Spectrum sensing by cognitive radios at very low SNR

Spectrum sensing is one of the enabling functionalities for cognitive radio (CR) systems to operate in the spectrum white space. To protect the primary incumbent users from interference, the CR is required to detect incumbent signals at very low signal-to-noise ratio (SNR). In this paper, we present a spectrum sensing technique based on correlating spectra for detection of television (TV) broadcasting signals. The basic strategy is to correlate the periodogram of the received signal with the a priori known spectral features of the primary signal. We show that according to the Neyman-Pearson criterion, this spectral correlation-based sensing technique is asymptotically optimal at very low SNR and with a large sensing time. From the system design perspective, we analyze the effect of the spectral features on the spectrum sensing performance. Through the optimization analysis, we obtain useful insights on how to choose effective spectral features to achieve reliable sensing. Simulation results show that the proposed sensing technique can reliably detect analog and digital TV signals at SNR as low as -20 dB.Comment: IEEE Global Communications Conference 200

The impact of space and space-related activities on a local economy. a case study of boulder, colorado. part i- the input-output analysis

Impact of space and space-related activities on industry and general economy of Boulder, Colorad

Impact of static dry-hopping rate on the sensory and analytical profiles of beer

Dry-hopping is a technique that has been used by brewers to increase the hop aroma and flavour of beer for centuries. Throughout the twenty first century, dry-hopping has become an increasingly popular method among craft brewers to impart intense hoppy aroma and flavour to beer. Many US craft brewers use extremely high dry-hop dosing rates of up to 2200 g/hL and this is both unsustainable and potentially wasteful. This study examines the impact of dry-hopping rate on the sensorial and analytical characteristics of dry-hopped beers. An unhopped pale beer was statically dry-hopped with whole cone Cascade from the 2015 harvest over a broad range of dry-hopping rates (200-1600 g/hL) in replicated, pilot scale (80 L) aliquots. Trained panellists using descriptive analysis scaled the overall and qualitative hop aroma intensity of these beers, as well as the unhopped base beer. Instrumental analysis was used to measure the levels of hop volatile and non-volatile extraction between the treatments. The relationship between dry-hopping rate and the sensorial and analytical characteristics of the finished beer was not linear and, based on the extraction efficiencies of select hop volatiles, had an ideal range between 400 and 800 g/hL. (C) 2018 The Institute of Brewing & Distillin

Sensory Directed Mixture Study of Beers Dry-Hopped with Cascade, Centennial, and Chinook

American craft beer style and flavor is often driven by the unique qualities of American hops. Cascade, Chinook, and Centennial hops are used prominently for dry-hopping singly and/or in blends to impart an intense hoppy aroma to beer. A sensory directed dry-hopping mixture study was performed to understand the contribution that each of these hops make to beer aroma. Utilizing a 4th degree simplex-lattice mixture-design, sixteen beers were prepared (including an "unhopped" control) by dry-hopping a common "unhopped" base beer with different blends of ground whole cone hops made from the three hop cultivars. The treatments were evaluated by trained panelists using descriptive analysis, where the response variables used by the panel encompassed the sensory attributes that described the unique aromatic features of these three hops, (i.e., citrus, tropical/fruity, tropical/catty, and herbal). Using these outputs, the sensory contributions of each individual cultivar, as well as mixtures of the cultivars, were examined on a per attribute basis. These results can be used to select combinations or blends of the three hops for use during dry-hopping that provide similar or dissimilar overall aroma intensity and quality in dry-hopped beer

Aroma Extract Dilution Analysis of Beers Dry-Hopped with Cascade, Chinook, and Centennial

Cascade, Chinook, and Centennial hops are used extensively throughout the brewing industry either individually or in various combinations to add hoppy aroma to beer. This high use of hops, particularly via late- or dry-hopping, creates a need to better understand the chemical contribution of these hop varieties during dry-hopping beer in order to predict brewing performance. Solvent-Assisted Flavor Evaporation (SAFE) and Aroma Extract Dilution Analysis (AEDA) was performed on unhopped beer that was dry-hopped individually with each of these varieties as well as the unhopped base. This technique was used to determine the aroma compounds that were the greatest contributors to the dry-hop character of these hops. The analysis of beer prepared with Cascade, Chinook, and Centennial identified 9, 10, and 11 character impact compounds, respectively. Commonalities were observed among the three varieties regarding 2-furanmethanol, linalool, geraniol, cis-geranic acid methyl ester, and n-decanoic acid in dry-hopped beer. Variation between the hop volatiles found to be important for Centennial and Chinook dry-hop aroma was a function of only a few character impact compounds, whereas Cascade was slightly different, anchored heavily by benzenacetaldeyde. The relative similarities and differences that these three hop cultivars attribute to beer during dry-hopping were revealed by comparing which compounds were important for the characteristic aroma profiles of these cultivars in single dry-hop beers.. This knowledge is important for brewers wishing to introduce potential replacement hops and/or reductions for these hop cultivars in the future and guide the direction of future blending studies

An Investigation of Methylsulfonylmethane as a Fermentation Aid

Fermentation time in the cellar directly affects potential brewery production as a whole. It is of practical interest to decrease time needed where possible and increase efficiency. Decreased lag time in beer fermentations allow for higher production and efficiency in the brewery as well as decreased risk of contamination. This study examined the use of methylsulfonylmethane (MSM) as a nutrient supplement to stimulate yeast growth during fermentation. Small-scale (1L), stirred fermentations were carried out at 15°C using a German lager yeast in a lightly hopped 11°P wort made from 70% pale 2-row malt and 30% high glucose liquid adjunct. Two pitching rates were examined, 1x106 and 1x105 cell/ml⋅°P, and four levels of MSM (0, 0.25, 0.5, and 075% w/w). Fermentation gravity and viable cell counts were monitored throughout fermentation until the final attenuation was achieved (approximately 5 days). The application of 0.25% w/w MSM resulted in the shortest lag time in both adequately (1x106 cell/ml⋅°P) and under-pitched (1x105 cell/ml⋅°P) ferments. Additionally, this treatment reached stable, maximum cell counts and final gravity the quickest. Increased concentrations of MSM trended with higher terminal gravities and lower fermentability irrespective of pitching rate. Application of MSM to beer fermentations has the potential to decreased lag time and increase peak rate in beer fermentations.Keywords: Fermentation aid, Methylsulfonylmethan

High Pressure Effects on Proteolytic and Glycolytic Enzymes Involved in Cheese Manufacturing

The activity of chymosin, plasmin, and Lactococcus lactis enzymes (cell envelope proteinase, intracellular peptidases, and glycolytic enzymes) were determined after 5-min exposures to pressures up to 800 MPa. Plasmin was unaffected by any pressure treatment. Chymosin activity was unaffected up to 400 MPa and decreased at 500 to 800 MPa. Fifty percent of control chymosin activity remained after the 800 MPa treatment. The lactococcal cell envelope proteinase (CEP) and intracellular peptidase activities were monitored in cell extracts of pressure-treated cells. A pressure of 100 MPa increased the CEP activity, whereas 200 MPa had no effect. At 300 MPa, CEP activity was reduced, and 400 to 800 MPa inactivated the enzyme. X-Prolyl-dipeptidyl aminopeptidase was insensitive to 5-min pressure treatments of 100 to 300 MPa, but was inactivated at 400 to 800 MPa. Aminopeptidase N was unaffected by 100 and 200 MPa. However, 300 MPa significantly reduced its activity, and 400 to 800 MPa inactivated it. Aminopeptidase C activity increased with increasing pressures up to 700 MPa. High pressure did not affect aminopeptidase A activity at any level. Hydrolysis of Lys-Ala-ρ-NA doubled after 300-MPa exposure, and was eliminated at 400 to 800 MPa. Glycolytic enzyme activities of pressure-treated cells were evaluated collectively by determining the titratable acidity as lactic acid produced by cell extracts in the presence of glucose. The titratable acidities produced by the 100 and 200 MPa samples were slightly increased compared to the control. At 300 to 800 MPa, no significant acid production was observed. These data demonstrate that high pressure causes no effect, activation, or inactivation of proteolytic and glycolytic enzymes depending on the pressure level and enzyme. Pressure treatment of cheese may alter enzymes involved in ripening, and pressure-treating L. lactis may provide a means to generate attenuated starters with altered enzyme profiles.Keywords: protease, cheese ripening, Lactococcus, peptidaseKeywords: protease, cheese ripening, Lactococcus, peptidas

Effect of Harvest Maturity on the Chemical Composition of Cascade and Willamette Hops

Considerable expertise is required to grow high-quality hops, and brewers and hop growers alike have a common goal of obtaining the highest quality hops possible. Change in the chemical composition of hops during plant maturation is a dynamic process requiring a comprehensive chemical and sensory analysis in order to maximize the characteristics of interest to brewers. The effect of harvest date, location, and cultivar on key chemical components of Willamette and Cascade hops was investigated for the 2010 and 2011 growing seasons. Hops were harvested at 3 time points (Early, Typical, and Late), within a 3-week interval from 2 different farms in the Willamette Valley, Oregon. A split-plot experimental design for each cultivar was used; each farm represented a main plot and harvest years were designated as subplots. American Society of Brewing Chemist standard methods of analysis were used to measure moisture content, hop acids and their homologs, hop storage index, total essential oil content and volatile profile by GC-FID. Additionally, difference testing, descriptive analysis, and consumer acceptance testing was conducted using beers brewed with either Typical or Late harvested Cascade hops from the 2010 harvest year. The response of analytes was dependent on the cultivar being examined, its location within the Willamette Valley, as well as timing of harvest. Hop acids did not change appreciably during plant maturation for the period examined, while hop oil content increased. Increases in oil quantity were strongly correlated (r > 0.90) with increases in α-pinene, β-pinene, myrcene, limonene, methyl heptanoate, and linalool concentrations. Clear sensory differences were found between beers brewed with Typical and Late harvested Cascade hops using triangle testing, consumer preference testing, and descriptive analysis.KEYWORDS: Essential Oil, Aroma, Terpenes, GC-FID, Hop Acid

Texture, proteolysis and viable lactic acid bacteria in commercial Cheddar cheeses treated with high pressure

High pressure processing was investigated for controlling Cheddar cheese ripening. One-month- or 4-month-old Cheddar cheeses were subjected to pressures ranging from 200 to 800 MPa for 5 min at 25 °C. The number of viable Lactococcus lactis (starter) and Lactobacillus (nonstarter) cells decreased as pressure increased. Subsequent storage of the control and pressure-treated cheeses at 10 °C caused viable cell counts to change in some cases. Free amino acid content was monitored as an indicator of proteolysis. Cheeses treated with pressures ≥400 MPa evolved free amino acids at significantly lower rates than the control. No acceleration in free amino acid development was observed at lower pressures. Pressure treatment did not accelerate the rate of textural breakdown compared with the non-pressure treated control. On the contrary, pressure treatment at 800 MPa reduced the time-dependent texture changes. Results indicate that high pressure may be useful in arresting Cheddar cheese ripening.KEYWORDS: Lactobacillus, high pressure processing, Lactococcus, cheese ripening, Cheddar cheeseThis is the publisher’s final pdf. The published article is copyrighted by Cambridge University Press and can be found at: http://journals.cambridge.org/action/displayJournal?jid=DA