This paper presents the findings of a comparative study investigating different input interfaces for a mobile phone games application. A standard mobile phone joystick interface is compared with a phone camera interface to detect the phone translation and tilt to control a ball's movement within various levels of difficulty of a virtual maze game. Game completion times together with the resultant user experience for each of the games was collected during the studies. Results indicate that the joystick control provided the fastest completion times for each game, but with the lowest levels of user engagement. The Tilt interface, although perceived as challenging by the participants, provided the greatest level of user involvement, independent of game complexity. The design of appropriate human interfaces which go beyond the standard phone keypad is suggested. The selection and design of these interfaces should also consider the intended user experience for the game.
In this study, we report on the first tests of Asetek's RackCDU direct-to-chip liquid cooling system for servers at NREL's ESIF data center. The system was simple to install on the existing servers and integrated directly into the data center's existing hydronics system. The focus of this study was to explore the total cooling energy savings and potential for waste-heat recovery of this warm-water liquid cooling system. RackCDU captured up to 64% of server heat into the liquid stream at an outlet temperature of 89°F, and 48% at outlet temperatures approaching 100°F. This system was designed to capture heat from the CPUs only, indicating a potential for increased heat capture if memory cooling was included. Reduced temperatures inside the servers caused all fans to reduce power to the lowest possible BIOS setting, indicating further energy savings potential if additional fan control is included. Preliminary studies manually reducing fan speed (and even removing fans) validated this potential savings but could not be optimized for these working servers. The Asetek direct-to-chip liquid cooling system has been in operation with users for 16 months with no necessary maintenance and no leaks. v This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. List of Acronyms AHU air handling unit BIOS basic input/output system Btu British thermal unit CDU cooling distribution unit cfm cubic feet per minute CPU central processing unit
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