土坝体隐患弹性波探测中的横波优势

用于土坝体隐患探测中的弹性波波媒主要包括纵波、横波、表面波等等,由于组成土坝体不同介质结构特有的弹性波波速特性,选择横波作为弹性波勘探的波媒具有比纵波优越的地球物理前提条件,而且通常具有能量强、分辨率高、波成分相对简单、易于对比分辨(极性特征)等特点;当然,横波具有主频频率低、激发效率低等不利特征.但综合来看,在土坝体隐患探测中,选择弹性波勘探方法,还是以横波作为波媒具有明显优势.

Design and application of refrigerant recoveryand fillingcontrol system based on MSP430

The control scheme of multifunctional refrigerant recovery and filling control system for air conditioning system is presented in this paper.The scheme of hardware circuit based on micro controller unit （MCU） MSP430 uses high-precision weighing sensor and high performance amplifier.The software program uses median average filtering algorithm.The device can recycle discarded refrigerant after purification and quantitative filling refrigerant.Meanwhile,the apparatus has the functions of recovery,filling,pressing,vaccumizing,refueling,etc.The system is proved to be of low cost,good stability and high practical value.

Enhancement effect of phase-conjugate waves of third order nonlinear medium in the Bragg microcavity

The enhancement effect of the phase-conjugate wave produced by a third order nonlinear optical medium in a （AB）^N （D）^2 （BA）^N Bragg microcavity made of one-dimensional photonic crystals is studied. The gain factor of the phase-conjugate wave is derived when the resonance condition is satisfied by the incident optical wave and the Bragg microcavity mode. Because of stronger resonance enhancement to incident pump beam given by the Bragg microcavity, the enhancement effect of the phase-conjugate wave produced by a third order nonlinear optical medium inside Bragg microcavity is more outstanding than that caused by the naked third order nonlinear optical medium. The theoretical analysis and the numerical calculation show the Bragg microcavity with larger number N of periods is identical with a Fabry-Perot cavity when the resonance condition is satisfied by the incident optical wave and the Bragg microcavity mode.

Traffic Scheduling in WDM Passive Optical Network with Delay Guarantee

WDM passive optical network becomes more favorable as the required bandwidth increases, but currently few media access control algorithms adapted to WDM acc ess network. This paper presented a new scheduling algorithm for bandwidth shari ng in WDM passive optical networks, which provides per-flow delay guarantee and supports variable-length packets scheduling. Through theoretical analysis and simulation, the end-to-end delay bound and throughput fairness of the algori thm was demonstrated.

The Role of Voluntary Youth Work in Media in Professional Development of Young People and Documentation of Urban Space in Wroclaw （Poland）

Wroclaw is mostly known for being a university town. In addition, the city is known in Poland for its sports history--basketball and football-and for many cultural events such as the Review of Stage Songs or African Culture Brave Festival. Because of the fact that Wroclaw is one of the largest and most important cities in Poland, it quickly becomes a subject of interest in new media, including the Internet, which becomes a field for community projects. This gives a tremendous opportunity to Wroclaw＇s youth who can participate in the life of Wroclaw, as well as by volunteering learn the basics of journalism and pursue their passions in an active and creative way. In perspective of those fact, the main aim of the planned paper is to describe evolution process of possibilities which Internet media gives to young people who would like to be a journalist. It is also a trial of analysis on how citizen journalism destroyed media voluntary youth work in Wroclaw, where in fact real citizen journalism was started by young people. What is more, paper＇s goal is to present methods of urban space documentation created by teenage journalists to show multicultural spectrum of Wroclaw.

Verlagsgruppe Passau, Orkla Media, and Mecom Analysis of Different Business Strategies on Polish Press Market

After socio-political breakthrough in 1989 foreign companies entered Polish media market. Firstly, investors appeared in the press sector, later on in the electronic media. One of the first groups presented in Poland was Orkla Media. The Norwegians launched a brand new regional daily. After subsequent failure they changed the pattern of business activity. When in 2006 Mecom bought out Orkla＇s shares, a new era began. The British fund was mainly interested in making their assets more profitable. The biggest shareholder of the regional press sector, however, is still Verlagsgruppe Passau （VGP）. The German group appeared in 1993, in disguise of a Swiss company and next year took over eight regional dailies. In due course, VGP bought out a couple of more regional titles and became the leader of this sector of the market. Although the Germans were competing against the Norwegians and the Brits, they showed a different style of managing their assets. The author attempts to describe different patterns of business strategy in the press sector in Poland, examining each investor＇s behavior and the results of their efforts. This can lead to conclusions about the past activities as well as to predictions about the future of the market.

Media Transition in Eastern Europe after 1989 Albania and Poland in Comparison

In this article the author compares the transformation of media systems of two countries belonging to the former Soviet bloc of Eastern Europe： Albania and Poland. The aim is to highlight differences that occurred in this process, in order to show how, albeit a similar past and the belonging to the same political and economic model until 1989. The diversity of media transition explains the existence of different national ways in which post-communism developed during the last 25 years.

Polish Media 22 Years After Socio-Political Breakthrough The Road to Professionalization and Democratization

Over two decades have passed by since Poland took the course of democratic changes. In the early 1990s the press sector was re-established as a consequence of de-monopolization and has been taken over by foreigners. The electronle media sector has been restricted for 15 years and foreign companies could only have one third of the ownership. The complexity of Polish media system reflects the long way from communism and governmental media towards free democratized market with some remnants of the previous era. It is hard to predict when it will be shaped in a brand new way and if it is generally possible.

Bit Loading Algorithm of VSF-OFCDM wireless communication

In VSF-OFCDM wireless communication, wireless channel is divided into component channels with the same frequency space according to the frequency, and the carriers on component channels are mutually orthogonal. When there are enough subcarriers, the bandwidth efficiency of the system is close to nyquist limit, which can ensure the utilization ratio of system frequency. Therefore, under the premise of ensuring orthogonal division of channels, the channels received a secondary division according to data rate requirements and power limit of business to make the frequency resource fully used and makes the total power minimal, which realizes the optimal distribution of wireless-communication system resources. The secondary division is represented by bit loading algorithm the best bit number of subcarrier allocation in symbol period. For the characteristics of wide-band multi-media services and granular division of VSF-OFCDM wireless communication, the subject proposes the idea of business-oriented subcarrier allocation, which means that the subcarriers are divided in symbol period with the business as the dominant. Based on the idea, the paper designs service-oriented bit loading algorithm of subcarrier, byte and power combined with distribution based on channel detection, and makes verification and performance analysis on the algorithm.

Asymmetry in Negative Refraction of Nonlinear Waves

Recently, inwardly propagating waves （called antiwaves, AWs） in nonlinear oscillatory systems have attracted much attention. An interesting negative refraction phenomenon has been observed in a bidomain system where one medium supports forwardly propagating waves （normal waves, NWs） and the other AWs. In this paper we find that negative refraction （NR） in nonlinear media has an asymmetric property, i.e., NR can be observed only by applying wave source with proper frequency to one medium, but not the other. Moreover, NR appears always when the incident waves are dense and the refractional waves are sparse. This asymmetry is a particular feature for nonlinear NR, which can neither be observed in linear refraction processes （both positive and negative refractions） nor in nonlinear positive refraction. The mechanism underlying the asymmetry of nonlinear NR are fully understood based on the competition of nonlinear waves.

Suppression of seismic surface waves based on adaptive weighted super-virtual interferometry

For land seismic surveys, the surface waves are the dominant noises that mask the effective signals on seismograms.The conventional methods isolate surface waves from the effective signals by the differences in frequencies or apparent velocities,but may not perform well when these differences are not obvious. Since the original seismic interferometry can only predict inter-receiver surface waves, we propose the use of super-virtual interferometry(SVI), which is a totally data-driven method, to predict shot-to-receiver surface waves, since this method relieves the limitation that a real shot should collocate with one of the receivers for adaptive subtraction. We further develop the adaptive weighted SVI(AWSVI) to improve the prediction of dispersive surface waves, which may be generated from heterogeneous media at the near surface. Numerical examples demonstrate the effectiveness of AWSVI to predict dispersive surface waves and its applicability to the complex near surface. The application of AWSVI on the field data from a land survey in the east of China improves the suppression of the residual surface waves compared to the conventional methods.

Terahertz generation based on four-wave mixing difference frequency by resonance-enhanced third-order nonlinear of media

Using nanosecond pulse near-infrared and mid-infrared laser pulses as the pump source, we obtain terahertz wave sources via four-wave difference frequency mixing. From the coupled wave theory, we analyze the four-wave mixing process of GaSe crystal and alkali metal vapor in detail, get the analytical expression of terahertz wave output power, and discuss the conditions for achieving phase matching. By adjusting the pump frequency, the third-order nonlinear polarization of alkali metal vapor is resonance-enhanced. This program offers a new type of high-power terahertz radiation source.

In-home Power Line Communication Media Access Control Protocol Based on Collision Resolution

Most existing media access control(MAC) protocols in power line communication(PLC) networks just discard the colliding data packets when collision occurs.The collision deteriorates throughput and delay performance of system under high traffic conditions.This article presents a novel media access scheme with fast collision resolution for in-home power line networks.It works by first recognizing the colliding stations through detecting the inserted unique ID sequence ahead of data packets,then the source nodes retransmitting their packets immediately after the collision slot.The proposed protocol maintains the benefits of ALOHA systems.It needs no scheduling overhead and is suitable for bursty sources,such as multimedia data packets.Computer simulations have demonstrated that this approach can achieve high throughput due to its ability of resolving collisions.