• Title/Summary/Keyword: Power-assisted

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Deposition of Al Doped ZnO Films Using ICP-assisted Sputtering on the Plastic Substrate (유도결합 플라즈마 스퍼터링을 이용한 플라스틱 기판 상의 Al이 도핑된 ZnO 박막 증착)

  • Jung, Seung-Jae;Han, Young-Hun;Lee, Jung-Joong
    • Journal of Surface Science and Engineering
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    • v.39 no.3
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    • pp.98-104
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    • 2006
  • Al-doped ZnO (AZO) films were deposited on the plastic substrate by inductively coupled plasma (ICP) assisted DC magnetron sputtering. The AZO films were produced by sputtering a metallic target (Zn/Al) in a mixture of argon and oxygen gases. AZO films with an electrical resistivity of ${\sim}10^3\;{\Omega}cm$ and an optical transmittance of 80% were obtained even at a low deposition temperature. In-situ process control methods were used to obtain stable deposition conditions in the transition region without any hysteresis effect. The target voltage was controlled either at a constant DC power. It was found that the ratio of the zinc to oxygen emission intensity, I (O 777)/I (Zn 481) decreased with increasing the target voltage in the transition region. The $Ar/O_2$ plasma treatment improve the adhesion strength between the polycarbonate substrate and AZO films.

Low Temperature Deposition of ITO Thin Films for Flat Panel Displays by ICP Assisted DC Magnetron Sputtering (유도결합 플라즈마(ICP) Sputtering에 의한 평판 디스플레이(FPD)용 ITO 박막의 저온 증착)

  • 구범모;정승재;한영훈;이정중;주정훈
    • Journal of Surface Science and Engineering
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    • v.37 no.3
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    • pp.146-151
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    • 2004
  • Indium tin oxide (ITO) is widely used to make a transparent conducting film for various display devices and opto-electric devices. In this study, ITO films on glass substrate were fabricated by inductively coupled plasma (ICP) assisted dc magnetron sputtering. A two-turn rf coil was inserted in the process chamber between the substrate and magnetron for the generation of ICP. The substrates were not heated intentionally. Subsequent post-annealing treatment for as-deposited ITO films was not performed. Low-temperature deposition technique is required for ITO films to be used with heat sensitive plastic substrates, such as the polycarbonate and acrylic substrates used in LCD devices. The surface roughness of the ITO films is also an important feature in the application of OLEDs along with the use of a low temperature deposition technique. In order to obtain optimum ITO thin film properties at low temperature, the depositions were carried out at different condition in changing of Ar and $O_2$ gas mixtures, ICP power. The electrical, optical and structural properties of the deposited films were characterized by four-point probe, UV/VIS spectrophotometer, atomic force microscopy(AFM) and x-ray diffraction (XRD). The electrical resistivity of the films was -l0$^{-4}$ $\Omega$cm and the optical transmittance in the visible range was >85%. The surface roughness ( $R_{rms}$) was -20$\AA$.>.

Two-Dimensional Pilot Symbol Assisted Channel Estimation for OFDM Systems over Frequency Selective Rayleigh Fading Channel (주파수 선택적 레일리 페이딩 채널에서 OFDM 시스템을 위한 2-D PSA에 의한 채널 추정)

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    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2001.10a
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    • pp.336-340
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    • 2001
  • In this paper we analyze the performance of 2-D PSAM for wireless OFDM systems. We apply the analysis of single-carrier PSAM to the 2-D time-frequency lattice of OFDM. To estimate channel fading, we use interpolation filter which minimizes the average power of error as compensation method and analyze the affects on the system performance of the pilot symbol pattern on the 2-D tine-frequency lattice. Finally according to the CP and the Doppler frequency, we analyze the performance of 2-D PSA-16QAM for OFDM systems over frequency selective Rayleigh fading channel model.

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Statistical Life Prediction on IASCC of Stainless Steel for PWR Core Internals (가압형 경수로 스테인리스강 내부 구조물의 조사유기 응력부식균열에 대한 통계적 수명 예측)

  • Kim, Sung-Woo;Hwang, Seong-Sik;Lee, Yeon-Ju
    • Korean Journal of Metals and Materials
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    • v.50 no.8
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    • pp.583-589
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    • 2012
  • This work is concerned with a statistical approach to the life prediction on irradiation-assisted stress corrosion cracking (IASCC) of stainless steel (SS) for core internals of a pressurized water reactor (PWR). The previous results of the time-to-failure of IASCC measured on neutron-irradiated stainless steel components were statistically analyzed in terms of stress and irradiation. The accelerating life testing model of IASCC of cold worked Type 316 SS was established based on an inverse power model with two stress-variables, the applied stress and irradiation dose. Considering the variation of the yield strength and applied stress with the irradiation dose in the model, the remaining life of the baffle former bolt was statistically predicted during operation under complex environments of stress and irradiation.

Characterization of Anthraquinone-Based Electron Acceptors for Organic Solar Cells (유기태양전지용 안트라퀴논 기반 전자 받게 분자의 특성 분석)

  • Hyun, Chang-Seok;An, Byeong-Kwan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.4
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    • pp.366-371
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    • 2022
  • Recently many efforts have been made to develop a novel class of non-fullerene electron acceptor materials for high-performance organic solar cells. In this work, anthraquinone derivatives, TMAQ and THAQ, were prepared and their availability as electron acceptor materials for organic solar cells were investigated in terms of optical, thermal, electrochemical properties, and solar cell devices. Compared to TMAQ, a significant bathochromic shift of absorption band was observed for THAQ owing to intramolecular hydrogen-bond-assisted CT interactions. Thanks to the fused aromatic ring structure and benzoquinone unit, both TMAQ and THAQ exhibited a high thermal stability and an efficient electron reduction process. In particular, the intramolecular O-H---O=C hydrogen bond of THAQ plays an important role in improving the thermal stability and electron reduction properties. In the P3HT:acceptor solar cell system, THAQ-based devices had more than ca. 6 times higher power conversion efficiency than TMAQ -based devices. These results serve as a guide for developing high-efficient anthraquinone-based electron acceptor materials.

Short packet communication in underlay cognitive network assisted by an intelligent reflecting surface

  • Pham Ngoc Son;Tran Trung Duy;Pham Viet Tuan;Tan-Phuoc Huynh
    • ETRI Journal
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    • v.45 no.1
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    • pp.28-44
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    • 2023
  • We propose short packet communication in an underlay cognitive radio network assisted by an intelligent reflecting surface (IRS) composed of multiple reconfigurable reflectors. This scheme, called the IRS protocol, operates in only one time slot (TS) using the IRS. The IRS adjusts its phases to give zero received cumulative phase at the secondary destination, thereby enhancing the end-to-end signal-to-noise ratio. The transmitting power of the secondary source is optimized to simultaneously satisfy the multi-interference constraints, hardware limitations, and performance improvement. Simulation and analysis results of the average block error rates (BLERs) show that the performance can be enhanced by installing more reconfigurable reflectors, increasing the blocklength, lowering the number of required primary receivers, or sending fewer information bits. Moreover, the proposed IRS protocol always outperforms underlay relaying protocols using two TSs for data transmission, and achieves the best average BLER at identical transmission distances between the secondary source and secondary destination. The theoretical analyses are confirmed by Monte Carlo simulations.

Performance analysis of SWIPT-assisted adaptive NOMA/OMA system with hardware impairments and imperfect CSI

  • Jing Guo;Jin Lu;Xianghui Wang;Lili Zhou
    • ETRI Journal
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    • v.45 no.2
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    • pp.254-266
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    • 2023
  • This paper investigates the effect of hardware impairments (HIs) and imperfect channel state information (ICSI) on a SWIPT-assisted adaptive nonorthogonal multiple access (NOMA)/orthogonal multiple access (OMA) system over independent and nonidentical Rayleigh fading channels. In the NOMA mode, the energy-constrained near users act as a relay to improve the performance for the far users. The OMA transmission mode is adopted to avoid a complete outage when NOMA is infeasible. The best user selection scheme is considered to maximize the energy harvested and avoid error propagation. To characterize the performance of the proposed systems, closed-form and asymptotic expressions of the outage probability for both near and far users are studied. Moreover, exact and approximate expressions of the ergodic rate for near and far users are investigated. Simulation results are provided to verify our theoretical analysis and confirm the superiority of the proposed NOMA/OMA scheme in comparison with the conventional NOMA and OMA protocol with/without HIs and ICSI.

Resource Allocation and Offloading Decisions of D2D Collaborative UAV-assisted MEC Systems

  • Jie Lu;Wenjiang Feng;Dan Pu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.18 no.1
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    • pp.211-232
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    • 2024
  • In this paper, we consider the resource allocation and offloading decisions of device-to-device (D2D) cooperative UAV-assisted mobile edge computing (MEC) system, where the device with task request is served by unmanned aerial vehicle (UAV) equipped with MEC server and D2D device with idle resources. On the one hand, to ensure the fairness of time-delay sensitive devices, when UAV computing resources are relatively sufficient, an optimization model is established to minimize the maximum delay of device computing tasks. The original non-convex objective problem is decomposed into two subproblems, and the suboptimal solution of the optimization problem is obtained by alternate iteration of two subproblems. On the other hand, when the device only needs to complete the task within a tolerable delay, we consider the offloading priorities of task to minimize UAV computing resources. Then we build the model of joint offloading decision and power allocation optimization. Through theoretical analysis based on KKT conditions, we elicit the relationship between the amount of computing task data and the optimal resource allocation. The simulation results show that the D2D cooperation scheme proposed in this paper is effective in reducing the completion delay of computing tasks and saving UAV computing resources.

Optimization of microwave-assisted extraction process for blue honeysuckle (Lonicera coerulea L.) using response surface methodology (반응표면분석법을 이용한 댕댕이 기능성성분의 마이크로웨이브추출조건 최적화)

  • Park, Daehee;Lee, Jae-Jun;Park, Jongjin;Park, Sanghwan;Lee, Wonyoung
    • Food Science and Preservation
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    • v.24 no.5
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    • pp.623-630
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    • 2017
  • Functional compounds including flavonoids, anthocyanins, polyphneols and antioxidants were extracted from blue honeysuckle (Lonicera caerulea L.) using highly efficient microwave-assisted extraction. And extraction process was modeled and optimized according to response surface methodology (RSM). The independent variables ($X_n$) were ethanol concentration ($X_1$: 0, 25, 50, 75, 100%), irradiation time ($X_2$: 1, 3, 5, 7, 9 min), and microwave power ($X_3$: 60, 120, 180, 240, 300 W). Dependent variables ($Y_n$) were total flavonoid contents ($Y_1$), total anthocyanin contents ($Y_2$), total polyphenol contents ($Y_3$) and antioxidant activity ($Y_4$). Four-dimensional response surface plots were generated based on the fitted second-order polynomial models to get optimal conditions. Estimated optimal conditions for 4 responses were ethanol concentration of 54-72%, irradiation time of 7.1-7.6 min, and microwave power of 243-251 W. Ridge analysis predicted the maximal responses of total flavonoid content, total anthocyanin content, total polyphenol content and antioxidant activity were 38.00 mg RE/g, 6.80 mg CGE/g, 14.90 mg GAE/g, 89.10%, respectively. Verification experiment was carried out at predicted optimal conditions and experimental values for total flavonoid content, total anthocyanin content, total polyphenol content and antioxidant activity were 38.10 mg RE/g, 6.72 mg CGE/g, 14.91 mg GAE/g and 89.13%, respectively. No significant difference was observed between predicted and experimental values, indicating good fitness of fitted model and successful application of RSM.

Performance Analysis of Signal Acquisition in L2C Assisted GPS Receivers (L2C AGPS 수신기의 신호 획득 성능 분석)

  • Song, Seung-Hun;Park, Ji-Won;Park, Ji-Hee;Sung, Tae-Kyung
    • Journal of Institute of Control, Robotics and Systems
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    • v.17 no.1
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    • pp.61-67
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    • 2011
  • The GPS new civil signal is modulated on the L2 carrier at a frequency of 1227.6MHz. The L2C signal is composed of two multiplexed code signals, which include CM code with a 10,230 chip sequency repeating every 20ms, and CL code which has a 767,250 chip sequency repeating every 1.5 seconds. Thus, the new civil signal have much improved cross correlation properties so that the position fixing can be possible even with very weak signals. However, it requires very long acquisition time because of its long code length. This paper presents an efficient signal acquisition method for L2C AGPS receiver. Snapshot mode and coarse time assistance are assumed and total integration time is given by 1.5 sec. By SNR worksheet and computer simulation, it is proven that L2C signal can be acquired with very weak power less than -150dBm. Considering the acquisition time and the sensitivity, it is recommended that the highest power signal is acquired with CM code first to reduce TTFF. By the timing synchronization, at this time, search space of the code phase for other signals can be greatly reduced so that CL code can be used in signal acquisition to maximize sensitivity with small computation.