School of Computing, Science and Engineering

Software development teams in large scale offshore enterprise development programmes are often under intense pressure to deliver high quality software within challenging time contraints. Project failures can attract adverse publicity and damage corporate reputations. Agile methods have been advocated to reduce project risks, improving both productivity and product quality. This article uses practitioner descriptions of agile method tailoring to explore large scale offshore enterprise development programmes with a focus on product owner role tailoring, where the product owner identifies and prioritises customer requirements. In glob-alised projects, the product owner must reconcile competing business interests, whilst generating and then prioritising large numbers of requirements for numerous development teams. The study comprises eight international companies, based in London, Bangalore and Delhi. Interviews with 46 practitioners were conducted between February 2010 and May 2012. Grounded theory was used to identify that product owners form into teams. The main contribution of this research is to describe the nine product owner team functions identified: groom, prioritiser, release master, technical architect, governor, communicator, traveller, intermediary and risk assessor. These product owner functions arbitrate between conflicting customer requirements, approve release schedules, disseminate architectural design decisions, provide technical governance and propogate information across teams. The functions identified in this research are mapped to a scrum of scrums process, and a taxonomy of the functions shows how focusing on either decision-making or information dissemination in each helps to tailor agile methods to large scale offshore enterprise development programmes. Keywords agile software development · scrum · large scale offshore enterprise development programmes · product owner · product owner teams · grounded theory.

Context: Large-scale offshore software development programmes are complex, with challenging deadlines and a high risk of failure. Agile methods are being adopted, despite the challenges of coordinating multiple development teams. Agile processes are tailored to support team coordination. Artefacts are tangible products of the software development process, intended to ensure consistency in the approach of teams on the same development programme. Objective: This study aims to increase understanding of how development processes are tailored to meet the needs of large-scale offshore software development programmes, by focusing on artefact inventories used in the development process. Method: A grounded theory approach using 46 practitioner interviews, supplemented with documentary sources and observations, in nine international companies was adopted. The grounded theory concepts of open coding, memo-ing, constant comparison and saturation were used in data analysis. Results: The study has identified 25 artefacts, organised into five categories: feature, sprint, release, product and corporate governance. It was discovered that conventional agile artefacts are enriched with artefacts associated with plan-based methods in order to provide governance. The empirical evidence collected in the study has been used to identify a primary owner of each artefact and map each artefact to specific activities within each of the agile roles. Conclusion: The development programmes in this study create agile and plan-based artefacts to improve compliance with enterprise quality standards and technology strategies, whilst also mitigating risk of failure. Management of these additional artefacts is currently improvised because agile development processes lack corresponding ceremonies.

A longitudinal embedded case study has been used to investigate innovation processes at Add Latent Ltd. The company provides asset integrity and maintenance management consulting services in the energy sector. Desktop software applications have been redesigned to create a new set of cloudhosted software services. The innovation team adapted an agile scrum process to include exploratory prototyping and manage the geographical distribution of the team members. A minimum
viable product was developed that integrated functional elements of previous software tools into an end-to-end data collection, analysis and visualisation product called AimHi which uses a cloud-hosted web services approach. The paper illustrates how the scrum software development method was tailored for a product innovation context. Extended periods of evaluation and reflection (field trials), prototyping and requirement refinement were combined with periods of incremental feature development using sprints. The AimHi product emerged from a technology transfer and innovation project that has successfully reconciled conflicting demands from customers, universities, partner companies and project staff members.

In this paper, behaviour of Helium gas bubble in liquid of Nitrogen and Oxygen in acoustic
field under ambient pressure and low temperature is investigated theoretically.
Initially, it is introduced the derivation of equation of moving the liquid around the bubble
(radius bubble equation) beginning from the Keller–Kolodener equation (which derived from
the continuity, momentum, and energy equations). Also two cases are suggested to solve this
equation numerically.
In the first case, it is considered that, heat is transferred across the bubble wall. And bubble
wall temperature is assumed to be constant.
In the second case, it is considered that the bubble is adiabatic and its internal pressure obeyed
the adiabatic law.
Radius, velocity of the bubble wall, internal pressure and temperature at the bubble center are
calculated according to the two cases. Also, comparison is made between the cases.
It is showed that the physical quantities in the adiabatic bubble case have higher values than the
other cases. In each case, the effects of evaporation and condensation process are neglected.

Low Reynolds number environment of high-altitude flight places severe demands on the aerodynamic design and stability & control of high-altitude long-endurance uninhabited air vehicles (HALE UAVs). The required lift coefficient is high when compared to the more conventional lower-altitude aircraft due to the reduced air density. Aerofoils of tailless aircraft should be selected or designed carefully. The stability requirement condition strongly affects the aerofoil selection process which relates to the design approach to achieve stability requirements. Another constraint of the selection is the thickness required to hold fuel tanks and/or batteries and the required structural elements for adequate strength & stiffness.
In this paper, new aerofoils with varying thicknesses for an aft- swept flying wing UAV have been designed using MATLAB coding which consists of two parts in addition to the aerodynamic solver XFOIL. The first part generates the aerofoil section geometry using a combination of PARSEC and Bezier-curve parameterization functions. PARSEC parametrization has been used to represent the camber line while the Bezier-curve has been used to select the thickness distribution. This combination is quite efficient using an optimisation search process because of the capability to define a range of design variables that can quickly generate a suitable aerofoil. The second part contains the optimisation code using a genetic algorithm. The primary target was to design a number of aerofoils with high lift/drag ratios (C_l/C_d) for a specific pitching moment limit in addition to a constraint on the maximum thickness. Another target was to give more prominence to the lift coefficient by including the C_l^(3/2)/C_d  factor. The cruise angle of attack was set at 6 degrees with respect to the free stream and the chosen mean aerodynamic chord based Reynolds number was 0.5 million.
According to the set of result obtained so far, the initial observation of the aerodynamic performance of the newly designed aerofoils is that the lift/drag ratio in general is higher than that of the existing ones used in many current generation HALE aircraft. Another observation is that increasing the maximum thickness of the aerofoil leads to a decrease in the maximum lift/drag ratio. In addition, as expected this ratio sharply drops after the maximum value of some of these aerofoils.

In this paper, a development of a low order composite structure module has been introduced. This module can design the wing structure for the given aerodynamic load. The wing structure is broken down into non-spar elements and spars. The weight of non-spar elements are estimated by using empirical equations that were used by NASA for solar powered high altitude UAVs. The Spar is sized by using a numerical approach, which is developed in this paper. The spar is modelled as a composite rectangular wing-box and assumed to withstand the entire load with no contribution from the secondary wing components. The required numbers of laminate on each side of the spar are found iteratively until no failure or buckling is detected. The orientation of laminate of each side of spar was inspired by the existing high altitude aircraft structure. A linear finite beam element is used to evaluate the wing-box deflection under the internal and the aerodynamic loads while only a quasi-static equilibrium is considered during the sizing process. The module has been written in MATLAB. This tool can be used either in the conceptual design stage or in an optimisation process because it facilitates rapid computation. This module has been validated with a high order commercial package (ANSYS). The deflection calculation shows excellent agreement with less than 0.25 % error. The stress calculations show a reasonable agreement with ANSYS with maximum error margin of about 4% at the maximum shear stress level. However, this amount of error could be unimportant as a high factor of safety is usually taken in the design of composite structures. The weight prediction function also has been validated using reference to a NASA Pathfinder aircraft. The predicted weight seems reasonable with a 1.6 % difference from the expected weight of the case study.

In this paper, a previously developed conceptual design tool has been used to study the impact of the latitude, altitude, and the flight duration on the weight estimation and the main characteristics of a high altitude, long endurance and solar powered unmanned aerial vehicle. The available solar energy during the daylight hours has been calculated at given locations and altitudes for specific periods to be used in the pre-conceptual design stage. The pre-conceptual design methodology is based on an analytical and continuous method, which consists of establishing the relationships between all the components with analytical functions using the component characteristics. This design approach can directly provide a unique and optimal design. This study is conducted for a solar aircraft designed for a surveillance mission over Iraq. It is concluded that increasing the operational altitude can lead to a heavier aircraft in spite of the high levels of the available solar energy that can be absorbed. Hence, at high altitude, the surface area required for solar power generation is less than that needed to obtain adequate lift. Increasing the maximum solar irradiance during the daylight hours can lead to further lowering of the aircraft weight. Moreover, an increase in the daylight hours can be beneficial if the charging and discharging losses of the fuel cells are considered.

In this paper, an in-house developed pre-conceptual design methodology and a composite structure module have been used to study the impact of aerodynamic performance, payload requirements and wing thickness to estimate the weight. In the first part, a pre-conceptual design methodology is introduced to examine the weight estimation for a conceptual high altitude, long endurance, solar powered aircraft, called ‘SUMER’, operating at 17 km altitude and 31o latitude (southern Iraq). The impact of aerodynamic performance parameters such as lift, drag and span efficiencies on the weight estimation are investigated. The study also includes estimation of the payload and the power consumption. This pre-conceptual design methodology establishes all the relationships between the components with analytical functions using their characteristics. This approach can directly provide a unique and optimal design for a given set of mission requirements. In the second part, an in-house developed low order composite structure module has been used to design and optimise the wing structure in addition to studying the impact of the maximum thickness of the wing and the spar dimensions on the weight. Detailed buckling characteristics were also taken into account during the study. The final conceptual design of the SUMER is introduced as a case study in this investigation.

In this paper, a description of newly developed conceptual and preliminary design approaches is introduced, to design a high altitude long endurance solar powered unmanned aerial vehicle. The conceptual design approach is based on representing the mass and the power requirement of each aircraft element as a fraction, in order to produce the total mass equation. The fractions have been gathered statistically from available data of existing aircraft of the same type. The mass equation will be solved for the expected range of the aspect ratio and span of the wing to generate a possible design space. The optimal design is then concluded from the design space as the minimum weight. This approach has been validated using existing data of related aircraft. In the preliminary design tool, the aircraft shape and the wing geometry are designed using the main characteristics of aircraft which were obtained from a previous design stage. An appropriate twist and sweep of the wing are then found using an optimisation tool which contains the aerodynamic and the structure models. The outcome at this stage must be a flyable aircraft geometry capable of meeting the mission requirements. Moreover, a case study of designing a solar powered aircraft is introduced using the developed design approaches.