Two-stage Series Research Articles

Intra-urban risk assessment of occupational injuries and illnesses associated with current and projected climate: Evidence from three largest Australian cities

BackgroundIncreased risk of occupational injuries and illnesses (OI) is associated with ambient temperature. However, most studies have reported the average impacts within cities, states, or provinces at broader scales. MethodsWe assessed the intra-urban risk of OI associated with ambient temperature in three Australian cities at statistical area level 3 (SA3). We collected daily workers’ compensation claims data and gridded meteorological data from July 1, 2005, to June 30, 2018. Heat index was used as the primary temperature metric. We performed a two-stage time series analysis: we generated location-specific estimates using Distributed Lag Non-Linear Models (DLNM) and estimated the cumulative effects with multivariate meta-analysis. The risk was estimated at moderate heat (90th percentile) and extreme heat (99th percentile). Subgroup analyses were conducted to identify vulnerable groups of workers. Further, the OI risk in the future was estimated for two projected periods: 2016–2045 and 2036–2065. ResultsThe cumulative risk of OI was 3.4% in Greater Brisbane, 9.5% in Greater Melbourne, and 8.9% in Greater Sydney at extreme heat. The western inland regions in Greater Brisbane (17.4%) and Greater Sydney (32.3%) had higher risk of OI for younger workers, workers in outdoor and indoor industries, and workers reporting injury claims. The urbanized SA3 regions posed a higher risk (19.3%) for workers in Greater Melbourne. The regions were generally at high risk for young workers and illness-related claims. The projected risk of OI increased with time in climate change scenarios. ConclusionsThis study provides a comprehensive spatial profile of OI risk associated with hot weather conditions across three cities in Australia. Risk assessment at the intra-urban level revealed strong spatial patterns in OI risk distribution due to heat exposure. These findings provide much-needed scientific evidence for work, health, and safety regulators, industries, unions, and workers to design and implement location-specific preventative measures.

Analysis of Pressure Impact Characteristics of a Hydraulic Position Servo System Based on Series Servo Valves

As one of the causes of system vibration and noise, pressure impact is always undesired. Analysis of pressure impact characteristics of a hydraulic position servo system based on a two-stage series servo valve is carried out to reduce the system impact. The influence of factors such as system flow rate, additional servo valve opening gain, external load, and system overflow pressure on the system pressure impact is analyzed. The results show that the series servo valve scheme can bring down the peak impact pressure at the inlet of the hydraulic cylinder by 8%~11% when the system flow rate or overflow pressure is low to a certain extent. In most other cases, the suppression effect of the impact peak pressure is unapparent. The impact pressure overshoot is always decreased accompanied by an easier trend to overflow for the system. At last, another new idea of application promotion with higher reliability and adaptability is proposed.

Nested Magnetic Field Compensation With Regulated Coefficients for Bio-Magnetic Field Measurement

For a spin-exchange relaxation free (SERF) optically pumped magnetometer (OPM) that obtains its best performance in a zero magnetic field, an operation environment with approximately zero magnetic field is desired. This article proposes a nested magnetic field compensation system for a magnetic shielding room (MSR) to suppress the magnetic field. Two sets of coils, one set located outside of the MSR and the other one placed inside of the MSR, are combined in the system. The magnetic fields outside of the MSR are measured by tunneling magnetoresistance (TMR) sensors, while the fields inside the MSR are monitored by SERF OPMs. The two kinds of sensors complement each other in terms of measurement range and sensitivity. A nested two-stage proportional-integral (PI) closed-loop control strategy is employed to compensate for the magnetic field inside the MSR. The control parameters are regulated by the magnitude of the magnetic field to take advantage of the two kinds of sensors. The effect of the proposed system is experimentally tested. The three-axis field fluctuations are reduced by 97.52%, 98%, and 98.64% by the proposed method, respectively. The proposed method is compared with a conventional two-stage series PI control system. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -axis magnetic field fluctuations of the conventional PI control system and the proposed system are 75.81 and 11.71 pT, respectively. The magnetic fluctuation of the proposed system is about 15.5% of the fluctuation of the conventional PI system. To validate the feasibility of the proposed magnetic field compensation system for ultra-weak bio-magnetic field measurement, magnetocardiography (MCG) and magnetoencephalography (MEG) signals are measured.

Experimental study on the factors affecting the performance of wire-plate Biefeld-Brown thrust unit

Biefeld-Brown effect (B-B effect for short) refers to the phenomenon that when a high voltage is applied to an asymmetric capacitor, the capacitor generates an additional force. In order to explore the influencing factors and series characteristics of the B-B effect of wire-plate asymmetric capacitors in atmospheric pressure, a set of experimental devices with adjustable parameters was designed. Based on this device, the effects of different wire-plate lengths, power supply types and electrode application modes on the thrust and efficiency of B-B effect are studied. At the same time, the optimal parameters are selected to study the series characteristics. The research shows that the thrust generated by B-B effect is directly proportional to the length of the wire plate. The thrust generated by applying positive emission voltage to the copper wire and grounding the aluminum plate is the largest, and the two-stage series connection can achieve multiple increase of the thrust, with better performance.

온도 지표에 따른 도시와 농촌의 열사망 위험도 격차

Heat impact on human health is a global concern due to climate change which has been accelerating. Recently, previous studies have contended that it is necessary to consider different vulnerabilities to heat by temperature metrics and urbanicity when setting the heat alarming system; however, the current heat alarm system in Korea is based on the maximum temperature solely. Therefore, this study aimed to examine whether the heat-related mortality risks differ by the urban and rural areas with sub-population groups, using two temperature metrics, the daily minimum temperature and the maximum temperature.BR We collected 229 nationwide district-level (sigungu) daily time-series data including the minimum temperature, the maximum temperature, and the all-cause mortality during the summer season (June ~ Sep) of the study period (2011 ~ 2017). Using the two-stage time series analysis with a distributed lag non-linear model (DLNM), we estimated heat-mortality risk estimates based on the minimum and maximum temperatures, individually. The risk estimates were pooled with meta-regression by urban and rural area. BR The maximum temperature is associated with mortality risk in both urban and rural areas. However, the minimum temperature has a significant impact on mortality only in the urban area. In addition, heat-related mortality risks differed by the sup-population (sex and age group), regions, and temperature metrics.BR In conclusion, heat-mortality risk between urban and rural areas differs by temperature metrics and characteristics of sub-populations. The results suggest that more elaborated heat definitions and heat alarming systems should be established to increase the efficiency of the alarming system and address unequal vulnerability to heat.

Same-day discharge following catheter ablation and venous closure with VASCADE MVP: A postmarket registry.

Early and safe ambulation can facilitate same-day discharge (SDD) following catheter ablation, which can reduce resource utilization and healthcare costs and improve patient satisfaction. This study evaluated procedure success and safety of the VASCADE MVP venous vascular closure system in patients with atrial fibrillation (AF). The AMBULATE SDD Registry is a two-stage series of postmarket studies in patients with paroxysmal or persistent AF undergoing catheter ablation followed by femoral venous access-site closure with VASCADE MVP. Efficacy endpoints included SDD success, defined as the proportion of patients discharged the same day who did not require next-day hospital intervention for procedure/access site-related complications, and access site sustained success within 15 days of the procedure. Overall, 354 patients were included in the pooled study population, 151 (42.7%) treated for paroxysmal AF and 203 (57.3%) for persistent AF. SDD was achieved in 323 patients (91.2%) and, of these, 320 (99.1%) did not require subsequent hospital intervention based on all study performance outcomes. Nearly all patients (350 of 354; 98.9%) achieved total study success, with no subsequent hospital intervention required. No major access-site complications were recorded. Patients who had SDD were more likely to report procedure satisfaction than patients who stayed overnight. In this study, 99.7% of patients achieving SDD required no additional hospital intervention for access site-related complications during follow-up. SDD appears feasible and safe for eligible patients after catheter ablation for paroxysmal or persistent AF in which the VASCADE MVP is used for venous access-site closure.

Excess mortality and the COVID-19 pandemic: causes of death and social inequalities

BackgroundDuring the coronavirus diseases 2019 (COVID-19) pandemic, population’s mortality has been affected not only by the risk of infection itself, but also through deferred care for other causes and changes in lifestyle. This study aims to investigate excess mortality by cause of death and socio-demographic context during the COVID-19 pandemic in South Korea. MethodsMortality data within the period 2015–2020 were obtained from Statistics Korea, and deaths from COVID-19 were excluded. We estimated 2020 daily excess deaths for all causes, the eight leading causes of death, and according to individual characteristics, using a two-stage interrupted time series design accounting for temporal trends and variations in other risk factors.ResultsDuring the pandemic period (February 18 to December 31, 2020), an estimated 663 (95% empirical confidence interval [eCI]: -2356–3584) excess deaths occurred in South Korea. Mortality related to respiratory diseases decreased by 4371 (3452–5480), whereas deaths due to metabolic diseases and ill-defined causes increased by 808 (456–1080) and 2756 (2021–3378), respectively. The increase in all-cause deaths was prominent in those aged 65–79 years (941, 88–1795), with an elementary school education or below (1757, 371–3030), or who were single (785, 384–1174), while a decrease in deaths was pronounced in those with a college-level or higher educational attainment (1471, 589–2328).ConclusionNo evidence of a substantial increase in all-cause mortality was found during the 2020 pandemic period in South Korea, as a result of a large decrease in deaths related to respiratory diseases that offset increased mortality from metabolic disease and diseases of ill-defined cause. The COVID-19 pandemic has disproportionately affected those of lower socioeconomic status and has exacerbated inequalities in mortality.

An Analytical Design Method of PI and PID Controllers for Industrial Series Cascade Processes With Time Delay Under Robustness Constraints

In this paper, an analytical method is proposed to design Proportional-Integral (PI) and Proporional-Integral-Derivative (PID) controllers for two-stage industrial series cascade processes with transport delay under robustness constraints. The main rationale behind using series cascade control structure is that the disturbances in the inner loop are suppressed by the secondary controller before being transmitted to the outer loop. The presented design procedure consists of two steps: In the first step, the controller Cb(s) in the inner loop is designed, while in the second step the controller Ca(s) in the outer loop is obtained. The obtained controller is of PI or PID-type structure depending on the number of selected terms used in Maclaurin’s approximation of the transfer function of the high-order controller. By specifying the robustness constraints within design procedure one define values of adjustable parameters to achieve compromise between robustness and performance indicators. The result is efficient suppression of load disturbances, evaluated by the integral of the absolute error (IAE). The step reference response can be additionally reshaped by using Two Degree of Freedom – 2DoF control structure via suitable selection of set-point weighting factor b, 0≤b≤1, which acts on the control signal through displaced proportional action of the controller. The proposed design method is analyzed with simulations on wide class of typical representatives of industrial processes including stable, integral and unstable processes with time delay. A comparison with recent studies shows the effectiveness of the proposed tuning method for industrial cascade processes.

Characteristics of the cylindrical reflex triode driven by a four-stage linear transformer driver.

A cylindrical reflex triode was designed and directly driven by a four-stage linear transformer driver to generate high intensity pulsed warm x rays. We developed a numerical model of the cylindrical reflex triode and simulated and studied the experimental electron distribution and the radiation characteristics. The working voltage of the cylindrical reflex triode is 220kV, and the current is about 600kA. Under the voltage pulse with a rise time of 100ns, the electron beam spot is uniform, and the duration of the gap without short circuit reaches 200ns. The x-ray dose is 385rad (Si), with an irradiation area of 615cm2 and a uniformity of less than 2:1. The radiation field distribution is basically consistent with the simulation results. Compared with the two-stage series diode on the Flash-II accelerator, the x-ray conversion efficiency of the cylindrical reflex triode is increased about 1.6 times.

Trends in temperature-mortality projections across urban and rural regions under different climate change scenarios in Switzerland

Temperature vulnerability tends to be heterogenous between urban and rural regions, with usually larger risks in the former. However, it is unclear whether this pattern will persist under different climate change scenarios. Climate change combined with population growth, ageing and urbanization is expected to amplify the current temperature-related mortality burden, particularly since these drivers will follow diverse trajectories across urban and rural areas in the future. This study aimed to compare the impact of climate change regarding changes in heat- and cold-related mortality under various warming scenarios across urban/rural districts in Switzerland, while also accounting for changes in population demographics. We first estimated the district-age-specific (&amp;#x3c;75/&amp;#x3e;=75years) temperature-mortality association between 1990-2010 in Switzerland using a two-stage time series design with distributed-lag nonlinear models. We then projected heat- and cold-related mortality under 1.5C, 2.0C, 3.0C and 4.0C warming scenarios using downscaled temperature projections under RCP8.5 while accounting for the Shared Socio-economic pathway (SSP5) population development storyline. In Switzerland, heat- and cold-related mortality will increase by 2,420(95%CI:1654;3,884) and 993(82;1883) deaths /year, respectively, under 4.0C warming (vs. 1990-2010). Urban areas are more affected by both heat and cold and this pattern appears to be amplified under warmer scenarios. In particular, per 100 heat-related deaths in rural areas, there will be an increase from 362 to 391 deaths in urban areas, with similar results for cold (from 262 to 286 per 100 deaths in rural areas), indicating a slight increase in vulnerability to climate change in urban regions in the near future. Our preliminary findings suggest that climate change will increase current heat and cold-related mortality in Switzerland, and moreover, urban areas will continuously more be disproportionately affected. Further analyses will aim to account for urbanization projections and disentangle the contribution of the different drivers across urban and rural regions.

Counteracting increased heat-related mortality through adaptation: a quantitative assessment in a multi-country multi-city setting.

Background &amp;#x26; aims: Climate change is exacerbating the current heat-related health burden and will continue to do so at a higher speed in the coming decades if no adaptation occurs. Although previous studies have suggested potential paths of adaptation, there is little quantitative evidence on the degree of adaptation needed to counteract the increased heat-related mortality under different climate change scenarios. Methods: We performed a health impact projection analysis using observed data on 451 locations in 23 countries included in the MCC database and modelled temperature from 3 global circulation models (CMIP5 - ISMIP2b). For each city, we combined present-time risk functions, represented by the exposure-response association obtained from a two-stage time series analysis of the observed temperature-mortality data, with projected daily temperature in 20-year warming scenarios consistent with an increase in global mean temperature of 2, 3 and 4ºC from the preindustrial period. Using a novel optimization method, we estimated a risk reduction factor to be applied to the present-time exposure-response association representing the level of adaptation needed to counteract the increased heat-mortality burden under each warming target. Results: Assuming constant vulnerability and population, climate change would progressively amplify heat-related mortality reaching 3.9% (95%CI:0.6;0.9) of all-cause mortality due to heat at 4ºC warming scenario (vs. 0.4% (0.2-0.6) in baseline 1986-2005). To counteract the impact of the progressive increase of temperatures, present-time heat-related risks should reduce on average by 70% (35;104), 84% (60;104) and 91% (80;103) under the 2, 3 and 4ºC scenarios, respectively. Conclusions: Our preliminary findings show that substantial reductions in vulnerability would be required to counteract the increase in heat-mortality burden driven by climate change. Further steps will aim to extend the current analysis over a larger sample of locations and consider scenarios of population development. Keywords: climate change, adaptation, heat, mortality, projections, methods.

Ambient formaldehyde and mortality: A time series analysis in China.

The potential health impact of low-level ambient formaldehyde has been historically overlooked. We conducted a two-stage time series analysis to investigate associations between ambient formaldehyde and daily nonaccidental, circulatory, and respiratory mortality and six subtypes based on 5,325,585 deaths in 275 Chinese counties between 2013 and 2018 and estimated a concentration-response curve to identify overall associations. After controlling for confounders from meteorological factors, air pollutants, time trend, and day of the week effect, with a 1-part per billion (ppb) increase in the daily concentration of formaldehyde on lag0 day, we found that mortality risks in nonaccidental, circulatory, and respiratory diseases increased by 0.36%, 0.36% and 0.41%, respectively. The curve indicated a possible threshold concentration at approximately 5 ppb for significant impact on nonaccidental and circulatory diseases. We suggest that ambient formaldehyde may represent a potential threat to public health and needs further investigation to support timely pollution regulation and health protection.

Subsampling bootstrap in network DEA

Data Envelopment Analysis (DEA), provides an empirical estimation of the production frontier, based on an observed sample of decision making units (DMUs). Except for the single input-single output case, the asymptotic distribution of the DEA estimator can only be approximated through bootstrapping approaches. Therefore, bootstrapping techniques have been widely applied in the DEA literature to make statistical inference for the cases when the production process has a single-stage structure. However, in many cases, the transformation of inputs into outputs has an inner structure that needs to be considered. This paper examines the applicability of the subsampling bootstrap procedure in the approximation of the asymptotic distribution of the DEA estimator when the production process has a network structure, and in the presence of undesirable factors. Evidence on the performance of subsampling bootstrap is obtained through Monte Carlo experiments for the case of two-stage series structures, where overall and stage efficiency estimates are calculated using the additive decomposition approach. Results indicate great sensitivity both to the sample and subsample size, as well as to the data generating process. Subsampling methodology is then applied to construct confidence interval estimates for the overall and stage efficiency scores of railways in 22 European countries, where the railway transport process is decomposed into two stages and the railway noise pollution problem is considered as an undesirable output.

Semi-analytic semi-numerical analysis of dynamic characteristics of a two-stage coupled series PGT based on IHB and MsP methods

This paper conducts an analytical investigation of the dynamic response characteristics of a two-stage coupled series system (TsCSS) with a planetary gear transmission (PGT), consisting of dual-power branches. An improved incremental harmonic balance (IHB) method, based on the arc length extension technique, is proposed. The results are compared with those of the numerical integration method, in order to verify the feasibility and efficiency of the improved method. Afterwards, the multi-scale perturbation (MsP) method is applied to the proposed TsCSS. The frequency response equations of the primary resonance, subharmonic resonance and superharmonic resonance, are solved in order to generate the frequency response characteristic curves of the planetary transmission system. A comparison between the results obtained by the MsP method and the numerical integration method demonstrates that the former is ideal and credible in most of the regions. Considering the parameters of TsCSS excitation frequency and damping, the nonlinear response characteristics of steady-state motion are mutually converted. The impact of the time-varying parameters and nonlinear deenthing caused by the gear teeth clearance on the amplitude–frequency characteristics of the TsCSS components, is finally studied.

Thermodynamic and techno-economic performance comparison of two-stage series organic Rankine cycle and organic Rankine flash cycle for geothermal power generation from hot dry rock

• The performance of two geothermal energy cascade utilization systems is optimized. • The thermodynamic and techno-economic performance of the systems are compared. • The influence of heat source temperature on the operating condition is studied. • The exergy destruction of each component in the systems is compared and analyzed. To improve the utilization rate of geothermal resource using organic Rankine cycle (ORC), an organic Rankine flash cycle (ORFC) combined with insufficient evaporation and flash process is proposed to reduce the irreversibility of the power generation cycle. The thermodynamic performance and techno-economic performance of ORFC and two-stage series organic Rankine cycle (TSORC) are optimized, respectively. The effects of evaporation temperature, flash temperature and outlet dryness on the performance of two systems are discussed. The results show that with the increase of heat source temperature, the optimal operating condition value of the system increases, which leads to improving the thermodynamic and techno-economic performance significantly. R601a and R601 are the most suitable working fluids for TSORC and ORFC, respectively. The heat exchanger is the main component that causes the exergy destruction of the system, and its improvement potential is the highest in all components. The thermodynamic performance and techno-economic performances of ORFC are better than those of TSORC. The irreversible loss of the system can be reduced by the insufficient evaporation combined with flash separator.

A Novel Enhanced Russell Graph Efficiency Measure in Network DEA

Hitherto, the presented models for measuring the efficiency score of multi-stage decision-making units (DMUs) either are nonlinear or require to specify the weights for combining their divisional efficiencies. The nonlinearity leads to high computational complexity for these models, especially when used for problems with enormous dimensions, and also assigning various weights to the divisional efficiencies causes to obtain different efficiency scores for the multi-stage network system. To tackle these problems, this study contributes to network DEA by introducing a novel enhanced Russell graph (ERG) efficiency measure for evaluating the general two-stage series network structures. Then, the proposed model is extended into the general multi-stage series network structures. This study also describes the managerial and economic implications of measuring the efficiency score of the multi-stage DMUs and provides two numerical and empirical examples for illustrating the use of our proposed model.

Two-Stage Series Model Predictive Torque Control for PMSM Drives

A two-stage series model predictive torque control for permanent magnet synchronous motor drives is proposed in this article. First, the control of torque and flux linkage is converted to double-torque control (i.e., the control of active torque and reactive torque) based on the instantaneous power theory to eliminate the weighting factor in conventional model predictive torque control. Then, the double-torque prediction trajectory and double-torque reference are extrapolated to two control periods. The concept of two-stage series predictive control is proposed in this article, in which the cost functions of two prediction instants are designed to form series control structure. In the proposed method, the first-stage prediction is used to select candidate voltage vectors and the second-stage prediction is used to evaluate the optimal voltage vector. Since the cost function of two control periods in the future is considered when selecting the voltage vectors, the possibility that the same voltage vector is applied to adjacent control periods increases, thereby reducing the switching frequency of the system. Finally, the effectiveness of the proposed method is verified by experiments.

Merging two-stage series network structures: A DEA-based approach

Merging two-stage series network structures: A DEA-based approach

Aerodynamic Optimization and Noise Reduction of a Two-Stage Series Compact Fan

AbstractThis paper focused on the aerodynamic optimization and noise reduction of a two-stage series compact fan. The space constraints of compact fans limit the design space, which poses several c...

An investigation on the bubble transportation of a two-stage series venturi bubble generator

In this paper, we designed a new venturi bubble generator, which mainly consist of two serial rectangular perspex venturi channels with the same geometrical dimension. Visualization experimental method combined with digital image analysis was adopted to study the motion, deformation and breakup process of bubbles when the micro-bubble generator was installed vertically. The bubble foaming frequency which is defined as the amount of forming bubbles within one second from the air injection hole was significantly enhanced with the increase of water flow rate, but was not sensitively affected by the air flow rate. The discrete bubbles moved in a two-stage venturi channel and experienced collapse or breakup in the divergent section. The Sauter mean diameter of bubbles which recorded in each divergent outlet decreased gradually. The Reynolds numbers of water had a significant effect on the breakup characteristics of bubbles. With the increasing of Re, the bubbles experienced binary breakage and multiple breakup successively. Under the effect of complex turbulence vortex, the bubbles presented different breakup patterns in each stage. When Reth>19793, the bubble breakup ratio of the first stage divergent section was larger than that of the second stage, and the difference of the generated bubble Sauter mean diameter in each divergent outlet was minimized accordingly. The surface stability of the daughter bubble was enhanced, and it was difficult to breakup significantly under the effect of recirculation flow. The numerical simulation results by Computational Fluid Dynamics (CFD) indicated that the area of the vortex was increased for larger second stage divergent angle, which intensify the phase interaction and promote the possibility of sub-micron bubble breakup.