Lateral Slope Research Articles

Finite element stress analysis of Aramany class I maxillectomy defect with single- and two-piece closed bulb obturators.

To evaluate the stress on the surrounding structures of Aramany class I maxillectomy defect restored with different obturator prostheses. Definitive three-dimensional (3D) finite element (FE) model of Aramany class I defect rehabilitated with single- and two-piece closed bulb obturator prostheses was constructed based on patient computed tomography (CT) using a software. Unilateral defect restored with tripodal design single-piece closed bulb obturator was used as FE model 1- and two-piece magnet retained closed bulb obturators as FE model 2. Finite element analysis (FEA) with three different load (150N, 200N and 250N) applications was used to calculate the equivalent von Mises stress. A least stress value of 62.28MPa was observed in two-piece closed bulb design with 150N force, and highest stress value of 104.15MPa was observed in single-piece obturator with application of 250N force. Minor difference in stress distribution pattern was observed between single-piece obturator and two-piece obturator, and stress value was comparatively lesser in two-piece than single-piece obturator. The stress pattern, distribution and numerical values increased with increase in magnitude of forces. More stress was observed on the lateral slopes of obturator closer to defect than in other areas of the obturator.

Analysis of the lateral slope’s impact on the calculation of water-filled rut depth

Accurate calculation of the water-filled rut depth is critical for assessing hydroplaning potential. Nevertheless, due to the difficulty in collecting and calculating the water-filled rut depth, most transportation agencies do not use i, especially in the case of lateral slopes, although water-filled rut depth is a key parameter that impacts driving safety. Contributions of this paper are development of a methodology to reliably compute the water-filled rut depth and quantitatively evaluate the influence of lateral slope on the water-filled rut depth. The proposed method include: 1) acquisition of the high-resolution 3D point cloud data of rut, 2) smooth processing of rut profile through moving average method with Matlab programming, 3) water-filled rut depth computation at different lateral slopes with the assistance of key points based on rut sections. With the variation of water-filled rut depth (ΔWD), its change rate (δWD), and the calculation error between the rut depth and the water-filled rut depth (Δn) as evaluation indexes, the variation law of water-filled rut depth under different lateral slopes is analyzed when considering the severity level and rut shape of the rut profile. Results show that: 1) the increase in lateral slope leads to the reduction of water-filled rut depth; 2) the water-filled rut depth is affected by the rut shape, including rut side wall’s slope and the key points’ elevation. The accurate calculation of the water-filled rut depth can provide reliable suggestions for safe driving.

Linear Anterior-Posterior Computed Tomography Parameters Used to Quantify Trochlear Dysplasia Are More Reliable Than Angular Measurements

(1) To evaluate the reliability of 9 commonly used quantitative parameters of the trochlear morphology on computed tomography (CT) and (2) to analyze for differences in the reliability regarding patient subgroups (patellofemoral instability [PFI] vs non-PFI). A retrospective analysis of lower-limb CT scans performed between August 1996 and February 2013 was performed. The CT scans of all patients with PFI and 30 randomly selected cases without a history of PFI (non-PFI) were included. The following measurements were performed on 1 proximal axial CT slice at the entrance of the trochlear groove and 1 slice 5 mm further distal: relative medial, central, and lateral trochlear height; trochlear depth; relative transverse trochlear shift; trochlear facet asymmetry; sulcus angle; and medial and lateral trochlear slope. Four investigators performed the measurements independently, and intraclass correlation coefficients (ICCs) were calculated for the entire study group, as well as for the PFI and non-PFI groups separately. In total, 66 cases (36 PFI cases) were included in the study. We found almost perfect inter-rater and intrarater agreement for the trochlear height on both axial CT slices (ICC, 0.831-0.977). For the other measurements, we found only fair reliability (ICC < 0.4) on the proximal CT slice, whereas on the distal CT slice, at least moderate reliability (ICC > 0.4) was observed. ICCs were lower for many parameters in the PFI group. Angular values were less reliable than linear values. In particular, measurements involving the medial facet (i.e., sulcus angle, medial trochlear slope, and trochlear facet asymmetry) were less reliable. When interpreting quantitative parameters defining the trochlear morphology, one must taken into account the considerably lower reliability of angular parameters such as the commonly used sulcus angle compared with linear measurements. Radiologic measurements are less reliable in cases of PFI than in subjects without instability. Level III, retrospective case-control study.

Trochlear Morphology Development: Study of Normal Pediatric Knee MRIs.

Trochlear dysplasia is a known risk factor for patellar dislocations yet normal trochlea development is not well described. This study will define the articular cartilage (AC) and subchondral trochlear morphology development in pediatric patients using magnetic resonance imaging (MRI) evaluation. A retrospective knee MRI review included patients aged 3 to 16 years with nonpatellofemoral-related diagnoses. International classification of diseases-9/International classification of diseases-10 codes were used to identify eligible study patients. Measurements of the trochlea were made on the basis of previously established methods using the axial MRI just distal to the physis at the deepest portion of the trochlear groove. Three linear [lateral trochlear height (LTH), medial trochlear height (MTH), and central trochlear height (CTH)] and 3 angular [sulcus angle (SA), lateral trochlear slope (LTS), and medial trochlear slope (MTS)] were made at AC and subchondral bone (SCB). The 12 measurements were made independently by 2 study authors. Inter-rater reliability was assessed using an interclass correlation coefficient for absolute agreement to the average of the scores. Trochlea measurements were summarized across age quartiles defined as first quartile (age, 5.1 to 8.3 y), second quartile (8.3 to 11.5 y), third quartile (11.5 to 14.3 y), fourth quartile (14.3to 16.9 y). Associations between age and trochlea measures were assessed using linear regression with Huber-White-adjusted SEs to account for clustering from a small number of patients (N=16) with >1 MRI. In total, 246 knee MRIs from 230 patients were included in this study; 113 patients (51%) were female, whereas 117 (49%) were male. A total of 116 MRIs (47%) were of the left knee and 130 (53%) were right knee. The average patient age was 11.4±3.4 years. Inter-rater agreement was high across all measures with interclass correlation coefficient values >0.7. Mean values for measurements are presented by age quartiles. LTH, MTH, and CTH showed a linear increase with age (range, 2 to 2.6 cm/y; P<0.001). SA, LTS, MTS measured at AC showed no change with age (P>0.05); however, LTS and MTS measured at SCB showed significant increases with age (0.6 and 0.9 degrees/y; P<0.001), whereas SA showed a decrease with age (-1.4 degrees/y; P<0.001). There were no significant differences found in the age associations by laterality, left versus right. There were no sex differences in the age associations for SA, LTS (P>0.05); however, for MTH, LTH, and CTH, males were found to have a significantly greater growth rate (P<0.001). This study found an increase in AC and SCB MTH, LTH, and CTH over time, as well as an increase in SCB LTS and MTS, with a decrease in SA. However, AC of the LTS and SA remained constant, with no significant change throughout growth. This normative data indicate that the LTS and SA of AC are predictors of final trochlea shape in normal development. Final trochlear morphologic development is nearly complete around age 12 years, with no significant changes occurring thereafter.

Difference in sex and the effect of a dominant lower extremity in the posterior tibial slope angle in healthy Japanese subjects

Background/objectiveAnterior cruciate ligament injuries are prone to re-injury, and it is crucial to prevent the primary injury. One of the anatomical risk factors for anterior cruciate ligament injury is the posterior tibial slope angle. Investigating the characteristics of healthy individuals with respect to the posterior tibial slope angle is important to elucidate the risk of developing anterior cruciate ligament injuries. The purpose of this study was to determine the characteristics related to sex and of the posterior tibial slope angle in healthy Japanese subjects, and the effect of the dominant lower extremity. MethodsSixty-two knees of 31 healthy Japanese college students (15 males and 16 females) were included in this study. Magnetic resonance images of both knee joints of the subjects were measured using a 0.3 T scanner. The medial and lateral posterior tibial slope angles were measured from the obtained magnetic resonance images. Magnetic resonance images of the knee joint of the dominant lower extremity were used to compare differences in sexes between the medial and lateral posterior tibial slope angles. Bilateral knee joint magnetic resonance images were used to compare the dominant and non-dominant lower extremities. Independent t-tests were used to compare the differences regarding sex in the medial and lateral posterior tibial slope angles and to compare the dominant and non-dominant lower extremities. ResultsA comparison of the mean lateral posterior tibial slope angle showed that males had a 8.8 ± 1.7° angle, while females had a 10.3 ± 2.2° angle, which was significantly greater (p = 0.047). There was no significant difference comparing the posterior tibial slope angle between the dominant and non-dominant lower extremities (p = 0.430). ConclusionsFrom the result of this study, the lateral posterior tibial slope angle was significantly higher in the female group than in the male group. However, both the medial and lateral posterior tibial slope angles were found to be unaffected by the dominant lower extremity.

Association Between MRI-Based Tibial Slope Measurements and Mucoid Degeneration of the Anterior Cruciate Ligament: A Propensity Score-Matched Case-Control Study.

Background:The cause of mucoid degeneration (MD) of the anterior cruciate ligament (ACL), which is commonly observed on magnetic resonance imaging (MRI) of patients with knee pain, has yet to be elucidated. Despite the limited evidence on the relationship between ACL lesions (injury and MD) and tibial morphologic features (ie, posterior tibial slope), the potential association between the presence of ACL MD and medial and lateral tibial slope (MTS and LTS) has not been well-established.Purpose:To investigate whether MTS and LTS measurements are associated with the presence of ACL MD.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Consecutive knee MRI examinations of patients referred by an orthopaedic surgeon for potential internal joint derangements were identified within a 4-year period. The presence of ACL MD and the MTS/LTS values were assessed by independent expert observers in consensus in a blinded fashion. From 413 consecutive knee MRI scans, a sample of 80 knees, including 32 knees with ACL MD (cases) and 48 knees with normal ACL (controls), were selected using propensity score matching method for age, sex, body mass index, and presence of severe medial tibiofemoral compartment cartilage damage. The association between ACL MD and MTS/LTS was evaluated using conditional regression models.Results:Knees with ACL MD had higher values of LTS (mean ± SD, 7.18° ± 3.58°) in comparison with control knees (5.32° ± 3.35°). Conditional regression analysis revealed a significant association between LTS measurements (not MTS) and ACL MD; every 1° increase in LTS was associated with a 17% (95% CI, 1%-35%) higher probability of having ACL MD.Conclusion:Excessive LTS was associated with the presence of ACL MD, independent of participants’ age, sex, BMI, and cartilage damage severity.

Influence of Dunes on Channel‐Scale Flow and Sediment Transport in a Sand Bed Braided River

AbstractCurrent understanding of the role that dunes play in controlling bar and channel‐scale processes and river morphodynamics is incomplete. We present results from a combined numerical modeling and field monitoring study that isolates the impact of dunes on depth‐averaged and near‐bed flow structure, with implications for morphodynamic modeling. Numerical simulations were conducted using the three‐dimensional computational fluid dynamics code OpenFOAM to quantify the time‐averaged flow structure within a 400 m × 100 m channel using digital elevation models (DEMs) for which (i) dunes and bars were present within the model and (ii) only bar‐scale topographic features were resolved (dunes were removed). Comparison of these two simulations shows that dunes enhance lateral flows and reduce velocities over bar tops by as much as 30%. Dunes influence the direction of modeled sediment transport at spatial scales larger than individual bedforms due to their effect on topographic steering of the near‐bed flow structure. We show that dunes can amplify, dampen, or even reverse the deflection of sediment down lateral bar slopes, and this is closely associated with 3‐D and obliquely orientated dunes. Sediment transport patterns calculated using theory implemented in depth‐averaged morphodynamic models suggest that gravitational deflection of sediment is still controlled by bar‐scale topography, even in the presence of dunes. However, improved parameterizations of flow and sediment transport in depth‐averaged morphodynamic models are needed that account for the effects of both dune‐ and bar‐scale morphology on near‐bed flow and sediment transport.

Femoral notch and proximal tibial morphology and their relationship with an anterior cruciate ligament injury in the Indian population: A magnetic resonance imaging-based study

Objectives: We aim to study the incidence of anterior cruciate ligament (ACL) injury to proximal tibia bone morphology in Indian patients. Materials and Methods: Forty male subjects who sustained non-contact ACL injury who presented to our center between October 2015 and December 2016 studied and compared to 40 non-ACL injury knee magnetic resonance imaging scans. Notch morphology and both medial and lateral posterior tibial slope measurements were performed and studied. Results: We noted that the difference in notch depth and notch angle between the two groups was not significant. There was a statistically significant higher incidence of ACL injury in patients with smaller notch widths. Both an increased medial and lateral posterior tibial slope did not demonstrate a statistically significant incidence in ACL injury. Conclusion: Notch width is a major contributing risk factor for ACL injury in Indian patients. This is in agreement with previously published literature.

A Simplified Classification of the Relative Tsunami Potential in Swiss Perialpine Lakes Caused by Subaqueous and Subaerial Mass-Movements

Historical reports and recent studies have shown that tsunamis can also occur in lakes where they may cause large damages and casualties. Among the historical reports are many tsunamis in Swiss lakes that have been triggered both by subaerial and subaqueous mass movements (SAEMM and SAQMM). In this study, we present a simplified classification of lakes with respect to their relative tsunami potential. The classification uses basic topographic, bathymetric, and seismologic input parameters to assess the relative tsunami potential on the 28 Swiss alpine and perialpine lakes with a surface area > 1 km2. The investigated lakes are located in the three main regions “Alps”, “Swiss Plateau”, and “Jura Mountains”. The input parameters are normalized by their range and a k-means algorithm is used to classify the lakes according to their main expected tsunami source. Results indicate that lakes located within the Alps show generally a higher potential for SAEMM and SAQMM, due to the often steep surrounding rock-walls, and the fjord-type topography of the lake basins with a high amount of lateral slopes with inclinations favouring instabilities. In contrast, the missing steep walls surrounding lakeshores of the “Swiss Plateau” and “Jura Mountains” lakes result in a lower potential for SAEMM but favour inundation caused by potential tsunamis in these lakes. The results of this study may serve as a starting point for more detailed investigations, considering field data.

Beighton Score, Tibial Slope, Tibial Subluxation, Quadriceps Circumference Difference, and Family History Are Risk Factors for Anterior Cruciate Ligament Graft Failure: A Retrospective Comparison of Primary and Revision Anterior Cruciate Ligament Reconstructions

To assess patient history, physical examination findings, magnetic resonance imaging (MRI) and 3-dimensional computed tomographic (3D CT) measurements of those with anterior cruciate ligament (ACL) graft failure compared with primary ACL tear patients to better discern risk factors for ACL graft failure. We performed a retrospective review comparing patients who underwent revision ACL reconstruction (ACLR) with a primary ACLR group with minimum 1-year follow-up. Preoperative history, examination, and imaging data were collected and compared. Measurements were made on MRI, plain radiographs, and 3D CT. Inclusion criteria were patients who underwent primary ACLR by a single surgeon at a single center with minimum 1-year follow-up or ACL graft failure with revision ACLR performed by the same surgeon. A total of 109 primary ACLR patients, mean age 33.7 years (range 15 to 71), enrolled between July 2016 and July 2018 and 90 revision ACLR patients, mean age 32.9 years (range 16 to 65), were included. The revision ACLR group had increased Beighton score (4 versus 0; P < .001) and greater side-to-side differences in quadricep circumference (2 versus 0 cm; P < .001) compared with the primary ACLR group. A family history of ACL tear was significantly more likely in the revision group (47.8% versus 16.5%; P < .001). The revision group exhibited significantly increased lateral posterior tibial slope (7.9° versus 6.2°), anterolateral tibial subluxation (7.1 versus 4.9 mm), and anteromedial tibia subluxation (2.7 versus 0.5 mm; all P < .005). In the revision group, femoral tunnel malposition occurred in 66.7% in the deep-shallow position and 33.3% in the high-low position. The rate of tibial tunnel malposition was 9.7% from medial to lateral and 54.2% from anterior to posterior. Fifty-six patients (77.8%) had tunnel malposition in ≥2 positions. Allograft tissue was used for the index ACLR in 28% in the revision group compared with 14.7% in the primary group. Beighton score, quadriceps circumference side-to-side difference, family history of ACL tear, lateral posterior tibial slope, anterolateral tibial subluxation, and anteromedial tibia subluxation were all significantly different between primary and revision ACLR groups. In addition, there was a high rate of tunnel malposition in the revision ACLR group.

Study of relationship of posterior tibial slope in anterior cruciate ligament injury

ObjectiveTo determine the relationship between Posterior Tibial slope in terms of medial and lateral in Anterior cruciate ligament deficient patients. MethodsMagnetic resonance images (MRI) of the knee of 100 ACL injured patients and 100 ACL intact patients were studied. Their medial and lateral posterior tibial slopes were measured using MRI. Of 200 subjects, 100 (Male- 63, Female- 37) were controls, other 100 (Male – 68, Female-32) were ACL injured cases. Using DIACOM viewer software,the slopes of both medial and lateral slopes were measured. Range of Variation, mean value and standard deviation of medial tibial plateau slope (MTS), lateral tibia plateau slope (LTS) of controls and ACL injured patients were measured. The data collected were entered into Microsoft excel worksheet and analysed using statistical package for social sciences, Version 15.0 (SPSS Inc. Chicago, IL, USA). Distribution of data was confirmed using Shapiro's Wilk Test and appropriate parametric statistics were applied. For all analysis p value < 0.05 was set to be significant. ResultsIn control (ACL uninjured) population mean MTS was 5.95° with SD 3.09°, mean LTS was 6.08° with SD 3.48°. In ACL injured population mean MTS 6.41° with SD 2.66°, mean LTS was 8.12° with SD 3.65°. So ACL injured population had MTS steeper than control population with no statistical significance (p value < 0.27) and LTS was steeper than control population with statistical significance (p value < 0.001),where as there were comparable results between male and females. ConclusionOur current results indicate that lateral PTS is a risk factor for patients with primary ACL tears as compared with ligament-intact controls. Therefore,PTS should be considered as independent modifiable risk factors in ACL injury.

Estimation of discharge correction factor of modified Parshall flume using ANFIS and ANN

Purpose: To evaluate and compare the capability of ANFIS (Adaptive Neuro-Fuzzy-Inference System), ANN (Artificial Neural Network), and MNLR (Multiple Non-linear Regression) techniques in the estimation and formulation of Discharge Correction Factor (Cd) of modified Parshall flumes as based on linear relations and errors between input and output data. Design/methodology/approach: Acknowledging the necessity of further research in this field, experiments were conducted in the Hydraulics Laboratory of Civil Engineering Department, National Institute of Technology, Kurukshetra, India. The Parshall flume characteristics, associated longitudinal slopes and the discharge passing through the flume were varied. Consequent water depths at specific points in Parshall flumes were noted and the values of Cd were computed. In this manner, a data set of 128 observations was acquired. This was bifurcated arbitrarily into a training dataset consisting of 88 observations and a testing dataset consisting of 40 observations. Models developed using the training dataset were checked on the testing dataset for comparison of the performance of each predictive model. Further, an empirical relationship was formulated establishing Cd as a function of flume characteristics, longitudinal slope, and water depth at specific points using the MNLR technique. Moreover, Cd was estimated using soft computing tools; ANFIS and ANN. Finally, a sensitivity analysis was done to find out the flume variable having the greatest influence on the estimation of Cd. Findings: The predictive accuracy of the ANN-based model was found to be better than the model developed using ANFIS, followed by the model developed using the MNLR technique. Further, sensitivity analysis results indicated that primary depth reading (Ha) as input parameter has the greatest influence on the prediction capability of the developed model. Research limitations/implications: Since the soft computing models are data based learning, hence the prediction capability of these models may dwindle if data is selected beyond the current data range, which is based on the experiments conducted under specific conditions. Further, since the present study has faced time and facility constraints, hence there is still a huge scope of research in this field. Different lateral slopes, combined laterallongitudinal slopes, and more modified Parshall flume models of larger sizes can be added to increase the versatility of the current research. Practical implications: Cd of modified Parshall flumes can be predicted using the ANNbased prediction model more accurately as compared to other considered techniques. Originality/value: The comparative analysis of prediction models, as well as the formulation of relation, has been conducted in this study. In all the previous works, little to no soft computing techniques have been applied for the analysis of Parshall flumes. Even the regression techniques have been applied only on Parshall flumes of standard sizes. However, this paper includes not only Parshall flume of standard size but also a modified Parshall flume in its pursuit of predicting Cd with the help of ANN and ANFIS based prediction models along with MNLR technique

Is There a Role of Meniscal Morphology in the Risk of Noncontact Anterior Cruciate Ligament Rupture? A Case–Control Study

The purpose of this study was to identify the anatomical risk factors and determine the role of meniscal morphology in noncontact anterior cruciate ligament (ACL) rupture. A total of 126 patients (63 with noncontact ACL rupture and 63 age- and sex-matched controls) with intact menisci were included in this retrospective case-control study. On knee magnetic resonance imaging (MRI), meniscal morphometry (anterior, corpus, and posterior heights and widths of each meniscus), tibial slope (medial and lateral separately), notch width index, roof inclination angle, anteromedial bony ridge, tibial eminence area, and Q-angle measurements were assessed. The data were analyzed using multiple regression analyses to identify independent risk factors associated with ACL rupture. Using a univariate analysis, medial and lateral menisci anterior horn heights (p < 0.001; p < 0.003), medial and lateral menisci posterior horn heights (p < 0.001; p < 0.001), lateral meniscus corpus width (p < 0.004), and notch width index (p < 0.001) were significantly higher in the control group. Lateral tibial slope (p < 0.001) and anteromedial bony ridge thickness (p < 0.001) were significantly higher in the ACL rupture group. Multivariate analysis revealed that decreased medial meniscus posterior horn height (odds ratio [OR]: 0.242; p < 0.001), increased lateral meniscus corpus width (OR: 2.118; p < 0.002), increased lateral tibial slope (OR: 1.95; p < 0.001), and decreased notch width index (OR: 0.071; p = 0.046) were independent risk factors for ACL rupture. Notch stenosis, increased lateral tibial slope, decreased medial meniscus posterior horn height, and increased lateral meniscus corpus width are independent anatomical risk factors for ACL rupture. Meniscal morphological variations also play a role in ACL injury. This is a Level III, retrospective case-control study.

Sex Differences in Anatomic Features Linked to Anterior Cruciate Ligament Injuries During Skeletal Growth and Maturation

Background: Several anatomic features of the knee have been shown to affect joint and anterior cruciate ligament (ACL) loading and the risk of subsequent injuries. While several studies have highlighted sex differences between these anatomic features, little is known on how these differences develop during skeletal growth and maturation. Hypotheses: (A) Anatomic features linked to an ACL injury will significantly change during skeletal growth and maturation. (B) The age-related changes in anatomic features linked to an ACL injury are different between male and female patients. Study Design: Cross-sectional study; Level of evidence, 3 Methods: After institutional review board approval, magnetic resonance imaging data from 269 unique knees (patient age 3-18 years; 51% female), free from any injuries, were used to measure femoral notch width, posterior slope of the lateral tibial plateau (lateral tibial slope), medial tibial depth, tibial spine height, and posterior lateral meniscal bone angle. Linear regression was used to test the associations between age and quantified anatomic indices. Patients were then divided into 4 age groups: preschool (3-6 years), prepubertal (7-10 years), early adolescent (11-14 years), and late adolescent (15-18 years). Also, 2-way analysis of variance with the Holm-Sidak post hoc test was used to compare morphology between male and female patients in each age group. Results: The femoral notch width, medial tibial depth, and tibial spine height significantly increased with age (P < .001). The lateral tibial slope decreased with age only in male patients (P < .001). Except for the posterior lateral meniscal bone angle, the age-related changes in anatomy were different between male and female patients (P < .05). On average, early and late adolescent female patients had smaller femoral notches, steeper lateral tibial slopes, flatter medial tibial plateaus, and shorter tibial spines compared with age-matched male patients (P < .01). Conclusion: Overall, the findings supported our hypotheses, showing sex-specific changes in anatomic features linked to an ACL injury during skeletal growth and maturation. These observations help to better explain the reported age and sex differences in the prevalence of ACL injuries. The fact that most of these anatomic features undergo substantial changes during skeletal growth and maturation introduces the hypothesis that prophylactic interventions (ie, activity modification) would have the potential to reshape a maturing knee in a manner that lowers the risk of noncontact ACL injuries.

The Impact of Pavement Permeability on Time of Concentration in a Small Urban Watershed with a Semi-Arid Climate

Despite the popularity of the permeable pavements in urban areas in recent years, a few empirical equations have been developed to estimate the time of concentration (Tc) on pervious surfaces, and almost none of them is evaluated over the permeable pavements. In this paper, we aim to investigate the effect of low impact development (LID) on Tc and develop a new equation for estimating overland flow Tc compatible with both permeable and impermeable pavements in small urban watersheds with a semi-arid climate. An experimental model was devised to determine the new equation. Synthetic rainfall (22–40 mm.h−1) was applied to a rectangular shaped (6 m × 1 m) test watershed with an adjustable longitudinal slope (0.5–8%) and zero lateral slope. Porous asphalt and permeable interlocking concrete paver (PICP) were employed as the permeable pavements. Then, to validate the obtained equation from experimental data, a field study was conducted over a 1-ha watershed during a Low intensity (<4 mm.h−1) rain event. The comparison between 13 empirical and semi-empirical equations (including the one developed in this study) for estimating Tc in the test condition indicates that Chen and Wong’s equation with −0.03 bias and the Nash-Sutcliffe efficiency (NSE) equal to 0.9 and 0.7 for impervious and pervious surfaces respectively is the most precise equation. On the other hand, for the field study, the newly developed formula outperformed other equations and estimated the Tc with a 3.7% error. Moreover, the results of experiments on the PICP surface showed that replacing 10 to 15% of an urban watershed surface by PICP in a region with the rainfall intensity less than 40 mm.h−1 and storm duration less than 1 h causes a considerable reduction (almost 100%) in the surface runoff.

Parametric modal analysis of an induced-strain actuated wing-like plate for pitch and heave coupling response

This article investigates the feasibility of a plate-like flapping wing with varying geometric and boundary conditions actuated by surface-bonded piezoelectric material devices. The most influential structural parameters that vary dynamic response and heave–pitch mode coupling are investigated. An analytically and experimentally validated dynamic finite element model is developed to analyze the structure. A parametric analysis is conducted by varying critical geometric parameters and boundary conditions, such as aspect ratio, actuator position, actuator angle, clamp size, and position; substrate thickness variation; and substrate-to-actuator-thickness ratio. Response metrics representing heave and pitch motions are taken as longitudinal curvature and lateral slope, respectively—the surface regression analysis and results leading to these choices are presented. Maximum longitudinal curvature and lateral slope amplitudes and phase shifts are reported for key parameter choices. Longitudinal curvature to lateral slope coupling is achieved with the introduction of a leading edge stiffener to the otherwise uniform thickness plate. Conditions and parameters that lead to and influence heave–pitch coupling are presented and discussed in detail. This article presents a unique approach to flapping mode of flight compared to the literature. The article proposes a purely induced-strain actuation approach rather than the typical “mechanisms” based approach.

Electrochemical machining of a rhombus hole with synchronization of pulse current and low-frequency oscillations

Abstract Metal gratings with rhombus holes are widely applied in lightweight aircraft components. Electrochemical machining (ECM) is a nontraditional processing technology with no tool loss and no thermal deformation that has unique advantages for the high-quality processing of rhombus holes. However, the flow paths of the electrolyte in the lateral gap are quite different, and stray corrosion easily occurs on the sidewall due to the different diagonal lengths of a rhombus hole. In this paper, a method was proposed to improve the flow field and processing localization by the synchronization of the pulse power supply and low-frequency oscillations. The on and off positions of the pulse power supply are symmetrical with respect to the wave trough of the oscillation waveform. Based on the coupled simulation of the gas-liquid two-phase flow field and electric field, the effects of assisting oscillations and synchronization of the pulses and oscillations on the void fraction, electrical conductivity, current density, dissolution rate and evolution of the anode profile were investigated. Moreover, the effects of assisting oscillations and synchronization of the pulses and oscillations on the lateral gap, sidewall slope, machining fillet and surface quality were experimentally studied. The experimental results of different ECM methods showed that the coupled simulation was effective and feasible. Moreover, the simulation analysis and experimental results both revealed that the processing accuracy and surface quality of a rhombus hole could be improved by using the synchronized ECM method. The lateral gap at the rhombus hole entrance was only 0.13 mm, the sidewall slope was 0.026 and the surface roughness was Ra0.134 μm under the optimized parameters.

Fluid seepage associated with slope destabilization along the Zambezi margin (Mozambique)

Evidences for active fluid seepages have been discovered along the Zambezi continental slope (offshore Southern Mozambique). These seepages are mostly associated with pockmarks which are aligned along a trend parallel to the slope and running closely upstream of the headwall scarp of a wide zone of slope destabilization. Fluid seepages are interpreted as a potential trigger for the slope destabilization. Acoustic anomalies within the water column have been interpreted as related to moderate bubble seepages mostly located outside and only punctually inside the destabilization zone. Exploration with the SCAMPI towed camera system in the widest pockmark (diameter 200 m wide) has shown fluid seepages associated to authigenic carbonate crusts and possibly bacterial mats. These fluid seepages are also associated to the presence of chemiosynthetic organisms (Vesicomyidae and Thyasiridae bivalves, Siboglinidae tubeworms). The sampled gas in the sediment corresponds mainly to CH4 of microbial origin, generated by hydrogenotrophic methanogenesis from a substrate of organic origin, i.e. a conventional process of genesis of microbial gas in the marine domain. No evidence for thermogenic gas was detected. Another type of pockmarks has been observed within the core of the slope destabilization zone. Most of these pockmarks are inactive in terms of fluid seepage at present time and are associated to carbonate buildups forming chimney geometries. They probably correspond to diagenetic chimneys of former fluid migration pathways that have been exhumed during the mass sliding and the surrounding depression are related to recurrent activity of strong lateral slope currents which have scoured the sediments around. The spatial organization of the slope destabilization features is considered as representative of the temporal evolution of the landslide giving information about the dynamics of slope instability processes. This proposed evolution started by scattered seepages of formation water with dissolved gas. Then free gas seepages appeared notably in the upper part of the slope. This was followed by progressive shallow deformation in the sediments downslope of the main gas seepages. Finally, the whole slope was destabilized forming imbricated landslides exhuming locally former diagenetic chimneys.

Influence of Posterior Tibial Slope on Clinical Outcomes and Survivorship After Anterior Cruciate Ligament Reconstruction Using Hamstring Autografts: A Minimum of 10-Year Follow-Up

To investigate the influence of medial and lateral posterior tibial slope (PTS) on long-term clinical outcomes and survivorship after anterior cruciate ligament (ACL) reconstruction using hamstring autografts. A total of 232patients (mean age, 28.2 ± 8.9 years) who underwent primary ACL reconstruction from October 2002 to July 2007 were retrospectively reviewed. Patients with multiple ligament reconstruction, total meniscectomy, contralateral knee surgery before ACL reconstruction, open growth plate, and less than 10-year follow-up were excluded in the study. The medial and lateral PTS were measured from preoperative magnetic resonance imaging. Based on Li etal.'s previous study, the patients were divided into 2 groups according to their medial PTS (≤5.6° vs >5.6°) and lateral PTS (≤3.8° vs >3.8°), respectively. Clinical outcomes (clinical scores, stability tests and failure rate) were compared between the groups at the last follow-up. Furthermore, survival analysis was performed using the Kaplan-Meier method. All clinical scores (International Knee Documentation Committee subjective, Lysholm, and Tegner activity scores) and stability tests (physical examinations and side-to-side difference in Telos stress radiographs) were insignificantly different between the 2groups classified based on medial or lateral PTS. However, the failure rate was significantly higher in patients with medial PTS >5.6° (16.1% vs 5.1%, P= .01) or lateral PTS >3.8° (14.5% vs 4.7%; P= .01). The odds ratios of graft failure due to increased medial and lateral PTS were 3.18 (95% confidence interval, 1.22-8.28; P= .02) and 3.43 (95% confidence interval, 1.29-9.09; P= .01), respectively. In addition, the 10-year survivorship was significantly lower in patients with medial PTS >5.6° (83.9% vs 94.9%, P= .01) or lateral PTS >3.8° (85.5% vs 96.0%; P= .01). Increased medial (>5.6°) and lateral (>3.8°) PTS were associated with higher failure rate and lower survivorship at a minimum of 10-year follow-up after primary ACL reconstruction using hamstring autografts. Level III, retrospective comparative trial.

Morphological evolution of bifurcations in tide-influenced deltas

Abstract. In river-dominated deltas, bifurcations often develop an asymmetrical morphology; i.e. one of the downstream channels silts up, while the other becomes the dominant one. In tide-influenced systems, bifurcations are thought to be less asymmetric and both downstream channels of the bifurcation remain open. The main aim of this study is to understand how tides influence the morphological development of bifurcations. By using a depth-averaged (2DH, two-dimensional horizontal) morphodynamic model (Delft3D), we simulated the morphological development of tide-influenced bifurcations on millennial timescales. The schematized bifurcation consists of an upstream channel forced by river discharge and two downstream channels forced by tides. Two different cases were examined. In the first case, the downstream channels started with unequal depth or length but had equal tidal forcing, while in the second case the morphology was initially symmetric but the downstream channels were forced with unequal tides. Furthermore, we studied the sensitivity of results to the relative role of river flow and tides. We find that with increasing influence of tides over river, the morphology of the downstream channels becomes less asymmetric. Increasing tidal influence can be achieved by either reduced river flow with respect to the tidal flow or by asymmetrical tidal forcing of the downstream channels. The main reason for this behaviour is that tidal flows tend to be less unequal than river flows when geometry is asymmetric. For increasing tidal influence, this causes less asymmetric sediment mobility and therefore transport in both downstream channels. Furthermore, our results show that bedload tends to divide less asymmetrically compared to suspended load and confirm the stabilizing effect of lateral bed slopes on morphological evolution as was also found in previous studies. We show that the more tide-dominated systems tend to have a larger ratio of bedload-to-suspended-load transport due to periodic low sediment mobility conditions during a transition between ebb and flood. Our results explain why distributary channel networks on deltas with strong tidal influence are more stable than river-dominated ones.