Microchannel fabrication process in LTCC ceramics

This paper describes a simple method of fluidic microchannel fabrication in low temperature co-fired ceramic (LTCC) substrates. This method is based on a new two-step lamination process with using sacrificial volume material (SVM) materials. The research is carried out for five different microchannel widths (100 μm, 200 μm, 500 μm, 1 mm and 5 mm). The test structures are manufactured using three different lamination pressures (50, 100 and 200 atmospheres) and two different SVM materials – carbon-black paste and cetyl alcohol. The resulting structures’ mechanical properties are analyzed using a scanning electron microscope (SEM).     

Gathering few fat mobile robots in the plane

Autonomous identical robots represented by unit discs move deterministically in the plane. They do not have any common coordinate system, do not communicate, do not have memory of the past and are totally asynchronous. Gathering such robots means forming a configuration for which the union of all discs representing them is connected. We solve the gathering problem for at most four robots. This is the first algorithmic result on gathering robots represented by two-dimensional figures rather than points in the plain: we call such robots fat.     

A 3D Crouzeix-Raviart mortar finite element

A mortar finite element discretization of the second order elliptic problem in three dimensions, on non-matching grids, using the 3D Crouzeix-Raviart (CR) finite element in each subdomain, is proposed in this paper. The overall discretization is based on using only the nodal values on the mortar side of a subdomain interface for the calculation of the mortar projection, as opposed to applying the conventional approach where some nodal values in the interior of a subdomain are also required. Since the interior degrees of freedom disappear completely from the computation of the mortar projection, the proposed algorithm becomes less intricate and more flexible as compared to the conventional approach. An error estimate is given, and some numerical experiments are presented.     

High-pressure mass spectrometric investigations of ion-molecule reactions in hydrogen sulfide and ammonia mixtures

The positive ion-molecule reactions in the mixtures of hydrogen sulfide and ammonia have been examined by means of quadrupole mass spectrometer with high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. Mainly observed primary ions: NH₂⁺ (m/q=16), NH₃⁺ (m/q=17), S⁺ (m/q=32) and H₂S⁺ (m/q=34) were formed as the result of ionization and dissociative ionization by electrons with energy of 300 eV. For each mixture, major bimolecular ion-molecule reactions have been identified at total pressure from 0.5 to 33.3 Pa. The main secondary ions: NH₄⁺ (m/q=18), H₃S⁺ (m/q=35) and NH₃S⁺ (m/q=49) were observed.Relative intensities of ion currents for observed ions were determined as a function of total gas pressure inside ion source collision chamber, repeller potential and concentration of hydrogen sulfide in the mixture.     

Through-hole membranes of nanoporous alumina formed by anodizing in oxalic acid and their applications in fabrication of nanowire arrays

The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried out in 0.3 M oxalic acid at the temperature of 20 °C. This relatively high temperature shortens significantly the anodizing time and allows to fabricate quickly thick through-hole membranes without the additional operating cost of a cooling circuit. The structural features of anodic porous alumina such as pore diameter, interpore distance, porosity, pore density and pore circularity were investigated at various durations of pore opening/widening process carried out in 5% H₃PO₄. An excellent agreement of AAO structural features measured in FE-SEM images of the studied samples with results from software calculations was observed. The pore shape can be monitored qualitatively by fast Fourier transforms (FFTs) and quantitatively by calculation the percentage of pore circularity. Additionally, the regularity of the hexagonal arrangement of nanopores in through-hole AAO membranes was compared for various opening/widening time ranging from 40 to 100 min. It was shown that three-dimensional (3D) representations of FE-SEM images and their surface-height distribution diagrams provide interesting information about the surface roughness evolution during the pore opening/widening process. A template-assisted fabrication of Ag and Sn nanowire arrays by electrochemical deposition into the pores of the prepared AAO templates was also successfully demonstrated.     

Prediction of the Mechanical Properties of P91 Steel by Means of Magneto-acoustic Emission and Acoustic Birefringence

The paper describes an application of non-destructive volumetric magnetic and ultrasonic techniques for evaluation of the selected mechanical parameter variations of P91 steel having direct influence on its suitability for further use in critical components used in power plants. Two different types of deformation processes were carried out. First, a series of the P91 steel specimens was subjected to creep and second, one to plastic deformation in order to achieve the material with an increasing strain level up to 10%. Subsequently, non-destructive and destructive tests were performed. Magnetic methods based on measurements of magnetoacoustic emission and magnetic hysteresis loop changes as well as the ultrasonic method based on acoustic birefringence measurements, were applied. Finally, the static tensile tests were carried out in order to evaluate the mechanical parameters. It is shown that some relationships between the selected parameters coming from the non-destructive and destructive tests may be formulated.     

Polymer Microtips Fabricated at the Extremity of Photonic Crystal Fibers

In this paper, a simple method of manufacturing micrometer-sized polymer elements （microtips） at the extremities of the photonic crystal fibers （PCFs）, which are replacing standard optical fibers in many applications due to their unique properties, is presented. The method of microtips fabrication is based on the phenomena of photopolymerization, which is successfully used by the first time, to be best of our knowledge, to manufacture microtip at PCF. The three component photopolymerizable formulation consists of photo-initiating system and multifunctional triacrylate. The photopolymerization is carried out by green laser with the microtip growth controlled by the light exposure parameters （i.e. power and time）. Results of mic：rotip fabrication on standard fiber （SMF-28e＋） and large mode area PCF （LMA-10） are provided. Theinfluence of the initial process parameters on the final microtip characteristics （i.e., length, diameter and profile） is discussed. The potential applications of such polymer microtips are near-field scanning optical microscopy, coupling light sources with fibers and sensing.     

Radioluminescence and photoluminescence of hafnia-based Eu-doped phosphors

Crystal structures of hafnia are discussed and it is shown that addition of about 7 at.% of Lu to the HfO₂ host lattice enforces the mixed composition to crystallize in cubic structure even at room temperature. Without Lu HfO₂ crystallizes in monoclinic structure. Luminescence and luminescence excitation spectra of Hf_0.93Lu_0.07O_1.965 are presented and discussed for powders prepared at different temperatures (600–1000 °C) and with different content of Eu. It is shown that decay of the 595.4 nm luminescence is longer (2.5 ms) than the 610 nm (1.6 ms). Radioluminescence efficiency of the cubic Hf_0.93Lu_0.07O_1.965 is low and does not exceed 10% of the commercial Gd₂O₂S:Eu.     

Electromotive force measurements in liquid Ag-In-Pd lead-free alloys

Emf technique was employed to determine indium activities in the liquid Ag-In-Pd alloys using galvanic cells with yttria-stabilised-zirconia as solid electrolyte according to the scheme： kanthal/rhenium, Ag-In-Pd, In2O3 ｜ YSZ ｜ Ni, NiO, Pt. Composition and temperature measurement ranges were limited, because of very steep liquidus surface; 35 compositions for Xpd up to 0.3 were investigated and at temperatures from near-liquidus up to 1700 K. High temperature experiments required special moly furnace to be constructed with unique automatic gas supply system for fumace winding protective atmosphere. Emf readings were taken and recorded by automatic data acquisition system. Linear dependence of emf on temperature was observed for all compositions investigated, and results were approximated by straight line equa- tions. Then In activities were calculated using well-known relations and taking into account correction for thermoelectric power between kanthal and platinum. Results are to be used along with other existing data to perform assessment of the ternary system under accord.     

Effect of isosorbide dinitrate on pulmonary venous compliance

Irreversible poor pulmonary venous compliance (PV comp) could worsened natural course of patients (pts) with high pulmonary capillary wedge pressure especially pts with mitral stenosis. Nitrates (isosorbide dinitrate-ISDN) possessing venous dilating action could increase PV comp in most of pts. The main aim of that study was to assess hemodynamic effects of ISDN, in pts with MS, with special emphasis on PV com changes. PV comp was estimated according to Hirakawa equation (dV/dp = 0.4*k2*SV/(v-d) in 35 pts with MS, during preoperative right heart catheterisation with VYGON 5155-180 thermodilution catheters during rest and effort in supine position (25W). The same protocol was performed after Iso-Mack sprawy 3.75 mg. According to the PV comp response to ISDN, pts were divided in two groups: good responders (I)-15% and higher increase in PV comp and poor responders (II). ISDN increased PV comp in the whole group according to the response to ISDN, there were significant differences in stroke volume index (SVI) and heart rate (HR). In the group of good responders mean right atrial pressure (RA), mean pulmonary artery pressure (PAP), mean pulmonary wedge pressure (PWP) decreased significantly with simultaneous slight not significant decrease in SVI and not significant increase of HR. In the group of poor responders SVI decreased significantly by about 20% with significant increase of HR. In conclusion significant decrease in pulmonary pressures (PAP, PWP) in pts with good response to ISDN are secondary to the increase of PV comp, while among poor responders the same effects are due to diminished flow secondary to the decrease of the systemic venous return.