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A physical-layer secure data encryption algorithm is proposed and demonstrated using chaotic constellation mapping associated with probabilistic shaping (PS) for orthogonal frequency division multiplexing passive optical networks (OFDM-PONs). The constellation of the encrypted data is uniformly distributed after chaotic diffusion in quadratic-amplitude modulation (QAM) mapping, to eliminate the statistical characteristics, where a key space of ~10231 is created by a 4-dimensional hyper digital chaos. Moreover, PS is introduced to improve the OFDM signal transmission. A 9.4 Gb/s encrypted PS-16-QAM OFDM signal transmission is successfully demonstrated over 20 km standard single-mode fiber (SSMF), where the gain of receiver sensitivity is ~2 dB (bit-error rate @ 10−3) using PS.

Herein, potato starch residue derived carbon materials (PSRC) and KOH activated PSRC (denoted as APSRC) are successfully realized in this work. Interestingly, it is found that PSRC shows better electrochemical performance in potassium ion batteries (KIBs) than in sodium ion batteries (NIBs); however, the APSRC exhibits more excellent performance in NIBs than in KIBs. It is worth noting that the surface area and pore volume might be essential to Na+/K+ storage. For the PSRC with relatively lowered surface area and pore volome, the diffusion-controlled process is the main storage mode in NIBs. Nevertheless, the surface charge storage process is the main storage way for the PSRC in KIBs. On the other hand, the APSRC possesses large ratio of surface-dominated contribution to the whole capacity in NIBs and KIBs, which could be attributed to the more active sizes because of the larger surface area and higher pore volume. Furthermore, based on the optimal performance of APSRC in SIBs, sodium ion capacitors (NICs) utilizing APSRC as both cathode and anode materials are assembled. This NICs demonstrate satisfied performance with the energy density of 76.4 Wh kg−1 at the power density of 150 W kg−1.

Prussian blue analogue Na2Ni[Fe(CN)6] (Ni–PB) has been widely studied as a cathode material for sodium‐ion battery due to its excellent cycling performance. However, Ni–PB has a low theoretical capacity of 85 mAh g−1 because of the electrochemical inertness of Ni. Herein, ternary Ni–PB is successfully synthesized by double doping with Co and Fe at Ni‐site, and the effect of doping with Co and Fe on the electrochemical performance of Ni–PB is systematically investigated through theoretical calculations and electrochemical tests. The first principles calculations confirm that double doping with Co and Fe can significantly reduce the energy barrier and bandgap of Ni–PB. X‐ray diffraction and composition analysis results indicate that ternary NiCoFe–PB composite not only has good crystallinity and high Na content but also has low defects and crystal water. Electrochemical tests reveal that, besides the capacity contribution of high‐spin Co/Fe and low‐spin Fe, Co‐doping enhances the electrochemical activity of low‐spin Fe and Fe‐doping improves the activity of high‐spin Co; moreover, double doping can decrease the diffusion resistance of Na+ ions through solid electrolyte interface film, accelerate the kinetics for both ion diffusion process and Faradic reaction, and increase active sites. Under the synergistic effect of Co and Fe, this ternary NiCoFe–PB exhibits outstanding electrochemical performance with a high initial discharge capacity of 120.4 mAh g−1 at 20 mA g−1 and an extremely low capacity fading rate of 0.0044% per cycle at a high current density of 2 A g−1 even after 10,000 cycles, showing great application potential of ternary NiCoFe–PB in the field of large‐scale energy storage.

We report a 16.8 Tb/s true random number generator (TRNG) based on amplified spontaneous emission (ASE) of Erbium-doped fiber amplifier (EDFA), which is sliced into 42 parallel channels by an arrayed waveguide grating (AWG). The true randomness of ASE is enhanced and guaranteed by a novel extraction approach utilizing two orthogonal polarized components of ASE. Consequently, the random number generation rate (RNGR) can be significantly increased via higher sampling rate. The experimental results show that, the single-channel RNGR of 400 Gb/s is achieved, while the overall RNGR is 16.8 Tb/s for the full ASE spectrum. The proposed TRNG is of great significance in the field of secret key distribution and confidential communication.

Coal and gas outburst is still a major safety problem in the process of coal production in China. Correctly understanding of the migration law of outburst high gas and pulverized coal is an important basis for accurately predicting the occurrence time and possible scope of outburst. To reveal the airflow disturbance characteristics and coal-gas flow rule in coal and gas outburst process, outburst coal-gas migration simulations under different gas pressures were conducted using a self-developed visual outburst dynamic effect test device. The results showed that coal-gas flow state at the outburst port is divided into subcritical flow, critical flow, and supercritical flow state. The pulverized coal-gas flow migration in the roadway space can be divided into coal gas two-phase flow area, air compression area, and undisturbed area. Under the experimental conditions, the maximum propagation velocities of wave are 342.22~359.21 m/s, and the coal gas two-phase flow is far less than the propagation velocities of outburst wave, just 3.68~33.33 m/s. When the outburst energy is large, multiple compression waves can superimpose to form shock waves. The peak value of the wave does not necessarily appear in the first boosting range. The presence of pulverized coal leads to a faster attenuation of shock wave, but it makes a greater dynamic destructive force at the same speed.

In order to obtain similar materials with specific physical and mechanical parameters and adsorption and desorption indexes used in coal and gas outburst simulation tests, pulverized coal was selected as aggregate, sodium humate as cementing agent and river sand as auxiliary materials. Based on this, an orthogonal test with 6 factors and 5 levels was designed, and the tests of weighing, uniaxial compression, firmness and adsorption and desorption were carried out. The parameters such as density, uniaxial compressive strength, elastic modulus, firmness coefficient and adsorption-desorption index of similar materials with different ratios were obtained, and the sensitivity of each factor was analyzed by range analysis. The influence law of various factors on the parameters of similar materials was studied, the ratio model of similar materials was obtained and the reliability of the model was verified, and a complete method for determining the ratio model of similar materials of outburst coal was put forward. The results show that the density of similar materials increases with the increase of river sand content, the uniaxial compressive strength and elastic modulus increase significantly with the increase of pulverized coal ratio and sodium humate content, and the firmness coefficient increases linearly with the increase of pulverized coal ratio. The adsorption constant an increases linearly with the increase of sodium humate content, while the adsorption constant b decreases linearly with the increase of sodium humate content. The initial elution rate △p of similar materials increases at first and then decreases with the increase of sodium humate content.

Silicon (Si) is a promising anode candidate for next-generation lithium-ion batteries (LIBs) due to its high theoretical capacity. Solar Si photovoltaic waste possesses good purity and high output. Using it as the raw material for battery anodes can synchronously solve the problem of solid waste pollution and enable high energy density LIBs. A critical issue impeding the practical application of Si is the undesirable side reactions at the electrolyte-particle interface and the resulting increase in impedance during cycling. Herein, a Si-P core shell structure with chemical bonding at the Si-P interface is fabricated through a simple mechanical alloying reaction between red P and solar Si photovoltaic waste. The P nanoshell with thickness within 15 nm converts to Li3P during the initial lithiation process and maintains its phase on cycling. The as-formed Li3P nanolayer functions as a stable, ionically conductive protective layer that reduces the direct contact between Si and electrolytes, and thus suppresses undesired side reactions. The Si-P nanocomposite exhibits stable electrochemical cycling with a high reversible capacity of 1,178 mAhg−1 after 500 cycles at 1,200 mA g−1, as well as excellent rate capability (912 mAh g−1 at 2 C). With 15 wt% addition to graphite, a graphite/Si-P hybrid electrode shows a high overall reversible specific capacity of 447 mAh g−1 and 88.3% capacity retention after 100 cycles at high areal capacity of 2.64 mAh cm−2 at 100 mA g−1, indicating its promise as a drop-in anode in practical LIBs.

Porous FeP@C networks are realized via a one-step calcination process, using ferric nitrate and phytic acid as the precursors of FeP along with thiourea and melamine as N, S precursors. Benefited from the cooperative hydrogen bonding of melamine and phytic acid, two dimensional (2D) frameworks embedded with FeP can be formed. This porous architecture largely favors the penetration of electrolyte and shortens the transfer length of Li+ ions. Moreover, the conductive carbon on FeP can significantly alleviate the volume change upon cycling and boost the electronic conductivity. Owing to their unique build, the FeP@C networks exhibit competitive rate performance and cycling stability with a large reversible capacity of 293.0 mAh g−1 at 4 A g−1 after 1000 cycles. Even at the ultrahigh current density of 6 A g−1, there is still a large reversible capacity of 218.3 mAh g−1. Therefore, the lithium ion capacitors (LICs) are devised by selecting the conductive FeP@C networks as anode materials and porous carbon as cathode materials. As expected, the LIC indicates a high energy density of 91.4 Wh kg−1 at the power density of 390 W kg−1.

In this paper, we propose a dynamic key technique based on Cellular Neural Network (CNN) for security improvement in the orthogonal frequency division multiplexing passive optical network (OFDM-PON). To enhance the encryption scheme security, a six-dimensional CNN hyperchaotic system is employed to encrypt the data. And, the keys are divided into the dynamic and static. The dynamic key is randomly extracted from a key set by incorporating the random feature of the input data. Then, the chaotic sequence generated by the dynamic key is served as the synchronous sequence for encryption. Moreover, the chaotic sequences generated by the static keys are used to resist the chosen-plaintext attacks (CPAs) and scramble the phase of QAM symbols on the frequency domain. With these processing techniques, the multi-fold data encryption can create a key space of ∼10315 to protect against the exhaustive trial. The transmission of 10-Gb/s encrypted 16-QAM-based OFDM signal is demonstrated over 20-km single mode fiber (SMF) by experiment. The results show that our proposed scheme can provide excellent confidentiality of data transmission against the CPAs and brute-force attack.

Key distribution is a major challenge of secure communication. Computational approaches to key distribution are breached by quantum algorithms, while quantum key distribution (QKD) is an expensive, slow, and sophisticated solution. Secure key generation and distribution from unpredictable and inherent physical-layer properties of optical fiber channel is a classical, simple and cost-effective solution. However, the quasi-static nature of fiber channels dramatically limits the available key generation rate (KGR) to the order of ∼kbit/s. Here we effectively accelerate the KGR by six orders of magnitude using a developed high-speed chaotic polarization scrambler (CPS) driven by digital chaos in fiber channels. An error-free KGR of 284.8 Mbit/s is experimentally demonstrated over a 24 km standard single-mode fiber (SSMF), where the generated key passes the random test suite. Moreover, we fully analyze the security mechanism and find that a strong asymmetry exists between legal and illegal users, ensuring a high-level of security against potential fiber-tapping attacks. This scheme provides a major step towards the practical implementation of the “one-time-pad” in secure data transmission over fiber networks.

A physical-layer secure key generation and distribution (SKGD) scheme in classical fiber channel is proposed and demonstrated using a bidirectional wide-band polarization scrambler (WBPS), to alter rapidly and symmetrically the state of polarization (SOP) for the two counter-propagating optical signals in fiber. Due to the optical channel reciprocity, highly-consistent key bits can be extracted from the correlated SOP fluctuations, while the key secrecy is ensured by the fiber channel uniqueness. A final key generation rate (KGR) of 2.7 Gb/s is demonstrated over 10 km single mode fiber (SMF), where error-free and true randomness of the generated key are achieved after post-processing. The obtained KGR at Gb/s makes a further step towards the implementation of one-time-pad data encryption with perfect secrecy in fiber networks.

Post-processing is an essential step towards the practical deployment of physical-layer secure key distribution (SKD) in classical fiber channels. However, the comparison and combination of different post-processing methods are not explored yet. Here, we fully evaluate the post-processing protocol and analyze various combinations of quantization and information reconciliation (IR), and present the efficient solutions associated with the key entropy source between the legal parties. In addition, the SHA3-256 hash function-based privacy amplification is exploited to further enhance the robust key secrecy and randomness. The results show that, the proposed protocol significantly increases the achievable key generation rate (KGR) up to 130-205% using the combination of multi-bit adaptive quantizer and IR with syndrome-decoding LDPC, compared with the previous post-processing using the same original key waveforms extracted from physical-layer SKD.

Herein, CuO/Cu2O heterostructured arrays were successfully realized by in situ sculpturing Cu foam based on the hydrothermal protocol. Owing to the state-of-the-art design, CuO/Cu2O nanosheet arrays are tightly and intimately grown on Cu substrate. The abundant holes formed by the unique three-dimensional construction of Cu foam and the porous CuO/Cu2O nanosheets are significantly beneficial to the infiltration of electrolyte and enhancement of the Na+ diffusion efficiency. It is noted that CuO/Cu2O electrode shows superior areal capacity than that of the individual CuO and Cu2O electrodes. At the current density of 0.6 mA cm−2, there is a reversible capacity of 1.0 mAh cm−2 (322.6 mAh g−1) for the CuO/Cu2O anode. Even at 2.0 mA cm−2, a reversible capacity of 0.56 mAh cm−2 (180.6 mAh g−1) can be still obtained. The full sodium-ion battery demonstrates a high reversible capacity of 0.53 mAh cm−2 (170.9 mAh g−1) in the initial cycle at 0.5 mA cm−2.

Chronic infected wound healing is a critical challenge in clinical practice owing to the involvement of multiple physiological processes, including bacteria-related, inflammatory regulation and angiogenesis. Therefore, a multi-functional strategy with synergistic anti-bacterial, anti-inflammatory and pro-angiogenic effects should be developed. Owing to their biomimetic structural features and controlled delivery of active agents, electrospun nanofilms are promising biomaterials for the treatment of skin defects. In this study, we fabricated multi-functional nanofilms with pro-angiogenic, anti-bacterial and anti-inflammatory capacities. First, strontium (Sr) ions were incorporated into poly(L-lactic-co-caprolactone) (PLCL) nanofilms. Subsequently, polydopamine (PDA) and zinc oxide (ZnO) were decorated onto the surface of Sr-loaded PLCL nanofilms to prepare ZnO/PDA@PLCL@Sr nanofilms. In vitro results showed that ZnO/PDA@PLCL@Sr nanofilms were biocompatible, exhibited angiogenic activity and significantly inhibited the growth of Staphylococcus aureus and Escherichia coli upon near-infrared -light irradiation. Furthermore, ZnO/PDA@PLCL@Sr nanofilms were found to drive the transformation of macrophages into the M2 phenotype. In vivo results further validated that ZnO/PDA@PLCL@Sr nanofilms exhibited pro-angiogenic and anti-bacterial activities and regulated inflammation to accelerate wound -healing in a rat model of bacteria-infected skin defects. In conclusion, we successfully developed a multi-functional biomaterial with pro-angiogenic, anti-bacterial and anti-inflammatory capacities to treat chronic infected wounds.

Tin has been considered an ideal anode material for lithium ion batteries because of its high theoretical capacity. However, its practical application is limited due to the poor cycling stability, which is induced by the huge volume variation upon lithiation/delithiation. Moreover, amorphous and crystalline structures can significantly influence the electrochemical performance of Sn-based electrode for lithium ion batteries. Herein, the specific capacity, cycling performance, rate capability, and kinetic process of amorphous-Sn@C (am-Sn@C) and crystalline-Sn@C (cr-Sn@C) as anodes for lithium ion batteries have been compared. The am-Sn@C electrode exhibits higher capacity, better cycling stability (711 mAh g−1 after 200 cycles at 0.1 A g−1; 510 mAh g−1 after 500 cycles at 1 A g−1) and rate capability than cr-Sn@C electrode (574 mAh g−1 after 200 cycles at 0.1 A g−1; 156 mAh g−1 after 500 cycles at 1 A g−1) as anode for lithium ion batteries. The enhanced electrochemical performance of the am-Sn@C electrode can be attributed to the enhanced strain regulation to accommodate volume change and defect sites to improve lithium storage capacity. The preparation method can be viewed as a reference for the further development of alloy-based anodes with high capacity and long cycle life for lithium ion batteries.

Carrier velocity modulation by asymmetrical concave quantum barriers to improve the performance of AlGaN-based deep-ultraviolet light emitting diodes has been investigated. The concave structure is realized by inserting a low Al composition AlGaN layer in the barrier, and thus forming a concave region on energy band. The measured device performance shows a significant improvement under 0–250 mA operation current, with the maximum external quantum efficiency and light output power of 1.02% and 8.0 mW, which are more than double (2.32 and 2.35 times) of that for the conventional one, respectively. Simulation confirms that the concave quantum barriers make it possible for electrons to be scattered, which reduce the electron energy before being injected into quantum wells, and thus the capability of quantum wells to capture electrons is enhanced. Meanwhile, the vertical transport of holes within the active region is also enhanced because the asymmetrical setting of the concave layer in the quantum barriers helps holes accelerate under the polarization field, and then get more energy to overcome the barrier.

We reveal the key epitaxial growth mechanisms of single-crystalline GaN on single-crystalline graphene. We demonstrate that an AlN nucleation layer is significantly important. On the one hand, the AlN nucleation layer provides the c-axis oriented driving force for the epitaxy of GaN on graphene along the out-of-plane orientation. On the other hand, AlN islands on the dangling bonds of graphene uniformly follow the in-plane orientation of single-crystalline graphene. Moreover, the nucleation density of AlN can be increased by adjusting the pretreatment conditions of graphene. The insight gained from this work may be applied to the epitaxy of other materials on the diverse two-dimensional materials.

Growth of AlGaN-based multiple quantum wells (MQWs) has been attempted on nano-patterned sapphire substrates (NPSSs). By adopting a critical-temperature approach and optimizing the growth conditions including the V/III ratio and Si doping level, high-efficiency AlGaN-based MQWs with an internal quantum efficiency (IQE) greater than 80% at room temperature are realized with an emission wavelength shorter than 280 nm. Taking such high IQE MQWs as the active region, a deep-ultraviolet light-emitting-diode (DUV-LED) device is fabricated and presents single peak emission with a wavelength of 276.1 nm. The light output power (LOP) of this device reaches 17.3 mW at an injection current of 100 mA, presenting an excellent device performance.

With the increase of mining depth, the occurrence mechanism of coal and gas outburst becomes more complex, and stress‐dominated outburst disaster has become one of the major safety problems in deep coal mines. Therefore, stress relief of coal seam has become an urgent technical demand for outburst prevention method in deep mines. In this study, based on zonal disintegration characteristics of deep surrounding rock, a regional strip outburst prevention method, called strip stress relief combined with gas extraction through stress‐relief floor roadway, was proposed, and relevant in‐site investigations were carried out in the Qujiang coal mine in China. Our results show that the zonal disintegration phenomenon occurs in the high‐stress surrounding rock at great depths, and induces the stress‐relief effect on the upper coal seam, in which the permeability and extraction radius of boreholes are increased greatly. The results of deformation and failure of surrounding rock of floor roadway show that from the surface to deep regions, fractured and nonfractured zones were alternatively distributed in the surrounding rock of deep floor roadways, the damage degree of surrounding rock was gradually weakened, and the width of fractured area was gradually reduced. The displacement of surrounding rock also presented the characteristics of alternative distribution of wave peak and trough. Moreover, the deformation and failure of surrounding rock presented a time‐dependent rheological behavior. In the stress‐relief zone, the coal seam permeability was enhanced significantly, with the maximum value being 43 times larger than that of the original coal seam. The effective gas extraction radius of the borehole was improved by 15%‐45%. During the driving period of coal roadways, the outburst risk prediction indexes K1 and S of the working face were lower than the critical value, and the driving speed of the coal roadway improved from 40 m per month to 100 m per month. This indicates that the proposed strip regional outburst prevention method can simultaneously reduce the ground stress and the gas content, and can effectively eliminate the outburst risk of coal roadway in deep mines.

Herein, we successfully deposit V2O5 nanobelt arrays on Ni foam uniformly coated with reduced graphene oxides (rGO), to manufacture V2O5/rGO arrays directly as anode for SIBs. The ordered and open architecture of V2O5/rGO arrays greatly facilitates the transportation of sodium ions and electrons. In particular, the introduction of rGO can substantially advance the whole electronic conductivity of the V2O5/rGO anode, as well as efficaciously prevent the V2O5 arrays exfoliation from the substrate. Consequently, the electrochemical performance of V2O5/rGO arrays can be highly improved compared with bare V2O5 arrays. As expected, the V2O5/rGO arrays anode yields a reversible capacity of 0.62 mAh cm−2 after 100 cycles at 0.4 mA cm−2 in the potential range of 0.01–3 V. It can be predicted that this innovative trial in this article might pave the way for tailoring high performance V2O5-based anode materials.

The unique and random physical-layer properties of optical fiber channels have been exploited for a simple and cost-effective secure key generation and distribution (SKGD). However, state-of-the-art SKGD approaches focused mainly on initial key extraction, while the post-processing protocol has to be explored to guarantee error-free operation, effective key generation rate (KGR) and high key secrecy. Here we propose a full post-processing protocol for SKGD in fiber networks. A lossy quantizer is optimized to achieve the trade-off between the KGR and key disagreement rate. The distributed source coding based information reconciliation is used to remove quantization errors. The privacy amplification is applied to improve the randomness and secrecy of the generated key using hashing functions. The post-processing protocol provides a SKGD solution of error-free, high randomness and high secrecy in fiber networks.

P2-type Na2/3Ni1/3Mn2/3O2 (P2-NaNM) is a promising cathode material for practical applications in Na-ion batteries due to its high capacity. However, the rearrangement of Na+/vacancy order and cathodic charge order across the Na extraction/intercalation and structural rearrangements of P2-NaNM at high voltages result in rapid capacity fading and insufficient rate capability. Here, a combined structural modulation strategy was presented to solve these challenges via reducing the Na layers spacing through substituting Na sites by Mg ions while simultaneously stabilizing the transition metal (TM) layers through Mg/Ti co-doping. Benefited from the symbiotic effect, P2-NaNM exhibits a significantly enhanced cycling stability and rate capability in the voltage range of 3.0–4.4 ​V. We further revealed that Mn remains Mn4+ while Ni2+ becomes Ni3+ at the surface of Mg/Ti co-substituted P2-NaNM upon charge/discharge process.

Na3V2(PO4)2O2F (NVPOF) is considered as a promising cathode material for sodium-ion batteries due to its high structural stability and high average operating voltage (3.8 V). However, its low elect...

This study aimed to investigate the influence of local frequent dynamic disturbance on micro-structure evolution in different zones of coal-rock. To do so, we carried out a systematic experimental research on the micro-structure evolution of briquette and raw coal samples under local impact load by using self-developed pendulum hammer dynamic impact loading test device of coal-rock and ultrasonic testing equipment, and analyzed the localization effect of local impact load. The results show that Mn (micro-structure cumulative change factor) of briquette coal samples presents an inclined M-shaped four-stage evolution mode along and perpendicular to impact direction with cyclic impact times under conventional full impact load, whereas it shows more obvious anisotropy and localization under local impact load. Mn for both conventional full impact and local impact shows a nonlinear increasing trend with the increase in impulse, but their increasing gradients are different. The critical zone is the most affected, the impact zone comes next, and the non-impact zone is the least affected with the increase in impulse under local impact load. Mn in the impact zone and critical zone decreases exponentially with the increase in the impact loading area, while it increases exponentially in the non-impact zone. The micro-structures evolution in briquette and raw coal samples is similar, but the anisotropy and localization effect of micro-structure evolution for raw coal samples are more significant and more sensitive to the impact loading area. The micro-structure evolution of coal-rock under local impact load shows obvious localization effect. Mn in the critical zone is usually the largest, Mn in the impact zone is slightly less than that in the critical zone, and Mn in the non-impact zone is the least. The larger the impact loading area, the wider the influence enhancement area, and the smaller the non-influence area, yet the smaller the impact zone and critical zone are affected by local impact load.

A novel carbon modified Li1.2Mn0.54Ni0.13Co0.13O2 has been successfully fabricated by using activated carbon (AC) as template and carbon source via sol-gel method. The AC modified Li1.2Mn0.54Ni0.13Co0.13O2 (denoted as LLMO@AC) particles with less agglomeration show a nearly spherical structure with a size distribution range of 150~250 nm. As cathode material, such LLMO@AC delivers a significantly enhanced first capacity (245.7 mAh g−1) with a satisfied capacity retention ratio (87.4%) after 100 cycles at 150 mA g−1. Even if the current is increased to 1.5 A g−1, LLMO@AC still owns a high average discharge capacity of 161.1 mAh g−1. Electrochemical impedance spectroscopy results reveal that the LLMO@AC electrode has lower charge transfer resistance and higher lithium-ion diffusion coefficient compared with pristine LLMO and the LLMO synthesized by directly using glucose as carbon sources (LLMO@G). This work provides an effective modification strategy to improve the electrochemical performance of LLMO and promote the industrialization of LLMO.

Highlights The intrinsic negatively charged MXene nanosheets were assembled to the positively charged Ketjen black/sulfur (KB/S) or KB to constructing the interwoven composite.The KB/S@Ti3C2Tx architectures allow high sulfur loading and accommodate the corresponding volume change, while the structural integrity and the ionic and electric conducting pathways are well maintained.The KB@Ti3C2Tx interlayers further retard the polysulfide that escaped from the cathode. It is only 0.28 mg cm−2 in density and 3 μm in thickness—the effect on energy density is minimal. Electronic supplementary material The online version of this article (10.1007/s40820-020-00449-7) contains supplementary material, which is available to authorized users., The lithium-sulfur battery is the subject of much recent attention due to the high theoretical energy density, but practical applications are challenged by fast decay owing to polysulfide shuttle and electrode architecture degradation. A comprehensive study of the sulfur host microstructure design and the cell architecture construction based on the MXene phase (Ti3C2Tx nanosheets) is performed, aiming at realize stable cycling performance of Li–S battery with high sulfur areal loading. The interwoven KB@Ti3C2Tx composite formed by self-assembly of MXene and Ktejen black, not only provides superior conductivity and maintains the electrode integrality bearing the volume expansion/shrinkage when used as the sulfur host, but also functions as an interlayer on separator to further retard the polysulfide cross-diffusion that possibly escaped from the cathode. The KB@Ti3C2Tx interlayer is only 0.28 mg cm−2 in areal loading and 3 μm in thickness, which accounts a little contribution to the thick sulfur electrode; thus, the impacts on the energy density is minimal. By coupling the robust KB@Ti3C2Tx cathode and the effective KB@Ti3C2Tx modified separator, a stable Li–S battery with high sulfur areal loading (5.6 mg cm−2) and high areal capacity (6.4 mAh cm−2) at relatively lean electrolyte is achieved. Electronic supplementary material The online version of this article (10.1007/s40820-020-00449-7) contains supplementary material, which is available to authorized users.

Based on the analysis of shear movement characteristics of overlying strata under mining effect, a quantitative calculation model for shear displacement in the along‐strike and down‐dip directions of the overlying strata is established. The shear displacement at any point on the interface of overlying strata in composite rock beam under slice mining is analyzed. The evolution law of shear displacement and deformation of the overlying strata with the advancement of working face was inverted by physical simulation test. The results show that the shear movement of the overlying strata is characterized by a repeated pattern of "increase → decrease →increase → decrease.” The shear displacement of the overlying strata increases gradually after slice mining. The shear displacement of the overlying strata is in the shape of “W” after the lower seam mining, and the maximum shear displacement of the overlying strata by the lower seam mining is 1.67 times of that of the overlying strata after the upper seam mining. Field test of shear movement of the overlying strata was conducted on the panel 4308 of Chengzhuang coal mine. The results show that the shear displacement of the overlying strata above the coal seam increases with the burial depth. And the shear displacement of the overlying strata movement after mining has "time‐delay" effect. The larger the depth of the measuring point is, the larger value of the along‐strike shear displacement is. The breakage of the key strata of the overlying strata will cause the shear displacement of the overlying strata to increase rapidly. And there is a demarcation depth (127.98 m) for the shear displacement of the overlying strata. The shear movement of the overlying strata above the dividing point is not obvious, while the shear movement of the overlying strata below the dividing point is in the shape of "S" (amplitude of 50 mm). When the working face advanced beyond the test well, the overlying strata would experience multiple shear movement. When the working face advanced 34‐100 m ahead of the surface test well, the overlying strata experienced the most severe shear displacement. When the working face advanced to 74 m away from the surface test well, the shear displacement of the overlying strata between 10# (depth of 192.01 m) and 16# (depth of 300.07 m) is larger than that at the upper position, and down‐dip shear displacement is the most severe(about 315 mm). The shear displacement of the overlying strata is coincident with the along‐strike shear displacement, and the down‐dip shear displacement is smaller than the along‐strike shear displacement. This research provides theoretical guidance for the design of shale gas or coalbed methane surface wells and coal mine shaft under slice mining.

During the multiseam mining process, the overlying strata were damaged due to different mining disturbances, where a large number of fractures were produced which were the main seepage paths of gas and water, easy to cause gas or water inrush accidents. Thus, it is necessary to explore the development characteristics of the fractured zone in the overlying strata from multiseam mining. In this paper, laboratory triaxial compression tests were firstly conducted on the rock specimens subjected to different mining disturbances. In these tests, the specimen was loaded to different stress before a regular test to simulate the different damage effects on the rock strata caused by different mining disturbances. And the corresponding values of m and s could be obtained through a calculation based on the test results. Subsequently, the numerical simulation was conducted to simulate the field situation, in which the m and s values were used in the numerical model combined with the Hoek‐Brown–modified criterion, and the results show that the overburden failure height was increased with the mining disturbances from 48 to 120 m, and then, the effects of mining height and interval thickness on the development height of fracture zone were studied by numerical simulation. Finally, the leakage of roof drilling at different stages was tested and calculated in the field. The results showed that the loss of leakage drilling can directly reflect the development degree of roof cracks, and the detection results were close to the development height of the numerical simulation fracture zone. It is verified that the simulation method used in this paper is feasible and can be used as a reference for similar research.

In this letter, we report a quasi-vertical GaN Schottky barrier diode (SBD) fabricated on a hetero-epitaxial layer on silicon with low dislocation density and high carrier mobility. The reduction of dislocation is realized by inserting a thin layer with high density of Ga vacancies to promote the dislocation bending. The dislocation density is ${1.6}\times {10}^{{8}}$ cm−2 with a GaN drift layer thickness of $4.5~\mu \text{m}$ . The fabricated prototype GaN SBD delivers a high on/off current ratio of $10^{{10}}$ , a high forward current density of 1.6 kA/cm2@3 V, a low specific on-resistance of 1.1 $\text{m}\Omega \cdot \text {cm}^{{2}}$ , and a low ideality factor of 1.23.

Hollow nanostructured hosts are important scaffolds to achieve high sulfur loading, fast charge transfer, and conspicuous restraint of lithium polysulfides (LiPSs) shuttling in lithium-sulfur (Li-S) batteries. However, developing high-efficiency hollow hosts for improving utilization and conversion of aggregated sulfur in the hollow chamber remains a longstanding challenge. Herein, hollow N-doped carbon nanocubes confined petal-like ZnS/SnS

Real-time post-processing for physical-layer secure key distribution in fiber networks is implemented on FPGA, with quantization, information reconciliation and privacy amplification modules, where a key generation rate of 11.7 Mbps is achieved.

High-speed physical-layer secure key generation and distribution (SKGD) schemes via channel reciprocity are achieved using external electro-optical modulation or random source distribution via additional fiber links. Here, we propose and demonstrate an SKGD scheme using the fluctuation of polarization states from an amplified spontaneous emission (ASE) source, without any external electro-optical modulation or additional fiber link. Experimentally, an error-free key generation rate (KGR) of 10.1 Gb/s is achieved over a 10-km standard single-mode fiber (SSMF), with true randomness originating from ASE. Moreover, the single fiber channel can be shared for SKGD as well as data transmission, allowing the integration of the proposed SKGD with the deployed fiber infrastructure.

Identifying atomic configurations of impurities in semiconductors is of fundamental interest and practical importance in designing electronic and optoelectronic devices. C impurity acting as one of the most common impurities in GaN, it is believed for a long time that it substitutes at Ga site forming CGa with +1 charge-state in p-type GaN, while it substitutes at N site forming CN with -1 charge-state in n-type GaN. However, by combining x-ray absorption spectroscopy and first-principles simulations, we observed that C is mainly occupying the N site rather than the Ga one in p-GaN. We further reveal that this is due to an H-induced EF-tuning effect. During growth, the existing H can passivate Mg dopants and upshifts the EF to the upper region of bandgap, leading to the CN formation. After the p-type activation by annealing out H, although the EF is pushed back close to the valence band maximum, whereas the extremely large kinetic barrier can prevent the migration of C from the metastable CN site to ground-state CGa site, hence stabilizing the CN configuration. Additionally, the CN with neutral charge-state ([Formula: see text]) in the p-GaN is further observed. Therefore, the real C-related hole-killer in p-type GaN could be CN rather than the commonly expected CGa. Our work not only offers the unambiguous evidence for the C defect formation in p-GaN but also contributes significantly to an in-depth understanding of the C-related hole-killers and their critical role on electrical and optoelectrical properties of p-GaN and even p-AlGaN.

We present the high-speed physical-layer secure key generation and distribution in fiber networks. A key generation rate of 2.7 Gb/s is achieved over 10 km single-mode fiber using a specifically-designed bidirectional polarization scrambler.

Lithium–sulfur batteries have low material costs and high energy densities, which have attracted considerable research interest for application in next-generation energy-storage systems. However, the practical applications of Li–S batteries face challenges owing to their poor sulfur utilization, service lifetimes, and rate capability. Recently, great progress has been made in the design, synthesis, and application of micro/nanostructured metal sulfides to address obstacles facing Li–S batteries. This review aims to highlight valuable concepts from the latest reports. Major approaches to improve sulfur cathodes and strategies for preparing metal sulfide-based materials are first summarized with a particular focus on their main functions and useful properties. Then, the electrochemical activities of metal sulfides are classified and their applications in Li–S batteries are introduced to provide a fundamental understanding of the material interactions involved. In parallel, advancements in the use of interlayers, modification of separators, and protection of lithium anodes that involve metal sulfides are surveyed. Finally, special attention is paid to the general design principles, future prospects, and challenges facing metal sulfides for high-energy-density Li–S batteries.

We report on a highly sensitive gallium nitride (GaN) micro-electromechanical (MEMS) resonator with a record quality factor (Q) exceeding 105 at the high resonant frequency (f) of 911 kHz by the strain engineering for the GaN-on-Si structure. The f of the double-clamped GaN beam bridge is increased from 139 to 911 kHz when the tensile stress is increased to 640 MPa. Although it is usually regarded that the energy dissipation increases with increasing resonant frequency, an ultra-high Q-factor which is more than two orders of magnitude higher than those of the other reported GaN-based MEMS is obtained. The high Q-factor results from the large tensile stress which can be intentionally introduced and engineered in the GaN epitaxial layer by utilizing the lattice mismatch between GaN and Si, leading to the stored elastic energy and drastically decreasing the energy dissipation. The developed GaN MEMS is further demonstrated as a highly sensitive mass sensor with a resolution of 10���12 g/s through detecting the microdroplet evaporation process. This work provides an avenue to improve the f �� Q product of the MEMS through an internally strained structure.

Nowadays, the water jet technique has been more frequently used for coal bed methane stimulation. As the ultimate component of the water jet system, the nozzle has important influence on the rock breaking ability of water jet. To optimize the nozzle, a simplified model for impinging water jet was established. The effects of geometric structure (cylindrical, conical, and conical‐straight) and parameters (outlet diameter d, conical angle α, and length L) on the flow field of the impinging water jet are simulated through computational fluid dynamics software Fluent14.0. Besides, the effects of inlet pressure (Pin) and target distances (S) on the jet dynamics are also discussed based on the simulation results. The results show that the jet dynamic parameters including dynamic pressure, velocity, and impinging pressure vary with different nozzles. The jet dynamic parameters linearly increase with the inlet pressure, while they first increase then decrease with the increase in target distance. Additionally, the optimal nozzle designed based on the numerical simulation was used in the field test, and the results indicate that this technique can effectively improve the gas drainage efficiency.