1,452 research outputs found
Performance Prediction of Two-Stepped Planing Hulls Using Morphing Mesh Approach
No full textChange in body shape characteristics is one of the ways to reduce the resistance and thereby increasing the speed of planing hulls. Creating the transverse steps is one of these variations. The main reason to use the steps in high-speed planing craft is that the wetted surface of the vessel is divided into small parts with higher width-length ratio in high velocities and in this situation, the generated lift force is more efficient. In this article, by performing a three-dimensional numerical solution, motion characteristics of a two-stepped planing hull with transverse steps in calm water have been examined. For this purpose, the vessel is free to trim and sinkage, and by using the morphing mesh approach, the numerical simulation continued until the equilibrium condition of the two-stepped planing hull is satisfied. Resistance, lift, trim angle, and wetted surface in various velocities have been computed and compared against existing experimental data. Analysis of considered two-stepped hull in calm water shows that the numerical solution for resistance, trim, and lift are relatively precise in comparison to model test data. Furthermore, various hull characteristics such as wetted length of keel, chine wetted length, spray angle and, ventilation length have been investigated.
1. Introduction
In recent years, naval architectures have proposed significant modifications in planing hulls' design by creating steps, tunnel, and other geometric features. By considering these geometric variations, the hull wetted surface and, consequently, its resistance have been reduced and planing hulls velocity can be increased. In this regard, the step is one of the main hull's modifications which can lead to resistance reduction. Generally, lift of stepped planing hulls is distributed over the forward, middle, and stern plane of the hull (Fig. 1), and therefore, its ride quality will also be improved. Moreover, planing hulls with various step configurations have been used in high-speed craft since 1910, and various types of step with different shapes and arrangements have been used in planing hulls.
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Marzieh Abbas: Cook Prize 2025, Silver Medal Acceptance Speech
No full textAuthor Marzieh Abbas gives an acceptance speech for Yasmeen Lari, Green Architect: The True Story of Pakistan’s First Woman Architect (Clarion)https://educate.bankstreet.edu/cook/1014/thumbnail.jp
A Theoretical Method to Explore the Influence of Free Roll Motion on the Behavior of a High-Speed Planing Vessel through a Steady Yawed Motion
No full textThis paper introduces a theoretically-based method to compute the behaviour of a planing hull in a steady yawed motion when it is free to roll. This method was developed by using 2D+T theory and the oblique-water entry of an asymmetric wedge. Sectional forces were determined using added mass theory. The forces and moments acting on the boat were computed by extending the sectional forces in the longitudinal direction. Trim angle and centre of gravity (CG) rise were found by solving the motion equations for the rigid body of the vessel. The results were compared against experimental data, and suggests that the current method has reasonable prediction accuracy for these parameters. Moreover, cases of free-to-roll and fixed-in-roll were determined and compared against each other, indicating that the trim angle of a boat is reduced, while CG rise increased in free roll
Calm-water performance of a boat with two swept steps at high-speeds: Laboratory measurements and mathematical modeling
No full textLaboratory measurements are performed to find the performance in calm water of a planing hull with two swept steps.
Furthermore, a mathematical model, based on the 2D+T theory, is adapted to provide a fast and accurate simulation for performance prediction of this craft. The trim angle of the vessel is seen to reach to two peaks, one in pre-planing and on in the early planing speed, then converges to a small value around 2 degrees. A small wetted area is seen to appear near the chine of the middle body of the vessel at early planing speed. Laboratory measurements and mathematical computations are seen to be in good agreement, especially at very high-speeds. Overall, the mathematical model is found to be a useful tool for performance prediction of boats with swept steps, which can have different, but better performance in comparison with stepless and boats with transverse steps
Introduction to the Special Issue on Decision Analysis and Social Media
No full textPublished as:
Ali E. Abbas, Jay Simon, Chris Smith (2017) Introduction to the Special Issue on Decision Analysis and Social Media. Decision
Analysis 14(4):227-228. https://doi.org/10.1287/deca.2017.036
Methodology matters ⋯ but so does interpretation!
No full text[No abstract available]Abbas O, 2009, BRIT J DERMATOL, V161, P228, DOI 10.1111-j.1365-2133.2009.09250.x; Abbas O, 2011, J EUR ACAD DERMATOL, V25, P311, DOI 10.1111-j.1468-3083.2010.03791.x; Amoh Y, 2005, P NATL ACAD SCI USA, V102, P17734, DOI 10.1073-pnas.0508440102; Amoh Y, 2005, P NATL ACAD SCI USA, V102, P5530, DOI 10.1073-pnas.0501263102; Amoh Y, 2004, P NATL ACAD SCI USA, V101, P13291, DOI 10.1073-pnas.0405250101; Amoh Y, 2011, EUR J DERMATOL, V21, P209, DOI 10.1684-ejd.2011.1306; Chiou SH, 2008, CLIN CANCER RES, V14, P4085, DOI 10.1158-1078-0432.CCR-07-4404; FIALKOW PJ, 1967, P NATL ACAD SCI USA, V58, P1468, DOI 10.1073-pnas.58.4.1468; HAMBURGER AW, 1977, SCIENCE, V197, P461, DOI 10.1126-science.560061; Hoang MP, 2009, BRIT J DERMATOL, V160, P609, DOI 10.1111-j.1365-2133.2008.09015.x; Kanoh M, 2008, EUR J DERMATOL, V18, P518, DOI 10.1684-ejd.2008.0485; Li LN, 2003, P NATL ACAD SCI USA, V100, P9958, DOI 10.1073-pnas.1733025100; Lim YC, 2011, ORAL ONCOL, V47, P83, DOI 10.1016-j.oraloncology.2010.11.011; Mahalingam M, 2010, AM J DERMATOPATH, V32, P774, DOI 10.1097-DAD.0b013e3181dafd8c; Mignone JL, 2007, CELL CYCLE, V6, P2161; Misago N, 2009, BRIT J DERMATOL, V160, P1128, DOI 10.1111-j.1365-2133.2009.09075.x; Reya T, 2001, NATURE, V414, P105, DOI 10.1038-35102167; Ryuge S, 2011, CHEST, V139, P862, DOI 10.1378-chest.10-1121; Sakuma H, 2009, J DERMATOL, V36, P453, DOI 10.1111-j.1346-8138.2009.00675.x; Sellheyer K, 2011, J CUTAN PATHOL, V38, P460, DOI 10.1111-j.1600-0560.2010.01671.x; Sellheyer K, 2010, J AM ACAD DERMATOL, V63, P93, DOI 10.1016-j.jaad.2009.07.013; Singh SK, 2004, ONCOGENE, V23, P7267, DOI 10.1038-sj.onc.1207946; Uchugonova A, 2011, J CELL BIOCHEM, V112, P2046, DOI 10.1002-jcb.23122; Wang JCY, 2005, TRENDS CELL BIOL, V15, P494, DOI 10.1016-j.tcb.2005.07.004; Wang Y, 2006, CELL BIOL INT, V30, P144, DOI 10.1016-j.cellbi.2005.09.0050
An attempt to predict planing hull motions using machine learning methods
No full textDesigning a high-speed craft for better seakeeping in waves can contribute significantly to higher safety and human comfort. Early in the design process, mathematical models such as the 2D+T method are commonly used, while high-fidelity computational fluid dynamics (CFD) and experimental models are used later in the process. Some of the limitations of such models are that they are not fast enough to be used in the ship's system for real-time monitoring or to develop a digital twin. Recently, machine learning methods have demonstrated great promise in building surrogate models from data. These methods include deep learning and recurrent neural network (RNN). In this paper, a systematic investigation of the network architectures and the used optimizers to train the network is presented. Adam, Adagrad, RMSprob and SGD are investigated in training the network. To train the model almost 35000 data points were collected for Fridsma hull operating in 18 regular waves using a 2D+T model. The result showed that gated recurrent unit (GRU) outperformed long short-term memory (LSTM) and RNN in predicting the heave motion. Also, one hidden layer with 5 neurons was enough to achieve mean absolute error of 0.000298 and to predict unseen waves when trained with more than 24000 data points.QC 20230811</p
Pemikiran Syekh Abbas Kutakarang tentang Hisab Penentuan Awal Bulan Hijriah
No full textPerkembangan keilmuan falak merupakan buah karya atas kembalinya para ulama ke Indonesia dari Makkah maupun Timur Tengah. Mulai saat itu lahir beberapa tokoh falak dengan karyanya dengan model perhitungan yang bermacam-macam dan terus berkembang hingga sekarang. Salah satu ulama Aceh yang masih dikenal adalah Syekh Abbas Kutakarang. Ia terkenal sebagai ahli astronomi maupun astrologi di dunia Melayu. Karya Syekh Abbas Kutakarang yang fenomenal adalah kitab Tāj al-Mulūk, di dalamnya terdapat konsep hisab urfi yang unik dan berbeda dengan hisab aboge dalam penentuan awal bulan Hijriah. Selama ini hisab urfi seperti aboge hanya dikenal di Jawa. Faktanya, Syekh Abbas Kutakarang juga menggunakan hisab seperti sistem aboge tetapi dengan konsep yang berbeda. Ia juga menggunakan kaidah ilmu falak tidak hanya untuk keperluan ibadah, melainkan untuk menghitung hari baik dan buruk, untuk pertanian dan menghitung musim. Berangkat dari hal tersebut, maka penulis ingin menelusuri bagaimana latar belakang, tipologi, dan kontribusi pemikiran Syekh Abbas Kutakarang tentang hisab penentuan awal bulan Hijriah.
Penelitian ini menggunakan historical approach. Penulis menggunakan penelitian jenis library research untuk mengumpulkan data tentang pemikiran Syekh Abbas Kutakarang dengan karyanya Tāj al-Mulūk yang terkait dengan hisab penentuan awal bulan Hijriah sebagai sumber primer. Dengan metode content analysis, penulis menganalisis pemikiran Syekh Abbas Kutakarang berdasarkan latar belakang internal dan eksternalnya. Metode komparasi penulis gunakan untuk membandingkan pemikiran Syekh Abbas Kutakarang tentang hisab penentuan awal bulan Hijriah dengan hisab urfi sistem aboge.
Pada masa Syekh Abbas Kutakarang, penggunaan ilmu falak umumnya bersifat fiqh oriented, akan tetapi Syekh Abbas Kutakarang mempunyai paradigma yang berbeda dalam penggunaan kaidah ilmu falak. Pemikirannya berakulturasi dengan kebudayaan masyarakat Aceh yang berkembang pada waktu itu, misalnya dalam hal penggunaan kaidah falakiyah untuk memprediksikan hari, bulan, dan jam yang baik dalam melaksanakan seluruh ritual kegiatan, baik yang berhubungan dengan ibadah dan kegiatan sehari-hari seperti bertani, dan menentukan hari pernikahan. Oleh karena itu, pemikiran Syekh Abbas Kutakarang dalam kajian ilmu falak tergolong dalam etnomatematik oriented yaitu kajian yang menghubungkan antara matematika dan budaya dalam penggunaan kaidah falak. Kajian falak dalam kitab Tāj al-Mulūk tergolong pada periode awal, di mana ilmu falak masih bercampur dengan ilmu lain, artinya ilmu falak belum berdiri sendiri sebagai suatu disiplin ilmu. Kontribusi pemikiran Syekh Abbas Kutakarang dalam penentuan awal bulan Hijriah berupa konsep yang berbeda yang dapat menambah kekayaan khazanah ilmu falak khususnya sistem hisab urfi. Secara umum kontribusi pemikiran Syekh Abbas Kutakarang terhadap kajian ilmu falak dalam definisi sains masih tergolong minim, karena dalam kitab Tāj al-Mulūk hanya terdapat kajian tentang penentuan awal bulan Hijriah. Meskipun pemikirannya tentang awal bulan Hijriah masih etnomatematik oriented, namun pemikiran Syekh Abbas Kutakarang merupakan embrio ilmu falak di Aceh. Kitab Taj al-Mulūk adalah arus penanda bagi perkembangan ilmu falak selanjutnya di Aceh.
ABSTRACK
The development of the Islamic astronomy is the work of the scholars return from Makkah to Indonesia and the Middle East. From that point were born some of the figures in his work with the model calculations diverse and continues to grow until now. One of which is still known scholars of Aceh was Shekh Abbas Kutakarang. He is the best known as an expert in the world of astronomy and astrology Malay. The work of Syekh Abbas is a phenomenal book Taj al-Mulūk, in which there is a unique concept of hisāb urfi different with hisāb aboge in the initial determination of the Hijri month. All the time, hisāb urfi like Aboge only known in Java. In fact, Syekh Abbas Kutakarang also use it but with a different concept. He also uses the rules of astronomy not only for worship, but to calculate the good and bad days, to agriculture and counting season. Departing from this, the authors wanted to explore how background, typology, and the contribution of Syekh Abbas Kutakarang thinking about computation preliminary determination Hijri month. This study uses a historical approach. The author uses research type of library research to collect data about the thought of Shaykh Abbas Kutakarang with his Taj al-Muluk. With content analysis, the authors analyzed the thought of Syekh Abbas Kutakarang based on internal and external background. Comparative method I use to compare Sheikh Abbas Kutakarang thinking about reckoning with the initial determination of the Hijri month of reckoning urfi Aboge system. This study produce that At the time of Syekh Abbas Kutakarang, the use of Islamic astronomy generally is oriented fiqh, but Syekh Abbas Kutakarang have a different paradigm in the use of the rules of Islamic astronomy. His thoughts acculturated with Acehnese culture that developed at that time. Therefore, Syekh Abbas Kutakarang thinking in the study of Islamic astronomy is classified to etnomatematik oriented. Syekh Abbas Kutakarang thoughtful contributions in the initial determination of a Hijri month is a different concept (the leap year lies in 2, 5 and 7) that can add to the legacy of Islamic astronomy in hisāb urfi
Effects of Vertical Motions on Roll of Planing Hulls
No full textRoll motion of a planing hull can be easily triggered at high speeds, causing a significant change in hydrodynamic pressure pattern, which can threaten the stability of the vessel. Modeling and investigating roll motion of a planing vessel may require a strong coupling between motions in vertical and transverse planes. In the present paper, we have used a mathematical model to analyze the roll of a planing hull by coupling surge, heave, pitch, and roll motions using 2D + T theory to study the effects of roll-induced vertical motions on roll coefficients and response. Mathematically computed forces and moments as well as roll dynamic response of the vessel are seen to be in fair quantitative agreement with experimentally measured values of previously published data. Using the 2D + T method, it has been shown that to model the roll of a planing hull at high speeds, we need to consider the effects of heave, pitch, and surge motions. Through our mathematical modeling, it is found that freedom in vertical motions increases time-dependent roll damping and added mass coefficients, especially at early planing speeds. The results of dynamic response simulations suggest that freedom in the vertical plane can decrease the roll response
Piezoelectric energy harvesting from roadway
No full textEnergy harvesting technologies have attracted much attention as an alternative power source of roadway accessories in different scales. Piezoelectric materials, which have been widely used in sensor technologies due to their cost-effectiveness, are capable of producing electrical energy from mechanical energy. Therefore, piezoelectric transducers can be designed to harvest the wasted mechanical energy generated under wheel loading that can be stored in an electronic capacitor or integrated with sensors for in-situ road condition monitoring. This dissertation aims to develop a novel design of a piezoelectric transducer with optimized geometry for energy harvesting under vehicular loading in the roadway. The novel Bridge transducer with layered poling is designed to increase the piezoelectric coefficient and the relative dielectric permittivity, which produces much higher energy than traditional transducers. Finite element analysis (FEA) was conducted to predict the generated energy output and the resulted mechanical stress in the lead zirconate titanate (PZT) transducer. The results of the optimization analysis indicate that the optimized geometry parameters can generate the maximum energy output within the stress failure criteria. Later, an energy harvester module that contains multiple stacked transducers, 64 novel transducers, was fabricated and tested under single pulse and cyclic loading events. The main objectives of this part were to evaluate the energy output and fatigue behavior of the piezoelectric energy harvester using laboratory testing and numerical simulation. The analysis results showed that two different material failure models need to be considered in relation to mechanical failure of the Bridge transducer, namely tensile and shear failure. This emphasizes that the optimum design of energy module should consider the balance of energy output and fatigue life that are affected by the fabrication of a single Bridge transducer and the packaging design of the energy module. To take into account the nature of the energy harvester-pavement interaction and to achieve better computation efficiency, the effect of this interaction on pavement responses was studied using a decoupled approach. First, a 3D pavement model was built, and then the pavement responses under the tire contact stresses were calculated. The effects of energy harvester-pavement interaction at different locations, horizontally and vertically, were also analyzed. The results show that the maximum power output of the energy harvester module is around 122mW at a vehicle speed of 65mph and 3 inches embedded depth. Furthermore, embedding the energy harvesting module below 3 inches from the pavement surface is the best location to maximize both power output and service life. Finally, to reveal the potentials of some important technologies for harvesting energy from a pavement network, a case study is discussed, which uses the New Jersey roadway network as the example for analysis. The potential of electrical energy generation for thermoelectric and piezoelectric (cymbal and novel bridge design) technologies were considered. Based on available energy harvesting technologies, a thermoelectric-based pipe system covering the entire New Jersey roadway network may potentially collect 20.11 GWh electrical energy per day, while a piezoelectric transducer system may collect around 3.74 and 10.01MWh of electrical energy per day for cymbal and novel bridge transducer designs, respectively.Ph.D.Includes bibliographical referencesby Abbas Fadhil Jasi
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