Усовершенствованная модель прессования порошковой смеси в валковом прессе

A new mathematical model of mineral fertilizer compacting using a roll compactor is developed. This model is based on the transition to the values of stress tensor components averaged over the cross-sectional area of the powder mixture flow. To define these stresses, equations of equilibrium of the elementary layer determined in the mixture by two planes perpendicular to the flow direction are composed. To obtain relatively simple analytical relations in the calculations, the hypothesis of a power-law dependence of hydrostatic pressure on mixture density, accepted in the framework of the Johansen model, was used. In order to take into account changes in the mechanical characteristics of the mixture (angle of internal friction, coefficient of external friction, transverse strain coefficient) while compacting, we approximated the known experimental dependencies of the corresponding characteristics on the density. The inter-particle cohesion parameter was taken to be proportional to the hydrostatic pressure. The model allows calculating the gap between the rolls surfaces for a given initial bulk density and the required flake density. With the known gap value, the distribution of the axial average stresses in the powder mixture, the normal and shear stresses on the rolls’ surfaces are determined. The results of the calculations of the rolls surface gap and the normal roll pressure diagram are compared with the experimental data given in the literature for the urea compacting process.Разработана математическая модель прессования минерального удобрения на валковом прессе. Данная модель основана на переходе к усредненным по площади поперечного сечения потока порошковой смеси значениям компонент тензора напряжений. Для определения этих напряжений составляются уравнения равновесия элементарного слоя, выделяемого в смеси двумя плоскостями, перпендикулярными к направлению потока. Для обеспечения возможности получения относительно простых аналитических соотношений при расчетах использована принятая в рамках модели Йохансена гипотеза о степенной зависимости гидростатического давления от плотности смеси. Для учета изменения механических характеристик смеси (угла внутреннего трения, коэффициента внешнего трения, коэффициента поперечной деформации) в процессе прессования производилась аппроксимация известных экспериментальных зависимостей соответствующих характеристик от плотности. Параметр межчастичного сцепления принимался пропорциональным гидростатическому давлению. Модель позволяет вычислить значение зазора между поверхностями валов при заданных значениях исходной насыпной плотности смеси и требуемой плотности плитки. При известном значении зазора устанавливаются распределения осевых усредненных напряжений в порошковой смеси, нормального и сдвигового напряжений на поверхности валов. Результаты расчетов зазора между поверхностями валов и эпюры нормального давления на вал сопоставлены с приведенными в литературных источниках экспериментальными данными для процесса прессования мочевины

Моделирование радиальных колебаний подпружиненного валка вальц-пресса

Carried out simulation of oscillations of a spring-loaded roll in a roll compactor when interacting the powder being compacted with the rolls. Considering the separation of the feed and compaction areas in the contact area of the roll with the material being compacted, we obtain the dependence of the force acting on the roll on the gap size between the rolls. It is shown that this dependence is non-linear, and it can be described with a sufficiently high accuracy degree by an exponential function with a negative exponent in the working range. The given numerical solution of the equation of free nonlinear oscillations of the spring-loaded roll has shown that considering the deformation of the material being compacted leads to a reduction of the natural frequency of the system by 20–25 % compared to the case, where the pressure force of the powder on the roll is assumed to be independent of the gap size. The nonlinearity of the dependence of the pressure force on the gap also leads to the increase by 10 % in the calculated values of the maximum displacements. The developed approach to the calculation of oscillations of the spring-loaded roll in the roll compactor enables to take into account the peculiarities of deformation of the powder being compacted during its interaction with the rolls. In addition, it allows estimating the frequencies and oscillation amplitudes and setting the optimum range of spring rate values, at which the occurrence of resonance in the machine is not possible.Выполнено моделирование колебаний подпружиненного валка вальц-пресса при взаимодействии прессуемого порошка с валками. С учетом выделения в области контакта валка с прессуемым материалом зон подачи и прессования, получена зависимость силы, действующей на валок, от величины зазора между валками. Показано, что эта зависимость имеет нелинейный характер, причем в рабочем диапазоне с достаточно высокой степенью точности может быть описана степенной функцией с отрицательным показателем степени. Приведено численное решение уравнения свободных нелинейных колебаний подпружиненного валка, которое продемонстрировало, что учет деформирования сжимаемого материала приводит к снижению частот собственных колебаний системы на 20–25 % по сравнению со случаем, при котором сила давления порошка на валок принимается не зависящей от величины зазора. Нелинейность зависимости силы давления от зазора приводит также к увеличению на 10 % расчетных значений максимальных смещений. Разработанный подход к расчету колебаний подрессоренного валка вальц-пресса позволяет учесть особенности деформирования прессуемого порошка при его взаимодействии с валками, а также позволяет, наряду с оценкой частот и амплитуд колебаний, установить оптимальный диапазон значений коэффициента жесткости пружины, при котором появление резонанса в машине будет невозможно

Birefringence of nanoporous alumina: Dependence on structure parameters

We report on experimental and theoretical investigations of the birefringence of free-standing nanoporous anodic alumina membranes in the optical range. The value of birefringence is analyzed for the samples with different porosities by measuring polarization dependent transmission spectra at different angles of incidence. The experimental data are compared to the results of birefringence simulations in accordance with the modified Bruggeman effective-medium approximation. It is both experimentally and theoretically shown that the birefringence value increases with porosity increases in the low porosity region. The porous alumina samples under investigation possess the greatest value of birefringence (0.062) up to the present

Macroscale alignment of CdSe/CdS nanorods by porous anodic alumina templates

Centimeter-scale assemblies of highly ordered CdSe/CdS core-shell nanorods have been successfully fabricated by infiltration of the nanorods into the pores of a transparent porous anodic alumina membrane. The high degree of the nanorod ordering is proved by the demonstration of both highly polarized PL and absorption of the aligned nanorods. The measured PL linear polarization degree is 53%. We have found that both the elongated CdS shell and the nearly spherical CdSe core exhibit a strong dependence of absorption on polarization angle with respect to the nanorod axis. We conclude that both CdS shell and CdSe core absorb more efficiently light with polarization along the axis of the nanorod

Er-doped Oxidized Porous Silicon Waveguides

The present work reports Er-doped channel oxidized porous silicon waveguides (OPSWG) formed from n+-type Si by the two-step anodisation process. Er has been introduced into porous silicon before oxidation by a cathodic treatment in 0.1 M Er (NO3)3 aqueous solution. A correlation between Er concentration and refractive index profiles has shown dominant core doping with Er relative to cladding regions. Reported Er concentration of 0.8 at.% in the OPSWG is large enough to attain the amplification effect

Еколого-економічний експеримент у містах Дніпродзержинську і Кривому Розі: аналіз п’ятирічного досвіду та перспективи

Results on environmental management experiment in the cities of Dniprodzerzhinsk and Kryvyi Rig are discussed. Parameters of the state of environment in 2000-2004 have steady tendency for worsening.Обговорюються результати еколого-економічного експерименту в містах Дніпродзержинську та Кривому Розі. Показники стану навколишнього середовища в 2000–2004 рр. мають стійку тенденцію погіршення.Обговорюються результати еколого-економічного експерименту в містах Дніпродзержинську та Кривому Розі. Показники стану навколишнього середовища в 2000–2004 рр. мають стійку тенденцію погіршення

Deposition of Erbium Containing Film in Porous Silicon from Ethanol Solution of Erbium Salt

Electrochemical treatment of porous silicon (PS) in ethanol solution of Er(NO3)3 was investigated to obtain material suitable for optoelectronic application. The voltammograms of n+-type and p-type PS vs. an Ag/AgCl reference electrode were examined and compared with these of a Pt electrode. The basic cathode reactions were marked out the voltammograms: (i) the formation and the adsorption of atomic hydrogen; (ii) the formation of molecular hydrogen; (iii) the electrolysis of water and ethanol. No zones relating to on electrochemical transitions of Er ions were revealed on the voltammograms. Nevertheless, with the cathode polarization, the formation of an Er-containing deposit was observed at the surface of the cathode. The IR and SIMS analysis were used to study the composition of the deposits. The scheme of the electrochemical and chemical reactions at the cathode is discussed

CLINICAL AND HISTOLOGIC FEATURES OF UTERINE MYOMA IN REPRODUCTIVE-AGE WOMEN UNDER THE TREATMENT BY SELECTIVE PROGESTERONE RECEPTOR MODULATORS

Aim of the study was to investigate the clinical features of reproductive age women with uterine body myoma and the production of vascular endothelial growth factor (VEGF) in the dominant myoma node and perifocal myometrium under the preoperative use of ulipristal acetate (UA). Material and methods. 140 samples of 35 women surgical material were studied, VEGF content in the incubation medium of samples of myoma and myometrium was measured using enzymelinked  immunosorbent assay.Results and discussion. The treatment by UA before myoma surgery according to the standard regimen per 5 mg daily for 13 weeks deals with significantly reduced production of VEGF in the dominant myoma node compared to perifocal myometrium (p < 0.001), which is similar to patients of the control group. However, when comparing tumor nodes, a significantly lower content of VEGF was revealed in the UA-group (p = 0.026); unlike the perifocal myometrium samples. Conclusion. The use of a selective modulator of progesterone receptors downregulates the production of VEGF by the cells of the myoma nodes and doesn’t impact on the perifocal myometrium

The analysis of the prevalence of extragenital pathology in infertile women with external genital endometriosis

Background. External genital endometriosis (EGE) is often the cause of infertility, while coagulation of its foci leads to the restoration of fertility. Often, non-invasivepreoperative diagnosis of EGE is difficult. Today, the issue of laparoscopy in infertility and whether there is a need for additional indications for its implementation remains controversial. Identification of the relationship between certain extragenital diseases with EGE is promising in terms of both understanding the pathogenesis of EGE and predicting its development.The aim. Identification of the relationship of extragenital diseases with the presence of EGE in infertile women of reproductive age.Materials and methods. In preparation for assisted reproductive technology programs at the Vitromed Clinic, 1 132 women of reproductive age were examined from 2019 to 2021. Collection and processing of clinical and anamnestic data were carried out. The diagnosis of EGE was verified by laparoscopy with histological examination. The results were analyzed using exact test and binary logistic regression to build a model of the relationship between EGE and somatic pathology.Results. EGE was detected in 222 patients. A number of somatic diseases were found that are most common in EGE: bowel diseases; minor cardiac maldevelopments; chronic anemia; pathology of the pancreas; chronic tonsillitis; allergy. A logistic regression model was constructed to predict the presence of EGE in patients with the indicated somatic pathology with a sensitivity of 81.53 % and a specificity of 97.25 %.Conclusion. Identification of comorbid extragenital diseases associated with EGE in women with infertility can serve as a basis for expanding the scope of therapeutic and diagnostic measures, in particular for laparoscopy