The propulsor as a noise source

On seagoing vessels, propulsor systems cause two types of noise. There’s the noise you hear onboard the ship, called onboard noise. And then there’s the kind you hear underwater, also known as underwater radiated noise (URN).

Although the former has been of concern for some time, the latter is gaining in importance. What’s being done? Well, as you’ll see, we’re designing systems and conducting research to reduce both onboard noise and URN.

A whale of a problem

Ultimately, the requirements for noise reduction hinge on the type of shipping being done. While onboard noise tends to disturb passengers on passenger ships, URN is much more harmful to delicate underwater ecosystems. Take, for example, the Arctic or the Antarctic, sensitive areas where URN might affect seagoing creatures and habitats.

In the areas surrounding the Port of Vancouver, officials implemented reduced harbor fees for ships that met certain URN criteria, due to the sensitivity of the local native whale and mammal populations.

Around the world, fishing vessels are concerned with URN causing evasive behavior of fish, and research vessels often cite this noise as degrading the quality of underwater signal measurements.

Classification societies, such as DNV-GL, have also started implementing noise limits. Currently, not many vessels are URN classified, but that’s expected to change in the near future.

Noise Illustration 1
Figure 1: Example distribution of sound pressure level near a CRP ECO unit.

What causes the noise?

To meet demand for new or modified URN classified vessels, designers and shipyards should give due attention to all major noise sources on board.

On the propulsion side, they should concentrate on mitigating the two primary sources of propulsor noise. That means designing propellers and drive trains to be more silent. Propellers cause noise through water cavitation, and drive trains make noise with mechanical power transmissions and gears.


At Steerprop, we’re addressing both problems. Our CRP solution limits propeller noise by having two separate propellers, each with a lower loading, which helps prevent cavitation and lowers both onboard noise and URN.

We’ve also worked to reduce drive train noise with our special LM unit. Integrated with a permanent magnet (PM) motor, the LM unit removes the upper gear, replacing it with a more silent electric motor.

Noise Illustration 2
Figure 2: Example distribution of sound pressure level on the structure interface of a CRP ECO unit.

Studies for deeper insight

We also continue to seek new ways of understanding and reducing noise through joint research projects. We have been collaborating with Finland-based ATA Gears to study the impact of various geometries and components on noise. Using FEM calculations, we’ve studied noise excitation and noise transmission mechanisms in our Z, L and M units.  

For a RoPax ferry and an expedition cruise vessel, we have made both structure-borne noise and URN measurements. The latter were made together with Luode Oy, which specializes in underwater measurements.

While we’ve made some strides, many issues with onboard noise and URN are still difficult to predict since there aren’t public databases on the issue, especially for URN. For example, navies around the world hold URN data dear since they can use the URN to determine a vessel’s signature and figure out what type of vessel is in the water.

Regardless, we’re intent on conducting ongoing research and doing what we can to improve our solutions. That includes researching absolute noise levels, as well as gathering data and determining methods to help design and engineer quieter and quieter vessels.

We’re proud to be carrying out measurements with reliable partners and doing what we can to address the needs of customers and the environment.

Kari Kyyrö

About the Author:

Kari Kyyrö, Consulting Naval Architect. With 25 years working at a shipyard and 4 years working for Steerprop, Kari has accumulated vast experience in the various facets of designing ship hydrodynamics. One area in particular that interests him is how to reduce the amount of noise that ships produce, creating more comfort and sustainability with shipping.

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In shipping, it’s not easy being green

In a competitive international shipping industry, it’s not easy to balance environmental concerns with business demands.

But the world is changing, and something needs to be done. After all, 97% of all research shows that climate change is caused by humans and is harmful to the earth and everyone on it. And shipowners should also be willing to change their ways. If not, there are new regulations and prohibitive fee structures in place to encourage them to do so.

Sure, there’s a lot of talk in boardrooms about the issue of climate change and what to do about it. But business is business.

When capital is tight, shipowners and financiers tailor investment strategies to address short-term budgetary constraints. Too often, they are not in thinking of the environmental benefits of making a wise large capital investment that will pay out considerable operational savings down the road.

A shipowner, for example, might consider investing in a new ship – or upgrading an existing vessel – with an energy-efficient hybrid or electric propulsion system based on a permanent magnet (PM) machine that not only delivers long-term cost savings but also helps the environment. But these high-end components are often the first to be axed if a company is looking to keep costs in line in the near term.

At Steerprop, we think this needs to change. Therefore, we encourage the industry to take a more long-term view. It might cost more up front to invest in new technologies. However, the future savings from increased efficiency coupled with more eco-friendly operations can quickly lead to a sizeable return on investment. Upgrading to newer technologies means making a difference in the short run, while also future-proofing your vessels for the long term.

At Steerprop, we design each of our propulsor systems with unrivaled reliability, energy efficiency and low maintenance requirements – helping limit overall costs. Plus, you can reach the dock quicker, because azimuth propulsors allow excellent maneuverability.

Moreover, integrating our propulsors with the latest PM machines reduces the system footprint and makes it easier to install them into the vessel. Together, these technologies lower energy consumption and deliver more added value over the vessel’s lifetime. What’s more, each of our propulsor units features a Steerprop Care condition monitoring system. This tool provides predictive maintenance oversight that enables service scheduling at future port stops to help eliminate the need for emergency repairs on the high seas. As a result, we can help maintain service intervals that are significantly longer than any other system supplier on the market.

These are just the latest capabilities of a company that has proven dedication, experience and expertise. Since 2000, we have supplied over 800 propulsors to cruise, arctic, passenger, workboat and offshore vessels, as well as outfitted more than 85 ice-class units and made deliveries to 8 icebreakers. Now, with solutions such as Steerprop propulsors integrated with PM machines, we’ve begun a green revolution in the maritime industry. Our aim is not just to save fuel and improve operational performance – but also to shape the future of the world’s environment.


About the Author:

Mika Koli heads up the Sales and Marketing for Steerprop. Since joining the company in March 2018, his vision has been to drive a lasting change for the world by enabling vessels to operate in an environmentally sustainable and future-proof way.

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Industry expert appointed to drive Steerprop strategic ambition

Steerprop’s Board of Directors has appointed Riku-Pekka Hägg as the new Chief Executive Officer (CEO) of the company. Hägg will begin in his new role at the start of January 2020.

As former Vice President of Ship Design at Wärtsilä, Hägg brings decades of maritime technology know-how, digital and strategic experience to Steerprop. This appointment will help strengthen the company’s strategic ambitions to take advantage of the upcoming changes in the marine industry.

“Steerprop shares my passions and values to ensure efficient and sustainable shipping in the future. Together with Steerprop’s skilled personnel, we have the possibility to make great things to happen for the company, the industry and the environment.” says Hägg.

Hägg is a well-known maritime technology strategist and thought leader internationally. He has been a strong advocate for safe, efficient and sustainable shipping in his role at Wärtsilä as well as in his role as Chairman of the Management Board at the ONE SEA alliance, an organization that is leading the way toward an autonomous maritime ecosystem by 2025.

Hannu Heino, Chairman of Steerprop’s Board of Directors, describes Hägg to be an experienced business leader and strategist with strong experience in numerous leading positions. With his experience and technical background, the company can achieve a stronger position as a solution provider in the fast-changing maritime industry.

Riku-Pekka Hägg_crop

“I’m very much looking forward to being part of one of the leading azimuth propulsion companies in the world. My main focus will be to bring greater value to Steerprop’s partners, suppliers and customers,” adds Hägg.


For more information:

Mrs. Johanna Innola
Marketing Communications Planner
Mobile: +358 44 750 1125

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Shifting focus to ship-scale CFD in the marine industry

With the recent advent of high-end computing power, computational fluid dynamics (CFD) has become an indispensable tool in the marine industry. Beyond predicting performance parameters, a detailed flow pattern study enables designers to better design products to avoid undesirable flow features, such as separation on the housing, which in addition to increased drag can also subject the propeller to significant non-uniform inflow.

Ship-scale CFD is now gaining traction in a much broader way when it comes to propulsion solutions – from the predesign stage to final tailoring of the unit’s propeller blades. These state-of-the-art computational tools have also greatly extended our design capabilities at Steerprop, enabling our designers to offer tailor-made solutions.

Below are just some of the ways that ship-scale CFD is bringing new benefits to vessel designers, shipowners and system integrators.  

Capture of a hub vortex: Identifying energy losses is essential to improving the performance of the propulsor unit.

Choice of propulsors: When shipowners select the right propulsion units for their vessels, the decision is still primarily based on comparative performance using model scale tests.

With a greater shift towards using azimuth propulsors in modern ships, however, unit performance is significantly affected by scale effects. The reliability of traditional empirical methods in scaling the performance of these units, especially ducted ones and podded propulsors, is still a great concern. Therefore, a need is opened up to supplement model scale tests with CFD tools to accurately predict the azimuth propulsor performance.

Shape your housing: An optimized gear housing is essential from the perspective of overall azimuth propulsor unit performance. CFD, coupled with 3D modeling tools, has enabled us to carry out detailed investigations by defining and optimizing the housing in terms of geometry parameters, like housing length, torpedo diameter, strut distance from propellers and more.

A better understanding of their individual and combined effects through interaction on overall propulsor performance has enabled designers at Steerprop to better design our units, even in off-design and steering conditions.

With developed accuracy and confidence in modern computational tools, our focus has nowadays been more on optimizing the housing and thus our units at ship scale, rather than defining the unit’s performance with model tests.

Design your propeller for actual flow conditions: In times when there are conflicting design requirements for minimum-to-no-cavitation, low-noise and high-efficiency propeller units, it becomes more essential for designers to ensure that the inflow conditions are properly captured.

Traditionally, the design of propeller blades considers the nominal wake data obtained from model test and couples it with not-so-reliable empirical extrapolation schemes. Today, computational tools, like BEM-RANS coupling, further improve the design process by making ship-scale effective wake available.

This has greatly improved our ability to predict behind-the-ship cavitation performance and thus avoids overly conservative designs.

A sea of new opportunities

The integration of these tools in our daily design process, with the level of detail in their prediction, is limited only by computing power. Additionally, the growing availability of on-board monitoring data on modern vessels will further extend the reliability and performance of these tools in days to come. At Steerprop, we’re always on the lookout for new ways to put our computational tools to use for improved propulsion power.

About the author:

Mahish Mohan brought his CFD knowledge to Steerprop just over one year ago. He is now driving the company’s and team’s capabilities forward in their use of computational tools for tailor-made customer solutions. After Steerprop brought this advanced capability in-house, the company now has a competitive edge when putting this special expertise into practice.

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Steerprop joins European Tugowners’ Association to enhance information sharing

During summer 2019, Steerprop joined the European Tugowners’ Association (ETA), which represents the interests of the towage sector at the EU level. This new membership aims to strengthen Steerprop’s ability to gain insight on evolving trends in the tug market sector and offers the company an opportunity to share knowledge about the latest propulsion development with other members.  

The European Tugowners’ Association has transformed over the years from a purely London-based association in 1963 to now representing the towage industry at a continental level. The association advocates the tug sector’s interests both in Brussels as well as in other European capitals and helps distribute information about the crucial role of this sector for the EU economies.

According to Tapio Aho, Sales Development Manager for Steerprop, this new membership allows Steerprop to keep up to date with the latest developments in the tug market and to participate in the association’s events.

“We’re also looking forward to meeting the decision-makers in the sector. This is a wonderful opportunity for us to share our knowledge of how the technology for main propulsion is developing and the benefits that Steerprop has to offer this particular workboat sector,” he says.

The ETA mission

The European Tugowner’s Association’s mission statement is: To be the voice of the European towage industry, to foster safety values and protection of the environment as well as to promote the interests and respond to the needs of the members.

Through policy and technical expertise, sharing best practice, and public affairs and communication activities, ETA aims to promote the towage industry interests and its contribution to EU trade. It also plays a significant role in implementing safety and sustainability in maritime activities.

Steerprop’s contribution to tugboats

Specifically for tugs and workboats, where endurance, reliability and agility are essential, Steerprop offers specialized designs and world-class expertise. The company’s ducted propulsors have proven their quality in tugboats all over the world. The latest generation of propulsors raises efficiency and robustness to unprecedented levels. They offer hydrodynamic enhancements for superior bollard pull and high free-running efficiency. With ice conditions or transit, Steeprop’s CRP is the right choice.

For more information:
Tapio Aho, Sales Development Manager, Steerprop Tel. +358 40 727 1203

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Celebrity Flora, the first expedition mega yacht of its kind specifically designed for the Galapagos Islands, started maiden voyage with Steerprop CRP

Shipyard De Hoop in the Netherlands selected Steerprop to deliver two contra-rotating propulsors (CRP) to Celebrity Flora, the brand-new innovative luxury expedition cruise vessel. On May 18, the ship set off on its maiden voyage towards Las Palmas before it crosses the Atlantic. For Steerprop, this marks the first delivery of its high-efficiency CRP technology to a seagoing cruise vessel.

In 2016, Steerprop was contacted by Shipyard De Hoop to give a proposal for a luxury cruise vessel propulsion system that required the highest levels of efficiency along with low noise and vibrations, both inside the vessel and under the water. De Hoop chose Steerprop as one of the contenders based on the good cooperation the two companies have enjoyed since 2001, the year Steerprop was founded.

“We’re really proud and excited to have been involved in this prestigious project,” says Jussi Tarvainen, Sales Manager at Steerprop. “This type of luxury vessel has extremely high demands for efficiency and performance, and we were able to fulfill them.”

“Expedition mega yachts like Celebrity Flora are a growing segment, and our propulsion technology and special expertise are perfect for sensitive environments and ice classes,” he continues.

Built-in efficiency

SP 20 CRP units were selected for the vessel based on their unsurpassed efficiency and ability to operate in strictly regulated marine environments. The dual-end CRP offers exceptional hydrodynamic qualities with its specially engineered underwater body. Noise levels and vibrations are extremely low, which was vital for this particular vessel.

In addition, CRP provides outstanding maneuverability with its advanced azimuth propulsor design and excellent efficiency. The vessel will also be able to take advantage of the high fuel savings and low emissions that the propulsion system provides.

To date, Steerprop has delivered over 800 propulsors operating reliability on a wide range of vessels, including ice-class units.

More about Celebrity Flora

Celebrity Flora began sailing in the Galápagos from Baltra on June 30, 2019. The most energy-efficient ship of its kind in the region, Celebrity Flora was designed specifically to explore the Galapagos. Celebrity’s signature outward-facing design concept gives guests 360-degree views of the islands at virtually every turn. The all-suite luxurious accommodations surround guests with every creature comfort, including service provided by personal attendants. Unique to Celebrity Flora are the first-ever glamping experience at sea in the Galapagos, new dining venues, an open-air stargazing platform, expert-led ecological seminars, and custom-designed Novurania yacht tenders, which create a seamless sea-to-shore experience. Bookings are open at or through a travel advisor, for the ship’s alternating seven-night inner and outer loop itineraries and selection of 10-, 11-, and 16-night packages, which feature either pre- or post-cruise expeditions.

More about Shipyard De Hoop

Shipyard De Hoop was founded in 1889 and has developed into one of the most established yards of the Dutch shipbuilding industry. At Shipyard De Hoop, the focus is on designing, engineering and building custom vessels, both for the inland and seagoing markets. Celebrity Flora was built at De Hoop Lobith, in the eastern Dutch province of Gelderland, one of the shipyard’s two shipbuilding facilities.

For more information, please contact:
Jussi Tarvainen, Sales Manager, Steerprop,
Tel. +358 44 750 1114

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Atlantic Towing aims for best-in-class energy efficiency with Steerprop’s propulsors

Steerprop will deliver two of its hallmark contra-rotating propulsor (CRP) units to Canadian Atlantic Towing Limited’s latest platform supply vessel (PSV), the Atlantic Harrier. The vessel will be designed and built by Havyard Ship Technology in Norway and is scheduled for delivery in April 2020. The new vessel is part of Atlantic Towing’s strategy to offer its customers large cargo capacities with outstanding fuel efficiency and low emissions.

Steerprop was selected thanks to its long relationship with Havyard Ship Technology and numerous successful propulsion projects that they have completed together. Atlantic Towing is a new customer for the shipbuilder.

“This marks another contract between Havyard Ship Technology and Steerprop, and a new ship to service,” says Hannu Jukola, Senior Sales Manager at Steerprop. “Our CRP technology is perfectly suited for this particular type of hull. Additionally, the propulsion system enables Atlantic Towing to reach the high level of energy efficiency that they aim to attain with their new large cargo PSVs.”

“We look forward to having Steerprop on board with us for this exciting project and have, as always, high expectations both for performance and the cooperation,” says Hanne Reite Keyn, Purchasing Manager at Havyard Ship Technology AS.

Steerprop will deliver two SP35 CRP propulsion units with a power of 2,100 kW per unit. The technology has been specifically designed for vessels that need to operate in the harsh Atlantic coastal conditions in the North Atlantic and North Sea. Along with having an Ice Class 1B notation, the new 294-foot-long PSV has a 10,785-square-foot deck area, large cargo tankage and can accommodate up to 54 people. 

Innovative dual-end contra-rotating propeller (CRP)

The Steerprop 35 CPR propulsor system offers outstanding speed and unsurpassed efficiency, thanks to the hydrodynamic qualities of the underwater body design. The dual-end CRP combines the exceptional maneuverability of azimuth propulsors with low-pressure pulses and noise levels.

To date, Steerprop has delivered over 800 propulsor units to vessels throughout the world. The design has been tested and verified in action for decades.

For more information, please contact:
Hannu Jukola, Senior Sales Manager, Steerprop, Tel. +358 40 838 8643

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New propulsion order for a newbuild icebreaker

Steerprop has received a new order for two 2.5 MW SP 60 PULL ARC propulsors to be delivered to a newbuild icebreaking vessel. This strengthens Steerprop’s position as a global supplier of propulsors of this size that can operate in extreme arctic conditions.

As the Arctic summer sea ice continues to melt, arctic routes are experiencing substantial increases in traffic. Although transiting via the arctic waters may cut as much as 50% off the days at sea, it also adds more risk of uncertainty to the route. With the ever increasing number of shipowners investing in vessels capable of navigating through ice, Steerprop’s 2.5 MW PULL ARC propulsors are gaining popularity for vessels that need free-running efficiency and ice-milling capabilities in icy waters.

Experience matters

“We were selected to deliver this special solution to a newbuild icebreaker, thanks to our long-term experience in delivering robust propulsion technology to icebreaking vessels,” says Tapio Aho, Sales Manager at Steerprop.

To date, Steerprop has delivered over 85 ice-class units, most of them now operating in some of the harshest arctic conditions. “This order strengthens our position in the market when it comes to providing demanding icebreaker applications,” he continues. “And we hope that this will open up other new similar opportunities in this niche business sector.”

Rugged throughout

The Steerprop SP 60 PULL ARC propulsion units have been designed and built with multiple layers of redundancies and fail-safes for safe, reliable and efficient operations in the most extreme operating conditions. These advanced propulsors combine ice-breaking power with the reliability of mechanical construction and the accurate controls of modern automation technology.  

This special azimuth propulsor technology provides outstanding performance in all kinds of ice management operations. The ability to direct the vectored thrust from the propeller in a full 360 degrees allows the vessel to widen fairways, blow ice ridges or free arctic installations from the ice.

For more information, please contact:
Tapio Aho, Sales Manager, Steerprop, Tel. +358 40 727 1203

True power train optimization is holistic

Optimizing how something as powerful as vessels use of energy is a huge endeavor. Luckily, there are ways that support your work to achieve maximum efficiency, starting with the propeller.

What exactly leads to hydrodynamic propulsion efficiency? Instead of trying to optimize the individual components within a power train, our approach at Steerprop is to consider all critical components in a holistic manner. This includes frequency converters, generators and other power consumers. We also look at the cooling and auxiliary equipment, that add to the total cost, but are often forgotten.

We start with the propeller. This is where mechanical energy is converted to thrust to propel the vessel. If the propeller is inefficient – or the best propulsion efficiency is not achieved for every type of vessel operation – the rest of the power train needs to be overdimensioned to transmit the power required for different propulsion needs.

When the power train is overdimensioned, it is constantly operating in partial load mode. This means the best possible efficiency cannot be achieved through the power train.

Figure 1 shows how power train losses are born. By increasing efficiency on the right side, the losses on the left become automatically smaller as you move from right to left.

Figure 1. The basis of Steerprop’s efficiency doctrine: fuel to thrust chart.

To help shipowners and design offices analyze the efficiency of their entire drive train and reach the best possible performance at sea, we have created an approach that considers the holistic power train.

Together with partners in our ecosystem, we can deliver a complete power train that encompasses the propulsor drive solution, our propulsor and permanent magnet generators for efficient power distribution. With this solution, the vessel’s electrical power is created with permanent magnet variable-speed generators connected via inverters to a common DC link. The generators and power battery bank continuously operate in parallel. Energy storage systems, such as a battery, can be used for peak-shaving functionality. Other power sources can also be included.

When combining these with a careful design and thoughtful decision on the choice of propulsor, the efficiency of the whole propulsion line can improve significantly.

This energy optimization balancing act, when done right provides both short- and long-term benefits that include more profitability though greater hydrodynamic efficiency, less chance of disruptions such as surges and blackouts, lower and more predictable maintenance costs.

What’s more, an optimized solution offers the flexibility to use power input from different sources. This enables vessels to be designed using alternative power sources to reduce their carbon footprint and meet the increasingly more stringent CO2 regulations. 

About the author:

Juho Rekola works as Chief Design Engineer at Steerprop. He has been involved in marine technology from the beginning of his career, focusing on high-efficiency solutions for the industry.

Today, he works closely with electrical and hybrid power to bring the marine industry the best solutions for tackling climate change and rising operational costs. He feels that optimizing the entire power train holistically is the best way to achieve maximum efficiency.

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Successful project management propels us forward

The key to successful project management is simple: we always need to deliver on time and without any extra costs. This is critical in each project.

Over the years, Steerprop has built up a solid reputation among our customers for excellent project management, specifically for these reasons. We’ve focused on setting the bar high for ourselves by choosing responsible project managers who have excellent communication skills, strong technical backgrounds and are outstanding team players.

One thing that makes our project management style unique is that we take responsibility for all aspects of our projects, including the classification process. While this means more time and responsibility for us, it also gives us better control over the projects we work with. As a result, our customers benefit considerably. That’s because of our wider commitment to ensuring each project reaches a successful completion and gives them exactly what they asked for.

We use various programs to track each project’s progress. All documentation, including any agreed-upon changes, are saved online in one unified place. This allows everyone involved in the project instant access to detailed information at any time.

We work hard to keep our projects on course and make sure that our suppliers deliver the required components both on time and up to quality standards. If any component delivery is late, there may be project delays. This is when communication with our customers is highly important.

Our style is such that we are always honest with our customers. Should anything steer our projects off course, we let them know immediately. Steerprop has highly skilled personnel who are committed to putting in additional hours to solve any problems that may arise.

For any problem we run into, I know there’s always a solution. Sometimes, it is easy to find. Other times, it can be challenging. Regardless, we just closely work with every department, supplier and customer to make sure our fast communication and flexibility result in successful project delivery.

We also make sure to ask our customers for feedback on meeting their expectations and how well they feel their expectations were met. This is how we can single out ways to improve on our delivery. At the end of the day, we want our customers to be happy. Pleasingly, our proactive management style has received good feedback. Recently, the manager of a Russian shipyard asked for a face-to-face meeting to express his satisfaction with an ongoing project. 

Another – and possibly most important – component to Steerprop’s success in project management is our highly skilled and talented personnel. We believe in motivating each other through humor and a positive attitude. This, in turn, allows us to give our best to our customers, helping them complete their projects on time and within budget.

We feel this is something we always do well – because it’s simply the Steerprop way.

About the author:

Juha Jusi has worked as Project Manager at Steerprop for nearly two years. Before starting at the company, he was involved in project management in various fields for many years. 

In his opinion, successful project management requires proactive communications, complete honesty and outstanding teamwork. These are some of the main reasons Steerprop has earned its unrivaled reputation for excellent project management among customers worldwide.

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