bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Local Wall Thinned Pipeline Under Combined Bending and Pressure
Authors: Shim D. J. , Choi J. B. , Kim Y. J. , Kim J. W. , Park C. Y.
Published: July 2003

Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G are still useful for assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element (FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress (σu,t) were obtain from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.
Resolution of Defects in Degenerated Shell Elements Through Modification of Gauss Integration
Authors: Kwon Y. D. , Goo N. S. , Lim B. S.
Published: July 2003

In this paper, the modified Gauss integration method is developed to eliminate the shear and membrane locking phenomena of the degenerated shell element. The behavior of the element based on the Mindlin/Reissner theory in plates and shells sometimes causes a problem. In displacement-based shell elements, the full integration of stiffness matrices leads to a 'locking' or over-stiff behavior. The selective or reduced integration procedures may often overcome these difficulties, while overstiff solutions may still occur in the analysis with a highly constrained boundary. Except for the six zero-energy modes associated with shell rigid body movements, during the reduced integration of the stiffness matrices, many extra zero spurious energy modes are introduced due to reduced integration. This is a serious defect of degenerated shell element. In previous studies, several methods such as the addition of nonconforming displacement modes, an assumed strain method, and hybrid and mixed elements have been introduced in an attempt to overcome these difficulties. In this study a newly modified Gauss integration method combining both a selective and a weight-modified integration is suggested. Numerical experiments show that the new selective integration and weight-modified integration rule is very effective in eliminating the shear and membrane locking in static and modal analyses, and removes spurious zero-energy modes as well. Also, the effectiveness of proposed shell element is tested by applying it to some example problems. We solved post-buckling problem by the Riks arc-length method and dynamic problem by the Newmark's time integration method, as well as static problems.
Analysis for Material Behavior of Sabot/Rods During Launch by Finite Element Method
Authors: Kim Jin Bong , Kim Man Geun
Published: July 2003

This study has been investigated to predict the deformation and states of stress and strain by axial and lateral acceleration during launch. Because a gun tube is not perfectly straight at its initial state while under gravity loading, the projectile deforms due to the change of contacts points with the flexible gun tube. Numerical simulations were used for gravity loading and the other type is initial shape and gravity loading. The ANSYS engineering analysis code was used to generate a parametric model of the projectile and conduct finite element analyses. Four types of nonlinear material and contact elements were incorporated into the model to account for the plastic deformation and contact between the penetrator, sabot, and tube.
A Study on the Crack Propagation Behavior of Aluminum Alloy Plates with a Single Edge Crack under Random Loading Spectrum
Authors: Hwang Young Jin , Kang Ki Kyung , Kim Jong-Bum , Lee Seok Soon
Published: July 2003

Modern aircraft are designed using the damage tolerance concept. Fatigue cracks will be occurred at the initial flaw such as micro flaws in the material and scratches during the material manufacturing process. And stress concentration on notches, fillets and rivet holes under random loads caused to initiate the crack. This crack will propagate by repeated loads and finally failure. Therefore aircraft parts must be performed the damage tolerance test to prove the safety of the design life under the loads during operation. In this study, we have tested and analyzed the crack propagation behavior of aluminum alloy 2024-T3 plate under random loads. The crack lengths measured by the fractography analysis were compared to the analysis results with the retardation effect.
Examination of Ellipticity and Stress Intensity Factors by Photoelastic and Caustic Methods
Authors: Ezumi Tsutomu , Suzuki Katsunao
Published: July 2003

In the field of linear elastic fracture mechanics, the stress intensity factor approach has been widely accepted as a valid means for predicting the behavior of a material in the presence of a crack or flaw. To optimize their dimension and to ensure their safety in service, a practical study of the strength under centrifugal force is important. In this paper, it is investigated that the stress intensity factors K_ and K_ on the rotating elliptic disks having outside cracks by means of combining the photoelastic freezing method and the caustics method. Stress intensity factors K and K were determined by using two experimental methods, as a function of ellipticity of the elliptic disk and at two different velocities. The results of these experimental methods was nearly agreement, and attracted the interest.
Contactless Measurement of Thin Film Conductivity by a Microwave Compact Equipment
Authors: Ju Yang , Hirosawa YO , Saka Masumi , Abé Hiroyuki
Published: July 2003

A method for contactless measurement of the conductivity of thin conducting film was demonstrated. In order to apply the technique to on-line testing, a large standoff distance of 35 mm was obtained by using a reflector focusing sensor. The measurement was preformed by using a microwave compact equipment working at 94 GHz which was developed for decreasing the system cost. Indium Tin Oxide films having conductivity of 8.2 × 104 ~ 6.6 × 105 S/m on the glass substrates were used as the samples. Evaluation equation for determining the conductivity of Indium Tin Oxide films was generated.
Combinatorial Synthesis of Exohedrally Modified Fullerene Derivatives
Authors: Kawamura Yasuhiko , Akai Yasuyuki , Tsukayama Masao
Published: July 2003

Fulleropyrrolidines have been very welcomed in a community of a fullerene science. But sometimes the synthesis ends up with disappointing yields of the products. In order to overcome the problem and to explore more environmentally benign method for synthesizing fullerene derivatives having various attachment on the surface of the fullerenes, a solid-phase synthesis is examined. We found that the dipolar cycloaddition of an azomethine ylide, i.e., 2-phenyl-N-benzylideneglycine methyl ester, supported on a Wang resin, proceeded feasibly with C 60 and the objective fulleropyrrolidines were afforded in good yields (>75%). The method is expected to be utilized with wide range of application and it is therefore able to provide a compound library of modified fullerenes which is hard to obtain by other methods employed so far.
Application of Damage Tolerance Approach for Turbine Disk Life Extension
Authors: Nahm Seung Hoon , Suh Chang Min , Jung Min Woo , Kim Jong Yup , Yang Chang Hwan
Published: July 2003

For gas turbine engines, the safe life methodology has historically been used for fatigue life management of failure critical engine components. The safe retirement limit is necessarily determined by a conservative life evaluation procedure, thereby many components which have a long residual life are discarded. The objective of this study is to introduce the damage tolerant design concept into the life management for aircraft engine component instead of conservative fatigue life methodology which has been used for both design and maintenance. The residual lives of turbine disk component under various temperatures and conditions using creep-fatigue crack initiation and growth data were estimated. As the result of analysis, it was confirmed that retirement for cause concept was applicable to the evaluation of residual life of retired turbine disk which had been designed based on the conventional fatigue life methodology.
The Characteristics of Propagation for Mixed-Mode Fatigue Crack under Stress Re-Distribution at Fatigue Crack Tip
Authors: Song Sam Hong , Lee Jeong Moo
Published: July 2003

The practical condition of applied load represents mixed-mode loading condition due to complications of element geometry and applied load. Also, the characteristics of fatigue crack propagation under mixed mode were affected by constrained shape of structures and applied load variation. There are continuous variations of stress condition at crack tip on the fatigue crack during propagation. Therefore, it is necessary to investigate the propagation behavior of mixed-mode fatigue crack under stress redistribution condition. We established the experimental method in order to form the stress redistribution condition. It is assumed that the stress around the crack tip under mixed-mode fatigue loading is redistributed. This test consisted of the 1st and the 2nd round of tests. The stress re distribution was formed by changing the loading direction at propagating mixed-mode fatigue crack tip. In this study, the behavior of mixed-mode fatigue crack affected by stress redistribution was investigated by comparing fatigue crack propagation rate, fatigue crack propagation paths and fatigue crack branch angle. From the experiment, as loading application angle and thickness change, the fatigue crack propagation rate and angle under mixed mode were affected by stress redistribution.
Analysis on Influential Factors in ${\rm C}^*_{\rm ref}$ Estimation of Cracked Tubular Components
Authors: Han Moon Sik , Kwon Oh Geon
Published: July 2003

Available methodologies used in evaluating the fracture mechanics parameters K, σref and C* for the cracked component specimen have been examined to determine their suitability. The fracture mechanics parameters were applied to correlate crack growth rate in the cracked tubular components operated at elevated temperature. The solutions from previous works were adopted and compared with other solutions to validate the feasibility of using a particular formula. The C* values from the reference stress method [Formula: see text] for the tubular components was validated provided an upper bound solution procedure was adopted.
Influence of Free Nitrogen on Creep Crack Growth of C-Mn Steel
Authors: Han Moon Sik , Kwon Oh Geon
Published: July 2003

Different chemical compositions and heat-treatments of the C-Mn steels were investigated to characterise a susceptibility to cracking on cold bent tube. The C-Mn steels were categorised in terms of the content of free nitrogen. Ultimate tensile strengths, yield strengths and elongations were measured from the tensile testing at ambient, 250°C and 360°C. Significant increase in ultimate tensile strength and decrease in elongation were observed in high free nitrogen material at 250°C the temperature at which free nitrogen is most active. The lower ductility of the high free nitrogen material has provided higher susceptibility to cracking in the creep crack growth tests at 360°C. Cracking in the high free nitrogen material A was approximately three times faster than the low free nitrogen material C at the same C* value. The creep cracking and rupture life in the high free nitrogen materials were more sensitive to the material condition, for example, pre-straining and/or heat treatment because of the role of the free nitrogen in the steels.
Degradation Evaluation of HK40 Steel Using Magnetic Properties
Authors: Nahm Seung Hoon , Park Jong Seo , Kim Si Cheon , Ryu Kwon Sang , Kim Jeong Min , Son De Rac , Han Sang In
Published: July 2003

The effect of isothermal heat treatments, which simulate the microstructural changes observed in furnace heater tube steel at the service temperature, on the magnetic properties was investigated. HK40 steel specimens with five different periods of aging were prepared by an isothermal heat treatment at 1050°C. Magnetic properties such as susceptibility were measured. The magnetic susceptibility at room temperature monotonously increased with the extent of degradation of the material. The Vickers hardness also increased with the extent of degradation. The correlation between the measured magnetic susceptibility and the Vickers hardness was studied. In addition, the applicability of magnetic susceptibility measurements to the evaluation of degraded HK40 steel was discussed. As result, the magnetic susceptibility method could predict the thermal degradation of HK40 steel with high reliability.
Evaluation of Defects in the Bonded Area of Shoes by Using Infrared Thermal Vision Camera
Authors: Yang Dong Jo , Kim Chang Hyun , Kim Jae Yeol
Published: July 2003

Diagnosis or measurements using Infrared thermo-image hasn't been available. A quick diagnosis and thermal analysis can be possible when that kind of system is introduced to the investigation of each part. In this study, Infrared Camera, Thermo-vision 900 of AGEMA Company was used in order to investigate. Infrared Camera usually detects only Infrared wave from the light in order to illustrate the temperature distribution. Infrared diagnosis system can be applied to various the field. But the defect discrimination can be automatic or mechanization on the special shoes total inspection system. Also, it is more effective to development and composition on the shoes total inspection system. In this study, it is introduction method of special shoes nondestructive total inspection. Performance of the proposed method are shown by through thermo-Image.
A Study on the Stress Analysis and Optimum Design of S-Shape Wheel for Rolling Stock
Authors: Sung Ki Deug , Yun Tae Hyeok , Lee Geun Sun , Kim Ki Hong
Published: July 2003

The mechanical stress due to the wheel-rail contact and thermal stress due to the drag braking increase the incidence of wheel failure. So, firstly, stress analyses(mechanical, thermal and combined stress) of wheel plate are performed using 3-dimensional finite element method(FEM). Secondly, the optimum design of wheel plate is investigated in order to reduce weight of the wheel based on results of stress analysis. The optimum design is performed using 2-dimensional axisymmetric F.E. model and its results are verified by 3-dimensional F. E. analysis.
Analysis of LIPCA-C Actuators
Authors: Goo Nam Seo , Yoon K. Joon
Published: July 2003

This paper has focused on the analysis of newly proposed Lightweight Piezo-composite Curved Actuator. LIPCA was born from the idea that the heavy metal layers of THUNDERTM were replaced by lightweight fiber reinforced plastic layers. Several combinations of composites and PZT wafer have been tested and finally two types are chosen: LIPCA-C1 and C2. Finite element code, developed in the previous work, has been used for the investigation of their static and dynamic behaviors. The maximum actuation displacements and fundamental frequency with respect to the design parameters are presented.
Thermal Ratcheting Behavior of a Cylindrical Structure with Plate-to-Shell Junction
Authors: Lee Hyeong Yeon , Kim Jong Bum , Lee Jae Han , Lee Jong Min
Published: July 2003

In this study the progressive inelastic deformation behavior of the 316L stainless steel cylindrical structure with plate-to-shell weld junction under cyclic thermal loads was carried out by structural test and analysis. This structural test intends to simulate the thermal ratcheting behavior occurring at the thermal liner of the liquid metal reactor as free surface of hot sodium pool moves up and down under plant heat-up, cool down and other thermal transients. A thermal ratchet load that heats the cylindrical structure up to 550°C was applied cyclically and residual deformation was measured. The temperature distribution of the test specimen along the axial direction was measured and was used for the ratcheting analysis. The thermal ratchet deformations were analyzed with the constitutive equation of the non-linear combined hardening model and the analysis results were compared with those of the test. The ratcheting deformations for different plate thickness in plate-to-shell junction and different traveling lengths obtained by the analysis using the combined hardening model were in reasonable agreement with those of the structural tests.
Design Optimization of a Curved Actuator with Piezoelectric Fibers
Authors: Kim Cheol , Lee Dong Yeub
Published: July 2003

Piezoelectric Fiber Composite with Interdigitated Electrodes (PFCIDE) was previously introduced as an alternative to monolithic wafers with conventional electrodes for applications of structural actuation. This paper is an investigation into the performance improvement of piezoelectric fiber composite actuators by optimizing the stacking sequence and changing the matrix material. This paper presents the numerical optimization of a piezoelectric fiber/piezoelectric matrix composite actuator with IDE (PFPMIDE). Various concepts from different backgrounds, including three-dimensional linear elastic and dielectric theories, have been incorporated into the present linear piezoelectric model. To see the structural responses of the actuator integrated with the PFPMIDE, three dimensional finite element formulations were derived. Numerical analyses show larger center displacement of the curved actuator with the PFPMIDE due to optimization of the piezoelectric fiber angles. This paper presents the concept of a curved actuator that occurs naturally via thermal residual stress during the curing process, as well as the optimization of the maximum curved actuator displacement, which is accomplished using the Davidon-Fletcher-Powell (DFP) method.
Derivement of Constraint Equations of Driving Motor for Rotary Crane Systems
Authors: Lee Jong Gyu , Terashima Kazuhiko , Lee Sang Ryong
Published: July 2003

In this paper, the dynamical model of rotary crane systems becomes nonlinear state equations. These equations are obtained by nonlinear equations of motion which are derived from transfer function of driving motors and equations of motion for a load. From these state equations, Lyapunov function of rotary crane systems is derived from integral method. This function secures stability of autonomous rotary crane systems. Also Constraint equations of rotation motor, boom motor, and hoist motor are derived from this function.
Determination of Stress-Strain Curve for Microelectronic Solder Joint by ESPI Measurement and FE Analysis
Authors: Lee Baik Woo , Jeong Jeung Hyun , Jang Woosoon , Kim Ju Young , Kim Dong Won , Kwon Dongil , Nah Jae Woong , Paik Kyung Wook
Published: July 2003

Many thermomechanical reliability studies on microelectronics and microsystems have relied upon computational analysis, since experimental work is rather difficult and very time-consuming. For computational analysis, it is essential to use as input accurate material properties; if not, the results of a reliability analysis may be very inaccurate. However, it is still quite difficult to arrive at unified material properties for modeling microelectronic assemblies because of the absence of standards for micro-material characterization, the difference between bulk and in-situ material properties, and so forth. The goal of this study was to determine the uniaxial stress-strain curve of a solder in a flip-chip assembly, using experimental measurements and finite-element analysis (FEA) of the solder's thermal deformation characteristics with increasing temperature. The thermal deformation of flip-chip solder joints was measured by electronic speckle pattern interferometry (ESPI). For the scale of evaluation required, the measurement magnification was modified to allow its application to micromaterials by using a long-working-distance microscope, iris and zoom lens. Local deformation of solder balls could be measured at submicrometer scale, and stress-strain curves could be determined using the measured thermal deformation as input data for finite-element analysis. The procedure was applied to an Sn-36Pb-2Ag flip-chip solder joint.
The Best Dimensional Standard Analysis Concerning Center Hole in Dabo
Authors: Noguchi Tetsuo , Ezumi Tsutomu
Published: July 2003

The destruction of the center hole becomes a big accident in lathe processing. This paper advocates the safety standard concerning the center hole. It is a simulation concerning the center hole by using of experimental mechanics and computational dynamics together. This study is composed by some analysis methods. The method is an isochromatic line, an isoclinic line by the photoelastic method, method of caustics, and two dimension finite element method, a tridimensionality finite element method. In the photoelasticity method, it was done that the test specimen model by which the real machine parts straight side direction section dimensional standard was copied was done. The test specimen model dimensional standard used by the photoelastic method was analyzed in two dimension finite element method. The model by which real machine parts was faithfully reproduced was analyzed in the tridimensionality finite element method. In method of caustics, an artificial crack was inserted in the test specimen model. The fracture process of the center hole was understood as a research result, and the equation to obtain the maximum stress was obtained. It is forecast that safety in the processing with the lathe can be secured if you follow the research result.
Effects of Pre-Damage on HCF Behaviors of Ti-6Al-4V Alloy
Authors: Park Taewon , Mall Shankar , Nicholas Thedore
Published: July 2003

The effects of pre-damage on the fatigue strength of Ti-6Al-4V were investigated by applying the low cycle fatigue(LCF) as a pre-damage prior to high cycle fatigue(HCF) test. The fatigue strengths were obtained by means of step-loading method. The pre-damage condition was decided as 900MPa, 0.5R, 50,000 cycles through LCF test, and was introduced before step-loading test. The fatigue strength of Ti-6Al-4V alloy derived from step-loading test without pre-damage was about 639MPa. The introduction of pre-damage deteriorates the fatigue strength about 6%. Progressive change in elongation with increasing cycles was observed. The strain accumulated by pre-damage varies the displacement in the next loading step, but afterward this doesn't change the displacement any more. The strain formed by pre-damage is thought to result in earlier failure and lower fatigue strength.
Fabrication of Variable Capacitor by Thin Copper Film with Electroplating
Authors: Seo Chang Taeg , Lee Jae Ho , Lee Jong Hyun , Bae Young Ho
Published: July 2003

The tunable capacitors have been fabricated by copper electroplating and MEMS(Micro-Electro-Mechanical Systems) technology. The thickness of electroplated copper which is used for moving electrode for variable capacitor below 0.5μm for lower actuation voltage. The fabricated tunable capacitors have been tested from 0V~42V and the resulting tuning range was between 62.3% and 90.2%. Also, the error rates have been presented ± 2.7% below.
Intriguing Aspects of Oriental Languages
Authors: Suen Ching Y. , Mori Shunji , Rim Hae-Chang , Wang Patrick S. P.
Published: July 2003

This paper includes a description of 3 affiliated oriental languages: Chinese, Japanese, and Korean. It includes a description of the origins of these 3 languages and the inter-relationship among them. Drawn from the viewpoints of several experienced researchers in the field of OCR (Optical Character Recognition) and computational linguistics, it attempts to bring out the intriguing aspects of these 3 ideographic languages, including the formation and composition of pictograms, special features, learning, understanding, contextual information, and recognition of characters and words, and their relations to poetic expressions and pattern recognition techniques. Numerous references are given and comments on future trends are also presented.
The Generation of Oriental Characters
Authors: Plamondon Réjean , Guerfali Wacef , Li Xiaolin
Published: July 2003

We recently developed a general theory of rapid human movements and applied it to the generation of western handwriting. The goal of this paper is to summarize the key concepts behind the so-called vectorial delta-lognormal model that results from this theory and to show how this model could be used for Chinese character analysis and processing.
Ink Matching of Cursive Chinese Handwritten Annotations
Authors: Lopresti Daniel P. , Ma Matthew Y. , Wang Patrick S. P. , Crisman Jill D.
Published: July 2003

In this paper, we discuss the notion of treating electronic ink as first class data without attempting to recognize it by presenting two different variations of approximate ink matching (AIM) for searching ink data. We also illustrate a pen-based electronic document annotating and browsing system and methods for searching handdrawn personal notes employing the described matching schemes. Adapting from the Learning by Knowledge paradigm, we propose a semantic matching network that applies semantics of Chinese language early in the process of ink matching. Finally we evaluate several key components in our entire ink matching network via experiments. Preliminary experimental results show the approximate ink matching algorithms perform well, despite the informal and highly variable nature of Chinese handwriting. Our experiments also show some promising results on semantic matching and the feasibility of our semantic matching architecture.
A Self-Organizing Hierarchical Classifier for Multi-Lingual Large-Set Oriental Character Recognition
Authors: Park Hee-Seon , Song Hee-Heon , Lee Seong-Whan
Published: July 2003

In this paper, we propose a practical scheme for multi-lingual, multi-font and multi-size large-set Oriental character recognition using a self-organizing hierarchical neural network classifier. In order to absorb the variation of the character shapes in multi-font and multi-size characters, a modified nonlinear shape normalization method based on dot density was introduced, and also to represent the different topological structures of multi-lingual characters effectively, a hierarchical feature extraction method was adopted. For coarse classification, a tree classifier and SOFM/LVQ based classifier which is composed of an adaptive SOFM coarse-classifier and an LVQ4 language-classifier were considered. For fine classification, a classifier based on LVQ4 learning algorithm has been developed.

The experimental results revealed that the proposed scheme has the highest recognition rate of 98.27% for testing data with 7,320 kinds of multi-lingual classes and the time performance of more than 40 characters per second on 486DX-2 66MHz PC.
Comparison of Feature Performance and its Application to Feature Combination in Off-Line Handwritten Korean Alphabet Recognition
Authors: Seo Kukhwan , Kim Jongyeol , Yoon Jongmin , Chung Kyusik
Published: July 2003

This paper presents (1) a quantitative performance comparison of the features used in off-line handwritten Korean alphabet recognition, and (2) some experimental results based on the feature combination approach. We classified the features into three: geometrical/topological, statistical and global. For each class, we selected four or five features and performed recognition experiments with PE92 database using neural network classifiers. We compared their recognition performances and selected the top four among those thirteen features: Up Down Left Right Hole, Gradient, Structure, and Mesh. With the combination of some or all of the four features, we repeated recognition experiments. Experimental results show that (1) as a whole, geometrical/topological features outperform the other two feature classes in terms of the recognition rate, and (2) UDLRH and Gradient features in geometrical/topological feature class outperform the other features, (3) the feature combination approach can result in performance improvement.
An Image-Recognition System Implemented On Hierarchical Parallel Architectures
Authors: Ancona Fabio , Rovetta Stefano , Zunino Rodolfo
Published: July 2003

The paper describes a parallel implementation of a vision system based on associative memories. The proposed real-time image-recognition system is based on the associative 'noise-like coding' model and is implemented on transputer-based tree structures. A high-performance device, the 'complex node' (CN), is introduced. The CN integrates two transputers by a dual-port memory and supports a total of eight links. Tree structures increase their throughput performance when CNs are included. A CN-including tree architecture is compared with a standard transputer-based tree structure having the same computational power. A comparative performance analysis shows the improvement in efficiency obtained when the novel device is used. In addition, theoretical derivations lead to a formula for the system's efficiency, and one demonstrates that expected values fit with measured ones, thus confirming the validity of the overall approach.
An Adaptive Parallel Computer Vision System
Authors: Kim Jeong-Min , Kim Youngsik , Kim Shin-Dug , Han Tack-Don , Yang Sung-Bong
Published: July 2003

An approach for designing a hybrid parallel system that can perform different levels of parallelism adaptively is presented. An adaptive parallel computer vision system (APVIS) is proposed to attain this goal. The APVIS is constructed by integrating two different types of parallel architectures, i.e. a multiprocessor based system (MBS) and a memory based processor array (MPA), tightly into a single machine. One important feature in the APVIS is that the programming interface to execute data parallel code onto the MPA is the same as the usual subroutine calling mechanism. Thus the existence of the MPA is transparent to the programmers. This research is to design an underlying base architecture that can be optimally executed for a broad range of vision tasks. A performance model is provided to show the effectiveness of the APVIS. It turns out that the proposed APVIS can provide significant performance improvement and cost effectiveness for highly parallel applications having a mixed set of parallelisms. Also an example application composed of a series of vision algorithms, from low-level and medium-level processing steps, is mapped onto the MPA. Consequently, the APVIS with a few or tens of MPA modules can perform the chosen example application in real time when multiple images are incoming successively with a few seconds inter-arrival time.
Principle of a Parallel Vision System Adapted to Textures
Authors: Landraud-Lamole Anne M.
Published: July 2003

A number of methods for classifying textures and for segmentation of textured images make use of multichannel filtering techniques because of their computational simplicity. On the other hand, biological experiments have shown the existence and the properties of visual channels and make it possible for us to select the "best" filter bank. In a performing artificial vision system, three important problems are to be solved: the rigorous sampling of the spatial frequencies, the scale related problem and parallel processing. This paper presents a mathematical solution to the logarithmic 1-D sampling of the spatial frequencies of a signal characterized by its energy spectrum. This solution obeys the signal theory. It is then extended to the 2-D sampling of the output energy image generated by what we call a "homothetic filter bank". While verifying the Shannon theorem, our system is compatible with the visual cells' sensitivities to frequencies and orientations. Scale problems are often encountered in computer vision, especially in methods using multichannel filtering. Our approach gives us a representation of an input textured image with a continuous multiresolution. With this representation, an interpretation of the information content of the image, invariant to scale and to orientation, is made possible. Any scale change in the image is represented by a simple translation along a logarithmic frequency-axis. In the same manner, a rotation corresponds to a translation along a linear orientation-axis. In our "homothetic visual-filter bank" (HFB) theory, it is shown that the frequency-filter function can be changed according to the application under consideration. In cases where texture discrimination is difficult, e.g. if two different textures have the same power spectrum, the solution may be to extract phase information using a classical complex Gabor function. But, we have shown that in order to design a parallel vision system, it is more pertinent to use the differences of Gaussian functions (DOG) which are real functions.
Discrimination of Facial Regions Based on Dynamic Grids of Point Representations
Authors: Herpers R. , Sommer G.
Published: July 2003

The application of an elastic graph-matching approach to discriminate facial image regions is presented. In contrast to the dynamic link architecture introduced by the Malsburg group, our application is not an identification task but a classification task. Therefore, our approach differs in several important aspects:

(1) the choice of the filter set,

(2) the selection of the positions of the nodes of the graph to represent the characteristic image information,

(3) the generation of a representative reference pattern needed for the calculation of the classifications, and

(4) a new two-step graph-matching approach based on the simulated annealing technique.

The approach was tested on facial regions taking the eye region as an example target. A classification performance for the verification of eye regions of more than 93% was achieved.
Learning Subspace Classifiers and Error-Corrective Feature Extraction
Authors: Laaksonen Jorma , Oja Erkki
Published: July 2003

Subspace methods are a powerful class of statistical pattern classification algorithms. The subspaces form semiparametric representations of the pattern classes in the form of principal components. In this sense, subspace classification methods are an application of classical optimal data compression techniques. Additionally, the subspace formalism can be given a neural network interpretation.

There are learning versions of the subspace classification methods, in which error-driven learning procedures are applied to the subspaces in order to reduce the number of misclassified vectors. An algorithm for iterative selection of the subspace dimensions is presented in this paper. Likewise, a modified formula for calculating the projection lengths in the subspaces is investigated.

The principle of adaptive learning in subspace methods can further be applied to feature extraction. In our work, we have studied two adaptive feature extraction schemes. The adaptation process is directed by errors occurring in the classifier. Unlike most traditional classifier models which take the preceding feature extraction stage as given, this scheme allows for reducing the loss of information in the feature extraction stage. The enhanced overall classification performance resulting from the added adaptivity is demonstrated with experiments in which recognition of handwritten digits has been used as an exemplary application.
Neural Networks Inspection System for Glass Bottles Production
Authors: Hamad D. , Betrouni M. , Biela P. , Postaire J.-G.
Published: July 2003

This paper describes a vision system that detects cracks in glass bottles production. The first step consists in collecting prototypes of bottles with and without defects. A sequence of 16 images is captured by a matrix camera while each bottle rotates in front of a specific lighting system. The second step is concerned with morphometric and photometric features extraction. The subsequent decision step is performed by different neural networks, such as MLP, RBF, PNN and LVQ. Finally, performances of these networks have been compared. All the images of bottles without defects have been recognized but a few images with small cracks, which are very important defects, have not been identified. However, since each bottle is represented by a sequence of 16 images, cracks will appear in at least three or four images, so that a defective bottle can be detected at least one time through the sequence. Therefore the decision system recognizes good and defective bottles with a very high rate of success.
Situated Image Understanding in a Multiagent Framework
Authors: Bianchi N. , Bottoni P. , Mussio P. , Spinu C. , Garbay C.
Published: July 2003

The paper addresses the problem of controlling situated image understanding processes. Two complementary control styles are considered and applied cooperatively, a deliberative one and a reactive one. The role of deliberative control is to account for the unpredictability of situations, by dynamically determining which strategies to pursue, based on the results obtained so far and more generally on the state of the understanding process. The role of reactive control is to account for the variability of local properties of the image by tuning operations to subimages, each one being homogeneous with respect to a given operation. A variable organization of agents is studied to face this variability. The two control modes are integrated into a unified formalism describing segmentation and interpretation activities. A feedback from high level interpretation tasks to low level segmentation tasks thus becomes possible and is exploited to recover wrong segmentations. Preliminary results in the field of liver biopsy image understanding are shown to demonstrate the potential of the approach.
Semi-Supervised Point Prototype Clustering
Authors: Bensaid Amine M. , Bezdek James C.
Published: July 2003

This paper describes a class of models we call semi-supervised clustering. Algorithms in this category are clustering methods that use information possessed by labeled training data Xd⊂ ℜp as well as structural information that resides in the unlabeled data Xu⊂ ℜp. The labels are used in conjunction with the unlabeled data to help clustering algorithms partition Xu ⊂ ℜp which then terminate without the capability to label other points in ℜp. This is very different from supervised learning, wherein the training data subsequently endow a classifier with the ability to label every point in ℜp. The methodology is applicable in domains such as image segmentation, where users may have a small set of labeled data, and can use it to semi-supervise classification of the remaining pixels in a single image. The model can be used with many different point prototype clustering algorithms. We illustrate how to attach it to a particular algorithm (fuzzy c-means). Then we give two numerical examples to show that it overcomes the failure of many point prototype clustering schemes when confronted with data that possess overlapping and/or non uniformly distributed clusters. Finally, the new method compares favorably to the fully supervised k nearest neighbor rule when applied to the Iris data.
Recognition of Partially Occluded Objects with Back-Propagation Neural Network
Authors: Ng Geok See , Sim Hak Chuah
Published: July 2003

The problem of occlusion in a two-dimensional scene introduces errors into many existing vision algorithms that cannot be resolved. Occlusion occurs where two or more objects in a given image touch or overlap one another. Since occlusion will be present in all but the most constrained environment, the recognition of partially occluded objects is important for industrial machine vision applications to solve real problems in the military domain and in factory automation. A new method is proposed in this paper to identify and locate objects lying on a flat surface. The method is based on a local and compact description of the objects' boundaries and a new fast recognition method involving neural networks. The merit of such approach is that it provides strong robustness for partially occluded object recognition. The method is integrated into a vision system that couples with an industrial robot arm to provide automatic picking and repositioning of partially occluded industrial parts.
Error-Correcting Graph Isomorphism Using Decision Trees
Authors: Messmer B. T. , Bunke H.
Published: July 2003

In this paper we present a fast algorithm for the computation of error-correcting graph isomorphisms. The new algorithm is an extension of a method for exact subgraph isomorphism detection from an input graph to a set of a priori known model graphs, which was previously developed by the authors. Similar to the original algorithm, the new method is based on the idea of creating a decision tree from the model graphs. This decision tree is compiled off-line in a preprocessing step. At run time, it is used to find all error-correcting graph isomorphisms from an input graph to any of the model graphs up to a certain degree of distortion. The main advantage of the new algorithm is that error-correcting graph isomorphism detection is guaranteed to require time that is only polynomial in terms of the size of the input graph. Furthermore, the time complexity is completely independent of the number of model graphs and the number of edges in each model graph. However, the size of the decision tree is exponential in the size of the model graphs and the degree of error. Nevertheless, practical experiments have indicated that the method can be applied to graphs containing up to 16 vertices.
Obtaining the Correspondence Between Bayesian and Neural Networks
Authors: Stassopoulou A. , Petrou M.
Published: July 2003

We present in this paper a novel method for eliciting the conditional probability matrices needed for a Bayesian network with the help of a neural network. We demonstrate how we can obtain a correspondence between the two networks by deriving a closed-form solution so that the outputs of the two networks are similar in the least square error sense, not only when determining the discriminant function, but for the full range of their outputs. For this purpose we take into consideration the probability density functions of the independent variables of the problem when we compute the least square error approximation. Our methodoloy is demonstrated with the help of some real data concerning the problem of risk of desertification assessment for some burned forests in Attica, Greece where the parameters of the Bayesian network constructed for this task are successfully estimated given a neural network trained with a set of data.
Generating Pictures Using Random Forbidding Context
Authors: Ewert Sigrid , van der Walt Andries
Published: July 2003

We use random context picture grammars to generate pictures through successive refinement. At any stage a picture consists of a shape divided into smaller shapes, each containing a variable or terminal. A variable may be rewritten according to a production of the underlying grammar. This entails either dividing the shape containing it into smaller shapes, or substituting a variable or terminal for it. For visualization purposes every terminal is associated with a color, and its shape is filled with that color. We show pictures generated with random context picture grammars, then concentrate on grammars which use forbidding context only and present a shrinking lemma for the corresponding languages.
From Shape from Shading to Object Recognition
Authors: Ortega Ana , Shah Mubarak
Published: July 2003

Recognition of objects is one of the main goals of computer vision. Several approaches have been proposed to solve this problem using 3-D shapes. In most of them it is assumed that the 3-D shape (depth map) is available. Several object recognition systems use range images to extract the 3-D shape.

We present a method that uses a shape from shading algorithm to perform 3-D object recognition for simple objects. This method extracts the 3-D information from a single intensity image, then segments the object into regions. After computing the properties of the regions, it compares the input object with the model objects in the database. To test our method, several images with slightly different viewing angles of single objects are matched against five models in the database.
Structural Recognition for Table-Form Documents Using Relaxation Techniques
Authors: Lin Chi-Fang , Hsiao Cheng-Yi
Published: July 2003

A novel method is proposed in this study to recognize the line structure of table-form documents, e.g. telephone bills and office documents. The line structures of table-form documents are mainly composed of horizontal and vertical line segments. By treating the segment structure as line patterns, the problem of structure recognition is turned out to be the searching of line pattern matching, which can be solved by adopting the technique of relaxation. The proposed method consists of a learning phase and a recognition phase. In the former phase, line structures of various kinds of table-form documents are taken as templates and are extracted through a line extraction algorithm, in which an unique number functioning as a form ID is assigned to each line pattern. In the latter, by adopting the method of relaxation, the line pattern of the testing document is matched to those patterns created in the previous phase and the form ID of the best matching is chosen as the ID of the testing document. To increase the performance of the proposed method, an algorithm was presented to reduce the number of line segments in the matching process. The experimental results reveal the practicability of the proposed methods.
Empirical Comparison of Various Discretization Procedures
Authors: Berka Petr , Bruha Ivan
Published: July 2003

The genuine symbolic machine learning (ML) algorithms are capable of processing symbolic, categorial data only. However, real-world problems, e.g. in medicine or finance, involve both symbolic and numerical attributes. Therefore, there is an important issue of ML to discretize (categorize) numerical attributes.

There exist quite a few discretization procedures in the ML field. This paper describes two newer algorithms for categorization (discretization) of numerical attributes. The first one is implemented in the KEX (Knowledge EXplorer) as its preprocessing procedure. Its idea is to discretize the numerical attributes in such a way that the resulting categorization corresponds to KEX knowledge acquisition algorithm. Since the categorization for KEX is done "off-line" before using the KEX machine learning algorithm, it can be used as a preprocessing step for other machine learning algorithms, too.

The other discretization procedure is implemented in CN4, a large extension of the well-known CN2 machine learning algorithm. The range of numerical attributes is divided into intervals that may form a complex generated by the algorithm as a part of the class description.

Experimental results show a comparison of performance of KEX and CN4 on some well-known ML databases. To make the comparison more exhibitory, we also used the discretization procedure of the MLC++ library. Other ML algorithms such as ID3 and C4.5 were run under our experiments, too. Then, the results are compared and discussed.