Solving Travelling Salesman Problem in a Simulation of Genetic Algorithms with DNA

In this paper it is explained how to solve a fully connected N-City travelling salesman problem (TSP) using a genetic algorithm. A crossover operator to use in the simulation of a genetic algorithm (GA) with DNA is presented. The aim of the paper is to follow the path of creating a new computational model based on DNA molecules and genetic operations. This paper solves the problem of exponentially size algorithms in DNA computing by using biological methods and techniques. After individual encoding and fitness evaluation, a protocol of the next step in a GA, crossover, is needed. This paper also shows how to make the GA faster via different populations of possible solutions.

Travelling waves in a complex Ginzburg-Landau equation with time-delay feedback

One of the simplest ways to create nonlinear oscillations is the Hopf bifurcation. The spatiotemporal dynamics observed in an extended medium with diffusion (e.g., a chemical reaction) undergoing this bifurcation is governed by the complex Ginzburg-Landau equation, one of the best-studied generic models for pattern formation, where besides uniform oscillations, spiral waves, coherent structures and turbulence are found. The presence of time delay terms in this equation changes the pattern formation scenario, and different kind of travelling waves have been reported. In particular, we study the complex Ginzburg-Landau equation that contains local and global time-delay feedback terms. We focus our attention on plane wave solutions in this model. The first novel result is the derivation of the plane wave solution in the presence of time-delay feedback with global and local contributions. The second and more important result of this study consists of a linear stability analysis of plane waves in that model. Evaluation of the eigenvalue equation does not show stabilisation of plane waves for the parameters studied. We discuss these results and compare to results of other models.

Performance enhancement of asymmetric filtered 40 Gb/s carrier suppressed return to zero-differential phase shift keying receiver in a 50 GHz grid

The authors present the impact of asymmetric filtering of strong (e.g. 35 GHz) optical filters on the performance of 42.7 Gb/s 67% (carrier suppressed return to zero)-differential phase shift keying systems. The performance is examined (in an amplified spontaneous emission (ASE) noise-limited regime and in the presence of chromatic dispersion) when offsetting the filter at the receiver by substantial amounts via balanced, constructive and destructive single-ended detections. It is found that with a slight offset (vestigial side band) or an offset of almost half of the modulation frequency (single-side band), there is a significant improvement in the calculated 'Q'. © The Institution of Engineering and Technology 2013.

An Effective Exact Algorithm for One Particular Case of the Travelling-Salesman Problem

The article presents the exact algorithm for solving one case of the job-scheduling problem for the case when the source matrix is ordered by rows.

Phase noise tolerance study in coherent optical circular QAM transmissions with Viterbi- Viterbi carrier phase estimation

We present a performance evaluation of a non-conventional approach to implement phase noise tolerant optical systems with multilevel modulation formats. The performance of normalized Viterbi-Viterbi carrier phase estimation (V-V CPE) is investigated in detail for circular m-level quadrature amplitude modulation (C-mQAM) signals. The intrinsic property of C-mQAM constellation points with a uniform phase separation allows a straightforward employment of V-V CPE without the need to adapt constellation. Compared with conventional feed-forward CPE for square QAM signals, the simulated results show an enhanced tolerance of linewidth symbol duration product (ΔvTs) at a low sensitivity penalty by using feed-forward CPE structure with C-mQAM. This scheme can be easily upgraded to higher order modulations without inducing considerable complexity.

Multi-band carrier-less amplitude and phase modulation for bandlimited visible light communications systems

Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communications by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370-780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation formats such as orthogonal frequency-division multiplexing. In this article we introduce a new modulation scheme into the VLC domain; multiband carrier-less amplitude and phase modulation (m-CAP) and describe in detail its performance within the context of bandlimited systems.

Simultaneous multichannel carrier-suppressed return-to-zero to non-return-to-zero format conversion using a fiber Bragg grating

A novel multichannel carrier-suppressed return-to-zero (CSRZ) to non-return-to-zero (NRZ) format conversion scheme based on a single custom-designed fiber Bragg grating (FBG) with comb spectra is proposed. The spectral response of each channel is designed according to the algebraic difference between the CSRZ and NRZ spectra outlines. The tailored group delays are introduced to minimize the maximum refractive index modulation. Numerical results show that four-channel 200-GHz-spaced CSRZ signals at 40 Gbits/s can be converted into NRZ signals with high Q-factor and wide-range robustness. It is shown that our proposed FBG is robust to deviations of bandwidth and central wavelength detuning. Another important merit of this scheme is that the pattern effects are efficiently reduced owing to the well-designed spectra response.

Mitigation of EEPN in long-haul n-PSK coherent transmission system using modified optical pilot carrier

We present the compensation of the equalization enhanced phase noise (EEPN) in the long-haul n-level phase shift keying (n-PSK) coherent optical transmission system, by employing a scheme of phase modulated optical pilot carrier. © OSA 2013.

Effect of spatial inhomogeneity of charge carrier mobility on current-voltage characteristics in organic field-effect transistors

A semi-quantitative model is put forward elucidating the role of spatial inhomogeneity of charge carrier mobility in organic field-effect transistors. The model, based on electrostatic arguments, allows estimating the effective thickness of the conducting channel and its changes in function of source-drain and gate voltages. Local mobility gradients in the direction perpendicular to the insulator/semiconductor interface translate into voltage dependences of the average carrier mobility in the channel, resulting in positive or negative deviations of current-voltage characteristics from their expected shapes. The proposed effect supplements those described in the literature, i.e., density-dependent mobility of charge carriers, short-channel effects, and contribution of contact resistance.

Impact of the carrier relaxation paths on two-state operation in quantum dot lasers

We study InGaAs QD laser operating simultaneously at ground (GS) and excited (ES) states under 30ns pulsed-pumping and distinguish three regimes of operation depending on the pump current and the carrier relaxation pathways. An increased current leads to an increase in ES intensity and to a decrease in GS intensity (or saturation) for low pump range, as typical for the cascade-like pathway. Both the GS and ES intensities are steadily increased for high current ranges, which prove the dominance of the direct capture pathway. The relaxation oscillations are not pronounced for these ranges. For the mediate currents, the interplay between the both pathways leads to the damped large amplitude relaxation oscillations with significant deviation of the relaxation oscillation frequency from the initial value during the pulse.

Analysis of carrier phase extraction methods in 112-Gbit/s NRZ-PDM-QPSK coherent transmission system

We present a comparative analysis on three carrier phase extraction approaches, including a one-tap normalized least mean square method, a block-average method, and a Viterbi-Viterbi method, in coherent transmission system considering equalization enhanced phase noise. © OSA 2012.

Practical and cost-effective high-fidelity optical carrier dissemination using coherent communication techniques

We report a unidirectional frequency dissemination scheme for high-fidelity optical carriers deployable over telecommunication networks. For the first time, a 10 Gb/s Binary Phase Shift Keying (BPSK) signal from an ultra-narrow linewidth laser was transmitted through a field-installed optical fibre with round-trip length of 124 km between Cork City and town of Clonakilty, without inline optical amplification. At the receiver, using coherent communication techniques and optical injection-locking the carrier was recovered with noise suppression. The beat signal between the original carrier at the transmitter and recovered carrier at the receiver shows a linewidth of 2.8 kHz. Long term stability measurements revealed fractional instabilities (True Allan deviation) of 3.3 × 10-14 for 1 s averaging time, prior to phase noise cancellation.

Isolator-free switchable uni- and bidirectional hybrid mode-locked erbium-doped fiber laser

An Erbium-doped fibre ring laser hybrid mode-locked with single-wall carbon nanotubes (SWNT) and nonlinear polarisation evolution (NPE) without an optical isolator has been investigated for various cavity conditions. Precise control of the state of polarisation (SOP) in the cavity ensures different losses for counter-propagating optical fields. As the result, the laser operates in quasi-unidirectional regime in both clockwise (CW) and counter-clockwise (CCW) directions with the emission strengths difference of the directions of 22 dB. Furthermore, by adjusting the net birefringence in the cavity, the laser can operate in a bidirectional generation. In this case, a laser pumped with 75 mW power at 980 nm generates almost identical 790 and 570 fs soliton pulses with an average power of 1.17 and 1.11 mW. The operation stability and pulse quality of the soliton pulses in both unidirectional regimes are highly competitive with those generated in conventional ring fibre lasers with isolator in the cavity. Demonstrated bidirectional laser operation can find vital applications in gyroscopes or precision rotation sensing technologies.

Az Európai Unió kibővítésének hatása a lisszaboni stratégia hatékonyságára. Tapasztalatok az Európa 2020 stratégia tervezéséhez (The effects of EU enlargement on the effectiveness of the Lisbon strategy - conclusion for the Europe 2020 strategy)

A tanulmány azt vizsgálja, hogy a lisszaboni stratégia utódja, az Európa 2020 stratégia esetén indokolt lehet-e a régi és az új tagállamok eltérő kezelése. Mindehhez elsősorban a lisszaboni stratégia tapasztalatait, illetve a tagállamok teljesítményét tekinti át. Arra következtetésre jutottunk, hogy a kutatás-fejlesztés valamint a környezeti fenntarthatósági szempontot tükröző energiaintenzitási mutató esetében kiemelten szükséges a stratégia finomhangolása. A K+F célkitűzés csak hosszú távon releváns a felzárkózó országok számára, rövid távon elsősorban a kohéziót hatékonyabban támogató beruházásélénkítésre kell helyezni a hangsúlyt. A differenciált megközelítés a foglalkoztatási területre is igaz. E terület sajátossága azonban, hogy a tagállamok közötti törésvonal itt nem az EU15-ök és az EU12-ek között húzódik, hanem megfigyelhető a jól ismert észak-dél törésvonal is. A foglalkoztatás terén tehát a déli tagállamok differenciált kezelése is indokolt lehet. / === / The paper asks whether the differential treatment of EU member states would be warranted in case the successor of the Lisbon Strategy, the Europe 2020 Strategy. It examines the performance of member states in the past decade, and arrives to the conclusion that some "fine-tuning" would be required in case of the new strategy, especially in the fields of R&D and energy intensity. R&D is only relevant for the new member states in the longer run, in the short run however policies promoting cohesion seem more important. Differential treatment would also be required in issues related to employment, but here the main divide is not between the old and new member states, but rather between the northern and southern ones.

Tanulságok a gazdasági és monetáris unió számára a 2008-as világgazdasági válság kapcsán (Lessons for the Economic and Monetary Union from the 2008 global economic crisis)

Írásunkban a 2008-ban kitört világgazdasági válságnak a Gazdasági és Monetáris Unióra gyakorolt hatásait elemezzük. Tanulmányunkban rávilágítunk a Gazdasági és Monetáris Unió két olyan problémájára, amelyek a válság után váltak igazán nyilvánvalóvá. Egyrészt a görög államcsődveszély, illetve egyes, korábban jól teljesítő országok botladozása jelzi, hogy a Monetáris Unió intézményrendszere legalábbis hiányos. A másik kérdés összefügg az előzővel, és azon országok szemszögéből érdekes, amelyek csatlakozni kívánnak a GMU-hoz: felerősödtek azok a vélemények, amelyek a csatlakozás elhalasztása mellett foglalnak állást. Tanulmányunk második részében ezt a kérdést járjuk körbe. / === / In our paper we are analyze the effects of the economic crisis of 2008 on the Economic and Monetary Union. We are focusing on two core problems of the EMU which came to surface only after the outbreak of the crisis. First, we address the fiscal problems of Greece and other member states which performed well before the crisis. These problems show that there are major institutional shortcomings in the Monetary Union. The second question is connected to the first one and concerns the new member states of the European Union and their strategies to join the Euro zone. After the crisis more and more voices in the new member states suggest postponing EMU membership.