Differences In Depth Research Articles

The use of singlebeam echo-sounder depth data to produce demersal fish distribution models that are comparable to models produced using multibeam echo-sounder depth.

Seafloor characteristics can help in the prediction of fish distribution, which is required for fisheries and conservation management. Despite this, only 5%–10% of the world's seafloor has been mapped at high resolution, as it is a time‐consuming and expensive process. Multibeam echo‐sounders (MBES) can produce high‐resolution bathymetry and a broad swath coverage of the seafloor, but require greater financial and technical resources for operation and data analysis than singlebeam echo‐sounders (SBES). In contrast, SBES provide comparatively limited spatial coverage, as only a single measurement is made from directly under the vessel. Thus, producing a continuous map requires interpolation to fill gaps between transects. This study assesses the performance of demersal fish species distribution models by comparing those derived from interpolated SBES data with full‐coverage MBES distribution models. A Random Forest classifier was used to model the distribution of Abalistes stellatus, Gymnocranius grandoculis, Lagocephalus sceleratus, Loxodon macrorhinus, Pristipomoides multidens, and Pristipomoides typus, with depth and depth derivatives (slope, aspect, standard deviation of depth, terrain ruggedness index, mean curvature, and topographic position index) as explanatory variables. The results indicated that distribution models for A. stellatus, G. grandoculis, L. sceleratus, and L. macrorhinus performed poorly for MBES and SBES data with area under the receiver operator curves (AUC) below 0.7. Consequently, the distribution of these species could not be predicted by seafloor characteristics produced from either echo‐sounder type. Distribution models for P. multidens and P. typus performed well for MBES and the SBES data with an AUC above 0.8. Depth was the most important variable explaining the distribution of P. multidens and P. typus in both MBES and SBES models. While further research is needed, this study shows that in resource‐limited scenarios, SBES can produce comparable results to MBES for use in demersal fish management and conservation.

Implementation of Beam Matching Concept for the New Installed Elekta Precise Treatment System Medical LINACs in Indonesia

A concept of radiation beam matching of some medical linear accelerators (LINACs) that have identical characteristics of the models, radiation quality, and multileaf collimator features may be implemented as long as the manufacturer provides complete specifications so that a Treatment Planning System (TPS) can be used for many beam-matched LINACs. This paper describes a preliminary study on the implementation of the beam matching concept for five units Elekta Precise Treatment System LINACs that have recently been installed in Indonesia. The beam matching criteria were based on the percentage depth dose (PDD) and beam profile for photon and electron beams. Dosimetry measurements were carried out by using an SNC 125 ionization chamber of 0.125 cm 3 in volume, PTW Pinpoint 3D of 0.016 cm 3 in volume, and PTW Farmer Chamber of 0.6 cm 3 in volume. The results indicated that the PDD 10 of 6 and 10 MV photon beams among installed five units LINACs have excellent compatibility each others with a maximum deviation of less than 0.4 %, while the maximum deviation for dose depth of 80 % (R 80 ) for the electron beams with nominal energies of 4, 6, 8, 10, 15 and 18 MeV is 1 mm. The measurement results for the flatness profile were less than 6 %, and symmetry profiles were less than 3 %. It also outlines the determination of the absorbed dose to water under reference conditions. The results of the calibration of output doses show that the absorbed dose in the water was 1 cGy ≈ 1 MU. The data obtained from measurements for each LINAC conform with the requirements of the beam matching process set by the manufacturer.

Aspects about bouncing of plough caused by random

In this paper the author deals aspects about the vertical motion (named bouncing) of a tractor with plough mounted on the rear frame, during displacement over the random excitation surface of the agricultural land. Final results of the simulation process, performed on the model of tractor-plough with 3 degree of freedoms, show the difference between digging depth function as velocity motion and longitudinal profile of the terrain. Thus, the deviation of the plough depth from the reference depth is evaluated.

Synoptic Mesoscale to Basin Scale Variability in Biological Productivity and Chlorophyll in the Kuroshio Extension Region

The Kuroshio current separates from the Japanese coast to become the eastward flowing Kuroshio Extension (KE) characterized by a strong latitudinal density front, high levels of mesoscale (eddy) energy, and high chlorophyll a (Chl). While satellite measurements of Chl show evidence of the impact of mesoscale eddies on the standing stock of phytoplankton, there have been very limited synoptic, spatially resolved in situ estimates of productivity in this region. Here, we present underway measurements of oxygen/argon supersaturation (ΔO2/Ar), a tracer of net biological productivity, for the KE made in spring, summer, and early autumn. We find large seasonal differences in the relationships between ΔO2/Ar, Chl, and sea level anomaly (SLA), a proxy for local thermocline depth deviations driven by mesoscale eddies derived from satellite observations. We show that the KE is a pronounced hotspot of high ΔO2/Ar in spring, but corresponding surface Chl values are low and have no correlation with ΔO2/Ar. In summer, there is a hotspot of productivity associated with the Oyashio front, where ΔO2/Ar and Chl are strongly positively correlated. In autumn, ΔO2/Ar and Chl are consistently low throughout the region and also positively correlated. By combining our analysis of the in situ ΔO2/Ar data with complementary Argo, BGC‐Argo, repeat hydrography, and SLA observations, we infer the combination of physical and biological controls that drive the observed distributions of ΔO2/Ar and Chl. We find that the KE and Oyashio currents both act to supply nutrients laterally, fueling regions of high productivity in spring and summer, respectively.

A new inertial navigation system for guiding implant placement. An in-vitro proof-of-concept study.

The aim of this study was to assess the potential use of a new advanced inertial navigation system for guiding dental implant placement and to compare this approach with standard stereolithographic template guiding. A movement processing unit with a 9-axis absolute orientation sensor was adapted to a surgical handpiece and wired to a computer navigation interface. Sixty implants were placed by 10 operators in 20 jaw models. The 30 implants of the test group were placed in 10 models guided by the new inertial navigation prototype. The 30 implants of the control group were placed in another 10 models using a CAD-CAM template. Both groups were subdivided into experienced and non-experienced operators. Pre- and postoperative computer tomography images were obtained and matched to compare the planned and final implant positions. Four deviation parameters (global, angular, depth, and lateral deviation) were defined and calculated. The primary outcome was the angular deviation between the standard stereolithographic approach and the new inertial navigation system. Results showed no significant differences between both groups, suggesting that surgical navigation based on inertial measurement units (IMUs) could potentially be useful for guiding dental implant placement. However, more studies are still needed to translate this new approach into clinical practice.

Improving the precision of micro-EDM for blind holes in titanium alloy by fixed reference axial compensation

Abstract During the electrical discharge machining (EDM) process, the tool electrode wear is inevitable, which affects the process precision of the micro-hole. In the present experimental investigation, a fixed reference axial compensation (FRAC) method is proposed to enhance the machining precision of micro-hole. The effect of pulse power, compensation methods, and electrode materials on the depth and roundness factor of micro-hole are explored. The experiment results show that the FRAC method can realize the accurate compensation and reach the expected depth hole processing. When the FRAC is used, the depth deviation is less than 0.43%, and the minimum difference from the expected depth is only 0.106 µm. In addition, the micro-holes of tungsten steel and brass electrodes machine by the FRAC method were close to the expected depth, the difference from the expected depth less than 0.7%, but the bottom of micro-hole produced a cone. However, compared to tungsten steel and brass electrodes, the copper electrode has a better processing performance, the roundness factor is up to 79.8%. When the long-pulse power supply is applied, the expected depth of 400–1,600 µm blind holes with a better processing shape, and the phenomenon of the cone at the bottom are not apparent. Therefore, the proposed FRAC method can be utilized in many high-end manufacturing fields to improve the precision of the micro-hole for micro features.

Investigating the ability of multiple reanalysis datasets to simulate snow depth variability over mainland China from 1981 to 2018

AbstractThough the use of reanalysis datasets to analyze snow changes is increasingly popular, the snow depth variability in China simulated by multiple reanalysis datasets has not been well evaluated. Also, the extent of regional snow depth variability and its driving mechanisms are still unknown. In this study, monthly snow depth observations from 325 stations during the period of 1981–2018 were taken to evaluate the ability of five reanalysis datasets (JRA55, MERRA2, GLDAS2, ERA5, and ERA5L) to simulate the spatial and temporal variability of snow depth in China. The evaluation results indicate that MERRA2 has the lowest root-mean-square deviation of snow depth and a high spatial correlation coefficient with observations. This may be partly related to the high accuracy of precipitation and temperature in MERRA2. Also, the 31 combinations of the five reanalysis datasets do not yield better accuracy in snow depth than MERRA2 alone. This is because the other four datasets have larger uncertainty. Based on MERRA2, four hotspot regions with significant snow depth changes from 1981–2018 were identified, including the central Xinjiang (XJ-C), the southern part of the Northeastern Plain and Mountain (NPM-S), and the southwestern (TP-SW) and southeastern (TP-SE) of the Tibetan Plateau. Snow depth changes mostly occurred in spring in TP-SW and winter in XJ-C, NPM-S, and TP-SE. The snow depth increase in XJ-C, NPM-S, and TP-SW is mainly caused by increased seasonal precipitation, while the snow depth decrease in TP-SE is attributed to the combined effects of decreased precipitation and warming temperature in winter.

Needle insertion planning for obstacle avoidance in robotic biopsy

Abstract Understanding the underlying pathology in different tissues and organs is crucial when fighting pandemics like COVID-19. During conventional autopsy, large tissue sample sets of multiple organs can be collected from cadavers. However, direct contact with an infectious corpse is associated with the risk of disease transmission and relatives of the deceased might object to a conventional autopsy. To overcome these drawbacks, we consider minimally invasive autopsies with robotic needle placement as a practical alternative. One challenge in needle based biopsies is avoidance of dense obstacles, including bones or embedded medical devices such as pacemakers. We demonstrate an approach for automated planning and visualising suitable needle insertion points based on computed tomography (CT) scans. Needle paths are modeled by a line between insertion and target point and needle insertion path occlusion from obstacles is determined by using central projections from the biopsy target to the surface of the skin. We project the maximum and minimum CT attenuation, insertion depth, and standard deviation of CT attenuation along the needle path and create two-dimensional intensity-maps projected on the skin. A cost function considering these metrics is introduced and minimized to find an optimal biopsy needle path. Furthermore, we disregard insertion points without sufficient room for needle placement. For visualisation, we display the color-coded cost function so that suitable points for needle insertion become visible. We evaluate our system on 10 post mortem CTs with six biopsy targets in abdomen and thorax annotated by medical experts. For all patients and targets an optimal insertion path is found. The mean distance to the target ranges from (49.9 ± 12.9)mm for the spleen to (90.1 ± 25.8)mm for the pancreas.

A Tillage Depth Monitoring and Control System for the Independent Adjustment of Each Subsoiling Shovel

Subsoiling can break the compacted hardpan without turning or mixing soil layers. It has significant advantages in improving soil structure, promoting rainwater infiltration, and increasing air permeability of soil. The soil compacted hardpan will not be completely broken and more power consumption will be generated unless the desired tillage depth is obtained. However, due to uneven surface between and within each row of subsoiling shovel in the field, the existing adjustment methods, adjusting via the lifting device of the whole machine or a group of tillage components, cannot ensure each subsoiling shovel avoiding undesired tillage depth. Therefore, a tillage depth monitoring and control system for the independent adjustment of each subsoiling shovel was developed, and the methods of detecting, adjusting, displaying, and recording tillage depth were described. Field experiments were conducted to evaluate detecting accuracy, stability of tillage depth, transient response time, and advantages. The results showed that the value obtained by sensor differed from manual measurement at the speed of 3 km/h, 4 km/h, and 5 km/h averagely by 8.28%. The mean value of the coefficient of the tillage depth stability at three speeds were all greater than 94%. The mean transient response time was 0.6 s. The standard deviation of tillage depth obtained under system control was 38.31, which was less than the 51.52 obtained by only adjusting on the three-point suspension. The subsoiler equipped with this system was capable of obtaining a desired tillage depth of each subsoiling shovel in every second.

Influence of plume attenuation under high power laser welding of copper using visible wavelengths

Joining of copper materials has become a key factor in laser material processing of electric components like electric engines, batteries, or power electronics. A paramount challenge is the design of the laser welding process, which has to fulfil the requirements of high energy efficiency and highest seam quality at the same time. By now, high-power laser beam sources emitting visible laser radiation are available to promote the well-suited noncontact joining method, which is furthermore characterized by local energy input and high automation potential. These laser sources can now face the challenges of welding highly conductive and reflective materials, such as copper, which originate mainly in the low absorption of conventionally used infrared wavelengths at room temperature and the rapid jump of absorptivity at transition from solid to liquid state. An increase in absorption of electromagnetic radiation to more than 40% for copper at room temperature for λ = 515 nm leads to increasing energy input in the material and promotes a more efficient process therefore. However, up to now, mostly the heat conduction welding regime has been examined and the effects of shorter wavelengths on deep penetration welding have not been understood in detail. A strong deviation in weld seam depth between infrared and green laser radiation is observed for identical process parameters depending on the use of additional gas supply [F. Kaufmann, A. Meier, J. Ermer, S. Roth, and M. Schmidt, “Influence of defocusing in deep penetration welding of copper by using visible wavelength,” in Proceedings of the Eleventh International WLT-Conference on Lasers in Manufacturing, Munich, 21–24 June 2021 (M. Reth, Munich, 2021)]. Consequently, radiation attenuation by the metal vapor inside and above the keyhole plays a substantial role in the case of 515 nm laser welding [M. Haubold, A. Ganser, T. Eder, and M. F. Zäh, “Laser welding of copper using a high power disc laser at green wavelength,” Procedia CIRP 74, 446–449 (2018)]. In this work, we investigate in situ measurements of plume attenuation during laser beam welding of copper with 515 and 1030 nm laser beam sources. Both laser sources are equipped with comparable optical setups to achieve identical focal diameters on the material surface. We investigate the plume characteristics in the deep penetration welding mode of copper. A range of industry-relevant process parameters are investigated to create a basis for comparison with theoretical models. It is found that a significant difference in the attenuation of both laser wavelengths occurs in the case of deep penetration welding copper specimen and blowing the vapor plume out of the beam path is recommended therefore for an efficient welding process.

LV-GCNN: A lossless voxelization integrated graph convolutional neural network for surface reconstruction from point clouds

Surface reconstruction from a 3D point cloud is a long-standing problem in the field of computer graphics and vision, especially for point clouds that are sparse and noisy. To solve this problem, a novel method, termed LV-GCNN, that combines lossless voxelization and a graph convolutional neural network is proposed in this paper. Firstly, a lossless voxelization method for point clouds, which achieves lossless conversion from disordered point clouds to ordered volumetric maps, is proposed. Secondly, with the generated voxel, the feature pyramid is extracted through a 3D convolutional neural network. Thirdly, based on the similarity between the graph and surface mesh, the graph neural network is initialized as a unit spherical mesh. The coordinate relationship between the graph vertices and feature voxel units is used to match the corresponding hierarchical features for graph vertices. The initial spherical mesh is progressively deformed and upsampled via graph convolution and graph unpooling to achieve coarse-to-fine optimization of the surface mesh. Finally, because the deformation-based approach cannot reconstruct objects with a genus greater than zero, a genus optimization method is designed. Experiments show that the surface meshes generated by the LV-GCNN are comparable to or better than the results of state-of-the-art methods under several evaluation criteria. In addition, the reconstruction effect under different situations is discussed. Ablation experiments show the importance of several applied modules in LV-GCNN. Extra experiments show that the proposed method can achieve impressive results for point sets with diverse densities or that contain different levels of noise. The LV-GCNN results outperform other methods when the input point cloud is exceptionally sparse (256 points) or contains Gaussian noise with a standard deviation of 0.05. The chamfer distance (CD), Hausdorff distance (HD), voxel difference (VD), and depth difference (DD) of the reconstruction results of the LV-GCNN are 0.0494, 0.1457, 0.7390, and 18,402 when 256 points are used as input and are 0.0654, 0.1582, 0.6735, and 21,150 when points with noise with a standard deviation of 0.05 are used as input.

Robotic Assistance System for Cone-Beam Computed Tomography-Guided Percutaneous Needle Placement

PurposeThe study aimed to evaluate a new robotic assistance system (RAS) for needle placement in combination with a multi-axis C-arm angiography system for cone-beam computed tomography (CBCT) in a phantom setting.Materials and MethodsThe RAS consisted of a tool holder, dedicated planning software, and a mobile platform with a lightweight robotic arm to enable image-guided needle placement in conjunction with CBCT imaging. A CBCT scan of the phantom was performed to calibrate the robotic arm in the scan volume and to plan the different needle trajectories. The trajectory data were sent to the robot, which then positioned the tool holder along the trajectory. A 19G needle was then manually inserted into the phantom. During the control CBCT scan, the exact needle position was evaluated and any possible deviation from the target lesion measured.ResultsIn total, 16 needle insertions targeting eight in- and out-of-plane sites were performed. Mean angular deviation from planned trajectory to actual needle trajectory was 1.12°. Mean deviation from target point and actual needle tip position was 2.74 mm, and mean deviation depth from the target lesion to the actual needle tip position was 2.14 mm. Mean time for needle placement was 361 s. Only differences in time required for needle placement between in- and out-of-plane trajectories (337 s vs. 380 s) were statistically significant (p = 0.0214).ConclusionUsing this RAS for image-guided percutaneous needle placement with CBCT was precise and efficient in the phantom setting.

A Retrospective Study on the Transferring Accuracy of a Fully Guided Digital Template in the Anterior Zone.

The accuracy of implant placement with a fully guided digital template can be influenced by many factors, such as arch difference, alveolar bone density, timing of implant placement and open flap. The purpose of this article was to evaluate the factors presumptively affecting the accuracy of implant placement assisted by the fully guided template in the anterior zone. In 40 patients with missing anterior teeth, a total of 52 implants were placed with tooth-borne, fully guided templates after CBCT evaluation, in West China Hospital of Stomatology, Sichuan University. After overlapping the pre-and post-operative DICOM data, measurements were taken in the dental implant planning software (Nobel Clinician®) to calculate linear and angular deviations between virtual placement plan and actual implant placement. Grouping was categorized according to three factors that possibly have an influence on accuracy: arch type (maxilla/mandible), timing of implant placement (immediate/delayed), surgical technique (open flap/flapless). The data was analyzed with independent sample t-test (p < 0.05). The results showed that the apical, coronal, depth and angular mean deviations of implant positions in anterior zone were 1.13 ± 0.39 mm, 0.86 ± 0.33 mm, 0.41 ± 0.66 mm, 3.32 ± 1.65° with the fully guided templates. The accuracy at apex level, coronal level and the angulation were similar between the maxilla and mandible, and the magnitude of all four deviations between immediate and delayed implantation, open flap and flapless technique were small. No statistically significant difference was observed (p > 0.05). Whereas there was significant difference in depth deviation between maxilla and mandible (p < 0.05). Conclusively, the implant site, alveolar bone density, timing of implant placement and surgical techniques merely compromise the implant placement accuracy under the assistance of a fully guided template.

Evaluation on applicationof virtual reality technology in dental implant process training

Objective: To explore the application effect and evaluation of virtual reality technology in oral implant therapy training. Methods: In November 2018, one adult patient (female, 36 years old) with missing right mandibular first molar was treated in the Department of Implantology, School and Hospital of Stomatology, Fujian Medical University. The three-dimensional virtual models of mandible and implant surgery tools were established, and the virtual reality software (Unity 3D 5.5.1) was imported. Combined with the virtual reality head mounted display, a virtual reality training system simulating the dental implant treatment process was independently developed. Ten refresher doctors and 20 graduate students in Department of Implantology, School and Hospital of Stomatology, Fujian Medical University from September 2018 to December 2019 were recruited as the experimental objects (no clinical experience was found). According to the level and seniority of doctors, they were randomly divided into virtual training group and conventional training control group, which made the two groups comparable, with 15 in each group. Subjective scores (including anatomical structure, surgical field of vision, cavity preparation, implant placement and process mastery) were given after the corresponding training in the two groups, and the virtual reality training system was used to test. The mesial and distal direction, buccolingual direction, depth and angle deviation of implants before and after the training were analyzed, and the differences between the two groups were compared. Results: The subjective scores of five dimensions in the virtual training group were significantly higher than those in the conventional training control group (P<0.05). In the virtual training group, the mesial and distal, buccolingual, depth and angle deviation of implants were (0.73±0.33), (0.78±0.41), (0.61±0.32) mm and 6.66°±3.87°. All of them were significantly lower than those in the control group [(0.85±0.32), (1.12±0.38), (0.89±0.24) mm and 9.68°±3.74°] (P<0.05). Conclusions: The self-developed virtual reality system of oral implant has good application effect, good operability and predictability. It can be effectively carried out in implant education and training, and it can strengthen skills of doctors, and is conducive to the practical operation.

Heat accumulation and surface roughness evolution in CO2 nanosecond laser ablation of quartz glass

Quartz glass is frequently used for optical components, but traditional machining methods, particularly for aspherical optics, are often associated with long process times and high costs. One possible approach to achieve higher efficiencies and higher speeds in contactless processing is laser ablation using CO2 laser radiation. This study investigates the evolution of surface topography during laser ablation of quartz glass using nanosecond pulses from a Q-switched CO2 laser beam source. The special focus of a broad empirical study lay on ablation depth, ablation rate, ablation efficiency and resulting surface roughness for an ablation process using 300 ns laser pulses at a maximum laser power of 115 W and pulse frequencies up to 150 kHz. Ablation efficiency shows a characteristic logarithmic dependency on laser fluence. It was revealed that local heat accumulation significantly affects the optical penetration depth, which reduces the threshold fluence for multi-pulse laser ablation down to approx. 0.37 J/cm2. Ablation rates of up to 1.48 mm3 min−1 W−1 were achieved, which exceeds results achieved for laser ablation using cw laser radiation or ultra-short pulses. An ablation rate of up to 170 mm3/min is a particularly noteworthy result. Therein, a maximum ablation efficiency of approx. 64% shows that the largest part of the incident laser energy was used for material ablation. Finally, based on a simplified model, numerical calculations and experimental results, pulse stability was identified to have a decisive impact on the evolution of the resulting surface roughness. The resulting surface roughness Sa is typically increased in pulsed laser processing and depends linearly on standard deviation of ablation depth and the square root of the number of ablation layers.

Wellbore Temperature and Pressure Field in Deep-water Drilling and the Applications in Prediction of Hydrate Formation Region

In the process of deep-water drilling, gas hydrate is easily formed in wellbores due to the low temperature and high pressure environment. In this study, a new, systematic, and accurate prediction method of temperature, pressure, and hydrate formation region in wellbores is developed. The mathematical models of wellbore pressure and transient heat transfer are established, the numerical solution method based on fully implicit finite difference method is developed, and the accuracy is verified by comparing with the field measured data. Combined with the hydrate phase equilibrium model, the hydrate formation region in wellbore is predicted, and the sensitivity effects of nine factors on wellbore temperature, pressure, and hydrate formation region are analyzed. Finally, the influence regularities and degree of each parameter are obtained. The increases of circulation time, geothermal gradient, displacement of drilling fluid, and injection temperature will inhibit the formation of hydrate in wellbores, and the influence degree increases in turn; the increases of wellhead backpressure and seawater depth will promote the formation of hydrate in wellbores, and the influence degree increases in turn. The changes of drilling fluid density, well depth, and hole deviation angle have little effect on the formation of hydrate in wellbores.

`3D PRINTING IN IMPLANT DENTISTRY-A REVIEW

Three-dimensional (3D) printing is an additive manufacturing method in which by laying down successive layers of material a 3D item is formed. Charles Hull created the 3D printer which used the technique of stereolithography, as well as the first program for virtualization.Various types of polymers,gels , resins and powders are the materials employed in 3D printing.3D printing techniques includes liquid based, solid based and powder based using which surgical guides and implant abutment can be fabricated .The accuracy of 3D printed implants is assessed by global deviation, angular deviation, depth deviation and lateral deviation. Even though the complications and disadvantages are associated with 3D printing, they can achieve higher precision and accuracy in implant placement. However, further studies are needed to evaluate their clinical outcome over time and function..

Surface morphology characteristics and mechanical properties of corroded cold-formed steel channel sections

The effects of corrosion on the surface morphology characteristics and mechanical properties of corroded cold-formed steel were investigated. 26 coupon specimens accelerated corrosion by the outdoor periodic spray test were subjected to monotonic tensile test to obtain the mechanical properties. The surface topography of 10 coupon specimens were scanned to obtain the three-dimensional coordinate data. The relationship between the corrosion characteristic parameters, the mechanical properties of corroded cold-formed steel and the corrosion rate was proposed. The corrosion morphology and mechanical properties of corroded hot-rolled steel and cold-formed steel were compared and analyzed. Finally, the finite element model based on the corrosion morphology was established. Results indicated that for the specimens with the same mean of corrosion depth, the standard deviation of corrosion depth and maximum corrosion depth of the hot-rolled steels were larger than those of the cold-formed steels. The reduction in the elastic modulus, the yield strength and the ultimate strength of the hot-rolled steels was obviously lower than that of the cold-formed steels. The yield ratio did not change significantly with the increaseing corrosion rate for two types of steel. The finite element model can accurately predict the failure modes, fracture position and stress-strain curves of the corroded coupon specimens. The cold-worked operation and small thickness can accelerate the degradation of mechanical properties of corroded specimen, so more attention should be paid to the corrosion problem of cold-formed steel.

Processing strategy for symmetrical ablation profile in pulsed laser patterning of high-performance broadband spiral antennas

High-performance broadband spiral antennas are considered as non-substitutable parts in the field of aerospace, and the nanosecond pulsed laser (NPL) patterning has shown a broad prospect in the processing of the high-performance broadband spiral antennas, in which the characteristic of ablation profile is always considered as the most significant issue. However, for the pattern of antenna with complex curve feature, the position for the highest overlapping rate of laser spot offset from the spot center to the curvature center of scanning trajectory, and then the laser energy cumulative loses the symmetry for the complex curve scanning trajectory on the machining parts surface, which induces the location deviation of the maximum ablation depth for the curve pattern. Meanwhile, the curve with the maximum ablation depth will deviate from the ideal designed antenna line, resulting in a direct impact on the antenna performance. In this study, the curvature characteristic of the scanning trajectory is innovatively taken into consideration in the NPL processing of pattern with complex feature. Thus, the ablation profile symmetry and the according assessment are proposed with mathematical model, and the asymmetry of ablation profile is carefully revealed to obtain the deviation of maximum ablation depth for pattern with both large and fine radius feature. Furtherly, based on the proposed model, the processing strategies are extended that the side-step distance is generated in pulsed laser ablation of pattern with large radius feature and the scanning trajectory is optimized for the downsized pattern with finer radius feature. As a consequence, the experimental results satisfactorily verify the theoretical side-step distance and also verify that the position curve of maximum ablation depth is optimized with a deviation distance reduction of more than 74%. With the proposed processing strategies, a good and concerned guide is provided for the precise NPL patterning of high-performance broadband spiral antennas.

Whole-Process Digitalization-Assisted Immediate Implant Placement and Immediate Restoration in the Aesthetic Zone: A Prospective Study.

BackgroundThis study explored the clinical effects of whole-process digitalization (WD)-assisted immediate implant placement (IIP) and immediate restoration (IR) in the aesthetic zone and clarified the clinical procedures.Material/MethodsPatients who received maxillary aesthetic region IIP and IR treatment were randomly distributed into WD-assisted and conventional groups. Postoperative assessment included implant accuracy, marginal bone loss, aesthetic evaluation, and patient satisfaction evaluation. The aesthetic evaluation included visual analog score (VAS), pink aesthetic score (PES), and white aesthetic score (WES). Numerical data, measurement data, and grade data were analyzed by χ2 test, t test, and Mann-Whitney U test.ResultsThe WD-assisted group exhibited decreased implant accuracy, including coronal deviation, apical deviation, angular deviation, and depth deviation, compared with the conventional group (P<0.05). The marginal bone loss in both the mesiodistal direction and the buccolingual direction were significantly lower in the WD-assisted group than in the conventional group (P<0.05). The VAS, PES, and WES were all significantly higher in the WD-assisted group than in the conventional group at 3, 6, and 12 months after surgery (P<0.05). Patients in the WD-assisted group also reported a higher satisfaction level than those in the conventional group (P<0.05).ConclusionsWD-assisted IIP and IR treatment in the aesthetic zone increased implant accuracy, decreased marginal bone loss, improved aesthetic effect, and increased patient satisfaction compared with conventional treatment. Therefore, WD-assisted IIP and IR treatment constitutes a promising approach in clinical oral implantology.