Blocking Performance Research Articles

Energy control and block performance optimization of bench blasting

In this study, rock-like model blast tests with varying toe burdens are conducted and the evolution of blast-induced fractures is analyzed using the digital image correlation (DIC) method. In addition, post-blast fragmentations are image-processed to quantitatively investigate the blasting performance. A three-dimensional numerical model is developed and validated against the experimental results. The effects of blasthole inclination (70°, 80°, and 90°) and short delays on fragment size distribution (FSD) are numerically investigated. Field trials are conducted to verify the numerical results. The experimental results reveal that the overall fragment size increases significantly in proportion to the toe burden. The explosion energy utilization rates range from 3.56 % to 13.16 %, with a tendency to initially increase and subsequently decrease. The numerical results demonstrate that fragments are more evenly distributed with a blasthole inclination of 70°, resulting in a remarkable improvement in rock fragmentation compared to a vertical blasthole. Compared to the toe burden, the influence of short delays on concrete fragmentation is insignificant. The field test results indicate that a narrower FSD range and stable pit walls are achieved by utilizing inclined blastholes in bench blasting. This study provides theoretical guidance for optimizing bench blasting parameters, which has practical significance for improving explosive energy utilization and production efficiency in open-pit mines.

Efficacy of ultrasound-guided classical versus parasacral parallel shift technique of sacral plexus block for lower limb surgeries – A randomised controlled trial

Background and Aims: Ultrasound-guided sacral plexus block has been used for anaesthesia and analgesia in lower limb surgeries. This study aimed to compare the block performance characteristics after ultrasound-guided (USG) sacral plexus nerve block (SNB) using the parasacral parallel shift (PSPS) approach versus the classical approach in patients undergoing orthopaedic below-knee limb surgeries. Methods: In this randomised study, 144 adult patients were randomised to receive USG SNB either by the classical approach (Group C) or the PSPS approach (Group P). A fixed dose of 20 ml of 0.5% ropivacaine was administered. Patients also received USG femoral nerve block with 10 ml of 0.5% ropivacaine. The primary outcome was the scanning time between the two groups. Secondary outcomes were the needling time, sensory and motor block onset and postoperative analgesic characteristics between the two groups. A P value of <0.05 was considered statistically significant. Results: The needling time and the scanning time were significantly lesser in Group P than in Group C (P < 0.05). Complete sensory and motor nerve blockade of the sciatic nerve was significantly higher in Group P (P = 0.029). Block performance time, time for sensory block and time for motor block were significantly less in Group P compared to Group C (P < 0.001). The postoperative analgesic characteristics were comparable between the two groups. Conclusion: The sacral plexus block with ultrasound-guided parasacral parallel shift technique had a lower block performance time with lesser needling and scanning time than the classical approach.

Interfacial evaporation device based on melamine foam supported MOFs-derived CuS nanosheets for highly efficient water evaporation

Sunlight-driven interfacial evaporation has been considered an effective solution to address water scarcity and seawater desalination with minimal environmental impact. We designed a sunlight-driven interfacial evaporation device using the porous melamine foam (MF) as the carrier to stabilize the loading of metal−organic frameworks (MOFs) derived CuS nanosheets. The MOFs-derived CuS nanosheets (M-CuS) have a full-spectrum solar light absorption rate of 95% and the porous channels existing inside M-CuS effectively improve the light capturing ability and contribute to the rapid thermal response of M-CuS. The M-CuS was loaded on the MF through the adhesion of polyvinyl alcohol (PVA) to obtain an integrated M-CuS/MF aerogel with a stable structure. PVA further improves the hydrophilicity of MF and ensures a continuous supply of water to M-CuS/MF during the evaporation process. The unique porous structure of M-CuS/MF further promotes the absorption of sunlight, and the low thermal conductivity of MF (0.036 Wm-1K-1) could reduce the radiative and convective heat loss from the material to the surrounding environment. The evaporation rate and photothermal conversion efficiency of CuS/MF are 1.46kgm-2h-1 and 86% under one sunlight, respectively. The continuous seawater evaporation cycle experiments (15 times) show that the device can maintain a stable evaporation rate. The excellent salt blocking performance of M-CuS/MF suggest the promising long-term stable desalination applications.

Improved medical image inpainting using automatic multi-task learning driven deep learning approach

Distorted medical images can drastically reduce diagnosis accuracy using computer-aided diagnostic (CAD) systems. The objective of medical image classification is to improve diagnostic imaging precision and restore regions degraded by image inpainting. Deep Learning (DL) methods like Generative Adversarial Networks (GANs) are being used to solve these medical image inpainting issues. Recently, various improved GAN models were proposed for improved image inpainting, but challenges like computational inefficiency, unreliable restoration quality, and lack of correct analysis of discriminator block. To overcome these problems, a novel GAN model is proposed with modified Generator and Discriminator blocks for improved medical image inpainting. To improve image inpainting quality with minimum computational complexity, the Multi-Task Learning (MTL)-based generator block is designed. The MTL encoder is connected with three decoders for three tasks edge detection, organ boundary generation, and image completion. The MTL-based encoder and decoders are modified with an optimum number of layers and regularization functions to improve the outcomes. The output of the generator block is input into the discriminator block, where we designed the relevant feedback strategy to decrease generator loss by automatically changing the weights on wrong classifications. The simulation results revealed the efficiency of the proposed medical image inpainting approach and discriminator block performances over the state-of-the-art. Due to the modified MTL-based generator and discriminator block in the proposed approach, the PSNR is improved by 14.31 %, SSIM is improved by 8.56%, UQI is improved by 9.45%, and MSE is reduced by 22.78% using the proposed model compared to the state-of-the-arts.

Magnetic restoring forces on rocking blocks

AbstractThis study investigates the idea of adding an extra magnetic restoring force to a rocking block to improve its overall dynamic performance. The proposed concept ensues by introducing a pair of identical magnets to the rocking block. Both magnets are considered lumped on their respective volume centers and are embedded within the rocking block and the supporting base. When properly magnetized, this pair of magnets provides the rocking block with an extra magnetic restoring force which, although it takes on its maximum value when the two magnets are in contact, decreases as the distance between the two magnets increases. The proposed concept, subjected to pulse‐type base excitations, reveals the inherent problem of magnetic restoring forces. From the overturning spectra of the rocking block, it is found that there are cases where the block fails (overturning) in the presence of magnets, while the same free‐of‐magnets block rocks safely (no overturning) when its own weight acts as the only restoring force. This interesting finding appears to be counterintuitive. Is it possible that by providing additional restoring force the block is “driven” to overturn? This study shows that when the rocking block returns toward the vertical position, the angular velocity, in the presence of magnets, is higher than the angular velocity, in the absence of them. This increase in the angular velocity is a direct outcome of the nature of the magnetic restoring forces, and it is mainly the reason that causes the overturning of the rigid block during its free vibration regime. To mitigate the shortcomings of using magnetic restoring forces, the idea of a semi‐active control of the pair of magnets is introduced and explained in detail. This paper concludes with the advantages and potential disadvantages of the overall performance of rigid blocks in the presence of magnetic restoring forces.

Seasonal variation of physical, perceptual, and cognitive function measures in professional academy soccer players

Soccer match play and training have been documented to significantly impair players' physical function and affect their perceptual wellness, indicating the necessity of evaluating the response to mixed-content training across a soccer season (Deely et al., 2022, Front Physiol, 13, 911009; Brownstein et al., 2017, Front Physiol, 8, 831; Thomas et al., 2017, Med Sci Sports Exer, 49, 955-964). This study aimed to assess seasonal variation in physical, perceptual, and cognitive functions in response to training among professional academy soccer players, to identify whether players develop increased physical robustness or encounter greater physiological and psychological impairments due to the demanding training and match schedule. Ethical approval was granted for sixteen academy players (age: 18 ± 1 years) to undergo a range of tests at three seasonal points - early, mid, and late - at baseline, immediately post-strenuous training, and at 24, 48, and 72 h. The testing regime encompassed physical performance (countermovement jump [CMJ], ten-to-five repeated jump test [10/5 RJT]), cognitive function (Stroop task, Four-Choice Reaction Time [FCRT] test, Corsi Block Test), and perceptual responses via an adapted Short Questionnaire of Fatigue (SQF). Linear mixed modelling (LMM) was employed to analyse the impact of season phase and testing time-points on training response, incorporating testing measures as dependent variables. Jump performance varied across time-points, with performance maintained immediately post-training, although displaying decrements at 24 h (P < 0.001), 48 h (P < 0.01), and remained unresolved at 72 h (P < 0.05). Season phase exerted a fixed effect on physical function, with vertical jumps decreasing from both early- (P = 0.033, CMJ; P < 0.001, 10/5 RJT) and mid-season (P < 0.001, CMJ; P < 0.001, 10/5 RJT) to late-season. Perceptual measures—soreness, fatigue, and readiness to train—varied across the week, with immediate post-session impairments recovering by 48 and 72 hours. Cognitive function remained relatively stable across the training week, with only a decline in Corsi Block performance noted immediately post-session. An improvement in FCRT from early to mid-season was observed, though accuracy decreased from early to late-season. No interaction between season phase and training week time-points was found across any variable, indicating a consistent training response throughout the season, despite substantial impairments in physical function and declines in perceptual wellness observed post-training. The decrease in physical function during the late-season phase underscores the need for enhanced recovery focus and training load monitoring as the season progresses.

Comparison of the classical approach and costoclavicular approach of ultrasound-guided infraclavicular block: A systematic review and meta-analysis

Background and Aims: The infraclavicular brachial plexus block (ICB) provides analgesia and anaesthesia of the upper limb. It is given using the classical or the more recently described costoclavicular (CC) approach at the level of cords. This systematic review aimed to assess which approach is better for the ICB in terms of onset, performance, and safety. Methods: This PROSPERO (vide registration number CRD42022361636) registered meta-analysis included randomised trials of patients undergoing upper limb surgery in ultrasound-guided ICB from MEDLINE, EMBASE, SCOPUS, and IRCTP from inception to March 2023. The quality of evidence was assessed using GradePro software. The primary outcomes were sensory and motor block onset time and the number of patients having complete block at 30 minutes. Secondary outcomes included block performance time (BPT), number of attempts, duration of the block, and any incidence of complications. Results: Five trials with 374 adult patients (classic = 185, CC = 189) were included. No significant difference was found in the sensory (Mean difference (MD): 1.44 minutes [95% confidence interval (CI): 3.06, 5.95]; I2 = 95%; very low level of evidence (LOE); P = 0.53) and motor block onset times (MD: 0.83 minutes [95% CI: 0.96, 2.62]; I2 = 84%; very low LOE P = 0.36) and BPT (MD: 5.06 seconds [95% CI: 38.50, 48.63]; I2 = 98%; very low LOE; P = 0.82) in classic and CC approach of ICB. Trial sequential analysis revealed our sample size to be 0.65% of the required sample size to achieve 80% power, deeming our study underpowered. Conclusion: Costoclavicular approach was not superior or inferior to the classical technique for infraclavicular brachial plexus block. However, the quality of evidence is low and further studies are needed to corroborate the findings.

Utility and performance of cell blocks in cerebrospinal fluid cytology: Experience at two teaching hospitals.

Cytology cell blocks (CBs) are not routinely made for cerebrospinal fluid (CSF) specimens. The goal of this study was to identify when CSF CB preparation improves diagnostic performance. Under institutional review board approval, a retrospective review of CSF cytology cases was conducted at a tertiary university-based hospital and an affiliated county hospital. Patient history, CSF volume, final diagnosis, use of stains, and whether the CB was contributory was determined from the cytopathology report. CSF nucleated cell count data was obtained from the medical record. A total of 69 CSF specimens with CBs from January 2006 to March 2023 were identified from 61 patients. The median CSF volume was 8mL (interquartile range, 4-13mL; range, 1-800mL), with immunohistochemical stains performed on 29 (42%) cases. Per cytology report, CB was contributory in 23 cases (33%), not contributory in 34 cases (49%), and not discussed in 12 cases (17%). The median volume was 8mL for cases in which CB was contributory, not contributory, or not discussed. There was no difference in average nucleated cell counts between cases in which CB was contributory versus not contributory (73.9 vs. 40.0, p=.175). CBs for CSF samples were contributory in a subset (33%) of cases. The authors were unable to identify any specific pre-analytic factors, including specimen volume and average nucleated cell counts, for cases in which CB was contributory. Further evaluation is needed to identify if there are scenarios in which CSF CBs should be routinely prepared.

Preparation and Performance Evaluation of Temperature-Resistant and Salt-Resistant Gels.

In order to improve the plugging performance of high-temperature and high-salt oil reservoir plugging agents, this paper utilizes a copolymer composed of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid (AM/AMPS) as the polymer, polyethyleneimine as the cross-linking agent, and nylon fiber as the stabilizer to develop a high-temperature- and high-salt-resistant gel system. This study analyzed and evaluated the temperature resistance, salt resistance and blocking performance of the gel system. The evaluation results show that the gel-forming strength of this gel system can reach an H level, and it has good thermal stability at the high temperature of 130 °C. At the high salinity of 240,720 mg/L, the syneresis rate remains below 2.5%, and the gel-forming time is greater than 15 h; the higher the temperature, the shorter the gelling time. The results of our sand-filled pipe-plugging experiment show that the gel system can adapt to sand-filled pipes with different levels of permeability, and reaching a plugging rate of 94%.

Ultrasonication-based preparation of raw chitin nanofiber and evaluation of its reinforcement effect on chitosan film for functionalization with curcumin

Raw chitin nanofibers (CNF) through an 8-min high-power sonication process were successfully prepared. Well-preserved nanofibers with diameters of 50–100 nm and lengths of 3–10 μm were observed by atomic force microscopy. The high aspect ratio induced strong entanglement under high shear rates, leading to a typical nanofiber four-region shear-thinning behavior. These native chitin nanofibers were incorporated into chitosan film-forming solutions at different concentrations. FTIR results indicated intermolecular hydrogen bonds between CS and CNF. Tensile strength was significantly enhanced with the inclusion of CNF, with the highest stress at 30% CNF incorporation. Elongation at break increased up to 35% with 10% CNF concentration, gradually decreasing with higher CNF content. CS with 20% addition of CNF content was chosen for curcumin addition considering the high mechanical performance and low grammage value. Oxygen transmission rate reduced slowly with increasing CNF concentration, and a significant drop by about 90% was observed upon curcumin inclusion. UV blocking performance and antioxidant ability were drastically improved after curcumin inclusion. The utilization of raw CNF as a film reinforcement nanofiller offers several advantages, including ease of preparation, higher aspect ratio, longer length, and superior mechanical performance. CNF-reinforced chitosan films emerge as potent candidates for functional food packaging materials.

Embodied Energy and Thermal Performance of Alternate Walling Materials in Affordable Housing in the Composite Climate of Delhi

Meeting the affordable housing shortage in India in a short time has its environmental and social challenges. It not only requires huge resources but is also a big social responsibility to provide economical and comfortable housing for the marginalized section of society. Improper selection of construction materials may lead to the locking up of massive energy as embodied energy of materials and uncomfortable indoor living conditions. The present study focuses on the need for consideration of both embodied energy and thermal performance in the selection of materials for the building envelope in naturally ventilated affordable housing in India. Walling materials form a major part of the building envelope and thus it's crucial to assess their performance. This paper presents an analysis of embodied energy and thermal performance of fly ash Bricks, AAC blocks, and RCC precast panels as walling options in comparison to conventional walling material of burnt clay brick in the composite climate zone of Delhi. This analysis is being carried out for the alternate walling solutions in practice or emerging for mid to high-rise EWS housing construction in this region. The embodied energy values per cubic meter are compared for each wall assembly for the lifecycle stage cradle to gate. Thermal simulation results are presented in terms of indoor operative temperatures achieved by each wall type material and compared with the comfort temperature range prescribed by the comfort model IMAC-R, 2022 to find out the ‘discomfort degree hours’. The results of the study underscore the suitability of fly ash bricks and AAC blocks as sustainable alternatives due to their lower embodied energy compared to traditional burnt clay bricks base case. Fly ash bricks even outperform the base case in terms of thermal comfort. The study discourages the use of burnt clay bricks due to very high embodied energy. The study also strongly discourages the use of RCC panels in the composite climate as they exhibit both poor thermal comfort and high embodied energy. The study findings would help government agencies to make environmentally and socially conscious decisions about the use of walling materials on a large scale in meeting the affordable housing demand.

Water-dispersible macromolecular antioxidants for toughening and strengthening cellulose membranes

Biodegradable packaging materials from cellulose are eco-friendly alternatives to traditional petroleum-based plastics. Balancing its mechanical properties as well as protective values (antioxidation, oxygen barrier, etc.) is critical. However, most studies to improve its antioxidation performance were accompanied by sacrificed mechanical properties. In the current work, a series of linear -COOH functionalized phenolic polymers were prepared from phenolic compounds (vanillin, 3,4-dihydroxy benzaldehyde) through a facile tri-component thiol-aldehyde polycondensation. While circumventing the cumbersome protection-deprotection of phenol groups, the one-pot strategy also affords water dispersible polymers for fabricating composites with cellulose nanofibers in an aqueous medium. After introducing 5–10 wt% of the copolymers, a minor soft phase was formed inside the composites, contributing to enhanced mechanical strength, toughness, antioxidation capability, and ultra-violet blocking performance, while its oxygen barrier property was well maintained.

EVALUATING THE PERFORMANCE AND DURABILITY OF CONCRETE PAVING BLOCKS ENHANCED BY BIO-CEMENT POSTTREATMENT

Concrete pavement often experiences accelerated deterioration due to water and chemical ingress through micro-cracks and surface voids. Particularly, the ingress of aggressive agents into the concrete matrix results in irreversible changes and deterioration on its endurance. Numerous studies unveiled that hydrophobic surface protection could be an inexpensive and effective way of enhancing the durability of concrete. This research work aims to assess the feasibility of bio-cement posttreatment for facilitating hydrophobic surface protection, thus enhancing the performance and durability of concrete blocks. Enzyme induced carbonate precipitation (EICP) is one of the promising bio-cement methods. Concrete blocks casted in four different grades were subjected to EICP treatment with different treatment schemes and recipes of cementation media. The treated blocks were tested for water absorption, ultrasonic pulse velocity (UPV) measurements, unconfined compressive strength (UCS), thermal performance, and scanning electron microscopy (SEM). The results indicated that the concrete blocks subjected to EICP posttreatment showed over a 55% reduction in water absorption, a 15% higher UCS and a 6.7% higher UPV when compared with control blocks. The analysis suggested that the EICP posttreatment could enhance the durability of concrete paving blocks by enabling a layer of calcite on the surface and by plugging the transport pore channels of the concrete. Although most of the posttreatment strategies investigated herein were found to be operative, a better response was seen in the posttreatment by spraying scheme with 0.5mol/L cementation media (CM). With the successful demonstration, the EICP treatment prior to the use of concrete blocks can be recommended to the pavement construction industry.

New and Sustainable Coal Char-Based Paving Blocks for Roadway Applications

Paving blocks are widely used in engineering construction for durable pavement surfaces characterized by their interlocking capability to enhance structural integrity. This study explores the potential use of char as a byproduct from coal pyrolysis and an alternative raw material to natural aggregates in developing paving blocks, aiming to reduce the associated environmental issues associated with the uncontrolled and excessive mining of natural resources. This study finds the paving blocks made from char to have the required engineering properties as mentioned by ASTM standard C936. Trass and trass-lime are added as supplementary cementitious materials (SCMs) to enhance the performance of char-based paving blocks. The incorporation of SCMs as a cement replacement also aims to reduce the carbon footprint arising from increased cement use. The compressive strength increased from 55.7 MPa to 65.71 MPa at 12.5% cement replacement with trass-lime. The water absorption is reduced to 4.63% from 4.95%. Beneficial effects towards freeze–thaw durability and abrasion resistance are also observed on trass-lime-incorporated paving blocks. This study signifies the remarkable potential use of coal-derived char and SCMs in developing light, high-strength, and durable paving blocks, showcasing their competitive engineering performance. These new char-based paving blocks will contribute towards a more sustainable construction environment and advance the current construction and engineering practices.

Student Performance and Stress in Histology and Cell Biology in a Redesigned Preclinical Undergraduate Medical Curriculum

In the legacy curriculum at TTUHSC School of Medicine, histology and cell biology were taught in dedicated units in Block 2: Biology of Cells & Tissues (BCT). In Fall 2021 (Class of 2025), a new compressed organ-based integrated curriculum with restructured delivery of histology and cell biology and permanent change to pass/fail grading was implemented. Therein, basic histology was integrated into Unit 1 of Block 1: Anatomy, Histology & Embryology (AHE). Cell biology was divided into AHE and the second unit of Block 2: General Principles (GPX). Our objective was to evaluate performance in histology and cell biology and influential factors, such as student stress and academic and personal concerns in the new organ-based integrated curriculum. For AHE and GPX students completed pre- and post-block surveys regarding stress and academic and personal concerns. Deidentified scores for performance on the 10 most diffcult histology questions on the fall 2021 AHE Exam 1 were compared to the same exam questions in BCT in fall 2020. Scores for the 10 most diffcult cell biology questions on the fall 2021 GPX Exam 2 were compared to those for same exam questions in BCT in fall 2020. Biochemistry performance also was evaluated, as its instruction remained similar to that in the legacy curriculum. Fall 2021 histology scores were markedly lower than scores in fall 2020 (p = 0.002); however, end of block NBME exam scores for histology were comparable to scores in fall 2020 (p = 0.445). Cell biology scores in fall 2021 were moderately lower than in fall 2020 (p = 0.0035). Surprisingly, scores for the 13 most diffcult biochemistry topics in fall 2021 were lower than in fall 2020 (p = 0.0051). AHE pre- and post-block surveys indicated students anticipated dedicating 12% of their time studying histology, but actually allocated 10% of their time. At the start of AHE, the top concern was the amount of material in the block; by the end, it was learning histology. GPX post-surveys indicated student stress was comparable or even less than anticipated. Top concerns were curriculum design, biochemistry, and amount of material. Over 50% of students felt overwhelmed by the amount of material in GPX. In the new curriculum, student performance in histology on the unit exam was attenuated, but NBME exam scores were on par with the legacy curriculum. Student acclimation to the rigors of school and honing of time management skills may explain improved performance at the end of AHE. Lower performance in cell biology and biochemistry might be due in part to inclusion of medical genetics and pharmacology that were not taught in the analogous legacy block. Whether such trends in student performance in these foundational blocks persist in subsequent iterations of the curriculum and potential influence of student perception on performance are being evaluated. Funded through TTUHSC-SOM. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Use and Clinical Relevancy of Pericapsular Nerve Block (PENG) in Total Hip Arthroplasty: A Systematic Review and Meta-analysis.

Ultrasound-guided pericapsular nerve group (PENG) block is an emerging regional anesthesia technique that may provide analgesia for patients undergoing total hip arthroplasties (THA). There are clinical studies comparing this fascial plane block to other established methods; however, evidence on the actual efficacy of this block for THA continues to evolve. Available clinical studies conducted over the past 4 years were reviewed to evaluate the analgesic efficacy and effectiveness of PENG block in patients undergoing THAs. A meta-analysis of randomized controlled trials (RCTs) in patients undergoing THA, where PENG block was compared to no block, placebo/sham block (injection with saline), or other analgesic techniques including suprainguinal fascia iliaca block (FIB), or periarticular infiltration (PAI) was performed. Our primary outcome was opioid consumption during the first 24 hours. Secondary outcomes were postoperative rest and dynamic pain scores at 6-12, 24 and 48 hours, block performance time, sensory-motor assessment, quadriceps weakness, the incidence of postoperative falls, first analgesic request, block and opioid-related complications, surgical complications, patient satisfaction scores, postanesthesia care unit length of stay, hospital length of stay, and functional and quality of life outcomes. We included 12 RCTs with a total of 705 patients. Data showed that PENG block decreased 24-hour oral morphine milligram equivalent consumption by a mean difference (MD) of 3.75mg (95% CI: -5.96,-1.54; P =0.0009). No statistically significant differences in rest or dynamic pain were found, except for a modest MD reduction in dynamic pain score of 0.55 points (95% CI: -0.98, -0.12; P =0.01), measured 24 hours after surgery in favor of PENG block. Our systematic review and meta-analysis suggest that PENG block provides better analgesia, measured as MME use, in the first 24 hours after THA, with no real impact on postoperative VAS scores. Despite statistical significance, the high heterogeneity across RCTs implies that PENG's benefits may not surpass the minimal clinically important difference threshold for us to recommend PENG as best practice in THA.

Blocking mechanisms in area-selective ALD by small molecule inhibitors of different sizes: Steric shielding versus chemical passivation

Small molecule inhibitors (SMIs) hold great promise for area-selective deposition due to their vapor-phase application being compatible with industrial processing. However, to date only a handful of SMIs have been studied, and the mechanisms of precursor blocking require further understanding. In this study, we explore the inhibition of SiO2 ALD on Al2O3 surfaces comparing three SMIs of different sizes: acetic acid (HAc), acetylacetone (Hacac), and 2,2,6,6-tetramethyl-3,5-heptanedione (Hthd). The goal is to unravel the contributions of two important factors to their blocking performance: steric shielding, i.e. physically covering reactive surface sites, and chemical passivation, i.e. chemically consuming surface reactive sites. Experimentally, it is found that HAc and Hthd outperform the previously studied Hacac, as revealed by longer nucleation delays on Al2O3 from in-situ spectroscopic ellipsometry, and by enhanced Si precursor blocking inferred from in-situ infrared spectroscopy. Through density functional theory and random sequential adsorption simulations, we illustrate that varying the size of SMIs brings benefits from either higher steric shielding or better chemical passivation. As compared to Hacac, HAc performs better due to its smaller size, yielding denser packing and thus higher chemical passivation. Hthd on the other hand, benefits from its bulkiness with a higher contribution from steric shielding.

Influence of Microstructure on the Mechanical Properties and Polishing Performance of Large Prehardened Plastic Mold Steel Blocks

The microstructures throughout a 696 × 1360 mm cross-section of an ISO 1.2738 prehardened steel block for a plastic mold were characterized via optical and electron microscopy and electron backscatter diffraction. The hardness, strength, and polishing performance of the steel block were also tested. The results showed that the microstructure of the steel bloom from the edge to the core consisted of tempered sorbite, tempered bainite, and pearlite microstructures. Abnormal upper bainite and coarse carbides were also found. The bloom sections with hardness values of 37.4 to 39.3 HRC comprised tempered sorbite and bainite. The hardness of the core was approximately 36.5 HRC due to the presence of pearlite. The tensile and yield strengths were the same in the edge and middle areas mainly owing to tempered sorbite. The polishing performance was affected by the microstructure. Tempered sorbite produced the best polishing performance due to its fine and uniform microstructure, whereas that of tempered bainite and pearlite, which contained large carbide particles and mixed phases, was worse.

Preparation and performance influencing factors of sludge-based non-sintering ceramsite foam concrete block

In this study, the preparation of ceramsite foam block using Sludge-based Non-sintering Ceramsite (SNSC) was investigated through orthogonal test and performance optimization test to investigate the effects of different coal fly ash addition, volume ratio of SNSC, water binder ratio and sodium silicate concentration on the performance of the concrete block, and the optimal material mixing ratios were obtained as follows: cement was 400 kg/m3, coal fly ash was 100 kg/m3, SNSC was 371 kg/m3, water binder ratio was 0.43, CaCl2 was 10 kg/m3, and Na2SO4 was 5 kg/m3. The performance of Sludge-based Non-sintering Ceramsite Foam Concrete Block under these conditions meets the specification requirements of GB/T 36534–2018 "Ceramsite Foam Concrete Block". Its compressive strength was 7.76 MPa, dry bulk density was 948.7 kg/m3, the water absorption was 20.75 %, and the softening coefficient was 0.861. XRD and SEM analyses revealed that the internal physical phase of the concrete blocks under the optimal conditions was tightly bonded, with fewer and uniformly distributed pores, and that the hydration generated C-S-H, C-A-H gel-like substances, calcium alumina (AFt), and hydrated calcium chloroaluminate generated by hydration could significantly improve the physical and mechanical properties of concrete blocks.

Wave blocking performance of the symmetrical double-wing floating breakwater

In this paper, a double-wing floating breakwater (DWFB) is proposed, that is, the wing with a curved upper surface and flat lower surface is installed on both sides of the box-type floating breakwater (FB). The analytical model of the DWFB under wave action is established to solve the wave diffraction problem. The modified mild slope equation (MMSE) is used to deal with the unsteady water depth problem above the wing, and the reflection coefficient, transmission coefficient, and the wave excitation force in the surge, heave, and pitch are obtained. After the analytical model is verified, the effect of the wing shape and wing size (height and length) on the wave blocking performance of the DWFB is analyzed, and then the single-wing FB and DWFB are compared. The results show that the increase in wing length is obvious to reduce the transmission coefficient. The single-wing floating breakwater (SWFB) with a longer wing length but similar cross-sectional area to the DWFB has a smaller transmission coefficient when the wave number is between 0.45 and 0.85. However, as the wave number continues to increase, the wave blocking performance of the DWFB is relatively better.