Engineering Encounters: Reverse Engineering
McGowan, Veronica Cassone; Ventura, Marcia; Bell, Philip
2017-01-01
This column presents ideas and techniques to enhance your science teaching. This month's issue shares information on how students' everyday experiences can support science learning through engineering design. In this article, the authors outline a reverse-engineering model of instruction and describe one example of how it looked in our fifth-grade…
Zhang, Rong; Li, Qian-Wen; Tang, F. R.; Yang, X. Q.; Bai, L.
2017-08-01
We investigate the performance at a given power of a thermoelectric heat engine with broken time-reversal symmetry, and derive analytically the efficiency at a given power of a thermoelectric generator within linear irreversible thermodynamics. A universal bound on the efficiency of the thermoelectric heat engine is achieved under a strong constraint on the Onsager coefficients, and some interesting features are further revealed. Our results demonstrate that there exists a trade-off between efficiency and power output, and the efficiency at a given power may surpass the Curzon-Ahlborn limit due to broken time-reversal symmetry. Moreover, optimal efficiency at a given power can be achieved, which indicates that broken time-reversal symmetry offers physically allowed ways to optimize the performance of heat engines. Our study may contribute to the interesting guidelines for optimizing actual engines.
Reverse Engineering of RFID devices
Bokslag, Wouter
2015-01-01
This paper discusses the relevance and potential impact of both RFID and reverse engineering of RFID technology, followed by a discussion of common protocols and internals of RFID technology. The focus of the paper is on providing an overview of the different approaches to reverse engineering RFID technology and possible countermeasures that could limit the potential of such reverse engineering attempts.
Reverse Engineering Malicious Applications
Ioan Cristian Iacob
2015-06-01
Full Text Available Detecting new and unknown malware is a major challenge in today’s software. Security profession. A lot of approaches for the detection of malware using data mining techniques have already been proposed. Majority of the works used static features of malware. However, static detection methods fall short of detecting present day complex malware. Although some researchers proposed dynamic detection methods, the methods did not use all the malware features. In this work, an approach for the detection of new and unknown malware was proposed and implemented. Each sample was reverse engineered for analyzing its effect on the operating environment and to extract the static and behavioral features.
Reverse Core Engine with Thrust Reverser
Suciu, Gabriel L. (Inventor); Chandler, Jesse M. (Inventor)
2017-01-01
An engine system has a gas generator, a bi-fi wall surrounding at least a portion of the gas generator, a casing surrounding a fan, and the casing having first and second thrust reverser doors which in a deployed position abut each other and the bi-fi wall.
Universal bounds on efficiency and power of heat engines with broken time-reversal symmetry
2015-01-01
Ever since James Watt's steam engine, the urge to explore the fundamental principles governing the performance of devices that convert thermal energy into useful work was one of the major quests in thermodynamics. From a conceptual point of view, such heat engines can be divided into two classes. Cyclic engines use a reciprocating piston to generate mechanical work by periodically compressing and expanding a working fluid at varying temperature. Thermoelectric engines consist of two heat and ...
Time reversal communication system
Candy, James V.; Meyer, Alan W.
2008-12-02
A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.
Reverse Engineering Adverse Outcome Pathways
Perkins, Edward; Chipman, J.K.; Edwards, Stephen; Habib, Tanwir; Falciani, Francesco; Taylor, Ronald C.; Van Aggelen, Graham; Vulpe, Chris; Antczak, Philipp; Loguinov, Alexandre
2011-01-30
The toxicological effects of many stressors are mediated through unknown, or poorly characterized, mechanisms of action. We describe the application of reverse engineering complex interaction networks from high dimensional omics data (gene, protein, metabolic, signaling) to characterize adverse outcome pathways (AOPs) for chemicals that disrupt the hypothalamus-pituitary-gonadal endocrine axis in fathead minnows. Gene expression changes in fathead minnow ovaries in response to 7 different chemicals, over different times, doses, and in vivo versus in vitro conditions were captured in a large data set of 868 arrays. We examined potential AOPs of the antiandrogen flutamide using two mutual information theory methods, ARACNE and CLR to infer gene regulatory networks and potential adverse outcome pathways. Representative networks from these studies were used to predict a network path from stressor to adverse outcome as a candidate AOP. The relationship of individual chemicals to an adverse outcome can be determined by following perturbations through the network in response to chemical treatment leading to the nodes associated with the adverse outcome. Identification of candidate pathways allows for formation of testable hypotheses about key biologic processes, biomarkers or alternative endpoints, which could be used to monitor an adverse outcome pathway. Finally, we identify the unique challenges facing the application of this approach in ecotoxicology, and attempt to provide a road map for the utilization of these tools. Key Words: mechanism of action, toxicology, microarray, network inference
REVERSE ENGINEERING AND ITS REALISTIC APPLICATIONS
Nikita Bakshi; Shruti Gujral
2014-01-01
Reverse-engineering is used for many purposes like as a learning tool, as a way to make compatible products that are cheaper than what is currently on the market. This paper discusses what is software, its type, reverse engineering, applications of reverse engineering and their tools.
REVERSE ENGINEERING AND ITS REALISTIC APPLICATIONS
Nikita Bakshi
2014-06-01
Full Text Available Reverse-engineering is used for many purposes like as a learning tool, as a way to make compatible products that are cheaper than what is currently on the market. This paper discusses what is software, its type, reverse engineering, applications of reverse engineering and their tools.
Quinn, H; /SLAC
2009-01-27
This talk briefly reviews three types of time-asymmetry in physics, which I classify as universal, macroscopic and microscopic. Most of the talk is focused on the latter, namely the violation of T-reversal invariance in particle physics theories. In sum tests of microscopic T-invariance, or observations of its violation, are limited by the fact that, while we can measure many processes, only in very few cases can we construct a matched pair of process and inverse process and observe it with sufficient sensitivity to make a test. In both the cases discussed here we can achieve an observable T violation making use of flavor tagging, and in the second case also using the quantum properties of an antisymmetric coherent state of two B mesons to construct a CP-tag. Both these tagging properties depend only on very general properties of the flavor and/or CP quantum numbers and so provide model independent tests for T-invariance violations. The microscopic laws of physics are very close to T-symmetric. There are small effects that give CP- and T-violating processes in three-generation-probing weak decays. Where a T-violating observable can be constructed we see the relationships between T-violation and CP-violation expected in a CPT conserving theory. These microscopic effects are unrelated to the 'arrow of time' that is defined by increasing entropy, or in the time direction defined by the expansion of our Universe.
Detecting A Botnet By Reverse Engineering
Oesman Hendra Kelana
2013-06-01
Full Text Available Abstract— Botnet malware is a malicious program. Botnet that infects computers, called bots, will be controlled by a botmaster to do various things such as: spamming, phishing, keylogging Distributed Denial of Service (DDoS and other activities that are generally profitable to the owner of the bot (botmaster or those who use botnet services. The problem is that many computers have been controlled by botnets without the knowledge of the computer owner. There are many ways to examine botnets, for example by studying the traffic from the botnet network, studying how botnets communicate to each, studying how each robot receives orders to do something, and so forth. Of the many methods, the most frequently and commonly used is the reverse engineering, where researchers study how a botnet works by botnet debugging. In this study the author tries to understand or research botnets by taking a type of botnet, namely Agobot, using reverse engineering. One of the result of the research is that malware program files in general and in particular botnet has a technique to obscure the way that research using reverse engineering. Another result also shows that the botnet Agobot runs on computers by using the Windows service, and by changing the Windows registry so that every time the computer starts, Agobot always actively works in the computer memory. Keywords— Malware, Bot, Botnet, Botmaster, Agobot, Spam, Distributed Denial of Services, Identity Theft, Computer Security, Reverse Engineering, Debug, Windows Service, the Registry.
Szilard engine reversibility as quantum gate function
Mihelic, F. Matthew
2012-06-01
A quantum gate is a logically and thermodynamically reversible situation that effects a unitary transformation of qubits of superimposed information, and essentially constitutes a situation for a reversible quantum decision. A quantum decision is a symmetry break, and the effect of the function of a Szilard engine is a symmetry break. A quantum gate is a situation in which a reversible quantum decision can be made, and so if a logically and thermodynamically reversible Szilard engine can be theoretically constructed then it would function as a quantum gate. While the traditionally theorized Szilard engine is not thermodynamically reversible, if one of the bounding walls of a Szilard engine were to be constructed out of the physical information by which it functions in such a manner as to make that information available to both sides of the wall simultaneously, then such a Szilard engine would be both logically and thermodynamically reversible, and thus capable of function as a quantum gate. A theoretical model of the special case of a reversible Szilard engine functioning as a quantum gate is presented and discussed, and since a quantum decision is made when the shutter of a Szilard engine closes, the coherence of linked reversible Szilard engines should be considered as a state during which all of the shutters of linked Szilard engines are open simultaneously.
Time reversibility, computer simulation, and chaos
Hoover, William Graham
1999-01-01
A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful
Reverse Engineering Adverse Outcome Pathways in Ecotoxicology
The toxicological effects of many stressors are mediated through unknown, or incompletely characterized, mechanisms of action. We describe the application of reverse engineering complex interaction networks from high dimensional omics data (gene, protein, meabolic, signaling) t...
Time reversibility, computer simulation, algorithms, chaos
Hoover, William Graham
2012-01-01
A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful vocabulary and a set of concepts, which allow a fuller explanation of irreversibility than that available to Boltzmann or to Green, Kubo and Onsager. Clear illustration of concepts is emphasized throughout, and reinforced with a glossary of technical terms from the specialized fields which have been combined here to focus on a common theme. The book begins with a discussion, contrasting the idealized reversibility of ba...
Time reversal and holography with spacetime transformations
Bacot, Vincent; Labousse, Matthieu; Eddi, Antonin; Fink, Mathias; Fort, Emmanuel
2016-10-01
Wave control is usually performed by spatially engineering the properties of a medium. Because time and space play similar roles in wave propagation, manipulating time boundaries provides a complementary approach. Here, we experimentally demonstrate the relevance of this concept by introducing instantaneous time mirrors. We show with water waves that a sudden change of the effective gravity generates time-reversed waves that refocus at the source. We generalize this concept for all kinds of waves, introducing a universal framework which explains the effect of any time disruption on wave propagation. We show that sudden changes of the medium properties generate instant wave sources that emerge instantaneously from the entire space at the time disruption. The time-reversed waves originate from these `Cauchy sources’, which are the counterpart of Huygens virtual sources on a time boundary. It allows us to revisit the holographic method and introduce a new approach for wave control.
Time-reversible Hamiltonian systems
Schaft, Arjan van der
1982-01-01
It is shown that transfer matrices satisfying G(-s) = G(s) = G^T(-s) have a minimal Hamiltonian realization with an energy which is the sum of potential and kinetic energy, yielding the time reversibility of the equations. Furthermore connections are made with an associated gradient system. The
Open Data: Reverse Engineering and Maintenance Perspective
Kienle, Holger M
2012-01-01
Open data is an emerging paradigm to share large and diverse datasets -- primarily from governmental agencies, but also from other organizations -- with the goal to enable the exploitation of the data for societal, academic, and commercial gains. There are now already many datasets available with diverse characteristics in terms of size, encoding and structure. These datasets are often created and maintained in an ad-hoc manner. Thus, open data poses many challenges and there is a need for effective tools and techniques to manage and maintain it. In this paper we argue that software maintenance and reverse engineering have an opportunity to contribute to open data and to shape its future development. From the perspective of reverse engineering research, open data is a new artifact that serves as input for reverse engineering techniques and processes. Specific challenges of open data are document scraping, image processing, and structure/schema recognition. From the perspective of maintenance research, mainten...
Fringe Projection Measurement System in Reverse Engineering
林朝辉; 何海涛; 郭红卫; 陈明仪; 石璇; 俞涛
2005-01-01
Acquisition of physical data with high precision is a key step in reverse engineering ( RE). It is an important stimulative for the progress of reverse engineering with which various digitizing devices are invented, developed and made applicable. This paper introduces a three dimensional optical measurement method based on digital fringe projection technique in RE to improve the technique through its application. A practical example is presented and the result demonstrates the applicability and feasibility of the measurement system as well as the reliability and validity of relevant methods and algorithms.
Reverse engineering of relational database applications
Vermeer, W.W.M.; Apers, P.M.G.
1995-01-01
This paper presents techniques for reverse engineering of relational database applications. The target of such an effort is the definition of a fully equipped object-oriented view of the relational database, including methods and constraints. Such views can be seen as a full specification of the dat
Remote Whispering Applying Time Reversal
Anderson, Brian Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-07-16
The purpose of this project was to explore the use of time reversal technologies as a means for communication to a targeted individual or location. The idea is to have the privacy of whispering in one’s ear, but to do this remotely from loudspeakers not located near the target. Applications of this work include communicating with hostages and survivors in rescue operations, communicating imaging and operational conditions in deep drilling operations, monitoring storage of spent nuclear fuel in storage casks without wires, or clandestine activities requiring signaling between specific points. This technology provides a solution in any application where wires and radio communications are not possible or not desired. It also may be configured to self calibrate on a regular basis to adjust for changing conditions. These communications allow two people to converse with one another in real time, converse in an inaudible frequency range or medium (i.e. using ultrasonic frequencies and/or sending vibrations through a structure), or send information for a system to interpret (even allowing remote control of a system using sound). The time reversal process allows one to focus energy to a specific location in space and to send a clean transmission of a selected signal only to that location. In order for the time reversal process to work, a calibration signal must be obtained. This signal may be obtained experimentally using an impulsive sound, a known chirp signal, or other known signals. It may also be determined from a numerical model of a known environment in which the focusing is desired or from passive listening over time to ambient noise.
Simulations of Time Reversing Arrays in Shallow Ocean Waters
2016-06-07
using a customized version of RAM that allows us to recover the amplitude and phase of the computed field. We have also developed Monte-Carlo...Simulations of Time Reversing Arrays in Shallow Ocean Waters David R. Dowling Department of Mechanical Engineering and Applied Mechanics University...1-0628 http://www.personal.engin.umich.edu/~drd LONG-TERM GOAL The long term goals of this project are: i) to predict and understand time reversing
Integrated Product and Process Design Using a Reverse Engineering System
A; Ajmal; T; S; Tat
2002-01-01
Computer-integrated manufacturing (CIM) and revers e engineering (RE) have changed drastically the concept of product re-design, pla nning and manufacture of components. However, the main problems currently facing the developers of reverse engineering system, is the time consuming digitis ation of 3D data and the conversion of large amounts of data into a concise and manageable format and linking it to a CAD/CAM system. Automated 3-D profile gen eration, measurements and inspection of manufactured comp...
Reverse engineering of multi-layer films
Effendi Widjaja; Marc Garland
2011-01-01
This contribution introduces the combined application of Raman microscopy and band-target entropy minimization (BTEM) in order to successfully reverse-engineer a multi-layer packaging material. Three layers are identified, namely, polyethylene, a paper and talc layer (with two distinct cellulose forms), and a poly-styrene co-polymer composite containing anatase and calcite. This rapid and non-destructive approach provides a unique opportunity for the assessment of multi-layer composites, incl...
Reverse engineering of multi-layer films
Effendi Widjaja
2011-03-01
Full Text Available This contribution introduces the combined application of Raman microscopy and band-target entropy minimization (BTEM in order to successfully reverse-engineer a multi-layer packaging material. Three layers are identified, namely, polyethylene, a paper and talc layer (with two distinct cellulose forms, and a poly-styrene co-polymer composite containing anatase and calcite. This rapid and non-destructive approach provides a unique opportunity for the assessment of multi-layer composites, including the constitution of the additives present.
Understanding Virtual Objects through Reverse Engineering
Vera Moitinho
2012-11-01
Full Text Available The main objective of our research is to develop a new methodology, based on Reverse Engineering processes – 3D scan, quantitative data analysis and Artificial Intelligence techniques, in particular simulation – to study the relationship between form and function of artefacts. Furthermore, we aim to provide new data, as well as possible explanations of the archaeological record according to what it expects about social activity, including working processes, by simulating the potentialities of such actions in terms of input-output relationships.
Reverse Engineering and Cognition Panglossian Memories?
Liliana Chaves Castaño
2014-08-01
Full Text Available Daniel C. Dennett has dedicated a great part of his work to the conception of an application of reverse engineering and adaptationism in order to explain the evolution of the human mind. Dennett sees this perspective as a promising possibility in the development of a scientific psychology, in contrast to the “eliminative materialism” of neuroscience. The article provides a conceptual approach and examines a philosophical precedent in the discussions regarding adaptationism in biology and evolutionary psychology: intentionality or the theory of intentional systems.
Mobile Timekeeping Application Built on Reverse-Engineered JPL Infrastructure
Witoff, Robert J.
2013-01-01
Every year, non-exempt employees cumulatively waste over one man-year tracking their time and using the timekeeping Web page to save those times. This app eliminates this waste. The innovation is a native iPhone app. Libraries were built around a reverse- engineered JPL API. It represents a punch-in/punch-out paradigm for timekeeping. It is accessible natively via iPhones, and features ease of access. Any non-exempt employee can natively punch in and out, as well as save and view their JPL timecard. This app is built on custom libraries created by reverse-engineering the standard timekeeping application. Communication is through custom libraries that re-route traffic through BrowserRAS (remote access service). This has value at any center where employees track their time.
A SYSTEM DESIGN PROCESS TAILORED FOR REVERSE ENGINEERING AND REENGINEERING
Tae-Hun Yoon
2010-10-01
Full Text Available This paper discusses a system design process using a reverse engineering. The Reverse Engineering Approach, if possible, is a cost-effective and easy approach to be used in a system design. All industries use this approach consciously or unconsciously to reduce system development risks. It can be a part of formal process, simple requirement reuse, or adoption of industry standards. The reverse engineering approach can be considered as an effective system design method in immature system engineering environments. This paper proposes a system design process using reverse engineering which can be tailored for large complex system development projects. The proposed process composed of two stages to produce system specification generation. The reverse engineering stage is performed to define functional and physical architecture of legacy system used as reference model when they are not available. The reengineering stage takes outputs of the reverse engineering stage to define the rest of logical and physical solutions.
Data requirements of reverse-engineering algorithms.
Just, Winfried
2007-12-01
Data Sets used in reverse engineering of biochemical networks contain usually relatively few high-dimensional data points, which makes the problem in general vastly underdetermined. It is therefore important to estimate the probability that a given algorithm will return a model of acceptable quality when run on a data set of small size but high dimension. We propose a mathematical framework for investigating such questions. We then demonstrate that without assuming any prior biological knowledge, in general no theoretical distinction between the performance of different algorithms can be made. We also give an example of how expected algorithm performance can in principle be altered by utilizing certain features of the data collection protocol. We conclude with some examples of theorems that were proven within the proposed framework.
Binary Code Disassembly for Reverse Engineering
Marius Popa
2013-01-01
Full Text Available The disassembly of binary file is used to restore the software application code in a readable and understandable format for humans. Further, the assembly code file can be used in reverse engineering processes to establish the logical flows of the computer program or its vulnerabilities in real-world running environment. The paper highlights the features of the binary executable files under the x86 architecture and portable format, presents issues of disassembly process of a machine code file and intermediate code, disassembly algorithms which can be applied to a correct and complete reconstruction of the source file written in assembly language, and techniques and tools used in binary code disassembly.
Educational Approach of Refactoring in Facilitating Reverse Engineering
Mazni Omar
2010-05-01
Full Text Available Refactoring improves software codes and design. This activity often neglected by software developers because they need time to decide tactically where and when to refactor codes. Although the concepts theoretically instilled in the developer’s mind, this activity is not easy to apply and visualize. This situation became more problematic when deals with inexperienced developers. Therefore, there is a need to develop an educational approach to comprehend refactoring activity.This activity was applied through reverse engineering tasks. Thesoftware engineering (SE teams were required to apply reverseengineering activity in order to check the consistency betweencodes and design. The teams were encouraged to apply Model-View-Controller (MVC pattern architecture in order to facilitatethe activities. Findings revealed that Extreme Programming (XPteams managed to complete reverse engineering tasks earlierthan Formal teams. This study found that the approach is important to increase understanding of refactoring activities in reverse engineering process. This approach will be furthered applied for others SE teams to gain more insight and perceptions towards improving SE course.
Time reversibility in the quantum frame
Masot-Conde, Fátima [Escuela Superior Ingenieros, Dpt. Física Aplicada III, Universidad de Sevilla Isla Mágica, 41092- Sevilla (Spain)
2014-12-04
Classic Mechanics and Electromagnetism, conventionally taken as time-reversible, share the same concept of motion (either of mass or charge) as the basis of the time reversibility in their own fields. This paper focuses on the relationship between mobile geometry and motion reversibility. The goal is to extrapolate the conclusions to the quantum frame, where matter and radiation behave just as elementary mobiles. The possibility that the asymmetry of Time (Time’s arrow) is an effect of a fundamental quantum asymmetry of elementary particles, turns out to be a consequence of the discussion.
Application of time reversal in underwater communication
LU Minghui; ZHANG Bixing; WANG Chenghao
2004-01-01
Time reversal is applied to the underwater spreading spectrum coding communication. On the base of analyzing the focusing characteristics of the time reversal in underwater waveguide, the time reversal is studied to overcome the wave distortion of the encoded signal caused by the multi-path effect. The experiment research for underwater coding communication is carried out in a lab water tank and the corresponding theoretical analysis is also conducted by Binary Phase Shift Keying (BPSK) encoding and Barker code with 7 chips for the spreading spectrum signal. The results show that the time reversal can improve the focusing gain and increase the ratio of the principal to the second lobe of the coding signal, and can decrease the bit error rate and increase the communication distance.
Test of time reversal invariance with TRINE
Soldner, T; Schreckenbach, K; Bussière, A; Kossakowski, R; Liaud, P; Zimmer, O
2000-01-01
The new detector TRINE (time reversal invariance neutron experiment) was developed to test the time reversal invariance in the neutron decay. The precision of former experiments can be improved by one order of magnitude with an improved proton detection, a better background suppression and an angular resolving measurement using multiwire proportional chambers in coincidence with plastic scintillators, and the higher neutron flux and polarization available today. The concept of the detector and the status of the project is discussed.
Test of time reversal invariance with TRINE
Soldner, T.; Beck, L.; Schreckenbach, K.; Bussiere, A.; Kossakowski, R.; Liaud, P.; Zimmer, O
2000-02-11
The new detector TRINE (time reversal invariance neutron experiment) was developed to test the time reversal invariance in the neutron decay. The precision of former experiments can be improved by one order of magnitude with an improved proton detection, a better background suppression and an angular resolving measurement using multiwire proportional chambers in coincidence with plastic scintillators, and the higher neutron flux and polarization available today. The concept of the detector and the status of the project is discussed.
Time reversal techniques in electromagnetic wave propagation
Yi, Jiang
The time reversal method is a novel scheme utilizing the scattering components in a highly cluttered environment to achieve super-resolution focusing beyond Rayleigh criteria. In acoustics, time reversal effects are comprehensively analyzed and utilized in underwater target detection and communication. Successful demonstrations of the time reversal method using low frequency waveform in acoustics have generated wide interest in utilizing time reversal method by radio frequency electromagnetic waves. However, applications of the time reversal method in electromagnetics are considered to be emerging research topics and lack extensive analyses and studies. In this thesis, we present a systematic study in which a series of novel time reversal techniques have been developed for target detection and imaging in highly cluttered environments where higher order scattering is substantial. This thesis also contributes to insightful understanding of basic time reversal properties in electromagnetic (EM) wave propagation in such environment. EM time reversal focusing and nulling effects using both single and multiple antennas are first demonstrated by FDTD simulations. Based on these properties, single antenna time reversal detection indicates significant enhancement in detection capability over traditional change detection scheme. A frequency selection scheme utilizing the frequencies with strong constructive interference between the target and background environment is developed to further improve the performance of the time reversal detector. Moreover, a novel time reversal adaptive interference cancellation (TRAIC) detection scheme developed based on TR properties can obtain null of the background through the time reversal nulling effect and achieve automatic focusing on the target through the time reversal focusing effect. Therefore, the detection ability, dynamic range and signal to noise ratio of a radar system can be significantly enhanced by the time reversal method
An Open Toolkit for Reverse Engineering Data Visualisation and Exploration
Telea, A.; Maccari, A.; Riva, C.
2002-01-01
Maintenance and evolution of complex software systems (such as mobile telephones) involves activities such as reverse engineering (RE) and software visualisation. The RE conceptual framework for describing software understanding and concept abstraction is implemented up to different degrees by sever
Vertical Integration and Reverse Engineering of Agricultural Enterprises
Gang; WU; Yong; DU
2014-01-01
This paper studies the potential effects of agricultural enterprise’s vertical integration and reverse engineering on downstream firms.Suppliers who invest reverse engineering technology can exploit customer’s information. An integrated supplier can obtain at no cost the information from its subsidiary. Based on repeated game and considered corporate " good" or " bad" type,this paper analysis supplier’s selection and downstream investment in innovation. The results showed that: when the cost is higher than the threshold value no company invest in reverse engineering,when the cost is lower than the threshold value the integration company invest in reverse engineering; in the second period,vertical integration reduce the downstream independent enterprise’s innovation investment and profits,integrated enterprise increase innovation investment and profits; during the first period of the game,the independent downstream firms being " completely foreclosure".
Novel combination of reverse engineering and vapid prototyping in medicine
Schenker, R
1999-08-01
Full Text Available The technologies of reverse engineering and rapid prototyping are emerging as useful new tools in medicine. One application is of particular interest in orthopaedic, dental and reconstructive surgery. It involves the imaging, modelling...
Computer-based Reverse Engineering of a Manual Weighting ...
PROF. O. E. OSUAGWU
2013-06-01
Jun 1, 2013 ... Keywords: Reverse Engineering, Weighting Spring balance, Systematic reconstruction, Digital interface, Digital ... Our body, food we eat and ... video display unit a corresponding and the ... structure, function, and operation.
Time reversal signal processing for communication.
Young, Derek P.; Jacklin, Neil; Punnoose, Ratish J.; Counsil, David T.
2011-09-01
Time-reversal is a wave focusing technique that makes use of the reciprocity of wireless propagation channels. It works particularly well in a cluttered environment with associated multipath reflection. This technique uses the multipath in the environment to increase focusing ability. Time-reversal can also be used to null signals, either to reduce unintentional interference or to prevent eavesdropping. It does not require controlled geometric placement of the transmit antennas. Unlike existing techniques it can work without line-of-sight. We have explored the performance of time-reversal focusing in a variety of simulated environments. We have also developed new algorithms to simultaneously focus at a location while nulling at an eavesdropper location. We have experimentally verified these techniques in a realistic cluttered environment.
Revisiting time reversal and holography with spacetime transformations
Bacot, Vincent; Eddi, Antonin; Fink, Mathias; Fort, Emmanuel
2015-01-01
Wave control is usually performed by spatially engineering the properties of a medium. Because time and space play similar roles in wave propagation, manipulating time boundaries provides a complementary approach. Here, we experimentally demonstrate the relevance of this concept by introducing instantaneous time mirrors. We show with water waves that a sudden change of the effective gravity generates time-reversed waves that refocus at the source. We generalize this concept for all kinds of waves introducing a universal framework which explains the effect of any time disruption on wave propagation. We show that sudden changes of the medium properties generate instant wave sources that emerge instantaneously from the entire space at the time disruption. The time-reversed waves originate from these "Cauchy sources" which are the counterpart of Huygens virtual sources on a time boundary. It allows us to revisit the holographic method and introduce a new approach for wave control.
Electromagnetic Time Reversal Imaging: Analysis and Experimentation
2010-04-26
Biomedical Imaging: From Nano to Macro, ISBI, Paris, Friance, May 14-17, 2008 [6] Y. Jin, J. M. F. Moura, N. O’Donoughue, "Adaptive Time Reversal...Zhu, and Q. He, “Breast cancer detection by time reversal imaging,” 5th IEEE International Symposium on Biomedical Imaging: From Nano to Macro...target (a galvanized steel sheet) is surrounded by a large amount of PVC rods. Our experiments showed that the collected EM data in frequency and
Investigation of Finite Sources through Time Reversal
Kremers, Simon; Brietzke, Gilbert; Igel, Heiner; Larmat, Carene; Fichtner, Andreas; Johnson, Paul A.; Huang, Lianjie
2010-05-01
Under certain conditions time reversal is a promising method to determine earthquake source characteristics without any a-priori information (except the earth model and the data). It consists of injecting flipped-in-time records from seismic stations within the model to create an approximate reverse movie of wave propagation from which the location of the hypocenter and other information might be inferred. In this study, the backward propagation is performed numerically using a parallel cartesian spectral element code. Initial tests using point source moment tensors serve as control for the adaptability of the used wave propagation algorithm. After that we investigated the potential of time reversal to recover finite source characteristics (e.g., size of ruptured area, rupture velocity etc.). We used synthetic data from the SPICE kinematic source inversion blind test initiated to investigate the performance of current kinematic source inversion approaches (http://www.spice-rtn.org/library/valid). The synthetic data set attempts to reproduce the 2000 Tottori earthquake with 33 records close to the fault. We discuss the influence of various assumptions made on the source (e.g., origin time, hypocenter, fault location, etc.), adjoint source weighting (e.g., correct for epicentral distance) and structure (uncertainty in the velocity model) on the results of the time reversal process. We give an overview about the quality of focussing of the different wavefield properties (i.e., displacements, strains, rotations, energies). Additionally, the potential to recover source properties of multiple point sources at the same time is discussed.
Focusing over Optical Fiber Using Time Reversal
Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel
2015-01-01
A time-reversal array in multimode fiber is proposed for lossless remotely controlled switching using passive optical splitters. The signal to be transmitted is digitally pre-distorted so that it is routed through the physical layer in order to arrive at only one receiver in an array. System...
Study of Time Reversal in Complex Systems
2014-01-02
In this paper we present conclusions of a study of irreversibility in physical processes, using the conceptual formalism of the epsilon -machine. The...irreversibility, and is examined in more detail in the framework of topological epsilon -machines. Detailed study of the mechanisms involved in time-reversal of
FORMING FREEFORM SURFACE SHEET METAL USINGINTEGRATED REVERSE ENGINEERING TECHNOLOGY
XING; Yuan(
2001-01-01
［1］Puntambekar N V, Jablokow A G, Sommer H J. Unified review of 3D model generation for reverse engineering[J]. Computer Integrated Manufacturing System,1994,7(4):259～268.［2］Chikofsky E J. Reverse engineering and design recovery: a taxonomy[J]. IEEE Software,1990,6(3):13～17.［3］Chou Hon-yue. Application of reverse engineering in die and mold manufacturing[A]. 3rd Int Conf on Mould & Die Technique in Asia[C]. Taibei, China,1995.753～764.［4］Dipl-Ing Thomas Haller. Rapid mould and die making using reverse engineering and rapid prototyping[A]. 3rd Int Conf on Mould & Die Technique in Asia[C]. Taibei, China,1995.739～752.［5］Abella R J, Daschbach J M. Reverse engineering industrial applications[J]. Computers Ind Engng,1994,26(2):381～385.［6］Chen Y D, Tang X J. Automatic digitization of freeform curves by coordinate measuring machines[J]. ASME PED,1992,62:113～125.［7］Antonie van Rensburg. Implementing IDEF techniques as simulation modeling specifications[J]. Computers Ind Engng,1994,29(1-4):467～571.［8］Eastma C M, Fereshetian N. Informaiton models for use in product design: a comparison[J]. Computer-Aided Design.1994,26(7):551～572.
Genetic program based data mining to reverse engineer digital logic
Smith, James F., III; Nguyen, Thanh Vu H.
2006-04-01
A data mining based procedure for automated reverse engineering and defect discovery has been developed. The data mining algorithm for reverse engineering uses a genetic program (GP) as a data mining function. A genetic program is an algorithm based on the theory of evolution that automatically evolves populations of computer programs or mathematical expressions, eventually selecting one that is optimal in the sense it maximizes a measure of effectiveness, referred to as a fitness function. The system to be reverse engineered is typically a sensor. Design documents for the sensor are not available and conditions prevent the sensor from being taken apart. The sensor is used to create a database of input signals and output measurements. Rules about the likely design properties of the sensor are collected from experts. The rules are used to create a fitness function for the genetic program. Genetic program based data mining is then conducted. This procedure incorporates not only the experts' rules into the fitness function, but also the information in the database. The information extracted through this process is the internal design specifications of the sensor. Uncertainty related to the input-output database and the expert based rule set can significantly alter the reverse engineering results. Significant experimental and theoretical results related to GP based data mining for reverse engineering will be provided. Methods of quantifying uncertainty and its effects will be presented. Finally methods for reducing the uncertainty will be examined.
Time-reversal of nonlinear waves: Applicability and limitations
Ducrozet, G.; Fink, M.; Chabchoub, A.
2016-09-01
Time-reversal (TR) refocusing of waves is one of the fundamental principles in wave physics. Using the TR approach, time-reversal mirrors can physically create a time-reversed wave that exactly refocus back, in space and time, to its original source regardless of the complexity of the medium as if time were going backward. Laboratory experiments have proved that this approach can be applied not only in acoustics and electromagnetism, but also in the field of linear and nonlinear water waves. Studying the range of validity and limitations of the TR approach may determine and quantify its range of applicability in hydrodynamics. In this context, we report a numerical study of hydrodynamic time-reversal using a unidirectional numerical wave tank, implemented by the nonlinear high-order spectral method, known to accurately model the physical processes at play, beyond physical laboratory restrictions. The applicability of the TR approach is assessed over a variety of hydrodynamic localized and pulsating structures' configurations, pointing out the importance of high-order dispersive and particularly nonlinear effects in the refocusing of hydrodynamic stationary envelope solitons and breathers. We expect that the results may motivate similar experiments in other nonlinear dispersive media and encourage several applications with particular emphasis on the field of ocean engineering.
An Application Study of Transition Surface Reconstruction in Reverse Engineering
LUJing-ping; HEYu-lin; LIAOXiao-ping
2004-01-01
the reconstruction of transition surface is one of time consuming activities during surface modeling in reverse engineering. Yet currently available software applications suffer from shortcoming in processing the connection among free form surfaces. In this paper, a new method is put forward combining Surfacer with Unigraphics to resolve this problem: Curves and surfaces are first constructed in Surfacer, then, the finished data is imported into Unigraphics based on IGES format. At last, the transition surface can be reconstructed in Unigraphics. The application of this method in transition surface reconstruction is illustrated by means of two case studies,showing the connection between free form surfaces; filleting and rounding among multiple surfaces; transition surface between two sets of surfaces.
Android Application Protection against Static Reverse Engineering based on Multidexing
Nak Young Kim
2016-11-01
Full Text Available DEX files are executable files of Android applications. Since DEX files are in the format of Java bytecodes, their Java source codes can be easily obtained using static reverse engineering tools. This results in numerous Android application thefts. There are some tools (e.g. bangcle, ijiami, liapp that protect Android applications against static reverse engineering utilizing dynamic code loading. These tools usually encrypt classes.dex in an APK file. When the application is launched, the encrypted classes.dex file is decrypted and dynamically loaded. However, these tools fail to protect multidex APKs, which include more than one DEX files (classes2.dex, classes3.dex, ... to accommodate large-sized execution codes. In this paper, we propose a technique that protects multidex Android applications against static reverse engineering. The technique can encrypt/decrypt multiple DEX files in APK files and dynamically load them. The experimental results show that the proposed technique can effiectively protect multidex APKs.
FORMING FREEFORM SURFACE SHEET METAL USINGINTEGRATED REVERSE ENGINEERING TECHNOLOGY
邢渊
2001-01-01
This paper presented a model of integrated reverse engineering system and set up its various data output flowchart, which is easy to be associated with other systems. The idea of integrated reverse engineer is introduced to the system of forming sheet metal with complex surface and using IDEF0 method sets up the function model of the system. The freeform surface reconstruction and CAD modeling of the system are described and decomposed. This paper discussed some problems, such as the feature expression, feature modeling and feature translation of the sheet parts and dies.
Parametric Optimization Design of Brake Block Based on Reverse Engineering
Jin Hua-wei
2017-01-01
Full Text Available As one of the key part of automotive brake,the performance of brake block has a direct impact on the safety and comfort of cars. Modeling the brake block of disc brake in reverse parameterization by reverse engineering software, analyzing and optimizing the reconstructed model by CAE software. Processing the scanned point cloud by Geomagic Studio and reconstructing the CAD model of the brake block with the parametric surface function of the software, then analyzing and optimizing it by Wrokbench. The example shows that it is quick to reconstruct the CAD model of parts by using reverse parameterization method and reduce part re-design development cycle significantly.
Effective dissipation: breaking time-reversal symmetry
Brown, Aidan I
2016-01-01
At molecular scales, fluctuations play a significant role and prevent biomolecular processes from always proceeding in a preferred direction, raising the question of how limited amounts of free energy can be dissipated to obtain directed progress. We examine the system and process characteristics that efficiently break time-reversal symmetry at fixed energy loss; in particular for a simple model of a molecular machine, an intermediate energy barrier produces unusually high asymmetry for a given dissipation. Such insight into symmetry-breaking factors that produce particularly high time asymmetry suggests generalizations to a broader class of systems.
Time reversal invariance in polarized neutron decay
Wasserman, E.G.
1994-03-01
An experiment to measure the time reversal invariance violating (T-violating) triple correlation (D) in the decay of free polarized neutrons has been developed. The detector design incorporates a detector geometry that provides a significant improvement in the sensitivity over that used in the most sensitive of previous experiments. A prototype detector was tested in measurements with a cold neutron beam. Data resulting from the tests are presented. A detailed calculation of systematic effects has been performed and new diagnostic techniques that allow these effects to be measured have been developed. As the result of this work, a new experiment is under way that will improve the sensitivity to D to 3 {times} 10{sup {minus}4} or better. With higher neutron flux a statistical sensitivity of the order 3 {times} 10{sup {minus}5} is ultimately expected. The decay of free polarized neutrons (n {yields} p + e + {bar v}{sub e}) is used to search for T-violation by measuring the triple correlation of the neutron spin polarization, and the electron and proton momenta ({sigma}{sub n} {center_dot} p{sub p} {times} p{sub e}). This correlation changes sign under reversal of the motion. Since final state effects in neutron decay are small, a nonzero coefficient, D, of this correlation indicates the violation of time reversal invariance. D is measured by comparing the numbers of coincidences in electron and proton detectors arranged symmetrically about a longitudinally polarized neutron beam. Particular care must be taken to eliminate residual asymmetries in the detectors or beam as these can lead to significant false effects. The Standard Model predicts negligible T-violating effects in neutron decay. Extensions to the Standard Model include new interactions some of which include CP-violating components. Some of these make first order contributions to D.
An Open Toolkit for Prototyping Reverse Engineering Visualizations
Telea, Alexandru; Maccari, Alessandro; Riva, Claudio
2002-01-01
Maintenance and evolution of complex software systems (such as mobile telephones) involves activities such as reverse engineering (RE) and software visualization. Although several RE tools exist, we found their architecture hard to adapt to the domain and problem specific requirements posed by our c
Recognition vs Reverse Engineering in Boolean Concepts Learning
Shafat, Gabriel; Levin, Ilya
2012-01-01
This paper deals with two types of logical problems--recognition problems and reverse engineering problems, and with the interrelations between these types of problems. The recognition problems are modeled in the form of a visual representation of various objects in a common pattern, with a composition of represented objects in the pattern.…
Reverse breeding: a novel breeding approach based on engineered meiosis
Dirks, R.; Dun, van K.P.M.; Snoo, de B.; Berg, van den M.; Lelivelt, C.L.C.; Voermans, W.; Woudenberg, L.; Wit, de J.P.C.; Reinink, K.; Schut, J.W.; Jong, de J.H.S.G.M.; Wijnker, T.G.
2009-01-01
Reverse breeding (RB) is a novel plant breeding technique designed to directly produce parental lines for any heterozygous plant, one of the most sought after goals in plant breeding. RB generates perfectly complementing homozygous parental lines through engineered meiosis. The method is based on re
Teach CAD and Measuring Skills through Reverse Engineering
Board, Keith
2012-01-01
This article describes a reverse engineering activity that gives students hands-on, minds-on experience with measuring tools, machine parts, and CAD. The author developed this activity to give students an abundance of practical experience with measuring tools. Equally important, it provides a good interface between the virtual world of CAD 3D…
Teach CAD and Measuring Skills through Reverse Engineering
Board, Keith
2012-01-01
This article describes a reverse engineering activity that gives students hands-on, minds-on experience with measuring tools, machine parts, and CAD. The author developed this activity to give students an abundance of practical experience with measuring tools. Equally important, it provides a good interface between the virtual world of CAD 3D…
An Open Toolkit for Prototyping Reverse Engineering Visualizations
Telea, Alexandru; Maccari, Alessandro; Riva, Claudio
2002-01-01
Maintenance and evolution of complex software systems (such as mobile telephones) involves activities such as reverse engineering (RE) and software visualization. Although several RE tools exist, we found their architecture hard to adapt to the domain and problem specific requirements posed by our
Reverse engineering of multilayer coatings for ultrafast laser applications.
Trubetskov, M; Amotchkina, T; Tikhonravov, A; Pervak, V
2014-02-01
We propose a reliable reverse engineering approach for a postproduction characterization of complicated optical coatings for ultrafast laser applications. We perform the postproduction characterization on the basis of in situ broadband monitoring data and validate the results using ex situ transmittance data and group delay measurements.
Time-reversal symmetry and random polynomials
Braun, D; Zyczkowski, K
1996-01-01
We analyze the density of roots of random polynomials where each complex coefficient is constructed of a random modulus and a fixed, deterministic phase. The density of roots is shown to possess a singular component only in the case for which the phases increase linearly with the index of coefficients. This means that, contrary to earlier belief, eigenvectors of a typical quantum chaotic system with some antiunitary symmetry will not display a clustering curve in the stellar representation. Moreover, a class of time-reverse invariant quantum systems is shown, for which spectra display fluctuations characteristic of orthogonal ensemble, while eigenvectors confer to predictions of unitary ensemble.
Contact mechanics of reverse engineered distal humeral hemiarthroplasty implants.
Willing, Ryan; King, Graham J W; Johnson, James A
2015-11-26
Erosion of articular cartilage is a concern following distal humeral hemiarthroplasty, because native cartilage surfaces are placed in contact with stiff metallic implant components, which causes decreases in contact area and increases in contact stresses. Recently, reverse engineered implants have been proposed which are intended to promote more natural contact mechanics by reproducing the native bone or cartilage shape. In this study, finite element modeling is used in order to calculate changes in cartilage contact areas and stresses following distal humeral hemiarthroplasty with commercially available and reverse engineered implant designs. At the ulna, decreases in contact area were -34±3% (p=0.002), -27±1% (pengineered and cartilage reverse engineered designs, respectively. Peak contact stresses increased by 461±57% (p=0.008), 387±127% (p=0.229) and 165±16% (p=0.003). At the radius, decreases in contact area were -21±3% (p=0.013), -13±2% (p0.999), 241±32% (p=0.010) and 61±10% (p=0.021). Between the three different implant designs, the cartilage reverse engineered design yielded the largest contact areas and lowest contact stresses, but was still unable to reproduce the contact mechanics of the native joint. These findings align with a growing body of evidence indicating that although reverse engineered hemiarthroplasty implants can provide small improvements in contact mechanics when compared with commercially available designs, further optimization of shape and material properties is required in order reproduce native joint contact mechanics.
Elastic least-squares reverse time migration
Feng, Zongcai
2017-03-08
We use elastic least-squares reverse time migration (LSRTM) to invert for the reflectivity images of P- and S-wave impedances. Elastic LSRTMsolves the linearized elastic-wave equations for forward modeling and the adjoint equations for backpropagating the residual wavefield at each iteration. Numerical tests on synthetic data and field data reveal the advantages of elastic LSRTM over elastic reverse time migration (RTM) and acoustic LSRTM. For our examples, the elastic LSRTM images have better resolution and amplitude balancing, fewer artifacts, and less crosstalk compared with the elastic RTM images. The images are also better focused and have better reflector continuity for steeply dipping events compared to the acoustic LSRTM images. Similar to conventional leastsquares migration, elastic LSRTM also requires an accurate estimation of the P- and S-wave migration velocity models. However, the problem remains that, when there are moderate errors in the velocity model and strong multiples, LSRTMwill produce migration noise stronger than that seen in the RTM images.
Multiples least-squares reverse time migration
Zhang, D. L.
2013-01-01
To enhance the image quality, we propose multiples least-squares reverse time migration (MLSRTM) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. Since each recorded trace is treated as a virtual source, knowledge of the source wavelet is not required. Numerical tests on synthetic data for the Sigsbee2B model and field data from Gulf of Mexico show that MLSRTM can improve the image quality by removing artifacts, balancing amplitudes, and suppressing crosstalk compared to standard migration of the free-surface multiples. The potential liability of this method is that multiples require several roundtrips between the reflector and the free surface, so that high frequencies in the multiples are attenuated compared to the primary reflections. This can lead to lower resolution in the migration image compared to that computed from primaries.
Time reversal for a single spherical scatterer.
Chambers, D H; Gautesen, A K
2001-06-01
We show that the time reversal operator for a planar time reversal mirror (TRM) can have up to four distinct eigenvalues with a small spherical acoustic scatterer. Each eigenstate represents a resonance between the TRM and an induced scattering moment of the sphere. Their amplitude distributions on the TRM are orthogonal superpositions of the radiation patterns from a monopole and up to three orthogonal dipoles. The induced monopole moment is associated with the compressibility contrast between the sphere and the medium, while the dipole moments are associated with density contrast. The number of eigenstates is related to the number of orthogonal orientations of each induced multipole. For hard spheres (glass, metals) the contribution of the monopole moment to the eigenvalues is much greater than that of the dipole moments, leading to a single dominant eigenvalue. The other eigenvalues are much smaller, making it unlikely multiple eigenvalues could have been observed in previous experiments using hard materials. However, for soft materials such as wood, plastic, or air bubbles the eigenvalues are comparable in magnitude and should be observable. The presence of multiple eigenstates breaks the one-to-one correspondence between eigenstates and distinguishable scatterers discussed previously by Prada and Fink [Wave Motion 20, 151-163 (1994)]. However, eigenfunctions from separate scatterers would have different phases for their eigenfunctions, potentially restoring the ability to distinguish separate scatterers. Since relative magnitudes of the eigenvalues for a single scatterer are governed by the ratio of the compressibility contrast to the density contrast, measurement of the eigenvalue spectrum would provide information on the composition of the scatterer.
Tissue-Engineered Skeletal Muscle Organoids for Reversible Gene Therapy
Vandenburgh, Herman; DelTatto, Michael; Shansky, Janet; Lemaire, Julie; Chang, Albert; Payumo, Francis; Lee, Peter; Goodyear, Amy; Raven, Latasha
1996-01-01
Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myofibers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid Implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postimtotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.
Synthetic modular systems--reverse engineering of signal transduction
Pawson, Tony; Linding, Rune
2005-01-01
During the last decades, biology has decomposed cellular systems into genetic, functional and molecular networks. It has become evident that these networks consist of components with specific functions (e.g., proteins and genes). This has generated a considerable amount of knowledge and hypotheses...... concerning cellular organization. The idea discussed here is to test the extent of this knowledge by reconstructing, or reverse engineering, new synthetic biological systems from known components. We will discuss how integration of computational methods with proteomics and engineering concepts might lead us...
Reverse engineering: algebraic boundary representations to constructive solid geometry.
Buchele, S. F.; Ellingson, W. A.
1997-12-17
Recent advances in reverse engineering have focused on recovering a boundary representation (b-rep) of an object, often for integration with rapid prototyping. This boundary representation may be a 3-D point cloud, a triangulation of points, or piecewise algebraic or parametric surfaces. This paper presents work in progress to develop an algorithm to extend the current state of the art in reverse engineering of mechanical parts. This algorithm will take algebraic surface representations as input and will produce a constructive solid geometry (CSG) description that uses solid primitives such as rectangular block, pyramid, sphere, cylinder, and cone. The proposed algorithm will automatically generate a CSG solid model of a part given its algebraic b-rep, thus allowing direct input into a CAD system and subsequent CSG model generation.
Reverse engineering gene networks: Integrating genetic perturbations with dynamical modeling
Tegnér, Jesper; Yeung, M. K. Stephen; Hasty, Jeff; Collins, James J.
2003-01-01
While the fundamental building blocks of biology are being tabulated by the various genome projects, microarray technology is setting the stage for the task of deducing the connectivity of large-scale gene networks. We show how the perturbation of carefully chosen genes in a microarray experiment can be used in conjunction with a reverse engineering algorithm to reveal the architecture of an underlying gene regulatory network. Our iterative scheme identifies the network topology by analyzing the steady-state changes in gene expression resulting from the systematic perturbation of a particular node in the network. We highlight the validity of our reverse engineering approach through the successful deduction of the topology of a linear in numero gene network and a recently reported model for the segmentation polarity network in Drosophila melanogaster. Our method may prove useful in identifying and validating specific drug targets and in deconvolving the effects of chemical compounds. PMID:12730377
The Research on Improved Design and Drawing of Product Forms Based on Reverse Engineering Technology
Chunxia Geng
2013-06-01
Full Text Available In the analysis of the reverse engineering system model based on the reverse engineering system based on local surface reconstruction model based on existing measurement data directly to display 3D images and rapid prototyping, greatly reducing the time required for reverse engineering, eliminates the difficulties of a large number of complex surface modeling. In the study, the improved design of the form of product related to the free-form surface treatment, but the use of the product form the point cloud data to obtain a satisfactory surface reconstruction is difficult. NURBS surface fitting technique, the appearance of the product 1st be classified according to form and then accordingly the product shape reconstruction, it is much easier. Facts have proved that the conditions does not require high precision, the use of NURBS fitting to reconstruct the free surface able to obtain a satisfactory product form. This improved design of the product form is practical.
DELAUNAY-BASED SURFACE RECONSTRUCTION ALGORITHM IN REVERSE ENGINEERING
无
2002-01-01
Triangulation of scattered points is the first important section during reverse engineering. New concepts of dynamic circle and closed point are put forward based on current basic method. These new concepts can narrow the extent which triangulation process should seek through and optimize the triangles during producing them. Updating the searching edges dynamically controls progress of triangulation. Intersection judgment between new triangle and produced triangles is changed into intersection judgment between new triangle and searching edges. Examples illustrate superiorities of this new algorithm.
Image Stitching of PCBs for Reverse Engineering and Metrological Application
Simran pal singh bawa
2016-01-01
This paper addresses the solution towards the problem of lacking CAD data of the PCBs for repair and reverse engineering industries. In this work, concept of image mosaicking is employed. Where special distortion free optics is used to acquire images of the PCB and later theses images are stitched together to extract the pads location. Stitching Algorithm here incorporates the use of Harris corner detection for the extraction of interest points and then using popular RANSAC algorithm for the ...
Theory of the time reversal cavity for electromagnetic fields.
Carminati, R; Pierrat, R; de Rosny, J; Fink, M
2007-11-01
We derive a general expression of the electric dyadic Green function in a time-reversal cavity, based on vector diffraction theory in the frequency domain. Our theory gives a rigorous framework to time-reversal experiments using electromagnetic waves and suggests a methodology to design structures generating subwavelength focusing after time reversal.
A Predictive Approach to Network Reverse-Engineering
Wiggins, Chris
2005-03-01
A central challenge of systems biology is the ``reverse engineering" of transcriptional networks: inferring which genes exert regulatory control over which other genes. Attempting such inference at the genomic scale has only recently become feasible, via data-intensive biological innovations such as DNA microrrays (``DNA chips") and the sequencing of whole genomes. In this talk we present a predictive approach to network reverse-engineering, in which we integrate DNA chip data and sequence data to build a model of the transcriptional network of the yeast S. cerevisiae capable of predicting the response of genes in unseen experiments. The technique can also be used to extract ``motifs,'' sequence elements which act as binding sites for regulatory proteins. We validate by a number of approaches and present comparison of theoretical prediction vs. experimental data, along with biological interpretations of the resulting model. En route, we will illustrate some basic notions in statistical learning theory (fitting vs. over-fitting; cross- validation; assessing statistical significance), highlighting ways in which physicists can make a unique contribution in data- driven approaches to reverse engineering.
Osman, Mohd Hafeez Bin
2015-01-01
Software design documentation is a valuable aid in software comprehension. However, keeping the software design up-to-date with evolving source code is challenging and time-consuming. Reverse engineering is one of the options for recovering software architecture from the implementation code.
Osman, Mohd Hafeez Bin
2015-01-01
Software design documentation is a valuable aid in software comprehension. However, keeping the software design up-to-date with evolving source code is challenging and time-consuming. Reverse engineering is one of the options for recovering software architecture from the implementation code. However
Osman, Mohd Hafeez Bin
2015-01-01
Software design documentation is a valuable aid in software comprehension. However, keeping the software design up-to-date with evolving source code is challenging and time-consuming. Reverse engineering is one of the options for recovering software architecture from the implementation code. However
The Two-Time Interpretation and Macroscopic Time-Reversibility
Yakir Aharonov
2017-03-01
Full Text Available The two-state vector formalism motivates a time-symmetric interpretation of quantum mechanics that entails a resolution of the measurement problem. We revisit a post-selection-assisted collapse model previously suggested by us, claiming that unlike the thermodynamic arrow of time, it can lead to reversible dynamics at the macroscopic level. In addition, the proposed scheme enables us to characterize the classical-quantum boundary. We discuss the limitations of this approach and its broad implications for other areas of physics.
Multisource Least-squares Reverse Time Migration
Dai, Wei
2012-12-01
Least-squares migration has been shown to be able to produce high quality migration images, but its computational cost is considered to be too high for practical imaging. In this dissertation, a multisource least-squares reverse time migration algorithm (LSRTM) is proposed to increase by up to 10 times the computational efficiency by utilizing the blended sources processing technique. There are three main chapters in this dissertation. In Chapter 2, the multisource LSRTM algorithm is implemented with random time-shift and random source polarity encoding functions. Numerical tests on the 2D HESS VTI data show that the multisource LSRTM algorithm suppresses migration artifacts, balances the amplitudes, improves image resolution, and reduces crosstalk noise associated with the blended shot gathers. For this example, multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution, and fewer migration artifacts compared to conventional RTM. The empirical results suggest that the multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with similar or less computational cost. The caveat is that LSRTM image is sensitive to large errors in the migration velocity model. In Chapter 3, the multisource LSRTM algorithm is implemented with frequency selection encoding strategy and applied to marine streamer data, for which traditional random encoding functions are not applicable. The frequency-selection encoding functions are delta functions in the frequency domain, so that all the encoded shots have unique non-overlapping frequency content. Therefore, the receivers can distinguish the wavefield from each shot according to the frequencies. With the frequency-selection encoding method, the computational efficiency of LSRTM is increased so that its cost is
Reverse engineering of pelvic bone for hip joint replacement.
Popov, I; Onuh, S O
2009-01-01
Research into fabrication of hip joint replacements combines knowledge from distinct domains, such as engineering, materials and medical fields. Recent computer assisted technologies have played an important role in the medical field. Unlike the modelling of most of the human bones, the creation of an accurate 3D model of a pelvic bone has been a challenging task. The main source of difficulties in this case has proven to be the complexity of the structure of the pelvis, having basically a free-form shape with a hole in the middle constituting some over-shadowed areas (undercuts), various cavities, areas with high form curvature, variable wall thickness with some very thin sections and inside layers with different mechanical properties. In this research work, a pelvic bone is generated using reverse engineering, rapid prototyping and rapid tooling techniques. The geometric data obtained from reverse engineering through laser scanning are used and manipulated to create accurate 3D CAD representations of these devices. These CAD models can be used for various virtual tests and simulations, as well as for reproduction through rapid manufacturing processes and then used as prototypes in tooling, physical tests and planning of surgical operations.
Multi-source least-squares reverse time migration
Dai, Wei
2012-06-15
Least-squares migration has been shown to improve image quality compared to the conventional migration method, but its computational cost is often too high to be practical. In this paper, we develop two numerical schemes to implement least-squares migration with the reverse time migration method and the blended source processing technique to increase computation efficiency. By iterative migration of supergathers, which consist in a sum of many phase-encoded shots, the image quality is enhanced and the crosstalk noise associated with the encoded shots is reduced. Numerical tests on 2D HESS VTI data show that the multisource least-squares reverse time migration (LSRTM) algorithm suppresses migration artefacts, balances the amplitudes, improves image resolution and reduces crosstalk noise associated with the blended shot gathers. For this example, the multisource LSRTM is about three times faster than the conventional RTM method. For the 3D example of the SEG/EAGE salt model, with a comparable computational cost, multisource LSRTM produces images with more accurate amplitudes, better spatial resolution and fewer migration artefacts compared to conventional RTM. The empirical results suggest that multisource LSRTM can produce more accurate reflectivity images than conventional RTM does with a similar or less computational cost. The caveat is that the LSRTM image is sensitive to large errors in the migration velocity model. © 2012 European Association of Geoscientists & Engineers.
Reverse-Engineering a Watermark Detector Using an Oracle
Jun Yu
2007-12-01
Full Text Available The Break Our Watermarking System (BOWS contest gave researchers three months to defeat an unknown watermark, given three marked images and online access to a watermark detector. The authors participated in the first phase of the contest, defeating the mark while retaining the highest average quality among attacked images. The techniques developed in this contest led to general methods for reverse-engineering a watermark algorithm via experimental images fed to its detector. The techniques exploit the tendency of watermark algorithms to admit characteristic false positives, which can be used to identify an algorithm or estimate certain parameters.
Reverse-Engineering a Watermark Detector Using an Oracle
Craver Scott
2007-01-01
Full Text Available The Break Our Watermarking System (BOWS contest gave researchers three months to defeat an unknown watermark, given three marked images and online access to a watermark detector. The authors participated in the first phase of the contest, defeating the mark while retaining the highest average quality among attacked images. The techniques developed in this contest led to general methods for reverse-engineering a watermark algorithm via experimental images fed to its detector. The techniques exploit the tendency of watermark algorithms to admit characteristic false positives, which can be used to identify an algorithm or estimate certain parameters.
Reverse-engineering a detector with false alarms
Craver, Scott; Yu, Jun
2007-02-01
Inspired by results from the Break Our Watermarking System (BOWS) contest, we explored techniques to reverse-engineer watermarking algorithms via oracle attacks. We exploit a principle called "superrobustness," which allows a watermarking algorithm to be characterized by its resistance to specific distortions. The generic application of this principle to an oracle attack seeks to find a severe false alarm, or a point on the watermark detection region as far as possible from the watermarked image. For specific types of detection regions, these severe false positives can leak information about the feature space as well as detector parameters. We explore the specific case of detectors using normalized correlation, or correlation coefficient.
Database Reverse Engineering based on Association Rule Mining
Nattapon Pannurat
2010-03-01
Full Text Available Maintaining a legacy database is a difficult task especially when system documentation is poor written or even missing. Database reverse engineering is an attempt to recover high-level conceptual design from the existing database instances. In this paper, we propose a technique to discover conceptual schema using the association mining technique. The discovered schema corresponds to the normalization at the third normal form, which is a common practice in many business organizations. Our algorithm also includes the rule filtering heuristic to solve the problem of exponential growth of discovered rules inherited with the association mining technique.
Graphite Intended for Green Engineering Developed by Noncontaminant Reverse Abrasion
Roberto Baca Arroyo
2016-01-01
Full Text Available Graphite intended for green engineering was synthesized by noncontaminant reverse abrasion, which consists of graphite layers assembled with thickness controlled on SiC sandpaper as insulating substrate. Phase formation of the graphite layers was validated by X-ray diffraction studies and its finished profile by Atomic Force Microscopy (AFM. Transport parameters of only three layers were evaluated from current-voltage curves. Mathematical functions such as derivative and modulation of a signal have been built by graphite circuits using different performance principles, compared to those used with silicon devices. The trends related to electronic engineering should be achieved with design of the graphite-based devices to facilitate their mass production in the near future.
Systems Biology: The Role of Engineering in the Reverse Engineering of Biological Signaling
Pablo A. Iglesias
2013-05-01
Full Text Available One of the principle tasks of systems biology has been the reverse engineering of signaling networks. Because of the striking similarities to engineering systems, a number of analysis and design tools from engineering disciplines have been used in this process. This review looks at several examples including the analysis of homeostasis using control theory, the attenuation of noise using signal processing, statistical inference and the use of information theory to understand both binary decision systems and the response of eukaryotic chemotactic cells.
Adding Robustness to Support Vector Machines Against Adversarial Reverse Engineering
Alabdulmohsin, Ibrahim
2014-01-01
Many classification algorithms have been successfully deployed in security-sensitive applications including spam filters and intrusion detection systems. Under such adversarial environments, adversaries can generate exploratory attacks against the defender such as evasion and reverse engineering. In this paper, we discuss why reverse engineering attacks can be carried out quite efficiently against fixed classifiers, and investigate the use of randomization as a suitable strategy for mitigating their risk. In particular, we derive a semidefinite programming (SDP) formulation for learning a distribution of classifiers subject to the constraint that any single classifier picked at random from such distribution provides reliable predictions with a high probability. We analyze the tradeoff between variance of the distribution and its predictive accuracy, and establish that one can almost always incorporate randomization with large variance without incurring a loss in accuracy. In other words, the conventional approach of using a fixed classifier in adversarial environments is generally Pareto suboptimal. Finally, we validate such conclusions on both synthetic and real-world classification problems. Copyright 2014 ACM.
Theoretical and Experimental Study of Time Reversal in Cubic Crystals
陆铭慧; 张碧星; 汪承灏
2004-01-01
The self-adaptive focusing of the time reversal in anisotropic media is studied theoretically and experimentally. It is conducted for the compressional wave field in the cubic crystal silicon. The experimental result is in agreement with our theoretical analysis. The focusing gain and the displacement distributions of the time reversal field are analysed in detail. It is shown that the waves from different elements of the transducer array arrive at the original place of the source simultaneously after the time reversal operation. The waveform distortions caused by the velocity anisotropy can automatically be compensated for after the time reversal processing.
Nonlinear time reversal in a wave chaotic system.
Frazier, Matthew; Taddese, Biniyam; Antonsen, Thomas; Anlage, Steven M
2013-02-01
Exploiting the time-reversal invariance and reciprocal properties of the lossless wave equation enables elegantly simple solutions to complex wave-scattering problems and is embodied in the time-reversal mirror. Here we demonstrate the implementation of an electromagnetic time-reversal mirror in a wave chaotic system containing a discrete nonlinearity. We demonstrate that the time-reversed nonlinear excitations reconstruct exclusively upon the source of the nonlinearity. As an example of its utility, we demonstrate a new form of secure communication and point out other applications.
Reversibility and Adiabatic Computation Trading Time and Space for Energy
Li, Maozhen; Li, Ming; Vitanyi, Paul
1996-01-01
Future miniaturization and mobilization of computing devices requires energy parsimonious `adiabatic' computation. This is contingent on logical reversibility of computation. An example is the idea of quantum computations which are reversible except for the irreversible observation steps. We propose to study quantitatively the exchange of computational resources like time and space for irreversibility in computations. Reversible simulations of irreversible computations are memory intensive. Such (polynomial time) simulations are analysed here in terms of `reversible' pebble games. We show that Bennett's pebbling strategy uses least additional space for the greatest number of simulated steps. We derive a trade-off for storage space versus irreversible erasure. Next we consider reversible computation itself. An alternative proof is provided for the precise expression of the ultimate irreversibility cost of an otherwise reversible computation without restrictions on time and space use. A time-irreversibility tra...
Time-reversed wave mixing in nonlinear optics.
Zheng, Yuanlin; Ren, Huaijin; Wan, Wenjie; Chen, Xianfeng
2013-11-19
Time-reversal symmetry is important to optics. Optical processes can run in a forward or backward direction through time when such symmetry is preserved. In linear optics, a time-reversed process of laser emission can enable total absorption of coherent light fields inside an optical cavity of loss by time-reversing the original gain medium. Nonlinearity, however, can often destroy such symmetry in nonlinear optics, making it difficult to study time-reversal symmetry with nonlinear optical wave mixings. Here we demonstrate time-reversed wave mixings for optical second harmonic generation (SHG) and optical parametric amplification (OPA) by exploring this well-known but underappreciated symmetry in nonlinear optics. This allows us to observe the annihilation of coherent beams. Our study offers new avenues for flexible control in nonlinear optics and has potential applications in efficient wavelength conversion, all-optical computing.
Nonlinear time reversal of classical waves: experiment and model.
Frazier, Matthew; Taddese, Biniyam; Xiao, Bo; Antonsen, Thomas; Ott, Edward; Anlage, Steven M
2013-12-01
We consider time reversal of electromagnetic waves in a closed, wave-chaotic system containing a discrete, passive, harmonic-generating nonlinearity. An experimental system is constructed as a time-reversal mirror, in which excitations generated by the nonlinearity are gathered, time-reversed, transmitted, and directed exclusively to the location of the nonlinearity. Here we show that such nonlinear objects can be purely passive (as opposed to the active nonlinearities used in previous work), and we develop a higher data rate exclusive communication system based on nonlinear time reversal. A model of the experimental system is developed, using a star-graph network of transmission lines, with one of the lines terminated by a model diode. The model simulates time reversal of linear and nonlinear signals, demonstrates features seen in the experimental system, and supports our interpretation of the experimental results.
Reverse Engineering Cellular Networks with Information Theoretic Methods
Julio R. Banga
2013-05-01
Full Text Available Building mathematical models of cellular networks lies at the core of systems biology. It involves, among other tasks, the reconstruction of the structure of interactions between molecular components, which is known as network inference or reverse engineering. Information theory can help in the goal of extracting as much information as possible from the available data. A large number of methods founded on these concepts have been proposed in the literature, not only in biology journals, but in a wide range of areas. Their critical comparison is difficult due to the different focuses and the adoption of different terminologies. Here we attempt to review some of the existing information theoretic methodologies for network inference, and clarify their differences. While some of these methods have achieved notable success, many challenges remain, among which we can mention dealing with incomplete measurements, noisy data, counterintuitive behaviour emerging from nonlinear relations or feedback loops, and computational burden of dealing with large data sets.
Reverse engineering of a Hamiltonian by designing the evolution operators.
Kang, Yi-Hao; Chen, Ye-Hong; Wu, Qi-Cheng; Huang, Bi-Hua; Xia, Yan; Song, Jie
2016-07-22
We propose an effective and flexible scheme for reverse engineering of a Hamiltonian by designing the evolution operators to eliminate the terms of Hamiltonian which are hard to be realized in practice. Different from transitionless quantum driving (TQD), the present scheme is focus on only one or parts of moving states in a D-dimension (D ≥ 3) system. The numerical simulation shows that the present scheme not only contains the results of TQD, but also has more free parameters, which make this scheme more flexible. An example is given by using this scheme to realize the population transfer for a Rydberg atom. The influences of various decoherence processes are discussed by numerical simulation and the result shows that the scheme is fast and robust against the decoherence and operational imperfection. Therefore, this scheme may be used to construct a Hamiltonian which can be realized in experiments.
Femur Model Reconstruction Based on Reverse Engineering and Rapid Prototyping
Tang, Tongming; Zhang, Zheng; Ni, Hongjun; Deng, Jiawen; Huang, Mingyu
Precise reconstruction of 3D models is fundamental and crucial to the researches of human femur. In this paper we present our approach towards tackling this problem. The surface of a human femur was scanned using a hand-held 3D laser scanner. The data obtained, in the form of point cloud, was then processed using the reverse engineering software Geomagic and the CAD/CAM software CimatronE to reconstruct a digital 3D model. The digital model was then used by the rapid prototyping machine to build a physical model of human femur using 3D printing. The geometric characteristics of the obtained physical model matched that of the original femur. The process of "physical object - 3D data - digital 3D model - physical model" presented in this paper provides a foundation of precise modeling for the digital manufacturing, virtual assembly, stress analysis, and simulated surgery of artificial bionic femurs.
Novel adaptive laser scanning sensor for reverse engineering measurement
Zhao Ji; Ma Zi; Lin Na; Zhu Quanmin
2007-01-01
In this paper, a series of new techniques are used to optimize typical laser scanning sensor. The integrated prototype is compared with traditional approach to demonstrate the much improved performance. In the research and development, camera calibration is achieved by extracting characteristic points of the laser plane, so that the calibration efficiency is improved significantly. With feedback control of its intensity, the laser is automatically adjusted for different material. A modified algorithm is presented to improve the accuracy of laser stripe extraction. The fusion of data extracted from left and right camera is completed with re-sampling technique. The scanner is integrated with a robot arm and some other machinery for on-line measurement and inspection, which provides a flexible measurement tool for reverse engineering.
Reverse Engineering Boolean Networks: From Bernoulli Mixture Models to Rule Based Systems
Saeed, Mehreen; Ijaz, Maliha; Javed, Kashif; Babri, Haroon Atique
2012-01-01
A Boolean network is a graphical model for representing and analyzing the behavior of gene regulatory networks (GRN). In this context, the accurate and efficient reconstruction of a Boolean network is essential for understanding the gene regulation mechanism and the complex relations that exist therein. In this paper we introduce an elegant and efficient algorithm for the reverse engineering of Boolean networks from a time series of multivariate binary data corresponding to gene expression data. We call our method ReBMM, i.e., reverse engineering based on Bernoulli mixture models. The time complexity of most of the existing reverse engineering techniques is quite high and depends upon the indegree of a node in the network. Due to the high complexity of these methods, they can only be applied to sparsely connected networks of small sizes. ReBMM has a time complexity factor, which is independent of the indegree of a node and is quadratic in the number of nodes in the network, a big improvement over other techniques and yet there is little or no compromise in accuracy. We have tested ReBMM on a number of artificial datasets along with simulated data derived from a plant signaling network. We also used this method to reconstruct a network from real experimental observations of microarray data of the yeast cell cycle. Our method provides a natural framework for generating rules from a probabilistic model. It is simple, intuitive and illustrates excellent empirical results. PMID:23284654
Reversible S-Nitrosylation in an Engineered Azurin
Tian, Shiliang; Liu, Jing; Cowley, Ryan E.; Hosseinzadeh, Parisa; Marshall, Nicholas M.; Yu, Yang; Robinson, Howard; Nilges, Mark J.
2016-01-01
S-nitrosothiols are known as reagents for NO storage and transportation, and as regulators in many physiological processes. While the S-nitrosylation catalyzed by heme proteins is well known, no direct evidence of S-nitrosylation in copper proteins has been reported. Here we report reversible insertion of NO into a copper-thiolate bond in an engineered copper center in Pseudomonas aeruginosa azurin by rational design of the primary coordination sphere and tuning its reduction potential via deleting a hydrogen bond in the secondary coordination sphere. The results not only provide the first direct evidence of S-nitrosylation of Cu(II)-bound cysteine within metalloproteins, but also shed light on the reaction mechanism and structural features responsible for stabilizing the elusive Cu(I)-S(Cys)NO species. The fast, efficient, and reversible S-nitrosylation reaction is used to demonstrate its ability to prevent NO inhibition of cytochrome bo3 oxidase activity by competing for NO binding with the native enzyme under physiologically relevant conditions. PMID:27325093
Testing time series reversibility using complex network methods
Donges, Jonathan F; Kurths, Jürgen
2012-01-01
The absence of time-reversal symmetry is a fundamental property of many nonlinear time series. Here, we propose a set of novel statistical tests for time series reversibility based on standard and horizontal visibility graphs. Specifically, we statistically compare the distributions of time-directed variants of the common graph-theoretical measures degree and local clustering coefficient. Unlike other tests for reversibility, our approach does not require constructing surrogate data and can be applied to relatively short time series. We demonstrate its performance for realisations of paradigmatic model systems with known time-reversal properties as well as pickling up signatures of nonlinearity in some well-studied real-world neuro-physiological time series.
Internet-based dimensional verification system for reverse engineering processes
Song, In Ho [Ajou University, Suwon (Korea, Republic of); Kim, Kyung Don [Small Business Corporation, Suwon (Korea, Republic of); Chung, Sung Chong [Hanyang University, Seoul (Korea, Republic of)
2008-07-15
This paper proposes a design methodology for a Web-based collaborative system applicable to reverse engineering processes in a distributed environment. By using the developed system, design reviewers of new products are able to confirm geometric shapes, inspect dimensional information of products through measured point data, and exchange views with other design reviewers on the Web. In addition, it is applicable to verifying accuracy of production processes by manufacturing engineers. Functional requirements for designing this Web-based dimensional verification system are described in this paper. ActiveX-server architecture and OpenGL plug-in methods using ActiveX controls realize the proposed system. In the developed system, visualization and dimensional inspection of the measured point data are done directly on the Web: conversion of the point data into a CAD file or a VRML form is unnecessary. Dimensional verification results and design modification ideas are uploaded to markups and/or XML files during collaboration processes. Collaborators review the markup results created by others to produce a good design result on the Web. The use of XML files allows information sharing on the Web to be independent of the platform of the developed system. It is possible to diversify the information sharing capability among design collaborators. Validity and effectiveness of the developed system has been confirmed by case studies
Neutron tomography as a reverse engineering method applied to the IS-60 Rover gas turbine
Roos, TH
2011-09-01
Full Text Available Probably the most common method of reverse engineering in mechanical engineering involves measuring the physical geometry of a component using a coordinate measuring machine (CMM). Neutron tomography, in contrast, is used primarily as a non...
Time reversal method for guided wave inspection in pipes
Fei DENG; Bin WU; Cunfu HE
2008-01-01
The application of the time reversal method in pipe-like structures based on finite element method (FEM) is investigated. A steel pipe model measuring 70 mm × 3.5 mm is used to analyze the reflection coef-ficient of the L(0,2) mode with the time reversal process. Simulation results show that the time reversal array method is beneficial to the improvement of the signal-to-noise ratio of a guided wave inspection system. As the intercepting window is widened, more energy is included in re-emitted signals, which leads to a large reflection coefficient of the L(0,2) mode. In parallel, a circumferential locating method based on the time reversal method is described. The time reversal process used for guided wave inspection leads to the temporal and spatial focusing. When the time reversal signals are re-emitted, the angular profile obtained at the axial loca-tion of the defect can be used to determine the circumfer-ential location of the defect. Except for a pipe with one defect, the circumferential locating method has been veri-fied on another pipe model with two defects. Meanwhile, the elements number of the time reversal array has been discussed for enhancing the discrimination of the defect circumferential location.
Reducing current reversal time in electric motor control
Bredemann, Michael V
2014-11-04
The time required to reverse current flow in an electric motor is reduced by exploiting inductive current that persists in the motor when power is temporarily removed. Energy associated with this inductive current is used to initiate reverse current flow in the motor.
Reversal of Hartmann's procedure following acute diverticulitis: is timing everything?
Fleming, Fergal J
2012-02-01
BACKGROUND: Patients who undergo a Hartmann\\'s procedure may not be offered a reversal due to concerns over the morbidity of the second procedure. The aims of this study were to examine the morbidity post reversal of Hartmann\\'s procedure. METHODS: Patients who underwent a Hartmann\\'s procedure for acute diverticulitis (Hinchey 3 or 4) between 1995 and 2006 were studied. Clinical factors including patient comorbidities were analysed to elucidate what preoperative factors were associated with complications following reversal of Hartmann\\'s procedure. RESULTS: One hundred and ten patients were included. Median age was 70 years and 56% of the cohort were male (n = 61). The mortality and morbidity rate for the acute presentation was 7.3% (n = 8) and 34% (n = 37) respectively. Seventy six patients (69%) underwent a reversal at a median of 7 months (range 3-22 months) post-Hartmann\\'s procedure. The complication rate in the reversal group was 25% (n = 18). A history of current smoking (p = 0.004), increasing time to reversal (p = 0.04) and low preoperative albumin (p = 0.003) were all associated with complications following reversal. CONCLUSIONS: Reversal of Hartmann\\'s procedure can be offered to appropriately selected patients though with a significant (25%) morbidity rate. The identification of potential modifiable factors such as current smoking, prolonged time to reversal and low preoperative albumin may allow optimisation of such patients preoperatively.
Faraday waves under time-reversed excitation.
Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas
2013-03-01
Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.
Reverse engineering human neurodegenerative disease using pluripotent stem cell technology.
Liu, Ying; Deng, Wenbin
2016-05-01
With the technology of reprogramming somatic cells by introducing defined transcription factors that enables the generation of "induced pluripotent stem cells (iPSCs)" with pluripotency comparable to that of embryonic stem cells (ESCs), it has become possible to use this technology to produce various cells and tissues that have been difficult to obtain from living bodies. This advancement is bringing forth rapid progress in iPSC-based disease modeling, drug screening, and regenerative medicine. More and more studies have demonstrated that phenotypes of adult-onset neurodegenerative disorders could be rather faithfully recapitulated in iPSC-derived neural cell cultures. Moreover, despite the adult-onset nature of the diseases, pathogenic phenotypes and cellular abnormalities often exist in early developmental stages, providing new "windows of opportunity" for understanding mechanisms underlying neurodegenerative disorders and for discovering new medicines. The cell reprogramming technology enables a reverse engineering approach for modeling the cellular degenerative phenotypes of a wide range of human disorders. An excellent example is the study of the human neurodegenerative disease amyotrophic lateral sclerosis (ALS) using iPSCs. ALS is a progressive neurodegenerative disease characterized by the loss of upper and lower motor neurons (MNs), culminating in muscle wasting and death from respiratory failure. The iPSC approach provides innovative cell culture platforms to serve as ALS patient-derived model systems. Researchers have converted iPSCs derived from ALS patients into MNs and various types of glial cells, all of which are involved in ALS, to study the disease. The iPSC technology could be used to determine the role of specific genetic factors to track down what's wrong in the neurodegenerative disease process in the "disease-in-a-dish" model. Meanwhile, parallel experiments of targeting the same specific genes in human ESCs could also be performed to control
Buried-object detection using time-reversed acoustics
Pierson, David Michael
The work presented here is a comprehensive study of using time reversal to detect objects located in an inhomogeneous environment using backscattered signals with an emphasis on littoral environments. Time reversal of acoustic signals in the ocean has been studied for more than two decades with the emphasis on the use of the forward scattered field. All studies share similar geometries where both the acoustical source and an adjacent array of transducers are placed in the water column. This configuration, known as a time-reversal mirror (TRM), is not practical when detecting an object that is located in a different environment than the TRM, such as beneath the ocean floor. Little work has been done to study the efficacy of a single transceiver performing the time-reversal operation on the backscattered signals from targets buried beneath the ocean floor. Here, I start by presenting the theory for such a system in both time and frequency domains for scattering by a sphere. Then by using simulations I show that time reversal of backscattered signals provides a robust method to detect targets buried in an acoustically inhomogeneous sediment using a point transceiver in the water column several meters above the sea floor. Effects of the time-reversal window (TRW) on the iterative time-reversal operation are also presented. I define a signal-to-noise ratio (SNR) that treats the return with the sphere as the signal and the return without the sphere as noise to quantify improvements to the sphere returns. I consider two different sediment models and angle of incidence to show that the TRO operates independently of the sediment type and transceiver orientation. Theoretical analysis reveals that the time-reversal of backscattered signals converges to a subset of waveforms defined by the target and time-reversal window, not the initial pulse. Analysis further reveals that the time-reversal operator detects the sphere after only two iterations of the TRO, with more iterations
Anomaly indicators for time-reversal symmetric topological orders
Wang, Chenjie
2016-01-01
Some time-reversal symmetric topological orders are anomalous in that they cannot be realized in strictly two-dimensions without breaking time reversal symmetry; instead, they can only be realized on the surface of certain three-dimensional systems. We propose two quantities, which we call {\\it anomaly indicators}, that can detect if a time-reversal symmetric topological order is anomalous in this sense. Both anomaly indicators are expressed in terms of the quantum dimensions, topological spins, and time-reversal properties of the anyons in the given topological order. The first indicator, $\\eta_2$, applies to bosonic systems while the second indicator, $\\eta_f$, applies to fermionic systems in the DIII class. We conjecture that $\\eta_2$, together with a previously known indicator $\\eta_1$, can detect the two known $\\mathbb Z_2$ anomalies in the bosonic case, while $\\eta_f$ can detect the $\\mathbb Z_{16}$ anomaly in the fermionic case.
Reverse engineering biological networks :applications in immune responses to bio-toxins.
Martino, Anthony A.; Sinclair, Michael B.; Davidson, George S.; Haaland, David Michael; Timlin, Jerilyn Ann; Thomas, Edward Victor; Slepoy, Alexander; Zhang, Zhaoduo; May, Elebeoba Eni; Martin, Shawn Bryan; Faulon, Jean-Loup Michel
2005-12-01
Our aim is to determine the network of events, or the regulatory network, that defines an immune response to a bio-toxin. As a model system, we are studying T cell regulatory network triggered through tyrosine kinase receptor activation using a combination of pathway stimulation and time-series microarray experiments. Our approach is composed of five steps (1) microarray experiments and data error analysis, (2) data clustering, (3) data smoothing and discretization, (4) network reverse engineering, and (5) network dynamics analysis and fingerprint identification. The technological outcome of this study is a suite of experimental protocols and computational tools that reverse engineer regulatory networks provided gene expression data. The practical biological outcome of this work is an immune response fingerprint in terms of gene expression levels. Inferring regulatory networks from microarray data is a new field of investigation that is no more than five years old. To the best of our knowledge, this work is the first attempt that integrates experiments, error analyses, data clustering, inference, and network analysis to solve a practical problem. Our systematic approach of counting, enumeration, and sampling networks matching experimental data is new to the field of network reverse engineering. The resulting mathematical analyses and computational tools lead to new results on their own and should be useful to others who analyze and infer networks.
Proceedings of the 1st workshop on aspect reverse-engineering, Delft, 09.11.2004
Tourwé, T.; Bruntink, M.; Marin, A.M.; Shepherd, D.
2005-01-01
This technical report contains the papers submitted to and presented at the 1st Workshop on Aspect Reverse-Engineering, held in conjunction with the 11th Working Conference on Reverse Engineering (WCRE), in Delft, The Netherlands. The aims of this workshop was to bring together researchers and pract
Mohammadreza Shahriari
2016-02-01
Full Text Available One of the basic purposes in developing countries had been reduction of their technological gap in different eras. So, technology transfer in developing countries has become one of the key factors of economic growth. But technology transfer is a difficult and complex process, so it can be unsuccessful and may waste time and money or undermine the national technology if performed without enough considering and study. Therefore, according to high ability of interior experts and scientists and country's condition to have a successful technology transfer, Reverse Engineering is used as an effective factor. In this paper supporting 15 experts and using Fuzzy Delphi Method, the effective factors on success of technology transfer by reverse engineering in aviation engines industry will be recognized and then prioritized by members of statistical sample and Analytical Network Process (ANP. Finally, we will have three components, technical knowledge for redesign, technical knowledge for producing, and organizational association with original country that are the most important among the other ten selected components.
Time-Reversal of Nonlinear Waves - Applicability and Limitations
Ducrozet, G; Chabchoub, A
2016-01-01
Time-reversal (TR) refocusing of waves is one of fundamental principles in wave physics. Using the TR approach, "Time-reversal mirrors" can physically create a time-reversed wave that exactly refocus back, in space and time, to its original source regardless of the complexity of the medium as if time were going backwards. Lately, laboratory experiments proved that this approach can be applied not only in acoustics and electromagnetism but also in the field of linear and nonlinear water waves. Studying the range of validity and limitations of the TR approach may determine and quantify its range of applicability in hydrodynamics. In this context, we report a numerical study of hydrodynamic TR using a uni-directional numerical wave tank, implemented by the nonlinear high-order spectral method, known to accurately model the physical processes at play, beyond physical laboratory restrictions. The applicability of the TR approach is assessed over a variety of hydrodynamic localized and pulsating structures' configu...
High-resolution and super stacking of time-reversal mirrors in locating seismic sources
Cao, Weiping
2011-07-08
Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high-resolution and super-stacking properties. These benefits of time reversal mirrors have been previously verified with computer simulations and laboratory experiments but not with exploration-scale seismic data. We now demonstrate the high-resolution and the super-stacking properties in locating seismic sources with field seismic data that include multiple scattering. Tests on both synthetic data and field data show that a time reversal mirror has the potential to exceed the Rayleigh resolution limit by factors of 4 or more. Results also show that a time reversal mirror has a significant resilience to strong Gaussian noise and that accurate imaging of source locations from passive seismic data can be accomplished with traces having signal-to-noise ratios as low as 0.001. Synthetic tests also demonstrate that time reversal mirrors can sometimes enhance the signal by a factor proportional to the square root of the product of the number of traces, denoted as N and the number of events in the traces. This enhancement property is denoted as super-stacking and greatly exceeds the classical signal-to-noise enhancement factor of. High-resolution and super-stacking are properties also enjoyed by seismic interferometry and reverse-time migration with the exact velocity model. © 2011 European Association of Geoscientists & Engineers.
Time-reversal symmetry breaking in quantum billiards
Schaefer, Florian
2009-01-26
The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally
Time reversal invariance, entropy production and work dissipation in stochastic thermodynamics
Gaveau, B.; Moreau, M.
2015-07-01
We consider the work production in a mesosccopic Markov system obeying discrete stochastic dynamics with time-dependent constraints. Using asymmetry relations presented elsewhere, which result from time reversal invariance of the underlying microscopic system, we derive, beside known equalities in stochastic thermodynamics, a new result: the "Carnot equality", that generalizes the Carnot relation for macroscopic bi-thermal engines. Such equalities, which extend the classical inequalities of thermodynamics, result from microscopic time reversal invariance only. On the other hand we show that, on the mesoscopic level, notions such as entropy production and power dissipation per transition cannot always be defined. In the absence of a precise mechanical model, such definitions are possible if, and only if, the asymmetry relations due to microscopic time reversal invariance are supplemented by space symmetry relations, equivalent to parity, which are not always satisfied. This article is supplemented with comments by J.M.R. Parrondo and L. Granger and a final reply by the authors.
Quantum transport enhancement by time-reversal symmetry breaking.
Zimborás, Zoltán; Faccin, Mauro; Kádár, Zoltán; Whitfield, James D; Lanyon, Ben P; Biamonte, Jacob
2013-01-01
Quantum mechanics still provides new unexpected effects when considering the transport of energy and information. Models of continuous time quantum walks, which implicitly use time-reversal symmetric Hamiltonians, have been intensely used to investigate the effectiveness of transport. Here we show how breaking time-reversal symmetry of the unitary dynamics in this model can enable directional control, enhancement, and suppression of quantum transport. Examples ranging from exciton transport to complex networks are presented. This opens new prospects for more efficient methods to transport energy and information.
Analysis of the reverse jet influence on particle ingestion at the engine inlet
Krasheninnikov, S. Yu.; Pudovikov, D. E.
2015-06-01
The reverse mode of an operating near-ground jet engine is considered. The air flow and particle trajectories under the engine intake are calculated. On the base of numerical and theoretical analysis of the air flow and particle trajectories, some conclusions about reducing the probability of transportation of large particles to the engine are drawn.
Mrinal Kanti Sarkar
2013-09-01
Full Text Available The Unified Modeling Language (UML has been accepted as a standard for modeling object oriented system. It helps the designer to understand a problem well by focusing on one aspects of a problem at a time. In this paper we present a novel approach in which reverse engineering is performed and we have chosen UML as the modeling language to achieve a representation of the implemented system. In this work we have considered java programs. After a brief introduction to the subject, we present some analyses which go beyond mere enumeration of methods and fields. We sketch a method which determines classes and their attribute, operation and relationship: generalization, aggregation, association and various kind of dependencies in form of a simple class diagram that can be understood by a programmer when inspecting the source code of a given java programs. To fully understand the behavior of a system, it is crucial to have efficient techniques to reverse static views of the system. In this paper, we focus on the reverse engineering to find UML class diagram from an object oriented system and analysis of its static behavior.
Three myths about time reversal in quantum theory
Roberts, Bryan W
2016-01-01
Many have suggested that the transformation standardly referred to as 'time reversal' in quantum theory is not deserving of the name. I argue on the contrary that the standard definition is perfectly appropriate, and is indeed forced by basic considerations about the nature of time in the quantum formalism.
Marcucio, Ralph S; Qin, Ling; Alsberg, Eben; Boerckel, Joel D
2017-06-29
The fields of developmental biology and tissue engineering have been revolutionized in recent years by technological advancements, expanded understanding, and biomaterials design, leading to the emerging paradigm of "developmental" or "biomimetic" tissue engineering. While developmental biology and tissue engineering have long overlapping histories, the fields have largely diverged in recent years at the same time that crosstalk opportunities for mutual benefit are more salient than ever. In this perspective article, we will use musculoskeletal development and tissue engineering as a platform on which to discuss these emerging crosstalk opportunities and will present our opinions on the bright future of these overlapping spheres of influence. The multicellular programs that control musculoskeletal development are rapidly becoming clarified, represented by shifting paradigms in our understanding of cellular function, identity, and lineage specification during development. Simultaneously, advancements in bioartificial matrices that replicate the biochemical, microstructural, and mechanical properties of developing tissues present new tools and approaches for recapitulating development in tissue engineering. Here, we introduce concepts and experimental approaches in musculoskeletal developmental biology and biomaterials design and discuss applications in tissue engineering as well as opportunities for tissue engineering approaches to inform our understanding of fundamental biology. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Reverse engineering: a key component of systems biology to unravel global abiotic stress cross-talk.
Friedel, Swetlana; Usadel, Björn; von Wirén, Nicolaus; Sreenivasulu, Nese
2012-01-01
Understanding the global abiotic stress response is an important stepping stone for the development of universal stress tolerance in plants in the era of climate change. Although co-occurrence of several stress factors (abiotic and biotic) in nature is found to be frequent, current attempts are poor to understand the complex physiological processes impacting plant growth under combinatory factors. In this review article, we discuss the recent advances of reverse engineering approaches that led to seminal discoveries of key candidate regulatory genes involved in cross-talk of abiotic stress responses and summarized the available tools of reverse engineering and its relevant application. Among the universally induced regulators involved in various abiotic stress responses, we highlight the importance of (i) abscisic acid (ABA) and jasmonic acid (JA) hormonal cross-talks and (ii) the central role of WRKY transcription factors (TF), potentially mediating both abiotic and biotic stress responses. Such interactome networks help not only to derive hypotheses but also play a vital role in identifying key regulatory targets and interconnected hormonal responses. To explore the full potential of gene network inference in the area of abiotic stress tolerance, we need to validate hypotheses by implementing time-dependent gene expression data from genetically engineered plants with modulated expression of target genes. We further propose to combine information on gene-by-gene interactions with data from physical interaction platforms such as protein-protein or TF-gene networks.
Pressure Sensitivity Kernels Applied to Time-reversal Acoustics
2009-06-29
Edelmann [14] showed that it is possible to encode phase information in the time- reversed Green’s function that can then be recovered at the receiver end...conjugation experiment in shallow water. J. Acoustic Soc. Am., 105:1597–1604, 1999. [14] G. F. Edelmann , T. Akal, W. S. Hodgkiss, S. Kim, W. A...15] S. Kim, W. A. Kuperman, W. S. Hodgkiss, H. C. Song, and G. F. Edelmann . Robust time-reversal focusing in the ocean. J. Acoustic Soc. Am., 114:145
Real-time graphics rendering engine
Bao, Hujun
2011-01-01
""Real-Time Graphics Rendering Engine"" reveals the software architecture of the modern real-time 3D graphics rendering engine and the relevant technologies based on the authors' experience developing this high-performance, real-time system. The relevant knowledge about real-time graphics rendering such as the rendering pipeline, the visual appearance and shading and lighting models are also introduced. This book is intended to offer well-founded guidance for researchers and developers who are interested in building their own rendering engines. Hujun Bao is a professor at the State Key Lab of
Mirror reading can reverse the flow of time.
Casasanto, Daniel; Bottini, Roberto
2014-04-01
How does culture shape our concepts? Across many cultures, people conceptualize time as if it flows along a horizontal timeline, but the direction of this implicit timeline is culture specific: Later times are on the right in some cultures but on the left in others. Here we investigated whether experience reading can determine the direction and orientation of the mental timeline, independent of other cultural and linguistic factors. Dutch speakers performed space-time congruity tasks with the instructions and stimuli written in either standard, mirror-reversed, or rotated orthography. When participants judged temporal phrases written in standard orthography, their reaction times were consistent with a rightward-directed mental timeline, but after brief exposure to mirror-reversed orthography, their mental timelines were reversed. When standard orthography was rotated 90° clockwise (downward) or counterclockwise (upward), participants' mental timelines were rotated, accordingly. Reading can play a causal role in shaping people's implicit time representations. Exposure to a new orthography can change the direction and orientation of the mental timeline within minutes, even when the new space-time mapping directly contradicts the reader's usual mapping. To account for this representational flexibility, we propose the hierarchical mental metaphors theory, according to which culturally conditioned mappings between space and time are specific instances of a more general mapping, which is conditioned by the relationship between space and time in the physical world. Conceptualizations of time are culture specific at one level of analysis but may be universal at another.
A NEW REVERSE ENGINEERING APPROACH TO CONVERT FORM FILL FORMAT DOCUMENT INTO UML CLASS DIAGRAM
Mohammad I. Muhairat
2014-12-01
Full Text Available This paper propose a new reverse engineering approach to convert a form fill format document into a set of related tables that can be used to generate the entity relationship diagram. A relationship between the set of tables is generated. In addition, the entity relationship diagram will be converted into a UML class diagram. However, this approach will be very helpful for researchers and practitioners in Software Engineering field, since most of the reverse engineering approaches are based on source code. This approach is tested by using several word form fill format documents and the results show a high accuracy rates comparing with the forward engineering.
Vierdy Sulfianto Rahmadani
2015-04-01
Full Text Available The purpose of this research is to apply the application of reverse engineering to determine interaction patterns of the Sequence diagram that can be used by system analysts as a template for designing UML sequence diagrams. Sample applications from android are used as dataset for reverse engineering and pattern identification. The first step is collecting application datasets. The next stage is identifying the features and applications activity, reverse engineering to obtain a sequence diagram model, and then synthesize all of the models into an interaction pattern of sequence diagram. The final step is to test the patterns by implementing it in an application development case stud. The evaluation results concludes that interaction patterns of sequence diagram designs obtained in reverse engineering steps is able to be implemented in software development that contained similar features with the obtained features in this research.
DSP-Based Focusing over Optical Fiber Using Time Reversal
Piels, Molly; Porto da Silva, Edson; Estaran Tolosa, Jose Manuel;
2014-01-01
A time-reversal array in multimode fiber is proposed for lossless switching using passive optical splitters. Numerical investigations are performed, and a two-transmitter array that routes a 3GBd QPSK signal through the physical layer is demonstrated experimentally....
Linearized inverse scattering based on seismic reverse time migration
op 't Root, T.J.P.M.; Stolk, C.C.; de Hoop, M.V.
2012-01-01
In this paper we study the linearized inverse problem associated with imaging of reflection seismic data. We introduce an inverse scattering transform derived from reverse time migration (RTM). In the process, the explicit evaluation of the so-called normal operator is avoided, while other different
Time Reversal of Volterra Processes Driven Stochastic Differential Equations
L. Decreusefond
2013-01-01
Full Text Available We consider stochastic differential equations driven by some Volterra processes. Under time reversal, these equations are transformed into past-dependent stochastic differential equations driven by a standard Brownian motion. We are then in position to derive existence and uniqueness of solutions of the Volterra driven SDE considered at the beginning.
Reverse engineering by design: using history to teach.
Fagette, Paul
2013-01-01
Engineering students rarely have an opportunity to delve into the historic antecedents of design in their craft, and this is especially true for biomedical devices. The teaching emphasis is always on the new, the innovative, and the future. Even so, over the last decade, I have coupled a research agenda with engineering special projects into a successful format that allows young biomedical engineering students to understand aspects of their history and learn the complexities of design. There is value in having knowledge of historic engineering achievements, not just for an appreciation of these accomplishments but also for understanding exactly how engineers and clinicians of the day executed their feats-in other words, how the design process works. Ultimately, this particular educational odyssey confirms that history and engineering education are not only compatible but mutually supportive.
Reverse engineering and identification in systems biology: strategies, perspectives and challenges
Villaverde, A. F.; Julio R Banga
2014-01-01
The interplay of mathematical modelling with experiments is one of the central elements in systems biology. The aim of reverse engineering is to infer, analyse and understand, through this interplay, the functional and regulatory mechanisms of biological systems. Reverse engineering is not exclusive of systems biology and has been studied in different areas, such as inverse problem theory, machine learning, nonlinear physics, (bio)chemical kinetics, control theory and optimization, among othe...
Wave-Based Turing Machine: Time Reversal and Information Erasing.
Perrard, S; Fort, E; Couder, Y
2016-08-26
The investigation of dynamical systems has revealed a deep-rooted difference between waves and objects regarding temporal reversibility and particlelike objects. In nondissipative chaos, the dynamic of waves always remains time reversible, unlike that of particles. Here, we explore the dynamics of a wave-particle entity. It consists in a drop bouncing on a vibrated liquid bath, self-propelled and piloted by the surface waves it generates. This walker, in which there is an information exchange between the particle and the wave, can be analyzed in terms of a Turing machine with waves as the information repository. The experiments reveal that in this system, the drop can read information backwards while erasing it. The drop can thus backtrack on its previous trajectory. A transient temporal reversibility, restricted to the drop motion, is obtained in spite of the system being both dissipative and chaotic.
Wave-Based Turing Machine: Time Reversal and Information Erasing
Perrard, S.; Fort, E.; Couder, Y.
2016-08-01
The investigation of dynamical systems has revealed a deep-rooted difference between waves and objects regarding temporal reversibility and particlelike objects. In nondissipative chaos, the dynamic of waves always remains time reversible, unlike that of particles. Here, we explore the dynamics of a wave-particle entity. It consists in a drop bouncing on a vibrated liquid bath, self-propelled and piloted by the surface waves it generates. This walker, in which there is an information exchange between the particle and the wave, can be analyzed in terms of a Turing machine with waves as the information repository. The experiments reveal that in this system, the drop can read information backwards while erasing it. The drop can thus backtrack on its previous trajectory. A transient temporal reversibility, restricted to the drop motion, is obtained in spite of the system being both dissipative and chaotic.
Time reversal and the spatio-temporal matched filter
Lehman, S K; Poggio, A J; Kallman, J S; Meyer, A W; Candy, J V
2004-03-08
It is known that focusing of an acoustic field by a time-reversal mirror (TRM) is equivalent to a spatio-temporal matched filter under conditions where the Green's function of the field satisfies reciprocity and is time invariant, i.e. the Green's function is independent of the choice of time origin. In this letter, it is shown that both reciprocity and time invariance can be replaced by a more general constraint on the Green's function that allows a TRM to implement the spatio-temporal matched filter even when conditions are time varying.
A Process Re-engineering Framework for Reverse Logistics based on a Case Study
Hing Kai Chan
2010-09-01
Full Text Available Reverse logistics has gained increasing attention in recent years as a channel for companies to achieve operational excellence. The process involves manipulation of returned materials, or even products, which forms a pivotal role in sustainable development throughout the whole supply chains. To make reverse logistics possible, process re-engineering may need to be carried out. However, the processes involved in reengineering are practically complicated. Objectives, benefits, and applicability of any process re-engineering require a careful and detailed strategic planning. This paper aims to propose an easy-to-follow step-by-step framework for practitioners to perform process re-engineering, to learn and identify the critical issues in each step, and to be successful in applying process re-engineering in order to enhance reverse logistics performance. A learner-centred approach is adopted based on a case study of process re-engineering, which is demonstrated in the paper for explanation.
How to reverse time in stochastic particle tracking models
Thygesen, Uffe Høgsbro
2011-01-01
Many oceanographic studies perform individual-based simulations of the transport and dispersal of particles such as fish larvae and eggs. An increasing number of these studies take place in reverse time, for example as to locate the origins of a particle observed at a given time and position. Thi...... probabilities. We illustrate the conceptual and algorithmic differences between the approaches. © 2011 Elsevier B.V. All rights reserved....
Reversible and Irreversible Time-Dependent Behavior of GRCop-84
Lerch, Bradley A.; Arnold, Steven M.; Ellis, David L.
2017-01-01
A series of mechanical tests were conducted on a high-conductivity copper alloy, GRCop-84, in order to understand the time dependent response of this material. Tensile, creep, and stress relaxation tests were performed over a wide range of temperatures, strain rates, and stress levels to excite various amounts of time-dependent behavior. At low applied stresses the deformation behavior was found to be fully reversible. Above a certain stress, termed the viscoelastic threshold, irreversible deformation was observed. At these higher stresses the deformation was observed to be viscoplastic. Both reversible and irreversible regions contained time dependent deformation. These experimental data are documented to enable characterization of constitutive models to aid in design of high temperature components.
A new slicing method of reverse engineering based on the principle of refraction and reflection
LIU Ya-xiong; ZONG Xue-wen; TANG Yi-ping; LU Bing-heng
2006-01-01
The traditional slicing method of reverse engineering has been used in product measure from time immemorial.This method however has the disadvantage of low contrast of the cross-sectional pictures of an object.In order to overcome the said shortcoming,a new slicing method of reverse engineering,based on the principle of refraction and reflection of a prism,has been propounded.According to the reflectivity of the object,one of the illuminating methods-straight illuminating or inclined illuminating-is adopted.These methods can enable one to obtain the image of the cross-section of a bright object with a dark background or the opposite.Experiments have proved to show the advantages of this new slicing method for high contrast of the cross-sectional pictures.To eliminate geometrical distortions caused by the refraction and reflection of the prism,a mathematical transformation model can be set up to correct the image by using relevant software.Eventually,a RP model of a temporomandibular joint fabricated according to its slicing pictures is illustrated.
A digital matched filter for reverse time chaos
Bailey, J. Phillip, E-mail: mchamilton@auburn.edu; Beal, Aubrey N.; Dean, Robert N.; Hamilton, Michael C. [Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36489 (United States)
2016-07-15
The use of reverse time chaos allows the realization of hardware chaotic systems that can operate at speeds equivalent to existing state of the art while requiring significantly less complex circuitry. Matched filter decoding is possible for the reverse time system since it exhibits a closed form solution formed partially by a linear basis pulse. Coefficients have been calculated and are used to realize the matched filter digitally as a finite impulse response filter. Numerical simulations confirm that this correctly implements a matched filter that can be used for detection of the chaotic signal. In addition, the direct form of the filter has been implemented in hardware description language and demonstrates performance in agreement with numerical results.
Optical-Model Description of Time-Reversal Violation
Hnizdo, V
1994-01-01
A time-reversal-violating spin-correlation coefficient in the total cross section for polarized neutrons incident on a tensor rank-2 polarized target is calculated by assuming a time-reversal-noninvariant, parity-conserving ``five-fold" interaction in the neutron-nucleus optical potential. Results are presented for the system $n + {^{165}{\\rm Ho}}$ for neutron incident energies covering the range 1--20 MeV. From existing experimental bounds, a strength of $2 \\pm 10$ keV is deduced for the real and imaginary parts of the five-fold term, which implies an upper bound of order $10^{-4}$ on the relative $T$-odd strength when compared to the central real optical potential.
Analysis of Time Reversible Born-Oppenheimer Molecular Dynamics
Lin Lin
2013-12-01
Full Text Available We analyze the time reversible Born-Oppenheimer molecular dynamics (TRBOMD scheme, which preserves the time reversibility of the Born-Oppenheimer molecular dynamics even with non-convergent self-consistent field iteration. In the linear response regime, we derive the stability condition, as well as the accuracy of TRBOMD for computing physical properties, such as the phonon frequency obtained from the molecular dynamics simulation. We connect and compare TRBOMD with Car-Parrinello molecular dynamics in terms of accuracy and stability. We further discuss the accuracy of TRBOMD beyond the linear response regime for non-equilibrium dynamics of nuclei. Our results are demonstrated through numerical experiments using a simplified one-dimensional model for Kohn-Sham density functional theory.
Loschmidt echo and time reversal in complex systems.
Goussev, Arseni; Jalabert, Rodolfo A; Pastawski, Horacio M; Wisniacki, Diego A
2016-06-13
Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years.
Time reversal and exchange symmetries of unitary gate capacities
Harrow, A W; Harrow, Aram W.; Shor, Peter W.
2005-01-01
Unitary gates are an interesting resource for quantum communication in part because they are always invertible and are intrinsically bidirectional. This paper explores these two symmetries: time-reversal and exchange of Alice and Bob. We will present examples of unitary gates that exhibit dramatic separations between forward and backward capacities (even when the back communication is assisted by free entanglement) and between entanglement-assisted and unassisted capacities, among many others. Along the way, we will give a general time-reversal rule for relating the capacities of a unitary gate and its inverse that will explain why previous attempts at finding asymmetric capacities failed. Finally, we will see how the ability to erase quantum information and destroy entanglement can be a valuable resource for quantum communication.
Crashworthiness Analysis of a Minibus Body in White Through Reverse Engineering
王青春; 范子杰; 桂良进; 陈宗渝; 宋宏伟
2004-01-01
To investigate the crashworthiness of a minibus body in white (BIW) and create a digital model for further analysis and improvement, the crash behavior of the BIW was quantitatively analyzed using reverse engineering.Each part of the BIW was identified and digitalized to conduct a finite element model.A frontal crash was simulated numerically using the explicit finite element analysis software LS-DYNA.BIW crash tests were conducted to validate the finite element model.The computational results agree well with the test data, not only for the collapse mode, but also in the force-time and acceleration-time correlation curves.The methods used to create the finite element model can be used to further improve or develop safer vehicles.
Noise of model target type thrust reversers for engine-over-the-wing applications
Stone, J. R.; Gutierrez, O. A.
1974-01-01
The present work reports on experiments concerning the noise generated by V-gutter and semicylindrical target reversers with circular and short-aspect-ratio slot nozzles having equivalent diameters of about 5 cm. At subsonic jet velocities of interest for engine-over-the-wing (OTW) powered-lift aircraft, the reversers were noisier than the nozzles alone and had a more uniform directional distribution and more high-frequency noise. Reverser shape was more important than nozzle shape in determining the reverser noise characteristics. An estimate is made of perceived noise level along the 152-m sideline for a hypothetical OTW powered-lift airplane.
Anisotropy signature in extended images from reverse-time migration
Sava, Paul
2012-11-04
Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.
Parity and time-reversal non-conservation in atoms
Lynn, B.W.
1984-08-01
We examine the implications of parity and time-reversal non-conservation for atomic physics. We conclude that a determination of Q/sub W//N to 10% would give an indirect determination of M/sub Z/ competitive with that available from high-energy physics, limits on the electric dipole moments of neutrons and electrons give non-trivial constraints on model building of CP non-conservation.
A model for discussing entropy and time reversibility
Castellani, Tommaso
2014-01-01
In this article we discuss a model used to introduce the concept of entropy with secondary school students. It can be used to discuss with students the reversibility of time, the tendency towards homogeneity and the link between probability theory and second law of thermodynamics. The model is useful to introduce crucial epistemological issues and helps student to understand the deep connection between the macroscopic and the microscopic.
Imaging volcanic infrasound sources using time reversal mirror algorithm
Kim, Keehoon; Lees, Jonathan M.
2015-09-01
We investigate the capability of Time Reversal Mirror (TRM) algorithm to image local acoustic sources (acoustic waves) is often challenging due to pronounced volcanic topography and emergent arrivals of infrasound signals. While the accuracy of the conventional approaches (e.g. triangulation and semblance method) can be severely compromised by the complex volcanic settings, a TRM-based method may have the potential to properly image acoustic sources by the use of full waveform information and numerical modelling of the time-reversed wavefield. We apply the TRM algorithm to a pyroclastic-laden eruption (sustained for ˜60 s) at Santiaguito Volcano, Guatemala, and show that an ordinary TRM operation can undergo significant reduction of its focusing power due to strong topographic propagation effects (e.g. reflection and diffraction). We propose a weighted imaging condition to compensate for complicated transmission loss of the time-reversed wavefield and demonstrate that the presented condition significantly improves the focusing quality of TRM in the presence of complex topography. The consequent TRM source images exhibit remarkable agreement with the visual observation of the eruption implying that the TRM method with a proper imaging condition can be used to localize and track acoustic sources associated with complex volcanic eruptions.
Gordon, Richard; Melvin, Cameron A
2003-01-01
Our desire to educate engineers to be able to understand the component processes of embryogenesis, is driven by the notion that only when principles borrowed from mathematics, fluid mechanics, materials science, etc. are applied to classical problems in developmental biology, will sufficient comprehension be achieved to permit successful understanding and therapeutic manipulation of embryos. As it now stands, biologists seldom possess either skills or interest in those areas of endeavor. Thus, we have determined that it is easier to educate engineers in the principles of developmental biology than to help biologists deal with the complexities of engineering. We describe a graduate course that has been taken, between 1999 and 2002, by 17 engineering students. Our goal is to prepare them to reverse engineer the embryo, i.e., to look at it as an object or process whose construction, albeit self-construction, might be explicable in terms of engineering principles applied at molecular, cellular and whole embryo levels.
Anti-Aliasing filter for reverse-time migration
Zhan, Ge
2012-01-01
We develop an anti-aliasing filter for reverse-time migration (RTM). It is similar to the traditional anti-aliasing filter used for Kirchhoff migration in that it low-pass filters the migration operator so that the dominant wavelength in the operator is greater than two times the trace sampling interval, except it is applied to both primary and multiple reflection events. Instead of applying this filter to the data in the traditional RTM operation, we apply the anti-aliasing filter to the generalized diffraction-stack migration operator. This gives the same migration image as computed by anti-aliased RTM. Download
Efficient hybrid method for time reversal superresolution imaging
Xiaohua Wang,Wei Gao,; Bingzhong Wang
2015-01-01
An efficient hybrid time reversal (TR) imaging method based on signal subspace and noise subspace is proposed for electromagnetic superresolution detecting and imaging. First, the locations of targets are estimated by the transmitting-mode decom-position of the TR operator (DORT) method employing the signal subspace. Then, the TR multiple signal classification (TR-MUSIC) method employing the noise subspace is used in the estimated target area to get the superresolution imaging of targets. Two examples with homogeneous and inhomogeneous background mediums are considered, respectively. The results show that the proposed hybrid method has advantages in CPU time and memory cost because of the combination of rough and fine imaging.
Reverse engineering and identification in systems biology: strategies, perspectives and challenges.
Villaverde, Alejandro F; Banga, Julio R
2014-02-06
The interplay of mathematical modelling with experiments is one of the central elements in systems biology. The aim of reverse engineering is to infer, analyse and understand, through this interplay, the functional and regulatory mechanisms of biological systems. Reverse engineering is not exclusive of systems biology and has been studied in different areas, such as inverse problem theory, machine learning, nonlinear physics, (bio)chemical kinetics, control theory and optimization, among others. However, it seems that many of these areas have been relatively closed to outsiders. In this contribution, we aim to compare and highlight the different perspectives and contributions from these fields, with emphasis on two key questions: (i) why are reverse engineering problems so hard to solve, and (ii) what methods are available for the particular problems arising from systems biology?
Order from disorder in closed systems via time reversal violation
Goldman, T
2012-01-01
Definitions of entropy usually assume time-reversal (T) invariance of interactions, yet microscopically T is known to be violated. We present a detailed computational example of (uncharged) particle species separation (Maxwell demon) using an interaction that violates both parity (P) and T so that PT is preserved, consistent with the CPT invariance required in quantum field theory (C is charge conjugation). This illustrates how T-violating forces can produce more organized states from disorganized ones, contrary to expectations based on increase of entropy. We also outline several scenarios in which T-violating forces could lead to an organized state in the early Universe, starting from a still earlier disorganized state.
Probing material nonlinearity at various depths by time reversal mirrors
Payan, C.; Ulrich, T. J.; Le Bas, P. Y.; Griffa, M.; Schuetz, P.; Remillieux, M. C.; Saleh, T. A.
2014-04-01
In this Letter, the time reversal mirror is used to focus elastic energy at a prescribed location and to analyze the amplitude dependence of the focus signal, thus providing the nonlinearity of the medium. By varying the frequency content of the focused waveforms, the technique can be used to probe the surface, by penetrating to a depth defined by the wavelength of the focused waves. The validity of this concept is shown in the presence of gradual and distributed damage in concrete by comparing actual results with a reference nonlinear measurement and X ray tomography images.
Probing material nonlinearity at various depths by time reversal mirrors
Payan, C. [LMA UPR CNRS 7051, Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille (France); Ulrich, T. J.; Le Bas, P. Y.; Remillieux, M. C. [Los Alamos National Laboratory, EES-17, Los Alamos, New Mexico 87545 (United States); Griffa, M.; Schuetz, P. [Swiss Federal Laboratories for Materials Science and Technology (EMPA), Überlandstrasse 129, 8600 Dübendorf (Switzerland); Saleh, T. A. [Los Alamos National Laboratory, MST-16, Los Alamos, New Mexico 87545 (United States)
2014-04-07
In this Letter, the time reversal mirror is used to focus elastic energy at a prescribed location and to analyze the amplitude dependence of the focus signal, thus providing the nonlinearity of the medium. By varying the frequency content of the focused waveforms, the technique can be used to probe the surface, by penetrating to a depth defined by the wavelength of the focused waves. The validity of this concept is shown in the presence of gradual and distributed damage in concrete by comparing actual results with a reference nonlinear measurement and X ray tomography images.
Sparse least-squares reverse time migration using seislets
Dutta, Gaurav
2015-08-19
We propose sparse least-squares reverse time migration (LSRTM) using seislets as a basis for the reflectivity distribution. This basis is used along with a dip-constrained preconditioner that emphasizes image updates only along prominent dips during the iterations. These dips can be estimated from the standard migration image or from the gradient using plane-wave destruction filters or structural tensors. Numerical tests on synthetic datasets demonstrate the benefits of this method for mitigation of aliasing artifacts and crosstalk noise in multisource least-squares migration.
Reverse time migration of multiples for OBS data
Zhang, Dongliang
2014-08-05
Reverse time migration of multiples (RTMM) is applied to OBS data with sparse receiver spacing. RTMM for OBS data unlike a marine streamer acquisition is implemented in the common receiver gathers (CRG) and provides a wider and denser illumination for each CRG than the conventional RTM of primaries. Hence, while the the conventional RTM image contains strong aliasing artifacts due to a sparser receiver interval, the RTMM image suffers from this artifacts less. This benefit of RTMM is demonstrated with numerical test on the Marmousi model for sparsely sampled OBS data.
Random Dirac operators with time-reversal symmetry
Sadel, Christian
2009-01-01
Quasi-one-dimensional stochastic Dirac operators with an odd number of channels, time reversal symmetry but otherwise efficiently coupled randomness are shown to have one conducting channel and absolutely continuous spectrum of multiplicity two. This follows by adapting the criteria of Guivac-Raughi and Goldsheid-Margulis to the analysis of random products of matrices in the group SO$^*(2L)$, and then a version of Kotani theory for these operators. Absence of singular spectrum can be shown by adapting an argument of Jaksic-Last if the potential contains random Dirac peaks with absolutely continuous distribution.
Time-Reversal Acoustics and Maximum-Entropy Imaging
Berryman, J G
2001-08-22
Target location is a common problem in acoustical imaging using either passive or active data inversion. Time-reversal methods in acoustics have the important characteristic that they provide a means of determining the eigenfunctions and eigenvalues of the scattering operator for either of these problems. Each eigenfunction may often be approximately associated with an individual scatterer. The resulting decoupling of the scattered field from a collection of targets is a very useful aid to localizing the targets, and suggests a number of imaging and localization algorithms. Two of these are linear subspace methods and maximum-entropy imaging.
A trivial observation on time reversal in random matrix theory
Kaplan, L [Department of Physics, Tulane University, New Orleans, LA (United States); Leyvraz, F [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico (Mexico); Pineda, C [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico (Mexico); Seligman, T H [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico (Mexico)
2007-12-07
It is commonly thought that a state-dependent quantity, after being averaged over a classical ensemble of random Hamiltonians, will always become independent of the state. We point out that this is in general incorrect: if the ensemble of Hamiltonians is time-reversal invariant, and the quantity involves the state in higher than bilinear order, then we show that the quantity is only a constant over the orbits of the invariance group on the Hilbert space. Examples include fidelity and decoherence in appropriate models. (fast track communication)
Time-Reversal-Breaking Weyl Fermions in Magnetic Heusler Alloys
Wang, Zhijun; Vergniory, M. G.; Kushwaha, S.; Hirschberger, Max; Chulkov, E. V.; Ernst, A.; Ong, N. P.; Cava, Robert J.; Bernevig, B. Andrei
2016-12-01
Weyl fermions have recently been observed in several time-reversal-invariant semimetals and photonics materials with broken inversion symmetry. These systems are expected to have exotic transport properties such as the chiral anomaly. However, most discovered Weyl materials possess a substantial number of Weyl nodes close to the Fermi level that give rise to complicated transport properties. Here we predict, for the first time, a new family of Weyl systems defined by broken time-reversal symmetry, namely, Co-based magnetic Heusler materials X Co2Z (X =IVB or VB; Z =IVA or IIIA). To search for Weyl fermions in the centrosymmetric magnetic systems, we recall an easy and practical inversion invariant, which has been calculated to be -1 , guaranteeing the existence of an odd number of pairs of Weyl fermions. These materials exhibit, when alloyed, only two Weyl nodes at the Fermi level—the minimum number possible in a condensed matter system. The Weyl nodes are protected by the rotational symmetry along the magnetic axis and separated by a large distance (of order 2 π ) in the Brillouin zone. The corresponding Fermi arcs have been calculated as well. This discovery provides a realistic and promising platform for manipulating and studying the magnetic Weyl physics in experiments.
Electromagnetic time reversal focusing of near field waves in metamaterials
Chabalko, Matthew J.; Sample, Alanson P.
2016-12-01
Precise control of electromagnetic energy on a deeply subwavelength scale in the near field regime is a fundamentally challenging problem. In this letter we demonstrate the selective focusing of electromagnetic energy via the electromagnetic time reversal in the near field of a metamaterial. Our analysis begins with fundamental mathematics, and then is extended to the experimental realm where focusing in space and time of the magnetic fields in the near field of a 1-Dimensional metamaterial is shown. Under time reversal focusing, peak instantaneous fields at receiver locations are at minimum ˜200% greater than other receivers. We then leverage the strong selective focusing capabilities of the system to show individual and selective powering of light emitting diodes connected to coil receivers placed in the near field of the metamaterial. Our results show the possibility of improving display technologies, near field imaging systems, increasing channel capacity of near field communication systems, and obtaining a greater control of energy delivery in wireless power transfer systems.
Plane-wave least-squares reverse-time migration
Dai, Wei
2013-06-03
A plane-wave least-squares reverse-time migration (LSRTM) is formulated with a new parameterization, where the migration image of each shot gather is updated separately and an ensemble of prestack images is produced along with common image gathers. The merits of plane-wave prestack LSRTM are the following: (1) plane-wave prestack LSRTM can sometimes offer stable convergence even when the migration velocity has bulk errors of up to 5%; (2) to significantly reduce computation cost, linear phase-shift encoding is applied to hundreds of shot gathers to produce dozens of plane waves. Unlike phase-shift encoding with random time shifts applied to each shot gather, plane-wave encoding can be effectively applied to data with a marine streamer geometry. (3) Plane-wave prestack LSRTM can provide higher-quality images than standard reverse-time migration. Numerical tests on the Marmousi2 model and a marine field data set are performed to illustrate the benefits of plane-wave LSRTM. Empirical results show that LSRTM in the plane-wave domain, compared to standard reversetime migration, produces images efficiently with fewer artifacts and better spatial resolution. Moreover, the prestack image ensemble accommodates more unknowns to makes it more robust than conventional least-squares migration in the presence of migration velocity errors. © 2013 Society of Exploration Geophysicists.
Reverse Flow Engine Core Having a Ducted Fan with Integrated Secondary Flow Blades
Kisska, Michael K. (Inventor); Princen, Norman H. (Inventor); Kuehn, Mark S. (Inventor); Cosentino, Gary B. (Inventor)
2014-01-01
Secondary air flow is provided for a ducted fan having a reverse flow turbine engine core driving a fan blisk. The fan blisk incorporates a set of thrust fan blades extending from an outer hub and a set of integral secondary flow blades extending intermediate an inner hub and the outer hub. A nacelle provides an outer flow duct for the thrust fan blades and a secondary flow duct carries flow from the integral secondary flow blades as cooling air for components of the reverse flow turbine engine.
Least-squares reverse time migration of multiples
Zhang, Dongliang
2013-12-06
The theory of least-squares reverse time migration of multiples (RTMM) is presented. In this method, least squares migration (LSM) is used to image free-surface multiples where the recorded traces are used as the time histories of the virtual sources at the hydrophones and the surface-related multiples are the observed data. For a single source, the entire free-surface becomes an extended virtual source where the downgoing free-surface multiples more fully illuminate the subsurface compared to the primaries. Since each recorded trace is treated as the time history of a virtual source, knowledge of the source wavelet is not required and the ringy time series for each source is automatically deconvolved. If the multiples can be perfectly separated from the primaries, numerical tests on synthetic data for the Sigsbee2B and Marmousi2 models show that least-squares reverse time migration of multiples (LSRTMM) can significantly improve the image quality compared to RTMM or standard reverse time migration (RTM) of primaries. However, if there is imperfect separation and the multiples are strongly interfering with the primaries then LSRTMM images show no significant advantage over the primary migration images. In some cases, they can be of worse quality. Applying LSRTMM to Gulf of Mexico data shows higher signal-to-noise imaging of the salt bottom and top compared to standard RTM images. This is likely attributed to the fact that the target body is just below the sea bed so that the deep water multiples do not have strong interference with the primaries. Migrating a sparsely sampled version of the Marmousi2 ocean bottom seismic data shows that LSM of primaries and LSRTMM provides significantly better imaging than standard RTM. A potential liability of LSRTMM is that multiples require several round trips between the reflector and the free surface, so that high frequencies in the multiples suffer greater attenuation compared to the primary reflections. This can lead to lower
Compact Reversed-Field Pinch Reactors (CRFPR): preliminary engineering considerations
Hagenson, R.L.; Krakowski, R.A.; Bathke, C.G.; Miller, R.L.; Embrechts, M.J.; Schnurr, N.M.; Battat, M.E.; LaBauve, R.J.; Davidson, J.W.
1984-08-01
The unique confinement physics of the Reversed-Field Pinch (RFP) projects to a compact, high-power-density fusion reactor that promises a significant reduction in the cost of electricity. The compact reactor also promises a factor-of-two reduction in the fraction of total cost devoted to the reactor plant equipment (i.e., fusion power core (FPC) plus support systems). In addition to operational and developmental benefits, these physically smaller systems can operate economically over a range of total power output. After giving an extended background and rationale for the compact fusion approaches, key FPC subsystems for the Compact RFP Reactor (CRFPR) are developed, designed, and integrated for a minimum-cost, 1000-MWe(net) system. Both the problems and promise of the compact, high-power-density fusion reactor are quantitatively evaluated on the basis of this conceptual design. The material presented in this report both forms a framework for a broader, more expanded conceptual design as well as suggests directions and emphases for related research and development.
Time reversal invariance - a test in free neutron decay
Lising, Laura Jean [Univ. of California, Berkeley, CA (United States)
1999-01-01
Time reversal invariance violation plays only a small role in the Standard Model, and the existence of a T-violating effect above the predicted level would be an indication of new physics. A sensitive probe of this symmetry in the weak interaction is the measurement of the T-violating ''D''-correlation in the decay of free neutrons. The triple-correlation Dσ_{n}∙p_{e} x p_{v} involves three kinematic variables, the neutron spin, electron momentu, and neutrino (or proton) momentum, and changes sign under time reversal. This experiment detects the decay products of a polarized cold neutron beam with an octagonal array of scintillation and solid-state detectors. Data from first run at NIST's Cold Neutron Research Facility give a D-coefficient of -0.1 ± 1.3(stat.) ± 0.7(syst) x 10^{-3} This measurement has the greatest bearing on extensions to the Standard model that incorporate leptoquarks, although exotic fermion and lift-right symmetric models also allow a D as large as the present limit.
Applications of Time-Reversal Processing for Planetary Surface Communications
Barton, Richard J.
2007-01-01
Due to the power constraints imposed on wireless sensor and communication networks deployed on a planetary surface during exploration, energy efficient transfer of data becomes a critical issue. In situations where groups of nodes within a network are located in relatively close proximity, cooperative communication techniques can be utilized to improve the range, data rate, power efficiency, and lifetime of the network. In particular, if the point-to-point communication channels on the network are well modeled as frequency non-selective, distributed or cooperative beamforming can employed. For frequency-selective channels, beamforming itself is not generally appropriate, but a natural generalization of it, time-reversal communication (TRC), can still be effective. Time-reversal processing has been proposed and studied previously for other applications, including acoustical imaging, electromagnetic imaging, underwater acoustic communication, and wireless communication channels. In this paper, we study both the theoretical advantages and the experimental performance of cooperative TRC for wireless communication on planetary surfaces. We give a brief introduction to TRC and present several scenarios where TRC could be profitably employed during planetary exploration. We also present simulation results illustrating the performance of cooperative TRC employed in a complex multipath environment and discuss the optimality of cooperative TRC for data aggregation in wireless sensor networks
Plane-wave Least-squares Reverse Time Migration
Dai, Wei
2012-11-04
Least-squares reverse time migration is formulated with a new parameterization, where the migration image of each shot is updated separately and a prestack image is produced with common image gathers. The advantage is that it can offer stable convergence for least-squares migration even when the migration velocity is not completely accurate. To significantly reduce computation cost, linear phase shift encoding is applied to hundreds of shot gathers to produce dozens of planes waves. A regularization term which penalizes the image difference between nearby angles are used to keep the prestack image consistent through all the angles. Numerical tests on a marine dataset is performed to illustrate the advantages of least-squares reverse time migration in the plane-wave domain. Through iterations of least-squares migration, the migration artifacts are reduced and the image resolution is improved. Empirical results suggest that the LSRTM in plane wave domain is an efficient method to improve the image quality and produce common image gathers.
Signatures of time reversal symmetry breaking in multiband superconductors
Maiti, Saurabh
Multiband superconductors serve as natural host to several possible gound states that compete with each other. At the boundaries of such competing phases, the system usually compromises and settles for `mixed' phases that can show intriguing properties like co-existence of magnetism and superconductiivty or even co-existence of different superconducting phases. The latter is particularly interesting as it can lead to non-magnetic ground states that spontaneously break Time-Reversal symmetry. While the experimental verification of such states has proved to been challenging, the theoretical investigations have provided exciting new insights into the nature of the ground state and its excitations all of which have experimental consequences of some sort. These include extrinsic properties like spontaneous currents around impurity sites, and intrinsic properties in the form of collective excitations. These collective modes bear a unique signature and should provide clear evidence for time reversal symmetry broken state. While the results are general, in light of recent Raman scattering experiments, its direct relevance to extremely hole doped Ba(1-x)K(FeAs)2 will be presented where a strong competition of s-wave and d-wave ground state is expected.
Spontaneous breaking of time-reversal symmetry in topological insulators
Karnaukhov, Igor N., E-mail: karnaui@yahoo.com
2017-06-21
Highlights: • Proposed a new approach for description of phase transitions in topological insulators. • Considered the mechanism of spontaneous breaking of time-reversal symmetry in topological insulators. • The Haldane model can be implemented in real compounds of the condensed matter physics. - Abstract: The system of spinless fermions on a hexagonal lattice is studied. We have considered tight-binding model with the hopping integrals between the nearest-neighbor and next-nearest-neighbor lattice sites, that depend on the direction of the link. The links are divided on three types depending on the direction, the hopping integrals are defined by different phases along the links. The energy of the system depends on the phase differences, the solutions for the phases, that correspond to the minimums of the energy, lead to a topological insulator state with the nontrivial Chern numbers. We have analyzed distinct topological states and phase transitions, the behavior of the chiral gapless edge modes, have defined the Chern numbers. The band structure of topological insulator (TI) is calculated, the ground-state phase diagram in the parameter space is obtained. We propose a novel mechanism of realization of TI, when the TI state is result of spontaneous breaking of time-reversal symmetry due to nontrivial stable solutions for the phases that determine the hopping integrals along the links and show that the Haldane model can be implemented in real compounds of the condensed matter physics.
Time reversal invariance - a test in free neutron decay
Lising, Laura J.
1999-05-18
Time reversal invariance violation plays only a small role in the Standard Model, and the existence of a T-violating effect above the predicted level would be an indication of new physics. A sensitive probe of this symmetry in the weak interaction is the measurement of the T-violating ''D''-correlation in the decay of free neutrons. The triple-correlation D{sigma}{sub n}{center_dot}p{sub e} x p{sub v} involves three kinematic variables, the neutron spin, electron momentu, and neutrino (or proton) momentum, and changes sign under time reversal. This experiment detects the decay products of a polarized cold neutron beam with an octagonal array of scintillation and solid-state detectors. Data from first run at NIST's Cold Neutron Research Facility give a D-coefficient of -0.1 {+-} 1.3(stat.) {+-} 0.7(syst) x 10{sup -3}. This measurement has the greatest bearing on extensions to the Standard model that incorporate leptoquarks, although exotic fermion and lift-right symmetric models also allow a D as large as the present limit.
Topological Field Theory of Time-Reversal Invariant Insulators
Qi, Xiao-Liang; Hughes, Taylor; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-19
We show that the fundamental time reversal invariant (TRI) insulator exists in 4 + 1 dimensions, where the effective field theory is described by the 4 + 1 dimensional Chern-Simons theory and the topological properties of the electronic structure is classified by the second Chern number. These topological properties are the natural generalizations of the time reversal breaking (TRB) quantum Hall insulator in 2 + 1 dimensions. The TRI quantum spin Hall insulator in 2 + 1 dimensions and the topological insulator in 3 + 1 dimension can be obtained as descendants from the fundamental TRI insulator in 4 + 1 dimensions through a dimensional reduction procedure. The effective topological field theory, and the Z{sub 2} topological classification for the TRI insulators in 2+1 and 3+1 dimensions are naturally obtained from this procedure. All physically measurable topological response functions of the TRI insulators are completely described by the effective topological field theory. Our effective topological field theory predicts a number of novel and measurable phenomena, the most striking of which is the topological magneto-electric effect, where an electric field generates a magnetic field in the same direction, with an universal constant of proportionality quantized in odd multiples of the fine structure constant {alpha} = e{sup 2}/hc. Finally, we present a general classification of all topological insulators in various dimensions, and describe them in terms of a unified topological Chern-Simons field theory in phase space.
Time reversal for ultrasonic transcranial surgery and echographic imaging
Tanter, Mickael; Aubry, Jean-Francois; Vignon, Francois; Fink, Mathias
2005-09-01
High-intensity focused ultrasound (HIFU) is able to induce non-invasively controlled and selective destruction of tissues by focusing ultrasonic beams within organs, analogous to a magnifying glass that concentrates enough sunlight to burn a hole in paper. The brain is an attractive organ in which to perform ultrasonic tissue ablation, but such an application has been hampered by the strong defocusing effect of the skull bone. Our group has been involved in this topic for several years, providing proofs of concept and proposing technological solutions to this problem. Thanks to a high-power time-reversal mirror, presented here are in vivo thermal lesions induced through the skull of 12 sheep. Thermal lesions were confirmed by T2-weighted magnetic resonance post-treatment images and histological examination. These results provide striking evidence that noninvasive ultrasound brain surgery is feasible. A recent approach for high-resolution brain ultrasonic imaging will also be discussed with a skull aberration correction technique based on twin arrays technology. The correction of transcranial ultrasonic images is implemented on a new generation of time-reversal mirrors relying on a fully programmable transmit and receive beamformer.
Optimal Time-Reversed Wideband Signals for Distributed Sensing
Kim, Jerry; Mokole, Eric
2015-01-01
This paper considers a distributed wave-based sensing system that probes a scene consisting of multiple interacting idealized targets. Each sensor is a collocated transmit-receive pair that is capable of transmitting arbitrary wideband waveforms. We address the problem of finding the space-time transmit waveform that provides the best target detection performance in the sense of maximizing the energy scattered back into the receivers. Our approach is based on earlier work that constructed the solution by an iterative time-reversal (TR) process. In particular, for the case of idealized point-like scatterers in free space, we examine the frequency dependence of the eigenvalues of the TR operator, and we show that their behavior depends on constructive and destructive interference of the waves traveling along different paths. In addition, we show how these eigenvalues are connected to the poles of the Singularity Expansion Method. Our study of the frequency behavior distinguishes this work from most previous TR ...
Muthyala, Sudhakar; Raj, V R Rana; Mohanty, Mira; Mohanan, P V; Nair, Prabha D
2011-05-01
Type 1 diabetes is a chronic disorder resulting from the autoimmune destruction of insulin-producing cells, a leading cause of morbidity and mortality all over the world. In this study a tissue engineering approach was compared with a macroencapsulation approach to reverse type 1 diabetes in a rat model, using mouse pancreatic progenitor cell (PPC)-derived islet-like clusters and mouse islets. For the tissue engineering approach the cells were cultured on gelatin scaffolds cross-linked with EDC in the presence of polyvinylpyrrolidone in vitro (GPE scaffolds), while for the macroencapsulation approach the cells were encapsulated in polyurethane-polyvinylpyrrolidone semi-interpenetrating networks. In the combination approach the cells cultured on GPE scaffolds were further encapsulated in a polyurethane-polyvinylpyrrolidone capsule. Real time PCR studies and the glucose challenge assay have shown that cells on GPE scaffolds could express and secrete insulin and glucagon in vitro. However, under in vivo conditions the animals treated by the tissue engineering approach died within 15-20 days and showed no reversal of their diabetes, due to infiltration of immune cells such as CD4 and CD8 cells and macrophages. In the macroencapsulation approach the animals showed euglycemia within 25 days, which was maintained for further 20 days, but after that the animals died. Interestingly, in the combination approach the animals showed reversal of hyperglycemia, and remained euglycemic for up to 3 months. The time needed to achieve initial euglycemia was different with different cell types, i.e. the combination approach with mouse islets achieved euglycemia within 15 days, whereas with PPC-derived islet-like clusters euglycemia was achieved within 25 days. This study confirmed that a combination of tissue engineering and macroencapsulation with mouse islets could reverse diabetes and maintain euglycemia in an experimental diabetes rat model for 90 days.
Reverse time migration based on normalized wavefield decomposition imaging condition
YU Jianglong; HAN Liguo; ZHOU Yan; ZHANG Yongsheng
2016-01-01
With the increasing complexity of prospecting objectives,reverse time migration (RTM)has attracted more and more attention due to its outstanding imaging quality.RTMis based on two-way wave equation,so it can avoid the limits of angle in traditional one-way wave equation migration,image reverse branch,prism waves and multi-reflected wave precisely and obtain accurate dynamic information.However,the huge demands for storage and computation as well as low frequency noises restrict its wide application.The normalized cross-correlation ima-ging conditions based on wave field decomposition are derived from traditional cross-correlation imaging condition, and it can eliminate the low-frequency noises effectively and improve the imaging resolution.The practical proce-dure includes separating source and receiver wave field into one-way components respectively,and conducting cross-correlation imaging condition to the post-separated wave field.In this way,the resolution and precision of the imaging result will be promoted greatly.
Methylcellulose Based Thermally Reversible Hydrogel System for Tissue Engineering Applications
Ram V. Devireddy
2013-06-01
Full Text Available The thermoresponsive behavior of a Methylcellulose (MC polymer was systematically investigated to determine its usability in constructing MC based hydrogel systems in cell sheet engineering applications. Solution-gel analyses were made to study the effects of polymer concentration, molecular weight and dissolved salts on the gelation of three commercially available MCs using differential scanning calorimeter and rheology. For investigation of the hydrogel stability and fluid uptake capacity, swelling and degradation experiments were performed with the hydrogel system exposed to cell culture solutions at incubation temperature for several days. From these experiments, the optimal composition of MC-water-salt that was able to produce stable hydrogels at or above 32 °C, was found to be 12% to 16% of MC (Mol. wt. of 15,000 in water with 0.5× PBS (~150mOsm. This stable hydrogel system was then evaluated for a week for its efficacy to support the adhesion and growth of specific cells in culture; in our case the stromal/stem cells derived from human adipose tissue derived stem cells (ASCs. The results indicated that the addition (evenly spread of ~200 µL of 2 mg/mL bovine collagen type -I (pH adjusted to 7.5 over the MC hydrogel surface at 37 °C is required to improve the ASC adhesion and proliferation. Upon conﬂuence, a continuous monolayer ASC sheet was formed on the surface of the hydrogel system and an intact cell sheet with preserved cell–cell and cell–extracellular matrix was spontaneously and gradually detached when the grown cell sheet was removed from the incubator and exposed to room temperature (~30 °C within minutes.
A 'reverse network engineering' framework to develop tourism using a lifestyle approach
Kamann, DJF; Strijker, D; Sijtsma, FJ
1998-01-01
This paper uses the network approach in the design of policies for regional development focusing on tourism in rural and peripheral areas. The methodology applied - 'reverse network engineering' - is a combination of a top-down and a bottom-up approach, The top-down approach starts with the demand s
Plasma engineering design of a Compact Reversed-Field Pinch Reactor (CRFPR)
Bathke, C. G.; Embrechts, M. J.; Hagenson, R. L.; Krakowski, R. A.; Miller, R. L.
1983-11-01
The rationale for and the characteristics of the high-power-density Compact Reversed-Field Pinch Reactor (CRFPR) are discussed. Particular emphasis is given to key plasma engineering aspects of the conceptual design, including plasma operations, current drive, and impurity/ash control by means of pumped limiters or magnetic divertors. A brief description of the Fusion-Power-Core integration is given.
An Interactive Reverse Engineering Environment for Large-Scale C++ Code
Telea, Alexandru; Voinea, Lucian
2008-01-01
Few toolsets for reverse-engineering and understanding of C++ code provide parsing and fact extraction, querying, analysis and code metrics, navigation, and visualization of source-code-level facts in a way which is as easy-to-use as integrated development environments (IDEs) are for forward enginee
An Interactive Reverse Engineering Environment for Large-Scale C plus plus Code
Telea, Alexandru; Voinea, Lucian; Spencer, SN
2008-01-01
Few toolsets for reverse-engineering and understanding of C++ code provide parsing and fact extraction, querying, analysis and code metrics, navigation, and visualization of source-code-level facts in a way which is as easy-to-use as integrated development environments (IDEs) are for forward enginee
Scope of Reversible Engineering at Gate-Level : Fault - Tolerant Combinational Adders
M.Bharathi
2012-05-01
Full Text Available Reversible engineering has been one of the thrust areas ensuring that continual process of the innovation trends that explore and sustain the resources of the nature. This reversible engineering is used in many fields like quantum computing, low power CMOS design, nanotechnology, optical information processing, digital signal processing, cryptography, etc. These are the digital domain implementations of Reversible and Fault-Tolerant logic gates. Any arbitrary Boolean function can be synthesized by using the proposed parity preserving reversible gates. Not only the possibility of detecting errors is induced inherently in the proposed high speed adders at their output side but also it allows any fault that affects no more than a single signal that is detectable. The fault tolerant reversible full adder circuits are realized by using two IG gates only. The derived fault tolerant full adder is used for designing other arithmetic- logic circuit by using it as fundamental building block. The proposed reversible gate is designed to have less hardwarecomplexity and efficiecyt in terms of gate count, garbage outputs and constant input. In this paper, we design BCD adder using carry select logic, Carry-select and Bypass adders using FG gates, and newly designed TG gates.
Scope of Reversible Engineering at Gate-Level : Fault - Tolerant Combinational Adders
M.Bharathi
2012-04-01
Full Text Available Reversible engineering has been one of the thrust areas ensuring that continual process of the innovation trends that explore and sustain the resources of the nature. This reversible engineering is used in many fields like quantum computing, low power CMOS design, nanotechnology, optical information processing, digital signal processing, cryptography, etc. These are the digital domain implementations of Reversible and Fault-Tolerant logic gates. Any arbitrary Boolean function can be synthesized by using the proposed parity preserving reversible gates. Not only the possibility of detecting errors is induced inherently in the proposed high speed adders at their output side but also it allows any fault that affects no more than a single signal that is detectable. The fault tolerant reversible full adder circuits are realized by using two IG gates only. The derived fault tolerant full adder is used for designing other arithmetic- logic circuit by using it as fundamental building block. The proposed reversible gate is designed to have less hardware complexity and efficiecyt in terms of gate count, garbage outputs and constant input. In this paper, we design BCD adder using carry select logic, Carry-select and Bypass adders using FG gates, and newly designed TG gates.
Radiation Mitigation for Power Line Communications Using Time Reversal
Amilcar Mescco
2013-01-01
Full Text Available Power Line Communication (PLC is the response for nowadays high demand of multimedia services in domestic environment, not only for its fast and reliable transfer characteristics but also for its flexible low cost implementation, since the PLC technology uses the existing electrical network infrastructure and the omnipresent outlets throughout the home. The transfer of such a high bit rate through the mains network generates acceptable radiated emission regulated by international standards, but the increment in speed for new generation PLC may cause higher levels of emissions. This paper explains the use of the Time Reversal (TR technique to mitigate radiated emissions from PLC systems. This method was probed experimentally in real electrical networks with excellent results: in 40% of the observations, the Electromagnetic Interference (EMI generated by PLC transmission could be reduced by more than 3 dB, and this EMI mitigation factor could increase to more than 10 dB in particular configurations.
Supersymmetric Time Reversal Violation in Semileptonic Decays of Charged Mesons
Wu, G H; Wu, Guo-Hong; Ng, John N.
1997-01-01
We provide a general analysis of time reversal violation arising from misalignment between quark and squark mass eigenstates. In particular, we focus on the possibility of large enhancement effects due to the top quark mass. For semileptonic decays of the charged mesons, $K^+ \\rightarrow \\pi^0 \\mu^+ the lepton $P^{\\bot}_l$ is a $T$-odd observable that is of great experimental interest. It is noted that under favorable choice of parameters, $P^{\\bot}_{\\mu}$ in $K^+_{\\mu3}$ decay can be detectable at the ongoing KEK experiment and it holds a promising prospect for discovery at the proposed BNL experiment. Furthermore, $P^{\\bot}_{\\tau}$ in $B^{\\pm}$ decay could well be within the reach of $B$ factories, but $P^{\\bot}_{\\mu}$ in $D^{\\pm}$ decay is not large enough for detection at the proposed $\\tau$-charm factory.
Least-squares reverse time migration with radon preconditioning
Dutta, Gaurav
2016-09-06
We present a least-squares reverse time migration (LSRTM) method using Radon preconditioning to regularize noisy or severely undersampled data. A high resolution local radon transform is used as a change of basis for the reflectivity and sparseness constraints are applied to the inverted reflectivity in the transform domain. This reflects the prior that for each location of the subsurface the number of geological dips is limited. The forward and the adjoint mapping of the reflectivity to the local Radon domain and back are done through 3D Fourier-based discrete Radon transform operators. The sparseness is enforced by applying weights to the Radon domain components which either vary with the amplitudes of the local dips or are thresholded at given quantiles. Numerical tests on synthetic and field data validate the effectiveness of the proposed approach in producing images with improved SNR and reduced aliasing artifacts when compared with standard RTM or LSRTM.
Experimental demonstration of the time reversal Aharonov-Casher effect.
Bergsten, Tobias; Kobayashi, Toshiyuki; Sekine, Yoshiaki; Nitta, Junsaku
2006-11-10
We demonstrate the time reversal Aharonov-Casher (AC) effect in small arrays of mesoscopic semiconductor rings. By using an electrostatic gate we can control the spin precession rate and follow the AC phase over several interference periods. We show that we control the precession rate in two different gate voltage ranges; in the lower range the gate voltage dependence is strong and linear and in the higher range the dependence in almost an order of magnitude weaker. We also see the second harmonic of the AC interference, oscillating with half the period. We finally map the AC phase to the spin-orbit interaction parameter alpha and find it is consistent with Shubnikov-de Haas analysis.
Time-reversal-breaking induced quantum spin Hall effect
Luo, Wei; Shao, D. X.; Deng, Ming-Xun; Deng, W. Y.; Sheng, L.
2017-01-01
We show that quantum spin Hall (QSH) effect does not occur in a square lattice model due to cancellation of the intrinsic spin-orbit coupling coming from different hopping paths. However, we show that QSH effect can be induced by the presence of staggered magnetic fluxes alternating directions square by square. When the resulting Peierls phase takes a special value , the system has a composite symmetry ΘΡ− with Θ the time-reversal operator and Ρ− transforming the Peierls phase from γ to γ − , which protects the gapless edge states. Once the phase deviates from , the edge states open a gap, as the composite symmetry is broken. We further investigate the effect of a Zeeman field on the QSH state, and find that the edge states remain gapless for . This indicates that the QSH effect is immune to the magnetic perturbation. PMID:28220858
Time-reversal-noninvariant, parity-conserving nuclear interactions
Haxton, W.C. [Washington Univ., Seattle, WA (United States)]|[Melbourne Univ., Parkville, VIC (Australia). Dept. of Physics; Hoering, A. [Washington Univ., Seattle, WA (United States)
1993-04-01
The work that has been done in compound nucleus studies of time-reversal-noninvariant (TRNI), parity-conserving (PC) NN interactions is reviewed. The general form of TRNI PC meson-exchange potentials that can be constrained by such studies is discussed a la Simonius. The competing limits that can be obtained from atomic electric dipole moments produced by weak radiative corrections to long-ranged TRNI PNC interactions are then explored. Both classes of constraints limit the magnitude of typical TRNI PC matrix elements to about 10{sup {minus}3} of those for strong interactions. These limits are contrasted with those recently obtained from short-ranged one- and two-loop weak radiative corrections.
Time-reversal-noninvariant, parity-conserving nuclear interactions
Haxton, W.C. (Washington Univ., Seattle, WA (United States) Melbourne Univ., Parkville, VIC (Australia). Dept. of Physics); Hoering, A. (Washington Univ., Seattle, WA (United States))
1993-01-01
The work that has been done in compound nucleus studies of time-reversal-noninvariant (TRNI), parity-conserving (PC) NN interactions is reviewed. The general form of TRNI PC meson-exchange potentials that can be constrained by such studies is discussed a la Simonius. The competing limits that can be obtained from atomic electric dipole moments produced by weak radiative corrections to long-ranged TRNI PNC interactions are then explored. Both classes of constraints limit the magnitude of typical TRNI PC matrix elements to about 10[sup [minus]3] of those for strong interactions. These limits are contrasted with those recently obtained from short-ranged one- and two-loop weak radiative corrections.
Francesco Gregoretti
Full Text Available The reverse engineering of gene regulatory networks using gene expression profile data has become crucial to gain novel biological knowledge. Large amounts of data that need to be analyzed are currently being produced due to advances in microarray technologies. Using current reverse engineering algorithms to analyze large data sets can be very computational-intensive. These emerging computational requirements can be met using parallel computing techniques. It has been shown that the Network Identification by multiple Regression (NIR algorithm performs better than the other ready-to-use reverse engineering software. However it cannot be used with large networks with thousands of nodes--as is the case in biological networks--due to the high time and space complexity. In this work we overcome this limitation by designing and developing a parallel version of the NIR algorithm. The new implementation of the algorithm reaches a very good accuracy even for large gene networks, improving our understanding of the gene regulatory networks that is crucial for a wide range of biomedical applications.
Reconstruction of Dispersive Lamb Waves in Time Plates Using a Time Reversal Method
Jeong, Hyun Jo [Wonkwang University, Iksan (Korea, Republic of)
2008-02-15
Time reversal (TR) of nondispersive body waves has been used in many applications including ultrasonic NDE. However, the study of the TR method for Lamb waves on thin structures is not well established. In this paper, the full reconstruction of the input signal is investigated for dispersive Lamb waves by introducing a time reversal operator based on the Mindlin plate theory. A broadband and a narrowband input waveform are employed to reconstruct the A{sub 0} mode of Lamb wave propagations. Due to the frequency dependence of the TR process of Lamb waves, different frequency components of the broadband excitation are scaled differently during the time reversal process and the original input signal cannot be fully restored. This is the primary reason for using a narrowband excitation to enhance the flaw detectability
Designing MPC controllers by reverse-engineering existing LTI controllers
Hartley, Edward N
2011-01-01
This technical report presents a method for designing a constrained output-feedback model predictive controller (MPC) that behaves in the same way as an existing baseline stabilising linear time invariant output-feedback controller when constraints are inactive. The baseline controller is cast into an observer-compensator form and an inverse-optimal cost function is used as the basis of the MPC controller. The available degrees of design freedom are explored, and some guidelines provided for the selection of an appropriate observer-compensator realisation that will best allow exploitation of the constraint-handling and redundancy management capabilities of MPC. Consideration is given to output setpoint tracking, and the method is demonstrated with three different multivariable plants of varying complexity.
Earthquake Source Modeling using Time-Reversal or Adjoint Methods
Hjorleifsdottir, V.; Liu, Q.; Tromp, J.
2007-12-01
In recent years there have been great advances in earthquake source modeling. Despite the effort, many questions about earthquake source physics remain unanswered. In order to address some of these questions, it is useful to reconstruct what happens on the fault during an event. In this study we focus on determining the slip distribution on a fault plane, or a moment-rate density, as a function of time and space. This is a difficult process involving many trade offs between model parameters. The difficulty lies in the fact that earthquakes are not a controlled experiment, we don't know when and where they will occur, and therefore we have only limited control over what data will be acquired for each event. As a result, much of the advance that can be made, is by extracting more information out of the data that is routinely collected. Here we use a technique that uses 3D waveforms to invert for the slip on a fault plane during rupture. By including 3D wave-forms we can use parts of the wave-forms that are often discarded, as they are altered by structural effects in ways that cannot be accurately predicted using 1D Earth models. However, generating 3D synthetic is computationally expensive. Therefore we turn to an `adjoint' method (Tarantola Geoph.~1984, Tromp et al.~GJI 2005), that reduces the computational cost relative to methods that use Green's function libraries. In it's simplest form an adjoint method for inverting for source parameters can be viewed as a time-reversal experiment performed with a wave-propagation code (McMechan GJRAS 1982). The recorded seismograms are inserted as simultaneous sources at the location of the receiver and the computed wave field (which we call the adjoint wavefield) is recorded on an array around the earthquake location. Here we show, mathematically, that for source inversions for a moment tensor (distributed) source, the time integral of the adjoint strain is the quantity to monitor. We present the results of time-reversal
Self-adaptive focusing by time reversal through interface between different media
WEI Wei; WANG Chenghao
2000-01-01
The time reversal is an unique self-adaptive focusing technique important to ultrasonic imaging. In this paper, the principle and the analytic expression of the ultrasound field in the realization of time reversal during the presence of an interface between two media are presented. Experimental results of time reversal are given and found to agree with theoretical ones.
Least-squares reverse time migration in elastic media
Ren, Zhiming; Liu, Yang; Sen, Mrinal K.
2017-02-01
Elastic reverse time migration (RTM) can yield accurate subsurface information (e.g. PP and PS reflectivity) by imaging the multicomponent seismic data. However, the existing RTM methods are still insufficient to provide satisfactory results because of the finite recording aperture, limited bandwidth and imperfect illumination. Besides, the P- and S-wave separation and the polarity reversal correction are indispensable in conventional elastic RTM. Here, we propose an iterative elastic least-squares RTM (LSRTM) method, in which the imaging accuracy is improved gradually with iteration. We first use the Born approximation to formulate the elastic de-migration operator, and employ the Lagrange multiplier method to derive the adjoint equations and gradients with respect to reflectivity. Then, an efficient inversion workflow (only four forward computations needed in each iteration) is introduced to update the reflectivity. Synthetic and field data examples reveal that the proposed LSRTM method can obtain higher-quality images than the conventional elastic RTM. We also analyse the influence of model parametrizations and misfit functions in elastic LSRTM. We observe that Lamé parameters, velocity and impedance parametrizations have similar and plausible migration results when the structures of different models are correlated. For an uncorrelated subsurface model, velocity and impedance parametrizations produce fewer artefacts caused by parameter crosstalk than the Lamé coefficient parametrization. Correlation- and convolution-type misfit functions are effective when amplitude errors are involved and the source wavelet is unknown, respectively. Finally, we discuss the dependence of elastic LSRTM on migration velocities and its antinoise ability. Imaging results determine that the new elastic LSRTM method performs well as long as the low-frequency components of migration velocities are correct. The quality of images of elastic LSRTM degrades with increasing noise.
Automation of reverse engineering process in aircraft modeling and related optimization problems
Li, W.; Swetits, J.
1994-01-01
During the year of 1994, the engineering problems in aircraft modeling were studied. The initial concern was to obtain a surface model with desirable geometric characteristics. Much of the effort during the first half of the year was to find an efficient way of solving a computationally difficult optimization model. Since the smoothing technique in the proposal 'Surface Modeling and Optimization Studies of Aerodynamic Configurations' requires solutions of a sequence of large-scale quadratic programming problems, it is important to design algorithms that can solve each quadratic program in a few interactions. This research led to three papers by Dr. W. Li, which were submitted to SIAM Journal on Optimization and Mathematical Programming. Two of these papers have been accepted for publication. Even though significant progress has been made during this phase of research and computation times was reduced from 30 min. to 2 min. for a sample problem, it was not good enough for on-line processing of digitized data points. After discussion with Dr. Robert E. Smith Jr., it was decided not to enforce shape constraints in order in order to simplify the model. As a consequence, P. Dierckx's nonparametric spline fitting approach was adopted, where one has only one control parameter for the fitting process - the error tolerance. At the same time the surface modeling software developed by Imageware was tested. Research indicated a substantially improved fitting of digitalized data points can be achieved if a proper parameterization of the spline surface is chosen. A winning strategy is to incorporate Dierckx's surface fitting with a natural parameterization for aircraft parts. The report consists of 4 chapters. Chapter 1 provides an overview of reverse engineering related to aircraft modeling and some preliminary findings of the effort in the second half of the year. Chapters 2-4 are the research results by Dr. W. Li on penalty functions and conjugate gradient methods for
Anisotropy signature in reverse-time migration extended images
Sava, Paul C.
2014-11-04
Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the Earth, i.e., at common-image-point gathers, carry rich information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. However, characterizing the anisotropy influence on such extended images is a challenge. Extended common-image-point gathers are cheap to evaluate since they sample the image at sparse locations indicated by the presence of strong reflectors. Such gathers are also sensitive to velocity error that manifests itself through moveout as a function of space and time lags. Furthermore, inaccurate anisotropy leaves a distinctive signature in common-image-point gathers, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography. It specifically admits a V-shaped residual moveout with the slope of the "V" flanks depending on the anisotropic parameter η regardless of the complexity of the velocity model. It reflects the fourth-order nature of the anisotropy influence on moveout as it manifests itself in this distinct signature in extended images after handling the velocity properly in the imaging process. Synthetic and real data observations support this assertion.
Imaging Method Based on Time Reversal Channel Compensation
Bing Li
2015-01-01
Full Text Available The conventional time reversal imaging (TRI method builds imaging function by using the maximal value of signal amplitude. In this circumstance, some remote targets are missed (near-far problem or low resolution is obtained in lossy and/or dispersive media, and too many transceivers are employed to locate targets, which increases the complexity and cost of system. To solve these problems, a novel TRI algorithm is presented in this paper. In order to achieve a high resolution, the signal amplitude corresponding to focal time observed at target position is used to reconstruct the target image. For disposing near-far problem and suppressing spurious images, combining with cross-correlation property and amplitude compensation, channel compensation function (CCF is introduced. Moreover, the complexity and cost of system are reduced by employing only five transceivers to detect four targets whose number is close to that of transceivers. For the sake of demonstrating the practicability of the proposed analytical framework, the numerical experiments are actualized in both nondispersive-lossless (NDL media and dispersive-conductive (DPC media. Results show that the performance of the proposed method is superior to that of conventional TRI algorithm even under few echo signals.
Wu, Qi-Cheng; Huang, Bi-Hua; Chen, Ye-Hong; Shi, Zhi-Cheng; Song, Jie; Xia, Yan
2017-10-01
We propose a method to design shortcuts to adiabaticity for implementing perfect quantum state engineering by the combination of the counterdiabatic driving and the reverse engineering technique. Based on the method, we can design simple schemes to realize the intended dynamics. For the sake of clearness, we apply this method to several examples including two-level, three-level and four-level system. We show that fast quantum state engineering can be realized by utilizing simply-designed auxiliary Hamiltonian. Furthermore, a suitable choice of the control parameters can eliminate the additional couplings in the introduced auxiliary Hamiltonian. Numerical simulation reveals that the constructed scheme is reliable and robust against various dissipation effects and the fluctuations of control parameters in current technology.
Elastic Reverse Time Migration (RTM) From Surface Topography
Akram, Naveed; Chen, Xiaofei
2017-04-01
Seismic Migration is a promising data processing technique to construct subsurface images by projecting the recorded seismic data at surface back to their origins. There are numerous Migration methods. Among them, Reverse Time Migration (RTM) is considered a robust and standard imaging technology in present day exploration industry as well as in academic research field because of its superior performance compared to traditional migration methods. Although RTM is extensive computing and time consuming but it can efficiently handle the complex geology, highly dipping reflectors and strong lateral velocity variation all together. RTM takes data recorded at the surface as a boundary condition and propagates the data backwards in time until the imaging condition is met. It can use the same modeling algorithm that we use for forward modeling. The classical seismic exploration theory assumes flat surface which is almost impossible in practice for land data. So irregular surface topography has to be considered in simulation of seismic wave propagation, which is not always a straightforward undertaking. In this study, Curved grid finite difference method (CG-FDM) is adapted to model elastic seismic wave propagation to investigate the effect of surface topography on RTM results and explore its advantages and limitations with synthetic data experiments by using Foothill model with topography as the true model. We focus on elastic wave propagation rather than acoustic wave because earth actually behaves as an elastic body. Our results strongly emphasize on the fact that irregular surface topography must be considered for modeling of seismic wave propagation to get better subsurface images specially in mountainous scenario and suggest practitioners to properly handled the geometry of data acquired on irregular topographic surface in their imaging algorithms.
Time-reversed lasing in the terahertz range and its preliminary study in sensor applications
Shen, Yun, E-mail: shenyunoptics@gmail.com [Department of Physics, Nanchang University, Nanchang 330031 (China); Liu, Huaqing [Department of Physics, Nanchang University, Nanchang 330031 (China); Deng, Xiaohua [Institute of Space Science and Technology, Nanchang University, Nanchang 330031 (China); Wang, Guoping [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China)
2017-02-05
Time-reversed lasing in a uniform slab and a grating structure are investigated in the terahertz range. The results show that both the uniform slab and grating can support terahertz time-reversed lasing. Nevertheless, due to the tunable effective refractive index, the grating structure can not only exhibit time-reversed lasing more effectively and flexibly than a uniform slab, but also can realize significant absorption in a broader operating frequency range. Furthermore, applications of terahertz time-reversed lasing for novel concentration/thickness sensors are preliminarily studied in a single-channel coherent perfect absorber system. - Highlights: • Time-reversed lasing are investigated in the terahertz range. • The grating structure exhibit time-reversed lasing more effectively and flexibly than a uniform slab. • THz time-reversed lasing for novel concentration/thickness sensors are studied.
Improving the gradient in least-squares reverse time migration
Liu, Qiancheng
2016-04-01
Least-squares reverse time migration (LSRTM) is a linearized inversion technique used for estimating high-wavenumber reflectivity. However, due to the redundant overlay of the band-limited source wavelet, the gradient based on the cross-correlated imaging principle suffers from a loss of wavenumber information. We first prepare the residuals between observed and demigrated data by deconvolving with the amplitude spectrum of the source wavelet, and then migrate the preprocessed residuals by using the cross-correlation imaging principle. In this way, a gradient that preserves the spectral signature of data residuals is obtained. The computational cost of source-wavelet removal is negligible compared to that of wavefield simulation. The two-dimensional Marmousi model containing complex geology structures is considered to test our scheme. Numerical examples show that our improved gradient in LSRTM has a better convergence behavior and promises inverted results of higher resolution. Finally, we attempt to update the background velocity with our inverted velocity perturbations to approach the true velocity.
Time Reversal Acoustic Communication Using Filtered Multitone Modulation
Lin Sun
2015-09-01
Full Text Available The multipath spread in underwater acoustic channels is severe and, therefore, when the symbol rate of the time reversal (TR acoustic communication using single-carrier (SC modulation is high, the large intersymbol interference (ISI span caused by multipath reduces the performance of the TR process and needs to be removed using the long adaptive equalizer as the post-processor. In this paper, a TR acoustic communication method using filtered multitone (FMT modulation is proposed in order to reduce the residual ISI in the processed signal using TR. In the proposed method, FMT modulation is exploited to modulate information symbols onto separate subcarriers with high spectral containment and TR technique, as well as adaptive equalization is adopted at the receiver to suppress ISI and noise. The performance of the proposed method is assessed through simulation and real data from a trial in an experimental pool. The proposed method was compared with the TR acoustic communication using SC modulation with the same spectral efficiency. Results demonstrate that the proposed method can improve the performance of the TR process and reduce the computational complexity of adaptive equalization for post-process.
Reverse time migration of prism waves for salt flank delineation
Dai, Wei
2013-09-22
In this paper, we present a new reverse time migration method for imaging salt flanks with prism wave reflections. It consists of four steps: (1) migrating the seismic data with conventional RTM to give the RTM image; (2) using the RTM image as a reflectivity model to simulate source-side reflections with the Born approximation; (3) zero-lag correlation of the source-side reflection wavefields and receiver-side wavefields to produce the prism wave migration image; and (4) repeating steps 2 and 3 for the receiver-side reflections. An advantage of this method is that there is no need to pick the horizontal reflectors prior to migration of the prism waves. It also separately images the vertical structures at a different step to reduce crosstalk interference. The disadvantage of prism wave migration algorithm is that its computational cost is twice that of conventional RTM. The empirical results with a salt model suggest that prism wave migration can be an effective method for salt flank delineation in the absence of diving waves.
A Neural Network Approach on Reverse Engineering Surface Reasoning in the Manufacturing Field
无
2001-01-01
This paper applied the neural network technology to surfacereasoning in reverse engineering and established the neural network computation model. One of the main advantages of reasoning solid surface using neural network is that no knowledge about surface is needed, and the limited measured points on the surface will do sufficiently. This paper listed the related reasoning cases, including the elementary analytical surfaces and freeform surfaces, discussed the various issues occurring during reasoning process and proved the feasibility and efficiency of this approach from theory and practical computing cases. The results show that a neural network is an excellent aided analysis means for surface reasoning in reversing engineering and possesses practical use for the surface that is complex, incomplete and partially worn-out or damaged.
Reveal, A General Reverse Engineering Algorithm for Inference of Genetic Network Architectures
Liang, Shoudan; Fuhrman, Stefanie; Somogyi, Roland
1998-01-01
Given the immanent gene expression mapping covering whole genomes during development, health and disease, we seek computational methods to maximize functional inference from such large data sets. Is it possible, in principle, to completely infer a complex regulatory network architecture from input/output patterns of its variables? We investigated this possibility using binary models of genetic networks. Trajectories, or state transition tables of Boolean nets, resemble time series of gene expression. By systematically analyzing the mutual information between input states and output states, one is able to infer the sets of input elements controlling each element or gene in the network. This process is unequivocal and exact for complete state transition tables. We implemented this REVerse Engineering ALgorithm (REVEAL) in a C program, and found the problem to be tractable within the conditions tested so far. For n = 50 (elements) and k = 3 (inputs per element), the analysis of incomplete state transition tables (100 state transition pairs out of a possible 10(exp 15)) reliably produced the original rule and wiring sets. While this study is limited to synchronous Boolean networks, the algorithm is generalizable to include multi-state models, essentially allowing direct application to realistic biological data sets. The ability to adequately solve the inverse problem may enable in-depth analysis of complex dynamic systems in biology and other fields.
Spatiotemporal control of cell-cell reversible interactions using molecular engineering
Shi, Peng; Ju, Enguo; Yan, Zhengqing; Gao, Nan; Wang, Jiasi; Hou, Jianwen; Zhang, Yan; Ren, Jinsong; Qu, Xiaogang
2016-10-01
Manipulation of cell-cell interactions has potential applications in basic research and cell-based therapy. Herein, using a combination of metabolic glycan labelling and bio-orthogonal click reaction, we engineer cell membranes with β-cyclodextrin and subsequently manipulate cell behaviours via photo-responsive host-guest recognition. With this methodology, we demonstrate reversible manipulation of cell assembly and disassembly. The method enables light-controllable reversible assembly of cell-cell adhesion, in contrast with previously reported irreversible effects, in which altered structure could not be reused. We also illustrate the utility of the method by designing a cell-based therapy. Peripheral blood mononuclear cells modified with aptamer are effectively redirected towards target cells, resulting in enhanced cell apoptosis. Our approach allows precise control of reversible cell-cell interactions and we expect that it will promote further developments of cell-based therapy.
The limitations of the reverse-engineering approach to cognitive modeling.
Rueckl, Jay G
2012-10-01
Frost's critique reveals the limitations of the reverse-engineering approach to cognitive modeling--the style of psychological explanation in which a stipulated internal organization (in the form of a computational mechanism) explains a relatively narrow set of phenomena. An alternative is to view organization as both the explanation for some phenomena and a phenomenon to be explained. This move poses new and interesting theoretical challenges for theories of word reading.
Manufacturing of lower-limb custom fit prostethics sockets using reverse engineering
2012-01-01
The objective of this project is the construction of an orthopaedic prosthesis for a person who has been lower limb amputated, above the knee, taking attention to the specifications of the amputation stump. Through this method the actual process of prosthesis design in rehabilitation technology is improved by applying reverse engineering and additive manufacturing technologies. The outcome of this work is a personalized prosthesis building procedure that should allow a stu...
Un-Building Blocks: A Model of Reverse Engineering and Applicable Heuristics
2015-12-01
academic. Subjects on which Messler does not have professional experience (such as the pyramid of Khufu, or the Antikythera mechanism) appear to be...terms are often used interchangeably. How do we visually model reverse engineering? The general scheme is as follows. The model will consist of two...the battle. Our goal is like the strategist’s. Figure 10 continues the development of a scheme for achieving this goal. In the previous figure, the
Using a Formal Approach for Reverse Engineering and Design Recovery to Support Software Reuse
Gannod, Gerald C.
2002-01-01
This document describes 3rd year accomplishments and summarizes overall project accomplishments. Included as attachments are all published papers from year three. Note that the budget for this project was discontinued after year two, but that a residual budget from year two allowed minimal continuance into year three. Accomplishments include initial investigations into log-file based reverse engineering, service-based software reuse, and a source to XML generator.
Frolova A. O.
2012-01-01
Reverse engineering of gene regulatory networks is an intensively studied topic in Systems Biology as it reconstructs regulatory interactions between all genes in the genome in the most complete form. The extreme computational complexity of this problem and lack of thorough reviews on reconstruction methods of gene regulatory network is a significant obstacle to further development of this area. In this article the two most common methods for modeling gene regulatory networks are surveyed: Bo...
LEAST-SQUARES METHOD-BASED FEATURE FITTING AND EXTRACTION IN REVERSE ENGINEERING
无
2003-01-01
The main purpose of reverse engineering is to convert discrete data points into piecewise smooth, continuous surface models.Before carrying out model reconstruction it is significant to extract geometric features because the quality of modeling greatly depends on the representation of features.Some fitting techniques of natural quadric surfaces with least-squares method are described.And these techniques can be directly used to extract quadric surfaces features during the process of segmentation for point cloud.
Manufacturing of lower-limb custom fit prostethics sockets using reverse engineering
Curralo, Ana; Queijo, Luís; Rocha,João
2012-01-01
The objective of this project is the construction of an orthopaedic prosthesis for a person who has been lower limb amputated, above the knee, taking attention to the specifications of the amputation stump. Through this method the actual process of prosthesis design in rehabilitation technology is improved by applying reverse engineering and additive manufacturing technologies. The outcome of this work is a personalized prosthesis building procedure that should allow a stu...
Fingerprinting Reverse Proxies Using Timing Analysis of TCP Flows
2013-09-01
masking where the content is truly hosted. Reverse proxies interact over the HyperText Transfer Protocol (HTTP), which is delivered via the Transmission...where the content is truly hosted. Reverse proxies interact over the HyperText Transfer Protocol (HTTP), which is delivered via the Transmission...FSM Finite State Machine HTML Hypertext Markup Language HTTP Hypertext Transfer Protocol HTTPS Hypertext Transfer Protocol Secure ICMP Internet Control
Reverse Engineering and Its Application%逆向工程及应用
李玉蓉
2011-01-01
现代先进制造技术的发展,将实物的样件或模型转化为CAD数据模型,在利用快速成型系统、计算机辅助设计系统等对其进行数据处理,并不断的进行修改和优化设计这就是逆向工程技术.逆向工程实现了从实际物体到几何建模的直接转换.逆向工程技术涉及计算机图形学、计算机图像处理、微分几何、概率统计等学科.%Modern advanced manufacturing technology converts sample or model into CAD data model, then rapid prototyping systems and computer-aided design systems conduct its data processing. and continue to modify and optimize the design it is the reverse engineering. Reverse engineering achieves the direct conversion from object to geometrc modeling Reverse engineering techniques related to computer graphics, computer image processing. differential geometry, probability and statistics etc.
Time Reversal Signal Processing in Communications - A Feasibility Study
Meyer, A W; Candy, J V; Poggio, A J
2002-01-30
A typical communications channel is subjected to a variety of signal distortions, including multipath, that corrupt the information being transmitted and reduce the effective channel capacity. The mitigation of the multipath interference component is an ongoing concern for communication systems operating in complex environments such as might be experienced inside buildings, urban environments, and hilly or heavily wooded areas. Communications between mobile units and distributed sensors, so important to national security, are dependent upon flawless conveyance of information in complex environments. The reduction of this multipath corruption necessitates better channel equalization, i.e., the removal of channel distortion to extract the transmitted information. But, the current state of the art in channel equalization either requires a priori knowledge of the channel or the use of a known training sequence and adaptive filtering. If the ''assumed'' model within the equalization processor does not at least capture the dominant characteristics of the channel, then the received information may still be highly distorted and possibly useless. Also, the processing required for classical equalization is demanding in computational resources. To remedy this situation, many techniques have been investigated to replace classical equalization. Such a technique, the subject of this feasibility study, is Time Reversal Signal Processing (TRSP). Multipath is particularly insidious and a major factor in the deterioration of communication channels. Unlike most other characteristics that corrupt a communications channel, the detrimental effects of multipath cannot be overcome by merely increasing the transmitted power. Although the power in a signal diminishes as a function of the distance between the transmitter and receiver, multipath further degrades a signal by creating destructive interference that results in a loss of received power in a very localized area
Application of Carbonate Reservoir using waveform inversion and reverse-time migration methods
Kim, W.; Kim, H.; Min, D.; Keehm, Y.
2011-12-01
inversion results are quite reliable. Different thicknesses of reservoir models were also described and the results revealed that the lower boundary of the reservoir was not delineated because of energy loss. From these results, it was noted that carbonate reservoirs can be properly imaged and interpreted by waveform inversion and reverse-time migration methods. This work was supported by the Energy Resources R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2009201030001A, No. 2010T100200133) and the Brain Korea 21 project of Energy System Engineering.
Iyyappan, I.; Ponmurugan, M.
2017-09-01
We study the performance of a three-terminal thermoelectric device such as heat engine and refrigerator with broken time-reversal symmetry by applying the unified trade-off figure of merit (\\dotΩ criterion) which accounts for both useful energy and losses. For the heat engine, we find that a thermoelectric device working under the maximum \\dotΩ criterion gives a significantly better performance than a device working at maximum power output. Within the framework of linear irreversible thermodynamics such a direct comparison is not possible for refrigerators, however, our study indicates that, for refrigerator, the maximum cooling load gives a better performance than the maximum \\dotΩ criterion for a larger asymmetry. Our results can be useful to choose a suitable optimization criterion for operating a real thermoelectric device with broken time-reversal symmetry.
A time reversal damage imaging method for structure health monitoring using Lamb waves
Zhang Hai-Yan; Cao Ya-Ping; Sun Xiu-Li; Chen Xian-Hua; Yu Jian-Bo
2010-01-01
This paper investigates the Lamb wave imaging method combining time reversal for health monitoring of a metal-lic plate structure.The temporal focusing effect of the time reversal Lamb waves is investigated theoretically.It demonstrates that the focusing effect is related to the frequency dependency of the time reversal operation.Numerical simulations are conducted to study the time reversal behaviour of Lamb wave modes under broadband and narrowband excitations.The results show that the reconstructed time reversed wave exhibits close similarity to the reversed nar-rowband tone burst signal validating the theoretical model.To enhance the similarity,the cycle number of the excited signal should be increased.Experiments combining finite element model are then conducted to study the imaging method in the presence of damage like hole in the plate structure.In this work,the time reversal technique is used for the recompression of Lamb wave signals.Damage imaging results with time reversal using broadband and narrowhand excitations are compared to those without time reversal.It suggests that the narrowband excitation combined time reversal can locate and determine the size of structural damage more precisely,but the cycle number of the excited signal should be chosen reasonably.
Ramoni Marco F
2007-05-01
Full Text Available Abstract Background Reverse engineering cellular networks is currently one of the most challenging problems in systems biology. Dynamic Bayesian networks (DBNs seem to be particularly suitable for inferring relationships between cellular variables from the analysis of time series measurements of mRNA or protein concentrations. As evaluating inference results on a real dataset is controversial, the use of simulated data has been proposed. However, DBN approaches that use continuous variables, thus avoiding the information loss associated with discretization, have not yet been extensively assessed, and most of the proposed approaches have dealt with linear Gaussian models. Results We propose a generalization of dynamic Gaussian networks to accommodate nonlinear dependencies between variables. As a benchmark dataset to test the new approach, we used data from a mathematical model of cell cycle control in budding yeast that realistically reproduces the complexity of a cellular system. We evaluated the ability of the networks to describe the dynamics of cellular systems and their precision in reconstructing the true underlying causal relationships between variables. We also tested the robustness of the results by analyzing the effect of noise on the data, and the impact of a different sampling time. Conclusion The results confirmed that DBNs with Gaussian models can be effectively exploited for a first level analysis of data from complex cellular systems. The inferred models are parsimonious and have a satisfying goodness of fit. Furthermore, the networks not only offer a phenomenological description of the dynamics of cellular systems, but are also able to suggest hypotheses concerning the causal interactions between variables. The proposed nonlinear generalization of Gaussian models yielded models characterized by a slightly lower goodness of fit than the linear model, but a better ability to recover the true underlying connections between
The effects of non-uniform loss on time reversal mirrors
Biniyam Tesfaye Taddese
2014-08-01
Full Text Available Time reversal mirrors work perfectly only for lossless wave propagation; dissipation destroys time-reversal invariance and limits the performance of time-reversal mirrors. Here, a new measure of time-reversal mirror performance is introduced and the adverse effect of dissipation on this performance measure is investigated. The technique of exponential amplification is employed to partially overcome the effect of non-uniform loss distributions, and its success is tested quantitatively using the new performance measure. A numerical model of a star graph is employed to test the applicability of this technique on realizations with various random spatial distributions of loss. A subset of the numerical results are also verified by experimental results from an electromagnetic time-reversal mirror. The exponential amplification technique is a simple way to improve the performance of emerging technologies based on time-reversed wave propagation such as directed communication and wireless power transfer.
Acoustic Longitudinal Field NIF Optic Feature Detection Map Using Time-Reversal & MUSIC
Lehman, S K
2006-02-09
We developed an ultrasonic longitudinal field time-reversal and MUltiple SIgnal Classification (MUSIC) based detection algorithm for identifying and mapping flaws in fused silica NIF optics. The algorithm requires a fully multistatic data set, that is one with multiple, independently operated, spatially diverse transducers, each transmitter of which, in succession, launches a pulse into the optic and the scattered signal measured and recorded at every receiver. We have successfully localized engineered ''defects'' larger than 1 mm in an optic. We confirmed detection and localization of 3 mm and 5 mm features in experimental data, and a 0.5 mm in simulated data with sufficiently high signal-to-noise ratio. We present the theory, experimental results, and simulated results.
Propagation of time-reversed Lamb waves in bovine cortical bone in vitro.
Lee, Kang Il; Yoon, Suk Wang
2015-01-01
The present study aims to investigate the propagation of time-reversed Lamb waves in bovine cortical bone in vitro. The time-reversed Lamb waves were successfully launched at 200 kHz in 18 bovine tibiae through a time reversal process of Lamb waves. The group velocities of the time-reversed Lamb waves in the bovine tibiae were measured using the axial transmission technique. They showed a significant correlation with the cortical thickness and tended to follow the theoretical group velocity of the lowest order antisymmetrical Lamb wave fairly well, consistent with the behavior of the slow guided wave in long cortical bones.
Cross-correlation least-squares reverse time migration in the pseudo-time domain
Li, Qingyang; Huang, Jianping; Li, Zhenchun
2017-08-01
The least-squares reverse time migration (LSRTM) method with higher image resolution and amplitude is becoming increasingly popular. However, the LSRTM is not widely used in field land data processing because of its sensitivity to the initial migration velocity model, large computational cost and mismatch of amplitudes between the synthetic and observed data. To overcome the shortcomings of the conventional LSRTM, we propose a cross-correlation least-squares reverse time migration algorithm in pseudo-time domain (PTCLSRTM). Our algorithm not only reduces the depth/velocity ambiguities, but also reduces the effect of velocity error on the imaging results. It relieves the accuracy requirements on the migration velocity model of least-squares migration (LSM). The pseudo-time domain algorithm eliminates the irregular wavelength sampling in the vertical direction, thus it can reduce the vertical grid points and memory requirements used during computation, which makes our method more computationally efficient than the standard implementation. Besides, for field data applications, matching the recorded amplitudes is a very difficult task because of the viscoelastic nature of the Earth and inaccuracies in the estimation of the source wavelet. To relax the requirement for strong amplitude matching of LSM, we extend the normalized cross-correlation objective function to the pseudo-time domain. Our method is only sensitive to the similarity between the predicted and the observed data. Numerical tests on synthetic and land field data confirm the effectiveness of our method and its adaptability for complex models.
Real-Time Monitoring of Reverse Osmosis Membrane Integrity
Surawanvijit, Sirikarn
2015-01-01
Reverse osmosis (RO) membrane desalination is the primary technology for seawater and brackish water desalination, agricultural drainage desalting, as well as municipal wastewater recycling for potable water reuse applications. RO membranes achieve high salt rejection (>95%) and in principle should provide a complete physical barrier to nanosize pathogens (e.g., waterborne enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20-30 n...
Engine control system having speed-based timing
Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL
2012-02-14
A control system for an engine having a cylinder is disclosed having an engine valve movable to regulate a fluid flow of the cylinder and an actuator associated with the engine valve. The control system also has a controller in communication with the actuator. The controller is configured to receive a signal indicative of engine speed and compare the engine speed signal with a desired engine speed. The controller is also configured to selectively regulate the actuator to adjust a timing of the engine valve to control an amount of air/fuel mixture delivered to the cylinder based on the comparison.
Indeterminacy of reverse engineering of Gene Regulatory Networks: the curse of gene elasticity.
Arun Krishnan
Full Text Available BACKGROUND: Gene Regulatory Networks (GRNs have become a major focus of interest in recent years. A number of reverse engineering approaches have been developed to help uncover the regulatory networks giving rise to the observed gene expression profiles. However, this is an overspecified problem due to the fact that more than one genotype (network wiring can give rise to the same phenotype. We refer to this phenomenon as "gene elasticity." In this work, we study the effect of this particular problem on the pure, data-driven inference of gene regulatory networks. METHODOLOGY: We simulated a four-gene network in order to produce "data" (protein levels that we use in lieu of real experimental data. We then optimized the network connections between the four genes with a view to obtain the original network that gave rise to the data. We did this for two different cases: one in which only the network connections were optimized and the other in which both the network connections as well as the kinetic parameters (given as reaction probabilities in our case were estimated. We observed that multiple genotypes gave rise to very similar protein levels. Statistical experimentation indicates that it is impossible to differentiate between the different networks on the basis of both equilibrium as well as dynamic data. CONCLUSIONS: We show explicitly that reverse engineering of GRNs from pure expression data is an indeterminate problem. Our results suggest the unsuitability of an inferential, purely data-driven approach for the reverse engineering transcriptional networks in the case of gene regulatory networks displaying a certain level of complexity.
Space Shuttle Main Engine real time stability analysis
Kuo, F. Y.
1993-01-01
The Space Shuttle Main Engine (SSME) is a reusable, high performance, liquid rocket engine with variable thrust. The engine control system continuously monitors the engine parameters and issues propellant valve control signals in accordance with the thrust and mixture ratio commands. A real time engine simulation lab was installed at MSFC to verify flight software and to perform engine dynamic analysis. A real time engine model was developed on the AD100 computer system. This model provides sufficient fidelity on the dynamics of major engine components and yet simplified enough to be executed in real time. The hardware-in-the-loop type simulation and analysis becomes necessary as NASA is continuously improving the SSME technology, some with significant changes in the dynamics of the engine. The many issues of interfaces between new components and the engine can be better understood and be resolved prior to the firing of the engine. In this paper, the SSME real time simulation Lab at the MSFC, the SSME real time model, SSME engine and control system stability analysis, both in real time and non-real time is presented.
A reverse engineering methodology for nickel alloy turbine blades with internal features
Gameros, A.; De Chiffre, Leonardo; Siller, H.R.
2015-01-01
The scope of this work is to present a reverse engineering (RE) methodology for freeform surfaces, based on a case study of a turbine blade made of Inconel, including the reconstruction of its internal cooling system. The methodology uses an optical scanner and X-ray computed tomography (CT......) equipment. Traceability of the measurements was obtained through the use of a Modular Freeform Gage (MFG). An uncertainty budget is presented for both measuring technologies and results show that the RE methodology presented is promising when comparing uncertainty values against common industrial tolerances....
Reverse engineering gene networks using singular value decomposition and robust regression
Yeung, M. K. Stephen; Tegnér, Jesper; Collins, James J.
2002-01-01
We propose a scheme to reverse-engineer gene networks on a genome-wide scale using a relatively small amount of gene expression data from microarray experiments. Our method is based on the empirical observation that such networks are typically large and sparse. It uses singular value decomposition to construct a family of candidate solutions and then uses robust regression to identify the solution with the smallest number of connections as the most likely solution. Our algorithm has O(log N) sampling complexity and O(N4) computational complexity. We test and validate our approach in a series of in numero experiments on model gene networks. PMID:11983907
Structure-guided residence time optimization of a dabigatran reversal agent.
Schiele, Felix; van Ryn, Joanne; Litzenburger, Tobias; Ritter, Michael; Seeliger, Daniel; Nar, Herbert
2015-01-01
Novel oral anticoagulants are effective and safe alternatives to vitamin-K antagonists for anticoagulation therapy. However, anticoagulation therapy in general is associated with an elevated risk of bleeding. Idarucizumab is a reversal agent for the direct thrombin inhibitor, dabigatran etexilate (Pradaxa®) and is currently in Phase 3 studies. Here, we report data on the antibody fragment aDabi-Fab2, a putative backup molecule for idarucizumab. Although aDabi-Fab2 completely reversed effects of dabigatran in a rat model in vivo, we observed significantly reduced duration of action compared to idarucizumab. Rational protein engineering, based on the X-ray structure of aDabi-Fab2, led to the identification of mutant Y103W. The mutant had optimized shape complementarity to dabigatran while maintaining an energetically favored hydrogen bond. It displayed increased affinity for dabigatran, mainly driven by a slower off-rate. Interestingly, the increased residence time translated into longer duration of action in vivo. It was thus possible to further enhance the efficacy of aDabi-Fab2 based on rational design, giving it the potential to serve as a back-up candidate for idarucizumab.
Oud, Bart; Maris, Antonius J A; Daran, Jean-Marc; Pronk, Jack T
2012-01-01
Successful reverse engineering of mutants that have been obtained by nontargeted strain improvement has long presented a major challenge in yeast biotechnology. This paper reviews the use of genome-wide approaches for analysis of Saccharomyces cerevisiae strains originating from evolutionary engineering or random mutagenesis. On the basis of an evaluation of the strengths and weaknesses of different methods, we conclude that for the initial identification of relevant genetic changes, whole genome sequencing is superior to other analytical techniques, such as transcriptome, metabolome, proteome, or array-based genome analysis. Key advantages of this technique over gene expression analysis include the independency of genome sequences on experimental context and the possibility to directly and precisely reproduce the identified changes in naive strains. The predictive value of genome-wide analysis of strains with industrially relevant characteristics can be further improved by classical genetics or simultaneous analysis of strains derived from parallel, independent strain improvement lineages. PMID:22152095
Reverse engineering the mechanical and molecular pathways in stem cell morphogenesis.
Lu, Kai; Gordon, Richard; Cao, Tong
2015-03-01
The formation of relevant biological structures poses a challenge for regenerative medicine. During embryogenesis, embryonic cells differentiate into somatic tissues and undergo morphogenesis to produce three-dimensional organs. Using stem cells, we can recapitulate this process and create biological constructs for therapeutic transplantation. However, imperfect imitation of nature sometimes results in in vitro artifacts that fail to recapitulate the function of native organs. It has been hypothesized that developing cells may self-organize into tissue-specific structures given a correct in vitro environment. This proposition is supported by the generation of neo-organoids from stem cells. We suggest that morphogenesis may be reverse engineered to uncover its interacting mechanical pathway and molecular circuitry. By harnessing the latent architecture of stem cells, novel tissue-engineering strategies may be conceptualized for generating self-organizing transplants.
Oud, Bart; van Maris, Antonius J A; Daran, Jean-Marc; Pronk, Jack T
2012-03-01
Successful reverse engineering of mutants that have been obtained by nontargeted strain improvement has long presented a major challenge in yeast biotechnology. This paper reviews the use of genome-wide approaches for analysis of Saccharomyces cerevisiae strains originating from evolutionary engineering or random mutagenesis. On the basis of an evaluation of the strengths and weaknesses of different methods, we conclude that for the initial identification of relevant genetic changes, whole genome sequencing is superior to other analytical techniques, such as transcriptome, metabolome, proteome, or array-based genome analysis. Key advantages of this technique over gene expression analysis include the independency of genome sequences on experimental context and the possibility to directly and precisely reproduce the identified changes in naive strains. The predictive value of genome-wide analysis of strains with industrially relevant characteristics can be further improved by classical genetics or simultaneous analysis of strains derived from parallel, independent strain improvement lineages.
Islam Md. Tasbirul
2017-01-01
Full Text Available This paper presents reverse engineering (RE of a complex automobile structural part, B-pillar. As a major part of the automobile body-in white (BiW, B-pillar has substantial opportunity for weight reduction by introducing variable thickness across its sections. To leverage such potential, an existing B-pillar was reverse engineered with a 3D optical scanner and computer aided design (CAD application. First, digital data (i.e. in meshes of exiting B-pillar was obtained by the scanner, and subsequently, this information was utilized in developing a complete 3D CAD model. CATIA V5 was used in the modeling where some of the essential work benches were “Digitized Shape Editor”, “Quick Surface Reconstruction”, “Wireframe and Surface Design”, “Freestyle”, “Generation Shape Design” and “Part design”. In the final CAD design, five different thicknesses were incorporated successfully in order to get a B-pillar with non-uniform sections. This research opened opportunities for thickness optimization and mold tooling design in real time manufacturing.
Real-Time Aircraft Engine-Life Monitoring
Klein, Richard
2014-01-01
This project developed an inservice life-monitoring system capable of predicting the remaining component and system life of aircraft engines. The embedded system provides real-time, inflight monitoring of the engine's thrust, exhaust gas temperature, efficiency, and the speed and time of operation. Based upon this data, the life-estimation algorithm calculates the remaining life of the engine components and uses this data to predict the remaining life of the engine. The calculations are based on the statistical life distribution of the engine components and their relationship to load, speed, temperature, and time.
Reverse Time Migration: A Seismic Imaging Technique Applied to Synthetic Ultrasonic Data
Sabine Müller
2012-01-01
Full Text Available Ultrasonic echo testing is a more and more frequently used technique in civil engineering to investigate concrete building elements, to measure thickness as well as to locate and characterise built-in components or inhomogeneities. Currently the Synthetic Aperture Focusing Technique (SAFT, which is closely related to Kirchhoff migration, is used in most cases for imaging. However, this method is known to have difficulties to image steeply dipping interfaces as well as lower boundaries of tubes, voids or similar objects. We have transferred a processing technique from geophysics, the Reverse Time Migration (RTM method, to improve the imaging of complicated geometries. By using the information from wide angle reflections as well as from multiple events there are fewer limitations compared to SAFT. As a drawback the required computing power is significantly higher compared to the techniques currently used. Synthetic experiments have been performed on polyamide and concrete specimens to show the improvements compared to SAFT. We have been able to image vertical interfaces of step-like structures as well as the lower boundaries of circular objects. It has been shown that RTM is a step forward for ultrasonic testing in civil engineering.
Detecting a subsurface cylinder by a Time Reversal MUSIC like method
Solimene, Raffaele; Dell'Aversano, Angela; Leone, Giovanni
2014-05-01
In this contribution the problem of imaging a buried homogeneous circular cylinder is dealt with for a two-dimensional scalar geometry. Though the addressed geometry is extremely simple as compared to real world scenarios, it can be considered of interest for a classical GPR civil engineering applicative context: that is the subsurface prospecting of urban area in order to detect and locate buried utilities. A large body of methods for subsurface imaging have been presented in literature [1], ranging from migration algorithms to non-linear inverse scattering approaches. More recently, also spectral estimation methods, which benefit from sub-array data arrangement, have been proposed and compared in [2].Here a Time Reversal MUSIC (TRM) like method is employed. TRM has been initially conceived to detect point-like scatterers and then generalized to the case of extended scatterers [3]. In the latter case, no a priori information about the scatterers is exploited. However, utilities often can be schematized as circular cylinders. Here, we develop a TRM variant which use this information to properly tailor the steering vector while implementing TRM. Accordingly, instead of a spatial map [3], the imaging procedure returns the scatterer's parameters such as its center position, radius and dielectric permittivity. The study is developed by numerical simulations. First the free-space case is considered in order to more easily introduce the idea and the problem mathematical structure. Then the analysis is extended to the half-space case. In both situations a FDTD forward solver is used to generate the synthetic data. As usual in TRM, a multi-view/multi-static single-frequency configuration is considered and emphasis is put on the role played by the number of available sensors. Acknowledgement This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar." [1] A. Randazzo and R
Quality assessment of reverse engineering process based on full-field true-3D optical measurements
Kujawinska, Malgorzata; Sitnik, Robert
2000-08-01
In the paper the sequential steps of reverse engineering based on the data gathered by full-field optical system are discussed. Each step is concerned from the point of view of its influence on the final quality of the shape of manufactured object. At first the modern shape measurement system based on the combination of fringe projection, Grey code and experimental calibration is presented. The system enables the determination of absolute coordinates of the object measured from many directions. The dependence of the quality of the cloud of points on the type of object and the measurement procedure is discussed. Then the methods of transferring the experimental data into CAD/CAM/CAE system are presented. The quality of the virtual object in the form of closed triangular mesh is analyzed. Basing on this virtual object the copy of initial body is produced and measured. The accuracy of the object manufactured is determined and the main sources of errors are discussed. The modifications of the system and algorithms that minimize the errors are proposed. The reverse engineering sequence is presented is illustrated by several examples.
A shape-based inter-layer contours correspondence method for ICT-based reverse engineering.
Duan, Liming; Yang, Shangpeng; Zhang, Gui; Feng, Fei; Gu, Minghui
2017-01-01
The correspondence of a stack of planar contours in ICT (industrial computed tomography)-based reverse engineering, a key step in surface reconstruction, is difficult when the contours or topology of the object are complex. Given the regularity of industrial parts and similarity of the inter-layer contours, a specialized shape-based inter-layer contours correspondence method for ICT-based reverse engineering was presented to solve the above problem based on the vectorized contours. In this paper, the vectorized contours extracted from the slices consist of three graphical primitives: circles, arcs and segments. First, the correspondence of the inter-layer primitives is conducted based on the characteristics of the primitives. Second, based on the corresponded primitives, the inter-layer contours correspond with each other using the proximity rules and exhaustive search. The proposed method can make full use of the shape information to handle industrial parts with complex structures. The feasibility and superiority of this method have been demonstrated via the related experiments. This method can play an instructive role in practice and provide a reference for the related research.
Qualification of a 3D structured light sensor for a reverse engineering application
Guarato, Alexandre Z.; Loja, Alexandre C.; Pereira, Leonardo P.; Braga, Sergio L.; Trevilato, Thales R. B.
2016-11-01
This paper deals with the qualification of a 3D structured light scanning system for an application of reverse engineering of a mechanical part. As this white light scanner is an electro-optical device and based on the principle of optical triangulation, the measurement accuracy is affected by the measured part geometry and its position within the scanning window. The effects of the scan depth and the projected angle, characterizing the surface normal of the measured surface to the scanning point of view, on the measurement of accuracy are not considered in the standard calibration process of manufacturers and have been identified by experiments in the present work. The digitization errors are analyzed and characterized thanks to a measurement protocol based on quality indicators. Theses quality indicators are evaluated thanks to simple calibrated artifacts. The aim of this work is to redefine the ideal relative distance and relative angle for minimizing the digitizing errors in relation to those stated by the manufacturer for a reverse engineering application.
Reverse-engineering a watermark detector based on a more precise model
Yu, Jun; Craver, Scott
2010-01-01
Detection results obtained from an oracle can be used to reverse-engineer the underlying detector structure, or parameters thereof. In particular, if a detector uses a common structure like correlation or normalized correlation, detection results can be used to estimate feature space dimensionality, watermark strength, and detector threshold values. Previous estimation techniques used a simplistic but tractable model for a watermarked image in the detection cone of a normalized correlation detector; in particular a watermarked image is assumed to lie along the axis of the detection cone, essentially corresponding to an image of zero magnitude. This produced useful results for feature spaces of fewer dimensions, but increasingly imprecise estimates for larger feature spaces. In this paper we model the watermarked image properly as a sum of a cover vector and approximately orthogonal watermark vector, offsetting the image within the cone, which is the geometry of a detector using normalized correlation. This symmetry breaking produces a far more complex model which boils down to a quartic equation. Although it is infeasible to find its symbolic solution even with the aid of computer, our numerical analysis results show certain critical behavior which reveals the relationship between the attacking noise strength and the detector parameters. The critical behavior predicted by our model extends our reverse-engineering capability to the case of detectors with large feature space dimensions, which is not uncommon in multimedia watermarking algorithms.
Time Reversal in Subwavelength-Scaled Resonant Media: Beating the Diffraction Limit
Fabrice Lemoult
2011-01-01
Full Text Available Time reversal is a physical concept that can focus waves both spatially and temporally regardless of the complexity of the propagation medium. Time reversal mirrors have been demonstrated first in acoustics, then with electromagnetic waves, and are being intensively studied in many fields ranging from underwater communications to sensing. In this paper, we will review the principles of time reversal and in particular its ability to focus waves in complex media. We will show that this focusing effect depends on the complexity of the propagation medium rather than on the time reversal mirror itself. A modal approach will be utilized to explain the physical mechanism underlying the concept. A particular focus will be given on the possibility to break the diffraction barrier from the far field using time reversal. We will show that finite size media made out of coupled subwavelength resonators support modes which can radiate efficiently in the far field spatial information of the near field of a source. We will show through various examples that such a process, due to reversibility, permits to beat the diffraction limit using far field time reversal, and especially that this result occurs owing to the broadband inherent nature of time reversal.
Mingjian Sun
2015-01-01
Full Text Available Photoacoustic imaging is an innovative imaging technique to image biomedical tissues. The time reversal reconstruction algorithm in which a numerical model of the acoustic forward problem is run backwards in time is widely used. In the paper, a time reversal reconstruction algorithm based on particle swarm optimization (PSO optimized support vector machine (SVM interpolation method is proposed for photoacoustics imaging. Numerical results show that the reconstructed images of the proposed algorithm are more accurate than those of the nearest neighbor interpolation, linear interpolation, and cubic convolution interpolation based time reversal algorithm, which can provide higher imaging quality by using significantly fewer measurement positions or scanning times.
Nonlinear Time Reversal Acoustic Method of Friction Stir Weld Assessment Project
National Aeronautics and Space Administration — The goal of the project is demonstration of the feasibility of Friction Stir Weld (FSW) assessment by novel Nonlinear Time Reversal Acoustic (TRA) method. Time...
Fast time-reversible algorithms for molecular dynamics of rigid-body systems
Kajima, Yasuhiro; Hiyama, Miyabi; Ogata, Shuji; Kobayashi, Ryo; Tamura, Tomoyuki
2012-06-01
In this paper, we present time-reversible simulation algorithms for rigid bodies in the quaternion representation. By advancing a time-reversible algorithm [Y. Kajima, M. Hiyama, S. Ogata, and T. Tamura, J. Phys. Soc. Jpn. 80, 114002 (2011), 10.1143/JPSJ.80.114002] that requires iterations in calculating the angular velocity at each time step, we propose two kinds of iteration-free fast time-reversible algorithms. They are easily implemented in codes. The codes are compared with that of existing algorithms through demonstrative simulation of a nanometer-sized water droplet to find their stability of the total energy and computation speeds.
Insights gained from the reverse engineering of gene networks in keloid fibroblasts
Phan Toan
2011-05-01
Full Text Available Abstract Background Keloids are protrusive claw-like scars that have a propensity to recur even after surgery, and its molecular etiology remains elusive. The goal of reverse engineering is to infer gene networks from observational data, thus providing insight into the inner workings of a cell. However, most attempts at modeling biological networks have been done using simulated data. This study aims to highlight some of the issues involved in working with experimental data, and at the same time gain some insights into the transcriptional regulatory mechanism present in keloid fibroblasts. Methods Microarray data from our previous study was combined with microarray data obtained from the literature as well as new microarray data generated by our group. For the physical approach, we used the fREDUCE algorithm for correlating expression values to binding motifs. For the influence approach, we compared the Bayesian algorithm BANJO with the information theoretic method ARACNE in terms of performance in recovering known influence networks obtained from the KEGG database. In addition, we also compared the performance of different normalization methods as well as different types of gene networks. Results Using the physical approach, we found consensus sequences that were active in the keloid condition, as well as some sequences that were responsive to steroids, a commonly used treatment for keloids. From the influence approach, we found that BANJO was better at recovering the gene networks compared to ARACNE and that transcriptional networks were better suited for network recovery compared to cytokine-receptor interaction networks and intracellular signaling networks. We also found that the NFKB transcriptional network that was inferred from normal fibroblast data was more accurate compared to that inferred from keloid data, suggesting a more robust network in the keloid condition. Conclusions Consensus sequences that were found from this study are
Time complexity of tape reduction for reversible Turing machines
Axelsen, Holger Bock
2012-01-01
, it is known that the reduction from k tapes to 1 tape in general leads to a quadratic increase in time. For k to 2 tapes, a celebrated result shows that the time overhead can be reduced to a logarithmic factor. We show that identical results hold for multitape RTMs. This establishes that the structure...
Time reversibility from visibility graphs of non-stationary processes
Lacasa, Lucas
2015-01-01
Visibility algorithms are a family of methods to map time series into networks, with the aim of describing the structure of time series and their underlying dynamical properties in graph-theoretical terms. Here we explore some properties of both natural and horizontal visibility graphs associated to several non-stationary processes, and we pay particular attention to their capacity to assess time irreversibility. Non-stationary signals are (infinitely) irreversible by definition (independently of whether the process is Markovian or producing entropy at a positive rate), and thus the link between entropy production and time series irreversibility has only been explored in non-equilibrium stationary states. Here we show that the visibility formalism naturally induces a new working definition of time irreversibility, which allows to quantify several degrees of irreversibility for stationary and non-stationary series, yielding finite values that can be used to efficiently assess the presence of memory and off-equ...
Broken versus Non-Broken Time Reversal Symmetry: Irreversibility and Response
Sara Dal Cengio
2016-07-01
Full Text Available We review some approaches to macroscopic irreversibility from reversible microscopic dynamics, introducing the contribution of time dependent perturbations within the framework of recent developments in non-equilibrium statistical physics. We show that situations commonly assumed to violate the time reversal symmetry (presence of magnetic fields, rotating reference frames, and some time dependent perturbations in reality do not violate this symmetry, and can be treated with standard theories and within standard experimental protocols.
Ding, Shuai; Zang, Rui; Zou, Lianfeng; Wang, Bing-Zhong; Caloz, Christophe
2014-01-01
A novel time-reversal subwavelength transmission technique, based on pulse shaping circuits (PSCs), is proposed. This technique removes the need for complex or electrically large electromagnetic structures by generating channel diversity via pulse shaping instead of angular spectrum transformation. It is shown that, compared to our previous time-reversal system based on chirped delay lines, the PSC approach offers greater flexibility and larger possible numbers of channels, i.e. ultimately higher transmission throughput. The PSC based time-reversal system is also demonstrated experimentally.
Mitigating the effect of non-uniform loss on time reversal mirrors
Taddese, Biniyam Tesfaye; Ott, Edward; Anlage, Steven M
2012-01-01
Time reversal mirrors work perfectly only for lossless wave propagation. Here, the performance of time-reversal mirrors is quantitatively defined, and the adverse effect of dissipation on their performance is investigated. The technique of exponential amplification is proposed to overcome the effect of dissipation in the case of uniform loss distributions, and, to some extent, in the case of non-uniform loss distributions. A numerical model of a star graph was employed to test the applicability of this technique on realizations with various random spatial distributions of loss. The numerical results are also verified by an experimental result from an electromagnetic time-reversal mirror.
Time Reversal Self-Focusing in a Solid-Plate Waveguide
ZHANG Bi-Xing; WU Hao; WANG Cheng-Hao
2004-01-01
@@ Acoustic self-adaptive focusing in a solid-plate waveguide is theoretically and experimentally studied. The multipath effect exists in the solid plate. A pulse will be widened into a pulsed train and the waveform is distorted. The time-reversal mirrors are applied to study the self-adaptive focusing. The time-reversal effect can be characterized by the focusing gain and the ratio of the principal to the second lobe. It is found theoretically and experimentally that the time-reversal mirrors can compensate automatically for the waveform distortion caused by the multi-path effect.
Dutta, Gaurav
2013-08-20
Attenuation leads to distortion of amplitude and phase of seismic waves propagating inside the earth. Conventional acoustic and least-squares reverse time migration do not account for this distortion which leads to defocusing of migration images in highly attenuative geological environments. To account for this distortion, we propose to use the visco-acoustic wave equation for least-squares reverse time migration. Numerical tests on synthetic data show that least-squares reverse time migration with the visco-acoustic wave equation corrects for this distortion and produces images with better balanced amplitudes compared to the conventional approach. © 2013 SEG.
Measurement of Wave Chaotic Eigenfunctions in the Time-Reversal Symmetry-Breaking Crossover Regime
Chung, S H; Wu, D H; Bridgewater, A; Anlage, S M; Chung, Seok-Hwan; Gokirmak, Ali; Wu, Dong-Ho; Anlage, Steven M.
1999-01-01
We present experimental results on eigenfunctions of a wave chaotic system in the continuous crossover regime between time-reversal symmetric and time-reversal symmetry-broken states. The statistical properties of the eigenfunctions of a two-dimensional microwave resonator are analyzed as a function of an experimentally determined time-reversal symmetry breaking parameter. We test four theories of eigenfunction statistics in the crossover regime. We also find a universal correlation between the one-point and two-point statistical parameters for the crossover eigenfunctions.
Modeling planarian regeneration: a primer for reverse-engineering the worm.
Lobo, Daniel; Beane, Wendy S; Levin, Michael
2012-01-01
A mechanistic understanding of robust self-assembly and repair capabilities of complex systems would have enormous implications for basic evolutionary developmental biology as well as for transformative applications in regenerative biomedicine and the engineering of highly fault-tolerant cybernetic systems. Molecular biologists are working to identify the pathways underlying the remarkable regenerative abilities of model species that perfectly regenerate limbs, brains, and other complex body parts. However, a profound disconnect remains between the deluge of high-resolution genetic and protein data on pathways required for regeneration, and the desired spatial, algorithmic models that show how self-monitoring and growth control arise from the synthesis of cellular activities. This barrier to progress in the understanding of morphogenetic controls may be breached by powerful techniques from the computational sciences-using non-traditional modeling approaches to reverse-engineer systems such as planaria: flatworms with a complex bodyplan and nervous system that are able to regenerate any body part after traumatic injury. Currently, the involvement of experts from outside of molecular genetics is hampered by the specialist literature of molecular developmental biology: impactful collaborations across such different fields require that review literature be available that presents the key functional capabilities of important biological model systems while abstracting away from the often irrelevant and confusing details of specific genes and proteins. To facilitate modeling efforts by computer scientists, physicists, engineers, and mathematicians, we present a different kind of review of planarian regeneration. Focusing on the main patterning properties of this system, we review what is known about the signal exchanges that occur during regenerative repair in planaria and the cellular mechanisms that are thought to underlie them. By establishing an engineering-like style
Modeling planarian regeneration: a primer for reverse-engineering the worm.
Daniel Lobo
Full Text Available A mechanistic understanding of robust self-assembly and repair capabilities of complex systems would have enormous implications for basic evolutionary developmental biology as well as for transformative applications in regenerative biomedicine and the engineering of highly fault-tolerant cybernetic systems. Molecular biologists are working to identify the pathways underlying the remarkable regenerative abilities of model species that perfectly regenerate limbs, brains, and other complex body parts. However, a profound disconnect remains between the deluge of high-resolution genetic and protein data on pathways required for regeneration, and the desired spatial, algorithmic models that show how self-monitoring and growth control arise from the synthesis of cellular activities. This barrier to progress in the understanding of morphogenetic controls may be breached by powerful techniques from the computational sciences-using non-traditional modeling approaches to reverse-engineer systems such as planaria: flatworms with a complex bodyplan and nervous system that are able to regenerate any body part after traumatic injury. Currently, the involvement of experts from outside of molecular genetics is hampered by the specialist literature of molecular developmental biology: impactful collaborations across such different fields require that review literature be available that presents the key functional capabilities of important biological model systems while abstracting away from the often irrelevant and confusing details of specific genes and proteins. To facilitate modeling efforts by computer scientists, physicists, engineers, and mathematicians, we present a different kind of review of planarian regeneration. Focusing on the main patterning properties of this system, we review what is known about the signal exchanges that occur during regenerative repair in planaria and the cellular mechanisms that are thought to underlie them. By establishing an
Multi-Scale Analysis Based Curve Feature Extraction in Reverse Engineering
YANG Hongjuan; ZHOU Yiqi; CHEN Chengjun; ZHAO Zhengxu
2006-01-01
A sectional curve feature extraction algorithm based on multi-scale analysis is proposed for reverse engineering. The algorithm consists of two parts: feature segmentation and feature classification. In the first part, curvature scale space is applied to multi-scale analysis and original feature detection. To obtain the primary and secondary curve primitives, feature fusion is realized by multi-scale feature detection information transmission. In the second part: projection height function is presented based on the area of quadrilateral, which improved criterions of sectional curve feature classification. Results of synthetic curves and practical scanned sectional curves are given to illustrate the efficiency of the proposed algorithm on feature extraction. The consistence between feature extraction based on multi-scale curvature analysis and curve primitives is verified.
Modified high-accuracy 3D shape data conversion system for reverse engineering applications
Sitnik, Robert; Kujawinska, Malgorzata
2001-10-01
In the paper the sequential steps of reverse engineering based on the data gathered by full-field optical system are discussed. The compete conversion process of a cloud of point coordinates to CAD/CAM is presented. The triangulation algorithm, which automatically creates the triangle mesh from the input cloud of points is described. Each block of this algorithm is explained din details with special attention paid to the parameters controlling the quality of the data conversion process. The adaptive process of reducing the number of the triangles on the base of second derivative of local curvature of objects' surface is explained. The error analysis is discussed at each step of the cloud data processing in dependency of the algorithm initial parameters.
King, Gary; Pan, Jennifer; Roberts, Margaret E
2014-08-22
Existing research on the extensive Chinese censorship organization uses observational methods with well-known limitations. We conducted the first large-scale experimental study of censorship by creating accounts on numerous social media sites, randomly submitting different texts, and observing from a worldwide network of computers which texts were censored and which were not. We also supplemented interviews with confidential sources by creating our own social media site, contracting with Chinese firms to install the same censoring technologies as existing sites, and--with their software, documentation, and even customer support--reverse-engineering how it all works. Our results offer rigorous support for the recent hypothesis that criticisms of the state, its leaders, and their policies are published, whereas posts about real-world events with collective action potential are censored.
ANALYSIS AND RESEARCH OF COMPUTER-AIDED MODEL OF HIP JOINT BASED ON REVERSE ENGINEERING
Hu Xin; Xi Juntong; Jin Ye; Gu Dongyun; Dai Kerong
2003-01-01
Former research work about the modeling of hip joint focus on the upper segment of femoral, and assumes the acetabulum cup is sphere concave, and the acetabulum prostheses is semisphere. A method of acquiring the point data on the surface of the hipbone using the reverse engineering technology is presented. After analyzing the acetabulum surface fitting error, a rotation ellipsoid CAD model is applied to fit the acetabulum surface, and then optimization technique is used to find the geometric parameters of the model. The fitting error between the sphere and rotation ellipsoid is compared and gets the result that the fitting error of rotation ellipsoid is smaller than sphere, and the rotation ellipsoid can describe the shape of the acetabulum better.
Lin, Kuang; Husmeier, Dirk; Dondelinger, Frank; Mayer, Claus D; Liu, Hui; Prichard, Leighton; Salmond, George P C; Toth, Ian K; Birch, Paul R J
2010-01-01
The objective of the project reported in the present chapter was the reverse engineering of gene regulatory networks related to quorum sensing in the plant pathogen Pectobacterium atrosepticum from micorarray gene expression profiles, obtained from the wild-type and eight knockout strains. To this end, we have applied various recent methods from multivariate statistics and machine learning: graphical Gaussian models, sparse Bayesian regression, LASSO (least absolute shrinkage and selection operator), Bayesian networks, and nested effects models. We have investigated the degree of similarity between the predictions obtained with the different approaches, and we have assessed the consistency of the reconstructed networks in terms of global topological network properties, based on the node degree distribution. The chapter concludes with a biological evaluation of the predicted network structures.
Frolova A. O.
2012-06-01
Full Text Available Reverse engineering of gene regulatory networks is an intensively studied topic in Systems Biology as it reconstructs regulatory interactions between all genes in the genome in the most complete form. The extreme computational complexity of this problem and lack of thorough reviews on reconstruction methods of gene regulatory network is a significant obstacle to further development of this area. In this article the two most common methods for modeling gene regulatory networks are surveyed: Boolean and Bayesian networks. The mathematical description of each method is given, as well as several algorithmic approaches to modeling gene networks using these methods; the complexity of algorithms and the problems that arise during its implementation are also noted.
Neural network approach for modification and fitting of digitized data in reverse engineering
JU Hua(鞠华); WANG Wen(王文); XIE Jin (谢金); CHEN Zi-chen(陈子辰)
2004-01-01
Reverse engineering in the manufacturing field is a process in which the digitized data are obtained from an existing object model or a part of it, and then the CAD model is reconstructed. This paper presents an RBF neural network approach to modify and fit the digitized data. The centers for the RBF are selected by using the orthogonal least squares learning algorithm. A mathematically known surface is used for generating a number of samples for training the networks. The trained networks then generated a number of new points which were compared with the calculating points from the equations. Moreover, a series of practice digitizing curves are used to test the approach. The results showed that this approach is effective in modifying and fitting digitized data and generating data points to reconstruct the surface model.
Neural network approach for modification and fitting of digitized data in reverse engineering~
鞠华; 王文; 谢金; 陈子辰
2004-01-01
Reverse engineering in the manufacturing field is a process in which the digitized data are obtained from an existing object model or a part of it, and then the CAD model is reconstructed. This paper presents an RBF neural network approach to modify and fit the digitized data. The centers for the RBF are selected by using the orthogonal least squares learning algorithm. A mathematically known surface is used for generating a number of samples for training the networks. The trained networks then generated a number of new points which were compared with the calculating points from the equations. Moreover, a series of practice digitizing curves are used to test the approach. The results showed that this approach is effective in modifying and fitting digitized data and generating data points to reconstruct the surface model.
Engineered reversal of the β-oxidation cycle for the synthesis of fuels and chemicals.
Dellomonaco, Clementina; Clomburg, James M; Miller, Elliot N; Gonzalez, Ramon
2011-08-10
Advanced (long-chain) fuels and chemicals are generated from short-chain metabolic intermediates through pathways that require carbon-chain elongation. The condensation reactions mediating this carbon-carbon bond formation can be catalysed by enzymes from the thiolase superfamily, including β-ketoacyl-acyl-carrier protein (ACP) synthases, polyketide synthases, 3-hydroxy-3-methylglutaryl-CoA synthases, and biosynthetic thiolases. Pathways involving these enzymes have been exploited for fuel and chemical production, with fatty-acid biosynthesis (β-ketoacyl-ACP synthases) attracting the most attention in recent years. Degradative thiolases, which are part of the thiolase superfamily and naturally function in the β-oxidation of fatty acids, can also operate in the synthetic direction and thus enable carbon-chain elongation. Here we demonstrate that a functional reversal of the β-oxidation cycle can be used as a metabolic platform for the synthesis of alcohols and carboxylic acids with various chain lengths and functionalities. This pathway operates with coenzyme A (CoA) thioester intermediates and directly uses acetyl-CoA for acyl-chain elongation (rather than first requiring ATP-dependent activation to malonyl-CoA), characteristics that enable product synthesis at maximum carbon and energy efficiency. The reversal of the β-oxidation cycle was engineered in Escherichia coli and used in combination with endogenous dehydrogenases and thioesterases to synthesize n-alcohols, fatty acids and 3-hydroxy-, 3-keto- and trans-Δ(2)-carboxylic acids. The superior nature of the engineered pathway was demonstrated by producing higher-chain linear n-alcohols (C ≥ 4) and extracellular long-chain fatty acids (C > 10) at higher efficiency than previously reported. The ubiquitous nature of β-oxidation, aldehyde/alcohol dehydrogenase and thioesterase enzymes has the potential to enable the efficient synthesis of these products in other industrial organisms.
Joshi Anagha
2009-05-01
Full Text Available Abstract Background A myriad of methods to reverse-engineer transcriptional regulatory networks have been developed in recent years. Direct methods directly reconstruct a network of pairwise regulatory interactions while module-based methods predict a set of regulators for modules of coexpressed genes treated as a single unit. To date, there has been no systematic comparison of the relative strengths and weaknesses of both types of methods. Results We have compared a recently developed module-based algorithm, LeMoNe (Learning Module Networks, to a mutual information based direct algorithm, CLR (Context Likelihood of Relatedness, using benchmark expression data and databases of known transcriptional regulatory interactions for Escherichia coli and Saccharomyces cerevisiae. A global comparison using recall versus precision curves hides the topologically distinct nature of the inferred networks and is not informative about the specific subtasks for which each method is most suited. Analysis of the degree distributions and a regulator specific comparison show that CLR is 'regulator-centric', making true predictions for a higher number of regulators, while LeMoNe is 'target-centric', recovering a higher number of known targets for fewer regulators, with limited overlap in the predicted interactions between both methods. Detailed biological examples in E. coli and S. cerevisiae are used to illustrate these differences and to prove that each method is able to infer parts of the network where the other fails. Biological validation of the inferred networks cautions against over-interpreting recall and precision values computed using incomplete reference networks. Conclusion Our results indicate that module-based and direct methods retrieve largely distinct parts of the underlying transcriptional regulatory networks. The choice of algorithm should therefore be based on the particular biological problem of interest and not on global metrics which cannot be
The criterion for time symmetry of probabilistic theories and the reversibility of quantum mechanics
Holster, A. T.
2003-10-01
Physicists routinely claim that the fundamental laws of physics are 'time symmetric' or 'time reversal invariant' or 'reversible'. In particular, it is claimed that the theory of quantum mechanics is time symmetric. But it is shown in this paper that the orthodox analysis suffers from a fatal conceptual error, because the logical criterion for judging the time symmetry of probabilistic theories has been incorrectly formulated. The correct criterion requires symmetry between future-directed laws and past-directed laws. This criterion is formulated and proved in detail. The orthodox claim that quantum mechanics is reversible is re-evaluated. The property demonstrated in the orthodox analysis is shown to be quite distinct from time reversal invariance. The view of Satosi Watanabe that quantum mechanics is time asymmetric is verified, as well as his view that this feature does not merely show a de facto or 'contingent' asymmetry, as commonly supposed, but implies a genuine failure of time reversal invariance of the laws of quantum mechanics. The laws of quantum mechanics would be incompatible with a time-reversed version of our universe.
Lihong ZHU; Kun YIN; Qingyan WANG; Yong HUANG
2008-01-01
In order to satisfy operating requirements for constant core drilling technology in reverse circulation with hollow-through DTH,the power unit of G-3 engineering driller was ameliorated. The new one with dual channel drive shaft, achieved the perfect assemble with transmission structure of the original power unit. It could interconvert according to need by using two sets of drive shafts with direct and reverse circulation. The repacked G-3 engineering driller carried on experiment in the field test in Luanchuan molybdenum mine of Henan, whose effect was very good.
Time Reversal Acoustic Structural Health Monitoring Using Array of Embedded Sensors Project
National Aeronautics and Space Administration — Time Reversal Acoustic (TRA) structural health monitoring with an embedded sensor array represents a new approach to in-situ nondestructive evaluation of air-space...
Time reversal, fermion doubling, and the masses of lattice Dirac fermions in three dimensions
Herbut, Igor F.
2011-06-01
Motivated by recent examples of three-dimensional lattice Hamiltonians with massless Dirac fermions in their (bulk) spectrum, I revisit the problem of fermion doubling on bipartite lattices. The number of components of the Dirac fermion in a time-reversal and parity-invariant d-dimensional lattice system is determined by the minimal representation of the Clifford algebra of d+1 Hermitian Dirac matrices that allows a construction of the time-reversal operator with the square of unity, and it equals 2d for d=2 and 3. Possible mass terms for (spinless) Dirac fermions are listed and discussed. In three dimensions, there are altogether eight independent masses, out of which four are even and four are odd under time reversal. A specific violation of time-reversal symmetry that leads to (minimal) four-component massless Dirac fermion in three dimensions at low energies is constructed.
Necessary N-representability Constraints from Time-reversal Symmetry for Periodic Systems
Rubin, Nicholas C
2016-01-01
The variational calculation of the two-electron reduced density matrix (2-RDM) is extended to periodic molecular systems. If the 2-RDM theory is extended to the periodic case without consideration of time-reversal symmetry, however, it can yields energies that are significantly lower than the correct energies. We derive and implement linear constraints that enforce time-reversal symmetry on the 2-RDM without destroying its computationally favorable block-diagonal structure from translational invariance. Time-reversal symmetry is distinct from space-group or spin (SU(2)) symmetries which can be expressed by unitary transformations. The time-reversal symmetry constraints are demonstrated through calculations of the metallic hydrogen chain and the one-dimensional lithium hydride crystal.
Time Reversed Electromagnetics as a Novel Method for Wireless Power Transfer
Challa, Anu; Anlage, Steven M.; Tesla Team
Taking advantage of ray-chaotic enclosures, time reversal has been shown to securely transmit information via short-wavelength waves between two points, yielding noise at all other sites. In this presentation, we propose a method to adapt the signal-focusing technique to electromagnetic signals in order to transmit energy to portable devices. Relying only on the time-reversal invariance properties of waves, the technique is unencumbered by the inversely-proportional-to-distance path loss or precise orientation requirements of its predecessors, making it attractive for power transfer applications. We inject a short microwave pulse into a complex, wave-chaotic chamber and collect the resulting long time-domain signal at a designated transceiver. The signal is then time reversed and emitted from the collection site, collapsing as a time-reversed replica of the initial pulse at the injection site. When amplified, this reconstruction is robust, as measured through metrics of peak-to-peak voltage and energy transfer ratio. We experimentally demonstrate that time reversed collapse can be made on a moving target, and propose a way to selectively target devices through nonlinear time-reversal. University of Maryland Gemstone Team TESLA: Frank Cangialosi, Anu Challa, Tim Furman, Tyler Grover, Patrick Healey, Ben Philip, Brett Potter, Scott Roman, Andrew Simon, Liangcheng Tao, Alex Tabatabai.
Engine control system having pressure-based timing
Willi, Martin L.; Fiveland, Scott B.; Montgomery, David T.; Gong, Weidong
2011-10-04
A control system for an engine having a first cylinder and a second cylinder is disclosed having a first engine valve movable to regulate a fluid flow of the first cylinder and a first actuator associated with the first engine valve. The control system also has a second engine valve movable to regulate a fluid flow of the second cylinder and a sensor configured to generate a signal indicative of a pressure within the first cylinder. The control system also has a controller that is in communication with the first actuator and the sensor. The controller is configured to compare the pressure within the first cylinder with a desired pressure and selectively regulate the first actuator to adjust a timing of the first engine valve independently of the timing of the second engine valve based on the comparison.
Mechanism, time-reversal symmetry, and topology of superconductivity in noncentrosymmetric systems
Scheurer, M. S.
2016-05-01
We analyze the possible interaction-induced superconducting instabilities in noncentrosymmetric systems based on symmetries of the normal state. It is proven that pure electron-phonon coupling will always lead to a fully gapped superconductor that does not break time-reversal symmetry and is topologically trivial. We show that topologically nontrivial behavior can be induced by magnetic doping without gapping out the resulting Kramers pair of Majorana edge modes. In the case of superconductivity arising from the particle-hole fluctuations associated with a competing instability, the properties of the condensate crucially depend on the time-reversal behavior of the order parameter of the competing instability. When the order parameter preserves time-reversal symmetry, we obtain exactly the same properties as in the case of phonons. If it is odd under time reversal, the Cooper channel of the interaction will be fully repulsive leading to sign changes of the gap and making spontaneous time-reversal-symmetry breaking possible. To discuss topological properties, we focus on fully gapped time-reversal-symmetric superconductors and derive constraints on possible pairing states that yield necessary conditions for the emergence of topologically nontrivial superconductivity. These conditions might serve as a tool in the search for topological superconductors. We also discuss implications for oxide heterostructures and single-layer FeSe.
Santos, Vinicius Rafael N.; Teixeira, Fernando L.
2017-04-01
Ground penetrating radar (GPR) is a useful sensing modality for mapping and identification of underground infrastructure networks, such as metal and concrete pipes (gas, water or sewer), phone conduits or cables, and other buried objects. Due to the polarization-dependent response of typical targets, it is of interest to investigate the optimum antenna arrangement and/or combination of arrangements that maximize the detection and classification capabilities of polarimetric GPR imaging systems. Here, we provide a preliminary study of time-reversal-based techniques applied to target detection by GPR utilizing different relative orientations of linear-polarized antenna elements (with respect to each other, as well as to the targets). We modeled three different pipe materials (metallic, plastic and concrete) and GPR systems operating at center frequencies of 100 MHz and 200 MHz. Full-wave numerical simulations are adopted to account for mutual coupling between targets. This type of assessment study may contribute to the improvement of GPR data interpretation of infrastructure networks in urban area surveys and in other engineering studies.
Imaging Fracking Zones by Microseismic Reverse Time Migration for Downhole Microseismic Monitoring
Lin, Y.; Zhang, H.
2015-12-01
Hydraulic fracturing is an engineering tool to create fractures in order to better recover oil and gas from low permeability reservoirs. Because microseismic events are generally associated with fracturing development, microseismic monitoring has been used to evaluate the fracking process. Microseismic monitoring generally relies on locating microseismic events to understand the spatial distribution of fractures. For the multi-stage fracturing treatment, fractures created in former stages are strong scatterers in the medium and can induce strong scattering waves on the waveforms for microseismic events induced during later stages. In this study, we propose to take advantage of microseismic scattering waves to image fracking zones by using seismic reverse time migration method. For downhole microseismic monitoring that involves installing a string of seismic sensors in a borehole near the injection well, the observation geometry is actually similar to the VSP (vertical seismic profile) system. For this reason, we adapt the VSP migration method for the common shot gather to the common event gather. Microseismic reverse-time migration method involves solving wave equation both forward and backward in time for each microseismic event. At current stage, the microseismic RTM is based on 2D acoustic wave equation (Zhang and Sun, 2008), solved by the finite-difference method with PML absorbing boundary condition applied to suppress the reflections of artificial boundaries. Additionally, we use local wavefield decomposition instead of cross-correlation imaging condition to suppress the imaging noise. For testing the method, we create a synthetic dataset for a downhole microseismic monitoring system with multiple fracking stages. It shows that microseismic migration using individual event is able to clearly reveal the fracture zone. The shorter distance between fractures and the microseismic event the clearer the migration image is. By summing migration images for many
Engine control system having fuel-based timing
Willi, Martin L [Dunlap, IL; Fiveland, Scott B [Metamora, IL; Montgomery, David T [Edelstein, IL; Gong, Weidong [Dunlap, IL
2012-04-03
A control system for an engine having a cylinder is disclosed having an engine valve movable to regulate a fluid flow of the cylinder and an actuator associated with the engine valve. The control system also has a sensor configured to generate a signal indicative of an amount of an air/fuel mixture remaining within the cylinder after completion of a first combustion event and a controller in communication with the actuator and the sensor. The controller may be configured to compare the amount with a desired amount, and to selectively regulate the actuator to adjust a timing of the engine valve associated with a subsequent combustion event based on the comparison.
Experimental study on multiple-input/multiple-output communication with time reversal in deep ocean
Shimura, Takuya; Kida, Yukihiro; Deguchi, Mitsuyasu; Watanabe, Yoshitaka; Ochi, Hiroshi
2017-07-01
Multiple-input/multiple-output (MIMO) communication using adaptive time reversal is examined by comparing orthogonal frequency division multiplexing (OFDM) with simulated MIMO test signals by synthesizing experimental data in deep ocean. The experiment was carried out in a 1,100-m-depth area at a range of 10 km with a bandwidth of 500 ± 50 Hz. Although time variance is not included in analysis of OFDM, it is impossible to increase the numbers of MIMO channels with OFDM. On the other hand, with adaptive time reversal, it is possible to achieve 8 × 20 and 6 × 20 MIMO communication with binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK), respectively, in spite of time variance and input signal-to-noise ratio (SNR) degradation due to synthesized signals. Thus, it is demonstrated that adaptive time reversal shows a much better performance than OFDM in MIMO underwater acoustic communication.
Kim, W.; Kim, Y.; Min, D.; Oh, J.; Huh, C.; Kang, S.
2012-12-01
vertical CO2 migration at injection point, the reverse time migration yields better images than Kirchhoff migration does. On the other hand, Kirchhoff migration images horizontal CO2 migration clearer than the reverse time migration does. From these results, we can conclude that the reverse-time migration and Kirchhoff migration can complement with each other to describe the behavior of CO2 in the subsurface. Acknowledgement This work was financially supported by the Brain Korea 21 project of Energy Systems Engineering, the "Development of Technology for CO2 Marine Geological Storage" program funded by the Ministry of Land, Transport and Maritime Affairs (MLTM) of Korea and the Korea CCS R&D Center (KCRC) grant funded by the Korea government (Ministry of Education, Science and Technology) (No. 2012-0008926).
Time-lapse seismic within reservoir engineering
Oldenziel, T.
2003-01-01
Time-lapse 3D seismic is a fairly new technology allowing dynamic reservoir characterisation in a true volumetric sense. By investigating the differences between multiple seismic surveys, valuable information about changes in the oil/gas reservoir state can be captured. Its interpretation involves different disciplines, of which the main three are: reservoir management, rock physics, and seismics. The main challenge is expressed as "How to optimally benefit from time-lapse seismic". The chall...
REVERSE ENGINEERING IN MODELING OF AIRCRAFT PROPELLER BLADE - FIRST STEP TO PRODUCT OPTIMIZATION
Muhammad Yasir Anwar
2014-12-01
Full Text Available ABSTRACT: Propeller aircrafts have had many ups and downs throughout their use in the aviation history. Due to the current economic recession and price hikes in fuels, propeller aircrafts may yet again be a choice for aerial transport and has thus re-emerged as an active area for research. On modern propeller aircrafts old aluminum propellers are being replaced with fiber reinforced composite propellers. However, owing to their reliability, strength, and integrity, aluminum propellers are still used in military aircrafts. One of the challenges that engineers of these aircraft-type have had to deal with is the non-availability of engineering drawings of these propellers. It is practically impossible to carry out any study, research or modification on such propellers in the absence of correct CAD data. This article proposes a methodology wherein a CAD model of a C-130 aircraft propeller blade can be constructed using reverse engineering techniques. Such a model would help in future aerodynamic as well as structural analyses which includes investigation on structural integrity and the fluid dynamics characteristics of propeller blades. Different steps involved in this process are discussed; starting from laser scanning to obtain the cloud of points data and subsequently generating a CAD model in a commercial CAD software. The model is then imported into an analysis software where quality surface meshes are generated using tetrahedral elements. The purpose is to prepare a meshed model for future computational analysis including CFD (Computational Fluid Dynamics and FE (Finite Element analysis. ABSTRAK: Pesawat bebaling mempunyai tempoh pasang surutnya sepanjang penggunaanya dalam sejarah penerbangan. Kini disebabkan oleh kemelesetan ekonomi dan kenaikan harga minyak, pesawat bebaling mungkin akan merupakan pengangkutan udara pilihan dan seterusnya muncul semula sebagai ruangan aktif penyelidikan. Pada pesawat bebaling moden, bebaling aluminium yang
Time reversal focusing of elastic waves in plates for an educational demonstration.
Heaton, Christopher; Anderson, Brian E; Young, Sarah M
2017-02-01
The purpose of this research is to develop a visual demonstration of time reversal focusing of vibrations in a thin plate. Various plate materials are tested to provide optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the vibration coupling efficiency from a shaker to the plate are quantified to illustrate why a given plate provides the best spatially confined focus as well as the highest focal amplitude possible. A single vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing. Table salt is sprinkled onto the plate surface to allow visualization of the high amplitude, spatially localized time reversal focus; the salt is thrown upward only at the focal position. Spatial mapping of the vibration focusing on the plate using the SLDV is correlated to the visual salt jumping demonstration. The time reversal focusing is also used to knock over an object when the object is placed at the focal position; some discussion of optimal objects to use for this demonstration are given.
Application of Reverse Transcription-PCR and Real-Time PCR in Nanotoxicity Research
Mo, Yiqun; Wan, Rong; Zhang, Qunwei
2016-01-01
Reverse transcription-polymerase chain reaction (RT-PCR) is a relatively simple and inexpensive technique to determine the expression level of target genes and is widely used in biomedical science research including nanotoxicology studies for semiquantitative analysis. Real-time PCR allows for the detection of PCR amplification in the exponential growth phase of the reaction and is much more quantitative than traditional RT-PCR. Although a number of kits and reagents for RT-PCR and real-time PCR are commercially available, the basic principles are the same. Here, we describe the procedures for total RNA isolation by using TRI Reagent, for reverse transcription (RT) by M-MLV reverse transcriptase, and for PCR by GoTaq® DNA Polymerase. And real-time PCR will be performed on an iQ5 multicolor real-time PCR detection system by using iQ™ SYBR Green Supermix. PMID:22975959
Modelling and Comparative Performance Analysis of a Time-Reversed UWB System
Popovski K
2007-01-01
Full Text Available The effects of multipath propagation lead to a significant decrease in system performance in most of the proposed ultra-wideband communication systems. A time-reversed system utilises the multipath channel impulse response to decrease receiver complexity, through a prefiltering at the transmitter. This paper discusses the modelling and comparative performance of a UWB system utilising time-reversed communications. System equations are presented, together with a semianalytical formulation on the level of intersymbol interference and multiuser interference. The standardised IEEE 802.15.3a channel model is applied, and the estimated error performance is compared through simulation with the performance of both time-hopped time-reversed and RAKE-based UWB systems.
Time-lapse seismic within reservoir engineering
Oldenziel, T.
2003-01-01
Time-lapse 3D seismic is a fairly new technology allowing dynamic reservoir characterisation in a true volumetric sense. By investigating the differences between multiple seismic surveys, valuable information about changes in the oil/gas reservoir state can be captured. Its interpretation involves d
Time-lapse seismic within reservoir engineering
Oldenziel, T.
2003-01-01
Time-lapse 3D seismic is a fairly new technology allowing dynamic reservoir characterisation in a true volumetric sense. By investigating the differences between multiple seismic surveys, valuable information about changes in the oil/gas reservoir state can be captured. Its interpretation involves d
Time-lapse seismic within reservoir engineering
Oldenziel, T.
2003-01-01
Time-lapse 3D seismic is a fairly new technology allowing dynamic reservoir characterisation in a true volumetric sense. By investigating the differences between multiple seismic surveys, valuable information about changes in the oil/gas reservoir state can be captured. Its interpretation involves
Prestack reverse-time depth migration of arbitrarily wide-angle wave equations
HE Bing-shou; ZHANG Hui-xing; ZHANG Jing
2008-01-01
Based on arbitrarily wide-angle wave equations, a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques, a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is appficable of dip angle reflector imaging.
Yadav, Vinod Kumar; Kumar, Akinchan; Mann, Anita; Aggarwal, Suruchi; Kumar, Maneesh; Roy, Sumitabho Deb; Pore, Subrata Kumar; Banerjee, Rajkumar; Mahesh Kumar, Jerald; Thakur, Ram Krishna; Chowdhury, Shantanu
2014-01-01
Building molecular correlates of drug resistance in cancer and exploiting them for therapeutic intervention remains a pressing clinical need. To identify factors that impact drug resistance herein we built a model that couples inherent cell-based response toward drugs with transcriptomes of resistant/sensitive cells. To test this model, we focused on a group of genes called metastasis suppressor genes (MSGs) that influence aggressiveness and metastatic potential of cancers. Interestingly, modeling of 84 000 drug response transcriptome combinations predicted multiple MSGs to be associated with resistance of different cell types and drugs. As a case study, on inducing MSG levels in a drug resistant breast cancer line resistance to anticancer drugs caerulomycin, camptothecin and topotecan decreased by more than 50-60%, in both culture conditions and also in tumors generated in mice, in contrast to control un-induced cells. To our knowledge, this is the first demonstration of engineered reversal of drug resistance in cancer cells based on a model that exploits inherent cellular response profiles.
de Vries, Natalie Jane; Carlson, Jamie; Moscato, Pablo
2014-01-01
Online consumer behavior in general and online customer engagement with brands in particular, has become a major focus of research activity fuelled by the exponential increase of interactive functions of the internet and social media platforms and applications. Current research in this area is mostly hypothesis-driven and much debate about the concept of Customer Engagement and its related constructs remains existent in the literature. In this paper, we aim to propose a novel methodology for reverse engineering a consumer behavior model for online customer engagement, based on a computational and data-driven perspective. This methodology could be generalized and prove useful for future research in the fields of consumer behaviors using questionnaire data or studies investigating other types of human behaviors. The method we propose contains five main stages; symbolic regression analysis, graph building, community detection, evaluation of results and finally, investigation of directed cycles and common feedback loops. The ‘communities’ of questionnaire items that emerge from our community detection method form possible ‘functional constructs’ inferred from data rather than assumed from literature and theory. Our results show consistent partitioning of questionnaire items into such ‘functional constructs’ suggesting the method proposed here could be adopted as a new data-driven way of human behavior modeling. PMID:25036766
Natalie Jane de Vries
Full Text Available Online consumer behavior in general and online customer engagement with brands in particular, has become a major focus of research activity fuelled by the exponential increase of interactive functions of the internet and social media platforms and applications. Current research in this area is mostly hypothesis-driven and much debate about the concept of Customer Engagement and its related constructs remains existent in the literature. In this paper, we aim to propose a novel methodology for reverse engineering a consumer behavior model for online customer engagement, based on a computational and data-driven perspective. This methodology could be generalized and prove useful for future research in the fields of consumer behaviors using questionnaire data or studies investigating other types of human behaviors. The method we propose contains five main stages; symbolic regression analysis, graph building, community detection, evaluation of results and finally, investigation of directed cycles and common feedback loops. The 'communities' of questionnaire items that emerge from our community detection method form possible 'functional constructs' inferred from data rather than assumed from literature and theory. Our results show consistent partitioning of questionnaire items into such 'functional constructs' suggesting the method proposed here could be adopted as a new data-driven way of human behavior modeling.
Paraquat-Melanin Redox-Cycling: Evidence from Electrochemical Reverse Engineering.
Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; Panzella, Lucia; Alfieri, Maria Laura; Napolitano, Alessandra; Bentley, William E; Payne, Gregory F
2016-08-17
Parkinson's disease is a neurodegenerative disorder associated with oxidative stress and the death of melanin-containing neurons of the substantia nigra. Epidemiological evidence links exposure to the pesticide paraquat (PQ) to Parkinson's disease, and this link has been explained by a redox cycling mechanism that induces oxidative stress. Here, we used a novel electrochemistry-based reverse engineering methodology to test the hypothesis that PQ can undergo reductive redox cycling with melanin. In this method, (i) an insoluble natural melanin (from Sepia melanin) and a synthetic model melanin (having a cysteinyldopamine-melanin core and dopamine-melanin shell) were entrapped in a nonconducting hydrogel film adjacent to an electrode, (ii) the film-coated electrode was immersed in solutions containing PQ (putative redox cycling reductant) and a redox cycling oxidant (ferrocene dimethanol), (iii) sequences of input potentials (i.e., voltages) were imposed to the underlying electrode to systematically engage reductive and oxidative redox cycling, and (iv) output response currents were analyzed for signatures of redox cycling. The response characteristics of the PQ-melanin systems to various input potential sequences support the hypothesis that PQ can directly donate electrons to melanin. This observation of PQ-melanin redox interactions demonstrates an association between two components that have been individually linked to oxidative stress and Parkinson's disease. Potentially, melanin's redox activity could be an important component in understanding the etiology of neurological disorders such as Parkinson's disease.
Genetic Network Inference: From Co-Expression Clustering to Reverse Engineering
Dhaeseleer, Patrik; Liang, Shoudan; Somogyi, Roland
2000-01-01
Advances in molecular biological, analytical, and computational technologies are enabling us to systematically investigate the complex molecular processes underlying biological systems. In particular, using high-throughput gene expression assays, we are able to measure the output of the gene regulatory network. We aim here to review datamining and modeling approaches for conceptualizing and unraveling the functional relationships implicit in these datasets. Clustering of co-expression profiles allows us to infer shared regulatory inputs and functional pathways. We discuss various aspects of clustering, ranging from distance measures to clustering algorithms and multiple-duster memberships. More advanced analysis aims to infer causal connections between genes directly, i.e., who is regulating whom and how. We discuss several approaches to the problem of reverse engineering of genetic networks, from discrete Boolean networks, to continuous linear and non-linear models. We conclude that the combination of predictive modeling with systematic experimental verification will be required to gain a deeper insight into living organisms, therapeutic targeting, and bioengineering.
A Critical Analysis of a Hand Orthosis Reverse Engineering and 3D Printing Process
Gabriele Baronio
2016-01-01
Full Text Available The possibility to realize highly customized orthoses is receiving boost thanks to the widespread diffusion of low-cost 3D printing technologies. However, rapid prototyping (RP with 3D printers is only the final stage of patient personalized orthotics processes. A reverse engineering (RE process is in fact essential before RP, to digitize the 3D anatomy of interest and to process the obtained surface with suitable modeling software, in order to produce the virtual solid model of the orthosis to be printed. In this paper, we focus on the specific and demanding case of the customized production of hand orthosis. We design and test the essential steps of the entire production process with particular emphasis on the accurate acquisition of the forearm geometry and on the subsequent production of a printable model of the orthosis. The choice of the various hardware and software tools (3D scanner, modeling software, and FDM printer is aimed at the mitigation of the design and production costs while guaranteeing suitable levels of data accuracy, process efficiency, and design versatility. Eventually, the proposed method is critically analyzed so that the residual issues and critical aspects are highlighted in order to discuss possible alternative approaches and to derive insightful observations that could guide future research activities.
A Critical Analysis of a Hand Orthosis Reverse Engineering and 3D Printing Process
2016-01-01
The possibility to realize highly customized orthoses is receiving boost thanks to the widespread diffusion of low-cost 3D printing technologies. However, rapid prototyping (RP) with 3D printers is only the final stage of patient personalized orthotics processes. A reverse engineering (RE) process is in fact essential before RP, to digitize the 3D anatomy of interest and to process the obtained surface with suitable modeling software, in order to produce the virtual solid model of the orthosis to be printed. In this paper, we focus on the specific and demanding case of the customized production of hand orthosis. We design and test the essential steps of the entire production process with particular emphasis on the accurate acquisition of the forearm geometry and on the subsequent production of a printable model of the orthosis. The choice of the various hardware and software tools (3D scanner, modeling software, and FDM printer) is aimed at the mitigation of the design and production costs while guaranteeing suitable levels of data accuracy, process efficiency, and design versatility. Eventually, the proposed method is critically analyzed so that the residual issues and critical aspects are highlighted in order to discuss possible alternative approaches and to derive insightful observations that could guide future research activities. PMID:27594781
A Critical Analysis of a Hand Orthosis Reverse Engineering and 3D Printing Process.
Baronio, Gabriele; Harran, Sami; Signoroni, Alberto
2016-01-01
The possibility to realize highly customized orthoses is receiving boost thanks to the widespread diffusion of low-cost 3D printing technologies. However, rapid prototyping (RP) with 3D printers is only the final stage of patient personalized orthotics processes. A reverse engineering (RE) process is in fact essential before RP, to digitize the 3D anatomy of interest and to process the obtained surface with suitable modeling software, in order to produce the virtual solid model of the orthosis to be printed. In this paper, we focus on the specific and demanding case of the customized production of hand orthosis. We design and test the essential steps of the entire production process with particular emphasis on the accurate acquisition of the forearm geometry and on the subsequent production of a printable model of the orthosis. The choice of the various hardware and software tools (3D scanner, modeling software, and FDM printer) is aimed at the mitigation of the design and production costs while guaranteeing suitable levels of data accuracy, process efficiency, and design versatility. Eventually, the proposed method is critically analyzed so that the residual issues and critical aspects are highlighted in order to discuss possible alternative approaches and to derive insightful observations that could guide future research activities.
Three-Dimensional Geometrical Modelling of Wild Boar Head by Reverse Engineering Technology
Liang Xu; Min-xu Lin; Jian-qiao Li; Zhao-liang Wang; B. Chirende
2008-01-01
In this paper, a wild boar head was taken as the bionic research object for the development of new ridgers, a kind of plough."The reverse engineering technology was adopted to obtain the surface geometrical information of the head. Several three-dimensional (3D) point clouds of the head were captured first using a non-touch laser scanner, and an integrated point cloud was generated by aligning these point clouds using UG/Imageware. Then, the digital surface model of the head was rebuilt by means of CATIA. The characteristic curves of the surface model were analyzed. The results show that the average error between the rebuilt surface and the point cloud is -0.431 mm. The max curvature of the ridge on the neb of the head is 0.187 mm-1, and the max and rain Gauss curvatures on the surface are 0.008 mm-2 and -0.002 mm-2. These geometrical information are the essential parameters for biomimetics study of the ridger.
de Vries, Natalie Jane; Carlson, Jamie; Moscato, Pablo
2014-01-01
Online consumer behavior in general and online customer engagement with brands in particular, has become a major focus of research activity fuelled by the exponential increase of interactive functions of the internet and social media platforms and applications. Current research in this area is mostly hypothesis-driven and much debate about the concept of Customer Engagement and its related constructs remains existent in the literature. In this paper, we aim to propose a novel methodology for reverse engineering a consumer behavior model for online customer engagement, based on a computational and data-driven perspective. This methodology could be generalized and prove useful for future research in the fields of consumer behaviors using questionnaire data or studies investigating other types of human behaviors. The method we propose contains five main stages; symbolic regression analysis, graph building, community detection, evaluation of results and finally, investigation of directed cycles and common feedback loops. The 'communities' of questionnaire items that emerge from our community detection method form possible 'functional constructs' inferred from data rather than assumed from literature and theory. Our results show consistent partitioning of questionnaire items into such 'functional constructs' suggesting the method proposed here could be adopted as a new data-driven way of human behavior modeling.
Bineli, Aulus Roberto Romao; Gimenez Perez, Ana Paula; Bernardes, Luiz Fernando; Munhoz, Andre Luiz Jardini; Maciel Filho, Rubens [Universidade de Campinas (LOPCA/UNICAMP), SP (Brazil). School of Chemical Engineering. Laboratory of Optimization, Design and Advanced Process Control], Email: aulus@feq.unicamp.br
2010-07-01
The propose of this work is to present high precision microfabrication facilities using computer aided technologies as Reverse Engineering (RE) and Rapid Manufacturing (RM) to analyze, design and construct micro reactors to produce high content hydrogen gas. Micro reactors are very compact, have a high surface to volume ratio, exhibit enhanced heat and mass transfer rates, denotes extremely low pressure drop and allow improved thermal integration in the processes involved. The main goals of micro reactors are the optimization of conventional chemical plants and low footprint, opening different ways to research new process technologies and synthesis of new products. In this work, a microchannels plate and housing structure of these plates were fabricated using DMLS method (Direct Metal Laser Sintering). The plates were analyzed to verify the minimum thickness wall that machine can produce, and the housing structure were digitalized, using a 3D scanning, to perform a 3D inspection and to verify the deflection of the constructed part in comparison with original CAD design models. It was observed that DMLS systems are able to produce micro reactors and microchannels plates with high precision at different metallic materials. However, it is important to choose appropriate conditions to avoid residual stresses and consequently warping parts. (author)
Reverse engineering nuclear properties from rare earth abundances in the r process
Mumpower, M. R.; McLaughlin, G. C.; Surman, R.; Steiner, A. W.
2017-03-01
The bulk of the rare earth elements are believed to be synthesized in the rapid neutron capture process or r process of nucleosynthesis. The solar r-process residuals show a small peak in the rare earths around A∼ 160, which is proposed to be formed dynamically during the end phase of the r process by a pileup of material. This abundance feature is of particular importance as it is sensitive to both the nuclear physics inputs and the astrophysical conditions of the main r process. We explore the formation of the rare earth peak from the perspective of an inverse problem, using Monte Carlo studies of nuclear masses to investigate the unknown nuclear properties required to best match rare earth abundance sector of the solar isotopic residuals. When nuclear masses are changed, we recalculate the relevant β-decay properties and neutron capture rates in the rare earth region. The feedback provided by this observational constraint allows for the reverse engineering of nuclear properties far from stability where no experimental information exists. We investigate a range of astrophysical conditions with this method and show how these lead to different predictions in the nuclear properties influential to the formation of the rare earth peak. We conclude that targeted experimental campaigns in this region will help to resolve the type of conditions responsible for the production of the rare earth nuclei, and will provide new insights into the longstanding problem of the astrophysical site(s) of the r process.
Reverse engineering nuclear properties from rare earth abundances in the $r$ process
Mumpower, M R; Surman, R; Steiner, A W
2016-01-01
The bulk of the rare earth elements are believed to be synthesized in the rapid neutron capture process or $r$ process of nucleosynthesis. The solar $r$-process residuals show a small peak in the rare earths around $A\\sim 160$, which is proposed to be formed dynamically during the end phase of the $r$ process by a pileup of material. This abundance feature is of particular importance as it is sensitive to both the nuclear physics inputs and the astrophysical conditions of the main $r$ process. We explore the formation of the rare earth peak from the perspective of an inverse problem, using Monte Carlo studies of nuclear masses to investigate the unknown nuclear properties required to best match rare earth abundance sector of the solar isotopic residuals. When nuclear masses are changed, we recalculate the relevant $\\beta$-decay properties and neutron capture rates in the rare earth region. The feedback provided by this observational constraint allows for the reverse engineering of nuclear properties far from ...
Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch
Hedqvist, Anders; Rachlew-Källne, Elisabeth
1998-09-01
Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.
Swihert, John M
1958-01-01
A brief investigation of a target-type thrust reverser on a single-engine fighter model has been conducted in the Langley 16-foot transonic tunnel at Mach numbers from 0.20 to 1.05.At Mach numbers of 0.80, 0.92, and 1.05, a hydrogen peroxide turbojet-engine simulator was operated with the thrust reverser extended. The angle of attack was varied from 0 degrees to 5 degrees at these Mach numbers. The Reynolds number of the free stream, based on the mean aerodynamic chord, was about 5 x 10(6). It was estimated that reversed jet operations separated the model boundary-layer flow over the upper surface of the horizontal tail and upper part of the afterbody. This resulted in a positive pitch increment due to reversed jet operation. Jet-on operation also tended to stabilize the severe lateral oscillations which occurred with the reverser extended and the jet off. It appeared that these jet-off oscillations were the result of an alternating separation and reattachment of the flow on the rearmost portions of the fuselage afterbody.
Engineering applications of discrete-time optimal control
Vidal, Rene Victor Valqui; Ravn, Hans V.
1990-01-01
of some well-known and new results in discrete time optimal control methods applicable to practical problem solving within engineering. Emphasis is placed on dynamic programming, the classical maximum principle and generalized versions of the maximum principle for optimal control of discrete time systems......Many problems of design and operation of engineering systems can be formulated as optimal control problems where time has been discretisized. This is also true even if 'time' is not involved in the formulation of the problem, but rather another one-dimensional parameter. This paper gives a review...
Engineering applications of discrete-time optimal control
Vidal, Rene Victor Valqui; Ravn, Hans V.
1990-01-01
Many problems of design and operation of engineering systems can be formulated as optimal control problems where time has been discretisized. This is also true even if 'time' is not involved in the formulation of the problem, but rather another one-dimensional parameter. This paper gives a review...... of some well-known and new results in discrete time optimal control methods applicable to practical problem solving within engineering. Emphasis is placed on dynamic programming, the classical maximum principle and generalized versions of the maximum principle for optimal control of discrete time systems...
Short Baseline Positioning with an Improved Time Reversal Technique in a Multi-path Channel
Zhuang Li; Gang Qiao; Zongxin Sun; Haiyang Zhao; Ran Guo
2012-01-01
The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system.In this paper,the application of a time reversal mirror to the short baseline positioning system was investigated.The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment,which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing.The signal-to-noise ratio (SNR) of the time reversal operator greatly increased and could be obtained by ensonifying the water,The technique was less affected by the environment and therefore more applicable to a complex shallow water environment.Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.
Short baseline positioning with an improved time reversal technique in a multi-path channel
Li, Zhuang; Qiao, Gang; Sun, Zongxin; Zhao, Haiyang; Guo, Ran
2012-06-01
The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system. In this paper, the application of a time reversal mirror to the short baseline positioning system was investigated. The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment, which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing. The signal-to-noise ratio (SNR) of the time reversal operator greatly increased and could be obtained by ensonifying the water. The technique was less affected by the environment and therefore more applicable to a complex shallow water environment. Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.
Time reversal of parametrical driving and the stability of the parametrically excited pendulum
Stannarius, Ralf
2009-02-01
It is well known that the periodic driving of a parametrically excited pendulum can stabilize or destabilize its stationary states, depending upon the frequency, wave form, and amplitude of the parameter modulations. We discuss the effect of time reversal of the periodic driving function for the parametric pendulum at small elongations. Such a time reversal usually leads to different solutions of the equations of motion and to different stability properties of the system. Two interesting exceptions are discussed, and two conditions are formulated for which the character of the solutions of the system is not influenced by a time reversal of the driving function, even though the trajectories of the dynamic variables are different.
Structural health monitoring using time reversal and cracked rod spectral element
Lucena, R. L.; Dos Santos, J. M. C.
2016-10-01
Structural health monitoring (SHM) has received substantial attention in the last decades. Damage detection methods based on dynamic analysis seem to be appropriate to detect large damages, but fail for small ones. Alternative methods use elastic wave propagation allowing a quick and long range test. In this paper, a new approach based on the combination of Time Reversal Method (TRM) and Spectral Element Method (SEM) is proposed to perform structural damage detection. The main novelty is to combine wave-based spectral element model together with time reversal signal processing. Although the methodology is evaluated by numerical simulation, this combination of numerical modeling and time reversal signal processing can be applied as an experimental approach to provide a useful tool for damage detection. Simulated examples of the damage detection method using rod-like structures are illustrated and the results discussed and compared with those from literature.
Time-reversal Aharonov-Casher effect in mesoscopic rings with spin-orbit interaction
Zhu, Zhenyue; Wang, Yong; Xia, Ke; Xie, X. C.; Ma, Zhongshui
2007-09-01
The time-reversal Aharonov-Casher (AC) [Phys. Rev. Lett. 53, 319 (1984)] interference effect in the mesoscopic ring structures, based on the experiment in Phys. Rev. Lett. 97, 196803 (2006), is studied theoretically. The transmission curves are calculated from the scattering matrix formalism, and the time-reversal AC interference frequency is singled out from the Fourier spectra in numerical simulations. This frequency is in good agreement with analytical result. It is also shown that in the absence of magnetic field, the Altshuler-Aronov-Spivak type [JETP Lett. 33, 94 (1981)] (time reversal) AC interference is retained under the influence of strong disorder, while the Aharonov-Bohm type [Phys. Rev. 115, 485 (1959)] AC interference is suppressed.
Exploring the potentials and limitations of the time-reversal imaging of finite seismic sources
S. Kremers
2011-06-01
Full Text Available The characterisation of seismic sources with time-reversed wave fields is developing into a standard technique that has already been successful in numerous applications. While the time-reversal imaging of effective point sources is now well-understood, little work has been done to extend this technique to the study of finite rupture processes. This is despite the pronounced non-uniqueness in classic finite source inversions.
The need to better constrain the details of finite rupture processes motivates the series of synthetic and real-data time reversal experiments described in this paper. We address questions concerning the quality of focussing in the source area, the localisation of the fault plane, the estimation of the slip distribution and the source complexity up to which time-reversal imaging can be applied successfully. The frequency band for the synthetic experiments is chosen such that it is comparable to the band usually employed for finite source inversion.
Contrary to our expectations, we find that time-reversal imaging is useful only for effective point sources, where it yields good estimates of both the source location and the origin time. In the case of finite sources, however, the time-reversed field does not provide meaningful characterisations of the fault location and the rupture process. This result cannot be improved sufficiently with the help of different imaging fields, realistic modifications of the receiver geometry or weights applied to the time-reversed sources.
The reasons for this failure are manifold. They include the choice of the frequency band, the incomplete recording of wave field information at the surface, the excitation of large-amplitude surface waves that deteriorate the depth resolution, the absence of a sink that should absorb energy radiated during the later stages of the rupture process, the invisibility of small slip and the neglect of prior information concerning the fault
Standardization of Rocket Engine Pulse Time Parameters
Larin, Max E.; Lumpkin, Forrest E.; Rauer, Scott J.
2001-01-01
Plumes of bipropellant thrusters are a source of contamination. Small bipropellant thrusters are often used for spacecraft attitude control and orbit correction. Such thrusters typically operate in a pulse mode, at various pulse lengths. Quantifying their contamination effects onto spacecraft external surfaces is especially important for long-term complex-geometry vehicles, e.g. International Space Station. Plume contamination tests indicated the presence of liquid phase contaminant in the form of droplets. Their origin is attributed to incomplete combustion. Most of liquid-phase contaminant is generated during the startup and shutdown (unsteady) periods of thruster pulse. These periods are relatively short (typically 10-50 ms), and the amount of contaminant is determined by the thruster design (propellant valve response, combustion chamber size, thruster mass flow rate, film cooling percentage, dribble volume, etc.) and combustion process organization. Steady-state period of pulse is characterized by much lower contamination rates, but may be lengthy enough to significantly conh'ibute to the overall contamination effect. Because there was no standard methodology for thruster pulse time division, plume contamination tests were conducted at various pulse durations, and their results do not allow quantifying contaminant amounts from each portion of the pulse. At present, the ISS plume contamination model uses an assumption that all thrusters operate in a pulse mode with the pulse length being 100 ms. This assumption may lead to a large difference between the actual amounts of contaminant produced by the thruster and the model predictions. This paper suggests a way to standardize thruster startup and shutdown period definitions, and shows the usefulness of this approach to better quantify thruster plume contamination. Use of the suggested thruster pulse time-division technique will ensure methodological consistency of future thruster plume contamination test programs
SHORT GAMMA-RAY BURSTS IN THE ''TIME-REVERSAL'' SCENARIO
Ciolfi, Riccardo [Physics Department, University of Trento, Via Sommarive 14, I-38123 Trento (Italy); Siegel, Daniel M., E-mail: riccardo.ciolfi@unitn.it, E-mail: daniel.siegel@aei.mpg.de [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, D-14476 Potsdam-Golm (Germany)
2015-01-10
Short gamma-ray bursts (SGRBs) are among the most luminous explosions in the universe and their origin still remains uncertain. Observational evidence favors the association with binary neutron star or neutron star-black hole (NS-BH) binary mergers. Leading models relate SGRBs to a relativistic jet launched by the BH-torus system resulting from the merger. However, recent observations have revealed a large fraction of SGRB events accompanied by X-ray afterglows with durations ∼10{sup 2}-10{sup 5} s, suggesting continuous energy injection from a long-lived central engine, which is incompatible with the short (≲ 1 s) accretion timescale of a BH-torus system. The formation of a supramassive NS, resisting the collapse on much longer spin-down timescales, can explain these afterglow durations, but leaves serious doubts on whether a relativistic jet can be launched at the merger. Here we present a novel scenario accommodating both aspects, where the SGRB is produced after the collapse of a supramassive NS. Early differential rotation and subsequent spin-down emission generate an optically thick environment around the NS consisting of a photon-pair nebula and an outer shell of baryon-loaded ejecta. While the jet easily drills through this environment, spin-down radiation diffuses outward on much longer timescales and accumulates a delay that allows the SGRB to be observed before (part of) the long-lasting X-ray signal. By analyzing diffusion timescales for a wide range of physical parameters, we find delays that can generally reach ∼10{sup 5} s, compatible with observations. The success of this fundamental test makes this ''time-reversal'' scenario an attractive alternative to current SGRB models.
Time-quantifiable Monte Carlo method for simulating a magnetization-reversal process
Cheng, X. Z.; Jalil, M. B. A.; Lee, H. K.; Okabe, Y.
2005-09-01
We propose a time-quantifiable Monte Carlo (MC) method to simulate the thermally induced magnetization reversal for an isolated single domain particle system. The MC method involves the determination of density of states and the use of Master equation for time evolution. We derive an analytical factor to convert MC steps into real time intervals. Unlike a previous time-quantified MC method, our method is readily scalable to arbitrarily long time scales, and can be repeated for different temperatures with minimal computational effort. Based on the conversion factor, we are able to make a direct comparison between the results obtained from MC and Langevin dynamics methods and find excellent agreement between them. An analytical formula for the magnetization reversal time is also derived, which agrees very well with both numerical Langevin and time-quantified MC results, over a large temperature range and for parallel and oblique easy axis orientations.
Finite time exergoeconomic performance optimization of a thermoacoustic heat engine
Xuxian Kan, Lingen Chen, Fengrui Sun, Feng Wu
2011-01-01
Full Text Available Finite time exergoeconomic performance optimization of a generalized irreversible thermoacoustic heat engine with heat resistance, heat leakage, thermal relaxation, and internal dissipation is investigated in this paper. Both the real part and the imaginary part of the complex heat transfer exponent change the optimal profit rate versus efficiency relationship quantitatively. The operation of the generalized irreversible thermoacoustic engine is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the generalized irreversible thermoacoustic engine is performed by taking profit rate as the objective. The analytical formulas about the profit rate and thermal efficiency of the thermoacoustic engine are derived. Furthermore, the comparative analysis of the influences of various factors on the relationship between optimal profit rate and the thermal efficiency of the generalized irreversible thermoacoustic engine is carried out by detailed numerical examples. The optimal zone on the performance of the thermoacoustic heat engine is obtained by numerical analysis. The results obtained herein may be useful for the selection of the operation parameters for real thermoacoustic heat engines.
Enhancement of Time-Reversal Subwavelength Wireless Transmission Using Pulse Shaping
Ding, Shuai; Zou, Lianfeng; Wang, Bingzhong; Caloz, Christophe
2014-01-01
A novel time-reversal subwavelength transmission technique, based on pulse shaping circuits (PSCs), is proposed. Compared to previously reported approaches, this technique removes the need for complex or electrically large electromagnetic structures by generating channel diversity via pulse shaping instead of angular spectrum transformation. Moreover, the pulse shaping circuits (PSCs) are based on Radio Analog Signal Processing (R-ASP), and therefore do not suffer from the well-known issues of digital signal processing in ultrafast regimes. The proposed PSC time-reversal systems is mathematically shown to offer high channel discrimination under appropriate PSC design conditions, and is experimentally demonstrated for the case of two receivers.
Time-reversal focusing of an expanding soliton gas in disordered replicas
Fratalocchi, Andrea
2011-05-31
We investigate the properties of time reversibility of a soliton gas, originating from a dispersive regularization of a shock wave, as it propagates in a strongly disordered environment. An original approach combining information measures and spin glass theory shows that time-reversal focusing occurs for different replicas of the disorder in forward and backward propagation, provided the disorder varies on a length scale much shorter than the width of the soliton constituents. The analysis is performed by starting from a new class of reflectionless potentials, which describe the most general form of an expanding soliton gas of the defocusing nonlinear Schrödinger equation.
The $Z_2$ Index of Disordered Topological Insulators with Time Reversal Symmetry
Katsura, Hosho
2015-01-01
We study disordered topological insulators with time reversal symmetry. Relying on the noncommutative index theorem which relates the Chern number to the projection onto the Fermi sea and the magnetic flux operator, we give a precise definition of the $Z_2$ index which is a noncommutative analogue of the Atiyah-Singer $Z_2$ index. We prove that the noncommutative $Z_2$ index is robust against any time-reversal symmetric perturbation including disorder potentials as long as the spectral gap at the Fermi level does not close.
Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors
Schemm, E. R.; Levenson-Falk, E. M.; Kapitulnik, A.
2017-04-01
The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of 3He-B, all of the known or suspected chiral - that is to say time-reversal symmetry-breaking (TRSB) - superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.
Topology of time-reversal invariant energy bands with adiabatic structure
Gat, Omri
2015-01-01
We classify the topology of bands defined by the energy states of quantum systems with scale separation between slow and fast degrees of freedom, invariant under fermionic time reversal. Classical phase space transforms differently from momentum space under time reversal, and as a consequence the topology of adiabatic bands is different from that of Bloch bands. We show that bands defined over a two-dimensional phase space are classified by the Chern number, whose parity must be equal to the parity of the band rank. Even-rank bands are equivalently classified by the Kane-Mele index, an integer equal to one half the Chern number.
Study of self-focusing in underwater waveguide by time reversal method
ZHANG Bixing; WANG Chenghao; LU Minghui
2003-01-01
Acoustic wave time reversal self-focusing in underwater waveguide is studied. The acoustic wave time reversal is theoretically and experimentally investigated in a half-infinite fluid medium and a shallow fluid layer placed on a hard half-infinite solid medium, respectively.The ray approach method is adopted to study the far field of the acoustic field in theory, and the ultrasonic experiments have been carried out in laboratory to model the underwater waveguide.It is shown by theoretical and experimental results that the focusing gain can be improved by 12 dB or more.
A time reversal transmission approach for multi-user UWB communications
Nguyen, Tuan Hung; Kovacs Z., Istvan; Eggers, Patrick
2005-01-01
In this paper we propose and evaluate the performance of the time reversal technique in impulse radio UWB communications. The evaluation was based on measured channel impulse responses in the UWB frequency band of 3 to 5 GHz of a 4x1 MISO system with both vertical and horizontal polarization...... at the receiver. The results show that there is a great potential in combining time reversal and UWB technique with respect to both reducing the receiver complexity and improving the system performance. Simultaneous communication is illustrated with 5 users with a BER of less than $10^{-3}$ at an average SNR...
Time reverse modeling of acoustic emissions in a reinforced concrete beam.
Kocur, Georg Karl; Saenger, Erik H; Grosse, Christian U; Vogel, Thomas
2016-02-01
The time reverse modeling (TRM) is applied for signal-based acoustic emission (AE) analysis of reinforced concrete (RC) specimens. TRM uses signals obtained from physical experiments as input. The signals are re-emitted numerically into a structure in a time-reversed manner, where the wavefronts interfere and appear as dominant concentrations of energy at the origin of the AE. The experimental and numerical results presented for selected AE signals confirm that TRM is capable of localizing AE activity in RC caused by concrete cracking. The accuracy of the TRM results is corroborated by three-dimensional crack distributions obtained from X-ray computed tomography images.
Development of nuclear power plant real-time engineering simulator
LIN Meng; YANG Yan-Hua; ZHANG Rong-Hua; HU Rui
2005-01-01
A nuclear power plant real-time engineering simulator was developed based on general-purpose thermal-hydraulic system simulation code RELAP5. It main1y consists of three parts: improved thermal-hydraulic system simulation code RELAP5, control and protection system and human-machine interface. A normal transient of CHASHMA nuclear power plant turbine step load change from 100% to 90% of full power, was simulated by the engineering simulator as an application example. This paper presents structure and main features of the engineering simulator, and application results are shown and discussed.
On the Reverse Modeling of Vehicle Logo Based on Re-verse Engineering%基于逆向工程的车标逆向建模
苑丽
2014-01-01
Reverse engineering has been more and more widely used in modern product design and manufacturing. Taking a cer-tain vehicle logo as an example, with the two kinds of softwares Geomagic Studio and UG as the platform, this paper introduces the modeling process of the product. The main process includes the point cloud data processing of vehicle logo, point cloud trian-gular patching and curved surface reconstruction in the Geomagic Studio software, and then importing data into UG software to im-plement data reconstruction and complete the vehicle logo model. Through this example, the characteristics and applications of dif-ferent reverse engineering software are found, in order to provide references for reverse modeling.%逆向工程在现代产品设计制造中得到了越来越广泛的应用。本文以某款车车标为实例，以Geomagic Stu-dio及UG两种软件为平台，介绍了此产品的建模过程。主要过程包括在Geomagic Studio软件中进行车标点云数据的处理、点云三角面片化以及曲面的建构，然后将数据导入到UG软件中，进行了数据的重构，得到了完成的车标模型。通过此实例，可以看到不同逆向软件的特点及适应场合，为逆向建模提供参考。
Real-time embedded systems design principles and engineering practices
Fan, Xiaocong
2015-01-01
This book integrates new ideas and topics from real time systems, embedded systems, and software engineering to give a complete picture of the whole process of developing software for real-time embedded applications. You will not only gain a thorough understanding of concepts related to microprocessors, interrupts, and system boot process, appreciating the importance of real-time modeling and scheduling, but you will also learn software engineering practices such as model documentation, model analysis, design patterns, and standard conformance. This book is split into four parts to help you
Time Reversal Mirrors and Cross Correlation Functions in Acoustic Wave Propagation
Fishman, Louis; Jonsson, B. Lars G.; de Hoop, Maarten V.
2009-03-01
In time reversal acoustics (TRA), a signal is recorded by an array of transducers, time reversed, and then retransmitted into the configuration. The retransmitted signal propagates back through the same medium and retrofocuses on the source that generated the signal. If the transducer array is a single, planar (flat) surface, then this configuration is referred to as a planar, one-sided, time reversal mirror (TRM). In signal processing, for example, in active-source seismic interferometry, the measurement of the wave field at two distinct receivers, generated by a common source, is considered. Cross correlating these two observations and integrating the result over the sources yield the cross correlation function (CCF). Adopting the TRM experiments as the basic starting point and identifying the kinematically correct correspondences, it is established that the associated CCF signal processing constructions follow in a specific, infinite recording time limit. This perspective also provides for a natural rationale for selecting the Green's function components in the TRM and CCF expressions. For a planar, one-sided, TRM experiment and the corresponding CCF signal processing construction, in a three-dimensional homogeneous medium, the exact expressions are explicitly calculated, and the connecting limiting relationship verified. Finally, the TRM and CCF results are understood in terms of the underlying, governing, two-way wave equation, its corresponding time reversal invariance (TRI) symmetry, and the absence of TRI symmetry in the associated one-way wave equations, highlighting the role played by the evanescent modal contributions.
Reverse Engineering and Security Evaluation of Commercial Tags for RFID-Based IoT Applications.
Fernández-Caramés, Tiago M; Fraga-Lamas, Paula; Suárez-Albela, Manuel; Castedo, Luis
2016-12-24
The Internet of Things (IoT) is a distributed system of physical objects that requires the seamless integration of hardware (e.g., sensors, actuators, electronics) and network communications in order to collect and exchange data. IoT smart objects need to be somehow identified to determine the origin of the data and to automatically detect the elements around us. One of the best positioned technologies to perform identification is RFID (Radio Frequency Identification), which in the last years has gained a lot of popularity in applications like access control, payment cards or logistics. Despite its popularity, RFID security has not been properly handled in numerous applications. To foster security in such applications, this article includes three main contributions. First, in order to establish the basics, a detailed review of the most common flaws found in RFID-based IoT systems is provided, including the latest attacks described in the literature. Second, a novel methodology that eases the detection and mitigation of such flaws is presented. Third, the latest RFID security tools are analyzed and the methodology proposed is applied through one of them (Proxmark 3) to validate it. Thus, the methodology is tested in different scenarios where tags are commonly used for identification. In such systems it was possible to clone transponders, extract information, and even emulate both tags and readers. Therefore, it is shown that the methodology proposed is useful for auditing security and reverse engineering RFID communications in IoT applications. It must be noted that, although this paper is aimed at fostering RFID communications security in IoT applications, the methodology can be applied to any RFID communications protocol.
Jeong, Sanghyun
2017-07-25
Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Organic foulants on the RO membrane were also quantified and fractionized. The bacterial community structures in liquid (seawater and effluent) and biofilm (DMF and RO) samples were analyzed using 454-pyrosequencing. The DMF IV fed with the chlorinated seawater demonstrated the highest reductions of DOC including LMW-N as well as AOC among the other DMFs. The DMF IV was also effective in reducing organic foulants on the RO membrane surface. The bacterial community structure was grouped according to the sample phase (i.e., liquid and biofilm samples), sampling location (i.e., DMF and RO samples), and chlorination (chlorinated and non-chlorinated samples). In particular, the biofilm community in the DMF IV differed from the other DMF treatments, suggesting that chlorination exerted as stronger selective pressure than pH adjustment or coagulation on the biofilm community. In the DMF IV, several chemoorganotrophic chlorine-resistant biofilm-forming bacteria such as Hyphomonas, Erythrobacter, and Sphingomonas were predominant, and they may enhance organic carbon degradation efficiency. Diverse halophilic or halotolerant organic degraders were also found in other DMFs (i.e., DMF I, II, and III). Various kinds of dominant biofilm-forming bacteria were also investigated in RO membrane samples; the results provided possible candidates that cause biofouling when DMF process is applied as the pretreatment option for the RO process.
Reverse Engineering and Security Evaluation of Commercial Tags for RFID-Based IoT Applications
Fernández-Caramés, Tiago M.; Fraga-Lamas, Paula; Suárez-Albela, Manuel; Castedo, Luis
2016-01-01
The Internet of Things (IoT) is a distributed system of physical objects that requires the seamless integration of hardware (e.g., sensors, actuators, electronics) and network communications in order to collect and exchange data. IoT smart objects need to be somehow identified to determine the origin of the data and to automatically detect the elements around us. One of the best positioned technologies to perform identification is RFID (Radio Frequency Identification), which in the last years has gained a lot of popularity in applications like access control, payment cards or logistics. Despite its popularity, RFID security has not been properly handled in numerous applications. To foster security in such applications, this article includes three main contributions. First, in order to establish the basics, a detailed review of the most common flaws found in RFID-based IoT systems is provided, including the latest attacks described in the literature. Second, a novel methodology that eases the detection and mitigation of such flaws is presented. Third, the latest RFID security tools are analyzed and the methodology proposed is applied through one of them (Proxmark 3) to validate it. Thus, the methodology is tested in different scenarios where tags are commonly used for identification. In such systems it was possible to clone transponders, extract information, and even emulate both tags and readers. Therefore, it is shown that the methodology proposed is useful for auditing security and reverse engineering RFID communications in IoT applications. It must be noted that, although this paper is aimed at fostering RFID communications security in IoT applications, the methodology can be applied to any RFID communications protocol. PMID:28029119
Reverse Engineering and Security Evaluation of Commercial Tags for RFID-Based IoT Applications
Tiago M. Fernández-Caramés
2016-12-01
Full Text Available The Internet of Things (IoT is a distributed system of physical objects that requires the seamless integration of hardware (e.g., sensors, actuators, electronics and network communications in order to collect and exchange data. IoT smart objects need to be somehow identified to determine the origin of the data and to automatically detect the elements around us. One of the best positioned technologies to perform identification is RFID (Radio Frequency Identification, which in the last years has gained a lot of popularity in applications like access control, payment cards or logistics. Despite its popularity, RFID security has not been properly handled in numerous applications. To foster security in such applications, this article includes three main contributions. First, in order to establish the basics, a detailed review of the most common flaws found in RFID-based IoT systems is provided, including the latest attacks described in the literature. Second, a novel methodology that eases the detection and mitigation of such flaws is presented. Third, the latest RFID security tools are analyzed and the methodology proposed is applied through one of them (Proxmark 3 to validate it. Thus, the methodology is tested in different scenarios where tags are commonly used for identification. In such systems it was possible to clone transponders, extract information, and even emulate both tags and readers. Therefore, it is shown that the methodology proposed is useful for auditing security and reverse engineering RFID communications in IoT applications. It must be noted that, although this paper is aimed at fostering RFID communications security in IoT applications, the methodology can be applied to any RFID communications protocol.
Aspect-oriented software reverse engineering%面向侧面的软件逆向工程
苏旸; 李凡; 胡圣明; 陈平
2006-01-01
To solve the identification and comprehension problem of crosscutting concerns in existing legacy software system, a framework of aspect-oriented software reverse engineering is proposed. An approach on re-modularizing traversal features of legacy system is presented based on various unified modeling language (UML) diagrams. While modeling crosscutting concerns in UML use case diagrams, the non-functional requirements that affect several use case modules can be enveloped into aspect modules with a stereotype mechanism. The recurring message transmission patterns can be re-modularized as aspects in UML sequence diagrams with UML collaborations. Standard UML activity diagram notations are extended and modified by node fusion and addition, which support the graphical composition operation between crosscutting behaviors and primary business rules of concurrent systems. Case study indicates that traversal features of software system can be extracted and re-modularized from various perspectives in aspect-oriented reverse engineering,which improves comprehensibility and maintainability of legacy systems.
Status report on a real time Engine Diagnostics Console for rocket engine exhaust plume monitoring
Bircher, F. E.; Gardner, D. G.; Vandyke, D. B.; Harris, A. B.; Chenevert, D. J.
1990-01-01
This paper describes the work done on the Engine Diagnostics Console during the past year of development at Stennis Space Center. The Engine Diagnostics Console (EDC) is a hardware and software package which provides near real time monitoring of rocket engine exhaust plume emissions during ground testing. The long range goal of the EDC development program is to develop an instrument that can detect engine degradation leading to catastrophic failure, and respond by taking preventative measures. The immediate goal for the past year's effort is the ability to process spectral data, taken from a rocket engine's exhaust plume, and to identify in an automated and high speed manner, the elemental species and multielemental materials that are present in the exhaust plume.
On time-reversal anomaly of 2+1d topological phases
Tachikawa, Yuji
2016-01-01
We describe a method to find the anomaly of the time-reversal symmetry of 2+1d topological quantum field theories, by computing the fractional anomalous momentum on the cross-cap background. This allows us, for example, to identify the parameter $\
Agrahari, J K; Kapuria, S
2016-08-01
To develop an effective baseline-free damage detection strategy using the time-reversal process (TRP) of Lamb waves in thin walled structures, it is essential to develop a good understanding of the parameters that affect the amplitude dispersion and consequently the time reversibility of the Lamb wave signal. In this paper, the effects of adhesive layer between the transducers and the host plate, the tone burst count of the excitation signal, the plate thickness, and the piezoelectric transducer thickness on the time reversibility of Lamb waves in metallic plates are studied using experiments and finite element simulations. The effect of adhesive layer on the forward propagation response and frequency tuning has been also studied. The results show that contrary to the general expectation, the quality of the reconstruction of the input signal after the TRP may increase with the increase in the adhesive layer thickness at certain frequency ranges. Similarly, an increase in the tone burst count resulting in a narrowband signal does not necessarily enhance the time reversibility at all frequencies, contrary to what has been reported earlier. For a given plate thickness, a thinner transducer yields a better reconstruction, but for a given transducer thickness, the similarity of the reconstructed signal may not be always higher for a thicker plate. It is important to study these effects to achieve the best quality of reconstruction in undamaged plates, for effective damage detection.
Norbury, John W.
1989-01-01
The invariance of classical electromagnetism under charge-conjugation, parity, and time-reversal (CPT) is studied by considering the motion of a charged particle in electric and magnetic fields. Upon applying CPT transformations to various physical quantities and noting that the motion still behaves physically demonstrates invariance.
The nucleon electric dipole form factor from dimension-six time-reversal violation
de Vries, J.; Mereghetti, E.; Timmermans, R. G. E.; van Kolck, U.
2011-01-01
We calculate the electric dipole form factor of the nucleon that arises as a low-energy manifestation of time-reversal violation in quark-gluon interactions of effective dimension 6: the quark electric and chromoelectric dipole moments, and the gluon chromoelectric dipole moment. We use the framewor
The effective chiral Lagrangian from dimension-six parity and time-reversal violation
de Vries, J.; Mereghetti, E.; Timmermans, R.G.E.; van Kolck, U.
2013-01-01
We classify the parity- and time-reversal-violating operators involving quark and gluon fields that have effective dimension six: the quark electric dipole moment, the quark and gluon chromo-electric dipole moments, and four four-quark operators. We construct the effective chiral Lagrangian with had
More on time-reversal anomaly of 2+1d topological phases
Tachikawa, Yuji
2016-01-01
We prove an explicit formula conjectured recently by Wang and Levin for the anomaly of time-reversal symmetry in 2+1 dimensional fermionic topological quantum field theories. The crucial step is to determine the crosscap state in terms of the modular S matrix and $\\mathsf{T}^2$ eigenvalues, generalizing the recent analysis by Barkeshli et al. in the bosonic case.
Optimal One Bit Time Reversal For UWB Impulse Radio In Multi-User Wireless Communications
Nguyen, Hung Tuan
2008-01-01
In this paper, with the purpose of further reducing the complexity of the system, while keeping its temporal and spatial focusing performance, we investigate the possibility of using optimal one bit time reversal (TR) system for impulse radio ultra wideband multi-user wireless communications...
Test of the Universality of Naive-Time-Reversal-Odd Fragmentation Functions
Boer, Daniel; Kang, Zhong-Bo; Vogelsang, Werner; Yuan, Feng
2010-01-01
We investigate the "spontaneous'' hyperon transverse polarization in e(+)e(-) annihilation and semi-inclusive deep inelastic scattering processes as a test of the universality of the naive-time-reversal-odd transverse momentum dependent fragmentation functions. We find that universality implies defi
Multi-path propagation of acoustical wave and time reversal field in a solid plate
WU Hao; ZHANG Bixing; WANG Chenghao
2005-01-01
The multi-path effect of the acoustical wave in a solid plate is studied. The multireflection and wave conversion of the cylindrical compressional and shear waves, which are excited by an infinite strip on a free surface of the solid plate, are analyzed thoroughly by the far-field approximation method. The concise analytical representations of the cylindrical waves are obtained. The time reversal processing is then applied to the propagation of the cylindrical waves and analyzed theoretically and experimentally. It is shown that the waves coming from different array elements and different paths all arrive at the original place after the time reversal operation. It indicates that the time reversal can compensate automatically the wave aberration caused by the multi-path effect. The self-adaptive focusing of the time reversal field is also analyzed quantificationally by the focusing gain and the ratio of the principal to the second lobe. The effects of the focus position and the aperture of the transducer array on the focused field are also investigated. It shows that theoretical and experimental results are consistent to each other very well.
Evaluation of massive MIMO systems using time-reversal beamforming technique
Mbeutcha, Marie; Fan, Wei; Hejselbæk, Johannes
2016-01-01
In this paper, we investigate the performance of a massive MIMO system using the time-reversal beamforming technique. The massive MIMO channels are simulated with ray-tracing at 3.5 GHz with a 200 MHz-bandwidth. We use a 64-element uniform cylindrical array as base station (BS) and we equip two...
Stopping and time reversal of light in dynamic photonic structures via Bloch oscillations.
Longhi, Stefano
2007-02-01
It is theoretically shown that storage and time reversal of light pulses can be achieved in a coupled-resonator optical waveguide by dynamic tuning of the cavity resonances without maintaining the translational invariance of the system. The control exploits the Bloch oscillation motion of a light pulse in the presence of a refractive index ramp, and it is therefore rather different from the mechanism of adiabatic band compression and reversal proposed by Yanik and Fan in recent works [Phys. Rev. Lett., 92, 083901 (2004); 93, 173903 (2004)].
Fluctuation theorem, nonlinear response, and the regularity of time reversal symmetry
Porta, Marcello
2010-06-01
The Gallavotti-Cohen fluctuation theorem (FT) implies an infinite set of identities between correlation functions that can be seen as a generalization of Green-Kubo formula to the nonlinear regime. As an application, we discuss a perturbative check of the FT relation through these identities for a simple Anosov reversible system; we find that the lack of differentiability of the time reversal operator implies a violation of the Gallavotti-Cohen fluctuation relation. Finally, a brief comparison to Lebowitz-Spohn FT is reported.
High spatial resolution imaging for structural health monitoring based on virtual time reversal
Cai, Jian; Shi, Lihua; Yuan, Shenfang; Shao, Zhixue
2011-05-01
Lamb waves are widely used in structural health monitoring (SHM) of plate-like structures. Due to the dispersion effect, Lamb wavepackets will be elongated and the resolution for damage identification will be strongly affected. This effect can be automatically compensated by the time reversal process (TRP). However, the time information of the compensated waves is also removed at the same time. To improve the spatial resolution of Lamb wave detection, virtual time reversal (VTR) is presented in this paper. In VTR, a changing-element excitation and reception mechanism (CERM) rather than the traditional fixed excitation and reception mechanism (FERM) is adopted for time information conservation. Furthermore, the complicated TRP procedure is replaced by simple signal operations which can make savings in the hardware cost for recording and generating the time-reversed Lamb waves. After the effects of VTR for dispersive damage scattered signals are theoretically analyzed, the realization of VTR involving the acquisition of the transfer functions of damage detecting paths under step pulse excitation is discussed. Then, a VTR-based imaging method is developed to improve the spatial resolution of the delay-and-sum imaging with a sparse piezoelectric (PZT) wafer array. Experimental validation indicates that the damage scattered wavepackets of A0 mode in an aluminum plate are partly recompressed and focalized with their time information preserved by VTR. Both the single damage and the dual adjacent damages in the plate can be clearly displayed with high spatial resolution by the proposed VTR-based imaging method.
Katrin Vogt
Full Text Available Animals need to associate different environmental stimuli with each other regardless of whether they temporally overlap or not. Drosophila melanogaster displays olfactory trace conditioning, where an odor is followed by electric shock reinforcement after a temporal gap, leading to conditioned odor avoidance. Reversing the stimulus timing in olfactory conditioning results in the reversal of memory valence such that an odor that follows shock is later on approached (i.e. relief conditioning. Here, we explored the effects of stimulus timing on memory in another sensory modality, using a visual conditioning paradigm. We found that flies form visual memories of opposite valence depending on stimulus timing and can associate a visual stimulus with reinforcement despite being presented with a temporal gap. These results suggest that associative memories with non-overlapping stimuli and the effect of stimulus timing on memory valence are shared across sensory modalities.
New results for time reversed symplectic dynamic systems and quadratic functionals
Roman Simon Hilscher
2012-05-01
Full Text Available In this paper, we examine time scale symplectic (or Hamiltonian systems and the associated quadratic functionals which contain a forward shift in the time variable. Such systems and functionals have a close connection to Jacobi systems for calculus of variations and optimal control problems on time scales. Our results, among which we consider the Reid roundabout theorem, generalize the corresponding classical theory for time reversed discrete symplectic systems, as well as they complete the recently developed theory of time scale symplectic systems.
Multi-scale symbolic time reverse analysis of gas-liquid two-phase flow structures
Wang, Hongmei; Zhai, Lusheng; Jin, Ningde; Wang, Youchen
Gas-liquid two-phase flows are widely encountered in production processes of petroleum and chemical industry. Understanding the dynamic characteristics of multi-scale gas-liquid two-phase flow structures is of great significance for the optimization of production process and the measurement of flow parameters. In this paper, we propose a method of multi-scale symbolic time reverse (MSTR) analysis for gas-liquid two-phase flows. First, through extracting four time reverse asymmetry measures (TRAMs), i.e. Euclidean distance, difference entropy, percentage of constant words and percentage of reversible words, the time reverse asymmetry (TRA) behaviors of typical nonlinear systems are investigated from the perspective of multi-scale analysis, and the results show that the TRAMs are sensitive to the changing of dynamic characteristics underlying the complex nonlinear systems. Then, the MSTR analysis is used to study the conductance signals from gas-liquid two-phase flows. It is found that the multi-scale TRA analysis can effectively reveal the multi-scale structure characteristics and nonlinear evolution properties of the flow structures.
The Science of Solubility: Using Reverse Engineering to Brew a Perfect Cup of Coffee
West, Andrew B.; Sickel, Aaron J.; Cribbs, Jennifer D.
2015-01-01
The Next Generation Science Standards call for the integration of science and engineering. Often, the introduction of engineering activities occurs after instruction in the science content. That is, engineering is used as a way for students to elaborate on science ideas that have already been explored. However, using only this sequence of…
The Science of Solubility: Using Reverse Engineering to Brew a Perfect Cup of Coffee
West, Andrew B.; Sickel, Aaron J.; Cribbs, Jennifer D.
2015-01-01
The Next Generation Science Standards call for the integration of science and engineering. Often, the introduction of engineering activities occurs after instruction in the science content. That is, engineering is used as a way for students to elaborate on science ideas that have already been explored. However, using only this sequence of…
Real-time Simulation of Turboprop Engine Control System
Sheng, Hanlin; Zhang, Tianhong; Zhang, Yi
2017-05-01
On account of the complexity of turboprop engine control system, real-time simulation is the technology, under the prerequisite of maintaining real-time, to effectively reduce development cost, shorten development cycle and avert testing risks. The paper takes RT-LAB as a platform and studies the real-time digital simulation of turboprop engine control system. The architecture, work principles and external interfaces of RT-LAB real-time simulation platform are introduced firstly. Then based on a turboprop engine model, the control laws of propeller control loop and fuel control loop are studied. From that and on the basis of Matlab/Simulink, an integrated controller is designed which can realize the entire process control of the engine from start-up to maximum power till stop. At the end, on the basis of RT-LAB platform, the real-time digital simulation of the designed control system is studied, different regulating plans are tried and more ideal control effects have been obtained.
Real-time earthquake monitoring using a search engine method
Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong
2014-12-01
When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquake’s parameters in <1 s after receiving the long-period surface wave data.
Real-time earthquake monitoring using a search engine method.
Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong
2014-12-04
When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquake's parameters in <1 s after receiving the long-period surface wave data.
Real Time Engineering Analysis Based on a Generative Component Implementation
Kirkegaard, Poul Henning; Klitgaard, Jens
2007-01-01
The present paper outlines the idea of a conceptual design tool with real time engineering analysis which can be used in the early conceptual design phase. The tool is based on a parametric approach using Generative Components with embedded structural analysis. Each of these components uses...... without jumping from aesthetics to structural digital design tools and back, but to work with both simultaneously and real time. The engineering level of knowledge is incorporated at a conceptual thinking level, i.e. qualitative information is used in stead of using quantitative information. An example...... with a static determinate roof structure modelled by beam components is given. The example outlines the idea of the tool for conceptual design in early phase of a multidisciplinary design process between architecture and structural engineering....
Test of feasibility of a novel high precision test of time reversal invariance
Samuel, Deepak
2007-07-01
The first results of a feasibility test of a novel high precision test of time reversal invariance are reported. The Time Reversal Invariance test at COSY (TRIC) was planned to measure the time reversal violating observable A{sub y,xz} with an accuracy of 10{sup -6} in proton-deuteron (p-d) scattering. A novel technique for measuring total cross sections is introduced and the achievable precision of this measuring technique is tested. The correlation coefficient A{sub y,y} in p-d scattering fakes a time-reversal violating effect. This work reports the feasibility test of the novel method in the measurement of A{sub y,y} in p-p scattering. The first step in the experimental design was the development of a hard real-time data acquisition system. To meet stringent latency requirements, the capabilities of Windows XP had to be augmented with a real-time subsystem. The remote control feature of the data acquisition enables users to operate it from any place via an internet connection. The data acquisition proved its reliability in several beam times without any failures. The analysis of the data showed the presence of 1/f noise which substantially limits the quality of our measurements. The origin of 1/f noise was traced and found to be the Barkhausen noise from the ferrite core of the beam current transformer (BCT). A global weighted fitting technique based on a modified Wiener-Khinchin method was developed and used to suppress the influence of 1/f noise, which increased the error bar of the results by a factor 3. This is the only deviation from our expectations. The results are presented and discussed. (orig.)
Engine Control Improvement through Application of Chaotic Time Series Analysis
Green, J.B., Jr.; Daw, C.S.
2003-07-15
The objective of this program was to investigate cyclic variations in spark-ignition (SI) engines under lean fueling conditions and to develop options to reduce emissions of nitrogen oxides (NOx) and particulate matter (PM) in compression-ignition direct-injection (CIDI) engines at high exhaust gas recirculation (EGR) rates. The CIDI activity builds upon an earlier collaboration between ORNL and Ford examining combustion instabilities in SI engines. Under the original CRADA, the principal objective was to understand the fundamental causes of combustion instability in spark-ignition engines operating with lean fueling. The results of this earlier activity demonstrated that such combustion instabilities are dominated by the effects of residual gas remaining in each cylinder from one cycle to the next. A very simple, low-order model was developed that explained the observed combustion instability as a noisy nonlinear dynamical process. The model concept lead to development of a real-time control strategy that could be employed to significantly reduce cyclic variations in real engines using existing sensors and engine control systems. This collaboration led to the issuance of a joint patent for spark-ignition engine control. After a few years, the CRADA was modified to focus more on EGR and CIDI engines. The modified CRADA examined relationships between EGR, combustion, and emissions in CIDI engines. Information from CIDI engine experiments, data analysis, and modeling were employed to identify and characterize new combustion regimes where it is possible to simultaneously achieve significant reductions in NOx and PM emissions. These results were also used to develop an on-line combustion diagnostic (virtual sensor) to make cycle-resolved combustion quality assessments for active feedback control. Extensive experiments on engines at Ford and ORNL led to the development of the virtual sensor concept that may be able to detect simultaneous reductions in NOx and PM
Fast binarized time-reversed adapted-perturbation (b-TRAP) optical focusing inside scattering media
Ma, Cheng; Liu, Yan; Wang, Lihong V
2015-01-01
Light scattering inhibits high-resolution optical imaging, manipulation and therapy deep inside biological tissue by preventing focusing. To form deep foci, wavefront-shaping and time-reversal techniques that break the optical diffusion limit have been developed. For in vivo applications, such focusing must provide high gain, high speed, and a large number of spatial modes. However, none of the previous techniques meet these requirements simultaneously. Here, we overcome this challenge by rapidly measuring the perturbed optical field within a single camera exposure followed by adaptively time-reversing the phase-binarized perturbation. Consequently, a phase-conjugated wavefront is synthesized within a millisecond, two orders of magnitude shorter than the digitally achieved record. We demonstrated real-time focusing in dynamic scattering media, and extended laser speckle contrast imaging to new depths. The unprecedented combination of fast response, high gain, and large mode count makes this work a major strid...
Scalable time reversal of Raman echo quantum memory and quantum waveform conversion of light pulse
Moiseev, E S
2013-01-01
We have found the new hidden symmetry of time reversal light-atom interaction in the photon echo quantum memory with Raman atomic transition. The time-reversed quantum memory provides generalized condition for ideal compression/decompression of time duration and wavelength conversion of the input light pulse. Based on a general analytical approach to this scheme, we have studied the optimal conditions of the light field compression/decompression in resonant atomic systems characterized by realistic spectral properties. The demonstrated effective quantum conversion of the light waveform and wavelength are also discussed for various possible realizations of the quantum memory scheme. The performed study promises new capabilities for fundamental study of the light-atom interaction and for deterministic quantum manipulation of the light field interested for quantum communication and quantum computing.
A Baseline-Free Defect Imaging Technique in Plates Using Time Reversal of Lamb Waves
Hyunjo Jeong; Sungjong Cho; Wei Wei
2011-01-01
@@ We present an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves.We first consider the flexural wave (A mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver.The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect.The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of- flight information on the defect location.One of the side-band signals is then extracted as a pure defect signal.A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors.The simulation results show that the proposed scheme enables the accurate, baseline-free imaging of a defect.
A simple block representation of reversible cellular automata with time-symmetry
Arrighi, Pablo
2012-01-01
Reversible Cellular Automata (RCA) are a physics-like model of computation consisting of an array of identical cells, evolving in discrete time steps by iterating a global evolution G. Further, G is required to be shift-invariant (it acts the same everywhere), causal (information cannot be transmitted faster than some fixed number of cells per time step), and reversible (it has an inverse which verifies the same requirements). An important, though only recently studied special case is that of Time-symmetric Cellular Automata (TSCA), for which G and its inverse are related via a local operation. In this note we revisit the question of the Block representation of RCA, i.e. we provide a very simple proof of the existence of a reversible circuit description implementing G. This operational, bottom-up description of G turns out to be time-symmetric, suggesting interesting connections with TSCA. Indeed we prove, using a similar technique, that a wide class of them admit an Exact block representation (EBR), i.e. one...
A compact time reversal emitter-receiver based on a leaky random cavity
Luong, Trung-Dung; Hies, Thomas; Ohl, Claus-Dieter
2016-11-01
Time reversal acoustics (TRA) has gained widespread applications for communication and measurements. In general, a scattering medium in combination with multiple transducers is needed to achieve a sufficiently large acoustical aperture. In this paper, we report an implementation for a cost-effective and compact time reversal emitter-receiver driven by a single piezoelectric element. It is based on a leaky cavity with random 3-dimensional printed surfaces. The random surfaces greatly increase the spatio-temporal focusing quality as compared to flat surfaces and allow the focus of an acoustic beam to be steered over an angle of 41°. We also demonstrate its potential use as a scanner by embedding a receiver to detect an object from its backscatter without moving the TRA emitter.
Application of time-reversal-based processing techniques to enhance detection of GPR targets
Santos, Vinicius R N
2016-01-01
In this paper we analyze the performance of time-reversal (TR) techniques in conjunction with various Ground Penetrating Radar (GPR) pre-processing methods aimed at improving detection of subsurface targets. TR techniques were first developed for ultrasound applications and, by exploiting the invariance of the wave equation under time reversal, can yield features such as superresolution and statistical stability. The TR method was examined here using both synthetic and actual GPR field data under four different pre-processing strategies on the raw data, namely: mean background removal, eigenvalue background removal, a sliding-window space-frequency technique, and a noise-robust spatial differentiator along the scan direction. Depending on the acquisition mode, it was possible to determine with good precision the position and depth of the studied targets as well as, in some cases, to differentiate the targets from nearby clutter such as localized geological anomalies. The proposed methodology has the potential...
Dupré, Matthieu; Fink, Mathias; Lerosey, Geoffroy
2016-01-01
Materials which possess a high local density of states varying at a subwavelength scale theoretically permit to focus waves onto focal spots much smaller than the free space wavelength. To do so metamaterials -manmade composite media exhibiting properties not available in nature- are usually considered. However this approach is limited to narrow bandwidths due to their resonant nature. Here, we prove that it is possible to use a fractal resonator alongside time reversal to focus microwaves onto $\\lambda/15$ subwavelength focal spots from the far field, on extremely wide bandwidths. We first numerically prove that this approach can be realized using a multiple channel time reversal mirror, that utilizes all the degrees of freedom offered by the fractal resonator. Then we experimentally demonstrate that this approach can be drastically simplified by coupling the fractal resonator to a complex medium, here a cavity, that efficiently converts its spatial degrees of freedom into temporal ones. This allows to achie...
Differt, Dominik; Hensen, Matthias; Pfeiffer, Walter
2016-05-01
Spatiotemporal nanolocalization of ultrashort pulses in a random scattering nanostructure via time reversal and adaptive optimization employing a genetic algorithm and a suitably defined fitness function is studied for two embedded nanoparticles that are separated by only a tenth of the free space wavelength. The nanostructure is composed of resonant core-shell nanoparticles (TiO2 core and Ag shell) placed randomly surrounding these two nanoparticles acting as targets. The time reversal scheme achieves selective nanolocalization only by chance if the incident radiation can couple efficiently to dipolar local modes interacting with the target/emitter particle. Even embedding the structure in a reverberation chamber fails improving the nanolocalization. In contrast, the adaptive optimization strategy reliably yields nanolocalization of the radiation and allows a highly selective excitation of either target position. This demonstrates that random scattering structures are interesting multi-purpose optical nanoantennas to realize highly flexible spatiotemporal optical near-field control.
Partial time-reversal transformation and entanglement negativity in fermionic systems
Shapourian, Hassan; Ryu, Shinsei
2016-01-01
We propose a definition of partial transpose for a fermionic density matrix based on time-reversal transformation in the Grassmannian coherent state representation of fermions. Using this definition, we present a path-integral picture and develop methods to compute the entanglement negativity associated with the partial time-reversal. For noninteracting fermions, we derive an exact formula for the entanglement negativity which can be straightforwardly computed for any lattice models. We benchmark our method against two examples: Majorana chain and Su-Schrieffer-Heeger model, where we also provide analytical expressions for the negativity in the fixed-point limits of topological phases as well as at the criticality. The results at the criticality match with previous conformal field theory calculations. Our definition of partial transpose is intrinsically fermionic and goes beyond previous definitions by capturing not only the singlet bonds but also the Majorana bonds between two subsystems. Finally, we uncover...
Time reversal odd fragmentation functions in semi-inclusive deep inelastic lepton-hadron scattering
Mulders, P.J. [National Inst. for Nuclear Physics and High Energy Physics, Amsterdam (Netherlands); Levelt, J. [Univ. of Erlangen-Nuernberg (Germany)
1994-04-01
In semi-inclusive scattering of polarized leptons from unpolarized hadrons, one can measure a time reversal odd structure function. It shows up as a sin({phi}) asymmetry of the produced hadrons. This asymmetry can be expressed as the product of a twist-three {open_quotes}hadron {r_arrow} quark{close_quotes} profile function and a time reversal odd twist-two {open_quotes}quark {r_arrow} hadron{close_quotes} fragmentation function. This fragmentation function can only be measured for nonzero transverse momenta of the produced hadron. Its appearance is a consequence of final state interactions between the produced hadron and the rest of the final state.
Time-reversed particle dynamics calculation with field line tracing at Titan - an update
Bebesi, Zsofia; Erdos, Geza; Szego, Karoly; Juhasz, Antal; Lukacs, Katalin
2014-05-01
We use CAPS-IMS Singles data of Cassini measured between 2004 and 2010 to investigate the pickup process and dynamics of ions originating from Titan's atmosphere. A 4th order Runge-Kutta method was applied to calculate the test particle trajectories in a time reversed scenario, in the curved magnetic environment. We evaluated the minimum variance directions along the S/C trajectory for all Cassini flybys during which the CAPS instrument was in operation, and assumed that the field was homogeneous perpendicular to the minimum variance direction. We calculated the magnetic field lines with this method along the flyby orbits and we could determine those observational intervals when Cassini and the upper atmosphere of Titan could be magnetically connected. We used three ion species (1, 2 and 16 amu ions) for time reversed tracking, and also considered the categorization of Rymer et al. (2009) and Nemeth et al. (2011) for further features studies.
Ruan, Haowen; Yang, Changhuei
2015-01-01
Focusing light inside scattering media in a freely addressable fashion is challenging, as the wavefront of the scattered light is highly disordered. Recently developed ultrasound-guided wavefront shaping methods are addressing this challenge, albeit with relatively low modulation efficiency and resolution limitations. In this paper, we present a new technique, time-reversed ultrasound microbubble encoded (TRUME) optical focusing, which is able to focus light with improved efficiency and sub-ultrasound wavelength resolution. This method ultrasonically destructs microbubbles, and measures the wavefront change to compute and render a suitable time-reversed wavefront solution for focusing. We demonstrate that the TRUME technique can create an optical focus at the site of bubble destruction with a size of ~2 microns. Due to the nonlinear pressure-to-destruction response, the TRUME technique can break the addressable focus resolution barrier imposed by the ultrasound focus. We experimentally demonstrate a 2-fold ad...
Robust and Reversible Audio Watermarking by Modifying Statistical Features in Time Domain
Shijun Xiang
2017-01-01
Full Text Available Robust and reversible watermarking is a potential technique in many sensitive applications, such as lossless audio or medical image systems. This paper presents a novel robust reversible audio watermarking method by modifying the statistic features in time domain in the way that the histogram of these statistical values is shifted for data hiding. Firstly, the original audio is divided into nonoverlapped equal-sized frames. In each frame, the use of three samples as a group generates a prediction error and a statistical feature value is calculated as the sum of all the prediction errors in the frame. The watermark bits are embedded into the frames by shifting the histogram of the statistical features. The watermark is reversible and robust to common signal processing operations. Experimental results have shown that the proposed method not only is reversible but also achieves satisfactory robustness to MP3 compression of 64 kbps and additive Gaussian noise of 35 dB.
Efficiency at maximum power output of quantum heat engines under finite-time operation
Wang, Jianhui; He, Jizhou; Wu, Zhaoqi
2012-03-01
We study the efficiency at maximum power, ηm, of irreversible quantum Carnot engines (QCEs) that perform finite-time cycles between a hot and a cold reservoir at temperatures Th and Tc, respectively. For QCEs in the reversible limit (long cycle period, zero dissipation), ηm becomes identical to the Carnot efficiency ηC=1-Tc/Th. For QCE cycles in which nonadiabatic dissipation and the time spent on two adiabats are included, the efficiency ηm at maximum power output is bounded from above by ηC/(2-ηC) and from below by ηC/2. In the case of symmetric dissipation, the Curzon-Ahlborn efficiency ηCA=1-Tc/Th is recovered under the condition that the time allocation between the adiabats and the contact time with the reservoir satisfy a certain relation.
Efficiency at maximum power output of quantum heat engines under finite-time operation.
Wang, Jianhui; He, Jizhou; Wu, Zhaoqi
2012-03-01
We study the efficiency at maximum power, η(m), of irreversible quantum Carnot engines (QCEs) that perform finite-time cycles between a hot and a cold reservoir at temperatures T(h) and T(c), respectively. For QCEs in the reversible limit (long cycle period, zero dissipation), η(m) becomes identical to the Carnot efficiency η(C)=1-T(c)/T(h). For QCE cycles in which nonadiabatic dissipation and the time spent on two adiabats are included, the efficiency η(m) at maximum power output is bounded from above by η(C)/(2-η(C)) and from below by η(C)/2. In the case of symmetric dissipation, the Curzon-Ahlborn efficiency η(CA)=1-√(T(c)/T(h)) is recovered under the condition that the time allocation between the adiabats and the contact time with the reservoir satisfy a certain relation.
Includes papers in the following fields: Aerospace Engineering, Agricultural Engineering, Chemical Engineering, Civil Engineering, Electrical Engineering, Environmental Engineering, Industrial Engineering, Materials Engineering, Mechanical...
Yachini, Michal; Bahabad, Alon
2016-01-01
It is shown theoretically that the use of accelerating spatiotemporal quasi-phase-matching (QPM) modulation patterns in media with parametric optical interactions makes it possible to generate a time-reversed replica of the pump pulse envelope in a frequency converted signal. The conversion is dependent on the group-velocity mismatch between the fundamental and up-converted harmonics, and controlled by the acceleration rate (chirp) of the QPM phase pattern. Analytical results are corroborated by numerical simulations.
Reversible Conformational Changes of PsbO Protein Detected by Terahertz Time-Domain Spectroscopy
CHEN Hua; CHEN Gui-Ying; LI Shu-Qin; WANG Li
2009-01-01
We used a terahertz time-domain spectroscope (THz-TDS) to detect the reversible conformations2 changes of PsbO protein induced by N-bromosuccinimide and Guanidine Hydrochloride.The veracity and sensitivity are confirmed by the fluorescence emission spectra.The results demonstrate that THz-TDS has both advantages and disadvantages in monitoring the denaturation process of proteins,which is important in applying THz-TDS technique to studying biomolecules.
Boltzmann-Gibbs Distribution of Fortune and Broken Time-Reversible Symmetry in Econodynamics
Ao, P
2005-01-01
Within the description of stochastic differential equations it is argued that the existence of Boltzmann-Gibbs type distribution in economy is independent of the time reversal symmetry in econodynamics. Both power law and exponential distributions can be accommodated by it. The demonstration is based on a mathematical structure discovered during a study in gene regulatory network dynamics. Further possible analogy between equilibrium economy and thermodynamics is explored.
Square root of gerbe holonomy and invariants of time-reversal-symmetric topological insulators
Gawȩdzki, Krzysztof
2017-10-01
The Feynman amplitudes with the two-dimensional Wess-Zumino action functional have a geometric interpretation as bundle gerbe holonomy. We present details of the construction of a distinguished square root of such holonomy and of a related 3 d-index and briefly recall the application of those to the building of topological invariants for time-reversal-symmetric two- and three-dimensional crystals, both static and periodically forced.
Facility for parity and time reversal experiments with intense epithermal (eV) neutron beams
Bowman, C. D.; Bowman, J. D.; Herczeg, P.; Szymanski, J.; Yuan, V. W.; Anaya, J. M.; Mortensen, R.; Postma, H.; Delheij, P. P. J.; Baker, O. K.; Gould, C. R.; Haase, D. G.; Mitchell, G. E.; Roberson, N. R.; Zhu, X.; McDonald, A. B.; Benton, D.; Tippens, B.; Chupp, T. E.
1988-12-01
A facility for polarized epithermal neutrons of high intensity is set up at the Los Alamos National Laboratory for parityviolation and time reversal experiments at neutron resonances over a wide range of neutron energies. The beam is polarized with the aid of a polarized proton target used as a neutronspin filter. Total cross section measurements as well as capture gamma-ray experiments will be carried out. The main features of this system will be discussed.
Semiclassical matrix model for quantum chaotic transport with time-reversal symmetry
Novaes, Marcel, E-mail: marcel.novaes@gmail.com
2015-10-15
We show that the semiclassical approach to chaotic quantum transport in the presence of time-reversal symmetry can be described by a matrix model. In other words, we construct a matrix integral whose perturbative expansion satisfies the semiclassical diagrammatic rules for the calculation of transport statistics. One of the virtues of this approach is that it leads very naturally to the semiclassical derivation of universal predictions from random matrix theory.
Time-reversal duality of high-efficiency RF power amplifiers
Reveyrand, T; Ramos, I; Popovic, Z
2012-12-06
The similarity between RF power amplifiers and rectifiers is discussed. It is shown that the same high-efficiency harmonically-terminated power amplifier can be operated in a dual rectifier mode. Nonlinear simulations with a GaN HEMT transistor model show the time-reversal intrinsic voltage and current waveform relationship between a class-F amplifier and rectifier. Measurements on a class-F-1 amplifier and rectifier at 2.14 GHz demonstrate over 80% efficiency in both cases.
Real-time measurements of jet aircraft engine exhaust.
Rogers, Fred; Arnott, Pat; Zielinska, Barbara; Sagebiel, John; Kelly, Kerry E; Wagner, David; Lighty, JoAnn S; Sarofim, Adel F
2005-05-01
Particulate-phase exhaust properties from two different types of ground-based jet aircraft engines--high-thrust and turboshaft--were studied with real-time instruments on a portable pallet and additional time-integrated sampling devices. The real-time instruments successfully characterized rapidly changing particulate mass, light absorption, and polycyclic aromatic hydrocarbon (PAH) content. The integrated measurements included particulate-size distributions, PAH, and carbon concentrations for an entire test run (i.e., "run-integrated" measurements). In all cases, the particle-size distributions showed single modes peaking at 20-40nm diameter. Measurements of exhaust from high-thrust F404 engines showed relatively low-light absorption compared with exhaust from a turboshaft engine. Particulate-phase PAH measurements generally varied in phase with both net particulate mass and with light-absorbing particulate concentrations. Unexplained response behavior sometimes occurred with the real-time PAH analyzer, although on average the real-time and integrated PAH methods agreed within the same order of magnitude found in earlier investigations.
Longhi, S
2012-01-01
Recent works [Y.D. Chong {\\it et al.}, Phys. Rev. Lett. {\\bf 105}, 053901 (2010); W. Wan {\\it et al.}, Science {\\bf 331}, 889 (2011)] have shown that the time-reversed process of lasing at threshold realizes a coherent perfect absorber (CPA). In a CPA, a lossy medium in an optical cavity with a specific degree of dissipation, equal in modulus to the gain of the lasing medium, can perfectly absorb coherent optical waves at discrete frequencies that are the time-reversed counterpart of the lasing modes. Here the concepts of time-reversal of lasing and CPA are extended for optical radiation emitted by a laser operated in an arbitrary (and generally highly-nonlinear) regime, i.e. for transient, chaotic or periodic coherent optical fields. We prove that any electromagnetic signal $E(t)$ generated by a laser system \\textbf{S} operated in an arbitrary regime can be perfectly absorbed by a CPA device $\\bf{S'}$ which is simply realized by placing inside \\textbf{S} a broadband linear absorber (attenuator) of appropriat...
Momentum-independent reflectionless transmission in the non-Hermitian time-reversal symmetric system
Zhang, X.Z.; Song, Z., E-mail: nkquantum@gmail.com
2013-12-15
We theoretically study the non-Hermitian systems, the non-Hermiticity of which arises from the unequal hopping amplitude (UHA) dimers. The distinguishing features of these models are that they have full real spectra if all of the eigenvectors are time-reversal (T) symmetric rather than parity-time-reversal (PT) symmetric, and that their Hermitian counterparts are shown to be an experimentally accessible system, which have the same topological structures as that of the original ones but modulated hopping amplitudes within the unbroken region. Under the reflectionless transmission condition, the scattering behavior of momentum-independent reflectionless transmission (RT) can be achieved in the concerned non-Hermitian system. This peculiar feature indicates that, for a certain class of non-Hermitian systems with a balanced combination of the RT dimers, the defects can appear fully invisible to an outside observer. -- Highlights: •We investigate the non-Hermitian system with time reversal symmetry. •The Hermitian counterpart is experimentally accessible system. •The behavior of momentum-independent reflectionless transmission can be achieved. •A balanced combination of reflectionless transmission dimers leads to invisibility. •It paves an alternative way for the design of invisible cloaking devices.
Damage Detection of Closed Crack in a Metallic Plate Using Nonlinear Ultrasonic Time Reversal Method
Wang Zhang
2013-01-01
Full Text Available Initial cracks in metallic structures incline to be closed at rest. Such incipient damage generally fails to be detected and located with traditional linear ultrasonic techniques because ultrasonic waves penetrate the contact area of the closed crack. In this paper, an imaging algorithm based on nonlinear ultrasonic time reversal method is proposed to detect closed cracks in aluminum plates. Two surface-bonded piezoelectric transducer arrays are used to generate, receive, and reemit ultrasonic wave signals. The closed crack is simulated by tightening a bolt on the aluminum plate. By applying large amplitude excitation voltage on the PZT transducers, the closed crack could be opened and closed. The transmitted waves recorded by PZT array contain nonlinear components, the signals are time reversed and emitted back, and the tone burst reconstructions are achieved. The linear reciprocity and the time reversibility break down due to the presence of the nonlinear components. The correlation coefficient between the original excitation signal and the reconstructed signal is calculated to define the damage index for individual sensing path and is used to develop an imaging algorithm to locate the closed crack on the plate. The experimental results demonstrate that incident wave signals and their reconstructed signals can be used to accurately detect and locate closed cracks.
Differential geometric invariants for time-reversal symmetric Bloch-bundles: The "Real" case
De Nittis, Giuseppe; Gomi, Kiyonori
2016-05-01
Topological quantum systems subjected to an even (resp. odd) time-reversal symmetry can be classified by looking at the related "Real" (resp. "Quaternionic") Bloch-bundles. If from one side the topological classification of these time-reversal vector bundle theories has been completely described in De Nittis and Gomi [J. Geom. Phys. 86, 303-338 (2014)] for the "Real" case and in De Nittis and Gomi [Commun. Math. Phys. 339, 1-55 (2015)] for the "Quaternionic" case, from the other side it seems that a classification in terms of differential geometric invariants is still missing in the literature. With this article and its companion [G. De Nittis and K. Gomi (unpublished)] we want to cover this gap. More precisely, we extend in an equivariant way the theory of connections on principal bundles and vector bundles endowed with a time-reversal symmetry. In the "Real" case we generalize the Chern-Weil theory and we show that the assignment of a "Real" connection, along with the related differential Chern class and its holonomy, suffices for the classification of "Real" vector bundles in low dimensions.
Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors
Schemm, E.R., E-mail: eschemm@alumni.stanford.edu [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Levenson-Falk, E.M. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kapitulnik, A. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Department of Applied Physics, Stanford University, Stanford, CA 94305 (United States); Stanford Institute of Energy and Materials Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
2017-04-15
Highlights: • Polar Kerr effect (PKE) probes broken time-reversal symmetry (TRS) in superconductors. • Absence of PKE below Tc in CeCoIn{sub 5} is consistent with dx2-y2 order parameter symmetry. • PKE in the B phase of the multiphase superconductor UPt3 agrees with an E2u model. • Data on URu2Si2 show broken TRS and additional structure in the superconducting state. - Abstract: The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of {sup 3}He-B, all of the known or suspected chiral – that is to say time-reversal symmetry-breaking (TRSB) – superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.
Elastic reverse-time migration based on amplitude-preserving P- and S-wave separation
Yang, Jia-Jia; Luan, Xi-Wu; Fang, Gang; Liu, Xin-Xin; Pan, Jun; Wang, Xiao-Jie
2016-09-01
Imaging the PP- and PS-wave for the elastic vector wave reverse-time migration requires separating the P- and S-waves during the wave field extrapolation. The amplitude and phase of the P- and S-waves are distorted when divergence and curl operators are used to separate the P- and S-waves. We present a P- and S-wave amplitude-preserving separation algorithm for the elastic wavefield extrapolation. First, we add the P-wave pressure and P-wave vibration velocity equation to the conventional elastic wave equation to decompose the P- and S-wave vectors. Then, we synthesize the scalar P- and S-wave from the vector Pand S-wave to obtain the scalar P- and S-wave. The amplitude-preserved separated P- and S-waves are imaged based on the vector wave reverse-time migration (RTM). This method ensures that the amplitude and phase of the separated P- and S-wave remain unchanged compared with the divergence and curl operators. In addition, after decomposition, the P-wave pressure and vibration velocity can be used to suppress the interlayer reflection noise and to correct the S-wave polarity. This improves the image quality of P- and S-wave in multicomponent seismic data and the true-amplitude elastic reverse time migration used in prestack inversion.
Time-reversal techniques for MISO and MIMO wireless communication systems
Fouda, Ahmed E.; Teixeira, Fernando L.; Yavuz, Mehmet E.
2012-10-01
We consider the application of different time-reversal (TR) signal processing and beamforming techniques to multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) wireless communication systems. Conventional TR beamforming provides spatial focusing at the intended receiver; however, it does not yield perfect channel equalization. Time-reversed pilot can be normalized to provide perfect equalization at the expense of power level. This equalization is particularly important for high data rates where the bit error rate performance is dominated by internal noise due to intersymbol interference. To increase physical layer covertness, TR beamforming is combined with the multiple-signal-classification (MUSIC) technique to produce null fields at eavesdroppers. This technique is also applied to MIMO setups to eliminate interuser interference and hence increase system capacity. Differential TR is used to obtain and update pilot signals for passive moving receivers, i.e., those that cannot (or do not) transmit pilot signals. Time-reversed differential backscattered signal is able to provide satisfactory spatial and temporal focusing at the moving receiver.
Time reversal invariance for a one-dimensional model of contact acoustic nonlinearity
Blanloeuil, Philippe; Francis Rose, L. R.; Veidt, Martin; Wang, Chun H.
2017-04-01
The interaction of a one-dimensional (1D) wave packet with a contact interface characterized by a unilateral contact law is investigated analytically and through a finite difference model. It is shown that this interaction leads to the generation of higher harmonic, sub-harmonic and zero-frequency components in the reflected wave, resulting in a pulse distortion that is attributable to contact acoustic nonlinearity. However, the results also show that the re-emission of a time reversed version of this distorted first reflection results in a healing of the distortions and a perfect recovery of the original pulse shape, thereby demonstrating time reversal invariance for this type of contact acoustic nonlinearity. A step-by-step analysis of the contact interaction provides insights into both the distortion arising from the first interaction and the subsequent healing during the second interaction. These findings suggest that time reversal invariance should also apply more generally for scatterers exhibiting non-dissipative contact acoustic nonlinearity.
反求工程的参数体系分析%Analysis of Parameter System of Reverse Engineering
栗全庆; 李明
2014-01-01
对原型的精确重构和基于原型的再设计是反求工程的应用目标之一。在制造业中，由于制造误差、测量误差、三维拟合精度等多种因素，使得依据实物原型重构而形成的制造数据与原型参数有较大的差距，在某种情况下，反求出的产品将会失去使用性能。针对此问题，提出了反求工程中存在有实物原型参数、重构参数和原始设计参数的参数体系，阐述了在不同的场合根据不同的要求应求出不同的参数，并提出了应用在制造业中的反求工程应逆求出制造实物原型所依据的原始设计参数，并依此作为制造新产品的依据。分析结果对强化反求工程在制造业的应用、突出反求工程的“创新”功能具有重要意义。%Accurate reconstruction of prototype and redesign based on prototype is one of the application goals of reverse engi-neering. In manufacture industry,because of many kinds of facts,such as,manufacturing errors,measuring errors and three-dimen-sional fitting precision,and so on,there was obvious gap between prototype parameter and manufacturing data that was formed based on objective prototype reconstruction,in some cases,the product to be reversed lost its using performance. Aimed at this problem,it puts forward that there is a parameter system that includes the objective prototype parameters,reconstruction parameters and original design parameters in the reverse engineering,and expounds that the different parameters must be obtained according to the different demands in a different situation. It proposed that the reverse engineering used in manufacture industry should find reversely the original design parameters that are foundation of making objective prototype,and should use it as the basis of making new products. The analysis result has great significance to strengthen the application of reverse engineering in the manufacturing industry,and highlight the
Anselmetti, Dario; Bartels, Frank Wilco; Becker, Anke; Decker, Björn; Eckel, Rainer; McIntosh, Matthew; Mattay, Jochen; Plattner, Patrik; Ros, Robert; Schäfer, Christian; Sewald, Norbert
2008-02-19
Tunable and switchable interaction between molecules is a key for regulation and control of cellular processes. The translation of the underlying physicochemical principles to synthetic and switchable functional entities and molecules that can mimic the corresponding molecular functions is called reverse molecular engineering. We quantitatively investigated autoinducer-regulated DNA-protein interaction in bacterial gene regulation processes with single atomic force microscopy (AFM) molecule force spectroscopy in vitro, and developed an artificial bistable molecular host-guest system that can be controlled and regulated by external signals (UV light exposure and thermal energy). The intermolecular binding functionality (affinity) and its reproducible and reversible switching has been proven by AFM force spectroscopy at the single-molecule level. This affinity-tunable optomechanical switch will allow novel applications with respect to molecular manipulation, nanoscale rewritable molecular memories, and/or artificial ion channels, which will serve for the controlled transport and release of ions and neutral compounds in the future.
Støvring, Henrik; Pottegård, Anton; Hallas, Jesper
2017-01-01
Purpose: To introduce the reverse waiting time distribution (WTD) and show how it can be used to estimate stopping fractions and real-time prevalence of treatment in pharmacoepidemiological studies. Methods: The reverse WTD is the distribution of time from the last dispensed prescription of each ...
Delay time and Hartman effect in strain engineered graphene
Chen, Xi, E-mail: xchen@shu.edu.cn; Deng, Zhi-Yong [Department of Physics, Shanghai University, 200444 Shanghai (China); Ban, Yue, E-mail: yban@shu.edu.cn [Department of Electronic Information Materials, Shanghai University, 200444 Shanghai (China)
2014-05-07
Tunneling times, including group delay and dwell time, are studied for massless Dirac electrons transmitting through a one-dimensional barrier in strain-engineered graphene. The Hartman effect, the independence of group delay on barrier length, is induced by the strain effect, and associated with the transmission gap and the evanescent mode. The influence of barrier height/length and strain modulus/direction on the group delay is also discussed, which provides the flexibility to control the group delay with applications in graphene-based devices. The relationship between group delay and dwell time is finally derived to clarify the nature of the Hartman effect.
GUO Guoqiang; YANG Yixin; SUN Chao
2009-01-01
Abstract Combined the decomposition of time reversal operator and the time reversal reverberation nulling, a new time reversal processing approach for echo-to-reverberation ratio enhancement is proposed. In this method, a 2-dimensional signal subspace for the range of the target and two bottom focusing weight vectors for the ranges near the target are obtained by the decomposition of time reversal operator. From the signal subspace and focusing weight vectors, a constrained optimal excitation weight vector of source receiver array can be deduced to null the acoustic energy on the corresponding bottom and maximize the energy at the target. This method remedies the shortages of conventional time reversal processing, time reversal reverberation nulling and time reversal selective focusing method. It focuses sound energy at the target and nulls the energy at the bottom near the target range simultaneously, therefore enhancing the echo-to-reverberation ratio without probe source and prior-knowledge of the relative scattering intensity of target and bottom. Numerical simulations in typical shallow water environments showed the effectiveness of the proposed method and its improved performance for echo-reverberation enhancement than conventional time reversal processing.
Two effective approaches to reduce data storage in reverse time migration
Sun, Weijia; Fu, Li-Yun
2013-07-01
Prestack reverse time migration (RTM) requires extensive data storage since it computes wavefields in forward time and accesses wavefields in reverse order. We first review several successful schemes that have been proposed to reduce data storage, but require more computational redundancies. We propose two effective strategies to reduce data storage during RTM. The first strategy is based on the Nyquist sampling theorem, which involves no extra computational cost. The fact is that the time sampling intervals required by numerical algorithms or given by field records is generally several times smaller than that satisfied by the Nyquist sampling theorem. Therefore, we can correlate the source wavefields with the receiver wavefields at the Nyquist time step, which helps decrease storage of time history. The second strategy is based on a lossless compression algorithm, which is widely used in computer science and information theory. The compression approach reduces storage significantly at a little computational cost. Numerical examples show that the two proposed strategies are effective and efficient.
Computational intelligence in time series forecasting theory and engineering applications
Palit, Ajoy K
2005-01-01
Foresight in an engineering enterprise can make the difference between success and failure, and can be vital to the effective control of industrial systems. Applying time series analysis in the on-line milieu of most industrial plants has been problematic owing to the time and computational effort required. The advent of soft computing tools offers a solution. The authors harness the power of intelligent technologies individually and in combination. Examples of the particular systems and processes susceptible to each technique are investigated, cultivating a comprehensive exposition of the improvements on offer in quality, model building and predictive control and the selection of appropriate tools from the plethora available. Application-oriented engineers in process control, manufacturing, production industry and research centres will find much to interest them in this book. It is suitable for industrial training purposes, as well as serving as valuable reference material for experimental researchers.
Multiuser underwater acoustic communication using single-element virtual time reversal mirror
YIN JingWei; WANG YiLin; WANG Lei; HUI JunYing
2009-01-01
Pattern time delay shift coding (PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acous-tic networks.Single-element virtual time reversal mirror (VTRM) is presented in this paper and validated by the lake trial results.Employing single-element VTRM in multiuser communication system based on SS-PDS can separate different users' information simultaneously at master node as indicated in the simulation results.
Time-reversed two-photon interferometry for phase super-resolution
Ogawa, Kazuhisa; Kobayashi, Hirokazu; Nakanishi, Toshihiro; Kitano, Masao
2013-01-01
We observed two-photon phase super-resolution in an unbalanced Michelson interferometer with classical Gaussian laser pulses. Our work is a time-reversed version of a two-photon interference experiment using an unbalanced Michelson interferometer. A measured interferogram exhibits two-photon phase super-resolution with a high visibility of 97.9% \\pm 0.4%. Its coherence length is about 22 times longer than that of the input laser pulses. It is a classical analogue to the large difference between the one- and two-photon coherence lengths of entangled photon pairs.
Maes, Michaël; Willebrords, Joost; Crespo Yanguas, Sara; Cogliati, Bruno; Vinken, Mathieu
2016-01-01
Summary Although connexin production is mainly regulated at the protein level, altered connexin gene expression has been identified as the underlying mechanism of several pathologies. When studying the latter, appropriate methods to quantify connexin mRNA levels are required. The present chapter describes a well-established reverse transcription quantitative real-time polymerase chain reaction procedure optimized for analysis of hepatic connexins. The method includes RNA extraction and subsequent quantification, generation of complementary DNA, quantitative real-time polymerase chain reaction and data analysis. PMID:27207283
Extending compile-time reverse mode and exploiting partial separability in ADIFOR
Bischof, C.H.; El-Khadiri, M.
1992-10-01
The numerical methods employed in the solution of many scientific computing problems require the computation of the gradient of a function f: R[sup n] [yields] R. ADIFOR is a source translator that, given a collection of subroutines to compute f, generates Fortran 77 code for computing the derivative of this function. Using the so-called torsion problem from the MINPACK-2 test collection as an example, this paper explores two issues in automatic differentiation: the efficient computation of derivatives for partial separable functions and the use of the compile-time reverse mode for the generation of derivatives. We show that orders of magnitudes of improvement are possible when exploiting partial separability and maximizing use of the reverse mode.
Sambo, Francesco; de Oca, Marco A Montes; Di Camillo, Barbara; Toffolo, Gianna; Stützle, Thomas
2012-01-01
Reverse engineering is the problem of inferring the structure of a network of interactions between biological variables from a set of observations. In this paper, we propose an optimization algorithm, called MORE, for the reverse engineering of biological networks from time series data. The model inferred by MORE is a sparse system of nonlinear differential equations, complex enough to realistically describe the dynamics of a biological system. MORE tackles separately the discrete component of the problem, the determination of the biological network topology, and the continuous component of the problem, the strength of the interactions. This approach allows us both to enforce system sparsity, by globally constraining the number of edges, and to integrate a priori information about the structure of the underlying interaction network. Experimental results on simulated and real-world networks show that the mixed discrete/continuous optimization approach of MORE significantly outperforms standard continuous optimization and that MORE is competitive with the state of the art in terms of accuracy of the inferred networks.
S.I. engine idle control improvement by using automobile reversible alternator
Kouadio, L.; Bidan, P.; Valentin, M.; Berry, J.P.
1995-12-31
This paper describes the improvements which can be made to spark ignition engine by extensive use of automatic control. Particular emphasis is placed on fast transient phases produced by simultaneous action on the throttle and the electronic fuel injection device. The aim is to achieve better performance for the fuel/air ratio regulation system, thereby improving engine efficiency and exhaust emission during these transient phases. The authors begin by presenting an average dynamic model of the intake manifold validated on an engine test bench and goes on to develop a closed-loop system controlling average pressure in the intake manifold using the reference tracking model method. The air supply control system is combined with a predictor to compensate for delays in the injection procedure. The paper concludes with a comparison between the results obtained using simulation and those obtained experimentally from the engine. (authors) 15 refs.
Time reversal imaging for sensor networks with optimal compensation in time.
Derveaux, Grégoire; Papanicolaou, George; Tsogka, Chrysoula
2007-04-01
Using extensive numerical simulations, several distributed sensor imaging algorithms for localized damage in a structure are analyzed. Given a configuration of ultrasonic transducers, a full response matrix for the healthy structure is assumed known. It is used as a basis for comparison with the response matrix that is recorded when there is damage. Numerical simulations are done with the wave equation in two dimensions. The healthy structure contains many scatterers. The aim is to image point-like defects with several regularly distributed sensors. Because of the complexity of the environment, the recorded traces have a lot of delay spread and travel time migration does not work so well. Instead, the traces are back propagated numerically assuming that there is some knowledge of the background. Since the time at which the back propagated field will focus on the defects is unknown, the Shannon entropy or the bounded variation norm of the image is computed and the time where it is minimal is picked. This imaging method performs well because it produces a tight image near the location of the defects at the time of refocusing. When there are several defects, the singular value decomposition of the response matrix is also carried out.
Engineering metal complexes of chiral pentaazacrowns as privileged reverse-turn scaffolds.
Che, Ye; Brooks, Bernard R; Riley, Dennis P; Reaka, Andrea J H; Marshall, Garland R
2007-02-01
Reverse turns are common structural motifs and recognition sites in protein/protein interactions. The design of peptidomimetics is often based on replacing the amide backbone of peptides by a non-peptidic scaffold while retaining the biologic mode of action. This study evaluates the potential of metal complexes of chiral pentaazacrowns conceptually derived by reduction of cyclic pentapeptides as reverse-turn mimetics. The possible conformations of metal complexes of chiral pentaazacrown scaffolds have been probed by analysis of 28 crystal structures complexed with six different metals (Mn, Fe, Co, Ni, Cu, and Zn). The solvated structures as well as the impact of complexation with different metals/oxidation states have been examined with density functional theory (DFT) calculation as explicitly represented by interactions with a single water molecule. The results suggest that most reverse-turn motifs seen in proteins could be mimicked effectively with a subset of metal complexes of chiral pentaazacrown scaffolds with an RMSD of approximately 0.3 A. Due to the relatively fixed orientation of the pendant chiral side groups in these metal complexes, one can potentially elicit information about the receptor-bound conformation of the parent peptide from their binding affinities. The presence of 20 H-atoms on the pentaazacrown ring that could be functionalized as well as the conformational perturbations available from complexation with different metals offer a desirable diversity to probe receptors for reverse-turn recognition.
The influence of heavy doping effects on the reverse recovery storage time of a diode
Jain, S. C.; Van Overstraeten, R. J.
1983-05-01
During the reverse recovery process in a modern Si p- n junction diode, the value of JEO/ JBO (the ratio of emitter to base dark saturation currents) increases and the recombination of carriers in the emitter becomes important due to heavy doping effects. A theory is developed to take these effects into account. The emitter and the base components of the current during the reverse recovery phase are found to vary with time. However, their sum remains equal to the constant reverse current JR, which flows in the external circuit. The ratio of the total quantity of charge present in the base to that present in the emitter is found to increase rapidly with time. Values of the storage time ts for different values of JEO/ JBO are calculated. In a typical case, the storage time is reduced by a factor 5 in a diode with JEO/ JBO = 2. In such cases, the values of lifetime τB calculated using measured ts values and the Kingston's formula, become inaccurate. Theoretical expression for the total charge QBS left in the base at t = ts in a base dominated diode is derived. An earlier semi-empirical formula known as Kuno's formula is derived theoretically. It is found that the formula is valid both for the base dominated diode as well as in a diode with large contribution of the emitter but only when JR/ JF is small. According to this formula ts vs 1n(1 + JF/ JR) plot is approximately a straight line with slope approximately equal to τB in both cases. For large values of JR/ JF when ts values are small, the correct formula shows that the plot is highly curved. An analysis of this part of the curve yields a value of JEO/ JBO.
Sajjad Alizadeh
2014-04-01
Full Text Available Conventional Time Reversal (TR technique suffers from performance degradation in time varying Multiple-Input Multiple-Output Ultra-Wideband (MIMO-UWB systems due to outdating Channel State Information (CSI over time progressions. That is, the outdated CSI degrades the TR performance significantly in time varying channels. The correlation property of time correlated channels can improve the TR performance against other traditional TR designs. Based on this property, at first, we propose a robust TR-MIMO-UWB system design for a time-varying channel in which the CSI is updated only at the beginning of each block of data where the CSI is assumed to be known. As the channel varies over time, pre-processor blindly pre-equalizes the channel during the next symbol time by using the correlation property. Then, a novel recursive power allocation strategy is derived over time-correlated time-varying TR-MIMO-UWB channels. We show that the proposed power loading technique, considerably improves the BER performance of TR-MIMO-UWB system in imperfect CSI with robust pre-filter. The proposed algorithms lead to a cost-efficient CSI updating procedure for the TR optimization. Simulation results are provided to confirm the new design performance against traditional method.
Geomagnetic Field Reversals and Life on the Earth in Phanerozoic Time
Pechersky, D. M.
2014-10-01
Global paleomagnetic and biostratigraphic data are generalized. As a result it is found out that the direct connection between geomagnetic reversals, biozones and maxima of mass extinction of a biota is absent. At the same time it is noted close to a synchronous total picture of consistent changes of biozones and geomagnetic polarity. It is explained by the general source - the Earth's diurnal rotation. The reversal polarity of a geomagnetic field prevailed during the Phanerozoic that is agreed with the Earth's counterclockwise rotation. Change of polarity of a field, most likely, is connected with acceleration or deceleration of rotation speed of the internal core relative to the Earth's mantle. Lack of direct interrelation between changes in the biosphere and geomagnetic field indicate a lack of influence of a field on life evolution on Earth. It follows also from the fact that life on Earth developed from primitive unicellular forms to mammals and the man and diversity of biota was grew against a close condition of a geomagnetic field during ~2,5 billion years and irrespective of numerous geomagnetic reversals. Main conclusion: evolutionary development of life on Earth doesn't depend both on large changes of a geomagnetic field, and on the extreme catastrophic events conducting to mass extinction of a biota.
ZHANG Yuan-zhi; LU Sheng; XU Yong-qing; SHI Ji-hong; LI Yan-bing; FENG Zi-liang
2009-01-01
Objective: To provide a new method in the fixation of sacral fracture by means of three-dimensional reconstruc-tion and reverse engineering technique.Methods: Pelvis image data were obtained from three-dimensional CT scan in patients with sacral fracture. The data were transferred into a computer workstation. The three-dimensional models of pelvis were reconstructed using Amira 3.1 software and saved in STL format. Then the three-dimensional fracture models were imported into Imageware 9.0 software. Different situations of reduction (total reduction, half reduction and non-reduction) were simulated using Imageware 9.0 software. The best direction and loca-tion of extract iliosacral lag screws were defined using re-verse engineering according to these three situations and navigation templates were designed according to the ana-tomic features of the postero-iliac part and the channel. The exact navigational template was made by rapid prototyping.Drill guides were sterilized and used intraoperatively to as-sist in surgical navigation and the placement of iliosacral lag screws.Results: Accurate screw placement was confirmed with postoperative X-ray and CT scanning. The navigation template was found to be highly accurate. Conclusion: The navigation template may be a useful method in minimal-invasive fixation of sacroiliac joint fracture.
De Cegli, Rossella; Iacobacci, Simona; Flore, Gemma; Gambardella, Gennaro; Mao, Lei; Cutillo, Luisa; Lauria, Mario; Klose, Joachim; Illingworth, Elizabeth; Banfi, Sandro; di Bernardo, Diego
2013-01-01
Gene expression profiles can be used to infer previously unknown transcriptional regulatory interaction among thousands of genes, via systems biology 'reverse engineering' approaches. We 'reverse engineered' an embryonic stem (ES)-specific transcriptional network from 171 gene expression profiles, measured in ES cells, to identify master regulators of gene expression ('hubs'). We discovered that E130012A19Rik (E13), highly expressed in mouse ES cells as compared with differentiated cells, was a central 'hub' of the network. We demonstrated that E13 is a protein-coding gene implicated in regulating the commitment towards the different neuronal subtypes and glia cells. The overexpression and knock-down of E13 in ES cell lines, undergoing differentiation into neurons and glia cells, caused a strong up-regulation of the glutamatergic neurons marker Vglut2 and a strong down-regulation of the GABAergic neurons marker GAD65 and of the radial glia marker Blbp. We confirmed E13 expression in the cerebral cortex of adult mice and during development. By immuno-based affinity purification, we characterized protein partners of E13, involved in the Polycomb complex. Our results suggest a role of E13 in regulating the division between glutamatergic projection neurons and GABAergic interneurons and glia cells possibly by epigenetic-mediated transcriptional regulation.
Fouda, Ahmed E.
Time-reversal (TR) was originated in acoustics as a technique for re-focusing waves around their source location. Under certain conditions, the wave equation is invariant under TR, therefore, waves emanated from a source or scattered from a passive target, and recorded by a transceivers array, will retrace their forward path and automatically focus at the source/target location if back propagated in a time-reversed (last-in first-out) fashion from that array. Focusing resolution of time-reversed back propagation in rich scattering environments beats that in free space, yielding what is known as 'superresolution'. Moreover, under ultrawideband (UWB) operation, TR exhibits the distinctive property of 'statistical stability', which makes it an attractive technique for imaging in disordered media whose characteristics are not known deterministically (random media). Over the past few years, TR has been exploited in a variety of electromagnetic sensing and imaging applications such as ground penetrating radar, breast cancer detection, nondestructive testing, and through-wall imaging. In addition, TR has been extensively applied in UWB wireless communication providing myriad of advantages including reduced receiver complexity, power saving, increased system capacity, and enhanced information secrecy. In this work, we introduce new TR-based signal processing techniques for imaging, tracking, and communicating with targets/users embedded in rich scattering environments. We start by demonstrating, both numerically and experimentally, the statistical stability of UWB TR imaging in inhomogeneous random media, under different combinations of random medium parameters and interrogating signal properties. We examine conditions under which frequency decorrelation in random media provides a more effective 'self-averaging' and therefore better statistical stability. Then, we devise a technique for detecting and tracking multiple moving targets in cluttered environments based on
Real Time Engineering Analysis Based on a Generative Component Implementation
Kirkegaard, Poul Henning; Klitgaard, Jens
2007-01-01
The present paper outlines the idea of a conceptual design tool with real time engineering analysis which can be used in the early conceptual design phase. The tool is based on a parametric approach using Generative Components with embedded structural analysis. Each of these components uses...... the geometry, material properties and fixed point characteristics to calculate the dimensions and subsequent feasibility of any architectural design. The proposed conceptual design tool provides the possibility for the architect to work with both the aesthetic as well as the structural aspects of architecture...... with a static determinate roof structure modelled by beam components is given. The example outlines the idea of the tool for conceptual design in early phase of a multidisciplinary design process between architecture and structural engineering....
Adewole, K. K.
2014-01-01
Full Text Available This paper presents an experimental investigation of the effects of reverse bending and straightening process on the mechanical properties of a typical carbon steel bar used for civil engineering applications. Twenty four specimens each were used for the metallogarphy, microhardness and tensile tests. The investigation revealed that the reverse bending and straightening process has no significant effect on the bars’ through-thickness microstructure and hardness. However, the reverse bending and straightening process reduces the yield load, ultimate load, and displacement at fracture of the bars by 4.27%, 2.58%, and 18.62% respectively. These results highlight the need to take into consideration the effects of the previous loading history of the bars/wires, particularly the reduction in the displacement at fracture and consequently, the ductility of the bars/wires in the design and fitness for purpose assessment of components made from them, since the bars/wires could experience high strain during installation and in service due to overloads.
Passive optical coherence elastography using a time-reversal approach (Conference Presentation)
Nguyen, Thu-Mai; Zorgani, Ali; Fink, Mathias; Catheline, Stefan; Boccara, A. Claude
2017-02-01
Background and motivation - Conventional Optical Coherence Elastography (OCE) methods consist in launching controlled shear waves in tissues, and measuring their propagation speed using an ultrafast imaging system. However, the use of external shear sources limits transfer to clinical practice, especially for ophthalmic applications. Here, we propose a totally passive OCE method for ocular tissues based on time-reversal of the natural vibrations. Methods - Experiments were first conducted on a tissue-mimicking phantom containing a stiff inclusion. Pulsatile motions were reproduced by stimulating the phantom surface with two piezoelectric actuators excited asynchronously at low frequencies (50-500 Hz). The resulting random displacements were tracked at 190 frames/sec using spectral-domain optical coherence tomography (SD-OCT), with a 10x5µm² resolution over a 3x2mm² field-of-view (lateral x depth). The shear wavefield was numerically refocused (i.e. time-reversed) at each pixel using noise-correlation algorithms. The focal spot size yields the shear wavelength. Results were validated by comparison with shear wave speed measurements obtained from conventional active OCE. In vivo tests were then conducted on anesthetized rats. Results - The stiff inclusion of the phantom was delineated on the wavelength map with a wavelength ratio between the inclusion and the background (1.6) consistent with the speed ratio (1.7). This validates the wavelength measurements. In vivo, natural shear waves were detected in the eye and wavelength maps of the anterior segment showed a clear elastic contrast between the cornea, the sclera and the iris. Conclusion - We validated the time-reversal approach for passive elastography using SD-OCT imaging at low frame-rate. This method could accelerate the clinical transfer of ocular elastography.
Axis retrieval of a supersonic source in a reverberant space using time reversal
Mahenc, Guillaume; Éric Bavu; Hamery, Pascal; Hengy, Sébastien; Melon, Manuel
2017-08-01
Localizing the axis of the Mach cone created by the supersonic displacement of a bullet in a reverberant environment is a challenging task, not only because of the high velocity of the moving source, but also because of the multiple wave reflections off of the walls. Although time reversal (TR) techniques allow static acoustic source localization in a reverberant space, they have not been explored yet on non stationary waves caused by supersonic displacements in urban canyons. The acoustic wave produced by a supersonic projectile has a conical wavefront and a N-shaped acoustic pressure signature. In this paper, this acoustic wave is reproduced using a line array of point-like sources (simulations) and loudspeakers (experiments). During the propagation of this conical wave in an urban canyon, the resulting pressure signals are measured using a time reversal array flush mounted into the ground. These acoustic signals allow to automatically retrieve with a high accuracy the location of the Mach cone axis using time reversal techniques. This inverse problem is solved using the maximization of a fourth-order statistical criterion of the backpropagated pressures. This criterion allows to estimate the intersections between the Mach cone axis and several vertical planes in the urban canyon. These estimations are then fitted to a 3D trajectory with a robust three dimensional interpolation technique based on the Random Sample Consensus (RANSAC) algorithm. This method allows to automatically retrieve the axis of the supersonic source with an angular accuracy of less than 0.5° and a misdistance of 0.5 cm for both numerical simulations and experimental measurements.
Fuel from Bacteria, CO2, Water, and Solar Energy: Engineering a Bacterial Reverse Fuel Cell
None
2010-07-01
Electrofuels Project: Harvard is engineering a self-contained, scalable Electrofuels production system that can directly generate liquid fuels from bacteria, carbon dioxide (CO2), water, and sunlight. Harvard is genetically engineering bacteria called Shewanella, so the bacteria can sit directly on electrical conductors and absorb electrical current. This current, which is powered by solar panels, gives the bacteria the energy they need to process CO2 into liquid fuels. The Harvard team pumps this CO2 into the system, in addition to water and other nutrients needed to grow the bacteria. Harvard is also engineering the bacteria to produce fuel molecules that have properties similar to gasoline or diesel fuel—making them easier to incorporate into the existing fuel infrastructure. These molecules are designed to spontaneously separate from the water-based culture that the bacteria live in and to be used directly as fuel without further chemical processing once they’re pumped out of the tank.
Deconvolution of acoustic emissions for source localization using time reverse modeling
Kocur, Georg Karl
2017-01-01
Impact experiments on small-scale slabs made of concrete and aluminum were carried out. Wave motion radiated from the epicenter of the impact was recorded as voltage signals by resonant piezoelectric transducers. Numerical simulations of the elastic wave propagation are performed to simulate the physical experiments. The Hertz theory of contact is applied to estimate the force impulse, which is subsequently used for the numerical simulation. Displacements at the transducer positions are calculated numerically. A deconvolution function is obtained by comparing the physical (voltage signal) and the numerical (calculated displacement) experiments. Acoustic emission signals due to pencil-lead breaks are recorded, deconvolved and applied for localization using time reverse modeling.
Observation of coherence in the time-reversed relativistic photoelectric effect.
Tashenov, S; Banaś, D; Beyer, H; Brandau, C; Fritzsche, S; Gumberidze, A; Hagmann, S; Hillenbrand, P-M; Jörg, H; Kojouharov, I; Kozhuharov, Ch; Lestinsky, M; Litvinov, Yu A; Maiorova, A V; Schaffner, H; Shabaev, V M; Spillmann, U; Stöhlker, Th; Surzhykov, A; Trotsenko, S
2014-09-12
The photoelectric effect has been studied in the regime of hard x rays and strong Coulomb fields via its time-reversed process of radiative recombination (RR). In the experiment, the relativistic electrons recombined into the 2p_{3/2} excited state of hydrogenlike uranium ions, and both the RR x rays and the subsequently emitted characteristic x rays were detected in coincidence. This allowed us to observe the coherence between the magnetic substates in a highly charged ion and to identify the contribution of the spin-orbit interaction to the RR process.
Time reversal symmetry broken fractional topological phases at zero magnetic field
Meng, Tobias; Sela, Eran
2014-12-01
We extend the coupled-wire construction of quantum Hall phases, and search for fractional topological insulating states in models of weakly coupled wires at zero external magnetic field. Focusing on systems beyond double copies of fractional quantum Hall states at opposite fields, we find that spin-spin interactions can stabilize a large family of fractional topological phases with broken time reversal invariance. The latter is manifested by spontaneous spin polarization, by a finite Hall conductivity, or by both. This suggests the possibility that fractional topological insulators may be unstable to spontaneous symmetry breaking.
Noncolocated Time-Reversal MUSIC: High-SNR Distribution of Null Spectrum
Ciuonzo, Domenico; Rossi, Pierluigi Salvo
2017-04-01
We derive the asymptotic distribution of the null spectrum of the well-known Multiple Signal Classification (MUSIC) in its computational Time-Reversal (TR) form. The result pertains to a single-frequency non-colocated multistatic scenario and several TR-MUSIC variants are here investigated. The analysis builds upon the 1st-order perturbation of the singular value decomposition and allows a simple characterization of null-spectrum moments (up to the 2nd order). This enables a comparison in terms of spectrums stability. Finally, a numerical analysis is provided to confirm the theoretical findings.
Effective dissipation: Breaking time-reversal symmetry in driven microscopic energy transmission
Brown, Aidan I.; Sivak, David A.
2016-09-01
At molecular scales, fluctuations play a significant role and prevent biomolecular processes from always proceeding in a preferred direction, raising the question of how limited amounts of free energy can be dissipated to obtain directed progress. We examine the system and process characteristics that efficiently break time-reversal symmetry at fixed energy loss; in particular for a simple model of a molecular machine, an intermediate energy barrier produces unusually high asymmetry for a given dissipation. We relate the symmetry-breaking factors found in this model to recent observations of biomolecular machines.
Białous, Małgorzata; Yunko, Vitalii; Bauch, Szymon; Ławniczak, Michał; Dietz, Barbara; Sirko, Leszek
2016-09-01
We present experimental studies of the power spectrum and other fluctuation properties in the spectra of microwave networks simulating chaotic quantum graphs with violated time reversal invariance. On the basis of our data sets, we demonstrate that the power spectrum in combination with other long-range and also short-range spectral fluctuations provides a powerful tool for the identification of the symmetries and the determination of the fraction of missing levels. Such a procedure is indispensable for the evaluation of the fluctuation properties in the spectra of real physical systems like, e.g., nuclei or molecules, where one has to deal with the problem of missing levels.
Time reversal of continuous-wave, monochromatic signals in elastic media
Anderson, Brian E [Los Alamos National Laboratory; Guyer, Robert A [Los Alamos National Laboratory; Ulrich, Timothy J [Los Alamos National Laboratory; Johnson, Paul A [Los Alamos National Laboratory
2009-01-01
Experimental observations of spatial focusing of continuous-wave, steady-state elastic waves in a reverberant elastic cavity using time reversal are reported here. Spatially localized focusing is achieved when multiple channels are employed, while a single channel does not yield such focusing. The amplitude of the energy at the focal location increases as the square of the number of channels used, while the amplitude elsewhere in the medium increases proportionally with the number of channels used. The observation is important in the context of imaging in solid laboratory samples as well as problems involving continuous-wave signals in Earth.
Time reversal Aharonov-Casher effect using Rashba spin-orbit interaction
Nitta, Junsaku [Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Bergsten, Tobias [CREST-JST, Kawaguchi Center Building, 4-1-8 Honcho Kawaguchi-shi, Saitama 332-0012 (Japan)
2007-09-15
We propose a spin interferometer using Rashba spin-orbit interaction. A spin interference effect is demonstrated in small arrays of mesoscopic InGaAs rings. This spin interference is the time reversal Aharonov-Casher (AC) effect. The AC interference oscillations are controlled over several periods. This result shows evidence for electrical manipulation of the spin precession angle in an InGaAs two-dimensional electron gas channel. We control the precession rate in a precise and predictable way with an electrostatic gate.
Pairing state with a time-reversal symmetry breaking in FeAs-based superconductors.
Lee, Wei-Cheng; Zhang, Shou-Cheng; Wu, Congjun
2009-05-29
We investigate the competition between the extended s+/--wave and dx2-y2-wave pairing order parameters in the iron-based superconductors. Because of the frustrating pairing interactions among the electron and the hole Fermi pockets, a time-reversal symmetry breaking s+id pairing state could be favored. We analyze this pairing state within the Ginzburg-Landau theory and explore the experimental consequences. In such a state, spatial inhomogeneity induces a supercurrent near a nonmagnetic impurity and the corners of a square sample. The resonance mode between the s+/-- and dx2-y2-wave order parameters can be detected through the B1g Raman spectroscopy.
Classification of Topological Insulators with Time-Reversal and Inversion Symmetry*
LIU Lan-Feng; CHEN Bo-Lun; KOU Su-Peng
2011-01-01
In this paper, we find that topological insulators with time-reversal symmetry and inversion symmetry featuring two-dimensional quantum spin Hall (QSH) state can be divided into 16 c/asses, which are characterized by four Z2 topological variables ζk = O,1 at four points with high symmetry in the Brillouin zone. We obtain the corresponding edge states for each one of these sixteen classes of QSHs. In addition, it is predicted that massless fermionic excitations appear at the quantum phase transition between different QSH states. In the end, we also briefly discuss the threedimensional case.
FAST TRACK COMMUNICATION: A trivial observation on time reversal in random matrix theory
Kaplan, L.; Leyvraz, F.; Pineda, C.; Seligman, T. H.
2007-12-01
It is commonly thought that a state-dependent quantity, after being averaged over a classical ensemble of random Hamiltonians, will always become independent of the state. We point out that this is in general incorrect: if the ensemble of Hamiltonians is time-reversal invariant, and the quantity involves the state in higher than bilinear order, then we show that the quantity is only a constant over the orbits of the invariance group on the Hilbert space. Examples include fidelity and decoherence in appropriate models.
Popoff, Sébastien Michel; Lerosey, Geoffroy; Fink, Mathias; Boccara, Albert-Claude; Gigan, Sylvain
2011-01-01
We report on the experimental measurement of the backscattering matrix of a weakly scattering medium in optics, composed of a few dispersed gold nanobeads. The DORT method (Decomposition of the Time Reversal Operator) is applied to this matrix and we demonstrate selective and efficient focusing on individual scatterers, even through an aberrating layer. Moreover, we show that this approach provides the decomposition of the scattering pattern of a single nanoparticle. These results open important perspectives for optical imaging, characterization and selective excitation of nanoparticles.
Time-Reversal Invariance Violation in Neutron Scattering at Spallation Neutron Sources
Gudkov, Vladimir
2014-09-01
The Time Reversal Invariant Violating (TRIV) effects in neutron transmission through a nuclei target are discussed. We explore the possibility to search TRIV at new high flux Spallation Neutron Sources using two important advantages of neutron nuclei interactions: the possibility of an enhancement of T-violating observables by many orders of magnitude, and the relatively large number of the nuclear targets, which provides the assurance of avoiding possible ``accidental'' cancelations of TRI-violating effects due to unknown structural factors related to the strong interactions. This include the absence of final state interactions for a set of specific observables, the possibility to avoid of false asymmetries arising from combinations of time-reversal-invariant interactions and asymmetries in real experiment, and the comparison of expected results with existing limits on neutron, nuclear and atomic electric dipole moments (EDMs). It is shown that TRIV observables are complementary to the EDM experiments and have potential for essential improving of the current limits on the TRIV interactions. The Time Reversal Invariant Violating (TRIV) effects in neutron transmission through a nuclei target are discussed. We explore the possibility to search TRIV at new high flux Spallation Neutron Sources using two important advantages of neutron nuclei interactions: the possibility of an enhancement of T-violating observables by many orders of magnitude, and the relatively large number of the nuclear targets, which provides the assurance of avoiding possible ``accidental'' cancelations of TRI-violating effects due to unknown structural factors related to the strong interactions. This include the absence of final state interactions for a set of specific observables, the possibility to avoid of false asymmetries arising from combinations of time-reversal-invariant interactions and asymmetries in real experiment, and the comparison of expected results with existing limits on neutron
2008-01-01
It has been proved that when the retarded effect (or multiple moment effect) of radiation fields is taken into account,the high order stimulated radiation and stimulated absorption probabilities of light are not the same so that time reversal symmetry would be violated,though the Hamiltonian of electromagnetic interaction is still unchanged under time reversal. The reason to cause time reversal symmetry violation is that certain filial or partial transition processes of bound atoms are forbidden or cannot be achieved due to the law of energy conservation and the special states of atoms themselves. These restrictions would cause the symmetry violation of time reversal of other filial or partial transition processes which can be actualized really. The symmetry violation is also relative to the asymmetry of initial states of bound atoms before and after time reversal. For the electromagnetic interaction between non-bound atoms and radiation field,there is no such kind of symmetry violation of time reversal. In this way,the current formula on the parameters of stimulated radiation and absorption of light with time reversal sym-metry should be revised. A more reliable foundation can be established for the theories of laser and nonlinear optics in which non-equilibrium processes are in-volved.
MEI XiaoChun
2008-01-01
It has been proved that when the retarded effect (or multiple moment effect) of radiation fields is taken into account, the high order stimulated radiation and stimulated absorption probabilities of light are not the same so that time reversal symmetry would be violated, though the Hamiltonian of electromagnetic interaction is still unchanged under time reversal.The reason to cause time reversal symmetry violation is that certain filial or partial transition processes of bound atoms are forbidden or cannot be achieved due to the law of energy conservation and the special states of atoms themselves.These restrictions would cause the symmetry violation of time reversal of other filial or partial transition processes which can be actualized really.The symmetry violation is also relative to the asymmetry of initial states of bound atoms before and after time reversal.For the electromagnetic interaction between non-bound atoms and radiation field, there is no such kind of symmetry violation of time reversal.In this way, the current formula on the parameters of stimulated radiation and absorption of light with time reversal sym-metry should be revised.A more reliable foundation can be established for the theories of laser and nonlinear optics in which non-equilibrium processes are in-volved.
Visser, A.; Broers, H.P.; Grift, B. van der; Bierkens, M.F.P.
2007-01-01
Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We i
Visser, A.; Broers, H.P.; Grift, B. van der; Bierkens, M.F.P.
2007-01-01
Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We
Shrestha, Lok Kumar; Sato, Takaaki; Dulle, Martin; Glatter, Otto; Aramaki, Kenji
2010-09-23
We use small-angle X-ray scattering and dynamic light scattering to investigate the structural and dynamical properties of trehalose polyisostearate, abbreviated as TQ-n (n = 3, 5, and 7), in different organic solvents, where n represents the number of isosterate chains per surfactant molecule. TQ-n spontaneously assembles into reverse micelles without addition of water at 25 °C. We found that for TQ-5 and TQ-7, steric hindrance of the lipophilic surfactant tail causes significant reduction of the aggregation number, whose scheme is clearly distinguished from the modification of the critical packing parameter. Increasing the hydrocarbon chain length of oils from octane to hexadecane favors one-dimensional micellar growth, leading to the formation of rodlike micelles due to different penetration tendencies of oils into the lipophilic shell of the surfactant. Subtle differences in solvent polarity also plays a crucial role in the micellar size, which is decreased when liquid paraffin is replaced with squalene. A further decrease is attained in more polar mixed triglyceride oils. A rising temperature also results in the same direction. The extrapolated structure factor to the zero scattering vector, S(q → 0), for the TQ-3/decane systems almost exactly follows that predicted for hard spheres, demonstrating that osmotic compressibility of the system is well explained if accounting for the excluded volume. However, we found that the effective diffusion coefficient decreases with surfactant concentration, which is an opposite trend to what is expected for hard spheres. This apparent contradiction is likely to be due to the occurrence of transient interdigitation between the lipophilic tails of neighboring reverse micelles at higher concentration. Our data highlight the relevance of the concept of "tunable reverse micellar geometry" in the novel trehalose-based nonionic surfactant binary mixtures, in which lipophilic tail architecture, solvent engineering, concentration
Shinmoto, Kazuya; Kadowaki, Kazunori; Nishimoto, Sakae; Kitani, Isamu
This paper describes experimental study on NO removal from a simulated exhausted-gas using repetitive surface discharge on a glass barrier subjected to polarity-reversed voltage pulses. The very fast polarity-reversal with a rise time of 20ns is caused by direct grounding of a charged coaxial cable of 10m in length. Influence of voltage rise time on energy efficiency for NO removal is studied. Results of NO removal using a barrier-type plasma reactor with screw-plane electrode system indicates that the energy efficiency for the very fast polarity reversal caused by direct grounding becomes higher than that for the slower polarity reversal caused by grounding through an inductor at the cable end. The energy efficiency for the direct grounding is about 80g/kWh for 50% NO removal ratio and is about 60g/kWh for 100% NO removal ratio. Very intense discharge light is observed at the initial time of 10ns for the fast polarity reversal, whereas the intensity in the initial discharge light for the slower polarity reversal is relatively small. To confirm the effectiveness of the polarity-reversed pulse application, comparison of the energy efficiency between the polarity-reversed voltage pulse and ac 60Hz voltage will be presented.
Dutta, Gaurav
2014-10-01
Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic modeling operator for forward modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.
Plane-Wave Least-Squares Reverse Time Migration for Rugged Topography
Jianping Huang; Chuang Li; Rongrong Wang; Qingyang Li
2015-01-01
We present a method based on least-squares reverse time migration with plane-wave encod-ing (P-LSRTM) for rugged topography. Instead of modifying the wave field before migration, we modify the plane-wave encoding function and fill constant velocity to the area above rugged topography in the model so that P-LSRTM can be directly performed from rugged surface in the way same to shot domain reverse time migration. In order to improve efficiency and reduce I/O (input/output) cost, the dynamic en-coding strategy and hybrid encoding strategy are implemented. Numerical test on SEG rugged topography model show that P-LSRTM can suppress migration artifacts in the migration image, and compensate am-plitude in the middle-deep part efficiently. Without data correction, P-LSRTM can produce a satisfying image of near-surface if we could get an accurate near-surface velocity model. Moreover, the pre-stack P-LSRTM is more robust than conventional RTM in the presence of migration velocity errors.
Extraordinary focusing of sound above a soda can array without time reversal
Maznev, A A; Sun, Shu-yuan; Xu, Jun; Shen, Yong; Fang, Nicholas; Zhang, Shu-yi
2014-01-01
Recently, Lemoult et al. [Phys. Rev. Lett. 107, 064301 (2011)] used time reversal to focus sound above an array of soda cans into a spot much smaller than the acoustic wavelength in air. In this study, we show that equally sharp focusing can be achieved without time reversal, by arranging transducers around a nearly circular array of soda cans. The size of the focal spot at the center of the array is made progressively smaller as the frequency approaches the Helmholtz resonance frequency of a can from below, and, near the resonance, becomes smaller than the size of a single can. We show that the locally resonant metamaterial formed by soda cans supports a guided wave at frequencies below the Helmholtz resonance frequency. The small focal spot results from a small wavelength of this guided wave near the resonance in combination with a near field effect making the acoustic field concentrate at the opening of a can. The focusing is achieved with propagating rather than evanescent waves. No sub-diffraction-limite...
Bogoliubov Fermi Surfaces in Superconductors with Broken Time-Reversal Symmetry
Agterberg, D. F.; Brydon, P. M. R.; Timm, C.
2017-03-01
It is commonly believed that, in the absence of disorder or an external magnetic field, there are three possible types of superconducting excitation gaps: The gap is nodeless, it has point nodes, or it has line nodes. Here, we show that, for an even-parity nodal superconducting state which spontaneously breaks time-reversal symmetry, the low-energy excitation spectrum generally does not belong to any of these categories; instead, it has extended Bogoliubov Fermi surfaces. These Fermi surfaces can be visualized as two-dimensional surfaces generated by "inflating" point or line nodes into spheroids or tori, respectively. These inflated nodes are topologically protected from being gapped by a Z2 invariant, which we give in terms of a Pfaffian. We also show that superconducting states possessing these Fermi surfaces can be energetically stable. A crucial ingredient in our theory is that more than one band is involved in the pairing; since all candidate materials for even-parity superconductivity with broken time-reversal symmetry are multiband systems, we expect these Z2-protected Fermi surfaces to be ubiquitous.
Newmark-Beta-FDTD method for super-resolution analysis of time reversal waves
Shi, Sheng-Bing; Shao, Wei; Ma, Jing; Jin, Congjun; Wang, Xiao-Hua
2017-09-01
In this work, a new unconditionally stable finite-difference time-domain (FDTD) method with the split-field perfectly matched layer (PML) is proposed for the analysis of time reversal (TR) waves. The proposed method is very suitable for multiscale problems involving microstructures. The spatial and temporal derivatives in this method are discretized by the central difference technique and Newmark-Beta algorithm, respectively, and the derivation results in the calculation of a banded-sparse matrix equation. Since the coefficient matrix keeps unchanged during the whole simulation process, the lower-upper (LU) decomposition of the matrix needs to be performed only once at the beginning of the calculation. Moreover, the reverse Cuthill-Mckee (RCM) technique, an effective preprocessing technique in bandwidth compression of sparse matrices, is used to improve computational efficiency. The super-resolution focusing of TR wave propagation in two- and three-dimensional spaces is included to validate the accuracy and efficiency of the proposed method.
Imaging Faults with Reverse-Time Migration for Geothermal Exploration at Jemez Pueblo in New Mexico
Huang, Lianjie [Los Alamos National Laboratory; Albrecht, Michael [TBA Power; Kaufman, Greg [Jemez Purblo; Kelley, Shari [NM Bureau of Geology and Mineral Researces; Rehfeldt, Kenneth [Los Alamos National Laboratory; Zhang, Zhifu [EES-17 visitor
2011-01-01
The fault zones at Jemez Pueblo may dominate the flow paths of hot water, or confine the boundaries of the geothermal reservoir. Therefore, it is crucial to image the geometry of these fault zones for geothermal exploration in the area. We use reverse-time migration with a separation imaging condition to image the faults at Jemez Pueblo. A finite-difference full-wave equation method with a perfectly-matching-layer absorbing boundary condition is used for backward propagation of seismic reflection data from receivers and forward propagation of wavefields from sources. In the imaging region, the wavefields are separated into the upgoing and downgoing waves, and leftgoing and rightgoing waves. The upgoing and downgoing waves are used to obtain the downward-looking image, and the leftgoing and rightgoing waves are used to form the left-looking image and right-looking image from sources. The left-looking and right-looking images are normally weaker than the downward-looking image because the reflections from the fault zones are much weaker than those from sedimentary layers, but these migration results contain the images of the faults. We apply our reverse-time migration with a wavefield separation imaging condition to seismic data acquired at Jemez Pueblo, and our preliminary results reveal many faults in the area.
Bittner, S; Dietz, B; Harney, H L; Miski-Oglu, M; Richter, A; Schäfer, F
2014-03-01
Scattering experiments with microwave cavities were performed and the effects of broken time-reversal invariance (TRI), induced by means of a magnetized ferrite placed inside the cavity, on an isolated doublet of nearly degenerate resonances were investigated. All elements of the effective Hamiltonian of this two-level system were extracted. As a function of two experimental parameters, the doublet and the associated eigenvectors could be tuned to coalesce at a so-called exceptional point (EP). The behavior of the eigenvalues and eigenvectors when encircling the EP in parameter space was studied, including the geometric amplitude that builds up in the case of broken TRI. A one-dimensional subspace of parameters was found where the differences of the eigenvalues are either real or purely imaginary. There, the Hamiltonians were found to be PT invariant under the combined operation of parity (P) and time reversal (T) in a generalized sense. The EP is the point of transition between both regions. There a spontaneous breaking of PT occurs.
Time reversibility and nonequilibrium thermodynamics of second-order stochastic processes.
Ge, Hao
2014-02-01
Nonequilibrium thermodynamics of a general second-order stochastic system is investigated. We prove that at steady state, under inversion of velocities, the condition of time reversibility over the phase space is equivalent to the antisymmetry of spatial flux and the symmetry of velocity flux. Then we show that the condition of time reversibility alone cannot always guarantee the Maxwell-Boltzmann distribution. Comparing the two conditions together, we find that the frictional force naturally emerges as the unique odd term of the total force at thermodynamic equilibrium, and is followed by the Einstein relation. The two conditions respectively correspond to two previously reported different entropy production rates. In the case where the external force is only position dependent, the two entropy production rates become one. We prove that such an entropy production rate can be decomposed into two non-negative terms, expressed respectively by the conditional mean and variance of the thermodynamic force associated with the irreversible velocity flux at any given spatial coordinate. In the small inertia limit, the former term becomes the entropy production rate of the corresponding overdamped dynamics, while the anomalous entropy production rate originates from the latter term. Furthermore, regarding the connection between the first law and second law, we find that in the steady state of such a limit, the anomalous entropy production rate is also the leading order of the Boltzmann-factor weighted difference between the spatial heat dissipation densities of the underdamped and overdamped dynamics, while their unweighted difference always tends to vanish.
Time-reversal symmetric Kitaev model and topological superconductor in two dimensions
Nakai, R.; Ryu, S.; Furusaki, A.
2012-04-01
A time-reversal invariant Kitaev-type model is introduced in which spins (Dirac matrices) on the square lattice interact via anisotropic nearest-neighbor and next-nearest-neighbor exchange interactions. The model is exactly solved by mapping it onto a tight-binding model of free Majorana fermions coupled with static Z2 gauge fields. The Majorana fermion model can be viewed as a model of time-reversal-invariant superconductor and is classified as a member of symmetry class DIII in the Altland-Zirnbauer classification. The ground-state phase diagram has two topologically distinct gapped phases which are distinguished by a Z2 topological invariant. The topologically nontrivial phase supports both a Kramers’ pair of gapless Majorana edge modes at the boundary and a Kramers’ pair of zero-energy Majorana states bound to a 0-flux vortex in the π-flux background. Power-law decaying correlation functions of spins along the edge are obtained by taking the gapless Majorana edge modes into account. The model is also defined on the one-dimension ladder, in which case again the ground-state phase diagram has Z2 trivial and nontrivial phases.
Subtleties in the BaBar measurement of time-reversal violation
Applebaum, Elaad; Grossman, Yuval; Nir, Yosef; Soreq, Yotam
2013-01-01
A first measurement of time-reversal (T) asymmetries that are not also CP asymmetries has been recently achieved by the BaBar collaboration. We analyze the measured asymmetries in the presence of direct CP violation, CPT violation, wrong strangeness decays and wrong sign semi-leptonic decays. We note that the commonly used S_{\\psi K} and C_{\\psi K} parameters are CP-odd, but have a T-odd CPT-even part and a T-even CPT-odd part. We introduce parameters that have well-defined transformation properties under CP, T and CPT. We identify contributions to the measured asymmetries that are T conserving. We explain why, in order to identify the measured asymmetries with time-reversal violation, there is no need to assume the absence of direct CP violation. Instead, one needs to assume (i) the absence of wrong strangeness decays or of CPT violation in strangeness changing decays, and (ii) the absence of wrong sign decays.
The effective chiral Lagrangian from dimension-six parity and time-reversal violation
Vries, J. de, E-mail: devries.jordy@gmail.com [KVI, Theory Group, University of Groningen, 9747 AA Groningen (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Mereghetti, E. [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Timmermans, R.G.E. [KVI, Theory Group, University of Groningen, 9747 AA Groningen (Netherlands); Kolck, U. van [Institut de Physique Nucléaire, Université Paris Sud, CNRS/IN2P3, 91406 Orsay (France); Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)
2013-11-15
We classify the parity- and time-reversal-violating operators involving quark and gluon fields that have effective dimension six: the quark electric dipole moment, the quark and gluon chromo-electric dipole moments, and four four-quark operators. We construct the effective chiral Lagrangian with hadronic and electromagnetic interactions that originate from them, which serves as the basis for calculations of low-energy observables. The form of the effective interactions depends on the chiral properties of these operators. We develop a power-counting scheme and calculate within this scheme, as an example, the parity- and time-reversal-violating pion–nucleon form factor. We also discuss the electric dipole moments of the nucleon and light nuclei. -- Highlights: •Classification of T-odd dimension-six sources based on impact on observables. •Building of the chiral Lagrangian for each dimension-six source. •Calculation of the PT-odd pion–nucleon form factor for each source. •Discussion of hadronic EDMs for each source and comparison with the theta term.
Performance analysis of an acoustic time reversal system in dynamic and random oceanic environments
Khosla, Sunny Rajendra
This dissertation provides a theoretical framework along with specific performance predictions for an acoustic time reversal system in shallow oceanic environments. Acoustic time-reversal is a robust means of retrofocusing acoustic energy, in both time and space, to the original sound-source location without any information about the acoustic environment in which it is deployed. The effect of three performance limiting oceanic complexities addressed, include (i)ambient noise field, (ii)reflection and volume scattering from a deterministic soliton internal wave traveling on the thermocline between two water masses, and (iii)volume scattering from a random superposition of linear internal waves convecting a gradient in the sound speed profile. The performance analysis establishes acoustic time reversal to be a promising technology for a two-way communication system in an oceanic medium. For an omni-directional noisy environment a general formulation for the probability of retrofocusing is developed that includes the effect of the medium, accounts for the system hardware and the acoustic parameters. Monte-Carlo simulations in both, a free-space environment and a shallow-ocean sound-channel environment compare well with theory. A 41 element TRA spanning a shallow water depth of 60 m is predicted to return a 70% focal probability at -15 dB SNR for a source to array range of 6 km. Preliminary research with broadband signals suggest that they should outperform narrowband response in both free space and sound channel environments. The impact of the nonlinear solitary waves is addressed using a two-path Green's function to treat the presence of a flat thermocline, and the single scattering Born approximation to address scattering from the soliton internal wave. It is predicted that a stationary soliton located along ray turning paths between the source and the TRA can lead to both enhanced and degraded focal performance. Based on extension of previous research in wave
Measuring the spin Chern number in time-reversal-invariant Hofstadter optical lattices
Zhang, Dan-Wei; Cao, Shuai
2016-10-01
We propose an experimental scheme to directly measure the spin Chern number of the time-reversal-invariant Hofstadter model in optical lattices. We first show that this model can be realized by using ultracold Fermi atoms with two pseudo-spin states encoded by the internal Zeeman states in a square optical lattice and the corresponding topological Bloch bands are characterized by the spin Chern number. We then propose and numerically demonstrate that this topological invariant can be extracted from the shift of the hybrid Wannier center in the optical lattice. By spin-resolved in situ detection of the atomic densities along the transverse direction combined with time-of-flight measurement along another spatial direction, the spin Chern number in this system is directly measured.
Application of time reversal mirror technique in microwave-induced thermo-acoustic tomography system
无
2009-01-01
Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.
Statistical analysis of strait time index and a simple model for trend and trend reversal
Chen, Kan; Jayaprakash, C.
2003-06-01
We analyze the daily closing prices of the Strait Time Index (STI) as well as the individual stocks traded in Singapore's stock market from 1988 to 2001. We find that the Hurst exponent is approximately 0.6 for both the STI and individual stocks, while the normal correlation functions show the random walk exponent of 0.5. We also investigate the conditional average of the price change in an interval of length T given the price change in the previous interval. We find strong correlations for price changes larger than a threshold value proportional to T; this indicates that there is no uniform crossover to Gaussian behavior. A simple model based on short-time trend and trend reversal is constructed. We show that the model exhibits statistical properties and market swings similar to those of the real market.
Andersen, P.; Skjærbæk, P. S.; Kirkegaard, Poul Henning
with the smoothed quanties which have been obtained from SARCOF. The results show the usefulness of the technique for identification of a time varying civil engineering structure. It is found that all the techniques give reliable estiates of the frequencies of the two lowest modes and the first mode shape. Only...
Digital Sequences and a Time Reversal-Based Impact Region Imaging and Localization Method
Weifeng Qian
2013-10-01
Full Text Available To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs is developed to record the impact region of impacts on-line. It is small in size, lightweight and has low power consumption, but there are two problems with the impact alarm region localization method of the digital monitor at the current stage. The first one is that the accuracy rate of the impact alarm region localization is low, especially on complex composite structures. The second problem is that the area of impact alarm region is large when a large scale structure is monitored and the number of PZTs is limited which increases the time and cost of damage inspections. To solve the two problems, an impact alarm region imaging and localization method based on digital sequences and time reversal is proposed. In this method, the frequency band of impact response signals is estimated based on the digital sequences first. Then, characteristic signals of impact response signals are constructed by sinusoidal modulation signals. Finally, the phase synthesis time reversal impact imaging method is adopted to obtain the impact region image. Depending on the image, an error ellipse is generated to give out the final impact alarm region. A validation experiment is implemented on a complex composite wing box of a real aircraft. The validation results show that the accuracy rate of impact alarm region localization is approximately 100%. The area of impact alarm region can be reduced and the number of PZTs needed to cover the same impact monitoring region is reduced by more than a half.
Adding a visualization feature to web search engines: it's time.
Wong, Pak Chung
2008-01-01
It's widely recognized that all Web search engines today are almost identical in presentation layout and behavior. In fact, the same presentation approach has been applied to depicting search engine results pages (SERPs) since the first Web search engine launched in 1993. In this Visualization Viewpoints article, I propose to add a visualization feature to Web search engines and suggest that the new addition can improve search engines' performance and capabilities, which in turn lead to better Web search technology.
Aspect, Alain
In the early 1980's, observation of a magneto-resistance anomaly in metallic thin films was attributed to the phenomenon of weak localization of electrons and to time-reversal symmetry breaking due to a magnetic field acting upon charged particles. We have observed weak localization of ultra-cold atoms in a 2D configuration, placed in a disordered potential created by a laser speckle. In order to manipulate time-reversal symmetry with our neutral atoms, we take advantage of the slow evolution of our system, and we observe the suppression and revival of weak localization when time reversal symmetry is cancelled and reestablished. References: K. Muller, J. Richard, V. V. Volchkov, V. Denechaud, P. Bouyer, A. Aspect, and V. Josse, ''Suppression and Revival of Weak Localization through Control of Time-Reversal Symmetry,'' Physical Review Letters 114 (20) (2015) and references in. Work supported by the ERC Avanced Grant Quantatop.
VANDENBROEK, L; WIERDA, JMKH; SMEULERS, NJ; VANSANTEN, GJ; LECLERCQ, MGL; HENNIS, PJ
1994-01-01
Study Objective: To evaluate the time course of action, dose requirement, reversibility, and pharmacokinetics of rocuronium (Org 9426) under 3 anesthetic techniques (nitrous oxide-fentanyl supplemented with propofol halothane, or isoflurane). Design: Prospective, randomized study. Setting: Operating
Sarlis, N. V.; Christopoulos, S.-R. G.; Bemplidaki, M. M.
2015-01-01
The entropy S in natural time as well as the entropy in natural time under time reversal S- have already found useful applications in the physics of complex systems, e.g., in the analysis of electrocardiograms (ECGs). Here, we focus on the complexity measures Λl which result upon considering how the statistics of the time series Δ S≤ft[\\equiv S- S-\\right] changes upon varying the scale l. These scale-specific measures are ratios of the standard deviations σ(Δ S_l) and hence independent of the mean value and the standard deviation of the data. They focus on the different dynamics that appear on different scales. For this reason, they can be considered complementary to other standard measures of heart rate variability in ECG, like SDNN, as well as other complexity measures already defined in natural time. An application to the analysis of ECG —when solely using NN intervals— is presented: We show how Λl can be used to separate ECG of healthy individuals from those suffering from congestive heart failure and sudden cardiac death.
2007-10-16
1999. [93] H. Song, "Iterative Time Reversal in the Ocean," J. Acoust. Soc. Am., vol. 105, no. 6. [94] S. Kim, G. Edelmann , W. Kuperman, W. Hodgkiss, and...Channel Time-Reversal Acoustics," Appl. Phys. Lett., vol. 80, pp. 694-696, 2002. [97] G. Edelmann , T. Akal, W. Hodgkiss, S. Kim, K. W.A., and H. Song, "An
Rethinking fast and slow based on a critique of reaction-time reverse inference.
Krajbich, Ian; Bartling, Björn; Hare, Todd; Fehr, Ernst
2015-07-02
Do people intuitively favour certain actions over others? In some dual-process research, reaction-time (RT) data have been used to infer that certain choices are intuitive. However, the use of behavioural or biological measures to infer mental function, popularly known as 'reverse inference', is problematic because it does not take into account other sources of variability in the data, such as discriminability of the choice options. Here we use two example data sets obtained from value-based choice experiments to demonstrate that, after controlling for discriminability (that is, strength-of-preference), there is no evidence that one type of choice is systematically faster than the other. Moreover, using specific variations of a prominent value-based choice experiment, we are able to predictably replicate, eliminate or reverse previously reported correlations between RT and selfishness. Thus, our findings shed crucial light on the use of RT in inferring mental processes and strongly caution against using RT differences as evidence favouring dual-process accounts.
渐开线斜齿圆柱齿轮逆向工程%Reverse Engineering of Involute Helical Gear
程友斌
2012-01-01
论述了用三坐标测量机扫描斜齿轮齿廓面,获得齿轮型面点云,再应用专业逆向工程软件Imageware精确测绘单齿齿轮获得齿轮相关数据,并用Excel软件完成齿轮参数计算的方法.%How to use CMM scan helical gear tooth profile surface is discussed, the point cloud of the gear moulding surface is obtained. Then the single gear is precisely measured by the reverse engineering software Image-ware , the correlation data of the gear is obtained, and the calculation method gear parameter is accomplished by using the Excel soft.
Huang Xiaoping; Xiong Youlun
2001-01-01
For reverse engineering a CAD model, it is necessary to integrate measured points from several views of an object into a common reference frame. Given a rough initial alignment of point cloud in different views with point-normal method, further refinement is achieved by using an improved iterative closest point (ICP) algorithm. Compared with other methods used for multi-view registration, this approach is automatic because no geometric feature, such as line, plane or sphere needs to be extracted from the original point cloud manually. A good initial alignment can be acquired automatically and the registration accuracy and efficiency is proven better than the normal point-point ICP algorithm both experimentally and theoretically.
Wang, Jiming; Chen, Weibin; Zhan, Qiwen
2010-10-11
We report a new method to create high purity longitudinally polarized field with extremely long depth of focus in the focal volume of a high numerical aperture (NA) objective lens. Through reversing the radiated field from an electric dipole array situated near the focus of the high-NA lens, the required incident field distribution in the pupil plane for the creation of an ultra-long optical needle field can be found. Numerical examples demonstrate that an optical needle field with a depth of focus up to 8λ is obtainable. Throughout the depth of focus, this engineered focal field maintains a diffraction limited transverse spot size (<0.43λ) with high longitudinal polarization purity. From the calculated pupil plane distribution, a simplified discrete complex pupil filter can be designed and significant improvements over the previously reported complex filters are clearly demonstrated.
Reverse engineering of a Hamiltonian for a three-level system via the Rodrigues’ rotation formula
Kang, Yi-Hao; Huang, Bi-Hua; Lu, Pei-Min; Xia, Yan
2017-02-01
We propose a scheme to reversely construct a three-level Hamiltonian via the Rodrigues’ rotation formula and an auxiliary unitary transformation. The main goal of the scheme is designing feasible pulses to drive a three-level system to evolve rapidly from an arbitrary initial state to a desired final state. Numerical simulations demonstrate that the scheme is not only fast but also robust against the decoherence caused by fluctuations of control parameters and some dissipation factors. Besides, we apply the idea to implement a Hadamard gate in a three-level system, and the results show the present scheme is much faster compared with stimulated Raman adiabatic passage (STIRAP). Therefore, the scheme may be useful to find out an effective shortcut to the adiabatic passage in a three-level system.
Real-time diagnostics for a reusable rocket engine
Guo, T. H.; Merrill, W.; Duyar, A.
1992-01-01
A hierarchical, decentralized diagnostic system is proposed for the Real-Time Diagnostic System component of the Intelligent Control System (ICS) for reusable rocket engines. The proposed diagnostic system has three layers of information processing: condition monitoring, fault mode detection, and expert system diagnostics. The condition monitoring layer is the first level of signal processing. Here, important features of the sensor data are extracted. These processed data are then used by the higher level fault mode detection layer to do preliminary diagnosis on potential faults at the component level. Because of the closely coupled nature of the rocket engine propulsion system components, it is expected that a given engine condition may trigger more than one fault mode detector. Expert knowledge is needed to resolve the conflicting reports from the various failure mode detectors. This is the function of the diagnostic expert layer. Here, the heuristic nature of this decision process makes it desirable to use an expert system approach. Implementation of the real-time diagnostic system described above requires a wide spectrum of information processing capability. Generally, in the condition monitoring layer, fast data processing is often needed for feature extraction and signal conditioning. This is usually followed by some detection logic to determine the selected faults on the component level. Three different techniques are used to attack different fault detection problems in the NASA LeRC ICS testbed simulation. The first technique employed is the neural network application for real-time sensor validation which includes failure detection, isolation, and accommodation. The second approach demonstrated is the model-based fault diagnosis system using on-line parameter identification. Besides these model based diagnostic schemes, there are still many failure modes which need to be diagnosed by the heuristic expert knowledge. The heuristic expert knowledge is
Mattia Zampieri
Full Text Available BACKGROUND: The concept of reverse engineering a gene network, i.e., of inferring a genome-wide graph of putative gene-gene interactions from compendia of high throughput microarray data has been extensively used in the last few years to deduce/integrate/validate various types of "physical" networks of interactions among genes or gene products. RESULTS: This paper gives a comprehensive overview of which of these networks emerge significantly when reverse engineering large collections of gene expression data for two model organisms, E. coli and S. cerevisiae, without any prior information. For the first organism the pattern of co-expression is shown to reflect in fine detail both the operonal structure of the DNA and the regulatory effects exerted by the gene products when co-participating in a protein complex. For the second organism we find that direct transcriptional control (e.g., transcription factor-binding site interactions has little statistical significance in comparison to the other regulatory mechanisms (such as co-sharing a protein complex, co-localization on a metabolic pathway or compartment, which are however resolved at a lower level of detail than in E. coli. CONCLUSION: The gene co-expression patterns deduced from compendia of profiling experiments tend to unveil functional categories that are mainly associated to stable bindings rather than transient interactions. The inference power of this systematic analysis is substantially reduced when passing from E. coli to S. cerevisiae. This extensive analysis provides a way to describe the different complexity between the two organisms and discusses the critical limitations affecting this type of methodologies.
Nojima, Kazuhisa; Ge, Sheng; Katayama, Yoshinori; Ueno, Shoogo; Iramina, Keiji
2010-05-01
The aim of this study is to investigate the effect of the stimulus frequency and pulses number of repetitive transcranial magnetic stimulation (rTMS) on the inter-reversal time (IRT) of perceptual reversal on the right superior parietal lobule (SPL). The spinning wheel illusion was used as the ambiguous figures stimulation in this study. To investigate the rTMS effect over the right SPL during perceptual reversal, 0.25 Hz 60 pulse, 1 Hz 60 pulse, 0.5 Hz 120 pulse, 1 Hz 120 pulse, and 1 Hz 240 pulse biphasic rTMS at 90% of resting motor threshold was applied over the right SPL and the right posterior temporal lobe (PTL), respectively. As a control, a no TMS was also conducted. It was found that rTMS on 0.25 Hz 60 pulse and 1 Hz 60 pulse applied over the right SPL caused shorter IRT. In contrast, it was found that rTMS on 1 Hz 240-pulse applied over the right SPL caused longer IRT. On the other hand, there is no significant difference between IRTs when the rTMS on 0.5 Hz 120 pulse and 1 Hz 120 pulse were applied over the right SPL. Therefore, the applying of rTMS over the right SPL suggests that the IRT of perceptual reversal is effected by the rTMS conditions such as the stimulus frequency and the number of pulses.
Observation of Quantum Spin Hall States in InAs/GaSb Bilayers under Broken Time-Reversal Symmetry
Du, Lingjie; Knez, Ivan; Sullivan, Gerard; Du, Rui-Rui
2014-03-01
Topological insulators (TIs) are a novel class of materials with nontrivial surface or edge states. Time-reversal symmetry (TRS) protected TIs are characterized by the Z2 topological invariant. The fate of the Z2 TIs under broken TRS is a fundamental question in understanding the physics of topological matter but remains largely unanswered. Here we show, a two-dimensional TI is realized in an inverted electron-hole bilayer engineered from InAs/GaSb semiconductors which retains robust helical liquid (HL) edge states under a strong magnetic field. Wide conductance plateaus of 2e2/h value are observed; they persist to 10T applied in-plane field before transitioning to a trivial semimetal. In a perpendicular field up to 35T, broken TRS leads to a spatial separation of the movers in Kramers pair and consequently the intra-pair backscattering phase space vanishes, i.e., the conductance increases from 2e2/h in strong fields manifesting chiral edge transport. We propose a phenomenological phases diagram, where inside the topological gap the HL transfers into a ``canned helical state'' driven by perpendicular fields. Our findings suggest that once established, the HL is remarkably resilient and only undergoes adiabatic deformation under TRS breaking. The work at Rice was supported by DOE, NSF, and Welch Foundation.
Galunin, Evgeny [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Alba, Maria D.; Aviles, Miguel A. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Cientificas - Universidad de Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain); Santos, Maria J. [Departamento de Quimica, Universidade Estadual de Londrina, Londrina, PR, 86051-990 (Brazil); Vidal, Miquel, E-mail: miquel.vidal@ub.edu [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)
2009-12-30
The sorption reversibility of La and Lu (considered as actinide analogues) onto a set of smectites (bentonite FEBEX; hectorite, HEC; MX80; saponite, SAP; Otay montmorillonite, SCa-3; and Texas montmorillonite, STx-1) was studied to estimate actinide retention by smectites that are candidates for use as engineered barriers in deep geological repositories. The sorption distribution coefficients (K{sub d}) and the reversibility parameters (desorption distribution coefficients (K{sub d,des}), adjusted distribution coefficients (K{sub d,adj}), and desorption rates (R{sub des})) were determined from batch tests in two ionic media: deionized water and Ca 0.02 mol L{sup -1}. The latter simulates possible conditions due to the presence of concrete leachates. The results varied greatly depending on the ionic medium, the lanthanide concentration and the clay structure. The high values of K{sub d,des} obtained (up to 1.1 x 10{sup 5} and 9.2 x 10{sup 4} L kg{sup -1} for La and Lu in water, and 2.8 x 10{sup 4} and 4.1 x 10{sup 4} L kg{sup -1} for La and Lu in the Ca medium) indicate the suitability of the tested smectites for lanthanide (and therefore, actinide) retention. Based on all the data, SCa-3, HEC and FEBEX clays are considered the best choices for water environments, whereas in Ca environments the suitable clays depended on the lanthanide considered.
Relational Database Reverse Engineering Based on Object-Oriented Model%基于面向对象模型的关系数据库逆向工程研究
马恕; 余永红; 徐洁磐
2000-01-01
Recently, researchers have paid more attention on software reverse engineering, this paper mainly discusses the basic problems of relational database reverse engineering based on object-oriented model,it also presents a method which can be used to implement relational database reverse engineering based on EXPRESS object-oriented model. The research can play an important role on improving the quality of software reengineering,and extending the domain of object-oriented methodology.
Thomson, D.B. (comp.)
1987-11-01
These Proceedings contain the formal contributed papers, the workshop papers and workshop summaries presented at the International Workshop on Engineering Design of Next Step RFP Devices held at Los Alamos, July 13-17, 1987. Contributed papers were presented at formal sessions on the topics: (1) physics overview (3 papers); (2) general overview (3 papers); (3) front-end (9 papers); (4) computer control and data acquisition (1 paper); (5) magnetics (5 papers); and (6) electrical design (9 papers). Informal topical workshop sessions were held on the topics: (1) RFP physics (9 papers); (2) front-end (7 papers); (3) magnetics (3 papers); and (4) electrical design (1 paper). This volume contains the summaries written by the Chairmen of each of the informal topical workshop sessions. The papers in these Proceedings represent a significant review of the status of the technical base for the engineering design of the next step RFP devices being developed in the US, Europe, and Japan, as of this date.
Fringe Projection Measurement System in Reverse Engineering%光栅投射技术在逆向工程中的应用
林朝辉; 何海涛; 郭红卫; 陈明仪; 石璇; 俞涛
2005-01-01
Acquisition of physical data with high precision is a key step in reverse engineering (RE). It is an important stimulative for the progress of reverse engineering with which various digitizing devices are invented, developed and made applicable. This paper introduces a three dimensional optical measurement method based on digital fringe projection technique in RE to improve the technique through its application. A practical example is presented and the result demonstrates the applicability and feasibility of the measurement system as well as the reliability and validity of relevant methods and algorithms.
REAL TIME FUEL INJECTION IN SI ENGINE USING ELECTRONIC INSTRUMENTATION
V. VINOTH KUMAR, M.E
2012-05-01
Full Text Available To meet the present stringent emission norms. These systems are enerally termed as Electronic Fuel Injection (EFI systems. The fuel is injected into the throttle body or into the inlet manifold through an electronic fuel injector, which is controlled by an Electronic Control Unit (ECU. The quantity of fuel injected by the injector plays a vital role as far as performance and emission characteristics of spark ignition engines are concerned. This paper deals with the static and dynamic fuel injection characteristics of two gasoline fuelinjectors. The effect of different injection parameters like fuel injection pressure, injection duration, supply voltage to injector and engine speed on the quantity of fuel injected have been studied for two injectors. The injection dead time and its variation with respect to fuel pressure and supply voltage to injector have beenanalyzed. Based on the analysis of results, an empirical formula has been obtained to determine the dynamic fuel injection quantity from the static fuel injection characteristics and it was compared with the measured values. It is found that the empirical formula developed in this work gives reasonably good results and therefore, it can be used with confidence for predicting the dynamic characteristics of any given injector from its static injection characteristics.
Polarized proton-deuteron scattering as a test of time-reversal invariance
Uzikov, Yu. N.; Haidenbauer, J.
2016-09-01
Scattering of protons with transversal polarization pyp on deuterons with tensor polarization Px z provides a null-test signal for time-reversal (T) invariance violating but parity (P) conserving effects. We calculate the corresponding null-test observable at beam energies 100 -1000 MeV within the spin-dependent Glauber theory considering T-violating P-conserving nucleon-nucleon interactions. The S -wave component of the deuteron wave function as well as the D wave are taken into account and the latter is found to play an important role for the magnitude and the energy dependence of the observable in question. Specifically, with inclusion of the D wave the maximum of the obtained signal is shifted to higher beam energies, i.e., to 700 -800 MeV.
Polarized proton-deuteron scattering as a test of time-reversal invariance
Uzikov, Yu N
2016-01-01
Scattering of protons with transversal polarization $p_y^p$ on deuterons with tensor polarization $P_{xz}$ provides a null-test signal for time-reversal (T) invariance violating but parity (P) conserving effects. We calculate the corresponding null-test observable at beam energies 100-1000 MeV within the spin-dependent Glauber theory considering T-violating P-conserving nucleon-nucleon interactions. The S-wave component of the deuteron wave function as well as the D-wave are taken into account and the latter is found to play an important role for the magnitude and the energy dependence of the observable in question. Specifically, with inclusion of the D wave the maximum of the obtained signal is shifted to higher beam energies, i.e. to 700-800 MeV.
Polar Kerr Effect as Probe for Time-Reversal Symmetry Breaking in Unconventional Superconductors
Kapitulnik, A.
2010-05-26
The search for broken time reversal symmetry (TRSB) in unconventional superconductors intensified in the past year as more systems have been predicted to possess such a state. Following our pioneering study of TRSB states in Sr{sub 2}RuO{sub 4} using magneto-optic probes, we embarked on a systematic study of several other of these candidate systems. The primary instrument for our studies is the Sagnac magneto-optic interferometer, which we recently developed. This instrument can measure magneto-optic Faraday or Kerr effects with an unprecedented sensitivity of 10 nanoradians at temperatures as low as 100 mK. In this paper we review our recent studies of TRSB in several systems, emphasizing the study of the pseudogap state of high temperature superconductors and the inverse proximity effect in superconductor/ferromagnet proximity structures.
Time Reversibility, Correlation Decay and the Steady State Fluctuation Relation for Dissipation
Denis J. Evans
2013-04-01
Full Text Available Steady state fluctuation relations for nonequilibrium systems are under intense investigation because of their important practical implications in nanotechnology and biology. However the precise conditions under which they hold need clarification. Using the dissipation function, which is related to the entropy production of linear irreversible thermodynamics, we show time reversibility, ergodic consistency and a recently introduced form of correlation decay, called T-mixing, are sufficient conditions for steady state fluctuation relations to hold. Our results are not restricted to a particular model and show that the steady state fluctuation relation for the dissipation function holds near or far from equilibrium subject to these conditions. The dissipation function thus plays a comparable role in nonequilibrium systems to thermodynamic potentials in equilibrium systems.
Wideband nonlinear time reversal seismo-acoustic method for landmine detection.
Sutin, Alexander; Libbey, Brad; Fillinger, Laurent; Sarvazyan, Armen
2009-04-01
Acoustic and seismic waves provide a method to localize compliant mines by vibrating the top plate and a thin soil layer above the mine. This vibration is mostly linear, but also includes a small nonlinear deviation. The main goal of this paper is to introduce a method of processing that uses phase-inversion to observe nonlinear effects in a wide frequency band. The method extracts a nonlinear part of surface velocity from two similar broadcast signals of opposite sign by summing and cancelling the linear components and leaving the nonlinear components. This phase-inversion method is combined with time reversal focusing to provide increased seismic vibration and enhance the nonlinear effect. The experiments used six loudspeakers in a wood box placed over sand in which inert landmines were buried. The nonlinear surface velocity of the sand with a mine compared to the sand without a mine was greater as compared to a linear technique.
Depth profile of a time-reversal focus in an elastic solid.
Remillieux, Marcel C; Anderson, Brian E; Ulrich, T J; Le Bas, Pierre-Yves; Payan, Cedric
2015-04-01
The out-of-plane velocity component is focused on the flat surface of an isotropic solid sample using the principle of time reversal. This experiment is often reproduced in the context of nondestructive testing for imaging features near the surface of the sample. However, it is not clear how deep the focus extends into the bulk of the sample and what its profile is. In this paper, this question is answered using both numerical simulations and experimental data. The profiles of the foci are expressed in terms of the wavelengths of the dominant waves, based on the interpretation of the Lamb's problem and the use of the diffraction limit. Published by Elsevier B.V.
Xiao, Bo; Yu, Yang; Ma, Tzuhsuan; Shvets, Gennady; Anlage, Steven M
2016-01-01
Photonic topological insulators are an interesting class of materials whose photonic band structure can have a bandgap in the bulk while supporting topologically protected unidirectional edge modes. Recent studies on bianisotropic metamaterials that emulate the electronic quantum spin Hall effect using its electromagnetic analog are examples of such systems with relatively simple and elegant design. In this paper, we present a novel rotating magnetic dipole antenna, composed of two perpendicularly oriented helical coils, that can efficiently excite the unidirectional topologically protected surface waves in the bianisotropic metawaveguide (BMW) structure recently realized by Ma, et al., despite the fact that the BMW does not break time-reversal invariance. In addition to achieving high directivity, the antenna can be tuned continuously to excite reflectionless edge modes to the two opposite directions with various amplitude ratios. We demonstrate its performance through experiment and compare to simulation re...
Korotaev, S M; Kiktenko, E O; Budnev, N M; Gorohov, J V
2015-01-01
Although the general theory macroscopic quantum entanglement of is still in its infancy, consideration of the matter in the framework of action-at-a distance electrodynamics predicts for the random dissipative processes observability of the advanced nonlocal correlations. These correlations were really revealed in our previous experiments with some large-scale heliogeophysical processes as the source ones and the lab detectors as the probe ones. Recently a new experiment has been performing on the base of Baikal Deep Water Neutrino Observatory. The thick water layer is an excellent shield against any local impacts on the detectors. The first annual series 2012/2013 has demonstrated that detector signals respond to the heliogeophysical processes and causal connection of the signals directed downwards: from the Earth surface to the Baikal floor. But this nonlocal connection proved to be in reverse time. In addition advanced nonlocal correlation of the detector signal with the regional source-process: the random...
Time reversal constraint limits unidirectional photon emission in slow-light photonic crystals
Lang, Ben; Oulton, Ruth
2016-01-01
Photonic crystal waveguides are known to support C-points - point-like polarisation singularities with local chirality. Such points can couple with dipole-like emitters to produce highly directional emission, from which spin-photon entanglers can be built. Much is made of the promise of using slow-light modes to enhance this light-matter coupling. Here we explore the transition from travelling to standing waves for two different photonic crystal waveguide designs. We find that time-reversal symmetry and the reciprocal nature of light places constraints on using C-points in the slow-light regime. We observe two distinctly different mechanisms through which this condition is satisfied in the two waveguides. In the waveguide designs we consider, a modest group-velocity of $v_g \\approx c/10$ is found to be the optimum for slow-light coupling to the C-points.
Ergodic time-reversible chaos for Gibbs' canonical oscillator
Hoover, William Graham, E-mail: hooverwilliam@yahoo.com [Ruby Valley Research Institute, Highway Contract 60, Box 601, Ruby Valley, NV 89833 (United States); Sprott, Julien Clinton [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Patra, Puneet Kumar [Advanced Technology Development Center, Department of Civil Engineering, Indian Institute of Technology, Kharagpur, West Bengal, 721302 (India)
2015-12-04
Nosé's pioneering 1984 work inspired a variety of time-reversible deterministic thermostats. Though several groups have developed successful doubly-thermostated models, single-thermostat models have failed to generate Gibbs' canonical distribution for the one-dimensional harmonic oscillator. A 2001 doubly-thermostated model, claimed to be ergodic, has a singly-thermostated version. Though neither of these models is ergodic this work has suggested a successful route toward singly-thermostated ergodicity. We illustrate both ergodicity and its lack for these models using phase-space cross sections and Lyapunov instability as diagnostic tools. - Highlights: • We develop cross-section and Lyapunov methods for diagnosing ergodicity. • We apply these methods to several thermostatted-oscillator problems. • We demonstrate the nonergodicity of previous work. • We find a novel family of ergodic thermostatted-oscillator problems.
Detailed balance study of time reversal invariance with interfering resonancesrefid="FN1">*
Mitchell, G. E.; Bilpuch, E. G.; Bybee, C. R.; Drake, J. M.; Shriner, J. F.
1993-06-01
Bunakov and Weidenmüller suggested that large enhancement of time reversal invariance violation may be observed near two interfering resonances via a test of detailed balance. In our (p, α) resonance data on 23Na, 27Al, 31P, 35Cl, and 39K, there are 33 pairs of adjacent resonances which have the same spin and parity. The difference in the differential cross sections for the (p, α 0) and (α, p 0) reactions was calculated for these resonance pairs using experimental values for the partial widths. The collision matrix elements were obtained for a Hamiltonian H = H0 + iH', following the approach of Moldauer. The differences show striking dependence on energy and angle and on the particular pair of resonances, with the relative sensitivity of the detailed balance test varying by many orders of magnitude. These preliminary results indicate that this class of experiments may be more sensitive than previous detailed balance tests.
Common-image gathers in the offset domain from reverse-time migration
Zhan, Ge
2014-04-01
Kirchhoff migration is flexible to output common-image gathers (CIGs) in the offset domain by imaging data with different offsets separately. These CIGs supply important information for velocity model updates and amplitude-variation-with-offset (AVO) analysis. Reverse-time migration (RTM) offers more insights into complex geology than Kirchhoff migration by accurately describing wave propagation using the two-way wave equation. But, it has difficulty to produce offset domain CIGs like Kirchhoff migration. In this paper, we develop a method for obtaining offset domain CIGs from RTM. The method first computes the RTM operator of an offset gather, followed by a dot product of the operator and the offset data to form a common-offset RTM image. The offset domain CIGs are then achieved after separately migrating data with different offsets. We generate offset domain CIGs on both the Marmousi synthetic data and 2D Gulf of Mexico real data using this approach. © 2014.
Nagasawa, Fumiya; Takagi, Jun; Kunihashi, Yoji; Kohda, Makoto; Nitta, Junsaku
2012-02-01
A geometric phase of electron spin is studied in arrays of InAlAs/InGaAs two-dimensional electron gas rings. By increasing the radius of the rings, the time-reversal symmetric Aharonov-Casher oscillations of the electrical resistance are shifted towards weaker spin-orbit interaction regions with their shortened period. We conclude that the shift is due to a modulation of the spin geometric phase, the maximum modulation of which is approximately 1.5 rad. We further show that the Aharonov-Casher oscillations in various radius arrays collapse onto a universal curve if the radius and the strength of Rashba spin-orbit interaction are taken into account. The result is interpreted as the observation of the effective spin-dependent flux through a ring.
Grusdt, Fabian; Abanin, Dmitry; Demler, Eugene
2013-05-01
Recently experiments with ultracold atoms started to explore topological phases in 1D optical lattices. While transport measurements are challenging in these systems, ways to directly measure topological quantum numbers using a combination of Bloch oscillations and Ramsey interferometry have been explored (Atala et al., arXiv:1212.0572). In this talk I will present ways to measure the Z2 topological quantum numbers of two and three dimensional time-reversal invariant (TR) topological insulators. In this case non-Abelian Bloch oscillations can be combined with Ramsey interferometry to map out the topological properties of a given band-structure. Our method is very general and works even in the presence of accidental degeneracies. The applicability of the scheme is discussed for different theoretically proposed implementations of TR topological insulators using ultracold atoms. F. G. is grateful to Harvard University for hospitality and acknowledges financial support from Graduate School Materials Science in Mainz (MAINZ).
Trani, F.; Campagnano, G.; Tagliacozzo, A.; Lucignano, P.
2016-10-01
We study possible applications of high critical temperature nodal superconductors for the search for Majorana bound states in the DIII class. We propose a microscopic analysis of the proximity effect induced by d -wave superconductors on a semiconductor wire with strong spin-orbit coupling. We characterize the induced superconductivity on the wire employing a numerical self-consistent tight-binding Bogoliubov-de Gennes approach, and analytical considerations on the Green's function. The order parameter induced on the wire, the pair correlation function, and the renormalization of the Fermi points are analyzed in detail, as well as the topological phase diagram in the case of weak coupling. We highlight optimal Hamiltonian parameters to access the nontrivial topological phase which could display time-reversal invariant Majorana doublets at the boundaries of the wire.
Time-reversal-invariance-violating nucleon-nucleon potential in the 1/N_c expansion
Samart, Daris; Schindler, Matthias R; Phillips, Daniel R
2016-01-01
We apply the large-$N_c$ expansion to the time-reversal-invariance-violating (TV) nucleon-nucleon potential. The operator structures contributing to next-to-next-to-leading order in the large-$N_c$ counting are constructed. For the TV and parity-violating case we find a single operator structure at leading order. The TV but parity-conserving potential contains two leading-order terms, which however are suppressed by 1/$N_c$ compared to the parity-violating potential. Comparison with phenomenological potentials, including the chiral EFT potential in the TV parity-violating case, leads to large-$N_c$ scaling relations for TV meson-nucleon and nucleon-nucleon couplings.
Time-reversal symmetry breaking hidden order in Sr2(Ir,Rh)O4
Jeong, Jaehong; Sidis, Yvan; Louat, Alex; Brouet, Véronique; Bourges, Philippe
2017-04-01
Layered 5d transition iridium oxides, Sr2(Ir,Rh)O4, are described as unconventional Mott insulators with strong spin-orbit coupling. The undoped compound, Sr2IrO4, is a nearly ideal two-dimensional pseudospin-1/2 Heisenberg antiferromagnet, similarly to the insulating parent compound of high-temperature superconducting copper oxides. Using polarized neutron diffraction, we here report a hidden magnetic order in pure and doped Sr2(Ir,Rh)O4, distinct from the usual antiferromagnetic pseudospin ordering. We find that time-reversal symmetry is broken while the lattice translation invariance is preserved in the hidden order phase. The onset temperature matches that of the odd-parity hidden order recently highlighted using optical second-harmonic generation experiments. The novel magnetic order and broken symmetries can be explained by the loop-current model, previously predicted for the copper oxide superconductors.
Studies of parity and time reversal symmetries in neutron scattering from165Ho
Haase, D. G.; Gould, C. R.; Koster, J. E.; Roberson, N. R.; Seagondollar, L. W.; Soderstrum, J. P.; Schneider, M. B.; Zhu, X.
1988-12-01
We describe searches for parity and time reversal violations in the scattering of polarized neutrons from polarized and aligned165Ho targets. We have completed a search with 7.1 and 11.0 MeV neutrons for PoddTodd terms in the elastic scattering forward amplitude of the form s. ( I×K), where s is the neutron spin, I is the target spin and k is the neutron momentum vector. The target was a single crystal of holmium, polarized horizontally along its b axis by a 1 Tesla magnetic field. The neutrons were polarized vertically. Differences in the neutron transmission were measured for neutrons with spins parallel (antiparallel) to I×k. The P,T violating analyzing powers were found to be consistent with zero at the few 10-3 level: ρP,T(7.1 MeV)=-0.88 (±2.02) x 10-3, ρP,T(11.0 MeV)=-0.4 (±2.88) x 10-3. We have also attempted to find enhancements with MeV neutrons in P-violation due to the term s k. We are preparing an aligned target cryostat for investigations of PevenTodd terms {bd(Ik)(I×k)s} in neutron scattering. The target will be a single crystal cylinder of165Ho cooled to 100 mK in a bath of liquid helium and rotated by a shaft from a room temperature stepping motor. The cylinder will be oriented vertically and the alignment ( c) axis oriented horizontally. Warming or rotation of the sample allows one to separate effects that mimic the sought-after time reversal violating term.
Real-time determination of human telomerase reverse transcriptase mRNA in gastric cancer
Li-Hua Hu; Feng-Hua Chen; Yi-Rong Li; Lin Wang
2004-01-01
AIM: To set up a real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay,to detect human telomerase reverse transcriptase (hTERT)messenger RNA in gastric carcinomas, and to evaluate quantitative determination of hTERT mRNA in the diagnostic value of gastric carcinomas, and to analyze the correlation between the expression level of hTERT mRNA and dinicopathological parameters in patients with gastric cancer.METHODS: A real-time quantitative RT-PCR (RQ-PCR)based on TaqMan fluorescence methodoloogy and the LightCyder system was used to quantify the full range of hTERT mRNA copy numbers in 35 samples of gastric carcinomas and corresponding adjacent non-cancerous tissues. The normalized hTERT (NhTERT) was standardized by quantifying the number of GAPDH transcripts as internal control and expressed as 100× (hTERT/GAPDH) ratio. Variables were analyzed by the Student's t-test, χ2 test and Fisher's exact test.RESULTS: NhTERT from gastric carcinomas and corresponding adjacent non-cancerous tissues was 6.27±0.89 and 0.93±0.18,respectively (t= 12.76, P＜0.001). There was no significant association between gastric cancer hTERT mRNA expression level and patient's age, gender, tumor size, location and stage (pTNM), but a significant correlation was found between hTERT mRNA expression level in gastric carcinomas and the degree of differentiation.CONCLUSION: Quantitative determination of hTERT mRNA by RQ-PCR is a rapid and sensitive method. hTERT might be a potential biomarker for the early detection of gastric cancer.
Time Reversal Violation from the entangled B0-antiB0 system
Bernabeu, J; Villanueva-Perez, P
2012-01-01
We discuss the concepts and methodology to implement an experiment probing directly Time Reversal (T) non-invariance, without any experimental connection to CP violation, by the exchange of "in" and "out" states. The idea relies on the B0-antiB0 entanglement and decay time information available at B factories. The flavor or CP tag of the state of the still living neutral meson by the first decay of its orthogonal partner overcomes the problem of irreversibility for unstable systems, which prevents direct tests of T with incoherent particle states. T violation in the time evolution between the two decays means experimentally a difference between the intensities for the time-ordered (l^+ X, J/psi K_S) and (J/psi K_L, l^- X) decays, and three other independent asymmetries. The proposed strategy has been applied to simulated data samples of similar size and features to those currently available, from which we estimate the significance of the expected discovery to reach many standard deviations.