Compact Type Research Articles

Numerical investigation of thermal-hydraulic design of a printed circuit steam generator

Steam generator is the biggest component of SMR. Therefore, reducing the size of the steam generator will ultimately affect the overall size of the module. Printed Circuit Heat Exchanger (PCHE) is a compact type of heat exchanger that offers a promising prospect for replacing conventional U-tube heat exchangers. Due to its high heat transfer surface area to volume ratio and its capability in high-pressure applications, PCHE can be used as steam generators in SMRs. This study investigates the possibility of using PCHE heat exchanger as a steam generator using Computational Fluid Dynamics (CFD). CFD study was performed on a reduced numerical model consisting a of single unit cell of the PCHE block keeping in view of the periodic structure of the geometry. CFD model was validated against the results of Haratyk et al. Thermal hydraulic performance of zigzag channel geometry was also analyzed for various bend angles ranging from 15°, 25°, 35°, and 45° for mass fluxes ranging from 1000 kg/m2s to 2250 kg/m2s. The friction factor, Nusselt Number and performance factor are calculated for various mass flow rates. Nusselt Number increases with bend angle and mass flux, whereas the friction factor decreases with mass flux and increases with bend angle. A maximum value of 1.45 for the performance factor was attained for a bend angle of 35° in comparison to the straight channel. The performance factor was improved further to 1.5 by introducing a short straight section having a length of 5 mm at each zigzag bend with a bend angle of 35°.

Plant Architecture Influences the Population Transpiration and Canopy Temperature in Winter Wheat Genotypes

To study how plant architecture affects the canopy traits and water use of wheat, the Triticum aestivum L. population is expected to provide important information for cultivar improvement and the ideal population structure establishment for conserving water without causing an enormous grain yield loss. This study was conducted for three consecutive growing seasons using two genotypes with contrasting plant architectures as the materials, the upright-leafed compact type Jing 411 and the flat-leafed loose type Jinmai 47. The population-scale transpiration (PT) and soil evaporation (E) were partitioned from the evapotranspiration (ET) using micro-lysimeters, and the canopy traits population density and the canopy temperature depression (CTD) were also monitored during the period from the jointing to early grain filling stage—the largest water requirement period of wheat crops. Jinmai 47 showed a lower E than Jing 411, but a similar PT and ET, though it had a higher population density at the sowing density. The total evapotranspiration (TET) for the whole growing season was also similar in the two genotypes. This indicated that Jinmai 47 performed better in water conservation than Jing 411. With a similar PT and TET, however, Jinmai 47 showed a rather larger CTD and a significantly higher grain yield than Jing 411. If the higher population density and higher leaf net photosynthetic rate could explain its higher grain yield, the higher leaf stomotal conductance and transpiration rate and the higher population density could not explain the similar PT, ET and TET to Jing 411. Presumably, the involvement of the plant architecture disrupted the original higher transpiration–larger CTD relation, and broke up the prevailing saving water-losing yield concept. Thus, the study might suggest the important water saving value of the flat-leafed loose architecture in wheat crops and demonstrate the possibility of conserving irrigation water without causing serious grain yield loss by taking advantage of the distinct plant architecture to establish an appropriate population structure.

Mineralogical alteration of a type A CAI from Allende CV3 chondrite: Formation of secondary dmisteinbergite and its phase transition to anorthite

AbstractDmisteinbergite, a hexagonal form of CaAl2Si2O8, was found in a compact type A Ca‐Al‐rich inclusion (CAI) in the Allende CV3 chondrite. Scanning and transmission electron microscopic observations show that dmisteinbergite was always in contact with grossular and grossular was in contact with melilite. In addition, there is a crystallographic relationship between dmisteinbergite and anorthite. Based on the textural and crystallographic evidence, the following mineralogical alteration processes are proposed to have occurred in the CAI. (1) Melilite was replaced by grossular. High densities of vesicles in the grossular indicate that hydrogrossular might have been the primary alteration phase and dehydrated by later metamorphism. (2) Dmisteinbergite formed from (hydro)grossular through a reaction with Si‐rich fluid. (3) Nano‐sized minerals are formed within dmisteinbergite. (4) Dmisteinbergite was transformed to anorthite. (5) Both anorthite and dmisteinbergite were altered to nepheline. (6) Hydrogrossular was dehydrated to grossular. (Hydro)grossular, dmisteinbergite, anorthite, and nepheline in the CAI seem to have formed in the course of metasomatism that occurred in the Allende parent body. Except for the hydrogrossular dehydration, these reactions could have occurred at moderate temperature (200–250°C) in high pH fluids (pH 13–14) according to past experimental studies. Episodic changes in fluid composition seem to have occurred before reactions (2), (4), and (5), because these reactions were not completed before the next reaction started. Higher temperature is required for reactions (5) and (6) to occur. Our observation of the CAI suggests that it experienced multiple episodes of metasomatism as temperatures were rising in the Allende parent asteroid.

Comparative investigation of laboratory and field compaction techniques for designing roller compacted concrete pavements (RCCP)

ABSTRACT The disparity in the compaction mechanism associated with optimum moisture content determination & specimen fabrication process in the laboratory and actual pavement construction leads to either underestimation or overestimation of Roller Compacted Concrete Pavements (RCCP) performance. Hence, in this investigation, different techniques to design RCCP, such as modified Proctor (MP), vibratory hammer (VH), vibratory table (VT), and gyratory compactor (GC), are studied and compared with the field specimens (FS); the considered fresh, mechanical, and functional properties are dry density, compressive strength, flexural and indirect-tensile strength, elastic modulus, water absorption, porosity, and abrasion & skid resistance. The laboratory results indicated that the compaction mechanism greatly affects the fresh and mechanical characteristics of RCCP. Further, it was observed that the strength properties are sensitive to the cohesion between the particles, which in turn, depends on the compaction type used to compact the RCCP. Compared with the field slab, only MP could produce comparable properties; other techniques manifested either higher or lower fresh and mechanical properties, except flexural strength. Although GC could simulate the field compaction mechanisms, it cannot mimic field properties, which necessitates further optimisation of gyratory compaction parameters (angle, pressure, and gyrations) to represent the actual pavement properties. Moreover, to achieve the field properties, the considered compaction methods shall impart a degree of compaction near to theoretical maximum constituent density.

Exploring the seasonality of surface urban heat islands using enhanced land surface temperature in a semi-arid city

Understanding the seasonal variations in surface urban heat island (SUHI) in different local climate zones (LCZs) is crucial to efforts to reduce the impacts of urban warming on local residents. However, such an understanding is constrained by the lack of land surface temperatures (LSTs) at both high spatial and temporal resolutions. This study created time series LSTs by fusing Landsat 8 satellite data and gap-filled MODIS products to further analyses of the SUHI seasonality in a semi-arid city, Xi'an, China. The results showed that LSTs of the open building types were generally lower than those of the compact building types. The highest SUHI intensity (7.17 °C) was found in ‘compact mid-rise buildings’ (LCZ2), whereas lowest (3.62 °C) was found in ‘open high-rise buildings’ (LCZ4) in July. The SUHI intensity peaked about 17–23 days later than the background LST. The annual SUHI hysteresis cycles exhibited an anti-clockwise concave-up pattern in the monsoon-influenced hot-summer humid continental climate (Dwa per Köppen-Geiger climate scheme). The SUHI intensity in autumn was higher than in spring under the same background LST. These results provide valuable information for developing heat mitigation strategies in different seasons.

On Some New Types of Fuzzy Soft Compact Spaces

In this article, we apply the concept of fuzzy soft δ -open sets to define new types of compactness in fuzzy soft topological spaces, namely, δ -compactness and δ ∗ -compactness. We explore some of their basic properties and reveal the relationships between these types and that which are defined by other authors. Also, we show that δ ∗ -compactness is more general than that which is presented in other papers. To clarify the obtained results and relationships, some illustrative examples are given.

A case study on analyzing the performance of microplate heat exchanger using nanofluids at different flow rates and temperatures

A microplate heat exchanger is one of the most compact types of heat exchanger used for cooling systems, and not much research was carried out to study the performance of this type of heat exchanger with hybrid nanofluids. In this regard, the performance analysis of the microplate heat exchanger is carried out by estimating the convective heat transfer coefficient in terms of Nusselt number using a hybrid nanofluid. In current research work, Microplate heat exchangers tested using TiO2/ethylene glycol, ZnO/ethylene glycol nanofluids, and a hybrid nanofluid with varied nanoparticle volume fractions. Based on the results, it was found that the thermal conductivity of hybrid nanofluids and the overall heat transfer coefficient by applying hybrid nanofluids show better enhancement than nanofluids. The maximum thermal conductivity ratio between the hybrid nanofluid and the base fluid is 2.10. The maximum Nusselt number of 35.8 was observed for hybrid (TiO2–ZnO/ethylene glycol) at 50 °C and a volume fraction of 4%.

Compactness and Neutrosophic Topological Space via Grills


 The aim of this paper is to introduce the concept of various types of compactness in neutrosophic topological space via grills. We shall generalize neutrosophic C - compact space and neutrosophic G - compact space and introduce C(G) - compact space in neutrosophic topological space with respect to grills. We shall call it as neutrosophic C - compact with respect to grills and term it as neutrosophic C(G) - compact space. We shall also investigate some of its basic properties and characterization theorems. We shall also study the neutrosophic quasi - H - closed space with respect to a grill.

Pullout behaviour of polymeric strips embedded in mixed recycled aggregate (MRA) from construction & demolition (C&D) waste – Effect of type of fill and compaction

Recycling and reusing construction and demolition (C&D) waste is the pressing priority, and the use of such non – conventional structural fill in reinforced soil structures (RSS) is gaining momentum. However, the utilisation of mixed recycled aggregate (MRA) from processed C&D waste as structural fill with polymeric strips (PS) and the effect of poorly compacted structural fill on the pullout interaction is not reported. This research presents the viability of using MRA as a structural fill for reinforced soil structures, appraising the physical, mechanical and electrochemical properties of MRA and the pullout behaviour of polymeric strips embedded in MRA at different relative densities in a large-scale pullout box. The results for MRA were compared with those obtained using locally available coarse and fine sands. The test results showed that MRA was alkaline (pH < 9) and had good mechanical properties and shear strength suitable for reinforced soil structures. Pullout testing results exhibited high values of the interface apparent coefficient of friction (μS/GSY) under dense conditions and a 70–80% reduction in loose conditions. The present study reinforces the viability of using MRA as an alternative structural fill with PS and highlights the effect of construction variability on μS/GSY.

Seasonal Variations of the Relationship between Spectral Indexes and Land Surface Temperature Based on Local Climate Zones: A Study in Three Yangtze River Megacities

Urban heat islands are representative problems in urban environments. The impact of spectral indexes on land-surface temperature (LST) under different urban forms, climates, and functions is not fully understood. Local climate zones (LCZs) are used to characterize heterogeneous cities. In this study, we quantified the contribution of three cities to high-temperature zones and surface urban heat island intensity (SUHII) across LCZs and seasons, used Welch and Games–Howell tests to analyze the difference in LST, then described the spatial pattern characteristics of LST, and used a geographically weighted regression model to analyze the relationship between spectral indexes and LST. The results showed that compact midrise, compact low-rise (LCZ 3), large low-rise (LCZ 8), heavy industry (LCZ 10), and bare rock or paved (LCZ E) contributed greatly to high-temperature zones and had strong SUHII. There were 92–98% significant differences between different LCZs. The spatial aggregation of LST gradually weakened with a decrease in temperature. The modified normalized difference water index (MNDWI) in most LCZs of all seasons for Wuhan could reduce LST well, while MNDWI only had cooling effects in winter for Nanjing and Shanghai. Normalized difference vegetation index (NDVI) in most LCZs performed a cooling role during summer and transition seasons (spring and autumn), while it showed a warming effect in winter. The cooling effect of NDVI in open building types was stronger than that of compact building types, while the cooling effect of MNDWI was better in compact building types than in open building types. With the increase of normalized difference built-up index (NDBI), all LCZs showed warming effects, and the magnitude of LST increase varied in different cities and seasons. These results contribute further insight into thermal environment in heterogeneous urban areas.

Effect of Cotton Varieties and Plant Spacing on Yield and Yield Components of Compact Type Cotton Under HDPS.

Effect of Cotton Varieties and Plant Spacing on Yield and Yield Components of Compact Type Cotton Under HDPS.

Design and analysis of a compact micro-ring resonator signal emitter to reduce the uniformity-induced phase distortion and crosstalk in orbital angular momentum (OAM) division multiplexing.

To improve the transmission capacity of an optical system, different multiplexing schemes have been proposed, such as optical time division multiplexing (OTDM), wavelength division multiplexing (WDM), polarization division multiplexing (PolDM), spatial division multiplexing (SDM), etc. One kind of SDM technique to boost the capacity is through modifying the spatial phase structure of an optical beam, which is known as the orbital angular momentum (OAM) division multiplexing. Moreover, the OAM signal emitter can be produced by using mature and high-yield silicon photonic (SiPh) technology, without the need of using bulky optical components or expensive spatial light modulator (SLM). The SiPh-based micro-ring resonator is one of the promising OAM signal emitter candidates, since it is simple, compact and easy to fabricate. However, the device performance is highly subjected to the structural design, and the uniformity-induced phase distortion will significantly degrade the purities of OAM beams; hence, introducing severe OAM signal crosstalk during the OAM division multiplexing. In this work, a compact SiPh-based micro-ring resonator type OAM signal emitter with detailed design parameters is presented and the output signal uniformity issue is comprehensively investigated. Two kinds of the structural optimization are performed by adjusting the angular grating width as well as the grating height. The results indicate that a significant improvement in output OAM beam uniformity can be achieved, with the attenuation factor being improved over 88% at the price of acceptable 4 ∼ 5% coupling efficiency reduction. The variations of the transmission and the uniformity induced by the fabrication error are also analyzed.

Mechanics of textiles used as composite preforms: A review

Textiles have been used as preforms for high-performance composite materials. Fiber architecture of the preform has a decisive effect on mechanical properties of composite. As a kind of flexible reinforcement, textile preforms can deform easily in the manufacture process of complex shaped composite structures. Mechanical behavior of textile materials is specific due to their fibrous nature. The objective of this paper is to give an overview of the literatures dedicated to the mechanics of textiles used as composite preforms. Experimental test methods and mechanical models are reviewed. The experimental tests are categorized with respect to the type of load, including tension, compaction, bending, shearing and forming. Mechanical models of textile materials are classified into macro-scale continuum, discrete, semi-discrete and hybrid element models according to the scale of investigation and the numerical simulation method. The advantages and limitations of different approaches are discussed.

Compactness index: a radiosurgery outcome predictor for patients with unruptured brain arteriovenous malformations.

The goal of the study was to define and quantify brain arteriovenous malformation (bAVM) compactness and to assess its effect on outcomes after Gamma Knife radiosurgery (GKRS) for unruptured bAVMs. Unsupervised machine learning with fuzzy c-means clustering was used to differentiate the tissue constituents of bAVMs on T2-weighted MR images. The percentages of vessel, brain, and CSF were quantified. The proposed compactness index, defined as the ratio of vasculature tissue to brain tissue, categorized bAVM morphology into compact, intermediate, and diffuse types according to the tertiles of this index. The outcomes of interest were complete obliteration and radiation-induced changes (RICs). A total of 209 unruptured bAVMs treated with GKRS were retrospectively included. The median imaging and clinical follow-up periods were 49.2 and 72.3 months, respectively. One hundred seventy-three bAVMs (82.8%) achieved complete obliteration after a median latency period of 43.3 months. The rates of RIC and permanent RIC were 76.1% and 3.8%, respectively. Post-GKRS hemorrhage occurred in 14 patients (6.7%), resulting in an annual bleeding risk of 1.0%. Compact bAVM, smaller bAVM volume, and exclusively superficial venous drainage were independent predictors of complete obliteration. Diffuse bAVM morphology, larger bAVM volume, and higher margin dose were independently associated with RICs. The compactness index quantitatively describes the compactness of unruptured bAVMs. Moreover, compact bAVMs may have a higher obliteration rate and a smaller risk of RICs than diffuse bAVMs. This finding could help guide decision-making regarding GKRS treatment for patients with unruptured bAVMs.

THE STUDY OF EQUILIBRIA FOR GENERALIZED GAMES IN HAUSDORFF TOPOLOGICAL VECTOR SPACES

Recent fixed point theory of the author is used to establish equilibria to multiperson games for majorized coercive or compact type maps defined on Hausdorff topological vector spaces.

Exergy efficiency and exergy destruction assessment of heat transfer and fluid flow through spiral passages using source-sink model

Exergy efficiency and exergy destruction of forced turbulent convective fluid flow through spiral passages using sourcesink model are assessed. Constant and temperature dependent thermophysical properties of process fluid in sink regions have been considered, while in the source regions phase change material is kept at constant temperature. Moreover, the effect of a secondary flow phenomenon due to spiral motion of the fluid flow through narrowing spiral passages has been evaluated in the sink passage domain. It was found that this phenomenon plays an important role in decreasing the exergy destruction as a result of energy exchange between source and sink in this compact type of energy carrier or storage equipment. It was found that the De (Dean Number) whose magnitude is a measure of the secondary flow, has positive impact on exergy efficiency while decreasing along the spiral passage. The fluid properties that are temperature dependent have a significant influence on the enhancement of heat transfer process, exergy efficiency and exergy destruction. It is concluded that the source-sink model could be considered from engineering point of view as a good simple model for evaluating the thermodynamic performance of this type of thermal energy process device.

Comparison of quantizations of symmetric spaces: cyclotomic Knizhnik–Zamolodchikov equations and Letzter–Kolb coideals

Abstract We establish an equivalence between two approaches to quantization of irreducible symmetric spaces of compact type within the framework of quasi-coactions, one based on the Enriquez–Etingof cyclotomic Knizhnik–Zamolodchikov (KZ) equations and the other on the Letzter–Kolb coideals. This equivalence can be upgraded to that of ribbon braided quasi-coactions, and then the associated reflection operators (K-matrices) become a tangible invariant of the quantization. As an application we obtain a Kohno–Drinfeld type theorem on type $\mathrm {B}$ braid group representations defined by the monodromy of KZ-equations and by the Balagović–Kolb universal K-matrices. The cases of Hermitian and non-Hermitian symmetric spaces are significantly different. In particular, in the latter case a quasi-coaction is essentially unique, while in the former we show that there is a one-parameter family of mutually nonequivalent quasi-coactions.

Aerodynamic Design of Cooling Guide for Electrical Machine in Electric Ducted Fan

Abstract Electric ducted fan has newly emerged as the most compact type of propulsion fan for flying cars, because of its flexible configuration arrangement, low noise level and high safety level operation. Typically, an electric ducted fan is composed of a hub-driven fan and a hub-mounted inner rotor electrical machine. The thermal management of the hub-mounted electrical machine is essential because it determines the machine's continuous output power and reliability, as well as the fan thrust force. The heat transmitted from the stator winding to the cooling guide vane (CGV) is dissipated by introducing the air flow at hub region to the CGV. Therefore, in order to better improve the thermal performance of the CGV, an aerodynamic design of CGV is proposed in this paper for better thermal management of stator end-windings. First, for a certain desired power output of electrical machine under temperature constraints of stator winding, lumped thermal network is established to derive the requirement of heat transfer coefficients of the CGV. Then, from engineering feasibility, three different CGVs including straight type, arc-shape type and airfoil-shape type are tested by computational fluid dynamics. The evaluation of the CGV designs include the flow characteristics, power requirements, and thermal characteristics for stator winding cooling purposes. In comparison with the conventionally straight type CGV, improvements are gained from the designed arc-shape type and airfoil-shape type cooling configurations, whereas the fan thrust force remains the same simultaneously. It is verified that the arc-shape type and airfoil-shape type CGVs are promising in enhancing the thermal management performance of the electrical machine stator winding without power requirement.

On Momentum Operators Given by Killing Vectors Whose Integral Curves Are Geodesics

The paper considers momentum operators on intrinsically curved manifolds. Given that momentum operators are Killing vector fields whose integral curves are geodesics, the corresponding manifold is flat or of the compact type with positive constant sectional curvature and dimensions equal to 1, 3, or 7. Explicit representations of momentum operators and the associated Casimir element are discussed for the 3-sphere S3. It is verified that the structural constants of the underlying Lie algebra are proportional to 2 ℏ/R, where R is the curvature radius of S3 and ℏ is the reduced Planck’s constant. This results in a countable energy and momentum spectrum of freely moving particles in S3. The maximal resolution of the possible momenta is given by the de Broglie wave length, λR=πR, which is identical to the diameter of the manifold. The corresponding covariant position operators are defined in terms of geodesic normal coordinates, and the associated commutator relations of position and momentum are established.

Curvature Invariants of Equivariant Isometric Minimal Immersions into Grassmannian Manifolds

Using theories of principal fibre bundles and connections in [11], we study curvature invariants as Riemannian submanifolds for equivariant isometric minimal immersions from Riemannian or Hermitian symmetric spaces of compact type into Grassmannian manifolds. First we calculate principal curvatures of all equivariant full isometric minimal immersions from the complex projective line to complex quadrics. It is shown that they do not depend on the parameter of the moduli space. According to the preceding research, it is important for the study of curvature invariants to examine the behavior of higher order covariant derivative of the second fundamental form. It also enables us to distinguish those maps by curvature invariants in the moduli space. In addition, we calculate principal curvatures of all equivariant full holomorphic isometric embeddings between the complex projective spaces.