A Study of Disk Performance Optimization.

Response time is one of the most important performance measures associated with a typical multi-user system. Response time, in turn, is bounded by the performance of the input/output (I/O) subsystem. Other than the end user and some external peripherals, the slowest component of the I/O subsystem is the disk drive. One standard strategy for improving I/O subsystem performance uses high-performance hardware like Small Computer Systems Interface (SCSI) drives to improve overall response time. SCSI hardware, unfortunately, is often too expensive to use in low-end multi-user systems. The low-end multi-user systems commonly use inexpensive Integrated Drive Electronics (IDE) disk drives to keep overall costs low. On such IDE based multi-user systems, reducing the Central Processing Unit (CPU) overhead associated with disk I/O is critical to system responsiveness. This thesis explores the impact of PCI bus mastering Direct Memory Access (DMA) on the performance of systems with IDE drives. DMA is a data transfer protocol that allows data to be sent directly from an attached device to a computer system’s main memory, thereby reducing CPU overhead. PCI bus mastering allows modern IDE disk controllers to manipulate main memory without utilizing motherboard-resident DMA controllers. Using a series of experiments, this thesis examines the impact of PCI bus mastering DMA on IDE performance for synchronous I/O, relative to Programmed Input/Output (PIO) and SCSI performance. Experiment results show that PCI bus mastering DMA, when used properly, improves the responsiveness and throughput of IDE drives by as much as a factor of seven. The magnitude of this improvement shows the importance of operating system support for DMA in low-end multi-user systems. Additionally, experimental results demonstrate that performance gains associated with SCSI are dependent on system usage and operating system support for advanced SCSI capabilities. Therefore, under many circumstances, high-performance SCSI drives are not cost effective when compared with IDE bus mastering DMA capable drives

Meteorological satellite data: A tool to describe the health of the world's agriculture

Local area coverage data acquired aboard the TIROS-N satellite family by the advanced very high resolution radiometer systems was examined to determine the agricultural information current. Albedo differences between channel 2 and channel 1 of the advanced very high resolution radiometer LAC (called EVI) are shown to be closely correlated to the Ashburn vegetative index produced from LANDSAT multispectral scanner data which have been shown to vary in response to "greenness", soil moisture, and crop production. The statistical correlation between the EVI and the Ashburn Vegetative Index (+ or - 1 deg) is 0.86

Analysis of crashes involving First Responder Vehicles

First responders face many hazards that put their lives at risk while on duty. Over the period of 1992-97, 887 law enforcement personnel and 259 firefighters were killed in the line of duty (Clarke, 1999). An inherent danger comes with the duties of emergency response. A review of the National Law Enforcement Officers Memorial Fund statistics shows that 553 police officers died in the line-of-duty between 2008 and 2017 as a direct result of a traffic related incidents. That represents more than 36 percent of all on-duty fatalities and is even higher than the number of police officers lost to gun violence over the same period. Sadly, the nation’s first responders are exposed to factors which make them uniquely vulnerable to traffic related injuries and deaths. The goal of this research is to investigate and analyze crashes involving first responder vehicles. This will be achieved by gathering police, fire, and ambulance vehicle crash reports from Signal Four Database from across the state of Florida from 2016 to 2018. Based on the database, approximately 1% of the crashes were first responder vehicles. The data set will be used to look at frequency and severity levels between first responders and the general public. Additionally, an evaluation will be conducted on individual responder vehicle groups; police, fire, and ambulance. This project is expected to help identify factors and situations that can lead to increased risk for first responders on Florida roadways. Potential recommendations discovered through this research should be used to protect the lives of first responders. REFERENCES Clarke, C., & Zak, M. J. (1999). Fatalities to Law Enforcement Officers and Firefighters, 1992-97 [Electronic version]. Compensation and Working Conditions, 3-7

Managing Misinformation on Social Media: Targeted Newsfeed Interventions and Freedom of Thought

Whether it is being told a particular politician consumes children, or drinking cow urine will cure your disease, or that Jimi Hendrix is alive and well living the good life in Drumnadrochit, misinformation affects societies in myriad ways. Its spread online via social media platforms raises questions concerning how it can be addressed. This article engages with a related problem: Can the use of targeted behavioral interventions on social media newsfeeds to reduce the spread of misinformation be reconciled with the human right to freedom of thought

Evolution of the Florida Launch Site Architecture: Embracing Multiple Customers, Enhancing Launch Opportunities

The impending conclusion of the Space Shuttle Program and the Constellation Program cancellation unveiled in the FY2011 President's budget created a large void for human spaceflight capability and specifically launch activity from the Florida launch Site (FlS). This void created an opportunity to re-architect the launch site to be more accommodating to the future NASA heavy lift and commercial space industry. The goal is to evolve the heritage capabilities into a more affordable and flexible launch complex. This case study will discuss the FlS architecture evolution from the trade studies to select primary launch site locations for future customers, to improving infrastructure; promoting environmental remediation/compliance; improving offline processing, manufacturing, & recovery; developing range interface and control services with the US Air Force, and developing modernization efforts for the launch Pad, Vehicle Assembly Building, Mobile launcher, and supporting infrastructure. The architecture studies will steer how to best invest limited modernization funding from initiatives like the 21 st elSe and other potential funding

Comparison of Driver Brake Reaction Times to Multimodal Rear-end Collision Warnings

This study examined the effectiveness of rear-end collision warnings presented in different sensory modalities as a function of warning timing in a driving simulator. Drivers experienced four warning conditions: no warning, visual, auditory, and tactile. The warnings activated when the time-to-collision (TTC) reached a critical value of 3.0 or 5.0 s TTC. Driver reaction time (RT) was captured from the time the driver crossed the warning activation threshold to brake initiation. Mean driver RT data showed that the tactile warning significantly outperformed the visual warning, providing support for tactile displays as effective rear-end collision warnings