Compact Structure Research Articles

A data density-based measure of dexterity for continuum robots and its comparative study

Abstract Continuum robot-based surgical systems are becoming an effective tool for minimally invasive surgery. A flexible, dexterous, and compact robot structure is suitable for carrying out complex surgical operations. In this paper, we propose performance metrics for dexterity based on data density. Data density at a point in the workspace is higher if the number of reachable points is higher, with a unique configuration lying in a small square box around a point. The computation of these metrics is performed with forward kinematics using the Monte Carlo method and, hence, is computationally efficient. The data density at a particular point is a measure of dexterity at that point. In contrast, the dexterity distribution property index is a measure of how well dexterity is distributed across the workspace according to desired criteria. We compare the dexterity distribution property index across the workspace with the dexterity index based on the dexterous solid angle and manipulability-based approach. A comparative study reveals that the proposed method is simple and straightforward because it uses only the position of the reachable point as the input parameter. The method can quantify and compare the performance of different geometric designs of hyper-redundant and multisegment continuum robots based on dexterity.

Ethanol Processable Inorganic‐Organic Hybrid Hole Transporting Layers Enabled 20.12 % Efficiency Organic Solar Cells

AbstractIn this study, a high‐performance inorganic‐organic hybrid hole transporting layer (HTL) was developed using ethanol‐soluble alkoxide precursors and a self‐assembled monolayer (SAM). Three metal oxides‐vanadium oxide (VOx), niobium oxide (Nb2O5), and tantalum oxide (Ta2O5)‐were synthesized through successive low‐temperature (100 °C) thermal annealing (TA) and UV‐ozone (UVO) treatments of their respective precursors: vanadium oxytriethoxide (EtO−V), niobium ethoxide (EtO−Nb), and tantalum ethoxide (EtO−Ta). Among these, the Nb2O5 film exhibited excellent transmittance, a high work function, and good conductivity, along with a more compact and uniform structure featuring fewer interfacial defects, which facilitated efficient charge extraction and transport. Furthermore, the deposition of a SAM of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) on top of Nb2O5 further passivated defects, enhancing interfacial contact with the photoactive layer. The resulting inorganic‐organic hybrid HTL of Nb2O5/2PACz demonstrated excellent compatibility with various photoactive blends, achieving impressive power conversion efficiencies of 19.44 %, 19.18 %, and 20.12 % for the PM6:L8‐BO, PM6:BTP‐eC9, and D18:BTP‐eC9 based organic solar cells, respectively. 20.12 % is the best performance for bulk heterojunction organic solar cells with binary components as the photoactive layer.

Discovery of CRBN-Dependent WEE1 Molecular Glue Degraders from a Multicomponent Combinatorial Library.

Small molecules promoting protein-protein interactions produce a range of therapeutic outcomes. Molecular glue degraders exemplify this concept due to their compact drug-like structures and ability to engage targets without reliance on existing cognate ligands. While cereblon molecular glue degraders containing glutarimide scaffolds have been approved for treatment of multiple myeloma and acute myeloid leukemia, the design of new therapeutically relevant monovalent degraders remains challenging. We report here an approach to glutarimide-containing molecular glue synthesis using multicomponent reactions as a central modular core-forming step. Screening the resulting library identified HRZ-1 derivatives that target casein kinase 1 α (CK1α) and Wee-like protein kinase (WEE1). Further medicinal chemistry efforts led to identification of selective monovalent WEE1 degraders that provide a potential starting point for the eventual development of a selective chemical degrader probe. The structure of the hit WEE1 degrader complex with CRBN-DDB1 and WEE1 provides a model of the protein-protein interface and ideas to rationalize the observed kinase selectivity. Our findings suggest that modular synthetic routes combined with in-depth structural characterization give access to selective molecular glue degraders and expansion of the CRBN-degradable proteome.

Varying the Core Topology in All-Glycidol Hyperbranched Polyglycerols: Synthesis and Physical Characterization.

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG-g-hbPG) in the molecular weight range of 103-106gmol-1. Linear graft hyperbranched polyglycerol (linPG-g-hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk. The morphology study of the high molecular weight structures using atomic force microscopy revealed a spherical shape for cPG-g-hbPG and hbPG, and a cylindrical shape for linPG-g-hbPG in the nanometric range. Small angle X-ray scattering confirmed the compact particle-like structure of this family of hbPG architectures. Interestingly, the glass transition temperature showed a structure dependence, with cPG-g-hbPG having the highest values and hbPG having the lowest values for the same molecular weight. This study is a step forward in the generation of water-soluble polymers with tailored structure and functionality for advanced applications.

Optimizing Exciton Diffusion and Carrier Transport for Enhanced Efficiency in Q‐PHJ and BHJ Organic Solar Cells

AbstractExciton diffusion and carrier transport are two critical factors that determine the efficiency of organic photovoltaics (OPVs). However, the relationship between these two factors has not been extensively studied. Designing non‐fullerene acceptors (NFAs) with efficient diffusion coefficients and high electronic transmittance is a key area of focus. In this study, materials for bulk‐heterojunction (BHJ) and quasiplanar‐heterojunction (Q‐PHJ) devices are synthesized to validate the desired differences in crystallinity. The single crystal of BOBO4Cl‐βδ demonstrated the most compact packing structure, with an improved planar configuration and closer π···π distances, resulting in higher electron mobility and superior exciton diffusion coefficient. Consequently, BOBO4Cl‐βδ‐based devices achieved a power conversion efficiency (PCE) of 17.38% in Q‐PHJ, compared to a lower PCE of 14.75% in BHJ devices. Furthermore, incorporating BOBO4Cl‐βδ into the D18/L8‐BO Q‐PHJ system increased the PCE from 17.98% to 18.81%, one of the highest values recorded for Q‐PHJ devices. This improvement is attributed to strong crystallinity of BOBO4Cl‐βδ, which enhances the packing arrangement and improves the exciton diffusion coefficient. Our work highlights the importance of molecular design with tunable exciton diffusion and carrier transport for BHJ and Q‐PHJ OPV architectures and reveals the relationship between them, which contributes to the achievement of high‐performance NFAs.

A microstrip bandpass filter using coupled lines loaded by open stubs

A compact simple structure bandpass filter based on terminated three coupled line structures with high selectivity is introduced through odd and even-mode analysis. The proposed filter consists of three coupled lines loaded by open and short circuit stubs. The parallel-coupled lines structure is used to obtain high selectivity with transmission zeros near the passband. Meanwhile, simultaneously tuning on bandwidth and center frequency are introduced by coupled line. One type of bandpass filter based on terminated coupled line structure is theoretically analyzed, simulated, and measured. The stepped impedance structures at the input and output ports have been used to improve the attenuation level at the stopband region and create the multiple attenuation poles. The center frequency of 1.3 GHz, the fractional bandwidth (FBW) of about 65%, the low insertion loss of 0.25 dB, and the high return loss of 30 dB are obtained. Also, a flat group delay lower than 1.4 ns is achieved. Experimental and simulated results are presented, which are in good agreement.

Study on Welding Characteristics and Parameters of Gas Metal Arc Welding for A516 Grade 70 Steel with ER70S-6 and ER308LSi Filler Materials.

Welding is a crucial process in joining metals, especially in the fabrication industry. Thisresearch aimed to investigate the effects of using two different filler materials, ER70S-6 and ER308LSi, with nine combinations of wire feeder speed (WFS) and shielding gas flow rate (GFR), on weld joints. The study focused on the weld quality and material properties of Gas Metal Arc Welded (GMAW) butt joints of ASTM A516 G70 plates, characterized through visual inspection, liquid penetrant testing, tensile testing, hardness testing, and optical microscopy. Results indicated that the highest ultimate tensile strength and hardness were achieved at 4 m/min WFS and 15 L/min GFR with ER70S-6, and 5 m/min WFS and 20 L/min GFR with ER308LSi. The specimens welded with ER308LSi demonstrated superior mechanical properties compared to those welded with ER70S-6. Additionally, the study revealed the influence of microstructural changes from the base metal (BM) to the heat-affected zone (HAZ) and fusion zone (FZ), with finer and more compact grain structures contributing to higher hardness values. These findings underscore the importance of selecting appropriate filler materials, WFS, and GFR to achieve the desired weld quality and material properties for A516 G70 low-carbon steel welded joints.

Sintering Behavior of Molybdenite Concentrate During Oxidation Roasting Process in Air Atmosphere: Influences of Roasting Temperature and K Content.

Sintering is a common phenomenon, which often takes place during the oxidation roasting process of molybdenite concentrate in multiple-hearth furnaces. The occurrence of sintering phenomena has detrimental effects on the product quality and the service life of the furnace. In this work, the influence of two key factors (roasting temperature and K content) on the sintering behavior is investigated using molybdenite concentrate as the raw material. Different technologies such as XRD, FESEM-EDS, and phase diagrams are adopted to analyze the experimental data. The results show that the higher the roasting temperature is, the greater the mass loss and the more serious the sintering degree will be. The results also show that with the increase in K content, the mass loss of the raw material is first increased and then decreased, while its sintering degree is still gradually increased. The sintering products obtained during the oxidation roasting process are often tightly combined with the bottom of the used crucible with a smooth and dense surface structure, while their internal microstructures are very complicated, which not only includes numerous MoO3 species, but also unoxidized MoS2, Mo sub-oxide, SiO2, and a variety of molybdates. Among them, both MoO3 and molybdates can be easily dissolved into the ammonia solution, leading to a residue mainly composed of SiO2 and CaMoO4. This study also finds that the sintering phenomenon is caused by the increase in local temperature and the formation of various low-melting-point eutectics. It is suggested that decreasing the roasting temperature and K content, especially the K content, are effective methods for reducing the sintering degree of molybdenite concentrate during the oxidation roasting process.

Deacetylation enhances the structure and gelation properties of konjac glucomannan/soy protein isolate cold-set gels

This study aimed to investigate the effect of the deacetylated konjac glucomannan (DKGM), with varying degree of deacetylation (DD), on the physicochemical and structural properties of transglutaminase-induced soy protein isolate (SPI) cold-set gels. Compared with native konjac glucomannan (KGM), DKGM significantly enhanced the gel strength, water-holding capacity, and thermal stability of the composite gels, with DK3 (DKGM with 65.85 % deacetylation) showing the most significant improvement. The secondary and tertiary structures of SPI in the DK3 group were the most stable. Compared with the KGM group, the DK3 group showed a 58.32 % increase in hydrophobic interaction and a 37.98 % decrease in free sulfhydryl content. The microstructure results demonstrated that DK3 was uniformly dispersed within the SPI network, promoting the formation of a continuous and dense network structure. This was mainly due to DK3 having a moderate particle size and low viscosity. Therefore, DKGM with a moderate DD is conducive to forming a more ordered and dense gel network structure, imparting optimal gel performance to the SPI cold-set gel.

Design and optimization of a planar anti-buckling compliant rotational joint with a remote center of motion

Compliant mechanisms (CMs) exhibit some excellent mechanical properties and provide numerous innovative solutions for many existing mechanical applications. Among them, planar compliant rotational joints have made substantial contributions to precision engineering. To achieve high-precision positioning with a compliant rotational joint, it is essential to study characteristics such as anti-buckling and constant stiffness. The remote center of motion (RCM) mechanism, with its compact structure and ease of precise control, is expected to enhance overall rigidity and reduce parasitic displacements. Here, we propose a planar anti-buckling compliant rotational joint with a RCM. Static modeling and model validation are conducted for different geometric configurations, including single and combined structures. A distributed configuration with bidirectional anti-buckling properties is selected for optimization. Using a global parameter optimization model, single-objective optimization studies are conducted for three distinct characteristics. Subsequently, a multi-objective optimization model for constant stiffness and high precision is established. Based on the optimization results, a compliant rotational joint with bidirectional anti-buckling, constant rotational stiffness, and high precision is designed. Finally, the effectiveness of the optimization method is validated through physical experiments.

Effect of chitosan molecular weight and protein to polysaccharide ratio on the rheological and physicochemical properties of milk proteins–chitosan complex coacervate

The small amplitude oscillatory shear (SAOS) rheological properties of complex coacervate of milk proteins with high (HMC), medium (MMC), and low (LMC) molecular weight chitosan in the optimal ratios of milk proteins to chitosan (15:1, 10:1, and 5:1, respectively) were measured. In addition, the morphological (SEM), structural (XRD), and thermal (DSC) properties of the complex coacervates were investigated in comparison with the milk protein concentrate. Complex coacervates showed the shear-thinning behavior due to a linear decrease of complex viscosity with increasing frequency. Furthermore, the highest complex modulus and the more compact structure under optimal conditions, in terms of the ratio of protein to chitosan and pH, revealed strong electrostatic bonding between proteins and chitosan. All coacervates showed a G′ > G″ (Tanδ<1), indicating the formation of an interconnected gel-like structure that was described by the power law model. The maximum fracture stress was obtained at optimum conditions (R = 15:1, pH =6.7 for HMC; R = 10:1, pH =5.5 for MMC and R = 5:1, pH =4.6 for LMC), indicating the highest intermolecular interaction between milk proteins and chitosan. The coacervates had a completely amorphous structure similar to MPC, and according to DSC results, the ionic bonds between milk proteins and chitosan were not destroyed up to 300 °C. Coacervation leads to purified milk proteins at a low cost. In addition, the coacervates can be used for the encapsulation of heat-sensitive compounds, and also as a stabilizer to improve the texture of food.

Research of Reducing Liquid Damping of Liquid Inertia Vibration Eliminator

The liquid inertia vibration eliminator (LIVE) is a type of dynamic anti-resonance vibration isolation (DAVI) devices with compact structure and light weight, which is mainly used in vibration control in the main transmission of helicopters. To investigate the influence of damping generated by the internal liquid flow on the vibration isolation performance, a model and the equations of motion of the LIVE system are established. The friction head loss, local resistance loss and damping coefficient caused by liquid movement in the tuning port of LIVE are calculated. The factors affecting the damping coefficient of the liquid are analyzed. Parameter sensitivity analyses are carried out to reveal the order of importance and interaction of the parameters. Results show that the damping of the LIVE has a negative impact on the vibration isolation performance. The liquid damping is affected by many parameters and the model has a high degree of non-linearity and complexity. The liquid damping can be effectively reduced through the selection of appropriate liquid properties and the design of the structural parameters of the LIVE.

Comparative Research on Landing and Rollout Characteristics of Skid-Equipped and Wheeled Aircraft

Skid landing gear is a specialized landing device known for its compact structure and lightweight. However, current research on the dynamic characteristics of skid-equipped aircraft on concrete runways is limited, which raises uncertainties about its practical applications. To address this gap, a general aircraft model based on a modular concept is first constructed, considering the coupling effects of aerodynamic, buffer, and ground forces. On this basis, the differences in motion characteristics between skid-equipped and wheeled aircraft are compared in detail. Then, the impact of various factors on the landing characteristics of skid-equipped aircraft is analyzed, such as initial longitudinal velocity, pitching angle, and friction coefficient of skid. Simulation results show that the lack of buffering capability provided by tires results in a 10.57% increase in overload for skid-equipped aircraft and a 15.39% decrease in the efficiency of the main landing gear buffer. Notably, the initial pitching angle has a critical impact on the landing overload of skid-equipped aircraft. Due to the significant differences in the mechanical properties of the landing gears, the skid-equipped aircraft without nose wheel steering ability is a statically unstable system during the rollout phase. The intervention of asymmetric disturbances would pose a serious threat to the rollout safety.

A fully integrated temperature sensor with an inaccuracy of ±0.4 °C (3σ) from −55 to 150 °C

A high-accuracy fully integrated temperature sensor for a wide temperature range up to 150 °C is presented in this article. The sensing circuits with the asymmetric operational amplifier and bias current optimization is applied to eliminate the component mismatch error and enhance the accuracy. The asymmetric operational amplifier can remove the offset voltage avoiding the switching noise compared with the chopping method. An extended counting analog-to-digital convertor (ADC) is proposed as the readout interface due to its compact structure and high efficiency. An easily-achieved dynamic range improvement is devised. Benefited by the dynamic range improvement, the 14-bit ADC can achieve a resolution of 0.0156 °C. This temperature sensor is fabricated in a 0.18-μm CMOS process, and it achieves an accuracy of ±0.4 °C (3σ) from −55 to 150 °C.

A compact structure and high-speed actuator designed by imitating the movement of wave

By imitating the natural phenomenon of waves pushing leaves, a compact novel wave-type piezoelectric actuator is proposed in this paper. Compared to traditional inchworm piezoelectric actuators, it combines the clamping unit and driving unit into an arc-shaped flexible driving foot (AFDF). Clamping and driving functions are realized by alternately controlling two ends of the AFDF using two piezoelectric stacks (PESs). One motion unit instead of two makes control simpler, the structure more compact and a faster movement speed. The static model of the AFDF is developed to characterize the mapping laws between structural dimensions and actuator amplification ratios, and the dynamic model represents the relationship between the control signals and move displacements, thus demonstrating the feasibility of the actuator. Finally, a prototype was fabricated, and a testing system was set up to conduct performance evaluations of its motion capabilities. At the driving frequencies of 370 Hz and 380 Hz, the maximum forward and reverse motion speeds can reach 4.345mm/s and 4.537mm/s, respectively. In the range of 0.1-10N, there is no significant change in motion speed, and it has good stability. Its resolution for forward and reverse motion can reach 106nm and 109nm, respectively.

Thermal-hydraulic analysis of He-Xe gas mixtures in triangular rod bundle wrapped with different shaped wire wraps

Gas-cooled reactors employing a helium-xenon (He-Xe) gas mixture as the coolant are regarded as one of the most promising technologies for megawatt-scale space energy systems. One technical solution to achieve high power density, reduced mass, and a compact structure in gas-cooled space reactors is the use of fuel arranged in triangular bundles encased with wire wraps. Nevertheless, research on the flow and heat transfer characteristics of He-Xe gas within such configurations remains scarce. In order to enhance the heat transfer performance of He-Xe reactor cores, thermal–hydraulic simulation methods were employed using computational fluid dynamics (CFD) in order to investigate the thermal–hydraulic characteristics within a triangular rod bundle channel equipped with wire wraps. The study examined the impact of wire wrap structures on velocity and temperature fields, inter-subchannel mixing, and the distribution of hot spots. The findings indicate that the wire wrap structure has the effect of promoting transverse flow, inter-channel mixing and vortex formation. Conversely, this also gives rise to the issue of hot spots, particularly at the contact angles between the wire wrap and the fuel rod. At a wall heat flux of 91,477.3 kW m−2, the maximum temperature at the circular wire wrap hot spot can reach 1217 K, while the average wall temperature of the corresponding cross-section is only 770 K. Furthermore, the flow and heat transfer characteristics of three wire wrap geometries—circular, rectangular, and trapezoidal—were evaluated and compared across a Reynolds number range of 2.6 × 104 to 1.4 × 105. The findings indicate that the trapezoidal wire wrap configuration results in the lowest wall hot spot temperature and the smallest temperature inhomogeneity. Furthermore, an analysis of the heat transfer coefficients (Nusselt number) and thermo-hydraulic performance ratios (THPR) demonstrates that the trapezoidal wire wrap exhibits superior heat transfer performance compared to the other two geometries.

Revealing synergistic relationship of thermal conduction and electromagnetic shielding of reduced graphene oxide film

The present work tries to explore the evolution process of electro-magnetic interference shielding effectiveness and thermal conductivity of graphene film. There is an obvious promotion of electrical conductivity (from 3.51×10-3 to 769.20 S m-1) when GO is thermally reduced at 1100°C. Correspondingly, the reduced graphene oxide (rGO) achieves the highest EMI shielding effectiveness (∼54.84 dB) at 1100°C which is an synergetic result of electrical conductivity and porous structure with rich defects. The rGO is furtherly graphitized at 2800°C (G-rGO) to repair the defects and C-C network and then mechanically rolled to a densified film with bulk density of 1.64 g cm-3 (called as DG-rGO). The thermal conductivity of DG-rGO membrane increases to 720.56 W m-1 K-1 after graphitization and rolling. Porous structure and defects are beneficial to higher EMI shielding effectiveness while dense structure without defects lead to higher thermal conductivity. Therefore, the highest EMI shielding effectiveness and thermal conductivity cannot be obtained simultaneously. A reference range is provided to fulfill the request of EMI shielding and thermal conductivity.

Influence of Si-addition on tribological and corrosion properties of Ta-Si-C coatings

Ta-Si-C coatings with Si content varying from 2.7 to 30.8 at.% were synthesized by magnetron co-sputtering. Their microstructure, tribological properties and corrosion performance were investigated. The coatings exhibited two distinct structural forms: a Ta(C, Si) solid solution for the lower silicon contents (2.7 and 5.6 at.% Si) and a Ta(C, Si)/a-C:Si nanocomposite for higher Si content (13.7, 20.8 and 30.8 at.% Si). Notably, the Ta(C, Si) solid solution at 5.6 at.% Si demonstrated the highest hardness of 44±2.7 GPa, resulting from the solid solution strengthening. Furthermore, this solid solution also demonstrated the lowest wear rate (1.21×10-6 mm3N-1m-1), due to its superior hardness and H3/E2 ratio. Additionally, the coating with 5.6 at.% Si displayed the most outstanding corrosion resistance, attributed to its higher crystalline quality and denser structure, which effectively prevented the permeation of corrosive media through the coating to the substrate.

A synergistic strategy for formulating a facile and cost-effective soybean protein-based adhesive via co-crosslinking and inorganic hybridization.

Soybean protein-based adhesives (SPAs) are environmentally friendly, sustainable, and renewable, but their wide applications are limited by moderate bonding strength, poor water resistance, undesirable flame retardancy, and high costs. Inspired by the organic-inorganic hybridization of oysters, a facile and cost-effective SPA was developed in this study via co-crosslinking branched melamine-urea-glyoxal (MUG) and polyamidoamine-epichlorohydrin (PAE) resins, as well as inorganic hybridization by using the mineral bentonite (BT). Low-cost branched MUG resins that could efficiently co-crosslink with PAE resin and substitute for 40 % expensive PAE resin were optimally copolymerized from melamine, urea, and glyoxal. This approach provided more co-crosslinkable sites for constructing denser multiple covalently-crosslinked SP-PAE-MUG networks via MUG-protein crosslinking and MUG-PAE co-crosslinking. 30 wt% of low-cost layered mineral BT was intercalated to further reinforce the mechanical properties and flame retardancy of SPA by forming a compact organic-inorganic hybridized structure. The coordination of MUG-PAE co-crosslinking and BT inorganic hybridization resulted in a cost-effective and robust SPA with a 61.2 % higher dry strength, a soaked wet strength of 126.0 %, an aged wet strength of 86.0 %, a residual carbon content after combustion of 94.3 %, and reduced the raw material cost for formulating adhesive by 19.5 % compared with controlled commercial SPA. This novel strategy highlights the potential applications of the SP in bio-adhesives and bio-composites with excellent bonding strength, water resistance, and flame retardancy.

The Green Monster Hiding in Front of Cas A: JWST Reveals a Dense and Dusty Circumstellar Structure Pockmarked by Ejecta Interactions

JWST observations of the young Galactic supernova remnant Cassiopeia A revealed an unexpected structure seen as a green emission feature in colored composite MIRI F1130W and F1280W images—hence dubbed the Green Monster—that stretches across the central parts of the remnant in projection. Combining the kinematic information from NIRSpec and the MIRI Medium Resolution Spectrograph with the multiwavelength imaging from NIRCam and MIRI, we associate the Green Monster with circumstellar material (CSM) that was lost during an asymmetric mass-loss phase. MIRI images are dominated by dust emission, but their spectra show emission lines from Ne, H, and Fe with low radial velocities indicative of a CSM nature. An X-ray analysis of this feature in a companion paper supports its CSM nature and detects significant blueshifting, thereby placing the Green Monster on the nearside, in front of the Cas A supernova remnant. The most striking features of the Green Monster are dozens of almost perfectly circular 1″–3″ sized holes, most likely created by interaction between high-velocity supernova ejecta material and the CSM. Further investigation is needed to understand whether these holes were formed by small 8000–10,500 km s−1 N-rich ejecta knots that penetrated and advanced out ahead of the remnant’s 5000–6000 km s−1 outer blast wave or by narrow ejecta fingers that protrude into the forward-shocked CSM. The detection of the Green Monster provides further evidence of the highly asymmetric mass loss that Cas A’s progenitor star underwent prior to its explosion.