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Dipak K. Maiti,Sateesh B. 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.1
Vibration is an undesirable phenomenon in a dynamic system like lightly damped aerospace structures and active vibration control has gradually been employed to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid based damper for vibration control of a typical nose landing gear. They offer the adaptability of active control devices without requiring the associated large power sources. A torsional damper is designed and developed based on Bingham plastic shear flow model. The numerical analysis is carried out to estimate the damping coefficient and damping force. The designed damper is fabricated and an experimental setup is also established to characterize the damper and these results are compared with the analytical results. A typical FE model of Nose landing gear is developed to study the effectiveness of the damper. Open loop response analysis has been carried out and response levels are monitored at the piston tip of a nose landing gear for various loading conditions without damper and with MR-damper as semi-active device. The closedloop full state feedback control scheme by the pole-placement technique is also applied to control the landing gear instability of an aircraft.
Dipak Kumar,K. N. Pandey 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
In this work, the effect of sol–gel deposited top-coat on thermal fatigue resistance of thermal barrier coatings (TBCs) subjectedto thermal fatigue loading is evaluated experimentally. To obtain non-conventional sol–gel thermal barrier coatings(SGTBC), coated samples underwent thermal fatigue loading at 1100 °C for 10 min heating and cooling. The tested sol–gelthermal barrier coatings were then compared to conventional air plasma sprayed (APS) thermal barrier coatings as well. Thelife of samples was investigated as a function of number of sustaining thermal cycles to times. Furthermore, the performedexperiment was analyzed using scanning electron microscope, energy dispersive spectroscopy and X-ray diffractometer. Theobtained results indicated that the non-conventional sol–gel thermal barrier coatings exhibited 1.46 times better thermalfatigue life in IN800SGTBC against 1.31 times thermal fatigue life of IN718SGTBC but overall thermal fatigue life wasfound to be better in IN718 SGTBC, signified effects of metallic substrates in thermal fatigue life determination. However,the nanostructured SGTBC had higher thermal cyclic resistance than conventional APS TBC, resulted in improved lifetimeindicating the increased adherence at the substrate interface. Results also showed that the dominant failure mechanism ofTBCs was destabilization of top-coat (YSZ), resulting composition of (Al, Cr)2O3 and spinel as reaction products for depletingY2O3producing from yttria stabilized zirconia (YSZ). Furthermore, the results showed that the amount of the porositypercent in the sol–gel TBCs was 2.3% higher than the conventional TBCs.
Sero-Prevalence of Viral Hepatitis B Infection in the General Population of Chitwan District, Nepal
( Dipak Mahaseth ),( Jay Prakash Sah ),( Aman Nigam ),( Anusha Magar ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1
Aims: Hepatitis B is one of the most common viral infection worldwide. Almost one-third of the World´s population has been infected with this virus and about 350 million people live with chronic infection, sometimes causing jaundice and death of the patients. However, in developing countries like Nepal, hepatitis B infection is endemic with predominant vertical transmission leading to chronicity and death. Hence, the present study was conducted to access the prevalence of viral hepatitis B infection in the people of Chitwan district which represents almost all ethnic groups of people of Nepal. Methods: A cross-sectional study was conducted among 283 subjects attending International Reference Laboratory (IR-Lab), Bharatpur-10, Chitwan, Nepal during the period of six months (September 2020 to February 2020). The hepatitis B surface antigen (HBsAg) was studied from the serum obtained from the participating subjects using the diagnostic HBsAg-ELISA kit. The data obtained were analyzed using the SPSS version-24. Results: Out of 283 subjects tested for HBsAg, 74.2% (210) were male whereas 25.8% (73) were female. The subjects were from the age of 0.3 to 91 years old. The highest percentage of subjects participated in this research was 26 to 55 years old. Among 283 subjects, 2.5% (7) were diagnosed as viral hepatitis B infected patients. The prevalence of hepatitis B infection was higher (2.9%) in males than females (1.4%). The highly infected patients were the age group of 26-55 years old. The ethnic group, Gurung was found to be predominantly infected. Conclusions: In comparison to the previous report, our finding explores that hepatitis B infection has been gradually increasing even though the literacy of the urbanized population is satisfactory than the past. It is a big challenge for the Nepalese government for viral hepatitis elimination. Implementation of newborn HBV-vaccination, as well as social awareness and health campaigns, are required.
Dipak Sen,Moon-Gab Kim 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.3
The excess molar volumes Vm E and excess molar enthalpies Hm E at T=298.15 K and atmospheric pressure for the binary systems {x1CH3CHClCH2Cl+x2CH3(CH2)n−1OH} (n=1 to 4) have been determined from density measurements by using a digital vibrating-tube densimeter and an isothermal calorimeter with flow-mixing cell, respectively. The 1-alkanols are methanol, ethanol, 1-propanol and 1-butanol. The Vm E values of the binary mixtures increase with chain length of the 1-alkanols, resulting in entire negative Vm E values for methanol, ‘S-shaped’ for ethanol, being nega- tive at low and positive at high mole fraction of 1,2-dichloropropane, and entire positive Vm E values for both 1-propanol and 1- butanol. The Hm E values for all systems show an endothermic effect (positive values), which exhibits a regular increase in magnitude when the number of -CH2- group in 1-alkanols is progressively increased and maximum values of Hm E varying from 741 J·mol−1 (methanol) to 1,249 J·mol−1 (1-butanol) around x1=0.63-0.72. The experimental results of both Hm E and Vm E were fitted to Redlich-Kister equation to correlate the composition dependence. The experimental Hm E data were also used to test the suitability of the Wilson, NRTL, and UNIQUAC models. The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results except for the system containing methanol.
Vibration control of mechanical systems using semi-active MR-damper
Dipak K. Maiti,P.P. Shyju,K. Vijayaraju 국제구조공학회 2006 Smart Structures and Systems, An International Jou Vol.2 No.1
The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MR-fluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.