Extension Length Research Articles

Influence of specimen geometry on the energy release rate in concrete

The energy release rate during the crack propagation in concrete was studied using three-point bending (TPB) beams with different geometries. Expressions for determining the energy release rate were established. A total of 44 beams, i.e., TPB specimens with the height of 150 mm and various spans and the same span of 800 m but different heights, named as Series-T and Series-TH, respectively, were tested. The obtained results reveal that (1) with the crack propagation, the energy release rate curves (GR-curves) monotonically increased and convergence to the fracture energy of each specimen, and the average values were 161.136 N/m and 112.343 N/m for Series-T and Series-TH. (2) For Series-T, with increasing the specimen span from 300 mm to 900 mm, the maximum fracture process zone (FPZ) length kept constant of 68.317 mm, and for Series-TH, the result increased by 187.6 % with increasing the specimen height from 100 mm to 300 mm. Moreover, the relative FPZ length was not affected by the spans and depths of the specimens. (3) The evolution of crack tip opening displacement was only affected by the specimen ligament length, i.e. for the same crack extension length, a larger value was noticed for longer ligament length. (4) The stability during crack propagation can be analyzed using GR-curves.

Titanium/steel composites were prepared by composite interlayer and two pass laser welding

In this study, a composite sandwich was used as an intermediate layer and TC4/304 stainless steel was joined by explosion welding. First, intermetallic compounds with different butt joint sizes were added. When the length of the butt joint was kept at 4 mm, the mechanical properties of the joint increased with the extension length. The maximum tensile strength of the joint was 600 MPa when the extension length was varied between 1 and 2.5 mm. A "net basket organization" was formed in the titanium-side weld, and α → β and β → α ′ phase transitions occurred. Comparative microstructural analysis shows that the aspect ratio of the organization decreases with the increase of the length of the titanium side weld.

Abstract 224: Morphological characteristics of carotid webs associated with stroke risk and clot burden

Introduction Carotid webs (CaWs) have been established as an ischemic stroke etiology although lesion characteristics that may lead to increased stroke risk are still uncertain (1). We aim to evaluate the associations between CaW morphological features evaluated via computed tomography angiography (CTA) with clinical and radiological variables. Methods This is a retrospective analysis of a prospectively collected mechanical thrombectomy database. Individuals that presented with a suspected symptomatic CaW since July 2014 were selected after appropriate workup. The database included symptomatic CaW, asymptomatic CaW contralateral to the symptomatic side in case of bilateral lesions, and incidentally identified CaW (asymptomatic patients). We recorded the following CaW variables (Figure 1): length, base, thickness, caudal/middle/cranial angles in relationship to the vessel axis, area as well as perimeter of the pocket. We used mixed‐effects models to compare measurements between symptomatic and asymptomatic webs in the complete sample and paired Wilcoxon tests to compare webs of individuals with contralateral, symptom‐discordant CaW. Measurements were evaluated against clot burden via Poisson regression.a Results 118 webs (85 symptomatic and 33 asymptomatic) from 98 stroke patients were included. Median [IQR] for age was 52[42‐58] years old, 69.0% were female, 68.4% presented with a single symptomatic web, 18.4% had both a symptomatic and an asymptomatic web, 11.2% had only an asymptomatic web, whereas 2.0% had bilaterally asymptomatic webs. Symptomatic CaW were significantly larger in length (2.5mm[2.1‐3.5] vs. 2.2mm[1.7‐2.7];p=0.004) and pocket area (1.5mm²[0.9‐2.6] vs. 0.9 mm²[0.2‐1.3];p=0.007) compared to the asymptomatic lesions. The cranial angle was more acute for symptomatic CaW (66.9°[57.1°‐78.4°] vs. 76.2°[66.9°‐88.7°];p=0.046). No other significant associations were noted. Among the 18 patients who were analyzed for contralateral/symptom‐discordant webs, symptomatic CaW also showed more extensive lengths (2.9mm[2.3‐4.0] vs. 2.2mm[1.6‐3.1];p=0.009) but less acute rostral angles (33.1°[25.3°‐43.5°] vs. 27.9°[16.8°‐35.9°]) than their asymptomatic counterparts. Among symptomatic webs, clot burden was not significantly associated with base, length, thickness, perimeter or pocket area. Nevertheless, each 15° increase in the angle within the pocket was associated with a 1.1‐fold increase in clot burden (exp(β) = 1.1(95%CI1.0‐1.2), p = 0.044) for each 15° increase), with more obtuse angles indicating a higher intracranial vessel occlusion thrombus load. Conclusion Symptomatic carotid webs displayed larger lengths and pocket areas as compared to asymptomatic lesions. The angles that determine pocket area and degree of stenosis differed between symptomatic and asymptomatic webs.

Dynamic mechanical response and fracture mechanism of granite with structural plane containing planar and circular filling simultaneously: The influence of extension length

Weakly filled structural planes are an important influence on the stability control of engineering rock mass. Weak fillings with different geometrical characteristics are randomly distributed in the natural rock mass. To investigate the dynamic mechanical response and fracture mechanism of granite containing both planar and circular weak filling, the Split Hopkinson Pressure Bar (SHPB) experimental system was used to conduct the dynamic impact test. In this paper, the dynamic mechanical properties, the fracture process, the energy evolution and the micro-morphological characteristics of the fragments are mainly analyzed. The results show that: (1) the dynamic uniaxial compressive strength (DUCS), peak strain, and deformation modulus are synergistically affected by the extension length (L) of planar filling and strain rate. The presence of planar weak filling leads to a decrease in strain rate dependence while weakening the specimens' DUCS, and improves the overall synergistic deformation capacity of the specimen. (2) Strain rate and L jointly affect the energy distribution and evolution characteristics of the specimen; L has an enhancement effect on the distribution of reflected energy and a weakening effect on the distribution of transmitted energy. The effect of L on the dissipation of energy is transformed by the strain rate. The strain rate and L are the dominant factors in the variability of stress waveform conversion. (3) At a low strain rate, L has a positive effect on the intensification of the degree of fragmentation, however, at a high strain rate, the effect is characterised by a shift between positive and negative. The degree of fragmentation has a strain rate effect. As L increases, L has a “negative effect” on the “strain rate effect” that affects the degree of fragmentation. (4) The degree of fragmentation of macroscopic fragments is closely related to the energy dissipation density, the relationship between the two appears as a logarithmic function change. The presence of weak filling does not significantly change the microscopic morphology of granite fragments. The loose and porous microstructure of gypsum is the main reason for the altered propagation characteristics of the stress waves.

Simulation study on single-event burnout in field-plated Ga2O3 MOSFETs

This paper presents the 2-D numerical simulation results of the heavy-ion induced single-event burnout (SEB) and single event gate rupture (SEGR) in the depletion-mode gallium-oxide (Ga2O3) field-plated metal-oxide-semiconductor field-effect transistors (FP-MOSFETs). The employed simulation physics models and material parameters were validated by the basic electrical characteristics in experiments. The SEB sensitive region was proven to be from the gate edge to the drain edge of the structure. The SEB failure could result from the large number of mobile holes that diffused into the strong electric field to form a very large joule heat power to induce thermal failure. Meanwhile, the SEGR sensitive region overlapped with that of the SEB. The accumulated at the gate channel interface could produce a high-density hole pool that formed a large positive potential to induce an SEGR. Based on the simulations, a catastrophic SEB was triggered at a drain voltage of around 350 V, which was 46.4 % of breakdown voltage. Besides, a severe leakage current degradation could be estimated at about 175 V. However, for the SEGR performance, an SEGR could be triggered even at 0 V. Finally, the influences of the field plate extension length on SEB and SEGR were investigated that the SEB sensitive region and maximum electric field during SEGR could be both improved.

Ethnobotanical study on medicinal plants used by Bulang people in Yunnan, China

BackgroundDespite the popularity of modern medicine, medicinal plants remain a cornerstone of treatment for numerous diseases, particularly among ethnic groups and tribal communities around the globe. Ethnomedicine offers advantages such as ease of use, convenience, and economic benefits. Medicinal plant knowledge within Bulang ethnic community of southwest China is a valuable complement to Chinese ethnomedicine systems. Accumulated medical knowledge is due to the extensive length of occupation by Bulang People, considered the earliest inhabitants of Xishuangbanna; this has resulted in the development of various traditional treatment methods with local characteristics and unique curative effects. Therefore, there is exceeding value in exploring the medical knowledge of Bulang.MethodsA total of 175 local informants participated in the interviews and distribution of questionnaires in 10 Bulang villages in Menghai County, Xishuangbanna Prefecture, Yunnan Province, China. We documented the community of Bulang's use of medicinal herbs, and we used both the informant consensus factor (ICF) and use value (UV) methodologies to analyze the data. Furthermore, we conducted a comparative study to explore the potential of Bulang traditional medicine by comparing it to traditional Dai medicine.ResultsThe study recorded 60 medicinal plant species belonging to 41 families and 59 genera, including 22 species of herb, 22 species of shrub, nine species of trees, and seven species of liana. Araceae, Compositae, Lamiaceae and Leguminosae were found to have the highest number of species. The affordability and cultural heritage of Bulang medicine make it advantageous, Investigated Informants report that increased usage of Western medicine (88%), less availability of herbal medicine (95.43%), and the reduction in medicinal plant resources (80.57%) pose significant threats to Bulang medicine. All Bulang medicinal plants are naturally grown, with only 22 per cent being cultivated. Camellia sinensis (0.94) and Zingiber officinale (0.89) showed the highest UV values, while the function of Phyllanthus emblica L. and Houttuynia cordata Thunb. were also noted. The ICF revealed digestive system related diseases were the most commonly treated, with conditions of the motor system using the highest number of plant species. Finally, a comparison with traditional Dai medicine determined that 22 plants (36.67%) of the 60 surveyed had higher medicinal value in Bulang medicine.ConclusionBulang communities primarily source medicinal plants from the wild. Should environmental damage lead to the extinction of these medicinal plants, it could result in a shift toward modern Western medicine as a preferred medical treatment. Bulang ethnomedicine is a vital supplement to China's traditional medicine, particularly aspects of ethnic medicine relevant to daily life. Future research should emphasize inter-ethnic medical studies to reveal the untapped potential of medicinal plants.

Peri-zygomatic complications on zygomatic implants with or without penetrating the external surface of zygoma: A 2-year retrospective study.

The main purpose of this retrospective study was to assess the difference in the incidence of peri-zygomatic complications (PZCs) when zygomatic implants (ZIs) penetrate or do not penetrate the external surface of zygoma. This study included 32 patients with edentulous maxillae or potentially edentulous maxillae undergo zygomatic implantation. The patients were divided into the penetration group (P-group) and the non-penetration group (N-group) according to whether the apex of implants penetrated the external surface of zygoma in postoperative CBCT. The extension length, the penetration section of the implants, and the skin thickness at the corresponding position were simultaneously measured. Clinical follow-up was conducted regularly until 2 years after surgery. The occurrence of PZCs (including peri-zygomatic infection, skin numbness, non-infectious pain, and foreign body sensation) was recorded. A mixed effect logistic model was used to compare the difference of complication rate between the P-group and the N-group, and odds ratio (OR) was calculated. Then identify the impact of the extension length, penetration section and skin thickness in P-group with the same model. A total of 71 ZIs were implanted in 32 patients, including 37 implants in the P-group and 34 implants in the N-group. During the 2-year follow-up, a total of 13 implants occurred PZCs, with an overall complication rate of 18.3%. Thereinto, the incidence rate was 29.7% in the P-group, and 5.9% in the N-group (OR = 6.77). In P-group, there was a significant difference in complication rate of different extension lengths, while the penetration section and skin thickness had no statistical significance on the complication rate. Under the limitation of this study, to minimize the risk of PZCs, ZI should be placed in a manner that avoids the apex penetrating the external surface of the zygoma.

Effects of thermal treatment on the fracture behavior of rock-concrete bi-material specimens containing an interface crack

The study of the fracture characteristics of rock-concrete structure containing an interface crack under high temperature is vitally significant for the durability and stability assessment of concrete construction projects on rock foundations. Brazilian splitting tests were performed on rock-concrete cracked straight-through Brazilian disc (CSTBD) specimens after different heat treatment temperatures. The crack extension process of the specimen was analyzed using digital image correlation (DIC) technique. The effects of temperature, interface crack inclination and concrete strength on fracture characteristics were investigated. The results indicate that at high temperatures, free water and structural water escape from rock and concrete, and crystal structure of the mineral composition is altered, which induces the development of internal pores and microcracks in the material and weakens the mechanical properties. The specimen displays brittle fracture behavior at 25 °C-300 °C, and plastic fracture behavior at 500 °C-700 °C. The wing crack extension in concrete (weak material) occurs preferentially, and this phenomenon becomes more apparent with raising temperature. When α ≤ 45°, the length of crack extension along the interface increases with increasing temperature, while when α > 45°, the increase in temperature makes the crack initiation closer to the disc center. The fracture energy and the difference in fracture energy between varying inclinations decrease with raising temperature. Furthermore, temperature has an essential impact on fracture toughness. As temperature increases, the fracture toughness generally decreases, the difference in mixed fracture toughness between different inclination angles gradually increases, and the fracture propagation resistance weakens.

Fracability evaluation of the middle–upper Permian marine shale reservoir in well HD1, western Hubei area

Taking the HD1 well as the research target, through intensive core sampling, experimental test analysis, comprehensive logging interpretation and other methods, the fracability of shale reservoirs was discussed in this paper. The results show that the Gufeng–Dalong Formation in the HD1 well has a high organic carbon content, and the organic-rich shale developed in the lower part of the Gufeng and Dalong Formations with thicknesses of 30 m and 15 m, respectively. For the low-porosity and ultralow-permeability shale reservoir type, the natural fractures are undeveloped in the lower part of the Dalong Formation, with a lower linear density, while they are well developed in the Xiayao and Longtan Formations and the lower part of the Gufeng Formation, and the interlayer bedding fractures are relatively developed. The Gufeng–Dalong Formation shale also has a high mineral brittleness index (average of 44.5%), high static Young’s modulus (20–70 GPa), low static Poisson’s ratio (0.10–0.31), and high horizontal pressure difference coefficient of two phases (0.17–0.56). It is concluded that the shale reservoir is favorable for fracture development in the lower part of the Dalong Formation, with depths of 1249–1289.5 m, and the lower part of the Xiayao, Longtan and Gufeng Formations, with depths of 1300–1335.3 m. Overall, the fracable shale section with high brittleness and rock strength is beneficial to fracturing. However, the existence of a large number of shale bedding fractures increases the complexity of the fractures, and at the same time, it has a certain negative impact on fracture generation. Double wing fractures are easily formed because of the high two-phase horizontal pressure difference. Therefore, the leakage caused by shale bedding fractures and the influence on the fracture height and extension length should be considered comprehensively in fracturing design.

Study of stress-driven cracking behavior and competitive crack growth in functionally graded thermal barrier coatings

Thermal barrier coatings' (TBCs) stability and toughness are essential for insulating aero-engine parts. However, during service, the thickness of thermally grown oxide (TGO) will have an impact on the growth of internal vertical and horizontal cracks as well as the cracking and spalling of the coating, which may ultimately fail as a result of the aforementioned factors. The competitive growth of vertical and horizontal fractures in three functional gradient thermal barrier coatings (FG-TBCs) created with varied gradient index P magnitudes is investigated in this study. Gaining a thorough grasp of how competitive growth affects coating failure under various compositional and gradient structural parameters is the goal. Additionally, this work explores the effects of various TGO thicknesses on early crack expansion as well as the stress characteristics within the FG-TBCs. The research takes into account how crack growth changes the stress condition as well as the implications of crack extension rate, route, and form on coating failure. Our results show that the stress step phenomena in the FG-TBCs occurs in various places for various P values. The expansion of cracks in the top coat (TC) is fueled by this stress phase. Furthermore, a greater vertical crack extension length is obtained with a higher P value, with further expansion being prevented by horizontal cracks along the extension path. Notably, thicker TGO coatings change the direction and rate of expansion of cracks, both vertical and horizontal.

Elucidation of the Mechanism of Occasional Anterior Longitudinal Ligament Rupture with Posterior Correction Procedure for Adult Spinal Deformity Using LLIF-Finite Element Analysis of the Impact of the Lordotic Angle of Intervertebral LLIF Cage.

Background and Objectives: There are several advantages of using lateral lumbar interbody fusion (LLIF) for correction surgeries for adult spinal deformity (ASD); however, we currently have unresolved new issues, including occasional anterior longitudinal ligament (ALL) rupture during the posterior correction procedure. When LLIF was initially introduced, only less lordotic cages were available and ALL rupture was more frequently experienced compared with later periods when more lordotic cages were available. We performed finite element analysis (FEA) regarding the mechanism of ALL rupture during a posterior correction procedure. Methods: A spring (which mimics ALL) was introduced at the location of ALL in the FEA and an LLIF cage with two different lordotic angles, 6 and 12 degrees (6DC/12DC), was employed. To assess the extent of burden on the ALL, the extension length of the spring during the correction procedure was measured and the location of the rotation center was examined. Results: We observed a significantly higher degree of length extension of the spring during the correction procedure in the FEA model with 6DC compared with that of 12DC. We also observed that the location of the rotation center was shifted posteriorly in the FEA model with 6DC compared with that of 12DC. Conclusions: It is considered that the posterior and rostral edge of the less lordotic angle cage became a hinge, and the longer lever arm increased the burden on ALL as the principle of leverage. It is important to use an LLIF cage with a sufficient lordotic angle, that is compatible with the degree of posterior osteotomy in ASD correction.

Understanding the Impact of Extension Region on Stacked Nanosheet FET: Analog Design Perspective

This work incorporates an in-depth physics-based investigation of Nanosheet FET’s (NSFET’s) extension region for analog circuit design. When extension length (LEXT) is changed from 8 nm to 3 nm, the NSFET exhibits an increment in IOFF (∼8×) and subthreshold swing ‘SS’ (∼5mV/dec), with a ∼1.5× enhancement in ION. Though driving capacity does not increase proportionally on stacking the sheets owing to the location of contacts, however the ION/IOFF ratio increases by ∼ 10× on stacking two more sheets. A common source (CS) amplifier is utilized for the analysis of the circuit-level performance. The gain-bandwidth profile is worth highlighting that the extension region gives feasibility to modulate the gain and bandwidth of the amplifier as compared to sheet stacking. It is investigated that a higher extension length (8 nm) gives a ∼27% higher gain, while a lower LEXT (3 nm) gives ∼2× higher bandwidth. Though sheet stacking increases the ON current, it does not significantly impact the gain, bandwidth, or phase shift.

Effects evaluation of Fin layouts and configurations on discharging performance of double-pipe thermochemical energy storage reactor

Thermochemical energy storage (TCES) based on hydrated salts is gaining popularity because it can provide high storage capacity at low costs. It is critical to improving heat storage efficiency and capacity due to technical challenges such as low thermal conductivity of thermochemical materials (TCMs) and poor mass transfer. The reversible reaction of strontium bromide monohydrate (SrBr2·H2O) and water vapor forming strontium bromide hexahydrate (SrBr2·6H2O) for TCES is used in numerical simulation, aiming to investigate the discharging performance of a double-pipe closed TCES reactor considering the influences of fin layouts (radial and longitudinal fins) by evaluating several indicators such as the reaction time and outlet temperature. The results show that the use of fins can improve the exothermic process. The discharging time of the reactor with upward L-shaped fins is reduced by 8.6% for radial fins and by 8.9% for the reactor with four longitudinal fins. The addition of fins expands the heat transfer area and makes the hydration rate of TCM around fins significantly higher than other parts. The Taguchi method is adopted to optimize the structure parameters of case 7 as it has the highest heat transfer amount of heat transfer fluid (HTF), and the optimal combination (A (fin number) = 4, B (fin extension length) = 20 mm, C (fin thickness) = 2 mm) increases the peak value of average outlet temperature by 1.47% and the heat exchange efficiency by 4.7% compared with case 7.

Differences in Kinematic Changes From Self-Selected to Fast Speed Gait in Asymptomatic Adults With Radiological Signs of Femoro-Acetabular Impingement.

Femoro-acetabular impingement (FAI) may present as alterations in the skeletal morphology of the hip. Repercussions of FAI can be witnessed in self-selected speed walking as well as physical exercise such as running or fast speed walking. The aim of this study was to investigate changes in kinematics at different gait speeds in subjects presenting with radiological findings invoking FAI. One hundred thirty asymptomatic adults underwent biplanar X-rays with a calculation of 3D hip parameters: acetabular anteversion, abduction and tilt, vertical center edge angle (VCE), femoral anteversion, neck-shaft angle, acetabular coverage of the femoral head, femoral head diameter and neck length. Parameters were classified according to FAI clinical thresholds. Two groups were created: Control group (63 subjects having up to one subnormal hip parameter in favour of FAI) and Radiographic FAI group (67 subjects having ≥2 subnormal hip parameters that might cause FAI). All subjects underwent 3D gait analysis at self-selected and fast speed, from which kinematic parameters were generated. Arithmetic differences between fast and self-selected speed gait were considered as gait changes. Subjects in the Radiographic FAI group had decreased acetabular tilt (24 vs. 19˚), anteversion (19 vs. 16˚), abduction (55 vs. 53˚), femoral anteversion (18 vs. 14˚) and increased VCE (29 vs. 33˚, all p<0.05), compared to controls.Changes from self-selected to fast speed showed that subjects in the Radiographic FAI group had lower range of motion (ROM) pelvic rotation (7 vs. 4˚) and ROM hip flexion/extension (10 vs. 7˚), reduced hip extension (-4 vs. -2˚) and step length (16 vs. 13 cm; all p<0.05). The Radiographic FAI group had decreased acetabular abduction, anteversion and femoral anteversion in favour of FAI. When adapting from self-selected to fast speed gait, the Radiographic FAI group seemed to limit pelvic rotation and hip flexion/extension resulting in a decrease in step length. These kinematic limitations were previously reported in subjects with symptomatic FAI. Gait analysis could be considered as a functional diagnostic tool to assess FAI along with radiological assessment.

Analisa Menambah Surat Gugat dapat dilakukan Sepanjang tidak Merubah dan Menambah Kejadian Materiel Berdasarkan Pasal 127 RV (Perkara No. 79/Pdt.G/2020/PN JKT.SEL)

&#x0D; Sri Bintang Pamungkas, as Plaintiff and Fahrizal Fardiansyah as Main Director of PT. Eora Mitra Sejati as Defendant. The Plaintiff prevented the auction process for the Wilis parcels by the Auction Center through BCA, which was borrowed incorrectly by the Defendant as Collateral to obtain a credit facility from BCA in the amount of Rp. 1,800,000,000,- which ended in default by exchanging Collateral from the Wilis parcels with the central Kalibata parcels. The plaintiff intends to obtain control over all assets of PT. Eora Mitra Sejati which is still left from the proceeds from receiving the BCA credit facility. On July 16, 2014, a Bank BCA credit agreement was held. Based on the credit agreement, BCA agreed to provide local credit facilities not exceeding Rp. 1,200,000,000.- to the Defendant (PT. Eora Mitra Sejati) Which facility will be used for the company's working capital, the length of the loan extension as of July 17 2014 ending July 17 2015 credit interest must be paid at 14.25% per year on loans made stated that it is paid every month, which credit interest can be reviewed, for the first time on May 9, 2019 by providing details of the amount of debt that must be repaid without notification to the Plaintiff and Mrs. Emalia. According to his statement, the Plaintiff has paid more than 5 years to BCA approximately 60 times each in the amount of Rp. 20,000,000, - which is considered as a loan interest payment, while the principal loan payment is only paid once, namely in November 2019 in the amount of Rp. 100,000,000, - then the Plaintiff and Mrs. Emalia on 23 December 2019 met the head of the BCA office in the Bidakara building and the Plaintiff added a payment of Rp. 70,000,000, - the plaintiff requested permission to change to the Panel of Judges to include certificate of ownership no. 03554/Mampang with an area of ​​2,114 m2 in the name of Defendant (now please call Defendant I) MA jurisprudence No. 547K/SIP/1973 states: changes to the lawsuit regarding the subject matter of the case are changes to the subject matter of the lawsuit. Therefore, it must be rejected. 03554 Mampang with an area of ​​2,114 m2 on behalf of the Defendant (now please call it Defendant I) considering that because the Plaintiff had crossed the tolerance limit in changing the lawsuit, the panel of judges considered that the plaintiff's lawsuit must be rejected.&#x0D;

Modeling and fracture behavior of mesoscale concrete considering actual aggregate shapes and placement domain shapes

The establishment of meso-concrete models under complex boundary conditions still faces great challenges at present. In this study, a numerical framework for constructing concrete meso-structures in irregularly placement domains is developed based on the dot matrix idea. In addition, a solution to quickly obtain numerous 3D aggregates with realistic morphology as well as 2D cross-section aggregates is proposed. On this basis, wedge splitting (WST) tests with different coarse aggregate contents are conducted and the numerical results agree well with experimental results. The fracture mechanism of the wedge splitting specimen was then investigated by analyzing the contact force chain and crack evolution. Finally, parametric analysis was used to investigate the impact of aggregate and mortar strength on the fracture characteristics of WST specimens. The results show that the numerical framework has good robustness. Tensile stress is the driving force for crack extension in WST specimens, the area of the pure tensile stress zone and the distance between the front end of the pure tensile stress zone and the crack tip decreases as the crack extension length increases. With the increase of coarse aggregate content, the deflection effect of the crack is intensified, the crack path becomes more tortuous, and the fracture zone range also increases. The mechanical properties of concrete and the crack extension path are significantly influenced by the strength of the mortar and the aggregate, but the aggregate does not contribute as much to the overall strength of the concrete structure as the mortar matrix does.

Hemodynamics of different configurations of the left subclavian artery parallel stent graft for thoracic endovascular aortic repair

Background and objectiveParallel (chimney and periscope) graft technique is an effective approach for left subclavian artery (LSA) reconstruction in patients treated by thoracic endovascular aortic repair (TEVAR) for the inadequate landing zone. However, certain stent graft (SG) configurations may promote thrombosis and reduce distal blood flow, increasing risks of cerebral infarction and reintervention. MethodsIn this paper, we first attempt to systematically evaluate the hemodynamic performances of different parallel graft techniques as potential determinants of complication risks. Based on the patient-specific 3D aortic geometry undergoing parallel graft technique, fifteen models in total for five kinds of LSA branched SG configurations (Forward, Backward, Extended, Elliptical and Periscopic) were designed virtually, and the hemodynamic discrepancies between them were analyzed by computational fluid dynamics. ResultsResults show that flow rate of patients undergoing periscope technique reduces by half compared with chimney technique, suggesting that periscope SG may cause more serious flow obstruction to LSA, leading to stroke. For chimney stent structure, the extension length 0has little influence on energy loss and other parameters. Conversely, hemodynamic differences between the retrograde curvature and the antegrade curvature are significant (time average WSS: 47.07%), so the retrograde curvature might prompt SG displacement. Furthermore, the flatter chimney SG induces more aggressive hemodynamic forces, among which the difference of the maximum WSS between the flatter SG and nearly round SG reaches 65.56%, leading to the greater risk of vascular wall damage. ConclusionsResults obtained might provide suggestions for physicians to formulate appropriate parallel graft technique schemes in TEVAR.

On the correlation between roping, texture, and morphology of aluminium alloy sheets

Roping is a troublesome surface defect of aluminium alloy sheets that hinders their application in the automobile industry. When the aluminium alloy sheets are subjected to tension, the texture components of various distributions will lead to non-uniform morphology and thus initiate roping. In the current paper, the correlation of roping defect with texture and surface morphology is probed by experiments and crystal plasticity simulation in four aluminium alloy sheets. Depending on the extension length of roping lines along the rolling direction, short and long roping are identified from the tested aluminium alloy sheets. With crystal plasticity simulation, texture variances for different roping degrees are comparatively analysed. The short roping is induced by short clusters of individual hard components, while the long roping is initiated by the long bands where different hard components are mixed. The experimental and simulation results also indicate that roping does not result from specific textures in the aluminium alloy sheets, and the alternative spatial aggregation of soft and hard texture components plays a predominant role in roping development. A roping intensity index RI is also proposed to quantitatively grade roping intensity and show excellent accuracy and robustness in practice.

Frequency and predictors of implant-related complications after posterior cervical fusion

Study design Retrospective, observational study Purpose To determine the frequency and predictors of implant-related complications in adults after posterior cervical fusion. Overview of literature Published literature on lumbosacral fusion suggest that implant-related complications are not uncommon. Although posterior cervical fusion is a common operation, data on frequency and predictors of implant-related complications after posterior cervical fusion is still scarce. Methods 86 patients (with 740 screws) who underwent posterior cervical fusion were included. Implant-related complications were identified by the presence of: (1) halo sign, (2) screw pull-out/breakage (3) post-operative kyphosis and (4) implant-related complications requiring revision surgery. These were stratified into two groups: (a) minor – isolated halo sign or screw pull-out/breakage (b) major – post-operative kyphosis > 10 degrees, and revision surgery. Demographic, operative and radiological data was collected. Rates of implant-related complications were determined and associated risk factors identified. Results 33 (38.4%) patients had signs of implant-related complications. Of these, 29 (87.9%) had minor complications and 4 (12.1%) had major complications. Charlson Comorbidity Index (CCI) (p = 0.03179) and pre-op C2–C7 sagittal vertical alignment (SVA) (p = 0.02449) were the only significant risk factors for all-cause implant-related complications during multivariate logistic regression. Other intraoperative parameters (type of screw, length of fusion, levels decompressed, and extension of fusion beyond the levels decompressed) were not significantly associated with implant-related complications. Conclusions Implant-related complications are not uncommon but rarely require revision surgery. Higher pre-operative SVA and CCI were significant risk factors; length of construct and extent of decompression were not. These findings may assist clinicians when deciding the extent of fusion and in selecting patients for closer follow-up.

Mechanical behaviour and spatial fracture characteristics of granite containing weak inclusions under uniaxial loading revealed by 3D DIC and AE monitoring: The influence of extension length of planar inclusions

The destabilisation failure characteristics of weakly filled rock masses are important influencing factors in rock engineering stability control. To investigate the changes in the mechanical behaviour and spatial fracture characteristics of granite in the presence of both planar and circular weak inclusions, two experimental non-destructive monitoring methods, 3D DIC and AE, were used together. This paper summarises the experimental results and investigates the effect of the extension length of the planar inclusions on the mechanical behaviour and spatial fracture characteristics. The results show that the presence of planar weak inclusions leads to the appearance of “plasticity” before the peak stress, the weakening of “brittleness” and the enhancement of “ductility” after the peak stress, and the increase of extension length will weaken the resistance to deformation and the overall load carrying capacity. When the extension length of planar inclusions varies, there are three main modes of specimen failure: “X” shear failure; crushing and crumbling failure; overall shear failure. The distribution of AE parameters is dominated by the proportion of low-amplitude hit signals, with a wide range of energy distribution, but the concentration in low-amplitude energy and slightly longer signal duration. The correlations of energy-amplitude, count-amplitude, and duration-amplitude are different and similar. The fracture area of the specimen and the spatial location of the fracture event concentration distribution overlap, with the planar inclusions serving as the weak surface, and the fracture event showing the distribution trend of the planar weak inclusions serving as the central area.