The Cambridge Engineer: Michaelmas Edition 2017

THE CAMBRIDGE ENGINEER

Cambridge University Engineering Society Michaelmas • Nov 2017

Automating our Future How automation plays a role

Contents 04 Moving closer to

autonomous driving 07 Career Profile: Arm 10 The next generation :

automated testing for RuneScape 15 Hydrogen or Electricity:

What’s next for transport?

18 Career Profile: Amazon 22 Making machines chat

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From the Editor In our Michaelmas issue this year, we look into the theme of automation. This has definitely been a buzzword in recent years,

Our Sponsors MAIN SPONSORS

especially in giant tech companies. We try to look at how automation fits into our world in different ways, and how it plays a role in a variety of industries.

Automation could potentially help to solve problems with urban transport, through self-driving cars, or strengthen our manufacturing capabilities, with the big push towards Industry 4.0. And of course, other than dealing with the huge problems we face in modern society, there are the everyday conveniences that automation can help us through, with gadgets such as the Amazon Echo and Alexa with it.

Finally, best of luck with the rest of Michaelmas, and hopefully this issue offers a little break in between all the projects and supervisions!

Magazine Editor Sze Ning Chng magazine@cues.org.uk

ASSOCIATE SPONSORS

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MOVING CLOSER TO AUTONOMOUS DRIVING Niharika Bhargava (Newnham 2011) from Jaguar Land Rover writes about the key technologies driving the future for autonomous vehicles.

The automotive landscape is changing at an ever increasing pace. As a technology company, Jaguar Land Rover is continuously innovating to assist and ultimately enhance the driving experience. UK Autodrive is a consortium of leading technology and automotive businesses, local authorities and academic institutions working together on a three-year UK trial of Connected and Autonomous technologies. It is aimed at establishing the UK as a global hub for research, development and integration of automated and connected vehicles into society. It will also investigate other aspects of automated driving, including safety, cyber-security, legal and insurance issues as well as the public’s acceptance of connected and autonomous vehicles.

In June 2017, as part of the ÂŁ20 million UK Autodrive research and development

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Image courtesy of Jaguar Land Rover

project, Jaguar Land Rover showcased

then decides the optimal route. It navi-

Connected vehicle technologies allow

both autonomous and connected

gates the complex urban environment

cars to talk to each other, as well as

technologies such as Autonomous

and stops in a safe location (kerbside

to the roadside infrastructure such as

Urban Drive, Intersection Collision

or parking bay) upon reaching the

traffic lights. Three such technologies

Risk Warning, In Vehicle Signage and

destination. This technology brings us

were demonstrated as part of the UK

Emergency Vehicle Warning.

a step closer to achieving ‘Level Four’

Autodrive project at MIRA.

autonomy in Jaguar Land Rover’s Autonomous Urban Drive, prototype

future vehicles within the next decade.

Intersection Collision Risk Warning

technology designed and developed

Level four autonomous vehicles, as

(ICRW) warns the driver in advance

in-house and trialled at the HORIBA

defined by the Society of Automotive

when it is not safe to enter an inter-

MIRA Proving Ground, enables the

Engineers (SAE), are capable of carry-

section because of a high probability

vehicle to operate autonomously

ing out the entire driving task for spe-

of a collision. ICRW could reduce the

through the city circuit, obey traffic

cific environments such as towns and

number (and severity) of collisions and

lights as well as negotiate T-junctions

cities without any driver intervention.

reduce congestion.

and roundabouts. Using this technol-

Level one and Level two features like

ogy, passengers can select a loca-

adaptive cruise control and traffic jam

In Vehicle Signage (IVS) sends road

tion on the on-screen map and the

pilot are currently available in market.

and traffic information such as road-

Range Rover Sport research vehicle

works or a change of speed limit

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Image courtesy of Jaguar Land Rover

Image source: IBM

directly to the car’s display, minimis-

autonomous cars before tests on

ing dependence on physical road-

public roads in Milton Keynes and

side signs. This connected technology

Coventry. These will initially take place

aims to reduce accidents and conges-

on closed roads before evolving into

tion.

open-road trials and demonstrations as the UK Autodrive project draws to

Emergency Vehicle Warning (EVW) tells drivers when an emergency vehicle is approaching, and from which direction. This connected technology aims to improve safety, reduce response time for the emergency vehicle and cut congestion by helping drivers pull over more quickly and less stressfully.

These demonstrations marked the final set of trials of connected and

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a close in summer 2018.

Jaguar Land Rover offers Graduate scheme opportunities and Undergraduate summer placements for penultimate year students, as well as sponsorship under the Women in Engineering and Systems/Electronic/Electrical/ Control/Computer & Software Engineering schemes that are open to all undergraduate years.

These are currently open for applications till December 2017.

For more information, please visit jaguarlandrovercareers.com

John Penton (Trinity, 1996)

CAREER PROFILE: ARM What did you study at Cambridge?

on your phone, or the M-class (e.g.

Cortex-M4) processor that you might

John Penton (Trinity, 1996), is an alumni of CUED and Arm’s Cortex R-Class CPU Architect.

In this interview, he shares more about his experiences working with ARM.

I matriculated at Trinity in ‘96, initially

find on a dev board microcontroller.

studying Natural Sciences (physical)

Cortex-R processors run as the brain

but with half a mind towards what

for many real-time control-systems.

I eventually did which was switch

They target safety-critical applications

to EIST (Electrical and Information

like robotics, automotive, and aero-

Sciences) for Part II. I might other-

space, as well as hard discs and solid-

wise have been a physicist or even

state discs, and are found in phones

a geologist. My fourth year choices

controlling the modem. Because they

were focused on semiconductors and

are often controlling physical systems

related topics, which built on physics

like engines or motors, they need to

to some extent, and my project was

provide real-time control and because

on high voltage devices on Silicon-

they are embedded there is more

on-Sapphire substrates with Dr. (now

scope for specialized features for

Prof.) Udrea.

safety, responsiveness etc.

What do you work on now?

How did your career progress to this point?

I am Arm’s lead CPU architect for ‘R’-Class processors. R-class,R-class

I had a summer job at ARM in ‘99 but

or “deeply embedded” processors

after graduating took a year out (work-

are the ones that you never hear

ing as an AV technician for a Christian

about, unlike the A-class processor

charity) before joining as a gradu-

(e.g. Cortex-A75) which runs the apps

ate. I have stayed in the same group

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throughout my time, primarily developing R-Class processors. After working on a number of different projects

What are some of your most memorable, challenging, or enjoyable experiences, working at Arm?

in design, verification and test, I was

ing at Arm: it takes a while for Cortex-R processors to appear in products, but they have good longevity and there are now billions of products of hun-

asked to lead a project (upgrading

The most memorable things have

dreds of types containing IP that I

Cortex-R4), and since then I have lead

often been the most challenging, but

contributed to!

three more processor design projects

are also the things that I have learned

– most recent being the Cortex-R52 –

most from. Late projects have devel-

among other things.

oped my skills in managing and track-

What does day in the life of an Arm CPU Architect involve?

ing work. Nine months working on Last year I moved from ‘product engi-

a design which we threw away and

At the moment I am working on the

neering’ to a ‘technology architect’

started again taught me the value of

early stages of a project so I am

role, looking forward to what we

being critical (though it is still difficult

attending meetings to explain the

should develop next, and still work-

to be ruthless!).

goals, learn about the results of the

ing closely with the teams developing

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investigations that the team are per-

the next R-class processors. This year

On the positive side, I most enjoy

forming and contribute my ideas and

at our internal engineering confer-

interacting with partners on a detailed

opinions to the development. Later

ence, I was recognized as an Arm

technical

understanding

in a project I will typically be working

Distinguished Engineer, so now my

their problems and discussing how

with the project manager to track the

job title is “Architect & Dist. Eng –

we might solve them, and helping

project’s progress against the plan,

Cortex R”, because it has to fit into 40

to develop other engineers and best

deal with issues as they arise, support

characters.

practices in Arm. I’m proud of the

the engineers with problem-solving

global impact I have had while work-

and the details of the specification,

level

-

“

Arm is quite an open company - there are few boundaries in terms of grade and organization which means that anyone can learn from anyone else.”

Images courtesy of Arm

and reviewing some of their work.

presentation and then was taken to

IP which was in development. When

my desk to meet my manager to start

I started as a graduate at Arm I was

I interact a lot with Arm’s partners to

work and I picked up the rest and

similarly part of the flagship project

understand what their requirements

got to know people as I went along.

which was ongoing at the time and

are, or to explain existing or forthcom-

For my first few projects I did a wide

today’s graduates also contribute to

ing Arm technology and discuss how it

variety of tasks which gave me experi-

ongoing projects.

might fit their needs. I also get to pro-

ence in a number of areas. Nowadays

pose work and shape the Arm prod-

we are more organized in the way that

Arm is quite an open company - there

uct roadmaps by making the case to

new starters are introduced to the

are few boundaries in terms of grade

managers within my own group, and

company with specific events to help

and organization which means that

through influencing managers and

them understand the structure of the

anyone can learn from anyone else.

technologists in other groups which

company and meet people, and we

In my early days that meant I could

produce products related to Cortex-R

organize rotations so that graduates

go and seek advice from senior engi-

processors.

get to perform a variety of tasks in

neers and now that I have been at Arm

their first year.

a while I get to share my experience

What has it been like, working at Arm? What can aspiring graduates expect?

with and thereby contribute to the One thing which has remained con-

development of new graduates, and

stant though is that it is work con-

where I have expertise in a particular

tributing to real ongoing projects. I

area I get asked to help other projects

Arm has grown a lot since I first worked

enjoyed my fourth year project con-

or groups that are new to it.

here - from a few hundred employees

ducting novel research and similarly

to thousands.

When I started as a

my summer job at Arm was develop-

graduate I had an hour’s induction

ing the test suite for a new piece of

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Images courtesy of Jagex

THE NEXT GENERATION : AUTOMATED TESTING FOR RUNESCAPE

Jagex shares they developed their tools for automated testing of their games, particularly as they move RuneScape into a mobile platform.

At Jagex, we have always focused on making widely

will quickly cover the architecture of the original Compat

accessible high-quality adventures happen. Since 2001,

Control and move onto discussing the design behind the

RuneScape has been home to hundreds of millions of

new mobile testing system.

adventurers - 254 million to be precise (Guinness World Records, 2017). As discussed in the 2016 Michaelmas edi-

Compat Control interfaces with our Compat Lab. The

tion of The Cambridge Engineer, our new C++ RuneScape

Compat Lab is a museum of 50 computers running on 3

NXT game client aimed to run the game on a 12 year

operating system platforms spread across a decade of

legacy hardware range, while also effectively utilising new

hardware. The machines have been setup to mimic a home

graphical chipsets. This improved game visuals for new

environment. They are connected to a KVM switch, which

technologies, while guaranteeing that players with older

allows easy access from the internal office network. Having

hardware can still enjoy the adventures they love. To guar-

a release schedule of at least one game client release a

antee the quality of a new game client for the world’s most

week, this setup allows a small team of QA experts, with

prolifically updated MMORPG (1,054 times by 2017) in a

limited time, to remote test each release on a plethora of

cost-effective manner, we developed extensive automated

Compat Lab machines. The range of devices allows for a

testing tools. Having successfully released the client, we

wide hardware test coverage, while the connectivity allows

are now undertaking an even more ambitious task - intro-

for haste and convenience, both speeding up the process

ducing RuneScape to the world of mobile. Alongside the

and increasing the quality guarantee of each release.

monumental task of developing this, our team has been busy building the next generation of quality assurance (QA)

Built to interact with the Compat Lab, Compat Control is

automation tools.

a Master Test Server, which communicates with a Python Slave Test Agent on each Compat machine over HTTP.

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The development of the original automation tools, named

The Agents receive instructions from the Master Server

Compat Control, supplemented our existing computer

on which game tests to run, conducting image compari-

Compatibility Laboratory (Compat Lab). Compat Control

sons and measuring game performance metrics, such as

currently offers automated testing for 3 RuneScape (RS)

CPU, GPU and Memory usage. Once tests are completed

game clients and has recently started introducing tests

and results are finalised on the Agent, they are sent as

for our RuneScape Old School (RSOS) client. Additionally,

a report to the Master. The Master Server is written as a

we are developing a mobile extension to test our newly

PHP-PostgreSQL web API, which provides the main user

announced RSOS and RS mobile applications. This article

interface for scheduling tests, as well as a widely available

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way of retrieving results. In addition to the user interface, our build systems have been configured to push and test every new game client build automatically.

Compat Control started as a proof of concept, but has since become a significant part of the RS Technical QA team dayto-day operations. The system saves hundreds of hours of effort each day, by simultaneously running on multiple Agents, allowing a small team to effectively test all releases.

The extensive and consistent reporting, allows reliable comparisons. Coupled with easy access, this allows for quick and painless dissemination of results and comparisons to developers, guiding the development of better performing software.

Similar to computers, mobile devices now have wildly diverse specifications - especially when cross-platform Android/iOS releases are concerned. With different screen sizes, operating systems, operating system versions and hardware, guaranteeing the compatibility of a game client in such an environment is no easy task. Adding to this complexity, our goal still remains the same - to provide all the adventures of Runescape with the quality guarantee of our computer clients on as wide of a range of mobile devices as possible. To achieve this, we firstly added more than 30 different mobile devices ranging in operating system, version and hardware to our Compat Lab. All of these can be signed out physically or accessed through computers on the KVM switch.

Having added the mobiles to the Compat Lab, we needed to find a way to introduce the Compat Control capabilities to them. The first challenge was inheriting the codebase.

This was a challenge as we were not directly involved in the original development of Compat Control and it was written in an unfamiliar to the team programming language.

To address this, a new Spring Boot Java API interface was seamlessly added to the Master Server to handle the Mobile Compat Control. By doing this, we guaranteed that the team could develop a high quality interface in a timely fashion, without accumulating more technical debt and hindering maintenance.

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While Java and PHP was inter-

mobile device was mostly identi-

changeable on the Master Server

cal. Implementing a test factory

side, we saw little reason to change

allowed us to construct the cor-

the Slave Agent language. Python

rect automated test on demand by

is versatile enough as it allowed for

providing a minimum number of

the ease of cross-platform proto-

test specific properties. All identi-

typing we needed and provided the

cal setup was handled behind the

right type of UI automation librar-

scenes, with the factory allowing

ies, while also providing the power

selective overriding should new

of Object Oriented Programming.

preferences arise. As a result, new

In other words, it was still the right

bespoke tests can be created and

tool for the job.

added to production in a few hours.

Having solved the tools selection

Introducing a test which can run

challenges, we turned our atten-

hundreds of hours of device test-

tion to system planning. Adding

ing, before the end of the work day

to the existing capabilities dis-

adds substantial power and value

cussed in the previous section, the

in a time pressured environment.

system needed to be capable of

Adding this power to our already

simultaneously running multiple

existing

processes and conducting rela-

Control framework meant that we

tively complex set-ups for both

can now automate our mobile ven-

iOS and Android, which included

tures, with all the functionality of

parallelising Appium servers with

the existing automation system and

Android SDK and iOS development

improved test development capa-

tools. While test setup was com-

bilities.

plex, from a design perspective the relationship of each test to a

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and

familiar

Compat

“

The system saves hundreds of hours of effort each day, by simultaneously running on multiple Agents, allowing a small team to effectively test all releases.�

HYDROGEN OR ELECTRICITY: WHAT’S NEXT FOR TRANSPORT? Shell shares some ideas about how we might fuel the future of transport.

Transport accounts for more than one

well over a century. In 1892, we suc-

quarter of the world’s total energy use

cessfully transported the first shipment

and one fifth of global energy-related

of oil through the Suez Canal on a tank-

carbon dioxide emissions. This means

er. Since then, we have continuously

that the transport sector has a funda-

broken boundaries, including develop-

mental role to play in helping global

ing the first high-octane aviation fuel,

efforts to reduce emissions.

which allowed propeller-powered aircraft to fly faster.

Changes in the way the world produces and uses energy are underway.

This number of vehicles, moving peo-

There are many significant changes

ple, parcels and produce, has helped

taking place in the world- and at Shell

make Shell one of the world’s largest

we understand the need to be agile,

retailers with around 43,000 branded

and change with it.

sites in more than 70 countries. We handle around 25 million retail cus-

The transition to a low carbon future

tomer transactions a day on these sites.

will unfold over the course of the century and it will move at different paces

But a successful past does not ensure

in different sectors in different coun-

a successful future.

tries.

The global energy system will take Since the invention of the wheel, inno-

time to transform. All forms of drive

vation – the carriage, the steam engine,

- train, the components which power

the internal combustion engine – has

a car – and energy sources will be

allowed each generation to travel fur-

required to meet the growing

ther, faster and more frequently than

demand for mobility, from battery elec-

the one before them.

tric to hydrogen electric.

Shell has been a part of the develop-

In a recent article written by Executive

ment of the transportation sector for

Vice President of New Energies at

15

16

Images courtesy of Shell

road today, we must continue to plan for tomorrow. The development of battery electric vehicles (BEVs) is progressing and at Shell we look at how charging services can complement our existing business. There is no doubt that wider deployment of BEVs will happen, but it’s also clear that the infrastructure challenges will be significant. The power demand to recharge a BEV is not quite like plugging in your toaster or putting on the kettle. It is more like plugging in an extra house.

Shell, Mark Gainsborough, he outlined three things that he

At Shell we also believe that not all electric vehicles will

believes are essential to a successful lower carbon future

be powered by batteries. Hydrogen electric vehicles also

in transport;

have a lot to offer. For example, they are quick to refuel, drive similar distances to petrol or diesel cars, and only emit

Cutting Emissions Today

water vapour.

Firstly, we need to leverage the technology we have avail-

A Level Playing Field

able to us today. In 2030, the majority of cars globally will still use an internal combustion engine – so let’s work on

Finally, we need policies that allow a range of technolo-

improving their environmental performance. Combustion

gies and fuels to compete openly and fairly on the market.

engines need liquid transport fuels – but this doesn’t have

Sustainable conventional biofuels, for example, should be

to mean petrol and diesel. Sustainable biofuels offer a via-

judged on their carbon performance – and recognised for

ble alternative. A Shell joint venture in Brazil called Raízen

the important role they can play in meeting decarbonisation

is a leading producer of sugar-cane ethanol. From cultiva-

and renewable targets.

tion to use, this biofuel can reduce CO2 emissions by up to 70% compared to petrol. Combined with greater engine

Because everyone’s journeys differ and because consum-

efficiency, sustainable biofuels can be a valuable part of the

ers have different needs in different places, policies must

energy mix to reduce CO2 emissions in the transport sector.

also embrace a range of emerging fuels, technologies and markets. Together, policy makers, manufacturers, and fuel

Preparing for Tomorrow

suppliers can help achieve decarbonisation goals. As Henry Ford said: Coming together is a beginning, staying together

Secondly, as we work to reduce emissions of cars on the

is progress, and working together is success.

17

CAREER PROFILE: AMAZON 18

Catherine Breslin is the manager of a team of machine learning scientists working on the speech and language technology behind Amazon Alexa (Cambridge, UK). She shares with us her experience working on Alexa with Amazon.

What is your current position at Amazon and how long have you been there?

I joined Amazon 3 and a half years ago as the only one on my team in Cambridge UK, and now I lead a team of scientists here. We work to make the speech recognition and language understanding behind Alexa, Amazon’s cloud-based voice service, smarter all the time.

Working at Amazon What attracted you to choose this position at Amazon?

Images courtesy of Amazon

I joined Amazon before Alexa had launched because I was excited to find out what Amazon were working on in the area of speech technology.

I’ve always been interested in applying technology to real-world problems, and Amazon is a great place to do that.

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Could you describe what a typical day might be like?

calendar, control compatible smart

and language understanding to solve

home devices, and more. Voice is

new problems.

the most natural and convenient user In a typical day I split my time between

interface, and Alexa combines auto-

working with my team, and collabo-

matic speech recognition, language

rating with other science and engi-

understanding and text-to-speech so

neering teams in Amazon. It is impor-

that you can just ask.

tant that we work closely with other teams because the problems we work on are new, and we need different views from different people to come up with the best solutions for Amazon

What was your experience like working on Alexa? Was there a moment where you felt was really satisfying?

Or particularly challenging?

I would say that machine learning is a great field to be thinking about working in now because we are just starting to see how much potential it has to impact the world. Still, the

customers.

One project which was both rewarding

technology is guided by those who

What are your favourite things about working for Amazon? And on the other side, what might be challenging about working there?

and challenging at the same time was

build it and so we need to encourage

bringing Alexa to the Amazon FireTV.

a diversity of people to enter the field.

This project challenged me by taking

In my team we combine machine

me well outside of my comfort zone. I

learning with software engineering, to

It’s very rewarding to work on prod-

had to learn new technology and also

build and deploy systems at a large

ucts and technologies that are used

learnt to while working with teams

scale. Those who apply typically have

by millions of customers around the

who were new to machine learning,

either a Masters or a PhD in machine

globe and to tackle the difficult prob-

but it was very satisfying to complete

learning or a related field. However,

lems that arise from working at such

the project.

there are many roles on the Alexa

a large scale. On the other side, there is a lot of interest in machine learning right now so the area is very fast moving with new and interesting papers

team, from software engineer through

What do you think are the major trends in speech recognition? What is the next breakthrough needed?

published every week. Keeping up with all the latest developments and

In the past few years we have seen

ideas in the field can be challenging.

an increasing use of deep learning and neural networks in speech

Alexa, and future trends in this area

recognition, which has led to large improvements in accuracy of these

Could you briefly describe the technology behind Alexa?

systems and enabled them to be useful in services like Alexa. In the future, I believe that we will see improvements

20

What advice would you give students interested in your line of work? What sort of skills might they need? How do people normally enter this field?

Alexa is a cloud-based voice service

in speech recognition combined with

to play music, make calls, check your

other technology like computer vision

to data specialist and user interface designer, each of which has different requirements.

“

In the future, I believe that we will see improvements in speech recognition combined with other technology like computer vision and language understanding to solve new problems.�

21

MAKING MACHINES CHAT In midst of a very warm day, an auton-

machine management system that

omous car is driving down a road in

allows conveyor belts to communi-

Brighton. The passenger orders the car

cate directly with each other, this is

to open its electrically-powered win-

anything but a problem. The belt esti-

dows but something is wrong: nothing

mates that it will last another twelve

happens. In Cambridge, another car of

days without maintenance if its cur-

the same model receives a message

rent workload is reduced by 20% and

from a friend: in warm days, take care

sends out a message to other belts

of your window circuitry, or otherwise

asking if they could share some of its

it might stop working! Immediately,

loads. After checking their own condi-

the car in Cambridge changes its

tions, two belts offer to take up 5% and

cooling algorithms to ensure that the

15% of the belt’s workload, respec-

circuitry is kept at a safe temperature.

tively, and the other two declined the request as they are not as healthy.

At the same time, in one of the marble

Therefore, the workload for this par-

quarries of Scotland, the owner is wor-

ticular belt is reduced and the owner

ried about the vibrations of one of five

of the quarry is able to deliver marbles

conveying belts, and a maintenance

on time.

is scheduled for this particular belt

22

in six days. He has just secured a

In

the

Distribution

Information

generous order from a construction

Automation Laboratory (DIAL), PhD

company and to meet the demand on

students Adrià Salvador and Hao Li

time, he needs all conveyor belts up

are looking into how to make these

and running for at least another ten

scenarios a widespread reality in the

days. Thanks to the newly purchased

manufacturing industry. Hao’s focus is

Adrià Salvador and Hao Li are PhD students at the Distribution Information Automation Laboratory (DIAL) at the Institute of Manufacturing.

We learn more about the research they work on at DIAL.

Images courtesy of Adrià Salvador and Hao Li

on getting a fleet of assets performing

allows for each individual machine

increasingly reliable and intelligent

similar tasks in a production system to

develop its own predictive models,

machines as the customer pays per

coordinate in order to come up with

while updating it with information from

working hour and the maintenance

the optimal operation and mainte-

the rest of the fleet. In this system,

and operational costs affect directly

nance plan that is best for the system,

machines talk with each other in order

the profits of the manufacturing firms.

not necessarily the most desirable

to update neural network models that

for the individual asset. This poses

then are used to improve their failure

With its contribution to the world of

great challenges, as it means that

predictions. Adrià’s approach will be

applied artificial intelligence, DIAL’s

the machines must somehow “under-

tested in a fleet of hundreds of Gas

Asset Management team tries to

stand” a very broad array of processes

Turbines located all around the world.

enable a more sustainable, efficient,

and inter-relations typical of a manufacturing firm.

and comfortable world. Maybe next Hao’s and Adrià research is motivated

time you take a gossiping break by

by a trend in industry known as serviti-

the coffee machine, you and your

Adrià’s focus is on distributed intel-

zation: companies are starting to sell

colleague will not be the only ones

ligence in large fleets of machines. He

services instead of things. This means

chatting there!

has developed an architecture that

that there is an incentive to build

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CAMBRIDGE UNIVERSITY ENGINEERING SOCIETY

W W W.C U ES .O R G .U K