Static Tests Research Articles

Sustainability outcomes of volunteer tourism in rural communities: empowerment and the role of volunteer tourism organizations

PurposeResearch on the sustainability outcomes of volunteer tourism (VT) in rural communities is rare. Drawing on the perspectives and theoretical concepts related to multiple forms of capital, empowerment, and sustainability, this paper presents the sustainability outcomes of VT and the role of empowerment and volunteer tourism organizations (VTOs) in attaining greater sustainability.Design/methodology/approachA total of 37 semi-structured interviews and 4 documents were conducted with stakeholders on the perceived socio-cultural impacts of VT on two farm communities in Vietnam. A qualitative thematic coding analysis was used to identify themes that explain the sustainability outcomes of VT.FindingsThe results of this study were divided into the nine themes of relationships, community resource development, job opportunities, educational effects, cultural exchanges, health, awareness of environmental conservation, physical changes, and promoting local products and tourism.Practical implicationsVTOs should involve the local community in the decision-making process for volunteer activities. It is essential to share their voices and concerns about how the VT is set up to ensure that they meet the community’s expectations. Moreover, the government can act as a bridge between VTOs and host communities, providing training and support services to locals after volunteers leave.Originality/valueThis research creates a model for connecting the sustainability outcomes of VT, empowerment, and the role of VTOs.

Micro-Scale Fracture Characteristics of Emulsified Asphalt Cold Recycled Mixture Based on Discrete Element Method

Asphalt pavement often experiences structural failure due to repeated vehicle loading. The discrete element method (DEM) model was established based on the semicircle bending test (SCB) to investigate the fracture damage mechanism of emulsified asphalt cold recycled mixture (CRME) under loading. The micro-mechanical parameters of CRME were determined through a reliable validation process using the uniaxial compression static creep test. The microscopic fracture characteristics of CRME were investigated through the load-displacement curve, stress distribution, and force chain distribution. The fracture energy was used as the evaluation index to analyze the influence of prefabricated notch length and aggregate gradation on the fracture performance of CRME. The results indicate that the emulsified asphalt mortar-aggregate interface was the critical weak position of the mixture fracture; the failure of the tension chain was the main destructional form of the SCB test. The development of cracks affected the stress concentration phenomenon and stress concentration level of the mixture. Fine-grained mixture exhibited crack resistance. The number and length of cracks were affected by gradation. As the prefabricated notch length increased, the influence gradually diminished. The research results could provide theoretical and data support for the design of CRME.

Perceptions, experiences and concerns with sexually transmitted infections among current and former PrEP users: a longitudinal qualitative study of gay, bisexual and queer men in Canada

Background Pre-exposure prophylaxis (PrEP) use has been attributed to heightened rates of sexually transmitted infections (STIs), ostensibly due to increased condomless anal sex (CAS) and greater frequency of STI testing. Few qualitative studies have assessed how gay, bisexual and queer men (GBQM) who use PrEP perceive STIs and how these attitudes have evolved post-PrEP uptake. We investigated the perspectives of current and former PrEP users on STIs. Methods Annual, in-depth longitudinal interviews were conducted with 38 current and former PrEP users in Ontario (n = 18) and British Columbia (n = 20), Canada, as part of a mixed-methods implementation science study (2020–2022). Over 3 years, 109 interviews were conducted. Data analysis included reflexive thematic coding and longitudinal recurrent cross-sectional analysis using NVivo 12. Results Four STI-related themes emerged: (1) lack of STI-related concerns due to treatment and prevention optimism, (2) stigma-related concerns, (3) perceived risk among other PrEP users due to increased CAS, and (4) inconsistent testing concerns among non-PrEP users. Over time, some STI-related anxieties decreased with increased knowledge and reduced stigma. However, concerns persisted for other participants due to perceived risky sexual behaviours among other PrEP users and non-PrEP users. Both current and former PrEP users who expressed STI-related apprehensions consistently indicated adopting risk-reduction strategies, including condom use and having fewer sexual partners throughout the study. Conclusions Findings show how varied STI perceptions and experiences among current and former PrEP users shaped sexual decision-making over time. Providers, public health experts, and policymakers should develop a more comprehensive strategy to address STI concerns among GBQM.

The Thermomechanical, Functional and Biocompatibility Properties of a Au–Pt–Ge Alloy for PFM Dental Restorations

A high-noble Au–Pt–Ge porcelain-fused-to-metal (PFM) dental alloy without the known adverse metallic elements and with the addition of germanium (Ge) was produced as a more cost-effective alternative to other precious alloying metals, with investigations for determining the functionality and clinical use of this alloy. The thermomechanical, biocompatibility, durability, workability and economic characteristics of the produced dental alloy were investigated. These properties were investigated with in vitro biocompatibility testing on human gingival fibroblasts (HGFs); static immersion testing for metal ion release; DSC analysis; hardness, tensile testing, density and coefficient of thermal expansion (CTE) measurements; metallographic and SEM/EDX microstructure investigations; and finally with the production of a test PFM dental bridge. The results of the thermomechanical testing showed alloy properties suitable for dental restorations and clinical use, with somewhat lower mechanical properties, making the alloy not suitable for extensive multiunit fixed restorations. The microstructure investigations showed segregations of Ge in the homogeneous alloy matrix, which reduce the alloy’s mechanical properties. The produced PFM dental bridge showed excellent workability of the alloy in a dental laboratory setting, as well as a high standard of the final dental restoration. The ion release was negligible, well below any harmful quantities, while the cell viability examination showed significantly higher viability ratings on polished alloy samples as compared to as-cast samples. The results showed that a dental substructure in direct contact with oral tissue and fluids should be highly polished. The performed investigations showed that the produced PFM dental alloy is suitable for clinical use in producing high-quality dental restorations with high biocompatibility for patients prone to metal allergies.

Temporal summation of pain in sickle cell disease: comparison of adolescents and young adults with chronic vs. infrequent pain.

This study examined the role of central sensitization in the experience of pain among adolescents and young adults with the most severe genotypes of sickle cell disease (SCD). We hypothesized that adolescents and young adults with chronic SCD pain would demonstrate a higher perceptual response to repeated stimulation of identical intensity (i.e., temporal summation of pain, TSP) compared to counterparts with infrequent pain. We also examined psychological risk factors that can impact pain sensitivity. Patients ages 12-21 years, diagnosed with SCD type Hb SS or Hb S Beta0Thalasemia, who reported infrequent pain (≤2 pain days/month; n = 25) or met AAPT criteria for chronic SCD pain (n = 25) were enrolled. Patients were age- and sex-matched, with similar proportions receiving chronic blood transfusion and hydroxyurea. Patients completed static quantitative sensory testing (QST) and dynamic TSP testing to assess pain sensitivity. Patients and a caregiver completed demographic and psychological measures (depression, anxiety, pain interference, pain catastrophizing). Simple slope analysis revealed differentially elevated heat TSP among adolescents and young adults with chronic SCD pain (b = 3.14, p = .002) but not those with infrequent pain (b = 0.45, p = .61). Faster habituation was further observed for those with chronic compared to infrequent pain. Adolescents and young adults with chronic pain reported more frequent depression, anxiety, and pain interference symptoms; however, psychological symptoms and pain catastrophizing were not associated with QST or TSP (ps >.17). Current results demonstrate that a well-established, prognostic, QST risk marker (i.e., TSP) may distinguish chronic from infrequent pain subgroups of adolescents and young adults with SCD.

Effect of Particle Shape on Cyclic Shear Behavior of Granular Mixtures–Geogrid Interface

The cyclic shear stiffness and damping ratio of angular and round particle geogrid interfaces is of much concern in reinforcement structure seismic analysis. In this study, various component percentages of crushed limestone and spherical granular medium mixtures were used to investigate the role of particle regularity in static and cyclic direct shear tests. The test results revealed that an increase in the proportion of round particles decreased cyclic shear strength and volume change. The phenomenon of shear softening was observed with a high amplitude of shear displacement when the proportion of round particles was increased in the mixture. As the percentage of round particles increased, the maximum interface shear stiffness decreased significantly from, 39.69 to 28.28 MPa/m, but a reverse trend in the maximum damping ratio was observed, from 0.308 to 0.37. The effect of cyclic shear history and proportion of round particles on interface strength parameters was also analyzed. A linear regression model was fitted to the data for quantifying the relationship between the proportion of round particles and friction angle. The results suggest that different percentages of round and angular particles can produce varying degrees of particle interlock between aggregate and geogrid, influencing the macro-mechanical behavior of the reinforced soil interface.

An FBG-based method for load measurement of a cylindrical rolling element bearing

Abstract Contact forces between raceways and rolling elements of a bearing stand as crucial operational aspects defining the bearing’s performance. While monitoring bearing load through load cells or strain gauges on the shaft or housing is feasible, it may not precisely reflect the distributed load transmitted by the rollers directly to the raceways. This paper introduces a method to calculate these contact forces, relying on a linear assumption correlating the loads to the measured strains on the outer race of a bearing. In our research, we conducted both static and dynamic tests on cylindrical roller bearings through simulations and experiments. We designed an experimental test rig to conduct both static and dynamic experiments and utilized FBG optical fiber sensors for contact force measurement in bearings due to their multiple advantages, including high sensitivity, resistance to corrosion and magnetic interference, and ease of installation on the bearing outer race due to their shape and size. Our findings indicate a consistent linear relationship between contact forces and strains measured on the bearing’s outer race. Furthermore, we calculated the linear coefficient K values from three test groups: static tests under simulation study, static tests under experimental study, and dynamic tests under experimental study. The K values obtained from static tests (simulation and experimental studies) and dynamic tests (experimental study) align consistently. Following this, we calculated contact forces in both static and dynamic experiments by multiplying the measured strains with K. Our calculations resulted in an error percentage of less than 2% for static tests and below 5% for dynamic tests, highlighting the accuracy of our approach in determining these contact forces.

Effect of suspension training intervention on the balance ability of juvenile deaf-mute patients

Maintaining balance is essential for daily activities; deficits in hearing-impaired adolescents can severely impact their academics and daily life. Suspension training is employed to enhance the coordination of multiple muscle groups within the body and ultimately to improve balance. A total of 105 students with non-genetic hearing impairments, comprising 65 boys and 40 girls, participated in the study. Balance training using the TRS suspension belt included exercises such as prone elbow brace, supine back brace, kneeling elbow brace, lateral elbow brace, prone hip flexion, and supine hip lift. Strength training using equipment involved exercises like single-leg suspension squat, flying bird brace, supine suspension arm flexion, seated static brace, and standing butterfly pinch chest. The main outcome measures included static balance tests (lambda footwork, Wolfson postural stress test), dynamic balance tests (functional forward reach test, balance beam walk test), and vestibule function tests (rotation-walk test). The results of the lambda footwork and Wolfson postural stress tests revealed highly significant differences between 8 weeks and 16 weeks of intervention (p < 0.01). The Functional Forward Stretch test demonstrated a significant difference between 8 weeks of intervention and 2 weeks of intervention at 16 weeks (p < 0.05). The balance beam walking test indicated a significant improvement at 8 weeks (p < 0.05) and a highly significant improvement at 16 weeks (p < 0.01). In the spin-walk test, no statistically significant differences were observed between the pre-experimental test, the 8-week intervention, and the 16-week intervention (p > 0.05). Leveraging the expropriation system to mediate skeletal muscle movement and muscle contraction coordination can improve balance. Suspension training significantly improved balance during activities requiring static non-interference maintenance. However, suspension training did not demonstrate a significant effect on improving vestibule function. Overall, suspension training was effective in enhancing balance in all patients with non-hereditary deafness.

A qualitative study about the public's perception of primary care providers.

With the growth of physician associates/assistants (PAs) and NPs providing primary care services, we sought to understand the public's perception of the different types of healthcare providers (HCPs) they might encounter in a clinical setting, such as primary care. This study aimed to evaluate public perceptions about various types of primary care providers (PCPs), identify public preferences for PCPs in relation to experience and training, and examine public preferences for PCP credentials. We conducted semistructured interviews with adults, and used inductive and deductive coding and reflexive thematic analysis to analyze the data. We reached thematic saturation after 12 completed interviews. Participants reported confusion about the types of HCPs they might encounter in a primary care setting (for example, physician, PA, NP). Participants who reported a preference for a physician valued more years in training and their role in the hierarchy of medicine; those who reported a preference for a PA or NP indicated that compassion, patience, and longer clinic visit times were most important to them. Previous reports suggested that the public might be confused by the different types of HCPs they might encounter during a primary care visit. Participants identified specific characteristics that are important when they are choosing their PCP. A direct, coordinated marketing campaign may be needed to educate the public and reduce confusion about different types of PCPs, how they contribute to safe and high-quality care, and ensure preference-concordant care.

Systematic Approach to Prevent Code Vulnerabilities using CI/CD Pipelines

This paper discusses a systematic approach to integrating Static Application Security Testing (SAST), Software Composition Analysis (SCA), Code Coverage, and Code Quality Checks into Continuous Integration/Continuous Delivery (CI/CD) pipelines. Modern CI/CD pipelines accelerate software delivery but introduce significant security and quality challenges. By incorporating SAST and SCA for security testing, along with code coverage and quality checks, organizations can prevent code vulnerabilities and ensure the maintainability and reliability of their applications. This approach helps development teams shift security and quality controls left, catching issues early in the development lifecycle. Keywords — CI/CD, DevSecOps, Static Application Security Testing (SAST), Software Composition Analysis (SCA), Code Coverage, Code Quality, Vulnerability

A Study on Development in Engineering Properties of Dense Grade Bituminous Mixes with Coal Ash by Using Natural Fiber

Coal-based thermal power plants in India produce significant waste, primarily fly ash and bottom ash, which poses environmental and health risks when disposed of in large quantities. This research explores the effective use of these waste products in bituminous paving mixes, substituting natural aggregates to conserve resources. Dense-graded bituminous macadam (DBM) specimens were prepared using natural coarse aggregates, bottom ash as fine aggregate, and fly ash as filler, with sisal fiber as a reinforcing additive. Varying percentages (0–1%) and lengths (5–20 mm) of SS1 emulsion- coated sisal fiber were tested to optimize the mix’s engineering properties. VG30 bitumen, chosen for its superior Marshall characteristics, resulted in an optimum binder content of 5.57%, fiber content of 0.5%, and fiber length of 10 mm, achieving a Marshall stability of 15 kN. Additional performance tests, including moisture susceptibility, indirect tensile strength (ITS), creep, and tensile strength ratio assessments, confirmed that the coal ash and sisal fiber mix significantly enhances pavement durability. This approach offers an eco-friendly and economical solution for bituminous pavement construction, addressing coal ash disposal challenges and conserving natural aggregates. Keywords: Bottom ash, Fly ash, Sisal fiber, Emulsion, Indirect tensile strength, Static creep test, Tensile strength ratio.

From traditional to digital contexts: new characteristics of the public’s spatial perception of urban streets in the age of technology

The constant development of internet technology in the digital age has changed the way people interact with space. To explore whether and what changes have occurred in the public’s spatial perception of the street during the shift from the traditional to the digital age, this paper compares the public’s spatial perception characteristics in the two contexts through a classical theory review and empirical coding analysis with the Xiaolouxiang historic district as an empirical case. The frameworks of public spatial perception characteristics are similar in both contexts, with a focus on the three dimensions of objects, buildings and spaces, and activities. However, compared with that in the traditional context, the public’s spatial perception of the street in the digital context of Xiaolouxiang has undergone new changes in three aspects: from focusing on the three-dimensional experience of space to focusing on the two-dimensional visual aesthetics of space, from emphasizing spatial totality to focusing on spatial details, and from focusing on the use of space to emphasizing the cultural characteristics of space. Research emphasizes that, within the context of digitalization, spatial design should place greater emphasis on visual aesthetics, detail processing, and cultural expression to better meet the needs and expectations of the public. This work identifies new features of the public’s perception of urban street space in the context of digitalization and accordingly provides suggestions for the future design of urban street space. The findings of this study not only enrich the foundational research content of spatial perception theory but also offer new perspectives for designers and planners in the practice of urban block renovation.

Water Quality Analysis of a 300 Mvar Large-Scale Dual Internal Water Cooling Synchronous Condenser External Cooling System and Exploration of Optimal Water Treatment Agent Dosage at Different Temperatures

The external cooling water system of a 300 Mvar dual internal water cooling synchronous condenser at a certain ultra-high voltage converter station continued to exhibit significant scaling and corrosion, even with regular addition of scale and corrosion inhibitors. To solve this problem, the external cooling water of the synchronous condenser was sampled and tested periodically, with the main test items including conductivity, pH value, turbidity, hardness, alkalinity, and other water quality parameters directly related to corrosion and scaling. The trends of these parameters over time were also analyzed. The results showed that as the operation time increased, the cooling water became concentrated during multiple circulation cycles, and the various dissolved or suspended substances underwent a certain degree of enrichment. However, the addition of scale and corrosion inhibitors did not dynamically adjust according to the changes in water quality, and there was always an excessive dosage. Thus, using the external cooling water as the experimental sample, static scale inhibition tests and rotating coupon corrosion tests were conducted to evaluate the scale and corrosion inhibition performance of the commercial AS-582 scale and corrosion inhibitor used at this ultra-high voltage converter station under different conditions. Considering the more obvious corrosive tendency of this water sample, the focus was on testing its corrosion inhibition performance. When the dosage was 600 ppm, the scale inhibition effect was optimal, with an inhibition rate of 92.15%. The corrosion inhibition effect of this scale and the corrosion inhibitor were significantly related to water temperature. At 25 °C, when the dosage was 500 ppm, the corrosion inhibition effect was optimal, with an inhibition rate of 86.79%. However, when the temperature increased to 40 °C, the corrosion inhibition effect under each dosage was significantly worse, unable to meet the requirements, and the use of other corrosion inhibitors in combination was necessary. This work will provide a reference for the scientific use of scale and corrosion inhibitors.

Characteristics of Successful Leadership: Perspectives From Asian Nursing Leaders.

The development of nursing leaders is an important topic in changing healthcare environments. Successful nursing leadership is critical to the reconstruction, implementation, and evaluation of healthcare systems worldwide. However, the characteristics of successful nursing leadership remain unclear, especially in a global context. Furthermore, despite the growing importance of cultural intelligence, cross-cultural concepts of successful nursing leadership have been inadequately addressed in the literature. This study was designed to identify the characteristics of successful leadership in nursing from the perspective of Asian leaders in four countries (United States, Taiwan, Korea, and Japan) and to make recommendations for successful leadership in nursing in the future. A qualitative approach employing five strategies, including in-depth discussions through face-to-face and email discussions, an integrated literature review using multiple databases, responses to 10 topics related to nursing leadership, and written note summaries of the characteristics of successful leadership, was used in this study. A total of 10 nursing leaders from four countries were recruited as participants using snowball sampling. The collected qualitative data were analyzed using line-by-line coding and simple content analysis to extract the characteristics of successful leadership in nursing. The final sample included seven nursing leaders aged between 55 and 70 years. All of the participants were in nursing leadership positions at schools/colleges of nursing or professional organizations for at least two decades and had extensive leadership experience through their schools/colleges, professional organizations, and/or governments. Five key themes related to the characteristics of successful leadership were identified from the participants: (a) culturally and historically prescribed, (b) overcoming gendered experience, (c) equipped with good character, (d) guiding with a vision, and (e) with contextualized leadership. Five characteristics of successful leadership were identified from the perspective of Asian nursing leaders. All of the participants recommended that successful nursing leadership be based on contextual leadership and that successful nursing leadership help meet rapidly changing needs, enable mutual trust, and actively commit and complete necessary risks. Moreover, future successful leadership should have a clear vision and strongly guide the implementation of changes as well as be equipped with cultural intelligence. Finally, successful nursing leadership should be based on ethical, trustable, and humane behaviors while promptly and adequately responding to the changing needs of their institutions/organizations. Cross-regional research on successful nursing leadership is essential to enrich the global evidence and knowledge on developing the next generation of nursing leaders.

Deflection function of a novel bolt-connected precast concrete floor

Owing to the post-cast procedure and relatively complex joint configuration, composite precast floors limit the full display of advantages of precast concrete systems. The development of fully assembled precast floors is of necessity; therefore, a novel bolt-connected precast concrete floor was proposed in this study to meet the increasing demand for quick assembly, lightweight, and good insulation in flooring systems. The proposed floors consist of precast sandwich unit slabs that are fully assembled to an integral floor with dry-type bolted connectors. Field static loading tests were conducted on four full-scale precast concrete floors. The test results indicate that the floors exhibited a two-way flexural ability due to the involvement of the bolted connectors. The restraining mechanism at anchorage and load-transferring mechanism at joints were investigated through a theoretical analysis. Based on the theory of plates and shells, a simplified theoretical method of solving the deflection function of the floors was established and validated to provide a reference for designing such fully assembled floors. The comparison between the theoretical and experimental results indicates that the arrangement of joint connectors could affect the theoretical calculation accuracy due to its influence on the performed continuity simplification. The application scope of the proposed theoretical method was evaluated through a finite element analysis.

Age-Related Influence on Static and Dynamic Balance Abilities: An Inertial Measurement Unit-Based Evaluation

Balance control, a complex sensorimotor skill, declines with age. Assessing balance is crucial for identifying fall risk and implementing interventions in the older population. This study aimed to measure age-dependent changes in static and dynamic balance using inertial measurement units in a clinical setting. This study included 82 healthy participants aged 20–85 years. For the dynamic balance test, participants stood on a horizontally swaying balance board. For the static balance test, they stood on one leg. Inertial measurement units attached to their bodies recorded kinematic data, with average absolute angular velocities assessing balance capabilities. In the dynamic test, the younger participants had smaller average absolute angular velocities in most body parts than those of the middle-aged and older groups, with no significant differences between the middle-aged and older groups. Conversely, in the single-leg stance tests, the young and middle-aged groups outperformed the older group, with no significant differences between the young and middle-aged groups. Thus, dynamic and static balance decline at different stages with age. These results highlight the complementary role of inertial measurement unit-based evaluation in understanding the effect of age on postural control mechanisms, offering valuable insights for tailoring rehabilitation protocols in clinical settings.

Robustness analysis of dynamic progressive collapse of precast concrete beam–column assemblies using dry connections under uniformly distributed load

A series of dynamic progressive collapse tests using the uniformly distributed load (UDL) was conducted, to analyze the robustness of three precast concrete (PC) beam–column assemblies using dry connections of top-and-seat angles (TSA-D), strengthened top-and-seat angles (STSA-D), and high-ductility reinforcement (DSTSA-D), under a middle column removal scenario. Finite element (FE) models were also developed to accurately simulate the collapse process. Based on the tests and FE models, comparative studies were conducted on dynamic and static collapse responses of the PC assemblies with identical configuration, loading regime, and boundary conditions. The results showed that: the horizontal reaction force developments were similar under dynamic and static collapse scenarios; under dynamic collapse scenarios, the initial stiffness of the PC assemblies increased due to the strain rate effect, while the peak vertical reaction forces under the compressive arch action (CAA) were smaller than those under static collapse scenarios, attributed to dynamic damage; under both dynamic and static collapse scenarios under UDL, the beam deformed in a downward convex curved shape, with local material deformation becoming more concentrated under dynamic collapse scenarios. An energy-based method for calculating dynamic collapse resistance was evaluated and revised: 1) the traditional method, which converts static responses from static analysis into dynamic responses was found to underestimate the resistance under small deformations due to neglecting the strain rate effect, and to overestimate ultimate resistance by ignoring dynamic damage; 2) by using dynamic vertical reaction forces instead, a more accurate prediction of the dynamic collapse resistance was achieved with a single dynamic collapse analysis. Additionally, dynamic amplification factors for the PC assemblies were calculated based on FE models and static test results providing basic knowledge in whole PC structural level research.

Green hybrid composites partially reinforced with flax woven fabric and coconut shell waste-based micro-fillers

This research is focused on hybrid green composites using flax woven fabric in which the matrix phase was further reinforced with coconut shell waste-based cellulosic microparticles as fillers. Mesoscale mechanical models were successfully developed to simulate the tensile properties of such hybrid composites based on hybridization of fibers and biobased materials using epoxy resin. S-glass fabrics with plain, twill and biaxial constructions, were used as the outer layers, while plain-woven flax fabric was used as the middle layer. A high level of agreement was observed between the experimental and predicted values. The static tensile tests were followed by cyclic tensile tests, microscopic analysis of fracture surfaces and dynamic mechanical analysis. The influence of the hybrid fabric geometry and combination with biowaste-based micro cellulosic material was observed to significantly influence the tensile properties determined by both experimental and numerical analysis. Dynamic mechanical analysis also validated the quasistatic measurements. A higher storage modulus and loss modulus were registered for the hybrid composites impregnated with a 1 % bio filler-based matrix. The damping factor (tan delta) was lower for the hybrid composites than for the nonhybrid samples and the control samples from the pure matrix. This difference is attributed to the stronger interface between the fibers and the particle-based matrix, which restricts the molecular mobility and increases the stiffness of the composites. Fractographic images were obtained by scanning electron microscopy (SEM) to study the failure modes and mechanisms of the composite samples. The microparticles were uniformly dispersed in the epoxy resin and thus enabled microcracking rather than macrocracks. The failure mainly occurred due to fiber failure, matrix cracking and delamination. Such hybrid composites are useful for exterior and interior components in automotive applications.

Effect of the connection structure of zirconia dental implants on biomechanical properties

The connection structure of zirconia dental implants significantly influences their biomechanical behavior and plays a crucial role in the overall service performance of the implant system. This study aims to compare the stress distribution of zirconia implants featuring various internal connection structures under different working conditions. Four distinct types of connection structures were designed for zirconia dental implants: triangular, quadrilateral, hexagonal, and hexalobular plus connections. Additionally, the finite element method was employed to analyze these structures under three working conditions: a static load test model, a bone level model, and a torsion model. Results indicated that in the static load test model, the hexagonal structure experienced the highest stress value at 1284.9 MPa due to its thin neck wall, whereas the hexalobular plus connected implant exhibited the lowest stress value at 1252.9 MPa. In the bone level model, the triangular connection structure demonstrated poor stress distribution for cortical bone and cancellous bone at 69.606 MPa and 7.8191 MPa, respectively. Conversely, the hexalobular plus connection yielded superior stress results for cortical bone and cancellous bone, with values of 69.606 MPa and 7.8191 MPa, respectively. In the torsion model, the hexalobular plus-connected implant exhibits the highest stress value at 210.37 MPa, while maintaining the smallest force transmission angle. Therefore, given that the abutment necessitates a greater range of installation angles and improved torque transmission, the hexalobular plus connection structure may represent the optimal choice.

Full-Scale Load Testing for Evaluating Crack Performance in Precast Prestressed Concrete Communication Towers with Annular Sections

Tall prestressed concrete poles with annular cross-sections are increasingly used as communication towers. The annular section subjected to bending moments has a smaller extreme tension area, resulting in higher stress increments in the materials within this region. As slender concrete structures, their bending behavior and crack resistance performance need to be critically examined. However, large-scale tower structures have rarely been experimentally investigated. Moreover, current code-specified crack width calculation methods are designed for square sections, so their applicability to concrete members with annular sections requires further investigation. To address these issues, this study conducted full-scale static loading tests on two 30-meter-high tower structures made of prestressed high-strength concrete and evaluated the accuracy of code methods for estimating the maximum crack width. During the static loading tests, displacement, cracking moments, crack widths, and crack spacings were meticulously recorded, and a theoretical methodology for calculating the stress in the extreme tension bars was developed. Four calculation methods specified in structural codes were compared: the Concrete Design Code of China (GB50010), Eurocode 2, ACI 224R, and the Concrete Design Guideline of Japan (JGC2007). The experimental results showed that diameter significantly affects the stiffness and displacement of the structure, with reloading stiffness of the full-scale tower reducing by up to 11% after exceeding the serviceability limit state. Regarding crack width prediction, substantial deviations were observed among the results of the four methods. On average, GB50010 underestimated crack widths, while JSCE, Eurocode 2, and ACI 224R overestimated them. Eurocode 2 and ACI 224R provided relatively conservative and accurate predictions. These findings highlight the need for improved and tailored code provisions for annular sections. It is also noted that the comparison was limited to crack widths less than 0.1 mm and a relatively small amount of data. Future research should focus on developing prediction methods specifically for prestressed concrete tower structures with annular sections.