Millimeter Wave Outdoor Cellular Networks: Stochastic Geometry Channel Modeling And Performance Analysis

Future cellular networks will use millimeter wave (MMW) spectrum to enable extremely high data rates. Although this spectrum offers numerous significant performance improvements in wireless networks, MMW frequencies also have unique propagation characteristics and hardware constraints, which require revisiting the prior channel modeling and system design. In this thesis, we develop a geometry-based stochastic channel model to characterize the effect of the first-order reflection paths. We consider random locations, sizes and orientations of buildings and derive a closed-form expression for the power delay profile contributed by the first-order reflection paths. We show that wireless networks can benefit from buildings in the communication area, as the external building surfaces render reflection paths whose signal powers are comparable to that of the direct path. Dense base station (BS) deployments are required to overcome the signal losses due to blockages, which unfortunately introduce additional interference at the receiver. We propose a BS coordination scheme to improve the user performance in the dense MMW cellular networks. We derive expressions for the signal-to-interference and noise ratio (SINR) coverage probability and area spectral efficiency (ASE) by incorporating the peculiarity characteristics of MMW communications. Our results show a significant improvement in performance in terms of SINR coverage probability and ASE. In this thesis, we also investigate the uplink performance of the MMW cellular networks. We model the locations of users as of a Poisson cluster process and develop an analytical expression to evaluate the SINR coverage probability. We study the performances of a typical BS for two association strategies, i.e., the closest-selection (CS) and the strongest-selection (SS). Our results show that regarding SINR coverage probability, the SS strategy outperforms the CS strategy in the environment with dense blockages

Analytical Model for Outdoor Millimeter Wave Channels using Geometry-Based Stochastic Approach

The severe bandwidth shortage in conventional microwave bands has spurred the exploration of the millimeter wave (MMW) spectrum for the next revolution in wireless communications. However, there is still lack of proper channel modeling for the MMW wireless propagation, especially in the case of outdoor environments. In this paper, we develop a geometry-based stochastic channel model to statistically characterize the effect of all the first-order reflection paths between the transmitter and receiver. These first-order reflections are generated by the single-bounce of signals reflected from the walls of randomly distributed buildings. Based on this geometric model, a closed-form expression for the power delay profile (PDP) contributed by all the first-order reflection paths is obtained and then used to evaluate their impact on the MMW outdoor propagation characteristics. Numerical results are provided to validate the accuracy of the proposed model under various channel parameter settings. The findings in this paper provide a promising step towards more complex and practical MMW propagation channel modeling.Comment: Accepted to appear in IEEE Transactions on Vehicular Technolog

Photocatalytic CO2-hydrogen conversion via RWGSR over Ni/TiO2 nanocatalyst dispersed in Layered MMT Nanoclay

The production of cleaner fuels from renewable and safer energy resources are highly demanding to mitigate energy crises and global warming. In this study, the use of cleaner photo-technology for selective and enhanced CO2 reduction to fuels over nickel (Ni) modified titanium dioxide (TiO2) dispersed in structured montmorillonite (MMT) nanoclay for photocatalytic CO2-hydrogen conversion via reverse water gas shift (RWGS) reaction has been investigated. The catalyst samples, prepared by a single step sol-gel method, were characterised by XRD, FTIR, FESEM and UV-visible spectroscopy. XRD results revealed reduced in TiO2 crystallite size with Ni and MMT loading and produced anatase phase of TiO2. MMT is found efficient for the enhanced dispersion of TiO2 while Ni-promoted efficient charges separation with hindered recombination rate over the structured MMT/TiO2 nanocomposite. The photoactivity of Ni/TiO2-MMT composite for CO2 reduction was conducted in a continuous flow photoreactor using hydrogen as the reducing agent. The main products detected were CO and CH4 with appreciable amounts of C2H4, C2H6 and C3H6 hydrocarbons. The maximum yield of CO produced as the main product over 3 wt% Ni-10 wt% MMT/TiO2 catalyst was 9,429 µmole/g-cat, 209-fold higher than the amount of CO detected over the pure TiO2. Evidently, Ni-promoted TiO2 photocatalytic activity, while MMT is favourable for improved dispersion of Ni/TiO2 catalyst. The dynamic and selective CO evolution was evidently due to efficient light distribution, enlarged active surface area and efficient charges separation with their hindered recombination rate by Ni and MMT. The stability of Ni/TiO2 dispersed over MMT sustained over the irradiation time. With the use of green nanocomposite catalyst, CO2 can be efficiently converted to cleaner fuels with all sustainable systems

Electrochemical Generation of Hydrogen and Methanol using ITO Sheet Decorated with Modified-Titania as Electrode

Current issues of global warming and environmental pollution due to extensive use of fossil fuels has been reached to an alarming position. Being CO2 as main byproduct of fossil fuel consumption and water as abundantly available on earth surface has great potential to replace fossil fuels as energy source. Herein, electrocatalytic CO2 reduction with water for methanol and hydrogen gas (H2) production over ITO sheet decorated with modified-Titanium nanorods (TiO2 NR), has been investigated. The performance comparison of electrocatalytic activity of hydrothermally modified-titania with commercial TiO2 microparticles (MP) were further investigated. Electrochemical reactor containing KHCO3 aqueous solution with CO2 as an electrolyte and modified TiO2 nanorods (NR) as working electrodes offer an eco-friendly system to produce clean and sustainable energy system. The typical rates of product, i.e. methanol and H2 generation from the ITO sheet decorated with modified TiO2 NR layer recorded higher than those for the ITO sheet with commercial TiO2 microparticle. At 2.0V applied potential vs Ag/AgCl as reference electrode, the modified TiO2 NR electrocatalyst yielded methanol at a rate of 3.32 µmol.cm−2.L−1 and H2 at a rate of 6 µmol.cm−2.L−1 which was higher than that of commercial TiO2 MP electrocatalyst (methanol = 1.5 µmol.cm−2.L−1 and H2 = 3.7 µmol.cm−2.L−1). The enhancement in product yields of methanol and H2 was mainly due to the notable improvements and modification in texture of TiO2 working electrode interface. Hence, it is concluded that the modified TiO2 NR can be considered as a competent candidate for sustainable energy conversion applications. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Settlement reduction of dredged marine soils (DMS) admixed with cement & waste granular materials (WGM): 1-D compressibility study

Dredged marine soils (DMS) are considered as geo-waste and commonly disposed far into the sea. Environmental impacts raised from dredging such as turbidity and disturbance of marine ecosystem had increased the social demand to reuse DMS in engineering application. Typically, DMS have low shear strength and low bearing capacity. Hence, the DMS could be strengthened up by soil solidification. In present study, waste granular materials (WGM) such as coal bottom ash (BA) and palm oil clinker (POC) were utilized as additional binder to cement. The DMS were solidified with 3 series of admixtures; namely cement and/or WGM. The factor that influenced the compressibility of the soil sample such as percentages of admixtures were considered. Proportioned samples of 10, 15 and 20 % of cement, and/or 50 and 150 % of WGM of dry weight of DMS were subjected to one-dimensional oedometer test. The test samples were cured for 7 days in room temperature. Results show that cement- and WGM-admixed DMS have reduced the soil’s compressibility considerably than the untreated sample. As expected, the cemented soil had significantly reduced the settlement better than WGM-admixed soil. Hence, homogeneous samples of 15C50BA and 10C100POC produced almost similar reduction of compressibility as sample 20C. Therefore, reusing WGM as partial replacement of cement in DMS could provide beneficial reuse of these materials

Inflation uncertainty and economic growth: evidence from the LAD ARCH model

In this paper, we combined the panel data and least absolute deviation autoregressive conditional heteroscedastic (ARCH) (L 1-ARCH) model to infer on the relationship between inflation uncertainty and economic growth in five emerging market economies. Two interesting findings emerged from the analysis; first, we confirmed that the inflation uncertainty has a significant and negative effect on economic growth. Second, inflation is also an important variable and it is detrimental to economic prospects in the fast-growing Association of Southeast Asian Nations (ASEAN) economies. All in all, the empirical findings suggest that greater stability in the economy may be desirable in order to stimulate economic growth in the region

Memformulasikan pelajar institusi pengajian tinggi ke arah kerjaya usahawan

Kajian-kajian telah menunjukkan terdapatnya perhubungan secara langsung di antara keusahawanan dengan pembangunan ekonomi sesebuah negara.Negara yang mempunyai ramai usahawan adalah lebih maju ke hadapan dalam perkembangan ekonominya.Dalam hal ini institusi pendidikan, khasnya institusi pengajian tinggi (IPT) boleh menjadi laluan penting dalam memformulasikan pelajarnya ke arah kerjaya usahawan.Formulasi ini boleh dilaksanakan melalui program-program pendidikan keusahawanan yang bersesuaian.Kajian ini akan membincangkan sejauh manakah program pendidikan keusahawanan secara hands-on melalui Program Siswaniaga (PS), Universiti Utara Malaysia (UUM) ke arah melahirkan usahawan siswazah.Secara khususnya tiga objektif kepada kajian ini ialah i) melihat profil bekas peserta PS yang telah mengikuti PS ii) menilai pencapaian PS dari aspek jumlah bekas peserta PS yang menjadi usahawan selepas tamat pengajian, dan iii) meninjau bilakah bekas peserta PS yang menjadi usahawan sepenuh masa memulakan perniagaan selepas tamat pengajian.Kajian ini menggunakan pendekatan kuantitatif di mana soal selidik digunakan sebagai instrumen kajian. Sampel kajian terdiri daripada 171 bekas peserta PS yang telah tamat pengajian di peringkat sarjana muda dalam tempoh lima tahun selepas bergraduat.Berdasarkan analisis deskriptif, dapatan utama kajian ini ialah lebih separuh bekas peserta PS telah menjadi usahawan dan hampir 20 peratus bekas peserta memulakan perniagaan sejurus selepas tamat pengajian. Golongan usahawan siswazah ini berpotensi untuk merangsang perkembangan negara ke arah ekonomi berpendapatan tinggi di masa depan.Justeru itu, kajian ini mencadangkan pelajar IPT perlu didedahkan dan diberi peluang untuk menjadi usahawan kampus di mana mereka terlibat secara hands-onmenjalankan perniagaan semasa mereka berada di universiti.Tindakan ini dapat meningkatkan peratusan golongan usahawan siswazahyang boleh membantu melonjakkan ekonomi negara dan sekaligus membantu mengurangkan pengangguran siswazah

Level of polychlorinated biphenyls (PCBs) in selected marine fish (pelagic) from Straits of Malacca

Fish is a good source of protein, supply important vitamins and other essential nutrients including essential fatty acids (EFA), the EPA and DHA which help to reduce risk of death from coronary heart diseases. However, diet and food of animals’ origin are the most predominant sources of polychlorinated biphenyls (PCBs) to human which accounts to over 90%, with fish as one of the major routes of contaminants in human body. PCBs are a group of extremely stable aromatic chlorinated compounds which are relatively resistant to biological degradation and very persistent in the environment. This study has identified the type and level of 12 congeners of PCBs that are most toxic to humans. The maximum permitted level of PCBs in muscles meat of fish and fishery products is 4 pg/g, as recommended by World Health Organization (WHO) using the WHO-TEFs. Meanwhile, the highest amount of PCBs concentration was in Rastrelliger kanagurta (Indian mackerel), with the level of PCBs at 1.37 pg/g wet weight. Other species like Scomberomorus guttatus (Spanish mackerel), Pampus argenteus (Silver pompret), Megalapsis cordyla (Hardtail scad), Eleutheronema tradactylum (Fourfinger threadfin) and Chirocentrus dorab (Dorab wolfherring) showed PCBs levels ranging from 0.35 pg/g to 1.05 pg/g wet weight. Thus, the PCBs in all the samples were below the permitted level. It can be concluded that the studied pelagic fish are safe to consume. Although the levels were not high, it is still important to set limits for the PCBs in fish and shellfish species so as to make a better estimation of the risk of exposure to human through dietary intake of fish, specifically fatty fish to meet nutritional requirement for EPA and DHA

PCDDs and PCDFs in pelagic fish along the straits of Malacca

Fish and shellfish are rich sources of long chain fatty acids, especially DHA and EPA. High consumption of fish helps to elevate the level of these compounds in the body. However, fish also are easily exposed to chemical contaminants, such as dioxins (PCDDs) and furans (PCDFs). Exposure to PCDDs and PCDFs may lead to negative health effects, such as cancer, chloracne, hyperpigmentation and others. Level and type of PCDDs and PCDFs were determined in 20 pelagic fish samples of six different species collected from the Straits of Malacca using HRGC/HRMS. The most toxic congener (2,3,7,8-TCDD) was found in all the samples at a very low level of 0.04-0.05 pg/g sample, except in Spanish mackerel (south-T2) and Indian mackerel (middle-T1). Meanwhile, the level of the total PCDDs and PCDFs ranged from 0.13 pg/g to 0.38 pg/g of the wet weight of the samples. The value of the total PCDDs and PCDFs was in a descending order of Hardtail scad, Spanish mackerel, Indian mackerel, fourfinger threadfin, silver pomfret and dorab wolfherring. Generally, the results of this study indicate that fish and shellfish caught along the Straits of Malacca are safe as in terms of PCDDs and PCDFs levels and the data can serve as baseline information for future monitoring of these organochlorine compounds

Experimental Evaluation on Physical and Mechanical Properties of Concrete Containing Green Mussel Shell (Perna viridis) Powder as an Admixture

Mussel shell is a type of waste that is generated abundantly. However, the presence of chemical components such as calcium (CaCO3) in mussel shells has shown its potential as filler materials in concrete designing. Therefore, this paper presents the experimental result for the physical and mechanical properties of concrete containing 1%, 2%, 3% and 4% Mussel Shell Powder (MSP) as additional material under 2.73% sodium chloride solution. The MSP has been cleaned, grinded and sieved 75μm sizes in order to obtain its final product. Compressive strength, split tensile, and capillary water absorption were determined. Statistical analysis was performed to investigate the correlation and level of significance using IBM SPSS in determining the optimal mix design for modified concrete. The performance of MSP concrete and control specimens are the main factor that been observed in this study. The increment percentages of MSP in concrete had led to reduce on its mechanical strength, however improved in its absorption rates. According to statistical analysis, it shows that low MSP percentages giving a significant value for compressive strength and very strong correlation coefficient compared to control specimens, thus it indicated minimum MSP percentages are more potential in improving concrete physical and mechanical performance