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Verification of Speed-up Mechanism of Pedestrian-level Winds Around Square Buildings by CFD
Hideyuki Tanaka,Qiang Lin,Yasuhiko Azegami,Yukio Tamura Council on Tall Building and Urban Habitat Korea 2022 International journal of high-rise buildings Vol.11 No.4
Various studies have been conducted on pedestrian-level wind environments around buildings. With regard to the speed-up mechanism of pedestrian-level winds, there are references to downwash effect due to the vertical pressure gradient of boundary layer flow and venturi effect due to flow blocking by the building. Two factors contribute to increase or decrease of downwash effect: change in twodimensional / three-dimensional air flow pattern (Type 1) and change in downwash wind speed due to building size that does not accompany change in airflow pattern (Type 2). Previous studies have shown that downwash effect has a greater influence in increasing or decreasing the area of strong wind than venturi effect. However, these considerations are derived from the horizontal mean wind speed distribution at pedestrian level and are not the result of three-dimensional flow field around the building. Therefore, in this study, Computational Fluid Dynamics using Large Eddy Simulation were performed to verify the downwash phenomena that contributes to increase in wind speed at pedestrian level.
Aerodynamic and Flow Characteristics of Tall Buildings with Various Unconventional Configurations
Tanaka, Hideyuki,Tamura, Yukio,Ohtake, Kazuo,Nakai, Masayoshi,Kim, Yong Chul,Bandi, Eswara Kumar Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3
Tall buildings have been traditionally designed to be symmetric rectangular, triangular or circular in plan, in order to avoid excessive seismic-induced torsional vibrations due to eccentricity, especially in seismic-prone regions like Japan. However, recent tall building design has been released from the spell of compulsory symmetric shape design, and free-style design is increasing. This is mainly due to architects' and structural designers' challenging demands for novel and unconventional expressions. Another important aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind excitations, which are a key issue in tall-building wind-resistant design. A series of wind tunnel experiments and numerical simulation have been carried out to determine aerodynamic forces and wind pressures acting on tall building models with various configurations: corner cut, setbacks, helical and so on. Dynamic wind-induced response analyses of these models have also been conducted. The results of these experiments have led to comprehensive understanding of the aerodynamic characteristics of tall buildings with various configurations.
Takashi Tamura,Yasunobu Yamashita,Kazuki Ueda,Yuki Kawaji,Masahiro Itonaga,Shin-ichi Murata,Kaori Yamamoto,Takeichi Yoshida,Hiroki Maeda,Takao Maekita,Mikitaka Iguchi,Hideyuki Tamai,Masao Ichinose,Jun 대한소화기내시경학회 2017 Clinical Endoscopy Vol.50 No.4
Background/Aims: Endoscopic ultrasonography-guided fine-needle aspiration (EUS-FNA) has been used to diagnose gastrointestinal submucosal tumors (SMTs). Although rapid on-site evaluation (ROSE) has been reported to improve the diagnostic accuracy of EUS-FNA for pancreatic lesions, on-site cytopathologists are not routinely available. Given this background, the usefulness of ROSE by endosonographers themselves for pancreatic tumors has also been reported. However, ROSE by endosonographers for diagnosis of SMT has not been reported. The aim of this study was to evaluate the diagnostic accuracy of EUS-FNA with ROSE by endosonographers for SMT, focusing on diagnosis of gastrointestinal stromal tumor (GIST), compared with that of EUS-FNA alone. Methods: Twenty-two consecutive patients who underwent EUS-FNA with ROSE by endosonographers for SMT followed by surgical resection were identified. Ten historical control subjects who underwent EUS-FNA without ROSE were used for comparison. Results: The overall diagnostic accuracy for SMT was significantly higher in cases with than without ROSE (100% vs. 80%, p=0.03). The number of needle passes by FNA with ROSE by endosonographers tended to be fewer, although accuracy was increased (3.3±1.3 vs. 5.9±3.8, p=0.06). Conclusions: ROSE by endosonographers during EUS-FNA for SMT is useful for definitive diagnosis, particularly for GIST.
Peak Pressures Acting on Tall Buildings with Various Configurations
Bandi, Eswara Kumar,Tanaka, Hideyuki,Kim, Yong Chul,Ohtake, Kazuo,Yoshida, Akihito,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3
Twenty six pressure models of high rise buildings with various cross-sections including twisted models were tested in a boundary layer wind tunnel. The cross-sections were triangular, square, pentagon, hexagon, octagon, dodecagon, circular, and clover. This study investigates variations in peak pressures, and effects of various cross-sections and twist angles on peak pressures. To study the effects of various configurations and twist angles on peak pressures in detail, maximum positive and minimum negative peak pressures at each measurement point of the building for all wind directions are presented and discussed. The results show that peak pressures greatly depend on building cross-section and twist angle.
Yasunobu Yamashita,Kazuki Ueda,Yuki Kawaji,Takashi Tamura,Masahiro Itonaga,Takeichi Yoshida,Hiroki Maeda,Hirohito Magari,Takao Maekita,Mikitaka Iguchi,Hideyuki Tamai,Masao Ichinose,Jun Kato 거트앤리버 소화기연관학회협의회 2016 Gut and Liver Vol.10 No.4
Background/Aims: Transpapillary forceps biopsy is an effective diagnostic technique in patients with biliary stricture. This prospective study aimed to determine the usefulness of the wire-grasping method as a new technique for forceps biopsy. Methods: Consecutive patients with biliary stricture or irregularities of the bile duct wall were randomly allocated to either the direct or wire-grasping method group. In the wiregrasping method, forceps in the duodenum grasps a guidewire placed into the bile duct beforehand, and then, the forceps are pushed through the papilla without endoscopic sphincterotomy. In the direct method, forceps are directly pushed into the bile duct alongside a guide-wire. The primary endpoint was the success rate of obtaining specimens suitable for adequate pathological examination. Results: In total, 32 patients were enrolled, and 28 (14 in each group) were eligible for analysis. The success rate was significantly higher using the wire-grasping method than the direct method (100% vs 50%, p=0.016). Sensitivity and accuracy for the diagnosis of cancer were comparable in patients with the successful procurement of biopsy specimens between the two methods (91% vs 83% and 93% vs 86%, respectively). Conclusions: The wire-grasping method is useful for diagnosing patients with biliary stricture or irregularities of the bile duct wall.