arXiv subjects

Sergij V. Goncharov

Publications and source records attributed to Sergij V. Goncharov.

5 recordsLinked to original sources

arXiv2019

On sound ranging in some non-proper metric spaces

We consider the sound ranging, or source localization, problem --- find the unknown source-point from known moments when the spherical wave of linearly, with time, increasing radius reaches known sensor-points --- in some non-proper metric spaces (closed ball is not always compact). Under certain conditions we approximate the solution to arbitrary precision by the iterative processes with and without a stopping criterion. We also consider this problem in normed spaces with a strictly convex norm when the sensors are dense on the unit sphere. Appended is the implementation of the approximation algorithm in Julia language.

math.FA↗

arXiv2019

Using fuzzy bits and neural networks to partially invert few rounds of some cryptographic hash functions

We consider fuzzy, or continuous, bits, which take values in [0;1] and (-1;1] instead of {0;1}, and operations on them (NOT, XOR etc.) and on their sequences (ADD), to obtain the generalization of cryptographic hash functions, CHFs, for the messages consisting of fuzzy bits, so that CHFs become smooth and non-constant functions of each bit of the message. We then train the neural networks to predict the message that has a given hash, where the loss function for the hash of predicted message and given true hash is backpropagatable. The results of the trainings for the standard CHFs - MD5, SHA1, SHA2-256, and SHA3/Keccak - with small number of (optionally weakened) rounds are presented and compared.

cs.CR↗

arXiv2018

On sound ranging in proper metric spaces

We consider the sound ranging, or source localization, problem - find the source-point from the moments when the wave-sphere of linearly, with time, increasing radius reaches the sensor-points - in the proper metric spaces (any closed ball is compact) and, in particular, in the finite-dimensional normed spaces. We approximate the solution to arbitrary precision by the iterative process with the stopping criterion.

math.FA↗

arXiv2017

On covering a ball by congruent subsets in normed spaces

We consider the covering of a ball in certain normed spaces by its congruent subsets and show that if the finite number of sets is not greater than the dimensionality of the space, then the centre of the ball either belongs to the interior of each set, or doesn't belong to the interior of any set. We also provide some examples when it belongs to the interior of exactly one set. These are the specific cases of the modified problem originally posed for dissection.

math.FA↗

arXiv2017

On sound ranging in Hilbert space

We consider the sound ranging problem, which is to find the position of the source-point from the moments when the wave-sphere of linearly, with time, increasing radius reaches the sensor-points, in the infinite-dimensional separable Euclidean space H, and describe the solving methods, for entire space and for its unit sphere. In the former case, we give some sufficient conditions for uniqueness of the solution. We also provide two examples with the sets of sensors being a basis of H: 1st, when sound ranging problem and so-called dual problem both have single solutions, and 2nd, when sound ranging problem has two distinct solutions.

math.FA↗