 Subjects -> MILITARY (Total: 106 journals)
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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
- Pilot Symbol Error Re - Orthogonalization in 2 × 2 MIMO Systems of
Wireless Communication
Abstract: A 2×2 MIMO wireless communication system with channel estimation is simulated, in which two transmit, and two receive antennas are employed. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting. Data are modulated by coherent binary phase-shift keying, whereupon an orthogonal space-time block coding subsystem encodes information symbols by using the Alamouti code. Based on the simulation, it is ascertained a possibility to decrease the bit-error rate by substituting the Hadamard sequences for the sequences having irregular structures, and constituting the eight known orthogonal bases. Considering a de-orthogonalization caused by two any pilot sequence symbol errors, the bit-error rate is decreased by almost 2.9 %. If de-orthogonalizations are caused by two repeated indefinite, and definite pilot sequence symbol errors, the decrements are almost 16 % and 10 %, respectively. Whichever sequences are used for piloting, the 2×2 MIMO system is ascertained to be resistant to the de-orthogonalization if the frame is of 128 to 256 symbols piloted with 32 to 64 symbols, respectively.
PubDate: Fri, 23 Oct 2020 00:00:00 GMT
- Controlling the Operation of a Ship’s Electric Power Supply Using
Fuzzy Controllers
Abstract: The paper presents dynamical models of controlling voltage and frequency of ship’s electric supply set. The simulation model of synchronous generator, implemented in Matlab/Simulink, was described. For the developed simulation model, developed control systems using fuzzy controllers type P and PD were presented. Simulation research for resistance, inductive and capacitive loads were carried out for these regulators. Sample results of simulation tests are presented in the form of voltage waveforms at the output of the generator and rotational speed of the internal combustion engine for various load conditions. The conducted tests allow to assess the quality of the control process using fuzzy controllers and thus ensure the selection of the optimal solution.
PubDate: Fri, 23 Oct 2020 00:00:00 GMT
- Nonhomogeneus Generalisations of Poisson Process in the Modeling of Random
Processes Related to Road Accidents
Abstract: The stochastic processes theory provides concepts, and theorems, which allow to build the probabilistic models concerning accidents. “Counting process” can be applied for modelling the number of road, sea, and railway accidents in the given time intervals. A crucial role in construction of the models plays a Poisson process and its generalizations. The nonhomogeneous Poisson process, and the corresponding nonhomogeneous compound Poisson process are applied for modelling the road accidents number, and number of people injured and killed in Polish roads. To estimate model parameters were used data coming from the annual reports of the Polish police.
PubDate: Fri, 23 Oct 2020 00:00:00 GMT
- The Effect on Constant Heel on Circulation of a Vessel Calculated on the
Basis of Investigations of M/S “Ziemia Zamojska” Model
Abstract: The article presents modeling research on the M/S “Ziemia Zamojska” reduced model, carried out in an open fresh water area by a team of employees of the Department of Operating of Floating Vessels, Polish Naval Academy, Gdynia. The research involved circulating the model with constant angle of heel on the selected side, and the main engine set to full speed ahead. Using a real ship to carry this type of investigations is risky. It may lead to some failures like e.g. rudder failure, steering gear malfunction, overload and in some circumstances even main engine seizure. For this reason, ships are not tested with the rudder put to starboard or to port at the full speed ahead setting, even during a “Crash Stop” maneuver. However, based on the analysis of accidents at sea, and practical experience, it appears that during real operating conditions of vessels, there may occur situations when, for the sake of safety, the maneuver mentioned above must be carried out. Therefore, the authors had to conduct model tests of a floating vessel for the described case of ship operation
PubDate: Fri, 23 Oct 2020 00:00:00 GMT
- Ice Drift in the Arctic Ocean
Abstract: The paper presents results of research based on analysis of historical and present studies of the Arctic ice drift. Current information about Arctic ice drift comes from the scientific expedition organized by the Alfred-Wrgener-Institut Helmholtz Centre for Polar and Marine Research (AWI) from Bremerhaven (Germany) in the Arctic Ocean, as a part of the Multidiscipli-nary drifting Observatory for the Study of Arctic Climate (MOSAiC), coming from the deck of the icebreaker RV “Polarstern”. The main purpose of the article was to collect and illustrate information on the phenomenon of ice drift in the Arctic Ocean, considering data from ongoing research during the MOSAiC expedition. The average movement speed of the icebreaker RV “Polarstern” frozen in Arctic ice during the first three legs of the expedition was over 5 Nm/day, which is characteristic of the current data relating to the speed of the Arctic ice drift in the place of research. On the other hand, the article is popular science, and presents the overall characteristics of Arctic ice drift with an indication of the general directions, and speed of its movement. Ice drift speeds in the Arctic can reach exceptionally high values under favorable conditions. The drift of sea ice reaching at its intensity/intensity values close to the limit (dangerous criterion) in these extreme cases is called the “ice river”. The speed of “ice rivers” can reach up to 1–2 knots, however, in extreme conditions up to 9 knots. Based on data from the AWI, correlation points were identified between the speed of Arctic ice drift and the speed of winds and atmospheric pressure values.
PubDate: Fri, 23 Oct 2020 00:00:00 GMT
- Modern Integrated Platform Management System Laboratory for Polish Naval
Academy: Design and Implementation
Abstract: This article contains a description of the implemented STANTOS™ Integrated Platform Management System (IPMS) laboratory created by Research and Development Center Maritime Technology Center for the Polish Naval Academy in Gdynia. The author briefly described the topology of the solution, justifies the choice of hardware and software solutions. Concept of use was written, where the usefulness of the implemented laboratory was motivated, with a focus on cases where safety plays a key role.
PubDate: Thu, 09 Jul 2020 00:00:00 GMT
- Detection of Unmanned Aerial Vehicles Using Computer Vision Methods: A
Comparative Analysis
Abstract: Detection of small objects in the airspace is a crucial task in the military. In the era of today’s unmanned aerial vehicles (UAVs) technology, many military units are exposed to recognition and observation through flying objects. They are often equipped with optoelectronic warhead making a way to collect essential and secret data of the military unit. Modern technical solutions make it possible to implement some methods facilitating detection of flying objects. A lot of them utilize computer vision techniques based on image processing algorithm. Therefore, in this article, we present an analysis of the most promising algorithm for detection of small flying objects.
PubDate: Thu, 09 Jul 2020 00:00:00 GMT
- Mechanical Properties of Welded Joints of 1.3964 Steel for Computer Aided
Engineering (CAE) Purposes
Abstract: The article presents the study of mechanical properties of welded steel from which the hull of a modern mine destroyer was made. Keeping the tightness of ship compartments during operation depends on the strength of these joints. The results of testing the mechanical properties of 1.3964 steel and its welded joints subjected to a static tensile test were presented, and a Johnson – Cook material model was proposed. The material model can be used in CAE (Computer Aided Engineering) simulations related to hull strength analysis.
PubDate: Thu, 09 Jul 2020 00:00:00 GMT
- Accessibility and Usability of Landsat 8 Data for the Purpose of
Satellite-Drived Bathymetry of the South Baltic Near-Shore Waters on the
Example of Gulf of Gdańsk
Abstract: The paper presents the analysis of accessibility and usability of Landsat 8 Satellite Imagery for the purpose of Satellite Derived Bathymetry (SGB) products generation of the area of near-shore waters of the Polish coast. General assumptions of the SDB, Landsat program and factors affecting the products generation process have been described in details. Examples of SDB results, generated using both GIS software and Matlab, are presented on the example of chosen areas of Gulf of Gdańsk. The advantages and disadvantages of the SDB method are presented in the discussion and conclusion part with the proposed directions for the future works.
PubDate: Thu, 09 Jul 2020 00:00:00 GMT
- The Use of a Microcontrollers in Hygrometric Measurements Application
Abstract: The article presents the possibility of using microcontroller systems as one of elements of a teaching position. The Arduino Mega system based on the ATMega 2560 microcontroller from the AVR family was used to build the station. At the beginning, a virtual hygrometer model was designed in the AUTOCAD program and then the air channels were made using 3D printing. After assembling the station, it was compared to a laboratory aspiration hygrometer. The analysis was presented in the final part of the article.
PubDate: Thu, 09 Jul 2020 00:00:00 GMT
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