Online paging and file caching with expiration times

AbstractWe consider a paging problem in which each page is assigned an expiration time at the time it is brought into the cache. The expiration time indicates the latest time that the fetched copy of the page may be used. Requests that occur later than the expiration time must be satisfied by bringing a new copy of the page into the cache. The problem has applications in caching of documents on the World Wide Web (WWW). We show that a natural extension of the well-studied least recently used (LRU) paging algorithm is strongly competitive for the uniform retrieval cost, uniform size case. We then describe a similar extension of the recently proposed Landlord algorithm for the case of arbitrary retrieval costs and sizes, and prove that it is strongly competitive. The results extend to the loose model of competitiveness as well

Teacher Hiring: The disconnect between research based best practice and processes used by school principals

Student success is dependent on teacher quality; therefore, it is imperative that principals hire the teachers most likely to experience success as measured by the impact on student outcomes. This study investigated teacher hiring processes to determine the extent to which practices that are supported by selection science and teacher quality research are utilized by school principals. Data were gathered using a survey e-mailed to principals in ten states in the southern and western regions of the United States. Analysis indicated that principals do not use consistent processes and vary the hiring approach based on their opinion of conditions. Principals favor traditional interviews as the primary teacher selection instrument and are unlikely to utilize predictive screening tools or research-based structured interviews. In most cases, principals do not make final hiring decisions based on measurable data or research-based qualities known to be predictive of high teacher performance. Most principals reported extremely limited teacher selection training through one-time workshops and graduate courses. This research is limited by the participation of principals in only ten states but implies that there is a disconnect between research-based best practices for teacher hiring and the actual processes used by principals

The Impact of Virtual Employment Interviews on the Teacher Hiring Process

The purpose of this qualitative study was to understand the perceptions of school administrators regarding the benefits of the virtual teacher hiring processes adopted when in-person interviews were impossible due to COVID19. Specifically, this research investigated the ways that teacher hiring changed during school closures and the extent to which those changes reflected best practice, whether school leaders felt that their virtual interviews were effective, and how leaders believe the experience of hiringusing virtual interviews would change future teacher selection processes. Semi-structured interviews served as the data collection tool and a sequential process of first and second cycle coding were used to analyze interview transcripts. Results indicatedwhen school leaders used virtual interviews, they were forced to adopt more reliable teacher selection practices, including careful screening of resumes, interview questions designed to uncover values and effective teaching behaviors, authentic assessmentof skills, and attention to teaching artifacts in digital portfolios. School leaders did not intentionally align their new selection processes with research-based best practices, but they were aware of the practical value of the changes made to their hiring processes and indicated that they intended to maintain at least some of the practices in the future

Teacher Hiring: The Disconnect Between Principals’ Perceptions, Processes and Research Based Best Practice

Student success is highly dependent on teacher quality, therefore; it is imperative that principals hire only the most outstanding teachers. This study investigated school hiring processes in order to determine the extent to which research based practices are utilized in districts of various configurations. Data was gathered using a 42 question electronic survey e-mailed to principals in ten states in the southern and western regions of the United States. Preliminary analysis indicates that in all types of districts the principal is the primary decision maker about the structure of the hiring processes including candidate selection. The vast majority of principals believe they are using research based processes, yet responses to specific questions indicate both structure and decision making criteria are not aligned with practices most likely to identify candidates who will have a high impact on student achievement. Most principals are confident in their ability to hire high quality teachers but report extremely limited training through one-time workshops and graduate courses. This research is limited by the distribution to only ten states in two geographic regions but implies that there is a disconnect between principals’ perceptions of their hiring practices and the actual alignment of process and outcomes to research based best practices

The visual analysis of heterogeneous sex role interactions: a content analysis of popular music videos

Hip Hop cultured music videos have raised concern among our nation’s leaders, parents and communities. Since the introduction of music videos in the early 1980s the medium has crossed cultural, regional and ethnic boundaries (Rose, 1994). This medium has been well researched since the 1980s. The focus of this study is Hip Hop cultured music videos from years 1989-2006. The uniqueness of this study is that it focuses on nonverbal sex role interactions in this genre of music videos. This study found many useful trends. For example, men were portrayed as more dominant and/or vertical than women in the sampled music videos

Inflight and ground-based simulation of handling qualities of very large airplanes in landing approach

Inflight and ground based simulation of Boeing 367-80 variable stability aircraft handling qualities during landing approac

On the Construction of Fiber-Optic Cables

In recent years, much research has been devoted to the improvement of RAID; however, few have enabled the analysis of active networks. After years of structured research into thin clients, we prove the visualization of virtual machines. Our focus in this paper is not on whether red- black trees can be made flexible, omniscient, and modular, but rather on introducing an algorithm for context-free grammar (Toph)

Potential Clinical Applications for Human Pluripotent Stem Cell-Derived Blood Components

The ability of human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) to divide indefinitely without losing pluripotency and to theoretically differentiate into any cell type in the body makes them highly attractive cell sources for large scale regenerative medicine purposes. The current use of adult stem cell-derived products in hematologic intervention sets an important precedent and provides a guide for developing hESC/iPSC based therapies for the blood system. In this review, we highlight biological functions of mature cells of the blood, clinical conditions requiring the transfusion or stimulation of these cells, and the potential for hESC/iPSC-derivatives to serve as functional replacements. Many researchers have already been able to differentiate hESCs and/or iPSCs into specific mature blood cell types. For example, hESC-derived red blood cells and platelets are functional in tasks such as oxygen delivery and blood clotting, respectively and may be able to serve as substitutes for their donor-derived counterparts in emergencies. hESC-derived dendritic cells are functional in antigen-presentation and may be used as off-the-shelf vaccine therapies to stimulate antigen-specific immune responses against cancer cells. However, in vitro differentiation systems used to generate these cells will need further optimization before hESC/iPSC-derived blood components can be used clinically

GPIM AF-M315E Propulsion System

The NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) Technology Demonstration Mission (TDM) will demonstrate an operational AF-M315E green propellant propulsion system. Aerojet-Rocketdyne is responsible for the development of the propulsion system payload. This paper statuses the propulsion system module development, including thruster design and system design; Initial test results for the 1N engineering model thruster are presented. The culmination of this program will be high-performance, green AF-M315E propulsion system technology at TRL 7+, with components demonstrated to TRL 9, ready for direct infusion to a wide range of applications for the space user community

Optimization of electric propulsion orbit raising

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.Includes bibliographical references (leaf 82).by Michael Scott Kimbrel.S.M