• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.52 no.4
• /
• pp.347-355
• /
• 2016

In this study, a new designed propeller was applied on 24 ton class squid jigging vessel to reduce of fuel consumption. The selected squid jigging boat was under construction at the shipyard to determine the resistance of the hull through the model experiment. The propeller design was carried out by using the experimental data and ITTC procedures. Sea trials were performed by measuring the speed and the horsepower required by the condition of five power levels of engine load, namely 70%, 80%, 90%, MCR and maximum engine power. The speed and delivered horse power were compared between the conventional propeller and the new design propeller. Delivered horse power by installing the new propeller takes 90% engine load at start-up conducted by decreased 9.06%. The measuring speed is increased up to the 0.6 knots in the low-speed range to high range. This study showed that only the design and installation of a new propeller can improve the propulsion efficiency of the boats; furthermore, reduce fuel costs can be achieved at the same time by improving the increased cruising speed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.3
• /
• pp.218-224
• /
• 2007

Although piezoelectric materials such as PZT have been widely used as actuators in the field of active vibration suppression, the use of bare PZT as an actuator may cause some drawbacks such as critical breaks in the installation process, short circuits in the host material and low fatigue performance. The LIPCA-C2 (lightweight piezocomposite actuator) was developed to alleviate these problems. We implemented the LIPCA as an actuator to suppress the vibration of an aluminum cantilever beam with a tip mass. In our test, we used positive position feedback control algorithm. The filter frequency for this type of feedback should be tuned to the natural frequency of the target mode. The first three experimental natural frequencies of the aluminum cantilever beam agree well with the results of finite element analysis. The effectiveness of using the LIPCA as an actuator in active vibration suppression was investigated with respect to the time and frequency domains, and the experimental results show that LIPCAs with PPF control can significantly reduce the amplitude of forced vibrations and the settling time of free vibrations. For a case study, the forced vibration control of several beams with different thicknesses were performed.

• Fire Science and Engineering
• /
• v.32 no.5
• /
• pp.34-39
• /
• 2018

In this study, the experiment conditions for the variation of heat release rate in compartment space were constructed to analyze the effects of fire spread and the operation time of sprinkler in accordance with the heat loss of the sprinkler's heat element. The compartment composed of fire board (width = 0.3 m, height = 0.5 m, length = 3.0 m), are manufactured to measure the temperature distributions in the inner space, the mass loss rate and heat release rate during the experiment of N-heptane pool fire test. Also, the operation time of sprinkler is analyzed with the installation of sprinkler and C-factor using Fire Dynamics Simulator Ver.6 under the experiment conditions. The results show that the operation time of sprinkler, which has RTI $100(m{\cdot}s)^{0.5}$ operating temperature $70^{\circ}C$, is 30 s~60 s for C-factor = 0 and 1, 62 s~92 s for C-factor = 3, and 120 s over for C-factor = 5, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.10
• /
• pp.67-79
• /
• 2016

Waveform micropile is an advanced construction method that combined the concept of conventional micropile with jet grouting method. This new form of micropile was developed to improve frictional resistance, which consequently leads to achieving higher bearing capacity and cost efficiency. Two field tests were conducted to examine the field applicability as well as to verify the effects of bearing capacity enhancement. In particular, waveform micropile construction using jet grouting method was performed to evaluate the viability of waveform micropile installation. After testing, the surrounding ground was excavated to check the accomplishment on the shape of waveform micropile. The result showed that waveform micropile can be installed by adjusting the grouting time and pressure. In the loading tests, waveform micropile's bearing capacity increased by 1.4 to 2.3 times depending on their shapes when compared with conventional micropile. Overall results clearly demonstrated that waveform micropile is an enhanced construction method that can improve bearing capacity.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.3
• /
• pp.75-79
• /
• 2013

The frost depth is one of important factors in the design of structures such as roadways, buried pipeline, and foundations. A frost indicator with methylene blue solution has several advantages with respect to installation cost, maintenance, and simple measurement. However, as a geotechnical engineering aspect, the accuracy of the frost indicator has not been proved yet. This paper presents experimental and field investigations of the accuracy of the frost indicator and contour maps of maximum frost depth. The contour maps of maximum frost depth can be applied to design geo-infrastructure in South Korea.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.3
• /
• pp.13-22
• /
• 2004

In case of the lateral movement accurring at soft ground where a row of piles are installed, the crown failure at external arch zone of soil arching is firstly developed, and the cap failure at wedge zone in front of piles is lastly developed. Therefore, the lateral earth pressure acting on a row of piles due to soil movement should be calculated in each condition of crown and cap failures around piles. A theoretical equation of crown failure can be proposed using a cylindrical cavity expansion theory. The theoretical equation of crown failure is mainly affected by two factors. One is related to soil properties such as internal friction angle, cohesion and horizontal pressure, and the other is related to pile factors such as diameter, installation interval. Meanwhile, the yield range of lateral earth pressure is established in the estimation of theoretical equation based on crown and cap failures around piles. The theoretical values based on crown and cap failures are compared with the experimental values. The experimental values are located in the range proposed by theoretical values. Thus, it is confirmed that the theoretical values proposed in the study are very reasonable.

• Aerospace Engineering and Technology
• /
• v.3 no.1
• /
• pp.155-169
• /
• 2004

Space launch vehicles and reentry vehicles are exposed to extreme heating conditions due to high aerodynamic heating while flying at high Mach numbers in the atmosphere. To protect the vehicle itself or the payload from the aerodynamic heating, the thermal load imposed on the surface should be exactly predicted and proper thermal protection should be applied based on the prediction results. But this requires rigorous thermal analysis and testing to prevent loss of payload capacity caused by excessive heat shielding, and the amount of thermal protection material to be applied is determined through aerodynamic heating tests. Various design points to be considered to upgrade the prototype aerodynamic thermal simulation facility(ATSF) used for the KSR-series sounding rocket development to the one suitable for the KSLV(Korean Space Launch Vehicle)-series launch vehicle are considered in this research. The need and limitation for the facility are first considered, and the functions required for KSLV testing are determined. The specifications of the upgraded facility are briefly suggested and these results will be used for the future fabrication and installation of the facility.

• Korean Chemical Engineering Research
• /
• v.40 no.6
• /
• pp.676-680
• /
• 2002

The specific gravity meter is the instrument used to measure the density of fluids under the reference conditions and it can be widely used in industrial areas, especially in massive flow rate natural gas industry. This study has been carried out in an attempt to improve measurement accuracy of natural gas flow rate calculation, providing the adequate installation and proper operation conditions of specific gravity meter. The test results are 1) the density measurement errors in case of using methane and standard gas as calibration gases are smaller than using methane and nitrogen gas, 2) the periodical calibration to maintain accurate density measurements is essential, and 3) the specific gravity meter is sensitive to changes of environmental conditions, especially environmental temperature surrounding the specific gravity meter.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.292-298
• /
• 2008

Seoul Metro and Seoul Metropolitan Rapid Transit Corp. have started installing screen doors at subway platforms to improve the environment of subways and prevent passengers' accidents since 2006. They are still installing screen doors at subway platforms and Metropolitan Rapid Transit Corporations in other areas are also proceeding with installment of screen doors or making preparations for it. Grounding is necessary for installing PSD systems. In case that PSD grounding is connected with existing electrical equipment grounding system, it was decided to install separate grounding for safe operation of PSD system and passenger safety. However, it's very difficult to install new grounding at the subway station compound. A way to improve this condition is that we proceed with grounding by composing grounding station by carbon grounding rod. This paper will mainly deal with how to design and construct carbon ground rod, which has been applied to PSD system grounding since 2006, including its experimental examples. In this paper, ways to secure ground resistance below 5 ohms, which is resistance necessary for PSD grounding, and to compose grounding system were also discussed. Furthermore, a ground test to check the ability to fulfill a role of PSD grounding system was conducted. As a result of applying carbon grounding module, PSD system is being operated without any problem and the installment of PSD system will be continuously expanded in the future. It's also thought that a way to integrate grounding of each functional room which has been installed at the subway station compound and to arrange equipotential grounding should be reviewed and performed promptly.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.7 no.1
• /
• pp.42-58
• /
• 2008

Nowadays the installation of Real-time Traffic Signal Control system is gradually spread, in order to solve the traffic problem which become serious. The most important thing are reliability of data collection and functionality of system in Real-time Traffic Signal Control System. But, the evaluation for those introduction system are defective after system constructing. So, many systems are not working properly to those systems's primarily purpose. This study is executed expansion through field test and analysis which check performance and advise of system operation. It has purpose to establish of the maintenance system of Real-time Traffic Signal Control system. As the result of analysis, we could find the several problems in this study. So, we also could guess that the effective maintenance systems of the Real-time Traffic Signal Control system is necessary within few years.