• Journal of Korean Clinical Health Science
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• v.3 no.2
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• pp.372-377
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• 2015

Purpose: The aim of this study is to compare total high order aberrations between surgery which uses TransPRK and general laser assisted sub-epithelial keratomileusis. Methods: The patients who had general laser assisted sub-epithelial and TransPRK laser assisted sub-epithelial by visiting ophthalmic clinic in Ulsan from January 2014 to August 2014 was researched. Results: When comparing total high order aberrations before and after operation, it was found that total high order aberration in general laser assisted sub-epithelial group increased to $0.222{\pm}0.078{\mu}m$ from $0.074{\pm}0.019{\mu}m$ while that in TransPRK assisted sub-epithelial group increased to $0.179{\pm}0.045{\mu}m$ from $0.076{\pm}0.032{\mu}m$. When comparing the increment in total high order aberrations between two groups after surgery, it was found that the increments of TransPRK assisted sub-epithelial group were statistically smaller than that of general laser assisted sub-epithelial group (p<0.05). Conclusions: This study made a comparative analysis of total high order aberrations between general laser assisted sub-epithelial and TransPRK assisted sub-epithelial which was introduced recently and the result showed a significant difference. The findings of this study suggest that TransPRK assisted sub-epithelial can be used widely in simply improving eye sight and quality of vision by reducing an increase in high order aberration caused by orthokeratology surgery. It is expected that TransPRK assisted sub-epithelial will be helpful for improving the understanding quality of eye sight which occurs by several methods of vision correction surgery.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.199-206
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• 2015

In this study, a new diagnosis method which can predict the working states of a pipe or its element in realtime is proposed by using an artificial neural network. The displacement data of an inspection element of a piping system are obtained by the use of PIV (particle image velocimetry), and are used for teaching a neural network. The measurement system consists of a camera, a light source and a host computer in which the artificial neural network is installed. In order to validate the constructed monitoring system, performance test was attempted for two kinds of mobile phone of which vibration modes are known. Three values of acceleration (minimum, maximum, mean) were tested for teaching the neural network. It was verified that mean values were appropriate to be used for monitoring data. The constructed diagnosis system could monitor the operation condition of a gas pipe.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.473-482
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• 2015

Recent development in science and technology has enabled vehicles to be equipped with advanced autonomous functions. ADAS (Advanced Driver Assistance Systems) are examples of such advanced autonomous systems added. Advanced systems have several operational modes and it has been observed that drivers could be unaware of the mode they are in during vehicle operation, which can be a contributing factor of traffic accidents. In this study, possible mode confusions in a simulated environment when vehicles are equipped with an adaptive cruise control system were investigated. The mental model of the system was designed and verified using the formal analysis method. Then, the user interface was designed on the basis of those of the current cruise control systems. A set of human-in-loop experiments was conducted to observe possible mode confusions and redesign the user interface to reduce them. In conclusion, the clarity and transparency of the user interface was proved to be as important as the correctness and compactness of the mental model when reducing mode confusions.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.391-400
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• 2008

Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.43
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• pp.117-142
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• 2009

The purpose of this paper is to examine the basic principles for the examination of documents in terms of the basic duty to examine the documents, the time allowed to the banks to examine the documents, linkage among the documents, the originality of documents and their issuers, and the rejection formula of documents. Further this author would look at the changes of particular transport document including bill of lading, charter-party bill of lading and so on. From the seller's perspective, the changes of the principles and individual documents under UCP600 are the most important in the sense that they affect the criteria against which the payment is made. The major changes include the omission of the phrase "with reasonable care", in terms of the basic examination principles, substitute the phrase "five banking days following the day of presentation" for the phrase "reasonable time, not to exceed seven banking days following the days of receipt of documents", introduce the new wording about the linkage between the documents tendered, and make clear the meaning of the originality of documents as well as the rejection formula. For transport documents, even though dealing with bill of lading, charter-party bill of lading, transport document covering at least two different modes of transport, freight-forwarder bill of lading and freight collect transport documents, this paper focuses on the "transhipment" of bill of lading and the definition of charter-party bill of lading. Thus, UCP has been changed several times to reflect the new banking customs and practice. It, however, would not answer every questions which users and banks will raise. These questions may be best answered in the particular underlying contract. The UCP are necessary but not a sufficient instrument for the smooth operation of an international trade transaction. The rules are now out: it remains to be seen what the players do with it.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.435-444
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• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.1
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• pp.59-71
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• 2016

The Nuclear and Fossil Steam Turbines record a considerable number of failures annually. Some of these failures reported are as result of blade failure. The failure of the L-0 blade in a Steam Turbine is one of the most reported blade failure in Nuclear and Fossil steam turbines. This paper seeks to identify the best Non Destructive Evaluation (NDE) method or methods to be used in the steam turbine L-0 blades inspection process. The development of systems engineering processes presents an opportunity to apply NDE inspection to the L-0 blades. This process apply computer modelling of the L-0 using ANSYS and by simulating the stresses experienced by the L-0 blade during operation it is possible to identify the most susceptible areas for crack formation and growth. The results from these models compared to industry data for validation. The analysis of these results used to predict the most probable failure location and failure modes. Therefore NDE inspection can be applied to these areas with greater degree of accuracy. This would be beneficial in the increasing the accuracy in the detection of cracks and hence save inspection time and the overall inspection cost. Furthermore, not only the location for crack formation and NDE inspection determined but also best the NDE inspection technique/techniques to be applied appropriately on the L-0 blade are prescribed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.138-142
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• 2018

This study used HILS to test an expansion joint, which is vulnerable to the water hammer effect. The operation data for the HIL simulator was the length rate of the expansion joint by the water hammer, which was used for life prediction based on the vibration durability. For the vibration durability test, the internal pressure of the expansion joint was assumed to be a factor of the durability life, and the lifetime prediction model equation was obtained by curve fitting the lifetime data at each pressure. During the test, the major failure modes of crack and water leakage occurred on the surface of the bellows part. The lifetime prediction model typically follows an inverse power law model. The pressure is a stress factor, and the model is effective in only a specific environment. Therefore, another stress factor such as temperature will be added and considered for a mixed lifetime prediction model in the future.

• Proceedings of the KSRS Conference
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• v.1
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• pp.7-10
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• 2006

Four programs, i.e. TRMM, ADEOS2, ASTER, and ALOS are going on in Japanese Earth Observation programs. TRMM and ASTER are operating well, and TRMM operation will be continued to 2009. ADEOS2 was failed, but AMSR-E on Aqua is operating. ALOS (Advanced Land Observing Satellite) was successfully launched on $24^{th}$ Jan. 2006. ALOS carries three instruments, i.e., PRISM (Panchromatic Remote Sensing Instrument for Stereo Mapping), AVNIR-2 (Advanced Visible and Near Infrared Radiometer), and PALSAR (Phased Array L band Synthetic Aperture Radar). PRISM is a 3 line panchromatic push broom scanner with 2.5m IFOV. AVNIR-2 is a 4 channel multi spectral scanner with 10m IFOV. PALSAR is a full polarimetric active phased array SAR. PALSAR has many observation modes including full polarimetric mode and scan SAR mode. After the unfortunate accident of ADEOS2, JAXA still have plans of Earth observation programs. Next generation satellites will be launched in 2008-2012 timeframe. They are GOSAT (Greenhouse Gas Observation Satellite), GCOM-W and GCOM-C (ADEOS-2 follow on), and GPM (Global Precipitation Mission) core satellite. GOSAT will carry 2 instruments, i.e. a green house gas sensor and a cloud/aerosol imager. The main sensor is a Fourier transform spectrometer (FTS) and covers 0.76 to 15 ${\mu}m$ region with 0.2 to 0.5 $cm^{-1}$ resolution. GPM is a joint project with NASA and will carry two instruments. JAXA will develop DPR (Dual frequency Precipitation Radar) which is a follow on of PR on TRMM. Another project is EarthCare. It is a joint project with ESA and JAXA is going to provide CPR (Cloud Profiling Radar). Discussions on future Earth Observation programs have been started including discussions on ALOS F/O.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.243-251
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• 2010

The military has been putting great efforts into applying data communication on existing voice communication systems being used in NCW(Network Centric Warfare). Data communication will be an effective choice in one of many effort to yield a minimum kill chain, comparing to legacy voice communications, when tactical units conduct their missions. However, the required budget will be enormous, in case of the replacement of a lot of legacy communication systems with new one. As a cost-effective alternative, the tactical data communication systems using the conventional radio systems instead of the development of new radio systems has been proposed. It is mandatory, though, to ensure QoS while maintaining data communication by making use of legacy radio systems already in use. This paper focuses on the performance issues experimented and analyzed for tactical data communication through the legacy radio systems as the first step towards guaranteed QoS. We have conducted various experiments such as the transmission error rate on certain tactical messages, performance evaluation of redundant transfers, the relationship between the transmission frame size and rate of error, the identification of error points in the transmission frame, and techniques to reduce the errors in both hopping and non-hopping modes. As a result of the performance experiments, The adaptive communication module which decides the redundant transmission or the Forward Error Correction(FEC) technique by analyzing channel status and current transmission status(hopping/non-hopping) of the legacy radio should be designed. the FEC technique in non-hopping, and the redundant transmission technique in hopping mode was recommended from the result of experiment with the frame size is 20bytes in non-hopping and 10Bytes frame size in hopping mode.