Journal of Marine-Earth Science and Technology

Abstract. Small fast passenger boats serve to carry passengers at certain routes particularly in short distance between the islands. The passengers preferred those transport mode due to its short travel time. In fact, there are many accidents occur during boat operation which end up with the loss of life and materials at sea.  An intensive study was executed by the authors with the purpose to obtain an unsinkable boat. The boat data of existing boats were collected and be used for re-designing process. During the design process, some solid boxes, expanded bags were provided inside boat to reduce the incoming water. Meanwhile, the bags were fitted outside the boat (side floater) to provide additional buoyancy and righting moment for stability performance. A boat model was developed and tested to confirm the design results. In addition, a full-scale boat was developed and equipped with solid boxes, air bags and side floaters. The theoretical computation and extrapolated results from model proved that the required volume for inside solid boxes and air bags are 1.213 m³ and 0.511 m³ respectively. Meanwhile, the required volume of outside air bags is 0.357 m³. It was found that the total boat weight, passengers and incoming water of 4.259 tons are balanced by weight displacement of 5.025 tons. There was reserve buoyancy of 0.766 tons that supports the boat to be float and side floater to prevent the boat from capsize. The result of sea trial showed that with all loading conditions the boat was still afloat (unsinkable).  

Abstract. Hydrofoil ship usually experiences high resistance and excessive heave and pitch that may lead to downgrade her seakeeping performance. Therefore, a reliable investigation on prediction of a seakeeping performance of a hydrofoil ship in head-seas is obviously required. To achieve this objective, an analysis of Computational Fluid Dynamic (CFD) approach on hydrofoil ship motion is then proposed. Several parameters such as angle of stern foil and Froude Number have been accordingly taken into account in the simulation, where the fore foil angle is constantly 5^o. In general, the results revealed that the increase of the stern foil angle was proportional to the heave motion of the hydrofoil ship. As compared to the magnitude of the stern foil angle of 5^o and 10^o, the heave motion of the hydrofoil ship has sufficiently decreased at the stern foil angle of 7.5^o, which leads to have a better seakeeping performance. Furthermore, the subsequent increase of Froude number pointing towards reduction of heave motion, which was inversely proportional to the magnitude of her pitch motion. Inherently, these have led to degrade of the hydrofoil ship seakeeping performances presented in the form of high Response Amplitude Operators (RAO). In general, this CFD simulation is very beneficial to ensure an operational effectiveness of hydrofoil design in high sea states with respect to the aforementioned design parameter.

In the GNSS data analysis to obtain tropospheric parameters and station positions, study GNSS meteorology in Arief and Heki (2020), did not estimate them myself but downloaded them from appropriate data sets available from various research centers, such as UNR and GSI. Arief and Heki (2020), studies are performed for heavy rain episodes in the Japan area where large number of GNSS stations are available. In this study, I try to analyze the GNSS data taken in Indonesia. Here, I estimate tropospheric parameters as well as station positions using an alternative way, i.e. data analysis made by myself using an appropriate GNSS software package.

UNAVCO (https://www.unavco.org/software/data-processing/postprocessing/postprocessing.html) says that there are 3 distributions of GNSS software based on their use: “Research-Level”, “Open-Source” and “Commercial”. The usage of Open-Source software in Indonesia is quite promising and will develop rapidly considering that it is easy to obtain and simple to operate to get results.

The goal of this chapter is simply to show that GNSS meteorology can be applied in Indonesia as well as in Japan (Arief and Heki 2020), by estimating zenith tropospheric delays (ZTD) from continuous GNSS stations in Indonesia, using one such software package “goGPS”.

Abstract- The subsitution SBE in limestone can significantly improve the characteristics of limestone as a landfill material, especially in increasing the CBR hardness value without changing the limestone grain size distribution. This is because SBE acts as a filler in the SBE-limestone mixture. The existence of SBE in the mixture does not change the value of the mixture plasticity index, because SBE and limestone are both not plastic. SBE material can be used as substitution material (matrix material) up to 30% by weight in the SBE-limestone mixture. The role of SBE as a filler becomes very important in mixed materials for non-limestone structural material requirements, especially for matrix material sizes from 0.4 to 10 mm or sand to gravel. Of course, more research is needed on the physical and mechanical characteristics of mixed materials due to the use of SBE as a filler in matrix multi grand size (sand to gravel).