1. A hydraulic suction fuse for use with a debris collection trap, said fuse comprising in combination:
a) an apertured cover;
b) a shroud extending about said aperture in said cover;
c) a flexible disc for sealing said aperture in said cover, said disc being captured by said shroud, said disc being adapted to bend to pass through said aperture in said cover in response to a suction force within the trap and to become displaced from said aperture in said cover; and
d) a stem extending from said disc, said stem being adapted to accommodate manually drawing said displaced disc into capture by said shroud to seal said aperture in said cover.
2. A hydraulic suction fuse as set forth in claim 1 including a ring extending from said stem for manual engagement, said ring being adapted to retain said displaced disc proximate said aperture in said cover.
3. A hydraulic suction fuse as set forth in claim 1 wherein said shroud includes a cylinder circumscribing said aperture and said disc and a radially inwardly extending lip for retaining said disc within said cylinder.
4. A hydraulic suction fuse as set forth in claim 3 including a ring extending from said stem and adapted for manual engagement, said ring being adapted to bear against said lip to retain said displaced disc proximate the aperture in said cover.
5. A method for relieving the suction force of a drain in a swimming pool or spa, which drain is in fluid communication with a debris collection trap receiving water from the drain in response to a suction pump drawing water from the trap, said method comprising in combination:
a) sealing an aperture of the trap;
b) opening the aperture in response to an increase in suction force within the trap resulting in a drop of water level in the trap; and
c) maintaining a gravity induced flow of water through the aperture and into the trap until the aperture of the trap is resealed.
6. The method as set forth in claim 5 including the step of manually resealing the aperture.
7. The method as set forth in claim 5 wherein said step of sealing includes the step of sealing the aperture with a flexible disc.
8. A hydraulic suction fuse for use with a swimming pool or spa, said fuse comprising in combination:
a) a compartment disposed at an elevation below the surface of the water in the swimming pool;
b) an apertured bracket defining the upper end of said compartment;
c) a shroud extending about said aperture in said bracket;
d) a flexible disc for sealing said aperture in said bracket, said disc being captured by said shroud, said disc being adapted to bend to pass through said aperture in said bracket in response to a suction force within said compartment and to become displaced from said aperture in said bracket; and
e) a stem extending from said disc, said stem being adapted to accommodate manually drawing said displaced disc into capture by said shroud to seal said aperture in said bracket.
9. A hydraulic suction fuse as set forth in claim 8 including a ring extending from said stem and adapted for manual engagement, said ring being adapted to retain said displaced disc proximate said aperture in said bracket.
10. A hydraulic suction fuse as set forth in claim 8 wherein said shroud includes a cylinder circumscribing said aperture and said disc and a radially inwardly extending lip for retaining said disc within said cylinder.
11. A hydraulic suction fuse as set forth in claim 10 including a ring extending from said stem for manual engagement, said ring being adapted to bear against said lip to retain said displaced disc proximate said aperture in said bracket.
12. A method for relieving the suction force of a drain in a swimming pool or a spa, which drain is in fluid communication with a compartment receiving water from the drain in response to a suction pump drawing water from the compartment, said method comprising in combination:
a) sealing an aperture of the compartment;
b) opening the aperture in response to an increase in suction force within the compartment resulting in a drop of water level in the compartment; and
c) maintaining a gravity induced flow of water through the aperture and into the compartment until the aperture of the compartment is resealed.
13. The method as set forth in claim 12 including the step of manually resealing the aperture.
14. The method as set forth in claim 12 wherein said step of sealing includes the step of sealing the aperture with a flexible disc.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An unauthorized-alteration detecting method comprising:
a step in which a processing section specifies a modulus P, an order N which is an even number equal to or larger than 2, and a root \u03b1, which are parameters of number theoretic transform;
a step in which the processing section reads from a storage section an original-image block fi,j(x, y) obtained by block-dividing an original image f to which embedding is to be applied;
a step in which the processing section uses the modulus P, the order N, and the root \u03b1 specified, to apply the number theoretic transform to the original-image block fij(x, y) to calculate the number-theoretic-transformed block Fi,j(x, y) of the original-image block;
a step in which the processing section determines an embedding position (x\u2032, y\u2032) of a signature image in each block according to a predetermined randomizing function which uses information of a left adjacent block, a right adjacent block, or a surrounding predetermined block as a parameter;
a step in which the processing section reads from the storage section a pixel value gi,j of the signature image to be embedded;
a step in which the processing section obtains an integer having the minimum absolute value and satisfying Fi,j(x\u2032, y\u2032)+\u03b4=gi,j(mod \u03b5) as an embedding amount \u03b4 in each block from the number-theoretic-transformed block Fi,j(x\u2032, y\u2032) of the original-image block at the embedding position, the pixel value gi,j of the signature image, and embedding strength \u03b5;
a step in which the processing section adds or subtracts the embedding amount \u03b4 to or from the number-theoretic-transformed block Fi,j(x, y) of the original-image block, based on (x, y) to obtain the number-theoretic-transformed block Hi,j(x, y) of an embedding-applied-image block;
a step in which the processing section applies inverse number theoretic transform to the number-theoretic-transformed block Hi,j(x, y) to obtain the embedding-applied-image block hi,j(x, y); and
a step in which the processing section obtains the embedding-applied-image block hi,j(x, y) for each of all (i, j) blocks to obtain an embedding-applied image h, and stores it in the storage section andor outputs it from an output section or an interface.
2. An unauthorized-alteration detecting method according to claim 1, further comprising a step in which the processing section transmits the modulus P and the embedding-applied image h, and, if necessary, the order N to an extraction-side apparatus through the output section or the interface.
3. An unauthorized-alteration detecting method of claim 1, further comprising a step in which the processing section obtains the original image h according to the embedding-applied image h and the signature image h.
4. An unauthorized-alteration detecting method of claim 1, wherein P is any compound number generated by a power of a prime number.
5. An unauthorized-alteration detecting method of claim 1, wherein N is common to an embedding side and an extraction side of the signature image and stored in advance in the storage section, or is transferred from the embedding side to the extraction side.
6. An unauthorized-alteration detecting method of claim 1, wherein the processing section selects the order N among candidates of the order N, obtained by N|GCD(P1\u22121), (P2\u22121), . . . , (Pm\u22121) according to a predetermined priority.
7. An unauthorized-alteration detecting method of claim 1, wherein the processing section calculates the root \u03b1 uniquely determined according to a predetermined expression of the Chinese remainder theorem or others, based on the modulus P and the order N specified.
8. An unauthorized-alteration detecting method of claim 1, wherein
the processing section specifies P expressed by P=p1r1p2r2 . . . pmrm, where pi is a prime number and ri is a positive integer;
the processing section selects the order N among positive integers satisfying N|GCD(p1\u22121), (p2\u22121), . . . , (pm\u22121), or reads the order N from the storage section;
the processing section calculates a root \u03b11,i of the order N with respect to the modulus pi;
the processing section obtains a root \u03b12,i of the order N with respect to the modulus piri from \u03b11,i; and
the processing section obtains the root \u03b1 of the order N with respect to the modulus P from \u03b12,i according to the Chinese remainder theorem.
9. An unauthorized-alteration detecting method of claim 1, wherein the processing section uses P, N, and \u03b1 to execute the number theoretic transform between x(n) and X(k) by the following expressions,
X
\u2061
(
k
)
=
\u2211
n
=
0
N
–
1
\u2062
x
\u2061
(
n
)
\u2062
\u2062
\u03b1
kn
\u2062
\u2062
(
mod
\u2062
\u2062
P
)
(
1
)
x
\u2061
(
n
)
=
N
–
1
\u2062
\u2062
\u2211
k
=
0
N
–
1
\u2062
X
\u2061
(
k
)
\u2062
\u2062
\u03b1
–
kn
\u2062
\u2062
(
mod
\u2062
\u2062
P
)
(
2
)
wherein P is any compound number generated by a power of a prime number, \u03b1 is a positive integer, N is the minimum positive integer satisfying \u03b1N=1 (mod P),
X=Tx
x=T\u22121X
T is a transformation matrix, and T\u22121 is an inverse transformation matrix.
10. An unauthorized-alteration detecting method of claim 1, wherein the randomizing fimction uses the value of the modulus P andor a pixel value in an adjacent block or a pixel value in a predetermined block which is not changed by an embedding process, as a parameter, and determines the position uniquely.
11. A computer readable medium encoding an unauthorized-alteration detecting program for making a computer execute each of the following steps, the following steps including:
a step in which a processing section specifies a modulus P, an order N which is an even number equal to or larger than 2, and a root \u03b1, which are parameters of number theoretic transform;
a step in which the processing section reads from a storage section an original-image block fi,j(x, y) obtained by block-dividing an original image f to which embedding is to be applied;
a step in which the processing section uses the modulus P, the order N, and the root \u03b1 specified, to apply the number theoretic transform to the original-image block fi,j(x, y) to calculate the number-theoretic-transformed block Fi,j(x, y) of the original-image block;
a step in which the processing section determines an embedding position (x\u2032, y\u2032) of a signature image in each block according to a predetermined randomizing function which uses information of a left adjacent block, a right adjacent block, or a surrounding predetermined block as a parameter;
a step in which the processing section reads from the storage section a pixel value gi,j of the signature image to be embedded;
a step in which the processing section obtains an integer having the minimum absolute value and satisfying Fi,j(x\u2032, y\u2032)+\u03b4=gi,j (mod \u03b5) as embedding amount \u03b4 in each block from the number-theoretic-transformed block Fi,j(x\u2032, y\u2032) of the original-image block at the embedding position, the pixel value gi,j of the signature image, and embedding strength \u03b5;
a step in which the processing section adds or subtracts the embedding amount \u03b5 to or from the number-theoretic-transformed block Fij(x, y) of the original-image block, based on (x, y) to obtain the number-theoretic-transformed block Hi,j(x, y) of an embedding-applied-image block;
a step in which the processing section applies inverse number theoretic transform to the number-theoretic-transformed block Hi,j(x, y) to obtain the embedding-applied-image block hi,j(x, y); and
a step in which the processing section obtains the embedding-applied-image block hi,j(x, y) for each of all (i, j) blocks to obtain an embedding-applied image h, and stores it in the storage section andor outputs it from an output section or an interface.