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Published: 7 September 2020
Abstract:
Span>As conventional drug delivery system is being improved rapidly by target-based drug delivery system, finding suitable Drug Delivery System (DDS) for new drugs remains a challenge. Although there are many drug delivery vehicles in existence, a significant improvement is required to some DDS such as for local, implant-based treatments used for musculoskeletal infections. Many polymers have been considered for providing the improvement in DDS. Synthetic polymer, for example, has gained popularity for broad-spectrum physicochemical and mechanical properties. This article reviews the biomedical applications of Poly(TriMethylene Carbonate-co-Caprolactone) (PTMCC), which has attracted attention due to its biocompatibility, biodegradability and rubber-like properties. Its synthesis, physical properties, and degradation are also discussed here. Although it is relatively new in biomedical applications, it is readily usable for the fabrication of differing format of DDS of superior mechanical strength and degradation properties. The use of PTMCC is expected to increase in coming years as more is revealed about its potentials.
Published: 25 March 2018
Abstract:
Span>In the space industry, structures undergo several vibration and acoustic tests in order to verify their design and give confidence that they will survive the launch and other critical in-orbit dynamic scenarios. At component level, vibration tests are conducted with the aim to reach local or global interface loads without exceeding the design loads. So, it is often necessary to control and limit the input based on a load criterion. This means the test engineer should be able to assess the interface loads, even when load cannot be measured. This paper presents various approaches to evaluate interface loads using measured accelerations and by referring to mass operators. Various methods, from curve fitting techniques to finite element-based methods are presented. The methods are compared using signals with known imperfection to identify strengths and weaknesses of each mass operator definition.
Published: 25 July 2017
Abstract:
Span>Passive dynamic vibration absorbers (DVAs) are often used to suppress the excessive vibration of a large structure due to their simple construction and low maintenance cost compared to other vibration control techniques. A new type of passive DVA consists of two pendulums connected with spring and dashpot element is investigated. This research evaluated the performance of the DVA in reducing the vibration response of a two degree of freedom shear structure. A model for the two DOF vibration system with the absorber is developed. The nominal absorber parameters are calculated using a Genetic Algorithm(GA) procedure. A parametric study is performed to evaluate the effect of each absorber parameter on performance. The simulation results show that the optimum condition for the absorber frequencies and damping ratios is mainly affected by pendulum length, mass, and the damping coefficient of the pendulum's hinge joint. An experimental model validates the theoretical results. The simulation and experimental results show that the proposed technique is able be used as an effective alternative solution for reducing the vibration response of a multi degree of freedom vibration system.
S.Y. Yu, H.S. Choi, K.S. Park, Y.T. Kim,
Structural Engineering and Mechanics, Volume 62, pp 381-389; https://doi.org/10.12989/sem.2017.62.4.381

Abstract:
Advanced procedure for estimation of pipeline embedment on soft clay seabed seabed embedment;soft clay;dynamic installation;dynamic environment;pipe-soil interaction; In the present study, the advanced procedure has been proposed to estimate higher accuracy of embedment of pipes that are installed on soft clay seabed. Numerical simulation by OrcaFlex simulation code was performed to investigate dynamic seabed embedment, and two steps, i.e., static and dynamic analysis, were adopted. In total, four empirical curves were developed to estimate the seabed embedment including dynamic phenomena, i.e., behaviour of vessel, environmental condition, and behaviour of nonlinear soil. The obtained results were compared with existing methods (named general method) such as design code or guideline to examine the difference of seabed embedment for existing and advance methods. Once this process was carried out for each case, a diagram for estimating seabed embedment was established. The applicability of the proposed method was verified through applied examples with field survey data. This method will be very useful in predicting seabed embedment on soft clay, and the structural behaviours of installed subsea pipelines can be changed by the obtained seabed embedment in association with on-bottom stability, free span, and many others.
Yeong-Man Kwon, , , Gye-Chun Cho
Published: 25 May 2017
Geomechanics and Engineering, Volume 12, pp 753-770; https://doi.org/10.12989/gae.2017.12.5.753

Abstract:
ε-polylysine biopolymer for coagulation of clay suspensions ${\varepsilon}-polylysine$;sedimentation;biopolymer;coagulation;flocculation; The coagulation or flocculation of cohesive clay suspensions is one of the most widely used treatment technologies for contaminated water. Flocculated clay can transport pollutants and nutrients in ground water. Coagulants are used to accelerate these mechanisms. However, existing coagulants (e.g., polyacrylamide, polyaluminum chloride) are known to have harmful effects in the environment and on human health. As an alternative, eco-friendly coagulant, this study suggests ${\varepsilon}-polylysine$, a cationic biopolymer fermented by Streptomyces. A series of sedimentation experiments for various ${\varepsilon}-polylysine$ concentrations were performed, and the efficiency of sedimentation with ${\varepsilon}-polylysine$ was estimated by microscopic observation and light absorbance measurements. Two types of sedimentation were observed in the experiments: accumulation sedimentation (at 0.15%, 0.20%, 0.25% ${\varepsilon}-polylysine$) and flocculation sedimentation (at 0%, 0.1%, 0.5%, 1.0%, 2.0% ${\varepsilon}-polylysine$). These sedimentation types occur as a result of the concentration of counter ions. Additionally, the performance of ${\varepsilon}-polylysine$ was compared with that of a previously used environmentally friendly coagulant, chitosan. The obtained results indicate that flocculation sedimentation is appropriate for contamination removal and that ${\varepsilon}-polylysine$ functions more efficiently for clay removal than chitosan. From the experiments and analysis, this paper finds that polylysine is an alternative eco-friendly coagulant for removing chemical contaminants in groundwater.
R. Usharani, , M. Umapathy, S.B. Choi
Published: 25 May 2017
Smart Structures and Systems, Volume 19, pp 567-576; https://doi.org/10.12989/sss.2017.19.5.567

Abstract:
A new broadband energy harvester using propped cantilever beam with variable overhang broadband;energy harvester;piezoelectric;propped beam;resonance;vibration; Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.
Published: 25 May 2017
Smart Structures and Systems, Volume 19, pp 539-551; https://doi.org/10.12989/sss.2017.19.5.539

Abstract:
Thermoelectric viscoelastic materials with memory-dependent derivative magneto-thermo-viscoelasticity;thermoelectric materials;memory-dependent derivative;time-delay;kernel function;numerical results; A mathematical model of electro-thermoelasticity has been constructed in the context of a new consideration of heat conduction with memory-dependent derivative. The governing coupled equations with time-delay and kernel function, which can be chosen freely according to the necessity of applications, are applied to several concrete problems. The exact solutions for all fields are obtained in the Laplace transform domain for each problem. According to the numerical results and its graphs, conclusion about the proposed model has been constructed. The predictions of the theory are discussed and compared with dynamic classical coupled theory. The result provides a motivation to investigate conducting thermoelectric viscoelastic materials as a new class of applicable materials.
, Toshiki Yokoi, Lukas Neumann, Hiroyuki Yasukochi, Kentaro Soeda, Tsuyoshi Totani, Masashi Wakita,
Advances in aircraft and spacecraft science, Volume 4, pp 281-296; https://doi.org/10.12989/aas.2017.4.3.281

Yaguang Yang, Zhiqiang Zhou
Advances in aircraft and spacecraft science, Volume 4, pp 335-351; https://doi.org/10.12989/aas.2017.4.3.335

Chaitra Raghunath, Layne T. Watson, Mohamed Jrad, Rakesh K. Kapania, Raymond M. Kolonay
Advances in aircraft and spacecraft science, Volume 4, pp 317-334; https://doi.org/10.12989/aas.2017.4.3.317

Redha Yeghnem, Hicham Zakaria Guerroudj, Lemya Hanifi Hachemi Amar, Sid Ahmed Meftah, , , El Abbas Adda Bedia
Published: 25 May 2017
Computers and Concrete, Volume 19, pp 579-588; https://doi.org/10.12989/cac.2017.19.5.579

, An T.P. Tran, , Gye-Chun Cho
Published: 25 May 2017
Geomechanics and Engineering, Volume 12, pp 815-830; https://doi.org/10.12989/gae.2017.12.5.815

Abstract:
Dynamic properties of gel-type biopolymer-treated sands evaluated by Resonant Column (RC) Tests biopolymer treatment;gellan gum;xanthan gum;shear modulus;damping ratio; Due to numerous environmental concerns in recent years, the search for and the development of sustainable technologies have been pursued. In particular, environmentally friendly methods of soil improvement, such as the potential use of biopolymers, have been researched. Previous studies on the use of biopolymers in soil improvement have shown that they can provide substantial strengthening efficiencies. However, in order to fully understand the applicability of biopolymer treated soils, various properties of these soils such as their dynamic properties must be considered. In this study, the dynamic properties of gel-type biopolymer treated soils were observed through the use of resonant column tests. Gellan gum and Xanthan gums were the target gel-type biopolymers used in this study, and the target soil for this study was jumunjin sand, the standard sand of Korea. Through this study it was demonstrated that biopolymers can be used to enhance the dynamic properties of the soil, and that they offer possibilities of reuse to reduce earthquake related soil failures.
Min-Kyung Jeon, , Jin-Sung Park,
Published: 25 May 2017
Geomechanics and Engineering, Volume 12, pp 849-862; https://doi.org/10.12989/gae.2017.12.5.849

Abstract:
In situ viscoelastic properties of insoluble and porous polysaccharide biopolymer dextran produced by Leuconostoc mesenteroides using particle-tracking microrheology complex shear modulus;biopolymer;dextran;particle tracking micro-rheology; With growing interests in using bacterial biopolymers in geotechnical practices, identifying mechanical properties of soft gel-like biopolymers is important in predicting their efficacy in soil modification and treatment. As one of the promising candidates, dextran was found to be produced by Leuconostoc mesenteroides. The model bacteria utilize sucrose as working material and synthesize both soluble and insoluble dextran which forms a complex and inhomogeneous polymer network. However, the traditional rheometer has a limitation to capture in situ properties of inherently porous and inhomogeneous biopolymers. Therefore, we used the particle tracking microrheology to characterize the material properties of the dextran polymer. TEM images revealed a range of pore size mostly less than $20{\mu}m$, showing large pores > $2{\mu}m$ and small pores within the solid matrix whose sizes are less than $1{\mu}m$. Microrheology data showed two distinct regimes in the bacterial dextran, purely viscous pore region of soluble dextran and viscoelastic region of the solid part of insoluble dextran matrix. Diffusive beads represented the soluble dextran dissolved in an aqueous phase, of which viscosity was three times higher than the growth medium viscosity. The local properties of the insoluble dextran were extracted from the results of the minimally moving beads embedded in the dextran matrix or trapped in small pores. At high frequency (${\omega}>0.2Hz$), the insoluble dextran showed the elastic behavior with the storage modulus of ~0.1 Pa. As frequency decreased, the insoluble dextran matrix exhibited the viscoelastic behavior with the decreasing storage modulus in the range of ${\sim}0.1-10^{-3}Pa$ and the increasing loss modulus in the range of ${\sim}10^{-4}-1\;Pa$. The obtained results provide a compilation of frequency-dependent rheological or viscoelastic properties of soft gel-like porous biopolymers at the particular conditions where soil bacteria produce bacterial biopolymers in subsurface.
Sheng-Huoo Ni, Yu-Zhang Yang, Chia-Rong Lyu
Published: 25 May 2017
Smart Structures and Systems, Volume 19, pp 513-521; https://doi.org/10.12989/sss.2017.19.5.513

, Habib Uysal
Published: 25 May 2017
Computers and Concrete, Volume 19, pp 589-597; https://doi.org/10.12989/cac.2017.19.5.589

Abstract:
Reinforcement detailing of a corbel via an integrated strut-and-tie modeling approach computer-aided design;strut-and-tie model;structural optimization;performance decision;reinforced concrete;steel reinforcement; Strut-and-tie modeling method, which evolved on truss-model approach, has generally been preferred for the design of complex reinforced concrete structures and structural elements that have critical shear behavior. Some structural members having disturbed regions require exceptional detailing for all support and loading conditions, such as the beam-column connections, deep beams, short columns or corbels. Considering the general expectation of exhibiting brittle behavior, corbels are somewhat dissimilar to other shear critical structures. In this study, reinforcement layout of a corbel model was determined by the participation of structural optimization and strut-and-tie modeling methods, and an experimental comparison was performed against a conventionally designed model.
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