Abstract: Embodiments of the present invention include methods and apparatus for the detection of objects using acoustic imaging. Vibrational resonance characteristics of man-made objects may be significantly different from those of the surrounding natural materials, allowing an acoustic image to highlight the position of the object, even if the object is concealed from visual imaging.

Abstract: An internal-combustion engine includes a cylinder having an upper, generally planar bounding surface formed by an inner wall portion of a cylinder head; a fuel injection device and a spark plug held in the cylinder head and opening into the cylinder; a piston axially slidably disposed in the cylinder; a combustion chamber defined between the upper bounding surface of the cylinder head and the top piston face when the piston is in its upper dead center position; and an annular ridge situated on the top piston face. The annular ridge subdivides the combustion chamber into an inner partial combustion chamber and an outer partial combustion chamber surrounding the inner partial combustion chamber. The inner partial combustion chamber is situated in an effective range of the fuel injection device and the spark plug. Further, throughgoing apertures are provided in the annular ridge for maintaining a continuous communication between the inner and outer partial combustion chambers.

Abstract: A saw guard for a circular saw having a saw blade and a work piece holder which moves relative to the saw blade to cut the work piece, the saw guard being mounted on the leading edge of the work piece holder and having means for moving the saw guard into a shielding position adjacent the cutting edge of the saw blade while the work piece holder is in a restocking cycle.