Prediction of 3-d surface topography in ultra-precision machining

2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Negative time delay for wave reflection from a one-dimensional semi-harmonic well

It is reported that the phase time of particles which are reflected by a one-dimensional semi-harmonic well includes a time delay term which is negative for definite intervals of the incoming energy. In this interval, the absolute value of the negative time delay becomes larger as the incident energy becomes smaller. The model is a rectangular well with zero potential energy at its right and a harmonic-like interaction at its left.Comment: 6 pages, 5 eps figures. Talk presented at the XXX Workshop on Geometric Methods in Physics, Bialowieza, Poland, 201

Vertex importance extension of betweenness centrality algorithm

Variety of real-life structures can be simplified by a graph. Such simplification emphasizes the structure represented by vertices connected via edges. A common method for the analysis of the vertices importance in a network is betweenness centrality. The centrality is computed using the information about the shortest paths that exist in a graph. This approach puts the importance on the edges that connect the vertices. However, not all vertices are equal. Some of them might be more important than others or have more significant influence on the behavior of the network. Therefore, we introduce the modification of the betweenness centrality algorithm that takes into account the vertex importance. This approach allows the further refinement of the betweenness centrality score to fulfill the needs of the network better. We show this idea on an example of the real traffic network. We test the performance of the algorithm on the traffic network data from the city of Bratislava, Slovakia to prove that the inclusion of the modification does not hinder the original algorithm much. We also provide a visualization of the traffic network of the city of Ostrava, the Czech Republic to show the effect of the vertex importance adjustment. The algorithm was parallelized by MPI (http://www.mpi-forum.org/) and was tested on the supercomputer Salomon (https://docs.it4i.cz/) at IT4Innovations National Supercomputing Center, the Czech Republic.808726

Emotional Fuzzy Sliding-Mode Control for Unknown Nonlinear Systems

[[abstract]]The brain emotional learning model can be implemented with a simple hardware and processor; however, the learning model cannot model the qualitative aspects of human knowledge. To solve this problem, a fuzzy-based emotional learning model (FELM) with structure and parameter learning is proposed. The membership functions and fuzzy rules can be learned through the derived learning scheme. Further, an emotional fuzzy sliding-mode control (EFSMC) system, which does not need the plant model, is proposed for unknown nonlinear systems. The EFSMC system is applied to an inverted pendulum and a chaotic synchronization. The simulation results with the use of EFSMC system demonstrate the feasibility of FELM learning procedure. The main contributions of this paper are (1) the FELM varies its structure dynamically with a simple computation; (2) the parameter learning imitates the role of emotions in mammalians brain; (3) by combining the advantage of nonsingular terminal sliding-mode control, the EFSMC system provides very high precision and finite-time control performance; (4) the system analysis is given in the sense of the gradient descent method.[[notice]]補正完

A report on a randomly sampled questionnaire survey about renal stone disease in Hong Kong

Objectives: To investigate the prevalence and characteristics of patients with renal stone in Hong Kong, and awareness of corresponding prevention strategies. Design: Telephone public survey. Setting: Hong Kong community. Participants: A public telephone survey concerning the occurrence of renal stone disease and the public awareness of the condition was performed. Respondents whose telephone numbers were randomly selected by computer and the family member of the household who had the closest birthday to that date was chosen for interview. Data collected were further adjusted for the gender and age distribution of the Hong Kong population in mid-2007. Results: A total of 1010 Hong Kong citizens aged 18 years or above were successfully interviewed in November 2007. Among them, 25 respondents themselves had a history of renal stones, yielding a point prevalence of 2.5%. In addition, 70 respondents had family members with a history of renal stones, yielding an estimated household point prevalence of 6.9%. Stone patients were mainly older, male, and imbibed less fluids than the average for all respondents. The public's concepts with regard to the diet necessary and the importance of taking more fluid to prevent stone formation was poor. Conclusion: Hong Kong has a relatively low prevalence of renal stone disease, compared to neighbouring areas. However, the local public and affected patients had little knowledge and awareness about this important health problem.published_or_final_versio

Validity and Reliability of Curl-Up Test on Assessing the Core Endurance for Kindergarten Children in Hong Kong

Objective: The purpose of this study was to examine the test-retest reliability and the criterion validity of a curlup test (CUT) as a measure of core stability, core endurance and dynamic stability in kindergarten children. CUT performance was also compared to half hold lying test (HHLT) and walking time on course (WTC) among without obstacle, with low obstacle and high obstacle measures of core stability, core endurance and dynamic stability. Methods: To estimate reliability, 33 males and 27 female kindergarten children (M aged=4.5 years old) performed the CUT on 2 different days. In the validity phase of the study, scores of all participants were obtained on three field test measures of core stability, core endurance and dynamic stability (CUT, HHLT and WTC). Results: Results indicate that the MCU test has no significant correlation on intra-class test-retest reliability (R=0.13, p>0.01). The criterion validity of the CUT for kindergarten children has is comparable to that of the HHLT(r=0.98, p<0.01) and WTC without obstacle(r=0.96, p<0.01), with low obstacle (r=0.96, p<0.01) and with high obstacle (r=0.98, p<0.01). Result indicates that the CUT test cannot produces reasonably accurate and stable measures of core stability, core endurance and dynamic stability. Conclusion: These preliminary findings provide evidences into the CUT test cannot produces reasonably accurate and stable measures of core stability, core endurance and dynamic stability for kindergarten children

American Society for Echocardiography Software Suite for Verification and

The imminent balloting of the draft DICOM 3.0 module on ultrasound represents a major step forward in the progress of digital storage formats for echocardiography. In this paper, we discuss a software suite soon to be released into the public domain for reading, parsing and verifying DICOM 3.0 ultrasonic objects. The software is designed to allow the user to verify that a Jle consisting of digital ultrasound data, claiming DlCOM 3.0 conformance, does in fact adhere to the standard. A graphical user-interface for the software suite is also provided, allowing the playback of cin& mode images in real-time on standard computer hardware, and across a TCP/IP network

Displacements analysis of self-excited vibrations in turning

The actual research deals with determining by a new protocol the necessary parameters considering a three-dimensional model to simulate in a realistic way the turning process on machine tool. This paper is dedicated to the experimental displacements analysis of the block tool / block workpiece with self-excited vibrations. In connexion with turning process, the self-excited vibrations domain is obtained starting from spectra of two accelerometers. The existence of a displacements plane attached to the tool edge point is revealed. This plane proves to be inclined compared to the machines tool axes. We establish that the tool tip point describes an ellipse. This ellipse is very small and can be considered as a small straight line segment for the stable cutting process (without vibrations). In unstable mode (with vibrations) the ellipse of displacements is really more visible. A difference in phase occurs between the tool tip displacements on the radial direction and on the cutting one. The feed motion direction and the cutting one are almost in phase. The values of the long and small ellipse axes (and their ratio) shows that these sizes are increasing with the feed rate value. The axis that goes through the stiffness center and the tool tip represents the maximum stiffness direction. The maximum (resp. minimum) stiffness axis of the tool is perpendicular to the large (resp. small) ellipse displacements axis. FFT analysis of the accelerometers signals allows to reach several important parameters and establish coherent correlations between tool tip displacements and the static - elastic characteristics of the machine tool components tested

Quantum nondemolition measurement of mechanical motion quanta

The fields of opto- and electromechanics have facilitated numerous advances in the areas of precision measurement and sensing, ultimately driving the studies of mechanical systems into the quantum regime. To date, however, the quantization of the mechanical motion and the associated quantum jumps between phonon states remains elusive. For optomechanical systems, the coupling to the environment was shown to preclude the detection of the mechanical mode occupation, unless strong single photon optomechanical coupling is achieved. Here, we propose and analyse an electromechanical setup, which allows to overcome this limitation and resolve the energy levels of a mechanical oscillator. We find that the heating of the membrane, caused by the interaction with the environment and unwanted couplings, can be suppressed for carefully designed electromechanical systems. The results suggest that phonon number measurement is within reach for modern electromechanical setups.Comment: 8 pages, 5 figures plus 24 pages, 11 figures supplemental materia

Nonlinear atom interferometer surpasses classical precision limit

Interference is fundamental to wave dynamics and quantum mechanics. The quantum wave properties of particles are exploited in metrology using atom interferometers, allowing for high-precision inertia measurements [1, 2]. Furthermore, the state-of-the-art time standard is based on an interferometric technique known as Ramsey spectroscopy. However, the precision of an interferometer is limited by classical statistics owing to the finite number of atoms used to deduce the quantity of interest [3]. Here we show experimentally that the classical precision limit can be surpassed using nonlinear atom interferometry with a Bose-Einstein condensate. Controlled interactions between the atoms lead to non-classical entangled states within the interferometer; this represents an alternative approach to the use of non-classical input states [4-8]. Extending quantum interferometry [9] to the regime of large atom number, we find that phase sensitivity is enhanced by 15 per cent relative to that in an ideal classical measurement. Our nonlinear atomic beam splitter follows the "one-axis-twisting" scheme [10] and implements interaction control using a narrow Feshbach resonance. We perform noise tomography of the quantum state within the interferometer and detect coherent spin squeezing with a squeezing factor of -8.2dB [11-15]. The results provide information on the many-particle quantum state, and imply the entanglement of 170 atoms [16]