Optimal Reference Research Articles

Research on the performance of ultra-low temperature cascade refrigeration system based on low GWP refrigerants

The EU Security Council and Parliament have tentatively agreed to ban fluorinated gases with a global warming potential (GWP) higher than 150 in split air conditioners and heat pumps from 2027. This will further motivate the refrigeration industry to accelerate the search for refrigerants with low GWP and zero ozone depletion potential (ODP). At present, research into low GWP refrigerants for cascade systems is limited, focusing mainly on single refrigerant substitutes without comprehensive comparisons and lax GWP restrictions. In this study, the cascade refrigeration cycle (CRS) system is established to meet the demand of −100 to −50 °C. The GWP of the refrigerants is strictly controlled below 150, and a comprehensive screening of the four generations of refrigerants is carried out to identify refrigerant pairs that meet environmental and refrigeration requirements. The relationship between the high-temperature cycle (HTC) evaporation temperature and the optimal coefficient of performance (COP) is determined, and the effects of the low-temperature cycle (LTC) evaporation temperature Te concerning with mass flow rate, discharge temperature of compressor, compressor power consumption, exergy destruction, and exergy efficiency are analyzed in detail. The thermodynamically superior refrigerant pairs are identified by comparison with several conventional refrigerant pairs. The results show that when Te > −67 °C, R170/R600a is preferred, and when Te ≤ −67 °C, R170/R1270 is preferred. In the temperature range of −100 ∼ −50 °C, R170/R1270 is the better refrigerant pair, which can improve the performance by 6.39–13.11 % than traditional refrigerant pairs. Finally, the exergy destruction analysis of CRS components is carried out, which provides a reference for refrigerant selection and system optimization of CRS in the field of ULT.

Structural Parameter Optimization of a Tomato Robotic Harvesting Arm: Considering Collision-Free Operation Requirements

The current harvesting arms used in harvesting robots are developed based on standard products. Due to design constraints, they are unable to effectively avoid obstacles while harvesting tomatoes in tight spaces. To enhance the robot’s capability in obstacle-avoidance picking of tomato bunches with various postures, this study proposes a geometric parameter optimization method for a 7 degree of freedom (DOF) robotic arm. This method ensures that the robot can reach a predetermined workspace with a more compact arm configuration. The optimal picking posture for the end-effector is determined by analyzing the spatial distribution of tomato bunches, the main stem position, and peduncle posture, enabling a quantitative description of the obstacle-avoidance workspace. The denavit–hartenberg (D-H) model of the harvesting arm and the expected collision-free workspace are set as constraints. The compactness of the arm and the accessibility of the harvesting space serve as the optimization objectives. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) multi-objective genetic algorithm is employed to optimize the arm length, and the results were validated through a virtual experiment using workspace traversal. The results indicate that the optimized structure of the tomato harvesting arm is compact, with a reachability of 92.88% in the workspace, based on the collision-free harvesting criteria. This study offers a reference for structural parameter optimization of robotic arms specialized in fruit and vegetable harvesting.

Improved convective cloud differential (CCD) tropospheric ozone from S5P-TROPOMI satellite data using local cloud fields

Abstract. We present the CHORA (Cloud Height Ozone Reference Algorithm) for retrieving tropospheric-ozone columns from S5P-TROPOMI (Sentinel-5 Precursor–TROPOspheric Monitoring Instrument). The method uses a local-cloud reference sector (CLC – CHORA Local Cloud) to determine the stratospheric (above-cloud) column, which is subtracted from the total column in clear-sky scenes in the same zonal band to retrieve the tropospheric column. The standard CCD (convective cloud differential) approach uses cloud data from the Pacific region (CPC – CHORA Pacific Cloud) instead. An important assumption for the standard method is the zonal invariance of stratospheric ozone. The local-cloud approach is the first step to diminish this constraint in order to extend the CCD method to mid-latitudes, where stratospheric-ozone variability is larger. An iterative approach has been developed for the automatic selection of an optimal local-cloud reference sector around each retrieval grid box varying latitudinally by ± 1° and longitudinally between ± 5 and ± 50°. The optimised CLCT (CHORA Local Cloud Theil–Sen) algorithm, a follow-up from the CLC, employs a homogeneity criterion for total ozone from the cloud reference sector in order to overcome the inhomogeneities in stratospheric ozone. It directly estimates the above-cloud column ozone for a common reference altitude of 270 hPa using the Theil–Sen regression. The latter allows for the combination of the CCD method with the cloud-slicing algorithm that retrieves upper-tropospheric ozone volume mixing ratios. Monthly averaged tropospheric-column ozone (TCO) using the Pacific cloud reference sector (CPC) and the local-cloud reference sector (CLC, CLCT) has been determined over the tropics and subtropics (26° S–22° N) using TROPOMI for the time period from 2018 to 2022. The accuracy of the various methods was investigated by means of comparisons with spatially collocated NASA/GSFC SHADOZ (Southern Hemisphere Additional Ozonesondes) measurements and the ESA TROPOMI level-2 tropospheric-ozone product. At eight out of nine tropical stations, tropospheric-ozone columns using the CLCT yield better agreement with ozonesondes than the CPC. In the tropical region (20° S–20° N), the CLCT shows a significantly lower overall mean bias and dispersion of 1 ± 7 %, outperforming both the CPC (12 ± 10 %) and CCD-ESA (22 ± 10 %). The CLCT surpasses the ESA operational product, providing more accurate tropospheric-ozone retrievals at eight out of nine stations in the tropics. For the Hilo station, with a larger stratospheric-ozone variability due to its proximity to the subtropics, the bias of +30 % (CPC) is effectively reduced to −5 % (CLCT). Similarly, in the subtropics (Reunion, Irene, Hanoi, and King's Park), the CLCT algorithm provides an overall bias and scatter of −11 ± 9 % with respect to sondes. The CLCT effectively reduces the impact of stratospheric-ozone inhomogeneity, typically at higher latitudes. These results demonstrate the advantage of the local-cloud reference sector in the subtropics. The algorithm is therefore an important basis for subsequent systematic applications in current and future missions of geostationary satellites, like GEMS (Geostationary Environment Monitoring Spectrometer, Korea), ESA Sentinel-4, and NASA TEMPO (Tropospheric Emissions: Monitoring of POllution), predominantly covering the middle latitudes.

A feedback linearization sliding mode decoupling and fuzzy anti-surge compensation based coordinated control approach for PEMFC air supply system

With the application of proton exchange membrane fuel cell (PEMFC) in the field of transportation and energy, the requirements for air flow and pressure tracking performance, efficiency and stability of PEMFC air supply system become higher and higher. To improve PEMFC cathode air flow and pressure control performance under load variation and avoid surge of air compressor, a novel feedback linearization sliding mode decoupling and fuzzy anti-surge compensation based coordinated control approach is proposed. Firstly, optimal references of oxygen excess ratio (OER) and cathode air pressure under different load are calculated based on net output power of PEMFC system analysis. Then, an extended state observer is designed to estimate the cathode air pressure and flow in real time, a feedback linearization sliding mode based decoupling controller is designed to enhance OER and air pressure tracking control performance and robustness. Considering on the operating trajectory and surge line of air compressor, a fuzzy logic based anti-surge compensator is designed to prevent air compressor from surge by compensating both air flow and pressure simultaneously. The proposed control approach is implemented in PEMFC air supply control experiments and the results demonstrates its effectiveness.

Study on the Flow Characteristics of Non-Newtonian Drilling Fluid Through Vibrating Screen Meshes

Summary Composite screens are a critical component of drilling fluid shale shakers, and their performance directly affects the recovery efficiency of drilling fluid. This study focuses on the composite screens of shale shakers and simulates the flow of non-Newtonian drilling fluids through different structures of composite screens to investigate the impact of drilling fluid rheological parameters and screen compositions on screening performance. The research results indicate that the flow velocity of the drilling fluid is the highest while passing through the lower screen, and the turbulent kinetic energy (TKE) is at its maximum in the lower screen area, where energy dissipation is also the greatest. An increase in the rheological parameters of the four-parameter model drilling fluid generally increases the difficulty of passing through the screen, with the flow behavior index and viscosity coefficient having a particularly significant impact on the pressure drop coefficient. Compared with the plain composite screen, the herringbone composite screen and plain patterned composite screen have lower pressure drop coefficients, with the herringbone composite screen demonstrating the best screening performance. These findings provide theoretical references for flow analysis and structural optimization of shale shaker screens in drilling fluid applications.

On-chip warped three-dimensional InGaN/GaN quantum well diode with transceiver coexistence characters

Featured with light emission and detection coexistence phenomenon, nitride-based multiple-quantum-well (MQW) diodes integrated chip has been proven to be an attractive structure for application prospects in various fields such as lighting, sensing, optical communication, and other fields. However, most of the recent reports are based on planar structures. Three-dimensional (3D) structures offer extra advantages in direction and polarization and absorption modulation and may start a new way to make the same thing over and over with interesting properties. In this paper, we designed and fabricated a single-cantilever InGaN/GaN MQW diode with warped 3D microstructure via standard microfabrication technology. Experimental results indicate that the strain architecture of the multi-layer materials is the key principle for the self-warped device. The planar structure will bear greater compressive stress while the warped beam part has less stress, resulting in differences in the optical and electrical performance. The strain-induced band bending highly influences the emission and detection properties, while the warped structure will introduce direction selectivity to the 3D device. As an emitter, 3D structures have a directional emission with lower turn-on voltage, higher capacitance, increased luminous intensity, higher external quantum efficiency (EQE), high -3dB bandwidth, and redshifted peak wavelength. Besides, it can serve as an emitter for directional-related optical communication. As a receiver, 3D structures have lower dark-current, higher photocurrent, and red-shifted response spectrum and also show directional dependence. These findings not only deepen the understanding of the working principle of the single-cantilever GaN devices but also provide important references for device performance optimization and new applications in visible light communication (VLC) technology.

A composite structure device: vibration control and energy harvesting of tool system in aviation thin-walled parts milling process

Abstract The intense vibration generated by the high-speed milling cutter in the processing process not only seriously affects the surface roughness but also may damage important components of the machine tool, resulting in significant economic losses. Therefore, a composite structure of piezoelectric energy-collector (PEC) and nonlinear energy sink (NES) is innovatively constructed by combining theoretical research and numerical analysis to achieve more efficient vibration suppression and energy recovery in milling. Using the Hamilton principle, the electromechanical model of the composite structure is developed. Then, based on the Galerkin truncation to discretized displacement functions, we solve the amplitude-frequency response of the tool structure by using the harmonic balance method. The validity analysis of the proposed method can be verified by rigorous comparison with the results of the Runge-Kutta method. A novel NES-PEC composite structure presented in this work shows excellent vibration suppression capability in the milling process. More importantly, the structure also enables self-powered sensing of the tool system, significantly reducing dependence on external power sources. This innovative design substantially improves the stability and reliability of milling processes and opens up new ways to optimize the energy efficiency of tool systems. In summary, this paper’s modeling and solving methods, vibration reduction techniques, and energy harvesting strategies have laid a solid foundation for applying a high-speed milling cutter system. More relevant literature on applying vibration suppression and energy harvesting devices in milling must be reviewed. This paper fills in the research gap and provides a valuable reference for future tool systems design and optimization.

Feasibility of transperineal intestinal ultrasound in assessing ulcerative proctitis during pregnancy.

This study explored the use of transperineal intestinal ultrasound (TPIUS) for assessment of ulcerative colitis (UC) in pregnancy. 8 pregnant women with UC underwent TP-US, clinical assessment and fecal calprotectin. TP-IUS was well tolerated and feasible with adequate rectal views obtained in all trimesters of pregnancy. No correlation between TP-IUS, clinical, or biochemical rectal disease activity assessment was found in this small cohort. Further studies are required to define the optimal technique and references ranges in the pregnant population.

Kinetic Analysis and Metabolism of Poly(Adenosine Diphosphate-Ribose) Polymerase-1-Targeted 18F-Fluorthanatrace PET in Breast Cancer.

The poly(adenosine diphosphate-ribose) polymerase inhibitors (PARPi) have demonstrated efficacy in ovarian, breast, and prostate cancers, but current biomarkers do not consistently predict clinical benefit. 18F-fluorthanatrace (18F-FTT) is an analog to rucaparib, a clinically approved PARPi, and is a candidate biomarker for PARPi response. This study intends to characterize 18F-FTT pharmacokinetics in breast cancer and optimize image timing for clinical trials. A secondary aim is to determine whether 18F-FTT uptake in breast cancer correlates with matched frozen surgical specimens as a reference standard for PARP-1 protein. Methods: Thirty prospectively enrolled women with a new diagnosis of breast cancer were injected with 18F-FTT and imaged dynamically 0-60 min after injection over the chest, with an optional static scan over multiple bed positions starting around 70 min. Kinetic analysis of lesion uptake was performed using blood-pool activity with population radiometabolite corrections. Normal breast and normal muscle reference tissue models were compared with PARP-1 protein expression in 10 patients with available tissue. Plasma radiometabolite concentrations and uptake in tumor and normal muscle were investigated in mouse xenografts. Results: Pharmacokinetics of 18F-FTT were well fit by Logan plot reference region models of reversible binding. However, fits of 2-tissue compartment models assuming negligible metabolite uptake were unstable. Rapid metabolism of 18F-FTT was demonstrated in mice, and similar uptake of radiometabolites was found in tumor xenografts and normal muscle. Tumor 18F-FTT distribution volume ratios relative to normal muscle reference tissue correlated with tissue PARP-1 expression (P < 0.02, n = 10). The tumor-to-normal muscle ratio from a 5-min frame between 50 and 60 min after injection, a potential static scan protocol, closely corresponded to the distribution volume ratio relative to normal muscle and correlated to PARP-1 expression (P < 0.02, n = 10). Conclusion: This study of PARPi analog 18F-FTT showed that uptake kinetics invivo corresponded to expression of PARP-1 and that 18F-FTT quantitation is influenced by radiometabolites that are increasingly present late after injection. Radiometabolites can be controlled by using optimal image acquisition timing or normal muscle reference tissue modeling in dynamic imaging or a tumor-to-normal muscle ratio. Optimal image timing for tumor-to-normal muscle quantification in humans appears to be between 50 and 60 min after injection. Therefore, a clinically practical static imaging protocol commencing 45-55 min after injection may sufficiently balance 18F-FTT uptake with background clearance and radiometabolite interference for quantitative interpretation of PARP-1 expression invivo.

The effect of magnetic nanofilm morphology on spintronic terahertz emission performance

Femtosecond laser-driven spintronic terahertz (THz) emitters based on magnetic nanofilms are poised to be the next-generation mainstream THz radiation devices due to their low cost, high performance, ultra-broadband, and easy integration. The radiation performance of spintronic THz emitters is related to the material characteristics, heterostructure interfaces, pump laser, and magnetic field intensity. Additionally, the THz emission performance is greatly reliant on the material surface morphology. Here, we employed ultrafast THz scattering-type scanning near-field optical microscopy with nanoscale spatial resolution to obtain the static THz scattering nano-imaging of ferromagnetic/antiferromagnetic heterostructures (W/Co20Fe60B20/IrMn3). We established the relationship between surface morphology and THz scattering intensity. Utilizing laser-induced THz emission technology, we achieve injection and detection of nanoscale ultrafast spin current without the external magnetic field. The strong consistency of the THz emission nanoscopy with the atomic force microscopy topography demonstrates that the sample surface morphology is critical to the THz radiation performance. This study serves as a valuable reference for the further optimization of spintronic THz emitters and promotes the development of high-performance, strong-field spintronic THz sources.

Identification of the optimal reference genes for atrial fibrillation model established by iPSC-derived atrial myocytes

BackgroundAtrial fibrillation (AF) stands as a prevalent and detrimental arrhythmic disorder, characterized by intricate pathophysiological mechanisms. The availability of reliable and reproducible AF models is pivotal in unraveling the underlying mechanisms of this complex condition. Unfortunately, the researchers are still confronted with the absence of consistent in vitro AF models, hindering progress in this crucial area of research.MethodsHuman induced pluripotent stem cells derived atrial myocytes (hiPSC-AMs) were generated based on the GiWi methods and were verified by whole-cell patch clamp, immunofluorescent staining, and flow cytometry. Then hiPSC-AMs were employed to establish the AF model by HS. Whole-cell patch clamp technique and calcium imaging were used to identify the AF model. The stability of 29 reference genes was evaluated using delta-Ct, GeNorm, NormFinder, and BestKeeper algorithms;ResultsHiPSC-AMs displayed atrial myocyte action potentials and expressed the atrial-specific protein MLC-2 A and NR2F2, about 70% of the cardiomyocytes were MLC-2 A positive. After HS, hiPSC-AMs showed a significant increase in beating frequency, a shortened action potential duration, and increased calcium transient frequency. Of the 29 candidate genes, the top five most stably ranked genes were ABL1, RPL37A, POP4, RPL30, and EIF2B1. After normalization using ABL1, KCNJ2 was significantly upregulated in the AF model; Conclusions: In the hiPSC-AMs AF model established by HS, ABL1 provides greater normalization efficiency than commonly used GAPDH.

Optimization of territorial ecological space under the constraint of ecosystem service externalities

Ecosystem services are dynamic, following specific paths between regions and generating externalities. However, research on these externalities and the mechanisms within ecological networks remains limited. The quantification, spatial patterns, and evolution of these externalities are still unclear and need further study. Utilizing land use, topography, precipitation, and socio-economic data from 2010 and 2020, the study aims to quantify the externalities of ecosystem services and analyze their spatial distribution and network transmission characteristics within the Territorial Ecological Space (TES) of Jintan District. Using the InVEST model, we assessed the externalities of ecosystem services and integrated these with an ecological network model to reveal the impact of network structure on the flow of externalities. We propose an ecological space optimization plan with various scenarios, offering a reference for regional ecological space optimization. Key findings indicate that ecosystem service externalities exist and display spatial differentiation, with ecological source areas and corridors participating in the flow and dissipation of these services. Based on these findings, an ecological space optimization plan is proposed, consisting of multiple scenarios, which offers a reference for regional ecological space optimization. The study contributes to the sustainable management of ecological spaces by providing new insights and methodological advancements, particularly in the context of optimizing ecological spatial structures and ensuring regional ecological security. By elucidating the spatial dynamics and network transmission of ecosystem service externalities, this research supports informed decision-making in ecological conservation and land use planning.

Molecular epidemiological characteristics, variant spectrum and genotype-phenotype correlation of glucose-6-phosphate dehydrogenase deficiency in China: A population-based multicenter study using newborn screening.

Newborn screening (NBS) for glucose-6-phosphate dehydrogenase (G6PD) deficiency by biochemical tests is being used worldwide, however, the outcomes arising from combined genetic and biochemical tests have not been evaluated. This research aimed to evaluate the outcomes of application of combined genetic and biochemical NBS for G6PD deficiency and to investigate the molecular epidemiological characteristics, variant spectrum, and genotype-phenotype correlation of G6PD deficiency in China. A population-based cohort of 29,601 newborns were prospectively recruited from eight NBS centers in China between February 21 and December 30, 2021. Biochemical and genetic NBS was conducted simultaneously. The overall prevalence of G6PD deficiency was 1.12% (1.86% for male, and 0.33% for female; 1.94% for South China and 0.08% for North China). Genetic NBS identified 10 male patients undetected by biochemical NBS. The overall positive predictive values (PPVs) of biochemical and genetic NBS were 79.95% and 47.57%, respectively. A total of 15 variants were identified, with the six most common variants being c.1388G > A, c.1376G > T, c.95A > G, c.871G > A, c.1024C > T and c.392G > T (94.2%). The activity of G6PD was correlated with the type and WHO classification of variants. This study highlighted that combined screening could enhance the efficiency of current NBS for diagnosing G6PD deficiency. The prevalence, variant spectrum and allele frequency of G6PD deficiency vary across different regions. Our data provide valuable references for clinical practice and optimization of future screening strategies for G6PD deficiency.

Exploring the scale effect of nonpoint source pollution risk on water quality in Lake Basins of Central Yunnan Plateau using the Minimum Cumulative Resistance model.

Nonpoint source (NPS) pollution has emerged as the predominant water environment issue confronting plateau lakes in central Yunnan. Quantitative analysis of the impact of NPS pollution on water quality constitutes the key to preventing and controlling water pollution. However, currently, there is a dearth of research on identifying NPS pollution risks and exploring their relationship with water quality based on the Minimum Cumulative Resistance (MCR) model in the plateau lake basins of central Yunnan. Particularly, studies on the spatial heterogeneity of the impact of NPS pollution on water quality from a multi-scale perspective are scarce. Therefore, this study focuses on three typical lake basins in the Central Yunnan Plateau-Fuxian Lake, Xingyun Lake, and Qilu Lake (the Three Lakes). Utilizing the MCR model to identify NPS pollution risks, the study analyzes seven different scales, including sub-basins, riparian buffer zones (100 m, 300 m, 500 m, 700 m, and 1,000m) and lakeshore zones, to reveal the multi-scale effects of NPS pollution on water quality through correlation analysis. The results indicate that: (1) Over 60% of the areas in the Three Lakes Basin are at high or extremely high risk, mainly concentrated in flat terrain and around inflow rivers; (2) The area of NPS pollution from paddy field source landscape (PFSL) is greater than that from construction land source landscape (CLSL), and the high-risk areas of NPS pollution are also larger for PFSL compared to CLSL; (3) The mean resistance values of PFSL and CLSL show a significant negative correlation with monthly mean values of water quality indexes (NH3-N, TP, CODCr), with the 1,000 m riparian buffer zone scale showing the greatest correlation with most water quality indexes, especially NH3-N; (4) The correlation between the mean resistance value of CLSL and the monthly mean values of water quality indexes is significantly higher than that of PFSL, indicating a greater impact of CLSL on water quality compared to PFSL. In summary, PFSL and CLSL are the primary sources of NPS pollution in the Three Lakes Basins. The 1,000 m riparian buffer zone scale is the most sensitive to the impact of NPS pollution on water quality. This study provides scientific references for landscape pattern optimization and precise control of NPS pollution risks in the Central Yunnan Plateau lake basins and offers a new research perspective for exploring multi-scale effects of NPS pollution on water quality.

Cloud Server-based Questionnaire System for Cultural Services in Blue-green Spaces

Parks are important carriers of urban blue-green space and cultural services, which are vital to beautify the city and improve the quality of life of residents. Constructing a questionnaire system for cultural services in blue-green spaces is of great significance for evaluating and studying the supply of regional cultural services and quantifying residents' cultural needs. In this paper, we take Zhengzhou city park as the evaluation object, and based on AliCloud server ECS and WebGIS technology, combined with drone orthophoto and real-life three-dimensional model, we make the questionnaire survey system of blue-green space cultural service to collect residents' social value preference and suggestions for the park. Respondents enter the system through any device with internet access, browse park pictures and profiles, and participate in the online questionnaire survey, and the collected data on residents' value preferences can be used to assess the value of the park's cultural services by methods such as the SolVES model. The system solves the shortcomings such as heavy workload and low response rate of distributing questionnaires in the field. The system integrates a variety of digital technologies and improves the questionnaire survey method, which can effectively improve the efficiency and quality of the questionnaire survey and analyze the problems and deficiencies of the park with the opinions of the respondents, so as to provide the management with references for optimization and standardization, and to promote the enhancement of the quality of cultural services.

Electromagnetic performance analysis of a novel radial compound differential field-modulated magnetic gears

Purpose The purpose of this study is to propose a new magnetic gearing device and the proposed transmission model can be applied in the field of wind power and wave energy generation gearboxes. Design/methodology/approach A novel radial differential field-modulated two-stage magnetic gear is introduced, using a unique radial differential linkage to integrate two single-stage magnetic gears. This design incorporates a magnetic isolation ring to enhance transmission efficiency by minimizing magnetic interference and preventing power circulation. The two-stage modulating ring rotor operates synchronously via a connecting bridge, ensuring system stability and efficiency. This configuration not only boosts the gear ratio but also maintains a compact structure, improving power density and efficiency. Leveraging the magnetic field modulation and differential transmission, a finite element model of this gear is developed and its electromagnetic performance is analyzed. Findings The torque density of the new radial differential field-modulated two-stage magnetic gear has increased by 44.97% compared to the traditional tandem two-stage magnetic gear. It achieves a high transmission ratio of 64 and maintains comparable power density, indicating strong torque transfer capabilities suitable for low-speed, high-torque applications. During steady-state operation, the torque pulsation difference between the two stages is minimal, ensuring stable working torque. Social implications This research not only propels the forefront of magnetic gear technology through heightened efficiency and streamlined design but also bears profound societal significance in fostering sustainable energy paradigms. By facilitating superior energy conversion efficiencies in wind turbines and wave energy converters, it plays a pivotal role in mitigating carbon emissions and accelerating the global pivot towards cleaner, renewable energy landscapes. Originality/value A magnetic gear transmission device is proposed, which can achieve high power density and large transmission ratio at the same time, and this study provides a useful reference for the design optimization of new high-performance multistage magnetic gears.

Discovery of cyanoguanidine derivatives as biased μ-opioid receptor agonists

Opioid agonists, including morphine and its derivatives, have historically been utilized in conventional pain relief therapies. However, the morphine-like side effects associated with these compounds have constrained their broader application in clinical environments. Fortunately, novel compounds that selectively activate μ-opioid receptors (MOR) without activating the β-arrestin2 pathway, such as PZM21 and TRV130, demonstrate the potential to mitigate side effects while maintaining analgesic efficacy. In this study, we structurally modified PZM21 to get a series of compounds with a 2-cyanoguanidine scaffold, the majority of which display significant analgesic effects. Notably, Compound I-11 exhibited an analgesic effect comparable to that of morphine and selectively activates μ-opioid receptors while avoiding the activation of the β-arrestin2 pathway. Our work not only introduces a novel biased μ-opioid receptor agonist but also serves as a valuable reference for the further optimization of PZM21.

Multi-objective optimization design of automobile seat backrest considering coupling effect

To investigate the impact of the coupling effects of carbon fiber reinforced polymer in the seat back layer on the performance of car seats, this paper presents a comprehensive optimization design method for composite materials. In detail, the finite element models firstly established and validated through five typical working conditions of automotive seats based on experimental data. Then, the optimized variables are divided and determined through backrest stress nephograms for each working conditions of the automotive seats, in which the various perspective are taken into account, such as the total mass of seat backrest, safety performance, and comfort index. Subsequently, an optimization strategy for unequal thickness layers lay-up design is constructed, which combines strength factors, optimal Latin hypercube sampling, best-worst method, gray relational analysis, and Visekriterijumsko KOmpromisno Rangiranje method for the optimal design of the automotive CFRP seat backrest. Additionally, the impact of layer coupling effects on different performance indices of the seat is examined through simulating and analyzing the seat backrest with various layer coupling types, while incorporating the classical laminate theory. The study reveals that by minimizing the laminate coupling effect, the comfort of the seat can be enhanced. Finally, a comprehensive comparative analysis of the optimal trade-off solution is carried out in terms of optimization strategies. The results show that ensuring the safety performance, the total mass of the seat backrest decreased by 21.3%, as a result of the optimization strategy proposed in this paper, and the comfort performance is also improved to some extent. Therefore, the multi-objective optimization strategy proposed in this paper performs well in terms of effectiveness and provides a reliable reference for related composite material multi-objective optimization.

Size-Dependent Mechanical Properties and Excavation Responses of Basalt with Hidden Cracks at Baihetan Hydropower Station through DFN–FDEM Modeling

Basalt is an important geotechnical material for engineering construction in Southwest China. However, it has complicated structural features due to its special origin, particularly the widespread occurrence of hidden cracks. Such discontinuities significantly affect the mechanical properties and engineering stability of basalt, and related research is lacking and unsystematic. In this work, taking the underground caverns in the Baihetan Hydropower Station as the engineering background, the size-dependent mechanical behaviors and excavation responses of basalt with hidden cracks were systematically explored based on a synthetic rock mass (SRM) model combining the finite-discrete element method (FDEM) and discrete fracture network (DFN) method. The results showed that: (1) The DFN–FDEM model generated based on the statistical characteristics of the geometric parameters of hidden cracks can consider the real structural characteristics of basalt, whereby the mechanical behaviors found in laboratory tests and at the engineering site could be exactly reproduced. (2) The representative elementary volume (REV) size of basalt blocks containing hidden cracks was 0.5 m, and the mechanical properties obtained at this size were considered equivalent continuum properties. With an increase in the sample dimensions, the mechanical properties reflected in the stress–strain curves changed from elastic–brittle to elastic–plastic or ductile, the strength failure criterion changed from linear to nonlinear, and the failure modes changed from fragmentation failure to local structure-controlled failure and then to splitting failure. (3) The surrounding rock mass near the excavation face of underground caverns typically showed a spalling failure mode, mainly affected by the complex structural characteristics and high in situ stresses, i.e., a tensile fracture mechanism characterized by stress–structure coupling. The research findings not only shed new light on the failure mechanisms and size-dependent mechanical behaviors of hard brittle rocks represented by basalt but also further enrich the basic theory and technical methods for multi-scale analyses in geotechnical engineering, which could provide a reference for the design optimization, construction scheme formulation, and disaster prevention of deep engineering projects.

Numerical simulation of thermal and stress fields for multilayer and multi-pass weaving WAAM of magnesium alloy

Purpose A 3D finite element (FE) model based on the double ellipsoidal heat source was developed to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process. This paper aims to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process by developing a 3D finite element (FE) model based on the double ellipsoidal heat source. Design/methodology/approach Experimental thermal cycle curves and residual stresses were obtained by thermocouples and X-ray diffraction, respectively. The validity of the model was verified by the corresponding experimental results. Findings The deposition process of the upper pass led to the partial remelting of the lower deposited pass. The thermal process of the current-deposited pass alleviated the stress concentration in the previous-formed passes. A more uniform temperature distribution could be obtained by using the reciprocating deposition path. Compared to the reciprocating deposition path, the peak values of the transverse and longitudinal tensile residual stresses of the deposited sample under the unidirectional deposition path were reduced by 15 MPa and increased by 13 MPa, respectively. The heat conduction in the deposited passes could be improved by extending the inter-pass cooling time appropriately. With an increase in the inter-pass cooling time, the longitudinal residual stress in the middle region of sample along longitudinal and transverse directions showed increase and decrease–increase trends, respectively, while the transverse residual stress exhibited decrease trend. Originality/value This study enhances the understanding of temperature and stress fields evolution during the multilayer and multi-pass cold metal transfer-WAAM processes of magnesium alloy and provides the reference for parameter optimization.