Hydrodynamic performance of a vertical slotted breakwater

George, Arun,Cho, Il Hyoung The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

The wave interaction problem with a vertical slotted breakwater, consisting of impermeable upper, lower parts and a permeable middle part, has been studied theoretically. An analytical model was presented for the estimation of reflection and transmission of monochromatic waves by a slotted breakwater. The far-field solution of the wave scattering involving nonlinear porous boundary condition was obtained using eigenfunction expansion method. The empirical formula for drag coefficient in the near-field, representing energy dissipation across the slotted barrier, was determined by curve fitting of the numerical solutions of 2-D channel flow using CFD code StarCCM+. The theoretical model was validated with laboratory experiments for various configurations of a slotted barrier. It showed that the developed analytical model can correctly predict the energy dissipation caused by turbulent eddies due to sudden contraction and expansion of a slotted barrier. The present paper provides a synergetic approach of the analytical and numerical modelling with minimum CPU time, for better estimation of the hydrodynamic performance of slotted breakwater.

Anti-slosh effect of a horizontal porous baffle in a swaying/rolling rectangular tank: Analytical and experimental approaches

George Arun,Cho Il Hyoung 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

The horizontal porous baffle and its effect as an anti-slosh device have been investigated intensively in a swaying and rolling rectangular tank. To accurately assess the level at which porous baffles reduce liquid sloshing, the Matched Eigenfunction Expansion Method (MEEM) has been utilized as an analytical tool. The velocity potentials in the horizontal baffle-covered fluid region are expressed by the sum of the homogeneous and particular solutions to avoid solving the complex dispersion equation. By applying an equivalent linearized quadratic loss model, the nonlinear algebraic equation is derived and solved by implementing the NewtoneRaphson iterative scheme. To prove the validity of the present theoretical model, a series of experiments have been conducted with different centered horizontal porous baffles with varying porosities and submerged depths in a swaying and rolling rectangular tank. Reasonably good agreements are obtained regarding the analytical solutions and the experiment's findings. The influence of porosity, submerged depth, and length of a centered horizontal porous baffle on anti-slosh performance have been analyzed, especially at resonance modes. The developed predictive tool can potentially provide guidelines for optimal design of the horizontal porous baffle.

Hydrodynamic performance of a vertical slotted breakwater

George, Arun,Cho, Il Hyoung The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

The wave interaction problem with a vertical slotted breakwater, consisting of impermeable upper, lower parts and a permeable middle part, has been studied theoretically. An analytical model was presented for the estimation of reflection and transmission of monochromatic waves by a slotted breakwater. The far-field solution of the wave scattering involving nonlinear porous boundary condition was obtained using eigenfunction expansion method. The empirical formula for drag coefficient in the near-field, representing energy dissipation across the slotted barrier, was determined by curve fitting of the numerical solutions of 2-D channel flow using CFD code StarCCM+. The theoretical model was validated with laboratory experiments for various configurations of a slotted barrier. It showed that the developed analytical model can correctly predict the energy dissipation caused by turbulent eddies due to sudden contraction and expansion of a slotted barrier. The present paper provides a synergetic approach of the analytical and numerical modelling with minimum CPU time, for better estimation of the hydrodynamic performance of slotted breakwater.

Epidemiology of Oral Lichen Planus in a Cohort of South Indian Population: A Retrospective Study

Soma Susan Varghese,Giju Baby George,Sreenivasan Bargavan Sarojini1,Sankar Vinod,Philips Mathew,Deepu George Mathew,Joseph Sebastian,Arun George 대한암예방학회 2016 Journal of cancer prevention Vol.21 No.1

Background: Oral lichen planus (OLP) is an immune-mediated potentially malignant disorder of the oral cavity. Dysplastic OLP has an altered cytogenic profile and can progress into oral squamous cell carcinoma. The epidemiology of OLP is well-described in several relatively large series from various geographic locations, whereas such series from southern India is rare. The aim of the present study was to determine the epidemiology of OLP in a cohort of South Indian population. Methods: All the case data records of 29,606 patients who visited Mar Baselios Dental College and Hospital, Kerala, India from 2014 to 2015 were retrospectively reviewed. For data review, 122 patients of OLP were selected Estimated were type, number, and location of lesions, clinical manifestation, age of the patient, gender, onset and duration of lesion, stressful life style, habits, skin involvement and associated systemic illness, and presence/absence of dysplasia. Results: When the distribution of OLP among the gender was considered, we found more prevalence in females than males. Fifty-seven percent of patients were associated with stressful lifestyle. Reticular lichen planus was the most common clinical subtype found. Bilateral buccal mucosal was the common site, when the distribution of sites of OLP were compared (P < 0.05). Hypersensitivity reaction was frequently associated with systemic illness with OLP (P < 0.05). Anaplasia was found among 5% of lichen planus lesions. Conclusions: OLP patients had high incidence of hypersensitivity reactions and 5% of OLP lesions showed anaplasia. Long term follow-up is necessary to monitor the recurrence, prognosis, and malignant transformation of OLP.

Study on various hot-gas defrosting configurations for CO2-NH3 cascade deep freezer

Arun B. S.,Ninan George,Murali Sariki,Samuel Manoj,Kumar Sumit,Vaishak S.,Dasgupta Mani Sankar,Kochunni Sarun Kumar,Hafner Armin,Widell Kristina Norne 대한설비공학회 2024 International Journal of Air-Conditioning and Refr Vol.32 No.1

Four hot-gas bypass defrosting configurations for CO2-NH3 cascade blast freezer for application in fish processing firm are numerically investigated. Due to the high moisture content of fish, defrosting is necessary after every 4 to 5 h of batch operation. A thermodynamic model for the cascade system and defrosting was developed to study various defrosting configurations formulated by rearranging the existing compressor to operate as a defrosting compressor and with the addition of an external defrosting compressor. From the simulation findings, it can be summarized that the conventional hot-gas bypass defrosting without defrost compressor is suitable for a high-capacity cascade refrigeration system with more than three evaporators. For low cooling capacity refrigeration systems, a defrosting compressor is necessary to elevate the temperature above the cascade condensing temperature. A dedicated defrosting compressor with a power consumption of 3.1 kW and a modified refrigeration/defrosting compressor with a power consumption of 6.8 kW can deliver 33.3 kW of heating at a temperature of +10 °C (45 bar). Incorporating a desuperheater between the main and defrosting compressors reduces compressor temperature and maintains the lubricating oil stability, without change in defrosting energy consumption and less exergy loss. The defrosting efficiency is obtained in the range of 39.7–42% which is in agreement with published literature.

Near-infrared Laser Energy Transmission through Teeth with Crack Lines: An In-vitro Study

Ashita Sapra,Arun Darbar,Roy George 대한의학레이저학회 2021 MEDICAL LASERS Vol.10 No.4

Background and ObjectivesTo evaluate the difference in near-infrared (810 nm) laser energy transmission through teeth with and without cracks.Materials and MethodsExtracted teeth were sectioned and examined visually for the presence of cracks with the aid of photographs and a trans-illuminator. Fourteen sections, each with cracks (Group A) and no cracks (Group B) were identified and placed 15 mm from the tip of a 300 micron fiber, prior to activation with an 810 nm diode laser (0.1W, 50 ms interval,100 ms duration). A power meter positioned behind the tooth recorded the average energy that was transmitted through the samples. Unpaired t-test analysis was used to determine if the tooth sections with cracks allowed higher power passage compared to sound teeth. ResultsThe mean power recording for the cracked teeth (Group A) was significantly greater (p = 0.0005) than that for the non-cracked teeth (Group B). ConclusionWithin the limitations of this study, it is evident that significantly higher laser energy passes through teeth with cracks in comparison to teeth without cracks. A recent clinical study has also shown that lasers could be used to assess symptomatic cracked teeth. Hence, further research is required to determine the relative increase in energy required to identify symptomatic cracked teeth.

Experimental study of multiple hemisphere wave energy converters arrayed in a water channel resonator

김정록,김동은,GEORGE ARUN,조일형 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-

In this study, the performance of multiple hemisphere Wave Energy Converters (WECs) arrayed in a Water Channel Resonator (WCR) has been investigated in irregular waves. First, we determine the characteristics of wave responses from model tests, using 16 wave probes in a WCR. Second, the pitch motion responses of three WECs in a WCR are determined. Experimental results are compared with the numerical solutions using the time-domain SeaFEM and OrcaFlex commercial code and agree well with the numerical results. Both experimental and numerical results indicate that when the incident peak period is close to one of the natural periods in a closed WCR, resonance occurs in the WCR. This resonance induces a large wave response and causes a high pitch motion response of WECs. The present study highlights the advantages of using a WCR for energy amplification and lays the necessary foundation for the commercialization of the present WEC system.

A New Framework for Encryption and Authentication of Multimedia Data

Sudhish N. George,R. Arun Raj,P. P. Deepthi 보안공학연구지원센터 2013 International Journal of Multimedia and Ubiquitous Vol.8 No.5

One cycle controlled three input three output DC to DC converter

P. Hema Rani,Arun Kumar Behera,Syam S. Sundar,Saly George,S. Ashok 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.1

A single renewable source is insufficient for providing a reliable and continuous power supply. The multi-input DC to DC converter (MIDC) provides for the hybridization of different energy sources with a single output. Various grid voltages exist and different applications require different DC voltages. If the MIDC provides multiple outputs, it becomes a multi-input multi-output (MIMO) converter. In this paper, a triple input triple output (TITO) DC–DC buck-boost converter is proposed for voltage regulation and power management. It combines the feature of multi-input and multi-output. The proposed converter consists of only one inductor, which reduces the number of active elements. A control circuit with a one-cycle control strategy is proposed to achieve this objective. A fixed ratio power management strategy is proposed for power management. The rising edge synchronization PWM method is realized as a suitable switching strategy for the converter. To design the compensator for the converter control system, a small signal model of the converter is developed. A PI controller is used to regulate the output voltage and the one cycle control (OCC) technique is used for current control. The operating characteristics of the proposed converters are validated by hardware results obtained from an Opal-RT real-time simulator.

A sub-micron metallic electrothermal gripper

Park, Daniel Sang-Won,Nallani, Arun Kumar,Cha, DonKyu,Lee, Gil-Sik,Kim, Moon J.,Skidmore, George,Lee, Jeong-Bong,Lee, Jeong-Soo Springer-Verlag 2010 Microsystem Technologies Vol.16 No.3