This report details the design and development of an agar/NaCl gel-like tissue phantom mimicking the electrical properties of wet human skin. The skin phantom provides a reliable, reproducible testing ground for dry-contact polydimethylsiloxane (CNT/PDMS) electrodes, with the aim of recording electroencephalograms (EEGs) and stimulating brain activity in a controlled environment. These electrodes are being designed for the development of an in-ear brain-computer interface (BCI).
The electrical properties of biological tissue are referred to as the conductivity σ and permittivity ε and denote the ability for a material to conduct and trap electric charge respectively. These properties are frequency dependent and particularly for EEGs, a frequency range of 1-1000 Hz is of interest (with some added leeway). Wet skin hereby has a conductivity of around 0.1 Siemens to 0.2 Siemens in the 1-1000 Hz frequency range whereas the permittivity ranges from 5.7 * 10^5 to 5.2 * 10^5. Different agar and agar/NaCl solutions are created to try and obtain solutions with the mentioned electric properties. Specifically, NaCl is added to improve the conductivity and obtain a non-linear frequency response similar to that of human skin. The electrical properties of the phantoms were verified/measured using the parallel plate method. This method is essentially sandwiching a material under test (MUT) (in this case the fabricated gel-like agar and agar/NaCl solutions) between two conducting plates. This method is most suited for measurements in the lower frequency spectrum.
The skin phantom consisting of 3.04 mass fraction weight (wt.%) agar and 0.539 wt.% NaCl shows the closest similarity to the conductivity of wet skin. Namely, a conductivity of ~ 0.1 Siemens to 0.45 Siemens in the frequency range of 1-1000 Hz. A decrease of 0.250 wt.% NaCl will most likely achieve the desired conductivity response of 0.1 Siemens to 0.2 Siemens in the frequency range of 1-1000 Hz. The skin phantom consisting of 3.00 wt.% agar and 1.02 wt.% NaCl showed the permittivity closest to that of wet skin, but might have been a noisy outlier. Its permittivity ranges from 10 * 10^6 and 7.5 * 10^6. This is still a large error margin from the desired 5.7 * 10^5 to 5.2 * 10^5. Additional fillers like glycine or Al powder need to be added to the solutions to obtain a permittivity close to that of wet human skin. Multi-day and difference in applied pressure measurements are performed to check the sensitivity and reproducibility of the phantoms. Applied pressure hereby has little to no influence whereas a longer life-span of the fabricated phantom shows a drastic decrease of the electrical properties of the phantoms after day 1. The changes then seem to settle. Worth mentioning is that the change is only drastic when the solution has a high conductivity. This is generally not the case for solutions with conductivities close to wet skin.

This paper is the result of the first collaboration project between Delft University of Technology and Sohar University. The project team consisted of 6 core- members from both Sohar University and TU Delft along with 5 more students, together appointed to help find an answer for a problem stated by Sohar Industrial Port Company and Majis Industrial Services.
This paper proposes a deep seawater intake for the cooling water system of Sohar Industrial Port, Oman. In the region’s summers, surface water temperatures tend to rise to very high levels. Among other things, this results in inefficient cooling of the processes associated with the steel manufacturers, petrochemical plants, refineries and power plants present in the port. The proposed inlet subtracts water 4 km offshore at an average temperature of 24.9 ±C. Using this colderwater, the demand is expected to go downwith approx. 2% in the winter and 16% in the summer, saving system capacity and pumping costs. The 2,148 MW generated power at Sohar port is expected to increase efficiency by 0.72%. Furthermore, the coastal waters are vulnerable to algal blooms. These toxic algae can not be filtered out efficiently and lead to temporary closure of the desalination plants (mainly Reverse Osmosis) causing a threat to the drinking water supply in the entire north of Oman. This paper concludes however that there is not an (economically) feasible inlet location that is unaffected by the algal blooms. Other water characteristics such as turbidity and organic content are also expected not to show significant improvement at the proposed inlet location but more elaborate measurements should validate this.
A technical feasibility study was conducted to find the optimal system design. Multiple alternative materials being metals, alloys, HDPE and concrete have been investigated to serve as water conveyors to transport the water from the inlet to the shore. A possible design for the off-shore water inlet structure was made as well as a recommended design for the connection of the pipelines with the current facilities. Site selection, material selection, friction head loss calculations, pipeline sizing, concrete ballast weights, seabed pipeline stability and planning have been discussed in this report. Finally, a financial feasibility study has been conducted. A model was built and costs have been quantitatively estimated based on the technical design. Benefits have been quantified where possible and if not, were qualitatively described. It is concluded that it is not financially feasible to build a deep seawater intake for the entire port. Building a limited-scale variant, only providing RO and power plants, is a better solution but still unfeasible. Recommendation is done to scrutinise the processes within power plants and RO-plants further as their potential benefits are considerable.