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- The Analysis of the Strength of the Ship’s Hull After Running
Aground
Abstract: The article presents a simulation of a ship running aground. It introduces the analytical description, as well as the methodology of carrying out strength calculations when creating engineering tasks related to the topic. It shows the state of stresses and deformations of the hull of a modern minehunter after a collision with the bottom for two immersion depths. Research and development opportunities for future considerations are highlighted in the conclusions.
PubDate: Tue, 08 Mar 2022 00:00:00 GMT
- The Assessment of Unmanned Vessel Operation in Heavy Traffic Areas. Case
Study of the North Sea Crossing by Unmanned Surface Vessel Sea-Kit
Abstract: The continuous development of autonomous and unmanned technology is accelerating the adoption of unmanned vessels for various maritime operations. Despite the technological developments there is still a lack of clear regulatory and organizational frameworks for testing and exploiting the potential of unmanned surface vessels (USVs) in real-world maritime conditions. Such real-world testing becomes ever more complex when operating in multiple nations territorial waters. In May 2019 USV ‘Maxlimer’ crossed the North Sea from the United Kingdom to Belgium and back, carrying goods, to demonstrate the ability of unmanned surface vessels to interact with real marine traffic in an uncontrolled environment. The paper presents this mission in light of the current state of marine autonomy projects as well as the regulatory works conducted by various organizations worldwide.
PubDate: Tue, 08 Mar 2022 00:00:00 GMT
- Directions of Development of the Autonomous Unmanned Underwater Vehicles.
A Review
Abstract: In the paper review of unmanned underwater vehicle (AUV) is presented. The description of main systems is depicted with focus on autonomous single vehicle as well as a swarm. As a consequence of development of AUV technology, research centers are focused on issues related to increasing the degree of their autonomy. Nowadays, mostly navigation and communication as well as high-efficient propeller systems are being developed. There are problems linking this issues. Their solutions includes development of new control laws containing algorithms to prevent collisions - for unmanned vehicles with elements of the underwater environment and for several underwater vehicles cooperating with each other in a swarm.
PubDate: Tue, 08 Mar 2022 00:00:00 GMT
- Arima Model Optimal Selection for Time Series Forecasting
Abstract: A fast-and-flexible method of ARIMA model optimal selection is suggested for univariate time series forecasting. The method allows obtaining as-highly-accurate-as-possible forecasts automatically. It is based on effectively finding lags by the autocorrelation function of a detrended time series, where the best-fitting polynomial trend is subtracted from the time series. The forecasting quality criteria are the root-mean-square error (RMSE) and the maximum absolute error (MaxAE) allowing to register information about the average inaccuracy and worst outlier. Thus, the ARIMA model optimal selection is performed by simultaneously minimizing RMSE and Max-AE, whereupon the minimum defines the best model. Otherwise, if the minimum does not exist, a combination of minimal-RMSE and minimal-MaxAE ARIMA models is used.
PubDate: Tue, 08 Mar 2022 00:00:00 GMT
- Impact of Starting Outlier Removal on Accuracy of Time Series Forecasting
Abstract: The presence of an outlier at the starting point of a univariate time series negatively influences the forecasting accuracy. The starting outlier is effectively removed only by making it equal to the second time point value. The forecasting accuracy is significantly improved after the removal. The favorable impact of the starting outlier removal on the time series forecasting accuracy is strong. It is the least favorable for time series with exponential rising. In the worst case of a time series, on average only 7 % to 11 % forecasts after the starting outlier removal are worse than they would be without the removal.
PubDate: Tue, 08 Mar 2022 00:00:00 GMT
- An Operational Calculus Model with the () - Symmetric Difference
Abstract: The paper determines a non-classical Bittner operational calculus model, in which the derivative is understood as an -symmetric difference Dm,n{x (k)} := {x (k+m)− x (k− n). By considering an operation Dm,n,b{x (k)} := {x (k+m)− b (k)x (k− n), the formulated model has been generalized.
PubDate: Thu, 31 Dec 2020 00:00:00 GMT
- Mobile Wheeled Robot to Support the Task of the Alarm Sub - Unit
Abstract: The article is a presentation, and detailed description of a mobile, vehicular robot whose task is to support the alarm sub-unit. The project was created in response to the increasing need for monitoring, and recognition of the areas. The robot’s interface was created with the use of integrated development environments for Python. The software implementation was possible due to a minicomputer Raspberry Pi 4 B. The robot’s frame is made out of components which are based on the main chassis. The robot is equipped with compatible sensors and cameras. Those, combined with the interface, are able to give a real-time preview of the area in which the robot is in.
PubDate: Thu, 31 Dec 2020 00:00:00 GMT
- Tracking of Unmanned Aerial Vehicles Using Computer Vision Methods: A
Comparative Analysis
Abstract: Tracking of small objects in any given airspace is an integral part of modern security systems. In these systems, there are embedded methods that employ the techniques based on either radio waves, or acoustic signals, or light radiation. The computer vision operation, springing from the light radiation-based technique, has prompted interest in its research. This operation has the advantage of being less expensive than radars and acoustic systems. In addition, it can solve complex security problems by detecting and tracking humans, vehicles, and flying objects. Therefore, this article evaluates the usefulness of the varying computer vision algorithms for tracking of small flying objects.
PubDate: Thu, 31 Dec 2020 00:00:00 GMT
- Doppler Effect in 2 × 2 to 4 × 4 Mimo Systems of Wireless Communication
with Orthogonal Pilot Channel Estimation
Abstract: The Doppler effect in 2×2, 3×3, 4×4 MIMO wireless communication systems with channel estimation is studied. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting, along with the eight alternative orthogonal sets similar to the Walsh set. MIMO transmissions are simulated for 10 cases of the frame length and pilot symbols per frame by no Doppler shift to 1100 Hz Doppler shift with a step of 100 Hz. Based on the simulation, it is ascertained that MIMO transmissions of shorter frames are less sensitive to the Doppler effect. Despite increasing the number of antennas does not mitigate the Doppler effect, and the bit-error rate performance of 4×4 MIMO systems worsens faster than that of 2×2 MIMO systems, it is better to use the maximum number of antennas. The Doppler effect does badly worsen the performance at highway and express train speeds (100 km/hr, and faster), leaving only possibility to further shorten transmissions. This, however, decreases the data rate, but the respective accuracy-versus-data-rate tradeoff must be acceptable.
PubDate: Thu, 31 Dec 2020 00:00:00 GMT
- Possibilities of Detection of the Jamming of the GNSS Receiver with the
Helical Antenna
Abstract: Jamming of GNSS signals is lately treated as essential threat for GNSS users. It is especially dangerous in the face of common usage of GPS-like systems in everyday life, and the great belief of everyday users in the truth of devices indications. In spite of the legal prohibition of using them, jammers are commonly accessible, especially in the Internet. Last years showed however that such threat generated purposely also some governments, what is clearly visible in armed conflicts, and during military exercises. Of course this creates the great threat for civilian users if will be in the vicinity.
PubDate: Thu, 31 Dec 2020 00:00:00 GMT
- Determination of Dynamic Characteristics of Austenitic Steel to be
Utilized in Fem Simulation and its Verification
Abstract: This paper presents the dynamic mechanical properties of austenitic steel with improved durability, which is used in the construction of hulls of minesweepers, mine destroyers, submarines and other naval vessels. Dynamic tensile tests performed on the steel samples using a rotary hammer with a strain rate of up to 1000 s-1 allowed determination of elastic-plastic characteristics of the material in the form of a polynomial of Johnson-Cook constitutive model, taking into account the influence of strain rate and temperature. A characteristic of this type is utilized in numerical calculations in the CAE software. The obtained characteristics were experimentally verified by bending tests of flat samples with a drop-weight type impact hammer. Simultaneously numerical calculations were performed in order to compare the deformation state.
PubDate: Fri, 29 Jun 2018 00:00:00 GMT
- Report on Research with Biomimetic Autonomous Underwater Vehicle —
Navigation and Autonomous Operation
Abstract: The paper presents the second part of the final report on all the experiments with biomimetic autonomous underwater vehicle (BAUV) performed within the confines of the project entitled ‘Autonomous underwater vehicles with silent undulating propulsion for underwater ISR’, financed by Polish National Center of Research and Development. The report includes experiments on the swimming pool as well as in real conditions, that is, both in a lake and in the sea. The tests presented in this part of the final report were focused on navigation and autonomous operation.
PubDate: Fri, 29 Jun 2018 00:00:00 GMT
- Static Analysis of the Tubular Electromagnetic Linear Actuator with
Permanents Magnets
Abstract: In this paper a results of a static analysis of the tubular linear electromagnetic actuator is presented. The linear actuator consist of two parts: a cylindrical unmovable coils surrounded by a soft ferromagnetic case, and a runner made from sequence of permanent magnet with a soft ferro-magnetic gasket. In the first part of the paper the analytical method was performed for preliminary analysis. In the second part of the paper the more detailed analysis was depicted with using finite element method (FEM). The magnetic circuit shape and impact of selected dimensions on static characteristics is presented. Then the axial and radial electromagnetic force as a function of the runner dimensions were analysed.
PubDate: Fri, 29 Jun 2018 00:00:00 GMT
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