bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Improvement of GaN Based Laser Diode Using Pd/Ni/Au Metallization Ohmic Contact
Authors: Wang Wenjie , Xie Wuze , Deng Zejia , Yang Haojun , Liao Mingle , Li Junze , Luo Xiaojia , Sun Song , Zhao Degang
Published: April 2019

We report an investigation of the effects of different metal systems and surface treatment on the contact performance of GaN lasers. We found that multi-element metal alloy and surface chemical treatment are the keys to achieve good ohmic behavior contacts on GaN laser diodes. Pd/Ni/Au contact demonstrates excellent thermal stability and lowest specific contact resistivity in these metal systems. Properly adjusting the thickness of the Pd and Ni layer and pretreating with the KOH solution can further improve the ohmic contact performance. The improved ohmic behavior of the KOH solution pretreated Pd/Ni/Au contact is attributed to removing surface oxides and the reduction of the schottky barrier heights due to the metal Pd has a high work function and the interfacial reactions occurring between the Pd, Ni, Au, and GaN extends into the GaN film. As a result, a low contact resistivity of 1.66 × 10−5 Ω·cm2 can be achieved from Pd(10 nm)/Ni(10 nm)/Au(30 nm) contacts with KOH solution pretreated on top of the laser diode structure. The power of the GaN based laser diode with the Pd/Ni/Au metallization ohmic contact can be enhanced by 1.95 times and the threshold current decreased by 37% compared to that of the conventional ohmic contact Ni/Au.
A Surfeit of Studies: What Have We Learned from All the Box Turtle (Terrapene carolina and T. ornata) Home Range Studies?
Authors: Habeck Christopher W. , Figueras Miranda P. , Deo Jean E. , Burke Russell L.
Published: April 2019

Home range (HR) studies are a particularly common approach to investigations of animal habitat use, resource availability, and response to management manipulation such as relocations. Terrapene carolina (Eastern box turtle) and its sister taxon T. ornata (Ornate box turtle) are especially popular subjects of HR studies because they are relatively easily tracked. Terrapene HR studies have revealed a wide variation in HR sizes within and between populations, due to factors such as differences in ecoregion and analytical approach (e.g., minimum convex polygons, kernel analysis, bivariate normal, multivariate Ornstein–Uhlenbeck stochastic process, harmonic means). We performed a meta-analysis of the available literature, including unpublished work to avoid bias due to under-publication, to explore the causes for variation in HR size. We found 19 studies reporting T. carolina HR sizes and seven studies reporting T. ornata HR sizes; the resulting meta-analysis revealed patterns that are not visible in the individual studies. We found important differences between the species: female T. ornata had smaller HRs than males, whereas the opposite is true for T. carolina, and T. ornata HRs were influenced by ecoregion, while T. carolina HRs were not similarly influenced. Not surprisingly, we found that choice of analysis technique affected HR estimate; analyses using ellipses resulted in larger HR estimates than all the other techniques, while kernels were smaller than minimum convex polygons. Although not indicated by individual studies, our meta-analysis showed that the HRs of relocated T. carolina females were significantly larger than those of non-relocated females. Although the number of individual turtles in studies varied from three to 25, the sample size did not significantly affect HR size.
Natural Cities Generated from All Building Locations in America
Authors: Jiang Bin
Published: April 2019

Authorities define cities—or human settlements in general—through imposing top-down rules in terms of whether buildings belong to cities. Emerging geospatial big data makes it possible to define cities from the bottom up, i.e., buildings determine themselves whether they belong to a city using the notion of natural cities and based on head/tail breaks, which is a classification and visualization tool for data with a heavy-tailed distribution. In this paper, we used 125 million building locations—all building footprints of America (mainland) or their centroids more precisely—to generate 2.1 million natural cities in the country (see the URL as shown in the note of Figure 1). In contrast to government defined city boundaries, these natural cities constitute a valuable data source for city-related research.
The Design of a Thermoelectric Generator and Its Medical Applications
Authors: Kumar Palanisamy Mohan , Jagadeesh Babu Veluru , Subramanian Arjun , Bandla Aishwarya , Thakor Nitish , Ramakrishna Seeram , Wei He
Published: April 2019

Growing energy demands are driving people to generate power in every possible way. New energy sources are needed to plug the energy gap. There is a growing interest in distributed energy generation due to its remarkable advantages such as flexibility, reliability, adaptability and minimal transmission losses. Thermoelectric generators (TEGs) are one such distributed power source that relies on thermal energy for electricity generation. The current review focusses on the design and optimization of TEGs to maximize the power output from the available thermal sources. The basic principle of thermoelectricity generation and suitable architecture for specific applications are explained with an overview of materials and manufacturing processes. Various cooling techniques to dissipate heat from the cold side and their influence on overall efficiency are reviewed in this work. Applications of TEGs for powering biomedical sensors have been discussed in detail. Recent advancements in TEGs for various implantable devices and their power requirements are evaluated. The exploitation of TEGs to generate power for wearable sensors has been presented, along with published experimental data. It is envisioned that this study will provide profound knowledge on TEG design for specific applications, which will be helpful for future endeavours.
Dual Band-Notched Rectangular Dielectric Resonator Antenna with Tunable Characteristic
Authors: Liu Beijia , Qiu Jinghui , Chen Lijia , Li Guoqiang
Published: April 2019

A dual band-notched reconfigurable dielectric resonator antenna (DRA) is proposed in this paper. A rectangular dielectric resonator excited by stepped offset microstrip feedline generates multiple resonant modes for wideband performance. Moreover, the typical stepped impedance feedline and partial ground plane with one rectangular notch are adopted for contributing for better impedance matching. On this basis, a five-line coupler resonator (FLCR) composed by inverted U-shaped and 山-shaped structures is introduced as a bandstop filter in the microstrip feedline, and dual rejected bands are created. Tunable notched frequencies are achieved by the varactor between these two structures. The proposed antenna size is 24 × 28 × 5.637 mm3. For the presented work, both simulated and measured results for the proposed tunable antenna ranging from 5.3 to 5.84 GHz and from 8.74 to 8.98 GHz within the wide bandwidth of 6.06 GHz are presented, demonstrating the accuracy of this design. There capabilities make the proposed antenna applicable for wideband systems with the requirement of avoiding interferences.
Downlink Channel Estimation in Massive Multiple-Input Multiple-Output with Correlated Sparsity by Overcomplete Dictionary and Bayesian Inference
Authors: Lu Wei , Wang Yongliang , Wen Xiaoqiao , Peng Shixin , Zhong Liang
Published: April 2019

We exploited the temporal correlation of channels in the angular domain for the downlink channel estimation in a massive multiple-input multiple-output (MIMO) system. Based on the slow time-varying channel supports in the angular domain, we combined the channel support information of the downlink angular channel in the previous timeslot into the channel estimation in the current timeslot. A downlink channel estimation method based on variational Bayesian inference (VBI) and overcomplete dictionary was proposed, in which the support prior information of the previous timeslot was merged into the VBI for the channel estimation in the current timeslot. Meanwhile the VBI was discussed for a complex value in our system model, and the structural sparsity was utilized in the Bayesian inference. The Bayesian Cramér–Rao bound for the channel estimation mean square error (MSE) was also given out. Compared with other algorithms, the proposed algorithm with overcomplete dictionary achieved a better performance in terms of channel estimation MSE in simulations.
An Analysis on Barriers to Biomass and Bioenergy Development in Rural China Using Intuitionistic Fuzzy Cognitive Map
Authors: Ma Linmao , Yu Jing , Zhang Long
Published: April 2019

Biomass is viewed as one of the critical renewable energies and it widely exists in nature. Developing bioenergy has been promoted as a viable mean of dealing with environment issues that are related to the utilization of fossil fuel. However, due to many obstacles, the biomass and bioenergy technology has not won widespread support in developing countries, like China, with vast land area, particularly in rural area. Furthermore, most existing researches just focused on the description of the influence factors, along with the solution to the technical problems, while many social factors are overlooked. In fact, the process of developing biomass is indeed complicated due to the need for consensus and active participation of the various stakeholders, such as the government, the industry, and the local residents. Therefore, while integrating the intuitionistic fuzzy logic and fuzzy cognitive map, this study constructs an intuitionistic fuzzy cognitive map (IFCM) that is in line with experts’ suggestions and the current literature to investigate how to promote the development of biomass through enhancing public acceptance. We conduct several simulations from the perspective of different stakeholders, according to the IFCM. The analysis results reveal the influence mechanism in the system and illustrate the effect of various factors that are stressed by every stakeholder. The research design also provides a reference for future studies.
Determination of a Methodology to Derive Correlations Between Window Opening Mass Flow Rate and Wind Conditions Based on CFD Results
Authors: Stamatopoulos Panagiotis , Drosatos Panagiotis , Nikolopoulos Nikos , Rakopoulos Dimitrios
Published: April 2019

This paper presents a methodology for the development of an empirical equation which can provide the air mass flow rate imposed by single-sided wind-driven ventilation of a room, as a function of external wind speed and direction, using the results from Computational Fluid Dynamics (CFD) simulations. The proposed methodology is useful for a wide spectrum of applications, in which no access to experimental data or conduction of several CFD runs is possible, deriving a simple expression of natural ventilation rate, which can be further used for energy analysis of complicated building geometries in 0-D models or in object-oriented software codes. The developed computational model simulates a building, which belongs to Rheinisch-Westfälische Technische Hochschule (RWTH, Aachen University, Aachen, Germany) and its surrounding environment. A tilted window represents the opening that allows the ventilation of the adjacent room with fresh air. The derived data from the CFD simulations for the air mass flow were fitted with a Gaussian function in order to achieve the development of an empirical equation. The numerical simulations have been conducted using the Ansys Fluent v15.0® software package. In this work, the k-w Shear Stress Transport (SST) model was implemented for the simulation of turbulence, while the Boussinesq approximation was used for the simulation of the buoyancy forces. The coefficient of determination R2 of the curve is in the range of 0.84–0.95, depending on the wind speed. This function can provide the mass flow rate through the open window of the investigated building and subsequently the ventilation rate of the adjacent room in air speed range from 2.5 m/s to 16 m/s without the necessity of further numerical simulations.
Impact of Fe3O4, CuO and Al2O3 on the AC Breakdown Voltage of Palm Oil and Coconut Oil in the Presence of CTAB
Authors: Mohamad Nur Aqilah , Azis Norhafiz , Jasni Jasronita , Ab Kadir Mohd Zainal Abidin , Yunus Robiah , Yaakub Zaini
Published: April 2019

This paper presents an experimental study on the AC breakdown voltages of Refined, Bleached and Deodorized Palm Oil (RBDPO) Olein and Coconut Oil (CO) in the presence of conductive (Iron (II,III) Oxide, Fe3O4), semi-conductive (Copper (II) Oxide, CuO) and insulative (Aluminium Oxide, Al2O3) nanoparticles without and with surfactant. The type of surfactant used in this study was Cetyl Trimethyl Ammonium Bromide (CTAB). The volume concentrations range of Fe3O4, CuO and Al2O3 was varied from 0.001% to 0.05%. Transmission Electron Microscope (TEM) was used to characterize the nanoparticles in RBDPO and CO. AC breakdown voltage tests were carried out for RBDPO and CO of which the AC breakdown voltage at 1% probability was determined based on Weibull distribution. It is found that only Al2O3 can improve the average AC breakdown voltage of RBDPO and CO. The AC breakdown voltages at 1% probability for RBDPO and CO can be improved through introduction of Fe3O4, CuO and Al2O3 at certain volume concentrations. Al2O3 provides the highest enhancement of AC breakdown voltages at 1% probability for RBDPO and CO with the highest percentage of improvement can be up to 52%. CTAB has no clear effect on the improvement of AC breakdown voltages of RBDPO and CO based Fe3O4, CuO and Al2O3 nanofluids.
Reactive Power Capability Model of Wind Power Plant Using Aggregated Wind Power Collection System
Authors: Sarkar Moumita , Altin Müfit , Sørensen Poul E. , Hansen Anca D.
Published: April 2019

This article presents the development of a reactive power capability model for a wind power plant (WPP) based on an aggregated wind power collection system. The voltage and active power dependent reactive power capability are thus calculated by using aggregated WPP collection system parameters and considering losses in the WPP collection system. The strength of this proposed reactive power capability model is that it not only requires less parameters and substantially less computational time compared to typical detailed models of WPPs, but it also provides an accurate estimation of the available reactive power. The proposed model is based on a set of analytical equations which represent converter voltage and current limitations. Aggregated impedance and susceptance of the WPP collection system are also included in the analytical equations, thereby incorporating losses in the collection system in the WPP reactive power capability calculation. The proposed WPP reactive power capability model is compared to available methodologies from literature and for different WPP topologies, namely, Horns Rev 2 WPP and Burbo Bank WPP. Performance of the proposed model is assessed and discussed by means of simulations of various case studies demonstrating that the error between the calculated reactive power using the proposed model and the detailed model is below 4% as compared to an 11% error in the available method from literature. The efficacy of the proposed method is further exemplified through an application of the proposed method in power system integration studies. The article provides new insights and better understanding of the WPPs’ limits to deliver reactive power support that can be used for power system stability assessment, particularly long-term voltage stability.
Sliding Mode Observer-Based Load Angle Estimation for Salient-Pole Wound Rotor Synchronous Generators
Authors: Lopac Nikola , Bulic Neven , Vrkic Niksa
Published: April 2019

Synchronous generator load angle is a fundamental quantity for power system stability assessment, with possible real-time applications in protection and excitation control systems. Commonly used methods of load angle determination require additional measuring equipment, while existing research on load angle estimation for wound rotor synchronous generator has been limited to the estimator based on the generator’s phasor diagram and estimators based on artificial neural networks. In this paper, a load angle estimator for salient-pole wound rotor synchronous generator, based on a simple sliding mode observer (SMO) which utilizes field current, stator voltages, and stator currents measurements, is proposed. The conventional SMO structure is improved with use of hyperbolic tangent sigmoid functions, implementation of the second order low-pass filters accompanied with corresponding phase delay compensation, and introduction of an adaptive observer gain proportional to the measured field current value. Several case studies conducted on a generator connected to a power system suggest that the proposed estimator provides an adequate accuracy during active and reactive power disturbances during stable generator operation, outperforming the classical phasor diagram-based estimator by reducing mean squared error by up to 14.10%, mean absolute error by up to 41.55%, and maximum absolute error by up to 8.81%.
Towards Sustainable Energy Trends in the Middle East: A Study of Four Major Emitters
Authors: Bayomi Norhan , E. Fernandez John
Published: April 2019

Energy is a key ingredient to facilitate economic development in the Middle East. Expectations for a rapidly growing economy in the next decade will likely cause an increase in the fraction of energy consumed domestically limiting what is available for export. These challenges are the biggest for resource-rich countries, since their economy is heavily dependent on fossil fuel exports alongside an energy-intensive economy. Thus, the paper addresses the question of how the development of energy systems among resource-rich countries has changed over the past three decades and what role can they play in the sustainable development of the region’s energy system and emission reduction goals? To address this question, we present an overview on energy trends in four resource-rich countries in the Middle East, which nearly account for 76% of the region’s energy-related emissions and about 77% of total energy consumption. These countries are namely, Iran, Saudi Arabia, Kuwait, and the UAE. Accordingly, we present a comparative energy analysis between the four countries through examining historical and current energy trends, the structure of energy supply, the status of renewable deployment and energy-related carbon dioxide (CO2) emissions. Results from the analysis showed that inefficient energy production and consumption have played a role in the deterioration of the energy landscape of the four countries compared to the global energy system. Thus, this highlights the necessity for suitable energy strategies and effective policies that will be central to sustainable energy development. The analysis presented here could be used to better understanding of the impacts of current gaps and inefficiencies in large energy consumers in the Middle East.
Costs of Demand Response from Residential Customers’ Perspective
Authors: Safdar Madia , Hussain Ghulam Amjad , Lehtonen Matti
Published: April 2019

Electricity demand in a certain locality varies during the day, depending on weather conditions, daily life routines, or a social event in a town. During high/peak demands, expensive power plants are put into operation, which affects electricity prices. Moreover, power lines are overloaded. If generation capacity is insufficient, a blackout may result. Demand response (DR) programs are widely proposed in energy research to tackle these problems. Although the benefits of DR programs are well known, customer response levels to these programs is low. This is due to the small fraction of benefits they receive against the loss of comfort, lost leisure time, and other inconveniences. The objective of this work is to study DR costs from the customer perspective by considering these factors. A customer survey-based direct approach is used to evaluate the willingness of customers to accept (WTA) a certain compensation when shifting the load is adopted. Two different methods are used to calculate DR costs: percentage compensation, which customers are WTA, and one based on a macroeconomic model, which considers the dependency factor of customers on loads and hourly wage. A linear mathematical model is presented based on both these techniques. This study reveals that DR costs are much less than interruption costs paid by the utility company, and hence is in the best interests of all stakeholders, i.e., customers, utility company, and transmission company.
A Study on Deep Neural Network-Based DC Offset Removal for Phase Estimation in Power Systems
Authors: Kim Sun-Bin , Sok Vattanak , Kang Sang-Hee , Lee Nam-Ho , Nam Soon-Ryul
Published: April 2019

The purpose of this paper is to remove the exponentially decaying DC offset in fault current waveforms using a deep neural network (DNN), even under harmonics and noise distortion. The DNN is implemented using the TensorFlow library based on Python. Autoencoders are utilized to determine the number of neurons in each hidden layer. Then, the number of hidden layers is experimentally decided by comparing the performance of DNNs with different numbers of hidden layers. Once the optimal DNN size has been determined, intensive training is performed using both the supervised and unsupervised training methodologies. Through various case studies, it was verified that the DNN is immune to harmonics, noise distortion, and variation of the time constant of the DC offset. In addition, it was found that the DNN can be applied to power systems with different voltage levels.
Arm Power Control of the Modular Multilevel Converter in Photovoltaic Applications
Authors: Acharya Anirudh Budnar , Ricco Mattia , Sera Dezso , Teodorescu Remus , Norum Lars Einar
Published: April 2019

In this paper, a control method is proposed that allows the extraction of maximum power from each individual photovoltaic string connected to the Modular Multilevel Converter (MMC) and inject balanced power to the AC grid. The MMC solution used does not need additional DC–DC converters for the maximum power point tracking. In the MMC, the photovoltaic strings are connected directly to the sub-modules. It is shown that the proposed inverter solution can provide balanced three-phase output power despite an unbalanced power generation. The maximum power of the photovoltaic string is effectively harnessed due to the increased granularity of the maximum power point tracking. An algorithm that tracks the sub-module capacitor voltages to their respective voltage references is proposed. A detailed modeling and control method for balanced operation of the proposed topology is discussed. The operation of the MMC under unbalanced power generation is discussed. Simulation results are provided that show the effectiveness of the proposed control under unequal irradiance.
Robust Control Method for DC Microgrids and Energy Routers to Improve Voltage Stability in Energy Internet
Authors: Hua Haochen , Qin Yuchao , Xu Hanxuan , Hao Chuantong , Cao Junwei
Published: April 2019

The energy internet (EI) is a wide area power network that efficiently combines new energy technology and information technology, resulting in bidirectional on-demand power transmission and rational utilization of distributed energy resources (DERs). Since the stability of local network is a prerequisite for the normal operation of the entire EI, the direct current (DC) bus voltage stabilization for each individual DC microgrid (MG) is a core issue. In this paper, the dynamics of the EI system is modeled with a continuous stochastic system, which simultaneously considers related time-varying delays and norm-bounded modeling uncertainty. Meanwhile, the voltage stabilization issue is converted into a robust H ∞ control problem solved via a linear matrix inequality approach. To avoid the situation of over-control, constraints are set in controllers. The problem of finding a balance between voltage regulation performance and constraints for the controllers was also extensively investigated. Finally, the efficacy of the proposed methods is evaluated with numerical simulations.
Research on the Impact of Various Emission Reduction Policies on China’s Iron and Steel Industry Production and Economic Level under the Carbon Trading Mechanism
Authors: Duan Ye , Han Zenglin , Mu Hailin , Yang Jun , Li Yonghua
Published: April 2019

To study the emission reduction policies’ impact on the production and economic level of the steel industry, this paper constructs a two-stage dynamic game model and analyzes various emission reduction policies’ impact on the steel industry and enterprises. New results are observed in the study: (1) With the increasing emission reduction target (15%–30%) and carbon quota trading price (12.65–137.59 Yuan), social welfare and producer surplus show an increasing trend and emission macro losses show a decreasing trend. (2) Enterprises’ reduction ranges in northwestern and southwestern regions are much higher than that of the other regions; the northeastern enterprise has the smallest reductions range. (3) When the market is balanced (0.8543–0.9320 billion tons), the steel output has decreased and the polarization in various regions has been alleviated to some extent. The model is the abstraction and assumption of reality, which makes the results have some deviations. However, these will provide references to formulate reasonable emissions reduction and production targets. In addition, the government needs to consider the whole and regional balance and carbon trading benchmark value when deciding the implementation of a single or mixed policy. Future research will be more closely linked to national policies and gradually extended to other high-energy industries.
Development of an Energy Saving Strategy Model for Retrofitting Existing Buildings: A Korean Case Study
Authors: Song Kwonsik , Ahn Yonghan , Ahn Joseph , Kwon Nahyun
Published: April 2019

The building sector accounts for approximately 40% of national energy consumption, contributing to the environmental crisis of global warming. Using energy saving measures (e.g., improved thermal insulation, highly energy-efficient electrical and mechanical systems) provides opportunities to reduce energy consumption in existing buildings. Furthermore, if the life cycle cost (i.e., installation, operation and maintenance cost) of the measures is considered with their energy saving potential, it is possible to establish a cost-effective energy retrofit plan. Therefore, this research develops an energy saving strategy model considering its saving potential and life cycle cost of the measures for reducing energy consumption in existing buildings. To test the validity of the proposed model, a case study is carried out on an educational facility in South Korea, in response to its overconsumption of energy. The results demonstrate that in terms of energy saving and life cycle cost, the optimal energy retrofit plan is more cost-effective than the existing plan. Also, the break-even point for the optimal energy retrofit plan is within five years, and then revenue from energy saving continually occurs until 2052. For energy retrofit of existing buildings, using the proposed model would enable building owners to maximize energy savings while minimizing the life cycle cost.
Multi-Objective Particle Swarm Based Optimization of an Air Jet Impingement System
Authors: Martínez-Filgueira Pablo , Zulueta Ekaitz , Sánchez-Chica Ander , Fernández-Gámiz Unai , Soriano Josu
Published: April 2019

Air jet impingement systems have proven to be a very efficient way of heat transfer in single phase flows, which has allowed them to be applied in several industries. However, the complexity of the physical phenomena that take place in the cooling or heating processes makes the task of designing and sizing a system of this type very difficult. The objective of this work is to develop a methodology for the optimization of the impingement plate for electronic components cooling systems. The component chosen to exemplify this work is an insulated gate bipolar transistor (IGBT) such as those employed in photovoltaic inverters. The proposed methodology is divided into the thermo-hydraulic calculation process and the optimization of the system. This optimization is carried out using a multi-objective particle swarm optimization (PSO) algorithm that seeks the best compromise between two variables: Component temperature and manufacturing time of the impingement plate. The result is a calculation tool that can quickly find the solution that meets the requirements of the designer without the need to evaluate all possible solutions.
A Comprehensive Review of Operation and Control, Maintenance and Lifespan Management, Grid Planning and Design, and Metering in Smart Grids
Authors: Hernández-Callejo Luis
Published: April 2019

New technological advances based on software, hardware and new materials must be implemented in smart grids. In addition, these advanced electrical grids must incorporate elements of artificial intelligence. Advances in software development must be complemented with the development of new hardware (power electronics and active distribution among others). The aforementioned must rely on the development of new materials and sensors, which should be integrated into the smart grid. Therefore, the four areas of research based on the technologies are: Operation and Control, Maintenance and Lifespan Management, Grid Planning and Design, and Metering. The review presents the algorithms, materials, devices and others paradigms applied to smart grids, classifying the works according to the four areas of research. This review has focused on the four fundamental pillars of smart grids, on the one hand, the need for more efficient operation and control, followed by advanced maintenance management, to continue planning and designing the new grids, and for conclude with the advanced measurement. As you will see in the article, new devices, new techniques, and future scenarios will make possible the transition from the current grid to the future smart grid.
Sustainable Supply Chain Management Strategy Influence on Supply Chain Management Functions in the Oil and Gas Distribution Industry
Authors: Florescu Margareta Stela , Ceptureanu Eduard Gabriel , Cruceru Anca Francisca , Ceptureanu Sebastian Ion
Published: April 2019

This paper analyses the influence of Sustainable Supply Chain Management strategies—Supplier Selection, Product Stewardship and Logistics Management—on Supply Chain Management functions—Planning, Execution, Coordination and Collaboration in the oil and gas distribution industry. Using multiple regression analyses, we performed the study on 79 companies from Romania and the Republic of Moldova operating in the oil and gas distribution industry. We concluded that Sustainable Supply Chain Management strategies have a positive and significant influence on Supply Chain Management functions, both overall and on each of the functions considered in the study. Overall, the findings of this study can be used by companies operating in oil and gas distribution to design Sustainable Supply Chain Management strategies to better address the requirements for more environmentally and socially responsible activities in their supply chains and to optimize their Supply Chain Management to better cope with Sustainable Supply Chain Management requirements and expectations.
SPOF—Slave Powerlink on FPGA for Smart Sensors and Actuators Interfacing for Industry 4.0 Applications
Authors: Valente Giacomo , Muttillo Vittoriano , Muttillo Mirco , Barile Gianluca , Leoni Alfiero , Tiberti Walter , Pomante Luigi
Published: April 2019

We here present a new PLC-POWERLINK industrial solution for Industry 4.0 applications. The proposed solution provides the capability to separate the sensing functionality from the PLC-side, in demand for the reconfigurable FPGA implementation. In particular, we here provide a framework that supports the interfacing between the POWERLINK protocol and commonly used standards, such as I2C, SPI, and UART. This has been obtained by using a framework built around a soft IP-core Application Processor, which manages the interfacing with several POWERLINK slaves, able to support the data exchange with the POWERLINK Communication Processor. A practical application example and related implementation details are presented in the paper.
Hydropower Plants Frequency Regulation Depending on Upper Reservoir Water Level
Authors: Platero Carlos A. , Sánchez José A. , Nicolet Christophe , Allenbach Philippe
Published: April 2019

This paper presents a novel method of hydro power plant operation, based on the control of the injectors’ or wicked gates opening time as a function of the upper reservoir level. In this way, a faster power injection, depending on the current water level on the upper reservoir, could be achieved. When this level is higher, the opening time could be shorter; hence, hydropower ramps could be steeper. Due to this control, frequency excursions and load shedding trips are smaller, thus the power quality is enhanced. This method has been tested and validated by computer simulations in a case study located in El Hierro island, Canary Archipelago (Spain). The simulations made show significant improvements, dependent on upper reservoir water level, in power quality.
Impacts of Nonnative Species on the Health of Natural and Planted Forests
Authors: Guo Qinfeng , Potter Kevin M. , Koch Frank H. , Riitters Kurt H.
Published: April 2019

Despite conservation efforts, most forest ecosystems worldwide are affected by biotic invasions; however, the specific impacts vary across different geographic regions and forest types. The relative contributions of the main drivers such as propagule pressure (e.g., due to human population, travel, and trade), climate, land use, and habitat invasibility remain uncertain. The special issue “Impacts of Nonnative Species on the Health of Natural and Planted Forests” was organized to facilitate timely communications among scientists and managers in different regions and to assist in attempts to improve forest health and maintain long-term sustainability. The special issue addresses broad issues related to forest invasions, including the impacts of nonnative species in various forest ecosystems (e.g., natural vs. urban) and the contributions of land use (e.g., fragmentation), human activity, and climate change to invasion. The new findings include identifying hotspots of potential invasion impacts and their causes, which can help inform policy makers as they develop effective strategies for prevention, early detection or eradication, and forest management.
The Effect of Vegetation Enhancement on Particulate Pollution Reduction: CFD Simulations in an Urban Park
Authors: Qin Hongqiao , Hong Bo , Jiang Runsheng , Yan Shanshan , Zhou Yunhan
Published: April 2019

Vegetation in parks is regarded as a valuable way to reduce particulate pollution in urban environments but there is little quantitative information on its effectiveness. The aim of this study was to conduct on-site measurements and computational fluid dynamic (CFD) simulations to determine the aerodynamic and deposition effects of vegetation enhancement on particulate matter (PM) dispersions in an urban park in Xi’an, China. Initially, the airflow characteristics and deposition effects of vegetation were predicted and compared with measured air velocities and particulate pollution data to validate the numerical modeling. Then, associated coverage ratios and supplementary green areas (tree coverage ratio, crown volume coverage (CVC), and roof greening) were added to numerical simulations. After a series of numerical simulations and comparisons, results indicated that: (1) Numerical models with simplified vegetation method could reproduce the distribution of particulate matter concentrations in the real park environment; (2) with a tree coverage ratio >37.8% (or CVC > 1.8 m3/m2), the pedestrian-level PM2.5 could meet the World Health Organization’s air quality guidelines (IT-1) standards in the park; (3) roof greening on leeward buildings produced greater PM removal effects compared with windward buildings; and (4) the most economical and reasonable tree coverage ratio and CVC to reduce atmospheric PM in urban parks should be 30% and 1.8 m3/m2, respectively. These results are useful guidelines for urban planners towards a sustainable design of vegetation in urban parks.
Yeast Life Span and its Impact on Food Fermentations
Authors: Aranda Agustín , Orozco Helena , Picazo Cecilia , Matallana Emilia
Published: April 2019

Yeasts are very important microorganisms for food production. The high fermentative capacity, mainly of the species of the genus Saccharomyces, is a key factor for their biotechnological use, particularly to produce alcoholic beverages. As viability and vitality are essential to ensure their correct performance in industry, this review addresses the main aspects related to the cellular aging of these fungi as their senescence impacts their proper functioning. Laboratory strains of S. cerevisiae have proven a very successful model for elucidating the molecular mechanisms that control life span. Those mechanisms are shared by all eukaryotic cells. S. cerevisiae has two models of aging, replicative and chronological. Replicative life span is measured by the number of daughter cells a mother can produce. This kind of aging is relevant when the yeast biomass is reused, as in the case of beer fermentations. Chronological life span is measured by the time cells are viable in the stationary phase, and this is relevant for batch fermentations when cells are most of the time in a non-dividing state, such as wine fermentations. The molecular causes and pathways regulating both types of aging are explained in this review.
Preliminary Screening of Growth and Viability of 10 Strains of Bifidobacterium spp.: Effect of Media Composition
Authors: Matejčeková Zuzana , Vlková Eva , Liptáková Denisa , Valík Ľubomír
Published: April 2019

Lactic acid bacteria (LAB) alone or with special adjunct probiotic strains are inevitable for the preparation of specific functional foods. Moreover, because of their growth and metabolism, final products are preserved for a certain time. Thus, in this work, growth and metabolic activity of novel animal origin isolates and culture collection strains of Bifidobacterium spp. were investigated. The influence of milk media (reconstituted or ultra-high-temperature (UHT) milk), compared with synthetic modified Wilkins–Chalgren (WCH) broth under aerobic conditions was investigated. All tested bifidobacterial strains (n = 10) were grown well (1–2 log colony-forming units (CFU)/mL for 24 h at 37 °C) in all substrates and levels higher than 5 log CFU/mL remained during the cold storage period. Generally, different substrates determined almost the same maximal population densities (MPD) after 24 h that range within the average values of 8.96 ± 0.43 log CFU/mL, 8.87 ± 0.52 log CFU/mL, and 8.75 ± 0.54 log CFU/mL in reconstituted milk, UHT milk, and WCH broth, respectively. After 28 days of storage, the pH levels in milk media and broth were reduced to 4.50–5.60 and 4.60–4.90, respectively, representing a decrease of 0.8–2.13 units.
Fabrication of a Fluorophore-Doped Cylindrical Waveguide Structure Using Elastomers for Visual Detection of Stress
Authors: Hirose Chie , Fukuda Nobuko , Sassa Takafumi , Ishibashi Koji , Ochiai Tsuyoshi , Furukawa Rei
Published: April 2019

A fiber-optic strain sensor that can show strain via color change and which can be viewed using human eyes has demand in the civil engineering field for alerting purposes. A previous sensor was fabricated using PMMA (Poly(methyl methacrylate)), which had the exceeding hardness to exhibit satisfactory sensor performance. In this research, an elastomer-based fiber-optic structure was fabricated to enhance the elastic response of such sensors and to enlarge the waveguide cross section. Various organic fluorophores were added to the core and cladding regions of the elastic waveguide to induce energy flow from the core to the cladding when stress is applied to the waveguide. Elastomer pairs suitable for the core and cladding were selected from among several candidate materials having high transparency. A method of dispersing fluorophores to each host elastomer and constructing an excellent core–cladding interface using the selected materials was proposed. To investigate the time-dependent changes in the fluorescence of the doped elastomer waveguide, the absorption and emission spectra were monitored after the host elastomers were cured.
Turbulence Model Assessment in Compressible Flows around Complex Geometries with Unstructured Grids
Authors: Araya Guillermo
Published: April 2019

One of the key factors in simulating realistic wall-bounded flows at high Reynolds numbers is the selection of an appropriate turbulence model for the steady Reynolds Averaged Navier–Stokes equations (RANS) equations. In this investigation, the performance of several turbulence models was explored for the simulation of steady, compressible, turbulent flow on complex geometries (concave and convex surface curvatures) and unstructured grids. The turbulence models considered were the Spalart–Allmaras model, the Wilcox k- ω model and the Menter shear stress transport (SST) model. The FLITE3D flow solver was employed, which utilizes a stabilized finite volume method with discontinuity capturing. A numerical benchmarking of the different models was performed for classical Computational Fluid Dynamic (CFD) cases, such as supersonic flow over an isothermal flat plate, transonic flow over the RAE2822 airfoil, the ONERA M6 wing and a generic F15 aircraft configuration. Validation was performed by means of available experimental data from the literature as well as high spatial/temporal resolution Direct Numerical Simulation (DNS). For attached or mildly separated flows, the performance of all turbulence models was consistent. However, the contrary was observed in separated flows with recirculation zones. Particularly, the Menter SST model showed the best compromise between accurately describing the physics of the flow and numerical stability.
Practical Modeling of Large-Scale Galactic Magnetic Fields: Status and Prospects
Authors: Jaffe Tess R.
Published: April 2019

This is a review of the status of efforts to model the large-scale Galactic magnetic field (GMF). Though important for a variety of astrophysical processes, the GMF remains poorly understood despite some interesting new tracers being used in the field. Though we still have too many models that might fit the data, this is not to say that the field has not developed in the last few years. In particular, surveys of polarized dust have given us a new observable that is complementary to the more traditional radio tracers, and a variety of other new tracers and related measurements are becoming available to improve current modeling. This paper reviews: the tracers available; the models that have been studied; what has been learned so far; what the caveats and outstanding issues are; and one opinion of where the most promising future avenues of exploration lie.
On the Race for More Stretchable and Tough Hydrogels
Authors: Grijalvo Santiago , Eritja Ramon , Díaz Díaz David
Published: April 2019

Hydrogels are tridimensional networks that are able to retain important amounts of water. These soft materials can be obtained through self-assembling processes involving either hydrophilic molecules or polymers, allowing the formation of the corresponding covalently and physically cross-linked networks. Although the applicability of hydrogels in biomedicine has been exponentially growing due to their biocompatibility and different responses to stimuli, these materials have exhibited the particular feature of poor mechanical strength, and consequently, are brittle materials with low deformation. Due to this reason, a race has started to obtain more stretchable and tough hydrogels through different approaches. Within this context, this review article describes the most representative strategies and examples involving synthetic polymers with potential for biomedical applications.
Metagenomics-Guided Survey, Isolation, and Characterization of Uranium Resistant Microbiota from the Savannah River Site, USA
Authors: Jaswal Rajneesh , Pathak Ashish , Edwards III Bobby , Lewis III Robert , Seaman John C. , Stothard Paul , Krivushin Kirill , Blom Jochen , Rupp Oliver , Chauhan Ashvini
Published: April 2019

Despite the recent advancements in culturomics, isolation of the majority of environmental microbiota performing critical ecosystem services, such as bioremediation of contaminants, remains elusive. Towards this end, we conducted a metagenomics-guided comparative assessment of soil microbial diversity and functions present in uraniferous soils relative to those that grew in diffusion chambers (DC) or microbial traps (MT), followed by isolation of uranium (U) resistant microbiota. Shotgun metagenomic analysis performed on the soils used to establish the DC/MT chambers revealed Proteobacterial phyla and Burkholderia genus to be the most abundant among bacteria. The chamber-associated growth conditions further increased their abundances relative to the soils. Ascomycota was the most abundant fungal phylum in the chambers relative to the soils, with Penicillium as the most dominant genus. Metagenomics-based taxonomic findings completely mirrored the taxonomic composition of the retrieved isolates such that the U-resistant bacteria and fungi mainly belonged to Burkholderia and Penicillium species, thus confirming that the chambers facilitated proliferation and subsequent isolation of specific microbiota with environmentally relevant functions. Furthermore, shotgun metagenomic analysis also revealed that the gene classes for carbohydrate metabolism, virulence, and respiration predominated with functions related to stress response, membrane transport, and metabolism of aromatic compounds were also identified, albeit at lower levels. Of major note was the successful isolation of a potentially novel Penicillium species using the MT approach, as evidenced by whole genome sequence analysis and comparative genomic analysis, thus enhancing our overall understanding on the uranium cycling microbiota within the tested uraniferous soils.
Characteristics of Future Models of Integrated Outpatient Care
Authors: Leviton Alan , Oppenheimer Julia , Chiujdea Madeline , Antonetty Annalee , Ojo Oluwafemi William , Garcia Stephanie , Weas Sarah , Fleegler Eric , Chan Eugenia , Loddenkemper Tobias
Published: April 2019

Replacement of fee-for-service with capitation arrangements, forces physicians and institutions to minimize health care costs, while maintaining high-quality care. In this report we described how patients and their families (or caregivers) can work with members of the medical care team to achieve these twin goals of maintaining—and perhaps improving—high-quality care and minimizing costs. We described how increased self-management enables patients and their families/caregivers to provide electronic patient-reported outcomes (i.e., symptoms, events) (ePROs), as frequently as the patient or the medical care team consider appropriate. These capabilities also allow ongoing assessments of physiological measurements/phenomena (mHealth). Remote surveillance of these communications allows longer intervals between (fewer) patient visits to the medical-care team, when this is appropriate, or earlier interventions, when it is appropriate. Systems are now available that alert medical care providers to situations when interventions might be needed.