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An integrated recording-rendering array system is constructed for three-dimensional reverberant environments. The array system is comprised of a hybrid microphone array consisting of a circular array with vertical extension for recording and a 3-layered loudspeaker array playback system. In the sound field analysis (SFA) stage, the hybrid microphone array is used to encode the sound field on the basis of plane-wave decomposition. The bearing and amplitude information of the plane waves can be retrieved using either a one-stage Newton's (NT) algorithm or a two-stage method. In the two-stage method, localization can be handled using either the minimum power distortion response beamformer or the multiple signal classification algorithms, followed by signal separation using either Tikhonov regularization (TIKR) algorithm or the NT method. In the sound field synthesis stage, to construct the room response model as required in field matching process, uniformly distributed plane waves are assumed. A two-step procedure is employed to select the regularization parameters in the TIKR algorithm to strike a balance between reconstruction performance and audio quality. A 3-layered loudspeaker array is implemented for reproducing the sound field that is parameterized previously in the SFA stage. The proposed acoustic array system is validated in a series of localization and listening tests.

We report fabrication and measurements of single-layer SnSe2/chemical vapor deposition (CVD) graphene/hexagonal boron nitride (h-BN) field-effect device. The coherent magnetotransport properties of such a hybrid system are systematically studied so as to obtain a good understanding of the structure which may find potential applications in thermoelectricity, flexible electronics, quantum coherent sensor as well as stress sensing. We observed weak localization well described by the Hikami-Larkin-Nagaoka model and the phase coherence length is around 540 nm for V BG = −20 V at 1 K. The phase coherence length could be effectively changed by controlling the temperature and gate voltage. We also obtain good field-effect dependent properties of atomic-scale SnSe2 ultrathin film/graphene system. Given the current challenges in tuning single-layer SnSe2/CVD graphene on h-BN with a suitable dielectric layer, our results suggest the potential of quantum coherent effect, an effective way for development of future quantum nano-switch device.

Estimating six degrees of freedom poses of a planar object from images is an important problem with numerous applications ranging from robotics to augmented reality. While the state-of-the-art Perspective-n-Point algorithms perform well in pose estimation, the success hinges on whether feature points can be extracted and matched correctly on target objects with rich texture. In this work, we propose a two-step robust direct method for six-dimensional pose estimation that performs accurately on both textured and textureless planar target objects. First, the pose of a planar target object with respect to a calibrated camera is approximately estimated by posing it as a template matching problem. Second, each object pose is refined and disambiguated using a dense alignment scheme. Extensive experiments on both synthetic and real datasets demonstrate that the proposed direct pose estimation algorithm performs favorably against state-of-the-art feature-based approaches in terms of robustness and accuracy under varying conditions. Furthermore, we show that the proposed dense alignment scheme can also be used for accurate pose tracking in video sequences.

We have used low-damage O 2 plasma treatment (O 2 -LDPT), with chemically reactive radicals generated in an inductively coupled plasma system equipped with a complementary filter, to prepare large-area graphene oxide (GO) sheets. Raman spectroscopy and X-ray photoelectron spectroscopy demonstrated that oxidative functionalities were formed on the graphene surfaces. However, the carboxyl group, which is the most important functional group for biological applications, only occupied about 6.1% of the GO sheets formed using O 2 -LDPT. By adding H 2 during O 2 -LDPT, the compositional ratio of carboxyl group could be greatly increased to 10.8%. Optical emission spectroscopy revealed that this enhancement was achieved because of the presence of hydroxyl radicals in O 2 /H 2 -LDPT.

We propose a system for real-time six degrees of freedom (6DoF) tracking of a passive stylus that achieves sub-millimeter accuracy, which is suitable for writing or drawing in mixed reality applications. Our system is particularly easy to implement, requiring only a monocular camera, a 3D printed dodecahedron, and hand-glued binary square markers. The accuracy and performance we achieve are due to model-based tracking using a calibrated model and a combination of sparse pose estimation and dense alignment. We demonstrate the system performance in terms of speed and accuracy on a number of synthetic and real datasets, showing that it can be competitive with state-of-the-art multi-camera motion capture systems. We also demonstrate several applications of the technology ranging from 2D and 3D drawing in VR to general object manipulation and board games.

Accurately tracking the six degree-of-freedom pose of an object in real scenes is an important task in computer vision and augmented reality with numerous applications. Although a variety of algorithms for this task have been proposed, it remains difficult to evaluate existing methods in the literature as oftentimes different sequences are used and no large benchmark datasets close to realworld scenarios are available. In this paper, we present a large object pose tracking benchmark dataset consisting of RGB-D video sequences of 2D and 3D targets with ground-truth information. The videos are recorded under various lighting conditions, different motion patterns and speeds with the help of a programmable robotic arm. We present extensive quantitative evaluation results of the state-of-the-art methods on this benchmark dataset and discuss the potential research directions in this field. The proposed benchmark dataset is available online at media.ee.ntu.edu.tw/research/OPT.

Circular microphone arrays (CMAs) are sufficient in many immersive audio applications because azimuthal angles of sources are considered more important than the elevation angles in those occasions. However, the fact that CMAs do not resolve the elevation angle well can be a limitation for some applications which involves three-dimensional sound images. This paper proposes a 2.5-dimensional (2.5-D) CMA comprised of a CMA and a vertical logarithmic-spacing linear array (LLA) on the top. In the localization stage, two delay-and-sum beamformers are applied to the CMA and the LLA, respectively. The direction of arrival (DOA) is estimated from the product of two array output signals. In the separation stage, Tikhonov regularization and convex optimization are employed to extract the source amplitudes on the basis of the estimated DOA. The extracted signals from two arrays are further processed by the normalized least-mean-square algorithm with the internal iteration to yield the source signal with improved quality. To validate the 2.5-D CMA experimentally, a three-dimensionally printed circular array comprised of a 24-element CMA and an eight-element LLA is constructed. Objective perceptual evaluation of speech quality test and a subjective listening test are also undertaken.

The aim of this study was to compare algorithms for solving inverse problems generally encountered in spatial audio signal processing. Tikhonov regularization is typically utilized to solve overdetermined linear systems in which the regularization parameter is selected by the golden section search (GSS) algorithm. For underdetermined problems with sparse solutions, several iterative compressive sampling (CS) methods are suggested as alternatives to traditional convex optimization (CVX) methods that are computationally expensive. The focal underdetermined system solver (FOCUSS), the steepest descent (SD) method, Newton’s (NT) method, and the conjugate gradient (CG) method were developed to solve CS problems more efficiently in this study. These algorithms were compared in terms of problems, including source localization and separation, noise source identification, and analysis and synthesis of sound fields, by using a uniform linear array (ULA), a uniform circular array (UCA), and a random array. The derived results are discussed herein and guidelines for the application of these algorithms are summarized.

Tennis Real Play (TRP) is an interactive tennis game system constructed with models extracted from videos of real matches. The key techniques proposed for TRP include player modeling and video-based player/court rendering. For player model creation, we propose the process for database normalization and the behavioral transition model of tennis players, which might be a good alternative for motion capture in the conventional video games. For player/court rendering, we propose the framework for rendering vivid game characters and providing the real-time ability. We can say that image-based rendering leads to a more interactive and realistic rendering. Experiments show that video games with vivid viewing effects and characteristic players can be generated from match videos without much user intervention. Because the player model can adequately record the ability and condition of a player in the real world, it can then be used to roughly predict the results of real tennis matches in the next days. The results of a user study reveal that subjects like the increased interaction, immersive experience, and enjoyment from playing TRP.

Estimating 3D pose of a known object from a given 2D image is an important problem with numerous studies for robotics and augmented reality applications. While the state-of-the-art Perspective-n-Point algorithms perform well in pose estimation, the success hinges on whether feature points can be extracted and matched correctly on targets with rich texture. In this work, we propose a robust direct method for 3D pose estimation with high accuracy that performs well on both textured and textureless planar targets. First, the pose of a planar target with respect to a calibrated camera is approximately estimated by posing it as a template matching problem. Next, the object pose is further refined and disambiguated with a gradient descent search scheme. Extensive experiments on both synthetic and real datasets demonstrate the proposed direct pose estimation algorithm performs favorably against state-of-the-art feature-based approaches in terms of robustness and accuracy under several varying conditions.

Studying mechanobiology in three-dimensional (3D) cell cultures better recapitulates cell behaviors in response to various types of mechanical stimuli in vivo. Stiffening of the extracellular matrix resulting from cell remodeling potentiates many pathological conditions, including advanced cancers. However, an effective tool for measuring the spatiotemporal changes in elastic properties of such 3D cell cultures without directly contacting the samples has not been reported previously. We describe an ultrasonic shear-wave-based platform for quantitatively evaluating the spatiotemporal dynamics of the elasticity of a matrix remodeled by cells cultured in 3D environments. We used this approach to measure the elasticity changes of 3D matrices grown with highly invasive lung cancer cells and cardiac myoblasts, and to delineate the principal mechanism underlying the stiffening of matrices remodeled by these cells. The described approach can be a useful tool in fields investigating and manipulating the mechanotransduction of cells in 3D contexts, and also has potential as a drug-screening platform., Summary: Use of a non-direct-contact platform for measurement of the spatiotemporal dynamics of matrix elasticity when remodeled by cells cultured in three-dimensional contexts.

Gaze tracking systems have high potential to be used as natural user interface devices; however, the mainstream systems are designed with infrared illumination, which may be harmful for human eyes. In this paper, a real-time eye localization, blink detection, and gaze estimation system is proposed without infrared illumination. To deal with various lighting conditions and reflections on the iris, the proposed system is based on a continuously updated color model for robust iris detection. Moreover, the proposed algorithm employs both the simplified and the original eye images to achieve the balance between robustness and accuracy. Experimental results show that the proposed system can achieve the accuracy of 96.8% for blink detection and the accuracy of 1.973 degree for gaze estimation with the processing speed of 10–11fps. The performance is comparable to previous works with infrared illumination.

To repair damaged cardiac tissue, the important principle of in vitro cell culture is to mimic the in vivo cell growth environment. Thus, micro-sized cells are more suitably cultured in three-dimensional (3D) than in two-dimensional (2D) microenvironments (ex: culture dish). With the matching dimensions of works produced by microfluidic technology, chemical engineering and biochemistry applications have used this technology extensively in cellular works. The 3D scaffolds produced in our investigation has essential properties, such has high mass transfer efficiency, and variable pore sizes, to adapt to various needs of different cell types. In addition to the malleability of these innovative scaffolds, fabrication procedure was effortless and fast. Primary neonatal mice cardiomyocytes were successfully harvested and cultured in 3D scaffolds made of gelatin and collagen. Gelatin and gelatin–collagen scaffold were produced by the formation of microbubbles through a microfluidic device, and the mechanical properties of gelatin scaffold and gelatin–collagen scaffold were measured. Cellular properties in the microbubbles were also monitored. Fluorescence staining results assured that cardiomyocytes could maintain in vivo morphology in 3D gelatin scaffold. In addition, it was found that 3D scaffold could prolong the contraction behavior of cardiomyocytes compared with a conventional 2D culture dish. Spontaneously contracted behavior was maintained for the longest (about 1 month) in the 3D gelatin scaffold, about 19 days in the 3D gelatin–collagen scaffold. To sum up, this 3D platform for cell culture has promising potential for myocardial tissue engineering.

Estimation of a object pose from camera is a well-developing topic in computer vision. In theory, the pose from a calibrated camera can be uniquely determined. But in practice, most of the real-time pose estimation algorithms suffer from pose ambiguity due to low accuracy of the target object. We think that pose ambiguityiXtwo distinct local minima of the according error functioniXexist because of the phenomenon of geometric illusions. Both of the ambiguous poses are plausible. After obtaining the solution of two minima (pose candidates), we develop a real-time algorithm for stable pose estimation of a target objects with a motion model. In the experimental results, the proposed algorithm diminish the significance of pose jumping and pose jittering effectively. To the best of our knowledge, this is the first work to solve the pose ambiguity problem with motion model in real-time application.

Tennis Real Play (TRP) is an interactive tennis game system constructed with models extracted from videos of real matches. The key techniques proposed for TRP include player modeling and video-based player/court rendering. For player model creation, we propose a database normalization process and a behavioral transition model of tennis players, which might be a good alternative for motion capture in the conventional video games. For player/court rendering, we propose a framework for rendering vivid game characters and providing the real-time ability. We can say that image-based rendering leads to a more interactive and realistic rendering. Experiments show that video games with vivid viewing effects and characteristic players can be generated from match videos without much user intervention. Because the player model can adequately record the ability and condition of a player in the real world, it can then be used to roughly predict the results of real tennis matches in the next days. The results of a user study reveal that subjects like the increased interaction, immersive experience, and enjoyment from playing TRP.

Tennis Real Play (TRP) is an interactive tennis game system constructed with models extracted from real game videos. The key techniques proposed for TRP include player modeling and video-based player/court rendering. Experiments show that vivid rendering results can be generated.

Herein, we wish to tear down the traditional boundaries between physics and life sciences by demonstrating a physically based, flow-focusing method to encapsulate mammalian cells into alginate-based microspheres in a very short period of time. We paid particular attention to the physical properties of the alginate solution as it was critical to create a physiologically relevant environment within the alginate microspheres. The cells we cultured when re-culturing them on Petri dishes could still be maintained for at least 4 days after microsphere encapsulation. We believe that this study would provide interesting insight in biophysics, polymer physics, and applied physics.