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A new method is proposed for generation of high density diamond nuclei in the dc glow discharge chemical vapor deposition. Application of dc negative valtage together with high methane content has been found to generate diamond nuclei as high as 1010/cm2 on mirror-polished Si wafer. It has been indicated that carbon over-saturation, negative voltage and hydrogen play an important role in this new pretreatment process.

A microcircuit was designed and fabricated on a diamond anvil cell for alternating current impedance spectroscopy measurement under high pressure. Sputtered molybdenum film on a diamond anvil was used as an electrode, maintained the contact between the sample and the electrode stable, and reduced the electrode effect on the impedance measurement. By the empty cell and short circuit tests, the parasitic capacitive impedance from the sample chamber wall was observed to be larger than 10(5) Ω at a frequency lower than 1.0 MHz and could be ignored for samples with higher conductivity. The wire inductance was only 1.0 μH and just appeared at frequency higher than 20 kHz, which could be subtracted from measured impedance for the samples with higher impedance than several hundred ohms. Using this apparatus, the impedances of the II-VI group cadmium sulfide were measured. The pressure dependence of the grain interior conductance of CdS crystal was obtained, which reflected that the phase transitions of CdS under high pressure are the same as the single crystal measurement results.

By studying the multiple granularities of time constraints’ descriptions and consistency problems, in this paper, we establish a dynamic fine-grained access control model, thereby improve the access control precision, quality and efficiency. This paper describes the related concepts of time and the time constraints of multi-granularity. It proposes a kind of TRBAC model with multiple granularities of time constraints by extending the time dimension of the RBAC model. At the same time, it discusses and analyzes the maintenance of the state of the consistency of the system, which enhances the ability of system portray authority in reality and brings it with stronger, more comprehensive description of system security capabilities.

A method for in situ Hall effect measurement under high pressure was developed on a diamond anvil cell. The electrode was accurately integrated on one diamond anvil with regular shape. A uniform and strong magnetic field was introduced into the sample zone. The voltage errors brought by some negative effects during the measurement were well eliminated. The correction factor of the Hall coefficient, brought by the nonpoint contact between the electrode and the sample, was 4.51%. The measurement error of the magnetic field did not exceed 1%. The carrier character of ZnTe powders was studied up to 23 GPa. The evolution of conductivity with pressure was explained based on the variation of the carrier behavior.

The thermal stability and electronic transport properties of polyamorphous ${\text{Ce}}_{75}{\text{Al}}_{25}$ metallic glass (MG) have been investigated using in situ high-pressure, high-temperature, energy-dispersive synchrotron x-ray diffraction and in situ high-pressure and low-temperature, four-probe resistance measurements. The results are compared with the properties of ${\text{La}}_{75}{\text{Al}}_{25}$ MG. The pressure dependence of the crystallization temperature and resistance of the ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG exhibited turning points at the polyamorphic transition pressure, 1.5 GPa, and they clearly presented different behaviors below and above 1.5 GPa. In contrast, no turning points were observed in the ${\text{La}}_{75}{\text{Al}}_{25}$ MG (La has no $4f$ electron). Additionally, the pressure-tuned temperature coefficient of resistance of the ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG was observed. These results revealed switchable properties in the polyamorphous ${\text{Ce}}_{75}{\text{Al}}_{25}$ MG that are linked with $4f$ electron delocalization.

Publish/subscribe paradigm is seen as a good candidate in constructing distributed applications due to its unique and powerful features such as anonymity, asynchrony and many-to-many communication. As applications based on publish/subscribe increases greatly it is required to support different quality of service properties. However, most current solutions adopt simple matching strategies without distinguishing crucial tasks from non-crucial ones, which lead to poor performance of key tasks when publish/subscribe systems are in heavy load. In this paper, we introduce the notion of subscription priority, and propose a new marginal revenue based scheduling (MRBS) algorithm which considers subscription priority. MRBS uses priorities of attribute constraints to sort the matching order for an event, and in such a way MRBS can distinguish important subscriptions from less important ones. MRBS is proven to be able to produce the maximum event matching revenue. A priority-sensitive algorithm for subscription information maintenance is also given. Finally, we conduct detailed experimental evaluation to verify the effectiveness of our approach.

Feature extraction plays a very important role in object recognition and categorization. In this paper, we present a method for extracting corner-based feature from images. This feature is invariant to image scale and rotation, and is shown robust to addition of noise and changes in 3D viewpoint. This paper also describes an approach to using the feature for object recognition. As baselines for comparison, we implemented three additional recognition systems using signature, moment invariant and Fourier descriptor as features. They provide a good basis for judging the importance of representation in learning. The performance analysis on the obtained experimental results demonstrates that the proposed method is effective and efficient.

This paper presents a novel method for recognizing objects using corner features. As one of the most important local features, corner contains lots of information with the shape of the objects. Our approach detects corner points from images and describes the objects based on them. The features are highly distinctive, in the sense that a single feature can be correctly matched with high probability against a large database of features from many images. The recognition proceeds by matching individual features to a database of features from known objects using a fast nearest-neighbor algorithm. The performance on the obtained experimental results demonstrates that the proposed method is efficient.

Ta/anodized Ta2O5/Al is used as metal-insulator-metal (MIM) clement in experiments. The current-voltage (I-V) characteristic of the MIM element depends on the chamber pressure in I,cat-treating anodized Tn(2)O(5) him. Good nonlinear I-V characteristic has been obtained in the pressure range from 10(-2) to 10(-4) Torr. Meanwhile, the conductivity coefficient alpha of the Poole-Frenkel (PF) equation which describes the I-V characteristic can be regulated by about two orders of magnitude in this pressure range, while the non-linearity coefficient beta of the PF equation is not affected by the chamber pressure.

Diverse pose estimation of three-dimensional (3D) object in the whole view-space remains a challenge in the field of pattern recognition. In this paper, a pose estimation algorithm of 3D object named isomap-eigenanalysis-regression (Isomap-E-R), which estimates arbitrary pose of 3D object in the whole view space, is proposed. For the training set, the low-dimensional embedding of input pattern set is computed by isomap, and the eigen-images of the embedding are deduced on the basis of an eigenspace. A different projection direction in low dimensional embedding is utilized to improve the accuracy of pose estimation. The metrics on each direction, derived by linear regression, is then used to further deduce the projection of the training set. For a given new sample, its projection onto the eigen-images is first computed, and the training images nearest to those deduced for the new sample by the algorithm give the estimation poses. The performance analysis on the obtained experimental results demonstrated that the proposed method could estimate the diverse pose of 3D object with significant efficiency and precision. Finally, the algorithm can be also extended to real-time pose estimate of 3D object and other potential applications.

There are many algorithms to simplify meshes. But, most of them are to realize real-time rendering circumstance or models in virtual reality. This paper introduces a novel scheme to simplify meshes from a different view point--visual resolution. This paper uses visual recognizing object principle to simplify meshes. The model or scheme gives a reasonable standard which decides what extent the 3D model is simplified. This scheme can be used in the 3D object-recognition and the robot vision. In this paper, 3D model is the convex model.

A method is presented to obtain maps between the high-dimensional data and the low-dimensional space deduced by locally linear embedding (LLE). Since LLE does not provide a parametric function that build maps between the image space and the low-dimensional manifold. In this paper, multivariate linear regression is applied to deduce the maps. It can successfully project a new data point onto the embedded space. Also it can be extended to supervised LLE. The performance analysis on the obtained experimental results demonstrated that the proposed method is effective and efficient.

Diverse pose estimation of 3D object in the whole view-space is a problem perplexed many researchers. In this paper we propose an algorithm extended from LLE which can estimate the arbitrary pose of 3D object in the whole view space. First, we compute the eigen-images of training set by introducing the idea of PCA using the low-dimensional embedding coordinate deduced from LLE. For a new sample we can compute its projection to the eigen-images, and the nearest training images from the new sample are the estimation poses. Next, we set different weight for different projection direction depends on its eigen-value when computing the distance between the new sample and the training images. Experimental results obtained demonstrated that the performance of the proposed method could estimate the diverse pose of 3D object efficiently and precisely, also our algorithm can be extended to real-time pose estimate, is of a potential future.

The effect of crystallization water on the structural and electrical properties of CuWO4 under high pressure has been investigated by in situ X-ray diffraction and alternating current impedance spectra measurements. The crystallization water was found to be a key role in modulating the structural stability of CuWO4 at high pressures. The anhydrous CuWO4 undergoes two pressure-induced structural transitions at 8.8 and 18.5 GPa, respectively, while CuWO4·2H2O keeps its original structure up to 40.5 GPa. Besides, the crystallization water makes the electrical transport behavior of anhydrous CuWO4 and CuWO4·2H2O quite different. The charge carrier transportation is always isotropic in CuWO4·2H2O, but anisotropic in the triclinic and the third phase of anhydrous CuWO4. The grain resistance of CuWO4·2H2O is always larger than that of anhydrous CuWO4 in the entire pressure range. By analyzing the relaxation response, we found that the large number of hydrogen bonds can soften the grain characteristic frequency o...

The electrical transport properties of Mg2Ge under high pressure were studied with the in situ temperature-dependent resistivity and Hall-effect measurements. The theoretically predicted metallization of Mg2Ge was definitely found around 7.4 GPa by the temperature-dependent resistivity measurement. Other two pressure-induced structural phase transitions were also reflected by the measurements. Hall-effect measurement showed that the dominant charge carrier in the metallic Mg2Ge was hole, indicating the “bad metal” nature of Mg2Ge. The Hall mobility and charge carrier concentration results pointed out that the electrical transport behavior in the antifluorite phase was controlled by the increase quantity of drifting electrons under high pressure, but in both anticotunnite and Ni2In-type phases it was governed by the Hall mobility.

The charge transport behavior of lithium niobate has been investigated by in situ impedance measurement up to 40.6 GPa. The Li+ ionic conduction plays a dominant role in the transport process. The relaxation process is described by the Maxwell-Wagner relaxation arising at the interfaces between grains and grain boundaries. The grain boundary microstructure rearranges after the phase transition, which improves the bulk dielectric performance. The theoretical calculations show that the decrease of bulk permittivity with increasing pressure in the Pnma phase is caused by the pressure-induced enhancement of electron localization around O atoms, which limits the polarization of Nb-O electric dipoles.

Using a diamond anvil cell, the evolutions of alternate-current impedance spectra and direct- current resistivity in B12As2 have been investigated up to 51.9 GPa. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The grain boundary resistance shows a relatively smaller contribution to the total resistance above 16.8 GPa. By using the double-Schottky barrier model, the space charge potential was obtained. A pressure-induced inversion of charge defect concentration in the space charge layer was found at 20.7 GPa. The high-temperature resistivity measurements indicate that the transport activation energy is determined by defect energy levels in the band gap.

Nucleation control is one of the key questions in quantum dots preparation and application. This paper reports the experimental results of orthogonal alignment InAs islands formed on (001) InP substrate by low-pressure metal-organic chemical vapor deposition. As a nucleation control layer, the tensile strained GaAs epilayer with orthogonal trench structure was grown firstly on (001) InP substrate under Stranski-Krastanov growth mode. Then, the InAs islands were grown selectively on the trench edges by using strain effect. This growth technique results in the formation of orthogonal alignment InAs islands without any preprocessing technique prior to the growth.

The atomic force microscopy study was made on the quaternary Ga0.16In0.84As0.80Sb0.20 epilayer prepared on GaSb substrate by metalorganic chemical vapor deposition. The island-like defects were found on the substrate surface pretreated chemically. With the growth process going, these island-like defects could be buried by the epilayer. In the initial stage, two-dimensional-growth-mode was followed. When the epilayer thickness reached 70 nm, three-dimensional (3D)-growth-mode occurred and the perfect 3D islands were observed.

In this paper the pressure dependence of crystal field (CF) parameters and free-ion parameters of the Eu3+ ion in Y2O2S:Eu is studied experimentally in the pressure range from 0 to 13 GPa. Pressure strengthens the interionic interaction in the crystal. The CF strength parameter S increases by a factor of 11%. The Slater parameter F2 and the spin-orbit parameter show about 0. 4 % and 0. 2 % decrease, respectively.

High quality diamond epitaxial film has been obtained on high pressure synthesized cubic boron nitride crystal surface by dc glow discharge chemical vapor deposition. The growth characteristics of the epitaxial film have been investigated by scanning electron microscope. The quality of the film has been confirmed by Raman spectroscope to be close to that of natural diamond.

Pressure-induced electrical transport properties of Bi2Se3, including Hall coefficient, carrier concentration, mobility, and electrical resistivity, have been investigated under pressure up to 29.8 GPa by in situ Hall-effect measurements. The results indicate that the structural and electronic phase transitions of Bi2Se3 induce discontinuous changes in these electrical parameters. The significant anomaly in Hall coefficient at 5 GPa reveals an electronic topological transition deriving from the topological change of the band extremum (Van Hove singularity). Additionally, electrical resistivity measurements under variable temperatures show that the insulating state of Bi2Se3 becomes increasingly stable with an increase of pressure below 9.7 GPa. But above 9.7 GPa, Bi2Se3 enters into a fully metallic state. As the metallization occurs, the topological property of Bi2Se3 disappears.

We report an anomalous phase transition in compressed In2Se3. The high-pressure studies indicate that In2Se3 transforms to a new isosymmetric R-3m structure at 0.8 GPa whilst the volume collapses by ∼7%. This phase transition involves a pressure-induced interlayer shear glide with respect to one another. Consequently, the outer Se atoms of one sheet locate into the interstitial sites of three Se atoms in the neighboring sheets that are weakly connected by van der Waals interaction. Interestingly, this interlayer shear glide changes the stacking sequence significantly but leaves crystal symmetry unaffected. This study provides an insight to the mechanisms of the intriguing isosymmetric phase transition.

The structural stability and electrical properties of AlB2-type MnB2 were studied based on high pressure angle-dispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell (DAC) and first-principles calculations under high pressure. The x-ray diffraction results show that the structure of AlB2-type MnB2 remains stable up to 42.6 GPa. From the equation of state of MnB2, we obtained a bulk modulus value of 169.9±3.7 GPa with a fixed pressure derivative of 4, which indicates that AlB2-type MnB2 is a hard and incompressible material. The electrical resistance undergoes a transition at about 19.3 GPa, which can be explained by a transition of manganese 3d electrons from localization to delocalization under high pressure.

The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300?423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W?Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0.49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.

The ability to probe charge carriers transport behavior under pressure has the potential to unlock many key questions in photoconduction, resistive switch, solid ion transport, etc. We utilize the Hall-effect measurements and the first-principles calculations on Ag2S to reveal the pressure induced changes in its electrical transport parameters. Beyond 7.8 GPa, the donor level in modified monoclinic phase moves away from the conduction-band minimum as the pressure increases, and then Ag2S changes its dominant majority carriers from electrons to holes around 13.5 GPa. Additionally, increasing the pressure makes the electrical resistivity of Ag2S trend to decrease with temperature. At 15.8 GPa, Ag2S undergoes a transformation from metallic-like conduction to semiconductor conduction. These results are beneficial to achieve unique properties of high-pressure phases and develop Ag2S applications under ambient or extreme conditions.

Accurate high pressure in situ Hall-effect and temperature dependent electrical resistivity measurements have been carried out on Bi2Te3, a topological insulator. The pressure dependent electrical resistivity, Hall coefficient, carrier concentration, and mobility show the abnormal inflection points at 8, 12, and 17.8 GPa, indicating that the pressure-induced structural phase transitions of Bi2Te3 can result in a series of changes in the carrier transport behavior. In addition, the Hall coefficient shows a significant discontinuous change at 4 GPa, which is caused by the electronic topological transition. A sign inversion of Hall coefficient from positive to negative is found around 8 GPa. Furthermore, the temperature dependent electrical resistivity shows that the sample undergoes a semiconductor-to-metal conversion around 9.2 GPa, indicating that the insulating gap of Bi2Te3 becomes closed at this pressure. As the metallization occurs in the sample, the topological property of Bi2Te3 disappears.

We report a quantitative analysis of by-pass current effect on the accuracy of resistivity measurement in a diamond anvil cell. Due to the by-pass current, the sample resistivity calculated by the van der Pauw method is obviously smaller than the actual value and the problem becomes more serious for a high-resistivity sample. For the consideration of high accuracy of resistivity measurement, a method is presented that the inside wall of the sample chamber should be covered by a polymethylmethane layer. With this highly insulating layer, the by-pass current is effectively prevented and the current density distribution inside the sample is very close to the ideal case.

We studied the temperature and pressure structural stability of 5 nm BaTiO3 particles by using high resolution synchrotron X-ray diffraction, high pressure Raman spectroscopy, and high pressure impedance technique. A coexistence of the tetragonal and orthorhombic phases is observed in 5 nm Barium titanate BaTiO3 particles with weight fractions 67(6.6)% and 33(8.0)% at ambient condition, respectively. In the temperature range from −123 °C to 177 °C, the phase boundaries of 5 nm BaTiO3 are diffusive and several phases coexist. Pressure dependent Raman spectra of 5 nm BaTiO3 indicates that there exist two phase transitions: the first is at 7.5 GPa when the coexisting phases of orthorhombic and tetragonal undergoes transition to tetragonal phase; the second is around 17.3 GPa when the tetragonal transforms to cubic phase. Observed transitions were confirmed by the high pressure impedance property measurement.

In situ electrical resistivity measurement of graphite compressed in two different pressure cycles in one single experiment at room temperature in the pressure range of 0-34 GPa has been reported. The electrical results indicate that less superhard graphite formed in the second cycle than in the first one. Our experiments identify the phase transition of the graphite at 15.1 and 17.9 GPa for the first and second pressure cycles, respectively, and explain why the superhard post-graphite cannot indent diamond films. The scanning electron microscopy of the graphite powders before and after pressure annealing helps to support the conclusion that both the phase transitions and the formation of superhard post-graphite are sensitive to the grain size of the initial graphite sample under high pressure.

The evolutions of alternate current (AC) impedance spectra, direct current (DC) resistivity and Raman spectra in polycrystalline BaTeO3 have been investigated at high pressures. The abrupt changes observed in electrical transport measurements at 12.73 GPa indicated a kind of phase transition, which was confirmed to be related to the structural phase transition by high-pressure Raman scattering experiments. From the impedance spectra, both grain resistance and grain boundary resistance decreased with increasing pressure, and two clear discontinuities occurred at 12.73 GPa and 17.47 GPa, respectively. After the transition, the contribution to the total resistance by the grain boundary effect dramatically declined and the grain resistance began to play a dominant role. Besides, the electric polarization process was changed due to the phase transition, and it led to a significant rise of the relaxation frequency. From the decompression impedance spectra, it could be clearly seen that the phase transition was irreversible, and it was probably attributed to the irreversible change of the grain boundary for the two different crystal structures. By varying the temperature, the transport behaviour at high pressure was still of semiconductor type but with different slopes for the ambient and high-pressure phases. High-pressure Raman measurements revealed an irreversible structural phase transition occurring above 15 GPa, and the results were consistent with the observed changes of the electrical properties at high pressures.

Using high pressure impedance spectroscopy measurement system, the dielectric property of rock-salt CdS was investigated up to 22.9 GPa. Below 10.0 GPa ɛ r′′ decreased with frequency linearly and ɛ r′ showed one-step decrease, which was due to the electron hopping transport between impurity levels. From 10.0 GPa to 11.6 GPa and from 15.8 GPa to 22.9 GPa, the one-step decrease of ɛ r′ with frequency was assigned to the electron transport along one path, from impurity level to Σ v and to L v, respectively, and the two-step decrease from 11.6 GPa to 15.8 GPa was caused by the electron transport along the two paths mentioned above. The dielectric constant of CdS grain was calculated and showed w-shape with pressure, which was affected by the pressure induced band structure change.

The electrical transport behavior of SnS under high pressure has been investigated by the temperature dependence of electrical resistivity measurement, the in situ Hall-effect measurement, and the first-principle calculation. The experimental results show that SnS undergoes a semiconductor to semimetal transition at ∼10.3 GPa, and this transition is further substantiated by the band-structure calculation. The total and partial density of states predict that the semimetal character of SnS is attributed to the enhanced coupling of Sn-5s, Sn-5p, and S-3p states with application of pressure. In addition, dramatic changes in electrical transport parameters such as the electrical resistivity, the carrier concentration, and the carrier mobility are observed at 12.6 GPa, which are correlated to the pressure-induced Pnma-Cmcm structural phase transition.

In situ impedance spectroscopy of nanophase and bulk γ-Fe2O3 were performed using a fabricated microcircuit on a diamond anvil cell. The results provide evidence for the existence of grain and grain boundary effects that are separated in the frequency region. The analysis establishes that the grain boundary conductance of nanocrystalline γ-Fe2O3 is higher than that of the bulk material. Both the grain and grain boundary resistances of γ-Fe2O3 smoothly decrease with pressure. A remarkable phenomenon of discontinuity appears at 7.4 GPa for the nanocrystals. This critical value is interpreted by the space charge model and changes in charge densities between the grain boundaries. The impedance analysis further reveals that the relaxation frequency gradually increased with the effect of pressure and the γ-Fe2O3 samples’ impedance imaginary part exhibits a typical capacitive characteristic. Within the given pressure range, the relaxation frequency of γ-Fe2O3 follows the Arrhenius behavior. This result was attri...

The magnetoresistivity (MR) of nano-powdered magnetite has been measured under pressures up to 19.0 GPa and magnetic fields up to 15 kG. An unexpected quasi-linear positive MR below 6.0 GPa and an MR transition from positive to negative around 6.0 GPa have been found. The abnormal positive MR below 6.0 GPa originates from the confinement effect caused by nano-scale heterogeneity at the contact surface between Mo and Fe3O4 sample and the high negative spin polarization of magnetite. The MR transition at about 6.0 GPa comes from a phase transition from half-metal to metal induced by pressure.

In this paper, a W-Ta thin-film thermocouple has been integrated on a diamond anvil cell by thin-film deposition and photolithography methods. The thermocouple was calibrated and its thermal electromotive force was studied under high pressure. The results indicate that the thermal electromotive force of the thermocouple exhibits a linear relationship with temperature and is not associated with pressure. The resistivity measurement of ZnS powders under high pressure at different temperatures shows that the phase transition pressure decreases as the temperature increases.

The electronic structure of TiS2 and its transport properties under high pressure have been studied using first-principles calculation and in situtransport parameters measurement. Both the theoretical and experimental results support the conclusion that TiS2 is a semimetal rather than a semiconductor and maintains its semimetallic behavior under high pressure. Although there is no significant change in density of state at Fermi level up to 20 GPa, the transport behavior change drastically at around 15 GPa, manifested by the change in the slope of resistivity and electronic concentration versus pressure curves. This pressure response of transport properties of TiS2 may be associated with conduction of pressure-induced ionization of impurity levels.

Using a diamond anvil cell, the variable-frequency alternate current impedance spectrum of β-boron has been measured upon increasing the pressure from 3.2 to 27.5 GPa. The analysis has established that both the bulk resistance and the grain boundary resistance of β-boron smoothly decrease with the pressure, and that a remarkable phenomenon of discontinuity occurs at 23.9 GPa; this critical value has been interpreted as the pressure threshold above which the van der Waals forces and the interactions between the β-boron grain boundaries significantly emerge. Thence, the grain boundary contribution to the total resistance dramatically declines and results in an enhanced conduction. Besides, the β-boron sample impedance imaginary part exhibits a typical iron-core inductor frequency characteristic.

We have determined the unit-cell parameters of diaspore α-AlO(OH) at high pressures (13.5–27.8 GPa) and at high temperature (1900 K). Experimental data are compared with the theoretically predicted crystal structure variations derived from density functional theory (DFT) calculations. The experimental analysis establishes that the a axial direction is more compressible than the b and c axial directions in the low-pressure range (13.5–18 GPa) and at 1900 K, whereas all three directions show similar behaviors in the high-pressure range (18–27.8 GPa). The diaspore isothermal bulk modulus KT values are 137.6 GPa, 124.8 GPa, and 141.3 GPa, respectively, at 300 K, at 1900 K, and again at 300 K after quenching. By comparison, the diaspore isothermal bulk modulus KT computed at 300 K and at ambient pressure in the framework of the plane-wave pseudopotential approach is equal to 129.3 GPa.

A phase transition concerning B–C–N compound (g-B0.47C0.23N0.30 to w-B0.47C0.23N0.30) was observed. High pressure synchrotron x-ray diffraction was used to explore its structure in a diamond anvil cell to 30.03 GPa. We found the phase transition is incomplete even till the highest pressure in the experiments. The new phase has a wurtzite structure with space group C6V (P63mc). The lattice parameters of w-B0.47C0.23N0.30 at high-pressure are calculated. Different from the starting materials, the new phase shows much greater isotropy in compressibility with increasing pressure. Bulk modulus was estimated being 275(±26) GPa using a Brich–Murnaghan equation of state, which is one of the highest bulk modulus but smaller than that of w-BN, c-BN, and hexagonal diamond and the value predicted from theory.

By use of electrical field analysis method, the accuracy of electrical resistivity measurement with the van der Pauw method in a diamond anvil cell (DAC) was investigated for the situation that sample and gasket were electrically shorted. It is revealed that metal gasket could not be used in electrical measurement in DAC if the inside wall of the sample chamber was not insulated. When the shorted area was less than 20% of the inside wall of the sample chamber, the relative error was smaller than 10%. Once the shorted area exceeded 25%, the relative error increased rapidly.

Two-electrode configuration was developed for in situ electrical impedance detecting on diamond anvil cell under high pressure. The metal gasket was used as one electrode and the risk coming from electrical short between sample and interside wall of the gasket was eliminated. The configuration was evaluated and proved to be effective by measuring the electric impedance of nanocrystalline ZnS under high pressure.

The high-pressure behavior of zinc oxide (ZnO) nanotube has been investigated to 38.7 GPa by in situ synchrotron x-ray diffraction in a diamond anvil cell at room temperature. The transformation from the hexagonal wurtzite (B4) to the cubic rocksalt (B1) phase started at 10.5 GPa and completed at 18.4 GPa. The initial transition pressure of nanotube is found identical to that in bulk crystal but lower than in nanodots, while the completion pressure of nanotube is identical to that in nanodots but higher than in bulk crystal. This indicates that the c-direction of hexagonal ZnO crystal plays a more important role in the initiation of the phase transition, and the a-direction controls its completion. These prove that the B4-B1 transition undergoes a hexagonal path. It is also found that the c/a ratio of the B4 phase decreases slightly before the phase transition and tends to increase during the phase transition, which is also consistent with the theoretical hexagonal-path model. The bulk moduli of B4 and B1 phases were, respectively, 152 and 242 GPa, indicating higher energy is required to compress ZnO nanotube than ZnO bulk crystal only in the B1 phase.

The Third Asian Conference on High Pressure Research, ACHPR-3, was held at Lijiang City, Yunnan Province of China from October 16th–October 20th, 2006. The host organization for ACHPR-3 was the National Lab of Superhard Materials, Jilin University of China. The conference was intended to provide an international forum for high pressure researchers in the Asian countries. We wished not only to bring together researchers working on a wide range of physical properties of matter under high pressure, but also to provide an interactive environment for the exchange of new ideas. About hundred delegates from China, Japan, Korea, India, Russia, USA, France, Sweden and Canada attended the ACHPR-3. Fourteen symposia were organized for the oral and poster presentation. The symposia are listed below: Geophysical and Planetary Aspects of Pressure Effect Semiconductors and Low Dimensional Systems High Pressure Techniques Phase Transitions and Amorphizations Physical Properties of Materials Synthesis of Novel Materials Diamond and Related Superhard Materials Shock Compression and Shock Waves Shock Synthesis Energetic Materials and Detonation Hypervelocity Impact Phenomenon Equation of State Laser and matter interactions New Technologies We acknowledge the editors of Journal of Physics: Condensed Matter for agreeing to publish the selected papers as a special issue of the journal. We hope that readers will see many excellent papers in this special issue and the aim of the conference is achieved.

We synthesized polycrystal AgSbPb18Te20 by using the method of high pressure and high temperature, and found that the defects produced by high pressure and high temperature caused the changes of transport properties. X-ray diffraction patterns showed that the cell parameters did not change obviously with synthesis at high pressure, apart from a small fluctuation. The electrical resistivity first increased, and then decreased to one quarter of the original value, as the synthesis pressure changed from low to high. The Seebeck coefficient decreased with the increase of synthesis pressure, and then changed from positive to negative. High pressure and high temperature could cause AgSbPb18Te20 to change from a p-type to n-type semiconductor, increase the carrier concentration at maximum by two orders of magnitude, and shift the infrared absorption edge to a higher energy range. All of these phenomena were regarded as showing that high pressure and high temperature favored the formation of certain defects which could change the band structure and thereby change the transport properties.