Infrared-visible sum frequency generation investigation of Cu corrosion inhibition with benzotriazole

Infrared-visible sum frequency generation spectroscopy is used to investigate the corrosion inhibitor benzotriazole (BTAH) adsorbed on Cu(100) and Cu(111) in acidic solution. Potential-dependent in situ spectra indicate that the adsorbed molecule is the benzotriazole anion (BTA-) at all potentials investigated. The Cu(100) surface is shown to form an ordered adlayer at all potentials probed, while the Cu(111) face is shown to be disordered at negative potentials, but to order with applied positive potential. The ordered adlayer is shown to consist of the BTA- in two configurations, one coordinated to the surface and Cu+ ions in solution and the other coordinated only to the surface. The BTA- coordinated to Cu+ is shown to be more stable with respect to Cl- addition than BTA- coordinated to only the surface. This study demonstrates the viability of using sum frequency generation to study corrosion inhibition in situ.     

Applicability and limitations of the Adam mathematical phantom with respect to radiological protection

Monte Carlo (MC) simulation of radiation transport is applied to an anthropomorphic mathematical (ADAM) or Zubal's voxel phantom, representing a male adult. The purpose is to compare absorbed energy in various organs (liver, kidneys, lungs, pancreas, spleen, adrenals and heart) in the simplified (mathematical) and more realistic (voxel) anatomy. A broad beam of monodirectional and monoenergetic photons (20 keV to 10 MeV), perpendicular to the longitudinal body axis, is incident on the front (AP) or the back (PA) of the phantom. Two MC codes, MCNP-4C and MCNPX-2.1.5, are used for the calculations. Specific absorbed fraction as a function of energy reflects the shielding of an organ by other organs. Comparison of the results for the two phantoms enables an evaluation of the applicability and the limitations of ADAM with respect to radiological protection. The cases studied indicate no urgent need to replace the (commonly used) mathematical phantom by a more sophisticated voxel phantom.     

X-ray structural parameter for coal

It has been shown that the interatomic distance of ≈0.43 nm in coal is predominantly due to turbostratic-graphitic order. The height of the corresponding peak in the G(r) function which is the Fourier transform of the properly corrected and normalized X-ray diffractogram, has been investigated as a function of the concentration of volatile matter and the heat treatment of the coal. The results clearly show that this new parameter which is based on the whole diffraction pattern, is a useful aid in the study of coal, in particular when the structural changes within one coal are investigated.     

Investigations of optically pumped submillimeter wave laser modes

A complete theory for waveguide laser modes for oversized metallic and dielectric waveguides with circular cross section has been developed for the submm wavelength region. The experimental investigations have been done by a submm heterodyne technique for the first stage using a Schottky barrier diode in an open structure mixer.     

Determination of laser frequencies by mixing experiments between two submillimeter lasers

The radiation of optically pumped submillimeter lasers has been investigated using a heterodyne system with a Schottky barrier diode in a quasi optical mixer. The laser frequency, the mode purity and the total linewidth was determined by mixing experiments between two submillimeter lasers. The uncertainty of the measured laser frequency is about 200 kHz.     

A Markov-Based Channel Model Algorithm for Wireless Networks

Techniques for modeling and simulating channel conditions play an essential role in understanding network protocol and application behavior. In [11], we demonstrated that inaccurate modeling using a traditional analytical model yielded suboptimal error control protocol parameters choices. In this paper, we demonstrate that time-varying effects on wireless channels result in wireless traces which exhibit non-stationary behavior over small window sizes. We then present an algorithm that extracts stationary components from a collected trace in order to provide analytical channel models that, relative to traditional approaches, more accurately represent characteristics such as burstiness, statistical distribution of errors, and packet loss processes. Our algorithm also generates artificial traces with the same statistical characteristics as actual collected network traces. For validation, we develop a channel model for the circuit-switched data service in GSM and show that it: (1) more closely approximates GSM channel characteristics than traditional Markov models and (2) generates artificial traces that closely match collected traces' statistics. Using these traces in a simulator environment enables future protocol and application testing under different controlled and repeatable conditions.     

An advanced method in fetal phonocardiography

The long-term variability of the fetal heart rate (FHR) provides valuable information on the fetal health status. The routine clinical FHR measurements are usually carried out by the means of ultrasound cardiography. Although the frequent FHR monitoring is recommendable, the high quality ultrasound devices are so expensive that they are not available for home care use. The passive and fully non-invasive acoustic recording called phonocardiography, provides an alternative low-cost measurement method. Unfortunately, the acoustic signal recorded on the maternal abdominal surface is heavily loaded by noise, thus the determination of the FHR raises serious signal processing issues. The development of an accurate and robust fetal phonocardiograph has been since long researched. This paper presents a novel two-channel phonocardiographic device and an advanced signal processing method for determination of the FHR. The developed system provided 83% accuracy compared to the simultaneously recorded reference ultrasound measurements.