数字化拟合WALA嵴平面与下颌体轴平面以及平面相关性研究

目的:分析拟合WALA嵴平面拟合度及其与下颌体轴平面、平面的相关性。方法:纳入59例正畸患者的CBCT图像,建立3D模型。取WALA嵴骨性标志点的坐标值,运用最小二乘法拟合WALA嵴平面,将实际坐标值带入平面公式求得相应拟合值、误差百分比。测量拟合WALA嵴平面、下颌体轴平面、平面分别与5个标准平面之间的夹角,记为三组角度值,对所得数据进行统计学分析。结果:拟合值与实际值无统计学差异(P>0.05),且相关性显著(P<0.01);X、Y、Z各组数值的误差百分比的均值,标准差均小于0.1;3组角度值相关性显著(P<0.05)。结论:最小二乘法拟合的WALA嵴平面拟合度优,拟合WALA嵴平面、下颌体轴平面、平面三者间相关性显著,均可考虑作为正畸科研中的测量平面。

安氏Ⅰ类错畸形平面与上气道形态功能及舌骨位置的相关性

目的 :探讨安氏Ⅰ类错畸形平面与上气道形态功能与舌骨位置的相关性及其临床意义。方法:随机选取2014年1月-2019年1月治疗的安氏Ⅰ类错畸形患者120例,观察正畸治疗前与治疗3个月时上气道形态功能指标(SNA、SNB、ANB、SPPS、MPS、IPS、S-PNS、Ba-PNS)变化情况;根据平面角度(OP-SN)将患者分为A(35例,10°≤OP-SN<15°)、B(45例,15°≤OP-SN<20°)、C(40例,20°≤OP-SN<25°)3组,观察治疗3个月时3组患者睡眠指标变化[平均血氧饱和度(MSaO2)、最低血氧饱和度(LSaO2)、氧减指数、平均脉率]以及平面(OP-SN)、上气道形态功能与舌骨位置(H-PS、H-VPS)变化情况,采用SPSS 20.0软件中的Pearson相关性分析评价平面与上气道形态功能以及与舌骨位置的相关性。结果:正畸治疗后SNA、MPS、IPS、S-PNS、Ba-PNS较治疗前显著升高(P<0.05),而SNB、ANB、SPPS较治疗前显著下降(P<0.05);3组不同平面中OP-SN、ANB角随平面角度升高而升高,而SNA、SNB角随平面角度升高而降低,组间差异具有统计学意义(P<0.05);OP-SN与SNA、SNB呈负相关(P<0.05),与ANB呈正相关(P<0.05);SNA、SNB、ANB、SPPS、MPS、TPS上气道形态测量指标与H-PS、H-VPS指标呈正相关(P<0.05)。结论:安氏I类错畸形人群平面与上气道形态功能及舌骨位置密切相关。

平面与下颌矢状向位置关系的X线头影测量研究

目的明确下颌处于不同矢状向位置时的牙形态,以及下颌矢状向位置与平面倾斜度的关系,为下颌矢状向位置异常患者的非手术正畸治疗提供策略依据。方法选取114例女性正畸患者治疗前的114张头影侧位片,根据ANB角的大小分为3组,每组各测量25项指标。对3组之间及两两组之间的差异进行方差分析和多重比较分析,对骨性指标与牙性指标的相关性进行直线相关分析。结果后牙平面(OP-P)倾斜度和上颌第二磨牙的垂直高度与下颌矢状向位置相关(P<0.05)。下颌后缩时,上颌第二磨牙垂直向萌出相对不足,OP-P倾斜度增加;下颌前伸时,上颌第二磨牙垂直向萌出相对过度,OP-P更平坦。当下颌处于不同位置时,牙轴近远中倾斜度有不同的代偿。下颌后缩患者上颌牙列牙轴远中倾斜,下颌牙列牙轴近中倾斜;下颌前突患者上颌牙列牙轴近中倾斜,下颌牙列牙轴远中倾斜。结论不同骨性环境下形态各有不同,正畸治疗下颌位置异常的患者时应重视后牙垂直高度的控制和对OP-P倾斜度的改变。

两种拔牙模式矫治后相关平面的变化研究

目的研究拔除4颗第一前磨牙(上四下四)和拔除双侧上颌第一前磨牙和下颌第二前磨牙(上四下五)2种拔牙模式矫治前后腭平面、平面及下颌平面的变化。方法固定正畸矫治患者166例,拔除上四下四62例,拔除上四下五7 6例,不拔牙2 8例,测量矫治前后的腭平面角、咬合平面角和下颌平面角等项目。结果 2种拔牙模式患者腭平面和平面的变化差异无统计学意义;拔除上四下四矫治的均角型患者矫治后下颌平面角轻微增加(t=2.97,P<0.05);其余患者的改变差异没有统计学意义。结论拔除上四下四和拔除上四下五2种拔牙模式不会导致腭平面、平面的改变,拔除上四下四矫治的均角型患者下颌平面角轻微增加。

数字化牙模、口内侧面像及头颅侧位片平面角度的差异

目的比较隐形矫治排牙软件中数字化牙模与口内侧面验像及头颅侧位片中胎平面角度的差异。方法本研究为横断面研究,纳入使用不同隐形矫治系统(A:隐适美隐形矫治器;B:时代天使隐形矫治器)矫治患者各40例。测量隐形排牙软件中牙模初始位置侧面照片、口内侧面验像和自然头位下头侧位片中上颌解剖贻平面的角度,以平面与地面水平线的夹角表示。采用单因素重复测量方差分析比较三种资料中胎平面角度的差异,采用独立样本1检验比较A及B两种隐形矫治系统中胎平面角度的差异。结果数字化牙模的侧面胎平面角度为1.8°±2.7°,小于口内侧面像中的平面角度3.1°±2.5(P=0.003)及头颅侧位片中的平面角度11.0°±3.8(P<0.001)。A组和B组数字化牙模的胎平面角度(分别为2.7°±2.2°、1.0°±2.8°)有统计学差异(P=0.003)。结论隐形排牙软件中初始数字化牙模的侧面贻平面接近与地面平行,与口内侧面胎像中比较一致,而与自然头位下头颅侧位片的真实验平面角度差异较大,提示在软件排牙前有必要校正验平面角度,以防影响正畸矫治效果。

A novel self-alignment method for high precision silicon diffraction microlens arrays preparation and its integration with infrared focal plane arrays

Silicon(Si)diffraction microlens arrays are usually used to integrating with infrared focal plane arrays(IRFPAs)to improve their performance.The errors of lithography are unavoidable in the process of the Si diffrac-tion microlens arrays preparation in the conventional engraving method.It has a serious impact on its performance and subsequent applications.In response to the problem of errors of Si diffraction microlens arrays in the conven-tional method,a novel self-alignment method for high precision Si diffraction microlens arrays preparation is pro-posed.The accuracy of the Si diffractive microlens arrays preparation is determined by the accuracy of the first li-thography mask in the novel self-alignment method.In the subsequent etching,the etched area will be protected by the mask layer and the sacrifice layer or the protective layer.The unprotection area is carved to effectively block the non-etching areas,accurately etch the etching area required,and solve the problem of errors.The high precision Si diffraction microlens arrays are obtained by the novel self-alignment method and the diffraction effi-ciency could reach 92.6%.After integrating with IRFPAs,the average blackbody responsity increased by 8.3%,and the average blackbody detectivity increased by 10.3%.It indicates that the Si diffraction microlens arrays can improve the filling factor and reduce crosstalk of IRFPAs through convergence,thereby improving the perfor-mance of the IRFPAs.The results are of great reference significance for improving their performance through opti-mizing the preparation level of micro nano devices.

A monolithic integrated medium wave Mercury Cadmium Telluride polarimetric focal plane array

A medium wave(MW)640×512(25μm)Mercury Cadmium Telluride(HgCdTe)polarimetric focal plane array(FPA)was demonstrated.The micro-polarizer array(MPA)has been carefully designed in terms of line grating structure optimization and crosstalk suppression.A monolithic fabrication process with low damage was explored,which was verified to be compatible well with HgCdTe devices.After monolithic integration of MPA,NETD<9.5 mK was still maintained.Furthermore,to figure out the underlying mechanism that dominat⁃ed the extinction ratio(ER),specialized MPA layouts were designed,and the crosstalk was experimentally vali⁃dated as the major source that impacted ER.By expanding opaque regions at pixel edges to 4μm,crosstalk rates from adjacent pixels could be effectively reduced to approximately 2%,and promising ERs ranging from 17.32 to 27.41 were implemented.

基于VisualC^(++)的平面四连杆机构的CAI系统

介绍利用VisualC++工具开发平面四连杆机构的计算机辅助教学系统的总体结构、功能和方法。

Effects of sonic speed on location accuracy of acoustic emission source in rocks

To quantitatively study the location errors induced by deviation of sonic speed, the line and plane location tests were carried out. A broken pencil was simulated as acoustic emission source in the rocks. The line and plane location tests were carried out in the granite rod using two sensors and the cube of marble using four sensors, respectively. To compare the position accuracy between line and plane positions, the line poison test was also carried out on the marble surface. The results show that for line positioning, the maximum error of absolute distance is about 0.8 cm. With the speed difference of 200 m/s, the average value of absolute difference from the position error is about 0.4 cm. For the plane positioning, in the case of the sensor array of 30 cm, the absolute positioning distance is up to 8.7 cm. It can be seen that the sonic speed seriously impacts on the plane positioning accuracy. The plane positioning error is lager than the line positioning error, which means that when the line position can satisfy the need in practical engineering, it is better to use the line position instead of the plane location. The plane positioning error with the diagonal speed is the minimum one.

Prestack Gaussian beam depth migration under complex surface conditions

In areas with a complex surface,the acquisition and processing of seismic data is a great challenge.Although elevation-static corrections can be used to eliminate the influences of topography,the distortions of seismic wavefields caused by simple vertical time shifts still greatly degrade the quality of the migrated images.Ray-based migration methods which can extrapolate and image the wavefields directly from the rugged topography are efficient ways to solve the problems mentioned above.In this paper,we carry out a study of prestack Gaussian beam depth migration under complex surface conditions.We modify the slant stack formula in order to contain the information of surface elevations and get an improved method with more accuracy by compositing local plane-wave components directly from the complex surface.First,we introduce the basic rules and computational procedures of conventional Gaussian beam migration.Then,we give the original method of Gaussian beam migration under complex surface conditions and an improved method in this paper.Finally,we validate the effectiveness of the improved method with trials of model and real data.

Diffraction separation by plane-wave prediction filtering

Seismic data processing typically deals with seismic wave reflections and neglects wave diffraction that affect the resolution. As a general rule, wave diffractions are treated as noise in seismic data processing. However, wave diffractions generally originate from geological structures, such as fractures, karst caves, and faults. The wave diffraction energy is much weaker than that of the reflections. Therefore, even if wave diffractions can be traced back to their origin, their energy is masked by that of the reflections. Separating and imaging diffractions and reflections can improve the imaging accuracy of diffractive targets. Based on the geometrical differences between reflections and diffractions on the plane-wave record; that is, reflections are quasi-linear and diffractions are quasi-hyperbolic, we use plane-wave prediction fltering to separate the wave diffractions. First, we estimate the local slope of the seismic event using plane- wave destruction filtering and, then, we predict and extract the wave reflections based on the local slope. Thus, we obtain the diffracted wavefield by directly subtracting the reflected wavefield from the entire wavefield. Finally, we image the diffracted wavefield and obtain high-resolution diffractive target results. 2D SEG salt model data suggest that the plane-wave prediction filtering eliminates the phase reversal in the plane-wave destruction filtering and maintains the original wavefield phase, improving the accuracy of imaging heterogeneous objects.

Band Structure of Three-dimensional Phononic Crystals

By using the plane-wave-expansion method, the band structure of three-dimension phononic crystals was calculated, in which the cuboid scatterers were arranged in a host with a face-centered-cubic （FCC） structure.The influences of a few factors such as the component materials, the filling fraction of scatterers and the ratio （RHL） of the scatterer＇s height to its length on the band-gaps of phononic crystals were investigated.It is found that in the three-dimension solid phononic crystals with FCC structure, the optimum case to obtain band-gaps is to embed high-velocity and high-density scatterers in a low-velocity and low-density host. The maximum value of band-gap can be obtained when the filling fraction is in the middle value. It is also found that the symmetry of the scatterers strongly influences the band-gaps. For RHL＞1, the width of the band-gap decreases as RHL increases. On the contrary, the width of the band-gap increases with the increase of RHL when RHL is smaller than 1.

FLOW FIELD ANALYSES OF PLANE JET AT LOW REYNOLDS NUMBERS USING LATTICE BOLTZMANN METHOD

A two-dimensional（2-D） incompressible plane jet is investigated using the lattice Boltzmann method（LBM） for low Reynolds numbers of 42 and 65 based on the jet-exit-width and the maximum jet-exit-velocity. The results show that the mean centerline velocity decays as x-1/3 and the jet spreads as x2/3 in the self-similar region, which are consistent with the theoretical predictions and the experimental data. The time histories and PSD analyses of the instantaneous centerline velocities indicate the periodic behavior and the interaction between periodic components of velocities should not be neglected in the far field region, although it is invisible in the near field region.

Numerical Simulation of the Influence of Mean Sea Level Rise on Typhoon Storm Surge in the East China Sea

In this paper, ECOMSED （Estuarine Coastal Ocean Model with sediment transport） model is employed to simulate storm surge process caused by typhoon passing across East China Sea in nearly years. Capability of ECOMSED to simulate storm surge is validated by comparing model result with observed data. Sensitivity experiments are designed to study the influence of sea level rise on typhoon storm surge. Numerical experiment shows that influence of mean sea level rise on typhoon storm surge is non-uniform spatially and changes as typhoon process differs. Maybe fixed boundary method would weaken the influence of mean sea level rise on storm surge, and free boundary method is suggested for the succeeding study.

Anti-Plane Elasticity Problem and Mode Ⅲ Crack Problem of Cubic Quasicrystal

The fracture theory of cubic quasicrystal was developed. The exact analytic solution of a Mode Ⅲ Griffith crack in the material was obtained by using the Fourier transform and dual integral equations theory, and so the displacement and stress fields, the stress intensity factor and strain energy release rate were determined. The results show that the stress intensity factor is independent of material constants, and the strain energy release rate is dependent on all material constants. These provide important information for studying the deformation and fracture of the new solid material.

Coral Reef and High Sea Level at Luhuitou, Hainan Island during the Holocene

According to the field survey and ^14C dating at Luhuitou, southern Hainan Island, a subsiding area, the authors conclude the high sea level history recorded by coral reef in the Holocene. At least 4 sea level high-stands can be identified from the distribution of coral reef ages： 7300 - 6000 cal.aBP, 4800 - 4700 cal.aBP, 4300 - 4200 cal.aBP and 3100 - 2900 cal.aBP. The highest sea level occurred around 7300 - 6700 cal.aBP, and biological-morphological zones took their shape during the stage. The later coral reefs developed in ponds, depressions, and developed outwards on both sides of Luhuitou peninsula. The modern coral reefs are developing in out reef flat and reef-front slope. Moreover, the time of high sea levels in the northern South China Sea recorded by coral reefs in the Luhuitou peninsula can link up with that in other parts of South China Sea. That means the high sea levels in the South China Sea during the Holocene, which are relative to the warming climate, have the global background.

Sub-pixel extraction of laser stripeand itsapplication in laser plane calibration

For calibrating the laser plane to implement 3D shape measurement, an algorithm for extracting the laser stripe with sub-pixel accuracy is proposed. The proposed algorithm mainly consists of two stages： two-side edge detection and center line extraction. First, the two-side edge of laser stripe is detected using the principal component angle-based progressive probabilistic Hough transform and its width is calculated through the distance between these two edges. Secondly, the center line of laser strip is extracted with 2D Taylor expansion at a sub-pixel level and the laser plane is calibrated with the 3D reconstructed coordinates from the extracted 2D sub-pixel ones. Experimental results demonstrate that the proposed method can not only extract the laser stripe at a high speed, nearly average 78 ms/frame, but also calibrate the coplanar laser stripes at a low error, limited to 0.3 mm. The proposed algorithm can satisfy the system requirement of two-side edge detection and center line extraction, and rapid speed, high precision, as well as strong anti-jamming.

Analysis of plane strain bending of a strain hardening curved beam based on unified yield criterion

The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. The solutions for the mechanical properties of plane strain bending are derived, which are adapted for various kinds of non-strength differential materials and can be degenerated to those based on the Tresca, von Mises, and twin-shear yield criteria. The dependences of the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane on different yield criteria and Poisson’s ratios are discussed. The results show that the influences of different yield criteria and Poisson’s ratio on the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane of the curved beam are significant. Once the value of bis obtained by experiments, the yield criterion and the corresponding solution for the materials of interest are then determined.

Effects of freeze-thaw cycles on fracture behavior of epoxy asphalt concrete

According to the winter temperature of Peking,the freeze-thaw（FT） condition in laboratory was determined.Seven groups of epoxy asphalt concrete（EAC） specimen were exposed to different FT cycles.The flexural modulus and fracture energy（G_F） of EAC exposed to different FT cycles were obtained through the 3-point bending test.Meanwhile,the plane strain fracture toughness（K_（IC）） of EAC was obtained through numerical simulation.The results show that the flexural modulus of the FT conditioned EAC samples decreases with the increase of FT cycles.The FT damage of flexural modulus is 60%after 30 FT cycles.Nevertheless,with the increase of FT cycles,the G_F and K_（IC） of EAC decrease first and then increase after 15 FT cycles.

Static Induction Devices with Planar Type Buried Gate

Based on the surface-gate and buried-gate structures,a novel buried-gate structure called the planar type buried-gate (PTBG) structure for static induction devices (SIDs) is proposed.An approach to realize a buried-gate type static induction transistor by conventional planar process technology is presented.Using this structure,it is successfully avoided the second epitaxy with a high degree of difficulty and the complicated mesa process in conventional buried gate.The experimental results demonstrate that this structure is desirable for application in power SIDs.Its advantages are high breakdown voltage and blocking gain.