United States Maritime Administration

abatement costs are less favorable for the fossil cofeed pathways.

A new method for the parallel fabrication of carbon nanotube (CNT) electronic devices is described. Self‐assembly via magnetic entrapment exploits magnetic fields generated within micrometer‐ or nanometer‐scale devices for the controlled deposition of susceptible species onto predefined contacts (see Figure). The fabrication of carbon nanotube field‐effect transistors (CNFETs) using this method are discussed.

Low-frequency sound from large vessels is a major, global source of ocean noise that can interfere with acoustic communication for a variety of marine animals. Changes in vessel activity provide opportunities to quantify relationships between vessel traffic levels and soundscape conditions in biologically important habitats. Using continuous deep-sea (890 m) recordings acquired ∼20 km (closest point of approach) from offshore shipping lanes, we observed reduction of low-frequency noise within Monterey Bay National Marine Sanctuary (California, United States) associated with changes in vessel traffic during the onset of the COVID-19 pandemic. Acoustic modeling shows that the recording site receives low-frequency vessel noise primarily from the regional shipping lanes rather than via the Sound Fixing and Ranging (SOFAR) channel. Monthly geometric means and percentiles of spectrum levels in the one-third octave band centered at 63 Hz during 2020 were compared with those from the same months of 2018–2019. Spectrum levels were persistently and significantly lower during February through July 2020, although a partial rebound in ambient noise levels was indicated by July. Mean spectrum levels during 2020 were more than 1 dB re 1 μPa 2 Hz –1 below those of a previous year during 4 months. The lowest spectrum levels, in June 2020, were as much as 1.9 (mean) and 2.4 (25% exceedance level) dB re 1 μPa 2 Hz –1 below levels of previous years. Spectrum levels during 2020 were significantly correlated with large-vessel total gross tonnage derived from economic data, summed across all California ports ( r = 0.81, p < 0.05; adjusted r 2 = 0.58). They were more highly correlated with regional presence of large vessels, quantified from Automatic Identification System (AIS) vessel tracking data weighted according to vessel speed and modeled acoustic transmission loss ( r = 0.92, p < 0.01; adjusted r 2 = 0.81). Within the 3-year study period, February–June 2020 exhibited persistently quiet low-frequency noise and anomalously low statewide port activity and regional large-vessel presence. The results illustrate the ephemeral nature of noise pollution by documenting how it responds rapidly to changes in offshore large-vessel traffic, and how this anthropogenic imprint reaches habitat remote from major ports and shipping lanes.

This report examines the potential benefits, feasibility, and barriers to the use of biofuels in place of heavy fuel oil (HFO) and marine gas oil for marine vessels. More than 90% of world’s shipped goods travel by marine cargo vessels powered by internal combustion (diesel) engines using primarily low-cost residual HFO, which is high in sulfur content. Recognizing that marine shipping is the largest source of anthropogenic sulfur emissions and is a significant source of other pollutants including particulates, nitrogen oxides, and carbon dioxide (CO2), the International Maritime Organization enacted regulations to lower the fuel sulfur content from 3.5 wt.% to 0.5 wt.% in 2020. These regulations require ship operators either to use higher-cost, low-sulfur HFO or to seek other alternatives for reducing sulfur emissions (i.e., scrubbers, natural gas, distillates, and/or biofuels). The near-term options for shipowners to comply with regulations include fueling with low-sulfur HFO or distillate fuels or installing emissions control systems. However, few refineries are equipped to produce low-sulfur HFO. Likewise, the current production rates of distillates do not allow the necessary expansion required to fuel the world fleet of shipping vessels (which consume around 330 million metric tons). This quantity is more than twice that used in the United States for cars and trucks. The other near-term option is to install emission control systems, which also requires a significant investment. All of these options significantly increase operational costs. Because of such costs, biofuels have become an attractive alternative since they are inherently low in sulfur and potentially also offer greenhouse gas benefits. Based on this preliminary assessment, replacing HFO in large marine vessels with minimally processed, heavy biofuels appears to have potential as a path to reduced emissions of sulfur, CO2, and criteria emissions. Realizing this opportunity will require deeper knowledge of (1) the combustion characteristics of biofuels in marine applications, (2) their compatibility for blending with conventional marine fuels (including HFO), (3) needs and costs for scaling up production and use, and (4) a systems assessment of their life cycle environmental impacts and costs. It is recommended that a research program investigating each of these aspects be undertaken to better assess the efficacy of biofuels for marine use.

Abstract The classic machine repair problem is extended and modeled as a cyclic queue for the purpose of determining the number of spares and repair channels for a population of items subject to stochastic failure. In this system the operating units, removal of failed units, transportation to repair depot, and the repair itself are treated as four multi-server stations, each with exponential holding times. An exact model is developed from the literature on networks and cyclic queues and compared with a series approximation. Under a constraint requiring a high availability of spares which insures “light traffic queues,” the approximate model is found to be very accurate and computationally more efficient.

In-use emission rates for a marine vessel operating on hydrotreated algae biofuel are reported for the first time. Emission measurements were made on a four-stroke marine diesel engine from a Stalwart class vessel to compare the emission profile from burning ultra low sulfur diesel (ULSD) to a 50:50 blend of ULSD and algae biofuel (A50). In-use emission measurements followed the International Organization for Standardization (ISO) 8178-4 D2 certification test cycle protocol. Particulate matter (PM2.5), nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2) were sampled in accordance with the ISO 8178-2 protocol for each mode of the test cycle. Switching fuel from ULSD to A50 resulted in significant ∼35% lower PM2.5 emissions for 25 and 50% load and an overall weighted PM2.5 reduction of ∼25%. Overall reductions of 30 and 20% were observed in elemental carbon (EC) and organic carbon (OC), respectively. PM2.5 was dominated by OC (77–94%) for both fuels. NOx emissions were reduced by ∼10% on switching from ULSD to A50. Overall, the emissions of CO2 and CO were reduced by 5 and 18%, indicating a slight improvement in fuel economy for this engine while operating on A50.

The classic machine repair with spares (finite source) queueing model assumes all calling units are identical in failure and repair characteristics. This paper develops, for a first-come first-served discipline, a procedure for treating nonhomogeneous populations, specifically, a population with two types of items, each with exponential failure and repair times but with different mean values. Exact solutions are obtained for small population sizes and compared to approximate procedures using the classical theory. The exact model is essentially a two-stage cyclic queue with two classes of customers. Extensions of the model to N stages and M customer classes, priority disciplines, and other disciplines, including blocking, are discussed.

Abstract This study assessed the long‐term annual biofuel production capacity potential and price in the United States and shed light on the prospect of biofuel adoption for marine propulsion. A linear programming model was developed to assist the projections and provide insightful analyses. The projected long‐term (2040) maximum annual capacity of biofuels in the United States is 245 million metric tons (Mt) or 65 billion gallons of heavy fuel oil gallon equivalent (HFOGE) when based on the median feedstock availability. Between 2022 (near‐term) and 2040, the potential biofuel capacity increases by over 40%, attributed to increased feedstock availability. At a price range up to $500/t, biodiesel is the main product, and the annual capacity (12 Mt) is limited to feedstock availability constraints. Biodiesel and corn ethanol are the main biofuels at a price range up to $750/t. At a higher price point (above $750/t), the biofuel types and annual capacities increase substantially (218 Mt per year). Biofuels above this price include gasoline‐, jet‐, and diesel‐range blendstocks, as well as bio‐methanol, bio‐propane, and biogas. This study concludes that the US domestic feedstock availability coupled with advanced conversion technologies can produce substantial amounts of biofuels to achieve a critical mass and be impactful as alternative marine fuels. There is also a need to improve the biofuel price for marine shipping adoption. Policies and economic incentives that provide temporary financial support would help facilitate maritime biofuel adoption. © 2022 Alliance for Sustainable Energy, LLC. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

This paper presents a life-cycle emissions analysis of conventional and natural gas-based marine transportation in the United States. We apply a total fuel cycle—or “well-to-propeller”—analysis that evaluates emissions along the fuel production and delivery pathway, including feedstock extraction, processing, distribution, and use. We compare emissions profiles for methanol, liquefied natural gas, and low sulfur marine fuel in our analysis, with a focus on exploring tradeoffs across the following pollutants: greenhouse gases, particulate matter, sulfur oxides, and nitrogen oxides. For our greenhouse gas analysis, we apply global warming potentials that consider both near-term (20-year) and long-term (100-year) climate forcing impacts. We also conduct uncertainty analysis to evaluate the impacts of methane leakage within the natural gas recovery, processing, and distribution stages of its fuel cycle. Our results indicate that natural-gas based marine fuels can provide significant local environmental benefits compared to distillate fuel; however, these benefits come with a near-term—and possibly long-term—global warming penalty, unless such natural gas-based fuels are derived from renewable feedstock, such as biomass. These results point to the importance of controlling for methane leaks along the natural gas production process and the important role that renewable natural gas can play in the shipping sector. Decision-makers can use these results to inform decisions related to increasing the use of alternative fuels in short sea and coast-wise marine transportation systems.

A systematic procedure is developed utilizing computer techniques to determine the optimum combination of length, beam, draft, block coefficient, and depth to satisfy a predetermined "least cost" criterion for a dry cargo ship, which will meet a given set of owner's requirements for speed, fueling range, stowage factor and cargo deadweight. The least cost ship is obtained from a family of ships resulting from the permutation of four values each of five basic design variables. Selection of the least cost ship is dependent upon the computer programming of standard preliminary design processes which define only those ships consistent with good design practice and existing regulatory requirements. The methodology, examples of actual applications, and analysis of results obtained, are the principal features of the paper.

A two-year study of the occupational exposure of workers in a lumber mill to a wood preservative containing chlorophenol has been conducted. The methods were biological (urine) monitoring, industrial hygiene assessment and a questionnaire related to worker-perceived health effects. Approximately 40 workers exposed to the wood preservative and 40 unexposed controls working in other locations of the plant participated in the study. Evaluation of work conditions, assessment of urinary levels of tetra- and pentachlorophenol, and administration of a medical questionnaire were performed at a six-month intervals over a two-year period. Industrial hygiene ratings of exposures and adequacy of protection were evaluated in relation to the results of biological monitoring. Workers who came into contact with freshly treated and still wet wood had consistently higher urinary levels of tetrachlorophenol. Workers stationed adjacent to the spray applicator also had higher tetrachlorophenol levels. There was no statistically significant relationship between the subjective ratings by the industrial hygienist of exposure and adequacy of worker protection with the urinary levels of tetrachlorophenol. Nor was there a consistent pattern linking exposure ratings with adequacy of protection. The short half-life of tetrachlorophenol in the urine makes this a good indicator of only the most recent exposure. The differences in urinary levels between controls and exposed workers were large, with averages of 240.4 ppb for exposed workers and 14.6 for controls. Traditional industrial hygiene evaluation techniques, in conjunction with biological monitoring, proved to be the most effective method of assessing both exposure and work practices. Exposed workers reported a statistically significant increase of positive answers to known signs and symptoms of chlorophenol exposure compared with the controls. There was no statistically significant relationship between the number of these health problems reported and the mean urinary levels of tetra- or pentachlorophenol for the exposed group; however, for certain variables (heavy vs. light exposure, inadequate vs. adequate protection, greater than 100 ppb urinary tetrachlorophenol vs. less than 100 ppb), those with heavier exposure, inadequate protection or higher urinary tetrachlorophenol reported on the average more health problems over the two-year period. Firm statistical conclusions could not be drawn because of the small size of the study population.

Submerged ship surfaces are often inhabited by diverse sessile and sedentary marine organisms, which can directly impact vessel operations and increase the likelihood of non-indigenous species (NIS) establishment and impacts. Ship in-water cleaning (IWC) systems are now being incorporated into biofouling policy, and rigorous, transparent, and predictive verification testing is vital to regulatory success. Performance criteria for IWC approval should focus on environmental protection goals by including: qualified and independent testing; quantitative, robust, and statistically sound data, rather than qualitative observations; water sampling at all critical control points to characterize the release of harmful materials, including dissolved and particulate biocides; measurable and protective endpoints, rather than percent reductions; determinations of presence or absence of macro-organisms, irrespective of species origins or physiological state; and appropriately trained IWC operators.

In-use emissions aboard a Stalwart class vessel, the T/S State of Michigan, were measured from a four-stroke marine diesel generator operating on two fuels: ultra-low-sulfur diesel (ULSD) fuel and ULSD mixed with Amyris renewable diesel (S33; 33% by volume) produced from sugarcane feedstocks with 67% by volume ULSD. Measurements followed the International Organization for Standardization (ISO) 8178 procedures and protocols. Gaseous emissions reported include nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2), while reported particulate matter (PM) emissions include PM2.5 mass, elemental carbon (EC), and organic carbon (OC). Overall, a 4% reduction in NOx emissions, a 10% increase in CO, and a 2% increase in CO2 were observed with S33. For PM, no statistically significant differences were seen with S33. PM2.5 was dominated by OC for both fuels. Overall, there was a 26% reduction in EC and an 8% reduction in OC with S33.

A recent workshop on channel design and vessel maneuverability brought together channel designers, naval architects, pilots, and ship operators to review and share design approaches and standards that affect safety of operations. The desire was to develop policy recommendations that can be implemented both in the way channels are laid out and enlarged and how ships of various types using them should be designed and handled. Resulting recommendations based on the discussions promise to improve overall safety of ship operations in restricted waterways.

Mycobacterium avium ssp. paratuberculosis (MAP) is the etiological agent of paratuberculosis, a disease that affects ruminants worldwide. Despite global interest in the control of this disease, gaps exist in our knowledge of fecal shedding patterns and concurrent serological patterns. This longitudinal study in dairy cattle herds with high MAP seroprevalence in France aimed at accurately describing fecal shedding patterns over 1 year; relating those shedding patterns to individual animal characteristics (age, breed, parity); and exploring the association between fecal shedding patterns and serological patterns. To describe temporal fecal shedding patterns and continuity of shedding, along with the standard quantitative PCR (qPCR) threshold cycle we used a cutoff value that related to low or nonculturable fecal shedding. We also defined a threshold cycle indicative of shedding in high quantities to describe infection progression patterns. Twenty-one herds completed the study, and 782 cows were tested 4 times each. We obtained 4 sets of paired fecal qPCR and serum ELISA results from 757 cows. Although we targeted highly likely infectious animals, we found a large diversity of shedding patterns, as well as high variability between herds in the proportion of animals showing a given pattern. The fecal qPCR results of almost 20% of the final study sample were positioned at least once in the range that indicated low or nonculturable fecal shedding (between the adjusted and the standard cutoff value). Although these animals would typically be classified as non-shedders, they could be important to infection dynamics on the farm. Animals that shed at least twice consecutively and animals that shed in high quantities rarely reverted to negativity. Repeated fecal qPCR can be used to detect temporal fecal shedding traits, and the decision to cull an animal could practically be based on temporal, semiquantitative results. Overall, we found a mismatch between fecal shedding and ELISA seropositivity (637 animals were ELISA-negative 4 times, but only 13% of those animals were qPCR-negative 4 times). We found that having more than 2 ELISA-positive samples was strongly related to persistent and continuous shedding. We suggest that although serological testing is much less sensitive than qPCR, it can also be used, particularly over the course of multiple testing events, to identify animals that are most likely to contribute to the contamination of the farm environment.

Image registration is a crucial progress in detecting oil spilled on the sea and is also important for estimating the volume of the oil spill, especially when one image cannot cover the entire polluted region. In this article, a new algorithm is proposed to register geometrically distorted aerial images of oil spill accurately and automatically. There are two stages in this algorithm: coarse registration and fine registration. Invariants-based similarity and relative space distance are applied to coarse matching. Then improved iterative closest point (ICP) algorithm is used for registering images finely, which is the combination of ICP and a method of solving assignment problem to deal with mismatches. The performance of the proposed algorithm is evaluated by registering oil spill ultraviolet (UV) and infrared (IR) images, respectively. Compared with traditional ICP and other algorithms, the efficiency and accuracy of the proposed algorithm are highly improved.

In this paper, the need for further maneuvering criteria and standards is indicated. Possible means for advancing existing IMO ship maneuverability standards are discussed, together with the uncertainties associated in this process. It is believed that more accurate modeling tools can be developed with the aid of new and greatly improved shipboard instrumentation. These tools will enable further development of ship maneuverability performance standards with a methodology for assuring required capabilities through analytical means that do not require running of full-scale tests in impractical conditions. Through these means ship design, ship operational safety and maritime ship controllability standards can be developed and come to a practical implementation.

t, respectively. Marine sources were identified as the largest non-road mobile source contributor accounting for 73.66% of total emissions, followed by non-road mobile machinery (21.66%). Emissions from civil aircraft and locomotives were relatively lower. Generally, emissions from non-road mobile sources increase from March (spring) to November and decrease from the beginning and the end of the year (winter). Emissions are mainly distributed in suburban districts where there is flourishing agriculture, downtown areas with dense populations, urban construction areas, ports, railway lines, and airports. Uncertainty in the inventory results is mainly due to the lack of key data, such as local emission factors and actual activity levels.

The objective of the program was to evaluate improved materials for oil-lubricated stern-tube bearing and face-seal applications. Once good candidates were found for oil, they were then evaluated in seawater to show that if the seal fails and the bearing cavity is flooded with seawater, the bearing can still function at some reduced load and speed. The selected plastics were subjected to soak tests and friction and wear tests. Based on the tests, the following materials were recommended for bearing and face seals: polyimide, 15-percent graphite powder filled; polyamide-imide, 3-percent PTFE and 12-percent graphite powder filled; and phenolic, 15-percent graphite powder filled. The liner materials could be the same as those which are currently used: ABS Grade 2 and flame-sprayed Cr2O3 for bearings, and Niresist Type 2 for face seals. The selected plastic materials could also be successfully used in seawater lubrication.

Surface texture of tribological interfaces has the potential to improve friction and lubrication performance of various mechanical components. This review paper emphasizes on the current status of the research of surface texture, including the features, the effects on tribological performance, the forming techniques, and the modeling and simulation of surface texture. It is intended to help readers to gain a more comprehensive view on surface texture of tribological interfaces.