Relationships Between Ventilation and Indoor Air Quality: A Review

Abstract Adjustment of ventilation rates in buildings is widely practised, both to provide good air quality on a proactive basis and to mitigate air quality problems associated with occupant complaints. However, both cross-sectional and experimental epidemiological studies have reported mixed results and have for the most part failed to establish definitive relationships between ventilation rates and symptom prevalence or dissatisfaction with air quality. The difficulties involved in establishing such relationships may be due to a variety of confounding factors which include limitations in study design and interaction effects; difficulties in controlling ventilation rates in experimental studies; inadequate mixing of supply air in occupied spaces; high source strengths for some contaminants; dynamic interactions between sources and ventilation rates that result in increased contaminant emissions; contaminant dose-response sensory effects which are log-linear; potential contaminant generation within ventilation systems themselves; and multifactorial genesis of sick building symptoms. There is limited evidence to suggest that ventilation rate increases up to 10 L/s person may be effective in reducing symptom prevalence and occupant dissatisfaction with air quality and that higher ventilation rates are not effective. Because of complex relationships between ventilation rates, contaminant levels, and building-related health complaints/dissatisfaction with air quality, the use of ventilation as a mitigation measure for air quality problems should be tempered with an understanding of factors which may limit its effectiveness.     

Using GPS to learn significant locations and predict movement across multiple users

Wearable computers have the potential to act as intelligent agents in everyday life and to assist the user in a variety of tasks, using context to determine how to act. Location is the most common form of context used by these agents to determine the user's task. However, another potential use of location context is the creation of a predictive model of the user's future movements. We present a system that automatically clusters GPS data taken over an extended period of time into meaningful locations at multiple scales. These locations are then incorporated into a Markov model that can be consulted for use with a variety of applications in both single-user and collaborative scenarios.     

Phase-Transition Interlayer Enables High-Performance Solid-State Sodium Batteries with Sulfide Solid Electrolyte

All-solid-state sodium (Na) batteries (ASSSBs) using sulfide-based solid electrolytes (SEs) have attracted intensive attention due to their superior safety, high energy density, and low cost. However, the interfacial issue is one of the biggest challenges to achieve high-performance sulfide-based ASSSBs due to the serious reactions between active Na metal and sulfide SEs at the interface. To address the interfacial challenges, a simple and efficient approach by introducing a phase transition polymer electrolyte as an interlayer to stabilize the interface is proposed. Na₃SbS₄ as a model sulfide SE is used to demonstrate the interlayer strategy to stabilize the interface by preventing the detrimental reactions and inhibiting Na dendrites. As a result, stable Na plating/stripping is observed in Na symmetric cells under the current density of 0.1 mA cm⁻². Moreover, ASSSBs with Na metal and TiS₂ electrode deliver long-term stability over 300 cycles remaining a specific capacity above 100 mAh g⁻¹, and FeS₂||Na cells exhibit an impressive specific capacity of up to 200 mAh g⁻¹ after the 20th cycles. This study demonstrates an efficient strategy to address interfacial challenges between sulfide SEs and Na metal, which contributes to the development of ASSSBs in next-generation energy storage systems.     

Recent progress in CFD for naval architecture and ocean engineering

An overview is provided of CFDShip-Iowa modeling, numerical methods and high performance computing(HPC), including both current V4.5 and V5.5 and next generation V6. Examples for naval architecture highlight capability and needs. High fidelity V6 simulations for ocean engineering and fundamental physics describe increased resolution for analysis of physics of fluids. Uncertainty quantification research is overviewed as the first step towards development stochastic optimization.     

Universal design: lessons for wearable computing

When we as developers and designers create a system that requires user interaction-whether it is computer software, a kitchen appliance, or a door knob-we often fall victim to a common mistake: we use ourselves as the model for our system's potential users. Even developing for an "average user" is a pitfall that results in numerous users whose needs are overlooked. The average user might account for the largest spike under a bell curve, but nonaverage users account for a much larger percentage of the general population. Additionally, the number of people possessing all of the average attributes being considered in a design is very small. So, the designers' goal should be to broaden the section of the bell curve that their system targets. This concept is called universal design, and it's especially important in wearable computing because using a system while mobile and while in different environments can have a major effect on its usability.     

Real-time American sign language recognition using desk andwearable computer based video

We present two real-time hidden Markov model-based systems for recognizing sentence-level continuous American sign language (ASL) using a single camera to track the user's unadorned hands. The first system observes the user from a desk mounted camera and achieves 92 percent word accuracy. The second system mounts the camera in a cap worn by the user and achieves 98 percent accuracy (97 percent with an unrestricted grammar). Both experiments use a 40-word lexicon     

Wearable computing for the developing world

The project was simple to describe: create a "world computer" that could assist the developing world in leapfrogging the industrial stage of economic development. The World Center for Computing and Human Resources carried out experiments with 6502 machines such as the Apple II, Atari 400, and Atari 800 and established a pilot project in Senegal. In the end, the expense of the computers and the weight of politics limited the project. Yet, several new efforts are reexamining the concept, commonly termed information and communication technologies (ICT) for development.     

Powerful change part 1: batteries and possible alternatives for the mobile market

Mobile phone companies sell more batteries than phones to consumers. The devices users buy generally include rechargeable batteries so that they are immediately useful. Companies try to protect their batteries with various design and utility patents to keep third-party vendors from competing too heavily with their after-market sales. This protection is necessary because battery technology changes slowly-consumers receive little incentive to upgrade their batteries unless they fail or the consumer desires a larger one. Power is a difficult issue and is often overlooked in mobile computers. However, innovative opportunities abound for exploring this problem. We introduce the issue and propose some alternatives to batteries. In subsequent issues we'll address methods of being more power efficient by using resources both on the body and in the environment.     

Free standing aluminum nanostructures as anodes for Li-ion rechargeable batteries

The free standing aluminum nanorods were grown on electrode and evaluated electrochemically as the anodes in the half-cell of Li-ion battery. The average diameter and length of the nanorods are 80 nm and 200 nm, respectively. The aligned nanorods demonstrated high capacity of 1243 mAh g⁻¹ at rate of 0.5 C. A gradual decrease of the initial capacity was observed. The characterization of the anodes shows that the changes of the crystalline structure and morphology during cycling may be responsible for the capacity decay. The appropriate selection of the substrate can overcome the problems and lead the sustainable high capacity.