Significant Quality Degradation Research Articles

Influence of anode and filter material on image quality and glandular dose for screen-film mammography

The influence of anode and filter materials on the performance (image quality and dose) of a mammography system is investigated. The image quality is evaluated with the image quality index method. A computer simulation has been developed to calculate the physical parameters of the image quality index (contrast, resolution and noise) as well as the mean glandular dose. The calculations take into account the successive steps of the process: X-ray production, filtration, interaction with the test object, anti-scatter grid, interaction with the image detector (screen-film system). An excellent correlation is obtained between the results predicted by the model and those of experimental measurements, suggesting that the model may be used for the prediction of the performance of mammographic equipment. The experimental conclusions are confirmed: the use of a tungsten anode with a rhodium filter allows a dose reduction without a significant degradation of image quality. The computer program can also be used to simulate the influence of factors which are difficult to combine in practice, e.g., various anode and filter materials, monoenergetic X-rays, etc.

Environmental Aspects of Heavy-Oil Recovery by Thermal EOR Processes

Summary This paper summarizes the major U.S. and State of California environmental regulations relevant to thermal EOR processes and assesses their impact on the process. The environmental laws that have the greatest impact on thermal EOR processes pertain to air quality, water processes pertain to air quality, water quality, hazardous wastes, and environmental quality. This paper also identifies the source and type of pollutant likely to be generated in a pollutant likely to be generated in a typical thermal EOR facility. Introduction In recent years, thermal EOR operators have faced increasingly stringent environmental regulations oriented toward preventing significant degradation of air and water quality and land misuse. These environmental laws and regulations significantly affect the design and operation of thermal EOR processes. U.S. federal, state, local agencies are involved in the enactment and implementation of various environmental laws and regulations. Because jurisdictions frequently overlap, confusion can occur. For example, in California both the Dept. of Health Services and the Regional Water Quality Control Board may be involved in determining the level of cleanup of old oilfleld sumps and in improvements. The reason is that the Dept. of Health Services regulates hazardous wastes while the Regional Water Quality Control Board regulates any waste placed on land that may affect water quality. Although a company's environmental specialists may be familiar with environmental laws and regulations and aware of the agencies responsible for enforcing them, other personnel may not have that knowledge. Technical and operating personnel responsible for reporting actions must also be aware of these regulations to avoid inadvertent noncompliance with applicable environmental rules and regulations. The purpose of this paper is to familiarize thermal EOR practicing engineers and other interested personnel with applicable environmental rules and regulations. The paper provides a summary review of may but not all, environmental laws ad regulations that could be applied to thermal EOR facilities ad operations. The environmental laws that have the greatest impact on thermal EOR processes pertain to air quality water quality, processes pertain to air quality water quality, hazardous wastes, and environmental quality. In California, separate federal, state, and often regional or local laws and regulations pertain to these environmental areas. Because pertain to these environmental areas. Because California is the hub for thermal EOR operations in the U.S., California regulations are emphasized. The applicable regulations for those states where thermal EOR is being implemented, or is likely to be implemented, are summarized elsewhere. The material in this paper was assembled by consulting publications of various federal, state, and private organizations. While every attempt was made to acquire the most recent applicable regulations or standards, regulatory processes are constantly evaluated, ad the processes are constantly evaluated, ad the findings presented here may not be current. At best, the information presented here was applicable up to late 1990. Furthermore, because the interpretations and enforcement standards in various regions can and do differ appreciably, the future potential constraints to thermal recovery processes cannot be defined readily.

Low-voltage scanning electron microscopy: A surface sensitive technique

The advancements in electron optics have made it possible to cover a wide electron energy range without significant degradation in the imaging quality of a scanning electron microscope. The secondary electron emission and the surface sensitivity are enhanced when using low voltages. The addition of an energy dispersive x-ray spectrometer with a thin window allows the detection of low energy emission lines, thus making the technique comparable, or at least complementary to surface techniques such as Auger electron and x-ray photoelectron spectroscopies. In this paper, aspects of low-voltage SEM are discussed and factors affecting the secondary electron images are examined. The surface sensitivity is evaluated and is compared to Auger electron spectroscopy. Study cases from the printed circuit board manufacturing area are presented.

Toxicity and accumulation of chromium inCeratophyllum demersum L.

As a result of heavy metal pollution, significant degradation in water quality has occurred leading to acute scarcity of safe drinking water. Efforts have recently been made to develop simple but reliable biological systems to upgrade the water quality. In this process several aquatic plants effective in heavy metal uptake were identified. Recently, a few aquatic species have been reported to accumulate chromium. However, not much information is available on Cr uptake by the aquatic vascular plants. Chromium, which is one of the highly toxic metals is being released to the water bodies in high concentrations through the effluents from industries like leather, dye, paint, ink, electroplating and paper. The interest on C. demersum a submerged aquatic plant was aroused because of its common occurrence and luxuriant growth in a polluted water body which contained 0.05 to 0.22 ppm Cr. Plants analyzed from this site also showed high accumulation of Cr. In view of this it was considered worthwhile to evaluate chromium uptake ability of this plant under the laboratory conditions.

Teletransmission of radiographic images. Preliminary report.

A digital system for transmission of images over telephone lines using a 256 X 256 X 6 bits matrix provided for communication between a county hospital and a university hospital is presented. During a three-month period radiologic diagnostic problems encountered in 62 patients (computed tomography in 46 and conventional radiography in 16) were referred by transmitting selected images from each examination. Transmission of computed tomograms was performed without significant degradation of image quality and there was no loss of diagnostic information. Deterioration of image quality was noticed when conventional films especially those of the chest, were digitized and transmitted, though in no instance were they non-diagnostic. The consultations gave valuable information to the transmitting radiologist in approximately 50 per cent of the cases. Review by the consulted radiologists of all original films in each of the examinations 6 months later did not improve the diagnostic results. Thus, a few carefully selected images, digitized and transmitted over telephone lines, may be sufficient for adequate consultation.

Cross-polarization coupling measured for 800 MHz radio transmission in and around houses and large buildings

The scatterers and reflectors that produce multipath propagation in the portable radiotelephone environment also scatter energy from the transmitted polarization into the orthogonal polarization. This cross-polarization coupling improves the signal quality on portable radio links by mitigating the effects of random antenna orientation and by providing an additional signal path for diversity combining. Measurements were made of cross-polarization coupling at 800 MHz within and around eight suburban houses and within two commercial buildings. Nearly complete coupling between polarization was seen for all propagation paths except for a few residential paths having high co-polarized signal levels. Because of the high cross-polarization coupling, random orientation of portable radio sets will not cause significant degradation of signal quality.

There is no central stimulus encoding during saccadic eye shifts: A case against general parallel processing notions

Three experiments are reported about the question whether perceptual processing of a signal viewed during a fixation, can continue during a subsequent saccadic eye shift to another signal. In the first experiment it was found that the size of the effect of degraded signal quality, measured in a traditional choice reaction task, was fully reflected in the duration of the fixation. The results of the second experiment showed that presentation time of the signal had no effect on fixation duration. In a final study the signal was preceded by a tone. Subjects were instructed to start the saccade upon hearing the tone, which had the effect that the signal was only briefly viewed. The results showed, first, that this instruction was hard to obey and, second, that, when obeyed, processing only continued when fixating the next signal and not during the saccade. Together, the results are most consistent with a serial sequence and difficult to reconcile with a parallel notion of perceptual encoding and saccadic shift.

Stream Dissolved Oxygen Analysis and Control

Buffalo Bayou, a major stream in Houston, Texas, was the subject of a detailed water quality study. The stream is heavily stressed by domestic waste loads and has shown significant degradation in water quality since 1970. Currently, the stream reaches critically low DO values through much of its length during low flow, high temperature periods. The QUAL‐IITX model was calibrated, verified, and applied to simulate worst case conditions and to test a series of stream protection alternatives. A combined program of sewage plant regionalization, stream aeration, and flow augmentation was found to be the most cost‐effective solution.

Epitaxial film transfer technique for producing single crystal Si film on an insulating substrate

Epitaxial film transfer, a new technique for producing a single crystal Si film with both large size and high quality on an insulating substrate, is demonstrated. The technique in which an epitaxial Si film is transferred to a secondary substrate by using three fundamental processes of epitaxial growth, bonding of two wafers, and substrate elimination, can produce a 2-in. single crystal Si film as thin as 1.5 μm on a insulating substrate. Thickness variation can be controlled to ±0.06 μm across a 2-in. wafer. An epitaxial Si film is transferred without significant degradation in quality although a fine film waving exists.

Application of wagner coding method to multi‐DPSK system

AbstractThe Wagner coding method utilizing analog information of a received signal in the decoding of single parity check code is known to have a similar ability to that of single error correcting code. Also, it possesses a simple decoding operation. This paper proposes a concrete example of the Wagner coding method applicable to multi‐ DPSK system. Example solutions are shown to the problems such as in the parity check coding scheme which can be used in the DPSK channel, extracting scheme of the channel measurement information in the case of multi‐DPSK system, and the error correcting scheme which can be applied after the differential decoder. Further, the theoretical analyses of BER (Bit Error Rate) performance are made for the case where white Gaussian noise is offered as a signal quality degradation factor and the case where phase jitter is contained in the recovered carrier. Consequently, it is clarified that by simply adding some peripheral circuits to the conventional DPSK modulator/demodulator, the proposed scheme compares favorably with the conventional 4‐DPSK system by 2‐dB improvement in the BER performance against white Gaussian noise and also offers considerable immunity against phase jitter. the equipment is actually fabricated in the case where the proposed method is applied to a 4‐DPSK system and the effectiveness of the proposed method is confirmed through experiments.

Reversible optical recording in trilayer structures

The reversible optical recording of FM video signals is reported. The recording medium is based upon the amorphous-to-crystalline phase transition of pure tellurium, incorporated into a trilayer antireflection structure. In excess of 50 record/erase cycles have been demonstrated, with no significant degradation in playback signal quality or erasability. The irreversible process of ablative pit formation (hole opening) has been inhibited by the use of a silicon dioxide capping layer.

Cumulative silvicultural impacts on watersheds: A hydrologic and regulatory dilemma

Because of the nature of watersheds, the hydrologic and erosional impacts of logging and related road-building activities may move offsite, affecting areas downslope and downstream from the operation. The degree to which this occurs depends on the interaction of many variables, including soils, bedrock geology, vegetation, the timing and size of storm events, logging technology, and operator performance. In parts of northwestern California, these variables combine to produce significant water quality degradation, with resulting damage to anadromous fish habitat.

Closed-system ionography for diagnostic radiology.

Three methods are described whereby radiographic electrostatic images are transferred from inside of a liquid ionography chamber to the outside. One of these methods is implemented showing that multiple-charge images can be transferred from a single original without significant degradation of image quality and each copy may be developed with a different amount of edge contrast. This new method of imaging was applied to a radiograph of a test pattern and a hand phanton. An exposure of about 6 mR to the imaging chamber is needed to produce a useful image with a resolution of about 8 1p/mm.

Proposal of QAM-OFDM System with IDAR Method Designed for Satellite Channel

The future satellite communication systems are required to support the higher transmission data rate for providing multimedia services by employing the efficient modulation method such as multilevel QAM. However, the employment of conventional single carrier transmission method with multi-level QAM which has larger PAPR (Peak to Averaged Power Ratio) would cause the fatal degradation of signal quality due to the non-linear amplifiers located at the earth station and satellite. To overcome this problem, this paper proposes broadband satellite communication systems by using the multilevel QAM-OFDM technique with IDAR (Improved Decision Aided Reconstruction) method, which is designed for satellite channel. In the IDAR method, the characteristics of non-linear amplifiers are required to be known at the receiver for mitigating the intermodulation noise. This paper also proposes the estimation method for AM-AM and AM-PM conversion characteristics of non-linear amplifiers by using low PAPR preamble symbols. The various computer simulations are conducted in this paper to verify the effectiveness of proposed system in the non-linear satellite channel.

Mitigation of Non-linear Distortion Using PTS and IDAR Method for Multi-Level QAM-OFDM System

The future satellite communication systems are required to support the higher transmission data rate for providing the multimedia services by employing the efficient modulation method such as multi-level QAM. The employment of single carrier transmission with multi-level QAM would cause the fatal degradation of signal quality due to the non-linear amplifiers located at the earth station and satellite. To overcome this problem, we have proposed the multilevel QAM-OFDM technique with IDAR (Improved Decision Aided Reconstruction) method designed for non-linear satellite channel. However, the proposed method could not mitigate the non-linear distortion sufficiently when modulation level becomes higher such as 64QAM. This paper proposes the combined scheme of partial transmission sequence (PTS) and OFDM-IDAR methods so as to enable the usage of higher multi-level QAM method, which can achieve the higher transmission data rate with keeping the better bit error rate performance in the non-linear satellite channel. The various computer simulations are conducted in this paper to verify the effectiveness of proposed method in the non-linear satellite channel.