摘要:

AbstractThird generation CTs which acquire projection data using wide fan‐beam X‐rays that cover the cubic surface of the test object have two widely used tomogram reconstruction algorithms: i.e., the direct method and the arrangement method. The direct method applies fan‐like back projection directly in Cartesian coordinates. The arrangement method rearranges data to transform them into parallel fan beams. This paper proposes a new fast reconstruction algorithm in which polar coordinates are established that are spatially synchronous with the measurement geometry, reconstructed images are obtained by performing back projection in the polar coordinates and coordinate transformation is achieved from the polar coordinates to Cartesian coordinates. The features of this method are (1) computation is fast because the results of the many calculations are tabulated; (2) the remaining calculations are only product sums; and (3) it is easy to implement this method in hardware. The quality of images produced by the direct method is compared with that of the arrangement method and the present method using both computer simulation data and clinical data. The comparison shows that (1) spatial resolution of images produced by this method is better than that of the arrangement method, but almost equal to that of the direct method; and (2) the number of artifacts generated by calculations is

ISSN:0882-1666    

DOI:10.1002/scj.4690170701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA trend in computer development aiming at high‐speed processing is high‐level parallel processing using a large number of processing elements. This scheme is becoming more realistic with the recent progress of VLSI technology. On the other hand, there arises a problem of how to cope with the generation of faults with the increased number of processing elements. A faulttolerant computer with multiple redundancy has been developed, but no method has been presented in the parallel computer environment whereby sufficient redundancy against fault can be provided, to recover from fault and to continue the computation without a system down. In general, completeness of data is lost by a fault. In the field of numerical computation, however, there are problems with less stringent requirement for completeness of data (e.g., in iterative solution of a system of equations). This paper discusses the case where such a problem is solved by a parallel computer with lattice topology. Three structural types are proposed for dynamic fault recovery during execution, mutual connection and the method of recovery. The result of evaluation by simulation is sh

ISSN:0882-1666    

DOI:10.1002/scj.4690170702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe X‐ray CT has a high resolution with respect to the absorption coefficient, while its spatial resolution is inferior to other X‐ray imaging techniques. Consequently, the improvement of its spatial resolution is strongly desired. This paper theoretically analyzes the frequency component of the projection data, obtained by the third‐generation CT system using a wide‐angle fan beam. It is shown that the projection data contain the effective frequency component above the Nyquist frequency determined by the spacing between detectors. Then a new algorithm is proposed which utilizes that effective frequency component. The usefulness of the algorithm is examined by an experiment using a phantom and the human body. It is shown as a result that the new algorithm can realize spatial resolution corresponding to approximately twice the Nyquist frequency determined by the detector spacing. Using this algorithm, the spatial resolution of the CT image can be improved without decreasing the detector

ISSN:0882-1666    

DOI:10.1002/scj.4690170703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractCharacter segmentation is a technique which separates individual characters from character line image. It is one of the most important prerequisites for character recognition. In the past, segmentation of individual characters from a general object, such as mailing address and existing document, had strong constraints imposed on the character segmentation. These included contact between adjacent characters and separation of a single character, thereby preventing the segmentation technique from being a systematic approach. This paper discusses character segmentation, an indispensable means of pre‐processing in character recognition which has been considered to cope with the individual cases. A character segmentation method is proposed which is based on the clustering for the character cluster interval histogram by linear square‐error function, and on the dynamic programming using the minimum variance criterion for separation between character sectioning candidate positions in a line image. The first method is applied to the estimation of the character pitch, i.e., estimating the statistically best character pitch. It also extracts the parameters representing the placement properties for a series of characters. The second method is used to determine in a stable way a series of character sectioning positions. In the experiment, the method is applied to English language mail addresses, containing fixed and unspecified character pitches as well as contact between adjacent characters. A 99.2% correct segmentation rate was obtained for characters and 98.0% was obtained for words, indicating the effectiveness of the met

ISSN:0882-1666    

DOI:10.1002/scj.4690170704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe automation of each stage in the design and manufacture of computer systems is now being considered. The design language simulators, physical design systems and test systems are already in practical use. At present, however, the required verification of each stage is mostly performed manually. In consideration of this, the authors designed and developed an automatic system for constructing logic circuit diagrams (RADICS) aiming at easy manual verification and documentation. Seven criteria are specified for the visibility, which include the signal flow from input to output as well as the criteria adopted in the previous placement and routine system. This paper describes the aims and outlines of each algorithm in RADICS. The algorithms are then analyzed and evaluated.

ISSN:0882-1666    

DOI:10.1002/scj.4690170705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractOne of the important items in the automatic recognition of LSI cell drawings is the representation and interpretation of the overlapped part (overlap portion) composed of more than one line, different colors, or solid and dashed lines. This paper discussed first the representation of the overlap portion, and proposes a new representation method which has less ambiguity in the automatic interpretation of the overlap portion and makes the drawing easy for the designer. The algorithm is proposed which automatically interprets the overlap portion by this representation. The algorithm is composed of three parts: recognition of overlap symbol, search of the boundary of the overlap portion, and estimation of the overlapped paths. In particular, the estimation of the overlapped paths includes the rule‐type description for the major part and a heuristic method, which estimates the paths by adaptively enlarging the range of search. A program based on the proposed algorithm is combined into the cell‐drawing input device. The result of recognition for an actual cell drawing is presen

ISSN:0882-1666    

DOI:10.1002/scj.4690170706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper proposes a symbolic description of music information, which includes folk music. The method aims at the high‐level music information processing in the future with a high describing ability and a description handled easily by human abilit

ISSN:0882-1666    

DOI:10.1002/scj.4690170707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractPreviously, we proposed the state‐change‐bounded rectangular‐array cellular‐space acceptor, which is a rectangular‐array cellular‐space acceptor with cells of bounded state‐changes. At that time, we also discussed its basic properties. The major purpose of this paper is to describe the relations among the accepting power of the state‐change‐bounded rectangular‐array cellular‐space acceptor with square pattern as the input and those of other various kinds of two‐dimensional automata. It is shown, for example, that the deterministic rectangular‐array cellular‐space acceptor with the state‐change bounded by a constant, can be simulated by the two‐dimensional alternating finite automaton. At the end of this paper, a family of sets of square tapes which are accepted by the state‐change‐bounded rectangular‐array cellular‐space acceptor, is considered. Also, the closure properties of the operations, such as union, inte

ISSN:0882-1666    

DOI:10.1002/scj.4690170708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractTableau queries are known as abstract models of queries for relational databases. When two tableau queries are given, the problem of determining whether the result of one of the tableau queries always contains that of the other (containment decision problem), is of fundamental importance in obtaining the optimization procedure of tableau queries. The tableau queries defined by Aho et al. can express joins, projections and selections by equalities in the relational algebra. Under this definition, Aho et al. have shown that the containment decision problems are generally NP‐complete and that there exist a class of problems which can be decided in a polynomial time. In this paper, we classify the tableau queries which are obtained so as to be able to express the selections by inequalities into two groups by whether or not they are totally ordered. We show that if inequality selections are added to problems which can be solved in a polynomial time without inequality selection, then the containment decision problems are NP‐complete even though the tableau queries are totally ordered. Also, for queries which are not totally ordered, it is shown that even if stronger restriction is added, the containment decision problems are co‐NP‐c

ISSN:0882-1666    

DOI:10.1002/scj.4690170709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe memory subsystem hierarchical disk‐cache (MESSIAH) discussed in this paper aims at realization of high‐speed access to secondary memory. MESSIAH uses a large‐capacity buffer memory (A) for the input‐output device and a small‐capacity buffer (B) for each disk‐device. (A) realizes the traditional disk‐cache function. (B) realizes reduction of the disk‐rotations waiting time due to a miss in RPS (rotational position sensing), reduction of overlap between disk write‐in and search time, and immediate delivery of look‐ahead data. In other words, in MESSIAH (A) realizes a cache memory of sufficient capacity and (B) copes with RPS misses, which increase with size of the transfer block between disk and (A). (B) also realizes high‐speed write‐in and read‐out of the disk. Thus, MESSIAH provides greater advantage than the multiple effects of disk‐cache function and the B‐disk (buffer‐installed disk device). This paper proposes an architecture for MESSIAH and verifi

ISSN:0882-1666    

DOI:10.1002/scj.4690170710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY