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In this study, four kinds of In2O3 photocatalysts were prepared by a facile calcination process at different temperatures and used for the removal of perfluorooctanoic acid (PFOA) from contaminated...

Ceramic particle reinforced iron-based alloys have been widely used in aerospace, land transportation and other aspects, so it has attracted tremendous attention. Aiming at the preparation and interfacial reaction of ceramic particle reinforced iron-based alloys, the preparation methods for interfacial reactions, reinforcement selection and design of ceramic particle reinforced iron-based alloys are introduced in this paper. Combined with the recent studies on ceramic particle reinforced iron-based alloys, this paper focuses on the ceramic particle reinforced iron-based interface and strengthening models/mechanisms, based on existing research, prospects for further ceramic particle reinforced iron-based alloys were studied.

Securing cyber-physical systems (CPS) against malicious attacks is of paramount importance because these attacks may cause irreparable damages to physical systems. Recent studies have revealed that control programs running on CPS devices suffer from both control-oriented attacks (e.g., code-injection or code-reuse attacks) and data-oriented attacks (e.g., non-control data attacks). Unfortunately, existing detection mechanisms are insufficient to detect runtime data-oriented exploits, due to the lack of runtime execution semantics checking. In this work, we propose Orpheus , a new security methodology for defending against data-oriented attacks by enforcing cyber-physical execution semantics. We first present a general method for reasoning cyber-physical execution semantics of a control program (i.e., causal dependencies between the physical context/event and program control flows), including the event identification and dependence analysis. As an instantiation of Orpheus , we then present a new program behavior model, i.e., the event-aware finite-state automaton ( e FSA). e FSA takes advantage of the event-driven nature of CPS control programs and incorporates event checking in anomaly detection. It detects data-oriented exploits if a specific physical event is missing along with the corresponding event dependent state transition. We evaluate our prototype’s performance by conducting case studies under data-oriented attacks. Results show that e FSA can successfully detect different runtime attacks. Our prototype on Raspberry Pi incurs a low overhead, taking 0.0001s for each state transition integrity checking, and 0.063s $\sim$ ∼ 0.211s for the cyber-physical contextual consistency checking.

Background To investigate osteointegration at the graft-bone interface and the prevention of osteoarthritis after anterior cruciate ligament (ACL) reconstruction using a silk-collagen scaffold with both ends modified by hydroxyapatite (HA) in a rabbit model. Methods The HA/silk-collagen scaffold was fabricated using a degummed, knitted silk scaffold, collagen I matrix, and simulated body fluid (SBF). The HA/silk-collagen scaffold was rolled up to make a graft for replacing the native ACL in the experimental group (HA group), and the silk-collagen scaffold was used in the control (S group). All specimens were harvested at 16 weeks postoperatively to evaluate graft-bone healing and osteoarthritis prevention. Results Histological staining revealed the massive formation of more mature bone at the tendon-bone interface, and immunohistochemistry staining revealed more collagen I and osteocalcin deposition in the HA group than in the S group. Higher signals indicating more bone mineral formation were detected in the HA group than in the S group, which was consistent with the results of biomechanical testing. Better osteoarthritis prevention was also observed in the HA group, indicating a more stable knee joint in the HA group than in the S group. Conclusion The HA/silk-collagen scaffold promotes osteointegration at the tendon-bone interface after ACL reconstruction and has great potential for clinical applications.

In this article, ultra-broadband photoluminescence in near-infrared is achieved in KZnF3 glass ceramics doped with Er3+and Ni2+ ions. Er3+-Ni2+ co-doped fluorosilicate glass and glass ceramics embedded with perovskite nanocrystals were fabricated and efficient energy transfer (ET) from Er3+ to Ni2+ ions was confirmed by luminescence spectra and decay curves. In the glass ceramic samples, Ni2+ ions were effectively sensitized by Er3+, and ultra-broadband photoluminescence from 1400 to 2300 nm was observed when a 980 nm laser was used as a pump, as shown in Fig. 1. The temperature and humidity stability of the glass ceramic samples was characterized from the measured transmittance. These results demonstrated that Ni2+-Er3+ co-doped glass ceramics have significant potential for application in optical communication and broadband amplifiers.

peer-reviewed Lead germanate glass samples with different Er3+/Yb3+ concentrations co-doped were prepared and the color variation of the up-conversion emissions in these glasses was observed using 980 nm laser pump power. A practical optical integrated device based on Er3+-Yb3+ co-doped lead germanate glass microsphere and a special fiber structure, consisting of single mode fiber (SMF), multimode fiber (MMF) and a suspended tri-core hollow fiber (STCHF) is proposed. As the pump light is coupled into the microsphere from the cores suspended inside the STCHF, the microsphere fixed in the air hole of the STCHF is excited and the up-conversion emissions can also be observed. Furthermore, when the pump power is increased, the luminescence output color of the microsphere can be readily tuned from yellow to green due to the change of the luminescence intensity ratio of the red to green emissions. This in-fiber microsphere resonator integrated device has the potential to be widely applied in multicolor displays, optical sensors and laser devices owing to its compact structure and excellent performance.

We present our results on an experimental and theoretical investigation into a glass microsphere laser emitting at 2 μm wavelength. First, we fabricated Ho 3+ -doped tellurite glass fiber and measured the absorption and emission spectra, and the fluorescence lifetime. Using this fiber, a tellurite glass microsphere with a Q-factor of 2 × 10 6 was also prepared, and a single-mode laser output with a low threshold of 342 μW was observed using a 1150 nm laser as the pump source. The dynamic characteristics of the microsphere laser were studied theoretically by considering rare-earth ion spectroscopy, the rate equation of the rare-earth energy level, and the light-matter interactions in the microsphere. This work can be used to study laser emissions with low thresholds in rare-earth doped compound glass microresonators for a wide range of applications, such as gas sensing, integrated photonics, and medical surgery.

During repackaging, malware writers statically inject malcode and modify the control flow to ensure its execution. Repackaged malware is difficult to detect by existing classification techniques, partly because of their behavioral similarities to benign apps. By exploring the app's internal different behaviors, we propose a new Android repackaged malware detection technique based on code heterogeneity analysis . Our solution strategically partitions the code structure of an app into multiple dependence-based regions (subsets of the code). Each region is independently classified on its behavioral features. We point out the security challenges and design choices for partitioning code structures at the class and method level graphs, and present a solution based on multiple dependence relations. We have performed experimental evaluation with over 7,542 Android apps. For repackaged malware, our partition-based detection reduces false negatives (i.e., missed detection) by 30-fold, when compared to the non-partition-based approach. Overall, our approach achieves a false negative rate of 0.35 percent and a false positive rate of 2.97 percent.

This paper proposes an unsupervised way for Phonocardiogram (PCG) analysis, which uses a revised auto encoder based on distribution density estimation in the latent space. Auto encoders especially Variational Auto-Encoders (VAEs) and its variant β−VAE are considered as one of the state-of-the-art methodologies for PCG analysis. VAE based models for PCG analysis assume that normal PCG signals can be represented by latent vectors that obey a normal Gaussian Model, which may not be necessary true in PCG analysis. This paper proposes two methods DBVAE and DBAE that are based on estimating the density of latent vectors in latent space to improve the performance of VAE based PCG analysis systems. Examining the system performance with PCG data from the a single domain and multiple domains, the proposed systems outperform the VAE based methods. The representation of normal PCG signals in the latent space is also investigated by calculating the kurtosis and skewness where DBAE introduces normal PCG representation following Gaussian-like models but DBVAE does not introduce normal PCG representation following Gaussian-like models.

Fault prognosis plays a key role in the framework of Condition-Based Maintenance (CBM). Limited by the inherent disadvantages, most traditional intelligent algorithms perform not very well in fault prognosis of hydraulic pumps. In order to improve the prediction accuracy, a novel methodology for fault prognosis of hydraulic pump based on the bispectrum entropy and the deep belief network is proposed in this paper. Firstly, the bispectrum features of vibration signals are analyzed, and a bispectrum entropy method based on energy distribution is proposed to extract the effective feature for prognostics. Then, the Deep Belief Network (DBN) model based on the Restrict Boltzmann Machine (RBM) is proposed as the prognostics model. For the purpose of accurately predicting the trends and the random fluctuations during the performance degradation of the hydraulic pump, the Quantum Particle Swarm Optimization (QPSO) is introduced to search for the optimal value of initial parameters of the network. Finally, analysis of the hydraulic pump degradation experiment demonstrates that the proposed algorithm has a satisfactory prognostics performance and is feasible to meet the requirements of CBM.

This study aims to investigate the cooling performance of various film cooling holes, including combined hole, cylinder hole, conical hole, and fan-shaped hole. For film cooling technology, a novel combined hole configuration is first proposed to improve the cooling protection for gas turbine engines. This combined hole consists of a central cylinder hole (an inclination angle of 35°) and two additional side holes (a lateral diffusion angle of 30°). Film holes for four-hole configurations have the same inlet diameter of 8 mm. The adiabatic film cooling effectiveness for each hole configuration is analyzed for varying blowing ratios (M = 0.25, 0.5, 0.75, and 1.0). Results show that the best cooling performance for the conical and fan-shaped holes is obtained at the blowing ratio of 0.75. In addition, the combined hole configuration provides a more uniform cooling protection and a better cooling performance than the other hole configurations.

In this work, we present a packaged whispering gallery mode (WGM) device based on an optical nanoantenna as the coupler and a glass microsphere as the resonator. The microspheres were fabricated from either SiO2 fiber or Er3+-doped fiber, the latter creating a WGM laser with a threshold of 93 µW at 1531 nm. The coupler-resonator WGM device was packaged in a glass capillary. The performance of the packaged microlaser was characterized, with lasing emission both excited in and collected from the WGM cavity via the nanoantenna. The packaged system provides isolation from environmental contamination, a small size, and unidirectional coupling while maintaining a high quality (Q-) factor (∼108).

As a vital power propulsion device, gas turbines have been widely applied in aircraft. However, fly ash is easily ingested by turbine engines, causing blade abrasion or even film hole blockage. In this study, a three-dimensional turbine cascade model is conducted to analyze particle trajectories at the blade leading edge, under a film-cooled protection. A deposition mechanism, based on the particle sticking model and the particle detachment model, was numerically investigated in this research. Additionally, the invasion efficiency of the AGTB-B1 turbine blade cascade was investigated for the first time. The results indicate that the majority of the impact region is located at the leading edge and on the pressure side. In addition, small particles (1 μm and 5 μm) hardly impact the blade’s surface, and most of the impacted particles are captured by the blade. With particle size increasing, the impact efficiency increases rapidly, and this value exceeds 400% when the particle size is 50 μm. Invasion efficiencies of small particles (1 μm and 5 μm) are almost zero, and the invasion efficiency approaches 12% when the particle size is 50 μm.

Negative curvature hollow core fiber (NCHCF) is a promising candidate for sensing applications, however, research on NCHCF based fiber sensors starts only in the recent two years. In this work, an all-fiber interferometer based on an NCHCF structure is proposed for the first time. The interferometer was fabricated by simple fusion splicing of a short section of an NCHCF between two singlemode fibers (SMFs). Both simulation and experimental results show that multiple modes and modal interferences are excited within the NCHCF structure. Periodic transmission dips with high spectral extinction ratio (up to 30 dB) and wide free spectral range (FSR) are produced, which is mainly introduced by the modes coupling between HE11 and HE12. A small portion of light guiding by means of Anti-resonant reflecting optical waveguide (ARROW) mechanism is also observed. The transmission dips, resulting from multimode interferences (MMI) and ARROW effect have a big difference in sensitivities to strain and temperature, thus making it possible to monitor these two parameters with a single sensor head by using a characteristic matrix approach. In addition, the proposed sensor structure is experimentally proven to have a good reproducibility.

Cryptographic API misuses seriously threatens software security. Automatic screening of cryptographic misuse vulnerabilities has been a popular and important line of research over the years. However, the vision of producing a scalable detection tool that developers can routinely use to screen millions of line of code has not been achieved yet. Our main technical goal is to attain a high precision and high throughput approach based on specialized program analysis. Specifically, we design inter-procedural program slicing on top of a new on-demand flow-, context- and field- sensitive data flow analysis. Our current prototype named CryptoGuard can detect a wide range of Java cryptographic API misuses with a precision of 98.61%, when evaluated on 46 complex Apache Software Foundation projects (including, Spark, Ranger, and Ofbiz). Our evaluation on 6,181 Android apps also generated many security insights. We created a comprehensive benchmark named CryptoApi-Bench with 40-unit basic cases and 131-unit advanced cases for in-depth comparison with leading solutions (e.g., SpotBugs, CrySL, Coverity). To make CryptoGuard widely accessible, we are in the process of integrating CryptoGuard with the Software Assurance Marketplace (SWAMP). SWAMP is a popular no-cost service for continuous software assurance and static code analysis.

A low-cost optical fibre sensor based on two cascaded balloon-like bent fibre (BBF) structures for simultaneous displacement and temperature measurement is reported. The sensor is fabricated by cascading two balloon-like bent single-mode fibres (SMFs) which with different bending radii, generating two separate interference dips within a limited wavelength range. The wavelength of the two interference dips exhibits different responses to external displacement and temperature variations, hence simultaneous measurement of displacement and temperature is realized. Experimental results show that the proposed optical fibre sensor achieves a displacement sensitivity of −318.8 pm/μm and a temperature sensitivity of 47.4 pm/°C. Taking advantage of its low-cost, ease of fabrication, and experimentally determined high sensitivity, the sensor in this investigation can be potentially applied in both displacement and temperature measurement fields.

peer-reviewed An angled polished multimode (APM) fibre structure is described for the first time, to the best our knowledge, and its polarization dependence investigated theoretically and experimentally. Two angled planes are established in the multimode fibre (MMF) section of a single-mode-multimode-single-mode (SMS) fibre structure using the fibre side-polishing technique, forming the APM fibre structure. This designed circular asymmetric geometry induces different propagation characteristics for the TE and TM modes within the MMF. Simulated and experimental results both show that this difference is enhanced as the polishing angle increases, and a maximum extinction ratio (ER) of the spectrum of 13 dB is achieved at a polishing angle of 85°. This polarization-dependent device has a simple fabrication process and is free from the limitation of coating functional materials, which is expected to be applied in non-linear optics, fibre laser and optical fibre sensing fields.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 15/05/2022 In this article, a high sensitivity, low temperature-crosstalk strain sensor based on a microsphere embedded Fabry–Perot interferometer (FPI) is reported and experimentally demonstrated. The sensor is fabricated by embedding a microsphere inside a tapered hollow-core fiber (HCF) whose ends are enclosed by two standard single-mode fibers (SMFs). The reflections occurring at the SMF/HCF interface and the surfaces of the microsphere, result in a three-beam interference. The cavity length of the formed FPI can be flexibly changed by controlling the diameter of the tapered HCF and the size of the embedded microsphere, and the maximum extinction ratio (ER) of the reflection spectrum is greater than 11 dB. This novel microsphere embedded FPI structure significantly enhances the sensing performance of traditional FPIs for strain measurement, providing a high strain sensitivity of 16.2 pm/με with a resolution of 1.3 με. Moreover, it is demonstrated that this strain sensor has a very low temperature-strain cross-sensitivity of 0.086 με/oC, which greatly enhances the potential for applications in the field of precision strain measurement ACCEPTED peer-reviewed

peer-reviewed A high sensitivity temperature sensor based on a singlemode-no-core-singlemode (SNCS) fibre structure and surrounded with alcohol within a silica capillary is described. In this investigation, no-core fibre (NCF) is used as the multimode waveguide and alcohol is chosen as the temperature sensitive medium. By packaging the alcohol solution with a short length of NCF enclosed within a silica capillary, the surrounding temperature can be detected by monitoring the variations of transmission loss at a specific wavelength. The theoretical analysis predicts this temperature sensor can provide high sensitivity, and the experimental results support this. The maximum temperature sensitivity of the sample is 0.49 dB/°C with a potential temperature resolution of 0.02 °C at the operating wavelength of 1545.9 nm. In addition, the repeatability and response time of the sensor of this investigation are investigated experimentally.

We report a novel composite of α-Fe2O3/BiVO4 with n-n heterojunctions for the first time and application in detecting low concentration NO2 gas. The flower-like α-Fe2O3 hierarchical nanostructures were prepared by the solvothermal method followed by BiVO4 nanoparticles decorated on α-Fe2O3 surface by metal-organic decomposition to structure the heterojunctions of α-Fe2O3/BiVO4. The structure and morphology of material were characterized and the sensing properties to NO2 were examined. The results show that the α-Fe2O3/BiVO4 composite (atomic ratio of 8:1:1 for Fe: Bi: V) to 2 ppm NO2 exhibits a four times higher response than pristine α-Fe2O3 at 110 °C, excellent selectivity, and long-term stability. The enhanced sensing properties can be attributed to the porous hierarchical structure of composite and the formation of inner electronic field (IEF) caused by n-n heterojunction at interface between α-Fe2O3 and BiVO4.

One dimensional ZnO-SnO2 hollow nanofibers were synthesized via a one-step electrospinning method and annealing treatment. The morphology and structure of the nanofibers have been characterized by various analysis methods, and the sensing properties to 0.5–5 ppm NO2 have also been examined. The results reveal that the 20 atm%Zn composite not only exhibits the highest response that is 9 and 5.2 times higher than that of pristine ZnO and SnO2 respectively, but also exhibits rapid response, excellent selectivity and stability at low operating temperature of 90 °C. So, herein synthesized composite is a promising sensing material for detection of NO2. The enhancing sensing mechanism is discussed in detail, which is attributed to the unique one-dimensional hollow nanostructures and the formation of heterojunctions at interface between both metal oxides.

A relative humidity (RH) sensor based on a simple singlemode-side polished multimode-singlemode (SSPMS) fiber hybrid structure is investigated, which is capable of working over a relatively high-temperature range, at which many RH sensors based on moisture sensitive material coatings cannot operate. The beam propagation method is used to analyze the light transmission characteristics within the side polished multimode fiber (SPMMF) structure. Experimental results show that the SPMMF surface roughness has a significant influence on the sensor's humidity sensing performance, as a result of the adsorption and desorption of water molecules along the side polished surface. A higher surface roughness results in an increased RH sensitivity. It is concluded that the SSPMS fiber structure based RH sensor can achieve around 0.069 dB/%RH within the humidity range of 30%RH–90%RH for a temperature range of 70 °C to 90 °C. In addition, the temperature cross-sensitivity has been investigated experimentally. The developed fiber optic sensor in this investigation provides a simple and effective approach for RH measurement in a variety of production applications.

Film cooling, as an effective protection technology, is widely applied in gas turbines to prevent components like vane blades from the hot mainstream. However, ash and other contaminants contained in the gas easily deposit on blade surfaces, which results in blockages inside the film holes and a reduction of the coverage area of the coolant air. Two blockage configurations (hemispherical and tetrahedral blockages) with a similar blockage ratio are analyzed in this study. In addition, mist injection with three droplet sizes (1 μm, 5 μm and 10 μm) is also considered. It is found that the position of the blockage configuration shows almost no influence on the cooling performance. In addition, the hemispherical blockage configuration results in a lower lateral film cooling effectiveness than the tetrahedral one. Finally, it is also concluded that the 5 μm droplet case shows more uniform distribution than other cases.

Hyper-crosslinked polymers (HCPs) are promising materials for gas capture and storage because of their low cost and easy preparation. In this work, we report the massive preparation of coumarone-indene resin-based hyper-crosslinked polymers via one-step Friedel-Crafts alkylation. Low-cost coumarone-indene resin serves as the new building block and chloroform is employed as both solvent and external crosslinker. A maximum surface area of 966 m2·g−1 is achieved, which is comparable with that of previously-reported coal tar-based porous organic polymers. Most importantly, a large number of heteroatoms including inherent oxygen atoms and introduced chlorine atoms in obtianed HCPs further enhance the interaction between specific sorbate molecule and adsorbent. Therefore, optimal structural and chemical property endow the new coumarone-indene resin-based HCPs with decent gas storage capacity (14.60 wt% at 273 K and 0.1 MPa for CO2; 1.18 wt% at 77.3 K and 0.1 MPa for H2). These results demonstrate that new HCPs are potential candidates for applications in CO2 and H2 capture.

To probe the influence of the porous morphology of carbon materials on their microwave absorption performance, hierarchically porous carbons (HPCs) with designed structures have been successfully prepared starting from poly(divinylbenzene) by emulsion template polymerization. There exist two levels of pores in the obtained HPCs. One level of micro-scale pores templates from the water drops, and the other level of nano-scale pores is created during KOH activation in the subsequent carbonization process. By adjusting the water volume fraction during polymerization and the KOH dosage, both micro- and nano-scale porous structures can be accurately tuned. The influences of pores with diverse scales on microwave adsorption capacity are investigated in detail. Eventually, the maximum reflection loss of −56.4 dB and an effective adsorption bandwidth of 6.0 GHz are achieved. The superior microwave absorption performance of HPCs is attributed to the superimposed contributions of the two-level pores to the enhancement of polarization abilities and the multiple reflections of the microwave.

Turbine blades operate under a harsh environmental condition, and the inlet temperature of gas turbines is increasing with requirement of high engine efficiency. Some cooling schemes are adopted to prevent these blades from the thermal erosion of the hot mainstream. Film cooling technology is used widely and effectively in gas turbines. The coolant air is suppressed to the wall by the mainstream after jetting out of the film hole. A new hole configuration is first proposed to improve the film cooling characteristics in this paper. Comparison between a conventional cylindrical hole and a new combined hole is conducted by computational fluid dynamics, and effects of various blowing ratios and droplet sizes are also investigated. Results show that the combined hole configuration provides a wider coverage than that in the cylindrical hole configuration case at high blowing ratios (M = 1.0 and M = 1.5). In addition, the film cooling with mist injection also provides a significant enhancement on cooling performance especially for the combined hole case with a small droplet size (10−5 m).

The Chinese government established a counterpart support mechanism and ecological civilization construction to promote socioeconomic development and ecological protection after the Wenchuan earthquake. However, the contradiction between the ecological environment and socioeconomic is still has not changed fundamentally. How to coordinate the relationship between the socioeconomic and ecological environment in the disaster area has become a key issue to the sustainable development after the Wenchuan earthquake. The purpose of this paper is to research the coupling and coordination relationship between socioeconomic and ecological environment to provide reference for Wenchuan earthquake disaster area to achieve regional sustainable development goals (SDGs) and high-quality development. Based on this, the dynamic deviation maximization (DM) method and coupling coordination model (CCD) were used to calculate the indicator weight and the overall coordination relationship between socioeconomic (SE) and ecological environment (EE) in Wenchuan earthquake disaster area by using the data from 2005 to 2018. The results showed that the CCD of the Wenchuan earthquake disaster area has increased from 2005 to 2018. From the spatial characteristics, the comprehensive evaluation score of CCD decreased from northeast to southwest in the disaster area, and there is still a significant spatial difference in the disaster area. Besides, the interesting finding is that post-disaster reconstruction and recovery capacity are closely related to location factors, population factors and altitude factors. On this basis, the causes of regional differences are analyzed, and some corresponding concrete suggestions are proposed, involving strengthen the policies to prevent labor loss, expand the characteristic industries of each country according to local conditions, and increase investment in technological innovation.

Hierarchically porous carbon (HPC) materials with interconnected pore texture are produced from porous poly(divinylbenzene) precursor, synthesized by polymerizing high internal phase emulsion. After carbonation, the macroporous structures of the poly(divinylbenzene) precursor are preserved and enormous micro/mesopores via carbonation with KOH are produced, resulting in interconnected hierarchical pore network. The prepared HPC has a maximum specific surface area of 2189 m2 g-1. The electrode materials for supercapacitor and capacitive deionization (CDI) device employing the formed HPC exhibit high specific capacity of 88 mAh g-1 through a voltage range of 1V (319 F g-1 at 1 A g-1) and superior electrosorption capacity of 21.3 mg g-1 in 500 mg L-1 NaCl solution, respectively. The excellent capacitive performance could be ascribed to the combination of high specific surface area and favorable hierarchical porous structure.

A series of N-doped porous carbon materials have been successfully prepared by using nitrogen-rich triarylisocyanurate-cored polymers as carbon precursor. The cross-linked networks explain the precursor with high carbonaceous residues in the following carbonization. The influence of KOH dosage and activation temperature on the specific surface area and nitrogen content of the resultant carbon materials is investigated in detail. Eventually, a maximum specific surface area of 2341 m2 g–1 and nitrogen content of 1.7 wt % are achieved in the resultant carbon materials. High CO2 capacity (30.2 wt % at 273 K/1 bar and 17.2 wt % at 298 K/1 bar) is attributed to abundant microporous structures and basic sites, superior to that of the most porous carbon materials reported in the previous literature. In addition, the carbon materials also demonstrate high H2 and CH4 uptake (2.7 wt % at 77.3 K/1.13 bar and 3.8 wt % at 273 K/1.13 bar, respectively). The characters of easy preparation and high gas uptake capacity end...

A novel relative humidity sensor based on a singlemode-side polished multimode-singlemode fibre structure coated with gelatin material is reported. The sensing principle and fabrication method of the proposed sensor are presented. The experimental method is demonstrated to provide the optimum thickness of coating layers in order to achieve the highest sensitivity of 0.14 dB/%RH and a fast response time of 1000 ms for a given relative humidity sensing range. The developed humidity fibre optic sensor based on a gelatin coating shows great potential for many applications such as industrial production, food processing, and environmental monitoring.

Core–shell Fe3O4@polypyrrole (PPy) composites with excellent electromagnetic wave absorption properties have been prepared by a sequential process of etching, polymerization, and replication. Templating from pre-prepared Fe3O4 microspheres, ferric ions were released from the skin layer of the microspheres by acid etching and initiated the oxidative polymerization of pyrrole in suit. The morphological and textural evolution of core–shell Fe3O4@PPy composites depending on etching time was investigated by scanning and transmission electron microscope. A maximum reflection loss of as much as −41.9 dB (>99.99% absorption) at 13.3 GHz with a matching layer thickness of 2.0 mm was achieved when the etching time was 5 min. In comparison with other conductive polymer-based core–shell composites reported previously, the Fe3O4@PPy composites in this study not only possess better reflection loss performance but also demonstrate a wider effective absorption bandwidth (

For safe disposal and environmentally benign recycling, lignocellulosic biomass wastes are increasingly studied for use as precursors for the preparation of value-added porous carbon materials. However, conventional chemical vapor deposition is time consuming and difficult to perform on a large scale. Herein, we obtained nitrogen-doped porous carbon materials (NPCMs) with high supercapacitor performance by one-pot copyrolysis of a carbon precursor (wheat straw), nitrogen precursor (melamine), and salt templating (mixed salt of KCl/ZnCl2 at 51:49). The NPCM with 7.78% nitrogen content exhibited an excellent gravimetric capacitance of 223.9 F g–1, which is mainly attributed to the increase in surface area by the activation of salt templating and the decrease in ion-transport resistance by N doping of the NPCM. The removal of silicon in pyrolysis products efficiently enhanced the capacitance of materials, but there was a negative effect on capacitance if the silicon was removed from feedstocks before pyrolys...

Preventing release of refractory pollutants from contaminated sediments is of growing concern. In situ remediation of sediments becomes more popular because of its low cost and noninterference of benthic ecosystems compared with conventional sediment dredging. In this study, a low-cost rice husk biochar (RHB) was used as a capping material to prevent the release of representative inorganic (Cu2+) and organic (4-chlorophenol, 4-CP) pollutants from synthetic contaminated sediments. In addition, the release dynamics of pollutants was investigated under different environmentally relevant conditions. The experimental results indicated that RHB can efficiently suppress the release of Cu2+ and 4-chlorophenol from the sediments and a select thickness of RHB can maintain the concentrations of these model pollutants below the national criterion at pH = 5 and 7, even when the concentrations of these pollutants are very high (1600 mg kg–1 of Cu2+ or 100 mg kg–1 of 4-CP). Fitting the release data of pollutants to the ...

An optical fiber curvature sensor based on a twisted multimode fiber (MMF) sandwiched between two single-mode fibers (SMF) is proposed and investigated theoretically and experimentally. The measured transmission spectrum exhibits good agreement with theoretical predictions. Compared with a traditional single-mode-multimode-single-mode fiber structure sensor, the proposed configuration offers a higher average curvature sensitivity of -2.42 nm/m -1 over a curvature measurement range of 0-1.7390 m -1 and -7.09 dB/m -1 at an operating wavelength of 1537 nm. The temperature sensitivity of this sensor has been determined as 0.01 nm/°C over a wavelength range of 1535-1550 nm and circa 0.007 dB/°C at the wavelength of 1537 nm, over a measured temperature range of 21-121 °C.

To circumvent the intractable disadvantages of a hyper-cross-linked strategy based on the Friedel–Crafts reaction, a new type of microporous organic polymer (MOP) has been successfully prepared using fumaronitrile and divinylbenzene via alternating radical polymerization. The obtained MOPs exhibit a maximum surface area of 805 m2 g−1 and excellent thermochemical stability. By pyrolyzing the copolymer precursor, a rich nitrogen-doped porous carbon material can be produced, which possesses a specific surface area of 1450 m2 g−1 with a CO2 uptake of 30 wt% at 273 K. The porous carbon also shows a high specific capacitance of 330 F g−1 at a current density of 1.0 A g−1 and a good cycling stability of 96.8% retention after 8000 cycles in a three electrode system. The unique synthesis strategy inspires researchers to seek novel building blocks for the scaled-up preparation of MOPs and the resulting porous carbon has promising application for gas adsorption and energy storage.

Fast pyrolysis of biomass wastes which is usually finished in a few seconds for the preparation of porous carbonaceous materials (PCMs) is much faster and more energy-efficient than the conventional hydrothermal carbonization (HTC) method and does not require the use of solvents. In this study, PCMs were prepared using corn gluten meal (CGM) waste by fast pyrolysis combined with chemical activation by KOH, and the capacitance performance of the resulting PCMs was investigated. The specific capacitance of PCMP500 (fast pyrolysis at 500 °C) was 488 F g−1 at a current density of 0.5 A g−1, which is better than those of PCMs obtained at other pyrolytic temperatures (PCMP300 and PCMP400). Under the same conditions, the PCMs prepared by the HTC process exhibited relatively lower supercapacitance performance, i.e., PCMH250 (HTC at 250 °C) is 433 F g−1. The high performance of PCMP500 was mainly attributed to the high specific surface area and pore structure, which depends on the thermal treatment methods. This work demonstrates that fast pyrolysis may be a promising technology for massive production of high performance PCMs from biomass wastes.

A series of hierarchically structured porous polyureas are prepared through the polymerization of diisocyanate monomers and H2O via a one-step and template-free strategy. This simple archetypal reaction combines carbon dioxide foaming process and hyper-crosslinking reaction. The obtained hierarchically porous polyureas (HPUs) consist of micro- and mesopores created by hyper-crosslinking reaction, and macropores generated by carbon dioxide foaming process. The HPUs have a high surface area up to 483.3 m2/g, and large pore volume (0.76 cm3/g). Besides, the nitrogen-doped carbon materials prepared by pyrolyzing the HPUs show a high specific capacitance (209 F/g at 1.0 A/g) and good cycling stability (99.8% capacitance retention after 5000 cycles), demonstrating the advantages of the hierarchically porous structure and nitrogen-rich chemical composition of HPUs.

Cryptographic API misuses, such as exposed secrets, predictable random numbers, and vulnerable certificate verification, seriously threaten software security. The vision of automatically screening cryptographic API calls in massive-sized (e.g., millions of LoC) programs is not new. However, hindered by the practical difficulty of reducing false positives without compromising analysis quality, this goal has not been accomplished. CryptoGuard is a set of detection algorithms that refine program slices by identifying language-specific irrelevant elements. The refinements reduce false alerts by 76% to 80% in our experiments. Running our tool, CryptoGuard, on 46 high-impact large-scale Apache projects and 6,181 Android apps generated many security insights. Our findings helped multiple popular Apache projects to harden their code, including Spark, Ranger, and Ofbiz. We also have made progress towards the science of analysis in this space, including manually analyzing 1,295 Apache alerts, confirming 1,277 true positives (98.61% precision), and in-depth comparison with leading solutions including CrySL, SpotBugs, and Coverity.

Cryptographic API misuses seriously threaten software security. Automatic screening of cryptographic misuse vulnerabilities has been a popular and important line of research over the years. However, the vision of producing a scalable detection tool that developers can routinely use to screen millions of line of code has not been achieved yet. Our main technical goal is to attain a high precision and high throughput approach based on specialized program analysis. Specifically, we design inter-procedural program slicing on top of a new on-demand flow-, context- and field- sensitive data flow analysis. Our current prototype named CryptoGuard can detect a wide range of Java cryptographic API misuses with a precision of 98.61%,, when evaluated on 46 complex Apache Software Foundation projects (including, Spark, Ranger, and Ofbiz). Our evaluation on 6,181 Android apps also generated many security insights. We created a comprehensive benchmark named CryptoAPI-Bench with 40-unit basic cases and 131-unit advanced cases for in-depth comparison with leading solutions (e.g., SpotBugs, CrySL, Coverity). To make CryptoGuard widely accessible, we are in the process of integrating CryptoGuard with the Software Assurance Marketplace (SWAMP). SWAMP is a popular no-cost service for continuous software assurance and static code analysis.

In this letter, an Nd3+-doped compound fluorosilicate glass was successfully fabricated with the method of melt-quenching. Under the excitation of a 808 nm laser, enhanced near-infrared photoluminescence emission at the range from 1,065 to 1,140 nm was observed in the glass sample. To characterize its stability and resistance to environmental effects, transmission spectra at the range of NIR-MIR were measured under different environments, including humidity and temperature. In addition, the obtained fluorosilicate glass was also developed as a microsphere resonator by using CO2 laser heating method. When the diameter of the microsphere was controlled at 61.5 µm, coupling with a tapered fiber, single-multimode lasing in the wavelength range ~1,056–1,071 nm was achieved with a low lasing threshold of 1.5 mW. Compared to silica and phosphate glasses, this fluorosilicate glasses have lower phonon energy, which can reduce the probability of non-radiative transitions and improve the photoluminescence efficiency. Therefore, using it as the raw material, the developed microsphere resonator offers a high transition temperature and with a low lasing threshold, which are promising it for high performance sensing and detection applications.

Optical fiber based twist sensors usually suffer from high cross sensitivity to strain. Here we report a strain independent twist sensor based on an uneven platinum coated hollow core fiber (HCF) structure. The sensor is fabricated by splicing a section of ~4.5-mm long HCF between two standard single mode fibers, followed by a sputter-coating of a very thin layer of platinum on both sides of the HCF surface. Experimental results demonstrate that twist angles can be measured by monitoring the strength change of transmission spectral dip. The sensor’s cross sensitivity to strain is investigated before and after coating with platinum. It is found that by coating a platinum layer of ~9 nm on the HCF surface, the sensor’s cross sensitivity to strain is significantly decreased with over two orders of magnitude less than that of the uncoated sensor sample. The lowest strain sensitivity of ~2.32×10−5 dB/𝜇𝛆 has been experimentally achieved, which is to the best of our knowledge, the lowest cross sensitivity to strain reported to date for optical fiber sensors based on intensity modulation. In addition, the proposed sensor is capable of simultaneous measurement of strain and twist angle by monitoring the wavelength shift and dip strength variation of a single spectral dip. In the experiment, strain and twist angle sensitivities of 0.61 pm/𝜇𝛆 and 0.10 dB/° have been achieved. Moreover, the proposed sensor offers advantages of ease of fabrication, miniature size, and a good repeatability of measurement.

Conventional nondestructive evaluation methods have difficulties in finding internal defects of the aviation foam materials because of its loose structure and thermal insulation. It has become a challenge in nondestructive evaluation field. In this paper, a low-cost terahertz nondestructive evaluation technology is presented. The system uses a 0.1 THz avalanche diode and pyroelectric detector, combined with a 3D printing lens and a three-dimensional scanning system to obtain the interior THz image of the aerial materials. A novel frequency domain filtering algorithm is proposed to obtain higher quality internal image aiming at reducing the error of scanning system and the diffraction of low-frequency terahertz wave. This technology has important potential value in application of nondestructive evaluation.

Cr3+-Yb3+ codoped bulk glass-ceramics containing KZnF3 nanocrystals are fabricated by thermal treatment of cast glass samples and characterized by X-ray diffraction and transmission electron microscopy. The luminescent properties of the glass and glass ceramic are investigated from the measured photoluminescence spectra and fluorescent lifetime. The measurement results demonstrate that Cr3+ and Yb3+ ions are both predominantly hosted in the KZnF3 nanocrystals, and the energy absorbed by Cr3+ ions is efficiently transferred to Yb3+ ions when excited at 450 nm. Compared to the glass, the near-infrared emission in the Cr3+-Yb3+ codoped glass ceramics is significantly enhanced when the excitation wavelength lies in the range λ~400–800 nm of a solar simulator. Results indicate that the Cr3+-Yb3+ codoped KZnF3 glass ceramic provides a promising material for spectral conversion from visible sunlight to near-infrared emission and a novel gain material for solar pumped fiber laser.

Photoelectrochemical (PEC) water splitting technology offers a sound strategy for the production of chemical energy using abundant solar energy. Herein, a ternary photoanode of SnO2/BiVO4/rGO was fabricated by plain chemical vapor deposition (CVD) and metal-organic decomposition followed by spin-coated rGO on the SnO2/BiVO4 junction. The ternary photoanode yields the highest photocurrent density of 2.05 mA cm−2 at 1.23 V vs. RHE, which is 3.73 times of the BiVO4 photoanode (0.55 mA cm−2). The incident photon-to-electron conversion efficiency (IPCE) of the ternary photoanode is 2.47 times that of the BiVO4 photoanode at 400 nm, and the onset potential exhibits a cathodic shift of ∼300 mV. This enhancement can be attributed to the formation of n-n heterojunctions between the SnO2 and BiVO4, and decoration of rGO on said heterojunctions because they synergistically improve the absorption of visible light, enhance the efficiency of charge separation , and accelerate electron transfer at the electrode/electrolyte interface.

A finite element model based on Abaqus/Explicit is built. Micro cutting mechanism of Al7075 with different cutting depth is simulated and analyzed. The simulation results show that if the cutting depth is more than 10μm, the chip is a kind of continuous curl. If the cutting depth is less than 10μm, the chip is a kind of feathery squeeze debris. When the cutting depth is very small (3μm), the shape of chips is just like discontinuous wrinkle. By contrasting the simulation results of cutting force with its theoretical values, they have the same result. The model of the chip prediction could achieve ideal simulation results.

The production of phenol in high yield and selectivity by direct catalytic hydroxylation of benzene (HOB) is challenging. In this study, a carbon supported bimetallic Cu–Ag NPs composite was synthesized (Cu–Ag/C) via one-pot fast pyrolysis of Cu–Ag preloaded sawdust. Characterization of the product using various techniques illustrated that Cu and Ag NPs were monodispersed on the biochar, which were obtained during the fast pyrolysis of biomass. The as-synthesized Cu–Ag/C efficiently catalyzed the HOB reaction, resulting in the production of phenol. The maximum yield of phenol was 34.9%, whereas the selectivity for phenol was 96% at 50 °C. The experimental results using various solvents at different retention times incorporated with GC/MS, ESR, and H2-TPD determinations suggested that ˙OH radicals played a dominant role in the catalytic HOB reaction, where Cu and Ag offered a synergistic interaction. This study may provide a new avenue for the preparation of catalysts and offer insight into the synergistic interaction of bimetallic catalytic HOB reactions.

In view of the problem that the actual degradation status of rolling bearing has a poor distinguishing characteristic and strong fuzziness, a rolling bearing degradation state identification method based on multidomain feature fusion and dimension reduction of manifold learning combined with GG clustering is proposed. Firstly, the rolling bearing all-life data is preprocessed by local characteristic-scale decomposition (LCD) and six typical features including relative energy spectrum entropy (LREE), relative singular spectrum entropy (LRSE), two-element multiscale entropy (TMSE), standard deviation (STD), RMS, and root-square amplitude (XR) are extracted and compose the original multidomain feature set. And then, locally preserving projection (LPP) is utilized to reduce dimension of original fusion feature set and genetic algorithm is applied to optimize the process of feature fusion. Finally, fuzzy recognition of rolling bearing degradation state is carried out by GG clustering and the principle of maximum membership degree and excellent performance of the proposed method is validated by comparing the recognition accuracy of LPP and GA-LPP.

A novel TiC-TiN/Al2O3 tandem solar selective absorbing coating was successfully deposited on Si (1 0 0) and stainless steel (SS) substrates by reactive RF magnetron sputtering deposition. The spectral characteristics, microstructure, thermal stability and solar-thermal conversion efficiency of the coating before and after a long annealing in vacuum were investigated systematically. The optical constants of the coating are measured by an Ultraviolet–visible-near-infrared (UV/Vis/NIR) spectrometer, and the chemical composition analysis, structure information and surface morphology are investigated using XRD, XPS and FESEM. An excellent absorptance (α = 0.92) and a low emittance (e = 0.11) at 82 °C are obtained by the as-prepared coatings. After annealed at 500 °C for 100 h in vacuum, there is no significant change in micromorphology and optical properties of the coating, which produces a good solar-thermal conversion efficiency. These results indicate that it can be applied as a potential coating material to a high temperature concentrated solar power (CSP) system.

The ultra-wide-gap β-Ga2O3 has been regarded as a promising material for next-generation power electronic and deep-ultraviolet (UV) photodetectors. Exploring a suitable electrode is vital for realizing high performance β-Ga2O3 based nanodevices. Herein, the structural and contact properties of graphene/Ga2O3 interfaces are tuned and investigated by using the first-principles calculations. Results show that the small n-type Schottky barrier of about 0.07 eV for the graphene/Ga2O3 interface with weak interlayer interaction is irrespective of the interface stacking arrangement. Moreover, the intrinsic electronic property of Ga2O3 is well preserved in the interface. More interestingly, the n-type Schottky barrier to Ohmic contact transition can be obtained by shorting the interlayer distance, or increasing the graphene layers or applying a negative external electric field for the interface. Moreover, applying a large positive external electric field can realize the p-type Schottky barrier to Ohmic contact transition for graphene/Ga2O3 interface. These results are uncovered by analyzing the interfacial dipole and potential step of graphene/Ga2O3 interface, and expected to enhance the application potential of graphene electrode in the β-Ga2O3 based electronic and optoelectronic devices.