Volumetric Ratio Research Articles

Anaerobic Co-digestion of the Liquid Fraction of Food Waste with Waste Activated Sludge

The present study investigated the feasibility of the anaerobic co-digestion (AcoD) of condensate, resulting from drying food waste, with Waste Activated Sludge in a pilot scale continuous stirred tank reactor. Different parameters were assessed in order to enhance the AcoD performance; the condensate potency (condensate A: 13 gCOD/L and condensate B: 4 gCOD/L), the volumetric ratio of condensate to WAS (0–67% v/v) and the hydraulic retention time (HRT) (20, 15 and 12 days). The results showed that increasing the condensate content in the feed from 0 to 67% v/v, enhances the organic load removal (up to 41% increased total COD removal) and the bioenergy production (up to 35% increased biomethane production). Moreover, in the case of condensate A, the reduction of HRT from 20 to 15 days enhanced the bioenergy production (up to 19% increased biomethane production) while the reduction of HRT from 20 to 12 days in the case of condensate B did not significantly affect the reactor’s performance. Overall it is concluded that condensate can be safely introduced in existing facilities for anaerobic digestion, while maintaining a more stable operation and improved effluent quality and bioenergy production in comparison with conventional anaerobic sludge digestion.Graphical

Characterization of acorn oil and its application on carnauba wax-based oleogel and chocolate spread

This study aimed to characterize acorn oil (AO) and carnauba wax-based acorn oil oleogel (AOG) and the effect of AOG replacement on the textural and sensorial properties of chocolate spread. Oil yields from cold-pressing (Quercus longipes) were around 14%wt with a nice nutty smell. The main fatty acids of AO were included oleic, linoleic, and palmitic acid (44, 38, and 10%wt) respectively. The prepared AOG using 6%wt of carnauba wax (CW) showed high strength (G' > 100 mPa) and oil binding capacity ∼87 %. Based on microstructure assays platelet-like and β’ polymorphic triglyceride crystalline networks were formed in AOG. The Pickering AOG/water emulsions in the volumetric ratio of from 90:10 up to 40:60 were stable due to the placement of CW-based AOG particles at the interface of water/oil as Pickering stabilizer. The high physical stability of the emulgel against phase separation is considered an important advantage for using oleogel in chocolate spread formulations instead of vegetable oils, which usually have a high percentage of oil release. The spreads prepared by replacing 50%wt AOG with butter showed acceptable textural and sensorial properties.

Use of Technetium-99m-Pyrophosphate Single-Photon Emission Computed Tomography/Computed Tomography in Monitoring Therapeutic Changes of Eplontersen in Patients With Hereditary Transthyretin Amyloid Cardiomyopathy.

Hereditary transthyretin amyloid cardiomyopathy (hATTR-CM) is a progressive and fatal disease. Recent evidence indicates that bone scintigraphy may serve as a tool to monitor the effectiveness of hATTR-CM treatment. The objective of this study was to examine how eplontersen therapy influences the semiquantitative uptake of technetium-99m-pyrophosphate in individuals diagnosed with hATTR-CM. We retrospectively analyzed a prospective cohort from the NEURO-TTRansform trial, including patients with hATTR-CM receiving eplontersen (45 mg/4 weeks). A control group comprised patients with hATTR-CM who had not received eplontersen, inotersen, tafamidis, or patisiran. Technetium-99m-pyrophosphate single-photon emission computed tomography/computed tomography was conducted at baseline and during follow-up. Thirteen patients with hATTR-CM were enrolled, with 6 receiving eplontersen and 7 serving as the control group. The median follow-up time was 544 days. The eplontersen group exhibited a significant decrease in volumetric heart and lung ratio (3.774 to 2.979, P=0.028), whereas the control group showed no significant change (4.079 to 3.915, P=0.237). Patients receiving eplontersen demonstrated a significantly greater reduction in volumetric heart and lung ratio compared with the control group (-20.7% versus -3.4%, P=0.007). The volumetric heart and lung ratio used to quantify technetium-99m-pyrophosphate uptake showed a significant reduction subsequent to eplontersen treatment in individuals diagnosed with hATTR-CM. These findings suggest the potential efficacy of eplontersen in treating hATTR-CM and highlight the value of technetium-99m-pyrophosphate single-photon emission computed tomography/computed tomography as a tool for monitoring therapeutic effectiveness.

Toward the Scalable, Rapid, Reproducible, and Cost-Effective Synthesis of Personalized Nanomedicines at the Point of Care.

Organic nanoparticles are used in nanomedicine, including for cancer treatment and some types of COVID-19 vaccines. Here, we demonstrate the scalable, rapid, reproducible, and cost-effective synthesis of three model organic nanoparticle formulations relevant to nanomedicine applications. We employed a custom-made, low-cost fluid mixer device constructed from a commercially available three-dimensional printer. We investigated how systematically changing aqueous and organic volumetric flow rate ratios determined liposome, polymer nanoparticle, and solid lipid nanoparticle sizes, size distributions, and payload encapsulation efficiencies. By manipulating inlet volumes, we synthesized organic nanoparticles with encapsulation efficiencies approaching 100% for RNA-based payloads. The synthesized organic nanoparticles were safe and effective at the cell culture level, as demonstrated by various assays. Such cost-effective synthesis approaches could potentially increase the accessibility to clinically relevant organic nanoparticle formulations for personalized nanomedicine applications at the point of care, especially in nonhospital and low-resource settings.

Greens assessment of RP-UPLC method for estimating Triamcinolone Acetonide and its degraded products compared to Box-Behnken and Six Sigma designs

ABSTRACT A study on green analytical chemistry aims to develop eco-friendly alternatives to hazardous substances and minimize waste generation. The study thoroughly examined various tools to determine their greenness. A newly validated RP-UPLC method was then employed quantitatively to detect Triamcinolone Acetonide (TRA) in a creamy pharmaceutical formulation using UPLC BEH C18 (50 × 2.1 mm, 1.7μm) column for analysis, with a detection wavelength set at 240 nm. The Box-Behnken design was developed to efficiently determine the optimal chromatographic conditions while minimizing the required trials. The study effectively assessed the impact of three independent variables on various responses, including retention time, tailing factor, and theoretical plates. The variables examined ethanol ratio, pH levels, and flow rate were meticulously tested to optimize experimental conditions. The utilization of desirability and overlay plots, along with a mobile phase of ethanol and purified water in a volumetric ratio of 30:70 and pH adjustment to 5.0. Calibration curves were constructed to assess the linearity of TRA within the concentration range of 2.5-50 µg/mL, yielding correlation coefficients (r = 0.9999). The accuracy was validated through recovery studies with the acceptable range of 99.6-101.2%. The specificity of the method has been validated by conducting forced degradation studies per ICH guidelines.

Improving microfiltration efficiency of fruit beverages through backpulsing: Impact on permeate flux, cost-effectiveness and bioactive compounds retention

ABSTRACT Cross-flow microfiltration (CFM) combined with ultra-clean or aseptic packaging offers a promising solution to meet consumer demand for more natural, non-heat treated ready-to-drink fruit beverages. However, membrane fouling can significantly reduce the efficiency of CFM and increase the production cost. To address this issue, we studied the effect of backpulsing on the performance of a semi-industrial CFM equipment featuring 2 m2 of ceramic membranes with 0.2 μm pore size. Using an optimum transmembrane pressure of 150 kPa, we found that backpulsing with a high frequency (every minute) at the beginning of microfiltration and then slowing down the frequency (every 2 min) resulted in higher (+14%) and more consistent average fluxes (100 l.h−1.m−2) while reaching volumetric concentration ratio up to 11. Additionally, the overall specific energy requirements are reduced by 12.5% to 0.0376 kWh.l-1 of treated juice, which is the lowest value among all known de-bacterizing processes, including thermal pasteurization. Importantly, our results showed that backpulsing reduces the retention of the main bioactive compounds of blackberry, including anthocyanins and ellagitannins. These findings demonstrate that CFM with backpulsing is a more cost-effective process that allows for the production of stabilized fruit juices with higher content of bioactive compounds.

Effects of pilot injection on ignition performance for F-24/Gasoline fuel blends

This study experimentally investigates the effects of pilot injection on first stage and overall ignition behavior for different fuel blends. A conventional petroleum-derived fuel (F-24) with a Derived Cetane Number (DCN) of 48.5 and gasoline (GAS), which has a low DCN of 21.4 but high volatility, were blended at different volumetric ratios. These blends were injected into a high temperature, pressure vessel using either a single or pilot-main injection strategy. Four optical diagnostics (formaldehyde PLIF, OH* chemiluminescence, schlieren, and Mie scattering) were employed to visualize the ignition process and to evaluate liquid length, penetration distance, heat release rate, the first stage, and overall ignition delays. It is shown that the higher GAS blend ratios result in longer ignition delay and less overall heat release attributed to the poor reactivity of GAS. In such cases, the contributions of the extended first stage ignition delay to the extended overall ignition delay decrease with GAS blend ratio. Furthermore, some of the high GAS blend fuels exhibit no overall ignition at all due to the excessive fuel-air mixing. The study then shows that this decrease in ignition performance with GAS can be mitigated by introducing pilot injection, which shortens the ignition delays and provides more overall heat release. Specifically, at low GAS blend ratios, the ignition exhibits mixing controlled combustion where the ignition of pilot fuel-air mixture induces the main fuel ignition. For pilot-main injections, the decrease in first stage ignition delay accounts for the average of 87 % of the reduced overall ignition delay, suggesting that the reduced ignition delay with pilot injection is primarily due to the reduced time for fuel atomization, vaporization, and decomposition of the main fuel. These results will contribute to the development of ignition models capable of capturing the impact of fuel composition and pilot injection on ignition performance.

OPTIMIZATION OF PROCESS PARAMETER OF BIODIESEL DERIVED FROM A HYBRID BLEND OF KARANJA AND CHLORELLA VULGARIS OIL

In this study, the response surface approach was employed to predict and optimize the biodiesel yield. Blend of Karanja and Chlorella vulgaris oil was used in a volumetric ratio of 75:25 to lower the free fatty acid content. The biodiesel production process parameters from this hybrid oil were optimized through a single-step transesterification process. The optimized conditions resulted in a maximum biodiesel yield of 97.55% . These conditions included a catalyst amount of 1.09% (w/w), a reaction time of 91.47 minutes, a reaction temperature of 56.86°C, and a methanol-to-oil molar ratio of 8.46:1. The experimental biodiesel yield was compared with the predicted response obtained from the response surface methodology (RSM). The comparison demonstrated good agreement between the experimental and predicted values.

Experimental and numerical investigation of high-pressure methane catalytic synthesis from H2 and CO2

The catalytic synthesis of methane from H2 and CO2, which is an efficient way for the production of synthetic natural gas (SNG) by utilizing the H2 originating from carbon-free renewable power sources and the greenhouse gas CO2, was investigated in a non-isothermal channel-flow reactor coated with Ni/Al2O3 at pressures 1.5–10 bar, H2:CO2 volumetric ratios 4–6, and surface temperatures 450–760 K. In situ, spatially resolved Raman measurements of gas-phase species concentrations across the channel height were complemented by gas chromatography analysis of the exhaust gas. Two-dimensional simulations were carried out, using elementary catalytic and gaseous chemical reaction mechanisms and detailed transport. Comparisons of the Raman data and simulations revealed that the preferential diffusion of H2 drastically altered the local H2:CO2 ratios at the catalytic walls, which attained values up to 8 times higher than the corresponding inlet values. This behavior exemplified the caution needed when performing kinetic studies in the mixed kinetically/transport controlled regime. The production of methane increased with increasing pressure and decreasing H2:CO2 ratio. At the highest ratio H2:CO2 = 6, the simulations underpredicted (overpredicted) the measured reactant (product) mole fractions, however, as H2:CO2 decreased, the trend was reversed. The discrepancies reduced with increasing pressure, resulting in a model overprediction of methane by 7.4% at 10 bar. Methane was produced from C(s) via successive hydrogenation. C(s) was in turn produced from COOH(s), followed by dissociation of COOH(s) to CO(s), and finally H-assisted dissociation of CO(s) to C(s). Gas-phase chemistry was negligible over the investigated conditions. The in-channel Raman measurements in conjunction with the exhaust gas analysis facilitated the construction of a global step for the studied reaction. The methane synthesis was assessed to follow a ∼p0.41 pressure dependence over the temperature range 520–680 K.

Parametric study of depth to maximum bending moment for prestressed concrete piles resisting lateral load

Seismic design of prestressed concrete piles requires transverse spiral reinforcement to be proportioned to confine and thus retain an intact concrete core during inelastic rotation cycles. Prescriptive provisions of the International Building Code require a prescriptive minimum volumetric ratio of confinement reinforcement relative to the pile cross section and a minimum in-ground depth to which the confinement reinforcement must extend. This study seeks to determine a practical maximum depth to maximum in-ground bending moment for 12, 14, and 16 in. (300, 360, and 410 mm) prestressed concrete piles subjected to displacement consistent with lateral seismic loads. A commercially available lateral analysis software was used to conduct a parametric analytical study of square and octagonal piles embedded in substantially varied soil conditions. Piles were modeled to remain elastic. Depth to maximum in-ground moment was recorded. Maximum depth values for each pile type were reported. Analysis of results indicates that prescriptive depth requirements may be overly conservative for 12 and 14 in. square piles in nonliquefiable soils. It was concluded that a reduction could be made to the code-prescribed depth of ductile reinforcement for some pile types in nonliquefiable conditions.

Reversible dye extraction from aqueous matrices using ammonium salt-based deep eutectic solvents

Recovery of dyes present in liquid solutions was achieved with efficiencies higher than 99 %, using deep eutectic solvents composed of tetrabutylammonium chloride and decanoic acid. The method produces a totally decolorized water. Both the reuse of the clean water and of the extracted dye is plausible via this treatment, as the colorant can be recovered from the organic phase after the liquid–liquid extraction. The solvent is physically and chemically characterized, in a wide arrange of temperatures, and its behavior in liquid–liquid equilibria with water was also studied. The process works for a broad range of dye concentrations, and with a very low consumption of solvent (optimized volumetric ratio between organic and aqueous phases was 1/16). Optimized processing times set the duration of the treatment at 20 min, including the recovery of the dye from the extracted phase. The capabilities of the solvent were tested against synthetic effluents composed by industrial dyes and auxiliary agents that typically appear on dyeing processes, maintaining efficiencies above 99 %. The deep eutectic solvents also work equally well for extracting mixtures of dyes.

Deposition of Composite Nanoparticle-Based Thin Films for Gas Sensing

Working principle of conductometric gas sensors is based on modulation in electrical conductivity of the sensing material due to adsorption-desorption reactions between the target gas and the sensor surface. Nano-structuring the sensing material increases the effective surface area for interaction between the target gas and the sensing material thereby enhancing the sensorial response. Metal oxide semiconductors (MOS) have shown remarkable sensing performance to oxidizing and reducing gases. The combination of different MOS has often demonstrated to synergistically improve the gas sensing performance via the formation of highly sensitive heterojunctions at their interface.In this work, we deposited thin films composed of nanoparticles (NPs) of p-type CuOx and n-type WOx to enhance the effective surface area of the material and to realize the maximum number of nano p-n heterojunctions in the material. The films were prepared using the Nanogen-Trio NP source equipped with three 1′′ magnetrons, mounted on a custom-built deposition chamber and sputtered by a DC power supply. Depositions were executed in Ar+O2 gas mixture. The O2 admixture may significantly enhance the mass flux of NPs. Furthermore, the O2 admixture allows one to tune the desired stoichiometry of the respective metal oxides. On the other hand, the pronounced hysteresis complicates the deposition of WOx NPs. The deposition process was controlled using an in-house developed software to prepare thin films composing a mixture of NPs with a defined volumetric ratio of the individual materials.This work demonstrates the versatility of our custom-built gas aggregation source that facilitates the preparation of multi-composite NP-based thin film giving the best sensorial response.

Controlled sputter deposition of oxide nanoparticles-based composite thin films

This study explores the feasibility of deposition of composite films based on nanoparticles (NPs) using a magnetron-based gas aggregation source of NPs. First, we investigate the deposition conditions and properties of the individual components of the composite films, namely, NPs prepared using Cu and W targets. We thoroughly discuss that the generation of NPs might be more efficient in the Ar atmosphere in the case of W target due to an enhanced direct emission of NP seeds from the target and/or a longer lifetime of the seeds in the plasma. To operate reasonable fluxes of NPs for both targets, O2 was added into the gas mixture. Lower O2 flow rates promote enhanced seed formation of NPs, while higher flow rates exhibit a dominant target poisoning effect, reducing the flux of NPs. We demonstrate that a fine-tuning of O2 flow rate allows us to control the resulting crystal structure of the NPs. Fully oxidized NPs were produced at O2 flow rates of 1.30sccm and 1.50sccm for Cu and W targets, respectively. Subsequently, CuO/WO3 composite films were prepared using our in-house-built software as alternating NPs-based layers. To demonstrate the capabilities of the deposition technique, three different CuO/WO3 multilayers were prepared, each with a specific thickness of the individual layers (80nm, 40nm, and 10nm, which corresponds to a monolayer of NPs). Scanning electron microscopy imaging shows well-defined layers with the intended thickness. In addition, XRD analysis confirms that all three multilayers exhibit practically identical patterns, indicating the same volumetric ratio of CuO and WO3 NPs in the investigated films.

Axial Compression Behavior of Large-Diameter, Concrete-Filled, Thin-Walled Galvanized Helical Corrugated Steel Tubes Column Embedded with Rebar

Thin-walled galvanized helical corrugated steel tubes (HCSTs) filled with concrete are promising composite members, consisting of concrete, an anti-corrosion shell, and a multifunctional exterior corrugated steel tube. To investigate the synergistic working mechanism of concrete-filled HCSTs (CFHCSTs), six specimens were designed for axial compression tests, with the inner diameter of the column and the volumetric steel ratios of the longitudinal reinforcement as the variation parameters. The results show that HCSTs can better confine the concrete core and increase its strength. The failure mode of HCSTs is significantly influenced by the column’s diameter, and those with a smaller diameter are prone to slide failure and lock seam tearing. The strains and stresses on HCSTs are discussed in detail to elucidate the confinement effect. This paper proposes a suitable design method to predict the ultimate axial compression load capacity of CFHCST columns based on early studies on steel tube-confined concrete.

Experimental investigation on the freeze-thaw durability of a phase change concrete in cold regions

In cold regions, freeze-thaw induced damage to concrete is among the most severe issues that affect structures, leading to shortened lifespans of concrete-related structures and causing substantial economic losses. Therefore, it is crucial to enhance the freeze-thaw durability in cold regions. To achieve this aim, we combined n-tetradecane (C14) and expanded perlite (EP) to produce a composite phase change material (EPC14) with cement encapsulation. The essential material performances of the EPC14 were characterized through a series of physical and chemical tests. The measurement results show that the EPC14 possesses an appropriate phase change temperature, chemical stability, and mechanical reliability. Hence, it is an excellent candidate material for producing phase change concrete. In this study, we selected five volumetric replacement ratios of the EPC14 to fine aggregates (0%, 10%, 20%, 30%, and 40%) to prepare the phase change concretes (PCC-EPC14s). After these PCC-EPC14s samples were properly cured and then underwent 0, 50, 100, and 200 freeze-thaw cycles (FTCs), their physical and mechanical properties were systematically measured through nuclear magnetic resonance (NMR), resonance frequency tests, and uniaxial compression tests. The comprehensive measurement results demonstrate that at 0 FTCs, a higher content of the EPC14 results in larger porosity in the PCC-EPC14s, leading to lower compressive strength and relative dynamic modulus of elasticity. However, after 200 FTCs, the PCC-EPC14 (20%) exhibits the highest compressive strength and relative dynamic modulus of elasticity, whereas the PCC-EPC14 (0%) exhibits the lowest values for both of these properties. Furthermore, fractal theory was employed to analyze the mechanical properties of the PCC-EPC14s from a microscopic perspective. The results indicate that the PCC-EPC14 (20%) exhibits the largest NMR fractal dimension after 200 FTCs, signifying the least complexity and integration in its pore structure. In comparison to the PCC-EPC14s (0%, 10%, 30%, 40%), it is less prone to developing damage cracks under compression. In conclusion, we advise using the PCC-EPC14 (20%) in practical construction projects. The PCC-EPC14s prepared in this paper offer valuable insights for enhancing the freeze-thaw durability of concrete in cold regions.

Auxetic cementitious composites (ACCs) with excellent compressive ductility: Experiments and modeling

Auxetic cementitious composites (ACCs) with improved mechanical properties are created, by casting 3D printed polymeric auxetic reinforcement structures inside cementitious mortar. Four types of ACCs incorporating reinforcement with different auxetic mechanisms were prepared: “re-entrant” (RE), “rotating-square” (RS), “chiral” (CR) and “missing-rib” (MR). Experiments and finite element models were used to study the compressive behavior of the ACCs. The results indicate that all ACCs have high compressive ductility. Specifically, the RE shows the highest ductility, manifested by 853% and 708% higher energy absorption than the reference mortar and the auxetic structure itself, respectively. In addition, the RE and RS are found to exhibit stronger crack-arresting effect under compression. Therefore, they achieved comparable compressive strength to the reference mortar, which is considerably higher than CR and MR. Furthermore, decreasing the volumetric ratio of the auxetic structure by half, the ductility of the RS reduces by 32.2%, while decreasing the water-to-binder ratio of the cementitious matrix from 0.4 to 0.3 only increases the compressive strength by 18.5%. Moreover, the two-dimensional finite element analyses used herein show a good match with experiments but become less accurate at high strain levels, due to their inability to capture the out-of-plane failure of the ACCs.

Preparation of refined phosphoric acid with recycling of raffinate acid by the extraction of metal impurities

Solvent extraction is the most effective method to remove impurities from wet-process phosphoric acid (WPA). However, the raffinate acid produced by this method cannot be effectively utilized because of a high impurity content and high viscosity, resulting in the waste of phosphorus resources. In this paper, a new process is proposed for extracting metal impurities and purifying the raffinate acid, and utilizing purified raffinate acid to prepare refined phosphoric acid. The effects of the extraction temperature, volumetric phase ratio (R), extraction time, and agitation speed on the metal-ion extraction were investigated. The MER (mass ratio of the sesquioxide content to the P2O5 content, MER = w(Fe2O3 + Al2O3 + MgO)/w(P2O5)) of the raffinate acid was reduced from 0.1516 to 0.1001 under the optimum conditions: temperature = 60 °C, R = 6, reaction time = 30 min, and agitation speed = 500 rpm. More than that, the MER value was reduced to 0.0357 through five-stage cross-current extraction. The theoretical number of stages to reduce the MER of the raffinate to 0.086 was obtained by the McCabe-Thiele method and found to be two stages. Finally, the purified raffinate acid obtained in the pilot experiment was used to prepare refined phosphoric acid, of which the product quality reached food-grade. In addition, the phosphorus yield of the whole process was 95.5%. The application of this new process will significantly improve the recovery ratio of phosphorus in refined phosphoric acid industry.

Effect of ultra‐high performance concrete repair layer thickness on the behavior of concrete columns

AbstractThe use of ultra‐high‐performance fiber reinforced concrete (UHPFRC) to repair or rehabilitate old concrete structures has been shown to be appropriate due to its properties, such as higher compressive strength, ductility, and durability than conventional concretes. One of the studied strengthening techniques is the reinforced concrete columns jacketing by UHPFRC. Some recent research evaluated some parameters, such as the repair thickness and the volumetric ratio of stirrups. However, other important parameters, such as UHPFRC jacketing thickness in different column cross‐sections and the concrete core compressive strength, need to be addressed. In addition, the analytical models presented in the literature are restricted to only one concrete grade. The present study aims to evaluate the behavior of short reinforced concrete columns strengthened with UHPFRC subjected to centered compression. Numerical analyses of three‐dimensional models were performed using the finite element method, validated, and calibrated using experimental results. The influence of the concrete core compressive strength, the UHPFRC jacketing thickness, and the shape of the cross‐section were evaluated. Numerical simulations concluded that the lower concrete core compressive strength columns showed the best relative increase performance. Moreover, the concrete core strength was inversely proportional to the resistance capacity of the repair system. In addition, the increase in repair thickness contributes to the axial strength of the column. Furthermore, the cross‐section influences the distribution of stresses and strains, showing the best performance for circular sections. Finally, regardless of cross‐section type, the proposed equations accurately predicted the numerical results.

Experimental and numerical study on seismic behavior of special shaped steel truss and concrete composite shear wall

A steel truss-concrete composite (STCC) shear wall is fabricated by replacing the reinforcement of the shear wall by steel truss, which has high bearing capacity, good fire resistance, good seismic performance, and an easy construction. In order to investigate the seismic performance of special shaped composite shear wall, a quasi-static test was carried out on four T-shaped and two L-shaped composite shear walls. The results showed that the change of diagonal bracing form from strip steel to channel steel can improve the ductility and energy dissipation capacity of the shear wall and delay the strength degradation. Increasing the thickness of steel vertical supports can effectively improve the initial stiffness, while decreasing the thickness of diagonal braces will reduce the bearing capacity of the wall. The strength and stiffness of shear walls loaded along the web in the positive direction (flange in tension) is high, but the ductility is relatively poor when compared with walls loaded in the negative direction (flange in compression). Numerical models were established by ABAQUS, in which the steel hysteretic constitutive model was adjusted to simulate the influence of bond-slip effect. The influence of shear span ratio, axial load ratio, steel ratio of vertical support, volumetric ratio of diagonal brace, tilt angle of diagonal brace and horizontal force direction on the seismic performance of T & L shaped composite shear walls were analyzed. Finally, a design method was proposed, and the calculated results by the design method were in good agreement with the test.

Investigation on physico-mechanical properties and microstructural evolution patterns of heated granite after liquid nitrogen cooling

Liquid nitrogen (LN2) fracturing is recognized as an innovative reservoir enhancement technique, demonstrating significant potential in establishing high permeability pathways in geothermal development. Understanding the physico-mechanical properties and microscopic mechanisms of hot dry rock post LN2 cooling treatment is pivotal for promoting the effective deployment of LN2 fracturing. This study undertook physical and mechanical testing on a quintessential hot dry rock type-granite-post various temperature and LN2 cooling treatments. Subsequently, a multi-scale investigation was conducted on the thermal fracture-pore structure's morphological features and the evolution of mineral components. The experimental findings indicated that LN2 cooling exerts a pronounced impact on the physico-mechanical properties of high-temperature granite. Temperature-induced damage to granite can be delineated into three phases: initial phase up to 200 °C where its effects are relatively imperceptible; an intermediate phase from 200 to 500 °C characterized by gradual deterioration; and a pronounced degradation phase evident at 600 °C. Correlations between the changes in the micro pore-fracture structure of granite and its physico-mechanical property degradation were subsequently established. As temperature escalated, the area of micro-defects in the CT-reconstructed spatial distribution increased progressively. The volumetric porosity damage ratio and fractal dimensions were quantitatively introduced to characterize the fractal geometric features and distribution patterns of internal thermal fractures in granite post thermal shock. Concurrently, NMR experiments indicated that with the escalation of temperature, micropore develop and interlink to form mesopore and macropore, enhancing rock porosity connectivity. These macropores significantly influence granite's physico-mechanical and permeability characteristics. A mineral stability analysis revealed that various minerals undergo physico-chemical reactions, such as dehydration, phase transitions, decomposition, and chemical bond fractures at elevated temperatures, altering mineralogical composition and mineral strength, thus impacting the rock's macroscopic properties. Ultimately, the study delved into the damage mechanisms of granite's physico-mechanical properties from both heating and cooling perspectives during various temperature phases. The insights garnered from this investigation offer novel value in comprehending the thermal damage characteristics induced by LN2 cooling.