Modeling Hidden Nodes Collisions in Wireless Sensor Networks: Analysis Approach

This paper studied both types of collisions. In this paper, we show that advocated solutions for coping with hidden node collisions are unsuitable for sensor networks. We model both types of collisions and derive closed-form formula giving the probability of hidden and visible node collisions. To reduce these collisions, we propose two solutions. The first one based on tuning the carrier sense threshold saves a substantial amount of collisions by reducing the number of hidden nodes. The second one based on adjusting the contention window size is complementary to the first one. It reduces the probability of overlapping transmissions, which reduces both collisions due to hidden and visible nodes. We validate and evaluate the performance of these solutions through simulations

Pathways towards regional circular economy evaluated using material flow analysis and system dynamics

Circular Economy (CE) offers insights to sustainable production and consumption by integrating environmental analysis to the socioeconomic system. To promote sustainable development in Guangdong Province, this study integrates System Dynamics (SD) and Material Flow Analysis (MFA) into CE theories to establish a framework to comprehensively evaluate regional economies. Nine development scenarios are further developed to provide strategic recommendations for the development of CE in Guangdong. The results of these scenarios show that the CE of Guangdong is most effective among the nine scenarios when the birth rate is reduced by about 2%, the growth rates of the primary and secondary industries are reduced by 2%, and the growth rate of the tertiary industry increased by 2%. The biological substance consumption, fossil fuel consumption, building mineral consumption, industrial exhaust emissions and solid waste emissions are 88.39 Mt, 86.63 Mt, 108.16 Mt, 280.90 Mt, and 69.02 Mt respectively. The total material input (TMI) of 10,000 RMB of GDP and the total material output (TMO) of 10,000 RMB of GDP are 49.64 kt/10,000 RMB and 42.70 kt/10,000 RMB in 2022 respectively. Based on the status quo and simulated results, this study acknowledges the importance of population control and highlights the vigorous development of tertiary industry in economic construction. Policy interventions such as building pilot demonstrative smart cities and industrial parks would facilitate long-term sustainability of urban systems

Catalytic steam reforming of toluene as model tar compound using Ni/coal fly ash catalyst

Coal fly ash (CFA), a solid waste from power plants, was selected as the support of Ni-based catalysts used for steam reforming of toluene in a fixed-bed reactor. The CFA support was thermally pretreatment first, followed by chemical activation with different treatment time (6 h to 4 days) in 2-mol/L HNO(3)solution. Then, series low-cost catalysts were prepared by wet impregnation. The prepared catalysts were characterized suitably by X-ray diffraction (XRD), Brunauere-Emmette-Teller (BET), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and Raman techniques. According to the catalyst characterization, the chemical pretreatment could improve the support property by adjusting the chemical composition. The Fe-rich Fe-Ni and Ni-Co alloy was formed by H(2)reduction on the Ni/CFA-6h and Co-Ni/CFA-6h catalysts, respectively. In the catalytic steam reforming of toluene, the Ni/CFA-6h had the best catalytic active among all monometallic catalysts, which could be attributed to the existence of Fe(0.94)Ni(0.06)particles, and its performance could be further improved after partly replacing Ni by Co. The Co-Ni/CFA-6h catalyst exhibited the best ability of carbon deposit resistance, implying that its catalytic performance slightly lower than Ni/SiO(2)was due to the too large S(BET)surface area gap

Rheological Performance of High-Temperature-Resistant, Salt-Resistant Fracturing Fluid Gel Based on Organic-Zirconium-Crosslinked HPAM

Development of low-cost, high-temperature-resistant and salt-resistant fracturing fluids is a hot and difficult issue in reservoir fluids modification. In this study, an organic zirconium crosslinker that was synthesized and crosslinked with partially hydrolyzed polyacrylamide (HPAM) was employed as a cost-effective polymer thickener to synthesize a high-temperature-resistant and salt-resistant fracturing fluid. The rheological properties of HPAM in tap water solutions and 2 × 104 mg/L salt solutions were analyzed. The results demonstrated that addition of salt reduced viscosity and viscoelasticity of HPAM solutions. Molecular dynamics (MD) simulation results indicated that, due to electrostatic interaction, the carboxylate ions of HPAM formed an ionic bridge with metal cations, curling the conformation, decreasing the radius of rotation and thus decreasing viscosity. However, optimizing fracturing fluids formulation can mitigate the detrimental effects of salt on HPAM. The rheological characteristics of the HPAM fracturing fluid crosslinking process were analyzed and a crosslinking rheological kinetic equation was established under small-amplitude oscillatory shear (SAOS) test. The results of a large-amplitude oscillation shear (LAOS) test indicate that the heating effect on crosslinking is stronger than the shear effect on crosslinking. High-temperature-resistant and shear-resistant experiments demonstrated good performance of fracturing fluids of tap water and salt solution at 200 °C and 180 °C

Steam reforming of toluene over nickel catalysts supported on coal gangue ash

The development of high performance and low-cost catalyst is very important to remove tar during biomass gasification. Solid waste coal gangue ash (CGA), which mainly contains SiO2, Al2O3, Fe2O3 and CaO, was selected as support for Ni-based catalyst. The prepared low-cost catalysts were characterized suitably by XRD, BET, TPR, SEM, TG and Raman techniques. Toluene was selected as typical biomass tar model compounds to test the catalyst performance and compared with traditional catalysts Ni/Al2O3 and Ni/SiO2. Ni/CGA-1d exhibited the highest catalytic performance with the toluene conversion and H-2 yield accounting for 91.5% and 58.2% respectively, at 800 degrees C. It was showed that the performance of Ni/CGA-1d was higher than traditional catalysts Ni/Al2O3 and Ni/SiO2, and comparable with other polymetallic reforming catalysts. Due to the good resistance of carbon deposition, the Ni/CGA-1d catalyst also per formed better catalytic activity stability. The ability should be attributing to the existence of some metal elements such as Fe, Mg, K, Ca et al. in coal gangue ash support. (C) 2020 Published by Elsevier Ltd

Effect of Promoters on Steam Reforming of Toluene over a Ni-Based Catalyst Supported on Coal Gangue Ash

The exploration of high-value-added materials using inorganic solid waste is a very important contribution to sustainable development. Coal gangue ash (CGA) as a solid waste was chosen as catalyst support. Five low-cost catalysts modified by different promoters (Co, Ce, Fe, Mn, and Mo) were prepared using a co-impregnation method. The toluene steam reforming tests were carried out at 800 degrees C under S/C = 2 (steam-to-carbon mole ratio). Catalyst characteristics were evaluated using X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method, temperature-programmed reduction (TPR), and Raman spectroscopy. The results showed that most promoters could interact with a Ni active compound and enhance the toluene conversion and H-2 yield. The Mo-Ni/CGA-1d (1d means the I acid pretreatment time) catalyst performed the best catalytic activity, and corresponding toluene conversion and H-2 yield was equal to 92.6 and 62.3%, respectively, and it should be due to the formation of Mo-Ni alloy. Meanwhile, the Mo-Ni/CGA-1d catalyst exhibited higher stability during the runtime of 300 min compared with the Mn-Ni/CGA-1d catalyst, which can be attributed to the formation of the Mo2C structure with high-carbon-resistance ability. This is perhaps because the dissociation of CO2 or H2O on the Mo2C structure surface is beneficial to the production of free oxygen species, which can accelerate the removal of carbon deposition on the catalyst surface

Distribution characteristics of low molecular weight organic acids in seawater of the Changjiang Estuary and its adjacent East China Sea: Implications for regional environmental conditions

In this study, components, concentrations, distribution characteristics and sources of low molecular weight organic acids (LMWOAs) in seawater of the Changjiang Estuary and its adjacent East China Sea were investigated in March 2015. Lactic, acetic and formic acids were identified with their concentration range of 0-16.7, 0-42.7 and 0-6.7 mu mol.L-1, respectively. In the surface seawater, high concentrations of LMWOAs appeared in the sea area close to the estuary and along the coast. LMWOAs were important fractions of dissolved organic carbon and acetic acid was dominant component of LMWOAs. Riverine, terrestrial input, phytoplankton and sediment release were important sources for the LMWOAs, and human activities were considered as dominant sources for them in sampling period. The consistency of regions with high concentrations of LMWOAs, eutrophication, seasonal hypoxia and frequent red tide occurrence suggested LMWOAs as potential indicators for evaluating pollution status in coastal areas

Construction of ultrasonic nanobubbles carrying CAIX polypeptides to target carcinoma cells derived from various organs

Abstract Background Ultrasound molecular imaging is a novel diagnostic approach for tumors, whose key link is the construction of targeted ultrasound contrast agents. However, available targeted ultrasound contrast agents for molecular imaging of tumors are only achieving imaging in blood pool or one type tumor. No targeted ultrasound contrast agents have realized targeted ultrasound molecular imaging of tumor parenchymal cells in a variety of solid tumors so far. Carbonic anhydrase IX (CAIX) is highly expressed on cell membranes of various malignant solid tumors, so it’s a good target for ultrasound molecular imaging. Here, targeted nanobubbles carrying CAIX polypeptides for targeted binding to a variety of malignant tumors were constructed, and targeted binding ability and ultrasound imaging effect in different types of tumors were evaluated. Results The mean diameter of lipid targeted nanobubbles was (503.7 ± 78.47) nm, and the polypeptides evenly distributed on the surfaces of targeted nanobubbles, which possessed the advantages of homogenous particle size, high stability, and good safety. Targeted nanobubbles could gather around CAIX-positive cells (786-O and Hela cells), while they cannot gather around CAIX-negative cells (BxPC-3 cells) in vitro, and the affinity of targeted nanobubbles to CAIX-positive cells were significantly higher than that to CAIX-negative cells (P < 0.05). Peak intensity and duration time of targeted nanobubbles and blank nanobubbles were different in CAIX-positive transplanted tumor tissues in vivo (P < 0.05). Moreover, targeted nanobubbles in CAIX-positive transplanted tumor tissues produced higher peak intensity and longer duration time than those in CAIX-negative transplanted tumor tissues (P < 0.05). Finally, immunofluorescence not only confirmed targeted nanobubbles could pass through blood vessels to enter in tumor tissue spaces, but also clarified imaging differences of targeted nanobubbles in different types of transplanted tumor tissues. Conclusions Targeted nanobubbles carrying CAIX polypeptides can specifically enhance ultrasound imaging in CAIX-positive transplanted tumor tissues and could potentially be used in early diagnosis of a variety of solid tumors derived from various organs