Optimal Depth Research Articles

FedSHE: privacy preserving and efficient federated learning with adaptive segmented CKKS homomorphic encryption

Unprotected gradient exchange in federated learning (FL) systems may lead to gradient leakage-related attacks. CKKS is a promising approximate homomorphic encryption scheme to protect gradients, owing to its unique capability of performing operations directly on ciphertexts. However, configuring CKKS security parameters involves a trade-off between correctness, efficiency, and security. An evaluation gap exists regarding how these parameters impact computational performance. Additionally, the maximum vector length that CKKS can once encrypt, recommended by Homomorphic Encryption Standardization, is 16384, hampers its widespread adoption in FL when encrypting layers with numerous neurons. To protect gradients’ privacy in FL systems while maintaining practical performance, we comprehensively analyze the influence of security parameters such as polynomial modulus degree and coefficient modulus on homomorphic operations. Derived from our evaluation findings, we provide a method for selecting the optimal multiplication depth while meeting operational requirements. Then, we introduce an adaptive segmented encryption method tailored for CKKS, circumventing its encryption length constraint and enhancing its processing ability to encrypt neural network models. Finally, we present FedSHE, a privacy-preserving and efficient Federated learning scheme with adaptive Segmented CKKS Homomorphic Encryption. FedSHE is implemented on top of the federated averaging (FedAvg) algorithm and is available at https://github.com/yooopan/FedSHE. Our evaluation results affirm the correctness and effectiveness of our proposed method, demonstrating that FedSHE outperforms existing homomorphic encryption-based federated learning research efforts in terms of model accuracy, computational efficiency, communication cost, and security level.

Leverage Effective Deep Learning Searching Method for Forensic Age Estimation.

Dental age estimation is extensively employed in forensic medicine practice. However, the accuracy of conventional methods fails to satisfy the need for precision, particularly when estimating the age of adults. Herein, we propose an approach for age estimation utilizing orthopantomograms (OPGs). We propose a new dental dataset comprising OPGs of 27,957 individuals (16,383 females and 11,574 males), covering an age range from newborn to 93 years. The age annotations were meticulously verified using ID card details. Considering the distinct nature of dental data, we analyzed various neural network components to accurately estimate age, such as optimal network depth, convolution kernel size, multi-branch architecture, and early layer feature reuse. Building upon the exploration of distinctive characteristics, we further employed the widely recognized method to identify models for dental age prediction. Consequently, we discovered two sets of models: one exhibiting superior performance, and the other being lightweight. The proposed approaches, namely AGENet and AGE-SPOS, demonstrated remarkable superiority and effectiveness in our experimental results. The proposed models, AGENet and AGE-SPOS, showed exceptional effectiveness in our experiments. AGENet outperformed other CNN models significantly by achieving outstanding results. Compared to Inception-v4, with the mean absolute error (MAE) of 1.70 and 20.46 B FLOPs, our AGENet reduced the FLOPs by 2.7×. The lightweight model, AGE-SPOS, achieved an MAE of 1.80 years with only 0.95 B FLOPs, surpassing MobileNetV2 by 0.18 years while utilizing fewer computational operations. In summary, we employed an effective DNN searching method for forensic age estimation, and our methodology and findings hold significant implications for age estimation with oral imaging.

Optimal depth and a novel approach to variational unitary quantum process tomography

In this work, we present two new methods for variational quantum circuit (VQC) process tomography (PT) onto n qubits systems: unitary PT based on VQCs (PT_VQC) and unitary evolution-based variational quantum singular value decomposition (U-VQSVD). Compared to the state of the art, PT_VQC halves in each run the required amount of qubits for unitary PT and decreases the required state initializations from 4 n to just 2 n , all while ensuring high-fidelity reconstruction of the targeted unitary channel U. It is worth noting that, for a fixed reconstruction accuracy, PT_VQC achieves faster convergence per iteration step compared to quantum deep neural network and tensor network schemes. The novel U-VQSVD algorithm utilizes variational singular value decomposition to extract eigenvectors (up to a global phase) and their associated eigenvalues from an unknown unitary representing a universal channel. We assess the performance of U-VQSVD by executing an attack on a non-unitary channel quantum physical unclonable function. By using U-VQSVD we outperform an uninformed impersonation attack (using randomly generated input states) by a factor of 2 to 5, depending on the qubit dimension. For the two presented methods, we propose a new approach to calculate the complexity of the displayed VQC, based on what we denote as optimal depth.

A comparison of static and rotordynamic characteristics for two types of liquid annular seals with and without helical grooved stator

Less leakage is a benefit of parallel grooved liquid seals (labyrinth seals). But researches show that the liquid seal with parallel grooves on the rotor harms the rotor stability. The seal with helical grooves on stator performs well in terms of rotordynamics, and its leakage is sensitive to the rotating speed. To make use of the advantages of both seals and improve seal stability, based on the Smooth-stator/Parallel Grooved-rotor (SPG) liquid seal, a Helical Grooved-stator/Parallel Grooved-rotor (HGPG) liquid seal is designed. To evaluate two liquid seals’ leakage, rotordynamic characteristics and drag power loss, a transient computational fluid dynamics-based method is employed. This method is based on the multi-frequency elliptical-orbit rotor whirling model and the mesh deformation technique. The published experimental data of the leakage and rotordynamic force coefficients for an SPG liquid seal are used to validate the accuracy and dependability of the current method. Seal leakage and force coefficients are presented and compared for the SPG liquid seal and the HGPG liquid seal at various pressure drops. The influences of parallel groove depth on the leakage and rotordynamic properties for the HGPG liquid seals at two rotational speeds (2000, 6000 r/min) are analyzed. The numerical findings demonstrate that the novel HGPG liquid seal has a lower leakage flow rate (by ∼22.3%) than the traditional SPG liquid seal. There is an optimal parallel groove depth that minimizes leakage. The presented novel HGPG liquid seal significantly improves rotordynamic stability, due to the similar effective stiffness and the obviously larger positive effective damping. Reducing parallel groove depth can increase the positive effective damping. In terms of leakage and rotordynamic characteristics, the novel HGPG liquid seal is a better seal design for liquid turbomachinery.

Geogrid reinforcement for improving bearing capacity and stability of square foundations

Abstract Shallow foundations are often the most economical option for building support, as they distribute structural weight to soil layers, require minimal earthwork, and do not necessitate specialized machinery. The most common type of soil in the city of Karbala is sandy soil. It is granular and loose by nature which has a relatively low bearing capacity. According to previous studies, the soil weakness is one of the problems with shallow foundation construction. Thus, the aim of this study is to improve the properties of the soil using geogrid reinforcement. Three critical parameters are examined, including depth, size, and number of geogrid layers in the soil reinforcement process to increase bearing capacity and decrease soil settling. The effect of geogrid depth (u) was studied by considering four depth ratios (u/B = 0.5, 1.0, 1.5, and 2.0) in order to determine the ideal depth of the geogrid layer, where (B) refers to the width of the footings. The results indicated that a decrease in depth ratio significantly increased the bearing capacity of footings built on reinforced soil layers compared to those built on natural soil, and the settlement reduction ratio (SRR) also increased. The size of the geogrid layer (i.e., width of the geogrid layer (b) was evaluated by evaluating four size ratios (b/B = 1.5, 3.0, 4.5, and 6.0). With an increasing size ratio of the geogrid layer, the bearing capacity ratio (BRC) was significantly improved. Additionally, the study examined the optimal number of geogrid layers, focusing on single and multiple layers with N = 1, 2, 3, and 4. The results showed a higher BRC for footings on reinforced soil layers, as well as a significant rise in SRR with an increase in the number of geogrid layers. Finally, it was concluded that the optimal depth ratio was u/B = 0.5, the size ratio was b/B = 4.5, and reinforced with three geogrid layers, which provided the highest bearing capacity and SRR. The experimental test results were verified by comparing them with those calculated using theoretically developed models. The variation between the experimental and theoretical results is reasonable, confirming that the experimental testing results exhibit a high degree of accuracy.

Optimizing fertilization depth to promote yield performance and economic benefit in maize for hybrid seed production

Fertilization depth adjustment is a well-known strategy for increasing crop yields. However, the precise mechanism associated with this strategy remains unclear, particularly regarding increased nutrient absorption and utilization, and maize seed production. Thus, we examined the effects of different nitrogen fertilization depths [0 cm (L0), 5 cm (L5), 15 cm (L15), and 25 cm (L25)] on maize crop growth, nutrient uptake and distribution, fertilizer use efficiency, grain yield, and economic benefits in a field study conducted for two years (2021–2022) in Hexi Oasis Irrigation Area, northwest China. The optimal nitrogen fertilization depth was crucial for enhancing growth, dry matter production, and the grain yield. In particular, compared with L15 and L5, L25 significantly (P < 0.05) increased the average plant height by 5.00 % and 10.36 %, respectively, and dry matter accumulation by 2.65 % and 3.39 %. Furthermore, compared with L5 and L15, the total nutrient uptake was 19.17 % (P < 0.05) and 7.11 % higher under L25, respectively, and the average grain nutrient uptake was 23.33 % higher (P < 0.05). Moreover, L25 significantly increased the N, P, and K fertilizer utilization efficiency compared with L5 and L15, and the highest dry matter to grain translocation occurred under L25. Structural equation modeling confirmed that deep nitrogen fertilization promoted growth, dry matter translocation to grain, and the uptake and distribution of nutrients in maize plants to significantly improve the fertilizer use efficiency and yield. These findings are important for guiding fertilization management practices to increase maize seed production in regions with similar climate conditions.

Theoretical analysis on the behavior of SPM anchor piles embedded in sand under oblique pullout load with emphasis on the padeye depth

Single-point mooring (SPM) system has been used in offshore engineering for its superiority in overcoming severe sea conditions. However, researches focused on the interaction mechanism between the anchor pile and soil in SPM systems remains insufficient, especially regarding the calculation method for oblique pullout bearing capacity that considers padeye depth. Based on the p-y curve method and load transfer method, this paper presents a simple prediction method for the behavior of anchor piles embedded in sand under oblique pullout load. The theoretical predictions are validated through comparing with results from the three-dimensional finite element method and existing centrifuge model tests. The effect of the loading angle and the padeye depth are analyzed and discussed. A negative bending moment peak and axial force discontinuity phenomenon appear at the padeye depth. The optimal padeye depth for anchor piles in this study ranges from approximately 0.53 to 0.80 times the pile length. When the padeye depth is less than 0.33 times of the pile length, the ultimate bearing capacity of the anchor pile increases with increasing load angles. Conversely, when the padeye depth exceeds 0.33 times the pile length, the ultimate bearing capacity decreases with the increasing load angles.

Influence of geometric design variables on the performance of a novel V-shaped cavity receiver

This study presents a novel cavity receiver for parabolic trough concentrators, incorporating a triangular envelope, a trapezoidal cavity, and a semi-circular flow channel. A total of 5120 designs were examined by tuning the rim angle of parabolic mirrors, the width and angle of the receiver's opening, and the depth of the absorber for different operating flow rates and temperatures. Batch simulations of these designs were automated by coupling newly developed and validated models of Monte Carlo ray tracing and semi-analytical 1-D energy balances in SOLTRACE® and MATLAB® to determine the heat fluxes and surface temperatures of the receiver, respectively. The results show that the rim angle must be reduced to maximize sun rays' interception, and the opening angle has the largest impact on performance. All dimensions must be decreased when operating at low flow rates and high temperatures to avoid excessive thermal losses. This results in maximum energy and exergy efficiencies of 74.7 % and 40.7 %, respectively. When operating at low temperatures and large flow rates, the largest energy and exergy efficiencies increase and decrease to 80.5 % and 27 %, corresponding to optimal rim angle, absorber depth, opening width, and opening angle of 60°, 85 mm, 200 mm, and 100°, respectively.

Research on the surface modification and microstructure evolution during gear profile grinding based on cellular automaton

The matrix structure of high-strength gears mainly comprises martensite with high stacking fault energy. The dominant mechanism of microstructure evolution in the surface layer during profile grinding is continuous dynamic recrystallization. However, the understanding of continuous dynamic recrystallization structure evolution during gear profile grinding remains limited. In this study, a predictive model based on cellular automaton for martensite structure evolution during gear profile grinding is proposed. Coupled with the finite element method, the microstructure evolution prediction of high-strength steel gears in profile grinding is conducted. The proposed model demonstrates good consistency with experimental data in calculating the proportion of low angle grain boundaries during grinding process. By combining experimental and theoretical prediction results, the mechanism of the influence of grinding depth on grain refinement in surface layer during gear profile grinding is elucidated. The dislocation density increases with the increase of grinding depth, leading to the generation and transformation of more subgrains. By analyzing the grain size and the proportion of subgrain boundaries, an optimal grinding depth threshold under dry grinding conditions is determined. This study provides valuable insights into the continuous dynamic recrystallization structure evolution during gear profile grinding process.

Assessing flood-depth effects on water quality, nutrient uptake, carbon sequestration, and rice yield cultivated on Histosols

In the Everglades Agricultural Area (EAA), Florida, cultivating rice in flooded paddies is becoming increasingly popular to conserve water and soil health. Flood depth is a critical factor affecting the discharged water quality, soil carbon, and yield production. However, few studies have comprehensively investigated the optimal flood depth in EAA, considering multi-functional indices. To address this gap, we investigated drainage water quality, water quantity, nutrient uptake, soil carbon, and rice yield in rice paddies in histosol soils over a two-year period at four flood depths (5, 10, 15, and 20 ​cm). For each flood depth, averaged over two years, total outflow loadings of suspended solids, nitrogen, phosphorus, and potassium were significantly reduced by 40 ​%, 38 ​%, 36 ​%, and 32 ​%, respectively, compared to inflow water loadings (p ​< ​0.001). Soil organic carbon (SOC) in 5, 10, 15, and 20 ​cm flood treatments increased annually at a rate of 3.85 ​%, 5.64 ​%, 6.86 ​%, and 6.86 ​%, respectively; for these same treatments, soil active organic carbon (AOC) decreased annually at rates of 11.75 ​%, 8.63 ​%, 20.07 ​%, and 8.48 ​%, and rice grain yield was 4488, 5103, 5450, and 5386 ​kg ​ha−1, respectively. Overall, considering the water quality, SOC, AOC, and rice yield production, irrigating rice paddies at a flood depth of 15 ​cm most effectively improves water quality, increases carbon sequestration, reduces active carbon, and yields more rice than other flood depths. By evaluating the effects of flood depth on the soil–water–plant nexus in a holistic manner, we propose a more sustainable and environmentally friendly mode of rice cultivation within the EAA.

Influence of Tank Water Depths on Reproductive Performance of Catfish (Heterobranchus longifilis) Valenciennes, 1840

Aims: To determine the optimum water depth required for catfish spawning in hatcheries. Study Design: Treatments were assigned using complete randomized design. Place and Duration of Study: Fish Farm Complex of the Akwa Ibom State University (AKSU), Nigeria. Methodology: Eighteen (18) similarly-sized H. longifilis broodstock (2.51-2.53 kg, 64 – 66 cm): comprising six broodstock of three males and three females, were held for six months at 0.50 m, 0.75 m and 1.0 m pond water depth. All males were sacrificed for milt extraction without hormonal inducement; with milt from each treatment diluted with normal saline solution. Female broodstock from each treatment were separately induced with ovaprim hormones at a single dosage of 0.5ml/kg body weight of fish and allowed for 16 hours before manual stripping; 3g of egg from each broodstock and mixed with the diluted milt and activated with 100 ml of normal saline. The fertilized eggs were incubated and thereafter assessed for percentage fertilization, hatchability, survival and fry production success. Results: broodstock reproductive parameters significantly increased (P = 0.00) with water depth of broodstock culture tank. Percentage fertilizations were: 49.50±0.78, 68.17±0.93, and 82.50±1.44; respectively. Percentage hatchability of broodstock eggs were: 91.37±1.65 significantly higher for 1.0 m water depth group than 67.79±4.58 from 0.75 m water depth treatment while the least value of hatchability 50.31± 0.78 was recorded for broodstock raised at 0.50 m water depth. The fish group raised at 1.0 m water depth also exhibited highest percentage survival value of 97.02 ± 1.09 and fry production success value of 73.08 ± 0.53 while broodstock raised at 0.50 m water depth indicated the least values: % survival, 8.38 ± 0.48 and fry production success of 2.07 ± 0.07. Conclusion: In times or places of water scarcity, H. longifilis broodstock may be raised at pond water of 0.5 m to 1.0 m. But the water depth that would afford the best breeding and reproductive performance is at 1.0 m depth.

Variability in depth for national-level swimmers’ freestyle dive starts, push starts and tumble turns

The dive start and tumble turn are key skills in freestyle swimming and are the fastest part of a race (Higgs, Pease &amp; Sanders, 2016, J Sports Sci, 35, 995-1003). Consistency in performing them, to a high-level, is crucial when races can be won by &lt;0.1s. Many studies have investigated dives, tumble turns and underwater undulatory swimming performance, however, very few have examined the effect of depth (West et al., 2022, Sports Med Open, 8). Swimming depth will affect wave drag, total distance travelled underwater and, possibly, kick amplitude. Collectively, these will impact dive and tumble turn performance. The current project aims to quantify the variability of a swimmer’s freely chosen depth when performing a freestyle dive start, push start and turn. Ethics approval for this study was provided by the School of Medicine’s Research ethics board. We aim to recruit 14 participants (7=male, 7=female), over the age of 16 and currently competing at a national level in freestyle events. After a 10-min self-determined warm-up, participants are asked to perform three freestyle dives, push starts, and tumble turns in a randomised order. There are three minutes rest between each task and five minutes between three tasks. Each of the nine tasks will be recorded using a custom-built CONTEMPLAS camera system, using 12 cameras filming at 100Hz. Participants are provided with 5-min to complete a self-determined cool-down. Video recordings will be analysed using SIMI Motion capture to perform manual digitisation. A coefficient of variance analysis and a repeated measures Anova and intraclass correlation to quantify the variability in depth within the dives, push starts and the turns at both an individual and group level. As part of this study, we are also assessing the reliability and validity of an automated digitising software package. The validity and reliability of the automatic digitisation method versus the manual digitisation method was analysed via a Bland Altman analysis to obtain the limits of agreement between the two methodologies. The results are pending, although they will be used to assign individual swimmers with target depth ranges for subsequent experiments that aim to identify the optimum depth for these skills.

Optimising needle depth in temporomandibular joint arthrocentesis: a magnetic resonance-based study for safety and efficacy

The aim of this paper was to determine the optimal needle depth for temporomandibular joint (TMJ) arthrocentesis using magnetic resonance imaging (MRI), with the aim of improving procedural safety and efficacy in clinical practice. A retrospective analysis of 264 TMJ MRIs from 132 patients at Istanbul Medipol Mega University Hospital was conducted. T2-weighted MRI sequences were utilised to measure distances from skin to joint capsules at varying needle entry points, applying the double puncture technique. The study adhered to ethical standards with appropriate approvals. The analysis revealed significant gender-related variations in needle depths (females showing shorter distances than males, p < 0.05). No significant gender differences were found in condylar angles. An inverse correlation between age and condylar angle suggested age-related anatomical changes. Crucially, a 20 mm needle depth was identified as safer and more effective than the previously recommended 25 mm. This study underscores the necessity of revising needle depth to 20 mm in TMJ arthrocentesis. These findings hold significant implications for improving procedural safety and catering to demographic variations.

Investigation on the effect of different groove depth and width on the tip clearance leakage flow of hydrofoil

Abstract Due to the complexity of axial-flow hydraulic machinery structure and the difficulty of flow field analysis, this paper takes three-dimensional hydrofoil as the research object to analyse the flow characteristics of clearance flow and carry out research on clearance leakage control. The 3-D hydrofoil model with two kinds of gap widths was calculated by using the numerical model method, and compared with the experiment; the influence law of different groove depth and width on the gap leakage flow characteristics and energy characteristics was studied. The results show that with the increase of groove depth, the clearance leakage increases, the lift-drag ratio decreases, and the pressure coefficient increases. Higher axial velocity is shown with increasing groove depth under the small tip clearance, while the opposite is true for large gaps. The optimal groove depth is determined to be D=1mm. When the groove width is 2mm, the pressure coefficient of the hydrofoil is the highest and the vorticity coefficient is the smallest, so the hydrofoil has better performance. In summary, when groove depth D=1mm and groove width W=2mm, the clearance leakage flow rate is smaller and the lift-drag ratio is higher. This study provides a new method for improving the flow field and running stability of turbine-machines with tip clearance in practical engineering.

“Bubble Behind Iris” Technique in Descemet Membrane Endothelial Keratoplasty for Vitrectomized Eyes

Purpose: Performing Descemet membrane keratoplasty (DMEK) in vitrectomized eyes can be challenging, owing to the compromised stability of the iris–lens diaphragm. This study presents a “bubble behind iris” technique in DMEK to achieve a shallower anterior chamber in vitrectomized and pseudophakic eyes. Methods: The patients with vitrectomized eyes who underwent DMEK between October 2022 and March 2023 were enrolled in this study. Following the insertion of the donor tissue into the anterior chamber, a 30-gauge blunt cannula was used to introduce an air bubble posterior to the iris. The depth of the anterior chamber was confirmed before unfolding the graft. Subsequently, the air bubble was carefully replaced with balanced salt solution insertion using the blunt cannula, and the anterior chamber was filled with gas for graft attachment. Results: This study included 3 eyes of 3 patients (3 men; mean age 62.3 ± 8.5 years). The best spectacle corrected visual acuity and central corneal thickness improved in all eyes with no notable complications. Conclusions: The “bubble behind iris” technique is a straightforward and minimally invasive approach for maintaining an optimal anterior chamber depth during DMEK in vitrectomized and pseudophakic eyes.

Prognosis of deep margin excisions within or beyond subcutaneous fat for invasive acral melanoma of the sole: A multi-institutional retrospective study.

9582 Background: There is scant evidence concerning the optimal deep margins for wide excision (WE) of primary tumors in melanoma surgery. Despite the importance of preserving plantar subcutaneous fat in the sole for cushioning function, no study data exists on the optimal depth margins for acral melanoma of the sole (sole AM). Thus, we aimed to compare the prognosis associated with different deep margin excisions for sole AM. Methods: We conducted a retrospective review of clinical records from patients with invasive resectable sole AM who underwent WE of the primary tumor across 41 Japanese institutions. The prognosis was compared between two groups based on different deep margin excisions: those with tumors excised within (S-group) or beyond (D-group) the subcutaneous fat. Kaplan—Meier analysis and multivariable Cox proportional hazard models were used to estimate the survival probabilities. Propensity-score matching (PSM) was used to adjust for numerical differences in baseline characteristics. Results: This study included a total of 425 patients (median age 73 years) with invasive sole AM, who underwent WE based on the peripheral surgical margins recommended in the National Comprehensive Cancer Network guidelines. The median follow-up period was 48 months. The S-group included 263 patients and the D-group 162 patients. The baseline characteristics significantly differed between the two groups in terms of Breslow thickness ( P &lt; 0.01), presence of ulcer ( P &lt; 0.01), and presence of in-transit, satellite, and regional lymph node metastasis ( P &lt; 0.01). The other baseline characteristics were similar. Although local recurrence-free survival (LRFS) did not significantly differ between groups, the S-group showed significantly longer disease-free (DFS) and overall survival (OS) than the D-group (5-year LRFS, 96% vs. 90%; P = 0.08; 5-year DFS, 70% vs. 41%; P &lt; 0.01; 5-year OS, 84% vs. 69%; P &lt; 0.01). In contrast, multivariable Cox proportional hazard models showed no significant differences in LRFS, DFS, and OS between the two groups (LRFS, hazard ratio [HR], 1.87, P = 0.18; DFS, HR, 1.05, P = 0.77; OS, HR, 1.08, P = 0.72). After PSM, the groups were balanced at a 1:1 ratio (128 patients in each group) and no statistical significance was found in LRFS, DFS, or OS between the adjusted groups (5-year LRFS, 97 % vs. 91 %; P = 0.40; 5-year DFS, 65 % vs. 48 %; P = 0.053; 5-year OS, 80 % vs. 73%; P = 0.18). Subgroup analysis of stage I, II, and III also indicated no statistical significance in LRFS, DFS, and OS between the two groups (stage I: LRFS, P = 0.11; DFS, P = 0.65; OS, P = 0.26; stage II: LRFS, P = 0.37; DFS, P = 0.06; OS, P = 0.85; stage III: LRFS, P = 0.29; DFS, P = 0.67; OS, P = 0.85). Conclusions: In sole AM, WE with excessive deep margins beyond the subcutaneous fat did not improve prognosis. Excision of the primary tumor within the subcutaneous fat may be an optimal deep margin for sole AM.

Numerical study on the dynamic pressure control for self-forming roadways using CHRCT in thin coal seams with thick and hard roofs

Close-hole roof-cutting technology (CHRCT, also called “dense drilling”) has been widely applied in coal mines due to its economic and safety benefits. Inappropriate cutting parameters and support schemes can lead to dynamic pressure disturbances in self-forming roadways with thick and hard roofs. Moreover, fully characterizing the procedure and process of self-forming roadways using CHRCT in the field is difficult, resulting in unconvincing results. Therefore, this study aims to fill the gaps in theoretical knowledge and methodology. First, the dynamic pressure characteristics of the self-forming roadway using CHRCT were investigated, and the dynamic pressure types of the roadway were classified. There are three main types: roof cut off along the coal wall side of, severe deformation, and overhanging roof of a roadway after the second working face mining. The effects of different hole parameters (inclination angle, depth and spacing) on the roof cutting to form a roadway were also investigated. The optimal hole inclination, depth and spacing of 15°, 8 m, and 200 mm were determined through a series of experiments. Then, three support schemes embedded in the roadway were compared in terms of stress evolution, bolt and cable axial forces, roof displacement, and structure. Finally, this study proposes a dynamic pressure mitigation strategy through the optimization of parameters for close-hole roof-cutting and support schemes, monitoring and controlling ground pressure in roadways, and taking auxiliary measures for pressure relief. The results show that this strategy can effectively eliminate the dynamic pressure of the roadway and meet the stability requirements of the full mining cycle. This paper presents a methodology for analysing CHRCT via numerical simulation. Moreover, this approach is of great theoretical and practical importance for dynamic pressure control for self-forming roadways using CHRCT in thin coal seams with thick and hard roofs.

Investigation on the Impact Fracture Mechanism of Rock in Microgravity Environment Using the Continuum-Discontinuum Element Method

Abstract In-depth analysis of asteroid samples will provide a key scientific basis for understanding its evolution history, resource utilization, and life origin. Obtaining rock samples from asteroids is getting more and more attention. However, successful sampling in asteroid is difficult due to extremely complex environmental conditions. In this paper, the dynamic processes of rock failure by sampling device are investigated by a continuum-discontinuum element method (CDEM) to instruct the rock sampling in asteroid. The deformation and failure of rock samples under different conditions (impact speeds, impact positions, rock cut-slot numbers, cut-slot spacings, cut-slot depths and cut-slot widths, etc.) are analyzed, and the relationships between the rock failure and hammer impact method are obtained. The results show that the cut-slot formed by grinding wheel increases the free surface of rock sample, which is beneficial to impact fracture and asteroid sampling. The relative distance between cut-slot free surface and impact position significantly affects the rock fracture under impact loading. The fracture degree of rock with single cut-slot is obviously smaller than that of rock with double cut-slots, the cut-slot scheme of double grinding wheels is more suitable for asteroid sampling. Under the impact loading, the rock fracture is negatively correlated with the cut-slot spacing formed by double grinding wheel cutting, the effective spacing of double cut-slots is 12 mm. The fracture unit number of rock varies nonlinearly with an increase of the depth from impact position, there is an optimal cut-slot depth corresponding to a certain impact velocity, and the rock crushing efficiency of asteroid sampling can be improved as the cut-slot depth matches the crack propagation depth.

Optimized sand tube irrigation combined with nitrogen application improves jujube yield as well as water and nitrogen use efficiencies in an arid desert region of Northwest China

Efficient water-saving irrigation techniques and appropriate nitrogen (N) application are keys to solving the problems of water scarcity and irrational fertilization in jujube cultivation. In this study, first, the effects of sand tube irrigation (STI) on surface and subsurface wetted characteristics were investigated using in-situ infiltration tests in a jujube garden. Compared with surface drip irrigation (SD), STI reduced surface wetted area by 57.4% and wetted perimeter of the surface wetted circle by 37.1% and increased subsurface maximum infiltration distance of wetting front by 64.9%. At the optimal sand tube depth of 20 cm, surface wetted area of the surface wetted circle decreased by 65.4% and maximum infiltration distance of the wetting front increased by 70.9%, compared with SD. Two-year field experiments then investigated the effects of STI and SD on soil water storage, jujube leaf chlorophyll, net photosynthetic rate, actual water consumption, fruit yield, and water (WUE) and N (NUE) use efficiencies at four levels of N (pure nitrogen: N1, 0; N2, 286 kg ha–1; N3, 381 kg ha–1; N4, 476 kg ha–1) at the same irrigation amount (45 mm irrigation–1, total of 8). Compared with SD, STI increased soil water storage 18.0% (2021) and 15.6% (2022) during the entire growth period and also chlorophyll content, nitrogen balance index, and net photosynthetic rate, with both increasing and then decreasing with increasing N. Compared with SD, STI increased yields by 39.1% and 36.5% and WUE by 44.3% and 39.7% in 2021 and 2022, respectively. Nitrogen use efficiency was 2.5 (2021) and 1.6 (2022) times higher with STI than with SD. STI combined with N3 had the highest yield, WUE, NUE, and net income and is thus recommended as the optimal water–N combination. In conclusion, STI combined with appropriate N application can be an effective water-saving irrigation technology alternative to SD in jujube cultivation in arid areas.

Optimum embedment depths for CFST column-to-foundation connections: Analytical and reliability-based approach

In the present study, the pullout capacity models were developed to derive analytical expressions for the minimum required depths of embedment for conventional and two recently published schemes of connection for circular and square concrete-filled steel tubular (CFST) columns. The models were developed by equating the pullout strength of the tube with the pullout capacity of the reinforced concrete (RC) footing. The pullout capacity of the RC footing was a function of the strength of cement grout, footing concrete, and RC footing reinforcement. The analytical expressions derived for the minimum required depths of embedment were utilized to deduce limit state functions. These limit state functions were then employed for the reliability calculations by means of the Monte Carlo Simulation (MCS) technique. The reliability calculations provide optimum embedment depths for CFST columns for the given reliability level. It was shown for the required reliability index of 3.0, the requirements of nominal embedment depth for the second column-to-foundation connecting scheme for circular and square CFST columns are 37.3% and 45.2% less than their corresponding first schemes of connection. This outcome proves the superiority of the second scheme (as a result of mechanical interlocking) over the first scheme. A few parametric studies were also conducted to obtain results of practical value.