• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.195-202
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• 2020

The production of larger of ships is a survival strategy for global shipping companies to pursue the economics of scale. According to this strategy, to respond to this situation, many containers are loading/unloading simultaneously in the hub port. Additionally, the container terminals are promoting the introduction of automation to expand the terminal facilities and increase efficiency/productivity of the container yards. European ports have introduced automation to address rising labor costs and shortages of labor. Recently, the construction of fully automated container terminals is increasing in the United States and China to resolve problems such as the slow growth of the global economy, the emergence of large ships, air pollution, and safety accidents. Domestic ports are at an early stage compared to the world's advanced container terminals, and countermeasures are being prepared to respond to the changing ports. However, research on the recognition difference analysis that examines the opinions of stakeholders is insufficient. As a result of analyzing the recognition among the groups, it was found that container terminal operators reduced labor costs, improved shipping services for shipping companies, prevented safety accidents for port union labor, and increased service for port authority and government agencies. Thus, to closely examine the perception among the groups, one-way ANOVA was performed, and then the implications were deduced as the basic data for the smooth introduction of automation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2806-2811
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• 2013

New technologies such as multi-antenna and small cell were proposed as key technology for the next generation mobile system to cope with the explosively increasing mobile data traffic. In particular, heterogeneous mobile communication network which can improve spatial reuse factor by exploiting macro and small cells simultaneously is attracting attention. However, the heterogeneous network has a problem that the utilization of small cells becomes low because the transmit power of macro base stations is much higher than that of small base stations and then the probability that mobile stations are attached to the macro base stations becomes high. This problem is dominant in uplink. The concept of cell range expansion bias to mitigate the problem was proposed by 3GPP and the corresponding standardization is in progress. In this paper, we analyze the downlink performance of the heterogeneous mobile communication network based on a system level simulator with the cell range expansion bias in terms of average cell spectral efficiency.

• Journal of Information Management
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• v.40 no.3
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• pp.61-77
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• 2009

Recently, enterprises are protecting information assets with the various means of control and management. Nevertheless, they are confronted with the dilemma which the higher securitylevel they request, the lesser efficiency and productivity in short terms they acquire by the inconvenience of business process. In addition, in spite of the steady increase of organization's investment on information protection, the systematic way for the performance measurement of information protection has not been suggested, so that in reality, it is difficult to make the decision to invest on information-protection and elicit the direction to improve it. For this reason, this study intended to establish the concept of the protection and security of information assets of enterprises and to categorize the type of activities to protect information assets into management activity and control activity, and analyze the effects of management activity and control activity for information asset protection on the performance of information asset protection activity and organization. For this research, questionnaire survey was conducted with literature study and the PLS(Partial Least Square) was used to analyze the measurement model and hypotheses testing. The PLS analysis results indicate that management activity for information asset protection affects information asset protection performance. Further, organizational performance is influenced by information asset protection performance. Practical implications of these findings and future research implications are also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1036-1043
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• 2014

The installation of PV system to the power distribution system is being increased as one of solutions for environmental pollution and energy crisis. Because the output efficiency of PV system is getting decreased because of the aging phenomenon and several operation obstacles, the technology development of output prediction and state diagnosis of PV modules are required in order to improve operation performance of PV modules. The conventional methods for output prediction by considering various parameters and standard test condition values of PV modules may have difficult and complex computation procedure and also their prediction values may produce large error. To overcome these problems, this paper proposes an optimal prediction algorithm and state diagnosis algorithm of PV modules by using least square methods of linear regression analysis. In addition, this paper presents a state diagnosis evaluation system of PV modules based on the proposed optimal algorithms of PV modules. From the simulation results of proposed evaluation system, it is confirmed that the proposed algorithms is a practical tool for state diagnosis of PV modules.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.103-110
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• 2010

In this paper, a new mode changeable asymmetric full bridge dc/dc converter is proposed to solve the freewheeling current problem of the conventional zero voltage switching(ZVS) phase shift full bridge(PSFB) dc/dc converter of low output voltage and high output current applications. The proposed converter is operated as an asymmetric full bridge converter when the duty cycle is less than 50% and active clamp full bridge converter when the duty cycle is greater than 50%. As a result, since its freewheeling current is eliminated, the conduction loss is lower than that of the conventional ZVS PSFB dc/dc converter. Moreover, ZVS of all power switches can be ensured along a wide load ranges and output current ripple is very small. Therefore, high efficiency of the proposed converter can be achieved. Especially since its operation mode is changed to the active clamp full bridge converter during hold up time and can be operated with 50~100% duty ratio, it can produce the stable output voltage along wide input voltage range. The operational principles, theoretical analysis and design considerations are presented. To confirm the operation, validity and features of the proposed converter, experimental results from a 1.2kW($400V_{dc}/12V_{dc}$) prototype are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.329-329
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• 2007

Photoconductive poly crystalline lead oxide coated on amorphous thin film transistor (TFT) arrays is the best candidate for direct digital x-ray detector for medical imaging. Thicker films with lessening density often show lower x-ray induced charge generation and collection becomes less efficient. In this work, we present a new methodology used for the high density deposition of PbO. We investigate the structural properties of the films using X-ray diffraction and electron microscopy experiments. The film coatings of approximately $200\;{\mu}m$ thickness were deposited on $2"{\times}2"$ conductive-coated glass substrates for measurements of dark current and x-ray sensitivity. The lead oxide (PbO) films of $200\;{\mu}m$ thickness were deposited on glass substrates using a wet coating process in room temperature. The influence of post-deposition annealing on the characteristics of the lead oxide films was investigated in detail. X-ray diffraction and scanning electron microscopy, and atomic force microscopy have been employed to obtain information on the morphology and crystallization of the films. Also we measured dark current, x-ray sensitivity and linearity for investigation of the electrical characteristics of films. It was found that the annealing conditions strongly affect the electrical properties of the films. The x-ray induced output charges of films annealed in oxygen gas increases dramatically with increasing annealing temperatures up to $500^{\circ}C$ but then drops for higher temperature anneals. Consequently, the more we increase the annealing temperatures, the better density and film quality of the lead oxide. Analysis of this data suggests that incorporation and decomposition reactions of oxygen can be controlled to change the detection properties of the lead oxide film significantly. Post-deposition thermal annealing is also used for densely film. The PbO films that are grown by new methodology exhibit good morphology of high density structure and provide less than $10\;pA/mm^2$ dark currents as they show saturation in gain (at approximate fields of $4\;V/{\mu}m$). The ability to operate at low voltage gives adequate dark currents for most applications and allows voltage electronics designs.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.34-38
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• 2009

Nitrous oxide, which is used as an anesthetic gas, has been shown to be a chronic health hazard. It is necessary to monitor and control the nitrous oxide exposure of the operating theaters staff. In this study, N2O exposure level of the operating nurses is assessed with a GC-ECD. The nitrous oxide gas is collected on a molecular sieve 5A contained in a glass tube and desorbed for 12 hours at $100^{\circ}C$ in heating block. As a result of the test using GC-ECD, calibration curve's $R^2$ of $N_2O$ is 0.9992, LOD is $0.96{\mu}g$/injection, LOQ is $3.21{\mu}g$/injection, desorption efficiency is 94.78 4.50% in average and break through is within 10% compared with the concentration. The average concentration before operation is 5.12ppm and it is 42.3ppm during operation. There are a significant difference showing that the P value is lower than 0.05. Assessing exposure level to nitrous oxide based on nurses' working positions, the exposure levels do not show significant difference( P>0.005). And $N_2O$ in active sampling method is higher than passive sampling method(P<0.05).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.323-335
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• 2015

Mobile healthcare is a fusion of information technology and biotechnology and is a new type of health management service to keep people's health at anytime and anywhere without regard to time and space. The WBAN(Wireless Body Area Network) technology that collects bio signals and the data analysis and monitoring technology using mobile devices are essential for serving mobile healthcare. WBAN consisting of users with mobile devices meet another WBAN during movement, WBANs transmit data to the other media. Because of WBAN conflict, several nodes transmit data in same time slot so a collision will occur, resulting in the data transmission being failed and need more energy for re-transmission. In this thesis, we proposed a MAC protocol for WBAN with mobility to solve these problems. First, we proposed a superframe structure for WBAN. The proposed superframe consists of a TDMA(Time Division Muliple Access) based contention access phase with which a node can transmit data in its own time slot and a contention phase using CSMA/CA algorithm. Second, we proposed a network merging algorithm for conflicting WBAN based on the proposed MAC protocol. When a WBAN with mobility conflicts with other WBAN, data frame collision is reduced through network reestablishment. Simulations are performed using a Castalia based on the OMNeT++ network simulation framework to estimate the performance of the proposed superframe and algorithms. We estimated the performance of WBAN based on the proposed MAC protocol by comparing the performance of the WBAN based on IEEE 802.15.6. Performance evaluation results show that the packet transmission success rate and energy efficiency are improved by reducing the probability of collision using the proposed MAC protocol.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.328-328
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• 2007

Large area matrix-addressed image detectors are a recent technology for x-ray imaging with medical diagnostic and other applications. The imaging properties of x-ray pixel detectors depend on the quantum efficiency of x-rays, the generated signal of each x-ray photon and the distribution of the generated signal between pixels. In a phosphor coated detector the light signal is generated by electrons captured in the phosphor screen. In our study we simulated the lateral spread distributions for phosphor coupled detector by Monte Carlo simulations. Most simulations of such detectors simplify the setup by only taking the conversion layer into account neglecting behind. The Monte Carlo code MCNPX has been used to simulate the complete interaction and subsequent charge transport of x-ray radiation. This has allowed the analysis of charge sharing between pixel elements as an important limited factor of digital x-ray imaging system. The parameters are determined by lateral distribution of x-ray photons and x-ray induced electrons. The primary purpose of this study was to develop a design tool for the evaluation of geometry factor in the phosphor coupled optical imaging detector. In order to evaluate the spatial resolution for different phosphor material, phosphor geometry we have developed a simulation code. The developed code calculates the energy absorption and spatial distribution based on both the signal from the scintillating layer and the signal from direct detection of x-ray in the detector. We show that internal scattering contributes to the so-called spatial resolution drop of the image detector. Results from the simulation of spatial distribution in a phosphor pixel detector are presented. The spatial resolution can be increased by optimizing pixel size and phosphor thickness.

• The Journal of Engineering Research
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• v.1 no.1
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• pp.5-14
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• 1997

The purpose of thesis is to analyze the radiation characteristics of an offset gregorian antenna in order to design the satellite-loaded antenna. In order to compute the radiation pattern of the sub-reflector, the reflected wave is obtained by GO(Geometric Optics) at an arbitrary shaped sub-reflector. Then the total radiation EM wave is obtained by summing the diffracted fields obtained by UTD(Uniform Geometrical Theory of Diffraction) and the GO fields. In order to calculate the far field radiation pattern of the main reflector, the radiation integral equation is derived from the induced current density on reflector surface using PO(Physical Optics). The kernel is expanded in terms of Jacobi-Bessel series for increasing the computational efficiency, then the modified radiation integral is represented as the double integral equation independent of observation points. When the incident fields are assumed to be x-or y-polarized field, the characteristics of radiation patterns in the gregorian antenna is analyzed in case of the main reflector having the focal length of 62.4$\lambda$, diameter of 100$\lambda$, and offset height of 75$\lambda$, and the sub-reflector having the eccentricity of 0.501, the inter focal length og 32.8$\lambda$, the horn axis angle of $9^{\circ}$ and the half aperture angle of $15.89^{\circ}$. The cross-polarized level and side lobe level in the offset geogorian reflector are reduced by 30dB and 10dB, respectively, in comparison with those of the offset parabolic antenna.