Key factors in web latency savings in an experimental prefetching system

Although Internet service providers and communications companies are continuously offering higher and higher bandwidths, users still complain about the high latency they perceive when downloading pages from the web. Therefore, latency can be considered as the main web performance metric from the user's point of view. Many studies have demonstrated that web prefetching can be an interesting technique to reduce such latency at the expense of slightly increasing the network traffic. In this context, this paper presents an empirical study to investigate the maximum benefits that web users can expect from prefetching techniques in the current web. Unlike previous theoretical studies, this work considers a realistic prefetching architecture using real traces. In this way, the influence of real imple- mentation constraints are considered and analyzed. The results obtained show that web prefetching could improve page latency up to 52% in the studied traces. ©Springer Science+Business Media, LLC 2011De La Ossa Perez, BA.; Sahuquillo Borrás, J.; Pont Sanjuan, A.; Gil Salinas, JA. (2012). Key factors in web latency savings in an experimental prefetching system. Journal of Intelligent Information Systems. 39(1):187-207. doi:10.1007/s10844-011-0188-xS187207391Balamash, A., Krunz, M., & Nain, P. (2007). Performance analysis of a client-side caching/prefetching system for web traffic. Computer Networks, 51(13), 3673–3692.Bestavros, A. (1995). Using speculation to reduce server load and service time on the www. In Proc. of the 4th ACM international conference on information and knowledge management. Baltimore, USA.Bestavros, A., & Cunha, C. (1996). Server-initiated document dissemination for the WWW. In IEEE data engineering bulletin. [Online]. Available: http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.128.266 . Accessed 29 November 2011.Bouras, C., Konidaris, A., & Kostoulas, D. (2004). Predictive prefetching on the web and its potential impact in the wide area. In World Wide Web: Internet and web information systems (Vol. 7, No. 2, pp. 143–179). The Netherlands: Kluwer Academic.Changa, T., Zhuangb, Z., Velayuthamc, A., & Sivakumara, R. (2008). WebAccel: Accelerating web access for low-bandwidth hosts. Computer Networks, 52(11), 2129–2147.Davison, B. D. (2002). The design and evaluation of web prefetching and caching techniques. Ph.D. dissertation, Rutgers University.de la Ossa, B., Gil, J. A., Sahuquillo, J., & Pont, A. (2007). Delfos: The oracle to predict next web user’s accesses. In Proc. of the IEEE 21st international conference on advanced information networking and applications. Niagara Falls, Canada.de la Ossa, B., Pont, A., Sahuquillo, J., & Gil, J. A. (2010). Referrer graph: A low-cost web prediction algorithm. In Proc. of the 25th ACM symposium on applied computing (pp. 831–838). doi: 10.1145/1774088.1774260 .de la Ossa, B., Sahuquillo, J., Pont, A., & Gil, J. A. (2009). An empirical study on maximum latency saving in web prefetching. In Proc. of the 2009 IEEE/WIC/ACM international conference on web intelligence (WI’09).Dom̀enech, J., Gil, J. A., Sahuquillo, J., & Pont, A. (2006a). DDG: An efficient prefetching algorithm for current web generation. In Proc. of the 1st IEEE workshop on hot topics in web systems and technologies (HotWeb). Boston, USA.Domènech, J., Gil, J. A., Sahuquillo, J., & Pont, A. (2006b). Web prefetching performance metrics: A survey. Performance Evaluation, 63(9–10), 988–1004.Domènech, J., Sahuquillo, J., Gil, J. A., & Pont, A. (2006c). The impact of the web prefetching architecture on the limits of reducing user’s perceived latency. In Proc. of the international conference on web intelligence. Piscataway: IEEE.de la Ossa, B., Gil, J. A., Sahuquillo, J., & Pont, A. (2007). Improving web prefetching by making predictions at prefetch. In Proc. of the 3rd EURO-NGI conference on next generation internet networks design and engineering for heterogeneity (NGI’07) (pp. 21–27).Duchamp, D. (1999). Prefetching hyperlinks. In Proc. of the 2nd USENIX symposium on internet technologies and systems. Boulder, USA.Fan, L., Cao, P., Lin, W., & Jacobson, Q. (1999). Web prefetching between low-bandwidth clients and proxies: Potential and performance. In Proc. of the ACM SIGMETRICS conference on measurement and modeling of computer systems (pp. 178–187).HTTP/1.1. [Online]. Available: http://www.faqs.org/rfcs/rfc2616.html . Accessed 29 November 2011.Kroeger, T. M., Long, D., & Mogul, J. C. (1997). Exploring the bounds of web latency reduction from caching and prefetching. In Proc. of the 1st USENIX symposium on internet technologies and systems. Monterrey, USA.Link prefetching in mozilla faq (2011). [Online]. Available: https://developer.mozilla.org/en/Link_prefetching_FAQ .Markatos, E., & Chronaki, C. (1998). A top-10 approach to prefetching on the web. In Proc. of INET. Geneva, Switzerland.Márquez, J., Domènech, J., Pont, A., & Gil, J. A. (2008). Exploring the benefits of caching and prefetching in the mobile web. In Second IFIP symposium on wireless communications and information technology for developing countries (WCITD 2008).Padmanabhan, V., & Mogul, J. C. (1996). Using predictive prefetching to improve World Wide Web latency. In Proc. of the ACM SIGCOMM conference. Stanford University, USA.Palpanas, T., & Mendelzon, A. (1999). Web prefetching using partial match prediction. In Proc. of the 4th international web caching workshop. San Diego, USA.Schechter, S., Krishnan, M., & Smith, M. D. (1998). Using path profiles to predict http requests. In Proc. of the 7th international World Wide Web conference. Brisbane, Australia.Teng, W., Chang, C., & Chen, M. (2005). Integrating web caching and web prefetching in client-side proxies. IEEE Transactions on Parallel and Distributed Systems, 16(5), 444–455

A taxonomy of web prediction algorithms

Web prefetching techniques are an attractive solution to reduce the user-perceived latency. These techniques are driven by a prediction engine or algorithm that guesses following actions of web users. A large amount of prediction algorithms has been proposed since the first prefetching approach was published, although it is only over the last two or three years when they have begun to be successfully implemented in commercial products. These algorithms can be implemented in any element of the web architecture and can use a wide variety of information as input. This affects their structure, data system, computational resources and accuracy. The knowledge of the input information and the understanding of how it can be handled to make predictions can help to improve the design of current prediction engines, and consequently prefetching techniques. This paper analyzes fifty of the most relevant algorithms proposed along 15 years of prefetching research and proposes a taxonomy where the algorithms are classified according to the input data they use. For each group, the main advantages and shortcomings are highlighted. © 2012 Elsevier Ltd. All rights reserved.This work has been partially supported by Spanish Ministry of Science and Innovation under Grant TIN2009-08201, Generalitat Valenciana under Grant GV/2011/002 and Universitat Politecnica de Valencia under Grant PAID-06-10/2424.Domenech, J.; De La Ossa Perez, BA.; Sahuquillo Borrás, J.; Gil Salinas, JA.; Pont Sanjuan, A. (2012). A taxonomy of web prediction algorithms. Expert Systems with Applications. 39(9):8496-8502. https://doi.org/10.1016/j.eswa.2012.01.140S8496850239

Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that the wood in the starch composites did not prevent water loss from the samples.Peer reviewe

Web Prefetching Techniques in Real Environments

Esta tesis estudia la aplicación a la World Wide Web (WWW) de las técnicas de prebúsqueda desde un punto de vista realista y práctico. La prebúsqueda se aplica a la web para reducir la latencia percibida por los usuarios ya que, básicamente, consiste en predecir y preprocesar los siguientes accesos de los usuarios. Hasta ahora, la literatura disponible acerca de la prebúsqueda web se ha concentrado en cuestiones teóricas y no ha considerado algunos de los problemas que aparecen al implementar la técnica en condiciones reales. Por otra parte, los trabajos de investigación existentes usan para la evaluación modelos simplificados que no consideran cómo los aspectos prácticos afectan realmente a la implementación de una técnica de prebúsqueda. Además, apenas unos pocos trabajos han usado índices de prestaciones que sean relevantes para los usuarios en la evaluación de los beneficios que la prebúsqueda puede lograr. Con objeto de superar estas tres restricciones se ha desarrollado Delfos, un entorno de prebúsqueda web que implementa predicción y prebúsqueda en un sistema real, puede integrarse en la arquitectura web sin realizar modificaciones en los protocolos web estándar, y es compatible con los programas existentes. Delfos también puede usarse para evaluar y comparar técnicas de prebúsqueda y algoritmos de predicción así como ayudar en el diseño de otros nuevos ya que proporciona información estadística detallada de los experimentos llevados a cabo. A modo de ejemplo, Delfos se ha usado para proponer, probar y evaluar una nueva técnica (Predecir en la Prebúsqueda, PAP) que es capaz de reducir considerablemente la latencia percibida por el usuario sin costes adicionales respecto al mecanismo de prebúsqueda básico. Los algoritmos de predicción propuestos en la literatura de investigación que alcanzan la mayor precisión incurren en un alto coste computacional, y esto representa un problema para incluirlos en sistemas reales. Para aminorar este inconveniente, en esta tesis se propone un nuevo algoritmo de predicci on de bajo coste, (Referrer Graph, RG).De La Ossa Pérez, BA. (2011). Web Prefetching Techniques in Real Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15574Palanci

Bioartificial Sponges for Auricular Cartilage Engineering

Auricle reconstruction due to congenital, post-infective or post-traumatic defects represents a challenging procedure in the field of aesthetic and reconstructive surgery due to the highly complex three-dimensional anatomy of the outer ear. Tissue engineering aims to provide alternatives to overcome the shortcomings of standard surgical reconstructive procedure. In the present study, poly(vinyl alcohol)/gelatin (PVA/G) sponges at different weight ratios were produced via emulsion and freeze-drying, and crosslinked by exposure to glutaraldehyde vapors. PVA/G sponges gave rise to highly porous, water stable and hydrophilic scaffolds. Characterization of PVA/G sponges showed round-shaped interconnected pores, high swelling capacity (>200%) and viscoelastic mechanical behavior. The PVA/G 70/30 (w/w) scaffold was selected for in vitro biological studies. Bone marrow derived human mesenchymal stromal cells (hMSCs) were used and differentiated towards chondrogenic lineage under different culture conditions: 1) commercial versus handmade differentiation medium; 2) undifferentiated versus pre-differentiated hMSC seeding; and 3) static versus dynamic culture [i.e. ultrasound (US) or bioreactor stimulation]. Histological results highlighted intense glycosaminoglycan, glycoprotein and collagen syntheses after three weeks, mostly using the commercial medium, whereas round morphology was observed in pre-differentiated cells. In static culture, immunohistochemistry for chondrogenic markers revealed an early differentiation stage, characterized by the expression of Sox-9 and collagen type I fibers. The application of US on cell/scaffold constructs increased extracellular matrix deposition and resulted in 30% higher collagen type II expression at the gene level. Bioreactor culture induced collagen type II, aggrecan and elastin formation. This study demonstrated that 70/30 PVA/G sponge is a suitable candidate for auricle reconstruction

Revista Temas Agrarios Volumen 26; Suplemento 1 de 2021

1st International and 2nd National Symposium of Agronomic Sciences: The rebirth of the scientific discussion space for the Colombian Agro.1 Simposio Intenacional y 2 Nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano

The Effects of Cinacalcet in Older and Younger Patients on Hemodialysis: The Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) Trial.

This article contains supplemental material online at http://cjasn. asnjournals.org/lookup/suppl/doi:10.2215/CJN.07730814/-/ DCSupplemental.BACKGROUND AND OBJECTIVES: The calcimimetic cinacalcet reduced the risk of death or cardiovascular (CV) events in older, but not younger, patients with moderate to severe secondary hyperparathyroidism (HPT) who were receiving hemodialysis. To determine whether the lower risk in younger patients might be due to lower baseline CV risk and more frequent use of cointerventions that reduce parathyroid hormone (kidney transplantation, parathyroidectomy, and commercial cinacalcet use), this study examined the effects of cinacalcet in older (≥65 years, n=1005) and younger (3-fold higher in younger relative to older patients and were more frequent in patients randomized to placebo. In older patients, the adjusted relative hazard (95% confidence interval) for the primary composite (CV) end point (cinacalcet versus placebo) was 0.70 (0.60 to 0.81); in younger patients, the relative hazard was 0.97 (0.86 to 1.09). Corresponding adjusted relative hazards for mortality were 0.68 (0.51 to 0.81) and 0.99 (0.86 to 1.13). Reduction in the risk of severe unremitting HPT was similar in both groups. CONCLUSIONS: In the EVOLVE trial, cinacalcet decreased the risk of death and of major CV events in older, but not younger, patients with moderate to severe HPT who were receiving hemodialysis. Effect modification by age may be partly explained by differences in underlying CV risk and differential application of cointerventions that reduce parathyroid hormone.The Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) trial was funded by Amgen

ПОЯСНЮВАЛЬНА ЗАПИСКА кваліфікаційної роботи бакалавра студента Варганова_Дмитра_Дмитровича напряму підготовки 124 Системний аналіз

Об’єкт дослідження – підприємство КПШНЗ «СДЮСШОР з кінного спорту» ДМР. Предмет дослідження – приготування кормів для годування тренованих і спортивних коней. Мета дослідження: оптимізація витрат підприємства шляхом удосконалення технологій виробництва і рецептів кормів для тренованих і спортивних коней, підвищення їх якості та зниження питомих витрат на виробництво. Методи дослідження: методи багатокритеріальної та нечіткої оптимізації Економічна ефективність: очікується позитивною завдяки розробці оптимальних кормових сумішей, які дозволяють отримувати більше користі для коней та знизити витрати на компоненти, це дозволяє збільшити прибуток підприємства.Кваліфікаційна робота ступеня бакалавр напряму підготовки 124 Системний аналіз, НТУ "Дніпровська політехніка", м. Дніпро, 2020 р. Практична цінність роботи полягає у розробці математичних моделей, які дозволяють визначити оптимальну суміш корму, котра буде відповідати необхідним умовам