Konveksi Alam Dalam Medium Berpori = Natural Convection in Porous Media

ABSTRACT Natural convection in porous media is a complex phenomenon. Consequently the govening equations related are also complicated and verry difficult to solve exatly. The objective of the research is to determine the influence of thermophysical properties of the porous media on the natural convection heat transfer. The reasearch investigated the effect of Rayleigh number on convection heat transfer in porous media filled water in a 50 cm length, 5 cm width and 50 cm heigh model heated isothermally from below. From four variations of the media Rayleigh number, 42.23, 165.81, 374.53 and 421.84, it is concluded that the higher in Rayleigh number the higher in convection heat transfer. Key words : porous media, natural convection, Rayleigh numbe

Mechanical and thermal properties of the waste low and high density polyethylene-nanoclay composites

In extension with the previous work, recycling of the waste polyolefins by dissolution/reprecipitation method, has been investigated. The goal of study was to explore the influence of organo-modified/unmodified sodium montmorillonite clays, on the behaviours of waste polyolefins inclusive low density polyethylene (LDPE) and high density polyethylene (HDPE). 1-5 wt % of unmodified (MMT) and Organo-modified clay (OMMT) were added to the polyolefins, to prepare polyolefin-clay nanocomposites by melt intercalation method. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) were used to estimate the dispersion of clay in the polymer matrices and the morphology of nanocomposites. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) were used to analyse the change in the thermic properties of the waste polyolefins nanocomposites. The XRD and FESEM results showed an intercalated structure in the HDPE and LDPE with Organo-clay nanocomposites, whereas no exfoliation was observed with unmodified clay in both waste HDPE and LDPE, respectively. DSC and TGA, showed an improved thermal behaviours in the HDPE/Organo-clay nanocomposites (3 wt%) clay loading. Melting temperature and crystallization percentage were observed to increase in 1, 2, and 3 wt% loadings. In waste LDPE/clay nanocomposites, no improvement was established in the thermal stability

The global burden of cancer attributable to risk factors, 2010-19 : a systematic analysis for the Global Burden of Disease Study 2019

Background Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. Methods The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk-outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. Findings Globally, in 2019, the risk factors included in this analysis accounted for 4.45 million (95% uncertainty interval 4.01-4.94) deaths and 105 million (95.0-116) DALYs for both sexes combined, representing 44.4% (41.3-48.4) of all cancer deaths and 42.0% (39.1-45.6) of all DALYs. There were 2.88 million (2.60-3.18) risk-attributable cancer deaths in males (50.6% [47.8-54.1] of all male cancer deaths) and 1.58 million (1.36-1.84) risk-attributable cancer deaths in females (36.3% [32.5-41.3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20.4% (12.6-28.4) and DALYs by 16.8% (8.8-25.0), with the greatest percentage increase in metabolic risks (34.7% [27.9-42.8] and 33.3% [25.8-42.0]). Interpretation The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe

The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND: Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. METHODS: The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk–outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. FINDINGS: Globally, in 2019, the risk factors included in this analysis accounted for 4·45 million (95% uncertainty interval 4·01–4·94) deaths and 105 million (95·0–116) DALYs for both sexes combined, representing 44·4% (41·3–48·4) of all cancer deaths and 42·0% (39·1–45·6) of all DALYs. There were 2·88 million (2·60–3·18) risk-attributable cancer deaths in males (50·6% [47·8–54·1] of all male cancer deaths) and 1·58 million (1·36–1·84) risk-attributable cancer deaths in females (36·3% [32·5–41·3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20·4% (12·6–28·4) and DALYs by 16·8% (8·8–25·0), with the greatest percentage increase in metabolic risks (34·7% [27·9–42·8] and 33·3% [25·8–42·0]). INTERPRETATION: The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden

Hybrid Energy Harvesting-Based Cooperative Spectrum Sensing and Access in Heterogeneous Cognitive Radio Networks

In order to design energy efficient and energy harvesting (EEH) cooperative spectrum sensing (EEH-CSS), four fundamental constraints must be considered: 1) collision constraint to protect primary users from the collision with secondary users (SUs); 2) energy-causality constraint which states that the energy harvested by a time instant must be greater than or equal to the consumed energy until that time instant; 3) energy half-duplex (EHD) constraint which prevents the batteries from charging and discharging at the same time; and 4) correlation constraint which limits the information about the primary channel (PC) state of next time slot can be extracted from the current PC state. In this regard, we consider a hybrid energy harvesting SU (EH-SU) model which can harvest energy from both renewable sources, e.g., solar and ambient radio frequency signals. A heterogeneous EEH-CSS scheme is first proposed to handle EH-SUs with nonidentical harvesting, sensing, and reporting characteristics by permitting them to sense and report at different sensing accuracy. Formulating the energy state evolution of EH-SUs with and without EHD constraint, we analyze the asymptotic activity behavior of a single EH-SU by deriving the theoretical upper bound for the chance of being active to sense and transmit. Thereafter, we develop a convex framework to find maximum achievable total throughput by optimizing the asymptotic active probability, sensing duration, and detection threshold of each SU subject to above constraints. Given a potential set of SUs, determining the optimal subset of cooperating EH-SUs is of the essence to achieve maximum achievable total throughput. Since EH-SU selection is inherently a combinatorial problem, a fast yet high performance solution is proposed based on SUs\u27 energy harvesting, sensing, and reporting attributes. Finally, a myopic access procedure is developed to determine the active set of EH-SUs given the best subset of SUs

Hybrid Energy Harvesting Cooperative Spectrum Sensing in Heterogeneous CRNs

Energy Harvesting and Energy Efficient (EEH) Cognitive Radio Networks (CRNs) is one of the key technologies to meet the next generation wireless network demands for high energy and spectrum efficiency. EEH-CRNs can enable self-sustaining green communications by reducing the energy cost and harvesting the ambient energy sources while capitalizing the idle spectrum simultaneously. In this paper, we first propose a hybrid EH-SU model to harvest energy from both renewable sources, e.g. solar, and ambient radio frequency signals. A general hybrid cooperative spectrum sensing (CSS) scheme is then considered with and without energy half-duplex (EHD) constraint which prevents SUs from charging and discharging the battery at the same time. As an alternative to common homogeneity assumption, we propose a heterogeneous EEH-CSS scheme to exploit heterogeneous sensing and reporting channel characteristics of SUs. After formulating the energy state evolution under stochastic energy arrivals, a convex myopic EEH-CSS policy optimization framework is then developed to jointly obtain the optimal harvesting ratio, sensing duration and detection threshold of each SU to maximize the total achievable throughput subject to collision and energy-causality constraints. Obtained results show that the proposed heterogeneous approach delivers %45 and %230 more throughput than the homogeneous one with and without EHD constraint, respectively. Furthermore, if the EHD constraint is mitigated, proposed heterogeneous approach provides %400 and %240 more throughput than the EHD constrained homogeneous and heterogeneous EHE-CSS schemes, respectively

Energy Harvesting in Heterogeneous Networks with Hybrid Powered Communication Systems

In this paper, we investigate an energy efficient and energy harvesting (EH) system model in heterogeneous networks (HetNets) where all base stations (BSS) are equipped to harvest energy from renewable energy sources. We consider a hybrid power supply of green (renewable) and traditional micro-grid, such that traditional micro-grid is not exploited as long as the BSS can meet their power demands from harvested and stored green energy. Therefore, our goal is to minimize the networkwide energy consumption subject to users\u27 certain quality of service and BSS\u27 power consumption constraints. As a result of binary BS sleeping status and user-cell association variables, proposed is formulated as a binary linear programming (BLP) problem. A green communication algorithm based on binary particle swarm optimization is implemented to solve the problem with low complexity time

Microstrip reflectarray using second iteration Minkowski-like radiating element

A new class of reflectarray unit cell with increased phase-shift using single-layer second iteration Minkowski-like with triangles at the four corners of radiating element at frequency of 14GHz is proposed. The structure provides increased number of edges which contributes to increased reflection phase of the element. Using this method, the proposed structure was found to have wide phase-range of 393°. A centre-fed reflectarray antenna is designed and from simulation results, the structure is found to have low SLL -15dB, realized gain of 28dB, and overall efficiency of 94.85% at operating frequency 14GHz