Maximum Response Research Articles

GaAs-based antenna-coupled field effect transistors as direct THz detectors across a wide frequency range from 0.2 to 29.8 THz

High-power coherent terahertz (THz) radiation from accelerator facilities such as free-electron lasers (FELs) is frequently used in pump-probe experiments where the pump or probe (or both) signals are intense THz pulses. Detectors for these applications have unique requirements that differ from those of low-power table-top systems. In this study, we demonstrate GaAs antenna-coupled field effect transistors (FETs) as a direct THz detector operating across a broad frequency spectrum ranging from 0.2 THz to 29.8 THz. At approximately 0.5 THz, the maximum current responsivity (ℜ I ) of 0.59 mA/W is observed, signifying a noise equivalent power (NEP) of 2.27 nW/√Hz. We report an empirical roll-off of f−3 for an antenna-coupled GaAs TeraFET detector. Still, NEP of 0.94 μW/√Hz and a current responsivity ℜ I = 1.7μA/W is observed at 29.8 THz, indicating that with sufficient power the FET can be used from sub-mm wave to beyond far-infrared frequency range. Current and voltage noise floor of the characterized TeraFET is 2.09 pA and 6.84 μV, respectively. This characteristic makes GaAs FETs more suitable for applications requiring higher frequencies, ultra-broadband capabilities and robustness in the THz domain, such as beam diagnostics and alignment at particle accelerators.

Abstract 4139170: Relationship between hemodynamics and oxygen consumption in hypertrophic cardiomyopathy during maximal stress testing

Background: Hypertrophic cardiomyopathy (HCM) is a global heart disease with great variability in disease severity, which can lead to significant impairment of exercise capacity. In healthy populations, oxygen consumption is related to cardiac output and arteriovenous oxygen difference. We sought to determine the relationship between hemodynamics (cardiac output and stroke volume) and oxygen consumption in HCM compared to healthy controls during maximal stress testing. Aims: To evaluate associations between the trajectories of hemodynamic function and oxygen consumption in HCM compared to healthy controls. Methods: Twenty individuals with HCM (51±15 years old, body mass index (BMI): 28±3 kg/m 2 , females, n=4) and 16 healthy controls (66±7 years old, 27±6 kg/m 2 , females, n=6) were included in the present study. Participants completed a maximal-graded stress test coupled with non-invasive hemodynamic bioreactance (cardiac output, stroke volume) and gas exchange (oxygen consumption, VO 2 ) measurements. Data were analyzed in quartiles (exercise only) and phases (rest, pre-pedalling, exercise and recovery) of the maximal-graded stress test. Results: In HCM, cardiac output declined in the fourth quartile of the exercise phase of the stress test (-0.39 L/min, p <0.001) whilst VO 2 increased (3.86 ml/kg/min, p <0.001). There was a significant difference in the gradient of cardiac output between HCM and controls in the final quartile of the test (-1.6 vs. 18.1 L/min, p<0.001). In coherence, stroke volume declined in the fourth quartile of the test (-18.4 ml, p <0.01) in response to increasing VO 2 in HCM. The rates of recovery were faster in HCM compared to the control group for VO 2 (-4.3 vs -2.6 mL/second, p<0.001), cardiac output (-0.03 vs -0.02 L/second, p<0.001), heart rate (-0.17 vs -0.10 beats/second, p<0.001), and stroke volume (-0.18 vs -0.07 L/second, p<0.001). Conclusions: In HCM, cardiac output declined during the later stages of maximal stress testing whereas in controls it continued to rise, indicating impaired maximal cardiac output responses to exercise. These findings have implications for exercise prescription and training regimens in HCM suggesting avoidance of maximal exercise levels.

Indium Oxide Thick-Films Decorated with PdO and PtO2 Particles for Oxygen Detection in Humid Environments

Abstract Thick film indium oxide chemiresistive sensors decorated with PdO and PtO2 particles were investigated for oxygen detection under humid conditions (tested ranging from 20%- 80% RH) across a temperature range of 50 °C to 400 °C. The PtO2-decorated In2O3 sensors demonstrated a significantly higher response to oxygen, showing a 500% increase at 200 °C compared to the PdO-decorated sensors (response values of 41 and 8, respectively). Tests in dry air were conducted to assess the effect of humidity on sensor performance, revealing a maximum response of 74 for PtO2-In2O3 at 400 °C, more than three times higher than the response of 22 for PdO-In2O3. Selectivity tests confirmed that the sensors responded more strongly to oxygen than to interfering gases. The integration of an active carbon cloth (ACC) filter effectively reduced interferences from isobutylene and ethylene, enhancing sensor’s selectivity. A comparison of both sensors demonstrated that PtO2-decorated In2O3 has greater potential as an alternative to existing Pb-based electrochemical oxygen sensors, particularly in humid environments.

Allowable stress rating compared to load and resistance factor rating for timber bridges with and without steel-beam retrofit

This paper presents the relevancy of the Allowable Stress Rating (ASR) and the Load and Resistance Factor Rating (LRFR) methods for timber bridges. Benchmark bridges constructed in the 1930′s are upgraded with hollow structural steel (HSS) beams and three-dimensional finite element models provide technical information that is necessary for examining their behavior and rating evaluations. Complying with published manuals, a total of 17 rating vehicles are considered across three categories (Design, Legal, and Permit) so as to generate the maximum responses of the bridges. The position of the vehicles dominates the deflection profiles of the unrepaired bridges. After installing the HSS beams, the live loads are redistributed and stiffness enhancement is noticed in the transverse direction of the bridges. The rating factors calculated with ASR exceed those with LRFR for the unrepaired bridges, regardless of vehicle configurations, and the level of disparity between these rating approaches increases when the bridges are repaired owing to differences in load factors. In terms of sensitivity to average daily truck traffic, the LRFR factors of the bridges under the Legal vehicles are more responsive than the factors subjected to other vehicle types. From a probability perspective, the compatibility of these rating methodologies varies contingent upon vehicle categories and the presence of the HSS beams. Practice guidelines are proposed to facilitate the conversion of rating factors between ASR and LRFR as a function of the present condition of constructed timber bridges.

On the dual-phase-lag thermal response in the pulsed photoacoustic effect: A theoretical and experimental 1D-approach

In a recent work, assuming a Beer–Lambert optical absorption and a Gaussian laser time profile, it was shown that the exact solutions for a 1D photoacoustic (PA) boundary-value-problem predict a null pressure for optically strong absorbent materials. In order to overcome this inconsistency, a heuristic correction was introduced by assuming that heat flux travels a characteristic length during the duration of the laser pulse [M. Ruiz-Veloz et al., J. Appl. Phys. 130, 025104 (2021)] τp. In this work, we obtained exact analytical solutions in the frequency domain for a 1D boundary-value-problem for the Dual-Phase-Lag (DPL) heat equation coupled with a 1D PA-boundary-value-problem via the acoustic wave equation. Temperature and pressure solutions were studied by assuming that the sample and its surroundings have a similar characteristic thermal lag response time τT; therefore, the whole system is assumed to have a similar thermal relaxation. A second assumption for τT is that it is considered as a free parameter that can be adjusted to reproduce experimental results. Solutions for temperature and pressure were obtained for a one-layer 1D system. It was found that for τT<τp, the DPL temperature has a similar thermal profile of the Fourier heat equation; however, when τT≥τp, this profile is very different from the Fourier case. Additionally, via a numerical Fourier transform, the wave-like behavior of DPL temperature is explored, and it was found that as τT increases, thermal wave amplitude is increasingly attenuated. Exact solutions for pressure were compared with experimental PA signals, showing a close resemblance between both data sets, particularly in time domain, for an appropriated value of τT; the transference function was also calculated, which allowed us to find the maximum response in frequency for the considered experimental setup.

PSA Kinetics Affect Prognosis in Patients With Castration-resistant Prostate Cancer Treated With Enzalutamide.

There is little evidence regarding the predictive value of prostate-specific antigen (PSA) kinetics in patients with castration-resistant prostate cancer treated with an androgen receptor signaling inhibitor. This study investigated the correlation between PSA kinetics and prognosis in patients with castration-resistant prostate cancer treated with enzalutamide. We analyzed data from 103 patients who received enzalutamide as primary treatment for castration-resistant prostate cancer at our hospital, focusing on the associations between overall survival and PSA kinetics variables, such as maximal PSA response, PSA nadir, and time to PSA nadir. The median PSA level at the initiation of enzalutamide was 18.1 ng/ml (interquartile range=7.9-61.2 ng/ml). The median maximal PSA response rate was 88% (interquartile range 55-98), and the median PSA nadir was 1.84 (interquartile range (IQR)=0.38-14.7) ng/ml. The median time to PSA nadir was 19 (IQR=6-28.5) weeks. Maximal PSA response rate <90% [hazard ratio (HR)=2.28, 95% confidence interval (CI)=1.03-5.03, p=0.0413], PSA nadir >2 ng/ml (HR=2.30, 95%CI=1.05-5.07, p=0.0379), time to nadir <19 weeks (HR=2.48, 95%CI=1.15-5.35, p=0.0204) were all independently predictive of shortened overall survival even after adjusting for pre-treatment factors. Maximal PSA response, PSA nadir, and time to PSA nadir correlated with survival in patients with castration-resistant prostate cancer receiving enzalutamide as a first-line therapy.

Buffeting performance of long-span bridges with different span affected by parametric typhoon wind

Currently, typhoon-related performance of long span bridges usually focus on a specific wind record such as wind speed and turbulence intensity during a full typhoon, however, the inter-correlation among wind characteristic parameters under typhoon wind climate is ignored. The existing investigation about structural responses during typhoon attacks are still limited at case-study analysis, and hardly provide a generalized framework to evaluate the structural performance especially for typhoon landing whole process. This study utilizes the measured wind speeds of the strong typhoon "Hagupit" to establish a unified typhoon parametric model, during which the correlation of typhoon wind parameters including angle of attack (AoA), turbulence intensity, integral length scale and mean wind speed were taken into consideration. The measured typhoon process charactered with center-through effect with M-type average wind speed curve. Furthermore, the structural performance of long-span bridges with different spans from 1500 m to 2500 m main span was systematically studied. The aerodynamic parameters of the bridge deck section, including the aerostatic coefficients, flutter derivatives at different AoAs, and aerodynamic admittance under different oncoming flow conditions were identified through wind tunnel tests. Finally, the wind-induced buffeting performance was calculated by the buffeting frequency domain algorithm, showing various structural wind effect characteristics during the typhoon landing whole process. The maximal buffeting response is not necessarily related with the wind speed, and other wind characteristics especially turbulence intensity and AoA, etc. also affect on the results.

Temporal asynchrony analysis for dynamic operation of hydraulic-thermal-electricity multiple energy networks based on holomorphic embedding method

Analyzing the operational states of multiple energy networks (MEN) in multi-energy systems is crucial for ensuring system stability. The dynamic operational characteristics of different energy flows pose challenges for computational analysis. Traditional steady-state methods are inadequate for addressing the dynamics of MEN, especially when dealing with temporal discrepancies between hydraulic and thermal flows in thermal networks (TN) and the heterogeneity between TN and electrical networks. Therefore, this paper proposes a novel holomorphic embedding method (HEM) based on multi-stage decomposition method. The developed HEM constructs a time coefficient matrix and utilize inner-outer loop recursion to handle the time lag between thermal flow and hydraulic flow in the TN. Additionally, we reconstruct a holomorphic matrix, integrating hydraulic flow to bridge thermal and electric power flows, thereby improving the operational heterogeneity among different networks. Real-case simulations show that when the Taylor expansion order in HEM is equal to 4, the proposed method achieves a mere 1% discrepancy from actual operational data, enhancing computational efficiency by 60% compared to the Newton-Raphson method. Moreover, in this real-case, the TN exhibits a maximum delay response time of 180s compared to electrical networks. Exploiting this delay time effectively increases renewable energy generation within multi-energy systems by 961.58kW per day.

Perovskite-structured LaFeO3 gas sensor modified by polyoxometalate electron acceptor with high sensitivity and low detection limit for acetone gas☆

Lanthanum ferrite is a representative perovskite-structured rare earth-based bimetallic oxide, which has been widely studied in magnetic materials, sensors, catalysts and batteries. Herein, we designed and prepared polyoxometalate electron acceptor decorated LaFeO3 gas-sensitive composite materials with one-dimensional nanoribbons morphology by electrospinning. The effects of different mass fraction of Keggin type phosphotungstic acid (PW12) on the gas-sensitive properties of LaFeO3 nanoribbons were investigated. The results show that the response value of LaFeO3/PW12 sensor to acetone gas first increases and then decreases with the increase of PW12 content. The LaFeO3/3%PW12 sensor exhibits a maximum response of 3.35 to 5 ppm acetone at 250 °C, a 2.6 times increase in response value and a 90 °C reduction in operating temperature compared to pure LaFeO3 nanoribbons. The LaFeO3/3%PW12 sensor exhibits good linear relation in ppb-level concentrations and the lowest detection concentration is 100 ppb. The sensors also show good repeatability in 6 tests and excellent long-term stability in 30 d. The improvement of the gas sensitive properties of the composite can be attributed to the synergistic effect between the two components. As an electron acceptor, PW12 promotes carrier migration between PW12 and LaFeO3, thereby improving the gas sensing performance of LaFeO3. This work promotes the practical application of polyoxometalate to promote rare earth-based gas sensitive materials in sensing field.

Numerical simulations for the flow-induced vibrations of tandem dual flexible circular cylinders

The three-dimensional large-eddy-simulation coupled with a mode superposition method was applied to numerically simulate the flow-induced vibrations (FIVs) of tandem dual flexible cylinders at Re = 1000 with three different spacing ratios (Sx/D = 2.5, 3.5, and 5, Sx is center-to-center spacing for tandem cylinders, and D is the diameter of the cylinder), corresponding to the reattachment flow, transition flow, and co-shedding flow regimes in stationary tandem cylinders, respectively. The effects of Sx/D on structural vibrations, flow fields, distributions of the surface pressures, and energy properties were investigated to reveal the mechanism for the FIV. Increasing Sx/D weakens the influence of the upstream cylinder on maximum response amplitudes and lock-in region for downstream cylinder. The wake patterns for tandem flexible cylinders are more complex compared to stationary or vibrated rigid tandem cylinders. The shielding effect reduces surface pressure on the downstream cylinder significantly when its vibrations are smaller, leading to a decrease in mean power as well. Furthermore, different mechanisms contribute to amplified FIV in downstream cylinders depending on Sx/D: when Sx/D = 2.5, the upstream vortices collide with the downstream cylinder's front surface and merge with the vortices generated by the downstream cylinder, increasing negative pressure on both front and rear surfaces of the downstream cylinders and promoting FIV; however when Sx/D =3.5 and 5, a binary vortex street forms behind the downstream cylinder without obvious negative pressures on its front surface, the dominant causes of FIV are primarily attributed to interactions among upstream and downstream vortices.

Gradient Mo1−xWxSe2 monolayer Alloys: Synthesis and multifunctional applications

With the continuous and rapid development of electronic information technology, the demand for new materials with miniaturization, high integration, high performance, and multifunction is becoming increasingly urgent. However, it is difficult for existing photodetectors based on a single material to achieve multi-functionality while maintaining excellent performance, and the devices based on heterostructures are faced with complex preparation and compatibility problems. In this work, gradient Mo1−xWxSe2 monolayer alloys with high crystal quality have been synthesized by an evaporation-assisted chemical vapor deposition method. The composition of the synthesized Mo1−xWxSe2 monolayer alloys varies gradually with x ranging from 0 to 1. The Mo1−xWxSe2 based photodetector shows superior photoresponse performance in the visible wavelength with maximum responsivity of 26 A/W and external quantum efficiency up to 6320 % under 520 nm laser irradiation. Besides, the Mo1−xWxSe2 device is capable of high-resolution imaging, which can be used as image sensor. Moreover, nonvolatile memory function has also been realized in the device because the band gap of Mo1−xWxSe2 can be effectively adjusted by the gradient distribution of the component and the deep energy levels caused by Se vacancies can be modulated to shallow energy levels. A thrilling discovery is that the gradient Mo1−xWxSe2 alloy device can simulate the biological synapses successfully, including paired-pulse facilitation, short-term plasticity, long-term plasticity and learning process. The realization of high-performance photodetection, visualization, nonvolatile memory and synaptic simulation based on a single gradient crystal offers a new type of material to develop advanced optoelectronic devices with multiple functions.

Regulating surface terminals and interlayer structure of Ti3C2Tx for superior NH3 sensing

MXene materials have exhibited potential in electrochemistry, particularly in gas sensing, due to their excellent conductivity, large specific surface area of layered materials, and unique functional groups. However, the gas sensing performance of intrinsic 2D MXene materials is often limited by their fluorine-containing terminals and interfacial structure. In this study, based on intrinsic Ti3C2Tx, we employed alkali treatment and annealing to prepare oxygen-rich Ti3C2(OH)x/Ti3C2Ox with expanded interlayer spacing, achieving enhanced gas sensing performance for NH3. The surface chemistry and structure of the sensing materials have been optimized through the synergistic regulation of MXene's unique surface terminations and the intercalation effect of layered materials. Compared to intrinsic Ti3C2Tx, the interlayer spacing of oxygen-rich Ti3C2(OH)x/Ti3C2Ox increased from 9.1 Å to 12.1 Å. The surface terminations of oxygen-rich Ti3C2(OH)x/Ti3C2Ox have been defluorinated and oxygenated. The maximum response value of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3 was 35.66, approximately twice that of the original Ti3C2Tx at an NH3 concentration of 200 ppm. DFT (Density functional theory) calculations and DRIFT (In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy) tests explained the interaction between the surface terminals and NH3, indicating good selectivity and sensitivity of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3. The results demonstrated that the synergistic effects of surface chemistry and structural engineering are crucial for MXene to optimize the electrochemical performance, particularly the gas sensing performance. This provides a feasible approach for the performance optimization of intrinsic MXene materials.

A new processing method of ground acceleration data for fast and accurate evaluation of maximum seismic structural response

AbstractA new processing method of ground acceleration data is proposed for the fast and accurate evaluation of the maximum seismic structural responses. The proposed method consists of a trimming method and a down‐sampling method. The proposed trimming method is based on ground acceleration power and contains compensation procedures for the trimmed ground acceleration. The proposed down‐sampling method effectively uses FIR filter, whose weight coefficients are derived from the correspondence between the responses under a triangular wave and the equivalent impulse input. It is demonstrated through numerical examples for response spectrums and a full‐scale high‐rise building model that the proposed method enables fast and accurate evaluation of the maximum seismic structural responses.

Transition from p-type to n-type semiconductor in V₂O₅ nanowire-based gas sensors: Synthesis and understanding of the sensing mechanism

Vanadium pentoxide (V2O5) nanowires (NWs) were grown via hydrothermal method, followed by annealing treatment at 500 °C in air. Morphological characterization showed that the V2O5 material consists of nanowires with a diameter of 200 nm and an average length of 2.5 μm. The nanowires were used to make an NH3 sensor that operates at room temperature (28 °C) and relative humidity of 40 % RH, giving a relative response of 6.0 % to 500 ppm. The V2O5 nanowires show a change in behavior from p-type semiconductor to n-type semiconductor when the temperature exceeds 50 °C. The maximum response (35 %) was recorded at a working temperature of 200 °C (when the semiconductor behaves as an n-semiconductor) and showed good response and recovery speed over 500 ppm NH3. The performance of the sensor was studied and a sensing mechanism that takes into account the change of majority charge carriers in the semiconductor was hypothesized.

Seismic response of a mid-story isolated stilted structure in mountainous areas

Research on the SSI effect on flat sites has yielded many valuable conclusions. However, current research on the impacts of various special local terrains on structural dynamics remains limited. For mountainous areas, it is common to construct houses in a multi-step, climbing, and laterally staggered architectural form that follows the mountain terrain. Only through the analysis of the combined action of the upper and lower parts can the seismic performance of this type of structural form be better revealed; considering the influence of SSI effects will be closer to the actual seismic effects. Therefore, to identify the damage factors of the mid-story isolated stilted structures under earthquakes and provide optimized design plans for the structures, six models are established considering three slopes and two types of foundations based on the engineering case in Chongqing, China. Through the elastic-plastic time-history analysis under earthquakes in the down and transverse-slope directions, concludes, compared with not considering SSI, the seismic response of the mid-story isolated stilted structures considering SSI in mountainous areas is amplified. With the increase of the mountain slope, the seismic response of the structures considering SSI increases, and the amplification coefficients are between 1–1.8. The amplification coefficients of the structures without SSI are concentrated around 1, which is less influenced by the slope. The damage to the stilted isolated layer is mainly concentrated in the column and the beam end, and the maximum seismic response appears in the short columns. The foundation soil stress increases with the increase of the mountain slope.

Comparative study of the effects of preferential left ventricular and biventricular pacing on echocardiographic and cardiorespiratory indices and clinical status of heart failure patients: preliminary

Abstract Introduction Nonresponse to cardiac resynchronization therapy (CRT) has been related with right ventricular dysfunction. Preferential left ventricular pacing (pLV-P) can achieve left ventricle resynchronization allowing for intrinsic activation of the right side, and benefit cardiac output while reducing atrial fibrillation occurrence. Moreover, the AdaptivCRT® algorithm also automatically adjusts interventricular (V-V) delay every minute. Methods We evaluated the effects of a pLVP algorithm on 100 systolic heart failure patients ( all Caucasians, 49% male; 67 +/- 8 years old; 51% ischemic cardiomyopathy; 44% diabetics; NYHA II-III) following randomization to standard biventricular pacing and pLVP, on echocardiographic and cardiopulmonary exercise test indices of functional status. Device programming was based on echocardiography-evaluated maximization of stroke volume and subsequent interventricular and atrioventricular delay adjustments delegated to the device. The follow-up consisted of 6 and 12-months visits; after the 1rst month of optimizing maximum CRT response. Results Significant comparative effects of pLV-P over optimized CRT were noted regarding right ventricle systolic velocity in TDI at 12-months from baseline (mean (SE); 4.5(0.8), p=0.035); decrease in end-diastolic volume of left ventricle (mean (SE); 11.33(7), p=0.035); decrease in right ventricle strain mean ((SE); 9.2(2.1), p=0.03). According to other echocardiographic indices, again taking into account baseline levels, patients in pLV-P group exhibited lower E/e value at 6-months (mean (SE); 8.390(4,3), p=0.04), and at 12 -months (mean (SE); 7.45(3.9), p=0.035); improved values in left atrium contractility strain at 12-months (mean (SE); 8.390(0.8), p=0.04); a borderline improvement in left ventricular ejection fraction (mean (SE); 8.7(433), p=0.05) at 12-months; and borderline improvement in left ventricular longitudinal strain at 6-months (mean (SE); 4.9(2.6), p=0.035), compared to optimized CRT. In CPET, taking into account baseline levels, patients in the pLVP group showed higher METs at 12-months (mean (SE); 1,16(0.8), p=0.03) compared to opt CRT group; higher predicted Ventilation rate (%) even from 6-months (mean (SE); 8.167(5,7), p=0.03) and higher predicted peak VO2 (%) at 6 months (mean (SE); 34,13(14), p=0.03) and borderline significance at 12 months (mean (SE); 4.88(3), p=0.08), compared to opt CRT. Conclusions In the preliminary findings of READAPT study, it seems that pLVP optimized by a standardized echocardiographic protocol in patients with preserved AV conduction and LBBB, can achieve improvement in parameters of right ventricular and left atrium structure and function, as well as in survival-predictive parameters of CPET compared to optimized CRT during the 12-months of follow-up.

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

Seismic Response Analysis of Hydraulic Tunnels Under the Combined Effects of Fault Dislocation and Non-Uniform Seismic Excitation

Hydraulic tunnels are prone to pass through faults and high-intensity earthquake areas, which will cause serious damage under fault dislocation and earthquake action. Fault dislocation and seismic excitation are often considered separately in previous studies. For tectonic earthquakes with higher frequency in seismic phenomena, fault dislocation and ground motion are often associated, and fault dislocation is usually the cause of earthquake occurrence, so it is limiting to consider the two separately. Moreover, strong earthquake records show that there will be significant differences in the mainland vibration within 50 m. The uniform ground motion inputs in previous studies are not suitable for long hydraulic tunnels. This paper begins with the simulation of non-uniform stochastic seismic excitations that consider spatial correlation. Based on stochastic vibration theory, multiple multi-point acceleration time-history curves that can reflect traveling wave effects, coherence effects, attenuation effects, and non-stationary characteristics are synthesized. Furthermore, a fault velocity function is introduced to account for the velocity effect of fault dislocation. Finally, numerical analyses of the response patterns of the tunnel lining under four different conditions are conducted based on an actual engineering project. The results indicate the following: (a) the maximum lining response values occur under the combined effects of fault dislocation and non-uniform seismic excitation, indicating its importance in the seismic resistance of the tunnel. (b) Compared to uniform seismic excitation, the peak displacement of the tunnel under non-uniform seismic excitation increases by up to 6.42%, and the peak maximum principal stress increases by up to 28%. Additionally, longer tunnels exhibit a noticeable delay effect in axial deformation during an earthquake. (c) Under non-uniform seismic excitation, the larger the fault dislocation magnitude, the greater the peak displacement and peak maximum principal stress at the monitoring points of the lining. The simulation results show that the extreme response values primarily occur at the crown and haunches of the tunnel, which require special attention. The research can provide valuable references for the seismic design of cross-fault tunnels.

Shaking table test and numerical simulation of rocking wall frame structure considering dynamic soil-structure interaction

This study investigates the seismic response of a rocking wall frame structure considering dynamic soil-structure interaction (DSSI) through shaking table tests. A comparison with conventional frame structures and structures with fixed-base foundations is made to examine the influence of DSSI effects on various aspects including structural damage distribution, dynamic characteristics, and floor responses. Test results indicate that the presence of a rocking wall reduces structural responses across different site conditions, although the reduction is less significant under soft soil conditions compared to fixed-base foundation conditions. Overall, DSSI diminishes the mitigating effect of the rocking wall on the maximum structural response. Furthermore, a three-dimensional finite element model of the shaking table test is established. The numerical model employs the equivalent linear method to simulate the soil's nonlinear behavior and incorporates the concept of the rocking wall. Comparative analysis between experimental and simulated results demonstrates that the model effectively predicts the dynamic response of the rocking wall frame structure in DSSI systems.

Request Deadline Split and Interference‐Aware Request Migration in Edge Cloud

ABSTRACTEdge computing extends computing resources from the data center to the edge of the network to better handle latency‐sensitive tasks. However, with the rise of the Internet of Things, edge devices with limited processing capabilities face difficulties in executing requests with fluctuating request peaks. In order to meet the deadline constraints of latency‐sensitive tasks, a feasible solution is to offload some latency‐sensitive tasks to other nearby edge devices. This article studies the problem of request migration in edge computing systems and minimizes the request deadline violation rate based on actual online arrival patterns, performance interference phenomena, and deadline constraints. Since a request contains multiple services and request migration will lead to changes in server resource competition pressure, we split the problem into three sub‐problems, dividing the request deadline to determine the maximum response time of the service, determining the performance of the service under different resource pressures and the request migration strategies. To this end, we propose two deadline splitting methods, a performance interference model under multi‐resource pressure, and two heuristic request migration strategies. Since this article considers online edge scenarios, the number and type of requests are black boxes. We conduct simulation experiments and find that our method has only one‐third the number of request violations of other methods.