In this study, AZ91 Magnesium alloy is produced by cold chamber high pressure die casting (HPDC) method. Different combinations of the cold chamber HPDC process parameters were selected as; in-mold pressure values of 1000 bar and 1200 bar, the gate speed of 30 m/s and 45 m/s, the casting temperatures of 640°C and 680°C. In addition, the test samples were produced by conventional casting method. Tensile test, hardness test, dry sliding wear test and microstructure analysis of samples were performed. The mechanical properties of the samples produced by the cold chamber HPDC and the conventional casting method were compared. Using these parameters; the casting temperature 680°C, in-mold pressure 1000 bar and the gate speed 30 m/s, the highest tensile strength and the hardness value were obtained. Since the cooling rate in the conventional casting method is slower than that of the cold chamber HPDC method, high mechanical properties are obtained by the formation of a fine-grained structure in the cold chamber HPDC method. In dry sliding wear tests, it was observed that there was a decrease in friction coefficient and less material loss with the increase of hardness values of the sample produced by the cold chamber HPDC method.
The article examines the legal status of sea harbours in Poland. The author discusses drafting history of the current Act on Ports and Harbours (1996) and analyzes proposals for its amendment raised by the Sea Cities and Communes Union. The new draft centers on the notion that deciding on legal status of sea harbours should be entrusted to the local government.
The paper presents precipitation results from cold thermal water deposits that are the main cause of clogging in absorbent geothermal wells and borehole areas. As a result of physical and chemical analysis, laboratory tests and observation of the operation of a geothermal installation, a new method was developed to prevent the precipitation of sludge from cooled thermal water. The method being a modification of soft acidising was tentatively named as a super soft acidising method
The concentration or the partial pressure of oxygen in an environment can be determined using different measuring principles. For high temperature measurements of oxygen, ceramic-based sensors are the most practical. They are simple in construction, exploration and maintenance. A typical oxygen potentiometric sensor consists of an oxygen ion conducting solid electrolyte and two electrodes deposited on the two sides of the electrolyte. In this paper different structures of potentiometric oxygen sensors with a solid state reference electrode were fabricated and investigated. The fabricated structures consisted of oxygen ion conducting solid electrolyte from yttria stabilized zirconia, a sensing platinum electrode and nickel-nickel oxide reference electrode. The mixture of nickel-nickel oxide was selected as the reference electrode because it provides reliable electrochemical potential in contact with oxygen conducting electrolyte. To avoid oxidation of nickel the reference electrode is sealed from ambient and the mixture of nickel-nickel oxide was formed electrochemically from nickel oxide after sealing. The effectiveness of the sealing quality and the effectiveness of nickel-nickel oxide mixture formation was investigated by impedance spectroscopy.
The paper presents the application of liquid crystal thermography for temperature determination and visualisation of two phase flow images on the studied surface. Properties and applications of thermochromic liquid crystals are discussed. Liquid crystals were applied for two-dimensional detection of the temperature of the heating foil forming one of the surfaces of the minichannel along which the cooling liquid flowed. The heat flux supplied to the heating surface was altered in the investigation and it was accompanied by a change in the color distribution on the surface. The accuracy of temperature measurements on the surface with liquid crystal thermography is estimated. The method of visualisation of two-phase flow structures is described. The analysis of monochrome images of flow structures was employed to calculate the void fraction for some cross-sections. The flow structure photos were processed using Corel graphics software and binarized. The analysis of phase volumes employed Techsystem Globe software. The measurement error of void fraction is estimated.
Planning a construction project, the investor frequently faces the choice of the option of the planned investment. Assessment of options is difficult due to the complex nature of construction projects. Various methods of multicriteria evaluation are successfully applied in the assessment and analysis of options. For those methods to work, a handful of information must be prepared beforehand. Among others, it is necessary to establish the assessment criteria and determine their weight for specific cases. This stage is implemented in cooperation with experts. The results of evaluations, obtained on the basis of the experts' opinions, must be processed and prepared. The paper will discuss one possible option for assessing the experts' opinion.
In this paper we propose an original configuration of a compliant mini-gripper for handling chemicals. The compliant mini-gripper is 3D modeled and analyzed with finite element method. To use it in a wider range of containers designed for laboratories we made several variants of fasteners. In order to obtain a functional prototype in a scale appropriate to characterize the system, we determined the material properties of the gripper and developed an experimental stand for characterizing the system with mini-gripper. Finally, we compared the movements of the experimental grip, made according to the movement of the bellows type actuator, determined based on, analytical and numerical results.
This article discusses the last Sunday in the Pre-Lenten period in the liturgical tradition of the Orthodox Church known as “Cheese-fare Sunday” or “Forgiveness Sunday”. The faithful’s attention is concentrated on the need to forgive others as one of the main conditions of crossing the threshold of Great Lent. Particularly noteworthy is the explanation of the very term “forgiveness”, as well as the kind of theological and moral message that the Fathers of the Church and the authors of the texts of the services of Great Lent find in it. Furthermore, it also clearly points out the tragic consequences of the fall of man, which is why has also been called “The Sunday of the Expulsion of Adam and Eve from Paradise.” The main reason for recollecting this tragic event is the purely didactic aspect. There are two perspectives of spiritual life for a man who begins the trial of a fast way. On the one hand, endowed with free will - like the protoplasts - has the opportunity to choose a life in accordance with God’s commandments, which will result in constant communion with Him and saturating the gift of His grace. On the other hand, he observes what the lack of temperance and disobedience to the Creator causes. Great Lent is therefore an attempt to show the right way to return to Paradise reality and unity with God and people.