Passive evaporative cooling through water-filled bricks: a preliminary investigation

Direct evaporative cooling is widely known to be an energy efficient air-conditioning option for arid and semi-arid climates. However, care must be taken on humidity ranges achieved indoors. Existing literature presents several options for integrating evaporative cooling within buildings for passive cooling applications. This work aims at expanding the current knowledge by focusing on the use of water-filled hollow bricks to implement evaporative cooling of air in contact with the brick’s surfaces. A prototype is built and experimentally characterized under controlled air velocity, air temperature and relative humidity conditions. Results on the psychrometric conditions achieved under different geometric arrangements (i.e., with one, two or three rows of four bricks each) are presented and discussed. Insights on likely building integration of the system for passive cooling purposes in farms and agriculture applications are eventually given.

Offshore Platform Topsides Structural Design: Using Topology Optimization to Generate Novel Design Concept

The paper presents topology optimization performed for the concept study of a semi-submersible platform topsides structure. The topsides truss system consisting of I beams carries the equipment payload and the environment loads. The structural weight needs to be reduced in order to maximize the allowable equipment weight, and the structural strength criterion must be satisfied for the harsh ocean environment. Topology optimization is a powerful tool to generate designs that optimally distribute the structural material for the balance between structural weight and strength. A finite-element-based topology optimization method assigns a density value to each structural element and updates this density value using topology optimization algorithms during each design iteration. Elements in the load-transferring path retain high density value at the end cycle and form an efficient structural shape under the given design load conditions and constraints. The topology optimization generated novel and optimal geometric arrangements for the topsides structure. Two corresponding innovative topsides truss concepts were developed. The new topsides designs were compared with an existing benchmark design for the structural weight and strength to demonstrates the advantages of topology optimization over conventional empirical approach for offshore platform topsides structural design. At the same strength level, the novel designs reduced the structural weight significantly. One novel design was selected for practical semi-submersible designs at Exmar Offshore Company.

Geometric Features of the Pial Arteriolar Networks in Spontaneous Hypertensive Rats: A Crucial Aspect Underlying the Blood Flow Regulation

BackgroundSeveral studies indicate that hypertension causes major changes in the structure of the vessel wall by affecting the regulation of blood supply to the tissues. Recently, it has been observed that capillary blood flow is also considerably influenced by the structural arrangement of the microvascular networks that undergo rarefaction (reduction of the perfused vessel number). Therefore, this study aimed to assess the geometric arrangements of the pial arteriolar networks and the arteriolar rhythmic diameter changes in spontaneously hypertensive rats (SHRs).MethodsFluorescence microscopy was utilized to observe in vivo the pial microcirculation through a closed cranial window. Pial arterioles were classified according to Strahler’s method. The arteriolar rhythmic diameter changes were evaluated by a generalization short-time Fourier transform.ResultYoung SHRs showed four orders of vessels while the adult ones only three orders. The diameter, length, and branching number obeyed Horton’s law; therefore, the vessels were distributed in a fractal manner. Larger arterioles showed more asymmetrical branches than did the smaller ones in young SHRs, while in adult SHRs smaller vessels presented asymmetrical branchings. In adult SHRs, there was a significant reduction in the cross-sectional area compared with the young SHRs: this implies an increase in peripheral resistance. Young and adult age-matched normotensive rats did not show significant alterations in the geometric arteriolar arrangement with advancing age, both had four orders of arteriolar vessels, and the peripheral resistance did not change significantly. Conversely, the frequency components evaluated in arteriolar rhythmic diameter changes of young and adult SHRs showed significant differences because of a reduction in the frequency components related to endothelial activity detected in adult SHRs.ConclusionIn conclusion, hypertension progressively causes changes in the microarchitecture of the arteriolar networks with a smaller number of vessels and consequent reduced conductivity, characteristic of rarefaction. This was accompanied by a reduction in the formation and release of independent and dependent – endothelial nitric oxide components regulating arterial vasomotion.

The General Features and Status of the Illumination Art in the Great Seljuk Period

The most important reason for the enrichment of decorative arts (especially illumination art) in Islamic societies in various periods is the prohibition of depiction in Islam. The art of illumination, which was mostly used to decorate the Qur'an in different historical periods of Iran, including the Great Seljuk period, was influenced by the arts of previous periods and became a source of creativity and inspiration for Muslims and sometimes non-Muslim artists in other countries. This research was carried out in order to examine the status and general characteristics of illumination art during the Great Seljuk period. The descriptive-analytical method was used in the research. As a result, during the Great Seljuk period, the Qur'an manuscripts were made of paper instead of leather. The richness of motifs, patterns and colours, the use of various colours and geometric arrangements draw attention to the illuminations of this period. According to the results of this study, the most important illumination examples of the Great Seljuk period were used in the Quran manuscripts. In these manuscripts, it is seen that motifs such as schemes, six and eight-pointed stars and golden circles are used to decorate the headlines (serlevha pages), the heads of the sura, the interlines and zahriye parts. In addition, the illumination samples of the Great Seljuk period positively affected the later periods, especially the Ilkhanid and Memlukid periods, as well as all other arts. Great Seljuk elegant illumination samples with the beauty of their patterns, the order and delicacy of the motifs and the use of colours are masterpieces of Islamic art.

Simulation and Characterization of Nanoparticle Thermal Conductivity for a Microscale Selective Laser Sintering System

Additive Manufacturing (AM) technologies are often restricted by the minimum feature size of parts they can repeatably build. The microscale selective laser sintering (μ-SLS) process, which is capable of producing single micron resolution parts, addresses this issue directly. However, the unwanted dissipation of heat within the powder bed of a μ-SLS device during laser sintering is a primary source of error that limits the minimum feature size of the producible parts. A particle scale thermal model is needed to characterize the thermal properties of the nanoparticles undergoing sintering and allow for the prediction of heat affected zones (HAZ) and the improvement of final part quality. Thus, this paper presents a method for the determination of the effective thermal conductivity of metal nanoparticle beds in a microscale selective laser sintering process using finite element simulations in ANSYS. CAD models of nanoparticle groups at various timesteps during sintering are developed from Phase Field Modeling (PFM) output data, and steady state thermal simulations are performed on each group. The complete simulation framework developed in this work is adaptable to particle groups of variable sizes and geometric arrangements. Results from the thermal models are used to estimate the thermal conductivity of the copper nanoparticles as a function of sintering duration.

Edge Metric and Fault-Tolerant Edge Metric Dimension of Hollow Coronoid

Geometric arrangements of hexagons into six sides of benzenoids are known as coronoid systems. They are organic chemical structures by definition. Hollow coronoids are divided into two types: primitive and catacondensed coronoids. Polycyclic conjugated hydrocarbon is another name for them. Chemical mathematics piques the curiosity of scientists from a variety of disciplines. Graph theory has always played an important role in making chemical structures intelligible and useful. After converting a chemical structure into a graph, many theoretical and investigative studies on structures can be carried out. Among the different parameters of graph theory, the dimension of edge metric is the most recent, unique, and important parameter. Few proposed vertices are picked in this notion, such as all graph edges have unique locations or identifications. Different (edge) metric-based concept for the structure of hollow coronoid were discussed in this study.

Numerical study of the effect of geometric arrangement of the truss on the response modification factor of the special truss moment frame (STMF)

The purpose of the present study was to investigate the effect of the geometric arrangement of the trusses on the response modification factor of the special truss moment frame. For this purpose, six different geometric arrangements for the three types of trusses (Vierendeel, multiple Vierendeel panels, and X-diagonals) were considered. The results were obtained based on non-linear static analysis of two- and three-span frames for 4- and 8-story structures with the given geometric arrangements. According to the results obtained, different truss arrangements can affect the response modification factor by about 4 to 10%. Additionally, using multiple Vierendeel panels and the X-diagonals can increase the response modification factor by 1.06 and 1.74 times, respectively. Article Highlights Different truss arrangements do not have a significant effect on the coefficient of behavior. The addition of several Vierendeel panels does not have much effect on the behavior of these structures. Adding cross diameters almost doubles the coefficient of behavior and significantly improves the performance of the structure.

Alternative Geometric Arrangements of the Nozzle Outlet Orifice for Liquid Micro-Jet Focusing in Gas Dynamic Virtual Nozzles

Liquid micro-jets are crucial for sample delivery of protein crystals and other macromolecular samples in serial femtosecond crystallography. When combined with MHz repetition rate sources, such as the European X-ray free-electron laser (EuXFEL) facility, it is important that the diffraction patterns are collected before the samples are damaged. This requires extremely thin and very fast jets. In this paper we first explore numerically the influence of different nozzle orifice designs on jet parameters and finally compare our simulations with the experimental data obtained for one particular design. A gas dynamic virtual nozzle (GDVN) model, based on a mixture formulation of Newtonian, compressible, two-phase flow, is numerically solved with the finite volume method and volume of fluid approach to deal with the moving boundary between the gas and liquid phases. The goal is to maximize the jet velocity and its length while minimizing the jet thickness. The design studies incorporate differently shaped nozzle orifices, including an elongated orifice with a constant diameter and an orifice with a diverging angle. These are extensions of the nozzle geometry we investigated in our previous studies. Based on these simulations it is concluded that the extension of the constant diameter channel makes a negligible contribution to the jet’s length and its velocity. A change in the angle of the nozzle outlet orifice, however, has a significant effect on jet parameters. We find these kinds of simulation extremely useful for testing and optimizing novel nozzle designs.

Numerical simulation and constructal design applied to plates with different heights of traverse and longitudinal stiffeners

Martins Nogueira, Vinícius Torres Pinto, Luiz Alberto Oliveira Rocha, Elizaldo Domingues dos Santos and Liércio André Isoldi Right click to download the paper PDF (550K) Abstract: This study applied the Constructal Design Method (CDM) associated with the Finite Element Method (FEM) through computational models to perform a geometric analysis on rectangular stiffened plates of steel subjected to a uniform transverse loading, in order to minimize its maximum and central out-of-plane deflections. Considering a non-stiffened plate as reference and maintaining the total volume of steel constant, a portion of material volume deducted from its thickness was transformed into stiffeners through the ϕ parameter, which represents the ratio between the material volume of the stiffeners and the reference plate. Adopting ϕ = 0.30, 27 geometric arrangements of stiffened plates were established, being 9 arrangements for each 3 different stiffeners' thicknesses adopted: ts = 6.35 mm, ts = 12.70 mm and ts = 25.40 mm. For each ts value, the number of longitudinal (Nls) and transverse (Nts) stiffeners were varied from 2 to 4. Thus, in each plate arrangement configured, the influence of the ratio between the height of the transverse and longitudinal stiffeners (hts/hls) was analyzed, taking into account the values 0.50; 0.75; 1.00; 1.25; 1.50; 1.75 and 2.00, regarding to the maximum and central deflections. The results have shown that transforming a portion of steel from a non-stiffened reference plate into stiffeners can reduce the maximum and central deflections by more than 90%. Moreover, it was observed that to reduce the deflections it is more effective consider hts > hls, once the ratio hts/hls = 2.00 was the one that led to the better mechanical behavior among the analyzed cases.