Since the production of scallop aquaculture in Japan has increased largely, the automatic drilling machines
has been used by the almost aquaculture bodies. Because of shell shape varying on size by growth and non automatic control mechanism built in drilling machines, severe problem has occurred that the machines always can not succeed to make a hole in the ear portion on a shell as expected.
In this paper, the three respectable drilling areas were defined near by the byssal notch and by the ligament
on the anterior ear of a shell. After confirmed of these parts obeying allometric growth, the successful rate (P) to
drilling was estimated by some geometrical non-dimensioned parameters based on the vertical shell height (VH).
The results of simulation were revealed as follows. 1) Near by the byssal notch : P was over 70% in case of
VH over 60mm with 1.4-2.0 mm diameter of a drill chip (d), and P became up to 92% with VH=70mm and d
= 1.6mm as normal use. 2) On the anterior ear : P reached to over 99. 6% with VH=40-55mm and d=1. 5-
2.0mm, also P showed to 99. 9% with VH=50mm and d=1.6mm for nomal use. 3) By the ligament : P was
ranged from 30 to 77%, especially, P=70% under the nomal operation as same as 2).
To locate the center of a drill chip according to the vertical shell height would rise up the successful rate to
drilling through the ear part on a shell more higher than now.
In the field of aviation, it is argued the necessity of the wide area DGPS that is a new system demanding
highly precise positioning accuracy. This new system has the available range of over 1000-km around the reference
station, and practical use begins to be investigated. It is expected that an idea of this wide area DGPS that
will be applied to the sea and the ground in the future.
In this study, We paid attention to influence caused to the position accuracy of DGPS in the wide area. The
influence could be made clear in the simulation and the experiment. The simulation confirmed the delay of the
correction value confirmed to influence the positioning accuracy. The positioning accuracy was found a tendency
to deteriorate in a ratio of 0.0031m/sec2 according to the delay time. In the observation, several medium frequency
beacon DGPS station data were used. The results of these observation, the distance between the reference
station and users (it is called base line length) was confirmed to influence the effect of DGPS positioning. It became
clear that the position error increases in proportion to the base line length at the rate of only a few 0.12m/100km.
These results show the effectiveness of the wide area DGPS.
The purpose of this study is to investigate cause of engine trouble conceming valve-seizure occurred on main
engine of Tokyo university of fisheries, the research and training vessel Shinyo Maru. For this purpose, an experimental
measurement of the valve stem clearance had been carried out when the valve stem guide was inserted
into the cylinder cover. The results showed that the mean value of valve stem clearance reduction was 0.008 mm.
The valve stem clearance of measurement value has lowered than the minimum value (0.06.mm) of maker recommendation.
It was confirmed that valve-seizure in main engine could cause a dangerous operation. By taking point
of view to prevent the engine trouble, these results lead to the suggestion that the valve stem guide should be
finished accurately to the desired inside diameter with hand reamer, when the valve stem guide was changed.
Numerical experiments were conducted to estimate the change of flow condition and the distribution of
phytoplankton and nutrient by a submerged structure for upwelling in vertically 2-D steady flow field, using a
coupled physical-biological model with changing parameters which are inflow velocity and turbulent diffusion
coefficient. Nutrient uptake and the loss of phytoplankton including physiological death, exudation of organic
substances and predation by zooplankton are considered as biological terms in the goveming equations. The
computational domain is 2km long and 50.5m deep. The structure with 10m height is set lkm downstream from
the inflow boundary.
As increasing the inflow velocity, the phytoplankton decreases in the upper and middle layers and, on the
contrary, nutrients increases. However, they reaches certain values when the inflow velocity is over 0.3m/s.
Biological tems are dominant in the surface layer. On the other hand, the physical terms (advection and
diffusion) are dominant in the bottom layer. In the middle layer, the increment by nutrient uptake balances with
decrease by advection, diffusion and the loss.
The authors investigated inboard lighting-one of residential environment elements-of the fisheries training
ship. The reflective properties of the ceiling and wall decrease year by year. As the average age of the crew
members rises, there is an increased desire for better lighting. The lighting problem tends to be neglected in
favor of environmental factors such as noise and vibration. Nonetheless, it is necessary to set a recommended
level of illumination for the ship which will offer a comfortable and adequate inboard environment. Authors
regard that lighting equipment should be upgraded within 10 years of construction, if economically possible, in
order to maintain a positive inboard environment.
Deep sea water has been tried to be used actively in fisheries for increasing basic production of sea area.
It is requested that the deep sea water must be lifted up to photic zone.
This paper presents the theory and the numerical calculation program about buoyant jets in quiescent
Stratified ambient fluids. As the operative example, assuming a jet spouted out river water from a pipe at sea
bottom, the rising height and discharge of the jet are calculated by the program.