1. A pronunciation assessment system for evaluating a user’s pronunciation, said pronunciation assessment system comprising: a computer; one or more distinctive feature assessors, each distinctive feature assessor including a feature extractor for extracting acoustic features specific to a corresponding distinctive feature from an input speech waveform, and a distinctive feature classifier for computing degree of inclination of the corresponding distinctive feature based on the extracted acoustic features, and each said distinctive feature assessor being realized according to specific characteristics of the corresponding distinctive feature;
wherein said pronunciation assessment system uses more than one said distinctive feature assessors, an assessment controller and an integrated phone grader to construct a phone assessor and evaluate a user’s pronunciation;
wherein said assessment controller identifies phonemes in the input speech waveform and dynamically decides to adopt or intensify some of said distinctive feature assessors, and said integrated phone pronunciation grader outputs various types of ranking result for the phone pronunciation assessment.
2. The pronunciation assessment system as claimed in claim 1, wherein said pronunciation assessment system uses a text-to-phone converter, a phone aligner, said phone assessor and an integrated utterance pronunciation grader to construct a continuous speech pronunciation assessor and evaluate a user’s pronunciation.
3. The pronunciation assessment system as claimed in claim 2, wherein the input of said pronunciation assessment system is continuous speech and its corresponding text.
4. The pronunciation assessment system as claimed in claim 3, wherein said text-to-phone converter converts said text to a phone string, and said phone aligner aligns the speech waveform to a phone sequence using said phone string.
5. The pronunciation assessment system as claimed in claim 2, wherein said integrated utterance pronunciation grader integrates the scores of all phones assessed by the phone assessor and gets a final pronunciation score for a word or a sentence.
6. The pronunciation assessment system as claimed in claim 2, wherein said phone assessor feeds distinctive feature detection results back to said phone aligner.
7. The pronunciation assessment system as claimed in claim 2, wherein said text-to-phone converter is done by manually prepared information or by computer automatically on-the-fly.
8. The pronunciation assessment system as claimed in claim 1, wherein each distinctive feature assessor further includes a score mapper to standardize the output for of each said distinctive feature assessor.
9. The pronunciation assessment system as claimed in claim 1, wherein said feature extractor is to detect different features or characteristics of phonetic distinction.
10. The pronunciation assessment system as claimed in claim 1, wherein said distinctive feature classifier is a binary classifier specifically designed and trained for the corresponding distinctive feature.
11. The pronunciation assessment system as claimed in claim 1, wherein the output of a distinctive feature assessor is a variable with value.
12. The pronunciation assessment system as claimed in claim 1, wherein the distinctive features are specified by users.
13. A pronunciation assessment method used in a pronunciation assessment system which evaluates a user’s pronunciation, comprising a step of building one or more distinctive feature assessors each said distinctive feature assessor being realized according to specific characteristics of a corresponding distinctive feature; wherein each distinctive feature assessor performs the steps of:
extracting acoustic features specific to the corresponding distinctive feature from an input speech waveform using a feature extractor;
computing degree of inclination of the corresponding distinctive feature based on the extracted acoustic features using a distinctive feature classifier;
wherein said pronunciation assessment method comprises a step of constructing a phone assessor for evaluating a user’s pronunciation by using more than one distinctive feature assessors, an assessment controller and an integrated phone grader;
wherein said phone assessor performs proceeds as the following steps: identifying phones in the input speech waveform and dynamically deciding to adopt or intensify one or more distinctive feature assessors by using said assessment controller; and outputting multiple types of ranking result for the phone pronunciation assessment by using said integrated phone grader.
14. The pronunciation assessment method as claimed in claim 13, wherein said distinctive feature classifier is a binary classifier specifically designed and trained for the corresponding distinctive feature.
15. The pronunciation assessment method as claimed in claim 13, wherein each said distinctive feature assessor further performs a step of standardizing the output of each said distinctive feature assessor.
16. The pronunciation assessment method as claimed in claim 13, wherein said pronunciation assessment method further includes a step of generating a final pronunciation score for inputted continuous speech and its corresponding text through a continuous speech pronunciation assessor.
17. The pronunciation assessment method as claimed in claim 16, wherein said continuous speech phone assessor performs the following steps:
(c1) inputting continuous speech and its corresponding text, and converting said text to a phone string;
(c2) using said phone string to align the speech waveform to a phone sequence; and
(c3) using said phone assessor to obtain a score for each phone, and integrating said score of each phone to get the final pronunciation score for a word or a sentence.
18. The pronunciation assessment method as claimed in claim 17, wherein at step (c3), the score obtained from said phone assessor is fed back to a phone aligner to adjust phone alignment into a finer and more precise segmentation of speech waveform.
19. The pronunciation assessment method as claimed in claim 15, wherein before the step (b1), a step of user setting is included for dynamically adjusting the distinctive features to specify the focus of pronunciation assessment.
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. A sputtering apparatus comprising:
a DC power supply;
an inverter that converts DC voltage from the DC power supply to AC voltage;
a matching circuit that transforms the AC voltage from the inverter;
a rectifier that converts the AC voltage transformed by the matching circuit to direct current; and
a sputtering load having an impedance that varies in a predetermined range, to which is supplied the DC voltage obtained from the rectifier,
wherein the matching circuit comprises: a transformer that transforms the AC voltage from the inverter; an inductance placed in series with at least one of a primary winding and a secondary winding of the transformer; and a condenser which is placed in parallel between the inductance and the rectifier and which is connected in parallel to the sputtering load via the rectifier.
2. A sputtering apparatus according to claim 1, wherein a turns ratio (number of secondary turnsnumber of primary turns) of the transformer is less than the ratio of a maximum rated voltage required for the sputtering load to the voltage of the DC power supply (the maximum rated voltagethe voltage of the DC power supply).
3. A sputtering apparatus according to claim 1, further comprising a power detection device which measures the power supplied to the sputtering load and performs pulse width modulation control of the inverter based on a signal from the power detection device.
4. A sputtering apparatus according to claim 3, wherein the inverter is a bridge inverter provided with two upper arm semiconductor switches and two lower arm semiconductor switches each having an anti-parallel diode, and power supplied to the sputtering load is regulated to the rated power by pulse width modulation control of each arm semiconductor switch based on an error signal between the power detected by the power detection device and a predetermined power.
5. A sputtering apparatus according to claim 3, wherein the inverter is a bridge inverter provided with two upper arm semiconductor switches and two lower arm semiconductor switches each having an anti-parallel diode, and power supplied to the sputtering load is regulated to the rated power by applying an on signal controlled by pulse width modulation based on an error signal between the power detected by the power detection device and a predetermined power.
6. A sputtering apparatus according to claim 1, wherein the transformer has a core and primary and secondary windings provided on the core while being separated from each other, and at least a portion of the inductance is a leakage inductance of the transformer.
7. A sputtering apparatus according to claim 1, wherein the transformer core has first and second legs, and primary and secondary windings each split into two parts and wound around the first leg and second leg, and at least a portion of the inductance is a leakage inductance of the transformer.
8. A sputtering apparatus according to claim 3, wherein the power detection device is provided with a voltage sensor that measures the voltage supplied to the sputtering load, a current sensor that measures the current supplied to the sputtering load, and a multiplier that multiplies the voltage value and current value detected by the voltage and current sensors and outputs a power value.
9. A sputtering apparatus according to claim 1, wherein a portion of the condenser is a stray distributed capacity of the secondary winding of the transformer.
10. A sputtering apparatus according to claim 1, wherein a turns ratio (number of secondary turnsnumber of primary turns) is less than the ratio of a maximum rated voltage required for the sputtering load to the voltage of the DC power supply (the maximum rated voltagethe voltage of the DC power supply); and
a voltage is transformed by using a resonance which is caused by the inductance and the condenser of the matching circuit in a case of a high impedance load.
11. A sputtering apparatus according to claim 10, wherein a trigger voltage which is higher than a highest rated voltage is applied.
12. A sputtering apparatus according to claim 1, wherein the rectifier is a double voltage rectification circuit and a turns ratio (number of secondary turnsnumber of primary turns) is less than half a ratio of the maximum rated voltage to the minimum DC voltage (the maximum rated voltage(2\xd7(the voltage of the DC power supply))).
13. A sputtering apparatus according to claim 2, wherein a value of the inductance is equal to or less than (n\xd7E8 (Im\xd7f)) when a voltage of the DC power supply is E(V), n is the turns ratio (number of secondary turnsnumber of primary turns), Im is a maximum rated current of the DC power supply, and f is a switching frequency (Hz).
14. A sputtering apparatus according to claim 1, the predetermined range is a fourfold range.