Papers by Author: Eui Jung Choi

Abstract: On the human-rifle system, the human body is affected by the firing impact. The firing impact will reduce the firing accuracy and change the initial shooting posture. Therefore the study of biomechanical characteristics using human-rifle modeling and numerical investigation is needed. The muscle-skeleton model was developed by the finite element method using beam and spar elements. In this study, a structural analysis has been performed in order to investigate the human body impact by firing a 5.56mm small caliber machine gun. The firing experiments with a standing shooting posture were performed to verify analytical results. The result of this study shows analytical displacements of the human-rifle system and experimental displacements of real firing. In the results, the analytical displacement on the human body is presented.

Abstract: In the conventional weapon system, such as gun and small arms, it is a general trend that for maximization of its performance and enhancement of its effectiveness, the fire control system; FCS is developed and applied with the guns and small arms in the world. The FCS of the small arms for infantry man is composed of a few of sensors for acquisition of input data of FCS, such as range measurement, position sensing of weapon, temperature, etc., computer, displayer and power pack, and also the air burst ammunition is developed in parallel for the maximization of effectiveness. Since setting fuse of the flight time for the air burst ammunition is adapted for next rifle, the measuring device of the muzzle velocity is needed to overcome the variation of muzzle velocity due to producing procedures and the differences of the using temperatures and so maintain the burst position accuracy. This paper contained the technical information on the development of the measuring device of muzzle velocity, which designed in compact & light weight configuration with reliability and accuracy.

Abstract: The hit rate is affected by the shooting impact of the human-rifle system. The impact response of the human-rifle system is determined mainly by the geometrical parameters and contact boundary conditions. In this study, the height and weight of the considered human model are 170 cm and 60 kg, as these parameters mirror 50 per cent of Korean males in their twenties. The rifle model is applied on the K-2. The impact path analysis of three typical shooting postures: the standing, kneeling and prone shooting postures is performed with experimental impulse-time history during a shooting test. The biomechanical response such as impact transfer path, force history and displacement history are investigated.

Abstract: This study is launched to get exact bore-sighting value in the process of assembly for XK11. Image processing method with Charged Coupled Device camera is chosen for the Error reduction of bore-sighting. The results of this method by using a CCD camera and the Testing Target Method are described in this paper. After we confirm the performance of the Dual-Barrel Weapon and that of the Firing Control System in the Dual Barrel Weapon System, the bore-sighting which is a part of the process in the system assembly is accomplished. In this process, the position of the barrel is identified by using the Testing Target Method that is an existing bore-sighting method. Then the fixing line of the Firing Control System is checked by a Day-Optical part. The precision of the boresighting is required within 1 mil, however the manual method using the human eyes makes it worse. Therefore CCD camera is installed in the eyepieces. Next, we can get the image of the sighting and the center coordinate values of the laser-pointer from each barrel by image processing method. Required bore-sighting value is calculated from the eccentricity of the center coordinate. Finally, we will plan to adopt this result in the assembly process of XK11.

Abstract: The rifle impact on human body is affected by the posture of human for rifling. The interaction human-rifle system influences on a firing accuracy. In this paper, impact analysis of human model for standing posture is carried out. ADAMS code and LifeMOD are used in impact analysis of human model and modeling of the human body, respectively. At the shooting, human model is affected by rifle impact during 0.001 second. Performed simulation time for shooting is 0.3second. Applied constraint condition to human-rifle system is rotating and spherical condition. As the results, displacement of the rifle and transfer path analysis of impact on human model is presented.

Abstract: Extracellular signal-regulated kinases (ERKs) are phosphorylated on threonine and tyrosine residues at 183 and 185, respectively, and then translocated from cytosol to nucleus. ERK2 is retained in the nucleus for several hours by nerve growth factor (NGF), and this sustained retention of ERK2 in the nucleus has effect on the fate of biological response toward differentiation by neurite outgrowth in PC12 cells. The overexpression of Green Fluorescent Protein (GFP)-ERK2 and mutated GFP-ERK2 constructs without anchoring protein MEK1 were distributed throughout the resting and the activated cells. When GFP-ERK2 coexpressed along with MEK1, cytosolic localization of GFP-ERK2 is retained by MEK1 in the resting PC12 cells. This cytosolic retention was due to the binding of ERK2 to the MEK1. Upon stimulation by growth factors, the association between GFP-ERK2 and MEK1 was detached from each other, and then GFP-ERK2 was translocated into the nucleus. However, inactive form of the MKP-3 cytosolic phosphatase forced ERK cytosolic retention in PC12 cells were either left untreated or stimulated by NGF. When the transfected PC12 cells were treated for 72hrs with NGF, GFP-ERK2 was distributed the cytosol. Regarding its subcellular localization, the roles of residues 179-185 located in the activation loop of ERK2 were examined. The substitution of residues in the activation loop to alanine showed different localization on the nuclear translocation of ERK2 in PC12 cells.