Abstract: In a racket frame, a yoke part is disposed between left and right portions of a bifurcated throat part continuous with a head part and with a shaft part. A ball-hitting face is formed with the yoke part and the head part. The head part and the yoke part have a plurality of string holes formed in penetration therethrough to insert longitudinal and transverse strings therethrough. Longitudinal string holes formed outside left and right sides of the yoke part connected with the left and right portions of the throat part are extended to the throat part to form extended longitudinal string holes open on an outer surface of the throat part.

Abstract: A tennis racket frame is composed of a laminate of prepregs each containing carbon fibers serving as a reinforcing fiber thereof. At least one part of layers of the laminate is formed as a hard layer consisting of a prepreg composed of the reinforcing carbon fibers and a hard carbon film (DLC film) formed on the surface of the carbon fibers.

Abstract: In a tennis racket having a racket frame composed of a fiber reinforced resin, the moment of inertia Ic of the tennis racket in a center direction thereof is set to not less than 13000 g·cm2 nor more than 17000 g·cm2, the moment of inertia Ig around a center of gravity thereof is set to not less than 80000 g·cm2 nor more than 200000 g·cm2, and the moments of inertia Ic and Ig are so set as to satisfy a relationship expressed by [30×(Ic)?(Ig)]/10000?31.

Abstract: A tennis racket frame (10), including a sleeve composed of a fiber reinforced resin, having a weight not less than 180 g nor more than 270 g, when strings are not mounted in a ball-hitting face thereof surrounded with a head part thereof. Supposing that the strings are not mounted in the ball-hitting face, a secondary natural frequency (F1) of the racket frame in an in-plane direction thereof is set to not less than 200 Hz nor more than 320 Hz, a secondary natural frequency (F2) thereof in an out-of-plane direction thereof is set to not less than 480 Hz nor more than 650 Hz, and F1/F2 is set to not less than 0.3 nor more than 0.6.

Abstract: A racket frame (10) including a laminate having not less than two fiber reinforced resinous layers layered one upon another and one or more modified fiber reinforced resinous layers (20) each containing a modified resinous composition, as a matrix resin, having a loss factor (=tan ?) not less than 0.5 nor more than 3.0, when the loss factor is measured at a temperature of 0° C. to 10° C. and a frequency of 10 Hz. A weight of the modified fiber reinforced resinous layers (20) is set to not less than 1% nor more than 10% of a weight of the fiber reinforced resinous layers.

Abstract: In a tennis racket having a racket frame composed of a fiber reinforced resin, the moment of inertia Ic of the tennis racket in a center direction thereof is set to not less than 13000 g·cm2 nor more than 17000 g·cm2, the moment of inertia Ig around a center of gravity thereof is set to not less than 80000 g·cm2 nor more than 200000 g·cm2, and the moments of inertia Ic and Ig are so set as to satisfy a relationship expressed by [30×(Ic)?(Ig)]/10000?31.

Abstract: A tennis racket frame (10), including a sleeve composed of a fiber reinforced resin, having a weight not less than 180 g nor more than 270 g, when strings are not mounted in a ball-hitting face thereof surrounded with a head part thereof. Supposing that the strings are not mounted in the ball-hitting face, a secondary natural frequency (F1) of the racket frame in an in-plane direction thereof is set to not less than 200 Hz nor more than 320 Hz, a secondary natural frequency (F2) thereof in an out-of-plane direction thereof is set to not less than 480 Hz nor more than 650 Hz, and F1/F2 is set to not less than 0.3 nor more than 0.6.

Abstract: A racket frame (10) including a laminate having not less than two fiber reinforced resinous layers layered one upon another and one or more modified fiber reinforced resinous layers (20) each containing a modified resinous composition, as a matrix resin, having a loss factor (=tan ?) not less than 0.5 nor more than 3.0, when the loss factor is measured at a temperature of 0° C. to 10° C. and a frequency of 10 Hz. A weight of the modified fiber reinforced resinous layers (20) is set to not less than 1% nor more than 10% of a weight of the fiber reinforced resinous layers.

Abstract: A racket frame (1) has a pipe-shaped racket-frame body (2) made of a fiber reinforced resin and composed of a head (3), a throat part (4), a shaft part (5), and a grip part (6) sequentially arranged and a yoke (10) connected to the racket-frame body (2). In this construction, supposing that the head (3) is a clock face and that the top position of the head (3) is 12 o'clock, a yoke rigidity value at a central position P1, vertical to a ball-hitting face (F), of the yoke (10) in a longitudinal direction thereof is in a range of 10% to 70% of a face rigidity value which is an average of a rigidity value at a 12 o'clock position (P2) vertical to the ball-hitting face (F) and a rigidity value at a three o'clock position (P3) vertical to the ball-hitting face (F).

Abstract: A frame body (2) is formed separately from a yoke (10) connecting right and left parts of the frame body (2) to each other. The yoke (10) and the frame body (2) are connected to each other by a mechanical connection means, with both ends of the yoke (10) in contact with the right and left parts of the frame body (2) in an area of not less than 10 cm2 (1.6 in2). A shear force generated when the racket frame (1) deforms is collectively applied to a connection surface of the frame body (2) and that of the yoke (10) to increase a vibration-damping performance of the racket frame (1).

Abstract: A racket frame (1) has a pipe-shaped racket-frame body (2) made of a fiber reinforced resin and composed of a gut-stretched part (3), a throat part (4), a shaft part (5), and a grip part (6) sequentially arranged and a yoke (10) connected to the racket-frame body (2). In this construction, supposing that the gut-stretched part (3) is a clock face and that the top position of the gut-stretched part (3) is 12 o'clock, a yoke rigidity value at a central position P1, vertical to a ball-hitting face (F), of the yoke (10) in a longitudinal direction thereof is in a range of 10% to 70% of a face rigidity value which is an average of a rigidity value at a 12 o'clock position (P2) vertical to the ball-hitting face (F) and a rigidity value at a three o'clock position (P3) vertical to the ball-hitting face (F).

Abstract: A frame body (2) is formed separately from a yoke (10) connecting right and left parts of the frame body (2) to each other. The yoke (10) and the frame body (2) are connected to each other by a mechanical connection means, with both ends of the yoke (10) in contact with the right and left parts of the frame body (2) in an area of not less than 10 cm2. A shear force generated when the racket frame (1) deforms is collectively applied to a connection surface of the frame body (2) and that of the yoke (10) to increase a vibration-damping performance of the racket frame (1).

Abstract: Disclosed is a structural material excelling in lightness of weight, strength, flexural modulus and other properties, being made from polyamide resin reinforced with continuous fiber and/or long filament reinforcing material. This structural material can be fabricated by a monomer casting method by arranging said fiber reinforcing material preliminarily in a desired shape, putting it into a mold, pouring molten &ohgr;-lactams containing a polymerization catalyst and an initiator into said mold, and heating to obtain polyamide resin.

Abstract: A surface current heating apparatus including a plurality of hollow heat generating members each of which is made of a ferromagnetic material and has a through-hole and which are spaced apart from each other so as to provide an array of the hollow heat generating members, and an electrically conductive wire electrically insulated and extending through the through-hole of each hollow heat generating member, and wherein an alternating current from a power source is applied to the electrically conductive wire, to cause a surface current to flow through a skin layer of each hollow heat generating member which is located near an inner surface of the through-hole, whereby heat is generated from the said skin layer of the heat generating member.

Abstract: A method of evaluating a program in which a second program is inserted into an instruction processing of a first program, includes the steps of: latching an address value of a stack pointer when executing an instruction for calling the second program; comparing the address value of the stack pointer held with an address value of a stack pointer during a subsequent instruction execution; and when they are coincident with each other, judging the termination of execution of the second program.

Abstract: A video camera unit is separated into a holder for receiving lenses and a base on which a solid-state image pickup chip is mounted. The holder and the base are assembled together with the distance between them made variable so that it is possible to adjust the back focus of the lens. Further, a video camera unit has a holder which is separated into a first holder for receiving lenses and a second holder for receiving a solid-state image pickup device so that both holders can be assembled together with the distance between them made variable. Therefore, it is also possible to adjust the back focus of the lens.

Abstract: A method for forming a shock resistant tool comprising reinforcing fiber used as a reinforcing material and cyclopentadiene resin used as matrix resin by reaction injection molding method. Cyclopentadiene resin is superior in shock resistant performance and has a low melt viscosity, thus allowing fiber to be contained in the shock resistant tool at a high percentage.

Abstract: A video camera unit is separated into a holder for receiving lenses and a base on which a solid-state image pickup chip is mounted. The holder and the base are assembled together with the distance between them made variable so that it is possible to adjust the back focus of the lens. Further, a video camera unit has a holder which is separated into a first holder for receiving lenses and a second holder for receiving a solid-state image pickup device so that both holders can be assembled together with the distance between them made variable. Therefore, it is also possible to adjust the back focus of the lens.

Abstract: An imaging assembly, which is particularly useful for a video camera unit, comprising a set of lenses, some of which have a non-refractive surface, and an image sensor. A holder is provided for holding both the set of lenses and the image sensor to be aligned with one another. Circuitry is also provided so that the sensitivity of the image sensor can be electrically varied.

Abstract: The tennis racket frame according to the present invention has a total weight of 230-300 g and total length of 52-67 cm and a periodic damping ratio of 0.5-4.0%, which is constituted of a fiber reinforced resin composed of polyamide resin reinforced by a continuous fiber and/or long fiber reinforcing material. A resin layer containing a non-woven fabric may be provided at the inside, outside or/and in the middle of the fiber reinforced resin layer. Because of this structure, the tennis racket frame of the present invention can be light in weight and compact in size with a large periodic damping property, making it possible to avoid tennis elbow.