[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

A scheme is developed for classifying the types of motion perceived by a humanlike robot. It is assumed that the robot receives visual images of the scene using a perspective system model. Equations, theorems, concepts, clues, etc., relating the objects, their positions, and their motion to their images on the focal plane are presented. >

http://ieeexplore.ieee.org/iel2/815/3148/00100651.pdf

Robot vision

/pdf/remote-sensing-of-the-environment-4yfxjaaswe.pdf

Remote sensing of the environment

This paper provides a comprehensive review of the domain of physical layer security in multiuser wireless networks. The essential premise of physical layer security is to enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without relying on higher-layer encryption. This can be achieved primarily in two ways: without the need for a secret key by intelligently designing transmit coding strategies, or by exploiting the wireless communication medium to develop secret keys over public channels. The survey begins with an overview of the foundations dating back to the pioneering work of Shannon and Wyner on information-theoretic security. We then describe the evolution of secure transmission strategies from point-to-point channels to multiple-antenna systems, followed by generalizations to multiuser broadcast, multiple-access, interference, and relay networks. Secret-key generation and establishment protocols based on physical layer mechanisms are subsequently covered. Approaches for secrecy based on channel coding design are then examined, along with a description of inter-disciplinary approaches based on game theory and stochastic geometry. The associated problem of physical layer message authentication is also briefly introduced. The survey concludes with observations on potential research directions in this area.

/pdf/principles-of-physical-layer-security-in-multiuser-wireless-3w4jvwpgy4.pdf

Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey

In this paper, we propose a unified framework to generate a pleasant and high-quality street-view panorama by stitching multiple panoramic images captured from the cameras mounted on the mobile platform. Our proposed framework is comprised of four major steps: image warping, color correction, optimal seam line detection and image blending. Since the input images are captured without a precisely common projection center from the scenes with the depth differences with respect to the cameras to different extents, such images cannot be precisely aligned in geometry. Therefore, an efficient image warping method based on the dense optical flow field is proposed to greatly suppress the influence of large geometric misalignment at first. Then, to lessen the influence of photometric inconsistencies caused by the illumination variations and different exposure settings, we propose an efficient color correction algorithm via matching extreme points of histograms to greatly decrease color differences between warped images. After that, the optimal seam lines between adjacent input images are detected via the graph cut energy minimization framework. At last, the Laplacian pyramid blending algorithm is applied to further eliminate the stitching artifacts along the optimal seam lines. Experimental results on a large set of challenging street-view panoramic images captured form the real world illustrate that the proposed system is capable of creating high-quality panoramas.

A Unified Framework for Street-View Panorama Stitching.

Pulsed eddy current (PEC) responses would intersect at a point for a nonferrous plate when only liftoff distance is varied. In this paper, the behaviors of liftoff point of intersection (LOI) points due to a plate with varying conductivity and thickness were investigated and interpreted in physics by means of simulations and experiments. LOI points result from the invariance of the phase spectrum of PEC responses to liftoff effect, and the time of LOI points would increase with an increase of phase spectrum. Subsequently, the signatures of LOI points were compared with the peak heights and time to peaks of PEC signals and their derivatives. The results demonstrate that the signatures of LOI points possess the comparable performances in terms of sensitivity, linearity and measurement range. Moreover, the signatures of LOI points are immune to liftoff variations in nature, which shall enhance the accuracy and reliability of PEC evaluation.

Thickness measurement using liftoff point of intersection in pulsed eddy current responses for elimination of liftoff effect

Carbon fibre reinforced plastic (CFRP) has been widely used in industry. In order to detect and evaluate impact damage defects within this material, a non-destructive testing and evaluation (NDT&E) method of eddy current pulsed thermography (ECPT) is proposed. The idea of divergence characterisation of the expansion (or contraction) rate of the object and fluid volume can be extended to the thermal pattern characterisation of ECPT. This paper enables the extraction of this value of divergence at an appropriate time period to yield several desirable properties unique to NDT&E problems. The relationship between divergence and transient thermal patterns, as well as divergence and impact energy, are provided and analysed. The positive and negative values of the divergence and their relationship between composite structures and material state are investigated. Quantitative non-destructive evaluation (QNDE) of impact damage with ECPT from divergence patterns and image areas is derived. The results of this proposed method illustrate that defect areas are highly affected by impact energies. This proposed work can be applied for impact damage detection and quantitative evaluation in CFRP, which can be further used in life-cycle assessment and condition based maintenance.

Quantitative non-destructive evaluation method for impact damage using eddy current pulsed thermography

One of the challenges in structural health monitoring (SHM) is that defects, such as metal cracks and corrosions, can occur with multiple material properties and multilayer structure, entangled with influences from the reader system and the environment. This paper presents a multiresonance chipless radio frequency identification (RFID) sensor tag and the chipless RFID sensor reader applying principal component analysis (PCA) for multiparameter estimation in metal defect characterization. The proposed sensor tag is composed of the crossed diagonal dipole patches and the L-shaped patches generating six resonance peaks within 2-6-GHz band. The frequency signature of the sensor tag is acquired and processed by a chipless RFID reader implemented using an ultra-wideband impulse radar (UWB-IR) transceiver module. We demonstrate that the multiresonance chipless RFID sensor tag in conjunction with PCA-based feature extraction and selection can be applied for the characterization of metal crack with different widths and orientations. Furthermore, the proposed technique can find a robust feature indicating corrosion stages under a coating layer regardless of the sample orientation. This paper paves the way for multiparameter defect sensing and monitoring using a chipless RFID sensor system.

Multiresonance Chipless RFID Sensor Tag for Metal Defect Characterization Using Principal Component Analysis

For many non-destructive testing (NDT) applications, more information and greater reliability can be gained by using different techniques for defect detection, especially when the methods are particularly sensitive to different types of defects. However, this will often lead to a much longer and more expensive test and is not always practical due to time and cost constraints. We have previously discussed initial experiments using a new dual-probe combining electromagnetic acoustic transducers (EMATs) generating and detecting ultrasonic surface waves, and a pulsed eddy current (PEC) sensor [1]. This enables more reliable detection and sizing of surface and near-surface defects, with a reduced testing time compared to using two NDT techniques separately. In this paper, we present experiments using the dual-probe on samples which are more representative of real defects, for example testing for surface defects in rails. Several aluminium calibration samples containing closely spaced and angled slots have been measured, in addition to rail samples containing manufactured and real defects. The benefits of using the dual-probe are discussed.

Dual EMAT and PEC non-contact probe: applications to defect testing

Wireless sensor networks (WSNs) are one of the most able technologies in the structural health monitoring (SHM) field. Through intelligent, self-organising means, the contents of this paper will test a variety of different objects and different working principles of sensor nodes connected into a network and integrated with data processing functions. In this paper the key issues of WSN applied in SHM are discussed, including the integration of different types of sensors with different operational modalities, sampling frequencies, issues of transmission bandwidth, real-time ability, and wireless transmitter frequency. Furthermore, the topology, data fusion, integration, energy saving, and self-powering nature of different systems will be investigated. In the FP7 project “Health Monitoring of Offshore Wind Farms,” the above issues are explored.

/pdf/investigation-of-wireless-sensor-networks-for-structural-41phvlunuc.pdf

Gui Yun Tian

Papers

Thickness measurement using liftoff point of intersection in pulsed eddy current responses for elimination of liftoff effect

Quantitative non-destructive evaluation method for impact damage using eddy current pulsed thermography

Multiresonance Chipless RFID Sensor Tag for Metal Defect Characterization Using Principal Component Analysis

Dual EMAT and PEC non-contact probe: applications to defect testing

Investigation of Wireless Sensor Networks for Structural Health Monitoring