Sensing of minute airflow motions near walls using pappus-type nature-inspired sensors

This work describes the development and use of pappus-like structures as sensitive sensors to detect minute air-flow motions. We made such sensors from pappi taken from nature-grown seed, whose filiform hairs' length-scale is suitable for the study of large-scale turbulent convection flows. The stem with the pappus on top is fixated on an elastic membrane on the wall and tilts under wind-load proportional to the velocity magnitude in direction of the wind, similar as the biological sensory hairs found in spiders, however herein the sensory hair has multiple filiform protrusions at the tip. As the sensor response is proportional to the drag on the tip and a low mass ensures a larger bandwidth, lightweight pappus structures similar as those found in nature with documented large drag are useful to improve the response of artificial sensors. The pappus of a Dandelion represents such a structure which has evolved to maximize wind-driven dispersion, therefore it is used herein as the head of our sensor. Because of its multiple hairs arranged radially around the stem it generates uniform drag for all wind directions. While still being permeable to the flow, the hundreds of individual hairs on the tip of the sensor head maximize the drag and minimize influence of pressure gradients or shear-induced lift forces on the sensor response as they occur in non-permeable protrusions. In addition, the flow disturbance by the sensor itself is limited. The optical recording of the head-motion allows continuously remote-distance monitoring of the flow fluctuations in direction and magnitude. Application is shown for the measurement of a reference flow under isothermal conditions to detect the early occurrence of instabilities

ФОТОСЕНСИБИЛИЗИРУЮЩЕЕ ДЕЙСТВИЕ БИЛИРУБИНА НА КЛЕТКИ ЖИВОТНЫХ В КУЛЬТУРЕ

The studies performed in this work have shown that the radiation exposure to LED sources with an emission band maximum of about 465 nm corresponding to the absorption spectrum of bilirubin is able to cause damaging effects on animal cells in culture, being in a logarithmic growth stage, that have been pre-incubated with bilirubin. The photobiological effect is caused by photo dynamic processes with participation of singlet oxygen generated by a triplet-excited sensitizer. The type of cell survival depending on an energy dose indicates that the sensitizer serves as bilirubin but not its photoproducts. Исследования, выполненные в настоящей работе, показали, что воздействие излучения светодиодных источников с максимумом полосы излучения около 465 нм, соответствующего спектру поглощения билирубина, способно оказывать повреждающее действие на клетки животных в культуре, находящиеся в логарифмической стадии роста, предварительно инкубированные с билирубином. Фотобиологический эффект обусловлен фотодинамическими процессами с участием синглетного кислорода, генерируемого триплетно возбужденным сенсибилизатором. Вид зависимости выживаемости клеток от энергетической дозы указывает на то, что сенсибилизатором выступает билирубин, а не его фотопродукты

Stress state of plate with incisions under the action of oscillating concentrated forces

This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of oscillating forces. Calculation of dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithmis based on the method of mechanical quadratures and collocation technique. The algorithm is effective in the analysis of the stress state caused by steady-state vibrations of plates

Dynamic stress concentration at the boundary of an incision at the plate under the action of weak shock waves

This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of weak shock waves. For solution of the problem it uses the integral and discrete Fourier transforms. Calculation of transformed dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithm is based on the method of mechanical quadratures and collocation technique. For calculation of originals of the dynamic stresses it uses modified discrete Fourier transform. The algorithm is effective in the analysis of the dynamic stress state of defective plates

Diffraction of resilient waves in endless plates with holes of rectangular form

Розроблено методику дослідження динамічної концентрації напружень біля отворів складної форми у нескінченних пластинках при усталених коливаннях. Для розв’язання поставленої задачі використано метод граничних інтегральних рівнянь у поєднанні з апаратом теорії функцій комплексної змінної та методом механічних квадратур, що дало можливість проводити дослідження областей практично довільної форми. На основі розробленої методики проведено розрахунки напруженого стану нескінченних пластинок з отворами неканонічної форми.The method of research of concentration of tensions near holes of no the canon form in endless plates under steady-state oscillations is developed. A task is solved by the methods of the boundary integral equation, theories of functions of complex variable, mechanical quadrature. Executed test tasks confirm exactness of offered approach. Computations of tense state of endless plates with the rectangular holes are conducted