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The dynamic tensile spall failure of additively manufactured (AM) two-layered bimetallic GRCop-84—Inconel® 625 alloys, with planar and slanted interfaces, is investigated using uniaxial-strain plate-impact gas-gun experiments. Multiple photon Doppler velocimetry (PDV) is used to monitor the back (free) surface velocity profiles and to determine the influence of the interface geometry on the spall failure. Micrographs of cross sections of recovered impacted samples reveal failure along the interface as well as in-material regions. Spall strengths determined from pull-back signals captured with the use of the multiple PDV probes illustrate different location-specific values for the same sample, corresponding to failure occurring in Inconel® 625, or GRCop-84, or along their interface, depending on the geometry of the interface. The results obtained from the experiments employing multiple PDV probes correlated with microstructural observations of cross sections of recovered impacted samples, provide a useful method for determining the complex spall failure response of two-layered bimetallic alloys, including the differentiation of the response of the respective alloy materials relative to that of the interface, in the same experiment.

Double-layered shaped charge (DLSC) is a special type of shaped charge which has been recently attracted to enhance the penetration performance. The DLSC consists of a co-axial double-layered charge composed of outer high-velocity explosive and inner low-velocity explosive. In this paper, numerical simulations and experiments are carried out to investigate the usefulness of the DLSC compare to an ordinary shaped charge (OSC) at different stand-off distances. Jet properties of shaped charges are measured by simulation models and compared with the experimental penetration depths. It was found that the penetration performance strongly depends on the existence of jet breakup and the DLSCs performed better than the OSC only when no jet breakup occurs before reaching the target. The comparison study between the simulations and experiments also revealed that the jet properties such as kinetic energy, cumulative jet mass, and the initial jet breakup distance are highly related to the penetration performance.

Background: This study aimed to investigate the characteristics, severity, and treatment of patients with acute appendicitis in Korea over a 2-year period during the coronavirus disease (COVID-19) pandemic compared to those before the pandemic. We also investigated whether there were any changes in clinical characteristics of acute appendicitis before and after vaccination against the coronavirus.Methods: We retrospectively reviewed the medical records of patients who were diagnosed with acute appendicitis at our institution between March 1, 2019, and August 31, 2021. We divided the patients into three groups (pre-pandemic, before vaccination, and after vaccination) and analyzed the clinical outcomes.Results: The time from symptom onset to hospital arrival and the time from symptom onset to operation increased during the COVID-19 pandemic period compared to the pre-pandemic period. The rate of complicated appendicitis during the pandemic was higher than that before the pandemic. In addition, the number of new daily cases showed a positive correlation with the time from symptom onset to hospital arrival (OR, 0.03; 95% CI, 0.02 to 0.04; PConclusions: Employing hospital-wide efforts, such as screening by rapid PCR testing, to avoid further time delays, and nationwide efforts, such as vaccination, to shorten the time from symptom onset to hospital arrival, are necessary to maintain the quality of treatment of acute appendicitis during an infectious disease pandemic.

The recent development of the coal-fired power plant purposes to enhance environmental-friendliness and efficiency. In order to achieve these goals, many research studies are underway to develop advanced ultra-supercritical (A-USC) boilers, which requires materials that can withstand extreme conditions. Integrated materials and product design (IMPD) is a new approach for designing products able to yield effective operation in extreme conditions. Based on the IMPD approach, we optimized the geometry of the superheater tube of the A-USC boiler as well as its constituent materials. To apply the IMPD to the tube design problem, we developed a creep deformation model based on finite element analysis, a heat transfer model, and two material models constructed via artificial neural networks. The material models predict creep properties and thermal conductivity for a given heat treatment condition and weight ratio of the chemical constituents. These four models are used in combination to form an analysis model chain, which is subsequently incorporated into an optimization routine for finding optimum material constituents and shapes of the superheater tube at the same time. An optimal tube design was developed to achieve minimum creep deformation and maximum heat transfer amount under the stringent operating conditions of the A-USC boiler.

Fully dense structures of high solids loaded polymer composites printed via material extrusion additive manufacturing are of interest across many applications, including biomedical scaffolds and energetic materials. It is common to observe defects such as interfilament voids in space-filling structures, particularly during material extrusion printing with high solids inks, which exit the nozzle in a circular structure and require applied forces to deform. An understanding of the impact of process parameters on the void volume and structure, which can ultimately affect material performance, is necessary. Here we examine the effects of four key process parameters, layer height, extrusion rate, print speed and nozzle diameter, on the filament geometry and interfilament void formation. The layer height, extrusion rate and print speed all impact the width of the printed lines, but the layer height plays the most significant role in the line aspect ratios and void formation in printed structures. We find that in material extrusion of high solids loaded inks there is a critical layer height; below the critical height, the ink will spread to fill in gaps between filaments, and above it the filament will maintain a rounded shape and lead to formation of interfilament voids. The results illuminate a pathway to control porosity of fully dense structures with high solids loaded inks using the layer height parameter while maintaining geometric accuracy in the printed design.

We report the fabrication of high performance transparent conducting films (TCFs) comparable to commercialized ITO by efficiently combining CVD-grown graphene with a 1D periodic Au nanograte (Au-NG). This high performance is attributed to the unique structure of the Au-NG (a high aspect ratio (approx. 20) and narrow width (approx. 15 nm)), which provides a density (sub μm pitch) that is much higher than that of the graphene domains and hence significantly improves the conductivity of polycrystalline graphene by providing direct charge carrier pathways between each graphene single domain without loss of transparency. In addition, the substrate embedding of the Au-NG provides flexibility, a flat surface, and excellent adhesion to polymer substrates for practical applications. This hybrid TCF was successfully applied to a flexible polymer solar cell, which was found to exhibit a power conversion efficiency, 6.38%, that is comparable to a device with commercialized ITO.

Thermite composites are lightweight and high-strength multifunctional energetic structural materials with a high reaction energy. In this study, the shear induced reaction of Al-Fe2O3-epoxy thermite composites using a modified BAM Fallhammer tester is investigated. The standard BAM Fallhammer tester is modified for better transport of impact energy under low velocity impact conditions. The mean Al particle size and the volume ratio of Al to Fe2O3 are varied using the factorial design of experiments to find their effect on the reactivity. From the experimental results, we observed that the epoxy binder increases the reaction sensitivity of the thermite mixture. Also, the composites containing smaller sized Al particles exhibit increased reaction sensitivity, whereas the sensitivity of the composites containing larger Al particles is higher in the fuel-rich (non-stoichiometric) composition compared to the stoichiometric composition.

The development of a practical alternative to indium tin oxide (ITO) is one of the most important issues in flexible optoelectronics. In spite of recent progress in this field, existing approaches to prepare transparent electrodes do not satisfy all of their essential requirements. Here, we present a new substrate-embedded tall (∼350 nm) and thin (∼30 nm) three-dimensional (3D) metal grid mesh structure with a large area, which is prepared via secondary sputtering. This structure satisfies most of the essential requirements of transparent electrodes for practical applications in future opto-electronics: excellent optoelectronic performance (a sheet resistance of 9.8 Ω□(-1) with a transmittance of 85.2%), high stretchability (no significant change in resistance for applied strains

The development of a simple and cost-effective method for fabricating ≈10 nm scale nanopatterns over large areas is an important issue, owing to the performance enhancement such patterning brings to various applications including sensors, semiconductors, and flexible transparent electrodes. Although nanoimprinting, extreme ultraviolet, electron beams, and scanning probe litho-graphy are candidates for developing such nanopatterns, they are limited to complicated procedures with low throughput and high startup cost, which are difficult to use in various academic and industry fields. Recently, several easy and cost-effective lithographic approaches have been reported to produce ≈10 nm scale patterns without defects over large areas. This includes a method of reducing the size using the narrow edge of a pattern, which has been attracting attention for the past several decades. More recently, secondary sputtering lithography using an ion-bombardment technique was reported as a new method to create high-resolution and high-aspect-ratio structures. Recent progress in simple and cost-effective top-down lithography for ≈10 nm scale nanopatterns via edge and secondary sputtering techniques is reviewed. The principles, technical advances, and applications are demonstrated. Finally, the future direction of edge and secondary sputtering lithography research toward issues to be resolved to broaden applications is discussed.

The design of multiscale materials and products has necessitated an inductive and robust design approach to ensure satisfying the performance goals for complex engineering problems. Inductive design exploration method is a performance-driven design approach that explores feasible design spaces while considering the effect of uncertainty that leads to performance variability. However, the existing design method suffers from high computational costs for pre-defined sample data, which sacrifices the accuracy of solution spaces. In this study, we present an improved implementation of the inductive design exploration method by applying the active learning algorithm that is mainly used in machine learning techniques. The purpose of this study is to minimize the sampling effort while maintaining reasonable accuracy in the exploration of design spaces, thereby alleviating computational burden. The capabilities of the improved method are highlighted and demonstrated via a design problem of the blast resistant sandwich panel.

Correction for ‘A three-dimensional metal grid mesh as a practical alternative to ITO’ by Sungwoo Jang et al., Nanoscale, 2016, 8, 14257–14263.

The development of strain-insensitive stretchable transparent conductors (TCs) is essential for manufacturing stretchable electronics. Despite recent progress, achieving a high optoelectronic performance under applied strain of 50% continues to present a significant challenge in this research field. Herein, an ultratall and ultrathin high aspect ratio serpentine metal structure is described that exhibits a remarkable stretching ability (the resistance remains constant under applied strain of 100%) and simultaneously provides an excellent transparent conducting performance (with a sheet resistance of 7.6 Ω -1 and a transmittance of 90.5%). It is demonstrated that the highly stretchable transparent conducting properties can be attributed to the high aspect ratio feature. A high aspect ratio (aspect ratio of 17-367) structure permits facile deformation of the serpentine structure with in-plane motion, leading to a high stretching ability. In addition, this structural feature avoids the classic tradeoff between optical transmittance and electrical conductance, providing a high electrical conductance without decreasing the optical transmittance. The practical utility of these devices is tested by using these TCs as stretchable interconnectors among LEDs or in wearable VOC gas sensors.

Aluminum foam is a useful material for lightweight structural and impact attenuation applications due to its excellent energy-absorbing characteristics. The aim of this study is to further enhance the performance of closed-cell aluminum foam-cored sandwich panels while satisfying given design requirements. A new design approach is employed, whereby the materials and product design are integrated, and which incorporates multilevel design optimization under various types of uncertainty in the analysis and manufacturing processes. Sandwich panels are designed by controlling the processing parameters for the foam core and panel geometry according to the design methods being used. The design variables are optimized through traditional multilevel optimization and analytical target cascading method. Inductive design exploration method is introduced to identify the feasible regions for the design variable in a design hierarchy to be insensitive to uncertainty. This work presents an in-depth examination of the design results and the efficiency of the design methods for pursuing robust design solutions.

The overall characteristics of the OH internal energy distributionsfor both reactions were qualitatively similar. The population propensity of the П(A′) Λ-doublet sub-levelsuggested that both reactions proceeded via an insertion/elimination mechanism. Bimodal rotational populationdistributions supported the existence of two parallel mechanisms for OH production, i.e., statistical insertionand nonstatistical insertion. However, detailed analysis revealed that, despite the higher exoergicity of thereaction, the rotational distribution of the OH following the reaction of O(

In modern armour warfare, crew survivability is of paramount importance. One way to ensure survivability is to protect soldiers from anti-tank mines with Blast Resistant Panels (BRPs). A BRP is a lightweight sandwich structure with a low-relative-density core in between two high-density panels. The aim of this project is to further enhance the performance of BRPs using lighter structures, in order to mitigate the kinetic energy induced by shock waves. We employ a new design approach, using integrated material and a product design which utilizes a distributed framework. This approach eliminates the inherent limitations of pre-designed materials used in conventional, material-selection-based design. In this context, the limitations of BRPs designed in the conventional approach are examined and compared with the new BRP design. An artificial neural network-based material model is introduced to demonstrate the practicality and feasibility of this new design paradigm. The BRP design is then validated using FEA. Design results of the new BRP are compared to those using the conventional material-selection-based design.

Nopp140 is a highly phosphorylated protein that resides in the nucleolus of mammalian cell and is involved in the biogenesis of the nucleolus. It interacts with a variety of proteins related to the synthesis and assembly of the ribosome. It also can bind to a ubiquitous protein kinase CK2 that mediates cell growth and prevents apoptosis. We found that Nopp140 is an intrinsically unfolded protein (IUP) lacking stable secondary structures over its entire sequence of 709 residues. We discovered that mitoxantrone, an anticancer agent, was able to enhance the interaction between Nopp140 and CK2 and maintain suppressed activity of CK2. Surface plasma resonance studies on different domains of Nopp140 show that the C-terminal region of Nopp140 is responsible for binding with mitoxantrone. Our results present an interesting example where a small chemical compound binds to an intrinsically unfolded protein (IUP) and enhances protein-protein interactions.

(matrix assisted laser desorption/ionization) mass spectrometry. The structures of the degradation products were determined and the relative compositions were estimated. The MALDI-TOF mass spectra of the thermally degraded PTT sample showed three main series of oligomer products with different end groups, which were carboxyl/carboxyl, carboxyl/allyl, and allyl/allyl. In contrast to the thermal degradation of polyethylene terephthalate (PET), the oligomers containing terephthalic anhydrides were not detected, whereas the formation of oligomers containing the unsaturated allyl ester group was confirmed by mass assignment. From these results, it was concluded that the thermal degradation of PTT proceeds exclusively through the βCH hydrogen transfer mechanism, which is in accordance with the proposed reaction mechanism for the thermal degradation of polybutylene terephthalate (PBT).

The structural analysis of polytrimethylene terephthalate (PTT) and characterization of the hydrolytic degradation products after acid hydrolysis were performed using MALDI-TOF mass spectrometry. Mass spectra of the PTT samples were analyzed using a self-calibration method as well as an internal calibration method with standard materials of known masses. PTT structures constituting the samples were determined from the analyses of the spectra, and their relative compositions were estimated. The MALDI-TOF mass spectra of the acid-hydrolyzed PTT sample showed three main series of oligomer products with different end groups in accordance with the hydrolysis schemes. From the spectra of both Na + and K + adducts, it was concluded that the PTT samples have higher affinity for Na

Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound (VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices. The ICS displays highly sensitive and stable sensing of representative VOCs (including toluene, hexane, propanal, ethanol, and acetone) that are found in the exhaled breath of lung cancer patients. In particular, the sensor is found to be fully operational even after being subjected to long-term storage or harsh environmental conditions (relative humidity of 85% or temperature of 100 °C) or severe mechanical deformation (bending to a radius of curvature of 1 mm, or stretching strain of 100%), which can be an effective method to realize a human-adaptive and skin-attachable biosensor platform for daily use and early diagnosis.

The OH(X 2 II, υ"=0, 1) internal state distributions from the reaction of electronically ground state oxygen atoms with HSiCl 3 were measured using laser-induced fluorescence. The ground-state 0( 3 Pi) atoms with kinetic energies above the reaction barrier were produced by photolysis of NO 2 at 355 nm. The OH product revealed strong vibrational population inversion, P(υ"=1)/Pυ"=0) = 4.0 ± 0.6, and rotational distributions in both vibrational states exhibit substantial rotational excitations to the limit of total available energy. However, no preferential populations in either of the two A doublet states were observed from the micropopulations, which supports a mechanism involving a direct abstraction of hydrogen by the atomic oxygen. It was also found that the collision energy between O and HSiCl 3 is effectively coupled into the excitation of the internal degrees of freedom of the OH product ( = 0.62, and = 0.20). The dynamics appear consistent with expectations for the kinematically constrained reaction which supports the reaction type, heavy + light-heavy → heavy-light + heavy (H + LH'→ HL + H'). The dynamics of oxygen atom collision with HSiCl 3 are discussed in comparison to those with SiH 4 .

We report the application of time-dependent density functional theory (TDDFT) to the calculation of potential energy profile relevant to the excited state intramolecular proton transfer (ESIPT) processes in title molecules. The TDDFT single point energy calculations along the reaction path have been performed using the CIS optimized structure in the excited state. In addition to the Stokes shifts, the transition energies including absorption, fluorescence, and 0-0 transition are estimated from the TDDFT potential energy profiles along the proton transfer coordinate. The excited state TDDFT potential energy profile of SA and 3ASA resulted in very flat function of the OH distance in the range R OH = 1.0-1.6 A, in contrast to the relatively deep single minimum function in the ground state. Furthermore, we obtained very shallow double minima in the excited state potential energy profile of SA and 3ASA in contrast to the single minimum observed in the previous work. The change of potential energy profile along the reaction path induced by the substitution of electron donating groups (-NH 2 and -OCH 3 ) at different sites has been investigated. Substitution at para position with respect to the phenolic OH group showed strong suppression of excited state proton dislocation compared with unsubstitued SA, while substitution at ortho position hardly affected the shape of the ESIPT curve. The TDDFT results are discussed in comparison with those of CASPT2 method.

MALDI-TOF-MS technique was applied to obtain structural and compositional information of synthetic polyamides, Nylon6 and Nylon66. Mass spectra of both the original and the hydrolyzed polyamide samples were analyzed using the self calibration method as well as the internal calibration method with the standard materials of known masses. The MALDI-TOF mass spectra of Nylon6 samples showed the presence of protonated, sodiated, and potassiated ions that were assigned to cyclic and NH2/COOH terminated linear oligomers. From the MALDI-TOF mass spectra of Nylon66 samples, the potassiated linear oligomers with three different end groups are identified as well as the cyclic oligomers, i.e., NH2/COOH terminated oligomers, NH 2 /NH 2 terminated oligomers, and COOH/COOH terminated oligomers. Full characterization of the molecular species and end groups present in the polyamide samples has been achieved, and also the changes in mass spectral patterns after the hydrolysis of the samples are presented.

The development of high resolution, high aspect ratio metal dichalcogenide nanostructures is one of the most important issues in 2D material researchers due to the potential to exploit their properties into high performance devices. In this study, for the first time a way of fabricating metal dichalcogenide nanostructures with high resolution ( 120) by chemical vapor deposition assisted secondary sputtering phenomenon is reported. This approach can universally synthesize various types of metal dichalcogenides including MoS2, WS2, and SnS2, implying the possibility for further utilization with selenides and tellurides. Also, this method can produce highly periodic complex patterns such as hole–cylinder, concentric rings, and line patterns, which are unprecedented in previous reports. The feature size and aspect ratio of the metal dichalcogenide structures can be manipulated by controlling the dimensions of the photoresist prepatterns, while the pattern resolution and layer orientation can be manipulated by controlling the thickness of the deposited metal film. It is demonstrated that nanostructures with high resolution and high aspect ratio significantly improve gas-sensing properties compared with previous metal dichalcogenide films. It is believed that the method can be a foundation for synthesizing various materials with complex patterns for future applications.

Integrated Materials and Products Design (IMPD) differs in the way that materials as well as product layout are designed or optimized in a concurrent manner to meet design requirements. IMPD allows the specific performance required in a product to be achieved by tailoring materials and product, since system performance will not be limited by a pre-chosen material employed in conventional, material-selection-based design. In this study, Blast Resistance Panels (BRPs) with square honeycomb core are designed based on this new design approach to further enhance the performance of BRPs. We employ multi-level design methods for the integrated design of blast resistance panels and materials. Along with the traditional multi-level optimization of BRP, another design approach, Analytical Target Cascading (ATC) is introduced for a comparative design study in the BRP design. In this article, we compare the design results and design exploration efficiency of the two multi-level design methods in designing the blast resistance panels as well as those materials. We also discuss the advantage and disadvantage of the methods observed in this study.

We present a simple nanopatterning method for flexible substrates with high resolution (approx. 15 nm) that uses the secondary sputtering phenomenon (SSP) and no solvents at room temperature, and characterize flexible and transparent conducting films that have performances comparable to that of ITO films yet higher mechanical stability.