Study on secondary flow losses modellig in compressor cascades using Reynolds averaged Navier-Stokes techniques

The present study explores the feasibility of using the GEKO turbulence model in Ansys Fluent software to analyze secondary flow losses in turbomachinery compressors. This turbulence model includes free parameters that can be adjusted to enhance simulation accuracy. The model was calibrated to match reference data obtained from a Large Eddy Simulation (LES), by focusing on two dimensional simulations at the midspan of the compressor blade. Subsequently, the obtained calibrated values were used to perform three dimensional simulations. The calibrated GEKO model showed similar results to the default GEKO model, indicating limited improvement. However, both GEKO models outperformed the standard k − ω model in predicting pressure losses. Vortical structures, such as the tip leakage vortex, were captured by all simulations. The positioning of the vortex in the GEKO simulations was consistent with the reference data. However, the k −ω model showed displacements with respect to the LES simulation. These findings highlight the potential of the GEKO model for practical applications in turbomachinery compressor analysis

The Case Study on Significance of Daylight in Classroom Setting at Sarajevo Campus

When designing schools, universities, or any educational centers, daylight in classrooms is usually one of the essential issues that take the architect's attention. Its importance comes from the fact that daylight can impact students' health, mood, and visual performance. Providing an appropriate amount of uniformly distributed light with glare protection is a significant factor in classroom design (Zomorodian Z S, 2016). This study is based on a literature review, studies, and articles researching the effect of daylight in a classroom environment on students' performance. It tends to define the significance of daylight design in the learning environment. This paper also deals with specifying and exploring all the conditions, factors, and elements that contribute to creating this successful daylight design in classrooms. Besides, it investigates the daylight design of the buildings at the campus of Sarajevo that will, later on, contribute to the creation of a design manual of all the considerations that need to be taken for schools and educational centers’ daylight design. The study is conducted at the campus of Sarajevo in the academic year 2019. The literature review, data study, and previous studies define the significance of daylight in the classroom environment and show the correlation between daylight and students' achievement in the classroom environment. It defines the elements and conditions of successful daylight design in classroom settings. The study explored the current state of the daylight design at the campus of Sarajevo detecting its lacks and obstacles regarding adequate illumination. Based on the literature review, an appropriate solution for the investigated classroom environment has been designed

A NOVEL LIQUID DESICCANT AIR CONDITIONING SYSTEM WITH MEMBRANE EXCHANGERS AND VARIOUS HEAT SOURCES

Liquid desiccant air conditioning (LDAC) has received much attention in recent years. This is mainly because LDAC systems are able to control latent loads in a more energy efficient way than conventional air conditioning systems. Although many research studies have been conducted on LDAC technologies, the following gaps in the scientific literature are addressed in this thesis: (1) carryover of desiccant droplets in air streams, (2) direct comparisons between different configurations of LDAC systems, (3) fundamentals of capacity matching in heat-pump LDAC systems, (4) optimal-control strategies for heat-pump LDAC systems, and (5) importance of transients in evaluating the performance of a LDAC system. Items (1) to (4) are addressed using TRNSYS simulations, and item (5) is addressed using data collected from a field test. The use of liquid-to-air membrane energy exchangers (LAMEEs) as dehumidifiers and regenerators in LDAC systems eliminate the desiccant droplets carryover problem in air streams. This is because LAMEE separate the air and solution streams using semi-permeable membranes, which allow the transfer of heat and moisture but do not allow the transfer of the liquid desiccant. A preliminary configuration for a membrane LDAC system, which uses LAMEEs as the dehumidifier and regenerator, is proposed and investigated under fixed operating conditions in this thesis. The influences of key design and operating parameters on the heat and mass transfer performances of the membrane LDAC system are evaluated. Results show that the membrane LDAC technology is able to effectively remove latent loads in applications that the humidity to be controlled. A comprehensive evaluation is conducted in this thesis for the thermal, economic and environmental performances of several configurations of membrane LDAC systems. The solution cooling load is covered using a cooling heat pump in all systems studied, while the solution heating load is covered using one of the following five different heating systems: (1) a gas boiler, (2) a heating heat pump, (3) a solar thermal system with gas boiler backup, (4) a solar thermal system with heat pump backup, and (5) the condenser of the solution cooling heating pump. Each of the membrane LDAC systems studied is evaluated with/without an energy recovery ventilator (ERV) installed in the air handling system. The influence of operating the ERV under balanced/unbalanced operating conditions is studied. It is found that the most economic membrane LDAC system is the one which uses the evaporator and condenser of the same heat pump to cover the solution cooling and heating loads, respectively (i.e. heat-pump membrane LDAC system). No clear guidance was found in the literature for sizing the evaporator and condenser in a heat-pump LDAC system to simultaneously meet the solution cooling and heating loads. When the heating and cooling provided by the heat pump exactly match the heating and cooling requirements of the solution, the system is “capacity matched”. A parametric study is conducted on a heat-pump membrane LDAC system to identify the influence of key operating and design parameters on achieving capacity matching. It is concluded that the solution inlet temperatures to the dehumidifier and regenerator are the most influential parameters on the moisture removal rate, capacity matching and coefficient of performance (COP). Three control strategies are developed for heat-pump membrane LDAC systems, where these strategies meet the latent loads and achieve one of the following three objectives: (1) meet the sensible loads, (2) achieve capacity matching, or (3) optimize the COP. Results show that the COP of a heat-pump LDAC system can be doubled by selecting the right combination of solution inlet temperatures to the regenerator and dehumidifier. The importance of transients in evaluating the performance of a LDAC system is addressed in the thesis using a data collected from a field test on a solar LDAC system. It is found that the sensible, latent and total cooling energy, and the total primary energy consumption of the LDAC system are changed by less than 10% during an entire test day when transients are considered. Thus, it can be concluded that steady-state models are reliable to evaluate the energy performances of LDAC systems

Wavelet Based Analysis for Transmission Line Fault Location

This paper presents wavelet based analysis for transmission line fault location. Faults in power transmission lines cause transients that travel at a speed close to the speed of light and propagate along the line as traveling waves (TWs). Traveling wave theory is utilized in capturing the travel time of the transients along the monitored lines between the fault point and the protective relay. This will help in proposing an accurate fault location technique based on high frequency components of fault current. Time resolution for these components is provided by the wavelet transform. This approach has the advantages of being independent of the fault impedance and fault inception angle. The application of the proposed technique for typical faults is illustrated using transient simulations obtained by MATLAB Simulink program. Keywords: travelling waves, wavelet transform, fault location, MATLAB Simulink

Vázquez Montalbán´s Galíndez, Eduar El-Jarrat´s The Road of the Vulture: Typologie of the contemporary historical novel

En este trabajo se abordan dos obras que son fieles exponentes de al menos dos variantes de la novela histórica actual propiamente dicha: Galíndez de Manuel Vázquez Montalbán y El camino del águila de Eduar El-Jarrat. La naturaleza de este estudio plantea más de un escollo, especialmente, porque trata dos obras escritas cada una en un idioma diferente: el castellano y el árabe, pertenecientes a dos culturas distintas que han tenido, por separado, una evolución sociohistórica propia. Sin embargo, no es menos cierto que según la teoría literaria y un nuevo enfoque crítico, es posible enfocar los textos elegidos desde una perspectiva concreta. Y he aquí que a ambos escritores les une una visión literaria innovadora: escriben un relato moderno, trasgresor de géneros y de personalísimas estéticas.In the present study we analyze two contemporary novels as variants of the contemporary historical novel: Vázquez Montalbán´s Galíndez, and Eduar El-Jarrat´s The Road of the Vulture. Given its nature, this study faces several obstacles, specially because it addresses two books written in two different languages - Spanish and Arabic - which are part of two different cultures that have undergone a very different social and historical development. However, both texts can be read from a specific perspective based on the principles of Literary Theory and a new critical approach. The authors do share a very innovative literary vision: they have written two modern novels that transgress literary genres and suggest a very personal poetics

Weighted Cauchy-type problem of a functional differ-integral equation

In this work, we are concerned with a nonlinear weighted Cauchy type problem of a differ-integral equation of fractional order. We will prove some local and global existence theorems for this problem, also we will study the uniqueness and stability of its solution

Determination of the absolute configuration of new piperidin-4-one derivative from pellacalyx saccardianus by NOESY spectroscopy

A new alkaloid, pellacalyxin was isolated from the leaves of Pellacalyx saccardianus of Rhizophoraceae family. Pellacalyxin was analyzed using nuclear Overhauser spectroscopy (NOESY) nuclear magnetic resonance (NMR) technique to determine the absolute configuration. The analysis of absolute configuration of pellacalyxin was supported by X-ray crystallography.1H-1H NOESY NMR spectroscopy exhibited that pellacalyxin possesses two chiral centers (3S) and (6R)

On the stability of a fractional-order differential equation with nonlocal initial condition

The topic of fractional calculus (integration and differentiation of fractional-order), which concerns singular integral and integro-differential operators, is enjoying interest among mathematicians, physicists and engineers. In this work, we investigate initial value problem of fractional-order differential equation with nonlocal condition. The stability (and some other properties concerning the existence and uniqueness) of the solution will be proved

On the stability of some fractional-order non-autonomous systems

The fractional calculus (integration and differentiation of fractional-order) is a one of the singular integral and integro-differential operators. In this work a class of fractional-order non-autonomous systems will be considered. The stability (and some other properties concerning the existence and uniqueness) of the solution will be proved