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Effect of Hinge Stiffness on Flutter Characteristics of Flat Plate Wing with Flap
Pratik Shrestha,Min-Soo Jeong,In Lee 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.4
Flutter of flight vehicle structure can lead to catastrophic structural failure of aircraft. For this reason, aeroelastic simulation should be performed to understand flutter characteristics and to avoid any disastrous event which may occur due to such dynamic aeroelastic phenomenon. In this paper, the stiffness of the hinge, connecting the lifting surface to the control surface, is examined to see its effect on flutter characteristics by performing aeroelastic analysis. Flat plate wing with flap is modeled using MSC. Patran Flight Loads. Modal and flutter analysis of the wing for varying hinge stiffness is conducted using MSC.NASTRAN solver. P-k method is used for carrying out flutter analysis in MSC.NASTRAN solver. Results obtained from the analysis shows improved flutter characteristics with increase in hinge stiffness.
Pratik Shrestha,Jin-Hyuk Kim,Yurim Park,Chun-Gon Kim 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11
Low velocity impacts can cause barely visible impact damages on composite structure which are difficult to detect through conventional non-destructive inspection approach. Therefore continuous structural health monitoring (SHM) of the composite structure is needed to identify such impacts. In this paper, impact localization on composite plate is investigated using fiber Bragg grating (FBG) sensors while the structure is being excited using a shaker to simulate operational noise conditions. A high speed FBG interrogator is used to sample the impact signals at 100 kHz and reference database impact localization algorithm is used for estimating the location of the impact point. Moreover, through the present study it is demonstrated that even under simulated noise conditions the use of FBG sensors together with reference database algorithm can effectively localize the impact location on the composite specimen with maximum localization error of less than 35 mm from the actual impact location.
Pratik Shrestha,Min-Soo Jeong,In Lee,Jae-Sung Bae,Kyo-Nam Koo 한국항공우주학회 2013 International Journal of Aeronautical and Space Sc Vol.14 No.2
Morphing aircraft capable of varying their wing form can operate efficiently at various flight conditions. However, radical morphing of the aircraft leads to increased structural complexities, resulting in occurrence of dynamic instabilities such as flutter, which can lead to catastrophic events. Therefore, it is of utmost importance to investigate and understand the changes in flutter characteristics of morphing wings, to ensure uncompromised safety and maximum reliability. In this paper, a study on the flutter characteristics of the folding wing type morphing concept is conducted, to examine the effect of changes in folding angles on the flutter speed and flutter frequency. The subsonic aerodynamic theory Doublet Lattice Method (DLM) and p-k method are used, to perform the flutter analysis in MSC.NASTRAN. The present baseline flutter characteristics correspond well with the results from previous study. Furthermore, enhancement of the flutter characteristics of an aluminum folding wing is proposed, by varying the outboard wing folding angle independently of the inboard wing folding angle. It is clearly found that the flutter characteristics are strongly influenced by changes in the inboard/outboard folding angles, and significant improvement in the flutter characteristics of a folding wing can be achieved, by varying its outboard wing folding angle.
Composite Structure Damage Detection Using FBG Sensor and Reference Database Algorithm
Pratik Shrestha,Jin-Hyuk Kim,Yurim Park,Chun-Gon Kim 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4
Continuous structural health monitoring (SHM) instead of conventional non-destructive inspection (NDI) of the composite structure is needed to detect and localize low velocity impacts which can cause barely visible impact damages (BVID). Furthermore, SHM system to identify occurrence of damage due to such low velocity impact is highly desirable. In this paper, damage detection on composite plate is investigated using fiber Bragg grating (FBG) sensors. A high speed FBG interrogator is used to sample the response signals from the FBG sensor at 100 kHz and a damage detection algorithm based on similarity comparing reference database method is used for identifying undamaged or damaged state of the composite specimen. Moreover, through the present study it is demonstrated that FBG sensors together with reference database algorithm are suitable not only for localizing the impact location on the composite specimen but also for detecting damage on the composite specimen.
Pratik Shrestha,Jin-Hyuk Kim,Yurim Park,Chun-Gon Kim 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4
Composite materials are widely being used as an alternative to conventional materials for their superior material properties. However, these material have damage mechanism significantly differing from the conventional materials, which makes it considerably challenging to inspect for damages though traditional structural maintenance approach. Low velocity impacts on composite materials can cause barely visible impact damages, hence continuous structural health monitoring (SHM) of the composite structure is needed to identify such impacts. Therefore, in this paper impact localization on composite plate is investigated using fiber Bragg grating (FBG) sensors. A high speed FBG interrogator is used to sample the impact signals at 100 kHz and reference database impact localization algorithm is used to localize the impact point. Moreover, through the present study it is demonstrated that using FBG sensors can effectively localize the impact location on the composite specimen with maximum localization error limited to within 28 mm of the actual impact location.
MicroRNA Biomarkers in Neurodegenerative Diseases and Emerging Nano-Sensors Technology
Pratik Shah,조석근,Peter Waaben Thulstrup,Morten Jannik Bjerrum,이필휴,강주희,방용주,양성욱 대한파킨슨병및이상운동질환학회 2017 Journal Of Movement Disorders Vol.10 No.1
MicroRNAs (miRNAs) are essential small RNA molecules (20–24 nt) that negatively regulate the expression of target genes at the post-transcriptional level. Due to their roles in a variety of biological processes, the aberrant expression profiles of miRNAs have been identified as biomarkers for many diseases, such as cancer, diabetes, cardiovascular disease and neurodegenerative diseases. In order to precisely, rapidly and economically monitor the expression of miRNAs, many cutting-edge nanotechnologies have been developed. One of the nanotechnologies, based on DNA encapsulated silver nanoclusters (DNA/AgNCs), has increasingly been adopted to create nanoscale bio-sensing systems due to its attractive optical properties, such as brightness, tuneable emission wavelengths and photostability. Using the DNA/AgNCs sensor methods, the presence of miRNAs can be detected simply by monitoring the fluorescence alteration of DNA/AgNCs sensors. We introduce these DNA/ AgNCs sensor methods and discuss their possible applications for detecting miRNA biomarkers in neurodegenerative diseases.
Giant leiomyoma in distal, intra-thoracic oesophagus: Is laparoscopic approach feasible?
Pratik Biswas,Vishakha Kalikar,Tanveer Majeed,Roy Patankar 소화기인터벤션의학회 2021 International journal of gastrointestinal interven Vol.10 No.3
Leiomyomas are the most common benign tumor of the oesophagus. symptomatic patients are candidates for excision, we have discussed a case report of a 43-year-old male patient who had complains of progressive dysphagia. Imaging studies suggested a distal oesophageal mass with calcific foci. The tumor was enucleated laparoscopically with an operative time of 160 minutes. The patient was gradually started on oral feeds from the 3rd postoperative day after an upper gastrointestinal contrast study. The patient was discharged on the 5th postoperative day. We found this minimally invasive approach to be effective with a shorter hospital stay and a faster recovery as compared to a thoraco abdominal approach.
Pratik Suthar,Sonal Shah,Pushkar Waknis,Gandhali Limaye,Aditi Saha,Pranav Sathe 대한구강악안면외과학회 2020 대한구강악안면외과학회지 Vol.46 No.1
Objectives: The need for proper wound closure is of paramount importance after any intra-oral surgery. Various wound closure techniques have been described in literature using traditional non-absorbable suture materials. These include like synthetic absorbable sutures, surgical staples and tissue adhesives. Cyanoacrylates are among the most commonly used biocompatible tissue adhesives. To evaluate and compare intraoral wound healing using 3-0 silk sutures and n-butyl-2-cyanoacrylate after alveoloplasty. Materials and Methods: A total of 20 patients requiring bilateral alveoloplasty in the same arch (upper or lower) were included in this study. Patients with any pre-existing pathology or systemic disease were excluded. After alveoloplasty was performed, the wound was closed using 3-0 braided silk sutures on one side, and using n-butyl-2-cyanoacrylate bio adhesive on the other side. Patients were evaluated based on the following parameters: time required to achieve wound closure; the incidence of immediate and postoperative hemostasis; the time to the use of the first rescue medication; the side where pain first arises; and the side where wound healing begins first. Results: Compared to 3-0 silk sutures, cyanoacrylate demonstrated better hemostatic properties, reduced operative time, reduced postoperative pain and better wound healing. Conclusion: These data suggest that cyanoacrylate glue is an adequate alternative to conventional sutures to close the surgical wound after alveoloplasty, and better than are 3-0 silk sutures.