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Hiroshi IZUI, Michiharu OKANO
Article type: Article
Pages
195-196
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This research focuses on the sintering and its mechanical properties of hydroxyapatites by spark plasma sintering (SPS) process. Sintering conditions are heating rate, sintering temperature, sintering time, sintering pressure, etc. The sintering conditions intricately affect each other. To determine the optimum sintering conditions, many sintered compacts are typically fabricated using all the combinations of sintering conditions. In this research, the optimum sintering conditions of HAp powders were determined by using the methodology of Robust Engineering. The optimum conditions can be determined with fewer compacts without sintering under all combinations of sintering conditions using this methodology. The mechanical properties of HAp sintered compacts were discussed.
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Kenzo Asaoka, Masayuki Kon
Article type: Article
Pages
197-198
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Sintered porous titanium compacts, which have continuous pores, were fabricated by spark plasma sintering (SPS) process. Three different spherical particle sizes of Ti powders (45,150 and 250μm under) were employed to sinter the specimens. To evaluate the degree of sintering by SPS process, the sintered specimens were annealed at 1000℃ for 24 hours in an evacuated furnace. Compressive stress-strain curve of the annealed specimens were measured, and compared with those of the specimens by only SPS process. The sintered compacts were immersed in simulated body fluid (SBF) and evaluate the biocompatibility. Calcium phosphate (HAp) were precipitated on the sintered particles. Because precipitated HAp, is a main component of bone structure, the compact developed might be an advanced biomaterial with excellent biocompatibility and could control its mechanical properties by the heat treatment after SPS process.
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Taizo NOGUCHI, Akihiro AMANO, Yoshihiko NOMURA, Norihiko KATO
Article type: Article
Pages
199-200
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This research aims at investigating the relation between contour_and brightness perception in the Kanizsa figure of a visual illusion. And the method of a psychophysical experiment is examined_to make the measurement highly accurate. The characteristics of brightness and contour perception of the proposed psychophysical experiment method were compared with other method, and effectiveness of the proposed method was verified. Brightness and contour perception are expressed with respect to the quantity of the stimulus called the rate of perception. As a result, it was found that the brightness perception and the contour perception never occur simultaneously, and, therefore, they would not be the reverse phenomena induced from the same cause.
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Yoshihiko NOMURA, Masato OGAWA, Norihiko KATO, Hirokazu Matsui, Tokuhi ...
Article type: Article
Pages
201-202
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper describes a, integrated cut point detection techniques. The authors examined some existing techniques from the viewpoint of easiness when tuning the thresholds for discrimination, and found out that the existing techniques are defective to the dark scenes and the scenes capturing moving objects. They proposed the integrated method that is composed of a bloc division technique, the L*a*b* color space system, and an optical flow-based technique, and confirmed the effectiveness of the integrated method against the dark and motion scenes through the experiments of some movies.
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Marie OHNO, Taichi SATO, Kihachiro TANAKA
Article type: Article
Pages
203-204
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A lot of people express a sound by the same onomatopoeia. In order to solve the relationship between a continuous sound and the corresponding onomatopoeia, sounds were made on the basis of word information of onomatopoeia. We performed the auditory sensory tests by using the prepared sounds. Furthermore, the actual sounds were analyzed by using a one-third-octave analyzer. By comparing the auditory sensory test results with actual sound, we clarified that the frequency of the sound to hear as onomatopoeia is close to the frequency of the actual sound.
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Masahiro OHKA, Hiroshi KOGA, Yasunaga MITSUYA
Article type: Article
Pages
205-206
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper describes effective evaluation methods for a pin-typed tactile display to present virtual striped textures. Each pin of the tactile display was driven by a bimorph PZT ceramic actuator; the stroke of the pin was about 1mm. The size of the pin-array was 8-by-8; the pin-array typed tactile display was mounted on a mouse. Two display pads were produced; one's pitch of tactile pins was 1mm; the other's was 1.8mm. In order to obtain a suitable procedure for evaluating presentation capabilities of the tactile display, we compared two experimental procedures : one was a constant stimuli method in which seven human subjects judged various pairs of textures and they answered textures of each pair were same or not; the other was an adaptive method in which they adjusted a crossed-axes angle of a comparison texture to be equivalent to a standard texture. From the experimental results, it was found that both of the constant stimuli method and the adaptive method can be treated equivalently and that 1 and 1.8mm pitch displays does not cause different precision presenting virtual textures.
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Takeshi KAWAHARA, Masahiro OHKA, Yasunaga MITSUYA
Article type: Article
Pages
207-208
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Abstract An optical three-axis tactile sensor is comprised of a silicone-rubber sheet, an acrylic plate, a CCD camera and a light source. A silicone-rubber sheet has an array of 8×9 sensor cells consisting of a columnar feeler and 2-by-2 conical feelers. Since the 2-by-2 conical feelers are detached from the acrylic board under too large horizontal force, the three-axis tactile sensor can detect friction coefficient of the object surface with limited range of horizontal force only. In the present paper, the authors proposed three sensing elements : in type-I element a columnar feeler has a conical feeler, in type-II one has 2-by-2 conical feelers; in type-III one has 8 conical feelers. To evaluate the these sensing elements, we conducted a series of experiments using an x-z stage and a two-axis force sensor. It was found that the element consisting of a columnar feeler and 8 conical feelers shows almost linear relationship between centroid movement and horizontal force. Therefore, the Type-III element is suitable for the present sensing method estimating horizontal force from centroid movement.
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Seiichi OHKUBO, Junich HINO, Toshio YOSHIMURA
Article type: Article
Pages
209-210
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A prediction method of chatter vibration is proposed in high-speed end milling operation. Chatter vibration occurring in mechanical part gives rise to poor surface finish and dimensional accuracy in machined part, reduction of tool life, and even damages machined machine tools. The purpose of this study is too develop and expert system for predicting chatter vibrations in high-speed end milling using wavelet packet transform and fuzzy neural network models. The proposed method is applied to a jig grinding machine, and the results demonstrate the effectiveness of the chatter prediction procedure.
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Kazuyuki SAKIYAMA, Hidetoshi KOTERA, Tsunemasa NISHIDA
Article type: Article
Pages
211-212
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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New millimeter wave antenna is presented in this paper. We have noticed the microstrip antenna (MSA), that characteristic is fixed by electric and magnetic current distributions on the substrate circuit. We devised the feasible model that can reconfigure the current distribution. It is assumed that construction is made by small regions of conductor and insulator, which can is designed by the topological apply of meta material, in order to control the current distributions. This optimum design method is the topology search technique based on electromagnetic field simulation and Genetic Algorithm. The new slow wave antenna applied by this method is shown in this paper. The slow wave structure is approximated by meta material mode 1,and some special features are discussed in this approach.
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Yoshihisa FUKUDA, Kazuyuki SAKIYAMA, Isaku KANNO, Hidetoshi KOTERA
Article type: Article
Pages
213-214
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper presents a frequency and directivity reconfigurable antenna for millimeter-wave communication. Reconfiguration is achieved by actuating conductor matrix element with micro actuator. The conductor matrix elements are arranged in the upper conductor layer and the lower conductor layer. If a distance between the upper and the lower conductor elements is short enough, the separated conductor elements act as continuous antenna line. By actuating the conductor elements, the electrically connected antenna line is easily disconnected. Consequently, the shape of antenna is reconfigured fitting to wavelength and receiving/radiating wave direction. As a first step, we have fabricated a millimeter antenna device and measured its characteristic. We have confirmed the characteristic radiation of the millimeter wave antenna, indicating this structure is effective to control the path of millimeter current.
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Hayato KIMURA, Hiroyuki UKIDA, Katsunobu KONISHI
Article type: Article
Pages
215-216
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, we propose the method to trace an object in the large area with high speed using the arm robot and high speed pan-tilt moving cameras. Here, we also propose the method to trace a high speed object by the prediction of the object position. We can get three-dimensional position of the object from the turn angles of robot and two cameras. The object position can be predicted from the polynomial equations using three-dimensional position. In addition, in order to trace an object in general case, we use the color histogram for the feature detection. In this study, we compare the color histogram of a reference image with that of a local region in an input image hierarchically, and detect the position of the object in the input image. As a result of the experiments by using this system, the object trace can be done when the movement speed is fast.
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Hiroki OTA, Taichi SATO, Joji OKAMOTO, Makoto NAGAI, Katsuaki NAGAHASH ...
Article type: Article
Pages
217-218
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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We developed a new method for accurate estimation of the excitation force of an electric motor by indirect method using measured acceleration response. usually, an electric motor is attached to a supporting structure in some points. Therefore, we have to estimate the amplitude and phase of motor excitation forces. The amplitude and phase of motor excitation forces were estimated by solving an inverse dynamical problem with measured values of the acceleration. To solve this inverse problem, we employed an accelerometer to measure the accelerations of the supporting beams of the motor. In the experiment, the acceleration of a beam was measured when the motor was in operation. Additionally, the transfer matrix for the testing system was created by using the equations of motor for both the motor and the supporting beams. The results obtained by this method agreed well with the results of the excitation force measured by using a load cell directly.
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Susumu HARA
Article type: Article
Pages
219-220
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Many power-assist systems for industrial uses possess simple power-assisting function only. Conveyance of controlled objects is generally processed by another system. This study proposes a positioning method of a cart with motor by means of a smooth switching from the servo access control for the conveyance function to the impedance control for the power-assisting function. We apply the idea of the nonstationary optimal control method to obtaining the smooth switching. The effectiveness of the method is verified by experiments.
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Hironobu ENDO, Isaku KANNO, Hidetoshi KOTERA
Article type: Article
Pages
221-222
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The paper presents the possibility of a low-voltage micro-switch for RF application. The switches, we fabricated, consist of micro-cantilevers using piezoelectric PZT thin films with the length of 300μm and the width of 50μm. The cantilevers are actuated as unimorph actuators that can be deflected by applying voltage between upper and lower electrodes. We could obtain large deflection of 4.3μm even at the low voltage of 6.0V, which is well compatible with conventional IC drivers. This result indicates that the RF-MEMS switch using piezoelectric PZT thin films is much advantageous to the low voltage switching devices compared with conventionally proposed electrostatic ones.
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Yutaka TANAKA, Hirohito HAGIWARA, Taichi MIZUNO, Hirokuni BEPPU, Daiji ...
Article type: Article
Pages
223-224
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In conventional tele-operated systems using a camera image or flat display image, it is difficult for operators to manipulate objects remotely without presence transmitted from the remote location. In this paper, the tele-operated remote manipulation system with immersive virtual environment for operators has been proposed and developed. The immersive display system, the Vision Dome with 3D computer graphics in the virtual workspace is used to give an illusion for the operator in the presence of the real workspace. It is experimentally verified that time delay for data transmitted from the remote location and uncomfortable feeling using flat display images are compensated with the immersive virtual environment.
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Kenichiro TERADA, Isaku KANNO, Hidetoshi KOTERA
Article type: Article
Pages
225-226
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper we propose hybrid piezoelectric materials composed of thin film PZT on organic layer. It is well-known that the PZT film shows excellent piezoelectric properties and is easy for microfabrication as MEMS devices. However deposition of PZT films need high process temperature as high as 500℃ which makes it difficult to integrate them on flexible organic materials. In this study we prepared PZT films on epitaxial MgO substrates in advance, and then they were glued onto adhesive polyimide layer. Finally the MgO substrates were etched away and the PZT films combined with the polyimide layer could be obtained as the hybrid materials. We have fabricated microactuators for micropumps using this film. The PZT films on the polyimide layer were integrated on Si substrates with microchannel and pressure cavities, and piezoelectric actuation was evaluated using laser Doppler displacement meter. We have observed clear piezoelectric displacement as high as 250nm at 10V, indicating the hybrid piezoelectric materials is useful for the MEMS applications.
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Shinichi YOKOTA, Ryutaro ABE, Kazuya EDAMURA
Article type: Article
Pages
227-228
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Electro-Conjugate Fluid (ECF) is a kind of dielectric fluids and a kind of functional fluids, which produces jet-flow (ECF-jet) by applying high voltage between electrodes. The ECF-jet genreated between needle-type electrodes and ring-type electrodes is called ECF-jet with needle-type electrodes. It is ascertained that the pressure due to ECF-jet with needle-type electrodes is increased by miniaturizing dimensions of the electrodes. The characteristics are suitable for microactuator. Therefore, the purpose of this study is the realization of novel micro manipulators using ECF-jet. In this paper, first, characteristics of ECF-jet with needle-type electrode are experimentally investigated. Second, a novel microactuator which is actuated by the same principle as well-known Bourdon tubes is proposed and fabricated. Third, static characteristics of the microactuator is experimentally investigated. Finally, another type microactuator, two-degree-of-freedom micro ECF manipulator is proposed and fabricated. Future works are fabrication and investigation of a microhand constructed with more than three micromanipulators.
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Kazuhiro YOSHIDA, Yeon Oh JUNG, Takeshi SETO, Kunihiko TAKAGI, Jung Ho ...
Article type: Article
Pages
229-230
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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For fluid microactuators and microfactory, the authors have proposed a novel high output micropump using inertia effect of fluid which has a pipeline element in place of an outlet check valve and verified the effectiveness with a fabricated micropump. To increase the output power and to miniaturize the size, the paper establishes a simple mathematical model with lumped parameters and verifies the effectiveness comparing the simulation and experimental results. Also, the optimal pump structure is investigated through simulations.
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Yoshihiko HIMURA, Toru WATANABE, Kazuto SETO
Article type: Article
Pages
231-232
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This study deals with a fundamental research on non-contact control of vibration by utilizing acoustic radiation pressure. To obtain direct control system of acoustic radiation pressure by applying feedback control theories, transfer function from certain control input to acoustic radiation pressure as an output is needed. In this report, the frequency transfer function is measured by using an experimental system of oscillating current is controlled electromechanically as a control input. The property of obtained transfer functions is discussed precisely. Moreover, the applicability of electronic control is also considered.
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Naoya IWATA, Tetsuo MIYAKE, Satoshi HORIHATA
Article type: Article
Pages
233-234
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Various applications such as the construction of 3D shape search engine for finding similar shape, the estimation of deformation measure from standard object, and design and design evaluations of product become possible if similarity between two shapes can be estimated based on proper information that does not depend on the posture of the object. In this study, we propose a method for estimating the similarity measure of 3D shapes. The similarity is defined by the spectrum that is obtained from expansion coefficients of spherical harmonic function in relation to shape characteristics. Simulation using an area and a perimeter of multidirectional projected images of the 3D object as the shape characteristics shows the validity of this method.
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Kenta KAIDOU, Shigeharu MIYATA
Article type: Article
Pages
235-236
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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There is a research for an augmented desk type interface system that offers the environment that manipulates both a virtual object projected and a real object on the desk with their own hands. As an application of this system, the tool drawing and moving figures on the desk with fingertips was suggested. In this paper, aiming at the construction of the above system, we propose a method for manipulating the virtual object on the monitor, while tracking the fingertip using local correlation matching between successive image frames. We consider the software algorithm for moving and rotating the virtual objects.
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Shigeharu MIYATA, Kenta KAIDO
Article type: Article
Pages
237-238
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The teleoperation system via internet communication for rescue operation in a disaster area or a danger one attracts public attention, with the advance of information technology and robotic one. We made the small vehicle without a camera, maneuvered precisely via internet by the client PC. In order to improve the operability of the vehicle, the vehicle needs to mount the camera, which is able to be panned. This repot describes the teleoperation system for the camera and its motor driver's module. The control of camera pan angle is done by a input module with dial, which is advantageous for human-computer interaction.
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Sumio TAKAMATSU, Hiroyuki UKIDA, Katsunobu KONISHI
Article type: Article
Pages
239-240
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, we propose a shape reconstruction method combining a binocular stereo method and a photometric stereo method with three light sources. From a stereo images taken by a stereo image scanner, first, we estimate heights at edge points on the object by the binocular stereo method. Next, we obtain the albedo on the object surface near edge points by using estimated height. And we recover the object shape by the photometric stereo method with estimated albedos. In the experimental results, we show the effectiveness of the proposed method by recovering a cylindrical object shape from real stereo images.
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Kazuma AOKI, Hiroyuki UKIDA, Katsunobu KONISHI
Article type: Article
Pages
241-242
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In the computer vision, it is important problem to recover a three-dimensional object from a two-dimensional image. Because, in the industry field, it is necessary to develop a vision system to improve productivity and efficiency. But this problem is very difficult and there are various devices were studied. However there are some problems using these devices, it costs much time to measure the 3D shape, the resolution of shape data is low, and the devices are very expensive. In this paper, to improve such problems, we propose the method to recover the 3D shape of an object using a color image scanner which has three light sources. By using the image scanner, the 3D shape data will be able to get more easily. Hence, our final goal is to change the image scanner into the shape scanner.
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Tsuyoshi TAKAMA, Hiroyuki UKIDA, Katsunobu KONISHI
Article type: Article
Pages
243-244
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In the field of the computer vision, it is important to recover the three-dimensional scene from the two-dimensional images. In this study, we address the depth measuring by the pattern projection. The method of using two cameras is proposed as a general method for the depth measuring. In this method, the depth from the target object to the camera cannot be measured for some objective shape, surface pattern, etc. In this study, we put on a projector one side of two viewpoints in the stereo method, and coded pattern images are projected from it to measuring space, and the depth from the target object to the camera is measured from the coded pattern images. In this depth measuring, it is important to investigate the internal parameters and the external parameters of camera and projector. So, in this study, we investigate these parameters by the calibration.
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Masayasu HATAZAWA, Wakana TAKEDA
Article type: Article
Pages
245-246
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Oscillatory flow in the thermoacoustic sound wave generator is described. In oscillatory pipe flow, characteristic Richardson effect occurs in the vicinity of the wall. Its flow plays an important role in thermoacoustic phenomena in which direct energy conversion from heat to work (sound waves), and vice versa, is performed with no moving parts. Also, flow in the resonance tube is influenced by its flow on the stack. Fluid work in stack and the resonance tube are discussed.
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Mie ISOBE, Souichi SAEKI, Sinichi FUJINAKA, Kakuji OGAWARA
Article type: Article
Pages
247-248
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, presented is an experimental study of thermal flow-induced vibration in a looped heat pipe. Pressure and temperature variation inside the tubes was measured to investigate the oscillation mechanism. It was heated at the bottom to control temperature by circulator, while was cooled at the top to keep temperature constant. Two kinds of oscillation are observed; i. e. vertical oscillation of liquid column and the rapid vibration over adjacent turns. As a result of measurement, temperature difference between adjacent adiabatic tubes is found to be excited qusi-periodically, just when the pressure difference abruptly becomes large. In contrast, temperature in heat section was observed to decrease due to the movement of liquid column from adiabatic section. Accordingly, boiling liquid could follow the increase in the pressure, which is thought to cause the vibration of over adjacent turns.
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Yuki UEDA, Tethushi BIWA, [in Japanese], Uichiro Mizutani
Article type: Article
Pages
249-250
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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We have built a thermoacoustic engine composed of a regenerator, two heat exchangers and a looped tube. When a temperature gradient is set up along the regenerator by the pair of the heat exchangers, an acoustic wave spontaneously generates. By using pressure sensors, we simultaneously measure the pressure oscillations of the acoustic wave at 15 points along the looped tube. As a result, we found that a traveling acoustic wave runs around the tube and trough the regenerator from its cold to hot ends.
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Akira NAKAMURA, Nobuyuki TAKENAKA, Masathugu HASE
Article type: Article
Pages
251-252
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Many pipes branch off from the main pipe in plants. When the main flow in the main pipe is hotter than the fluid in a branch pipe that branches off downward, the hot water penetrates into the branch pipe with the cavity flow. The strength of this cavity flow varies with long period. The thermal stratification in the branch pipe is, therefore, fluctuated by this cavity flow. Some experiments and numerical simulations were conducted to investigate this fluctuation in a straight branch pipe. The swirling vortex structures were observed in experiments and numerical simulations. The transient temperatures of the water near the wall in numerical simulation showed good agreement with the experimental results. These fluctuating temperatures were synchronized with the swirling flow velocities in long period. The period of these were about 60-140 seconds. The amplitude of the fluctuating temperature became small with long time span.
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Shinzaburo UMEDA, Seizou HASEGAWA, Masahiro SONOO, Wen Jei YANG
Article type: Article
Pages
253-254
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The flipping and flopping behavior inside diamond-shaped cylinder bundles is a new flow phenomenon in fluids engineering. In order to promote applications and development of flip-flop flow, its quantitative explanation of interaction between the intersecting main streams and wake flow in the diverging-flow region of the flow passages is definitely needed. An experimental study was performed to investigate flow characteristics in the diverging-flow region with flip-flop phenomenon inside diamond-shaped cylinder bundles by means of two-dimensional laser Doppler velocimetry (LDV). The oscillation characteristics of the flip-flop are clarified. It is also disclosed that the flow exhibits the characteristics of a jet tone.
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Naoki NAKATANI, Kakuji OGAWARA, Souichi SAEKI
Article type: Article
Pages
255-256
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper presents a novel actuator for flow control, namely Plasma Synthetic Jet Actuator. This is a glow-discharge actuator, which is composed of the electrodes with AC signal. In this present study, it was applied to the separation control of airfoil. To observe behavior of the actuator, in this experiment, flow visualization was used for flow with Plasma Synthetic Jet Actuator. And the NACA0012 blade, in which this actuator was embedded, was set in the wind tunnel. The wake velocity behind blade was measured with or without operating the actuator. Consequently, the desirable effect of proposed actuator could be observed. These results show that the actuator can execute flow control to the surface on airfoil.
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Hajime Fujita
Article type: Article
Pages
257-258
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The characteristics of the Aeolian tone generated from elliptic and rectangular cylinder with cross sectional aspect ratio of 1 to 4 are studied experimentally. The characteristics of the Aeolian tone from elliptic cylinders are affected by relatively small change of the Reynolds number. The aspect ratio shows some critical value for the occurrence of the reattachment of the flow to the side surface
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Masanori KIKUCHI, Takahide MAEDA, Akio ICHIKAWA, Kimitaka HIRANO
Article type: Article
Pages
259-260
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A new transport system : "Aerotrain" has been recently proposed. It has wings and flies close to ground along a guide way of an open channel. The aerodynamic characteristics of the wing are strongly affected by the ground. In order to elucidate the aerodynamic stability of the aerotrain wing, it is necessary to analyze the ground effects on the unsteady aerodynamic forces and flutter speed. In this paper, the aerodynamic forces and moments on the two dimensional aerofoil are analyzed in the assumption that it is in the proximity to the ground and oscillating in the incompressible flow. The equation of motion of the aerofoil is derived by considering the balance of the inertia, elastic, aerodynamic, and exciting forces. The flutter speeds are obtained by the U-g methods considering a structural damping. The flutter speed is decreased as the center of gravity is shifted to backwards from the pitching axis, when it is close to the ground.
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Takashi ESAKI, Satoshi YOKOTA, Masato MIKAMI, Naoya KOJIMA
Article type: Article
Pages
261-262
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The flow-induced noise was experimentally studied for an expansion-cavity-type muffler with pulsating flow. The resonance noises of the cavity have already been found to have the contribution to the total flow-induced noise from the muffler with pulsating flow. The main sound source in a low-Mach-number flow is pressure fluctuation on the solid boundaries. The distribution of the sound source strength on the inner surface of the cavity was clarified through the correlation analysis between the pressure fluctuation on the inner surface and the radiated sound pressure. The results showed that the sound source strength attained maximum at the exit wall of the cavity, where the jet flow collided. The sound strength depends on both time derivative of the pressure on the surface and correlation area, in which the pressure fluctuation shows simultaneity. The characteristics of sound source were discussed considering the correlation area and the pressure fluctuation strength.
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Kunisato SETO, Md. Tawhidul Islam Khan, Zhi Xiang XU
Article type: Article
Pages
263-264
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Experiments were carried out to eliminate the screech tone generated from a supersonic jet by using a spherical reflector. In order to reduce the jet screech the reflector was placed at the nozzle exit. The placement of the spherical reflector at the nozzle exit controlled the location of the image source as well as minimized the sound pressure at the nozzle exit. The weak sound pressure did not excite the unstable disturbance at the exit. Thus the loop of the feedback mechanism could not be accomplished and the jet screech was eliminated. The technique of screech reduction with a flat plate was also examined and compared with the present method. A good and effective performance in canceling the screech component by the new method was found. Experimental results indicate that the new system suppresses not only the screech tones but also the broadband noise components and reduces the overall noise of the jet. The spherical reflector was found very effective in reducing overall sound pressure level in the upstream region of the nozzle compared to a flat reflector
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Shigeki SUGIMOTO, Kimihiko NAKANO, Takashi SAITO, Toshiaki MAKIMO, Mic ...
Article type: Article
Pages
265-266
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This study treats aluminum alloy double skin structures, utilized for car bodies of high-speed railway vehicles. The vibration characteristics of the structure is calculated using the Finite Element Method to obtain transmissibility and mode shapes. To simplify the model, the authors propose to treat the structures as elastic beams in calculations. The comparisons of the results with the calculation results using a shell model and experimental results show that the proposed method is valid.
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Katsunari Murai, Masashi Shoda, Shigehiko Kaneko, Tatsuo Watanabe
Article type: Article
Pages
267-268
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Recently, research and development of micro gas turbine centered micro co-generation system is conducted actively. To operate such a system, gas compressor is necessary because pressure level in the supply gas pipeline is lower than the required pressure level. It well known that in the gas supply pipeline system pressurized by a reciprocating compressor, pressure pulsation of the supply pipeline is often induced by the resonance of the gas column. In this paper, first we report data observed in the actual system and then propose an idea of countermeasure by utilizing the combination of Roots blower and a small size tank to avoid resonance. We also investigated the effect of anti-resonance device by changing the location of the device through measurement of the pressure level and finally found the optimal location for installing the device.
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Fuminori IWAKI, Ken MITSUBORI, Hidetoshi TAGUCHI, Andrew MECH, Masakaz ...
Article type: Article
Pages
269-270
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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One of the important goals in the design of a turbocharger is to reduce the resonance stress of the turbine blade. The resonance stress is influenced greatly by fluctuations of total pressure at the inlet of the blade. In this study, we have compared two kinds of mixed-flow type casings, Type-α and Type-β, that differ only in tongue geometry. Because of this difference, each casing creates a different pressure distribution at the blade inlet. Total pressure was measured at various circumferential locations in the two turbine casings. Then Fourier analysis was used to calculate the excitation force component caused by the total pressure fluctuations. Also, resonance stress was measured for the turbine blade for each casing. The experiments showed that the Type-β casing experienced higher total pressure fluctuations and produced higher blade resonance stress than the Type-α casing.
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Kenji HIRAKU, Kenichiro TOKUO
Article type: Article
Pages
271-272
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The hydraulic simulator was proposed for designing the high-pressure fuel pump of direct injection gasoline engine. Currently a single-plunger pump is the major trend for high-pressure fuel pump. The advantage of single-plunger pump is simple structure and small size. However, this type of pump has a demerit of large pressure pulsation. Therefore, adjusting the layout of fuel-pipe is the crucial process for removing the pressure pulsation. In addition, fuel flow rate should be improved at high engine speed, and steady flow should be achieved by flow-rate control. Our newly developed hydraulic simulator can evaluate dynamic characteristics of total fuel supply system, which consists of a pump, pipe, injector, etc. The simulation results of the hydraulic simulator coincide with experiment results well. As a result, the improvement of the development speed can be expected with this simulator.
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Ryo TOKUI, Masahiro WATANABE
Article type: Article
Pages
273-274
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper deals with a study of whirling unstable vibration of a rotating cylinder partially submerged in water. In order to investigate the dynamic characteristics and the stability, the displacement of the rotating cylinder is measured with increasing the rotating speed. Experiments are carried out with the variation in the gap width between the rotating cylinder and outer casing, and the depth of the rotating cylinder submersion in water. The results clarify the critical rotational speed at which the unstable vibration occurs and whirling direction. Moreover, it is clarified that the unstable vibration occurs in the forward and backward whirling motion.
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Yuichiro MORIMOTO, Haruki MADARAME, Koji OKAMOTO
Article type: Article
Pages
275-276
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Flow pattern and fluctuation of void fraction of two-phase flow through a vertical channel with contraction were examined experimentally. The two-phase fluid consisted of water and nitrogen gas. The pipe diameters were 0.1[m] and 0.05[m]. which were before and after the contraction, respectively. Superficial gas and liquid velocity were changed form 0.42 to 2.55[m/s] and from 2.26 to 4.53[m/s]. Time series data of void fraction were measured using a single-needle void probe and flow pattern at downstream from the contraction was visualized using a high speed video camera. Intermittent flow was observed at downstream of the contraction. The pulsation can be seen to be caused by wave of bubbles thick and thin. Frequency of fluctuation of the void fraction was almost constant when flow pattern before the contraction was bubble flow. In the case where flow pattern before the contraction was churn flow, the frequency increased with superficial liquid velocity. The frequency was also confirmed with the result of image processing using the movies captured by the high speed video camera.
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Takashi NISHIHARA, Shigehiko KANEKO, Tatsuo WATANABE
Article type: Article
Pages
277-278
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Fluid force acting on a circular cylinder oscillating in the streamwise direction in a cross flow was measured by forced oscillation test in a water tunnel under the condition of low reduced velocity and small cylinder amplitude. Added mass and added damping coefficients were calculated based on the measured dynamic drag. They reasonably explain the characteristics of the in-line oscillation such as soft oscillator in the 1st excitation region and hysteresis in the 2nd excitation region. The mean drag coefficient and dynamic lift coefficient attain to their maximum at the reduced velocity between the 1st and 2nd excitation region where the added damping coefficient has its local maximum. It suggests that the increase of the mean drag coefficient induced by the formation of alternate vortices magnifies fluid damping effect and it contributes to the damping region between the 1st and 2nd excitation region.
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Njuki W. MUREITHI, Tomomichi NAKAMURA
Article type: Article
Pages
279-280
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper presents some results of a group theoretic analysis of a 2D cylinder wake under forced excitation. Both inflow and cross-flow cylinder excitations are considered. For inflow excitation, subharmonic bifurcations are shown to be the dominant dynamic phenomenon. The existence of the instability is confirmed by considering general maps equivariant relative to the general wake symmetry. Interestingly inflow (rather than cross-flow) cylinder oscillations are found to be more effective for the control of vortex shedding.
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Baoshan ZHU, Kyoji KAMEMOTO, Tomohiro SATO
Article type: Article
Pages
281-282
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, the influence of impact or intermittent touching between a flow-induced oscillating circular cylinder and an obstacle structure was investigated experimentally. The cross-flow vibrations of the circular cylinder touching with the obstacle were obtained in a water tank. Results show that when a circular cylinder of cantilever vibrating in a uniform flow meets with restriction of collision with another structure, the oscillation characteristics seem to change from those at free oscillation to other different ones. It is conformed that the impact does not necessarily reduce the vortex-induced vibration of the cylinder, and under specific conditions, however, it may possibly cause the increase of vibration amplitude to some extent.
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Hiromitsu HAMAKAWA, Tohru FUKANO, Kiyoshi AIDA, Kouichiro MORI
Article type: Article
Pages
283-284
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In the present paper the attention is focused on the vortex shedding from the tube banks with acoustic resonance which occurred in the two-dimensional model of boiler. There were three sets of in-line tube banks which installed rigidly in the model. We measured the sound pressure level, phase delay of acoustic pressures, velocity fluctuation and the gap velocity. As a result, we found many peak frequencies of SPL with different Strouhal numbers, mainly about S_t=0.15,0.26 and 0.52. The vortex shedding of S_t=0.15 were generated inside of the tube banks without acoustic resonance. When the acoustic resonance occurred, the vortex was shed at the resonant frequencies, mainly about 395 (S_t=0.15), 765 (S_t=0.26) and 1110Hz (S_t=0.52). The resonant noise at 395Hz (S_t=0.15) generated from the space between two sets of tube banks. Using the node number of acoustic pressure mode in longitudinal and transverse direction, the resonant frequency of 395Hz (S_t=0.15) was (1,2) mode, 765Hz (S_t=0.26) was (1,4) mode, and 1128Hz (S_t=0.52) was (0,8) mode.
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Tomomichi NAKAMURA, Kengo SHIMAMURA, Toshihiko IWASE, Seishi NISHIDA
Article type: Article
Pages
285-286
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The fluidelastic instability threshold of tube arrays can be estimated with the measured unsteady fluid force, usually assumed that the fluid force is completely correlated along the tube axis. However, the flow in the two-phase flow is no longer steady, in space or in time. Thus, the correlation of the fluid force acting along the tube axis should be introduced. In this report, the average correlation length is derived from critical flow velocities of U-bend tubes in several two-phase flow conditions, based on the approximate theory for the two-phase flow condition when the unsteady fluid force for a short span model has been measured. As a result, the average correlation length gives the critical flow velocities of each U-bend tube. The result gives a good explanation why the critical factor in the U-bend tube is larger than that in short span models.
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Arata MOTOKI, Kiyotaka YAMASHITA, Jun AGATA, Masatsugu YOSHIZAWA
Article type: Article
Pages
287-288
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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It is now well-known that a cantilevered pipe conveying fluid is subject to an instability as flow velocity is increased. In this paper, the experimental results for 2nd-mode and 3rd-mode flutters of a fluid-conveying cantilevered pipe with a rigid cylindrical end mass and spring supported are presented. The experiments were conducted with the silicon rubber pipe conveying fluid. The lateral oscillation of a fluid-conveying cantilevered pipe was measured by the image processing system. The system is based on the images from two CCD cameras. The features of the self-excited vibrations were investigated by the linear analysis and confirmed qualitatively by the experimental results. Furthermore the phenomenon was observed to be supercritical condition or subcritical condition from the viewpoint of nonlinear stability.
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Eiji TACHIBANA, Masahiro WATANABE, Kensuke HARA, Nobuyuki KOBAYASHI
Article type: Article
Pages
289-290
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper deals with a theoretical study of in-plane parametric vibrations of a curved bellows subjected to oscillating internal fluid pressure excitation. In the theoretical analysis, the curved bellows is modeled as a combination of beam models including the effect of the internal fluid and fluid pressure by the finite element method. Mathieu's type equation is derived from the basic equation of the bellows. The natural frequencies of the curved bellows and the parametric instability boundaries are examined. As a result, the curved bellows have two types of parametric vibrations, longitudinal and transverse vibrations. The longitudinal parametric instability boundaries become broader with increasing the curved ratio of the bellows. On the other hand, the transverse parametric instability boundaries become narrower.
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Mikael A. LANGTHJEM, Hideyuki MORITA, Tomomichi NAKAMURA, Masami NAKAN ...
Article type: Article
Pages
291-292
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A mathematical model of a slender, flexible rod in annular leakage flow is discussed. Both laminar and turbulent flow may be possible, and a variety of boundary conditions are considered. Off-set of the equilibrium position of the rod is also included. The equations of motion for the fluid and the rod are discretized by application of the finite element method. Stability analysis of the small oscillations of the rod about its equilibrium position is described.
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Daisuke INAMURA, Masahiro WATANABE
Article type: Article
Pages
293-294
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper deals with an experimental study on flow induced vibration of an elastic orifice. In the experiment, the vibration of the orifice plate is measured with increasing the flow rate. Moreover, the behavior of fluid flow is visualized when the orifice plate undertakes unstable vibration. From the experimental results, it is clarified that the unstable vibration occurs to the elastic orifice in the opposite phase mode. The critical flow rates of unstable vibration are depended on the gap width and the rigidity of the orifice plate. The unstable vibration occurs coupled with the switching phenomenon of the jet flow.
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