Vibrational method of cleaning of surfaces from homogeneous waste materials

Cleaning of contaminated surfaces is closely related to the study of adhesion forces between particles and the surface. Despite numerous technological advancements, the adhesion of particles and surfaces is a phenomenon that is far from being fully understood. This is due to many factors acting during process, - such as the surface roughness and material type, size, shape, electrostatic properties of particles, etc. A surface cleaning device based on nonlinear vibration of the contact element is presented in this paper. Relationships describing the periodic motion in steady state operating regimes are obtained. Characteristics of motion as functions of the frequency of excitation are investigated. Experimental investigations were performed for the determination of the influence of the cleaning velocity on the vibration frequency. It is shown that this dependence is directly related to adhesion forces between particles and the surface. Test results are in good accordance with theoretical predictions

Квазистатические магнитные свойства и высокочастотные энергетические потери в наночастицах CoFe₂O₄

Две серии наноразмерных частиц кобальтовых ферритов-шпинелей CoFe₂O₄ синтезированы из солей металлов с применением высокоэнергетической шаровой мельницы с добавлением NaCl в качестве агента роста (серия CFO-NaCl) или без него (серия CFO). Свойства частиц охарактеризованы с помощью атомной силовой микроскопии, магнитных и калориметрических измерений. Показано, что средние размеры нано- частиц составляют ∼5,6 и ∼10,3 нм для CFO и CFO-NaCl серий соответственно. Выполнены магнитостатические измерения и определены параметры, необходимые для анализа магнитного состояния и процессов перемагничивания наночастиц. Показано, что температура блокировки составляет ≈ 160 К для образцов серии CFO и ≈ 300 К для образцов серии CFO-NaCl. Сделан вывод, что при 293 К частицы серии CFO пребы- вают в суперпарамагнитном, а частицы серии CFO-NaCl — в блокированном состояниях. Измерена экспериментально и оценена теоретически удельная мощность, которая рассеивается ансамблями синтезированных наночастиц при помещении их в переменное магнитное поле. Проанализирована природа процессов, определяющих тепловые характеристики наночастицДві серії нанорозмірних частинок кобальтових феритів-шпінелей CoFe₂O₄ синтезовано із солей металів з використанням високоенергетичного шарового млина з додаванням NaCl в якості агенту росту (серія CFO-NaCl) або без нього (серія CFO). Властивості частинок охарактеризовано за допомогою атомної силової мікроскопії, магнітних і калориметричних вимірювань. Показано, що середні розміри наночастинок складають ∼5,6 та ∼10,3 нм для CFO й CFO-NaCl серій відповідно. Виконано магнітостатичні вимірювання і визначено параметри, необхідні для аналізу магнітного стану і процесів перемагнічування наночастинок. Показано, що температура блокування складає ≈ 160 К для зразків серії CFO та ≈ 300 К для зразків серії CFO-NaCl. Зроблено висновок, що при 293 К частинки серії CFO знахо- дяться в суперпарамагнітному, а частинки серії CFO-NaCl — в блокованому станах. Виміряно експериментально і оцінено теоретично питому потужність, яка розсіюється ансамблями синтезованих наночастинок при поміщенні їх у змінне магнітне поле. Проаналізовано природу процесів, які визначають теплові характеристики наночастинок.Two series of nanosized cobalt spinel ferrites CoFe₂O₄ are synthesized from metal salts using high-energy ball milling with the addition of NaCl as a growth agent (series CFO-NaCl), and without (CFO Series). The particle properties are characterized using atomic force microscopy, as well as magnetic and calorimetric measurements. It is shown that the average sizes of the nanoparticles were ∼5.6 and ∼10.3 nm for CFO and CFO-NaCl series, respectively. We performed magnetostatic measurements and determined the parameters that are required to analyze the magnetic state and remagnetization processes of the nanoparticles. It is shown that the blocking temperature is ≈160 K for CFO samples and ≈300 K for the CFO-NaCl series. It was concluded that at 293 K the CFO series particles exhibit a superparamagnetic state, whereas the CFO-NaCl series are in the blocked state. The specific loss power that is scattered by the synthesized nanoparticle ensembles placed in an alternating magnetic field, is measured experimentally and theoretically assessed. The nature of the processes that determine the thermal characteristics of the nanoparticles is analyzed

Oxidation of Stainless Steel by Laser Cutting

Oxidation of erosion products was studied by means of the Mössbauer spectroscopy and X-ray diffraction methods when the strip of stainless steel was cut with the laser. Different content of wustite and chromium doped magnetite $Fe_{3-x}Cr_{x}O_{4}$ was found in the samples of erosion products depending on the place where the erosion products were collected in relation to the cutting slot. Conversion electron Mössbauer spectroscopy data showed that more magnetite was found at the surface while wustite distributes in the whole volume of particles of erosion products

Ecosystem size and flooding drive trophic dynamics of riparian spiders in a fire-prone Sierra Nevada river system

Disturbance can play an important role in structuring stream food webs. Although floods have received the greatest attention as a disturbance agent in rivers, wildfire â which can strongly influence fluvial ecosystem structure and function â may also drive consumer trophic dynamics. We measured the relative effects of wildfire, hydrologic disturbance, ecosystem size, and canopy openness (as a proxy for in-stream productivity) on trophic position and reliance on aquatically-derived nutritional subsidies of riparian spiders of the family Tetragnathidae along two rivers on the west slope of the Sierra Nevada in California, USA. Ecosystem size received strong support as an environmental determinant of both trophic measures, with variability in flood magnitude emerging as an important mechanism linking ecosystem size and trophic responses. Piecewise linear regression revealed significant breakpoints in spider trophic position and reliance on aquatically-derived nutritional subsidies that were related to thresholds in fire extent within the catchment. These non-linear relationships with wildfire may lend additional insight into the potential interactions among ecosystem size, productivity, and disturbance that determine stream-riparian food web architecture.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author