Abstract: A lithium ion battery lifetime prediction method executes, by a computer, acquiring training data including cycle measurement data and lifetime data of a battery, learning a lifetime prediction model using the training data with respect to one or more cycle numbers at which a prediction is made, to acquire a set of learned lifetime prediction models corresponding to the cycle numbers at which the prediction is made, respectively, successively acquiring cycle measurement data for prediction of a battery that is a prediction target, up to the cycle numbers at which the prediction is made, respectively, and inputting the cycle measurement data for prediction acquired up to the cycle numbers at which the prediction is made, to the learned lifetime prediction models of the corresponding cycle numbers at which the prediction is made, and acquiring a probability distribution of a lifetime at the cycle numbers at which the prediction is made, respectively, as an output.

Abstract: A golf club head includes a weight object and a weight object receiving portion that is provided on an outer surface of the head and in which at least a part of the weight object is housed. The weight object or the weight object receiving portion includes a shape change mechanism that enables the weight object or the weight object receiving portion to change a shape of itself. The weight object receiving portion includes: a rotational force applying part that applies a rotational force on the weight object as a reaction generated when the weight object is pressed by the shape change; and a rotation prevention part that is located at a position abutting against the weight object when the rotational force is applied and that stops the weight object from being rotated by the rotational force and prevents rotation of the weight object.

Abstract: A golf club head includes: a head body that includes a cavity; a weight that is detachably attached to the cavity; and a cover that is openably and closably attached to the head body and that covers at least a part of the cavity when the cover is in a closed state. The weight is attached to the cavity in a state where the weight is slidingly movable in the cavity. In the closed state, the cover applies a pressing force to the weight. The weight may be fixed to the cavity by a static frictional force increased by the pressing force. The cavity may form a slide groove.

Abstract: A golf club head includes: a head body that includes a cavity; a weight that is detachably attached to the cavity; and a cover that is openably and closably attached to the head body and that covers at least a part of the cavity when the cover is in a closed state. The weight is attached to the cavity in a state where the weight is slidingly movable in the cavity. In the closed state, the cover applies a pressing force to the weight. The weight may be fixed to the cavity by a static frictional force increased by the pressing force. The cavity may form a slide groove.

Abstract: A golf club head includes a weight object and a weight object receiving portion that is provided on an outer surface of the head and in which at least a part of the weight object is housed. The weight object or the weight object receiving portion includes a shape change mechanism that enables the weight object or the weight object receiving portion to change a shape of itself. The weight object receiving portion includes: a rotational force applying part that applies a rotational force on the weight object as a reaction generated when the weight object is pressed by the shape change; and a rotation prevention part that is located at a position abutting against the weight object when the rotational force is applied and that stops the weight object from being rotated by the rotational force and prevents rotation of the weight object.

Abstract: A golf club includes a head, a shaft, and a grip. The head has a center-of-gravity depth of greater than or equal to 23.5 mm. The head has a center-of-gravity distance of less than or equal to 39 mm. The shaft has a forward flex of greater than or equal to 110 mm. When f1 denotes the forward flex of the shaft and f2 denotes a backward flex of the shaft, f2/f1 may be greater than or equal to 0.8 and less than or equal to 0.9. The head may have a volume of greater than or equal to 380 cc. The shaft may have a weight of less than or equal to 50 g.

Abstract: A golf club head includes a face portion including a striking face. The face portion includes a metal face portion made of a metal and a urethane layer member disposed outside the metal face portion and made of a polyurethane. A covered part, which is covered by the urethane layer member, of an outer surface of the metal face portion has a surface roughness of greater than 4.5 ?m when expressed by an arithmetic mean roughness Ra or has a surface roughness of greater than 25 ?m when expressed by a maximum peak-to-valley height Rz. In the golf club head, the surface roughness of the outer surface of the metal face portion may be greater than 4.5 ?m when expressed by the arithmetic mean roughness Ra and greater than 25 ?m when expressed by the maximum peak-to-valley height Rz.

Abstract: A golf club includes a head, a shaft, and a grip. The head has a center-of-gravity depth of greater than or equal to 23.5 mm. The head has a center-of-gravity distance of less than or equal to 39 mm. The shaft has a forward flex of greater than or equal to 110 mm. When f1 denotes the forward flex of the shaft and f2 denotes a backward flex of the shaft, f2/f1 may be greater than or equal to 0.8 and less than or equal to 0.9. The head may have a volume of greater than or equal to 380 cc. The shaft may have a weight of less than or equal to 50 g.

Abstract: A head includes a face portion, a crown portion, a sole portion, and a hosel portion. The crown portion includes a protruding portion on a crown outer surface. The protruding portion does not form any part of an outer contour line of the head in a front view of the head as viewed from a face side. The protruding portion forms an outer contour line of the head in a heel projection figure in which the head that is placed on a ground plane such that a shaft axis line is perpendicular to the ground plane and a face angle is 0° is viewed from a heel side along the ground plane. In this head, aerodynamic drag and lifting force at a position at which the shaft axis line becomes parallel to the ground plane during downswing can be increased. In this head, air resistance at impact can be suppressed.

Abstract: A state of a head placed such that its shaft axis is vertical to a horizontal plane and a face normal line is parallel to a perpendicular plane on which the shaft axis lies is defined as a 0-degree state. A direction parallel to the perpendicular plane and parallel to the horizontal plane is defined as a projection direction. A projected area of the head projected in the projection direction when the head is rotated by ?° about the shaft axis toward a back side from the 0-degree state is denoted by WA?. WA? is divided by the shaft axis into an area Af? and an area Ab?. Airflow causes a force acting on the area Af? in a face-closing direction and a force acting on the area Ab? in a face-opening direction. (Af90?Ab90) is ?4500 (mm2) or less. (Af15?Ab15) is 4700 (mm2) or less.

Abstract: A positive electrode mixture layer for a lithium-ion secondary battery suitable for producing a lithium-ion secondary battery with high rate characteristics at an ordinary temperature and low temperatures and low internal resistance (DCR) at low temperatures, characterized by including a positive electrode active material, a binder, and a conductive additive, in which the conductive additive includes carbon black, a carbon nanotube (1) having an average fiber diameter of 80 to 400 nm, and a carbon nanotube (2) having an average fiber diameter of 0.4 to 3.0 nm, the content rates of the carbon black, the carbon nanotube (1), and the carbon nanotube (2) in the conductive additive are 40 to 80% by mass, 10 to 50% by mass, and 1 to 30% by mass, respectively, and the content rate of the conductive additive in the positive electrode mixed layer is 0.1 to 5.0% by mass.

Abstract: A head includes a body member that has an opening, and a face member that includes a striking face and closes the opening. The face member includes a face portion that forms the striking face, and a peripheral portion that extends from a peripheral edge of the face portion toward a back side. The peripheral portion of the face member is welded to the body member. A weld bead that juts from the inner surface of the head is formed at a boundary position between the peripheral portion and the body member. A wall thickness at a face-side end point of the weld bead is greater than a wall thickness at a body-side end point of the weld bead. The peripheral portion has a length of less than or equal to 6 mm.

Abstract: A positive electrode mixture layer for a lithium-ion secondary battery suitable for producing a lithium-ion secondary battery with high rate characteristics at an ordinary temperature and low temperatures and low internal resistance (DCR) at low temperatures, characterized by including a positive electrode active material, a binder, and a conductive additive, in which the conductive additive includes carbon black, a carbon nanotube (1) having an average fiber diameter of 80 to 400 nm, and a carbon nanotube (2) having an average fiber diameter of 0.4 to 3.0 nm, the content rates of the carbon black, the carbon nanotube (1), and the carbon nanotube (2) in the conductive additive are 40 to 80% by mass, 10 to 50% by mass, and 1 to 30% by mass, respectively, and the content rate of the conductive additive in the positive electrode mixed layer is 0.1 to 5.0% by mass.

Abstract: A head includes a face portion, a sole portion, and an internal weight portion provided on an inner surface of the sole portion and located apart from the face portion. The internal weight portion includes a base portion, and a protruding portion protruding from the base portion toward a face side and located apart from the inner surface of the sole portion. The protruding portion is positioned on the face side with respect to the head center of gravity. A thickness of a toe-side part of the protruding portion and/or a thickness of a heel-side part of the protruding portion is greater than a thickness of a middle part of the protruding portion. Alternatively, a middle part of the protruding portion in a toe-heel direction is absent. The internal weight portion may be formed integrally with the sole portion, or may be a different member from the sole portion.

Abstract: A lithium ion battery lifetime prediction method executes, by a computer, acquiring training data including cycle measurement data and lifetime data of a battery, learning a lifetime prediction model using the training data with respect to one or more cycle numbers at which a prediction is made, to acquire a set of learned lifetime prediction models corresponding to the cycle numbers at which the prediction is made, respectively, successively acquiring cycle measurement data for prediction of a battery that is a prediction target, up to the cycle numbers at which the prediction is made, respectively, and inputting the cycle measurement data for prediction acquired up to the cycle numbers at which the prediction is made, to the learned lifetime prediction models of the corresponding cycle numbers at which the prediction is made, and acquiring a probability distribution of a lifetime at the cycle numbers at which the prediction is made, respectively, as an output.

Abstract: A golf club head includes a weight object and a weight object receiving portion that is provided on an outer surface of the head and in which at least a part of the weight object is housed. The weight object or the weight object receiving portion includes a shape change mechanism that enables the weight object or the weight object receiving portion to change a shape of itself. The weight object receiving portion includes: a rotational force applying part that applies a rotational force on the weight object as a reaction generated when the weight object is pressed by the shape change; and a rotation prevention part that is located at a position abutting against the weight object when the rotational force is applied and that stops the weight object from being rotated by the rotational force and prevents rotation of the weight object.

Abstract: A golf club head includes: a head body that includes a cavity; a weight that is detachably attached to the cavity; and a cover that is openably and closably attached to the head body and that covers at least a part of the cavity when the cover is in a closed state. The weight is attached to the cavity in a state where the weight is slidingly movable in the cavity. In the closed state, the cover applies a pressing force to the weight. The weight may be fixed to the cavity by a static frictional force increased by the pressing force. The cavity may form a slide groove.

Abstract: A golf club head includes: a head body that includes a cavity; a weight that is detachably attached to the cavity; and a cover that is openably and closably attached to the head body and that covers at least a part of the cavity when the cover is in a closed state. The weight is attached to the cavity in a state where the weight is slidingly movable in the cavity. In the closed state, the cover applies a pressing force to the weight. The weight may be fixed to the cavity by a static frictional force increased by the pressing force. The cavity may form a slide groove.

Abstract: A state of a golf club head placed such that a shaft axis line is vertical to a horizontal plane and a normal line is parallel to a first perpendicular plane on which the shaft axis line lies is defined as a 0-degree state. A direction parallel to the first perpendicular plane and parallel to the horizontal plane is defined as a projection direction. A projected area of the head projected in the projection direction when the head is rotated by ?°about the shaft axis line toward a back side from the 0-degree state is denoted by WA?. WA? is divided by the shaft axis line into a first region (having an area denoted by Af?) and a second region (having an area denoted by Ab?), and a difference (Af?-Ab?) is denoted by S?. S90 is -4500 (mm2) or less. S15 is 4700 (mm2) or less.

Abstract: A head includes a face portion, a sole portion, and an internal weight portion provided on an inner surface of the sole portion and located apart from the face portion. The internal weight portion includes a base portion, and a protruding portion protruding from the base portion toward a face side and located apart from the inner surface of the sole portion. The protruding portion is positioned on the face side with respect to the head center of gravity. A thickness of a toe-side part of the protruding portion and/or a thickness of a heel-side part of the protruding portion is greater than a thickness of a middle part of the protruding portion. Alternatively, a middle part of the protruding portion in a toe-heel direction is absent. The internal weight portion may be formed integrally with the sole portion, or may be a different member from the sole portion.