## 2 Simulation Based Resource Optimization
### Description of Mobile Harbor Simulation  
We employ the Technomatix Plant Simulation 9 software (SIMENS, Germany) which is a discrete event simulation to construct simulation models. To build operation logic for the offshore port service, we worked collaboratively with KLNET, which is a port operation system IT company. We assume that the port is aware of the anticipated arrival of a ship 24 h before it actually arrives. Arriving ships carry import containers and remain in an offshore waiting location until there is an available offshore mooring location. For this study, there are six mooring locations available and the mobile harbor will freely move around to the ships in these locations as needed. After all the import containers on the ship are unloaded, the container will be loaded with the export containers. After this operation, the ship departs the system. The ship's waiting time is the difference between the ship's service start time and its port arrival time. The ship service time is calculated as time of departure minus the service start time. To build scheduling heuristics of MH to handle container ships, we implement two priority rules for container ships. Ships are served in a first come first serve (FCFS) manner by the mobile harbor. Import containers are given higher priority than export containers on a given ship. As each mobile harbor becomes available, it is assigned to its next job based on the ship information such as arrival time and import/export container volume. Each mobile harbor will remove a complete load of containers if the containers are available; otherwise, it will take as many as there are. If a mobile harbor's next job is to load or unload a containership, it immediately proceeds to the offshore service location. The mobile harbor waits for any mooring locations. As soon as possible, the mobile harbor will moor with the container ship and conduct its business. Upon completing service, it will unmoor and seek its next job. The mobile harbor travels to the land side waiting location if it has no task assigned or all land births are occupied. The number of births at the land-sea interface is an input parameter that can be changed to guarantee the service level and minimize cost. If a land berth becomes available and there is work to do (unloading or loading at the land-sea interface), the mobile harbor proceeds to that location. Waiting mobile harbors are given priority at the land berths in an FCFS manner. There are fixed mooring and unmooring times at the land berths. Because ship arrival information is available 24 h before the ship arrives, mobile harbors can prepare for the next ship service activity in advance. If there are no jobs required for a mobile harbor when it completes a job, it will wait in the designated land waiting shelter. This land side shelter idea was inspired by the operation of mid-stream lighters in Hong Kong (personal communications with Captain [PERSON], CEO of the Hong Kong Mid-Stream Operators Association). When a mobile harbor idiles at the land shelter, it checks for new tasks every 30 simulated minutes. The overall work process for the mobile harbor is depicted in Figure 2.  
Figure 2: Overall work process of the MH. The simulation layout of the MH is depicted in Figure 3. The ship generator produces a ship object based on a pre-determined inter-arrival and cargo distribution function. The ship waits in an anchorage in an ocean waiting place if there is no empty offshore working place. After finishing all cargo transfers in a ship, it leaves the port and records its finishing time. The number of mooring points of each offshore working place can be up to six and it varies according to the size of the container ship and the MH. The MH generator produces an MH object based on a pre-determined specification such as travel speed, operation speed, and capacity. MHs move between the mooring point and land berth to transfer import and export cargo via a transfer way.