1,020 research outputs found
Field test of a practical secure communication network with decoy-state quantum cryptography
We present a secure network communication system that operated with
decoy-state quantum cryptography in a real-world application scenario. The full
key exchange and application protocols were performed in real time among three
nodes, in which two adjacent nodes were connected by approximate 20 km of
commercial telecom optical fiber. The generated quantum keys were immediately
employed and demonstrated for communication applications, including unbreakable
real-time voice telephone between any two of the three communication nodes, or
a broadcast from one node to the other two nodes by using one-time pad
encryption.Comment: 10 pages, 2 figures, 2 tables, typos correcte
New D- A- A- - Configured Small Molecule Donors Employing Conjugation to Red- shift the Absorption for Photovoltaics
Four new donor- acceptor- acceptor- (D- A- A- )- configured donors, CPNT, DCPNT, CPNBT, and DCPNBT equipped with naphtho[1,2- c:5,6- c- ²]bis([1,2,5]- thiadiazole) (NT) or naphtho[2,3- c][1,2,5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A- ), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)- based analogues owing to improved electron- withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70, together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum- processed organic photovoltaics (OPV)s. OPVs based on DCPNT- :- C70 active layers displayed the best power conversion efficiency (PCE)=8.3%, along with an open circuit voltage of 0.92- V, a short circuit current of 14.5- mA- cm- 2 and a fill factor of 62% under 1 sun intensity, simulated AM1.5G illumination. Importantly, continuous light- soaking with AM 1.5G illumination has verified the durability of the devices based on CPNT:C70 and DCPNT- :- C70 as the active blends. The devices were examined for their feasibility of indoor light harvesting under 500 lux illumination by a TLD- 840 fluorescent lamp, giving PCE=12.8% and 12.6%, respectively. These results indicate that the NT- based D- A- A- - type donors CPNT and DCPNT are potential candidates for high- stability vacuum- processed OPVs suitable for indoor energy harvesting.New donor- acceptor- acceptor- (D- A- A- )- configured small molecule donors with extended Ï - conjugation for red- shifting the absorption were characterized. The OPV comprising the donor DCPNT bearing naphtho[1,2- c:5,6- c- ²]bis([1,2,5]- thiadiazole) (NT) as A, cyano as A- , and acceptor C70 displayed the power conversion efficiency of 8.3% under AM 1.5G and 12.8% under 500 lux of TLD- 840 lamp, indicating the potential for indoor photovoltaics application.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/3/asia202000635.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/2/asia202000635-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156487/1/asia202000635_am.pd
Synthesizing Speech Test Cases with Text-to-Speech? An Empirical Study on the False Alarms in Automated Speech Recognition Testing
Recent studies have proposed the use of Text-To-Speech (TTS) systems to
automatically synthesise speech test cases on a scale and uncover a large
number of failures in ASR systems. However, the failures uncovered by synthetic
test cases may not reflect the actual performance of an ASR system when it
transcribes human audio, which we refer to as false alarms. Given a failed test
case synthesised from TTS systems, which consists of TTS-generated audio and
the corresponding ground truth text, we feed the human audio stating the same
text to an ASR system. If human audio can be correctly transcribed, an instance
of a false alarm is detected. In this study, we investigate false alarm
occurrences in five popular ASR systems using synthetic audio generated from
four TTS systems and human audio obtained from two commonly used datasets. Our
results show that the least number of false alarms is identified when testing
Deepspeech, and the number of false alarms is the highest when testing
Wav2vec2. On average, false alarm rates range from 21% to 34% in all five ASR
systems. Among the TTS systems used, Google TTS produces the least number of
false alarms (17%), and Espeak TTS produces the highest number of false alarms
(32%) among the four TTS systems. Additionally, we build a false alarm
estimator that flags potential false alarms, which achieves promising results:
a precision of 98.3%, a recall of 96.4%, an accuracy of 98.5%, and an F1 score
of 97.3%. Our study provides insight into the appropriate selection of TTS
systems to generate high-quality speech to test ASR systems. Additionally, a
false alarm estimator can be a way to minimise the impact of false alarms and
help developers choose suitable test inputs when evaluating ASR systems. The
source code used in this paper is publicly available on GitHub at
https://github.com/julianyonghao/FAinASRtest.Comment: 12 pages, Accepted at ISSTA202
Metropolitan all-pass and inter-city quantum communication network
We have demonstrated a metropolitan all-pass quantum communication network in
field fiber for four nodes. Any two nodes of them can be connected in the
network to perform quantum key distribution (QKD). An optical switching module
is presented that enables arbitrary 2-connectivity among output ports.
Integrated QKD terminals are worked out, which can operate either as a
transmitter, a receiver, or even both at the same time. Furthermore, an
additional link in another city of 60 km fiber (up to 130 km) is seamless
integrated into this network based on a trusted relay architecture. On all the
links, we have implemented protocol of decoy state scheme. All of necessary
electrical hardware, synchronization, feedback control, network software,
execution of QKD protocols are made by tailored designing, which allow a
completely automatical and stable running. Our system has been put into
operation in Hefei in August 2009, and publicly demonstrated during an
evaluation conference on quantum network organized by the Chinese Academy of
Sciences on August 29, 2009. Real-time voice telephone with one-time pad
encoding between any two of the five nodes (four all-pass nodes plus one
additional node through relay) is successfully established in the network
within 60km.Comment: 9 pages, 2 figures, 2 table
AMiBA Wideband Analog Correlator
A wideband analog correlator has been constructed for the Yuan-Tseh Lee Array
for Microwave Background Anisotropy. Lag correlators using analog multipliers
provide large bandwidth and moderate frequency resolution. Broadband IF
distribution, backend signal processing and control are described. Operating
conditions for optimum sensitivity and linearity are discussed. From
observations, a large effective bandwidth of around 10 GHz has been shown to
provide sufficient sensitivity for detecting cosmic microwave background
variations.Comment: 28 pages, 23 figures, ApJ in press
AMiBA: Broadband Heterodyne CMB Interferometry
The Y. T. Lee Array for Microwave Background (AMiBA) has reported the first
science results on the detection of galaxy clusters via the Sunyaev Zel'dovich
effect. The science objectives required small reflectors in order to sample
large scale structures (20') while interferometry provided modest resolutions
(2'). With these constraints, we designed for the best sensitivity by utilizing
the maximum possible continuum bandwidth matched to the atmospheric window at
86-102GHz, with dual polarizations. A novel wide-band analog correlator was
designed that is easily expandable for more interferometer elements. MMIC
technology was used throughout as much as possible in order to miniaturize the
components and to enhance mass production. These designs will find application
in other upcoming astronomy projects. AMiBA is now in operations since 2006,
and we are in the process to expand the array from 7 to 13 elements.Comment: 10 pages, 6 figures, ApJ in press; a version with high resolution
figures available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/mtc_highreso.pd
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