• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.58-68
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• 2006

This work proposes a 10b 250MS/s $1.8mm^2$ 85mW 0.13um CMOS A/D Converter (ADC) for high-performance integrated systems such as next-generation DTV and WLAN simultaneously requiring low voltage, low power, and small area at high speed. The proposed 3-stage pipeline ADC minimizes chip area and power dissipation at the target resolution and sampling rate. The input SHA maintains 10b resolution with either gate-bootstrapped sampling switches or nominal CMOS sampling switches. The SHA and two MDACs based on a conventional 2-stage amplifier employ optimized trans-conductance ratios of two amplifier stages to achieve the required DC gain, bandwidth, and phase margin. The proposed signal insensitive 3-D fully symmetric capacitor layout reduces the device mismatch of two MDACs. The low-noise on-chip current and voltage references can choose optional off-chip voltage references. The prototype ADC is implemented in a 0.13um 1P8M CMOS process. The measured DNL and INL are within 0.24LSB and 0.35LSB while the ADC shows a maximum SNDR of 54dB and 48dB and a maximum SFDR of 67dB and 61dB at 200MS/s and 250MS/s, respectively. The ADC with an active die area of $1.8mm^2$ consumes 85mW at 250MS/s at a 1.2V supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.37-47
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• 2006

This work proposes a 10b 25MS/s $0.8mm^2$ 4.8mW 0.13um CMOS A/D Converter (ADC) for high-performance wireless communication systems such as DVB, DAB and DMB simultaneously requiring low voltage, low power, and small area. A two-stage pipeline architecture minimizes the overall chip area and power dissipation of the proposed ADC at the target resolution and sampling rate while switched-bias power reduction techniques reduce the power consumption of analog amplifiers. A low-power sample-and-hold amplifier maintains 10b resolution for input frequencies up to 60MHz based on a single-stage amplifier and nominal CMOS sampling switches using low threshold-voltage transistors. A signal insensitive 3-D fully symmetric layout reduces the capacitor and device mismatch of a multiplying D/A converter while low-noise reference currents and voltages are implemented on chip with optional off-chip voltage references. The employed down-sampling clock signal selects the sampling rate of 25MS/s or 10MS/s with a reduced power depending on applications. The prototype ADC in a 0.13um 1P8M CMOS technology demonstrates the measured DNL and INL within 0.42LSB and 0.91LSB and shows a maximum SNDR and SFDR of 56dB and 65dB at all sampling frequencies up to 2SMS/s, respectively. The ADC with an active die area if $0.8mm^2$ consumes 4.8mW at 25MS/s and 2.4mW at 10MS/s at a 1.2V supply.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.813-821
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• 2000

The engineering of satellite communication systems at frequencies above 10GHz requires a method for estimating rain-caused outage probabilities on the earth-satellite path. A procedure for predicting a rain attenuation distribution from a point rainfall rate distribution is, therefore, needed. In order to predict rain attenuation on the satellite link, several prediction models such as ITU-R, Global, SAM, DAH model, have been developed and used at a particular propagation condition, they may not be appropriate to a propagation condition in Korean territory. In this paper, a new rain attenuation prediction method appropriate to a propagation condition in Korea is introduced. Based on the results from ETRI measurements, a new method has been derived for an empirical approach with an identification on the horizontal correction factor as in current ITU-R method, and the vertical correction factor has been suggested with decreasing power law as a function of rainfall rate. This proposed model uses the entire rainfall rate distribution as input to the model, while the ITU-R and DAH model approaches only use a single 0.01% annual rainfall rate and assume that the attenuation at other probability levels can be determined from that single point distribution. This new model was compared with several world-wide prediction models. Based on the analysis, we can easily know the importance of the model choice to predict rain attenuation for a particular location in the radio communication system design.

• Journal of Intelligence and Information Systems
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• v.16 no.4
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• pp.147-157
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• 2010

With the immergence of the iPhone, the interest in Smartphones is getting higher as services can be provided directly between service providers and consumers without the network operators. As the number of international tourists increase, individual tourists are also increasing. According to the WTO's (World Tourism Organization) prediction, the number of international tourists will be 1.56 billion in 2020,and the average growth rate will be 4.1% a year. Chinese tourists, in particular, are increasing rapidly and about 100 million will travel the world in 2020. In 2009, about 7.8 million foreign tourists visited Korea and the Ministry of Culture, Sports and Tourism is trying to attract 12 million foreign tourists in 2014. A research institute carried out a survey targeting foreign tourists and the survey results showed that they felt uncomfortable with communication (about 55.8%) and directional signs (about 21.4%) when they traveled in Korea. To solve this inconvenience for foreign tourists, multilingual servicesfor traffic signs, tour information, shopping information and so forth should be enhanced. The appearance of the Smartphone comes just in time to provide a new service to address these inconveniences. Smartphones are especially useful because every Smartphone has GPS (Global Positioning System) that can provide users' location to the system, making it possible to provide location-based services. For improvement of tourists' convenience, Seoul Metropolitan Government hasinitiated the u-tour service using Kiosks and Smartphones, and several Province Governments have started the u-tourpia project using RFID (Radio Frequency IDentification) and an exclusive device. Even though the u-tour or u-tourpia service used the Smartphone and RFID, the tourist should know the location of the Kiosks and have previous information. So, this service did not give the solution yet. In this paper, I developed a new convenient service which can provide location based information for the individual tourists using GPS, WiFi, and 3G. The service was tested at Insa-dong in Seoul, and the service can provide tour information around the tourist using a push service without user selection. This self-tour service is designed for providing a travel guide service for foreign travelers from the airport to their destination and information about tourist attractions. The system reduced information traffic by constraining receipt of information to tourist themes and locations within a 20m or 40m radius of the device. In this case, service providers can provide targeted, just-in-time services to special customers by sending desired information. For evaluating the implemented system, the contents of 40 gift shops and traditional restaurants in Insa-dong are stored in the CMS (Content Management System). The service program shows a map displaying the current location of the tourist and displays a circle which shows the range to get the tourist information. If there is information for the tourist within range, the information viewer is activated. If there is only a single resultto display, the information viewer pops up directly, and if there are several results, the viewer shows a list of the contents and the user can choose content manually. As aresult, the proposed system can provide location-based tourist information to tourists without previous knowledge of the area. Currently, the GPS has a margin of error (about 10~20m) and this leads the location and information errors. However, because our Government is planning to provide DGPS (Differential GPS) information by DMB (Digital Multimedia Broadcasting) this error will be reduced to within 1m.

• Journal of Intelligence and Information Systems
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• v.19 no.3
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• pp.73-91
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• 2013

Advertising market has been facing new challenges due to dramatic change in advertising channels and the advent of innovative media such as mobile devices. Recent research related to mobile devices is mainly focused on the fact that mobile devices could identify users'physical location in real-time, and this sheds light on how location-based technology is utilized to achieve competitive advantage in advertising market. With the introduction of smartphone, the functionality of smartphone has become much more diverse and context awareness is one of the areas that require further study. This work analyses the influence of context awareness value resulted from the transformation of advertising channel in mobile communication market, and our research result reflects recent trend in advertising market environment which is not considered in previous studies. Many constructs has intensively been studied in the context of advertising channel in traditional marketing environment, and entertainment, irritation and information are considered to be the most widely accepted variables that has positive relationship with advertising value. Also, in smartphone advertisement, four main dimensions of context awareness value are recognized: identification, activity, timing and location. In this study, we assume that these four constructs has positive relationship with context awareness value. Finally, we propose that advertising value and context awareness value positively influence smartphone advertising attitude. Partial Least Squares (PLS) structural model is used in our theoretical research model to test proposed hypotheses. A well designed survey is conducted for college students in Korea, and reliability, convergent validity and discriminant validity of constructs and measurement indicators are carefully evaluated and the results show that reliability and validity are confirmed according to predefined statistical criteria. Goodness-of-fit of our research model is also supported. In summary, the results collectively suggest good measurement properties for the proposed research model. The research outcomes are as follows. First, information has positive impact on advertising value while entertainment and irritation have no significant impact. Information, entertainment and irritation together account for 38.8% of advertising value. Second, along with the change in advertising market due to the advent of smartphone, activity, timing and location have positive impact on context awareness value while identification has no significant impact. In addition, identification, activity, location and time together account for 46.3% of context awareness value. Third, advertising value and context awareness value both positively influence smartphone advertising attitude, and these two constructs explain 31.7% of the variability of smartphone advertising attitude. The theoretical implication of our research is as follows. First, the influence of entertainment and irritation is reduced which are known to be crucial factors according to previous studies related to advertising value, while the influence of information is increased. It indicates that smartphone users are not likely interested in entertaining effect of smartphone advertisement, and are insensitive to the inconvenience due to smartphone advertisement. Second, in today' ubiquitous computing environment, it is effective to provide differentiated advertising service by utilizing smartphone users'context awareness values such as identification, activity, timing and location in order to achieve competitive business advantage in advertising market. For practical implications, enterprises should provide valuable and useful information that might attract smartphone users by adopting differentiation strategy as smartphone users are sensitive to the information provided via smartphone. Also enterprises not only provide useful information but also recognize and utilize smarphone users' unique characteristics and behaviors by increasing context awareness values. In summary, our result implies that smartphone advertisement should be optimized by considering the needed information of smartphone users in order to maximize advertisement effect.

• The Korean Journal of Emergency Medical Services
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• v.13 no.3
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• pp.41-58
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• 2009

Objective : The purpose of this study is to identify actual operations and issues of wireless paging system operation for the aged living alone as the end users of wireless paging system primarily in Gwangyang city, and thereby to explore possible advanced and integrated ways to promote social safety network for the aged. Methods : The survey tool used in this study was a structured questionnaire form consisting of question items. The researcher hereof conducted this survey by means of direct visit and interview during two seasons, i.e. from February to August, 2008 and from December 2008 to March 2009, respectively. Results : 1) For general demographic characteristics, it was found that 90.9% of all respondents were women and 61.2% of all respondents were at age 75 to 84. for health conditions, it was found that more than 90% of all respondents often took medicines due to their unhealthy body, and most of respondents suffered from musculoskeletal diseases 79.3% and circulatory diseases 61.6%. for walking capacity, it was found that 45.5% of all respondents used walking aids, and disable respondents (11.5% of all respondents) were represented primarily by those with physical disability (52.6% of disable respondents). for actual use of medical institutions, it was found 47.3% of all respondents relied on local clinics, since they preferred neighborhood hospitals or clinics they can trust for medical care. for social activities and supports, it was found that 43.6% respondents had 'needs for assistance at times' and 33.9% respondents have 'no need for assistance'. And it was found that the major difficulties in living alone at old age were represented primarily by health problems 37.8% and economic difficulties 33.5%. 2) For characteristics related to wireless paging system, it was found that 90.3% respondents used wireless paging system recommended by firemen, and 28.5% respondents used this system. and it was found that 59.6% respondents used this system once, and 85.2% respondents used it because of acute or chronic diseases. more than 90% respondents thought that they knew about wireless paging system and considered themselves safe, but 83.6% respondents didn't attach a remote control on their upper clothes, and even 49.1% respondents turned off the power of wireless paging system due to their concern about electricity bill and noise. 3) It was found that 83.6% respondents felt it necessary to use wireless paging system, and wireless paging users felt more satisfied with using the system than non-users, and 50.7% showed high satisfaction at certain psychological benefits like 'confidence in coping with critical situations' and 'a sense of relief'. In addition, it was found that some respondents who answered that 'they didn't turn off the paging system as they knew how it works' and those who answered that they knew 'how to use it' showed relatively high satisfaction. And some respondents who kept it well and felt it necessary also showed high satisfaction. 4) It was found that the level of satisfaction our respondents felt with using wireless paging system varied significantly availability($x^{2}$ = 12.759, p = .002), psychological advantages($x^{2}$ = 12.174, p = .002), knowledge about how to use system($x^{2}$ = 7.021, p = .016), power on/off($x^{2}$ = 13.221, p = .001), level of knowledge about system($x^{2}$ = 21.002, p = .000), maintenance($x^{2}$ = 9.871, p = .007) and level of necessity($x^{2}$ = 34.939, p = .000) on the statistical basis.

• 한국체육학회지인문사회과학편
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• v.57 no.3
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• pp.345-356
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• 2018

Objective: The purpose of this study was to investigate the local stability of the lower extremity joints and muscle activation patterns of the lower extremity during walking between falling and non-falling group in the elderly women. Method: Forty women, heel strikers, were recruited for this study. Twenty subjects (age:72.55±5.42yrs; height:154.40±4.26cm; mass:57.40±6.21kg; preference walking speed:0.52±0.17m/s; fall frequency=1.70±1.26 times) had a history falls(fall group) within two years and Twenty subjects (71.90±2..90yrs; height:155.28±4.73cm; mass:56.70±5.241kg; preference walking speed: 0.56±0.13m/s) had no history falls(non-fall group). While they were walking on a instrumented treadmill at their preference speed for a long while, kinematic and EMG signals were obtained using 3-D motion capture and wireless EMG electrodes, respectively. Local stability of the ankle and knee joint were calculated using Lyapunov Exponent (LyE) and muscles activation and their co-contraction index were also quantified. Hypotheses were tested using one-way ANOVA and Mann-Whitey. Spearman rank was also used to determine the correlation coefficients between variables. Level of significance was set at p<.05. Results: Local stability in the knee joint adduction-abduction was significantly greater in fall group than non-fall group(p<.05). Activation of anterior tibials that acts on the foot segment dorsal flexion was greater in non-fall group than fall group(p<.05). CI between gastrocnemius and anterior tibials was found to be significantly different between two groups(p<.05). In addition, there was significant correlation between CI of the leg and LyE of the ankle joint flexion-extention in the fall group(p<.05). Conclusion: In conclusion, muscles that act on the knee joint abduction-adduction as well as gastrocnemius and anterior tibials that act on the ankle joint flexion-extention need to be strengthened to prevent from potential fall during walking.