516 research outputs found
Replication Data for: "Sediment load determines the shape of rivers"
No full textMeasured depth and sediment flux profiles for experimental laminar rivers described in P Popovic, O Devauchelle, A Abramian, and E Lajeunesse (2021), "Sediment load determines the shape of rivers", PNAS, accepted. The data were originally collected by A Abramian, O Devauchelle, and E Lajeunesse (2020), "Laboratory rivers adjust their shape to sediment transport", Physical Review E, 102(5), 053101.
Dataset consists of five experiments with varying sediment discharge. For each experiment, we provide a depth profile (experiment_X_depth.csv) and a sediment flux profile (experiment_X_sediment_flux.csv).
experiment_X_depth.csv contains three columns:
y[cm] - transverse coordinate in cm;
D_raw [cm] - raw measurement of depth in cm;
D_smooth [cm] - smoothed depth in cm used in the analysis in the paper.
experiment_X_sediment_flux.csv contains two columns:
y[cm] - transverse coordinate in cm;
qs [grains/cm/s] - sediment flux in grains/cm/s.
The sediment discharge (in grains/s) for each experiment is provided in sediment_discharge.csv with the corresponding uncertainties provided in sediment_discharge_std.csv. Experimental parameters and their uncertainties are summarized in parameters.csv and parameters_std.csv
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Idealized Models of Arctic Sea Ice Melt Ponds
No full textAs Arctic sea ice starts to melt in the summer, melt ponds form on its surface and, in a matter of days, cover large portions of the ice. Due to their low reflectivity, melt ponds greatly accelerate ice melt. Despite their importance, they are poorly understood due the many processes that control their evolution, which operate on widely separated length-scales. In this thesis, we use idealized models of melt ponds with a goal to provide a fundamental understanding of their evolution.
First, we study the case of late-summer ponds that exist on highly permeable first-year sea ice. Assuming that ice is fully permeable, we show that pond coverage evolution can be approximately determined by solving two uncoupled ordinary differential equations (ODEs) in which the rate of change of pond coverage fraction is a function of itself, of the initial ice surface hypsographic curve, and of average melt rates of different regions of the ice. In this way, we show that it is possible to greatly reduce the complexity of pond evolution on permeable ice and to summarize all of the environmental conditions with only a few aggregate parameters.
Second, we show that melt pond geometry on both first and multi-year ice can be accurately captured by a simple geometric model where ponds are represented as voids that surround randomly sized and placed circles that represent snow dunes. There are only two model parameters: the characteristic circle radius and the pond coverage fraction. We set these parameters by matching two correlation functions, which determine the typical pond size and their connectedness, between the model and aerial photographs of melt ponds. With parameters calibrated in this way, we reproduce the previously-observed pond size distribution and fractal dimension as a function of pond size over the entire observational range of more than 6 orders of magnitude. Surprisingly, by further studying the correlation functions, we find that late-summer ponds are organized close to the critical percolation threshold. Moreover, we find that ponds from different years and documented at different locations have very similar typical sizes.
Third, we explain the observation we made previously that the ponds are organized close to the percolation threshold. We show that, since ponds drain through large holes, the percolation threshold is an upper bound on pond coverage following pond drainage. Furthermore, because of the universality of systems close to the percolation threshold, we show that the pond fraction as a function of the number of open holes follows a universal curve. This curve governs pond evolution during and after pond drainage, which allows us to formulate an equation for pond coverage evolution that captures the dependence on physical properties of the ice and is supported by observations.
Finally, we generalize the void model we developed earlier and show that it accurately captures the pre-melt distribution of snow-depth. We find that the snow depth is distributed according to a Gamma distribution which can be fully characterized by the mean and the variance of snow depth. This allows us to derive an analytical formula for pond evolution during early summer when ice is impermeable.
By combining all of our results, we find that nearly the entire pond evolution since the onset of melt can be captured with computationally inexpensive analytical models that do not sacrifice accuracy and reveal relationships between pond evolution and measurable ice parameters that would not be captured using more complex models. These findings have significant potential to improve our parameterizations of sea ice albedo in large-scale climate models, thereby advancing our ability to predict the fate of Arctic sea ice.
This work was led, performed, and written by Predrag Popovic under supervision of Dorian Abbot and Mary Silber
Animals and philosophers: Preface to my critics
No full textThe author is here seeking to expose his book Philosophical Animal zoographical persuasion to philosophy, to his own remorseless analysis - and that way defend the book from potential criticism by the others. On the other hand, the author believes that this will open up the space for discussion about the book and themes that book provokes. This discussion is not going to be mere neatly registered response and/or appropriate praise but a contribution inspired by the book, resonating back to it
"Author Meets Critics: Predrag Cicovacki, Author of Gandhi's Footprints, Meets Critics Sanjay Lal and Carlo Filice"
No full textTwo critics respond to Predrag Cicovacki’s book, Gandi’s Footprints. Cicovacki opens the discussion by presenting his motivations for exploring a paradox, that Gandhi’s work is widely revered but not widely emulated. Cicovacki explores a resolution to the paradox by suggesting how Gandhi’s promising visions may be followed without being imitated, especially Gandhi’s insight that we must seek spiritual grounding for life in a materialistic world. Critic Sanjay Lal affirms Cicovacki’s insight but suggests that precisely because Gandhi’s aspirations for spiritual life were profoundly transformative we should take care not to dilute them into our conventional wisdoms. Critic Carlo Filice asks how Gandhi’s commitment to unified reality could be more clearly articulated once a distinction is drawn between spirit and matter, also how Gandhi’s nonviolence could manage to embrace important exceptions. In reply to critics, Cicovacki proposes an approach to Gandhi informed by the insights of Tagore
(In)Visible Hand(s)
No full textIn this paper, the author discusses the regulatory role of the state and legal norms, in market economy, especially in so-called transition countries. Legal policy, and other questions of the state and free market economy are here closely connected, because the state must ensure with legal norms that economic processes are not interrupted: only the state can establish the legal basis for a market economy. The free market’s invisible hand is acting in questions such as: what is to be produced, how much is to be produced, for whom it is to be produced, how it is to be produced. During the transition period but also in the establishnig EU, the role of legal norms is much more important then it (is) would be expected: problems of transition are more connected with ethics and psychology, then with legislation.Law and economics, legal norms, (de)regulation, State
Integrated fluxgate compass for portable applications
No full textModern applications in industry, navigation and medicine demand small and sensitive magnetic field sensors. In this thesis we have developed a new planar micro fluxgate magnetometer. High resolution, low power consumption and orthogonal fields detection makes it suitable for portable compass applications. The developed sensor is a fully integrated device based on CMOS process that provides driving and readout electronics, plus the metallization layers for the excitation and pickup coils. A soft amorphous ferromagnetic material is bonded and structured, using an additional, postprocess implemented on a whole 6 inch wafer to form sensor core on the surface of the chip. The single core principle was selected with the intention to elongate the core, reduce the power consumption and increase sensitivity. We employed a new extraction method, based on the detection of mean value of the induced voltage peaks in the pickup coil, which carry the information on the external field. Several models and tools for the optimization of the core geometry, excitation, as well as pickup coils have been developed. For the first time, the effect of perming has been investigated. Perming is manifested as a change in sensor offset after the magnetic shock. A model was developed, which uses equivalent magnetic pole pieces to account for the contribution of the "frozen" domains not affected by the excitation. Model shows that the effect is predominantly dependent on the level of the core saturation. The electronics has been integrated in a conventional 1 µm CMOS process. Apart from the excitation, a single electronic circuit is used for both axes in order to decrease the power consumption, reduce the chip size, and obtain better matching. The signal extraction principle is accomplished using a box-car circuit. To reduce the influence of the 1/f noise of the amplifiers, we implemented a modulation technique, using an additional modulator. Modulated signal is amplified and finally demodulated using the correlated double sampling demodulator. We have implemented a new digital feedback, for the first time applied on the excitation coils. It consists of comparator, 8-bit U/D counter and current sources to create magnetic field for contra action. The output of the counter represents the digital information on the external field and is transmitted using I2C communication block integrated on chip. The fabricated sensor works from a single 2.5 V power supply and consumes 8.5 mW in open loop mode and 10 mW with a feedback. With the excitation at 350 kHz, the magnetometer exhibits the sensitivity of 2950 V/T and 8 kHz bandwidth. Equivalent noise spectral density at 1 Hz is equal to 12 nT/√Hz. When used as a compass, the sensor has the angular error of ± 1° without and ± 3° using feedback. Measured perming is equal to 1.4 µT, after the shock of 200 mT. Performance of the developed micro-fluxgate is better in terms of noise, angular error, perming, operational voltage, as well as power consumption, than any other fully integrated micro fluxgate presented up to date. In addition, the fabrication is based on the batch and low cost CMOS technology and compatible post-process so we can expect commercialisation in the near future
Ascending the Nonviolence Continuum: Sanjay Lal, Author of \u3cem\u3eViolence, Nonviolence, and Moral Worth, \u3c/em\u3eMeets Critics
No full textIn this author-meets-critics discussion, Sanjay Lal presents the main ideas of his book Violence, Nonviolence, and Moral Worth, arguing that nonviolence meets violence along a continuum where there are degrees of greater and lesser examples, including a wide range of examples that combine both tendencies. Lal defines nonviolence in terms of three components that emphasize attitudes over actions: (1) a willingness to not harm others, (2) wanting to facilitate the well-being of others, (3) and not sacrificing one\u27s own moral worth. Three critics share their praises and concerns: Predrag Cicovacki challenges Lal to be more specific on the definition of moral worth, on the relationship between violence and nonviolence, and on the account that he gives for value theory and value conflict. Jennifer Kling asks if beliefs can serve as pre-existing grounds for action, if reconceptualizations of pop culture are bound to any limits, and if there are good reasons for assuming that all people are approachable. Danielle Poe asks what it means to reconceptualize popular culture as an approachable resource of nonviolent insight. Answering these questions, Lal reflects on what it means to be inspired by Gandhi’s example
A middleware for distributing XML data between mobile application servers
No full textThis research seeks to introduce architecture of new approach of distributing XML data files between different mobile application servers. The importance of this study is to set a multi level of security defense for interchanging XML data files between different servers. The main objective and goal of this study is to transmit XML data files between different Mobile Application Server (MAS) using internet cloud infrastructure in a secured manner coupled with reliability and quality of communication. Taking into consideration that the system architecture attribute is to be independent, scalable and flexible of using cloud computing. Furthermore, this architecture designed to minimize the risk of any alteration, data loss, data abuse, data misuse of XML critical business data information. As cloud computing, using existing cloud network infrastructure to get advantage of the scalability, operational efficiency, and control of data flow are big consideration in this architecture. A test has been made to measure the performance of the Real-time Interactive Data Exchange system (RIDX), one by using standard TCP protocol, and one by using RIDX UDP protocol. As a result, starting from 4 nodes up to 10 nodes in the cloud, RIDX architecture performance showed good results, conversely the study showed that using RIDX UDP protocol as a transport protocol gives better performance than standard TCP, moreover, using RIDX UDP transport protocol assures the reliability and lossless of data transmission to all nodes, therefore, RIDX acts as a reliable multicast transmission
Understanding philosophical animal
No full textIn this paper, inspired by the Predrag Krstić's book Philosophical Animal author is trying to find hers way through a broad and complex web of philosophies and roles that different animals play in them. The main question is how to understand philosophy itself in a present day context, which philosophy is supposed to think and rethink through. Animals as presented in concepts, more precisely philosophical contexts, open one interesting and innovative way to deal with this question, balancing between tradition of philosophy and its presence, structure of philosophical arguments and questioning of language of philosophy, abstract and individual. In this frame philosopher as the true philosophical animal is revealed as the main symbol that requires analysis in his philosophical strategies
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