• Journal of the Korean GEO-environmental Society
• /
• v.21 no.9
• /
• pp.25-32
• /
• 2020

The underground utilities installed under the ground is an important civil engineering structure, such as water supply and sewerage pipes, underground power lines, various communication lines, and city gas pipes. Such underground utilities can be exposed to risk due to external factors such as concentrated rainfall and vehicle load, and it is important to select and construct an appropriate backfill material. Currently, a method mainly used is to fill the soil around the underground utilities and compact it. But it is difficult to compact the lower part of the buried pipe and the compaction efficiency decreases, reducing the stability of the underground utilities and causing various damages. In addition, there are disadvantages such as a decrease in ground strength due to disturbance of the ground, a complicated construction process, and construction costs increase because the construction period becomes longer, and civil complaints due to traffic restrictions. One way to solve this problem is to use a liquid filler. The liquid filler has advantages such as self-leveling ability, self-compaction, fluidity, artificial strength control, and low strength that can be re-excavated for maintenance. In this study, uniaxial compression strength test and fluidity test were performed to characterize the mixed soil using marine clay, stabilizer, and in-situ soil as backfill material. A freezing-thawing test was performed to understand the strength characteristics of the liquid filler by freezing, and in order to examine the effect of the filling materials on the corrosion of the underground pipe, an electrical resistivity test and a pH test were performed.

• Journal of Advanced Navigation Technology
• /
• v.18 no.1
• /
• pp.84-89
• /
• 2014

Worldwide Interoperability for Microwave Access (WiMAX) is an efficient technology for 20th century communication system. The technology provides broadband speed without the need for cables and is based on the IEEE 802.16 standard(also called Wireless MAN). Mobile WiMAX is defined as IEEE802.16e which is advanced and efficient technology for mobile telecommunication rather than GSM, CDMA technology. In this work link budget calculation for WiMAX have been done. Cell range have been calculated over digital modulations and they are BPSK, QPSK and QAM. Here different types of models like Cost 231 model have been used for different types of areas like open, rural and urban areas and Erceg-Greenstein model for sub-urban areas. Effect of various parameters like frequency, base station antenna height, transmission power and SNR over cell range have been studied. Analysis have done for both uplink and downlink.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.340-347
• /
• 2019

This study investigated the brewing properties of rice beer made with yeast isolated from traditional whole wheat nuruk. The experimental method was followed by alcohol fermentation and quality analysis for six months after separating the yeast from nuruk. The yeasts isolated from traditional nuruk showed normal fermentation characteristics, like those of commercial yeast, in terms of alcohol production capability, sugar content, and pH reducing power. Especially, the yeast (KCCM 301) isolated from whole wheat nuruk showed higher contents of glycogen and trehalose than that of commercial yeast, and so KCCM 301 yeast has excellent yeast vitality. Meanwhile, the yeast (KCCM 90301) isolated from traditional Nuruk produced significantly higher alcohol and ester contents than that of commercial yeast. This has a positive effect for supplementing the taste and aroma of rice beer. In conclusion, the yeasts isolated from whole wheat nuruk showed the general alcohol fermentation pattern and aroma content of rice beer. These yeasts seem to be effective in strengthening the flavor of rice beer.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.135-139
• /
• 2017

The main reason for heat accidents occurring at the after stern tube bearing (STB) is excessive local pressure caused by the deflection of the propulsion shaft due to propeller loads. The probability of a heat accident is increased by the low flexibility of the shaft system in very large crude oil carriers (VLCCs) as the engine power and shaft diameter increase and the distance decreases between the forward and after STBs. This study proposed shaft system with only an after STB and no forward STB for a flexibility acquisition method for a VLCC shaft system under hull deformation. A Hertzian contact condition was applied, which assumes a half-elliptical pressure distribution along the contact width for the calculation of the local squeeze pressure. The propeller loads, heat effect, and hull deflection under engine operating conditions are also considered. The results show that the required design criteria were satisfied by building a partial slope at the white metal, which is the material at the axial contact side in the after STB. This system could reduce building cost by simplification of the shaft system.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.2
• /
• pp.151-158
• /
• 2016

Tidal farm is a multi-arrayed turbine system for utilizing tidal stream energy. For horizontal-axis turbine(HAT) system, it is recommended that each unit has to be deployed far apart in order to avoid hydrodynamic interference among turbines, as proposed by the European Marine Energy Centre(EMEC). But there is no rule for the arrangement of vertical-axis turbine(VAT) yet. Moreover it has been reported that a proper arrangement of adjacent turbines can enhance the overall efficiency even greater than an arrangement without mutual interference effect. This paper suggests the layout of VATs showing the better performances, which turned out to be quite different from HATs' arrangement. Numerical calculations were performed to investigate the performance variation in terms of the rotational direction as well as the distance between turbines. It has been shown that the best combination of rotational direction and distance between turbines can increase its performance higher about 9.2% than that of two independently operated turbines. It is likely that such improvement is due to the increased velocity between adjacent turbines. For diagonally arranged turbines, the maximum normalized mean power coefficient was obtained to be higher about 5.6% than that of two independent turbines. It is expected that the present results can be utilized for conceptual design of tidal farm to harness the tidal stream energy.

• Journal of Energy Engineering
• /
• v.24 no.2
• /
• pp.167-173
• /
• 2015

This paper attempts to estimate the electricity demand function in Korea with quarterly data of average temperature, GDP and electricity price over the period 2005-2013. We apply lagged dependent variable model and ordinary least square method as a robust approach to estimating the parameters of the electricity demand function. The results show that short-run price and income elasticities of the electricity demand are estimated to be -0.569 and 0.631, respectively. They are statistically significant at the 1% level. Moreover, long-run income and price elasticities are estimated to be 1.589 and -1.433, respectively Both of results reveal that the demand for electricity is price- and income-elastic in the long-run. The relationship between electricity consumption and temperature is supported by many of references as a U-shaped relationship, and the base temperature of electricity demand is about $15.2^{\circ}C$. It is shown that power of explanation and goodness-of-fit statistics are improved in the use of the lagged dependent variable model rather than conventional model.

• Journal of Sensor Science and Technology
• /
• v.7 no.1
• /
• pp.67-72
• /
• 1998

The crystallized CuPc and PbTe films are formed by thermal evaporation and pulsed ArF excimer laser ablation. Structural and electrical properties of thin film is observed by XRD and current-voltage(I-V) curves. From XRD analysis, both PbTe and CuPc thin films show a-axis oriented structure. For the measurement of photovoltaic effect, the transverse current-voltage curve of CuPc/Si, PbTe/Si and PbTe/CuPc/Si junctions have been analyzed in the dark and under illumination. The PbTe/CuPc/Si junction exthibits a strong photovoltaic characteristics with short circuit current($J_{sc}$) of $25.46\;mA/cm^{2}$ and open-circuit voltage($V_{oc}$) of 170 mV. Quantum efficiency and power conversion efficiency are calculated to be 15.4% and $3.46{\times}10^{-2}$, respectively. Based on the results of QE and ${\eta}$, the photocurrent process of PbTe/CuPc/Si junction can be explained as following three effective steps; photocarrier generation in the CuPc layer, carrier separation at PbTe/CuPc interface, and finally a transportation of electrons through the PbTe layer.

• Korean Journal of Food Science and Technology
• /
• v.39 no.4
• /
• pp.386-389
• /
• 2007

The antioxidant activities of Phellinus igniarius (PI) and Ganoderma lucidum (GL) extracts were evaluated after far-infrared (FIR) irradiation. PI and GL were irradiated at $120^{\circ}C$ for 30, 60, 90 and 120 min with a FIR heater (2-14 ${\mu}m$), and then extracted by distilled water for 1 hr. Total sugar contents (TSC), total phenolic contents (TPC), radical scavenging ability (RSA), and reducing power (RP) were significantly increased by FIR irradiation. When PI was irradiated for 120 min, the TSC, TPC, RSA, and RP values of the PI extracts increased from 10.1 to 25.9 mg/g, 6.1 to 13.4 mg/g, 23.8 to 51.5%, and 0.222 to 0.363, respectively, compared to the untreated controls. The GL extracts, under the same conditions ($120^{\circ}C$ for 120 min), also increased in TSC, TPC, RSA, and RP from 11.1 to 22.6 mg/g, 2.5 to 5.8 mg/g, 14.5 to 18.6%, and 0.271 to 0.296, respectively. These results indicate that appropriate FIR irradiation of PI and GL could enhance the antioxidant activities of their extracts by increasing amounts of phenolic and sugar compounds.

• Korean Journal of Food Science and Technology
• /
• v.17 no.6
• /
• pp.415-420
• /
• 1985

In this study, changes in physical and chemical properties of glutinous rice during various soaking periods (0, 0.08, 1, 3, 5, 7, 10 days) were investigated in order to clarify the relations ship between soaking period and expansion volume in the preparation of Gang Jung. The longer the soaking period was, the greater the expansion volume of Gang Jung was. Higher maximum viscosity and breakdown in amylogram of glutinous rice flour were observed as the soaking period was increased, As the length of soaking period increased, hardness of glutinous rice and size of flour particle significantly decreased, while sweeling power and solubility of glutinous rice flour showed no significant difference. Increased length of soaking period was associated with higher fatty acidity, higher acidity of water extract and lower pH of glutinous rice flour. Control of flour particle size distribution resulted in significantly larger expansion volume of Gang Jung. Brabender's amylogram showed that the increase of expansion volume of Gang Jung associated with the increase of soaking period was related to the change of rheological properties of glutinous rice. It seemed that changes in viscometric properties of glutinous rice was attributed to the different flour particle size distribution resulted from changes in hardness of rice during soaking.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.8
• /
• pp.5541-5549
• /
• 2015

This paper introduces a safer and more power efficient heater by using induction heating, to apply to the semiconductor wafer fabrication exhaust gas cleaning system. The exhaust gas cleaning system is currently made with filament heater that generates an endothermic reaction of N2 gas for the removal of moisture. Induction theory, through the bases of theoretical optimization and electronic implementation, is applied in the design of the induction heater specifically for the semiconductor wafer exhaust system. The new induction heating design provides a solution to the issues with the current energy inefficient, unreliable, and unsafe design. A robust and calibrated design of the induction heater is used to optimize the energy consumption. Optimization is based on the calibrated ZVS induction circuit design specified by the resonant frequency of the exhaust pipe. The fail-safe energy limiter embedded in the system uses a voltage regulator through the feedback of the MOSFET control, which allows the system performance to operate within the specification of the N2 Heater unit. A specification and performance comparison from current conventional filament heater is made with the calibrated induction heater design for numerical analysis and the proof of a better design.