Initial Strength Research Articles

A Novel Policy Alignment and Enhancement Process to Improve Sustainment of School-Based Physical Activity Programming.

The purpose of the current study was twofold: (1) to evaluate the strength and comprehensiveness of district wellness policies in one central Michigan intermediate school district (ISD; 16 districts), and (2) to pilot a novel policy alignment and enhancement process in one district within the ISD to improve sustainment of district-wide physical activity (PA) programming. Policy evaluation and alignment were determined using WellSAT 3.0. The Exploration, Preparation, Implementation, Sustainment (EPIS) framework was used to guide a seven-step policy alignment and enhancement process. Initial evaluation of the PA policy for the ISD revealed a strength score of 19/100 (i.e., included weak and non-specific language) and 31/100 for comprehensiveness (i.e., mentioned few components of the Comprehensive School Physical Activity Program). For the pilot school district, initial strength scores were 19/100 and 38/100 for comprehensiveness (exploration). An alignment of the tailored PA policy with current practices resulted in a 100% increase in strength (score of 38/100), and 132% increase in comprehensiveness (score of 88/100; preparation). However, district administrators encountered barriers to adopting the tailored policy and subsequently integrated the PA requirements into their curriculum guide and school improvement plan (implementation and sustainment). Future research should examine the effectiveness of our EPIS-informed policy evaluation, alignment, and enhancement process to promote widespread increases in student PA.

Cationic Polymerized Epoxy and Radiation Cured Acrylate Blend Nanocomposites Based on WS2 Nanoparticles—Part A: Curing Processes and Kinetics

Cationic photo-initiated and polymerized epoxies are characterized by good adhesion, high modulus, zero volatiles, low shrinkage and living polymerization characteristics. Radiation—cured acrylate resins are characterized by rapid initial curing with increased initial strength. The combination of radiation-cured acrylates and epoxies may present advantageous attributes. Thus, the system investigated is a hybrid epoxy/methyl acrylate and three different initiators for cationic polymerization of epoxies, the radical reaction of acrylates and the thermal initiator. When incorporating additives like opaque WS2 nanoparticles (NPs), absorption of the photo radiation takes place, which may lead to low photo activity. Curing kinetics measurements revealed that the absorbing/masking effect of WS2 was insignificant, and surprisingly, the level of curing was enhanced when the WS2 NPs were incorporated. FTIR results demonstrated that covalent bonds were formed between the inorganic fullerenes (IF-WS2) and the crosslinked matrix. Viscosity measurements showed a surprising reduction of five to ten times in the low-shear viscosity upon NPs incorporation compared to neat resins. It was concluded that the decrease of viscosity by the inorganic NPs, in addition to the enhanced level of conversion, has profound advantages for structural adhesives and 3D printing resins. To the best of our knowledge, this investigation is the first to report on a radiation-induced curing system containing opaque WS2 NPs that leads to an enhanced degree of curing and reduced shear viscosity.

Techno-Economic and Environmental Analysis of Decommissioned Flowline, Umbilical, and Tubular for Breakwaters

This paper presents the application of recycled tubular, flowline, and umbilical in coastal protection structures. Flowline and tubular are found to improve the load resistance capacity of concrete beams. Embedment of flowline, umbilical, and tubular into concrete beams would be beneficial to the structural performance, which do not noticeably alter the initial cracking strength of the concrete beam but will provide good post-cracking resistance. A techno-economic analysis was performed, which revealed that coastal protection concrete structures with decommissioned components accounting for more than 25% of the concrete weight could be both economically viable and environmentally friendly options. Since global warming is the most dominant environmental impact (i.e., 63%), recycling these decommissioned components from offshore structures could impose positive environmental impacts. Given the limited supply of construction materials in the remote coastal area as well as its proximity to decommissioned oil and gas rig sites, these decommissioned components could have great potential for use as construction materials in the coastal areas adjacent to the oil exploration. This preliminary study finds no showstopper for the concept of recycling the mentioned decommissioned components as coastal protection concrete structures from structural performance, environmental impact, and economic perspectives.

The effect of tricalcium silicate incorporation on bioactivity, injectability, and mechanical properties of calcium sulfate/bioactive glass bone cement

The conventional Polymethyl methacrylate (PMMA) bone cement is not biodegradable and not bioactive to bond with the native bone and causes tissue necrosis resulting from its high exothermic polymerization. Hence, biodegradable bioactive bone cements with suitable setting time and mechanical properties should be introduced. In this study, novel bioactive bone cements containing Calcium Sulfate Hemihydrate (CSH), Bioactive Glass (BG), and Tricalcium Silicate (TSC) were developed. Firstly, CSH and BG binary system was optimized based on preliminary setting and mechanical tests. Secondly, the composite bioactive bone cements were obtained by adding different quantities of TCS to the optimized CS-BG (1.3:1 wt % ratio) system. All groups exhibited desirable handling properties, an initial setting time of lower than 15 min, injectability of greater than 85%, and controlled degradability. Moreover, they demonstrated initial compressive strength values of higher than 12 MPa, superior to trabecular bone. After 28 days of hydration, the compressive strength of the cement containing 30% TCS reached 51.04 MPa. Furthermore, the present bone cements showed favorable bioactivity and bone-bonding ability as a result of calcium carbonate and hydroxyapatite (HA) formation. Furthermore, this novel bone cement exhibited appropriate biocompatibility and mesenchymal stem cell attachment, suggesting its potential for clinical applications.

Experimental Study on Toughness of Engineered Cementitious Composites with Desert Sand.

In this paper, engineered cementitious composites (ECCs) were prepared with desert sand instead of ordinary sand, and the toughness properties of the ECCs were studied. The particle size of the desert sand was 0.075-0.3 mm, which is defined as ultrafine sand. The ordinary sand was sieved into one control group with a size of 0.075-0.3 mm and three other reference groups. Together with the desert sand group, a total of five groups of ECC specimens were created. Through a uniaxial tensile test, three-point bending test and single-seam tensile test on the ECC specimens, the influence of aggregate particle size and sand type on the ECC tensile strength, deformation capacity, initial crack strength, cement-matrix-fracture toughness, multiple cracking characteristics and strain-hardening properties were studied. The experimental results show that the 28d tensile strain of the four groups of the ordinary sand specimens was 8.13%, 4.37%, 4.51% and 4.23%, respectively, which exceeded 2% and satisfied the requirements for the minimum strain of the ECCs. It is easier to achieve the ECC strain hardening with sand with a fine particle size; thus, a particle size below 0.3 mm is preferred when preparing the ECCs to achieve a high toughness. The multiple cracking performance (MCP) and the pseudostrain hardening (PSH) of desert sand and ordinary sand with a 0.075-0.3 mm grain size were 2.88 and 2.33, and 8.76 and 8.17, respectively, all of which meet the strength criteria and energy criteria and have similar properties. The tensile strength and tensile deformation of the desert sand group were 4.97 MPa and 6.78%, respectively, and the deformation capacity and strain-strengthening performance were outstanding. It is verified that it is feasible to use desert sand instead of ordinary sand to prepare the ECCs.

Magnetic fields do not suppress global star formation in low metallicity dwarf galaxies

ABSTRACT Many studies concluded that magnetic fields suppress star formation in molecular clouds and Milky Way like galaxies. However, most of these studies are based on fully developed fields that have reached the saturation level, with little work on investigating how an initial weak primordial field affects star formation in low metallicity environments. In this paper, we investigate the impact of a weak initial field on low metallicity dwarf galaxies. We perform high-resolution arepo simulations of five isolated dwarf galaxies. Two models are hydrodynamical, two start with a primordial magnetic field of 10$^{-6} \, \mu$G and different sub-solar metallicities, and one starts with a saturated field of 10$^{-2} \, \mu$G. All models include a non-equilibrium, time-dependent chemical network that includes the effects of gas shielding from the ambient ultraviolet field. Sink particles form directly from the gravitational collapse of gas and are treated as star-forming clumps that can accrete gas. We vary the ambient uniform far ultraviolet field, and cosmic ray ionization rate between 1 per cent and 10 per cent of solar values. We find that the magnetic field has little impact on the global star formation rate (SFR), which is in tension with some previously published results. We further find that the initial field strength has little impact on the global SFR. We show that an increase in the mass fractions of both molecular hydrogen and cold gas, along with changes in the perpendicular gas velocity dispersion and the magnetic field acting in the weak-field model, overcome the expected suppression in star formation.

Circular-Economy-Based Approach to Utilizing Cardboard in Sustainable Building Construction

Circular-economy-based sustainability approaches in construction are gaining wide acceptance due to the volume of waste generation and increasing demand for natural materials. Propelled by the recent timber shortage in Australia and the issues of waste management of cardboard, this study aims to analyse the possibilities of using cardboard as a construction material, based on its initial strength and multiple recycling options. A systematic review of research papers published in the last 40 years has been undertaken using a single keyword search to select the database. The review is presented in terms of the characteristics of the cardboard, dimensional stability, durability, structural strength, design, and analysis of cardboard. Recurring themes are evaluated using a latent Dirichlet allocation approach to identify the factors that ascertain the suitability of cardboard. Analysis reveals that despite certain constraints, such as water absorption and fire resistance, cardboard can be used as a replacement for timber by overcoming such limitations. This observation has benefits for the construction industry and the recycling industry. This study found that cardboard adheres to the circular economy principles, which should inspire policymakers. The paper concludes by highlighting the current circumstances and scientific challenges that impede the usage of cardboard in construction and recommends potential works needed to address these challenges for the benefit of practitioners and researchers.

An Investigation of the Impact of Water on Certain of the Mechanical and Physical Properties of Laminated Veneer Lumber (LVL) as Used in Construction

Timber and timber products are renewable materials that, due to their durability and strength properties, meet the requirements of the construction industry, are widely used in buildings. An analysis of the scientific literature has shown that there is a lack of detailed research that fully investigates the influence of the rate of increase of the moisture content of the timber on the mechanical and, especially, the strength properties of the LVL panels. Upon immersion into water of the bottom of the specimen, the water starts rising quite quickly at the edge of the specimen, and the first six hours are the most critical. The levels of water rise inside the LVL specimen were less significant than at the edges. It was found that water significantly affects the bending strength of the panels, which, when the strength of the wet panel compared to the strength of the dry panel, decreases to 45% after one soak cycle and almost to 52% after two soak cycles. The tensile strength of the wet specimens is ~40% less than that of the dry specimens. The strength of the panels that were dried back to their initial state was found to be sufficient again, different from the initial strength only within the error limits; the strength properties of the building structure will not be affected.

Carbonation Resistance of Mortar Mixed with Electrolysis Alkaline Aqueous Solution and Blast Furnace Slag

Cement production is the primary source of global CO2 emissions in the construction industry. Blast furnace slag (BFS) has been examined as a potential substitute for cement to reduce CO2 emissions. In addition, this substitution increases the long-term strength and improves the chemical resistance of mortar. However, a glassy film is formed on the surface of BFS while it is generated as a byproduct, lowering the initial strength of mortar. Notably, this film is destroyed in an alkaline environment. Thus, several studies have used solutions with various alkali activators. However, alkali activators are unsafe, as they are strong alkaline materials, and have low economic efficiency. This study experimentally improved the initial hydration reactivity of a mortar containing BFS as a substitute for cement, thereby improving its initial strength. We observed an increase in carbonation resistance. In addition, this study focused on evaluating the compressive strength and carbonation resistance of mortar prepared using BFS and alkaline water obtained from the electrolysis of a K2CO3 electrolyte. Results show that alkali-activated mortar using an electrolyzed alkaline aqueous solution has higher strength and contains more hydration products than that using conventional mixing water.

Ply-Resolved Quantification of Thermal Degradation in Carbon Fibre-reinforced Polymers

This study focuses on thermal degradation of carbon fibre-reinforced polymers depending on the specimen depth. For this purpose, the commercial composite HexPly® 8552/IM7 was thermally irradiated from one side with an infrared lamp at constant heat flux of 50 W/cm2 under varying exposure time. Subsequently, a defined number of plies was removed to prepare micro samples from different depths of the bulk material. Non-destructive and destructive testing methods were used to characterize the thermal degradation mechanism and mechanical properties of these specimens. The results showed that during thermal loading temperature and consequently damage gradients manifest along the material cross-section. Thereby, the damage distribution could be divided into the regions rI with matrix depletion, rII with and rIII without structural damage such as delaminations, cracks and pores. By means of ply-resolved investigations, the influence of these regions and corresponding decomposition processes on the mechanical properties could be determined. As a result, a simple damage model was introduced to calculate the residual strength from the initial strength, region sizes and sensitivity factors representing the effect of thermo-induced damage on strength types.

Wave interactions in pressureless Cargo–LeRoux model with flux perturbation

In this article, we discuss the wave interactions in pressureless Cargo–LeRoux model with flux perturbation. The corresponding Riemann solution in terms of a one‐parameter family of curves is presented. We prove the existence and uniqueness of the solution to the Riemann problem and construct estimates for the components of the solution. Relevant amplitudes are determined while presenting the interactions of weak discontinuity with contact discontinuity and shock waves. Further, we discuss the interaction of weak shocks in detail. Finally, some test cases are treated to understand the effect of initial data and strength of the shock on the transmitted, reflected amplitudes, and jump in the acceleration of the shock.

Characterization of gradient plastic deformation in gradient nanotwinned Cu

Gradient nanostructured (GNS) metals exhibit high overall extra strengths relative to their non-gradient counterparts. However, the spatial distribution of local extra strengths stemming from plastic strain gradients remains elusive. This work is focused on characterizing the gradient distribution of plastic strains in a representative GNS metal of gradient nanotwinned (GNT) Cu. Full-field strain mapping reveals the gradient distributions of lateral strains in the transverse cross section of GNT Cu samples undergoing uniaxial tensile deformation. We find that the lateral strain gradient increases but the maximum lateral strain difference decreases in GNT samples with increasing structural gradient. The latter arises because the softest layer with the lowest initial yield strength gains the largest local extra strength during tensile deformation, and vice versa. Such a gradient distribution of local extra strengths results from the combined strengthening effects of plastic strain gradient and grain size. These experimental results are used to inform a strain gradient plasticity model for revealing the gradient distributions of local extra back stresses and local extra strengths with increasing load. The coupled experimental and modeling characterization of gradient plastic deformation provides an in-depth mechanistic understanding of the spatial-temporal evolution of gradient strengthening effects in gradient nanostructures.

ОЦЕНКА МЕХАНИЧЕСКИХ ХАРАКТЕРИСТИК КАМЕННОЙ КЛАДКИ СУЩЕСТВУЮЩИХ ЗДАНИЙ

An analysis of known methods for evaluation the compressive strength and modulus of elasticity of existing masonry structures have been carried out. A method for determining the mechanical characteristics of masonry, based on tests of the specimens cutted from the body of the masonry in the form of triangular prisms have been given. Comparison of compressive strength, initial shear strength and angle of internal friction, obtained from the results of tests of prism specimens, with the results of tests of masonry specimens in accordance with the standards STB EN 1052-1 and STB EN 1052-3 has been carried out. Satisfactory agreement between the values of the compressive strength of the masonry and the secant modulus of elasticity obtained by testing the prisms with a compressive load acting perpendicular to the plane of the horizontal mortar joints with the test results according to the STB EN 1052-1 method has been shown. The initial shear strength of masonry, obtained from the results of tests according to STB EN 1052-3, differed downward from the strength established from the results of tests of prism specimens for compression, while the values of the angle of internal friction determined by the two methods were close.

Effect of acidic media on flexural strength and fatigue of CAD-CAM dental materials.

To investigate the effect of acidic media, including beverages and gastric fluids on flexural strength and fatigue of CAD-CAM materials. Four CAD-CAM materials (high-translucency zirconia (Ceramill Zolid HT+), lithium disilicate (IPS e-max CAD), hybrid ceramic (Vita Enamic), and nanohybrid resin composite (Grandio Blocs) were prepared and immersed in one of five media (gastric HCl, white wine, Coca-Cola, orange juice, and artificial saliva) in an incubator (37℃, 24h). Surface topography and roughness were obtained using a scanning electron microscope (SEM) and a stylus contact profilometer, respectively. Initial 3-point flexural strength was measured for half of the bars (n=20/gp) using a universal testing machine (0.5mm/min). The other bars underwent 106 cyclic fatigue loadings before measurement of residual 3-point flexural strength. Data were statistically analyzed (two-way and three-way ANOVA, Tukey's post-hoc, p<0.05). Weibull distributions were plotted for reliability analysis. Zirconia bars has the highest initial flexural strengths followed by lithium disilicate, while resin composite and hybrid ceramic groups had the lowest strength regardless of the erosive medium. Cyclic fatigue significantly reduced initial flexural strengths for all materials except for hybrid ceramic and resin composite. Weibull moduli were the highest for zirconia, lithium disilicate and resin composite and lowest for hybrid ceramic. Erosive media significantly changed surface roughness of CAD-CAM materials except for zirconia and resin composite without jeopardizing the flexural strength of the CAD-CAM materials. Despite the higher flexural strengths for zirconia and lithium disilicate, resin composite and hybrid ceramic were more resistant to cyclic fatigue.

The influence of blended polypropylene and polyethylene fibres on mechanical and durability properties of concrete

Steel fibers are always known to have been found to be an integral part of the concrete matrix. Since long, fibers of various materials have been used to prepare the mix and cast the structural components. The work presented in this paper is about the influence of polypropylene and polyethylene blended fibers on the initial strength gained and the concrete characteristics. The mixes of different proportions of fibers such as 1.8 kg/m3, 3 kg/m3, and 4.5 kg/m3 along with partially replaced quantity of cement with Ground Granulated Blast-furnace Slag (GGBS) were experimented. Twelve sample each with varied proportions of GGBS and fibers have been prepared and were tested. The results indicate that the specimens made out of GGBS with 15% replacement of cement and 3 kg/m3 fibers have shown the higher values of initial strength in compression, strength against splitting and strength in flexure to extent of 25%, 25% and 27.5% respectively. The durability properties were significantly improved when the GGBS was introduced to the extent of 30% of cement at both 28 and 56 days.

A study on Real time strength assessment of concrete by maturity method

The Nurse-Saul technique is employed to ascertain a member’s strength. Because the concrete members’ strength is being estimated in real-time concrete members. Using the Nurse-Saul maturity method, the member is precisely strengthened at a specific temperature, and after achieving its initial strength, the formwork is removed. The benefits of using the maturity process are covered, along with alternative methods for calibrating indicator of maturity. the capability of a structure, which can be determined in a number of destructive (or) non-destructive ways, is a crucial component for a suitable operational condition in terms of conditional assessment. The maturity approach is one such non-destructive technique that delivers excellent outcomes. Usually, after a mixture has fully cured, test cylinders are cast to measure its strength. The results are then analyzed in a lab (3, 7, 28 days). This technique takes more time to ascertain the strength of a certain mixture. Using the maturity approach, we calculated the member’s temperature and used that information to resolve the problem. Because this maturity process has already been employed by other researchers for standard concrete mix designs, this work will concentrate on unusual concretes. Due to the rarity of experiments on unique concrete, this process was tested using concrete blocks. As a result, this maturity approach is is a method for evaluating the strength of any concrete elements by measuring the temperature of the structure.

Investigation of effect of mixing procedure and alkaline solution to binder ratio on the strength of geopolymer concrete

This paper presents research on the influence of mixing and adding extra water on the strength of geopolymer concrete blended with 10% of 43-grade OPC. Two mixing methods were investigated. NaOH flakes were added in the first method; during dry mixing, heat generated by NaOH - water reaction was used to accelerate the setting time of OPC and geopolymerisation reaction. The second method was adding NaOH solution of molarity 12 M prepared 24 h before mixing concrete. In the first method, the heat generated was insufficient, and increased molarity was needed to achieve the required heat, which proved uneconomical and unsafe for the user. Also, the compressive strength of concrete prepared by adding NaOH flakes was noted to be lower than that of concrete prepared with the addition of NaOH solution. The addition of extra water in concrete was also investigated by considering two different water-to-binder ratios. During experiments, the water-to-binder ratio was initially established as 0.25 so that excess water obtained from the mix design is assumed to be utilized by OPC, making both the water-cement ratio and water-binder ratio 0.25. And again, the water-to-binder ratio was established as 0.7 to avoid extra water in the mix design. It was observed that geopolymer concrete without extra water increased its initial strength more than geopolymer concrete with extra water. But the 28th day strength of both the concrete was observed to be almost the same. It is concluded that the mixing method and extra water influence the early gain of strength and cost of concrete.

Two-dimensional numerical study of effect of magnetic field on evolution of laser-driven jets

Astrophysical jets are highly collimated supersonic plasma beams distributed across various astrophysical backgrounds. The triggering mechanism, collimation transmission, and stability of jets have always been a research hotspot of astrophysics. In recent years, observations and laboratory research have found that the magnetic field plays a crucial role in jet collimation, transmission, and acceleration. In this work, the two-dimensional numerical simulation of the jet in front of the CH plane target driven by an intense laser is carried out by using the open-source MHD FLASH simulation program. We systematically investigate the dynamic behaviors of jet evolution caused by the Biermann self-generated magnetic field, the external magnetic field with different directions and initial strengths and compare them with each other. Simulation results show that the Biermann self-generated magnetic field does not affect the jet interface dynamics. The external magnetic field has a redirecting effect on the plasma outflow. The external magnetic field, which is parallel to the direction of the plasma outflow center in front of the target, is conducive to the generation and collimation of the jet. The evolution of the jet goes through three stages: antimagnetic ellipsoid cavity, conical nozzle, and collimated jet. Its formation process and evolution process result from competition among plasma thermal, magnetic, and ram pressure. In terms of force, plasma thermal pressure gradient and magnetic pressure forces play a decisive role in the jet evolution process. The presence of magnetic pressure significantly limits the radial expansion of the jet to achieve axial collimation transmission. The length-diameter ratio of the jet is positively correlated with the initial axial applied magnetic field intensity. In addition, we observe in the simulation that there are many node-like structures in the jet evolution zone, similar to the jet node in YSO. The results provide a reference for future experimental research related to jets and contribute to a more in-depth understanding of the evolution of celestial jets.

The contribution of the alternative pathway in complement activation on cell surfaces depends on the strength of classical pathway initiation.

The complement system is an important component ofinnate immunity. The alternative pathway (AP) amplification loop is considered an essential feed forward mechanism for complement activation. However, the role of the AP in classical pathway (CP) activation has only been studied in ELISA settings. Here, we investigated its contribution on physiologically relevant surfaces of human cells and bacterial pathogens and in antibody-mediated complement activation, including in autoimmune haemolytic anaemia (AIHA) setting with autoantibodies against red blood cells (RBCs). We evaluated the contribution of the AP to complement responses initiated through the CP on human RBCs by serum of AIHA patients and recombinant antibodies. Moreover, we studied complement activation on Neisseria meningitidis and Escherichia coli. The effect of the AP was examined using either AP-depleted sera or antibodies against factor B and factor D. We show that the amplification loop is redundant when efficient CP activation takes place. This is independent of the presence of membrane-bound complement regulators. The role of the AP may become significant when insufficient CP complement activation occurs, but this depends on antibody levels and (sub)class. Our data indicate that therapeutic intervention in the amplification loop will most likely not be effective to treat antibody-mediated diseases. The AP can be bypassed through efficient CP activation. The AP amplification loop has a role in complement activation during conditions of modest activation via the CP, when it can allow for efficient complement-mediated killing.

High-temperature resistant interconnection using Ni nanoparticles and Al microparticles paste sintered in an atmosphere

Next-generation power devices using wide bandgap semiconductors, such as SiC, are expected to operate at higher temperatures than conventional Si power devices, and their operating temperatures are expected to exceed 250 °C. We developed a novel high-temperature resistant interconnection technology for die-bonding of SiC power devices using Ni nanoparticles and Al microparticles composite paste. The bond strength of the Al-metallized Si chip to Ni-plated direct bonded copper substrate was evaluated using shear tests. The initial shear strength of samples from pressureless sintering at 350 °C for 15 min in the air exceeded 30 MPa. Furthermore, no significant degradation was observed in a high-temperature storage test at 250 °C for 1000 h.