• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.367-374
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• 2010

In this paper, the frequencies sharing possibility between TA(TalkAround) Radios and RFID system in 900MHz frequency band have been studied. The modulation technic for FHSS(Frequency Hopping Spread Spectrum) of TA is digital FSK and RFID system adapts digital ASK modulation technic. The communication mode of the tested RFID system for frequencies sharing possibility was FHSS. The field test was performed by five scenarios. The RFID field testing system for the frequencies sharing possibility was composed of four tags and two main devices made in USA. Four TA and Egilant spectrum analyzer was used for testing. The frequencies sharing possibility by differentiated modulation was theoretically analyzed. As result of simulation, it was proved that the frequencies sharing between each other modulation system is possible. And also as result of field testing it was confirmed that the signal of TA Radios have no effect on the signal of RFID system.

• Journal of IKEEE
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• v.26 no.4
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• pp.693-704
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• 2022

5G service uses mid-band (n78) than existing mobile communication frequencies, so it is necessary to improve 5G coverage by utilizing low-band frequencies below 2 GHz. To this end, the application of Dynamic Spectrum Sharing technology of LTE and 5G-NR system using most of the low-band frequencies is required. In this paper, signaling overhead factors for DSS application and RF issues for terminal implementation are derived, and signaling overhead ratios from the respective perspectives of 5G-NR and LTE for the 1.8GHz band (50MHz width) that can utilize wide-bandwidth among low-band frequencies are estimated. Also handset RF issues were analyzed. Based on the analysis results, if DSS technology using low band is applied, it is expected that excellent 5G service quality can be provided due to 5G coverage improvement when LTE traffic quickly migrates to 5G-NR.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1575-1581
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• 2019

Due to the mismatched line impedance among distributed generation units (DGs) and uncontrolled harmonic current, the droop controller has a number of problems such as inaccurate reactive power sharing and voltage distortion at the point of common coupling (PCC). To solve these problems, this paper proposes a resistive-capacitive virtual impedance control method. The proposed control method modifies the DG output impedance at the fundamental and harmonic frequencies to compensate the mismatched line impedance among DGs and to regulate the harmonic current. Finally, reactive power sharing is accurately achieved, and the PCC voltage distortion is compensated. In addition, adaptively controlling the virtual impedance guarantees compensation performance in spite of load changes. The effectiveness of the proposed control method was verified by experimental results.

• Korean Journal of Community Nutrition
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• v.8 no.3
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• pp.280-287
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• 2003

To investigate effects of the shared living on nutrient intakes,250 college male students who were living alone (104 men) or sharing accommodation with friends (134 men) were participated. Their average age was 22.6 years, their average height was 171.8 cm, their average weight was 65.6 kg and their average Body Mass Index (BMI) was 22.2. The caloric intakes of the men living alone or sharing accommodation were 55.9% and 72.5% of the Korean Recommended Dietary Allowance (RDA), respectively. The decreased caloric level of the group living alone seemed to be due to their decreased protein and fat consumption as compared to that of the group sharing accommodation. The group living alone consumed increased amounts of fiber for breakfast and half the carbohydrates, but more fat (p < 0.05) in snacks than the group sharing accommodation. The daily carbohydrate : protein : fat (C : P : F) ratio averaged 58.6 14.1 27.3, which is a lower carbohydrate and a higher fat ratio than the Korean recommended ratio. However, the group living alone was closer to the Korean recommended ratio than the group sharing accommodation. The food intake habits were evaluated as being poorer in the group living alone as compared to the group sharing accommodation, less frequent consumption of fried / pan-fried dishes, and fruits / juices, but more frequent consumption of instant / processed foods. In comparing the eating patterns of the two groups, the group living alone showed better eating habits, such as more“breakfast eating”and less“snacking in the morning, afternoon or late at night”whereas the group sharing accommodation showed better eating habits such as less“picky eaters”and less “eating out”. In the group living alone, their lower caloric intake was assumably due to their fewer side dishes, however they showed higher eating frequencies of instant i processed foods. Since the lifestyle of living alone seems to grow gradually among young men, we strongly recommend dietary education for them.

• ETRI Journal
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• v.44 no.4
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• pp.531-542
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• 2022

With the increasing demand for unlicensed spectrum, several regulators have been opening up the 6-GHz band for unlicensed use while ensuring compliance with the technical requirement to avoid harmful interference in the existing primary services (PSs). In this paper, we present two methodologies, a channel-based method and a frequency-based method, which are applicable to a frequency coordination system that calculates the permissible transmit power in the channels or frequencies available to a secondary service (SS). In addition, we have demonstrated that the available transmit power of an SS can be maximized by adjusting the power allocation of the assigned resource units under the condition that the channel of the SS is partially overlapped with that of the PS. Based on the analysis results, it is suggested that it would be better to utilize the two methods selectively according to the operating channel conditions of the PS and the SS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.7
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• pp.599-611
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• 2016

This paper proposes a cognitive engine platform that enables dynamic spectrum access(DSA) based on a spectrum sharing system for the military tactical network environment. The current military tactical wireless communication system is increasing need to secure a supplementary wireless spectrum to ensure that multiple wireless networks for different weapon systems co-exist, so that tactical wireless communication between the same or different systems can be operated effectively. This paper examined policy development and research activities engaged by the U.S. and European countries on wireless spectrum sharing to secure more spectrum. It also introduces the current status of cognitive engine development, which is the core technology of tactical wireless communication for DSA. In addition, based on the investigation performed into the latest trends, we propose a platform structure for a cognitive engine based on a spectrum sharing method where more frequencies can be added for tactical radio communication, so that DSA can be realized, and wireless networks of different weapon systems can co-exist.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.8
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• pp.1894-1912
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• 2012

This paper proposes a system called Wireless Link based on Global Communication Channel (WLGCC) to enhance the spectrum sharing between digital broadcasting (DB) services and the cognitive radio (CR) system in the licensed band of 470-790 MHz. The WLGCC aims to enhance the spectrum sensing and geolocation database (GLD) spectrum sharing methods in the CR system. Spectrum sensing can be enhanced by receiving the status of the used frequencies from the WLGCC, thereby eliminating the need for a low detection threshold (i.e., avoiding the hidden node problem). In addition, the GLD can be enhanced by providing a reliable communication link between the database and the CR device in the form of an unused TV white space that is reserved as the proposed Global Communication Channel (GCC). This paper analyzes the coexistence of the new WLGCC system and the DB service in terms of avoiding additional interference. Specifically, we mathematically determine the WLGCC parameters, such as the in-band and out-of-band power levels, and operation coverage, and verify them using Monte Carlo simulation. The results show that WLGCC does not degrade the existing DB service and reliably transmits information of the vacant (or used) frequency bands to the CR.

• Journal of Power Electronics
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• v.17 no.1
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• pp.200-211
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• 2017

Conventional boost-full-bridge and boost-hybrid-bridge two-stage inverters are widely applied in order to adapt to the wide dc input voltage range of photovoltaic arrays. However, the efficiency of the conventional topology is not fully optimized because additional switching losses are generated in the voltage conversion so that the input voltage rises and then falls. Moreover, the electrolytic capacitors in a dc-link lead to a larger volume combined with increases in both weight and cost. This paper proposes a higher efficiency inverter with time-sharing synchronous modulation. The energy transmission paths, wheeling branches and switching losses for the high-frequency switches are optimized so that the overall efficiency is greatly improved. In this paper, a contrastive analysis of the component losses for the conventional and proposed inverter topologies is carried out in MATLAB. Finally, the high-efficiency under different switching frequencies and different input voltages is verified by a 3 kW prototype.

• Journal of Families and Better Life
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• v.19 no.1
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• pp.1-16
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• 2001

This study examined the level of experienced problem and related variables of farming women as a part of study on problem diagnosis and status enhancement of rural women. The subjects were 980 married farming women living in rural area. Data were analyzed by frequencies, percentages, mean, standard deviation, factor analysis, t-test, ANOVA, Duncan-test, and multiple regression. The major findings were as follows : 1) Rural women experienced five categorized problems(farming work & health problem, institution & facilities problem, personality differences & communication problem with husband, child & in-law relatives problem, and husbands violence & sexual problem. 2) The significant variables that influenced on experienced problems were conflict coping behaviors, husbands housework participation, farming work time, age, the level of health, and income etc. Additionally socio-demographic factors, their vocational consciousness, housework sharing, and couples difference of sex-role attitude as related variables of the level of experienced problem of farming women were exmained and discussed the implication.

• Journal of the Korean housing association
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• v.14 no.3
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• pp.67-76
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• 2003

This study was to investigate the needs for the community in the elderly institution and the related factors. The raw data, collected in 2000, from the Study for the Silver Industry in Ulsan were used for the analysis. The sample consisted of 292 elderly aged 65 and over living in Ulsan, and the purpose was accomplished using frequencies, percentages, and chi-squared test with cross-tabulations. The results indicated that the elderly tends to have negative responses to the discriminations by health conditions and sharing the public spaces with neighbors. However it was more likely that the elderly wants to have separate public spaces and facilities by gender. They prefer private residential units rather than public spaces for the meals, baths, and receptions. It was also found that gender, with or without spouse, education level, and economic condition of the elderly have significant effects on the needs for the community in the elderly housing.