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In [[mathematics]], '''Struve functions''' <math>\mathbf{H}_\alpha(x)</math>, are solutions ''y''(''x'') of the non-homogenous [[Bessel's differential equation]]: | |||
: <math>x^2 \frac{d^2 y}{dx^2} + x \frac{dy}{dx} + (x^2 - \alpha^2)y = \frac{4{(x/2)}^{\alpha+1}}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})}</math> | |||
introduced by {{harvs|txt|last=Struve|first=Hermann|authorlink=Hermann Struve|year=1882}}. | |||
The [[complex number]] α is the '''order''' of the Struve function, and is often an integer. | |||
The '''modified Struve functions''' <math>\mathbf{L}_\alpha(x)</math> are equal to | |||
<math>-i e^{-i\alpha \pi /2} \mathbf{H}_\alpha(ix)</math>. | |||
==Definitions== | |||
Since this is a [[Ordinary differential equation#Nonhomogeneous equations|non-homogenous]] equation, | |||
solutions can be constructed from a single particular solution by adding the solutions of the homogeneous problem. | |||
In this case, the homogenous solutions are the [[Bessel function]]s, and the particular solution may be chosen as the corresponding Struve function. | |||
===Power series expansion=== | |||
Struve functions, denoted as <math>\mathbf{H}_\alpha(x)</math> have the following power series form | |||
:<math> \mathbf{H}_\alpha(x) = | |||
\sum_{m=0}^\infty \frac{(-1)^m}{\Gamma(m+\frac{3}{2}) \Gamma(m+\alpha+\frac{3}{2})} | |||
{\left({\frac{x}{2}}\right)}^{2m+\alpha+1} </math> | |||
where <math>\Gamma(z)</math> is the [[gamma function]]. | |||
The modified Struve function, denoted as <math>\mathbf{L}_{\nu}(z)</math> have the following power series form | |||
:<math> \mathbf{L}_{\nu}(z) = {\left({\frac{z}{2}}\right)}^{\nu+1} | |||
\sum_{k=0}^\infty \frac{1}{\Gamma(\frac{3}{2}+k) \Gamma(\frac{3}{2}+k+\nu)} | |||
{\left({\frac{z}{2}}\right)}^{2k} </math> | |||
===Integral form=== | |||
Another definition of the Struve function, for values of α satisfying <math>\operatorname{Re}\{ \alpha \} > -1/2</math>, is possible using an integral representation: | |||
:<math>\mathbf{H}_\alpha(x) = | |||
\frac{2{(x/2)}^{\alpha}}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})} | |||
\int_{0}^{\pi/2} \sin (x \cos \tau)\sin^{2\alpha}(\tau) d\tau.</math> | |||
==Asymptotic forms== | |||
For small x, the power series expansion is given [[#Power series expansion|above]]. | |||
For large x, one obtains: | |||
:<math>\mathbf{H}_\alpha(x) - Y_\alpha(x) \rightarrow | |||
\frac{1}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})} {\left(\frac{x}{2}\right)}^{\alpha-1} | |||
+ O\left({(x/2)}^{\alpha-3}\right) </math> | |||
where <math>Y_\alpha(x)</math> is the | |||
[[Bessel function#Bessel functions of the second kind : Y.CE.B1|Neumann function]]. | |||
==Properties== | |||
The Struve functions satisfy the following recurrence relations: | |||
:<math> | |||
\mathbf{H}_{\alpha -1}(x) + \mathbf{H}_{\alpha+1}(x) = | |||
\frac{2\alpha}{x} \mathbf{H}_\alpha (x) + \frac{{(x/2)}^\alpha}{\sqrt{\pi}\Gamma(\alpha + \frac{3}{2})} | |||
</math> | |||
:<math> | |||
\mathbf{H}_{\alpha -1}(x) - \mathbf{H}_{\alpha+1}(x) = | |||
2\frac{\mathrm{d}\mathbf{H}_\alpha}{\mathrm{d}x} - | |||
\frac{{(x/2)}^\alpha}{\sqrt{\pi}\Gamma(\alpha + \frac{3}{2})}. | |||
</math> | |||
==Relation to other functions== | |||
Struve functions of integer order can be expressed in terms of [[Anger function|Weber function]]s '''E'''<sub>''n''</sub> and vice versa: if ''n'' is a non-negative integer then | |||
:<math>\mathbf{E}_n(z)=\frac{1}{\pi} \sum_{k=0}^{[\frac{n-1}{2}]}\frac{\Gamma(k+1/2)(z/2)^{n-2k-1}}{\Gamma(n-1/2-k)}\mathbf{H}_n </math> | |||
:<math>\mathbf{E}_{-n}(z)=\frac{(-1)^{n+1}}{\pi}\sum_{k=0}^{[\frac{n-1}{2}]} \frac{\Gamma(n-k-1/2)(z/2)^{-n+2k+1}}{\Gamma(k+3/2)}\mathbf{H}_{-n}. </math> | |||
Struve functions of order ''n''+1/2 (''n'' an integer) can be expressed in terms of elementary functions. In particular if ''n'' is a non-negative integer then | |||
:<math>\mathbf{H}_{-n-1/2}(z) = (-1)^nJ_{n+1/2}(z)</math> | |||
where the right hand side is a [[spherical Bessel function]]. | |||
Struve functions (of any order) can be expressed in terms of the [[generalized hypergeometric function]] <sub>1</sub>F<sub>2</sub> (which is '''not''' the Gauss hypergeometric function <sub>2</sub>F<sub>1</sub>) : | |||
:<math>\mathbf{H}_{\alpha}(z) = \frac{(z/2)^{\alpha+1/2}}{\sqrt{2\pi}\Gamma(\alpha+3/2)}{}_1F_2(1,3/2,\alpha+3/2,-z^2/4).</math> | |||
==References== | |||
*{{cite journal|doi=10.1121/1.1564019|author=R.M. Aarts and Augustus J.E.M. Janssen|title=Approximation of the Struve function H1 occurring in impedance calculations|journal= J. Acoust. Soc. Am. |volume= 113 |pages= 2635–2637 |year= 2003|pmid=12765381|issue=5|bibcode = 2003ASAJ..113.2635A }} | |||
*{{AS ref|12|496}} | |||
*{{springer|id=S/s090700|first=A.B. |last=Ivanov}} | |||
*{{dlmf|id=11|Struve and Related Functions|first=R. B. |last=Paris}} | |||
*{{cite journal|doi=10.1002/andp.18822531319 |first=H. |last=Struve |title=Beitrag zur Theorie der Diffraction an Fernröhren |journal= Ann. Physik Chemie |volume= 17|issue=13 |year=1882 |pages= 1008–1016|bibcode = 1882AnP...253.1008S }} | |||
==External links== | |||
*[http://functions.wolfram.com/Bessel-TypeFunctions/StruveH/introductions/Struves/ Struve functions] at [http://functions.wolfram.com the Wolfram functions site]. | |||
{{DEFAULTSORT:Struve Function}} | |||
[[Category:Special functions]] | |||
[[Category:Struve family]] |
Revision as of 01:40, 25 October 2013
In mathematics, Struve functions , are solutions y(x) of the non-homogenous Bessel's differential equation:
introduced by Template:Harvs. The complex number α is the order of the Struve function, and is often an integer. The modified Struve functions are equal to .
Definitions
Since this is a non-homogenous equation, solutions can be constructed from a single particular solution by adding the solutions of the homogeneous problem. In this case, the homogenous solutions are the Bessel functions, and the particular solution may be chosen as the corresponding Struve function.
Power series expansion
Struve functions, denoted as have the following power series form
where is the gamma function.
The modified Struve function, denoted as have the following power series form
Integral form
Another definition of the Struve function, for values of α satisfying , is possible using an integral representation:
Asymptotic forms
For small x, the power series expansion is given above.
For large x, one obtains:
where is the Neumann function.
Properties
The Struve functions satisfy the following recurrence relations:
Relation to other functions
Struve functions of integer order can be expressed in terms of Weber functions En and vice versa: if n is a non-negative integer then
Struve functions of order n+1/2 (n an integer) can be expressed in terms of elementary functions. In particular if n is a non-negative integer then
where the right hand side is a spherical Bessel function.
Struve functions (of any order) can be expressed in terms of the generalized hypergeometric function 1F2 (which is not the Gauss hypergeometric function 2F1) :
References
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Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang