Area Coverage Rate Research Articles

Surface hardening of steel using a high power diode laser

Heat treating the surface of medium carbon steels to produce a hardened layer whilst retaining a tough core is widespread throughout general engineering and may be accomplished by using a number of different sources of energy; flame and induction heating being common. In addition, the use of high power lasers is also a well-established process. The benefits attributed to the use of lasers are that they provide localised heat input, negligible distortion, the ability to treat specific areas, access to confined areas and short cycle times. Nd:YAG and CO 2 systems have both been used in this application for a number of years but restrictions to the wide spread use of lasers can be related to factors such as capital cost, perceived reliability of equipment, low area coverage rates and complexity of operation. Recently, a new category of high power industrial lasers has become commercially available which have the potential to overcome some of these barriers. Based on semi-conductor technology, high power diode lasers are reliable, easy to use, compact systems capable of producing a relatively large output spot. The current work has investigated the relationships between laser power and processing speed when using a 1.2 kW diode laser to harden a plain carbon and an alloy steel. The steels, British Standard 080M40 and 817M40, have similar carbon contents (0.4%), similar Mn contents (0.8%), but in addition 817M40 contains 1.75% Ni, 0.8% Cr and 0.25% Mo. Laser powers in the range 400–1000 W were used in conjunction with surface speeds of 50–1700 mm/min. Microstructural examination of the treated surfaces revealed that conditions within the range examined were capable of producing structural changes and associated increases in hardness. Affected depths and maximum hardness achieved varied with power and speed, as well as with steel type. Hardened depths of greater than 0.5 mm were observed in both the plain carbon and the alloy steels. As would be expected, the maximum hardening effect was observed in the alloy steel, as was the maximum hardness. The work has demonstrated the technical capability of diode lasers in surface hardening both plain carbon and alloy steel with practical case depths being achieved.

Broadband transducer requirements and development for a synthetic aperture sonar

Broadband acoustic signal transmission and reception are key to enhancing the performance of underwater acoustical sensor systems to support functions like underwater acoustic communications and high resolution underwater imaging. In particular, synthetic aperture sonar (SAS) is an attractive technology for high-resolution imaging because of its ability to produce better cross range resolution than that of a real aperture array sonar of the same length. In addition, SAS systems can produce a cross range resolution that is independent of frequency and range. When the advantages of a SAS system are coupled with those gained from going to a broadband signal space, the performance enhancements can be significant. Specifically improvements in clutter rejection, object classification, and area coverage rate will be achieved. A description of the transducer requirements and expected payoffs for a SAS system designed to operate and image proud and buried objects in shallow waters will be presented. [Work supported by ONR.]

Matrigel increases the rate of split wound healing and promotes keratinocyte ;take' in deep wounds in rats.

The influence of matrigel, a mixture of the components of thebasement membrane, on the wound healing was studied in a modelof experimental wounds in rats. Matrigel was found to increasethe rate of epithelization of split-thickness wounds. The modelof deep wound was developed in which the host animal could notprovide enough migrating and proliferating keratinocytes tocover the wound area. The model is relevant to severe burns andinjuries in humans. When rat keratinocyte suspension wastransplanted into deep wounds, cell retention in the wound bedwas only observed if matrigel was added together with the cells.Increasing matrigel concentration in the wound was seen toenhance the rate of wound area coverage by the cells. Althoughthe process of healing seemed macroscopically normal, afterhistological screening of the biopsies cell in the wouldappeared as amorphous aggregates and tubules rather thenstratified epidermis.

Automatic mine detection by textural analysis of COTS sidescan sonar imagery

Sidescan sonar imagery of the sea floor is difficult to interpret visually, and classification techniques are now increasingly used to supplement the interpreter with reliable, quantitative results. Active high-resolution sonar has been shown to be the only sensor able to detect man-made objects and, in particular, mine-like objects on the sea bottom with a high probability of detection and an acceptably low false-alarm rate and a high area coverage rate. The actual distinction between the image of a mine and an object that physically resembles a mine is very complex, however, and relies on the recognition of subtle differences in shapes and textures. This study aimed to combine two different advances in sidescan sonar applications. Recent trials at sea have demonstrated that the latest generation of commercial off-the-shelf sidescan sonars was able to image mine types, even stealthy mines with low acoustic signatures. Concurrently, a method of advanced image analysis has been developed, based on the quantification and recognition of acoustic textures. This method has been extensively calibrated and ground-truthed in complex terrains, and the results presented here show that it can be applied successfully to the detection of mines.

A processing requirement and resolution capability comparison of side-scan and synthetic-aperture sonars

The processing requirements and resolution capabilities of both side-look sonar (SLS) and synthetic-aperture sonar (SAS) systems are outlined. Side-look sonar is presented as a real-beam imaging technique along with expressions for relevant system- and image-related parameters. Synthetic-aperture sonar is discussed, and the limitations imposed by the speed of sound in the ocean environment are identified. A specific side-look system (SeaMARC I) is presented under two configurations and comparable SAS designs are proposed. Based on the examples provided by the SeaMARC I system and the hypothetical SAS designs, it is shown that single-beam SAS systems can be designed to achieve area coverage rates comparable to single-beam side-scan systems, yet with improved azimuth resolution. >

Aerial Application of Insect Egg Parasites

ABSTRACT A delivery system was developed for releasing Sitotroga cerealella (Olivier) eggs containing the pupae of Qgg parasite wasps, Trichogramma spp., from aircraft for control of tobacco budworm and bollworm, Heliothis spp., in field crops. Two small release units, each con-taining 175-mL egg hoppers, were constructed and posi-tioned at the trailing edge of each wing of a Piper PA-25 aircraft. Application rates of up to 125 X 103 adult parasites/ha are possible when the area coverage rate does not exceed 2.4 ha/min. The delivery system was us-ed to successfully apply parasites to cotton test plots dur-ing two successive growing seasons (1978 and 1979).

Comparison of sonar system performance achievable using synthetic-aperture techniques with the performance achievable by more conventional means

A comparison is made of the signal-to-noise characteristics of synthetic-aperture sonar and conventional sonar. For the synthetic-aperture sonar case a design procedure is described which makes possible the choice of essentially any unambiguous range and any resolution. Often multiple beam receivers are required. It is shown for the synthetic-aperture sonar case that the horizontal aperture is the major factor affecting area coverage rate. The comparisons are made with as many parameter values as spossible identical for both the synthetic-aperture cases and the nonsynthetic-aperture cases. If identical physical aperture dimensions are used and other parameters held to identical values, the synthetic-aperture sonar gives higher signal-to-ratio than does the nonsynthetic-aperture sonar primarily because the latter must operate at higher acoustic frequencies for which signal attenuation becomes extremely large. If the sonar systems are operated at the same frequency, then the nonsynthetic aperture sonar can give a higher signal-to-noise ratio only when its physical aperture is larger than that used in the synthetic-aperture case. Subject Classification: 30.82; 60.20.

ARC Ignition Phenomena with a Transpiration Cooled Anode

This paper deals with the problem of ignition to the porous transpiration cooled anode of an arc in 1 atm. argon. This was observed for both porous graphite and sintered porous tungsten anodes, in the latter case causing melt spots to form which limited the useful life of the anode. A study was undertaken to overcome this problem in which the transient behavior of the arc current, voltage, anode surface area coverage and gas flow rate of transpiration gas was observed by high speed electronics and cinematography during the ignition period. From these data a computation of the anode current density vs. time showed abnormally high values during the first second or two following ignition; e.g. 1000 amps/cm2 averaged over the first second for a steady state arc current of 70 amps. The damage was attributed to excessive thermal loading during the arc growth period and eliminated by means of a properly control led ignition sequence.

ショットピーニングのエリアカバレージについて

This study describes the characteristic of the area-coverage obtained from the experiments with airless blasting machine.The results obtained are as follows;(1) The area-coverage consists of following three factors; the first is the number of dent per unit time and unit area on the workpiece, the second is the total area of dent per unit time and unit area, and the third is the rate of area-coverage for peening time.(2) The relation between area-coverage A (%) and the total area of dent per unit time and unit area Q (cm2/s-cm2) and the blasting time t (s) is as follows;λ=kλ·Q·tmherem=0.61.0, kλ=0.951.0 for λ<80%m=0.050.1, kλ=2.07.0 for λ>80%