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Chen C.-Y.,National Chiao Tung University | Jia W.-K.,National Chiao Tung University | Jia W.-K.,Institute for Information Industry III | Chen Y.-C.,National Chiao Tung University
IET Communications | Year: 2012

Orthogonal frequency division multiplexing (OFDM)-based wireless transmission technologies such as WiMAX are now widely deployed, and the frame check sequence (FCS) scheme is used to enhance the reliability of OFDM-based systems. As the padding overhead cannot be completely avoided in such systems when variable-length medium access control (MAC) frames are encapsulated, the authors propose a novel cyclic redundancy check (CRC)-based error-correction scheme that utilises the frame padding overhead to carry as much extra segmented FCS information as possible. In a multi-hop relay environment, a mobile station might receive a multicast frame more than once, so the error bit correction scheme could be triggered in the first transmission. In the IEEE's work, the original CRC scheme is optional and only has limited error-detection capability in upper MAC layer. FCS requires a few bits in a frame, but in our work, CRC is compulsory and all sub-FCSs are carried by padding space without using any extra bit. For the best error-correction capability, all transmissions must be padded as many sub-FCSs are possible in cross layer. The proposed approach achieves a significant performance improvement over the legacy FCS scheme in terms of error detection and correction of multicast frames in a transparent mode multi-hop relay network, and it is redundancy-free as well as energy efficient. The authors assess the performance improvement via both mathematical analysis and simulations. The results show that the mobile stations get significant improvement of goodput and utilisation in an error-prone WiMAX multi-hop relay network. © 2012 The Institution of Engineering and Technology.

Chen K.-T.,National Taiwan University | Chang C.-K.,Industrial Technology Research Institute of Taiwan | Kuo H.-L.,Industrial Technology Research Institute of Taiwan | Lee C.-K.,National Taiwan University | Lee C.-K.,Institute for Information Industry III
Smart Materials and Structures | Year: 2011

In this paper, we propose an innovative photoelectric material made of a mixture of liquid crystal and spiropyran which can be used to tailor the performance of piezoelectric sensors. The impedance variation of this photoelectric material can be controlled using different ultraviolet (UV) irradiation times. We found that the impedance of the liquid crystal-spiropyran mixture remains stable after the UV irradiation. Results showed that UV irradiation at 180 s resulted in the lowest mixture impedance. It appears that the electrical properties of the mixture have great potential to modulate a piezoelectric system since UV irradiation can be used to tailor the impedance of a photosensitive electrode made of a liquid crystal-spiropyran sensor for PZT (i.e. lead zirconate titanate) modal actuator/sensor applications. The main innovation of this paper is the demonstration of a new approach towards producing a positive and negative bias voltage in different regions of a sensor by using UV illumination for different time periods. A one-dimensional mode 2 sensor for a cantilever beam was designed and tested to verify the validity of this innovative approach. Since UV illumination can be changed in situ or in real time, this research also represents the creation of an optically defined/tailored modal sensor. In the future, a two-dimensional optical modal control could also be obtained using the method demonstrated.

Sung C.-H.,CNRS Quantum and Molecular Photonics Laboratory | Sung C.-H.,National Taiwan University | Chauvat D.,CNRS Quantum and Molecular Photonics Laboratory | Zyss J.,CNRS Quantum and Molecular Photonics Laboratory | And 2 more authors.
Optics Letters | Year: 2010

We detected single dye-stained latex nanospheres as small as 20 nm using a two-detection channel modified surface plasmon microscope. We found that a radially polarized incident beam leading to excitation of well-focused surface plasmons induces both fluorescence and elastic linear scattering from the spheres. The two complementary emitted signals were detected in parallel by the two separated channels, leading to well-colocalized images. We obtained high spatial resolutions for both channels down to 250 nm in the lateral direction and 300 nm along the longitudinal axis. We believe this multimodal microscope can be useful to track nano objects and to compensate for intermittent fluorescence, thanks to a permanently activated parallel scattering detection channel. © 2010 Optical Society of America.

Yu Y.-Y.,National Taiwan University | Chang C.-K.,Industrial Technology Research Institute of Taiwan | Lai M.-W.,Industrial Technology Research Institute of Taiwan | Huang L.-S.,National Taiwan University | And 2 more authors.
Applied Optics | Year: 2011

Using a femtosecond laser incident to an oxide-metal-oxide film engraved with a subwavelength annular aperture (SAA) structure, we generated a Bessel-like beam to ablate silicon. Experimental results show that the silicon can be ablated with a 0.05 J=cm2 input ablation threshold at 120 fs pulse duration. We obtained a surface hole possessing a diameter less than 1μm. Optical performance, including depth-of-focus and focal spot of the SAA structure, were simulated using finite-different time-domain calculations. We found that a far-field laser beam propagating through a SAA structure possesses a submicrometer focal spot and high focus intensity. Our method can be easily adopted for surface machining in microfabrication applications. © 2011 Optical Society of America.

Jan C.-M.,National Taiwan University | Lee Y.-H.,National Taiwan University | Wu K.-C.,National Taiwan University | Wu K.-C.,National Applied Research Laboratories NARL | And 2 more authors.
Optics Express | Year: 2011

A circularly polarized ellipsometer was developed to enable realtime measurements of the optical properties of materials. Using a four photo-detector quadrature configuration, a phase modulated ellipsometer was substantially miniaturized which has the ability to achieve a high precision detection limit. With a proven angular resolution of 0.0001 deg achieved by controlling the relative positions of a triangular prism, a paraboloidal and a spherical mirror pair, this new ellipsometer possesses a higher resolution than traditional complex mechanically controlled configurations. Moreover, the addition of an algorithm, FTA (fault tolerance algorithm) was adopted to compensate for the imperfections of the optomechanical system which can decrease system measurement reliability. This newly developed system requires only one millisecond or less to complete the measurement task without having to adopt any other modulation approach. The resolution achieved can be as high as 4x10-7 RIU (refractive index unit) which is highly competitive when compared with other commercially available instruments. Our experimental results agreed well with the simulation data which confirms that our quadrature-based circularly polarized ellipsometer with FTA is an effective tool for precise detection of the optical properties of thin films. It also has the potential to be used to monitor the refractive index change of molecules in liquids. © 2011 Optical Society of America.

Chen K.-T.,National Taiwan University | Huang S.-D.,National Taiwan University | Chien Y.-H.,National Taiwan University | Chang W.-C.,National Taiwan University | And 2 more authors.
Smart Materials and Structures | Year: 2012

A photosensitive electrode made of titanium oxide phthalocyanine (TiOPc) was modulated optically and integrated with a piezoelectric sensor/actuator which allowed us to obtain in situ tailoring of real-time spatial performance. The TiOPc thin film was formed using a spin-coating process. The experimental results showed that the impedance of the TiOPc thin film irradiated by visible light was 0.053 times that of the film not irradiated by visible light. With the successful tailoring of the impedance of the photosensitive electrode, we designed an optically modulated lead zirconate titanate (PZT) sensor/actuator and tested it for different applications. The influence of the impedance match between the TiOPc thin film and PZT of our various optically modulated PZT sensor/actuator designs is discussed in detail. The optically modulated PZT sensor was designed for one-dimensional mode 1 sensor applications. In addition, the successful implementation of the DC effect allowed us to control the mode shape using our optically modulated PZT actuator which was tailored in real time insitu with different optical images. Potential applications of this newly developed TiOPc thin film sensor/actuator include deformable mirrors, microfluidic control applications, and vibration sensing/actuating. © 2012 IOP Publishing Ltd.

Pao H.-K.,National Taiwan University of Science and Technology | Chen K.-T.,Academia Sinica, Taiwan | Chang H.-C.,National Taiwan University of Science and Technology | Chang H.-C.,Institute for Information Industry III
IEEE Transactions on Computational Intelligence and AI in Games | Year: 2010

The objective of this work is to automatically detect the use of game bots in online games based on the trajectories of account users. Online gaming has become one of the most popular Internet activities in recent years, but cheating activity, such as the use of game bots, has increased as a consequence. Generally, the gaming community disapproves of the use of bots, as users may obtain unreasonable rewards without making corresponding efforts. However, game bots are hard to detect because they are designed to simulate human game playing behavior and they follow game rules exactly. Existing methods cannot solve the problem as the differences between bot and human trajectories are generally hard to describe. In this paper, we propose a method for detecting game bots based on some dissimilarity measurements between the trajectories of either bots or human users. The measurements are combined with manifold learning and classification techniques for detection; and the approach is generalizable to any game in which avatars' movements are controlled by the players directly. Through real-life data traces, we observe that the trajectories of bots and humans are very different. Since certain human behavior patterns are difficult to mimic, the characteristic can be used as a signature for bot detection. To evaluate the proposed scheme's performance, we conduct a case study of a popular online game called Quake 2. The results show that the scheme can achieve a high detection rate or classification accuracy on a short trace of several hundred seconds. © 2010 IEEE.

Chen C-W.,National Kaohsiung First University of Science and Technology | Chang H.-Y.,National Kaohsiung First University of Science and Technology | Chen J.-H.,Cheng Shiu University | Weng R.,National Kaohsiung First University of Science and Technology | Weng R.,Institute for Information Industry III
International Journal of Mobile Communications | Year: 2016

Adoption of innovative products such as smartphones may be due to a mixture of experienced considerations and psychological perceptions. By synthesising adoption theories through reinforcement of the role of conformity. This study explores user intention to adopt innovative smartphones in the Taiwan telecommunication market. The survey data is analysed using structural equation modelling which is based on the constructs of ease of use, compatibility, and relative advantage, analysis results indicate that informational conformity and normative conformity are positively related to the intention to use smartphones. Additionally, early adopters and early majority users have a higher likelihood of conformity driven by informational influence, while the late majority users display a higher tendency towards normative conformity. The results of this study significantly contribute to efforts of mobile communication operators to anticipate and predict a customer's intention to adopt smartphones, thus provides further insight into the development of marketing strategies for smartphones. © Copyright 2016 Inderscience Enterprises Ltd.

Chen X.,University of Washington | Hwang J.-N.,University of Washington | Lee C.-N.,National Sun Yat - sen University | Chen S.-I.,Institute for Information Industry III
IEEE Journal on Selected Topics in Signal Processing | Year: 2015

The rapid increasing demands of wireless multimedia applications have boosted the developments of video delivery technologies with cross-layer designs, driven by optimizing quality of experiences (QoEs) of end users. In this paper, a near optimal power allocation scheme, targeting at maximizing QoE, is proposed for transmitting scalable video coding (SVC) based videos over multi-input multi-output (MIMO) systems. Both transmission errors in the physical (PHY) layer and video source coding characteristics in the application (APP) layer are jointly considered in the proposed scheme. A near optimal solution is achieved by decomposing the original optimization problem into several convex optimization sub-problems. Detailed algorithms with corresponding theoretical reasoning are provided. Since forward error corrections (FEC) techniques are widely implemented in modern wireless communication systems, the proposed scheme is further extended to the systems with Reed-Solomon (RS) code and a more practical approach with different modulation and coding schemes (MCSs). The near optimality of our proposed scheme, in terms of measured utilities, is shown by comparing with the exhaustive searched optimal solutions. Simulations with real H.264 SVC video traces demonstrate the effectiveness of our proposed scheme by comparing with other existing schemes in terms of well-accepted video quality assessment methods, such as peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) index. © 2014 IEEE.

Tsai T.-M.,Institute for Information Industry III | Yang P.-C.,Institute for Information Industry III | Wang W.-N.,Institute for Information Industry III
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

Social media has become the most convenient space to retrieve the tremendous consumers' experience, opinion and preference-toward each brands, products or even specific features. The real-time and big amount characteristics of Social media provide great opportunity for producer to know their customers (and potential ones) well. This paper proposes an Online to Offline (O2O) Commerce Service Model and takes the social relationship dashboard as an pilot study, which can help retailers or brands to understand their customers via social network existing data (especially Facebook for this case) by which we can adapt the current social commerce marketing strategy more quickly and responsively. © 2013 Springer International Publishing.

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