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When a flexible plate of machines and structures is in axial flow, increasing the flow velocity induces the dynamic instability. Also, the similar instability occurs for a thin film wound to a coil form and a band saw driven with high transport speed even if we consider there is no effect of fluid. However, if a flexible plate is very light, and the rigidity is weak, the dynamic instability of a plate is thought to be affected both by the transport speed of plate and by the surrounding fluid. In this paper, the stability analysis is performed using the velocity potential based on the boundary conditions between the surrounding fluid and the plate. The numerical studies are performed as for a cantilevered plate. The case of an axially moving plate in a still fluid, the case of a stationary plate subjected to an axial flow, and the case of an axially moving plate in neglecting the effect of surrounding fluid are examined. And, the effect of the transport speed of cantilevered plate on the dynamic stability is discussed. Furthermore, another stability analysis is also performed by using the non-circulatory aerodynamic theory, and the numerical analysis results are examined and discussed.Copyright © 2015 by ASME

Background: To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system. Methods and Materials: During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch. Results: The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position. Conclusion: The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.

When thin cylindrical shells having freely supported end such as heat-shielding shells of after-burners, labyrinth air seals and annular structures in large diameter pipings are subjected to axial annular flow, an unstable vibration and a fatigue failure are apt to be occurred. In this paper, the unstable vibration of thin cylindrical shells is investigated cconsidering the fluid structure interaction between shells and fluid flowing through a narrow passage. The coupled equation of motion between shells and fluid is derived using Flugge's shell theory and Navier-Stokes equation. Especially, focusing on the higher circumferential vibrations, the unstable phenomenon of thin cylindrical shells is clarified by using root locus based on the complex eigenvalue analysis by using the mode functions obtained by the exact solution. The influence of shell-dimensions and so forth on the threshold of the instability of the coupled vibration of shells and flowing fluid are investigated and discussed.

A tuned mass damper is usually used to reduce wind-induced vibration of towers and high rise buildings. However it is not so effective for the structures of which the natural frequency is varied for the case of building up bridge-towers. For these structures the semi-active controlling method seems to be effective in reducing the vibration. This paper proposes a new semi-active vibration controlling method and an adaptive tuned mass damper ATMD consists of a pendulum and an analogue controlling system. In this system the tuning condition of the ATMD is realized by retaining the phase lag of the damper mass to the main structure to be 90°. The effectiveness of the proposed ATMD is evaluated analytically and experimentally.

In this paper, the stability of a thin cylindrical sheel subjected to an axial leakage flow is discussed. Here, we focus on a lateral vibration of a cylindrical shell, that is the beam-like vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell's shell theory and the Navier Stokes equation. The influence of the axial velocity on the unstable vibration phenomena is clarified concerning the beam-like vibration mode of a shell. The applicable range of Donnel shell theorry is confirmed for axial leakage flow-induced vibration of a thin cylindrical shell. The numerical results on the shell theory are compared with those on beam theory which have been already reported by the authors. And, the numerical parameter studies are done for several dimensions of shell and fluid.

This paper deals with new-type dynamic vibration absorber for structures such as piping systems, buildings and towers. This dynamic absorber consists of balls and ball cases. It makes use of ball rotation for reducing the vibration of structures. The characteristics are shown as follows : (1) It is simple composition composed of some balls and ball cases and so it is low-cost type; (2) The frequency tuning is unnecessary, and so a preliminary measurement for adjustment is not necessary; (3) It is possible to correspond to any frequency without tuning; (4) It is compact and easy to install on structures. We applied this self-tuning dynamic absorber to a pipe branch of piping system and a view tower as a large structure. The effects of vibration reduction were evaluated by simulation analysis and vibration test using a shaking table.

Purpose To test the accuracy of a system for correcting for the rotational error of the clinical target volume (CTV) without having to reposition the patient using three fiducial markers and two orthogonal fluoroscopic images. We call this system "three-dimensional conformal setup" (3D-CSU). Methods and materials Three 2.0-mm gold markers are inserted into or adjacent to the CTV. On the treatment couch, the actual positions of the three markers are calculated based on two orthogonal fluoroscopies crossing at the isocenter of the linear accelerator. Discrepancy of the actual coordinates of gravity center of three markers from its planned coordinates is calculated. Translational setup error is corrected by adjustment of the treatment couch. The rotation angles (α, β, γ) of the coordinates of the actual CTV relative to the planned CTV are calculated around the lateral ( x ), craniocaudal ( y ), and anteroposterior ( z ) axes of the planned CTV. The angles of the gantry head, collimator, and treatment couch of the linear accelerator are adjusted according to the rotation of the actual coordinates of the tumor in relation to the planned coordinates. We have measured the accuracy of 3D-CSU using a static cubic phantom. Results The gravity center of the phantom was corrected within 0.9 ± 0.3 mm (mean ± SD), 0.4 ± 0.2 mm, and 0.6 ± 0.2 mm for the rotation of the phantom from 0–30 degrees around the x , y , and z axes, respectively, every 5 degrees. Dose distribution was shown to be consistent with the planned dose distribution every 10 degrees of the rotation from 0–30 degrees. The mean rotational error after 3D-CSU was −0.4 ± 0.4 (mean ± SD), −0.2 ± 0.4, and 0.0 ± 0.5 degrees around the x , y , and z axis, respectively, for the rotation from 0–90 degrees. Conclusions Phantom studies showed that 3D-CSU is useful for performing rotational correction of the target volume without correcting the position of the patient on the treatment couch. The 3D-CSU will be clinically useful for tumors in structures such as paraspinal diseases and prostate cancers not subject to large internal organ motion.

Purpose Synchronization of the techniques in real-time tumor-tracking radiotherapy (RTRT) and intensity-modulated RT (IMRT) is expected to be useful for the treatment of tumors in motion. Our goal was to estimate the feasibility of the synchronization from the viewpoint of excessive dose resulting from the use of fluoroscopy. Methods and materials Using an ionization chamber for diagnostic X-rays, we measured the air kerma rate, surface dose with backscatter, and dose distribution in depth in a solid phantom from a fluoroscopic RTRT system. A nominal 50–120 kilovoltage peak (kVp) of X-ray energy and a nominal 1–4 ms of pulse width were used in the measurements. Results The mean ± SD air kerma rate from one fluoroscope was 238.8 ± 0.54 mGy/h for a nominal pulse width of 2.0 ms and nominal 100 kVp of X-ray energy at the isocenter of the linear accelerator. The air kerma rate increased steeply with the increase in the X-ray beam energy. The surface dose was 28–980 mGy/h. The absorbed dose at a 5.0-cm depth in the phantom was 37–58% of the peak dose. The estimated skin surface dose from one fluoroscope in RTRT was 29–1182 mGy/h and was strongly dependent on the kilovoltage peak and pulse width of the fluoroscope and slightly dependent on the distance between the skin and isocenter. Conclusion The skin surface dose and absorbed depth dose resulting from fluoroscopy during RTRT can be significant if RTRT is synchronized with IMRT using a multileaf collimator. Precise estimation of the absorbed dose from fluoroscopy during RT and approaches to reduce the amount of exposure are mandatory.

Hysteresis elements such as elasto-plastic dampers are important elements for mechanical structures, especially for earthquake-proof structures. When such nonlinear supports are utilized for piping systems, the nonlinearities of the hysteresis elements and the geometrical complexity of the piping systems lead to complicated seismic responses, and thus further studies are required in order to enhance the reliability of the earthquake-proof design. In the seismic response analysis, the method of time history response analysis is widely used. In this paper, a method of nonlinear seismic response analysis for a piping systems using a combination of the FEM and the Differential Algebraic Equations (DAE) is proposed. As it is well known, the DAE is suitable for numerical analysis of time history responses for mechanical structures and machinery elements. According to the advantage of the DAE, the numerical modeling and simulation of a complex piping systems supported by the hysteresis elements can be easily carried out by using the proposed method. In order to verify the usefulness of the method, the time history responses of piping systems supported by a elasto-plastic damper is examined for seismic excitation by using the proposed method. The damper is modeled as a bilinear model. The effects of the second stiffness and the stiffness associated with the plastic deformation of the damper on the seismic responses are investigated using an actually recorded earthquake motion.

Hysteresis elements such as elasto-plastic dampers are important for mechanical structures. They have nonlinearities and thus the vibration characteristics of mechanical structures with hysteresis elements are not clarified yet and need further studies. In this paper, the investigation of the dynamical stability of mechanical structures with a hysteresis element is performed by means of describing function method, which is on the basis of linear approximation of the hysteresis element. The nonlinear vibration system is composed of a linear spring-mass-damper structure system of any order and a hysteresis damper. The describing function of a hysteresis damper is derived and it is shown that the function remains upper half plane in the complex plane. According to the passivity of the linear structure system, this fact leads to the vibration system that is stable for any harmonic excitation. Next, the responses for seismic excitation are examined in simulation by using two typical models of the hysteresis element, a bilinear model and a Ramberg-Osgood model. The effects of the second stiffness of the dampers and the amplitude of the excitation motion are investigated using an actually recorded earthquake motion. The simulation results imply that the determination of the second stiffness requires the trade-off between an oscillation and a drift for designing earthquake-proof mechanical structures with the hysteresis damper.

In this paper, the stability of the thin cylindrical shell subjected to an axial leakage flow is reported. We focus on the circumferential (ovaling) vibration of a shell in this study. Equations for a shell and a fluid are described by the Donnell's shell theory, and the Navier-Stokes equation respectively, and the coupled equations are derived. As a result, the added mass, added damping and added stiffness are calculated. The influence of the axial velocity on the unstable phenomena is clarified. The numerical simulations are shown as parameter studies.

Vibrational mechanisms of flow-induced vibration of a coil spring due to fluid flow were investigated and the mitigation methods were suggested. At first, as one of those vibrational behaviors, flow-induced vibration of a coil spring with a circular rod in the middle of it due to an axial flow was investigated experimentally using fundamental test apparatus. The effects of stiffness of springs, gap between springs and inner rod and initial compression of springs on the vibrational behavior were clarified, and a stability diagram is presented for the spring vibration. Based on the experimental results, the vibrational mechanisms of the coil spring with an inner rod were investigated. Finally, a design instruction on the mitigation of flow-induced vibration of coil springs including the cases of cross-flow-induced vibration and the axial-flow-induced vibration of a spring without an inner rod was summarized and suggested.

To reduce wind-induced vibration of tall buildings and bridge towers, tuned mass dampers are often used. These dampers are called “passive type” while the methods which reduce the vibration by controlling the motion of a large mass with an actuator are called “active type”. For these types we have to change or control the structural vibration characteristics themselves, therefore they need very large exciting forces, and the system will become very large for large structures. In this view point, new concepts have just begun to be studied, where the driving forces themselves will be controlled. In this paper, we proposed a new system for reducing the flow-induced vibration of the structures by utilizing fluid excitation force itself. In this system, as we control the direction of the driving forces, this system does not need so large control forces and the system becomes smaller and simpler. We investigated the feasibility of this system when applied to a bridge, a building and evaluated the effectiveness of driving forces by the wind test using a reduced scale model.

In this paper, the stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the first part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on axisymmetric vibration, that is, the ringlike vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell’s shell theory and the Navier-Stokes equation. The added mass, added damping and added stiffness matrices in the coupled equations are described by utilizing unsteady fluid forces on a shell. The influence of the axial flow velocity on the unstable phenomena is clarified concerning axisymmetric vibration mode of shell. The numerical calculations are performed taking the dimensions of shell and fluid as parameters.

In this paper, the stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the second part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on lateral vibration, that is, the beamlike vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell’s shell theory and the Navier-Stokes equation as same as the former paper. The influence of the axial velocity on the unstable vibration phenomena is clarified concerning the beamlike vibration mode of a shell. The numerical results on shell theory are compared with the ones on beam theory which have been already reported by the authors; and the numerical parameter studies are done for various dimensions of a shell and a fluid.

To investigate the three-dimensional (3D) intrafractional motion of liver tumors during real-time tumor-tracking radiotherapy (RTRT).The data of 20 patients with liver tumors were analyzed. Before treatment, a 2-mm gold marker was implanted near the tumor. The RTRT system used fluoroscopy image processor units to determine the 3D position of the implanted marker. A linear accelerator was triggered to irradiate the tumor only when the marker was located within a permitted region. The automatically recorded tumor-motion data were analyzed to determine the amplitude of the tumor motion, curve shape of the tumor motion, treatment efficiency, frequency of movement, and hysteresis. Each of the following clinical factors was evaluated to determine its contribution to the amplitude of movement: tumor position, existence of cirrhosis, surgical history, tumor volume, and distance between the isocenter and the marker.The average amplitude of tumor motion in the 20 patients was 4 +/- 4 mm (range 1-12), 9 +/- 5 mm (range 2-19), and 5 +/- 3 mm (range 2-12) in the left-right, craniocaudal, and anterior-posterior (AP) direction, respectively. The tumor motion of the right lobe was significantly larger than that of the left lobe in the left-right and AP directions (p = 0.01). The tumor motion of the patients with liver cirrhosis was significantly larger than that of the patients without liver cirrhosis in the left-right and AP directions (p0.004). The tumor motion of the patients who had received partial hepatectomy was significantly smaller than that of the patients who had no history of any operation on the liver in the left-right and AP directions (p0.03). Thus, three of the five clinical factors examined (i.e., tumor position in the liver, cirrhosis, and history of surgery on the liver) significantly affected the tumor motion of the liver in the transaxial direction during stereotactic irradiation. Frequency analysis revealed that for 9 (45%) of the 20 tumors, the cardiac beat caused measurable motion. The 3D trajectory of the tumor showed hysteresis for 4 (20%) of the 20 tumors. The average treatment efficiency of RTRT was 40%.Tumor location, cirrhosis, and history of surgery on the liver all had an impact on the intrafractional tumor motion of the liver in the transaxial direction. This finding should be helpful in determining the smallest possible margin in individual cases of radiotherapy for liver malignancy.