• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.440-449
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• 2008

In this paper, we propose a 16-QAM carrier recovery loop which is suitable for the implementation of Inmarsat M4 system receiver. Because the frequency offset of ${\pm}924\;Hz$ on signal bandwidth 33.6 kHz is recommended in Inmarsat M4 system specification, carrier recovery loop having stable operation in the channel environment with large relative frequency offset is required. the carrier recovery loop which adopts only PLL can't be stable in relatively large frequency offset environment. Therefore, we propose a carrier recovery loop which has stable operation in large relative frequency offset environment for Inmarsat M4 system. The proposed carrier recovery loop employed differential filter-based noncoherent UW detector which is robust to frequency offset, CP-AFC for initial frequency offset acquisition using UW signal, and 16-QAM DD-PLL for phase tracking using data signal to overcome large relative frequency offset and achieve stable carrier recovery performance. Simulation results show that the proposed carrier recovery loop has stable operation and satisfactory performance in large relative frequency offset environment for Inmarsat M4 system.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.61-68
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• 2009

In this paper, we propose a Cluster-based Cooperative Routing using ARQ (CCRA) for supporting both reliability and transmitting efficient service in mobile ad-hoc wireless sensor networks with Rayleigh fading environments. The main contributions and features of this paper are as follows. First, the clustering method which uses the position information of nodes as underlying structure for supporting reliable transmission services is used. Second, the cooperative data transmission method based on the underlying clustering informations is used to improve both reliability and data transmission efficiency. Third, the ARQ-based transmission is used to improve transmission reliability. Fourth, we consider a realistic approach, in the points of view of mobile ad-hoc wireless sensor networks, based on mobile sensor nodes as well as fixed sensor nodes in the sensor fields while the conventional research for sensor networks focus on mainly fixed sensor networks. The performance evaluation of proposed routing protocol implemented via simulation using Optimized Network Engineering Tool (OPNET) and theoretical analysis.

• 전자공학회논문지 IE
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• v.47 no.4
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• pp.18-27
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• 2010

This paper is designed the efficient Data Acquisition System for an vibration of rotatory machines. The Data Acquisition System is consist of the analog logic having signal filer and amplifier, and digital logic with ADC, DSP, FPGA and FIFO memory. The vibration signal of rotatory machines acquired from sensors is controlled by the FPGA device through the analog logic and is saved to FIFO memory being converted analog to digital signal. The digital signal process is performed by the DSP using the vibration data in FIFO memory. The vibration factor of the rotatory machinery analysis and diagnosis is defined the RMS, Peak to Peak, average, GAP, FFT of vibration data and digital filtering by DSP, and is need to follow as being happened the event of vibration and make an application to an warning system. It takes time to process the several analysis step of all vibration data and the event follow, also special event. It should be continuously performed the data acquisition and the process, however during processing the input signal the DSP can not be performed to the acquisited data after then, also it will be lose the data at several channel. Therefore it is that the system uses efficiently the DSP and FPGA devices for reducing the data lose, it design to process a part of the signal data to FPGA from DSP in order to minimize the process time, and a process to parallel process system, as a result of design system it propose to method of faster process and more efficient data acquisition system by using DSP and FPGA than signal DSP system.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.3
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• pp.191-202
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• 2017

KONEX (Korea New Exchange) is the organised stock exchange for small enterprises. It is a channel through which venture start-ups at their early stage can raise funds without a huge burden of debt. We explain the regulations in this market and examine the effects of major changes in the relevant regulations. The first change was replacing the call auction mechanism with the continuous auction mechanism. The change improved the information asymmetry among investors. The second was lowering the minimum deposit requirement for individual investors from 300 million won to 100 million won. As the result of the change, market liquidity increased a lot and the number of investors increased. The last change was introducing the small investment account. Although this raised the participation of individual investors but did not lead to the improvement in market liquidity or information asymmetry. In overall, encouraging more investors to participate in the transactions in KONEX is the fast way to boost the market, while the long-term strategy should focus more on improving the information asymmetry by helping information generating and transferring activities.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.633-643
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• 2015

In this study, we develop a highly efficient conical-air diffuser that generates fine bubble. By inserting a sufficient number of aerotropic microorganisms with dissolved oxygen from an air diffuser and minimizing the air-channel blockages within the air diffuser, we expect to improve the efficiency and durability of the decomposition process for organic waste. To upgrade the conventional air diffuser, we perform experiments and numerical analysis to develop a conical-type that generates fine bubble, and which is free from nozzle blockage. We complement the air-diffuser design by numerically analyzing the internal air-flow pattern within the diffuser. Then, by applying the diffuser to a mockup bioreactor, we experimentally and numerically study the bubble behavior observed in the diffuser and the 2-phase fluid flow in the bioreactor. The results obtained include statistics of the cord length and increased velocity, and we investigate the mechanisms of the fluid-flow characteristics including bubble clouds. Throughout the study, we systemize the design procedures for the design of efficient air diffusers, and we visualize the fluid-flow patterns caused by bubble generation within the mockup bioreactor. These results will provide a meaningful basis for further study as well as the detection of oxygen transfer and fluid-flow characteristics in real-scale bio-reactors using sets of air diffusers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.161-170
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• 2012

There are many factors to consider when attempting to improve the efficiency of fuel cell operation, such as the operation temperature, humidity, stoichiometry, operation pressure, geometric features, etc. In this paper, the effects of the operation pressure were investigated to find the current density and water saturation behavior on a cross section designated by the design geometry. A two-dimensional geometric model was established with a gas channel that can provide $H_2$ to the anode and $O_2$ and water vapor to the cathode gas diffusion layer (GDL). The results from this numerical modeling revealed that higher operation pressures would produce a higher current density than lower ones, and the water saturation behavior was different at operation pressures of 2 atm and 3 atm in the cathode GDL. In particular, the water saturation ratios are higher directly below the collector than in other areas. In addition, this paper presents the dependence of the velocity behavior in the cathode on pressure changes, and the velocity fluctuations through the GDL are higher in the output area than in inlet area. This conclusion will be utilized to design more efficient fuel cell modeling of real fuel cell operation.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.6
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• pp.1085-1091
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• 2002

Chang Chung-ching(張仲景) in the Later Han(Eastern Han) Dynasty of Chinese history wrote the treatise on Diseases Caused by Cold Factors(傷寒論; Shang Han Lun) on the basis of the fundamental theory of Emperor's Classic of Internal Medicine(黃帝內經; ECIM) after collecting medical treatment experiences until the Han Dynasty. It had great significance that Shang Han Lun was the origin of treating six-channels(六經) and there showed the peculiar guidelines on the diagnosis and treatment of oriental medicine to divide diseases into six-channels. The oriental medical doctors who had studied Shang Han Run thought highly of meridians and until now it was generally known that the chapter of heat in the Plain Questions of ECIM(黃帝內經, 素問ㆍ熱論) was the basis of Shang Han Run. The chapter of heat in the Plain Questions of ECIM was the first text in which the basic theory on six-channels according to the types of illness was introduced. In my point of view, the theory of treating six-channels had close relation to the Chapter of Channels in Miraculous Pivot of ECIM(黃帝內經, 靈樞ㆍ經脈篇) as well as the chapter of heat in the Plain Questions of ECIM. Therefore I took a look at the origin of treating six-channels in Shang Han Lun and illuminated again the meaning to compare the parts of in Shang Han Lun with the Chapter of Channels in Miraculous Pivot of ECIM. Conclusion: The, symptoms divided into six-channels in the chapter of channels in ECIM gave the fundamental basis of diagnosis and treatment basesd on overall analysis of signs and symptoms(辨證論治) an illness in the Zangfu(臟腑) in respect of meridians. Viewed in the light of diagnosis and treatment basesd on overall analysis of signs and symptoms(辨證論治), the symptoms of YangMing-channel(陽明經) in the Chapter of Channels in Miraculous Pivot of ECIM were, for the most part, accord with those of YangMing-disease in Shang Han Lun. Furthermore, the symptoms in Shang Han Lun were explained definitely and in detail. Therefore the theory of Shang Han Lun has been developed on the basis of ECIM with the changes of the times. YangMing-disease in Shang Han Lun implied medical cases in stomach meridian(胃經) and large intestine meridian(大腸經). Therefore Shang Han Lun was the foundation of treatment basesd on overall analysis of signs and symptoms(辨證論治) in respect of meridian as well as the text in which the steps of infectious diseases(外感病) of human bodies were explained.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.39-48
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• 2006

In this paper, we analyze the spectral efficiency of multicarrier-code division multiple access (MC-CDMA) scheme. First, we derive a generalized formula for the spectral efficiency according to the number of subcarriers involved in, code division multiplexing and the number of codes used (i.e., loading factor), under a given set of channel coefficients. Also, we derive a generalized formula for spectral efficiency of various reduced-complexity systems that divide the full sets of subcarriers into several groups of subcarriers for code division multiplexing. Then, through these derivations, we establish an inter-relationship between the frequency selectivity and diversity order according to the number of multipaths. From the results, we choose the smallest code length while maximizing the diversity effect, provide an optimum subcarrier allocation strategy, and finally suggest a system structure for capacity-maximizing under the smallest code length. Through numerical analyses under simulated environments, we analyze the properties of spectral efficiency of various systems with reduced complexity and choose a major contributing factors to system design and a better system design methodology. Finally, we compare the spectral efficiency of the MC-CDMA scheme and orthogonal frequency division multiplexing (OFDM) scheme to make a relationship between both schemes.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.1-11
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• 1998

One of the desired features for the realizations of high quality Information and Telecommunication services in future is "the Sensation of Reality". This will be achieved only with the visual communication based on the 3- dimensional (3-D) moving images. The main difficulties in realizing 3-D moving image communication are that there is no developed data transmission technology for the hugh amount of data involved in 3-D images and no established technologies for 3-D image recording and displaying in real time. The currently known stereoscopic imaging technologies can only present depth, no moving parallax, so they are not effective in creating the sensation of the reality without taking eye glasses. The more effective 3-D imaging technologies for achieving the sensation of reality are those based on the multiview 3-D images which provides the object image changes as the eyes move to different directions. In this paper, a multiview 3-D imaging system composed of 8 CCD cameras in a case, a RGB(Red, Green, Blue) beam projector, and a holographic screen is introduced. In this system, the 8 view images are recorded by the 8 CCD cameras and the images are transmitted to the beam projector in sequence by a signal converter. This signal converter converts each camera signal into 3 different color signals, i.e., RGB signals, combines each color signal from the 8 cameras into a serial signal train by multiplexing and drives the corresponding color channel of the beam projector to 480Hz frame rate. The beam projector projects images to the holographic screen through a LCD shutter. The LCD shutter consists of 8 LCD strips. The image of each LCD strip, created by the holographic screen, forms as sub-viewing zone. Since the ON period and sequence of the LCD strips are synchronized with those of the camera image sampling adn the beam projector image projection, the multiview 3-D moving images are viewed at the viewing zone.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.185-192
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• 2012

Call Center requires an ability of agents a lot more than face-to-face contact due to being achieved communication by non face-to face channel for contact with customers. In order to improve the ability of agents, Call Center carries out various educational training according to their work experience and function and with the accomplishment of educational training, Call Center is going to fulfill to develop its quality of counseling and productivity. On the other hand, due to investment of a lot of time and budget to educational training, it is needed to grasp and manage about its effectiveness that how helpful the training is for performance of work-site operations through evaluation of educational training. Having Seen researches about evaluation of educational training until these days, most researches have mainstream to measure satisfaction and a level of learning or degree that how the learning transfers to actions. It is found that a research about an entire evaluation model should be required. This study aims to investigate effectiveness of Call Center educational training from the level of recognition by reflecting Kirkpatrick's the four levels of learning evaluation. By the four levels, reaction, learning, behavior and results, the study found out a connection with standards of evaluation about each levels. In addition, by using structural equation modeling, it was examined goodness of fit about the entire model. Furthermore, by an alternative model, considering a direct relation between a factor of reaction and behavior, it was compared and examined goodness of fit of overall model of the study model and the alternative one.