著者
長谷川 雄太 青木 尊之 小林 宏充 白﨑 啓太
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 (ISSN:21879761)
巻号頁・発行日
vol.85, no.870, pp.18-00441, 2019 (Released:2019-02-25)
参考文献数
18

We implement and perform large-scale LES analysis for running groups of cyclists. The mesh-refined lattice Boltzmann method (LBM) and coherent-structure Smagorinsky model (CSM) are adopted for the simulations to achieve a high performance computing on the recent GPU supercomputer. In the simulation with 16 cyclists, the mesh spacing around cyclists is 4 mm, and the total number of the mesh is up to 8.1×108 and the number of GPUs utilized is up to 64. Each calculation took 4 or 5 days for the 8~11 seconds of physical duration. The flow around 16 cyclists in various arrangement is calculated, and the results show that the in-line arrangement is more effective than the rhomboid arrangement in the viewpoint of the total aerodynamic drag of the group; however, a specific person in rhomboid arrangement can obtain larger drag reduction and save the endurance. Results on two groups also suggest that the frontal group in rhomboid arrangement will be exploited as the wind protection of the backward groups.
著者
加藤 重男 仲谷 新治
出版者
一般社団法人 日本機械学会
雑誌
機械学會論文集 (ISSN:21851123)
巻号頁・発行日
vol.1, no.4, pp.323-328, 1935 (Released:2008-03-28)

機関車及び動車用ヂーゼル機関の各國並に我が國における發達と現状を説く。
著者
井上 喜雄 劉 涛 芝田 京子 園部 元康
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 (ISSN:21879761)
巻号頁・発行日
vol.83, no.851, pp.17-00029, 2017 (Released:2017-07-25)
参考文献数
11

We aim to clarify dynamics of the wrist turn of the golf swing and the effect of the parameters on dynamic behavior at the wrist turn using the double pendulum model and the modal analysis method. Eigenvalue analysis was carried out and natural frequency and mode were calculated by using linearized equation of motion assuming the exterior angle of the cock angle is small. We found out that the first mode is a rigid mode and the second one is a vibration mode of the double pendulum, and the mode shapes are constant during the wrist turn even though natural frequency changes. By applying the modal analysis method we obtained equations of motion for the rigid mode and the vibration mode separately. Furthermore, using the theory of linear superposition, the equation of motion for the vibration mode was separated again into 3 equations which can help to understand the mechanism of the wrist turn. After accuracy of the proposed method for small exterior angle of the cock angle was confirmed by comparing with the exact solution using numerical integration, the proposed method was applied to the general case with large exterior angle of the cock angle which has nonlinearity, and the mechanism of the wrist turn and the effect of the parameters of the arm and wrist torque on the dynamic behavior at the wrist turn were clarified qualitatively. Finally parameter survey using the numerical integration for the original nonlinear equation of motion was carried out to show the validity of the proposed method.
著者
奥野 航平 松尾 亜紀子
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 (ISSN:21879761)
巻号頁・発行日
vol.83, no.856, pp.17-00369-17-00369, 2017 (Released:2017-12-25)
参考文献数
20

The numerical analysis on the flight stability of the underwater projectiles are performed using computational fluid dynamics code which consists of gas/liquid phases analysis, 2D calculation method. The nose shape effect on the underwater flight stability is conducted. The ogival nose, the flat nose and the spike nose are used for the nose shapes. The static stability is determined by the direction of pressure on the projectile. The pressure on the flat nose makes projectile stable, although pressure on the ogival nose and the horizontal area of flat nose makes projectile unstable. The spike nose is statically unstable, however it is possible to increase the flight stability by changing the spike radius and the spike length. When the part of projectile gets out of the bubble and contacts with water, the water pressure acts as restoring force, which lead to improve the flight stability. This phenomenon is called ‘Tail slapping effect’. Tail slapping effect works most effectively when only backward of the center of gravity of the projectile contacts with water. The Effects is canceled as the angle of attack increases and the front of the projectile contacts with water. As a result, the improvement of stability due to the tail slapping effect is limited.
著者
長尾 不二夫 小早川 隆
出版者
一般社団法人 日本機械学会
雑誌
日本機械学會論文集 (ISSN:00290270)
巻号頁・発行日
vol.16, no.54, pp.118-121, 1950-11-20 (Released:2008-03-28)

焼玉機関の圧縮指数を種々な焼玉温度のもとに求め, これを用いて圧縮仕事に対する熱の出入の割合を計算し, さらに圧縮終りの温度を求め, 燃焼が起動時には高温度の焼玉から始り, 運轉時には圧縮された高温度の空氣によるものであることを確かめた.
著者
岸 祐希 金崎 雅博 牧野 好和 松島 紀佐
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 (ISSN:21879761)
巻号頁・発行日
vol.83, no.849, pp.16-00454-16-00454, 2017 (Released:2017-05-25)
参考文献数
20

When a wing of airplane is designed, it is necessary to have knowledge regarding planforms considered their optimum airfoils in order to design efficiently, because each wing planform has both of advantage and disadvantage. In this study, the wing design problem for supersonic transport is carried out for different planforms for two different planforms. Multi-objective problem, which is minimization drags for two supersonic cruise conditions (transonic and supersonic flight) is solved to obtain knowledge of the supersonic airfoil from the viewpoint of the multi-point design. Two types of planforms are considered—a cranked arrow wing with a high sweep-back angle and a single tapered wing with a low sweep-back angle. Optimization problems are carried out by efficient global optimization, which is evolutionary algorithm based on the Kriging surrogate model. To acquire design knowledge, a parallel coordinate plot and functional analysis of variance (functional ANOVA) are applied. The design results showed the difference airfoil between two planforms. The optimum airfoil for the single tapered wing has a small or negative camber at the leading edge to minimize the supersonic cruising. On the other hand, the optimum airfoil for the cranked arrow wing has an airfoil with a lower thickness and larger camber at the leading edge.
著者
岩壺 卓三 迫田 豊 岩田 荘司
出版者
一般社団法人 日本機械学会
雑誌
年次大会
巻号頁・発行日
vol.2011, pp._J231013-1-_J231013-4, 2011

A link model which is composed with a fisherman's arm, a fishing rod, a line and, a Sweet fish are used in order to simulate a fishing system by using the Multi-body Dynamics. Pictures of the landing of the fish are taken by high speed camera in order to compare the orbit of the fish with the simulated one and the accuracy of the simulation is evaluated. Then simulation of two fishing rods which are good feeling and bad feeling of landing are performed to investigate the physical parameters of the fishing behavior in the fishing. As a result, difference of the parameters for the good and the bad fishing rods are clarified.
著者
Shoko OIKAWA Yasuhiro MATSUI Asato WAKABAYASHI Sayaka GOMEI Hiromichi NAKADATE Shigeru AOMURA
出版者
一般社団法人 日本機械学会
雑誌
Journal of Biomechanical Science and Engineering (ISSN:18809863)
巻号頁・発行日
pp.15-00613, (Released:2016-04-06)
参考文献数
12
被引用文献数
7

For cyclist fatalities in 2014 in Japan, the head was the most frequently injured body region. In the present study, the authors analyzed the features of cyclist head injuries in real-world traffic accidents using the data of patients who were taken to the emergency room in Dokkyo Medical University Koshigaya Hospital in Japan, from 2011 to 2013. The results indicated that the percentage of skull fractures was the highest among cyclist head injuries. Assuming that a helmet can prevent head injuries sustained by cyclists in traffic accidents, the effect of wearing a helmet was investigated in impact tests against a vehicle and road pavement. In the tests, the severity of potential head injuries was determined from the Head Injury Criterion (HIC) obtained in an adult pedestrian head-form impactor with and without a helmet. The impact location selected for a vehicle was the A-pillar because the pillar had much higher stiffness than the vehicle bonnet or windshield. It was found that the HIC values for the head-form impactor wearing a helmet were much lower than the HIC values for the head-form impactor not wearing a helmet in both the head-versus-A-pillar impacts and head-versus-pavement impacts. The results suggest that wearing a helmet could reduce the possibility of skull fracture in cyclists.
著者
趙 希禄 胡 亜波 萩原 一郎
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 A編 (ISSN:03875008)
巻号頁・発行日
vol.76, no.761, pp.10-17, 2010
参考文献数
11
被引用文献数
2 11

During car frontal crash, crash energy is absorbed by the parts of front bumper, front side member, front panel member and so on. Previous research has indicated that front side member plays major role in energy absorption. For protecting the passengers, the front side member is expected to absorb crash energy as much as possible. In this study, we adopt cylindrical thin-walled structure using origami engineering as front side member instead of structure with box-shaped cross section which is generally used. We develop an optimization system of the cylindrical thin-walled structure using origami engineering, in which the objective function is to maximize the energy absorption of origami structure; the design variables are structural parameter, number of divisional sections along axis, number of edges of polygonal cross section and number of subdivision levels; the mass and initial peak load of optimal structure must be less than those of structure with box-shaped cross section. We then discuss the optimization results that the optimal structure is capable of absorbing energy 91% more than that of original box-shaped cross sectional structure which is usually bended on the way of being crashed, 37% more than that of original structure which is ideally crashed to bottom without bending.
著者
山田 貴志 渡辺 富夫
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集C編 (ISSN:18848354)
巻号頁・発行日
vol.79, no.807, pp.4340-4344, 2013 (Released:2013-11-25)
参考文献数
5
被引用文献数
1

In this study, we analyzed facial expressions during muscle strain using a head mounted display (HMD)-based virtual arm wrestling system designed for facial electromyography measurement. We found that facial expressions during muscle strain are characterized by tension of the corrugator supercilii and zygomaticus major muscles. In addition, facial expressions of laughter, anger, and fear, and those during muscle strain can be distinguished based on the active pattern of the corrugator supercilii and zygomaticus major muscles. These findings are useful in the evaluation of emotions based on facial expressions during muscle strain using the HMD-based virtual reality system.
著者
日浅 崇馬 佐藤 隆紀 風間 英気 明 愛国 下条 誠
出版者
一般社団法人 日本機械学会
雑誌
ロボティクス・メカトロニクス講演会講演概要集 2017 (ISSN:24243124)
巻号頁・発行日
pp.2P1-K06, 2017 (Released:2017-11-25)

Within limbs of typical animals, there are bi-articular muscle-tendon complex crossing two joints. In particular, it is known that the bi-articular muscle-tendon complex between hip joint and knee joint contributes to the dynamic motion such as high jumping and fast running. This realizes transfer of the torque between the two joints and storage and reuse of the elastic energy. In this paper, we introduce the muscle-tendon complex between hip joint and knee joint to the hind legs of the quadruped robot. In the vertical jump simulation, we confirmed that the mechanism enabled the leg to transfer the torque between the two joints and the leg with the mechanism realized higher jump than the one without it. A prototype of the mechanism has been fabricated also.
著者
小野寺 英輝
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 C編 (ISSN:03875024)
巻号頁・発行日
vol.74, no.746, pp.2371-2378, 2008-10-25 (Released:2011-03-04)
参考文献数
14

In Japan, western technology was rapidly introduced from the last stage of the Edo era. However, a lot of examples of technology transfer failure were included in the process. This paper deals with the cause of failure of the Kamaishi national iron mill. Lack of the domestic pig iron demand and insufficient marketing research, the Kamaishi iron mill generated large amount of deficit and was the greatest failure at that period. Analyzing several remained documents, it was under-stood that Japanese engineers throw large raw ore into the furnace under operation, to make it blockade. It was the simplest way to avoid further financial loss, and to conceal serious carelessness of preliminary survey. Blockage of the furnace was not the main factor of the iron mill business discontinuance, however, it had significant meaning. It was useful to minimize the initial risk of the following private enterprise, which succeeded the iron mill management. And it had big influence in iron manufacture which had grown up to the Japanese key industry in modern ages.
著者
島宗 亮平 中川 千鶴 大野 央人 白戸 宏明
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集C編 (ISSN:18848354)
巻号頁・発行日
vol.77, no.781, pp.3205-3210, 2011 (Released:2011-09-25)
参考文献数
13
被引用文献数
2 1

According to a speedup of the Shinkansen, it is increasing to feel the passage of the vertical curve. However, the actual situation is not clarified because it is hardly investigated the ride comfort about the vertical curve passage until now. Therefore, two kinds of subject experiments by the high-speed train were carried out to obtain the knowledge of the ride comfort in the vertical curve passage, and the following results were provided. It was suggested that not only the acceleration but also the jerk influenced the perception of the vertical curve. In the same condition as the passengers of the operating train, the perception ratios of the vertical curve were about 60 % at maximum speed 275 km/h, and about 70 % at that 320 km/h. In the vibration ride comfort of including the vertical curve, the railroad employees were strictly evaluated than general subjects, and young group subjects were strictly estimated than elder ones.
著者
木澤 新吾 灰塚 正次 田所 浩
出版者
一般社団法人 日本機械学会
雑誌
日本機械学会論文集 C編 (ISSN:03875024)
巻号頁・発行日
vol.70, no.699, pp.3339-3346, 2004-11-25 (Released:2011-03-04)
参考文献数
16

The friction loss and noise of gears has been studied for along time, but it has not yet been made clear. Moreover, JIS gear accuracy class is not necessarily linked with the performance operation of gears, and hence it is important to find the relations between the tooth form accuracy and performance of gears. In the present study, we carried out the experiments to obtain the influence of tooth profile error on the friction loss and noise of spur gears. Nine kinds of tooth profile error with grinding with the similar error amount were used and also we prepared a barrel polished gear which had tip relief by grind. Test results showed that tooth profile error shapes affect the friction loss and noise very much even if the amount of error is the same. Further, it was found that the friction loss and noise have a certain correlation with each other and a barrel polishing showed the lowest friction loss and noise.