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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Engineering
Journal Basic Information
Journal DOI :
Korean Society of Marine Engineers
Editor in Chief :
Volume & Issues
Volume 33, Issue 8 - Nov 2009
Volume 33, Issue 7 - Nov 2009
Volume 33, Issue 6 - Sep 2009
Volume 33, Issue 5 - Jul 2009
Volume 33, Issue 4 - May 2009
Volume 33, Issue 3 - May 2009
Volume 33, Issue 2 - Mar 2009
Volume 33, Issue 1 - Jan 2009
Selecting the target year
Fuel Cell System and BOP Technology
Ahn, Kook-Young ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1090~1094
DOI : 10.5916/jkosme.2009.33.8.1090
Trend and Case for the Development of PEM Fuel Cell Metallic Separator
Nam, Dae-Geun ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1095~1099
DOI : 10.5916/jkosme.2009.33.8.1095
A Study on the Cycle Analyzing and Intake Valve Control by the Miller Method with a High Expansion into Low-Speed Diesel Engine
Jag, Tae-Ik ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1100~1106
DOI : 10.5916/jkosme.2009.33.8.1100
Recently, there are quite a lot of attention is drown on the researches related to of Miller method applied high expansion cycle. For this study, high expansion cycles are formed and analyzed with the base view point of thermodynamics, and the features of each factors are also investigated. As a result of analysis, the expansion-compression ratio is expected with a decrease of effective compression ratio as intake valve closing time retarded, however, the decrease of mean effective pressure and its output is accompanied with the counterflow of intake air. Accordingly, as the consequence of such failure, it is expected that an alternative is needed for the realization of high expansion cycles, and the improvement over thermal efficiency. To materialize such cycle, the control system to delay the closing time of intake valve was designed and VVT, the 3 S/B low speed diesel engine, is applied to evaluate the efficiency. The result of the trial shows that there was no significant errors.
Performance Analysis of Marine Solid Oxide Fuel Cell and Gas Turbine Hybrid Power System (under Conditions of Turbine Cooling and Constant Temperature in Cathode Inlet)
Lim, Tae-Woo ; Kil, Byung-Lea ; Kim, Jong-Su ; Oh, Sae-Gin ; Park, Sang-Kyun ; Kim, Mann-Eung ; Kim, Myoung-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1107~1115
DOI : 10.5916/jkosme.2009.33.8.1107
The strengthened regulations for atmospheric emissions from ships like MARPOL Annex VI have caused a necessity of new, alternative power system in ships for the low pollutant emissions and the high energy efficiency. This paper attempts to investigate the configuration of SOFC/GT hybrid power system for marine applications like LNG tanker and to analyze the influence of design parameters on the system performance. The simulation results provide the basic data for the design and efficiency improvement of SOFC/GT hybrid system and indicate the guidelines for the safe system operation.
An Experimental Study on Characteristics of Cooler by Oil Pressure for Decreasing Heat Load in Cold Storage
Kim, Jae-Dol ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1116~1122
DOI : 10.5916/jkosme.2009.33.8.1116
As a result of this study, we reached the following conclusions. With appropriate setting of oil pressure and flow rate, it operated same rotation speed with existing cooler by electrical transmission. In initial operation, a temperature of a cold storage is lower rapidly. As an internal temperature of a cold storage is lower, a decreasing rate of temperature is lower. As a result of comparing the both type, the cooler of oil pressure type showed the following results. The decreasing rate of temperature was more faster and shorter operating time was more shorter than existing cooler of electric type. The actual case of a cold storage, the cooler of oil pressure type can prevent quality deterioration and decrease power consumption. As an internal temperature of a cold storage is lower, power consumption increased rapidly, the oil pressure type showed lower power consumption. COP of two of these types decreased continuously as the internal temperature of a cold storage being reach setting temperature, and that of oil pressure type showed higher amount about 25%. As a setting temperature is lower, the number of refrigerator`s operating times are less and operating time is longer, so power consumption is increased in the maintenance of a cold storage`s internal temperature, power consumption of hydraulic type showed lower amount about 21~25% in two of these types.
Analysis of Performance Characteristics of a Cascade Refrigeration System with Internal Heat Exchanger using Natural Refrigerants
Son, Chang-Hyo ; Oh, Hoo-Kyu ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1123~1128
DOI : 10.5916/jkosme.2009.33.8.1123
In this paper, the cycle performance characteristics of a cascade refrigeration system with internal heat exchanger using natural refrigerants is presented to offer the basic design data for the operating parameters of the system. This system considered in this study is consisted of a high temperature cycle using a carbon dioxide(R744) and low temperature cycle using refrigerants such as R290, R1270, R600a and Ethane. The main results were summarized as follows : The COP of the cascade refrigeration system of R600a with internal heat exchanger is the highest grade in low temperature cycle using refrigerants such as R290, R1270, R600a and Ethane. The COP of the cascade refrigeration system with internal heat exchanger only in high temperature cycle is the highest value among three type cycle, such as only low temperature cycle, only high temperature cycle and all the cycle.
Characteristics of Temperature Control by Hot-gas Bypass Flow Rate on Industrial Water Cooler
Baek, Seung-Moon ; Choi, Jun-Hyuk ; Byun, Jong-Yeong ; Moon, Choon-Geun ; Lee, Ho-Saeng ; Jeong, Seok-Kwon ; Yoon, Jung-In ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1129~1136
DOI : 10.5916/jkosme.2009.33.8.1129
The paper presents the performance characteristics for a cooling system using EEV. The water cooler was used to reduce thermal deformation and contraction due to high speed of machine tools and the EEV was used for capacity control for water cooler. The apparatus was designed for hot-gas bypass system which a hot-gas can flows from outlet of compressor to the inlet of evaporator. This experiment is the intermediary study for precise temperature control through PID control. The results show that the evaporator pressure increased and refrigeration capacity decreased as the EEV opening step of hot-gas bypass increased. These results can be used as basic data for the design of effective water cooler.
Heat Transfer Enhancement from Plain and Micro Finned Surfaces According to Liquid Subcooling
Lim, Tae-Woo ; You, Sam-Sang ; Choi, Hyeung-Sik ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1137~1143
DOI : 10.5916/jkosme.2009.33.8.1137
Experiments were conducted to evaluate pool boiling heat transfer performance between plain and micro finned surfaces with FC-72, which is chemically and electrically stable. Three kinds of micro fins with the dimension of
height) were fabricated on the surface of a silicon chip. The experiments were carried out on the liquid subcooling of 5, 10 and 15 K under the atmospheric condition. The micro finned surface with a larger fin width of
provided a better pool boiling heat transfer performance. Also, the micro finned surfaces showed a sharp increase in heat flux with increasing wall superheat and a larger heat transfer enhancement compared to a plain surface.
Analysis of Vapor Compression Refrigeration Cycle Performance Depending on Different Joining Method of Non-adiabatic Capillary Tube
Yi, Dae-Yong ; Park, Sang-Goo ; Kim, Hyun-Jung ; Jeong, Ji-Hawn ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1144~1151
DOI : 10.5916/jkosme.2009.33.8.1144
Refrigeration systems can be incorporated with non-adiabatic capillary tubes to improve their efficiency. The non-adiabatic capillary tube is constructed by joining the capillary tube with suction pipe to allow heat transfer between them, which is called capillary tube-suction line heat exchanger(SLHX). There are various joining methods and they may influence the characteristics of the refrigeration cycle. The present work aims to analyze the effect of widely-used two joining methods on the refrigeration cycle. The results show that soldered SLHX has much less thermal resistance than tapered SLHX but slightly outperforms in terms of coefficient of performance(COP) and cooling capacity. The soldered SLHX increased COP and cooling capacity of a refrigerator by 5.09% and 14.77% while the tapered SLHX did by 5.05% and 14.75%, respectively.
Measurement and Assessment on the Shaft Power Measurement of Diesel Engine using Strain Gauge in Marine Vessel
Lee, Don-Chool ; Song, Myong-Ho ; Kim, Sang-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1152~1161
DOI : 10.5916/jkosme.2009.33.8.1152
The power measurement of main propulsion system on the new vessels can be classified with the direct method acquired from the shaft`s strain using strain gauge and the indirect method converted and summed from all of cylinders combustion pressure using mechanical or electrical pickup device during the sea trial. This power is fluctuated by external factors which was influenced by various sea motions with long time interval and by internal factors which was influenced by varying torques of torsional vibration and bending moment, due to mis-aligned shaft and whirling vibration with short time interval. In this paper, the statistical analysis method for the shaft power measurement and assessment using strain gauge in marine vessels are introduced. And these are identified by the low speed two stroke diesel engine model and four stroke medium speed diesel engine model including reduction gear.
Electrochemical Evaluation on Corrosion Property of Welding Zone of 22APU Stainless Steel
Moon, Kyung-Man ; Kim, Yun-Hae ; Lee, Sung-Yul ; Kim, Jong-Do ; Lee, Myung-Hoon ; Kim, Jin-Gyeong ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1162~1169
DOI : 10.5916/jkosme.2009.33.8.1162
Two kinds of welding methods were carried out for 22APU stainless steel, one is a Laser welding and the other is the TIG welding. In this case, difference of corrosion characteristics of welded zone with two welding methods mentioned above was investigated with electrochemical methods such as measurement of corrosion potential, polarization curves and cyclic voltammogram etc.. Vickers hardness of all welded zone (WM:Weld Metal, HAZ:Heat Affected Zone, BM:Base Metal)in the case of Laser welding showed a relatively higher value than those of TIG welding. Futhermore their corrosion current density in all welding zone were also observed with a lower value compared to TIG welding. In particular corrosion current density of BM regardless of welding method indicated the lowest value than those of other welding zone. Intergranular corrosion was not observed at the corroded surface of all welding zone in the case of Laser welding, however it was observed at WM and HAZ with TIG welding, which is suggested that chromiun depletion due to forming of chromium carbide appears to WM and HAZ which is in the range of sensitization temperature. Therefore their zone can easily be corroded with more active anode. Consequently we can see that corrosion resistance of all welding zone of 22APU stainless steel can apparently be improved by using of Laser welding.
A Numerical Study on Analysis of Low Frequency Aero-acoustic Noise for a HAWT of NREL Phase VI
Mo, Jang-Oh ; Lee, Young-Ho ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1170~1179
DOI : 10.5916/jkosme.2009.33.8.1170
The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to
in the near field and
in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.
A Study on Flow Control of Open Cavity with Inclined Rear Walls
Cho, Dae-Hwan ; Jin, Wan-Bin ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1180~1186
DOI : 10.5916/jkosme.2009.33.8.1180
This experimental study is about the flow characteristics according to existence and nonexistence of the control rod and location in the flow field where it has the Inclined rear walls in the open cavity. By using the visualization of flow and particle image velocimetry (PIV), we performed about a change and speed of the Reynolds number. Our objective was what part of the control rod gives less effects to the characteristics of flow and how the shear mixing layer moves at what critical point of the Reynolds number. As a result, we differed the location of control rod. So finally, L/H
Coagulation Characteristics of Wastewater Treatment Process Using Completely Mixed Chamber
Kim, Dong-Jun ; Park, Sang-Kyoo ; Lee, Yong-Ho ; Yang, Hei-Cheon ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1187~1195
DOI : 10.5916/jkosme.2009.33.8.1187
The objective of this study is to investigate the coagulation characteristics of the completely mixed chamber for wastewater treatment. The completely mixed chamber system was composed of the reservoirs, the three-stage mixing and coagulation part with propeller impeller, the injection parts of coagulants, a sedimentation tank and a control panel. Wastewater sample of pH 8.5 and initial turbidity 1,000NTU was prepared using sludge taken from a tunneling work site. The efficiency of turbidity removal with increasing the dosage of coagulant aids increased by about 99%. Increasing coagulant above the optimal dosage, however, the efficiency of turbidity removal decreased.
Estimator Design of Underwater Environment Changes for ROV by Using Observer Techniques
Kim, Hwan-Seong ; You, Sam-Sang ; Choi, Hyeung-Sik ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1196~1202
DOI : 10.5916/jkosme.2009.33.8.1196
In this paper, an estimator design of underwater environment changes is proposed by using observer techniques for ROV control system. The underwater environment changes are considered as an external disturbance term for ROV model and it is added into the input term of ROV model. To estimate the environment changes, a PI observer which does not effect the external disturbance input term is proposed. To verify the effectiveness of the proposed method, the step and the sinusoidal environment changes are considered in simulation. The proposed method will be applied to design the haptic controller for ROV in future.
A Sliding Mode Control of an Underwater Robotic Vehicle under the Influence of Thrust Dynamics
Choi, Hyeung-Sik ; Park, Han-Il ; Roh, Min-Shik ; So, Myung-Ok ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1203~1211
DOI : 10.5916/jkosme.2009.33.8.1203
The dynamics of underwater vehicles can be greatly influenced by the dynamics of the vehicle thrusters. The control of the state of the hovering or very slow motion of the underwater vehicle is most important for automatic docking or control of the manipulator of the vehicle. The dynamics of the thruster based on the electric motor is nonlinear and has uncertain parameters. Since the dynamics of the vehicle coupled with the dynamics of the thruster is nonlinear and has uncertain parameters, a robust control is very effective for a desired motion tracking of the uncertain and nonlinear vehicle. In this paper a study was performed on the robust control scheme of the very slow motion or hovering motion of the underwater vehicle actuated by the electric motor. Also, a concurrent control on the state of the vehicle with nonlinearity and uncertain parameters was performed. A sliding mode control algorithm out of robust controllers was designed and applied, which compensates the nonlinear forces and uncertain parameters of the vehicle and actuator. Through a computer simulation, the proposed control scheme was compared with a linear PD controller and its superior performance was validated.
A Study of Robust Vibration Control for a Multi-Layer Structure
Kim, Chang-Hwa ; Jung, Byung-Gun ; Jung, Hae-Jong ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1212~1219
DOI : 10.5916/jkosme.2009.33.8.1212
In this paper, a state feedback gain controller using linear matrix inequality(LMI) for the multi-objective synthesis is designed, in the multi-layer structure with integral type servo system. The design objectives include
performance, asymptotic disturbance rejection, time-domain constraints, on the closed-loop pole location. The results of computer simulation show the validity of the designed controller.
Fabrication of tunable all-fiber feedback laser and its application
Sohn, Kyung-Rak ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1220~1225
DOI : 10.5916/jkosme.2009.33.8.1220
In this paper, a tunable fiber feedback laser based on the use of Sagnac loop filter and fiber Bragg grating (FBG) is proposed. The Sagnac loop filter using a high birefringence fiber provides precise 0.33-nm channel spacing as a multi-wavelength grid filter. Ni-Cr wire wound on the FBG is useful to induce the thermo-optic effect of the fiber. Two types of FBG structures, which have a different length of wire, are demonstrated to show the wavelength shift and separation. To tune FBG by resistant heat, some current is supplied into the wire. When the wavelength matched with one of the cavity modes of Sagnac loop filter, the mode-locked lasing is occurred. The electrical power sensitivity of the resonant wavelength is measured to 1.75pm/mW. This laser configuration can be applied the electrical power system for monitoring the power fluctuation.
A study on solar-wind hybrid power generation system
Oh, Jin-Seok ; Jo, Kwan-Jun ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1226~1231
DOI : 10.5916/jkosme.2009.33.8.1226
In this paper, a solar-wind hybrid system is decsribed for Stand-Alone(SA) power generation system. Mostly SA power generation system for ocean facilities composes a solar system. Normally, the output power of solar system is decreased with weather condition as cloudy and rainy. Solar-wind hybrid system can be operated as complement system each other. In this paper, the characteristic simulation of solar and wind is performed by LabVIEW. The hybrid power generation system is designed according to simulation results, and is tested for checking the complement characteristic.
A Study on the Digital Protective Relay for Generator Fault Protection
Jang, Nak-Won ; Park, Jeong-Do ; Lee, Sung-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1232~1238
DOI : 10.5916/jkosme.2009.33.8.1232
As power facilities are getting higher at capacity, the monitoring and diagnosis of generators for fault detection and protection has attracted intensive interest. In case of an after-fault in high capacity rotating machines, the recovering cost is usually very expensive and additional time is necessary for returning in a normal situation. In this paper, we developed the protection program for the generator fault protection system and each module of the digital protective relay H/W for loading the protection program. The protective relay H/W was designed to have EMC characteristics for prohibiting from fault operation in bad power systems.
A Study on Design of the Miniaturized Inverted-F Antenna Using Lumped Elements for Z-wave
Kwak, Min-Gil ; Kim, Dong-Seek ; Won, Young-Soo ; Cho, Hyung-Rae ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1239~1245
DOI : 10.5916/jkosme.2009.33.8.1239
Currently, so many approaching methods are being developed to optimize the antenna size. In this paper, We fabricated Inverted-F type antenna attaching lumped components to solve the limitation of antenna size. Through experiments, a basic Inverted-F type antenna was fabricated and satisfied the adequate radiation pattern. After this, we researched the effect of antenna varied by matching circuit consist of chip type resistor, inductor, and capacitor. Using that elements, the antenna was matched at aim frequency. The proposed antenna`s size is
that is very small size against the resonance frequence. Measuring the developed antenna, Its return loss was -18dB. Thus, this antenna can be used for Z-wave systems.
Implementation of a Fuzzy PI+PD Controller for DC Servo Systems
Hong, Soon-Ill ; Hong, Jeng-Pyo ; Jung, Sung-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1246~1253
DOI : 10.5916/jkosme.2009.33.8.1246
This paper presents derived a calculating form of fuzzy inference, based on decomposition of
-level sets. Based on the calculating form it is propose that fuzzy logic circuits of PI+PD controller are a body from fuzzy inference to defuzzificaion in cases where the command variable u directly is generated PWM. The effect of quantization on
-levels is investigated. with input/out characteristics of fuzzy controller by simulation. It is concluded that 4 quantization levels are sufficient result for fuzzy control performance of DC servo system. Simulation and experimental results demonstrated that the hardware implementation of the proposed controller can successfully provide good performance on the position control of DC servo system.
A Study on the Tele-Controller System of Navigational Aids Using CDMA Communication
Jeon, Joong-Sung ; Oh, Jin-Seok ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1254~1260
DOI : 10.5916/jkosme.2009.33.8.1254
CDMA tele-Controller system is designed with a low power consumption 8 bit microcontroller, ATmega 2560. ATmega 2560 microcontroller consists of 4 UART (Universal asynchronous receiver/transmitter) ports, 4 kbytes EEPROM, 256 kbytes flash memory, 4 kbytes SRAM. 4 URAT is used for CDMA modem, communication for GPS module, EEPROM is used for saving a configuration for program running, a flash memory of 256 kbytes is used for storing a F/W(Firm Ware), and SRAM is used for stack, storing memory of global variables while program running. We have tested the communication distance between the coast station and sea by the fabricated control board using 800 MHz CDMA modem and GPS module, which is building for the navigational aid management system by remote control. As a results, the receiving signal strength is above -80 dBm, and then the characteristics of the control board implemented more than 10 km in the distance of the communication.
A Study on the Sensorless Speed Control of Induction Motor using Direct Torque Control
Yoon, Kyoung-Kuk ; Oh, Sae-Gin ; Kim, Jong-Su ; Kim, Yoon-Sik ; Lee, Sung-Gun ; Kim, Sung-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1261~1267
DOI : 10.5916/jkosme.2009.33.8.1261
The Direct Torque Control[DTC] controls torque and flux by restricting the flux and torque errors within respective hysteresis bands, and motor torque and flux are controlled by the stator voltage space vector using optimum inverter switching table. And the Current Error Compensation method is on the basis of compensating current difference between the induction motor and its numerical model, in which the identical stator voltage is supplied for both the actual motor and the model so that the gaps between stator currents of the two can be forced to decay to zero as time proceeds. Consequently, the rotor speed approaches to the model speed, namely, setting value and the system can control motor speed precisely. This paper proposes a new sensorless speed control of induction motor using DTC and Current Error Compensation, which requires neither shaft encoder, speed estimator nor PI controllers. And through computer simulation, confirm effectiveness of proposed method.
Configuration of PID tuning simulator for evaluation of marine engineer`s ability
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1268~1274
DOI : 10.5916/jkosme.2009.33.8.1268
Various evaluation systems using simulators have been adopted widely for the purpose of training and examination, including marine engineering education area. This paper suggests a PC based evaluation scoring system for simulators where the operation ability of machineries and background knowledges of trainees or examinees are able to be assessed relatively. The scores are based on the 100 point resulted from their responses for a given evaluation scenario under a PID tuning simulation. The mistakes they make during the operation time are integrated firstly to get error sum, and the error sum is transformed secondly to 100 point score according to a formula where the knowledge level of examinee`s groups can be compensated and considered reasonably. The implementation result of evaluation system for the given control loop is described and analyzed to show the effectiveness of the suggested configuration as an evaluation tool.
Scouring and accumulation by tidal currents around cubic artificial reefs installed at Geogeom waterway
Kim, Dae-Kweon ; Lee, Jin-Young ; Suh, Sung-Ho ; Kim, Chang-Gil ; Cho, Jea-Kwon ; Cha, Byung-Yul ;
Journal of the Korean Society of Marine Engineering, volume 33, issue 8, 2009, Pages 1275~1280
DOI : 10.5916/jkosme.2009.33.8.1275
Tidal currents were observed at 1 station of artificial reefs group during 15days. Maximum current was 82.4cm/s, and mean current showed 12.8~28.0cm/s, respectively. Flood currents magnitude were bigger than ebb ones due to wake region. To grasp sediment distributions, sediments were sampled at 4-direction(E, W, S, N) around each station. According to the results of sample analysis, sediments showed different distribution by main current direction. It showed that sediments distribution at front and back of artificial reefs were differently occurred by change of main current direction. It suggest that artificial reefs need to install after confirming tidal currents direction and sediments type.