Loading Method Research Articles

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.

The Study of Water Content on the Coal Loading Performance of Thin Coal Seam Shearer Drum by Discrete Element Method (DEM)

ABSTRACTAs the main component of thin coal seam shearers, the drum bears the functions of loading and cutting, and its performance has become an important factor restricting mining efficiency and production safety. In response to the problem of low efficiency in installing thin coal seam shearers, this paper uses the Discrete Element Method (DEM) to study the effects of loading methods, helical angle of drum, drum rotation speed, and particle water content on coal loading rate. Research has found that the coal loading performance of the ejection loading method is much higher than that of the pushing loading method. As the helical angle increases, the average loading rate increases. As the rotation speed increases, the loading rate of wet coal particles gradually decreases. During production and thin coal seam mining, special attentions should be paid to the control of helical angle of drum and drum rotation speed. This study has guiding importance for improving the efficiency of thin coal seam mining.

Efficient Loading into and Controlled Release of Lipophilic Compound from Liposomes by Using Cyclodextrin as Novel Trapping Agent.

Lipid bilayer vesicles, liposomes are representative drug delivery carriers. High encapsulation efficiency and release control of drugs are essential for clinical application of liposomes. For efficient drug loading into liposomes, remote loading method using driving force like transmembrane gradients of pH and ions are utilized. Ions are called as "trapping agents," which are also critical for the controlled release of drugs loaded into liposomes inside. It is difficult to apply ions as trapping agents to various drugs because of limited physicochemical compatibility between drugs and ions. Cyclodextrins (CDs) with hydrophobic cavity can make inclusion complexes with various hydrophobic compounds. Therefore, we aimed to evaluate the potential of CDs as a novel trapping agent using sulfobutylether-β-cyclodextrin (SBE-β-CD) and ibuprofen (IB), a weak acid hydrophobic drug. Encapsulation efficiency of IB in liposomes with pH gradient was approximately 27%, and it was enhanced by intraliposomal SBE-β-CD inclusion in addition to pH gradient, which was SBE-β-CD concentration-dependent. In liposomes with pH gradient, a large fraction of IB was released in a short time. This early-stage rapid IB release was significantly suppressed by the inclusion of SBE-β-CD inside liposomes. Thus, novel remote loading technology by intraliposomal SBE-β-CD enabled the efficient encapsulation of the hydrophobic drug into the aqueous phase of liposomes as well as their controlled release. This technology should be applied to various drugs that can be included into CDs in order to enhance their therapeutic benefits.

Investigation into the flexural performance of novel precast sandwich wall panels

The paper focuses on investigating a novel sandwich panel, which incorporates extruded polystyrene foam boards placed between the inner and outer concrete panels. These are connected using various types of shear connectors to achieve a composite action, meeting the bending resistance requirements. To study the structural performance of the sandwich panels, three representative specimens were designed. These specimens employed different types of shear connectors, namely, steel truss connectors with inclined bars at 45°, and GFRP connectors with inclined bars at 45° and 30°, respectively. The specimens underwent full-scale testing using a step-by-step four-point loading method. The test results indicated shear-compression failure of the specimens, exhibiting consistent failure modes across all specimens, and a composite action in resisting bending moments. Based on theoretical stress–strain diagrams and considering the slip phenomenon between the concrete panel and the connectors, this paper establishes an analytical model. It can reasonably estimate the ultimate load-carrying capacity of sandwich insulation panels under shear-compression failure, which has implications for subsequent engineering applications.

A novel damage localization method of Circular Phased Array using Minimum Variance Distortionless Response Beamforming with Autocorrelation Matrix Diagonal Loading

Damage localization methods based on Acoustic Emission (AE) can be classified into time-based and waveform-based. However, the former requires a large number of sensors while the latter is limited to 2D plane localization. In order to address the challenge of achieving more accurate 3D localization using a reduced number of sensors, this paper proposes a Circular Phased Array using Minimum Variance Distortionless Response (MVDR) Beamforming with Autocorrelation Matrix Diagonal Loading (AMDL) method. Firstly, a sparse circular array is utilized to form multiple beamforming for coherent shear wave signals, decomposing the original 3D localization problem into Direction Of Arrival (DOA) estimation. Secondly, azimuth angle, elevation angle and autocorrelation matrix diagonal loading methods are introduced, working in conjunction with the MVDR beamforming algorithm. Finally, spatial integration is performed through matrix decomposition to solve geometric overdetermined equations. The effectiveness of the proposed method is validated through numerical simulations and experimental verifications under various damage conditions. Results indicate that estimation errors for azimuth and elevation angles are both less than 2 %, while 3D damage source localization errors remain within a range of less than 3 %. This proposed method extends beamforming technology from 2D plane localization to 3D localization, significantly reducing the complexity of sensor arrangement and lowering the cost of structural health monitoring systems by utilizing a small number of sensors.

Mechanical properties and energy evolution of outburst coal seams under different load regimes

AbstractCoal elasticity and gas expansion are important factors for coal and gas outburst. During the outburst process, the elastic strain energy of coal is mainly released from the stress region, and the gas expansion energy near the working face is larger, and it is not a continuous release process. To reveal the mechanical characteristics and energy evolution of outburst coal seam, uniaxial and triaxial compression tests were carried out on outburst coal seam samples under different loading methods. The experimental results show that the elastic characteristics become more obvious with the increase of loading rate, the peak strain increases, the elastic modulus is linearly related with the loading rate，and the overall degree of fragmentation increases with the increase of loading rate, which is consistent with the severity of macroscopic coal failure. The failure mode of coal under uniaxial compression conditions is often manifest as brittle failure. The strength characteristics of coal under different loading rates comply with the Mohr‐Coulomb criterion, and the peak strength is linearly related to the failure time and loading rate. With the increasing confining pressure causes the failure of coal samples to transition from ductile to brittle, and the failure mode develops from local shear to overall splitting. The elastic energy evolution curve is consistent with its stress‐strain curve. With the increase of confining pressure, the limiting elastic energy and peak total energy increase in a quasi‐linear manner. The accumulated limit elastic energy plays an important role in the failure of coal samples, and the macroscopic manifestation thereof is that the coal samples fail more severely under high confining pressure conditions than under low confining pressure conditions. The research results are of great significance for the comprehensive prevention and control of coal and gas outburst.

Electromagnetic radiation of granite under dynamic compression

To elucidate the characteristics and mechanism of electromagnetic radiation in granite under impact loading, based on the quasi-static compression tests, this paper conducts dynamic compression experiments on granite using Hopkinson pressure bar and one-stage light-gas gun as loading methods. Combined with experimental and theoretical analyses, the relationship between mechanical and electromagnetic responses under impact loads of different intensities, and the time-domain signals of electromagnetic radiation generated by a single crack under different strain rates are studied. The intensity and frequency of electromagnetic radiation increase with the increasing compressive strain rate. According to the thermal activation theory, it reveals the microscopic mechanism of the transition from intergranular microcracks to transgranular microcracks in terms of strain sensitivity. It also serves as the physical basis for the increase in electromagnetic radiation intensity amplitude and frequency with increasing compressive strain rate. Transgranular microcracks are the primary cause of electromagnetic radiation generated by fractures.

Design theory of self-centering column foot joint with dog bone weakened flange cover plate

Basing on the concept of post-earthquake repairability, plastic damage control, and self-centering, this study introduces a novel self-centering column foot joint with dog bone weakened flange cover plate (FCP) for prefabricated steel structure. The method and design theory for the target yield load and initial stiffness of the new joint were established. Parametric research was conducted using finite element simulation to assess the influence of the dog bone weakened FCP thickness, initial cable force, and axial compression ratio on the bearing performance of the new joint, thereby verifying the above method and theory. The results reveal the accuracy of the proposed method for determining the target yield load and initial stiffness, and provide practical design guidance for the new joint. The design theory values of the new joint and the simulation values demonstrate an error within 10%, which satisfies the engineering accuracy requirements. The corresponding procedures and suggestions for the design theory of this new joint were finally provided. Based on design theory, the overall plastic damage concentrates on the dog bone weakened FCP, successfully controlled by the new joint design, ensuring minimal damage to the main structure and demonstrating good bearing capacity and self-centering performance.

FastPTM: Fast weights loading of pre-trained models for parallel inference service provisioning

Pre-trained models (PTMs) have demonstrated great success in a variety of NLP and CV tasks and have become a significant development in the field of deep learning. However, the large memory and high computational requirements associated with PTMs can increase the cost and time of inference, limiting their service provisioning in practical applications. To improve the Quality of Service (QoS) of PTM applications by reducing waiting and response times, we propose the FastPTM framework. This general framework aims to accelerate PTM inference services in a multi-tenant environment by reducing model loading time and switching overhead on GPUs. The framework utilizes a fast weights loading method based on weights and model separation of PTMs to efficiently accelerate parallel inference services in resource-constrained environments. Furthermore, an online scheduling algorithm is designed to reduce the inference service time. The results of the experiments indicate that FastPTM can improve the throughput of inference services by an average of 4x and up to 8.2x, while reducing the number of switches by 4.7x and the number of overtimes by 15.3x.

The hysteresis loop on the near-threshold fatigue crack growth curves generated by stepped load reduction and constant-amplitude loading methods in a Ni-based superalloy

Fatigue crack growth (FCG) tests were conducted on compact tension specimens made of a Ni-based superalloy to investigate the near-threshold FCG behaviors using both the stepped load reduction method (LRM) and the constant-amplitude loading method (CALM) at three stress ratios (R = 0.05, 0.5 and 0.7) under ambient condition. It is found that after the FCG threshold being approached by the LRM, a remarkable hysteresis plateau occurs on the subsequent FCG curve generated by the CALM for R ≤ 0.5, resulting a hysteresis loop on the near-threshold region, but the situation becomes complicated at R = 0.7. In the appearance of hysteresis plateau, the FCG life to fracture can be over 107 cycles longer than that without hysteresis plateau. For FCG rate faster than 10−8 m/cycle, the fractography is dominated by transgranular feature which is insensitive to the microstructure of the alloy. In the hysteresis plateau region where FCG rate is lower than 10−9 m/cycle, fractography shows a wide optical dark zone where microstructure-sensitive crystallographic facet feature dominates, while when no hysteresis at R = 0.7, the optical dark zone is too narrow for the fracture feature transition so that crystallographic facet, transgranular as well as mosaic features can be observed simultaneously. As FCG in the hysteresis plateau under the CALM can be significantly slower than that under the stepped LRM, it is recommend that the stepped LRM should be used to generate the material basic FCG curves for fatigue life prediction of high durability structures.

Analysis of Railway Track Type Selection on the Lahat-Lubuklinggau Line

Currently, the railway line from Lahat to Lubuklinggau uses the R.42 rail type with a crossing power capacity of 2,106 > 5,106 tons/year. An increase in road class is needed to increase crossing capacity. This research aims to determine the feasibility and impact of upgrading the rail type from R.42 to R.54 to improve the operational efficiency and safety of the Lahat-Lubuklinggau railway line. In this study, the author uses the railway loading method using the beam on the elastic foundation (BoEF) concept to calculate rail permit voltage to ensure that the capacity of the railroad can accommodate the load of railway traffic. The study results in show that with the upgrade of the railroad class to class III with the R.54 rail type, this line can transport a load of 5,924,001.60 tons/year, an increase from 1,838,390.40 tons/year. In addition, the track with the R.54 rail type also meets the requirements for trains with the largest load, considering that the allowable voltage (1,097.18 kg/cm²) is smaller than the previous rail allowable voltage (1,738.14 kg/cm²). It is estimated that the R.54 rail type has a life resistance of 16-17 years against crossing power without the Babaranjang train and for 9-10 years against crossing power with the Babaranjang train for the coming year.

Structural Modification of Ru‐Bi Catalysts and its Impact on One‐Pot Synthesis of 2,3,5‐trimethyl‐1,4‐benzoquinone with Hydrogen Peroxide

AbstractOxidative transformation of phenols is an efficient route towards the production of moieties for naturally occurring quinones with a wide range of biological activities. Silica supported Ru−Bi catalysts were prepared by microwave‐assisted loading (MW) and deposition (DP) methods. The as‐prepared catalysts were characterized by XRD (X‐ray diffraction), N2 physisoption, SEM (Scanning electron microscopy), TEM (Transmission electron microscopy) and XPS (X‐ray photoelectron spectrometry) techniques. Catalysts with low Bi loading, 5 %Ru‐1 %Bi, have narrow particle size distributions that correspond to an average particle size of 2.21–2.59 nm. 5 %Ru‐5 %Bi catalysts consist of Ru−Bi nanochains. The outcome of the catalytic oxidation of 2,3,5‐trimethylhydroquinone (TMHQ, 1) to 2,3,5‐trimethyl‐1,4‐benzoquinone (TMBQ, 2) depends on the catalyst preparation method, promoter loading, solvent and temperature used. MW‐5Ru1Bi is the most active catalyst with conversions that range between 99–100 % at both room temperature (r.t) and under refluxing MeNO2 and MeOH. The highest yields of TMBQ (100 %) were obtained over MW‐5 %Ru‐1 %Bi and DP‐5 %Ru‐5 %Bi catalysts.

Falling weight impact acceleration-time signals analysis for road modulus detection: Theoretical and experimental investigations

Structural modulus detection is essential for construction and maintenance in road engineering. Falling weight impact loading method has significant strengths in large-scale, continuous, and rapid detection. To provide theoretical support for this, theoretical analysis and falling weight impact experiments were employed in this study to investigate the influence of road structure parameters and falling weight impact parameters on impact acceleration-time signals. First, the applicability of the Hertz model in road detection was analyzed, and theoretical formulas for peak acceleration amax and impact duration t2 were established, considering the perfectly elastic collision between falling weight and half-space. Second, the influence of layered structures’ properties on impact acceleration-time curves was studied through model box impact experiments. Third, field tests were conducted to study engineering applications. The results showed that the influence patterns were similar in both theoretical and experimental studies, with differences reflected in the time of compression and restitution phases due to the road materials’ viscosity and plasticity. Additionally, in indoor experiments, amax showed an excellent power function relationship with structural layer modulus, with R2 more than 0.95, and the contribution of each layer’s modulus to amax decreased from top to bottom. Finally, amax and resilient modulus of an old road also followed a good power function relationship, with R2 around 0.76. This study revealed that amax was recommended for road surface modulus detection based on solid theoretical and experimental support.

Two unequal shots in the same hole: statistical versus deterministic deconvolution

Determination of the source time function and earth impulse response for explosive source seismic reflection data is traditionally performed using predictive deconvolution, which assumes the reflection seismogram is the convolution of a minimum-phase wavelet with a white, random, stationary sequence of impulses. We compare this statistical method with a new deterministic method that uses two unequal shots close together in the same hole and assumes a seismogram is the convolution of a source time function with a Green's function, plus noise. The seismograms from the two shots share essentially the same Green's function to any receiver, because the shots are close together. The Green's function is estimated by deconvolving the two seismograms at a given receiver for the corresponding source time functions, modelled independently; source parameters are obtained by trial-and-error by minimising the difference between the two estimates of the Green's function. We test these competing theories using seismic reflection data acquired with two charges fired separately in the same hole into a receiver spread of 1178 bunched geophone groups at 10 m intervals: a 1 kg charge at 42 m depth and 2 kg at 40 m depth. The criterion for comparison of the theories is the similarity of the recovered impulse responses at any receiver. Each method recovers a wavelet, or source time function, for each shot and two estimates of the impulse response, or Green's function, at each receiver. The Green's functions recovered from the two shots using the deterministic method are almost identical and are measurably more similar than the impulse responses recovered using predictive deconvolution. That is, the deterministic method is better. The resolution of explosive source seismic reflection data can now be significantly improved with the new method and minimal additional field effort of loading one extra charge per shot hole.

Harnessing in-situ oxidation of nanostructured mxene to modulate the electronic structure for improved selectivity for electrochemical carbon dioxide reduction

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach to valorizing CO2. Ti3C2TX as a support material has received significant interest in enhancing CO2RR performance for tuning the electronic structure. However, there has been relatively less focus on changes to the Ti3C2TX electronic structure induced by loading catalysts onto the Ti3C2TX. Because Ti3C2TX has an intrinsic activity for both CO2RR and the competitive hydrogen evolution reaction (HER), electronic structure changes can affect the balance between CO2RR and HER selectivity. Therefore, tuning the electronic structure of Ti3C2TX can control the competition between CO2RR and HER and tune the selectivity and activity. Herein, we report that Ti3C2TX’s electronic structure can be tuned by the Ag+ loading method via redox interactions, tuning the reaction selectivity and activity for CO2RR. To illustrate this effect, we compare the CO2RR performance of in-situ formed Ag nanoparticles (NPs) on Ti3C2TX (0.9Ag-IS-Ti3C2TX) with physically mixed Ag NPs and Ti3C2TX (0.9Ag/P/Ti3C2TX). Here, ‘0.9’ refers to the molar ratio between Ag precursor and Ti3C2Tx, and ‘IS’ vs. ‘P’ refers to in-situ formed vs. physically mixed Ag NPs. 0.9Ag-IS-Ti3C2TX demonstrates a higher oxidation state for Ti and a higher proportion of Ti-O bonds than 0.9Ag/P/Ti3C2TX. Compared to 0.9Ag/P/Ti3C2TX, 0.9Ag-IS-Ti3C2TX exhibits higher CO Faradaic efficiency (FE), rising from 8.1 % with a partial current density of −2.0 mA cm−2 to 49.6 % with a partial current density of −20.1 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode). To harness this effect, we demonstrate control over the CO: H2 ratio of syngas formed from CO2RR over our Ti3C2TX-supported catalysts. Further electrochemical anodic oxidation experiments reveal the critical oxidation potential of Ti3C2TX (0.8 V vs. RHE) and show that HER can be partially suppressed by partial oxidation of Ti3C2TX. This work highlights the importance of considering the changes in Ti3C2TX (and other) supports when supporting catalysts for CO2RR and other electrochemical reactions.

A temperature rise calculation model of wind turbine gearbox gear considering crack fault and tooth number difference

AbstractThe crack fault of gear is usually accompanied by temperature rise. Therefore, to master the temperature characteristics of the cracked gear of the wind turbine gearbox, a temperature rise calculation model of wind turbine gearbox gear considering crack fault and tooth number difference is proposed. Firstly, the time‐varying meshing stiffness model of the cracked gear considering the tooth number difference is established based on the potential energy method. Secondly, the calculation method of the meshing surface normal load of the cracked gear is deduced. Thirdly, the temperature rise calculation model of the meshing surface of the cracked gear is constructed based on Blok flash temperature theory. Finally, the data of the high‐speed gear of a wind turbine gearbox in northern China is selected for simulation verification. By comparing with the finite element method, the effectiveness of the proposed method is verified. The simulation results reveal the gear temperature characteristics of the wind turbine gearbox with different crack ratios. The research can provide some theoretical support for the accurate fault diagnosis and maintenance of wind turbine gearbox, and can also be applied to the fault diagnosis of gear cracks in other mechanical structures with a large transmission ratio.

Simulation analysis of force and fatigue life of circular wheel of crawler vehicle

During loading and driving, the wheels bear the vertical load from the body mass and the excitation load generated by uneven road surface on the one hand, and bear the driving torque on the other hand. The load-bearing methods of wheels are generally divided into bottom load-bearing and top load-bearing. This paper describes the structural characteristics of the track system of the articulated track vehicle and the interaction relationship between the main components of the track system. Finite element calculation is carried out based on ANSYS software to obtain the stress distribution of each key component under various loading methods. It can be seen from the results that all key components of the track system can meet the strength and rigidity requirements; although there are also areas with large local stress, they are all within the safe range, which is mainly caused by stress concentration. Safe life is obtained through fatigue analysis.

Research on power metering method for nonlinear loads in power system based on improved S-transform

Abstract Traditional power metering algorithms are no longer suitable for new power systems to address the issue of distorted voltage and current waveforms caused by a growing number of nonlinear loads in modern power systems. The paper proposes a power-metering algorithm based on an Improved Stockwell Transform (IST). Based on the Stockwell transform, several parameters that can control the Gaussian window are introduced to improve the flexibility of the Gaussian window. Additionally, the inequality constraint based on the energy concentration measure is used to optimally select the best window parameters, enhancing the time–frequency domain analysis capability of the IST. The study uses IST to decompose and reconstruct the voltage and current fundamental characteristic signals and distortion characteristic signals in the power system. This provides good time resolution at low frequencies and good frequency-domain resolution at high frequencies. Power metering based on unsteady voltage and current is achieved by calculating the resulting fundamental and harmonic powers, respectively. The simulation results demonstrate that the IST-based power metering method has a higher level of accuracy than the existing metering methods.

Integrating model-driven and data-driven methods for under-frequency load shedding control

With the access of a high percentage of new energy sources, power system frequency stability is challenged. Under-frequency load shedding (UFLS) is one of the primary measures to maintain frequency stability. Due to the mismatch between the amount of load shed by the traditional UFLS methods and the actual active power deficit, a new UFLS method needs to be designed. An approach utilizing a deep deterministic policy gradient (DDPG) algorithm for the problem is proposed. First, the DDPG algorithm is modified to adapt to the UFLS problem. Then, the idea of model-driven is introduced to improve the validity of the model. Thus, a novel UFLS method is proposed, which integrates data-driven and model-driven ideas. Furthermore, a structure called the dual experience pool is designed to accelerate training speed and improve stability. Based on the proposed method, a UFLS control framework is designed. Finally, the suggested methodology is validated using the IEEE-39 bus system and the Fujian power grid as test cases.

A calculation method for ultimate and allowable loads in high-pressure thick-walled worn casing

Casing wear has become a critical issue in oil and gas drilling, significantly reducing casing burst strength. As exploration and development progress, the number of high-pressure, ultra-deep wells continues to rise, requiring high-strength, thick-walled casings capable of withstanding ultra-high internal pressures. However, research on the strength characteristics of worn high-strength, thick-walled casings under such conditions remains limited. This study fills that gap by quantitatively evaluating worn casings to determine the maximum allowable internal pressure, particularly for high-pressure, thick-walled casings. A systematic analysis of existing methods for calculating the ultimate load of casings is conducted, and a suitable approach for high-grade steel casings is proposed. A parametric finite element model (FEM) of worn casings was developed to assess the impact of various dimensionless structural parameters, including the thickness ratio (Do/t), wear percentage (h/t), wear circle ratio (2ri/Do), and nominal yield strength (Rp0.2), on the ultimate load. The results demonstrate that both wear depth and casing dimensions significantly affect the ultimate load. A new formula is proposed for calculating the ultimate and allowable loads of worn casings based on the results of a finite element analysis. This formula is applicable to high-strength casings of varying wall thicknesses, particularly under ultra-high pressure.