Time Variation Research Articles

Analysis of Opaque, Peel-Off and Flex Rejects in the Electro Plating Process Using the Six Sigma Dmaic Method

The modern manufacturing industry is faced with increasing pressure to achieve high levels of quality while remaining efficient in its production processes. One of the challenges faced by PT. Plating services in electroplating production have a high reject rate, which can cause increased costs and have a negative impact on the company's reputation. PT. Jasa Plating in the production process still has a high number of rejects, the rejects are dominated by opaque, peel-off and spots. PT. Plating services for each production contribute a high average of 2% defects per day, DPMO 20,000 and Sigma value 3.55. Quite a few rejections resulted in a decrease in turnover and increased production costs. The costs incurred due to these rejects are an average of Rp. 1,268,593 per day and an average of Rp. 35,698,907 per month as a result of data collection from January – September 2023. In this business process, this is very detrimental for the company. The aim of this research is to suppress blurry rejects, peel-offs and spots in the electro plating process at PT. Plating Services. The steps taken in conducting research include: identification stage, data collection and processing, analysis and recommendations for improvement, and conclusions. The method used in this research is the Six Sigma DMAIC (Define, Measure, Analysis, Improvement, Control) method. Through analysis, you can find several factors that cause high reject rates, including operational errors, discrepancies in the production process, or raw material quality problems. After implementing the improvement plan, then evaluate the results. This can include re- measuring the DPMO, analysis of the resulting products to see a decrease in reject rates, and comparisons between before and after implementing improvements. From the comparison results after the repairs were carried out, the data before the repairs were carried out, the NG amount was 1.99%, the DPMO was 6,646 and the Sigma value was 3.98. After improvements to NG 0.84%, DPMO 2,791 sigma value 4.28. Factors causing high levels of blurring, peel-off and spots, namely insufficient or excessive cleaning of the metal surface before the electroplating process, can cause problems such as peel-off. Contamination of the electroplating solution by foreign materials can cause blurring and flecks in the final layer. Machinery or equipment that is not properly calibrated, or experiences wear and tear, can produce products that do not meet standards. Variations in temperature, time, or electric current in the electroplating process can produce inconsistent coatings. Carefully monitor and control process-parameters to ensure stability.

Effect of bariatric surgery in the body burden of persistent and non-persistent pollutants: longitudinal study in a cohort of morbidly obese patients

IntroductionObesity is a pathological state that involves the dysregulation of different metabolic pathways and adipose tissue cells, constituting a risk factor for the development of other diseases. Bariatric surgery is the most effective treatment. The study of the behavior of pollutants in situations of extreme weight loss can provide biomonitoring information and tools to manage diseases of environmental etiology.AimTo determine the prevalence of serum persistent and non-persistent pollutants in obese patients subjected to bariatric surgery and analyze the impact of sociodemographic variables on these changes.MethodsGC-MS/MS and UHPLC-MS/MS were utilized to determine the detection rates and concentrations of 353 compounds, including persistent organic pollutants (POPs), pesticides, pharmaceuticals, and rodenticide, in serum samples of 59 obese patients before and after undergoing bariatric surgery.ResultsDetection rates of p,p’-DDE, HCB, β-HCH, naphthalene, phenanthrene and PCB congeners 138, 153 and 180 significantly increased due to surgery-induced weight loss. Serum levels of p,p’-DDE, PCB-138, PCB-153 and PCB-180 also increased after surgery. Correlations between naphthalene levels, weight loss, variation of total lipids and time after surgery were found. Additionally, correlations were observed between concentrations of PCB-138 and weight loss, and between phenanthrene levels and reduction of total lipids. No statistically significant differences were observed for other groups of contaminants, pharmaceuticals and other chemicals included in the quantification methods.ConclusionsIncrement of POPs was observed after bariatric surgery. Serum concentrations of POPs after surgery were influenced by adiposity-related variables. Although biomonitoring studies show a decreasing tendency of exposure, rapid weight loss leads to an increase of circulating POPs. Further research on the interplay between adipose tissue, POPs and peripheral organs is required.

Ultrabroadband invisibility cloaking design of a concentric multilayered cylindrical metamaterial

An ultrabroadband invisibility cloak is designed using a genetic algorithm (GA) for a cylindrical target with an infinite length. The cloaking band is 0.4 to 0.7µm, covering almost the entire visible light range. The invisibility cloaking medium consists of concentric multilayered cylindrical metamaterials (CM). When the cloaking target is covered with a well-designed 26+ layer CM, the average scattering cross-section is 6% or less of the uncloaked target’s cross-section. The cloaking performance of the structure designed by the GA was superior to that designed by analytical calculations based on a combination of the transformation optics and the effective medium approximation. The cloaking is confirmed through the time variation of the magnetic fields calculated using the finite-difference time-domain method. In addition, the mechanism of the cloaking is discussed.

Long-term prevalence of vitamin deficiencies after bariatric surgery: a meta-analysis.

Bariatric surgery can lead to short-mid-term vitamin deficiencies, but the long-term vitamin deficiencies is unclear. This study aimed to conduct a meta-analysis regarding the long-term prevalence (≥ 5years) of vitamin deficiencies after bariatric surgery. We searched the EMBASE, PubMed, and CENTRAL databases for clinical studies until June 2023. Meta-analysis, sensitivity, subgroup, and meta-regression analyses were performed. This meta-analysis included 54 articles with follow-up duration ranging from 5 to 17years. The most prevalent vitamin deficiencies after surgery were vitamin D (35.8%), followed by vitamin E (16.5%), vitamin A (13.4%), vitamin K (9.6%), and vitamin B12 (8.5%). Subgroup analyses showed that the prevalence of vitamin A and folate deficiencies increased with the follow-up time. Roux-en-Y gastric bypass had a higher rate of vitamin B12 deficiency than sleeve gastrectomy and biliopancreatic diversion with duodenal switch (BPD-DS). Studies conducted in Europe had higher vitamin A deficiency (25.8%) than in America (0.8%); Asian studies had more vitamin B12 but less vitamin D deficiency than European and American studies. Meta-regression analysis displayed that publication year, study design, preoperative age, BMI, and quality assessment score were not associated with vitamin A, B12, D, and folate deficiencies rate. A high prevalence of vitamin deficiencies was found after bariatric surgery in the long-term follow-up, especially vitamin D, E, A, K, and B12. The variation in study regions, surgical procedures, and follow-up time are associated with different postoperative vitamin deficiencies; it is necessary to develop more targeted vitamin supplement programs.

Organic matter decay and bacterial community succession in mangroves under simulated climate change scenarios.

Mangroves are coastal environments that provide resources for adjacent ecosystems due to their high productivity, organic matter decomposition, and carbon cycling by microbial communities in sediments. Since the industrial revolution, the increase of Greenhouse Gases (GHG) released due to fossil fuel burning led to many environmental abnormalities such as an increase in average temperature and ocean acidification. Based on the hypothesis that climate change modifies the microbial diversity associated with decaying organic matter in mangrove sediments, this study aimed to evaluate the microbial diversity under simulated climate change conditions during the litter decomposition process and the emission of GHG. Thus, microcosms containing organic matter from the three main plant species found in mangroves throughout the State of São Paulo, Brazil (Rhizophora mangle, Laguncularia racemosa, and Avicennia schaueriana) were incubated simulating climate changes (increase in temperature and pH). The decay rate was higher in the first seven days of incubation, but the differences between the simulated treatments were minor. GHG fluxes were higher in the first ten days and higher in samples under increased temperature. The variation in time resulted in substantial impacts on α-diversity and community composition, initially with a greater abundance of Gammaproteobacteria for all plant species despite the climate conditions variations. The PCoA analysis reveals the chronological sequence in β-diversity, indicating the increase of Deltaproteobacteria at the end of the process. The GHG emission varied in function of the organic matter source with an increase due to the elevated temperature, concurrent with the rise in the Deltaproteobacteria population. Thus, these results indicate that under the expected climate change scenario for the end of the century, the decomposition rate and GHG emissions will be potentially higher, leading to a harmful feedback loop of GHG production. This process can happen independently of an impact on the bacterial community structure due to these changes.

Flow-induced fabrication of ZnO nanostructures in pillar-arrayed microchannels.

The emergence of microfluidic devices integrated with nanostructures enables highly efficient, flexible and controllable biosensing, among which zinc oxide (ZnO) nanostructure-based fluorescence detection has been demonstrated to be a promising methodology due to its high electrical point and unique fluorescence enhancement properties. The optimization of microfluidic synthesis of ZnO nanostructures for biosensing on chip has been in demand due to its low cost and high efficiency, but still the flow-induced growth of ZnO nanostructures is not extensively studied. Here, we report a simple and versatile strategy that could manipulate the local flow field by creating periodically arranged micropillars within a straight microchannel. We have explored the effects of perfusion speed and flow direction of seed solution, localized flow variation of growth solution and growth time on the morphology of nanostructures. This provided a comprehensive understanding which governs nanostructure fabrication controlled by flow. The results demonstrated that localized flow in microfluidic devices was essential for the initiation and growth of zinc oxide crystals, enabling precise control over their properties and morphology. Furthermore, a model protein was used to demonstrate the intrinsic fluorescence enhancement of ZnO nanostructures as an example to reveal the morphology-related enhancement properties.

Generalistic Assessments of the Potential of Medical Drones in Urban Environment

At the current development stage, the lower airspace above urban areas is only used to a very limited extent. Recent developments in the drone industry are making this area more accessible. The leading use case for drone applications is currently seen in the medical sector. Individual evidence shows that the use of drones to transport medical personnel for first medical response brings significant improvements in terms of cost and response time. Advantages in urban applications are seen as promising by some research projects, but this is not scientifically proven yet. This study deals with the simulation of transportation times of medical proposals by ambulance and drone in the metropolitan region of Stavanger and the comparison of transport times. The proposed methodology develops transferable results from concrete use-cases. By using a drone 80% of the expected operations can benefit from a reduction in transport time of up to 10 minutes with a variation of +/- 4 minutes through adjusted flight speeds due to weather conditions and variations in ambulance travel times due to different traffic volumes. The data set cleaned for the local special cases shows potential for a reduction of up to 20 minutes for the remaining operations, while the extracted individual cases even showing improvements of up to 60 minutes.

A sentinel watching over inter-tidal seagrass phenology across Western Europe and North Africa

Seagrasses are marine flowering plants that form extensive meadows from the inter-tidal zone up to ~50 m depth. As biological and ecological Essential Biodiversity Variables, seagrass cover and composition provide a wide range of ecosystem services. Inter-tidal seagrass meadows provide services to many ecosystems, so monitoring their occurrence, extent, condition and diversity can be used to indicate the biodiversity and health of local ecosystems. Current global estimates of seagrass extent and recent reviews either do not mention inter-tidal seagrasses and their seasonal variation, or combine them with sub-tidal seagrasses. Here, using high-spatial and high-temporal resolution satellite data (Sentinel-2), we demonstrate a method for consistently mapping inter-tidal seagrass meadows and their phenology at a continental scale. We were able to highlight varying seasonal patterns that are observable across a 23° latitudinal range. Timings of peaks in seagrass extent varied by up to 5 months, rather than the previously assumed marginal to non-existent variation in peak timing. These results will aid management by providing high-resolution spatio-temporal monitoring data to better inform seagrass conservation and restoration. They also highlight the high level of seasonal variability in inter-tidal seagrass, meaning combination with sub-tidal seagrass for global assessments will likely produce misleading or incorrect estimates.

The Impact of Wide Discharge C-Rates on the Voltage Plateau Performance of Cylindrical Ternary Lithium-Ion Batteries

Battery voltage plateau characteristics are crucial for designing and controlling battery management systems. Utilising the plateau period attributes to their fullest extent can enable optimal battery control, enhance battery performance, and prolong battery lifespan. This research aimed to investigate the performance of cylindrical ternary lithium batteries at various discharge rates, focusing on the variations in terminal voltage, capacity, and temperature. The battery performance at different discharge rates was meticulously examined through cyclic charge/discharge experiments. The convexity of the voltage curve was used to analyse the voltage plateau characteristics at different rates. The findings revealed significant differences in battery performance under varying discharge rates. Higher discharge rates resulted in shorter discharge times and lower battery voltages at corresponding residual capacities. The discharge time, capacity, and voltage during the plateau phase decreased as the discharge rate increased. At discharge rates of 1 C, 3 C, 5 C, 7 C, 9 C, and 11 C, the proportion of discharged battery capacity ranged from 86.45% to 78.42%. At the same time, voltage and temperature variations during the plateau period decreased significantly compared to those before and after discharge. This research provides a crucial reference point for advancing battery design and thermal management systems.

Comprehensive analysis of the eclipsing binaries V527 Dra and V2846 Cyg

Abstract This is the first comprehensive study of the eclipsing binaries V527 Dra and V2846 Cyg, based on radial velocities and ground- and space-based light curves. We perform detailed modeling of these data to derive the absolute parameters and the orbital properties of the two systems. V527 Dra is found to be a semi-detached, and V2846 Cyg a contact binary. Both show continual out-of-eclipse variations that can be explained by migrating dark spots of magnetic origin. We also perform the eclipse timing variation (ETV) analysis which reveals that V527 Dra has a tertiary companion whose mass (∼1M⊙) and orbital inclination (∼70○) are additionally constrained by radial velocities. The ETV diagram of V2846 Cyg displays a quadratic trend accompanied by a low-amplitude cyclic variation, likely due to a magnetic cycle, although further eclipse times are needed to provide a clearer explanation. Lastly, we demonstrate a correlation between the variations in spot parameters obtained via light curve modeling for individual orbital cycles and the residual ETVs, essentially confirming the assumption of magnetic activity in both systems.

Grass curing-driven fire danger index in a protected mountainous grassland using fused MODIS and Sentinel-2

ABSTRACT This study assessed the spatio-temporal variation of the degree of curing (DoC) in the Golden Gate Highlands National Park (GGHNP) from 2016 to 2020. The estimation of the degree of grass curing was carried out with the high spatial resolution fused remotely sensed data of MODIS and Sentinel-2 employing Index-then-Blend (IB) data fusion methods on Google Earth Engine (GEE) to compute Grassland Curing Index (GCI) using soil and vegetation moisture content indices-based grassland curing algorithm. Grassland curing indices were computed on Google Earth Engine and converted into Grassland Curing Maps (GCMs), which were then synthesized into fire danger maps. The study showed that all selected indices have the highest DoC in the month of September, with the minor time variation observed in MODIS and Sentinel 2-derived GCI estimated using Shortwave Infrared Water Stress (GCI_SIWSI) in the months of August and March, respectively. The analysis further revealed that GCI_SIWSI (44%) derived from Sentinel-2 data yielded the highest area of extremely high fire danger, followed by GCI estimated using Normalized Difference Moisture Index (GCI_NDMI) (25%) derived from fused data, MODIS-derived GCI_SIWSI and fused-derived GCI estimated using Global Vegetation Monitoring Index (GCI_GVMI) (both 16%). The GCI_SIWSI derived from Sentinel-2 data also showed that more than 95% of the entire landmass of the study area was within a high to extremely high fire danger zone, making the park’s vegetation susceptible to fire. Among all the four selected indices correlated against fire point, only SIWSI revealed a positive relationship across MODIS, Sentinel-2 and Fused data. It is also evident from the study that GCMs derived from Fused data outperformed MODIS and Sentinel-2 with the highest R2 and F values of 0.65 and 380, respectively. These results indicate that GCI derived from fused remotely sensed data is a promising GCI for accurately assessing the DoC over mountainous grassland environments. The study paved the way for increasing the spatial resolution for estimating the DoC for fire and fuel management of parks and other fire agencies within mountainous grassland environments.

Evaluation of time in tight range and the glycaemia risk index in adults with type 1 diabetes using an advanced hybrid closed loop system: A 1-year real-world assessment.

To assess the long-term glycaemic outcomes, with additional metrics, in adults with type 1 diabetes (T1D) using the Tandem t:slim X2 with Control-IQ technology advanced hybrid closed-loop (AHCL) system. This was a single-centre, retrospective study involving 56 T1D patients who transitioned to the Tandem t:slim X2 with Control-IQ system. The primary and secondary endpoints consisted of variations in time in tight range (TiTR; 70-140 mg/dL) and the glycaemia risk index (GRI), respectively. Additional standardized continuous glucose monitoring (CGM) metrics, mean sensor glucose, coefficient of variation, the glucose management indicator (GMI), HbA1c and insulin daily dose, were also evaluated. Variables were measured at baseline and at 15 days, 3 months, 6 months and 1 year after Tandem t:slim X2 Control-IQ initiation. Glucose outcomes are expressed as mean (standard deviation). Use of Tandem t:slim X2 with Control-IQ over 1 year was associated with an increase in mean TiTR, from 38.11% (17.05%) to 43.10% (13.20%) (P = .059), and with a decline in the GRI, from 41.03 (25.48) to 28.55 (16.27) (P = .008). CGM metrics, including time in range and time above range, showed consistent improvements. Mean sensor glucose, the GMI and HbA1c decreased significantly over time. After an initial increase, insulin daily dose remained stable throughout the 12 months. The results highlight the sustained effectiveness of Tandem t:slim X2 with Control-IQ in improving glycaemic outcomes over 1 year and support the use of this technology for the management of T1D.

Probing secular changes in the gravitational constant with white dwarf spectra

Exploring variations in fundamental physics constants across cosmological space-time is of substantial importance in both theoretical and experimental physics. A crucial means of investigating such variations involves comparing laboratory measurements with astrophysical observations. In the present study, we employ a combination of laboratory data and observed Lyman transitions of H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$H_2$$\\end{document} identified in the white dwarf star GD133. Through this examination, we find the temporal variation of the gravitational constant, G˙/G=(0.016±0.098)×10-15year-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\dot{G}}}/{G} = (0.016 \\pm 0.098) \ imes 10^{-15}~\ ext {year}^{-1}$$\\end{document} with a gravitational potential ϕ≈104,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi \\approx 10^4,$$\\end{document} and an average total redshift of H2,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$H_2,$$\\end{document}zabs=0.0001820(10).\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_{abs} =0.0001820(10).$$\\end{document} This newly determined constraint on the time variation of G serves as an important tool for advancing discussions within unified theories.

Design and characterization of a nano‐pulsed atmospheric pressure plasma jet for biomedical applications

AbstractPlasma jets, crucial atmospheric pressure sources in biomedical applications, generate reactive species in liquids, with electrical fields playing a significant role, as variations in pulse rise times and durations in dielectric barrier discharges yield diverse effects. This study presents a novel nanosecond pulse plasma jet. Here, investigations with phosphate‐buffered saline and Ringer's saline elucidate critical parameters influencing species generation, such as treatment time and gas flow rate. Results showed increasing concentrations of H2O2 and NO2− over time, with NO2− degrading faster in Ringer's saline due to acidification. The nanosecond pulse jet exhibits superior energy efficiency than conventional jets, laying the groundwork for optimizing species generation and studying electrical field effects in future biological works.

Accurate Collisional Cross Section Measurement by Multipass Cyclic Ion Mobility Spectrometry.

Ion mobility-mass spectrometry (IM-MS) is a powerful analytical tool for structural characterization. IM measurement provides collision cross section (CCS) values that facilitate analyte identification. While CCS values can be directly calculated from mobility measurements obtained using drift tube ion mobility spectrometry (DT-IMS), this method has limited mobility resolution due to the practical constraints on the length of the ion drift path. Consequently, DT-IMS cannot differentiate analytes with similar mobilities or resolve fine mobility features of individual ions. Cyclic IMS (cIMS) instruments leverage a cyclic path enabled by traveling wave ion mobility (TWIM) technology and offer increased mobility solution to address this challenge. While TWIM devices must first be calibrated to enable CCS measurements, current calibration strategies are primarily tailored for single-pass analyses. This preference is partly attributed to the challenges associated with multipass calibration methods, which require both calibrants and analytes to experience the same number of passes. Achieving this consistency can be complicated due to factors like peak splitting and diffusion, and may not be feasible for online IM-MS analyses. A recent report employed average ion velocities obtained from multiple measurements under different separation pathlengths as a path length-independent metric for CCS calibration. However, the ability to exploit this averaging approach is limited by observed variation in ion drift time/velocity in these measurements. In this study, we introduce a novel calibration strategy designed for multipass cIMS analyses, directly targeting the root cause for the path length- and mobility-dependent variations in ion drift time. With this method, we demonstrate that CCS values derived from multipass measurements closely align with those obtained from single-pass analyses, with an average deviation of 0.1%. We apply this method to characterize four isomeric trisaccharides. Our approach not only results in excellent agreement between our measured cIMSCCS values and the reported DTCCS values, with an average difference of only 0.5%, but also allows us to effectively identify subtle mobility characteristics of each compound and determine their respective CCS values. This level of detail and accuracy was previously unattainable using DT-IMS or single-pass cIMS measurements. We developed an algorithm for reconstructing arrival time distribution in cases where wrap-around has resulted in peak splitting. Collectively, the new calibration strategy and the reconstruction procedure maintain reproducibility and precision in CCS measurements while largely eliminating the need for meticulous selection of separation times. We expect that our method will empower researchers to harness the high mobility resolution offered by multipass cIMS analyses without compromising the accuracy of CCS measurement, making it appropriate for straightforward use across a wide range of applications.

Numerical simulations of the heavy rain event in the Democratic People's Republic of Korea during 9–10 August 2020

Accurate forecasting of heavy rainfalls and understanding of their dynamics are important to minimize the damage caused by them in the Democratic People's Republic of Korea (DPR Korea). This study is conducted on a heavy rainfall event (452 mm) on 9–10 August 2020 over Pankyo region located on the midlands of the Korean peninsula. To verify the proper configuration of convection-permitting simulations, sensitivity experiments were performed with five microphysical schemes (Lin, Goddard, Thompson, Morrison and WDM6) of the Weather Research and Forecasting (WRF) model. The results suggested that all high-resolution simulations reflect the main characteristics of observed precipitation pattern well, but the location and intensity of maximum precipitation from scheme to scheme. Among the considered all the microphysics, the Lin scheme showed the best agreement with observed precipitation. Results also showed that the Lin scheme reproduced the vertical distribution and time variation of several hydrometeors, as well as dynamic and thermodynamic parameters associated with heavy rainfall well. These outcomes suggest that the suitable selection of microphysics schemes with WRF model is important to predict and understand heavy rainfall events over the DPR Korea.

Sensitivity and perturbation analysis of alpha-eigenvalue with time-dependent Monte Carlo perturbation techniques

Sensitivity analysis and perturbation calculation methods for prompt neutron decay constants α using the Monte Carlo method, such as iterative fission probability (IFP), differential operator sampling (DOS), and correlated sampling (CS), have been proposed thus far. However, these methods require a significant amount of memory storage. The method developed in this study applies DOS and CS techniques during a time-dependent Monte Carlo simulation for the pulsed neutron method in subcritical systems. The time variation of the neutron flux is fitted to an exponential function during the time range when the flux decays with the fundamental mode α. By applying the least squares method to the results of time-dependent DOS and CS, the sensitivity coefficients with respect to nuclear data and the change in α due to perturbation can be calculated. In contrast to the existing methods that require storing the total fission or time sources per generation over several (∼10) generations, the proposed method only needs to store the weighting coefficient of a single source particle until it dies. The additional memory storage per parameter is comparable to that of conventional time-dependent Monte Carlo simulations and much less than that of existing methods. Numerical tests for the proposed method have demonstrated the accuracy and usefulness of the time-dependent DOS and CS methods.

Possible criticality scenario and its mechanism of the Windscale Works criticality accident in 1970 analyzed by computational fluid dynamics and Monte Carlo neutron transport

The Windscale Works criticality accident in 1970 resulted from mixing an aqueous solution with an organic solvent with different plutonium concentrations and densities. Although this accident has been studied using improved computer capabilities in recent years, a precise criticality scenario has not yet been identified. This study aims to clarify a possible criticality scenario of the accident—the time variation of reactivity and its mechanism. The accident was simulated by combining the multiphase computational fluid dynamics solver of OpenFOAM and the delta-tracking-based Monte Carlo neutron transport code Serpent2. Consequently, the periodic uneven arrangement of fluids might have caused oscillations in neutron leakage and absorption, resulting in periodic wavy reactivity changes. Furthermore, the emulsion, which was thought to be the primary cause, might not be the dominant mechanism for reactivity change, although it contributed to the criticality of the accident.

Spatial accessibility and equity of community healthcare: unraveling the impact of varying time and transport mode

BackgroundAchieving a higher level of accessibility and equity to community healthcare services has become a major concern for health service delivery from the perspectives of health planners and policy makers in China.MethodsIn this study, we introduced a comprehensive door-to-door (D2D) model, integrating it with the open OD API results for precise computation of accessibility to community hospitals over different transport modes. For the D2D public transit mode, we computed the temporal variation and standard deviation of accessibility at different times of the day. Additionally, accessibility values for D2D riding mode, D2D driving mode, and simple driving mode were also computed for comparison. Moreover, we introduced Lorenz curve and Gini index to assess the differences in equity of community healthcare across different times and transport modes.ResultsThe D2D public transit mode exhibits noticeable fluctuations in accessibility and equity based on the time of day. Accessibility and equity were notably influenced by traffic flow between 8 AM and 11 AM, while during the period from 12 PM to 10 PM, the open hours of community hospitals became a more significant determinant in Nanjing. The moments with the most equitable and inequitable overall spatial layouts were 10 AM and 10 PM, respectively. Among the four transport modes, the traditional simple driving mode exhibited the smallest equity index, with a Gini value of only 0.243. In contrast, the D2D riding mode, while widely preferred for accessing community healthcare services, had the highest Gini value, reaching 0.472.ConclusionThe proposed method combined the D2D model with the open OD API results is effective for accessibility computation of real transport modes. Spatial accessibility and equity of community healthcare experience significant fluctuations influenced by time variations. The transportation mode is also a significant factor affecting accessibility and equity level. These results are helpful to both planners and scholars that aim to build comprehensive spatial accessibility and equity models and optimize the location of public service facilities from the perspective of different temporal scales and a multi-mode transport system.

Pilot-scale microalgae cultivation and wastewater treatment using high-rate ponds: a meta-analysis.

Microalgae cultivation in wastewater has been widely researched under laboratory conditions as per its potential to couple treatment with biomass production. Currently, only a limited number of published articles consider outdoor and long-term microalgae-bacteria cultivations in real wastewater environmental systems. The scope of this work is to describe microalgal cultivation steps towards high-rate algal pond (HRAP) scalability and identify key parameters that play a major role for biomass productivity under outdoor conditions and long-term cultivations. Reviewed pilot-scale HRAP literature is analysed using multivariate analysis to highlight key productivity parameters within environmental and operational factors. Wastewater treatment analysis indicated that HRAP can effectively remove 90% of NH4+, 70% of COD, and 50% of PO43-. Mean reference values of 210 W m-2 for irradiation, 18°C for temperature, pH of 8.2, and HRT of 7.7 are derived from pilot-scale cultivations. Microalgae biomass productivity at a large scale is governed by solar radiation and NH4+ concentration, which are more important than retention time variations within investigated studies. Hence, selecting the correct type of location and a minimum of 70mg L-1 of NH4+ in wastewater will have the greatest effect in microalgae productivity. A high nutrient wastewater content increases final biomass concentrations but not necessarily biomass productivity. Pilot-scale growth rates (~ 0.54day-1) are half those observed in lab experiments, indicating a scaling-up bottleneck. Microalgae cultivation in wastewater enables a circular bioeconomy framework by unlocking microalgal biomass for the delivery of an array of products.