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Analysis of land system resilience: Static and dynamic perspectives

Land system face multiple threats due to the long-term effects of climate change, global geopolitical and economic. Our research simulates the static and dynamic resilience of land systems under increasing socioeconomic pressures and frequent disturbances from natural disasters. We use an improved load-capacity model to simulate the cascading failure effects of agricultural land systems. The study finds that parameters change after deliberate attacks much earlier than random attacks that cause network collapse. The core nodes in the trade structure carry most of the functions, and such regions and land types should be focused on. Cascading failures make the network more vulnerable due to the transmissibility of pressure. Static attacks can cause network collapse when more than 30% of nodes are attacked, while dynamic attacks only need to attack 10% of nodes. According to parameter optimization, the node capacity should be maximized while reducing the gap in the initial load of the nodes, thereby weakening the cascading effect. To ensure the reliability of the results, the article conduct robustness tests. Finally, in order to develop sustainable land systems, the article propose that it is necessary to assess resilience, identify key elements, effectively monitor land systems, and develop sound land protection plans.

Digital Fracture Surface Morphology and Statistical Characteristics of Granite Brazilian Tests after Non-Steady-State Thermal Disturbance

With the widespread advent of digital technologies, traditional perspectives in rock mechanics research are poised for further expansion. This paper presents a Brazilian test conducted on granite after non-steady-state thermal disturbance at 25 °C, 200 °C, 400 °C, and 600 °C, with detailed documentation of the damage process and failure response using an acoustic emission (AE) apparatus and a digital image correlation (DIC) system. Subsequently, utilizing point cloud data captured by a three-dimensional (3D) laser scanning system, a digital reconstruction of the failed specimen’s fracture surface was accomplished. The 3D fractal characteristics and roughness response of the digitized fracture surface were studied using the box-counting method and least squares approach. Furthermore, texture information of the digitized fracture surface was calculated using the Gray Level Co-occurrence Matrix (GLCM), and statistical characteristics describing the elevation distribution were analyzed. The results elucidate the influence of thermal disturbance temperature on the mechanical parameters of the specimen, acoustic emission behavior, surface strain field evolution, and digital fracture morphology characteristics. The findings indicate a non-linear degradation effect of temperature on the specimen’s tensile strength, with a reduction reaching 80.95% at 600 °C, where acoustic emission activity also peaked. The rising thermal disturbance temperature inhibited the crack initiation load at the specimen’s center but expanded the high-strain concentration areas and the growth rate of horizontal displacement. Additionally, varying degrees of linear or non-linear relationships were discovered between thermal disturbance temperature and the 3D fractal dimension of the fracture surface, average roughness (Ra), peak roughness (Rz), and root mean square roughness (Rq), confirming the potential of Rsm in predicting the 3D fractal dimension of Brazilian test fracture surfaces. The study of the GLCM of the digitized 3D fracture surface demonstrated a high dependency of its four second-order statistical measures on thermal disturbance temperature. Finally, the statistical parameters of the fracture surface’s elevation values showed a significant non-linear relationship with thermal disturbance temperature, with a critical temperature point likely existing between 400 and 600 °C that could precipitate a sudden change in the fracture surface’s elevation characteristics.

Cold atom technology applied to ultra-high vacuum (UHV) measurements

Accurate measurements in ultrahigh vacuum (UHV) are increasingly critical for scientific research and industrial applications. Here, we report an experimental study of UHV measurements performed on a 7Li cold atom vacuum measurement setup. The setup enables cold atom vacuum measurements in the magneto-optical and magnetic traps (CAVM-MOT and CAVM-MT), respectively. The precision of the vacuum measurements in both traps was effectively improved after optimisation of the excited-state fraction data processing for CAVM-MOT and the initial loading control method for CAVM-MT. A comparison of the measurement methods was carried out in combination with an ionisation gauge, revealing the good linearity and accuracy of the CAVM. We believe that CAVM in the two potential traps have their own application situations and development directions, respectively.

Preventing Microbial Growth in Game Meat by Applying Polyphenolic Extracts from Olive Mill Vegetation Water.

We studied the efficacy of different formulations of polyphenol extracts (mainly containing hydroxytyrosol and tyrosol) from olive mill vegetation water on the microflora on the surfaces of game meat cuts with high or low initial bacterial loads. Meat with a high microbial load (>5 Log cfu/g; mean value = 6.83 ± 0.45 standard deviation) was immersed for 10 or 60 sec into 25% and 10% solutions of microencapsulated freeze-dried and non-encapsulated polyphenolic extracts. Aerobic colony, Enterobacteriaceae, Pseudomonas spp., and lactic acid bacteria counts were determined on treated samples compared to controls after 7 days of storage (in vacuum-packed conditions at +3 °C). Significant differences were registered only for aerobic colony count for a 10% liquid extract treatment (0.64 log reduction). In contrast, the dipping or immersion of game meat with low initial microbial loads (<5 Log cfu/g; mean value = 3.58 ± 0.72 standard deviation) in 10% solutions of the polyphenol extracts effectuated significant reductions in all bacteria counts (p < 0.002) at 7 and 14 days of storage for different extracts, independently from the application methods. The use of the extracts to inhibit bacterial growth in game meat should only be considered if a good hygienic baseline is guaranteed.

Optimum Stochastic Allocation for Demand Response for Power Markets in Microgrids

This research incorporates an electricity market model based on a stochastic allocation of distributed resources and the analysis of an optimal demand response for a smart microgrid. This research develops a methodology that allows the application and comparison of various demand-response mechanisms and the analysis of the differences between them and the case of no-demand response, emphasizing economics, environmental care, demand curves, and other factors. By enabling more active participation by residential users of the smart microgrid, these demand-response methods help to flatten the demand curve and support the goals set by the electricity market model. Both conventional and non-conventional generators compete in the electricity market, with renewable energy sources preferred to encourage green generation. Conventional generators are required to supply electricity gradually, starting with the lowest pollution level. In addition, conventional generators are compensated for dispatch, system reliability, and availability. In addition, random variables are used in this study to predict initial load, solar radiation analysis, and biomass input before resources are optimized to meet demand.

A relationship of tightening torque and initial load of dental implant of nano bio-silica and bamboo fiber-reinforced bio-composite material

Due to entry of body fluid like saliva, blood, etc. in the dental implant assembly lowers the preload value, thus dental implant abutment tightening torque loses. In this article a novel chitosan-reinforced bamboo and nano bio-silica-reinforced five composite materials (CP, CF, C1, C2, and C3) are fabricated using the hand layup method, and their mechanical, biocompatible, and moisture absorption properties are observed and discussed. The present study examines the impact of friction and Young’s modulus on the correlation between torque and starting load in dental implant abutment screws, utilizing the attributes of a bio-composite material. C2 bio-composite composite material exhibits the highest tensile strength (139.442 MPa), flexural strength (183.571 MPa), compressive strength (62.78 MPa), and a minimum value of 1.35% absorption of water. C3 is tested with no cytotoxicity, while C3 and CF exhibit weak biofilm resistance against S. aureus gram-positive bacteria. The C2 bio-composite material demonstrated a maximum initial load of 20 N with a tightening torque of 20 N-cm, under both 0.12 and 0.16 coefficients of friction. The simulated results were compared with several theoretical relations of torque and initial load and found that the Motos equation holds the nearest result to the obtained preload value from finite element analysis. Overall, the experimental findings suggest that the C2 bio-composite material holds significant potential as a prominent material for dental implants or fixtures.

Temperature Control and Data Exchange in Food Supply Chains: Current Situation and the Applicability of a Digitalized System of Time–Temperature-Indicators to Optimize Temperature Monitoring in Different Cold Chains

The current situation of temperature monitoring in perishable food supply chains and the optimization of temperature control was studied by combining two approaches. First, a survey among German companies (production, processing, logistics, wholesale, retail) was conducted to analyze the current temperature monitoring and data management conditions as well as the use of novel monitoring systems, such as Time–Temperature-Indicators (TTIs). Second, the temperature conditions in three different supply chains (B2C for raw pork sausage, B2B for fish, B2C e-commerce for mixed products) were investigated to analyze the applicability of TTIs with an app-based read-out system to identify weak points and to optimize cold chain management under practical conditions. The results of the survey showed that mainly static conditions are tested along the supply chain. Thus, the actors rely mostly on visual inspection or best-before date labeling while TTIs are not widely used. Currently, temperature data are barely exchanged by stakeholders. In the B2C chain, mean temperatures on different pallet levels were comparable, also reflected by TTIs and the app-based read-out system, respectively. In the B2B chain, temperature interruptions during the unloading process were detected, revealing main challenges in perishable supply chains. Temperature monitoring by TTIs on a box level was possible by positioning the label close to the product. Results in the e-commerce sector showed heterogeneous conditions in different boxes depending on initial product temperatures and loading. TTIs and the app-based read-out system showed reliable results based on different temperature scenarios, when TTIs are positioned close to the most sensitive product.

Multi-method comparison and multi-index evaluation of cracking characteristics of asphalt mixture

The micro crack inside asphalt pavement are potential and antecedent factors for macroscopic cracking of the pavement. The position and quantity of micro cracks have a significant impact on the service life and failure mode of asphalt pavement. The purpose of this study was to conduct multi-scale analysis and multi-index evaluation on the whole process of generation, expansion, and transformation of micro-crack inside asphalt pavement (asphalt mixture) based on multiple testing methods. Firstly, synchronous tests were conducted on the cracking process of asphalt mixture by using three-point bending loading method, acoustic emission (AE) monitoring method, and digital image correlation (DIC) analysis method. Secondly, a three-dimensional finite element model of the asphalt mixture beam was established for AE source location simulation. Finally, the advantages and limitations of multi-methods were compared and analyzed. The principal strain points with different sizes were randomly distributed in the tensile area of the asphalt mixture beam bottom at the initial loading stage, and the number of the principal strain points increased with the decrease of the loading rate. The macroscopic main crack of the asphalt mixture beam generated and expanded from the maximum principal strain point (P1) at the later loading stage. The AE dominant-frequency distribution ranges of micro-crack expanding process, macro-crack generating process, and failure process of asphalt mixture beam were 78.125–156.25 kHz, 234.375–312.5 kHz, and 0–78.125 kHz, respectively. Four stages of damage evolution and cracking process inside the asphalt mixture beam were obtained by the AE source location simulation. A comprehensive and systematic evaluation of bending cracking characteristics of asphalt mixture beam was realized by obtaining multiple indexes from multiple scales with multiple methods.

Strength Reduction Method for the Assessment of Existing Large Reinforced Concrete Structures

This work presents a new developed assessment methodology based on strength reduction and finite element methods which is suitable for existing large reinforced concrete structures commonly used in hydraulic constructions. The methodology is based on a reloading phase of the finite element model and is preceded by an intermediate reduction phase of concrete tensile strength and an initial loading phase up to service level. Rosenblueth’s point estimate method was used to compute a global resistance factor and to deduce a design resistance value of the structure. After validations, the methodology was applied to two existing complex and large hydraulic structures: a spiral case and a draft tube. If compared with existing methodologies using sophisticated non-linear finite element methods, the developed approach is simpler, more practical, and provides results that are on the conservative side. Considering the difficulties in characterizing the tensile peak and post-peak strength of concrete, along with uncertainties regarding the damage conditions of facilities, the developed methodology is deemed robust and well suited for assessing existing critical large reinforced concrete infrastructures.

Factors influencing the early neurological deterioration in intracranial branch atheromatous diseases

AbstractBackgroundIntracranial branch atheromatous disease (BAD)‐type cerebral infarction is often associated with a progressive worsening of neurological symptoms in the acute phase.AimTo investigate the factors influencing the occurrence of early neurological deterioration (END) in patients with BAD.MethodsWe included and evaluated 198 consecutive patients (150 patients with lenticulostriate artery [LSA‐BAD] and 48 patients with paramedian pontine artery [PPA‐BAD]) with onset within 24 h and with a modified Rankin scale score of ≤1 before admission for END retrospectively out of 235 patients with BAD‐type cerebral infarction admitted to our hospital from January 2019 to March 2023.ResultsEND was observed in 26 (17%) and 15 (31%) patients with LSA‐BAD and PPA‐BAD, respectively. Patients in the END group with LSA‐BAD had significantly higher rates of diabetes mellitus and blood glucose (BG) levels on admission and lower rates of initial clopidogrel loading therapy than those in the non‐END group. Patients in the END group with PPA‐BAD had significantly higher BG levels on admission than those in the non‐END group. In LSA‐BAD multivariate analysis, the BG level on admission and initial clopidogrel loading were identified as factors influencing END (BG level [per 10 mg/dL], odds ratio [OR] 1.084, 95% confidence interval [CI] 1.008–1.166; initial clopidogrel loading, OR 0.302, 95% CI 0.101–0.901).ConclusionsHigher BG levels at stroke onset were associated with END in patients with LSA‐BAD and PPA‐BAD. Additionally, initial clopidogrel loading therapy suppressed END in patients with LSA‐BAD.

A Study of Resistome in Mexican Chili Powder as a Public Health Risk Factor.

Chili powder is an important condiment around the world. However, according to various reports, the presence of pathogenic microorganisms could present a public health risk factor during its consumption. Therefore, microbiological quality assessment is required to understand key microbial functional traits, such as antibiotic resistance genes (ARGs). In this study, metagenomic next-generation sequencing (mNGS) and bioinformatics analysis were used to characterize the comprehensive profiles of the bacterial community and antibiotic resistance genes (ARGs) in 15 chili powder samples from different regions of Mexico. The initial bacterial load showed aerobic mesophilic bacteria (AMB) ranging between 6 × 103 and 7 × 108 CFU/g, sporulated mesophilic bacteria (SMB) from 4.3 × 103 to 2 × 109 CFU/g, and enterobacteria (En) from <100 to 2.3 × 106 CFU/g. The most representative families in the samples were Bacillaceae and Enterobacteriaceae, in which 18 potential pathogen-associated species were detected. In total, the resistome profile in the chili powder contained 68 unique genes, which conferred antibiotic resistance distributed in 13 different classes. Among the main classes of antibiotic resistance genes with a high abundance in almost all the samples were those related to multidrug, tetracycline, beta-lactam, aminoglycoside, and phenicol resistance. Our findings reveal the utility of mNGS in elucidating microbiological quality in chili powder to reduce the public health risks and the spread of potential pathogens with antibiotic resistance mechanisms.

Effects of processing conditions on the release of sodium chloride from fat crystal ‘shell’ stabilised water-in-oil emulsions

Over the last two decades, water-in-oil fat crystal stabilised Pickering emulsions have been increasingly studied for the controllable release of encapsulated (water-soluble) species. The stability inherent to Pickering emulsions has been shown to be enhanced by sintering to form an interfacial lipid 'shell' around the droplets, which improves the retention and prolongs the delivery of the enclosed species. Using a scraped surface heat exchanger/pin stirrer setup, the present work shows that processing conditions used to produced W/O emulsions with dispersed droplets enclosed in lipid shells, have a significant impact upon the subsequent release of NaCl enclosed within them. The best performing emulsion structure produced here is reported to retain about 98% of its initial salt load over a period of 100 days. NaCl release profiles were also used to calculate the interfacial rate constants for the transferal of salt across the lipid shells. Interfacial rate constants ranged from 5.5 to 3593.2×10−3 nm2/s and were significantly (up to three orders of magnitude) lower than those reported in literature for similar systems. Analysis revealed that depending on the specific conditions employed, the processing environment can enhance or compromise lipid shell integrity. Overall, the current study offers significant direction in terms of the optimum processing requirements that are necessary to produce fat-continuous emulsion microstructures that can successfully regulate the release of NaCl, paving the way for the successful development of food formulations of controlled salt-perception.

Cues to land softly and quietly result in acute reductions in ground reaction force loading rates in runners

BackgroundA common gait retraining goal for runners is reducing vertical ground reaction force (GRF) loading rates (LRs), which have been associated with injury. Many gait retraining programs prioritize an internal focus of attention, despite evidence supporting an external focus of attention when a specific outcome is desired (e.g., LR reduction). Research QuestionDoes an external focus of attention (using cues for quiet, soft landings) result in comparable reductions in LRs to those achieved using a common internal focus (forefoot striking while barefoot)? MethodsThis observational study included 37 injured runners (18 male; mean age 36 (14) years) at the OMITTED Running Center. Runners wore inertial measurement units over the distal-medial tibia while running on an instrumented treadmill at a self-selected speed. Data were collected for three conditions: 1) Shod-Control (wearing shoes, without cues); 2) Shod-Quiet (wearing shoes, cues for quiet, soft landings); and 3) Barefoot-FFS (barefoot, cues for forefoot strike (FFS)). Within-subject variables were compared across conditions: vertical instantaneous loading rate (LR, primary outcome); vertical stiffness during initial loading; peak vertical GRF; peak vertical tibial acceleration (TA); and cadence. ResultsVertical LR, stiffness, and TA were lower in the Shod-Quiet compared to Shod-Control p < 0.001). Peak vertical GRF and cadence were not different between Shod-Quiet and Shod-Control. Reductions in stiffness and LR were similar between Shod-Quiet and Barefoot-FFS, and GRF in Barefoot-FFS remained similar to both shod conditions. However, runners demonstrated additional reductions in TA and increased cadence when transitioning from Shod-Quiet to the Barefoot-FFS condition (p < 0.05). SignificanceThese results suggests that a focus on quiet, soft landings may be an effective gait retraining method for future research.

Fracture Performance Study of Carbon-Fiber-Reinforced Resin Matrix Composite Winding Layers under UV Aging Effect.

There is limited research on the fracture toughness of carbon-fiber-reinforced polymer (CFRP) materials under accelerated UV aging conditions. In this study, the primary focus was on investigating the influence of varying durations of ultraviolet (UV) irradiation at different temperatures on the Mode I, Mode II, and mixed-mode fracture toughness of CFRP laminates. The results indicate that with increasing UV aging duration, the material's Mode I fracture toughness increases, while Mode II fracture toughness significantly decreases. The mixed-mode fracture toughness exhibits an initial increase followed by a subsequent decrease. Furthermore, as the aging temperature increases, the change in the fracture toughness of the material is more obvious and the rate of change is faster. In addition, the crack expansion of the composite layer of crack-containing Type IV hydrogen storage cylinders was analyzed based on the extended finite element method in conjunction with the performance data after UV aging. The results reveal that cracks in the aged composite material winding layers become more sensitive, with lower initiation loads and longer crack propagation lengths under the same load. UV aging diminishes the overall load-bearing capacity and crack resistance of the hydrogen storage cylinder, posing increased safety risks during its operational service.

Rheological and Flexural Strength Characteristics of Cement Mixtures through the Synergistic Effects of Graphene Oxide and PVA Fibers.

This study investigates the synergistic effects of incorporating graphene oxide (GO) and polyvinyl alcohol (PVA) fibers into cement paste mixtures, aiming to modify their rheological properties and flexural behaviors with resistance to crack formation. The relationship between static yield stress and critical shear strain was examined in ten cement paste mixtures with varying concentrations of 6 mm and 12 mm PVA fibers and 0.05% GO. Additionally, viscosity analyses were performed. For the specimens fabricated from these mixtures, flexural strength tests were conducted using the Digital Image Correlation (DIC) technique for precise strain analysis under load history. The results indicated a significant increase in static yield stress, viscosity, and critical shear strain due to the combined addition of GO and PVA fibers, more so than when added individually. Notably, in PVA fiber-reinforced cement mixtures, the integration of GO increased the crack initiation load by up to 23% and enhanced pre-crack strain by 30 to 50%, demonstrating a notable delay in crack initiation and a reduction in crack propagation. Microstructural analyses using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) revealed a concentrated presence of GO around and on the PVA fibers. This promotes increased C-S-H gel formation, resulting in a denser microstructure. Additionally, GO effectively interacts with PVA fibers, enhancing the adherence of hydration products at their interface.

527 - Efficacy of upadacitinib for moderate-to-severe atopic dermatitis: analysis of time spent in skin clearance response states from the Measure Up 1, Measure Up 2, and Heads Up studies

Abstract Introduction/Background Atopic dermatitis (AD) is a debilitating chronic inflammatory skin disease with fluctuating disease severity that requires long-term control. Patients report that complete or almost complete skin clearance is highly important as a treatment goal. Upadacitinib is a selective oral Janus kinase (JAK) inhibitor with greater inhibitory potency for JAK1 vs JAK2, JAK3, and tyrosine kinase 2. Objectives In this post-hoc analysis of the upadacitinib phase 3/3b studies, we analyzed the time patients spent in skin clearance response states over 16 weeks with upadacitinib 15 mg (UPA 15) and 30 mg (UPA 30) compared to placebo and dupilumab. Methods Data were from phase 3/3b multicenter, randomized, double-blinded studies comparing the safety and efficacy of upadacitinib to either placebo (Measure Up 1 and Measure Up 2) or dupilumab (Heads Up) in patients with moderate-to-­severe AD. In the Measure Up 1 and Measure Up 2 studies, adults and adolescents were randomized to receive UPA 15, UPA 30, or placebo once daily for 16 weeks. In the Heads Up study, adults were randomized to receive UPA 30 once daily or dupilumab 300 mg every 2 weeks beginning at week 2 following an initial loading dose of 600 mg. The days patients spent in skin clearance response states based on Eczema Area Severity Index (EASI) improvements ≥75%/90%/100% (EASI 75/90/100) from baseline were assessed. Missing data at study visits were imputed using non-responder imputation. Response states between study visits were interpolated using last observation carried forward. Results Integrated data from Measure Up 1 and Measure Up 2 included 1683 adults and adolescents randomized to UPA 15 (N=557), UPA 30 (N=567), or placebo (N=559); 44.0% were female, and 48.8% had previously received systemic therapy. In the Heads Up study, 673 adults were randomized to UPA 30 (N=342) or dupilumab (N=331); 44.3% were female, and 52.7% had previously received systemic therapy. Patients in Measure Up 1 and 2 taking UPA 15 or UPA 30 cumulatively spent a greater proportion of days in EASI 75 (UPA 15: 54.2%, UPA 30: 64.6%, Placebo: 10.2%), EASI 90 (UPA 15: 32.0%, UPA 30: 44.0%, Placebo: 3.2%), and EASI 100 (UPA 15: 7.5%, UPA 30: 13.5%, Placebo: 0.6%) response states compared to placebo over 16 weeks. In the Heads Up study, patients taking UPA 30 vs dupilumab cumulatively spent a greater proportion of days in EASI 75 (67.1% vs 44.9%), EASI 90 (47.0% vs 23.2%), and EASI 100 (12.6% vs 3.6%) response states over 16 weeks. Conclusions Treatment of moderate-to-severe AD with UPA 15 or UPA 30 resulted in a greater proportion of days spent with higher levels of skin clearance (EASI 75/90/100) compared to placebo over 16 weeks, mirroring findings from the Heads Up study comparing UPA 30 to dupilumab. Increases in time spent with high levels of skin clearance with upadacitinib treatment may reflect improved long-term disease control and translate into more time spent experiencing a better quality of life that is less burdened by AD.

Shear buckling of ship structures rectangular elements

In the work to determine the spectrum of critical loads and the corresponding forms of a rectangular clamped panel (plate) buckling under the action of balanced tangential forces on its contour, the Bubnov-Galerkin method using polynomials in two coordinates is proposed. This problem of the ship skin element pure shift does not have an exact closed solution, and the known approximate solutions require an analysis of their accuracy and reliability. The aim of the work is to obtain and analyze analytical solutions using polynomials of various degrees. Approximating deflection functions satisfying all the boundary conditions of the problem are represented sequentially by polynomials of 10th, 12th, 14th, 16th and 18th degrees in two coordinates with undefined coefficients. The solution of the main differential equation of the problem is found approximately in the integral sense, as a result of which homogeneous systems of linear algebraic equations with respect to unknown coefficients of polynomials are obtained. These systems contain a shear load as a parameter. To obtain eigenvalues (critical loads), the determinants of the systems are equated to zero. Numerical results are obtained in the Maple analytical computing system. For each approximation (polynomial), a power equation with respect to the critical load, the solution of which is paired values differing in signs is obtained. The forms of buckling are oblique waves. For a ship skin square panel, the first form of buckling is a single bulge along the diagonal of the panel. The second form is obtained in the form of two bulges directed in opposite directions (symmetrically-antisymmetrically with respect to the diagonals), etc. The numerical results are compared with the results of other authors. It is established that with an increase in the number of the polynomial terms, the initial critical loads and forms of buckling are specified, first of all.

Effect of stacking angles on crashworthiness of CFRP square tubes considering low-velocity impact damage

To enhance the residual energy‐absorption (EA) of low-velocity impact-damaged CFRP square tubes, this study investigates the influence of stacking angles on the damaged tubes' residual EA. Through simulation and theoretical analysis, a well-designed stacking angles is proposed to optimize the residual EA. Initially, a simplified method of low-velocity impact damage of composite materials is proposed, by which a discontinuous damage mechanics finite element model is established and experimentally verified. Subsequently, various layup sequences are examined, and their impact on energy absorption is evaluated using several performance indices, including initial peak load, average load, energy absorption, specific energy absorption, and crushing load efficiency. The findings demonstrate that the designed stacking angles significantly enhances the residual energy absorption of low-velocity impact-damaged square tubes. Moreover, the study verifies the efficacy of the stacking angles design by investigating actual damage conditions, encompassing factors such as damage size, location, and stress concentration.

Thermal performance evaluation of an indigenously designed small-scale solar parabolic trough collector for manufacturing Indian milk products

ABSTRACT A small-scale solar parabolic trough collector system coupled with a jacketed vessel was designed and evaluated for its performance and quality of the products manufactured in it. The prototype having a 7.026 m2 aperture and 88.38° rim angle was installed in Mehsana, Gujarat, India. The study was conducted in May–June 2022 at different flow rates of sigma therm-k. The useful heat rate ranged from 567.82 W to 861.25 W. The daily average thermal efficiency was obtained in the range of 9.81–14.61% and maximum thermal efficiency achieved during the milk trials was 31.51%. Similarly, maximum absorber temperature achieved during stagnation was 193.4°C and during absorber fluid flow condition was 146.5°C. The maximum convective heat transfer coefficient of 49.5 W/m2K was calculated at Reynold number 1822 and Nusselt number 24.12. It was found that the quality parameters of manufactured milk products were at par with domestic food safety standards. Direct normal irradiance was found to be the most influencing factor followed by the initial milk load. The present system is a potential substitute for various small-scale Indian traditional heat-desiccated milk products, where higher thermal efficiency is not the primary requirement and emphasis is more on the importance of ease of operation.

Crack Propagation Phenomenon in Gangue Concrete Using the Digital Image Correlation (DIC) Method

In order to study the mode I crack propagation mechanism of coal gangue concrete with different contents, the digital image correlation (DIC) method was used to carry out the three-point bending fracture tests on coal gangue concrete with different contents. The results show that the process of the mode I crack propagation of coal gangue concrete with different contents can be divided into three stages as follows: the elastic stage before crack initiation, extended viscoelastic stage, and extended fracture stage. The amount of coal gangue has a significant impact on the crack propagation path. The more the amount of coal gangue, the more the crack penetrates through the coal gangue coarse aggregate, the smaller the bending degree of the failure path, and the faster the crack propagation to the penetration speed. The crack initiation load, ultimate load, external force work, gravity work, and fracture energy all decrease with the increase of the coal gangue content. The data obtained by the DIC method and displacement extensometer are in good agreement, which proves that the DIC method is feasible. Based on the DIC method, before reaching the horizontal displacement on both sides of the crack tip, the horizontal displacement of the horizontal pixel is very small and there is a jump increase after the ultimate load. There are obvious inflection points on the left and right, and the horizontal displacement remains unchanged after the inflection point. After the horizontal displacement field of crack propagation reaches the limit load, there is an obvious limit; the limit gradually extends upward, and the corresponding crack tip strain field is also gradually enhanced. The more the coal gangue is added, the smaller the corresponding horizontal displacement and strain field is at the same limit load moment. The shape of the crack generation area of coal gangue concrete takes the crack tip as the axis of symmetry and is “gourd shaped.” The more the content of the crack, the larger the crack generation area.