind turbines release the kinetic power by reducing the turbine speed, when the power command is higher than the available power. In addition, the pitch angle control systems of the wind turbines are also employed to limit the turbine speed not higher than the limitation value during the storing mode of kinetic energy. For coordinating the de-rated operation of the WT and the storing or releasing modes of the kinetic energy, the output power fluctuations are reduced by about 20%. The PSCAD/EMTDC simulations have been carried out for a 10-MW wind farm equipped with the permanent-magnet synchronous generator (PMSG) to verify the validity of the proposed method.

• Journal of Korean Society of Rural Planning
• /
• v.25 no.4
• /
• pp.119-128
• /
• 2019

Although the General Agricultural Fishing Village Development Project had a significant impact on the landscape formation and management in rural area, the rural landscape planning and project sectors was not stable by fluctuation variables. On the basic understanding the institutional status of rural landscape planning, some conclusions could be discussed as follows through the analysis of quantitative and qualitative changes and the background factors. The rural landscape plan lacked its own legal and institutional foundations, and the landscape project of the General Agricultural Fishing Village Development Project was mainly focused on the environment-improving H/W project for expanding the basic living infrastructures. In order to reflect the characteristics of the region and become independent rural landscape management, it is necessary to change the contents so that the S/W business such as the deepening landscape awareness and empowerment linked with improving the physical landscape. To this end, it is necessary to establish a foundation for the rural landscape planning system to have its own status, and it seems to seek to supplement with what is included S/W contents reflecting the context of higher level landscape planning. The landscape sector of the General Agricultural Fishing Village Development Project proved to be in the process of shrinking in both quantity and quality, despite the temporary expansion in the past. In addition, considering the distortion of the contents of landscape projects in rural sites, it seems that the rural landscape-related public project are now in a position to seek a new phase change beyond quantitative expansion. In particular, along with institutional improvements to secure the independent status of rural landscape planning that contributes to village community regeneration and social sustainability through the role of intermediary support organizations in landscape management activities. Through the integrated landscape plan, which is established in advance and led by the residents in the early stages, there is a need to change the direction to enhance meaning of the landscape planning goes beyond the facility design or space improvement.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.122-127
• /
• 2013

The paper includes the analytic results of pressure fluctuation data from the combustion of an oxidizer-rich preburner applicable to high-performance, closed-cycle liquid rocket engine systems. The combustion experiments went through two different steps of a chamber pressure during single run. Self-excited pressure fluctuations with a frequency of 78 Hz were observed only at the relatively low chamber pressure condition. These pressure fluctuations are regarded as a bulk mode. The intensity of pressure fluctuations by a root-mean-square value is 13.3% normalized by the chamber static pressure and no pressure excitation was observed at the design pressure condition. The bulk mode has an identical phase across the inside of the chamber and reveals the similar characteristics to the Helmholtz resonator.

• Current Optics and Photonics
• /
• v.4 no.4
• /
• pp.286-292
• /
• 2020

Imaging through multicore fiber (MCF) is of great significance in the biomedical domain. Although several techniques have been developed to image an object from a signal passing through MCF, these methods are strongly dependent on the surroundings, such as vibration and the temperature fluctuation of the fiber's environment. In this paper, we apply a new, strong technique called deep learning to reconstruct the phase image through a MCF in which each core is multimode. To evaluate the network, we employ the binary cross-entropy as the loss function of a convolutional neural network (CNN) with improved U-net structure. The high-quality reconstruction of input objects upon spatial light modulation (SLM) can be realized from the speckle patterns of intensity that contain the information about the objects. Moreover, we study the effect of MCF length on image recovery. It is shown that the shorter the fiber, the better the imaging quality. Based on our findings, MCF may have applications in fields such as endoscopic imaging and optical communication.

• Korean Journal of Metals and Materials
• /
• v.49 no.4
• /
• pp.321-328
• /
• 2011

The 30 nm-thick Ni layers was deposited on a flexible polyimide substrate with an e-beam evaporation. Subsequently, we deposited a Si layer using a catalytic CVD (Cat-CVD) in a hydride amorphous silicon (${\alpha}$-Si:H) process of $T_{s}=180^{\circ}C$ with varying thicknesses of 55, 75, 145, and 220 nm. The sheet resistance, phase, degree of the crystallization, microstructure, composition, and surface roughness were measured by a four-point probe, HRXRD, micro-Raman spectroscopy, FE-SEM, TEM, AES, and SPM. We confirmed that our newly proposed Cat-CVD process simultaneously formed both NiSi and crystallized Si without additional annealing. The NiSi showed low sheet resistance of < $13{\Omega}$□, while carbon (C) diffused from the substrate led the resistance fluctuation with silicon deposition thickness. HRXRD and micro-Raman analysis also supported the existence of NiSi and crystallized (>66%) Si layers. TEM analysis showed uniform NiSi and silicon layers, and the thickness of the NiSi increased as Si deposition time increased. Based on the AES depth profiling, we confirmed that the carbon from the polyimide substrate diffused into the NiSi and Si layers during the Cat-CVD, which caused a pile-up of C at the interface. This carbon diffusion might lessen NiSi formation and increase the resistance of the NiSi.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.411-419
• /
• 2020

The experiment of unsteady rip current generated at the successive ends of breaking wave crests of honeycomb pattern waves was conducted in a laboratory wave basin, and its time-varying evolution was observed by using ortho-rectified images. The present experiment utilized the generation of a quasi nodal line of the honeycomb-pattern waves formed by out-of-phase motion of two piston-type wavemakers arranged in the transverse direction, instead of the original honeycomb pattern waves which are generated when two wave trains propagate with slightly different wave directions. The velocities of rip current were measured by using the LSPIV (Large-Scale Particle Image Velocimetry) technique. As a result, the unsteady rip current was generated between successive ends of wave crests, and evolved with its shear fluctuations in this experiment. Also, the time series of LSPIV velocity of the unsteady rip current showd its short component due to waves and its long component due to wave-induced currents.

• Corrosion Science and Technology
• /
• v.20 no.6
• /
• pp.335-346
• /
• 2021

Since epoxy resin coating shows excellent properties in formability, adhesion, and corrosion resistance, they have been extensively used in many industries. However, various types of damages in the epoxy coated tube within a relative short time have been reported due to cavitation erosion, liquid impingement, variation of temperature and pressure. Nevertheless, there has been little research on the effect of temperature on the cavitation degradation of epoxy coatings. Therefore, this work used an ultrasonic cavitation tester to focus on the effect of solution temperature on the cavitation properties of 3 kinds of epoxy coatings in 3.5% NaCl. The cavitation properties were discussed basis on the material properties and environmental aspects. As the solution temperature increased, even though with large fluctuation, the cavitation degradation rates of A and B coatings were reduced rapidly, but the rate of C coating was decreased gradually. In addition to the cushioning effect, the reason that the cavitation degradation rate reduced with solution temperature was partly related to the brittle fracture and water absorptivity of the epoxy coatings, and the water density, but was little related to the shape and composition of the compound in the coatings or the phase transition of the epoxy coating.

• Journal of Hydrogen and New Energy
• /
• v.33 no.6
• /
• pp.723-732
• /
• 2022

Cracking ammonia inside solid oxide fuel cell (SOFC) stack is a compact and simple way. To prevent sharp temperature fluctuation and increase cell efficiency, the decomposition reaction should be spread on whole cell area. This leading to a question that, how does anode thickness affect the conversion rate of ammonia and the cell voltage? Since the 0D model of SOFC is useful for system level simulation, how accurate is it to use equilibrium solver for internal ammonia cracking reaction? The 1D model of ammonia fed SOFC was used to simulate the diffusion and reaction of ammonia inside the anode electrode, then the partial pressure of hydrogen and steam at triple phase boundary was used for cell voltage calculation. The result shows that, the ammonia conversion rate increases and reaches saturated value as anode thickness increase, and the saturated thickness is bigger for lower operating temperature. The similar cell voltage between 1D and 0D models can be reached with NH₃ conversion rate above 90%. The 0D model and 1D model of SOFC showed similar conversion rate at temperature over 750℃.

• Applied Biological Chemistry
• /
• v.46 no.1
• /
• pp.23-27
• /
• 2003

Lipoxygenase is the enzyme responsible for the formation of $C_6$-alcohols and $C_6$-aldehydes ($C_6$-compounds), which are well blown contributors to various types of 'green odor' In green tea. Changes in lipoxygenase activity and volatile compounds of green tea leaves were monitored daily during early growing season. The enzyme activity was spectrophotometrically measured using linoleic acid as a substrate. The volatile compounds were extracted through Solid Phase Micro-Extraction, and were subjected to GC and GC-MS analyses. Results showed that lipoxygenase activity and levels of $C_6$-compounds concomitantly increased or decreased during the early growing season, probably caused by the fluctuation in the daily temperature; increase in temperature led to the increase in enzyme activities and $C_6$-compound levels, whereas leaves plucked too early had low volatile compound levels. In this study, optimum plucking time of tea leaves for the production of high quality green tea with a wellbalanced aroma was determined.