Research on fiber-optic interferometric hydrophone array using frequency division multiplying technique

From the point of view of system design, a configuration of fiber-optic interferomet- ric hydrophone array and its modulation and demodulation approach using frequncy division multiplexing technique based on Phase Generated Carrier (PGC) is introduced. And the em- phasis on demonstrating the relationship among the number of units N, the detectable signal amplitude D and the detectable frequency ws through analyzing the frequency spectrum of the output signal of the J × K array and the key factor which restricts N, D, Ws for increasing are presented. The maximum phare shift and the law of its variation according to frequency are specially analyzed. The results induced from some relative theory were verified by experiments.

Two-Photon Transitions of ^(85)Rb 5D_(5/2) State by Using an Optical Frequency Comb and a Continuous-Wave Laser

A high-resolution two-photon spectrum of 5S1/2 → 5P3/2 → 5D5/2 transitions in a thermal SSRb vapor cell is presented by using an optical frequency comb and a cw laser. The fluorescence of 6P3/2 → 5S1/2 spontaneous emission is detected when the cw laser frequency is scanned from the 5S1/2 ground state to 5P3/2 hyperfine levels and the optical frequency comb repetition rate is fixed. The hyperfine splittings （Ff = 2-5） of the 5D5/2 excited state are well resolved. The dependences of fluorescence intensities on the cw laser intensity and temperature of SSRb vapor eel1 are studied, respectively. The experimental results are in good agreement with the theoretical analyses.

Absolutely Direct Frequency Measurement of Two-Photon Transition Using Multi-Peak Fitting Approach

The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring transition in Rb-87. The multi-peak fitting approach is used to eliminate the frequency shift affected by the neighboring transition. With locking the carrier envelope offset frequency at 1/4 repetition frequency, the transition frequency is measured to be 770569132739.9 +/- 5.8 kHz, which agrees well with the previous result recommended by Comite International des Poids et Mesures.

Frequency Domain Approach for Face Recognition Using Optical Vanderlugt Filters

In this paper human face machine identification is experienced using optical correlation techniques in spatial frequency domain. This approach is tested on ORL dataset of faces which includes face images of 40 subjects, each in 10 different positions. The examined optical setup relies on optical correlation based on developing optical Vanderlugt filters and its basics are described in this article. With the limitation of face database of 40 persons, the recognition is examined successfully with nearly 100% of accuracy in matching the input images with their respective Vanderlugt synthesized filters. Software simulation is implemented by using MATLAB for face identification.

A Study of the Use and Translation of Archaic Functional Vocabulary in the Berne Convention

The archaic functional vocabulary is highly with the legal features of formality and conservativeness and still holding a place in legal English.The Berne Convention is a good example to study the use and translation of the archaic functional vocabulary.By studying what archaic functional words or phrases are used in the Berne Convention,their meanings and the different use frequencies of them between the Berne Convention and the Copy Right Law of PRC,it has been found that arhcaic adverbs are used of low frequency,while some adjectives or adjectival groups as well as some prepositions or prepositional phrases are used of high frequencies.The use frequencies of the archaic functional vocabulary is higher in the Berne Convention than those in the Copy Right law of PRC.Some suggestions can be put forward to help improve translating Chinese legal documents into English or writing English legal documents.

A Single Pattern Matching Algorithm Based on Character Frequency

Based on the study of single pattern matching, MBF algorithm is proposed by imitating the string searching procedure of human. The algorithm preprocesses the pattern by using the idea of Quick Search algorithm and the already-matched pattern psefix and suffix information. In searching phase, the algorithm makes use of the!character using frequency and the continue-skip idea. The experiment shows that MBF algorithm is more efficient than other algorithms.

French Listening Strategies Used by Postgraduates of English Majors

The author intends to find out a set of French listening strategies used by postgraduates of English majors. Questionnaire is used in this research. It is designed according to a listening strategy study done by O'Malley and Chamot. After analyzing the data, a set of French listening strategies is worked out, as well as two orders concerning the strategies used: order of using frequency, order of importance.

Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

Visible light communication(VLC)is a promising solution to the increasing demands for wireless connectivity.Gallium nitride micro-sized light emitting diodes(micro-LEDs)are strong candidates for VLC due to their high bandwidths.Segmented violet micro-LEDs are reported in this work with electrical-to-optical bandwidths up to 655 MHz.An orthogonal frequency division multiplexing-based VLC system with adaptive bit and energy loading is demonstrated,and a data transmission rate of 11.95 Gb/s is achieved with a violet micro-LED,when the nonlinear distortion of the micro-LED is the dominant noise source of the VLC system.A record 7.91 Gb/s data transmission rate is reported below the forward error correction threshold using a single pixel of the segmented array when all the noise sources of the VLC system are present.

Midinfrared optical frequency comb based on difference frequency generation using high repetition rate Er-doped fiber laser with single wall carbon nanotube film

We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161 MHz high repetition rate fiber laser using a single wall carbon nanotube was fabricated. The output pulse was amplified in an Er-doped single mode fiber amplifier, and a 1.1–2.2 μm wideband supercontinuum(SC) with an average power of 205 m W was generated in highly nonlinear fiber. The spectrogram of the generated SC was examined both experimentally and numerically. The generated SC was focused into a nonlinear crystal, and stable generation of MIR comb around the 3 μm wavelength region was realized.

Non-uniform strain measurement along a f iber Bragg grating using optical frequency domain reflectometry

A novel method of measuring non-uniform strain along a fiber Bragg grating(FBG) using optical frequency domain reflectometry(OFDR) is proposed and experimentally demonstrated. This method can overcome the problems of traditional non-uniform strain measurement methods for FBGs, i.e., the likelihood of chirping and multiple peaking in the spectrum when FBG is subjected to inhomogeneous strain fields. Wavelength interrogation is realized by OFDR with a narrow-line-width tunable laser as the optical source. When non-uniform strain distributions along areas adjacent to structural damage are measured by this method, good agreement is obtained between measurements and theoretical simulation results.

Photonic-assisted approach for instantaneous microwave frequency measurement with tunable range by using Mach-Zehnder interferometers

A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.

Generation of ultra-flat optical frequency comb using a balanced driven dual parallel Mach–Zehnder modulator

We propose and experimentally demonstrate an ultra-fiat optical frequency comb （OFC） generator by a bal- anced driven dual parallel Mach-Zehnder modulator. Five- and seven-tone OFC with exactly equal intensity can be generated theoretically, Experimentally obtained five- and seven-tone OFC with flatness of 0.6 and 1.26 dB are demonstrated, respectively, which agrees well with the theoretical results.

Modulation-free laser frequency ofset locking using bufer gas-induced resonance

We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input intensity when an acousto-optic modulator is applied to shift the laser frequency from the resonance. We show the stabilization of a strong 795- nm laser detuned up to 550 MHz from the 87Rb 5S1/2 F=2→5P1/2F'=2 transition. The locking range can be modifed by controlling the bufer gas pressure. A laser line width of 2 MHz is achieved over 10 min.

The Social Context of Antibiotic Resistance

There are various socio-economic （poverty, self medication, and non-compliance to prescribed therapy） and behavior factors that affects the way of antibiotic use, which consequently brings the development of antibiotic resistance in patients. In the study, some of these social factors that might have an impact on the resistance of antibiotics in patients of regional of Vlora hospital during the period 2011-2012 were examined. The study was conducted using structured interviews on patients who were previously examined for bacterial cultures and sensitivity. The antibiotic resistance resulted really high in these patients. It is found out that the organisms with higher resistance were Streptococcus and Escherichia coli. 75% of the patients, whose cultures were positive, were resistant to at least one antibiotic and 31% to three or more antibiotics. A significant correlation between the structure of antibiotic resistance and the upper socio economic levels, the low educational level of the patients, self medication and the frequency of antibiotic use was found. These data have influence in the development of the awareness strategies in risky groups in order to clarify the concepts on the proper use of antibiotics.

Frequency up-conversion imaging with 60-dB gain using picosecond optical parametric amplifier

A weak infrared （IR） image amplifier with more than 60-dB optical gain and is developed from a picosecond （PS） 355-nm pumped gated optical parametric frequency up-conversion amplifier （OPA） in a/% BaB204 （BBO） crystal. The IR image at 1064 nm is amplified and up-converted into the visible region at 532 nm by parametric amplification and up-conversion. With the optimized optical gain, the lowest detectable energy of the image can be as low as 1.8 femto-Joule per pulse, which is three orders of magnitude lower than the detection limit of a charge-coupled device （CCD） camera. The transversal resolution of the OPA imaging is investigated, and the approaches for higher detection sensitivity and higher transversal resolution are proposed.

Effective generation of optical quadruple frequency millimeter-wave based on fiber laser using injection rational harmonic mode-locked technique

A method to generate the optical quadruple frequency millimeter-wave with high power efficiency is pro- posed and demonstrated based on the combination of the injection 2nd-order rational harmonic mode- locked fiber ring laser technique and the fiber grating notch filter. In this approach, the fiber Bragg grating notch filter is inserted into the laser cavity to prevent the undesired optical carrier, so that the pump power can be converted to 2nd-order harmonic wave more efficiently. In our experiment, the power efficiency of optical quadruple frequency millimeter-wave （40 GHz） generation is ten folds of that of our previous method based only on the rational harmonic mode-locked technique.

Three-dimensional Dominant Frequency Mapping Using Autoregressive Spectral Analysis of Atrial Electrograms of Patients in Persistent Atrial Fibrillation

Areas with high frequency activity within the atrium are thought to be 'drivers' of the rhythm in patients with atrial fibrillation (AF) and ablation of these areas seems to be an effective therapy in e-liminating DF gradient and restoring sinus rhythm. Clinical groups have applied the traditional FFT-based approach to generate the three-dimensional dominant frequency (3D DF) maps during electro-physiology (EP) procedures but literature is restricted on using alternative spectral estimation tech-niques that can have a better frequency resolution that FFT-based spectral estimation.

The Study of Thematic Progression Patterns in TEM8 News Discourse

This paper studies thematic progression patterns of 20 news items in TEM8 based on the theories of theme and rheme.The use frequencies of three thematic progression patterns are calculated and analyzed to propose some implications on improving listening comprehension.

Monitoring the spatio-temporal dynamics of swidden agriculture and fallow vegetation recovery using Landsat imagery in northern Laos

Swidden agriculture is an age-old, widespread but controversial farming practice in Montane Mainland Southeast Asia （MMSEA）. In the uplands of northern Laos, swidden ag- riculture has remained a predominant human-dominated land-use type for centuries. However swidden system has undergone dramatic transformations since the mid-1990s. Debates on changes in swidden cultivation are linked to globally critical issues, such as land use/cover changes （LUCC）, biodiversity loss and environmental degradation. Since the implementation of Reducing Emissions from Deforestation and Forest Degradation （REDD）, much attention has been paid nationally and internationally to swidden agriculture in the tropics. However, knowledge of the explicitly spatial characteristics of swidden agriculture and the conse- quences of these transitions at macroscopic scale is surprisingly scarce. In this study, the intensity of swidden use and fallow forest recovery in northern Laos in 1990, 2002, and 2011 were delineated by means of Landsat Thematic Mapper （TM） and Enhanced Thematic Mapper plus （ETM＋） imagery （30 m） using a decision tree classification approach, followed by an analysis of the spatio-temporal changes in swidden agriculture. Next, annual successive TM/ETM＋ images during 2000-2010 were used to delineate the dynamics of the burning and cropping phase. Subsequently, the burned pixels identified in 2000 were compared respectively with their counterparts in the following years （2001-2011） to investigate temporal trends, land-use frequency, and the swidden cycle using time-series Landsat-based Normalized Difference Vegetation Index （NDVI） data. Finally, as the swidden cycle changed from 1 to 11 years, the fallow vegetation recovery process was studied. The results showed that： （1） from 1990 to 2011, the area of swidden agriculture increased by 54.98%, from 1.54× 10^5 ha to 2.38×10^5 ha in northern Laos. The increased swidden cultivation area was mainly distributed in Luang Prabang and southern Bokeo, whereas the decreased parts were mainly found in Phongsali; （2） swidden agriculture increased mainly at elevations of 500-800 m, 300-500 m, and 800-1000 m and on slopes of 10°-20° and 200-30°. Over 80% of swidden fields were transformed from forests; （3） during 2000-2011, the frequency of swidden use in northern Laos was about two or three times. The interval between two successive utilization of a swidden ranged from one to seven years. Comparison of swidden cycles and the related proportions of swidden farming in 2000, 2003, and 2007 revealed that swidden cycles in most areas were shortened; and （4） there was a significant correlation （0.97） between fallow vegetation recovery and the swidden cycle. The NDVI of regenerated vegetation could approach the average level of forest when the swidden cycle reached 10 years.

How Urban Green Space Attracts the Elderly:A Preliminary Study on the Relationship Between External Environmental Characteristics and the Frequency of Use

A high-grade green space environment will provide necessary environmental support to the outdoor activities of disadvantaged groups including the elderly and is thus helpful for promoting their physical activity level and life quality.This paper takes the urban area of Dalian City as an example and divides the external environmental characteristics of a green space into three aspects including the diversity degree of facilities,the richness level of street functions,and the mixing degree of land use.Based on the data of a survey on activities by elderly in green space,the paper conducts an in-depth study on the statistical correlation between the external environmental characteristics of green space and the frequency of use by the elderly.The study shows that diversified facility types around a green space are conducive to a rise in the frequency of use of this space by the elderly,out of which the effect of functional facilities such as school and food market is the most significant.In addition,being adjacent to streets full of daily life or being mixed with residential land use will increase the frequency of use of the green space by the elderly.This paper puts forward certain environmental upgrading strategies for green space from the perspective of external environmental characteristics in order to help build up green space that is use-friendly to the elderly.