bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformation Mechanism and Stability Control of Roadway Surrounding Rock with Compound Roof: Research and Applications
Authors: Yu Yang , Wang Xiangyu , Bai Jianbiao , Zhang Lianying , Xia Hongchun
Published: March 2020

In view of problems with roadways with a compound roof, such as the occurrence of instability in the roof strata, ease of separation of the layer caving, difficulty of maintenance, and poor safety, we established a mechanical calculation model of a roadway with compound roof using the elastic mechanics theory, taking the stability control of a roadway with compound roof at a coal mine in Guizhou Province, China as the research background, and based on the actual characteristics of the coal seam and the roof and floor slate. Expressions of the separation layer and instability limit load of compound roof were derived, and the calculation and verification were carried out in combination with the actual conditions. By means of numerical simulation, the distribution and evolution laws of stress, displacement and plastic zone of roadways with a compound roof were studied, and the deformation characteristics and instability mechanism of roadways with a compound roof were revealed: (1) in early stage deformation of roadway, the amount is large, the speed is fast, and the scale is wide; (2) compound roofs are vulnerable to abscission and instability, the bearing capacity of the two sides is low due to softness and cracking, the shear failure of side angles and vertex angles weakens the strength of surrounding rock, and the self-bearing capacity of surrounding rock is low; (3) the bolt and anchor bear relatively large tensile force, and the support structure is easy to be broken up. On this basis, the stability control principle of a roadway with compound roof tunnel was put forward: fast and timely support; high-strength bolt strong support; improving the stability of the roof and the bearing capacity of the two sides; restraining the shear failure of the key bearing parts such as the side angles and the bottom angles, and targeted stability control technology for roadways with a compound roof was developed. The field industrial test showed that the deformation of this roadway with a compound roof was effectively controlled and the overall stability of the roadway was effectively improved. The results of this study could provide useful reference for a roadway with a compound roof under similar conditions.
‘Sticky’ Policies—Three Country Cases on Long-Term Commitment and Rooting of RE Policy Goals
Authors: Berg Annukka , Lukkarinen Jani , Ollikka Kimmo
Published: March 2020

Denmark, Germany, and Finland are countries that have emerged as technology leaders in key renewable energy fields—wind energy, solar power, and bioenergy. In this article, we dig into the policy trajectories of these countries and concentrate particularly on a phenomenon that is common for them all—the long-term commitment to promoting particular renewable energy (RE) technologies. Analyzing commitment, its causes and its consequences, can be considered important, as earlier findings show that long-term, consistent policy signals are a key for policy success. In this article, we point out that this ‘sticking’ to a RE technology has emerged and manifested in multiple ways in the case countries. Examples include relying on existing cultural capacities when navigating energy policy direction, strategically promoting scaling of technology markets to root new energy practices in society and developing energy policies as an extension of existing socio-technical structures. In order to understand these dynamics in more depth, we utilize literature on policy robustness and resilience. While all the case countries, Denmark, Germany, and Finland, have generated robust RE policy goals, Finland has failed to foster resilience simultaneously. We conclude that analysing stickiness of policy elements can be fruitful when seeking to understand and design transformative policies. Further, it can be taken as a complementary analytical perspective in the policy mix studies.
Bus Voltage Control of DC Distribution Network Based on Sliding Mode Active Disturbance Rejection Control Strategy
Authors: Wu Boning , Zhou Xuesong , Ma Youjie
Published: March 2020

The DC distribution network has more advantages in power transmission, grid connection of distributed energy, and reliability of power supply when compared with AC distribution network, but there are still many problems in the development of DC distribution network. DC bus voltage control is one of the hot issues in the research of DC distribution network. To solve this problem, in this paper, a new type of sliding mode active disturbance rejection control (SMADRC) controller for AC/DC converters is designed and applied to the voltage outer loop. The linear extended state observer (LESO) can observe the state variables and the total disturbance of the system. The SMADRC is composed of a sliding mode controller, LESO, and disturbance compensator, which can compensate the total disturbance observed by LESO properly. Therefore, it improves the dynamic. At the same time, it can also reduce the system jitter that is caused by sliding mode controller. The state variables that are observed by the LESO are used in the design of sliding mode controller, which greatly simplifies the design of sliding mode controller. Finally, the simulation results of Matlab/Simulink show that the controller has good start-up performance and strong robustness.
LCC-S Based Discrete Fast Terminal Sliding Mode Controller for Efficient Charging through Wireless Power Transfer
Authors: Ali Naghmash , Liu Zhizhen , Hou Yanjin , Armghan Hammad , Wei Xiaozhao , Armghan Ammar
Published: March 2020

Compared to the plug-in charging system, Wireless power transfer (WPT) is simpler, reliable, and user-friendly. Resonant inductive coupling based WPT is the technology that promises to replace the plug-in charging system. It is desired that the WPT system should provide regulated current and power with high efficiency. Due to the instability in the connected load, the system output current, power, and efficiency vary. To solve this issue, a buck converter is implemented on the secondary side of the WPT system, which adjusts its internal resistance by altering its duty cycle. To control the duty cycle of the buck converter, a discrete fast terminal sliding mode controller is proposed to regulate the system output current and power with optimal efficiency. The proposed WPT system uses the LCC-S compensation topology to ensure a constant output voltage at the input of the buck converter. The LCC-S topology is analyzed using the two-port network theory, and governing equations are derived to achieve the maximum efficiency point. Based on the analysis, the proposed controller is used to track the maximum efficiency point by tracking an optimal power point. An ultra-capacitor is connected as the system load, and based on its charging characteristics, an optimal charging strategy is devised. The performance of the proposed system is tested under the MATLAB/Simulink platform. Comparison with the conventionally used PID and sliding mode controller under sudden variations in the connected load is presented and discussed. An experimental prototype is built to validate the effectiveness of the proposed controller.
A Comprehensive Wind Power Forecasting System Integrating Artificial Intelligence and Numerical Weather Prediction
Authors: Kosovic Branko , Haupt Sue Ellen , Adriaansen Daniel , Alessandrini Stefano , Wiener Gerry , Delle Monache Luca , Liu Yubao , Linden Seth , Jensen Tara , Cheng William , Politovich Marcia , Prestopnik Paul
Published: March 2020

The National Center for Atmospheric Research (NCAR) recently updated the comprehensive wind power forecasting system in collaboration with Xcel Energy addressing users’ needs and requirements by enhancing and expanding integration between numerical weather prediction and machine-learning methods. While the original system was designed with the primary focus on day-ahead power prediction in support of power trading, the enhanced system provides short-term forecasting for unit commitment and economic dispatch, uncertainty quantification in wind speed prediction with probabilistic forecasting, and prediction of extreme events such as icing. Furthermore, the empirical power conversion machine-learning algorithms now use a quantile approach to data quality control that has improved the accuracy of the methods. Forecast uncertainty is quantified using an analog ensemble approach. Two methods of providing short-range ramp forecasts are blended: the variational doppler radar analysis system and an observation-based expert system. Extreme events, specifically changes in wind power due to high winds and icing, are now forecasted by combining numerical weather prediction and a fuzzy logic artificial intelligence system. These systems and their recent advances are described and assessed.
Regression Models for the Evaluation of the Techno-Economic Potential of Organic Rankine Cycle-Based Waste Heat Recovery Systems on Board Ships Using Low Sulfur Fuels
Authors: Baldasso Enrico , Mondejar Maria E. , Larsen Ulrik , Haglind Fredrik
Published: March 2020

When considering waste heat recovery systems for marine applications, which are estimated to be suitable to reduce the carbon dioxide emissions up to 20%, the use of organic Rankine cycle power systems has been proven to lead to higher savings compared to the traditional steam Rankine cycle. However, current methods to estimate the techno-economic feasibility of such a system are complex, computationally expensive and require significant specialized knowledge. This is the first article that presents a simplified method to carry out feasibility analyses for the implementation of organic Rankine cycle waste heat recovery units on board vessels using low-sulfur fuels. The method consists of a set of regression curves derived from a synthetic dataset obtained by evaluating the performance of organic Rankine cycle systems over a wide range of design and operating conditions. The accuracy of the proposed method is validated by comparing its estimations with the ones attained using thermodynamic models. The results of the validation procedure indicate that the proposed approach is capable of predicting the organic Rankine cycle annual energy production and levelized cost of electricity with an average accuracy within 4.5% and 2.5%, respectively. In addition, the results suggest that units optimized to minimize the levelized cost of electricity are designed for lower engine loads, compared to units optimized to maximize the overall energy production. The reliability and low computational time that characterize the proposed method, make it suitable to be used in the context of complex optimizations of the whole ship’s machinery system.
Synthesis and Verification of Finite-Time Rudder Control with GA Identification for Electric Rudder System
Authors: Wu Zhihong , Yang Ruifeng , Guo Chenxia , Ge Shuangchao , Chen Xiaole
Published: March 2020

The electric rudder system (ERS) is the executive mechanism of the flight control system, which can make the missile complete the route correction according to the control command. The performance and quality of the ERS directly determine the dynamic quality of the flight control system. However, the transient and static characteristic of ERS is affected by the uncertainty of physical parameters caused by nonlinear factors. Therefore, the control strategy based on genetic algorithm (GA) identification method and finite-time rudder control (FTRC) theory is studied to improve the control accuracy and speed of the system. Differently from the existing methods, in this method, the difficulty of parameter uncertainty in the controller design is solved based on the ERS mathematical model parameter identification strategy. Besides, in this way, the performance of the FTRC controller was verified by cosimulation experiments based on automatic dynamic analysis of mechanical systems (ADAMS) (MSC software, Los Angeles, CA, USA) and matrix laboratory (MATLAB)/Simulink (MathWorks, Natick, MA, USA). In addition, the advantages of the proposed method are verified by comparing with the existing strategy results on the rudder test platform, indicating that the control accuracy is improved by 70% and the steady-state error is reduced by at least 50%.
A Novel Energy Management Strategy for a Ship’s Hybrid Solar Energy Generation System Using a Particle Swarm Optimization Algorithm
Authors: Yang Rui , Yuan Yupeng , Ying Rushun , Shen Boyang , Long Teng
Published: March 2020

Due to the pressures caused by the energy crisis, environmental pollution, and international regulations, the largest ship-producing nations are exploring renewable resources, such as wind power, solar energy, and fuel cells to save energy and develop more environmentally-friendly ships. Solar energy has recently attracted a great deal of attention from both academics and practitioners; furthermore, the optimization of energy management has become a research topic of great interest. This paper takes a solar-diesel hybrid ship with 5000 car spaces as its research object. Then, following testing on this ship, experimental data were obtained, a multi-objective optimization model related to the ship’s fuel economy and diesel generator’s efficiency was established, and a partial swarm optimization algorithm was used to solve a multi-objective problem. The results show that the optimized energy management strategy for a hybrid energy system should be tested under different electrical loads. Moreover, the hybrid system’s economy should be taken into account when the ship’s power load is high, and the output power from the new energy generation system should be increased as much as possible. Finally, the diesel generators’ efficiency should be taken into consideration when the ship’s electrical load is low, and the injection power of the new energy system should be reduced appropriately.
Effect of Sky Discretization for Shading Device Calculation on Building Energy Performance Simulations
Authors: R. Maestre Ismael , Foncubierta Blázquez Juan Luis , González Gallero Francisco Javier , Mena Baladés J. Daniel
Published: March 2020

The calculation of sunlit surfaces in a building has always been a relevant aspect in building energy simulation programs. Due to the high computational cost, some programs use algorithms for shading calculation for certain solar positions after discretization of hemispherical sky. The influence of the level of discretization on the estimation of incident direct radiation on building surfaces, as well as on the required computational times, are studied in this work. The direct solar energy on a window for a year, with simulation time steps of five minutes, has been simulated by using an algorithm based on Projection and Clipping Methods. A total of 6144 simulations have been carried out, varying window sizes, window orientations, typologies of shading devices, latitudes and discretization levels of the hemispherical sky. In terms of annual incident solar energy, the results show that maximum error values are about 5% for a low level of angular discretization. Errors up to 22% in hourly incident solar energy have been estimated for some of the configurations analysed. Furthermore, a great number of configurations show errors of shading factor on a window of up to 30%, which could be most relevant in studies of natural lighting. The study also shows that the improvement achieved by the most accurate discretization level implies an increase in computational cost of about 30 times.
Eco-Efficiency Assessment of the Application of Large-Scale Rechargeable Batteries in a Coal-Fired Power Plant
Authors: Krawczyk Piotr , Śliwińska Anna
Published: March 2020

This article presents the results of an eco-efficiency assessment of the application of large-scale rechargeable battery technology in electricity generation from coal. The eco-efficiency of electricity production in a 350 MW coal-fired power plant was calculated. Two production variants were compared: with the use of a lithium-ion battery of a 400 MWh capacity to optimize the operation of power blocks and without using the battery. Hard coal is one of the main fossil fuels used to generate electricity in Poland. Despite the growing share of electricity from renewable sources, this situation will persist for many more years. The main reasons for this are the high costs and long-lasting process of moving away from fossil fuels in the energy sector. Therefore, any technical solutions that can temporarily reduce the negative impact of coal-based power engineering on the environment should be considered. At the same time, the economic aspects of such solutions must be taken into account. That is why the eco-efficiency assessment method was chosen, which integrates economic and environmental aspects. The obtained results of the analyses indicate the occurrence of environmental and economic benefits resulting from the use of the battery in coal-fired power plants. It has been found that battery-based technology is more eco-efficient than technology without such a battery. A sensitivity analysis was carried out, which allowed the impact of individual computational variables on the eco-efficiency assessment result to be assessed. The results indicate that fuel prices (coal and heavy fuel oil—mazout) and CO2 emission allowances have the greatest impact on the eco-efficiency of the analyzed technology. It was also found that the factors related to the battery, such as its efficiency, life span, decrease of the capacity after 10 years of operation, and construction cost, have a much smaller impact on the results.
Eco-Energetical Life Cycle Assessment of Materials and Components of Photovoltaic Power Plant
Authors: Piasecka Izabela , Bałdowska-Witos Patrycja , Piotrowska Katarzyna , Tomporowski Andrzej
Published: March 2020

During the conversion of solar radiation into electricity, photovoltaic installations do not emit harmful compounds into the environment. However, the stage of production and post-use management of their elements requires large amounts of energy and materials. Therefore, this publication was intended to conduct an eco-energy life cycle analysis of photovoltaic power plant materials and components based on the LCA method. The subject of the study was a 1 MW photovoltaic power plant, located in Poland. Eco-indicator 99, CED and IPCC were used as calculation procedures. Among the analyzed elements of the power plant, the highest level of negative impact on the environment was characterized by the life cycle of photovoltaic panels stored at the landfill after exploitation (the highest demand for energy, materials and CO2 emissions). Among the materials of the power plant distinguished by the highest harmful effect on health and the quality of the environment stands out: silver, nickel, copper, PA6, lead and cadmium. The use of recycling processes would reduce the negative impact on the environment in the context of the entire life cycle, for most materials and elements. Based on the results obtained, guidelines were proposed for the pro-environmental post-use management of materials and elements of photovoltaic power plants.
Bifacial p-Type PERC Solar Cell with Efficiency over 22% Using Laser Doped Selective Emitter
Authors: Zhang Caixia , Shen Honglie , Sun Luanhong , Yang Jiale , Wu Shiliang , Lu Zhonglin
Published: March 2020

In this paper, we report one bifacial p-type PERC solar cell with efficiency over 22% using laser doped selective emitter produced in larger-scale commercial line on 6-inch mono-crystalline wafer. On front side of the solar cell, square resistance of p-n junction was found to be closely related with laser power at certain laser scan speed and frequency. On the other side, the rear fingers with different ratios of height and width and rear silicon nitride (SiNx) layer with different thickness were optimized, and a highest rear efficiency of the bifacial solar cell was obtained. Finally, bifacial silicon solar cells with the front and rear efficiencies exceeding 22% and 15% (AM1.5, 1000 W/m2, 25 °C) were successfully achieved, respectively.
Frequency Response Modelling of Transformer Windings Connected in Parallel
Authors: Banaszak Szymon , Gawrylczyk Konstanty Marek , Trela Katarzyna
Published: March 2020

This paper describes the approach to the frequency response modelling of transformer windings consisting of coils connected in parallel. At present, computer models are intensively developed with the aim of simulating the influence of faults on the frequency response of the active part of power transformers. Frequency response analysis (FRA) is one of the standard methods used for the assessment of the mechanical condition of a transformer’s windings and core. The interpretation of the FRA results is crucial in the diagnostics of the active part of the transformer. Proper simulations of the FRA results allow the improvement and simplification of the interpretation process of the windings’ faults. Usually only serial winding wires are simulated in computer modelling and parallel wires are simplified, leading to simulation inaccuracies. In this work, a combined electromagnetic field/network method, which includes parallel connections of the coils, is proposed. The method is based on lumped RLC elements. The results of the analysis conducted by the computer model are referred to as the real transformer measurement. The modelling was also performed for the case of a winding with a fault. The results of modelling were assessed with four numerical indices used for FRA interpretation.
Multi-Objective Thermo-Economic Optimization of a Combined Organic Rankine Cycle (ORC) System Based on Waste Heat of Dual Fuel Marine Engine and LNG Cold Energy Recovery
Authors: Tian Zhen , Yue Yingying , Zhang Yuan , Gu Bo , Gao Wenzhong
Published: March 2020

In this paper, a combined organic Rankine cycle (ORC) system that can effectively utilize the cold energy of Liquefied Nature Gas (LNG) and the waste heat of dual fuel (DF) marine engine was proposed. Particularly, the engine exhaust gas and the jacket cooling water of the DF marine engine were used as heat sources. Firstly, a thorough assessment of thermo-economic performance was conducted for the combined ORC system using 11 environmentally friendly working fluids (WFs). Afterwards, the effects of evaporation and condensation pressures on the net output work, energy efficiency, exergy efficiency, total investment cost and payback period were examined. Furthermore, the thermo-economic performances of the ORC system were optimized via multi-objective optimization with a genetic algorithm. Finally, exergy destructions and investment costs of each component under the optimal operating conditions were analyzed to make suggestions for further improvement. The results show that R1150-R1234yf-R600a and R170-R1270-R152a are the two most promising WF combinations. The exergy destruction of the combined ORC system mainly exists in heat exchangers. Through WF optimization, the exergy destruction in the intermediate heat exchanger was reduced by 18.99%. The proportion of expanders investment cost could be greater than 50% and the payback period of the combined ORC system varies in the range of 7.68–9.43 years. This study demonstrated that the selection of WF and the optimization of operating conditions had important potential to improve thermo-economic performances of ORC systems.
PV System Predictive Maintenance: Challenges, Current Approaches, and Opportunities
Authors: Bosman Lisa B. , Leon-Salas Walter D. , Hutzel William , Soto Esteban A.
Published: March 2020

Within the United States solar energy industry, there is a general motto of “set it and forget it” with solar energy. This notion is derived from much of the research and reliability studies around the photovoltaic (PV) panels themselves, not necessarily the PV system as a whole (including the inverter and other components). This implies that maintenance and regular monitoring is not needed. Yet many things can go wrong to cause the actual performance to deviate from the expected performance. If failures and/or unanticipated degradation issues go undetected, they will lead to reduced energy generation (and associated electricity credits) and/or potential loss of component warranty because of manufacturer turnover. Given the size of the problem and gaps with current solutions, the authors propose that PV system owners need an unbiased third-party off-the-shelf system-level predictive maintenance tool to optimize return-on-investment and minimize time to warranty claim in PV installations. This paper reviews the literature highlighting challenges, current approaches, and opportunities for PV predictive maintenance. The paper concludes with a call to action for establishing a collaborative agenda toward prioritizing PV predictive maintenance.
A Qualitative Control Approach to Reduce Energy Costs of Hybrid Energy Systems: Utilizing Energy Price and Weather Data
Authors: Taebnia Mehdi , Heikkilä Marko , Mäkinen Janne , Kiukkonen-Kivioja Jenni , Pakanen Jouko , Kurnitski Jarek
Published: March 2020

Nowadays, many buildings are equipped with various energy sources. The challenge is how to efficiently utilize their energy production. This includes decreasing the share and costs of external energy—usually electrical energy delivered from the grid. The following study presents a qualitative approach with a combined control to solve the problem. The approach is demonstrated using a simulated residential building equipped with a hybrid energy system: a thermal energy storage combined with an electrical heater, a geothermal heat pump and a solar thermal collector. Consequently, the share of renewable energy was increased and, conversely, costs of the external energy from grid decreased by 12.2%. The results were based on a qualitative approach and the algorithm which predicts the need of energy of the building over the next 6 h with the aid of weather forecasting. This approach included a storage tank of 300 L. The energy costs can be further decreased 7.7% by increasing thermal storage capacity and modifying the control algorithm. In all cases, the indoor conditions were kept at a comfortable level. However, if the room temperature is temporarily allowed to slightly drop a few degrees during the heating season, the energy costs were further reduced.
Operation of the Hybrid Photovoltaic-Battery System on the Electricity Market—Simulation, Real-Time Tests and Cost Analysis
Authors: Małkowski Robert , Jaskólski Marcin , Pawlicki Wojciech
Published: March 2020

This paper presents research on a hybrid photovoltaic-battery energy storage system, declaring its hourly production levels as a member of a balancing group submitting common scheduling unit to the day-ahead market. It also discusses the variability of photovoltaic system generation and energy storage response. The major research questions were whether the operation of a hybrid photovoltaic-battery energy storage system is viable from the technical and economic viewpoint and how to size battery energy storage for that purpose. The DIgSILENT PowerFactory environment was used to develop the simulation model of postulated hybrid system. Then, tests were conducted on real devices installed in the LINTE^2 laboratory at Gdańsk University of Technology, Poland. Firstly, power generation in the photovoltaic system was modeled using hardware in the loop technique and tested in cooperation with emulated photovoltaic and real battery energy storage system (lithium-ion battery, 25 kWh). Secondly, a real photovoltaic power plant (33 kW) and real battery energy storage were applied. The results obtained from laboratory experiments showed that market operation of hybrid photovoltaic-battery energy storage system is feasible. However, developing a control strategy constitutes a great challenge, as the operator is forced to intervene more frequently than the simulation models indicate in order to keep the parameters of battery storage within accepted ranges, especially in view of a sudden weather breakdown. Levelized cost of electricity from photovoltaic-battery energy storage system varied from 314 to 455 $/MWh, which has proven to be from two to three times higher than the current annual average day-ahead market price in Poland.
Time-Varying Influences of Oil-Producing Countries on Global Oil Price
Authors: Jang Peter Y. , Beruvides Mario G.
Published: March 2020

This paper aims to investigate the time-varying influences of major crude oil-producing countries on Brent oil prices, with seven-panel data over the observation years of 1998 to 2018. We create seven panels with 36 monthly data for each and estimate the contributions of individual producing countries to oil price changes with a multivariate regression technique of ordinary least squares. Most existing researches have focused on identifying relationships among oil price, market fundamental factors, macroeconomic variables, and geopolitical events in broad perspectives. However, this paper undertakes a longitude/panel analysis of nine oil producers’ influences, with the Organisation for Economic Co-operation and Development (OECD) consumption and the U.S. Dollar Index (USDX) on oil prices in each panel and intends to identify which producers have statistically significant influencing weights on oil prices. We believe that this research contributes to the body of knowledge in better understanding the relative impacts of major oil-producing countries. Results show empirical evidences that the Organization of the Petroleum Exporting Countries (OPEC) production stayed as the greatest negative influence on the oil price in the periods of Panel 2 (2001–2003) and Panel 7 (2016–2018) only, while the U.S. Dollar Index took over the OPEC’s influencing role in most of the other periods, followed by Iran, the U.S., and China.
An Improved Control Method Based on Source Current Sampled for Shunt Active Power Filters
Authors: Cao Xudong , Dong Kun , Wei Xueliang
Published: March 2020

Active power filters (APFs) are dynamic power electronic devices that suppress harmonics and reactive power. To simplify the detection and extraction of traditional APF harmonics and reactive current, this paper proposes a direct source current control based on a three-phase three-wire shunt APF. The compensation principle and control method of the source current are analyzed systematically. The currents can be controlled without static errors by a proportional-integral (PI) controller in d-q rotating coordinates. Therefore, the compensation accuracy and dynamic performance of the system can be improved by the control strategy. Moreover, considering the grid voltage fluctuations, a droop regulator is proposed to address the impact of DC-link voltages on APF power losses and compensation performance. The regulator is combined with a traditional voltage outer loop PI control to achieve a comprehensive optimization between the power loss and compensation performance of the APF system. Finally, the inner current loop and the outer voltage loop form a double closed-loop cascade PI control structure to achieve the control effect of the APF. Simulation and experimental results verified the validity and feasibility of the APF control approach.
Design and Optimization of an Aeroservoelastic Wind Tunnel Model
Authors: Dillinger Johannes K. S. , Meddaikar Yasser M. , Lübker Jannis , Pusch Manuel , Kier Thiemo
Published: March 2020

Through the combination of passive and active load alleviation techniques, this paper presents the design, optimization, manufacturing, and update of a flexible composite wind tunnel model. In a first step, starting from the specification of an adequate wing and trailing edge flap geometry, passive, static aeroelastic stiffness optimizations for various objective functions have been performed. The second optimization step comprised a discretization of the continuous stiffness distributions, resulting in manufacturable stacking sequences. In order to determine which of the objective functions investigated in the passive structural optimization most efficiently complemented the projected active control schemes, the condensed modal finite element models were integrated in an aeroelastic model, involving a dedicated gust load alleviation controller. The most promising design was selected for manufacturing. The finite element representation could be updated to conform to the measured eigenfrequencies, based on the dynamic identification of the model. Eventually, a wind tunnel test campaign was conducted in November 2018 and results have been examined in separate reports.
Excess Mortality Due to External Causes in Women in the South African Mining Industry: 2013–2015
Authors: Wilson Kerry S. , Kootbodien Tahira , Naicker Nisha
Published: March 2020

Mining is a recognized high-risk industry with a relatively high occurrence of occupational injuries and disease. In this study, we looked at the differences in mortality between male and female miners in South Africa. Data from Statistics South Africa regarding occupation and cause of death in the combined years 2013–2015 were analyzed. Proportional mortality ratios (PMRs) were calculated to investigate excess mortality due to external causes of death by sex in miners and in manufacturing laborers. Results: Women miners died at a significantly younger age on average (44 years) than all women (60 years), women manufacturers (53 years), and male miners (55 yrs). There was a significantly increased proportion of deaths due to external causes in women miners (12.4%) compared to all women (4.8%) and women manufacturers (4.6%). Significantly increased PMRs were seen in car occupant accidents (467, 95% confidence interval (CI) 151–1447), firearm discharge (464, 95% CI 220–974), and contact with blunt objects (2220 95% CI 833–5915). Conclusion: This descriptive study showed excess deaths in women miners due to external causes. Road accidents, firearm discharge, and contact with blunt objects PMRs were significantly increased. Further research is required to confirm the underlying reasons for external causes of death and to develop recommendations to protect women miners.
Metal Concentration Assessment in the Urine of Cigarette Smokers Who Switched to Electronic Cigarettes: A Pilot Study
Authors: Prokopowicz Adam , Sobczak Andrzej , Szdzuj Jerzy , Grygoyć Katarzyna , Kośmider Leon
Published: March 2020

Background: E-cigarettes (ECs) seem to be a less harmful alternative for conventional cigarettes, however, very little is still known about the exposure to some elements, which are the components of this device and may contaminate the nicotine liquid. The aim of this study is to assess whether e-cigarette users are more exposed to 12 elements detected in aerosol than non-smokers and conventional cigarette smokers, using their concentrations in urine as exposure biomarkers. Methods: A cross-sectional, group-based survey was carried out using 90 volunteers classified into groups of non-smokers, EC-only users, dual EC users-cigarette smokers and cigarette-only smokers. Using inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS), Cr, Ni, Co, Ag, In, Mn, Ba, Sr, V, Sb, Cd and Pb levels were measured in spot urine samples. Among the selected groups, a comparison was made using the analysis of covariance and correlations with EC usage pattern were assessed by multiple linear regression. Results: Element concentrations in urine of EC-users were not significantly different from the levels found in non-smokers and smokers. Only in the case of Ba, Ni and Sb was a significant correlation found in relation to some e-cigarette usage patterns. Conclusion: Transfer of the investigated elements to the EC aerosol was not found to be a substantial source of exposure in EC users who quitted smoking.
The Relationship Between Widespread Pollution Exposure and Oxidized Products of Nucleic Acids in Seminal Plasma and Urine in Males Attending a Fertility Center
Authors: Poli Diana , Andreoli Roberta , Moscato Lucia , Pelà Giovanna , Palma Giuseppe de , Cavallo Delia , Petyx Marta , Pelosi Giorgio , Corradi Massimo , Goldoni Matteo
Published: March 2020

Background: In recent decades, there has been an increase in male infertility, and in many cases, the etiology remains unclear. Several studies relate male hypo-fertility to xenobiotic exposure, even if no data exist about multiple exposure at the environmental level. Methods: The study involved 86 males with diagnosis of idiopathic male infertility (IMI), and 46 controls with no alteration in sperm characteristics. Seminal plasma (SP) and urine samples were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) to quantify biomarkers of exposure (the main metabolites of benzene, toluene, 1,3-butadiene, 3-monochloropropanediol, styrene, and naphthol) and effect (oxidized products of nucleic acids).Results: Biomarker concentrations were similar in subjects with IMI and controls even if a stronger correlation between biomarkers of exposure and effects were observed in SP. Data show that, both in SP and urine, most metabolites were inter-correlated, indicating a simultaneous co-exposure to the selected substances at the environmental level. Principal component analysis showed in SP the clustering of mercapturic acids indicating a preferential metabolic pathway with Glutathione (GSH) depletion and, consequently, an increase of oxidative stress. This result was also confirmed by multivariable analysis through the development of explanatory models for oxidized products of nucleic acids. Conclusions: This study highlights how oxidative stress on the male reproductive tract can be associated with a different representation of metabolic pathways making the reproductive tract itself a target organ for different environmental pollutants. Our results demonstrate that SP is a suitable matrix to assess the exposure and evaluate the effects of reproductive toxicants in environmental/occupational medicine. The statistical approach proposed in this work represents a model appropriate to study the relationship between multiple exposure and effect, applicable even to a wider variety of chemicals.
Association between Leucocyte Telomere Length and Risk of Hearing Loss in the General Population: A Case-Control Study in Zhejiang Province, China
Authors: Zhang Huai , Wang Dahui , Ma Haiyan , Li Chenhui , Wang Shichang , Wang Yi , Yang Lei , Xu Liangwen
Published: March 2020

Limited studies have assessed the relation between telomere length and risk of hearing loss; moreover, they have reported equivocal associations. In the first case-control study, the subjects were chosen from the general population of Zhejiang province in order to assess the association between leucocyte telomere length and risk of hearing loss from 2016 to 2018. A total of 817 cases (55.93 ± 8.99 years) and 817 age-, sex- and residential city-matched controls (55.91 ± 9.03 years) were included for analysis. In the multivariable models, individuals in the top quartile of relative telomere length (RTL) had an odds ratio (OR) for hearing loss of 0.53 (95% confidence intervals [CI], 0.38–0.74) compared to those in the bottom quartile, and specifically, the OR was 0.45 (95% CI, 0.28–0.73) in females. In females, the risk of hearing loss decreased by 46% as RTL doubling increased; the standard deviation of RTL was associated with a 29% decrease in hearing loss risk. Additional analysis showed significant difference between participants in the female mild hearing loss group and corresponding controls. These results suggest that telomere length is associated with hearing loss in the general population, particularly in females with mild hearing loss. Telomere length might be a potential predictive biomarker of hearing loss at early stage.
“And Then He Got into the Wrong Group”: A Qualitative Study Exploring the Effects of Randomization in Recruitment to a Randomized Controlled Trial
Authors: Lehmann Birthe Andrea , Lindert Lara , Ohlmeier Silke , Schlomann Lara , Pfaff Holger , Choi Kyung-Eun
Published: March 2020

Background: Randomized controlled trials (RCTs) are regarded as the most internally valid means of estimating the effectiveness of complex public health interventions, but the recruitment of participants can be difficult. The aim of this study was to explore factors that may have affected the recruitment of employees with musculoskeletal disorders (MSDs) to a multicenter worksite health promotion program from the perspective of recruiting case managers. Methods: Factors in recruitment to the RCT were explored using three focus group discussions with case managers. Data were processed using MAXQDA and analyzed with a combination of content and sequence analysis. Results: Findings showed that randomization is a major challenge for recruitment. Case managers adapted their communication with, and approaches to possible participants because of the randomization design and employed coping strategies to compensate for allocation into the control arm of the study. Perceptions of the superiority of the intervention group over the control group, perceptions of the (mis)match of participants to one of the groups, as well as the understanding of the necessity of randomization for effectiveness evaluations, further affected recruitment. Perceived expectations of possible participants and their (emotional) reactions to the randomization allocation also complicated recruitment. Conclusion: We were able to gain insight into the challenges of randomization for the recruitment of participants to a multicenter RCT. This study assisted the development of strategies to overcome barriers in the ongoing implementation process of the trial (i.e., the adaption of best practice information sheets and newsletters). There remains a need to develop effective interventions to help those recruiting to trials.
An Observational Tool to Assess Activity Limitation in Ambulatory People with Cerebral Palsy When Performing Motor Skills
Authors: Roldan Alba , Sarabia José M. , Gómez-Marcos Guillermo , Reina Raul
Published: March 2020

Ratios of physical activity and sports participation in people with cerebral palsy (CP) are still low compared with people without a disability. For an adequate and useful practice, physical activity professionals should understand how different types of CP profiles constrain the performance of motor skills that are required during sports practice. This study aims to develop an observation-based assessment tool to evaluate activity limitations in individuals with a moderate level of CP when performing skills requiring jumping, sprinting, change of direction, coordination, and balance. Nineteen observers with different backgrounds from five world regions were recruited for this study, with accredited experience classifying/observing para-athletes with CP. All observers watched videos of 20 international para-athletes with different CP profiles (bilateral spasticity, athetosis/ataxia, unilateral spasticity; all Gross Motor Function Classification System level I) performing 16 motor tasks, and their observations were recorded throughout an ad-hoc data collection instrument. A total of 6080 units of qualitative information were recorded for data analysis. An observation-based tool with qualitative descriptors is derived from data analyses, describing how coordination and balance affected mainly in those with dyskinesia/ataxia, range of movement in those with diplegia, and asymmetries in those with hemiplegia. This tool would help sports practitioners and physical educators to better understand how different CP profiles constrain the performance of motor skills.
Tactile Discrimination, Praxis and Cognitive Impulsivity in ADHD Children: A Cross-Sectional Study
Authors: Romero-Ayuso Dulce , Maciver Donald , Richmond Janet , Jorquera-Cabrera Sara , Garra-Palud Luis , Zabala-Baños Carmen , Toledano-González Abel , Triviño-Juárez José-Matías
Published: March 2020

Background: The study of attention deficit hyperactivity disorder (ADHD) has traditionally focused on deficit of inhibitory control and cognitive impulsivity. However, the pathophysiology of ADHD has also been associated with the somatosensory cortex. The aim of this study was to explore if there were differences in tactile discrimination and praxis between neurotypical and ADHD children and whether these differences could be explained by cognitive impulsivity. Methods: A cross-sectional study was conducted. The sample comprised 74 children aged 7 to 11 years divided in two groups: 43 with neurotypical development, 31 with ADHD. To assess tactile discrimination, the finger localization and the graphestesia tests were used. Praxis was assessed with the Kaufman Assesment Battery for Children (K-ABC) hand movement subtest, the action program and the Zoo Map subtests of the Behavioral Assessment of Dysexecutive Syndrome, and the complex figure of Rey–Osterrieth test (ROCF). Cognitive impulsivity was assessed using the Magallanes Computerized Impulsivity Scale test (EMIC). Results: Children with ADHD showed greater cognitive impulsivity (p = 0.038) and scored lower in Zoo Map (p = 0.023) and hand-movement subtests (p = 0.002), and in ROCF test (p = 0.004). Differences in praxis skills still remained after controlling by gender and cognitive impulsivity. Conclusion: Praxis deficit might have repercussions not only on the characterization of ADHD but also on its treatment.
The Integration of Mental Health and Psychosocial Support and Disaster Risk Reduction: A Mapping and Review
Authors: Gray Brandon , Hanna Fahmy , Reifels Lennart
Published: March 2020

The field of disaster and emergency management has shifted in focus towards the goal of Disaster Risk Reduction (DRR). However, the degree to which the Mental Health and Psychosocial Support (MHPSS) field has followed this trend is relatively unknown. Therefore, the objectives of this review were to identify relevant projects, materials, and publications relating to MHPSS and DRR integration and define current domains of action in this integration. A review was conducted using a two-pronged approach for data collection. This approach included 1) a mapping exercise eliciting relevant documentation and project descriptions from MHPSS actors, and 2) a database and internet literature search. The mapping exercise was conducted between January and November 2019, while the literature search was completed in March 2019. The majority of identified materials concerned actions of capacity and systems building; preparedness; policy development, consensus building, and awareness raising; school- and child-focused DRR; inclusive DRR; and resilience promotion. Results also suggested that relatively little consensus exists in terms of formal definitions of and frameworks or guidance for integrating MHPSS and DRR. Moreover, domains of action varied in terms of current implementation practices and empirical evidence. Materials and projects are reviewed and discussed in terms of implications for advancing the integration of DRR and MHPSS and expanding MHPSS approaches to include building better before emergencies.