We examine the problem of source localization and spatial spectrum estimation using sensor arrays that are noncoherent collections of small, coherent subarrays. The covariance of the signal snapshots ...at each of the coherent subarrays are functions of, among other things, the signal source locations (or the spatial spectrum). Our approach is to derive functions of the subarray covariance matrices that are close approximations of the signal source locations (or the spatial spectrum). We also show how these functions may be considered generalizations of the multiple signal classification (MUSIC) algorithm and the minimum variance distortionless response (MVDR) criterion, respectively. We demonstrate via simulation that, using this approach and array architecture, it is possible to resolve directional ambiguities.
Oxide dispersion strengthened (ODS) steels are promising structural materials for future fusion reactors. The high-density (∼1023/m3) of highly stable Y-(Ti)-O nano-oxides provide high sink strength ...for radiation resistance and high-temperature (> 650 °C) creep strength. Concomitantly, helium management is enabled by trapping high density (∼1023/m3) of small (< 3 nm) helium bubbles in the vicinity of nano-oxides. However, conventional route of making ODS steels involves prolonged ball milling, canning, degassing, and laborious thermo-mechanical processing (TMP). Such route, especially the batch-by-batch ball milling step, faces persistent challenge with scalability and high costs. Gas atomization reaction synthesis (GARS) method has demonstrated the potential of making precursor ODS steel powders without ball milling, but the nano-oxide density was around 1021/m3 in the final consolidated form by conventional TMP. Taking advantage of GARS precursor powder, we use friction-based processing, including friction consolidation and extrusion, to manufacture ODS steel with further improved nano-oxide characteristics. Preliminary results showed that Y/Ti/O species were intimately mixed and rapidly reacted to form nano-oxides with a number density of ∼1022/m3.
Pelvic lymph node dissection in patients undergoing radical prostatectomy for clinically localised prostate cancer is not without morbidity and its therapeutical benefit is still a matter of debate. ...The objective of this study was to develop a model that allows preoperative determination of the minimum number of lymph nodes needed to be removed at radical prostatectomy to ensure true nodal status.
We analysed data from 4770 patients treated with radical prostatectomy and pelvic lymph node dissection between 2000 and 2011 from eight academic centres. For external validation of our model, we used data from a cohort of 3595 patients who underwent an anatomically defined extended pelvic lymph node dissection. We estimated the sensitivity of pathological nodal staging using a beta-binomial model and developed a novel clinical (preoperative) nodal staging score (cNSS), which represents the probability that a patient has lymph node metastasis as a function of the number of examined nodes.
In the development and validation cohorts, the probability of missing a positive lymph node decreases with increase in the number of nodes examined. A 90% cNSS can be achieved in the development and validation cohorts by examining 1-6 nodes in cT1 and 6-8 nodes in cT2 tumours. With 11 nodes examined, patients in the development and validation cohorts achieved a cNSS of 90% and 80% with cT3 tumours, respectively.
Pelvic lymph node dissection is the only reliable technique to ensure accurate nodal staging in patients treated with radical prostatectomy for clinically localised prostate cancer. The minimum number of examined lymph nodes needed for accurate nodal staging may be predictable, being strongly dependent on prostate cancer characteristics at diagnosis.
Background
The purpose of this work was to determine efficacy, toxicity, and patterns of recurrence after concurrent chemoradiation (CRT) in patients with extrahepatic bile duct cancer (EHBDC) and ...hilar cholangiocarcinoma (Klatskin tumours) in case of incomplete resection or unresectable disease.
Patients and methods
From 2003–2010, 25 patients with nonmetastasized EHBDC and hilar cholangiocarcinoma were treated with radiotherapy and CRT at our institution in an postoperative setting (10 patients, 9 patients with R1 resections) or in case of unresectable disease (15 patients). Median age was 63 years (range 38–80 years) and there were 20 men and 5 women. Median applied dose was 45 Gy in both patient groups.
Results
Patients at high risk (9 times R1 resection, 1 pathologically confirmed lymphangiosis) for tumour recurrence after curative surgery had a median time to disease progression of 8.7 months and an estimated mean overall survival of 23.2 months (6 of 10 patients are still under observation). Patients undergoing combined chemoradiation in case of unresectable primary tumours are still having a poor prognosis with a progression-free survival of 7.1 months and a median overall survival of 12.0 months. The main site of progression was systemic (liver, peritoneum) in both patient groups.
Conclusion
Chemoradiation with gemcitabine is safe and can be applied safely in either patients with EHBDC or Klatskin tumours at high risk for tumour recurrence after resection and patients with unresectable tumours. Escalation of systemic and local treatment should be investigated in future clinical trials.
Very low frequency (VLF) power line communications (PLC) presently has widespread use in AMR/AMI deployments and may also be useful for smart grid applications, largely due to its excellent ...propagative properties. However, noise within the VLF band is more energetic than at higher frequencies and without effective mitigation algorithms degrades channel capacity, possibly to the point of making the band impractical. Recent work has demonstrated that PLC noise in the low frequency band (LF) and above is effectively modeled as a cyclostationary random process. We present measurements of actual power line noise and argue that the cyclostationary model is unnecessarily restrictive and that VLF PLC channel may be modeled as having a non-trivial wide-sense periodic component. We demonstrate the preponderance of periodic noise in this band by means of constrained covariance estimation from power line noise measurements. This has important ramifications for receiver design and when employed appropriately will increase the post-processed SNR, making VLF PLC a more attractive prospect for smart grid communications.
Generalizing MUSIC and MVDR for distributed arrays Rieken, D.W.; Fuhrmann, D.R.
Conference Record of the Thirty-Sixth Asilomar Conference on Signals, Systems and Computers, 2002,
2002, Letnik:
1
Conference Proceeding
We examine the problem of combining data obtained from many subarrays of a distributed array to obtain an estimate of the spatial power spectrum and the location of the sources of any incident ...wavefields. Since the arrays are not coherent with respect to each other, the correlation between data vectors obtained from different arrays is unknown. Thus, well-known array processing algorithms are not applicable. However, it is possible to combine estimates obtained from each sub-array into one estimate. To this end, we introduce generalizations of MUSIC and MVDR. We demonstrate via simulation that the combined spatial spectrum estimates of source location estimates may provide for resolution of directional ambiguities, estimate of range as well as direction, and higher spatial resolution.
Interferometry has been used for decades to image distant electromagnetic sources at long wavelengths. However, the long data collection intervals have prevented imaging rotating objects such as ...planets. We show that one can craft an interferometric imaging algorithm using synthetic aperture beamforming techniques by linear beamforming in the correlation domain data rather than the signal-domain data. We then use this analogy to show how it is possible to create previously unrealized interferometric images of a rotating spherical blackbody.
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