Wideband printed bowtie antenna element development for post reception synthetic focusing surface penetrating radar

A printed bowtie antenna for a Post Reception Synthetic Focussing Surface Penetrating Radar (PRSF-SPR) has been developed with the aid of FDTD analysis. Antenna free space characteristics were compared against practical measurements and its performance was analysed when soil is present

A FDTD model for the post-reception synthetic focusing surface penetrating radar with mine detecting applications

Surface penetrating radar (SPR) is extensively used in military, civil, geophysical and archaeological applications. There has been an increasing emphasis on the use of SPR in the identification of buried unexploded ordnance, such as anti-tank mines, antipersonnel mines etc., which can be metallic or plastic in nature. Mine detection methods can be classified as destructive or non-destructive. Non-destructive mine detection methods employ metal detectors, magnetometers, infrared sensors and SPR. However, neither the metal detector nor the magnetometer can differentiate a mine from metallic debris and the infrared sensor merely notes a difference in thermal conductivity. In most battle fields the soil is contaminated by large quantity of shrapnel, metal scraps and cartridge cases which will give a high false alarm rate in the identification process. In this scenario the SPR is a promising technique for identification of both metallic and plastic mines. The use of finite difference time domain (FDTD) model to analyse the SPR, which makes use of post-reception synthetic focusing (PRSF) techniques, is presented

Capacity constraints and the prospects for external adjustment and economic growth: 1989-90

Manufactures ; Exports ; Balance of trade

Domestic open market operations during 2000

Open market operations ; Monetary policy ; Federal Open Market Committee

Highlights of domestic open market operations during 1998

The Trading Desk at the Federal Reserve Bank of New York uses open market operations to implement the policy directives of the Federal Open Market Committee (FOMC). The FOMC expresses its short-term objective for open market operations as a target level for the federal funds rate--the interest rate at which depository institutions lend balances at the Federal Reserve to other depository institutions. To keep the federal funds rate near the level specified by the FOMC, the Desk uses open market operations to bring the supply of balances at the Federal Reserve into line with the demand for them. In 1998, the level of balances that depository institutions were required to hold at the Federal Reserve continued to decline, to historic lows. The primary reason for this was the ongoing proliferation of retail "sweep" programs, which transfer depositors' funds from transaction accounts that are subject to reserve requirements into other deposit accounts that are not. In past years, declines in required balances had been associated with greater volatility in the federal funds rate because depository institutions have less flexibility in managing their daily balance positions. However, through the first three quarters of 1998, the funds rate behaved much as it had in 1997, even though required balances were lower. In the final quarter of 1998, funds rate volatility rose when market participants evinced greater concerns about the credit quality of their counterparties at a time of increased uncertainty in financial markets.Open market operations ; Monetary policy ; Federal funds market (United States)

Synthetically-focused surface-penetrating radar for operation from a moving vehicle

This paper reports on a research programme, started recently under DERA sponsorship, on applying synthetic focusing to an oblong horizontal stand-off array, where all the voxels in a vertical slice underneath the centre-line of the array are synthesised electronically, with the third dimension provided by the search vehicle's forward movement. This should permit a very high search rate for buried mines, in a wide range of ground conditions

The noise environment of a school classroom due to the operation of utility helicopters

Noise measurements under controlled conditions have been made inside and outside of a school building during flyover operations of four different helicopters. The helicopters were operated at a condition considered typical for a police patrol mission. Flyovers were made at an altitude of 500 ft and an airspeed of 45 miles per hour. During these operations acoustic measurements were made inside and outside of the school building with the windows closed and then open. The outside noise measurements during helicopter flyovers indicate that the outside db(A) levels were approximately the same for all test helicopters. For the windows closed case, significant reductions for the inside measured db(A) values were noted for all overflights. These reductions were approximately 20 db(A); similar reductions were noted in other subjective measuring units. The measured internal db(A) levels with the windows open exceeded published classroom noise criteria values; however, for the windows-closed case they are in general agreement with the criteria values

Some effects of the atmosphere and microphone placement on aircraft flyover noise measurements

The effects of varying atmospheric conditions on certification-type noise measurements were studied. Tests were made under various atmospheric conditions at two test sites, Fresno, California, and Yuma, Arizona, using the same test aircraft, noise, and weather measuring equipment, and operating personnel. Measurements were made to determine the effects of the atmosphere and of microphone placement on aircraft flyover noise. The measurements were obtained for characterization of not only the acoustic signature of the test aircraft, but also specific atmospheric characteristics. Data are presented in the form of charts and tables which indicate that for a wide range of weather conditions, at both site locations, noise data were repeatable for similar aircraft operating conditions. The placement of microphones at ground level and at 1.2 m over both spaded sand and concrete illustrate the effects of ground reflections and surface impedance on the noise measurements