Investigation of Membrane Fouling in Vacuum Membrane Distillation (VMD) Using Blocking Filtration Laws

VMD is one of the desalination technologies used for drinking water purification because of it higher permeate flux and lower energy consumption, and it uses low grade energy for operation. However, there are some critical problems related to VMD, one of which is membrane fouling. In the present study, the fouling phenomenon in VMD is investigated using constant pressure-blocking filtration laws. The results of constant pressure-blocking filtration law indicated that the permeate flux was initially unaffected by the cake layer, but with the passage of time as the pores began to constrict, a formation of a relatively thick cake layer was observed, which resulted in the decrease of permeate flux.

Intercompartmental communication between the cerebrospinal and adjacent spaces during intrathecal infusions in an acute ovine in-vivo model

Introduction The treatment of hydrocephalus has been a topic of intense research ever since the first clinically successful use of a valved cerebrospinal fluid shunt 72 years ago. While ample studies elucidating different phenomena impacting this treatment exist, there are still gaps to be filled. Specifically, how intracranial, intrathecal, arterial, and venous pressures react and communicate with each other simultaneously. Methods An in-vivo sheep trial (n = 6) was conducted to evaluate and quantify the communication existing within the cranio-spinal, arterial, and venous systems (1 kHz sampling frequency). Standardized intrathecal infusion testing was performed using an automated infusion apparatus, including bolus and constant pressure infusions. Bolus infusions entailed six lumbar intrathecal infusions of 2 mL Ringer’s solution. Constant pressure infusions were comprised of six regulated pressure steps of 3.75 mmHg for periods of 7 min each. Mean pressure reactions, pulse amplitude reactions, and outflow resistance were calculated. Results All sheep showed intracranial pressure reactions to acute increases of intrathecal pressure, with four of six sheep showing clear cranio-spinal communication. During bolus infusions, the increases of mean pressure for intrathecal, intracranial, arterial, and venous pressure were 16.6 ± 0.9, 15.4 ± 0.8, 3.9 ± 0.8, and 0.1 ± 0.2 mmHg with corresponding pulse amplitude increases of 2.4 ± 0.3, 1.3 ± 0.3, 1.3 ± 0.3, and 0.2 ± 0.1 mmHg, respectively. During constant pressure infusions, mean increases from baseline were 14.6 ± 3.8, 15.5 ± 4.2, 4.2 ± 8.2, and 3.2 ± 2.4 mmHg with the corresponding pulse amplitude increases of 2.5 ± 3.6, 2.5 ± 3.0, 7.7 ± 4.3, and 0.7 ± 2.0 mmHg for intrathecal, intracranial, arterial, and venous pulse amplitude, respectively. Outflow resistances were calculated as 51.6 ± 7.8 and 77.8 ± 14.5 mmHg/mL/min for the bolus and constant pressure infusion methods, respectively—showing deviations between the two estimation methods. Conclusions Standardized infusion tests with multi-compartmental pressure recordings in sheep have helped capture distinct reactions between the intrathecal, intracranial, arterial, and venous systems. Volumetric pressure changes in the intrathecal space have been shown to propagate to the intraventricular and arterial systems in our sample, and to the venous side in individual cases. These results represent an important step into achieving a more complete quantitative understanding of how an acute rise in intrathecal pressure can propagate and influence other systems.

Thermo-physical Investigations of oils, N-(2-aminoethyl)oleamide and Resulting Gels using TGA-DSC

Edible vegetable oils were gelled by using N-(2-aminoethyl)-oleamide. Oils in their free state were subjected to differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) analysis. The gels of these oils were prepared by using N-(2-aminoethyl)-oleamide as gelator and similar thermal analysis of the gels was carried out. The thermal analysis data obtained was used to determine specific heat capacity at constant pressure (Cp). The values were compared with the reported values of heat capacities. It is observed that the thermal properties and transitions of oils and gels, specific heat capacity is helpful parameter to understand the fundamentals of gels and gelation strategies.

A Constant-Pressure Hydraulic PTO System for a Wave Energy Converter Based on a Hydraulic Transformer and Multi-Chamber Cylinder

This paper presents a constant-pressure hydraulic PTO system that can convert stored pressure energy into electrical energy at a stable speed through hydraulic motors and generators. A multi-chamber cylinder can be connected to the main power generation circuit by check valves, and the motor displacement can be controlled by a fuzzy controller to maintain the main power generation circuit under stable pressure. The hydraulic transformer can control the forces applied to the floater. The hydrodynamic parameters of the floater are calculated by AQWA, and the optimal PTO damping of the hydraulic system is analyzed as the target of transformer control. MATLAB/Simulink and AMESim are used to carry out the co-simulation. Three kinds of wave elevation time-series for the specific state are designed for the simulation. In the co-simulation, three approaches are carried out for the simulation including no control strategy, fuzzy control with a fixed transformer ratio, and fuzzy control with a variable transformer ratio. Under the fuzzy control with a fixed transformer ratio, the floater displacement and captured energy do not increase significantly, but the oil pressure fluctuation is very stable, which indicates that the fuzzy controller maintains the stability of the main power circuit. While under fuzzy control with a variable transformer ratio, the power generation is not larger than those under no control strategy or fuzzy control with a fixed transformer ratio, which proves that this hydraulic transformer concept is less efficient.

Fuel Flowrate Control for Aeroengine and Fuel Thermal Management for Airborne System of Aircraft—An Overview

Fuel flowrate control system and fuel thermal management are very important for aeroengine and the overall aircraft, and it has been researched for several decades. This survey paper makes a comprehensive and systematic overview on the exiting fuel flowrate regulation methods, thermal load of fuel metering units, fuel-based thermal management, and the fuel tank’s thermal management topology network with drain and recirculation. This paper firstly reviews the mechanism, technical advantages, and technical challenges of the fuel metering unit with flowrate control valve and constant pressure difference valve compensator, flowrate control valve and variable displacement pump-based pressure difference compensator, and motor-based flowrate regulation. Then, the technical characteristics of above fuel flowrate control methods related to thermal management are discussed and compared. Meanwhile, the behaviors of recirculated fuel flow within single tank system and dual tank system are explored. Thirdly, the paper discusses the future directions of fuel flowrate control and thermal management. The survey is significant to the fuel flowrate control and fuel thermal management of the aircraft.

Lecturers and Students of Kyiv Higher Institute of People’s Education in the Early 1920s in the Context of the System of Soviet Ideological Control

Since the establishment of the Bolshevik regime, intellectuals as holders of knowledge, ideology and historical experience, were under systematic and constant pressure. Special attention was paid to political control over higher education institutions, particularly in Kyiv. This control concerned reorganization of Ukrainian universities (Russian universities were not reorganised). That is why particular attention should be paid to higher education changes during the early totalitarism period. Kyiv University served as a basis for establishment of Kyiv Higher Institute of People’s Education and other educational institutions. Besides, there was political and ideological purge of teachers and students at the same time. The forms of control over lecturers were detailed questionnaires and reports. Such famous scientists as Hryhoriy Pavlutskiy, Klyment Kvitka, and others were among those lectures. Students were controlled through commissions on political level checks (political registration). Those commissions were the ones that carried out a purge in 1921–1923s. All those actions changed the political and ideological situation in Kyiv Higher Institute of People’s Education.The subject matter of this article is to show forms and methods of control over the lecturers and students in Kyiv Higher Institute of People’s Education. The main sources used in the article are the documents of the fund P-346 (R-346) of the State Archives of Kyiv.

HYDRODYNAMIC CALCULATION OF CONTACTLESS SEALS WITH PLANE SLOTS IN DRIVES OF ELECTRIC POWER SYSTEMS

Non-contact seals with fl at slott ed gaps of drives of electric power systems used in switchgears of hydraulic units, as well as in pumps and hydraulic motors have been investigated. Calculation of seals based on average clearance results in an underestimation or overestimation of the leakage rate compared to the operational values. The regularity of the distribution of pressure and fl ow rate in the gap of a fl at conical slot is determined, and formulas for the fl ow rate (leakage) and friction forces acting on the walls of the conical slot are found. To solve the problem, the approximate Navier-Stokes and fl ow continuity equations are used. Several special cases of the fl ow of the working fl uid in diff erent gaps are considered: a plane-parallel gap with an oscillating wall and at a constant pressure gradient and a conical gap at diff erent ratios of the pressure drop and the frictional action of the moving channel wall. When the wall oscillates in a conical gap and constant pressure, the presence of an extremum is characteristic. In this case, an excess pressure appeared in the slott ed gap, creating a supporting force, and the pressure value became high enough. When the lower wall of the conical slot moves in the direction of the increasing gap, the pressure inside the slott ed channel, under certain conditions, can reach a complete vacuum, the value of which is limited by the bulk strength of the liquid and the pressure of saturated vapor at a given temperature. When the pressure drop and oscillations of the wall of the conical gap are additive, then at a suffi ciently high velocity of the wall movement, the pressure inside the slot can even increase and exceed the value of the supplied pressure.