Pieces Of Segments Research Articles

A lab unearthed: Plotting the grounds for future fields

A lab unearthed: Plotting the grounds for future fields

3D tooth segmentation in cone-beam computed tomography images using distance transform

Background and ObjectivesSegmentation of individual teeth from Cone-Beam Computed Tomography (CBCT) images is a significant step in computer-aided systems for orthodontic planning. Teeth segmentation is still problematic because the teeth have similar intensity with the bone tissue and the variation of jawbone intensity. This study focused on improving teeth segmentation in CBCT images. MethodsIn this paper, we propose a new approach for tooth segmentation in CBCT images and Three-Dimensional (3D) visualization from the segmented teeth. First, artifacts reduction is obtained by histogram adjusting and morphology filtering of teeth bone on axial slices. Second, by using Distance Transform (DT), the tooth tissue is segmented. Finally, we represent a 3D teeth view using segmented pieces based on the triangular patches method of scattered points belonging to tooth lines. ResultsFor all the used images, teeth boundaries are segmented with accuracy and efficiency. The results of our method are similar to the outcomes of segmentation acquired by the specialist. ConclusionExperimental results and simulations show that the proposed method is helpful for precise and effective teeth segmentation in CBCT images.

Volumetric and linear assessment of maxillary, mandibular and zygomatic bone as donor sites for alveolar ridge augmentation using CBCT

Objective: To analyze preoperative CBCT assessment of intraoral donor sites (symphysis, ramus buccal shelf of bone, zygomatic buttress and maxillary tuberosity) for purpose of autogenous block graft. Materials and Methods: Twenty (5 for each graft) participants were included in the study, (informed consent was signed by each participant) Participants were recruited according to certain eligibility criteria. Results: The measurements of the block grafts showed that there was a significant difference between different sites (p<0.001). The highest value was found in mandibular symphysis (1.56±0.44), followed by mandibular ramus (0.99±0.19), then zygomatic buttress (0.49±0.06), while the lowest value was found in maxillary tuberosity (0.31±0.07). Post hoc pairwise comparisons showed value of mandibular symphysis to be significantly higher than other sites (p<0.05). In addition, they showed mandibular ramus value to be significantly higher than values of zygomatic buttress and maxillary tuberosity (p<0.05). Conclusion: According to this study, mandibular donor sites showed larger segmented pieces and larger volumes than their maxillary counterparts. For multiple missing teeth, the most appropriate block grafts will be the symphysis and ramus spanning the largest mesio-distal dimension. In terms of implant stability, the rami and maxillary tuberosities showed the largest thicknesses, which will ultimately help in implant stability.

Nickel and chromium ion release from coated and uncoated orthodontic archwires under different pH levels and exposure times

ObjectivesThe purpose of this study was to determine and compare nickel and chromium ion release from traditional stainless steel and nickel titanium wires and newer esthetic archwires under different pH conditions, for different time intervals. MethodsTen pieces of 10-mm segments of five different orthodontic archwires were submerged in buffer solutions of pH 4.0, 5.5, and 7.0, for 4 and 13 weeks. The sample solutions were analyzed using ICP-MS. First, the results were analyzed by three-way ANOVA to determine any significant differences in metal concentration (ppb) between the different groups. Then, a post-hoc multiple pairwise comparison by Tukey's Studentized Range (HSD) Test was conducted to further compare the different materials and pH conditions. ResultsFor nickel, uncoated NiTi had the highest nickel ion release (ppb), while AO Iconix had the lowest average nickel ion release, with a significant difference (p < 0.0001). The average nickel release increased with time and decreased with pH. For chromium, materials with uncoated stainless steel had the highest average chromium ion release, whereas AO Iconix had the lowest average chromium ion release, with a statistically significant difference (p < 0.0001). Chromium ion release increased with time and decreased with pH. ConclusionsThere were significant differences in metal ion release between different pH conditions, materials, and time points. The metal ion release increased with increase in time and decrease in pH. Overall, the coated archwires showed less metal ion release than the uncoated wires.

Novel Thermally Stable Segmented Solid Paraboloid Antenna for High Surface Accuracy

The rapidly growing communication demands in our society require the design of high-performance solid paraboloid antennas with extremely high surface accuracy, which remains a challenge due to the inevitable thermal deformations. This paper proposes a novel design of thermally stable segmented solid surface antenna with high surface accuracy. In this novel design, the antenna reflector is divided into a certain number of segmented pieces, each of which is then individually supported by an innovative thermally stable grid structure. An analytical model based on Sanders improved first-approximation shell theory is developed to predict the thermal deformation of antenna surface, with which the proposed segmenting method in improving the surface accuracy of reflector antenna is theoretically approved. The working mechanism of the proposed thermally stable grid structure that the thermal deformations at the supporting points can maintain a minimum level is verified using finite element analysis. A case study is performed in a practical environment to demonstrate that a segmented antenna supported by thermally stable grid structure can largely suppress the thermal deformation compared with a continuous surface antenna. This study provides a novel and useful engineering solution for paraboloid solid surface antennas to achieve extremely high surface accuracy under various thermal conditions.

Methodology for Establishing Segmentation Strategy for Large Metal Components from Nuclear Power Plants with Consideration of Packaging into Containers

A methodology for segmenting large metal components from nuclear power plants has been developed with a view to minimizing the number of containers to emplace segmented pieces. Spherocylinder-type and rectangular prism-type objects are modeled in shapes, and equations to calculate heights, widths, lengths, or angles for segmentation and the number of pieces are derived using geometric theorems, with a hypothetical ‘virtual rectangle’ being introduced for simplification. Applicability of the new methodology is verified through case studies assuming that each segmented piece is packaged into a 200 L container, and a procedure for adjusting potential overestimation of the segmented pieces due to the virtual rectangle is proposed. The new approach results in fewer segmented pieces but more containers than an existing segmentation study using 3D modeling. It is demonstrated that the number of containers can be further reduced, however, if the generalized methodology is followed by 3D modeling. In addition, it is confirmed that the generalized approach is also applicable to a nonstandard shapes such as ellipsoidal shape but only under limited conditions. Sensitivity analyses are conducted by changing dimensions of the objects and container, which brings about an optimal dimension of container as well. The generalized approach would be utilized either alone in decommissioning planning to estimate waste from segmentation of large metal components or combined with 3D modeling to optimize segmentation operation.

Manufacture of Tungsten Heavy Alloy Tube by Diffusion Bonding of Semicircular Tubes

An innovative manufacturing method to fabricate tubular parts made of tungsten heavy alloy (THA) by diffusion bonding of sintered semicircular tubes is proposed and characterized in this study. THAs are produced by blending tungsten grains with a lower-melting-point Ni-Fe binder metal. During the liquid phase sintering (LPS) process of THA, the Ni-Fe liquid wets the tungsten and provides a soluble diffusion network for rapid sintering. Multi-phase THAs are usually very difficult to produce as a tubular piece. During the LPS of the powder compact, a gravity-induced slumping leads to some distortion in the bottom of the tubular parts. One possible alternative to handle this problem is to combine the segmented THA pieces by solid-state diffusion bonding to build up tubular piece. Thus, this study proposes combining the semicircular THA tubes using the diffusion bonding technique to manufacture the tubular THA parts. To provide uniform contact pressures along the joining surfaces, horizontal diffusion bonding is performed using a specially constructed supporting apparatus to reduce the gravity effect. An industry-applicable tube manufacturing process has been well characterized, and its feasibility has been demonstrated by bond quality that was assessed by optical metallography and mechanical testing.

Numerical predictions of fluid dynamics and wall erosion characteristics in a circular 90 deg. pipe bend with single and multi mitred joint

The present work compares the numerical fluid dynamic and wall erosion characteristics of a single phase fluid flowing through two vertical pipe bend assemblies: sharp (S) and mitred (M). Both the ‘S’ and ‘M’ pipe bend assemblies have circular section with double bends each having a 90° flow turning angle. The ‘S’ bends has a single weld joint and the ‘M’ bends were made of 2 pieces of miter segments, thus having three weld joints. Single phase fluid (water) was made to flow at five Reynolds numbers 1e5 < Re < 10e5 through these pipe bends. Computations were carried out separately on a smooth circular 90° pipe bend with different turbulence models. Grid independency studies were carried out with the chosen turbulence model to optimize the mesh density requirements. The computational results were validated with literature and found to show good agreement. Comparison of flow behaviour in the 90° S and M bends was discussed. Differences in the induced swirl flow at the outlet of these pipe assemblies were reported. Due to abrupt sharp flow turning, higher pressure drop and wall shear stresses were observed in S bend pipe assemblies. The numerical flow visualization results helps in understanding the detailed flow characteristics in the 90-S and 90-M pipe bends.

Study of flow behaviour in sharp and mitred pipe bends

The present work compares the flow characteristics of a single phase fluid flowing through two vertical pipe bend assemblies: sharp (S) and mitred (M), using CFD. Both the ‘S’ and ‘M’ pipe bend assemblies have circular section with double bends each having a 90° flow turning angle. The ‘S’ bends has a single weld joint and the ‘M’ bends were made of 2 pieces of miter segments, thus having three weld joints. Water was made to flow at five Reynolds numbers 1e5 < Re < 10e5 through these pipe bends. Computations were carried out for Re = 1e5, with different turbulence models to find the best suitable model for this type of problem. Grid independency studies were carried out with the chosen turbulence model to optimize the mesh density requirements. The computational methodology adopted was validated with literature results and found to show good agreement. Comparison of flow behaviour in the 90° S and M bends was discussed. Differences in the induced swirl flow at the outlet of these pipe assemblies were reported. Due to abrupt sharp flow turning, higher pressure drop and wall shear stresses were observed in S bend pipe assemblies. Vortex magnitudes describing the swirl strength was found larger in the sharp bends compared to that in the mitred bends. The gain/decay of vortex strength along the pipe axial direction are discussed in detail.

Hierarchical tunnel modeling from 3D raw LiDAR point cloud

Precise modeling of tunnel structures can be used to evaluate the performance and state of safety as an important construction analysis object. However, the problem of modeling on a large-scale tunnel is challenging, due to the poor-quality of the input data that is contaminated with severe missing areas, noise, outliers and the accessories. This work introduces the concept of hierarchical modeling to automatically derive a measured and accurate representation of a 3D shield tunnel. Our key observation is that the shield tunnel is composed of a certain number of segment pieces arranged in some designed patterns. We hereby apply hierarchical segmentation and element extraction, based on designed patterns, to intensity images without expensive computation. According to the corresponding relationship between the point cloud and the image, the segment pieces within the point cloud are extracted. Therefore, we construct the corresponding 3D models of the segment pieces to obtain the precise structure model of the tunnel. As a result, segment pieces are extracted robustly, even in the presence of noise and large occlusion. Quantitative and qualitative comparisons of the proposed algorithm are presented with state-of-the-art methods. We evaluate the modeling method on a variety of raw LiDAR scans, in terms of its robustness and accuracy. Moreover, our method has been successfully applied in a number of practical projects to discover the multi-level structures of the shield tunnels, which are used to evaluate the safety state of tunnels.

A comparative study of two meta-heuristic algorithms in optimizing cost of reinforced concrete segmental lining

In this work, we tried to automatically optimize the cost of the concrete segmental lining used as a support system in the case study of Mashhad Urban Railway Line 2 located in NE Iran. Two meta-heuristic optimization methods including particle swarm optimization (PSO) and imperialist competitive algorithm (ICA) were presented. The penalty function was used for unfeasible solutions, and the segmental lining structure was defined by nine design variables: the geometrical parameters of the lining cross-section, the reinforced feature parameters, and the dowel feature parameters used among the joints to connect the segment pieces. Furthermore, the design constrains were implemented in accordance with the American Concrete Institute code (ACI318M-08) and guidelines of lining design proposed by the International Tunnel Association (ITA). The objective function consisted of the total cost of structure preparation and implementation. Consequently, the optimum design of the system was analyzed using the PSO and ICA algorithms. The results obtained showed that the objective function of the support system by the PSO and ICA algorithms reduced 12.6% and 14% per meter, respectively.

Visualization of erythrocyte deformation induced by supraphysiological shear stress.

To elucidate development of shear-induced damage in erythrocytes, it is necessary to visualize erythrocytes under high-shear flow. Therefore, we prototyped a special shear flow chamber with a counter-rotating mechanism consisting of a transparent acrylic cone and a glass plate. The flow chamber was mounted on an inverted microscope and illuminated by a 350-W metal halide lamp. This experimental system made it possible for a digital video camera to record through the microscopes' objective lens the rheological behavior in shear flow of erythrocytes diluted in highly viscous polyvinyl pyrrolidone. We successfully visualized the blood cells' ellipsoidal deformation response to an unphysiological, high shear stress of 288 Pa, their shift into abnormal rheological behavior, and final collapse. When abnormality first appeared, the membrane surface of some ellipsoidal erythrocytes started undulating and their shape became more asymmetric. Finally, the erythrocytes appeared to fragment, although the fragments continued tumbling together suggesting that they were all still connected. One such abnormal erythrocyte became segmented through collision with other cell. The undulation of the membrane surface when erythrocytes experienced trauma suggests possible detachment of the lipid bilayer from the membrane cytoskeleton. As the damage increased, the morphological abnormality of cells became greater with less tank-treading, and then, the erythrocytes started tumbling. This unstable behavior increases the volume of flow region occupied by the erythrocytes and increases the chance that neighboring cells will hit them and break them into segmented pieces. This study clearly showed that the beginning of erythrocytes' morphological abnormality was induced by shear stress.

Analysis on Control Methods of Automotive Brake Tester Based on Mechanical Mechanics

The design of brake is one of the most initial parts in automotive design. In the period of design, road tests are not available. Therefore, simulation experiment on designed road test is conducted by specialized brake tester. Based on observable quantity and brake theories, this thesis lays out the relationship among all torques: Mb =Mz ‐Mq = J d dt   , and the differential equation model is I 20 dt Jdn    , which indicates that driving current depends on mathematical model of observable quantity. Moreover, on the given condition, the driving current is calculated as 174.205A. Next, the time is equally divided into n pieces of time segments. With the aid of k, the simulation coefficient of inertia, energy relation is founded. Then, instantaneous rotational speed in the previous time segment iterates the energy Bi J needed for current time segment by the utilization of MATLAB software. The model integral is used to draw out the relationship between current and observable quantity, and current of this time segment is calculated by previous time segment observation data.

Virtual occlusal definition for segmental orthognathic surgery

Background: Computer-assisted surgical simulation is being used increasingly in orthognathic surgery, but occlusal definition is still done by model surgery manually. We researched virtual occlusal definition for normal occlusion and proved it to be accurate and reliable. Many other authors have also proved that virtual occlusal definition for one piece maxilla was accurate with the accuracy of 1 mm. Objective: To investigate the accuracy of virtual occlusion on decompensation dentition and the accuracy for segmental virtual occlusion definition. Methods: 17 pairs of pre-surgery models were included in this study. For each pair, final occlusions were defined by a single investigator manually and digitised as gold standard. Maxillae in one piece as well as segmented pieces were moved to match mandibles in virtual environment to get virtual final occlusion of test groups. Marker points on fossae and cusps of test groups and gold standard were signed and compared. Findings: The average errors between the virtually set positions and the digitised manually positions were 0.69 mm, 0.71 mm, 0.79 mm and 0.79 mm, respectively and were all within 1 mm. Errors did not differ from different teeth nor from different groups (P > 0.05). Conclusion: Virtual occlusal definition for decompensation dentition, whether segmental or one-piece is accurate, and that accuracy does not decrease as the segments increase.

Spatial Inference of Traffic Transition Using Micro–Macro Traffic Variables

This paper proposes an online traffic inference algorithm for road segments in which local traffic information cannot be directly observed. Using macro-micro traffic variables as inputs, the algorithm consists of three main operations. First, it uses interarrival time (time headway) statistics from upstream and downstream locations to spatially infer traffic transitions at an unsupervised piece of segment. Second, it estimates lane-level flow and occupancy at the same unsupervised target site. Third, it estimates individual lane-level shockwave propagation times on the segment. Using real-world closed-circuit television data, it is shown that the proposed algorithm outperforms previously proposed methods in the literature.

Impact of Laser-Processed X'tal Cube Detectors on PET Imaging in a One-Pair Prototype System

The X'tal cube is our original PET detector, which is being developed to achieve isotropic 3D positioning detectability. The X'tal cube is based on a 3D segmented crystal block for which all surfaces are covered with photo-detectors. Previously, instead of our initial approach of gluing segmented pieces of crystals, we successfully constructed a crystal block segmented by laser processing, and we developed the X'tal cube with the laser-processed 3D square grids of 2 mm length. In this paper, we extend the laser processing to 3D square grids of 1 mm length. The volume of a 1-mm crystal segment is 1/8 of that of a 2-mm crystal segment. We also evaluate imaging resolution performance with a newly developed one-pair prototype system to simulate a ring-type scanner, while our previous reports were limited to development and evaluation of a single detector. In particular, we compare 1-mm X'tal cube detectors to 2-mm X'tal cube detectors. The one-pair prototype system consisted of two X'tal cubes, two rotating stages, and a 192-channel data acquisition system. Each X'tal cube consisted of the LYSO cubic crystal block of 18 × 18 × 18 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> in which the 3D grids of 1 mm pitch were fabricated by internal laser processing. The 4 × 4 arrays of multi pixel photon counters were optically coupled to each surface of the crystal block. The detector positions were automatically controlled to simulate a ring-type PET with a 14.6 cm diameter. Data were collected for all assumed detector positions and then a sinogram was obtained. The data were reconstructed using filtered backprojection. The average spatial resolution of the 2-mm X'tal cube was 1.9 mm full width at half maximum (FWHM) over the field-of-view (FOV). On the other hand, the average spatial resolution of the 1-mm X'tal cube was 1.3 mm FWHM over the FOV. By applying deconvolution with the assumption that the point source was a Gaussian function of 1.0 mm FWHM, we estimated the average spatial resolution of the 2-mm X'tal cube and the 1-mm X'tal cube as 1.6 mm FWHM and 0.83 mm FWHM, respectively. The average spatial resolution of the 1-mm X'tal cube was improved approximately 48% compared to the 2-mm X'tal cube. In conclusion, we confirmed the potential of the X'tal cube for uniform and high resolution imaging.

Jointing Edge Labeling and Geometrical Constraint for Lane Detection and its Application to Suspicious Driving Behavior Analysis

This paper presents a novel lane detection scheme for detecting and tracking various lanes directly from videos in real time. The key contribution of this paper is to propose a new edge labeling scheme for labeling each edge point to different types. Even under different lighting and weather conditions, different lane segments still can be effectively extracted from the labeling result. Only the subtraction and counting operators are involved in the labeling process. It is also flexible for detecting lanes with different types especially from an interchange area. To filter out false lane segments, this paper uses a pinhole camera model to derive a geometrical constraint for lane verification. The constraint is invariant to shadows and lighting changes. Thus, each lane line can be verified and then detected more accurately from roads. Since lanes seldom change their colors during two adjacent frames, we propose a kernel-based technique for tracking them even fragmented into pieces of segments. Then, different lanes can be more efficiently detected and tracked from videos captured under various lighting and weather conditions. With the lane information, different dangerous driving events like lane departure can be easily analyzed for driver assistances. All the involved operations are very simple and effective for hardware implementation. Extensive experimental results reveal the feasibility and superiority of the proposed approach in lane detection.

Vibration-type measurement pickup and its measuring tube

A measurement pickup, or transducer, includes at least one measuring tube for the conveying of a fluid. The measuring tube has an inlet end and an outlet end and vibrates at least at times. For enabling the fluid to be measured to flow through the measuring tube, the measuring tube communicates, via a first tube segment opening into the inlet end and via a second tube segment opening into the outlet end, with a pipeline connected therewith. For the oscillatable holding of the measuring tube, the measurement pickup further includes a support element having a first end piece containing a passageway for the securement of the first tube segment and having a second end piece containing a passageway for the securement of the second tube segment. Each of the two tube segments extends through its respective one of the two passageways and each of the two passageways has an inner diameter, which is greater than an outer diameter of its associated tube segment, so that an intermediate space is formed between each of the associated tube segments and end pieces. The measurement pickup further includes at least one, preferably metal, first spring element pushed onto one of the two tube segments. The spring element fills the intermediate space formed between tube segment and end piece at least partially, with the spring element being arranged in the intermediate space in such a manner that it contacts, at least sectionally, both its associated tube segment and also its associated end piece in such a manner that it is subjected, at least sectionally, to radially acting, deformation forces. As a result of elastic deformations accompanying such deformation forces, the spring element is held pressed against the associated tube segment and the associated end piece, whereby such tube segment is locked securely in the associated passageway.

Stability of Kerogen Classification with Regard to Image Segmentation

This paper investigates the stability of an automatic system for classifying kerogen material from images of sieved rock samples. The system comprises four stages: image acquisition, background removal, segmentation, and classification of the segmented kerogen pieces as either inertinite or vitrinite. Depending upon a segmentation parameter d, called “overlap”, touching pieces of kerogen may be split differently. The aim of this study is to establish how robust the classification result is to variations of the segmentation parameter. There are two issues that pose difficulties in carrying out an experiment. First, even a trained professional may be uncertain when distinguishing between isolated pieces of inertinite and vitrinite, extracted from transmitted-light microscope images. Second, because manual labelling of large amount of data for training the system is an arduous task, we acquired the true labels (ground truth) only for the pieces obtained at overlap d=0.5. To construct ground truth for various values of d we propose here label-inheritance trees. With thus estimated ground truth, an experiment was carried out to evaluate the robustness of the system to changes in the segmentation through varying the overlap value d. The average system accuracy across values of d spanning the range from 0 to 1 was 86.5%, which is only slightly lower than the accuracy of the system at the design value of d=0.5 (89.07%).

P.026 Nasal dermal sinus cyst with intracranial extension

Precise modeling of tunnel structures can be used to evaluate the performance and state of safety as an important construction analysis object. However, the problem of modeling on a large-scale tunnel is challenging, due to the poor-quality of the input data that is contaminated with severe missing areas, noise, outliers and the accessories. This work introduces the concept of hierarchical modeling to automatically derive a measured and accurate representation of a 3D shield tunnel. Our key observation is that the shield tunnel is composed of a certain number of segment pieces arranged in some designed patterns. We hereby apply hierarchical segmentation and element extraction, based on designed patterns, to intensity images without expensive computation. According to the corresponding relationship between the point cloud and the image, the segment pieces within the point cloud are extracted. Therefore, we construct the corresponding 3D models of the segment pieces to obtain the precise structure model of the tunnel. As a result, segment pieces are extracted robustly, even in the presence of noise and large occlusion. Quantitative and qualitative comparisons of the proposed algorithm are presented with state-of-the-art methods. We evaluate the modeling method on a variety of raw LiDAR scans, in terms of its robustness and accuracy. Moreover, our method has been successfully applied in a number of practical projects to discover the multi-level structures of the shield tunnels, which are used to evaluate the safety state of tunnels.