Initial Curve Research Articles

Short Pulse Initiation of an RDX‐Based Explosive Using Large Diameter Flyer‐Plate Impacts

AbstractTen impact experiments are presented that probe the initiation behavior of an RDX‐based explosive. The explosive pellets were impacted by thin aluminum impactors supported by low‐impedance polymers, thereby subjecting the pellets to short duration shocks. Impact conditions were used to determine impact tilt, pulse pressure and duration, sample transit time, and whether or not a detonation occurred. Exploding Foil Initiator (EFI) launchers were used as a baseline for evaluating the technique, and it was found that the present technique addresses multiple shortcomings of EFI‐based systems. The aluminum foil allowed impacts with pressure durations of 70–80 ns, resulting in input conditions closely matching those of EFI‐based systems. The thicker aluminum plate impactors resulted in pulse durations of approximately 600 ns and allowed access to a previously inaccessible region of the initiation curve. Initiation thresholds were bracketed using both impactors, and the data is compared with complementary initiation data from EFI‐based systems with good agreement. Based on the results and closely related work, a novel, physically‐based criterion is proposed to allow the initiation curve to be predicted based on the explosive's unreacted equation of state and sustained‐pulse, shock‐to‐detonation run distance (the “Pop‐plot”), giving a physical basis for previously published observations. Finally, the criterion is applied to the data available to propose a relationship between pressure, pulse duration, and run distance, suggesting that input pulse durations of 50–100 % higher than the critical condition should be applied to approximate the run distance of a sustained pulse.

Study of acetylated EGCG synthesis by enzymatic transesterification in organic media

(-)-Epigallocatechin-3-O-gallate (EGCG), the most abundant polyphenolic compound in catechins, exerts excellent physiological effects including antioxidant. However, with its high hydrophilicity and poor lipophilicity, the application of EGCG in oil products is limited. In this study, EGCG acetylated derivatives were prepared by transesterification of EGCG with vinyl ester in acetonitrile/isopropanol (1:1 v/v). Lipase Lipozyme RM IM was found to be the optimum catalyst at concentration of 12 U/g EGCG, with a molar ratio of 1:5 of EGCG to vinyl acetate as the substrates. And 83.2% conversion was obtained after 10 h reaction at 50 °C. Based on the ping-pong model, the kinetic equation was constructed to determine the reaction kinetic parameters. The analysis of the initial rate and progress curve indicated that the transesterification of EGCG and vinyl acetate was kinetically regulated. Two major acetylated derivatives were identified as 5″-O-acetyl-EGCG and 3″, 5″-di-O-acetyl-EGCG by LC-MS/MS and NMR. Their enhanced lipophilicity was confirmed by transmittance test and octanol–water partition coefficient. The antioxidant activity of di-acetylated EGCG was superior to mono-acetylated EGCG and EGCG, but slightly lower than tert-butyl hydroquinone (TBHQ) as determined by peroxide values (POV) and Rancimat test. Acetylated EGCG might be used as a potent antioxidant for controlling oxidation of oil.

Vortex-induced swing (VIS) motion for energy harvesters and flowmeters

Vortex-induced vibration (VIV) has been widely studied in the fields of vibration control, building construction, and underwater vehicles. Recently, researchers began utilizing the VIV phenomenon for flow energy harvesting. Here, we describe that vortex shedding causes periodic rotational motions and explore these vortex-induced swing (VIS) motions for harvesting flow energy and measuring flow speed. An arc-bluff structure was constructed to enlarge the VIS motions, and a phenomenological model was developed using the Van der Pol equation. Swing characteristics when flow velocities were in the range of (0.15, 0.45) m/s were assessed. Experiments showed that the maximum swing amplitude of the device is 120°, and it converges to 80° as the water velocity increases. The frequency, amplitude, and initial angle curve of the VIS device can be used to represent the water speed vector. The proposed flowmeter showed a flow rate sensitivity of 7∼10 Hz/(m·s−1) in the experimental range. Energy harvester prototypes demonstrated a peak-peak output of 3.28 V in water with a velocity of 0.45 m/s. The present work provides an approach for the flow measurement and energy harvesting under low-speed and low-frequency conditions.

Comparison of surgical and pathological parameters after laparoscopic transperitoneal pelvic/para-aortic lymphadenectomies

ObjectiveLymphadenectomy is an integral part of surgical staging and treatment for patients with gynecologic malignancies. Since its introduction, laparoscopic lymphadenectomy has proved feasible, safe, and oncologically adequate compared with open...

Spinal deformity in adolescent idiopathic scoliosis at the end of Chêneau brace treatment

Background. Brace treatment is frequently used in adolescent idiopathic scoliosis (AIS). However, due to different brace models, long-term results on spinal deformity development at the end of Chneau brace treatment are not often described and differ in results.
 Aim. The aim of this work was to analyze clinical and radiological data of AIS patients treated with Chneau braces from the beginning of treatment until the end of growth and brace therapy in order to define realistic treatment results and expectations in an everyday setting.
 Materials and methods. 52 AIS patients with Chneau brace treatment were followed from the beginning of treatment until the end of growth. Clinical data such as the initial Risser sign, age at treatment, gender, curve patterns and body mass index were analyzed.
 Results. At the beginning of brace therapy, the average age was 13.1 years and patients showed a mean scoliotic curve angle of 30.9. Four months of brace use reduced the scoliotic curve to 20.1. Nine months after the end of brace treatment and an average treatment duration of 17 months, scoliosis has increased up to 30.3 again. In children with a lower maturity status, the initial scoliotic curve was less than in more mature patients leading to less spinal deformity at the end of treatment. In addition, obese children had less scoliosis correction during brace therapy than normalweight children.
 Conclusion. In patients with AIS treated with a Chneau brace, the initial curvature correction was 35%. Nine months after the end of brace treatment, scoliotic curves identical to the deformities at the beginning of treatment could be observed.

COVID-19 screening of asymptomatic patients admitted through emergency departments in Alberta: a prospective quality-improvement study.

The prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among asymptomatic patients admitted to hospital has implications for personal protective equipment use, testing strategy and confidence in the safety of acute care services. Our aim was to estimate the positivity rate of reverse transcription polymerase chain reaction (RT-PCR) testing among people admitted to hospital without symptoms of coronavirus disease 2019 (COVID-19) in Alberta, Canada. Between Apr. 9 and May 24, 2020, we screened for COVID-19 symptoms and tested for SARS-CoV-2 infection in all consecutive adult patients (≥ 18 yr) admitted via emergency department to 3 Alberta hospitals. We summarized the parameters of the epidemic curve and assessed the performance of symptom screening versus RT-PCR results on nasopharyngeal or oropharyngeal swab samples. The study period encompassed Alberta's initial epidemic curve, with peak active cases per 100 000 of 71.4 (0.07%) on Apr. 30, 2020, and 14.7 and 14.6 at the beginning (Apr. 9, 2020) and end (May 24, 2020), respectively. Testing for SARS-CoV-2 infection (64.9% throat and 35.1% nasopharyngeal swabs) was done on 3375 adults (mean age 51, standard deviation 21, yr; 51.5% men). None of the asymptomatic patients (n = 1814) tested positive, and 71 of those with symptoms tested positive (n = 1561; 4.5%, 95% confidence interval [CI] 3.6%-5.7%). Sensitivity of symptom screening (v. RT-PCR) was 100% (95% CI 95%-100%), and specificity was 55% (95% CI 53%-57%). Posttest probabilities for prevalence of SARS-CoV-2 infection ranging from 1.5 to 14 times the peak prevalence of active cases during the study did not change when we assumed lower sensitivity (92%). In a region with low disease prevalence where protocolized symptom assessment was in place during the admission process, we did not identify people admitted to hospital without COVID-19 symptoms who were RT-PCR positive. There may not be additive benefit to universal testing of asymptomatic patients on hospital admission in a setting of low pretest probability and strong public health containment.

An enhanced quasicrystalline Ti1.4V0.6Ni alloy electrode modified by uniformly covered RGO for nickel metal hydride battery

Herein, we provided a facile route to coat a flat and uniformly covered reduced graphene oxide (RGO) film on Ti1.4V0.6Ni quasicrystal alloy electrode surface by electrodeposition of graphene oxide and subsequent reduction with HI vapor. Raman spectrum showed HI has a better reduced effect than electrochemical reduction. The RGO coated alloy electrode exhibited a higher discharge capacity of 290.3 mA h g−1 and 23.8% higher capacity retention than the bare one after 50 cycles for the RGO layer effectively forbidding the direct contact of electrode and electrolyte. Moreover, Ti1.4V0.6Ni quasicrystal alloy with RGO coating exhibited faster hydrogen uptake kinetics by initial activation curve of gaseous hydrogen storage measurement and higher maximum hydrogen storage performance of 1.66 wt% than the bare Ti1.4V0.6Ni alloy. Thus, the enhanced properties of RGO as a multifunctional layer for Ti1.4V0.6Ni quasicrystal alloy were proved which could be achieved by a facile route.

Closed ideal planar curves

In this paper we use a gradient flow to deform closed planar curves to curves with least variation of geodesic curvature in the $L^2$ sense. Given a smooth initial curve we show that the solution to the flow exists for all time and, provided the length of the evolving curve remains bounded, smoothly converges to a multiply-covered circle. Moreover, we show that curves in any homotopy class with initially small $L^3\lVert k_s\rVert_2^2$ enjoy a uniform length bound under the flow, yielding the convergence result in these cases.

Experimental System of Hydrodynamic Action of Dunhuang Mogao Grottoes under Temperature-Humidity-Mechanical (THM) Coupling

In order to thoroughly investigate the weathering mechanism of the murals in Dunhuang Mogao Grottoes, based on the independently developed hydrodynamic test system of the surrounding rocks under the combined action of temperature, humidity, and stress, this study performed the liquid water adsorption test and gaseous water adsorption test of the surrounding rocks of the support body of Dunhuang Mogao Grottoes, as well as the softening test of the strength of liquid water adsorbed by the rock samples. The experimental results are as follows: (a) Q–t curve and lnw–lnt curve of the three types of black sandstone rock samples obtained by analyzing the nonpressure water absorption experiment data indicate that the Q–t curve of the rock samples showed a similar trend with time, with the initial curve being steep and rapid increase in the water absorption; the double logarithmic curve of water absorption is convex and tends to be saturated. (b) The absorbing water softening test analysis was carried out for four types of siltstone specimens with intensity of pressure; bibulous rate was found to vary with time, and sample parameters such as compressive strength and elastic modulus decreased linearly with increasing water absorption at different times of uniaxial compression test. (c) Through the summer and winter and cave surrounding rock within the sample, the gas adsorption of water simulation was combined with the adsorption curve analysis, indicating that the adsorption characteristics of the surrounding rock and the correlation of larger sample depend on season. These research results provide a reliable theoretical basis and technical support for the protection of the murals in the Mogao Grottoes of Dunhuang and the prevention and control by salt damage.

Thoracic vertebral morphology in normal and scoliosis deformity in skeletally immature rabbits: A Longitudinal study.

ObjectiveTo measure age‐related changes in thoracic vertebral body heights (VBH) in skeletally immature normative and scoliotic rabbits to assess how VBH change during growth. To examine the potential link between the moment‐arm of the rib tether and vertebral wedging as well as the sum of the curvature angles at the apical level (T7). To assess the correlation between the magnitude of initial spine curve and final spine curve in the scoliotic group.MethodsEight healthy, skeletally immature normative New Zealand rabbits and ten skeletally immature scoliotic rabbits which underwent unilateral rib tethering were included retrospectively. Each rabbit was scanned at two to four time points (at 7, 11, 14 and 28 weeks). Three dimensional bone models of thoracic vertebrae (T1‐T12) were digitally segmented and reconstructed. VBH were calculated using surface landmark points from each thoracic vertebra. Apical level (T7) ± 2 levels in scoliotic rabbits were compared to their corresponding levels and time points in the normative group. The moment‐arms between the centroids of 2D projections of T3‐T9 vertebral bodies and the line which connects the centroids of the end levels were calculated.ResultsBilateral left‐right (L‐R) symmetry and anterior‐posterior (A‐P) asymmetry were observed in normative VBH. Bilateral concave‐convex (CC‐CX) asymmetry and (A‐P) asymmetry were observed in scoliotic VBH. No significant differences in growth rates were found between the normative and scoliotic groups. Vertebral wedging as well as curvature magnitude were positively correlated with the moment‐arms.ConclusionUnilateral rib tether applies compressive forces on both concave and convex sides, whereas compressive forces are lower on the latter. Knowing the amount of vertebral wedging or curve magnitude would enable us to predict the applied force (moment‐arms), which is important for planning a corrective surgery.

Modeling Runoff and Sediment Yield in Highly Gullied Regions of Kashmir using SWAT Model: A Case Study of Lolab Watershed

Soil erosion in highly gullied regions of Kashmir valley is a serious global issue due to its impacts on economic productivity and environmental consequences such as land disintegration and one of the most affected areas is Lolab which is flood-prone and has witnessed several disastrous floods in the past. This means assessment of hydrological behavior should be highly prioritized and the most problematic sub-basins contributing to the erosion and excessive runoff identified to formulate and apply proper management strategies. This study integrated the Soil and Water Assessment Tool (SWAT) with Arc software to simulate the runoff and sediment yield of Lolab Watershed. The method was applied due to its flexibility in inputting data requirements and the capability to model larger catchments and mountainous areas. Meanwhile, sensitivity analysis showed the most sensitive four parameters for runoff estimation with the initial soil conservation service curve number II rated to be the highest and two others were found for sediment estimation with channel erodibility factor rated highest. The calibration of the values of these sensitive parameters led to the provision of reliable NashSutcliffe (NSE) and Coefficient of determination(R2) efficiencies which makes SWAT a good analyzing tool to assess the hydrological behavior of highly gullied region and un-gauged basins of Kashmir. These factors were found to be above 0.90 for both runoff and sediment yield and the sediment yield rates were estimated using SWAT at individual sub-basin levels after which a prioritization map was prepared to determine the most problematic sub-basins in the watershed.

Safety and Feasibility of Robotic Natural Orifice Specimen Extraction Surgery in Colorectal Neoplasms During the Initial Learning Curve.

Aim: To analyze the learning curve (LC) for robotic natural orifice specimen extraction surgery (NOSES) for colorectal neoplasms and evaluate safety and feasibility during the initial LC.Method: Patients who consecutively underwent robotic NOSES performed by two surgeons between March 2016 and October 2019 were analyzed retrospectively. The operation time was evaluated using the cumulative sum method to analyze the LC. The clinicopathological data before and after the completion of LC were extracted and compared to evaluate safety and feasibility.Results: In total, 99 and 66 cases were scheduled for robotic NOSES by Prof. Yao and Prof. Li, respectively. The peak points of LC were observed at the 42nd and 15th cases of Yao and Li, respectively, then operation time began to decrease. Only the operation time for Yao before the completion of LC (213.3 ± 67.0 min) was longer than that after the completion of LC (143.8 ± 33.3 min). For Yao nor for Li, other indices, such as postoperative hospital stay, intraoperative blood loss, conversion to laparotomy, incidence of anastomotic leakage, reoperation rate, and 90-day mortality rate lacked significant statistical differences(P > 0.05). In terms of feasibility, the number of lymph nodes harvested, positive resection margin rate, and total cost before and after the completion of LC had no significant statistical difference (P > 0.05).Conclusion: The cases before the completion of LC for robotic NOSES in colorectal neoplasms varied from 15 cases to 42 cases. Robotic NOSES is safe and feasible during the initial LC.

Effect of P and Zr on the microstructure and magnetic properties of nanocomposite Pr2Fe14B/α-Fe ribbons

We have investigated the effect of P and Zr on the magnetic properties and microstructure of the as-spun ribbon Pr2Fe14B/α-Fe achieved at a wheel speed of 30 m/s. X-ray diffraction and TEM results reveal that P-addition can decrease the grain size of 2:14:1 hard phase whereas further Zr-addition decreases the soft α-Fe phase. The combination of doping P and Zr reduces overall grain size and refines the microstructure considerably, and results in enhanced coercivity significantly. The strong exchange coupling interaction in our ribbons were confirmed by Henkel plots, which leads to higher coercivity of 964 kA/m. The initial magnetization curves reveal the coercivity in P-added alloy is controlled by the nucleation of reversal domain and that in further Zr-added alloy is the domain wall pinning.

A Systematic Review of Complications Associated with Initial Learning Curve of Endoscopic Spine Surgery Highlighting the Necessity of Introducing an Effective Fellowship to Train Competent Endoscopic Spine Surgeons

Background: There is an increase in interest of endoscopic spine surgery as an option of minimally invasive spine surgery. Complications associated with learning curve are a big obstacle to starting a successful endoscopic career. A good endoscopic spine surgery fellowship can mitigate the risk of practice in early phase in endoscopic spine surgery. Methods: We conducted a systematic review in the PubMed database using the terms using three successive searches.10 articles met the criteria of learning curve in endoscopic surgeries evaluation of complications and operation timing. The most consistent parameters used in these studies to evaluate the learning curve were procedure time and complication rate as a function of chronologic case number, our analysis focused on these. The search strategy identified 10 original studies that included 618 endoscopic spine surgery procedures. Results: In the 10 studies, total number of complications was 45 cases (7.2%). 33 cases (5.3%) occurred in the early phase of learning curve. The most frequent reported complications were incomplete decompression (18 cases, 2.9%), incidental durotomies (13 cases; 2.1%), nerve root injuries (11 cases; 1.77%), discitis (2 cases; 0.32% of complications) and hematoma (1 case; 0.16%). The operative time was observed to decrease throughout these case series with no general consensus of number of cases required to reach asymptote. Conclusion: There is steep learning curve with high complications in the initial learning phase of endoscopic spine surgery. It is recommended to have an effective training or fellowship programme to train competent endoscopic spine surgeons.

A sixth order flow of plane curves with boundary conditions

For small-energy initial regular planar curves with generalised Neumann boundary conditions, we consider the steepest-descent gradient flow for the $L^2$-norm of the derivative of curvature with respect to arc length. We show that such curves between parallel lines converge exponentially in the $C^\infty$ topology in infinite time to straight lines.

Direct inverse linearization of piezoelectric actuator’s initial loading curve and its applications in full-field optical coherence tomography (FF-OCT)

Piezoelectric actuator (PEA) has become popular in spectroscopic optical coherence tomography (SOCT) as it can provide depth dependent spectra with sub‐nanometer positioning resolution. However, the inherent hysteresis of the PEA introduces unwanted distortions to the obtained spectra and image. OCT imaging can be completed during the first forward motion of the PEA, i.e., the initial loading curve (ILC). Therefore, this paper proposes a feedforward hysteresis compensation method for the linearization of the ILC, aiming at improving the spectroscopic and imaging accuracy of OCT without any feedback on the PEA’s displacement or feedback controllers. A polynomial operator is adopted as the hysteresis compensator and the coefficients are directly identified from the measured ILC, following the direct inverse modeling approach. Experimental results on a standalone PEA verifies that the proposed method is superior to the popular Prandtl-Ishlinskii model in the linearization of the ILC. This proposed method is further implemented on a full‐field OCT system to linearize the motion of the PEA‐driven scanner. Experimental results show that the ILC of the scanner can be efficiently linearized. In vivo skin imaging is then performed to evaluate the performance of the proposed method. Ultra-high precision linearization enables remarkable positioning accuracy in the skin constituents and skin layers observed in the in vivo forearm cross-sectional skin image. Depth-dependent spectral analysis could quantify molecular/chemical composition of the tissue constituents accurately.

Intelligent design method and system of trimming block for stamping dies of complex automotive panels

Trimming block is the most important working component of trimming die for automotive panels. Its structure and form are various and complex, resulting in its design quite tedious and time-consuming, which affected the efficiency and quality of die design. Aiming at the three problems of curve offset, surface construction, and flange uncertainty, an intelligent design method based on parameters and sketch driven is proposed to realize the rapid and intelligent design of trimming block. According to the curve offset criterion of trimming block, a 3D curve offset method based on the feature inflection point is proposed, which considers the characteristics of curve from offset direction, curvature, and perturbation, and meets the requirement of minimum offset distance, to maintain the shape following of initial curve. The offset spline curve ensures the minimum offset distance and its trend with the original curve. Combined with the group concept, it introduces a segmented surface construction method for trimming block surfaces based on non-uniform rational B-spline mesh surface and supplemented by filling surface, which can well track the tendency of trimming curve and meet the G1 continuity conditions between adjacent surfaces. It presents an interactive sketch to solve the diversity and uncertainty of flange, which can free to draw the 2D outline of any flange. Finally, the whole design process of trimming block is serialized by parameters and sketch driving to achieve the fully automated intelligent design method, which is integrated into the NX software, and an intelligent design system of trimming block is developed as a submodule in the modular design of the trimming die. The design example of the fender trimming block shows that the system can control the error well and guarantee the success of the onetime design. The designed trimming block has a smooth blade surface, a smooth transition, and excellent structural strength, which can significantly improve design quality and efficiency.

A prospective study of the components of operating room utilisation time for robotic urological surgery in a public teaching hospital setting

Introduction and aim: Although there are several publications on learning curves and patient outcomes in robotic surgery, the literature is lacking in depth analysis of operating room (OR) utilisation time which is an expansive healthcare resource for robotic surgery, especially in urology. Thus, we aimed to study individual operating theatre component times in order to improve performance and efficacy. Method: A cross-specialty robotic-surgery programme was established at our institution in mid-June 2016 using the daVinci Xi dual console robot. A detailed database was established before initiation of the project. The times taken for each element of the preparation and completion of robotic urological procedure were collected by an independent nurse for all the procedures. Primary outcome measures were total OR time, operative time and console time. Secondary outcome measures were port placement time, set-up time and non-operative time. The statistical significance was calculated by using the Student’s t-test, Fisher’s exact test or Wilcoxon matched pairs test where appropriate. Result: Thirty consecutive urological cases were analysed. Mean total OR time, operative time and console time were 320.86 (range 172–485), 235.7 (124–295) and 152.3 min (66–219) respectively. Console time accounted for about less than half of OR time. A significant proportion of OR time was non-operative time (almost one third). After an initial learning curve, set-up time was consistently maintained for most robotic procedures. Conclusions: The findings of this study have three implications for clinical practice. Firstly, console time contributed about half of the OR time. This can be optimised with experience. Secondly robot set-up time is likely to reduce with the experience of the whole team. Finally, non-operative OR time constitute a significant one third of the OR time during robotic surgery. Efforts to reduce non-surgical aspect of OR time will have potential to reduce cost and improve efficiency. Level of Evidence: 4

Labeling and clustering-based level set method for automated segmentation of lung tumor stages in CT images

An unconstrained growth of abnormal cells in the lung causes tumors. The aim of the work is the accurate diagnoses of tumor at its early stage through hybrid segmentation algorithm. The objective of this paper is to propose a novel labeled cluster active contour method to improve the performance of automated lung tumor segmentation from 2D CT slices. To the input 2D slice, an 8-connected component analysis is implemented to differentiate the image spatial information and obtain the RGB labeled data. The tumor location is foreseen using an unsupervised k-means clustering algorithm. Then, an automated level set algorithm is carried out to appropriately localize and extract the tumor region. The amount of initial level set curve evolution is controlled by the clustering efficiency of k-Means and labeling efficacy of connected component analysis. The quantitative evaluation of segmentation is carried out based on Shape features like area, perimeter, eccentricity, convex area, solidity, and roundness. The statistical object-based and distance-based metrics were used to find the similarity between manual and proposed methods. Also, performance metrics like accuracy, specificity, sensitivity, precision, and recall are used to validate the segmentation results of the proposed method. The proposed system is evaluated over 42 datasets from the commonly available large dataset LIDC (Lung Image Database Consortium). The accuracy, specificity, sensitivity and precision of the proposed hybrid method are 97.5%, 97.43%, 91.67%, and 98.79%, which exhibited the best competence as compared to traditional methods on the same dataset. The statistical and quantitative analysis shows the efficiency of the present work.

Hilbert sEMG data scanning for hand gesture recognition based on deep learning

Deep learning has transformed the field of data analysis by dramatically improving the state of the art in various classification and prediction tasks, especially in the area of computer vision. In biomedical engineering, a lot of new work is directed toward surface electromyography (sEMG)-based gesture recognition, often addressed as an image classification problem using convolutional neural networks (CNNs). In this paper, we utilize the Hilbert space-filling curve for the generation of image representations of sEMG signals, which allows the application of typical image processing pipelines such as CNNs on sequence data. The proposed method is evaluated on different state-of-the-art network architectures and yields a significant classification improvement over the approach without the Hilbert curve. Additionally, we develop a new network architecture (MSHilbNet) that takes advantage of multiple scales of an initial Hilbert curve representation and achieves equal performance with fewer convolutional layers.