Minimum weight design of symmetrically stiffened orthotropic cylinders under axial compression

Minimum weight design of symmetrically stiffened orthotropic cylinders under axial compressio

Computer science in Dutch secondary education: independent or integrated?

Nowadays, in Dutch secondary education, computer science is integrated within school subjects. About ten years ago computer science was considered an independent subject, but in the mid-1980s this idea changed. In our study we investigated whether the objectives of teaching computer science as an independent subject are met when computer science is integrated within school subjects. The main problem was that there was no formal curriculum of computer science as an independent subject. Therefore we interviewed 13 experts in the field of computer science and then compared this formal curriculum with the operational (integrated) curriculum, which is still in the development stage. It appears that most of the components of the formal curriculum are being covered by the operational curriculum, and we therefore concluded that these curricula are equivalent, although there may be differences in the level of teaching. In our opinion the best approach to computer science is to combine the independent and the integrated approaches

A theoretical determination of the eta-eta' mixing

The systematic large N_c limit within chiral perturbation provides an optimal eta-eta' mixing angle of about -27 degrees at leading order in p^2. In this frame, agreement with the data can be reached with higher order corrections of about 20%.Comment: 12 pages, 2 figures; reference to the two-mixing-angle scheme added, minor corrections; to appear in JHE

Coordinated Tax-Tariff Reforms, Informality, and Welfare Distribution

The paper studies the revenue, efficiency, and distributional implications of a simple strategy of offsetting tariff reductions with increases in destination-based consumption taxes so as to leave consumer prices unchanged. We employ a dynamic micro-founded macroeconomic model of a small open developing economy, which features an informal sector that cannot be taxed, a formal agricultural sector, and an import-substitution sector. The reform strategy increases government revenue, imports, exports, and the informal sector. In contrast to Emran and Stiglitz (2005), who ignore the dynamic effects of taxes and tariffs on factor markets, we find an efficiency gain, which is unevenly distributed. Existing generations benefit more than future generations, who - depending on pre-existing tax and tariff rates and the informal sector size - even may become worse off.tariff reform, consumption tax reform, informal sector, home production, transitional dynamics, overlapping generations, second-best outcome

Structural design synthesis approach to filamentary composites

Structural design methods for analysis of multilayer or laminated filamentary composite

Thermal Analysis of As-received and Clinically Retrieved Copper-Nickel-Titanium Orthodontic Archwires

Objective: To compare as-received copper-nickel-titanium (CuNiTi) archwires to those used in patients by means of differential scanning calorimetry (DSC). Also, the thermal or phase properties of 27°C, 35°C, and 40°C CuNiTi archwires were studied to ascertain if their properties match those indicated by the manufacturer. Materials and Methods: Six wires of 27°C, 35°C, and 40°C CuNiTi were tested as-received, and six each of the 27°C and 35°C wires were examined after use in patients for an average of approximately 9 and 7 weeks, respectively. Segments of archwire were investigated by DSC over the temperature range from −100°C to 150°C at 10°C per minute. Results: There were no significant differences between as-received and clinically used 27°C and 35°C wires for all parameters (heating onset, endset, and enthalpy and cooling onset, endset, and enthalpy), except the 27°C wires exhibited a significant decrease in the heating enthalpy associated with the martensite-to-austenite transition after clinical use. The heating endsets (austenite finish temperatures) of the 27°C and 35°C wires were within 2°C of those claimed by the manufacturer, but the 40°C wires were found to be nearer to 36°C than 40°C. Conclusions: Clinical use of CuNiTi wires resulted in few differences when compared with as-received wires analyzed by DSC. Two temperature varieties of CuNiTi are reasonably within the parameters of those identified by the manufacturer

An HI Imaging Survey of Asymptotic Giant Branch Stars

We present an imaging study of a sample of eight asymptotic giant branch (AGB) stars in the HI 21-cm line. Using observations from the Very Large Array, we have unambiguously detected HI emission associated with the extended circumstellar envelopes of six of the targets. The detected HI masses range from M_HI ~ 0.015-0.055 M_sun. The HI morphologies and kinematics are diverse, but in all cases appear to be significantly influenced by the interaction between the circumstellar envelope and the surrounding medium. Four stars (RX Lep, Y UMa, Y CVn, and V1942 Sgr) are surrounded by detached HI shells ranging from 0.36 to 0.76 pc across. We interpret these shells as resulting from material entrained in a stellar outflow being abruptly slowed at a termination shock where it meets the local medium. RX Lep and TX Psc, two stars with moderately high space velocities (V_space>56 km/s), exhibit extended gaseous wakes (~0.3 and 0.6 pc in the plane of the sky), trailing their motion through space. The other detected star, R Peg, displays a peculiar "horseshoe-shaped" HI morphology with emission extended on scales up to ~1.7 pc; in this case, the circumstellar debris may have been distorted by transverse flows in the local interstellar medium. We briefly discuss our new results in the context of the entire sample of evolved stars that has been imaged in HI to date.Comment: Accepted to AJ. A version with full resolution figures is available at http://www.haystack.mit.edu/hay/staff/lmatthew/matthews_HI_survey.pd