Excessive Strand End Slip in Prestressed Piles

This paper presents the results of a research project that investigated excessive strand end slip observed recently in some prestressed piles. From measurements taken in the field, it is apparent that the problem o excessive initial strand slip is independent of pile shape and size. Strand end slip is evident in piles of different manufacturers in different states in the Southeast. Excessive strand end slip was found in both the top and bottom of the cross section of the piles, although the top portion of the cross section generally exhibited much higher initial slip. Several preventive measures can be adopted to reduce the excessive strand end slip. These preventive measures include: a) proper concrete mixture proportioning to reduce top bar effect; b) use of higher-strength concrete with the lowest possible slump and setting time; c) assessment of the condition of the strands prior to installation to insure excellent bond characteristics; d) gradual release of prestress, with an optimal release sequence; and e) use of adequate vibration to ensure consolidation. The strand end slip measured at five prestressing plants in the Southeast is considerably higher than the allowable end slip and is expected to affect the pile performance. If the strand slip theory is adopted, the strand development length increases substantially due to the excessive strand end slip. A top bar effect factor similar to the one used in reinforced concrete design is recommended. To maintain the excellent quality of precast and prestressed concrete products, manufacturers should adopt a dynamic quality control process that follows the rapid changes in the industry. More tests are necessary to ensure excellent quality, such as the Moustafa or an equivalent test, to assess the bond capabilities of the strands, end slip measurements, and direct measurement of the transfer length. Installation of piles should proceed in a manner to alleviate the top bar effects by placing piles alternately in their best and worst directions

Energy Star: A Competitive Advantage?

Voluntary government programs such as ENERGY STAR have been created to promote energy efficiency within different organizations and businesses, and this study is dedicated to discovering whether or not businesses that become certified building partners with ENERGY STAR obtain a competitive advantage. Through two different methods of analysis, an observational analysis and a test of means, data on profitability ratios from twenty-five ENERGY STAR partners are examined to determine if partnering with ENERGY STAR results in a competitive advantage

Secretory traffic in the eukaryotic parasite Toxoplasma gondii: less is more

Name a single-celled eukaryote that boasts a small genome size, is easily cultivated in haploid form, for which a wide variety of molecular genetic tools are available, and that exhibits a simple, polarized secretory apparatus with a well-defined endoplasmic reticulum and Golgi that can serve as a model for understanding secretion. Got it? Now name a cell with all these attributes that contains at least a dozen distinct and morphologically well-defined intracellular organelles, including three distinct types of secretory vesicles and two endosymbiotic organelles. Not so sure anymore

The Effects of Music Genre on Cardiovascular Performance and Enjoyment in Young Adults

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Organizational Safety Culture in Pilot Training Schools: Case of North Texas in the USA and South Korea

The sudden increased need for qualified pilots can cause potential risks for aviation training schools in South Korea because new pilot training programs need to be created, or existing organizations need to be expanded quickly. This study investigates safety culture at pilot training schools, builds a conceptual framework, and identifies the relationship between the sub-safety culture category and safety culture level in commercial pilot training schools. The authors survey the safety culture and management for the organizational aspect of these pilot training schools to clarify essential concepts and generate a conceptual safety management model. The authors examine the differences in safety culture between pilot training schools in the USA and South Korea and the effects these differences have on the organizations. Results show that the safety culture between pilot training schools in north Texas in the USA and South Korea is different. A pilot training school has to have a well-defined safety culture and management procedures in place and an awareness of the diverse cultural backgrounds of its student pilots to avoid potential cultural clashes and needless accidents/incidents

Strategies for Improving Remedial Mathematics Performance Among Community College Students

Increasing numbers of underprepared students throughout the United States must enroll in college remedial math courses, which delays students’ graduation and increases withdrawal rates. Two-thirds of first-year college students at a rural community college in the southeastern United States were required to enroll in remedial mathematics. Only 65% completed the course. Guided by Bandura’s theory of self-efficacy, which maintains that belief in one’s ability improves success, the purpose of this qualitative study was to examine the perceptions of instructors, administrators, and students to explain the gap in performance in remedial mathematics and to use the results of this study to identify strategies to improve student performance. The study incorporated semi structured interviews with purposeful sampling of 15 remedial math students, 4 remedial math instructors, and the head of the mathematics department. Perceptions of the students and instructors were coded to identify and analyze emerging themes. Findings revealed the following themes: effectiveness of the remedial class, teaching and learning preferences, obstacles to learning, and suggestions for improvement. These findings led to the development of a 3-day professional development project to develop instructional strategies to improve students’ skills in task managing goals, tasks, and challenges; and to collaborate with local school districts to develop strategies to improve student performance in college mathematics. The study provides teachers and administrators with strategies that may lead to improved student preparation and success in remedial math, and opportunities to collaborate with local high schools to reduce the number of students requiring remedial mathematics

Seabed propagation of ULF/ELF electromagnetic fields from harmonic dipole sources located on the seafloor

The amplitudes of the quasi-static electromagnetic fields generated at points on the seafloor by harmonic dipole sources (vertically directed magnetic dipoles, horizontally directed magnetic dipoles, vertically directed electric dipoles, and horizontally directed electric dipoles) also located on the seafloor are computed using a numerical integration technique. The primary purpose of these computations is to obtain field amplitudes that can be used in undersea communication studies. An important secondary purpose is to examine the enhancements of the fields produced at moderate to large distances by the presence of the relatively less conducting seafloor, as compared with the fields produced at the same distances in a sea of infinite extent, for frequencies in the ULF/ELF bands (frequencies less than 3 kHz). These latter enhancements can be surprisingly large, with increases of 4 orders of magnitude or more being typical at distances of 20 seawater skin depths