Length Diameter Research Articles

Association between medial knee joint bone morphology and popliteal cyst: a retrospective MRI-based analysis.

Baker's cyst, or popliteal cyst, is a common knee condition associated with osteoarthritis and rheumatoid arthritis. While previous studies have explored the cyst's relationship with soft tissue abnormalities, the connection between popliteal cysts and medial knee bone morphology remains unclear. This study aims to assess the association between anatomical bone structures of the medial knee joint and popliteal cyst presence using magnetic resonance imaging (MRI). A retrospective analysis was conducted on 100 patients who underwent MRI for knee pain between June and December 2021. Group 1 (n = 50) consisted of patients with Baker's cysts, and group 2 (n = 50) included those without cysts. MRI measurements included medial condyle width, condyle length, distal and posterior articular diameters, medial tibial plateau depth, and tibial slope. Cyst dimensions and volume were measured. Statistical analyses, including Pearson correlation and chi-square tests, were performed, with significance set at p < 0.05. No significant differences in medial knee bone morphology were found between groups (p > 0.05). However, popliteal cyst size was positively correlated with age (p = 0.016, r = 0.339 and p = 0.020, r = 0.328, respectively). Higher Kellgren-Lawrence grades were also associated with cyst presence (p = 0.001). Gender correlated with knee measurements, showing smaller knee dimensions in women (p < 0.001). This study found no direct association between medial knee bone morphology and the presence of popliteal cysts. However, cyst size increased with age and degenerative changes, suggesting that inflammation and joint degeneration may play a significant role in cyst development. Further studies with larger cohorts are required to validate these findings.

Morphological evidence supports splitting of species in the North Atlantic Sebastes spp. complex.

The redfishes (genus Sebastes) are long-lived, commercial species in the North Atlantic. Excessive harvest through decades has led to a decline in the mature population of golden redfish (Sebastes norvegicus) in Norwegian waters, which is currently considered severely depleted. Accumulating genetic evidence suggests a more complex structure within this genus in the North Atlantic, which has recently inspired the hypotheses of cryptic species within S. norvegicus. Despite apparent genetic divergence between two types, they have yet to be verified morphologically. The morphology of genetically assigned fishes from Norwegian and Greenland waters was investigated using traditional morphometric methods, applying Linear Discriminant Analysis and Random Forest classification procedures to identify and evaluate the performance of descriptive characters. Combined with non-parametric meristic analysis, the results show that features such as beak length and eye diameter provide sufficient discrimination between the proposed cryptic species as well as separating them from the sympatric species S. mentella and S. viviparus. These findings support the presence of an additional redfish species in the North Atlantic, distinguishable both by morphological and genetic characters. This needs to be taken into consideration in future monitoring and management strategies for North Atlantic redfish.

Bacillus velezensis CE 100 controls anthracnose disease in walnut trees (Juglans regia L.) by inhibiting Colletotrichum gloeosporioides and eliciting induced systemic resistance.

Biological control of plant diseases is recognized as an effective and environmental friendly alternative to chemical fungicides. We demonstrated the dual biocontrol strategy of Bacillus velezensis CE 100 through the hydrolytic activity of chitinase and β-1,3-glucanase and the elicitation of induced systemic resistance (ISR) against Colletotrichum gloeosporioides that causes anthracnose disease in walnut trees. B. velezensis CE 100 produced a maximum of 62.1 units mL-1 (132.9 units mL-1) chitinase and 5.2 units mL-1 (9.4 units mL-1) β-1,3-glucanase enzymes in the broth culture (crude enzyme fraction), and inhibited spore germination and mycelial growth of C. gloeosporioides by 81.6% and 22.6%, respectively, at 100µlmL-1 of crude enzyme fraction. The inoculation of B. velezensis CE 100 induced the production of pathogenesis-related (PR) chitinase in walnuts by 2.1-fold, and to a lesser extent PR β-1,3-glucanase, and reduced anthracnose disease severity by 3.0-fold compared to the control group. The bacterium produced a maximum of 11.4µgmL-1 indole-3-acetic acid (IAA) and improved the chlorophyll content, shoot length, and root collar diameter of walnut trees compared to the fungicide treatment and control groups. B. velezensis CE 100 demonstrated the prospect of controlling walnut anthracnose by direct antagonism and ISR against C. gloeosporioides, while simultaneously enhancing walnut growth through IAA production.

Immunization with OPN5 increased seasonal degradation of reproductive activity in Magang ganders.

To investigate the regulatory mechanism mediated by hypothalamic OPN5 on seasonal changes in the reproductive activities of domestic geese, 60 Magang ganders in their breeding period were selected for the experiment and evenly divided into an immunization group(OPN5-IM) and a control group. On days 0, 15 and 30, ganders in the immunized group were immunized with OPN5-KLH protein vaccine, and ganders in the control were immunized with the same amount of blank emulsified vaccine. Additionally, 120 female geese were provided to stimulate the reproductive activities of male geese. The results showed that the arrangement of spermatogenic cells was disturbed, the number of sperm decreased, and the testicular weight, seminiferous tubule area, length diameter, spermatogenic epithelium thickness decreased significantly with the natural day length prolonged. Moreover, the concentration of testosterone and LH decreased significantly while PRL increased. The prolonged photoperiod significantly affected the gene expression of GnRH-I, VIP, FSHβ, FSHR, LHβ, PRL, and PRLR in ganders. Specifically, the gene expression of GnRH-I, FSHβ, and LHβ in the hypothalamus and pituitary decreased, while the gene expression of VIP, PRL, and PRLR increased. Following OPN5 immunization, the anti-OPN5 antibody titer of ganders in the OPN5-IM group was notably higher than in the control group. The testicular degeneration was severe in OPN5-IM group compared with the control, as evidenced by a significant reduction in seminiferous tubule area, length diameter, and thickness of spermatogenic epithelium in the immunized group on day 60. Additionally, the concentrations of testosterone and LH were lower in the OPN5-IM group than in the control group, whereas PRL was higher. Moreover, OPN5 immunization significantly affected the expression of GnRH-I, PRL, and PRLR. OPN5 mRNA and protein expression were higher in the immunized group, whereas TRH, DIO2, and TSHR mRNA expressions were lower. However, DIO3 mRNA and protein were up-regulated in the immunized group. In conclusion, our results indicated that the reproductive performance of Magang geese degraded from the breeding to the non-breeding period as daylight was extended. Immunization against OPN5 increased OPN5 expression and down-regulated the TSH-DIO2/DIO3 pathway, further to affect the HPG axis and accelerate the degradation of reproductive activity. Therefore, OPN5 may play an important mediating role in light-regulating seasonal reproductive degradation in Magang geese.

Potassium Sulfate Supplementation with Elevated Electrical Conductivity Was Unproductive for Hydroponic Strawberry at the Original Yamazaki Nutrient Solution Nitrogen Level

The production of strawberries (Fragaria ×ananassa) in hydroponic systems has been increasing. In hydroponic systems, precise nutrient management is crucial for optimal plant growth and fruit production. Among essential elements, potassium (K) is a key nutrient that affects fruit yield and quality in fruiting crops. The objective of this study was to investigate whether increasing the K concentration in the Yamazaki strawberry nutrient solution could enhance plant growth, fruit yield, and fruit quality in hydroponic strawberries. Bare-root plants of strawberry ‘Monterey’ and ‘San Andreas’ were planted in a deep water culture hydroponic system and grown with initial K concentrations of 117, 194, 271, and 348 mg·L−1 under the same initial nitrogen concentration of 77 mg·L−1. As the K concentration increased from 117 to 348 mg·L−1, the nutrient solution electrical conductivity increased from 1.0 to 1.9 dS·m−1. The experiment was conducted inside an indoor vertical farm at a 23 °C air temperature with an extended photon flux density (400–750 nm) of 350 µmol·m−2·s−1 under an 18-hour photoperiod. Increasing the K concentration from 117 to 348 mg·L−1 had minimal effects on plant growth characteristics of both cultivars, although root dry mass of ‘Monterey’ increased linearly with increasing K. Increasing the K concentration from 117 to 348 mg·L−1 did not affect the total fruit number or total fruit fresh mass of ‘Monterey’, but for ‘San Andreas’, it reduced the total fruit number by 34% and total fruit fresh mass by 45%. Additionally, increasing the K concentration from 117 to 348 mg·L−1 reduced the individual fruit mass, fruit length, and fruit diameter and increased titratable acidity in both cultivars. These results indicate that increasing the K concentration in the Yamazaki strawberry nutrient solution did not benefit plant growth, fruit yield, or fruit quality of the hydroponically grown strawberries ‘Monterey’ or ‘San Andreas’.

Cytology and Yields Analysis of Onions (Allium cepa l.) under Compost Application in Coastal Saline Soil

Onion (Allium cepa L.) is a valuable crop in Bangladesh for its diversified usage and availability of enriched germplasms including local and exotic ones. However, the cultivation of onions in the coastal regions of Bangladesh has become a major challenge because of salinity and soil fertility. Therefore, a pot experiment of coastal saline soil amendment with compost was carried out with mostly cultivated varieties i.e. Taherpuri and King. The treatments T1 (2.5 t/ha) and T2 (5.0 t/ha) significantly improved the plant height for the Taherpuri variety and revealed an escalation to the no. of the leaflet, root length and bulb diameter for the King variety. Compost application on saline soil didn’t increase the mitotic index (MI%) for all the treatments for both of the experimented varieties but increased the mitotic inhibition index (MII%) for the treatments T3 (7.5 t/ha) and T4 (10.0 t/ha) treatment for the Taherpuri and King varieties respectively. The correlation coefficient between the treatment and different yields of onion was found better for the Taherpuri than the King variety. J. Asiat. Soc. Bangladesh, Sci. 50(1-2): 89-99, June-December 2024

An ANN-based model for constructing undrained failure envelopes for circular piles under general loading

ABSTRACT This study introduces a novel approach in which three-dimensional finite element limit analysis (3D FELA) is employed to investigate an undrained circular pile under combined loads. The primary aim is to analyze how vertical (V), horizontal (H), and moment (M) loads affect the pile's ultimate capacity. Unique to this research is the exploration of the relationships between the overburden stress factor (n) and the pile length–diameter ratio (L/D) and the influence of normalised vertical loading (V/V0 ), normalised horizontal loading (H/suLD), and normalised moment loading (M/suL²D). A distinctive feature of this study is the use of total shear dissipation to identify failure zones and patterns within the soil, which reveals significant shearing and failure areas. Additionally, the study constructs a 3D failure envelope to assess the impact of the axis angle (β). The integration of an artificial neural network (ANN) with 8 hidden neurons represents a novel aspect of this research, offering advanced prediction of H/suLD and M/suL²D values. The ANN's effectiveness is validated through seven indices, demonstrating its accuracy in constructing the 3D failure envelope. The results highlight that the angle β has the most significant influence, with an 82.7% impact on the output parameters, underscoring the innovative contribution of combining finite element analysis with an ANN for enhanced prediction and analysis.

External Flow Field and Rock Erosion Characteristics of a Coaxial Straight‐Swirling Mixed Jet

ABSTRACTRadial jet drilling is an effective technology for mining coal‐bed methane. A self‐propelled jet bit greatly affects drilling efficiency. Simulations and laboratory experiments using a coaxial straight‐swirling mixed jet (CSMJ) were performed to study the flow field and rock erosion characteristics, and analyze laws influencing key structural parameters (straight‐swirling flow ratio N, slot length–width ratio dr/ds, mixing chamber length–diameter ratio Lq/Dq, and linear segment length–diameter ratio Lf/df) on the flow field and rock erosion characteristics, and study the change law of the axial velocity of the flow field under different structural parameters and the distribution law of the three‐dimensional velocity along the radial direction at the non‐dimensional injection distance of 5.56. The CSMJ displayed characteristics of a straight jet, having a high‐velocity area near the axis. The velocity was attenuated with increasing dimensionless jet distance Ls/df. The bit also displayed characteristics of a swirling jet, with an obvious jet diffusion with increased Ls/df. N affected the distribution ratio of the straight and swirling jets, and dr/ds mainly affected CSMJ rotational shear energy. With the centerline velocity and radial distribution of the CSMJ as evaluation indices, the optimal parameters of the CSMJ suitable for self‐propelled drilling were N = 0.46, dr/ds = 3.88, Lq/Dq = 0.67, and Lf/df = 0.56. Optimal flow field parameters also optimized the erosion capability, realizing the mutual verification of experimental and simulation results. The erosion hole crushing volume was used as the evaluation sequence. The parameter's sensitivity to the rock erosion volume was Ls/df &gt; Lq/Dq &gt; dr/ds &gt; N. The results provide engineering guidance for determining reasonable parameters for radial jet drilling.

Atherogenic index of plasma and cardiovascular outcomes in female patients undergoing percutaneous coronary intervention: insights from a retrospective cohort study

In this research, we explored the relationship between the AIP and clinical outcomes in patients undergoing PCI. A total of 2533 consecutive patients who underwent PCI were included in this retrospective cohort study, and the data from 2098 patients were used. AIP is calculated based on the log (triglycerides/high-density lipoprotein-cholesterol). MACCEs were defined at 29.8 months as a composite of all-cause mortality, AMI, repeat revascularization and stroke. An analysis of logistic regression proportional hazards was conducted to investigate the association between AIP and the prevalence of MACCEs. This study found that there was an association between MACCEs and age (p < 0.001), heart failure history (p < 0.001), previous AMI (p = 0.013), and diabetes mellitus(p = 0.002), LVEF (p < 0.001), DBP (p = 0.027), creatinine (p = 0.002), UA (p = 0.021), ACEI treatment (p = 0.003), number of diseased vessels, target lesion location, CTO (p < 0.001), stent length (p < 0.001), and stent diameter (p < 0.001). Multivariate logistic regression analysis showed that AIP was an independent prognostic factor for MACCE in female patients (OR = 2.45, 95%CI = 1.17 ~ 5.11, p = 0.018) but not in male patients. Our findings revealed a significant correlation between AIP and MACCEs in female patients.

One-Year Prognosis for Patients Diagnosed with Acute Coronary Syndrome Compared to Those with Chronic Coronary Syndrome Following Complex Coronary Procedures

Background: Acute coronary syndrome (ACS) remains the primary cause of mortality worldwide. Performing complex coronary intervention in patients with ACS is considered a significant factor for worsening prognosis. This study aimed to evaluate the prognosis of patients with ACS treated with complex procedures compared to patients with chronic coronary syndrome (CCS). Methods: Among 980 patients from the Polish Complex Registry, we enrolled 829 consecutive patients who underwent complex percutaneous coronary intervention (PCI) for acute or chronic coronary syndrome with a completed one-year follow-up. The primary endpoint is defined as the major adverse cardiac event (MACE) at 12 months, a composite endpoint including all-cause death, target lesion revascularization, target vessel revascularization, and non-fatal myocardial infarction. Results: The incidence of the composite endpoint of MACE at one-year follow-up was comparable between the patients with acute and chronic coronary syndrome who underwent complex PCI (12.4% vs. 7.6%, LogRank p = 0.035). Cox multivariate analysis indicated that ACS is an independent risk factor for death at one-year follow-up. Additionally, age and comorbidities, such as heart failure and chronic kidney disease, along with procedural factors, including lesion length and pre-procedural diameter stenosis, are independent predictors of death in patients with complex lesions. Independent risk factors for MACE at one-year follow-up include age, heart failure, previous PCI, in-stent restenosis, and pre-procedural diameter stenosis. Conclusions: The prognosis of patients with acute and chronic coronary syndrome in the annual follow-up is comparable in the context of cardiovascular events. The clinical presentation of ACS is an independent risk factor for all-cause death.

Development of a clinical and ultrasonic parameter-based nomogram model to predict restenosis after superficial femoral artery stenting.

Prediction of in-stent restenosis (ISR) is clinically important for patients with peripheral artery disease in their superficial femoral arteries (SFA) who have been treated with stenting. The aim of this study was to construct and validate a predictive model for ISR after SFA stenting based on a series of clinical and ultrasonic parameters. This retrospective study included 381 patients who were treated with self-expanding bare nitinol stents in their SFA at our hospital between January 1, 2018, and January 1, 2022. These patients were randomly allocated to a training cohort (266 patients) or a validation cohort (115). Clinical and ultrasonic parameters related to ISR (>50%) in the SFA at 12 months were derived by univariable and multivariable logistic regression analyses to create a nomogram model predictive of risk of ISR. Receiver operating characteristic (ROC) curve analyses were used to assess the recognition ability of the model. A calibration curve was used to evaluate the model's calibration ability, and decision curve analysis was used to validate the nomogram's clinical utility. Logistic regression analyses showed that sex, echogenicity of the target plaque, preoperative arterial runoff score, preoperative popliteal artery flow rate, lesion length, and residual diameter were risk factors for ISR; these parameters were used to construct the nomogram model. Internal and external validation showed that the areas under the ROC curves were 0.82 (95%CI: 0.77-0.87) and 0.70 (95%CI: 0.60-0.79), respectively, suggesting good recognition ability of the model. Additionally, calibration curves for the predictive model indicated good calibration, and decision curve analysis demonstrated clinical utility of the model. This novel nomogram that predicts ISR after SFA stenting demonstrated excellent discriminatory power, calibration capacity, and clinical usefulness.

Adaptation responses to salt stress in the gut of Poecilia reticulata

ABSTRACT Osmoregulation is essential for the survival of aquatic organisms, particularly teleost fish facing osmotic challenges in environments characterized by variable salinity. While the gills are known for ion exchange, the intestine’s role in water and salt absorption is gaining attention. Here, we investigated the adaptive responses of the intestine to salinity stress in guppies (Poecilia reticulata), observing significant morphological and transcriptomic alterations. Guppies showed superior salt tolerance compared to zebrafish (Danio rerio). Increasing salinity reduced villus length and intestinal diameter in guppies, while zebrafish exhibited damage to villus structure and loss of goblet cells. Transcriptomic analysis identified key genes involved in osmoregulation, tissue remodeling, and immune modulation. Upregulated genes included the solute carrier transporters slc2al and slc3al, which facilitate ion and water transport, as well as a transcription factor AP-1 subunit and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta, both of which participate in tissue repair and growth responses. In contrast, many genes related to the innate immune system (such as Tnfaip6) were downregulated, suggesting a shift toward the prioritization of osmoregulatory functions over immune responses. Interestingly, the differential expression of adaptation genes was linked to variations in epigenetic modifications and transcription factor activity. Transcription factors crucial for adapting to salt stress, such as bhlhe40, cebpd, and gata6, were progressively upregulated in guppies but remained downregulated in zebrafish. Our findings highlight the intricate mechanisms of adaptation to salinity stress in P. reticulata, providing insights into osmoregulatory mechanisms involving the intestine in aquatic organisms.

Automated Phenotypic Analysis of Mature Soybean Using Multi-View Stereo 3D Reconstruction and Point Cloud Segmentation

Phenotypic analysis of mature soybeans is a critical aspect of soybean breeding. However, manually obtaining phenotypic parameters not only is time-consuming and labor intensive but also lacks objectivity. Therefore, there is an urgent need for a rapid, accurate, and efficient method to collect the phenotypic parameters of soybeans. This study develops a novel pipeline for acquiring the phenotypic traits of mature soybeans based on three-dimensional (3D) point clouds. First, soybean point clouds are obtained using a multi-view stereo 3D reconstruction method, followed by preprocessing to construct a dataset. Second, a deep learning-based network, PVSegNet (Point Voxel Segmentation Network), is proposed specifically for segmenting soybean pods and stems. This network enhances feature extraction capabilities through the integration of point cloud and voxel convolution, as well as an orientation-encoding (OE) module. Finally, phenotypic parameters such as stem diameter, pod length, and pod width are extracted and validated against manual measurements. Experimental results demonstrate that the average Intersection over Union (IoU) for semantic segmentation is 92.10%, with a precision of 96.38%, recall of 95.41%, and F1-score of 95.87%. For instance segmentation, the network achieves an average precision (AP@50) of 83.47% and an average recall (AR@50) of 87.07%. These results indicate the feasibility of the network for the instance segmentation of pods and stems. In the extraction of plant parameters, the predicted values of pod width, pod length, and stem diameter obtained through the phenotypic extraction method exhibit coefficients of determination (R2) of 0.9489, 0.9182, and 0.9209, respectively, with manual measurements. This demonstrates that our method can significantly improve efficiency and accuracy, contributing to the application of automated 3D point cloud analysis technology in soybean breeding.

Impact of Blade Geometric Parameters on the Specific Cutting Energy of Willow (Salix viminalis) Stems

This article presents a model to estimate the specific energy demand for cutting annual willow stems, considering variations in plant moisture content and sliding-cutting angles. The study involved laboratory tests and statistical analyses. Key parameters were measured for 50 randomly selected annual willow shoots, including total plant weight, leaf weight, stem weight, centre of gravity of the shoot, shoot length, and stem diameter at specified heights: 0, 150, 500, 750, 1000, 1250, 1500, and 2000 mm. Five levels of willow shoot moisture content were evaluated. The study established a cutting force-deformation relationship through strength tests with an accuracy of 1 N, which was subsequently used to calculate shear stress and specific cutting energy. Steel blades with an angle of 30° and sliding-cutting angles of 0°, 15°, 30°, and 45° were used in the study. Ten repetitions were performed for each combination of variable parameters: shoot moisture content and blade sliding-cutting angle. Experimental results were evaluated using analysis of variance (ANOVA), while Duncan’s test was applied to identify and classify groups with homogeneous specific energy values. The developed characterisation offers valuable information for designing shredding units and optimising their operational parameters to reduce energy consumption.

Effects of Air Vortex Finder Length and Outlet Diameter Variations on Oil Palm Loose Fruit Collector

Oil palm is one of the largest economy sectors in Malaysia. Among the problems faced in the estates are oil palm loose fruits deposition which is currently being collected manually in the industry. Hence, an oil palm loose fruit collector is designed using cyclone separator mechanism and was studied using computational fluid dynamics (CFD). In the current study, Reynold’s stress model (RSM) and the Discrete phase model (DPM) was employed to navigate numerical simulations where the vortex finder of the cyclone separator was varied with two factors which are the vortex finder length and outlet diameter. Wall was set to a no slip condition with standard wall functions. Hydraulic diameter of the gas outlet is Bc=0.1 . Hydraulic diameters of the particle’s outlet are Jc=0.15 and 0.2 respectively. Turbulence intensity at the gas and particles outlet are specified at 5%. An injection with density 995.7 and 0.04 was set to simulate oil palm loose fruit collection into the system. Ultimately, effects of vortex finder and outlet variations on the pressure drop and collection efficiency were then analyzed. Results indicate that an outlet diameter of 0.18 m and vortex finder length of 0.405 m is favourable for the oil palm loose fruit machine with a collection efficiency of 88.71 % and pressure drop of 477.66 Pa.

Alkane selection as a critical factor in structuring reverse wormlike micelles.

The oil phase controls the persistence length and aqueous channel diameter of reverse wormlike micelles (RWLMs), specifically by tuning the cohesive energy density of alkanes. We explore the influence of alkanes with varying chain lengths on the rheological properties, structural parameters, and morphology of RWLMs. To establish a link between the solvent characteristics and the structure of RWLMs, we employ a diverse set of complementary techniques, including rheological analysis, small-angle X-ray scattering (SAXS), Fourier-transform infrared (FT-IR) spectroscopy, and cryogenic transmission electron microscopy (cryo-TEM). Our results show that the cross-sectional area and persistence length of reverse wormlike micelles (RWLMs) are influenced by the chain length of the alkanes in which the long aggregates are formed. We propose a model based on the Hildebrand solubility parameter to explain this behavior, where alkanes with higher cohesive energy density led to RWLMs with narrower aqueous channels. Selecting specific alkanes makes it possible to fine-tune the diameter of these channels, presenting promising opportunities for designing RWLMs tailored to confined media applications.

Agronomic performance, biomass production, and nutrient value of three napier grass cultivars (Pennisetum purpureum) in highland area

The study aims to determine the agronomic performance, biomass production, and nutrient value of three Pennisetum purpureum cultivar (Biovitas, Pakchong, and Mott) in 1000 meters above sea level (asl) highland area of Petungkriyono, Pekalongan, Central Java, Indonesia. The grasses were planted using vegetative stems and maintained for four months, following completely randomized design (CRD) with four replications for each cultivar. Agronomic performance was assessed before harvested. Napier grass was harvested to investigate the biomass production and nutrient values, including organic matter, crude protein, crude protein yield, crude fibre, and crude fat. Pakchong had the highest biomass and crude fiber content. Biovitas exhibited the highest agronomic performance, with superior plant height, leaf length, leaf width, and stem diameter, as well as the highest nutrient values in term of organic metters. Mott showed the highest tiller number and crude protein content among the cultivars. The distinct strength of each cultivar indicates their potential suitability for various agricultural applications in highland regions.

Preparation of High‐Temperature‐Resistant Polybenzoxazole Paper by a Two‐Step Method

Polybenzoxazole (PBO) paper, made of PBO chopped fibers and PBO fibrids, is used in many cutting‐edge fields because of its excellent properties. The rigid molecular structure makes PBO only dissolved in strong acids such as fuming sulfuric acid and polyphosphoric acid at a very high temperature. Due to the harsh preparation conditions, it is not easy to industrialize PBO fibrids. Herein, a two‐step method was used to prepare the PBO paper. Firstly, polyhydroxyamide (PHA) was synthesized in an organic solvent and used to prepare fibrids, and the PHA paper was then prepared using PHA fibrids with a traditional wet papermaking process, and the obtained PHA paper was further converted into PBO paper by thermal cyclization. The results show that the PHA fibrids have a high length–diameter ratio, film shape, and abundant hair structure, and the tensile index of the PHA base paper is as high as 123.3 N·m/g. After thermal cyclization, the structure and morphology of the paper have little change, and the mechanical properties of the paper have a certain loss. However, it is still much higher than that of PBO paper prepared directly from PBO fibrids and has excellent thermal stability, so it is suitable for preparing high‐temperature‐resistant paper‐based composites.

Mechanical response characteristics and cushioning of sealed airbags under different length–diameter ratios

In the event of a mine fire, rapidly constructing blast-resistant seals is one of the most effective measures to contain the disaster. This study conducted blast cushioning experiments on sealed airbags and numerical simulations by analysis system/Livermore software-dynamics (ANSYS/LS-DYNA), an explicit simulation software, to analyze the mechanical response characteristics and cushioning effectiveness of sealed airbags under different length-to-diameter ratios. The research results indicate that airbags with different length-to-diameter ratios all exhibit cushioning effects, and the airbag can recover its deformation after pressure release. As airbag length increases, vertical deformation along the pipeline appears, forming a radial compression failure mode. Stress concentrations are mostly located at the edges of the airbag, while arched structures can reduce the concentrated stress. Excessively long or short airbags significantly increase localized stress concentrations. The total energy absorbed by the airbag during cushioning shows a linear relationship with its length, and an energy absorption model for single-chamber airbags with varying length-to-diameter ratios was established. Under full-scale simulation conditions, the optimal length-to-diameter ratio range is 0.75:1. The reflected energy of shockwave encountering airbag is independent of airbag length and remains a fixed value when inflation pressure remains constant. These findings provide theoretical support for the design and application of explosion-resistant airbag.

Numerical simulation of secondary explosion in the external flow field after horizontal explosion venting of a narrow and long vessel

ABSTRACT Numerical simulation was conducted to investigate the secondary explosion in the external flow field following horizontal explosion venting of a narrow and long vessel. The study utilized Fluent software, employing the standard k–ε turbulence model and SIMPLE algorithm, to analyze the secondary explosion under different explosion venting pressures, equivalence ratios, and length–diameter ratios. The results show that after the explosion of the pipeline, the flame lagging behind the pressure wave ignites the residual methane discharged into the external flow field again, which is the cause of the secondary explosion. When the explosion venting pressure exceeds 240 kPa, a distinct peak in overpressure is observed in the external flow field with its strength and range increasing proportionally to the venting pressure, reaching a maximum influence range of 0.4 m. At an explosion venting pressure of 290 kPa, three explosions can be detected. The equivalence ratio primarily affects the overpressure rise rate within the container prior to membrane rupture but has no significant impact on secondary explosion intensity. On the other hand, the length–diameter ratio significantly influences the overpressure rise rate within the container before membrane rupture as well as affecting secondary explosion intensity.