An ultrasonic obstacle detector based on phase beamforming principles

A prototype of an ultrasonic obstacle detector developed as a part of a navigation system for blind and visually impaired people is presented. The detector, which employs a single ultrasound source and an array of microphones, determines the distance to the obstacle by measuring time between sending the pulse and receiving the reflected signal. Using the phase beamforming technique, borrowed from hydroacoustics, to process the output signals of microphones, it determines also the direction from which the reflected signal is received, thereby locating the obstacle. The obstacle detector was subjected to a series of tests in order to verify its design and to assess its ability to detect a broad range of obstacles. Presented test results show that most obstacles can be detected and recognized, and that the tested obstacle detector provides complete coverage of the safety zone in front of the user.     

An electrocoaters guide to selecting and maintaining rectifiers

Considering the critical contribution of your rectifier to the safe, effective, and reliable operation of your electrocoating process, the selection and maintenance of the optimum unit for your operation is time well spent.     

Cobol: perception and reality

The authors list the perceptions they have uncovered and counter them with the reality of Cobol. Some of the perceptions are: Cobol is a mainframe language-it has been available on PCs since their inception; Cobol stopped evolving in the 1970s, stopped growing in popularity in the 1980s, and stopped being used to develop client-server and Web-based applications in the 1990s; and Cobol is not an object-oriented language, when, in fact, it has objects galore     

Measurement of the double-differential cross section for electronic emission accompanying the interaction of fission fragments with nitrogen and carbon dioxide molecules

Conclusions Experimental data on the double-differential (with respect to angle of emergence and energy of the electrons) cross section for electron emission from nitrogen and carbon dioxide molecules bombarded with fission fragments were obtained under conditions of low data acquisition rate and high background level due to accompanying particles. Russian Science Center of the Russian Federation — A. I. Leipunskii Physics and Power Engineering Institute. Translated from Atomnaya énergiya, Vol. 82, No. 5, pp. 365–369, May, 1997.     

Arsenic deactivation enhanced diffusion and the reverseshort-channel effect

The effect of enhanced diffusion caused by the electrical deactivation of arsenic on the reverse short-channel effect (RSCE) in NMOS devices is investigated. A simple four-mask process was utilized to fabricate deep sub-micron NMOS devices. Source/drain (S/D) implant and anneal conditions were varied in order to determine their implications on the RSCE. Results indicate that when high concentrations of arsenic deactivate, enhanced diffusion occurs, leading to significantly more RSCE. This implies that the dose of the arsenic implant and the subsequent anneals should be carefully considered in source/drain engineering     

Characterization of artificially patinated layers on artistic bronze exposed to laboratory SO2 contamination

Artificially patinated artistic bronze was exposed to the action of 0.10 and 12.68 ppm SO2 contamination in the laboratory at 100% relative humidity. The surface layers were characterized using electrochemical, atomic absorption, X-ray powder diffraction techniques and Fourier transform–infrared spectrometry. Thermal and calorimetric studies were also performed. Some of the compounds identified were cuprite (Cu2O), digenite (Cu1.8S), yarrowite (Cu9S8), chalcocite (Cu2S), brochantite (Cu4(OH)6SO4), bonattite (CuSO4·3H2O) and Sn2S3.     

Ti3+ ion concentration and Ti:sapphire laser performance

The pulsed and CW laser performance of a range of titanium sapphire laser crystals is reported. Titanium ion concentration in the crystals ranged from 0.07 at.% to 0.25 and 0.41 at.% for some recently developed heavily doped crystals. Values of the crystal figure of merit lay between 30 and 220. Threshold, slope efficiency, tunability, and temporal response are assessed. Comparisons are made with the predictions of a simple rate equation model     

Causes of Decay of Fresh-cut Celery

A decay of fresh-cut celery (Apium graveolens) segments stored at < 5°C in sealed film bags began with a water soaking of the cut surfaces. Slimy moisture accumulated inside the bags. The segments water soaked completely, softened, discolored and sometimes disintegrated. Total aerobic bacterial populations isolated from decayed segments ranged from log₁₀ 7.0–7.7 CFU/g tissue weight. The predominant bacteria, identified by fatty acid analysis as Pseudomonas fluorescens and P. marginalis, caused water soaking, soft rot, and discoloration in freshly inoculated celery tissues stored at 5 or 25°C. Leuconostoc mesenteroides was also isolated and may have been responsible for slime production.