Interface between inorganic electrode and organic layer bears various problems, such as poor adhesion strength and charge injection barrier due to inconsistency in physicochemical properties of both materials. This paper reviews the experimental results of using self-assembled monolayers (SAMs) that have reactive terminal groups to resolve the problems of organic/inorganic interface. Polymer thin films that are covalently tethered to inorganic surfaces can be prepared by vapor-depositing monomer molecules on the substrates that were modified with SAMs having a function of polymerization initiator. The reactive units can be amino group for ring-opening polymerization, azo group for UV-assisted vinyl polymerization, and benzophenone unit for thermally-assisted vinyl polymerization. A polymer thin film prepared by spin-coating can also be tethered via a benzophenone-terminated SAM by photochemical reaction. The chemical tethering at the interface resulted in increase of adhesion strength, improvement of surface morphology, and increase of charge injection from the inorganic substrates.
PEDOT / PSS, has been a well-known π-conjugated polymer. A number of studies have been so far reported on an improvement of its conductivity. However, a control of a surface roughness of PEDOT / PSS electrode has been rarely demonstrated, in spite of an important factor corresponding to device failure on OLED or OPV application. We previously reported that the conductivity of PEDOT / PSS was increased by an addition of a large amount of a certain salt into PEDOT / PSS. Based on the results, we tried to modify the substrate with the SAM bearing a same moiety as the salts. We wish to disclose that the PEDOT / PSS film deposited on the surface-modified substrate prevents the increase of the roughness of the surface with an increase of its conductivity.
Patterned polymer thin films were prepared by spin-coating a solution consisting of an acryl monomer of 2-(9H-carbazol-9-yl)ethylmethacrylate, a photoinitiator of 4-(dimethylamino)benzophenone, and a phosphorescent dopant of iridium(III) bis(2-phenylpyridinate(4-vinylphenylpyridine)). The film was exposed to UV light through a photomask and rinsed with an organic solvent to develop a patterned polymer thin film. A mixture of tetrahydrofuran and 1,4-dioxane was used as the spin-coating solvent, and ethanol was used as the developing solution. The effects of solvent, exposure time, UV intensity, and the phosphorescent dopant were examined to optimize the patterning condition. The patterned film was utilized as an emissive layer to construct an organic light-emitting diode.
Complementary metal-oxide-semiconductor (CMOS) inverter circuits were fabricated using solution-processed field-effect transistors (FETs); p-type FET of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and n-type FET of Li-doped ZnO. As the source/drain electrodes of these FETs, reduced graphene oxide (RGO) films were prepared also by the solution process. The fabricated CMOS inverter device showed the voltage gain of 10.
Flexible solar cells made of organic semiconductors are promising for the application to the photovoltaic energy sources for flexible devices and those can be attached to any curved surfaces. Mixing and phase separation of different molecules are important for the formation of bulk-hetero junctions. We found that DNTT (dinaphtotienothiophene) and C60 spontaneously mixes when they are sequentially deposited. The driving force does not seem to be the charge transfer between p-type and n-type molecules but the maximization of van der Waals attraction coming from the molecular shapes.
Charge storage devices in the film-base flexible electronics are very important for the application of those devices in daily life. In order to examine the recently reported solid state capacitor with ionizable charge traps, we present an analysis of an electrostatic model. It shows a charge-voltage characteristic resembling a chemical battery. While the energy density per charge is great in these devices, the energy density of the capacitor with ionizable traps will be lower than that of an ordinary capacitor with metal electrodes, assuming the same withstanding voltage and the same geometry.
Organic photodetectors based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends with indium-tin-oxide (ITO) modified by phosphonic acid-based self-assembled monolayer treatment in a short time are investigated. The mixed self-assembled monolayers (SAMs) serve to tune the surface free energy and the work function of ITO by varying the blend ratio. The phosphonic acid-based SAM treatment results not only in lowering of the injection barrier at the ITO/organic layer interface but also in the lowering of the contact resistance between ITO and the organic layer by analysis of impedance spectroscopy in P3HT hole-only device with SAMs. P3HT:PCBM device with ITO modified by short treatment time of 1H,1H,2H,2H-perfluorooctanephosphonic acid exhibits the incident-photon-to-current conversion efficiency of above 50 % at -2 V, high on/off ratio and improved durability.
In order to improve biosensor performance namely, the sensitivity, response time, and linear range values, novel amerometric polypyrrole (PPy) glucose biosensors, achieved by three different immobilizing techniques namely, physical adsorption, coentrapment and a two steps method of coentrapment superimposed with physical adsorption had been studied. Different enzyme loading and material properties resulted in varied immobilizing techniques lead to dissimilarities in characteristics. In this study, Pt coated AnodiscTMs with 0.2 µm maximum pore size were used as electrodes to polymerize PPy at 0.3 mAcm-2 using a solution containing 0.05 mol/l pyrrole and 0.1 M NaPF6. The polymerization time was optimized to 90 s. In the coentrapment method, glucose oxidase (GOx) (1 mg/ml) was added to the monomer solution while an aliquot of GOx (5 µl) was placed on the pre-polymerized electrode for physical adsorption. A combined procedure of these two techniques was used as the last immobilization technique. Physical adsorption method gave a sensitivity of 3 mAcm-2 (mol/l)-1 and a linear range of 0.5-13×10-3 mol/l with a response time of a 3 s. Sensitivity in the case of coentrapment was 3.75 mAcm-2 (mol/l)-1 while it showed a value of 4.45 mAcm-2 (mol/l)-1 in two step immobilization thus giving 25 and 48% increases respectively. Response times of 9 and 8 s in latter cases reveal the possible repercussion taking place at enzyme immobilization in three dimensional (3-D) PPy matrix and the delay occur in glucose to reach the enzyme. Linear range of the two step method was extended up to 16×10-3 mol/l due to the reinforced enzyme loading.
We have already reported(3)-(6) that the capacitance of Surge Protective Devices (SPDs), such as varistor type SPDs, degraded the transmission rate of power line communication modems. Not only the capacitance of the varistor but also the inductance of the varistor and wiring of SPD cause LC series resonance and attenuate signal level at the resonant frequency. In this paper, we found that there is a close relationship among capacitance, maximum current, size of disk, and varistor voltage. The inductance is the sum of SPDs themselves and wiring connecting SPDs to AC power lines. Therefore how to install SPDs and connect them to Protection Earth (PE) is important. Typical varistor type SPDs that have 1000pF to 14000pF and wiring less than 50cm will have resonant frequency somewhere between 2MHz to 30MHz. We propose practical information to select and install SPDs on AC power lines, and to estimate PLC signal degradation.
In our previous research, we proposed a serial unequal error protection (UEP) code system for use with information sources that contain a mixture of both important and less important data. Previously, theoretical analyses were presented, and the effectiveness and the validity of the system for additive white Gaussian noise (AWGN) channels were confirmed using theoretical analyses and computer simulations. On the other hand, we proposed an adaptive error prediction filter with a decision feedback equalizer (AEPF-DFE) to achieve faster convergence and lower computational cost during the tracking period. In this paper, we proposed our UEP system using AEPF-DFE for time and frequency selective fading channels. We confirmed the improvement in BER performance and the effectiveness of adaptive equalization for the proposed system in fading channels. Also, we confirmed the predominance of the proposed system by comparing the previous scheme, that is, the case using a simple DFE.
To improve the reliability of medication record keeping, we have developed a cup-shaped medication recording device and system for taking intraoral pictures of pills. This device has a camera, a memory card with a wireless transmitter, a capacitance sensor, a processing unit, and a rechargeable battery in the cup. When the capacitance sensor used as the trigger switch detects water level change, the camera starts shooting and takes some intraoral pictures. Waterproofing is achieved by the use of wireless data transmission and wireless battery recharging to enable washability of the cup. In the first experiment, ten trials in one subject were conducted. There were 2.6±0.7 pictures per an action of taking pill. The pill was successfully photographed in all trials. Thirteen subjects participated in a second experiment. Intraoral pictures of pills were taken and sent to a PC or a server wirelessly in all subjects. These results show that this device can be expected to reliably record medication, to improve patient adherence, and reduction of medical labor.
This paper proposes a method for evaluating a patent race in a three-firm asymmetric model. Previous research has evaluated patent races between two firms using a game-theoretic real options approach; however, very little research has been done on the evaluation of R&D races in patent acquisition when three or more major firms exist in the market. Furthermore, the synergy created by technical cooperation has not been considered. Therefore, the present research expands on the previous research to formulate and evaluate a patent race model between three asymmetric firms using a game-theoretic real options approach. We formulated and evaluated one situation in which all three firms subject to evaluation are competing for patent acquisition and another situation in which two of the three firms are engaging in technical cooperation. In the situation in which two of the three firms engage in technical cooperation, we used numerical examples to consider the influence of a reduction in R&D cost due to the synergy created by the cooperation. Our research showed that the cost of cooperative R&D is within a realistic range in situations where technical cooperation is desirable.
In this study we propose a stabilizing controller for partially known systems. We assume that the partially known systems can be identified as polynomial systems on a neighborhood of equilibrium point. For polynomial systems we give a stabilizing controller and the domain of attraction(DOA) by means of the Lyapunov function. Since the reinforcement learning is carried out by the Lyapunov function, the reinforcement learning controller can be connected to the stabilizing controller of the polynomial systems on the DOA. To demonstrate the usefulness and validity of the proposed method, we apply the proposed control method to the Furuta pendulum.
Suppose a special district (group) that is composed of multiple companies (agents) imposed energy demand. We have proposed a Distributed Energy Management System (DEMS) that optimizes energy consumption of a group through energy trading in the group. In this paper, we propose an efficient operation planning method for DEMS with storage device. At first, we formulate the optimization problem for agents. Secondly, we propose a method to search a unit commitment state that depends on group composition. We confirmed that the proposed method enables efficient use of generators in groups.
In the field of cell biology, particle counting in intracellular images is important for investigating the cause of diseases. However, particles are manually counted by human observers now. Such manually counting takes a lot of time, and counting result becomes subjective. If an automatic counting method by computer is realized, we can treat a large number of images and it can obtain many objective data. The development of an automatic counting method much contributes to understand the case of disease. However, particle counting in intracellular images by a computer is new research field, and conventional methods are little. Thus, we propose counting method based on regression analysis. We use partial least squares regression and auto-correlation between 2 different types of features using mask patterns for higher-order local autocorrelation feature. The proposed method gives higher accuracy than counting by principal component regression, support vector regression and ImageJ. In experiment, the proposed method can count with small error in comparison with human counting. The effectiveness of our method is shown by experiments.
This paper proposes an active noise control (ANC) system based on speech enhancement using inverse notch filter (INF). Conventional ANC systems remove an observed signal, even if it includes a desired speech signal. To extract the desired speech signal, we introduce a speech reduction method as pre-processing of the ANC system. In this case, the ANC produces only the noise replica, since the input signal to the ANC does not include the speech signal. We inversely use a speech enhancement technique to achieve speech reduction. One of the useful speech enhancement techniques is a spectral gain method. Inherently, the spectral gain method based on the FFT provides a delay depending on the analysis frame length. Since the ANC system can work well under a low processing delay, we replace the FFT with the INF which is a narrow band-pass filter for reducing processing delay. Simulation results show that the proposed ANC system with INF is effective to extract the speech signal included in the observed signal.
In this paper, we introduce a new concept of hierarchical structure into solution space of a combinatorial optimization problem, and develop a novel combinatorial optimization method based on the concept. The introduction of the above new hierarchical structure concept “basin of attraction”, which is a set binding solutions by utilizing properties of local optimal solutions, enables us to construe solution space as not only set of solutions but also set of basins of attraction hierarchically. It is well known that the appropriate balance of two policies, intensification and diversification, is essential in the search of meta-heuristics. The proposed method clarifies the search policy by relating the hierarchical structure in solution space with intensification and diversification. In regard to diversification, we incorporate a movement strategy that has longer-term or more macroscopic viewpoint than before in the algorithm by utilizing the concept basin of attraction. The performance of the proposed combinatorial optimization method is inspected by numerical experiments using some typical benchmark problems of a traveling salesman problem, a knapsack problem, a flow-shop scheduling problem and a quadratic assignment problem.