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We demonstrate that the extreme ultraviolet free induction decay emission can be significantly enhanced by employing isolated attosecond pulses. In this work, the near infrared pulses are applied to excite the neon atoms into Rydberg states coherently, and isolated attosecond pulses are used to manipulate the populations of the Rydberg states and the subsequent free induction decay process. The time resolved experimental measurement of the dependence of the resonance emission yield would help to understand the buildup dynamics of population of excited states. The enhancement assisted by attosecod pulses can serve as a mechanism to develop high-flux extreme ultraviolet light sources.

Since it was first time proposed, the Space Solar Power Station (SSPS) has attracted great attention all over the world, which is a huge space system and provide energy for Earth. Although several schemes and abundant studies on SSPS have been proposed and conducted, it is still unrealized. The reason why SSPS is still an idea, not only because it is a giant and complex project, but also due to the requirement of various excellent space materials. Among the diverse required materials, we believe energy materials are the most important. Herein, we reviewed the space energy conversion materials for SSPS.

This paper briefly analyzed the operation mechanism and construction strategy of source grid load storage under the access of renewable energy, and discussed the method of constructing the source-grid-load-storage model under the access of renewable energy. The results of the study show that an economic efficiency of active distribution network operation can be improved by the coordinated optimisation of source network load storage.

Among the water quality indicators, permanganate and turbidity are important indicators to reflect the pollution status of water bodies. In order to study the correlation between the two, the water quality monitoring data of relevant water areas were obtained by designing a web crawler, and the water quality monitoring data set was constructed. After the data was cleaned, the correlation analysis was carried out. The experimental results show that there is a big difference in the correlation coefficient between the two indicators at different periods of the same monitoring point. The correlation between the two indicators in the abundant-water season is greater than that in the flat-water season, and the correlation between them in the flat-water season is greater than that in the poor-water season. Among them, there was a high positive correlation between the two indicators during the abundant-water season, and there is little correlation between them during the poor-water season.

Nowadays, the penetration of distributed power in distribution network increases the complexity of power supply restoration. For the recovery of the traditional method in the field of distributed power supply system restore deficiency, the improving measures are put forward based on the many kinds of operation constraints, proposes the mathematical model of multi-objective optimization. In addition to conventional constraints in the mathematical model, will also be the network structure and branch power flow constraints into consideration. In view of the model, using the rough set theory, a multi-objective optimization problem into a single objective problem, and on this basis, considering the characteristic of radial network and the characteristics of the different load, by using genetic algorithm to reconstruct network, finally through the corresponding example recovery strategy is feasible and efficient.

With the increasing demands toward large area plasma etching and deposition, the radial uniformity of capacitively coupled plasmas (CCPs) becomes one of the key factors that determine process performance in industrial applications. However, there is a variety of parasitic effects, e.g. electromagnetic and electrostatic edge effects, that typically lead to the formation of nonuniform radial plasma density profiles at various discharge conditions with a density peak appearing either at the center or near the edges of the electrodes. Moreover, in commercial CCPs different surface materials are in contact with the plasma at various positions as parts of boundary surfaces such as focus rings, masks, showerhead electrodes, wall and/or target materials. Via complex material specific plasma-surface interactions, the presence of such different surface materials affects plasma uniformity in a way that is typically not understood and, thus, not controlled. In this work, aided by 2d3v graphics processing unit accelerated particle-in-cell/Monte Carlo collision simulations, we study the effects of radial variations of electrode materials on the plasma via their different ion and electron induced secondary electron emission as well as electron reflection coefficients on the discharge characteristics. Based on such fundamental understanding we tailor the radial variation of boundary surface materials to improve plasma uniformity in low pressure CCPs. Such investigations are performed at different neutral gas pressures, where both center and edge high radial plasma density profiles form in the presence of radially uniform surface coefficients that resemble the presence of a single electrode material. It is demonstrated that by radially varying the surface coefficients at the grounded electrode, the radial plasma density profile can be finely adjusted and the plasma uniformity above the wafer placed at the powered electrode can be improved in both cases.

X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years. X-ray dark-field image is commonly retrieved by using discrete Fourier transform from the acquired phase-stepping data. The retrieval process assumes a constant phase step size and a constant flux for each stepped grating position. However, stepping errors and flux fluctuations inevitably occur due to external vibrations and/or thermal drift during data acquisition. Previous studies have shown that those influences introduce errors in the acquired phase-stepping data, which cause obvious moiré artifacts in the retrieved refraction image. This work investigates moiré artifacts in x-ray dark-field imaging as a result of flux fluctuations. For the retrieved mean intensity, amplitude, visibility and dark-field images, the dependence of moiré artifacts on flux fluctuation factors is theoretically derived respectively by using a first-order Taylor series expansion. Results of synchrotron radiation experiments verify the validity of the derived analytical formulas. The spatial frequency characteristics of moiré artifacts are analyzed and compared to those induced by phase-stepping errors. It illustrates that moiré artifacts can be estimated by a weighted mean of flux fluctuation factors, with the weighting factors dependent on the moiré phase and different greatly for each retrieved image. Furthermore, moiré artifacts can even be affected by object’s features not displayed in the particular contrast. These results can be used to interpret images correctly, identify sources of moiré artifacts, and develop dedicated algorithms to remove moiré artifacts in the retrieved multi-contrast images.

Herein, we report a Pt-decorated Ti3C2T x /TiO2 gas sensor for the enhanced NH3 sensing response at room temperature. Firstly, the TiO2 nanosheets (NSs) are in situ grown onto the two-dimensional (2D) Ti3C2T x by hydrothermal treatment. Similar to Ti3C2T x sensor, the Ti3C2T x /TiO2 sensor has a positive resistance variation upon exposure to NH3, but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti3C2T x /TiO2 sensor shows a negative response with significantly improved NH3 sensing performance. The shift in response direction indicates that the dominant sensing mechanism has changed under the sensitization effect of Pt NPs. At room temperature, the response of Pt-Ti3C2T x /TiO2 gas sensor to 100 ppm NH3 is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti3C2T x and Ti3C2T x /TiO2 gas sensors, respectively. The experimental detection limit of the Pt-Ti3C2T x /TiO2 gas sensor to detect NH3 is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti3C2T x /TiO2 gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH3), high selectivity and good stability. Considering both the response value and the response direction, the corresponding gas-sensing mechanism is also deeply discussed. This work is expected to shed a new light on the development of noble metals decorated MXene-metal oxide gas sensors.

This study presents an experimental demonstration of the crucial role of compositional interdiffusion at interfaces in GaAs/AlGaAs alternating superlattices for developing the terahertz quantum cascade lasers operating at high temperatures. By growing GaAs/Al0.3Ga0.7As superlattices using the molecular beam epitaxy technique, an aluminum interdiffusion width of 0.95 nm (equivalent to ∼3.4 monolayers) is estimated. Incorporating this interdiffusion width as an additional design parameter has resulted in a 20 K improvement in the maximum operating temperature of the laser. To quantify the magnitude of the interdiffusion scattering effects on electron dynamics, an independent self-energy that functions based on the axial correlation length is introduced in the non-equilibrium Green’s function model. It clarifies that changes in the lifetime of quantum states and also the population fractions are primarily influenced by the deformation of wave functions at the injector when the interfaces become interdiffused.

Vertical cavity surface emitting laser (VCSELs) as the ideal light source for rubidium (Rb) and cesium (Cs) atomic clocks is analyzed for its mode and polarization control. We fabricated three kinds of shapes: triangular, elliptic, and circular oxidation apertures which also have different sizes. We formed three different shape oxide apertures by wet-oxidation with 36 μm–39 μm circular mesa. Our results show that triangular oxidized-VCSEL has the advantages of mode and polarization selection over elliptic and circular oxide apertures. When triangular oxide-confined VCSELs emit in single mode, the measured side mode suppression ratio (SMSR) is larger than 20 dB and orthogonal polarization suppression ratio achieves 10 dB. Resonant blueshift of VCSELs with triangular and elliptic apertures is observed with the decrease of aperture size.

A conductive layer deposited on a rough surface can effectively improve the performance of a pressure sensor; however, its further application requires patterning of the conductive layer to obtain the corresponding electrical layout. In this paper, a facile patterning method with few steps was proposed for patterning silver nanowires on sandpaper. This method employed a photocurable resin as the key material to define the pattern using a photomask under UV exposure. It was found that greater cure depths and narrower light-transmitting areas require longer exposure times. A pattern with linewidth of approximately 40 μm was obtained on M-400 sandpaper (M-400 stands for the mesh number). Based on this method, pressure sensors consisting of interdigital electrodes with rough surfaces and sponge-sensing layers were fabricated. The best resulting sensor exhibited a high-pressure sensitivity of 21.89 kPa−11 for less than 2 kPa, a low detection limit (24.5 Pa), low operating voltage (0.01 V), and short response time (84 ms). Moreover, this patterning method has no special requirements for materials and substrates and thus can be applied to pattern other materials on rough or smooth surface substrates.

Fertilizer availability is crucial for global food security, and international fertilizer trade plays a vital role in reallocating fertilizers across multiple economies. However, the stability of international fertilizer trade relationships between economies has not been studied. Using 29 year records of the global fertilizer trade from 1990 to 2018, we construct three temporal networks linked to three primary nutrients (nitrogen N, phosphorus P2O5, and potash K2O). After introducing the link stability indicator to the international fertilizer trade system, which shows a very strong positive correlation with whether the trade will continue in the future, we analyze the factors influencing the stability of the fertilizer trade and provide advice for trading participants to establish highly stable transactions. The supply side has a greater impact on the stability of the fertilizer trade than the demand side. For exporting economies, stable exports need to focus on the counterparty’s real demand rather than its economic situation. For importing economies, intermediaries and producers with good economic conditions are stable trading partners, and trade that is geographically closer is always more stable. The methodology used for link stability analysis in this work can be applied to analyzing other directed temporal networks.

With the rapid development of deep learning methods, the variational auto-encoder (VAE) has been utilized for nonlinear process monitoring. However, most VAE-based methods hardly consider the inner independent and related relationship of each variable. To overcome this problem, a novel VAE named independent and related variable information concentrated variational auto-encoder (IRVIC-VAE) is proposed. To concentrate the independent and related information, a loading weight matrix regularization based on the mutual information of variables with gaussian distribution is introduced so that the variables can separate into two subspaces that contain independent and related information in latent variables. The original data space decomposed via IRVIC-VAE is orthogonal and approximate to normal distribution. For process monitoring, the independent variable space and related variable space are combined to establish two statistics according to Kullback-Leibler divergence and 2-norm. Finally, the performance and effectiveness of IRVIC-VAE are testified by Tennessee Eastman (TE) process.

X-ray analyzer-based imaging (ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from x-ray absorption, refraction, and scattering properties of the investigated sample. However, x-ray ABI setups can be susceptible to external vibrations, and mechanical imprecisions of system components, e.g., the precision of motor, which are unavoidable in practical experiments. Those factors will provoke deviations of analyzer angular positions and hence errors in the acquired image data. Consequently, those errors will introduce artefacts in the retrieved refraction and scattering images. These artefacts are disadvantageous for further image interpretation and tomographic reconstruction. For this purpose, this work aims to analyze image artefacts resulting from deviations of analyzer angular positions. Analytical expressions of the refraction and scattering image artefacts are derived theoretically and validated by synchrotron radiation experiments. The results show that for the refraction image, the artefact is independent of the sample’s absorption and scattering signals. By contrast, artefact of the scattering image is dependent on both the sample’s refraction and scattering signals, but not on absorption signal. Furthermore, the effect of deviations of analyzer angular positions on the accuracy of the retrieved images is investigated, which can be of use for optimization of data acquisition. This work offers the possibility to develop advanced multi-contrast image retrieval algorithms that suppress artefacts in the retrieved refraction and scattering images in x-ray analyzer-based imaging.

A novel visually meaningful image encryption algorithm is proposed based on a hyperchaotic system and compressive sensing (CS), which aims to improve the visual security of steganographic image and decrypted quality. First, a dynamic spiral block scrambling is designed to encrypt the sparse matrix generated by performing discrete wavelet transform (DWT) on the plain image. Then, the encrypted image is compressed and quantified to obtain the noise-like cipher image. Then the cipher image is embedded into the alpha channel of the carrier image in portable network graphics (PNG) format to generate the visually meaningful steganographic image. In our scheme, the hyperchaotic Lorenz system controlled by the hash value of plain image is utilized to construct the scrambling matrix, the measurement matrix and the embedding matrix to achieve higher security. In addition, compared with other existing encryption algorithms, the proposed PNG-based embedding method can blindly extract the cipher image, thus effectively reducing the transmission cost and storage space. Finally, the experimental results indicate that the proposed encryption algorithm has very high visual security.

Liquid air energy storage (LAES) uses air as both the storage medium and working fluid, and it falls into the broad category of thermo-mechanical energy storage technologies. The LAES technology offers several advantages including high energy density and scalability, cost-competitiveness and non-geographical constraints, and hence has attracted a growing interest in recent years. As a result, several reviews have been published on the topic. However, these reviews covered little in the following aspects of LAES: dynamic simulation and optimisation, key components for LAES, LAES applications through integration, and unified economic and cost models for LAES. This article provides a comprehensive review on the LAES technology and fills the above gaps. Apart from applications in electrical grids such as peak-shaving, load shifting, and dealing with intermittency of renewable generation, the review also shows a diverse range of other LAES applications through integration, including waste heat and cold energy recovery and utilisation, multi-energy vector service provision, and sector coupling for chemical production and carbon capture. The review also leads to the recommendation of several areas for future research and development, including dynamic characteristics of whole LAES system integrated with renewables and end users; thermo-economic and dynamic optimization of stand-alone LAES and integrated systems; and experimental study on commercial systems.

Effect of linear chirp frequency on the process of electron–positron pairs production from vacuum is investigated by the computational quantum field theory. With appropriate chirp parameters, the number of electrons created under combined potential wells can be increased by two or three times. In the low frequency region, frequency modulation excites interference effect and multiphoton processes, which promotes the generation of electron–positron pairs. In the high frequency region, high frequency suppression inhibits the generation of electron–positron pairs. In addition, for a single potential well, the number of created electron–positron pairs can be enhanced by several orders of magnitude in the low frequency region.

Noncoherent and coherent systems of linear frequency modulated continuous wave photonic radar under normal environmental conditions are constructed by co-simulation. In particular, the simulation models of different atmospheric humidity conditions are constructed to analyze the quantitative relationship between the system’s ability to detect targets and humidity. It is discussed the relationship between detection distance and channel parameters under the premise of reasonable signal-to-noise ratio (SNR). In particular, the SNR of the noncoherent photonic radar is reduced to less than 10 dB when relative humidity >40%, which the laser power is 8 dBm and the detection distance is 100 m. However, the coherent photonic radar has a good performance of more than 21.7 dB. The results show that the noncoherent system is more susceptible to atmospheric humidity than the coherent system, and the heterodyne detection coherent system can achieve longer detection distance and better weak echo signal detection capability.

Chlorobenzenes (CB) are important organic chemical and industrial product, which plays a more and more important role in chemistry and production. In this paper, the process design, process simulation and optimization of chlorobenzene wastewater produced in chlorobenzene production are carried out. The recovery of benzene and chlorobenzene in chlorobenzene wastewater can improve the economic benefit to a certain extent, which provides a theoretical basis and practical significance for the actual production operation. Based on the chlorobenzene wastewater of a chemical plant, this paper introduces a variety of processes and simple process comparisons. Finally, the stripping method is used to recycle benzene and chlorobenzene. Aspen Plus software is used to simulate and optimize the process, and the best process parameters are selected. In this paper, the process was simulated, and the sensitivity of the distillation column of the benzene and chlorobenzene separation unit was analyzed. Several operating parameters were compared and optimized to achieve the best separation effect. For the Case Study, the optimal number of trays for the rectifying tower is determined to be 20, the optimal feed position is the twelfth tray, the optimal reflux ratio is 0.70, and the optimal distillation ratio is 0.75.

The performance difference of the single battery has a significant impact on the cruising range, service life, charge and discharge control of an electric vehicle that uses multiple batteries as the power battery. Highly consistent performance is an essential process for lithium battery production. In order to verify the performance of the lithium battery automatic pack system, this paper used Flexsim software to establish a system simulation model, used the Dashboard data statistical method to analyze the running data of the simulation model, completed the system construction and testing, and used SPSS statistical analysis software to analyze the system test results. Using the paired sample T test, we verify that the system matching test results are accurate, that the cylindrical lithium battery matching automation equipment system has complete functions, is simple to interact with the computer, and meets the system design requirements.

The traditional design method of spacecraft power systems based on customization and the combination of two-port converters can no longer meet the increasing application demands of having high power and being modular and versatile. Three-port DC converter, standardized to form a redundant parallel power supply system with a distributed model, is a possible solution to meet the design requirements of the above spacecraft power supply system. In this paper, a three-port converter is designed to complete the MPPT control of the PV array at the input end to maximize the power generated by the PV array, complete the battery charge and discharge control, realize the bidirectional conversion and transmission of the battery charge and discharge power, and complete the control of the load voltage at the output end to ensure the stable and reliable power supply of the load. If the integrated DC converter is used to realize the power transmission and conversion between the three ports at the same time, the volume and weight of the system can be greatly reduced, and then the power density of the system can be improved.

This paper completed the development status and working principle of the handling robot, analyzed the performance index parameters and system functional requirements of the robot, and proposed an overall design scheme of the handling robot control system. The mechanical structure design of the handling robot was developed, and the selection of the core components of the system was studied and designed in detail based on theoretical analysis and calculation. Secondly, this paper selected the STM32 microcontroller as the core of the handling robot. It completed the circuit schematic diagram of the systems, and investigated the selection of core sensors for the navigation and positioning module, obstacle avoidance module, and wireless communication module. Finally, this paper studied the automatic control part of the handling robot, which mainly included the modeling of the robot’s manipulator, PID control, and MATLAB simulation verification. In addition, the application prospect of the handling robot was explored. It had the advantages of high efficiency, strong practicability, and perfect function, and had certain practical significance in the application of the logistics industry.

In order to better guide the mixed match of furnace-incoming coal in coal-fired power plants from the perspective of carbon emission, according to national carbon emission accounting guidelines for power generation facilities, regardless of the impact of coal storage on coal quality, we have built a coal quality information database for carbon emissions of factory-incoming coal through analyzing the factory-incoming coal source and industrial analysis data on coal quality in a coal-fired power plant as well as using the element carbon content information estimated by soft measurement of element carbon content verified through the test. Based on this, we have constructed the theoretical method to guide the mixed match of furnace-incoming coal, and obtain the optimized mixed match results through the mixed match analysis.

This paper is concerned with the characteristics of a tracking differentiator (TD) in arranging transition process for the physical system. In order to overcome disadvantages of linear TD (LTD) in practice, a novel variable parameter linear tracking differentiator (VLTD) is proposed. By designing the speediness factor as a function of the tracking error, the VLTD can track a large range of set values with reasonable speed and acceleration. Analysis shows that VLTD can converge to its set value under certain conditions. Meanwhile, the speed and acceleration bounds are added to the VLTD, which guarantees that the proposed transition signal really plays a transitional role. The numerical simulation results emphasize necessity for adding speed and acceleration bounds to the VLTD. By comparing VLTD with the nonlinear TD (NLTD) in the simulations and experiments, VLTD can achieve almost the same performance as the NLTD while it is easier to be implemented.

For large spacecraft such as space stations and spacecraft, due to their huge systems, when the power supply equipment and electrical equipment are remote away, it is necessary to lay a long power supply cable. Therefore, when high-power energy transmission is carried out, the voltage drop of the cable will cause the terminal voltage of the electrical equipment to fluctuate with the transmission power. This will have an impact on some load equipment with high demand for electricity, and even shorten the service life of the equipment. In order to ensure the stability of terminal voltage and controllable amplitude of fluctuation, this paper proposes a voltage stabilization technology for long-distance energy transmission in orbit, and the principle analysis, simulation, and experimental verification are carried out to confirm the effectiveness of the technology.

A fluorine-free strategy was developed for the hydrophobic modification of the melamine (MA) sponge, in which both the stearic acid-modified Fe3O4 nanoparticles (SA-Fe3O4) and the graphite oxide were immobilized on the MA sponge with the use of 3-aminopropyltriethoxysilane by a drop-coating method to prepare the SA-Fe3O4/GO/MA sponge for oil-water separation. The structure of the SA-Fe3O4/GO/MA sponge was investigated by FITR, WAXD, SEM, two-dimensional EDS mapping, TGA, and VSM. The contact angles of the SA-Fe3O4/GO/MA sponge prepared with different amounts of SA-Fe3O4 and GO were in the range of 140.2° − 145.0°, which confirmed the successful hydrophobic surface modification for the MA sponge. The demonstrations exhibited that the SA-Fe3O4/GO/MA sponge could separate the oil from the oil-water mixture by both direct absorption and gravity-driven filtration. Additionally, the SA-Fe3O4/GO/MA sponge possessed not only high absorption capacities for peanut oil, n-hexane, soybean oil, and diesel oil, but also good abilities of being able to recollect magnetically and reuse. The proposed preparation strategy and overall performance of SA-Fe3O4/GO/MA sponge were promising for the oil-water separation in the future.

Wire-based in-situ additive manufacturing (AM) technology is famous for the integration of material preparation and structure manufacturing. In the current study, the simulation method was adopted to study the thermal-stress evolution behavior during the process of the in-situ AM Ti-22Al-25Nb component. A single-layer multi-pass component was deposited firstly to prove the credibility of the simulation model. Then, the temperature-stress field evolution of the multi-layer single-pass component was revealed and analyzed systematically. This research is of great significance for suppressing the generation of cracks during forming process and promoting the wide application of Ti-22Al-25Nb alloys.

UiO-66 is a potential material for adsorption heat transformation (AHT) with high specific surface area, and excellent thermal and chemical stability. However, the low water adsorption capacity of UiO-66 in the low relative pressure range (0 < P/P 0 < 0.3) limits its application in AHT. We prepare the UiO-66 modified by MgCl2 through using the solvothermal method and impregnation method, and study their water vapor adsorption performances and heat storage capacities. Attributed to the extremely high saturated water uptake and excellent hydrophilicity of MgCl2, the water adsorption performance of UiO-66 is improved, although the introduction of MgCl2 reduces its specific surface area and pore volume. The water adsorption capacity at P/P 0 = 0.3 and the saturated water adsorption capacity of the UiO-66 (with MgCl2 content of 0.57 wt%) modified by the solvothermal method are 0.27 g/g and 0.57 g/g at 298 K, respectively, which are 68.8% and 32.6% higher than the counterparts of pure UiO-66, respectively. Comparing with pure UiO-66, the water adsorption capacity of the UiO-66 (with MgCl2 content of 1.02 wt%) modified by the impregnation method is increased by 56.3% and 14.0% at the same pressure, respectively. During 20 water adsorption/desorption cycles, the above two materials show high heat storage densities (∼ 1293 J/g and 1378 J/g). Therein, the UiO-66 modified by the solvothermal method exhibits the excellent cyclic stability. These results suggest that the introduction of an appropriate amount of MgCl2 makes UiO-66 more suitable for AHT applications.

Electron power absorption dynamics is investigated in radio-frequency (RF) argon capacitively coupled plasmas (CCPs) at low pressure (4–70 Pa) excited by a dual-frequency waveform with frequencies of 27.12 MHz and 1.937 MHz. Based on the spatio-temporal dynamics of the ambipolar electric field a novel interpretation of the mechanism of frequency coupling is given, which is not based on the hard wall model, as in previous explanations. Within this framework, frequency coupling arises due to the decreased size of the ambipolar region outside the sheath when the low-frequency sheath is close to its full expansion, which leads to decreased ionization in this region. It is shown, under the circumstances considered here, ohmic power absorption is dominant. The spatio-temporally averaged ambipolar power absorption shows nonmonotonic behaviour as a function of pressure, first increasing, then, after reaching a local maximum, decreasing as the pressure is increased. It is shown, that the reason for this nonmonotonic behaviour is ultimately connected to the frequency coupling mechanism.

This study developed a biodegradable composite porous polyurethane scaffold based on polycaprolactone and polyethylene glycol by sequential in-situ foaming salt leaching and freeze-drying process with responsive shape changing performance. Biomineral hydroxyapatite (HA) was introduced into the polyurethane matrix as inorganic fillers. Infrared spectroscopy results proved a successful synthesis, scanning electron microscopy showed that the scaffold’s porosity decreased with the addition of HA while the average pore size increased. X-ray diffraction and differential scanning calorimetry showed that the addition of HA lowered the melting point of the scaffold, resulting in a transition temperature close to the human body temperature. From the bending experiments, it could be demonstrated that PUHA20 has excellent shape memory performance with shape fixity ratio >98.9% and shape recovery ratio >96.2%. Interestingly, the shape-changing capacity could be influenced by the porous structures with variation of HA content. The shape recovery speed was further accelerated when the material was immersed in phosphate buffered saline at 37 °C. Additionally, in vitro mineralization experiments showed that the scaffold incorporating HA had good osteoconductivity, and implantation assessment proved that scaffolds had good in vivo biocompatibility. This scaffold is a promising candidate for implantation of bone defects.

Electron beam directed energy deposition (EB-DED) is a promising and efficient additive manufacturing technology, but the vacuum environment challenges the in situ parameters monitoring. In this paper, an in situ beam current monitoring method is developed based on the absorbed electrons. A series of experiments show that there is a linear relationship between the absorbed electron current and the impinging beam current. However, this relationship only holds when the beam power density is relatively low. When the power density is high, the absorbed electron current will be lower than the theoretical value determined by the linear relationship. This is mainly due to the massive generation and ionization of metal vapor. The critical power density depends on the melting point of the material. Nonetheless, the deviation of the absorbed electron current at high power density can roughly determine the relative position between the focal spot and the workpiece surface. In addition, the slope of the linear relationship is material-dependent, so this method can also distinguish different materials.

In acoustic engineering, sound-proofing ventilation barriers find wide applications in diverse situations. However, most of the structures only have responses with fixed frequencies and a very narrow frequency range, especially for low frequency acoustics. Here we show a subwavelength acoustic metamaterial based on labyrinthine structures, which possesses tunable sound insulation and ventilation properties. The Fano-like asymmetric transmission dips is formed by the interference between the resonant scattering of discrete states and the background scattering of continuous states. By adjusting the spacing between these two half zigzag molds, the sound insulation dip frequency can shift from 360 Hz to 575 Hz while the free ventilation area ratio is kept to over 36.3% and the total thickness is only about 0.06λ. Moreover, the noise peak frequency can be detected by a microphone detection and adaptive adjustment of the spacing with a small stepping motor is demonstrated, the results agree well with numerical simulations. We anticipate our design may find potential applications in acoustic air vents, soundproofing window and duct noise control.