Mixed Sequence Research Articles

Asymptotic normality of wavelet estimators in heteroscedastic regression model with ANA errors

. In this article, we mainly study the asymptotic normality of wavelet estimators in the heteroscedastic regression model with asymptotically negatively associated (ANA or ρ −, for short) errors. Under some mild conditions, the asymptotic normality of the wavelet estimators of g(⋅) in the heteroscedastic regression model with ANA errors is obtained when f(⋅) is a known or unknown function, respectively. At the same time, we derive a Berry-Esseen-type bound for the estimators of g(⋅). As a corollary, by making a certain choice of the weights, the Berry-Esseen-type bound of the estimator can reach nearly O ( n − 1 / 12 ) , which in some sense generalizes or improves the corresponding ones for negatively associated (NA, for short) random variables and φ−mixing sequence. Finally, the finite sample simulation study presented in this article shows the validity of our theoretical results.

Materials design and strength development of a novel cold recycled mixture with asphalt emulsion and geopolymer

ABSTRACT Cold recycling of asphalt pavement with asphalt emulsion is an important approach for achieving low-carbon and sustainable development in road engineering. Enhancing the performance of cold recycled mixtures has become a key research focus. The objective of this paper is to develop a novel cold-recycled asphalt mixture stabilised with asphalt emulsion and geopolymer (CRM-GE). Firstly, the effects of mixing sequence, geopolymer content, asphalt emulsion content and curing conditions on the strength of the mixture and its time-dependent law are studied. Then, the microstructure and composition of the mixture are analysed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results show that the optimum amount of asphalt emulsion is different under different geopolymer contents. The indirect tensile strength of the mixture specimen increases with the increase in the curing time and curing temperature. The microstructure analysis indicates that geopolymer reaction and asphalt emulsion demulsification in CRM-GE with 7-day curing are relatively limited, while asphalt film and the geopolymer reaction products are intertwined to achieve a denser microstructure in CRM-GE with 28-day curing. In addition, the element analysis further verifies the result of materials design and micromorphology analysis.

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

Influence of mixing protocols on flow retention of one-part alkali activated slag systems

Poor workability and rapid flowability loss are among several challenges hindering the wider acceptance of alkali-activated slag (AAS) (i.e. shrinkage, efflorescence). Several attempts were made to solve this issue, focusing more on selected ingredients, proportions, type and dosage of admixtures, and addition sequence. This study shifted the focus to mixing protocol, highlighting its potential and effects on AAS flow retention considering mixing duration, sequence, and relaxation time. Various one-part AAS mixtures activated by 6 %, 8 %, and 10 % sodium metasilicate were tested. Mixing protocols were applied for 10–90 min, mixing with and without relaxation time. Mini-slump, flowability-loss rate, setting time, the heat of hydration, rheological properties, and compressive strength were evaluated. Changes in hydration products were also examined by XRD, FTIR and TGA. Pearson correlation coefficient and ANOVA were applied to identify the dominant factors. Results reveal the dependency of the optimum mixing protocol on the used activator dosage. A long mixing period with r intervals was more effective for high activator dosages due to the continuous breakdown of formed hydration products' links. Modifying the mixing protocol did not alter the amount of formed hydration products, regardless of the activator dosage. These findings pave the way to understanding the role played by the mixing protocol in mineral hydration for wider in-situ implementation of AAS and the flourishing potential of the ready-mix AAS market.

Tuning polymer micelle size and dynamics with solvophobic block structure

Hypothesis: Micelles formed by copolymers with mixed solvophobic blocks have attracted much attention lately. It is expected that changing the mixed blocks sequence can be used as a tool to influence the micellization behavior in a way that is not equivalent to simply varying the incompatibility parameter for pure diblock-copolymers.Simulations: By using coarse-grained simulations, the micellization behavior of copolymers with twelve types of solvophobic blocks, which differed in the fraction f as well as the sequence of solvophilic units in the solvophobic blocks, was studied. To enable quantitative comparison of systems with different f, an “effective” incompatibility parameter was introduced.Findings: The micelles size distributions and dynamics were found to be significantly dependent on both f and the fine details of the sequence. When the solvophobic block sequences were obtained statistically using a model of copolymerization, a strong influence of the reactivity ratios on the resulting micelles was found. Even a moderate tendency to form gradient-like sequences resulted in a noticeable increase in the micelles size. The dynamic properties of the micelles were studied by investigating the rate at which the chains escape from them. The addition of soluble units into the solvophobic block was shown to dramatically decrease the tendency to form kinetically frozen states; gradient-like sequences demonstrated more sluggish dynamics. The physical reasons for the observed peculiarities are discussed in detail.

Pengaruh Urutan Pencampuran Pemlastis pada Komponding Karet Terhadap Kinetika Vulkanisasi Menggunakan Model Deng-Isayev dan Kamal-Sorour

Plasticizers play an important role in the rubber industry to facilitate the dispersion of additives into rubber. This research aims to study the effect of plasticizer mixing sequence on vulcanization kinetics. This relates to its effect on printing time and energy, as well as the cost of electricity used. Compound A was made by adding plasticizer at the mastication stage and compound B was made by adding plasticizer at the masterbatch stage. Kinetic parameters were determined using Deng-Isayev and Kamal-Sorour models. The results show that the Deng-Isayev model is closer to the experimental data than the Kamal-Sorour model. Compound A has a k value (3.0635x10-6 sec-1) and cure index (0.8403) slightly lower than compound B with a k value 3.3511x10-6 sec-1 and cure index 0.9260. However, the mixing order of the plasticizers did not significantly affect the vulcanization performance, either the reaction speed constant, reaction order, induction time, optimal vulcanization time, and cure index.

The unconventional petroleum system of a mixed siliciclastic-carbonate sequence: Irati Formation, Paraná Basin, Brazil

Widespread rhythmic intercalation of a millimeter- to meter-scale hydrocarbon source rock (organic-rich shale and marlstone) and a carbonate reservoir (micritic and peloidal dolostone) are unusual. Here, the case of the Irati Formation (Paraná Basin) is reported, in which source rock strata have high total organic carbon (averaging 10 to 20 wt%), with dominance of highly oil-prone kerogen type I and II. Multivariate statistical analyses were applied to find patterns in the geochemical multivariate data set. The data points to three main productive sectors in the basin: Paraná Sector, Santa Catarina Sector, and Rio Grande do Sul Sector. Quality, quantity, and petroleum potential vary both laterally and vertically. On the other hand, the reservoir carbonate beds are predominantly composed of low-primary pore space, in which the effective reservoir capacity is determined by the presence of postdepositional secondary porosity. In addition, the Paraná-Etendeka magmatism, which occurred during the break-up of the Atlantic Ocean, played an important role in thermal maturation and primary oil migration.

Icehouse mixed carbonate and siliciclastic sequence evolution based on 3D seismic analysis: Insights from the Eastern Shelf of the Permian Basin, Texas

Reciprocal model was introduced for mixed carbonate and siliciclastic sequences within the Virgilian (Upper Pennsylvanian – Gzhelian) and Wolfcampian (Lower Cisuralian) on the Eastern Shelf of the Permian Basin in Texas. This model emphasizes carbonate dominance during transgressive and highstand on the slope, and siliciclastic dominance in the basin during lowstand. Contradictory observations from other mixed basins, such as compositionally mixed lithology in slope cores, accumulation of siliciclastics behind carbonate highs on the outer shelf, off-shelf transport of siliciclastics during highstands, and carbonate deposition on the slope during falling stage, require a re-evaluation of the reciprocal model. This research examines mixed sequences in the Cisco Group and maps lithology distribution by integrating geological and geophysical data, using advanced seismic interpretation techniques, wireline-log crossplot analyses, model-based post-stack inversion, probabilistic neural networks, and supervised Bayesian classification. Observations from the investigation are presented at two scales. In ∼400kyr sequences, relative sea level fall starts with carbonate deposition on the slope while siliciclastics persist near the inner shelf. As the falling stage progresses, siliciclastics reach the shelf edge, forming offlapping fans at the toe of the slope, likely truncating part of the siliciclastic topsets. Subsequently, mixed facies were deposited during the early stages of rising relative sea level, followed by carbonate deposition on the slope and shelf throughout transgression. The mixed facies found inland of transgressive carbonates indicate that prodelta siliciclastics mixed with carbonate mud. Occasionally, transgressive carbonates create shelf-edge build ups, hindering the transport of highstand siliciclastics to the slope. In the composite sequence spanning ∼1200kyr, siliciclastic input decreases significantly with the onset of sea-level fall. The fall truncates topsets with limited siliciclastics, preserving carbonate and mixed facies-dominated foresets with offlapping fans at the toe of the slope. This study advances our understanding of mixed sequences, challenges existing models and lays the groundwork for future investigations in similar geological settings.

Examining intra-host genetic variation of RSV by short read high-throughput sequencing.

Every viral infection entails an evolving population of viral genomes. High-throughput sequencing technologies can be used to characterize such populations, but to date there are few published examples of such work. In addition, mixed sequencing data are sometimes used to infer properties of infecting genomes without discriminating between genome-derived reads and reads from the much more abundant, in the case of a typical active viral infection, transcripts. Here we apply capture probe-based short read high-throughput sequencing to nasal wash samples taken from a previously described group of adult hematopoietic cell transplant (HCT) recipients naturally infected with respiratory syncytial virus (RSV). We separately analyzed reads from genomes and transcripts for the levels and distribution of genetic variation by calculating per position Shannon entropies. Our analysis reveals a low level of genetic variation within the RSV infections analyzed here, but with interesting differences between genomes and transcripts in 1) average per sample Shannon entropies; 2) the genomic distribution of variation 'hotspots'; and 3) the genomic distribution of hotspots encoding alternative amino acids. In all, our results suggest the importance of separately analyzing reads from genomes and transcripts when interpreting high-throughput sequencing data for insight into intra-host viral genome replication, expression, and evolution.

Reconstructing SARS-CoV-2 lineages from mixed wastewater sequencing data

Wastewater surveillance of SARS-CoV-2 has emerged as a critical tool for tracking the spread of COVID-19. In addition to estimating the relative case numbers using quantitative PCR, SARS-CoV-2 genomic RNA can be extracted from wastewater and sequenced. There are many existing techniques for using the sequenced RNA to determine the relative abundance of known lineages in a sample. However, it is very challenging to predict novel lineages from wastewater data due to its mixed composition and unreliable genomic coverage. In this work, we present a novel technique based on non-negative matrix factorization which is able to reconstruct lineage definitions by analyzing data from across different samples. We test the method both on synthetic and real wastewater sequencing data. We show that the technique is able to determine major lineages such as Omicron and Delta as well as sub-lineages such as BA.5.2.1. We provide a method for determining emerging lineages in wastewater without the need for genomic data from clinical samples. This could be used for routine monitoring of SARS-CoV-2 as well as other emerging viral pathogens in wastewater. Additionally, it may be used to determine more full-genome sequences for viruses with fewer available genomes.

Synergic effects of silica aerogel (SA) particles on tensile behavior of cryo-conditioned epoxy: The role of particle morphology and mixing sequence

Cryogenic conditions are of crucial importance for gas storage tanks to provide increased storage density, reduced pressure requirements and minimized energy losses. Incorporation of silica aerogel (SA) particles as a nanostructured material with extremely low density and exceptional thermal insulating properties into epoxy matrices has the potential to facilitate the progress of high performance nanocomposite coatings for advanced cryogenic applications. The objective of this study is therefore to investigate the impacts of particle size, particle content, milling method and mixing sequence on toughness of the cryo-conditioned epoxy coatings. SA particles of varying size (50 μm to 300 μm) were prepared using two different techniques (planetary ball milling vs. 2-blade grinding). Nanocomposite samples were prepared using two distinct mixing sequences, i.e., adding particles (in 0, 0.5, 1 and 1.5%wt.) to epoxy followed by mixing with hardener or adding particles to epoxy/hardener (with 3 or 15 min delay). The nanocomposite samples were subjected to different cryogenic conditions (single 3-h immersion in liquid nitrogen vs. three consecutive 1-h immersions). Mechanical properties of the samples were evaluated by conducting fractography, dynamic mechanical thermal analysis (DMTA) and tensile tests. Large SA particles settled towards the bottom of nanocomposite and resulted in loss of mechanical properties at cryo-conditions. Mixing 1 wt% of optimized SA particles with epoxy/hardener system led to an enhanced tensile strength (26 %), stiffness (3 %) and toughness (71 %) by providing uniform cross-linking reactions and mitigating thermal shock effects at cryo-conditions. Toughening mechanisms included crack deflection, crack pinning, crack arrest and crack branching.

DNA dynamic coding image encryption algorithm with a meminductor chaotic system

With the acceleration of information technology development, the protection of information security becomes increasingly critical. Images, as extensively used multimedia tools, encounter serious challenges in safeguarding sensitive data, including personal privacy and business confidentiality. This research presents a novel algorithm for color image encryption, that combines a meminductor chaotic system and DNA encoding cross-coupling operations to enhance image security and effectively prevent unauthorized access and decryption. Initially, this paper designs an equivalent circuit model for the Meminductor and constructs the corresponding chaotic system, followed by an in-depth analysis of its nonlinear dynamic characteristics. Then, artificial neuron is employed to perturb the original chaotic sequence generated by the system, resulting in a highly random mixed sequence. The original image is then subjected to rearrangement and encoding through Arnold transformation and dynamic DNA encoding techniques. Additionally, this research introduces a DNA encoding cross-coupling operation method that operates at the block level of pixels to diffuse and confuse image data, enhancing the complexity of the image encryption algorithm. Finally, a dynamic decoding technique is employed to decode the encoded image, yielding the encrypted result. Experimental results show that the algorithm is capable of providing larger key space and higher complexity in image encryption applications, and is able to withstand various types of attacks.

Characterization and mixing sequence to enhance glass fiber performance in cement mixture

Characterization and mixing sequence to enhance glass fiber performance in cement mixture

An average-phase calibration method for the sensing matrix of a Modulated Wideband Converter

As a sub-Nyquist sampling structure based on compressed sensing (CS), a modulated wideband converter (MWC) is used for spectral blind sampling and reconstruction of multiband sparse signals. Sinusoidal signals with known phases have been theoretically used to study the calibration of the sensing matrix of MWC, but in practice, the initial phase of sinusoidal signals is unfortunately difficult to know in advance. Consequently, phase error will exist in the calibrated sensing matrix, which reduces the reconstruction signal-to-noise ratio (RSNR) of the reconstructed signal.In this paper, we first analyze the phase error uncertainty caused by the DC component of the periodic pseudo-random sequence. In addition, an average-phase calibration method based on a 0/1 mixing sequence is proposed to calibrate the sensing matrix. Each column of the sensing matrix is calibrated according to its average phase, which avoids introducing phase error when using sinusoidal signals with arbitrary unknown phases. Comparative experiments are conducted to evaluate the performance of the proposed method in terms of the RSNR and the reconstruction mean squared error (RMSE). The results show that the RSNR obtained by the proposed method is 40 dB, which is close to the signal-to-noise (SNR) of the input RF signal.

Comparative study on pore-connectivity and wettability characteristics of the fresh-water and saline lacustrine tuffaceous shales: triggering mechanisms and multi-scale models for differential reservoir-forming patterns

Although particular attention has been paid to responses of hydrocarbon storage and percolation capacity to the devitrification concerning lacustrine tuffaceous shale reservoirs in recent years, there is still a lack of systematical and comparative investigation on differential patterns and potential triggering mechanisms concerning development of the pore-microfracture systems and characteristics of surface wettability between the fresh-water and saline lacustrine settings, which is of considerable importance in fully understanding of genesis and spatial distribution of dessert reservoir intervals of tuffaceous shale reservoirs, and to provide further conceptual basis for deciphering shale-oil movability of saline lacustrine fine-grained mixed sedimentary sequences. In this study, tuffaceous shales from both the Upper Triassic Yanchang Formation in the Ordos Basin and Middle Permian Jingjingzigou Formation in the Junggar Basin are targeted to unravel the differential behavior of tuff devitrification and potential impacts on reservoir wettability and pore connectivity concerning fresh-water and saline lacustrine settings, and we present new results here from integrated analyses and combined interpretation of FE-SEM, Image Pro Plus (IPP) software image processing, contact angle and spontaneous imbibition experiments. In view of comparative analysis from representative samples, the tuffaceous shales from saline lacustrine environments are characterized by well-developed intergranular-intercrystalline and dissolution pores, and inorganic microfractures, generally yield a higher plane porosity of representative pore-fracture spaces and spontaneous imbibition slopes, a relatively lower average of n-decane contact angles and corresponding wettability parameters. The saline lacustrine tuffaceous shales are thus suspected to have undergone more intense devitrification resulting in a higher amount of devitrification and associated dissolution pores, and a relatively better connectivity between isolated micropore systems with adjacent microfractures. This would significantly facilitate the interface wettability reversal and occurrence of movable hydrocarbon fluid in microscopic reservoir spaces. Finally, a comprehensive and conceptual model is established illustrating the effects of differential devitrification on reservoir-forming patterns concerning tuffaceous shales developed in the fresh-water and saline lacustrine settings, respectively. These findings are of great theoretical and practical significance to enrich theory of high-quality reservoir formation and shale-oil accumulation in saline lacustrine tuffaceous shale reservoirs, and lay the foundation for guiding efficient exploration of continental fine-grained mixed sedimentary sequences.

Effects of Fly Ash and Graphene Oxide in Cement Mortar Considering the Local Recycled Material Context

Construction materials are at the forefront of global economic development as they provide the foundation for the infrastructure of other industries, with cementitious materials being predominantly used in construction projects. To promote sustainable development, alternative materials are added to cement mortar to increase durability and reduce emissions. In this regard, graphene oxide (GO) and fly ash (FA) are two alternative materials commonly used in cement mortar, which are readily available or are just the waste from other local material production. With different ratios, the amount of GO and FA can affect the properties of cement mortar positively or negatively. This study aims to determine the effects of GO and FA on cement mortar mixtures under material conditions. Research results show that 10 wt% FA and 0.036 wt% GO will give cement mortar the best physical and mechanical properties while ensuring other necessary properties, such as workability. When increasing FA to 30 wt% or GO to 0.05 wt%, the strength of the mortar mixture tends to decrease. Another issue is that the specific surface area of graphene is very high, which poses a significant challenge when uniform dispersion in the cement paste mixture is required. Polycarboxylate combined with a specific mixing sequence has demonstrated good dispersibility and high stability. Through this research, it is demonstrated that the addition of GO and FA has the potential for sustainable development of the construction industry by considering the contexts of the local recycled cementitious replacement materials.

Double Percolation of Poly(lactic acid)/Low-Density Polyethylene/Carbon Nanotube (PLA/LDPE/CNT) Composites for Force-Sensor Application: Impact of Preferential Localization and Mixing Sequence.

This study explores the enhancement of electrical conductivity in polymer composites by incorporating carbon nanotubes (CNTs) into a co-continuous poly(lactic acid)/low-density polyethylene (PLA/LDPE) blend, creating a double percolation structure. Theoretical thermodynamic predictions indicate that CNTs preferentially localize in the LDPE phase. The percolation threshold of CNTs in the PLA/LDPE/CNT composites was 0.208 vol% (5.56 wt%), an 80% reduction compared to the LDPE/CNT composite, due to the double percolation structure. This thermodynamic migration of CNTs from PLA to LDPE significantly enhanced conductivity, achieving a 13.8-fold increase at a 7.5 wt% CNT loading compared to the LDPE/CNT composite. The localization of CNTs was driven by thermodynamic, kinetic, and rheological factors, with viscosity differences between PLA and LDPE causing dense CNT aggregation in LDPE. Initial contact of CNTs with PLA reduced aggregation, allowing PLA to infiltrate CNT aggregates during melt-mixing, which influenced the final morphology and electrical conductivity. These findings provide new insights into the fabrication of conductive polymer composites for force sensor applications.

Improved carbon fibers dispersion in geopolymer composites

Carbon fibers (CFs) reinforced alkali-activated (AA) ground granulated blast furnace slag (GGBFS) geopolymer composites have excellent mechanical and thermoelectrical properties, as well as low energy consumption and low CO2 emissions during their production. However, the dispersion of CFs in the geopolymer matrix is always a technical issue in the preparation of the green composite material. Therefore, this study comparatively investigated various dispersion methods, including, mixing sequence (pre-mixing and after-mixing methods), dispersing agent (nano silicon dioxide [nSiO2]), and ultrasonic treatment time (0, 15, 30, and 45 min), as well as CFs content (0.5, 1.0, and 1.5 wt% of GGBFS). The distribution of CFs was then qualitatively and quantitatively evaluated by a series of tests, such as flowability, electrical resistivity, flexural strength, scanning electron microscope (SEM) analysis, and X-ray computed tomography (CT). The experimental results showed that the proposed pre-mixing method provided excellent dispersion characteristics for CFs compared with the after-mixing method. The introduction of nSiO2 can enhance the dispersion of CFs and the mechanical and electrical properties of AA GGBFS geopolymer composites. At a carbon fiber content of 1.5 %, the pre-mixing method and the addition of nSiO2 dispersant reduced the resistivity of the 28-day geopolymer composites by 17.0 % and 38 %, respectively, compared with the after-mixing method. It is feasible to use X-ray CT scanning with the gray-scale frequency map to analyze the dispersion effect of CFs in AA GGBFS geopolymer composites. However, the results were not intuitive when less agglomeration of CFs occurred for the low content of CFs. The scanning method is more applicable to the sample with over 1.0 wt% CFs. The average pixel areas of uniformly dispersed CF bundles in the 2D images of the pre-mixing method and the addition of nSiO2 dispersant specimens were 3.32 % and 6.55 % higher than those of the after-mixing method, respectively. The 2D and 3D scanning results from the dispersion characteristics of CFs were consistent. 2D scanning could provide a time-consuming option for the measurement of CFs dispersion characteristics.

On the Wittmann strong law for mixing sequences

On the Wittmann strong law for mixing sequences

The effect of mixing sequence on synthesis of PP-g-GMA compatibilizer for multilayer packaging (MLP) compounding

Melt recycling Multilayer Packaging (MLP) waste is difficult due to challenging separation procedures. However, blending techniques with compatibilizers can simplify MLP waste melt recycling. PP-g-GMA is a common compatibilizer in polyolefin and PET blends. PP-g-GMA compatibilizer was synthesized by utilizing an internal mixer at 175℃, 50 rpm, and 10 min using styrene as a comonomer. Titration was a method to examine effect of three different sequences of adding the BPO initiator on GMA grafting. Each sequence's PP-g-GMA samples were compounded with MLP waste using a twin-screw extruder and injection molded to make tensile test specimens. FTIR analysis shows that the GMA and Styrene monomers had grafted onto the PP polymer backbone, with the GMA grafting degree by varying mixing sequence. Sequence 3, which introduced initiator, GMA, and styrene simultaneously to PP melt, yielded PP-g-GMA with the most significant GMA grafting degree of 5.11%. Adding PP-g-GMA produced from sequence 3 into the MLP melt enhanced the highest increase in tensile strength and elongation at break of the MLP/PP-g-GMA compound.