Span Configuration Research Articles

112 Gb/s PM-QPSK transmission up to 6000 km with 200 km amplifier spacing and a hybrid fiber span configuration

We demonstrate transmission of 112 Gb/s PM-QPSK signals over a system with 200 km span lengths. Amplification is provided by hybrid backward-pumped Raman/EDFA amplifiers and reach lengths up to 6000 km for an 8 channel system and 5400 km for a 32 channel system are shown. As a means of maximizing OSNR, a simple hybrid fiber span configuration is used that combines two ultra-low loss fibers, one having very large effective area.

A Novel cathode material based on polyaniline used for lithium/sulfur secondary battery

Polyaniline polysulfide (SPAn) was prepared for high energy secondary lithium batteries as cathode material. Polyaniline was synthesized via a classical chemical oxidation way, and then HCl was used to substitute the H atoms on the 6 member rings, so that polyaniline chloride (CPAn) was gained. The SPAn was prepared by way of substitute the Cl atoms on the aromatic rings of CPAn by S atoms in assistant of Na 2S and element sulfur. Element analysis tests proved that there are more than 7 S atoms on each aniline structural group. FT-IR, Raman and XPS (X-ray photoelectron spectroscopy) analysis were used to confirm the SPAn's configuration. Button type battery was assembled, and charge–discharge test shows an initial discharge capacity of more than 980 mAh g −1, which is a grafting value.

Relationship Between Grade Span Configuration and Academic Achievement

In an effort to address the NCLB-mandated testing process, one of the issues to be considered is how best to configure student populations to maximize all aspects of the educational setting while simultaneously maximizing student achievement; one aspect is grade span configuration. We examined the relationship between the grade span configuration of all schools in Arkansas attended by sixth-grade students and the academic achievement of the combined population of students as measured by the Arkansas Benchmark Examination. We found no relationship between grade span configuration and academic achievement as measured by the Arkansas Benchmark Examination for sixth-grade students. However, the nonsignificant findings do not negate the importance of the study. The results imply that there are other factors that are affecting scores in the middles grades. The results of the study also revealed that over the time span examined, mathematics Benchmark achievement rose but the results for literacy were stagnant. These results suggest that newly implemented practices or other factors may have improved mathematics achievement, but not achievement in literacy. Grade span configuration alone does not account for sixth-grade students’ academic achievement as measured by the Arkansas Benchmark Examination. Decisions about campus configurations include other factors such as projected enrollments, transportation costs, size of schools, school goals, fiscal constraints, political tensions, geographic realities, and financial accountability. As student populations shift, educational leaders can look for grade span configurations that best fit their community culture and current facilities, focusing financial resources on other means of improving academic achievement.

Can Reorganizing K-8 Education Improve Academic Performance? The Impact of Grade Span on Student Achievement

Although rearranging school organizational features is a perennially popular method of school reform, no consensus exists regarding the best organizational structure for educating students. Instead, there is wide variation in school organization across the United States and even within school districts. This paper examines how student performance in eighth grade is shaped by the grade span configuration. Exploiting the variation in New York City, we estimate the impact of several distinct grade span configurations, controlling for school and student characteristics including third grade performance. We find that students in schools with longer grade spans (K-8 schools particularly) outperform students in schools with shorter grade spans. Thus, creating more K-8 schools and minimizing structural articulations in the K-8 years may improve student performance.

Rotation Requirements for Moment Redistribution in Steel Bridge I-Girders

One of the key assumptions in inelastic design is that members have adequate ductility to allow moments to redistribute. However, while AASHTO specifications contain moment redistribution provisions for steel I-girders, the amount of ductility that is adequate for this specific design situation has not been studied in detail. As a result, the scope of these specifications is limited to beam types known to have significant ductility, which restricts the use of these procedures and causes negative economic consequences. The goal of this work is to determine ductility requirements specifically applicable to AASHTO moment redistribution procedures that are valid for all I-girders. This is accomplished through an analytical procedure, detailed herein. The results of this work are empirical equations predicting the amount of rotation required as a function of the intended level of moment redistribution as well as the material properties and span configuration of the girder. With these requirements known, there is a basis for reducing the overly conservative nature of the existing AASHTO moment redistribution specifications.

Distributed hybrid‐fiber Raman amplifiers with a section of nonlinear microstructured optical fiber

AbstractA distributed hybrid‐fiber Raman amplifier with a 25‐km single‐mode fiber and a section of nonlinear microstructured optical fiber (NMOF) is proposed and experimentally investigated in detail. Three pump schemes and span configurations, as well as two NMOF types with different parameters and length were considered. The influence of the NMOF presence on the performance of the amplifier was analyzed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2267–2271, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21901

Optimization of a Raman/EDFA hybrid amplifier based on dual-order stimulated Raman scattering using a single-pump

Based on dual-order stimulated Raman scattering (SRS) of a single 1395 nm Raman fiber laser in 75 km single mode fiber and its corresponding dispersion compensation module, a hybrid Raman/Erbium doped fiber amplifier (EDFA) for long wavelength band (L-band) amplification is realized by inserting a segment of EDF within the span. By comparing the performance of gain and noise in four hybrid amplifiers with different span configurations, we find that the distribution of the secondary L-band amplification obtained from the EDF along the link has a great influence on the performance of the hybrid amplifier. Both gain and noise performance of hybrid amplifier can be improved significantly by optimizing the location of the EDF. Moreover, we can extend the flat gain bandwidth from L-band to central wavelength band (C-band) plus L-band by recycling the residual first-order SRS to pump a segment of EDF with proper length.

The Relationship between Middle Level Grade Span Configuration, Professional Development, and Student Achievement

One goal of professional development is to improve student achievement through improved teacher practice. The middle school philosophy, which supports the rationale that student learning is inextricably interwoven into the fabric of an active learning environment, contains many promising practices that “mirror” what is often considered to be high quality professional development. However, researchers’ efforts to identify and measure this relationship have proven difficult at best. In this study, levels of professional development as components of various school reform initiatives are identified, and their relationships to student learning are measured across various grade configurations, specifically, K-8, 6-8, and 7-12.This study found a significant percent of 6-8 middle level schools to be more highly engaged in professional development activities than their K-8 and 7-12 counterparts. However, when taken together, professional development and grade configuration were not found to have a direct relationship to student achievement. Some variance in state assessment scores, albeit not statistically significant, was found to be marginally related to grade configuration, indicating the need for further study. This finding, coupled with other analyses of the data, suggest that relationships among professional development, grade configuration, and student achievement may exist but cannot be fully explained until researchers are able to identify and account for other variables that may be related to the unexplained variance. Until empirical evidence is produced, policymakers are encouraged to continue discussions regarding the most appropriate means of addressing young adolescents’ academic needs regardless of other factors.

Strength and Performance of Fiber-Reinforced Concrete Composite Slabs

This research aimed to evaluate and compare the influence of 4 types of secondary reinforcement for temperature and shrinkage on the strength and behavior of composite slabs with a variety of loading conditions and span configurations. The 4 types of secondary reinforcement were welded wire fabric (WWF), and 3 types of fibers. The tests included 3-span composite slabs, with the steel deck continuous over the 3 spans but with no negative moment reinforcement used, subjected to a uniformly distributed load, and simple span slabs subjected to point and line loads. In conjunction with the slab tests, the flexural toughness and first-crack strength of the fiber-reinforced concrete mixes were determined using the ASTM C1018 standard test. The performance of the specimens reinforced with fibers is compared with that of the specimens reinforced with WWF. Results indicate that the strength, failure mode, crack initiation, and propagation, and load-deflection behavior are not much influenced by type of secondary reinforcement in the composite slab.

Strengthening of Short Shear Span Reinforced Concrete T Joists with Fiber-Reinforced Plasic Composites

In this work, the results of an experimental study conducted in a 1964-vintage building are presented. Twelve reinforced concrete (RC) T-joists strengthened with fiber-reinforced plastic (FRP) composites were loaded until failure in a short shear span configuration. Different strengthening schemes, including different FRP materials and a new FRP anchorage system, were adopted in order to compare the performance of the different installations. Carbon FRP and aramid FRP sheets in an epoxy matrix were bonded to the RC joists using the wet layup technique. All of the joists were loaded close to one end support and showed similar cracking patterns at failure. The design calculations were based on experimental results. All of the unanchored FRP strengthened beams showed failure due to peeling, while the anchored FRP strengthened members showed failure due to anchor pullout at higher load values. It was found that an increase in the amount of FRP did not result in a proportional increase in the shear capacity, a...

Comparison of span configurations of Raman-amplified dispersion-managed fibers

We evaluate the performance of dispersion-managed fiber transmission systems employing distributed Raman amplification with 50- and 100-km span length for three different span configurations. The evaluation considers the optical signal-to-noise ratio and the nonlinear phase shift as a measure for the impact of nonlinear effects. The simulation results indicate that a 100-km-long span with the dispersion compensating fiber placed in the span center achieves the best tradeoff between optical signal-to-noise degradation and nonlinear effects.

Impact of fibre span configuration on Raman gain shape in dispersion-flattened transmission systems

The precise inherent Raman gain shape of several types of dispersion-flattened fibre span was evaluated under different operating conditions in backward pumping. It was found that the overall gain shape greatly depends on the fibre span configuration rather than the operating condition in any fibre span configurations.

Performance of Bridge Timber Ties under Static and Fatigue Loading

This study is in response to the dramatic increase in railway car axle loads that has occurred over the last 50 years. The paper presents the results of an experimental program undertaken to evaluate the structural performance of treated timber bridge ties under different railway car load levels. A portion of a prototype bridge deck, consisting of eight prototype timber bridge ties, was tested under various loading and support configurations to determine the axle load distribution. The serviceability of the treated bridge timber ties was evaluated based on the fatigue strength of eight prototype timber ties under different load levels. A theoretical model, based on energy principles, was developed to predict the axle load distribution to the ties for different span configurations. The model compares well with the measured test results and it complies with the American Railway Engineering Association requirements.

EXPERIMENTS ON CONTINUOUS COMPOSITE BEAMS.

Tests are presented of six continuous composite beams of 9M length and having compact steel section. Two beams had limited rotation capacity and were tested under severe sagging rotation conditions; the other four were loaded symmetrically and included cases where local buckling contributed to failure. It is proposed that beams having a ductility parameter greater than 1.4 can be designed using simple plastic theory, without regard to loading and span configuration. An assessment is made of the vertical shear resistance of the slab at interior supports. It is concluded that simple plastic design incorporating full plastic moment values may be confidently used in continuous composite beams having compact steel section, adequate slab and shear connection, even under conditions of severe rotation requirement. (Author/TRRL)

Multiple and Continuous Span Elevated Guideway-Vehicle Dynamic Performance

Analyses are developed to determine the dynamic performance of vehicles interacting with single, multiple, and continuous span elevated structures. Operating conditions in which multispan resonant conditions occur are identified, and the resulting resonant amplitudes computed. Guideway design examples considering tracked, levitated vehicles are described to illustrate the influence of span configuration and vehicle speed and suspension properties upon guideway span design for vehicle-guideway systems required to provide specified passenger comfort levels. For the 150 and 300 mph (242 and 483 km/h) vehicle systems considered, continuous and multispan guideway configurations were found to have reduced span material requirements in comparison to single span systems which provide the same level of passenger comfort.