WO2005073736A2 - Method and system for measuring the speed of a vehicle - Google Patents
Method and system for measuring the speed of a vehicle Download PDFInfo
- Publication number
- WO2005073736A2 WO2005073736A2 PCT/FR2004/003315 FR2004003315W WO2005073736A2 WO 2005073736 A2 WO2005073736 A2 WO 2005073736A2 FR 2004003315 W FR2004003315 W FR 2004003315W WO 2005073736 A2 WO2005073736 A2 WO 2005073736A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- transducers
- vehicle
- speed
- acoustic
- pair
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
- G01P3/66—Devices characterised by the determination of the time taken to traverse a fixed distance using electric or magnetic means
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
- G08G1/054—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed photographing overspeeding vehicles
Definitions
- the invention relates to a method and a system for measuring the speed of a vehicle, and to a recording medium for their implementation. More specifically, the invention relates to a method of measuring the speed of a vehicle using acoustic transducers aligned parallel to the same common axis, this method comprising a step of measuring noise so that each transducer generates an acoustic signal representative of the sound wave generated by the vehicle during its movement.
- a method is, for example, described in French patent application FR 2 812 402.
- the method described in FR 2 812 402 consists in calculating an intercorrelation function between two acoustic signals measured respectively by a first and a second acoustic transducer .
- the intercorrelation function makes it possible to estimate the delay time between the signal measured by the first transducer and that measured by the second transducer.
- This delay time is representative of the angular position of the vehicle with respect to the axis passing through the two acoustic transducers. More precisely, this delay time represents the value of the angle between a first straight line passing through the middle of the two transducers and the position of the vehicle and a second straight line perpendicular to the axis on which these two acoustic transducers are aligned.
- the invention aims to remedy this drawback by proposing a method for measuring the speed of a vehicle using acoustic transducers which can be implemented without the distance separating the traffic lane from the acoustic transducers being known.
- the subject of the invention is therefore a method for measuring the speed as described above, characterized: - in that at least three acoustic transducers are used, these transducers being grouped together to form at least a first and a second pair of transducers, the first and second pairs of transducers respectively defining a first and a second median plane perpendicular to the common axis, the first median plane being located midway between the two transducers of the first pair, and the second median plane being located midway between the two transducers of the second pair, and - in that the method comprises: - a step of detecting a first and a second instants of passage at which the vehicle respectively crosses the first and the second median planes from the noise measured respectively by the first and second pairs of transducers, and
- the measurement method comprises a step of multiplication between them of the two acoustic signals measured by each pair of transducers so as to obtain a plane signal representative of the noise power in the median plane defined by this pair, and in that the detection step further consists in identifying the instant at which each plane signal is maximum, these instants when the signals of plane are maximum corresponding to the instants of passage of the vehicle in the median planes;
- - It includes a step of filtering the acoustic signals used during the detection step to eliminate from these signals the frequency components having a wavelength greater than four times the distance between two acoustic transducers;
- the step of establishing the speed of the vehicle comprises an operation of establishing a regression line whose slope is proportional or inversely proportional to the speed of the vehicle;
- - It includes a step of identifying one or more pure sinusoids in one or more of the acoustic signals measured so as to detect the use of an audible warning device;
- the invention also relates to an information recording medium, characterized in that it includes instructions for the implementation of a method for measuring the speed of a vehicle according to the invention, when these instructions are executed by an electronic computer.
- the invention also relates to a system for measuring the speed of a vehicle capable of performing a method for measuring this speed according to any one of the preceding claims, this system comprising: - acoustic transducers aligned parallel to a common axis for measuring the noise generated by the vehicle when it passes in front of these transducers, and - a computer capable of processing the acoustic signals measured to deduce the speed of the motor vehicle, characterized: - in that the system comprises at least three transducers these transducers being grouped together to form at least a first and a second pair of transducers, the first and second pairs of transducers respectively defining first and second median planes perpendicular to the common axis, the first median plane being located midway between the two transducers of the first pair, and the second median plane being located mid-way -distance between the two transducers of the second pair, and - in that the computer is capable of performing: - a step of detecting a first and a second moment of passage
- FIG. 1 is a schematic illustration of the architecture of a measurement system of the speed of a vehicle according to the invention
- - Figure 2 is a flow diagram of a method for measuring the speed of a vehicle according to the invention
- - Figure 3 is a graph representing the distance traveled by a vehicle as a function of measured transit times.
- FIG. 1 represents a system 2 for measuring the speed of a motor vehicle 4 moving on a traffic lane 6.
- Vehicle 4 is a conventional vehicle which, when traveling on a traffic lane, continuously generates a sound wave.
- the system 2 comprises at least three acoustic transducers connected to a unit 10 for acquiring and processing the acoustic signals measured by these transducers.
- all the acoustic transducers of the system 2 are aligned on a common axis 12 substantially parallel to the axis of the track 6.
- these acoustic transducers are arranged at regular intervals on this common axis 12.
- the distance separating two consecutive acoustic transducers is here denoted 2e.
- system 2 comprises five acoustic transducers referenced from left to right by the symbols Ci to C 5 .
- the distance e is chosen as large as possible so as to improve the resolution of the system 2. However, to limit the size of the system 2, this distance e is chosen here as being between 5 and 15 centimeters.
- Each transducer Ci is able to measure the sound wave generated by the vehicle 4 during its movement and to transmit an acoustic signal s ⁇ (t) corresponding to the unit 10 for processing.
- seven dotted lines referenced from left to right by the symbols Pi to P 7 each represent a median plane between two transducers Cj of a pair of acoustic transducers. More precisely, each pair of transducers Ci defines the position of a median plane perpendicular to the axis 12 and located midway between these two transducers Cj.
- the same median plane can correspond to several different pairs of transducers.
- the median plane P 4 corresponds to that defined by the pair of transducers C 2 , C 4 and the pair of transducers Ci, C 5 .
- the distance between two consecutive parallel mid-planes is equal to the distance e.
- the unit 10 is able to acquire the various acoustic signals measured by the transducers Ci and to process these signals so, moreover, to measure the speed of the vehicle 4.
- the unit 10 comprises an analog digital converter 20, suitable for converting the analog signals Si (t) into digital signals.
- the sampling frequency of this converter 20 is of the order of 6000 samples per second and the samples of each acoustic signal Si (t) are measured at the same times so as not to introduce phase shift between these different acoustic signals .
- the unit 10 includes a high pass filter 22 for eliminating digitized acoustic signals, the frequency components which are not very sensitive to the direction of the sound wave generated by the vehicle 4.
- the cut-off frequency f c of this filter is chosen so as to eliminate the frequency components whose quarter of the wavelength is greater than the distance 2e separating two consecutive transducers.
- the cut-off frequency f c is chosen so as to respect the following relationship: where it is the speed of sound in the air.
- the cutoff frequency f c is equal to c / 8e.
- the frequency components whose wavelength is greater than four times the distance 2e between transducers always arrive with a phase shift less than ⁇ r / 2 whatever the position of the vehicle. They therefore correspond to a product P ⁇ (t), explained below, always positive and therefore form a background noise which deteriorates the precision of the speed measurement if it is not eliminated.
- the acoustic signal Sj (t) after being filtered by the filter 22 is noted
- a multiplier 24 is provided in the unit 10 to multiply between them the signals shj (t) from the two acoustic transducers Cj and Ck of the same pair of acoustic transducers. At output, the multiplier 24 therefore delivers n (n-1) / 2 signals, here called plane signals P
- a low-pass filter 26 is connected to the output of the multiplier 24 so as to smooth the plane signals P
- This filter 26 is capable of delivering at output n (n-1) / 2 filtered plane signals Q ⁇ (t) obtained by calculating the sliding average of each plane signal P
- T is for example chosen equal to 5 to 20 times the sampling period.
- the signal Q ⁇ (t) is therefore for example obtained using the following relation: 1 Q ⁇ (t) ⁇ 3 P '(t + d) where d is a variable which varies in incremental steps equal to the period d' sampling from -T / 2 to T / 2.
- the unit 10 comprises an electronic computer 28 capable of processing the signals Q ⁇ (t) so as to further determine the speed of the vehicle 4 as well as other information, as described with reference to FIG. 2.
- the computer 28 is able to carry out the method of FIG. 2.
- the computer 28 is also able to control various peripheral devices associated with the unit 10 such as, for example, a camera 40 and a radio transmitter / receiver 42.
- the computer 28 is, for example, a conventional programmable computer capable of executing instructions recorded in a memory 44.
- the memory 44 contains the instructions necessary for the execution of the method of FIG. 2.
- the camera 40 is clean to photograph the vehicle 4 and in particular its license plate during its passage.
- the radio transmitter / receiver 42 is intended to transmit, via a wireless network, information acquired and processed by the unit 10 to other equipment.
- the transmitter / receiver 42 is capable of directly transmitting control instructions to a red light 48 installed near the unit 10.
- the transmitter / receiver 42 is also capable, here, of transmitting the information acquired and processed to a center 52 for road traffic management.
- the operation of the system 2 will now be described with reference to FIG. 2.
- each transducer Ci continuously measures, during a step 60, the sound waves coming from the channel 6 and transmits the acoustic signal Sj (t) corresponding to unit 10.
- the converter 20 digitizes, during a step 62, the set of acoustic signals Si (t) transmitted by the transducers Cj.
- the digitized acoustic signals are filtered, in a step 64, by the filter 22 and the signals obtained shj (t) are transmitted to the multiplier 24.
- the multiplier 24 calculates continuously for each pair of transducers Ci the corresponding plane signal P ⁇ (t).
- the multiplier 24 therefore continuously establishes ten signals P
- Each signal P ⁇ (t) is then filtered, during a step 68, by the filter low pass 26 so as to obtain the signal Q ⁇ (t).
- Steps 60 to 68 are carried out continuously and continuously for each signal Sj (t) measured. From each signal Q ⁇ (t) the computer 28 detects during a step 70, the instant of passage tpi of the vehicle 4 in the median plane defined by the pair of transducers corresponding to the index I.
- l 'index I corresponds to the number of a pair of transducers and not to the index of a median plane.
- the instant of passage in a median plane defined by a pair of transducers Ci corresponds to the instant when the plane signal presents a significant power or energy peak. Indeed, when the vehicle 4 crosses a median plane, the sound wave which it generates at this instant takes exactly the same time to reach the two transducers Ci of the pair of transducers which defines this median plane. Thus, the plan signal presents a maximum at this instant there.
- the property is used according to which the value of this instant of passage tpi is the value which minimizes the dispersion of the values of the signal Q ⁇ (t) over a time window W around this instant.
- the value of the instant tpi is therefore, for example, given by the following relation: where: - d is a variable varying in incremental steps equal to the sampling period over the interval [- W / 2; W / 2], W being the amplitude of the time window considered, and - 1 is time.
- the index I of the instant tpi is equal to the index I of the corresponding signal Q ⁇ (t) and therefore corresponds to a pair of known transducers Ci.
- the value W for the time window is chosen as a function of the average speed of the vehicles observed on track 6. It will be noted that since in this embodiment, several pairs of transducers Cj can define the same median plane, several instants of passage in the same median plane are calculated from different Q ⁇ (t) signals. It is therefore understood that there is a redundancy of the measured instants of passage which increases the robustness of the method described here with regard to parasitic noise such as, for example, with respect to the noise generated by fixed reflecting elements. the sound wave of the vehicle 4. Then, the computer 28 establishes, during a step 72, for each instant tpi a confidence index Sb
- Residual noise B is the noise measured by the pair of transducers of index I between two passages of a motor vehicle on track 6.
- the power of the residual noise is estimated by establishing the average of the minima of the signals Q ⁇ (t) over a longer period than the time window W. For example, this period will be at least 5W.
- the computer 28 then establishes, during a step 74, the speed of the vehicle 4 from the instants of passage tpi and from the distances separating the different median planes.
- the round dots represent the position of the vehicle at time tpi. This position is deduced from the index I.
- each index I is associated with a pair of transducers Ci and therefore corresponds to a known median plane.
- the position of each median plane is measured from the position of the Ci transducer. Therefore, the median plane PK is at the distance ke from the Ci transducer.
- the computer 28 determines, during an operation 76, the regression line passing as close as possible to these round points. This regression line corresponds to the square points in FIG. 3.
- This line is determined by a known method such as, for example, the method of least squares.
- the slope of this straight line then corresponds to the speed measured by system 2.
- the computer 28 also calculates, during a step 80, a confidence index Sb for the speed calculated during the step 74.
- the computer stores the speed of the vehicle 4 calculated, for example, during step 74 only when this confidence index Sb is maximum.
- the computer also stores the passage of this vehicle and, for example, increments a vehicle counter. Then, during a step 84, the computer compares the memorized speed with a predefined speed threshold S v . If the memorized speed exceeds the threshold S v then, the computer controls, during a step 86, the camera 40 so as to take a photo of the vehicle 4. At regular intervals, the computer 28 transmits, during a step 88, the different information stored in the management center 52 via the transmitter / receiver 42. This computer 28 also uses, if necessary, the information stored to control the activation of the red light 48, during a step 90. Steps 70 to 84 are carried out continuously and continuously.
- the computer performs a step 100 of detecting an accident such as, for example, the collision of the vehicle 4 against an obstacle.
- the computer 28 filters, during an operation 102 one or more signals Sj (t) using a high pass filter intended to allow the shock wave to pass.
- the instantaneous power of the or each filtered acoustic signal is calculated, during an operation 104, then compared, during an operation 106, with the average M a of the instantaneous power of the same signal over at least one second. If the instantaneous power of one of the signals is greater than at least twice M a , then the computer proceeds to an operation 108 of indication of this event.
- the computer 28 performs a step 110 of identifying one or more pure sinusoids in the signals Si (t) to detect an audible warning. To this end, the computer 28 calculates, during an operation 112, the correlation, for a time interval greater than one second, between one or more of the acoustic signals Sj (t) and N pure sinusoids whose frequencies are regularly distributed, for example, between 200 and 400 Hertz.
- the computer 28 searches in a history for the occurrence of a detection of a buzzer persistent for S consecutive seconds. corresponding to a first pulse ⁇ i alternating with a second pulse ⁇ 2. Dan s in the affirmative, the computer transmits, during an operation 118, to the management center 52 information according to which the audible warning of a priority vehicle has been detected.
- the computer 28 then proceeds to a step 120 during which, for example, the information according to which an audible warning device of a motor vehicle has been detected is memorized and then transmitted to the management center 52. Since the median planes defined by the transducers Ci are parallel to each other, it is not necessary using the method of FIG. 2 to know the distance between the transducers Ci and track 6 to measure the linear speed of vehicle 4. In addition, unlike known systems, it is not necessary for the axis 12 to be strictly parallel to the axis of the track 6. In fact, a slight misalignment has little impact on speed measured. The table below gives some examples of the influence of an alignment error on the speed measurement. The alignment error is here measured between axis 12 and the axis of track 6.
- System 2 also has the advantage of being insensitive to the height at which it is placed relative to track 6.
- System 2 has been described in the particular case where only one line of transducers Ci is used so as to reduce clutter.
- the system comprises several lines of transducers Ci.
- the method of FIG. 2 is executed for each line of transducers Cj.
- the transducers Ci have been described here as being aligned. However, this is not essential to define several median planes parallel to each other. For example, several pairs of transducers Ci can be offset in height with respect to each other while defining each of the median planes parallel to each other. For such an arrangement, the method of FIG. 2 is not modified.
- System 2 has been described in the particular case where it only comprises five transducers.
- the number of transducers Ci is chosen to be greater than 10, 20 or 30.
- the more the number of transducers is high the greater the number of instants of tpi passages calculated and the greater the precision and the insensitivity to parasitic noises of the system.
- the number of calculated transit instants increases exponentially with the number of transducers Cj and not linearly. It is therefore possible to calculate a large number of instants of passages using a reduced number of acoustic transducers.
- the system 2 has been described in the particular case where the transducers are distributed at regular intervals along the axis 12. This simplifies the calculations.
- the unit 10 includes an additional filter placed between the filter 22 and the multiplier 24. This additional filter is an adaptive filter . In this variant, the method of FIG.
- - k is an index which varies between 1 and, where dmax is the cd maximum distance between the transducers and the parasitic reflecting elements to be taken into account.
- the coefficients ak are calculated by conventional methods which minimize, for example, the quadratic error and using algorithms such as those of Levinson and Durbin, that of the least squares or that of the stochastic gradient.
- the other steps of the method of FIG. 2 remain unchanged except for the fact that it is the signal uhj (t) which is processed instead of the signal shj (t).
- the computer 28 uses a fast Fourier transform to identify one or more pure sinusoids in the signals Sj (t).
- the system has been described in the particular case of measuring the speed of a motor vehicle. However, system 2 can be applied to the measurement of the speed of any object generating a sound wave during its movement.
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04816448A EP1700285A2 (en) | 2003-12-30 | 2004-12-20 | Method and system for measuring the speed of a vehicle, and recording medium for carrying out same |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0315586A FR2864626B1 (en) | 2003-12-30 | 2003-12-30 | METHOD AND SYSTEM FOR MEASURING THE SPEED OF A VEHICLE, AND RECORDING MEDIUM FOR THEIR IMPLEMENTATION |
FR0315586 | 2003-12-30 |
Publications (2)
Publication Number | Publication Date |
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WO2005073736A2 true WO2005073736A2 (en) | 2005-08-11 |
WO2005073736A3 WO2005073736A3 (en) | 2006-03-30 |
Family
ID=34639705
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/FR2004/003315 WO2005073736A2 (en) | 2003-12-30 | 2004-12-20 | Method and system for measuring the speed of a vehicle |
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EP (1) | EP1700285A2 (en) |
FR (1) | FR2864626B1 (en) |
WO (1) | WO2005073736A2 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2096611A1 (en) | 2008-02-28 | 2009-09-02 | Neavia Technologies | Device and method for multi-technology detection of a vehicle |
WO2010142832A1 (en) * | 2009-06-09 | 2010-12-16 | Universidad Miguel Hernández De Elche | Sound-based kinemometer |
US10070238B2 (en) | 2016-09-13 | 2018-09-04 | Walmart Apollo, Llc | System and methods for identifying an action of a forklift based on sound detection |
US10656266B2 (en) | 2016-09-13 | 2020-05-19 | Walmart Apollo, Llc | System and methods for estimating storage capacity and identifying actions based on sound detection |
CN112230208A (en) * | 2020-10-14 | 2021-01-15 | 北京理工大学 | Automobile running speed detection method based on audio perception of smart phone |
CN115019521A (en) * | 2022-05-19 | 2022-09-06 | 河北工业大学 | Method and system for determining vehicle speed |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN106960581A (en) * | 2017-04-25 | 2017-07-18 | 中国计量大学 | Speed measurer for motor vehicle based on voice signal |
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US4173010A (en) * | 1975-05-01 | 1979-10-30 | Hoffmann Anton R | Traffic sign and improved system for recording vehicle speed |
FR2675610A1 (en) * | 1991-04-18 | 1992-10-23 | Alcuri Gustavo | METHOD AND INSTALLATION FOR EVALUATING A TRAFFIC FLOW OF ROAD VEHICLES. |
EP0635813A1 (en) * | 1993-07-21 | 1995-01-25 | Laboratoire Central Des Ponts Et Chaussees | Acoustic evaluation process of road vehicles traffic flow |
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DE19955164A1 (en) * | 1999-11-17 | 2001-05-23 | Thomas Moog | Emergency siren detector unit for cars sounds warning over car entertainment system speeds response |
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JPS6489895A (en) * | 1987-09-30 | 1989-04-05 | Sony Corp | Microphone device |
JP2908849B2 (en) * | 1990-07-25 | 1999-06-21 | 株式会社三共 | A prize ball dispensing device for gaming machines |
JPH09282581A (en) * | 1996-04-17 | 1997-10-31 | Hitachi Ltd | Method and device for detecting vehicle accident inside tunnel |
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2003
- 2003-12-30 FR FR0315586A patent/FR2864626B1/en not_active Expired - Fee Related
-
2004
- 2004-12-20 WO PCT/FR2004/003315 patent/WO2005073736A2/en not_active Application Discontinuation
- 2004-12-20 EP EP04816448A patent/EP1700285A2/en not_active Withdrawn
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US4173010A (en) * | 1975-05-01 | 1979-10-30 | Hoffmann Anton R | Traffic sign and improved system for recording vehicle speed |
FR2675610A1 (en) * | 1991-04-18 | 1992-10-23 | Alcuri Gustavo | METHOD AND INSTALLATION FOR EVALUATING A TRAFFIC FLOW OF ROAD VEHICLES. |
EP0635813A1 (en) * | 1993-07-21 | 1995-01-25 | Laboratoire Central Des Ponts Et Chaussees | Acoustic evaluation process of road vehicles traffic flow |
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PATENT ABSTRACTS OF JAPAN vol. 0133, no. 23 (E-791), 21 juillet 1989 (1989-07-21) & JP 01 089895 A (SONY CORP), 5 avril 1989 (1989-04-05) * |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2096611A1 (en) | 2008-02-28 | 2009-09-02 | Neavia Technologies | Device and method for multi-technology detection of a vehicle |
WO2010142832A1 (en) * | 2009-06-09 | 2010-12-16 | Universidad Miguel Hernández De Elche | Sound-based kinemometer |
ES2376209A1 (en) * | 2009-06-09 | 2012-03-12 | Universidad Miguel Hernández De Elche | Sound-based kinemometer |
US10070238B2 (en) | 2016-09-13 | 2018-09-04 | Walmart Apollo, Llc | System and methods for identifying an action of a forklift based on sound detection |
US10656266B2 (en) | 2016-09-13 | 2020-05-19 | Walmart Apollo, Llc | System and methods for estimating storage capacity and identifying actions based on sound detection |
CN112230208A (en) * | 2020-10-14 | 2021-01-15 | 北京理工大学 | Automobile running speed detection method based on audio perception of smart phone |
CN112230208B (en) * | 2020-10-14 | 2024-03-19 | 北京理工大学 | Automobile running speed detection method based on smart phone audio perception |
CN115019521A (en) * | 2022-05-19 | 2022-09-06 | 河北工业大学 | Method and system for determining vehicle speed |
Also Published As
Publication number | Publication date |
---|---|
FR2864626A1 (en) | 2005-07-01 |
WO2005073736A3 (en) | 2006-03-30 |
FR2864626B1 (en) | 2006-03-24 |
EP1700285A2 (en) | 2006-09-13 |
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