5,930 research outputs found
Transport Coefficients from Large Deviation Functions
We describe a method for computing transport coefficients from the direct
evaluation of large deviation function. This method is general, relying on only
equilibrium fluctuations, and is statistically efficient, employing trajectory
based importance sampling. Equilibrium fluctuations of molecular currents are
characterized by their large deviation functions, which is a scaled cumulant
generating function analogous to the free energy. A diffusion Monte Carlo
algorithm is used to evaluate the large deviation functions, from which
arbitrary transport coefficients are derivable. We find significant statistical
improvement over traditional Green-Kubo based calculations. The systematic and
statistical errors of this method are analyzed in the context of specific
transport coefficient calculations, including the shear viscosity, interfacial
friction coefficient, and thermal conductivity.Comment: 11 pages, 5 figure
Neural Lyapunov Control
We propose new methods for learning control policies and neural network
Lyapunov functions for nonlinear control problems, with provable guarantee of
stability. The framework consists of a learner that attempts to find the
control and Lyapunov functions, and a falsifier that finds counterexamples to
quickly guide the learner towards solutions. The procedure terminates when no
counterexample is found by the falsifier, in which case the controlled
nonlinear system is provably stable. The approach significantly simplifies the
process of Lyapunov control design, provides end-to-end correctness guarantee,
and can obtain much larger regions of attraction than existing methods such as
LQR and SOS/SDP. We show experiments on how the new methods obtain high-quality
solutions for challenging control problems.Comment: NeurIPS 201
Antioxidant Activities and Phenolic Acids in Different Raw and Boiled Potatoes and Sweet Potatoes
Antioxidants have attracted great interests from food industries and scientists in recent years, because they have the capacity to reduce the harmful oxidation reaction in human body. Phenolic compounds are the common antioxidants that are widely found in fruits and vegetables. In this study, three varieties of potatoes and four varieties of sweet potatoes were used to examine the profiles and contents of phenolics in the raw and boiled potatoes and sweet potatoes. The Red Garnet Sweet Potato (RGSP) was the richest in phenolic content and selected to study the changes of free phenolics, total phenolic content, and antioxidant activity at different boiling times. In general, gallic acid and six different chlorogenic acid derivatives were found in the potatoes and sweet potatoes. The varieties of phenolic acids in the sweet potatoes were much more than the potatoes. The content of each phenolic acid varied in different raw potatoes and sweet potatoes. The total phenolics content of raw RGSP was the highest among these samples. A short time of boiling processing for potatoes and sweet potatoes could cause a significant increase in free phenolic acids, except 3-O-caffeoylquinic acid and 3,4-O-dicaffeoylquinic acid which were found to decrease during the processing. After boiled for 10 min, RGSP had higher level of phenolics and antioxidant activity than its raw or the one boiled for longer time. Therefore, the level of free phenolics and antioxidant activity in potatoes and sweet potatoes changed during boiling. They generally reached the peak level in a short boiling time (10 min) and then decreased with extended boiling time
The Interaction between Parents and Children:three Essays on Family Economics
This thesis focuses on two aspects of parent-child interactions. First, in Chapter 2, I study the effect of attending daycare at age 0-2 on children's cognitive development at age 8 in the Netherlands. Despite the expanding evidence on the desirable effects of child care at age 3-6 on child outcomes, there is less evidence on the effect of child care at very young ages.
After establishing the relationship between parents and children at a very young age, in Chapter 3 this thesis turns to the adulthood stage. Chapter 3 explores the impact of parents’ housing wealth on children’s marriage prospects at marriageable ages in China. The hypothesis is that in an economy with an excess supply of males in the marriage market, such as China, parental housing wealth acts as a signal in the marriage market:.
Finally, I explore the impact of children on their parents’ wellbeing at older ages. In Chapter 4, I investigate the effect of the death of a child on parents’ physical and mental wellbeing in China. With the rapid aging of the population and the lack of a developed social security system in China, it is important to understand the effect of losing a child on individual wellbeing
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