Write-limited sorts and joins for persistent memory

To mitigate the impact of the widening gap between the memory needs of CPUs and what standard memory technology can deliver, system architects have introduced a new class of memory technology termed persistent memory. Persistent memory is byteaddressable, but exhibits asymmetric I/O: writes are typically one order of magnitude more expensive than reads. Byte addressability combined with I/O asymmetry render the performance profile of persistent memory unique. Thus, it becomes imperative to find new ways to seamlessly incorporate it into database systems. We do so in the context of query processing. We focus on the fundamental operations of sort and join processing. We introduce the notion of write-limited algorithms that effectively minimize the I/O cost. We give a high-level API that enables the system to dynamically optimize the workflow of the algorithms; or, alternatively, allows the developer to tune the write profile of the algorithms. We present four different techniques to incorporate persistent memory into the database processing stack in light of this API. We have implemented and extensively evaluated all our proposals. Our results show that the algorithms deliver on their promise of I/O-minimality and tunable performance. We showcase the merits and deficiencies of each implementation technique, thus taking a solid first step towards incorporating persistent memory into query processing. 1

Cyclic Response of Bolted and Hybrid Pultruded FRP Beam-Column Joints between I-Shaped Sections

This paper presents cyclic behaviour of bolted and hybrid–combined bolted and bonded fibre re-inforced polymer (FRP) beam-to-column joints between I-shaped members using steel and FRP cleats. Five full-scale cyclic tests are carried out to study moment-rotation behaviour, cyclic re-sponse, and failure patterns. The test parameters include position of cleat (flange or combined web and flange), fastening method (bolting or hybrid–combining bolting and bonding) and cleat ma-terial (steel or FRP). First two tests had bolted and hybrid joints with steel flange and web double angles. Next two tests had the same joint detailing but with no web cleats. Last test used bolted joint only with FRP web and flange cleats. Three failure modes were observed: shear-out failure of the beam’s bolted zone, adhesive debonding with shear-out failure and delamination cracking. Cyclic performance of the joints was assessed by hysteresis moment-rotation curves and accumulated dissipated energy. Hybrid joints showed the best overall cyclic performance with accumulated dissipated energy about 75% higher than the bolted joints. Bolted joints with FRP cleats exhibited the worst cyclic performance. Flange cleated joints showed similar performance to web and flange cleated joints

Bolted and hybrid beam-column joints between I-shaped FRP profiles Chapter Bolted and hybrid beam-column joints between I-shaped FRP profiles

Presented are test results from five full-scale pultruded FRP beam-to-column joints subjected to cyclic load-ing. The parameters include cleat position, connection method and cleat material. The joints’ behaviour is assessed through hysteresis moment rotation loops, accumulated dissipated energy and failure patterns. The hybrid joints with steel cleats showed the best overall cyclic performance with accumulated dissipated ener-gy 75% higher than the bolted joint. The bolted joint with FRP cleats exhibited the lowest dissipated energy, four times lower than the joint with steel cleats. The cyclic performance of web and flange cleated joint was same as flange cleated joint. Three failure patterns were noticed, namely shear-out failure of the beam’s bolted region (bolted joint with steel cleats), adhesive debonding followed by shear-out failure (hybrid joint with steel cleats) and delamination cracking (bolted joint with FRP cleats)

Local magnetic anisotropy in BaFe2_2As2_2: a polarized inelastic neutron scattering study

The anisotropy of the magnetic excitations in BaFe$_2$As$_2$ was studied by polarized inelastic neutron scattering which allows one to separate the components of the magnetic response. Despite the in-plane orientation of the static ordered moment we find the in-plane polarized magnons to exhibit a larger gap than the out-of-plane polarized ones indicating very strong single-ion anisotropy within the layers. It costs more energy to rotate a spin within the orthorhombic {\it a-b} plane than rotating it perpendicular to the FeAs layers.Comment: 4 pages, 4 figure

Dynamics of Tunneling Centers in Metallic Systems

Dynamics of tunneling centers (TC) in metallic systems is studied, using the technique of bosonization. The interaction of the TC with the conduction electrons of the metal involves two processes, namely, the screening of the TC by electrons, and the so-called electron assisted tunneling. The presence of the latter process leads to a different form of the renormalized tunneling frequency of the TC, and the tunneling motion is damped with a temperature dependent relaxation rate. As the temperature is lowered, the relaxation rate per temperature shows a steep rise as opposed to that in the absence of electron assisted process. It is expected that this behavior should be observed at very low temperatures in a careful experiment. The present work thus tries to go beyond the existing work on the {\it dynamics} of a two-level system in metals, by treating the electron assisted process.Comment: REVTeX twocolumn format, 5 pages, two PostScript figures available on request. Preprint # : imsc 94/3

Impact of graphene oxide and highly reduced graphene oxide on cement based composites

This study examines and compares the performance of two specific forms of graphene nanomaterials in the cement based composite, namely graphene oxide (GO) and reduced graphene oxide (rGO). A typical forms of GO with the average C:O ratio of 54:46 and a rGO with the average C:O ratio of 82:18 were used in the cement based paste composites. rGO was treated with superplasticizer to improve its dispersibility in water. Both GO and rGO were used as 0.02, 0.04, 0.06 wt% of cement. The effect of GO and rGO on workability, early age hydration, microstructure, mechanical and transport properties was determined. Different characteristics of GO and rGO such as molecular structure, functional groups, d spacing, size and physical strength influenced the properties of the cement based composites. The workability and final setting time of composite gradually decreased compared to 100% PC (control) with higher dosages of GO up to 0.06 wt% (of cement), which is due to the dominant oxygen functional groups and the hydrophilic nature of GO. To the contrary, the workability and final setting time increased in the rGO composites compared to the control mix due to the almost hydrophobic nature of rGO and the presence of superplasticiser. The XRD and TGA quantification of the hydration products shows that GO composites have a greater content of Ca(OH)2 and C-S-H compared to rGO composites measured at 1, 7 and 28 days. Micropores (smaller than ∼10 µm) in GO composites were observed to be filled with calcium silicate hydrate (C-S-H) gel and crystalline compounds. Random pore filling nature was observed in rGO composites and ettringite was more common element in those pores. Meso and gel pores

Conditions of Teaching and Research in Economics: Some Preliminary Findings

This paper reports onthe preliminary findings of a study initiated two years ago, at the initiative of the P.LD.E. to review the problems of teaching and research in economics and related subjects (ERS)! during the last two decades. The need for such a study has been felt for some time not only because of the common perception of declining standards in higher education generally and, economics, in particular, but also from the perceived competition economics has faced from other disciplines, especially business studies and computer science as a passport to the job market. After having enjoyed a relatively robust period of growth in the 1960s largely through the assistance of foreign donors such as the Ford Foundation, ERS in Pakistan have suffered in their development not only from the comparative paucity of resources allocated to them, but also as a result of an adverse change in the perceptions about the primacy of their usefulness for policy purposes. The demand for economics has also suffered some decline as a result of the diminished importance of the public sector and of planned development during the last two decades. While special branches of economics, such as finance, project evaluation, transport and energy economics have shown increased demand, mainly in the private sector or donor-related institutions, the demand for general economic analysts is not as strong as in the past and does not provide many gainful opportunities for professional advancement. Due to the continued disadvantage in terms of salaries and other rewards, the academic profession, remains unattractive

An evaluation of topical and local anesthesia in phacoemulsification

Objective: To assess the comparative efficacy of topical and local anesthesia in phacoemulsification.MATERIAL AND Methods: The medical records of 186 men and women between the ages of 45-85 years, who underwent elective cataract surgery by phacoemulsification technique, under the care of one surgeon, over a period of one year, from March 1999-March 2000 were reviewed.Results: Of 186 patients who underwent small incision, self-healing phacoemulsification cataract surgery, 124 received topical and 62 local anesthesia. The most common cataract types were nuclear sclerosis. The duration of surgery with topical anesthesia was shorter. Sutures and eye padding were more frequently applied for procedures done under local anesthesia. Uncorrected visual acuity in the first post-op week was between 20/20-20/50 for 53.6% of the cases done under topical compared to 30.9% in local anesthesia. A similar trend was noted in the visual acuity one month post operatively.CONCLUSION: The uncorrected visual acuity improves faster and the duration of surgery is shorter when topical anesthesia is used