Judul: Identification of Work Posture and Musculoskeletal disorders (MSDs) Risk on Kopal Collecting Activities in Gunung Walat Educational  Forest
Abstrak: Kegiatan pengumpulan kopal di Indonesia dilakukan secara manual oleh para pekerja. Beban kerja yang ditanggung pekerja pada saat kegiatan pengumpulan kopal dapat menyebabkan risiko tinggi terjadinya musculoskeletal disorders (MSDs). Identifikasi postur kerja pada kegiatan ini dianalisis menggunakan analisis objektif Rapid Entire Body Assessment (REBA), Rapid Upper Limb Assessment (RULA) dan Range of Motion (ROM) serta analisis subjektif Quick Expossure Check (QEC) dan Standard Nordic Quetionnaire (SNQ). Kelimanya merupakan instrumen pendugaan risiko MSDs. Analisis objektif menunjukkan bahwa risiko paling tinggi pada kegiatan pengumpulan kopal adalah pada saat pekerja melakukan elemen kerja mengangkat getah. Analisis subjektif memberikan hasil bahwa keluhan paling banyak pada bagian tubuh pekerja dari yang paling terdampak, yaitu punggung, pergelangan tangan kanan dan pinggul. Komparasi dilakukan pada kedua analisis tersebut dan memberikan hasil korelasi yang valid. Penyebab utama dari risiko yang tinggi pada kegiatan pengumpulan kopal karena faktor postur tubuh yang janggal, bobot beban berlebih dan fasilitas alat yang kurang memadai., In Indonesia, employees collect copal manually. The workload that workers face during copal collection tasks can put them at an increased risk of developing musculoskeletal diseases (MSDs). The identification of working postures in these activities is analyzed objectively through the use of the Rapid Entire Body Assessment (REBA), the Rapid Upper Limb Assessment (RULA), and Range of Motion (ROM), as well as subjectively through the use of the Quick Exposure Check (QEC) and the Standard Nordic Questionnaire (SNQ). Each of these five instruments is used to calculate the probability of developing MSDs. According to objective analysis, the greatest risk associated with copal collection activities occurs when workers undertake labor aspects such as lifting kopal, which carries a very high risk of MSDs. Subjective research reveals that the most frequently reported problems are to the back, right wrist, and hip. The comparison of the two analyses yields valid correlation results. The primary reasons for the increased risk in the collection of copal activities are awkward posture elements, excessive load weight, and inadequate tool facilities.
Keyword: kopal, MSDs, postur kerja, Range of Motion, risiko

Judul: Penilaian Postur Kerja dan Risiko Musculoskeletal Disorders Menggunakan Analisis Biomekanik Pada Kegiatan Penyadapan Kopal di Hutan Pendidikan Gunung Walat
Abstrak: Penyadapan kopal adalah salah satu kegiatan pemanfaatan hasil hutan bukan kayu (HHBK). Kegiatan penyadapan kopal memiliki risiko yang membahayakan kesehatan dan keselamatan pekerjanya seperti Musculoskeletal Disorders (MSDs). Tujuan penelitian ini adalah mengidentifikasi level risiko postur kerja menggunakan Range of Motion (ROM), menghitung gaya tekan lumbal 5 dan sakrum 1 (L5/S1) menggunakan analisis biomekanik, dan memberikan rekomendasi perbaikan postur kerja yang sesuai. Postur tubuh pekerja dianalisis dengan ROM yang kemudian dilanjutkan dengan analisis biomekanik menggunakan software 3DSSPP (3D Static Strength Prediction Program) serta beberapa analisis objektif lainnya seperti OWAS (Ovaki Working Posture Analysis System) dan QEC (Quick Exposure Check). Analisis biomekanik menyajikan hasil berupa compression force, shear force, strength percent capable, dan standing balance. Metode analisis data dilakukan pada setia postur kerja yang dihasilkan dalam kegiatan. Hasil analisis menunjukkan bahwa segmen tubuh yang sangat berpengaruh terhadap risiko MSDs yang diterima oleh pekerja yaitu leher, punggung, pergelangan tangan, pinggul, dan lutut., Copal tapping is one of the non-timber forest product (NTFP) utilization activities. Copal tapping activities have risks that endanger the health and safety of their workers, such as Musculoskeletal Disorders (MSDs). The purpose of this study was to identify the level of risk of working posture using Range of Motion (ROM), calculate the compressive force of the 5th lumbar and sacrum 1 (L5/S1) using biomechanical analysis, and provide recommendations for improving the appropriate working posture. Workers' body postures were analyzed by ROM which was then followed by biomechanical analysis using 3DSSPP software (3D Static Strength Prediction Program) as well as several other objective analyzes such as OWAS (Ovaki Working Posture Analysis System) and QEC (Quick Exposure Check). Biomechanical analysis presents the results in the form of compression force, shear force, strength percent capable, and standing balance. The data analysis method is carried out on each work posture generated in the activity. The results of the analysis show that the body segments that greatly influence the risk of MSDs received by workers are the neck, back, wrists, hips, and knees.
Keyword: 3DSSPP, L5/S1, compression force, tapping, risk

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
Keyword: