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Experimental and numerical flow analysis in hydraulic vane pump
Junichi SUEMATSU,Tetsuhiro TSUKIJI,Mariko WATANABE,Shinji YAKABE,Hirohito WATANABE,Yoshinari NAKAMURA,Kazunari SUZUKI 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
The purpose of this study is to conduct a three dimensional flow analysis of a hydraulic vane pump by using computational fluid dynamics (CFD), to evaluate an accuracy of volumetric flow rate in CFD compared to experimental value and to examine a influence of the evaporation coefficient and condensation coefficient in Zwart–Gerber–Belamri cavitation model to pressure in a vane chamber. In this study, standard k-ε turbulent model with the Zwart–Gerber–Belamri cavitation model is used to estimate the cavitating flow in vane pump. In CFD, two notch models are used. From results of experiments and CFD analysis of volumetric flow rate, there is little difference between the experiments and CFD results in the low speed range. However, for high speed range, in a case with no cavitation model, the CFD results of volumetric flow rate are different from the experimental ones. On the other hand, in the case with cavitation model, those agree with the experimental values. In this case, the error of volumetric flow rate is less than 1% in the low speed range and less than 2.5% in the high speed range. From CFD results of pressure fluctuation in a vane chamber when the evaporation coefficient and condensation coefficient in the cavitation model are varied, the surge pressure can be seen in a vane chamber. In conclusion, it could be considered that the CFD calculation with cavitation model is sufficiently accurate in volumetric flow rate. In addition, as the evaporation coefficient becomes large, amplitude of the pressure fluctuation in a vane chamber after a surge pressure becomes large, as the condensation coefficient becomes large, the surge pressure in a vane chamber becomes low.
Nitta, Junichi,Nojima, Masanori,Ohnishi, Hirofumi,Mori, Mitsuru,Wakai, Kenji,Suzuki, Sadao,Fujino, Yoshihisa,Lin, Yingsong,Tamakoshi, Koji,Tamakoshi, Akiko Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.3
Background: We investigated four factors, height, weight gain since age 20, physical activity, and alcohol drinking, for associations with risk of breast cancer (BC) according to menopausal status, using the latest data of the Japan Collaborative Cohort Study (JACC Study). Materials and Methods: We confined the analysis to 24 areas available of cancer incidence information, excluding women with a previous diagnosis of BC. Baseline data were collected from 38,610 (9,367 premenopausal, and 29,243 postmenopausal) women during 1988 and 1990. The study subjects were followed-up at the end of 2009, and 273 (84 premenopausal, and 189 postmenopausal) cases of BC were newly diagnosed in 501,907 person-years. The Cox model was used to estimate a hazards ratio (HR) and its 95% confidence interval (CI) of BC risk. Results: As a result of the multivariate analysis adjusting for age at baseline survey, age at menarche, number of live births, and, age at first delivery, weight gain since age 20 of 6.7 kg-9.9 kg, and ${\geq}10.0kg$ were significantly associated with increased risk for postmenopausal BC (HR=2.48, 95% CI 1.40-4.41, and, HR=2.94, 95% CI 1.84-4.70, respectively). Significantly increased trend of BC risk was also observed in weight gain since age 20 (p for trend, p<0.001). Amount of ethanol intake per day${\geq}15.0g$ was significantly associated with increased risk for postmenopausal BC in the multivariable-adjusted analysis (HR=2.74, 95% CI 1.32-5.70). Conclusions: Higher weight gain in adulthood and larger amounts of ethanol intake were significantly associated with increased risk of BC in Japanese postmenopausal women. None of the investigated factors were significantly associated with BC risk in Japanese premenopausal women.
Aoyama Ryoma,Yamane Junichi,Ninomiya Ken,Takahashi Yuichiro,Kitamura Kazuya,Nori Satoshi,Suzuki Satoshi,Shiraishi Tateru 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.5
Study Design: A retrospective study conducted at a single academic institution.Purpose: This study compared the postoperative alignment of consecutive double laminectomies according to their decompression levels and investigated the influence of the extension unit of the spinous process and its attached muscles on postoperative alignment.Overview of Literature: Many reports have investigated bony and soft tissue factors as the causes of postoperative cervical alignment disorders. To-this-date, no other article has clarified the importance of the attached muscles between the spinous processes of C3 and C6 to maintain local cervical alignment.Methods: In total, 155 consecutive patients who underwent muscle-preserving consecutive double laminectomies for cervical spondylotic myelopathy from 2005 to 2013 were included in this study. The imaging parameters included the C2–C7 angle, range of motion, C2–C7 sagittal vertical axis (SVA), C7 slope, C2–C5 angle, C5-C7 angle, local disk angle caudal to the decompression level, and the disk height between C2/C3 and C7/Th1.Results: The caudal disk angle of the decompression level decreased after consecutive double laminectomies, thus suggesting that the extension unit maintained the local lordosis at the lower disk of the decompression level. Postoperatively, in the C3–4 decompression cases, the C2–C7 angle decreased by 7.3°, and the C2–C7 SVA increased by 8.6 mm, thus indicating the appearance of an alignment disorder. Multivariate logistic regression analysis showed that cephalad laminectomy was a risk factor for C2–C7 angle decreases >10°. However, the postoperative recovery rate of Japanese Orthopedic Association scores after consecutive double laminectomies was reasonable, and the overall cervical alignment was well maintained in all decompression levels except C3–C4.Conclusions: The cervical extension unit maintained lordosis at the disk caudal to it. The extension unit was found to contribute more to the maintenance of lordosis of the entire cervical spine at the cephalad side.
Aoyama Ryoma,Yamane Junichi,Ninomiya Ken,Takahashi Yuichiro,Kitamura Kazuya,Nori Satoshi,Suzuki Satoshi,Shiraishi Tateru 대한척추외과학회 2023 Asian Spine Journal Vol.17 No.1
Study Design: A retrospective study at a single academic institution.Purpose: We aimed to understand the pathogenesis of cervical spondylolisthesis by analyzing whether narrowing of the disc height stabilizes the slipped disc level according to the degenerative cascade.Overview of Literature: According to Kirkaldy-Willis’ degenerative cascade, the narrowing of the disc height at slipped level contributes to intervertebral stability in lumbar spondylolisthesis. Conversely, the pathogenesis of cervical spondylolisthesis is unknown due to a scarcity of reports on the condition.Methods: The images of 83 patients with cervical single-level spondylolisthesis were studied. We looked at 52 slipped levels for anterior slippage and 31 for posterior slippage. The imaging parameters included slippage in the neutral, flexed, and extended positions, axial facet joint orientation, sagittal facet slope, global cervical alignment, C2–C7 angle, C2–C7 sagittal vertical axis, range of motion (ROM), and slipped disc angle ROM.Results: With the narrowing of the intervertebral disc height, slippage in the flexed position of both anterior and posterior spondylolisthesis increased. However, in both anterior and posterior spondylolisthesis, disc height narrowing did not show stability. The narrowing of the intervertebral disc height was found to be a risk factor for a translation of slippage of 1.8 mm or more in flexionextension motion in anterior spondylolisthesis in multivariate regression analysis.Conclusions: Narrowing the intervertebral disc height did not stabilize the translation of slippage in flexion-extension motion in cervical spondylolisthesis. Instead, narrowing of the disc height was associated with a translation of slippage of 1.8 mm or more in flexion-extension motion in cases of anterior slippage. Therefore, we discovered that degenerative cascade stabilization for cervical spondylolisthesis was difficult to achieve.
Tokeshi Soichiro,Eguchi Yawara,Suzuki Munetaka,Yamanaka Hajime,Tamai Hiroshi,Orita Sumihisa,Inage Kazuhide,Shiga Yasuhiro,Hagiwara Shigeo,Nakamura Junichi,Akazawa Tsutomu,Takahashi Hiroshi,Ohtori Seij 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.3
Study Design: A retrospective observational study was performed. Purpose: We investigated the relationships between skeletal muscle mass, bone mineral density (BMD), and trabecular bone score (TBS) in patients with osteoporotic vertebral compression fractures (VCFs). Overview of Literature: The TBS has attracted attention as a measurement of trabecular bone microarchitecture. It is derived from data obtained using dual-energy X-ray absorptiometry (DXA) and is a reported indicator of VCFs, and its addition to the Fracture Risk Assessment Tool increases the accuracy of fracture prediction. Methods: BMD, skeletal muscle mass, and TBS were measured in 142 patients who visited Shimoshizu National Hospital from April to August 2019. Patients were divided into a VCF group and a non-VCF group. Whole-body DXA scans were performed to analyze body composition, including appendicular skeletal muscle mass index (SMI; lean mass [kg]/height [m2]) and BMD. The diagnostic criteria for sarcopenia was an appendicular SMI <5.46 kg/m2. A logistic regression analysis was conducted to identify the risk factors for VCFs. Results: The significant (p<0.05) findings (VCF group vs. non-VCF group, respectively) included age (79 vs. 70 years), femoral BMD (0.50 vs. 0.58 g/cm2), TBS (1.25 vs. 1.29), and lower limb muscle mass (8.6 vs. 9.9 kg). The VCF group was significantly older and had a lower femur BMD and decreased leg muscle mass than the non-VCF group. Based on the multiple logistic regression analysis, lower femoral BMD and decreased leg muscle mass were identified as risk factors for vertebral fracture independent of age, but the TBS was not. Conclusions: Patients with VCFs had low BMD, a low TBS, and low skeletal muscle mass. Lower femoral BMD and decreased leg muscle mass were identified as risk factors for VCFs independent of age, whereas the TBS was not identified as a risk factor for VCFs.
Seiji Ohtori,Sumihisa Orita,Kazuyo Yamauchi,Yawara Eguchi,Yasuchika Aoki,Junichi Nakamura,Masayuki Miyagi,Miyako Suzuki,Gou Kubota,Kazuhide Inage,Takeshi Sainoh,Jun Sato,Yasuhiro Shiga,Koki Abe,Kazuki 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.3
Study Design: Retrospective case series. Purpose: To determine whether symptoms predict surgical outcomes for patients with discogenic low back pain (DLBP). Overview of Literature: Specific diagnosis of DLBP remains difficult. Worsening of pain on flexion is a reported symptom of DLBP. This study sought to determine whether symptoms predict surgical outcomes for patients with DLBP. Methods: We investigated 127 patients with low back pain (LBP) and no dominant radicular pain. Magnetic resonance imaging was used to select patients with disc degeneration at only one level. If pain was provoked during discography, we performed fusion surgery (87 patients). Visual analogue scale score and responses to a questionnaire regarding symptoms including worsening of pain on flexion or extension were assessed. Symptom sites before surgery were categorized into LBP alone, or LBP plus referred inguinal or leg pain. We followed 77 patients (average 3.0 years) and compared symptoms before surgery with surgical outcome. Results: Sixty-three patients with a good outcome showed postsurgical pain relief (≥60% pain relief) and 14 patients with a poor outcome did not (<60% pain relief). In patients with good outcomes, worsening of LBP was evident in 65% of cases on flexion and in 35% on extension. However, these findings were not significantly different from those in patients with poor outcomes. The percentage of patients with LBP alone was significantly lower and the percentage of patients with LBP plus referred inguinal or leg pain was significantly higher in the group with good surgical outcome compared with patients in the group with poor surgical outcome (p <0.05). Conclusions: Worsening of pain on extension may be a symptom of DLBP. Surgical outcomes were superior in patients with both LBP and either referred inguinal or leg pain compared with those having LBP alone.