• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.22-35
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• 1992

In highly automated machining centers, intelligent sensor fddeback systems are indispensable on order to monitor their operations, to ensure efficient metal removal, and to initate remedial action in the event of accident. In this study, an on-line tool wear detection system for thrning operations is developed, and experimentally evaluated. The system employs multiple sensors and the signals from these sensors are processed using a multichannel autoegressive (AR) series model. The resulting output from the signal processing block is then fed to a previously tranied artificial neural network (multiayered perceptron) to make a final decision on the state of the cutting tool. To learn the necessary input/output mapping for tool wear detection, the weithts and thresholds of the network are adjusted according to the back propagation (BP) method during off-line training. The results of experimental evaluation show that the system works well over a wide range of cutting conditions, and the ability of the system to detect tool wear is improved due to the generalization, fault-tolearant and self-ofganizing properties of the neural network.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.33-40
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• 1984

In the conventional pulsed doppler system, gated CW is used to excite a ultrasonic transducer so that a group of linear RF amplifiers are required to excite a ultrasonic array transducer in the scanning pulsed doppler system. A pulsed doppler system without linear high voltage RF amplifiers, which excites the transducer impulsively, is studied theoretically and experimentally. In this paper, an experimental 8-channel pulsed doppler system is implemented, which uses quadrature defection to detect the direction of motion and can compensate the attenuation effect. The designed pulsed doppler system shows the possibility of real time multichannel doppler flow meter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2165-2170
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• 2008

In this parer, it is implemented a Local distribution Audio System, based on AoIP(Audio over Internet Protocol) of a part of TCP/IP Network which belongs to Internet transmission technology. The system is controlled based on SNMP(Simple Network Management Protocol) and it is transferred to UDP as packet after changing from Analog audio sources to Digital audio sources. The implemented Local distribution Audio System have presented practical possibilities in PA system transmitting various audio sources to several areas, dispersedly and using multichannel audio like Home theaters in the limelight, recently.

• Journal of Magnetics
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• v.21 no.3
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• pp.330-339
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• 2016

A magnetic field sensing system with a single primary sensor and multiple reference sensors deployed locally and orthogonally, was proposed for downlink signal reception and interference cancelling for Through-the-Earth Communication (TEC). This paper mathematically analyzes a design optimization process for a search coil magnetometer (SCM), and applies that process to minimize the bandwidth of the primary SCM for TEC signal reception and the volume of reference SCMs for multiple distributions. The primary SCM achieves a 3-dB bandwidth of 7 Hz, a sensitivity threshold of 120 fT/${\surd}$Hz, and a volume of $2.32{\times}10^{-4}m^3$. The entire sensing system volume is as small as $10^{-2}m^3$. Experiments with interference from industrial frequency harmonics demonstrated an average of 36 dB and 18 dB improvements in signal-to-interference ratio and signal-to-interference plus noise ratio, respectively, using multichannel recursive-least-squares algorithm. Thus, the proposed sensing system can reduce the interference effectively and allows reliable downlink signal reception.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.21-26
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• 2003

We designed and constructed a multichannel superconducting quantum interference device (SQUID) magnetometer system to measure magnetic fields from the human brain. We used a new type of SQUID, the double relaxation oscillation SQUID (DROS). With high flux-to-voltage transfers of the DROS, about 10 times larger than the dc SQUIDs, simple flux-locked loop circuits could be used for SQUID operation. Also the large modulation voltage of the DROS, typically being 100 $mutextrm{V}$, enabled stable flux-locked loop operation against the thermal offset voltage drift of the preamplifier. The magnetometers were fabricated using the Nb/AlOx/Nb junction technology. The SQUID system consists of 37 signal magnetometers, distributed on a semispherical surface, and 11 reference channels were installed to pickup background noises. External feedback was used to eliminate the magnetic coupling with the adjacent channels. The liquid helium dewar has a capacity of 29 L and boil-off rate of about 4 L/d with the total 48 channel insert. The magnetometer system has an average noise level of 3 fT/√Hz at 100 Hz, inside a shielded loon, and was applied to measure auditory-evoked fields.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.17-21
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• 2001

There are some methods to enhance the ‘sweet spot’in loudspeaker-based 3D audio systems. Most of them can be only applied to narrow frequency band inherently. In this paper, we introduce the more robust 3D sound reproduction system which has far wider robust bandwidth. The system applies a sum and difference filter to the conventional three loudspeaker-based one.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.19-24
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• 2017

Nowadays, based on the advancement of IT techniques, innovative products combining IT techniques to PA system are developing. In this paper, we presented the hybrid mixer controller for digital PA system. We develop the integrated mixer controller which includes the digital mixer composing an existing digital PA system and function of digital integrated controller. Developed integrated mixer controller consists of multichannel mixer function with 16 audio input channels, 8 output channels. And, it has an equalizer for processing digital audio signal, matrix and limiter. Also, the developed controller has some features such as internet connection for controlling of overall PA system and remote monitoring of mixer process condition.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.4
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• pp.131-142
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• 2010

Due to the development of the Internet, Internet banking that we are liberated from time and space has evolved into banking system. So modern life became comfortable. However, Dysfunction (malicious Information leakage and hacking etc.) of the Internet development has become a serious social problem. According to this, The need for security is rapidly growing. In this paper, we proposed the Internet Banking Authentication System using a dual-channel in OTP(One Time Password) authentication. This technology is that A user transfer transaction information to Bank through one Internet channel then bank transfer transaction information to user using the registered mobile phone or smart phone. If user confirm transaction information then bank request user's OTP value. User create OTP value and transfer to bank and bank authenticate them throgth the ARS. If authentication is pass then transaction permitted. Security assessment that the proposed system, the security requirement that the confidentiality and integrity, authentication, repudiation of all of the features provide a key length is longer than the current Internet banking systems, such as using encryption, the security provided by the Financial Supervisory Service Level 1 rating can be applied to more than confirmed.

• Journal of Sensor Science and Technology
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• v.33 no.3
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• pp.165-172
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• 2024

In this study, we investigated the detection properties of piezoresistive carbon nanotubes/polydimethylsiloxane (CNT/PDMS) devices with porous structures under applied pressure. The device, having dimensions of 10 mm × 10 mm × 5 mm, was fabricated with a porosity of 74.5%. To fabricate piezoresistive CNT/PDMS devices, CNTs were added using two different methods. In the first method, the CNTs were mixed with PDMS before the fabrication of the porous structure, while in the second, the CNTs were coated after the fabrication of the porous structure. Various detection properties of the fabricated devices were examined at different applied pressures. The CNT-coated device exhibited stable outputs with lesser variation than the CNT-mixed device. Moreover, the CNT-coated device exhibited improved reaction properties. The response time of the CNT-coated device was 1 min, which was approximately about 20 times faster than that of the CNT-mixed device. Considering these properties, CNT-coated devices are more suitable for sensing devices. To verify the CNT-coated device as a real sensor, it was applied to the gripping sensor system. A multichannel sensor system was used to measure the pressure distribution of the gripping sensor system. Under various gripping conditions, this system successfully measured the distributed pressures and exhibited stable dynamic responses.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.155-161
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• 2010

Recently, the electromagnetic techniques of the eddy current testing(ECT), alternating current field testing, magnetic flux leakage testing and remote field testing have been used as a nondestructive evaluation method based on the electromagnetic induction. The eddy current testing is now widely accepted as a NDE method for the heat exchanger tube in the electric power industry, chemical, shipbuilding, and military. The ECT system mainly consists of the synthesizer module, analog module, analog-to-digital converter, power supplier, and data acquisition and analysis program. In this study, the synthesizer module and the analog module which are essential to the ECT system were primarily developed. The developed ECT system is basically a multifrequency type which is able to inject the maximum four frequencies based on the frequency and time domain multiplexing method. Conclusively, we confirmed that the EC signal was processed appropriately in each circuit modules, and the Lissajous EC signal was displayed in the impedance plane.