• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.135-142
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• 2021

In this work, multi-turn wings and guide plates are installed on recycled aggregate crushing devices to improve existing low recycled aggregate quality. Simulation analysis to evaluate the crushing efficiency of the new device shows enhanced crushing efficiency since the installation of guide plates shreds most of the inputs inside the crushing drum, and the multi-turn wings and guide plates induce rebound and circulation of the aggregate. Through this, the new device was found to be more economical and efficient than the existing recycled aggregate crushing device. Also, the amount of cement paste and mortar attached to the surface of the aggregate was smaller than that of the existing recycled aggregate, and it was found that the mechanical properties and elastic modulus deterioration were reduced. However, the carbonation resistance of concrete was not improved to the level of natural aggregates due to the remaining tiny cement paste and mortar on the surface of the new recycled aggregate. Therefore, it is deemed necessary to further research and experiment such as device improvement or binder development to reduce durability degradation of concrete mixed with new recycled aggregate.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.5
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• pp.12-17
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• 2011

In this work, the analog performances of n-MOSFET fabricated on strained-Si/relaxed Si buffer layer with Ge mole fractions and thermal annealing temperatures after device fabrication have been characterized in Depth. The effective electron mobility was increased with the increase of Ge mole fraction for all annealing temperatures. However the effective electron mobility was decreased at the Ge mole fraction of 32%. The analog performances were enhanced with the increase of Ge mole fraction at the room temperature but they were degraded at the Ge mole fraction of 32%. Since the degradation of the effective electron mobility of strained-Si layer is more significant than one of conventional Si layer at elevated temperature, the degradation of analog performances of SGOI devices were increased than those of SOI devices.

• Journal of the Korean Vacuum Society
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• v.14 no.1
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• pp.29-34
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• 2005

The degradation of the SiGe hetero-junction bipolar transistor(HBT) properties in SiGe BiCMOS process was investigated in this paper. The SiGe HBT prepaired by SiGe BiCMOS process, unlike the conventional one, showed the degraded DC characteristics such as the decreased Early voltage, the decreased collector-emitter breakdown voltage, and the highly increased base leakage current. Also, the cutoff frequency(f/sub T/) and the maximum oscillation frequency(f/sub max/) representing the AC characteristics are reduced to below 50%. These deteriorations are originated from the change of the locations of emitter-base and collector-base junctions, which is induced by the variation of the doping profile of boron in the SiGe base due to the high-temperature source-drain annealing. In the result, the junctions pushed out of SiGe region caused the parastic barrier formation and the current gain decrease on the SiGe HBT device.

• Journal of Conservation Science
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• v.33 no.6
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• pp.553-564
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• 2017

This report compared and analyzed the degree of surface change and results of a deterioration experiment to assess the possibility of using Dobak glue as an adhesive in the fossilizing treatment of the paint layer in earthen mural paintings. The weathering experiments were performed with a color-difference meter (CR-400, MINOLTA). After the experiment, Cinnabar 3% specimens, which exhibited diverse changes in the durability test, were additionally tested with a reflection-transmission device (CARY-5000, AGILENT). Post UV degradation, most of the Dobak-glue samples exhibited lesser color change than animal-glue samples, and after moisture absorption and drying, the 0.5% and 3% Dobak samples displayed a lower degree of change in the value of color difference. Furthermore, results of the reflection-transmission test after deterioration indicated that Dobak glue presented a lesser color change than animal glue. Therefore, if Dobak glue is used as a consolidating agent, discoloration on account of degradation is minimal.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.37-48
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• 2010

The seismic control effect of reinforced concrete structures with low energy dissipating capacity due to stiffness degradation is investigated through nonlinear time history analysis. The primary structure is idealized as a SDOF system of modified Takeda hysteresis rule and an elasto-perfectly-plastic nonlinear spring is added to represent a hysteretic damping device. Based on statistics of the numerical analysis, equivalent linearization techniques are evaluated, and empirical equations for response prediction are proposed. As a result, estimation of the ductility demand with proposed empirical equations is more desirable than the equivalent linearization techniques. The optimal yield strengths based on empirical equations are significantly different from the optimal yield strength of elasto-perfectly-plastic systems. Also, the results indicate that the reduction effect of the ductility demand is more remarkable for smaller natural periods.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.124-127
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• 2000

A new triode type Ti-silicided Si FEA(field emitter array) was realized by Ti-silicidation of Ti coated Si FEA and its field emission properties were investigated. In the fabricated device, the field emission properties through the unit pixel with $200{\mu\textrm{m}}{\times}200{$\mu\textrm{m}}$ tip array in the area of $1000{\mu\textrm{m}}{\times}1000{$\mu\textrm{m}}$ were as follows : the turn-on voltage was about 70V under high vacuum condition of $10^8Torr$, and the field emission current and steady state current degradation were about 2nA/tip and 0.3%/min under the bias of $V_A=500V\;and\;V_G=150V$. The low turn-on voltage and the high current stability during long term operation of the Ti silicided Si FEA were due to the thermal and chemical stability and the low work function of silicide layer formed at the surface of Si tip.

• The KIPS Transactions:PartD
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• v.14D no.7
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• pp.719-726
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• 2007

Recently, NAND flash memory has been used for a storage device in various mobile computing devices such as MP3 players, mobile phones and laptops because of its shock-resistant, low-power consumption, and none-volatile properties. However, due to the very distinct characteristics of flash memory, disk based systems and applications may result in severe performance degradation when directly adopting them on flash memory storage systems. Especially, when a B-tree is constructed, intensive overwrite operations may be caused by record inserting, deleting, and its reorganizing, This could result in severe performance degradation on NAND flash memory. In this paper, we propose an efficient buffer management scheme, called IBSF, which eliminates redundant index units in the index buffer and then delays the time that the index buffer is filled up. Consequently, IBSF significantly reduces the number of write operations to a flash memory when constructing a B-tree. We also show that IBSF yields a better performance on a flash memory by comparing it to the related technique called BFTL through various experiments.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1428-1435
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• 2019

The total ionizing dose (TID) and non ionizing energy loss (NIEL) effects of 100 MeV phosphorous ($P^{7+}$) and 80 MeV nitrogen ($N^{6+}$) ions on 200 GHz silicon-germanium heterojunction bipolar transistors (SiGe HBTs) were examined in the total dose range from 1 to 100 Mrad(Si). The in-situ I-V characteristics like Gummel characteristics, excess base current (${\Delta}I_B$), net oxide trapped charge ($N_{OX}$), current gain ($h_{FE}$), avalanche multiplication (M-1), neutral base recombination (NBR) and output characteristics ($I_C-V_{CE}$) were analysed before and after irradiation. The significant degradation in device parameters was observed after $100MeV\;P^{7+}$ and $80MeV\;N^{6+}$ ion irradiation. The $100MeV\;P^{7+}$ ions create more damage in the SiGe HBT structure and in turn degrade the electrical characteristics of SiGe HBTs more when compared to $80MeV\;N^{6+}$. The SiGe HBTs irradiated up to 100 Mrad of total dose were annealed from $50^{\circ}C$ to $400^{\circ}C$ in different steps for 30 min duration in order to study the recovery of electrical characteristics. The recovery factors (RFs) are employed to analyse the contribution of room temperature and isochronal annealing in total recovery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.497-505
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• 2015

Existing Wi-Fi networks require users to follow network settings of the AP (Access Point), resulting in inconveniences for users, and the password of the AP is shared by all users connected to the AP, causing security information leaks as time goes by. We propose, in this work, a personalized secure Wi-Fi network, in which each user is assigned her own virtual Wi-Fi network. One virtual Wi-Fi per user makes the user-centric network configuration possible. A user sets a pair of her own SSID and password on her device a priori, and the AP publishes its public key in a suitable way. The AP also maintains an open Wi-Fi channel, to which users can connect anytime. On user's request, the user device sends a connection request message containing a pair of SSID and password encrypted with the AP's public key. Receiving the connection request message, the AP instantiates a new virtual AP secured with the pair of SSID and password, which is dedicated to that single user device. This virtual network is securer because the password is not shared among users. It is more convenient because the network adapts itself to the user device. Experiments show that these advantages are obtained with negligible degradation in the throughput performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.28-34
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• 2011

In this paper, we proposed the architecture of the Hybrid Quadrature Polar transmitter which has the wideband characteristics available for the SRD(Short Range Device). First, we developed the simulation environment and carried out performance degradation analysis. Second, we considered the slewrate of the VVA(Voltage Variable Attenuator), time delay between magnitude signal and phase signal and the number of bits for DAC(Digital-to-Analog Converter) as the main performance factors. Then we obtained the minimum required values to meet the transmitting performance requirements of 3GPP standards through simulation results. Based on these results, we implemented the Wideband Hybrid Quadrature Polar transmitter platform and varified the performance requirements through practical measurement.