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Asteroids, as the primitive building blocks for the formation of our solar system, could reveal its evolution mechanism, and have attracted more and more attention from the public and professional institutions in recent years. Their physical properties, such as rotational period, spin axis and overall shape, can be inverted from ground- and space-based photometric observations. Since the inversion process is very time-consuming, this paper combines the genetic algorithm with the Levenberg–Marquardt (LM) algorithm, and presents a hybrid optimization algorithm based on a Cellinoid shape model for the inversion of rotational periods, which greatly improves the inversion efficiency. The proposed hybrid algorithm is applied to the synthetic lightcurves generated for an assumed Cellinoid shape model and the inverted rotational period results are consistent with the preset ones with a reduced search time, compared with the LM algorithm. Finally, multiple numerical experiments on the periods are performed on lightcurves and sparse observations of real asteroids to confirm that the proposed method can perform well in improving computational efficiency.

We demonstrated a scheme of bandwidth expansion and pulse shape optimized to afford 10 PW laser design via spectral shaping, which uses the existing Nd:glass amplifier chain of the SG PW laser. Compared to the amplified pulse with a gain-narrowing effect, the required parameters of injected pulse energy, spectral bandwidth, and shape are analyzed, together with their influence on the system B-integral, energy output capability, and temporal intensity contrast. A bandwidth expansion to 7 nm by using LiNbO3 birefringent spectral shaping resulted in an output energy of 2 kJ in a proof-of-principle experiment. The results are consistent with the theoretical prediction which suggests that the amplifier chain of SG PW laser is capable of achieving 6 kJ at the bandwidth of 7 nm and the B-integral < π. This will support a 10 PW laser with a compressed pulse energy of 4.8 kJ (efficiency = 80%) at 480 fs.

The non-polar a-AlGaN epitaxial film was successfully grown on the semi-polar r-sapphire substrate by metal-organic chemical vapor deposition technique. An Al-composition-graded AlxGa1−xN (x = 0.0 to 1.0) intermediate layer with varying film thickness from 260 to 695 nm was deposited between the high-temperature AlN layer and the non-polar a-AlGaN epitaxial film to enhance the morphological and crystalline quality. The non-polar a-AlGaN epitaxial films were investigated by using atomic force microscopy (AFM), high-resolution x-ray diffraction, photoluminescence (PL) spectroscopy and the Hall effect measurement techniques. The characterisation results indicate substantial improvements in surface morphology and crystalline quality for the non-polar a- AlGaN epitaxial film grown by adding an Al-composition-graded AlGaN intermediate layer. The surface roughness measured from AFM and the defect-related emission (yellow band) relative to the near-band-edge emission from PL spectra were decreased significantly by optimizing the layer thickness of the Al-composition-graded AlGaN layer. A relatively low background carrier concentration down to −4.4 × 10 17 cm−3 was achieved from Hall effect measurement for the non-polar a-AlGaN epitaxial film.

There are large differences between BIM and 3DGIS in model scale, data standards, information expression, etc., which brings great challenges to the conversion and integration between them. Through in-depth analysis of the current status, problems and difficulties about the integration of BIM models in 3DGIS scenes, aiming to the optimization of graphic information conversion, extraction and integration of attribute information, model light- weighting, shared scheduling, and integrated management of the entire life cycle, combined with IFC and CityGML, a framework for the transformation and integration of BIM models to 3DGIS scenes is proposed. Taking the management information system of the Changjiang Water Resources Committee as an example, after forming a preliminary three-dimensional terrain scene and building appearance model, the process of transforming and integrating a BIM building model into 3DGIS scene is discussed. The results show that the framework can effectively guide the entire process of conversion, publication, integration and application of BIM models in 3DGIS scene, and proves good practicability and operability.

With the rapid development of information technology, fundamental changes have taken place in the way people work. However, computer crime has also become the main type of cases in the Internet era. Therefore, computer forensics technology has become an important research content of computer crime evidence collection. Firstly, this paper analyzes the relationship between computer forensics and data recovery. Then, this paper analyzes the steps of computer forensics. Finally, this paper analyzes the application of anti-forensics technology and computer forensics technology.

To optimize the preparation process of the PCEs, this paper studied the synergistic effect of the three parameters of initiator dosage, synthesis temperature and synthesis time on the viscosity and the performance of the PCEs. The results showed:(1) For the viscosity of the PCEs, when the synthesis temperature was high, the viscosity could be improved by reducing the initiator dosage or by extending the synthesis time; When the synthesis temperature was low, the viscosity could be improved by increasing the amount of initiator dosage or shortening the synthesis time appropriately. At the same time, these three parameters had a similar synergistic relationship with the performance of the PCEs (2) Through kinetic factors, establish a process model of these three parameters and the viscosity of the PCEs: η = 2.97 * e R T 100 * t * m − 1 2 . The model provided a theoretical basis for the optimization of the preparation process of the PCEs. (3) When the viscosity of the PCEs was in the range of 200-370 mPa*s, its effect on cement dispersibility was better.

A neon plasma jet was generated in air, driven by a 9 kHz sinusoidal power supply. The characteristics of the plasma plume and the optical spectra with plasma propagation for different applied voltages were investigated. By increasing the applied voltage, the plasma plume first increases and then retracts to become short and bulky. The shortened effect of Ne plasma plume (about 10 mm) for the further voltage increasing is more apparent than that of He (about 3 mm) and Ar (about 1 mm). Emission intensity of the N2 (337 nm) increases with the applied voltage, gradually substituting the emission intensity of Ne (702 nm and 585 nm) as the noticeable radiation. At the nozzle opening, the Ne (702 nm) emission dominates, while the Ne (585 nm) emission is most noticeable around the tip of the plasma plume. The spatial distribution of the three spectral lines indicates that Ne (702 nm) emission decreases dramatically with plasma propagation while Ne (585 nm) and N2 (337 nm) emissions reach their maxima at the middle of the plasma plume. The results indicate that the Ne (702 nm) emission is much more sensitive to the average electron temperature and the density of the high-energy electrons, so it changes greatly at the tube nozzle and little at the tip region as the voltage increases. The population of high-energy electrons, the average electron temperature, the collision with air molecules and the Penning effect between Ne metastables and air molecules may explain their different variations with plasma propagating and voltage increasing.

Big data technology is one of the most fashionable computer science and technology. Through the rational use of big data technology, traditional enterprises can accelerate the promotion and transformation of business informatization and intelligence. After long-term accumulation and precipitation, the power industry has accumulated a large number of structured and unstructured data of production, operation and management. Based on the actual demand of the electric power industry and the characteristics of the existing information system and mass data, this paper studied the big data platform framework system of electric power enterprises, and carried out the big data framework design from the overall architecture, technical architecture, data architecture, logical deployment architecture and other aspects. The overall design idea conforms to the development concept of “big data +" and “Internet +", and has a good technical foundation and application support, which can be widely used in the design and construction of power big data platform.

In order to investigate the effects of the M229 and M307 locus in FUT1 gene on the carcass and meat quality of Congjiang pigs. In this study, PCR-SSCP, PCR-RFLP and direct sequencing methods were used to quickly type the M229 and M307 loci, and then the association between different genotypes and meat traits was analysed. Population genetic structure analysis showed that M229 locus of FUT1 gene was in Hardy-Weinberg equilibrium, with high polymorphism information content, rich genetic diversity and large space for directional breeding. However, the M307 locus had the opposite result, showing a skewed distribution. Correlation analysis showed that the average backfat thickness index of CT and TT genotypes from the M229 locus of FUT1 gene in Congjiang pigs was significantly lower than that of CC (P

The structural and optical properties for a nonpolar GaN epilayer grown with an in situ SiN x interlayer was studied intensively. The superficial defects were decreased by 83% and root-mean-square was reduced by 61% for nonpolar GaN with an SiN x interlayer. The in situ SiN x was revealed to be powerful to block basal-plane stacking faults (BSFs) in nonpolar GaN because BSF density was reduced from 1.83 × 105 to 8.13 × 104 cm−1 and BSF-related emission was remarkably suppressed by the SiN x interlayer. Moreover, the fast decay lifetime increased from 16.2 to 71.1 ps, which implied the non-radiative recombination in nonpolar GaN was significantly suppressed after the insertion of the SiN x layer.

An innovative multiple-step rapid thermal annealing (RTA) technique was developed for obtaining high hole concentration in the nonpolar a-plane Mg-delta-doped AlGaN films grown on semi-polar r-plane sapphire substrates with metal organic chemical vapor deposition. The structural, optical, and electrical properties of the nonpolar a-plane p-AlGaN epi-layers were characterized with high-resolution x-ray diffraction, photoluminescence spectra, and Hall effect measurement. The characterization results demonstrated that the dissociation efficiency of the Mg–H bonds in the nonpolar a-plane p-AlGaN films could be improved significantly with the multiple-step RTA process. In fact, a hole concentration as high as 1.9 × 1018 cm−3 was achieved with the multiple-step RTA technique, which was 35%, 9%, and 23% higher than those obtained with conventional one-step, two-step, and the recently renovated two-step RTA methods, respectively.

A two-dimensional self-consistent numerical simulation model is used to analyse the effects of the ramp reset pulses on the address discharge in a shadow mask plasma display panel (SM-PDP). Some basic parameters such as the slope of the ramp pulse and the terminal voltage of the ramp reset period are varied to investigate their effects. The simulation results illustrate that the wall voltage is mainly decided by the terminal voltage and the firing voltage at the end of the ramp reset period. Moreover, the variation of the ramp slope will also bring a few modifications to the wall voltage. The priming particles in the beginning of the addressing period are related to the slope of the ramping down voltage pulse. The simulation results can help us optimize the driving scheme of the SM-PDP.

A new type of ac plasma display panel (PDP) with shadow mask (SM-PDP) is presented for its effective structures with lower cost. A two-dimensional self-consistent fluid model is used to analyse the discharge characteristics of the SM-PDP cell in a simplified driving scheme. The effects of the addressing time, the sustaining frequency, the duty ratio of the sustain voltage and the rise time of the voltage pulse on the discharge efficiency are investigated in this paper. The simulation results can help us optimize the driving scheme of SM-PDP.

In this paper an analysis of microelectromechanical systems (MEMS) is performed by using the recently developed radial basis function (RBF) collocation method. Formulations for both static and dynamic analyses of electroactuated beams are derived. The spatial variables in the formulated model are approximated by the RBF whilst the central difference scheme and Newmark scheme are adopted to integrate the ordinary differential equations with respect to time. The Newton–Raphson scheme is also utilized to solve effectively the system of nonlinear equations resulting from the electric force. Numerical validations show that, with only a few nodes used in the computation, the RBF collocation method gives an identical result to other numerical methods, such as the reproducing kernel particle method, and experiments. The effects of residual stress and initial gap length on the pull-in voltage are also investigated.

MgN/AlGaN insertion layers were applied for the first time to the growth of nonpolar a-plane AlGaN epilayers by metal organic chemical vapor deposition technology. The full width at half maximum of the X-ray rocking curve for the a-plane AlGaN epilayers was reduced by approximately 50.6% and the root-mean-square roughness value of the surface was reduced by 74% by applying the MgN/AlGaN insertion layers with an optimized number of insertion pairs. These results reveal that the compressive strain within the a-plane AlGaN epilayers was effectively reduced, leading to significant improvements in crystalline quality and surface morphology. These improvements are very helpful in fabricating high-quality AlGaN-based ultraviolet light-emitting diodes.

The ultraviolet (UV) emitting AlGaN/GaN multiple quantum wells (MQWs) were grown on low dislocation density AlN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). The impact of the purg time on the interface quality of the AlGaN/GaN quantum well was studied. The high resolution x-ray diffraction (XRD) measurement results demonstrate that the density of dislocations was reduced significantly with the purge time after growth of AlGaN barrier layer and GaN well layer was determined to be 4 min and 2 min, respectively. The mechanism of defect formation in quantum wells was investigated by scanning electron microscope (SEM) measurement.

AC transformer load regulation is mainly used to adjust the load side voltage level, improve the quality of power supply, the voltage range is relatively narrow. In DC system, converter transformer is the core equipment of AC and DC power converter and inverter. converter transformer tap adjustment can maintain the normal operation of the converter in small angle range control, the absorption of reactive power, economic operation, valve less stress, valve damping circuit loss, AC / DC harmonic component is also smaller.In this way, the tap switch action is more frequent, and a large range of the tap switch adjustment is required. Converter transformer with a more load voltage regulation switch, the voltage regulation range of the switch is generally 20~30%, the adjustment of each file is 1%~2%. Recently it is often found that the tap switch of Converter Transformers is out of step in Converter station. In this paper, it is analyzed in detail the impact of tap switch out of step for differential protection, overexcitation protection and zero sequence over current protection. Analysis results show that: the tap switch out of step has no effect on the differential protection and the overexcitation protection including the tap switch. But the tap switch out of step has effect on zero sequence overcurrent protection of out of step star-angle converter transformer. The zero sequence overcurrent protection will trip when the tap switch out of step is greater than 3 for out of step star-angle converter transformer.

By combining spectroscopic ellipsometry (SE) and optical transmission (OT) characterization methods we have systematically investigated the influence of AlN intermediate layer and AlN transition layer on the optical properties of AlGaN epilayers grown on sapphire by metalorganic chemical vapor deposition (MOCVD) method. Most dielectric functions of III-nitrides obtained by different research groups show significant band-tail absorption—which is not anticipated for such a direct band gap material. The dielectric functions are studied for a series of AlGaN/AlN/Al2O3 structures, with a four-layer model taking into account both high temperature grown AlN layer and low temperature grown AlN layer. The results obtained by fitting the optical parameters to experimental data show that the band-tail absorption should originate from the transition layer. AlGaN film without high temperature AlN epilayer exhibited a redshift of band gap around 0.24 eV.

Nonpolar a-plane AlGaN epi-layers were grown on a semi-polar r-plane sapphire substrate with an innovative two-way pulsed-flows metal organic chemical vapor deposition growth technology. A root-mean-square value of 1.79 nm was achieved, and the relative light transmittance of the a-plane AlGaN epi-layer was enhanced by 36.9%. These results reveal that the innovative growth method is able to improve the surface morphology and reduce the defect density in nonpolar a-plane Al x Ga1– x N epi-layers, particularly those with an Al composition greater than 0.5, which are key materials for the fabrication of nonpolar AlGaN-based high light emission efficiency deep-ultraviolet light-emitting diodes.

A reformed flow-rate-modulation technology was developed for the metalorganic vapor phase epitaxy (MOVPE) growth of the N-polar GaN epitaxial layers. To improve the crystalline quality of the N-polar GaN epitaxial layers, a GaN nucleation layer was grown at relatively low temperature with carefully-controlled pulsed supply of Ga source and showed diverse morphology with atomic force microscope (AFM). Furthermore, the electrical and optical properties of the grown N-polar GaN epitaxial layers were investigated extensively by means of Hall effect, photoluminescence (PL), and X-ray rocking curve (XRC) measurements. The characterization results revealed that as compared with the N-polar GaN epitaxial layer grown over the conventional GaN nucleation layer which was deposited with continuous supply of both N and Ga sources, the electrical and optical properties of the N-polar GaN epitaxial layer grown with optimized supply of Ga source for the GaN nucleation layer were significantly improved.

We report the realization of Hardy's thought experiment in classical optical systems. Two different classical optical experiments are implemented. One is based on orbital angular momentum and polarization correlation in a classical optical beam, and the other is based on non-local classical correlation from two separated classical optical beams. All experimental results show that they are analogous to Hardy's paradox experiments. This means that Hardy's non-locality proof without inequalities, which is usually used in a quantum system, can also be achieved in classical optical systems.

We study the gamma-ray luminosity and beaming effect for Fermi blazars. Our results are as follows. (i) There are significant correlations between gamma-ray luminosity and radio core luminosity, and between gamma-ray luminosity and R-v, which suggests that the gamma-ray emissions have a strong beaming effect. (ii) Using the L-ext/M-abs as an indicator of environment effects, we find that there is no significant correlation between gamma-ray luminosity and L-ext/M-abs for all sources when we remove the effect of redshift. Flat spectrum radio quasars considered alone also do not show a significant correlation, but BL Lacertae objects (BL Lacs) still show a significant correlation when we remove the effect of redshift. These results suggest that the gamma-ray emission may be affected by the environment on a kiloparsec scale for BL Lacs.

The focusing properties of a dielectric-cylinder-type decagonal photonic quasicrystal flat lens observed at different dielectric refractive indexes are numerically analyzed, showing that, within certain index ranges, the lens can generate images with a resolution below the diffraction limit for a point source. The lens exhibits a double focusing effect within a range of refractive indexes and induces ring photon localization near a certain dielectric refractive index for the point source with the TM mode.

A series of AlxGa1−xN thin films with x = 0.20–0.60 were grown by metal organic chemical vapor deposition (MOCVD) on sapphire (0001) substrate using AlN buffer layer. High resolution X-ray diffraction (HRXRD) was performed for (0002), (0004), and (0006) reflections to investigate the threading dislocation density in variation with Al composition by X-ray analysis technique; Williamson–Hall (WH) plot. A symmetric high resolution 2θ–ω scans exhibit high crystal quality for all the AlGaN samples. A room temperature deep ultraviolet (DUV) photoluminescence (PL) spectroscopy (excitation at 248 nm) has also been employed to investigate the effect of various Al compositions on crystal structure of the thin film layers. It was observed that the band edge transition peak energy blueshifts from 3.87 eV for x = 0.23 to 4.55 eV for x = 0.47. In addition to the band edge transition, each spectrum also shows deep impurity transitions.

We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer (OBL) to form an ultrathin GeOx interfacial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. The GeOx interfacial layer is formed in oxidation reaction by oxygen passing through the Al2O3 OBL, in which the Al2O3 layer could restrain the oxygen diffusion and suppress the GeO desorption during thermal treatment. The thickness of the GeOx interfacial layer would dramatically decrease as the thickness of Al2O3 OBL increases, which is beneficial to achieving an ultrathin GeOx interfacial layer to satisfy the demand for small equivalent oxide thickness (EOT). In addition, the thickness of the GeOx interfacial layer has little influence on the passivation effect of the Al2O3/Ge interface. Ge (100) p-channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) using the Al2O3/GeOx/Ge gate stacks exhibit excellent electrical characteristics; that is, a drain current on-off (Ion/Ioff) ratio of above 1×104, a subthreshold slope of ~ 120 mV/dec, and a peak hole mobility of 265 cm2/Vs are achieved.

Si-doped n-InGaN/GaN composite current-spreading layers (CCSLs) inserted between the n-GaN layer and the InGaN/GaN multiple-quantum-well (MQW) active region were developed and optimized for the GaN-based light-emitting diodes (LEDs). It was found that with the optimized n-InGaN/GaN CCSLs lightly doped with Si, the crystalline quality as well as the electric and optical properties of the GaN-based LEDs, such as forward voltage V f, photoluminescence (PL) intensity, and electrostatic discharge (ESD) endurance could be significantly improved. In particular, an ESD pass yield as high as 99.49% at a 2000 V reverse bias has been achieved for the GaN-based LEDs with the 70 nm/70 nm n-InGaN/GaN CCSLs. This means that the n-InGaN/GaN CCSLs with carefully optimized layer thickness could play a key role in improving the crystalline quality and enhancing the device performance of the GaN-based LEDs.

GaN-based light-emitting diodes (LEDs) with specially designed electron blocking layers (EBLs) between the multiple quantum wells (MQWs) and the top p-GaN layer have been developed. The EBLs consist of Mg-doped p-AlGaN/GaN superlattice (SL) with the layer thickness of p-AlGaN varied from 1 to 10 nm and the layer thickness of p-GaN fixed at 1 nm in this study. It was found that under a 2000 V reverse bias voltage condition, the electro-static discharge (ESD) yield increased from 61.98 to 99.51% as the thickness of p-AlGaN in the EBLs was increased from 1 to 10 nm. Since the ESD yield was 97.80%, and maximum value for LEDs' light output power (LOP) and minimum value for the forward voltage (V f) were achieved when the thickness of p-AlGaN in the EBLs was 9 nm with a 20 mA injection current, it was concluded that the p-AlGaN/GaN SL EBLs with the combination of 9-nm-thick p-AlGaN and 1-nm-thick p-GaN would be beneficial to the fabrication of the GaN-based LEDs with high brightness, high ESD endurance, and low V f.

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with a novel patterned SiO2/Al2O3 passivation layer have been proposed and fabricated. Due to the excellent uniformity and compactness of atomic layer deposition (ALD) for the first Al2O3 layer, a high passivation effect has been achieved. The second SiO2 layer with patterned hemisphere arrays decreases the total internal reflection (TIR) and, hence, increases the light output power (LOP). With a 60 mA injection current, an enhancement of 21.6% in LOP was realized for the LED with an appropriately patterned SiO2/Al2O3 passivation layer as compared with the conventional LED with a SiO2 passivation layer.

A honeycomb lattice photonic crystal (HLPC) has been utilized to realize the Dirac point and cloaking effect. The dispersion bands and modal properties in the vicinity of the Dirac point were analyzed using the plane wave expansion (PWE) method, and the transmission characteristics were simulated by the finite element analysis (FEA) method. The fifth, sixth, and seventh bands intersect at the Dirac point, corresponding to a normalized frequency of a/λ=0.497 at the Γ point. It was demonstrated that a HLPC with perfect magnetic conductor (PMC) boundary conditions for an incident wave can be used to conceal objects (cloaking effect) at this frequency.

GaN-based light-emitting diodes (LEDs) coated with an Al mirror and a three-pair TiO2/Al2O3 distributed Bragg reflector (DBR) by atomic layer deposition (ALD) grown on a patterned sapphire substrate (PSS) were proposed and realized for the first time. A 43.1% enhancement in light output power (LOP) was realized at 60 mA with the LED coated with an Al mirror and a three-pair ALD-grown TiO2/Al2O3 DBR compared with the LED without a backside reflector, as well as a 10.7% enhancement compared with the LED with a conventional Al mirror and a three-pair TiO2/SiO2 DBR reflector.

GaSb is an attractive candidate for future high-performance III–V p-channel metal-oxide-semiconductor-field-effect-transistors (pMOSFETs) because of its high hole mobility. The effect of HCl based-chemical cleaning on removing the non-self limiting and instable native oxide layer of GaSb to obtain a clean and smooth surface has been studied. It is observed that the rms roughness of a GaSb surface is significantly reduced from 2.731 nm to 0.693 nm by using HCl:H2O (1:3) solution. The Ni/Pt/Au ohmic contact exhibits an optimal specific contact resistivity of about 6.89 × 10−7 Ω·cm2 with a 60s rapid thermal anneal (RTA) at 250°C. Based on the chemical cleaning and ohmic contact experimental results, inversion-channel enhancement GaSb pMOSFETs are demonstrated. For a 6 μm gate length GaSb pMOSFET, a maximum drain current of about 4.0 mA/mm, a drain current on-off (ION/IOFF) ratio of > 103, and a subthreshold swing of ~250 mV/decade are achieved. Combined with the split C–V method, a peak hole mobility of about 160 cm2/V·s is obtained for a 24 μm gate length GaSb pMOSFET.

A self-learning fractal interpolation algorithm to construct synthetic fields with statistical properties close to real turbulence is proposed. Different from our previous work [Phys. Rev. E 84 (2011) 026328, 82 (2010) 036311], the position mapping and stretching factors between the adjacent large and small scales are learned from the initial information. Using this method, a turbulence-like field with K41 spectra and without dissipation is constructed well through a coarse grid velocity signal from one experiment's data. After filtering the interpolated signal appropriately, the probability distribution of velocity, velocity structure functions and the anomalous scaling law of the synthetic field are close to those of the original signal.

A method for measuring surfaces of rotation in a cylindrical coordinate system by using multiple measuring columns and a rotary table is proposed. This method possesses lots of advantages such as high data collection efficiency and collision avoidance. The key techniques discussed in detail include the determination of coordinate system offsets of the columns with regards to the rotary table, the determination of the effective radii of the probing systems, error compensation, collision avoidance and protection measures, workpiece centering and data processing. The practice and experiments show that the measuring uncertainty of the machines is less than 0.01 mm which meets the general requirement in most cases.

A new type of ac-plasma display panel (PDP) with shadow mask (SMPDP) is presented with a cost effective structure. The standard SMPDP only includes two electrodes: a scan electrode and an address electrode, and the discharge is a vertical discharge between these two electrodes. A three-electrode SMPDP is described with increased design freedom to improved performance. A special circular waveform has been designed for the three-electrode SMPDP which is expected to result in a higher efficiency by combining the vertical discharge and the surface discharge.

The membrane?spring model was proposed by the authors to simulate the nonlinear mechanical responses of single-walled carbon nanotubes (CNTs). In order to investigate the complex behavior of multi-walled CNTs or CNT related structures, the van der Waals interaction between the non-bonded atoms should be included. In this paper, the van der Waals interaction is introduced into the membrane?spring model by using the atomic integration method. The nonlinear interaction is calculated at the atomic level, and then mapped to nodes. Consequently, the equations of motion are solved on nodes instead of atoms. The nonlinear deformations of single-?and multi-walled CNTs are investigated by using the proposed model.

Theoretical studies are made for recent attention-getting super carbon nanotubes. The so-called 'super carbon nanotube' is a self-similar structure constructed from low-order carbon nanotubes. Based on the Euler beam theory, the equivalent parameters of super tubes are derived from those of arm tubes, and verified by finite element simulations. Instead of the Young's modulus E, a new equivalent modulus E? is adopted, where ? is the ratio of thickness to diameter for arm tubes. The advantage of this equivalent modulus is that the Young's modulus and thickness do not need to be separated in stiffness calculations. The mechanical properties for composites made of super tubes and matrix are also discussed.