Articles and publications listed below are written by Visilab Signal Technologies's personnel. Some of them are scanned as PDF documents. Some of them are published elsewhere, some are unpublished. Use the local copy if the document server is not available.
Henrik Stenlund, "On Transforming Functions of a Certain Dot-Product Gradient Operator", arXiv:2107.12155v1 [math.GM] 21 July 2021 (local copy)
Visilab Report #2021-07
In this paper it is shown that a function of the constant dot product of the gradient operator acting on an arbitrary function can be transformed to a double three-dimensional integral. The inner one of them is a Fourier transform of the operator function. The result converted to one-dimensional problems is also useful in transforming complex differential expressions.
Henrik Stenlund, "On Transforming the Laplace Operator", IOSR Journal of Mathematics (IOSR-JM) e-ISSN: 2278-5728, p-ISSN: 2319-765X. Volume 17, Issue 3 Ser. I (May – June 2022), PP 59-64 www.iosrjournals.org 8 May 2021 (local copy)
Visilab Report #2021-05
In this communication it is shown that a function of the Laplace operator acting on an arbitrary function can be transformed to a three-dimensional integral. The cases of the exponential function and of an arbitrary function expressible as a power series, are treated. Two special cases of radial functions are presented based on elementary observations made here.
Henrik Stenlund, "Connection between the Inversion Formula and the Functional Power Series", IOSR Journal of Mathematics (IOSR-JM) e-ISSN: 2278-5728, p-ISSN: 2319-765X. Volume 16, Issue 6 Ser. II (Nov. – Dec. 2020), PP 22-25 www.iosrjournals.org 12 Mar 2020 (local copy)
Visilab Report #2020-11
This study derives the connection between the functional power series and the inversion formula, both given in series form. The link is established by differentiation of the inversion formula showing an expression of a functional power series for the reciprocal of the derivative in terms of the function itself.
Henrik Stenlund, "On the Basics of Linear Diffusion", IOSR Journal of Mathematics (IOSR-JM) e-ISSN: 2278-5728, p-ISSN: 2319-765X. Volume 16, Issue 2 Ser. III (Mar. – Apr. 2020), PP 44-49 www.iosrjournals.org 12 Mar 2020 (local copy)
Visilab Report #2020-04
This study handles the three-dimensional linear diffusion in a new way. A general solution is given without particular initial conditions. In addition, solutions are obtained for a source-sink as a constant in time but spatially varying in three dimensions and having an arbitrary time dependence. An auxiliary function for diffusion is given having an interesting relationship with the concentration. It appears that both the time derivative and the Laplacian of the concentration obey the diffusion equation. An integro-differential equation for diffusion is presented.
Henrik Stenlund, "On the Basics of the Nonlinear Diffusion", arXiv:2003.06282v1 [math.GM] 12 Mar 2020 (local copy)
Visilab Report #2020-03
This study handles spatial three-dimensional solution of the nonlinear diffusion equation without particular initial conditions. The functional behavior of the equation and the concentration have been studied in new ways. An auxiliary function for diffusion is given having an interesting relationship with the concentration. A set of new integro-differential equations is given for diffusion
Henrik Stenlund,"On Relations Between the Stirling Numbers of First and Second Kind", arXiv:1903.11947v1 [math.GM] 25 Mar 2019 (local copy)
Visilab Report #2019-04
Four new relations have been found between the Stirling numbers of first and second kind. They are derived directly from recently published relations.
Henrik Stenlund, "On Some Relations Between the Stirling Numbers of First and Second Kind", International Journal of Mathematics and Computer Research ISSN: 2320-7167 Volume 07 Issue 03 March-2019, Page no. - 1948-1950 Index Copernicus ICV: 57.55 DOI: 10.31142/ijmcr/v7i03.01(local copy)
Visilab Report #2019-03
The powers of the ordinary differential operator can be expanded in terms of the Cauchy-Euler differential operator and for the opposite case. The expansions involve the Stirling numbers of first and second kind as is well known. Two relations between the Stirling numbers of first and second kind will find their proof in this work, generated by the two expansions. A third relation is obtained by algebraic manipulation from the two known recursion relations.
Visilab Report #2018-06
The critical line of the Riemann zeta function is studied from a new viewpoint. It is found that the ratio between the zeta function at any zero and the corresponding one at a conjugate point has a certain phase and its absolute value is unity. This fact is valid along the whole critical line and only there. The common functional equation is used with the aid of the function ratio between any zero and its negative side pair, a complex conjugate. As a result, an equation is obtained for solving the phase along the critical line.
Visilab Report #2017-11
Visilab Report #2017-07
Henrik Stenlund, "On Transforming the Generalized Exponential Series", arXiv:1701.00515v1 [math.GM] 27 Dec 2016 (local copy)
Visilab Report #2016-12
- We transformed the generalized exponential power series to another functional form suitable for further analysis. By applying the Cauchy-Euler differential operator in the form of an exponential operator, the series became a sum of exponential differential operators acting on a simple exponential (e(-x)). In the process we found new relations for the operator and a new polynomial with some interesting properties. Another form of the exponential power series became a nested sum of the new polynomial, thus isolating the main variable to a different functional dependence. We studied shortly the asymptotic behavior by using the dominant terms of the transformed series. New series expressions were created for common functions, like the trigonometric and exponential functions, in terms of the polynomial.
Henrik Stenlund, "On Infinite Identities Generating Solutions for Series", arXiv:1611.01375v2 [math.GM] 30 Oct 2016 (local copy)
Visilab Report #2016-11
- In this paper we present a new identity and some of its variants which can be used for finding solutions while solving fractional infinite and finite series. We introduce another simple identity which is capable of generating solutions for some finite series. We demonstrate a method for generation of variants of the identities based on the findings. The identities are useful for solving various infinite products..
Henrik Stenlund,"Methods for the Summation of Infinite Series", International Journal of Mathematics and Computer Science, Volume 11, no. 2, 2016, (local copy)
Visilab Report #2016-08
Henrik Stenlund, "On Methods for Transforming and Solving Finite Series", arXiv:1602.04080v1 [math.GM] 28 Jan 2016 (local copy)
Visilab Report #2016-01
- In this work we present new methods for transforming and solving finite series by using the Laplace transform. In addition we introduce both an alternative method based on the Fourier transform and a simplified approach. The latter allows a quick solution in some cases.
Henrik Stenlund, "On Cauchy-Euler Operator", 20th November 2015
Visilab Report #2015-11
Henrik Stenlund, "A Closed-Form Solution to the Arbitrary Order Cauchy Problem with Propagators " , arXiv:1411.6890v1[math.GM] , 24th November 2014 (local copy)
Visilab Report #2014-12
Henrik Stenlund,"On Solving the Cauchy Problem with Propagators", arXiv:1411.1402v1[math.AP], 5th November 2014 (local copy)
Visilab Report #2014-11
Henrik Stenlund,"On a Method for Solving Infinite Series", arXiv:1405.7633v2[math.GM], 6th May 2014 (local copy)
Visilab Report #2014-05
Visilab Report #2014-02
Henrik Stenlund, "On Solving Some Trigonometric Series", arXiv:1308.2626v1[math.GM],5th Aug 2013 (local copy)
Visilab Report #2013-08
- This communication shows the track for finding a solution for a sin(kx)/k**2 series and a fresh representation for the Euler's Gamma function in terms of Riemann's Zeta function. We have found a new series expression for the logarithm as a side effect. The new series are useful both for analysis, approximations and asymptotic studies.
"Functional Power Series", arXiv:1204.5992[math.GM],
24th April 2012
Relations and Functional Equations for the Riemann Zeta Function", arXiv:1107.3479v3[math.GM],
18th Jul 2011
- New recursion relations for the Riemann zeta function are introduced. Their derivation started from the standard functional equation. The new functional equations have both real and imaginary increment versions and can be applied over the whole complex plane. We have developed various versions of the recursion relations eliminating each of the coefficient functions, leaving plain zeta functions.
Henrik Stenlund, "The
Inversion Formula Applied to Some Examples , 1st Jan 2011
- This work discusses a few applications of the recent inversion formula to various functions. The examples range from elementary to more involved. The purpose is to indicate the way of using the inversion formula in general. The target audience is among physicists, chemists, biologists and in other sciences with less inclination to formal mathematics. This article is subject to future modifications.
Henrik Stenlund, "Inversion Formula", arXiv:1008.0183v3[math.GM], 27th Jul 2010 (local copy)
Visilab Report #2010-07
- This work introduces a new inversion formula for analytical functions. It is simple, generally applicable and straightforward to use both in hand calculations and for symbolic machine processing. It is easier to apply than the traditional Lagrange-Bürmann formula since no taking limits is required. This formula is important for inverting functions in physical and mathematical problems.
- This study offers three solutions of the diffusion coefficient's dependence on concentration in general cases without any limitations by boundary conditions. They are all suitable for numerical analysis when the experimental concentration data and time series are available producing dependence functions. As they are also of general nature, the expressions can be used for further investigations and modeling and fitting. Two of the methods offer three-dimensional approaches to this problem and may prove useful when combined with present-day laser scanning volumetric sensors, atomic probe microscopes and high performance computers. This is particularly true in geometries more complex than the regular one consisting of two semi-infinite slabs.
Henrik Stenlund, "Report on Optimization of an Optical System", 01-15-2001
Henrik Stenlund, "Technical Report: A Research
on Mutual Interaction of Two Electron Beams via Space Charge", 12-13-1999
Henrik Stenlund, "Technical Report: Thin Cassette Oven for GC with a Silica Column", 03-12-1990
- A summary report of the development project for a high temperature oven. The target system was a thin small cassette for a narrow Silica gas chromatographic (GC) column. The temperature range is from +50 to +400 C with a very high control accuracy and very small temperature gradients inside the cassette. Theoretical work around thermal conductivity and temperature distributions of the cassette formed the basis. According to those results a few prototypes were built and tested. Verification of proper operation was made with true GC runs.
Henrik Stenlund, "Technical Report: Measuring Paper Formation with Beta Radiation",KCL P8622, 06-19-1986
- A theoretical report on measuring paper formation with beta radiation. Radioactive intensity calculations for required signal level are established with formulas.
Henrik Stenlund, "Technical Report: Measuring the Hydrodynamic Pressure
in a Wet Pressing Process", KCL P8630 06-03-1986
Henrik Stenlund, "Technical Report: Design and Implementation of Time-of-Flight Mass Spectrometer", TEKES 105/425/84;119/1985, 3-30-1986(in finnish)
- Final report of a project for designing two differing TOFMS of optimized reflection type. All technical details of electronics, mechanics and software are shown.
The purpose of the TOFMS project was to develop a
prototype being feasible for manufacturing as a product, having sensible
spectrometric features. A compact structure for the instrument was designed
by making it in axial form. As a result we have two prototypes both having
mass resolution much better than R > 1500 and the useful mass range over
1200 amu. The original specification was to exceed R = 400. The system is
able to deliver 5000 spectra / s on the screen of an oscilloscope. The free
length of flight was about 1000 mm and the ion optical mechanical parts
required some 800 mm in the vacuum chamber.
Henrik Stenlund, Karl Holmström, "Technical Report: Using Microwaves for Measuring Blade Play in a Fiber Grinding Machine",KCL P8636, 02-09-1986
- A preliminary report on feasibility of using microwaves for measuring blade play in a grinder. Continuous measurement would allow replacement of the blade in time and save in fiber quality, energy and productivity.
Henrik Stenlund, "Technical Report: Design of the Vacuum System for the Wet Press Simulator Instrument",KCL P8630 01-20-1986
- A vacuum pumping station was designed for measuring the hydrodynamic pressure of water and fiber mixture in a wet press for paper production. Pumping equations were solved and recommendations were given for proper building of the system.
Henrik Stenlund, "Technical Report: Measuring the Hydrodynamic Pressure in a Wet Pressing Process",KCL S8630 01-10-1986
- A theoretical report on measuring the hydrodynamic pressure of water and fiber mixture in a wet press for paper production. Part 2.
Henrik Stenlund, "Technical Report: Measuring the Hydrodynamic Pressure
in a Wet Pressing Process",
KCL S8545 12-04-1985
Henrik Stenlund, Department of Chemistry, University of Helsinki, "Time-of-Flight Mass Spectrometry", Finnish Physical Society Meeting, Oulu, 2-8-1985
- A prototype of a reflection type TOFMS is presented.
Henrik Stenlund, "Technical Report: Design of an Ultrasound Sensor Head
for Sinuscan Sinuitis Diagnosing Device", Orion Pharma Oy, Orion Analytica,
Henrik Stenlund, "Theory of Ionization", a lecture presented at Orion
Pharma Oy, Orion Analytica, 02-19-1981
Henrik Stenlund, "Design of a High Intensity
Electron Gun and Its Focusing System", Res. rep. 2/1980, Helsinki University
of Technology, Laboratory of Physics
Henrik Stenlund, "Quantum Theory of Interstitial Diffusion of Light Impurities in Si and Ge", University of Helsinki, Department of Theoretical Physics, 1979, a Licenciate Thesis
- A quantum mechanical treatment for calculating the diffusion coefficients of Li in Si and Ge. The theory is based on using multiphonon collision theory and transport theory.
Henrik Stenlund, "Quantum Theory of Interstitial Diffusion", University of Helsinki, 1979, a private study
- A quantum mechanical treatment for calculating the diffusion coefficients of Li in Si and Ge. The theory is based on using a restricted plane wave expansion in a special potential model and transport theory.
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