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박종필(Jong-phil Park),은창수(Changsoo Eun) 한국정보통신학회 2021 한국정보통신학회 종합학술대회 논문집 Vol.25 No.1
음향시스템을 구성하는 스피커의 임피던스는 고정된 값으로 인식되고 있다. 그러나 스피커의 임피던스는 입력신호의 주파수 변화에 따라 계속 변화하고 그 변화량은 스피커의 공진 주파수 대역에서 매우 크다. 스피커의 음압 레벨은 스피커를 구성하는 코일에 흐르는 전류에 따라 결정되는데 스피커를 전압구동 할 경우 변화하는 임피던스에 의해 음압 레벨의 왜곡이 발생한다. 스피커를 전류 구동 할 경우 이러한 문제는 해결되지만 저주파에서 공진의 영향으로 음압 레벨의 왜곡이 발생하는데 이는 음향시스템의 음질 저하를 가져올 수 있다. 본 논문에서는 전류구동 음향시스템의 음질 개선을 위해 DSP(Digital Signal Processing)를 이용하여 음압레벨의 왜곡을 보정하는 공진 보상회로를 제안한다. 본 논문은 스피커의 등가 모델을 이용한 음향시스템의 전류 구동 모의실험을 통해 주파수 변화에 따른 음압 레벨 왜곡을 확인하고 이를 보정하는 회로를 제안하는 것으로 구성하였다. 제안한 회로는 상태변수필터를 이용하여 구성하였고 주파수 및 출력이 조절 가능하여 다양한 음향 시스템에 적용 가능 할 것으로 보인다. The impedance of the speaker is likely to be recognized as a fixed value. However, speaker impedance continues to vary with frequency variation, especially larger in resonant frequency region. The sound pressure level of loudspeakers is determined by the current flowing throughout the coil that consists loudspeakers. If loudspeakers are driven by voltage, sound pressure level of the loudspeaker is distorted by the variation of loudspeaker impedance. Current-drive of loudspeakers can solve this problem, but distortion of sound pressure level occurs in low frequencies due to resonance. The distortion can degrade the sound quality of the sound system. So to solve this problem, In this paper, we propose a resonance compensation circuit using DSP. we simulates audio systems using an equivalent model of loudspeakers to verify distortion of sound pressure level due to impedance variation and propose a circuit to compensate it. The proposed circuit is configured using a state variable filter and it can adjust the center frequency and output, so it will be used various sound systems.
양영철(Yang Young Chul),박종필(Park Jong Phil),한문섭(Han Moon Sub),김주락(Kim Ju Rak),김용기(Kim Yong Ki) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-
For electric traction using a large power converter, harmonic problem in the p-ower quality and regenerating energy in side of efficiency are important. Recently, by advance in power electronics technology, some countries are considering regenerative inverter from the points of view. when the electric tractions are stopped or driven through the falling slope way, it is very useful to supply surplus energy to the power source by regenerating system in the efficient side of energy and it is very economical. these regenerating energy are supported electrical equipment through DC line. In this research, the purposes are suppressing extra DC-line voltage and saving energy generated while electric traction is been driving on the falling slope way or reducing speed for railway using a 1500V DC-voltage. Besides, the accompanied defects of current distortion, low power factor and the voltage unbalance will be solved by developing the algorism of inverter having ability to compensate current harmonic.
Anti-oxidative and Anti-melanogenic Properties of Stevia rebaudiana Flos
Gyeong Seop So(소경섭),Yuna Park(박윤아),Hyun Jung Koo(구현정),Sung Hyeok Kim(김성혁),Chang Woo Ha(하창우),Sang Eun Lee(이상은),Jong Phil Bak(박종필),Seung Namkoong(남궁승),Tae Hyung Kim(김태형),Eun Hwa Sohn(손은화) 한국약용작물학회 2018 한국약용작물학회 학술대회논문집 Vol.2018 No.2
IgE 매개 RBL-2H3 세포 활성화에 대한 정향 에탄올 추출물의 억제 효과
정준희 ( Joon Hee Chung ),김용민 ( Yong Min Kim ),박종필 ( Jong Phil Park ),김태연 ( Tae Yeon Kim ),김이화 ( Ee Hwa Kim ) 경락경혈학회 2014 Korean Journal of Acupuncture Vol.31 No.1
Objectives: In this report, we investigated the effect of ethanol extract of Syzygium aromaticum(L.) Merr. & Perry. (SAE) on the RBL-2H3 cell-mediated allergic response and studied its possible mechanisms of action. Methods: Cytotoxicity on RBL-2H3 cell was evaluated by MTT assay. Anti-allergic activity of SAE was assessed by β-Hexosaminidase and Histamine secretion, β- Hexosaminidase and Histamine secretion were measured by ELISA assay. Evaluate the mechanisms of effect of SAE on the secretion of degranulate mediators, we examined the effect of SAE on the activation of mitogen-activated protein kinases using western blot analysis. Results: SAE had no cytotoxicity on rat basophilic leukemia cell(RBL-2H3). Moreover SAE dose-dependently inhibited RBL-2H3 cell degranulation and histamine release. SAE specifically blocked the IgE-induced p38 mitogen-activated protein kinase activation. Conclusions: Our findings provide evidence that Syzygium aromaticum ethanol extract inhibits mast cell derived allergic reaction, and also demonstrate the involvement of p38 MAPK phosphorylation.