Optimal control of vibration by multiple tuned liquid dampers using Taguchi method

Nguyen Van Khang,Do The Duong,Nguyen Thi Van Huong,Nguyen Duc Thi Thu Dinh,Vu Duc Phuc 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

This paper investigates the multiple tuned liquid dampers (MTLD), which consist of a number of MTLD whose first natural frequencies of sloshing are distributed over a certain range around the natural frequency of a structure. The liquid motion in the MTLD as well as the MTLD-structure interaction are numerically simulated using a shallow water-wave theory. An optimal procedure based on Taguchi method is proposed to determine the optimum parameters of MTLD to suppress the vibration amplitude of the considered structure. A number of numerical tests are included to demonstrate and verify the effectiveness of the proposed procedure.

A two-step design of experiments approach to investigate the simultaneous effects of ion-pairing and chemical enhancers to improve the permeability of lornoxicam in a topical hydrogel patch

Nguyen Huu-Manh,Duong The-Khang,Nguyen Van-Khuyen,Nguyen Thi-Khanh-Ly,Dong Thi-Hoang-Yen,Nguyen Canh-Hung,Tung Nguyen-Thach 한국약제학회 2024 Journal of Pharmaceutical Investigation Vol.54 No.2

Purpose A two-step experimental design was used to develop a lornoxicam (LOR)-loaded topical hydrogel patch. We specifically focused on the simultaneous effect of the ion pair formation agent (triethanolamine [TEA]) and the chemical enhancer (cremophor RH40 [RH40]) on flux and conducted physicochemical studies and skin physiology assessments to obtain further information. Methods Drug-in-adhesive patches were fabricated using a micrometer-adjustable film applicator. The applied Design of Experiments (DoE) approach consisted of the Fractional Factorial Resolution V + design and the Central Composite Face design established by the MODDE® 12.0 software. Molecular-level drug-excipient interactions were investigated using infrared (IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The effects on skin physiological function was assessed using DermaLab Combo. Results DoE results revealed that TEA enhanced flux by 3.14-fold, whereas RH40 reduced it by 4.62-fold. The addition of RH40 resulted in the disappearance of the proton peak within the region of 12–13 ppm, suggesting competition for hydrogen bonding with LOR between TEA and RH40. The optimized formulation (4% TEA, 0% RH40, and 0.2% Al(OH)3) increased skin hydration by 6.20-fold. Opposing effects of TEA and RH40 on skin elasticity were observed. Conclusion Expected flux and adhesion strength for the optimized formulation were 7.18 μg·cm–2·h–1 and 11.79 mJ, respectively. Our understanding of the conflicting effects of TEA and RH40 has been advanced. The integrated use of the two-step DoE, physicochemical studies, and skin physiology assessments was proven to be effective in elucidating the simultaneous effects of different permeation-modifying strategies on patches, thus having substantial value for the successful execution of future research endeavors.

Ready and selective access to 2-arylquinazolines from α-amino acids via a new solvent-free domino transformation under synergistic nano Fe-Mo-Se catalyst

Khang X. Nguyen,Phuc H. Pham,An C.D. Nguyen,Chuc T. Nguyen,Tung T. Nguyen,Phong D. Tran,Nam T.S. Phan 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.92 No.-

A Fe-Mo-Se nanopowder, synthesized by a solvothermal protocol, was utilized as a heterogeneouscatalyst for the synthesis of 2-arylquinazolines from DL-α-phenylglycine-based α-amino acids and2-nitrobenzyl alcohols via domino transformations. High yields and selectivity were achieved undersolvent-free conditions. The Fe-Mo-Se catalyst offered considerably higher activity than numeroushomogeneous and heterogeneous catalysts. To our best knowledge, this domino reaction is new, and theutilization of iron-molybdenum selenide catalyst in the synthesis of quinazolines was not previouslyreported.

Design of a Substrate-Integrated Fabry-Pérot Cavity Antenna for<i>K</i>-Band Applications

Nguyen, Truong Khang,Park, Ikmo Hindawi Limited 2015 International journal of antennas and propagation Vol.2015 No.-

<P>This paper presents the design of a planar, low-profile, high-gain, substrate-integrated Fabry-Pérot cavity antenna for<I>K</I>-band applications. The antenna consists of a frequency selective surface (FSS) and a planar feeding structure, which are both lithographically patterned on a high-permittivity substrate. The FSS is made of a circular hole array that acts as a partially reflecting mirror. The planar feeding structure is a wideband leaky-wave slit dipole fed by a coplanar waveguide whose ground plane acts as a perfect reflective mirror. The measured results show that the proposed antenna has an impedance bandwidth of more than 8% (VSWR ≤ 2), a maximum gain of 13.1 dBi, and a 3 dB gain bandwidth of approximately 1.3% at a resonance frequency of around 21.6 GHz. The proposed antenna features low-profile, easy integration into circuit boards, mechanical robustness, and excellent cost-effective mass production suitability.</P>

Effects of Ensiled Cassava Tops on Rumen Environment Parameters, Thyroid Gland Hormones and Liver Enzymes of Cows Fed Urea-treated Fresh Rice Straw

Khang, Duong Nguyen,Wiktorsson, Hans Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.7

Four rumen-cannulated cows (330 kg average weight at 4 years) were used to evaluate the supplement of ensiled cassava tops (ECT) (variety KM 94, 39% DM) on rumen functions, thyroid hormones and liver enzymes. The treatments, arranged in a 4 $\times$4 Latin square design, were ECT at 0, 50, 100 and 150 g CP 100 kg$^{-1}$ body weight (BW), and a basal diet of urea-treated fresh rice straw (UFRS) ad libitum and 1.1 kg dry matter (DM) cassava root meal (CRM) in each 30 day study period. The results showed a continuous decrease in dry matter intake (DMI) of UFRS with increasing level of ECT supplement (p<0.001). The highest total DMI was observed for treatment ECT$_{150}$ (2.68 kg DM 100 kg$^{-1}$ BW day$^{-1}$) followed by treatments ECT$_{100}$, ECT$_{50}$ and ECT$_{0}$, with 2.47, 2.24 and 2.06 kg DM 100 kg$^{-1}$ BW⋅day$^{-1}$, respectively. Increasing levels of ECT supplement increased the concentration of total volatile fatty acids (p<0.05) and ammonia nitrogen (p<0.05) and resulted in a decrease in pH (p<0.05). Overall average plasma triiodothyronine and thyroxine concentrations were 0.80, 0.82, 0.85 and 0.69 ng ml$^{-1}$ (p>0.05), and 50.9, 49.5, 50.7 and 42.4 ng ml-1 (p>0.05) for treatments ECT$_{0}$, ECT$_{50}$, ECT$_{100}$ and ECT$_{150}$, respectively. There were non-significant differences in alanine aminotransferase and aspartate aminotransferase among treatments. It is concluded that ECT is a valuable protein-rich feed supplement to cattle, and the highest level of on average 2.48 kg DM ECT per cow and day (28% of total DMI) did not significantly affect thyroid gland hormones and liver enzymes in cows.

A regional approach for health risk assessment of toxicants in plastic food containers

Nguyen Lan Binh Thi,Thanh Truc Nguyen Thi,Nguyen Ngoc Tran Thi,Vu Dinh Khang,Lee Byeong-Kyu 한국독성학회 2023 Toxicological Research Vol.39 No.4

Plastic food containers are being used popularly, generating a waste of about 115 million tons in Vietnam. Such waste is causing environmental and health issues. This study conducted a field survey with 250 local people and selected 59 samples out of 135 plastic food containers collected in Go Vap district, Vietnam. Collected plastic samples identified compositions were PET 13.6%, PP 28.8%, PS 16.9%, and 40.7% undefined plastics. Collected plastic samples were classified based on the plastic type using recycling code and quantitatively analyzed with X-ray fluorescence spectroscopy method to assess concentrations of Cd, Sb, Pb, Hg, Sn, Cr, Br, Cl, and S. Most of these collected plastic samples (91.5%) were found to contain 8/9 hazardous substances and most elements contained in these plastics were below their standard thresholds. These elements in plastic samples could be divided as the result into three hazard groups: (1) high hazard group (Sb, Cl, and S); (2) medium hazard group (Cr, Br and Hg); and (3) low hazard groups (Cd, Pb and Sn). Among substances in the high hazard group, element Sb was assessed for its migration because only Sb is regulated in Vietnam in QCVN 12-1: 2011/BYT. Substances of Cl, S, Cr, Br, and Hg (group 1, 2) do not have regulations related to the method of decontamination. Thus, additional health risks need to be assessed using the USEtox model. Finally, this study proposed a screening process to assess the risk of toxicity of elements contained in plastic food containers through ISO 31000:2018.

CAN-Based Networked Control Systems: A Co-Design of Time Delay Compensation and Message Scheduling

NGUYEN Trong Cac,NGUYEN Xuan Hung,NGUYEN Van Khang 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.10(네트워크)

The goal of this paper is to consider a co-design approach between time delay compensation and the message scheduling for CAN-Based Networked Control Systems (NCS). First we propose a hybrid priority scheme for the message scheduling in order to improve the Quality of Service (QoS). Second we present the way to calculate the closed-loop communication time delay and then compensate this time delay using the pole placement design method in order to improve the Quality of Control (QoC). The final objective is the implementation of a co-design which is the combination of the compensation for communication time delays and the message scheduling in order to have a more efficient NCS design.

A compact spiral stripline-loaded monopole antenna with a vertical ground plane

Khang Nguyen, Truong,Lee, Keekeun,Choo, Hosung,Park, Ikmo Wiley Subscription Services, Inc., A Wiley Company 2008 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.50 No.1

<P>In this letter, we propose a compact spiral stripline-loaded monopole antenna on a vertical ground plane. The measured results show that the antenna has a fractional bandwidth of 12.1% for a voltage standing wave ratio (VSWR) less than 2 at the center frequency of 1.10 GHz, as well as a good omni-directional radiation pattern. The small size of 0.04 λ<SUB>o</SUB> × 0.04 λ<SUB>o</SUB> × 0.04 λ<SUB>o</SUB> makes it promising for use as an internal antenna in mobile handsets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 250–252, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23043</P>

Photoconductive dipole antennas for efficient terahertz receiver

Nguyen, Truong Khang,Kim, Won Tae,Kang, Bong Joo,Bark, Hyeon Sang,Kim, Kangho,Lee, Jaejin,Park, Ikmo,Jeon, Tae-In,Rotermund, Fabian Elsevier 2017 OPTICS COMMUNICATIONS - Vol.383 No.-

<P><B>Abstract</B></P> <P>We designed various photoconductive antennas applicable to efficient terahertz (THz) receivers and experimentally investigated their detection characteristics. Three different antennas based on Grischkowsky (H-), I-, and bowtie shapes were fabricated on a 1.2-μm-thick low-temperature GaAs layer that was grown on a semi-insulating GaAs substrate and subsequently attached to extended hemispherical silicon lenses. The experimental results showed different characteristics for detection responsivity and agreed well with the theoretical prediction. Measurements of the peak-to-peak amplitudes of the detected THz photocurrent were approximately 67, 42, and 59nA for the H-shaped, I-shaped, and bowtie-shaped antennas, respectively. The I- and bowtie-shaped antennas provided higher THz detection sensitivities than the H-shaped antenna in the low-frequency region, i.e., below 0.6THz. At a frequency of 0.2THz, the I- and bowtie-shaped antennas offered an approximately 3.6-fold and 6-fold enhancement, respectively, in THz detection sensitivity compared to the H-shaped antenna. The bowtie-shaped antenna produced better peak amplitude and a wider spectral bandwidth than the I-shaped antenna. The observed detection peak frequencies of the I-shaped and bowtie-shaped antennas possessing very long dipole arms indicate that the lowest limit of the frequency detected in a typical THz-TDS using a GaAs photoconductive antenna as emitter/detector is around 0.2THz.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We analysis, design, and characterization of three prototypes of photoconductive antennas namely Grischkowsky (H-shaped dipole) (Auston switch dipole), an I-shaped (stripline dipole), and a bowtie photoconductive antenna. </LI> <LI> A 'hybrid' numerical and analytical procedure for estimating the currents induced on the antenna and in the gap, when operating in the reception, is also discussed. The experimental results, which was obtained by a THz time-domain spectroscopy system, show different spectral detection responsivity and agree with the theoretical prediction. </LI> <LI> The experimental results show that the I-shaped and bowtie-shaped antennas could detect THz signals at low-frequency regions below 0.6 THz with a much higher sensitivity than the H-shaped antenna. Therefore, these two antennas could be promising for the sensitive room-temperature detection of THz radiation in the low THz frequency region or in THz wireless communication systems. </LI> <LI> The observed detection peak frequencies of the I-shaped and bowtie-shaped antennas possessing very long dipole arms indicate that the lowest limit of the frequency detected in a typical THz-TDS using a GaAs photoconductive antenna as emitter/detector is around 0.2 THz which has not been stated elsewhere. </LI> <LI> This study provides a good recommendation in THz output power improvement by tuning the frequency response of the antenna toward the frequency response of the photoconductive material for an enhanced coupling of THz radiation to antenna. </LI> </UL> </P>

Design of a wideband continuous-wave photomixer antenna for terahertz wireless communication systems

Nguyen, Truong Khang,Kim, Sangin,Rotermund, Fabien,Park, Ikmo Informa UK (TaylorFrancis) 2014 Journal of electromagnetic waves and applications Vol.28 No.8