Search results for: P.K. Chowdhury

Items from 1 to 13 out of 13 results

article

Enhanced crosstalk tolerance in RSOA based WDM-PONs by using coded RZ modulation

P.K. Chowdhury

Optik - International Journal for Light and Electron Optics > 2014 > 125 > 12 > 2959-2962

A centralized seeding source based loopback WDM-PON is fundamentally limited by Rayleigh backscattering (RB) noise. Here a novel modulation format, called as Coded RZ (CoRZ), is proposed to enhance the system performance in the presence of RB for RSOA based reflective access networks. The result shows that the proposed technique can be effectively improved the tolerance of signal-to-crosstalk ratio...

chapter

Performance Analysis of SINEMO: Seamless IP-Diversity Based Network Mobility

P.K. Chowdhury, A.S. Reaz, M. Atiquzzaman, W. Ivancic

2007 IEEE International Conference on Communications > 6032 - 6037

2007 IEEE International Conference on Communications

IETF has proposed mobile IPv6-based network mobility (NEMO) basic support protocol (BSP) to support network mobility. NEMO BSP inherits all the drawbacks of mobile IPv6, such as inefficient routing path, single point of failure, high handover latency and packet loss, and high packet overhead. To address these drawbacks, we proposed an IP diversity-based network mobility management scheme called seamless...

chapter

SAT04-5: Performance of End-to-End Mobility Management in Satellite IP Networks

P.K. Chowdhury, M. Atiquzzaman, W. Ivancic

IEEE Globecom 2006 > 1 - 5

IEEE Globecom 2006

IETF has developed Mobile IP to support mobility of IP hosts at the network layer. The national aeronautics and space administration has implemented mobile IP to handle handovers in space networks. Due to a number of limitations of Mobile IP, such as high handover latency, packet loss rate, and conflict with existing network security solutions, a new IP- diversity based mobility management scheme,...

chapter

Handover schemes in space networks: classification and performance comparison

P.K. Chowdhury, M. Atiquzzaman, W. Ivancic

2nd IEEE International Conference on Space Mission Challenges for Information Technology (SMC-IT'6) > 8 pp. - 108

2006 2nd IEEE International Conference on Space Mission Challenges for Information Technology

Third generation (3G) communication networks based on low Earth orbit (LEO) satellites provide a new trend in future mobile communications. LEO satellites provide lower end-to-end delays and efficient frequency spectrum utilization, making it suitable for personal communication services (PCS). However, ongoing communications using LEO satellite systems experience frequent handover due to high rotational...

chapter

SINEMO: an IP-diversity based approach for network mobility in space

P.K. Chowdhury, M. Atiquzzaman, W. Ivancic

2nd IEEE International Conference on Space Mission Challenges for Information Technology (SMC-IT'6) > 7 pp. - 115

2006 2nd IEEE International Conference on Space Mission Challenges for Information Technology

IETF proposed network mobility (NEMO) basic support protocol (BSP) to support network mobility. NEMO BSP is an extension of Mobile IP v6 (MIPv6), and inherits all the drawbacks of MIPv6 (like inefficient routing, high handover latency and packet loss rate). Satellites equipped with several IP-enabled devices are an example of network mobility in space networks. In this paper, we propose an IP-diversity...

article

Nuclear hyperfine structure in the X ³ Σ ⁺ state of ⁹ ¹ ZrC

S.J. Rixon, P.K. Chowdhury, A.J. Merer

Journal of Molecular Spectroscopy > 2004 > 228 > 2 > 554-564

Electronic band systems of zirconium monocarbide, ZrC, in the 16000-19000cm ^- ¹ region have been observed following the reaction of laser-ablated Zr atoms with methane under supersonic free-jet conditions. Rotational analyses of high-resolution spectra have shown that the ground state of ZrC is a ³ Σ state, with r ₀ =1.8066A and an unexpectedly small spin-spin parameter,...

article

Infrared multiphoton dissociation of propynal: time resolved observation of CO (ν=<1) IR emission at 4.7 μm

P.K. Chowdhury

Journal of Photochemistry & Photobiology, A: Chemistry > 2003 > 154 > 2-3 > 259-265

In contrast to the electronically excited propynal at 193nm undergoing aldehyde C-H and C-C bond ruptures, on pulsed TEA-CO ₂ laser irradiation, multiphoton vibrationally excited propynal undergoes concerted dissociation generating CO and acetylene. Vibrational excitation in the CO product is detected immediately following the CO ₂ laser pulse by observing infrared (IR) emission at...

article

A comparison of the excited-state processes of nearly symmetrical perylene quinones: hypocrellin A and hypomycin B

P.K. Chowdhury, K. Das, A. Datta, W.-Z. Liu, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2002 > 154 > 1 > 107-116

The excited-state photophysics of two naturally occurring nearly symmetrical perylene quinones are discussed: hypocrellin A and hypomycin B. Hypocrellin A has a hydroxyl group peri to a carbonyl group on either end of its long molecular axis in addition to a hydroxyl group on its seven-membered ring. On the other hand, hypomycin B is unique among this class of known naturally occurring perylene quinones...

article

Impulsive IR-multiphoton dissociation of acrolein: observation of non-statistical product vibrational excitation in CO (v=1-12) by time resolved IR fluorescence spectroscopy

P.K. Chowdhury

Chemical Physics > 2000 > 260 > 1-2 > 151-158

On IR-multiphoton excitation, vibrationally highly excited acrolein molecules undergo concerted dissociation generating CO and ethylene. The vibrationally excited products, CO and ethylene, are detected immediately following the CO ₂ laser pulse by observing IR fluorescence at 4.7 and 3.2 μm, respectively. The nascent CO is formed with significant vibrational excitation, with a Boltzmann population...

article

Infrared depletion spectroscopy suggests fast vibrational relaxation in the hydrogen-bonded aniline-tetrahydrofuran (C ₆ H ₅ -NH ₂ ...OC ₄ H ₈ ) complex

P.K. Chowdhury

Chemical Physics Letters > 2000 > 319 > 5-6 > 501-506

The vibrational spectrum of the 1:1 aniline-tetrahydrofuran complex, formed in a pulsed supersonic jet, has been observed in the NH stretching region using IR depletion spectroscopy cum REMPI time-of-flight MS. Two strong absorption features observed at 3370 and 3479.3 cm ^- ¹ are assigned to the H-bonded and free N-H stretching vibrations of the complex, respectively. The vibrational frequencies...

article

NH stretching bands of the hydrogen-bonded C ₆ H ₅ NH ₂ N(C ₂ H ₅ ) ₃ cluster

P.K. Chowdhury, K. Sugawara, T. Nakanaga, H. Takeo

Journal of Molecular Structure > 1998 > 447 > 1-2 > 7-12

The vibrational spectrum of the 1:1 aniline-triethylamine cluster, formed in a supersonic jet, has been observed in the NH stretching region using infrared depletion spectroscopy combined with REMPI/TOF mass spectrometry. The two absorption bands observed at 3328 and 3466 cm ^- ¹ are assigned to the hydrogen-bonded and free NH stretching vibrations of the cluster, respectively. The former...

article

Infrared spectroscopy of aniline-X (X = N ₂ , CH ₄ , CHF ₃ , CO) clusters and their corresponding cluster cations in the NH ₂ -stretching vibration region

R.P. Schmid, P.K. Chowdhury, J. Miyawaki, F. Ito, more

Chemical Physics > 1997 > 218 > 3 > 291-300

The NH ₂ -stretching vibrational modes of four different aniline-X clusters (X = N ₂ , CH ₄ , CHF ₃ , CO) and their corresponding cluster cations were investigated by ion-depletion spectroscopy. The observed frequency shifts of the neutral clusters have been found to be very small, and to be proportional to the red shift of the origin of the S ₁ ← S ₀ ...

article

IR multiphoton dissociation dynamics of 2,5-dihydrofuran. Time-resolved observation of concerted furan formation

P.K. Chowdhury, J.P. Mittal

Chemical Physics Letters > 1995 > 242 > 4-5 > 421-426

On infrared multiphoton excitation by a pulsed CO ₂ laser, vibrationally excited 2,5-dihydrofuran (DHF) undergoes concerted dissociation generating hydrogen and furan as products. The real time evolution of nascent furan as a photoproduct is monitored. The formation rate of transient vibrationally hot furan, which has an absorption at 245 nm, fits a single exponential with a rate constant...

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