In this article, in order to clarify inherent limitations in the device applications of the organic amorphous semiconductor, its characteristics of charge carrier transport and technical basis of present device applications such as xerographic photoreceptors and organic light emitting diodes, are discussed first. Then, the importance of molecular alignment in the semiconductor materials is pointed out for overcoming the limitations in the conventional organic semiconductors practically used. Finally, the charge carrier transport properties of mesophase materials and their high potential for device applications are discussed as a quality organic semiconductor that exhibits self-organizing molecular alignment.
We propose a double heterojunction type organic light emitting diodes (OLED) using zinc oxide (ZnO) films, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of novel OLED were obtained as high as 470cd/m2at 22V and 7.6mA/cm2. The results obtained here demonstrate that the vertical type organic light emitting transistor (OLET) using ZnO layer as an electron injection layer is expected as a key element for flexible sheet displays.
Recently, organic molecular electrical devices such as molecular thin film transistors have received considerable attentions as possible candidates for next generation electrical and optical devices. This paper reports fabricating technologies of flat metallic electrodes on insulating substrates with micro-gap separation. The key technologies of fabricating the planar type electrodes are liftoff method by the combination of bi-layer photoresist with overhang profile and electron beam evaporation of thin metal (Ti and Au) films and SiO2-CMP (Chemical Mechanical Polishing) method of CVD (Chemical Vapor Deposition) deposited TEOS (Tetraethoxysilane) - SiO2 layer. The raggedness of the electrode/insulator interface and the electrode surface on the micro-gap electrodes were less than 3 nm. The isolation characteristics of fabricated electrodes were in the order of 1013 ohm at room temperature, which is enough for analyzing electronic properties of organic thin film devices. Finally, pentacene FET characteristics are discussed fabricated on the micro-gap flat electrodes. The mobility of this FET was 0.015cm2/Vs, which was almost on the order of the previous results. These results suggest that high performance organic thin film transistors would be realized on these advanced electrode structures.
To realize an efficient electron injection electrode into organic layers by photolithography, we form a MgAu alloy electrode which has capability of low work function and high durability for humidity and organic solvents during photolithography process. The MgAu alloy thin film shows a work function of 3.7eV which is comparable with that of a neat Mg layer and 0.8eV lower than that of a neat Au layer. The low work function of 3.7eV was maintained even after the photolithography process, suggesting excellent stability for the solvent treatments. We examine a MgAu alloy comb bottom electrode for organic field-effect transistor (OFET) and successfully obtain FET operation of n-type driving. We also demonstrate efficient electron injection characteristics of a MgAu alloy cathode in organic light-emitting diodes (OLEDs). The MgAu alloy cathode can inject electrons efficiently similar to the conventional MgAg cathode.
We have fabricated high conducting organic wires and self-wired nano-transistors of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) charge transfer complex using co-evaporation method with an electric field. The conducting wires which directly bridge two gold electrodes indicated high-conductive ohmic contact with the gold electrode. Self-wired organic field effect transistor was formed at the connecting point of conductive wires. Field effect transistor characteristics of nano-transistor exhibited n-channel behavior with on/off ratio of 110. The length of active layer was estimated to be approximately a few nanometer.
Organic thin film FETs have been studied by using electron spectroscopic techniques. Ultraviolet photoelectron spectroscopy has revealed that photo polymerization is enhanced by fabricating FET structure. Energy levels and the effective mass of charge carriers are discussed based on the results of photoelectron spectroscopy and electron energy loss spectroscopy.
Surface modification of root dentin by mid-infrared (MIR) pulsed-laser irradiation is one of the candidates for a novel, non-invasive treatment to prevent root surface caries. To modify root dentin effectively and non-invasively it is essential to estimate quantitatively and qualitatively the laser parameters, such as the wavelength and the power density, required for surface modification. The key aspect is to bring about effective surface modification of root dentin while minimizing the unwanted removal of the underlying dentin. Using a tunable, MIR Free Electron Laser (FEL) in the wavelength region of 8.8-10.6 μm, we have investigated macroscopically the extent of surface modification (morphological and chemical changes) of root dentin. We have obtained experimental results related to the ablation depth, the MIR absorption spectrum, and the elemental chemical composition of the irradiated dentin. The observations showed that the surface modification of root dentin was inclined toward well-recrystallized, HAp-like material, leading to an increase in the acid resistance and dentinal tubule sealing. The laser parameters, at which efficient surface modification without enhanced ablation occurred, were estimated to be at λ= - 9.0 μm or - 9.7 μm and in the average power density region of - 10-20 W/cm2 (resulting in energy density per macropulse and peak power density regions of - 1-2 J/cm2 and - 66.7-133.3 kW/cm2). Thus, it was found that the surface modification of root dentin strongly depends on the laser conditions applied. We conclude that the optimum laser wavelengths for (1) root surface caries treatment without restorative procedure and (2) hard tissue ablation without water irrigation are around (1) λ= 9.0 μm or 9.7 μm and (2)λ= 9.0 μm in the absorption bands due to P-O stretching, respectively.
We made study of the comparative characteristic of transparent organic light emitting diodes by using three kinds of typical transparent conducting oxide ( ITO (In2O3-SnO2), IZO (In2O3-ZnO), AZO (ZnO-Al2O3) ). The cathode used for transparent conducting oxide were prepared by rf magnetron sputtering at room temperature. Each transparent conduction film was amorphous. We also study the effects of using alkali metal (Cs) dope layer. An electronic injection improved by doping Cs, and the decrease in driving voltage of TOLED and the improvement of luminance were observed.
Measurement of biological information appears to be an effective method to obtain an understanding of health conditions measures to maintain and improve the health of elderly people. However, every conventional bioinstrumentation technique imposes a sense of restraint that results in aversion against measurements that would last over consecutive days. To solve this problem, we propose a system for monitoring the respiration of sleepers, and it uses a fiber grating vision sensor, which is a type of optical range finder, to achieve non-contact and unrestrained monitoring. The signals obtained by the system include the respiration rate, shifts of the ventilation, and the body movement interval of the sleeper. The information enables to investigate the stability of the sleeper throughout the night. We examined the measuring accuracy, validity, and effectiveness of our proposed system. And all-night monitoring performed at elderly care facility revealed that respiratory disturbances during sleep occurred in many of the residents and that sleep apnea is a common syndrome, especially among residents who have senile dementia or have had a stroke. We were able to carry out the all-night monitoring with this system for a total of about 370 times, according to our schedule, without experiencing any failure, accident, or interruption. Our proposed system is highly effective for monitoring elderly dementia patients who are likely to become uncooperative during measurement with existing monitoring methods that use certain amounts of restraint.
It is often known that an EEG has the individual characteristic. However, there are no researches to achieve the considering of the individual characteristic. Then, the analyzed frequency components of the EEG have that the frequency components in which characteristics are contained significantly, and that not. Moreover, these combinations have the individual difference. We think that these combinations are the individual characteristic of the EEG. In this paper, the EEG analysis method by using the GA and the FA and the NN is proposed. The GA is used for selecting the individual characteristic. The FA is used for extracting the characteristics data of the EEG. The NN is used for estimating extracted the characteristics data of the EEG. Finally, in order to show the effectiveness of the proposed method, computer simulations are done by classifying the EEG pattern.
An individual recognition system using the genetic local search with respect to ear images has been examined. We generated a set of individuals which are ramdomly selected from the ear images consisted of 50 registrants, and carried out genetic operations to the set of the individuals in order to lead to new generation. The local search is applied to some top elites with the best fitnesses in the new generation. The best fitness is searched between some positions selected near the elite position. Individual recognition experiment using the ear image with the uncertain data was carried out in respect of the method. As the result, it is noted that the registrant recognition rate was 100 percent, and it became 100 percent, at the un-registrant denial rate.
In this paper, we propose a new method for a moving noise reduction with a numerical stability via 2-channel microphone array using the interior point least square(IPLS) algorithm. The noise reduction system is realized by the frequency domain generalized sidelobe canceller(FDGSC) and the IPLS algorithm is applied to form the null of array for the direction of moving noisy source adaptively. The IPLS algorithm is based on the interior point method for the constrained optimization method, and can guarantee the numerical stability at the learning and thus, we obtain the target sound extracted with a high S/N. A superior performance of the proposed method is presented by several computer simulation results when using the speech signal as the noisy source signal.
We propose a system which helps the visually impaired people to understand the character information in environment using a note PC and a CCD camera. The system captures a still image by the camera connected to the note PC, and extracts character regions from the image by using the general features of a character and a character sequence and the color information of a signboard region on which the character is drawn. Finally, OCR(Optical Character Recognition) analyzes the extracted character regions and outputs recognized characters by synthesized voice. We conducted an experiment by using 171 images captured in the real environment and obtained satisfactory results: among 417 character lines, 56.1% of lines are completely extracted, and 85.4% are done including lines in which more than half characters are extracted.
Moving object detection with a mobile image sensor is an important task in robotics and computer vision, when considering the practical use of robots in human environments. In this paper, we propose a robust method that detects moving objects in the environment using the omni-directional depth information obtained by a mobile Stereo Omni-directional System (SOS). In order to detect only the moving objects within the depth image that are obtained by a sensor in motion, we first estimate the ego-motion of the sensor, and generate a predicted depth image for the current time from the depth obtained at the previous time by only considering the ego-motion of the sensor. Then the predicted depth image is compared with the actual one obtained at the current time, and the inconsistent regions are detected as moving objects. When the senor moves, occlusions will occur in the scene and they will cause false detections. However, these false detections can be suppressed by estimating the occlusion regions using the ego-motion parameters of the sensor and the jump edges in the depth image. The effectiveness of the method is shown with the experiment results on a real environment.
Disable persons, motor functional disorder, can not take meal by their arms. Meal assistance orthosis, which assists to take meal, is developed for them. Meal assistance orthosis is actuated by use of human will which is analized based on EOG˜(Electroocurogram) signal. Besides, control theory for meal assistance orthosis is designed with safety policy. Effectiveness of the proposed meal assistace orthosis is assured by simulation and experimental work on normal person.
Abstract In this paper we present a neural-based algorithm for topological via-minimization (TVM) problem in two-layer channels. TVM problem requires not only assigning wires or nets between terminals without an intersection to one of the two layers, but also a minimization of the number of vias, which are the single contacts of nets between two layers. The proposed algorithm which is designed to embed the maximum numbers of nets without an intersection, uses gradient ascent learning of the coefficients to help the Hopfield network escape from local minima and find a global minimum. The proposed algorithm is applied to the split rectangular TVM (RTVM) problem and simulations are performed. The experimental results show that the proposed algorithm generates much better solutions than other existing algorithms for this problem.
The Multiple Traveling Salesmen Problem (MTSP) is extension of the Traveling Salesman Problem (TSP). This problem is widely applied to many real routing and scheduling problems. This paper proposes a gradient ascent learning algorithm of the elastic net approach for the MTSP. The learning model has two phases: an elastic net phase, and a gradient ascent phase. The elastic net phase tries to find the minimum of total distances. This procedure is equivalent to gradient descent of an energy function, and leads to a local minimum of energy that represents a good solution to the problem. Once the elastic net gets stuck in local minima, the gradient ascent phase attempts to fill up the valley by modifying parameters in a gradient ascent direction of the energy function. Thus, these two phases are iterated until the elastic net gets out of local minima. The simulations are conducted on a series of standard data in order to investigate the performance of the proposed algorithm. The proposed algorithm is shown to be capable of escaping from the elastic net local minima and generating superior solution in all instances compared to the original elastic net.
A new design algorithm based on highly optimized tolerance, recently introduced by Carlson and Doyle, is applied to a toy problem of determining the optimal arrangement of hypothetical biosensors in an airport terminal for risk aversion to epidemic outbreak. The hallmark of robust design for the arrangement of sensors is obtained, providing a power law in the probability of occurrence of epidemic outbreak as a function of the number of persons infected with pathogen.
Spectral imaging technique has attracted attention in the machine vision field to enhance measurement and inspection systems. This paper describes color analysis techniques using an imaging spectrograph for acquiring multispectral image in real-time. Two analysis cases are reported: one is the result of analyzing the relationship between skin color and the pigment by 2 kinds of multiple regression analysis, another is the result of analyzing the tone of the color of a coated surface with an undulating form using a power spectrum with shading compensation.
Individual and gender identification method have been studied, which based on the range data of human nose using principal component analysis. Approximately 86.31 percent of individual identification rate and 99.98 percent of gender identification rate was achieved.