1,510 research outputs found
3-Carboxymethyl-1H-indole-4-carboxylic acid
In the title compound, C11H9NO4, the carboxyl group bonded to the six-membered ring lies close to the plane of the 1H-indole ring system [dihedral angle = 13.13 (9)°], whereas the carboxylic acid group linked to the five-membered ring by a methylene bridge is close to perpendicular [78.85 (9)°]. In the crystal, O—H⋯O and N—H⋯O hydrogen bonds link the molecules, generating (110) sheets
A Practical Speed Loss Prediction Model at Arbitrary Wave Heading for Ship Voyage Optimization
This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading. In the model, the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed. A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation. The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles. The full-scale measurements from three different types of ships, i.e., a PCTC, a container ship, and a chemical tanker, are used to validate the proposed model for speed loss prediction in irregular waves. The effect of the improved model for\ua0speed loss prediction\ua0on a ship’s voyage optimization is also investigated. The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves
A semi-empirical model for ship speed loss prediction at head sea and its validation by full-scale measurements
This paper proposes a semi-empirical model to estimate a ship’s speed loss at head sea. In the model, the formulas to estimate a ship’s added resistance due to waves have been further developed to better consider the ship hull forms, in addition to other main particulars. Based on the model experimental tests of 11 ships in regular head waves, the new formulas have more flexible forms and can better fit the test results than other similar models. In addition, this model proposes a significant wave height based correction factor multiplied to the conventional integration to compute wave resistance in irregular waves. This factor is supposed to consider the impact of coupled ship motions in high waves on a ship’s added resistance due to waves. The model is validated by the full-scale measurement from two vessels, a PCTC and a chemical tanker. The encountered weather conditions along the sailing routes are extracted from the reanalysis metocean data. The results indicate that the proposed model can provide quite accurate predictions of ship speed loss in head sea operations
Voyage optimization combining genetic algorithm and dynamic programming for fuel/emissions reduction
Deterministic optimization algorithms generate optimal routes/paths and speeds along ship voyages. However, a ship can rarely follow pre-defined speeds because dynamic sea environments lead to continuous speed variation. In this paper, a voyage optimization method is proposed to optimize ship engine power to reduce fuel and air emissions. It is a combination of dynamic programming and genetic algorithm to solve voyage planning in three-dimensions. In this method, the engine power is discretized into several levels. The potential benefit of using this algorithm is investigated by a medium-size chemical tanker. A ship\u27s actual sailing is used to demonstrate benefits of the proposed method. On average 3.4% of fuel-saving and emission reduction can be achieved than state-of-the-art deterministic methods. If compared with the actual full-scale measurements, on average 5.6% reduction of fuel consumption and GHG emissions (about 275 tons) can be expected by the proposed method for the six case study voyages
Impact of ship operations aided by voyage optimization on a ship’s fatigue assessment
In this study, different operation factors affecting a ship’s wave statistics are studied, such as the slow steaming and voyage optimizations. Especially, the impact of various voyage optimization methods on the long-term wave statistics and corresponding fatigue damage during ship operations is investigated by comparing the encountered waves with the design wave scatter diagram. Three years of full-scale measurements from a container ship sailing in the North Atlantic are employed to study the impact, in addition to noon reports from two fleets of container ships and VLCCs. Furthermore, the benefits of using voyage optimizations for minimum fatigue damage accumulation during operation are discussed. The large difference of wave statistics is found when the ship follows routes generated by various optimization methods and the design diagram. For some westbound voyages, the voyage optimization methods can significantly decrease the ship’s fatigue damage accumulations, leading to longer fatigue life
A VLA Polarimetric Study of the Galactic Center Radio Arc: Characterizing Polarization, Rotation Measure, and Magnetic Field Properties
The Radio Arc is one of the brightest systems of non-thermal filaments (NTFs)
in the Galactic Center, located near several prominent HII regions (Sickle and
Pistol) and the Quintuplet stellar cluster. We present observations of the Arc
NTFs using the S-, C-, and X-bands of the Very Large Array interferometer. Our
images of total intensity reveal large-scale helical features that surround the
Arc NTFs, very narrow sub-filamentation, and compact sources along the NTFs.
The distribution of polarized intensity is confined to a relatively small area
along the NTFs. There are elongated polarized structures that appear to lack
total intensity counterparts. We detect a range of rotation measure values from
-1000 to -5800 rad m, likely caused by external Faraday rotation
along the line of sight. After correcting for Faraday rotation, the intrinsic
magnetic field orientation is found to generally trace the extent of the NTFs.
However, the intrinsic magnetic field in several regions of the Arc NTFs shows
an ordered pattern that is rotated with respect to the extent of the NTFs. We
suggest this changing pattern may be caused by an additional magnetized source
along the line of sight, so that we observe two field systems superposed in our
observations. We suggest that the large scale helical segments near the Radio
Arc could be components of such a source causing these changes in intrinsic
magnetic field, and some variations in the polarization and rotation measure
values along the NTFs.Comment: PDF should be 24 pages with 13 figure
VLASSICK: The VLA Sky Survey in the Central Kiloparsec
At a distance of 8 kpc, the center of our Galaxy is the nearest galactic
nucleus, and has been the subject of numerous key projects undertaken by great
observatories such as Chandra, Spitzer, and Herschel. However, there are still
no surveys of molecular gas properties in the Galactic center with less than
30" (1 pc) resolution. There is also no sensitive polarization survey of this
region, despite numerous nonthermal magnetic features apparently unique to the
central 300 parsecs. In this paper, we outline the potential the VLASS has to
fill this gap. We assess multiple considerations in observing the Galactic
center, and recommend a C-band survey with 10 micro-Jy continuum RMS and
sensitive to molecular gas with densities greater than 10^4 cm^{-3}, covering
17 square degrees in both DnC and CnB configurations ( resolution ~5"),
totaling 750 hours of observing time. Ultimately, we wish to note that the
upgraded VLA is not just optimized for fast continuum surveys, but has a
powerful correlator capable of simultaneously observing continuum emission and
dozens of molecular and recombination lines. This is an enormous strength that
should be fully exploited and highlighted by the VLASS, and which is ideally
suited for surveying the center of our Galaxy.Comment: 13 pages, 3 figures, a White Paper submitted to provide input in
planning the Very Large Array Sky Surve
Genomic Insights into Speciation History and Local Adaptation of an Alpine Aspen in the Qinghai–Tibet Plateau and Adjacent Highlands
Natural selection serves as an important agent to drive and maintain interspecific divergence. Populus rotundifolia Griff. is an alpine aspen species that mainly occurs in the Qinghai–Tibet Plateau (QTP) and adjacent highlands, whereas its sister species, P. davidiana Dode, is distributed across southwest and central to northeast China in much lower altitude regions. In this study, we collected genome resequencing data of 53 P. rotundifolia and 42 P. davidiana individuals across their natural distribution regions. Our population genomic data suggest that the two species are well delimitated in the allopatric regions, but with hybrid zones in their adjacent region in the eastern QTP. Coalescent simulations suggest that P. rotundifolia diverged from P. davidiana in the middle Pleistocene with following continuous gene flow since divergence. In addition, we found numerous highly diverged genes with outlier signatures that are likely associated with high‐altitude adaptation of these alpine aspens. Our finding indicate that Quaternary climatic changes and natural selection have greatly contributed to the origin and distinction maintenance of P. rotundifolia in the QTP
Sharp Multiple Instance Learning for DeepFake Video Detection
With the rapid development of facial manipulation techniques, face forgery
has received considerable attention in multimedia and computer vision community
due to security concerns. Existing methods are mostly designed for single-frame
detection trained with precise image-level labels or for video-level prediction
by only modeling the inter-frame inconsistency, leaving potential high risks
for DeepFake attackers. In this paper, we introduce a new problem of partial
face attack in DeepFake video, where only video-level labels are provided but
not all the faces in the fake videos are manipulated. We address this problem
by multiple instance learning framework, treating faces and input video as
instances and bag respectively. A sharp MIL (S-MIL) is proposed which builds
direct mapping from instance embeddings to bag prediction, rather than from
instance embeddings to instance prediction and then to bag prediction in
traditional MIL. Theoretical analysis proves that the gradient vanishing in
traditional MIL is relieved in S-MIL. To generate instances that can accurately
incorporate the partially manipulated faces, spatial-temporal encoded instance
is designed to fully model the intra-frame and inter-frame inconsistency, which
further helps to promote the detection performance. We also construct a new
dataset FFPMS for partially attacked DeepFake video detection, which can
benefit the evaluation of different methods at both frame and video levels.
Experiments on FFPMS and the widely used DFDC dataset verify that S-MIL is
superior to other counterparts for partially attacked DeepFake video detection.
In addition, S-MIL can also be adapted to traditional DeepFake image detection
tasks and achieve state-of-the-art performance on single-frame datasets.Comment: Accepted at ACM MM 2020. 11 pages, 8 figures, with appendi
Project Overview of the Beijing-Arizona Sky Survey
The Beijing-Arizona Sky Survey (BASS) is a wide-field two-band photometric
survey of the Northern Galactic Cap using the 90Prime imager on the 2.3 m Bok
telescope at Kitt Peak. It is a four-year collaboration between the National
Astronomical Observatory of China and Steward Observatory, the University of
Arizona, serving as one of the three imaging surveys to provide photometric
input catalogs for target selection of the Dark Energy Spectroscopic Instrument
(DESI) project. BASS will take up to 240 dark/grey nights to cover an area of
about 5400 deg in the and bands. The 5 limiting AB
magnitudes for point sources in the two bands, corrected for the Galactic
extinction, are 24.0 and 23.4 mag, respectively. BASS, together with other DESI
imaging surveys, will provide unique science opportunities that cover a wide
range of topics in both Galactic and extragalactic astronomy.Comment: 10 pages, submitted to PAS
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