Showing papers on "Literature survey published in 1992"

A literature survey for virtual environments: Military flight simulator visual systems and simulator sickness

Abstract: Researchers in the field of virtual environments VE, or virtual reality, surround a participant with synthetic stimuli, The flight simulator community, primarily in the U.S. military, has a great deal of experience with aircraft simulations, and VE researchers should be aware of the major results in this field. In this survey of the literature, we have especially focused on military literature that may be hard for traditional academics to locate via the standard journals. One of the authors of this paper is a military helicopter pilot himself, which was quite useful in obtaining access to many of our references. We concentrate on research that produces specific, measured results that apply to VE research. We assume no background other than basic knowledge of computer graphics, and explain simulator terms and concepts as necessary. This paper ends with an annotated bibliography of some harder to find research results in the field of flight simulators: • The effects of display parameters, including field-of-view and scene complexity; • The effect of lag in system response; • The effect of refresh rate in graphics update; • The existing theories on causes of simulator sickness; and • The after-effects of simulator use Many of the results we cite are contradictory. Our global observation is that with flight simulator research, like most human-computer interaction research, there are very few “correct” answers. Almost always, the answer to a specific question depends on the task the user was attempting to perform with the simulator.

Plant Responses to Temperature Under Conditions of Elevated CO2

Abstract: A literature survey of the interactive effects of CO2 enrichment and temperature on plant development and growth, indicated that the responses cannot be interpreted within a simple framework. For example, although plant development is generally accelerated by increased temperature, CO2enrichment can accelerate it even further in some instances, or CO2 enrichment may have neutral or even retarding effects in other cases. Where the temperature and CO2 effects are additive, it is argued that CO2 is operating in the same way as radiation to reduce a carbon limitation. If this were true, CO2 enrichment would be most likely to accelerate development in tropical regions during the low-radiation monsoon season. Similarly, while it would be expected that CO2-enrichment would have increasingly enhancing effects with increasing temperature on phytomass growth, this is not invariably the case. In extreme examples which followed the expected trend, plants grown in twice-normal CO2-enriched atmospheres performed progressively better than those grown at current levels of CO2 by 8.7% for every 1°C rise in temperature. However, the difference between the two CO2 treatments more commonly increased by only around 2% for every °C rise in temperature. Of examples examined, both sunflower and nodulated cowpea showed the reverse response to temperature, while non-nodulated cowpea, supplied with luxuriant levels of nutrition, showed no interaction with temperature but a strong interaction between CO2 and radiation. Other aspects of the environment such as nutrition and radiation strongly modify the responses to temperature. It is also clear that plant factors such as stage of development can alter the response to CO2. Long-term studies with several species are required which will take into account many environmental variables within a realistic envelope. One methodology for doing this is presented. There was no evidence among species that responses to CO2 arise through any consistent change in morphology such as via increased branching or increased leaf number. Plant plasticity is such that responses can be expressed in a variety of ways determined by other environmental variables.

EDI system integration: A definition and literature survey

Abstract: This paper defines electronic data interchange (EDI) in terms of its derivation from the wider group of strategic, interorganizational information systems. It discusses the topic from two viewpoints: the nature and derivation of EDI systems and the issues involved in integrating EDI systems into existing organizations, at both the technical and structural levels. The paper approaches the problem with an introduction to the concept of strategic information systems and then discusses the particular importance of interorganizational information systems (IOS). The literature pertaining to EDI is introduced, together with a discussion of EDI's historical development and the benefits it offers to implementing organizations. As an interorganizational information system, EDI is differentiated on the basis of its essentially cooperative role and EDI system integration issues are divided into the technical and organizational.

Stabilities of double- and triple-strand helical nucleic acids

Abstract: In this selected literature survey, we have seen that the stabilities of duplexes and triplexes are governed by the vertical base stacking, the horizontal specific base-paired H-bonding and the environmental parameters. The entropic contribution in the solvation/desolvation process is important in driving the aggregation of NA strands and duplex formation, but base stacking and specific H-bonding maintain the helical order. Triplex formation shares most of the physical environmental prerequisites with those of duplex NAs. However, some additional environmental conditions are often needed. Only in low pH solution is the polycytidylic strand protonated and, thus, it is possible for the strand to bind to a G.C duplex sequence to give the C+(G.C) triplex. High ionic strength is often necessary for the screening of inter-phosphate repulsion due to the high linear charge density in triplexes. The presence of specific counterions is important for complexation. In the absence of negative supercoiling, existence of an intramolecular triplex is rare except under very acidic conditions for the formation of C+(G.C)-type intramolecular triplex. As expected, the stabilities of both inter- and intramolecular triplexes increase with sequence length. The thermodynamic principles of helix-coil transition of oligo-duplex may be described by the van't Hoff relationship, which assumes a two-state cooperative melting profile. Thus, the enthalpy, entropy and free energy of transition can be evaluated from the experimental melting curves (e.g. OD, DSC). For polynucleotides, because of the non-two-state nature of transition, the simple van't Hoff relationship is no longer valid, and direct calorimetry is needed to obtain reliable thermodynamic parameters. The pH and salt concentration dependence of duplex stability can be formulated and derived from a van't Hoff equation. Base-stacking patterns are simple in duplexes but not so in triplexes due to the diversity in triplet schemes. The sequence dependence of base stacking for duplexes has been characterized and employed to predict the stability of an arbitrary sequence. In conclusion, the stability of duplex is relatively well-characterized by thermodynamic data in terms of both base stacking and specific H-bonding. Thermodynamic studies of triplexes have been far fewer in number. Oligonucleotides have found application in the detection and localization of a mRNA or its gene, the detection of bacterial or viral sequences, and the inhibition of the translation of mRNA and the transcription and replication of DNA (Englisch and Gauss, 1991). In a different approach, oligonucleotides have been targeted directly to a DNA duplex motif of a gene in order to inhibit the expression at the beginning of the transcriptional process.(ABSTRACT TRUNCATED AT 400 WORDS)

Discrete modelling of stress‐strain behaviour of granular media at small and large strains

Abstract: A general overview is presented on applications of the discrete element method (DEM) to granular media. A literature survey is performed of static and dynamic simulations using random arrays of compliant particles, and forty‐two references published mostly in the last ten years are identified and categorized according to a number of relevant criteria. It is concluded that the interest in the use of the technique is rapidly increasing in the research and engineering community, with applications concentrated in soil mechanics, rock mechanics, grain flow and engineering problems. Additional studies and verifications of some numerical aspects of the DEM technique are suggested including parametric studies and comparisons. Program CONBAL‐2 (CONTACT + TRUBAL in 2D) developed by the authors based on TRUBAL created by Strack and Cundall, is described. CONBAL‐2 uses the complete Mindlin solution for the contact between two spheres and thus can be used for small strain and cyclic loading. The program is applied to study the cyclic response of uniform, medium dense to dense rounded quartz sand. Cyclic strain‐controlled loading at constant volume is applied to isotropically consolidated, random arrays of 531 spheres, using cyclic strains ranging from 10–4% to 10–1%. The calculated shear modulus, Gmax, constrained modulus, D, and Poisson's ratio at small strains are correlated with the confining pressure, the porosity of the array, and the coordination number. The calculated variations of secant modulus and damping ratio with cyclic strain compare favourably with the experimental results on sands compiled by Seed and Idriss. Finally, ‘pore water pressure buildup’ and cyclic stiffness degradation of the material with number of cycles is calculated at a cyclic strain of 10–1%, and the prediction is found to represent closely cyclic undrained experiments on sands. The existence of a threshold strain, yt ≈ 10–2%, found experimentally, is also predicted by the simulations.

Flowers of annonaceae: Morphology, classification, and evolution

Abstract: The present paper describes the diversity in floral characters of Annonaceae and their distribution over the family, and discusses their value for classification and generic delimitation. Flower morphology predominated historical classifications of this family since Hooker & Thomson (1855) introduced floral characters to divide the Asiatic genera into a number of tribes. Since then, several taxonomists presented a classification of the Annonaceae using floral characters, which classifications, however, are generally felt as unnatural. A survey of the flower morphology of all genera reveals a reticulate distribution of floral character states. Classification of the genera, as presented in this study, learns that floral characters different from those in previous classifications should be used if one aims at a better correlation with non-floral features. The chromosome number in this respect turned out to be an important character. Classification of the neotropical genera is relatively easy compared with classification of the African and Asiatic genera. Current genus delimitations in many cases are disputable. The functional aspects of the flower morphology are discussed in connection with a literature survey of the results from field studies on flower biology of Annonaceae. Some remarks on evolutionary aspects are added.

Treatment of chronic wounds by means of electric and electromagnetic fields. Part 1. Literature review.

Abstract: The healing of a cutaneous wound is accompanied by endogeneous electrical phenomena. Not knowing whether they represent merely a side-effect of the physiological processes which take course during healing or whether they play a much more important role as mediators of healing, externally applied electricity was examined as a therapeutic tool for the enhancement of natural regenerative processes. In the present review a historical literature survey dealing with human applications of electric current for wound healing acceleration is given. It presents a complete palette of heterogeneous studies, differing in the parameters of applied electric current, in delivery modes as well as in the types of wounds being stimulated. Because of all these differences, comparing the efficacy of the described methods is difficult and could hardly be objective. Therefore greater stress was laid upon the discussion concerning the problems in designing clinical studies (size of the sample observed, control group, ethics of the procedures), rationales for the employment and possible underlying mechanisms of particular methods, and problems of evaluating their efficacy. In spite of the extensive work performed in the field of electrical wound healing we remain only part way towards explaining the mechanisms by which electricity reinforces the regenerative capabilities of injured tissue as well as only part way towards the selection of the optimal stimulation method from among the published reports.

Inheritance in natural language processing

Abstract: In this introduction to the special issues, we begin by outlining a concrete example that indicates some of the motivations leading to the widespread use of inheritance networks in computational linguistics This example allows us to illustrate some of the formal choices that have to be made by those who seek network solutions to natural language processing (NLP) problems We provide some pointers into the extensive body of AI knowledge representation publications that have been concerned with the theory of inheritance over the last dozen years or so We go on to identify the three rather separate traditions that have led to the current work in NLP We then provide a fairly comprehensive literature survey of the use that computational linguists have made of inheritance networks over the last two decades, organized by reference to levels of linguistic description In the course of this survey, we draw the reader's attention to each of the papers in these issues of Computational Linguistics and set them in the context of related work

Mycorrhizae in hawaiian pteridophytes: occurrence and evolutionary significance

Abstract: Forty-five percent of the Hawaiian pteridophyte flora were examined for mycorrhizae. Vesicular-arbuscular mycorrhizae were present in 66 of the 89 species examined. Nonmycotrophy was significantly higher in Hawaiian pteridophytes than in non-Hawaiian pteridophytes. The highest mycorrhizal colonization occurred in the leptosporangiate families Dicksoniaceae, Dryopteridaceae, and Lindsaeaceae. Mycotrophy was lower in the eusporangiate families. Substrate strongly influenced the presence of mycotrophy. Mycorrhizae were present in 83% of terricolous species, in 86% of epilithic species, in 55% of epiphytic species, and absent from aquatic species. A phylogram of pteridophyte families is constructed incorporating the intensity of mycorrhizal colonization as one criterion for classification. The occurrence of mycorrhizae in pteridophytes has received little attention in recent years, and Newman and Reddell (1987) found that only 180 species of ferns (fieldcollected) have been examined for mycorrhizae since 1960. In contrast, approximately 6,000 species of angiosperms and gymnosperms have been examined for mycorrhizae (Newman and Reddell, 1987; Trappe, 1987). The largest survey of ferns prior to 1960 was performed by Boullard (1957), who examined over 420 species for mycorrhizae. This study was not included in Newman and Reddell's literature survey of field-collected specimens, however, because the majority of the samples were not fresh collections. More than 75% of the sampled species consisted of fragments of roots and rhizomes removed from dried herbarium specimens (Boullard, 1957). The mycorrhizal status of Hawaiian ferns is largely unknown (Gemma and Koske, 1990; Koske and Gemma, 1990). The high islands of Hawaii are the most isolated group of oceanic islands (Howarth, 1987), and the native

Superfine and Ultrafine Grinding— A Literature Survey

Abstract: The growing demand for ultrafine powders, coupled with stringent quality requirements, calls for continuous improvements in all aspects of fine particles production. The high energy costs involved in comminution is also an additional motivator. The equipment most commonly used in fine particles processing and the related process parameters is described. Tumbling ball, stirred, vibratory and fluid energy mills are the most commonly used mill types. A number of factors influence the choice of equipment, including the end-use of the product, required product size distribution, sensitivity of the material to heat, and purity requirements. Stirred ball mills are used in ultrafine grinding because of their high unit outputs, while the low amplitude vibro-energy mills are used because of their low specific energy. Fluid energy mills are economic only in some specific applications as in treating heat sensitive materials, materials for plastics and ceramics where purity and delamination are the most important crit...

Recurrent cutaneous leiomyosarcoma.

Abstract: Background. Soft tissue sarcomas comprise approximately 0.7% of all malignant neoplasms. Superficial leiomyosarcoma, a rare malignant lesion, constitutes 4.0-6.5% of all soft tissue sarcomas, an overall incidence of approximately 0.04% among all cancers. Currently, less than 125 cumulative cases of cutaneous and subcutaneous leiomyosarcoma have been reported in the English literature. Methods. The authors report the case of a 70-year-old Japanese man with recurrent cutaneous leiomyosarcoma who was treated by wide local excision. A comprehensive literature survey is also presented. Results. The patient is free from recurrence 1 year after wide local excision of a second recurrence of cutaneous leiomyosarcoma. Moreover, superficial leiomyosarcoma can be subdivided into cutaneous leiomyosarcoma and subcutaneous leiomyosarcoma, based on histolopathologic and prognostic differences. Conclusions. The treatment of choice of superficial leiomyosarcoma is wide local excision. Cutaneous leiomyosarcoma is associated with local recurrence only, although subcutaneous leiomyosarcoma undergoes meta-static spread in 30-60% of cases, with a 30-40% mortality rate. Cancer 1992; 70:490–492.

Cefaclor-Associated Serum Sickness-Like Disease: Eight Cases and Review of the Literature

Abstract: OBJECTIVE:To describe the clinical features of serum sickness-like diseases (SSLD) in cefaclor-treated patients.DESIGN:Analysis of a case series spontaneously reported to Lyons Pharmacovigilance Center.SETTING:General and hospital practitioners and the French Network of Regional Pharmacovigilance Centers (FNRPC).PATIENTS:All reported cases with a possible causative relationship between cefaclor treatment and SSLD.MAIN RESULTS:Eight cases of SSLD following cefaclor treatment are described. The clinical features included cutaneous reactions, arthralgias, and moderate hyperthermia. In 50 percent of the patients, hospitalization was required because of incapacitating symptoms. The outcome was benign in all cases following discontinuation of the offending drug. All eight cases were reported in children under five years of age. Among 137 cefaclor-associated drug reactions collected by FNRPC, 27 cases of SSLD have been reported; 23 of these patients were younger than five years of age. A literature survey confir...

Hybrid managers — what do we know about them?

Abstract: . There is increasing interest in ‘hybrid managers’, a breed of managers who blend information management skills with general management skills. Such people are perceived as important in enabling organizations to exploit information systems effectively in today's competitive business environment. Based on a literature survey this paper summarizes what we know about hybrid managers, as expressed by both ‘expert opinion’ and formal research studies. We conclude that little substantive research has been conducted into hybrid managers. Much has still to be learnt about their possible role, characteristics and competences; and how organizations should recruit and develop them. Because of the paucity of published material about ‘hybrids’ in the information systems context, we have drawn inferences from appropriate analogues in other functions — namely personnel, finance and R&D. Relevant studies in related areas of information systems, general management, careers and management development are also put into the ‘hybrid’ context.

Air Pollution Emission Factors for Medical Waste Incinerators

Abstract: This paper presents the results of an extensive literature survey and data analysis conducted to determine uncontrolled and controlled pollutant emission factors (mass pollutant emitted per mass waste incinerated) for medical waste incinerators (MWI). Pollutant emission factors were calculated separately by type of medical waste (red bag, general hospital, and pathological waste), and add-on air pollution control (APC) equipment (wet scrubber systems, or dry scrubber/baghouse combinations). Pollutants for which emission factors were determined are particulate matter, carbon monoxide, hydrogen chloride, sulfur dioxide, nitrogen oxides, various metals, dioxins/furans, and selected volatile organic compounds (VOCs). In addition, the combustion gas produced per mass of waste incinerated was determined in order to compute expected pollutant concentrations in the exhaust gases based on the pollutant emission factors. Data from 40 MWIs burning various forms of medical waste and equipped with or without add-on ai...

Trees and their Response to Wind: Mid Flandrian Strong Winds, Severn Estuary and Inner Bristol Channel, Southwest Britain

Abstract: The response of contemporary trees to strong winds (gale force and greater) is repeatable and well defined, as shown by field studies in southeast Britain after the October 1987 and January 1990 events, combined with a wide-ranging literature survey. It involves the general processes of windprune, windsnap, windtilt and windthrow. Windprune depends on a range of physical and physiological mechanisms and leads to the loss of axial symmetry by a tree, especially where open-grown at an exposed site. Windsnap, windtilt and windthrow see the fall of a tree, as the result of either the breaking of the trunk or partial to full uprooting. Damage of this sort in a forest or woodland ranges from single trees, to scattered groups (swathes), to general devastation. In the main, perfectly healthy trees in youth or early maturity are affected by windsnap, windtilt and windthrow during strong wind events. Their fall-direction is readily established using the position of the rootball or snapped end of the trunk, the alignment of a broken trunk and stump, the taper of the trunk, the position on the trunk of relatively crowded branches (tree crown), and the position of the typically upward acute angle between branch and trunk. Contemporary trees overthrown by wind fall in a direction close to the wind. The variance of fall-directions in a sample due to a single wind event is observed to increase with the size of the woodland area from which the sample is drawn, but appears to become constant for sample areas in excess of 10 $^{2}$ -10 $^{3}$ ha. Because this constant variance is relatively small, the mean fall-direction becomes, in contemporary woodlands and forests, a trustworthy indicator of the general direction of the strong wind which felled the trees. Rooted peats of mid Flandrian age (ca. 6000-2500 conventional radiocarbon years) which include prostrate trees are widely present among the post-glacial estuarine silts exposed along the shores of the Severn Estuary and the inner Bristol Channel. The trees when overthrown appear in the main to have been perfectly healthy and in youth to early maturity. Oak and alder are the predominant species, and their fall-directions, as judged from the criteria listed from contemporary forests and woodlands, and measured at 18 horizons distributed over 14 sites, are highly coherent both locally and over the area as a whole. Using a model in which the variance of fall-directions observed for a single event is combined with a probability density for event mean directions, it appears that the trees fossilized in the peats were felled by strong winds which blew chiefly toward a range of directions from N.N.W. clockwise to S.S.E. A westerly zonal air-flow is indicated but, compared to the contemporary wind regime as measured at Avonmouth, the strong winds came from a wider range of directions than now, with a greater emphasis on both southerly and westerly to northwesterly blows.

Literature survey of the on-line preconcentration in flow-injection atomic spectrometric analysis

Abstract: The literature on the use of “on-line” preconcentration in flow injection atomic spectrometric analysis is reviewed, taking into account its application both in flame and electrothermal atomic absorption methods as well as in plasma emission spectrometry. The basis of the different preconcentration approaches, such as liquid-liquid extraction, column preconcentration and “on-line” precipitation are discussed. The literature survey reveals the analytical performance of the developed methodologies.

Literature survey on biomedical applications of thermography.

Abstract: Thermography is a noninvasive technique through which temperatures are monitored and recorded, thereby allowing visualization of heat flow There are three types of thermography: liquid crystal thermography (LCT), infrared thermography (IRT) and microwave thermography (MWT) This paper presents a survey of the literature pertinent to the biomedical applications of these types of thermography The noninvasive and high resolution characteristics of the thermographic systems make them valuable diagnostic as well as therapeutic aids Typical research areas include detection of blood flow, diagnosis of joint inflammation and cancer, thermal modeling of various body parts, and use in reproductive problems The survey discloses that thermography has found applications in various fields in medicine, veterinary medicine, pharmacy, and dentistry

Life prediction and constitutive models for engine hot section anisotropic materials program

Abstract: This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism.

[Meta-analysis of the prognosis of thoracic aortic dissection: changing mortality in the last four decades].

Abstract: The acute dissection of the thoracic aorta is a potentially lethal event with a death rate of 1 to 2% per hour urging for undelayed diagnosis and adequate treatment. First, this paper highlights both the demographic characteristics and the classification according to anatomical and prognostic criteria, i.e. class I to III according to DeBakey and type A and B according to Daily (or Stanford). Moreover, the etiology of aortic dissection is explained, including factors such as degenerative changes of the aortic media layer, chronic trauma from hypertension, primary connective tissue disease and acute deceleration trauma. Second, the clinical criteria of acute (within 14 days of the index event) and chronic dissection (> 14 days) is discussed with respect to the current literature. The dominant part of this paper represents a meta-analytic approach comprising all available literature sources with respect to emerging changes in the prognosis of thoracic aortic dissection over 40 years as a function of either the type, the anatomic location, the acuity or the impact of medical or surgical treatment of this disorder. The meta-analysis revealed that in acute and chronic type A dissection medical treatment alone failed to lead to a significant improvement of 30 day-mortality rate (Tables 1 and 2, Figure 1). However, with surgical interventions the 30 day-mortality rate was continuously lowered from 60% to 10% within the past 30 years. A similar evolution was observed for the chronic type A dissection (Tables 3 and 4, Figure 2). Furthermore, the meta-analysis revealed that the acute type B dissection benefits from medical treatment, especially antihypertensive medication since the 30 day-mortality of 40% in 1960 decreased to less than 10% at present with monitoring and effective medication (Tables 1 and 2, Figure 3). In case of chronic type B dissection the literature survey revealed mortality numbers fluctuating between 2% and 20% without a clearcut beneficial effect of medical therapy throughout these years, though possibly revealing some advantage over surgical treatment. Thus, both for the acute and chronic type B dissection the antihypertensive therapy is considered treatment of first choice, whereas surgical interventions may be necessary for complicated and progressive cases. In summary, compared to the natural course of thoracic aortic dissection with only 10% survival-rate after one year of onset (Table 9, Figure 5), any effective mode of treatment may significantly lower the high spontaneous death rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Towards maximising pupil endeavour : an enquiry into a learning approach centred on teamwork and simulation in the context of technology education

Abstract: The enquiry originated from observations of a series of learning events which appeared to generate high levels of pupil endeavour. These events were typified by being residential, employing commercial simulation, teamwork and a suspended timetable which allowed long periods of concentrated work on a design task. Observations provided the Impetus for an enquiry Intended to illuminate the learning approach and the origins of this increased endeavour. This enquiry employed a series of case studies with a parallel literature survey. The pre-enquiry learning events are described and an impression of the factors Involved established. The evolving nature of the enquiry Is explained. A literature survey is made of the key factors. The methods employed, Including their limits and limitations, are described. The case studies are summarised and discussed In relation to the literature survey. Conclusions are drawn and suggestions for further research are made. The key findings are that the enquiry indicates high levels of endeavour are replicable, given understanding of the factors involved. Pupils' perceptions of the relevance of the events is high. Pupils tend not to adopt a competitive approach on an inter- team basis but do respond to deadlines. Pupils tend to develop cooperative management structures rather than establish leaders which are not seen as relevant. Endeavour Is maximised in teams which are selected to be heterogeneous In terms of gender, friendship groupings, subject expertise and ability. Positive synergy Is Identified In terms of endeavour but not the range and quality of design ideas. Teachers, whilst recognising the value of granting autonomy to teams, find it difficult to release control and Intervene only when necessary. The contributions to knowledge lie in the areas of designing In teams under competitive pressure; pupil team reaction to competition and the response of staff to working In these learning contexts