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The Transverse Dynamic Stability of Hard-chine Planing Craft
Lewandowski, Edward-M. The Society of Naval Architects of Korea 1998 Journal of ship and ocean technology Vol.2 No.1
A method to predict the dynamic roll stability of hard-chine planing craft is presented. Starting with the equation of motion, an equation governing small roll perturbations is developed. The roll restoring moment acting on the hull is evaluated by considering “static”and dynamic contributions. The contribution of rudders and skegs, which is significant for this type of craft, is also determined. A worked example is presented to show how the method can be used to find the maximum center of gravity height for transverse stability.
Users' Understanding of Search Engine Advertisements
Lewandowski, Dirk Korea Institute of Science and Technology Informat 2017 Journal of Information Science Theory and Practice Vol.5 No.4
In this paper, a large-scale study on users' understanding of search-based advertising is presented. It is based on (1) a survey, (2) a task-based user study, and (3) an online experiment. Data were collected from 1,000 users representative of the German online population. Findings show that users generally lack an understanding of Google's business model and the workings of search-based advertising. 42% of users self-report that they either do not know that it is possible to pay Google for preferred listings for one's company on the SERPs or do not know how to distinguish between organic results and ads. In the task-based user study, we found that only 1.3 percent of participants were able to mark all areas correctly. 9.6 percent had all their identifications correct but did not mark all results they were required to mark. For none of the screenshots given were more than 35% of users able to mark all areas correctly. In the experiment, we found that users who are not able to distinguish between the two results types choose ads around twice as often as users who can recognize the ads. The implications are that models of search engine advertising and of information seeking need to be amended, and that there is a severe need for regulating search-based advertising.
Dynamic analysis of frames with viscoelastic dampers: a comparison of damper models
Lewandowski, R.,Bartkowiak, A.,Maciejewski, H. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.1
Frame structures with viscoelastic (VE) dampers mounted on them are considered in this paper. It is the aim of this paper to compare the dynamic characteristics of frame structures with VE dampers when the dampers are modelled by means of different models. The classical rheological models, the model with the fractional order derivative, and the complex modulus model are used. A relatively large structure with VE dampers is considered in order to make the results of comparison more representative. The formulae for dissipation energy are derived. The finite element method is used to derive the equations of motion of the structure with dampers and such equations are written in terms of both physical and state-space variables. The solution to motion equations in the frequency domain is given and the dynamic properties of the structure with VE dampers are determined as a solution to the appropriately defined eigenvalue problem. Several conclusions concerning the applicability of a family of models of VE dampers are formulated on the basis of results of an extensive numerical analysis.
Marek Lewandowski,Maria Bartoszewicz,Karolina Jaroszewska,Gérald Djéga-Mariadassou 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.116 No.-
This review gives a brief presentation of the types, structure, synthesis, and application of amorphoustransition metal borides (Mt-B) in particular the bulk or supported nickel and cobalt borides (NiB andCoB). Mt-B materials are amorphous metal-metalloid alloys and constitute an important group of catalyticsystems due to their special chemical and physical properties, including broad composition, structuralhomogeneity, and high concentration of coordination unsaturated sites. These features along withthe relatively cheap and simple methods of synthesis make them interesting alternative catalytic materialsfor numerous new, cost-effective, and environmentally sustainable yields and applications. Muchattention has been paid to Mt-B as an interesting alternative to the industrially applied catalysts basedon expensive and/or susceptible to sulphur poisoning, precious metals, and Raney nickel. Therefore, thisreview presents the application of Mt-B in different sectors: chemical production, energy storage/conversion,and environmental remediation. The current and future directions of research in this area areanalysed.
Dynamic analysis of frames with viscoelastic dampers: a comparison of damper models
R. Lewandowski,A. Bartkowiak,H. Maciejewski 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.1
Frame structures with viscoelastic (VE) dampers mounted on them are considered in this paper. It is the aim of this paper to compare the dynamic characteristics of frame structures with VE dampers when the dampers are modelled by means of different models. The classical rheological models,the model with the fractional order derivative, and the complex modulus model are used. A relatively large structure with VE dampers is considered in order to make the results of comparison more representative. The formulae for dissipation energy are derived. The finite element method is used to derive the equations of motion of the structure with dampers and such equations are written in terms of both physical and state-space variables. The solution to motion equations in the frequency domain is given and the dynamic properties of the structure with VE dampers are determined as a solution to the appropriately defined eigenvalue problem. Several conclusions concerning the applicability of a family of models of VE dampers are formulated on the basis of results of an extensive numerical analysis.
Parameters identification of fractional models of viscoelastic dampers and fluids
Roman Lewandowski,Mieczyslaw Slowik,Maciej Przychodzki 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.2
An identification method for determination of the parameters of the rheological models of dampers made of viscoelastic material is presented. The models have two, three or four parameters and the model equations of motion contain derivatives of the fractional order. The results of dynamical experiments are approximated using the trigonometric function in the first part of the procedure while the model parameters are determined as the solution to an appropriately defined optimization problem. The particle swarm optimization method is used to solve the optimization problem. The validity and effectiveness of the suggested identification method have been tested using artificial data and a set of real experimental data describing the dynamic behavior of damper and a fluid frequently used in dampers. The influence of a range of excitation frequencies used in experiments on results of identification is also discussed.
Rafał Janus,Mariusz Wa˛drzyk,Marek Lewandowski,Piotr Natka nski,Piotr Ła˛tka,Piotr Ku strowski 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.92 No.-
A series of mesoporous silicas with bimodal porosity combining the features of broad-mesoporousSBA-15 and narrow-mesoporous MCM-41 was synthesized by the pseudomorphic transformation ofSBA-15. The pore size of the MCM-41-like fraction was adjusted using different quaternary ammoniumsalts, while the degree of pseudomorphic transformation was tuned by the alkalinity of the mother-silicadissolving agent. The produced silicas were applied as hard templates for the synthesis of carbon replicasby nanocasting. The mechanism of pseudomorphic transformation of mesoporous silica was for thefirsttime investigated non-directly, employing the strategy of inverse carbon nanoreplication followed bycomprehensive study of the textural and structural parameters of replicas with regard to silica matrices. It was found that the conversion of SBA-15 into MCM-41 occurs simultaneously throughout the entireparticle’s body according to the mechanism of homogeneous pseudomorphic transformation. It wasevidenced that the strategy of inverse carbon replication could be successfully employed as an ingenioustool for non-direct investigation of suchlike silica transformations towards hierarchical porous systems. Furthermore, the unique bimodal mesoporosity of the carbons obtained from SBA-15 partiallytransformed into MCM-41 opens a possibility for their application in a variety of purposes, mainly incatalysis and adsorption.
해외저술 소개 : 임상 연구: 진단 ; 간세포암종 환자에서 경동맥 화학색전술 후 주 병변(primary index Lesion)의 영상학적 치료 반응 과 임상 경과(초)
( Ahsun Riaz ),( Frank H. Miller ),( Laura M. Kulik ),( Paul Nikolaidis ),( Vahid Yaghmai ),( Robert J. Lewandowski ),( Mary F. Mulcahy ),( Robert K. Ryu ),( Kent T. Sato ),( Ramona Gupta ),( Ed Wang 대한간암연구회 2010 대한간암학회지 Vol.10 No.-