Rate Criterion Research Articles

Investigation of crack propagation behavior on shales with different inclination based on ultra-fast time resolution method

The layer structures of shale greatly influence its crack propagation behavior. Nevertheless, the correlation between crack extension rates and mechanical parameters has not been well studied, especially, the relationship between the energy release rate and crack propagation rates. Consequently, there are unresolved issues regarding the effects of layer structure on the propagation of cracks in shale. In this paper, a series of three-point compressive loading tests were conducted on seven groups of shale semi-circular bend (SCB) samples with an inclination angle of 0°-90°. The entire fracture process was captured using the ultrafast time-resolution method with a resolution capability of up to 15 picoseconds. In addition, fracture surface information was obtained by a high-precision laser three-dimensional scanning system, and this information was utilized to categorize crack propagation behaviors, such as propagation along weak planes, intermittent penetration, and deflection penetration. Furthermore, a quantitative relationship was established between the energy-release rate and crack propagation rate, based on the first law of thermodynamics and the maximum energy release rate (MERR) criteria proposed by Griffith. The experimental results showed that there is a linear relationship between the energy-release rate and the propagation rate, which meets well with the established relationship. The experimental results indicated that symmetric loading does not result in significant angle localization during crack initiation. This suggests that crack propagation behavior in shale is a reflection of the interplay between energy-release rates and fracture resistance. Finally, this study evaluated the influence of the bedding angle on dissipated energy, and absorbed energy.

Study on the member fracture and collapse performance of single-layer grid structures using discrete solid element method

In this study, the discrete solid element method (DSEM) incorporating a softening model is proposed, to accurately simulate the dynamic crack propagation and the member fracture of the single-layer grid structure. Firstly, based on the fracture criteria of strain energy release rate, the bilinear softening model and the trilinear softening model are proposed to simulate the fracture in both elastic and elastic-plastic materials. Secondly, the validity of the proposed approach is assessed through a comparison with empirical results. Furthermore, the fracture of the rectangular beam, dynamic crack propagation of the circular tube and member fracture of the hexagonal spatial rigid frame are simulated and compared with other numerical methods. Finally, the DSEM with the softening model is employed to investigate the collapse performance of single-layer grid structures, and the whole process of member fracture is captured by the DSEM. A thorough analysis is conducted to evaluate the influence of material parameters, loading methods, and rise-span ratios on the bearing capacity and fracture occurrence of single-layer grid structures. The results show that the material property of steel is superior to aluminum for single-layer grid structures. Moreover, the single-layer grid structures adopting full node loading or high rise-span ratios are shown to exhibit premature member fracture and rapid structural collapse. The obtained results exhibit remarkable agreement with the experimental results and are superior to the finite particle method (FPM) and the extended finite element method (XFEM). Therefore, DSEM with the softening model possesses the potential to evolve into an effective numerical tool capable of solving complex problems such as dynamic crack propagation and structural collapse.

Full-scale fire resistance tests of lightweight steel framed floor systems

As cold-formed steel profiles are increasingly used for load-bearing structural systems, their fire design requires specific attention due to their thin-walled nature and high slenderness. In some specific applications such as in storage hall floor systems, these structures are used without sheathing or thermal protection on the fire-exposed side. Yet, there is a lack of data from fire resistance tests on full-scale load-bearing thin-walled steel structures, especially with directly exposed steel. This article describes two standard fire resistance tests on full-scale light gauge steel frame floors made of cold-formed steel lipped channel girders and joists topped by chipboard panels. The experimental program was designed to investigate the fire resistance of the unprotected girders. A specificity of this program was that the girders were subjected to a low load level to probe the ability to achieve without passive fire protection a 30-min fire resistance rating typical for storage hall structures in the Czech Republic. The absence of protection resulted in differences in thermal gradients and bracing compared to common fire tests, as well as a very low degree of utilization leading to an expected failure temperature higher than 800 °C. The results showed that the two floors remained stable during the 30 min with limited deflections, but failed the deflection rate criteria after 24 and 22 min, respectively. Comparison is provided with the calculation methods from the Eurocodes. The presented results provide new data on the response of full-scale, unprotected cold-formed steel floor systems subjected to fire, which can be used to calibrate numerical models and fire design methods outside of the range currently covered by the codes.

Experimental and numerical investigation on the failure behavior of multi-spar composite box under bending and shear

Multi-spar composite boxes (MSCB) are common elements in structural design due to their high load capacity in different loading conditions. This paper presents an experimental and numerical investigation of the failure behavior of MSCB subjected to a combined bending-shearing load. Quadratic failure criteria and mixed-mode strain energy release rate criteria are used to predict the onset and propagation of damage at the inter-laminar interfaces of the MSCB, which was implemented into Abaqus/Explicit analysis via a user-defined material subroutine VUMT. At last, a good agreement between tests and numerical prediction was observed.

Distributed Learning for Uplink Cell-Free Massive MIMO Networks

Cell-free massive multiple-input multiple-output (MIMO) can resolve the inter-cell interference issue in cellular networks through cooperative beamforming of the distributed access points (APs). This paper focuses on an uplink cell-free massive MIMO network and investigates novel methods to train the central processing unit (CPU), the APs, and the users in the network. To reduce the communication burden posed on the fronthaul, each AP applies receive beamforming to compress the vector signals into scalar ones before passing them to the CPU for centralized processing. By drawing analogies between an uplink cell-free network and a quasi-neural network and borrowing the idea of backpropagation algorithm, we propose a novel scheme named the distributed learning for uplink cell-free massive MIMO beamforming (DLCB), which can achieve the multi-AP cooperation without explicit estimation of their channel state information (CSI). The DLCB has low computational complexity and is applicable to various objective functions, such as the minimum mean squared error criterion and the maximum sum rate criterion. Extensive simulations verify that the proposed scheme achieves superior performance over the state-of-the-art methods.

웹 기반 쓰기 평가 기준 개발 연구

Objectives The purpose of this study is to improve the validity and reliability of writing evaluation by developing rating criteria for web-based writing evaluation.
 Methods In particular, it was intended to develop rating criteria for writing evaluation based on Google Docs, a wiki tool that is actively used among web-based writing tools. To this end, the results of previous studies and ‘language and media’ textbooks were reviewed to extract web-based evaluation elements. After that, by expert discussion and by calculating the response ratio, average, CVR, CVI of the importance on rating criteria, content validity was verified. Finally, infit MnSq of the rating criteria were examined through Two-facet Rasch analysis.
 Results First, the rating criteria for web-based writing evaluation consist of a total 9 10 rating criteria. Second, as a result of the importance rating, it was found that Korean language education experts consider presenting information for purposes more important than visual styles such as font, size, frames, and hyperlink in web-based writing. Third, it was found that Korean language education experts had a discriminatory perception of the importance of each rating criterion.
 Conclusions The web-based writing rating criteria developed in this study can be useful in obtaining information about students' web-based writing skills and designing teaching and learning to enhance web-based writing skills.

Analisis Perbandingan Top 10 Best-Value dan Top 10 Traveler-Ranked Hotel di Kota Ternate Menggunakan MOORA

There are a variety of factors that influence hotel visitors' decisions. The first consideration pertains to the room and amenities, while the second comprises prior guest ratings. Tripadvisor is frequently used to propose lodging and amenity services in different places. Using the MOORA decision support model, this study compares the top 10 best-value hotels in Ternate City to the top 10 most-recommended hotels by travelers. This research consists of four phases: the data gathering phase, the data analysis phase, the data interpretation phase, and the reporting phase. The data processing results utilizing the MOORA decision support model on the top 10 best-value hotels in Ternate City revealed a considerable disparity with the Tripadvisor rankings based on room and amenity criteria and guest reviews. Muara Hotel Ternate has a total scale of 0.491% based on parameters related to its rooms and amenities. Additionally, the order is dynamic and dependent on guest rating criteria. The Bela International Hotel ranks #1 if review data is considered because its reviews exceed 100. The same conclusion was drawn from the data processing findings of the top 10 traveler-ranked hotels in Ternate City, where the ranking results based on room and amenities criteria refer to the Ternate City Hotel with a total yi value of 0.79. The ranking results are also dynamic and dependent on guest rating criteria. If the number of reviews is considered, the Bela International Hotel will be ranked #1 because its number of studies is more significant than 100. This implies that information about rooms and hotel amenities and the number of guest evaluations on the Tripadvisor website can be crucial in influencing hotel guests' decisions regarding their stay.

Kinking prohibition enhancement of interface crack in artificial periodic structures with local resonators

In this study, the propagation and kinking of an interface crack between two dissimilar artificial periodic structures with local resonators is investigated. By Fourier transform, the dynamic fracture problem is derived as an equation with Wiener–Hopf type. An additional band gap can be created by local resonators. During the dynamic failure, elastic waves will be excited continuously from the crack tip and result in the energy dissipation. Moreover, the energy release ratio which characterizes the fracture resistance is obtained. The meta-arrest property of the artificial periodic structure with local resonators is illustrated. Based on inverse Fourier transform, the displacement field is given to further understand the deformation and oscillation of crack faces. Based on the crack-tip field, the maximum energy release rate criterion is presented to discuss about whether the crack can propagate through kinking out of the interface. Comparing with the model without local resonators, we find that crack kinking can be prohibited in the proposed artificial periodic structures. Finally, finite element simulation and experiment are performed to show the good agreement with the theoretical predictions.

Failure analysis of blowholes in welded boiler water walls

Water walls are subjected to thermo-mechanical loading, which potentially leads to fatigue crack initiation and growth from the weld defects. This study comprehensively analyzes the blowout failure (blowholes) occurring in boiler water walls. An experimental-simulation mixed approach has been adopted to establish the effect of weld defects on fatigue crack initiation, crack growth, and ultimate failure by blowhole. The effect of the defect position on the propagation and failure has also been modeled by extended Finite Element Method (XFEM) based on the criteria of energy release rate. A combination of XFEM and Direct Cyclic Analysis (DCA) is used to calculate low-cycle fatigue life. The cracks are shown to have originated from lack-of-fusion defects, causing the membrane to disconnect and reducing heat transfer efficiency, which may lead to localized thermal hotspots and membrane rupture, leaving molten slag residues on the airside of water walls.

The use of discourse markers across pragmatic performance levels and task types

Discourse markers establish relationships between topics in discourse and serve a range of pragmatic functions, such as mitigating dispreferred actions and maintaining the continuity of spoken interaction. This study examines the use of diverse discourse markers (e.g. but, and, actually, you know, well, yeah, okay) in second language (L2) task-based pragmatic performance with the following research questions: What are distinct pragmatic functions of discourse markers in task-based pragmatic performance? How does the use of discourse markers differ at pragmatic performance levels and task types? The data came from 102 L2 English test-takers’ pragmatic performances on monologic and interactive role-play pragmatic assessment tasks, scored by trained raters using analytical rating criteria. Sequential mixed methods were employed to answer the research questions. First, the sequential positions and pragmatic functions of discourse markers in task-based performances were analysed using conversation analysis, which formed the basis of a coding scheme and coder training. Second, the coded data were analysed using the CLAN program for quantitative analyses to answer the second research question. The findings revealed that the frequencies and quantitative power of the discourse markers in predicting the pragmatic performance levels were distinct across the task types that differed in terms of pragmatic demands and interactivity. For example, the use of discourse markers which function as transitioners of actions and acknowledgement tokens was more distinguishable for more interactive tasks with less formal pragmatic functions. The findings confirm that the pattern of discourse markers was associated with the pragmatic functions and interactional demands required in the tasks. Implications of the findings in understanding the role of discourse markers in task-based pragmatic teaching and assessment are discussed.

Remote patient monitoring strategies and wearable technology in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is highly prevalent and is associated with a heavy burden on patients and health systems alike. Exacerbations of COPD (ECOPDs) are a leading cause of acute hospitalization among all adult chronic diseases. There is currently a paradigm shift in the way that ECOPDs are conceptualized. For the first time, objective physiological parameters are being used to define/classify what an ECOPD is (including heart rate, respiratory rate, and oxygen saturation criteria) and therefore a mechanism to monitor and measure their changes, particularly in an outpatient ambulatory setting, are now of great value. In addition to pre-existing challenges on traditional 'in-person' health models such as geography and seasonal (ex. winter) impacts on the ability to deliver in-person visit-based care, the COVID-19 pandemic imposed additional stressors including lockdowns, social distancing, and the closure of pulmonary function labs. These health system stressors, combined with the new conceptualization of ECOPDs, rapid advances in sophistication of hardware and software, and a general openness by stakeholders to embrace this technology, have all influenced the propulsion of remote patient monitoring (RPM) and wearable technology in the modern care of COPD. The present article reviews the use of RPM and wearable technology in COPD. Context on the influences, factors and forces which have helped shape this health system innovation is provided. A focused summary of the literature of RPM in COPD is presented. Finally, the practical and ethical principles which must guide the transition of RPM in COPD into real-world clinical use are reviewed.

Analysis of processing map and parameters optimization during hot extrusion of 17 vol.% SiCp/2009Al composite

Hot extrusion process can improve the mechanical properties of materials. However, due to the presence of SiC particles, SiCp/Al composites are prone to fracture damage in the extrusion process. To determine the optimal processing parameters, the processing maps of 17 vol.% SiCp/2009Al composite were established using power dissipation rate and Murty instability criterion. Furthermore, taking aluminum canning into consideration, a three-dimensional macroscopic hot extrusion finite element model of SiCp/Al composite was constructed. The influences of initial temperature, canning morphology and canning thickness on extrusion properties were predicted, and verified by comparison of processing maps and experiments. The optimal extrusion parameters for SiCp/2009Al composite are located within the window of temperature, 450–475 °C and strain rate, 0.001–0.004 s−1 or 0.6–1 s−1. Additionally, the properties of the SiCp/Al composite can be greatly improved by hot extrusion with a suitable canning. Of these, the half canning finish the extrusion task faster, but the extrusion properties under the bottom canning are the best. When the ratio of the canning thickness to the diameter of the workpiece is about 0.17, the effective stress, strain and damage are minimum. The work performed in this research, for the first time, provides quantitative evaluations of process parameters on the hot deformation of SiCp/Al composite, which enables to provide useful guides for hot extrusion parameters selection of SiCp/Al composite.

A Molecular‐Scale Origin of Shear Thinning and Brittle Failure of Silicate Melt

AbstractShear thinning and brittle failure of silicate melt control the dynamics of volcanic eruptions, but their molecular‐scale origin is still unclear. Here, we conducted tension and compression experiments on silicate melts, using time‐resolved X‐ray diffraction. Our experiments revealed that the intermediate‐range ordering of silicate structures, that is, the ring size formed by the SiO4 tetrahedra, demonstrated elastic and anisotropic dilation under tension and shrinkage under compression in the non‐Newtonian regime. In contrast, there were no significant changes in short‐range ordering, such as Si–O and Si–Si distances. Based on these findings, we inferred that shear thinning observed under high stress originates from the formation of anisotropically deformed large and small rings in silicate structures that are energetically unfavorable and unstable. Brittle failure occurred under high‐stress conditions, in both tension and compression. We propose a stress criterion as a necessary and sufficient condition for magma failure, rather than a strain rate criterion.

Rapid Prestressed Concrete Retrofit with Prestressed Mechanically-Fastened Fiber-Reinforced Polymer: Field Performance and Observation for a Deteriorated Prestressed Concrete Bridge

This paper presents repairs to rural bridges in North Carolina that deteriorated as a result variously of aging, overweight traffic, and exposure to salts and sulfates. The prestressed concrete C-channel superstructures exhibited prestressing strand loss and displayed significant concrete spalling, with one structure having to be closed to traffic after a routine inspection. Analysis conducted using the American Association of State Highway and Transportations Officials (AASHTO) bridge load rating criteria concluded that repair techniques which strengthen deteriorated flexural elements without also restoring lost prestressing forces are insufficient to maintain load ratings in C-channel structures with heavily damaged prestressing tendons. A prestressed mechanically-fastened fiber-reinforced polymer (MF-FRP) retrofit solution was developed and successfully installed on three structures by the authors and North Carolina Department of Transportation maintenance crews. The most extensive of these three repairs is presented here in detail. The field applications and associated analysis show the temporary MF-FRP repair system is capable of restoring lost prestressing forces, allowing original inventory and operating ratings to remain in place until a permanent superstructure replacement can be scheduled. The most heavily repaired bridge remains in service after 23 months, its performance demonstrated by long-term monitoring data. As currently implemented, the MF-FRP repair is a viable temporary solution for maintaining traffic on a degraded structure while a replacement structure is designed, programmed, and implemented. Efforts to expand the MF-FRP repair into a longer-term solution are underway.

Establishment and interpretation of the gamma pass rate prediction model based on radiomics for different intensity-modulated radiotherapy techniques in the pelvis

Backgroundand objectives: Implementation of patient-specific quality assurance (PSQA) is a crucial aspect of precise radiotherapy. Various machine learning-based models have showed potential as virtual quality assurance tools, being capable of accurately predicting the dose verification results of fixed-beam intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) plans, thereby ensuring safe and efficient treatment for patients. However, there has been no research yet that simultaneously integrates different IMRT techniques to predict the gamma pass rate (GPR) and explain the model.Methods: Retrospective analysis of the 3D dosimetric verification results based on measurements with gamma pass rate criteria of 3%/2 mm and 10% dose threshold of 409 pelvic IMRT and VMAT plans was carried out. Radiomics features were extracted from the dose files, from which the XGBoost algorithm based on SHapley Additive exPlanations (SHAP) values was used to select the optimal feature subset as the input for the prediction model. The study employed four different machine learning algorithms, namely, random forest (RF), adaptive boosting (AdaBoost), extreme gradient boosting (XGBoost), and light gradient boosting machine (LightGBM), to construct predictive models. Sensitivity, specificity, F1 score, and AUC value were calculated to evaluate the classification performance of these models. The SHAP values were utilized to perform a related interpretive analysis on the best performing model.Results: The sensitivities and specificities of the RF, AdaBoost, XGBoost, and LightGBM models were 0.96, 0.82, 0.93, and 0.89, and 0.38, 0.54, 0.62, and 0.62, respectively. The F1 scores and area under the curve (AUC) values were 0.86, 0.81, 0.88, and 0.86, and 0.81, 0.77, 0.85, and 0.83, respectively. The explanation of the model output based on SHAP values can provide a reference basis for medical physicists when adjusting the plan, thereby improving the efficiency and quality of treatment plans.Conclusion: It is feasible to use a machine learning method based on radiomics to establish a gamma pass rate classification prediction model for IMRT and VMAT plans in the pelvis. The XGBoost model performs better in classification than the other three tree-based ensemble models, and global explanations and single-sample explanations of the model output through SHAP values may offer reference for medical physicists to provide high-quality plans, promoting the clinical application and implementation of GPR prediction models, and providing safe and efficient personalized QA management for patients.

Bursting Liability Criteria of Coal Mass Based on Energy Storage and Release Characteristics.

The bursting liability of coal, referring to the characteristic of coal to accumulate strain energy and produce impact damage, is an important factor influencing the occurrence and extent of rock burst disasters in coal mines. Two indicators-the elastic strain energy storage coefficient and energy release coefficient-are proposed based on the energy evolution characteristics of different stages during rock bursts. Twelve coal specimens from typical mines were selected for uniaxial compressive tests to analyze the damage characteristics of three types of typical coal specimens with different impact damage intensities in different loading stages. The initial kinetic energy of the coal specimens was obtained according to the principle of horizontal projectile motion. The bursting liability rating criteria according to the energy storage coefficient and energy release coefficient were determined based on the damage and motion characteristics of the coal mass, damage acoustic characteristics, and damage initial kinetic energy. The study demonstrated that the discrimination results based on the new criteria of coal mass bursting liability were consistent with the actual bursting liability level of the coal mass, thus providing a new method for determining coal mass bursting liability.

Robust stability/stabilization with variable convergence rate for uncertain impulsive stochastic systems

AbstractThis article researches the interval‐driven variable convergence rate robust stability/stabilization of uncertain impulsive stochastic systems. First, a new conception of variable convergence rate stability for uncertain impulsive stochastic systems is presented in conjunction with the idea of generalized pole configurations. Also, a new criterion for variable convergence rate robust stability/stabilization of uncertain impulsive stochastic systems is given, which can reflect and regulate the convergence rate of the system state. In addition, a new algorithm is designed by means of an interval‐driven stabilization method. This algorithm, combined with the variable convergence rate criterion, achieves accurate control of the convergence rate of the state at the operational level. Double instances are proposed to verify the superiority of the method.

Obtaining Stable Predicted Distributions of Response Times and Decision Outcomes for the Circular Diffusion Model

The circular diffusion model represents continuous outcome decision making as evidence accumulation by a two-dimensional Wiener process with drift on the interior of a disk, whose radius represents the decision criterion for the task. The hitting point on the circumference of the disk represents the decision outcome and the hitting time represents the decision time. The Girsanov change-of-measure theorem applied to the first-passage time distribution for the Euclidean distance Bessel process yields an explicit expression for the joint distribution of decision outcomes and decision times for the model. A problem with the expression for the joint distribution obtained in this way is that the change-of-measure calculation magnifies numerical noise in the series expression for the Bessel process, which can make the expression unstable at small times when the drift rate or decision criterion is large. We introduce a new method that uses an asymptotic approximation to characterize the Bessel process at short times and the series expression for the large times. The resulting expressions are stable across all parts of the parameter space likely to be of interest in experiments, which greatly simplifies the task of fitting the model to data. The new method applies to the spherical and hyperspherical generalizations of the model and to versions of it in which the drift rates are normally distributed across trials with independent or correlated components.

Discussion on three forms of coupled criterion for notch fatigue limit prediction: Comparison between point-wise and averaged stress (energy) criteria

In the framework of finite fracture mechanics, two coupled criteria were proposed by Leguillon and Carpinteri, respectively. Leguillon’s criterion uses the point-wise stress criterion, whereas Carpinteri’s criterion uses the averaged stress criterion. Both criteria employ the same incremental energy release rate criterion which can be considered as an averaged energy criterion. Mathematically, the averaged energy criterion can be transformed into an equivalent point-wise criterion. In this paper, a new coupled criterion based on the point-wise stress and energy criteria was proposed. The proposed criterion is equivalent to Carpinteri’s criterion when predicting notch fatigue limits. All the three forms of coupled criteria were checked and compared by a large number of experimental results including V-shaped and central hole specimens. When performing the coupled criteria, power functions derived from finite element analysis were used to express the energy release rate and notch stress distributions. The effect of notch size on the crack extension lengths were investigated.

ANALISIS PROYEK VIDEO MAHASISWA PGSD PADA MATA KULIAH PENDIDIKAN ANTIKORUPSI DI STKIP TAMAN SISWA BIMA

Based on the observations of the author of STKIP Taman Siswa Bima in the Elementary School Teacher Education study program, it is the study program that uses the most learning video media in providing material and assignments for students, more specifically in the Anti-Corruption Course the use of video as a model for student assignments has been carried out for the last three years . Where the form of assignment in the form of making an Anti-Corruption campaign video is expected to provide many opportunities for students to be creative and innovative in producing work and can provide motivation and self-expression abilities for the student in question. Learning outcomes other than limited face-to-face meetings also use the Hibrid method, namely by using the Google Classroom application and collecting assignments by uploading assignments in the form of videos on Youtube. The purpose of this study was to analyze student learning assignment videos in anti-corruption education courses. This research is a type of quantitative and qualitative descriptive research that seeks to analyze instructional videos including; the advantages and disadvantages of videos made by students. The method used is the observation of task assessment with certain criteria then data analysis displays Frequency distribution tables, Graphs, Means and standard deviation. The focus of the analysis is to look for errors in duration, originality of the recording, suitability with the presentation material, sound and image quality. The rating criteria scale used is 50-100. The results of the study found that the average score for student videos was 76. In terms of criteria, the lowest score was the quality of the material concept, which was 72. Meanwhile, the highest score was the duration and originality of the video, which were 79-80 respectively.