• Proceedings of the KSME Conference
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• 2000.04b
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• pp.644-649
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• 2000

A new cyclone system for the vacuum cleaner to collect dusts has been studied experimentally and numerically to meet the constant suction power, hygienic exhaust and a reduction of maintenance cost. The cyclone system of the vacuum cleaner consists of twin cyclones for improving dust collection efficiency. The first. cyclone catches large dust particles and the second one having two separated flows to decrease pressure drop collects small dust particles. The optimal design factors such as dust collection efficiency, pressure drop, and cut-size are investigated from the experimental results by the Taguchi method. Cyclone cleaner systems designed in this study has a good Performance taking into account the dust collection efficiency of 93% and the cut-size of $1.6{\mu}m$ in mass median diameter at the flow rate of 1 CMM. The cyclone vacuum cleaner showed the potential to be an effective method to collect dusts generated in the household.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.1017-1019
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• 2013

The radiation sources leaked from large-scale radiation leak accident like the Hukushima nuclear power plant accident or nuclear explosions can cause to the very large damage for us. So that the damage can be minimized, we have being developed a detector that can providing information about the location of the source to remove dangerous substances quickly than the conventional single detector. In this paper, we designed the shielding and collimator for the development of the Stereo Radiation detector in order to detect contaminants using MCNP Code. And we analyzed the results that is detected from the discretionary position of the radiation source. The results of this paper will be used as the basis for designing efficient structure for the radiation detectors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.149-155
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• 2015

MEMS-based louver and shutter type conventional variable emissivity radiators change their emissivity properties in accordance with a temperature condition to achieve efficient thermal control performance. However, there are some drawbacks such as a structural safety of the mechanical moving parts under sever launch environment and constant power consumption to maintain the intended emissivity. In this study, to overcome above drawbacks, we proposed a MEMS-based variable emissivity radiator, which can change the emissivity property according to the polarity change of electrodes by using electric charge of the bead. The effectiveness of the optimized radiator design has been demonstrated through the comparison of efficiency with the fixed emissivity radiator.

• Journal of Biosystems Engineering
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• v.36 no.3
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• pp.163-170
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• 2011

Analysis of load on major parts of the tractor power drive line is critical for efficient and optimum design of a tractor. The purpose of this study was to evaluate severeness of the tractor PTO driving axle during rotary tillage operation. First, S-N (stress vs. number of cycle) curve of a PTO driving gear was obtained through the fatigue life test using a PTO dynamometer. Second, PTO severeness was evaluated during rotary tillage operation. Torque measurement system was constructed with strain-gauge sensors to measure torque of a PTO axle, an I/O interface to acquire the sensor signals, and an embedded system to calculate severeness. The severeness of PTO was analyzed using measured torque data during rotary tillage. In the PTO gear life fatigue test, breakage time and bending stress of the gear were measured by tooth widths and torque change during the fatigue life test. The S-N curve showed a good linear relationship between bending stress and number of cycle (life) with a coefficient of determination of 0.97. For PTO severenss evaluation, rotary tillage operations were conducted at two PTO rotational speeds (level-1, level-2) under different paddy and upland field sites with different soil conditions. Results of averaged relative severeness for PTO level-1 and PTO level-2 were 1.96 and 3.34, respectively, at paddy field sites, and they were 1.36 and 2.51, respectively, at upland field sites. The results showed that the PTO driving axle experienced more severe load during rotary tillage at paddy fields than at upland sites, and relative severeness was greater at the higher PTO rotational speed under all of the soil conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5537-5555
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• 2017

Having the characteristics of unlinkability, anonymity, and unforgeability, blind signatures are widely used for privacy-related applications such as electronic cash, electronic voting and electronic auction systems where to maintain the anonymity of the participants. Among these applications, the blinded message is needed for a certain purpose by which users delegate signing operation and communicate with each other in a trusted manner. This application leads to the need of proxy blind signature schemes. Proxy blind signature is an important type of cryptographic primitive to realize the properties of both blind signature and proxy signature. Over the past years, many proxy blind signature algorithms have been adopted to fulfill such task based on the discrete logarithm problem (DLP) and the elliptic curve discrete log problem (ECDLP), and most of the existing studies mainly aim to provide effective models to satisfy the security requirements concerning a single blinded message. Unlike many previous works, the proposed scheme applies the signcryption paradigm to the proxy blind signature technology for handling multiple blinded messages at a time based on elliptic curve cryptography (ECC). This innovative method thus has a higher level of security to achieve the security goals of both blind signature and proxy signature. Moreover, the evaluation results show that this proposed protocol is more efficient, consuming low communication overhead while increasing the volume of digital messages compared to the performance from other solutions. Due to these features, this design is able to be implemented in small low-power intelligent devices and very suitable and easily adoptable for e-system applications in pervasive mobile computing environment.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.4
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• pp.249-254
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• 2013

A fast multiplier and ADC are essential to process the analog signals in real time. The double-base number system(DBNS) is known as an efficient method for this purpose. The DBNS uses the numbers 2 and 3 as the base numbers simultaneously. The system has an advantage of fast multiplication, less chip area, and low power consumption compared to the binary multiplier. However, the inherent errors of the log number's intrinsic tolerance in DBNS are accumulated in a FIR digital filter, so the signal-to-noise ratio(SNR) has a tendency to be degraded. In this paper, the nonlinear encoder of ADC is designed to compensate the accumulated errors of DBNS by analysing the error distributions of various filter coefficients. The new ADC does not sacrifice its own advantages because the encoder circuits are modified only. The experiments were done with an FIR filters those were designed to have -70dB of SNR in stop band. The proposed nonlinear ADC encoder could drop the SNR to -45dB in stop band, in contrast to -35dB with the linear encoder.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.995-1003
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• 2005

Since the sensor network nodes have a small size and limited battery power, there have been many studies for reducing their energy consumption. Each sensor node can show different energy usage according to the frequency of event sensing and data transmission, and thus they have different lifetime. So, some nodes may run out of energy that causes disconnection of paths and reduction of network lifetime. In this paper, we propose a new energy-efficient routing algorithm for sensor networks that selects a least energy-consuming path among the paths formed by node with highest remaining energy and provides long network lifetime and somewhat uniform energy consumption by nodes. Simulation results show that our algorithm extends the network lifetime and enhances the network reliability by maintaining relatively uniform remaining energy distribution among sensor nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.202-208
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• 2010

The performance of upstream transmission in SCM-PON is generally limited by the presence of OBI which is caused by the beating of two or more lasers. In this paper, we propose a novel approach for reducing OBI problem by using heterodyne detection with an additional LD as a local oscillator, resulting that the RF signal is shifted to the other spectal band. In addition, it is possible that the proposed method can provide the cost-effective solution thanks to the loop-back mechanism using R-SOA in ONUs. The performance is superior when the spectral width of LD is smaller and the power difference between the transmission LD and the oscillation LD is bigger. System configuration and design consideration are discussed. Performance of the systems is evaluated by simulator called OptSim. It is expected to provide WDM/SCM-PON system not only cost-effective but also efficient in increasing the number of subscribers.

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.254-260
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• 2005

By incorporating large core polymer waveguides, which have been developed for increased alignment tolerance in passive fiber attachment, highly efficient variable optical attenuators are proposed. In order to find optimum device structures, 3-dimensional beam propagation method (BPM) simulations are performed. Heat distribution over the polymer film is calculated to find the 3-dimensional index profile data for the BPM simulation. Due to the small index contrast between the core and cladding materials in the large core waveguide, heat-induced radiation occurs for small heating power. While the ordinary VOA needs the temperature to change over $150^{\circ}C$ for 20 dB attenuation, the large core VOA requires only $70^{\circ}C$. In addition to the merit of passive fiber attachment, the proposed VOA has enhanced attenuation efficiency for the lower temperature change.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.50-56
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• 2015

An efficient fast response hysteretic buck converter suitable for mobile application is propoesed. The problems of large output ripple and difficulty in using of small power inductor that conventional hysteretic converter has are improved by adding ramp generator. and the changeable switching frequency with load current is fixed by adding a delay time control circuit composed of PLL structure resulting in decrease of EMI noise. The circuits are implemented by using BCDMOS 0.35um 2-polt 4-metal process. Measurement results show that the converter operates with a switching frequency of 1.85MHz when drives 80mA load current. As the converter drives over 170mA load current, the switching frequency is fixed on 2MHz. The converter has output ripple voltage of less 20mV and more than efficiency 85% with 50~500mA laod current condition.