Orthogonal variability modeling to support multi-cloud application configuration

Cloud service providers benefit from a vast majority of customers due to variability and making profit from commonalities between the cloud services that they provide. Recently, application configuration dimensions has been increased dramatically due to multi-tenant, multi-device and multi-cloud paradigm. This challenges the configuration and customization of cloud-based software that are typically offered as a service due to the intrinsic variability. In this paper, we present a model-driven approach based on variability models originating from the software product line community to handle such multi-dimensional variability in the cloud. We exploit orthogonal variability models to systematically manage and create tenant-specific configuration and customizations. We also demonstrate how such variability models can be utilized to take into account the already deployed application parts to enable harmonized deployments for new tenants in a multi-cloud setting. The approach considers application functional and non-functional requirements to provide a set of valid multi-cloud configurations. We illustrate our approach through a case study

Tourist Shoppers’ Evaluation of Retail Service: A Study of Cross-Border versus International Outshoppers

This article extends the concept of customer perceived value (CPV) to the tourist outshopping context and explores the differences in antecedents and outcomes of CPV between cross-border and international outshoppers. A large-scale field survey in Hong Kong with cross-border outshoppers from mainland China and international shoppers from four Western countries (Australia, Canada, the United Kingdom, and the United States) shows that perceived product quality, risk, and value for money have a stronger effect on CPV for cross-border outshoppers, and employee service quality and lifestyle congruence for international outshoppers. CPV also has a stronger positive effect on satisfaction, word of mouth, and repeat purchase intentions for cross-border outshoppers, whereas satisfaction has a stronger positive impact on word of mouth and repeat purchase intentions for international outshoppers. We discuss the conceptual contribution and managerial implications of our findings for international retailers, researchers, and tourism organizations

A dynamic inequality generation scheme for polynomial programming

Hierarchies of semidefinite programs have been used to approximate or even solve polynomial programs. This approach rapidly becomes computationally expensive and is often tractable only for problems of small size. In this paper, we propose a dynamic inequality generation scheme to generate valid polynomial inequalities for general polynomial programs. When used iteratively, this scheme improves the bounds without incurring an exponential growth in the size of the relaxation. As a result, the proposed scheme is in principle scalable to large general polynomial programming problems. When all the variables of the problem are non-negative or when all the variables are binary, the general algorithm is specialized to a more efficient algorithm. In the case of binary polynomial programs, we show special cases for which the proposed scheme converges to the global optimal solution. We also present several examples illustrating the computational behavior of the scheme and provide comparisons with Lasserre’s approach and, for the binary linear case, with the lift-and-project method of Balas, Ceria, and Cornuejols

Chilled ceiling displacement ventilation design charts correlations to employ in optimized system operation for feasible load ranges

This paper expands Ghaddar et al. [N. Ghaddar, K. Ghali, R. Saadeh, A. Keblawi, Design charts for combined chilled ceiling displacement ventilation system (1438-RP), ASHRAE Transactions, 143 (2) (2008) 574-587] design charts of combined chilled ceiling (CC) displacement ventilation (DV) system to operating sensible load ranges from 40 W/m(2) to 100 W/m(2). It develops a global correlation of system load and operational parameters, with comfort measured by vertical temperature gradient and indoor air quality measured by the stratification height. The correlations are used for a known transient load profile in generating optimal settings of the CC/DV system operational parameters and associated energy consumption. An example is illustrated to show how the correlation could be used to size the system and to provide optimized control of the CC/DV system operation at low computational cost. Results of the current model are compared to the published case study of an optimized operation based on transient simulations of the space thermal model to achieve minimum operation cost [M. Mossolly, N. Ghaddar, K. Ghali, L Jensen, Optimized operation of combined chilled ceiling displacement ventilation system using genetic algorithm, ASHRAE Transactions, 143 (2) (2008) 541-554]. The design correlations resulted in good agreement with published data (within 3% error in energy consumption and average 6% error in predictions of comfort and stratification height) at 1/4 of the computational time. The presented methodology provides an alternative for using the correlation for supervisory online controllers for the CC/DV system based on physically derived correlations. (C) 2009 Elsevier B.V. All rights reserved

An optimal two-bout strategy with phase change material cooling vests to improve comfort in hot environment

Cooling vests incorporating phase change material (PCM) packets are used to improve comfort of workers in hot environments. This work aims to investigate by modeling and experimentation the effect of dividing the working duration into two bouts, where different PCM melting temperatures are used in each bout. An integrated bio-heat and fabric-PCM model predictions of physiological and subjective votes are validated via active human subject testing at hot conditions. A parametric study is performed to select, at two conditions (40 �C and 45 �C), the optimal PCM melting temperatures of the two bouts that would result with similar thermal comfort and sensation to the optimal single-bout case. The optimal case achieves most reductions in energy use for PCM regeneration, PCM carried weight and material cost. The results of the parametric study showed that heat storage is reduced in the second bout due to wearing the second vest with lower PCM melting temperature, thus thermal comfort and sensation are significantly improved. The optimal case at the 40 �C environment uses a vest with 21 �C PCMs in the first bout and a vest with 21 �C PCMs in the second bout (V21?V21). At 45 �C, the optimal case is V18?V10 with significant PCM weight reductions from the reference single bout case by a minimum of 47%. Thus, the issue of extra carried weight that affect metabolism and ease of movement when applying continuous cooling during work have been mitigated by using the two-bout strategy. 2017 Elsevier LtdThis publication was made possible by NPRP grant# [ NPRP 7�486 � 2�185 ] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors.Scopu