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[IEEE 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Rome (2018.6.19-2018.6.21)] 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Design of a Photoconductive Antenna for Pulsed-Terahertz Spectroscopy with Polarization Diversity
摘要： In the present paper, a photoconductive antenna is designed to work as both pulse-terahertz emitter and receiver. The proposed two-port antenna benefits from polarization diversity with high sensitivity of polarization detection. The antenna electrodes consist of three arms and two gaps that can be excited by laser illumination. An 800 nm wavelength laser beam with output power of 80 mW, 100 MHz repetition rate, and 100 fs laser pulse duration is considered as optical excitation. Each port stimulates a pulse that its polarization is orthogonal to that of the other one according to their arrangement. Along with GaAs as photoconductive substrate beneath the antenna electrodes, an anti-reflection coating of Taconic RF-35 is used for depreciating unwanted terahertz echoes. The simulated results clarify that the proposed antenna shows polarization diversity and also, proper broadband behavior.
关键词： spectroscopy,polarization diversity,pulsed terahertz,photoconductive antenna
更新于2025-09-23 15:23:52
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Chip-Scale Molecular Clock
摘要： An ultra-stable time-keeping device is presented, which locks its output clock frequency to the rotational-mode transition of polar gaseous molecules. Based on a high-precision spectrometer in the sub-terahertz (THz) range, our new clocking scheme realizes not only fully electronic operation but also implementations using mainstream CMOS technology. Meanwhile, the small wavelength of probing wave and high absorption intensity of our adopted molecules (carbonyl sulfide, 16O12C32S) also enable miniaturization of the gas cell. All these result in an 'atomic-clock-grade' frequency reference with small size, power, and cost. This paper provides the architectural and chip-design details of the first proof-of-concept molecular clock using a 65-nm CMOS bulk technology. Using a 231.061-GHz phase-locked loop (PLL) with frequency-shift keying (FSK) modulation and a sub-THz FET detector with integrated lock-in function, the chip probes the accurate transition frequency of carbonyl sulfide (OCS) gas inside a single-mode waveguide, and accordingly adjusts the 80-MHz output of a crystal oscillator. The clock consumes only 66 mW of dc power and has a measured Allan deviation of 3.8 × 10^{-10} at an averaging time of τ = 1000 s.
关键词： CMOS,molecular clock,rotational spectroscopy,Allan deviation,GPS,carbonyl sulfide (OCS),frequency stability,navigation
更新于2025-09-23 15:23:52
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Design and Simulation of Novel Gated Integrator for the Heavy ion Beam Monitors System
摘要： In this study, the objective is to realize a Gated Integrator (GI) circuit for silicon strip, Si(Li), CdZnTe and CsI detectors etc. With the development of radioactive ion beam physics, heavy-charged particles like carbon ions have been applied to the treatment of deep-seated inoperable tumors in the therapy terminal of the Heavy ion Research Facility in Lanzhou (HIRFL) located at the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS). A high resolution current measurement circuit was developed to monitor the beam current at 1pA range. The circuit consisted of a low current high sensitivity I/V converter and gated integrator in an energy spectroscopy. A low offset voltage precision amplifier and new guarding and shielding techniques were used in the I/V converter circuit which allowed to measure low current. This paper will show a MOS switch configuration which is used to prevent leakage current and novel technique to compensate a charge injection in the reset switch.
关键词： Noise,Gated Integrator,Energy Spectroscopy,Leakage Current Prevention,Charge Injection
更新于2025-09-23 15:23:52
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The Influence of Ceramic Far-Infrared Ray (cFIR) Irradiation on Water Hydrogen Bonding and its Related Chemo-physical Properties
摘要： The property of water is highly related to the earth's environment and climate change. The fundamental dynamical process of water is include formation and breaking of hydrogen bonds. This dynamic process, so far, is still poorly understood. We investigated weakening of the hydrogen bonds of water after ceramic Far-Infrared Ray (cFIR) irradiation and the resulting effects on physical and chemical properties of water. In this study, the Fourier transform infrared spectroscopy (FT-IR) was used to explore hydrogen bonding change of cFIR-irradiated water; in addition, capillary viscometers, Gas Chromatographs (GC), Differential Scanning Calorimetry (DSC), contact angles, Franz cells, High-Performance Liquid Chromatography (HPLC), and capillary electrophoresis analysis were used to evaluate its physical characteristics, such as viscosity, volatility, temperatures of water crystallization, surface tension, diffusion, hydrogen peroxide dissociation, solubility of solid particles, and changes in pH of acetic acid. The cFIR treated water decreased in viscosity and surface tension (contact angles), but increased in the solubility of solid particles, hydrogen peroxide dissociation, temperatures of water crystallization, and acidity of acetic acid. The weakening of water hydrogen bonds caused by cFIR irradiation is correspondent with our previous medical-biological studies on cFIR.
关键词： Hydrogen bonds,Fourier transform infrared spectroscopy (FT-IR),Contact angle,Ceramic far infrared ray (cFIR),Irradiation water,Solubility,Volatility
更新于2025-09-23 15:23:52
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Physical, Thermal and Spectroscopic Studies on Biofield Treated p-Dichlorobenzene
摘要： Para-dichlorobenzene (p-DCB) is widely used as a chemical intermediate in manufacturing of dyes, pharmaceuticals, polymers and other organic synthesis. The aim of present study was to evaluate the impact of biofield treatment on physical, thermal, and spectroscopic properties of p-dichlorobenzene. The p-dichlorobenzene sample was divided into two groups that served as treated and control. The treated group received Mr. Trivedi’s biofield treatment. Subsequently the control and treated samples were evaluated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV-Vis spectroscopy. XRD result showed an increase in crystallite size (4.93%) along with alteration in peak intensity of treated sample as compared to control. Furthermore, DSC analysis results showed that the latent heat of fusion of treated p-dichlorobenzene was considerably reduced by 8.66% as compared to control. The reduction in melting point of treated sample (54.99°C) was also observed as compared to control (57.01°C) p-dichlorobenzene. Moreover, TGA/DTG studies showed that Tmax (temperature, at which sample lost maximum of its weight) was increased by 6.26% and weight loss per degree celsius (°C) was decreased by 12.77% in biofield treated p-dichlorobenzene as compared to control sample. It indicates that thermal stability of treated p-dichlorobenzene sample might increase as compared to control sample. However, no change was found in UV-Vis spectroscopic character of treated p-dichlorobenzene as compared to control. These findings suggest that biofield treatment has significantly altered the physical and thermal properties of p-dichlorobenzene, which could make it more useful as a chemical intermediate.
关键词： Differential scanning calorimetry,Para-dichlorobenzene,Thermogravimetric analysis,and UV-Visible spectroscopy,Biofield treatment,X-ray diffraction study
更新于2025-09-23 15:23:52
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Resonance Tunneling Phenomena in Two-Dimensional Multilayer van der Waals Crystalline Systems
摘要： Works, mostly experimental, concerning the most interesting features of application of the resonant tunneling spectroscopy to a new type of heterosystems, van der Waals heterostructures, have been briefly reviewed. These heterostructures appeared after the recent discovery of two-dimensional crystals, which are a new class of materials beginning with graphene. The role of the angular matching of crystal lattices of conducting graphene electrodes of van der Waals systems in carrier tunneling between them has been analyzed together with the closely related problems of satisfaction of conservation laws in tunneling transitions. Manifestations of multiparticle correlation interactions between carriers in van der Waals systems such as Wigner crystallization of electrons in a two-dimensional electron gas in a magnetic field and Bose condensation of excitons in parallel two-dimensional electron gases have been briefly discussed.
关键词： angular matching,momentum conservation,resonant tunneling spectroscopy,graphene,two-dimensional crystals,Wigner crystallization,van der Waals heterostructures,Bose condensation
更新于2025-09-23 15:23:52
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Study of the Electronic and Electrical Properties of the C60F18 Polar Molecule on Au(111) Surface
摘要： For adequate description of the adsorption and self-assembly of C60F18 polar molecules on the surface Au(111), quantum-chemical studies of the electronic and electrical properties of a single molecule are performed. Using various procedures of density functional theory, the electric dipole moment of the molecule, distributions of the electrostatic potential, electric-field magnitude and electron density are calculated with controlled accuracy for the first time. An improved value of the electric dipole moment of the C60F18 molecule is obtained in a range from 10 to 11 D. The known approximation of a point dipole for electric-field strength is shown to be fulfilled within an accuracy of 30% even at distances twice greater than the size of the molecule. The structural fragments of the calculated lowest unoccupied and highest occupied molecular orbitals are assigned to their images, which were previously obtained using scanning tunneling microscopy and spectroscopy.
关键词： density functional theory,lowest unoccupied and highest occupied molecular orbitals,electric dipole moment,scanning tunneling spectroscopy,fullerene fluoride
更新于2025-09-23 15:23:52
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Use of near infrared spectroscopy and chemometrics to evaluate the shelf-life of cloudy sonicated apple juice
摘要： Fresh products, such as cloudy apple juice, could be preserved from early spoilage through the application of non-thermal processes such as sonication. However, shelf-life analyses based on microbiological and sensory evaluations are expensive and time consuming. Few studies have applied near infrared spectroscopy to evaluate the quality and decay of apple juices. Here, a feasibility trial was conducted to study the spectral behaviour at 1300–2500 nm combined with chemometric approaches. The shelf-life was monitored during two experiments, a challenge test with juices inoculated with spoilage yeasts (inoculated non-sonicated (INS)) and then submitted to sonication treatments (inoculated sonicated (IS)), and a storage test to evaluate the spoilage on non-inoculated juices (non-inoculated non-sonicated (NINS)) and sonicated non-inoculated juices (non-inoculated sonicated (NIS)). These experiments were investigated at six different refrigeration times 7, 14, 21, 28 and 60 days. Two functions were modelled to describe the behaviours of the first principal component according to the storage time. In agreement with a previous chemical and sensory evaluation, this approach allowed us to highlight shelf-life end points of 7 and 14 days for non-sonicated and sonicated samples, respectively. Three different models were evaluated for classification purposes: (1) sonicated versus non-treated samples, (2) end-point shelf-life evaluation at seven days for the NINS and INS juices and (3) end-point shelf-life discrimination at 14 days for IS and NIS samples. A partial least square-discriminant analysis enabled a group classification with accuracy values ranging from 0.63 to 1.00. The application of a variable importance in projection index to interpret the wavelengths of the spectral features suggests a contribution of organic acids and lipids to the prediction of decay. A canonical discriminant analysis provided a clearer separation of samples according to the storage time, especially in relation to the two time thresholds of 7 and 14 days.
关键词： Apple juice,spoilage,near infrared spectroscopy,shelf-life,sonication
更新于2025-09-23 15:23:52
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A variable importance criterion for variable selection in near-infrared spectral analysis
摘要： Variable selection is a universal problem in building multivariate calibration models, such as quantitative structure-activity relationship (QSAR) and quantitative relationships between quantity or property and spectral data. Significant improvement in the prediction ability of the models can be achieved by reducing the bias induced by the uninformative variables. A new criterion, named as C, is proposed in this study to evaluate the importance of the variables in a model. The value of C is defined as the average contribution of a variable to the model, which is calculated by the statistics of the models built with different combinations of the variables. In the calculation, a large number of partial least squares (PLS) models are built using a subset of variables selected by randomly re-sampling. Then, a vector of the prediction errors, in terms of root mean squared error of cross validation (RMSECV), and a matrix composed of 1 and 0 indicating the selected and unselected variables can be obtained. If multiple linear regression (MLR) is employed to model the relationship between the RMSECVs and the matrix, the coefficients of the MLR model can be used as a criterion to evaluate the contribution of a variable to the RMSECV. To enhance the efficiency of the method, a multi-step shrinkage strategy was used. Comparison with Monte Carlo-uninformative variables elimination (MC-UVE), randomization test (RT) and competitive adaptive reweighted sampling (CARS) was conducted using three NIR benchmark datasets. The results show that the proposed criterion is effective for selecting the informative variables from the spectra to improve the prediction ability of models.
关键词： multivariate calibration,multi-step strategy,variable selection,near-infrared spectroscopy
更新于2025-09-23 15:23:52
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A direct method to calculate second-order two-dimensional terahertz spectroscopy in frequency-domain based on classical theory
摘要： Previous theoretical researches on the two-dimensional terahertz spectroscopy (2DTS), which are conducted via inef?ciently time-consuming numerical simulation, deal with only single-mode system. To overcome the limitations, we derive a classical-theory-based analytical solution which is applicable to multi-modes system. Three typical weak sources of nonlinearities are introduced. The ?ndings suggest that the analytical results correspond well with those obtained by the traditional numerical simulation. Thus the study provides a more ef?cient and practical method to directly calculate 2DTS, and, in a broader sense, sheds new light on the theory of 2DTS.
关键词： terahertz,two-dimensional spectroscopy,classical method
更新于2025-09-23 15:23:52