David Siahaan
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The effect of geometric structure on stiffness and damping factor of wood applicable to machine tool structure Adi Widyanto, Susilo; Widodo, Achmad; Nugroho, Sri; Siahaan, David
International Journal of Science and Engineering (IJSE) Vol 4, No 2 (2013)
Publisher : Chemical Engineering Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (498.337 KB) | DOI: 10.12777/ijse.v4i2.4511

Abstract

Stiffness and vibration damping capability are important criteria in design of machine tool structure. In other sides, the weight of machine tool structure must be reduced to increase  the handling capability. This paper presents  an analysis of the effect of geometric structure on stiffness and vibration damping of wood structure.  The stiffness was analysed  using numerical method, so called finite element method (FEM), while the vibration damping capability was experimentally tested. Vibration testing was also performed to wood structures with sand powder filled  into  its rectangular hole to observe the its effect on damping factor. Simulation results show  that the cross ribs structure yielded minimum mass reduction ratio compared to the three square holes as well as the single rectangular hole structures. While the vibration test results explained that the damping factor of Shorea laevis wood was higher than that Hevea braziiensis wood. The use of sand powder as vibrating  mass in closed-box structure effectively increased the damping capability, for single rectangular hole structure the damping factor was increased from 0.048 to 0.079doi: http://dx.doi.org/10.12777/ijse.4.2.2013.57-60[How to cite the article: Widyanto, S. A., Widodo, A., Nugroho, S., & Siahaan, D. (2013). The effect of geometric structure on stiffness and damping factor of wood applicable to machine tool structure. INTERNATIONAL JOURNAL OF SCIENCE AND ENGINEERING, 4(2), 57-60. doi: http://dx.doi.org/10.12777/ijse.4.2.2013.57-60]
PENGARUH LATIHAN HORIZONTAL SWING DAN LATIHAN SIDE LATERAL RAISE TERHADAP KEMAMPUAN FOREHAND DRIVE DALAM PERMAINAN TENIS LAPANGAN Siahaan, David
JURNAL PRESTASI Vol 1, No 2 (2017): JURNAL PRESTASI
Publisher : JURNAL PRESTASI

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (168.84 KB)

Abstract

Tujuan penelitian  ini untuk mengetahui pengaruh dari latihan horizontal swing dan latihan side lateral raise untuk meningkatkan kemampuan forehand drive dalam permainan tennis lapangan. Metode yang digunakan dalam penelitian ini adalah quasi eksperiment design. Populasi dalam penelitian ini adalah siswa putra sekolah tenis Progress Unimed yang terdiri dari bebagai usia dengan rentang 11 tahun hingga 15 tahun dimana berjumlah sebanyak 9 orang. Populasi tersebut melakukan latihan tiga kali dalam satu minggu dan telah dapat melakukan teknik forehand drive dengan benar. Sampel penelitian sebanyak 8 orang yang diambil dengan teknik random sampling. Keseluruhan sampel dibagi menjadi dua kelompok dengan teknik matching and pairing. Satu kelompok diberikan latihan horizontal swing dan kelompok yang lain diberikan latihan side lateral raise. Teknik pengumpulan data dengan instrumen forehand drive hewitt tenis achievement test. Perlakuan dilaksanakan selama 18 kali pertemuan.  Untuk melihat pengaruh setiap variabel digunakan perhitungan statistiK uji- t berpasangan. Adapun hasil penelitian ini adalah : (1) Latihan horizontal swing secara signifikan dapat meningkatkan kemampuan forehand drive dalam permainan tennis lapangan. (2) Latihan side lateral raise secara signifikan dapat meningkatkan kemampuan forehand drive  dalam permainan tennis lapangan.  Kata Kunci : Latihan, Horizontal Swing, Side Lateral Raise, Forehand Drive, Tennis
UPAYA MENINGKATKAN KECEPATAN TENDANGAN MAEGERI CHUDAN MELALUI MODIFIKASI LATIHAN SQUAT JUMPS DAN LATIHAN SPLIT JUMPS PADA ATLET KARATE WADOKAI DOJO SMA NEGERI 11 MEDAN Purba, Pangondian Hotliber; Bangun, Sabaruddin Yunis; Siahaan, David
Journal Physical Education, Health and Recreation Vol 3, No 2 (2019): April
Publisher : Universitas Negeri Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24114/pjkr.v3i2.12724

Abstract

This study aims to increase the speed of the maegery chudan with modification of squat jumps and split jumps in karate. The subjects were Wadokai karateka in dojo SMA Negeri 11 Medan, They are totaling 10 athletes. The instrument is the speed test of maegery chudan and using a stopwatch. Based on the pre-test results it turns out that 10 athletes or overall Wadokai dojo karate athletes in Medan 11 High School have not reached the limit of achieving personal and group targets. Of the 10 athletes, there are no athletes who have achieved personal targets and group achievement limits of 0% with the average athlete's ability score of 76.14%.            The methodology used in this study is Class Action Research. The results of the first cycle after being given treatment in the form of modification of squat jumps and split jumps. Of the 10 athletes, there were 8 athletes (80%) who had reached the personal target limit, 2 athletes (20%) who had not reached the personal target limit and a group achievement limit of 80% with an average athlete's ability score of 82.41%. Based on the results of data analysis it can be said that through the application of modification exercises in squat jumps and split jumps training can increase the speed of the chudan kicks in the Wadokai dojo karate athletes in Medan 11 Public High School in 2018