Report of the Maziwa Zaidi Policy Forum on inclusive investment opportunities in Tanzania’s dairy value chains: Exploiting the evidence, Dar es Salaam, 23-24 May 2017

Irish Ai

MILP model for volt-var optimization considering chronological operation of distribution systems containing DERs

This paper presents a mixed-integer linear programming model for volt-var optimization considering the chro-nological operation of distribution systems containing distributed energy resources (DERs). The proposed model describes the operation problem of capacitor banks (CBs) and voltage regulators (VRs), and it is further based on the steady-state operation during each time interval contained in typical scenarios of distribution systems. A procedure using a K-means clustering algorithm is used to select the scenarios, thus preserving the simultaneity and chronological combination of different loads and DERs. According to the formulation that we developed, the regulation devices become sensitive to downstream load variations, since we use explicit current variables to control automatic CBs, and since we include means to compensate voltage drops along distribution lines in the control of VRs. The model is validated by comparing the results obtained during several tests of two typical cases with those obtained through nonlinear power flow. The typical case studies presented in the paper highlight the good agreement between the results obtained with the linearized model and with power flow method; further, the practical results confirm that the use of typical scenarios allows representing different levels of loads and DERs, while keeping the validity and performance of the proposed model

Estudo comparativo sobre representações visuais em interfaces com base em ícones de dispositivos móveis da Apple

Esta dissertação teve por objetivo verificar se existe um diferencial estético nas representações visuais nas interfaces gráficas dos dispositivos móveis da Apple e, se existir, se esse diferencial efetivamente influencia o vínculo do usuário com a marca e se o usuário tem consciência dele. Para tanto é apresentada uma breve análise diacrônica sobre as interfaces computacionais, bem como uma descrição de momentos chave na história da referida empresa. A partir disto, são abordadas questões que abrangem o posicionamento da marca Apple, pois desde a popularização das interfaces gráficas (GUI) a mesma tem sido associada tanto ao conceito de boas interfaces, quanto tem esta relação contestada. Existem ainda autores que consideram que o sucesso da marca Apple deve-se menos à qualidade de seus produtos (hardware e interfaces gráficas) que à força das ações de marketing da empresa. Para compreender de forma mais pontual as interfaces que eram objeto de estudo e as diretrizes que envolvem a construção de seu desenho, foram analisados os guias de desenvolvimento de interfaces da Apple para o iOS (iOS Human Interface Guidelines) e do Android (Android Developers), atualmente seu principal concorrente. A fim de tentar analisar a percepção que usuários têm das especificidades e dos diferenciais estéticos entre as referidas interfaces, foram construídas duas simulações, cada qual com características de um dos sistemas. Sessões experimentais com usuários, seguidas de entrevista, compuseram a fase empírica, de cunho qualitativo, em que se procurou verificar qual conjunto de ícones os participantes preferiam e por que. Os resultados encontrados apontam que questões estéticas são importantes na percepção que as pessoas têm das interfaces. Essa atenção às configurações estéticas parece contribuir para a percepção geral que se tem dos produtos onde os ícones se apresentam. A partir desses resultados é possível afirmar que a estética faz parte do conjunto de fatores, que constroem a percepção final – positiva ou negativa, de uma interface e, com ela, dos produtos de uma determinada marca. Por outro lado, embora o conjunto de ícones construído de acordo com os parâmetros do Guia de Desenvolvimento de Interfaces da Apple tenha sido preferido por dois terços dos participantes, não houve identificação daquele grupo de ícones com as interfaces da marca Apple. Isso sugere que a construção da marca é alicerçada na qualidade estética de suas interfaces, mas indica também a importância das ações de marketing na atribuição de maior qualidade estética às interfaces da Apple.This work aimed to verify whether there is a differential in aesthetic visual representations in the graphical interfaces of Apple’s mobile devices. If a difference was found, a second objective was to verify whether this differential effectively influences the bond between user and brand and if the user is aware of it. To this end, it starts with a brief diachronic analysis of computer interfaces, as well as a description of key moments in Apple's history of. Discussed issues include brand positioning, as, since the popularization of graphical user interfaces (GUI), Apple has been associated to the concept of good interfaces. However, at the same time, this relationship has also been challenged, as there are authors who believe that the success of the brand Apple is not due to the quality of its products (hardware and graphical interfaces) but to the strength of the marketing activities of the company. To understand the specific interfaces that were the object of this study and to know the guidelines that drive their design, we analyzed Apple iOS Human Interface Guidelines and its Android equivalent - Android Developers - (as Android is currently Apple's main competitor in the mobile market). In order to analyze users' perception of specific features and aesthetic differences between Apple and Android interfaces, two simulations were built, each with characteristics of either system. Experimental sessions with users were followed by interviews, comprising the empirical, qualitative study. These experiments aimed to verify which set of icons participants preferred and why. The results show that aesthetic considerations are important in the perception of interfaces. This attention to aesthetic settings seems to contribute to the general perception that people have of the digital products themselves. From these results we can say that aesthetics is part of the set of factors that build the final perception - positive or negative - of an interface, and with it, the products of a particular brand. However, although the icon set constructed in accordance with the parameters of iOS Human Interface Guidelines Apple has been preferred by two-thirds of the participants, the identification of that group of icons with Apple interfaces did not happen. This suggests that Apple's brand building can be founded on the aesthetic quality of its interfaces, but also indicates the importance of marketing actions in assigning greater aesthetic quality to Apple interfaces