985 research outputs found
When the reaper becomes a salesman: The influence of terror management on product preferences
The present research investigates how consumer choice is affected by Terror Management Theory’s proposition of Mortality Salience increasing one’s cultural worldview defense and self-esteem striving. The study builds empirically upon prior theorizing by Arndt, Solomon, Kasser and Sheldon (2004). During an experiment, we manipulated Mortality Salience and measured product preferences for conspicuousness and familiarity. Participants primed with death were more likely to choose conspicuous products, corroborating previous research of mortality salience raising materialistic tendencies. In addition, participants showed a tendency to prefer familiar brands. These results are in line with the Terror Management Theory framework
Proof of Luck: an Efficient Blockchain Consensus Protocol
In the paper, we present designs for multiple blockchain consensus primitives
and a novel blockchain system, all based on the use of trusted execution
environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using
TEEs for existing proof of work schemes can make mining equitably distributed
by preventing the use of ASICs. Next, we extend the design with proof of time
and proof of ownership consensus primitives to make mining energy- and
time-efficient. Further improving on these designs, we present a blockchain
using a proof of luck consensus protocol. Our proof of luck blockchain uses a
TEE platform's random number generation to choose a consensus leader, which
offers low-latency transaction validation, deterministic confirmation time,
negligible energy consumption, and equitably distributed mining. Lastly, we
discuss a potential protection against up to a constant number of compromised
TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital
AN INVESTIGATION OF THE ACTIVATION OF THE SUBDIVISIONS OF GLUTEUS MEDIUS DURING ISOMETRIC HIP CONTRACTIONS
Gluteus medius is involved in movement and stability of the hip and gluteus medius dysfunction is commonly implicated in many lower limb pathologies (Fredericson et al 2000). It is proposed that functional subdivisions exist within the gluteus medius muscle (Conneely and O’Sullivan 2008). There is however a lack of empirical evidence examining the role of the subdivisions of gluteus medius. This study compared the muscle activation of these subdivisions (anterior, middle and posterior) during isometric contractions of hip abduction, internal and external rotation in normal subjects
Gluteus Medius Muscle Activation During Isometric Muscle Contractions
Context: Functional subdivisions are proposed to exist in the gluteus medius (GM) muscle. Dysfunction of the GM, in particular its functional subdivisions, is commonly implicated in lower limb pathologies. However, there is a lack of empirical evidence examining the role of the subdivisions of the GM. Objectives: To compare the activation of the functional subdivisions of the GM (anterior, middle, and posterior) during isometric hip contractions. Design: Single-session, repeated-measures observational study. Setting: University research laboratory. Participants: Convenience sample of 15 healthy, pain-free subjects. Intervention: Subjects performed 3 maximal voluntary isometric contractions for hip abduction and internal and external rotation on an isokinetic dynamometer with simultaneous recording of surface electromyography (sEMG) activity of the GM subdivisions. Main Outcome Measures: sEMG muscle activity for each functional subdivision of the GM during each hip movement was analyzed using a 1-way repeated-measures ANOVA (post hoc Bonferroni). Results: The response of GM subdivisions during the 3 different isometric contractions was significantly different (interaction effect; P = .003). The anterior GM displayed significantly higher activation across all 3 isometric contractions than the middle and posterior subdivisions (main effect; both P < .001). The middle GM also demonstrated significantly higher activation than the posterior GM across all 3 isometric contractions (main effect; P = .027). There was also significantly higher activation of all 3 subdivisions during both abduction and internal rotation than during external rotation (main effect; both P < .001). Conclusions: The existence of functional subdivisions in the GM appears to be supported by the findings. Muscle activation was not homogeneous throughout the entire muscle. The highest GM activation was found in the anterior GM subdivision and during abduction and internal rotation. Future studies should examine the role of GM functional subdivisions in subjects with lower limb pathologies
Thermoelectric efficiency at maximum power in a quantum dot
We identify the operational conditions for maximum power of a
nanothermoelectric engine consisting of a single quantum level embedded between
two leads at different temperatures and chemical potentials. The corresponding
thermodynamic efficiency agrees with the Curzon-Ahlborn expression up to
quadratic terms in the gradients, supporting the thesis of universality beyond
linear response.Comment: 4 pages, 3 figure
Automatic Scenario Generation for Robust Optimal Control Problems
Existing methods for nonlinear robust control often use
scenario-based approaches to formulate the control problem as nonlinear optimization problems. Increasing the number of scenarios improves robustness while increasing the size of the optimization problems. Mitigating the size of the problem by reducing the number of scenarios requires knowledge about how the uncertainty affects the system. This paper draws from local reduction methods used in semi-infinite optimization to solve robust optimal control problems with parametric uncertainty. We show that nonlinear robust optimal control problems are equivalent to semi-infinite optimization problems and can be solved by local reduction. By iteratively adding interim globally worst-case scenarios to the problem, methods based on local reduction provide a way to manage the total number of scenarios. In particular, we show that local reduction methods find worst-case scenarios that are not on the boundary of the uncertainty set. The proposed approach is illustrated with a case study with both parametric and additive time-varying uncertainty. The number of scenarios obtained from local reduction is 101, smaller than in the case when all 2 14+3×192 boundary scenarios are considered. A validation with randomly-drawn scenarios shows that our proposed approach reduces the number of scenarios and ensures robustness even if local solvers are used
Automatic scenario generation for efficient solution of robust optimal control problems
Existing methods for nonlinear robust control often use scenario-based approaches to formulate the control problem as large nonlinear optimization problems. The optimization problems are challenging to solve due to their size, especially if the control problems include time-varying uncertainty. This paper draws from local reduction methods used in semi-infinite optimization to solve robust optimal control problems with parametric and time-varying uncertainty. By iteratively adding interim worst-case scenarios to the problem, methods based on local reduction provide a way to manage the total number of scenarios. We show that the local reduction method for optimal control problems consists of solving a series of simplified optimal control problems to find worst-case constraint violations. In particular, we present examples where local reduction methods find worst-case scenarios that are not on the boundary of the uncertainty set. We also provide bounds on the error if local solvers are used. The proposed approach is illustrated with two case studies with parametric and additive time-varying uncertainty. In the first case study, the number of scenarios obtained from local reduction is 101, smaller than in the case when all 2¹⁴⁺³×¹⁹² extreme scenarios are considered. In the second case study, the number of scenarios obtained from the local reduction is two compared to 512 extreme scenarios. Our approach was able to satisfy the constraints both for parametric uncertainty and time-varying disturbances, whereas approaches from literature either violated the constraints or became computationally expensive
Automatic scenario generation for efficient solution of robust optimal control problems
Existing methods for nonlinear robust control often use scenario-based
approaches to formulate the control problem as large nonlinear optimization
problems. The optimization problems are challenging to solve due to their size,
especially if the control problems include time-varying uncertainty. This paper
draws from local reduction methods used in semi-infinite optimization to solve
robust optimal control problems with parametric and time-varying uncertainty.
By iteratively adding interim worst-case scenarios to the problem, methods
based on local reduction provide a way to manage the total number of scenarios.
We show that the local reduction method for optimal control problems consists
of solving a series of simplified optimal control problems to find worst-case
constraint violations. In particular, we present examples where local reduction
methods find worst-case scenarios that are not on the boundary of the
uncertainty set. We also provide bounds on the error if local solvers are used.
The proposed approach is illustrated with two case studies with parametric and
additive time-varying uncertainty. In the first case study, the number of
scenarios obtained from local reduction is 101, smaller than in the case when
all extreme scenarios are considered. In the second case
study, the number of scenarios obtained from the local reduction is two
compared to 512 extreme scenarios. Our approach was able to satisfy the
constraints both for parametric uncertainty and time-varying disturbances,
whereas approaches from literature either violated the constraints or became
computationally expensive.Comment: arXiv admin note: substantial text overlap with arXiv:2204.14145
(IFAC conference submission
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