Segmental Construction Research Articles

Healthy Aging: An Automatic Analysis of Global and Regional Morphological Alterations of Human Brain

Morphologic changes of the human brain during healthy aging provide useful reference knowledge for age-related brain disorders. The aim of this study was to explore age-related global and regional morphological changes of healthy adult brains. T1-weighted magnetic resonance images covering the entire brain were acquired for 314 subjects. Image processing of registration, segmentation, and surface construction were performed to calculate the volumes of the cerebrum, cerebellum, brain stem, lateral ventricle, and subcortical nuclei, as well as the surface area, mean curvature index, cortical thickness of the cerebral cortex, and subjacent white matter volume using FreeSurfer software. Mean values of each morphologic index were calculated and plotted against age group for sectional analysis. Regression analysis was conducted using SPSS to investigate the age effects on global and regional volumes of human brain. Overall global and regional volume loss was observed for the entire brain during healthy aging. Moderate atrophy was observed in subcortical gray matter structures, including the thalamus (R(2) = 0.476, P < .001), nucleus accumbens (R(2) = 0.525, P < .001), pallidum (R(2)= 0.461, P < .001), and putamen (R(2) = 0.533, P < .001). The volume of hippocampus showed a slight increase by 40 years of age, followed by a relatively faster decline after the age of 50 years (R(2) = 0.486, P < .001). Surface area and mean curvature were less affected by aging relative to cortical thickness and subjacent white matter volume. Significant cortical thinning was mainly found in the parietal (R(2) = 0.553, P < .001) and insula regions (R(2) = 0.405, P < .001). Morphologic alterations of human brain manifested regional heterogeneity in the scenario of general volume loss during healthy aging. The age effect on the hippocampus demonstrated a unique evolution. These findings provide informative reference knowledge that may help in identifying and differentiating pathologic aging and other neurologic disorders.

Biomechanical comparison of anterior cervical spine instrumentation techniques with and without supplemental posterior fusion after different corpectomy and discectomy combinations

The objective of this study was to compare the stiffness and range of motion (ROM) of 4 cervical spine constructs and the intact condition. The 4 constructs consisted of 3-level anterior cervical discectomy with anterior plating, 1-level discectomy and 1-level corpectomy with anterior plating, 2-level corpectomy with anterior plating, and 2-level corpectomy with anterior plating and posterior fixation. Eight human cadaveric fresh-frozen cervical spines from C2-T2 were used. Three-dimensional motion analysis with an optical tracking device was used to determine motion following various reconstruction methods. The specimens were tested in the following conditions: 1) intact; 2) segmental construct with discectomies at C4-5, C5-6, and C6-7, with polyetheretherketone (PEEK) interbody cage and anterior plate; 3) segmental construct with discectomy at C6-7 and corpectomy of C-5, with PEEK interbody graft at the discectomy level and a titanium cage at the corpectomy level; 4) corpectomy at C-5 and C-6, with titanium cage and an anterior cervical plate; and 5) corpectomy at C-5 and C-6, with titanium cage and an anterior cervical plate, and posterior lateral mass screw-rod system from C-4 to C-7. All specimens underwent a pure moment application of 2 Nm with regards to flexion-extension, lateral bending, and axial rotation. In all tested motions the statistical comparison was significant between the intact condition and the 2-level corpectomy with anterior plating and posterior fixation construct. All other statistical comparisons between the instrumented constructs were not statistically significant except between the 3-level discectomy with anterior plating and the 2-level corpectomy with anterior plating in axial rotation. There were no statistically significant differences between the 1-level discectomy and 1-level corpectomy with anterior plating and the 2-level corpectomy with anterior plating in any tested motion. There was also no statistical significance between the 3-level discectomy with anterior plating and the 2-level corpectomy with anterior plating and posterior fixation. This study demonstrates that segmental plate fixation (3-level discectomy) affords the same stiffness and ROM as circumferential fusion in 2-level cervical spine corpectomy in the immediate postoperative setting. This obviates the need for staged circumferential procedures for multilevel cervical spondylotic myelopathy. Given that the posterior segmental instrumentation confers significant stability to a multilevel cervical corpectomy, the surgeon should strongly consider the placement of segmental posterior instrumentation to significantly improve the overall stability of the fusion construct after a 2-level cervical corpectomy.

Analysis of segmental piers consisted of concrete filled FRP tubes

Precast segmental construction technique is an excellent candidate for economic rapid bridge construction in highly congested urban environments and environmentally sensitive regions. This paper presents three dimensional nonlinear finite element models using ABAQUS⧹Standard for evaluating the behavior of segmental precast post-tensioned piers under lateral loads. The piers were constructed by stacking precast concrete filled fiber reinforced polymer tube segments one on top of the other and then connecting the assembly structurally with vertical post-tensioning tendons passing through ducts located in the precast segments. A stress–strain relationship for confined concrete was used to model the concrete. The post-tensioning tendons were modeled with beam elements. The model was able to predict the backbone curves for two piers subjected to cyclic loads. A parametric study indicated that increasing the applied post-tensioning force increases nominal strength. Finally, the model showed that the pier aspect ratio, cross sectional diameter size, pier size, and confinement have significant effects on the performance of the investigated piers.

Biomechanical Analysis of Sacral Screw Strain and Range of Motion in Long Posterior Spinal Fixation Constructs

A cadaveric biomechanical experiment was conducted to assess the range of motion (ROM) and screw strain at S1 in a long instrumented spinal fusion construct to compare the effects of various surgical strategies for L5-S1 stabilization. To directly quantify and compare S1 screw strains and lumbosacral ROM for 4 different L2-S1 posterior segmental instrumented fusion constructs: an L2-S1 pedicle screw (PS) construct alone and PS with each of 3 different augmentations, anterior lumbar intebody fusion (ALIF), anterior axial interbody threaded rod (AxiaLITR), or iliac screws. Iliac screws and anterior interbody devices are commonly used as augmentation to reduce the incidence of S1 screw loosening in long fusion constructs. Alternatives, such as AxiaLITR, may provide similar biomechanical advantages without many of the same long-term limitations and morbidities. Pure moment flexibility testing was performed in 6 cadaveric lumbosacral spines. Specimens were tested with 4 instrumentation constructs: (1) PS L2-S1, (2) PS with ALIF, (3) PS with AxiaLITR, and (4) PS with iliac screws. Bilateral S1 PS were instrumented with strain gauges, directly measuring screw loading while simultaneously measuring L5-S1 ROM with a noncontact camera system. Average S1 screw strains were the greatest with the PS group and were reduced by 38% with the ALIF group, 75% with the AxiaLITR group, and 78% with the iliac screw group in flexion-extension (P < 0.05). Similar trends were observed in torsion (P < 0.05). Strains in lateral bending were smaller in magnitude and were similar among all 4 constructs. The AxiaLITR and iliac screw groups demonstrated a similar ROM and significant reduction in ROM at L5-S1 compared with both the PS and ALIF groups (P ≤ 0.02 and P < 0.03). The results of this study indicated that iliac screws and AxiaLITR provide similar stability at L5-S1, while significantly reducing the strain on the S1 screws.

Study on the Election of Construction Schemes for the Entrance Segment of Tunnel with Unsymmetrical Loading through Large-Span Thin-Dover

Jiulian-mountain tunnel is an very important project for a section of Longyang Jiangxi in Da-guang highway. Because Jiulian-montain tunnel has a series of geological problems, like shallow-depth, bias-pressure, big-span,water-rich, rock burst and so on, which is a typical long - wide highway tunnel grew up under complex conditions, construction of the entrance segment is extremely difficult and slow in progress.In order to efficiently accomplish the construction of tunnel on time, it is necessory to elect rational construction scheme of the entrance segment. The numerical simulation for three construction methods,which are benching tunneling method、 method of core-keeping cut in stages and CD method , are carried out by means of Three-dimensional fast lagrangian analysis of continua method(FLAC3D) in this paper. Based on the result of the numerical simulation analysis and contrast, some conclusions and suggestions are proposed, some gist are offered in order to choose the construction method rationally ,and arrange the construction order scientifically, and control the construction pace optimally, and reduce the harm of the construction .

Dynamic behaviour of HPFRCC in tension

High Performance Fiber Reinforced Cementitious Composites belong to a new class of structural materials characterized by high strength and ductility. Thanks to the high energy absorbed during the fracture process, due to multiple cracking and pull-out phenomena, they are often suggested for dynamic loading applications. Current understanding of the dynamic response is very limited because of very few investigations have been actually carried out. An experimental research aimed at contributing to the understanding of the behaviour of advanced fiber-reinforced cementitious composites subjected to low and high strain rates was carried out. The material investigated is a High Performance Fiber Reinforced Cementitious Composites. Straight high carbon steel micro-fibers were used. The material behaviour was investigated at several strain rates and the tests results were compared with their static behaviour. Tests at intermediate strain rates were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates were investigated by exploiting a Split Hopkinson Tensile Bar (SHTB). A comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibers on the peak strength and post-peak behaviour at high strain rates. Finally, this material will be employed in the construction of an innovative tunnel segment designed for extreme conditions (high temperature and shock).

Study on the Election of Construction Schemes for the Entrance Segment of Tunnel with Unsymmetrical Loading through Large-Span Thin-Dover

Jiulian-mountain tunnel is an very important project for a section of Longyang Jiangxi in Da-guang highway. Because Jiulian-montain tunnel has a series of geological problems, like shallow-depth, bias-pressure, big-span,water-rich, rock burst and so on, which is a typical long - wide highway tunnel grew up under complex conditions, construction of the entrance segment is extremely difficult and slow in progress.In order to efficiently accomplish the construction of tunnel on time, it is necessory to elect rational construction scheme of the entrance segment. The numerical simulation for three construction methods,which are benching tunneling method、 method of core-keeping cut in stages and CD method , are carried out by means of Three-dimensional fast lagrangian analysis of continua method(FLAC3D) in this paper. Based on the result of the numerical simulation analysis and contrast, some conclusions and suggestions are proposed, some gist are offered in order to choose the construction method rationally ,and arrange the construction order scientifically, and control the construction pace optimally, and reduce the harm of the construction .

Building Spatiotemporal Anatomical Models using Joint 4-D Segmentation, Registration, and Subject-Specific Atlas Estimation.

Longitudinal analysis of anatomical changes is a vital component in many personalized-medicine applications for predicting disease onset, determining growth/atrophy patterns, evaluating disease progression, and monitoring recovery. Estimating anatomical changes in longitudinal studies, especially through magnetic resonance (MR) images, is challenging because of temporal variability in shape (e.g. from growth/atrophy) and appearance (e.g. due to imaging parameters and tissue properties affecting intensity contrast, or from scanner calibration). This paper proposes a novel mathematical framework for constructing subject-specific longitudinal anatomical models. The proposed method solves a generalized problem of joint segmentation, registration, and subject-specific atlas building, which involves not just two images, but an entire longitudinal image sequence. The proposed framework describes a novel approach that integrates fundamental principles that underpin methods for image segmentation, image registration, and atlas construction. This paper presents evaluation on simulated longitudinal data and on clinical longitudinal brain MRI data. The results demonstrate that the proposed framework effectively integrates information from 4-D spatiotemporal data to generate spatiotemporal models that allow analysis of anatomical changes over time.

Bridge on the road I/35 across Václavický Fishpond

The paper describes the design and construction of a bridge across a pond and a local road on the road I/35 Bílý Kostel - Hradek nad Nisou. The bridge comprises 5 spans with lenghts of 40,00 + 3 x 50,00 + 40,00 m. Total length of the bridge is 247 m.The substructure of the bridge consists of concrete abutments and four intermediate concrete piers. Abutment foundations are supported on bored piles and intermediate pillars on spread foundations. Two pillar foundations have been constructed on the lake bed which required sheet pile cofferdam.The superstructure was manufactured by sections in a dedicated area and launched using the incremental launching method. The continuous steel-concrete composite superstructure was designed as a twin steel plate girder with steel bracings and a top flange connected to a composite concrete haunch slab. Plate girders both of which rest upon a set of pot bearings are 2,5 m high and 7,0 m apart.The fabrication yard was stationary and located behind the abutment. A lightweight nose was fitted to the cantilever end of the superstructure to reduce the cantilever deformations during launching. The bridge supports were equipped with special teflon sliding bearings and friction was recorded at each jacking operation. Temporary support was incorporated between the abutment and the pier. The reinforced concrete composite haunch slab was cast on travelling formwork primarily at the midspans and subsequently above the piers.The construction was accomplished rapidly without any complications in the difficult access terrain. This proved the chosen steel concrete composite superstructure tangible, especially for the case of segmental launching construction.

The Post-Interstate Era

This essay highlights key themes of the five essays that comprise this special issue of the Journal of Planning History on the post-Interstate Era. It outlines in broad strokes the role of highway engineers and politicians in planning and financing the Interstate Highway System. The Interstates had a positive impact on economic growth and automobility, yet citizens groups in many cities challenged route decisions that destroyed neighborhoods and damaged sensitive environments. By the early 1970s, when the Interstate System was mostly completed, Congress opened up the Highway Trust Fund for mass transit alternatives. However, our authors emphasize the persistence of conflict over transportation planning and policy. Construction of late-developing Interstate segments in cities such as St. Paul, Minnesota and Huntsville, Alabama revived the freeway revolt, but unsuccessfully. Highway planners and policy experts developed controversial new strategies for moving traffic, as in Boston’s “Big Dig,” or for creative transportation financing, as with the Chicago Skyway and the Pennsylvania Turnpike. By the end of the twentieth century, planners and politicians in some cities sought to reverse poor route decisions of an earlier era by tearing down elevated freeway segments most judged ugly, onerous, and unnecessary. In the twenty-first century, the engineers, planners, and politicians who control the Interstate Highway System face new challenges as the aging highway infrastructure requires rebuilding and retrofitting in an era of economic decline and political cost cutting.

Fabrication and Erection of U-Trough Section Bridges

The U-trough section structure has been largely used in the last decade for Light Rail Transit and Mass Rapid Transit systems all over the world. Approximately 200 km of U-trough section bridges have been already built or are under construction. The typical deck carries one or two tracks; for single track the deck cross section is a small U around 5 m wide, and for two tracks the deck section is a wide U with around 10 m wide. The usual span length is in the range from 25 to 35 m.This paper reviews the applications and the construction technology for prestressed concrete decks using U-shaped precast segments or full precast span. For large-length viaducts it becomes cost effective to use precasting. The deck segments are cast in long line beds or individual cells and are assembled on site using post-tension. Full spans are cast in beds and pre-/post-tensioned on the precasting yard.This paper presents the different erection methods in terms of technical features for both segmental construction and full-span construction. Elements can be transported at ground level and lifted at deck level or transported at deck level and erected with an overhead launching gantry. In the case of full precast span, the erection could be realized by means of two cranes or special gantry.This paper also discusses the development of construction equipments for single-track deck and the interaction of U-shaped structural design and construction equipments.

Multi-Span Closure Construction and Optimization Analysis of the Main Channel Bridge on the Left Branch of Beijiang River

Multi stages such as side span closure, middle span closure, ten years after construction and so on are simulated with the finite element method in the main channel bridge on the left branch of Beijiang River. Many issues such as unreasonable incremental launching force in construction are found. The optimization made the vertical displacement of the main beam controlled, the secondary moment value on the top of the pier by the side bending of the anchorage and the secondary effect of pre-stressed tendons significantly reduced, and the force of anchorage more balanced. Construction sequence optimization can make the construction process more reasonable and provide a reference for the closing segment construction of the bridge.

Total synthesis of pyripyropene A

The total synthesis of pyripyropene A, a potent ACAT2 inhibitor with high isozyme selectivity, was completed. Key features of the synthetic strategy include Ti(III)-mediated radical cyclization and Peterson olefination for the construction of the AB ring segment and stereoselective dihydro-γ-pyrone formation (C-ring). The total synthesis provided pyripyropene A in 5.3% overall yield over 17 steps.

Experimental verification towards real construction of a slide type cotter formula segment

Experimental verification towards real construction of a slide type cotter formula segment

Alignment Control during Construction of Continuous Bridge Suspended by Triangle Frame

The features of a new type of continuous bridge suspended by triangle frame are introduced in this paper. In view of the segmental cantilever construction method engaged in main girder construction, we put forward to the method of pre-camber setting and the calculation of formwork elevation and field measurement of displacement.

Total synthesis of (±)-cycloclavine and (±)-5-epi-cycloclavine.

Novel routes to the naturally occurring indole alkaloid cycloclavine and its unnatural C(5)-epimer are described. Key features include the rapid construction of the heterocyclic core segments by two Diels-Alder reactions. An indole annulation was accomplished by a late-stage intramolecular Diels-Alder furan cycloaddition, and a methylenecyclopropane dienophile was used for a stereoselective intramolecular [4 + 2] cycloaddition to give the cyclopropa[c]indoline building block present in cycloclavine.

Reliability of construction control of cable-stayed bridges

Deck elevations and cable tensions change throughout the construction process of a long-span cable-stayed bridge. Accordingly, geometric errors of deck elevations and tension errors in cables are frequently encountered. The tolerance values of such errors are of great concern to the construction control of cable-stayed bridges. In order to obtain reasonable tolerance errors of deck elevations and cable tensions, the randomness of geometric parameters, the material parameters and the loading parameters of the bridge during erection should be considered. This paper presents a novel reliability-based approach to determine the tolerance errors for different construction stages of a cable-stayed bridge. In the proposed approach, an improved response surface method based on finite-element analysis of segmental construction of the bridge girder is used to yield the failure probabilities of construction control under different erection errors. Reasonable tolerance errors are then obtained based on the acceptable failure probabilities. For engineering applications, the proposed method is further applied to the reliability analysis of the construction contort of the newly built Huangpu Bridge across the Pearl River in Guangzhou. The new approach is also applicable to the construction control of other types of bridges.

The “T-construct” for spinopelvic fixation in neuromuscular spinal deformities. Preliminary results of a prospective series of 15 patients

We present the results of a prospective series of 15 patients treated for neuromuscular spinal deformities with an original spinopelvic construct using two sacral screws and two iliac screws. Results were compared to a prospective cohort of 62 patients treated for neuromuscular spinal deformities by spinopelvic fixation using iliosacral screws. From November 2005 to June 2007, the clinical data of every patient who underwent spinopelvic fixation for treatment of a neuromuscular spinal deformity were recorded prospectively. Fifteen patients weighting less than 35 kg were operated on with a special segmental construct using two sacral screws and two iliac screws for pelvic anchorage. Sixty-two patients had spinopelvic fixation using iliosacral screws. Severity of the curve (Cobb angle) and reducibility were statistically equal in both groups. Operative time and blood loss were statistically identical in both groups. Curve correction was similar in both groups and postoperative pelvic obliquity ranged between 2° and 4°. No significant loss of correction was noted at the last follow-up. Fifteen patients had early postoperative infection of the posterior wound requiring re-operation. Despite a high rate of infectious complications, optimal correction of pelvic obliquity requires extension of spinal instrumentation to the pelvis. Pelvic fixation with the "T-construct" did provide effective and improved spinal stabilization in these patients, while reducing the need for a postoperative cast or brace. As a result, patients had a favorable postoperative course with early mobilization and return to a comfortable sitting position.

Intelligent Approaches to interact with Machines using Hand Gesture Recognition in Natural way: A Survey

Hand gestures recognition (HGR) is one of the main areas of research for the engineers, scientists and bioinformatics. HGR is the natural way of Human Machine interaction and today many researchers in the academia and industry are working on different application to make interactions more easy, natural and convenient without wearing any extra device. HGR can be applied from games control to vision enabled robot control, from virtual reality to smart home systems. In this paper we are discussing work done in the area of hand gesture recognition where focus is on the intelligent approaches including soft computing based methods like artificial neural network, fuzzy logic, genetic algorithms etc. The methods in the preprocessing of image for segmentation and hand image construction also taken into study. Most researchers used fingertips for hand detection in appearance based modeling. Finally the comparison of results given by different researchers is also presented.

首都高速中央環状品川線シールドトンネルセグメント・床版の設計施工

本稿では，首都高速中央環状品川線の大橋行きシールドトンネルについて，大断面長距離シールドトンネルに求められる長距離・高速施工技術や耐久性・耐火性に配慮したセグメント設計概要を報告する。