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Takahiro Ishida,Keisuke Ohira,Rio Hosoi,Naoko Tokugawa,Takahiro Tsukahara 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.4
Extensive research to establish an index of roughness that causes abrupt turbulent transition downstream of the roughness and affect natural laminar flow is performed. This study investigates turbulent transitions dominated by the roughness-induced crossflow instability on a swept wing and a swept flat plate. Direct numerical simulations (DNS) are performed considering the swept wing to determine the critical roughness height that induces abrupt turbulent transition. Compared to its no-roughness counterpart, the roughness increases both the pressure drag and skin-friction drag and decreases the lift owing to the onset of upstream turbulence. The wind tunnel tests are performed considering a swept flat-plate boundary-layer model. The development of turbulent regions due to the roughness is investigated. The results reveal the occurrence of a laminar-to-turbulent transition and relaminarization, along the boundary between laminar and localized turbulent regions. Moreover, the DNS results reveal the generation of traveling crossflow vortices from the localized turbulent region.
Study on Flow Instability and Countermeasure in a Draft tube with Swirling flow
Takahiro Nakashima,Ryo Matsuzaka,Kazuyoshi Miyagawa,Koichi Yonezawa,Yoshinobu Tsujimoto 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4
The swirling flow in the draft tube of a Francis turbine can cause the flow instability and the cavitation surge and has a larger influence on hydraulic power operating system. In this paper, the cavitating flow with swirling flow in the diffuser was studied by the draft tube component experiment, the model Francis turbine experiment and the numerical simulation. In the component experiment, several types of fluctuations were observed, including the cavitation surge and the vortex rope behaviour by the swirling flow. While the cavitation surge and the vortex rope behaviour were suppressed by the aeration into the diffuser, the loss coefficient in the diffuser increased by the aeration. In the model turbine test the aeration decreased the efficiency of the model turbine by several percent. In the numerical simulation, the cavitating flow was studied using Scale-Adaptive Simulation (SAS) with particular emphasis on understanding the unsteady characteristics of the vortex rope structure. The generation and evolution of the vortex rope structures have been investigated throughout the diffuser using the iso-surface of vapor volume fraction. The pressure fluctuation in the diffuser by numerical simulation confirmed the cavitation surge observed in the experiment. Finally, this pressure fluctuation of the cavitation surge was examined and interpreted by CFD.
Takahiro Kitagawa,Narihito Nagoshi,Hideyuki Okano,Masaya Nakamura 대한척추신경외과학회 2022 Neurospine Vol.19 No.4
A spinal cord injury (SCI) is a destructive event that causes a permanent deficit in neurological function because of poor regenerative potential. Transplantation therapies have attracted attention for restoration of the injured spinal cord, and transplantation of neural precursor cells (NPCs) has been studied worldwide. Several groups have demonstrated functional recovery via this therapeutic intervention due to the multiple beneficial effects of NPC transplantation, such as reconstruction of neuronal circuits, remyelination of axons, and neuroprotection by trophic factors. Our group developed a method to induce NPCs from human induced pluripotent stem cells (hiPSCs) and established a transplantation strategy for SCI. Functional improvement in SCI animals treated with hiPSC-NPCs was observed, and the safety of transplanting these cells was evaluated from multiple perspectives. With selection of a safe cell line and pretreatment of the cells to encourage maturation and differentiation, hiPSC-NPC transplantation therapy is now in the clinical phase of testing for subacute SCI. In addition, a research challenge will be to expand the efficacy of transplantation therapy for chronic SCI. More comprehensive strategies involving combination treatments are required to treat this problematic situation.
Takahiro Utsumi,Mineo Iwatate,Wataru Sano,Hironori Sunakawa,Santa Hattori,Noriaki Hasuike,Yasushi Sano 대한소화기내시경학회 2015 Clinical Endoscopy Vol.48 No.6
Narrow-band imaging (NBI) is a new imaging technology that was developed in 2006 and has since spread worldwide. Because of its convenience, NBI has been replacing the role of chromoendoscopy. Here we review the efficacy of NBI with/without magnification for detection, characterization, and management of colorectal polyps, and future perspectives for the technology, including education. Recent studies have shown that the next-generation NBI system can detect significantly more colonic polyps than white light imaging, suggesting that NBI may become the modality of choice from the beginning of screening. The capillary pattern revealed by NBI, and the NBI International Colorectal Endoscopic classification are helpful for prediction of histology and for estimating the depth of invasion of colorectal cancer. However, NBI with magnifying colonoscopy is not superior to magnifying chromoendoscopy for estimation of invasion depth. Currently, therefore, chromoendoscopy should also be performed additionally if deep submucosal invasive cancer is suspected. If endoscopists become able to accurately estimate colorectal polyp pathology using NBI, this will allow adenomatous polyps to be resected and discarded; thus, reducing both the risk of polypectomy and costs. In order to achieve this goal, a suitable system for education and training in in vivo diagnostics will be necessary.
( Takahiro Ikeda ),( Osamu Aoyagi ),( Tae Hee Choi ),( Nam Ik Han ),( Kwang Soo Koo ),( Youn Shin Nam ),( Young Whan Seo ) 한국체육학회 2016 국제스포츠과학 학술대회 Vol.2016 No.1
Purpose: In recent years, the inactivity of Asian children has been cited. Japan and South Korea, which are located in the same Asian region, are neighboring countries that have many similarities as well as unique aspects. Thus, this study aimed to compare factorial structures of pleasure derived from physical activity between Japanese and South Korean elementary school pupils. Method: 1,689 Japanese and South Korean elementary school pupils in the fifth and sixth grades (461 Japanese boys and 406 girls; 395 Korean boys and 427 girls) answered a questionnaire, which consisted of 22 items presuming 10 factors developed by Tokunaga and Hashimoto (1980). First, factor analysis was conducted on Japanese data. Next, factor analysis with incomplete Procrustes rotation was successively conducted on Korean data using Japanese factorial structure as a hypothetical structure. Result: The following new factors of pleasure from physical activity by Japanese children were extracted (cumulative factor contribution= 52.0%): “F1: Pleasure factor from challenging and creative activities” (factor contribution=4.42, rate of factor contribution=21.4%); “F2: Pleasure factor from winning and group activities” (3.66, 16.6%); and “F3: Pleasure factor from watching physical activity and cheering” (3.06, 13.9%). However, pleasure factors such as competition, admiration, self-realization, good health, and sense of thrill were not extracted from the Japanese data. Thus, Procrustes-rotation factor analysis was applied to the Korean data targeting the 12 items related to the factors of “challenge,” “creative activities,” “sense of winning,” and “watching and cheering.” As a result, the following two factors were extracted: Pleasure factors consisting of two items involved with group activity and competition (Factor contribution=2.734) and factors including all items except for the items contained in the first (9.240). Conclusion: Tokunaga (2016) assumed the hierarchical structure of pleasure factors for physical activity. Based on this, it can be understood that F3 in Japanese factorial structure is located at a low level and F1 at a high level. That is to say, the factorial structure of pleasure for physical activity by Japanese children is diverse depending on their level of physical fitness and tastes, indicating that they derive pleasure from physical activity from various viewpoints. On the other hand, Korean children derived their pleasure from physical activity from a one-dimensional and simple perspective. In specific terms, their factors can be characterized by whether they are generated in the context of their relationship with friends or rivals participating in exercises, or not, and by pleasure produced due to other factors.
Photodynamic Therapy for Esophageal Cancer
Takahiro Inoue,Ryu Ishihara 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.4
Photodynamic therapy, a curative local treatment for esophageal squamous cell carcinoma, involves a photosensitizing drug(photosensitizer) with affinity for tumors and a photodynamic reaction triggered by laser light. Previously, photodynamic therapywas used to treat superficial esophageal squamous cell carcinoma judged to be difficult to undergo endoscopic resection. Recently,photodynamic therapy has mainly been performed for local failure after chemoradiotherapy. Although surgery is the most promisingtreatment for local failure after chemoradiotherapy, its morbidity and mortality rates are high. Endoscopic resection is feasible forlocal failure after chemoradiotherapy but requires advanced skills, and its indication is limited to within the submucosal layer bydepth. Photodynamic therapy is less invasive than surgery and has a wider indication than endoscopic resection. Porfimer sodium(a first-generation photosensitizer) causes a high frequency of side effects related to photosensitivity and requires the long-termsun-shade period. Talaporfin (a second-generation photosensitizer) requires a much shorter sun-shade period than porfimersodium. Photodynamic therapy will profoundly change treatment strategies for local failure after chemoradiotherapy.