bluuebunny/crossref_metadata_2025 huggingface dataset:
Implementation of a PSO-Based Security Defense Mechanism for Tracing the Sources of DDoS Attacks
Authors: Lin Hsiao-Chung , Wang Ping , Lin Wen-Hui
Published: December 2019

Most existing approaches for solving the distributed denial-of-service (DDoS) problem focus on specific security mechanisms, for example, network intrusion detection system (NIDS) detection and firewall configuration, rather than on the packet routing approaches to defend DDoS threats by new flow management techniques. To defend against DDoS attacks, the present study proposes a modified particle swarm optimization (PSO) scheme based on an IP traceback (IPTBK) technique, designated as PSO-IPTBK, to solve the IP traceback problem. Specifically, this work focuses on analyzing the detection of DDoS attacks to predict the possible attack routes in a distributed network. In the proposed approach, the PSO-IPTBK identifies the source of DDoS attacks by reconstructing the probable attack routes from collected network packets. The performance of the PSO-IPTBK algorithm in reconstructing the attack route was investigated through a series of simulations using OMNeT++ 5.5.1 and the INET 4 Framework. The results show that the proposed scheme can determine the most possible route between the attackers and the victim to defend DDoS attacks.
Evaluation of the Performance of the Drag Force Model in Predicting Droplet Evaporation for R134a Single Droplet and Spray Characteristics for R134a Flashing Spray
Authors: Zhou Zhi-Fu , Zhu Dong-Qing , Lu Guan-Yu , Chen Bin , Wu Wei-Tao , Li Yu-Bai
Published: December 2019

Drag force plays an important role in determining the momentum, heat and mass transfer of droplets in a flashing spray. This paper conducts a comparative study to examine the performance of drag force models in predicting the evolution of droplet evaporation for R134a single droplet and spray characteristics for its flashing spray. The study starts from single moving R134a droplet vaporizing in atomispheric environment, to a fully turbulent, flashing spray caused by an accidental release of high-pressure R134a liquid in the form of a straight-tube nozzle, using in-house developed code and a modified sprayFoam solver in OpenFOAM, respectively. The effect of the nozzle diameter on the spray characteristics of R134a two-phase flashing spray is also examined. The results indicate that most of the drag force models have little effect on droplet evporation in both single isolated droplet modelling and fully two-phase flashing spray simulation. However, the Khan–Richardson model contributes to different results. In particular, it predicts a much different profile of the droplet diameter distribution and a much lower droplet temperature in the radial distance. The nozzle diameter has a significant impact on the flashing spray. A smaller diameter nozzle leads to more internse explosive atomization, shorter penetration distance, lower droplet diameter and velocity, and a faster temperature decrease.
Optimization of Galloping Piezoelectric Energy Harvester with V-Shaped Groove in Low Wind Speed
Authors: Zhao Kaiyuan , Zhang Qichang , Wang Wei
Published: December 2019

A square cylinder with a V-shaped groove on the windward side in the piezoelectric cantilever flow-induced vibration energy harvester (FIVEH) is presented to improve the output power of the energy harvester and reduce the critical velocity of the system, aiming at the self-powered supply of low energy consumption devices in the natural environment with low wind speed. Seven groups of galloping piezoelectric energy harvesters (GPEHs) were designed and tested in a wind tunnel by gradually changing the angle of two symmetrical sharp angles of the V-groove. The GPEH with a sharp angle of 45° was selected as the optimal energy harvester. Its output power was 61% more than the GPEH without the V-shaped groove. The more accurate mathematical model was made by using the sparse identification method to calculate the empirical parameters of fluid based on the experimental data and the theoretical model. The critical velocity of the galloping system was calculated by analyzing the local Hopf bifurcation of the model. The minimum critical velocity was 2.53 m/s smaller than the maximum critical velocity at 4.69 m/s. These results make the GPEH with a V-shaped groove (GPEH-V) more suitable to harvest wind energy efficiently in a low wind speed environment.
The Impact of International Oil Prices on the Stock Price Fluctuations of China’s Renewable Energy Enterprises
Authors: Hsiao Cody Yu-Ling , Lin Weishun , Wei Xinyang , Yan Gaoyun , Li Siqi , Sheng Ni
Published: December 2019

In order to address a series of issues, including energy security, global warming, and environmental protection, China has ranked first in global renewable investment for the seventh consecutive year. However, developing a renewable energy industry requires a significant capital investment. Also, the international oil price fluctuations have an important impact on the stock prices of renewable energy firms. Thus, in order to provide implications for market investment as well as policy recommendations, this paper studied the spillover effect of international oil prices on the stock prices of China’s renewable energy listed companies. We used a Vector Autoregressive (VAR) model with innovations using a Factor-GARCH (Generalized Autoregressive Conditional Heteroskedasticity) process to evaluate the impact of market co-movements and time-varying volatility and correlation between the international oil price and China’s renewable energy market. The results show that the international oil price has a significant price spillover effect on the stock prices of China’s renewable energy listed companies. Moreover, the fluctuations of international oil prices have an influence on the stock price variations of Chinese renewable energy listed companies.
Secretory Proteins in the Skin Mucus of Nile Tilapia (Oreochromis niloticus) are Modulated Temporally by Photoperiod and Bacterial Endotoxin Cues
Authors: C. Lazado Carlo , Skov Peter Vilhelm
Published: December 2019

Although it is well known that the biological and physical characteristics of skin mucus in fishes are strongly affected by changes in environmental conditions, the influence of photoperiod and time-dependent bacterial endotoxin stimulation is not well documented. In the present study, we determined the diel variations in the basal activities of secretory proteins with known defense functions in the skin mucus of Nile tilapia (Oreochromis niloticus) maintained under two photic environments: equal length of day and night (12L:12D, LD) or total darkness (0L:24D, DD). A second experiment was conducted to determine how time-dependent (i.e., day versus night) lipopolysaccharide (LPS) challenge could influence these skin mucosal defenses. The results revealed that LD signal differentially modulated the activities of mucosal immune molecules. Fish subjected to LD regime showed significantly higher levels of skin mucus lysozyme and protease at nighttime than at daytime. This distinct feature was not observed in fish under DD. There was no general mucosal response patterns to time-dependent LPS challenge. Nonetheless, protease and lysozyme, which were identified to be at elevated levels at night, were significantly modulated when the endotoxin was administered at nighttime. Ceruloplasmin was the only molecule that responded to LPS challenge at daytime, where its activity significantly increased at 8 h post-stimulation. Collectively, the results revealed that photoperiod cues influenced the activities of mucosal defenses and this may play, at least in part, in the temporal sensitivity to bacterial endotoxin.
Analysis of Transition for a Flow in a Channel via Reduced Basis Methods
Authors: Pascarella Gaetano , Kokkinakis Ioannis , Fossati Marco
Published: December 2019

The study of the flow mechanisms leading to transition in a planar channel flow is investigated by means of a reduced basis method known as Dynamic Mode Decomposition (DMD). The problem of identification of the most relevant DMD modes is addressed in terms of the ability to (i) provide a fairly accurate reconstruction of the flow field, and (ii) match the most relevant flow structures at the beginning of the transition region. A comparative study between a natural method of selection based on the energetic content of the modes and a new one based on the temporal dynamics of the modes is here presented.
3DGPR for the Non-Destructive Monitoring of Subsurface Weathering of Sandstone Masonry
Authors: Johnston Brian J. , Ruffell Alastair , Warke Patricia , McKinley Jennifer
Published: December 2019

Remote sensing techniques, such as LiDAR and photogrammetry, are used by researchers exploring the spatial distribution of weathering features in historic masonry. These well-established tools provide users with a perspective of the processes affecting the surface of masonry blocks; however, they cannot provide information on the alteration occurring subsurface. Geophysical tools are being explored as a potential approach to observe the variation in material properties beneath masonry block surfaces and to examine the patterns of deterioration across wall sections. Applying such techniques inform the development of conceptual models of weathering at the block to building wall scale. In this study, ground-penetrating radar (GPR) was selected to inspect the subsurface condition of the wall section of an historic church wall, where areas of granular disintegration and flaking can be observed. 3DGPR was selected for this task, as its use of regular grids during data collection make it better suited for detecting features within an area. Three high-frequency antennas, 1.2 Ghz, 1.6 Ghz and 2.3 Ghz, were run across the study area in a series of 80 cm by 80 cm grids. The data were collated within GIS, where observed features were annotated onto a schematic of the wall surface. The 3DGPR outputs identified anomalies within this structure that could not have been as easily interpreted using a 2DGPR transect. However, as 3DGPR relies upon interpolative techniques to estimate the returns between observation transects, the validity of features detected in these locations need to be tested. The results of this application of 3DGPR identified variable weathering response across the wall section, relative to elevation. These observations were used to develop a conceptual model linking these findings to seasonal variation in the capillary rise of groundwater, upward from the base of the church wall. Through these findings it is possible to see how GPR can assist in developing our understanding of the processes threatening heritage buildings.
Descriptors for High Throughput in Structural Materials Development
Authors: Steinbacher Matthias , Alexe Gabriela , Baune Michael , Bobrov Ilya , Bösing Ingmar , Clausen Brigitte , Czotscher Tobias , Epp Jérémy , Fischer Andreas , Langstädtler Lasse , Meyer Daniel , Raj Menon Sachin , Riemer Oltmann , Sonnenberg Heike , Thomann Arne , Toenjes Anastasiya , Vollertsen Frank , Wielki Nicole , Ellendt Nils
Published: December 2019

The development of novel structural materials with increasing mechanical requirements is a very resource-intense process if conventional methods are used. While there are high-throughput methods for the development of functional materials, this is not the case for structural materials. Their mechanical properties are determined by their microstructure, so that increased sample volumes are needed. Furthermore, new short-time characterization techniques are required for individual samples which do not necessarily measure the desired material properties, but descriptors which can later be mapped on material properties. While universal micro-hardness testing is being commonly used, it is limited in its capability to measure sample volumes which contain a characteristic microstructure. We propose to use alternative and fast deformation techniques for spherical micro-samples in combination with classical characterization techniques such as XRD, DSC or micro magnetic methods, which deliver descriptors for the microstructural state.
An Actuarial Pricing Method for Air Quality Index Options
Authors: Liu Zhuoxin , Zhao Laijun , Wang Chenchen , Yang Yong , Xue Jian , Bo Xin , Li Deqiang , Liu Dengguo
Published: December 2019

Poor air quality has a negative impact on social life and economic production activities. Using financial derivatives to hedge risks is one of the important methods. Air quality index (AQI) options are designed to help enterprises cope with the operational risk caused by air pollution. First, the expanded Ornstein–Uhlenbeck model is established using an autoregressive-generalized autoregressive conditional heteroscedasticity (AR-GARCH) method to predict AQI for a city. Next, the average AQI is constructed to be as the underlying index for the AQI options. We then priced AQI options using an actuarial method with an Esscher transform. Meanwhile payoff functions for the options are established to let enterprises hedge against the operational risk caused by air pollution. Finally, we determined the price of AQI options using data from Xi’an, China, and the example of a tourism enterprise as a case study of how AQI options can be applied to hedge against operational risk for enterprises. With AQI options trading, enterprises can hedge against operational risks caused by air pollution. The applicability of AQI options is wide, it can also be applied in other cities or regions.
Correlation between Executive Network Integrity and Sarcopenia in Patients with Parkinson’s Disease
Authors: Lee Chih-Ying , Chen Hsiu-Ling , Chen Pei-Chin , Chen Yueh-Sheng , Chiang Pi-Ling , Wang Cheng-Kang , Lu Cheng-Hsien , Chen Meng-Hsiang , Chou Kun-Hsien , Huang Yu-Chi , Lin Wei-Che
Published: December 2019

Background: Sarcopenia is critically associated with morbidity and mortality in the progression of Parkinson’s disease (PD). However, analyses of clinical severity and brain changes, such as white matter (WM) alterations in PD patients with sarcopenia are limited. Further understanding of the factors associated with sarcopenia may provide a focused screen and potential for early intervention in PD patients. Methods: 52 PD patients and 19 healthy participants accepted dual-energy X-ray absorptiometry to measure the body composition. Using diffusion tensor imaging, the difference of WM integrity was measured between PD patients with sarcopenia (PDSa) and without sarcopenia (PDNSa). Multivariate analysis was performed to explore the relationships between clinical factors, WM integrity, and sarcopenia in PD patients. Results: 21 PD patients (40.4%) had sarcopenia. PDSa had a higher Unified Parkinson’s Disease Rating Scale (UPDRS III) score, lower body mass index (BMI) and lower fat weight compared with the PDNSa. Additionally, PDSa patients exhibited lower fractional anisotropy accompanied by higher radial diffusivity and/or higher mean diffusivity in the fronto-striato-thalamic circuits, including bilateral cingulum, left superior longitudinal fasciculus, left genu of corpus callosum, and right anterior thalamic radiation, which participate in the executive function. In addition, decreased muscle mass was associated with worse WM integrity in these regions. Multiple linear regression analysis revealed that WM integrity in the left cingulum, right anterior thalamic radiation, together with gender (male) significantly predicted muscle mass in PD patients. Conclusions: WM alterations in the executive network, such as the fronto-striato-thalamic circuits, may indicate a risk factor for ongoing sarcopenia in PD patients. The effectiveness of using executive function to serve as a prodromal marker of sarcopenia in PD patients should be evaluated in future studies.
Patient Satisfaction in the Spanish National Health Service: Partial Least Squares Structural Equation Modeling
Authors: Valls Martínez María del Carmen , Ramírez-Orellana Alicia
Published: December 2019

The aim of this article was to determine which key indicators influence patient satisfaction with the Spanish NHS to provide useful information for policy decision-making. A total of 33 variables for each of the 17 Spanish autonomous communities were collected from the statistical portal of the Spanish Ministry of Health, Social Services, and Equality between 2005 and 2016. A cross-sectional study was applied using Partial Least Squares to a Structural Equation Model (PLS-SEM). The influence of expenditures, resource allocation, and safety were hypothesized about patient satisfaction. Gross Domestic Product (GDP) and life expectancy were used as control variables. Moreover, the influence of resource allocation on use was tested. The model explained 57.1% of patient satisfaction with the Spanish NHS. It was positively influenced mainly by resource allocation and expenditures, followed by safety and life expectancy. Additionally, resources directly influenced the level of use. The number of hospital beds, hemodialysis equipment, rate of adverse drug reactions, and expenditure positively influenced patient satisfaction. In contrast, the number of posts in day hospitals, the hospital infection rate, and the percentage of pharmacy spending negatively influenced patient satisfaction.
Impact of Maternal Smoking on the Onset of Breastfeeding versus Formula Feeding: A Cross-Sectional Study
Authors: Lechosa Muñiz Carolina , Paz-Zulueta María , Cornejo del Río Elsa , Mateo Sota Sonia , Sáez de Adana María , Madrazo Pérez María , Cabero Pérez María Jesús
Published: December 2019

This study sought to estimate the prevalence of maternal smoking and its association with exclusive breastfeeding vs. formula feeding. A cross-sectional study was performed on postpartum women at a public hospital in Spain, between January and August 2018. The main variables studied were their age, level of study, smoking habits, and chosen mode of infant feeding. In total, 948 postpartum women were included. Of these, 12.45% were smokers who smoked a mean of 7.23 cigarettes/day. Among the group of smokers, the probability of feeding the newborns with formula milk was multiplied by 2.32 ([95%CI 1.50–3.58] p < 0.001). When stratifying tobacco use into mild, moderate and severe, we found a statistically significant dose–response pattern. These associations and their statistical significance were maintained when adjusting by age and level of study. In conclusion, in the group of postpartum mothers who smoked, the probability of feeding the newborns with formula milk doubled. Our data highlight the need to improve health education programs in women of childbearing age, especially during pregnancy.
Coping with Cybervictimization: The Role of Direct Confrontation and Resilience on Adolescent Wellbeing
Authors: Brighi Antonella , Mameli Consuelo , Menin Damiano , Guarini Annalisa , Carpani Francesca , Slee Phillip T.
Published: December 2019

Background. Recent studies have consistently identified the negative consequences of cyberbullying on adolescent mental health. Nevertheless, not all cybervictims are alike, and in the last few years some evidence has appeared indicating that faced with cyberbullying, victims may manifest different emotional outcomes. In this study, we explored whether cybervictim resilience fully or partially mediates the effects of cybervictimization and whether a confrontational coping strategy impacts emotional symptoms. Methods. The study was carried out with a sample of 474 high school students equally distributed between males and females. Data were collected using a questionnaire comprising four measures assessing cybervictimization, direct confrontation coping strategy, resilience and emotional symptoms. Results. Structural equation modelling indicated that the effects of cybervictimization and confrontational coping strategy on emotional symptoms were mediated by resilience, with cybervictimization showing a positive effect while direct confrontation a negative effect. Cybervictimization also showed a positive direct effect on emotional symptoms. Conclusions. These results are presented in light of their implications for designing effective interventions able to protect and promote adolescents’ psychological wellbeing.
Interpretation and Working through Contemptuous Facial Micro-Expressions Benefits the Patient-Therapist Relationship
Authors: Datz Felicitas , Wong Guoruey , Löffler-Stastka Henriette
Published: December 2019

Introduction: The significance of psychotherapeutic micro-processes, such as nonverbal facial expressions and relationship quality, is widely known, yet hitherto has not been investigated satisfactorily. In this exploratory study, we aim to examine the occurrence of micro-processes during psychotherapeutic treatment sessions, specifically facial micro-expressions, in order to shed light on their impact on psychotherapeutic interactions and patient-clinician relationships. Methods: In analyzing 22 video recordings of psychiatric interviews in a routine/acute psychiatric care unit of Vienna General Hospital, we were able to investigate clinicians’ and patients’ facial micro-expressions in conjunction with verbal interactions and types. To this end, we employed the Emotion Facial Action Coding System (EmFACS)—assessing the action units and microexpressions—and the Psychodynamic Intervention List (PIL). Also, the Working Alliance Inventory (WAI), assessed after each session by both patients and clinicians, provided information on the subjective quality of the clinician–patient relationship. Results: We found that interpretative/confrontative interventions are associated with displays of contempt from both therapists and patients. Interestingly, displays of contempt also correlated with higher WAI scores. We propose that these seemingly contradictory results may be a consequence of the complexity of affects and the interplay of primary and secondary emotions with intervention type. Conclusion: Interpretation, confrontation, and working through contemptuous microexpressions are major elements to the adequate control major pathoplastic elements. Affect-cognitive interplay is an important mediator in the working alliance.
Microstructure and Pitting Corrosion of Austenite Stainless Steel after Crack Arrest
Authors: Zhang Zhuwu , Pan Guangguo , Jiang Yan , Chen Song , Zou Song , Li Wei , Xu Chengwei , Zhang Jingwei
Published: December 2019

With synergy of plastic deformation near crack tip and pulse current treatment, complex phase transformation and recrystallization occur in the metallographic structure, with the austenite transforming to fine grain structure and deformation-induced martensite; but, without the plastic deformation, the phase transformation, and recrystallization it was difficult for the crack arrest process to take place only undergoing the pulse current treatment. The nano-indentation experiment showed that the phase transformation region contained the maximum residual compressive stress consisting of four parts: the plastic stress, the explosion stress, the thermal stress, and the transformation stress, which was beneficial to restrain the crack growth. However, the solidification structure and the deformation-induced martensite structure was vulnerable to pitting corrosion through scanning microelectrode technology (SMET) and pitting corrosion experiment, but the pitting corrosion resistance could be improved through the solution heat treatment.
High-Temperature Dielectric Relaxation Behaviors in Mn3O4 Polycrystals
Authors: Wang Songwei , Zhang Xin , Yao Rong , Fan Liguo , Zhou Huaiying
Published: December 2019

High temperature dielectric relaxation behaviors of single phase Mn3O4 polycrystalline ceramics prepared by spark plasma sintering technology have been studied. Two dielectric relaxations were observed in the temperature range of 200 K–330 K and in the frequency range of 20 Hz–10 MHz. The lower temperature relaxation is a type of thermally activated relaxation process, which mainly results from the hopping of oxygen vacancies based on the activation energy analysis. There is another abnormal dielectric phenomenon that is different from the conventional thermally activated behavior and is related to a positive temperature coefficient of resistance (PTCR) effect in the temperature region. In line with the impedance analyses, we distinguished the contributions of grains and grain boundaries. A comparison of the frequency-dependent spectra of the imaginary impedance with imaginary electric modulus suggests that both the long range conduction and the localized conduction are responsible for the dielectric relaxations in the Mn3O4 polycrystalline samples.
Experimental Investigations on the Effect of Axial Homogenous Magnetic Fields on Propagating Vortex Flow in the Taylor–Couette System
Authors: Ilzig Thomas , Stöckel Katharina , Odenbach Stefan
Published: December 2019

Experimental investigations of propagating vortex flow states (pV states) in a short Taylor–Couette system with asymmetric boundary conditions are presented. The flow state was established in a ferrofluid showing no magneto-viscous effect and was exposed to axial magnetic fields. It was found that the magnetic field led to a change in the spatial and temporal behavior of the pV state, indicating complex interactions between the flow field and magnetic field. A stepwise applied axial magnetic field destabilized the pV state, leading to an intermittent flow state. Gradually increasing the axial magnetic fields changed the temporal behavior of the regime. Up to magnetic field strengths of 20 kA/m, the orbital frequency, as a measure for the temporal periodicity, was increased with field strength.
Friction and Wear between Polymer and Metal in the Mixing Process
Authors: Pan Yiren , Zhu Lin , Liu Huaqiao , Zhang Meng , Han Wenwen , Wang Chuansheng , Bian Huiguang
Published: December 2019

In order to obtain a longer mixing chamber life, a layer of hard alloy coating is generally welded on the surface. However, when the mixing chamber is used for a long time, the surface will be worn due to friction with small fillers and rubber. As a result, there will be a large gap between the mixing chamber and the rotor, which will further affect the quality of the mixed rubber. In this paper, the dispersion process of the reinforcing system is simulated at first, and the mixed rubber samples are obtained from different dispersion stages in preparation for experiments with the chamber material. On this basis, the friction experiment is carried out with the same material as the mixing chamber on the friction experiment machine employed in the improved test part. The experiment shows that the friction and wear between the mixture and metal produced in each mixing stage are different. The wear in the stage with high friction is not necessarily large. The wear will be intensified in the middle and later mixing periods, while the friction will tend to be stable. In this paper, besides the exploration on the friction of fillers and rubber on the mixing chamber in different mixing stages, the most important thing is to change the mixing process of rubber formula, so as to extend the service life of the mixing chamber without changing the comprehensive physical properties of the mixing rubber.
Chemical, Physical, and Mechanical Properties and Microstructures of Laser-Sintered Co–25Cr–5Mo–5W (SP2) and W–Free Co–28Cr–6Mo Alloys for Dental Applications
Authors: Okazaki Yoshimitsu , Ishino Akira , Higuchi Shizuo
Published: December 2019

We examined the chemical, physical, and mechanical properties and microstructures of laser-sintered Co–25Cr–5Mo–5W (SP2) and W–free Co–28Cr–6Mo alloys. The tensile and fatigue properties of the laser-sintered Co–Cr–Mo alloys were extremely superior to those of dental-cast alloys. The ultimate tensile strength (σUTS) and total elongation (T.E.) were close to those of hot-forged Co–28Cr–6Mo alloys. The fatigue strengths (σFS) at 107 cycles of the 90°-, 45°-, and 0°-direction-built Co–28Cr–6Mo alloys were ~500, ~560, and ~600 MPa, respectively. The ratio σFS /σUTS was ~0.4. These superior mechanical properties were attributed to the fine π-phase particles in the grains and grain boundaries of the fine face–centered cubic (fcc) matrix formed owing to the rapid solidification. The chemical composition of 20-times-laser-sintered Co–Cr–Mo alloy without the virgin powder added was approximately the same as that of the alloy laser-sintered with the virgin powder. σFS of the 90°-direction-built alloys after laser sintering 20 times was also ~500 MPa. σUTS of hot-forged Co–28Cr–6Mo alloys decreased with increasing annealing temperature, whereas T.E. increased. For the Co–Cr–Mo alloys annealed at 1000 to 1150 °C for 30 min after laser sintering, the rates of decrease in σUTS were small. σFS/σUTS increased to near those of annealed Co–28Cr–6Mo alloys after hot forging. The durability of clasps fabricated by laser sintering was superior to that of dental-cast clasps.
Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides
Authors: Zhou Gege , Geng Wentong , Sun Lu , Wang Xue , Xiao Wei , Wang Jianwei , Wang Ligen
Published: December 2019

Ceria is one of the most important functional rare-earth oxides with wide industrial applications. Its amazing oxygen storage/release capacity is attributed to cerium’s flexible valence conversion between 4+ and 3+. However, there still exists some debate on whether the valence conversion is due to the Ce-4f electron localization-delocalization transition or the character of Ce–O covalent bonds. In this work, a mixed valence model was established and the formation energies of oxygen vacancies and electronic charges were obtained by density functional theory calculations. Our results show that the formation energy of oxygen vacancy is affected by the valence state of its neighboring Ce atom and two oxygen vacancies around a Ce4+ in CeO2 have a similar effect to a Ce3+. The electronic charge difference between Ce3+ and Ce4+ is only about 0.4e. Therefore, we argue that the valence conversion should be understood according to the adjustment of the ratio of covalent bond to ionic bond. We propose that the formation energy of oxygen vacancy be used as a descriptor to determine the valence state of Ce in cerium oxides.
Heterogeneity Challenges in Multiple-Element-Modified Lead-Free Piezoelectric Ceramics
Authors: Condurache Oana Andreea , Radan Kristian , Prah Uroš , Otoničar Mojca , Kmet Brigita , Kapun Gregor , Dražić Goran , Malič Barbara , Benčan Andreja
Published: December 2019

We report on a heterogeneity study, down to the atomic scale, on a representative multiple-element-modified ceramic based on potassium sodium niobate (KNN): 0.95(Na0.49K0.49Li0.02)(Nb0.8Ta0.2)O3–0.05CaZrO3 with 2 wt % MnO2. We show that different routes for incorporating the MnO2 (either before or after the calcination step) affect the phase composition and finally the functionality of the material. According to X-ray diffraction and scanning electron microscopy analyses, the ceramics consist of orthorhombic and tetragonal perovskite phases together with a small amount of Mn-rich secondary phase. The addition of MnO2 after the calcination results in better piezoelectric properties, corresponding to a ratio between the orthorhombic and tetragonal perovskite phases that is closer to unity. We also show, using microscopy techniques combined with analytical tools, that Zr-rich, Ta-rich and Mn-rich segregations are present on the nano and atomic levels. With this multi-scale analysis approach, we demonstrate that the functional properties are sensitive to minor modifications in the synthesis route, and consequently to different material properties on all scales. We believe that detecting and learning how to control these modifications will be a step forward in overcoming the irreproducibility problems with KNN-based materials.
Investigation of AlGaN/GaN Heterostructures Grown on Sputtered AlN Templates with Different Nucleation Layers
Authors: Liu Chuan-Yang , Zhang Ya-Chao , Xu Sheng-Rui , Jiang Li , Zhang Jin-Cheng , Hao Yue
Published: December 2019

In this work, a sputtered AlN template is employed to grow high-quality AlGaN/GaN heterostructures, and the effects of AlN nucleation layer growth conditions on the structural and electrical properties of heterostructures are investigated in detail. The optimal growth condition is obtained with composited AlN nucleation layers grown on a sputtered AlN template, resulting in the smooth surface morphology and superior transport properties of the heterostructures. Moreover, high crystal quality GaN material with low dislocation density has been achieved under the optimal condition. The dislocation propagation mechanism, stress relief effect in the GaN grown on sputtered AlN, and metal organic chemical vapor deposition AlN nucleation layers are revealed based on the test results. The results in this work demonstrate the great potential of AlGaN/GaN heterostructures grown on sputtered AlN and composited AlN nucleation layers for microelectronic applications.
The Constitutive Relationship for Corroded Steel Bars: Model and Analysis
Authors: Xiong Cheng , Zeng Chaoqun , Li Yanru , Li Ly , Li Ping , Li Dawang
Published: December 2019

Combining the theoretical derivation and numerical calculations, the characteristic changes of the tensile constitutive relation of corroded steel bars and their underlying mechanisms are studied. Corroded steel bars are regarded as a combination of three parts, which include uncorroded part, corroded part with variable cross section, and uniform corroded part. It is assumed that in all three parts the steel material follows a simplified trilinear constitutive relation of a mild steel material (elasticity, yielding, and hardening), from which an analytical model describing the overall tensile constitutive relation of the corroded steel bar is developed. Based on the experimental data of slotted steel bars, the validation of the present analytical model is provided. The results show that the trilinear model can give relatively accurate prediction of the characteristic parameters of corroded steel bars. The influences of corrosion rate on the mechanical properties of corroded steel bars are examined using the proposed model.
Assessment of Retained Austenite in Fine Grained Inductive Heat Treated Spring Steel
Authors: Olina Anna , Píška Miroslav , Petrenec Martin , Hervoches Charles , Beran Přemysl , Pechoušek Jiří , Král Petr
Published: December 2019

Advanced thermomechanical hot rolling is becoming a widely used technology for the production of fine-grained spring steel. Different rapid phase transformations during the inductive heat treatment of such steel causes the inhomogeneous mixture of martensitic, bainitic, and austenitic phases that affects the service properties of the steel. An important task is to assess the amount of retained austenite and its distribution over the cross-section of the inductive quenched and tempered wire in order to evaluate the mechanical properties of the material. Three different analytical methods were used for the comparative quantitative assessment of the amount of retained austenite in both the core and rim areas of the sample cross-section: neutron diffraction—for the bulk of the material, Mössbauer spectroscopy—for measurement in a surface layer, and the metallographic investigations carried by the EBSD. The methods confirmed the excessive amount of retained austenite in the core area that could negatively affect the plasticity of the material.
Evaluation of Stress–Strain Behavior of Self-Compacting Rubber Lightweight Aggregate Concrete under Uniaxial Compression Loading
Authors: Lv Jing , Zhou Tianhua , Du Qiang , Li Kunlun , Sun Kai
Published: December 2019

The recycling of waste tires in lightweight aggregate concrete (LC) would achieve huge environmental and societal benefits, but the effects of rubber particles on the partial properties of LC are not clear (e.g., the stress–strain relationship). In this paper, uniaxial compressive experiments were conducted to evaluate the stress–strain relationship of self-compacting rubber lightweight aggregate concrete (SCRLC). Rubber particles were used to replace sand by volume, and substitution percentages of 0%, 10%, 20%, 30%, 40%, and 50% were set as influence factors. Experimental results indicate that with increased rubber particles substitution percentage, the cubic compressive strength and axial compressive strength of SCRLC decreased, while the failure modes of SCRLC prism specimens gradually changed from brittle to ductile failure. As the rubber particles substitution percentage increased from 0% to 50%, the peak strain of SCRLC increased whereas peak stress, elastic modulus, and peak secant modulus of SCRLC deceased, the descending stage of stress–strain curves became softer. The rubber particles substitution percentage of 30% was the critical point at which an obvious change in the properties of SCRLC occurred. Based on the data collected from experimental studies, a predictive model for SCRLC was established and a further prediction of the SCRLC stress–strain relationship was given.
Psychometric Properties of the World Health Organization’s Quality of Life (WHOQOL-BREF) Questionnaire in Medical Students
Authors: Ilić Irena , Šipetić-Grujičić Sandra , Grujičić Jovan , Živanović Mačužić Ivana , Kocić Sanja , Ilić Milena
Published: December 2019

Background and Objectives: Studies on the effects of studying on a medical student’s quality of life are sparse. The World Health Organization Quality of Life (WHOQOL-BREF) questionnaire is a widely used scale that enables the assessment and international comparisons of the quality of life. The aim of this study was to evaluate psychometric properties of the WHOQOL-BREF questionnaire among Serbian medical students. Material and Methods: We conducted a cross-sectional study that involved 760 medical students at a state medical faculty at the University of Kragujevac, Serbia. The reliability of the WHOQOL-BREF was evaluated using Cronbach’s alpha coefficient and test–retest analysis, and the validity was examined using principal component analysis, with Promax rotation method. Results: Cronbach’s alpha coefficient for the whole WHOQOL-BREF scale was 0.896. Internal reliability for all domains was above 0.70, except for the domain “Social Relationships” (0.533). The test–retest reliability for all domains was significant at p < 0.01 level, showing good stability of the scale. Principal component analysis with Promax rotation method indicated four main components that explained 49.5% of variance. Conclusion: The Serbian version of the WHOQOL-BREF scale showed satisfactory psychometric properties that facilitate estimation of the quality of life of medical students.
The Effect of Primary Duodenogastric Bile Reflux on the Presence and Density of Helicobacter pylori and on Gastritis in Childhood
Authors: Agin Mehmet , Kayar Yusuf
Published: December 2019

Background and Objectives: Although there are many studies that investigate the relationship between duodenogastric reflux (DGR) and Helicobacter pylori in adult patients, the reported data are contradictory. In addition, there are very few studies in the literature investigating the relationship between DGR and H. pylori in the pediatric age group. In the present study, we investigated the effect of primary DGR on H. pylori and gastritis. Materials and Methods: A total of 361 patients who were referred to the clinic of our hospital with dyspeptic complaints who had an upper gastrointestinal system endoscopy and a gastric biopsy were included in the study. Results: DGR was detected in 45 cases, and 316 cases that did not have DGR were considered as the control group. Comparisons were made between the DGR cases and the control group in terms of risk factors (age, gender), the presence and density of H. pylori, and the presence and severity of gastritis. The average age of the patients who were included in the study was 11.6 ± 4.6 years. A total of 128 (36%) of the cases were male and 233 (64%) were female. DGR was present in 45 (13%) of the cases. The average age of the patients with DGR was 13.9 ± 3.1 years, the average age of the control group was 11.3 ± 4.7, and there were statistically significant differences (p < 0.001). No significant differences were detected in terms of gender between DGR and the control group (p > 0.05). H. pylori (+) was detected in 29 (64%) of patients with DGR, and in 202 (64%) of the control group. No significant differences were detected between H. pylori prevalence (p = 0.947). Gastritis was detected in 37 (82%) of the patients with DGR, and in 245 (77%) of the control group (p = 0.476). No significant differences were detected between the presence and density of H. pylori, gastritis presence, severity and DGR (p > 0.05). Conclusions: The ages of patients with DGR were significantly higher than in the control group, and advanced age was shown to be a risk factor for primary DGR. It was found that the presence of DGR has no effect on the presence and severity of H. pylori. Given this situation, we consider it is important to eradicate H. pylori infection, especially in the case where H. pylori is present together with DGR.
The Effects of the Dietary Approaches to Stop Hypertension (DASH) Diet on Metabolic Syndrome in Hospitalized Schizophrenic Patients: A Randomized Controlled Trial
Authors: Sorić Tamara , Mavar Mladen , Rumbak Ivana
Published: December 2019

The relationship between the Dietary Approaches to Stop Hypertension (DASH) diet and metabolic syndrome (MetS) in people with schizophrenia is unknown and remains to be investigated. Therefore, we have conducted a three-month parallel-group randomized controlled trial. Sixty-seven hospitalized schizophrenic patients with MetS [n = 33 in the intervention group (IG) and n = 34 in the control group (CG)] completed the intervention. The IG followed the DASH diet with the caloric restriction of approximately 1673.6 kJ/day (400 kcal/day) when compared to the standard hospital diet followed by the CG. Simultaneously, both groups participated in a nutrition counseling program. Anthropometric and biochemical parameters and blood pressure were measured at the baseline and after three months, while nutrient intakes during the intervention were assessed using three non-consecutive 24-hour dietary recalls. The analyses were carried out based on the per-protocol approach. At three months, the MetS prevalence significantly decreased in both the IG and the CG (75.8%, p = 0.002, and 67.7%, p = 0.0003, respectively; odds ratio = 0.9; 95% confidence interval = 0.43–1.87). No significant differences in the prevalence of MetS and its features were found between the groups.
Experimental and Numerical Study on Gas-Liquid Two-Phase Flow Behavior and Flow Induced Noise Characteristics of Radial Blade Pumps
Authors: Si Qiaorui , Shen Chunhao , Ali Asad , Cao Rui , Yuan Jianping , Wang Chuan
Published: December 2019

Miniature drainage pumps with a radial blade are widely used in situations with critical constant head and low noise requests, but the stable operation state is often broken up by the entraining gas. In order to explore the internal flow characteristics under gas–liquid two phase flow, pump performance and emitted noise measurements were processed under different working conditions. Three-dimensional numerical calculations based on the Euler inhomogeneous model and obtained experimental boundaries were carried out under different inlet air void fractions (IAVFs). A hybrid numerical method was proposed to obtain the flow-induced emitted noise characteristics. The results show there is little influence on pump characteristics when the IAVF is less than 1%. The pump head slope degradation was found to increase with air content. The bubbles adhere to the impeller hub on the blade’s suction side and spread to the periphery with a big IAVF, leading to unstable operation. It is obvious that vortices appear inside the impeller flow passage as IAVF reaches 6.5%. The two-phase flow pattern has a small effect on the characteristic frequency distribution of pressure fluctuation and emitted noise, but the corresponding pulsation intensity and noise level will increase. The study could provide some reference for low noise design of the drainage pump.
Systematic Separation and Purification of Alkaloids from Euchresta tubulosa Dunn. by Various Chromatographic Methods
Authors: Li Wei-Xin , Wang Huan , Dong Ai-Wen
Published: December 2019

High-speed countercurrent chromatography (HSCCC) and silica gel column chromatography were used to separate and purify alkaloids from Chinese herbal medicine Euchresta tubulosa Dunn. The purpose of this study is to provide a system mode for rapid separation of alkaloids from natural products. In the experiment, the eluent of silica gel column chromatography was screened by thin layer chromatography (TLC) to obtain four components with different polarity. Then, the two-phase solvent systems of different components were selected and purified by HSCCC. Four alkaloids with relatively high content were obtained by this mode successfully, including matrine (28 mg), oxymatrine (32 mg), N-formyl cytisine (24 mg), and cytisine (58 mg). The purity was higher than 91% by high performance liquid chromatography–ultraviolet (HPLC-UV) and their chemical structures were identified by nuclear magnetic resonance (NMR) and electron ionization mass spectrometry (EI-MS). The results showed that the combination of HSCCC and silica gel column chromatography could make alkaloids from natural products separate systematically.
Protective Low-Density Polyethylene Residues from Prepreg for the Development of New Nanocomposites with Montmorillonite: Recycling and Characterization
Authors: Rodrigues Passos Severino Pamela , Larissa do Amaral Montanheiro Thaís , Ferro Orestes , Roberto Passador Fábio , Stieven Montagna Larissa
Published: December 2019

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications.