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Monoclinic α-MoP2, with the OsGe2-type structure (space group C2/m, Z = 4) and lattice parameters a = 8.7248(11) Å, b = 3.2322(4) Å, c = 7.4724(9)Å, and β = 119.263°, was synthesized under a pressure of 4~GPa at a temperature between 1100 °C and 1200 °C. The structure of α-MoP2 and its relationship to other transition metal diphosphides are discussed. Surprisingly, the ambient pressure phase orthorhombic β-MoP2 (space group Cmc21) is denser in structure than α-MoP2. Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition from β-MoP2 to α-MoP2, suggesting that α-MoP2 is a stable phase at ambient conditions; this is also supported by the total energy and phonon calculations.

Aiming at the failure of PMU caused by cyber-attacks and extreme natural disasters, a bi-level optimization model of PMU fault recovery based on observability is proposed in this paper. By optimizing the sequential restoration of PMU, the control center can maximize the state observability of the system under the condition of limited recovery resources and adjust the power in real time according to the recovered observable nodes, so as to alleviate the power imbalance caused by a disturbance in the recovery process. The upper optimization model takes the maximum observable branch power flow as the optimization objective, and the lower optimization model is constructed as the DC optimal power flow model with the lowest power generation cost. The upper and lower models are coupled by the branch power flow and the node observation state. Then, the lower model is transformed into KKT conditions through Lagrange multiplication, and the nonlinear objectives and constraints are linearized so that the bi-level model can be transformed into a single-level mixed integer linear programming model for solving. Finally, the effectiveness of the proposed strategy is verified by simulation analysis of IEEE39 standard systems.

Epilepsy is a nervous system disease, which is caused by abnormal discharge of brain neurons. The clinical manifestations are generalized seizures, clonus, loss of consciousness, and shock. An electroencephalogram (EEG) can accurately capture the changes in EEG activities. Therefore, EEG signals are used to detect seizures. In this paper, an epilepsy detection model based on a time-gated feature network (TFGN) is proposed. Firstly, the original EEG signal is preprocessed, and the preprocessed signal is sent into the TFGN detection model which integrates feature extraction, feature selection, and classification to obtain the detection results of epilepsy. Through the verification of data from different ages and channels, the detection accuracy of the TFGN detection model is higher than that of the traditional detection model, and the validity and comprehensiveness of the TFGN detection model are verified.

Fourier ptychographic microscopy (FPM) computational imaging is a newly developed microscopic computational imaging technology in recent years, which can realize large field-of-view (FOV) and high-resolution microscopic imaging. In this paper, the SwinIR physical model is introduced to solve the problems of a slightly long reconstruction time and poor reconstruction effect of the FPM reconstruction algorithm based on physical learning. Different from the traditional CNN network structure, this physical model completes the reconstruction of images by introducing modular design and feature fusion. Through a series of simulation experiments on ideal images and real images, it is proved that the reference physical model has better reconstruction quality than the comparison algorithm.

Low-frequency oscillation (LFO) appears in power systems with fast excitation of a unit or large-scale connections. An LFO signal exhibits typical nonstationary and time-varying characteristics. The paper proposed an LFO analyzing technique through the Hilbert spectrum of stationary wavelet transform (SWT). The SWT-based Hilbert spectrum contains time-varying and frequency information of LFO. The analytic framework is introduced, SWT is formulated to decompose an LFO signal into the sum of several coefficient components, the instantaneous parameters of each coefficient are then individually calculated, the complete time-frequency distribution is combined, and finally, the time-varying oscillations characteristics parameters are extracted. The simulation shows that the proposed method effectively reveals time-frequency features of the LFO signal.

Fourier ptychographic microscopy reconstruction mostly adopts the traditional alternating iterative phase recovery method and optimization method, which has high computational complexity, high redundancy of image acquisition data, low reconstruction quality and high time consumption. In this paper, the model of residual transfer networks based on Resnet152 is proposed for Fourier ptychographic microscopy reconstruction, the learning process of deep convolution neural network is introduced, and the image reconstruction method based on deep learning realizes the end-to-end reconstruction of low-resolution images to high-resolution images. Through comparative experiments and analysis, the residual network can overcome the gradient explosion, make the feature information more complete and efficient, and the incremental up-sampling reconstruction network has higher image quality, lower computational complexity and shorter running time.

A static pressure-induced decomposition of cadmium iodide into cadmium and iodine solids is reported in this work using a structure prediction approach combined with first-principles calculations. By compression, CdI2 decomposes into Cd and I at 61.5 GPa, which goes against the common intuition that applying pressure makes the material stable and dense. The increase in the term and with pressure between the compound and the element contributes to the increase in the enthalpy difference, leading to the decomposition of CdI2. On the other hand, the analyses of interatomic interaction demonstrate that under the action of pressure, the decrease of charge transfer between atoms leads to the decrease of the Coulomb interaction, which finally induces CdI2 to decompose into Cd and I solids. Our work represents a significant step toward an understanding of the high-pressure behaviors of Cd-I systems and draws attention to the influence of pressure parameters in certain materials.

In this work, we used nanocomposite saturable absorbers (SAs) in order to precisely design and modulate the process of compositing the light absorption by band gap engineering. Due to the higher absorption intensity of our MoS2/MXene nanocomposite, we have successfully shortened the pulse duration (1.2 μs) of SA with enhancing saturable absorption intensity (7.22 MW cm−2), and the ultra-fast fiber laser based on this nanocomposite SA has shown wider Q-switching stable range in the case of high pump power. This strategy can efficiently improve the performance of SA and shows the potential application prospect of nanocomposites in nonlinear optics.

We observed an isostructural phase transition in the solid nitrogen λ-N2 at approximately 50 GPa accompanied by anomalies in lattice parameters, atomic volume and Raman vibron modes. The anomalies are ascribed to a slight reorientation of the nitrogen molecules, which does not seem to affect the monoclinic symmetry (space group P21/c). Our ab initio calculations further confirm the phenomena, and suggest an optimized structure for the λ-N2 phase. In addition, a new high-pressure amorphous phase of η′-N2 was also discovered by a detailed investigation of the pressure-temperature phase diagram of nitrogen with the aim of probing the phase stability of λ-N2. Our result may provide helpful information about the crystallographic nature of dissociation transitions in diatomic molecular crystals (H2, O2, N2, etc).

In this work, the multilevel resistive random access memories (RRAMs) have been achieved by using the structure of Pt/MoO3/Hf/MoO3/Pt with four stable resistance states. The devices show good retention property of each state (>104s) and large memory window (>104). The simulation and experimental study reveal that the resistive switching mechanism is ascribed to combination of the conductive filament in the stack of MoO3/Hf next to the top electrode and redox reaction at the interface of Hf/MoO3 next to bottom electrode. The fitting results of current-voltage (I-V) characteristics under low sweep voltage indicate that the conduction of HRSs is dominated by the Poole-Frenkel (P-F) emission and that of LRS is governed by the Ohmic conduction. Based on the RRAM, the tunable high-pass filter (HPF) with configurable filtering characteristics has been realized. The gain-frequency characteristics of the programmable HPF show that the filter has high resolution and wide programming range, demonstrating the viability of the multilevel RRAMs for future spiking neural network and shrinking the programmable filters with low power consumption.

In order to clarify the toxic effects of petroleum hydrocarbons in sediments on bivalve mollusks, the acute toxicity and effects of petroleum hydrocarbons on antioxidant enzyme activities were studied using Maoctra veneriformis as a test organism. Our results showed that the health status of the Maoctra veneriformis gradually weakened with the increase of exposure time and concentration of petroleum hydrocarbon, and mortality occurred in the high-concentration group at the end of the exposure. The activities of peroxidase (POD) showed a trend of first decrease and then increase with the prolong of exposure time, and POD activity was significantly induced in some concentration groups at the beginning and the end of the exposure (P < 0.01). The activities of superoxide dismutase (SOD) generally decreased first and then increased as the petroleum hydrocarbons concentration increased. With the prolong of exposure time, the SOD activity decreased first and then increased and then decreased. Our results showed that petroleum hydrocarbons in the sediment produced a certain toxic effect on Maoctra veneriformis, and there was a certain time-dose-effect relationship between anti-oxidase activity and petroleum hydrocarbons. Meanwhile, petroleum hydrocarbons can produce significant induction or inhibition effect on anti-oxidase activity.

In this paper, a novel ammonia detection hybrid film is proposed based on a graphene oxide (GO)/graphene stack, which shows excellent sensing characteristics at room temperature. It is attributed to the cooperation of GO layer serving as molecular capture layer while graphene serving as conductive layer. GO layer is obtained on chemical vapor deposited graphene film by a simple drop-casting method. The prepared GO/graphene hybrid film is directly transferred to the target substrate without any additional transfer vehicle to reduce possible contamination. The success of the transfer depends on the mechanical strength of GO layer. The thickness of GO layer can scale down to 55 nm while sustaining the transfer process. The best ammonia gas sensing performance is obtained at about 275 nm GO layer thickness and the ammonia detection limit is calculated to be 1.5 ppb. In conclusion, the ammonia gas sensing performance of GO/graphene hybrid film can be significantly improved through GO layer thickness optimization.

With the rapid development of the global IoT and various information technologies, the construction of “smart city” has been gradually put on the agenda, and at the same time, the smart management of the National Agricultural Science and Technology Park will also become the key content of smart city construction. This paper proposes a scheme design of smart platform for the agricultural science and technology park, and lists the basic contents of the construction of the smart park. The proposed scheme design of smart platform applies 5G, AI, cloud computing, Internet of Things, mobile Internet and other new ICT technologies to solve the long-term pain points faced by traditional agricultural science and technology parks, including poor service experience, weak comprehensive security, low operational efficiency, high management costs, difficult business innovation, and so on. Because of the construction of the smart park has many contents and a long construction period, this paper discusses the specific design options of smart platform for the agricultural science and technology park. It can provide users with better service perception and help enterprises achieve innovative development through digital transformation. Based on the proposed smart platform, the business subsystem of the agricultural science and technology park is opened horizontally, through data fusion to business integration, to help customers more efficiently and agilely solve business problems that are difficult or even impossible to solve with traditional technical means. The future development and the impact on the life of people.

Intermediate washer of automobile clutch is taken as research object, blanking clearance, radius of corner of punch, blanking speed, blank holder force, counter force and tooth angle of blank holder are selected as influencing factors, length of shear zone is chosen as evaluation index. Orthogonal test with six factors and three levels is established, and Deform-2D is used to simulate fine blanking process of intermediate washer at different combinations of process parameters. Blanking clearance has a significant influence on length of shear zone by variance analysis. The influence sequence of fine blanking process parameters on length of shear zone is blanking clearance, counter force, radius of corner of punch, blank holder force, blanking speed and tooth angle of blank holder. In addition, the optimal combination of process parameters of fine blanking for intermediate washer are as follows: blanking clearance is 8%t, radius of corner of punch is R0.09 mm, blanking speed is 15 mm•s−1, tooth angle of blank holder is 45°, blank holder force is 450 kN and counter force is 150 kN. The simulation value and experimental value of length of shear zone for optimized scheme are 3.945 mm and 3.438 mm respectively, the relative error between simulation value and experimental value is 12.9%. Therefore, it provides an important reference for the actual production of enterprise.

Recently the most essential research in machine learning is to discover correct topics from large scale of electronic documents, and many studies about text modeling have been made in natural language process with the environment of big data. This paper discusses a fundamental way for people to form words while talking and describing ideas, the document is considered as words convergence and a new method for text modeling based on the relational analysis about verbs, nouns, and modifiers is proposed. Additionally the paper introduces a new algorithm for estimating parameters in the generative probabilities of the model, which can alleviate the process about statistics-based text analysis from computational complexity. Experimental results show that the method improves the quality for learning a document.

The group-IIB elements, including zinc (Zn), cadmium (Cd), and mercury (Hg) are studied at multi-TPa pressures using first-principle electronic structure calculations coupled to an efficient structural prediction method. The experimental structural transition sequence with increasing pressure is successfully reproduced, and most metallic elements structures, for instance, simple cubic (sc), body-centered cubic (bcc) and samarium-type (Sm-type) are not stable at terapascal pressures of the group-IIB elements. In addition, the high-pressure hexagonal-close-packed (hcp) phase of Zn, Cd and Hg, can remain up to 6 TPa, and double hexagonal-close-packed (dhcp) and faced-centered cubic (fcc) phases transitions have been observed in Zn and Cd. Hg transforms directly from hcp to fcc, with dhcp absent. The calculated results also show that the c/a ratios of Zn and Cd have a similar transformation, and Hg goes towards the ideal value of 1.633 for a hexagonal close packing at high pressures. The calculated electronic properties indicate that Zn are high-pressure electrides with some of the electrons localized at interstitial sites enclosed by the surrounding atoms. The structural changes from hcp to dhcp and fcc are associated with a dynamical instability, and the soft mode phase transition mainly corresponds to the phase transition mechanism.

This work presents an effective algorithm for radio frequency interference (RFI) identification using dynamic power spectrum statistics in the frequency domain. Statistical signal processing techniques such as hypothesis testing and variance analysis are utilized to derive a test statistic for effective and efficient RFI identification. Starting from the generalized likelihood ratio test (GLRT), we formulate the problem systematically and propose a practical test statistic T(x; f), shown to be distributed, for RFI identification. A threshold approach working on this test statistic is developed to identify the presence of narrowband RFI in the power spectrum with additive Gaussian noise and/or solar flare background, corresponding to a desired constant false alarm rate (CFAR). Detailed analysis on detector performance and effect of RFI duty cycle are also provided. The proposed statistical test is applied to experimental solar data collected by our frequency-agile solar radio telescope (FASR) subsystem testbed (FST) to demonstrate the robustness and scalability of the algorithm, as well as its capability for real-time implementation.

This paper investigates the adhesive contact between a smooth rigid sphere and a smooth elastic layered medium with different layer thicknesses, layer-to-substrate elastic modulus ratios and adhesion energy ratios. A numerical model is established by combining elastic responses of the contact system and an equation of equivalent adhesive contact pressure which is derived based on the Hamaker summation method and the Lennard–Jones intermolecular potential law. Simulation results for hard layer cases demonstrate that variation trends of the pull-off force with the layer thickness and elastic modulus ratio are complex. On one hand, when the elastic modulus ratio increases, the pull-off force decreases at smaller layer thicknesses, decreases at first and then increases at middle layer thicknesses, while increases monotonously at larger layer thicknesses. On the other hand, the pull-off force decreases at first and then increases with the increase in the layer thickness. Furthermore, a critical layer thickness above which the introduction of hard layer cannot reduce adhesion and an optimum layer thickness under which the pull-off force reaches a minimum are found. Both the critical and optimum layer thicknesses become larger with an increase in the Tabor parameter, while they tend to decrease with the increase in the elastic modulus ratio. In addition, the pull-off force increases sublinearly with the adhesion energy ratio if the layer thickness and elastic modulus ratio are fixed.

The high-pressure Raman and IR measurements of NaN3 were performed at room temperature with pressure up to 35.0 and 26.0 GPa, respectively. Three phase transitions of β-NaN3 → α-NaN3 → γ-NaN3 → δ-NaN3 were revealed at 0.5, 14.0, and 27.6 GPa. All fundamental vibrational modes were analyzed based on experimental and theoretical methods. The phase transition from β-NaN3 to α-NaN3 is attributed to the shearing distortion of unit cell and the rotation of the azide ions with increasing pressure. The abnormal symmetric evolution of bending modes observed in IR measurements reveals the rotational behavior of azide groups upon compression. Moreover, the azide ions might evolve into an energetically favorable arrangement under a higher pressure.

Electronic, elastic and piezoelectric properties of two-dimensional (2D) group-IV buckled monolayers (GeSi, SnSi and SnGe) are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d 11 of SnSi and SnGe are 5.04 pm/V and 5.42 pm/V, respectively, which are much larger than 2D MoS2 (3.6 pm/V) and are comparable with some frequently used bulk materials (e.g., wurtzite AlN 5.1 pm/V). Charge transfer is calculated by the Löwdin analysis and we find that the piezoelectric coefficients (d 11 and d31) are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

A facile, efficient, and versatile approach is presented to synthesize pH-responsive nanocapsules (∼120 nm) by combining the advantages of metal-organic frameworks (MOFs) and metal-organic thin films. ZIF-8 nanoparticles are used as templates on which a thin film coating of iron(III)-catechol complexes is derived from the coordination between dopamine-modified alginate (AlgDA) and iron(III) ions. After the template removal, nanocapsules with a pH-responsive wall are obtained. Doxorubicin (Dox), a typical anticancer drug, is first immobilized in ZIF-8 frameworks through coprecipitation and then encapsulated in nanocapsules after the removal of ZIF-8. The structure of the iron(III)-catechol complex varies with pH value, thus conferring the Dox@Nanocapsules with tailored release behavior in vitro. Cytotoxicity tests illustrate the highly effective cytotoxicity of Dox@Nanocapsules towards cancer cells. This study provides a new method for preparing smart nanocapsules and offers more opportunities for the controlled delivery of drugs.

We report a theoretical study into the two- and three-mode entanglement inside an atom-like optical cavity. A five-level system is considered and the influence of the multi-dressed parametric amplification four-wave mixing (PA-FWM) process on the quantum correlation of fluctuation spectra is researched. Three-mode entanglement is determined by the coupling of two nonlinear gains; one of enhanced gains via the dressing state plays a dominant role in controlling and optimizing the profile of three-mode entanglement via vacuum Rabi splitting, enhancement/suppression of entanglement as well as two-mode. Specifically, increasing the quantity of dressing fields may result in the single-channel entanglement turning into nonlocal multichannel (multiple anti-crossing behaviors). Moreover, these entanglement channels can be squashed via the lateral squeezing effect of the cavity. Such multichannel entanglement has potential applications in nonlocal quantum imaging and quantum key distribution.

As magnetic smart materials (MSMs), magnetostrictive materials have great potential to be selected as coating materials for lightweight x-ray telescope mirrors due to their capability to tune the mirror profile to the desired shape under a magnetic field. To realize this potential, it is necessary to study the deformation of the mirror substrate with the MSM coating subjected to a localized magnetic field. In this paper, an analytical model is developed to calculate the deformation of rectangular coated samples locally affected by magnetostrictive strains driven by an external magnetic field. As a specific case to validate the model, a square glass sample coated with MSMs is prepared, and its deformation is measured in a designed experimental setup by applying a magnetic field. The measured deformation of the sample is compared with the results calculated from the analytical model. The comparison results demonstrate that the analytical model is effective in calculating the deformation of a coated sample with the localized mismatch strains between the film and the substrate. In the experiments, different shape patterns of surface profile changes are achieved by varying the direction of the magnetic field. The analytical model and the experimental method proposed in this paper can be utilized to further guide the application of magnetostrictive coating to deformable lightweight x-ray mirrors in the future.

The transport property of a graphene wedge channel is studied theoretically and its leakage current through field emission is estimated when considering the effect of the internal electric field. The transconductance of the graphene transistor is improved from 0.016 to 0.321 μS μm−1 when the graphene is folded into a wedge (with angle of wedge π/6 and radius curvature 2.7 nm at the tip), while the wedge height is much smaller than the space between the top-gate and the channel. The improved transconductance is due to the locally enhanced electric field, which results in a potential well and causes electron accumulation at the wedge tip. The leakage current through field emission J FE shows a super-linear increase with the channel conductive current J DS, where overall the electron supply for the field emission at the wedge tip is improved by the channel bias voltage V DS.

We demonstrate the influence of dressed states on two-mode optical entanglement in a double Λ-type energy level atomic ensemble of parametric amplification four-wave mixing (PA-FWM) processes. By injecting a coherent or Einstein–Podolsky–Rosen field into PA-FWM channels, we investigate the corresponding entanglement. The quantum entanglement may be enhanced or suppressed via a bright state or a dark state. In free space, the two-mode entanglement is determined by nonlinear gain, which can be manipulated by field dressing in an atomic ensemble (i.e. Autler–Towns splitting, dressed enhancement/suppression of entanglement). However, in a ring cavity, the cavity dressing brings about the AT-like splitting of entanglement. Such an entanglement profile may be modified by field dressing through vacuum Rabi splitting, vacuum-induced enhancement and suppression of entanglement.

This paper reports a comprehensive analysis of the performance for gas-lubricated bearing-rotor system in silicon microengine. The generalized lubrication model and dynamics model are developed and the effects of micro fabrication defects, temperature and viscous friction force on both steady-state and dynamic characteristics of bearing system are investigated. The results can serve as a useful tool for the design of silicon microbearing- rotor systems.

A numerical model of the rolling friction between a microsphere and a substrate is established by introducing the adhesion hysteresis between the front and rear sides of the contact region into Zhang's adhesive contact model. Effects of the size ratio which is defined as the sphere radius divided by the equilibrium separation, relative amount of adhesion hysteresis and Tabor parameter on the dimensionless maximum rolling friction torque in the case of zero normal force are inspected, and the quantitative relationship between the maximum rolling friction torque and the normal force is achieved. Results indicate that due to adhesion hysteresis at microscale, the dimensionless maximum rolling friction torque at zero normal force is not zero, which not only increases with decreasing size ratio, showing clear size effects, but also increases with increasing relative amount of adhesion hysteresis and Tabor parameter. In addition, the maximum rolling friction torque at microscale presents a sublinear relationship with the normal force, and the exponent of the normal force is influenced by the size ratio, relative amount of adhesion hysteresis and Tabor parameter, which are remarkably different from the superlinear relationship at macroscale.

A general scheme is proposed to construct systematically a family of superhard sp3 carbon phases of cold-compressed graphite by combining hexagonal to cubic diamond (named as X-Carbon). Based on calculations employing density functional theory (DFT), we find that our currently proposed X-carbon can occur by compressing disordered graphite, and the X-carbon is more stable in energy than the previously proposed M, Z, W, bct-C4, P allotropes. Thus, the X-carbon is predicted to be the transition of cold-compressed graphite. The results show that the simulated x-ray diffraction pattern, Vickers hardness and bulk modulus of X-Carbon match well with the experimental data (Mao et al Science 302, 425 (2003)). These new phases are transparent superhard materials with a large hardness and wide electronic band gaps comparable to cubic diamond.

Using the first-principles calculations, we systematically study the lattice structure and topological phase transitions driven by external strain and electric field in Sb(111) thin films. The results show that 1-bilayer film is a robust trivial semiconductor, and the band gap of a 4-bilayer film can be tuned by strain but without gap closing up to strains of 8%, indicating a robust two-dimensional topological insulator. However, for the remaining bilayers below 9 bilayers, the topological phase transitions are driven if a suitable value of strain is applied. Moreover, the electric field not only can induce the Rashba splitting, but also may induce the gap closing at other points rather than at time-reversal invariant momenta. Our theoretical results provide efficient methods to manipulate topological phase transitions of Sb films.

The phase transition and structural evolution of KN3 are systematically studied using first-principles density functional (DFT) methods and the particle swarm optimization (PSO) structure search algorithm under pressures up to 400 GPa. For the first time, we identify three stable phases with , and structure at pressures of 15.7, 41.4 and 298.6 GPa. The analysis of the crystal structures of three new predicted phases reveals that the transition of N3− ions goes from linear molecules to benzene-like rings and then to polymer chains induced by pressure. The study of atomic and electronic structures of three predicted phases reveals that the structural changes are accompanied and driven by the change of atomic orbital hybridization, first from sp to sp2, and then from sp2 to sp3. Our result provides a new view of the pressure-induced polymerization process of metal azides.

Mercury halides form an amazing number of solid phases and remarkably only the crystal structure of HgF2 at high pressure is not established. We here report a stabilization HgF2 high-pressure phase predicted by the density functional structural searches, which adopts the Pnma symmetric structure (12 atoms/cell, α-PbCl2–type, or cotunnite). The phase transition from the ambient conditions phase Fm-3m (phase I) to the Pnma phase (phase II) was confirmed at 4.7 GPa. The calculated equation of state suggests that this is a first-order phase transition. At this phase transition, the coordination number of Hg2+ increases from eight to nine, similar to the phase transition sequence of CaF2. Furthermore, a thorough CALYPSO structural search up to 100 GPa cannot find any other structure that is more stable than the Pnma structure.

The strain in GaN epitaxial layers grown on 6H-SiC substrates with an AlN buffer by metalorganic chemical vapor deposition is investigated. It is found that the insertion of a graded AlGaN layer between the GaN layer and the AlN buffer can change the signs of strain. A compressive strain in an overgrown thick (2 μm) GaN layer is obtained. High-resolution x-ray diffraction, Raman spectroscopy and photoluminescence measurements are used to determine the strain state in the GaN layers. The mechanism of stress control by inserting graded AlGaN in subsequent GaN layers is discussed briefly.

(BixBa1−x)(Znx/2Ti1−x/2)O3 [xBi(Zn1/2Ti1/2)O3-(1 − x)BaTiO3, x ≤ 0.30] solid solution ceramics with a pure perovskite structure were synthesized by a conventional solid-state reaction method. A change in symmetry from tetragonal to cubic was observed as the mole fraction of Bi(Zn1/2Ti1/2)O3 increased. All compositions show a dielectric anomaly over the temperature range 30–120 °C. In the tetragonal phase region, the temperature Tm of the maximum dielectric constant decreases with increasing Bi(Zn1/2Ti1/2)O3 content. In the cubic phase area, the compositions show general dielectric relaxation of linear dielectrics, and Tm increases with increasing Bi(Zn1/2Ti1/2)O3 content. The phase transition, dielectric and ferroelectric properties of (BixBa1−x)(Znx/2Ti1−x/2)O3 ceramics are sensitive to nano-regional chemistries.