Range Of Time Differences Research Articles

Study on the influence of traveling wave effect on Γ-type combined structure using equivalent simplified model.

The Γ-type combined structure is an unconventional high-rise long-span structure, and there is no research literature about the influence of traveling wave effect on such structure at present. This study established an accuracy equivalent simplified model for such structure, employed the modified large mass method to carry out a time history analysis on the seismic response such as the shear force, axial force, and bending moment of the model affected by the traveling wave effect, and summarized the corresponding laws through the analysis results of different working conditions such as time difference, mass ratio, and stiffness ratio. The results demonstrate that, with the increase in the input time difference of seismic wave, the bending moment of the control section increases gradually, while the shear force and axial force decrease first and then increase, and traveling wave effect response within a certain range of time difference is weaker than the uniform excitation response. The differences of traveling wave effect responses due to the change of mass ratio between the vertical and horizontal parts of the structure are less than 10%, while the differences due to the change of stiffness ratio are greater than 20%.

Experimental study on thermal performance of a loop heat pipe with a bypass line

The loop heat pipe with both flat evaporator and boiling pool (NLHP) has much higher maximum heat flux than conventional loop heat pipe (LHP). However, the serious temperature overshoot and the startup time difference between the evaporator and boiling pool have become a bottleneck of the NLHP. In this study, a loop heat pipe with a bypass line (BLHP) is proposed to improve the startup characteristics of the NLHP. The effects of the bypass line, time difference, boiling pool heat load and evaporator heat load on the thermal performance of the BLHP are experimentally investigated. The results indicate that the bypass line, which is installed between the condenser outlet and the first vapor line, accelerates the return of working fluid and reduces the adverse effect of the heat leakage. The temperature overshoot is virtually eliminated and the BLHP can operate stably at various evaporator and boiling pool heat loads under a broad range of time differences. Furthermore, the BLHP reduces the heating wall temperature by 3.9–8.1 °C and thermal resistance by more than 10% under various heat loads compared with the NLHP. While maintaining the heating wall temperature within 85 °C, the maximum heat flux is 39.3 W·cm−2, which is much higher than most conventional LHPs using methanol as working fluid.

Flows over surface-mounted bluff bodies with different spanwise widths submerged in a deep turbulent boundary layer

The spatio-temporal dynamics of separation bubbles induced by surface-mounted bluff bodies with different spanwise widths and submerged in a thick turbulent boundary layer is experimentally investigated. The streamwise extent of the bluff bodies is fixed at 2.36 body heights and the spanwise aspect ratio ($AR$), defined as the ratio between the width and height, is increased from 1 to 20. The thickness of the upstream turbulent boundary layer is 4.8 body heights, and the dimensionless shear and turbulence intensity evaluated at the body height are 0.23 % and 15.8 %, respectively, while the Reynolds number based on the body height and upstream free-stream velocity is 12 300. For these upstream conditions and limited streamwise extent of the bluff bodies, two distinct and strongly interacting separation bubbles are formed over and behind the bluff bodies. A time-resolved particle image velocimetry is used to simultaneously measure the velocity field within these separation bubbles. Based on the dynamics of the mean separation bubbles over and behind the bluff bodies, the flow fields are categorized into three-dimensional, transitional and two-dimensional regimes. The results indicate that the low-frequency flapping motions of the separation bubble on top of the bluff body with $\mathit{AR}=1$ are primarily influenced by the vortex shedding motion, while those with larger aspect ratios are modulated by the large-scale streamwise elongated structures embedded in the oncoming turbulent boundary layer. For $\mathit{AR}=1$ and 20, the flapping motions in the wake region are strongly influenced by those on top of the bluff bodies but with a time delay that is dependent on the $AR$. Moreover, an expansion of the separation bubble on the top surface tends to lead to an expansion and contraction of separation bubbles in the wake of $\mathit{AR}=20$ and 1, respectively. As for the transitional case of $\mathit{AR}=8$, the separation bubbles over and behind the body are in phase over a wide range of time difference. The dynamics of the shear layer in the wake region of the transitional case is remarkably more complex than the limiting two-dimensional and three-dimensional configurations.

All‐digital synchronous 2 × time‐difference amplifier based on time register

A novel 2 × time-difference amplifier (TDA) in 65 nm CMOS technology is presented. Unlike traditional analogue TDA, the proposed TDA, employing an all-digital synchronous architecture, achieves 2 × TDA in a time subtracting way based on time register. Multi-path negative skewed gated delay cells are utilised to minimise gating skew error in the time register. To make up for the delay mismatch in the two time registers, a foreground calibration scheme that calibrates the input offset of the phase detectors at the same time is applied. The TDA gain ranges from 1.99 to 2.02 over ± 150 ps input time-difference range and the standard variation of the gain is 0.02 under various process, voltage and temperature (PVT) conditions. The simulated average of power consumption is 62 μW under 100 MHz clock frequency.

Highly-linear time-difference amplifier with low sensitivity to process variations

A novel time-difference amplifier (TDA) is presented. The proposed circuit has a larger linear operation region with less sensitivity to process variations than the state-of-the-art TDAs. Two TDAs with gains of two and 20 have been simulated in a 65 nm CMOS process to validate the proposed architecture. Simulation results show less than 0.1% gain error for ±400 ps input time difference range, ten times the range of conventional TDAs. The proposed TDA consumes 740 μW from a 1 V supply.

Frame-Loss-Free Optical Line Switching System for In-Service Optical Network

Fiber-to-the-home (FTTH) has now reached the stage where it is providing real-time broadband services. Since even a temporary suspension of broadcasting and telephone services cannot be permitted, it has become important to improve the reliability of FTTH network operation. We have developed an advanced optical line switching system that diverts transmission signals from an in-service line to a spare line without interrupting communication. This system is realized by equalizing the transmission times of the signals sent through dualized lines composed of an in-service line and a spare line. The transmission times are equalized by employing two techniques in the dualized lines. One is a technique that uses a free space optics system to tune the optical line length continuously. The other is a technique for measuring a wide range of time differences between signals transmitted through the dualized lines. Since the dualized lines have a Mach-Zehnder interference structure, the differences can be detected with high accuracy by employing dual-light interferometry. We applied this switching system to a gigabit Ethernet passive optical network (GE-PON) during transmission and succeeded in switching in-service lines without inducing any frame loss.

Sound lateralisation in patients with left or right cerebral hemispheric lesions: relation with unilateral visuospatial neglect

OBJECTIVESTo localise the brain lesion that causes disturbances of sound lateralisation and to examine the correlation between such deficit and unilateral visuospatial neglect.METHODThere were 29 patients with right brain damage,...

Very long-range source localization with a small vertical array

Several processors are developed and used to perform source localization on the 3250-km San Diego–Hawaii path of the Acoustic Engineering Test (AET). Associated simulations are done to test the range-frequency limits of coherent matched-field processing using PE modeling through a simulated internal-wave environment. The AET experiment is presently well beyond the range of effective coherent matched-field processing. A mode filter was developed to extract 60 complex mode amplitudes from the data received on the 20-element vertical line array. A mode space depth estimator successfully localizes the source. A mode arrival time difference range estimator is developed and found to be biased by internal-wave induced mode coupling. The final processor developed utilizes the stability of early arriving wavefronts to determine the source range by matching wavefront arrival patterns.

Internal wave strength inversion and localization using long-range acoustic signals

The ATOC95 experiment was conducted in the winter of 1995 with transmission paths from Pioneer Seamount to Hawaii (range = 3515 km). The internal wave environment is strongly range dependent, and significant mode coupling occurs to the late arriving energy. The ability to localize a source is an indication of the remaining source information in the signal. A mode travel time difference range estimator was developed and shown to be biased by internal wave-induced mode coupling. A range estimator was developed which matched the received wavefronts with those of predicted wavefronts at various ranges. Forward simulations were done using a frequency interpolation method of the PE, and a set of random realizations of the Garrett–Munk spectra for internal waves. With this ensemble of calculations as a forward model, three different measures were calculated from the data and simulations to do an inversion for the background internal wave strength in the ocean. A method was developed to simultaneously invert the source location and the internal wave strength using the mode arrival time and mode spread as the two observables. a)Present address: Sci. Applications Intl. Corp., 10260 Campus Pt. Dr., San Diego, CA 92121.

Estimation of internal wave strength from mode space source localization

Internal waves have been shown to cause significant mode coupling for long-range acoustic transmissions [Colosi and Flatte, J. Acoust. Soc. Am. (in press)]. This coupling produces a variance and bias in a modal arrival time difference range estimator and a mode space depth estimator. The bias and variance induced by internal wave coupling is quantifiable. An inversion is therefore possible for the background strength of the internal wave field. The structure of the mode arrival time bias provides information on the depth of maximum internal wave activity. The success of the depth estimator reveals the limit of internal wave-induced mode coupling and places an upper bound on the energy in the Garrett–Munk spectrum. Broadband long-range simulations through internal wave realizations will be presented, quantifying the effect. Results from experimental data along different propagation paths (AET and ATOC95) will be presented, and an estimate of the internal wave strength parameter will be given for each.