Sequential Space Research Articles

Spatiotemporal Regulation of Hydrogel Actuators by Autocatalytic Reaction Networks.

Regulating hydrogel actuators with chemical reaction networks is instrumental for constructing life-inspired smart materials. Herein, hydrogel actuators are engineered that are regulated by the autocatalytic front of thiols. The actuators consist of two layers. The first layer, which is regular polyacrylamide hydrogel, is in a strained conformation. The second layer, which is polyacrylamide hydrogel with disulfide crosslinks, maintains strain in the first layer. When thiols released by the autocatalytic front reduce disulfide crosslinks, the hydrogel actuates by releasing the mechanical strain in the first layer. The autocatalytic front is sustained by the reaction network, which uses thiouronium salts, disulfides of β-aminothiols, and maleimide as starting components. The gradual actuation by the autocatalytic front enables movements such as gradual unrolling, screwing, and sequential closing of "fingers." This actuation also allows the transmission of chemical signals in a relay fashion and the conversion of a chemical signal to an electrical signal. Locations and times of spontaneous initiation of autocatalytic fronts can be preprogrammed in the spatial distribution of the reactants in the hydrogel. To approach the functionality of living matter, the actuators triggered by an autocatalytic front can be integrated into smart materials regulated by chemical circuits.

A novel multiport converter switching scheme to integrate multiple renewable energy sources

SummaryIn this paper, an innovative switching scheme named simultaneous space vector modulation (SSVM) is proposed for integrating various AC sources in the energy industry using a unified multiport converter. The proposed SSVM technique is applied to the multileg topology of a multiport converter, which is an encouraging option for the grid integration of renewable energy sources and multimachine drives. Considering the shared leg in the multileg converter, the proposed SSVM can utilize the utmost simultaneous switching states between different ports, resulting in lower switching loss and better DC‐link voltage utilization compared with the conventional sequential space vector modulation approach. A novel decision matrix concept is introduced to identify the simultaneous switching states. For this aim, according to the number of ports of the multileg converter, decision matrices containing valid simultaneous switching states are first calculated. Then, they are defined as look‐up tables in the proposed SSVM to be retrieved and exploited in every sampling period. The effectiveness of the proposed SSVM for a seven‐leg version of the multileg converter is assessed using the simulation analysis and real‐time validation. The capability of the proposed SSVM‐based multiport converter in grid integration of AC renewable energy sources is also verified considering two permanent magnet synchronous generator (PMSG)‐based wind turbines with real wind speed patterns. The simulation results confirm that the proposed SSVM is properly able to manage the power flow between different ports and improve the DC voltage utilization and switching loss compared with the sequential SVM.

Perception difference for approaching and receding sound sources of a listener in motion in architectural sequential spaces.

This study investigates the dynamic auditory perception in large sequential public spaces for listeners in motion with a stationary primary sound source. Virtual soundwalks, involving four music and voice sources and validated with in situ soundwalks, were conducted in an exhibition space. The perception differences between the approaching and receding sound sources were explored, and three major effects were found. The rising sound received a higher rating in each room with a greater perceived change in the loudness than the falling sound despite equal changes in both levels (approach effect). The difference was greater for the room connected to the source room. The loudness in the room connected to the source room receives a sharp drop (plummet effect) for the receding sound source, which was larger for music than for voice. The effect of the background sound impairing the perceptual priority of rising sound was profound in the receiving rooms. The loudness patterns could not be extended to other perceptual attributes, including reverberation. An increasing symmetry of the overall perception between the different sound source types was observed (convergence effect) either by the approaching or receding sound sources. The overall asymmetry of the directional aspects occurring with the noise and voice was not as distinguishable as with music.

Photoimageable Organic Coating Bearing Cyclic Dithiocarbonate for a Multifunctional Surface.

We report the fabrication of photocross-linkable and surface-functionalizable polymeric thin films using reactive cyclic dithiocarbonate (DTC)-containing copolymers. The chemical functionalities of these material surfaces were precisely defined with light illumination. The DTC copolymers, namely, poly(dithiocarbonate methylene methacrylate-random-alkyl methacrylate)s, were synthesized via reversible addition-fragmentation chain transfer polymerization, and the reaction kinetics was thoroughly analyzed. The copolymers were cross-linked into a coating using a bifunctional urethane cross-linker that contains a photolabile o-nitrobenzyl group and releases aniline upon exposure to light. The nucleophilic attack of the aromatic amine opens the DTC group, forming a carbamothioate bond and generating a reactive thiol group in the process. The surface concentrations of the unreacted DTC and thiol were effectively controlled by varying the amounts of the copolymer and the cross-linker. The use of methacrylate comonomers led to additional reactive surface functionality such as carboxylic acid via acid hydrolysis. The successful transformations of the resulting DTC, thiol, and carboxylic acid groups to different functionalities via sequential nucleophilic ring opening, thiol-ene, and carbodiimide coupling reactions under ambient conditions were confirmed quantitatively using X-ray photoelectron spectroscopy. The presented chemistries were readily adapted to the immobilization of complex molecules such as a fluorophore and a protein in lithographically defined regions, highlighting their potential in creating organic coatings that can have multiple functional groups under ambient conditions.

Construction of 4-spiroannulated tetrahydroisoquinoline skeletonsviaa sequential ring opening of aziridines and Pictet–Spengler reaction

A stepwise cyclization involving sequential ring opening of aziridines and Pictet–Spengler reaction has been developed for the synthesis of 4-spiroannulated tetrahydroisoquinoline compounds (22 examples).

Synthesis of 3C-alkylated active methylene substituted 2H-indazole derivatives via sequential ring opening of donor–acceptor cyclopropanes and reductive cyclization reaction

A facile synthesis of 3C-alkylated active methylene substituted 2H-indazoles from o-nitrocyclopropanes and primary arylamines catalyzed by Ni(ClO4)2.6H2O/SnCl2.2H2O is reported.

Grid integration of multiple wind turbines using a multi-port converter—A novel simultaneous space vector modulation

In this paper, an innovative approach of integrating multiple doubly-fed induction generator (DFIG)-based wind turbines using a single multi-port converter unit, named as a unified expandable power converter (UEPC) is presented. A novel partial simultaneous space vector modulation (PSSVM) scheme, adopted to the unified structure, is proposed to enhance the operational efficiency and DC-link utilization. The unified configuration can integrate two or more DFIGs through a multi-port converter in a cost-effective and efficient way. The unified structure enjoys compactness, plug & play capability, fewer switches, and a lower installation cost. Comparing with the conventional sequential space vector modulation (SSVM), which only uses the individual active vectors, the proposed PSSVM can utilize common active vectors between different ports, which is the main salient feature of this method. The performance of PSSVM is also validated via an OPAL-RT real-time simulator. The real-time outcomes prove that the proposed PSSVM can improve the DC-link voltage utilization and switching loss compared with the SSVM. The effectiveness of the proposed PSSVM based unified configuration in both normal and faulty conditions are evaluated and compared with the conventional structure using MATLAB/Simulink. The simulation results endorse the finding that regardless of the shared switches in the unified expandable power converter, the independent control and maximum power extraction from the wind are guaranteed using the proposed PSSVM.

Acoustic modeling of sequential spaces: A parametric study

Sound field modeling of sequential spaces is required for large-scale public buildings. A finite element model comprising five successive rooms was used for a parametric study considering, contextual factors (opening dimension and position, number of rooms), acoustic (absorption coefficient and distribution) and source factors (directional radiation from the opening and an additional source), with the following results: (i) In rooms with high absorption, the average sound pressure level (SPL) of the rooms is higher, and the level difference between rooms is smaller with larger opening dimensions. The opening position has a significant impact only for rooms with low absorption. (ii) The level differences between rooms are larger for oblique than horizontal radiation, especially for rooms close to the source. With an additional source (e.g., a heating, ventilation, and air conditioning system or human speech) in a room, the level in that room will be maintained or reduced by approximately ∼10 dB with increasing opening dimensions for high or low room absorption, respectively, whereas the levels in other rooms increase for high room absorption. (iii) Changes to low absorption coefficients have more significant effects. For a given absorption amount, the difference in average SPL in a room between uniform and nonuniform absorption distribution are greater with smaller opening dimensions. (iv) The effect on the average SPL in the first receiving room, caused by adding more sequential rooms is less when the absorption in those rooms is high (e.g., an absorption coefficient of 0.5), and the maximum difference with different absorption coefficients is ∼6 dB, depending on the number of rooms.

Thermoreversible poly(trimethylene carbonate)-based block copolymers containing reactive furfuryl groups via sequential ROP and ATRP

Block copolymers containing poly(trimethylene carbonate) (PTMC) middle block and poly(furfuryl methacrylate) PFMA end blocks were synthesized through sequential organocatalytic ring opening polymerization (ROP) of trimethylene carbonate and thermal and photoinitiated metal-free atom transfer radical polymerizations (ATRP) of furfuryl methacrylate. The thermal and mechanical properties of the triblock copolymers were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamical mechanical analysis (DMA). The crosslinking via Diels-Alder (DA) reaction between the furan groups of the block copolymers and bismaleimide and bisitaconimide was proved by FTIR and DSC and the thermoreversibility properties of the crosslinked polymer were subsequently investigated using DSC and solubility testing.

Further aspects of I K-convergence in topological spaces

In this paper, we obtain some results on the relationships between different ideal convergence modes namely, I K, I K∗ , I, K, I ∪ K and (I ∪K) ∗ . We introduce a topological space namely I K-sequential space and show that the class of I K-sequential spaces contain the sequential spaces. Further I K-notions of cluster points and limit points of a function are also introduced here. For a given sequence in a topological space X, we characterize the set of I K-cluster points of the sequence as closed subsets of X.

AK-SESC: a novel reliability procedure based on the integration of active learning kriging and sequential space conversion method

To deal with evaluating small failure probabilities, AK–SESC: a novel approach integrating an active learning Kriging meta-model (AK-MCS) and the SESC, a sequential space conversion method, is suggested. The efficiency of the proposed approach relies on the advantages of the AK-MCS and its updating feature to evaluate the actual performance function and the superiority of SESC in estimating small failure probabilities. Although there are effective methods for small probabilities, the beauty of this approach is that it is derived from the probability integral with no simplifications while providing results of high accuracy.Different problems were solved to study the AK–SESC applicability. The main effort of this method is reducing the function call numbers of the original SESC while reaching the same accuracy as Monte Carlo Simulation (MCS). The reliability analysis results were compared with the main reliability methods of the Importance Sampling (IS), Subset Simulation (SubSim), Line Sampling (LS), First and also Second-Order Reliability Method (FORM and SORM). The solved problems indicate that the proposed approach provides accurate answers with much fewer function calls than SESC. So, it can be a promising method for reliability analyses involving nonlinear or high-dimensional performance functions with small failure probabilities.

Delayed sequential abdominal wall closure in pediatric liver transplantation to overcome "large for size" scenarios.

Primary abdominal wall closure after pediatric liver transplantation (PLT) is neither always possible nor advisable, given the graft-recipient size discrepancy and its potential large-for-size scenario. Our objective was to report the experience accumulated with delayed sequential closure (DSC) guided by Doppler ultrasound control. Retrospective analysis of DSC performed from 2013 to March 2020. Twenty-seven DSC (26.5%) were identified out of 102 PLT. Transplant indications and type of grafts were similar among both groups. In patients with DSC, mean weight and GRWR were 9.4±5.5kg (3.1-26kg) and 4.7±2.4 (1.9-9.7), significantly lower and higher than the primary closure cohort, respectively. The median time to achieve definitive closure was 6days (range 3-23days), and the median number of procedures was 4 (range 2-9). Patients with DSC had longer overall PICU (22.5±16.9 vs. 9.1±9.7days, p<.05) and hospital stay (33.4±19.1 vs 23, 9±19.8days (p<.05). These differences are less remarkable if the analysis is performed in a subgroup of patients weighing less than 10kg. Two patients presented vascular complications (7.4%) within DSC group. No differences were seen when comparing overall, 3-year graft and patient survival (96% and 96% in the DSC group). DSC is a simple and safe technique to ensure satisfactory clinical outcomes to overcome "large for size" scenarios in PLT. In addition, we were able to avoid using a permanent biological material for closing the abdomen.

Bornology and duality in locally $ \mathbb K $-convex sequential spaces

Bornology and duality in locally $ \mathbb K $-convex sequential spaces

Historical volcanism in the Canary Islands; part 1: A review of precursory and eruptive activity, eruption parameter estimates, and implications for hazard assessment

Despite decadal–millennial repose periods, volcanoes of the Canary Islands pose significant, though poorly understood hazards to local communities and infrastructure. At least 13 volcanic eruptions forming monogenetic cones and lava flows have occurred in the archipelago since 1500 CE: six on the island of La Palma (in 1585, 1646, 1677–1678, 1712, 1949 and 1971), four on Tenerife (1704–1705, 1706, 1798 and 1909), two on Lanzarote (1730–1736 and 1824) and one on the submarine flank of El Hierro (2011–2012). In this paper, we synthesize available data on these historical eruptions, focusing on their physical characteristics and chronological development, and provide new estimates of eruption parameters, such as lava flow runout, area and volume, to inform volcanic hazard assessment in the archipelago. While incomplete and imprecise, historical records indicate that precursory seismicity began days to years prior to eruption onset, consistent with the three months of well-documented unrest for the 2011–2012 eruption. Excluding the atypical 1730–1736 event, eruptions lasted from ten days to a little under five months. Initial eruptive phases usually involved the opening of multiple vents along dike-fed fissures, with Strombolian explosive activity forming monogenetic cones. Lava flow emission generally quickly followed, and later eruptive phases were typically dominated by effusive behavior. Some eruptions (1704–1705, 1824 and 1949), however, had a complex evolution punctuated by the sequential opening of distinct vents several kilometers apart. Total lengths of vent-defined fissures range from 0.2 to 14.0 km, and maximum lava flow runout is 2.7–9.4 km, extending to the coastline in 75% of eruptions. Proximal eruptive deposits cover 1.8–7.8 km2. Published estimates of subaerial eruptive volumes average between 11 and 66 × 106 m3. In comparison, a new empirical relationship based on well-constrained lava flow area and volume data at other basaltic volcanoes yields volumes of 10–76 × 106 m3 for Canary Island eruptions. The 1730–1736 Timanfaya eruption on Lanzarote represents an outlier in the context of historical Canary Island volcanism, with a duration of 2055 days, a total fissure length ≥ 14.4 km defined by at least ten main emission centers, a maximum lava flow length of 21.7 km, a lava flow field area of 146 km2 and volume of at least 2.2–3.7 km3. Historical eruptive rates are low, at 1.0–2.1 × 106 m3/year or 7.3–11.0 × 106 m3/year including the 1730–1736 eruption, in agreement with long-term volcano growth rates based on geologic data. We find no evidence for time-predictable or volume-predictable behavior of the historical eruptive sequence, which has a mean recurrence interval of 39 ± 24 years. Our analysis outlines a useful framework for forecasting the onset, development and style of future eruptions in the archipelago. Further work, particularly detailed field-based studies of eruption deposits and petrologic reconstructions of eruption run-up processes, will help refine our understanding of historical volcanism and associated hazards in the Canary Islands.

Exploring energy-saving refrigerators through online e-commerce reviews: an augmented mining model based on machine learning methods

PurposeBased on climate issues and carbon emissions, this study aims to promote low-carbon consumption and compel consumers to actively shift to energy-saving appliances. In this big data era, online reviews in social and electronic commerce (e-commerce) websites contain valuable product information, which can facilitate firm business strategies and consumer comparison shopping. This study is designed to advance existing research on energy-saving refrigerators by incorporating machine learning models in the analysis of online reviews to provide valuable suggestions to e-commerce platform managers and manufacturers to effectively understand the psychological cognition of consumers.Design/methodology/approachThis study proposes an online e-commerce review mining and management strategy model based on “data acquisition and cleaning, data mining and analysis and strategy formation” through multiple machine learning methods, namely, Bayes networks, support vector machine (SVM), latent Dirichlet allocation (LDA) and importance–performance analysis (IPA), to help managers.FindingsBased on a case study of one of the largest e-commerce platforms in China, this study linguistically analyzes 29,216 online reviews of energy-saving refrigerators. Results indicate that the energy-saving refrigerator features that consumers are generally satisfied with are, in sequential order, logistics, function, price, outlook, after-sales service, brand, quality and space. This study also identifies ten topics with 100 keywords by analyzing 18 different refrigerator models. Finally, based on the IPA, this study allocates different priorities to the features and provides suggestions from the perspective of consumers, the government and manufacturers.Research limitations/implicationsIn terms of limitations, future research may focus on the following points. First, the topics identified in this study derive from specific points in time and reviews; thus, the topics may change with the text data. A machine learning-based online review analysis platform could be developed in the future to dynamically improve consumer satisfaction. Moreover, given that consumers' needs may change over time, e-commerce platform types and consumer characteristics, such as user profiles, can be incorporated into the model to effectively analyze trends in consumers' perceived dimensions.Originality/valueThis study fills the gap in previous research in this field, which uses small-sample data for qualitative analysis, while integrating management ideas and proposes an online e-commerce review mining and management strategy model based on machine learning methods. Moreover, this study considers how consumers' emotional and thematic preferences for products affect their purchase decision-making from the perspective of their psychological perception and linguistically analyzes online reviews of energy-saving refrigerators using the proposed mining model. Through the improved IPA model, this study provides optimizing strategies to help e-commerce platform managers and manufacturers.

How coronavirus disease will change the face of travel medicine.

The current article will review how the coronavirus disease 2019 pandemic has changed travel and travel medicine. Travelers spread severe acute respiratory syndrome coronavirus 2 globally and continue to spread variants. The characteristics of the virus, the place, and time created a perfect storm that allowed the virus to quickly spread globally. The virus spread by every mode of travel with risk of transmission influenced by proximity to an infected person, duration of trip, physical characteristics of the space, and ventilation. Superspreading events were common; a small percentage of infected people accounted for most of transmission. The travel and tourist industry was devastated as lockdowns and quarantines severely restricted domestic and international travel. A trip includes multiple segments and shared sequential spaces, mostly indoors. Creating safe travel requires attention to all segments of a trip. The coronavirus disease 2019 pandemic has affected every part of travel and travel medicine. The rapid development of multiple safe and effective vaccines and their deployment is allowing resumption of travel, yet many populations lack access to vaccines, and high levels of transmission continue in many areas. Providing documentation of vaccination or immunity in a consistent, verifiable, interoperable system is one of many active issues.

Sequential bipolar metric space and well-posedness of fixed point problems

In this paper, we introduce the concept of sequential bipolar metric spaces which is a generalization of bipolar metric spaces and bipolar b−metric spaces and in view of this concept we prove some fixed point theorems for a class of covariant and contravariant contractive mappings over such spaces. Supporting example have been cited in order to validity of the underlying space. Moreover, our fixed point results are applied to well-posedness of fixed point problems.

Sequential time space fractional diffusion equation including nonhomogenous initial boundary conditions

In this research, we discuss the construction of analytic solution of non-homogenous initial boundary value problem including PDEs of fractional order. By means of separation of variables method, the solution is constructed in the form of a Fourier series with respect to the eigenfunctions of a corresponding Sturm-Liouville eigenvalue problem including fractional derivative in Liouville-Caputo sense.

Sound attenuation and reverberation in sequential spaces: An experimental study

Sequential spaces are a spatial system comprising a series of single spaces connected in sequence by openings. They are not uncommon in the built environment and have similar acoustic characteristics with long and coupled spaces. To explore the sound attenuation and reverberation in such spaces, nine in situ measurements were conducted to examine the effects imposed by four factors, namely, opening on separating partition, number of separating partitions, source position, and acoustic absorption. Results revealed that if more rooms were connected by openings, although there could be significant changes in the distribution of sound pressure level, the resulting difference on the average level of each room is almost unobservable in the connecting rooms. In addition, T20 of each room decreases in the source and receiving rooms, especially in the rooms with a larger source distance. According to the source position, the level difference between adjacent rooms by the first separating partition is larger than those in the successive ones when the space is divided by different number of separating partitions in the same construction. A larger source–opening distance results in a larger level difference across the spaces unless the source is placed along the opening. Increasing acoustic absorption in some rooms did not affect the level difference between those unincreased rooms.

Synthesis and micellar property of amphiphilic brush-arm star copolymers via living ROMP

Norbornene macromonomers (MMs) with polystyrene (PS) or poly(tert-butyl acrylate) (PtBA) side chains were synthesized by a combination of atom-transfer radical polymerization (ATRP) and click reactions. A series of amphiphilic linear and star-shaped brush block copolymers were obtained through sequential ring opening metathesis polymerization (ROMP) of MMs by the use of the highly active olefin metathesis Blechert's catalyst and tri-functionalized Blechert's catalyst respectively, followed by hydrolysis reaction. These well-defined diblock molecular brushes can undergo further self-assembly to form spherical micelles in solution, which have been characterized using DLS, AF4-MALLS, AFM, TEM and fluorescence spectra. The dynamic diameter increases as the hydrophilic backbone content increases for the vast majority of the linear and star copolymers. Brush-arm star diblock amphiphilic copolymers have smaller hydrodynamic diameter and aggregation number than the corresponding linear analogues. Moreover, the critical micelle concentration (CMC) values of star diblock copolymers show less sensitive to the variety of composition.