bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave Liquid Crystal Technology
Authors: Maune Holger , Jost Matthias , Reese Roland , Polat Ersin , Nickel Matthias , Jakoby Rolf
Published: September 2018

Tunable Liquid Crystal (LC)-based microwave components are of increasing interest in academia and industry. Based on these components, numerous applications can be targeted such as tunable microwave filters and beam-steering antenna systems. With the commercialization of first LC-steered antennas for Ku-band e.g., by Kymeta and Alcan Systems, LC-based microwave components left early research stages behind. With the introduction of terrestrial 5G communications systems, moving to millimeter-wave communication, these systems can benefit from the unique properties of LC in terms of material quality. In this paper, we show recent developments in millimeter wave phase shifters for antenna arrays. The limits of classical high-performance metallic rectangular waveguides are clearly identified. A new implementation with dielectric waveguides is presented and compared to classic approaches.
Molecules and the Eigenstate Thermalization Hypothesis
Authors: Leitner David M.
Published: September 2018

We review a theory that predicts the onset of thermalization in a quantum mechanical coupled non-linear oscillator system, which models the vibrational degrees of freedom of a molecule. A system of N non-linear oscillators perturbed by cubic anharmonic interactions exhibits a many-body localization (MBL) transition in the vibrational state space (VSS) of the molecule. This transition can occur at rather high energy in a sizable molecule because the density of states coupled by cubic anharmonic terms scales as N3, in marked contrast to the total density of states, which scales as exp(aN), where a is a constant. The emergence of a MBL transition in the VSS is seen by analysis of a random matrix ensemble that captures the locality of coupling in the VSS, referred to as local random matrix theory (LRMT). Upon introducing higher order anharmonicity, the location of the MBL transition of even a sizable molecule, such as an organic molecule with tens of atoms, still lies at an energy that may exceed the energy to surmount a barrier to reaction, such as a barrier to conformational change. Illustrative calculations are provided, and some recent work on the influence of thermalization on thermal conduction in molecular junctions is also discussed.
The Informational Dynamics of Mean‒Variance Relationships in Fertilizer Markets: An Entropic Investigation
Authors: Lahmiri Salim , Bekiros Stelios
Published: September 2018

The risk‒return trade-off is a fundamental relationship that has received a large amount of attention in financial and economic analysis. Indeed, it has important implications for understanding linear dynamics in price returns and active quantitative portfolio optimization. The main contributions of this work include, firstly, examining such a relationship in five major fertilizer markets through different time periods: a period of low variability in returns and a period of high variability such as that during which the recent global financial crisis occurred. Secondly, we explore how entropy in those markets varies during the investigated time periods. This requires us to assess their inherent informational dynamics. The empirical results show that higher volatility is associated with a larger return in diammonium phosphate, potassium chloride, triple super phosphate, and urea market, but not rock phosphate. In addition, the magnitude of this relationship is low during a period of high variability. It is concluded that key statistical patterns of return and the relationship between return and volatility are affected during high variability periods. Our findings indicate that entropy in return and volatility series of each fertilizer market increase significantly during time periods of high variability.
On Differences between Deterministic and Stochastic Models of Chemical Reactions: Schlögl Solved with ZI-Closure
Authors: Vlysidis Michail , Kaznessis Yiannis N.
Published: September 2018

Deterministic and stochastic models of chemical reaction kinetics can give starkly different results when the deterministic model exhibits more than one stable solution. For example, in the stochastic Schlögl model, the bimodal stationary probability distribution collapses to a unimodal distribution when the system size increases, even for kinetic constant values that result in two distinct stable solutions in the deterministic Schlögl model. Using zero-information (ZI) closure scheme, an algorithm for solving chemical master equations, we compute stationary probability distributions for varying system sizes of the Schlögl model. With ZI-closure, system sizes can be studied that have been previously unattainable by stochastic simulation algorithms. We observe and quantify paradoxical discrepancies between stochastic and deterministic models and explain this behavior by postulating that the entropy of non-equilibrium steady states (NESS) is maximum.
Engaging Marginalized, “At-Risk” Middle-Level Students: A Focus on the Importance of a Sense of Belonging at School
Authors: Pendergast Donna , Allen Jeanne , McGregor Glenda , Ronksley-Pavia Michelle
Published: September 2018

The philosophy of middle level education is to intentionally create a learning environment that supports every young adolescent. The literature around engagement points to the need for students to experience (among other requirements) a sense of belonging at school (SOBAS). When the need for belonging is not achieved there may be significant consequences, including an impact on intellectual performance, and hence, learning potential may not be achieved. For students with marginalized identities, an intensification of factors that create challenges places them at-risk of disengaging and their sense of belonging at school is more likely to be compromised. Nurturing SOBAS is positively associated with the retention of students who are at-risk of dropping out of, thereby being an aspirational goal of education. Methods: The findings of a systematic literature review related to young adolescents and the importance of SOBAS forms a focused literature base. We highlight findings from a study that explored the effectiveness of engagement strategies for marginalized students in one educational jurisdiction in Australia. Data in the form of a series of interviews and focus groups conducted with 25 students, 25 of their teachers, and 39 school leaders provides a rich data set for thematic content analysis. Inductive analysis and in vivo coding led to a framework that summarized each of the sub-group data sets to convey emergent themes. Results: Five themes related to SOBAS emerged from the data: (a) Relationships in School; (b) School Climate; (c) Pedagogical Practices; (d) Specific Programs and Activities; and (e) Other Issues, mainly variables such as family, mental health, trauma and poverty that impacted on a student’s SOBAS. Conclusion: The systematic literature review and the findings of the empirical study presented in this paper highlight aspects of SOBAS that can be formalized into a series of strategies to increase retention of marginalized students.
An Adaptation Study of Measurement Properties for the Characteristics of Resilience in Sports Team Inventory
Authors: Gorgulu Recep , Senel Ender , Adilogulları İlhan , Yildiz Mevlut
Published: September 2018

This multi-study paper reports the translation process and the validity and reliability analysis of the Characteristics of Resilience in Sports Teams Inventory (CREST) for the use of Turkish population. In three related studies, 414 team sports athletes from Turkey were sampled. We adopted Beaton et al.’s (2000) methodology for the translation of self-report measures for cross-cultural adaption studies. The first study provided content validity for an initial item set as the preliminary study. The second study explored the factor analysis of the CREST structure. The third study explored re-testing of the explored structure in a different set of participants and criterion-related validity provided. The analysis of Study 1 revealed that the items were understood by the participants and ready for application for the general Turkish population. The exploratory factor analysis in the Study 2 revealed that the CREST had two sub-dimensions as it was in the original inventory. The Cronbach’s alpha values for the dimensions of demonstrating resilience characteristics and vulnerabilities shown under pressure were 0.94 and 0.90, respectively. The Kaiser-Meyer-Olkin value was 0.94. The confirmatory factor analysis in the third study showed that the structure of the inventory was confirmed in another sports context. Accordingly, the CREST is a valid and reliable tool for use by Turkish athletes and to measure team resilience that is one of the critical determinants of team performance. Further understanding of team resilience as a process can be gain by using the CREST, especially in future process-oriented research for team sports.
Physical Activation of Waste-Derived Materials for Biogas Cleaning
Authors: Papurello Davide , Santarelli Massimo , Fiorilli Sonia
Published: September 2018

Biogas produced from biomass is carbon neutral. In fact, the carbon feedstock of biomass is converted into gas phase. Biogas use in high efficient energy systems, such as Solid Oxide Fuel Cells is a viable choice. One of the most important drawbacks for such systems is related to the interaction between trace compounds and anode section. Gas cleaning through physical removal mechanisms is the simplest and cheapest method adopted in the literature. Coupled with this solution, the recovery of waste materials is an efficient application of the circular economy approach. In this work, a physical activation process was investigated experimentally for waste-derived materials at a temperature of 700 °C. The removal of H2S was considered as the most abundant trace compound. Activated biochar showed an adsorption capacity comparable to commercial sorbents, while the performance of ashes are still too poor. An important parameter to be considered is the biogas humidity content that enters in competition with trace compounds that must be removed.
Primary Frequency Controller with Prediction-Based Droop Coefficient for Wind-Storage Systems under Spot Market Rules
Authors: Zhang Shengqi , Mishra Yateendra , Yuan Bei , Zhao Jianfeng , Shahidehpour Mohammad
Published: September 2018

Increasing penetration levels of asynchronous wind turbine generators (WTG) reduce the ability of the power system to maintain adequate frequency responses. WTG with the installation of battery energy storage systems (BESS) as wind-storage systems (WSS), not only reduce the intermittency but also provide a frequency response. Meanwhile, many studies indicate that using the dynamic droop coefficient of WSS in primary frequency control (PFC) based on the prediction values, is an effective way to enable the performance of WSS similar to conventional synchronous generators. This paper proposes a PFC for WSS with a prediction-based droop coefficient (PDC) according to the re-bid process under real-time spot market rules. Specifically, WSS update the values of the reference power and droop coefficient discretely at every bidding interval using near-term wind power and frequency prediction, which enables WSS to be more dispatchable in the view of transmission system operators (TSOs). Also, the accurate prediction method in the proposed PDC-PFC achieves the optimal arrangement of power from WTG and BESS in PFC. Finally, promising simulation results for a hybrid power system show the efficacy of the proposed PDC-PFC for WSS under different operating conditions.
Visualization Investigation of the Influence of Chamber Profile and Injection Parameters on Fuel Spray Spreading in a Double-Layer Diverging Combustion Chamber for a DI Diesel Engine
Authors: Fu Yao , Feng Liyan , Tian Hua , Long Wuqiang , Dong Dongsheng , Leng Xianyin
Published: September 2018

The double-layer diverging combustion chamber (DLDC chamber) aims to improve the fuel–air mixing formation and promote in-cylinder air utilization by changing fuel spray spreading characteristics. In order to investigate how the DLDC chamber profile and injection parameters affect the fuel spray spreading, visualization of fuel injection and impingement tests were carried out on two different DLDC chambers with different fuel injection parameters. The visualization test results showed that double-layer fuel spray spreading was obtained in the two DLDC chambers and the peripheral top clearance of each chamber was utilized efficiently. The DLDC chamber with a 50% upper layer volume provided a larger fuel spray distribution region after the start of injection. The DLDC chamber with a 70% upper layer volume obtained a larger fuel spray distribution region with better top clearance utilization at the later stage of injection. The injection parameters mentioned in this research showed significant effects on the fuel spray spreading in the DLDC chamber. Increasing the injection pressure provided a larger fuel spray distribution area at the beginning of injection. Decreasing the nozzle hole diameter had a positive influence on obtaining a larger fuel spray distribution. Advancing the injection timing enabled the enlarging of the fuel distribution region.
Methane Desorption Characteristics of Coal at Different Water Injection Pressures Based on Pore Size Distribution Law
Authors: Zhao Dong , Gao Tao , Ma Yulin , Feng Zengchao
Published: September 2018

Methane desorption characteristics of coal under definite water pressure comprises a complex two-phase flow process. A series of mercury intrusion porosimetry (MIP) and desorption experiments at different water injection pressures are reported in this study. Three lumpy coal samples were used in desorption experiments at three different water injection pressures and at natural desorption for comparison. Samples comprising two ranks of coal were used for MIP measurements including the distribution of porosity and pore sizes. The results of this study enable the establishment of a new model that encompasses a critical theoretical pore size that is most effective for water injection into coalbeds and that can be related to water injection pressure, the length of residual water, and gas adsorption capacity. Data show that the use of different water injection pressures leads to different gas desorption capacities as well as variable time effects and degree of gas desorption. Critical pore size is therefore proposed as a new parameter that can be employed to describe high pressure water effects in the context of gas desorption and can be calculated using pore size and the volume distribution law, as well as via the moisture ratio that remains after experiments and the permanent desorption percentage.
Microgrid Spinning Reserve Optimization with Improved Information Gap Decision Theory
Authors: Zhang Hong , Sun Hao , Zhang Qian , Kong Guanxun
Published: September 2018

Distributed generation (DG) is an important method of energy generation that accelerates the decentralization process of centralized systems, and has been widely deployed in modern society due to its economical, sustainable, and environmentally friendly characteristics. However, with the tremendous development of DG, system reliability operations are facing increasingly severe challenges because of the fluctuations of the renewable generation. In this paper, a novel spinning reserve optimization method is proposed to maximize the maximum allowance of system uncertainty (MAoSU) under the premise of satisfying the preset system operational cost. Then, the success rate of DG off-grid operation is calculated by comparing the magnitude of optimal spinning reserve capacity with the power exchange between the main grid and the distributed grid. The simulation results show that decision-makers need to increase the operational cost to compensate for system uncertainty, and the percentage increase of the operational cost is in proportional to the MAoSU and system renewable energy penetration rate. Additionally, with the increase of the MAoSU, the system needs to prepare more spinning reserve capacity to maintain system reliability operations. Finally, with the decrease of the MAoSU, the success rate of system off-grid operation decreases sharply, especially when the MAoSU is less than 0.5.
RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine
Authors: Mejia Omar D. Lopez , Quiñones Jhon J. , Laín Santiago
Published: September 2018

Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.
The Creep-Damage Model of Salt Rock Based on Fractional Derivative
Authors: Zhou Hongwei , Liu Di , Lei Gang , Xue Dongjie , Zhao Yang
Published: September 2018

The use of salt rock for underground radioactive waste disposal facilities requires a comprehensive analysis of the creep-damage process in salt rock. A computer-controlled creep setup was employed to carry out a creep test of salt rock that lasted as long as 359 days under a constant uniaxial stress. The acoustic emission (AE) space-time evolution and energy-releasing characteristics during the creep test were studied in the meantime. A new creep-damage model is proposed on the basis of a fractional derivative by combining the AE statistical regularity. It indicates that the AE data in the non-decay creep process of salt rock can be divided into three stages. Furthermore, the authors propose a new creep-damage model of salt rock based on a fractional derivative. The parameters in the model were determined by the Quasi-Newton method. The fitting analysis suggests that the new creep-damage model provides a precise description of full creep regions in salt rock.
Correction: Gori, V.; Biddulph, P.; Elwell, C.A. A Bayesian Dynamic Method to Estimate the Thermophysical Properties of Building Elements in All Seasons, Orientations and with Reduced Error. Energies 2018, 11, 802
Authors: Gori Virginia , Biddulph Phillip , Elwell Clifford A.
Published: September 2018

The authors wish to make the following corrections to their paper [1]: [...]
A Compound Controller Design for a Buck Converter
Authors: Sun Yueping , Ma Li , Zhao Dean , Ding Shihong
Published: September 2018

In order to improve the performance of the closed-loop Buck converter control system, a compound control scheme based on nonlinear disturbance observer (DO) and nonsingular terminal sliding mode (TSM) was developed to control the Buck converter. The control design includes two steps. First of all, without considering the dynamic and steady-state performances, a baseline terminal sliding mode controller was designed based on the average model of the Buck converter, such that the desired value of output voltage could be tracked. Secondly, a nonlinear DO was designed, which yields an estimated value as the feedforward term to compensate the lumped disturbance. The compound controller was composed of the terminal sliding mode controller as the state feedback and the estimated value as the feedforward term. Simulation analysis and experimental verifications showed that compared with the traditional proportional integral derivative (PID) and terminal sliding mode state feedback control, the proposed compound control method can provide faster convergence performance and higher voltage output quality for the closed-loop system of the Buck converter.
A Pilot Study on Geothermal Heat Pump (GHP) Use for Cooling Operations, and on GHP Site Selection in Tropical Regions Based on a Case Study in Thailand
Authors: Chokchai Sasimook , Chotpantarat Srilert , Takashima Isao , Uchida Youhei , Widiatmojo Arif , Yasukawa Kasumi , Charusiri Punya
Published: September 2018

In order to reduce electricity consumption, the vertical loop geothermal heat pump (GHP) system coupled with a normal air conditioner was installed in an experimental room in the Parot Racha Building, Chulalongkorn University, Bangkok, Thailand for a comparative, long-term measurement program. The decrease in electricity consumption was approximately 30%. On the basis of the data derived from our measurements, the underground temperature seemed to be consistent and lower than the average outside air temperature, over two years. The underground system consisted mainly of two 50-m-long drilling wells and pipes with a total length of 170 m. The well performance was not examined, but both soil and groundwater aquifer (Bangkok aquifer) at 25 to 50 m. could be utilized for the cooling operation. Moreover, the major controlling factors of electricity consumption were found to be the outside air temperatures and the underground water circulation temperatures. In addition, we considered the geology, underground temperature, and aquifer of Bangkok concluding that almost all Bangkok areas are suitable for GHP installation, except for those where the subsurface temperature is too high compared with the outside air temperature.
Simulation of Fluid-Thermal Field in Oil-Immersed Transformer Winding Based on Dimensionless Least-Squares and Upwind Finite Element Method
Authors: Liu Gang , Zheng Zhi , Yuan Dongwei , Li Lin , Wu Weige
Published: September 2018

In order to study the coupling fluid and thermal problems of the local winding in oil-immersed power transformers, the least-squares finite element method (LSFEM) and upwind finite element method (UFEM) are adopted, respectively, to calculate the fluid and thermal field in the oil duct. When solving the coupling problem by sequential iterations, the effect of temperature on the material property and the loss density of the windings should be taken into account. In order to improve the computation efficiency for the coupling fields, an algorithm, which adopts two techniques, the dimensionless LSFEM and the combination of Jacobi preconditioned conjugate gradient method (JPCGM) and the two-side equilibration method (TSEM), is proposed in this paper. To validate the efficiency of the proposed algorithm, a local winding model of a transformer is built and the fluid field is computed by the conventional LSFEM, dimensionless LSFEM, and the Fluent software. While the fluid and thermal computation results of the local winding model of a transformer obtained by the two LSFEMs are basically consistent with those of the Fluent software, the stiffness matrix, which is formed by the dimensionless scheme of LSFEM and preconditioned by the JPCGM and TSEM, has a smaller condition number and a faster convergence rate of the equations. Thus, it demonstrates a broader applicability.
Investigation on the Application of NMR to Spontaneous Imbibition Recovery of Tight Sandstones: An Experimental Study
Authors: Lyu Chaohui , Wang Qing , Ning Zhengfu , Chen Mingqiang , Li Mingqi , Chen Zhili , Xia Yuxuan
Published: September 2018

In this paper, the nuclear magnetic resonance (NMR) technique is applied to exploring the spontaneous imbibition mechanism in tight sandstones under all face open (AFO) boundary conditions, which will benefit a better understanding of spontaneous imbibition during the development of oil & gas in tight formations. The advantages of nuclear magnetic resonance imaging (NMRI) and NMR T2 are used to define the distribution of remaining oil, evaluate the effect of micro structures on imbibition and predict imbibition recovery. NMR T2 results show that pore size distributions around two peaks are not only the main oil distributions under saturated condition but also fall within the main imbibition distributions range. Spontaneous imbibition mainly occurs in the first 6 h and then slows down and even ceases. The oil signals in tiny pores stabilize during the early stage of imbibition while the oil signal in large pores keeps fluctuating during the late stage of imbibition. NMRI results demonstrate that spontaneous imbibition is a replacement process starting slowly from the boundaries to the center under AFO and ending with oil-water mixing. Furthermore, the wetting phase can invade the whole core in the first 6 h, which is identical with the main period of imbibition occurring according to NMR T2 results. Factors influencing the history of oil distribution and saturation differ at different periods, while it is dominated by capillary imbibition at the early stage and allocated by diffusion at later time. Two imbibition recovery curves calculated by NMRI and NMR T2 are basically consistent, while there still exists some deviations between them as a result of the resolutions of NMRI and NMR T2. In addition, the heterogeneity of pore size distributions in the two samples aggravates this discrepancy. The work in this paper should prove of great help to better understand the process of the spontaneous imbibition, not only at the macroscopic level but also at the microscopic level, which is significant for oil/gas recovery in tight formations.
A Survey of Protocol-Level Challenges and Solutions for Distributed Energy Resource Cyber-Physical Security
Authors: Sundararajan Aditya , Chavan Aniket , Saleem Danish , Sarwat Arif I.
Published: September 2018

The increasing proliferation of distributed energy resources (DERs) on the smart grid has made distributed solar and wind two key contributors to the expanding attack surface of the network; however, there is a lack of proper understanding and enforcement of DER communications security requirements. With vendors employing proprietary methods to mitigate hosts of attacks, the literature currently lacks a clear organization of the protocol-level vulnerabilities, attacks, and solutions mapped to each layer of the logical model such as the OSI stack. To bridge this gap and pave the way for future research by the authors in determining key DER security requirements, this paper conducts a comprehensive review of the key vulnerabilities, attacks, and potential solutions for solar and wind DERs at the protocol level. In doing so, this paper serves as a starting point for utilities, vendors, aggregators, and other industry stakeholders to develop a clear understanding of the DER security challenges and solutions, which are key precursors to comprehending security requirements.
Landscape Diversity for Reduced Risk of Insect Damage: A Case Study of Spruce Bud Scale in Latvia
Authors: Bāders Endijs , Jansons Āris , Matisons Roberts , Elferts Didzis , Desaine Iveta
Published: September 2018

Spruce bud scale (Physokermes piceae (Schrnk.)) has gained attention due to recent outbreaks in the eastern Baltic Sea region—Poland, Lithuania, and Latvia. In the spring of 2010, it spread rapidly across Latvia, affecting large areas of Norway spruce stands. Therefore, the aim of our study was to assess the effects of landscape heterogeneity on the damage caused by spruce bud scale in Norway spruce stands. In this study, we evaluated landscape metrics for middle-aged (40 to 70 years old) Norway spruce-dominated stands (>70% of stand’s basal area) in four of the most affected forest massifs and two unaffected forest massifs. We used a binary logistic generalized linear mixed effects model (GLMMs) to assess the effect of environmental factors on the abundance of the spruce bud scale. Our results show that increased local diversity within 100 m of a forest patch apparently reduced the probability of spruce bud scale presence. We also found that the diversity within 1000 m of a patch was associated with an increased probability of spruce bud scale damage. A quantitative analysis of landscape metrics in our study indicated that greater landscape-scale diversity of stands may reduce insect damages.
Theory-of-Change Development for the Evaluation of Forest Stewardship Council Certification of Sustained Timber Yields from Natural Forests in Indonesia
Authors: Romero Claudia , Putz Francis E.
Published: September 2018

To illustrate the importance of theories-of-change (ToCs) for evaluation of conservation interventions, we consider the global ToC from the Forest Stewardship Council (FSC) and then develop a more explicit ToC focused on the sustained timber yield (STY) aspiration for natural forest management in Indonesia. We use these ToCs to consider certification implementation processes vis-à-vis indicators for STY extracted from FSC’s Indonesian Stewardship Standard that mentions STY explicitly in 45 and implicitly in 21 of 237 indicators. Analysis of 38 audit reports about 23 enterprises (2001–2017) revealed that only 77 of 504 major non-conformities assigned by auditors addressed STY. This apparent lack of attention to STY is surprising given the exhaustion of timber stocks in many production forests and the closure of many forest enterprises over the past two decades, but our ToC reveals numerous unsatisfied and unsatisfiable assumptions in certification that preclude detection of unsustainable harvests. Furthermore, compliance with governmental regulations on harvest intensities does not allow full timber recovery. To sustain yields, logging intensities need to be reduced and/or silvicultural treatments applied to increase yields, both of which reduce short-term profits. Declining yields might be accepted if the capacity of logged forests to grow timber is not impaired, but forest abandonment due to timber stock depletion is worrisome if it fosters illegal forest conversion.
Predictive Power Management for Wind Powered Wireless Sensor Node
Authors: Wu Yin , Li Bowen , Zhang Fuquan
Published: September 2018

A conventional Wireless Sensor Network (WSN) cannot have an infinite lifetime without a battery recharge or replacement. Energy Harvesting (EH), from environmental energy sources, is a promising technology to provide sustainable powering for a WSN. In this paper, we propose and investigate a novel predictive energy management framework that combines the Maximal Power Transferring Tracking (MPTT) algorithm, a predictive energy allocation strategy, and a high efficiency transmission power control mechanism: First, the MPTT optimal working point guarantees minimum power loss of the EH-WSN system; Then, by exactly predicting the upcoming available energy, the power allocation strategy regulates EH-nodes’ duty cycle accurately to minimize the power failure time; Ultimately, the transmission power control module further improves energy efficiency by dynamically selecting the optimum matching transmission power level with minimum energy consumption. A wind energy powered wireless sensor system has been equipped and tested to validate the effectiveness of the proposed scheme. Results indicate that compared with other predictive energy managers, the proposed mechanism incurs relatively low power failure time while maintaining a high-energy conversion rate.
Novel Model for the Angle and Skewness Dependent Transmission Behavior of Step-Index Polymer Optical Fiber
Authors: Becker Thomas , Engelbrecht Rainer , Schmauss Bernhard
Published: September 2018

Step-index polymer optical fibers (SI-POFs) are deployed in both sensing and data transmission systems. The optical transmission behavior of these fibers is complex and affected by intrinsic influences like modal dispersion, scattering and attenuation as well as extrinsic influences like the launching condition and the angular sensitivity of the receiver. Since a proper modeling of the transmission behavior is important in order to evaluate the suitability of the fiber for a specific application, we present a novel model for step-index multi-mode fibers (SI-MMFs) which considers all the previously mentioned impacts. Furthermore, the model differentiates scattering and attenuation for propagating rays not only by their propagating angle θ z but also by the skewness θ ϕ . It is therefore possible to distinguish between guided, tunneling and refracted modes. The model uses scatter and attenuation data from previously published measurements of an SI-POF and computes the impulse response of the transmission system which is transferred to the frequency domain to derive the amplitude and phase response. A possible application for SI-POF is the length or strain measurement of the fiber by measuring the phase of a harmonically modulated signal. These sensors rely on a linear relation between the length of the fiber and the phase of the modulated signal. We demonstrate the application of the model by simulating the length measurement error that occurs for these sensors by obtaining the phase response for the corresponding optical transmission system. Furthermore, we will demonstrate the flexibility of the model by varying several influences including the excitation of different mode categories and evaluate the impact on the measurement error. Finally, we compare the simulated length error derived from the model to real data obtained from a cutback measurement. An implementation of the model, which was used for all simulations in this paper, is publicly available.
Advancing the Science of Wildland Fire Dynamics Using Process-Based Models
Authors: Hoffman Chad M. , Sieg Carolyn H. , Linn Rodman R. , Mell William , Parsons Russell A. , Ziegler Justin P. , Hiers J. Kevin
Published: September 2018

As scientists and managers seek to understand fire behavior in conditions that extend beyond the limits of our current empirical models and prior experiences, they will need new tools that foster a more mechanistic understanding of the processes driving fire dynamics and effects. Here we suggest that process-based models are powerful research tools that are useful for investigating a large number of emerging questions in wildland fire sciences. These models can play a particularly important role in advancing our understanding, in part, because they allow their users to evaluate the potential mechanisms and interactions driving fire dynamics and effects from a unique perspective not often available through experimentation alone. For example, process-based models can be used to conduct experiments that would be impossible, too risky, or costly to do in the physical world. They can also contribute to the discovery process by inspiring new experiments, informing measurement strategies, and assisting in the interpretation of physical observations. Ultimately, a synergistic approach where simulations are continuously compared to experimental data, and where experiments are guided by the simulations will profoundly impact the quality and rate of progress towards solving emerging problems in wildland fire sciences.
Instrumental Reciprocity as an Error
Authors: Reuben Ernesto , Suetens Sigrid
Published: September 2018

We study the strategies used by experimental subjects in repeated sequential prisoners’ dilemma games to identify the underlying motivations behind instrumental reciprocity, that is, reciprocation of cooperation only if there is future interaction. Importantly, we designed the games so that instrumental reciprocity is a mistake for payoff-maximizing individuals irrespective of their beliefs. We find that, despite the fact that instrumental reciprocity is suboptimal, it is one of the most frequently used cooperative strategies. Moreover, although the use of instrumental reciprocity is sensitive to the costs of deviating from the payoff-maximizing strategy, these costs alone cannot explain the high frequency with which subjects choose to reciprocate instrumentally.
The Morphology of the Outflow in the Grazing Envelope Evolution
Authors: Shiber Sagiv
Published: September 2018

We study the grazing envelope evolution (GEE), where a secondary star, which orbits the surface of a giant star, accretes mass from the giant envelope and launches jets. We conduct simulations of the GEE with different half-opening angles and velocities, and simulate the onset phase and the spiralling-in phase. We discuss the resulting envelope structure and the outflow geometry. We find in the simulations of the onset phase with narrow jets that a large fraction of the ejected mass outflows along the polar directions. The mass ejected at these directions has the fastest velocity and the highest angular momentum magnitude. In the simulations of the spiralling-in phase, a large fraction of the ejected mass concentrates around the orbital plane. According to our findings, the outflow with the highest velocity is closer to the poles as we launch narrower jets. The outflow has a toroidal shape accompanied by two faster rings, one ring at each side of the equatorial plane. The interaction of the jets with the giant envelope causes these outflow structures, as we do not include in our simulations the secondary star gravity and the envelope self-gravity.
Vet Connect: A Quality Improvement Program to Provide Telehealth Subspecialty Care for Veterans Residing in VA-Contracted Community Nursing Homes
Authors: Hale Anne , Haverhals Leah M. , Manheim Chelsea , Levy Cari
Published: September 2018

Veterans residing in Veterans Health Administration (VA) contracted Community Nursing Homes (CNHs) receive primary care from the CNH they reside in, but often travel to Veterans Affairs Medical Centers (VAMCs) for specialty care services. The Vet Connect project is a quality improvement project aiming to implement video technology to support access to specialty care. Methods: Eight Denver VAMC specialty care providers and three project nurses underwent telehealth training and obtained appropriate equipment. To identify in-person visits eligible for substitution of video visits, project nurses review charts of CNH Veterans, consult directly with Veterans, and obtain recommendations from staff. Project nurses serve as tele-presenters within the CNHs, while VA specialists provide care from the VAMC. After each visit, team nurses coordinate care with and deliver specialty care recommendations to CNH staff. Results: We assessed clinical, business, and technical domains of the Vet Connect project, and utilized process mapping to identify barriers and facilitators to implementation. Clinically, starting on 26 June 2017 through 1 June 2018, N = 203 video visits have been conducted with 11 different CNHs in three subspecialties: geriatrics, palliative care, and mental health. These visits generated 49 referrals for 37 Veterans. Fiscally, cost analyses indicate that per visit, the health care system saves an estimated $310. Technologically, the success rate was 83%. Process mapping helped identify facilitators and barriers to implementation of the telehealth program, including cultivating buy-in from key stakeholders (i.e., medical and mental health providers, telehealth staff, and CNH staff), communication allowing for ongoing program adaptation, and building relationships. Conclusion: Subspecialty care delivery to nursing homes using video visit technology in the Vet Connect program is feasible using centralized organization to coordinate complex clinical, business and technical processes. Vet Connect has proved sustainable and has potential to expand within and outside of the VA.
Reducing the Future Risk of Trauma: On the Integration of Global Disaster Policy within Specific Health Domains and Established Fields of Practice
Authors: Reifels Lennart
Published: September 2018

The global increase in the frequency and severity of natural hazards and extreme climatic events necessitates more efficient global and national strategies to reduce the likelihood and impact of traumatic consequences for disaster-affected populations. The recent inclusion of mental health in the Sendai Framework for Disaster Risk Reduction marks a pivotal point in the recognition of the significant burden of disasters on mental health, and a global commitment to reducing its impacts. Nevertheless, effective agreement implementation and efforts to reduce disaster mental health risks are facing significant challenges. These include a lack of clarity about the conceptual interlinkages and place of disaster risk reduction principles within the field of disaster mental health, which is traditionally marked by a prevailing recovery orientation, and the need for effective translation into disaster mental health policy and practice. Therefore, this study drew on data from interviews with European disaster mental health and risk reduction experts in order to appraise the merit and implications of a global disaster risk reduction policy for advancing population mental health in the context of disaster. Study findings outline existing opportunities, challenges, and key strategies for the integration of disaster risk reduction within disaster mental health policy and practice.
Elevated Indoor Volatile Organic Compound Exposure in the Niger Delta Region of Nigeria
Authors: Kponee Kalé Z. , Nwanaji-Enwerem Jamaji C. , Fu Xianqiang , Kakulu Iyenemi I. , Weisskopf Marc G. , Jia Chunrong
Published: September 2018

The implications of environmental contamination on human health in the Niger Delta region of Nigeria remain a topic of growing international public health interest. To better understand ongoing air pollution and initiate remediation efforts, the United Nations Environmental Programme (UNEP) report recommended the monitoring of volatile organic compounds (VOCs) across different media (water, soil, and air) in Ogoniland, an at-risk population in the Niger Delta region of Nigeria. In this pilot study, we measured indoor VOC concentrations in the indoor air of 20 households in Ogale, an Ogoniland community whose groundwater system is contaminated with benzene at levels 900 times the World Health Organization guidelines and evaluated self-reported health conditions and predicted cancer risks and hazards from inhalation exposure to VOCs. We detected higher concentrations of benzene (mean = 25.7 μg/m3, SD = 23.2 μg/m3) and naphthalene (mean = 7.6 μg/m3, SD = 13.8 μg/m3) than has been reported in other regions. Although study participants reported health symptoms consistent with VOC exposure, we were underpowered to detect a significant association between select indoor VOCs and these self-reported health symptoms using univariate logistic regression models. These findings suggest that that the health symptoms reported by participants may be poor proxies for the underlying disease processes associated with adverse health outcomes due to VOC exposure in this community and that the burden of adverse health effects due to VOC exposure may stem from the contaminated groundwater system. We estimated a non-cancer hazard quotient of 3 from exposure to naphthalene and lifetime excess cancer risks from exposure to naphthalene, benzene, p-dichlorobenzene, carbon tetrachloride, and ethylbenzene of 3 × 10−4, 2 × 10−4, 6 × 10−5, 6 × 10−6, and 1 × 10−5, respectively. These results exceed common risk benchmarks in the United States, suggesting a need for further studies to characterize VOC exposures, sources, and associated health risks in the Niger Delta.
A Hybrid Forecasting Approach to Air Quality Time Series Based on Endpoint Condition and Combined Forecasting Model
Authors: Zhu Jiaming , Wu Peng , Chen Huayou , Zhou Ligang , Tao Zhifu
Published: September 2018

Air pollution forecasting plays a vital role in environment pollution warning and control. Air pollution forecasting studies can also recommend pollutant emission control strategies to mitigate the number of poor air quality days. Although various literature works have focused on the decomposition-ensemble forecasting model, studies concerning the endpoint effect of ensemble empirical mode decomposition (EEMD) and the forecasting model of sub-series selection are still limited. In this study, a hybrid forecasting approach (EEMD-MM-CFM) is proposed based on integrated EEMD with the endpoint condition mirror method and combined forecasting model for sub-series. The main steps of the proposed model are as follows: Firstly, EEMD, which sifts the sub-series intrinsic mode functions (IMFs) and a residue, is proposed based on the endpoint condition method. Then, based on the different individual forecasting methods, an optimal combined forecasting model is developed to forecast the IMFs and residue. Finally, the outputs are obtained by summing the forecasts. For illustration and comparison, air quality index (AQI) data from Hefei in China are used as the sample, and the empirical results indicate that the proposed approach is superior to benchmark models in terms of some forecasting assessment measures. The proposed hybrid approach can be utilized for air quality index forecasting.
Monitoring and Evaluation Indicators for Climate Change-Related Health Impacts, Risks, Adaptation, and Resilience
Authors: Ebi Kristie L. , Boyer Christopher , Bowen Kathryn J. , Frumkin Howard , Hess Jeremy
Published: September 2018

Climate change poses a range of current and future health risks that health professionals need to understand, track, and manage. However, conventional monitoring and evaluation (M&E) as practiced in the health sector, including the use of indicators, does not adequately serve this purpose. Improved indicators are needed in three broad categories: (1) vulnerability and exposure to climate-related hazards; (2) current impacts and projected risks; and (3) adaptation processes and health system resilience. These indicators are needed at the population level and at the health systems level (including clinical care and public health). Selected indicators must be sensitive, valid, and useful. And they must account for uncertainties about the magnitude and pattern of climate change; the broad range of upstream drivers of climate-sensitive health outcomes; and the complexities of adaptation itself, including institutional learning and knowledge management to inform iterative risk management. Barriers and constraints to implementing such indicators must be addressed, and lessons learned need to be added to the evidence base. This paper describes an approach to climate and health indicators, including characteristics of the indicators, implementation, and research needs.