Diffusion of hydroxyl groups in silica glass through an interface formed by binding between high-hydroxyl (ca. 1200 wt.ppm) and low-hydroxyl (ca. 130 wt.ppm)-containing silica glasses in the temperature range of 900–1150 °C was investigated. Although the theoretical curve with a hydroxyl-concentration-independent diffusion coefficient deviates from the experimental curve, the diffusion coefficients obtained by fitting to the experimental results by the least squares method coincided with the “effective diffusion coefficients” in the literature, which were obtained from the total absorption change in the IR absorption peak for the hydroxyl group using thin samples. By the analysis considering the hydroxyl concentration dependence of the diffusion coefficient, we showed that the diffusion coefficient is proportional to hydroxyl concentration at each temperature, which is consistent with the model of the diffusion: SiOSi + H2O = 2SiOH. On the basis of this scheme, we tried to evaluate the diffusion coefficients of molecular water using equilibrium constant in the literature.
Low femperature (600°C) (Ba, Sr)Ti03 (BST) capacitor process integration (LTB) based on SrRu03 (SRO) electrode is proposed to achieve gigabit scaled and embedded DRAMs. BST crystallizing temperature is successfully reduced by SRO, which has the same perovskite structure as BST film. Chemical Mechanical polishing (CMP) and O3 water etching are developed for a storage node (SN) electrode and a plate (PL) electrode patterning. A new low temperature post anneal method is also proposed in order to reduce oxygen vacancies at a top electrode-BST interface.
In this paper, a development of the sensor fusion algorithm for a visual control of mobile robot is presented. The visual sensor gives many kinds of valuable information and is especially important for the autonomously controlled mobile robots. The output data from the visual sensor include a time-lag due to the image processing computation. Moreover, in most cases, the sampling rate of the uisual sensor is considerably low so that it should be used with other sensors to control fast motion. The development of an algorithm to integmte the dota from multi-sensor system to obtain the optimal estimate of the state variables is a very important problem. The main purpose of this paper is to develop a method which constitutes a sensor fusion system to give the optimal state estimates. The proposed SenSOT fusion system combines the visual sensor and inertial sensor using a modified Kalman filter. A kind of multi-rate Ifalman filter ,which treats the slow sampling rate data from visual sensor is applied for the construction of the sensor fusion system. A n important feature of the multi-mte version of Kalman filter is the use of time-varying filter gain matrix.An expenmental mobile robot is developed which realizes a sensor fusion system combining a vision sensor system and an inertial sensor system. Experimental results show that the proposed sensor fusion algorithm gives the good estimates of the state variables combining the data from CCD camem images and the inertial sensors.
Propagation and stability of light pulses under the combined influence of the optical Kerr ellect, dispersion and diffraction are investigated by adopting a variational procedure. In particular, it is found thrt 'light bullets', i.e. radially symmetric pulses propagating without distortion, are not necessarily unstable under perturbations which do not maintain radial symmetry.
This paper presents a study of attenuation and shock absorbing characteristics of the docking system in space. A laboratory prototype of electromechanical shock absorbing system is developed in order to make a preliminary experimental study on the docking system.
IntroductionThe docking system is one of the most important functions for the space station and the orbiter such as space shuttle. Recently the construction of many large scale space stations is planned. Many kinds of docking/berthing system must be required for space construction, assembly and servicing. The docking systems are usually classified mainly according to their approach speed. The docking between the station and the orbiter is the 'soft' docking where the final approach speed is ultimately slow. Precise coiitrol of velocity and alignment is performed during the approach phase to minimize contact and stroking forces. On the other hand, 'hard' docking system will be utilized for docking between objects such as small conveyer vehicles, robots, construction equipments, etc. where rather high speed docking is inevitable and force attenuation during the c a p ture phase is more significant In the latter'case, the docking system is desired to make 'hard' docking as 'soft' as possible.The development of the docking system needs variably controlled actuators for energy absorption, compliance control and adjustment of a docking interface to eliminate misalignments. In space environment a hydraulic device can not be used because of fluid leaks and difficulty of maintenance. The use of an electromechanical actuator is considered to be most suitable for docking system in space. An electric docking actuator is considered to include range, rate and attitude sensors to adjust a docking interface in order to eliminate misalignments and to minimize contact and stroking forces. This paper presents a preliminary experimental study on the docking system in space. Main purpose of this research is the study of attenuation and shock absorbing characteristics of the docking system. A laboratory prototype of electromechanical docking system is developed which uses sonar ranging system as a substitute for the laser iange sensor and is controlled by a microprocessor. The configuration of experimental system consists of a rack and pinion gear actuator, a servo motor, sensors, a digital controller and a air-lifted docking target.The motion of docking system is considered to have three phases, i.e. approach, matching and capture phases. In approach phase, relative velocity, attitude and alignment are controlled to obtain suitable docking interface. In matching phase, the actua-*Furocho Chikusaku, Nagoya, 464 Japan Te1.052-781-5111 ext.4418,
Fax.052-781-4094tor is accelerated to match the velocity of the approaching target which i s assumed tohave constant velocity in this phase. In capture phase, the actuator is decelerated to attenuate the kinetic energy of the target. In this paper, control for matching and capture phases are considered.The attenuaior can be considered a...
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