Expansion Ratio Research Articles

A matching method for Twin-VGT systems under varying expansion ratios at high altitudes

In this study, we established a matching method for a twin variable geometry turbocharging (Twin-VGT) system under varying expansion ratios at high altitudes. In addition, we developed an equivalent thermodynamic model of a two-stage variable turbine with the effective flow areas of turbines obtained under velocity constraints for altitudes ranging from 0 to 5500 m. The effects of altitudes on the matching efficacy of a two-stage compressor under different operating conditions were evaluated. Additionally, an optimal distribution of the total boost pressure was determined to minimize the output power of the two-stage compressor during non-isothermal compression at various altitudes. Furthermore, the interplay between exhaust available energy (EAE), total expansion ratio (TER), exhaust temperature, and turbine power was investigated. Lastly, the peak efficiency of the turbocharging system was evaluated by analyzing the distribution of the TER and total enthalpy drop, aimed at optimizing EAE at different altitudes.

Performance analysis of a dual-ejector enhanced two-stage auto-cascade refrigeration cycle for ultra-low temperature refrigeration

Auto-cascade refrigeration cycle (ARC) is a cost-effective solution for ultra-low temperature refrigeration. This paper proposes a dual-ejector enhanced two-stage auto-cascade refrigeration cycle (ETARC). In ETARC, two ejectors replace the throttle valves at the liquid phase outlet of the two gas–liquid separators in the conventional two-stage auto-cascade refrigeration cycle (CTARC). They are connected in series to recover partial expansion work in the throttling process, aiming to lift the suction pressure of the compressor. The ternary mixture component is selected and R600a/R41/R1150 is supposed to be the working fluid due to the best performance. The mass fraction ratio of the refrigerant mixture components, the quality at the inlet of two separators and the expansion ratio of the throttle valve (EPR) of the two cycles are optimized using particle swarm optimization (PSO) with respect to the maximum COP. The performances of the two cycles at optimum operating conditions are compared using energetic and exergetic methods, and the effect of the evaporation temperature and the condensation temperature on cycle performances and operating characteristics are discussed in detail. The results show that applying the two ejectors effectively improves the performance of ETARC. Compared with the CTARC at the evaporation temperature of −85℃, and the condensation temperature of 45℃, the ETARC cycle exhibits 16.07% improvement in COP, 29.43% increase in the volumetric refrigeration capacity qv, 17.17% reduction in the total exergy destruction rate. ETARC shows significant performance improvement and has a remarkable energy-saving potential.

An investigation on asymmetric flow characteristics of asymmetric twin-scroll turbine

Asymmetry, as the most significant characteristic of asymmetric twin-scroll turbines, has a significant effect on the flow characteristics of asymmetric twin-scroll turbines. In this paper, the effect of asymmetry on flow parameters, efficiency, twin-scroll pressure ratio ( SPR), single admission twin-scroll flow parameters ratio ( SSMR) and twin-scroll divide wall of asymmetric twin-scroll turbines were investigated for the first time. First, several turbines with the same total critical section of twin scrolls and different asymmetries were designed, as well as several turbines with the same asymmetric twin scrolls and different heights of the divide wall. Subsequently, these asymmetric twin-scroll turbines were tested and studied on the turbine performance rig. Asymmetry had little influence on turbine flow characteristics under equal admission, but a great impact under partial and single admission. Meanwhile, SMR had a low slope linear relationship with the expansion ratio for every asymmetry turbine. Moreover, the asymmetry was approximately linear with the average single admission twin-scroll pressure ratio ( SSMR ave), which could be used to guide the early design of asymmetric twin-scroll turbines. Besides, divide wall schemes testing found that the length of divide wall had a certain effect on the SSMR ave, which is a control factor to maintain asymmetric property. Finally, the relation between the expansion ratio of small or large scroll turbines and lg(SPR) was approximately exponential function, and the exponential parameter was strongly correlated with SSMR and SSMR ave, which could be the key parameter reflecting the asymmetry.

Synthesis and fabrication of lightweight microcellular thermoplastic polyimide foams using supercritical CO2 foaming

Polyimide foams (PIFs) are usually synthesized by solution polymerization, followed by chemical foaming to prepare thermosetting foam. In this research, lightweight microcellular thermoplastic polyimide foams (TPIFs) were fabricated via a novel two-step foaming approach using supercritical carbon dioxide (scCO2) as a blowing agent. The poly(amic acid) (PAA) and polyester ammonium salt (PEAS) precursor solutions were synthesized with pyromellitic dianhydride (PMDA) as dianhydride reagents and polyether amine Jeffamine D230 as aliphatic diamine reagent via blending and solution polymerization, respectively. The solution polymerization process demonstrated a higher molecular weight and superior formability than the blending process. The optimum thermal imidization temperature of 200 °C was optimized via the thermal and rheological property analysis. The cell morphology and mechanical properties of the TPIFs could be turned by varying the saturation time, foaming pressure, and imidization temperature. At a thermal imidization temperature of 200 °C, the TPIFs exhibited a branched structure with a small mean cell diameter (123.78 μm), and a high compressive strength (0.4 MPa) under 10 % strain at high temperature and pressure, which was more than ten times that of the TPIFs with thermal imidization temperature of 130 °C. This research provides a feasible method for producing high volume expansion ratio TPIFs with adjustable microcellular structures and outstanding mechanical properties.

Construction of decorative, antibacterial, anti-aging and fire-retardant integrative coatings for wood substrates with super protective performances

To prevent the coatings applied in historical buildings from aging failure due to environmental factors, an integrative coating with decorative, antibacterial, weather-resistant and flame-retardant properties is particularly important in practical applications. The nanocomposite flame retardants named CPPBs are obtained from the successful grafting of the phosphate esters to the surface of cerium oxide nanoparticles, which are physically blended with film-forming polymer to construct integrative coating named MCPPBs. The results show that adding nano-CeO2 greatly strengthens the mechanical property, fire protection performances, weather resistance, antibacterial activity of the integrative coatings, and maintains high light transmittance in the meantime. Especially, when the addition of nano-CeO2 in flame retardant is 0.5 wt.%, the expansion ratio of the MCPPB3 coating increases to 65 and the char index reduces to 15.7cm3, concomitant with a high transparency of 80.3 %. By combining FTIR, SEM and EDS analyses, the MCPPBs char containing nano-CeO2 is compact and dense. In the accelerated aging test, the back equilibrium temperature of the MCPPB3 coating at 900 s is still less than 220 °C concomitant with a complete surface morphology after 6 aging cycles. In addition, the MCPPB3 coating exerts a negative effect on the growth of E. coli and S. aureus, and the antibacterial activities against E. coli and S. aureus are 92.8 % and 96.2 %, respectively.

Numerical simulations of flow past a backward-facing step under a strong transverse magnetic field

The flow of liquid metal over a backward-facing step (BFS) exhibits unique flow characteristics due to the influence of strong magnetic field. In this study, direct numerical simulation of the BFS flow under a strong magnetic field is conducted based on a quasi-two-dimensional model (with a large interaction number, N≫1, and a large Hartmann number, Ha≫1). The Reynolds number (Re), Hartmann number (Ha), and expansion ratio (ER) are investigated within the ranges of [100−80 000], [100−40 000], and [1.67−5], respectively. Three typical flow regimes are defined based on the evolution of the free shear layer vortices and the separation state of the boundary layer. Furthermore, a comprehensive flow regime map is presented for different ER, revealing a positive correlation between the critical Reynolds number (Rec1) and Ha at the onset of instability. Specifically, Rec1 is proportional to Ha0.5, Ha0.54, and Ha0.56 for ER = 5, 2.5, and 1.67, respectively. Moreover, the maximum relative thickness of the free shear layer at Hac1 appears in the range of approximately 0.7–0.78Lr for ER = 5, while for ER = 2.5, it appears in the range of approximately 0.80–0.85Lr, indicating that the instability position of the free shear layer occurs earlier for large ER. Our numerical investigation also demonstrates that an increase in the transverse magnetic field compresses the free shear layer and delays the process of vortex pairing, thereby suppressing the oscillatory behavior of the shear layer.

Experimental Study on the Flow Characteristics of Two-Stage Variable Turbines in a Twin-VGT System

The twin variable geometry turbocharger (VGT) System, through efficient use of exhaust energy, maximizes internal combustion engine (ICE) power, reduces exhaust emissions and improves reliability. However, the internal flow characteristics of the twin-VGT system are greatly affected by the environment. To ensure that the two-stage adjustable supercharged internal combustion engine is efficient in all geographical environments and under all operating conditions, it is necessary to conduct in-depth research on the internal flow characteristics of high- and low-pressure turbines. In this paper, an experimental system of the flow characteristics of a double variable-geometry turbocharging (twin-VGT) system is designed and developed. A two-stage variable turbine flow characteristic test was carried out, focusing on the relationship between the initial rotational velocity of high variable-geometry turbocharging (HVGT) and blade opening in low variable-geometry turbocharging (LVGT). The effects of high- and low-pressure variable-geometry turbocharger (VGT) blade opening on available exhaust energy, expansion ratio distribution, blade velocity ratio, compressor power consumption and isentropic efficiency were studied. The results show that when the available energy of exhaust gas is constant, with the increase in HVGT turbine speed, when the LVGT blade opening decreases by 10%, the low-pressure turbine expansion ratio increases by about 0.23.

#25 : The Prediction Value of EEVA in the Timelapse GERI Incubator for the Blastocyst Morphology

Background and Aims: Time-lapse monitoring of embryo development may represent a superior way to culture and select embryos in vitro. The EEVA Test records the development of each embryo with a cell-tracking system and predicts the potential (High, Medium or Low) that an embryo will form a blastocyst based on automated detection and analysis of time-lapse imaging information of early cell division stage. The blastocyst grade will help clinicians in selecting the best embryos for transfer to increase pregnancy rates and reduce multiple pregnancies. The aim of this study is to determine the correlation between EEVA score and some blastocyst morphological parameters. Methods: Retrospective analysis study on 2522 embryos with indication for prolonging embryo culture to the blastocyst stage in time-lapse GERI incubator from January 2020 to June 2022. Results: Embryos with E1 and E2 score had significant higher morphological ratios of ICM A, ICM B, TE A, TE B, blastocoele expansion ratios of BL5,6 and lower morphological ratios of ICM D, TE D,compared with embryos having E3, E4, E5 score, p<0.01. Embryos with E3 score had significant higher morphological ratios of ICM A, ICM B, TE A, TE B, blastocoele expansion ratios of BL5,6 and lower morphological ratios of ICM D, TE D, compared with embryos having E4, E5 score, p<0.01. Conclusions: The blastocyst morphological parameters were associcated with the EEVA score. The rate of blastocyst with the ICM A, ICM B, TE A, TE B, BL 5,6 tended to decrease and the rate of blastocyst with ICM D; TE D tended to increase for embryos with low EEVA score. In other words, the good quality blastocyst rate tended to decrease, and the bad quality blastocyst rate tended to increase for embryos with low EEVA score.

Mesenchymal and mononuclear stem cell therapy for acute ischemic stroke - A systematic review

Background: Studies have shown that stem cells have promising effect in ischemic stroke management. As an alternative therapy, the effectiveness and safety of mesenchymal (MSC) and mononuclear (MNC) stem cells in acute stroke are still unclear. This review evaluated the efficacy and safety of the use of MSC and MNC in acute ischemic stroke in terms of clinical and structural improvement. Methods: This is a systematic review which is conducted based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guideline. Our review focused on RCT, with acute ischemic stroke population using MSC or MNC, and evaluated the clinical and structural improvements, and safety outcome after administration of the stem-cells. Results: Eight studies were included, consisted of 155 patients in intervention and 408 in control group. In the MNC group, there was significant improvement of NIHSS within one month and achieved mRS ≤ 1 by six months. Slightly different from MNC, studies using MSC showed mRS improvement occurred after 3 months and NIHSS-motor improvement achieved after 2 years of infusion. One month after cell infusion, MRI showed structural improvement, with infarct expansion ratio of 0.9 ± 0.2 (p < 0.05). There was no differences in adverse events between intervention and control group in all studies. Conclusions: This review show that MSC and MNC stem-cells are effective and safe to use as alternative treatment in acute ischemic stroke if other definitive measures could not be done or not available.

Construction of a three-dimensional network in branched PETG to prepare PETG composite microcellular foam with outstanding mechanical properties at low temperatures

In response to the escalating demands in cold chain logistics, in this study, we developed a high-compression strength foam resistant to low temperatures using a proficient and accessible approach. The microcellular foam was prepared through chain modification and in situ-fibrillated technology of polytetrafluoroethylene (PTFE). An epoxy chain extender, ADR4468, was incorporated to enhance the foamability of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG). In addition, chain-extended PETG (CEPETG)–PTFE nanocomposites were formulated by integrating a PTFE three-dimensional (3D) nanofiber network. The PTFE nanofiber serves as an effective nucleation agent owing to its large specific surface area and undergoes a crystal-shaped transformation to further augment its strength. By leveraging the synergistic influence of these two principles, we employed the scCO2 foaming technology to obtain CEPETG–PTFE nanocomposite microcellular foam, which exhibited high-compression strength at low temperatures. The introduction of the chain extender improved the foaming characteristics of PETG. Consequently, the expansion ratio of the PETG foam increased from 5.18 to 36.01. Moreover, the formation of the PTFE 3D nanofiber network decreased the cell size from 16.16 to 2.38 μm. Furthermore, the low-temperature compression of the foam increased by 266 %, with an improvement in its toughness.

A Thermodynamic Perspective of Cancer Cells' Volume/Area Expansion Ratio.

The constructal law is used to improve the analysis of the resonant heat transfer in cancer cells. The result highlights the fundamental role of the volume/area ratio and its role in cancer growth and invasion. Cancer cells seek to increase their surface area to facilitate heat dissipation; as such, the tumour expansion ratio declines as malignant cells start to migrate and the cancer expands locally and systemically. Consequently, we deduce that effective anticancer therapy should be based on the control of some ion transport phenomena in an effort to increase the volume/area ratio. This emphasises restricting the local and systemic spatial expansion of the tumour system and thus gives further credence to the superior role of novel anti-migratory and anti-invasive treatment strategies over conventional anti-proliferative options only.

The Effect of Beneng Taro Flour (Xanthosoma undipes K. Koch) and Rice Bran (Oryza sativa L.) Substitution on the Physical and Sensory Characteristics of Bread

Beneng taro is an indigenous tuber from Banten which is rich of functional components such as dietary fiber and carotenoid pigments. So far, processing of beneng taro has not been developed. One of method to process it is to make into flour. Another material that is not utilized is rice bran. Rice bran is a by-product of rice milling which has only been used as animal feed, but the majority of functional components in rice accumulate in rice bran such as dietary fiber, oryzanol, and phytosterol compounds. The application of beneng taro flour and rice bran for food products can increase food diversification, beside of that it can reduce the use of wheat flour. The purpose of this study was to evaluate the effect of adding beneng taro flour and rice bran to bread on the physical and sensory characteristics. This study used a completely randomized design (CRD) with one factor, namely the ratio of wheat flour: beneng taro flour: rice bran (control, 65:30:5; 65:25:10; 65:20:15). This research was carried out in two repetitions. The result of this research were the increase of rice bran and the decrease of beneng taro flour substitution in bread decrease the expansion ratio, lightness (L*) of the crust and crumb, a* chromaticity of the crust, b* chromaticity of the crust and crumb, hue (oh) of the crust and crumb, and sensory acceptance. However, the increase of rice bran and decrease of beneng taro flour substitution increased density of dough, density of bread, and a* chromaticity of the crumb. Based on the results of sensory analysis, the bread with 65:30:5 formula was the best formula because it was close to the control.

Development of Eco-Friendly and High-Strength Foam Sensors Based on Segregated Elastomer Composites with a Large Work Range and High Sensitivity.

Achieving a high-strength piezoresistive foam with high sensitivity and a large workable range remains a major challenge. To realize these goals, we developed a facile, novel, and eco-friendly strategy for constructing segregated microcellular structures fabricated using coating, heat compression molding, and supercritical CO2 (ScCO2) foaming. The segregated poly(ether block amide) (PEBA)/carbon nanostructure (CNS) composites were fabricated via compression molding. This effectively improved the foamability and cell morphology of PEBA/CNS composites. Moreover, compared with the randomly distributed structure, the segregated structure also endowed the foams with better conductivity and sensing capability. Subsequently, the ScCO2 foaming was employed to fabricate segregated PEBA/CNS composite foams. The foaming gave composites a large compressibility and reduced their percolation threshold. Under 1 wt % CNS loading, via tuning the expansion ratio of foam from ∼2.1 to 4.1, the compression stress at 50% compression strain of foam varied from ∼3.3 to 0.5 MPa, and the conductivity changed from 4.89 × 10-3 to 1.93 × 10-6 s/m, implying a tunable conductivity. Additionally, the adjustable conductivity enabled the sensitivity of segregated composite foams to be regulated. The segregated PEBA/CNS foam (FCNS1-4.1) exhibited a good combination of high sensitivity (GF = 3.5), large work range (80% strain), and high compression strength (∼0.5 MPa at 50% strain) as well as a stable, reproducible, and durable sensing response under a low CNS content (∼0.11 vol %). Furthermore, the ΔI/I0 of FCNS1-4.1 (75.6% porosity) reached a high value of ∼810 and exhibited an ultrahigh sensitivity of ∼3706 () from 60 to 80% strain. Moreover, the foam sensor could be used as a sensing function sole for monitoring diverse human motions. Therefore, the segregated PEBA/CNS composite foams with outstanding piezoresistive performances show promising potential applications in monitoring human motions as wearable electronics and provides a new design strategy for a new generation of foam sensors with high performance.

Numerical and experimental investigation of a centrifugal compressor: Prospects of polymer additive manufacturing

This study numerically and experimentally investigates an optimized centrifugal compressor, fabricated by additive manufacturing technology. Additive manufacturing has attracted a lot of attention in industry and research and development studies due to its ability to fabricate parts of complex shapes with economic costs. In this regard, the compressor is designed based on iterative calculations of a 0D model in combination with loss models. The model can provide a preliminary geometry of the compressor according to the specifications. Then, the three-dimensional geometry of the compressor was optimized through the computational fluid dynamics calculation to find the best geometry and predict its performance. In addition, the structural aspect of the compressor rotor was analyzed through a numerical model. The components including the impeller and volute are fabricated by fused filament fabrication and stereolithography apparatus methods with polymers. The experimental results show the printed polymer rotor works properly at the speed of 52,000 r/min and can provide an expansion ratio of 0.66 with a maximum power of 250 W.

A multiscale electrochemo-mechanical model of porous electrode in lithium-ion batteries: The coupling of reaction and finite deformation

In this study, we present a novel multiscale electrochemo-mechanical model for porous electrodes in lithium-ion batteries (LIBs). Building upon the theory of finite deformation and the pseudo-two-dimensional framework introduced by Doyle et al. (Journal of the Electrochemical Society, 140, 6(1993)), our model incorporates the interaction between particle deformation and multiscale electrochemical processes, which has been lacking in previous research. The model is validated by the rate performance tests on SiO-based electrodes. By utilizing the model, we analyze the coupling effects among reaction distribution, porosity variation, and local geometrical distortion of the electrode at high current rates. We also investigate the relative importance of different electrochemo-mechanical coupling paths for materials with large volume expansion ratios. Comparing the comprehensive model with simplified versions, we find that diffusion stress is a priority due to its significant impact on ionic diffusion within particles. Porosity variation becomes equally significant at high current rates, as ionic transport in the electrolyte becomes the rate-limiting step. This work contributes to enhance understanding of the interplay between electrochemical and mechanical phenomena in LIB electrodes, especially for silicon-based materials.

The effect of extrusion condition and blend proportion on the physicochemical and sensory attributes of teff-soybean composite flour gluten free extrudates

The effects of soybean-to-teff ratio (SB), feed moisture content (FM) and barrel temperature (BT) on physico-chemical properties and sensory attributes of extruded product from teff-soybean flour blend was studied. Increase in BT resulted in increase in expansion ratio(ER), water absorption index (WAI), and water solubility index (WSI) whereas the bulk density (BD) and hardness decreased with increase in BT. Increase in the proportion of SB resulted in increased BD, hardness, and reduced water solubility index (WSI) and sensory scores. Three principal components explained 89.1 % of the variations where the first (PC1), the second (PC2) and the third (PC3) principal components explained 62.4, 20.2 and 6.5 % of the variations respectively. BD, WAI and Hardness are strongly and positively associated with each other whereas they are negatively associated with WSI, crispiness, Specific length (Lsp) and ER. Graphical optimization gave best results for BT between 128 and 137 °C and SB proportion between 2 and 7.3 % where the FM is fixed at 10 %. Besides, BT of 135 °C to137 °C, FM of 10–12 % when the SB proportion is fixed at 7.5 % gave optimal product quality. The numerical optimization resulted in optimal extrusion conditions for optimal product quality were BT of 135 °C, FM of 10 % and SB proportion of 5 % with a desirability value of 0.875. The results revealed that SB can be incorporated up to 7.5 % to obtain an acceptable product. Therefore it is possible to produce gluten-free extruded snack by blending teff and soybean flour.

Effect of soil conditioning on the permeability of coarse-grained soil in mechanized tunnelling

In coarse-grained soils, the reduction of soil permeability via conditioning can effectively prevent groundwater from entering the chamber, thus providing better tunnel face control and ultimately preventing excessive settlements of the surface. In this study, several mixtures of coarse-grained and soil-foam mixtures were utilized in experiments. In which, effects of the foam expansion ratio, foam injection ratio, soil water content, pressure, and grain size distribution on the soil permeability were investigated. In these experiments, two soil types of poorly graded sand (SP) and poorly graded sand with silt and gravel (SP-SM), with different grain sizes were utilized. Based on the experimental results, it has been observed that the soil permeability increases with increasing foam expansion ratio, water pressure, and the coarse-grained portion of the soil. Meanwhile, soil permeability decreases with increasing foam injection ratio and soil water content. Based on the observations, it can be inferred that optimal soil permeability for soil moisture of 15 %, the pressure of 1 bar with a certain grain size occurs at a foam expansion ratio of 7.5 and a foam injection ratio of 52 %.

High-performance chlorinated polyvinyl chloride/polyurea nanocomposite foam with excellent solvent resistance, flame-triggered shape memory effect and its upcycling

Facing the global environmental pollution crisis related to waste plastics, the recyclable design of polymer materials and composites, especially large commodities, is the most effective and fundamental solution. Herein, an upcycling chlorinated polyvinyl chloride/polyurea (CPVC/PUA) nanocomposite foam was designed by means of the “plasticizing-foaming-reinforcing” (PFR) strategy combined with catalytic carbonization of CPVC/PUA foams. On one hand, the foam with ultra-high expansion ratio (62 times) can be facilely prepared in supercritical CO2 at lower temperature, benefited of the reactive plasticizing function of PUA monomer-polymeric methylene diphenyldiisocyanate (PMDI). On the other hand, the obtained foam is reinforced by PMDI crosslinking reaction to in situ form nano-PUA phase in the CPVC matrix and realizing robust and superior solvent resistance and flame-triggered shape memory effect. Moreover, the foam possesses remarkable ablation resistance, which is attributed to super carbonization capacity of CPVC catalyzed by PUA. This carbonization behavior endows the foam directly upcycle into functional carbon foam accompanied by the formation of HCl gas and functional aromatics. The obtained carbon foam shows attractive electromagnetic interference shielding performance, which also may be used as potential carbon source or catalyst of producing vinyl chloride monomer in the chlor-alkali industry, especially in China.

Design and Thermodynamic Investigation of a Waste Heat‐Assisted Compressed Air Energy Storage System Integrating Thermal Energy Storage and Organic Rankine Cycle

Compressed air energy storage (CAES) technology has attracted growing attention because of the demand for load shifting and electricity cost reduction in energy‐intensive industries. To increase the round‐trip efficiency and energy storage density and simplify the structure of advanced adiabatic CAES (AA‐CAES) systems, a waste heat‐assisted CAES (WH‐CAES) design integrating a tube‐in‐tube thermal energy storage unit and an organic Rankine cycle (ORC) is described herein. Thermodynamic models of the proposed WH‐CAES system are established, and the effects of waste heat temperature, ratio of compression ratios, ratio of expansion ratios, and air storage cavern pressure on the performance of different systems, including AA‐CAES and WH‐CAES with and without ORC, are investigated. The results show that when the waste heat temperature is 500 °C, the input work of the compressors reaches its minimum value at a ratio of compression ratios of 1.14, and the optimal ratio of expansion ratios is 0.39. Under these optimal operating conditions, compared with the AA‐CAES system, the round‐trip storage efficiency, energy storage density, and system energy efficiency of the WH‐CAES system can be increased significantly. The findings validate the potential of the proposed WH‐CAES system.

Cooperative antagonistic mechanism driven by bidirectional pneumatic artificial muscles for soft robotic joints

Actuators and mechanisms are the most important components of soft robots. In this study, we introduce a novel actuator capable of bidirectional force transmission, and an antagonistic structural pair mechanism that can cooperate with actuators. A tendon that runs through the interior of the actuator allows bidirectional force transmission. Each contraction and expansion can produce 124.46 N and 122.80 N of force, and maximum contraction and expansion ratios of 75.1% and 402.1%, respectively. However, a cooperative antagonistic mechanism that can transmit force in the pushing direction using a soft frame and a closed-loop tendon has also been developed. Remarkably, it exhibits 2.58 times the lumped torque density compared to a traditional antagonistic mechanism. When integrated into a robotic arm, this mechanism enables the arm to lift a 2 kg object by 117° on a 30 cm moment arm. The robotic arm itself is efficiently designed, with a 340 mm upper arm and a 300 mm forearm, maintaining a lightweight structure at just 380 g.