A Viscous, Two-Layer Western Boundary Current Structure Function

The classic oceanographic problem of a 1.5-layer western boundary current evolving along a straight wall is considered. Here, building upon the previous work of Charney, Huang and Kamenkovich, we have derived, solved and validated a new numerical formulation for accounting for viscous effects in such systems. The numerical formulation is validated against rotating table experimental results.

Optimal and Robustly Optimal Consumption of Stretch Film Used for Wrapping Cylindrical Baled Silage

A conventional method for wrapping round bales of agricultural materials by wrappers with a rotating table or with rotating arms is considered. In contemporary agriculture, the demand for minimal consumption of the film used to wrap bales is very high, in order to apply this method with lower cost and less damage to the environment. A combined model-based problem of such a design, focusing on the width of stretch film and the overlap between adjacent film strips that minimizes film consumption, was mathematically formulated and solved. It was proven that the complete set of optimal film widths is defined by a simple algebraic equation described in terms of film, bale, and wrapping parameters. The optimal overlap ratios were found to be irreducible fractions in which the dividend is the divisor minus one; however, only the first three factions, 1 2 , 2 3 , and 3 4 , are practically significant. Next, the robustness to disturbances in the functioning of an actual bale wrapper, which leads to overlap ratio uncertainty, is examined. It was shown that, unfortunately, the optimal film widths applied together with the optimal overlaps do not provide any robustness to overlap variations. To overcome this inconvenience, the problems of a choice of the best commercially available film width guaranteeing minimal film consumption or maximal tolerance on the overlap uncertainty were formulated and solved. A new algorithm for a robust design of wrapping parameters was developed, motivated, and numerically verified to achieve a trade-off between satisfactory robustness and low film usage. For the resulting wrapping parameters, near-optimal film usage was achieved; the relative errors of the minimal film consumption approximation did not exceed 4%. It was proven that for the overlap, slightly more than 50%, i.e., 51% or 52%, provides both optimality and robustness of the overlap over disturbances, which are ensured regardless of the number of film layers. Moreover, it was found that for these overlaps and for the commercially available film widths selected according to the algorithm, the film consumption was more than twice as small than the film usage for exactly 50% overlap, if the actual overlap was smaller than pre-assumed. Similarly, an overlap of slightly more than the commonly used 67% will result in about 30% to 40% reduction in film usage in the presence of unfavorable disturbances, depending on the number of film layers and wrapping parameters.

PENILAIAN POSTUR OPERATOR DAN PERBAIKAN SISTEM KERJA DENGAN METODE RULA DAN REBA (STUDI KASUS)

Abstrak Penelitian ini bertujuan untuk mendapatkan nilai postur pekerja dan memberikan rekomendasi perbaikan sistem kerja pemasangan Extrude IE yang dilakukan secara manual. Penelitian dilakukan melalui tahapan sebagai berikut : 1) Mendokumentasikan postur operator yang dilakukan saat berkerja; 2) Mengetahui skor, level resiko dan level tindakan dengan metode RULA; 3) Mengetahui skor, level resiko dan level tindakan dengan metode REBA 4) Memberikan solusi terhadap resiko ergonomi pada pekerja. Hasil perhitungan RULA dan REBA masing-masing bernilai 7 dan 9. Artinya sistem kerja perlu mendapatkan penyesuaian untuk perbaikan. Adapun penyesuaian yang dilakukan adalah dengan menyesuaikan meja kerja dengan menambahkan alas meja yang dapat berputar. Selain perbaikan meja kerja, posisi operator harus dalam keadaan duduk dalam proses perakitan. Hasil perhitungan RULA dan REBA setelah simulasi meja kerja dengan alas meja berputar adalah 3 dan 5. Hasil rekomendasi sitem tersebut dapat meminimalisir cidera otot pada operator. AbstractThis study aims to obtain the value of worker posture and provide recommendations for repair work system installation of Extrude IE done manually. The research is done through the following stages: 1) Document the posture of the operator performed while working; 2) Knowing the score, level of risk and level of action with RULA method; 3) Knowing the score, the level of risk and the level of action with the REBA method 4) Provide solutions to the risk of ergonomics to workers. The results of RULA and REBA calculations are worth 7 and 9 respectively. This means that the work system needs to get adjustments for improvement. The adjustment is done by adjusting the work table by adding a rotating table mat. In addition to the repair workbench, the position of the operator must be in a sitting state in the assembly process. The results of RULA and REBA calculations after the simulation of the workbench with the rotating pads are 3 and 5. The result of the recommendation of the system can minimize muscle injury to the operator. Keywords: Posture; RULA; REBA; Work System

Vibration based condition monitoring of rotating machinery

This project looks at the different maintenance philosophies and the importance of vibration analysis in predictive maintenance. Since most industries and plants make use of rotational equipment, vibration analysis plays a major role in detecting machine defects and developing flaws before the equipment fails and potentially damages other related equipment and to avoid unwanted breakdowns and downtime. Vibration analysis can help increase the lifetime of equipment when the faults are diagnosed at the right time. Vibration analysis of a rotating table top model is also done to show that some faults might exist even though they are not visible to the naked eye.

Rotating panoramic view: interaction between visual and olfactory cues in ants

Insects use a navigational toolkit consisting of multiple strategies such as path integration, view-dependent recognition methods and olfactory cues. The question arises as to how directional cues afforded by a visual panorama combine with olfactory cues from a pheromone trail to guide ants towards their nest. We positioned a garden ant Lasius niger on a rotating table, whereon a segment of a pheromone trail relative to the stationary panorama was rotated while the ant walked along the trail towards its nest. The rotational speed of the table (3 r.p.m.) was set so that the table would rotate through about 90° by the time that an ant had walked from the start to the centre of the table. The ant completed a U-turn at about this point and so travelled in a nest-ward direction without leaving the trail. These results suggest that the ants persist on the pheromone trail and use visual input to determine their direction of travel along the trail.