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Purpose This study aims to introduce a deep neural network (DNN) to estimate the effective thermal conductivity of the flat heat pipe with spreading thermal resistance. Design/methodology/approach A total of 2,160 computational fluid dynamics simulation cases over up to 2,000 W/mK are conducted to regress big data and predict a wider range of effective thermal conductivity up to 10,000 W/mK. The deep neural networking is trained with reinforcement learning from 10–12 steps minimizing errors in each step. Another 8,640 CFD cases are used to validate. Findings Experimental, simulational and theoretical approaches are used to validate the DNN estimation for the same independent variables. The results from the two approaches show a good agreement with each other. In addition, the DNN method required less time when compared to the CFD. Originality/value The DNN method opens a new way to secure data while predicting in a wide range without experiments or simulations. If these technologies can be applied to thermal and materials engineering, they will be the key to solve thermal obstacles that many longing to overcome.

Developing catalysts with outstanding performance for oxygen evolution reaction (OER) is crucial to advance energy conversion technologies. In these regards, catalysts based on 3d transition metals have recently attracted much attention, yet further development is required. Here, we present a new type of heterostructure catalyst in which CoO nanowire arrays are hybridized with tungsten nanoparticles (W-CoO), and are self-supported on conductive carbon cloth (CC). Electronic coupling effects at the W-CoO heterointerface promote electron transfer and OER kinetics to expedite the formation of oxyhydroxide species, which are the active sites for OER processes. A variety of in situ and ex situ characterization methods are employed to reveal deep insights into surface transformations and investigate the relationship between the conversion to oxyhydroxide moieties and OER performance. This report presents new understanding of the rational design and synthesis of catalysts that exhibit outstanding performance as electrochemical water splitting electrode for OER.

Objective: Endoscopic surgical procedures rigorously underscore the significance of rapid hemostasis for unavoidable intraoperative bleeding, requiring advancement of the immediate hemostatic interventions for favorable clinical outcomes. Here, we report the efficacy of a new optical treatment with dual-wavelengths to develop an endoscopic hemostasis method. Methods: we combine visible (20-W 532 nm at 1.1 kW/cm2) and near-infrared (40-W 980 nm at 2.2 kW/cm2) wavelengths for facilitating noncontact thermal hemostasis on venous and arterial bleeders in in vivo leporine models. Results: Simultaneous irradiation of 60-W dual-wavelengths allows for an increased irradiance of 3.3 kW/cm2, involving both rapid light absorption by hemoglobin and deep thermal penetration. The collective thermal effects from the combined wavelengths contribute to a significant reduction in coagulation time and a high success rate of complete hemostasis for both venous and arterial bleeders. The enhanced hemostatic potential of the dual-wavelengths treatment accompanies minimal hemorrhage, reduces inflammatory responses, and facilitates re-epithelialization. Conclusion: The proposed dual-wavelengths method can achieve rapid and complete hemostasis for endoscopic procedures. Significance: We present the high-irradiance photothermal treatment using the dual-wavelengths as a novel method to regulate venous and arterial bleeding and potentially as a rapid noncontact hemostasis option to mitigate the risk associated with significant blood loss.

Fibrosis is a prevalent problem that pathologically accompanies chronic inflammatory diseases. Despite the availability of various fibrosis treatments, therapeutic efficacy must be further improved to achieve better clinical outcomes. The purpose of this study is to develop a novel treatment by combining phloroglucinol (PHL) with photobiomodulation (PBM) to prevent skin fibrosis. In in vitro, 635 nm PBM at 8 J/cm2 significantly reduced TNF-alpha levels, and 100 μg/ml of PHL suppressed the expression of α-smooth muscle actin and type I collagen due to the downregulation of SMAD 2/3 and MAPK signaling pathways. The 1470 nm laser light created the initial wound (97.1 mm2), leading to scar formation after complete wound closure (21 days) on rodent skin. In comparison to other groups, the dual treatment accelerated wound closure and achieved rapid and complete healing in 17 days. Histological analysis presented the reduced fibrotic scar and collagen deposition in the dual treatment group. PHL-combined PBM treatment enhanced the anti-inflammatory effect by 36% in comparison to single treatment groups. Overall, the proposed combined treatment promoted wound healing and enhanced anti-inflammatory and anti-fibrotic effects in the overexpressed in vitro and in vivo models.

Hybrid catalysts consisting of metal nanoparticles on a metal oxide support have emerged as a new class of catalysts that can improve various electrocatalytic reactions, but the origin of the improved performance is still unclear. Here we demonstrate that rationally designed hybrid catalysts through the in situ exsolution process of metallic nanoparticles on a B-site Ni-substituted lead ruthenate pyrochlore oxide improve both oxygen evolution reaction and hydrogen evolution reaction activity. A combination of operando X-ray absorption spectroscopy measurements and density functional theory calculations reveals that the generated oxygen and cation vacancies in the pyrochlore oxide support during the in situ exsolution process can decrease the charge-transfer energy, thereby facilitating charge transfer between exsolved metal nanoparticles–oxide support as well as hybrid catalyst–electrolyte. These findings establish a structure–property relationship of complicated hybrid catalysts for efficient water splitting, suggesting a new strategy in designing various hybrid catalysts for other electrochemical reactions.

The design of active and stable electrocatalysts for oxygen evolution reaction is a key enabling step toward efficient utilization of renewable energy. Along with efforts to develop high-performance electrocatalysts for oxygen evolution reaction, pyrochlore oxides have emerged as highly active and stable materials that function as catalysts as well as conductive supports for hybrid catalysts. The compositional flexibility of pyrochlore oxide provides many opportunities to improve electrocatalytic performance by manipulating material structures and properties. In this Outlook, we first discuss the recent advances in developing metallic pyrochlore oxides as oxygen evolution catalysts, along with elucidation of their reaction mechanisms, and then introduce an emerging area of using pyrochlore oxides as conductive supports to design hybrid catalysts to further improve the OER activity. Finally, the remaining challenges and emerging opportunities for pyrochlore oxides as electrocatalysts and conductive supports are discussed., This Outlook summarizes recent advances in pyrochlore oxides as oxygen evolution catalysts and introduces a new approach using pyrochlore oxides as a conductive support to design hybrid catalysts.

Simulation involving interaction with deformable objects often causes stability problems because a slowly updated force generates additional energy to the human user. This paper proposes a stable and transparent haptic rendering for simulation involving interaction between a rigid tool and deformable objects. This method computes visual and haptic feedback in the simulation and haptic feedback loops, respectively. A local stiffness matrix consisting of points around contact points is constructed based on collision detection between a virtual tool and a deformable object in the simulation loop. The haptic feedback is then computed at a higher update rate in the haptic feedback loop using the local stiffness matrix. Equivalent springs computed by using the equivalent stiffness energy are added to the boundary of the local stiffness matrix to minimize errors in the rendered force. The proposed method is compared with the virtual coupling widely used in simulation involving interaction with deformable objects. The proposed method reduces the x -, y -, and z -axis maximum force errors by up to 52%, 80%, and 70%, respectively, compared to the virtual coupling in the simulation involving interaction with the Stanford bunny object consisting of 2087 points and 9997 tetrahedrons.

With the lightening of the mobile devices, thinning of electrolytic copper foil, which is mainly used as an anode collection of lithium secondary batteries, is needed. As the copper foil becomes ultrathin, mechanical properties such as deterioration of elongation rate and tear phenomenon are occurring, which is closely related to microstructure. However, there is a problem that it is not easy to prepare and observe specimens in the analysis of the microstructure of ultrathin copper foil. In this study, electron backscatter diffraction (EBSD) specimens were fabricated using only mechanical polishing to analyze the microstructure of 8 μm thick electrolytic copper foil in plane view. In addition, EBSD maps and transmission electron microscopy (TEM) images were compared and analyzed to find the optimal cleanup technique for properly correcting errors in EBSD maps.

Heat pipe technology with latent heat has been a rising topic for various engineering applications such as electric cars and high-power computer chips. It has been studied for thermal resistance and model development as they are the key to infer effective thermal conductivity. In this article, computational fluid dynamics is investigated to look at the two-phase flow and heat transfer of a two-phase thermosyphon of which inside cannot be visualized experimentally. The Volume-of-Fluid model has been utilized as well as the Lee model. Thermal resistance tendencies are also examined for different amounts of water, heat pipe diameter, and heater power. As a result, the thermal resistance decreases when the water amount, heat pipe diameter, and heater power increase, indicating that temperature is quickly cooled down by latent heat. The thermal resistance for different conditions is modeled with a simple scaling analysis, and a good agreement is made between the model and the numerical results. Effective thermal conductivity is also calculated based on the thermal resistance results. An increase in thermal conductivity is observed as the diameter decreases, indicating the importance of an optimum thermosyphon design.

Microbial lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of crystalline polysaccharides including chitin and cellulose. The discovery of a large assortment of LPMO-like proteins widely distributed in insect genomes suggests that they could be involved in assisting chitin degradation in the exoskeleton, tracheae and peritrophic matrix during development. However, the physiological functions of insect LPMO-like proteins are still undetermined. To investigate the functions of insect LPMO subgroup I-like proteins, which contain an AA15 LPMO catalytic domain and a conserved C-terminal cysteine-rich motif, two evolutionarily distant species, Tribolium castaneum and Locusta migratoria, were chosen for study. RNAi for the T. castaneum protein, TcLPMO1, caused molting arrest at all developmental stages, whereas RNAi of the L. migratoria protein, LmLPMO1, prevented only adult eclosion. In both species, LPMO1-deficient animals were unable to shed their exuviae and died. TEM analysis revealed failure of turnover of chitinous cuticle, which is critical for completion of molting. Purified recombinant LPMO1-like protein from Ostrinia furnacalis (rOfLPMO1) exhibited oxidative cleavage activity and substrate preference for chitin. These results reveal for the first time the physiological importance of catalytically active LPMO1-like proteins from distant insect species and provide new insight into the enzymatic mechanism of chitin turnover during molting.

Microbial lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of crystalline polysaccharides including chitin and cellulose. The discovery of a large assortment of LPMO-like proteins widely distributed in insect genomes suggests that they could be involved in assisting chitin degradation in the exoskeleton, tracheae and peritrophic matrix during development. However, the physiological functions of insect LPMO-like proteins are still undetermined. To investigate the functions of insect LPMO15 subgroup I-like proteins (LPMO15-1s), two evolutionarily distant species, Tribolium castaneum and Locusta migratoria, were chosen. Depletion by RNAi of T. castaneum TcLPMO15-1 caused molting arrest at all developmental stages, whereas depletion of the L. migratoria LmLPMO15-1, prevented only adult eclosion. In both species, LPMO15-1-deficient animals were unable to shed their exuviae and died. TEM analysis revealed failure of turnover of the chitinous cuticle, which is critical for completion of molting. Purified recombinant LPMO15-1-like protein from Ostrinia furnacalis (rOfLPMO15-1) exhibited oxidative cleavage activity and substrate preference for chitin. These results reveal the physiological importance of catalytically active LPMO15-1-like proteins from distant insect species and provide new insight into the enzymatic mechanism of cuticular chitin turnover during molting.

Transition metal single atom catalysts have recently emerged in acid oxygen evolution reactions (OER) due to their maximum atomic efficiency and high durability. Herein, we report a 3d orbital level rearrangement in square planar symmetry according to the ligand type of a cobalt single atom catalyst. We fabricate cobalt single atom catalyst supported on pyrrole type nitrogen doped crumpled graphene (Pyrrolic CoN4-CG) for acidic OER and it shows orbital rearrangement phenomenon because of their longer Co-N bond distance than pyridine type CoN4 sites. When pyrrole type nitrogen is introduced as a ligand of a cobalt single atom catalyst, the degree of oxidation during OER reaction is much greater than when pyridine type nitrogen ligand is introduced, which is confirmed by Operando X-ray absorption spectroscopy measurements. In addition, the reduction of OH- adsorption energy according to the orbital level rearrangement of Pyrrolic CoN4 and the change in the rate determination step are revealed by density functional theory calculations.

van der Waals heterostructures composed of two-dimensional materials vertically stacked have been extensively studied to develop various multifunctional devices. Here, we report WSe

The sodium-air (Na–air) batteries are considered as a new promising energy storage devices due to their 1683 W h kg−1 of high theoretical specific energy density. However, these outstanding theoretical energy density performances cannot be achieved because undesirable sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) reaction kinetics on the air cathode side causes the high overpotential gap and low round-trip efficiencies during charge-discharge process. Therefore, the development of highly active bifunctional oxygen electrocatalysts is the key strategy to obtain the low overpotential gap with high energy density performance of Na-air batteries. In this work, a novel single crystalline thallium ruthenium oxide (Tl2Ru2O7) with pyrochlore structure was firstly revealed as an effective bifunctional electrocatalyst. Moreover, in order to enhance the surface chemical reactivity of Tl2Ru2O7, the surface of Tl2Ru2O7 is functionalized by using the dihydrogen phosphate ion (P-Tl2Ru2O7) for achieving the effective and rapid charge transfer behavior. The superior bifunctional catalytic activity of P-Tl2Ru2O7 can be explained by the degree of covalency of Ru-O bonds in Tl2Ru2O7 and enhanced covalent character by functionalized dihydrogen phosphate ion, which can afford favorable oxidation nature to Tl and Ru ions.

The sodium-air (Na-air) batteries are spotlighted as state-of-the-art electrical energy storage system, because of their high sodium-ion conductivity and specific energy density performance. However, the undesirable sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) kinetics limit the practical production of rechargeable Na-air batteries. Therefore, it is essential to develop highly effective bifunctional electrocatalysts for OER and ORR. Although the pyrochlore oxides (A2B2O7) exhibits great potential for highly-active bifunctional electrocatalyst, the lack of studies regarding to A-site cations have hindered the development of new pyrochlore catalysts with comprehensive understanding of catalytic activity. In this work, we report the use of a novel nanocrystalline bismuth ruthenate pyrochlore oxide (Bi2Ru2O7) as an effective oxygen electrocatalyst by using the favorable oxidation nature of Bi and Ru ions in Bi2Ru2O7. Further, the oxidized cations can donate the electrons to the surface and inner layers, providing the low-resistance pathway during OER and ORR. Finally, the bifunctional electrocatalytic activities of Bi2Ru2O7 are successfully translated to a practical device, an aqueous Na-air battery, for the first time.

We developed a guinea fowl jumping robot with a one-axis momentum wheel mechanism with a passive hallux model. The Guinea fowl jumping robot was able to perform stable vertical jumping due to the linkage structure designed as a passive hallux model. Furthermore, we used the one-axis momentum wheel mechanism in the jumping robot for making the compact balance control mechanism that can control the body angle of the robot. Through the experiment, the conventional jumping robot uses the inertial tail to adjust the body angle in the air for stable landing and jumping. However, in the case of an inertial tail, it has a large volume and has a disadvantage in that stability is highly reduced when it collides with obstacles due to the shape of the inertial tail. Moreover, we performed a theoretical analysis, simulation, and experiment to verify the performance of the momentum wheel mechanism, and we confirmed that the passive hallux structure contributed to the jumping stability. Besides, we proved that the momentum wheel could adequately land on the ground by adjusting the body angle after vertical jumping. In addition, we demonstrated that the stability of the momentum wheel is higher than the inertial tail through collision simulation.

Ir and its oxide are the only available oxygen evolution reaction (OER) electrocatalysts with reasonably high activity and stability for commercial proton-exchange membrane electrolyzers. However, the establishment of structure–performance relationships for the design of better Ir-based electrocatalysts is hindered by their uncontrolled surface reconstruction during OER in acidic media. Herein, we monitor the structural evolution of two model Ir nanocrystals (one with a flat surface enclosed by (100) facets and the other with a concave surface containing numerous high-index planes) under acidic OER conditions. Operando X-ray absorption spectroscopy measurements reveal that the promotion of surface IrOx formation during the OER by the concave Ir surface with high-index planes results in a gradual OER activity increase, while a decrease in activity and limited oxide formation are observed for the flat Ir surface. After the activation process, the Ir concave surface exhibits ~ 10 times higher activity than the flat surface. Density functional theory computations reveal that Ir high-index surfaces are thermodynamically preferred for the adsorption of oxygen atoms and the formation of surface oxides under OER conditions. Thus, our work establishes a structure–performance relationship for Ir nanocrystals under operating conditions, providing new principles for the design of nanoscale OER electrocatalysts.

Resonant elastic X-ray scattering has been widely employed for exploring complex electronic ordering phenomena, like charge, spin, and orbital order, in particular in strongly correlated electronic systems. In addition, recent developments of pump-probe X-ray scattering allow us to expand the investigation of the temporal dynamics of such orders. Here, we introduce a new time-resolved Resonant Soft X-ray Scattering (tr-RSXS) endstation developed at the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL). This endstation has an optical laser (wavelength of 800 nm plus harmonics) as the pump source. Based on the commissioning results, the tr-RSXS at PAL-XFEL can deliver a soft X-ray probe (400-1300 eV) with a time resolution about ~100 fs without jitter correction. As an example, the temporal dynamics of a charge density wave on a high-temperature cuprate superconductor is demonstrated., 7 figures, 2 tables

Chalcogenide-based materials have attracted widespread interest in high-performance thermoelectric research fields. A strategy for the application of two types of chalcogenide for improved thermoelectric performance is described herein. Tin selenide (SnSe) is used as a base material, and Te nanoneedles are crystallized in the SnSe, resulting in the generation of a composite structure of SnSe with Te nanoneedles. The thermoelectric properties with various reaction times are investigated to reveal the optimum conditions for enhanced thermoelectric performance. A reaction time of 4 h at 450 K generated a composite Te nanoneedles/SnSe sample with the maximum ZT value, 3.2 times larger than that of the pristine SnSe. This result is attributed to both the reduced thermal conductivity from the effective phonon scattering of heterointerfaces and the improved electrical conductivity value due to the introduction of Te nanoparticles. This strategy suggests an approach to generating high-performance practical thermoelectric materials.

Here we present our study on an impact print-type hot embossing process which can create dot patterns with various designs, widths, and depths in real time on polymer film. In addition, we implemented a control system for the on-off motion and position of the impact header to engrave different dot patterns. We performed dot patterning on various polymer films, such as polyester (PET) film, polymethyl methacrylate (PMMA) film, and polyvinyl chloride (PVC) film. The dot patterns were measured using a confocal microscope, and we confirmed that the impact print-type hot embossing process produces fewer errors during the dot patterning process. As a result, the impact print-type hot embossing process is found to be suitable for engraving dot patterns on different types of polymer films. In addition, unlike the conventional hot embossing process, this process does not use an embossing stamp. Therefore, the process is simple and can create dot patterns in real time, presenting unique advantages for mass production and small-quantity batch production.

Laser lights have been used by dermatologists for tattoo removal through photothermal interactions. However, most clinical studies used a visual scoring method to evaluate the tattoo removal process less objectively, leading to unnecessary treatments. This study aimed to develop a simple and quantitative imaging method to monitor the degree of tattoo removal in in vivo skin models. Sprague Dawley rat models were tattooed with four different concentrations of black inks. Laser treatment was performed weekly on the tattoos using a wavelength of 755 nm over six weeks. Images of non-treated and treated samples were captured using the same method after each treatment. The intensities of the tattoos were measured to estimate the contrast for quantitative comparison. The results demonstrated that the proposed monitoring method quantified the variations in tattoo contrast after the laser treatment. Histological analysis validated the significant removal of tattoo inks, no thermal injury to adjacent tissue, and uniform remodeling of epidermal and dermal layers after multiple treatments. This study demonstrated the potential of the quantitative monitoring technique in assessing the degree of clearance level objectively during laser treatments in clinics.

SUMMARYPrevious researches on analysis of stability of haptic simulation largely assume that the virtual environment is passive. But the virtual environment can become non-passive due to various reasons including discretization errors and interaction dynamics between virtual tools and objects. This paper provides an analysis of the stability and performance of the haptic simulation involving non-passive virtual environment. The dynamic interaction between the virtual tools and the objects is modeled using the two-port networks. The analysis is carried out using a velocity and force mapping matrix for six-DOF simulation. New stability condition resulting from the analysis is applied to an example simulation of a one-DOF virtual wall. Maximum stiffness satisfying the stability condition established in the previous literature, and the proposed condition is compared with the maximum stiffness experimentally determined with various time steps. The newly proposed stability condition manifests less standard deviation of errors than the widely applied absolute stability condition.