scholarly journals Transient events in bright debris discs: Collisional avalanches revisited

2018 ◽  
Vol 609 ◽  
pp. A98 ◽  
Author(s):  
P. Thebault ◽  
Q. Kral
Keyword(s):  
Optical Depth ◽  
State Of The Art ◽  
The State ◽  
Chain Reaction ◽  
Short Term ◽  
Self Consistent ◽  
Transient Events ◽  
Transient Structures ◽  
First Time ◽  
The Ideal

Context. A collisional avalanche is set off by the breakup of a large planetesimal, releasing vast amounts of small unbound grains that enter a debris disc located further away from the star, triggering there a collisional chain reaction that could potentially create detectable transient structures. Aims. We investigate this mechanism, using for the first time a fully self-consistent code coupling dynamical and collisional evolutions. We also quantify for the first time the photometric evolution of the system and investigate whether or not avalanches could explain the short-term luminosity variations recently observed in some extremely bright debris discs. Methods. We use the state-of-the-art LIDT-DD code. We consider an avalanche-favoring A6V star, and two set-ups: a “cold disc” case, with a dust release at 10 au and an outer disc extending from 50 to 120 au, and a “warm disc” case with the release at 1 au and a 5−12 au outer disc. We explore, in addition, two key parameters: the density (parameterized by its optical depth τ) of the main outer disc and the amount of dust released by the initial breakup. Results. We find that avalanches could leave detectable structures on resolved images, for both “cold” and “warm” disc cases, in discs with τ of a few 10-3, provided that large dust masses (≳1020−5 × 1022 g) are initially released. The integrated photometric excess due to an avalanche is relatively limited, less than 10% for these released dust masses, peaking in the λ ~ 10−20 μm domain and becoming insignificant beyond ~40–50 μm. Contrary to earlier studies, we do not obtain stronger avalanches when increasing τ to higher values. Likewise, we do not observe a significant luminosity deficit, as compared to the pre-avalanche level, after the passage of the avalanche. These two results concur to make avalanches an unlikely explanation for the sharp luminosity drops observed in some extremely bright debris discs. The ideal configuration for observing an avalanche would be a two-belt structure, with an inner belt (at ~1 or ~10 au for the “warm” and “cold” disc cases, respectively) of fractional luminosity f ≳ 10-4 where breakups of massive planetesimals occur, and a more massive outer belt, with τ of a few 10-3, into which the avalanche chain reaction develops and propagates.

A NEW LAYOUT DESIGN SYSTEM FOR MULTICHIP MODULES

1995 ◽  
Vol 06 (03) ◽  
pp. 509-538 ◽  
Author(s):  
BERNHARD M. RIESS ◽  
ANDREAS A. SCHOENE
Keyword(s):  
Efficient Algorithm ◽  
State Of The Art ◽  
Layout Design ◽  
The State ◽  
Design System ◽  
Multichip Modules ◽  
Analytical Technique ◽  
Cut Method ◽  
First Time ◽  
Three Components

A new layout design system for multichip modules (MCMs) consisting of three components is described. It includes a k-way partitioning approach, an algorithm for pin assignment, and a placement package. For partitioning, we propose an analytical technique combined with a problem-specific multi-way ratio cut method. This method considers fixed module-level pad positions and assigns the cells to regularly arranged chips on the MCM substrate. In the subsequent pin assignment step the chip-level pads resulting from cut nets are positioned on the chip borders. Pin assignment is performed by an efficient algorithm, which profits from the cell coordinates generated by the analytical technique. Global and final placement for each chip is computed by the state-of-the-art placement tools GORDIANL and DOMINO. For the first time, results for MCM layout designs of benchmark circuits with up to 100,000 cells are presented. They show a small number of required chip-level pads, which is the most restricted resource in MCM design, and short total wire lengths.

scholarly journals Learning from Interventions Using Hierarchical Policies for Safe Learning

2020 ◽  
Vol 34 (06) ◽  
pp. 10352-10360
Author(s):  
Jing Bi ◽  
Vikas Dhiman ◽  
Tianyou Xiao ◽  
Chenliang Xu
Keyword(s):  
Reaction Time ◽  
State Of The Art ◽  
The State ◽  
Policy Framework ◽  
Asymptotic Performance ◽  
Short Term ◽  
Learning From Demonstrations ◽  
Hierarchical Levels ◽  
Long Term Behavior

Learning from Demonstrations (LfD) via Behavior Cloning (BC) works well on multiple complex tasks. However, a limitation of the typical LfD approach is that it requires expert demonstrations for all scenarios, including those in which the algorithm is already well-trained. The recently proposed Learning from Interventions (LfI) overcomes this limitation by using an expert overseer. The expert overseer only intervenes when it suspects that an unsafe action is about to be taken. Although LfI significantly improves over LfD, the state-of-the-art LfI fails to account for delay caused by the expert's reaction time and only learns short-term behavior. We address these limitations by 1) interpolating the expert's interventions back in time, and 2) by splitting the policy into two hierarchical levels, one that generates sub-goals for the future and another that generates actions to reach those desired sub-goals. This sub-goal prediction forces the algorithm to learn long-term behavior while also being robust to the expert's reaction time. Our experiments show that LfI using sub-goals in a hierarchical policy framework trains faster and achieves better asymptotic performance than typical LfD.

scholarly journals Book Review Hospitality Marketing: Principles and Practice (2nd ed.)

2020 ◽  
Author(s):  
David Bowie ◽  
Francis A. Buttle
Keyword(s):  
State Of The Art ◽  
The State ◽  
Theory And Practice ◽  
Marketing Theory ◽  
Ideal Person ◽  
English Speaking ◽  
English Speaking World ◽  
Marketing Principles ◽  
The Ideal

The ideal person to write a review of books is definitely someone who has written a textbook himself. Bowie and Buttle indeed have made a promising effort to disseminate an important perspective on a subject related to hospitality. One might be quick to conclude that this text is just a dime a dozen and a window dressing of the first edition since not much space is dedicated to reflect on marketing theory and practice to the level of the state of the art. But this sort of unfair review is best left to those scholars who had experienced writing a textbook which is celebrated throughout the English speaking world, like Kotler or Drucker. The review here is a modest attempt to guide those who seek some idea and facts about the book before purchasing it.  

scholarly journals Amphibia, Anura, Brachycephalus didactylus (Izecksohn, 1971) and Zachaenus parvulus (Girard, 1853): distribution extension

Check List ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 242 ◽  
Author(s):  
Jane C. F. de Oliveira ◽  
Lívia Coco ◽  
Renata Valls Pagotto ◽  
Edicarlos Pralon ◽  
Davor Vrcibradic ◽  
...  
Keyword(s):  
Atlantic Forest ◽  
Geographic Range ◽  
The State ◽  
Short Term ◽  
Espírito Santo ◽  
Anuran Species ◽  
Forest Sites ◽  
Se Brazil ◽  
Espirito Santo ◽  
First Time

We report geographic range extensions for two anuran species, Brachycephalus didactylus (Bachycephalidae) and Zachaenus parvulus (Cycloramphidae), recorded during a short-term herpetofaunal survey carried out at mid-elevation (600-900 m) Atlantic Forest sites at the Serra das Torres mountains (21°00’ S, 41°13’ W), in the state of Espírito Santo, SE Brazil. These two species are reported for the first time in Espírito Santo, representing the northernmost records for both of them and raising to 135 the number of anuran species currently known to occur in the state.

scholarly journals Improving Electric Energy Consumption Prediction Using CNN and Bi-LSTM

2019 ◽  
Vol 9 (20) ◽  
pp. 4237 ◽  
Author(s):  
Tuong Le ◽  
Minh Thanh Vo ◽  
Bay Vo ◽  
Eenjun Hwang ◽  
Seungmin Rho ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Performance Metrics ◽  
Short Term Memory ◽  
State Of The Art ◽  
Electric Energy ◽  
The State ◽  
Short Term ◽  
Electric Energy Consumption ◽  
Energy Consumption Prediction ◽  
Consumption Prediction

The electric energy consumption prediction (EECP) is an essential and complex task in intelligent power management system. EECP plays a significant role in drawing up a national energy development policy. Therefore, this study proposes an Electric Energy Consumption Prediction model utilizing the combination of Convolutional Neural Network (CNN) and Bi-directional Long Short-Term Memory (Bi-LSTM) that is named EECP-CBL model to predict electric energy consumption. In this framework, two CNNs in the first module extract the important information from several variables in the individual household electric power consumption (IHEPC) dataset. Then, Bi-LSTM module with two Bi-LSTM layers uses the above information as well as the trends of time series in two directions including the forward and backward states to make predictions. The obtained values in the Bi-LSTM module will be passed to the last module that consists of two fully connected layers for finally predicting the electric energy consumption in the future. The experiments were conducted to compare the prediction performances of the proposed model and the state-of-the-art models for the IHEPC dataset with several variants. The experimental results indicate that EECP-CBL framework outperforms the state-of-the-art approaches in terms of several performance metrics for electric energy consumption prediction on several variations of IHEPC dataset in real-time, short-term, medium-term and long-term timespans.

“The Enthusiasm Expressed by Our Industry Friends”

Vulcan ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 100-124
Author(s):  
Adam Givens
Keyword(s):  
Long Range ◽  
State Of The Art ◽  
The State ◽  
Next Generation ◽  
Short Term ◽  
Us Army ◽  
The Face ◽  
Long Term Consequences ◽  
Fait Accompli

Abstract This article analyzes the groundbreaking 1952 plan by US Army leadership to develop a sizeable cargo helicopter program in the face of interservice opposition. It examines the influence that decision had in the next decade on the Army, the helicopter industry, and vtol technology. The Army’s procurement of large helicopters that could transport soldiers and materiel was neither a fait accompli nor based on short-term needs. Rather, archival records reveal that the decision was based on long-range concerns about the postwar health of the helicopter industry, developing the state of the art, and fostering new doctrinal concepts. The procurement had long-term consequences. Helicopters became central to Army war planning, and the ground service’s needs dictated the next generation of helicopter designs. That technology made possible the revolutionary airmobility concept that the Army took into Vietnam and also led to a flourishing commercial helicopter field.

scholarly journals Sandfly fauna (Diptera: Psychodidae) from caves in the state of Rondônia, Brazil

2016 ◽  
Vol 25 (1) ◽  
pp. 61-68 ◽  
Author(s):  
Guilherme Maerschner Ogawa ◽  
Antonio Marques Pereira Júnior ◽  
Fábio Resadore ◽  
Ricardo de Godoi Mattos Ferreira ◽  
Jansen Fernandes Medeiros ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Breeding Site ◽  
Abundant Species ◽  
The State ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
First Time

Abstract This study had the aim of ascertaining the sandfly fauna and possible presence ofLeishmania in these insects, collected in caves in the state of Rondônia, Brazil. Collections were conducted in eight caves located in two different areas of this state. Leishmania in the sandflies collected was detected using the polymerase chain reaction (PCR). This was the first study on sandflies from caves in Rondônia and, among the total of 1,236 individuals collected, 24 species and 10 genera were identified. The speciesEvandromyia georgii was collected for the first time in Rondônia and the most abundant species were Trichophoromyia ubiquitalis with 448 individuals (36.2%), followed by T. octavioi with 283 (22.9%) and E. georgii with 179 (14.5%). For the PCR, 17 pools were analyzed and five pools were positive (forT. auraensis in three pools and for Nyssomyia shawi and N. antunesi in one pool each). The kDNA region was amplified and the presence of Leishmania DNA was confirmed. The sandfly fauna in these caves can be considered diverse in comparison with similar studies in other regions. It may be that some species use caves as a temporary shelter and breeding site, while other species live exclusively in this environment. The detection of LeishmaniaDNA indicates that this pathogen is circulating in cave environments and that further studies are needed in order to ascertain the risks of infection by leishmaniasis in these locations with high touristic potential.

scholarly journals Short Term Electric Load Forecasting Based on Data Transformation and Statistical Machine Learning

2020 ◽  
Vol 11 (1) ◽  
pp. 158
Author(s):  
Nikos Andriopoulos ◽  
Aristeidis Magklaras ◽  
Alexios Birbas ◽  
Alex Papalexopoulos ◽  
Christos Valouxis ◽  
...  
Keyword(s):  
Distribution System ◽  
Short Term Memory ◽  
State Of The Art ◽  
Load Forecasting ◽  
The State ◽  
Neural Nets ◽  
Interactive System ◽  
Electric Load ◽  
Short Term ◽  
Electric Load Forecasting

The continuous penetration of renewable energy resources (RES) into the energy mix and the transition of the traditional electric grid towards a more intelligent, flexible and interactive system, has brought electrical load forecasting to the foreground of smart grid planning and operation. Predicting the electric load is a challenging task due to its high volatility and uncertainty, either when it refers to the distribution system or to a single household. In this paper, a novel methodology is introduced which leverages the advantages of the state-of-the-art deep learning algorithms and specifically the Convolution Neural Nets (CNN). The main feature of the proposed methodology is the exploitation of the statistical properties of each time series dataset, so as to optimize the hyper-parameters of the neural network and in addition transform the given dataset into a form that allows maximum exploitation of the CNN algorithm’s advantages. The proposed algorithm is compared with the LSTM (Long Short Term Memory) technique which is the state of the art solution for electric load forecasting. The evaluation of the algorithms was conducted by employing three open-source, publicly available datasets. The experimental results show strong evidence of the effectiveness of the proposed methodology.

scholarly journals Zakat Mal dalam Perspektif Hadis Maudhu'iy

2019 ◽  
Vol 11 (1) ◽  
pp. 151-184
Author(s):  
Hamzah Hamzah
Keyword(s):  
Poverty Reduction ◽  
Total Yield ◽  
The State ◽  
Poor People ◽  
Muslim Countries ◽  
The Poor ◽  
The Rich ◽  
First Time ◽  
Specific Amount ◽  
The Ideal

One of the major problems that the developing countries face is the lack of state revenues to cover all required expenses. Zakat is completely different from taxes, because it is a direct solution for poor people because it goes with the same type of property from the rich to the poor (not like the most of the poverty reduction programms which go in shape of projects for the poor), also Zakat has its own fixed resources and fixed legal channels of spending. Zakat is considered a form of charity that must be paid from a person`s wealth (when his/her wealth exceeds or reaches a “specific amount” of money (or othertypes of wealth like gold) So when the wealth reaches this level or (the specific amount ) the person who owns this wealth should pay a specific amount for the poor and this amount goes to the poor named Zakat. At the time of prophet Mohamed, he was sending the officials to collect money of Zakat, as it was mentioned for example , when he sent Muaaz Ibnu Jabal to govern Yemen, he ordered him to collect money of Zakat. Also in the time of the second gonernant in Islam (Khalifah). At the time of the third Khalifah Umar, where the state was expanded, Umar still interes ed in collecting Zakat but with a new way in terms of two perspectives, first collecting it from both outward and inward money, second by establishing “a Zakat organization” to be the ideal solution in dealing with Zakat. At the time of umar the revenues of Zakat became a huge amount, until Umar decided to give a salary for The periods after that the governants were not interested so much to collect Zakat by themselves and from the outward and inward money, because total toll became very huge so they decided to leave this mater up to the eligible Muslims to pay their Zakat, but in the later on periods of time the Muslims became less aware by the religious practises so the total toll of Zakat became less than periods of the prophet and Khalifah and not sufficient to satisfy the basic needs of the poor in the Muslim countries. To conclude from that, the best total yield of Zakat was happened when it was collected and distributed through an organization with a great attention from the leader of the state, so this paper will be describe about zakat persepective Hadis Maudu’ in the first time of Islam. 

Sign in / Sign up

Export Citation Format

Share Document