Selective Laser Melting (SLM) is a modern manufacturing method with many applications in medicine, aerospace and auto-motive industries. SLM processed materials are characterized by good dimensional accuracy and properties comparable or superior to materials obtained by traditional processing methods. In this paper an SLM process was used to obtain 316L stainless steel parts. This paper presents the microstructure, chemical and phase composition, physicochemical and electrochemical properties of 12 groups of tested samples, differentiated by the SLM processing parameters. Based on the investigation, it can be inferred that the selection of the appropriate SLM parameters is very important to determined final material properties. The samples producedwith the energy density E = 600 J/mm3 were observed to possess optimum properties - a homogeneous structure, density closest to the desired one, good wettability and pitting corrosion resistance.
Układy chłodzenia solarnego, wykorzystujące technologię absorpcyjną, mogą w znacznym stopniu pokryć zapotrzebowanie mocy chłodniczej oraz obniżyć zużycie energii elektrycznej. Stosowanie tego typu rozwiązań jest szczególnie uzasadnione w krajach Europy Południowej, ze względu na wyższą cenę energii elektrycznej w sezonie letnim oraz odpowiednie warunki klimatyczne. W Europie powstało wiele systemów klimatyzacji z napędem solarnym. Jeden z nich został zaprojektowany i zbudowany w CIESOL-Solar Energy Research Center znajdującym się w południowej części Hiszpanii.
The paper analyses the influence of chemical composition of silicone-based composites on their properties in the aspect of using them as long-term soft denture lining materials. Different concentrations of filler and methylhydrosiloxane-dimethylsiloxane copolymer were used. The filler was introduced into the composite with mechanical mixing combined with ultrasonic homogenization. Scanning electron microscopy was used to investigate the quality of filler dispersion. Shore A hardness, tensile strength, sorption, solubility and tensile bond strength to poly(methyl methacrylate) were measured. Tests show satisfactory results for some experimental composites, which met all the requirements for such materials.
The aim of the study was to evaluate the influence of different fillers on the chosen functional properties of experimental composites based on typical polymeric matrix, in order to understand the effect of different fillers on their properties and to develop a simple base composite for further investigations with experimental fillers, e.g. with antimicrobial properties. Previous experiments have been usually based on commercially available composites of unknown composition or compilation of monomers, without reinforcing fillers. Scanning electron microscopy was used to investigate the quality of fillers’ dispersion, which was satisfying. Results showed significant differences between materials’ diametral tensile strength (p = 0.0019), compressive strength (p < 0.0001), Vickers microhardness (p < 0.0001), flexural modules (p = 0.0018), and the degree of conversion (p < 0.0001), but flexural strength was not significantly different (p = 0.0583). Investigations indicated that no filler type had an especially positive impact on the mechanical properties, but reinforcement effect was achieved by proper compilation of silica nanofiller and variable glass fillers. Nanofiller decreased the degree of conversion.
Introduction: Multifactorial aetiologies of painful temporomandibular disorders (TMD) have an impact on correct diagnosis and consequently prevent proper treatment. Aim of the study: The aim of the study was to evaluate the effect of magnetic stimulation on electromyographic activity in temporal muscles and masseters in patients using occlusal splints. Materials and methods: The examined group consisted of 40 edentulous patients with TMD. The patients were examined based on Helkimo Index. Next, electromyographic activity of the temporal muscle and masseter were investigated using 8-channel surface electromyography. All patients received acrylic occlusal splints for 12 weeks. The group qualified for the study included 20 randomized patients, whose therapy was additionally carried out by extremely low-frequency magnetic fields for a period of 21 days. Following examinations were conducted after 3, 6 and 12 weeks with surface electromyography recording of the examined muscles. Patients received occlusal splint corrections using the T-Scan III system. The clinical evaluation of TMD was analysed using Helkimo index and VAS scale before and after the treatment. All the data were analysed using Statistica 12.5 PL. Results: Patients with combination therapy had lower asymmetry of temporal muscle activity. Conclusions: Combination therapy using magnetic stimulation reduced intensity of pain in patients with TMD and decreased values of the Helkimo indices.
W artykule zaprezentowano kontynuację zapoczątkowanych we wcześniejszych artykułach rozważań dotyczących sposobu opracowania konstrukcji i technologii wykonania dostatecznie skutecznego materiału opakowaniowego o właściwościach anizotropowych, który w niewielkim stopniu stanowiłby barierę dla wymiany ciepła podczas zamrażania, a z drugiej strony mógłby skutecznie chronić zamrożony produkt przed niekontrolowanym i szkodliwym oddziaływaniem środowiska zewnętrznego. W kolejnych przemyśleniach zmodernizowano opracowanie konstrukcji materiału i technologii wykonania przegrody termalnej. Zaproponowano nowy, bardziej rozwinięty model matematyczny oparty na równaniach przewodzenia ciepła w ośrodkach niejednorodnych obejmujący procesy przewodzenia, konwekcji i promieniowania cieplnego. Wykonano zaprojektowane kompozyty i przebadano je na specjalnie do tego celu zbudowanym stanowisku do pomiaru oporów cieplnych ciał stałych. Wyniki obliczeń zweryfikowano z wynikami badań eksperymentu. Uzyskano zgodność potwierdzającą teoretyczne rozważania o konstrukcji materiału „kierunkowego".
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The paper presents the continuation of the previous research papers on how to develop a design and technology to produce a sufficiently effective packaging material, which has anisotropic specificity, doesn't limit heat transfer during freezing and could protect a frozen product against uncontrolled and harmful influence of external environment in subsequent reflections, the development of the construction of the material and the technology of the thermal partition is modernized. A new, more advanced mathematical model based on heat conduction equations in heterogeneous media, including conduction, convection and heat radiation is proposed. Composite designs were made and tested on a specially designed bench for measuring the thermal resistance of solids. Results of calculations were verified by experimental work. Theoretical assumptions of the „directional" package construction were confirmed.
Purpose: This paper presents the study aimed at the development of crosslinked poly(methyl methacrylate)s (X-PMMA) of varied crosslink density and the investigation of the relationships between the polymer network structure and dynamic mechanical properties. Methods: A series of model X-PMMA networks were crosslinked by the introduction of: 1, 2, 5, 10 and 20% of triethylene glycol dimethacrylate (TEGDMA). The copolymerizations led to various glass-rubber relaxation properties of the polymer networks, as revealed by dynamic-mechanical analysis (DMA). Glass temperature (Tg) and storage modulus above the Tg ( ) Erubbery were a sensitive function of network architecture. DMA data were used for calculating the network parameter (Mc), crosslink density (q) and its alternative measure – the degree of crosslinking (DX). Results: The viscoelastic properties as well as structural parameters calculated from those showed correlation with the amount of the crosslinker. The increase in TEGDMA content resulted in the Tg, q and DX increases, whereas Mc decrease. The possible incomplete conversion of double bonds was detected in the DMA analysis, which was confirmed by the degree of conversion (DC), measured by FTIR spectroscopy. Additionally, some amount of sol fraction was found by 1H NMR experiments. Conclusions: The structure-property relationships developed for the system presented in this work could be useful in tissue engineering, where X-PMMA is applied. The direct measure of storage modulus values before and above glass transition may serve as a simple and fast indicator of the X-PMMA crosslink density.
Energia promieniowania słonecznego od dawna była wykorzystywana do rozniecania ognia, oświetlenia, ogrzewania pomieszczeń, utrwalania produktów żywnościowych itp. Współcześnie energię słoneczną wykorzystuje się do podgrzewania wody, w procesach produkcyjnych (tj. fermentacji sera, przygotowania pasz, podgrzewania wody technologicznej w małych zakładach przetwórstwa rolno-spożywczego, do suszenia roślin, ziarna, drewna i materiałów budowlanych), do podgrzewania powietrza (do regulacji mikroklimatu w przechowalniach płodów rolnych, ogrzewania pomieszczeń inwentarskich, hal, magazynów, szklarni, tuneli foliowych i budynków mieszkalnych). Suszenie należy do najstarszych metod konserwacji owoców, warzyw, mięsa i ryb. Również i dziś na całym świecie żywność suszy się, poddając ją działaniu słońca. W artykule zaprezentowano przegląd metod wykorzystania słonecznych instalacji powietrznych w technologii utrwalania bądź zagospodarowania różnych grup produktów (suszarnie płodów rolnych, kuchenki słoneczne, suszarnie osadów ściekowych, suszarnie biomasy, suszenie drewna). Opisano właściwości materiału poddawanego obróbce cieplnej oraz procesy wymiany ciepła i masy.
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Solar energy has long been used to kindle fire, lighting, heating, food preservation etc. Today, solar energy is used to heating water in production processes (i.e., fermented cheese, preparation of feed, water heating technology in small-scale food processing, food drying plants, grain, wood and construction materials), to heat the air (to regulate microclimate for storage of agricultural products, heating livestock sheds, halls, magazines, greenhouses, plastic tunnels and residential buildings). Drying is one of the oldest methods of preservation of fruits, vegetables, meat and fish. Even today, worldwide processes of drying food apply sun energy. Overview of the methods of using solar air systems in preservation technology or management of the different product groups (drying of agricultural products, solar cookers, drying of sewage sludge, drying of biomass, drying woods) was described. The properties of the material to be heat treated and the processes of heat and mass was described.
Purpose: The purpose of this study was to investigate the effect of different plasticizing aging solutions on wear resistance and hardness of selected universal resin-based dental composites. Methods: Three light cured (one nanofilled, two microhybride) and one hybride chemical cured composites were aged at 37 °C for 48 h in distillated water, ethyl alcohol solution or Listerine mouthwash. After aging the microhardness tests were carried out and then tribological tests were performed in the presence of aging solution at 37 °C. During wear testing coefficients of friction were determined. The maximal vertical loss in micrometers was determined with profilometer. Results: Aging in all liquids resulted in a significant decrease in hardness of the test materials, with the largest values obtained successively in ethanol solution, mouthwash and water. The effect of the liquid was dependent on the particular material, but not the type of material (interpreted as the size of filler used). Introduction of mouthwash instead of water or ethanol solution resulted in a significant reduction in the coefficient of friction. The lowest wear resistance was registered after aging in ethanol and for the chemical cured hybrid composite, but the vertical loss was strongly material dependent. Conclusions: The effect of different aging solution, including commercial mouthrinse, on hardness and wear was material dependent, and cannot be deduced from their category or filler loading. There is no simple correlation between hardness of resin-based dental composites and their wear resistance, but softening of particular composites materials during aging leads to the reduction of its wear resistance.
Purpose: Thermoplastic materials, such as acetal (AC) and polyamide (PA), constitute an alternative to polymethyl methacrylate (PMMA) based resins as the materials for removable partial dentures. However, none of the previous studies compared chewing efficiency and occlusal forces in the wearers of dentures made of various materials. Therefore, the aim of this study was to determine and compare the chewing efficiency and occlusal forces in PMMA, PA and AC RPDs’ wearers. The hypothesis was that the type of denture base material shows a significant effect on chewing efficiency (expressed as a degree of food fragmentation) and occlusal force. Methods: The experiment included the group of 30 patients using removable partial dentures. The dentures made of PMMA, acetal and polyamide were tested in each patient. Each denture was worn for 90 days, with a random sequence of the denture manufacturing and insertion. After 7, 30 and 90 days of each denture wear, chewing efficiency coefficient was determined with the aid of a sieving method, and occlusal force was measured with a dynamometer. Results: The use of dentures made of PMMA or acetal was reflected by a marked increase in chewing efficiency and occlusal force. None of these parameters changed significantly with the time of denture wear. Moreover, no significant correlation was found between chewing efficiency and occlusal forces. Conclusions: Denture base material exerts significant effects on the degree of food fragmentation and the level of occlusal forces. The use of dentures and clasps made of materials with lower modulus of elasticity is associated with lower chewing efficiency and lower occlusal forces.
The paper presents the evaluation of analgesic effect or magnetostimulation and magnetoledtherapy after implantation treatment. The study was conducted on 3 groups (Z applicator, IR applicator and conventional drug therapy) of 10 patients each of whom underwent a single implantation. Magnetostimulation was carried out using Viofor JPS Delux equipment. The patients were exposed to magnetic field for approx. 15 minutes before the treatment and during the visit after 6 hours after the implantation procedure. Pain perception of patients was recorded on the Visual Analogue Scale (VAS). Results: the most intense pain was reported in the control group. The least intense pain appeared in the group with Z applicator. Patients using Z and IR applicators took analgesics less frequently and used much weaker analgesics than the control group. Pain perceived in the first group was between 0 and 2, while in the second group – between 2 and 3, and in the control group – between 3 and 5 in VAS scale. Magnetostimulation reduces patient’s demand for analgesics after implantation procedures and yielded better effects in reduction of pain in comparison with magnetostimulation with LED therapy.
Introduction: Aesthetic restorations also hale a significant impact on the success of prosthetic treatment which recreates the proper functioning of the teeth. Suitable aesthetic effect is determined by the appropriate restoration of tooth shape and colour. Selecting the proper colour of artificial teeth is difficult and may suffer from many problems in everyday dentistry. In addition, visual assessment for the help of the unique is subjective and may give erroneous results. On the market there are auxiliary device for the instrumental assessment of the colour of teeth: spectrophotometers, calorimeters, colour analyzers computer. They are not commonly used in everyday medical practice. Goal: The aim of the study is to assess the applicability of Sopro 717 intraoral camera in the correct assessment of the colour of teeth. Methods: The study was conducted based on the evaluation of the natural tooth colour visually using the unique “Lumin - Vacuum” by the patient’s dental and medical students in natural light and using the intraoral camera having their own source of light. The experiment involved 40 people aged 22-46 years. The study was conducted to assess the colour of the surface of the cheek teeth 11 or 21 and 32 Takes into account a number of factors affecting the proper assessment of the colour of teeth such as colour space, light intensity, eye fatigue investigator. Results: The evaluation of the occurrence of differences in colour of the teeth within the two mentioned methods. Conclusions: Intraoral camera helps us to choosing the right colour of the tooth. Although this is still a subjective method allows us to reduce the number of errors made in the selection of the proper shade of hard tissues of the tooth.
Laboratory evaluation of spring constants (k) of wrought wire clasps (WWC) separated from removable partial denture (RPD) and the results of tibological tests which represent the dependence of enamel wear with normal force have been presented in the paper. The results of laboratory examinations have been combined with the results of clinical assessment of the level of abutment teeth wear. On the basis of the examinations performed it has been revealed that the following factors have the greatest impact on tribological wear of abutment teeth: the time of using RPD and the normal force exerted by WWC on abutment tooth. Normal force depends to a great extent on the place of contact of WWC with the tooth. It has also been found that abutment teeth featuring higher scale of wear are more loosened. The diameter of wire used for making WWC, total length of the arm and k determined for the total length of the arm did not have any impact upon the scale of wear of abutment teeth.
Artykuł opisuje badania przeprowadzone w celu wyznaczenia współczynników wnikania ciepła czynników z grupy substancji palnych i wykowych buchowych mogących współpracować ze strumienicowym obiegiem chłodniczym. Do badań wykorzystano cztery substancje palne. Otrzymane wyniki porównane zostały ze wzorami teoretycznymi dostępnymi w światowej literaturze.
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The article describes research conducted to determine the nucleate boiling heat transfer coefficient of flammable refrigerants from the group of organic solvents, which may work with ejector cooling systems. Tests have been performed on four substances. The results were compared with several theoretical models available in the literature.
W artykule przedstawiono wyniki badań procesu wrzenia węglowodorów wyższych na płaskiej powierzchni. Otrzymane współczynniki wnikania ciepła porównano z wzorami dostępnymi w literaturze, a także wykonano analizę regresji w oparciu o wzór Mostinskiego. Badania prowadzone były w zakresie temperatury wrzenia od 1,1°C do 20,4°C, pod katem możliwości wykorzystania badanych substancji jako czyn-ników roboczych w strumienicowym obiegu chłodniczym.
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This paper presents experimental results for the nucleate boiling of higher. Hydrocarbons on plain surface at temperature between l ,1 °C and 20,4°C. The obtained heat transfer coefficients were compared with various correlations. The validity of the correlation furnished by Mostinski was tested for the flammable refrigerants.
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The results of previous studies on the pressures beneath the mucous membrane-supported dentures are contrary to the prevailing pain sensations and discomfort reported in practice. In this work, a FEM analysis of large displacements was used for calculation of the contact stresses beneath a lower denture that accompany destabilization under the realistic oblique mastication forces and stabilization of a non-working flange at the balancing contacts. The pressure on the surface of a mucous membrane beneath a denture that was loaded in a stable manner with a vertical occlusal force of 100 N was lower than the pain threshold. It was even more surprising as the extremely unfavorable lower denture foundation conditions were selected for this analysis. The lateral mastication forces destabilized the denture by means of tilting it and reducing its supporting area. Significant pressures calculated for the destabilization are consistent with the clinically observed decrease or a complete lack of chewing efficiency in the cases of unfavorable foundation conditions. A fundamental importance of the balancing contacts for the chewing efficiency was confirmed quantitatively. A remarkable development which has been achieved in the modeling of the denture functioning conditions is crucial for further biomechanical investigations of the mucous membrane-supported dentures, as well as for the implant-retained dentures.
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W artykule przedstawiono różne warianty instalacji cieplnej budynku opierającej się na współpracy powietrznego skupiającego kolektora słonecznego z kamiennym złożem akumulacyjnym. Omówiono wyniki obliczeń modelowych oraz zaproponowano przykładowe rozwiązania architektoniczne dla rozpatrywanego systemu.
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In the paper different variants of the building heat installation based on cooperation of an air concentrating solar collector with accumulation stone deposit system are. The results of model calculations and proposes examples of architectural solutions for the system are discussed.
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W artykule opisano model obliczeniowy instalacji solarnych wbudowany w program użytkowy SOLARSYM 4. Sposób wyznaczania gęstości promieniowania słonecznego oraz temperaturę otoczenia oparto na danych pomiarowych uzyskanych z Obserwatorium Meteorologicznego Zakładu Klimatologii i Ochrony Atmosfery UWr. Za pomocą programu dokonywać można analiz pracy biwalentnego systemu solarnego ogrzewania wody użytkowej lub ogrzewania pomieszczeń. Analizy prowadzić można od pojedynczych dni aż do wielodniowego okresu zamkniętego, maksymalnie całego roku. Przedstawiono kilka przykładów przeprowadzonych analiz. Program obliczeniowy udostępniono do darmowego wykorzystania na stronie internetowej.
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In article, analytical model for solar installations built-in program SOLARSYM 4 was presented. Solar radiation and temperature of environment were determinate thanks to dates form Meteorological Observatory of University of Wroclaw. With the aid of SOLARSYM 4 is possible to make some analysis of work solar bivalent system which heats water or habitats. There is option for making analysis from single day to all year. Few realized examples of installations were presented. Program is available on web site.
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Purpose: of this examination was to evaluate the impact of saturation of adhesive materials by artificial saliva upon the generated bonding force. Design/methodology/approach: Four selected types of denture adhesives have been chosen. Measurements of bonding forces of the materials of different degree of saturation by artificial saliva have been carried out by dynamometer. The stamp covered by denture adhesive was pressed against the glass with force of 30 - 40 N and then keeping perpendicular movement against the glass, the stamp was pulled off and the joining was broken. It has been assumed that the bonding force was the equivalent of maximal pulling off force obtained in the test. The samples of different degree of saturation by artificial saliva have been exposed to tests of extensibility in a device of own design. The final denture adhesives have been put on the complete denture. It was pressed down against the denture bearing area model and next the values of retention forces were determined on a universal testing machine. Findings: Proper saturation of the samples by artificial saliva makes it possible to obtain approximate values of retention force for the majority of denture adhesives. However excessive saturation of adhesive materials can result in considerable reduction of their effectiveness. Research limitations/implications: The samples are handmade as well as part of the measurements are carried out manually and this is justified by the specific clinical conditions. Practical implications: Analysis of the impact of the level of saturation of denture adhesives by artificial saliva upon the generated bonding force highlights the need for individual selection of adhesive creams. The choice of material should be related to individual features such as secretion of saliva. It is advisable to introduce into clinical practice the option of adjusting the optimum saturation of particular denture adhesives by artificial saliva materials. Originality/value: The presented research work results allow to combine the secretion of saliva with the effectiveness of denture adhesives.
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Purpose: The application of single implant-retained dentures (SIDs) is still rare. It seems that the reason of that is the fear of the overloading of a bone tissue around the implant that alone bears the occlusal loads. In this paper, stress level in the bone tissue around the single mini-implant that alone retained the lower denture was investigated. This stress level depends on the denture joint (the attachment) to the implant. Design/methodology/approach: 3D finite element method (FEM) analysis was used in order to determine the transmission of occlusal loads between mucous membrane foundation and the bone tissue around small diameter (1.8 mm) implant. Standard rotationally and axially mobile denture attachments were compared with the laterally compliant silicone attachment. Oblique mastication loads were assumed for the purposes of a better simulation of realistic conditions. Findings: Both types of standard attachments, rotationally and axially mobile, born remarkable values of oblique mastication force. This load results in a high stress in the bone tissue around a single mini-implant, in the area convergent with clinically observed “funnel-shaped” marginal bone loss around the implant neck. The silicone attachment reduced the loading to a level, which did not create any stress that would be dangerous for the bone tissue. Research limitations/implications: In the FEM model a perfect denture adherence to mucous foundation was assumed and a perfect joint between the implant and bone tissue. Further simplification were the linear isotropic characteristics of used materials. Practical implications: The use of single mini-implants requires the highest quality of the alloy and surface finishing due to the risk of fatigue cracks in case of a quickly progressing “funnel-shaped” bone loss. The silicone attachment provided better utilization of the mucous membrane support that significantly improves safety of implant and diminishes the requirements of bone foundation conditions for an implantological treatment. Originality/value: Presented was a possibility to achieve a much more reliable SID by means of used silicone attachment.
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