Red polymer light-emitting devices based on dye-dispersed poly (9,9-dioctylfluorene-alt-benzothiadiazole)

A polymer-organic host-guest emitter (POHGE) system for obtaining polymer light-emitting diodes (PLEDs) with pure red emission and high luminance is proposed. The POHGE system was prepared by the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidy-9-enyl)-4H-pyran (DCJTB) doped in green-emitting polymer poly (9,9-dioctylfluorene-alt-benzothiadiazole) (BTF8). A photoluminescence (PL) quenching phenomenon was observed owing to the higher doping amount of DCJTB dopant. In this study, the red DCJTB dopant emits with high luminance and without concentration quenching when the host BTF8 emitting layer is doped with a small amount of the red guest DCJTB dopant. An optimal amount of DCCJTB dopant was obtained at 2 mg. Devices with a configuration of indium tin oxide (ITO)/poly (ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT:PSS)/BTF8:DCJTB/Ca/Al were fabricated. This device achieved an electroluminescence (EL) efficiency of 1.33 cd/A at 6 V. The emission area is 1.5 × 0.5 cm². The devices show the red light emission with a peak at about 630 nm. The color coordinate in Commission Internationale d’Eclairage (CIE) chromaticity is at x = 0.64 and y = 0.36.     

InGaAs and Ge MOSFETs with high κ dielectrics

InGaAs and Ge MOSFETs with high κ’s are now the leading candidates for technology beyond the 15 nm node CMOS. The UHV-Al₂O₃/Ga₂O₃(Gd₂O₃) [GGO]/InGaAs has low electrical leakage current densities, C-V characteristics with low interfacial densities of states (D_it’s) and small frequency dispersion in both n- and p-MOSCAPs, thermal stability at temperatures higher than >850 °C, a CET of 2.1 nm (a CET of 0.6 nm in GGO), and a well tuning of threshold voltage V_th with metal work function. Device performances in drain currents of >1 mA/μm, transconductances of >710 μS/μm, and peak mobility of 1600 cm²/V s at 1 μm gate-length were demonstrated in the self-aligned, inversion-channel high In-content InGaAs n-MOSFETs using UHV-Al₂O₃/GGO gate dielectrics and ALD-Al₂O₃. Direct deposition of GGO on Ge without an interfacial passivation layer has given excellent electrical performances and thermodynamic stability. Self-aligned Ge p-MOSFETs have shown a high drain current of 800 μA/μm and peak transconductance of 420 μS/μm at 1 μm gate-length.     

A Multiple-Rate, Multicarrier Direct-Sequence CDMA System with 2-D OVSF Codes in Fading Channels

In this paper, a multiple-rate, multicarrier direct- sequence code-division multiple-access (MC/DS-CDMA) system with the use of two-dimensional orthogonal variable spreading factor (2-D OVSF) codes is studied. They are the first 2-D codes that can be generated by the tree structure commonly used by one-dimensional OVSF codes in wideband-CDMA. The 2-D OVSF codes also preserve orthogonality among code matrices with different spreading factors in the code tree. The performances of the proposed system with RAKE receivers employing equal-gain and maximal-ratio combining methods are analyzed and compared. Our results show that our multiple-rate MC/DS-CDMA system with the 2-D OVSF codes is more suitable for a non-fading additive white Gaussian noise channel or a Rician weak-fading channel. However, in a Rayleigh fading channel, the system performance gets worse because the orthogonality of the 2-D OVSF codes is destroyed by the strong fading effect.     

Electrode wear-compensation of electric discharge scanning process using a robust gap-control

Robust gap-control is applied to compensate for electrode wear in an electric discharge scanning (ED-Scanning) process. This control compensates for the wear without reference to the wear ratio of the electrodes. An auxiliary gap-control loop in the vertical direction can compensate for the wear of the electrode, according to the discharge voltage when the electrode is driven along the two horizontal axes. A proportional controller for a gap-control system with maximal robustness is designed and robustly analyzed to override the non-linear and time-varying feedback. The simulated and practical responses of such a robust gap-control system yield favorable performances. The controller can maintain the location of the discharge on the vertical axis and fix the depth of the removal to that of a particular layer. The practical scanning process reveals that the dimension of a hole can be guaranteed only if the data concerning the depth of removal under specific discharge conditions and electrode diameters are applied.     

A Stabilized Multichannel Fast RLS Algorithm for Adaptive Transmultiplexer Receivers

The transmultiplexer (TMUX) system has been studied for its application to multicarrier communications. The channel impairments including noise, interference, and distortion draw the need for adaptive reconstruction at the TMUX receiver. Among possible adaptive methods, the recursive least squares (RLS) algorithm is appealing for its good convergence rate and steady state performance. However, higher computational complexity due to the matrix operation is the drawback of utilizing RLS. A fast RLS algorithm used for adaptive signal reconstruction in the TMUX system is developed in this paper. By using the polyphase decomposition method, the adaptive receiver in the TMUX system can be formulated as a multichannel filtering problem, and the fast algorithm is obtained through the block Toeplitz matrix structure of received signals. In addition to the reduction of complexity, simulation results show that the adaptive TMUX receiver has a convergence rate close to that of the standard RLS algorithm and the performance approaches the minimum mean square error solution.     

Suppressing Ion Migration across Perovskite Grain Boundaries by Polymer Additives

Passivation of organometal halide perovskites with polar molecules has been recently demonstrated to improve the photovoltaic device efficiency and stability. However, the mechanism is still elusive. Here, it is found that both polymers with large and small dipole moment of 3.7 D and 0.6 D have negligible defect passivation effect on the MAPbI₃ perovskite films as evidenced by photothermal deflection spectroscopy. The photovoltaic devices with and without the polymer additives also have comparable power conversion efficiencies around 19%. However, devices with the additives have noticeable improvement in stability under continuous light irradiation. It is found that although the initial mobile ion concentrations are comparable in both devices with and without the additives, the additives can strongly suppress the ion migration during the device operation. This contributes to the significantly enhanced electrical-field stress tolerance of the perovskite solar cells (PVSCs). The PVSCs with polymer additives can operate up to −2 V reverse voltage bias which is much larger than the breakdown voltage of −0.5 V that has been commonly observed. This study provides insight into the role of additives in perovskites and the corresponding device degradation mechanism.     

Lipid‐Containing Polymer Vesicles with pH/Ca2+‐Ion‐Manipulated,Size‐Selective Permeability

Polymeric vesicles attained from the self‐assembly of distearin (a diacylglycerol lipid)‐conjugated poly(acrylic acid) (PAAc) with various distearin contents in the aqueous phase show the capability of control over the vesicular‐wall permeability to hydrophilic solutes of varying sizes by a simple manipulation of the external pH. The pH sensitivity of the vesicle membranes in size‐selective permeability is largely dependent upon the lipid content of copolymer. By the addition of CaCl₂ in aqueous vesicle suspensions, the pH‐evolved assembly structure and the membrane permeability can be immobilized with promoted resistance to further pH alteration, along with an additional counterion screening effect that reduces the pH required for the onset of polar solutes of certain sizes to pass through the membranes. Small‐angle X‐ray scattering (SAXS) measurements of the vesicle structure in the aqueous phase indicate that the pH‐regulated permeability to polar solutes is virtually governed by the extent of hydration and swelling of the vesicle membranes, and the lipid residues within each vesicle wall are packed into the ≈4–5 repeating lamellar islet structure surrounded by PAAc segments.     

The Design Trade-Offs of BitTorrent-Like File Sharing Protocols

The BitTorrent (BT) file sharing protocol is very popular due to its scalability property and the built-in incentive mechanism to reduce free-riding. However, in designing such P2P file sharing protocols, there is a fundamental trade-off between keeping fairness and providing good performance. In particular, the system can either keep peers (especially those resourceful ones) in the system for as long as possible so as to help the system to achieve better performance, or allow more resourceful peers to finish their download as quickly as possible so as to achieve fairness. The current BT protocol represents only one possible implementation in this whole design space. The objective of this paper is to characterize the design space of BT-like protocols. The rationale for considering fairness in the P2P file sharing context is to use it as a measure of willingness to provide service. We show that there is a wide range of design choices, ranging from optimizing the performance of file download time, to optimizing the overall fairness measure. More importantly, we show that there is a simple and easily implementable design knob so that the system can operate at a particular point in the design space. We also discuss different algorithms, ranging from centralized to distributed, in realizing the design knob. Performance evaluations are carried out, both via simulation and network measurement, to quantify the merits and properties of the BT-like file sharing protocols.     

Data Center Switch for Load Balanced Fat-Trees

With the growing of cloud computing, the need of computing power no longer can be satisfied with a few powerful servers or small scale parallel computer systems. More and more servers are connected together as a data center network. Then, fault tolerance becomes an import issue when building a massive data center network. Currently, many researches focus on building fat-tree data center networks. In this paper, we propose a load balanced fat-tree architecture with uniform mapping connection patterns to provide higher fault tolerance capability for heavy traffic load networks. Two fault tolerated 4 × 4 banyan type switch designs are introduced to improve the fault tolerance capability of fat-tree networks. Finally, fault tolerance capability evaluations of link or switch faults in fat-tree network are given to support our idea, and a 4 × 4 banyan type switch IC is demonstrated as the commodity switch for building the fault tolerant fat-tree data center networks. The 4 × 4 banyan type switch IC is fabricated in 90 nm CMOS technology, and the maximum operation rate of the IC is 5.8 Gbps per channel or 23.2 Gbps total data rate with only 23 ps peak-to-peak jitter.     

Electric fields in bone marrow substructures at power-line frequencies

Bone marrow is known to be responsible for leukemia. In order to study the hypothesis relating power-line frequencies electromagnetic fields and childhood leukemia from a subcellular perspective, two models of bone marrow substructures exposed to electric field are computed numerically. A set of cancellous bone data obtained from computed tomography scan is computed using both the finite element method (FEM) and scalar potential finite difference method. A maximum electric field enhancement of 50% is observed. Another model of bone marrow stroma cells is implemented only in FEM using thin film approximation. The transmembrane potential (TMP) change across the gap junctions is found to range from several to over 200 microV. The two results suggest that imperceptible contact currents can produce biologically significant TMP change at least in a limited number of bone marrow stroma cells.