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365 results on '"Yasuda, Tatsuya"'

1. Stabilising nonlinear travelling waves in pipe flow using time-delayed feedback

Author

Yasuda, Tatsuya and Lucas, Dan

Subjects
Physics - Fluid Dynamics
Abstract

We demonstrate the first successful non-invasive stabilisation of nonlinear travelling waves in a straight circular pipe using time-delayed feedback control (TDF). The main novelty in this work is in the application of a "multiple time-delayed feedback" (MTDF) approach, where several control terms are required to attenuate a broad range of unstable eigenfrequencies. We implement a gradient descent method to dynamically adjust the gain functions, $G_i(t),$ in order to reduce the need for tuning a high dimensional parameter space. We consider the effect of the control terms via an approximate linear analysis and a frequency-domain analysis, which justifies the choice of MTDF parameters. By using an adaptive approach to setting the control gains, we advocate for a broad range of MTDF terms which are then free to find their own stabilising amplitudes for a given target solution, thereby removing trial and error when the instability of the target solution is unknown a'priori. This also enables travelling waves to be stabilised from generic turbulent states and with speculative starting parameters.

Published
2024

5. Stabilisation of exact coherent structures in two-dimensional turbulence using time-delayed feedback

Author

Lucas, Dan and Yasuda, Tatsuya

Subjects
Physics - Fluid Dynamics
Abstract

Time-delayed feedback control, attributed to Pyragas (1992 Physics Letters 170(6) 421-428), is a method known to stabilise periodic orbits in low dimensional chaotic dynamical systems. A system of the form $\dot{\mathbf{x}}(t)=f(\mathbf{x})$ has an additional term $G(\mathbf{x}(t)-\mathbf{x}(t-T))$ introduced where $G$ is some `gain matrix' and $T$ a time delay. The form of the delay term is such that it will vanish for any orbit of period $T,$ therefore making it also an orbit of the uncontrolled system. This non-invasive feature makes the method attractive for stabilising exact coherent structures in fluid turbulence. Here we begin by validating the method for the basic flow in Kolmogorov flow; a two-dimensional incompressible Navier-Stokes flow with a sinusoidal body force. The linear predictions for stabilisation are well captured by direct numerical simulation. By applying an adaptive method to adjust the streamwise translation of the delay, a known travelling wave solution is able to be stabilised up to relatively high Reynolds number. We discover that the famous `odd-number' limitation of this time-delayed feedback method can be overcome in the fluid problem by using the symmetries of the system. This leads to the discovery of 8 additional exact coherent structures which can be stabilised with this approach. This means that certain unstable exact coherent structures can be obtained by simply time-stepping a modified set of equations, thus circumventing the usual convergence algorithms., Comment: Published at Phy. Rev. Fluids

Published
2020
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8. Periodic orbits in Large Eddy Simulation of Box Turbulence

Author

van Veen, Lennaert, Martin, Alberto Vela, Kawahara, Genta, and Yasuda, Tatsuya

Subjects
Physics - Fluid Dynamics, 76F05, 76F20
Abstract

We describe and compare two time-periodic flows embedded in Large Eddy Simulation (LES) of turbulence in a three-dimensional, periodic domain subject to constant external forcing. One of these flows models the regeneration of large-scale structures that was observed in this geometry by Yasuda et al. ({\sl Fluid Dyn. Res.} {\bf 46}, 061413, 2014), who used a smaller LES filter length and thus obtained a greater separation of scales of coherent motion. We speculate on the feasibility of modelling the regenerative dynamics with time-periodic solutions in such a flow, which may require novel techniques to deal with the extreme ill-conditioning of the associated boundary value problems.

Published
2018
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9. Transitions in large eddy simulation of box turbulence

Author

van Veen, Lennaert, Kawahara, Genta, and Yasuda, Tatsuya

Subjects
Physics - Fluid Dynamics, Nonlinear Sciences - Chaotic Dynamics, 76F06, 35B32
Abstract

One promising decomposition of turbulent dynamics is that into building blocks such as equilibrium and periodic solutions and orbits connecting these. While the numerical approximation of such building blocks is feasible for flows in small domains and at low Reynolds numbers, computations in developed turbulence are currently out of reach because of the large number of degrees of freedom necessary to represent Navier-Stokes flow on all relevant spatial scales. We mitigate this problem by applying large eddy simulation (LES), which aims to model, rather than resolve, motion on scales below the filter length, which is fixed by a model parameter. By considering a periodic spatial domain, we avoid complications that arise in LES modelling in the presence of boundary layers. We consider the motion of an LES fluid subject to a constant body force of the Taylor-Green type as the separation between the forcing length scale and the filter length is increased. In particular, we discuss the transition from laminar to weakly turbulent motion, regulated by simple invariant solution, on a grid of $32^3$ points.

Published
2017
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10. Spatio-temporal intermittency of the turbulent energy cascade

Author

Yasuda, Tatsuya and Vassilicos, John Christos

Subjects
Physics - Fluid Dynamics
Abstract

In incompressible and periodic statistically stationary turbulence, exchanges of turbulent energy across scales and space are characterised by very intense and intermittent spatio-temporal fluctuations around zero of the time-derivative term, the spatial turbulent transport of fluctuating energy, and the pressure-velocity term. These fluctuations are correlated with each other and with the intense intermittent fluctuations of the interscale energy transfer rate. These correlations are caused by the sweeping effect, the link between non-linearity and non-locality, and also relate to geometrical alignments between the two-point fluctuating pressure force difference and the two-point fluctuating velocity difference in the case of the correlation between the interscale transfer rate and the pressure-velocity term. All these processes are absent from the spatio-temporal average picture of the turbulence cascade in statistically stationary and homogeneous turbulence.

Published
2017
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25. Fast Response, High‐Power Tunable Ultrathin Soft Actuator by Functional Piezoelectric Material Composite for Haptic Device Application (Adv. Electron. Mater. 9/2023)

Author

Shouji, Yoshinori, primary, Sekine, Tomohito, additional, Ito, Keita, additional, Ito, Naoya, additional, Yasuda, Tatsuya, additional, Wang, Yi‐Fei, additional, Takeda, Yasunori, additional, Kumaki, Daisuke, additional, Santos, Fabrice Domingues Dos, additional, Miyabo, Atsushi, additional, and Tokito, Shizuo, additional

Published
2023
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31. Preoperative and Postoperative Sitting Radiographs for Adult Spinal Deformity Surgery: Upper Instrumented Vertebra Selection Using Sitting C2 Plumb Line Distance to Prevent Proximal Junctional Kyphosis

Author

Yoshida, Go, Ushirozako, Hiroki, Hasegawa, Tomohiko, Yamato, Yu, Kobayashi, Sho, Yasuda, Tatsuya, Banno, Tomohiro, Arima, Hideyuki, Oe, Shin, Mihara, Yuki, Ide, Koichiro, Watanabe, Yuh, Yamada, Tomohiro, Togawa, Daisuke, and Matsuyama, Yukihiro

Published
2020
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38. Long additional rod constructs can reduce the incidence of rod fractures following 3-column osteotomy with pelvic fixation in short term

Author

Yamato, Yu, Hasegawa, Tomohiko, Togawa, Daisuke, Yoshida, Go, Banno, Tomohiro, Arima, Hideyuki, Oe, Shin, Mihara, Yuki, Ushirozako, Hiroki, Yasuda, Tatsuya, and Matsuyama, Yukihiro

Abstract

Study design: A retrospective analysis of a prospectively collected consecutive case series of patients with adult spinal deformity who underwent 3-column osteotomy (3-CO) with pelvic fixation. Objectives: The objectives were to verify the effect of additional rods and determine the optimal type of additional rod for preventing rod fracture (RF). Summary of background data: RF is a frequent complication following 3-CO surgery in patients with adult spinal deformity. Two types of additional rod constructs were utilized to prevent RF. Methods: We evaluated data retrieved from a prospectively collected single-center database. Patients were classified into two groups depending on rod constructs: conventional 2-rod and 2-rod constructs with additional rods. The additional rod constructs were also stratified into two groups according to the location that they covered: only osteotomy site (short additional rod) or osteotomy site and lumbosacral junction (long additional rod). Results: A total of 48 patients (average age 67.6 years; follow-up rate: 90.6%; 2-rod: 25 cases and additional rod: 23 cases) were included. No significant difference was observed in age, fusion level, operation time, blood loss, and rod composition. The incidence of RF in the additional rods (36%) was significantly lower than that in the 2-rod constructs (68%). Comparing the additional rod constructs, RF occurred in 7 cases (64%) in short additional rod and 2 cases (17%) in long additional rod. RF occurred at the level below the additional rod construct in 6 of 7 RF cases with short additional rod. Conclusions: Additional rods covering the osteotomy site and lumbosacral junction reduced the incidence of RF following 3-CO surgery with pelvic fixation in short term. Level of evidence: 3.

Published
2024
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46. Risk Factors for Cervical Deformity After Posterior Cervical Decompression Surgery: A Multicenter Study.

Author

Oe, Shin, Kurosu, Kenta, Hasegawa, Tomohiko, Shimizu, Satoshi, Yoshida, Go, Fujita, Tomotada, Kobayashi, Sho, Yamada, Tomohiro, Ide, Koichiro, Nakai, Keiichi, Yotsuya, Kumiko, Yamato, Yu, Yasuda, Tatsuya, Banno, Tomohiro, Arima, Hideyuki, Mihara, Yuki, Ushirozako, Hiroki, Watanabe, Yuh, and Matsuyama, Yukihiro

Subjects
SPINAL surgery, SURGICAL decompression, LAMINECTOMY, CERVICAL spondylotic myelopathy, MULTIPLE regression analysis, LOGISTIC regression analysis
Abstract

Study Design: Retrospective multicenter study. Objective: Posterior decompression surgery for cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL) is a common surgery; however, it can cause postoperative cervical deformity (CD). The purpose of this study was to investigate the risk factors for CD. Methods: The participants were 193 patients underwent laminoplasty or laminectomy for CSM or OPLL. CD was defined as a C2-7 sagittal vertical axis (SVA) ≥ 40 mm or a cervical lordosis angle (CL) ≤ −10°. The participants were divided into 2 groups: NCD (without CD before surgery), CD (with CD before surgery). NCD group was divided based on the presence of CD 1 year after surgery as follows: postoperative CD (PCD) and no PCD (NPCD). Results: There were 153 patients (NCD), 40 (CD), 126 (NPCD), and 27 (PCD). There was significant difference in the number of decompressed lamina (NPCD: PCD = 4.1:4.5), the presence of C2 decompression (2: 11%), and C5 palsy (0: 11%). The risk factors for onset of CD, PCD, and CL ≤ −10° as assessed by multiple logistic regression analysis were preoperative C2-7 SVA ≥ 30 mm (odds ratio [OR]: 19.0), decompression of C2 or C7 lamina (OR 3.1), and preoperative CL ≤ 2° (OR 42.0), respectively. Conclusions: To prevent postoperative CD, it is important to avoid decompression of the C2 or C7 lamina. Moreover, in case with C2-7 SVA ≥ 30 mm or CL ≤ 2° before surgery, it is important to explain the risks and consider adding fusion surgery. [ABSTRACT FROM AUTHOR]

Published
2023
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47. Selective Angiography to Detect Anterior Spinal Artery Stenosis in Thoracic Ossification of the Posterior Longitudinal Ligament

Author

Yoshida, Go, primary, Ushirozako, Hiroki, additional, Hasegawa, Tomohiko, additional, Yamato, Yu, additional, Yasuda, Tatsuya, additional, Banno, Tomohiro, additional, Arima, Hideyuki, additional, Oe, Shin, additional, Mihara, Yuki, additional, Yamada, Tomohiro, additional, Ide, Koichiro, additional, Watanabe, Yuh, additional, Ushio, Takasuke, additional, and Matsuyama, Yukihiro, additional

Published
2022
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48. Clinical outcome of condoliase injection treatment for lumbar disc herniation: Indications for condoliase therapy

Author

Banno, Tomohiro, Hasegawa, Tomohiko, Yamato, Yu, Yoshida, Go, Yasuda, Tatsuya, Arima, Hideyuki, Oe, Shin, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yu, Matsuyama, Yukihiro, Banno, Tomohiro, Hasegawa, Tomohiko, Yamato, Yu, Yoshida, Go, Yasuda, Tatsuya, Arima, Hideyuki, Oe, Shin, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yu, and Matsuyama, Yukihiro

Abstract

BackgroundCondoliase is a novel, potent chemonucleolytic drug available for clinical use for lumbar disc herniation (LDH) in Japan. The aim of this study was to assess the clinical outcome of condoliase therapy in patients with LDH, as well as factors affecting the clinical outcome.MethodsWe enrolled patients with LDH who were receiving condoliase injection. The following baseline data were collected: symptom duration; herniation level and type; T2 signal intensity of herniation; adverse events; rates of spondylolisthesis, posterior intervertebral angle of ≥5°, and vertebral body translation of ≥3 mm. Change in disc height, disc degeneration, herniation size, visual analogue scale (VAS) for leg and back pain, and Oswestry Disability Index (ODI) were evaluated at the baseline, and 3-month follow-up. These data were compared between patients with efficacious (VAS improvement of ≥20 mm; group E) and inefficacious (VAS improvement <20 mm or required operation; group I) for condoliase treatment.ResultsForty-seven patients (20 women, 27 men; mean age 48 years) were included. The herniation level was L2/3 in one patient, L3/4 in two, L4/5 in 23, and L5/S1 in 21. Median symptom duration was 8 months. The mean VAS and ODI improved significantly from the baseline to 3-month follow-up (p<0.01). Group E included 33 patients (70.2%) and group I included 14, three of whom had a history of discectomy. The rates of spondylolisthesis and posterior intervertebral angle ≥5° were significantly higher in group I than in group E. However, the rates of trans-ligamentous type and herniation with high signal intensity on T2-weighted images (highT2) were significantly higher in group E. Reduction of disc herniation was more frequently observed in group E.ConclusionsCondoliase injection resulted in significantly improved symptoms in patients with LDH. Condoliase therapy was less effective for patients with a history of discectomy, spondylolisthesis, or those with a posterior intervertebral an

Published
2022

49. Planned two-stage surgery using lateral lumbar interbody fusion and posterior corrective fusion: a retrospective study of perioperative complications

Author

Yamato, Yu, Hasegawa, Tomohiko, Yoshida, Go, Yasuda, Tatsuya, Banno, Tomohiro, Oe, Shin, Arima, Hideyuki, Mihara, Yuki, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yuh, Matsuyama, Yukihiro, Yamato, Yu, Hasegawa, Tomohiko, Yoshida, Go, Yasuda, Tatsuya, Banno, Tomohiro, Oe, Shin, Arima, Hideyuki, Mihara, Yuki, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yuh, and Matsuyama, Yukihiro

Abstract

Purpose: To determine the effect of planned two-stage surgery using lateral lumbar interbody fusion (LLIF) on the perioperative complication rate following corrective fusion surgery in patients with kyphoscoliosis.Methods: Consecutive patients with degenerative scoliosis who underwent corrective fusion were divided into a control group that underwent single-stage posterior-only surgery and a group that underwent planned two-staged surgery with LLIF and posterior corrective fusion. We collected the patient background and surgical data and assessed the perioperative complication rates. We also investigated spinopelvic parameters and patient-reported outcome measurements (PROMs).Results: One hundred and thirty-eight patients of mean age 69.8 (range, 50–84) years who met the study inclusion criteria were included. The two-stage group (n=75) underwent a staged anterior-posterior surgical procedure and the control group (n=63) underwent single-stage surgery. There was no significant between-group difference in the incidence of perioperative complications, except for deep wound infection (reoperation is necessary for surgical site infection). Revision surgery within 3 months of the initial surgery was more common in the control group (n=8, 12.7%) than in the two-stage group (n=3, 4.0%). Spinopelvic parameters and PROMs were significantly better in the two-stage group at 2 years postoperatively.Conclusion: The complication rate for planned two-stage surgery was similar to that of previous posterior-only single-stage surgery. However, early reoperation was less common, and the degree of spinal correction and clinical results were significantly better after two-stage surgery.

Published
2022

50. Characteristics affecting cervical sagittal alignment in patients with chronic low back pain

Author

Arima, Hideyuki, Yamato, Yu, Sato, Kimihito, Uchida, Yoshihiro, Tsuruta, Toshiyuki, Hashiguchi, Kanehisa, Hamamoto, Hajime, Watanabe, Eiichiro, Yamanaka, Kaoru, Hasegawa, Tomohiko, Yoshida, Go, Yasuda, Tatsuya, Banno, Tomohiro, Oe, Shin, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yuh, Matsuyama, Yukihiro, Arima, Hideyuki, Yamato, Yu, Sato, Kimihito, Uchida, Yoshihiro, Tsuruta, Toshiyuki, Hashiguchi, Kanehisa, Hamamoto, Hajime, Watanabe, Eiichiro, Yamanaka, Kaoru, Hasegawa, Tomohiko, Yoshida, Go, Yasuda, Tatsuya, Banno, Tomohiro, Oe, Shin, Ushirozako, Hiroki, Yamada, Tomohiro, Ide, Koichiro, Watanabe, Yuh, and Matsuyama, Yukihiro

Abstract

Background. Sagittal spino-pelvic malalignment in patients with chronic low back pain (CLBP) have been reported in the past, which may also affect cervical spine lesions. The purpose of this study is to investigate the cervical alignment in patients with CLBP.Method. Of the patients who visited an orthopedic specialist due to low back pain lasting more than three months, 121 cases (average 71.5 years old, 46 male and 75 female) with whole standing spinal screening radiographs were reviewed (CLBP group). Cervical parameters included cervical lordosis (CL), C2-C7 sagittal vertical axis (C2-7 SVA), and the T1 slope minus CL (T1S-CL). Cervical spine deformity was defined as C2-7 SVA>4cm, CL<0°, or T1S-CL≧20°. We compared the cervical alignment of these patients with 121 age and gender matched volunteers (control group).Results. The prevalence of cervical spine deformity was significantly higher in the CLBP group than in the control group (20.7% vs. 10.7%, P=0.034). The mean CL was smaller in the CLBP group than in the control group (16.1° vs. 21.4°, P=0.002). The mean C2-7 SVA was 17.6mm vs. 18.7mm in the CLBP group and in the control group, respectively (P=0.817). The mean T1S-CL was larger in the CLBP group than in the control group (9.1° vs. 3.5°, P<0.001). Multivariate analysis showed that people with CLBP were more likely to have cervical deformities than people without CLBP (odds ratio 2.16, 95% confidence interval 1.006 to 4.637).Conclusions. This study results suggest that people with CLBP present with worse cervical sagittal alignment and higher prevalence of cervical spine deformities than age and gender matched volunteers with no CLBP. This means CLBP impacts cervical spine lesions negatively.

Published
2022

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