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: Risk Assessment Musculoskeletal Disorders and Workload Recommendations with Biomechanical Approach of Copal Collection in Gunung Walat Educational Forest
Abstrak: Pengumpulan kopal merupakan salah satu kegiatan pemanfaatan hasil hutan bukan kayu (HHBK) yang berisiko menimbulkan gangguan keselamatan dan kesehatan kerja (K3). Kegiatan pengumpulan kopal mencakup berbagai kegiatan manual material handling (MMH) yang dapat menimbulkan musculoskeletal disorders (MSDs). Keluhan rasa sakit pada bagian tubuh pekerja dari yang paling terdampak, yaitu punggung, pergelangan tangan kanan, pinggul, bahu kanan, bahu kiri, dan pergelangan tangan kiri. Postur tubuh pekerja dianalisis dengan Range of Motion (ROM), kemudian dilanjutkan dengan analisis biomekanik menggunakan software 3 Dimension Static Strength Prediction Progam (3DSSPP). Analisis biomekanik menyajikan hasil compression force dan shear force pada lumbar ke-5 sacrum ke-1 (L5/S1), strength percent capable, dan standing balance. Postur kerja yang memiliki compression force >3400 N yaitu postur jongkok dan berdiri membungkuk pada elemen kerja mengangkat getah. Hasil Recommended Weight Limit (RWL) diperoleh sebesar 7,72 kg dan Lifting Index (LI) sebesar 2,59, yang artinya termasuk pekerjaan berisiko sedang., Copal colleting is one of the non-timber forest product (NTFP) utilization activities that has the risk of causing occupational safety and health (OSH) disturbances. Collecting copal include various manual material handling (MMH) activities that can cause musculoskeletal disorders (MSDs). Pain complaints against the body parts of the worker from the most affected such as the back, right wrist, hip, right shoulder, left shoulder, and left wrist. The body posture is analyzed with Range of Motion (ROM), then followed by biomechanical analysis with 3 Dimension Static Strength Prediction Progam (3DSSPP) software. The biomechanical analysis presents the results in compression force and shear force at 5th lumbar, 1st sacrum (L5/S1), strength percent capable, and standing balance. The working posture that has the highest compression force >3400 N is the squatting dan standing bent posture on the work element lifting latex. The Recommended Weight Limit (RWL) obtained 7.72 kg and the Lifting Index (LI) is 2.59, which means it is classified as a medium-risk job.
Keyword: biomekanik, L5/S1, MSDs, pengumpulan, RWL/LI

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.
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