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Article type: Cover
1997 Volume 97 Pages
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Published: September 25, 1997
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Article type: Appendix
1997 Volume 97 Pages
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Article type: Appendix
1997 Volume 97 Pages
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Article type: Index
1997 Volume 97 Pages
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Article type: Index
1997 Volume 97 Pages
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Yoshinori MIYAMOTO, Akio UCHIDA, Toshiharu KAKIHARA, Seiichi TAKEDA
Article type: Article
1997 Volume 97 Pages
1-6
Published: September 25, 1997
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An Experiment of differential GPS (DGPS) to study the effects of distance (base line length) between a reference station and a user station, was conducted during January 10 to February 8 in 1996. The reference station was set in Tachikawa city and a survey vessel "Shoyo", Japan Maritime Safety Agency, was used as the user station. The GPS data was sampled in cruising and mooring condition at the port pier in Guam. The DGPS correction was made using the pseudo range correction value obtained from post processing. In this cruise, the maximum base line length was about 4, 000km. The results at Guam and in cruising at sea were reported, and the effects of base line length with respect to the DGPS positioning dispersion were discussed in this paper. From this experiment, it was found that the DGPS positioning dispersion increases linearly with base line length at a rate of 0.51m/100km. In addition, it was suggested that the deviation of the ellipsoidal height derived from the DGPS could be used as an index value of estimation for the DGPS horizontal positioning dispersion.
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Sakae NAGAOKA, Midori TAKAHASHI, Osamu AMAI
Article type: Article
1997 Volume 97 Pages
7-14
Published: September 25, 1997
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This paper deals with a flight experiment for calibrating the bias errors of the measurement system of a height finding radar. The radar, namely, the Navigation Accuracy Measurement System (NAMS), uses a vertically rotating fan beam antenna and estimates the height of an aircraft flying with a constant speed and altitude within the coverage of the beam. An aircraft (B99) equipped with GPS receivers was used for obtaining the GPS data on the aircraft position. A post processing for the GPS data obtained from the onboard receiver and those at a base station installed near the radar site was carried out using a kinematic positioning software called Flykin. The positions obtained from the radar and kinematic GPS processing (KGPS) were compared and the biases of the radar were estimated by the least square method. This paper proposes the method for estimating biases using KGPS data and examples of the results are shown briefly.
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Satoru TAKASE, Kuniji KOSE, Noritaka HIRATA, Mitsunobu FURUMOTO, Duc M ...
Article type: Article
1997 Volume 97 Pages
15-22
Published: September 25, 1997
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To estimate the maneuvering hydrodynamic coefficients or construct the ship position control system, not only ship position but also motion must be measured with high accuracy. Kinematic GPS (KGPS) has an enough accuracy for such purpose. By using of more than three GPS antennas, six Degree Of Freedom motion at any points can be calculated from position data of these antennas. We carried out the experiment of KGPS using "KOJIMA" that is training ship. It is shown that the ship motion can be measured, and velocity, angular velocity, force and moment at the center of gravity are obtained. Then we derived the relationship between KGPS error and motion measurement error, and showed the notes for arrangement of antennas.
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Tatsuto YAMADA, Akira NAGASAWA, Satoru TAKASE, Noritaka HIRATA
Article type: Article
1997 Volume 97 Pages
23-30
Published: September 25, 1997
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Errors of a vessel's position by radar observations has not been determined sufficiently, because we do not have a high accuracy method to fix their positions at sea. But recently, a vessel's position can be obtained with high accuracy by using kinematic GPS (KGPS) in addition to a land survey in various fields. We carried out the experiments to compare radar positions with KGPS positions in the KURUSHIMA strait using the training vessel "KOJIMA" with the KGPS receiver on board. The positions of KOJIMA obtained by a radar were accepted from the radar sight which belongs to HONSHU-SHIKOKU Bridge Authority. After KGPS positions were exchanged to the plane coordinates, the difference between the two positions were examined and the results were as follows. 1. The radar positioning accuracy were 26.4m in length and 7.7m in width as 1σ. 2. The errors in width showed the normal distribution. 3. The vessel's course and speed estimated by radar observations often indicated sharp fluctuations. 4. The bearing errors of radar became greater at shorter distance.
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Masashi KAWAI
Article type: Article
1997 Volume 97 Pages
31-37
Published: September 25, 1997
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It is reported that periodic fluctuations of about 1-meter amplitude and about 12-hour period appear in post-fit range residuals of geosynchronous satellites. In order to explain the cause of the periodic fluctuations, two hypotheses were established in this study. They are as follows. (1) It was assumed that the along-track force acts on the only satellites which are spinning. (2) The tracking stations move horizontally with the earth's crusts due to tidal generating forces, the period of the crust movements is about 12 hours and the amplitude is 1 to 2 meters. The fluctuation of the mass distribution in the earth, such as solid earth tides and ocean tides, varies forces which act on the earth's crusts periodically, as a result, the crusts move horizontally. A model for the horizontal movement of the earth's crusts was developed, and it is confirmed that the periodic fluctuations in post-fit range residuals are removed by correcting the tracking station locations using the developed model in the orbital analysis of geosynchronous satellites. These results are reported in this paper.
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Ruri SHOJI, Hideki HAGIWARA
Article type: Article
1997 Volume 97 Pages
39-46
Published: September 25, 1997
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In this study, economic evaluation of the aircraft routes parallel to the optimum route was performed by the simulations. It was found that compared with the optimum route between San Francisco and Tokyo, the average fuel increases on the parallel routes passing 30, 50 and 100n.m. away from the optimum route were 0.1, 0.2 and 0.7%, respectively. Thus it can be said the parallel routes with 30 and 50n.m. separation distances have almost the same economic advantage as the optimum route. The effectiveness of rerouting (i.e. change of an aircraft's flight plan based on the updated wind forecast while the aircraft is en route) was also investigated by the simulations for New York-Tokyo route and San Francisco-Tokyo route. By executing the rerouting at the beginning of cruising, the fuel was saved by 0.5% on the average (1.3-2.2% at the maximum) and the flight time was shortened by 0.5-0.8% on the average (2.0-3.4% at the maximum), which verified the effectiveness of rerouting.
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Hayama IMAZU
Article type: Article
1997 Volume 97 Pages
47-54
Published: September 25, 1997
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The evaluation method of own ship's action by the distance of closest point of approach (DCPA) and the time to CPA (TCPA) is common method. But this method is attended with an inevitable fault like as two-dimensional function (distance and time) and difficulty in considering estimated error of targets vector. To solve these faults, new evaluation value of action for collision avoidance (EVAC) was considered. The underlying principles of EVAC is to evaluate own ship's action by estimated targets distance within a fixed time. The results of investigations about this method are summarized, (1) The physical meaning of this value is clear. (2) It is easy to take into consideration an estimated error of targets vector. (3) It is expected to be used a decision problem for collision avoidance in a congested water.
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Masato SASAKI, Shogo HAYASHI
Article type: Article
1997 Volume 97 Pages
55-63
Published: September 25, 1997
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It is difficult to establish radio communication with unknown vessel using present communication system, even if it is very short distance to the desired vessel. If it is easy to exchange mutual intention and information freely among unknown vessels, it makes traffic condition smooth. When the information for other's behavior or intention were not obtained, unsuitable maneuvering may possibly occur big disaster. Development and practical use of reliable communication system for unknown vessel is desired among the persons concerned. All present communication system must use exact call sign for establishing immediate communication. The authors propose new calling system to unidentified vessel using simple calling code which is composed from longitude and latitude of its position. This simple calling code is composed by a number of 6 figures as the least calling identification within a radius of 60 nautical miles. This paper describes this new concept. The possibility which was ascertained by field examinations is also reported
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Rihei KAWASHIMA, Kaname SATOH, Seiichi TAKEDA
Article type: Article
1997 Volume 97 Pages
65-71
Published: September 25, 1997
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It is essential to understand the actual characteristics of wave in the sea for the safety and sea keeping quality of fishing boats. From this point of view, attention should be paid to empirical knowledge : waves develop when wind and water currents have opposite directions. In this paper, we propose a simple method to forecast wave height based on experimental results in a wind-wave channel. We also applied this model to clarify the conditions of the sea during the actual capsize of a fishing boat and confirmed that the boat was subjected to very high waves generated by opposing wind and water currents. Judging from the results, we conclude that the simple forecasting method contributes to establish the safety guidelines for operation and navigation of fishing boats.
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Masayoshi KUBO, Tae KOMUNE, Katsuhiko SAITO, Kenji SASA
Article type: Article
1997 Volume 97 Pages
73-83
Published: September 25, 1997
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In ports and harbors facing to the open sea, mooring ships have sometimes encountered severe wave condition in the winter, then the mooring ropes and fenders are broken. As the results, the accident of ship body damage has happened. In order to avoid such accidents, we should set the mooring criteria for the ship shifting to outside of the harbor. For the target N-port facing to the Sea of Japan, the critical offshore wave hight is known to be 5m by our previous research, so we try to forecast the wave height before 2 or 4 hours earlier. We propose several high wave forecasting methods using waves, winds and both data. If we use the 5 parameters method of wind and wave, we can forecast the critical conditions with 77% accuracy and 12 parameters method of wind, then 91% accuracy.
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Shigeaki SHIOTANI
Article type: Article
1997 Volume 97 Pages
85-91
Published: September 25, 1997
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This paper deals with the wave-making by a wavedozer. A wavedozer was named after a bulldozer because of similar operation. In this paper a wavedozer of a wave-making board type are used. In the first place, the outline of wave-making phenomenon by a wavedozer in the towing tank or the circulating water channel is introduced, and the applied example of the generated waves is shown. In the second place, the calculated technique of the generated wave-profile and the pressure distribution on a wavedozer are explained. The calculated results were compared with the experimental ones and both were in good coincidence.
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Shigeo MITA, Kuniaki SHOJI
Article type: Article
1997 Volume 97 Pages
93-101
Published: September 25, 1997
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The pelprene protective device which is made from polyester elastomer named pelprene was developed for one of protection system contacted with bridge and absorbed colliding energy by elastic deformation of the protection. In this paper authors studied on the effect of shock absorption of this protection system by model experiment. Collision experiment of the bow model to the pelprene protective device was executed. The following results are obtained : -The shock absorption efficiency are about 50%, energy absorption efficiency are about 60% in first collision. And in case of repeated collision, it slightly fall, but the shape is almost restore. -These characteristics do not change by collision point or a collision angle or a inclined angle of bow. -The load-penetration curb is nearly equal to result of static penetration test.
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Masayoshi KUBO, Katsuhiko SAITO, Tsuyoshi OKI
Article type: Article
1997 Volume 97 Pages
103-111
Published: September 25, 1997
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In the previous papers, we proposed the prevention system of ship separation from quay wall. In this paper, we carry out a small scale model test which is similar to an actual mooring ship in order to clear some problems for practical application under wave condition. The obtained results are summarized as follows : (1) When moored ship is supported by the system, the center of roll motion becomes the lowest point of the system. (2) As the result, the distance between ship's body and the system becomes maximum at the water surface and becomes minimum at the lowest point of the system. (3) When the system's elasticity is hard, ship's body is apt to separate from the system. (4) High wave hight and long wave period are factors for enlargement of leak water into the system.
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Masayoshi KUBO, Kenji ASAKI, Kazusei YAMAMOTO, Tsuyoshi OKI
Article type: Article
1997 Volume 97 Pages
113-120
Published: September 25, 1997
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The authors have proposed a new device which encloses a hull with a curtain for preventing spilt oil diffusion. In this paper, the shapes of the curtain under steady flow are investigated on the basis of some model experiments. In the experiments, a few types of box shape hull models which are enclosed with a curtain are fixed in a circular tank and the shapes of the curtain are observed. The obtained results are summarized as follows. (1) An area of vertical section of "Region A", which is the region to contain spilt oil in the down-stream side, closely relates to a new non-dimensional number, F_s =<ρw> A_<cw> νw^2/Ws, where, ρw=water density, A_<cw>=An area of the curtain in the water, νw=flowing velocity, ws=weight of sinkers mounted on the foot of the curtain. (2) As Fs increases, the smooth outline of the curtain of the downstream side gets to break and a "furrow" is created back and forth. (3) The creation of the "furrow" mainly depends on Fs and Z_<bo> /L_<CR>, where, Z_<bo>=depth of the curtain under the ship's bottom, L_<CR>=length of the curtain round a ship. (4) To have sufficient ability of containing oil, the device should be designed so that the "furrow" is never created on the curtain.
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Kimihiko UENO, Kiyoshi AMAGAI, Nobuo KIMURA, Toshihiro IWAMORI
Article type: Article
1997 Volume 97 Pages
121-129
Published: September 25, 1997
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The previous paper which we reported before described a kind of damping function in the equation of single degree of freedom rolling motion which applicable to small fishing vessels. There is no problem in the application of the damping function to the free roll motion in the absence of the roll excitation moment, however there is something wrong in the case of the roll motion with roll excitation moment. This paper describes improvement on the above problem with consideration for the characteristics of angle-dependent damping. And, this paper describes a new method that is able to estimate the characteristics of roll damping in the case of large roll amplitude from free-decay data in the case of small roll amplitude. This method is based on an approximative solution by the averaging method and an analytical solution of the equation of the rolling motion. This method is useful in that it is not necessary to use many data to estimate.
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Nobuo KIMURA, Kiyoshi AMAGAI, Toshihiro IWAMORI, Takumi KODAMA
Article type: Article
1997 Volume 97 Pages
131-139
Published: September 25, 1997
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Lots of small fishing boats for the raising of scallop on the coastal area in Funka-Bay, Hokkaido have been sometimes compelled to work under the sever sea condition since it is actually main producing season in winter. So there should be great needs of sufficient seakeeping quality to secure a safety during the fishing operation. On basis of tank tests and researches of actual fishing operating condition, it is clarified the stability and rolling response characteristics of the fishing boats in various working conditions. In this paper, using wave data measured in fishing ground, the authors would propose the critical wave height that these fishing boats could be on the sea with safety. The results are obtained as follows ; (1) As the scallop would load on the deck from 0 to 5ton, the value of rolling response function would slightly increase. (2) As ship body would fix to the main rope of the raising facilities, the rolling responses would force little. Furthermore, the rolling motion to the mooring direction would become bigger than that to the opposite direction. (3) On the condition using the hydraulic crane, the rolling responses would fairly increase. (4) From the viewpoint of safety for all considerable conditions of the fishing operations, it would be estimated the significant wave height H_<1/3> that the fishing boats could do fishing is 1m.
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Kenichiro NAGAIWA
Article type: Article
1997 Volume 97 Pages
141-147
Published: September 25, 1997
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At present, loading operation plan at ferry terminal depends on operator's experience and intuition. We studied some solutions of maximum loading plan for a ferryboat. We considered formulation of loading order of cars, with a constraint first come first served' without parameter of car's weight. According to the hearing from ferry shipping company, we had indicated that loading plan should be considered including ship's trim and heel condition. So, this paper is concerned with solution of this problem that minimizes the trim, the heel and dissatisfaction of the car-users in terms of loading order. Generally these have the trade-off between these objectives. Hence this three-objective problem, which yields the pareto set of the feasible solution in decision space, is studied by using algorithms of branch and bound method. Finally some numerical results for this problem are provided by the algorithms implemented with C++.
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Toshio ISEKI, Shigeo TAO, Kohei OHTSU
Article type: Article
1997 Volume 97 Pages
149-154
Published: September 25, 1997
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Bayesian modelling procedure is applied to an inverse problem of how to estimate directional wave spectra from actual ship motion data. The data were recorded by the Voyage Data Recorder equipped on a real container carrier which was put on the North Pacific Line. As for the ordinary merchant ships, it is very difficult to know the actual parameters of rolling motion, such as natural periods, dumping coefficients and metacentric heights GM. And, it is almost impossible to get the hull form offset data which is required for the accurate calculation of the ship motion response functions. Therefore, it is the main purpose of this paper to clarify the availability of the Bayesian modelling procedure to the inverse problem under the unreliable conditions. Compared with the wave direction measured by visual observations, it has shown that the estimated directional wave spectra have some peaks in the observed wave direction. This concludes that the Bayesian modelling procedure is a powerful tool for estimating the wave direction.
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Tadatsugi OKAZAKI, Kouichi SHOJI, Naoki MIZUNO, Kohei OHTSU
Article type: Article
1997 Volume 97 Pages
155-164
Published: September 25, 1997
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Recently, the minimum time optimal solutions to various maneuvering problem has been given by the authors. However, it is impossible that these solutions cover all maneuvering patterns. In order to overtake this defect, it is effective that the maneuvering system provide some interpolation ability to deduce the minimum time maneuvering solutions from the close and similar ones computed in advance. This paper proposes to apply the recent neural network theory to such minimum time maneuvering interpolation problems. The problem treated with here is a minimum time parallel shifting one. As teaching signals to the neural network, the minimum time maneuvering solutions to these problems, which are calculated by the sequential conjugate gradient restoration algorithm (SCGRA), are provided. By simulation technique, the interpolation abilities of the neural network are assessed at first and then the full-scale ship's experiment are implemented using the neural network.
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Kohei OHTSU, Tadatsugi OKAZAKI, Takeshi ISHIBASHI
Article type: Article
1997 Volume 97 Pages
165-174
Published: September 25, 1997
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Recently, various minimum time maneuvering problems including course altering problem, berthing one, parallel shifting one etc. have been numerically solved. In order to realize the minimum time maneuvering method in safety and in certainty, however, it is necessary to have some maneuvering support system. This paper is described on such a supporting system that a maneuver can interrupt if necessarily and give appropriate signals to the control actuators during the automatic minimum time maneuvering. And to demonstrate the effectiveness of this system, a result of actual sea test is shown.
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Akinori YUMURO, Hiroshi UCHINO
Article type: Article
1997 Volume 97 Pages
175-182
Published: September 25, 1997
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In the present report, an optimal control force for ship maneuvering motion is evaluated on the basis of the linear optimal regulator theory under the constraint of input magnitude. And comparison is made between the result and the solution of the optimal control problem which is formulated by variational calculus with two point boundary values. Numerical calculation is made for course keeping maneuver under a wind disturbance. A tanker-type ship having a rudder as control input is employed. From the results of numerical simulation, it is indicated that some similarities are observed in control forces obtained by these procedures when the time taken in saturation of the control input is not so great. Moreover, it is pointed out that the former procedure based on the optimal regurator theory will be useful for evaluating the approximate optimal input.
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Akira FUKUCHI, Tsuneo FUKUTANI, Akihiko HORI, Syuzo TANAKA
Article type: Article
1997 Volume 97 Pages
183-190
Published: September 25, 1997
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For small vessel, it is important to run into the nearest harbor as soon as possible when the sea state deteriorates. However, under such condition, it is difficult to keep her course especially when scudding with strong wind. Therefore the authors proposed the method to strengthen course keeping ability by spreading a canvas around the flying bridge. In order to verify the effects of a canvas, model experiments were carried out at the wind tunnel with water tank to measure wind forces and moment and numerical investigations were conducted using these experimental data. The results were summarized and presented in terms of deviation ratio.
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Kinzo INOUE, Kenji MASUDA, Kiyoshi HARA, Makoto MIYASAKA
Article type: Article
1997 Volume 97 Pages
191-199
Published: September 25, 1997
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In order to clarify the difficulty of handling of a ship inside a harbour or at a narrow channel, an aggregate evaluation model to quantify the "Environment Stress for Land" due to the water restriction and the "Environment Stress for Ship" due to the traffic congestion is proposed. In the present paper, the methodology to estimate each value of the "Environment Stress" and the procedure to obtain the aggregate "Environment Stress" is introduced. These respective "Environment Stress" as an index of this assessment model are led on the basis of the common assessment algorithm and have a criteria to judge whether the given environmental condition can be accepted or not from mariner's viewpoint.
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Keiko MIYAZAKI, Masayoshi NUMANO, Kunihiko TANAKA, Yoshiyasu FUKUSUMI
Article type: Article
1997 Volume 97 Pages
201-211
Published: September 25, 1997
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We have aimed to improve safety of ship navigation at night and studied appropriate passage routes on ship handling simulator taking Kanmon Passage as an example. As we enhance recognition of the passage route, we prepared several ways such as changing character of light buoys or corresponding/cascading buoys lighting. We have represented lights of aids to navigation such as buoys and lighthouses accurately in our ship handling simulator and executed simulator experiments to test those ways. To represent accurate representation of lights, we have made several CGI (Computer Graphics Imagery) objects based on their colors, their luminosity and luminance of CGI on screen. A buoy chooses appropriate object automatically from them according to its own luminosity and a distance between the buoy and a viewpoint. Besides we have added equations of atmospheric transmittance to our program and realized visibility of light on our simulator. We discuss those methods and results of the simulator experiments in this paper.
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Akio SATORI, Masaki OHSHIMA
Article type: Article
1997 Volume 97 Pages
213-220
Published: September 25, 1997
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In maneuvering ship on the ocean, judging the surrounding situation correctly is very important to secure the safety of the ship. To provide useful supporting information for ship maneuvering various systems have been developed. However, to watch circumstances by operatiors is still important particularly under severe conditions such as navigation in passing narrow channel. It is desirable to provide new system in addition to the previously developed supporting systems of ship handling, because the confidence of the total system will be improved by plural different techniques. So we make experiments to extract and track ships in the spatiotemporal images. It is supposed to provide useful information instead of human eyes in the watching. Two computer vision techniques are applied to this purpose. The first is the template matching method and the second is optical flow method. These methods are applied complementally and extracted information are integrated. The results for a set of sequential images on the sightseeing ship have been so far satisfactory.
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Saburo TSURUTA, Hisayuki KUROKAWA, Masanori TODA
Article type: Article
1997 Volume 97 Pages
221-229
Published: September 25, 1997
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In this paper, we have studied the presentation method for support of lookout by Artificial Reality (AR). We tried fundamental experiment that subject find mark and presume aspect. Results are summarized as follows ; (1) In the size of mark, we require viewing angle in excess of 0.3 degrees by 0.1 degrees to find mark. (2) In the case of (1), form of mark don't affect finding time. (3) In color of mark, yellow and white is a short finding time, but blue and green is a long finding time. (4) Presumed accuracy of aspect is far improvement on depression angle of 10 degrees.
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Masao FURUSHO, Masaaki TOMONAGA, Tadahiko FUKUDA, Shigetoshi KAI
Article type: Article
1997 Volume 97 Pages
231-239
Published: September 25, 1997
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We have already reported on the characteristics of a lookout in the daytime and at night by using the eye-movement analyzer called "eye-pointer". This time, we show the remarkable points added the other new data in the twilight with the measurement of the eye-movement by the same way. The remarkable points of the characteristics of the eye-movement related a lookout of ship's operator are as follows ; 1. The extent of fixation point shown by the ellipse with the standard deviation of the fixation angle has a normal tendency being wide horizontally. But in case of the Jet-foil's navigator in the daytime and on the open sea, the extent of fixation point has a special tendency being wide vertically. 2. The average interval of fixation time at night and in the twilight is about 150msec. That in the daytime is about 60msec. On the other hand, by the average speed of sight-line displacement of the eye, the eye-movement of ship's operator is saccade movement in the daytime and in the twilight, and that is smooth pursuit movement at night. Ship's operators conduct the lookout affairs by looking and searching the obstructive targets at night and in the twilight, and by seeing them in the daytime, because of more or less of the visual informations from the ship's environment. 3. The relation every one unit observing duration (33msec) in the daytime between the average speed of sight-line displacement of the eye and the number of fixation point can be shown by the approximate formula ; Y=1827/X+31.8 (Y : the number of fixation point, X : the speed of sight-line displacement of the eye <average rate> (deg/sec), correlation coefficient : -0.82] 4. In the twilight, the average fixation time is more longer and the average speed of sight-line displacement of the eye is more faster, both than that in the daytime. So it is very difficult to catch the visual informations of the targets at sea, in the twilight, ship's operators should have special cautions for preventing ship's collision.
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Hiroki IWASAKI, Keisuke TSUJI, Yasumi KOTOH, Yoshitaka FUKUO
Article type: Article
1997 Volume 97 Pages
241-250
Published: September 25, 1997
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The finger pulse volume sences a finger's peripheral blood vessel. The volume decreases at a tense situation. In this study, a tension is estimated by this senser on student's training the ship's maneuvering. Their trainings are three scenarios, a slalom, a buoy approaching and an on the spot terning. Once more, the students are under the training both with a ship's simulator and a training ship (Oshima Maru : 220GT). Then, the students are devided two groups, an experience group with a simulator and no experience group. As the results, (1) In according to a pile of training, the mean of the tensions were high stabilized. (2) The tension's mean on the training of ship's maneuvering, at the actual ship's maneuvering was more increasingly then at a simulator's maneuvering. (3) At the buoy-approaching, the experience group was more low tension's mean than the no experience group.
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Haruo SATOH, Masaharu FUKUE
Article type: Article
1997 Volume 97 Pages
251-257
Published: September 25, 1997
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Experimental study on the holding power of anchors was performed to establish its estimation method. For the experiment, JIS-stockless anchors 5, 15 and 25kg in weight, were used respectively. As a result, it is shown that the holding power of anchor in muddy soil can be expressed by H=C_D ・c・A where H is the holding power of anchor, C_D is the coefficient of resistance, c is shearing strength and A is the vertical projected area of anchor. By using the formula above, the holding power of anchor on the sediments of the main bays in Japan were estimated. The results showed that the formula can be feasible to estimate the holding power of anchor in muddy soil.
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Hisashi MATSUMURA, Hozumi TANAKA
Article type: Article
1997 Volume 97 Pages
259-267
Published: September 25, 1997
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In the authors' previous studies, we developed a method of categorizing causes of collision accidents based on documents contained in the Reports of Judgement on Marine Accident Inquiry Agency. We first constructed a dictionary of technical terms manually. Terms for categorization were extracted from the Reports by the longest part matching method using this dictionary. The frequencies of these terms in the documents were then weighted to be used for categorization. In the present study, we constructed the dictionary automatically and evaluated the validity of it by the cross validation technique. Three kinds of terms for categorization were generated from a dictionary of navigation technical terms. They were (1) Combination of navigation technical terms. (2) Prefixes + navigation technical terms, or navigation technical terms+suffixes. (3) Kanji characters + longest matching part of two navigation technical terms. Navigation technical terms which occur on the Reports were also added to the generated terms and a dictionary of 628 terms was constructed by computer processing. The rate of successful categorization using the above dictionary increased by 5.7% compared to those found in the authors' previous research. It was also found that terms of low frequency have little contribution to catergorization.
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Hideyuki KITA
Article type: Article
1997 Volume 97 Pages
269-275
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
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For safer traffic environment in a congested bay, introducing a major marine roundabout is an effective countermeasure, which reduces the number of unsafe crossing encounters. However, No sufficient understanding has been obtained about the traffic behavior of ships on a major roundabout. Under this background, the authors proposed a mathematical model to clarify the effects of the roundabout on the traffic phenomena. This paper extends the model by introducing the distribution of ship size of the traffic to relax the unrealistic assumption that ship size is unique for all the ships in the model. The effects and the usefulness of taking the ship size distribution into analysis is demonstrated through numerical examples.
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Article type: Appendix
1997 Volume 97 Pages
App3-
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
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Article type: Appendix
1997 Volume 97 Pages
App4-
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
JOURNAL
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Article type: Appendix
1997 Volume 97 Pages
App5-
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
JOURNAL
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Article type: Appendix
1997 Volume 97 Pages
App6-
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
JOURNAL
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Article type: Cover
1997 Volume 97 Pages
Cover2-
Published: September 25, 1997
Released on J-STAGE: January 15, 2017
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