Multiscale modeling of reinforced/prestressed concrete thin-walled structures

Laskar, Arghadeep,Zhong, Jianxia,Mo, Y.L.,Hsu, Thomas T.C. Techno-Press 2009 Interaction and multiscale mechanics Vol.2 No.1

Reinforced and prestressed concrete (RC and PC) thin walls are crucial to the safety and serviceability of structures subjected to shear. The shear strengths of elements in walls depend strongly on the softening of concrete struts in the principal compression direction due to the principal tension in the perpendicular direction. The past three decades have seen a rapid development of knowledge in shear of reinforced concrete structures. Various rational models have been proposed that are based on the smeared-crack concept and can satisfy Navier's three principles of mechanics of materials (i.e., stress equilibrium, strain compatibility and constitutive laws). The Cyclic Softened Membrane Model (CSMM) is one such rational model developed at the University of Houston, which is being efficiently used to predict the behavior of RC/PC structures critical in shear. CSMM for RC has already been implemented into finite element framework of OpenSees (Fenves 2005) to come up with a finite element program called Simulation of Reinforced Concrete Structures (SRCS) (Zhong 2005, Mo et al. 2008). CSMM for PC is being currently implemented into SRCS to make the program applicable to reinforced as well as prestressed concrete. The generalized program is called Simulation of Concrete Structures (SCS). In this paper, the CSMM for RC/PC in material scale is first introduced. Basically, the constitutive relationships of the materials, including uniaxial constitutive relationship of concrete, uniaxial constitutive relationships of reinforcements embedded in concrete and constitutive relationship of concrete in shear, are determined by testing RC/PC full-scale panels in a Universal Panel Tester available at the University of Houston. The formulation in element scale is then derived, including equilibrium and compatibility equations, relationship between biaxial strains and uniaxial strains, material stiffness matrix and RC plane stress element. Finally the formulated results with RC/PC plane stress elements are implemented in structure scale into a finite element program based on the framework of OpenSees to predict the structural behavior of RC/PC thin-walled structures subjected to earthquake-type loading. The accuracy of the multiscale modeling technique is validated by comparing the simulated responses of RC shear walls subjected to reversed cyclic loading and shake table excitations with test data. The response of a post tensioned precast column under reversed cyclic loads has also been simulated to check the accuracy of SCS which is currently under development. This multiscale modeling technique greatly improves the simulation capability of RC thin-walled structures available to researchers and engineers.

Offsetting obstacles of any shape for robot motion planning

Laskar, Md Nasir Uddin,Viet, Hoang Huu,Choi, Seung Yoon,Ahmed, Ishtiaq,Lee, Sungyoung,Chung, Tae Choong Cambridge University Press 2015 Robotica Vol.33 No.4

<B>SUMMARY</B><P>We present an algorithm for offsetting the workspace obstacles of a circular robot. Our method has two major steps: It finds the raw offset curve for both lines and circular arcs, and then removes the global invalid loops to find the final offset. To generate the raw offset curve and remove global invalid loops, <I>O(n)</I> and <I>O((n+k)</I>log <I>m</I>) computational times are needed respectively, where <I>n</I> is the number of vertices in the original polygon, <I>k</I> is the number of self-intersections and <I>m</I> is the number of segments in the raw offset curve, where <I>m</I> ≤ <I>n</I>. Any local invalid loops are removed before generating the raw offset curve by invoking a pair-wise intersection detection test (PIDT). In the PIDT, two intersecting entities are checked immediately after they are computed, and if the test is positive, portions of the intersecting segments are removed. Our method works for conventional polygons as well as the polygons that contain circular arcs. Our algorithm is simple and very fast, as each sub-process of the algorithm can be completed in linear time except the last one, which is nearly linear. Therefore, the overall complexity of the algorithm is nearly linear. By applying our simple and efficient approach, offsetting obstacles of any shape make it possible to construct a configuration space that ensures optimized motion planning.</P>

Adsorption of Crystal Violet from Wastewater by Modified Bambusa Tulda

Nirban Laskar,Upendra Kumar 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

In the present study sodium carbonate modified Bambusa tulda was utilised for the removal of crystal violet dye from aqueoussolution. The functional group characterization and the surface morphology was done by Fourier Transform Infrared Spectroscopy(FTIR) and Scanning Electron Microscope (SEM). It confirms the hydroxyl groups and carboxyl group present on the surface ofmodified Bambusa tulda. The optimum condition for the removal of crystal violet was taken place at pH 7, 200 rpm, dose at 10gm/l,initial concentration 50 mg/l, at equilibrium time 60 minutes and 298 K temperature with maximum adsorption capacity of 20.84 mg/gm. The adsorption of crystal violet by modified Bambusa tulda best fits in Langmuir isotherm model with R2 value 0.924 andPseudo 2nd order rate equation model with R2 value of 0.999. Other parameters like isosteric heat analysis, thermodynamics profileand activation energy were investigated. Thus, modified Bambusa tulda can be an efficient and economically used as an alternativefor activated carbon for the removal of crystal violet from waste water.

A Preliminary Study on Effect of Posture on Percentage Finger Systolic Blood Pressure Assessing Peripheral Vascular Function for Diagnosing Hand-Arm Vibration Syndrome

Md. Shawkatuzzaman Laskar,Kenjiro Yokoyama,Masaiwa Inoue,Kumiko Suizu,Minoru Nakamoto,Noriaki Harada 한국소음진동공학회 2003 한국소음진동공학회 국제학술대회논문집 Vol.2003 No.8

Modeling any Obstacle Shapes for Motion Planning of Circular Robots

Md Nasir Uddin Laskar,Seung Y. Choi,Ishtiaq Ahmed,TaeChoong Chung 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10

This paper presents an algorithm to model the workspace obstacles of a circular robot. An obstacle of any shape can be represented by line and circular arc segments. Based on robot radius, geometric representation is applied for both line and circular arcs and the operation is known as offsetting. Result of our algorithm creates an efficient configuration space and helps planning high-quality motion paths. Our method works differently for line and circular arc segments. Two major steps are: (i) finding the raw offset curve for both lines and circular arcs and (ii) removing the global invalid loops. The process takes O(n) times to find the raw offset curve and O((n + k) logm) times to remove global invalid loops, where n is the number of vertices in the original polygon, k is the number of self-intersections, and m is the number of segments in the raw offset curve and always m≤n. Local invalid loops are removed before generating the raw offset curve by invoking a pair-wise intersection detection test (PIDT). Our algorithm is very fast and computational complexity is approximately linear.

EKF and K-means to Generate Optimized Paths of a Mobile Robot

Md Nasir Uddin Laskar,Hoang Huu Viet,TaeChoong Chung 보안공학연구지원센터 2013 International Journal of Control and Automation Vol.6 No.2

Seismic interaction of flexural ductility and shear capacity in reinforced concrete columns

Howser, Rachel,Laskar, A.,Mo, Y.L. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

The seismic performance of reinforced concrete (RC) bridge columns is a significant issue because the interaction of flexural ductility and shear capacity of such columns with varied amounts of lateral reinforcement is not well established. Several relationships between flexural ductility and shear capacity have been proposed by various researchers in the past. In this paper, a parametric study on RC bridge columns is conducted using a nonlinear finite element program, "Simulation of Concrete Structures (SCS)", developed at the University of Houston. SCS has been previously used to predict the seismic behavior of such columns. The predicted results were compared with the test results obtained from experiments available in literature. Based on the results of the parametric study performed in this paper, a set of new relationships between flexural ductility and shear capacity of RC columns is proposed for seismic design.

Effect of incorporation of soy protein isolate and inulin on quality characteristics and shelf-life of low–fat duck meat sausages

Moirangthem S.,Laskar S. K.,Das A.,Upadhyay S.,Hazarika R. A.,Mahanta J. D.,Sangtam H. M. 아세아·태평양축산학회 2022 Animal Bioscience Vol.35 No.8

Objective: Low fat duck meat sausages were prepared by replacing the fat in the formulations with soy protein isolate (SPI) and inulin to find the best formulation having superior shelflife without affecting its quality attributes. Methods: Four sausage mix formulations were prepared viz.control (0% SPI and inulin), T1 (2.5% inulin), T2 (2.5% SPI), and T3 (2.5% SPI+2.5% inulin) replacing duck fat as per the recipe. Five batches of duck meat sausages of each formulation were prepared, and the final products were evaluated for physico-chemical, organoleptic, and microbiological qualities. Results: The % moisture and crude protein content of the sausages revealed an increasing trend (p<0.01) from control to the treated formulations, while the % total ash contents were found to be non-significant (p>0.05). On the contrary, the per cent ether extract decreased significantly (p<0.01) from the control to the treated groups. In terms of calorie value, control samples exhibited the highest values with a significant (p<0.01) regression from control to treated formulation, respectively. The colour profile study (L, a*, b*) of the formulations were found to be non-significant. Texture profile study in terms of springiness, cohesiveness, chewiness, and resilience revealed no significant difference in all the treatment groups except the hardness scores, which revealed a significantly (p<0.01) increasing trend from control to the treated formulations. The total viable count showed a significant decrease in the treated groups. However, there was a significant increase in the bacterial load during the storage till day 15th. The total viable psychrophilic bacterial count showed a significant (p<0.01) increase in bacterial load from day 5th to 15th day of storage. Colititre counts were negative for all the formulations until the 15th day of storage. Conclusion: The present study results may conclude that duck meat sausages could be prepared satisfactorily by replacing duck fat with SPI and inulin at the rate of 2.5% of each with superior quality attributes. Objective: Low fat duck meat sausages were prepared by replacing the fat in the formulations with soy protein isolate (SPI) and inulin to find the best formulation having superior shelflife without affecting its quality attributes.Methods: Four sausage mix formulations were prepared viz.control (0% SPI and inulin), T₁ (2.5% inulin), T₂ (2.5% SPI), and T₃ (2.5% SPI+2.5% inulin) replacing duck fat as per the recipe. Five batches of duck meat sausages of each formulation were prepared, and the final products were evaluated for physico-chemical, organoleptic, and microbiological qualities.Results: The % moisture and crude protein content of the sausages revealed an increasing trend (p<0.01) from control to the treated formulations, while the % total ash contents were found to be non-significant (p>0.05). On the contrary, the per cent ether extract decreased significantly (p<0.01) from the control to the treated groups. In terms of calorie value, control samples exhibited the highest values with a significant (p<0.01) regression from control to treated formulation, respectively. The colour profile study (<i>L</i>, <i>a</i>*, <i>b</i>*) of the formulations were found to be non-significant. Texture profile study in terms of springiness, cohesiveness, chewiness, and resilience revealed no significant difference in all the treatment groups except the hardness scores, which revealed a significantly (p<0.01) increasing trend from control to the treated formulations. The total viable count showed a significant decrease in the treated groups. However, there was a significant increase in the bacterial load during the storage till day 15th. The total viable psychrophilic bacterial count showed a significant (p<0.01) increase in bacterial load from day 5th to 15th day of storage. Colititre counts were negative for all the formulations until the 15th day of storage.Conclusion: The present study results may conclude that duck meat sausages could be prepared satisfactorily by replacing duck fat with SPI and inulin at the rate of 2.5% of each with superior quality attributes.

Koch Fractal Shape Microstrip Bandpass Filters on High Resistivity Silicon for the Suppression of the 2<SUP>nd</SUP> Harmonic

Manos M. Tentzeris,Joy Laskar,Jong-Gwan Yook,Il Kwon Kim,Nickolas Kingsley,Matthew A. Morton,Stephane Pinel,John Papapolymerou 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.4

In this paper, the fractal shape is applied to microstrip band pass filters and integrated on a high-resistivity Si substrate to solve conventional 2<SUP>nd</SUP> harmonic problem. Conventional microstrip coupled line filters are popular in RF front ends, because they can be easily fabricated and integrated with other RF components. However, they typically have large second harmonics that can cause unwanted interference in interested frequency bands. Without any additional filters, the proposed Koch shape filters have suppressed the 2<SUP>nd</SUP> harmonics by about ?40㏈, so they can be used in systems such as direct conversion receiver with stringent harmonic suppression requirements.

A Quality-Improved Folded Inductor Embedded in MCM-L Organic Packaging Substrate Using an Unfilled Via Process

Sang-Woong Yoon,Laskar, J. IEEE 2009 IEEE transactions on components and packaging tech Vol.32 No.4

<P>This paper presents a folded inductor implemented with a multichip module, which involves a laminate organic packaging technology with an unfilled via process. The folded inductor had an increased inductor layer surface area because of the unfilled vias along the inductor layer. Thus, the quality (<I>Q</I>) factor of the inductor improved as the series resistance, resulting from the skin effect, decreased. The <I>Q</I>-factor for a folded inductor showed a maximum improvement of 32% by including contact resistances, in comparison with the <I>Q</I> -factors of a normal planar inductor.</P>