• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1001-1004
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• 2008

This study reviewed the results of utilization of insulation heat curing method using double layer bubble sheet in slab concrete and mass concrete in cold weather environment. First of all, when double layer bubble sheets are applied, it was shown that slab concrete was protected from early freezing by remaining between 6 and $10^{\circ}C$ even in case outside temperature drops $10^{\circ}C$ below zero until the 2nd day from piling, and in the case of mass concrete, with the maximum temperature difference between the center and surface less than $6^{\circ}C$, crack occurrence index was close to 2 and no hydration heat crack occurred by internal constraint. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.317-326
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• 2016

In this paper, a logic eFuse (electrical Fuse) OTP (One-Time Programmable) memory IP (Intellectual Property) using only logic transistors to reduce the development cost and period of OTP memory IPs is designed. To secure the reliability of other IPs than the OTP memory IP, a higher voltage of 2,4V than VDD (=1.5V) is supplied to only eFuse links of eFuse OTP memory cells directly through an external pad FSOURCE coming from test equipment in testing wafers. Also, an eFuse OTP memory cell of which power is supplied through FSOURCE and hence the program power is increased in a two-dimensional memory array of 128 rows by 8 columns being also able to make the decoding logic implemented in small area. The layout size of the designed 1kb eFuse OTP memory IP with the Dongbu HiTek's 110nm CIS process is $295.595{\mu}m{\times}455.873{\mu}m$ ($=0.134mm^2$).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.346-349
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• 2013

This paper describes a triple-input energy harvesting circuit using solar, vibration and thermoelectric energy with MPPT(Maximum Power Point Tracking) control. The designed circuit employs MPPT control to harvest maximum power available from a solar cell, PZT vibration element and thermoelectric generator. The harvested energies are simultaneously combined and stored in a storage capacitor, and then managed and transferred into a sensor node by PMU(Power Management Unit). MPPT controls are implemented using the linear relation between the open-circuit voltage of an energy transducer and its MPP(Maximum Power Point) voltage. The proposed circuit is designed in a CMOS 0.18um technology and its functionality has been verified through extensive simulations. The designed chip occupies $945{\mu}m{\times}995{\mu}m$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.35-38
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• 2018

This paper describes a low-power MPPT interface for DC-type energy harvesting sources. The proposed circuit consists of an MPPT controller, a bias generator, and a voltage detector. The MPPT controller consists of an MPG (MPPT Pulse Generator) with a schmitt trigger, a logic gate operating according to energy type (light, heat), and a sample/hold circuit. The bias generator is designed by employing a beta multiplier structure, and the voltage detector is implemented using a bulk-driven comparator and a two-stage buffer. The proposed circuit is designed with $0.35{\mu}m$ CMOS process. The simulation results show that the designed circuit consumes less than 100nA of current at an input voltage of less than 3V and the maximum power efficiency is 99.7%. The chip area of the designed circuit is $1151{\mu}m{\times}940{\mu}m$.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.309-314
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• 2015

Adsorption of brilliant blue FCF dye from aqueous solution using coconut shell based activated carbon was investigated. Batch experiments were carried out as function of adsorbent dose, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir and Freundlich model. The results indicate that Freundlich model provides the best correlation of the experimental data. Base on the estimated Freundlich constant (1/n=0.129~0.212), this process could be employed as effective treatment method. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy value (-4.81~-10.33 kJ/mol) and positive enthalpy value (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2064-2071
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• 1998

A new digital clock level translator has been designed in order to produce a clock source of the internal logic circuits. The translator output has 50% duty ratio from small sinusoidal input such as TCXO which oscillates itself in poratable components. The circuit consists of positive and negative comparators, RS latch, charge pump, and reference vol- tage generator. It detects pulse width of the output waveform and feedbacks the control signal to the input com-parator. It detects pulse width of the output waveform and feedbacks the control signal to the input com-parator reference, producing output waveform with valid 50% duty ratio of the digital signal level. The designed level translator can be used as a sampling clock source of ADC, PLL and the colck source of the clock synthesizer. The circuit wasdesigned in a 0.8.mu.m analog CMOS technology with double metal, double poly, and BSIM3 circuit simulation model. From our experimental results, a stable operating characteristics of 50 +3% duty ratio was obtained from the sinusoidal input wave of 370 mV.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.350-357
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• 2005

DSRC provides high speed radio link between Road Side Equipment and On-Board Equipment within the narrow communication area. In this paper, a 5.8 GHz up-conversion mixer for DSRC communication system was designed and fabricated using 0.8 m SiGe HBT process technology and IF/LO/RF matching circuits, IF/LO input balun circuits, and RP output balun circuit were all integrated on chip. The chip size of fabricated mixer was $2.7mm\times1.6mm$ and the measured performance was 3.5 dB conversion gain, -12.5 dBm output IP3, 42 dB LO to If isolation, 38 dB LO to RF isolation, current consumption of 29 mA for 3.0 V supply voltage.

• Composites Research
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• v.33 no.4
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• pp.205-212
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• 2020

In this study, HfC was coated on two types of carbon/carbon composites coated with SiC by vacuum plasma spraying(VPS). The experiment was performed using a plasma wind tunnel with heat flux of 5.06 MW/㎡ for 120 s heat flux before and after the coating. The mass ablation rate was calculated through the mass change before and after the test, and the length change was measured by using calipers and high speed camera. The oxidation/ablation behavior were observed by FE-SEM with EDS analysis of the specimens cross section. The plasma wind tunnel test results showed that the coated specimens had low weight loss and length change, and high oxidation/ablation resistance. However, two types of the specimens tested under the same conditions were different in the ablation behavior and ablation rate, and it was evaluated that the cylindrical type had higher oxidation/ablation resistance.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.32-38
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• 2017

Plasticizers play roles in increasing plasticity or fluidity during mixing. Representative plasticizers are DOS, DOA, IDP and BTTN. In particular, BTTN is an energy plasticizer that helps propellant performance and is widely used. However these compounds are sensitive relatively. So, in order to develop insensitive energetic plasticizer, synthesis of one of the derivatives of triazole, 4,5-bis (azido methyl)-(1-butyl)-1,2,3-triazole (1-DABTR), was studied. Also, the compound was characterized by NMR, IR spectroscopy, and physicochemical properties such as glass transition temperature, melting point, decomposition temperature, density, viscosity and impact sensitivity were measured. In addition, the heats of formation (${\Delta}H_f$) of 1-DABTR was also calculated using Gaussian 09.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.805-814
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• 2011

Aluminum plate-fin heat exchangers (ALPHEs) are widely used in petroleum and gas-treated processes. The performance of the ALPHE is strongly dependent on the distribution characteristics of the header and the distributors of each fluid. In this paper, we define the aspect ratio in the side-entry type distributor and analyze the distribution characteristics using CFD-based numerical methods. The phenomena of velocity deviation and distribution with the aspect ratio and the inlet Reynolds number were analyzed by applying relative and absolute maldistribution parameters, and an optimum aspect ratio with the inlet Reynolds number was presented.