Improving outdoor air quality based on building morphology: Numerical investigation

Due to rapid urbanization around the world, high concentrations of vehicular pollutants have deteriorated the outdoor air quality, which can affect the physical and psychological well-being of humans. Numerous strategies have been proposed to overcome these harmful impacts by improving the dispersion of air pollutants. Consequently, a question arises regarding the potential effects of building morphology on the dispersion of pollutants. Subsequently, transient three-dimensional Computational Fluid Dynamics (CFD) simulations are performed to examine the effect of building morphology on PM₁₀ dispersion. Eleven cases with various prototypes and morphological methods are compared with a simple building form to identify the patterns of PM₁₀ dispersion within a given time sequence under a prevailing inflow condition. The results indicate that the different designs of building morphology with varying Relative compactness (R_C) indicator highlight the importance of considering morphological factors to improve outdoor air quality. In addition, the proposed prototypes can reduce PM₁₀ concentrations by approximately 30%–90% at specific points in the studied time sequence. In particular, the vertical, horizontal, and grid folded prototypes can be considered more effective as an approximate decrease between 70% and 90% in PM₁₀ concentrations is observed, which reflects the influence of building morphology on improving outdoor air quality.     

Review of the phase change material (PCM) usage for solar domestic water heating systems (SDWHS)

The shortage in energy resources combined with the climb in greenhouse emissions is the main incentive beyond the deployment of solar energy resource in various applications. One of the most successful applications is the utilization of solar energy in the domestic water heating systems (DWHS) because 70% of the consumed energy in the residential segment is utilized for space heating and appliances in cold climates 1 . However, the full deployment of solar energy in domestic water heating is only possible when an energy storage system with acceptable price is available. Recently a new tendency for deploying phase change materials (PCMs) as an energy storage system is introduced in several solar DWHS. These systems are known as integrated PCM in solar DWHS and offer several advantages including high storage capacity, low storage volume, and isothermal operation during the charging and discharging phases. The present study reviews various techniques utilized for integrating the PCM in solar water heating systems and the utilized methods for enhancing the heat transfer characteristics of the PCM through the usage of extended surfaces and high conductive additives. Copyright © 2017 John Wiley & Sons, Ltd.     

Performance enhancement of direct methanol fuel cell using multi‐zone narrow flow fields

New serpentine and spiral flow field configurations were developed to enhance the performance of direct methanol fuel cells (DMFCs). The new configurations are based on two primary concepts, namely, narrowing the flow field and partitioning the total active area of the fuel cell. Three flow channel heights of 0.8, 0.4, and 0.2 mm were investigated in serpentine and spiral flow fields. The main active area is considered a single zone and is partitioned into two‐ and four‐zone designs while maintaining the total inlet mass flow rate of the reactant and oxidant. To determine the performance parameters of the newly proposed designs, a three‐dimensional single‐phase isothermal model was developed, numerically simulated, and validated through experimental measurements. The findings of the current study indicate that a serpentine flow field configuration with a channel height of 0.2 mm and two zones attains an enhancement of the net power density of 37% compared to a conventional single‐zone design with a flow channel height of 0.8 mm. Similarly, for a spiral flow field design, the maximum net power density increased by 26% using a two‐zone configuration with a channel height of 0.2 mm, in comparison to the conventional design of a single‐zone and a flow channel height of 0.8 mm. The newly developed designs utilize the lower height of the flow fields to decrease the dimensions of the fuel cell stacks and reduce the material costs required.     

Does environmental stress affect economic growth: evidence from the Gulf Cooperation Council countries?

Clean Technologies and Environmental Policy - The current paper empirically investigates the effect of environmental stress on economic growth in the Gulf Cooperation Council countries during...     

The stress corrosion cracking behavior of austenitic stainless steels in boiling magnesium chloride solutions

The change in the mechanism of stress corrosion cracking with test temperature for Type 304, 310 and 316 austenitic stainless steels was investigated in boiling saturated magnesium chloride solutions using a constant load method. Three parameters (time to failure; t_f, steady-state elongation rate; l_ss and transition time at which a linear increase in elongation starts to deviate; t_ss) obtained from the corrosion elongation curve showed clearly three regions; stress-dominated, stress corrosion cracking-dominated and corrosion-dominated regions. In the stress corrosion cracking-dominated region the fracture mode of type 304 and 316 steels was transgranular at higher temperatures of 416 and 428 K, respectively, but was intergranular at a lower temperature of 408 K. Type 310 steel showed no intergranular fracture but only transgranular fracture. The relationship between log l_ss and log t_f for three steels became good straight lines irrespective of applied stress. The slope depended upon fracture mode; −2 for transgranular mode and −1 for intergranular mode. On the basis of the results obtained, it was estimated that intergranular cracking was resulted from hydrogen embrittlement due to strain-induced formation of martensite along the grain boundaries, while transgranular cracking took place by propagating cracks nucleated at slip steps by dissolution.     

Harnessing Photochemical Shrinkage in Direct Laser Writing for Shape Morphing of Polymer Sheets

Structures that change their shape in response to external stimuli unfold possibilities for more efficient and versatile production of 3D objects. Direct laser writing (DLW) is a technique based on two‐photon polymerization that allows the fabrication of microstructures with complex 3D geometries. Here, it is shown that polymerization shrinkage in DLW can be utilized to create structures with locally controllable residual stresses that enable programmable, self‐bending behavior. To demonstrate this concept, planar and 3D‐structured sheets are preprogrammed to evolve into bio‐inspired shapes (lotus flowers and shark skins). The fundamental mechanisms that control the self‐bending behavior are identified and tested with microscale experiments. Based on the findings, an analytical model is introduced to quantitatively predict bending curvatures of the fabricated sheets. The proposed method enables simple fabrication of objects with complex geometries and precisely controllable shape morphing potential, while drastically reducing the required fabrication times for producing 3D, hierarchical microstructures over large areas in the order of square centimeters.     

A Fast and Effective Multiple Kernel Clustering Method on Incomplete Data

Multiple kernel clustering is an unsupervised data analysis method that has been used in various scenarios where data is easy to be collected but hard to be labeled. However, multiple kernel clustering for incomplete data is a critical yet challenging task. Although the existing absent multiple kernel clustering methods have achieved remarkable performance on this task, they may fail when data has a high value-missing rate, and they may easily fall into a local optimum. To address these problems, in this paper, we propose an absent multiple kernel clustering (AMKC) method on incomplete data. The AMKC method first clusters the initialized incomplete data. Then, it constructs a new multiple-kernel-based data space, referred to as K-space, from multiple sources to learn kernel combination coefficients. Finally, it seamlessly integrates an incomplete-kernel-imputation objective, a multiple-kernel-learning objective, and a kernel-clustering objective in order to achieve absent multiple kernel clustering. The three stages in this process are carried out simultaneously until the convergence condition is met. Experiments on six datasets with various characteristics demonstrate that the kernel imputation and clustering performance of the proposed method is significantly better than state-of-the-art competitors. Meanwhile, the proposed method gains fast convergence speed.     

Combining Bayesian optimization and Lipschitz optimization

Machine Learning - Bayesian optimization and Lipschitz optimization have developed alternative techniques for optimizing black-box functions. They each exploit a different form of prior about the...     

Evaluation of the Optical and Structural Properties of Constructed Bis-indole Derivatives Using (Sm2O3/SiO2) Catalyst

Silicon - (SiO2/Sm2O3) was successfully synthesized and examined using scanning electron microscopy; X-ray diffraction and Fourier transform infrared spectroscopy. Obtained data shows the formation...