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Second harmonic generation of ultrasonic waves propagating in unbounded media and plate-like structure has been vigorously studied for tracking material nonlinearity, however, second harmonic guided wave propagation in tube-like structures is rarely studied. Considering that second harmonics can provide sensitive information for structural health condition, this paper aims to study the second harmonic generation of guided waves in metallic tube-like structures with weakly nonlinearity. Perturbation method and modal analysis approach are used to analyze the acoustic field of second harmonic solutions. The conditions for generating second harmonics with cumulative effect are provided in present investigation. Flexible polyvinylidene fluoride comb transducers are used to measure fundamental wave modes and second harmonic ones. The work experimentally verifies that the second harmonics of guided waves in pipe have a cumulative effect with propagation distance. The proposed procedure of this work can be applied to detect material nonlinearity due to damage mechanism in tube-like structure.

Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates.

We present a mechanism that permits the parallel execution of multiple quantum gate operations within a single long linear ion chain. Our approach is based on large coherent forces that occur when ions are electronically excited to long-lived Rydberg states. The presence of Rydberg ions drastically affects the vibrational mode structure of the ion crystal giving rise to modes that are spatially localized on isolated sub-crystals which can be individually and independently manipulated. We theoretically discuss this Rydberg mode shaping in an experimentally realistic setup and illustrate its power by analyzing the fidelity of two conditional phase flip gates executed in parallel. Our scheme highlights a possible route towards large-scale quantum computing via vibrational mode shaping which is controlled on the single ion level., 7 pages and 5 figures

We show that in a gas of ultra cold atoms distance selective two-body loss can be engineered via the resonant laser excitation of atom pairs to interacting electronic states. In an optical lattice this leads to a dissipative Master equation dynamics with Lindblad jump operators that annihilate atom pairs with a specific interparticle distance. In conjunction with coherent hopping between lattice sites this unusual dissipation mechanism leads to the formation of coherent long-lived complexes that can even exhibit an internal level structure which is strongly coupled to their external motion. We analyze this counterintuitive phenomenon in detail in a system of hard-core bosons. While current research has established that dissipation in general can lead to the emergence of coherent features in many-body systems our work shows that strong non-local dissipation can effectuate a binding mechanism for particles.

We study the dynamics of an atomic Bose-Einstein condensate in an optical lattice in which the electronic groundstate of each atom is weakly coupled to a highly excited Rydberg state by a far off-resonant laser. This dressing induces a switchable effective soft-core interaction between groundstate atoms which, in the lattice, gives rise to on-site as well as long-range interaction terms. Upon switching on the dressing laser the Bose-Einstein condensate undergoes a nontrivial collapse and revival dynamics which can be observed in the interference pattern that is created after a release of the atoms from the optical lattice. This interference signal strongly depends on the strength and the duration of the dressing laser pulse and can be used to probe and characterize the effective interaction between Rydberg-dressed atoms., 7 pages, 4 figures

The objectives of this study were to evaluate the suitability of the TB-SA antibody test to diagnose tuberculosis in sputum smear negative (SS-) pulmonary tuberculosis (TB) patients and its applicability for monitoring treatment outcomes in these patients. This study was conducted in three counties/districts in Chongqing Municipality, Liaoning Province, China between June 2005 and June 2007. A total of 432 SS suspected pulmonary TB patients were recruited and their blood was collected prior to treatment, at the end of 1 month of treatment, 2 months of treatment and 6 months of treatment (E6MT). The serum samples were analyzed with a TB-SA antibody test kit. Of the 432 SS suspected pulmonary TB patients, serum samples were obtained at all time points in 316 patients and analyzed. The 316 patients were divided into three groups according to sputum smear and sputum culture results and the chest X-ray results before treatment and at E6MT. Ten point four percent were SS-/culture positive (C+), 73.1% were SS-/culture negative (C-) with X-rays abnormalities, and 16.5% were SS-/C- without X-rays abnormalities. The positive rates for TB-SA antibody in the three groups were 57.6, 44.6 and 44.2%, respectively, before treatment, and 18.2, 19.1 and 26.9%, respectively, at E6MT. There was a significant decrease in TB-SA antibody positivity with treatment for all 3 groups. The TB-SA antibody test may be a useful adjunct to diagnose tuberculosis in SS- pulmonary TB patients, and may be useful for monitoring treatment outcomes of SS- pulmonary TB patients.

Objectives To determine the length of delay in initial health-seeking in new pulmonary tuberculosis (PTB) cases among migrant population in the eastern part of China, and factors associated with it. Methods A cross-sectional study was conducted using a structured questionnaire in six counties in Shanghai, Guangdong and Jiangsu from May to October, 2008, to estimate the extent and factors responsible for delayed initial health-seeking of the new PTB cases. The interval between self-reported onset of TB symptoms and date of first attendance at any medical institution was determined. More than the median duration was defined as delayed health-seeking. Results A total of 323 new migrant PTB patients participated in the study. Only 6.5% had medical insurance. The median and mean durations to initial health-seeking were respectively 10 and 31 days. There was no significant association between socio-demographic factors and delayed initial health-seeking. Average monthly working days >24 (AOR, 1.61; 95% CI, 1.03–2.51), and hemoptysis or bloody sputum (AOR, 0.48; 95% CI, 0.28–0.85) were significantly associated with delayed initial health-seeking. Conclusions Interventions to improve health seeking behavior among the migrant population in China must focus on strengthening their labor, medical security and health education.

A new unsymmetrical photochromic diarylethene, 1-(2-cyanophenyl)-2-[2-methyl-5-(3-trifluoromethylphenyl)-3-thieny]perfluorocyclopentene (1a), was synthesized, and its photochromic properties were investigated. The compound exhibited good photochromism both in solution and in PMMA film with alternating irradiation by UV/VIS light. Upon irradiation with UV light, the colorless open-ring isomer 1a turned purple both in hexane and in PMMA film, and the maxima absorption of its closed-ring isomer 1b are 536 and 547 nm, respectively. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light and its closed-ring isomer showed weak fluorescence

We present a method for amplifying a single or scattered impurities immersed in a background gas of ultra cold atoms so that they can be optically imaged and spatially resolved. Our approach relies on a Raman transfer between two stable atomic hyperfine states that is conditioned on the presence of an impurity atom. The amplification is based on the strong interaction among atoms excited to Rydberg states. We perform a detailed analytical study of the performance of the proposed scheme with particular emphasis on the influence of many-body effects., 5 pages, 4 figures

Xi-Han Freeway is a unique freeway passing through a mountainous region with very challenging topography and complex climatic conditions. This freeway is built with many bridges and tunnels that greatly complicated the alignment design. Since its opening in 2007, the safety has become a serious concern due to the high crash risk. This paper presents the results of a crash analysis and consequent proposal on the crash countermeasures for Xi-Han Freeway are presented. This research provides evidence on how to improve safety of freeways in mountainous regions in China.

This paper studies a frequent violation at multi-phase signal intersection of Beijing, that large number of pedestrians twice crossing street in the left-turn phase. Based on a large number of measured data, the influence of this violation on intersection safety is analyzed by using the theory of traffic conflict. To solve the violation, some strategy and methods have also been summarized. As an important link in City Road system and a crucial section of the whole road net, the intersections in the city act as the nodes connecting the crossing roads and control the vehicle volume. Due to the complexity of traffic participants and the high concentration of traffic flow, traffic accidents are very liable to occur in the crossings. According to the traffic accident statistics in China (2008), there are 46148 traffic accidents in crossings, taking account of 17.40% of the total number of the traffic accidents and leading to 9549 death. (Ministry of Public Security, 2009) Therefore the studies on the influence factors of crossings safety have been considered as an urgent need. Multi-phase signal has been adopted in increasing amount as an effective method to improve the traffic safety. In this system, the left-turn phase is put forward to separate the straight flow and left-turn flow to different time sections, thus to decrease the traffic confliction points. However, the implementation of left-turn phrase will to some extent extend the waiting time for the pedestrians passing through the streets. The pedestrians are likely to break the traffic rules and cross the roads regardless of the traffic signal if the waiting time is too long or the waiting crowd has reached saturation. Normally they

The laser excitation of an ion crystal to high lying and long-lived electronic states is a genuine many-body process even if in fact only a single ion is excited. This is a direct manifestation of the strong coupling between internal and external dynamics and becomes most apparent in the vicinity of a structural phase transition. Here we show that utilizing highly excited states offers a new approach to the coherent manipulation of ion crystals. This permits the study of phenomena which rely on a strong coupling between electronic and vibrational dynamics and opens up a route towards the quantum simulation of molecular processes in a Paul trap., Comment: 5 pages, 4 figures

Since their first experimental observation, ultralong-range Rydberg molecules consisting of a highly excited Rydberg atom and a ground state atom [1, 2] have attracted the interest in the field of ultracold chemistry [3, 4]. Especially the intriguing properties such as size, polarizability and type of binding they inherit from the Rydberg atom are of interest. An open question in the field is the reduced lifetime of the molecules compared to the corresponding atomic Rydberg states [2]. In this paper we present an experimental study on the lifetimes of the 3Σ(5s − 35s) molecule in its vibrational ground state and in an excited state. We show that the lifetimes depend on the density of ground state atoms and that this can be described in the frame of a classical scattering between the molecules and ground state atoms. We also find that the excited molecular state has an even more reduced lifetime compared to the ground state which can be attributed to an inward penetration of the bound atomic pair due to imperfect quantum reflection that takes place in the special shape of the molecular potential [5].

We present subwavelength periodic gratings achieved by employing a metallic grating waveguide heterostructure (MGWHS). The mask can be designed to make one of its diffraction order (±mth) waves resonate with the surface plasmon wave supported by the MGWHS. With a finite-difference time-domain method, we numerically demonstrate that one-dimensional periodic structure of about 60 nm feature, which is far beyond the diffraction limit, can be patterned with the interference of the 3rd diffraction order waves of the mask at a wavelength of 546 nm. The technique can also be extended to two-dimensional patterns using circularly polarized incidence and for the incidence with an angle θ.

With the increase in cars and number of residents in Beijing, the shortage of urban road capacity has become increasingly conspicuous. In this paper, public transportation network evaluation factors such as the length of bus lines, line density, repeated factor, non-linear coefficient, site density, the average station distance and Geographic Information Systems (GIS) technology will be used to evaluate the public transportation network in Beijing inside of the 5th ring road to make appropriate improvements. In addition, the article conducts evaluation of the network to reveal the existing problems to find a reasonable solution and further develop the line optimization program. Finally, the results are used to improve public transportation ground to lay the foundation of operational efficiency.

The freeways crossing mountainous areas in China are playing a major role in economic development. In the past decade, building freeways in these regions have greatly stimulated economic development in all aspects and will also be a major factor in the areas’ sustainable development for the future. Due to the geometry of highways, freeway accidents have become a serious problem in these mountainous areas. This paper focused on the modeling of freeway safety with the consideration of geometry, traffic flow, and roadside environment. Particularly, the generalized regression model was developed based on the data collected from the mountainous areas.

High Dynamic Range Image (HDRI) is suitable for the real image, but its capture and display will require high end product with high price. For the common display and printer device, the HDR image must be transferred to Limited Dynamic Range (HDR) image. The traditional tone mapping will occupy more computing time and resource. In this paper, we present a fast adaptive tone mapping optimal based on a new optimal object function. After the HDR image is normalized by the log operator, we use a mixed strategy to optimal its performance and computing time complexity. The experiments on several HDR images demonstrate its super performance.

The development of (31)P DOSY NMR with diffusion coefficient-formula weight (D-FW) analysis is reported. Commercially available trialkyl phosphine internal references were used in a model system to establish the molecular weight of a phosphorous containing organolithium compound. The feasibility of (31)P DOSY D-FW studies is established. This extension of DOSY D-FW analysis expands its applicability to solution structure studies of a wide variety of compounds.

A combined codebook for limited feedback Multi-input Multi-output (MIMO) beamforming system is proposed, where two grassmannian codebooks are combined together to make a set of new codebooks, and from which to choose the codebook for quantification. The codebook selection information is implied in the feedback codeword indexes, thus we can to switch the codebook adaptively. Simulation results show that this method can be used to any channel models, and at the same BER, this method can reduce the feedback rate compare to grassmannian codebooks in correlated channels.

In the most application situation, signal or image always is corrupted by additive noise. As a result there are mass methods to remove the additive noise while few approaches can work well for the multiplicative noise. The paper presents an improved MAP-based filter for multiplicative noise by adaptive window denoising technique. A Gamma noise models is discussed and a preprocessing technique to differential the matured and un-matured pixel is applied to get accurate estimate for Equivalent Number of Looks. Also the adaptive local window growth and 3 different denoise strategies are applied to smooth noise while keep its subtle information according to its local statistics feature. The simulation results show that the performance is better than existing filter. Several image experiments demonstrate its theoretical performance.

In China, almost every college has set up computer major, and undergraduates majoring in computer outnumber any other majors. Since the skill to use computer has been regarded as one of the three basic capabilities in the 21th century, students have to learn computer courses ever from primary school. But the traditional method to teach computer in college that too much attention used to be paid to abstract concepts and boring theories, has been proven to be impractical according to the feedback collected from workplaces. Therefore, it is agreed that greater importance should be attached to the skills that are necessary in workplaces so as to improve students’ abilities to use computer, communication appliances and applied software as well as to design software and hardware. In this study, a novel Task-Driven strategy (TDS) for computer major teaching is proposed. This strategy enables undergraduates to better prepare themselves for future complicated tasks, rather than provide them with fragmentary and partial knowledge. In addition, it can help build up the students’ sense of achievement, and make computer education more interesting and attractive. This strategy, which provides enough chances for students to learn from near-real tasks, will pave the way to show undergraduates the whole work procedure from an integrated viewpoint, improve their capabilities to learn knowledge and to solve problems independently. The novel teaching strategy, TDS, has been proven to be effective.

In multiple-antenna broadcast channels, if the transmitter has no perfect channel state information (CSI), feedbacks are usually needed from the receivers. When the number of receivers is small, fixed feedback will lead to a sum rate ceiling as the SNR increases. In this paper, we analyze the methods to increase the throughput in codebook based feedback in MIMO broadcast channels. Three codebooks are used for comparison and the results show that, using finer codebook and regularized zero-forcing can increase the system's throughput. However, the sum rate ceiling still exists as long as fixed feedback is used. Feedback bits increase along with SNR seems to be the only way to solve this problem.

Since programming courses are compulsory for major of software engineering in all colleges, that how to improve the teaching effect has always been the main concern of the teachers. In view of the problems which have long existed, this paper presents some reform methodology on teaching contents, teaching methods, teacher team reconstruction, practice procedure and evaluation measures with the purpose of enhancing students’ programming ability and help them with employment and further studies after graduation. Teaching practice show that the proposed measures is effective.

Quantum reflection is a pure wave phenomena that predicts reflection of a particle at a changing potential for cases where complete transmission occurs classically. For a chemical bond, we find that this effect can lead to non-classical vibrational turning points and bound states at extremely large interatomic distances. Only recently has the existence of such ultralong-range Rydberg molecules been demonstrated experimentally. Here, we identify a broad range of molecular lines, most of which are shown to originate from two different novel sources: a single-photon associated triatomic molecule formed by a Rydberg atom and two ground state atoms and a series of excited dimer states that are bound by a so far unexplored mechanism based on internal quantum reflection at a steep potential drop. The properties of the Rydberg molecules identified in this work qualify them as prototypes for a new type of chemistry at ultracold temperatures., Comment: 6 pages, 3 figures, 1 table

A combined codebook constructing method is proposed for beamforming in correlated Multiple-input multiple-output (MIMO) channels, where the codebook is dynamically constructed based on the transmit covariance matrix of the channel. Monte Carlo simulations show performance close to optimal beamforming. Huffman coding is used to further reduce the feedback rate in correlated MIMO system.

We construct the invisible quantum barrier which represents the phenomenon of quantum reflection using the available data. We use the Abel equation to invert the data. The resulting invisible quantum barrier is double-valued in both axes. We study this invisible barrier in the case of atom and Bose-Einstein Condensate reflection from a solid silicon surface. A time-dependent, one-spatial dimension Gross-Pitaevskii equation is solved for the BEC case. We found that the BEC behaves very similarly to the single atom except for size effects, which manifest themselves in a maximum in the reflectivity at small distances from the wall. The effect of the atom-atom interaction on the BEC reflection and correspondingly on the invisible barrier is found to be appreciable at low velocities and comparable to the finite size effect. The trapping of ultracold atom or BEC between two walls is discussed., 13pages, 6figures

Objectives To investigate, in a randomized controlled study, the degree of continence after the creation of orthotopic ileocolonic and ileal neobladders after cystectomy and to explore a possible mechanism for the difference in continence between these 2 types of orthotopic neobladder. Methods From 2003 to 2007, 71 male patients underwent orthotopic lower urinary tract reconstruction with either an ileocolonic or ileal neobladder after radical cystectomy. The degrees of continence and voiding patterns were individually evaluated using urodynamic examinations and a detailed patient questionnaire. The abnormal upper tract was evaluated using intravenous urography and ultrasonography. Results Complete daytime continence was achieved in 90.9% and 89.4% of the patients and functional nocturnal continence 48.5% and 76.3% of patients in the ileocolonic neobladder and ileal neobladder groups, respectively. The urodynamic data showed that the initial volume of both the ileocolonic and the ileal neobladder appeared to not be significantly different statistically, although the compliance of the ileocolonic neobladder was lower than that of the ileal neobladder (P < .05). No difference was found in the parameters such as flow rate, urethral profile length, maximal urethral pressure, or neobladder neck pressure between the 2 neobladder types. Conclusions Although the ileocolonic and ileal neobladders can both achieve a large initial volume, the ileal neobladder has an advantage in the aspect of obtaining satisfactory nocturnal continence because of its greater compliance compared with that of the ileocolonic neobladder.

13C INEPT Diffusion-ordered NMR spectroscopy (DOSY) with an internal reference system was developed to study the aggregation state of THF-solvated LDA dimeric complex. Six components are clearly identified in the diffusion dimension, and their DOSY-generated 13C INEPT spectrum slices agree extremely well with their respective INEPT spectra. The correlation between log D and log FW of the linear least-squares fit to reference points of all components is exceptionally high: (r = 0.9985).

A new formulation of potential scattering in quantum mechanics is developed using a close structural analogy between partial waves and the classical dynamics of many non-interacting fields. Using a canonical formalism we find non-linear first-order differential equations for the low energy scattering parameters like scattering length and effective range. They significantly simplify typical calculations, as we illustrate for atom-atom and neutron-nucleus scattering systems. A generalization to charged particle scattering is also possible., Comment: 13 pages, 2 figures

Canny has proposed three continuous criteria to compare the performance of different filters: good detection, good localization and low-responses. Based on these criteria, the optimal filter, derivative of Gaussian function, for edge detection is selected. Unfortunately, it does not wok well when it was employed to detect edges of SAR image for the reason that the SAR image is polluted by the multiplicative noise which satisfied the Gamma distribution. In this paper, a new Canny-based edge detector for SAR image is proposed. The kernel function of edge detector is modified according to the noise, also preprocess is performed. Finally, the simulated results prove its superior to traditional Canny operator and others.

We study the conservative dynamics and stationary configurations of a vortex-antivortex pair in a harmonically trapped two-dimensional Bose-Einstein condensate. We establish the conceptual framework for understanding the stationary states and the topological defect trajectories, through considerations of different mechanisms of vortex motion and the bifurcation of soliton-like stationary solutions. Our insights are based on Lagrangian-based variational calculations, numerical solutions of both the time-dependent and time-independent Gross-Pitaevskii equations, and exact solutions for the non-interacting case., 7 pages, 8 figures. In v2, some details are moved to Appendix

Tracking dynamics on the GPS signal is still a big challenge to the receiver designer as the operating conditions are becoming more volatile. Usually, the phase-locked loop (PLL) is used in GPS receivers to track an incoming signal and to provide accurate carrier phase measurements. However, in high dynamic situations, the conflict between improving PLL tracking performance and the ability to track the signal necessitates some compromises in PLL design. Optimizing the stand-alone system for dynamics, generally, degrades the accuracy of measurements. The advanced signal processing techniques as maximum likelihood (ML) and extended Kalman filter (EKF) can be used to track a common trajectory exhibiting high dynamics. However, the estimated values of these algorithms can not be used directly to demodulate the signals. A combination of both inertial measurement unit (IMU) and GPS is an attractive method to deal with the problem of high dynamic tracking. Unfortunately, these units of IMU are often very expensive. In this paper, a new Kalman filter aided phase-lock loop is proposed to address this issue. Doppler derived from EKF is used to aid the carrier tracking loop for improving the performance under dynamic conditions. While the cost is significantly reduced compare with the IMU method. Simulations show that the method is feasible.

transparency [Phys. Rev. B 75, 184423 (2007)] Xiao-Tao Xie, Weibin Li, Jiahua Li, Wen-Xing Yang, Anming Yuan, and Xiaoxue Yang Received 24 May 2007; published 22 June 2007 DOI: 10.1103/PhysRevB.75.219903 PACS number s : 75.50.Xx, 43.25. y, 42.50.Gy, 99.10.Cd Equation 21b on page 5 is wrong. The correction is ũ= −2c2 c4 sech c2Z , c2 0, c4 0, c0=0. The function “sinh” should be replaced by “sech.” This change does not affect the conclusions of the paper. PHYSICAL REVIEW B 75, 219903 E 2007

We have studied the propagation properties of transverse acoustic wave in molecular magnets in the presence of a strong ac magnetic field. Due to quantum interference introduced by the strong electromagnetic field, the acoustic wave can propagate without absorption under appropriate conditions, which is a direct result of electromagnetically induced transparency effect. Meanwhile, the nonlinear effects should be considered in the propagation of the acoustic wave because electromagnetic induction transparency effect can greatly enhance nonlinear effects. The transverse acoustic wave propagation equation including nonlinear effects in molecular magnets has been investigated and the corresponding accurate analytic solutions have been obtained. We believe that our research may promote the understanding of the acoustic wave's properties in molecular magnets.

The measurement of acoustic nonlinear response of guided wave propagation has been explored as a promising tool for early detection of micro-damages. Considering the high sensitivity of the nonlinear ultrasonic approach and the great advantages of the guided wave techniques, the nonlinear guided wave techniques have drawn significant attention. Frequency tuning and mode selection play a critical role for practical nonlinear guided wave testing. Among all the guided wave modes, it is of particular interest to find the more suitable modes for the improvement of efficiency. Analytical expressions and experimental observations of second harmonic generation of guided waves in an isotropic plate, are presented in this talk. Nonlinear parameters of guided waves are newly derived as a function of wave mode, geometric information of waveguides and frequency. Nonlinear features of various phase matched modes are discussed for the comparison of efficiency of second harmonic generation. The experimental results are consistent with the theoretical predictions. This study shows that physically based feature selection is essential for efficient generation of second harmonic guided waves. The feasibility of Lamb waves mixing for nonlinear ultrasonic test is also discussed in this work.

We investigate the many-body dynamics of an effectively attractive one-dimensional Bose system confined in a toroidal trap. The mean-field theory predicts that a bright-soliton state will be formed when increasing the interparticle interaction over a critical point. The study of quantum many-body dynamics in this paper reveals that there is a modulation instability in a finite Bose system correspondingly. We show that Shannon entropy becomes irregular near and above the critical point due to quantum correlations. We also study the dynamical behavior of the instability by exploring the momentum distribution and the fringe visibility, which can be verified experimentally by releasing the trap, Comment: 6 pages,5 figures

Several auxiliary organic additives such as dodecylamine, Triton-X 100, triethanolamine and hexamethylenetetramine (HMTA) were all found to be able to improve thermal stability of the 1:1 molar ratio Zr/Ti mesoporous oxides prepared from inorganic salt precursors using cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. Particularly, a high surface area, i. e., 386 m2/g was available on the Ti-Zr mesoporous oxides prepared from CTAB and HMTA after calcinations at 450 °CC, meanwhile the mesoporous structures still retained on the calcined sample.