Search results for: Stephan Adams

Items from 1 to 8 out of 8 results

article

Artificial Noise Generation from Cooperative Relays for Everlasting Secrecy in Two-Hop Wireless Networks

Dennis Goeckel, Sudarshan Vasudevan, Don Towsley, Stephan Adams, more

IEEE Journal on Selected Areas in Communications > 2011 > 29 > 10 > 2067 - 2076

The secure transmission of information in wireless networks without knowledge of eavesdropper channels or locations is considered. Two key mechanisms are employed: artificial noise generation from system nodes other than the transmitter and receiver, and a form of multi-user diversity that allows message reception in the presence of the artificial noise. We determine the maximum number of independently-operating...

chapter

Multi-user diversity for secrecy in wireless networks

Sudarshan Vasudevan, Stephan Adams, Dennis Goeckel, Zhiguo Ding, more

2010 Information Theory and Applications Workshop (ITA) > 1 - 9

2010 Information Theory and Applications Workshop (ITA 2010)

The ability to transmit a message securely in the presence of eavesdroppers in a dense wireless network is considered. As with a number of recent schemes, system nodes other than the transmitter and receiver are chosen to generate noise that confuses the eavesdropper. By exploiting the dynamics of the fading, significantly improved performance is achieved beyond that generated from the standard multi-user...

article

Exact Solution of the AVZ-Hamiltonian in the Grand-Canonical Ensemble

Stephan Adams, Jean-Bernard Bru

Annales Henri Poincaré > 2004 > 5 > 3 > 405-434

The thermodynamic behavior of the Angelescu-Verbeure-Zagrebnov (AVZ) Hamiltonian [1], also called the superstable Bogoliubov model, is solved for any temperature and any chemical potential. It is found that its thermodynamics coincides with one for the Mean-Field Gas for small chemical potential or high temperature. However, for large chemical potential or low temperature, a non-conventional Bose...

article

A New Microscopic Theory of Superfluidity at All Temperatures

Stephan Adams, Jean-Bernard Bru

Annales Henri Poincaré > 2004 > 5 > 3 > 435-476

Following the program suggested in [1], we propose a new microscopic theory of superfluidity for all temperatures and densities. In particular, the corresponding phase diagram of this theory exhibits: (i) a thermodynamic behavior corresponding to the Perfect Bose Gas for small densities or high temperatures, (ii) the Landau-type excitation spectrum in the presence of non-conventional Bose condensation...

article

CT Fluoroscopy-assisted Puncture of Thoracic and Abdominal Masses: A Randomized Trial

Johannes Kirchner, Ralph Kickuth, Ulf Laufer, Esther Maria Schilling, more

Clinical Radiology > 2002 > 57 > 3 > 188-192

PURPOSE: We investigated the benefit of real-time guidance of interventional punctures by means of computed tomography fluoroscopy (CTF) compared with the conventional sequential acquisition guidance. MATERIAL AND METHODS: In a prospective randomized trial, 75 patients underwent either CTF-guided (group A,n=50) or sequential CT-guided (group B,n=25) punctures of thoracic (n=29) or abdominal (n=46)...

article

A Comparative Study of CT Fluoroscopy Combined with Fluoroscopy Versus Fluoroscopy Alone for Percutaneous Transhepatic Biliary Drainage

Ulf Laufer, Johannes Kirchner, Ralph Kickuth, Stephan Adams, more

CardioVascular and Interventional Radiology > 2001 > 24 > 4 > 240-244

Purpose: We compared CT fluoroscopy (CTF) for the initial puncture of bile ducts with conventional fluoroscopic guidance in patients with malignant jaundice in whom percutaneous transhepatic biliary drainage (PTBD) was planned. Methods: Forty consecutive patients were randomized to two study groups: group A underwent PTBD under CTF and fluoroscopic guidance, group B underwent PTBD under fluoroscopic...

article

A Comparative Study of CT Fluoroscopy Combined with Fluoroscopy Versus Fluoroscopy Alone for Percutaneous Transhepatic Biliary Drainage

Ulf Laufer, Johannes Kirchner, Ralph Kickuth, Stephan Adams, more

CardioVascular and Interventional Radiology > 2001 > 24 > 4

Purpose: We compared CT fluoroscopy (CTF) for the initial puncture of bile ducts with conventional fluoroscopic guidance in patients with malignant jaundice in whom percutaneous transhepatic biliary drainage (PTBD) was planned. Methods: Forty consecutive patients were randomized to two study groups: group A underwent PTBD under CTF and fluoroscopic guidance, group B underwent PTBD under fluoroscopic...

article

Staging of the neck in patients with oral cavity squamous cell carcinomas: a prospective comparison of PET, ultrasound, CT and MRI

Tankred Stuckensen, Adorján F. Kovács, Stephan Adams, Richard P. Baum

Journal of Cranio-Maxillo-Facial Surgery > 2000 > 28 > 6 > 319-324

Background: The choice of treatment in patients with oral malignancies depends on accurate pretreatment staging and particularly the detection of lymph node involvement. Therefore staging of the neck should be as accurate as possible. Patients: One hundred and six patients with histologically proven squamous cell carcinoma of the oral cavity. Study design: In a prospective study, PET using fluoro-desoxy-glucose...

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