Cold-water pipe (CWP) is a novel, most-challenging component of Ocean Thermal Energy Conversion (OTEC) floating structure which is installed to transport the deep seawater to the board. For ...commercial scale, the transported seawater flow rate will be in the order of 102 m3/s. This large amount of internal flow may trigger instability which leads to the failure of CWP. Considering this issue, the present paper aims to design commercial-scale OTEC CWP focusing on the effects of internal flow to the stability of the pipe. The design analysis is deliberated to select the pipe material, top joint configuration (fixed, flexible, pinned) and bottom supporting system (with and without clump weight). Initially, the analytical solution is built by taking into account the components of the pipe dynamics. Separately, a fully coupled fluid-structure interaction analysis between the pipe and the ambient fluid is carried out using ANSYS interface. Using scale models, the results obtained from the analytical solution are compared with the ones from numerical analysis to examine the feasibility of the analytical solution. After being verified, the analytical solution is used to observe the dynamic behavior of the CWP for 100 MW-net OTEC power plant in the full-scale model. The results yield conclusions that pinned connection at the top joint is preferable to decrease the applied stress, clump weight installation is necessary to reduce the motion displacement and Fiber Reinforced Plastic (FRP) is the most suitable material among the examined materials.
Introduction: Leptospirosis is a health problem in tropical countries where rats serve as the reservoir of Leptospira contamination. Previous investigations implementing the Bi-index to assess rat ...density in Leptospirosis endemic areas are highly limited. This study aimed to use the Bi-index in monitoring rat density and the associated factors in urban Leptospirosis endemic areas. Methods: Four endemic areas in Semarang City were selected as the study sites based on Leptospirosis data in Puskesmas Gayamsari. Live traps were positioned in one case house and 39-49 neighboring houses in a 100m radius, on three consecutive days. Trapped rats were collected for species identification, morphometrics evaluation, and calculation of Bi-index and rat indices, while environmental parameters were obtained through observation. Results and Discussion: 67.1% of participants were women, private employees, and aged 17-55, while trap success ranged from 2.5-26.5% with the Bi, diversity, dominance, and evenness indices of 0.02-0.32, 0.94-1.09, 0.36-0.44, and 0.79-0.96, respectively. Trapped species included Rattus norvegicus, Rattus tanezumi, and Mus musculus with proportions of 61.3%, 34.1%, and 4.7%, respectively. The presence of rats was associated with closeness to the river containing stagnant water, frequent flooding, water entering houses during floods, open trash bins, and rubbish bins around the houses. The high rat density, dominant species, and correlated environmental conditions are strategic targets in controlling Leptospirosis in Semarang City. Conclusion: The rat density (dominated by R. norvegicus) in Semarang City was correlated with water drainage and garbage management, hence further investigation was recommended to determine Leptospira bacterial infection in rodents.
This paper presents analytical and numerical analyses on self-induced vibration of Ocean Thermal Energy Conversion (OTEC) Cold Water Pipe (CWP) for a 100 MW-net OTEC power plant. The CWP is described ...as a vertically-hanged, top-tensioned riser subjected to internal flow effect (IFE) and ambient fluid effects (added mass and drag force). In the analytical analysis, two definitions of the drag force equation in the frequency-domain term and time-domain term are considered yielding a linear differential equation and a non-linear differential equation. The stability is assessed by discretizing the equations using Frobenius method and Galerkin Method and then plotting its eigenfrequencies or its eigenvalues in an Argand diagram. Separately, a fully-coupled fluid-structure interaction is carried out in a numerical simulation for particular cases. The scantlings of the riser are chosen from the available size of Fiber Reinforced Plastic (FRP) pipe in a manufacturer and varied accordingly for future production capacity development. The riser is pinned at the top and mounted at the bottom. Results indicate that the predicted critical velocity in the time domain is averagely 20% higher compared to the frequency domain. The effect of the clump weight on the critical velocity is more significant for light material compared with relatively high-density material.
This research aims to study the phenomenology of communication behavior of football supporters in giving support in Brebes Regency, Central Java, Indonesia. This research was also conducted using ...qualitative approach with phenomenology and ethnography design with critical ethnography type research. The sources of data were collected by research informants using Purposive Sampling and Snowball technique. Data collection technique was conducted by observation, interview, and documental study, data analysis was conducted inductively using interactive cycle by Miles and Huberman. The results show that the phenomenology of communication behavior of football supporters was influenced by identity, attributes, and action, as the forms of delivering messages with language and certain symbols. The messages proposed to football team which they supported and parties of their favourite football team. A verbal and non-verbal support for their favourite team that was given when it had a match in or outside the field was their way to communicate. Their messages were expected to be delivered and received by the team or other parties, so that there was a feedback for the messages.
Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce ...the capital cost, this paper introduces a concept design of the floating structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective floating structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.
The design of ship structural safety is crucial to ensure the ship’s survivability during the operation. Extensive research has been conducted on ship structural components, including box girders, ...stiffened panels, and plates, beyond the ideal conditions by considering the implication of manufacturing processes, vessel usage, and aging in the form of defects like cracks, corrosion, and imperfections, both locally and globally. Previous research has also explored various methodologies, conditions, and parameters to understand the impact of damages and imperfections on ship structure and strength. However, there is a significant need to bridge the gap in prior research to advance technology and ship structural strength analysis. A comprehensive benchmark study specifically focused on improving ship structural component needs, identifying differences and gaps among existing studies as challenging. This article thoroughly reviews ship structural components, such as box girders, stiffened panels, and plates, while examining the effects of structural defects like corrosion, cracks, and imperfections on ship structural integrity. It synthesizes the influence of various defect parameters, including crack length, angle, position, corrosion severity, pit corrosion, pit diameter, and pit models, using finite element modeling and experimental investigations, particularly emphasizing ship structural components. The comparative analysis of methods and parameters presented in this review will serve as a valuable reference for future investigations and studies related to ship structural strength and design. The article’s contribution is expected to enhance the understanding of ship structural strength, contributing to the sustainability and effectiveness of vessel design in the global maritime industry.
Fleas are hemophagous insects that spread the Yersinia pestis bacteria that causes bubonic plague through the bites of infected fleas. The purpose of this study was to determine the density, ...dominance, and infestation of larvae in several types of rodents and habitats in the Pes enzootic area. This research was conducted in May–June 2023 in Pasuruan Regency, East Java. The data analysis method used was descriptif. Samples of rat fleas were taken from rats captured in residential, garden, and forest habitats. The results showed that six species of small mammals were captured, namely, the Muridae family consisting of Niviventer fulvescens, Rattus exulans, Rattus tanezumi, and Rattus tiomanicus; the Erinaceidae family, namely Helomys suillus; and the Soricidae family, namely Suncus murinus, with the highest trap success in residential habitats by 10.9% and the highest density of rats in residential and garden habitats. The larval species obtained were Xenopsylla cheopis and Stivalius cognatus, with the highest flea infestation in the rat species Rattus exulans female (300%) and Rattus tanezumi female (64.2%).
A reliability-based approach is presented to investigate the effects of structural and load uncertainties on the reliability estimation of ship hull girders. Structural uncertainties included ...randomness in material properties, geometric properties, initial geometric imperfections, and corrosion behavior. Load uncertainties included statistical uncertainties, model uncertainties, environmental uncertainties, and uncertainties related to nonlinearity. The hull girder ultimate strength was calculated using Smith’s method, and the probabilistic density function was evaluated by employing Monte Carlo simulations. In the load estimation, the still water bending moment and wave-induced bending moment were calculated using a simplified formula of the International Association of Classification Societies-Common Structural Rules code and then modified with load parameters. The reliability index was estimated using a first-order reliability method considering the operating time, the duration of the ship in the alternate hold loading condition, and the severity of the corrosion rate. As a result, sagging conditions dominated the collapse mode. The reliability indexes were obtained for the observed cases, and the viability of the ship was assessed accordingly.
•The stiffening system of a seawater tank design in an OTEC facility is studied, including quantification of the applied parameters in the ultimate strength performance.•The non-linear finite element ...method (NLFEM) calculation is conducted by using ABAQUS through two dependent load steps.•The results show that at 0.16 MPa of applied pressure, the ultimate strength decreases by 4.1 MPa, or approximately 1.5%, for a span-over-bay ratio of 3.•The effect of the span-over-bay ratio on the ultimate strength is investigated, resulting in a more significant ultimate strength decrease at a higher span-over-bay ratio.•The sensitivity study is conducted to confirm the effect of the proposed parameters on the ultimate strength, for which it is found that the overall slenderness influences the ultimate strength reduction the most.
Ocean thermal energy conversion (OTEC) is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater. Due to the high static and dynamic pressures that are caused by seawater circulation, the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength. The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment. The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS. The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step, in which the axial compression was applied. The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels, and the significance of the stiffener parameters was assessed by using the sensitivity analysis method. As a result, the ultimate strength was reduced by approximately 1.5% for the span-over-bay ratio of 3 and by 7% for the span-over-bay ratio of 6.
Composites are becoming materials of the future. Composite applications have become popular in the air as airframes in the aerospace industry to the deepest seas in the form of underwater pipes. A ...sandwich structure is a composite with cores with low-density material pinned by a stiff facing. In this article, the sandwich material used is a Nomex-Aramid honeycomb as the core and carbon fiber composite as the facing sandwich structure. The main goal of this study is to obtain the characteristics of the sandwich structure, Nomex-Aramid carbon fiber, and study the effect of core variation on the overall strength of the sandwich structure. Numerical simulation testing was carried out to determine the characteristics of the sandwich structure. The loadings carried out were mainly three-point bending, tensile, compression, and torsional tests. In addition, this study also compared the geometry of cores and several materials to study the effect of core properties on the overall strength of the materials. The authors used the finite element method with ABAQUS. A mesh convergence study was also conducted in this article. The results of the numerical simulation showed that the structure sandwich had a major drawback in the local strength caused by the size of the cells used. In addition, the geometric shape and type of the core material also affected the strength of the sandwich structure.
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