Chotikakamthorn, Nopporn

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Chotikakamthorn, Nopporn
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Chotikakamthorn, N.
Chotikakamthornb, Nopporn
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nopporn.ch@kmitl.ac.th

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    A light-pointing method for virtual object selection and manipulation in a monoscopic viewing system
    (2005-12-01)
    Kanjanasupark, Pornchai
    ;
    Chotikakamthorn, Nopporn
    Virtual object selection and re-location are two basic object manipulations that can be found in most VR/VE applications. Many interaction metaphors have been developed for object manipulation in VR/VE environments. Of particular interest is the ray-casting method. The method applies a light ray metaphor in selecting and moving a virtual object. However, the method implicitly requires a stereoscopic viewing system to be efficiently use. With a monoscopic viewing system, inefficiency of the method in terms of task completion time is demonstrated in this paper. For a system using a monoscopic viewing device, a light-pointing method based on a laser-pointer metaphor is proposed to alleviate the shortcoming of the original ray-casting method. Compared with the ray-casting method, it was found from the experiment that the proposed method is noticeably more efficient in terms of task completion time. © 2005 IEEE.
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    Interactive public display using mobile web client
    (2017-07-01)
    Pattanakimhun, Patchara
    ;
    Chotikakamthorn, Nopporn
    ;
    Chinthammit, Winyu
    Large public displays are widely used in public spaces for serving information. Most of them lack user-content interaction due partly to the fact that a touch screen is not suitable. With nearly universal adoption of mobile smartphone devices worldwide, its use as a tool for interacting with a public display is a viable option. Lack of standard interaction methods, protocols, and wide-spread used mobile applications for this purpose is a problem that prevents its adoption. In this paper, we address these problems by proposing a method with a mobile phone device as a tool for interaction with a public display system. The method is based on a standard web client, preinstalled on all smartphone devices, thus avoiding the problem as mentioned. Standard mobile gestures were employed for ease of use. The problem of establishing a connection and getting control of the public display is addressed. Three pairing methods have been described and evaluated. The results and discussion are provided.
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    An interatvie stereoscopic viewing system using fast vision-based leg end-point position estimation
    (2005-12-01)
    Phutphuek, Narongsak
    ;
    Chotikakamthorn, Nopporn
    In this paper, a problem of interactive stereoscopic display is considered. To provide a stereo image pair with correct viewing angle, a stereoscopic system must be able to identify a viewer spatial location. A fast and low-cost viewer location estimation method using a single video camera is described in this paper. The method tracks a viewer's standing position by estimating his/her leg end-point on the floor. The so-obtained position is then transformed to a 3D coordinate by using a planar homographic projection. Because the estimated viewer position is noisy, a smoothing and semi-interactive updating algorithm is developed to reduce a flicker caused by the imprecise estimate. © 2005 IEEE.
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    Handwriting rearrangement for Thai calligraphy
    (2017-02-23)
    Tonmaithong, Karun
    ;
    Annanab, Supawan
    ;
    Chotikakamthorn, Nopporn
    In this paper we propose a new algorithm to rearrange handwriting for Thai online handwriting beautification. First, we segment the line into the right group (Line of tone level, Line of upper level, Line of body level and Line of lower level). Then we calculate the center point of each character by x average and y average value. After that we find the moving path that includes two perpendicular marks at the end of the path. Finally, we adjust Thai handwriting by moving the character up or down along the Moving line. The text's position is changed into the middle point of the Moving line.
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    Blockchain-based Learning Credential Revision and Revocation Method
    (2020-10-07)
    San, Aye Mi
    ;
    Chotikakamthorn, Nopporn
    ;
    Sathitwiriyawong, Chanboon
    Many blockchain-based learning credential systems have been proposed to reduce fraud and improve verification efficiency. In addition to a method for issuing and verifying credentials, a solution is needed to support the revision and revocation of an issued credential record. For the case of learning credentials, depending on how a revocation policy affects credential use that occurred before the revocation date, an additional mechanism may be needed for credential revision. Current digital learning credential methods offer only a revocation mechanism. So they do not fully meet such unique requirement in the education context. In this paper, a blockchain-based method for learning credential revision and revocation is proposed. It makes use of the revision and revocation addresses assigned to each batch of issuing credentials. To revise (revoke) one or more credentials, the proposed method stores the revision (revocation) list as a message in the OP_RETURN field of the revision (revocation) transaction, with the revision (revocation) address as one of its outputs. The concept of a local credential id has been introduced to allow a revision (revocation) list to be efficiently stored on a blockchain system. It is based entirely on a blockchain system and does not require any centralized authority. It is also applicable to most blockchain systems. A comparative study of the proposed method against existing credential revocation methods is also provided.
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    Seeing by drawing: Use of a force-feedback device for conveying basic geometric visual information
    (2000-12-01)
    Chotikakamthorn, Nopporn
    ;
    Hongboonme, Nattavadee
    In this paper, the problem of using a force-feedback device to display basic geometric information is considered. Two visual-haptic transformation methods are applied to display geometric-shape properties by a point-contact force-reflective device. With the first method, movement of a user's finger tip, attached to a force-feedback device's thimble, is limited to points on a contour representing an outline of the (1-D or 2-D) geometric shape under display. In the second method, a drawing force is applied to a thimble, to move a user's finger along the contour corresponding to the displayed shape. Drawing speed is adjusted to reflect some properties of the displayed data curve, such as evolution of its first or second derivatives over time or spatial reference axis. Implementation aspects of the two methods are discussed. Efficiency of the described haptic display methods has been investigated through experiments with basic geometric outline shapes and scientific data.
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    Near point light source location estimation from shadow edge correspondence
    (2015-09-23)
    Chotikakamthorn, Nopporn
    The problem of near point light source location estimation is considered. The approach described here is based on a relationship between the cast shadow edge, the shadow-casting surface, and the light source. Given an optical-depth image pair available from an RGB-D camera, a method for near point light source location estimation is described. The method can be applied to a shadow-casting object with arbitrary and unknown geometry. Exhaustive multidimensional search is avoided by the proposed iterative one-dimensional search algorithm. Experimental results with real images are included.
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    Attacks on feature-based affine-invariant watermarking methods
    (2005-12-01)
    Chotikakamthorn, Nopporn
    ;
    Pantuwong, Natapon
    A class of attacks targeting at a feature-based affine-invariant digital watermarking technique is addressed in this paper. First, it is pointed out that the use of feature points to revert an affine transform operation is equivalent to the use of a known image size or boundary for image normalization. Therefore, any method based on feature points suffers from point shifting in much the same manner as how the image normalization scheme suffers from cropping or reframing. Some simple methods to perform a (feature) point shifting attack are next described. Although use of a sufficient large number of candidate feature points can solve the problem, the paper further points out that this solution, like any secure template-based watermarking method, results in high detection complexity. A two-stage search scheme is proposed to avoid the attack, while retaining the overall detection complexity to a reasonable level. © 2005 IEEE.
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    Improved dynamic gesture segmentation for Thai sign language translation
    (2004-12-27)
    Werapan, Worawit
    ;
    Chotikakamthorn, Nopporn
    Sign languages normally make use of both static and dynamic gestures to achieve communication goal. In automated continuous gesture recognition, one of the problems found is how to separate a transitional gesture from a meaningful dynamic gesture. In addition, a variation in speed, absolute position and orientation of a dynamic gesture makes an automatic recognition task nontrivial. This paper proposes a segmentation method that alleviates these problems. The method is based on the fact that many (meaningful) dynamic gestures as appeared in Thai and other sign languages, are performed in an approximately (quasi) periodic manner. Therefore, such dynamic gestures can be distinguished from a transitional gesture by means of Fourier analysis, performed on samples (discrete signal) of hand shapes, positions, and orientation. The analysis, however, requires a good choice of data sample windowing. This paper describes a pre-processing method for estimation of the dynamic gesture data windowing period. The proposed method helps improving the accuracy of segmenting hand shape and location data samples into static, periodic, and non-periodic gestures. In addition, accuracy of the feature extracted from the Fourier analysis of a dynamic gesture signal is improved, thus increasing the recognition rate. Experimental results performed on a real data are included.
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    An efficient P2P searching and indexing strategy for multi-keyword query
    (2013-01-01)
    Jitnupong, Tanapon
    ;
    Chotikakamthorn, Nopporn
    Multi-keyword search in a P2P repository system based on DHT suffers from high traffic cost due to intersection operation of distributed inverted lists. Indexing by a set of keywords (term set) is one possible solution to reduce the cost. However, as the number of terms for each set increases, the number of possible term sets increases tremendously. Index pruning partly solves the problem, with the cost of reduced recall rate. In this paper, a multi-keyword search strategy for use with the term-set index pruning technique is proposed to increase recall rate, while retaining the same index size required for the case of a two-keyword search. Experimental result supports the predicted improvement.