PRO2FLUX – A software program for profile quantification and diffusive O2 flux calculations

A new software program, PRO₂FLUX, has been developed for the treatment of the vertical distribution of O₂ concentrations measured with microsensors in aquatic sediments. The program proposes a friendly graphical user interface to visualize and quantify oxygen profiles semi-automatically. Once a data set has been selected and various parameters (e.g., diffusivity) have been set in the program, the user can convert the raw data signal in concentration units and can define the position of the sediment–water interface for obtaining the depth profiles. Then, PRO₂FLUX enables the user to make diffusive O₂ calculations using three of the most widely used models: (1) Fick's first law of diffusion, (2) a quadratic curve-fitting approach, and (3) Berg's model. The PRO₂FLUX software creates two types of output ASCII files for each calculation technique: a summary file for the first two diffusive models and an automatically generated input data file necessary for running Berg's model.     

Fabrication and frequency response of dual-element ultrasonic transducer using PZT-5A thick film

Ultrasonic transducers based on PZT-5A thick films deposited onto polycrystalline Al₂O₃ substrates using screen-printing were successfully fabricated. Considering the relatively high sintering temperature of PZT-5A thick films and better impedance matching characteristics with PZT-5A, polished polycrystalline Al₂O₃ were used as substrates. For electrodes, high quality platinum (Pt) was deposited by a thin film process, because the surface state of electrodes greatly affects the quality of piezoelectric films. Applying Pt/PZT-5A/Pt/Al₂O₃ structures, dual-element ultrasonic transducers were assembled. The assembled transducers included a wear plate (normally alumina with 40.21 × 10⁶ kg/m² s of impedance), backing (tungsten carbide-epoxy), electrical matching, an epoxy glue layer, and a housing. The optimum measurement ranges of 5 and 10 MHz ultrasonic transducers were 2.51–300.2 and 2.50–250.1 mm, respectively. From the time and frequency response measurements of the assembled 10 MHz DEUTs, the value of −20 dB level waveform duration and the −6 dB bandwidth was 481.8 ns and 34.4%, respectively. Also, the measurement accuracies of both 5 and 10 MHz DEUTs assembled in this study were below 0.1 and 0.4%, respectively.     

Gas sensing properties of nanostructured bismuth oxychloride

In this work, nanostructured bismuth oxychloride (BiOCl) was prepared by a surfactant-assisted method. Bismuth trichloride and dioctyl sulfosuccinate (AOT) were dissolved in non-aqueous media, producing a fine precipitate. The calcination of the precipitated particles at 180 °C produced 3D hierarchical BiOCl semi-spherical architectures, assembled by microplates. The increase of the calcination temperature to 600 °C produced nanostructured ribbons, which are formed by the stacking of several BiOCl layers. Other microstructures can be formed at different calcination temperatures or by using other surfactants. Thick-films of the as-prepared BiOCl ribbons were made by its direct deposition on alumina substrates. The gas sensing characterization was performed at 300 and 400 °C using alternating current (AC). The tests gases were compressed air, CO, CO₂ and O₂. Humidity effects were discarded by using the extra dry version of these gases. At 300 °C, reproducible CO gas sensing patterns were obtained; however, the detection of CO₂ and O₂ produced unreliable results. At 400 °C, reliable gas sensing patterns were obtained in CO, CO₂ and O₂. According to its gas response, BiOCl behaved as a p-type seminconductor material.     

Interferometric porous silicon transducers using an enzymatically amplified optical signal

This paper describes a novel transducer principle converting biomolecular binding events into changes in porous silicon structural colour. An enzyme-catalysed reaction, horseradish peroxidase (HRP) mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), induced an amplified optical detection signal on an antibody-functionalised porous silicon film, which manifested as significant changes in the Fabry–Pérot fringe pattern. Exposing porous silicon to non-oxidised TMB and oxidised TMB products and measuring the resulting effective optical thickness (EOT) changes of the porous silicon layer, an amplified signal from porous silicon was found, caused by an intermediate radical cation produced during the enzymatic-catalysed oxidation of TMB. Finally, it was shown that this system could be used to detect a human immunoglobulin (IgG) at 0.2 μg/ml. This work may lead to the development of new biosensors where porous silicon acts as the sensing matrix and transducer element.     

Thermodynamic assessment of the Fe–V–O system

The Fe–V–O system over the whole composition range was optimized according to the reliable phase equilibria and thermodynamic data. The modified quasichemical model was used to describe the liquid phase from metal alloy to oxide melt. Based upon the Compound Energy Formalism, the FeV₂O₄–Fe₃O₄ spinel solution was described by a sublattice model considering the cation distribution between tetrahedral and octahedral sites. Wüstite, corundum and (VO₂)_s.s. were described using a simple Bragg-Williams model. A set of self-consistent model parameters was obtained and the available phase diagram and thermodynamic data were reproduced well within experimental error limits. The complex phase relations in the Fe–V–O system at various temperatures and oxygen partial pressures were elucidated.     

Magnetoelectric transducer with high quality factor for wireless power receiving

To achieve strong power coupling, a resonance-type magnetoelectric (ME) transducer with high quality factor is developed to achieve strong ME coupling. The ME transducer employs a type of iron–nickel-based ferromagnetic alloy with constant elasticity and piezoelectric Pb(Zr,Ti)O₃ (PZT8) material. The dynamic magnetomechanical behavior of the ferromagnetic alloy is investigated. The result indicates that the strain coefficient of the ferromagnetic alloy at resonance achieves 557.07 nm/A due to the high effective mechanical quality factor of the alloy. The transducer is designed to operate as a half-wavelength, longitudinal resonator. The dynamic performance of the transducer is evaluated by measuring its electrical and vibrational characteristics. The results reveal that (1) the resonance of the transducer occurs at the frequency of 26.9336 kHz with a strain coefficient of 314.74 nm/A, an effective mechanical quality factor of 1600; (2) the ME voltage coefficient achieves 30.07 V/Oe (i.e., 375.875 V/cm Oe) at resonance; (3) the ME output power density at optimal load resistance of 25 kΩ achieves 0.956 mW/cm³ under 0.3 Oe root-mean-square AC magnetic field. The performances indicate that the transducer is promising for ME energy conversion application.     

Physiological strain during kitchen work in relation to maximal and task-specific peak values

Six female and three male subjects from a hospital kitchen volunteered for the study. The subjects were working on a conveyor belt collecting and sorting dirty plates, glasses and cutlery for cleaning. In the study, a medical examination, a maximal clinical exercise test with a 12-lead electrocardiogram (ECG) and a maximal arm cranking test were performed in the laboratory. Further, each subject was studied for 30 min during a normal work shift in the kitchen. Oxygen uptake (VO₂) and heart rate (HR) were continuously registered. During the work period, a rating of perceived exertion (RPE) was asked at the 5th, 15th and 30th minute. Physiological responses were measured by a portable system (K4) both in the laboratory and in the field. VO₂ and HR measured in the field were proportioned to corresponding maximal values during cycling and to peak values during arm-cranking. The mean VO₂ for the male and the female subjects during kitchen work was 0.65±0.16 l min^-1. This corresponded to 24% of VO_2max and to 41% of VO_2peak during arm-cranking. The difference was significant (p<0.001). Owing to a magnetic field at the conveyor belt, reliable HR values were obtained only from the female subjects. The mean HR during work among the female subjects was 101 beats min^-1. It corresponded to 55% of HRmax and 67% of HR during arm-cranking (p<0.05). The present study shows that the peak relative work intensity is markedly higher when it is expressed relative to the corresponding muscle group's VO_2peak instead of the VO_2max. Similar difference was also seen in the HR response. More task-specific testing of physical capacity may provide improved evaluation of physical strain in a job.     

FBAR-on-diaphragm type electro-acoustic resonant micro-accelerometer: a theoretical study

We presented a theoretical study of the performance of a novel FBAR-on-diaphragm sensor-head structure for the FBAR-based electro-acoustic resonant micro-accelerometer. This structure overcomes disadvantages in the FBAR-beam structure for its limited cantilever beam thickness, and deficiencies in the embedded-FBAR structure for its complex micro-fabrication process. Its elastic diaphragm is made of silicon dioxide (SiO₂)/silicon nitride (Si₃N₄) bilayer film, which is not only more susceptible to the IC compatible integration process for the Si-based microstructure and the FBAR, but also improves sensitivity and temperature stability of the BAW accelerometer. FBAR-on-diaphragm type BAW accelerometer integrates the acceleration sensing structure, i.e., the SiO₂/Si₃N₄ bilayer diaphragm and the Si proof-mass, with the AlN FBAR electro-acoustic transducer. Preliminary performance analysis on FBAR-on-diaphragm type BAW accelerometer suggests that the FBAR-on-diaphragm structure is feasible. We obtained modal frequencies of the FBAR-on-diaphragm structure and stress distribution of the diaphragm under 0–100 g acceleration loads through the finite element modal analysis and static simulation, Applying the calculated maximum stress to the piezoelectric film in FBAR for qualitative analysis, and combining the dependency of elastic coefficient on stress in the Wurtzite AlN film calculated with the first-principle method, we roughly predicted the maximum elastic coefficient variation in the Wurtzite AlN film under different acceleration load. With the help of the RF simulation software ADS, we changed the longitudinal wave velocity corresponding to the elastic constants with variant acceleration loads. By comparing the resulted resonant frequencies of the sensor head without and with different acceleration loads, we qualitatively characterized its frequency shift and sensitivity. In our study, we gave further analysis of the simulation results. It reveals that the first-order modal frequency of the SiO₂/Si₃N₄ circular diaphragm is quite far away from the higher ones, which means less cross modal coupling. It also reveals that under the acceleration load, its resonant frequency with a quite linear acceleration–frequency shift characteristic will up-shift with the sensitivity of several KHz/g.     

Sprayed CdIn2O4 thin films for liquefied petroleum gas (LPG) detection

Nanocrystalline cadmium indium oxide (CdIn₂O₄) thin films of different thicknesses were deposited by chemical spray pyrolysis technique and utilized as a liquefied petroleum gas (LPG) sensors. These CdIn₂O₄ films were characterized for their structural and morphological properties by means of X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The dependence of the LPG response on the operating temperature, LPG concentration and CdIn₂O₄ film thickness were investigated. The results showed that the phase structure and the LPG sensing properties changes with the different thicknesses. The maximum LPG response of 46% at the operation temperature of 673 K was achieved for the CdIn₂O₄ film of thickness of 695 nm. The CdIn₂O₄ thin films exhibited good response and rapid response/recovery characteristics to LPG.     

Design of a six-axis wrist force/moment sensor using FEM and its fabrication for an intelligent robot

This paper describes the design of a six-axis force/moment sensor using FEM (finite element method) and its fabrication. In order to safely grasp an unknown object using an intelligent hand in robot, the hand has to perceive the weight of it. The weight is calculated by forces F_x, F_y, F_z measured from the six-axis wrist force/moment sensor attached to an intelligent robot's hand. And, in order to accurately push and pull an object, forces and moments should be measured. Also, the position of the robot's finger contacted on an object are calculated by forces F_x, F_y and F_z, and moments M_x, M_y and M_z measured from the six-axis wrist force/moment sensor. Therefore, an intelligent robot's hand should get a six-axis wrist force/moment sensor that can measure forces F_x, F_y and F_z, and moments M_x, M_y and M_z simultaneously. The size of the six-axis force/moment sensor for an intelligent robot’ wrist is very important. If its diameter is larger or its thickness (length) is longer, it cannot be mounted in robot's wrist or it will break down under the applied moment M_x or M_y. So, its size is similar to that of the wrist of human being, that is, the diameter is about 60–80 mm and the thickness (length) about 20–40 mm. But the manufactured sensors are not proper in size for the intelligent robot's wrist. Thus, the six-axis force/moment sensor should be developed for the intelligent robot's wrist.In this paper, the structure of a six-axis wrist force/moment sensor was modeled for an intelligent hand in robot newly. And the sensing elements of it were designed by using FEM and were fabricated by attaching strain-gages on the sensing elements. And, the characteristic test of the developed sensor was carried out. The rated outputs from FEM analysis agree well with the results from the experiments. The interference error of the sensor is less than 2.85%.     

New insight into the catalytic cycle about epoxidation of alkenes by N2O over a Mn–substituted Keggin-type polyoxometalate

Although epoxidation of alkenes by N₂O catalyzed by Mn–substituted polyoxometalates (POMs) has been studied both experimental and theoretical methods, a complete catalytic cycle has not been established currently. In the present paper, density functional theory (DFT) calculations were employed to explore possible reaction mechanism about this catalytic cycle. Our DFT studies reveal that the reaction pathway starts from a low–valent Keggin-type POM aquametal derivative [PW₁₁O₃₉Mn^IIIH₂O]⁴⁻. In the presence of N₂O pressure, the formation of the active catalytic species [PW₁₁O₃₉Mn^VO]⁴⁻ involves a ligand–substituted reaction about replacement of the aqua ligand with N₂O to generation of POM/N₂O adduct [PW₁₁O₃₉Mn^IIION₂]⁴⁻ and dissociation of N₂ from this adduct. The calculated free energy indicates that the ligand–substituted reaction is endergonic both in gas phase or various solvents. The partial optimization method reveals that the dissociation of N₂ from [PW₁₁O₃₉Mn^IIION₂]⁴⁻ involves crossing of the quintet state with a low-lying triplet state. Due to the high reactivity, the high–valent Mn^V–oxo species, [PW₁₁O₃₉Mn^VO]⁴⁻, may react with the excess N₂O and alkenes. Thus, two alternative reaction pathways corresponding to activation of N₂O and epoxidation of alkenes have been considered in this work. The calculated free energy profile indicates that epoxidation of alkenes pathway is the favorable routes. Finally, a complete catalytic cycle for this reaction has been proposed. The rate–determining step in this catalytic cycle is the dissociation of N₂ from the low–valent POM/N₂O adduct according to our DFT–M06L calculations.     

Development of a dehydrogenase-based glucose anode using a molecular assembly composed of nile blue and functionalized SWCNTs and its applications to a glucose sensor and glucose/O2 biofuel cell

A simple and new way to immobilize glucose dehydrogenase (GDH) enzyme onto nile blue (NB) covalently assembled on the surface of functionalized single-walled carbon nanotubes (f-SWCNTs) modified glassy carbon (GC) electrode (GDH/NB/f-SWCNTs/GC electrode) was described. The GDH/NB/f-SWCNTs/GC electrode possesses promising characteristics as glucose sensor; a wide linear dynamic range of 100-1700 μM, low detection limit of 0.3 μM, fast response time (1-2 s), high sensitivity (14 μA cm⁻² mM⁻¹), anti-interference ability and anti-fouling. Moreover, the performance of the GDH/NB/f-SWCNTs/GC bioanode was successfully tested in a glucose/O₂ biofuel cell. The maximum power density delivered by the assembled glucose/O₂ biofuel cell could reach 32.0 μW cm⁻² at a cell voltage of 0.35 V with 40 mM glucose. The present procedure can be applied for preparing a potential platform to immobilize different enzymes for various bioelectrochemical applications.     

Rigid body concept for geometric nonlinear analysis of 3D frames, plates and shells based on the updated Lagrangian formulation

In the nonlinear analysis of elastic structures, the displacement increments generated at each incremental step can be decomposed into two components as the rigid displacements and natural deformations. Based on the updated Lagrangian (UL) formulation, the geometric stiffness matrix [k_g] is derived for a 3D rigid beam element from the virtual work equation using a rigid displacement field. Further, by treating the three-node triangular plate element (TPE) as the composition of three rigid beams lying along the three sides, the [k_g] matrix for the TPE can be assembled from those of the rigid beams. The idea for the UL-type incremental-iterative nonlinear analysis is that if the rigid rotation effects are fully taken into account at each stage of analysis, then the remaining effects of natural deformations can be treated using the small-deformation linearized theory. The present approach is featured by the fact that the formulation is simple, the expressions are explicit, and all kinds of actions are considered in the stiffness matrices. The robustness of the procedure is demonstrated in the solution of several benchmark problems involving the postbuckling response.     

Thin-film calorimetric H2O2 gas sensor for the validation of germicidal effectivity in aseptic filling processes

In common aseptic filling processes, hydrogen peroxide vapour is a predominantly applied antimicrobial for the inactivation of microorganisms in packages. During this process, the germicidal effectivity of the antimicrobial treatment depends especially on the H₂O₂ concentration of the gas mixture. For the detection of H₂O₂ in aseptic filling processes, a novel thin-film calorimetric gas sensor based on a differential set-up of a catalytically activated and a passivated temperature sensing element has been realised in the present work. The sensor device contains two meander-shaped platinum resistances as temperature sensing elements; both have been passivated with spin-coated perfluoralkoxy. As catalytically active materials for the calorimetric gas sensor, palladium, platinum black and manganese oxide particles have been studied in the developed experimental set-up, wherein MnO₂ has shown the highest sensitivity of 0.57 °C/% (v/v) towards H₂O₂. Afterwards, the characteristic of the sensor device with MnO₂ particles as catalyst has been examined at various H₂O₂ concentrations and additionally, the influence of gas temperature and gas flow rate on the sensor signal has been validated in the experimental set-up.     

Investigation of diffusion behavior and mechanical properties of Mg-Zn system

The growth kinetics, diffusion kinetics and mechanical properties of intermetallics in Mg-Zn binary systems have been investigated in this work. Four intermetallic compounds (IMCs) Mg₂Zn₁₁, MgZn₂, Mg₂₁Zn₂₅, and Mg₄Zn₇ have been observed in the Mg-Zn diffusion zone at the temperature range of 523–593 K. The square of thickness for IMCs diffusion layer increases linearly with time, which is consistent with the parabolic growth law, and also indicates that the growth of IMCs is controlled by diffusion. Growth constants and growth activation energies of Mg-Zn IMCs have been evaluated. Average effective interdiffusion coefficient of each phase has been calculated by the Wagner's method based on the concentration distribution obtained by EPMA. The diffusion activation energy has been estimated and compared with the available results. Finally, displacement-unloading curve measured by nanoindentation was used to estimate the hardness and Young's modulus to characterize the mechanical and creep properties of Mg₂Zn₁₁, MgZn₂, Mg₂₁Zn₂₅ and Mg₄Zn₇. The present results should be beneficial to the design and performance of Mg-based alloys.     

Adjoint network method applied to the performance sensitivities of microwave amplifiers

This work focuses on the performance sensitivities of microwave amplifiers using the “adjoint network and adjoint variable” method, via “wave” approaches, which includes sensitivities of the transducer power gain, noise figure, and magnitudes and phases of the input and output reflection coefficients. The method can be extended to sensitivities of the other performance measure functions. The adjoint‐variable methods for design‐sensitivity analysis offer computational speed and accuracy. They can be used for efficiency‐based gradient optimization, in tolerance and yield analyses. In this work, an arbitrarily configured microwave amplifier is considered: firstly, each element in the network is modeled by the scattering matrix formulation, then the topology of the network is taken into account using the connection scattering‐matrix formulation. The wave approach is utilized in the evaluation of all the performance‐measurement functions, then sensitivity invariants are formulated using Tellegen's theorem. Performance sensitivities of the T‐ and Π‐types of distributed‐parameter amplifiers are considered as a worked example. The numerical results of T‐ and Π‐type amplifiers for the design targets of noise figure F_req = 0.46 dB ? 1,12 and V_ireq = 1, G_Treq = 12 dB ? 15.86 in the frequency range 2–11 GHz are given in comparison to each other. Furthermore, analytical methods of the “gain factorisation” and “chain sensitivity parameter” are applied to the gain and noise sensitivities as well. In addition, “numerical perturbation” is applied to calculation of all the sensitivities. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Participation of hydrogen peroxide in halogen activation in the low stratosphere

Measurements of hydrogen peroxide conversion into Caro's acid in sulphuric acid at T ≈ 298 K and H₂SO₄ content 78/95 wt% were performed to monitor the equilibriums: H₂O₂ + H₃O⁺ ? H₃O₂ ⁺ + H₂O and H₂O₂ + HSO₄ ^? ? HSO₅ ^? + H₂O yielded K(298)?=?8 × 10^?4 and K(298)?=?1.2 × 10^?2, respectively. The physical solubility of H₂O₂ as well as that including H₃O₂ ⁺ and HSO₅ ^? has been estimated. The calculation of the Henry's law coefficient (T?=?298) of H₂O₂ shows the typical salting-out effect, while for the case of H₃O_2(aq) ⁺ and HSO_5(aq) ^? this coefficient exhibits a sharp rising with H₂SO₄ content, starting from almost 50 wt%. An increase in the oxidative power of H₂O₂, H₃O_2(aq) ⁺ and HSO_5(aq) ^? is observed, as H₂SO₄ concentration increases. In addition, the kinetics of the liquid-phase reactions involving these reagents are analysed on the basis of a correlation between the rate constants and the thermodynamic data. Finally, the occurrence of sulphate aerosol reactions involving the components that affect halogen activation in the low stratosphere is discussed.     

Calculation of ternary mixing properties of melts and minerals from the bounding binaries

Among the several methods that have been used to predict thermodynamic properties of ternary alloys and oxides from three binary data, we used the models proposed by Kohler(1), Toop(2), and Muggianu (3) in order to evaluate the possibility of the application of these methods to geologically important systems, such as zeolites, clay minerals and silicate glasses. These models can represent the ternary excess Gibbs energy of the NaCl-KCl-H₂O and Ca-Mg-Fe²⁺ garnet (Ca₃Al₂Si₃O₁₂ - Mg₃Al₂Si₃O₁₂ - Fe₃Al₂Si₃O₁₂) systems relatively well without a ternary correction term. The deviation from the reference data increases in the central region of the composition triangle. Toop's model with constant mole fractions of NaCl and Mg best simulated the ternary systems among the models. The path independent Muggianu model was applied to diopside (CaMgSi₂O₆) -jadeite (NaAlSi₂O₆) - acmite (NaFe³⁺Si₂O₆) ternary as an example. Although there exists intrinsic uncertainty in calculation without the ternary interaction term, these models, especially, Muggianu and Kohler can be good approximation methods for prediction of the ternary excess properties of the natural mineral solid solutions, devoid of ternary experimental thermodynamic data.