A linear-time algorithm to find a pair of arc-disjoint spanning in-arborescence and out-arborescence in a directed acyclic graph

Suppose that we are given a directed graph D=(V,A) with specified vertices r₁,r₂V. In this paper, we consider the problem of discerning the existence of a pair of arc-disjoint spanning in-arborescence rooted at r₁ and out-arborescence rooted at r₂, and finding such arborescences if they exist. It is known (Bang-Jensen (1991) [1]) that this problem is -complete even if r₁=r₂. As a special case, it is only known (Bang-Jensen (1991) [1]) that this problem in a tournament can be solved in polynomial time. In this paper, we give a linear-time algorithm for this problem in a directed acyclic graph. We also consider an extension of our problem to the case where we have multiple roots for in-arborescences and out-arborescences, respectively.     

Dopant-Free Polymer HTM-Based CsPbI2Br Solar Cells with Efficiency Over 17% in Sunlight and 34% in Indoor Light

To abate the issue of moisture-assisted phase transition of CsPbI₂Br, caused by hygroscopic dopants used in the hole-transporting material (HTM), developing dopant-free HTMs is necessary. In this work, a new polymer, PDTDT, is developed as a dopant-free HTM for CsPbI₂Br solar cells, and the device performance and stability are systematically compared with cells employing dopant-free P3HT. CsPbI₂Br solar cells using PDTDT show an efficiency of 17.36% with V_OC of 1.42 V and FF of 81.29%, which is one of the highest values for CsPbI₂Br cells. Moreover, a record-high efficiency of 34.20% with V_OC of 1.14 V under 200 lux indoor light illumination and efficiency of 14.54% (certified efficiency of 13.86%) for a 1 cm² device under one sun are accomplished. Importantly, PDTDT shows superior/comparable device stability to P3HT, promising its potential to be an alternative to popular doped Spiro-OMeTAD and P3HT HTM.     

Miniature ceramic-anvil high-pressure cell for magnetic measurements in a commercial superconducting quantum interference device magnetometer

A miniature opposed-anvil high-pressure cell has been developed for magnetic measurement in a commercial superconducting quantum interference device magnetometer. Non-magnetic anvils made of composite ceramic material were used to generate high-pressure with a Cu-Be gasket. We have examined anvils with different culet sizes (1.8, 1.6, 1.4, 1.2, 1.0, 0.8, and 0.6 mm). The pressure generated at low temperature was determined by the pressure dependence of the superconducting transition of lead (Pb). The maximum pressure P(max) depends on the culet size of the anvil: the values of P(max) are 2.4 and 7.6 GPa for 1.8 and 0.6 mm culet anvils, respectively. We revealed that the composite ceramic anvil has potential to generate high-pressure above 5 GPa. The background magnetization of the Cu-Be gasket is generally two orders of magnitude smaller than the Ni-Cr-Al gasket for the indenter cell. The present cell can be used not only with ferromagnetic and superconducting materials with large magnetization but also with antiferromagnetic compounds with smaller magnetization. The production cost of the present pressure cell is about one tenth of that of a diamond anvil cell. The anvil alignment mechanism is not necessary in the present pressure cell because of the strong fracture toughness (6.5 MPa?m(1∕2)) of the composite ceramic anvil. The simplified pressure cell is easy-to-use for researchers who are not familiar with high-pressure technology. Representative results on the magnetization of superconducting MgB(2) and antiferromagnet CePd(5)Al(2) are reported.     

Feature map sharing hypercolumn model for shift invariant face recognition

In this article, we propose a shift-invariant pattern recognition mechanism using a feature-sharing hypercolumn model (FSHCM). To improve the recognition rate and to reduce the memory requirements of the hypercolumn model (HCM), a shared map is constructed to replace a set of local neighborhood maps in the feature extraction and feature integration layers. The shared maps increase the ability of the network to deal with translation and distortion variations in the input image. The proposed face recognition system employed a FSHCM neural network to perform feature extraction and use a linear support vector machine for a recognition task. The effectiveness of the proposed approach is verified by measuring the recognition accuracy using the misaligned ORL face database.     

Associative learning method in a hypercolumn model

We propose an associatively learnable hypercolumn model (AHCM). A hyper-column model is a self-organized, competitive, and hierarchical multilayer neural network. It is derived from the neocognitron by replacing each S cell and C cell with a two-layer hierarchical self-organizing map. The HCM can recognize images with variant object size, position, orientation and spatial resolution. However, feature maps may integrate some features extracted in the lower layer even if the features are extracted from input data which belong to different categories. The learning algorithm of the HCM causes this problem because it is an unsupervised learning used by a self-organizing map. An associative learning method is therefore introduced, which is derived from the HCM by appending associative signals and associative weights to traditional input data and connection weights, respectively. The AHCM was applied to hand-shape recognition. We found that the AHCM could generate an appropriate feature map and higher recognition accuracy compared with the HCM. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Face recognition under varying illumination using Mahalanobis self-organizing map

We present an appearance-based method for face recognition and evaluate its robustness against illumination changes. Self-organizing map (SOM) is utilized to transform the high dimensional face image into low dimensional topological space. However, the original learning algorithm of SOM uses Euclidean distance to measure similarity between input and codebook images, which is very sensitive to illumination changes. In this paper, we present Mahalanobis SOM, which uses Mahalanobis distance instead of the original Euclidean distance. The effectiveness of the proposed method is demonstrated by conducting some experiments on Yale B and CMU-PIE face databases. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Ni electroplating on a resist micro-machined by proton beam writing

In this paper we report fabrication of high-aspect-ratio micro-structure of Ni by electroplating, using a micro-machining technique of resists using proton beam writing (PBW) at Japan Atomic Energy Agency (JAEA). A micro-structure of 5 μm thick PMMA was fabricated by exposure using PBW at 1.7 MeV and by development. A Ni structure was then formed by electroplating on the micro-structure of PMMA. Vertical and smooth side walls observed by a scanning electron microscope (SEM) indicate that PBW can be a versatile tool for fabrication of resists and metal microstructure in combination with electroplating. The electroplated Ni structure can be used as a resolution standard, which enabled us to focus the proton beam down to 130 nm.     

Integrating vision, motion and language through mind

This paper presents an integrated comprehension and generation system for vision, motion and language. First, a computer model of mind proposed previously is reviewed as the basis of the integration. It consists of nine domains according to the contents of mental activities and five levels along the process of concept formation.Then, vision and motion are discussed based on the model. Real world objects are divided into four categories: substance, event, attribute and others. The first three are named as noun, verb and adjective, respectively. The comprehension process of the named objects and the generation process of the named motion are shown along the five levels. Furthermore, vision and motion are connected and controlled by planning.Next, language is considered to describe any data or processing in mind in our model. From this are derived three functions: surveying any mental object, organizing high-level thought, and communicating with others. The realization of these functions is discussed from the point of generation.Next, an integrated system for vision, motion, and language is implemented on workstations. The system, or an intellectual and emotional agent, simulates the protagonist or fox of an Aesop fable. Its mental and physical behavior is shown by graphic displays, a voice generator, and a music generator which expresses its emotional states.In conclusion, this system could be expected to provide a good framework for integrated comprehension and generation systems from the technological point of view.     

Numerical study by large-eddy simulation on effects and mechanism of air-cooling enhancing technologies

ABSTRACT

Learning from the lessons of the Fukushima Daiichi Nuclear Power Station incident in which a long-term station blackout occurred, we have been developing an air-cooling system that can operate without electricity for a virtually indefinite time. We developed air-cooling enhancing technologies by using heat transfer fins, turbulence-enhancing ribs and a micro-fabrication surface. To achieve further improvement of the heat transfer performance, it is important to understand the mechanism of the air-cooling enhancing technologies. In this study, we used numerical analysis to investigate the effects and the mechanism of the developed air-cooling enhancing technologies. We confirmed that the Nusselt number was increased 75% by the heat transfer fins. In the heat transfer enhancement by the turbulence- enhancing ribs, the Nusselt number was increased 43% by the turbulence-enhancing ribs. The enhancement ratio of the Nusselt number by the micro-fabrication surface can be explained by the apparent thermal conductivity. The Nusselt number was increased 4%–8% by adding the micro-fabrication to the surface of the pipe with the turbulence-enhancing ribs. For the combination of the micro-fabrication surface and the turbulence-enhancing ribs, the interaction between the better heat transport in the thermally conductive layer and the mixing effect by the large-scale vortex is the heat transfer enhancement mechanism.     

Layer-current waveform of coaxial multi-layer HTS cable considering the flux flow state

It is important to control the layer current distributions of coaxial multi-layer HTS cables because homogeneous layer current distribution decreases AC loss and increases the largest operational current. In a previous paper, we proposed a theory that can control current distribution based on the concept of flux conservation between two adjacent layers, and demonstrated the theory is in good agreement with experiment results. The theory was effective for an operational current less than the critical current of the cable. It is important to investigate current distribution under the condition of operational current more than the critical current of the cable because the cable experiences fault currents. We have extended the theory to treat the operational current more than the critical current by considering V-I nonlinear characteristics of HTS tapes including flux flow resistance and contact resistance between the cable and terminals. In order to verify the extended theory, we have fabricated a two-layer cable with the same twisting layer pitch, and hence caused inhomogeneous current distribution. It was observed that almost all of operational current less than the critical current flowed on the outer layer because of its lower inductance. When the operational current increased above the critical current of the second layer, the flux flow resistance appeared and distorted the current waveform with phase deviations. Finally, in the case of operational current more than the critical currents of both layers, flux flow resistance strongly affected current waveforms, and thereby the currents of both layers were determined by flux flow resistance. The extended theory simulated the layer current distribution waveforms and demonstrated good agreement with the experimental results under all operational current regions.