• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.2846-2866
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• 2022

Caenorhabditis elegans exhibits sophisticated chemotaxis behavior through two parallel strategies, klinokinesis and klinotaxis, executed entirely by a small nervous circuit. It is therefore suitable for inspiring fast and energy-efficient solutions for autonomous navigation. As a random search strategy, the Lévy walk is optimal for diverse animals when foraging without external chemical cues. In this study, by combining these biological strategies for the first time, we propose a spiking neural network model for search and contour tracking of specific concentrations of environmental variables. Specifically, we first design a klinotaxis module using spiking neurons. This module works in conjunction with a klinokinesis module, allowing rapid searches for the concentration setpoint and subsequent contour tracking with small deviations. Second, we build a random exploration module. It generates a Lévy walk in the absence of concentration gradients, increasing the chance of encountering gradients. Third, considering local extrema traps, we develop a termination module combined with an escape module to initiate or terminate the escape in a timely manner. Experimental results demonstrate that the proposed model integrating these modules can switch strategies autonomously according to the information from a single sensor and control steering through output spikes, enabling the model worm to efficiently navigate across various scenarios.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.42-48
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• 2023

Abstract: In this study, an induction heating system using resonance is developed to remove remaining moisture and contaminations which could be generated during fabricating secondary batteries. This system is composed of power supply and induction coil. Power supply needs an oscillator, zero crossing detection, frequency tracking function, and induction coil needs a dummy coil to obtain a uniform temperature distribution. It is very important to obtain a uniform heating temperature distribution of battery cell case in the induction heating system before pouring electrolyte into battery cell. Experimental results show a temperature distribution deviation of below 1℃ in the external position of battery cell cases. As well, the temperature of battery cell itself shows distribution of 40℃±3℃.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1911-1923
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• 2023

The nuclear safety assessment involving large transient simulations is forcing the community to develop methods for coupling thermal-hydraulics and neutronic codes and three-dimensional (3D) Computational Fluid Dynamics (CFD) codes. In this paper a set of dynamic boundary conditions are implemented in OpenFOAM^Ⓡ in order to apply zero-dimensional (0D) approaches coupling with 3D thermal-hydraulic simulation in a single framework. This boundary conditions are applied to model pipelines, tanks, pumps, and heat exchangers. On a first stage, four tests are perform in order to assess the implementations. The results are compared with experimental data, full 3D CFD, and system code simulations, finding a general good agreement. The semi-implicit implementation nature of these boundary conditions has shown robustness and accuracy for large time steps. Finally, an application case, consisting of a simplified open pool with a cooling external circuit is solved to remark the capability of the tool to simulate thermal hydraulic systems commonly found in nuclear installations.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.51-55
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• 2023

Measurement of the ferroelectric polarization hysteresis curve is an important means of overall evaluation and interpretation of the ferroelectric structure and dielectric properties. If a resistive component is included in the ferroelectric sample, an error is included in the measured value of the spontaneous polarization. When configuring the electrical circuit to measure the polarization, by properly utilizing the external resistance corresponding to the resistive component included in the sample, the error due to the resistive loss of the sample was excluded and the size of the ferroelectric polarization induced inside could be accurately measured. It is expected that the displacement and dielectric characteristics of ions inside the ferroelectric can be more accurately evaluated through the evaluation of such an accurate polarization hysteresis curve.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.113-121
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• 2016

Polymer electrolyte membrane fuel cell(PEMFC) requires cooling system to maintain the proper operating temperature(about $65^{\circ}C{\sim}75^{\circ}C$) because the efficiency and power are affected by operating temperature. In order to retain the operating temperature of PEMFC, cooling system and coolant control logic are needed. Hardware-in-the-loop simulation(HILS) is one of effective methods to study and evaluate control algorithm. In this paper, the HILS system was designed to study the coolant control algorithm. The models of HILS system consisted of PEMFC, heat exchanger, and external environment associated with temperature. The hardwares in HILS system are 3-way valves, pumps, and a heat exchanger. The priority control and the control target temperature were investigated to improve the control performance using HILS. The 3-way valve in $1^{st}$ cooling circuit was selected as priority control target. The under limit value of $2^{nd}$ 3-way valve set as a function of PEMFC power and $2^{nd}$ circuit coolant temperature to correct temperature control performance. As a result, the temperature of PEMFC is stably controlled.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.137-147
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• 2013

In this paper, an 1.2V 8b 1GS/s A/D Converter(ADC) based on a folding architecture with a resistive interpolation technique is described. In order to overcome the asymmetrical boundary-condition error of conventional folding ADCs, a novel scheme with an odd number of folding blocks and a fractional folding rate are proposed. Further, a new digital encoding technique with an arithmetic adder is described to implement the proposed fractional folding technique. The proposed ADC employs an iterating offset self-calibration technique and a digital error correction circuit to minimize device mismatch and external noise The chip has been fabricated with a 1.2V 0.13um 1-poly 6-metal CMOS technology. The effective chip area is $2.1mm^2$ (ADC core : $1.4mm^2$, calibration engine : $0.7mm^2$) and the power dissipation is about 350mW including calibration engine at 1.2V power supply. The measured result of SNDR is 46.22dB, when Fin = 10MHz at Fs = 1GHz. Both the INL and DNL are within 1LSB with the self-calibration circuit.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.1
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• pp.41-49
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• 2012

The effects of operating temperature and electrode gap distance on electricity generation were investigated in two-chamber type MFCs. Voltages across the external resistor $(100\;{\Omega})$ were enhanced approximately 1.4 times by the increase of operating temperature from $30^{\circ}C$ to $34^{\circ}C$. The open circuit voltages (OCVs) were increased by the increase of temperature and the maximum power of MFC was obtained at higher current condition by increasing temperature and reducing electrode gap distance. The maximum power densities were enhanced from 1.9 to 2.4 times according to the experimented electrode gap distances by increasing temperature of $4^{\circ}C$. The electricity generation was increased with the decrease of electrode gap distance. The effects of operating temperature and electrode gap distance were closely connected with the internal resistance of MFC system. That is, the increase of temperature and decrease of electrode gap distance reduced the internal resistance of MFC, resulting in the enhancement of electricity generation of MFC.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.1
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• pp.129-135
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• 2015

The Ubiquitous City (U-City) spatial information technology aimed to provide services freely anytime and anywhere by converging high-tech information & communication technology in urban infrastructure has been available in diverse patterns. In particular, there have been studies on the development of 3D spatial information after selecting and matching key points with stereo images from the many Closed Circuit TV (CCTV) in the U-City. However, the data mostly used in extracting matching points haven't considered external environmental impacts such as illuminance. This study tested how much the matching points needed to construct 3D spatial information with the CCTV whose image quality is dependent upon changes in illuminance fluctuate under the same hardware performances. According to analysis on the number of matching points by illuminance, the number of matching points increased up to 3,000Lux in proportion to the illuminance when IRIS, shutter speed and ISO were fixed. In addition, a border between an object and background became more distinctive. When there was too much light, however, the page became brighter, and noise occurred. Furthermore, it was difficult to name key points because of the collapse of an inter-object border. It appears that if filmed with the study results, the number of matching points would increase.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.91-96
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• 2011

In this paper, a low-power direct-conversion transmitter based on current-mode operation, which satisfies the IEEE 802.15.4 standard, is proposed and implemented in a $0.13{\mu}m$ CMOS technology. The proposed transmitter consists of DACs, LPFs, variable gain I/Q up-conversion mixer, a divide-by-two circuit with LO buffer, and a drive amplifier. By combining DAC, LPF, and variable gain I/Q up-conversion mixer with a simple current mirror configuration, the transmitter's power consumption is reduced and its linearity is improved. The drive amplifier is a cascode amplifier with gain controls and the 2.4GHz I/Q differential LO signals are generated by a divide-by-two current-mode-logic (CML) circuit with an external 4.8GHz input signal. The implemented transmitter has 30dB of gain control range, 0dBm of maximum transmit output power, 33dBc of local oscillator leakage, and 40dBc of the transmit third harmonic component. The transmitter dissipates 10.2mW from a 1.2V supply and the die area of the transmitter is $1.76mm{\times}1.26mm$.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.101-105
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• 2019

The adhesion reliability of the epoxy molding compound (EMC) and the printed circuit board (PCB) interface is critical to the quality and lifetime of the chip package since the EMC protects PCB from the external environment during the manufacturing, storage, and shipping processes. It is necessary to measure adhesion energy accurately to ensure product reliability by optimizing the manufacturing process during the development phase. This research deals with the measurement of EMC/PCB interfacial adhesion energy of chip package that has warpage induced by the coefficient of thermal expansion (CTE) mismatch. The double cantilever beam (DCB) test was conducted to measure adhesion energy, and the spring back force of specimens with warpage was compensated to calculate adhesion energy since the DCB test requires flat substrates. The result was verified by comparing the adhesion energy of flat chip packages come from the same manufacturing process.