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Tung Nguyen-Thach,Nguyen Canh-Hung,Nguyen Van-Duong,Nguyen Thi-Hong-Thuy,Nguyen Van-Lam,Tran Cao-Son,Pham Thi-Minh-Hue 한국약제학회 2020 Journal of Pharmaceutical Investigation Vol.50 No.4
Purpose The study aimed firstly to determine the release behavior of the model drug (berberine chloride) from the dry coated tablets. The second objective of this study was to evaluate the exact location of the dry coated tablets in in vivo. Methods The colon targeting tablets were developed by dry powder coating technique on pan coater. The drug release behavior was determined in the three continuous mediums: pH 1.2; 7.4 and 6.8 plus pectinase. The location of the dry coated tablets in the gastrointestinal tract of human volunteers was observed through the X-ray imaging of the dry coated tablets containing the optimized radiocontrast agents. Results The release kinetics of berberine chloride from the dry coated tablets was mainly controlled by erosion and enzyme sensitive mechanism. The optimum dry coated tablets having the coating powders of pectin 102:HPMC K4 M (2:1) with the coating level of 200%, and the tablet core with BaSO4 10% and iobitridol 30% as radiocontrast agents were observed in the caecum and ascending colon of human volunteers after 5–6 h of oral administration. Conclusion The successful development of these dosage forms is believed to have a high potential in precisely monitoring the release of highly potent drugs such as anti-inflammatory drugs in bowel diseases.
Nguyen Van Dung,유영준,이영백,Nguyen Thanh Tung,Bui Son Tung,Vu Dinh Lam 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.1
The influence of lattice constants on the electromagnetic behavior of a cut-wire-pair (CWP)structure has been elucidated. In this report, we performed both simulations and experiments todetermine the influence of polarization on the metamagnetic resonance of the CWP structure. Thekey finding is the result of an investigation on the plasmon hybridization between the two CWs,which showed that the polarization of the incident wave was affected. Good agreement betweennumerical simulation and measurement is achieved.
Tung Lam Nguyen,Hieu Tran Doan Trung,이우석,이호철 한국광학회 2021 Current Optics and Photonics Vol.5 No.6
In this study, we propose a biomimetic optical structure design methodology for investigating microoptical mechanisms associated with the compound eyes of insects. With these compound eyes, insects can respond fast while maintaining a wide field of view. Also, considerable research attention has been focused on the insect compound eyes to utilize these benefits. However, their nano micro-structures are complex and challenging to demonstrate in real applications. An effectively integrated design methodology is required considering the manufacturing difficulty. We show that photorealistic ray-traced visualization is an effective method for designing the biomimetic of a micro-compound eye of an insect. We analyze the image formation mechanism and create a three-dimensional computer-aided design model. Then, a ray-trace visualization is applied to observe the optical image formation. Finally, the segmented images are stitched together to generate an image with a wide-angle; the image is assessed for quality. The high structural similarity index (SSIM) value (approximately 0.84 to 0.89) of the stitched image proves that the proposed MATLAB-based image stitching algorithm performs effectively and comparably to the commercial software. The results may be employed for the understanding, researching, and design of advanced optical systems based on biological eyes and for other industrial applications.
Nguyen, Tung The-Lam,Sam-Dong Kim IEEE 2013 IEEE transactions on microwave theory and techniqu Vol.61 No.10
<P>We propose a gate-width scalable method for extracting the reliable parasitic elements of the 0.1- μm GaAs metamorphic high electron-mobility transistors. This method utilizes the de-embedding scheme for coplanar waveguide (CPW) feeding structure by considering the distributed extrinsic parasitic elements in our small-signal model. The parasitic capacitances are determined based on estimation of the sub-model (the model after de-embedding the contribution of the CPW feeding structure). We perform the parameter extraction at four different gate widths of the devices to examine the scaling effect. The model shows the best S-parameter effective fitting error of 9.85% among four different extraction methods evaluated in this study over the entire gate-width variation and in a frequency range of 0.5-110 GHz.</P>
Institutional Ownership and Stock Liquidity: International Evidence
Tung Lam Dang,Thanh Huong Nguyen,Nguyen Tram Anh Tran,Thi Thuy Anh Vo 한국증권학회 2018 Asia-Pacific Journal of Financial Studies Vol.47 No.1
This paper investigates the relation between institutional ownership and stock liquidity, and explores whether this relation differs across institutional settings. Using a comprehensive data set across 41 countries from 2000 to 2010, we find that institutional ownership is positively correlated with stock liquidity. Importantly, the positive association between institutional ownership and stock liquidity is stronger (weaker) for firms in countries with opaque (transparent) information environments or poor (good) institutional characteristics. Our additional analysis reveals that the positive association between institutional ownership and liquidity is attributable to non-block institutional investors.
Nguyen, Tung Lam,Ro, Seung-Kook,Park, Jong-Kweon Elsevier 2019 Mechanical systems and signal processing Vol.131 No.-
<P><B>Abstract</B></P> <P>In this paper, we propose a method to monitor the preload of an operational ball screw drive system mostly used in CNC machine tools by evaluating the natural frequency of the screw nut in the axial direction and the corresponding working table displacement. First, we derived a discrete dynamic model and used it to study the variation in the ball screw system preload. Second, we proposed a method for monitoring the ball screw preload in operational mode via the motor current signal and the screw nut axial vibration signal. We apply this method by acquiring and analyzing the signals from the system as it undergoes a transition in its motion, then compose the frequency response function (FRF) of the ball screw system. This enables us to detect the axial natural frequency of the ball screw drive system. The ball screw preload is then calculated and monitored as the system is operational. We provide an efficient and intuitive method to monitor the variation in preload level of an operational ball screw system. This method can be used as an indicator of the health status of the drive system in particular, as well as for the entire machine tool in general.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A discrete dynamic modeling of a ball screw drive system for investigating the relationship between preload level and axial natural frequency of the ball screw system is proposed. </LI> <LI> Preload level can be estimated from the axial natural frequency of the ball screw system and the current working table displacement. </LI> <LI> Signal processing method for measuring the real time preload level of ball screw drive system in operational mode is proposed. </LI> <LI> Three ranges of preload level (high, normal, low preload) are effectively and intuitively monitored during operational mode. </LI> <LI> (Revision) An impact test results was added to verify predicted natural frequency of axial mode of table. </LI> </UL> </P>