• ETRI Journal
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• v.45 no.6
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• pp.1046-1055
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• 2023

We introduce a display for virtual-reality (VR) fire training. Firefighters prefer to wear and operate a real breathing apparatus while experiencing full visual immersion in a VR fire space. Thus, we used a thin head-mounted display (HMD) with a light field and folded optical system, aiming to both minimize the volume for integration in front of the face into a breathing apparatus and maintain adequate visibility, including a wide viewing angle and resolution similar to that of commercial displays. We developed the optical system testing modules and prototypes of the integrated breathing apparatus. Through iterative testing, the thickness of the output optical module in front of the eyes was reduced from 50 mm to 60 mm to less than 20 mm while maintaining a viewing angle of 103°. In addition, the resolution and image quality degradation of the light field in the display was mitigated. Hence, we obtained a display with a structure consistent with the needs of firefighters in the field. In future work, we will conduct user evaluation regarding fire scene reproducibility by combining immersive VR fire training and real firefighting equipment.

• Journal of IKEEE
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• v.21 no.3
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• pp.268-271
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• 2017

In this paper, we propose the development of high resolution $360^{\circ}$ omnidirectional IP camera with 12 million pixels. The proposed 12-megapixel high-resolution $360^{\circ}$ omnidirectional IP camera consists of a lens unit with $360^{\circ}$ omnidirectional viewing angle and a 12-megapixel high-resolution IP camera unit. The lens section of $360^{\circ}$ omnidirectional viewing angle adopts the isochronous lens design method and the catadioptric facet production method to obtain the image without peripheral distortion which is inevitably generated in the fisheye lens. The 12 megapixel high-resolution IP camera unit consists of a CMOS sensor & ISP unit, a DSP unit, and an I / O unit, and converts the image input to the camera into a digital image to perform image distortion correction, image correction and image compression And then transmits it to the NVR (Network Video Recorder). In order to evaluate the performance of the proposed 12-megapixel high-resolution $360^{\circ}$ omnidirectional IP camera, 12.3 million pixel image efficiency, $360^{\circ}$ omnidirectional lens angle of view, and electromagnetic certification standard were measured.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.14-19
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• 2007

Angle sensors based on the principle of autocollimation, which are usually called autocollimators, can accurately measure small tilt angles of a light-reflecting flat surface. This paper describes a prototype micro-angle sensor that is based on the laser autocollimation technique. The new angle sensor is compact and consists of a laser diode as the light source and a quadrant photodiode as a position-sensing device. Because of its concise design, the microangle sensor facilitates dynamic measurements of the angular error motions of a precision stage without influencing the original dynamic properties of the stage. This is because the sensor only requires a small extra target mirror to be mounted on the stage. The sensitivity of the angle detection is independent of the focal length of the objective lens; therefore, an objective lens with a relatively short focal length is employed to reduce the size of the device. The micro-angle sensor uses a single lens for the both the laser collimation and focusing, which distinguishes it from the conventional laser autocollimation method that has separate collimate and objective lenses. The new micro-angle sensor has dimensions of $15.1\times22.0\times14.0mm$ and its resolution is better than 0.1 arc-second The optical design and performance of this micro-angle sensor were verified by experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.906-913
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• 2004

FFT algorithm is the most popular ISAR imaging technique from radar data. It requires polar formatting technique to make a focused image of the target as MTRC(Moving Through Resolution Cell) causes a blurred image when the data is from the wide azimuth angle. But there exits the angle limit for the application of the polar formatting and we cannot obtain clear images if the range of the azimuth angle is too wide to process with polar, formatting. This paper analyses the relative merits of the polar formatting algorithm accompanied by interpolation to the CDT algorithm that needs not the interpolation.

• Proceedings of the KIEE Conference
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• 2001.07e
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• pp.127-133
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• 2001

In SRM drive, the ON OFF angles of each phase switch should be accurately controlled in order to control the torque and speed stably. The accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor, that are used to provide the information of the rotor position and to control the SRM power circuit, respectively. However, as the speed increases, the amount of the switching angle deviation from the preset values is also increased. Therefore, the low cost encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper. As a result, a stable high speed SRM drive can be achieved by the high resolution switching angle control and it is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate for the practical low cost SRM drive.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1553-1561
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• 2024

Nondestructive radiography using cosmic ray muons has been used for decades to monitor nuclear reactor and spent nuclear fuel storage. Because nuclear fuel assemblies are highly dense and large, typical radiation probes such as x-rays cannot penetrate these target imaging objects. Although cosmic ray muons are highly penetrative for nuclear fuels as a result of their relatively high energy, the wide application of muon tomography is limited because of naturally low cosmic ray muon flux. This work presents a new image reconstruction algorithm to maximize the utility of cosmic ray muon in tomography applications. Muon momentum information is used to improve imaging resolution, as well as muon scattering angle. In this work, a new convolution was introduced known as M-value, which is a mathematical integration of two measured quantities: scattering angle and momentum. It captures the objects' quantity and density in a way that is easy to use with image reconstruction algorithms. The results demonstrate how to reconstruct images when muon momentum measurements are included in a typical muon scattering tomography algorithm. Using M-value improves muon tomography image resolution by replacing the scattering angle value without increasing computation costs. This new algorithm is projected to be a standard nondestructive radiography technique for spent nuclear fuel and nuclear material management.

• Journal of the Semiconductor & Display Technology
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• v.12 no.2
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• pp.63-66
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• 2013

Carbon Nanotube have been proposed for use in various applications for electromechanical systems. Nano-electromechanical resonators which provide high frequency resolution and long energy storage time, play an important role in wide area fields of science and engineering. Using the control of tension in carbon nanotube, can be made the tunable resonator. In the study, we analysis the tunable frequency change of resonator by tension changes due to the rotation angles of the single-walled carbon nanotube resonator. The frequency characteristics of a resonator as a function of the rotation angle. The tension was found to decrease with increasing rotation angle, and therefore the resonance frequencies could be changed by controlling the single-walled carbon nanotube rotation angle. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than $60^{\circ}$, these changes were marked.

• Applied Microscopy
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• v.42 no.4
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• pp.218-222
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• 2012

Modern aberration-corrected transmission electron microscope (TEM) with appropriate electron beam energy is able to achieve atomic resolution imaging of single and bilayer graphene sheets. Especially, atomic configuration of bilayer graphene with a rotation angle can be identified from the direct imaging and phase reconstructed imaging since atomic resolution Moir$\acute{e}$ pattern can be obtained successfully at atomic scale using an aberration-corrected TEM. This study boosts a reliable stacking order analysis, which is required for synthesized or artificially prepared multilayer graphene, and lets graphene researchers utilize the information of atomic configuration of stacked graphene layers readily.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1797-1802
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• 2005

In this study, we were developed an accuracy of the proposed two dimensional statical inclinometer what used a position sensitive detector(PSD) by an error analysis. The inclinometer consists of a laser source, a mass, an optic-fiber, and a PSD. The gravity direction on a base platform of the inclinometer is changed by an unknown inclination angle. And a laser spot is moved from the origin to another position of a PSD following a variation of an optical path by the gravity. These processes enable the inclinometer to estimate the inclination angle from distance information of the moving spot. A design methodology on the basis of a sensitivity analysis was applied to improve the measurement performance such as a full measuring range and a resolution. But it still has error factors, so we analyze the uncertainty of the inclinometer to evaluate the systematic errors from alignments, assembly error and so on. The experimental performance evaluation about the design objectives as a measuring range and a resolution was performed. And the validity and the feasibility of the design process were certified by an experimental process. Systematic errors eliminated to improve the accuracy of the inclinometer by the corrected measuring model from the calibration process between the inclination angle and the PSD position instead of the nominal measuring model. The ANOVA(analysis of variance) confirmed the effect of eliminating the systematic errors in the inclinometer. From these methodologies, the proposed inclinometer was able to measure with a high resolution(35.14sec) and a wide range(from $-15^{\circ}\;to\;15^{\circ}$

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.8
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• pp.875-881
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• 2014

The redundancy resolution of the seven DOF (Degree of Freedom) upper limb exoskeleton is key to the synchronous motion between a robot and a human user. According to the seven DOF human arm model, positioning and orientating the wrist can be completed by multiple arm configurations that results in the non-unique solution to the inverse kinematics. This paper presents analysis on the kinematic and dynamic aspect of the human arm movement and its effect on the redundancy resolution of the seven DOF human arm model. The redundancy of the arm is expressed mathematically by defining the swivel angle. The final form of swivel angle can be represented as a linear combination of two different swivel angles achieved by optimizing two cost functions based on kinematic and dynamic criteria. The kinematic criterion is to maximize the projection of the longest principal axis of the manipulability ellipsoid of the human arm on the vector connecting the wrist and the virtual target on the head region. The dynamic criterion is to minimize the mechanical work done in the joint space for each of two consecutive points along the task space trajectory. The contribution of each criterion on the redundancy was verified by the post processing of experimental data collected with a motion capture system. Results indicate that the bimodal redundancy resolution approach improved the accuracy of the predicted swivel angle. Statistical testing of the dynamic constraint contribution shows that under moderate speeds and no load, the dynamic component of the human arm is not dominant, and it is enough to resolve the redundancy without dynamic constraint for the realtime application.