Browsing by Issue Date, starting with "2018-10-15"

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Surface evolution and effect of V/III ratio modulation on etch-pit-density improvement of thin AlN templates on nano-patterned sapphire substrates by metalorganic chemical vapor deposition
(2018-10-15)
Wang, Tzu-Yu
;
Tasi, Chi-Tsung
;
Lin, Ku-Yen
;
Ou, Sin-Liang
;
Horng, Ray-Hua
A low defect-density AlN template film using V/III ratio modulation and nano-patterned sapphire substrate (NPSS) was achieved by metalorganic chemical vapor deposition. In contrast to conventional high-quality AlN/NPSS obtained with high coalescence thickness ( > 6 mu m) using high growth temperatures ( >= 1250 degrees C), this study reveals the high crystallinity of AlN with the lower thickness of 2.55 mu m grown under a lower temperature of 1130 degrees C. It could effectively increase the heater lifetime and reduce the epi-wafer warpage. The growth of AlN/NPSS dominated by epitaxial lateral overgrowth achieves a dramatic reduction of full width at half maximum values along (10 (1) over bar2) plane from 1640 to 714 arcsec, and lowest dislocation density of approximately 1 x 10(8) cm(-2), as well as a ultra-low etching pit density of 2.3 x 10(5) cm(-2). The crack-free AlN/NPSS with a compressive stress owing to the tensile stress was relaxed by the existence of some key-shaped holes upon the patterned region. Details of the surface evolution, mechanism and dislocation behavior of AlN/NPSS will be discussed and these results demonstrate this low-defect template technique of high potential for AlGaN-based device applications.
Task-related EEG and HRV entropy factors under different real-world fatigue scenarios
(2018-10-15)
Lin, Chin-Teng
;
Nascimben, Mauro
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King, Jung-Tai
;
Wang, Yu-Kai
;
腦科學研究中心
We classified the alertness levels of 17 subjects in different experimental sessions in a six-month longitudinal study based on a daily sampling system and related alertness to performance on a psychomotor vigilance task (PVT). As to our best knowledge, this is the first EEG-based longitudinal study for real-world fatigue. Alertness and PVT performance showed a monotonically increasing relationship. Moreover, we identified two measures in the entropy domain from electroencephalography (EEG) and heart rate variability (HRV) signals that were able to identify the extreme classes of PVT performers. Wiener entropy on selected leads from the frontal-parietal axis was able to discriminate the group of best performers. Sample entropy from the HRV signal was able to identify the worst performers. This joint EEG-HRV quantification provides complementary indexes to indicate more reliable human performance. (C) 2018 Elsevier B.V. All rights reserved.
Bioinorganic Chemistry of the Natural [Fe(NO)(2)] Motif: Evolution of a Functional Model for NO-Related Biomedical Application and Revolutionary Development of a Translational Model!
(2018-10-15)
Lu, Tsai-Te
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Wang, Yun-Ming
;
Hung, Chen-Hsiung
;
Chiou, Show-Jen
;
Liaw, Wen-Feng
Identification of the distinctive electron paramagnetic resonance signal at g = 2.03 in the yeast cells and liver of mice treated with carcinogens opened the discovery and investigation of the natural [Fe(NO)(2)] motif in the form of dinitrosyliron complexes (DNICs). In this Viewpoint, a chronological collection of the benchmark for the study of DNIC demonstrates that the preceding study of its biological synthesis, storage, transport, transformation, and function related to NO physiology inspires the biomimetic study of structural and functional models supported by thiolate ligands to provide mechanistic insight at a molecular level. During the synthetic, spectroscopic, and theoretical investigations on the structure-to-reactivity relationship within DNICs, control of the Fe-NO bonding interaction and of the delivery of NO+/(NO)-N-center dot/HNO/NO- by the supporting ligands and nuclearity evolves into the "redesign of the natural [Fe(NO)(2)] motif" as a strategy to develop DNICs for NO-related biomedical application and therapeutic approach. The revolutionary transformation of covalent a [Fe(NO)(2)] motif into a translational model for hydrogenase, triggered by the discovery of redox interconversion among [{Fe(NO)(2)}(9)-L-center dot] <-> {Fe(NO)(2)}(9) <-> {Fe(NO)(2)}(10) <-> [{Fe(NO)(2)}(10)-L-center dot](-) echoes the preceding research journey on [Fe]/[NiFe]-hydrogenase and completes the development of an electrodeposited-film electrode for electrocatalytic water splitting. Through the 50-year journey, bioinorganic chemistry of DNIC containing the covalent [Fe(NO)(2)] motif and noninnocent/labile NO ligands highlights itself as a unique metallocofactor to join the longitudinal study between biology/chemistry/biomedical application and the lateral study toward multielectron (photo/electro)catalysis for industrial application. This Viewpoint discloses the potential [Fe(NO)(2)] motif awaiting continued contribution in order to emerge as a novel application in the next 50 years, whereas the parallel development of bioinorganic chemistry, guided by inspirational Nature, moves the science forward to the next stage in order to benefit the immediate needs for human activity.
Helical pitch-dependent electro-optics of optically high transparent nano-phase separated liquid crystals
(2018-10-15)
Pagidi, Srinivas
;
Manda, Ramesh
;
Lim, Young Jin
;
Song, Seong Min
;
Yoo, Hyesun
Feeble light leakage in a dark state of conventional optically isotropic liquid crystal (OILC) device has a strong impact on the contrast ratio of a liquid crystal (LC) device. In order to overcome such intrinsic problem, we proposed an OILC in which the LC directors inside droplets are twisted by introducing chirality. The light leakage is effectively suppressed by matching the refractive indices between LC and polymer matrix; consequently, we achieved a high contrast ratio, 1:1401. Interestingly, the on-state transmittance is enhanced by similar to 49% compared to conventional OILC. The response time was also improved and the hysteresis was suppressed to be negligible. The improved electro-optic performances of the proposed OILC device would give diverse applications in upcoming flexible display and various photonic devices. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
An Analysis of the Performance of ML Blind OFDM Symbol Timing Estimation
(2018-10-15)
Lin, David W.
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Symbol timing offset (STO) estimation constitutes an important part in orthogonal frequency-division multiplexing (OFDM) signal synchronization, and many blind methods based on the maximum likelihood (ML) principle have been proposed. A theoretical analysis of the estimation performance, however, is very difficult, due in part to the discrete nature of the STO. As a result, most studies on OFDM STO estimation have relied only on computer simulation for performance evaluation. This paper presents a theoretical performance analysis for ML-based blind OFDM STO estimation. We start with a review of the formulation of ML blind STO estimation problem and its solution. We then conduct the said performance analysis. The analysis turns out to involve a study of the eigenvalues of some matrix functions of the autocorrelation of the received signal. As the general case leads to highly complicated mathematics, we treat the case of full-band OFDM in additive white Gaussian noise in more detail. In this case, we are able to obtain mathematically tractable bounds and approximation to the estimation error probability and the corresponding mean-square error. In high signal-to-noise ratio (SNR), these bounds and approximation show inverse power-law dependence on the SNR. We also compare the bounds with simulation results and with an existing approximation in the literature.
Contemporary sea level rise rates around Malaysia: Altimeter data optimization for assessing coastal impact
(2018-10-15)
Hamid, Amalina Izzati Abdul
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Din, Ami Hassan Md
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Hwang, Cheinway
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Khalid, Nur Fadila
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Tugi, Astina
The increase of anthropogenic activities has triggered global sea level rise to threaten many low-lying and unprotected coastal areas. Without measures, global sea levels will continue to rise at an accelerating rate in the 21st century. This paper quantifies sea level trends around the Malaysian seas using measurements from multiple altimeter missions over 1993-2015. Sea level anomalies (SLAs) are determined using data from the Radar Altimeter Database System (RADS) covering 8 altimeter missions. We use an enhanced processing strategy to optimize sea surface heights from RADS for the derivation of SLAs, including filtering, data gridding and moving average. Tidal height measurements at eight tide gauge stations around Peninsular Malaysia and East Malaysia are used to assess SLAs from altimetry. Our assessment results in similar patterns of SLAs, high correlation coefficients (> 0.9) and small (few cm) root mean square differences (RMSE) between SLAs from altimetry and tide gauges over the same period. Sea level trends are determined by the robust fit regression analysis for the SLA time series. Our result shows that sea level rise trends around Malaysia range from 3.27 +/- 0.12 mm yr(-1) off eastern Malaysia to 4.95 +/- 0.15 mm yr(-1) west of Malaysia. Over 1993-2015, the mean rising rate around Malaysia is 4.22 +/- 0.12 mm yr(-1), and the cumulative sea level rise is 0.05 m. This paper predicts the impact of such rising sea levels on environment, urban planning and climatology in the coastal areas of Malaysia.
Structure-preserving Gamma QR and Gamma-Lanczos algorithms for Bethe-Salpeter eigenvalue problems
(2018-10-15)
Guo, Zhen-Chen
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Li, Tiexiang
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Zhou, Ying-Ying
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應用數學系
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Department of Applied Mathematics
To solve the Bethe-Salpeter eigenvalue problem with distinct sizes, two efficient methods, called Gamma QR algorithm and Gamma-Lanczos algorithm, are proposed in this paper. Both algorithms preserve the special structure of the initial matrix. H = [(-(B) over bar) (A) (-(A) over bar) (B)], resulting the computed eigenvalues and the associated eigenvectors still hold the properties similar to those of dr. Theorems are given to demonstrate the validity of the proposed two algorithms in theory. Numerical results are presented to illustrate the superiorities of our methods. (C) 2018 Elsevier B.V. All rights reserved.
Covariant cubic approximation for many-body electronic systems
(2018-10-15)
Rosenstein, Baruch
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Li, Dingping
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電子物理學系
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Department of Electrophysics
An approximation scheme determining the excitations of an electronic model on the lattice with pairwise interactions is proposed. A systematic truncation of the set of Dyson-Schwinger equations for correlators, supplemented by a "covariant" calculation of correlators lead to a converging series of approximates. The covariance preserves all the Ward identities among correlators describing various condensed matter probes. It is shown that the third-order approximant of this kind beyond classical and Gaussian (Hartree-Fock) is precise enough and due to several fortunate features the complexity of calculation is surprisingly low so that a realistic material computation might be feasible. Focus here is on the electron field correlator describing the electron (hole) excitations measured in photoemission and other probes. The scheme is tested on several solvable benchmark models.
Multifunctional GQDs-Concanavalin A@Fe3O4 nanocomposites for cancer cells detection and targeted drug delivery
(2018-10-16)
Chowdhury, Ankan Dutta
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Ganganboina, Akhilesh Babu
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Tsai, Yuan-chung
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Chiu, Hsin-cheng
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Doong, Ruey-an
Multifunctional nanocomposites containing intrinsic property for serving as the sensing elements as well as targeted nanoconjugates are highly preferred in various therapeutic applications. In this work, nanocomposites of graphene quantum dots (GQDs) and Fe3O4 with conjugation of lectin protein, concanavalin A, to form GQD-ConA@ Fe3O4 nanocomposites are developed for both detection of cancer cell and release of drugs to HeLa cells. The GQD-ConA@ Fe3O4 nanocomposites deposited on Pt electrode can detect cancerous HeLa cells over normal endothelial cells with a dynamic linear range of 5 x 10(2) to 1 x 10(5) cells mL(-1) with a detection limit of 273 cell mL(-1). The GQD-ConA@ Fe3O4 also can serve as nanocarriers for loading and delivering doxorubicin (Dox). The in vitro cell images show that the Dox concentration in HeLa cells is enhanced more than double in the presence of external magnetic field due to the incorporation of Fe3O4 in the nanocarrier. The cytotoxicity assay indicates that the susceptibility of cancerous HeLa cells to Dox is 13% higher than that of normal cells, confirming the selective role of ConA in nanocarriers. Results clearly indicate the GQD-ConA@ Fe3O4 nanocomposites as a promising material for cancer cell detection and targeted Dox release toward HeLa cells which can serve as the multifunctional platform for novel cancer cell diagnostic and therapeutic applications. (C) 2018 Elsevier B.V. All rights reserved.
奈米組成物、其製造方法及其用途
(2018-10-16)
黃唯婷
;
江俞謙
;
劉典謨
本發明提供一種奈米組成物、其製造方法及其用途。其製造方法包含：混合雙性幾丁聚醣的第一溶液及含有抗癌成分的第二溶液，其中抗癌成分包含吉西他濱、薑黃素、其衍生物或其組合；使雙性幾丁聚醣藉由自組裝而包覆抗癌成分，以形成奈米粒子；以及將對一癌症具專一性的標靶分子與該奈米粒子進行嫁接，以得到奈米組成物。本發明之奈米組成物在乾燥後回溶於水相仍保有乾燥前的型態及性質，便於長期保存及運送。另外，本發明亦提供吉西他濱與去氧甲基薑黃素的較佳比例，藉其協同效應提升治療效果。
Reorientation of OH-group connecting bifurcated H-bond acceptors in liquid water
(2018-10-16)
Tang, Ping-Han
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Fan, Yi-Yao
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Hsu, Wei-Lin
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Wu, Ten-Ming
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物理研究所
The OH-group connecting bifurcated H-bond (HB) acceptors is one case of the three-centered HBs found in physical and biological systems. An example is the transition state of molecular reorientation jump mechanism in liquid water, ionic solutions, and hydration shells of biomolecules. In this Letter, the orientational time correlation functions of these special OH-groups in water were studied by performing molecular dynamics simulations and using the normal-mode approach developed recently. The reorientation angle of the OH-group before entering the diffusive regime can be estimated through the plateau in the mean-square rotational displacement calculated by several methods.
二維材料的製作方法
(2018-10-16)
侯拓宏
;
黃俊宏
本發明二維材料的製作方法包含以下步驟：於基板上形成具有至少一二維材料元素之薄膜；於薄膜上形成至少一包覆層；於包覆層形成後將薄膜進行退火，以形成二維材料膜。
非揮發性記憶體及其操作方法
(2018-10-16)
莊紹勳
;
謝易叡
本記憶體的第一儲存單元包括第一阻變式電晶體以及第一控制電晶體。第一儲存單元可使用第一阻變式電晶體進行儲存，從而做為快閃記憶體(flash memory)來使用。第二阻變式電晶體與第二控制電晶體可組成與第一儲存單元雷同的的第二儲存單元。隔離電晶體連接在第一儲存單元和第二儲存單元之間。然後，多個與上述相同架構的儲存單元可串聯並形成陣列。多個陣列可再形成為一個記憶體電路。隔離電晶體可具有與第一及第二控制電晶體相同的結構，其用以防止記憶體電路中的溜徑電流。
用於包覆肢體之包覆裝置
(2018-10-16)
楊秉祥
;
賴建穆
本發明提出一種用於包覆肢體之包覆裝置。所述包覆裝置包含具有第一轉環、第二轉環及複數個軸件之轉動模組；驅動第一轉環及第二轉環中至少其一進行轉動之驅動模組；以及設置於該第二轉環上之至少一按壓裝置。在所述包覆裝置中，第一轉環及第二轉環係相間隔地同軸設置，且該複數個軸件之每一個之兩端係分別連接該第一轉環及該第二轉環。另外，第一轉環包含由第一環內壁所圍繞形成之第一環孔，且第二轉環包含由第二環內壁所圍繞形成之第二環孔。所述至少一按壓裝置係朝第二環孔突出。
Environmentally and Mechanically Stable Selenium 1D/2D Hybrid Structures for Broad-Range Photoresponse from Ultraviolet to Infrared Wavelengths
(2018-10-17)
Chen, Yu-Ze
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You, Yen-Ting
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Chen, Pin Jung
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Li, Dapan
;
Su, Teng-Yu
Selenium (Se) is one of the potential candidates as photodetector because of its outstanding properties such as high photoconductivity (similar to 8 x 10(4) S cm(-1)), piezoelectricity, thermoelectricity, and nonlinear optical responses. Solution phase synthesis becomes an efficient way to produce Se, but a contamination issue that could deteriorate the electric characteristic of Se should be taken into account. In this work, a facile, controllable approach of synthesizing Se nanowires (NWs)/films via a plasma-assisted growth process was demonstrated at the low substrate temperature of 100 degrees C. The detailed formation mechanisms of nanowires arrays to thin films at different plasma powers were investigated. Moreover, indium (In) layer was used to enhance the adhesive strength with 50% improvement on a SiO2/Si substrate by mechanical interlocking and surface alloying between Se and In layers, indicating great tolerance for mechanical stress for future wearable devices applications. Furthermore, the direct growth of Se NWs/films on a poly(ethylene terephthalate) substrate was demonstrated, exhibiting a visible to broad infrared detection ranges from 405 to 1555 nm with a high on/off ratio of similar to 700 as well as the fast response time less than 25 ms. In addition, the devices exhibited fascinating stability in the atmosphere over one month.
Large-Scale Transparent Molybdenum Disulfide Plasmonic Photodetector Using Split Bull Eye Structure
(2018-10-18)
Sourav, Adhikary
;
Li, Zhiwen
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Huang, Zhonghui
;
Botcha, Venkata Divakar
;
Hu, Cong
A high performance photodetector array on transparent substrate is highly sought after for enabling next-generation imaging technology at the visible wavelengths. 2D materials such as molybdenum disulfide (MoS2) are attractive for such application owing to its superior optoelectronic properties and transparency when scaled to atomic thinness. Here, direct growth of MoS2 on centimeter-scale transparent Al2O3 substrate is reported using a high yield and scalable chemical vapor deposition approach. This enables a large area photodetector array to be demonstrated, wherein aluminum split bull eye (SBE) plasmonic structure is integrated to achieve further performance boost due to surface plasmon resonance (SPR) effect. For a wavelength of 405 nm, the plasmonic MoS2 detector achieves an ultralow noise equivalent power of approximate to 6.2 x 10-14 W Hz(-1/2) and a high responsivity of 7.26 A W-1 at a small bias of 1.0 V, which is more than 6x larger than the reference detector due to SPR effect. Finite-difference time-domain simulation confirms a higher concentration of optical field distribution at the center of the SBE structure, which is responsible for the enhancement of photocurrent and sensitivity even at low-light condition.
Isomerization of N2O4 in Solid N2H4 and Its Implication for the Explosion of N2O4-N2H4 Solid Mixtures
(2018-10-18)
Raghunath, Putikam
;
Lin, M. C.
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交大名義發表
;
National Chiao Tung University
The mechanism responsible for the explosion of solid mixtures of nitrogen tetroxide (N2O4) and hydrazine (HZ) or methyl-substituted HZs, detected experimentally by slow warming from 77 to 203-223 K, has been elucidated by quantum chemical calculations using the Vienna ab initio simulation package code. The result of the calculation for the reaction of a N2O4 molecule embedded in the middle of the N2H4 molecular crystal, N2O4@HZ(23), indicates that a loose nonconventional transition state (TS) occurring by stretching the O2N-NO2 bond up to 2.18 A with the concerted rotation of one of the NO2 groups producing the reactive ONONO2 isomer (ONONO2@HZ(23)) has a low 13.1 kcal/mol barrier at TS1; the process is exothermic by 45 kcal/mol, reflecting the much stronger ONONO2 binding with N2H4. A further simultaneous reaction of ONONO2 with 2N(2)H(4) in the same unit cell occurs with a small 1.4 kcal/mol barrier producing NO3- + NH2N(H)NO + N2H5+ with an overall exothermicity of 70.2 kcal/mol. The mechanism for this last-step reaction is distinctly different from that in the gas phase taking place via a five-centered concert mechanism giving N2H3NO and HNO3, which can further produce N2H5+NO3- by the rapid acid-base neutralization process. On the basis of the predicted structure, energy, and vibrational frequencies at TS1, we estimated the rate constant at 218 K for the N2O4-ONONO2 isomerization reaction in solid N2H4 to be 1.35 s(-1), giving the half-life of N2O4 @HZ 23 to be as short as 0.5 s. This result can explain why the slow warming of the solid mixtures of N2O4 and N2H4 from 77 K exploded reproducibly at 218 K.
Performance analysis of free space optical communication traffic integrated with passive optical network
(2018-10-18)
Yeh, C. H.
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Chow, C. W.
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Gu, C. S.
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Guo, B. S.
;
Cheng, Y. J.
In this Letter, a hybrid 10 Gbit/s on-off keying free space optics and passive optical network (FSO-PON) system is proposed and demonstrated. The experimental received sensitivities are -18 and -20 dBm at the back to back (BtB) and after 25 km fibre transmission, respectively, with 5 m free space traffic link. In the proposed analysis, FSO-PON system can support 32 and 16; and 8 and 4 remote optical wireless units for free space communication at BtB and after 25 km fibre link, respectively, when the free space transmission lengths are 150 and 300 m.
Negative-Differential-Resistance Devices Achieved by Band-Structure Engineering in Silicene under Periodic Potentials
(2018-10-18)
Chen, Chang-Hung
;
Li, Wen-Wu
;
Chang, Yuan-Ming
;
Lin, Che-Yi
;
Yang, Shih-Hsien
An important development in modern electronics is the realization of band-structure engineering for the design of novel materials and devices. One possible way to realize band-structure engineering is by addition of periodic potentials to two-dimensional (2D) materials, such as graphene, to form a superstructure, known as a "superlattice.' Unlike the band gap of graphene, the band gap of silicene can be tuned by an out-of-plane electric field owing to its unusual buckled structure. In this work, we use the designable band gap of silicene and the band structure of superlattices, together with the spin and valley degrees of freedom, to propose a design principle for optimizing the performance of spin-and valley-dependent negative-differential-resistance (NDR) devices using silicene superlattices. On the basis of the effective Hamiltonian formalism, we predict that the peak-to-valley current ratio could be larger than most recently reported results achieved by 2D materials, suggesting that the silicene superlattice is a good candidate for realizing NDR devices. The design principle proposed in this work could also be extended to other layered materials with tunable band gaps. This could pave the way for advanced material and device designs based on band-gap engineering of 2D materials.
Switching Failure Mechanism in Zinc Peroxide-Based Programmable Metallization Cell
(2018-10-19)
Simanjuntak, Firman Mangasa
;
Chandrasekaran, Sridhar
;
Lin, Chun-Chieh
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
The impact of peroxide surface treatment on the resistive switching characteristics of zinc peroxide (ZnO2)-based programmable metallization cell (PMC) devices is investigated. The peroxide treatment results in a ZnO hexagonal to ZnO2 cubic phase transformation; however, an excessive treatment results in crystalline decomposition. The chemically synthesized ZnO2 promotes the occurrence of switching behavior in Cu/ZnO2/ZnO/ITO with much lower operation current as compared to the Cu/ZnO/ITO (control device). However, the switching stability degrades as performing the peroxide treatment for a longer time. We suggest that the microstructure of the ZnO2 is responsible for this degradation behavior and fine tuning on ZnO2 properties, which is necessary to achieve proper switching characteristics in ZnO2-based PMC devices.