Phosphor-converted white light-emitting diodes (WLEDs) have received significant attention; however, the leaked light from their blue InGaN chips has an undesirable effect on human health. Hence, it ...is necessary to develop red, green, and blue-emitting phosphors, which can be excited by an NUV chip instead of a blue chip. Herein, green-emitting ZnO:Cu2+ phosphors have been successfully synthesized by a simple and facile thermal diffusion method. The obtained powder shows a broad emission band peaking at 525 nm and a strong absorption peak at 377 nm. The ZnO:5%Cu2+ phosphor annealed at 800 °C in 2 hours revealed a lifetime of 0.57 ms, an activation energy of 0.212 eV, and the highest emission intensity with (x, y) CIE colour coordinates (0.3130, 0.5253). A WLED prototype has been fabricated by coating the ZnO:5%Cu2+ phosphor on an NUV 375 nm LED chip, where this coated phosphor shows a high quantum efficiency (QE) of 56.6%. This is, so far, the highest reported QE value for ZnO-based phosphors. These results suggest that the ZnO:Cu2+ phosphor could be an excellent candidate for NUV-pumped phosphor-converted WLED applications.
This review provides focused insights into the contamination status, sources, and ecological risks associated with multiple classes of antibiotics in surface water from the East and Southeast Asia ...based on publications over the period 2007 to 2020. Antibiotics are ubiquitous in surface water of these countries with concentrations ranging from <1 ng/L to hundreds μg/L and median values from 10 to 100 ng/L. Wider ranges and higher maximum concentrations of certain antibiotics were found in surface water of the East Asian countries like China and South Korea than in the Southeast Asian nations. Environmental behavior and fate of antibiotics in surface water is discussed. The reviewed occurrence of antibiotics in their sources suggests that effluent from wastewater treatment plants, wastewater from aquaculture and livestock production activities, and untreated urban sewage are principal sources of antibiotics in surface water. Ecological risks associated with antibiotic residues were estimated for aquatic organisms and the prevalence of antibiotic resistance genes and antibiotic-resistant bacteria were reviewed. Such findings underline the need for synergistic efforts from scientists, engineers, policy makers, government managers, entrepreneurs, and communities to manage and reduce the burden of antibiotics and antibiotic resistance in water bodies of East and Southeast Asian countries.
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•Antibiotic contamination status in East/Southeast Asia's surface water is reviewed.•Antibiotics are ubiquitous in surface water, especially in aquaculture and urban areas.•Antibiotic levels varied greatly from few ng/L to hundreds μg/L in surface water.•Ecological risks and prevalence of antibiotic resistance were widely observed.•Regional monitoring studies and environmental guidelines for antibiotics are needed.
Foamed concrete material is a sustainable material which is widely used in the construction industry due to their sustainability. Accurate prediction of their compressive strength is vital for ...structural design. However, empirical methods are limited to consider simultaneously all influencing factors in predicting the compressive strength of foamed concrete materials. Thus, this study proposed a novel hybrid artificial intelligence (AI) model which couples the least squares support vector regression (LSSVR) with the grey wolf optimization (GWO) to consider effectively the influencing factors and improve the predictive accuracy in predicting the foamed concrete’s compressive strength. Performance of the proposed model was evaluated using a real-world dataset. Comparison results confirm that the proposed GWO–LSSVR model was superior than the support vector regression, artificial neural networks, random forest, and M5Rules with the improvement rate of 144.2–284.0% in mean absolute percentage error (MAPE). Notably, the evaluation results show that the GWO–LSSVR model showed the good agreement between the actual and predicted values with the correlation coefficient of 0.991 and MAPE of 3.54%. Thus, the proposed AI model was suggested as an effective tool for designing foamed concrete materials.
With 5G on the verge of being adopted as the next mobile network, there is a need to analyze its impact on the landscape of computing and data management. In this paper, we analyze the impact of 5G ...on both traditional and emerging technologies and project our view on future research challenges and opportunities. With a predicted increase of 10-100x in bandwidth and 5-10x decrease in latency, 5G is expected to be the main enabler for smart cities, smart IoT and efficient healthcare, where machine learning is conducted at the edge. In this context, we investigate how 5G can help the development of federated learning. Network slicing, another key feature of 5G, allows running multiple isolated networks on the same physical infrastructure. However, security remains the main concern in the context of virtualization, multi-tenancy and high device density. Formal verification of 5G networks can be applied to detect security issues in massive virtualized environments. In summary, 5G will make the world even more densely and closely connected. What we have experienced in 4G connectivity will pale in comparison to the vast amounts of possibilities engendered by 5G.
In this study, the operation parameters of a partial nitrification process (PN) treating saline wastewater were optimized using the Box–Behnken design via the response surface methodology (BBD-RSM). ...A novel strategy based on the control of the carbon/nitrogen ratio (C/N), alkalinity/ammonia ratio (K/A), and salinity in three stages was used to achieve PN in a sequence batch reactor. The results demonstrated that a high and stable PN was completed after 50 d with an ammonia removal efficiency (ARE) of 98.37 % and nitrite accumulation rate (NAR) of 85.93 %. Next, BBD-RSM was applied, where ARE and NAR were the responses. The highest responses from the confirmation experiment were 99.9 % ± 0.04 and 95.25 % ± 0.32 when the optimum C/N, K/A, and salinity were identified as 0.84, 2, and 5.5 (g/L), respectively. The results were higher than those for the nonoptimized reactor. The developed regression model adequately forecasts the PN performance under optimal conditions. Therefore, this study provides a promising strategy for controlling the PN process and shows how the BBD-RSM model can improve the PN performance.
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•A synthetic strategy was used for partial nitrification in saline wastewater.•This strategy controlled the C/N ratio, K/A ratio, and salinity instead of DO.•Ammonia oxidation and nitrite accumulation were optimized by the BBD-RSM model.•Optimal C/N and K/A ratios and salinity were 0.84, 2, and 5.5 g/L, respectively.•ARE = 99.9 % ± 0.04 and NAR = 95.25 % ± 0.32 occurred under optimal conditions.
Comprehensive studies on emerging contaminants like volatile methyl siloxanes in settled dust from different micro-environments are still limited. In this study, concentrations and distribution of ...cyclic volatile methyl siloxanes (CVMSs) including
D
3,
D
4,
D
5, and
D
6 were examined in indoor dust samples collected from various micro-environments in northern and central Vietnam. Concentrations of total CVMSs in the dust samples ranged from 86.0 to 5890 (median 755) ng/g and decreased in the order: waste processing workshops (median 1560; range 329–5890) > common houses (650; 115–1680) > university classrooms (480; 86.0–1540) > vehicle repair shops (295; 126–1950) ng/g. This observation suggests that informal waste processing activities are sources of CVMSs. Among the studied CVMSs,
D
5 was the most predominant compound (41 ± 14%), followed by
D
6 (26 ± 13%),
D
4 (23 ± 12%), and
D
3 (11 ± 11%). Moderate positive correlations between
D
3/
D
4,
D
4/
D
5, and
D
5/
D
6 were found. Median daily intake doses of
D
3,
D
4,
D
5, and
D
6 through dust ingestion were 0.016, 0.051, 0.11, and 0.054 ng/kg/d, respectively, which were comparable to water consumption and markedly lower than the air inhalation pathway.
Objectives
This study aimed to examine the association between six air pollutants and COVID‐19 infection in two main clusters, which accounted for 83% of total confirmed cases in Korea.
Methods
We ...collected the data on daily confirmed cases between February 24, 2020 and September 12, 2020. Data on six air pollutants (PM2.5, PM10, O3, NO2, CO and SO2) and four meteorological factors (temperature, wind speed, humidity and air pressure) were obtained on seven days prior to the research period. The generalised additive model and the distributed lag nonlinear model were applied to generate the relative risks (RRs) and 95% confidence intervals (CIs) for the associations. Pooled estimates for clusters were obtained by applying a random‐effects model.
Results
We found that NO2 concentration was positively associated with daily confirmed cases in both Seoul‐Gyeonggi and Daegu‐Gyeongbuk clusters, with RRs (95% CIs) of 1.22 (1.03–1.44) and 1.66 (1.25–2.19), respectively. However, SO2 concentration was observed to be associated with daily confirmed cases in the Seoul‐Gyeonggi cluster only (RR = 1.30, 95% CI = 1.10–1.54), whereas PM2.5 and CO concentrations were observed to be associated with daily confirmed cases in the Daegu‐Gyeongbuk cluster only (RR = 1.14, 95% CI = 1.02–1.27 and RR = 1.30, 95% CI = 1.15–1.48, respectively).
Conclusions
Our data found that NO2 concentration was positively associated with daily confirmed cases in both clusters, whereas the effect of PM2.5, CO and SO2 on COVID‐19 infection in two clusters was different.
The on‐body immunodetection of biomarkers in sweat would significantly augment the potential of wearable body‐interfaced biosensors for self‐testing but has been limited due to the difficulty of ...integrating liquid handling and immunobiosensing devices in a wearable platform. Herein, a stretchable microfluidic immunobiosensor (SMIB) patch with hollow microfibers of elastomeric nanocomposites for the highly sensitive on‐body biosensing of neuropeptide Y (NPY), a stress biomarker, in human sweat is reported. The SMIB patch is composed of a stretchable liquid handling device and an electrochemical impedimetric immunobiosensor made of hollow and conductive microfibers of reduced graphene oxide (rGO) and rGO‐Ag nanowires in polyurethane matrix, respectively. The patch possesses a low limit of detection of 50 fm, a large dynamic range (50 fm–1 nm), good linearity, no labeling or reagent requirements, and facile formation in a patch form factor. By combining handling of the biofluid and delivery of the washing solution by a simple finger‐touch operation as well as the analytical capability of NPY with an extremely low concentration in human sweat, the SMIB patch is a promising approach toward wearable non‐invasive immunodetection for self‐testing.
A stretchable microfluidic immunobiosensor (SMIB) patch for detection of neuropeptide Y (NPY) is developed. The SMIB patch is comprised of a microfiber‐based microfluidic device and an electrochemical immunobiosensor. Through enabling handling of the biofluid and the analytical capability of detecting extremely low concentrations of NPY in human sweat, the presented SMIB patch provides a promising approach toward wearable point‐of‐care testing.
Graphene-reinforced metal matrix composites exhibit excellent mechanical properties owing to dislocation impedance at the metal-graphene interface. Graphene coated on metal with composites fabricated ...using powder sintering can be applied as high-strength thin films across various fields (e.g., microelectromechanical systems, flexible electronics). In this study, a bilayer composite of multilayer graphene (MLG)-coated Ni is synthesized using the chemical vapor deposition (CVD) and transfer methods; mechanical properties are investigated using nanoindentation methods. MLG-coated Ni synthesized by CVD exhibits 195% and 470% increases in hardness and Young’s modulus, respectively, compared with single-layer Ni. In contrast, the Young modulus and hardness of MLG-coated Ni synthesized via the transfer method can be estimated using the rule of mixture for composite materials. Transmission electron microscopy (TEM) shows that in MLG-coated Ni synthesized by CVD, dislocations are dense and evenly distributed compared with that synthesized by the transfer method, leading to its high mechanical strength. Molecular dynamics (MD) simulations demonstrate that interface-induced hardening is effective in graphene-coated Ni(111) with a strongly coupled interface. Therefore, ultrahigh-strength MLG-coated metal films can be obtained by manipulating the interface property between the MLG and metal, offering the potential for use as a thin film resistor against external force.
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We show the low-lying excitations at filling factor ν = n + 1/3 with realistic interactions can be understood as quantum fluids with "Gaffnian quasiholes" as the proper elementary degrees of freedom. ...Each Laughlin quasihole can thus be understood as a bound state of two Gaffnian quasiholes, which in the lowest Landau level (LLL) behaves like "partons" with "asymptotic freedom" mediated by neutral excitations acting as "gluons." Near the experimentally observed nematic FQH phase in higher LLs, quasiholes become weakly bound and can fractionalize with rich dynamical properties. By studying the effective interactions between quasiholes, we predict a finite temperature phase transition of the Laughlin quasiholes even when the Laughlin ground state remains incompressible, and derive relevant experimental conditions for its possible observations.
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