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Highlights • The Lie-group shooting method does not require the special selection of parameters. • The proposed schemes are stable and effective for a large time span. • The Lie-group shooting method can retrieve the missing initial data very well. Abstract Based on the idea of the Lie-group shooting method and the backward group preserving scheme, a novel backward-forward algorithm is developed to solve non-linear, nonhomogeneous, multi-dimensional backward heat conduction problems under long time spans. For a nonhomogeneous, multi-dimensional, backward heat conduction problem, it is very difficult to integrate towards the time direction, even when using a high-order numerical scheme. To avoid time integration and increase the computational efficiency, a novel backward-forward Lie-group scheme is proposed. According to the quadratic equation of the Lie-group shooting method, a solution is applied to obtain the initial condition and to examine the final condition. Using the reciprocal relationship between the solutions of forward and backward schemes, the proposed algorithm can avoid the time integration of the numerical scheme and numerical divergence. To illustrate the effectiveness and accuracy of the proposed algorithm, several benchmarks in multi-dimensions are tested. The numerical results indicate that the proposed algorithm can achieve an efficient and accurate solution, even with noisy measurement data by comparing the estimation results with the existing literatures. [ABSTRACT FROM AUTHOR]

We study spans of cospans in a category C and explain how to horizontally and vertically compose these. When C is a topos and the legs of the spans are monic, these two forms of composition satisfy the interchange law. In this case there is a bicategory of objects, cospans, and 'monic-legged' spans of cospans in C. One motivation for this construction is an application to graph rewriting. [ABSTRACT FROM AUTHOR]

For a topos T, there is a bicategory MonicSp(Csp(T)) whose objects are those of T, morphisms are cospans in T, and 2-morphisms are isomorphism classes of monic spans of cospans in T. Using a result of Shulman, we prove that MonicSp(Csp(T)) is symmetric monoidal, and moreover, that it is compact closed in the sense of Stay. We provide an application which illustrates how to encode double pushout rewrite rules as 2-morphisms inside a compact closed sub-bicategory of MonicSp(Csp(Graph)). [ABSTRACT FROM AUTHOR]

We give several reformulations of action representability of a category as well as action representability of its category of morphisms. In particular we show that for a semi-abelian category ℂ, its category of morphisms is action representable if and only if the functor from the category of split extensions in ℂ to ℂ, sending a split extension to its kernel, is a prefibration. To obtain these reformulations we show that certain conditions are equivalent for right regular spans of categories. [ABSTRACT FROM AUTHOR]

Two new concrete bridge superstructure systems for short and medium span bridges are presented. The investigated systems consist of adjacent hollow precast concrete beams with and without concrete topping. The proposed configurations are compared with traditional adjacent box beam and decked bulb tee systems for spans that range from 24.4 m to 45.7 m. It is demonstrated that the proposed system that features concrete topping (PS2) is lighter than the adjacent box beam system, requires fewer strands, provides shallower superstructure depths, and exhibits lower cambers for spans equal to 24.4 m and 30.5 m. PS2 addresses the reflective cracking problems manifested in adjacent box beam systems by shifting the location of the longitudinal connections to the bottom flange and away from traffic loads. The system that features no topping (PS4) is slightly heavier than the decked bulb tee system, but features shallower superstructure depths, requires fewer strands, and exhibits lower live load deflections and camber. Transverse bending moments demand in PS4 are reduced compared to the decked bulb tee system due to the smaller span provided by the two web supports. Live load distribution factors (LLDF) for PS2 and PS4 can be conservatively estimated using AASHTO provisions for adjacent box and decked bulb tee systems, respectively. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the application of dielectric barrier discharge (DBD) plasma actuators on a slender delta wing to control the leading edge vortices (LEVs). The experiments are conducted in a wind tunnel with a Reynolds number of 50 000 based on the chord length. The smoke flow visualization reveals that the DBD plasma actuators at the leading edges significantly modify the vortical flow structure over the delta wing. It is noted that symmetric control at both semi-spans and asymmetric control at a single semi-span leads to opposite effects on the local LEVs. Particle image velocimetry (PIV) indicates that the shear layer is deformed by the actuators. Therefore, both the strength and the shape of the LEV cores are deeply affected. The six-component force measurement shows that the DBD plasma actuators have a limited effect on lift and drag while inducing relatively large moments. This suggests that the DBD plasma actuator is a promising technique for delta wing maneuvering. [ABSTRACT FROM AUTHOR]

It is shown that the general dynamics factor governing strength calculations of metallic spans is determined by the soil conditions and particularities of the interaction between support foundations and bases. The influence of the soil conditions for transverse oscillations of bridges increases with increasing support height and decreasing deformation characteristics of the base. It is noted that in order to make span structures more earthquake-resistant the foundation can be developed without changing the elements of the span structure. [ABSTRACT FROM AUTHOR]

The mechanical behavior of overhead conductors is described by a catenary function, stress-strain relations, the relation among three types of strains, and a tension balance equation. These functions are consolidated to form a single equation. The tension of a conductor in a ruling span is determined by solving this equation. It is a polynomial function of degree 4 or less and can be easily solved in Excel or by a simple code. For some special cases, analytical solutions can be found. This method is versatile. It covers a broad range of engineering applications, such as producing a stringing chart, establishing tension-temperature relations after load, determining the effect of creep, calculating the thermal-knee point, performing auto sagging, evaluating the temperature gradient effect, etc. It is also a powerful R&D tool, providing great insight into the mechanical behavior of overhead conductors. Many interesting features of conductors can be revealed or verified by it. The method aids in the investigation of the abnormality or failure of conductors observed in the field and in laboratories. [ABSTRACT FROM PUBLISHER]

This paper evaluates the overstrength, ductility, and response modification factors for low to mid-rise buckling restrained braced frames (BRBFs) designed as per the 2010 National Building Code of Canada. In addition to nonlinear static pushover analyses, dynamic time history analyses are performed to assess the seismic performance of four-, six-, and eight-story BRBFs. Different bracing configurations, including chevron (inverted-V) and split-X braces, are considered for the building frames with varied frame span lengths of 6 m and 8 m. The results confirm that the prescribed design values for overstrength and ductility factors provide reasonable estimations of the lower bound for these factors. The response modification factor obtained in this study ranged from 4.8 to 6 for different frames. The results also indicate that the response modification factor decreases with the increase of story height and span length. Moreover, bracing configurations may slightly affect the response modification factor for BRBFs. [ABSTRACT FROM AUTHOR]

In this paper, three dynamic linear models of the main span of suspension bridges are studied. The models describe vertical and torsional oscillations of the deck under the action of lateral wind. The problems correspond to the situations when both the midspan cable bands are loosened, both the midspan bands are fixed, and one midspan band is fixed and the other is loosened. Three corresponding eigenvalue and eigenvector problems are formulated and analysed. The continuous dependence of eigenvalues and eigenvectors on data are proved. The analysis of the three eigenvalue and eigenvector problems against flutter is carried out, which reveals possible reasons of the collapse of the original Tacoma suspension bridge. [ABSTRACT FROM AUTHOR]

Modal analysis of large span suspension bridge in different construction stages has to be carried out for the aerodynamic instability analysis. Based on the finite element (FE) model of a triple-tower twin-span (TTTS) suspension bridge in the completed stage, the FE models of the tower-cable-deck system corresponding to 0 %, 5 %, 10 %, 20 %, 30 %, and 40 % deck units erection stage are established respectively by a backward dismantling method. Then, the dynamic characteristics of each of the tower-cable-deck systems are analyzed to study the modal properties of TTTS suspension bridge in various deck erection stages. The results demonstrate that the natural frequencies of each erection stage are closely distributed in the low-order range. In the beginning of the deck units erection stage, the tower-cable-dominated modes are the primary modes and the deck-dominated modes come to next. Due to the strong interactions between deck unites and the cables, both the in-plane and out-of-plane vibrations of cables would excite the swing, lifting or torsional modes of the deck units. Both the in-plane and out-of-plane modes including in-phase and out-of-phase modes of the two main cables in the same span or symmetry and anti-symmetry modes of the neighboring-span cables as well as their corresponding combinations can be classified into groups. With more deck unites erected, the main girder is built up gradually, and thus the frequencies of deck-dominated mode would arise. The different frequency variations result in the modal crossover phenomena, which reflect the instability of the dynamic characteristics during the long deck erection period. At last, the aerodynamic stability of the suspension bridge is checked at each early erection stage, and a wind ropes application for the aerodynamic stability enhancement is investigated. The study of dynamic characteristics provides a reference for the wind-resistance analysis of the TTTS suspension bridge during the deck units erection stage. [ABSTRACT FROM AUTHOR]

Prestressed concrete wing-shaped members are frequently used in the construction of long-span roofs in precast concrete buildings. Roofs spanning more than 30 m (100 ft) are built by assembling a number of these thin-walled members. To optimize their design and take advantage of their potential load-carrying capacity, the transfer of large forces from the pretensioned strands to the concrete is critical. Information on the evolution of these forces and of the ensuing deformations is necessary, not only in the long run, but also immediately after concrete casting and during the first few weeks. The Department of Civil and Environmental Engineering of the University of Perugia in Italy and a major prefabrication firm of central Italy have completed an experimental program on pretensioned wing-shaped members to investigate the evolution of prestressing stresses and of camber during the different stages of concrete hardening. The result allowed the careful evaluation of the prestress losses that occur in the first three weeks during concrete placement and curing to emphasize the influence of the temperature history on the development of prestress losses and to calibrate suitable parameters for the prediction of camber growth. Numerical comparisons based on Eurocode 2 are also performed to check the reliability of the numerical procedure adopted by the authors and to ascertain whether using self-consolidating concrete (as in the manufacture of the specimens tested in this project) makes any sizeable difference with respect to the predictions based on Eurocode 2, which refers to ordinary concrete. [ABSTRACT FROM AUTHOR]

A full-scale experimental study was undertaken to observe and assess the behavior of continuous concrete beams with external prestressed bars. Three beams--a control beam and two comparable beams strengthened using external prestressed bars--were tested in two-point loading of the interior span of three continuous spans. The diameters of the external prestressed bars were 18 and 22 mm (0.71 and 0.87 in.), respectively. For the strengthened beams, V-shaped profiles were used with a deviator located at the middle bottom of the interior span, and the effective prestress was 45% of the yield strength of the external steel bars. Test results indicate that the external prestressing increased the load-carrying capacity by about 25% and the flexural stiffness by about l5%. An analytical model developed by the authors was applied that uses the beam collapse mechanism, plastic hinge length, and deformation of external bars depending on the beam deformation at the deviator point. Predictions of the nominal strength and the corresponding external bar stress compared closely to the test results. [ABSTRACT FROM AUTHOR]

A semitrailer hit several overhead steel truss members ofthe Interstate 5 (I-5) bridge over the Skagit River in Washington State, causing the north span to collapse. An emergency design-build contract required reopening of the permanent replacement span within 90 days of notice to proceed. Precast, prestressed concrete decked bulb tees of sand-lightweight concrete and full flexure-shear flange connections kept the weight of the superstructure within 5% of that of the original steel superstructure, allowing the undamaged substructure to be reused. Careful control of the girder geometry maintained vertical clearance over the Skagit River. Temporary posttensioning enabled the girders to resist construction-induced stresses. The replacement span was assembled alongside the existing bridge and skidded into place during a single 19-hour closure of I-5. [ABSTRACT FROM AUTHOR]

The Kaneda Viaduct was constructed as a part of Metropolitan Inter-City Expressway in Atsugi City, Kanagawa Prefecture, Japan. The viaduct comprises a couple of S-curved bridges with extremely large numbers of continuous spans. The Southbound Bridge is a 1019 m long 33-span continuous bridge. The Northbound Bridge is a 1042 m long 34-span continuous bridge. The Northbound Bridge has the largest number of continuous spans in Japan. The seismic design took into account the S-curved road alignment and dynamic behaviour of the bridge with seismic isolation bearings. Super-high-damping rubber bearings were adopted for all the piers to isolate seismic motions and to absorb seismic energy. Their shear deformations were adjusted after the completion of the structures using so-called post-sliding operations to minimise the size of the bearings. [ABSTRACT FROM AUTHOR]

Accomplishing maximum spans by creating new bridge systems has always been an interesting logical challenge. The concepts of modified cable-supported bridges have been proposed in the past that promise to surpass the more traditional cable-supported bridges in terms of maximum span length. The innovation in structural form, material technology and methods of analysis serve economy and better performance for longer span bridge structural system. The construction of long-span bridge is possible using high strength materials, innovative forms of structural system and novel method of analysis and design. The cable-stayed bridge and suspension bridge are structural systems used to achieve longer span bridges. The cable-stayed bridge has better structural stiffness and the suspension bridge has the ability to provide longer central span. To achieve a very long-span bridge with better structural behavior, a combination of the above two structural systems serves the purpose. The innovative form of hybrid cable-stayed suspension bridge with 1400 m main span and 700 m central suspension portion is considered for the analysis. The geometrical parameter like length of side span also plays an important role in the behavior of bridges. In this paper, bridge behavior is presented for variable length of side span. Nonlinear static analysis and modal analysis are carried out using SAP2000 software. The effects of side span length on the static performance of bridge are presented in the form of axial forces in deck and main cables. The dynamic behavior of the bridge is presented in the form of time period of bridge in lateral and vertical directions. [ABSTRACT FROM AUTHOR]

This article describes the development of an application for structural analysis of tubular trussed girders. Such structural components are widely used on roofs for which long span components are a necessity, e. g., supermarkets, distribution centers, etc. The application supplies hints to the project engineers as to the most economic solutions for a combination of span, loads, and other characteristics. Software development techniques are also explored. Such techniques can be divided into two large groups. In the first one, which is most widely known and used, software development complies with very rigid planning, where processes are more important than skills. This methodology is known as the Rigorous Development System (RDS). The second group, called Agile Development System (ADS), is conceived as an option for those not aligned with the RDS rules. This text describes the experience of an ADS based software development for truss design. In Section 2, the basis of ADS is presented. Section 3 describes the truss design application and civil engineering related concepts. Section 4 brings an example illustrating the application. Conclusions are in Section 5. [ABSTRACT FROM AUTHOR]

Cuprates possess a large pseudogap that spans much of their phase diagram. The origin of this pseudogap is as debated as the mechanism for high-temperature superconductivity. In one class of theories, the pseudogap arises from some instability not related to pairing, typically charge, spin or orbital current ordering. Evidence of this has come from a variety of measurements indicating symmetry breaking. On the other side are theories where the pseudogap is associated with pairing. This ranges from preformed pairs to resonating valence bond theories where spin singlets become charge coherent. Here, we study pairing in the cuprates by constructing the pair vertex using spectral functions derived from angle-resolved photoemission data. Assuming that the pseudogap is not due to pairing, we find that the superconducting instability is strongly suppressed, in stark contrast to what is actually observed. We trace this suppression to the destruction of the BCS logarithmic singularity from a combination of the pseudogap and lifetime broadening. Our findings strongly support those theories of the cuprates where the pseudogap is instead due to pairing. [ABSTRACT FROM AUTHOR]

Based on the capacity formulas in design codes, the corresponding failure functions are obtained for two typical cases, which are the light-weight steel arch structures under combined full-span dead load and half-span snow load and reinforced concrete (RC) frame columns under combined gravity load and horizontal earthquake action. Then, the complex characteristics of failure function were analyzed through multiple examples. It indicates that the snow load effect ratio is large for light-weight steel arch structure and the failure function is highly nonlinear for RC column with large eccentric compression. Furthermore, the reliability level was calibrated for these two typical cases. The results show that a more conservative design is needed for the light-weight steel arch structure under snow load combination due to its low reliability level; and the differences of failure probability of RC frame columns are large under different cases of seismic capacity design, and such differences are not able to be eliminated by a strategy that simply makes the strong column coefficient increase to a certain value, and an unsafe design of seismic capacity may be given by the current method, when the load effect ratio based on axial compressive force is negative. [ABSTRACT FROM AUTHOR]

The key issues of dynamic analysis for large span steel structure to anti-progressive collapse were studied in this research. The use of equivalent load transient unloading method for anti-progressive collapse of the structure dynamic analysis was introduced. Based on the U. S. codes, the method to determine the values of equivalent loads was proposed. The accuracy of applying equivalent load transient unloading to anti-progressive collapse analysis depends on the load time-history curve. The formula that calculates the minimum action time of equivalent load before the critical component failure was derived based on the dynamics knowledge. The predicted results agreed well with the results obtained from actual engineering example. Through finite element numerical calculation, the maximum unloading time of equivalent load was proposed to be 1/10 of the first order vertical vibration period of component failure model. The paper introduces the load carrying capacity and deformation acceptance criteria of anti-progressive collapse dynamic analysis based on practical engineering example and determines if the load carrying capacity and deformation exceeds limits after the key structural component failure. It is indicated that the equivalent load transient unloading method is applicable to simulate the force and deformation of large span steel structure after the key components failure, and is a complement to the static method for anti-progressive collapse analysis of large-span steel structure. [ABSTRACT FROM AUTHOR]

The viaduct over River Ulla is located in the Atlantic High Speed Railway Line between A Coruña and Pontevedra, in the northwest of Spain. Its location, close to the firth of Ulla, in a landscape of outstanding natural beauty and strong environmental constraints, was the object of a tender among the most renowned Spanish structural specialists. The solution chosen was a 1620 m long viaduct, with three main spans of 225 + 240 + 225 m and several approaching spans of 120 m length each, which meant a main span being about 20% longer than the Nantenbach bridge in Germany, the current world record in High Speed Railway composite steel and concrete truss girder beam bridges. The main spans have been designed with a double composite steel and concrete truss deck, with double composite action in hogging zones, and a total depth ranging from 9,15 m at the midspan section to 17,90 m at the section over the piers. The adjacent spans that give access to the depth-varying main ones have been designed with constant depth. This article describes the structural conception of the bridge and the three different constructive processes that had to be used due to the access and the environmental restrictions. [ABSTRACT FROM AUTHOR]

This paper addresses the optimization of an earthquake-resisting system (ERS) and pushover analysis in design of the approach spans of the new South Park Bridge in Seattle, Washington. An appropriate ERS is desired in bridge design, and it involves the application of both pinned column hinges and plastic hinges in seismic analysis to properly allocate the internal forces among bridge substructure components. The approach to derive the ERS is discussed. Conventionally, the column hinge is often modeled as a pinned hinge in pushover analysis, corresponding to the modeling in seismic elastic and plastic hinging analyses. In this design, the column hinge was also modeled as a plastic hinge with limited moment capacity. This novel modeling not only improves the performance-based design but also leads to new insights into pushover analysis. Finally, the design of intermediate piers is presented. [ABSTRACT FROM AUTHOR]

This study is concerned with the analysis of the dynamic response of an infinite periodic viaduct to non-uniform seismic waves. The periodic viaduct is assumed to be composed of an infinite number of spans, and each span is supposed to consist of a pier, two longitudinal beams (left and right beams) and three linking springs. The sequence Fourier transform method is used to decompose a non-uniform seismic wave into a set of spatially harmonic waves. By using the periodic condition of the viaduct and the transfer matrix method, the wavenumber domain response of the viaduct to each component of the non-uniform seismic wave is obtained. The space-domain response of the periodic viaduct is retrieved by applying the inverse sequence Fourier transform to the wavenumber domain solutions. Numerical results for energy bands of the periodic viaduct and those for the dynamic responses of the periodic viaduct to spatially harmonic waves as well as to non-uniform seismic waves are presented. It is found that there exist three kinds of characteristic waves for both the in-plane and out-of-plane wave vibrations of the periodic viaduct. Also, proposed numerical results show that when the periodic viaduct is subjected to traveling waves, serious resonance may occur. Resonance may occur at the bounding frequencies of the passbands for the characteristic waves. Also, due to the coincidence effect between traveling seismic waves and the characteristic waves, resonance may occur at frequencies in the passbands of the characteristic waves. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results from four three-span unbonded prestressed continuous concrete slabs that were 12.6m×1.5m×0.12m in size. The tests were designed to show the effect of the negative reinforcement length in the zone of negative moment and the influence of the sequence of the middle span and the edge span exposure to fire. Based on the standard temperature–time curve (ISO 834) used in the test, the processes involving water and cracks in the slabs were described. After the analysis, the deformation, the mechanism of the failure mode, the regularity of the prestressing and the force redistribution of the support were investigated. The study demonstrated that the failure mode of a slab under fire is mainly due to tensile fracture of the concrete and tendons. The sequence of spans under fire and the length of negative reinforcement have important effect on the deformation and the failure mode. Different lengths of negative reinforcement lead to destructive hinge presence at the different position. The presence of cracks ① and ② is attributed to the thermal bowing action and stiffness redistribution. The crack ④ extending to the top surface along the tendons is the effect of tensile splitting due to the lower temperature in the tendon. The reinforcment perpendicular to the trajectory of the tendon should be laid out and the minimum steel ratio 0.2% is recommended. The support force redistribution is attributed to the structural system change, which is caused by the fracture of the concrete and tendon under fire. [Copyright &y& Elsevier]

Abstract: Suspension bridges are widely used as engineering structures to across long spans and give rise to the usage of domains under the bridge. In the finite element analyses of suspension bridges, it is assumed that the structure is built and loaded in a second. However, this type of analysis does not always give the reliable and healthy solutions. Because, construction period of this type of the structures continue along time and loads may be changed during this period. Therefore, construction stages and time dependent material properties should be considered in the analysis to obtain the reliable and healthy results. This paper presents the construction stage analysis of suspension bridges using time dependent material properties. For this purpose, Humber Suspension Bridge built near Kingston upon Hull, England is chosen as an example. Finite element model of the bridge is constituted using SAP2000 program considering project drawings. Geometric nonlinearities are taken into consideration in the analysis using P-Delta large displacement criterion. The time dependent material strength of steel and concrete and geometric variations are included in the analysis. Time dependent material properties are considered as compressive strength, aging, shrinkage and creep for concrete, and relaxation for steel. The structural response of the bridge at different construction stages has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. As analyses result, variation of the displacement and internal forces such as bending moment, axial forces and shear forces for bridge deck and towers are given with detail. It can be seen from the study that there are some differences between both analyses (with and without construction stages) and the results obtained from the construction stages are bigger. So, it is thought that construction stage analysis using time dependent material properties and geometric nonlinearity should be considered in order to obtain more realistic structural response of suspension bridges. [Copyright &y& Elsevier]

Abstract: We present several algorithms for computing a feasible toolpath of certain characteristics for sculpting a given surface using a 5-axis numerically controlled (NC) machine. A toolpath specifies the orientations of a cutting tool at each point of a path taken by the tool. When a single toolpath does not exist, we find the minimum number of toolpaths needed by the cutting tool. Previous algorithms are all heuristics with no quality guarantee of a solution and with no analysis of the running time. We obtain optimal solutions and provide time analysis for all our algorithms. We model the problem using a directed, layered graph (representing the sculpting constraints) such that a feasible toolpath corresponds to a certain path in . We give efficient methods for several path problems in such graphs (e.g., finding a path in an unweighted or vertex-weighted version of , computing the minimum number of paths whose union spans all the layers of an edge-weighted , etc). [Copyright &y& Elsevier]

Webs moving through process machinery encounter several rollers, each of which might have unintentional taper in radius. The taper might have resulted from machining or from wear. The objectives of this study were to show, for a particular web, the level of cross machine direction registration error that might result for a given roller taper, the level of taper that will induce web trough instability in free spans, and the level of taper that will induce web wrinkle instabilities on rollers. [ABSTRACT FROM AUTHOR]

This scientific work presents the way in which the small, and very small span wings can be obtained starting from the great span wings and using the two scales of the similarity theory. Basing on two scales model it can transcribe from model at nature the coefficients cx, cy and lengthening λ of Gottingen - 612 profile. [ABSTRACT FROM AUTHOR]

The article focuses destruction caused to Transnet Freight Rail (TFR), a rail transport company in South Africa, with severe weather conditions, and derailment of trains. It mentions of a project that aims at fabrication, painting and quality control of TFR's yard in Sentrarand, Gauteng in South Africa. It discusses some of the requirement of the project which include ease of erection of temporary deck spans and faster erection time for the bridge decks.

This research examines the long-term performance of high-density polyethylene liners frequently used in rehabilitating pipeline networks. Buckling of two groups of samples--each consisting of 20 steel pipes lined with HDPE liners--was examined in the laboratory. Group A was subjected to a uniform external pressure equal to about one-half of the buckling pressure, determined experimentally in a similar short-term test. Group B was subjected to one-third to one-fourth of this short-term pressure. Most liners in Group A failed (buckled) prematurely before the required ASTM period of 10,000-h. However, all 20 samples in Group B sustained the applied pressure for over 10,000 h. It was concluded that a design safety factor of 3 to 4 should be applied to short-term pressure to establish the long-term resistance of a flexible liner. Changes in the liner pipe volume with time, under the uniform pressure, were also monitored to estimate long-term creep in the HDPE material. [ABSTRACT FROM AUTHOR]

Abstract: The performance of 60 user ring network topology is investigated in the presence of semiconductor optical amplifiers. This ring network topology is evaluated by considering the signal quality factor, eye closure and received power for different signal input power. Further, this ring network topology is investigated with multiple numbers of spans. It is reported that, the maximum number of nodes supported by this ring network is >300 with acceptable quality and received power. [Copyright &y& Elsevier]

Synchronous belt drives generate resonance on the belt spans between the driving and driven pulleys when the transverse natural frequency of the belt, matches the meshing frequency of the belt tooth and the pulley tooth. The resonance of the belt spans affects the accuracy of rotation transmission. In the present study, the mechanisms generating the transmission error in synchronous belt drives under installation tension and a pulley speed ratio of 1:1 are investigated theoretically and experimentally for the case in which the belt spans generate first mode vibration due to resonance. In addition, the change in the shaft load caused by resonance is examined. The calculated and experimental transmission errors show good agreement, and so the validity of our analysis is confirmed. Transmission error is generated by the difference in displacement between the upper and lower belt spans due to the convex or concave shape, the difference in the amount of belt climbing at the beginning and end of meshing, and the generation of torque due to the moment of inertia on the driven side. The transmission error has a period of 1/2 of one pitch of the pulley, and the generated change in the shaft load, which is the sum of the displacement due to the convex or concave shape of the upper and lower spans and the sum of the belt climbing at the beginning and end of meshing, has a period of one pitch of the pulley. [ABSTRACT FROM AUTHOR]