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주머니 모형을 이용한 고밀도 핵물질 내 케이 중간자에 관한 연구
현창호,유충열 대구대학교 2008 敎育硏究 Vol.4 No.1
본 연구에서는 케이 중간자의 반입자를 쿼크와 반쿼크의 결합체인 MIT 주머니로 취급하여 고밀도 핵물질 내에서 입자의 성질을 연구하였다. 우선 쿼크-중간자 결합 모형을 보완한 변형 쿼크-중간자 결합 모형을 바탕으로 케이 중간자를 주머니로 다룰 때 나타나는 케이 중간자의 질량 등을 주머니를 기술하는 변수들로 구하였다. 모형의 변수들 중에서 케이 중간자와 핵물질과의 상호작용을 나타내는 퍼텐셜 에너지의 결합상수는 그 값이 아직 결정되지 않은 상태이기 때문에 미지의 변수로 취급하였다. 이 결합상수의 값이 바뀜에 따라 케이 중간자의 질량 등이 자유 상태에 있을 때의 질량에 비해 어떻게 변화하는지 등을 고찰하였다. 수치계산의 결과는 i) 케이 중간자를 쿼크의 결합체인 주머니로 다룰 때의 성질 변화가 점입자로 다룰 때의 변화와 다르고 ii) 케이 중간자와 핵물질 간의 상호작용 퍼텐셜 에너지의 결합상수 값에 따라 변화가 상당한 차이를 보였으며 iii) 기묘도를 갖는 쿼크의 상호작용도 무시할 수 없을 정도의 기여도가 있음을 보였다. 케이 중간자가 고밀도 핵물질의 상태방정식에 미치는 영향을 알아보기 위하여 케이 중간자 응축이 중성자별 내부에서 발생할 때 중성자별의 크기와 질량을 계산하였다. 결과로서 케이 중간자 응축이 중성자 별의 크기, 질량 등에 미치는 영향은 가시적이기는 하나 하이퍼 중입자의 역할에 비해서는 부차적임을 알게 되었다.
Kaon Condensation in the Neutron Star with a Quark-Meson Coupling Model
현창호 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
We investigate the kaon condensation in dense matter with a quark model. The model describes the baryons and kaons as MIT bags, and their interactions by the exchange of mesons. Coupling constants at the kaon-meson vertices are determined by the depth of a kaon-nucleus optical potential, which is treated as a free parameter in our work. Equation of state of neutron star matter is calculated over a wide range of the depth of kaon-nucleus optical potential, and the mass-radius relation of the neutron star obtained by solving Oppenheimer-Volkoff equation. We found that the kaon condensation can affect non-negligibly the equation of state of dense matter and the particle composition in the neutron star interior. However, the effect on the neutron star mass is suppressed when hyperons are created and constitute a substantial fraction of the matter.
Alternative Identification of Wheeled Mobile Robots with Skidding and Slipping
현창호,강효석,박창우 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.4
This paper proposes the new identification of dynamics for Type(2,0) wheeled mobile robots(WMRs)in the presence of wheel skidding and slipping. This paper presents dynamics models that explicitly relate perturbationsto the vehicle skidding and slipping. They cause parameter uncertainties, input-additive, matched andunmatched perturbations of WMRs. To solve the problem, this paper determines the new identification of dynamicsfor WMRs with skidding and slipping. The proposed dynamics lay a base for the deployments of various controldesign techniques to overcome the addressed perturbations. Finally, this paper verifies the tracking performance ofthe proposed feedback linearization controller for simulation results.
현창호,김현태,김미진,문기학 대한비뇨의학회 2008 Investigative and Clinical Urology Vol.49 No.10
Fibroepithelial polyps are benign, easily treated, and tumors with a good prognosis in the urinary tract. Congenital fibroepithelial polyps of the external genitalia are rarely reported. We report a case of a congenital fibroepithelial polyp of the penoscrotal junction in an 18-month-old boy. The fibroepithelial polyp was noted at birth with continuous grow. The fibroepithelial polyp was soft, dark-red in color, non-tender, and had a cockscomb shape. We treated the fibroepithelial polyp with simple excision and the histopathologic finding was a fibroepithelial polyp without a malignant component.
요관 Access Sheath를 이용한 요관경하배석술의 유용성
현창호,송필현,김현태,정희창 대한비뇨의학회 2009 Investigative and Clinical Urology Vol.50 No.4
Purpose: The ureteral access sheath (UAS) was developed to facilitate difficult ureteroscopic procedures. However, some have questioned the safety of the UAS and its likelihood of causing significant ureteral traumas. We evaluated the efficacy and safety of a UAS for managing ureteral calculi. Materials and Methods: From July 2005 to June 2008, a total of 122 patients underwent ureteroscopic removal of stones (67 patients with UAS, 55 patients without UAS). Under local, spinal, or general anesthesia, all patients were treated by using a semirigid ureteroscope with or without UAS. The operative results of the patients were assessed with KUB, and excretory urography or ultrasonography were assessed postoperatively after 2 to 4 weeks. We also analyzed the success rates of stone removal and the complication rates for each procedure. Results: Mean stone size and mean operation time were 9.3 mm and 38.8 minutes, respectively, with UAS and 8.9 mm and 40.4 minutes, respectively, without UAS. Overall stone-free rates were 89.6% and 76.4%. Mean hospital stay was 2.0 days and 2.2 days. The time for operation was significantly decreased for upper ureteral stones treated with UAS (p= 0.022). The stone-free rates were higher for upper ureteral stones treated with UAS (28/32, 87.5%, p=0.027), especially for stones greater than 10 mm in size (p=0.048). Conclusions: The use of UAS is effective and safe. The stone-free rates of ureteroscopic removal of stones with UAS were significantly higher than the rates without UAS for large (≥10 mm) upper ureteral calculi.