Investigating the impacts of COVID-19 lockdown on air quality, surface Urban Heat Island, air temperature and lighting energy consumption in City of Melbourne

The COVID-19 pandemic has threatened city economies and residents' public health and quality of life. Similar to most cities, Melbourne imposed extreme preventive lockdown measures to address this situation. It would be reasonable to assume that during the two phases of lockdowns, in autumn (March) and winter (June to August) 2020, air quality parameters, air temperature, Surface Urban Heat Island (SUHI), and lighting energy consumption most likely increased. As such, to test this assumption, Sentinel 5, ERA-5 LAND, Sentinel 1 and 2, NASA SRTM, MODIS Aqua and Terra, and VIIRS satellite imageries are utilized to investigate the alterations of NO₂, SO₂, CO, UV Aerosol Index (UAI), air temperature, SUHI, and lighting energy consumption factors in the City of Melbourne. Furthermore, satellite imageries of SentiThe results indicate that the change rates of NO₂ (1.17 mol/m2) and CO (1.64 mol/m2) factors were positive. Further, the nighttime SUHI values increased by approximately 0.417 °C during the winter phase of the lockdown, while during the summer phase of the lockdown, the largest negative change rate was in NO₂ (−100.40 mol/m2). By contrast, the largest positive change rate was in SO₂ and SUHI at night. The SO₂ values increased from very low to 330 μm mol/m2, and the SUHI nighttime values increased by approximately 4.8 °C. From the spatial point of view, this study also shows how the effects on such parameters shifted based on the urban form and land types across the City of Melbourne by using satellite data as a significant resource to analyze the spatial coverage of these factors. The findings of this study demonstrate how air quality factors, SUHI, air temperature, and lighting energy consumption changed from pre-lockdown (2019) to lockdown (2020), offering valuable insights regarding practices for managing SUHI, lighting energy consumption, and air pollution

Investigating the relationship between land use/land cover change and land surface temperature using Google Earth Engine; case study: Melbourne, Australia

The rapid alteration to land cover, combined with climate change, results in the variation of the land surface temperature (LST). This LST variation is mainly affected by the spatiotemporal changes of land cover classes, their geospatial characteristics, and spectral indices. Melbourne has been the subject of previous studies of land cover change but often over short time periods without considering the trade-offs between land use/land cover (LULC) and mean daytimes summer season LST over a more extended period. To fill this gap, this research aims to investigate the role of LULC change on mean annual daytime LST in the hot summers of 2001 and 2018 in Melbourne. To achieve the study’s aim, LULC and LST maps were generated based on the cost-effective cloud-based geospatial analysis platform Google Earth Engine (GEE). Furthermore, the geospatial and geo-statistical relationship between LULC, LST, and spectral indices of LULC, including the Normalised Difference Built-up Index (NDBI) and the Normalised Difference Vegetation Index (NDVI), were identified. The findings showed that the mean daytime LST increased by 5.1 °C from 2001 to 2018. The minimum and maximum LST values were recorded for the vegetation and the built-up area classes for 2001 and 2018. Additionally, the mean daytime LST for vegetation and the built-up area classes increased by 5.5 °C and 5.9 °C from 2001 to 2018, respectively. Furthermore, both elevation and NDVI were revealed as the most influencing factors in the LULC classification process. Considering the R2 values between LULC and LST and their NDVI values in 2018, grass (0.48), forest (0.27), and shrubs (0.21) had the highest values. In addition, urban areas (0.64), bare land (0.62), and cropland (0.61) LULC types showed the highest R2 values between LST regarding their NDBI values. This study highlights why urban planners and policymakers must understand the impacts of LULC change on LST. Appropriate policy measures can be proposed based on the findings to control Melbourne’s future development

Urban Design and Walkability: Lessons Learnt from Iranian Traditional Cities

Physical activity is connected to public health in many ways, and walking is its most popular form. Modern planning models have been applied to cities to manage rapid urban expansions. However, this practice has led to low level of walkability and strong car-dependency in today’s cities. Hence, this study aims to provide a review of the most promising urban design parameters affecting walkability, using Frank Lawrence’s theory of “Objectively Measured Urban Form” (density, connectivity and accessibility, and mixed-use development) as the basis of discussion. The second part of this paper takes a case study approach, through discussing the main design elements of traditional Iranian cities (mosques, bazaars, residential quarters, and alleyways) and analyses their impacts on promoting walkability. This study concludes that incorporating inherent values of traditional urban design elements will complement modern planning and design practice

Optimization of antireflection coating design using pc1d simulation for c − si solar cell application

Minimizing the photon losses by depositing an anti-reflection layer can increase the conversion efficiency of the solar cells. In this paper, the impact of anti-reflection coating (ARC) for enhancing the efficiency of silicon solar cells is presented. Initially, the refractive indices and reflectance of various ARC materials were computed numerically using the OPAL2 calculator. After which, the reflectance of SiO2, TiO2, SiNx with different refractive indices (n) were used for analyzing the performance of a silicon solar cells coated with these materials using PC1D simulator. SiNx and TiO2 as single-layer anti-reflection coating (SLARC) yielded a short circuit current density (Jsc ) of 38.4 mA/cm2 and 38.09 mA/cm2 respectively. Highest efficiency of 20.7% was obtained for the SiNx ARC layer with n = 2.15. With Double-layer anti-reflection coating (DLARC), the Jsc improved by ∼0.5 mA/cm2 for SiO2 /SiNx layer and hence the efficiency by 0.3%. Blue loss reduces significantly for the DLARC compared with SLARC and hence increase in Jsc by 1 mA/cm2 is observed. The Jsc values obtained is in good agreement with the reflectance values of the ARC layers. The solar cell with DLARC obtained from the study showed that improved conversion efficiency of 21.1% is obtained. Finally, it is essential to understand that the key parameters identified in this simulation study concerning the DLARC fabrication will make experimental validation faster and cheaper

Optimization of effective doping concentration of emitter for ideal c-Si solar cell device with PC1D simulation

Increasing silicon solar cell efficiency plays a vital role in improving the dominant market share of photo-voltaic systems in the renewable energy sector. The performance of the solar cells can be evaluated by making a profound analysis on various effective parameters, such as the sheet resistance, doping concentration, thickness of the solar cell, arbitrary dopant profile, etc., using software simulation tools, such as PC1D. In this paper, we present the observations obtained from the evaluation carried out on the impact of sheet resistance on the solar cell’s parameters using PC1D software. After which, the EDNA2 simulation tool was used to analyse the emitter saturation current density for the chosen arbitrary dopant profile. Results indicated that the diffusion profile with low surface concentration and shallow junction depth can improve the blue response at the frontal side of the solar cell. The emitter saturation current density decreases from 66.52 to 36.82 fA/cm2 for the subsequent increase in sheet resistance. The blue response also increased from 89.6% to 97.5% with rise in sheet resistance. In addition, the short circuit density and open circuit voltage was also observed to be improved by 0.6 mA/cm2 and 3 mV for the sheet resistance value of 130 Ω/sq, which resulted in achieving the highest efficiency of 20.6%

Electronic Properties of Low-Dimensional Materials Under Periodic Potential

In the quest for the further miniaturization of electronic devices, numerous fabrication techniques have been developed. The semiconductor industry has been able to manifest miniaturization in highly complex and ultra low-power integrated circuits and devices, transforming almost every aspect of our lives. However, we may have come very close to the end of this trend. While advanced machines and techniques may be able to overcome technological barriers, theoretical and fundamental barriers are inherent to the top-down miniaturization approach and cannot be circumvented.As a result, the need for novel and natural alternatives to replace old materials is valued now more than ever. Fortunately, there exists a large group of materials that essentially has low-dimensional (quasi-one- or quasi-two-dimensional) structures. Graphene, a two-dimensional form of carbon, which has attracted a lot of attention in recent years, is a perfect example of a prime material from this group. Niobium tri-selenide (NbSe3), from a family of trichalcogenides, has a highly anisotropic structure and electrical conductivity. At sufficiently low temperatures, NbSe3 also exhibits two independent “sliding charge density waves”– an exciting phenomenon, which could be altered by changing the overall size of the material.In NbSe3 (and Blue Bronze K0.3MoO3 which has a similar structure and electrical behavior), the effect of a periodic potential could be seen in creating a charge density wave (CDW) that is incommensurate to the underlying lattice. The required periodic potential is provided by the crystal ions when ordered in a particular way. The consequence is a peculiar non-linear conductivity behavior, as well as a unique narrow-band noise spectrum. Theoretical and experimental studies have concluded that the dynamic properties of resulting CDW are directly related to the crystal impurity density, and other pinning potentials. Therefore, reducing the overall size of the crystal could potentially alter the CDW behavior in a significant way.Theoretical studies, as well as preliminary experimental results, suggest exceptionally interesting charge carrier behavior, including an energy gap opening and an anisotropic modulation of carrier mobility, in graphene when it is under a periodic potential. The fabrication process to achieve the desired periodic structure, with the required length scale on graphene is a challenging one. Therefore, in this manuscript, the fabrication process and its challenges are discussed.The arrangement of the manuscript is as follows: In Chapter 1, first, I study the theory of charge density waves and their dynamics. Next, I describe the fabrication process for thin NbSe3 and Blue Bronze crystals and devices. Finally, I discuss the device measurement results, and compare them with bulk crystals. In Chapter 2, I focus on the fabrication of periodic potentials on graphene layers. I begin by providing the theoretical background and motivations of the project. Then, the fabrication process is discussed in details. And lastly, I present the fabrication and preliminary electrical measurement results. Chapter 3 is a summary of additional experiments that I performed during the course of my PhD

On rational classical orthogonal polynomials and their application for explicit computation of inverse Laplace transforms

From the main equation ( a x 2 +bx+c ) y &Prime; n ( x )+( dx+e ) y &prime; n ( x )&minus;n( ( n&minus;1 )a+d ) y n ( x )=0 , n&isin; &Zopf; + , six finite and infinite classes of orthogonal polynomials can be extracted. In this work, first we have a survey on these classes, particularly on finite classes, and their corresponding rational orthogonal polynomials, which are generated by Mobius transform x=p z &minus;1 +q , p&ne;0 , q&isin;&Ropf; . Some new integral relations are also given in this section for the Jacobi, Laguerre, and Bessel orthogonal polynomials. Then we show that the rational orthogonal polynomials can be a very suitable tool to compute the inverse Laplace transform directly, with no additional calculation for finding their roots. In this way, by applying infinite and finite rational classical orthogonal polynomials, we give three basic expansions of six ones as a sample for computation of inverse Laplace transform.</p