In vitro evaluation of the antioxidant and cytotoxic activities of constituents of the mangrove Lumnitzera racemosa Willd.

Nguyen Phuong Thao,Bui Thi Thuy Luyen,Chau Ngoc Diep,Bui Huu Tai,김은지,강희경,이상현,장해동,Nguyen The Cuong,Nguyen Van Thanh,Nguyen Xuan Cuong,Nguyen Hoai Nam,Chau Van Minh,김영호 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.4

This study performed phytochemical and bioactiveassessments of the mangrove Lumnitzera racemosaWilld. leaves. Bioassay-guided fractionation of the methanolicextracts led to the identification of thirty-six compounds(1–36), their structures were elucidated using detailed NMRspectroscopic and MS analysis. The extracts, fractions, andthe isolated compounds were screened for potential antioxidantand cytotoxic activities. Antioxidant assays wereperformed using peroxyl radical-scavenging and reducingassays, whereas cytotoxicity was measured using MTTassays in HL-60 and Hel-299 cell lines. The methanolicextract, CH2Cl2 and n-BuOH fractions (10.0 lg/mL)exhibited potent antioxidant activity, with Trolox equivalent(TE) values of 24.94 ± 0.59, 28.34 ± 0.20, and27.09 ± 0.37 (lM), respectively. In addition, the isolatedcompounds exerted cytotoxic effects in a dose-dependentmanner; compounds 1 and 14 exhibited the most potentcytotoxicity in HL-60 cells, with IC50 values of 0.15 ± 0.29and 0.60 ± 0.16 lM, respectively. To clarify the mechanism(s) behind these cytotoxic effects, we measured thetime-dependent changes in apoptotic markers including thecondensation and fragmentation of nuclear chromatin, andthe downregulation of p-ERK1/2, p-AKT, and c-Myc levels.

Experimental Study on Application of an Optical Sensor to Measure Mooring-Line Tension in Waves

Nguyen Thi Thanh Diep,박지원(Ji Won Park),Van Minh Nguyen,윤현규,Jung Joseph Chul,Lee Michael Myung Sub 한국해양공학회 2022 韓國海洋工學會誌 Vol.36 No.3

Moored floating platforms have great potential in ocean engineering applications because a mooring system is necessary to keep the platform in station, which is directly related to the operational efficiency and safety of the platform. This paper briefly introduces the technical and operational details of an optical sensor for measuring the tension of mooring lines of a moored platform in waves. In order to check the performance of optical sensors, an experiment with a moored floating platform in waves is carried out in the wave tank at Changwon National University. The experiment is performed in regular waves and irregular waves with a semi-submersible and triangle platform. The performance of the optical sensor is confirmed by comparing the results of the tension of the mooring lines by the optical sensor and tension gauges. The maximum tension of the mooring lines is estimated to investigate the mooring dynamics due to the effect of the wave direction and wavelength in the regular waves. The significant value of the tension of mooring lines in various wave directions is estimated in the case of irregular waves. The results show that the optical sensor is effective in measuring the tension of the mooring lines.

Investigation of Seakeeping Performance of Trawler by the Influence of the Principal Particulars of Ships in the Bering Sea

Nguyen Thi Thanh Diep,VU HOANG THIEN,조애리,윤현규 한국해양공학회 2024 韓國海洋工學會誌 Vol.38 No.2

Investigating ship motion under real conditions is vital for evaluating the seakeeping performance, particularly in the design process stage. This study examined the influence of the principal particulars of a trawler on its seakeeping performance. The wave conditions in the Bering Sea are investigated using available data. The length-to-beam (L/B) and beam-to-draft (B/T) ratios of the ship are changed by 10% for the numerical simulation. The response amplitude operator (RAO) motion, root mean square (RMS) value and sensitivity analysis are calculated to evaluate the influence of the trawler dimensions on ship motions. The peak RAO motion affected the ship motions noticeably because of the resonance at the natural frequency. The L/B and B/T ratios are important geometric parameters of a ship that significantly influence its RMS motion, particularly in the case of roll and pitch. The change in the B/T ratio has a good seakeeping performance based on a comparison of the roll and pitch with the seakeeping criteria. The present results provide insights into the seakeeping performance of ships due to the influence of the principal dimensions in the design stage.

An Experimental Study on Hydrodynamic Forces of Korea Autonomous Surface Ship in Various Loading Conditions

Thi Thanh Diep Nguyen,Van Thuan Mai,이산,윤현규 한국항해항만학회 2022 한국항해항만학회지 Vol.46 No.2

Currently, shipping by sea is becoming common because of the low price and the safety of goods. The ship is designed as a larger vessel to meet the need of this development. In the design stage, the investigation of hydrodynamic forces acting on the ship hull is very important in predicting the ship's maneuverability. Given that the ship docks at various ports for loading or discharging goods, the ship usually operates in various loading conditions, depending on the site condition and other various factors. Hence, it is necessary to investigate the effect of the loading condition on the hydrodynamic forces acting on the ship, to most accurately determine the maneuverability of the ship. In this study, an experiment of Korea Autonomous Surface Ship (KASS) was conducted at the towing tank of Changwon National University to measure the hydrodynamic forces acting on the KASS. The loading condition considered in this experiment is determined based on the draft, which was decreased by 5% for each loading condition. The smallest draft is 85% of the design draft. The static test as Oblique Towing Test (OTT), Circular Motion Test (CMT), Circular Motion Test with Drift (CMTD) is performed in the various loading conditions. First, the hydrodynamic forces in the Oblique Towing test (OTT) are compared with the result of other institutes. Second, the hydrodynamic forces in various drift angle, yaw rate and loading conditions are measured. Finally, the influence of the loading conditions on the hydrodynamic coefficient is discussed.

An Experimental Study on the Motion of the Floater Moored near Port in Waves Generated by a Ship

Thi Thanh Diep Nguyen,Van Minh Nguyen,윤현규,김영훈 한국항해항만학회 2020 한국항해항만학회지 Vol.44 No.5

In the past, various research on the effects of waves generated by ships has been investigated. The most noticeable effect of the waves generated by a passing ship is the increase of the hydrodynamic forces and the unwanted large motion of the moored ship and high mooring forces that occur. Thus, it is crucial to investigate the effect of the waves generated by the passing ship near port on the motion of the moored ship and the tension of the mooring lines. A model test was performed with virtual ship-generated waves in a square tank at CWNU (Changwon National University). The IMU (Inertial Measurement Unit) and Optical-based system were used to measure the 6DOF (Six Degrees of Freedom) motion of the moored floater. Additionally the tension of mooring lines were measured by the tension gauges. The effects of the wave direction and wave height generated by the virtual ship-generated waves on the motion of the moored floater were analyzed.

A Study on Sensitivity Analysis of the Hydrodynamic Derivatives on the Maneuverability Prediction of KVLCC2 in Shallow Water by Model Test

Van Minh Nguyen,Thi Thanh Diep Nguyen,Hyeon Kyu Yoon 한국항해항만학회 2020 한국항해항만학회지 Vol.44 No.2

In recent years, there have been concerted efforts toward predicting ship maneuvering in shallow water since the majority of ship’s accidents near harbors commonly occur in shallow and restricted waters. Enhancement of ship maneuverability at the design stage is crucial in ensuring that a ship navigates safely. However, though challenging, establishing the mathematical model of ship maneuvering motion is recognized as crucial toward accurately predicting the assessment of maneuverability. This paper focused on a study on sensitivity analysis of the hydrodynamic coefficients on the maneuverability prediction of KVLCC2 in shallow waters. Hydrodynamic coefficients at different water depths were estimated from the experimental results conducted in the square tank at Changwon National University (CWNU). The simulation of standard maneuvering of KVLLC2 in shallow waters was compared with the results of the Free Running Model Test (FRMT) in shallow waters from other institutes. Additionally the sensitivity analysis of all hydrodynamic coefficients was conducted by deviating each hydrodynamic derivative from the experimental results. The standard maneuvering parameters including turning tests and zig-zag maneuvers were conducted at different water depths and their effects on the standard maneuvering parameters were assessed to understand the importance of different derivatives in ship maneuvering in shallow waters.

Numerical Study on Unified Seakeeping and Maneuvering of a Russian Trawler in Wind and Waves

Van Minh Nguyen,Thi Thanh Diep Nguyen,Hyeon Kyu Yoon,Young Hun Kim 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.3

The maneuvering performance of a ship on the actual sea is very different from that in calm water due to wave-induced motion. Enhancement of a ship’s maneuverability in waves at the design stage is an important way to ensure that the ship navigates safely. This paper focuses on the maneuvering prediction of a Russian trawler in wind and irregular waves. First, a unified seakeeping and maneuvering analysis of a Russian trawler is proposed. The hydrodynamic forces acting on the hull in calm water were estimated using empirical formulas based on a database containing information on several fishing vessels. A simulation of the standard maneuvering of the Russian trawler was conducted in calm water, which was checked using the International Maritime Organization (IMO) standards for ship maneuvering. Second, a unified model of seakeeping and maneuvering that considers the effect of wind and waves is proposed. The wave forces were estimated by a three-dimensional (3D) panel program (ANSYS-AQWA) and used as a database when simulating the ship maneuvering in wind and irregular waves. The wind forces and moments acting on the Russian trawler are estimated using empirical formulas based on a database of wind-tunnel test results. Third, standard maneuvering of a Russian trawler was conducted in various directions under wind and irregular wave conditions. Finally, the influence of wind and wave directions on the drifting distance and drifting angle of the ship as it turns in a circle was found. North wind has a dominant influence on the turning trajectory of the trawler.

The Impact of Foreign Ownership on Firm Performance

Quynh Nga DUONG,Thanh Binh VU,Thi-Phuong VO,Ngoc Hoan NGUYEN-LE,Van Diep NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.6

The purpose of the research examines the relationship between foreign ownership and listed firms’ performance in Vietnam. This study employs an extensive set of panel data comprising 288 non-financial listed Vietnamese firms, over a period from 2015 to 2019 taken for analysis. The results show that the higher the foreign ownership ratio, the higher the performance, however, the relationship between foreign ownership and firm’s performance is U-shaped. In contrast, when the foreign ownership ratio is becoming too high, it will reduce the firm’s performance and firm size, liquidity, financial leverage, capital intensity, and growth opportunities. Furthermore, we find that foreign ownership and performance are linked by an inverted U-shaped relationship. A firm’s performance increases with greater foreign ownership up to the range of 36.26%, and declines thereafter. The paper also found positive effects of firm size and growth opportunities, and an inverse relationship between liquidity, financial leverage and capital intensity, and firm’s performance. This study has several implications for the enhancement of information and understanding of the foreign ownership as it sheds light on the foreign ownershipfirm’s performance relationship. Moreover, the study findings contribute to the literature concerning the ownership structure in the context of developing countries.

Prediction of Motion State of a Docking Small Planing Ship using Artificial Neural Network

Hoang Thien Vu,Thi Thanh Diep Nguyen,윤현규(Hyeon Kyu Yoon) 한국항해항만학회 2024 한국항해항만학회지 Vol.48 No.2

Automatic docking of small planing ship is a critical aspect of maritime operations, requiring accurate prediction of motion states to ensure safe and efficient maneuvers. This study investigates the use of Artificial Neural Network (ANN) to predict motion state of a small planing ship to enhance navigation automation in port environments. To achieve this, simulation tests were conducted to control a small planing ship while docking at various heading angles in calm water and in waves. Comprehensive analysis of the ANN-based predictive model was conducted by training and validation using data from various docking situations to improve its ability to accurately capture motion characteristics of a small planing ship. The trained ANN model was used to predict the motion state of the small planing ship based on any initial motion state. Results showed that the small planing ship could dock smoothly in both calm water and waves conditions, confirming the accuracy and reliability of the proposed method for prediction. Moreover, the ANN-based prediction model can adjust the dynamic model of the small planing ship to adapt in real-time and enhance the robustness of an automatic positioning system. This study contributes to the ongoing development of automated navigation systems and facilitates safer and more efficient maritime transport operations.