Optimization of Adams-type difference formulas in Hilbert space W2(2,1)(0,1)W_2^{(2,1)}(0,1)

In this paper, we consider the problem of constructing new optimal explicit and implicit Adams-type difference formulas for finding an approximate solution to the Cauchy problem for an ordinary differential equation in a Hilbert space. In this work, I minimize the norm of the error functional of the difference formula with respect to the coefficients, we obtain a system of linear algebraic equations for the coefficients of the difference formulas. This system of equations is reduced to a system of equations in convolution and the system of equations is completely solved using a discrete analog of a differential operator $d^2/dx^2-1$. Here we present an algorithm for constructing optimal explicit and implicit difference formulas in a specific Hilbert space. In addition, comparing the Euler method with optimal explicit and implicit difference formulas, numerical experiments are given. Experiments show that the optimal formulas give a good approximation compared to the Euler method

COMBINED UNCOVERED SHEET-AND-TUBE PVT-COLLECTOR SYSTEM WITH BUILT-IN STORAGE WATER HEATER

This work describes the design and investigation of a simple combined uncovered sheet-and-tube photo-voltaic-thermal (PVT) collector system. The PVT-collector system consists of a support, standard PV module (1.22x0.305m, area=0.37m2, fill factor=0.75), sheet-and-tube water collector and storage tank-heater. The collector was fixed under PV module. Inclination angle of the PVT-collector to the horizontal plane was 45 degree. The storage tank-heater played double role i.e. for storage of hot water and for water heating. The PVT-collector system could work in the fixed and tracking modes of operation. During investigations of PVT-collector in natural conditions, solar irradiance, voltage and current of PV module, ambient temperature and water temperature in storage tank were measured. Average thermal and electrical powers of the PVT-collector system at the tracking mode of operation observed were 39W and 21W, with efficiencies of 15% and 8% respectively at the input power of 260W. The maximum temperature of the water obtained was 42oC. The system was observed efficient for low-temperature applications. The PVT-collector system may be used as a prototype for design of PVT-collector system for domestic application, teaching aid and for demonstration purposes

Immunological indicators of complications of surgical bowel disease in children

The article is devoted to the development of immunological indicators of intestinal inflammation in children, which is of great importance for health authorities when organizing specialized pediatric and surgical services. The proposed method contributes to the early diagnosis and prevention of complications of inflammatory surgical bowel diseases in children, which is of great practical importance. The purpose of the study: To develop immunological indicators of complications of surgical bowel diseases in children. A retrospective analysis of 867 case histories of children who received inpatient treatment at the Department of Pediatric Surgery of the Bukhara branch of the Republican Scientific Center of Emergency Medical Care from 2019 to 2022 for surgical diseases of the gastrointestinal tract was carried out. The authors conducted an immunological study of 91 pediatric patients. All children underwent immunological blood tests: cellular and humoral immunity, cytokines (TNFα, IFNα, IL-8, MCP-1 and vascular endothelial growth factor VEGF-A) were studied. For the prevention of postoperative complications of CKD in children, it is recommended to determine IFNα in the blood serum in the period before surgery to solve the indications for immunocorrection. A noticeable positive relationship was established between IFNα and CD8 – r = 0.34, between IFNα and CD23 – r = 0.38, between IFNα and IgA – r = 0.39, between IFNα and PCT – r = 0.36. At the same time, PCT has a noticeable negative relationship with CD16 – r = -0.31 and with CD8 – r = -0.31 against the background of a noticeable positive relationship with IgG – r = 0.32 and IFNα – r = 0.36. It was found that IFNα is a more informative indicator of the effectiveness of the immune response, and PCT is an indicator of the effectiveness of antibacterial therapy in surgical bowel diseases in childre

The Photo-Electrical Behavior of n-Si and p-Si/Orange Dye/ Conductive Glass Cells

The photo-electrical behavior of n-Si/orange dye/conductive glass and p-Si/orange dye/conductive glass sandwich type cells were investigated. In these cells crystal silicon of n-type and p-type and conductive glass (CG) electrodes were employed and the aqueous solution of organic dye (OD) was used as an electrolyte in the distilled water. Under filament lamp illumination, photo-induced open-circuit voltage and shortcircuit current exponentially dropped with time for the n-Si/orange dye/CG cell. In the p-Si/orange dye/CG cell, the photovoltaic effect was not observed. The n-Si/OD/CG cell showed high photo-electrical response under illumination. In the light-voltage/current conversion, these cells behaved as a differentiator and exhibited charge-storage properties

Pressure Sensitive Sensors Based on Carbon Nanotubes, Graphene, and Its Composites

Carbon nanotubes (CNTs) and graphene have attracted a great deal of interest due to their outstanding mechanical, optical, electrical, and structural properties. Most of the scientists and researchers have investigated the optical and electrical properties of these materials. However, due to unique electromechanical properties of these materials, it is required to explore the piezoresistive properties of bulk nanostructured CNTs, graphene, and CNT-graphene composites. We investigated and compared the sensitivities and piezoresistive properties of sandwich-type pure CNT, pure graphene, and CNT-graphene composite pressure sensors. For all the samples, increase in pressure from 0 to 0.183 kNm−2 results in a decrease in the impedance and direct current (DC) resistance. Sensitivity and percentage decrease in resistance and impedance of CNT-graphene composite were lower than pure CNT while being higher than pure graphene based sample. Moreover, under the same external applied pressure, the sensitivity and percentage decrease in impedance for pure CNT, pure graphene, and CNT-graphene composite were smaller than the corresponding sensitivity and percentage decrease in resistance. The achieved experimental results of the composite sample were compared with simulated results which exhibit reasonable agreement with each other. The deviations of simulated resistance-pressure and impedance-pressure curves from experimental graphs were 0.029% and 0.105%, respectively

THE ECONOMICS OF BIOGAS PRODUCTION

ABSTRACT: In this paper life-cycle cost analysis of three biogas digesters is presented. Results show that the cost of biogas depends on the construction of digesters, sizes of methane tank and possibility of heating of the slurry. Biogas and natural gas costs calaculated are observed and found to be comparable. It is recommended that the biogas digesters can be constructed and installed, in principle, for every family and there is no need to built long gas pipe lines.   ABSTRAK: Kertaskerja ini membentangkan analisis kos kitar hayat tiga pencerna biogas. Keputusan menunjukkan kos biogas bergantung kepada pembinaan pencerna, saiz tangki metana dan kemungkinan pemanasan buburan. Pengiraan kos biogas dan gas asli diambil kira dan ianya didapati setanding. Adalah disarankan pencerna biogas boleh dibina dan dipasang secara teorinya, bagi setiap keluarga tanpa memerlukan pembinaan paip gas yang panjang

THE ECONOMICS OF MICROHYDRO POWER PLANTS

ABSTRACT:  In this paper economics of a micro-hydropower plant installed in the village named Pashmi-Kuhna of Tajikistan and of a battery-based micro-hydropower plant on catamaran for free water flow operation designed, fabricated and tested in GIK Institute of Pakistan are discussed. For the economic evaluation of these power plants, the life-cycle costing approach is used.  Finally the costs of the produced energy by the micro-hydropower plants are calculated.   ABSTRAK: Menerusi kertas kerja ini, bidang ekonomi loji hidrokuasa mikro yang dibina di perkampungan  Pashmi-Kuhna, Tajikistan diperbincangkan. Loji hidrokuasa mikro di atas katamaran yang membolehkan gerakan air bebas berasaskan bateri direka, dicipta dan diuji di Institut Pakistan GIK. Untuk penilaian ekonomi loji ini, pendekatan pengekosan kitar hidup telah digunakan. Akhirnya, kos dihitung berdasarkan kuasa yang dihasilkan oleh loji hidrokuasa mikro

Effect of Temperature and Humidity on Electrical Properties of Organic Orange Dye Complex Films

In this study the effect of temperature and humidity on electrical properties of organic orange dye (OD) complex with vinyl-ethynyl-trimethyl-piperidole (VETP) have been examined. Thin films of OD (C17H17N5O2) and VETP (C12H19NO) complex were deposited from 10 wt.% (5 wt.% of each matter) solution in mixture of distilled water (80%) and spirit. The films were grown at room temperature under normal gravity conditions, i.e., 1 g and in a spin coater at an angular speed of 300 RPM. The Cu/OD-VETP/Cu surface type samples were fabricated and their low frequency (10 Hz) AC electric characteristics were evaluated for the temperature range 30-95 °C at ambient humidity of 45-80%. It was observed that at normal conditions the conductivity of the samples is temperature dependent and shows semi-conductive behavior with activation energy of 0.55 eV. It was found that with increase in humidity the resistance of the samples decreases and at humidity values equal to 60-70% the irreversible transition from semi-conductive to conductive state takes place. It is supposed that in the former state the conductive matrix is formed due to incorporation of the water molecules into OD-VETP complex

Electric Properties of Organic-on-Inorganic n-Si/VOPc Heterojunction

In the current study vanadyl-phthalocyanine (VOPc) thin films were deposited by vacuum evaporation on n-Si substrate resulting in an organic-on-inorganic (n-Si/VOPc) heterojunctions. Ag films were deposited as electrodes. Thicknesses of the VOPc films were in the range of 100-300 nm. The dark I-V characteristics exhibited rectification behavior. The rectification ratio (RR) decreased from 4 to 0.4 as the thickness of the VOPc film decreased. The dark I-V characteristics were simulated by modified Schokley equation and spaace-charge limited currents (SCLC) approach. Investigations were carried out to study the effect of VOPc films thickness on reverse saturation current , diode quality factor and mobility of charge carriers

Left Ventricular Function after Revascularization in Patients with Chronical Coronary Syndromes

Background: The purpose of this study was to determine the dynamics of morpho-functional and myocardial deformation characteristics of the left ventricle after revascularization in patients with chronic coronary syndromes (CCS). Methods and Results: The study included 136 CCS patients of both sexes with stable anginal symptoms [(i) clinical scenario] and asymptomatic coronary artery disease (CAD) at screening [(vi) clinical scenario]. Diagnosis of CCS was performed according to the 2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes. All patients underwent the following examinations: assessment of traditional risk factors, physical examination, general clinical and laboratory blood tests, 12-lead ECG, transthoracic echocardiography, two-dimensional speckle tracking echocardiography (STE), and coronary angiography (CAG). The SYNTAX score was calculated retrospectively according to the SYNTAX score algorithm. A total of 100 patients with CCS were enrolled in the main group (MG) and underwent revascularization by PCI with intracoronary stenting using drug-eluting stents. Among the main-group patients, one-vessel, two-vessel, and three-vessel CAD were detected in 36(26.5%), 34(25%), and 30(22.0%) cases, respectively. The comparison group (CG) included 36 CCS patients with hemodynamically non-significant coronary lesions (<50% stenosis). LVEF values were within the normal range in all groups, with the highest value in the CG, followed by the one-, two- and three-vessel lesion groups. LVEF obtained by the area-length method and modified biplane Simpson's method did not differ. The assessment of the contractile function of the LV myocardium was also obtained by assessing the global longitudinal strain (GLS) and global longitudinal strain rate (GLSR). The comparative analysis of the LV myocardial deformation properties in the studied groups showed that less negative GLS and GLSR were found in the three-vessel CAD, followed by the two-vessel and one-vessel CAD groups, and CG. CG demonstrated more negative GLS and GLSR than all MG subgroups. We analyzed the effect of revascularization on the GLS and found no statistically significant differences before and 48 hours after revascularization in all studied MG subgroups and CG. Thirty days after revascularization, GLS significantly showed more negative values in all MG subgroups: -18.12±0.63 versus -17.9±0.4 in one-vessel CAD, -16.13±0.71 versus -15.9±0.4 in two-vessel CAD and -13.91±1.25 versus -13.1±1.1 in three-vessel CAD. In CG with medical treatment only, GLS did not change statistically significantly but had more negative values than in the studied MG subgroups. Analysis of changes in LVEF after revascularization in the MG of patients with one-, two- and three-vessel CAD and in the CG after medical treatment did not reveal statistically significant dynamics. Conclusion: the results indicate the absence of statistically significant changes in myocardial deformation indicators and morpho-functional parameters of the left ventricle in CCS patients 48 hours after revascularization. Thirty days after revascularization, GLS significantly improves, while LVEF remains unchanged. GLS is superior to LVEF in visualizing improvement in LV function after revascularization in patients with CCS