Life cycle cost analysis for Scotland short sea ferries

The pathway to zero carbon emissions passing through carbon emissions reduction is mandatory in the shipping industry. Regarding the various methodologies and technologies reviewed for this purpose, Life Cycle Cost Analysis (LCCA) has been used as an excellent tool to determine economic feasibility and sustainability and to present directions. However, insufficient commercial applications cause a conflict of opinion on which fuel is the key to decarbonisation. Many LCCA comparison studies about eco-friendly ship propulsion claim different results. In order to overcome this and discover the key factors that affect the overall comparative analysis and results of the maritime field, it is necessary to conduct the comparative analysis considering more diverse case ships, case routes, and various types that combine each system. This study aims to analyse which greener fuels are most economically beneficial for the shipping sector and prove the factors influencing different results to LCCA. This study was conducted on hydrogen, ammonia, and electric energy, which are carbon-free fuels among various alternative fuels that are currently in the limelight. As the power source, PEMFC and Battery were used as the main power source, and the solar PV system was installed as an auxiliary power source to compare economic feasibility. Several cost data for LCCA were selected from various feasible case studies. As the difficulty caused by the storage and transportation of hydrogen and ammonia should not be underestimated, in this study, LCCA considers not only the CapEx and OpEx but also fuel transport costs. As a result, fuel cell propulsion systems with hydrogen as fuel proved financial effectiveness for short-distance ferries as more inexpensive than ammonia-fuelled PEMFC and batteries. The fuel cost takes around half of the total life cycle cost during the lifetime span

Regulatory gap analysis for risk assessment of ammonia-fuelled ships

The concept and design of ammonia as a marine fuel are still in the embryonic stage which requires an in-depth investigation of its applicability in terms of its safety and potential risks, both in the design and operational phases of a ship's lifecycle. The paper examines and compares the state-of-the-art safety regulations, rules, standards and guidelines relevant to ammonia-fuelled ships available in various classification societies reports and international regulations such as the IGF codes and summarises their gaps and limitations. The paper critically analyses three major hazards namely toxicity, chemical corrosion, fire and explosion and their potential impact on the human, environment and ship in the event of ammonia leakage. Various hazardous areas considered include ammonia leakage at the bunkering station, fuel preparation room, engine room and storage room and its impact on the ship's general arrangement. In addition, this study reviews and discusses various qualitative and quantitative risk assessment methods employed in ships using low-flashpoint fuels and their relevance and potential suitability for ships powered by ammonia. The paper concludes with important findings and recommendations to aid designers, operators, safety experts, and policymakers in the further development of safety within the framework of risk assessment and management. Overall, this study provides valuable insights into the safety considerations of using ammonia as a marine fuel and highlights the need for further research and development in this area

Safety evaluation on ammonia-fueled ship : gas dispersion analysis through vent mast

The maritime industry is exploring ammonia as an alternative fuel to reduce greenhouse gas emissions. However, the high toxicity of ammonia poses significant safety challenges for onboard handling and storage. This study investigates ammonia dispersion and toxicity levels from vent mast releases on ships, aiming to enhance safety measures for future ammonia-fueled vessels. Using CFD analysis on a 31,000-dwt general cargo ship model, the research examines various release scenarios, considering regulatory requirements, vent mast design, and environmental conditions. Results show that direct ammonia release from the vent mast poses fatal risks to the crew in the accommodation area and on adjacent ships, regardless of current regulatory stipulations. The study recommends installing an ammonia-catching system to reduce concentrations to safe levels of 30 ppm before release. These findings offer crucial insights for improving the safety of using ammonia as marine fuel through risk assessment and management

Neural Stem Cells and Its Derivatives as a New Material for Melanin Inhibition

The pigment molecule, melanin, is produced from melanosomes of melanocytes through melanogenesis, which is a complex process involving a combination of chemical and enzymatically catalyzed reactions. The synthesis of melanin is primarily influenced by tyrosinase (TYR), which has attracted interest as a target molecule for the regulation of pigmentation or depigmentation in skin. Thus, direct inhibitors of TYR activity have been sought from various natural and synthetic materials. However, due to issues with these inhibitors, such as weak or permanent ability for depigmentation, allergy, irritant dermatitis and rapid oxidation, in vitro and in vivo, the development of new materials that inhibit melanin production is essential. A conditioned medium (CM) derived from stem cells contains many cell-secreted factors, such as cytokines, chemokines, growth factors and extracellular vesicles including exosomes. In addition, the secreted factors could negatively regulate melanin production through stimulation of a microenvironment of skin tissue in a paracrine manner, which allows the neural stem cell CM to be explored as a new material for skin depigmentation. In this review, we will summarize the current knowledge regulating depigmentation, and discuss the potential of neural stem cells and their derivatives, as a new material for skin depigmentation

An Efficient Steady-State Analysis Method for Large Boolean Networks with High Maximum Node Connectivity.

Boolean networks have been widely used to model biological processes lacking detailed kinetic information. Despite their simplicity, Boolean network dynamics can still capture some important features of biological systems such as stable cell phenotypes represented by steady states. For small models, steady states can be determined through exhaustive enumeration of all state transitions. As the number of nodes increases, however, the state space grows exponentially thus making it difficult to find steady states. Over the last several decades, many studies have addressed how to handle such a state space explosion. Recently, increasing attention has been paid to a satisfiability solving algorithm due to its potential scalability to handle large networks. Meanwhile, there still lies a problem in the case of large models with high maximum node connectivity where the satisfiability solving algorithm is known to be computationally intractable. To address the problem, this paper presents a new partitioning-based method that breaks down a given network into smaller subnetworks. Steady states of each subnetworks are identified by independently applying the satisfiability solving algorithm. Then, they are combined to construct the steady states of the overall network. To efficiently apply the satisfiability solving algorithm to each subnetwork, it is crucial to find the best partition of the network. In this paper, we propose a method that divides each subnetwork to be smallest in size and lowest in maximum node connectivity. This minimizes the total cost of finding all steady states in entire subnetworks. The proposed algorithm is compared with others for steady states identification through a number of simulations on both published small models and randomly generated large models with differing maximum node connectivities. The simulation results show that our method can scale up to several hundreds of nodes even for Boolean networks with high maximum node connectivity. The algorithm is implemented and available at http://cps.kaist.ac.kr/∼ckhong/tools/download/PAD.tar.gz

The MEB-based network partition.

<p>For the network <i>G</i> in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145734#pone.0145734.g002" target="_blank">Fig 2A</a>, the MEB-based network partition consists of six blocks each of which has a single node (depicted as a red node). Each subnetwork <i>G</i>_<i>i</i> is constructed based on each block. Input nodes are depicted as green nodes.</p

A division into three subnetworks.

<p>A: A Boolean network model <i>G</i>. B: A division into three subnetworks (<i>e.g.,</i><i>G</i>₁, <i>G</i>₂, and <i>G</i>₃). Input nodes are depicted as green nodes.</p