Core-shell cage structures of Ga n As n (n = 10-15) clusters are obtained from simulated annealing structural search followed by geometry optimization within the density functional theory. All of these core-shell structures have C s symmetry with an endohedral As or Ga atom, whose binding energies are slightly lower than those of the hollow cage structures. For both core-shell and hollow cage structures, size-dependent cluster properties including binding energy, HOMO-LOMO gaps, adiabatic electron affinities, and photoelectron spectra have been computed and discussed.
This paper presents a hardware implementation of real time data compression and decompression circuits based on the LZW algorithm. LZW is a dictionary based data compression, which has the advantage of fast speed, high compression, and small resource occupation. In compression circuit, the design creatively utilizes two dictionaries alternately to improve efficiency and compressing rate. In decompression circuit, an integrated State machine control module is adopted to save hardware resource. Through hardware description and language programming, the circuits finally reach function simulation and timing simulation. The width of data sample is 12bits, and the dictionary storage capacity is 1K. The simulation results show the compression and decompression circuits have complete function. Compared to software method, hardware implementation can save more storage and compressing time. It has a high practical value in the future.
Sensorineural hearing impaired individuals have narrow hearing range, especially in high frequency. Due to acoustic diffusion masking, just amplifying speech can’t meet patients’ demands. Traditional methods restore the signal of high frequency in low frequency, which has two weaknesses. On the one hand high frequency covers low frequency, on the other hand the methods change the energy of speech. These two aspects severely decrease speech loudness, perception and recognition. To solve the above problems, we have proposed an improved frequency shifting compression method based on Auto Energy Gain Compensation (AEGC) which is used for hearing aids. Fully investigating the relationship of speech frequency with energy and recognition, the scheme selectively keeps the information of vital frequency band. Meanwhile, it compensates the speech loudness with AEGC module. With the proposed scheme, it has obviously improved the speech perception and recognition. Both the theoretical simulation result and subjective test in APP on android platform show the energy is compensated and the speech recognition ratios are enhanced 20%-30% in different environments, especially efficient in quiet, noisy and normal environment.
Abstract. The types of noise reduction asphalt pavement were summarized into the follows: single layer porous or two-layer porous asphalt pavement, elastic asphalt pavement, optimized surface texture pavement, and universally composable one based on these three types. Beijing of China was very drought and short of rainfall, there were large volume of traffic, heavy wheel load and many dirt things on the pavement surface taken by the tires too. So the dense asphalt-rubber pavement was the most common one for noise reduction, which was paved by gap-graded, macro-texture, dense asphalt concrete, belonging to the types of elastic and optimized surface texture noise reduction pavement. And it could reduce tire-pavement noise obviously and had excellent durability; all proved that it had gone through traffic and climate environment of Beijing well. It had measured tire-pavement noise of asphalt-rubber pavement and stone mustic asphalt pavement in Beijing from 2009 to 2012. This measurement was according to Measurement of close-proximity method which prepared by international organization for standardization in the year 2000. And the test vehicle was a trailer for measuring tire-pavement noise which met requirements of ISO/CD 11819-2:2000. The factors affecting tire-pavement noise spectrum were analyzed, such as temperature, speed, age of pavement and so on. It reveals that the tire-pavement noise sound level could get higher especially higher during the frequency 500Hz~2500Hz in the noise spectrum, while the testing speed increase, or the temperature decrease , or the age of pavement grow. While the frequency lay on the range of higher than 800 Hz, the asphalt-rubber pavement's noise sound level were lower than the stone mustic asphalt pavement's one in all situations, and when the temperature decreased from 30℃ to 0℃, the low limit frequency decreased from 800Hz to 63 Hz. It had tested dynamic modulus and phase angle of the two kinds of pavement materials under different temperature and load frequency with the help of Simple Performance Tester in order to show the reason, The result shows that, asphalt-rubber concrete has smaller Phase angle at wide temperature as well as frequency changes, it could be one of the main reasons to explain this phenomenon. It could provide reference for designing, constructing, maintaining and evaluating the noise reduction asphalt pavement.
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