• Nuclear Engineering and Technology
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• v.39 no.5
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• pp.591-602
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• 2007

The results of Reactivity-Initiated Accidents (RIA) experiments have been analysed and the main variables affecting the fuel failure propensity identified. Fuel burn-up aggravates the mechanical loading of the cladding, while corrosion, or better the hydrogen absorbed in the cladding as a consequence of corrosion, may under some conditions make the cladding brittle and more susceptible to failure. Experiments point out that corrosion impairs the fuel resistance for RIA transient occurring at cold conditions, whereas there is no evidence of important embrittlement effects at hot conditions, unless the cladding was degraded by oxide spalling. A fuel failure threshold correlation has been derived and compared with experimental data relevant for BWR and PWR fuel. The correlation can be applied to both cold and hot RIA transients, account taken for the lower ductility at cold conditions and for the different initial enthalpy. It can also be used for non-zero power transients, provided that a term accounting for the start-up power is incorporated. The proposed threshold is easy to use and reproduces the results obtained in the CABRI and NSRR tests in a rather satisfactory manner. The behaviour of advanced PWR alloys and of MOX fuel is discussed in light of the correlation predictions. Finally, a probabilistic approach has been developed in order to account for the small scatter of the failure predictions. This approach completes the RIA failure assessment in that after determining a best estimate failure threshold, a failure probability is inferred based on the spreading of data around the calculated best estimate value.

• Journal of Power System Engineering
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• v.20 no.4
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• pp.32-37
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• 2016

This paper proposes two measurement methods for injured rate of fish surface using color image segmentation method based on K-means clustering algorithm and Otsu's threshold algorithm. To do this task, the following steps are done. Firstly, an RGB color image of the fish is obtained by the CCD color camera and then converted from RGB to HSI. Secondly, the S channel is extracted from HSI color space. Thirdly, by applying the K-means clustering algorithm to the HSI color space and applying the Otsu's threshold algorithm to the S channel of HSI color space, the binary images are obtained. Fourthly, morphological processes such as dilation and erosion, etc. are applied to the binary image. Fifthly, to count the number of pixels, the connected-component labeling is adopted and the defined injured rate is gotten by calculating the pixels on the labeled images. Finally, to compare the performances of the proposed two measurement methods based on the K-means clustering algorithm and the Otsu's threshold algorithm, the edge detection of the final binary image after morphological processing is done and matched with the gray image of the original RGB image obtained by CCD camera. The results show that the detected edge of injured part by the K-means clustering algorithm is more close to real injured edge than that by the Otsu' threshold algorithm.

• Current Optics and Photonics
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• v.8 no.1
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• pp.65-71
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• 2024

We present a Yb-doped narrow-linewidth polarization-maintaining all-fiber amplifier that achieves a high mode-instability (MI) threshold, high output power, and 9.7-GHz spectral linewidth. Six wavelength-multiplexed laser diodes are used to pump this amplifier. First, we construct a high-power fiber amplifier based on a master oscillator-power amplifier configuration for experiments. Subsequently, we examine the MI threshold by individually pumping the amplifier with wavelengths of 976, 974, 981, 974, and 981 nm respectively. The experimental results demonstrate that the amplifier exhibits a high MI threshold (>3.5 kW) when pumped with a combination of wavelengths at 974 and 981 nm. Afterward, we inject an optimized phase-modulated seed with a nearly flat-top spectrum into this amplifier. Ultimately, laser output of 3.2 kW and 9.7 GHz are obtained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.444-461
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• 2016

A power-saving mechanism for smartphone devices is developed by analyzing the features of data that are received from Internet of Things (IoT) sensors devices to optimize the data processing policies. In the proposed GreenIoT architecture for power-saving in IoT, the power saving and feedback mechanism are implemented in the IoT middleware. When the GreenIoT application in the power-saving IoT architecture is launched, IoT devices collect the sensor data and send them to the middleware. After the scanning module in the IoT middleware has received the data, the data are analyzed by a feature evaluation module and a threshold analysis module. Based on the analytical results, the policy decision module processes the data in the device or in the cloud computing environment. The feedback mechanism then records the power consumed and, based on the history of these records, dynamically adjusts the threshold value to increase accuracy. Two smart living applications, a biomedical application and a smart building application, are proposed. Comparisons of data processed in the cloud computing environment show that the power-saving mechanism with IoT architecture reduces the power consumed by these applications by 24% and 9.2%.

• The KIPS Transactions:PartA
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• v.17A no.3
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• pp.121-126
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• 2010

This paper proposes a low-power MOS current-mode logic circuit with the low voltage swing technology and the high-threshold sleep-transistor. The sleep-transistor is used to high-threshold voltage PMOS transistor to minimize the leakage current. The $16{\times}16$ bit parallel multiplier is designed by the proposed circuit structure. Comparing with the conventional MOS current-model logic circuit, the circuit achieves the reduction of the power consumption in sleep mode by 1/104. The proposed circuit is achieved to reduce the power consumption by 11.7% and the power-delay-product by 15.1% compared with the conventional MOS current-model logic circuit in the normal mode. This circuit is designed with Samsung $0.18\;{\mu}m$ standard CMOS process. The validity and effectiveness are verified through the HSPICE simulation.

• ETRI Journal
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• v.27 no.6
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• pp.685-690
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• 2005

DC and RF characteristics of $0.15{\mu}m$ GaAs power metamorphic high electron mobility transistors (MHEMT) have been investigated. The $0.15{\mu}m{\times}100{\mu}m$ MHEMT device shows a drain saturation current of 480 mA/mm, an extrinsic transconductance of 830 mS/mm, and a threshold voltage of -0.65 V. Uniformities of the threshold voltage and the maximum extrinsic transconductance across a 4-inch wafer were 8.3% and 5.1%, respectively. The obtained cut-off frequency and maximum frequency of oscillation are 141 GHz and 243 GHz, respectively. The $8{\times}50{\mu}m$ MHEMT device shows 33.2% power-added efficiency, an 18.1 dB power gain, and a 28.2 mW output power. A very low minimum noise figure of 0.79 dB and an associated gain of 10.56 dB at 26 GHz are obtained for the power MHEMT with an indium content of 53% in the InGaAs channel. This excellent noise characteristic is attributed to the drastic reduction of gate resistance by the T-shaped gate with a wide head and improved device performance. This power MHEMT technology can be used toward 77 GHz band applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.889-897
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• 2004

In this Paper, we propose the algorithm to provide stable communication in OFDM system under the highly interfered environment by the same/different systems which use same bandwidth or other jamming signal, i.e., radar signal. The proposed Adaptive Subcarrier Assignment(ASA) method first estimates the received power of each subcarrier in the block or fin or OFDM receiver. Then we estimate the threshold level which is the average power of the transmitted OFDM signal with AWGN. The highly interfered subcarriers, which are greater powers than the specified threshold level, are rejected in the next transmission and the only non-interfered subcarriers are selected as the next transmission. This algorithm provides stable communication in any OFDM systems without changing the physical layer under the highly interfered communication environment. We estimated the status of the subcarriers based on the bandwidth and power of the jamming signal and showed the performance of the proposed algorithm by the simulation.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.165-173
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• 2011

In Mobile Ad-hoc Network(MANET), mobile nodes are operated by limited batteries. Therefore, it is very important to consume the battery power efficiently to prevent termination of the network. In this paper, we propose Energy-aware Dynamic Source Routing(EDSR) which is based on the Dynamic Source Routing(DSR) to increase the packet transmission and lifetime of the network. If the battery power of a node reaches threshold level, then the node gives up the function of relaying to save battery power except as a source and a destination node. While the conventional DSR doesn't consider the battery consumptions of the nodes, EDSR blocks the nodes from relaying whose battery powers are below the threshold level. Simulation results show the proposed EDSR is more efficient in packet transmission and network lifetime through the balanced battery consumption of the mobile nodes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.107-112
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• 2015

A smart phone and the number of wireless terminals are mobile-to the nature of the AP mobility are many call transfer between wireless terminals and AP (Access Point). Each wireless terminal that is the call processing process for each is relatively large to cause the wireless traffic, and a factor that inhibits the efficient use of the radio band on the AP. In this paper, we use the power intensity threshold and threshold timer of the AP received by the mobile station to reduce the amount of switching traffic between the AP's cause and traffic generation factors between the wireless device and the AP that can effectively utilize the radio traffic from the AP the measures proposed. The proposed method and the conventional method is improved by simulation to handle the amount of radio traffic from the AP it was confirmed that it is possible to effectively utilize the whole of the radio band.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1138-1147
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• 2018

Delayed hydride cracking (DHC) is an important failure mechanism for Zircaloy tubes in the demanding environment of nuclear reactors. The threshold stress intensity factor, $K_{IH}$, and critical hydride length, $l_C$, are important parameters to evaluate DHC. Theoretical models of them are developed for Zircaloy tubes undergoing non-homogenous temperature loading, with new stress distributions ahead of the crack tip and thermal stresses involved. A new stress distribution in the plastic zone ahead of the crack tip is proposed according to the fracture mechanics theory of second-order estimate of plastic zone size. The developed models with fewer fitting parameters are validated with the experimental results for $K_{IH}$ and $l_C$. The research results for radial cracking cases indicate that a better agreement for $K_{IH}$ can be achieved; the negative axial thermal stresses can lessen $K_{IH}$ and enlarge the critical hydride length, so its effect should be considered in the safety evaluation and constraint design for fuel rods; the critical hydride length $l_C$ changes slightly in a certain range of stress intensity factors, which interprets the phenomenon that the DHC velocity varies slowly in the steady crack growth stage. Besides, the sensitivity analysis of model parameters demonstrates that an increase in yield strength of zircaloy will result in a decrease in the critical hydride length $l_C$, and $K_{IH}$ will firstly decrease and then have a trend to increase with the yield strength of Zircaloy; higher fracture strength of hydrided zircaloy will lead to very high values of threshold stress intensity factor and critical hydride length at higher temperatures, which might be the main mechanism of crack arrest for some Zircaloy materials.