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Chronic post-operative pain is a recognized adverse consequence of surgery; managing and preventing it are always a better choice. Proper choice of Anesthetic technique, use of combined anesthesia and pre-emptive analgesia may prevent and decrease the incidence of chronic post-operative pain. Transverse abdominis plane block (TAP Block) is a regional anesthesia technique following abdominal surgeries which involve injection of a large amount of local anesthetics in TAP, an anatomical space between the internal oblique and transverse abdominis muscle. The aim of this review is to show the effect and uses of TAP block as a combined anesthesia and multimodal analgesia in preventing chronic post-operative pain.

Li3V2(PO4)3/C (LVP/C) composites have been modified by different ways of Zr-incorporation via ultrasonic-assisted solid-state reaction. The difference in the effect on the physicochemical properties and the electrochemical performance of LVP between Zr-doping and ZrO2-coating has also been investigated. Compared with pristine LVP/C, Zr-incorporated LVP/C composites exhibit better rate capability and cycling stability. In particular, the LVP/C-Zr electrode delivers the highest initial capacity of 150.4 mA h g−1 at 10C with a capacity retention ratio of 88.4% after 100 cycles. The enhanced electrochemical performance of Zr-incorporated LVP/C samples (LVZrP/C and LVP/C-Zr) is attributed to the increased ionic conductivity and electronic conductivity, the improved stability of the LVP structure, and the decreased charge-transfer resistance.

Understanding the semiconductor surface and its properties including surface stability, atomic morphologies, and even electronic states is of great importance not only for understanding surface growth kinetics but also for evaluating the degree to which they affect the devices' performance. Here, we report studies on the nanoscale fissures related surface instability in AlGaN/GaN heterostructures. Experimental results reveal that edge dislocations are actually the root cause of the surface instability. The nanoscale fissures are initially triggered by the edge dislocations, and the subsequent evolution is associated with tensile lattice-mismatch stress and hydrogen etching. Our findings resolve a long-standing problem on the surface instability in AlGaN/GaN heterostructures and will also lead to new understandings of surface growth kinetics in other hexagonal semiconductor systems.

Flexible and lightweight reduced graphene oxide wrapped Si/carbon fibers paper (Si@RGO/CFP) anodes have been prepared by pyrolysis of the common filter paper, which was soaked into the suspension containing graphene oxide and Si. The reduced graphene oxide wrapped Si nanoparticles (Si@RGO) homogeneously distributed on the interlaced carbon fibers and void among the carbon fibers. The Si@RGO/CFP as a flexible binder-free electrode exhibits an initial reversible capacity of 2055 mAh g −1 and 1092 mAh g −1 after 100 cycles for Si@RGO at 100 mA g −1 along with good rate performance. The superior electrochemical performance of the Si@RGO/CFP is attributed to the interconnected carbon fibers substrate, which provides electronic conduction pathways and works as mechanical support, and the void among carbon fibers accommodates the volume changes of Si and maintains the integrity of the electrode materials.

We propose and demonstrate a physical-layer encryption algorithm against chosen-plaintext attacks (CPAs) in optical orthogonal frequency-division multiplexing (OOFDM) transmission, where the cyphertexts are dynamically generated for the first time by incorporating the random feature of the input data. The multiple-fold encryption algorithm consists of chaotic subcarrier allocation scrambling in time/frequency domains, chaotic phase rotation of subcarriers, as well as chaotic training sequence, which creates a total huge key space of $10^{194}$ by using a 4-D hyperdigital chaos. The transmission of 8.9-Gb/s 16-QAM encrypted OOFDM data is demonstrated over 20-km standard single-mode fiber. The proposed encryption scheme provides excellent confidentiality of OOFDM transmission against the brute-force attacks and CPAs.

A novel Li 3 V 2 (PO 4 ) 3 composite modified with Fe-doping followed by C+SiO 2 hybrid layer coating (LVFP/C-Si) is successfully synthesized via an ultrasonic-assisted solid-state method, and characterized by XRD, XPS, TEM, galvanostatic charge/discharge measurements, CV and EIS. This LVFP/C-Si electrode shows a significantly improved electrochemical performance. It presents an initial discharge capacity as high as 170.8 mA h g −1 at 1 C, and even delivers an excellent initial capacity of 153.6 mA h g −1 with capacity retention of 82.3% after 100 cycles at 5 C. The results demonstrate that this novel modification with doping followed by hybrid layer coating is an ideal design to obtain both high capacity and long cycle performance for Li 3 V 2 (PO 4 ) 3 and other polyanion cathode materials in lithium ion batteries.

NiS is successfully grown on Ni foam via an in situ electrochemical corrosion method. It is proposed that H2O2 can act as cathodic depolarizer that promotes the corrosion of Ni, which is crucial for the formation of NiS. The NiS shows flower-like morphology with mean size about 2 µm, consisting of flocky particles with size range from 500 nm to 1 µm. The as prepared NiS/Ni can be directly used as binder free anode for Li-ion batteries, which shows excellent electrochemical performance. It delivers initial discharge and charge capacities are 836 and 668 mA h g−1 at a specific current of 150 mA g−1, respectively. After 70 cycles, the charge capacity can maintain of 589 mA h g−1.

All-optical high-speed turbo-switches can effectively increase the switching speed using cascaded semiconductor optical amplifiers (SOAs). The overall recovery time or the bandwidth of turbo-switch was numerically analyzed with time-domain and frequency-domain SOA models. The turbo-switch was explored from the fundamental carrier dynamics in SOAs for the purpose of further increasing its operation speed. An integrated turbo-switch was also been proposed and demonstrated, where a phase adjustable Mach-Zehnder interferometer (MZI) was applied as an optical band-pass filter between SOAs. Wavelength conversion was first demonstrated at 84.8 Gbit/s using the integrated turbo-switch.

NiO/C-Ni composite is prepared via a facile hydrothermal pretreatment and subsequent annealing, which shows excellent cycle stability and superior rate capability as binder free anode for lithium ion batteries. It delivers initial discharge and charge capacity of 971 and 672 mAh g −1 at 0.3C, maintaining of 700 and 669 mAh g −1 after 70 cycles. After 60 cycles at various rates from 0.3 to 12C, the discharge capacity of the NiO/C-Ni electrode can gradually restore when reverting the rate to 0.3C, maintaining of 692 mAh g −1 after 10 cycles. The impressive electrochemical performance demonstrates great potential of the NiO/C-Ni as anode for high performance lithium ion batteries.

In a search for novel small molecule calcium-sensing receptor (CaSR) antagonists as oral bone anabolic agents, we discovered dihydrobenzofuran cyclopropane carboxylic acid derivatives, such as 12f (IC50=27.6nM), are highly potent calcium-sensing receptor antagonists. Studies in rats established that compound 12f stimulates parathyroid hormone (PTH) release in a fast-acting, pulsatile manner.

Quasi-2D GaN layers inserted in an AlGaN matrix are proposed as a novel active region to develop a high-output-power UV light source. Such a structure is successfully achieved by precise control in molecular beam epitaxy and shows an amazing output power of ≈160 mW at 285 nm with a pulsed electron-beam excitation. This device is promising and competitive in non-line-of-sight communications or the sterilization field.

A three-dimensional carbon-coated SnO2/reduced graphene oxide (SnO2/RGO/C) foam has been prepared by using glucose as the carbon source and cross-linking agent through a one-step hydrothermal process followed by freeze drying. The foam, as a free-standing anode for lithium-ion batteries, exhibits a large capacity and excellent cycling stability (717 mAh g−1 after 130 cycles at 100 mA g−1). The outstanding electrochemical performance could be related to the synergistic effect between the nano-sized high-capacity SnO2, the excellent electronic conductivity and large specific surface area of RGO, and the carbon coating layer, which could enhance the bonding strength of SnO2 nanoparticles and RGO nanosheets, keep the structural integrity, and increase the electronic conductivity. The strong interaction between SnO2 and RGO, the high electronic conductivity, and the porous structure of the composite result in high electrochemical activity and stable cycling performance as a binder-free anode for lithium-ion batteries.

Highly flexible energy-storage devices strongly depend on both mechanical integrity of the constitutive materials and electrical properties. The preparations and electrochemical properties of reduced graphene oxide (RGO) foams used as electrodes in supercapacitors have been systematically investigated. The rational design of preparation led to excellent electrochemical performance in supercapacitors such as high specific capacitance (224 F g−1 at 0.1 A g−1) and rate performance. Highly flexible solid-state supercapacitors based on RGO foams exhibit high gravimetric specific capacitances (193 F g−1 at 0.1 A g−1) with excellent cycling stability (∼100% retention after 5000 cycles). This work provides the proper preparation of RGO foams by hydrothermal process with excellent electrochemical performance and high mechanical flexibility in solid-state supercapacitors, suggesting that the RGO foams have great potential in the development of lightweight high-performance flexible energy storage device.

Zinc carbonate hydroxide, Zn5(CO3)2(OH)6 is successfully prepared via a facile hydrothermal method, which shows flaky morphology with diameter of several micrometers and mean thickness of 200 nm. The Zn5(CO3)2(OH)6 is thermal stable below 200 °C, which gradually decomposes into ZnO in temperature region 210–450 °C. The electrochemical property of the as-prepared Zn5(CO3)2(OH)6 micro-flakes as a new anode material for lithium ion batteries is firstly studied, which exhibits obvious voltage plateaus and stable cycle performance, endowing it with potential application in lithium ion batteries.

Polymer electrodes are vital components of lithium-ion batteries and have gained great interest in recent years. Currently, the majority of electrodes are petroleum-based that are toxic and non-biodegradable, which consists of serious environmental concerns. Therefore, exploration of natural polymer electrolytes, such as seaweed extracts, balances non-toxicity and ion conductivity as new research directions. In this review, we mainly focus on the progress of polymer electrolytes based on alginate, kappa carrageenan, and other natural polymers of seaweed extracts, including agar and iota carrageenan. We first give a brief overview of the fundamentals of polymer electrolytes. Then, we discuss the structures and performances of seaweed extracts derived polymer electrolytes. Finally, we compare the ion conductivity of natural polymer derived electrolytes and synthetic polymers, and insights on the future direction for improvement of this field.

Vanadium pentoxide (V2O5) has been a promising insert-type cathode material and/or a potential high energy anode material for rechargeable lithium ion batteries (LIBs). However, the lithiation behavior of V2O5 anode has been a long-standing challenge. In this study, we design nanoflake-assembled three-dimensional hollow porous V2O5 microspheres via a one-step template-free solvothermal-based method to enhance its structural stability as well as electrochemical activity. Commendably, this original product evaluated as anode electrodes for LIBs exhibits outstanding cycling stability and rate capability. It delivers a high reversible capacity of 527 mAh g-1 after 100 cycles at 0.1 A g-1, and a stable capacity of 318 mAh g-1 at 3.0 A g-1 in the potential range of 0.01 V and 3.0 V (vs. Li/Li+). Furthermore, electrode kinetics and performance evolution was studied by use of electrochemical impedance spectroscopy (EIS). Following these efforts, a definite and tenable lithiation mechanism of V2O5 anode is presented based on redox behaviors, X-ray powder diffraction (XRD) results, and other convincing proofs, providing valuable revelation for the understanding of conversion reaction and reaction mechanism toward other vanadium oxide anode materials in lithium/sodium ions storage. Meanwhile, the research perspective and strategy presented herein can be extended to other active materials in LIBs and/or sodium ion batteries.

In light of the sluggish potassiation kinetics in potassium ion batteries, herein, we report a self-supported anode material composed of CuO/Cu clusters distributed in nitrogen-doped carbon microfibers (CuO/Cu-NCNFs electrode) via a simple electrospinning technology. By this way, a three-dimensional conductive networks interwoven by CuO/Cu-NCNFs microfibers were successfully obtained. As expected, this self-supported anode materials for potassium ion batteries reveals better electrochemical performance compared with nitrogen-doped carbon microfibers (NCNFs). There is still a reversible capacity of 205.9 mAh g−1 remained for the CuO/Cu-NCNFs electrode undergoing 100 cycles at 100 mA g−1. With the in-depth investigation, the CuO/Cu-NCNFs show more obvious pseudocapacitive characteristic than that of NCNFs. The improved capacitive contribution discloses the reason for the fast kinetics of CuO/Cu-NCNFs. It is believed that the presence of CuO/Cu significantly favors the advancement of mechanical property and stability of microfiber networks, giving rise to the fast kinetics of CuO/Cu-NCNFs. It can be predicted that this innovative potocol of CuO/Cu-NCNFs microfiber frameworks will provide explicit direction toward engineering high performance electrode materials for potassium ion batteries.

Red P is one of the most prospective anode material for sodium ion battery because of its highest theoretical capacity of 2596 mAh g−1 and satisfactory potentials for sodium ions insertion and extraction. However, the large volume expansion during cycles and poor intrinsic electronic conductivity limit the electrical performance practical application of red P. Herein, Mo-modified P/C (P Mo C) composite has been prepared through a simple mechanical milling using low-cost anthracite as carbon sources to increase the electrical conductivity and adapt to the volume variation. The addition of Mo plays a crucial role in enhancing electronic conductivity and structural stability of P Mo C composite during cycles. The formation of MoP2 facilitates the intimate contact of red P and Mo, providing the superior ionic diffusion and electron conducting pathways between the particles. The electrode of P Mo C exhibits high reversible capacity, excellent cycling and rate performance as anode for sodium ion battery. At 0.1 and 0.5 A g−1, the P Mo C electrode displays high reversible capacities of 763 and 705 mAh g−1 after 60 and 100 cycles, respectively. Due to the superior electrochemical performance, low cost and simple preparation, the P Mo C composite is a prospective negative electrode material for high-performance sodium ion battery.

The dynamic recrystallization (DRX) behavior of Ni-Fe-Cr based alloy was studied in temperature range of 980–1130 °C and strain rate range of 0.01–10s−1. By systematically analyzing the stress-strain data and microstructure evolution of Ni Fe Cr based alloy, the influences of strain rate, temperature and strain on the critical conditions for DRX behavior were investigated. Meanwhile, the constitutive equation of the correlation between peak stress and Z parameters was established by using hyperbolic sine constitutive equation. The DRX critical strain model, kinetics model and grain size model of the studied alloy were also established. The deformation activation energy is 496.92 kJ/mol. The DRX behavior of the studied alloy is sensitive to deformation temperature and strain rate. With the decrease of strain rates or the increase of deformation temperatures, the critical strain of DRX softening decreases, and the volume fraction of DRX increases. In addition, the three models can accurately predict and characterize DRX behavior of the studied alloy.

A floating GaN micro-ring is fabricated by standard semiconductor technology. Under pump power conditions, ultraviolet lasing with a quality factor of 3600 is obtained. Resonant mode analysis indicates that the lasing spectra contain two types of whispering gallery modes and one type of Fabry–Perot mode. With the increase in pumping power, the state filling induced Burstein–Moss effect is observed and understood through synchronous measurement of photoluminescence and time resolution photoluminescence spectra.

Offline digital signal processing is generally applied in secure optical orthogonal frequency division multiplexing (OFDM) transmission, however the real-time secure optical OFDM transmission is necessary to evaluate the security and transmission performances. Thus a real-time secure optical OFDM transmission with chaotic data encryption is developed to demonstrate the high-speed data transmission with high-level physical-layer confidentiality, where field-programmable gate array (FPGA) boards are employed for the real-time encryption and decryption of optical OFDM signals, along with pipeline analog-to-digital and digital-to-analog converters. The physical-layer security enhancement is attributed to hyper digital chaos, providing a huge key space of 1045. As a proof of concept, the real-time encrypted 16-QAM optical OFDM signal transmission at 435 Mb/s is successfully demonstrated over 22 km standard single-mode fiber (SSMF), without any degradation in transmission performance. The proposed FPGA prototype can be a good candidate for the practical implementation of secure data transmission in OFDM passive optical network.

Carrier compensation traps in n−-GaN drift layers grown on Si substrates were investigated using high-temperature deep-level transient spectroscopy (DLTS). The upper limit of the temperature range (700 K) allows for the study of deeper levels in the bandgap than those previously reported by conventional DLTS. Three trap states were revealed to be responsible for carrier compensation. Besides the residual carbon (C) acceptor, two deep electron traps detected in the DLTS high-temperature range, labeled E2 and E3 with energies EC of 0.98 and 1.38 eV, respectively, were also found to have contributions to the carrier compensation. A comprehensive investigation combining with positron annihilation spectroscopy measurements revealed that E2 and E3 are related to the (–/2–) and (0/–) acceptor levels of the VGa–ON complex, respectively. The relatively high concentrations of E2 and E3 imply that the VGa–ON complex is an essential carrier compensation source in the drift layer and plays a crucial role in developing kV-class vertical GaN power devices.

With the popularization of smart buses, the ways to obtain buses operation information are becoming increasingly diversified, and passenger flow prediction based on big data information has also emerged. In this work, Principal Component Analysis (PCA) and error Back Propagation (BP) neural networks were combined to propose a prediction model of short-term buses passenger flow on the basis of PCA-BP neural networks. Firstly, the PCA method was adopted to reduce the dimensionality of the indices of buses passenger flow and improve the input nodes of the BP networks. Secondly, the fully trained network was employed to predict the buses passenger flow. More specifically, the passenger flow data set pair of the 17th bus in Guiyang on November 29, 2019 was used to carry out the PCA-BP neural networks model test. The test results indicated that the predicted passenger flow of each time period was very close, and the passenger flow prediction error in most time periods was very small. Besides, the relative error could achieve a satisfactory fitting effect, which was able to provide a reliable basis for bus dispatch. We found that the proposed PCA-BP neural networks model had high prediction accuracy and prediction performance. Therefore, it is expected to be used as a model for final short-term passenger flow prediction.

The connection between the kink position and vertical leakage mechanisms in GaN-on-Si epitaxial layers has been investigated. Based on combined experimental data and TCAD simulation results, we demonstrate that band-to-band tunneling and Poole-Frenkel effect greatly affect the current-voltage behaviors of GaN-on-Si epitaxial layers. Band-to-band tunneling occurring in both GaN and AlGaN layers could change a kink position, and Poole-Frenkel effect happening at high biases increases the slope of J-V at the voltage region after the kink. On the other hand, we found that the kink position is related to the depletion region width at the AlN/Si interface by numerical simulation. When the connection between the kink and leakage mechanisms was considered, numerical simulation results are consistent well with the current-voltage-temperature experimental results in GaN-on-Si epitaxial layers.

We have investigated the growth of AlN films on hexagonal nano-concave-circle patterned Si substrates using metal–organic chemical vapor deposition. By depositing a thin AlN seed layer on the Si substrate before the pattern process, a high quality AlN film with a thickness of 2 μm has been obtained. The full width at half maximum values of X-ray diffraction rocking curves are as low as 409 and 677 arc sec for AlN (002) and (102) planes, respectively. Further experimental results indicate that the AlN seed layer can suppress the misorientation of the adjacent grains, as revealed by the lower twist and tilt angles of the mosaic structure, and thus only a few dislocations generated during the grain coalescence. In addition, the migration of Al adatoms is enhanced on the Al terminated surface of the AlN seed layer, which accelerates the coalescence process. All these improvements are attributed to the lower binding energy and diffusion barrier for Al adatoms on the Al terminated surface than that on the Si surface. Our results demonstrate an effective approach to obtain high quality AlN films for high performance ultraviolet light-emitting diodes on the Si substrate.

Graphene and amorphous carbon decorated β-Ga2O3 nanoparticles (β-Ga2O3@G/C) were fabricated via facile freezing-dry approach and subsequent sintering treatment. In the β-Ga2O3@G/C, β-Ga2O3 nanoparticles facilitate the lithium ion diffusion, and dual carbon decoration promotes the electron transfer, triggering high pseudocapacitive contribution for charge storage. The pseudocapacitive charge storage for the fresh electrode is 61.7%, reaching 62.5% after 50 cycles, and 66.7% after 100 cycles. Stable pseudocapacitive charge storage also leads to improved cyclability. The β-Ga2O3@G/C electrode exhibits high charge/discharge capacity of 517.9 and 521.8 mAh g−1 after 100 cycles at 0.2 A g−1, and 376.7/379.9 mAh g−1 after 150 cycles at 0.5 A g−1, respectively.

It has been established that hydrogen (H) plays a key role in p-type doping of GaN and it must be removed by dissociation of the Mg–H complex in order to achieve p-type conductivity. However, in carbon (C)-doped semi-insulating GaN, which is the core component of power electronic devices, the role of H, especially the formation and dissociation process of C–H defects, has remained to date a mystery. In this work, we provide a direct evidence for the interaction between H and C in the form of the C N − H i complex in as-grown C-doped GaN. The complex can be dissociated into C N − and H + after post-growth annealing. The activation energy is estimated to be about 2.3–2.5 eV from the temperature-dependent annealing experiments. Our study reveals that the C N − H i complex plays an essential role in understanding the variation of optical and electronic properties of C-doped GaN.

One of the challenges for GaN-on-Si radio frequency (RF) device applications is the RF loss, which is mainly associated with a parasitic channel formed at the interface of AlN and high-resistivity Si substrates. However, the type of conductivity and formation mechanism of the parasitic channel remains controversial. Here, we report unambiguous evidence of Al diffusion at the AlN/Si interface and its effect on RF loss. Hall measurements reveal p-type conductivity at the interface. By combining with secondary ion mass spectroscopy measurements, the p-type conductivity is attributed to the Al diffusion from the AlN layers into the Si substrates, with Al being an acceptor in Si. Experimental data and simulations are in good agreement. We also demonstrate that substrate nitridation can indeed promote the formation of an amorphous silicon nitride layer, which plays a role in suppressing the Al diffusion and, thus, reducing the RF loss.

Developing efficient active region structures with low sensitivity to threading dislocation density (TDD) is of great technical significance for AlGaN-based deep ultraviolet (DUV) light-emitting devices. Here, we propose an active region strategy by introducing bunching effect to form self-assembled sidewall quantum wells (SQWs) with much stronger carrier confinement, resulting in a significant enhancement of internal quantum efficiency (from 46% to 59%) compared to the commonly adopted multiple quantum wells (MQWs) due to the lower sensitivity to TDD. As a demo, an AlGaN-based DUV light-emitting diode (LED) with the proposed active region involving both SQWs and MQWs presents dual-band emission and a consequent 68% enhancement in light output power compared to the DUV-LED with only MQWs as the active region, suggesting that the proposed architecture is fully suitable for the development of high performance DUV light-emitting devices even based on poor or medium quality materials.

A modified Henon chaos mapping-based Tone Reservation (TR) method is presented to simultaneously improve the performance and security of orthogonal frequency division multiplexing passive optical network (OFDM-PON) system, which did not need any redundant sideband information. With the aid of high sensitivity of the low bits in the decimal part of chaos, the modified Henon chaos is constructed iteratively by extracting low bits of the previous chaotic value, which enhances the complexity and randomness of chaotic sequence values. And, by utilizing this chaos, the permutation vector can be conducted and is employed to scramble the distribution of reserved tones on the frequency domain and OFDM frames respectively, which can simultaneously achieve the peak-to-average power ratio (PAPR) reduction and data encryption. The feasibility of this scheme has been experimentally proven in 10-Gb/s OFDM-PON system through 20km fiber (SMF) transmission. Experimental results manifest that, compared to the common OFDM-PON system, the proposed scheme can achieve the ∼ 3dB PAPR reduction and ∼ 1dB BER improvement.

We experimentally demonstrate on-chip all-optical wavelength conversion (AOWC) of four-level pulse amplitude modulation (PAM-4) signals by cross-gain modulation in an InP monolithically integrated turbo-switch circuit based on semiconductor optical amplifiers (SOAs). Full characterization of the photonic integrated circuit (PIC) is given, where sevenfold reduction in effective gain recovery is achieved by the PIC turbo-switch compared with a case of single SOA switch. Wavelength conversion of 25 Gbit/s PAM-4 signal in the C -band is successfully demonstrated with ∼2 dB power penalty at 1 × 10−3 bit error rate. Moreover, the wavelength dependence of the converter is studied. The integrated AOWC device has the advantages of high-speed switching operation as well as small footprint, high stability, and low switching power.

With mining technology and mechanization degree being improving, fully mechanized caving mining technology (FCM) has become a main method for thick coal seam extraction in China. However, roof-coal caving characteristics in turn restrict its recovery efficiency, especially for the coal seam with complicated structure (CCS), that is, the coal seam comprises hard or soft coal and gangue. In order to explore the key factors influencing the roof-coal caving and recovery characteristics, related research work has been conducted as follows: firstly, a mechanical model of CCS has been established, which indicates the strength of the coal and gangue will directly affect the roof-coal recovery. Meanwhile, based on the geological settings of Qinyuan coal mine, numerical simulation on roof-coal caving law under different thicknesses of hard or soft coal and gangue has been performed using UDEC software. The results show that the maximum principal stress will increase with the increase of mining depth, making the roof-coal to break easily. Furthermore, the range of the plastic zone of the top coal and the damage degree of the top coal increase with the increase of mining depth. Physical modeling results show that when an extraction-caving ratio is 1, the number of times the coal arch forms is 0.43 at every caving, up to a maximum of 3; the number of times coal arch forms with an extraction-caving ratio of 2 is 4.65 times larger than that with an extraction-caving ratio of 1. The probability of coal arch formation with an extraction-caving ratio of 3 is minimal, about 0.4, which is due to that the arch span is large and the curvature is small, so it is difficult to form a stable arch structure. According to the mechanical characteristics of roof-coal in Qinyuan coal mine, deep-hole blasting technique has been used to reduce the fragments of roof-coal crushed. The results show that this technique can effectively improve the recovery of roof-coal.

The physical mechanism for recovery of 2D electron gas (2DEG) in down-scaled AlGaN/GaN heterostructures with SiNx layers grown by low-pressure chemical vapor deposition (LPCVD) was investigated by means of Hall-effect characterization, scanning Kelvin probe microscopy (SKPM), and self-consistent Poisson–Schrodinger calculations. Observations using SKPM show that the surface potential of the AlGaN/GaN heterostructure remained nearly unchanged (∼1.08 eV) as the thickness of the AlGaN barrier was reduced from 18.5 to 5.5 nm and likely originated from the surface pinning effect. This led to a significant depletion of 2DEG from 9.60 × 1012 to 1.53 × 1012 cm−2, as determined by Hall measurements, toward a normally OFF 2DEG channel. Based on a consistent solution of the Schrodinger–Poisson equations and analytical simulations, approximately 3.50 × 1013 cm−2 of positive fixed charges were confirmed to be induced by a 20-nm LPCVD-SiNx passivation over the AlGaN/GaN heterostructures. The interface charge exerted a strong modulation of band bending in the down-scaled AlGaN/GaN heterostructure, contributing to the efficient recovery of 2DEG charge density (∼1.63 × 1013 cm−2). E-mode ultrathin-barrier AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors with a low ON-resistance (RON), high ON/OFF current ratio, and steep subthreshold slope were implemented using LPCVD-SiNx passivation.

Developing a high-performance anode with high reversible capacity, rate performance, and great cycling stability is highly important for sodium-ion batteries (SIBs). MoS

The real-time implementation is demonstrated using Field-Programmable Gate Array (FPGA) hardware with Xilinx System Generator (XSG), for secure orthogonal frequency division multiplexing (OFDM) transmission. Vivado software and Verilog programming language are used for the purpose of the real-time system design and the OFDM data transmission. An encrypted 16-QAM OFDM data transmission and recovery are successfully carried out using FPGA. The multi-fold data encryption is achieved via the input data encryption using XOR, real and imaginary parts of QAM symbols encryption, where the chaotic sequences are generated by a hyper digital chaos. As a result, it provides a key space of ~1022 to enhance the confidentiality of OFDM data transmission.

This paper proposes a multi-fold optical frequency hopping (FH) scheme based on hyper digital chaos. The multi-fold data encryption is achieved by the incorporation of chaotic sequences into traditional FH scheme, where a hyper digital chaos is implemented to generate the optical carrier frequency, FH rate as well as the available frequency set respectively. As a result, a huge key space of 1058 is provided in the proposed multi-fold data encryption. The performances of data transmission and security enhancement of the proposed FH scheme are simulated and analyzed in details.

We propose a secure key generation and distribution scheme for data encryption in classical optical fiber channel. A Delay interferometer (DI) is used to track the random phase fluctuation inside fiber, while the reconfigurable lengths of polarization-maintaining (PM) fiber are set as the source of optical phase fluctuations. The output signals from DI are extracted as the secret key and shared between the two-legal transmitter and receiver. Because of the randomness of local environment and the uniqueness of fiber channel, the phase fluctuation between orthogonal polarization modes (OPMs) can be used as secure keys to enhance the level of security in physical layer. Experimentally, we realize the random key generation and distribution over 25-km standard single-mode fiber (SSMF). Moreover, the proposed key generation scheme has the advantages of low cost, compatible with current optical fiber networks and long distance transmission with optical amplifiers.

It is a fact that surface electron accumulation layer with sheet electron density in the magnitude of ~1013 cm&minus, 2 on InN, either as-grown or Mg-doped, makes InN an excellent candidate for sensing application. In this paper, the response of hydrogen sensors based on Mg-doped InN films (InN:Mg) grown by molecular beam epitaxy has been investigated. The sensor exhibits a resistance variation ratio of 16.8% with response/recovery times of less than 2 min under exposure to 2000 ppm H2/air at 125 &deg, C, which is 60% higher in the magnitude of response than the one based on the as-grown InN film. Hall-effect measurement shows that the InN:Mg with suitable Mg doping level exhibits larger sheet resistance, which accords with buried p-type conduction in the InN bulk. This work shows the advantage of InN:Mg and signifies its potential for sensing application.

Due to the intrinsic spontaneous and piezoelectric polarization effect, III-nitride semiconductor heterostructures are promising candidates for generating 2D electron gas (2DEG) system. Among III-nitrides, InN is predicted to be the best conductive-channel material because its electrons have the smallest effective mass and it exhibits large band offsets at the heterointerface of GaN/InN or AlN/InN. Until now, that prediction has remained theoretical, due to a giant gap between the optimal growth windows of InN and GaN, and the difficult epitaxial growth of InN in general. The experimental realization of 2DEG at an InGaN/InN heterointerface grown by molecular beam epitaxy is reported here. The directly probed electron mobility and the sheet electron density of the InGaN/InN heterostructure are determined by Hall-effect measurements at room temperature to be 2.29 × 103 cm2 V-1 s-1 and 2.14 × 1013 cm-2, respectively, including contribution from the InN bottom layer. The Shubnikov-de Haas results at 3 K confirm that the 2DEG has an electron density of 3.30 × 1012 cm-2 and a quantum mobility of 1.48 × 103 cm2 V-1 s-1. The experimental observations of 2DEG at the InGaN/InN heterointerface have paved the way for fabricating higher-speed transistors based on an InN channel.

Carbon (C) doping is essential for producing semi-insulating GaN for power electronics. However, to date the nature of C doped GaN, especially the lattice site occupation, is not yet well understood. In this work, we clarify the lattice site of C in GaN using polarized Fourier-transform infrared and Raman spectroscopies, in combination with first-principles calculations. Two local vibrational modes (LVMs) at 766 and $774\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ in C doped GaN are observed. The $766\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ mode is assigned to the nondegenerate ${A}_{1}$ mode vibrating along the $\mathbit{c}$ axis, whereas the $774\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ mode is ascribed to the doubly degenerate $E$ mode confined in the plane perpendicular to the $\mathbit{c}$ axis. The two LVMs are identified to originate from isolated ${\mathrm{C}}_{\mathrm{N}}^{\ensuremath{-}}$ with local ${C}_{3v}$ symmetry. Experimental data and calculations are in outstanding agreement both for the positions and the intensity ratios of the LVMs. We thus provide unambiguous evidence of the substitutional C atoms occupying the N site with a $\ensuremath{-}1$ charge state in GaN and therefore bring essential information to a long-standing controversy.

All-solid-state lithium batteries employing inorganic solid electrolytes have been regarded as an ultimate solution to safety issues because of their features of no leakage as well as incombustibility and they are expected to achieve higher energy densities owing to their simplified structure. Two-dimensional transition-metal dichalcogenides exhibit a great potential in energy storage devices because of their unique physical and chemical characteristics. In this work, 50 nm thick highly crystalline layered VS

Monoclinic Li3V2(PO4)3/C (LVP/C) and Li3V1.95Fe0.05(PO4)3/C (LVFP/C) composites were successfully modified by cobalt incorporation. The effects of cobalt incorporation on the structure, morphology and electrochemical performance of the LVP/C and LVFP/C composites were systematically investigated. The results show that most Co exists in the form of CoO and forms a hybrid layer with the carbon coating on the surface of the LVP and LVFP particles; moreover, a small part of Co enters into the LVP or LVFP lattices due to atomic diffusion. Compared with LVP/C and LVFP/C, Co-incorporated samples exhibit better electrochemical performance. In particular, under the common effect of doping and a hybrid layer (carbon and metal oxides) coating, the LVFP/C-Co electrode displays a prominent initial capacity of 124.7 mA h g−1 and a very low capacity fading of ∼0.04% per cycle even after 500 cycles at 20 C. This novel co-modification method with cation doping and a hybrid layer (carbon and metal oxide) coating is a highly effective way to improve the electrochemical performance and has great potential to be easily used to modify other cathode materials with poor electrical conductivity.

This paper proposes and demonstrates a physical layer security-enhanced transmission scheme for discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-S-OFDM) signals in a passive optical network. During the DFT-S-OFDM transmission, the reconfigurable DFT matrix, the subcarrier allocation, and the training sequence for OFDM symbol synchronization are well encrypted by digital chaotic sequences generated via a 4-D hyperdigital chaos, which provides a huge key space of ~1045. Secure transmission of 13.3-Gb/s encrypted DFT-S-OFDM signals is demonstrated over a 20-km standard single-mode fiber, which proves the excellent confidentiality of the proposed secure DFT-S-OFDM transmission. Moreover, the receiver sensitivity is improved ~2 dB (BER@10-3), which is due to the effective reduction of peak-to-average power ratio via DFT precoding. In addition, this scheme has the advantages of low computational complexity and has no requirement of redundant sideband information.

Reduced graphene oxide (rGO) incorporated Li3V1.94Fe0.06(PO4)3/C cathode materials were successfully prepared by a sol–gel method. Compared with Li3V2(PO4)3/C and single rGO-incorporated Li3V2(PO4)3/C, the rGO-incorporated Li3V1.94Fe0.06(PO4)3/C electrode has the highest initial capacity of 164.4 mA h g−1 with a capacity retention ratio of 83.5% after 100 cycles at 1C. When charged/discharged for 1000 cycles at 5C, it exhibits a prominent capacity of 129.3 mA h g−1 with a capacity retention ratio of 91.5% and a very low capacity fading of 0.0085% per cycle. The superior electrochemical performance of Fe-doped and rGO-incorporated Li3V2(PO4)3 can contribute to the reduced particle size, the improved electronic conductivity, and the increased Li-ion diffusion coefficient. We believe this novel co-modification with Fe-doping and rGO-incorporation is an efficient way for Li3V2(PO4)3 and any other polyanion cathode materials to realize their application in power lithium ion battery.

Prominent electrochemical performance of a Li3VO4/C–Ni electrode is achieved via hierarchically porous architecture design. The discharge/charge capacities can be maintained at 578/575 mA h g−1 after 190 cycles at various rates. After 2000 cycles at a high current rate of 10C, the discharge/charge capacities can both be maintained at 325 mA h g−1.

Reduced graphene oxide (RGO) decorated ternary Cu2SnS3 composite has been synthesized by one-step facile hydrothermal route. The formation of Cu2SnS3 nanoparticles and reduction of graphene oxide occur at the same time during the hydrothermal process. The Cu2SnS3 nanoparticles with a size of 5–10 nm are uniformly distributed on the RGO, which prevents effectively the agglomeration of Cu2SnS3 nanoparticles. The Cu2SnS3/RGO composite electrode exhibits an initial reversible capacity of 704 mAh g− 1 and 560 mAh g− 1 after 100 cycles. Such excellent electrochemical performance can be attributed to the presence of RGO, which improves the electronic conductivity and prevents the agglomeration of Cu2SnS3 nanoparticles. In addition, the Cu induced by the Cu2SnS3 reaction with lithium ions during the discharge process can increase the electronic conductivity.