• Journal of Computing Science and Engineering
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• v.5 no.4
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• pp.338-345
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• 2011

Nowadays mobile devices are used for various applications such as making voice/video calls, browsing the Internet, listening to music etc. The average battery consumption of each of these activities and the length of time a user spends on each one determines the battery lifetime of a mobile device. Previous methods have provided predictions of battery lifetime using a static battery consumption rate that does not consider user characteristics. This paper proposes an approach to predict a mobile device's available battery lifetime based on usage patterns. Because every user has a different pattern of voice calls, data communication, and video call usage, we can use such usage patterns for personalized prediction of battery lifetime. Firstly, we define one or more states that affect battery consumption. Then, we record time-series log data related to battery consumption and the use time of each state. We calculate the average battery consumption rate for each state and determine the usage pattern based on the time-series data. Finally, we predict the available battery time based on the average battery consumption rate for each state and the usage pattern. We also present the experimental trials used to validate our approach in the real world.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.12
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• pp.43-49
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• 2009

We present an efficient estimation method of the battery lifetime considering various power consumption profiles in wireless sensor nodes. The power profiles in single and periodic modes and the current dissipations in different operating modes are taken into account to find the total current consumption. Also, the self-discharge rate of a battery is taken into account to estimate the battery lifetime of a given sensor node. Finally we present a governing equation for finding the battery lifetime. We believe the proposed estimation method of the battery lifetime can be an efficient and effective method for low power design of sensor nodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.327.2-327.2
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• 2014

CIGS박막 태양전지의 온도에 의한 효율과 전기적 특성 변화를 알아보기 위해 $25^{\circ}C$, $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$에서 각각 100시간을 노출시킨 후 전기적인 특성들을 측정하여 초기 값들과 비교하였다. 태양전지의 온도 스트레스에 의한 특성 및 파라미터들의 변화들을 확인하기 위해 Light I-V와 Minority Carrier의 Lifetime을 측정하여 비교 분석하였다. 실험에 사용한 소자의 초기 파라미터들은 $25^{\circ}C$에서 측정하였고, 단락전류 11mA, 개방전압 0.64V, 곡선인자 60.49%, Lifetime 10.7s 효율 9.17%이다. 각 온도별 노출에 대해 CIGS박막 태양전지의 효율은 $50^{\circ}C$, $100^{\circ}C$에서는 초기 값과 비슷하였고, $150^{\circ}C$, $200^{\circ}C$에서 초기 값 대비 54%, 84% 감소 특성을 보였다. 단락전류는 $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$에서는 크게 변화하는 모습이 나타나지 않았고 $200^{\circ}C$에서 63% 감소하였다. 개방전압, 곡선인자, Lifetime은 효율과 마찬가지로 $150^{\circ}C$, $200^{\circ}C$에서 감소하는 모습이 나타났다. $150^{\circ}C$, $200^{\circ}C$에서 개방전압이 9.3%, 18.7%, 곡선인자는 45.8%, 56.3%정도 감소하였다. Lifetime은 64.4%, 80.1%정도 감소하였다. 이 실험을 통해 개방전압과 곡선인자, Minority Carrier의 Lifetime이 일정 온도부터 온도의 영향을 받아 감소하고, 그 영향으로 효율이 감소하게 되는 것을 확인하였다.

• Applied Microscopy
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• v.46 no.1
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• pp.6-13
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• 2016

Fluorescence lifetime imaging microscopy (FLIM) has been considered an effective technique to investigate chemical properties of the specimens, especially of biological samples. Despite of this advantageous trait, researchers in this field have had difficulties applying FLIM to their systems because acquiring an image using FLIM consumes too much time. Although analog mean-delay (AMD) method was introduced to enhance the imaging speed of commonly used FLIM based on time-correlated single photon counting (TCSPC), a real-time image reconstruction using AMD method has not been implemented due to its data processing obstacles. In this paper, we introduce a real-time image restoration of AMD-FLIM through fast parallel data processing by using Threading Building Blocks (TBB; Intel) and octa-core processor (i7-5960x; Intel). Frame rate of 3.8 frames per second was achieved in $1,024{\times}1,024$ resolution with over 4 million lifetime determinations per second and measurement error within 10%. This image acquisition speed is 184 times faster than that of single-channel TCSPC and 9.2 times faster than that of 8-channel TCSPC (state-of-art photon counting rate of 80 million counts per second) with the same lifetime accuracy of 10% and the same pixel resolution.

• Journal of the Korea Society of Computer and Information
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• v.20 no.12
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• pp.1-8
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• 2015

Wear leveling techniques have been studied to prolong the lifetime of NAND flash memory. Most of studies have used Program/Erase(P/E) cycles as wear index for wear leveling. Unfortunately, P/E cycles could not predict the real lifetime of NAND flash blocks. Therefore, these algorithms have the limited performance from prolonging the lifetime when applied to the SSD. In order to apply the real lifetime, wear leveling algorithms, which use raw Bit Error Rate(rBER) as wear index, have been studied in recent years. In this paper, we propose CrEWL(Cold data identification using raw Bit error rate in Wear Leveling), which uses rBER as wear index to apply to the real lifetime. The proposed wear leveling reduces an overhead of garbage collections by using HBSQ(Hot Block Sequence Queue) which identifies hot data. In order to reduce overhead of wear leveling, CrEWL does not perform wear leveling until rBER of the some blocks reaches a threshold value. We evaluate CrEWL in comparison with the previous studies under the traces having the different Hot/Cold rate, and the experimental results show that our wear leveling technique can reduce the overhead up to 41% and prolong the lifetime up to 72% compared with previous wear leveling techniques.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.499-502
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• 2018

We propose a wireless-powered multihop transmission scheme using inter-node cooperation in a linear network topology. The proposed protocol determines the energy transfer time for each node to make the lifetime of the each node be equal in order to maximize the lifetime of the multihop path. To make the lifetime of each node the same, we apply the flocking algorithm which imitates the behavior of a bird flock flying at the same velocity, so that the lifetime of the nodes is averaged locally. Simulation results show that the proposed algorithm can maximize the lifetime of the multihop path by making all nodes have the same lifetime.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.29 no.3
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• pp.137-143
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• 2018

Objectives: The present study aimed to investigate the relationships among the lifetime incidence of trauma, internalizing symptoms, and quality of life (QoL) in out-of-school youths (OSYs). Methods: We recruited 50 OSYs in South Korea. Participants completed the following surveys: completed Lifetime Incidence of Traumatic Events for children, Youth Self Report, and The KIDSCREEN-27 QoL measure for children and adolescents. Mediation analysis was conducted to test the research hypotheses. Results: The mean lifetime incidence of traumatic events among OSYs was 3.27 (standard deviation, 2.41). Internalizing symptoms significantly mediated the lifetime incidence of trauma and QoL. OSYs with fewer internalizing symptoms exhibited a better QoL in the domain of psychological well-being, although their lifetime incidence of trauma was higher. Conclusion: The results of current study suggest that assessment and therapeutic intervention with regard to internalizing symptoms are needed to increase the QoL of OSYs.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.227-237
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• 2016

Data collection is a key function for wireless sensor networks. There has been numerous data collection scheduling algorithms, but they fail to consider the deep and complex relationship among network lifetime, sink aggregated information and sample cycle for wireless sensor networks. This paper gives the upper bound on the sample period under the given network topology. An optimal schedule algorithm focusing on aggregated information named OSFAI is proposed. In the schedule algorithm, the nodes in hotspots would hold on transmission and accumulate their data before sending them to sink at once. This could realize the dual goals of improving the network lifetime and increasing the amount of information aggregated to sink. We formulate the optimization problem as to achieve trade-off among sample cycle, sink aggregated information and network lifetime by controlling the sample cycle. The results of simulation on the random generated wireless sensor networks show that when choosing the optimized sample cycle, the sink aggregated information quantity can be increased by 30.5%, and the network lifetime can be increased by 27.78%.

• Journal of Korea Foundry Society
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• v.25 no.6
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• pp.233-239
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• 2005

Contact material is widely used in the field of electrical parts. Ag-CdO has a good wear resistance and stable contact resistance. We studied a lifetime of Ag-CdO material because of getting better properties of Ag-CdO using Post-oxidation. The experimental procedure were melting using high frequency induction, heat treatment, rolling and internal oxidation. And we experimented on difference process, Post-oxidaion. Then we tested a lifetime and analysed. We obtained the optimizing oxidation temperature was $750^{\circ}C$. Using Pre-oxidation, coarse oxide and depleted oxidation layer existed but finer oxides were existed and depleted oxidation layer was not using Post-oxidation. In Post-oxidation, The density was 10 $g/cm^{3}$, the hardness was Hv 80 and the adhesive strength was 9000N. The specimen of Post-oxidation had better lifetime properties than that of Pre-oxidation. We predicted that the lifetime of Post-oxidation specimen is more longer twice than that of Pre-oxidation one.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.169-172
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• 2004

The effect of the process parameters on the stable lifetime in rapid thermal firing(RTF) was investigated in order to optimize the process for the Cz-silicon. The process temperature was varied between $700^{\circ}C\;and\;950^{\circ}C$ while the process time was chosen 1 s and 10 s. At below $850^{\circ}C$ the stable lifetime for 10 s is higher than that for 1 s and increases with increasing by the process temperature. However, at over $850^{\circ}C$ the improved stable lifetime is not dependent on the process time and temperature. On the other hand, two high temperature processes in solar cell fabrics are combined with the optimized process and the non-optimized process. The last process determines the stable lifetime. Also, the degraded stable lifetime could be increased by processing in optimized process. The decreased lifetime can increase using the optimized oxidation process, which is a final process in solar cells. Finally, the optimized and non-optimized processes are applied solar cells.