Relationship between impact characteristics and launch direction in softball hitting: A study involving elite players

In the game of softball, the batter should possess the necessary skills to hit the ball toward various directions with high initial speed. However, because various factors influence each other, there are limitations to the range that can be controlled by the batter’s skill. This study was aimed at extracting the impact characteristics associated with the launch speed/direction and batted ball spin and clarifying the important skills required to improve the batter’s hitting performance. In our experiments, 20 female softball players, who are members of the Japan women’s national softball team, hit balls launched from a pitching machine. The movements of the ball and bat before, during, or after the impact were recorded using a motion capture system. Stepwise multiple regression analysis was performed to extract factors relating the side spin rate. The undercut angle (elevation angle between the bat’s trajectory and the common normal between the ball and bat: ΔR2 = 0.560) and the horizontal bat angle (azimuth of bat’s long axis at ball impact: ΔR2 = 0.299) were strongly associated with the side spin rate (total R2 = 0.893, p < 0.001). The undercut angle in opposite-field hitting was significantly larger than that in pull-side hitting (p < 0.001). The side spin rate was associated with the undercut angle because the bat’s distal (barrel) side inclined downward (–29.6 ± 8.7°) at impact. The ball exit velocity was higher when it was hit at a smaller undercut angle (R2 = 0.523, p < 0.001). Therefore, it is deemed desirable to focus on maximizing the ball exit velocity rather than ball spin because the ball–bat impact characteristics vary inevitably depending on the launch direction. Meanwhile, the use of the ball delivery machine and the slower pitched ball are the limiting factors in the generalization of the findings.

Control of Head Smear Generated From DLC Films Using an External Electric Field

In this study, the dependence of the electric field between the magnetic disk and Si wafer, used as the counter surface, on the hydrocarbon smear generated from the diamond-like carbon (DLC) overcoat was investigated. As a result, the positive electric field from the disk to the Si wafer increased the amount of smear, and the negative field reduced it. The positive electric field was estimated to extract hydrocarbon ions from the thermal plasma toward the Si wafer, and the opposite field attracts the hydrocarbon ions to the DLC surface. Therefore, the electric field between the slider and disk possibly controls the smear generation from the DLC overcoat, which is heated by laser irradiation in the heat-assisted magnetic recording).

Standard of the Initial Ball Velocity for a Fly Ball in Baseball Hitting

This study aimed to determine the minimum required initial velocity to hit a fly ball toward the same field (left-field for right-handed batters), center field, and opposite field (right field for right-handed batters). Six baseball players hit fastballs launched by a pitching machine. The movements of the balls before and after bat-to-ball impact were recorded using two high-speed video cameras. The flight distance was determined using a measuring tape. Seventy-nine trials were analyzed, and the minimum required initial velocities of batted balls were quantified to hit balls 60, 70, 80, 90, 100, 110, and 120 m in each direction through regression analysis. As a result, to hit a ball 120 m, initial velocities of 43.0, 43.9, and 46.0 m/s were required for the same field, center field, and opposite field, respectively. The result provides a useful index for batters to hit a fly ball in each of the directions.

PENGEMBANGAN VARIASI PENYERANGAN PERMAINAN BOLAVOLI PADA EKSTRAKURIKULER DI SMP NEGERI 17 MALANG

The purpose of the volleyball game is dropping the ball as fast as possible inthe opposite field passes over the net using the entire limb. This product is valid andpractical to be used for volleyball game attacks variation training in extracurricularactivities in SMPN 17 Malang. Based on the results of the needs analysis showed thatthe strategy of attacking done very lacking, extracurricular participants had never beentaught the material about attacking strategy in volleyball small group of test data obtained88.37% and the results of the data analysis of a large group trial gained an averagepercentage of 81.32 %. The result of the product development strategy of attacking gameof volleyball for participants extracurricular volleyball high school students first, amongothers: (1) the strategy of attacking volleyball in the manual according to the needs ofextracurricular participants junior high students, (2) to see the strategy of attacking gameof volleyball made with color image and there is information which explain attackingprocess variation from the current position to receive smash.Keywords: attacking variation, volleyball, developmentAbstrak: Tujuan dari permainan bolavoli adalah menjatuhkan bola secepat mungkin dilapangan lawan melewati atas net menggunakan seluruh anggota badan. Produk ini validdan praktis digunakan untuk latihan variasi penyerangan permainan bolavoli padakegiatan ekstrakurikuler di SMPN 17 Malang. Berdasarkan hasil analisis kebutuhandiperoleh bahwa strategi menyerang yang dilakukan sangat kurang sekali, pesertaekstrakurikuler belum pernah diajarkan materi strategi menyerang bolavoli data uji cobakelompok kecil diperoleh hasil 88,37% dan dari data analisis uji coba kelompok besardiperoleh rata-rata persentase 81,32%. Hasil produk pengembangan strategi menyerangpermainan bolavoli untuk perserta ekstrakurikuler bolavoli siswa menengah pertamaantara lain: (1) variasi menyerang bolavoli dalam buku panduan sesuai dengankebutuhan peserta ekstrakurikuler siswa menengah pertama, (2) tampilan strategimenyerang permainan bolavoli dibuat dengan gambar yang berwarna dan terdapatketerangan yang menejelaskan proses variasi serangan mulai dari posisi receive sampaisaat smash.Kata Kunci: variasi menyerang, bolavoli, pengembangan