Mitsui Engineering and Shipbuilding (Japan)

The application of sandwich plates in marine structures provides a lightweight yet strong alternative to conventional steel plates. This study investigates the extent to which stiffener spacing on barge decks can be increased when using 5–15–5 mm sandwich plates, without exceeding the allowable stress limit. The analysis was conducted using the finite element method (FEM) in ANSYS Student R2 2024. The stiffener spacing configurations examined were 610 mm (32 stiffeners), 762 mm (24 stiffeners), 1016 mm (16 stiffeners), 1524 mm (8 stiffeners), and a model without stiffeners. The simulation results indicate that all models with stiffeners, up to a spacing of 1524 mm, satisfy the allowable stress limit of 175 MPa specified by Lloyd’s Register. In contrast, the model without stiffeners exceeds this limit and is therefore considered unsafe. Deformation analysis further shows that the maximum deflection tends to occur on the port side, particularly in regions not supported by beams or girders. As the stiffener spacing increases, the magnitude of deformation also increases, and its location shifts due to edge effects and asymmetrical support conditions. In addition, the use of sandwich plates leads to a substantial reduction in structural weight compared with conventional steel construction, ranging from 23.13% to 32.83%, depending on the stiffener spacing. Based on these results, a stiffener spacing of up to 1524 mm is considered optimal for maintaining structural safety while achieving significant weight reduction.

Control systems are critical for managing, commanding, and regulating the behavior of dynamic systems. A DC motor converts direct current electrical energy into kinetic energy, requiring positive and negative voltage terminals for operation. Due to their ease of control across wide speed ranges, DC motors are widely applied in various industrial sectors. Speed regulation is typically achieved using control devices tailored to specific system requirements. To optimize DC motor performance, this study employs mathematical modeling and control strategies using MATLAB software. The 42D29Y401 DC motor is modeled and simulated using the Linear Quadratic Regulator (LQR) and Linear Quadratic Tracking (LQT) methods. Simulation results show that the first-order DC motor achieved a stable step response with an amplitude of 3.40, a rise time of 3.11 seconds, and minor overshoot and undershoot values of 0.501% and 1.98%, respectively. The LQR-optimized system improved performance with an amplitude close to 1, a faster rise time of 1.1 seconds, and reduced overshoot and undershoot at 0.505%. Comparatively, the LQR-based system demonstrated better overall performance than the unoptimized model, while the LQT-based system yielded the highest level of performance among all configurations.

Abstract No rules specifically stipulate the structural foundation of a ship’s main engine from the perspective of resonance vibration. Additionally, a main engine is usually set on a more rigid foundation on land in shop tests conducted by an engine manufacturer. This means that the soundness of the main engine onboard the ship relies on the shipyard accounting for the difference in stiffness of the foundation between land and ship. Furthermore, we would like to adopt a less rigid foundation to reduce the hull weight, so we needed to demonstrate the soundness of the less-rigid foundation. First, we validated a method of estimating the natural frequency of the H-mode vibration of the main engine by comparing the results of finite element analyses with excitation test results for a real ship with a rigid foundation. Second, we calculated the natural frequency for the less-rigid foundation and found that it was not appreciably different when top bracings were used. Third, we clarified quantitatively that the effect of the foundation was less than that of the top bracings on the H-mode vibration using a simple mathematical model. We can therefore adopt the less-rigid foundation for a new merchant ship with effective top bracings.

Sistem transportasi peti kemas bertujuan untuk memudahkan alih muat barang dengan menyederhanakan sistem bongkar muat sehingga efektif dan efisien. Untuk mengoperasikan kapal peti kemas, bahan bakar merupakan aspek penting yang membutuhkan biaya operasional pada kisaran 70% dari biaya operasional kapal. Oleh karena itu, perusahaan pelayaran seharusnya selalu memantau konsumsi muatan BBMdi kapalnya secara ketat agar tidak ada pemborosan konsumsi BBM. Dengan tidak menggunakan sistem pemantauan konsumsi muatan BBM yang bekerja secara otomatis mengakibatkan manajemen pelayaran tidak mengetahui secara pasti konsumsi bahan bakar kapal, sehingga memicu terjadinya kecurangan yang dilakukan awak kapal terhadap BBM. Untuk itu, dilakukan penelitian menggunakan sensor flowmeter yang menggunakan PLC sebagai monitoring data sensor flowmeter yang kemudian datanya akan dikirimkan kepada webserver yang dapat diakses oleh pihak yang bertugas. Dengan menggunakan system ini, monitoring penggunaan bahan bakar dapat diakses kapanpun. Berdasarkan hasil pengujian pembacaan sensor flowmeter melalui outseal PLC didapatkan presentase error yaitu 1,23%; 2,07%, dan 2,06%. Oleh karena itu, dapat disimpulkan bahwa sensor flowemeter dapat digunakan sebagai monitoring bahan bakar Auxiliary Engine berbasis Outseal PLC dengan rentan waktu perliternya yaitu selama 1 menit 58 detik.

The presence of sulphur in marine fuel oil relates to health and environmental concerns, as the respective combustion generates sulphur dioxide (SO2). The only method to control this SO2 generation is to limit the quantity of sulphur in the fuel. Shipping activities, although not the main source, contribute around 13% of the total anthropogenic SO2 IMO-3GHG [2015. Third IMO Greenhouse Gas Study, 3rd ed. London: International Maritime Organisation]; on a positive note, this is expected to reduce after the worldwide implementation of 0.5% sulphur regulation for marine fuel. One of the accepted methods to comply with the regulatory criteria is the use of alternate fuel, i.e. liquefied natural gas (LNG). The analysis in hand discusses the potential benefits of LNG as a marine fuel. The technical limitation associated with the formation of sulphuric acid (H2SO4) is directly related to its Dew point, as it condenses below 160°C and causes acidic corrosion of machinery components. The prevalent combustion-based systems are maintaining a safe and economical exhaust gas range between 150°C and 170°C. If the exhaust gas temperature is higher than 170°C excessive heat is lost, which makes the plant inefficient; in contrast, if the temperature drops below 150°C there is the possibility of corrosion damage to the equipment. Considering that LNG is absolutely free from sulphur contamination, it can be used to overcome this technical limitation and add to the overall thermal efficiency due to the availability of increased operating range.

Recently, the development of computational fluid dynamics (CFD) has made it easy to obtain a detailed pressure distribution around the hull. However, it is difficult to confirm such outcome experimentally because it requires much labor and cost for measurement. In order to overcome such a situation, this paper proposes an FBG (Fiber Bragg Gratings) pressure sensor that can measure the surface pressure of multiple points at low cost and with high efficiency. First, calibration test of the developed FBG pressure sensor PS-1000 was conducted to grasp the basic performance. Next, the surface pressure of the model ship was measured, and compared with the measurement result by the conventional method and the calculation result by the CFD. As a result, it was shown that PS-1000 can measure the hull surface pressure with low cost, high efficiency and high accuracy. In order to solve the problem revealed in PS-1000, the improved sensor PS-1000-v3 was manufactured and it was confirmed that the stability of the measured value is improved. Finally, PS-1000-v3 was used to measure the hull surface pressure with and without energy saving device, and it was shown that the hull surface pressure measurement is effective for the development of high performance hull.

Abstract The structural rules of classification societies typically specify various loads corresponding to the most severe sea states which are expected to be encountered by a ship throughout her service life in order to ensure ship structural safety, and these rules also usually define a variety of simplified formulae to aid in the calculation of such loads. In most cases, such formulae have been developed using linear seakeeping codes and linear statistical predictions; such methods, however, do not typically take into account some complex phenomena due to theoretical and methodological limitations. For this reason, the use of values obtained through linear theory alone is often not sufficient to properly evaluate structural strength, and it is, therefore, necessary to consider other things such as non-linear effects and operational effects. Although the structural rules of classification societies normally take into account such effects, most of them generally treat such things simply as either a constant coefficient or as an implicit condition because of the difficulty of expressing such effects mathematically (i.e. as specific formulae) as well as a general lack of prior research related to such effects. In this paper, the authors present the results of tank tests and numerical calculations carried out in regular and irregular waves using a bulk carrier, a container carrier and a vehicles carrier, and discuss possible ways of improving the non-linear coefficients specified in the IACS Common Structural Rules (CSR) [1]. Load states, including their non-linear effects, were investigated by examining the behavior of ship motions and hydrodynamic pressure. In order to investigate the behavior of pressure in detail, the pressure acting upon the hull surfaces of the target ships was measured at over 300 locations using a FBG sensor, the latest in optical fiber sensor technology [2].

According with the exponential growth of Information Technology and current volatility world, the company has to drive uncertainty much rather than before. This is the time that keeping still shall result in termination of company. Therefore it is important to clarify the priority evaluation measure for continuing company operation, which we will define the vital power scale in this paper. Focusing working capital (Cash enable company to do legal payment to any stakeholders), which is essential to maintain company operation, evaluation measure for vital power of company (major measurable factor to evaluate working capital or practical measurable index for corporate management, corporate management is to enable to keep company alive) has been studied with TOC (Theory of constraints). Investigation has been done by using dice simulation having assumption of linkage and fluctuation in system, which is introduced by TOC, under the variable market price and varying company productivity.