Failure Patterns Research Articles

Vehicle Collision Analysis of the Reinforced Concrete Barriers Installed on Bridges Using Node-Independent Model

This paper focuses on improving vehicle collision simulations using finite element analysis (FEA) to examine interactions between reinforced concrete barriers and bridge decks. Three scenarios are explored: treating the barrier as a rigid body, analyzing reinforcement with a fixed base, and including the bridge deck’s cantilever portion beneath the barrier. Except for the rigid body model, a node-independent approach models the complex interactions between reinforcement and concrete in barriers on the bridge deck. This study evaluates barrier strength, occupant risk, and post-collision vehicle safety. Strength is assessed by examining stress in reinforcement and concrete, while occupant risk is measured using Theoretical Head Impact Velocity (THIV) and Post-impact Head Deceleration (PHD). Vehicle trajectory during collisions is also analyzed for stability. The results show significant differences in stress distribution and failure patterns when the bridge deck is considered compared to scenarios without it. Occupant risk evaluations suggest more flexible responses when the bridge deck is included. However, vehicle trajectory post-collision showed no significant differences across scenarios. These findings indicate that modeling efficiency varies based on evaluation criteria, suggesting a more realistic and effective approach for assessing barriers on bridges.

An ordered approach on geometric vitality function for risk measurement and its application in stock market analysis

In reliability analysis, the residual life of a component or system plays a key role in explaining a component's present condition as well as how long it will continue to function as intended under specific circumstances, thereby preventing premature failure and saving money. Based on this, Nair and Rajesh [Geometric vitality function and its applications to reliability. IAPQR Trans. 2000;25(1):1–8] proposed a new measure called the geometric vitality function that explains the system's failure pattern. In the present study, we have introduced the geometric vitality function in the context of order statistics by means of the relevation transform and also analysed the monotone and ordering properties of the proposed measure. The application of the proposed measure in the stock markets are explored in the present study. Finally, to estimate the proposed measure using a real life data set, a simple estimator has been introduced as well.

Decision-Making Model for Life Cycle Management of Aircraft Components

This paper presents a novel decision-making framework for the life cycle management of aircraft components, integrating advanced data analytics, artificial intelligence, and predictive maintenance strategies. The proposed model addresses the challenges of balancing safety, reliability, and cost-effectiveness in aircraft maintenance. By using real-time health monitoring systems, failure probability models, and economic analysis, the framework enables more informed and dynamic maintenance strategies. The model incorporates a comprehensive approach that combines reliability assessment, economic analysis, and continuous re-evaluation to optimize maintenance, replacement, and life extension decisions. The optimization method on the base of genetic algorithm (GA) is employed to minimize total life cycle costs while maintaining component reliability within acceptable thresholds. The framework’s effectiveness is demonstrated through case studies on three distinct aircraft components: mechanical, avionics, and engine. These studies showcase the model’s versatility in handling different failure patterns and maintenance requirements. This study introduces a data-driven decision-making framework for optimizing the life cycle management of aircraft components, focusing on reliability, cost-effectiveness, and safety. To achieve optimal maintenance scheduling and resource allocation, a GA is employed, allowing for an effective exploration of complex solution spaces and enabling dynamic decision-making based on real-time data inputs. The GA-based optimization approach minimizes total life cycle costs while maintaining component reliability, with the framework’s effectiveness demonstrated through case studies on key aircraft components. Key findings from the case study demonstrate significant cost reductions through optimization, with mechanical components showing a 10% more reduction in total life cycle costs, avionics components achieving a 14% more cost reduction, and engine components demonstrating a 7% more decrease in total costs. The research also presents an optimized dynamic maintenance schedule that adapts to real-time component health data, extending component lifespans and reducing unexpected failures. The framework effectively addresses key industry challenges such as no fault found events while minimizing unexpected failures and enhancing the overall reliability and safety of aircraft maintenance practices. Sensitivity analysis further demonstrates the model’s robustness, showing stable performance under varying failure rates, maintenance costs, and degradation rates. The study contributes a scalable approach to predictive maintenance, balancing safety, cost, and resource allocation in dynamic operational environments.

Performance Research and Engineering Application of Fiber-Reinforced Lightweight Aggregate Concrete

Low strength and low impact toughness are two of the main issues affecting the use of lightweight aggregate concrete in harsh cold environments. In this study, the strength of concrete was improved by adding high-strength fibers to bear tensile stress and organize crack propagation. Four sets of comparative experiments were designed with freeze–thaw cycles of 0, 50, 100, and 150 to study the mechanical properties of fiber-reinforced lightweight aggregate concrete under freeze–thaw conditions. A detailed study was conducted on the effects of freeze–thaw on the compressive strength, flexural strength, impact toughness, and microstructure of concrete with different fiber contents (3, 6, and 9 kg/m3). The results show that for ordinary lightweight aggregate concrete, under the freeze–thaw cycle, the internal pore water of the concrete froze and generated expansion stress, resulting in tensile cracks inside the concrete. The cracks gradually accumulated and expanded, ultimately leading to cracking and damage of concrete structures. After 150 cycles, the strength loss rate exceeded 25%. When adding a reasonable amount of fiber (6 kg/m3), the fiber took on the tensile stress and hindered the development of internal cracks, significantly enhancing the splitting tensile strength, flexural strength, and impact toughness of lightweight aggregate concrete. And the failure pattern of concrete was significantly improved. At the beginning of the freeze–thaw cycle, the internal tensile stress was less than the fiber tensile strength and the fiber–matrix bonding strength, and the strength reduction rate of the concrete was slow. Relying on the friction absorption capacity between the fiber and the matrix, the fiber used its own deformation to resist the tensile stress. In the late stage of the freeze–thaw cycle, due to the destruction of the fiber–matrix transition zone structure, the bond strength decreased, the crack resistance and toughening effect decreased, and the strength of the concrete decreased rapidly. Moreover, the reduction in impact toughness was greater than the compressive strength and flexural strength under static load.

SURG-43. PATTERNS OF FAILURE FOLLOWING REIRRADIATION WITH GAMMA KNIFE STEREOTACTIC RADIOSURGERY FOR RECURRENT HIGH-GRADE GLIOMAS

Abstract Re-irradiation with stereotactic radiosurgery (SRS) is an increasingly used treatment for recurrent high-grade glioma (HGG). We analyzed the patterns of failure and outcomes of salvage Gamma Knife SRS for recurrent HGG to better identify which patients would most benefit. We reviewed all patients who received SRS for recurrent HGG from January 2008 to May 2020. Pattern of failure was defined by the distance of recurrence from the SRS isodose line as follows: in-field local, marginal local, regional local, and distant failure. Overall survival (OS), progression-free survival (PFS), and local-failure free survival (LFS) were estimated using Kaplan-Meier methods, and regression model analysis was performed to analyze clinical predictors of failure. A total of 146 patients with HGG underwent SRS treatment to 410 target lesions. The median target volume was 3.3 cm3 and median total dose was 18 Gy. Sixty-one (41.8%) patients developed progression following SRS. PFS at 6 and 12 months were 65.8% and 37.3% respectively. Median OS was 12.4 months from salvage SRS. There were 113 (79.5%) local failures (53.1% in-field, 45.1% marginal, and 1.8% regional), 2 (1.4%) distant, and 27 (19%) concomitant local and distant failures. LFS at 6 and 12 months was 82.9% and 66.6%, respectively. Non-white race (HR = 0.37), SRS dose ≥ 20 Gy (HR = 0.34), age < 60 years (HR = 0.43), and KPS ≥ 70 (HR = 0.44) were associated with longer time to local failure. Non-white race (HR = 5.55) and SRS dose ≥ 20 Gy (HR = 5.62) were associated with more distant failure. No grade 4 or 5 toxicity was observed. In conclusion, the dominant pattern of failure remains local and in-field despite conformal dose distribution with SRS and infiltrative tumor histology. This supports the role of reirradiation with SRS in well selected patients with recurrent HGG.

CNSC-21. THE EFFICACY OF TUMOR TREATING FIELDS IN TREATING IDH-MUTANT ASTROCYTOMA, WHO GRADE 4: AN EARLY RESULT FROM SHANGHAI HUASHAN HOSPITAL

Abstract OBJECTIVES There is ongoing debate regarding the efficacy of Tumor Treating Fields (TTFields) for treating IDH-mutant grade 4 astrocytoma (IDHmA4). In fact, the evidence supporting TTFields in treating IDHmA4 is largely extrapolated from EF-14, of which the results stem form heterogeneous entities of glioblastoma lack of IDH status. This study was conducted by reviewing the database in our center following the release of WHO CNS 5, aiming to preliminarily explore the efficacy of TTFields and prognosticators of newly-diagnosed IDHmA4. METHODS This retrospective analysis included 53 consecutive patients with newly-diagnosed IDHmA4, who underwent radiotherapy at Huashan Hospital, Fudan University between September 2021 and December 2023. All patients were administered with concurrent and adjuvant temozolomide. Eleven patients received adjuvant TTFields after surgery. Information regarding patient baseline characteristics, treatment approaches and molecular markers were collected with the purpose of analyzing prognostic factors. RESULTS The median follow-up was 15.7 months. At the time of data cutoff of this analysis, 20 patients had tumor relapse; 3 patients died, all of them were without TTFields therapy. The most common tumor failure pattern was local recurrence (80%, 16/20). The median PFS for the entire cohort was 19.3 months, the median OS was not reached. Univariate analysis indicated that patients who received TTFields therapy tended to have longer median PFS than that of patients without TTFields therapy (24.4 months vs. 18.5 months, P=0.097). Additionally, patients younger than 40 years (24.4 vs. 18.5 months, P=0.107) or without homozygous deletion of CDKN2A/B (23.7 vs. 18.0 months, P=0.108) tended to have better median PFS. No significant independent prognostic factor was found in the multivariate analysis. CONCLUSIONS The overall prognosis of IDHmA4 is poor. TTFields may help to improve the outcome of patients with newly-diagnosed IDHmA4. Longer follow-up, larger sample size and prospective clinical trials are warranted for deeper comprehension.

Fracture Characteristics and Tensile Strength Prediction of Rock–Concrete Composite Discs Under Radial Compression

To investigate the fracture mechanism of rock–concrete (R–C) systems with an interface crack, Brazilian splitting tests were conducted, with a focus on understanding the influence of the interface crack angle on failure patterns, energy evolution, and RA/AF characteristics. The study addresses a critical issue in rock–concrete structures, particularly how crack propagation differs with varying crack angles, which has direct implications for structural integrity. The experimental results show that the failure paths in R–C disc specimens are highly dependent on the interface crack angle. For crack angles of 0°, 15°, 30°, and 45°, cracks initiate from the tips of the interface crack and propagate toward the loading ends. However, for angles of 60°, 75°, and 90°, crack initiation shifts away from the interface crack tips. The AE parameters RA (rise time/amplitude) and AF (average frequency) were used to characterize different failure patterns, while energy evolution analysis revealed that the highest percentage of energy consumption occurs at a crack angle of 45°, indicating intense microcrack activity. Moreover, a novel tensile strength prediction model, incorporating macro–micro damage interactions caused by both microcracks and macrocracks, was developed to explain the failure mechanisms in R–C specimens under radial compression. The model was validated through experimental results, demonstrating its potential for predicting failure behavior in R–C systems. This study offers insights into the fracture mechanics of R–C structures, advancing the understanding of their failure mechanisms and providing a reliable model for tensile strength prediction.

The Shear Performance of an Aircraft off Pin Made of Quartz Fiber Reinforced Phenolics: The Effect of the Fiber Distribution Property

Emergency breakaway pins (EBPs) have been widely used in aircraft, especially in the suspension connection between the engine device and the airfoil. Currently, the existing EBPs, which are made of metal materials, barely satisfy the lightweight requirement of the airplane industry. Thus, the construction of a novel EBP with quartz fiber reinforced phenolics is proposed in this study, and the shear response is examined experimentally using a double-sided shear test. The effect of the fiber distribution characteristic on the shear strength is then assessed quantitatively. The failure patterns, including the damage morphology of the two types of samples were then reconstructed using scanning electron microscopy (SEM). Experimental results showed that the breakaway composite pin fabricated by the laminated composite had a superior shear response than its counterpart with randomly distributed fibers for its uniaxially distributed fiber yarns provided a longer put-out damage trace that contributed to a higher shear-loading bearing capacity for the entire composite EBP. In specific, the average values of the shear strength and the shear stiffness for the former samples were higher by 61% and 22%, respectively, than that for the latter samples. Additionally, the composite EBP also has an excellent combination of lightweight advantage and stronger shear-bearing capacity over competing pins, providing novel insight for more secure designs for civil and military aviation.

Flexural behaviour of normal concrete circular beams strengthened with ECC and stainless steel tubes

The use of laminated fibres for strengthening reinforced concrete beams is challenging owing to bonding and compatibility issues, especially in scenarios where cost effectiveness and long-term performance are important. A novel flexural strengthening technique for normal concrete circular beams (NCCBs) is proposed, using engineered cementitious composites (ECCs) and stainless steel tubes (SSTs). To examine the application of the proposed strengthening method, five NCCBs were fabricated and tested under static loading until failure to investigate the effects of ECC thickness and SST thickness. The test results showed that the strengthening technique greatly improved the failure pattern and the ultimate flexural capacity of the tested NCCBs, and the enhancement increased with an increase in the thickness of the ECC and SST. Using Abaqus software, finite-element models were constructed to simulate the performance of the tested NCCBs. The accuracy of the finite-element modelling was confirmed by comparing the simulations with the experimental results. The validated model was used for a detailed parametric investigation of the effects of the thickness of the ECC and SST on the failure and ultimate bending capacity of the strengthened beams.

Performance Characteristics of a Calculated Index Control Method for the phi Multianalyte Assay with Algorithmic Analysis.

Multianalyte assays with algorithmic analysis (MAAAs), such as the Prostate Health Index (phi), are increasingly utilized for generating disease risk scores. Currently, imprecision and bias in phi are not directly monitored by quality control (QC) assessment of the index but rather by QC assessment of individual components. This may not be adequately controlling for imprecision and bias in the calculated multicomponent phi value itself. Inter- and intra-assay phi precision was compared to precision of the individual component assays. QC measurements from total prostate-specific antigen (PSA), free PSA, and p2PSA were used to calculate a single calculated phi QC metric (PHIc). The frequency of QC failure of PHIc, relative to individual components QC by Westgard rules (13S and 22S), was determined. The effects of varying analyte component assay bias on the resulting PHIc metric were also examined. Average measured phi imprecision (6.7% CV) was higher than individual phi analyte component imprecision (3.9-4.5% CV) across 2 Beckman Coulter Unicel DxI 800 instruments. A retrospective examination of PHIc QC over 84 quality control determinations was concurrently carried out for both PHIc and component assay failure patterns, which were dependent on SDs utilized for Westgard evaluation. Finally, reinforcing nonlinear changes in PHIc were observed in select cases of introduced simulated bias of individual component measurements. An additional calculated phi QC measure can be introduced to monitor MAAA precision/bias, and in principle calculated index controls may represent a complementary supplemental QC method that could be applied to other MAAA indices.

Asymmetric deformation and failure behavior of roadway subjected to different principal stress based on biaxial tests

The magnitude and direction of stress will affect the failure of roadway. The impact of stress magnitude and direction on roadway failure was investigated using a rock failure system equipped with true triaxial loading, acoustic emission (AE), and digital image correlation (DIC) technologies. The system allowed for the simulation of rock sample failures under various three-dimensional stress conditions, while real-time monitoring was conducted using a high-precision microseismic system. By prefabricating rectangular holes at different angles in sandstone specimens, roadways under different stress effects in engineering can be simulated. Biaxial loading tests were then performed on these prefabricated sandstone cube specimens to observe external fracture characteristics and internal fracture information using acoustic emission equipment. The peak strength of samples with holes is approximately 38–56% of that of intact samples. In the early and middle loading stages, the strain on the surface is on the order of 10-3. In the later loading stage, the strain on the surface is on the order of 10-2. The findings indicate that roadway failure primarily involves local particle ejection, fragment spalling, large-scale particle ejection, plate crack buckling, and eventual failure. The ultimate failure mode varies based on stress deflection angles: with no included angle, the roadway exhibits a ’V’ shaped failure zone on both sides, predominantly experiencing tensile failure. At included angles of 30°, 45°, and 60° between stress and roadway axis, the roadway displays a “—” failure pattern along the diagonal, characterized by a combination of tension and shear failure. The extension angle of the“—” failure zone varies depending on the stress deflection angle. At a 90° included angle, the roadway shows a ’V’ shaped failure in the roof and floor, primarily undergoing tensile failure. Real-time monitoring of the strain field evolution around the roadway during failure using DIC method revealed valuable insights. AE events at different deflection angles reflect the progression of micro cracks in the specimen, showing a strong correlation with macro failure. The research outcomes elucidate the mechanisms behind various forms of roadway failure induced by stress deflection and shed light on the failure mechanism at different stress deflection angles.

Recurrent Patterns in Patients With Nasopharyngeal Caricinoma and Risks Leading to Inaccurate Delineation in Marginal Failure in the Era of Intensity-Modulated Radiotherapy.

To investigate the failure patterns of recurrent nasopharyngeal carcinoma (NPC), especially to identify the relationship between the recurrent-prone anatomic structures and the tumor regression sites after the introduction of chemotherapy (IC). A cohort of 1121 non-metastatic patients with NPC was retrospectively enrolled. The pretreatment and recurrent images of each patient were registered to the planning CT. Tumor regression sites after IC (Vicr) overlapped with recurrent tumor (rGTV) were evaluated for the delineation accuracy and dose sufficiency in marginal failure patients. A total of 126 (11.24%) experienced tumor recurrence. Re-evaluation of 12 patients with local marginal recurrence, their rGTV within Vicr predominantly located at choanae, sphenoidal sinus, and cavernous sinus. The regression sites did not receive the full 70 Gy but over half receiving with 60Gy. Analysis from marginal failure that exempts tumor regression sites from GTV or an insufficient prescription dose of less than 70 Gy may contribute to marginal failure.

Experimental and numerical studies on corrosion-resistant aluminium foam sandwich panel subject to low-velocity impact

Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs.

Numerical Investigation with Failure Characteristic Analysis and Support Effect Evaluation of Deep-Turning Roadways

In recent years, tunnel-boring machines (TBMs) have been widely applied in deep coal mining. Turning is an inevitable challenge in TBM tunneling, and a TBM turning roadway exhibits greater instability than a straight roadway, as engineering experience has indicated. This study aimed to explore the failure mechanism and evaluate the support performance of a deep-turning roadway. Several numerical models were established to investigate the deformation of the roadway, the stress distribution, and the failure zone of the surrounding rocks under different tunneling conditions. The results show that the tunneling depth influences the failure pattern of the turning roadway: deep tunneling with high in situ stress can cause asymmetric failure of the turning roadway, while shallow tunneling with low in situ stress does not. Moreover, the change in turning radius, namely the change in roadway geometry, does not influence the stability of the turning roadway. In addition, the support actions for both the straight and turning roadways do not differ significantly, and the amount of controlled deformation of the surrounding rocks is proportional to their natural deformation.

Fracture Toughness of Ordinary Plain Concrete Under Three-Point Bending Based on Double-K and Boundary Effect Fracture Models.

Fracture tests are a necessary means to obtain the fracture properties of concrete, which are crucial material parameters for the fracture analysis of concrete structures. This study aims to fill the gap of insufficient test results on the fracture toughness of widely used ordinary C40~C60 concrete. A three-point bending fracture test was conducted on 28 plain concrete and 6 reinforced concrete single-edge notched beam specimens with various depths of prefabricated notches. The results are reported, including the failure pattern, crack initiation load, peak load, and complete load versus crack mouth opening displacement curves. The cracking load showed significant variation due to differences in notch prefabrication and aggregate distribution, while the peak load decreased nonlinearly with an increase in the notch-to-height ratio. The reinforced concrete beams showed a significantly higher peak load than the plain concrete beams, attributed to the restraint of steel reinforcement, but the measured cracking load was comparable. A compliance versus notch-to-height ratio curve was derived for future applications, such as estimating crack length in crack growth rate tests. Finally, fracture toughness was determined based on the double-K fracture model and the boundary effect model. The average fracture toughness value for C50 concrete from this study was 2.0 MPa·m, slightly smaller than that of lower-strength concrete, indicating the strength and ductility dependency of concrete fracture toughness. The fracture toughness calculated from the two models is consistent, and both methods employ a closed-form solution and are practical to use. The derived fracture toughness was insensitive to the discrete parameters in the boundary effect model. The insights gained from this study significantly contribute to our understanding of the fracture toughness properties of ordinary structural concrete, highlighting its potential to shape future studies and applications in the field.

Clinical outcomes, patterns of failure, and salvage therapies of a large modern cohort of patients with anal squamous cell carcinoma treated with definitive-intent IMRT

PurposePatterns of failure and salvage therapy options for patients with anal squamous cell carcinoma (ASCC) who recur after definitive-intent intensity-modulated radiotherapy (IMRT) with concurrent chemotherapy are not well described. Patients and MethodsWe identified consecutive patients with ASCC treated with definitive-intent IMRT between July 2005 and December 2019. Relevant patient and tumor parameters, disease outcomes (locoregional failure (LRF), distant failure (DF), progression-free survival (PFS), colostomy-free survival (CFS), and overall survival (OS)), patterns of failure, and salvage therapies were collected. Failures were analyzed by competing risks methods, whereas survival endpoints were estimated by Kaplan-Meier method. Univariate and multivariate analyses were performed. Landmark analyses were conducted by considering whether patients had LRF within 12 months from completing IMRT. Results375 patients were identified with a median follow-up of 6 years. Stage breakdown was 15%, 23%, and 62% for AJCC stage 0-I, II, and III, respectively. Six-year rates of LRF, DF, PFS, CFS, and OS were 12%, 13%, 73%, 76%, and 80%, respectively. Disease recurred in 74 patients. Among the 45 patients with LRF, 39 (87%) failed within the anorectum, with 25 anal canal, 6 anal margin, and 8 rectal recurrences. Only 4 (9%) patients had isolated nodal failure. Patients experiencing LRF had worse six-year OS than patients without LRF (44% versus 86%, P<0.0001). Approximately 30% of patients who underwent salvage therapy were alive ten years after recurrence, compared with none of the patients who were managed with chemotherapy alone or best supportive care. ConclusionsThis large ASCC cohort managed with definitive-intent IMRT demonstrated excellent rates of locoregional control and survival. Isolated regional nodal failures were uncommon, whereas the majority of LRFs occurred within the anorectum, despite dose escalation by tumor stage. We observed poor outcomes for patients experiencing locoregional disease recurrence, even after aggressive salvage treatment.

Interpreting the patterns of local failure following postoperative volumetric-modulated arctherapy in oral cavity and oropharynx cancers: Impact of the different methods of analysis

PurposeIntensity-modulated radiation therapy or volumetric-modulated arctherapy is nowadays the recommended radiation technique for the treatment of head and neck cancers. However, by providing a significant dose gradient between target volumes and organs at risk, there is a risk of target missing and thus recurrence in case of inadequate delineation. It is therefore necessary to determine the origin of these recurrences to improve clinical practice. Over the past years, different methods have been described for the analysis of recurrences. Using the patterns of failure of patients with oral cavity and oropharynx carcinoma, treated with postoperative volumetric-modulated arctherapy in our institution, the purpose of this work was to analyse the sites of local recurrences and to evaluate the disparity in the classification of recurrences when different methods were used. Material and methodsBetween 2011 and 2019, 167 patients who underwent postoperative volumetric-modulated arctherapy for oral cavity or oropharyngeal cancers were included (60 and 40 % respectively). Two or three dose levels were prescribed (54Gy, 59.4/60Gy±66Gy). Local recurrence occurred in 17 patients (10.2 %). We assessed the patterns of local recurrences according to four methods: 1/ volume-based method using the volume overlap between the recurrence volume and initial target volumes; 2/ volume-based method of overlap between the recurrence volume and the 95 % treatment isodose; 3/ point-based method using the position of the barycentre of the recurrence volume; 4/ combined centroid method classifying recurrences according to both the initial target volumes and dose distribution. Each case was reviewed to make a clinical judgment on these classifications and assessed them as “appropriate”, “possible”, or “inappropriate”. ResultsFor the volume-based method using overlap between the recurrence volume and the initial clinical target volume, this classification was clinically judged as inappropriate in 11 out of 17 cases (65 %). For the volume-based method using overlap between the recurrence volume and the 95 % prescribed isodose, this classification was clinically judged as appropriate in 15 out of 17 cases (88 %). For the point-based method, this classification was clinically judged as appropriate in 14 out of 17 cases (82 %). Thirteen out of 17 local recurrences had the same classification between this point-based method and the volume-based method of overlap between the recurrence volume and the 95 % prescribed isodose. For the combined centroid method, among 17 local recurrences nine were classified as type A, two as type B, two as type C, three as type D and one as type E. This classification was clinically judged as appropriate in 15 out of 17 cases (88 %). Only five out of 17 of the local recurrences were classified the same way according to the four different methods (29 %). ConclusionRecurrences that are “marginal” or “outfield” represent a major challenge for intensity-modulated radiation therapy/volumetric-modulated arctherapy quality assurance and improvement of delineation recommendations. To date, there are no published methods that give complete satisfaction.

Experimental study on multiscale strain localisation based on soil cell element model

The granular and natural characteristics of soil introduce size effects to its deformation and strength properties. Therefore, investigating the phenomenon of strain localisation in soil requires a multi-scale characterisation. This study examined the intrinsic scale patterns in samples with different sizes of reinforcing particles through triaxial compression tests. Additionally, the formation mechanism of microscopic shear bands was investigated using numerical simulation methods. Drawing from the soil cell model theory, the average strain energy release coefficient was introduced to validate the transformation of the overall strain energy of the specimen after reaching the peak stress. This reflects the progressive initiation and competitive process of multiple bands. The results indicate that samples with different sizes and types of reinforcing particles exhibit various failure patterns, including single-type, ‘x’-shaped, ‘v’-shaped, parallel and others. The soil exhibits size effects, with the ratio of intrinsic scale to particle size decreasing as the size of reinforcing particles increases. Prior to the stress peak, non-elastic dissipation energy begins to increase, indicating the initiation of plastic deformation in the soil. Localised strain zones are activated, and after the peak, there is a sharp increase in stress within the shear bands, accompanied by rebound outside the band.

Investigation of fracture resistance with different diameters of polyetherketoneketone posts and cores material: A pilot study

Objectives: The primary objective of this study is to investigate the resistance to fracture of Polyetherketoneketones PEKK, used as post and core by fabrication in different diameters in the canal, and comparing the test results for each group. Methods: Thirty extracted mandibular premolars were selected, endodontically treated and prepared to receive the post and cores milled from polyetherketoneketone disk. The specimens were randomly divided into five groups (n = 6) respectively: group 1 received pekk post with diameter = 0.70 mm, group 2 received pekk post with diameter = 0.90 mm, group 3 received pekk post with diameter = 1.10 mm, group 4 received pekk post with diameter = 1.50 mm, and group 5 received pekk post with diameter = 1.70 mm. All the posts were cemented using a self-adhesive resin cement. Fracture resistance was tested using a universal testing machine, failure patterns were then observed visually and radiographically. For the fracture resistance test, the Universal Testing machine employed the load cell of 10KN and the speed of the cross head of 1mm/min. Data was analyzed using Oneway analysis of variance (ANOVA) followed by Tukey post-hoc test in order to determine significant differences among groups and the materiality threshold was set at α = 0.05. Results: Statistical analysis revealed that the observed differences among the five groups were not significant. None of the PEKK posts caused any fracture in the root, and this observation was visually and radiographically confirmed across all groups. Conclusions: The dentist will be able to turn the diameter of the PEKK post and core as thin as 0.70mm till 1.70mm depending on the clinical requirement with no risk of root fracture, as specified by the guidelines of this research.

Preexisting Heart Disease Spectrum and In‐Hospital Outcomes for Patients With Acute Ischemic Stroke

Background Although many studies have examined the influence of individual preexisting heart conditions on stroke outcomes, the combined effects of these conditions remain understudied. Methods The data supporting this study's findings are available from the corresponding author upon reasonable request. Data on patients with acute ischemic stroke from the Third China National Stroke Registry were analyzed. Preexisting heart disease spectrum was defined based on the combination pattern of coronary heart disease, atrial fibrillation, and heart failure. In‐hospital stroke outcomes included moderate or severe stroke at admission (the National Institutes of Health Stroke Scale score ≥16), ambulation by day 2, and in‐hospital death. Results Among the 14 019 analyzed patients, 1856 (13.2%) had preexisting heart diseases, of which the most common single heart disease was coronary heart disease (1313 [70.7%]), and the most common combination was coronary heart disease and atrial fibrillation (116 [6.3%]). Patients with preexisting heart diseases had higherprevalence of moderate or severe stroke at admission (4.7% versus 1.9%; adjusted odds ratio [aOR], 2.25 [95% CI, 1.73–2.93]), in‐hospital mortality (0.5% versus 0.2%; aOR, 2.41 [95% CI, 1.11–5.25]), and a lower rate of ambulation by day 2 (73.9% versus 78.6%; aOR, 0.84 [95% CI, 0.75–0.95]). Atrial fibrillation alone (moderate or severe stroke: aOR, 4.82 [95% CI, 3.29–7.06]; in‐hospital mortality: aOR, 4.76 [95% CI, 1.58–14.36]; ambulation by day 2: aOR, 0.58 [95% CI, 0.46–0.72]) or in combination with coronary heart disease and heart failure (moderate or severe stroke: aOR, 11.47 [95% CI, 3.66–35.89]; ambulation by day 2: aOR, 0.41 [95% CI, 0.16–1.05]) had the strongest association with unfavorable outcomes. Conclusion Preexisting heart diseases, particularly atrial fibrillation combined with other heart diseases, are associated with unfavorable in‐hospital stroke outcomes.