Takafumi Hayashi

Application of digital image analysis to pattern formation in polymer systems

Digital image analysis (DIA) is applied to extract various types of physical information from an image of high‐order structures in polymer systems observed under an optical microscope. DIA can be applied to analyze the pattern formation phenomena in general. Various numerical operations in real and wave‐number space make it possible to extract physical information unobtainable by other methods, such as the use of light scattering. The possibility of valuable operations in DIA are presented with examples. The technique itself is useful not only in polymer systems but also in various fields such as studies of liquid crystals, biological systems, metals, and pattern formation in solution or chemical reaction.

Simple bone cyst: A clinical and histopathologic study of fifteen cases

Nineteen simple bone cysts found in 15 patients were studied by classifying them into younger and older age groups. The clinical, radiographic, and histopathologic features of 11 cysts in the younger group of 10 patients were consistent with those of previous reports. Among patients in the older age group, female predominance (80% vs 30%), involvement of the maxilla (25% vs 0%), multiple occurrence (60% vs 10%), simultaneous presence of radiopaque fibro-osseous lesions or hypercementosis (63% vs 0%), and loss of lamina dura of related teeth (83% vs 14%) resulting in exposure of their roots on surgical intervention were the characteristic features.

Zero-Correlation Zone Sequence Set Constructed from a Perfect Sequence

The present paper introduces the construction of sequences having a zero-correlation zone. The cross-correlation function and the side-lobe of the autocorrelation function of the proposed sequence set is zero for the phase shifts within the zero-correlation zone. The proposed zero-correlation zone sequence set can be generated from an arbitrary perfect sequence, the length of which is the product of a pair of odd integers ((2k + 1) (2n + 1) for k ges 1 and n ges 0). A zero-correlation zone sequence set that satisfies the theoretical bound of the sequence member size for the zero-correlation zone and the sequence period is called an optimal zero-correlation zone sequence set The proposed sequence construction can generate an optimal zero-correlation zone sequence set. The proposed sequence set can successfully provide CDMA communication without co-channel interference. In an ultrasonic synthetic aperture imaging system, the proposed sequence set can improve the signal-to-noise ratio of the acquired image.

Evolution of Software-Defined Sensor Networks

After a decade of extensive research on application-specific wireless sensor networks (WSNs), the recent development of information and communication technologies make it practical to realize new WSNs paradigm known as software-defined sensor networks (SDSNs). SDSNs are able to adapt to various application requirements and to fully explore the communication, computation and sensing resources of WSNs. Sensor nodes in SDSNs can be dynamically reprogrammed for different sensing tasks via the over-the-air-programming technique. In this paper, we introduce the concept of SDSNs and outline several pioneering related work and enabling technologies for the realization of SDSNs.

A Class of Zero-Correlation Zone Sequence Set Using a Perfect Sequence

This letter introduces a novel method of sequence construction having a zero-correlation zone. The cross-correlation function and the side-lobe of the auto-correlation function of the proposed sequence set is zero for the phase shifts within the zero-correlation zone. The proposed zero-correlation zone sequence set can be generated from an arbitrary perfect ternary sequence, the length of which is the product of a pair of odd integers ( (2k+1)(2n+1) for k ges 1 and n ges 0). The width of the zero-correlation zone of the proposed sequence set can be longer than the length of the perfect sequence that is used for constructing the proposed sequence set. The proposed sequence construction can generate an optimal zero-correlation zone sequence set that satisfies the theoretical bound of the sequence member size for the zero-correlation zone and the sequence period.

On Optimal Construction of Two Classes of ZCZ Codes

This paper presents constructions of two kinds of sets of sequences with a zero correlation zone, called ZCZ code, which can reach the upper bound of the member size of the sequence set. One is a ZCZ code which can be constructed by a unitary matrix and a perfect sequence. Especially, a ternary perfect sequence with elements ±1 and zero can be used to construct the proposed ZCZ code. The other is a ZCZ code of pairs of ternary sequences and binary sequences which can be constructed by an orthogonal matrix that includes a Hadamard matrix and an orthogonal sequence pair. As a special case, an orthogonal sequence pair, which consists of a ternary sequence and a binary sequence, can be used to construct the proposed ZCZ code. These codes can provide CDMA systems without co-channel interference.

Digital image analysis of droplet patterns in polymer systems: Point pattern

New techniques of digital image analysis which are especially suitable for analyzing particle‐distribution patterns are presented. Statistical mathematical methods are applied to the quantitative analysis of a spatial distribution of points in polymer systems. The techniques are useful for studying the spatial patterns of particles or droplets which are commonly observed in nucleation‐growth‐type phase separation and late‐stage spinodal decomposition in polymer mixtures, crystallization process, microphase separation in block copolymers, incompatible polymer alloys, and composite materials, etc. We can divide point patterns into three typical point patterns: the Poisson pattern, the clustered pattern, and the regular pattern. The kind and strength of interaction or force between points can be determined from spatial point‐distribution patterns. The point‐pattern analysis has been applied to phase‐separated structures of a polymer mixture, and it has been revealed that the pattern belongs to the regular pattern. The appearance of the regular pattern is probably a result of the Brownian coalescence mechanism for the droplet growth and it might also be due to a long‐range interaction among droplets through diffusion field.

Application of digital image analysis to the study of high‐order structure of polymers

A digital image analysis (DIA) technique has been applied directly to the study of the high‐order structure of polymers probably for the first time. Using this method, various types of physical information can be obtained in real and wave‐number (k) space. Included in this DIA method are operations such as two‐dimensional Fourier transformation, cross sectional profiles along various curves, the size and shape distribution of droplets, etc. This technique is widely applicable to any image obtained by optical microscopy, electron microscopy, ordinary photography, etc. In this communication, we apply the DIA method to the study of the pattern formation in polymers, namely the structure of spherulite and phase separation in polymer blends.

A software defined wireless sensor network

We propose a software-defined wireless sensor network system whose behavior can be redefined even after deployment by the injection of sensor node roles by means of wireless network communications. Two main technologies are used to develop this system, role generation and delivery mechanism, and a reconfigurable wireless sensor network with many reconfigurable sensor nodes. In the role generation and delivery mechanism, a scenario compiler generates roles for sensor nodes based on a user-defined scenario description and then delivers the roles to appropriate nodes. We also propose a reconfigurable sensor node composed of an ultra-low power field programmable gate array (FPGA) and a microcontroller unit (MCU) for altering network behavior. By assigning heavy tasks such as sensor and data processing to the FPGA, overloading of the MCU can be avoided. Using wireless communication, both configuration data for the FPGA and programs to run on the MCU can be injected as roles from outside of the sensor node, enabling easy alteration of sensor node functionality depending on situation and/or application. After introduction of a system overview, a prototype system is described and some experimental results are discussed.

Detectability of anterior displacement of the articular disk in the temporomandibular joint on helical computed tomographyThe value of open mouth position

OBJECTIVE The purpose of this study was to establish the diagnostic reliability of anterior displacement of the articular disk in the temporomandibular joint on helical computed tomography. STUDY DESIGN Ninety-four consecutive patients were examined through use of both computed tomography and magnetic resonance imaging. On axial computed tomography, anterior disk displacement was defined as the presence of an area of soft tissue density that was semilunar in shape and located in front of the mandibular condyle. RESULTS With magnetic resonance imaging taken as the diagnostic gold standard in evaluation of articular disk position, the sensitivity, specificity, and accuracy for computed tomography were 91%, 100%, and 97%, respectively, in the closed mouth position and 96%, 99%, and 98%, respectively, in the open mouth position. CONCLUSIONS The detectability on axial helical computed tomography of anterior displacement of the articular disk in the temporomandibular joint in the open mouth position was almost equal to that on magnetic resonance imaging. It is recommended that the open mouth position be added when helical computed tomography is used to evaluate patients with temporomandibular joint disease.