Effects of Serving Temperature on Sensory Perception and Acceptance of Brewed Coffee

Coffee continues to be one of the most widely consumed beverages worldwide. How an individual perceives a cup of coffee is impacted by a plethora of factors including origin, growing climate, roasting level, and consumption habits. This thesis utilized both trained descriptive panelists and untrained consumer panelists to analyze how serving/consumption temperature modulates sensory perception of brewed coffee in regards to appearance, aroma, flavor, taste, and mouthfeel. Three varieties of coffee (Colombia, Ethiopia, and Kenya) were brewed and served to panelists at four temperatures: 70, 55, 40, and 25 °C. In one study (Study 1, Chapter 3), results from descriptive analysis showed that product temperature had a larger effect in modulating sensory perception than did coffee variety. In another descriptive analysis study (Study 2, Chapter 3), trained panelists found that serving temperature had a more significant effect on perception than freshness, up to 90 minutes, of the brewed coffee sample of Ethiopian variety. Utilizing an untrained consumer panel and a Check-All-That-Apply (CATA) method to assess these same coffee samples, results showed that both serving temperature and coffee variety largely contributed to the variation in sensory perception. While these consumer panelists were more effective in differentiating between coffee varieties when assessing the samples at a lower (40 °C) temperature, liking of the sample was highest when served at hot temperatures (55 and 70 °C). This indicates that subtle attributes of brewed coffee may be easier to identify when served at lower temperatures. In a final study using CATA, additions of cream and sugar were added to the brewed coffee sample and served at four temperatures. Results showed that temperature is a significant modulator of sensory perception in enhanced coffee (i.e., brewed coffee with cream and/or sugar). The findings of this thesis show the importance of controlling temperature for the sensory evaluation of coffee products, since significant variations in both qualitative and quantitative sensory perception arise from changes in product temperature

Amplifying Voices: Co-researchers with Learning Disabilities Use a Co-designed Survey to “have a conversation with the public”

The concept of ‘giving voice’ in research and in the design of accessible technologies involving people with learning disabilities (LDs) has been often used to highlight the necessity for careful consideration of their opinions and needs. Those who ‘communicate differently’ are often portrayed as the beneficiaries of the technological advancements rather than contributors to the technology that can benefit everybody. Here, we present a case study whereby people with LDs co-designed an inclusive survey platform and created an online survey to “have a conversation with the public” and to challenge attitudes towards LDs. Over 800 participants with and without disabilities or impairments completed the survey and reflected on their learning experience. Using qualitative and quantitative methods, we found that the co-created platform enabled all – the co-researchers and the respondents – to have their ‘voices amplified’ and to be listened to in a meaningful way – just as in ‘a conversation’ between people

An iterative method based on boundary integrals for elliptic Cauchy problems in semi-infinite domains

In this study, we investigate the problem of reconstruction of a stationary temperature field from given temperature and heat flux on a part of the boundary of a semi-infinite region containing an inclusion. This situation can be modelled as a Cauchy problem for the Laplace operator and it is an ill-posed problem in the sense of Hadamard. We propose and investigate a Landweber-Fridman type iterative method, which preserve the (stationary) heat operator, for the stable reconstruction of the temperature field on the boundary of the inclusion. In each iteration step, mixed boundary value problems for the Laplace operator are solved in the semi-infinite region. Well-posedness of these problems is investigated and convergence of the procedures is discussed. For the numerical implementation of these mixed problems an efficient boundary integral method is proposed which is based on the indirect variant of the boundary integral approach. Using this approach the mixed problems are reduced to integral equations over the (bounded) boundary of the inclusion. Numerical examples are included showing that stable and accurate reconstructions of the temperature field on the boundary of the inclusion can be obtained also in the case of noisy data. These results are compared with those obtained with the alternating iterative method

An alternating potential based approach for a Cauchy problem for the Laplace equation in a planar domain with a cut

We consider a Cauchy problem for the Laplace equation in a bounded region containing a cut, where the region is formed by removing a sufficiently smooth arc (the cut) from a bounded simply connected domain D. The aim is to reconstruct the solution on the cut from the values of the solution and its normal derivative on the boundary of the domain D. We propose an alternating iterative method which involves solving direct mixed problems for the Laplace operator in the same region. These mixed problems have either a Dirichlet or a Neumann boundary condition imposed on the cut and are solved by a potential approach. Each of these mixed problems is reduced to a system of integral equations of the first kind with logarithmic and hypersingular kernels and at most a square root singularity in the densities at the endpoints of the cut. The full discretization of the direct problems is realized by a trigonometric quadrature method which has super-algebraic convergence. The numerical examples presented illustrate the feasibility of the proposed method

An iterative regularizing method for an incomplete boundary data problem for the biharmonic equation

An incomplete boundary data problem for the biharmonic equation is considered, where the displacement is known throughout the boundary of the solution domain whilst the normal derivative and bending moment are specified on only a portion of the boundary. For this inverse ill‐posed problem an iterative regularizing method is proposed for the stable data reconstruction on the underspecified boundary part. Convergence is proven by showing that the method can be written as a Landweber‐type procedure for an operator formulation of the incomplete data problem. This reformulation renders a stopping rule, the discrepancy principle, for terminating the iterations in the case of noisy data. Uniqueness of a solution to the considered problem is also shown

A boundary integral equation method for numerical solution of parabolic and hyperbolic Cauchy problems

We present a unified boundary integral approach for the stable numerical solution of the ill-posed Cauchy problem for the heat and wave equation. The method is based on a transformation in time (semi-discretisation) using either the method of Rothe or the Laguerre transform, to generate a Cauchy problem for a sequence of inhomogenous elliptic equations; the total entity of sequences is termed an elliptic system. For this stationary system, following a recent integral approach for the Cauchy problem for the Laplace equation, the solution is represented as a sequence of single-layer potentials invoking what is known as a fundamental sequence of the elliptic system thereby avoiding the use of volume potentials and domain discretisation. Matching the given data, a system of boundary integral equations is obtained for finding a sequence of layer densities. Full discretisation is obtained via a Nyström method together with the use of Tikhonov regularization for the obtained linear systems. Numerical results are included both for the heat and wave equation confirming the practical usefulness, in terms of accuracy and resourceful use of computational effort, of the proposed approach

Boundary-integral approach to the numerical solution of the Cauchy problem for the Laplace equation

We present a survey of a direct method of boundary integral equations for the numerical solution of the Cauchy problem for the Laplace equation in doubly connected domains. The domain of solution is located between two closed boundary surfaces (curves in the case of two-dimensional domains). This Cauchy problem is reduced to finding the values of a harmonic function and its normal derivative on one of the two closed parts of the boundary according to the information about these quantities on the other boundary surface. This is an ill-posed problem in which the presence of noise in the input data may completely destroy the procedure of finding the approximate solution. We describe and present the results for a procedure of regularization aimed at the stable determination of the required quantities based on the representation of the solution to the Cauchy problem in the form a single-layer potential. For given data, this representation yields a system of boundary integral equations with two unknown densities. We establish the existence and uniqueness of these densities and propose a method for the numerical discretization in two- and three-dimensional domains. We also consider the cases of simply connected domains of the solution and unbounded domains. Numerical examples are presented both for two- and three-dimensional domains. These numerical results demonstrate that the proposed method gives good accuracy with relatively small amount of computations

Recovering boundary data in planar heat conduction using boundary integral equation method

We consider a Cauchy problem for the heat equation, where the temperature field is to be reconstructed from the temperature and heat flux given on a part of the boundary of the solution domain. We employ a Landweber type method proposed in [2], where a sequence of mixed well-posed problems are solved at each iteration step to obtain a stable approximation to the original Cauchy problem. We develop an efficient boundary integral equation method for the numerical solution of these mixed problems, based on the method of Rothe. Numerical examples are presented both with exact and noisy data, showing the efficiency and stability of the proposed procedure and approximations

On the numerical solution of a Cauchy problem in an elastostatic half-plane with a bounded inclusion

We propose an iterative procedure for the inverse problem of determining the displacement vector on the boundary of a bounded planar inclusion given the displacement and stress fields on an infinite (planar) line-segment. At each iteration step mixed boundary value problems in an elastostatic half-plane containing the bounded inclusion are solved. For efficient numerical implementation of the procedure these mixed problems are reduced to integral equations over the bounded inclusion. Well-posedness and numerical solution of these boundary integral equations are presented, and a proof of convergence of the procedure for the inverse problem to the original solution is given. Numerical investigations are presented both for the direct and inverse problems, and these results show in particular that the displacement vector on the boundary of the inclusion can be found in an accurate and stable way with small computational cost

On a boundary integral solution of a lateral planar Cauchy problem in elastodynamics

A boundary integral based method for the stable reconstruction of missing boundary data is presented for the governing hyperbolic equation of elastodynamics in annular planar domains. Cauchy data in the form of the solution and traction is reconstructed on the inner boundary curve from the similar data given on the outer boundary. The ill-posed data reconstruction problem is reformulated as a sequence of boundary integral equations using the Laguerre transform with respect to time and employing a single-layer approach for the stationary problem. Singularities of the involved kernels in the integrals are analyzed and made explicit, and standard quadrature rules are used for discretization. Tikhonov regularization is employed for the stable solution of the obtained linear system. Numerical results are included showing that the outlined approach can be turned into a practical working method for finding the missing data