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Yoon, Jaehyuk,Park, Changkun Institute of Korean Electrical and Electronics Eng 2019 전기전자학회논문지 Vol.23 No.2
In this paper, a watt-level 2.4-GHz RFCMOS linear power amplifier (PA) with pre-distortion method using variable capacitance with respect to input power is demonstrated. The proposed structure is composed of a power detector and a MOS capacitor to improve the linearity of the PA. The pre-distortion based linearizer is embedded in the two-stage PA to compensate for the gain compression in the amplifier stages, it also improves the output P1dB by approximately 1 dB. The simulation results demonstrate a 1-dB gain compression power of 30.81 dBm at 2.4-GHz, and PAE is 29.24 % at the output P1dB point.
Yoon, Jaehyuk,Kim, Mijin,Song, Soonho,Chun, Kwang Min Elsevier 2011 Journal of aerosol science Vol.42 No.6
<P><B>Abstract</B></P><P>Recently, the diesel engine particulate matter (PM) emission standard was changed from being based on mass to being based on both number and mass. However, it is difficult to determine the mass- and number-weighted distributions simultaneously because of the complex shapes of PM.</P><P>We studied a new method to determine the mass-weighted distribution of PM using the primary particle density, and compared it with two conventional PM measurement methods using effective density and gravimetric filtration. In the method developed, the primary particle size was measured using transmission electron microscopy (TEM)-calibrated laser-induced incandescence (LII) to detect changes in the primary particle size in real-time. The number-weighted distribution of aggregates was measured with a scanning mobility particle sizer (SMPS). The mass–mobility exponent and the effective density were determined with an impactor and the SMPS. The differences in the mass concentrations for each technique were between 3.1% and 29.9%.</P> <P><B>Highlights</B></P><P>► Measurement of number- and mass-weighted distribution of diesel PM is conducted. ► Primary particle density is used for mass calculation. ► Result is compared with conventional mass measurement techniques. ► The difference of mass concentration is 3.1–29.9%.</P>
A CMOS LNA Using a Harmonic Rejection Technique to Enhance Its Linearity
Jaehyuk Yoon,Changkun Park IEEE 2014 IEEE microwave and wireless components letters Vol.24 No.9
<P>In this study, we design a differential low-noise amplifier (LNA) using a 0.18- μm RF CMOS process. To improve its linearity, we propose a harmonic rejection technique using RC feedback at the gain stage. The third harmonic component of the drain node of the common-gate transistor is fed back to the source node of the common-gate transistor to restrict the generation of the third harmonic component at the output of the LNA. To verify the feasibility of the proposed technique for a linear amplifier, we designed a typical LNA and the proposed LNA in an identical process and with the same design parameters apart from the feedback loop of the proposed LNA. The measured improvement of the input-referred P1 dB of the proposed LNA is approximately 3 dB compared to that of the typical LNA. From these measured results, we successfully prove the feasibility of the proposed linearization technique.</P>
Input Balun Embedded Low-Noise Amplifier With a Differential Structure
Jaehyuk Yoon,Changkun Park IEEE 2014 IEEE microwave and wireless components letters Vol.24 No.6
<P>In this study, we designed a 5 GHz low-noise amplifier (LNA) with a differential structure using 0.18 μm RFCMOS technology. An input balun is embedded into the LNA to enhance the gain, minimize the noise figure (NF), and miniaturize the overall chip size. The NF is minimized because the loss induced by the passive balun is removed. The first stage of the designed LNA performs the activities of the input balun and serves as the gain stage. To verify the feasibility of the proposed input-balun-embedded amplifier, we designed a typical LNA and the proposed LNA. We obtained a 29.4 dB gain with a NF of 1.85 dB. The measured dc power consumption is approximately 27 mW. The chip size is 1.0×0.74 mm<SUP>2</SUP>. From the measured results of the typical and proposed LNAs, we successfully prove the feasibility of the proposed method to minimize the NF and enhance the gain.</P>
Jaehyuk Yoon,Changkun Park 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.2
In this paper, a watt-level 2.4-GHz RFCMOS linear power amplifier (PA) with pre-distortion method using variable capacitance with respect to input power is demonstrated. The proposed structure is composed of a power detector and a MOS capacitor to improve the linearity of the PA. The pre-distortion based linearizer is embedded in the two-stage PA to compensate for the gain compression in the amplifier stages, it also improves the output P1dB by approximately 1 dB. The simulation results demonstrate a 1-dB gain compression power of 30.81 dBm at 2.4-GHz, and PAE is 29.24 % at the output P1dB point.
Jaehyuk Yang,Kyu-Hwan Moon,Yoon Kyu Lim 한국임상수의학회 2016 한국임상수의학회지 Vol.33 No.6
The object of this study was to evaluate the possibility and incidence of innate pacer in Jeju raceresource. This peculiar gait occurs naturally in some foreign breeds. To author’s knowledge, this is the first report of innatepacers on the Korean native horse. In order to determine the incidence of pacer in Jeju Ponies and Jeju Pony crossbreds,gait analysis and pedigree check were performed at the Let’s Run Park Jeju (total 547 ponies and pony crossbredracers) in 2013. Results of this study showed that 16 (8.1%) of the 198 examined Jeju Ponies. However, 349 JejuPony crossbreds had no innate pacers. Of the 16 Jeju Pony pacers, 11 males (68.8%) and 5 females (31.2%) areincluded in the present study. In conclusion, only the Jeju Pony was innate pacers like other foreign breeds. The authorssuspect that the causes of the difference of the breeds were origin of the pony and genetic differences.
JaeHyuk Lee,Maria Celeste Flores Gimenez,BumChul Yoon 대한스포츠물리치료학회 2017 정형스포츠물리치료학회지 Vol.13 No.1
Prolonged sitting is a high-risk factor for chronic neck pain. McKenzie exercises are commonly used in clinics. Mobile app-based care is increasingly popular, and providesaccess to health information. This study examined the effect of mobile app-based McKenzie exercise on pain intensity, functional disability, exercise adherence, fear avoidance, and quality of life. Twenty graduate students participated in the study to completion. Neck exercise was performed as directed by the mobile app in the workplace environment for at least 10 min/day, 3 days/week for 8 weeks. The Visual Analog Scale (VAS) score for pain intensity, the Neck Disability Index (NDI) for functional disability, the level of exercise adherence, the Fear-Avoidance Belief Questionnaire (FABQ), and the 36-Item Short-Form Health Survey (SF-36) for the quality of life were used to evaluate outcomes. After an 8-week intervention, the VAS (p < .001) and NDI(p < .001) scores were significantly improved with app-based neck exercise. The work-related subscale (p = 0.023) in the FABQ and physical component summary (p < .001) of the SF-36 showed significant improvement in psychological and physical health. The exercise adherence rate was 87.5 %. In conclusion, this study showed that app-based neck exercise can reduce pain intensity and functional disability.
Heat transfer characteristics of redan structure in large-scale test facility STELLA-2
Yoon, Jung,Lee, Jewhan,Kim, Hyungmo,Lee, Yong-Bum,Eoh, Jaehyuk Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.4
The construction of STELLA-2 facility is on-going to demonstrate the safety system of PGSFR and to provide comprehensive understanding of transient behavior under DBEs. Considering that most events are single-phase natural circulation flow with slow transient, STELLA-2 was designed with reduced-height of 1/5 length scale. The ratio of volume to surface area in the vessel can relatively increase resulting in excessive heat transfer. Therefore, a steady-state thermal-hydraulic analysis was performed and the effect of design change to reduce the heat transfer through redan was investigated. The heat transfer through single wall redan in STELLA-2 was 3% of the core power, comparable to 1% of the core power in PGSFR. By applying the insulated redan, about 70% of decrease effect was observed. The effect on transient behavior was also evaluated. The conclusion of this study was directly applied to the STELLA-2 design and the modified version is under construction.