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BackgroundNumerous clinical studies have shown that patients suffering from functional constipation can benefit by combining medication with acupuncture. There have been no published reviews or meta-analyses regarding the use of acupuncture in treating functional constipation in older adults. Therefore, we carried out a meta-analysis to assess the impact of acupuncture on elderly patients dealing with functional constipation.MethodsThis study retrieved randomized controlled trials (RCTs) on acupuncture therapy for functional constipation in the elderly from several electronic databases, including Embase, PubMed, Cochrane Library, Wanfang Database, Chinese BioMedical Literature Database, and China National Knowledge Infrastructure. In these databases, clinical investigators evaluated the effectiveness of acupuncture as a primary treatment for elderly people with functional constipation. The Cochrane Handbook for Systematic Reviews of Interventions was used by researchers to evaluate the quality of the study.ResultsA total of 469 elderly individuals were included in 8 RCTs. The meta-analysis yielded compelling findings: the application of acupuncture has significantly elevated the rates of treatment effectiveness compared to the control group. Compared with the control group, the treatment group exhibited a statistically significant difference in complete spontaneous bowel movements after treatment. The two groups showed no significant difference in spontaneous bowel movements. However, there was a significant difference in the Bristol Stool Scale scores. The Defecation Difficulty Score and Patient Assessment of Constipation Quality of Life (PAC-QOL) showed p-values that indicated no significant effect. However, acupuncture improved bowel movements, demonstrating a significant difference in the Clinic Constipation Score (CCS) when comparing the two groups. The Nitric Oxide Synthase (NOS) and 5-Hydroxytryptamine (5-HT) contents changed significantly after intervention in both groups. An article reported that the improvement of traditional Chinese medicine (TCM) symptom scores was better in the treatment group than in the control group.ConclusionThe analysis results indicated that acupuncture can be beneficial for elderly people with functional constipation; however, strong and comprehensive data are not yet obtainable. Given that our study is based on evidence that is of a low-to-moderate quality, further high-quality research is necessary to enhance the feasibility and practicability of this treatment.Systematic review registrationhttps://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024533215.

In recent years, negative Poisson's ratio structures have attracted many scholars' attention as a result of their distinctive mechanical properties and exceptional energy absorption ability. However, the geometry of structures with negative Poisson's ratio is generally complex, and the preparation of the model has become problematic. Therefore, the increasingly mature additive manufacturing industry can be used to prepare three-dimensional models. In this paper, five negative Poisson's ratio structures were fabricated by 3D printing, and cementitious materials were poured onto them. The purpose of this study is to investigate the mechanical properties of different structural reinforced concrete specimens under in-plane quasi-static uniaxial compression and obtain the deformation and failure modes of different structural reinforced concrete specimens. In the experiment, two-dimensional digital image correlation (2D-DIC) and acoustic emission (AE) techniques were used to obtain plane displacement and internal damage evolution, and the plane strain field was calculated using Vic-2D software. The experimental results show that the ductility and energy absorption capacity of structural reinforced concrete specimens have been significantly improved, and there are significant differences in the performance of different structural reinforced concrete due to different deformation modes.

Three-dimensional (3D) printed polymer-reinforced cementitious composites are expected to be used to improve the ductility of cement-based materials. However, research on the maximum flexural capacity and failure mode of lattice-reinforced cementitious composites remains insufficient. In this study, six types of cells with different volume fractions are designed, and mainly undergo bending and tensile deformation. According to the load characteristics during a three-point bending test, five kinds of graded lattice structures are designed. Moreover, a skin-lattice structure and uniform lattice structure are designed, and plain cement mortar is set to comprehensively evaluate the bending mechanical properties of graded lattice-reinforced cementitious composites. The crack evolution and failure mode of these composites under three-point bending load are studied using digital image correlation (DIC). The results show that compared with the uniform lattice, the graded lattice can improve the maximum bending capacity of cement-based materials, improve their cracking characteristics and failure modes during the bending process, and enhance their toughness while reducing the amount of required material. Compared with the plain cement mortar specimen, the graded lattice-reinforced specimen with the largest bending peak load is found to have a 175% increase in the bending peak load and a significant increase in the bending bearing capacity.

The lattice-reinforced cementitious composites prepared by placing 3D printed lattices in cementitious matrix has been proved to be effective in improving the bending mechanical properties of cement-based materials, such as improving ductility and brittleness. However, the compressive properties of 3D printed lattice-reinforced cementitious composites are still an open question. In this paper, the compressive properties of 3D printed polyamide 6 (PA6) lattice-reinforced cementitious composites with different structural forms were studies. Six kinds of lattices were fabricated by multi jet fusion (MJF) technique. The volumes of these lattices are identical to ensure that the volume enhancement ratio of the lattices in the cementitious composite specimen is the same. The plain cementitious matrix without lattice was set as the control group, and two nondestructive testing methods, AE and DIC, were used to compare the compressive properties between plain cementitious matrix and lattice-reinforced cementitious composites with different structural forms. The experimental results show that the 3D printed lattice can significantly improve the mechanical properties and failure modes of cement-based materials under uniaxial compression. In contrast, the six lattice forms used in this study can improve the maximum compressive bearing capacity and deformation capacity of the cement-based materials under uniaxial compression test, and reduce the damage of cement-based materials in the elastic deformation stage. This paper confirms that 3D printed lattices can improve the compressive properties of cement-based materials and provide a new method for improving the compressive strength of cement-based materials. At the same time, it provides new ideas for the development of ideal substitutes for steel bars in corrosive environments, energy conservation and emission reduction and the development of green buildings.

This paper presents a machine learning approach to localizing a five-peak narrow-band modulated sinusoidal signal excitation source within a composite panel. In particular, the Back Propagation (BP) neural network is used. The idea is to use the arrival time of the first wave packet in a five-peak wave signal to locate their source. Specifically, this paper divides the composite material board into multiple regions, designs 8 receiving points to receive the signal from the excitation source, and finds the region where each source is located. The COMSOL numerical simulation platform is used to build a composite plate model and simulate the propagation of five-peak waves to train and test the machine learning network. Correspondingly, carry out experimental verification and use a scanning laser Doppler vibrometer (SLDV) to build a non-contact experimental platform to obtain the wave field information in the composite material plate. The results show that BP neural networks can learn to map signal features to their sources in both contexts.

Microcapsule self-healing technology is an effective scheme to improve the durability of cementitious composites. In this paper, the compressive properties of microcapsule-based self-healing cementitious composites after freeze-thaw cycles were studied using acoustic emission (AE), and the changes in AE characteristics, compressive strength, mass loss rate, and electric flux of microcapsule-based self-healing cementitious composites with different microcapsule contents and freeze-thaw cycles were studied. The results show that if the content of the microcapsule is appropriate, with the increase in the number of freeze-thaw cycles, the AE hits will generally increase first and then decrease, and the early AE events will also decrease. Because of the different contents of microcapsules, the improvement effect and defect effect change dynamically with the number of freeze-thaw cycles, which is also reflected in the dynamic process of compressive strength. After 100 freeze-thaw cycles, the compressive strength of self-healing cementitious composite samples with 5% content of microcapsules and 3% content of microcapsules is the highest. The changes in mass loss rate and electric flux are similar to the AE characteristic parameters, which further verifies the results of AE. The research results of this paper provide experimental data and experimental methods for the engineering application of microcapsule self-healing cement-based composites in cold areas.

This study introduces a methodology for detecting the location of signal sources within a metal plate using machine learning. In particular, the Back Propagation (BP) neural network is used. This uses the time of arrival of the first wave packets in the signal captured by the sensor to locate their source. Specifically, we divide the aluminum plate into several areas, design eight receiving points for receiving the excitation signal, and determine the location of each sound source. In order to train and test the machine learning network, the aluminum plate model was established using the COMSOL numerical simulation platform and the propagation of five peak waves was simulated. Correspondingly, experimental verification was carried out and a scanning laser Doppler vibrometer (SLDV) was used to build an experimental platform to collect the corresponding wave field information to obtain a data set for machine learning. The results show that the trained BP neural network can classify the sound source region in both environments.

In this paper, the tensile tests of SiCp/Al composites were carried out, and the acoustic emission (AE) method was used to monitor the damage progress. The collected signals were analyzed in time-frequency domain. The AE signals were analyzed by principal component analysis (PCA) and fuzzy clustering method (FCM) to characterize the damage mode and failure mechanism of SiCp/Al composites. Three main damage modes of SiCp/Al composites were identified by FCM clustering: SiC/Al interface debonding, Al fracture and SiC particle fracture. After the tensile test, the fracture surface was analyzed by scanning electron microscope (SEM). The results of SEM and energy spectrum analysis confirmed the results of AE. The research results of this paper provide experimental support for the design and engineering application of SiCp/Al composites.

The present article investigates the microstructure and mechanical properties of A356 matrix composite reinforced with TiB2 particles synthesized by the salt metal reaction of as-cast and T6 state. Microscopic observations of the prepared composites reveal that in-situ grown TiB2 particles are characterized with regular shapes and nearly uniform distributed in the A356 matrix. A clear interface between the A356 matrix and TiB2 particles was observed. The detailed analysis of mechanical properties of synthesized composites of as-cast and T6 state show that the ultimate tensile strength and Young’s modulus of the synthesized composites increased with the increasing weight percentage (wt%) of in-situ TiB2 particles in the A356 matrix, but the Poisson’s ratio of the synthesized composites decreased with the increase of TiB2 particles wt%. The Young’s modulus of the composites increased by up to 10.8% and the Poisson’s ratio decreased by up to 3.2% with the increase of TiB2 particles wt%, compared to A356 alloy. With the increase of TiB2 particle wt%, the yield strength of the composites decreased at first (when the TiB2 particle wt% is less than 1%) then increased, while elongation and percent reduction in area increased at first and then decreased. Furthermore, T6 heat treatment can refine grain and effectively improve the mechanical properties of composites.

Soil salinization is one of the current global environmental problems. Current research on crops in saline-alkali land focuses on salt tolerance, but less on its ecological benefits. However, plants and the environment can interact and influence each other, which is the theory used to carry out Nature-based Solutions (NbS). Therefore, the research on crop plants with both ecological and economic benefits is novel and valuable work. Then three widely planted cash crops (Solanum melongena, Momordica charantia, Capsicum annuum) were selected for salt stress treatment (NaCl, 150mmol/L), some physiological indicators (chlorophyll, soluble protein, Proline (Pro), malondialdehyde (MDA)) of plant and the soil properties (electrical conductivity, pH, the soil salt content) were measured. The results showed that the salinity content of the three plant cultivation soils was significantly different (P

In this work, two types of self-healing composite laminates with embedded 6 and 12 wt% microcapsules respectively, were prepared. The guided waves were activated and captured using piezoelectric transducer in a pitch-catch approach. Mode I interlaminar fracture tests were conducted using double cantilever beam specimens, and the effects of concentration of microcapsules on the interlaminar properties of specimens were investigated. The interlaminar fracture surfaces of self-healing specimens were observed to support the analysis of mechanical tests and guided wave detecting results. The results show that the self-healing efficiency of specimens with high-concentration microcapsules is less than that of specimens with low-concentration microcapsules. Meanwhile, low-concentration microcapsules reduce the interlaminar properties of specimens. Two guided-wave parameters, namely signals peak value and waveform similarity, were set and correlated with the self-healing capability of specimens. When the specimens were damaged, the peak value of response signals decreases, and the waveform difference between the response signal and reference signal becomes larger. When the specimens were healed, the peak value of response signals rises, and the waveform difference between them becomes smaller.

In this paper, the model of SiC reinforced superalloy composite with different fiber content is established by Monte Carlo simulation method. The process of hot isostatic pressing of SiC reinforced superalloy composite is simulated, and the residual stress distribution under different fiber content is obtained. The results show that not only the fiber content has a great influence on the residual stress of hot isostatic pressing of SiC reinforced superalloy composite, but also the fiber distribution has a great influence on the residual stress. It is necessary to establish a finite element model of different fiber distribution to simulate the process of hot isostatic pressing of SiC reinforced superalloy composite.

In this paper, the residual stresses in hot isostatic pressed SiC/GH4738 composites were investigated using numerical simulation. First, the finite element model of the SiC/GH4738 composites was built using ABAQUS. Then, the hot isostatic press process was simulated, where the paths of temperature and pressure were considered. The residual stress distributions were obtained, and the changes in interfacial residual stresses with angle were analyzed. Finally, the effect of process parameters on residual stresses was analyzed. The simulation results show that maximum temperature, holding time, and fiber volume content have little influence on the distribution of interface residual stress but have great influence on the magnitude of interfacial residual stress. The results will help to influence the design and preparation of SiC/GH4738 composites.

In this paper, the mechanical properties of 3D printed PLA lattice structures were studied using digital image correlation (DIC), and the effect of process parameters on the mechanical properties of the samples was discussed. First, tensile samples and lattice structures of the PLA were prepared by Fused Deposition Modeling (FDM). Then the tensile experiments were carried out on the tensile samples, and the tensile strength and elastic modulus were obtained. Moreover, the compressive experiments were carried out on the 3D printed PLA lattice structures, and the yield strength, plastic platform stress and densification strain were obtained. The full field displacements and strains were obtained using DIC. Finally, scanning electron microscope (SEM) was used to study the cross-section of the sample, and the mechanism of the influence of process parameters on the sample was analyzed. The experimental results show that as the printing temperature increases, the tensile strength and elastic modulus tend to rise first and then decrease. When the printing temperature is 230 °C, the maximum tensile strength is 50.16 MPa, and the tensile elastic modulus is 4340.38 MPa. While the yield strength, plastic platform stress and densification strain of lattice structures show a downward trend. As the printing speed increases, the tensile strength and elastic modulus show an upward trend, and when the printing speed is 60 mm/min, the tensile strength and elastic modulus are 51.47 MPa and 5102.12 MPa respectively. Moreover, the yield strength, plastic platform stress of lattice structures show a downward trend, densification strain show an upward trend.

In this paper, the residual stress of SiC-reinforced GH4738 composites processed by hot isostatic pressing was studied using the finite element method. First, the unit cells with different fibers and uniform fiber content were constructed using Abaqus. Then, the pressure and temperature conditions were considered, and hot isostatic pressing process was simulated. The residual stresses of different unit cells were obtained, and the effect of the cell form on the residual stress of the SiC-reinforced GH4738 composites was analyzed. Finally, the maximum residual stresses of different unit cells were compared, and the effects of the simulation methods and models were discussed. The results show that different cell types have little effect on the maximum residual stress with the maximum deviation of approximately 20%, and the differences between most cells of less than 5%. The cell stress distributions in different forms are affected by the distribution of the fibers, and the maximum residual stress appears at the interface between the fiber and the matrix.

ABSTRACT: Determining the interfacial properties of thermal barrier coatings (TBCs) is imperative for their durability evaluation and further improvements. A ceramic coating (topcoat) and a NiCoCrALY bondcoat were atmospheric-plasma-sprayed (APS) on a stainless steel substrate. A modified three-point bending test was adopted to initiate and propagate the topcoat/bondcoat (TC/BC) interfacial crack. After a complete delamination, the fracture surfaces were examined by an optical microscope, which shows that the cracking plane was merely on the TC/BC interface. Based on the experimental results of load–displacement and crack length–displacement, the strain energy release rate G for crack propagation was calculated, and the averaged magnitude was 77.1 J/m2. Repeatable results have indicated that the method can be used for the evaluation of interfacial fracture toughness in thermal barrier coatings and other multi-layer structures. Keywords: Thermal barrier coatings, Three-point bending, Interfacial fracture toughness

In aerospace engineering, many titanium alloy structures are subjected to fatigue loads and thus fail. Based on the Seeger fatigue life theory and the improved Lemaitre damage evolution theory, the fatigue behavior of four Ti2AlNb alloys is investigated. First, finite element models of four structural parts are established by ABAQUS software. Meanwhile, the fatigue life of four Ti2AlNb alloys is predicted by referring to the damage model parameters determined by previous work. Under the same initial conditions, the average errors of the predicted fatigue lives of the four structural parts are 20.1, 19.8, 20.9, and 19.5 %, respectively. The effects of load amplitude, temperature, and structural characteristics on the fatigue properties of Ti2AlNb alloy structural parts are studied. The stability of the two fatigue life simulation methods is analyzed. By comparing fatigue data of Ti2AlNb structural parts from various literature, the rationality of the simulated data is confirmed. Finally, the application of the Ti2AlNb structural fatigue database to machine learning is illustrated. These results provide a numerical simulation method for evaluating the fatigue life of various Ti2AlNb alloy aviation structural parts. [ABSTRACT FROM AUTHOR]

Many titanium alloy subcomponents are subjected to fatigue loading in aerospace engineering, resulting in fatigue failure. The fatigue behavior of Ti2AlNb alloy subcomponents was investigated based on the Seeger fatigue life theory and the improved Lemaitre damage evolution theory. Firstly, the finite element models of the standard openhole specimen and Y-section subcomponents have been established by ABAQUS. The damage model parameters were determined by fatigue tests, and the reliability of fatigue life simulation results of the Ti2AlNb alloy standard open-hole specimen was verified. Meanwhile, the fatigue life of Ti2AlNb alloy Y-section subcomponents was predicted. Under the same initial conditions, the average error of fatigue life predicted by two different models was 20.6%. Finally, the effects of loading amplitude, temperature, and Y-interface angle on fatigue properties of Ti2AlNb Y-section subcomponents were investigated. These results provide a new idea for evaluating the fatigue life of various Ti2AlNb alloy subcomponents. [ABSTRACT FROM AUTHOR]