Noise figure measurement concept for acoustic amplifiers

Optimum length buffer crystals are used with an amplification section for measuring the noise figure for acoustic amplifiers. Measuring the time required to saturate with noise a signal, which is reflected back and forth in the circuit, gives a direct measurement of the amplifiers noise figure

The importance of scale economies and geographic diversification in community bank mergers

Mergers of community banks across economic market areas potentially reduce both idiosyncratic and local market risk. A merger may reduce idiosyncratic risk because the larger post-merger bank has a larger customer base. Negative credit and liquidity shocks from individual customers would have smaller effects on the portfolio of the merged entity than on the individual community banks involved in the merger. Geographic dispersion of banking activities across economic market areas may reduce local market risk because an adverse economic development that is unique to one market area will not affect a bank's loans to customers located in another market area. ; This paper simulates the mergers of community banks both within and across economic market areas by combining their call report data. We find that idiosyncratic risk reduction dominates local market risk reduction. In other words, a typical community bank can diversify away its idiosyncratic risk almost as completely by merging with a bank across the street as it can by merging with one located across the country. The bulk of the pure portfolio diversification effects for community banks, therefore, appear to be unrelated to diversification across market areas but, instead, are related to bank size. These findings help explain why many community banks have not pursued geographic diversification more aggressively, but they beg the question as to why more small community banks do not pursue in-market mergers.Bank supervision ; Bank mergers

Scale economies and geographic diversification as forces driving community bank mergers

Mergers of community banks across economic market areas potentially reduce both idiosyncratic and local market risk. Idiosyncratic risk may be reduced because the larger post merger bank has a larger customer base. Negative credit and liquidity shocks from individual customers would have smaller effects on the portfolio of the merged entity than on the individual community banks involved in the merger. Geographic dispersion of banking activities across economic market areas may reduce local market risk because an adverse economic development that is unique to one market area will not affect a bank*s loans to customers in different market areas. This paper simulates the mergers of community banks both within and across economic market areas by combining their call report data. We find that the potential for idiosyncratic risk reduction dominates the marginal contribution to risk reduction by diversifying across local markets. In other words, a typical community bank can reduce its insolvency risk about as much by merging with a bank across the street as it can by merging with one located across the country. The bulk of the pure portfolio diversification effects for community banks, therefore, appears to be unrelated to diversification across market areas and instead is related to bank size. These findings may help explain why many community banks have not pursued geographic diversification more aggressively, but they beg the question as to why more small community banks do not pursue in-market mergers.Community banks ; Bank mergers

The foreclosure crisis in 2008: predatory lending or household overreaching?

At least early in the financial crisis, the high rate of foreclosures seemed to be due more to households' overreaching than to predatory lending. A disproportionate number of those being foreclosed on were well-educated, well-off and relatively young people.Foreclosure ; Mortgage loans ; Housing - Finance

Reduction of blade-vortex interaction noise using higher harmonic pitch control

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels

Wastewater Sample Site Selection to Estimate Geographically Resolved Community Prevalence of COVID-19: A Sampling Protocol Perspective

Wastewater monitoring for virus infections within communities can complement conventional clinical surveillance. Currently, most SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) clinical testing is voluntary and inconsistently available, except for a few occupational and educational settings, and therefore likely underrepresents actual population prevalence. Randomized testing on a regular basis to estimate accurate population-level infection rates is prohibitively costly and is hampered by a range of limitations and barriers associated with participation in clinical research. In comparison, community-level fecal monitoring can be performed through wastewater surveillance to effectively surveil communities. However, epidemiologically defined protocols for wastewater sample site selection are lacking. Herein, we describe methods for developing a geographically resolved population-level wastewater sampling approach in Jefferson County, Kentucky, and present preliminary results. Utilizing this site selection protocol, samples (n = 237) were collected from 17 wastewater catchment areas, September 8 to October 30, 2020 from one to four times per week in each area and compared to concurrent clinical data aggregated to wastewater catchment areas and county level. SARS-CoV-2 RNA was consistently present in wastewater during the studied period, and varied by area. Data obtained using the site selection protocol showed variation in geographically resolved wastewater SARS-CoV-2 RNA concentration compared to clinical rates. These findings highlight the importance of neighborhood-equivalent spatial scales and provide a promising approach for viral epidemic surveillance, thus better guiding spatially targeted public health mitigation strategies