Methods and apparatus for quickly selecting an optimal excitation waveform from a codebook are presented herein. A method for controlling air circulation within a room having an aisle between racks with computer systems mounted thereon comprises supplying cooling air to computer systems in the racks via holes in a floor of the room and using a deflector to reduce flow of cooling air along the aisle toward an air intake of a cooling unit without passing the computer systems. The providing of material for the distance members comprises guiding at least some of the strips in a meandering pattern, and applying an adhesive to contact the strips on opposite edges thereof such that adhesion to the material of the first and second surfaces is enabled. The legs have respective interlocking elements that engage with the lamp structure. The valve unit also includes a pressure balancing passage which communicates front and rear ends of the valve element with one another and tending to aid in statically and dynamically balancing the fluid pressures acting on the valve element.