Release Rate Research Articles

Tannic acid coated ammonium polyphosphate: For flame retardant and UV resistant of polypropylene

Polypropylene (PP) has the advantages of excellent mechanical properties and easy molding, but its shortcomings such as high flammability and poor ultraviolet (UV) resistance cannot be ignored. In this paper, APP was used as the core, 1, 10-diamino-decane (DA) was used as a "bridge" to connect TA to the surface of APP, obtaining TAPP through oxidation self-polymerization. The addition of TAPP greatly improved the flame retardancy and UV resistance of PP matrix. The limiting oxygen index of the PP/22.5 %TAPP sample was increased to 31.0 %, and it was able to pass the UL-94 V-0 rating without droplet produced. Compared with PP samples, the peak heat release rate and peak smoke release rate of PP/22.5 %TAPP sample were reduced by 65.0 % and 44.7 %, respectively. In addition, the tensile strength and impact strength of PP/22.5 %TAPP samples decreased by only 2.7 % and 15.0 % after 60 h UV irradiation. The results showed that the addition of TAPP effectively improved the flame retardancy and UV aging resistance of PP. This study provides a feasible method for the preparation of anti-UV aging and flame-retardant PP composites.

Generative discovery of safer chemical alternatives using diffusion modeling: A case study in green solvent design for cyclohexane/benzene extractive distillation

Over the past century, advancements in chemistry have significantly propelled human innovation, enhancing both industrial and consumer products. However, this rapid progression has resulted in chemical pollution increasingly surpassing planetary boundaries, as production and release rates have outpaced our monitoring capabilities. To catalyze more impactful efforts, this study transitions from traditional chemical assessment to inverse chemical design, introducing a generative graph latent diffusion model aimed at discovering safer alternatives. In a case study on the design of green solvents for cyclohexane/benzene extraction distillation, we constructed a design database encompassing functional, environmental hazards, and process constraints. Virtual screening of previous design dataset revealed distinct trade-off trends between these design requirements. Based on the screening outcomes, an unconstrained generative model was developed, which covered a broader chemical space and demonstrated superior capabilities for structural interpolation and extrapolation. To further optimize molecular generation towards desired properties, a multi-objective latent diffusion method was applied, yielding 19 candidate molecules. Of these, 7 were identified in PubChem as the most viable green solvent candidates, while the remaining 12 as potential novel candidates. Overall, this study effectively designed green solvent candidates for safer and more sustainable industrial production, setting a promising precedent for the development of environmentally friendly alternatives in other areas of chemical research.

Targeted and Therapeutic Efficacy of 5-Fluorouracil-Loaded Polylactic Acid Nanocomplexes in Gastric Cancer

Gastric cancer (GC), arising from gastric mucosal cells, necessitates innovative treatment strategies beyond conventional surgical approaches. While 5-fluorouracil (5-FU) has demonstrated efficacy in various cancers, its lack of selectivity for cancer cells and limited half-life pose challenges. This study focuses on assessing the therapeutic potential of 5-FU-loaded L-polylactic acid (PLLA) nanofibers (NFs) for targeted GC treatment. The preparation of 5-FU/PLLA NFs involved refining the drug delivery approach to enhance drug impact on GC cell proliferation and apoptosis. Utilizing an organic phase separation methodology, 5-FU was incorporated into PLLA NFs, and the NF morphology was examined using scanning electron microscopy, with optical microscopy used for diameter measurement. Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) explored binding state and PLLA crystallinity. Drug loading (DL) capacity and in vitro release characteristics were evaluated by UV-visible spectrophotometry, while NF degradation and stability were assessed. The human gastric adenocarcinoma (AGS) cell line was employed in cell experiments, with three groups: normal culture (Normal group), single drug treatment with 5-FU (5 μmol/L, 5-FU group), and 5-FU-loaded PLLA group (5-FU/PLLA group) containing 5 μmol/L 5-FU. Cell Counting Kit-8 gauged cell proliferation and viability, and Annexin V-FITC/PI assay determined cell apoptosis. Results revealed a (1,230.8±18.9) nm diameter for 5-FU/PLLA NFs with 18.3% crystallinity. FTIR and DSC analyses indicated a simple physical mixture of 5-FU and PLLA in 5-FU/PLLA. DL capacity was (18.1±2.3)%, with a DL efficiency of (92.5±9.4)%. in vitro release performance of 5-FU/PLLA surpassed that of raw 5-FU. The mass loss rate of 5-FU/PLLA was consistent across different pH buffer solutions, with a stable drug release (DR) rate over various storage times. In cell experiments, both 5-FU and 5-FU/PLLA groups exhibited reduced proliferation and viability compared to the Normal group, with higher apoptosis rates (P < 0.05). Furthermore, the 5-FU/PLLA group showed decreased proliferation and viability compared to the 5-FU group, accompanied by higher apoptosis rates (P < 0.05). In conclusion, 5-FU-loaded PLLA NFs, with excellent DR properties, demonstrated significant inhibitory and cytotoxic effects on GC cells.

Leucine requirement determined in healthy young adult males using the indicator amino acid oxidation method.

BackgroundPrevious studies proposed varying leucine requirements for adults ranging from 25 to 40 mg⋅kg-1⋅d-1, but often these studies did not test intakes exceeding 40 mg⋅kg-1⋅d-1. Data using the indicator amino acid (IAAO) method suggest a higher requirement of 55 mg⋅kg-1⋅d-1 based on the total BCAA requirement, but not leucine independently. ObjectiveThe IAAO method was used to determine the leucine requirement in healthy young adult males. MethodsTen healthy adult males (26.9 ± 1.87 y, mean ± SEM) were studied at 7 leucine intakes; each studied over a 3-d period. Following 2-d of pre-adaptation to adequate protein intake (1.0 g⋅kg-1⋅d-1), subjects received experimental diets containing the randomly assigned test leucine intake (10, 20, 30, 40, 50, 65, and 75 mg⋅kg-1⋅d-1) for 8 h. The rate of release of 13CO2 from the oxidation of L-[1-13C]phenylalanine (F13CO2) was measured on the 3rd d, and the leucine requirement was determined using mixed-effect change-point regression and the F13CO2 data in R. The 95% CI was calculated using parametric bootstrap. The effect of leucine intake on the concentration of plasma amino acids (AAs), insulin and glucose were assessed using repeated measures ANOVA and linear-mixed effects. ResultsThe mean leucine requirement was 33.6 mg⋅kg-1⋅d-1 with a lower and upper 95% confidence of 26.16 to 41.04 mg⋅kg-1⋅d-1. Higher leucine intakes were associated with increased plasma leucine, and decreased valine, isoleucine, and serine concentrations. ConclusionThe leucine requirement of young adult males is approximately 34 mg⋅kg-1⋅d-1 which aligns with previously published tracer balance experiments. Clinical Trials Registry# NCT05394155, https://clinicaltrials.gov/study/NCT05394155?term=leucine%20young%20adult&rank=1Data described in the manuscript, code book, and analytic code will be made available upon request pending application and approval, and payment.

Fatigue and delamination of 6061 aluminum cold spray on a similar wrought substrate

Fatigue crack growth and fracture of a thick 6061 aluminum cold spray coating on 6061-T6 aluminum substrate were studied through in-situ observation of fatigue crack growth through the coating to the interface in notched four-point bend samples. Mode I cracking was observed through the coating before delamination at the substrate. Crack tip strain fields during the delamination event were plotted with DIC. Interfacial steady-state strain energy release rates were measured using the bimaterial four-point bend solutions by Charalambides. The interfacial crack primarily spread cleanly along the coating/substrate interface, with a post-fracture surface morphology containing a wavy structure with an amplitude on the same order of magnitude as the cold spray particle diameters. The in-situ video of crack propagation and coating-substrate delamination provides lessons for improving the coating-substrate interfacial toughness and thus expands use cases for structural cold spray applications

Fracture behavior of thermal mismatch in functionally graded materials using phase-field modeling

A phase-field modeling is presented to study the complex thermal mismatch fracture behavior in functionally graded materials. The fracture resistance in functionally graded materials is homogenized by the rule of mixtures of the energy release rate. For validation, the bi-material plates and rectangular plates coated with functionally graded materials under thermal load are examined and the obtained results are compared with existing theoretical and experimental data. In the bi-material plates, the model captures commonly experimentally observed crack patterns such as the perpendicular crack, benching, and the formation of two pairs of parallel cracks. Additionally, a detailed comparison of the correlation between crack depth and film thickness is conducted among theoretical, experimental, and phase-field model data. Notably, the results of the phase-field model exhibit good agreement with experiments compared to the theoretical model. Subsequently, the model is applied to examine the thermal mismatch fracture behavior in plates of different shapes. The analysis emphasizes three key aspects: (i) examining the damage field to understand crack initiation and propagation, (ii) analyzing the major principal stress field in the coatings to identify fracture-critical regions, and (iii) tracking the evolution of elastic/fracture/total energies to investigate the fracture/deformation behavior. This analysis enhances a fundamental understanding of thermal fracture mechanisms in functionally graded materials and provides a foundation for optimizing materials and structures in various engineering applications.

Enhancement of adhesion strength in viscoelastic unsteady contacts

We present a general energy approach to study the unsteady adhesive contact of viscoelastic materials. Under the assumption of infinitely short-range adhesive interactions, we exploit the principle of virtual work to generalize Griffith’s local energy balance at contact edges to the case of a non-conservative (viscoelastic) material, subjected to a generic contact time–history. We apply the proposed energy balance criterion to study the approach–retraction motion of a rigid sphere in contact with a viscoelastic half-space. A strong interplay between adhesion and viscoelastic hysteretic losses is reported which can lead to strongly increased adhesion strength, depending on the loading history. Specifically, two different mechanisms are found to govern the increase of pull-off force during either approach–retraction cycles and approach – full relaxation – retraction tests. In the former case, hysteretic losses occurring close to the circular perimeter of the contact play a major role, significantly enhancing the energy release rate. In the latter case, instead, the pull-off enhancement mostly depends on the glassy response of the whole (bulk) material which, triggered by the fast retraction after relaxation, leads to a sort of ‘frozen’ state and results in a flat-punch-like detachment mechanism (i.e., constant contact area). In this case, the JKR theory of adhesive contact cannot be invoked to relate the observed pull-off force to the effective adhesion energy, i.e. the energy release rate G, and strongly overestimates it. Therefore, a rigorous mathematical procedure is also proposed to correctly calculate the energy release rate in viscoelastic dissipative contacts.

Modulation of rapeseed protein nanoparticles by interaction with chitosan: Enhancing the physical stability, antioxidant activity and β-carotene slow-release properties of Pickering emulsion

This study aimed to investigate the physical stability, oxidation, digestibility and β-carotene sustained-release properties of Pickering emulsions stabilized by rapeseed protein (RP) complexed with chitosan (CS). The results showed that adding CS to RP decreased the RP mean particle size from 3575.0 to 130.9 nm, increased its zeta-potential from 29.6 to 41.4 mV, changed its tertiary structure, and enabled its uniform dispersion. Additionally, CS addition improved RP interfacial properties at air/water and oil/water interfaces, thereby enhancing its emulsification activity and stability. Rheological property analysis exhibited that RP/CS complex had a smaller storage modulus (G′) and loss modulus (G") as well as a higher apparent viscosity. Moreover, the RP/CS complex stabilized emulsions showed a smaller average particle size of 100–1500 nm, a higher zeta-potential of 58–66 mV and better physical stability, thus better tolerating environmental factors such as time, temperature and salt ions. Furthermore, the RP/CS complex stabilized emulsions showed better antioxidant properties with a lower peroxide value (POV) and thiobarbituric acid reactant value (TBARS). Finally, the RP/CS complex emulsions exhibited better antidigestive stability and could slow down the β-carotene release rate. These results provide a theoretical basis for the application of RP/CS complex as a new food emulsifier in the nanocolloid transport system.

A manganese doping deficient cerium base metal organic framework as radical scavenger for highly-durable proton exchange membrane water electrolysis

Eliminating hydrogen peroxide and free radicals from electrochemical reactions is crucial for mitigating chemical degradation and improving the durability of proton exchange membranes (PEMs). Herein, we prepare a metal–organic framework containing manganese and cerium ions that possesses oxygen vacancy defects and amino functional groups. The prepared Ce4MnBDC-NH2 acts as a catalyst for H2O2 decomposition and as a free radical scavenger, and it is incorporated into a perfluorosulfonic acid (PFSA) ionomer matrix. Featuring large pore volume, high porosity, and abundant amino groups, the Ce4MnBDC-NH2 is locked in a PEM. The obtained Ce4Mn-NH2BDC@PFSA composite membrane exhibits high dimensional stability, excellent proton conductivity and low high-frequency impedance, yielding a proton conductivity of up to 137 mS cm–1 and superior water electrolysis performance of up to 1.83 V at 3.0 A cm–2. Moreover, the obtained Ce4Mn-NH2BDC@PFSA membrane experiences lower weight loss during the Fenton reaction, a low fluoride-ion release rate, and excellent stability in high current density durability testing: its decay rate is only 5.2 μV h–1, which is lower than that of CeO2@PFSA and Nafion 117 membranes. This work provides a promising method to prepare efficient free radical scavengers for steady-state PEM water electrolysis.

Matrix metalloproteinase-responsive hydrogels with tunable retention for on-demand therapy of inflammatory bowel disease

Therapeutic options for addressing inflammatory bowel disease (IBD) include the administration of an enema to reduce intestinal inflammation and alleviate associated symptoms. However, uncontrollable retention of enemas in the intestinal tract has posed a long-term challenge for improving their therapeutic efficacy and safety. Herein we have developed a protease-labile hydrogel system as an on-demand enema vehicle with tunable degradation and drug release rates in response to varying matrix metalloproteinase-9 (MMP-9) expression. The system, composed of three tailored hydrogel networks, is crosslinked by poly (ethylene glycol) (PEG) with 2-, 4- and 8-arms through dynamic hydrazone bonds to confer injectability and generate varying network connectivity. The retention time of the hydrogels can be tuned from 12 to 36 h in the intestine due to their different degradation behaviors induced by MMP-9. The drug-releasing rate of the hydrogels can be controlled from 0.0003 mg/h to 0.278 mg/h. In addition, injection of such hydrogels in vivo resulted in significant differences in therapeutic effects including MMP-9 consumption, colon tissue repair, reduced collagen deposition, and decreased macrophage cells, for treating a mouse model of acute colitis. Among them, GP-8/5-ASA exhibits the best performance. This study validates the effectiveness of the tailored design of hydrogel architecture in response to pathological microenvironment cues, representing a promising strategy for on-demand therapy of IBD. Statement of significanceThe uncontrollable retention of enemas at the delivery site poses a long-term challenge for improving therapeutic efficacy in IBD patients. MMP-9 is highly expressed in IBD and correlates with disease severity. Therefore, an MMP-9-responsive GP hydrogel system was developed as an enema by linking multi-armed PEG and gelatin through hydrazone bonds. This forms a dynamic hydrogel characterized by in situ gelation, injectability, enhanced bio-adhesion, biocompatibility, controlled retention time, and regulated drug release. GP hydrogels encapsulating 5-ASA significantly improved the intestinal phenotype of acute IBD and demonstrated notable therapeutic differences with increasing PEG arms. This method represents a promising on-demand IBD therapy strategy and provides insights into treating diseases of varying severities using endogenous stimulus-responsive drug delivery systems.

Green synthesis of a P/N/B-containing aggregate for boosting fire-retardancy of PA6/aluminum diethylphosphinate composites

The intrinsic flammability of polyamide 6 (PA6) has significantly impeded its broad application regardless of its balanced physical properties. Aluminum diethylphosphinate (ADP), as a P-containing fire retardant, has been demonstrated to be effective in reducing flammability of PA6 because of its dual-phase modes of action by creating an intact protective char layer and inhibiting the burning process. However, the efficiency of ADP needs to be further improved for creating cost-effective fire-retardant PA6, in addition to its relatively high cost. To boost its efficiency, we, here, report a P/N/B-containing aggregate (MBA) as an effective synergist via green self-assembly of melamine (MA), boric acid (BA) and amino trimethylene phosphonic acid (ATMP) in an aqueous medium. The results show that the inclusion of 5 wt% MBA and 10 wt% ADP leads to a significantly reduced peak heat release rate (PHRR) by 52.5% compared to neat PA6, in addition to a desired UL-94 V-0 rating. A synergistic effect of 55.4 % is observed between MBA and ADP in terms of the PHRR value. This work provides a facile green strategy for developing eco-friendly multiple elements-containing fire retardants, which can be used as fire retardants alone or high-efficiency synergists for other fire retardants.

Novel biofuel blends for diesel engines: Optimizing engine performance and emissions with C. cohnii microalgae biodiesel and algae-derived renewable diesel blends

Fossil diesel is a significant global fuel; however, environmental concerns and resource scarcity necessitate alternative fuels. Third-generation microalgae biodiesel (MB), despite its carbon neutrality, leads to higher oxides of nitrogen (NOx) emissions and poor engine performance. Renewable diesel (RD), also known as hydrotreated vegetable oil (HVO), could reduce these issues. A quasi-dimensional multi-zone combustion model is employed in this study to look into how different fuel blends of diesel, C. cohnii MB, and algae-derived RD affect the performance, combustion, and emissions of a compression ignition (CI) engine. The study uses a 2000 rpm engine arrangement with different engine loads, and validates the computational analysis with an experimental test engine arrangement. The study aims to explore the potential of sustainable biofuels in CI engines. D70MB30 (70 vol% diesel, and 30 vol% MB) fuel blend leads to a higher ignition delay period (IDP) while lowering peak cylinder pressure (PCP) and peak heat release rate (PHRR) compared to D100; however, when RD is added to diesel-MB fuel blends, it reduces IDP and increases PCP and PHRR. Brake specific fuel consumption (BSFC) for the D70MB30 blend rises by 5.28–8.9 %, while brake thermal efficiency (BTE) reduces by 0.98–4.27 %. However, RD in MB blends reduces BSFC by 1.57–3.41 % and marginally enhances BTE, resulting in greater fuel economy and efficiency. D70MB30 fuel blend results in higher specific carbon dioxide (CO2) emissions and oxides of nitrogen (NOx) emissions while lowering particulate matter (PM) and smoke emissions compared to neat diesel due to its high intrinsic oxygen content. In contrast, RD with the MB blend reduces specific CO2 and NOx emissions; however, it increases PM and smoke emissions due to the NOx-PM trade-off. The optimum results occur with a full load and D70MB15RD15 (70 vol% diesel, 15 vol% MB, and 15 vol% RD) fuel blend. Compared to the D70MB30 blend, D70MB15RD15 reduces BSFC, specific CO2, and NOx by 2.15 %, ∼1%, and 8.37 %, respectively, while increasing PM emissions at 100 % load.

Enhancing diesel engine performance and emission reduction through hydrogen enrichment in algal biodiesel blends.

The introduction of hydrogen into the engine could enhance its combustion efficiency and emission characteristics. The current study examines the attributes of compression ignition (CI) engines by introducing hydrogen into a biodiesel blend derived from algae. The improved thermal properties of hydrogen, when combined with algae biodiesel, significantly affect the performance, combustion, and emissions of dual-fuel engines. A study was conducted to evaluate the impact of hydrogen enrichment levels of 5%, 10%, 15%, and 20% of the nozzle volume on a biodiesel blend fuel. In comparison to diesel, algal biodiesel reduces emissions of unburned hydrocarbons (HC), carbon monoxide (CO), and oxygen (O2) by 5.19%, 3.61%, and 2.83%, respectively, while increasing nitrogen oxide (NO) emissions by 4.73%. In contrast to biodiesel, diesel demonstrated superior brake thermal efficiency (BTE) and lower specific energy consumption (SEC). Injecting hydrogen into A20 blend fuel at volumes of 5%, 10%, 15%, and 20% results in a respective increase in brake thermal efficiency of 2.65%, 2.97%, 3.50%, and 4.15%. The addition of hydrogen gas to biodiesel blends further enhances their combustion qualities, leading to elevated peak cylinder pressure, temperature, and heat release rate. The results indicate that A20H5, A20H10, A20H15, and A20H20 fuel reduced CO emissions by 3.75%, 8.75%, 12.5%, and 16.25%, respectively, compared to the A20 blend. In the same vein, HC emissions decreased by 5.76%, 10.29%, 15.52%, and 18.98%, respectively, as compared to A20 fuel. However, NO emissions rose by 5.36%, 10.20%, 15.28%, and 23.23%, respectively, for A20H5, A20H10, A20H15, and A20H20 test fuels. Ultimately, the utilization of algal biodiesel and hydrogen enrichment in diesel engines was proven to substantially reduce pollutants while increasing efficiency. This study contributes valuable insights into the intersection of renewable fuels, hydrogen enrichment, and engine technology, with the potential to drive significant advancements in sustainable transportation and environmental conservation.

Carbon-Spaced Tandem-Disulfide Bond Bridge Design Addresses Limitations of Homodimer Prodrug Nanoassemblies: Enhancing Both Stability and Activatability.

Redox-responsive homodimer prodrug nanoassemblies (RHPNs) have emerged as a significant technology for overcoming chemotherapeutical limitations due to their high drug-loading capacity, low excipient-associated toxicity, and straightforward preparation method. Previous studies indicated that α-position disulfide bond bridged RHPNs exhibited rapid drug release rates but unsatisfactory assembly stability. In contrast, γ-disulfide bond bridged RHPNs showed better assembly stability but low drug release rates. Therefore, designing chemical linkages that ensure both stable assembly and rapid drug release remains challenging. To address this paradox of stable assembly and rapid drug release in RHPNs, we developed carbon-spaced double-disulfide bond (CSDD)-bridged RHPNs (CSDD-RHPNs) with two carbon-spaces. Pilot studies showed that CSDD-RHPNs with two carbon-spaces exhibited enhanced assembly stability, reduction-responsive drug release, and improved selective toxicity compared to α-/γ-position single disulfide bond bridged RHPNs. Based on these findings, CSDD-RHPNs with four and six carbon-spaces were designed to further investigate the properties of CSDD-RHPNs. These CSDD-RHPNs exhibited excellent assembly ability, safety, and prolonged circulation. Particularly, CSDD-RHPNs with two carbon-spaces displayed the best antitumor efficacy on 4T1 and B16-F10 tumor-bearing mice. CSDD chemical linkages offer novel perspectives on the rational design of RHPNs, potentially overcoming the design limitations regarding contradictory assembly ability and drug release rate.

A deep learning–based surrogate model for spatial-temporal temperature field prediction in subway tunnel fires via CFD simulation

The smoke temperature and toxic gas generated by subway tunnel fires cause difficulties to trapped personnel and hinder rescue work. In this study, with a view to ensuring that smoke movement is achieved quickly and contributing to the future development of subway tunnel fires to guide emergency rescue, a deep learning surrogate model based on a transposed convolution neural network (TCNN) was proposed to predict the spatial-temporal temperature field. A numerical database of subway tunnel fires was constructed based on the computational fluid dynamics (CFD) method. Considering different fire locations, heat release rates (HRRs), and ventilation velocities, 135 scenarios were conducted to collect fire data. An adaptive up-projection unit (AUPU) and axial attention fusion block were proposed to improve the TCNN. The results showed that, with the inputs of fire location, HRR, and ventilation velocity, the surrogate model can quickly identify given features and reproduce the spatial-temporal temperature field with 94% accuracy within 0.034 s. The proposed deep learning surrogate model can aid emergency control and rescue efforts in the context of subway tunnel fires.

Effect of direct water injection timing and quantity on combustion, performance, and emission characteristics of a homogeneous charge compression ignition engine − A CFD analysis

Direct water injection in an HCCI engine is a promising strategy to extend the operating load limit. The advantage of water injection depends on the percentage of water evaporated inside the cylinder, which further depends on the time available for the evaporation and the interaction of water spray plumes with the in-cylinder air-flow field. Here, CFD investigations are done to find the effect of water injection timing (WIT) and quantity on the load limit and performance and emission characteristics of the HCCI engine. Various WITs are considered for the study, varying from 100° CA before TDC to 20° CA before TDC. The water-to-fuel ratio is varied from 0 to 1 in steps of 0.2. A three-dimensional computational fluid dynamics model is used for the study, and CFD models used are validated from the available experimental data in the literature. The results show that WITs before 650° CA and after 670° CA are inappropriate for the HCCI engine, as heat release rate and MRPR are high in these cases. Also, the evaporation rate of water increases when the water injection is done in the region where the direction of the air-flow field is opposite to the direction of water injection. At the WIT of 60°, the HRR and MRPR are minimal, and the water vapor distribution is good compared to other cases. Also, it is seen that a water-to-fuel ratio of 0.8 gives more scope for extending the upper load limit with a marginal penalty of the IMEP; hence, a WIT of 60° with the water-to-fuel ratio of 0.8 is considered optimum. With the optimum case, it is feasible to increase the ER from 0.74 to 0.95, resulting in an increase of IMEP from 3.23 bar to 4.92 bar, which is 52.3 % more than without a water injection case at the ER of 0.74. Also, it showed minimum NOx emissions in all the water injection cases. Hence, these results address the primary challenges associated with HCCI engines, demonstrating that direct water injection can substantially improve the combustion controllability and operational range of HCCI engines.

Experimental study on the flame trajectory evolution of horizontal jet fires under reduced pressures

Jet fire including process pipeline/tank leakage, oil exploitation industry of tail gas treatment flare or other industrial combustors as a common phenomenon can be found at high altitude areas. This work characterizes the flame trajectory evolution of horizontal jet fires under reduced pressures, which is rarely studied. The experimental results show that the horizontal flame projection distance increases monotonously, but the vertical flame length first increases and afterward decreases with the increase of heat release rate and the decrease of ambient pressure. Meanwhile, flame trajectory length increases significantly and then slowly with increasing heat release rate, but first increases to a maximum value and afterward declines with decreasing ambient pressure. Meanwhile, the turning point of vertical flame length appears earlier than that of flame trajectory length with increasing heat release rate (or jet velocity at source) and decreasing ambient pressure. Then, a mathematical model based on the flame arc hypothesis and a dimensionless model were proposed to describe the flame trajectory length, the momentum-buoyancy length scale was used to normalize the flame trajectory length. The measured flame trajectory length in terms of the nozzle diameter, heat release rate, and ambient pressure was satisfactorily correlated by the proposed models.

Self-crosslinking phosphorus-containing durable flame retardants for cotton fabrics

The phosphorus-containing flame retardant that can enter the interior of cotton fiber and has self-crosslinking ability was designed and synthesized. The flame retardant contains two components, 2-(1-(dimethoxy phosphoryl)-2,5, 8-Triazectridecyl) phosphonate starch (PTPS) and 4-(hydroxymethyl)-10-((3-((5-(hydroxymethyl)-10-((3-((tris(hydroxymethyl)phosphonio)methyl)ureido)methyl)-2,6,8,12,14,18-hexaaza-4,10,16-Triphosphanonadecane (BPTP). The structure of PTPS and BPTP were detected by NMR and FTIR, and the results showed that the synthesis of PTPS and BPTP was successful. During the treatment, cellulose was first endowed with -NH groups. Then PTPS molecule and BPTP molecule were grafted onto cellulose through the reaction of P-CH2OH groups and -NH groups. After 50 laundering cycles (NFPA2112–2012 standard), the limiting oxygen indexes (LOIs) of the fabrics treated with 35 wt% CFN-PB and 30 wt% CFN-PB were 28.80% and 27.30%, respectively, and passed the vertical flame test (VFT). Compared with the raw cotton, the peak heat release rate (PHRR), the total heat rate (THR) and the flame growth rate (FGR) of the CNF-PB treatment fabric were reduced by 62.90 %, 29.43 % and 62.91 % respectively. These indicate that the flame retardant PB could be firmly fixed on the fibers and show good flame retardancy durability. In the VFT, and cone calorimetry test, the CFN-PB treated fabric showed the condensed phase flame retardant mechanism.

Simulation of fire combustion process in valve hall of DC converter power station

To investigate the fire danger of the valve hall, a 3D numerical model of the DC converter substation's valve hall is created by using the fire dynamics simulator (FDS) program and the fire burning process of the valve hall is simulated. In particular, the procedure of simulating the fire burning in the valve hall under various fire source positions is accomplished by varying certain parameters. The smoke spreading process, ambient temperature field, and heat release rate curve under various fire source placements are compared based on the results of the simulation calculations. The findings demonstrate that under various fire source locations, the valve hall's combustion process varies as well. This study compares the time for smoke to fill the entire valve hall, the maximum temperature within the valve hall, and the maximum fire source heat release efficiency in different fire scenes. The results indicate that in fire scenes where the fire source is closer to the middle position, the time for smoke to spread throughout the valve hall is shorter, and the fire source heat release rate is higher. Conversely, in fire scenes where the fire source is closer to the edge, the maximum temperature within the valve hall is higher. The numerical simulation of the valve hall in this DC converter station assessed the hazards under different fire scenes, aiming to maximize the safety of the valve hall. It provides reliable guidance for maximizing the safety of the valve hall and facilitating firefighting and rescue efforts, thus protecting personal safety and minimizing property damage.

Developing and analyzing photo-crosslinkable cinnamoyl-modified pullulan hydrogels for drug delivery applications

A hydrogel created by modifying pullulan with cinnamoyl groups (Pul-CM) through an esterification process was developed as an effective vehicle for delivering the well-known drug model, caffeine. Initially, pullulan biopolymer was expanded, followed by the addition of cinnamoyl groups using cinnamoyl chloride. These modifications were confirmed through various spectroscopic and instrumental techniques, verifying their proposed chemical structures. The newly created Pul-CM hydrogel demonstrated the ability to crosslink without initiators when exposed to UV light for sufficient durations. This crosslinking is attributed to the creation of cyclobutane rings that link the pullulan chains via a [2π+2π] cyclization process facilitated by the cinnamoyl groups’ –CH=CH– bonds. The progress of Pul-CM crosslinking was tracked by the reduction in the UV spectral peak associated with the cinnamate groups, followed by an examination of the gel’s efficiency and its swelling behavior under UV light. Furthermore, these hydrogel derivatives show significant promise as drug delivery systems, offering adjustable drug release rates by altering the hydrogel’s crosslinking level through either cinnamoyl modification or the duration of UV light exposure.