Excess Width Research Articles

In-plane Rotation Response of Skewed Simply Supported Bridges Considering Multi-point Pounding Effect

Previous earthquake events have shown that the in-plane rotation of skewed bridges can induce multi-point pounding at longitudinal expansion joints and transversely between the decks and shear keys. These pounding phenomena may result in damage to girders and excessive deck movement. To explore the interaction between multi-point pounding and in-plane rotation response of decks in multi-span skewed simply supported bridges under seismic excitation, simplified equations for estimating bi-directional pounding forces were derived based on the force equilibrium principle. Finite-element models of skewed simply supported bridges incorporating pounding effects were developed, and time-history analyses were conducted to investigate the influence of skew angle, expansion joint width, and shear key capacity on the seismic response of bridges. The analytical results demonstrate the accuracy of the simplified pounding force estimation equations. The interaction mechanism indicates a positive feedback loop between multi-point pounding and in-plane rotation response, in which the two phenomena mutually amplify the responses. Parametric analysis reveals that the maximum seismic response can occur at a skew angle of 30°, an expansion joint width of 10cm, or a shear key capacity exceeding 20%. With increasing expansion joint width and shear key capacity, the multi-point pounding effect and in-plane rotation response can be mitigated. However, an excessive expansion width may induce greater deck displacements, and a higher shear key capacity can lead to damage in the piers.

A new method to evaluate fluoroscopic system collimator performance.

Fluoroscopy uses collimators to limit the radiation field size. Collimators are often evaluated annually during equipment performance evaluations to maintain compliance with regulatory and/or accreditation bodies. A method to evaluate and quantify fluoroscopy collimator performance was developed. A radiation field and displayed image measurement device consisting of radiopaque rulers and radiochromic film strips was placed on the x-ray source assembly exit window to evaluate fluoroscopy collimator performance. This method was used to evaluate collimator performance on 79 fluoroscopic imaging systems including fixed C-arms, mobile C-arms, mini C-arms, and radiographic fluoroscopic systems. The excess length (EL), excess width (EW), and sum EL + EW of the radiation field relative to the displayed image were measured and compared to the limits specified in 21CFR1020.32. Four systems exceeded these limits. Placing the radiation measurement device at the x-ray source assembly exit window relative to the image receptor cover increased the film exposure rate by a factor up to 14.6. The time required to set up and complete the fluoroscopy collimator performance measurements using this method ranged from 5 to 10 min. This method provides an easily implemented quantitative measure of fluoroscopy system collimator performance that satisfies regulatory and accreditation body requirements.

Infrared photodetectors based on wide bandgap two-dimensional transition metal dichalcogenides via efficient two-photon absorption

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention due to their outstanding optoelectronic properties and ease of integration, making them ideal candidates for high-performance photodetectors. However, the excessive width of the bandgap in some 2D TMDs presents a challenge for achieving infrared photodetection. One approach to broaden the photoresponse wavelength range of TMDs is through the utilization of two-photon absorption (TPA) process. Unfortunately, the inefficiency of TPA hinders its application in infrared photodetection. In this study, we propose the design of two photodetectors utilizing high TPA coefficient materials, specifically ReSe2 and MoS2, to exploit their TPA capability and extend the photoresponse to the near-infrared region at 1550 nm. The ReSe2 photodetector demonstrates an unprecedented responsivity of 43 μA W−1, surpassing that of current single-material TPA photodetectors. Similarly, the MoS2 photodetector achieves a responsivity of 18 μA W−1, comparable to state-of-the-art TPA photodetectors. This research establishes the potential of high TPA coefficient 2D TMDs for infrared photodetection.

Vat photopolymerization of silicon carbide strengthened alumina ceramic composites with honeycomb structure for heat insulation and oil/water separation

In this study, the effects of different silicon carbide (SiC) particle sizes on the viscosity and curing behavior of alumina (Al2O3) ceramic suspensions were thoroughly investigated. The findings revealed that increasing the size of SiC particles led to a noticeable decrease in the viscosity of the suspension. The Al2O3 ceramic suspension with 0.6 μm SiC powder demonstrated a shallower cure depth and wider excess width compared to the suspension with 1.0 μm SiC powder. Sintering tests demonstrated that the properties of the SiC–Al2O3 ceramics improved at higher sintering temperatures. Moreover, a high-performance honeycomb ceramic was successfully designed and fabricated with a porosity and compressive strength of 30.8 % and 188 MPa, respectively. Finally, the SiC–Al2O3 honeycomb ceramics were effectively applied in heat insulation and oil-water separation applications, demonstrating their remarkable capabilities.

Digitization method for a photonic analog-to-digital converter with phase-shifted optical quantization.

This Letter proposes a novel, to the best of our knowledge, matrix digitization method for a photonic analog-to-digital converter with phase-shifted optical quantization (PSOQ-ADC). This method overcomes the issues of excessive bit width of the output code and the generation of invalid codes encountered by the traditional direct digitization method. A PSOQ-ADC was fabricated on a lithium niobate on insulator (LNOI) platform, and an experimental platform was built. The results show that RF signals at 1/2/5 GHz, which were sampled by a 50GS/s optical pulse train, were digitized successfully with the matrix digitization method, producing 5-bit codes without invalid codes. In comparison, the direct digitization method yields 10-bit codes, and as the optical signal-to-noise ratio (OSNR) decreases, the ratio of invalid codes increases in the direct digitization method; even with Hamming distance correction, its effective number of bits (ENOB) remains smaller than that of the matrix digitization.

High-performance aluminum nitride made by Vat photopolymerization through optimization of resin refractive index and plasticizer content

In this study, we evaluated the effects of three resins with different refractive index on the viscosity and curing behavior of aluminum nitride (AlN) ceramic suspensions. Our findings indicate that the viscosity of the AlN suspensions increased with the concentration of polyethylene glycol o-phenylphenyl ether acrylate (OPPEA). Conversely, the viscosity decreased with increasing concentrations of cyclic trimethylolpropane formal acrylate (CTFA) and ethylene glycol phenyl ether acrylate (PHEA). Regarding the curing behavior, the AlN ceramic suspension prepared with OPPEA exhibited the largest cure depth and excess width, whereas the suspension prepared with CTFA had the lowest cure depth and excess width. Further analysis of the sensitivity and critical energy revealed that the suspension containing OPPEA demonstrated the highest sensitivity in the vertical direction and the lowest sensitivity in the horizontal direction. This implies that the smallest critical energy is in the vertical direction, and the largest critical energy is in the horizontal direction. Additionally, an increase in the content of the plasticizer dibutyl phthalate (DBP) was beneficial for reducing cracks in the AlN ceramic debinding bodies. Finally, high-performance AlN ceramics were produced, exhibiting a relative density exceeding 98 %, a bending strength of 470.39 ± 6.5 MPa, and a thermal conductivity of 163.45 W/m·K.

Etiology, clinical manifestations, and management methods of cryptitis beside the preputial frenulum in men

BackgroundInflammatory diseases may occur within the crypt beside the preputial frenulum in men. This study was performed to gain an understanding of the etiology, clinical manifestations, and management methods of cryptitis beside the preputial frenulum in men.ResultsThirteen patients treated for cryptitis beside the preputial frenulum served as the observation group, and 40 healthy individuals served as the control group. The patients’ clinical manifestation was the presence of a yellowish oily substance embedded in the crypt. Wiping off the substance revealed a conical blind cavity-like structure with an opening diameter of 1 to 5 mm (2.8 ± 1.3 mm) and depth of 1 to 4 mm (2.5 ± 1.1 mm). No blind cavity-like structures in the crypt were found in the control group. The shortest distance between the opening edges of the bilateral crypts in the observation and control groups was 6 to 14 mm (10.3 ± 2.4 mm) and 2 to 10 mm (3.9 ± 1.9 mm), respectively, with a statistically significant difference. Examination for pathogens in the secretions from skin lesions showed that the three most common pathogens were Candida albicans, Staphylococcus aureus, and Escherichia coli. All patients recovered after antibiotic treatment.ConclusionsA blind cavity-like structure in the crypt may be related to excessive width of the preputial frenulum. Cryptitis may be a secondary infection caused by smegma trapped in the blind cavity-like structure. Maintaining cleanliness in the frenulum area may help to prevent the occurrence of cryptitis. Antibiotic treatment is effective.

Effects of dispersant concentration on the properties of hydroxyapatite slurry and scaffold fabricated by digital light processing

For the UV-curable hydroxyapatite (HA) slurry used in digital light processing (DLP), the optimal dispersant concentration is always selected based on the viscosity and stability of the slurry. However, the interaction mechanism between the dispersant and HA particles and its influence on the fabrication process were overlooked. In this study, the dispersion mechanism of BYK111 and its effects on the rheology, stability, and curing behavior of the HA slurry, as well as the linear shrinkage and layer morphology of the HA scaffold, were systematically investigated. The results indicated that changes in viscosity and stability affected the penetration of UV light and the propagation rate of the polymerization reaction. Insufficient dispersion of the slurry (3 wt% BYK111) led to reduced printing precision due to high viscosity, settling, and scattering. Interestingly, the lower viscosity and enhanced stability of HA slurry with 4 wt% BYK111 did not yield both the deepest curing depth and narrowest excess curing width. The high curing accuracy of the HA slurry (4 wt% BYK111) was evidenced by the largest broadening depth. Moreover, the improved slurry performance also helped reduce printing defects and improve surface quality.

Study on the influence of buried thread nasal augmentation on dorsal soft tissue of nose and revision rhinoplasty

To investigate the influence of buried thread nasal augmentation on dorsal soft tissue of nose and revision rhinoplasty. A clinical data of 29 patients requesting revision rhinoplasty after buried thread nasal augmentation, who were admitted between July 2017 and July 2019 and met the selection criteria, was retrospectively analyzed. All patients were female with an average age of 26.8 years (range, 18-43 years). The patiens were admitted to the hospital at 3-48 months after buried thread nasal augmentation (median, 15 months). Among them, there were 18 cases of insufficient nasal tip projection, 22 cases of insufficient nasal root projection, 7 cases of threads ectasia, 5 cases of threads exposure, 3 cases of infection, and 10 cases with two or more conditions. There were 9 cases of combined short nose deformity, 1 case of spherical hypertrophy of the nasal tip, 3 cases of deviation of the nasal columella, 3 cases of excessive width of the nasal base, and 1 case of nasal hump. Three infected patients only underwent threads removal and debridement. The rest patients underwent revision rhinoplasty, and the dorsum of the nose was made with polytetrafluoroethylene expansion; the tip of the nose was reshaped by taking autologous rib cartilage and alar cartilage in 16 cases, and by taking autologous septal cartilage and alar cartilage in another 10 cases. The threads and surrounding tissue specimens removed during operation were subjected to histologic observation. Nasal length and nasal tip projection were measured after revision rhinoplasty and the ratio was calculated to evaluate the nasal morphology; patient satisfaction was evaluated using the Likert 5-grade scale. Patients were followed up 12-48 months (mean, 18 months). Inflammation was controlled in 3 patients with infections caused by buried thread nasal augmentation. The remaining 26 patients had satisfactory results immediately after revision rhinoplasty. Before revision rhinoplasty and at 7 days and 6 months after revision rhinoplasty, the nasal length was (4.11±0.34), (4.36±0.25), and (4.33±0.22) cm, respectively; the nasal tip projection was (2.34±0.25), (2.81±0.18), and (2.76±0.15) cm, respectively; and the nasal tip projection/nasal length ratio was 0.57±0.08, 0.65±0.05, and 0.64±0.04, respectively. There were significant differences in the nasal length and the nasal tip projection between time points ( P<0.05). There was a significant difference in the nasal tip projection/nasal length ratio between pre- and post-operation ( P<0.05), but there was no significant difference between 7 days and 6 months after operation ( P>0.05). The Likert score for satisfaction ranged from 1.5 to 5.0 (mean, 4.05). During follow-up period of 26 patients, no nasal prosthesis was exposed, and the shape of the nose was stable, and the nasal skin of 5 patients with exposed threads could be seen with different degrees of scarring; there was no infection, cartilage resorption, and no cartilage deformation, displacement, or exposure. Histological observation showed that absorbable threads were not only absorbed after implantation, but also with the prolongation of time, the inflammatory changes in the surrounding tissues caused by decomposition and absorption of the threads showed a gradual aggravation of the first, the heaviest inflammatory reaction in 6 to 12 months, and then gradually reduce the trend. After implantation of the absorbable thread into the subcutaneous tissue of the nasal dorsum, the nature of the thread is different from the body's own tissue, which will affect the soft tissue compliance of the nasal dorsum. The degradation and absorption of the thread will stimulate the infiltration of inflammatory cells and the proliferation of fibroblasts in the surrounding tissue and then form scar tissue, which will affect the design and effect of revision rhinoplasty.

Effect of particle size on rheology, curing kinetics, and corresponding mechanical and thermal properties of aluminum nitride (AlN) ceramic by digital light processing (DLP)-based vat photopolymerization

In this work, the influence of AlN particle size (250 nm, 1.2 µm, and 5 µm) on the curing behavior, stability and viscosity of ceramic suspensions was evaluated. It was revealed that an increase in the particle size of AlN powders reduced the stability and viscosity of the suspension. For curing behavior, the ceramic suspension prepared with 250 nm AlN powder exhibited the smallest curing depth and excess width, whereas the 5-μm ceramic suspension had the largest curing depth. The analysis of the scattering length revealed that a decrease in AlN powder particle size reduced the scattering length. After sintering, both the 250-nm and 1.2-μm samples could be sintered densely at temperatures more than 1800 °C with the relative density greater than 99%. Finally, following a 5 h sintering at 1850 °C, the 250-nm and 1.2-μm samples obtained thermal conductivities of 171 and 174 W/mK, respectively.

Volumetric T2 -weighted spin echo imaging with improved SNR using localized quadratic encoding and a spiral readout trajectory.

To demonstrate T2 -weighted (single-echo) spin-echo (SE) imaging with near-optimal acquisition efficiency by applying SNR-efficient RF slice encoding and spiral readout. A quadratic-phase (frequency swept) excitation RF pulse replaced the conventional excitation in T2 -weighted SE sequence to excite a thick slab that is internally spatially encoded by a variable phase along the slice direction. Highly overlapping slabs centered at every desired slice location were acquired in multiple passes, such that the entire imaging volume was excited by contiguous slabs in any given pass. Following 90° excitation, each slab was refocused with a conventional 180° RF to produce a SE signal, followed by a spiral in-out readout. A noise-insensitive reconstruction removed the quadratic phase in the spatial frequency domain, yielding desired slice resolution and improved SNR. Increasing the RF frequency sweep (hence, excitation width) allowed more frequent encoding of each slice over the multiple passes, improving final image SNR, until crosstalk ensued at excessive slab widths compared to their center-to-center spacing. With an optimized slab width, the proposed technique used all passes to acquire every prescribed slice, with substantially improved SNR over conventional SE or 2D-turbo-spin-echo (TSE) scans. Quantitative SNR measurements indicated similar SNR as 3D-TSE, but radiologist scoring favored 3D-TSE, mainly because of spiral-related artifacts and possibly because of regularized reconstructions in 3D-TSE. Using SNR-efficient slice excitation scheme and spiral readout helped eliminate SNR and temporal inefficiencies in conventional T2 -weighted imaging, yielding SNR independent of TR or number of passes.

Pure shear model for crack width analysis of reinforced concrete members

Reinforcement corrosion in concrete structures with excessive crack width poses a high risk of reducing the structure's service life. The crack width behavior is one of the most complex aspects of the mechanics of reinforced concrete (RC). With most of the models used in practice being semi–empirical or empirical, very few analytical approaches have been proposed. However, the analytical models lack either accuracy or simplicity, or both. This paper presents a new analytical model, termed the Pure Shear Model, that predicts mean crack width by a simple formula. It is based on the partial interaction tension stiffening model considering a short RC tie subjected to short–term loading. The model assumes elastic material properties and neglects shrinkage, internal cracking, and slip at the interface. It presumes that the only deformations that occur in concrete are the shear strains due to shear lag that are taken constant across the cover thickness. Deplanation of concrete section due to shear lag results in crack width linearly increasing from zero at the bar to its maximum value on the surface of the RC member. Despite the simplicity of the proposed model, its accuracy in predicting mean crack width was shown to be comparable to that of the design code methods.

Nonsurgical Rhinoplasty in Patients of African Descent: A Retrospective Review.

There is a paucity of research on nonsurgical rhinoplasty in the population of African descent. In this group, underlying anatomy and aesthetic ideals vary, necessitating differences in the consultation process and in treatment. The authors present a case series from a single clinician's practice performing nonsurgical rhinoplasty on patients of African descent. A retrospective chart review was completed on eligible patients who underwent nonsurgical rhinoplasty treatment with hyaluronic acid filler injections performed by the first author (A.H.) from March of 2018 to February of 2021. Demographic variables, indications for treatment, patient-reported outcomes, and adverse events were reviewed. The authors also share the first author's technique for nonsurgical rhinoplasty in this patient cohort. A total of 487 patients of African descent or mixed race including African descent were included in this study. The most common indications for treatment were lack of bridge definition (63.9%), excessive alar width (61.6%), and a bulbous tip (61.6%). Median filler volume was 0.6 mL (range, 0.3 to 2.1 mL) at the initial treatment visit. There were no reported cases of infection, vascular occlusion, or necrosis. This study is the first to illustrate the effectiveness and safety profile of nonsurgical rhinoplasty in a population of African descent. Anatomical variations and the desire for racially congruent results must be acknowledged to ensure satisfactory outcomes. Therapeutic, IV.

Flexural and deflection behaviour of synthetic fibre reinforced concrete beams reinforced with glass fibre reinforced polymers bars under sustained service load

Glass fibre reinforced polymers (GFRP) bars have attracted increasing interest as a promising alternative for conventional steel reinforcement for its contribution towards sustainability and significantly improving the flexural performance of structural members. To mitigate the excessive deflections and crack widths exhibited by the FRP reinforced concrete members, fibre reinforced concrete (FRC) is employed which improves the toughness and cracking capacity of members. However, available research on the structural performance of FRC has focused on metallic fibres. The research presented in this paper is aimed at experimentally evaluating the influence of synthetic fibres on the time-dependent flexural behaviour of FRC beams reinforced with GFRP bars. Eight simply supported beams with varying synthetic fibre contents and GFRP bar diameters (but same reinforcement ratio) were tested under sustained service load. Creep under compression, concrete shrinkage, cracking moment, and deflection behaviour over 90 days were monitored and analyzed. Investigation revealed that the inclusion of synthetic fibres reduced the concrete deformations under creep and shrinkage by up to 22% and 26% respectively, increased the cracking capacity by 27%, increased the effective moment of inertia by 75%, and also resulted in up to 43% lower deflections. Suitability of several codes to predict the deformations and deflections under short and long-term conditions was also evaluated through comparison of the prediction models to the experimental results. Model proposed by ACI 440.1R-15 was found to predict the instantaneous deflection in beams without fibres with reasonable accuracy, however in FRC-GFRP beams, all models tend to overestimate the deflection. Presented research highlights the need for further investigation on non-metallic fibres and their contribution towards improvement of residual and flexural performance of FRC members to improve the validity of existing analytical prediction models.

The Disc Miner

Detecting planets in the early stages of formation is key to reconstructing the history and diversity of fully developed planetary systems. The aim of this work is to identify potential signatures from planet-disc interaction in the circumstellar discs around MWC 480, HD 163296, AS 209, IM Lup, and GM Aur, through the study of molecular lines observed as part of the ALMA large program MAPS. Extended and localised perturbations in velocity, line width, and intensity have been analysed jointly using the DISCMINER modelling framework, in three bright CO isotopologues, 12CO, 13CO, and C18O J = 2−1, to provide a comprehensive summary of the kinematic and column density substructures that planets might be actively sculpting in these discs. We find convincing evidence for the presence of four giant planets located at wide orbits in three of the discs in the sample: two around HD 163296, one in MWC 480, and one in AS 209. One of the planet candidates in HD 163296, P94, previously associated with velocity signatures detected in lower velocity resolution 12CO data, is confirmed and linked to localised velocity and line width perturbations in 13CO and C18O too. We highlight that line widths are also powerful tracers of planet-forming sites as they are sensitive to turbulent motions triggered by planet-disc interactions. In MWC 480, we identified non-axisymmetric line width enhancements around the radial separation of candidate planet-driven buoyancy spirals, which we used to narrow the location of the possible planet to an orbital radius of R = 245 au and PA = 193°, at a projected distance of 1.33″ from the star. In the disc of AS 209, we found excess 12CO line widths centred at R = 210 au, PA = 151°, at a projected distance of 1.44″, spanning around the immediate vicinity of a circumplanetary disc candidate proposed previously, which further supports its presence. We report no clear localised or extended kinematic signatures in the discs of IM Lup or GM Aur that could be associated with the presence of planets or gravitational instabilities. On the other hand, we demonstrate that pressure minima exhibit line width minima counterparts in optically thick emission, making them robust tracers of gaps in the gas surface density when analysed together with azimuthal velocity flows. Finally, we show that nine out of eleven millimetre dust continuum rings in the sample are co-located with pressure bumps traced by kinematic modulations, indicating that aerodynamic confinement via pressure traps is a common mechanism for the formation of dust substructures in these discs. Overall, our analysis reveals that all discs in the sample present a remarkable level of substructure in all the line profile observables considered, regardless of the CO isotopologue. However, the magnitude and morphology of the substructures vary between discs and tracers, indicating that the kinematics and thermodynamic properties are likely shaped by different physical mechanisms in each object. We propose that the main kinematic signatures identified in the discs of MWC 480, HD 163296, and AS 209 have a planetary origin, although they do not always manifest as highly localised perturbations, while the discs of IM Lup and GM Aur do not yield clear signatures pointing to the presence of massive planets. Our simultaneous analysis of multiple tracers and observables aims to lay the groundwork for robust studies of molecular line properties focused on the search for young planets in discs.

Gaia Data Release 3

Context. The Gaia Radial Velocity Spectrometer (RVS) provides the unique opportunity of a spectroscopic analysis of millions of stars at medium resolution (λ/Δλ ∼ 11 500) in the near-infrared (845−872 nm). This wavelength range includes the Ca II infrared triplet (IRT) at 850.03, 854.44, and 866.45 nm, which is a good indicator of magnetic activity in the chromosphere of late–type stars. Aims. Here we present the method devised for inferring the Gaia stellar activity index from the analysis of the Ca II IRT in the RVS spectrum, together with its scientific validation. Methods. The Gaia stellar activity index is derived from the Ca II IRT excess equivalent width with respect to a reference spectrum, taking the projected rotational velocity (vsini) into account. We performed scientific validation of the Gaia stellar activity index by deriving a R′IRT index, which is largely independent of the photospheric parameters, and considering the correlation with the R′HK index for a sample of stars. A sample of well-studied pre-main-sequence (PMS) stars is considered to identify the regime in which the Gaia stellar activity index may be affected by mass accretion. The position of these stars in the colour–magnitude diagram and the correlation with the amplitude of the photometric rotational modulation is also scrutinised. Results.Gaia DR3 contains a stellar activity index derived from the Ca II IRT for some 2 × 106 stars in the Galaxy. This represents a ‘gold mine’ for studies on stellar magnetic activity and mass accretion in the solar vicinity. Three regimes of the chromospheric stellar activity are identified, confirming suggestions made by previous authors based on much smaller R′HK datasets. The highest stellar activity regime is associated with PMS stars and RS CVn systems, in which activity is enhanced by tidal interaction. Some evidence of a bimodal distribution in main sequence (MS) stars with Teff ≳ 5000 K is also found, which defines the two other regimes, without a clear gap in between. Stars with 3500 K ≲ Teff ≲ 5000 K are found to be either very active PMS stars or active MS stars with a unimodal distribution in chromospheric activity. A dramatic change in the activity distribution is found for Teff ≲ 3500 K, with a dominance of low activity stars close to the transition between partially- and fully convective stars and a rise in activity down into the fully convective regime.

The Influence of Oscillation Parameters on the Formation of Overhead Welding Seams in the Narrow-Gap GMAW Process

Thick-walled X80 pipelines for oil and gas transportation are difficult to relocate due to their large size. In the process of narrow-gap overhead welding, welding defects, such as bulges and lack of sidewall fusion, can appear easily. To avoid these defects and to improve the welding quality of thick-walled pipelines, the GMAW welding method is adopted in this paper. The formation characteristics of the weld and the influence of arc oscillation parameters, such as the oscillation width and sidewall dwell time, on the formation process of narrow-gap overhead welding seams are studied. In this research, it was found that, in the NG-GMAW overhead welding position, there was a downward trend in the middle of the formed surface of the weld pool. Defects, such as finger-shaped penetrations and lack of sidewall fusion, were prone to occur due to gravity. The increased oscillation width was beneficial for reducing the protrusion in the middle of the weld seam, but an excessive oscillation width can easily cause undercut defects. The sidewall dwell time has little effect on the protrusion in the middle of the weld seam, but it can increase sidewall penetration, thereby avoiding the occurrence of incomplete sidewall penetration.

Solution approaches for the bi-objective Skiving Stock Problem

The Skiving Stock Problem (SSP) aims to determine an optimal plan for producing as many large objects as possible by combining small items. The skiving process may need different considerations depending on the production environment and the product characteristics. In this study, we address bi-objective 1D-SSP with two conflicting objectives. One common objective is to minimize the trim loss remaining after skiving, as removing the excess width is an extra procedure. When welding is an element of the skiving process, increasing the number of items for each product indicates compromised quality. Therefore, minimizing the number of small items for each product becomes a primary objective in such cases. To solve this bi-objective version of the NP-hard problem, we implement a Lexicographic Method (LM) in which the importance of the objectives imposes their preference orders. We propose two methodologies within the LM framework. The first methodology integrates Column Generation (CG) and Branch & Bound (B&B) to search for an exact solution. Given the excessive computational time an exact solver may require for tight or large-sized problems, we propose a heuristic method integrating the Dragonfly Algorithm (DA) and a Constructive Heuristic (CH). Real-world application results validate the exact solver and demonstrate comparable results for the heuristic solver in terms of solution quality and computational time. The efficiency of the solution methodologies for a preemptive multi-objective SSP aims to support decision-makers with make-or-buy decisions.

The relationship between electric processing condition and microstructure in the solidification of multicomponent oxides

Systematic characterization for the relationship between the electropulse processing conditions and microstructure has been carried out in the present work. It is found that electropulse can refine porosity and alter grain morphology considerably. A processing with optimum electropulsing parameters can reduce over 75% volume fraction of porosity and more than 70% average pore diameter in comparison with that of reference sample without electric treatment. Electric current treatment promotes the growth of dendrites with smaller thickness of primary arms dendrite and prevents the liquid entrapping between the growing solid grains. The former is caused by the effect of electricity-enhanced kinetic mobility on the radius of curvature at the tip of dendrite. The latter is attributed to the effects of electric thermodynamics on the microstructural formation such as the enhanced connectivity of conductive phase. The microstructures obtained by electropulsing treatment are favourable for heat conduction, structural strength and crack prohibition. However, the excess pulse frequency and pulse width can generate unwanted heat to counteract electric effect. The research reveals the relationship between electric processing conditions and microstructure in a perfectly controversial solidification condition in oxide materials to that of the metals and alloys. The results confirm from the opposite side the validity of the pulsated solidification.

Effects of roadside trees three-dimensional morphology characteristics on traffic-related PM2.5 distribution in hot-humid urban blocks

Urban plants play a significant role in improving the deterioration of air quality caused by extremely heavy traffic. This study aims at exploring the effects of three-dimensional morphology characteristics of road-trees on traffic-related PM2.5 distribution through ENVI-met simulations. Firstly, this study verifies the performance of ENVI-met pollutants dispersion model by comparison with field measurements. Then a typical high-density block model is built and thirteen simulation groups under varied morphology parameters of height of tree, height of trunk and width of crown are designed in ENVI-met. The results indicate that planting 10 m-height roadside trees is effective for pollutant dilution in the vertical direction, and the trees with high trunk height have a strong capacity in clearing the traffic-related PM2.5 at pedestrian level and promote the diffusion of PM2.5, but excessive crown width would cause PM2.5 escaping from the block hardly and increase pedestrian exposure levels. A practical range of plant morphological parameters is recommended and applied in landscape design that takes seasonal requirements into account.