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Hideyuki Suzuki Koichiro Yoshida Kazuhiro Iijima 《Journal of Marine Science and Technology》1996,1(5):255-267
The land area of Japan, especially flat land, is very small compared with its economic size. Large-scale floating structures
are one solution to satisfy the demand for space by utilizing the ocean. This paper presents a general view of the dynamic
response characteristics of large-scale floating structures, pontoons and semi-submersibles. For example, it is shown that
the natural frequencies of eigenmodes are higher than the natural frequency of heaving motion. The response of the outer framework
of a structure is shown to be generally larger than the response of the central part. Within the limits of our present understanding
of the general dynamic response characteristics of such structures, the design and analysis of semi-submersible, large-scale
floating structures is discussed. For a pontoon-type large-scale floating structure, a type whose perimeter structure has
been modified to become lighter and more rigid is proposed. With this modification, the dynamic response of the whole structure
is imporved. 相似文献
3.
Keisuke Watanabe Hideyuki Suzuki Koichiro Yoshida 《Journal of Marine Science and Technology》1998,3(3):151-160
The trend towards deepwater development requires a new approach to underwater installation of offshore structures. The present
method using crane vessels has some drawbacks in operations at more than 2000 m depth. The natural period of the coupled system
of the rigged structure and the crane vessel becomes longer, so that it is no longer possible to manipulate the cranes to
achieve the desired positioning accuracy. This paper examines the application of an active control technique for underwater
installations as one of the solutions to the present problems. An active control technique also has the advantage that it
can deal with the structural flexibility which allows the structure to be large and light-weight. This structural flexibility
imposes problems of suppressing the elastic responses and securing the stability of the control system. In this paper, anH
∞ controller combined with a low authority control/high authority control (LAC/HAC) feedback controller is designed for cases
where structural flexibility cannot be ignored. A robust model-following controller is examined for cases where the structure
can be treated as rigid. In order to confirm the control algorithm and verify the possibility of the active control installation
method, basin tests are executed using two types of neutrally buoyant flexible models with ultrasound ranging systems and
thrusters. 相似文献
4.
Firman Permana Wandani Maimunah Siti Masashi Yamamoto Yuichiro Yoshida 《国际交通安全学会研究报告》2018,42(2):76-85
The purpose of this paper is to verify the justification provided for a centralized national road policyin Indonesia, namely, that trips on national roads are typically inter-urban, by measuring the spatialdimensions of automobile and motorcycle trips on national roads in Indonesia. The study finds thatmotorcycle trips are characteristically local; by contrast, automobile trips extend beyond city boundaries,although to a limited extent. The results suggest the decentralization of transportation policies for thedevelopment and maintenance of national roads by granting autonomy to local governments when nofiscal externality exists. The results also indicate that road capacity, gasoline prices, income, populationand worker density, city size, and the number of public buses are strong predictors of vehicle kilometerstraveled. 相似文献
5.
Yuki Yoshida Yoshiaki Takahashi Hiroharu Kato Akira Masuko Osamu Watanabe 《Journal of Marine Science and Technology》1997,2(1):1-11
For the theoretical consideration of a system for reducing skin friction, a mathematical model was derived to represent, in a two-phase field, the effect on skin friction of the injection of micro air bubbles into the turbulent boundary layer of a liquid stream. Based on the Lagrangian method, the equation of motion governing a single bubble was derived. The random motion of bubbles in a field initially devoid of bubbles was then traced in three dimensions to estimate void fraction distributions across sections of the flow channel, and to determine local bubble behavior. The liquid phase was modeled on the principle of mixing length. Assuming that the force exerted on the liquid phase was equal to the fluid drag generated by bubble slip, an equation was derived to express the reduction in turbulent shear stress. Corroborating experimental data were obtained from tests using a cavitation tunnel equipped with a slit in the ceiling from which bubbly water was injected. The measurement data provided qualitative substantiation of the trend shown by the calculated results with regard to the skin friction ratio between cases with and without bubble injection as function of the distance downstream from the point of bubble injection.List of symbols
B
law of wall constant
-
C
f
local coefficient of skin friction
-
C
f0
local coefficient of skin friction in the absence of bubbles
-
d
b
bubble diameter [m]
-
g
acceleration of gravity [m/s2]
-
k
1 k4
proportional coefficient
-
k
L
turbulent energy of the liquid phase [m2/s2]
-
L
representative length [m]
-
l
b
mean free path of a bubble [m]
-
m
A
added mass of a single bubble [kg]
-
m
b
mass of a single bubble [kg]
-
N
x
,N
y
,N
z
force perpendicular to the wall or ceiling exerted on a bubble adhering to that wall or ceiling [N]
-
P
absolute pressure [Pa]
-
Q
G
rate of air supply [/min]
-
q
L
(i)
turbulent velocity at the ith time increment [m/s]
-
R>
ex
Reynolds number defined by Eq. 32
-
T
*L
integral time scale of the liquid phase [s]
-
U
velocity of the main stream [m/s]
-
,¯v,¯w
time-averaged velocity components [m/s]
-
u,v,w
turbulent velocity components [m/s]
-
û
L
,vL
root mean square values of liquid phase turbulence components in thex- and y-directions [m/s]
-
V
volume of a single bubble [m3]
-
X,Y,Z
components of bubble displacement [m]
-
x
s
,y
s
,z
s
coordinate of a random point on a sphere of unit diameter centered at the coordinate origin
-
root mean square of bubble displacement in they-direction in reference to the turbulent liquid phase velocity [m]
-
local void fraction
-
m
mean void fraction in a turbulent region
-
regular random number
- R
v
increment of the horizontal component of the force acting on a single bubble, defined by Eq. 22 [N]
- t
time increment [s]
- 1
reduction of turbulent stress [N/m2]
-
L
rate of liquid energy dissipation [m2/s3]
-
m
coefficient defined by Eq. 30
-
law of wall constant in the turbulent region in absence of bubbles
-
1
law of wall constant in the turbulent region in presence of bubbles 相似文献
6.
日本超导磁悬浮列车的技术开发 总被引:1,自引:0,他引:1
介绍了日本超导磁悬浮列车技术开发方面取得的成果,以及2016年前的研发计划。 相似文献
7.
In recent years, traffic congestion, traffic accidents, and deterioration of the environment because of growing population, increasing urbanization, and increasing car ownership have become serious problems in the Asia-Pacific regions. Intelligent transport systems (ITS) are systems that try to solve various road traffic issues using information communication technologies. Several countries are endeavoring to solve such traffic issues by deploying an ITS and achieving positive results. However, there are some problems in advancing ITS deployment in these countries, such as lack of technical know-how, a lack of coordination among systems, lack of a master plan, and financial constraints. In order to introduce ITSs, it is important to select suitable technologies and applications appropriate for each country. An appropriate plan and evaluation of the ITS project are also important for the introduction of ITS.In this paper, we propose methods for the utilization and introduction of ITS technologies to solve urban traffic issues in various countries, based on the lessons learned from the deployment of an ITS in Japan. 相似文献
8.
Efforts are underway in Japan to promote “Smartway” next-generation roadways, which provide a variety of services through the use of advanced ITS technologies. In recent years, the National Institute for Land and Infrastructure Management (NILIM), part of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), has conducted public-private joint research on next-generation road services using ITS technologies. Field operational tests (FOTs) of services including forward obstacle information provision and merging assistance using 5.8 GHz dedicated short range communication (DSRC) were conducted on the Tokyo Metropolitan Expressway through FY2007. In FY2008-2009, FOTs were conducted in three major metropolitan areas—Tokyo, Nagoya, and Keihanshin (Kyoto, Osaka, and Kobe)—to promote future deployment nationwide. These included tests of information provision services to alert drivers to forward obstacles hidden beyond the crest of an incline and prevent excessive speed on sharp curves. This paper presents an overview of these FOTs conducted by NILIM in recent years and their results. 相似文献
9.
Koichi Sakai 《国际交通安全学会研究报告》2019,43(4):207-209
The concept of mobility-as-a-service (MaaS) was conceived in Finland, and it is characteristically user-oriented. Interest in MaaS has quickly spread across Europe along with the rapid advances in information and communications technology and the internet of things in recent years, as the realization of MaaS is consistent with the policy directions of the EU member states promoting the use of public transport.This paper describes the MaaS concept in EU, the birth of the concept in Finland and its background, and EU-wide policy level initiatives and their characteristics. 相似文献
10.
Koichi Koyama 《Journal of Marine Science and Technology》2013,18(2):145-165
A theory on an optimum screw propeller is described. The optimum means optimum efficiency of a propeller, that is, maximizing thrust horse power for a given shaft horse power. The theory is based on the propeller lifting surface theory. Circulation density (lift density) of the blade is determined by the lifting surface theory on a specified condition in general. However, it is shown that, in the case of optimum condition, the circulation density is not determined by the lifting surface theory, although the circulation distribution which is the chordwise integral of the circulation density is determined. The reason is that the governing equation of the optimization by the lifting surface theory is reduced to that by the lifting line theory. This theoretical deduction is the main part of this paper. The importance of the lifting line theory in the design of the optimum propeller is made clear. Numerical calculations support the conclusion from the deduction. This is shown in the case of freely running propellers and in the case of wake adapted propellers. 相似文献