bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Polyoxymethylene Particles via the Solution-Dissolution Process and Application to the Powder Bed Fusion of Polymers
Authors: Dechet Maximilian A. , Baumeister Ina , Schmidt Jochen
Published: April 2020

In this study, the development of a polyoxymethylene (POM) feedstock material for the powder bed fusion (PBF) of polymers is outlined. POM particles are obtained via liquid-liquid phase separation (LLPS) and precipitation, also known as the solution-dissolution process. In order to identify suitable POM solvent systems for LLPS and precipitation, in the first step, a solvent screening based on solubility parameters was performed, and acetophenone and triacetin were identified as the most promising suitable moderate solvents for POM. Cloud point curves were measured for both solvents to derive suitable temperature profiles and polymer concentrations for the solution-dissolution process. In the next step, important process parameters, namely POM concentration and stirring conditions, were studied to elucidate their effect on the product’s properties. The product particles obtained from both aforementioned solvents were characterized with regard to their morphology and size distribution, as well as their thermal properties (cf. the PBF processing window) and compared to a cryo-milled POM PBF feedstock. Both solvents allowed for precipitation of POM particles of an appropriate size distribution for PBF for polymer concentrations of at least up to 20 wt.%. Finally, a larger powder batch for application in the PBF process was produced by precipitation from the preferred solvent acetophenone. This POM powder was further analyzed concerning its flowability, Hausner ratio, and mass-specific surface area. Finally, test specimens, namely a complex gyroid body and a detailed ornament, were successfully manufactured from this feedstock powder showing appropriate bulk solid and thermal properties to demonstrate PBF processability. In summary, a processable and suitable POM PBF feedstock could be developed based on the non-mechanical solution dissolution process, which, to the authors’ best knowledge, has not been reported in previous studies.
Study on Low-Temperature Cracking Performance of Asphalt under Heat and Light Together Conditions
Authors: Li Limin , Guo Zhaoyang , Ran Longfei , Zhang Jiewen
Published: April 2020

The low-temperature cracking performance of asphalt is considered one of the main deteriorations in asphalt pavements. However, there have been few studies on the low-temperature cracking performance of asphalt under heat and light together. Hence, the ductility test, bending beam rheometer (BBR) test, and asphalt composition analysis test are combined to investigate the low-temperature cracking performance under heat and light together based on the climatic conditions of China. The styrene–butadiene–styrene block copolymer (SBS)-modified asphalt binders were prepared with different modifier types and base asphalt in this research. The results show that the low-temperature cracking resistance of asphalt reduces under heat and light together. It is obviously reduced at the early stage, and it becomes worse with the increase of the aging time, temperature, and ultraviolet (UV) intensity. The asphalt composition has a significant impact on its low-temperature cracking performance, and the SBS modifier can improve the low-temperature cracking resistance of asphalt. The rational selection of base asphalt and modifier can improve the low-temperature cracking performance of asphalt. Under heat and light together, whether base asphalt or modified asphalt, the change trends of their ductility and component content are similar. Therefore, to improve the anti-cracking ability of the asphalt pavement, it is suggested to use the ductility of asphalt aged by heat and light together for 15 days as the evaluation index of the low-temperature cracking performance of asphalt, and asphalt should be selected according to the temperature and UV intensity of the asphalt pavement use area.
Mechanical Assessment of Fatigue Characteristics between Single- and Multi-Directional Cyclic Loading Modes on a Dental Implant System
Authors: Kim Won Hyeon , Song Eun Sung , Ju Kyung Won , Lim Dohyung , Han Dong-Wook , Jung Tae-Gon , Jeong Yong-Hoon , Lee Jong-Ho , Kim Bongju
Published: April 2020

Mechanical testing based on ISO 14801 standard is generally used to evaluate the performance of the dental implant system according to material and design changes. However, the test method is difficult to reflect on the clinical environment because the ISO 14801 standard does not take into account the various loads from different directions during chewing motion. In addition, the fracture pattern of the implant system can occur both in the horizontal and the vertical directions. Therefore, the purpose of this study was to compare fatigue characteristics and fracture patterns between single directional loading conditions based on the ISO 14801 standard and multi-directional loading condition. Firstly, the static test was performed on five specimens to derive the fatigue load, and the fatigue load was chosen as 40% of the maximum load measured in the static test. Subsequently, the fatigue test was performed considering the single axial/occlusal (AO), AO with facial/lingual (AOFL) and AO with mesial/distal (AOMD) directions, and five specimens were used for each fatigue loading modes. In order to analyze the fatigue characteristics, the fatigue cycle at the time of specimen fracture and displacement change of the specimen every 500 cycles were measured. Field emission scanning electron microscopy (FE-SEM) was used to analyze the fracture patterns and the fracture surface. Compared to the AO group, the fatigue cycle of the AOFL and AOMD groups showed lower about five times, while the displacement gradually increased with every 500 cycles. From FE-SEM results, there were no different surface morphology characteristics among three groups. However, the AOMD group showed a vertical slip band. Therefore, our results suggest that the multi-directional loading mode under the worst-case environment can reproduce the vertical fracture pattern in the clinical situation and may be essential to reflect on the dental implant design including connection types and surface treatments.
Effects of Volume Fraction and Surface Area of Aggregates on the Static Yield Stress and Structural Build-Up of Fresh Concrete
Authors: Ivanova Irina , Mechtcherine Viktor
Published: April 2020

With increasing interest in the use of additive manufacturing techniques in the construction industry, static rheological properties of fresh concrete have necessarily come into focus. In particular, the knowledge and control of static yield stress (SYS) and its development over time are crucial for mastering formwork-free construction, e.g., by means of layered extrusion. Furthermore, solid understanding of the influences of various concrete constituents on the initial SYS of the mixture and the structural build-up rate is required for purposeful material design. This contribution is concentrated on the effect of aggregates on these rheological parameters. The volume fraction of aggregates was varied in the range of 35% to 55% by volume under condition of constant total surface area of the particles. The total surface area per unit volume of cement paste was equal to 5.00, 7.25 and 10.00 m²/L, conditioned on the constant volume fraction of aggregates. Both variations were enabled by changing the particle size distributions of the aggregates while holding the cement paste composition constant for all concrete mixtures. To characterise the SYS and the structural build-up, constant shear rate tests with a vane-geometry rotational rheometer were performed. It was found that in the ranges under investigation the variation in volume fraction had a more pronounced effect on the static rheological properties of concrete than did the variation in surface area. An accurate mathematical description of the relationship between the initial SYS of concrete and the relative volume fraction of aggregate based on the Chateau–Ovarlez–Trung model was proposed. Challenges in deriving a similar relationship for the structural build-up rate of concrete were highlighted.
Magnetic Properties of Electrospun Magnetic Nanofiber Mats after Stabilization and Carbonization
Authors: Fokin Nadine , Grothe Timo , Mamun Al , Trabelsi Marah , Klöcker Michaela , Sabantina Lilia , Döpke Christoph , Blachowicz Tomasz , Hütten Andreas , Ehrmann Andrea
Published: April 2020

Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with a high aspect ratio. Since PAN is a typical precursor for carbon, the magnetic nanofiber mats were stabilized and carbonized after electrospinning. The magnetic properties of nanofiber mats containing magnetite or nickel ferrite nanoparticles were found to depend on the nanoparticle diameters and the potential after-treatment, as compared with raw nanofiber mats. Micromagnetic simulations underlined the different properties of both magnetic materials. Atomic force microscopy and scanning electron microscopy images revealed nearly unchanged morphologies after stabilization without mechanical fixation, which is in strong contrast to pure PAN nanofiber mats. While carbonization at 500 °C left the morphology unaltered, as compared with the stabilized samples, stronger connections between adjacent fibers were formed during carbonization at 800 °C, which may be supportive of magnetic data transmission.
Long-Term Clinical Outcomes of Treatment with Dental Implants with Acid Etched Surface
Authors: Velasco-Ortega Eugenio , Jimenez-Guerra Alvaro , Monsalve-Guil Loreto , Ortiz-Garcia Ivan , Nicolas-Silvente Ana I. , Segura-Egea Juan J. , Lopez-Lopez Jose
Published: April 2020

Implant dentistry constitutes a therapeutic modality in the prosthodontic treatment of partially and totally edentulous patients. This study reports a long-term evaluation of treatment by the early loading of acid-etched surface implants. Forty-eight partially and totally edentulous patients were treated with 169 TSA Defcon® acid-etched surface implants for prosthodontic rehabilitation. Implants were loaded after a healing free-loading period of 6–8 weeks in mandible and maxilla, respectively. Implant and prosthodontic clinical findings were followed during at least 17 years. Clinical results indicate a survival and success rate of implants of 92.9%, demonstrating that acid-etched surface achieves and maintains successful osseointegration. Five implants in three patients were lost during the healing period. Sixty-five prostheses were placed in 45 patients over the remaining 164 implants, 30 single crowns, 21 partially fixed bridges, 9 overdentures, and 5 full-arch fixed rehabilitations. A total of 12 implants were lost during the follow-up period. Mean marginal bone loss was 1.91 ± 1.24 mm, ranging from 1.1 to 3.6 mm. The most frequent complication was prosthetic technical complications (14.2%), followed by peri-implantitis (10.6%). The mean follow-up was of 214.4 months (208–228 months). Prosthodontic rehabilitation with an early-loading protocol over acid-etched surface implants is a successful implant treatment.
The Influence of Cryogenic Conditions on the Process of AA2519 Aluminum Alloy Cracking
Authors: Kotyk M. , Boroński D. , Maćkowiak P.
Published: April 2020

This study presents the results of tests involving determining quantities used to describe fracture toughness of a heat-treated AA2519 aluminum alloy applied in, among other things, constructing American military amphibians. These quantities were determined using the J–R curve method for two temperature values, 293 K and 77 K. The low temperature was provided by putting the tested specimen into a liquid nitrogen bath and keeping it there throughout the experiment. Based on the tests results, cryogenic conditions cause an increase in the maximum experimental value of the J–JQ integral, from 66.3 to 87.3 kJ/m2 Moreover, an analysis of the fatigue fracture microstructure revealed differences between specimens tested in ambient temperature and those tested in cryogenic temperature.
Fiber Bragg Sensors on Strain Analysis of Power Transmission Lines
Authors: Juraszek Janusz
Published: April 2020

The reliability and safety of power transmission depends first and foremost on the state of the power grid, and mainly on the state of the high-voltage power line towers. The steel structures of existing power line supports (towers) have been in use for many years. Their in-service time, the variability in structural, thermal and environmental loads, the state of foundations (displacement and degradation), the corrosion of supporting structures and lack of technical documentation are essential factors that have an impact on the operating safety of the towers. The tower state assessment used to date, consisting of finding the deviation in the supporting structure apex, is insufficient because it omits the other necessary condition, the stress criterion, which is not to exceed allowable stress values. Moreover, in difficult terrain conditions the measurement of the tower deviation is very troublesome, and for this reason it is often not performed. This paper presents a stress-and-strain analysis of the legs of 110 kV power line truss towers with a height of 32 m. They have been in use for over 70 years and are located in especially difficult geotechnical conditions—one of them is in a gravel mine on an island surrounded by water and the other stands on a steep, wet slope. Purpose-designed fiber Bragg grating (FBG) sensors were proposed for strain measurements. Real values of stresses arising in the tower legs were observed and determined over a period of one year. Validation was also carried out based on geodetic measurements of the tower apex deviation, and a residual magnetic field (RMF) analysis was performed to assess the occurrence of cracks and stress concentration zones.
Improvement of Photoresponse in Organic Phototransistors through Bulk Effect of Photoresponsive Gate Insulators
Authors: Park Hea-Lim , Kim Min-Hoi , Kim Hyeok
Published: April 2020

In this study, we investigate the bulk effect of photoresponsive gate insulators on the photoresponse of organic phototransistors (OPTs), using OPTs with poly(4-vinylphenol) layers of two different thicknesses. For the photoresponse, the interplay between the charge accumulation (capacitance) and light-absorbance capabilities of a photoresponsive gate insulator was investigated. Although an OPT with a thicker gate insulator exhibits a lower capacitance and hence a lower accumulation capability of photogenerating charges, a thicker poly(4-vinylphenol) layer, in contrast to a thinner one, absorbs more photons to generate more electron–hole pairs, resulting in a higher photoresponse of the device. That is, in these two cases, the degree of light absorption by the photoresponsive gate insulators dominantly governed the photoresponse of the device. Our physical description of the bulk effect of photoresponsive insulators on the performance of OPTs will provide a useful guideline for designing and constructing high-performance organic-based photosensing devices and systems.
Novel Extruded Starch-Beet Pulp Composites for Packaging Foams
Authors: Abbès Boussad , Lacoste Catherine , Bliard Christophe , Maalouf Chadi , Simescu-Lazar Florica , Bogard Fabien , Polidori Guillaume
Published: April 2020

This article concerns the elaboration and the characterization of a novel biobased potato starch-beet pulp composite for packaging applications as cushion foams. A twin-screw extruder was used to elaborate composite foams. SEM observations of these materials were conducted, and thermomechanical properties were studied in terms of thermal transitions (TGA, DSC) and viscoelastic properties (DMA). The effect of relative humidity content on viscoelastic properties was analyzed as a function of frequency. The different test results show that the composite structures are homogeneously mixed. The sponge-like structure of the beet-pulp disappears indicating a good compatibility between the two mixed constituents. The DSC curve of starch-beet pulp foam shows a single thermal transition at 153.6 °C, indicating the thermal homogeneity of the obtained composite material. The density value of starch-beet pulp foam is higher than conventional foams, but this can be optimized by adjusting the technological parameters of the extruder. The viscoelastic properties of the developed materials depend on the relative humidity.
Q-Switch Nd:YAG Laser-Assisted Elimination of Multi-Species Biofilm on Titanium Surfaces
Authors: Namour Melanie , Verspecht Tim , El Mobadder Marwan , Teughels Wim , Peremans Andre , Nammour Samir , Rompen Eric
Published: April 2020

(1) Background: The relatively high prevalence of peri-implantitis (PI) and the lack of a standard method for decontamination of the dental implant surface have pushed us to conduct further research in the field. Bacterial biofilms were found to play a primordial role in the etiology of PI. Therefore, the aim is to evaluate the efficacy of a laser-assisted elimination of biofilm protocol in the removal of a multi-species biofilm on titanium surfaces. (2) Methods: In total, 52 titanium discs (grade 4) were used. The study group consisted of 13 titanium disks contaminated with multi-species biofilms and subsequently irradiated with the laser (T + BF + L). The control groups consisted of the following types of titanium disks: 13 contaminated with multi-species biofilms (T + BF), 13 sterile and irradiated (T + L), 13 sterile and untreated (T). Q-Switch Nd:YAG laser Irradiation parameters were the following: energy density equal to 0.597 J/cm2 per pulse, power equal to 270 milliwatt per pulse, 2.4 mm of spot diameter, and 10 Hz repetition rate for pulse duration of six nanoseconds (ns). The laser irradiation was made during 2 s of total time in non-contact and at 0.5 mm away from the titanium disc surface. After treatment, presence of biofilms on the disks was evaluated by staining with crystal violet (CV), which was measured as optical density at six hundred thirty nm, and statistical analyses were done. (3) Results: the optical density values were 0.004 ± 0.004 for the study group T + BF + L, 0.120 ± 0.039 for group T + BF, 0.006 ± 0.003 for group T + L, and 0.007 ± 0.007 for group T. For the study group, laser treatment resulted in a total elimination of the biofilm, with mean values statistically significantly lower than those of contaminated titanium surfaces and similar to those of sterile titanium surfaces. (4) Conclusions: Our irradiation protocol provided a significant elimination of the multi-species biofilm on titanium surfaces. Laser treated titanium surfaces were biofilm-free, similar to the sterile ones.
Transverse Impact on Rectangular Metal and Reinforced Concrete Beams Taking into Account Bimodularity of the Material
Authors: Beskopylny Alexey , Meskhi Besarion , Kadomtseva Elena , Strelnikov Grigory
Published: April 2020

This article is devoted to the stress–strain state (SSS) study of metal and reinforced fiber-reinforced concrete beam under static and shock loading, depending on the bimodularity of the material, the mass of the beam, and the location of the reinforcing bars in zones under tension and compression. It is known that many materials have different tensile and compression properties, but in most cases, this is not taken into account. The calculations were carried out by using load-bearing metal beams made of silumin and steel and reinforced concrete beams under the action of a concentrated force applied in the middle of the span. The impact load is considered as the plastic action of an absolutely rigid body on the elastic system, taking into account the hypothesis of proportionality of the dynamic and static characteristics of the stress–strain state of the body. The dependences of the maximum dynamic normal stresses on the number of locations of reinforcing bars in zones under tension and compression, the bimodularity of the material, and the reduced mass of the beam are obtained. A numerical study of SSS for metal and concrete beams has shown that bimodularity allows the prediction of beam deflections and normal stresses more accurately.
Effect of Hydrogen and Absence of Passive Layer on Corrosive Properties of Aluminum Alloys
Authors: Włodarczyk Paweł P. , Włodarczyk Barbara
Published: April 2020

This paper reports the results of research on the effect of hydrogen permeation and the absence of passive layers on the variations in the corrosive properties of aluminum alloys. The study demonstrated that such variations contribute to the deterioration of corrosive properties, which in turn contributes to shortening the reliability time associated with the operation of aluminum alloy structures. The analysis involved structural aluminum alloys: EN AW-1050A, EN AW-5754, and EN AW-6060. It was demonstrated that the absorption of hydrogen by the analyzed alloys led to the shift of the electrode potential to the negative side. The built hydrogen corrosion cells demonstrate in each case the formation of electromotive force (EMF) cells. The initial EMF value of the cell and its duration depends on the duration of hydrogenation. As a result of removing the passive layers, the electrode potential also changes to the negative side. Following the removal of the passive layer from one of the electrodes, the cells also generated a galvanic (metal) cell. The duration of such a cell is equivalent to the time of restoration of the passive layer. The formation of such hydrogen and metal galvanic cells changes the electrochemical properties of aluminum alloys, therefore deteriorates the corrosive properties of aluminum alloys.
Study of the Microstructure Characteristics of Three Different Fine-grained Tailings Sand Samples during Penetration
Authors: Shi Yueqi , Li Changhong , Long Dayu
Published: April 2020

This paper explores the microstructural evolution characteristics of tailings sand samples of different types of infiltration failure during the infiltration failure process. The homemade small infiltration deformation instrument is used to test the infiltration failure characteristics of the tailings sand during the infiltration failure process. Evolutionary characteristics of the internal microstructure pores and particle distribution were also studied. Using CT (computerized tomography) technology to establish digital image information, the distribution of the microscopic characteristics of the particle distribution and pore structure after tailing sand infiltration were studied. Microscopic analysis was also performed to analyze the microscopic process of infiltration and destruction, as well as to see the microscopic structural characteristics of the infiltration and destruction of the total tailings. The test results show that there are obvious differences in the microstructure characterization of fluid soil and piping-type infiltration failures. Microstructure parameters have a certain functional relationship with macrofactors. Combining the relationship between macrophysical and mechanical parameters and microstructural parameters, new ideas for future research and the prevention of tailings sand infiltration and failure mechanisms is provided.
Investigation of Parameters Affecting the Equivalent Yield Curvature of Reinforced Concrete Columns
Authors: Hasgul Umut
Published: April 2020

In this study, the response quantities affecting the equivalent yield curvature, which is important in the deformation-based seismic design and assessment of structural systems, are investigated for reinforced concrete columns with a square cross-section. In this context, the equivalent yield curvatures were determined by conducting moment–curvature analyses on various column models, in which the axial load level, cross-section dimension, longitudinal reinforcement ratio, and concrete compression strength were changed parametrically, and the independent and/or combined effects of the relevant parameters were discussed. Depending on the axial load levels of P/Agfc′ < 0.3, P/Agfc′ = 0.3, and P/Agfc′ > 0.3 for the considered columns, the yielding of reinforcement, yielding of reinforcement and/or concrete crushing, and concrete crushing governed the yield conditions, respectively. It can be noted that the cross-section dimension and axial load level became the primary parameters. Even though the independent effects with regard to particular parameters remained at minimal levels, the combined effects of them with the axial load became important in terms of the equivalent yield curvature.
AIBH: Accurate Identification of Brain Hemorrhage Using Genetic Algorithm Based Feature Selection and Stacking
Authors: Alawad Duaa Mohammad , Mishra Avdesh , Hoque Md Tamjidul
Published: April 2020

Brain hemorrhage is a type of stroke which is caused by a ruptured artery, resulting in localized bleeding in or around the brain tissues. Among a variety of imaging tests, a computerized tomography (CT) scan of the brain enables the accurate detection and diagnosis of a brain hemorrhage. In this work, we developed a practical approach to detect the existence and type of brain hemorrhage in a CT scan image of the brain, called Accurate Identification of Brain Hemorrhage, abbreviated as AIBH. The steps of the proposed method consist of image preprocessing, image segmentation, feature extraction, feature selection, and design of an advanced classification framework. The image preprocessing and segmentation steps involve removing the skull region from the image and finding out the region of interest (ROI) using Otsu’s method, respectively. Subsequently, feature extraction includes the collection of a comprehensive set of features from the ROI, such as the size of the ROI, centroid of the ROI, perimeter of the ROI, the distance between the ROI and the skull, and more. Furthermore, a genetic algorithm (GA)-based feature selection algorithm is utilized to select relevant features for improved performance. These features are then used to train the stacking-based machine learning framework to predict different types of a brain hemorrhage. Finally, the evaluation results indicate that the proposed predictor achieves a 10-fold cross-validation (CV) accuracy (ACC), precision (PR), Recall, F1-score, and Matthews correlation coefficient (MCC) of 99.5%, 99%, 98.9%, 0.989, and 0.986, respectively, on the benchmark CT scan dataset. While comparing AIBH with the existing state-of-the-art classification method of the brain hemorrhage type, AIBH provides an improvement of 7.03%, 7.27%, and 7.38% based on PR, Recall, and F1-score, respectively. Therefore, the proposed approach considerably outperforms the existing brain hemorrhage classification approach and can be useful for the effective prediction of brain hemorrhage types from CT scan images (The code and data can be found here: http://cs.uno.edu/~tamjid/Software/AIBH/code_data.zip).
More Results on Italian Domination in Cn□Cm
Authors: Gao Hong , Wang Penghui , Liu Enmao , Yang Yuansheng
Published: April 2020

Italian domination can be described such that in an empire all cities/vertices should be stationed with at most two troops. Every city having no troops must be adjacent to at least two cities with one troop or at least one city with two troops. In such an assignment, the minimum number of troops is the Italian domination number of the empire/graph is denoted as γ I . Determining the Italian domination number of a graph is a very popular topic. Li et al. obtained γ I ( C n □ C 3 ) and γ I ( C n □ C 4 ) (weak {2}-domination number of Cartesian products of cycles, J. Comb. Optim. 35 (2018): 75–85). Stȩpień et al. obtained γ I ( C n □ C 5 ) = 2 n (2-Rainbow domination number of C n □ C 5 , Discret. Appl. Math. 170 (2014): 113–116). In this paper, we study the Italian domination number of the Cartesian products of cycles C n □ C m for m ≥ 6 . For n ≡ 0 ( mod 3 ) , m ≡ 0 ( mod 3 ) , we obtain γ I ( C n □ C m ) = m n 3 . For other C n □ C m , we present a bound of γ I ( C n □ C m ) . Since for n = 6 k , m = 3 l or n = 3 k , m = 6 l ( k , l ≥ 1 ) , γ r 2 ( C n □ C m ) = m n 3 , (the Cartesian product of cycles with small 2-rainbow domination number, J. Comb. Optim. 30 (2015): 668–674), it follows in this case that C n □ C m is an example of a graph class for which γ I = γ r 2 , which can partially answer the question presented by Brešar et al. on the 2-rainbow domination in graphs, Discret. Appl. Math. 155 (2007): 2394–2400.
The Derived Subgroups of Sylow 2-Subgroups of the Alternating Group, Commutator Width of Wreath Product of Groups
Authors: Skuratovskii Ruslan
Published: April 2020

The structure of the commutator subgroup of Sylow 2-subgroups of an alternating group A 2 k is determined. This work continues the previous investigations of me, where minimal generating sets for Sylow 2-subgroups of alternating groups were constructed. Here we study the commutator subgroup of these groups. The minimal generating set of the commutator subgroup of A 2 k is constructed. It is shown that ( S y l 2 A 2 k ) 2 = S y l 2 ′ A 2 k , k > 2 . It serves to solve quadratic equations in this group, as were solved by Lysenok I. in the Grigorchuk group. It is proved that the commutator length of an arbitrary element of the iterated wreath product of cyclic groups C p i , p i ∈ N equals to 1. The commutator width of direct limit of wreath product of cyclic groups is found. Upper bounds for the commutator width ( c w ( G ) ) of a wreath product of groups are presented in this paper. A presentation in form of wreath recursion of Sylow 2-subgroups S y l 2 ( A 2 k ) of A 2 k is introduced. As a result, a short proof that the commutator width is equal to 1 for Sylow 2-subgroups of alternating group A 2 k , where k > 2 , the permutation group S 2 k , as well as Sylow p-subgroups of S y l 2 A p k as well as S y l 2 S p k ) are equal to 1 was obtained. A commutator width of permutational wreath product B ≀ C n is investigated. An upper bound of the commutator width of permutational wreath product B ≀ C n for an arbitrary group B is found. The size of a minimal generating set for the commutator subgroup of Sylow 2-subgroup of the alternating group is found. The proofs were assisted by the computer algebra system GAP.
Prescribed Performance Adaptive Backstepping Control for Winding Segmented Permanent Magnet Linear Synchronous Motor
Authors: Zhang Weiming , Li Dapan , Lou Xuyang , Xu Dezhi
Published: April 2020

In this paper, a prescribed performance adaptive backstepping control (PPABC) strategy is proposed to control the speed of a winding segmented permanent magnet linear synchronous motor (WS-PMLSM) with variable parameters and an unknown load disturbance. Firstly, a mathematical model of WS-PMLSM is provided. Then, the prescribed performance technique is introduced in the adaptive backstepping control to improve the transient performance and ensures the tracking error converges within a predetermined range. In addition, a constrained command filter is introduced to address the problem of differential expansion which exists in the traditional backstepping method, and a filter compensation signal is designed against the filter error. Moreover, the adaptive law is designed based on Lyapunov stability theory to estimate the uncertainties caused by parameter changes and load disturbances. The stability of the proposed control strategy is given and the simulation of the control system is carried out under the proposed PPABC in contrast with another backstepping control and traditional PI control. Finally, the experiment is conducted to further show the effectiveness of the proposed controller.
LC–HRMS and Chemical Derivatization Strategies for the Structure Elucidation of Caribbean Ciguatoxins: Identification of C-CTX-3 and -4
Authors: Kryuchkov Fedor , Robertson Alison , Miles Christopher O. , Mudge Elizabeth M. , Uhlig Silvio
Published: April 2020

Ciguatera poisoning is linked to the ingestion of seafood that is contaminated with ciguatoxins (CTXs). The structural variability of these polyether toxins in nature remains poorly understood due to the low concentrations present even in highly toxic fish, which makes isolation and chemical characterization difficult. We studied the mass spectrometric fragmentation of Caribbean CTXs, i.e., the epimers C-CTX-1 and -2 (1 and 2), using a sensitive UHPLC–HRMS/MS approach in order to identify product ions of diagnostic value. We found that the fragmentation of the ladder-frame backbone follows a characteristic pattern and propose a generalized nomenclature for the ions formed. These data were applied to the structural characterization of a pair of so far poorly characterized isomers, C-CTX-3 and -4 (3 and 4), which we found to be reduced at C-56 relative to 1 and 2. Furthermore, we tested and applied reduction and oxidation reactions, monitored by LC–HRMS, in order to confirm the structures of 3 and 4. Reduction of 1 and 2 with NaBH4 afforded 3 and 4, thereby unambiguously confirming the identities of 3 and 4. In summary, this work provides a foundation for mass spectrometry-based characterization of new C-CTXs, including a suite of simple chemical reactions to assist the examination of structural modifications.
11β,20β-Epoxybriaranes from the Gorgonian Coral Junceella fragilis (Ellisellidae)
Authors: Su Tung-Pin , Kuo Tsu-Jen , Yang San-Nan , Lee Gene-Hsiang , Lee Yen-Tung , Wang Yi-Chen , Chen Jih-Jung , Wen Zhi-Hong , Hwang Tsong-Long , Sung Ping-Jyun
Published: April 2020

Two 11,20-epoxybriaranes, including a known compound, juncenolide K (1), as well as a new metabolite, fragilide X (2), have been isolated from gorgonian Junceella fragilis collected off the waters of Taiwan. The absolute configuration of juncenolide K (1) was determined by single-crystal X-ray diffraction analysis for the first time in this study and the structure, including the absolute configuration of briarane 2 was established on the basis of spectroscopic analysis and compared with that of model compound 1. One aspect of the stereochemistry of the known compound 1 was revised. Briarane 2 was found to enhance the generation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) release from RAW 264.7 cells.
Synchronous Cervical Adenocarcinoma and Ovarian Serous Adenocarcinoma—A Case Report and Literature Review
Authors: Bacalbasa Nicolae , Balescu Irina Cecilia , Diaconu Camelia , Dima Simona , Iliescu Laura , Vilcu Mihaela , Filipescu Alexandru , Halmaciu Ioana , Cretoiu Dragos , Brezean Iulian
Published: April 2020

Background/Aim: Synchronous gynecological malignancies are rarely encountered, and most often these cases are represented by synchronous ovarian and endometrial cancer. The aim of this paper is to present the case of a 53-year-old patient who was diagnosed with synchronous cervical and ovarian cancer. Case presentation: The patient had been initially investigated for vaginal bleeding and was submitted to a biopsy confirming the presence of a cervical adenocarcinoma. Once the diagnostic of malignancy was confirmed, the patient was submitted to a computed tomography which revealed the presence of large abdominal tumoral nodules of peritoneal carcinomatosis and was submitted to palliative chemotherapy with poor response. Eighteen months later she developed intestinal obstruction and was submitted to surgery. At that moment, synchronous ovarian and cervical tumors were diagnosed. Total radical hysterectomy with bilateral adnexectomy, pelvic and para-aortic lymph node dissection, omentectomy, and pelvic peritonectomy was performed; in the meantime, the histopathological studies confirmed the presence of two synchronous malignancies. Conclusion: Although synchronous lesions are rarely encountered, this eventuality should not be omitted. In such cases, surgery should be taken in consideration and the intent of radicality should regard both lesions.
Flow-Stress Model of 300M Steel for Multi-Pass Compression
Authors: Chen Rongchuang , Zeng Jiao , Yao Guichuan , Feng Fei
Published: April 2020

In this work, multi-pass compressions were performed at various strain rates (0.01 s−1, 0.1 s−1, 1 s−1, 10 s−1), temperatures (950 °C, 1050 °C, 1150 °C), inter-pass holding time (1 s, 10 s, 30 s, 120 s, 600 s), interrupt strains (0.3, 0.4, 0.5, 0.6), and total pass numbers (1, 2, 3, 4). The intriguing finding was that the recrystallized fraction, average dislocation density, and plastic cumulative strain were partly eliminated during inter-pass holding, resulting in the early occurrence of recrystallization in subsequent compression. Therefore, a parameter (Θ) to evaluate the overall softening fraction due to recrystallization was proposed, and it was then used to iteratively rectify the average dislocation density and plastic cumulative strain in flow-stress modeling. The flow-stress model parameters of 300M steel for multi-pass compression were identified using an optimization technique based on non-derivative method integrated in MATLAB software. The average deviation of calculated and experimental flow-stress was 0.88 MPa (1.35%), showing good accuracy of the flow-stress model. The microstructure evolution of 300M steel was analyzed by the change of softening fraction during multi-pass compression, which provided a useful reference for the research of stress–microstructure relationships of high-strength steels.
Strain-Ageing of Low-Alloyed Multiphase High-Strength Steels
Authors: Samek Ludovic , Dykas Jakub , De Moor Emmanuel , Grajcar Adam
Published: April 2020

The strain-aging of low alloyed, multiphase high-strength steels with strain-induced austenite to martensite transformation was studied. The influence of prestrain, aging time, and temperature dependence of the static strain aging was carried out. Ageing temperatures between 60 and 220 ∘ C and aging times from 20 to 10,000 min were investigated. The choice of steel composition allowed studying the influence of alloying elements, such as Si and Al, on the static strain aging behavior. Samples after aging were studied using light-optical microscopy, X-ray diffraction, and in-depth transmission electron microscopy (TEM). The Harper model was used to describe the precipitation mechanisms occurring during aging. The study of thin foils after aging using TEM showed the precipitation of low temperature transition carbides in the microstructure, which was observed between 60 and 5000 min. By using X-ray diffraction, it was revealed that aging at 170 ∘ C for a long time caused a slight decrease of the retained austenite volume fraction, but the C content remained constant.
Development of an Artificial Intelligence Powered TIG Welding Algorithm for the Prediction of Bead Geometry for TIG Welding Processes using Hybrid Deep Learning
Authors: Kesse Martin A. , Buah Eric , Handroos Heikki , Ayetor Godwin K.
Published: April 2020

Recent developments in artificial intelligence (AI) modeling tools allows for envisaging that AI will remove elements of human mechanical effort from welding operations. This paper contributes to this development by proposing an AI tungsten inert gas (TIG) welding algorithm that can assist human welders to select desirable end factors to achieve good weld quality in the welding process. To demonstrate its feasibility, the proposed model has been tested with data from 27 experiments using current, arc length and welding speed as control parameters to predict weld bead width. A fuzzy deep neural network, which is a combination of fuzzy logic and deep neural network approaches, is applied in the algorithm. Simulations were carried out on an experimental test dataset with the AI TIG welding algorithm. The results showed 92.59% predictive accuracy (25 out of 27 correct answers) as compared to the results from the experiment. The performance of the algorithm at this nascent stage demonstrates the feasibility of the proposed method. This performance shows that in future work, if its predictive accuracy is improved with human input and more data, it could achieve the level of accuracy that could support the human welder in the field to enhance efficiency in the welding process. The findings are useful for industries that are in the welding trade and serve as an educational tool.
Mg-Based Materials with Quasiamorphous Phase Produced by Vertical Twin-Roll Casting Process
Authors: Liu Hai , Li Wenxin , Pei Zhipu , Yan Mengyuan
Published: April 2020

Metallic materials with micron grains, submicron grains, or amorphous structures have attracted great interest in recent decades owing to their excellent mechanical properties and corrosion resistance. Compared with traditional forming processes, rapid solidification technology has shown great superiority and potential in the preparation of materials in such structures. In this study, fine-grained quasiamorphous Mg-based alloy strips fabricated by a twin-roll strip casting process were explored using simulation and experimental methods. The concept of critical casting speed was proposed to reflect the optimum casting conditions. The product of critical casting speed and strip thickness was used to evaluate the cooling capacity of the casting system. Based on simulation results, a twin-roll strip-casting experiment was performed on a Mg-rare earth alloy. A novel puddle-like microstructure of the as-cast alloy strip was obtained. Tensile testing results showed that the novel strip exhibited improved ductility.
Performance Comparison of Parametric and Non-Parametric Regression Models for Uncertainty Analysis of Sheet Metal Forming Processes
Authors: Marques Armando E. , Prates Pedro A. , Pereira André F. G. , Oliveira Marta C. , Fernandes José V. , Ribeiro Bernardete M.
Published: April 2020

This work aims to compare the performance of various parametric and non-parametric metamodeling techniques when applied to sheet metal forming processes. For this, the U-Channel and the Square Cup forming processes were studied. In both cases, three steel grades were considered, and numerical simulations were performed, in order to establish a database for each combination of forming process and material. Each database was used to train and test the various metamodels, and their predictive performances were evaluated. The best performing metamodeling techniques were Gaussian processes, multi-layer perceptron, support vector machines, kernel ridge regression and polynomial chaos expansion.
Additive Layer Manufacturing using Metal Deposition
Authors: Peyre Patrice
Published: April 2020

Among the additive layer manufacturing techniques for metals, those involving metal deposition, including laser cladding/Direct Energy Deposition (DED, with powder feeding) or Wire and Arc Additive Manufacturing (WAAM, with wire feeding), exhibit several attractive features [...]
Novel Miniature and Selective Combustion-Type CMOS Gas Sensor for Gas-Mixture Analysis—Part 1: Emphasis on Chemical Aspects
Authors: Shlenkevitch Dima , Stolyarova Sara , Blank Tanya , Brouk Igor , Nemirovsky Yael
Published: April 2020

There is an ongoing effort to fabricate miniature, low cost, sensitive, and selective gas sensors for domestic and industrial uses. This paper presents a miniature combustion-type gas sensor (GMOS) based on a thermal sensor, where a micromachined CMOS–SOI transistor integrated with a catalytic reaction plate acts as a sensing element. This study emphasizes GMOS performance modeling, technological aspects, and sensing-selectivity issues. Two deposition techniques of a Pt catalytic layer suitable for wafer-level processing were compared, magnetron sputtering and nanoparticle inkjet printing. Both techniques have been useful for the fabrication of GMOS sensor, with good sensitivity to ethanol and acetone in the air. However, a printed Pt nanoparticle catalyst provides almost twice as much sensitivity as compared to that of the sputtered catalyst. Moreover, sensing selectivity in the ethanol/acetone gas mixture was demonstrated for the GMOS with a Pt nanoparticle catalyst. These advantages of GMOS allow for the fabrication of a low-cost gas sensor that requires a low power, and make it a promising technology for future smartphones, wearables, and Internet of Things (IoT) applications.
Beyond Just Bacteria: Functional Biomes in the Gut Ecosystem Including Virome, Mycobiome, Archaeome and Helminths
Authors: Vemuri Ravichandra , Shankar Esaki M. , Chieppa Marcello , Eri Rajaraman , Kavanagh Kylie
Published: April 2020

Gut microbiota refers to a complex network of microbes, which exerts a marked influence on the host’s health. It is composed of bacteria, fungi, viruses, and helminths. Bacteria, or collectively, the bacteriome, comprises a significant proportion of the well-characterized microbiome. However, the other communities referred to as ‘dark matter’ of microbiomes such as viruses (virome), fungi (mycobiome), archaea (archaeome), and helminths have not been completely elucidated. Development of new and improved metagenomics methods has allowed the identification of complete genomes from the genetic material in the human gut, opening new perspectives on the understanding of the gut microbiome composition, their importance, and potential clinical applications. Here, we review the recent evidence on the viruses, fungi, archaea, and helminths found in the mammalian gut, detailing their interactions with the resident bacterial microbiota and the host, to explore the potential impact of the microbiome on host’s health. The role of fecal virome transplantations, pre-, pro-, and syn-biotic interventions in modulating the microbiome and their related concerns are also discussed.
Investigating Algal Communities in Lacustrine and Hydro-Terrestrial Environments of East Antarctica Using Deep Amplicon Sequencing
Authors: Hirose Yuu , Shiozaki Takuhei , Otani Masahiro , Kudoh Sakae , Imura Satoshi , Eki Toshihiko , Harada Naomi
Published: April 2020

Antarctica has one of the most extreme environments on Earth, with low temperatures and low nutrient levels. Antarctica’s organisms live primarily in the coastal, ice-free areas which cover approximately 0.18% of the continent’s surface. Members of Cyanobacteria and eukaryotic algae are important primary producers in Antarctica since they can synthesize organic compounds from carbon dioxide and water using solar energy. However, community structures of photosynthetic algae in Antarctica have not yet been fully explored at molecular level. In this study, we collected diverse algal samples in lacustrine and hydro-terrestrial environments of Langhovde and Skarvsnes, which are two ice-free regions in East Antarctica. We performed deep amplicon sequencing of both 16S ribosomal ribonucleic acid (rRNA) and 18S rRNA genes, and we explored the distribution of sequence variants (SVs) of these genes at single nucleotide difference resolution. SVs of filamentous Cyanobacteria genera, including Leptolyngbya, Pseudanabaena, Phormidium, Nodosilinea, Geitlerinama, and Tychonema, were identified in most of the samples, whereas Phormidesmis SVs were distributed in fewer samples. We also detected unicellular, multicellular or heterocyst forming Cyanobacteria strains, but in relatively small abundance. For SVs of eukaryotic algae, Chlorophyta, Cryptophyta, and Ochrophyta were widely distributed among the collected samples. In addition, there was a red colored bloom of eukaryotic alga, Geminigera cryophile (Cryptophyta), in the Langhovde coastal area. Eukaryotic SVs of Acutuncus antarcticus and/or Diphascon pingue of Tardigrada were dominant among most of the samples. Our data revealed the detailed structures of the algal communities in Langhovde and Skarvsnes. This will contribute to our understanding of Antarctic ecosystems and support further research into this subject.