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At present, the cylindrical shell was regarded as the dominating structure in underwater vehicles, which raised the crucial significance to research underwater vehicles’ vibration and acoustic radiation features. In this study, the analytical expression of vibration–acoustic theory had been given according to the derivation with the vibration–acoustic theory of ribless cylindrical shell structure. Meanwhile, the effects of key parameters on vibration–acoustic characteristics are investigated including modulus, density, thickness, loss factor, etc. The research shows that the stiffness and damping of the shell directly affected the vibration of the structure. Furthermore, the performance of vibration attenuation and noise reduction of the shell had been enhanced by increasing the modulus, thickness, and loss factor in materials.

To investigate the influence of residual stress on the fracture performance of T-joint welded joints in 6063 aluminum alloy, ABAQUS simulation was utilized to obtain the post-weld residual stress fields for different welding methods. A finite element model for toughness fracture of T-joints was established using the Johnson-Cook constitutive and damage models, aiming to analyze the impact of welding residual stress on fracture performance. The results indicate that under the same tensile rate, residual stress can lead to earlier fracture occurrence in the welded joints, thereby reducing the overall fracture performance. Among the different welding methods, the double-sided corner weld exhibits the best fracture performance, while the butt joint with a backing plate can effectively mitigate the influence of post-weld residual stress on fracture performance. Through the comparison of experiments and simulations, the material constitutive and damage parameters of each welding zone are verified, and the hardness test is carried out. The results indicate that the average hardness in the weld zone is approximately 63.8 HV, which is higher than the average hardness of 60.2 HV in the heat-affected zone. However, both the weld zone and the heat-affected zone have lower hardness values compared to the average hardness value of 81.5 HV in the base metal zone. Furthermore, it is observed that residual tensile stresses are predominantly distributed in the weld zone, which is one of the reasons contributing to the lower hardness at the center of the weld. [ABSTRACT FROM AUTHOR]

With the continuous implementation of the rural revitalisation strategy, the social and economic landscape of China's countryside has undergone significant changes and the structure and functions of rural production space have gradually become more complex and diversified. The theory of rural production space and its multifunctionality provides a new perspective for the study of rural human–land relationship patterns. Taking Western Chongqing, one of the national pilot zones for integrated urban–rural development, as an example, a scientific evaluation index system is established from the perspective of rural production space and its multifunctionality. The evaluation takes into account the consensus indicators of existing academic results, the regional characteristics of Western Chongqing, and relevant policies. On this basis, a regression model is constructed to investigate the factors influencing multifunctional regional differentiation, and a weighted clustering algorithm is used to classify the units in the study area into functional zones. The results of the study are as follows: (1) A multifunctional evaluation system with 24 indicators in five dimensions was constructed through the principle of scientific selection of indicators. (2) All functions in the rural production space of Western Chongqing have the respective geographical differentiation characteristics. In particular, the high-value and low-value agglomerations are generally distributed in strips or clusters, and the high-value and low-value agglomerations are intermingled, with each influencing factor driving the differentiation process of each function in the form of inhibition and reinforcement. (3) Western Chongqing can be divided into four types of functional areas: balanced development, lagging development–ecological recreation, urban development, and modern agriculture. Differentiated development strategies are proposed for different types of functional areas. We conclude that the study of the multifunctional spatial differentiation of rural production and functional zoning can provide a clearer analysis of the current status of rural development in Western Chongqing, and also enriches the perspective and methodology of the study of rural areas in western China. [ABSTRACT FROM AUTHOR]

A 70-day feeding trial was conducted to determine the effects of the replacement of fishmeal (FM) by soybean meal (SM) in diets on growth performance, digestion, hepatic metabolism, antioxidant capacity, and innate immunity of juvenile large yellow croaker (Larimichthys crocea). Four iso-lipidic and iso-nitrogenous diets replacing 0, 15, 30, and 45 FM protein by SM protein were formulated, named FM, SM15, SM30, and SM45, respectively. Results indicated that the specific growth rate (FM = 1.55, SM15 = 1.50, SM30 = 1.48, and SM45 = 1.34%) of fish showed a significant linear trend (P < 0.05). With increasing dietary SM, the activity of trypsin (262.02, 179.34, 144.41, and 123.92 U/mg·prot) significantly decreased (linear trend, P < 0.05). The content of high-density lipoprotein cholesterol showed a significant linear trend and quadratic trend, and the maximum was observed in fish fed the diet with 45% protein from SM (P < 0.05). The mRNA expression of the mechanistic target of rapamycin (m-tor) and ribosomal protein S6 (rps6) showed a significant linear trend (P < 0.05). The content of malondialdehyde (81.82, 92.91, 79.64, and 126.45 nmol/mg·prot) showed a significant linear trend and quadratic trend; the minimum was observed in fish fed the diet with 30% protein from SM (P < 0.05). The activity of acid phosphatase (328.45, 300.08, 254.03, and 223.51 U/mg·prot) significantly decreased with increasing dietary SM substitution levels (linear trend, P < 0.05). A significant quadratic trend was observed in the mRNA expression of interferon-γ and interleukin-1β, while the maximum was observed in fish fed the diet with 45% protein from SM (P < 0.05). In conclusion, this study demonstrated that the replacement of FM by SM in diets can decrease the growth performance, digestion, antioxidant capacity, and innate immunity and affect the hepatic metabolism of juvenile large yellow croaker. The minimum negative effect was obtained when 30% of FM was replaced by SM. [ABSTRACT FROM AUTHOR]

A simple analytical model to estimate the longitudinal strength of ship hulls in composite materials under buckling, material failure and ultimate collapse is presented in this paper. Ship hulls are regarded as assemblies of stiffened panels which idealized as group of plate-stiffener combinations. Ultimate strain of the plate-stiffener combination is predicted under buckling or material failure with composite beam-column theory. The effects of initial imperfection of ship hull and eccentricity of load are included. Corresponding longitudinal strengths of ship hull are derived in a straightforward method. A longitudinally framed ship hull made of symmetrically stacked unidirectional plies under sagging is analyzed. The results indicate that present analytical results have a good agreement with FEM method. The initial deflection of ship hull and eccentricity of load can dramatically reduce the bending capacity of ship hull. The proposed formulations provide a simple but useful tool for the longitudinal strength estimation in practical design.

[Objectives] To explore the influence of core materials on the vibration of composite grid sandwich panels,[Methods] taking the panels as the research object, the vibration response of rubber-core grid sandwich panels and buoyancy-core grid sandwich panels under different conditions is compared by means of experiment, with emphasis given to the analysis of vibration suppression effect of core material on the two composite panels.[Results] The results show that the mid-frequency and low-frequency(0-1 000 Hz) vibration response of the buoyancy-core grid sandwich panels in air is low, while the high-frequency(1 000-3 000 Hz) vibration response of the rubber-core grid sandwich panels is low. The influence of the factors such as the mass of the sandwich panel and the damping of the core on the vibration response of the panel is weakened due to the added mass effect and the added damping effect and the integral of the sandwich structure and the local bending stiffness of the panel are the main factors. The vibration response of the buoyancy-core grid sandwich panel within full-frequency band (0-3 000 Hz) is lower than that of the rubber-core grid sandwich panel.[Conclusions] To reduce the vibration response of the panel, the core stiffness of the grid sandwich panel shall be close to the grid stiffness. In addition, the smaller the density and damping of the core, the greater the difference between the vibration response in air and water.

Fruit color is one of the quality indicators to judge the freshness of a plum. The coloring process of plum skin is valuable for research due to the high nutritional quality of anthocyanins found in plums. 'Cuihongli' (CHL) and its precocious mutant variety 'Cuihongli Red' (CHR) were used to analyze the changes of fruit quality and anthocyanin biosynthesis during plum development. The results showed that, during the development of the two plums, the total soluble solid and soluble sugar contents were highest at the mature stage, as the titratable acid trended gradually downward as the fruits of the two cultivars matured, and the CHR fruit showed higher sugar content and lower acid content. In addition, the skin of CHR turned red in color earlier than CHL. Compared with CHL, the skin of CHR had higher anthocyanin concentrations, higher activities of phenylalanine ammonia-lyase (PAL), chalcone isomerase (CHI), dihydroflavonol-4-reductase (DFR), and UDPglucose: flavonoid-3-O-glucosyltransferase (UFGT), and higher transcript levels of genes associated with anthocyanin production. In the flesh of the two cultivars, no anthocyanin content was detected. Taken together, these results suggest that the mutation exerted a major effect on anthocyanin accumulation via modification of the level of transcription; thus, CHR advances the ripening period of 'Cuihongli' plum and improves the fruit quality. [ABSTRACT FROM AUTHOR]

This article proposes a new grid impedance detection method incorporating the complex coefficient filter (CCF) with full-order capacitor current observer for a T-type three-level grid-connected inverter controlled by the inverter output current feedback. Compared with conventional CCF impedance detection algorithms, the proposed method reduces the number of current sensors and detects the grid impedance accurately. First, based on the sampled inverter output current and grid-connected voltage signals, the grid-connected current is estimated. Then, the CCF method is used to extract harmonics from the grid-connected current and voltage signals to calculate the grid impedance. Finally, the correctness of the full-order capacitor current observer is verified by simulation and the feasibility and effectiveness of the proposed algorithm are verified experimentally based on a laboratory prototype. [ABSTRACT FROM AUTHOR]

Taking certain CNC camshaft grinder as the subject its motion error analysis and modeling were studied. The movement forms and types of errors between the moving parts were analysed, the movement between coordinate systems of the adjacent bodies was used to express the movement between the two adjacent bodies, and the ideal motion equation and actual motion equation in case of errors between the adjacent bodies were set up. Actual motion equation between adjacent bodies was made and further extended to analyse arbitrary low-order body arrays, which provides a theoretical basis for studying the multi-branch CNC camshaft grinding machine error modeling. Complex multi-branch chain CNC camshaft grinder simplified was made as a simple multibody system, and corresponding body coordinate systems and motion reference coordinate systems for moving parts were established to calculate the corresponding transformation matrix between adjacent bodies. Moving parts of the machine were divided into “workpieces-bed” and “wheel-bed” two kinematic chains. The precision constraint equation of the machine is Pt = Pw in case of using errors influence, and the constraint equation was solved. It provides necessary conditions for study of CNC camshaft grinder error compensation. Results show that the machine precision is significantly improved after error compensation.

In the selective laser melting (SLM) process, the experimental approach to determine the optimal process parameters is labor-intensive, material-intensive, and time-consuming. The use of simulation methods also requires more time support and higher hardware requirements. In this paper, a three-dimensional transient heat transfer model and a neural network optimization process parameter model in the process of preparing copper alloys by SLM are developed by combining finite element simulation methods with neural network prediction. The thermal behavior of the multitrack molten pools was investigated by ANSYS APDL, and the effects of different laser powers and scanning speeds on the temperature field and structure dimensions of the molten pools were discussed. The results show that the current single-track has a significant preheating effect on the unmachined single-track and a reheating effect on the machined single-track during the multitrack forming process. The laser power and scanning speed can be controlled to regulate the temperature, 3D size, and heat spread area of the molten pool to avoid over-melting and under-melting. The accuracy of the temperature field model was verified by single-track experiments. A neural network prediction model was constructed to predict the maximum temperature and size of the molten pool by optimizing the backpropagation neural network with a genetic algorithm, providing a methodological guide for the study of SLM process parameters. [ABSTRACT FROM AUTHOR]

A 70-day feeding experiment was carried out to assess the replacement of dietary fishmeal (FM) protein with degossypolized cottonseed protein (DCP) on large yellow croaker (Larimichthys crocea) with initial body weight (13.09 ± 0.50 g). Five isonitrogenous and isolipidic diets replaced fishmeal protein with 0%, 20%, 40%, 60%, and 80% DCP were formulated and named as FM (the control group), DCP20, DCP40, DCP60, and DCP80, respectively. Results displayed that weight gain rate (WGR) and specific growth rate (SGR) in the DCP20 group (263.91% and 1.85% d-1) were significantly increased compared with the control group (194.79% and 1.54% d-1) (P < 0.05). Furthermore, fish fed the diet with 20% DCP significantly increased the activity of hepatic superoxide dismutase (SOD) compared with the control group (P < 0.05). Meanwhile, the content of hepatic malondialdehyde (MDA) in the DCP20, DCP40, and DCP80 groups was significantly lower than that in the control group (P < 0.05). The activity of intestinal trypsin in the DCP20 group was significantly degraded compared with that in the control group (P < 0.05). The transcription of hepatic proinflammatory cytokine genes (interleukin-6 (il-6); tumor necrosis factor-α (tnf-α); and interferon-γ (ifn-γ)) in the DCP20 and DCP40 groups was significantly upregulated compared with that in the control group (P < 0.05). As to the target of rapamycin (TOR) pathway, the transcription of hepatic target of rapamycin (tor) and ribosomal protein (s6) was significantly up-regulated, while the transcription of hepatic eukaryotic translation initiation factor 4E binding protein 1 (4e-bp1) gene was significantly downregulated in the DCP group compared with the control group (P < 0.05). In summary, based on the broken line regression model analysis of WGR and SGR against dietary DCP replacement levels, the optimal replacement level was recommended to be 8.12% and 9.37% for large yellow croaker, respectively. These results revealed that FM protein replaced with 20% DCP could promote digestive enzyme activities and antioxidant capacity and further activate immune response and the TOR pathway so that growth performance of juvenile large yellow croaker was improved. [ABSTRACT FROM AUTHOR]

Octanoate is a type of classical medium-chain fatty acids, which is widely used to treat neurological and metabolic syndrome. However, the specific role of octanoate in repairing intestinal health impairment is currently unknown. Therefore, we investigated whether dietary octanoate repaired the intestinal damage induced by surplus soybean oil in Larimichthys crocea. In this study, dietary octanoate alleviated abnormal morphology of the intestine and enhanced expression of ZO-1 and ZO-2 to improve intestinal physical barrier. Further, dietary octanoate increased antioxidant enzymic activities and decreased the level of ROS to alleviate the intestinal oxidative stress. Dietary octanoate also attenuated the expression of proinflammatory cytokines and the polarity of macrophage to reduce the intestinal inflammatory response. Moreover, the result of intestinal microbial 16S rRNA sequence showed that dietary octanoate repaired the intestinal mucosal microbial dysbiosis, and increased the relative abundance of Lactobacillus. Dietary octanoate supplementation also increased the level of acetic acid in intestinal content and serum through increasing the abundance of acetate-producing strains. Overall, in Larimichthys crocea , dietary octanoate might alleviated oxidative stress, inflammatory response and microbial dysbiosis to repair the intestinal damage induced by surplus soybean oil. This work provides vital insights into the underlying mechanisms and treatment strategies for intestinal damage in vertebrates. [ABSTRACT FROM AUTHOR]

A molecular spring isolator comprising ZIF-8 with hydrophobic micropores, water, and a cylinder/piston unit is introduced. Liquid water can be intruded into the micropores of ZIF-8 under critical pressure. In the meantime, mechanical energy is stored. And once the external pressure is withdrawn, spontaneous capillary evaporation will occur. The stored energy, meanwhile, is released. This behavior is similar to a coil spring. The Laplace–Washburn equation is used to describe the force equilibrium of a single water column in a micropore. After that, the result of water infiltrating a great deal of hydrophobic pores is revealed by theoretical analysis and an experiment. An averaging method is devoted to computing the primary resonance response and its accuracy is proved by the fourth-order Runge–Kutta method. Furthermore, the energy transmissibility is used to estimate its vibration isolation capability. Finally, a vibration isolation test indicated that the inherent frequency of the isolator is as low as 1.3 Hz. [ABSTRACT FROM AUTHOR]

This paper describes the mechanism and trend of High gloss polymer compounds replacing of paintable plastic parts in automobile industry, and gives some solution overcoming the appearance defects that Painting free parts form easily flow marks and Weld lines in injection molding. [ABSTRACT FROM AUTHOR]

Traditionally, potholes are mainly paved for maintenance, and the asphalt mixture needs to be compacted. But due to the construction quality problem, the compacting degree of asphalt mixture may not be enough and the void ratio of asphalt mixture may not meet the requirements, resulting in the premature damage of the potholes after repair. If the repair material can be prefabricated, this problem will be well solved. So, based on the structure form of the prefabricated rapid maintenance of asphalt pavement, this paper aims to determine the most unfavorable loading position in pothole repair, which was established by the ANSYS software with the finite element model. The results show that the most unfavorable loading position of tensile stress for patch materials and joint filling material is C1-1 (A2-2) and the most unfavorable loading position of shear stress for joint filling material and leveling layer is B2-1 and C1-5. Subsequently, the influences of the material modulus, size, thickness, and modulus of the old pavement material on the potholes are calculated by using the finite element model under the most unfavorable loading position. [ABSTRACT FROM AUTHOR]

The surface quality of polyurethane pad attached to the polishing tool is of great importance to the polishing performance, and it is usually maintained by a dressing process. In this study, in order to improve the pad dressing quality, optimization of motion control during the dressing process is presented, from the aspects of the uniformity of the particle trajectories on the pad and the consistency of the relative velocity of each point on the dressed surface. First, kinematic modeling of the particles on the dressing tool based on multibody theory was proposed, which expresses the particle trajectories as a function of the key motion parameters $n_{g}$ and $n_{b}$. Subsequently, with the above model, simulations were conducted to find the optimized range of $n_{g}$ and $n_{b}$. The results have shown that the particle trajectories do not distribute uniformly while $n_{g}$ = $n_{b}$ , and along with the increase in the difference between $n_{g}$ and $n_{b}$ , the uniformity of the particle trajectories would improve. After that, to further optimize these motions, the relative velocity of each point on the dressed surface that involves $n_{g}$ and $n_{b}$ was calculated and compared. The results indicated that only if $n_{g}$ > $n_{b}$ are the consistencies of the relative velocity of various points on the dressed surface preferred. Consequently, $n_{g}$ > $n_{b}$ is the premise to satisfy both the particle trajectories and the relative velocity. Furthermore, by considering the limitation of the dressing machine and dressing efficiency, the optimized ranges for $n_{g}$ and $n_{b}$ are 500–1000 and 100–200 r/min, respectively. Finally, experimental validation was conducted and the result agreed well with the above conclusion, which proved the optimization of the motions. [ABSTRACT FROM AUTHOR]

Cross-border capital flows have been a major force driving economic globalization. Foreign direct investment (FDI) plays a decisive role in seeking out market technology brands and enhancing the global competitiveness among international inflows. With the requirement of economic development, this paper focused on a performance evaluation of FDI in China. However, because of the planned transformation to a market economy in China, FDI has been promoted with a regional cascade structure. Similar to the development track of the Chinese economy, it is necessary to evaluate FDI quality more than purely quantity from a provincial point of view. Therefore, this paper evaluated the Chinese provincial FDI total factor productivity using the dynamic Malmquist model. In contrast to traditional evaluations, this paper focused on inter-temporal influence in FDI performance evaluation. To understand the inter-temporal effects, physical capital stock was defined as a dynamic variable in FDI sustainability performance. Additionally, with the pressure to reduce emissions, energy consumption was also considered during the evaluation. The empirical results revealed that the dynamic variable is the bottleneck in FDI performance for most Chinese provinces. It is only efficient in a few municipalities and provinces, such as Shanghai and Guangdong. Additionally, energy conservation was more efficient in the performance evaluation of eastern regions in China. [ABSTRACT FROM AUTHOR]

A 70-day feeding trial was conducted to investigate effects of dietary lysolecithin on growth performance, serum biochemical indexes, antioxidant capacity, lipid metabolism and inflammation-related genes expression of juvenile large yellow croaker (Larimichthys crocea) with initial weight of 6.04 ± 0.08 g. A formulated diet containing approximately 42% crude protein and 12.5% crude lipid was used as the control diet (CON). The other three experimental diets were formulated with supplementation of 0.2%, 0.4% and 0.6% lysolecithin based on the control diet, respectively. Results showed that weight gain rate (WGR) and specific growth rate (SGR) significantly increased in fish fed diets with lysolecithin compared with those in the control diet (P < 0.05). Fish fed diets with 0.4% and 0.6% lysolecithin had notably higher lipid content in muscle than that in the control diet (P < 0.05). When fish were fed diets with lysolecithin, serum high-density lipoprotein cholesterol (HDL-c) content was notably higher than that in the control diet (P < 0.05), while fish fed the diet with 0.6% lysolecithin had a significant lower serum low-density lipoprotein cholesterol (LDL-c) content than that in the control diet (P < 0.05). Meanwhile, serum aspartate transaminase (AST) and alanine transaminase (ALT) activities in fish fed diets with lysolecithin were remarkably lower than those in the control diet (P < 0.05). With the increase of dietary lysolecithin from 0.2% to 0.6%, mRNA expression of stearoyl-coenzyme A desaturase 1 (scd1), diacylglycerol acyltransferase 2 (dgat2) and sterol-regulatory element binding protein 1 (srebp1) showed decreasing trends. Furthermore, mRNA expression of carnitine palmitoyl transferase 1 (cpt1) and lipoprotein lipase (lpl) among each dietary lysolecithin treatment were significantly higher than those in the control diet (P < 0.05). In terms of inflammation, mRNA expression of tumor necrosis factor α (tnf-α) and interleukin-1 β (il-1β) were significantly down-regulated in fish fed diets with lysolecithin compared with those in the control diet (P < 0.05), while the mRNA expression of interleukin-10 (il-10) was significantly higher than that in the control diet (P < 0.05). In conclusion, dietary lysolecithin could promote the growth performance, improve hepatic lipid metabolism and regulate inflammation response in juvenile large yellow croaker, and the optimal supplement level of lysolecithin was approximately 0.4% in this study. • Dietary lysolecithin could significantly improve growth performance of juvenile large yellow croaker. • Diets supplemented with lysolecithin could enhance lipid metabolism and alleviate fat accumulation in liver. • Lysolecithin could exert beneficial effects on antioxidant capacity and inflammation response to improve health status. [ABSTRACT FROM AUTHOR]

As a vital pathway for cellular energy production, mitochondrial fatty acid β-oxidation (FAO) is essential in regulating immune responses to bacterial pathogens and maintaining intracellular homeostasis in vertebrates. However, the specific role of FAO in antiviral innate immune response in macrophages remains insufficiently understood. In this study, virus infection simulated by poly(I:C) inhibited FAO, as indicated by the reduced expression of FAO-related genes and proteins in the head kidney of large yellow croaker, with similar results observed in poly(I:C)-stimulated macrophages. Then, inhibition of FAO by supplementary mildronate in vivo and etomoxir treatment in vitro revealed varying increases in the mRNA expression of antiviral innate immune response genes after stimulated by poly(I:C) in the head kidney and macrophages. Notably, etomoxir significantly facilitated the transcriptional up-regulation of the IFNh promoter by IRF3. Moreover, inhibiting FAO by knockdown of cpt1b promoted antiviral innate immune response triggered by poly(I:C) in macrophages. Conversely, activating FAO through overexpression of cpt1b or cpt2 significantly reduced the mRNA levels of antiviral response genes in macrophages stimulated by poly(I:C). Unlike etomoxir, cpt1b overexpression inhibited the transcriptional up-regulation of the IFNh promoter by IRF3. Furthermore, in vivo dietary palm oil feeding and in vitro exposure to palmitic acid inhibited the antiviral innate immune response triggered by poly(I:C) in the head kidney and macrophages, respectively. These effects were partly associated with FAO activation, as evidenced by etomoxir. In summary, this study elucidates FAO's critical role in regulating antiviral innate immune response in head kidney macrophages. These findings not only deepen insights into the interaction between metabolic remodeling and host immune responses, but also offer valuable guidance for developing nutritional strategies to improve antiviral immunity in aquaculture., (Copyright © 2024. Published by Elsevier Ltd.)