24,894 research outputs found
On the orbital evolution of a giant planet pair embedded in a gaseous disk. II. A Saturn-Jupiter configuration
We carry out a series of high-resolution (1024 X 1024) hydrodynamic
simulations to investigate the orbital evolution of a Saturn-Jupiter pair
embedded in a gaseous disk. This work extends the results of our previous work
by exploring a different orbital configuration---Jupiter lies outside Saturn
(q<1, where q= M_i/M_o is the mass ratio of the inner planet and the outer
one). We focus on the effects of different initial separations (d) between the
two planets and the various surface density profiles of the disk, where \sigma
\propto r^{-\alpha}. We also compare the results of different orbital
configurations of the planet pair. Our results show that: (1) when the initial
separation is relatively large(d>d_{iLr}, where d_{iLr} is the distance between
Jupiter and its first inner Lindblad resonance), the two planets undergo
divergent migration. However, the inward migration of Saturn could be halted
when Jupiter compresses the inner disk in which Saturn is embedded. (2)
Convergent migration occurs when the initial separation is smaller (d<d_{iLr})
and the density slope of the disk is nearly flat (\alpha<1/2). Saturn is then
forced by Jupiter to migrate inward when the two planets are trapped into mean
motion resonances (MMRs), and Saturn may get very close to the central star.
(3) In the case of q<1, the eccentricity of Saturn could be excited to a very
high value (e_{S}~0.4-0.5) by the MMRs and the system could maintain stability.
These results explain the formation of MMRs in the exoplanet systems where the
outer planet is more massive than the inner one. It also helps us to understand
the origin of the "hot Jupiter/Saturn" undergoing high eccentric orbit.Comment: 17 pages, 12 figures, 2 table
Determination of organic acids evolution during apple cider fermentation using an improved HPLC analysis method
An efficient method for analyzing ten organic acids in food, namely citric, pyruvic, malic, lactic, succinic, formic, acetic, adipic, propionic and butyric acids, using HPLC was developed. Boric acid was added into the mobile phase to separate lactic and succinic acids, and a post-column buffer solution [5 mmol/L p-toluensulfonic acid (p-TSA) + 20 mmol/L bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane (bisÂżtris) + 100 Âżmol/L sodium ethylenediaminetetraacetic (EDTA-2Na)] was used to improve the sensitivity of detection. The average spiked recoveries for the ten organic acids ranged from 82.9 to 127.9% with relative standard deviations of 1.44Âż4.71%. The linear ranges of determination were from 15 to 1,000 mg/L with correlation coefficients of 0.9995Âż0.9999. The metabolism of organic acids in cider, and the effect of nutrients including diammonium phosphate (DAP), thiamine, biotin, niacinamide and pantothenic acid on their metabolism, were studied using this method of analysis. We found that before cider brewing, additions of 200 mg/L DAP and 0.3 mg/L thiamine to apple juice concentrate results in a high quality cider
Gap formation in a self-gravitating disk and the associated migration of the embedded giant planet
We present the results of our recent study on the interactions between a
giant planet and a self-gravitating gas disk. We investigate how the disk's
self-gravity affects the gap formation process and the migration of the giant
planet. Two series of 1-D and 2-D hydrodynamic simulations are performed. We
select several surface densities and focus on the gravitationally stable
region. To obtain more reliable gravity torques exerted on the planet, a
refined treatment of disk's gravity is adopted in the vicinity of the planet.
Our results indicate that the net effect of the disk's self-gravity on the gap
formation process depends on the surface density of the disk. We notice that
there are two critical values, \Sigma_I and \Sigma_II. When the surface density
of the disk is lower than the first one, \Sigma_0 < \Sigma_I, the effect of
self-gravity suppresses the formation of a gap. When \Sigma_0 > \Sigma_I, the
self-gravity of the gas tends to benefit the gap formation process and enlarge
the width/depth of the gap. According to our 1-D and 2-D simulations, we
estimate the first critical surface density \Sigma_I \approx 0.8MMSN. This
effect increases until the surface density reaches the second critical value
\Sigma_II. When \Sigma_0 > \Sigma_II, the gravitational turbulence in the disk
becomes dominant and the gap formation process is suppressed again. Our 2-D
simulations show that this critical surface density is around 3.5MMSN. We also
study the associated orbital evolution of a giant planet. Under the effect of
the disk's self-gravity, the migration rate of the giant planet increases when
the disk is dominated by gravitational turbulence. We show that the migration
timescale associates with the effective viscosity and can be up to 10^4 yr.Comment: 24 pages, 13 figures, accepted by RA
The 1st International Workshop on Context-Aware Recommendation Systems with Big Data Analytics (CARS-BDA)
Motivation and Goals. With the explosive growth of online service platforms, increasing number of people and enterprises are doing everything online. In order for organizations, governments, and individuals to understand their users, and promote their products or services, it is necessary for them to analyse big data and recommend the media or online services in real time. Effective recommendation of items of interest to consumers has become critical for enterprises in domains such as retail, e-commerce, and online media. Driven by the business successes, academic research in this field has also been active for many years. Though many scientific breakthroughs have been achieved, there are still tremendous challenges in developing effective and scalable recommendation systems for real-world industrial applications. Existing solutions focus on recommending items based on pre-set contexts, such as time, location, weather etc. The big data sizes and complex contextual information add further challenges to the deployment of advanced recommender systems. This workshop aims to bring together researchers with wide-ranging backgrounds to identify important research questions, to exchange ideas from different research disciplines, and, more generally, to facilitate discussion and innovation in the area of context-aware recommender systems and big data analytics. In a broad sense, the objective of such a workshop is to present results of the research undertaken in the area of data driven context-aware recommender systems, as a fishow and tellfi occasion. To some extent, the workshop is an exercise in showcasing research activities and findings, rather than in and not of fiworkshoppingfi or holding group discussions on research. This orientation, and the large number of presentations which are being made, means that tight timelines have to be followed. An intensive series of presentations is made, the downside of which is that the time available for group discussion is limited
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