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Radiative Decays of the $K^-p$ System in the Baryon Pole Model
유병길,Tae Keun Choi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.III
The radiative widths of K..p ! and K..p ! 0 decays are estimated within the baryon pole model and are compared with recent experimental rates. In the present calculation the role of the vector meson K1(1270) is shown to be important for the consistent agreement with the experimental data, subsidiary to the signicance of (1405) exchange from the parity conservation. Our results are presented for both of pseudoscalar and pseudovector couplings and are compared with those of other model calculations. Based on these results, discussions are given for estimates of the radiative widths ..1405! and ..1405!0 .
유병길 한국물리학회 2005 새물리 Vol.51 No.6
Using the Born approximation, we developed a prescription for the gauge invariance of pion electroproduction with electromagnetic and hadronic form factors included. If generality in formulating the gauge invariance is to be ensured, the form factors must satisfy the Ward-Takahashi identity for current conservation and the generalized Ward-Takahashi identity for the $\gamma\pi NN$ interaction vertex. As a consequence, the Born approximation for electroproduction is obtained with gauge invariance, which is consistent with Ohta's prescription for hadronic form factors in photoproduction. Born 근사 (Born approximation)를 사용하여 전기 생성 (electroproduction) 반응을 기술할 때 진폭에 들어오는 전자기 형태인자 (electromagnetic form factor)와 강작용 (hadronic) 형태인자에 대해서 게이지 불변을 유지시키는 방법을 전개하였다. 게이지 불변을 유도하는 과정이 보편성을 가지기 위하여 이들 형태인자들은 전류 보존에 대한 Ward-Takahashi 항등식과 $\gamma\pi NN$ 작용점 (vertex)에 대해 일반화한 Ward-Takahashi 항등식 (generalized Ward-Takahashi identity)을 만족하도록 하였으며 그 결과 광생성 반응에서 강작용 형태인자에 대한 Ohta의 게이지 불변 방식과 부합되는 전기생성 반응의 Born 근사를 유도하였다.
Galvannealed steel의 점 용접성에 미치는 전극 팁의 영향
유병길,강춘식 대한용접접합학회 1987 대한용접·접합학회지 Vol.5 No.3
Effects of electrode tips shapes of spot welding on the galvannealed steel have been studied, and the results obtained from this studies are as follows. 1) Expulsion had no effect on the shear strength of the specimen but been observed on the tensile strength of the specimen. 2) Effect of holding time after welding was neglegible when the spot welding supplies enough heat input. 3) Depending on the sopt welding tip shape it has different weldbility. It has better weldability in the order of pointed shape, truncated shape and dome shape. But the effect of coolind was just the opposite of the above order.
문턱 에너지 파이온 전기 생성 반응에서 벡터 메존 기여도
유병길 한국항공대학교 1999 論文集 Vol.37 No.-
We consider the effects of t-channel vector meson contributions ρ,ω on the threshold amplitudes of ??? electroproduction and present a new method to calculated them in a consistent manner with the μ expansion scheme of low energy theorem(LET). For applications, we attempt to make an analysis of the experimental data on the threshold amplitudes of the ??? process, based on our previous work[1]. It is found taht our treatment of vector mesons ρ, ω with our own device yields a better agreement with the experimental data.
유병길,이경돈 대한용접접합학회 1999 대한용접·접합학회지 Vol.17 No.2
Weld bead quality in tailored blank(TB) is critically affected by edge preparation of sheets. The edge quality of prepared sheets for TB can be classified into straightness and the cross section quality of sheared plane such as a ratio of shear face, shear plane angle, etc. In order to have a good edg quality for butt-welding sheets, precision shearing will be recommended. In this paper, the feasibility of a conventional mechanical shearing as the edge preparation for tailored blanks is studyied. It reveals that fine shearing may not be the unique solution as it is generally accepted. To obtain the good shearing condition with a conventional mechanical shearing, experiments were carried out using Tahuchi method. The major parameters affecting a sheared contour are the clearance between upper blade and lower blade, and shear angle. The optimal shearing condition yields a very good straightness along the entire length of the cut, which gives a butt joint gap less than 10% of the base material thickness. The good cross section of sheared plane is also achieved in the optimal shearing condition such as a ratio of the shear face above 65%, a cross section's shear plane angle above 85%, little burr, which is providing finally good weld beads.
독립적인 이중 공진 모드 합성을 이용한 광대역 SDR 무전기 안테나 설계
유병길,동문호,조지행,한성우,Yu, Byunggil,Dong, Moo-Ho,Cho, Ji-Haeng,Han, Sung-Woo 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.1
In this paper, we have proposed a wide band antenna for manpack SDR(Software Defined Radio). The proposed antenna consists of feeding post, flexible gooseneck and two radiating elements composed of a upper and lower radiators. The upper radiator has a longer electrical length than the lower radiator in order to operate in the lower frequency. Also, the resonant frequency and impedance characteristics of the antenna can be adjusted independently for two radiators. Therefore, the proposed antenna can be achieved wide impedance bandwidth by the combination of two independent resonance modes. To analyze the characteristics of the antenna in the design process is employed the equivalent circuit theory and EM(Electro-Magnetic) simulation. The measurement results show that the proposed antenna have the sufficient wide bandwidth, above -3.4dBi of the gain and fairly good radiation pattern over the wide bandwidth.
$\gamma N\to K\Theta^+$ 반응의 보존 법칙과 펜타쿼크 세타의 패리티
유병길 한국물리학회 2006 새물리 Vol.52 No.2
Pentaquark $\Theta^+$ parity, Photoproduction, Angular momentum and parity conservation, Differential cross section, Photon polarization asymmetry 광생성 반응을 통하여 펜타쿼크 세타입자의 패리티를 모형에 의존하지 않고 어떻게 결정할 수 있는가를 논의하였다. 각운동량-패리티 보존법칙과 문턱 운동학을 바탕으로 미분 단면적과 편광 비대칭을 해석하였다. $\gamma n \to K^-\Theta^+$ 과정에서는 패리티에 따라서 이들 관측량의 각도 분포가 매우 다른 반면에 $\gamma p \to \bar{K}^0\Theta^+$ 과정에는 그렇지 않다는 %각도 분포의 차이가 없다는 것을 보였다. 이러한 발견들은 본질적으로 보존 법칙으로 부터 나오는 결과이기 때문에 모형에 의존하지 않고 세타의 패리티를 구분할 수 있는 중요한 지침이 될 수 있다.