Entire Topography Research Articles

Resetting-mediated navigation of an active Brownian searcher in a homogeneous topography.

Designing navigation strategies for search-time optimization remains of interest in various interdisciplinary branches in science. Herein, we focus on active Brownian walkers in noisy and confined environments, which are mediated by one such autonomous strategy, namely stochastic resetting. As such, resetting stops the motion and compels the walkers to restart from the initial configuration intermittently. The resetting clock is operated externally without any influence from the searchers. In particular, the resetting coordinates are either quenched (fixed) or annealed (fluctuating) over the entire topography. Although the strategy relies upon simple governing laws of motion, it shows a significant ramification for the search-time statistics, in contrast to the search process conducted by the underlying reset-free dynamics. Using extensive numerical simulations, we show that the resetting-driven protocols enhance the performance of these active searchers. This, however, depends robustly on the inherent search-time fluctuations, measured by the coefficient of variation of the underlying reset-free process. We also explore the effects of different boundaries and rotational diffusion constants on the search-time fluctuations in the presence of resetting. Notably, for the annealed condition, resetting is always found to expedite the search process. These features, as well as their applicability to more general optimization problems from queuing systems, computer science and randomized numerical algorithms, to active living systems such as enzyme turnover and backtracking recovery of RNA polymerases in gene expression, make resetting-based strategies universally promising.

Generation of Artificial Learning Data to Train Functional Meta-Models of Micro Gears

The complexity of products increases considerably and key functions can often only be realized by using high-precision components. As a result, the requirements of high-precision components reach technological manufacturing limits. This is of particular importance for micro components, such as micro gears, where the manufacturing deviations are relatively large compared to the component size and therefore have a large influence on the functional characteristics of the assembled product. A potential solution is to develop a meta-model with machine learning (ML) methods, which enables the real-time prediction of functional characteristics of micro gears in terms of kinematic transmission error (KTE), based on optical in-line measurements of the entire topography of the gear. To train a suitable ML model large amounts of data are needed. This poses a challenge because real measurements cannot cover the entire spectrum of all deviations and also require a large amount of resources in terms of time, material and costs. In this paper, an approach for the generation of learning data on the basis of virtual and deviated gear models is developed with the help of Skin Model Shapes. The objective is to generate gear data that reflects the nominal shape as well as the process-related manufacturing deviations and the random scatter. For validation, the artificially generated gears are compared with a reference dataset both geometrically and functionally. Therefore, both the standard deviations and the KTE are calculated for both data sets.

Thirty years after Balbina Dam: Diversity and floristic composition of the downstream floodplain forest, Central Amazon, Brazil

AbstractThe construction of hydroelectric dams causes changes in the diversity and floristic composition of floodplain forests due to the irregularity of the hydrological regime in rivers downstream from the dams. In the Amazon Basin, plans for the construction of dams are threatening the igapós, forests flooded by blackwater rivers. In these floodplains, the distribution of tree species is synchronized with periodic flood events of the topographic gradient. Previous studies on the Balbina Dam show an altered flood pulse downstream. This work discusses the potential long‐term impacts on the diversity and floristic composition of an igapó downstream of the dam (Uatumã River) and compares it with an area unaffected by the dam (Abacate River). An evaluation of the vegetation strata—adults, saplings, and seedlings—showed that for all strata, diversity was greater in the high igapó (higher topographies) in the Uatumã area. This may be due to the near‐total absence of flooding in the high igapó and to the extent of flooding in the low igapó (low topographies). Thus, in the Uatumã area, seeds of species typical of flooded areas cannot reach the high igapó by water and, thus, tend to be replaced by upland forest species (mainly seedlings). In the low igapó, the typical species have difficulty establishing. Therefore, the Uatumã vegetation forms two different communities, which does not occur in the Abacate area. These effects of the dam led to irreversible changes in the diversity and floristic composition across all strata throughout the entire topography in the downstream region.

The Black Box of the Present: Time in the Age of Algorithms

The Black Box of the Present:Time in the Age of Algorithms Ed Finn (bio) as i click on the link to the news site, a cascading series of actions unfurls behind the static pixels of my screen, obscured from human view not just by design but also by the boundaries of my temporal perception. In a matter of milliseconds, my request for the page has reached one of the company's servers, triggering a flurry of activity as the site identifies me through cookies, IP address, and other means. The server contacts other machines in the company network to pull together not just "the news" but my news, curated in various ways to capture and maintain my attention (e.g., through recommendations for what to read next) and establish a familiar context by referencing previous interactions with the site (e.g., items saved in my "history"). But before the page loads, my query also triggers a number of other requests to companies, including Google, Facebook, and Twitter. Advertising algorithms engage in an automated auction to decide which ads will be shown to me on the news site, taking into account prevailing bids as well as my own history, social media presence, and membership or nonmembership in various predetermined target populations. Over the space of perhaps a half-second, tens if not hundreds of machines have participated in a complex set of automated negotiations and interactions to shape, format, and present to me an experience of the "current news." The experience of clicking on a link might seem instantaneous, but the gap between request and answer is vast by computational standards, and filled with activities in which I am not the observer but the observed. [End Page 557] Eliminating latency has long been a fetish of technologists, and the history of the modern Internet can be measured by the diminishing gap between query and response. A rule of thumb in interface design states that "to create the illusion of direct manipulation, a user interface must be faster than 0.1 second," which roughly correlates with the speed of our own nervous system's sensory responses (Nielsen 2009). Designing systems that react so quickly leads to a sense not only of immediacy, but also of control. It creates the illusion that the Internet is an extension of ourselves: a structure integrated into the central nervous system. But this immediacy obscures all the work we are not in control of, the framing and targeting that increasingly tailors the foreground and the horizons of our unique, individual informational worlds. What seems immeasurably fast or instantaneous to us is quite slow for the machines, giving them plenty of time to do the real work. From the static-laden gurgles of early dial-up modems to Google's decision to include a measurement of response time in all its search results, we have been constructing a computational model of contemporaneity for decades. Today the logic of immediacy, of the update feed, of the news cycle sublimated into an endless live stream, has transformed our understanding of the present tense in ways that reach beyond user interfaces and server architecture. Manuel Castells has called this "timeless time," both ephemeral and eternal (Castells 2000, 494). When we speak of the contemporary in the twenty-first century, we are almost always talking about something that requires computation to access. After all, there are billions of dollars changing hands over the question of who gets to construct the present for you. When you access a website, perhaps to find out what is happening in the world "right now," hundreds of servers are involved in the micro-auctions that determine which advertisements will appear on the page, and maybe in organizing its content according to models that predict your interest in different topics. Services like Google Now seek to understand and anticipate our desires and interests—ideally, to predict the entire topography of the contemporary for each of us. [End Page 558] The stakes of the algorithm are fundamentally about the social production of time and a fundamental shift in our experience of the present. I will pursue this in three stages: framing the algorithm as culture machine, defining the...

Evaluation of surface topography of SiCp/Al composite in grinding

As the main processing technique of SiCp/Al composite, grinding directly affects usability performance. However, cavity defects usually occur during the SiCp/Al grinding process. In this study, the surface micro-topography of SiCp/Al composite in grinding was observed by means of SEM, and the chemical ingredients over the cavity defect surface were analyzed by energy dispersive spectrometry. The surface topography was reconstructed with bilinear interpolation algorithm by a point cloud, and the contour map including cavity defects was obtained. Based on the contour map including cavity defects, a new relationship curve between the projection area ratio and contour height was proposed. A novel comprehensive evaluation system was established and included four aspects, namely the profile height and surface roughness of the entire topography, profile height, and equivalent surface roughness of the cavity defect. The optimized algorithm was proposed with the objective function of maximum grinding efficiency and constraints of profile height and surface roughness. The optimized grinding process parameters were obtained and verification experiments were carried out. The results demonstrated that the predicted results were consistent with the experimental results, and the comprehensive evaluation system including cavity defects can reflect the surface topography intuitively. The comprehensive evaluation system for the surface topography including cavity defects in grinding provides guidance for the usability performance of SiCp/Al composite.

High-resolution shape model of Ceres from stereophotoclinometry using Dawn Imaging Data

We present a high-resolution global shape model of Ceres determined using the stereophotoclinometry technique developed at the Jet Propulsion Laboratory by processing Dawn's Framing Camera data acquired during Approach to post-Low Altitude Mapping Orbit (LAMO) phases of the mission. A total of about 38,000 images were processed with pixel resolutions ranging from 35.6 km/pixel to 35 m/pixel and the final global shape model was produced with 100-m grid spacing. The final SPC-derived topography was computed relative to the (482 km, 482 km, 446 km) mean ellipsoid, which ranges from −7.3 km to 9.5 km. For the purpose of validation, we performed various error analyses to assess and quantify realistic uncertainties in the derived topography, such as dividing the data into different subsets and re-computing the entire topography. Based on these studies, we show that the average total height error of the final global topography model is 10.2 m and 88.9% of the surface has the total height error below 20 m. We also provide improved estimates of several physical parameters of Ceres. The resulting GM estimate is (62.62905 ± 0.00035) km3/s2, or the mass value of (938.392 ± 0.005) × 1018 kg. The volume estimate is (434.13 ± 0.50) × 106 km3 with a volumetric mean radius of 469.72 km. Combined with the mass estimate, the resulting bulk density is (2161.6 ± 2.5) kg/m3. Other improved parameters include the pole right ascension, α0 = (291.42763 ± 0.0002)°, pole declination, δ0 = (66.76033 ± 0.0002)°, and prime meridian and rotation rate of (W0 = 170.309 ± 0.011)° and (dW/dt = 952.1532635 ± 0.000002) deg/day, respectively. Also, for geophysical and geological studies, we provide spherical harmonic coefficients and a gravitational slope map derived from the global shape model.

Space-filling scan paths and Gaussian process-aided adaptive sampling for efficient surface measurements

A method combining space-filling scan paths and adaptive sampling is proposed for surface measurements. Scan paths including a fractal Hilbert curve and a spiral pattern are mainly investigated. The adaptive sampling is based on iterative Gaussian process (GP) inference. Sampling positions are intelligently suggested along the scan path and the final sampled data are trained in a GP-model to reconstruct the entire topography. Simulations and experiments on different surfaces demonstrated the capability of the proposed method. When the special scan paths are employed alone, the required data amount is reduced to about 10%–13% of the uniform sampling and the relative error of surface reconstruction is within 10%. If the GP-aided adaptive sampling is further integrated, the data amount can be reduced to approximately 3%–4%. In addition, time-consumption in scanning is significantly eliminated. Compared with the raster scan, the integration of special scan paths and GP-aided adaptive sampling has several prominent advantages such as eliminating data amount, preserving surface reconstruction accuracy, maintaining a single-pass scan and saving time-cost. The measurement method has a potential application in situations where the efficiency is of critical importance.

Quantifying the quality of higher and technical education: salient perspectives

The paper facilitates salient perspectives on research work accomplished in the assessment of quality in Higher/Technical Education (HTE) till date. The art and science of quantifying quality is systematically analysed, providing a classified overview of various attributes and their implications on the quality. For planned and orderly review, the entire range of referred research work is broadly classified into three perspectives. Various attributes/dimensions are adequately identified presenting entire topography of quality of HTE and the spread of its attributes. Their implications on the overall assessment of quality from different perspectives are critically examined. Several quality models in HTE that facilitated both, system descriptions and prescriptions for further improvements, are discussed. Inherent limitations of various exercises of quality assessment are carefully listed. The paper concludes by citing possible scope for further studies involving combinations of methodologies neutralising the influence of their limitations. The paper contributes differently to broad understanding of TQM concepts in HTE and their impact on its performance measures. The research findings presented in this paper are valuable and useful to the policy makers in HTE, for effectively assessing the level of quality of services, from any particular perspective of concern.

The Political and/or Politics

If our politics is no longer simply and strictly that of sovereign states, then it is no longer ‘politics’ as we have known it for a very long time. Where then to put ‘politics’ if its place is no longer identifiable? This is one way to put the question that comes to me after and according to Derrida. An uncertain and erratic question, because the ‘where’ of that question remains obscure to me: where indeed are the possible ‘places’? Without a doubt it is necessary to rework the entire topography. But still, it is all the same a question of ‘place’: we need the right place for politics, a place that is neither ‘all’ nor ‘nothing’.