Numerical and experimental investigations on the mechanical behavior of additively manufactured novel composite materials for biomedical applications

Dhinakaran Veeman,Duraisami Dhamodharan,Mohankumar Subramaniyan,G.J. Surendhar,Chunhui Yang,Hun-Soo Byun 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-

Polymer composites have a great scope which provides improvised mechanical and chemical propertiesthan matrix material. Although most composite materials are relatively strong, they are not sustainable. The sustainability and reusability of the material is significantly affected by the incorporation of nondegradablefillers. Bael bark is a naturally occurring material with numerous medical properties; in thisstudy, Bael bark was dried, synthesized and converted into nano-filler for integrating them in polylactide(PLA) matrix. PLA is a widely used biopolymer in the biomedical sector. The filler and matrix material areboth biodegradable; therefore, the resulting composite is also expected to be biodegradable. This studyaims to develop a composite comprising Bael bark and PLA, which is a better alternative to PLA in termsof strength and sustainability. Bael bark-reinforced PLA matrices were synthesized with different Baelbark compositions, i.e., 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%. Subsequently, the resulting compositeswere subjected to filament characterization tests such as single fiber tensile test (SFTT), scanning electronmicroscopy (SEM), and X-ray diffraction (XRD). Notably, all extruded composites exhibited a uniform distributionof filler materials. Tensile, compression, and flexural tests were also conducted on the additivelyfabricated samples. The tensile strength, compressive strength and Flexural strength of composite specimenswere higher than neat PLA material, with increments of 39%, 33.8%, and 33.9%, respectively, for thecomposite made with 15 wt.% composites. Using a commercial finite element code ABAQUS, numericalsimulations were performed on tensile, compression and flexural specimens. The simulation resultsare in good agreement with the experimental results.

Compressive Strength and Chloride Resistance of Metakaolin Concrete

G. Dhinakaran,S. Thilgavathi,J. Venkataramana 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.7

In the present research work, investigations were carried out to improve the performance of concrete in terms of strength and resistance to chloride-ion-penetration by incorporating metakaolin (MK) as mineral admixture in concrete. Parametric study was carried out by considering w/cm ratio, various percentage of MK and age of concrete as parameters to understand the effect of each parameter. The study was conducted for different water-to-cement metakaolin ratio (w/cm) ratios of 0.32, 0.35, 0.4 and 0.5. The MK proportion was varied from 0 to 15% with an increment of 5% and ages of concrete from 3 to 90 days were considered and experiments performed accordingly. The effects of above said parameters on the various properties of concrete such as workability,compressive strength, chloride penetrability (Rapid chloride permeability test as per ASTM C 1202), pH of concrete and depth of penetration of chloride ions were investigated, and the results of MK concrete were compared with the conventional concrete. From the results, it was observed that MK concrete showed greater strength for higher w/cm ratios (0.4 and 0.5) and its resistance to chloride ion penetration was more or less consistent for all w/cm ratios and the optimal amount of MK resulted significant reduction in chloride ion penetration. A Multiple non-linear regression analysis was used to develop a statistical model to predict the strength and found to have good correlation between the observed and predicted values. It was concluded that the concrete developed in this study have significant potential for use on real time projects.

V-TCP: A Novel TCP Enhancement Technique

Nagamalai, D.,Dhinakaran, B. C.,Choi, B.-S.,Lee, J.-K. SPRINGER-VERLAG 2005 Lecture Notes in Computer Science Vol.3421 No.-

Durability characteristics of recycled aggregate concrete

Saravanakumar, Palaniraj,Dhinakaran, Govindasamy Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

Strength and durability studies on high strength concrete using ceramic waste powder

B. Karthikeyan,G. Dhinakaran 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.2

This paper summarizes the study on effect of ceramic waste powder as partial substitute to cement in binary blend and along with silica fume in ternary blend high strength concrete in normal and aggressive environments. Strength parameters such as compression & tension and durability indices such as corrosion measurement, deterioration, water absorption and porosity were studied. Ceramic waste powder was used in three different percentages namely 5, 10 and 15 with constant percentage of silica fume (1%) as substitutes to cement in ternary blend high strength concrete was investigated. After a detailed investigation, it was understood that concrete with 15% ceramic waste powder registered maximum performance. Increase of ceramic waste powder offered better resistance to deterioration of concrete.

Novel Mechanism to Defend DDoS Attacks Caused by Spam

Dhinaharan Nagamalai,Cynthia Dhinakaran,Jae Kwang Lee 보안공학연구지원센터 2007 International Journal of Smart Home Vol.1 No.2

Corporate mail services are designed to perform better than public mail services. Fast mail delivery, large size file transfer as an attachments, high level spam and virus protection, commercial advertisement free environment are some of the advantages worth to mention. But these mail services are frequent target of hackers and spammers. Distributed Denial of service attacks are becoming more common and sophisticated. The researchers have proposed various solutions to the DDOS attacks. Can we stop these kinds of attacks with available technology? These days the DDoS attack through spam has increased and disturbed the mail services of various organizations. Spam penetrates through all the filters to establish DDoS attacks, which causes serious problems to users and the data. In this paper we propose a novel approach to defend DDoS attack caused by spam mails. This approach is a combination of fine tuning of source filters, content filters, strictly implementing mail policies, educating user, network monitoring and logical solutions to the ongoing attack. We have conducted several experiments in corporate mail services; the results show that this approach is highly effective to prevent DDoS attack caused by spam. The novel defense mechanism reduced 60% of the incoming spam traffic and repelled many DDoS attacks caused by spam.

Experimental and numerical study on smectic aligned zirconium phosphate decorated graphene oxide hybrids effects over waterborne epoxy multi-functional properties enhancement

DURAISAMI DHAMODHAR-AN,Veeman Dhinakaran,Radhika Nagavaram,Pradnya Prabhakar Ghoderao,Hun-Soo Byun,Lixin Wu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-

Waterborne epoxy (WEP) resins are of great significance as multifunctional properties recently. Nevertheless, their curing process, which involves the formation of numerous micro-pores via waterevaporation, has limited applications in the industrial utilizations. In this work, we have synthesizedand enhanced the water-dispersible Zirconium phosphate decorated graphene oxide (ZrP@GO) nanocompositesthrough a one-step preparation method of graphene oxide (GO) sheets decorated with ZrPnanoparticles, and the as-prepared ZrP@GO nanocomposites were introduced as nanofillers for WEP systemin order to enhance its multifunctional properties. The as-prepared GO, ZrP, and ZrP@GO hybridswere scrutinized by XRD, XPS, Raman, TGA, and its morphology study were investigated with the assistanceof AFM, TEM, and FESEM. The anticorrosive properties were analyzed using natural salt spray tests(NSS). The ZrP@GO mixed WEP coatings exhibit better protection towards corrosion when compared toWEP/GO and WEP/ZrP coatings. Also, the excellent mechanical and thermal properties were achievedwith the incorporation of ZrP@GO hybrids with the WEP system. The better performance of ZrP@GOwas achieved through enhanced dispersion, exfoliation, and the outstanding shielding effect of the smecticaligned layers of ZrP@GO hybrids. Besides, a finite element model proposed through this research topredict the tensile behaviors are good in agreement with the measured vales.

Durability characteristics of recycled aggregate concrete

Palaniraj Saravanakumar,Govindasamy Dhinakaran 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

An In-depth Analysis of Spam and Spammers

Dhinaharan Nagamalai,Beatrice Cynthia Dhinakaran,Jae Kwang Lee 보안공학연구지원센터 2008 International Journal of Security and Its Applicat Vol.2 No.2

Electronic mail services have become an important source of communication for millions of people all over the world. Due to this tremendous growth, there has been a significant increase in spam traffic. Spam messes up user’s inbox, consumes network resources and spread worms and viruses. In this paper we study the characteristics of spam and the technology used by spammers. In order to counter anti spam technology, spammers change their mode of operation, therefore continues evaluation of the characteristics of spam and spammers technology has become mandatory. These evaluations help us to enhance the existing anti spam technology and thereby help us to combat spam effectively. In order to characterize spam, we collected four hundred thousand spam mails from a corporate mail server for a period of 14 months from January 2006 to February 2007. For analysis we classified spam based on attachment and contents. We observed that spammers use software tools to send spam with attachment. The main features of this software are hiding sender’s identity, randomly selecting text messages, identifying open relay machines, mass mailing capability and defining spamming duration. Spammers do not use spam software to send spam without attachment. From our study we observed that, four years old heavy users email accounts attract more spam than four years old light users mail accounts. Relatively new email accounts which are 14 months old do not receive spam. But in some special cases like DDoS attacks, we found that new email accounts receive spam and 14 months old heavy users email accounts have attracted more spam than 14 months old light users. We believe that this analysis could be useful to develop more efficient anti spam techniques.

Strength and durability of ultra fine slag based high strength concrete

Pichaiya Sharmila,Govindasamy Dhinakaran 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.3

The use of ground granulated blast furnace slag (GGBFS) from steel industries waste is showing perspective application in civil engineering as partial substitute to cement. Use of such waste conserves natural resources and minimizes the space required for landfill. The GGBFS used in the present work is of ultra fine size and hence serves as micro filler. In this paper strength and durability characteristics of ultra fine slag based high strength concrete (HSC) (with a characteristic compressive strength of 50 MPa) were studied. Cement was replaced with ultra fine slag in different percentages of 5, 10, and 15% to study the compressive strength, porosity, resistances against sulfate attack, sorptivity and chloride ion penetration. The experiments to study compressive strength were conducted for different ages of concrete such as 7, 28, 56, and 90 days. From the detailed investigations with 16 mix combinations, 10% ultra fine slag give better results in terms of strength and durability characteristics.