Identification of Characteristic Features of Envelopes of Testing Pulses with the Help of the Diade Convolution Adaptable to Noise Level: I. Identification of Types of Characteristic Features

A method has been suggested for binary coding of envelopes of measured pulses from eddy-current transducers. The method enables one to identify their characteristic features of various types, such as leading edge, trailing edge, maximum, minimum, horizontal portion, start point of leading edge, end point of leading edge, start point of trailing edge, and end point of trailing edge, using weighted sums of no more than four Hadamard-ordered Walsh functions with numbers 0, 1, 2 ^n–1, and 2 ^n–1 + 1. The paper demonstrates the existence of obvious diade correlations of coded combinations corresponding to specific fragments with both one another and distortions of a current sampling simulated by adding an error vector. These properties make possible an identification of types of characteristic features in current samplings of binary data with four levels of a noise immunity, which are selected in the process of adaptation to the noise intensity with due account of the significance of identified features.     

Detection of the Increment of an Instantaneous Phase in a Long-Base Laser Meter of Small Vibrations

A phase meter for processing signals of a laser meter of small displacements and vibrations at long base distances is described. Vibrations of objects are transformed into small increments of a signal phase at an RF carrier, which are detected by the phase meter and are outputted as signals proportional to microvibrations in the acoustic range. At a given carrier frequency f _c = 10.7 MHz, vibrations are detected within a band f = 3 kHz. Such vibrations produce phase fluctuations of 10^–42, which correspond to magnitudes of 1 nm for a laser wavelength 10 m.     

Time-of-Flight Characteristics of Scintillation Counters with Fine-Mesh Photomultipliers

The characteristics of the time-of-flight system of scintillation counters with the -527 and R5505 fine-mesh-dynode photomultipliers for high-magnetic-field environment were measured. Scintillation counters with thin plastic scintillators 1, 3, and 5 mm thick were designed to operate in comparatively strong stray magnetic fields of up to several kilogauss. The measurements were carried out in beams of the U-10 proton synchrotron (Institute of Theoretical and Experimental Physics) with proton, ⁺-meson, and ^–-meson momenta of 0.63, 1.03, and 1.28 GeV/c. For counters with scintillator sizes of 1 × 20 × 154 mm (BI-408) and 3 × 20 × 200 and 5 × 20 × 200 mm (Kuraray and SCSN-81), time resolutions of 45–180 ps were obtained. The time resolution of the scintillation counters, in which scintillators 20 mm thick and -527 photomultipliers were used, was found to be 50–80 ps.     

Error Corrections in a Sampling Sliding Along a Pulse Envelope Based on Decoding Tables

Code combinations of 2 ⁿ symbols +1 and –1 suggested for identification of characteristic features leading edge, trailing edge, maximum, minimum, horizontal portion, start of leading edge, end of leading edge, start of trailing edge, and end of trailing edge in a binary-code envelope of a pulse measured by an eddy-current transducer (ECT) scanning a tested surface generate a group code. This group code ensures for four levels of noise immunity the maximal likelihood in identification of reference sequences distorted by noise. The structure of a product code, which is also generated by the reference fragments, results in a higher capability of correcting for errors in moving samplings of signal envelopes, in particular, it reduces the degree of uncertainty in identification of the most important features of ECT pulses. The paper suggests simple decoding algorithms and regular logical structures that provide a high efficiency of the procedure eliminating errors in binary sequences of coded envelopes.     

The PIBETA spectrometer for studying rare and forbidden decays of muons and pions

The construction and characteristics of the PIBETA spectrometer are described. This spectrometer is designed to implement a program of precise measurement of pion decay ^{+ 0} + e ⁺ + _e at the Paul Scherrer Institute (Switzerland). A spherical calorimeter, consisting of 240 crystals of pure CsI scintillator and embracing a solid angle of 3, is the main detector of the setup. In addition, the spectrometer is composed of an active collimator (which also acts as a beam degrader), a segmented active plastic target, two multiwire cylindrical proportional chambers, a 20-element cylindrical plastic hodoscope, and veto counters of cosmic muons.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 39–48.Original Russian Text Copyright © 2005 by Baranov, Kalinnikov, Karpukhin, Khomutov, A. Korenchenko, S. Korenchenko, Kravchuk, Kuchinskii, Mzhaviya, Rozhdestvenskii, Sidorkin, Tsamalaidze, Sakhelashvili, Frlez, Poanic, Li, Minehart, Smith, Stephens, Ziock, Bertl, Horisberger, Ritt, Schnyder, Wirtz, Ritchie, Supek, Kozlowski.     

An integral method for measuring the <Emphasis Type="Italic">P</Emphasis>-odd asymmetry on a reactor at neutron polarization switching frequencies higher than the frequencies of the main spectrum of the neutron noise power

P-odd asymmetry is measured when frequencies of switching neutron polarization exceed the frequencies of the reactor power fluctuations that govern the spectral density of noise power. A principle for recording the current signals in these measurements is described. This method was used for the first time at the Konstantinov Institute of Nuclear Physics in Gatchina (Russia). The results suggest that the accuracy of measurements at an increased equipment-switching frequency is even higher than the accuracy obtained using compensation for reactor power fluctuations; hence, this compensation becomes superfluous. Following this method, it is possible to take measurements with a single detector and to dispense with a monitor, thereby rendering the equipment and the measuring technique less complex. A strategy of measurements was developed. An experimental model of the facility was produced and tested with a small-amplitude calibration signal in the presence of reactor power fluctuations caused by rays from reaction ¹⁰B(n )⁷ Li* ⁷Li + . The results from the test measurements of the P-odd effect in reaction ³⁵Cl(n, )³⁶Cl are presented.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 62–71.Original Russian Text Copyright ¢ 2004 by Vesna, Shulgina.     

Numerical Simulation of a Fusion Power Measurement Using Inelastic Neutron Scattering by Carbon Nuclei

The possibility of using prompt rays from the 4.439-MeV excited level of carbon nuclei in the ¹²C(n, n)¹²C reaction and scattered neutrons for measuring the power of a thermonuclear facility is studied. It is shown that the angular distributions of rays and scattered neutrons can be measured using three -ray spectrometers and three neutron detectors. The detectors must be installed around the carbon sample at angles of 140.8°, 90.0°, and 39.2°. The obtained total cross sections of the scattered-neutron and -ray angular yields are compared to the published data.     

Time-of-Flight Trigger Based on a Time-to-Amplitude Converter

A time-of-flight trigger based on a time-to-amplitude converter and differential discriminator is described. The trigger has a short decision time (60 ns) and high (100%) efficiency of useful event selection.     

Surface diffusion and flow activation energies of perfluoropolyalkylether

Surface diffusion of perfluoropolyalkylether (PFPE) Fomblin Z15 and Fomblin Zdol (hydroxyl terminated PFPE) on silicon wafers was investigated over the temperature range of 25 to 50°C using scanning microellipsometry. Zdol exhibits a much lower mobility and a distinctly different thickness profile as compared to Z15. The activation energy for surface diffusion of Zdol is higher than that of Z15, reflecting the stronger affinity of its hydroxyl end groups for the substrate. The viscosity flow activation energy E ^* is compared with that of surface diffusion E _d ^* yielding E _d ^* E ^* for Z15, and E _d ^* 1.5E ^* for ZOn leave from Korea Insitute of Science and Technology, PO Box 131, Cheongryang, Seoul, Korea 305-701.     

Measurement of Sub-Nanometer Lubricant Films Using Ultra-Thin Film Interferometry

The ultra-thin film interferometric method of measuring the thickness of very thin films in lubricated contacts has been refined so as to be able to measure films down to 0.3nm with a standard deviation of 0.15nm. The main remaining source of measurement variation for films below 3nm thick is the surface roughness of the contacting solids. This modified technique has been applied to study the film-forming properties of three fluids, hexadecane, a dilute solution of surfactant in hexadecane, and cyclohexane. Purified hexadecane shows a very slightly enhanced oil-film thickness below 1nm. The long-chain surfactant forms a boundary film 2nm thick. Cyclohexane behaves as though it forms a surface layer about 1nm thick with viscosity three times the bulk fluid viscosity.     

Reconstruction of Coordinates of Scintillations in a Large-Size Cylindrical Detector with Radially Arranged Photomultipliers

An algorithm for calculating the scintillation coordinates developed for a large-size coordinate-sensitive detector is developed. The detector based on a liquid scintillator has nine radially arranged -174 photomultipliers. The results of simulation of the dependence of the coordinate resolution at the detector center on -quanta energy between 0.2 and 8 MeV are presented. The experimental data obtained with a collimated beam of -quanta from a ⁶⁰Co source, which irradiated the central part of the detector, were processed by using this algorithm. The -ray spectrum measured by the detector and the results of determining the scintillation coordinates for a -quanta beam are presented. The accuracy of coordinate measurements at the central region of the detector with this algorithm is 10 mm.     

General Shear-Thinning Dynamics of Confined Fluids

The shear properties for a number of thin fluid films under high pressure were investigated as a function of sliding velocity (shear rate) using the surface forces apparatus. It was found that the relationship between the effective viscosity _eff and shear rate in the shear-thinning regime could be expressed by a simple equation, log_10eff=C-nlog₁₀, where C4.7±0.2 and n0.9±0.1. This equation can be applied to a variety of fluid systems from simple liquids to polymer melts, which transition to glasslike phases in confined geometries. Since the effect of confinement on the slowing down of molecular motions is equivalent to that of decreasing temperature, this universally can be explained using conventional glass-transition theories for bulk fluids. Assuming the confined fluid to be in a state where dynamics are dominated by excluded volume effects, its _eff should correspond to that of the bulk at or near the glass-transition temperature. Thus, characteristic relaxation times in the system should correlate with the time scales of the primary relaxation processes associated with submolecular rearrangements, which are an essential feature of the glass transition and not very different for various fluid materials.     

An Autonomous Sorption Refrigerator for Cooling to 0.3 K

A two-stage refrigerator with sorption evacuation of ⁴He and ³He is described. The apparatus needs no external pumps or gas lines. The refrigerator is constructed in the form of an insert 80 mm in diameter immersed in a helium cryostat and ensures a sample temperature of 0.31 K for 20 h after the condensation of ³He at a useful heat load of 10 W. The recycling time is 0.5 h.     

An Apparatus for Studying Condensed Impurity Systems in Liquid Helium

The design of an apparatus that ensures the injection of gaseous ⁴He with water vapor impurities or vapors of other molecular liquids into the experimental cell, which is filled with superfluid He-II, is described. It is shown that, when a ⁴ + ₂ gas mixture condenses, porous semitransparent samples (icebergs) with a characteristic size of 1 cm form under the surface of the superfluid. The volume concentration of water in the samples is 10²⁰molecules/cm³. When heated above T , icebergs in normal He-I may decompose into ice and ⁴He. The temperature T _dat which intense disintegration begins depends on the pressure of the vapor above the liquid: T _d 2.5 K at a pressure of 0.2 atm, and, at a pressure of 1 atm, T _drises up to 4 K. In an atmosphere of gaseous ⁴He, icebergs begin disintegrating into parts under warming above 1.8 K. This indicates the discovery of a new highly porous form of ice in liquid helium—a water gel, the dispersed phase (solid frame) of which is formed by water clusters surrounded by a solidified helium layer; liquid helium serves as a dispersing medium.     

Burr detection by using vision image

In this paper, a practical force model for the deburring process is first presented. It will be shown that the force model is more general than Kazerooni's model and it is suitable for both upcut and down-cut grinding. In terms of this force model, an algorithm of burr detection by using a 2D vision image is proposed. In the burr detection algorithm, the relevant data of burrs, such as frequency, cross-section area, and height are simplified so that they are functions of the burr contour only. Then, a fast tracking method of the burr contour (BCTM) is developed to obtain the contour data. Experiments show that the BCTM of this passive (i.e. without lighting) image system can be as fast as 18.2 Hz and its precision is 0.02 mm, so online burr detection and control by using the vision sensor is feasible.Nomenclature A _burr cross-section area of the burr - A _chamfer cross-section area of the chamfer - A _n proportional factor - A _work cross section area in the contact zone while deburringA _work=A _burr+A _chamfer - w cutting width - w _root thickness of the root of the burr - a depth of cut - a _root burr heighta _root=a(w _root) - C ₁ static cutting edge density - D equivalent wheel diameter - d _s wheel diameter - d _w workpiece diameterD=d _w d _s/(d _w±d _s)D=d _s andd _w for the deburring process - F _h horizontal grinding force - F _v vertical grinding force - F _n normal grinding force - F _t tangential grinding force - F _n(K) normal grinding force of the Kazerooni's model - F _t(K) tangential grinding force of the Kazerooni's model - F _o threshold thrust force - f _burr burr frequency - f _n normal grinding force per active grain - f _t tangential grinding force per active grain - f _r first resonant frequency of the robot - f _tool resonant frequency of the end-effector at the normal direction - exponential constant for describing the edge distribution = [(1 +n) + (1 –n)]/2 = (1 +n)/2 for = 0 [21] - K proportional factor of the force model of the grinding processK =A _n ^1–n / - K ₀ specific contact force per contact length - K ₁ specific chip formation force per contact length - V _s wheel speed - V _w workpiece speed - _w metal-removal parameter - K ₂ specific metal-removal parameter per wheel speedK ₂ = _w/V _s - K _c specific chip formation force per area - K _f specific friction force per area - k constant for the parabolic burr - k ₁,k ₂,k ₃,k ₄ constants for the circular burr - L contact width between the wheel and the workpieceL is equal to the chamfer's hypotenuse length, orL=w _root when there is no chamfer - l contact length - l _k contact length between the wheel and the workpiece - m exponential constant for describing the edge shape 0m1m=1 for the deburring process [21] - N _dyn number of engaged cutting edges per wheel surface - n exponential constant for describing the cutting process 0n1n=1 for the pure chip formation process andn=0 for the pure friction process [22] - average contact pressure - p exponential constant for describing the relationship between the static cutting edge and the wheel surface depth 1p2p=1 for linear case [21] - Q magnitude of the individual chip cross-section in the contact zone - r radius of the circular burr - Z _w metal-removal rate - ,, exponential constants for describing the edge distribution [21] = (p –m)/(p + 1) = 0 form = 1,p = 1 =p/(p) + 1 = 1/2 forp = 1 = (1 –n) = 1n/2 for = 1/2 - actual contact area between the wheel and the workpiece - coefficient of the sliding friction - variable of the contact angle - _k maximum contact angle - _m mean rotating angle - _t half of the tip angle of the grains - ratio of tangential chip formation force to the normal chip formation force. Usuihideji has pointed out that = /(4tan_t) [29]     

A Two-Section Gas-Filled Ionization Chamber for Neutron Flux Measurements

A promising design of a -type two-section gas-filled ionization chamber is described for the first time. A relationship between the design parameters, gas pressure, and characteristics of the material is determined, under which full compensation of the background currents from the -radiation and the measurement of thermal neutron fluxes in a range of 400 to 7 ×10⁹cm^–2s^–1at a load characteristic with a 5% nonlinearity are provided. Test results of the chamber are presented.     

An Optical-Fiber Setup for Inert Particle Concentration Measurements

An optical-fiber setup employing laser light designed to measure concentrations of 50-to 500-m particles moving with a speed of up to 10 m/s is described. The time resolution, the measurement time, and the counting of pulses reflected from the particles are programmed. The setup has the following basic parameters: time resolution is 10 s, spatial resolution is 50 m, sample size is up to 32 × 10³, and particle counting error is within 1%. The setup was applied to measurement of the solid-phase concentration in a two-phase flow in a volum concentration range of up to 30%.     

A Microwave Generator on a Gunn Diode with an Open Resonator

An oscillator on a Gunn diode with an open resonator is described. The diode is located in a cut of one of two mirrors, which consists of two parts. This mirror simultaneously plays a role of the electrodes and cooling system. The main characteristics of the oscillator operating at a frequency of 40 GHz are as follows: 30 mW (the output power), 20 kHz (the oscillation linewidth), 10^–7 (the relative short-term stability), and up to 2 GHz (the range of mechanical tuning within a single zone at a slope of the tuning characteristic of 1.19 GHz/mm).     

Desorption Kinetics of Polyether Lubricants from Surfaces

Desorption or evaporation is one of the mechanisms for loss of perfluoropolyalkylether (PFPE) lubricants from the surfaces of data storage media. One approach to minimizing PFPE loss to desorption is the use of lubricants with increasing molecular weight or increasing average chain length. In order to understand the effects of chain length on the lubricant evaporation kinetics we have studied the desorption kinetics of monolayer films of oligomeric ethers with varying chain length adsorbed on the surface of graphite. The desorption pre-exponents, v, and desorption barriers, E _des , have been measured for poly(ethylene glycol) dimethyl ethers, CH₃O(CH₂CH₂O) _m CH₃, with m=1,2,3,4,8 and 10. These are models for the PFPE known as Fomblin Z, which has a structure CF₃O(CF₂CF₂O) _x (CF₂O) _y CF₃. The results show that the desorption pre-exponents are independent of chain length and have an average value of v=10^18.7±0.3 s^–1. The E _des for the poly(ethylene glycol) dimethyl ethers vary non-linearly with chain length and can be fit with a power law expression of the form E _des =a+bN , where N is the total number of atoms in the oligomer backbone (N=3m+3) and the scaling exponent has a value of 1/2. This non-linear dependence of E _des on chain length has also been observed in recent studies of the desorption kinetics of straight chain alkanes from graphite. A desorption mechanism is described that explains the non-linearity of E _des for the poly(ethylene glycol) dimethyl ethers. The implication for the lifetime of lubricants on data storage media is that the long chain PFPE lubricants desorb more rapidly than one might expect based on simple linear scaling of the E _des of lower molecular weight PFPEs.     

Plastic snapfit fastener design

This paper presents a systematic procedure for selecting and designing snapfits integrated into plastic parts. A classification is proposed based on the geometry of the parts to be assembled and the ease of dismantling. The part geometry influences the type and shape of the snapfit. Depending on the space available, recommendations are made for choosing from a classical straight beam shape, a tapered shape, an L shape and a U shape. The snapfit fastener may be separable if so designed. A distinction should be made between: dismantling with or without a tool (screwdriver or specialised tool); access to the insertion face only; access to insertion face and opposite or lateral faces.