• Nuclear Engineering and Technology
• /
• v.53 no.8
• /
• pp.2640-2645
• /
• 2021

We report the development of a gamma-ray imaging device, named Large-Area Hybrid Gamma Imager (LAHGI), featuring high imaging sensitivity and good imaging resolution over a broad energy range. A hybrid collimation method, which combines mechanical and electronic collimation, is employed for a stable imaging performance based on large-area scintillation detectors for high imaging sensitivity. The system comprises two monolithic position-sensitive NaI(Tl) scintillation detectors with a crystal area of 27 × 27 cm² and a tungsten coded aperture mask with a modified uniformly redundant array (MURA) pattern. The performance of the system was evaluated under several source conditions. The system showed good imaging resolution (i.e., 6.0-8.9° FWHM) for the entire energy range of 59.5-1330 keV considered in the present study. It also showed very high imaging sensitivity, successfully imaging a 253 µCi ¹³⁷Cs source located 15 m away in 1 min; this performance is notable considering that the dose rate at the front surface of the system, due to the existence of the ¹³⁷Cs source, was only 0.003 µSv/h, which corresponds to ~3% of the background level.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.45 no.6
• /
• pp.149-156
• /
• 2008

SLAM(Simultaneous Localization and Mapping) system is to find a global position and build a map with sensing data when an unmanned-robot navigates an unknown environment. Two kinds of system were developed. One is used distance measurement sensors such as an ultra sonic and a laser sensor. The other is used stereo vision system. The distance measurement SLAM with sensors has low computing time and low cost, but precision of system can be somewhat worse by measurement error or non-linearity of the sensor In contrast, stereo vision system can accurately measure the 3D space area, but it needs high-end system for complex calculation and it is an expensive tool. In this paper, we implement the SLAM system using a single camera image and a PSD sensors. It detects obstacles from the front PSD sensor and then perceive size and feature of the obstacles by image processing. The probability SLAM was implemented using the data of sensor and image and we verify the performance of the system by real experiment.

• Journal of Internet Computing and Services
• /
• v.18 no.3
• /
• pp.37-48
• /
• 2017

Touch interface has been introduced as one of the most common input devices that are widely used in the Smart Device. Recently Force-Touch interface, a new approach of input method, having the power recognition mechanism, has been appeared in Smart industries. Force-Touching determining multiple things (the geographical and pressure values of touching point) in one touching act allows users to provide more than one input methods in a limited environments. Force-Touching Device is required different user communicational interaction than other common Smart devices because it is possible to recognize various inputs in the one act. It means that Force-Touching is only able to understand and to use the pressure sensitive values, not other Smart input methods. So, we built Force-Touch-Cover that makes typical Smart-Device to have Force-Touching interfaces. We analysis the accuracy of the Force-Touching-Cover's sensor and also assessment the changes in pressure values depending on the pressure position. Via this Paper, We propose the implement of user-oriented Force-Touching interface that is based on users' feedback as our conclusion.

• Journal of the Institute of Convergence Signal Processing
• /
• v.25 no.2
• /
• pp.77-85
• /
• 2024

The suspension device that connects the prosthetic leg and the residual limb allows lower limb amputees to wear prosthetic limbs, and is the most sensitive part when using prosthetic limbs as it is always in contact with the residual limb not only while walking but also in everyday life. In this paper, using the principles of attraction and repulsion of permanent magnets, we developed a magnetic lock suspension device that can fix the amputees and prosthetic legs of lower limb amputees by changing the polarity of the magnet. The operation method of the magnetic lock is that when neodymium magnets are placed on the left and right as NNSS based on a non-magnetic brass core, the magnetic force flows outward beyond the brass core using the adsorption member as a medium to generate bonding force. When rotated 90 degrees, the magnet moves to NSNS. The principle is that as the position moves, the magnetic force flows inward and cancels out.Based on this, we conducted a bonding test using tensile strength and a short-term comparative evaluation of the prosthesis with the shuttle lock suspension system, which was a comparison group, to verify reliability and evaluate satisfaction with the prototype. As a result, the tensile strength exceeding the appropriate bonding strength was confirmed, and the magnetic lock showed higher satisfaction than the shuttle lock. In the future, we plan to conduct long-term ADL clinical trials for commercialization and develop a product that can be distributed to actual amputees.

• Journal of Biomedical Engineering Research
• /
• v.31 no.5
• /
• pp.401-406
• /
• 2010

Recently, many implantable medical devices have been developed and manufactured in many countries. In these devices, generally, energy is supplied by a transcutaneous method to avoid the skin penetration due to the power wires. As the most transcutaneous power transmission methods, the electromagnetic coupling between two coils and resonance at a specific frequency has been used widely. However, in case of a transcutaneous power transmitter with a fixed switching frequency to drive an electromagnetic coil, inefficient power transmission and thermal damage by the undesirable current variation may occur, because the electromagnetic coupling state between a primary coil and a secondary coil is very sensitive to skin thickness of each applied position and by person. In order to overcome these defects, a transcutaneous power transmitter of which operating frequency can be automatically tracked into the resonance frequency at each environment has been designed and implemented. Through the results of experiments for different coil surroundings, we have been demonstrated that the implemented transcutaneous power transmitter can track automatically into a varied resonance frequency according to arbitrary skin thickness change.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1417-1422
• /
• 2005

Among the sensors mainly used for displacement measurement, there are a linear CCD(Charge Coupled Device) and a PSD(Position Sensitive Detector) as a non-contact type. Their structures are different very much, which means that the signal processing of both sensors should be applied in the different ways. Most of the displacement measurement systems to get the 3-D shape profile of an object using a linear CCD are a computer-based system. It means that all of algorithms and mathematical operations are performed through a computer program to measure the displacement. However, in this paper, the developed system has microprocessor and other digital components that make the system measure the displacement of an object without a computer. The thing different from the previous system is that AVR microprocessor and FPGA(Field Programmable Gate Array) technology, and a comparator is used to play the role of an A/D(Analog to Digital) converter. Furthermore, an ATC(Automatic Threshold Control) algorithm is applied to find the highest pixel data that has the real displacement information. According to the size of the light circle incident on the surface of the CCD, the threshold value to remove the noise and useless data is changed by the operation of AVR microprocessor. The total system consists of FPGA, AVR microprocessor, and the comparator. The developed system has the improvement and shows the better performance than the system not using the ATC algorithm for displacement measurement.

• Nuclear Engineering and Technology
• /
• v.55 no.9
• /
• pp.3133-3139
• /
• 2023

Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on ⁶LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 ㎛ thick ⁶LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.4
• /
• pp.308-317
• /
• 2009

In the present work, a sensor system composed of an oscillator sensor and a Lamb wave sensor is proposed for the purpose of structural health monitoring. The oscillator sensing system detecting the shift of a structural resonant frequency in proportion to the amount of defects in the structure is a pretty sensitive and simple device, but its detectable range is limited to its local zone. The Lamb wave sensor system, however, is applicable to global detection of the defects. This study is aimed at investigating the feasible combination of the two systems to exploits their merits simultaneously. The scheme to use PZT patches as the oscillator sensor as well as the Lamb wave sensor was proposed to identify the position, length and number of cracks by means of TOF and amplitude of signals, and its validity was confirmed through experiments.

• Progress in Superconductivity
• /
• v.7 no.1
• /
• pp.28-35
• /
• 2005

We propose a method to measure atrial arrhythmias (AA) such as atrial fibrillation (Afb) and atrial flutter (Afl) with a SQUID magnetocardiograph (MCG) system. To detect AA is one of challenging topics in MCG. As the AA generally have irregular rhythm and atrio-ventricular conduction, the MCG signal cannot be improved by QRS averaging; therefore a SQUID MCG system having a high SNR is required to measure informative atrial excitation with a single scan. In the case of Afb, diminished f waves are much smaller than normal P waves because the sources are usually located on the posterior wall of the heart. In this study, we utilize an MCG system measuring tangential field components, which is known to be more sensitive to a deeper current source. The average noise spectral density of the whole system in a magnetic shielded room was $10\;fT/{\surd}Hz(a)\;1\;Hz\;and\;5\;fT/{\surd}Hz\;(a)\;100\;Hz$. We measured the MCG signals of patients with chronic Afb and Afl. Before the AA measurement, the comparison between the measurements in supine and prone positions for P waves has been conducted and the experiment gave a result that the supine position is more suitable to measure the atrial excitation. Therefore, the AA was measured in subject's supine position. Clinical potential of AA measurement in MCG is to find an aspect of a reentry circuit and to localize the abnormal stimulation noninvasively. To give useful information about the abnormal excitation, we have developed a method, separative synthetic aperture magnetometry (sSAM). The basic idea of sSAM is to visualize current source distribution corresponding to the atrial excitation, which are separated from the ventricular excitation and the Gaussian sensor noises. By using sSAM, we localized the source of an Afl successfully.

• The KIPS Transactions:PartC
• /
• v.11C no.6 s.95
• /
• pp.843-850
• /
• 2004

As mobile devices prevail, requests for various services using mobile devices have increased. Requests for application services that require large data space such as multimedia, game and database [1] specifically have greatly increased. However, mobile appliances have difficulty in applying various services like a wire environment, because the storage capacity of one is not enough. Therefore, research (5) which provides remote storage service for mobile appliances using iSCSI is being conducted to overcome storage space limitations in mobile appliances. But, when iSCSI is applied to mobile appliances, iSCSI I/O performance drops rapidly if a iSCSI client moves from the server to a far away position. In the case of write operation, $28\%$ reduction of I/O performance occurred when the latency of network is 64ms. This is because the iSCSI has a structural quality that is very .sensitive to delay time. In this paper, we will introduce an intermediate target server and localize iSCSI target to improve the shortcomings of iSCSI performance dropping sharply as latency increases when mobile appliances recede from a storage server.