基于改进 SIFCM 和区域生长的三维 CT 图像缺陷体积测量

针对工件三维CT图像中孔洞和空腔缺陷体积测量问题,本文提出了一种基于改进型空间直觉模糊C均值聚类(NL-SIFCM)和三维区域生长的内部缺陷体积自动测量算法。首先对采集得到三维CT图像进行预处理;随后使用NL-SIFCM在三维CT图像上分割得到二值化缺陷图像组,同时针对三维CT图像切片间具有空间相似性改进得到快速算法;最后对二值化图像组进行三维区域生长得到缺陷体素数和空间结构,并将缺陷空间结构显示于三维可视化软件中辅助检测人员分析缺陷。实验结果表明,对用于模拟缺陷的标准球体积测量值相对误差在1.0%以内,具有较高测量精度;并通过实际工件检测验证了该算法适用性可有效满足CT检测需求。     

基于矩形亥姆霍兹线圈的大均匀区改进型三维磁场发生器设计与特性

为了克服传统磁场发生器空间利用率低的缺陷,提出了改进的三维磁场发生器,具有结构紧凑、更大的均匀区。相比传统的亥姆霍兹线圈,每个维度引入了一双辅助线圈。要设计这紧凑场发生器,五个模型参数需要根据用户的要求对均匀性进行优化。最后,研发了一台磁场发生器,用于测试新型线圈的性能以验证其设计方法。实验结果表明,测试的磁场结果与设计值吻合得很好,最大的设计偏差仅为0.12%。更重要的是,产生相同体积的均匀区,这种磁场发生器的体积仅为传统亥姆霍兹线圈的1/13.6。     

Analysis of independent gate operation in Si nano tube FET and threshold prediction model using 3D numerical simulation

In this paper, silicon nanotube field effect transistors (SiNT-FETs) are investigated for independent gate operation using 3D numerical simulation. The parameters, \(\mathrm{I_{ON} , I_{OFF}, V_{T}}\), and the unity gain cut-off frequency \(\mathrm{(f_{T}}\)) are studied in the independent-gate mode. The SiNT-FET we have considered has two gates, namely outer and inner gates, and can be simultaneously driven or independently driven. The physical gate oxide thicknesses of the outer and inner gates of the device are to be converted into effective gate oxide thicknesses due to the non-Euclidean geometry associated with the tube structure. The effective gate oxide thicknesses are different for the same outer and inner physical gate oxide thickness. Since the inner and outer gates are asymmetric, the device parameters extracted at the outer and inner gates are different. Since the independent gate operation allows dynamic threshold voltage adjustment, a model to predict the threshold voltage also known as the threshold voltage sensitivity model is developed for the SiNT device by modifying the double gate FinFET model. These models are verified by TCAD simulation results to validate their accuracy.     

Optimized electrical properties of (Bi 1/2 K 1/2 )TiO 3 - bi(Mn 2/3 Sb 1/3 )O 3 lead-free ceramics in mixing phase region

A new lead-free (1-x)(Bi1/2K1/2)TiO3-xBi(Mn2/3Sb1/3)O3 (BKT-BMS) piezoelectric ceramics were prepared by conventional solid-state route. The experiments show that the addition of BMS induces the occurrence of a mixed tetragonal and pseudocubic phases, and the fraction of tetragonal to pseudocubic phases closes to 50:50 around the composition x = 0.015, at where the dielectric, ferroelectric and piezoelectric properties is optimized. It is highlighted that the Td for the composition x = 0.015 keeps at an adequately-high level around 205 °C. All these competitive properties of the composition x = 0.015 demonstrate the potential application for lead-free piezoelectric ceramics over a broad temperature range.     

Distributed phase shifters using (Ba,Sr)TiO3 thin films on sapphire and glass substrates

Abstract

Sol-gel solutions were synthesized by using various alkoxides of polyhydric alcohol, carboxylate and stabilizer. Stability of modified sol-gel solution was good enough to keep its properties after at least three months although that of ordinary sol-gel solution is not good.

SBT films were fabricated on Pt(200nm)/Ti(20nm)SiO₂(500nm)/Si substrate at under 700°C by using modified sol-gel solution. Range of drying temperature was 200 to 400°C and that of RTA was 550 to 700°C. At high drying temperature, decrease of crystallinity for SBT films was observed accompanied by nucleation of Sr carbonate. On the other hand, SBT film dried at under 250°C and crystallized at 700°C shows high crystallinity of layer perovskite.

SBT film derived from conventional sol-gel solution used to show strong crystal orientation of c-axis. In case of modified sol-gel solution, RTA temperature and amount of added stabilizer influenced crystal orientation of film. So it was possible that to control crystal orientation of SBT films by adjust RTA condition and amount of stabilizer. Stability of sol-gel solution and property of SBT films were influenced by component of solvent, electric properties of SBT films especially I-V property were improved.

Using low temperature deposition process at 650°C, SBT films derived from modified sol-gel solution show superior ferroelectric properties to SBT thin films derived from conventional MOD solution.     

Functional MRI at 3T using intermolecular double-quantum coherence (iDQC) with spin-echo (SE) acquisitions

Object To reinvestigate the dependence of the signal and contrast on sequence parameters and tissue relaxation times for intermolecular double-quantum coherence (iDQC) signals, and to explore the possibility to use a spin-echo (SE)-iDQC sequence for detecting activation signals at 3T. Materials and methods Brain activations were detected in five human volunteers in a visual simulation study using a SE-iDQC sequence, in addition to a GE-iDQC and a conventional single-quantum coherence (SQC) blood-oxygenation-level-dependent (BOLD) sequence. A brain phantom was also used for some quantitative measurements. Results By choosing an optimal echo time TE (~T2) and iDQC evolution time τ(~20 ms), robust brain activations were detected using the SE-iDQC sequence, in addition to the GE-iDQC and a conventional single-quantum coherence (SQC) BOLD sequence. A higher percentage signal change due to activation was observed for both the iDQC-based measurements in comparison to the conventional SQC acquisition. Conclusion Even though a phenomenological analysis consistent with the experimental results was provided, a detailed model is still needed for the contrast mechanism at microscopic level to guide potential applications of brain functional imaging based on the SE-iDQC.     

Power system harmonic parameter estimation using Bilinear Recursive Least Square (BRLS) algorithm

The impact of nonlinear loads produces harmonic pollution in electrical power system. It is considered as a serious concern now a day. Whereas, many algorithms have been proposed for harmonic estimation to improve the power quality performance but till date the accurate estimation of power quality parameters remains a challenge. In this paper a non-linear adaptive algorithm, called Bilinear Recursive Least Square (BRLS), has been applied for the first time for estimating the amplitudes, phases and frequency in case of time varying power signals containing harmonics, sub harmonics, inter harmonics in presence of White Gaussian Noise. The technique is applied and tested for both stationary as well as dynamic signals containing harmonics. Practical validation of the proposed algorithm is also made along with the real time data obtained from a Variable Frequency Drive (VFD) panel used for controlling the speed and torque of the induction motor used at a large paper industry. Comparison of the results achieved with the proposed BRLS algorithm with two recently reported non-linear adaptive algorithms, Volterra Least Mean Square (VLMS), and Volterra Recursive Least Square (VRLS), reveals that the proposed BRLS algorithm is the best in terms of estimation accuracy and computational time.     

Online critical clearing time estimation using an adaptive neuro-fuzzy inference system (ANFIS)

This paper describes an approach using an adaptive neuro-fuzzy inference system (ANFIS) for the assessment of online critical clearing time (CCT). The ANFIS can integrate neural networks and fuzzy logic principles, and has a potential to combine the advantages of both in a single framework. In this paper, the ANFIS is applied for the prediction of CCT by varying load levels and fault locations in buses and transmission lines. The IEEE 39-bus system and 9-bus western system coordinating council are tested and implemented in this study. All machines of the IEEE 39-bus system are considered as the classical model without considering any generator’s exciters. While three machines in the 9-bus western system coordinating council are considered as detailed models, forth-order differential equation is described for all machines by considering the excitation system controller. CCT values obtained by the time domain simulation method using step-by-step calculation are used as the benchmark. The power world version 17 is used for transient simulation, and the ANFIS is implemented using MATLAB version 2014B. The results obtained from the ANFIS approach are quite satisfied with high accurate solutions and much lower computation time. Finally, the graphical user interface in MATLAB is applied for the online CCT estimation of two test power systems by using appropriate ANFIS models obtained from simulations.     

Transport phenomena of poly(3-alkylthiophene) at the solid-liquid phase transition

We have tried to confirm the sign inversion of the photocarrier in regiorandom poly(3-octadecylthiophene), PAT18, by means of the time-of-flight (TOF) method. It was found that the hole mobility decreases with increasing temperature. At the temperature near the solid-liquid phase transition, the hole mobility decreases drastically, and eventually the melting temperature, it was impossible to evaluate the hole mobility from noisy transient photocurrent. On the other hand, transient photocurrents based on electron transport are observed above the melting point. The negative carrier mobility was evaluated in the range from 10/sup -6/ to 10/sup -5/ cm/sup 2//Vs, which is comparably the hole mobility at the solid state. Moreover, the electrical conductivity changes drastically at the instant of the solid-liquid phase transition, and transport in the liquid state was not influenced remarkably by applied hydrostatic pressure, which suggests electronic transport and not ionic transport. These facts suggest that the same mechanism, for example interchain hopping limits carrier transport, and the negative carrier is electron. This unique phenomenon is interpreted as modulation of electronic energy state caused by conformational change of the main chain.     

Online and stable parameter estimation based on normalized brain emotional learning model (NBELM)

Recently, a computational model of Amygdala based on the brain emotional learning is presented by psychologists. This brain emotional learning model (BELM) that has a neuro‐inspired architecture is utilized to train the weights which are in Amygdala and Orbitofrontal. In this paper, unknown parameters of dynamic systems are estimated by developing the normalized BELM (NBELM). To this end, after proving the stability of the model output, the sufficient condition for weights convergence is extracted while the sensitivity analysis is applied for this model. In order to evaluate the performance of NBELM, in the first example, the matrices of a twin rotor MIMO system are estimated and compared with the equation error method (EEM). In the second example, the nonlinear model of a servomotor is utilized as a case study. In the third example, the performance of the NBELM in experimental systems is validated using a reaction wheel with a DC motor. An important feature of the brain emotional system is its fast response, leading the NBELM to have a high speed performance in estimating the parameters of dynamic systems. A few number of adjustable parameters and low computing complexity also cause the NBELM to be an appropriate method for online estimation of the unknown parameters of dynamic systems.     

基于语义矩阵反馈的多特征融合三维模型检索方法

为解决相关反馈三维模型检索方法存在用户不能确定模型是否相似的问题,提出了一种基于语义矩阵反馈的多特征融合三维模型检索方法。首先,采用形状分布和球面调和两种特征提取算法进行多特征提取。然后,对每种特征进行检索计算,将得到的相似度进行基于语义的反馈,根据反馈结果对不同特征分配不同的权值。最后,对迭代反馈结果的权求和得到检索模型的相似度。实验结果表明,本方法的检索结果比用单一的特征提取方法得到的结果准确。     

Field-induced successive phase transitions of Pb(Zn1/3Nb2/3)O3-x%PbTiO3 crystals

The field-induced structural phase transitions of Pb[(Zn_1/3Nb_2/3)_1−x Tix]O₃ (PZN-x%PT) with x = 0.09 and 0.045 were investigated by the high-resolution micro-Brillouin scattering. PZN-9%PT crystals undergo two first order phase transitions, while PZN-4.5%PT undergo a second order phase transition under the zero-field cooling. Under the field-cooling, the higher phase transition of PZN-9%PT changed into a second order phase transition and the temperature range of a tetragonal phase was widened. Whereas a lower phase transition kept the nature of a first order phase transition. On the other hand, elastic anomaly was appeared on phase transition of PZN-4.5%PT under the field cooling.     

三维摄影测量技术在水轮机叶片制造中的应用

利用三维摄影测量技术对叶片铸件进行检测,有效避免了接触式测量方法效率低和测量范围小的缺点。本文重点介绍了三维摄影测量技术的测量原理,并针对某水电站叶片铸件进行了三维摄影测量实验,最后对实验结果进行了分析。     

Structural and dielectric properties of (1-x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 ceramics with the morphotropic phase boundary composition

(1-x)Bi(Ni_1/2Ti_1/2)O₃-xPbTiO₃ (BNT-xPT, 0.42????x????0.52) ceramics were prepared by the conventional mixed oxide method. With the increase of PT content, a change from rhombohedral phase to tetragonal phases, and while the morphotropic phase boundary (MPB) composition is located in the range of x?=?0.46?C0.48. For x?=?0.46 sample, it exhibited a high Curie temperature (T _c) of 410?°C and good piezoelectric properties, d ₃₃ ~230pC/N, k _p ~40?% and k _t ~22?%. For 0.46????x????0.50 samples, it can be found that depolarization temperature is around 350?°C by thermal depoling method.     

Harmonic estimation using RLS algorithm and elimination with improved current control technique based SAPF in a distribution network

This paper presents the application of well known recursive least square (RLS) harmonic estimation technique and its elimination with improved current control technique based shunt active power filter (SAPF) in a distorted power network. The estimation of amplitude and phase angle of fundamental and harmonics is performed using RLS algorithm, known for their simplicity of computation, accuracy and good convergence properties. The estimates are updated recursively as samples of the harmonic signals are received. In order to eliminate harmonics produced by the nonlinear load connected in the distribution network, a three-phase SAPF with modified current control technique is employed. In this paper, based on the analysis and modeling of SAPF with closed-loop control, a feed forward compensation path of load current and a new pulse width modulation (PWM) control scheme is proposed to improve the dynamic performance of the SAPF. In this case the amplitude and phase angle of the converter AC voltage should be adjusted using PWM, thus producing either leading or lagging reactive power. Harmonic contented in the signal is estimated at the point of common coupling (PCC) with and without SAPF. The comparative results of amplitude and phase angle of fundamental and selected harmonics are determined considering installation of SAPF in the distribution network. The system is studied using MATLAB environment to justify the effectiveness of proposed control technique in comparison to the other techniques discussed in the recent literature.     

Dielectric relaxation in paraelectric phase of Ba(Ti,Sn)O3 ceramics

Study on dielectric relaxation of various ferroelectric perovskites in their paraelectric phase had been reported recently. A common accepted idea is oxygen vacancy should be responsible for the observed nonferroelectric dielectric relaxation. The present authors had observed low-frequency dielectric relaxations in the paraelectric phase of Ba(Ti,Sn)O₃ ceramics. In the temperature range of 100 to 450 °C, peaks of loss tangent shift to higher temperature for higher frequency. The results of redox treatment excluded the possibility of defect polarization of oxygen vacancy. It is argued that hopping of localized hole contribute to the dielectric relaxation and to the electronic conducting characteristics.     

Pressure dependent phase transitions in (Pb,Ca)TiO3: Determination of structure using high pressure synchrotron X-ray and Raman studies

Pressure dependent studies on technologically important ferroelectric material Pb_0.70Ca_0.30TiO₃ show the occurrence of a new hitherto unreported pressure dependent phase transition around 4 GPa. In the pressure range 4–14 GPa, the parent tetragonal (P4mm) phase of Pb_0.70Ca_0.30TiO₃ transforms in to a monoclinic (Cm) phase before attaining its paraelectric cubic (Pm3m) phase around 15 GPa. High pressure Raman studies reveal the presence of a critical pressure above which the ferroelectric phase starts to reappear in the paraelectric phase. This critical pressure is found to be much lower than the critical pressure observed in pure PbTiO₃. Possible reasons for this lowering of the critical pressure are presented.     

Investigation of La-doped 0.25Pb(Zn1/3Nb2/3)O3-0.75Pb(ZrxTi1-x)O3 ceramics near morphotropic phase boundary

La-doped 0.25Pb(Zn_1/3Nb_2/3)O₃-0.75Pb(Zr_xTi_1-x)O₃ (x = 0.51–0.57) ceramics were prepared by a conventional mixed oxide method. The piezoelectric and dielectric properties of various compositions near the morphotropic phase boundary (MPB) were investigated. The MPB was determined by X-ray diffraction (XRD) patterns. The optimal properties were obtained in the specimen with Zr/Ti = 53/47: d₃₃ = 570 pC/N, k_p = 0.60, ε_r = 3900, tgδ = 1.9%, T_c = 204°C, P_r = 35.21 μC/cm², E_c = 11.62 kV/cm, which means it is a good candidate for applications.     

复合BaTiO3的Li0.5La0.5TiO3固体电解质的制备和性能

采用高温固相法合成具有高离子电导率的固体电解质Li0.5La0.5TiO3,并以Li0.5La0.5TiO3为母体,通过复合高介电纳米BaTiO3制得一系列不同复合量的复合电解质。对样品进行XRD、SEM分析,并应用交流阻抗技术测试其电导率。母体钛酸镧锂(LLTO)为存在超结构的立方晶体,30℃时晶粒电导率为1.1×10-3S/cm。在复合样品中,LLTO与BaTiO3形成具有棒状结构的钙钛矿型固溶体(Li、La、Ba)TiO3。在低的复合量下(小于10%),复合样品的晶粒电导率比纯样晶粒电导率高。120℃时,母体与复合5%样品的晶粒电导率分别为0.84×10-2、2.39×10-2S/cm,活化能分别为0.22、0.40eV。