A bucketing algorithm for the orthogonal segment intersection search problem and its practical efficiency

The orthogonal segment intersection search problem is stated as follows: given a setS ofn orthogonal segments in the plane, report all the segments ofS that intersect a given orthogonal query segment. For this problem, we propose a simple and practical algorithm based on bucketing techniques. It constructs, inO(n) time preprocessing, a search structure of sizeO(n) so that all the segments ofS intersecting a query segment can be reported inO(k) time in the average case, wherek is the number of the reported segments. The proposed algorithm as well as existing algorithms is implemented in FORTRAN, and their practical efficiencies are investigated through computational experiments. It is shown that ourO(k) search time,O(n) space, andO(n) preprocessing time algorithm is in practice the most efficient among the algorithms tested.Supported by the Grant-in-Aid for Scientific Research of the Ministry of Education, Science and Culture of Japan under Grant No. 62550270 (1987).     

A New Model for the Pollucite Thermal Expansion Mechanism

The thermal expansion behavior of cubic pollucite (CsAlSi₂O₆) in the temperature range 298 to 1473 K was investigated from the viewpoint of crystal structure, based on the model proposed in this study, with Rietveld analysis and high-temperature X-ray powder diffraction. Consequently, it has been found that the CsAlSi₂O₆ structure provides an enlargement-contraction mechanism for two kinds of rings, each composed of six (Si,Al)O₄ tetrahedra in a three-dimensional aluminosilicate framework, in the temperature range 298 to 673 K.     

Collaborative Prediction by Multiple Bayesian Networks and Its Application to Printer Usage Modeling

Bayesian networks (BNs) have become increasingly popular tools for learning and prediction in the context of user modeling. However, due to the lacks of individual training data especially for inactive or new users, separate treatments of individual users often become quite problematic. In this article, we propose a novel scheme of ‘collaborative’ prediction, in which multiple BNs (each for a single user) are cooperatively employed for prediction of a single target user’s actions. The core idea is to simply use the Bayesian principle, but in a rather intricate way. Our method is simple, and thus readily applicable to rather difficult, cases with heterogeneous and preliminary unknown structures of individual BNs. We demonstrate the usefulness of our method with a real dataset related to our motivating user modeling task, i.e., printer usage prediction. The results show that our Bayesian collaboration method effectively improves the prediction accuracy from both non-collaborative and other naive collaborative approaches, especially in cases with small sample sizes. It also appears that our method can improve such a low prediction accuracy that is possibly caused by poor optimization in the structure learning.

     

Experimental study of LIM-driven,attraction-type magnetically levitated carrying system

Recently, many kinds of magnetic levitation systems have been proposed and developed for use in factory automation systems. This progress in the development depends on the appearance of new types of permanent magnets and new control theories. On the other hand, some systems have simple structures in which couples roles are given for both levitation and conveyance. As for these systems, however, many trials are needed to establish the system configurations and the control theory. The authors have developed a new magnetically levitated carrying system driven by LIM (linear-induction motor). The system can be completely detached from a guideway both in mechanical and electrical meanings. In this paper, the experimental results, especially the driving characteristics of a vehicle without any contacts to the LIM guideway, are discussed.     

Space charge behavior in an antistatic polymer including polymer solid electrolyte

A polymer dielectric material tends to be easily charged and may cause an electrostatic discharge, due to the serious problems that result when consequent electromagnetic noise damages the electronic circuits in various kinds of apparatus. The antistatic polymers that have been developed to prevent electrostatic discharge contain polymer solid electrolytes so that space charge originally exists inside them. The mechanism of the antistatic discharge effect of the polymer has been investigated by measuring the space charge distribution using the high-resolution pulsed-electroacoustic method. The experimental results suggest that the internal space charge of the polymer accumulates at the surface and forms heterocharge distribution at the interface between the electrodes and the specimen. Thus, internal space charge compensates the applied electric field, resulting in preventing the increase of the surface potential. In addition, internal space charge behavior relates to the dispersion condition of the polymer solid electrolyte that depends on the quantity of the electrolytes and the specimen procedures.     

Spherical silicon solar cell with reflector cup fabricated by decompression dropping method

A spherical Si solar cell with a reflector cup was successfully fabricated by a dropping method at decompression state. In the dropping method, melted Si droplets were instilled at decompression state (0.5× 105Pa) to reduce crystal growth rate, dominating crystal quality such as dislocation density in crystal grains. Spherical Si solar cells were fabricated using the spherical Si crystals with a diameter of 1 mm and then mounted on a reflector cup. The current-voltage measurement of the solar cell shows an energy conversion efficiency of 11.1% (short-circuit current density ( Jsc ):24.7 mA·cm-2,open-circuit voltage: 601 mV, fill factor:74.6%). Minority carrier diffusion length determined by surface photovoltage method was 98 μm. This value can be enhanced by the improvement of crystal quality of spherical Si crystals. These results demonstrate that spherical Si crystals fabricated by the dropping method has a great potential for substrate material of high-efficiency and low-cost solar cells.     

Estimating power-frequency characteristics in power systems by means of spectral analysis techniques

This paper shows that normal power system operating data may be used to determine the power-frequency characteristics in power systems. Data are processed as random signals using spectral analysis techniques, and the results estimate the generator and load power-frequency characteristics as transfer functions. The generator characteristics K_g are determined as a transfer function of the system in which input signals are frequency fluctuation ΔF and generator power setting signal ΔP_g, and output signal is generator power output ΔP_e, To estimate the load characteristics K_l, a difficulty arises. There is a relation ΔP_/ = ΔL_o + K_lΔF between actual load ΔP_l, ideal load under the state of nominal frequency ΔL_o, and fluctuation of system frequency ΔF. Because it is impossible to measure ΔL_o directly, ΔL_o and K_lΔF cannot be separated. With regard to a partial system, when its capacity is small enough compared with the total system capacity, the contribution of ΔL_o in a partial system to ΔF of the total system may be ignored, that is, ΔF and ΔL_o are considered as independent phenomena. Thus the cross spectrum of ΔF and ΔL_o decreases to zero according to the increase of data in number, and K_l of the partial system can be estimated.     

Mechanical properties of poly(vinyl chloride)-poly(acrylonitrile-co-butadiene) blends with modulated structure

By solution-casting we prepared poly(vinyl chloride)-poly(acrylonitrile-co-butadiene) blends with a modulated structure (a co-continuous two-phase structure with periodic distance of a few micrometres or less). Mechanical properties of the film specimens were investigated by the uniaxial tensile test combined with small-angle light scattering. A 50: 50 plastic-rubber blend has a high initial modulus which is close to that of the rigid plastic. Nevertheless, it can deform to a large extension ratio up to 6. It cannot immediately recover to its original length after the stress-strain test, i.e. residual strain in the stress-strain curve persists. However, after release from the instrument the film gradually shrinks to its original length at room temperature. After strain recovery the film shows a stress-strain curve almost identical to the original. It seems that the stretched film healed simply by resting at room temperature. Based on the light-scattering studies, a helical spring model is derived for the two-phase system with modulated structure, exhibiting the characteristic mechanical properties mentioned above. The spring model interprets well the dependence of Young's modulus on the blend composition and the periodic distance of the modulated structure.     

An evaluation method of PV systems

Data evaluation methods have wide adaptations, such as feedbacks to PV system operation management and design. The authors have already developed sophisticated verification method (SV method) of PV systems, which is a simple evaluation method to identify six kinds of system loss rates using basic information and simple four measurable data. This time, the authors introduced quality diagnosis to our previous model for compensating the measurement errors in field data, and improved the algorithm of the model. Consequently, validity of the evaluation result became better than the previous model.