Search Results (4)

The emergence of the Industrial Internet of Things (IIoT) has accelerated the adoption of Industrial Wireless Sensor Networks (IWSNs) for numerous applications. Effective communication in such applications requires reduced end-to-end transmission time, balanced energy consumption and increased communication reliability. Graph routing, the main routing method in IWSNs, has a significant impact on achieving effective communication in terms of satisfying these requirements. Graph routing algorithms involve applying the first-path available approach and using path redundancy to transmit data packets from a source sensor node to the gateway. However, this approach can affect end-to-end transmission time by creating conflicts among transmissions involving a common sensor node and promoting imbalanced energy consumption due to centralised management. The characteristics and requirements of these networks encounter further complications due to the need to find the best path on the basis of the requirements of IWSNs to overcome these challenges rather than using the available first-path. Such a requirement affects the network performance and prolongs the network lifetime. To address this problem, we adopt a Covariance-Matrix Adaptation Evolution Strategy (CMA-ES) to create and select the graph paths. Firstly, this article proposes three best single-objective graph routing paths according to the IWSN requirements that this research focused on. The sensor nodes select best paths based on three objective functions of CMA-ES: the best Path based on Distance (PODis), the best Path based on residual Energy (POEng) and the best Path based on End-to-End transmission time (POE2E). Secondly, to enhance energy consumption balance and achieve a balance among IWSN requirements, we adapt the CMA-ES to select the best path with multiple-objectives, otherwise known as the Best Path of Graph Routing with a CMA-ES (BPGR-ES). A simulation using MATALB with different configurations and parameters is applied to evaluate the enhanced graph routing algorithms. Furthermore, the performance of PODis, POEng, POE2E and BPGR-ES is compared with existing state-of-the-art graph routing algorithms. The simulation results reveal that the BPGR-ES algorithm achieved 87.53% more balanced energy consumption among sensor nodes in the network compared to other algorithms, and the delivery of data packets of BPGR-ES reached 99.86%, indicating more reliable communication. Full article

Studying the effect of surface ozone (O₃) and water stress on tree growth is important for planning sustainable forest management and forest ecology. In the present study, a 22-year long time series (1998–2019) on basal area increment (BAI) and fructification severity of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H.Karst.) at five forest sites in Western Germany (Rhineland Palatinate) was investigated to evaluate how it correlates with drought and stomatal O₃ fluxes (PODY) with an hourly threshold of uptake (Y) to represent the detoxification capacity of trees (POD1, with Y = 1 nmol O₃ m⁻² s⁻¹). Between 1998 and 2019, POD1 declined over time by on average 0.31 mmol m⁻² year⁻¹. The BAI showed no significant trend at all sites, except in Leisel where a slight decline was observed over time (−0.37 cm² per year, p < 0.05). A random forest analysis showed that the soil water content and daytime O₃ mean concentration were the best predictors of BAI at all sites. The highest mean score of fructification was observed during the dry years, while low level or no fructification was observed in most humid years. Combined effects of drought and O₃ pollution mostly influence tree growth decline for European beech and Norway spruce. Full article

To verify the responses of visible foliar injury (VFI), we exposed seedlings of three oak species for 4.5 months in an open air facility, using differing ozone (O₃) and drought treatments: O₃ (three levels from ambient to ×1.4 ambient), and drought (three levels of irrigation from 40% to 100% field capacity). We related the accumulated phytotoxic O₃ dose (POD₁) and cumulative drought index (CDI) to the O₃ and drought VFI and assessed growth increment (height, diameter, leaf number), biomass (of all organs), and physiological parameters: net photosynthesis per plant (P_n), photosynthetic nitrogen (PNUE) and phosphorus use efficiency (PPUE)). The results indicated that an increase in POD₁ promoted O₃ VFI in Quercus robur and Quercus pubescens, while Quercus ilex was asymptomatic. The POD₁-based critical level at the onset of O₃ VFI was lower for Q. robur than for Q. pubescens (12.2 vs. 15.6 mmol m⁻² POD₁). Interestingly, drought reduced O₃ VFI in Q. robur but increased it in Q. pubescens. Both O₃ and drought were detrimental to the plant biomass. However, Q. robur and Q. pubescens invested more in shoots than in roots, while Q. ilex invested more in roots, which might be related to a hormetic mechanism. P_n, PNUE and PPUE decreased in all species under drought, and only in the sensitive Q. robur (PPUE) and Q. pubescens (PNUE) under O₃. This study confirms that POD₁ is a good indicator to explain the development of O₃ VFI and helps a differential diagnosis of co-occurring drought and O₃ VFI in oak forests. Full article

This study investigated visible foliar ozone (O₃) injury in three deciduous tree species with different growth patterns (indeterminate, Alnus glutinosa (L.) Gaertn.; intermediate, Sorbus aucuparia L.; and determinate, Vaccinium myrtillus L.) from May to August 2018. Ozone effects on the timing of injury onset and a plant injury index (PII) were investigated using two O₃ indices, i.e., AOT40 (accumulative O₃ exposure over 40 ppb during daylight hours) and POD_Y (phytotoxic O₃ dose above a flux threshold of Y nmol m⁻² s⁻¹). A new parameterization for POD_Y estimation was developed for each species. Measurements were carried out in an O₃ free-air controlled exposure (FACE) experiment with three levels of O₃ treatment (ambient, AA; 1.5 × AA; and 2.0 × AA). Injury onset was found in May at 2.0 × AA in all three species and the timing of the onset was determined by the amount of stomatal O₃ uptake. It required 4.0 mmol m⁻² POD₀ and 5.5 to 9.0 ppm·h AOT40. As a result, A. glutinosa with high stomatal conductance (g_s) showed the earliest emergence of O₃ visible injury among the three species. After the onset, O₃ visible injury expanded to the plant level as confirmed by increased PII values. In A. glutinosa with indeterminate growth pattern, a new leaf formation alleviated the expansion of O₃ visible injury at the plant level. V. myrtillus showed a dramatic increase of PII from June to July due to higher sensitivity to O₃ in its flowering and fruiting stage. Ozone impacts on PII were better explained by the flux-based index, POD_Y, as compared with the exposure-based index, AOT40. The critical levels (CLs) corresponding to PII = 5 were 8.1 mmol m⁻² POD₇ in A. glutinosa, 22 mmol m⁻² POD₀ in S. aucuparia, and 5.8 mmol m⁻² POD₁ in V. myrtillus. The results highlight that the CLs for PII are species-specific. Establishing species-specific O₃ flux-effect relationships should be key for a quantitative O₃ risk assessment. Full article