Showing papers in "Communications in Physics in 2016"
20 citations
TL;DR: In this paper, the authors investigated the quality of a nano-beam resonator with different vibration modes using the finite element method and showed that the quality is lower at low order modes than at high order modes.
Abstract: The obtainable quality factor for a nano beam resonator is limited due to internal damping such as thermoelastic damping. Therefore, understanding how internal damping varies with the respective resonant modes is very important to design a high performance nanoresonator. In this research, we investigate thermoelastic damping depending on vibration modes of nano beam resonators using finite element method. The study results show that the quality factor of a nanoresonator is lower than at high order modes. The silicon nano beam resonator with the quality factor larger than one million can be achieved by optimizing the dimensions of the resonant beam.
16 citations
TL;DR: In this paper, a hydrothermal approach for the synthesis of zinc stannate (Zn2SnO4) nanocrystals was reported, where the effect of the molar ratio of initial chemicals, reaction temperature and reaction duration on the phase composition and the fluorescence properties were investigated.
Abstract: Abstract. In this work we report a hydrothermal approach for synthesis of zinc stannate (Zn2SnO4)nanocrystals. Our research focused on the effect of the molar ratio of initial chemicals, reaction temperature and reaction duration on the phase composition and the fluorescence properties.Structural and optical properties of the final products were investigated in detail. X-ray diffractionanalysis indicated that the Zn2SnO4 nanocrystals possess face-centered cubic crystal structure.Raman scattering spectra exhibit two characteristic vibrational modes of Zn2SnO4 crystals. Optical band gap of Eu3+-doped Zn2SnO4 nanocrystals obviously depends on Eu3+content. Theroom-temperature emission spectra of the undoped Zn2SnO4 nanocrystals show two broad bands,while the photoluminescence spectra of Eu3+-doped Zn2SnO4 nanocrystals exhibit the emissionpeaks related to the radiative intra-configurational f-f tr ansitions of Eu3+ions. The absorptiontransitions within Eu3+ions were observed both in the photoluminescence excitation spectra andin the diffuse reflection spectra.
10 citations
TL;DR: In this paper, the authors introduce spacetimes with pseudosymmetric energy-momentum tensors and characterize the perfect fluid spacetimewith pseudosymmetric EMT tensors.
Abstract: The object of the present paper is to introduce spacetimes with pseudosymmetricenergy-momentum tensor. In this paper at first we consider the relation \(R(X,Y)\cdot T=fQ(g,T)\), that is, the energy-momentumtensor \(T\) of type (0,2) is pseudosymmetric. It is shown that in a general relativistic spacetimeif the energy-momentum tensor is pseudosymmetric, then the spacetime is also Ricci pseudosymmetricand the converse is also true. Next we characterize the perfect fluid spacetimewith pseudosymmetric energy-momentum tensor. Finally, we consider conformally flat spacetime withpseudosymmetric energy-momentum tensor.
6 citations
TL;DR: In this article, a colloidal paste of TiO2 embedded with graphene was fabricated and used to spread TiO(2) film photo-electrode of DSSC solar cells.
Abstract: Colloidal paste of TiO2 embedded with graphene (GS) was fabricated and used to spread TiO\\(_2\\) film photo-electrode of DSSC solar cells. The dye N179 and Iodine-based electrolyte were used in the DSSC solar cells. Raman scattering, SEM images were used to identify the material phases and microstructure of the film photo-electrode. I/V characteristics of the DSSC cells were recorded at room temperature. Open-circuit voltage Voc, short-current \\(J_{sc}\\) and efficiency η of the DSSC cells were estimated. It shows that graphene addition has affected on \\(V_{oc}\\),\\(J_{sc}\\) and \\(\\eta\\). The \\(V_{oc}\\),\\(J_{sc}\\) and \\(\\eta\\) abnormally depend on graphene content. The efficiency reached a maximal value with graphen concentration of 0.005 wt %, after that decreased. It is supposed to be related with an improving the charge transfer in the working photo-electrode of DSSC.
4 citations
TL;DR: ZnS:Mn nanoparticles were synthesized by co-precipitation method from the precursors solutions of 0.1M Zn(CH3COO)2, Na2S and Mn(CH 3COO), and then were capped with polyvinyl pyrrolidone.
Abstract: ZnS:Mn nanoparticles were synthesized by co-precipitation method from the precursors solutions of 0.1M Zn(CH3COO)2, Na2S and Mn(CH3COO)2 then were capped with polyvinyl pyrrolidone. The XRD patterns showed that the ZnS:Mn nanoparticles possessed the T 2 d −F43̄m cubic structure with the average crystallite size of several nanometers. At 300 K, the obtained photoluminescence spectra showed only a wide yellow-orange band centered at 603 nm, which should be attributed to the radiation transition of [T1(G)→A1(S)] of Mn2+(3d5) cations in the ZnS matrix. The excitation spectra recorded at 300 K on the other hand featured a strong photoluminescence band around 344 nm, which were assigned to the near band-edge absorption transition of ZnS host lattice, in addition with three weaker bands relating to the absorption transitions of [A1(S)→ T2(D)]: 430 nm, [A1(S)→ A1(G) – 4E(4G)]: 468 nm, and [A1(S)→ T2(G)]: 492 nm of Mn2+(3d5) cations. It was shown that the capping affected only the intensities of emissions bands.
3 citations
TL;DR: In this paper, the authors focused on assessing radiation doses caused by radioactive substances released from the Ninh Thuan 1 nuclear power plant (NPP) to the environment under scenario of an INES-level 7 nuclear accident caused by two incidents: Station Black Out (SBO) and Loss of Coolant Accident (LOCA) using software RASCAL4.
Abstract: Based on guidance RG 1.109, RG 1.111 published by United States Nuclear Regulatory Commission (USNRC) our research concentrates on assessing radiation doses caused by radioactive substances released from the Ninh Thuan 1 nuclear power plant (NPP) to the environment under scenario of an INES-level 7 nuclear accident caused by two incidents: Station Black Out (SBO) and Loss of Coolant Accident (LOCA) using software RASCAL4.3 provided by the Emergency Operations Center of USNRC. The Ninh Thuan 1 NPP is assumed to use the VVER-1200 technology with a total power of 2400 MWefrom two units. The input data for the model calculations is built based on the accident scenario, the technical parameters of VVER-1200 technology and the meteorology. In this work the meteorological data on dry and rainy seasons which are typical for the Ninh Thuan region was considered. The maximum dose distributions were calculated within 40 km from the NPP site.The distributions are strongly affected by meteorological conditions. In the rainy season the dose values near the plant are higher than those in the dry season due to the deposition effect of the radioactive substances. The calculation results show that consequences of the accident are very serious. A total radioactivity of radiological equivalence 225,000 TBq to 131I released to the atmosphere. Within 20 km the Total Effective Dose Equivalence (TEDE) values are very high, about several tens of times greater than the dose limit. It is requested to establish National Steering Board for Accident Response to direct the relevant authorities in response for the accident consequences and ensure for security in the area of NPP. The public communication, emergency preparedness plan, people evacuation must be implemented under the guidance of Circular 25/2014/TT-BKHCN.
3 citations
2 citations
TL;DR: In this article, a set of experiments on photo-heating in tissues containing gold nanoshells (NSs) and nanorods (NRs) were performed, and the temperature of tissues were measured with different amounts gold NSs and NRs under illumination of a continuous diode laser at 808 nm and power density from 20 to 62 W/cm.
Abstract: We perform a set of experiments on photo-heating in tissues containing gold nanoshells (NSs) and nanorods (NRs). The temperature of tissues were measured with different amounts gold NSs and NRs under illumination of a continuous diode laser at 808 nm and power density from 20 to 62 W/cm\\(^{2}\\). The temperature of the tissues injected gold nanoparticles increased to $66 \\pm 4\\(^{\\circ}\\)C for \\(2.1 \\times 10^{8}\\) NSs and \\(73\\pm 4\\) \\(^{\\circ}\\)C for gold \\(5.4 \\times 10^{9}\\) NRs after 10 min exposition at power density 35 W/cm\\(^{2}\\). The control tissue without gold nanoparticles demonstrated a significantly lower temperature \\(40 \\pm 4\\) \\(^{\\circ}\\)C in the same time of illumination. The temperature can be reached up to around 100\\(^{\\circ}\\)C for tissue with both NSs and NRs at 62 W/cm\\(^{2}\\) inrradiation for \\(7-10\\) min.
1 citations
TL;DR: In this paper, the optical bistability of an electromagnetically induced transparency medium placed in a conventional unidirectional ring cavity is investigated numerically, where the medium is excited by a coupling and probe laser lights via a five-level cascade scheme.
Abstract: Optical bistability (OB) of an electromagnetically induced transparency (EIT) medium placed in a conventional unidirectional ring cavity is investigated numerically. The medium is excited by a coupling and probe laser lights via a five-level cascade scheme. It is shown that optical bistabe states with controllable switching threshold intensities and width establish simultaneously in three spectral regions corresponding to EIT windows. The current numerical result is compared to a previous analytical result showing influence of coherence terms neglected in the analytical model.
1 citations
TL;DR: In this paper, the structure of the ligand and the complex were investigated by nuclear magnetic resonance spectroscopy; by single crystal X-ray diffraction; and by UV-VIS absorption spectrum analysis.
Abstract: This study aims to synthesize the Cu+/bipyridyl-based complex using Sonogashira cross coupling. The structure of the ligand and the complex were investigated by nuclear magnetic resonance spectroscopy; by single crystal X-ray diffraction and by UV-VIS absorption spectroscopy. The obtained experimental results were in good agreement with the theoretical calculations. The complex is a potential candidate to be the photo sensitizer in dye-sensitized solar cells.
TL;DR: The structure of neuroglobin was still very stable although the disulfide bridge was absent and the increasing distance between the distal histidine and heme group could allow oxygen to bind more easily.
Abstract: In this paper, we investigated the role of the disulfide bridge in the structural stability of wild-type human neuroglobin. The classical simulation of the neuroglobin without the disulfide bridge was performed for a long simulation run of 240 ns using a new parameter set of Gromos96 force field and the latest data entry as the initial topologies. We used the analyzed data of original neuroglobin with the remained disulfide bridge to compare to the ones from this simulation. Our results showed that, the structure of neuroglobin was still very stable although the disulfide bridge was absent. There was only a few residues in B and C helices having a higher mobility. The most interesting result we obtained was that the increasing distance between the distal histidine and heme group could allow oxygen to bind more easily.
TL;DR: In this paper, the optical performance and characteristics of diode-end-pumped passively Cr4+:YSO Q-switched solid-state Cr3+:LiSAF lasers using a rate equation system extended to multi-wavelength were investigated.
Abstract: We have numerically investigated, for the first time, the optical performance and characteristics of diodeend-pumped passively Cr4+:YSO Q-switched solid-state Cr3+:LiSAF lasers using a rate equation system extended to multi-wavelength. Homogeneously broadened emission spectra of the laser crystal and broad absorption spectra of Cr4+:YSO saturable absorber have been respected in the investigation. A tunable passively Q-switched laser operation is also developed with a birefringent filter plate used as an intracavity selective element. As a result, improved understanding of passively Q-switched Cr4+:YSO solid-state Cr3+:LiSAF lasers has been obtained in broadband and tunable laser operations. Characteristics of the tunable passively Q-switched Cr3+:LiSAF laser were demonstrated to be clearly dependent on wavelength. The spectro-temporal evolution of a single pulse emitted from the passively Q-switched Cr3+:LiSAF laser has been reported.
TL;DR: In this article, the results of an experimental study of three samples containing various elements in the near-surface layers were investigated by Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA).
Abstract: This paper presents the results of an experimental study of three samples containing various elements in the near-surface layers. The depth profiles of all the elements of different atomic masses from hydrogen to silver were investigated by Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA). The experiments were performed by using the low-energy (about 2 MeV) 4 He + ion beams. The obtained results demonstrate the possibility of the RBS and ERDA methods in the investigation of depth profiles of any mass element with an atomic concentration of about 0.01 at.% and a depth resolution close to 10 nm.
TL;DR: In this article, the authors discuss about Robertson-Walker space-time with quadratic equation of state and dynamical cosmological parameter Λ and obtain exact solutions of Einstein's field equations for three cases.
Abstract: This paper discusses about Robertson-Walker space-time with quadratic equation of state and dynamical cosmological parameter Λ. Some exact solutions of Einstein’s field equations for three cases have been obtained. Physical behaviors of the models are discussed in detail.
TL;DR: In this article, a gamma ray spectrometer protected by a lead shield (Model 747E Canberra lead shield) and an active shield made of an 80cm × 80 cm × 3 cm plastic scintillator plate in anticoincidence on top of the lead shield is described.
Abstract: The article describes a gamma ray spectrometer protected by a lead shield (Model 747E Canberra lead shield) and an active shield made of an 80 cm × 80 cm × 3 cm plastic scintillator plate in anticoincidence on top of the lead shield. The detector used as low background gamma-spectrometer is a high purity Germanium crystal of model GC2018 Canberra. The background count rate currently achieved (30-2400 keV) is 1.27 cps without anticoincidence. The level of background suppression obtained from the active protection is 0.80 overall and about 0.43 for the 511 keV gamma line. The gamma ray spectrometer is installed and operated in the Nuclear Laboratory, Department of Nuclear Physics, University of Science, HCMC-Vietnam National University.
TL;DR: In this paper, the second-order correlation data of the Hanbury Brown -Twiss interferometer was used to measure the antibunching effect from single Rhodamine B dye molecules and single CdTe quantum dots in dilute solution.
Abstract: Antibunching is a quantum effect demonstrating clearly the quantum nature of the radiation field. Its detection through measurements of the second order correlation function is a direct proof of the presence of single molecule or single nano particle. In this paper we present the experimental setup of the Hanbury Brown - Twiss interferometer and the measurement results of the antibunching effect from single Rhodamine B dye molecules and single CdTe quantum dots in dilute solution. By fitting the second order correlation data, we derive a fluorescence lifetime of approximately 2 ns for Rhodamine B and 45 ns for CdTe quantum dots. Our results demonstrate an alternative way for determining the fluorescence lifetime using the antibunching effect.
TL;DR: In this article, the influence of surface plasmon of gold nanoparticles on the optical properties of the fluorescent nanoparticles in aqueous solution was investigated, and it was shown that fluorescence enhancement or quenching is attributed to the increase or decrease of radiative recombination rates, respectively.
Abstract: The influence of the surface plasmon of gold nanoparticles on the optical properties of the fluorescent nanoparticles in aqueous solution have been investigated. The fluorescence of nanoparticles can be enhanced or quenched in the presence of gold nanoparticles depending on the domination of energy transfer mechanisms: radiating surface plasmon coupling emission or Förster energy transfer from fluorescent particles to gold particles, which exciting absorbing plasmon. The fluorescence enhancement or quenching is attributed to the increase or decrease of radiative recombination rates, respectively. The parameters of the energy transfer between fluorescent nanoparticles (dye molecules encapsulated in silica nanoparticles) and nano golds have been estimated. The results show that the interactions between nanoparticles depend on the size of both fluorophores (as donors) and gold nanoparticles (as acceptors).
TL;DR: In this paper, the L-band microwave radiometers were used for measuring the brightness temperature of the bare soil and the experimental results showed that the model of Choudhury et al. for surface roughness correction provided a better fit to radiometric data over the angular range between 20° and 50° for n = 0.
Abstract: Since 2012, the experts of Space Technology Institute have carried out the field experiments to obtain a high-resolution dataset of microwave radiometers for land surface parameters (soil moisture, soil temperature, vegetation water content), in order to improve the soil moisture retrieval methodology. L-band radiometers were used for measuring the brightness temperature of the bare soil. Field experiments for passive microwave remote sensing of soil moisture were carried out in Hoai Duc District in 2012. L-band microwave radiometers were used for measuring the microwave emission of bare agricultural fields. The radiometers, which are used for soil moisture measurement, worked well during the experimental campaign and produced volumetric soil moisture estimates that compared well with the ground-truth measurements. Explanations for the observed discrepancies are presented. The experimental results showed that the model of Choudhury et al. for surface roughness correction provides a better fit to radiometric data over the angular range between 20° and 50° for \\(n = 0\\) (i.e., the \\(\\cos ^{2}\\theta\\) factor in the exponential in (15) is suppressed). Based on the results of the experiments conducted over two experimental sites with different soils, namely sandy loam at Hoai Duc Agrometeorologyl Center, it may be concluded that the testing of both the radiometric equipment and the method for soil moisture retrieval was very successful, and the main goal of the experiments was fulfilled.
TL;DR: A self-similarity approximation model for three-wave resonant interaction in transient backward stimulated Raman scattering (BSRS) was derived by Abdolvand et al..
Abstract: A self-similarity approximation model for three-wave resonant interaction in transient backward stimulated Raman scattering (BSRS) was derived. Interestingly, as its asymptotic solution, the train of solitary backward Raman pulse train is possibly formed. This result can be considered as an increment of “single” soliton observed previously [A. Abdolvand et al ., Phys. Rev. Lett 103 , 183902 (2009)].
TL;DR: In this article, the experimental method to determinate photo luminescence (PL) quantum yield (QY) of CdSe quantum dot was described and the experimental condition which depends on QY was investigated.
Abstract: The fluorescence quantum yield or the efficiency of the fluorescence process is defined as the ratio of the number of photons emitted to the number of photons absorbed. In this report the experimental method to determinate photo luminescence (PL) quantum yield (QY) of CdSe quantum dot will be described. The experimental condition which depends on QY will be investigated. The QY values of CdSe which were prepared at Nano Materials Physics Laboratory Research Center for Dielectric and Advanced Matters Physics Pusan National University will be carried out and compared with the commercial CdSe sample.
TL;DR: In this article, the authors considered a nonlinear system with random telegraph noises in a Raman ring laser by modeling the laser pump light as a pre-Gaussian process and found an exactly soluble equation for the stationary probability distribution of fluctuations in this system under the influence of two-telegraph noise.
Abstract: In this paper, we will consider a nonlinear system with random telegraph noises in a Raman ring laser by modeling the laser pump light as a pre-Gaussian process and find an exactly soluble equation for the stationary probability distribution of fluctuations in this nonlinear system under the influence of two-telegraph noise. As a consequence, we will obtain the so-called noise reduction in this system: the Stokes output of this laser tends to stabilize under the influence of the broad-band two-telegraph pre-Gaussian pump and compare this result with that obtained in our previous paper (Cao Long Van, Doan Quoc Khoa, Opt. Quant. Electron. 43 (2012) 137) for the case of one-telegraph noise.
TL;DR: In this article, the dependence of luminescence intensity on alkali borotellurite (ABTe) ions concentration in ABTe glasses has been studied and the method of Van Uitert was used to find the dominant interaction mechanism for energy transfer process.
Abstract: The dependence of luminescence intensity on Sm\\(^{3 + }\\) ions concentration in alkali borotellurite (ABTe) glasses has been studied. The quenching of luminescence intensity happens around 0.75 mol% concentration of Sm\\(^{3 + }\\) ions and it can relate the energy transfer process through cross--relaxation (CR), the CR channels in ABTe: Sm\\(^{3 + }\\) have been shown. The method of Van Uitert was used to find the dominant interaction mechanism for energy transfer process.
TL;DR: In this paper, the authors reviewed the recent progress in the generation and amplification of ultraviolet laser emissions using LiCAAlF material as a gain medium and investigated improvements and proposed possibilities to generate and amplify ultraviolet short-pulse Ce:LiCAF laser emission to high peak power of terawatt.
Abstract: We review the recent progresses in generation and amplification of ultraviolet laser emissions using Ce$^{3 + }$:LiCaAlF$_{6}$ (Ce:LiCAF) material as a gain medium. Basing on comparative studies, we have investigated improvements and proposed possibilities to generate and amplify ultraviolet short-pulse Ce:LiCAF laser emission to high peak power of terawatt.