Naik Muhammad - Academia.edu (original) (raw)

Papers by Naik Muhammad

Applied Ocean Research

Abstract Offshore floating wind turbines are widely recognized as promising renewable energy devi... more Abstract Offshore floating wind turbines are widely recognized as promising renewable energy devices capable of harnessing wind energy in deep water. In addition to mooring lines, hydrostatic stiffness of the floating platform plays a key role in the stability of the offshore floating wind turbine. Apart from the geometry of platform, hydrostatic stiffness depends on its degrees of freedom. Therefore, it changes with motions of floating wind turbine and should be computed instantaneously. However, it is common practice to neglect the platform degrees of freedom and use linear hydrostatic stiffness in floating wind turbines analysis. Linear hydrostatic stiffness neglects the platform's motion and is computed at its undisplaced position. These shortcomings of linear hydrostatic stiffness can significantly influence the dynamic response of floating wind turbine. In the current study, a nonlinear hydrostatic stiffness with the purpose of its use in the analysis of offshore floating wind turbines is presented. The presented nonlinear hydrostatic stiffness uses the instantaneous position of floating platform and takes into account platform degrees of freedom. The effect of nonlinear hydrostatic stiffness is demonstrated through analysis of three leading types of floating wind turbines. The results show influence of hydrostatic nonlinearity on dynamic responses of floating wind turbines.

Journal of Medical Sciences, Apr 21, 2020

The booming demand for wind energy has pushed the offshore wind turbine into much deeper water. A... more The booming demand for wind energy has pushed the offshore wind turbine into much deeper water. At water depth greater than 60 m the floating wind turbines are considered to be the most economical and feasible alternative to that of the fixed supported offshore wind turbines. The stability of floating platform is one of the major challenges and is primarily achieved through mooring lines and hydrostatic buoyancy of the platform. Based on the assumption of the small displacement of the platform, in most of the studies, the hydrostatic stiffness is considered to vary linearly with the platform position. The present study is focused on the effect of nonlinear hydrostatic stiffness on the response of floating wind turbine. The floating wind turbine is modeled as a multi-body system and the equation of motion is obtained from the principle of conservation of momentum. The effect of hydrostatic nonlinearity is demonstrated through the analysis of OC3-Hywind floating wind turbine model. In...

World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 2017

Objectives: To compare efficacy of mometasone furoate topical intranasal therapy alone and combin... more Objectives: To compare efficacy of mometasone furoate topical intranasal therapy alone and combination of oral anti-histamine and anti-leukotriene therapy in seasonal allergic rhinitis. Methods: A randomized control trial at Department of Otorhinolaryngology, Head and Neck surgery, Pakistan Institute of Medical Sciences, Islamabad, and Khyber Teaching Hospital, Peshawar-Pakistan, was done in 1 year, from 25th Oct 2016 to 24th Oct 2017. A total of 146 patients were selected and divided into group A & group B (each group have 73 patients). The treatment given was topical Steroid (Mometasone) to Group A and oral antihistamine (loratadine 10mg), antileukotriene (Montelukast 10mg) to Group B. All patients who were included in our study were examined on three consecutive occasions, i.e. at zero presentation day, at 2 weeks and 4 weeks. Patient nasal symptom score was recorded and improvement noticed. Results: All146 patients were selected and were divided into two groups with each group c...

Journal of Applied and Emerging Sciences, 2019

Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to t... more Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to the classical solutions such as cable supported bridge, immersed tunnel or underground tunnel. An SFT is subjected to extreme waves, currents, earthquakes and other environmental loadings. The effect of key structural and waves parameters are important from the design perspective for an SFT. This study, the dynamic responses of SFT are evaluated using truss and catenary cables to check the effect of cable stiffness. The second part of this study deals with the effect of wave height and wave period on the dynamic responses of SFT. 3D truss and 3D catenary cables give very similar dynamic responses under waves and vertical ground motions. The wave height and wave period mainly control the dynamic behavior of SFT.

Submerged floating tunnel (SFT) is a new solution for the transportation infrastructure through s... more Submerged floating tunnel (SFT) is a new solution for the transportation infrastructure through sea straits, fjords, and inland waters and can be a good alternative to long span suspension bridges and immersed tunnels. The mooring cables/anchors are main structural components to provide restoring capacity to the SFT. The time domain dynamic problem of SFT moored by vertical and inclined mooring cables/anchors is formulated. The dynamic analysis of SFT subjected to hydrodynamic and seismic excitations is performed. As the cable stiffness determines the deformation ability of SFT, therefore it becomes crucial to evaluate the effect of mooring cable stiffness on the response of SFT. The displacements and internal forces of SFT clearly specify that the vertical/tension leg mooring cables provide very small stiffness as compared to inclined mooring cables. In order to keep the SFT displacements within an acceptable limit, the effect of cable stiffness should be properly evaluated for pra...

Journal of Applied and Emerging Sciences, 2020

Cable stayed bridges are most widely used in the modern medium to long bridge construction due to... more Cable stayed bridges are most widely used in the modern medium to long bridge construction due to their efficient response, economic viability, faster construction, and eye-catching aesthetics. The dynamic response of a single tower cable stayed bridge is studied by performing both nonlinear static and dynamic analyses using finite element method based software ANSYS. A three dimensional bridge model was developed using ANSYS. The steel cables were simulated using a single element approach to minimize the time and data use. Due to the complexity of cable stayed bridges, it is tried to avoid the convergence problems by adopting the displacement convergence approach. The bridge exhibits complex modal shapes due to the coupling effects for the free vibrations. The response of the bridge in vertical direction is more elastic and flexible as compared to the longitudinal and transverse direction. Response of the critical sections of girder, tower, and cables was also studied by time-history analysis using the ground acceleration data of the EI-Centro 1940 earthquake. A 10 second ground data with 0.0001 second time step was used. It was observed that stiffness in the vertical direction is a key player in the dynamic behavior of the cable stayed bridge. The response of the right and left span is similar which adds to the accuracy of the analysis. Time history analysis of the bridge shows that the largest displacements or peak responses are not related to the peak ground accelerations, rather they are dependent on many other factors like bridge stiffness, nature of the earthquake ground excitations and mass distribution. However, the results show the general trend of cable stayed bridges.

MATEC Web of Conferences, 2017

Mooring line is a major source of stability and plays a key role in the global response of offsho... more Mooring line is a major source of stability and plays a key role in the global response of offshore floating wind turbine. In the current state of the research, a formulation based on the analytical catenary equation is most commonly used for the analysis of mooring lines. However, due to the inability of catenary equations to consider the ocean current drag forces on mooring lines, the effect of drag forces on fairlead restoring forces has not been investigated yet. In this study, we have investigated the influence of drag forces on fairlead forces using discrete catenary formulation for modeling mooring line. The discrete catenary formulation has the ability to incorporate ocean current drag forces. Three types of elements; fully suspended, touchdown and seabed element are formulated to model the suspended, touchdown and seabed portion of a slack mooring line, respectively. The influence of viscous drag on the fairlead restoring forces is demonstrated through the analysis of OC3-Hywind mooring system subjected to ocean currents. It was found that the viscous drag significantly influences the fairlead forces.

Journal of Applied and Emerging Sciences, 2020

The accumulated stress based porewater pressure (PWP) generation model is a simplified model usin... more The accumulated stress based porewater pressure (PWP) generation model is a simplified model using the concept of damage parameter. The only input of this PWP model is liquefaction resistance curve (CRR-N). The model is very useful since the CSR-N curves can be developed empirically from in-situ penetration tests measurements. In this research work the estimation of excess PWP development during seismic loading by using stress based PWP generation model is compared with a rigorous plasticity model. One dimensional (1D) effective stress nonlinear site response analyses were conducted in DEEPSOIL and Opensees using the stress based PWP model and PressureDependentMultiYield02 (PDMY2) model, respectively. The site response analysis were performed on a sand column 30 m in depth comprises of a low density liquefiable layer in between two dense non-liquefiable layers. Three bed rock outcropping motions with peak ground acceleration (PGA) level of 0.11 g, 0.124 g and 0.357 g were used as in...

Oceanography & Fisheries Open access Journal, 2019

Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings and a... more Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings and are more economical compared to the conventional structures such as cable-supported bridges, underground tunnels or immersed tunnels. The dynamic behaviors of SFT under real train loads is the primary design requirement of an SFT, However, it is not investigated using realistic train models. In this study, the China-star high-speed train is used to evaluate the dynamic displacements, internal forces and cable tensions of SFT. The tunnel is modeled by FEM, the cables are modeled by elastic catenary cables, and ocean waves and currents are modeled by Airy's wave theory. The SFT displacements, bending moments and cable tensions were significantly influenced by moving trains. The SFT experienced extreme vertical displacements and there was a large drop in the minimum cable tensions. The mooring cables were slacked both by magnitudes and speed of the moving trains, which should be avoided for the safety of SFT. This study recommends the additional buoyancies for the stability of SFT subjected to high speed trains.

International Journal of Steel Structures, 2018

An effective numerical method is proposed for the three-dimensional nonlinear analysis of mooring... more An effective numerical method is proposed for the three-dimensional nonlinear analysis of mooring cables using catenary theory. In this method, the mooring line is divided into finite number of catenary elements. In addition to self-weight, each catenary element is subjected to drag force due to steady ocean currents. The proposed procedure is validated by comparing the results with those of the shooting optimization and the finite element methods. Finally, a parametric study is conducted to study the effect of extensibility on the static response of mooring cables. The effects of fluid drag forces and cable extensibility on mooring cable tension, equilibrium configurations, and stressed lengths are illustrated for two-and three-dimensional mooring cable problems. From the numerical results, the method is found to be numerically stable, and it provides a more rational static response for mooring cables.

Ocean Engineering, 2019

The hydrostatic forces of a floating platform play an important role in the stability and dynamic... more The hydrostatic forces of a floating platform play an important role in the stability and dynamic behavior of floating wind turbines. Hydrostatic forces are most commonly obtained from a linear hydrostatic stiffness matrix. Linear hydrostatic stiffness is based on the initial position of the floating platform and thus neglects the rotational motion of the floating wind turbine. In this article, the nonlinear hydrostatic stiffness of a floating spar platform was analytically derived with the aim of studying the effect of hydrostatic nonlinearity on the dynamic response. The floating wind turbine was modeled as a multibody system for which the equation of motion was obtained by using the Newton-Euler approach. The mooring lines connected to the floating wind turbine were modeled quasi-statically using catenary equations. A sensitivity analysis based on the comparison of linear and nonlinear hydrostatic forces was conducted to quantitatively evaluate the importance of hydrostatic nonlinearity. The effect of hydrostatic nonlinearity on the response of the floating wind turbine was investigated through analysis of the OC3-Hywind wind turbine in extreme environmental conditions. Results showed that in the case of large amplitude rotations, the use of nonlinear hydrostatic stiffness predicted the response with improved accuracy by accounting for rotational motion.

Applied Sciences, 2017

Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings, such... more Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings, such as sea-straits, fjords and lakes. As the width and depth of straits increase, the conventional structures such as cable-supported bridges, underground tunnels or immersed tunnels become uneconomical alternatives. For the realization of SFT, the structural response under extreme environmental conditions needs to be evaluated properly. This study evaluates the displacements and internal forces of SFT under hydrodynamic and three-dimensional seismic excitations to check the global performance of an SFT in order to conclude on the optimum design. The formulations incorporate modeling of ocean waves, currents and mooring cables. The SFT responses were evaluated using three different mooring cable arrangements to determine the stability of the mooring configuration, and the most promising configuration was then used for further investigations. A comparison of static, hydrodynamic and seismic response envelope curves of the SFT is provided to determine the dominant structural response. The study produces useful conclusions regarding the structural behavior of the SFT using a three-dimensional numerical model.

Doboku Gakkai Ronbunshu, 1997

Abstract Today's advanced muscular sensing and processing technologi... more Abstract Today's advanced muscular sensing and processing technologies have made the acquisition of electromyography (EMG) signal which is valuable. EMG signal is the measurement of electrical potentials generated by muscle cells which is an indicator of muscle activity. Other than rehabilitation engineering and clinical applications, EMG signals can also be employed in the field of human computer interaction (HCI) system. In this work, the detection of different hand movements (left, right, up and down) was obtained using ...

Journal of the American Association for Laboratory Animal Science : JAALAS, 2012

Ulcerative dermatitis (UD) is a common, spontaneous condition in mice with a C57BL/6 background. ... more Ulcerative dermatitis (UD) is a common, spontaneous condition in mice with a C57BL/6 background. Although initial lesions may be mild, UD is a progressive disease that often results in ulcerations or debilitating fibrotic contractures. In addition, lesions typically are unresponsive to treatment. Euthanasia is often warranted in severe cases, thereby affecting study outcomes through the loss of research subjects. Because the clinical assessment of UD can be subjective, a quantitative scoring method and documentation of the likely time-frame of progression may be helpful in predicting when animals that develop dermatitis should be removed from a study. Such a system may also be helpful in quantitatively assessing success of various treatment strategies and be valuable to clinical laboratory animal veterinarians. In this 1.5-y, prospective cohort study, we followed 200 mice to monitor the development and course of UD. Mice were examined every 2 wk. A clinical sign (alopecia, pruritus,...

Biological Trace Element Research, 2011

The purpose of this study was to assess insoluble salts containing gadolinium (Gd 3+) for effects... more The purpose of this study was to assess insoluble salts containing gadolinium (Gd 3+) for effects on human dermal fibroblasts. Responses to insoluble Gd 3+ salts were compared to responses seen with Gd 3+ solubilized with organic chelators, as in the Gd 3+-based contrast agents (GBCAs) used for magnetic resonance imaging. Insoluble particles of either Gd 3+-phosphate or Gd 3+-carbonate rapidly attached to the fibroblast cell surface and stimulated proliferation. Growth was observed at Gd 3+ concentrations between 12.5 and 125 μM, with toxicity at higher concentrations. Such a narrow window did not characterize GBCA stimulation. Proliferation induced by insoluble Gd 3+ salts was inhibited in the presence of antagonists of mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways (similar to chelated Gd 3+) but was not blocked by an antibody to the platelet-derived growth factor receptor (different from chelated-Gd 3+). Finally, high concentrations of the insoluble Gd 3+ salts failed to prevent fibroblast lysis under low-Ca 2+ conditions while similar concentrations of chelated-Gd 3+ were effective. In conclusion, while insoluble Gd 3+ salts are capable of stimulating fibroblast proliferation, one should be cautious in assuming that GBCA dechelation must occur in vivo to produce the profibrotic changes seen in association with GBCA exposure in the subset of renal failure patients that develop nephrogenic systemic fibrosis.

Applied Ocean Research

Abstract Offshore floating wind turbines are widely recognized as promising renewable energy devi... more Abstract Offshore floating wind turbines are widely recognized as promising renewable energy devices capable of harnessing wind energy in deep water. In addition to mooring lines, hydrostatic stiffness of the floating platform plays a key role in the stability of the offshore floating wind turbine. Apart from the geometry of platform, hydrostatic stiffness depends on its degrees of freedom. Therefore, it changes with motions of floating wind turbine and should be computed instantaneously. However, it is common practice to neglect the platform degrees of freedom and use linear hydrostatic stiffness in floating wind turbines analysis. Linear hydrostatic stiffness neglects the platform's motion and is computed at its undisplaced position. These shortcomings of linear hydrostatic stiffness can significantly influence the dynamic response of floating wind turbine. In the current study, a nonlinear hydrostatic stiffness with the purpose of its use in the analysis of offshore floating wind turbines is presented. The presented nonlinear hydrostatic stiffness uses the instantaneous position of floating platform and takes into account platform degrees of freedom. The effect of nonlinear hydrostatic stiffness is demonstrated through analysis of three leading types of floating wind turbines. The results show influence of hydrostatic nonlinearity on dynamic responses of floating wind turbines.

Journal of Medical Sciences, Apr 21, 2020

The booming demand for wind energy has pushed the offshore wind turbine into much deeper water. A... more The booming demand for wind energy has pushed the offshore wind turbine into much deeper water. At water depth greater than 60 m the floating wind turbines are considered to be the most economical and feasible alternative to that of the fixed supported offshore wind turbines. The stability of floating platform is one of the major challenges and is primarily achieved through mooring lines and hydrostatic buoyancy of the platform. Based on the assumption of the small displacement of the platform, in most of the studies, the hydrostatic stiffness is considered to vary linearly with the platform position. The present study is focused on the effect of nonlinear hydrostatic stiffness on the response of floating wind turbine. The floating wind turbine is modeled as a multi-body system and the equation of motion is obtained from the principle of conservation of momentum. The effect of hydrostatic nonlinearity is demonstrated through the analysis of OC3-Hywind floating wind turbine model. In...

World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 2017

Objectives: To compare efficacy of mometasone furoate topical intranasal therapy alone and combin... more Objectives: To compare efficacy of mometasone furoate topical intranasal therapy alone and combination of oral anti-histamine and anti-leukotriene therapy in seasonal allergic rhinitis. Methods: A randomized control trial at Department of Otorhinolaryngology, Head and Neck surgery, Pakistan Institute of Medical Sciences, Islamabad, and Khyber Teaching Hospital, Peshawar-Pakistan, was done in 1 year, from 25th Oct 2016 to 24th Oct 2017. A total of 146 patients were selected and divided into group A & group B (each group have 73 patients). The treatment given was topical Steroid (Mometasone) to Group A and oral antihistamine (loratadine 10mg), antileukotriene (Montelukast 10mg) to Group B. All patients who were included in our study were examined on three consecutive occasions, i.e. at zero presentation day, at 2 weeks and 4 weeks. Patient nasal symptom score was recorded and improvement noticed. Results: All146 patients were selected and were divided into two groups with each group c...

Journal of Applied and Emerging Sciences, 2019

Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to t... more Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to the classical solutions such as cable supported bridge, immersed tunnel or underground tunnel. An SFT is subjected to extreme waves, currents, earthquakes and other environmental loadings. The effect of key structural and waves parameters are important from the design perspective for an SFT. This study, the dynamic responses of SFT are evaluated using truss and catenary cables to check the effect of cable stiffness. The second part of this study deals with the effect of wave height and wave period on the dynamic responses of SFT. 3D truss and 3D catenary cables give very similar dynamic responses under waves and vertical ground motions. The wave height and wave period mainly control the dynamic behavior of SFT.

Submerged floating tunnel (SFT) is a new solution for the transportation infrastructure through s... more Submerged floating tunnel (SFT) is a new solution for the transportation infrastructure through sea straits, fjords, and inland waters and can be a good alternative to long span suspension bridges and immersed tunnels. The mooring cables/anchors are main structural components to provide restoring capacity to the SFT. The time domain dynamic problem of SFT moored by vertical and inclined mooring cables/anchors is formulated. The dynamic analysis of SFT subjected to hydrodynamic and seismic excitations is performed. As the cable stiffness determines the deformation ability of SFT, therefore it becomes crucial to evaluate the effect of mooring cable stiffness on the response of SFT. The displacements and internal forces of SFT clearly specify that the vertical/tension leg mooring cables provide very small stiffness as compared to inclined mooring cables. In order to keep the SFT displacements within an acceptable limit, the effect of cable stiffness should be properly evaluated for pra...

Journal of Applied and Emerging Sciences, 2020

Cable stayed bridges are most widely used in the modern medium to long bridge construction due to... more Cable stayed bridges are most widely used in the modern medium to long bridge construction due to their efficient response, economic viability, faster construction, and eye-catching aesthetics. The dynamic response of a single tower cable stayed bridge is studied by performing both nonlinear static and dynamic analyses using finite element method based software ANSYS. A three dimensional bridge model was developed using ANSYS. The steel cables were simulated using a single element approach to minimize the time and data use. Due to the complexity of cable stayed bridges, it is tried to avoid the convergence problems by adopting the displacement convergence approach. The bridge exhibits complex modal shapes due to the coupling effects for the free vibrations. The response of the bridge in vertical direction is more elastic and flexible as compared to the longitudinal and transverse direction. Response of the critical sections of girder, tower, and cables was also studied by time-history analysis using the ground acceleration data of the EI-Centro 1940 earthquake. A 10 second ground data with 0.0001 second time step was used. It was observed that stiffness in the vertical direction is a key player in the dynamic behavior of the cable stayed bridge. The response of the right and left span is similar which adds to the accuracy of the analysis. Time history analysis of the bridge shows that the largest displacements or peak responses are not related to the peak ground accelerations, rather they are dependent on many other factors like bridge stiffness, nature of the earthquake ground excitations and mass distribution. However, the results show the general trend of cable stayed bridges.

MATEC Web of Conferences, 2017

Mooring line is a major source of stability and plays a key role in the global response of offsho... more Mooring line is a major source of stability and plays a key role in the global response of offshore floating wind turbine. In the current state of the research, a formulation based on the analytical catenary equation is most commonly used for the analysis of mooring lines. However, due to the inability of catenary equations to consider the ocean current drag forces on mooring lines, the effect of drag forces on fairlead restoring forces has not been investigated yet. In this study, we have investigated the influence of drag forces on fairlead forces using discrete catenary formulation for modeling mooring line. The discrete catenary formulation has the ability to incorporate ocean current drag forces. Three types of elements; fully suspended, touchdown and seabed element are formulated to model the suspended, touchdown and seabed portion of a slack mooring line, respectively. The influence of viscous drag on the fairlead restoring forces is demonstrated through the analysis of OC3-Hywind mooring system subjected to ocean currents. It was found that the viscous drag significantly influences the fairlead forces.

Journal of Applied and Emerging Sciences, 2020

The accumulated stress based porewater pressure (PWP) generation model is a simplified model usin... more The accumulated stress based porewater pressure (PWP) generation model is a simplified model using the concept of damage parameter. The only input of this PWP model is liquefaction resistance curve (CRR-N). The model is very useful since the CSR-N curves can be developed empirically from in-situ penetration tests measurements. In this research work the estimation of excess PWP development during seismic loading by using stress based PWP generation model is compared with a rigorous plasticity model. One dimensional (1D) effective stress nonlinear site response analyses were conducted in DEEPSOIL and Opensees using the stress based PWP model and PressureDependentMultiYield02 (PDMY2) model, respectively. The site response analysis were performed on a sand column 30 m in depth comprises of a low density liquefiable layer in between two dense non-liquefiable layers. Three bed rock outcropping motions with peak ground acceleration (PGA) level of 0.11 g, 0.124 g and 0.357 g were used as in...

Oceanography & Fisheries Open access Journal, 2019

Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings and a... more Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings and are more economical compared to the conventional structures such as cable-supported bridges, underground tunnels or immersed tunnels. The dynamic behaviors of SFT under real train loads is the primary design requirement of an SFT, However, it is not investigated using realistic train models. In this study, the China-star high-speed train is used to evaluate the dynamic displacements, internal forces and cable tensions of SFT. The tunnel is modeled by FEM, the cables are modeled by elastic catenary cables, and ocean waves and currents are modeled by Airy's wave theory. The SFT displacements, bending moments and cable tensions were significantly influenced by moving trains. The SFT experienced extreme vertical displacements and there was a large drop in the minimum cable tensions. The mooring cables were slacked both by magnitudes and speed of the moving trains, which should be avoided for the safety of SFT. This study recommends the additional buoyancies for the stability of SFT subjected to high speed trains.

International Journal of Steel Structures, 2018

An effective numerical method is proposed for the three-dimensional nonlinear analysis of mooring... more An effective numerical method is proposed for the three-dimensional nonlinear analysis of mooring cables using catenary theory. In this method, the mooring line is divided into finite number of catenary elements. In addition to self-weight, each catenary element is subjected to drag force due to steady ocean currents. The proposed procedure is validated by comparing the results with those of the shooting optimization and the finite element methods. Finally, a parametric study is conducted to study the effect of extensibility on the static response of mooring cables. The effects of fluid drag forces and cable extensibility on mooring cable tension, equilibrium configurations, and stressed lengths are illustrated for two-and three-dimensional mooring cable problems. From the numerical results, the method is found to be numerically stable, and it provides a more rational static response for mooring cables.

Ocean Engineering, 2019

The hydrostatic forces of a floating platform play an important role in the stability and dynamic... more The hydrostatic forces of a floating platform play an important role in the stability and dynamic behavior of floating wind turbines. Hydrostatic forces are most commonly obtained from a linear hydrostatic stiffness matrix. Linear hydrostatic stiffness is based on the initial position of the floating platform and thus neglects the rotational motion of the floating wind turbine. In this article, the nonlinear hydrostatic stiffness of a floating spar platform was analytically derived with the aim of studying the effect of hydrostatic nonlinearity on the dynamic response. The floating wind turbine was modeled as a multibody system for which the equation of motion was obtained by using the Newton-Euler approach. The mooring lines connected to the floating wind turbine were modeled quasi-statically using catenary equations. A sensitivity analysis based on the comparison of linear and nonlinear hydrostatic forces was conducted to quantitatively evaluate the importance of hydrostatic nonlinearity. The effect of hydrostatic nonlinearity on the response of the floating wind turbine was investigated through analysis of the OC3-Hywind wind turbine in extreme environmental conditions. Results showed that in the case of large amplitude rotations, the use of nonlinear hydrostatic stiffness predicted the response with improved accuracy by accounting for rotational motion.

Applied Sciences, 2017

Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings, such... more Submerged floating tunnels (SFTs) are innovative structural solutions to waterway crossings, such as sea-straits, fjords and lakes. As the width and depth of straits increase, the conventional structures such as cable-supported bridges, underground tunnels or immersed tunnels become uneconomical alternatives. For the realization of SFT, the structural response under extreme environmental conditions needs to be evaluated properly. This study evaluates the displacements and internal forces of SFT under hydrodynamic and three-dimensional seismic excitations to check the global performance of an SFT in order to conclude on the optimum design. The formulations incorporate modeling of ocean waves, currents and mooring cables. The SFT responses were evaluated using three different mooring cable arrangements to determine the stability of the mooring configuration, and the most promising configuration was then used for further investigations. A comparison of static, hydrodynamic and seismic response envelope curves of the SFT is provided to determine the dominant structural response. The study produces useful conclusions regarding the structural behavior of the SFT using a three-dimensional numerical model.

Doboku Gakkai Ronbunshu, 1997

Abstract Today's advanced muscular sensing and processing technologi... more Abstract Today's advanced muscular sensing and processing technologies have made the acquisition of electromyography (EMG) signal which is valuable. EMG signal is the measurement of electrical potentials generated by muscle cells which is an indicator of muscle activity. Other than rehabilitation engineering and clinical applications, EMG signals can also be employed in the field of human computer interaction (HCI) system. In this work, the detection of different hand movements (left, right, up and down) was obtained using ...

Journal of the American Association for Laboratory Animal Science : JAALAS, 2012

Ulcerative dermatitis (UD) is a common, spontaneous condition in mice with a C57BL/6 background. ... more Ulcerative dermatitis (UD) is a common, spontaneous condition in mice with a C57BL/6 background. Although initial lesions may be mild, UD is a progressive disease that often results in ulcerations or debilitating fibrotic contractures. In addition, lesions typically are unresponsive to treatment. Euthanasia is often warranted in severe cases, thereby affecting study outcomes through the loss of research subjects. Because the clinical assessment of UD can be subjective, a quantitative scoring method and documentation of the likely time-frame of progression may be helpful in predicting when animals that develop dermatitis should be removed from a study. Such a system may also be helpful in quantitatively assessing success of various treatment strategies and be valuable to clinical laboratory animal veterinarians. In this 1.5-y, prospective cohort study, we followed 200 mice to monitor the development and course of UD. Mice were examined every 2 wk. A clinical sign (alopecia, pruritus,...

Biological Trace Element Research, 2011

The purpose of this study was to assess insoluble salts containing gadolinium (Gd 3+) for effects... more The purpose of this study was to assess insoluble salts containing gadolinium (Gd 3+) for effects on human dermal fibroblasts. Responses to insoluble Gd 3+ salts were compared to responses seen with Gd 3+ solubilized with organic chelators, as in the Gd 3+-based contrast agents (GBCAs) used for magnetic resonance imaging. Insoluble particles of either Gd 3+-phosphate or Gd 3+-carbonate rapidly attached to the fibroblast cell surface and stimulated proliferation. Growth was observed at Gd 3+ concentrations between 12.5 and 125 μM, with toxicity at higher concentrations. Such a narrow window did not characterize GBCA stimulation. Proliferation induced by insoluble Gd 3+ salts was inhibited in the presence of antagonists of mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways (similar to chelated Gd 3+) but was not blocked by an antibody to the platelet-derived growth factor receptor (different from chelated-Gd 3+). Finally, high concentrations of the insoluble Gd 3+ salts failed to prevent fibroblast lysis under low-Ca 2+ conditions while similar concentrations of chelated-Gd 3+ were effective. In conclusion, while insoluble Gd 3+ salts are capable of stimulating fibroblast proliferation, one should be cautious in assuming that GBCA dechelation must occur in vivo to produce the profibrotic changes seen in association with GBCA exposure in the subset of renal failure patients that develop nephrogenic systemic fibrosis.