MAGIA – RELIGIA – OSTENTACJA. KAPTORGI Z WCZESNOŚREDNIOWIECZNEGO CMENTARZYSKA W RADOMIU W UJĘCIU KOMPARATYSTYCZNYM

This article presents an analysis of two brass lockets, rectangular in shape, discovered in a richly equipped grave no. 62 in an early-medieval grave field in Radom (the 4th quarter of the 11-12th centuries). As a result of the analysis, their cognitive value can be estimated in a comprehensive way against the background of other finds of the type excavated in graves. On the other hand, it has allowed to enrich the knowledge of burying the dead with objects of magical and religious nature. The lockets discovered in Radom were made locally, most probably as imitations of more sophisticated pendants. Most probably, they were used as containers for magical or healing amulets, possibly contact relics (brandeum, eulogiae) or perfumes. They were probably buried after mid-11th century, during the religious transformation taking place in the early Piast state, bearing material testimony to the intertwining pagan rites and the ceremonies of the new faith.

Production of Nanocellulose Crystal Derived from Enset Fiber Using Acid Hydrolysis Coupled with Ultrasonication, Isolation, Statistical Modeling, Optimization, and Characterizations

Currently, many scholars are looking for renewable biomass sources for the isolation of nanomaterials that have a sustainable property and are ecofriendly. Thus, effectively synthesize and characterization enset fiber nanocellulose using acid hydrolysis with sonication is focus of study. Additionally, process optimization for isolation of nanocellulose (CNCs) from raw enset fiber using RSM-CCD and characterizations of obtained CNCs was explored. The quadratic model was selected, and optimized values for CNCs yield (77.69%) that were acquired to be H2SO4: 51.6 wt. %, reaction temperature: 47°C, and time: 66.5 min. Chemical composition analysis, XRD, FTIR, PSA, SEM, and TGA were used for characterizing CNCs. The particle size distribution of CNCs is 66 nm. It has a crystalline index of 80.91% and excellent thermal stability. FTIR and chemical composition result indicated the reduction and removal of lignin and hemicellulose components that are usually available in the raw enset fibers. The SEM analysis reveals the structure and arrangement of the fiber bundles inside the raw material to nanocellulose. This property shows its endowing as a possibly consistent load-bearing material. This study could be given a noteworthy thought for designing and emerging CNC isolation, optimization, and industrial application.

An Experimental Study of Tribological Behavior of Journal Bearing Material under Powder and Granular Lubrication

Proper lubrication of mechanical components is very important for the reliable efficiency and useful life. The working temperature of the components can affect the lubricating oil and can degrade the lubricating characteristics of oil. This paper presents the experimental investigation on tribological behaviour of journal bearing material. Two types of additives are used in lubricating oili.e., powder and granular types of additives. The investigation is carried out on pin-on-disc apparatus to determine the wear and coefficient of friction. The statistical analysis is performed using design of experiments and Taguchi robust design to determine the optimum parameters of lubricating additives. It is found that for constant speed of 400 rpm with 5% concentration with varying size the granular lubrication have lower values than powder lubrication for all load conditions Keywords: Lubrication, pin-on-disc, Taguchi, additives.

Excellent Seizure and Friction Properties Achieved with a Combination of an a-C:H:Si DLC-Coated Journal and an Aluminum Alloy Plain Bearing

Friction occurring between the crank journal and main bearings accounts for a large share of the mechanical losses of automotive engines. The effects of higher in-cylinder pressures and narrower bearings have raised the specific load applied to bearings, making it essential to secure sufficient seizure resistance as well. For the purpose of meeting both requirements, we have endeavored to reduce friction and improve seizure resistance by applying a diamond-like carbon (DLC) coating to the crank journal. In the present study, a bearing tester was used that has received international standard certification from the International Organization for Standardization for reproducing the sliding behavior occurring between the crank journal and main bearings in actual engines. Test results indicated that a silicon-containing hydrogenated amorphous carbon (a-C:H:Si) DLC-coated journal showed a definite friction reduction and a marked improvement in seizure resistance. An acoustic emission (AE) analysis revealed that an adhesion-induced AE peak observed for a steel journal was not seen for the DLC-coated journal. Additionally, tin and aluminum elements in the bearing material that were transferred to and observed on the sliding surface of the steel journal were not seen on the DLC-coated journal. Accordingly, the low affinity of the DLC coating with these metal elements presumably led to the clear friction reduction and superior seizure resistance displayed by the DLC coating.

CONSTRUCTION OF A MODEL FOR OBTAINING PRESS OIL IN OIL-COMPRESSION UNITS TAKING INTO ACCOUNT THE HYDRODYNAMICS OF THE LAYERED FLOW OF THE MATERIAL OF NON-NEWTONIAN RHEOLOGY

Решением уравнения Навье–Стокса в задачах Куэтта–Пуазейля были определены границы, в рамках которых описан процесс отжима прессового масла с помощью геометрических и скоростных параметров витков шнека. Вычисления производились для материала с высокой вязкостью, имеющего характеристики эффективной вязкости неньютоновской реологии. С использованием балансовых соотношений потоков удалось спрогнозировать работу маслоотжимных агрегатов в режиме форпрессования и экспеллера. В результате выведена модель отжима растительных масел на основе гидродинамики слоистого течения масличного материала в маслоотжимных агрегатах с учетом распределения потока и гидростатического давления в каналах витков шнека. Использование модели двумерного слоистого течения на основе решения задачи Куэтта–Пуазейля базируется на уравнении Навье–Стокса для установившегося режима. Результаты моделирования основаны на технологических параметрах мезги, поступающей на прессование, начальной масличности подсолнечной мезги и начальном расходе, равном 380 кг/ч, который определяется согласно пропускной способности как аналитическое решение этой задачи. Верхняя граница применимости модели слоистого течения масличного материала определяется соотношением геометрии витка шнека с минимальной пропускной способностью 154 кг/ч и содержанием масла в этом материале в диапазоне от 0 до 0,5 кг на 1 кг масличного материала. Нижняя граница применимости этой модели определяется идеализированным случаем экструдирования мезги по каналам шнека при отсутствии отжима. Зависимости изменения давления от расхода мезги, получаемые на основе слоистой модели, позволяют надежно интерполировать распределение давления по виткам шнека в процессе отжима масличного материала. На практике достигнута остаточная масличность жмыха 10% при производительности 200 кг/ч, что дает хорошее совпадение с полученными расчетными значениями. By solving the Navier–Stokes equation in the Couette–Poiseuille problems, the boundaries were determined, within which the process of pressing oil is described using the geometric and speed parameters of the auger turns. The calculations were performed for a high viscosity material having non-Newtonian rheology effective viscosity characteristics. Using the balance flow ratios, it was possible to predict the operation of the oil-pumping units in the pre-pressing and expeller mode. As a result, a model of vegetable oil extraction is derived based on the hydrodynamics of the layered flow of oilseed material in oil-pressing units, taking into account the flow distribution and hydrostatic pressure in the channels of the auger turns. The use of a two-dimensional layered flow model based on the solution of the Couette–Poiseuille problem is based on the Navier–Stokes equation for the steady-state regime. The simulation results are based on the technological parameters of the pulp entering the pressing – the initial oil content of the sunflower pulp and the initial flow rate of 380 kg/h, which is determined according to the throughput as an analytical solution to this problem. The upper limit of the applicability of the model of layered flow of oil-bearing material is determined by the ratio of the geometry of the auger turn with a minimum throughput of 154 kg/h and the oil content in this material in the range from 0 to 0,5 kgper 1 kgof oil-bearing material. The lower limit of the applicability of this model is determined by the idealized case of extrusion of pulp through the auger channels in the absence of pressing. The dependences of the pressure change on the pulp flow rate, obtained on the basis of the layered model, allow us to reliably interpolate the pressure distribution along the auger turns during the pressing of oilseed material. The residual oil content of the oilcake is about 10% at a capacity of 200 kg/h, which gives a good match with the calculated values.

ANALYSIS AND MODELING OF THE KINETICS OF THE EXTRACTION OF VEGETABLE OILS ON THE TURNS OF OIL-PRESSING UNITS

Используемые в промышленности форпрессы для предварительного съема масла и экспеллеры для окончательного отжима различаются геометрией витков шнекового вала. В настоящее время наметилась тенденция к объединению этих аппаратов в единый маслоотжимной агрегат на основе геометрии наборов витков форпресса и экспеллера или двух совращающихся шнековых валов, позволяющих значительно увеличить продолжительность процесса за счет увеличения длины шнековых каналов. Предложено аналитическое решение математической модели распределения потока и гидростатического давления масличного материала в процессе отжима растительного масла непрерывным способом в канале витка шнекового пресса. Показана возможность математического моделирования этого процесса на основе двумерной модели слоистого течения неньютоновской жидкости с учетом геометрии витков шнекового вала и скорости его вращения, позволяющая рассмотреть этот процесс для современных маслоотжимных агрегатов на основе геометрии наборов витков форпресса и экспеллера или двух совращающихся шнековых валов. Получена оценка пропускной способности канала с учетом сопротивлений выходного устройства, а также аналитическое решение распределения потока и гидростатического давления масличного материала в процессе отжима растительного масла. Used in the industry the pre-oil extraction pre-presses and the expellers for the final spin differ in the geometry of the screw shaft turns. Currently, there is a tendency to combine these devices into a single oil-pumping unit based on the geometry of the sets of turns of the forpress and expeller or two rotating screw shafts, which can significantly increase the duration of the process by increasing the length of the screw channels. An analytical solution is proposed for a mathematical model of the distribution of flow and hydrostatic pressure of oil-bearing material in the process of pressing vegetable oil in a continuous way in the channel of the screw press. The possibility of mathematical modeling of this on the basis of a two-dimensional model of a layered flow of a non-newtonian fluid, taking into account the geometry of the turns of the screw shaft and the speed of its rotation, is shown, which makes it possible to consider this process from a single point of view of using modern oil-extracting units, both on the basis of the geometry of sets of turns of the forpress and expeller, and two screw shafts. As a result of the conducted studies, an estimate of the channel capacity was obtained, taking into account the resistances of the output device, as well as an analytical solution for the distribution of the flow of oilseed material and the hydrostatic pressure of the oilseed material during the extraction of vegetable oil.

Myxomycetes biodiversity in Gaziantep Province (Turkey) with four new records

Myxomycetes were cultured in moist chambers using substrate material collected in Gaziantep province, Turkey, during 2017–2019. Fruit bodies of wild myxomycetes were collected at ten locations. Rotten or live tree bark, leaves, debris, vegetable, and animal material, which were considered likely to contain spores, were also collected. Natural samples were immediately dried, and potential spore-bearing material was kept in a warm and humid environment with the moist chamber technique. A total of 537 samples were studied and 203 myxomycetes isolates were obtained, 33 of which were natural samples, 76 were obtained with the moist chamber technique and 94 were obtained both naturally and with the moist chamber technique in the laboratory. Six orders, 9 families, 16 genera and 42 species were identified in 3 subclasses. All species were new in Gaziantep province and four myxomycetes were identified as new records in Turkey; Didymium atrichum Henney & Alexop., Didymium serpula Fr., Craterium obovatum Peck and Physarum bivalve Pers. were added to the Turkish mycota.

Finding the optimum layout for cable-stayed bridge in conceptual design

<p>In the cable-stayed bridges the primary cost components of the load-bearing material, in the longitudinal direction of the bridge, are the cables. The longer the bridge, the higher the share of the costs of the load-bearing material. The quantity of the cables and the cost optimized cable and tower topology can be reliably solved, already in very early design stages, using a simple calculation method proposed in this article. The cables are considered as a curtain structure and the cable forces are calculated for the permanent load balance. The solutions are performed mathematically by using integral calculus based on a force length method and a unit bridge concept. The results provide a good idea of the optimum pylon height for both one-pylon and two-pylon bridges. The optimum pylon height depends on the span ratio and the chosen cable system.</p>