The aim of this research is to develop methods to rapidly create rough three dimensional shape models for free-formed. objects. Such methods are useful for designing concept models of products and animation characters. Conventional parametric surface modelling methods are too cumbersome for this aim. The basic representation of the shape in this approach is a triangular mesh (a polygon with triangular faces), thus it is easy to change the shape. The theory of “Welch-Witkin Approximations to Thin Plate Surfaces” is used to give surface characteristics to the mesh and makes it possible to manipulate the triangular mesh as if it were a surface model. Based on this theory, two kinds of modelling methods, surface faring and surface subdivision, are proposed for generating triangular mesh models.
This paper presents a methodology to support collaboration in engineering whose style is called asynchronous and idea integrative. “Idea integrative” style means that multiple engineers are involved in the same subject and make ideas for the subject. “Asynchronous” style means that engineers' working time are different from each other and it is difficult for them to have meetings for discussion on the subject. The key to support this kind of collaboration style is to make media with which engineers can talk as if they talk with partners to understand thought of the partners and know history of engineering. Visualization method of history and ways of interaction between engineers and this media are proposed from the viewpoint of virtual re-experience of other engineers' engineering processes. In this paper, a prototype system is also presented.
The purpose of this research is the reduction of relative motion between two locations of main functional part of precision device under various conditions. First, sensitivity analysis is described which takes only one location, relative motion or objective frequency band into consideration in conventional method. Next, new sensitivity analysis is proposed to consider not only objective frequency band but also relative motion. The new method is applied for a simple numerical model and experimental model, and structural modification is carried out for the reduction of relative motion to compare of conventional methods. Moreover, relative motion between objective lens and stage that are main functional part in microscope for inspection of large scale integration circuit is analyzed by new sensitivity method for reducing relative motion in low frequency band. The image deflection can be reduced by structural modification and evaluated using two dimensional position sensor quantitatively.
InGaAs/GaAs strained-layer single quantum well (SSQW) structures have been grown at temperatures from 200 to 540°C by migration enhanced epitaxy (MEE). Fabricated structures were characterized by comparing the measured wavelength of photoluminescence (PL) emission peak with the theoretically calculated one for ideal quantum wells. In the SSQWs made at high temperatures (400 - 540°C), large PL peak shifts to the shorter wavelengths than the calculated ones were observed. This blue shift of the PL peak was attributed to the surface segregation and desorption of In atoms. Lowering the growth temperature of MEE below 300°C, the In segregation was suppressed and the designed PL wavelength from the SSQW was obtained. It was shown that the preparation of GaAs (2 × 4) -As surface without excess Assticking and the long migration time of group III atoms were needed to obtain the high PL intensity from SSQW.
To improve flexibility and productivity for a manufacturing system, a comprehensive monitoring system is proposed in this study. The system is integrated with three main components acting in parallel, and with two elements. First component is the evaluation system of the cutting states in the general situation. Second is the quantitative estimation system based on achievement, and last one is the qualitative estimation system based on analogy of experience and knowledge. These componets monitor the cutting condition with different level based on the thinking process of a skilled worker. One of elements is the classification system to determine the utilization of the qualitative or quantitative estimation system. The other element is to give notice of the cutting state to a worker. Those main systems in this paper were constructed with artifical neural networks based on sensing the cutting force signals for the estimation of the tool wear in face milling. It was found that the normal and abnormal cutting conditions were recognized by the evaluation system. The average relative error of tool life was 6.3 % for the quantitative estimation, and 19.0 % for the qualitative one. From the results obtained, it can he inferred that former system improves productivity, later one develops the flexibility of machining systems, and the proposed estimation system is used to improve the reliability of the manufacturing.
Mechanical properties of sweet potato are examined experimentally by compressive tests. And the computer simulation is conducted using FEM, on the separating process that sweet potato is cut by a knife-edged cutter with flat blade. The results obtained are as follows : (1) The calculation result almost corresponds to the process which sweet potato is separated by the preceding crack caused by a cutter except initiation. (2) The variety of cutting force is also the same as the experiment on each blade angle of a cutter. (3) In calculation, the effect of blade angle on two factors, the peak of cutting force and the cutting energy, is similar to the experiment. But both calculated values are higher than the experiment due to the high frictional coefficient between the separated surface and a cutter, which is obtained by a simple frictional test.
Temperature distribution of the CNC surface grinding machine, SPG-25, during the warmingup operation and the thermally induced relative displacement between the wheel spindle and the machine table are discussed. The test machine shows relatively high temperature elevation around the hydrostatic oil slides and top of the column on which the AC servomotor is mounted. The relative displacement in Y-axis, δy, reaches 9.5μm after the 3-hour warming-up and it gradually decreases. The displacement in X and Z axes are relatively small and stable. Thermal deformation of the test machine is theoretically investigated by using the finite element method, and δy is confirmed to be mainly caused by the convex deformation of the machine bed due to the temperature elevation around the hydrostatic oil slides. In order to compensate the relative displacement, the oil temperature is set 2 degrees less than the room temperature and δy was diminished by 30%.
A Laser Beam Writing machine is very easy to use for making various patterns such as photo masks. In the Laser Beam Writing machine, line width control is effective to shorten the patterning time. Two means for line width control are presented and tested, these are changing the focusing lenses and controlling laser power. The test results in the fact that 30 times of line width control is achieved using 4 types of focusing lenses and laser power control. The thickness of the photo-resist affects the line width, and this is proved by the experiments. The bank shape of the exposed lines depends on the numerical aperture of these lenses, so that the mixed use of these lenses is effective for a specific pattern. Additionally, the mechanism of exposure is analysed theoretically and compared with the experiment. The analysis meets well with the experiment in the case of a low numerical aperture lenses. The effect of thickness of photo-resist on the exposed line width is verified to he presented as the threshold energy of the photo-resist.
By using renormalized molecular dynamics (RMD) proposed by the authors, computer experiments of machining defectless monocrystal silicon of various size have been carried out to investigate crack initiation process. The results show that a defectless monocrystal silicon can be machined in ductile mode in any scale in an absolute vacuum but exhibits brittle-ductile transition depending on the scale of machining in normal atmosphere. The effect of atmosphere taken into account in this study is adsorption and invation of atmospheric molecules into microcrevices created in both static and dynamic manners in a crystal during machining. The paper describes detailed mechanism of the process of crack initiation together with the discussion from micro dynamics points of view why ductile mode machining is always possible either in small scale or in case of f.c.c. metals.
In this paper, relationship between the residual stress in the ground surface of silicon nitrides, with various grinding conditions and the grinding factor was investigated, in order to make clear the foundamental grinding factors which affect the residual stress. Moreover the force acting on a grain cutting edge which was dynamic force in grinding was calculated, and relationship between the force acting on a grain cutting edge and the residual stress was investigated. The results are summarized as follows : (1) The compressive residual stress in the ground surface becomes large with the increase of the grain size and the hardness of bonding material of grinding wheel. (2) The compressive residual stress tends to increase with the increase of the surface roughness. (3) Considering only mechanical stress, the compressive residual stress is increased with the increase of the obtained force acting on a grain cutting edge, and the stress is saturated at a certain value.
This paper presents a potential image processing method to determine the in-plane geometrical distortion of an STM image and to calibrate it using a regular crystalline lattice. The method is based on two-dimensional FFT analysis, that is, the dimension of a raw STM image is calibrated through comparing the two-dimensional power spectrum of the raw STM image with the ideal one of a regular crystalline lattice. A dual tunneling unit STM with one X-Y stage and two tunneling units independently controlled in the two Z-axes has been utilized for comparative length measurement using a regular crystalline lattice as reference scale. To improve the measurement accuracy, the present method is applied in processing the raw images obtained from the dual tunneling unit STM. The experimental results, in which highly oriented pyrolytic graphite (HOPG) is used as a reference scale for measurement of 10-1 000 nm length, show the feasibility of the present image processing method and the possibility of a comparative length measurement with sub-nanometer resolution using the dual tunneling unit STM.
A high-accuracy algorithm for kinematic analysis of closed loop mechanisms using pair-axis motor and link-pair graph has been developed. This paper added to the algorithm an efficient procedure called Gap-Pair Method for reducing the augmented error through iterative integration. At any time when the error must be checked, the mechanism is reconstructed according to the computed value of relative angular displacement at each pairs beginning from the root link along the tree-path of link-pair graph. The coordinate system of leaf link at the initial node of co tree pair is calculated twice along positive and negative tree-path in order to determine the Gap-Pair axis motor and the gap angle. The Gap-Pair is inserted between the two leaf links as a new drive pair of a virtual mechanism where the original drive pair is locked. Then the new pair is driven until the gap is reduced and the correct angular displacement at every original pair is given. Computational experiments are performed to confirm the accuracy improvement by this method.
This paper describes the prototype of a 3-D shape measuring apparatus for inspection of LSI chips. The measuring principle of the apparatus is based on a shape from focus method. A maj or problem of the shape from focus method for practical use is the time required for acquisition of images at distinct focal planes. The newly developed mechanism has greatly reduced the time. This mechanism has simple structure and performs real-time (video rate) acquisition of the images with high positioning repeatability. In the experiment using the prototype of the apparatus, the acquisition time of 8 distinct focal plane images was within 0.15s and the repeatability was within 0.25 μ m in standard deviation.
This paper describes a measurement of surface profile along a circle with no standard. For the measurement, spacings between two unknown surfaces located almost in parallel are measured along a circle. One of the surfaces is rotated around the center of the circle and spacings are measured again. This measuring procedure is repeated until the one is rotated all round. The profiles along the circle on two unknown surfaces are calculated using the spacing data. A new algorithm using Fourier expansion for the spacing data is given to reduce the calculating time. Computer simulation shows the validity of the algorithm and the effect of the measuring error of the spacing on the calculated profiles. The algorithm is also applied to the experimental data and the calculated profile agrees well with the profile obtained with a 3-dimensional measuring machine.