Application of Laser Vibrometry to Assess Defects in Ship Hull’s Welded Joints’ Technical Condition

The paper presents the measurement process and test results for six thin-walled plates with different dynamic characteristics caused by different defects of welded joints. The tests were carried out using non-destructive testing (NDT). The authors made an attempt to determine the validity of the use and degree of effectiveness of the tests based on laser vibrometry in detecting defects in welded joints. The tests of welded plates were carried out using displacement laser sensors and piezoelectric accelerometers, while the source of vibration extortion was a modal hammer. In the adopted measurement methodology, the application of accelerometers was to obtain the reference data, which allowed for comparison with the measurement data obtained from the laser vibrometer. The analysis of the obtained measurement data, in the fields of time and frequency, made it possible to verify the correctness of the data obtained by means of laser vibrometry and to determine the requirements which are necessary for the correct performance of NDT tests and in the future structural health monitoring (SHM) system of welded joints with the use of a laser vibrometer. The mathematical model developed in the MSC software Pastran-Nastran was also used in the work. The model was developed for the purpose of mutual verification of the measurement and calculation tests. At the present stage of work, it can be stated that the results obtained by laser vibrometry methods should be treated as a supplement to the research conducted with traditional piezoelectric accelerometers. In certain situations, they can be used as an alternative to accelerometers, due to the fact that laser sensors do not require direct contact with the examined object. Where the object under test may be in a strong electromagnetic field, optical sensors are better suited than contact sensors

Central management of laboratory workstations’ software based on PiNet system and Raspberry Pi computers

W pracy przedstawiono metodę tworzenia infrastruktury laboratoryjnej pozwalającej, za pośrednictwem serwera, na sieciowe uruchamianie (ang. network booting) różnych programów na stanowiskach laboratoryjnych. Prezentowana metoda wykorzystuje oprogramowanie PiNet do stworzenia instancji systemu operacyjnego Raspbian na serwerze. Metoda ta wykorzystuje także odpowiednio przygotowane jednostki startowe (ang. boot file) umieszczane na kartach pamięci w komputerach typu Raspberry Pi. Dzięki tej konfiguracji, zaraz przy uruchomieniu, urządzenia te łączą się z serwerem i użytkują serwerową instancję Raspbiana. Dla każdego użytkownika pracującego na urządzeniach przygotowywane jest osobne konto, co pozwala na jednoczesną pracę wielu użytkowników w trybie multi-user-mode.The paper presents a metod of creating laboratory infrastructure that allows network booting from a laboratory server. This method uses PiNet software to create a single Raspbian OS instance on the server. By putting network boot files on Raspberry Pis memory cards, it allows Raspberry Pis to use the single Raspbian OS instance that was placed on the server. For every user working on the Raspberry devices there is a user account created. This metod allows multiple users to be logged in at the same time in spite of having only one instance of Raspbian OS. Having only one instance of Raspbian OS makes configuring the laboratory infrastructure easier. The Raspbian placed on the server can be chrooted at any moment to install additional applications, execute bash scripts or edit configuration files. Properly configured Raspbian can be used |to teach programming, networking and managing databases. Moreover Raspbian can be used as a terminal that uses SSH to work on a server ex. to execute queries on PostgreSQL server

METHODS OF CRACKS DETECTION IN MARINE STRUCTURES' WELDED JOINTS BASED ON SIGNALS' TIME WAVEFORM ANALYSIS

The paper presents two methods of crack detection in ship hulls. The methods are dedicated for structural health monitoring (SHM) of responsible welded joints. The system will be based on vibrodiagnostic - signals will be measured by piezoelectric accelerometers and/or fibre optic sensors. In SHM systems of welded joints of thin-walled structures, a vibrodiagnostic method is the most promising. Its most important advantage is that it is both effective and relatively low costly. There are two general methods of vibrodiagnostic signal analysis: the most frequently used are spectrum analysis and time waveform analysis. The spectrum analysis concerns changes of natural frequency. In marine exploitation conditions, the frequencies changes might be imperceptible. The first method presented in the article is based on the evaluation of the mean value distribution of the amplitude spectrums calculated with the time window method. Second proposed method was based on the determination of damping decrement in function of time. Due to the complexity of the responses run, the proposed method consisted of calculating the damping decrement using the response approximation with different functions. It has been shown that the changes analysis of damping decrement applied to welded plates enables the assessment of the quality associated with the weld. A calculation algorithm as well as and the exemplary results from the proposed methods used for some selected samples with different type of welds are included in the paper. The results of the tests show that the analysis based on proposed methods indicates that they differ significantly depending on the welds, indicating their quality and cracks that are associated with them

Using QOS with PCQ in university laboratories in order to enhance students access to laboratory servers

W pracy przedstawiono metodę konfiguracji sieci lokalnej na potrzeby laboratoriów komputerowych. Zastosowano QoS (ang. Quality of Service) z PCQ (ang. Per Connection Queueing) w celu zapewnienia studentom dostępu o równej przepustowości do serwerów laboratoryjnych. Metoda ta umożliwia zarówno priorytetyzację konkretnego ruchu sieciowego, ograniczanie przepustowości do konkretnych, z góry ustalonych wartości, jak i gwarantowanie prędkości transferu na poziomie przepływności pozostałych użytkowników. Metoda ta jest skalowalna i możliwa do zastosowania w większości routerów programowalnych.The paper presents a method of configuring the computers laboratiories’ local network. The QOS with PCQ was used in order to guarantee an equal bandwith for students connecting to laboratories’ servers. This method allows both prioritizing specific type of network traffic, limiting bandwith to pre-established values and guarantiing the same bandwith for every user. This metod is scalable and can be applied by using most of programmable routers. A basic configuration of QoS with PCQ that made clients get equal bandwith was presented in the second chapter. This configuration consisted of one parent query that created a structure in which sub-queries configured with PCQ were placed. The third chapter showed a configuration that pioritized traffic on specific port (port 22) above other taffic. This configuration was also configured with PCQ to share the bandwith equaly for every client that made prioritized traffic. In order to create the configuration, firewall mangle rules were created to mark connections (upload and download) and to mark packets (packets send or received on port 22 and packets not send or received on this port). The marks were used to allow QoS to select the packets that were ment to be prioritized and give them the highest priority. In collaboration with PCQ the configuration prioritized port 22 traffic while splitting the bandwith equaly amongst clients

Diagnostic benchmarks on dynamic characteristics of thin-walled marine damaged structures

Among structural health monitoring (SHM) methods of thin-walled structures, a vibrodiagnostic method is one of the most promising. The accelerometer recorded responses provide diagnostic information that requires mathematical processing to extract the essential dynamic characteristics. The authors have been looking for new parameters - diagnostic benchmarks which can be applied to non-destructive, automatic testing of thin-walled marine structures (especially their welded joints) like ship hulls. All characteristics have been based on recorded data generated during the vibration tests of welded joints with and without failures. For this purpose, the authors proposed method based on: FFT windowing analysis, benchmark with using 2D or 3D time – frequency dynamic characteristics and the determination of damping decrement in function of time. The work presents the algorithm and exemplary results obtained from the application of proposed method to several selected sample plates with different type of welds

Długoterminowa analiza eksploatacji miejskiej sieci ciepłowniczej z uwzględnieniem aspektów ochrony środowiska

The article presents methods for the location of leakages in heating pipelines. The advantages and disadvantages of each of the described methods are presented. The exploitation and modernization of the actual heating network in the city of up to 30,000 inhabitants over the space of 10 years have been characterized. The examined heating network was analyzed for the degree and categories of malfunctions occurring in the examined time space in the network and impact on the natural environment was determined. The article also examines the impact of various factors, such as the amount of make-up water, the amount of heat required to heat the supplementary carrier, the total cost of heat to replenish the carrier, networks total disruption and the amount of water exchange in the system and its impact on the natural environment. At the same time, an assessment of the impact of the modernization of the heating network combined with its munition to reduce the impact of these factors on environmental protection was made.W artykule przedstawiono metody lokalizacji nieszczelności rurociągów ciepłowniczych. Przedstawiono wady i zalety każdej z opisanych metod. Scharakteryzowano eksploatację i modernizację rzeczywistej sieci ciepłowniczej w mieście do 30 tysięcy mieszkańców na przestrzeni 10 lat. W badanej sieci ciepłowniczej przeanalizowano stopień i kategorie awarii występujących w badanej przestrzeni czasu w sieci oraz określono ich wpływ na środowisko naturalne. W artykule zbadano również oddziaływanie rożnych czynników, takich jak: ilość wody uzupełniającej, ilość ciepła do podgrzania nośnika na uzupełnienie, koszt łączny ciepła przeznaczony do uzupełnienia nośnika, zład łączny sieci oraz ilość wymian wody w systemie i jej wpływ na środowisko naturalne. Równolegle, podjęto ocenę wpływu modernizacji sieci ciepłowniczej, połączonej z jej uzbrojeniem, na zmniejszenie oddziaływania wymienionych czynników na ochronę środowiska

Analiza wykorzystania undervoltingu do redukcji zużycia energii elektrycznej w urządzeniach komputerowych i oddziaływania na środowisko

This paper presents a method of lowering the processor’s voltage and temperature in which the computer operates by performing an operation called undervolting. By using undervolting it is possible to reduce electricity consumption and the amount of heat generated by computer workstations by up to 30%. This problem is particularly relevant for institutions that use a large number of computers. The more the computers are subjected to the higher computational load, the more effective the mechanism of undervolting is. Undervolting the processor does not reduce its performance, but lowers its operating temperature, has a positive impact on its life span and power consumption. Maintaining a low temperature of operation for computer hardware is essential to reduce operating and repair costs. The paper also presents the results of environmental research aimed at assessing the validity and effectiveness of undervolting.W pracy przedstawiono metodę obniżania napięcia procesora i temperatury pracy komputera poprzez wykonanie operacji zwanej undervoltingiem. Przez zastosowanie undervoltingu można obniżyć nawet o 30% zużycie energii elektrycznej i ilość wydzielanego ciepła przez stanowiska komputerowe. Problem ten jest szczególnie istotny w przypadku instytucji, które korzystają z dużej liczby komputerów. Skuteczność mechanizmu jest tym większa im komputery poddane undervoltingowi są bardziej obciążone obliczeniowo. Wykorzystywanie undervoltingu w konfiguracji procesora nie zmniejsza jego wydajności, a obniża jego temperaturę pracy, wpływa pozytywnie na jego żywotność i zużycie energii elektrycznej. Utrzymanie dobrej kultury pracy sprzętu komputerowego jest kluczowe, by obniżyć koszty eksploatacji oraz napraw. W pracy przedstawiono również wyniki badań środowiskowych, których celem była ocena zasadność i efektywności stosowania undervoltingu

Containerization of Server Services

Businesses are increasingly confronted with server-related problems. More and more, businesses are enabling remote working and need to rely on network services. The provision of network services requires rebuilding the network infrastructure and the way employees are provided with data. Web applications and server services use common dependencies and require a specific network configuration. This often involves collisions between network ports and common dependencies’ configuration. This problem can be solved by separating the conflicting applications into different servers, but this involves the cost of maintaining several servers. Another solution may be to isolate applications with virtual machines, but this involves a significant overhead on server resources, as each virtual machine must be equipped with an operating system. An alternative to virtual machines can be application containerization, which is growing in popularity. Containerization also allows to isolate applications, but operates on the server’s native operating system. This means eliminating the overhead on server resources present in virtual machines. This article presents an example of web application containerization

Providing the Ability of Working Remotely on Local Company Server via VPN

Increasingly popular remote work requires the use of modern network technologies to provide employees in a remote location with access to the company’s IT resources. The answer to the needs of remote access to files and server services can be the use of clouds and VPS. However, this involves high costs and requires entrusting the enterprise’s data to the providers of these services. Both for reasons of data security and too high costs, enterprises sometimes cannot use these technologies. The solution to the problem may be the use of encrypted VPN tunneling, which allows the device to be connected at a remote location to the company’s local network and use its resources as if it was connected to the local network with physical transmission medium

Ensuring Equal Bandwidth for Remote Connections to the Local Company Server

Creating the required IT infrastructure to enable the ability for comfortable remote working is not an easy task. Improper configuration can create the possibility of taking over the whole bandwidth of the link by one device. Increasing bandwidth introduces extra costs and does not completely eliminate the problem – it will be more difficult to take over the whole bandwidth, but it is still possible. The solution to the problem may be the use of clouds and VPS, but it is associated with high costs and the need to entrust company data to providers of these services. Due to security and too high costs, this may not be an optimal solution. An alternative solution may be to use QoS along with PCQ. This mechanism allows to ensure equal division of the bandwidth between the devices under its control. With an appropriate configuration, QoS can eliminate the problem of taking over the whole bandwidth and ensure equal access to resources