22,501 research outputs found
Visual motion processing and human tracking behavior
The accurate visual tracking of a moving object is a human fundamental skill
that allows to reduce the relative slip and instability of the object's image
on the retina, thus granting a stable, high-quality vision. In order to
optimize tracking performance across time, a quick estimate of the object's
global motion properties needs to be fed to the oculomotor system and
dynamically updated. Concurrently, performance can be greatly improved in terms
of latency and accuracy by taking into account predictive cues, especially
under variable conditions of visibility and in presence of ambiguous retinal
information. Here, we review several recent studies focusing on the integration
of retinal and extra-retinal information for the control of human smooth
pursuit.By dynamically probing the tracking performance with well established
paradigms in the visual perception and oculomotor literature we provide the
basis to test theoretical hypotheses within the framework of dynamic
probabilistic inference. We will in particular present the applications of
these results in light of state-of-the-art computer vision algorithms
General scores for accessibility and inequality measures in urban areas
In the last decades, the acceleration of urban growth has led to an
unprecedented level of urban interactions and interdependence. This situation
calls for a significant effort among the scientific community to come up with
engaging and meaningful visualizations and accessible scenario simulation
engines. The present paper gives a contribution in this direction by providing
general methods to evaluate accessibility in cities based on public
transportation data. Through the notion of isochrones, the accessibility
quantities proposed measure the performance of transport systems at connecting
places and people in urban systems. Then we introduce scores rank cities
according to their overall accessibility. We highlight significant inequalities
in the distribution of these measures across the population, which are found to
be strikingly similar across various urban environments. Our results are
released through the interactive platform: www.citychrone.org, aimed at
providing the community at large with a useful tool for awareness and
decision-making
Kajian terhadap ketahanan hentaman ke atas konkrit berbusa yang diperkuat dengan serat kelapa sawit
Konkrit berbusa merupakan sejenis konkrit ringan yang mempunyai kebolehkerjaan yang
baik dan tidak memerlukan pengetaran untuk proses pemadatan. Umum mengenali
konkrit berbusa sebagai bahan binaan yang mempunyai sifat kekuatan yang rendah dan
lemah terutama apabila bahan binaan ini dikenakan tenaga hentaman yang tinggi.
Namun begitu, konkrit berbusa merupakan bahan yang berpotensi untuk dijadikan
sebagai bahan binaan yang berkonsepkan futuristik. Binaan futuristik adalah binaan yang
bercirikan ringan, ekonomi, mudah dari segi kerja pembinaan dan yang paling penting
adalah mesra alam. Dalam kajian ini, konkrit berbusa ditambah serat buangan pokok
kelapa sawit untuk untuk meningkatkan sifat kekuatan atau rapuh. Serat kelapa sawit juga
berfungsi mempertingkatkan ketahanan hentaman terutamanya aspek nilai penyerapan
tenaga hentaman dan nilai tenaga hentaman. Kandungan peratusan serat kelapa sawit
yang digunakan adalah 10%, 20% dan 30% dengan dua ketumpatan konkrit berbusa iaitu
1000kg/m3
dan 1400kg/m3
. Untuk menentukan nilai penyerapan tenaga hentaman dan
nilai tenaga hentaman, ujikaji Indentasi dan ujikaji hentaman dilakukan ke atas sampel�sampel yang telah diawet selama 28 hari. Luas bawah graf tegasan-terikan yang
diperolehi daripada ujikaji Indentasi merupakan nilai penyerapan tenaga hentaman bagi
sampel konkrit berbusa. Untuk ujikaji hentaman, keputusan ujikaji dinilai berdasarkan
nilai tenaga hentaman untuk meretakkan sampel yang diperolehi daripada mesin ujikaji
dynatup. Secara keseluruhannya, hasil dapatan utama bagi kedua-dua ujikaji
menunjukkan sampel yang mengandungi peratusan serat kelapa sawit sebanyak 20%
mempunyai nilai penyerapan tenaga hentaman dan nilai tenaga hentaman yang tinggi.
Serapan tenaga maksimum adalah sebanyak 4.517MJ/m3
untuk ketumpatan 1400kg/m3
.
Ini menunjukkan ketumpatan 1400kg/m3
berupaya menyerap tenaga lebih baik
berbanding ketumpatan 1000kg/m3
. Manakala untuk nilai tenaga hentaman maksimum
adalah sebanyak 27.229J untuk ketumpatan 1400kg/m3
. Hasil dapatan tersebut menunjukkan ketumpatan 1400kg/m3
dengan peratusan serat sebanyak 20% berupaya
mengalas tenaga hentaman yang lebih banyak sebelum sampel retak. Kesimpulannya,
peningkatan ketumpatan konkrit berbusa dan pertambahan serat buangan kelapa sawit ke
dalam konkrit berbusa dapat meningkatkan ciri ketahanan hentaman konkrit berbusa
khususnya aspek nilai penyerapan tenaga hentaman dan nilai tenaga hentaman
Empowering and assisting natural human mobility: The simbiosis walker
This paper presents the complete development of the Simbiosis Smart Walker. The device is equipped with a set of sensor subsystems to acquire user-machine interaction forces and the temporal evolution of user's feet during gait. The authors present an adaptive filtering technique used for the identification and separation of different components found on the human-machine interaction forces. This technique allowed isolating the components related with the navigational commands and developing a Fuzzy logic controller to guide the device. The Smart Walker was clinically validated at the Spinal Cord Injury Hospital of Toledo - Spain, presenting great acceptability by spinal chord injury patients and clinical staf
Feedback Control of an Exoskeleton for Paraplegics: Toward Robustly Stable Hands-free Dynamic Walking
This manuscript presents control of a high-DOF fully actuated lower-limb
exoskeleton for paraplegic individuals. The key novelty is the ability for the
user to walk without the use of crutches or other external means of
stabilization. We harness the power of modern optimization techniques and
supervised machine learning to develop a smooth feedback control policy that
provides robust velocity regulation and perturbation rejection. Preliminary
evaluation of the stability and robustness of the proposed approach is
demonstrated through the Gazebo simulation environment. In addition,
preliminary experimental results with (complete) paraplegic individuals are
included for the previous version of the controller.Comment: Submitted to IEEE Control System Magazine. This version addresses
reviewers' concerns about the robustness of the algorithm and the motivation
for using such exoskeleton
- …