ALBERT

Notes: Abstract Field tests assessed forest fireline construction capabilities of two power-assisted tooling systems—a chain saw system and a hydraulic power unit system. These were compared with the conventional handtool system as to fireline construction rate, cost, and other considerations.

Notes: Abstract There is a need for an effective means of controlling smoke inhalation among forest fire fighters. It then seems logical that the bulk of the detrimental effects of the smoke on the fire fighter could be avoided by the use of a purely mechanical respirator.

Notes: Abstract Off-gas toxicity data on materials commonly found in the kitchen are presented to provide a practical perspective on relative toxicity.

Notes: Abstract This paper compares the physical and combustion-related properties of the liquid state of hydrogen (LH2) and methane (LCH4). This type of comparison is important for studying the safe use of these chemicals as aircraft fuels, although it cannot yield definite conclusions because the actual effect on safety depends on the conditions of the accident.

Notes: Abstract A mathematical analysis of arcing phenomenon is presented as related to fire. It is shown that arcing has a great destructive power while a short circuit has not. Experimental results are also given.

Notes: Abstract Federal funding strategies greatly affect investment in urban transportation facilities in the United States. This analysis concentrates on the implications of varying federal aid matching requirements, structuring aid programs as categorical or block grants, and allo cating funds on a discretionary basis or according to formula. Toward this end the effects of recent federal transit aid arrangements are assessed. Increased federal matching share broadens program participation, especially among smaller cities. However, when offered a choice, communities' preference for more generous federal aid shares is tempered by their election of discretionary grants (e.g., Urban Mass Transportation Administration - UMTA - Section 3) instead of drawing on formula funds (e.g., UMTA Section 5 or highway fund transfers). Formula funds are easier to administer, distributed quite evenly in the UMTA case, and generally more suitable than discretionary funds except where expenditures are large relative to budgets. Categorical aid programs shift local priorities, and thus should be used with caution Overall, results suggest that one must begin with established transportation objectives against which to evaluate the effectiveness of funding arrangements. In particular, it is critical to make clear the rationale for federal involvement in funding specific programs. Four such federal funding intents are distinguished: compelling national interest, regional development, stimulation of recipient investment in the given program, or financial relief for the aid recipient. Conclusions are drawn as to the desirability of various funding policies according to such program intent.

Notes: Abstract This paper comments on the possible future of the taxicab industry within the context of a familiar economic-growth model. The future capability of the taxicab industry to check increases in real costs is shown to be an important determinant in the industry's long-term viability. More importantly, the effect of rising real incomes on the demand for taxicabs is postulated also to have a strong effect on future demand. The strength of this effect and the exact position of the taxicab in the “transit tree” have important implications not only for the future demand for taxis but also for the more traditional modes of public transport.

Notes: Abstract The effect of motor vehicles upon older neighborhoods has received increasing attention as residents of these areas seek to preserve the quality of life in their neighborhoods. In order to reduce through traffic in residential neighborhoods, numerous techniques have been developed, ranging from turn prohibitions to physical barriers. Since these measures have negative impacts on previous users of the streets, there has been substantial opposition to them. This paper reviews the major areas of conflict as revealed through court challenges. Nine court cases were identified by the researchers. In four, the court decision supported the control measures; in five, the courts decided against the actions. Six of the nine cases are reviewed in this paper. Major legal issues which are identified include the appropriate use of municipal police power, reasonableness in the exercise of police power, the integration of control measures into an overall transportation plan, appropriate consideration of emergency vehicle needs and the rights of access to property, and public participation in the decision. The authors conclude that properly planned and executed diversion strategies can be implemented and can withstand challenges by negatively affected parties.

Notes: Abstract This study was designed to examine the relationship between actual and perceived values of cost and time for the work trip and to examine how perceptions have changed over a period of dramatically increased travel costs. Variations in the relationship between perceived and actual values were examined as a function of situational and attitudinal variables. Two telephone surveys were conducted one year apart (Fall 1978 and Fall 1979). On the next working day following a survey, a research assistant recreated the respondent's work trip, recorded time values and used distance measures, car type information and parking costs to compute travel cost. The first survey revealed that most auto users were unable to articulate dollars-and-cents driving costs for the work trip, but auto users in the second survey were able to provide fairly accurate cost estimates. Dramatic changes in fuel prices between surveys is probably the main reason for the change in driving cost awareness. Auto users were also asked to rate relative costs of driving a car compared to using the bus for the work trip. These ratings showed that auto users tended to underestimate driving costs relative to bus costs, but this tendency decreased from the first to the second time period. Commuters in all modal groups at both time periods tended to overestimate travel times. Perception of travel time varied as a function of mode, perceived comfort (for car users), and perceived convenience and number of transfers (for bus users).

Notes: Abstract This paper reviews a number of recent innovations in the regulation and operation of taxicabs in U. S. cities. The paper discusses the growing involvement of various levels of government in public transportation programs which affect the taxicab industry, and identifies the opportunities and problems created for the industry by this increased government activity. Innovations in the types of public transportation services which can be provided by taxicabs are discussed first, followed by a review of the administrative procedures which can be employed to involve taxicab companies in publicly funded programs. Proposals for changes in the regulations governing taxicab services and prices are discussed next, with particular attention to significant regulatory changes which have been implemented in U.S. cities in recent years. Finally, innovations in the technology of taxicab operations are reviewed, including improvements to vehicles, computerized dispatching techniques, and procedures and equipment for computing fares for taxicab services.

Notes: Abstract A psychological scaling technique, magnitude estimation, is used to rate time spent on various elements of bus transit trips. Relative values of time are found for in-vehicle portions of trips, walking, waiting and transferring. Because magnitude estimation produces a ratio scale, results can be directly incorporated into modal choice analyses, route planning and evaluation procedures where monetary values of time are not necessarily required.

Notes: Abstract Transportation study home interview surveys normally underestimate the amount of trip-making by residents of a study area, and the data has to be adjusted subsequently to compensate for this effect. One important reason for the shortfall appears to be the incomplete recall and reporting of travel information by respondents. The paper examines the influence of the survey instrument on recall by comparing reported travel behaviour in two surveys conducted in the same town, one using a conventional travel diary and the other an activity diary. The latter format appears to encourage a more complete response, giving rise to significantly higher reported trip rates and travel times. The paper discusses some research and policy implications of this finding and concludes with tentative suggestions for improved travel survey instruments.

Notes: Abstract Models of individual choice behavior have been extensively developed and used in travel prediction during the last ten years. These models are generally formulated with utility functions that are linear in parameters. Theories of economics and psychology suggest that the true relationship between service variables and utility is non-linear. In this paper we demonstrate that non-linear transformations of time and cost variables produce statistically significant improvements in the model estimated, have a theoretically appealing interpretation, and lead to managerially important differences in policy evaluations. These results support the need to refine the specification of choice utility functions based on theoretical considerations and empirical research.

Notes: Abstract As the number of married women working outside the home continues to grow, questions arise as to the impact of a wife's employment on household travel patterns. In this paper we examine the effects of a wife's employment status on her own travel activity pattern and on that of her husband. Using data from the Uppsala Household Travel Survey, in which sample-household members kept detailed travel diaries for 35 days, we first compare the travel patterns of married women employed full time with those of married women employed part time and married women not working outside the home. We then compare the travel patterns of the three corresponding groups of husbands. Measures of travel activity patterns that were used include indices of overall travel frequency for different purposes, amount of time spent and distances travelled for different purposes, indices of the level of variety in the individual's destination choice set, and measures of mode use. The results show that women employed full-time do reduce their participation in some non-work activities although their distances travelled to activity sites are not shorter than those travelled by the other women. Few significant intergroup differences distinguish the travel activity patterns of the three groups of men. The evidence suggests that a woman's full-time employment does bring significant changes to her own travel pattern but has little impact on that of her husband. The paper concludes with a discussion of policy implications and a review of several Swedish programs that could eventually result in greater similarity in the travel activity patterns of men and women.

Notes: Abstract Virtually every U.S. bus system today charges its customers flat fares. Recent trends, however, suggest that passengers are traveling farther and proportionally more during peak hours, factors which have contributed toward transit's cost spiral. As deficits continue to soar and available funding tightens, current pricing rationales must be seriously questioned. This paper assesses the efficiency and equity impacts of three California transit agencies' fare structures. Short-distance, off-peak patrons are found to heavily cross-subsidize long-haul commuters. Fares differentiated by distance and time-of-day, in contrast, could improve the transit industry's fiscal posture while eliminating differences in payment rates. Barriers to their implementation remain formidable, however, both in terms of current fare collection capabilities and political acceptability.

Notes: Abstract In a number of articles in this journal the use of generalised cost in travel demand analysis and transport planning has been subject to debate. However, some of the fundamental problems raised in these articles are left unanswered — e.g., the precise relationship between conventional microeconomic consumer demand theory and generalised cost, an issue with which this article is concerned. It is shown here that necessary and sufficient conditions for expressing travel demand in terms of generalised cost are that this cost, when measured in monetary units, is linear, and that the time variable is weighted by a constant marginal value of time. It is also shown that these conditions imply strong assumptions about the consumer's behaviour — e.g., that the willingness to pay to save time whilst travelling is not a function of real income.

Notes: Abstract Two on-board surveys were conducted to determine how transit riders perceive transfers. The surveys were conducted before and after the imposition of a transfer in the middle of an existing bus route. Results of the surveys showed that riders perceive bus transit trips as significantly worse when the trip requires a transfer, even if transfer time is neglibible.

Notes: Abstract Since 1976, major Denver metropolitan area firms have been required to encourage employees to use mass transit, carpooling, bicycling, and other “alternate transportation modes” to commute to work. The encouragement programs of 36 firms were clearly associated with greater use of alternate transportation modes, with the portion of variance in alternate transportation use explained by differences in employer programs of approximately 15%. The effects of the programs on deterring alternate mode users from returning to solo driving are consistently weaker than their effects on persuading drivers to try alternate transportation modes initially. Recommendations for the conduct of alternate transportation encouragement programs are made, based on these and other results. In addition, two recommendations are made concerning the evaluation of encouragement programs: that aggregate percentage change in alternate transportation use should not be used as the sole measure of success, and that environmental variables such as the availability of and pressure for use of alternate transportation modes should be measured and controlled.

Notes: Abstract Having accepted the need for the development of simpler and less cumbersome transport demand models, the paper concentrates on one possible line for simplification: estimation of trip matrices from link volume counts. Traffic counts are particularly attractive as a data basis for modelling because of their availability, low cost and nondisruptive character. It is first established that in normal conditions it may be possible to find more than one trip matrix which, when loaded onto a network, reproduces the observed link volumes. The paper then identifies three approaches to reduce this underspecification problem and produce a unique trip matrix consistent with the counts. The first approach consists of assuming that trip-making behaviour can be explained by a gravity model whose parameters can be calibrated from the traffic counts. Several forms of this gravity model have been put forward and they are discussed in Section 3. The second approach uses mathematical programming techniques associated to equilibrium assignment problems to estimate a trip matrix in congested areas. This method can also be supplemented by a special distribution model developed for small areas. The third approach relies on entropy and information theory considerations to estimate the most likely trip matrix consistent with the observed flows. A particular feature of this group is that they can include prior, perhaps outdated, information about the matrix. These three approaches are then compared and their likely areas for application identified. Problems for further research are discussed and finally an assessment is made of the possible role of these models vis-a-vis recent developments in transport planning.

Notes: Abstract Transportation planners and transit operators alike have become increasingly aware of the need to diffuse the concentration of peak period travel in an effort to improve gasoline economy and reduce peak load requirements. An evaluation of the potential effectiveness of strategies directed to achieve this end requires an understanding of factors which affect commuter trip timing decisions. The research discussed in this article addresses this particular problem through the development and estimation of a commuter departure time (to work) choice model. A number of conclusions were drawn based on the departure time model results and related analyses. It was found that work schedule flexibility, mode, occupation, income, age, and transportation level of service all influence departure time choice. The uncertainty in work arrival time and the consequences of various work arrival times may also be determinants of commuter departure time choice. The estimated model represents improvements over previous work in that it more explicitly considers work arrival time uncertainty and travelers' perceived loss associated with varying work arrival times, and additional socio-demographic factors which can potentially affect departure time choice. Furthermore, the estimated model includes consideration of transit commuters, in addition to single occupant auto and carpool work travelers. The inclusion of transit commuters represents a particularly important contribution for policy analysis, since the model could potentially be used to study the effect of service and employment policies on transit system peak load requirements.

Notes: Preface This paper is an adaptation of the first Reuben Smeed Memorial Lecture given at University College London on 12 March. This series of lectures has been promoted by the late Reuben Smeed's former friends, colleagues and admirers as a tribute to him for his contributions to traffic science and engineering over a quarter of a century. Reuben Smeed's unique combination of imagination, rigorous objectivity and determination, coupled with his humour and warmth brought him rare distinction as a researcher and teacher. The subject of the paper is wide ranging and complex and it has not been possible to treat all parts of it with the thoroughness that Reuben Smeed would have sought. However there is little doubt that it would have appealed to him as one well worth tackling.

Notes: Abstract Because of the existence of “limited designation” gateways, i.e., gateways for international air travel where entry by U.S. flag carriers is limited (in many cases to only one carrier), the U.S. Civil Aeronautics Board (CAB) has announced a policy of “gateway competition.” This policy seeks to maximize inter-gateway competition as a goal of the carrier selection process. The paper reviews the rationale and history of this policy and the economic principles of gateway competition. After addressing exceptions where gateway competition does not enhance competitive goals, the issue of how to enforce the credibility of the bidding process in route awards is addressed. The paper concludes by identifying circumstances where competitive objectives are not advanced through application of the principle gateway competition.

Notes: Abstract This paper examines attempts by planners and policy makers to analyze and bring about the coordination of rail and bus transit in the San Francisco Bay Area. Drawing on studies and plans before and after the creation of the rapid rail system BART (Bay Area Rapid Transit), the author points to technical, analytical and political problems in attempts to link BART and buses. Some options and cautions are presented for planners considering route coordination, feeder buses, transfers and institutional arrangements to manage bus and rail services.

Notes: Abstract Based on an analysis of observed automobile routes, an investigation is made into the factors affecting choice of routes. As in previous studies, the attempt to determine the influence of time and distance simultaneously was unsuccessful. However, time was found to be an important factor in the description of route choice behaviour. An improved description of route choice behaviour is achieved if a differentiation according to road type is made or if intersections are included in the model as explanatory variables. The subjective or perceived generalized times caused by intersections are approximately 0.88 minutes and those caused by left-turn movements are 2.55 minutes. The result could further be improved by dividing the difference in generalized times between two routes by the root of the generalized times. A great advantage of this approach is also that it links up better with stochastic assignment models, in which traffic is randomly distributed over alternative routes. In particular for studies on extraneous traffic and the consequences of traffic-controls, the method presented here serves as a start for further investigation.

Notes: Abstract The word “delay” is so widely used that it may be assumed to be a simple concept which is well understood. It is taken to be a name for wasted time on a journey, but attempts to quantify it in order to use it as a measure of performance of a transportation facility have not given complete satisfaction. Drivers are observed to behave in ways which reveal attitudes to wasted time which differ from those of the researcher. These problems have been reported in many studies but do not seem to have been pursued. This paper discusses the concept of delay. A basic definition leads to problems of measurement which suggest alternative definitions which have more apparent relevance to traffic networks in which more than one cause of delay is of interest. Further speculation about these definitions points to the fact that delay can be either of two separate concepts. In conclusion it is argued that delay should no longer be regarded as an objective quantity capable of direct measurement. Instead of delay being thought the cause of driver annoyance, it should be taken that it is the existence of driver frustration which converts time lost into delay. It is better to define delay as unwanted journey time.

Notes: Summary Floor Loading and Movement Along the Coalface Total roof to floor convergence, floor loading, horizontal and vertical movements of floor along three selected longwall faces were investigated. Empirical equations expressing the above noted linearly time-dependent factors in strata mechanics are developed. It was observed that the contribution of floor to the total roof to floor closure is between 31 to 63%, dependent upon the strength of roof and floor layers encountered.

Notes: Résumé Anisotropie de la dilatance des roches schisteuses Les petites déformations de schistes ardoisiers, mesurées au cours d'essais de compressions triaxiales, montrent une orthotropie de révolution élastique initiale dont les coefficients varient avec la pression de confinement. Lorsque la déformation croît, comme pour les roches pseudo-isotropes, mais seulement pour certaines plages d'orientation de la structure par rapport au tenseur contrainte, prend naissance le mécanisme de dilatance. Le seuil de dilatance dépend de cette orientation et de la pression de confinement. La dilatance croît avec la contrainte suivant une loi proche du second degré.

Notes: Summary On the Determination of Some Important Geotechnical Joint Properties by Means of Integral Geometry Simple equations are presented which are useful to evaluate properties of joints important in rock mechanics, e. g. the length of linear of intersected joints, the joint area, the joint opening, the joint volume, and the edge length of rock blocks defined by joints. Also, the integral-geometrical derivation of the equations is presented to compare these with previously published expressions for such joint properties. Methods of measurement are illustrated to record the features from which the joint properties are evaluated: simply determinable numbers of points and lengths along measuring lines and numbers of points on measuring areas. The potential usefulness of the integral-geometrically derived equations is tested on a weathering profile of a Upper Devonian siltstone.

Notes: Summary Approach to Complete Limit Equilibrium Analysis for Rock Wedges — The Method of “Artificial Supports” Since the movement of rock wedges or blocks is the primary phenomenon in rock mass failure, it is convenient to use limit equilibrium approaches for stability analysis. In spite of their wide use, limit equilibrium analysis is often restricted due to: 1) the usual procedural simplifications (regarding geometry, force application, failure modes), and 2) basic deficiencies of the limit equilibrium approach (the fundamentally indeterminate rigid body problem requires assumptions regarding the force reactions). The method of artificial supports intends to circumvent or reduce many of these restrictions. In particular, the problem of unknown force distribution on the supporting plane is reduced by specifically considering and optimizing a variety of reactions on these planes. All sliding modes of failure — i. e., translational, free and restrained rotational sliding — can be correctly modelled. Particularly significant is the result that the usual assumption oftranslational sliding can be incorrect andunsafe, if forces other than the weight are significant. The methodologies employed in the artificial support model can be extended to all modes of failure, i. e., lifting off and toppling in addition to the previously mentioned sliding modes; this is demonstrated with a procedure for a “complete” stability analysis for a 2-joint wedge.

Notes: Zusammenfassung Das neotektonische Spannungsfeld in den Regionen von Shaanxi, Gansu, Ningxia und Qinghai (China) Geologische, seismologische, geodätische und geomorphologische Daten wurden verwendet, um die Richtung der überregionalen, neotektonischen Hauptnormalspannungen im nördlichen Zentralchina zu bestimmen. Es wird gezeigt, daß die maximale Druckspannung eine NE-SW-Richtung hat (N 40° E). Im Detail scheint es eine Rotation der maximalen Druckspannungsrichtung von N 7° E im Ladakh bis N 33° E im chinesischen Westxizang und bis ca. N 70° E im Südwesten der hier untersuchten Region zu geben. Dies kann ein Hinweis dafür sein, daß, abgesehen vom Effekt einer Kollision zwischen der eurasischen und indischen tektonischen Platte, sich auch der Effekt der Kollision zwischen der eurasischen und pazifischen Platte bemerkbar macht.

Notes: Summary Size Distributions of Rock Blocks from Measurements on Rock Faces In this model rock blocks are regarded to have spherical shape and they are described by a distribution of diameters of spheres. The measured quantities are the lengths of chords which are recorded along measuring lines across rock faces. The volume fractions of the size classes of rock blocks are derived from the distribution of chord lengths. Three methods are discussed for obtaining the sphere diameter distribution from counts of chord numbers on sections. An example is given for the size distribution of rock blocks in a weathering profile of an Upper Devonian siltstone.

Notes: Zusammenfassung Geomechanische Modelluntersuchungen für die Gründung von Talsperren Das Verhalten hoher bestehender Talsperren für Großspeicher, einige besondere Vorkommnisse bei der Nutzung derselben sowie einige Unfälle haben gezeigt, daß der Frage der Gründung von Talsperren besondere Bedeutung zukommt, da ein einwandfreies Zusammenwirken von Sperrenkörper und Gründungskörper für die potentiellen Lastfälle Voraussetzung für die Standsicherheit von Talsperren ist. Somit wird die Frage der Gründung von Talsperren bereits im Planungsstadium zu einem wesentlichen Bestandteil jeder ernsthaften Projektierung. Bei der Ausarbeitung von Alternativlösungen für den Talabschluß eines Speicherbeckens kann diese Frage sowie die Beurteilung des künftigen Verhaltens des Untergrundes der Sperre und des Speicherbeckens für die Dauer der vorgesehenen Nutzung die Wahl eines Sperrentyps maßgebend beeinflussen. Während wir für den Sperrenkörper mit Baustoffen arbeiten, deren Festigkeitsund Verformungseigenschaften wohlbekannt sind, ist dies für den Sperrenuntergrund, auch bei sorgfältig durchgeführten Voruntersuchungen und Aufschlußarbeiten während der Bauzeit nicht der Fall und auch nicht zu erwarten. Rechnerische und experimentelle Untersuchungen zur Erfassung des wahrscheinlichen Verhaltens des Untergrundes für ein Speicherbecken werden unter diesen Voraussetzungen in den meisten Fällen mit Schwierigkeiten behaftet sein; diese nehmen mit der Höhe der Talsperre als auch mit der Größe des Speicherraums zu. Die heute in der Talsperrenstatik üblichen Berechnungsmethoden, die das Untergrundverhalten in die Betrachtung mit einbeziehen, sind keineswegs so, daß sie als vollbefriedigend angesehen werden können. Über diese Tatsache kann auch der Einsatz von hochgezüchteten, für geomechanische Betrachtungen mehr oder weniger geeigneten Computerprogrammen beim Entwurf von Talsperren nicht hinwegtäuschen. Anhand von Prinzipskizzen von Talsperren verschiedener Typen wird die Frage der Kraftübertragung vom Sperrenkörper in den Untergrund im Zusammenhang mit den damit verbundenen Problemen erläutert, sowie auf die Grundzüge der bei der Planung von Sperren gebräuchlichen Berechnungsverfahren (mathematische Modelle) eingegangen. Der Aussagewert dieser Berechnungen im Hinblick auf die Beurteilung des Tragvermögens des Sperrenuntergrundes ist begrenzt und trägt — der Problemlösung inhärent — Zeichen einer ingenieurmäßig fundierten Abschätzung. Ein weiteres wertvolles Hilfsmittel für die Problemlösung steht dem planenden Ingenieur mit der Anwendung geomechanischer Modelluntersuchungen zur Verfügung. Bei Untersuchungen dieser Art werden das Gefügesystem (Groß- und Kleinklüfte) und Störungen im Felsuntergrund unter Berücksichtigung der Gefügeeigenschaften nachgebildet. In Abhängigkeit von den Anforderungen, dem Arbeitsaufwand und der angewandten Versuchstechnik wird die Qualität der Ergebnisse derartiger Untersuchungen sein. In vielen Fällen wird die Aussage nur qualitativen oder bestenfalls halb-quantitativen Charakter haben, jedoch in sehr anschaulicher Weise, z. B. potentielle gefährliche Verformungsvorgänge aufzeigen. Hauptsächlich dadurch sind sie ein wertvolles Hilfsmittel für den Entwurf, sowie für konstruktive und meßtechnische Entscheidungen. Je nach Aufgabenstellung werden derartige Versuche zweioder dreidimensional durchgeführt. Anhand einiger Beispiele werden die Einsatz- und Aussagemöglichkeiten von geomechanischen Versuchen erläutert, auf Entwicklungsmöglichkeiten bei der Anwendung sowohl für die Grundlagenforschung als auch für die projektbezogene Forschung wird hingewiesen. Abschließend wird festgestellt, daß die Bedeutung geomechanischer Untersuchungen in unserer Zeit des Computers nicht übersehen werden darf, da geeignete Berechnungsverfahren und adäquate Modelluntersuchungen als notwendige und gleichwertige, sich ergänzende Partner zu betrachten und heranzuziehen sind, um schwierige und verantwortungsvolle Entscheidungen bei der Errichtung von hohen Talsperren mit größtmöglicher Sicherheit treffen zu können; dies war grundsätzlich immer so, ist aber mit einer gewissen Euphorie der „allmächtigen“ Computer mancherorts in Vergessenheit geraten. Die Komplexität der Problemlösung einerseits und die der Verantwortung für ein einwandfreies Verhalten von Talsperren andererseits lassen die Notwendigkeit der Heranziehung aller bewährten Hilfsmittel zur bestmöglichen Erfassung der vielfältigen Aspekte der Problemstellung erkennen, um damit den Spielraum der Unsicherheiten in der Beurteilung der Standsicherheit einer Talsperre weitgehend einzuengen.

Notes: Résumé Les géotextiles sont devenus aujourd'hui, pour les ingénieurs de Génie civil, des matériaux indispensables dans de multiples utilisations. Si ces premières utilisations et propriétés des géotextiles commencent à être bien connues, par contre, les caractéristiques des fibres ellesmêmes, qui constituent les matériaux élémentaires des géotextiles ainsi que leurs divers modes d'assemblage, restent des notions mal assimilées dans le monde des utilisateurs. Pourtant, ces caractéristiques des fibres et modes de liaisons déterminent, pour l'essentiel, les propriétés principales que les géotechniciens peuvent attendre des produits. Cet article, illustré de nombreux schémas et micrographies optiques et électroniques, décrit les différents types de géotextiles existant sur le marché. Les propriétés physico-chimiques des matières textiles utilisées pour la fabrication des géotextiles sont brièvement rappelées. Les procédés d'assemblage et de liaison des fibres et/ou filaments textiles sont suffisamment détaillés et illustrés pour permettre une bonne compréhension des propriétés respectives des divers types de géotextiles tissés, non-tissés, tricotés, composites.

Notes: Abstract The institute has developped and constructed a special permeameter to study the hydraulic properties of geotextiles. This apparatus has been designed for: the determination of reproducible results for the permeability for flow both normal to the plane and in the plane of geotextiles both alone and embedded in soil materials; the samples of geotextile are loaded statically and the deformations are obtained. The permeameter is described here in some detail. Some initial results for flow normal to the plane have already been obtained. In general, they show that the coefficient of permeability is dependent upon hydraulic gradient. It is also considerably influenced by the stress applied normal to the geotextile.

Notes: Résumé Les qualités particulières des géotextiles sur les plans mécanique et hydraulique conduisent à prévoir que l'emploi de ces matériaux se développera dans des applications nouvelles, à condition que les caractéristiques des géotextiles puissent être connues et mesurées de façon satisfaisante et que la durabilité soit assurée. L'article mentionne les ouvrages hydrauliques et maritimes; les étanchéités souples et le renforcement des ouvrages en terre; il s'étend un peu plus longuement sur l'emploi des géotextiles associé au bitume, comme interface antifissure sous une couche de roulement de chaussée et comme élément de continuité dans un enduit superficiel.

Notes: Abstract To date, the results of studies which attempted to estimate residential water demand models have varied, but the source of these variations is not evident because the studies have applied different methodologies and data bases to different regions. The purpose of this paper is to develop models of residential water demand for watershed regions and test the null hypothesis that a single model is adequate to explain variations for all of the individual regions. Primary data collected from questionnaires and utility company records is used in a regression analysis to estimate a generalized water demand model for the state as well as one for each of the subregions. The null hypothesis is rejected which indicates that there are other factors which influence the demand for water and the use of a single model could result in biased estimates.

Notes: Abstract This paper examines the impact of age on migration by providing estimates of identically specified migration equations for each of six age groups. Hypothesized effects of age on the relative importance of various explanatory variables are developed from a model viewing migration as an investment decision. The effects of economic opportunity differentials on migration are found to decline sharply with age. Lagged migration, the “friends and relatives effect,” is found to be the most significant explanatory variable in all age group equations. Past migration is the only variable found to significantly influence the migration of persons over 65.

Notes: Abstract Reported here are results of an empirical analysis of regional growth in the European Economic Community for the period 1950–75. Data limitations ruled out the specification of a formal regional growth model. Accordingly the analysis is limited to the testing of various hypotheses of growth determinants using multiple regression analysis. The analysis was applied to GDP per capita data for 74 regions. A clear and consistent pattern of convergence was found. Significant growth determinants included economic structure, urbanization and centrality. The sunbelt hypothesis was confounded. Regional policy subsidies were not significant. The most important individual determinant was the growth of the rest of the state in which the region was located although there was a progressive weakening of this effect over time. The results allow for interesting comparisons with similar studies of State growth in the U.S.

Notes: Abstract Housing segregation directly affects the employment opportunities for blacks by reducing access to jobs. In addition, an indirect effect exists if, holding other factors constant, employers tend to hire workers who reflect the racial composition of the surrounding area. This tendency implies that a change in the distribution of black residences (with an offsetting change in the distribution in white residences) will have an impact on the spatial distribution of employment opportunities for blacks who donot move. Empirical evidence is presented for both the direct and indirect effects for the Chicago SMSA in 1970 using the Journey to Work data from the Census.

Notes: Abstract We examine the trend in timber production models from the earliest preference for volume maximization through modern economic value maximization models, and conclude with a glimpse at technological trends and their implications for future production modeling. Our contribution lies in the suggestion that each model may have been rational in its own historic biological and economic context. Biological and economic managers have focused their debate on the optimal production period. We examine the production period, and the debate, and predict the latter will vanish as new timber production technologies become widespread.

Notes: Abstract This paper presents derivations and empirical tests of three formulas for estimating output multipliers with only limited input-output type data. The first formula assumes only knowledge of the proportion of the value of output of the firm or industry in question which is respent within the region, as well as an estimate of the average of this value over all industries. The second formula assumes this value as well as the relative values of the I-O “row totals.” The third equation assumes data equivalent to a column in the I-O matrix is known for the specific firm or industry in question. The data requirements for all three formulas are modest but are more for (2) than for (1) and are more for (3) than for (2). All three formulas are shown to be quite reliable but the third gives especially close estimates of the actual multipliers for the several models tested. It is concluded that fairly rough estimates of the average interindustry proportion can be safely used but it is important to obtain the firm or industry expenditure (direct effects) data as accurately as possible.

Notes: Abstract This paper investigates methodological issues in forecasting tourism demand. We demonstrate that the employment of extended Box-Cox autoregressive tests for functional form and ridge regression to control for substantial and changing patterns of collinearity among the explanatory variables substantially increases forecast precision relative to extensively used OLS techniques.

Notes: Abstract This paper is concerned with extending understanding of short cut approaches to deriving regional economic multipliers. It focuses on the work of Burford and Katz. Seven regional input-output tables are analysed using the Burford Katz formula. Rules of thumb are developed to assist the regional analyst in making decisions on the appropriateness of applying short-cut formulae in order to estimate input-output multipliers when no input-output table exists.

Notes: Abstract Studies of the relationship between national and regional fluctuations have often found evidence of consistent space-time lags in regional economic adjustment. Some researchers have argued that depressed and peripheral regions take longer to adjust to national fluctuations than more central and prosperous regions. In this paper, a series of hypotheses are suggested to account for variations in space-time economic adjustments at the local level. The spatial and temporal transmission of market outcomes, uncertainty and the role of money are shown to be particularly important determinants of adjustment regardless of industrial location patterns. Emphasis is placed on inventory adjustments and unanticipated changes in sales by firms operating under conditions of imperfect competition. Following Hicks, the model is dependent upon fix-price quantity adjustment assumptions and is primarily short-run oriented.

Notes: Abstract One of the fundamental contributions of Hotelling's classic “Stability in Competition” paper is the focus on the interaction of the price and location choice variables. In most of the subsequent research in this area, the price dimension has been assumed away. In this paper the jointness of the two decisions is reintroduced and the results for N firms in a linear market are compared to the parametric price equilibria developed by Lerner and Singer and Eaton and Lipsey. Their conclusions are found to be valid for the N-2 interior firms in the more general model. But what has been lost because of the equal price assumption is the actions of the two exterior firms who exploit their uniqueness by charging higher prices to their “captive” buyers. A simulation of the dynamics of the price and location choice process confirms the analytically defined equilibria.

Notes: Abstract This paper uses state data for the late 1970's in a regression model to assess the relative importance of several hypotheses that have been advanced to explain the significant relative deterioration in youth employment opportunities. The paper also attempts to evaluate the nature and importance of regional differences with respect to the variables that are associated with youth employment opportunities. In particular the paper focuses on the effects of minimum wages and efforts to alter wages by unions, the expanded youth population and the changing labor force participation of females, differences in labor market tightness, expenditures on job training, schooling decisions on the part of young people and the general influence of poverty. Drawing on the empirical evidence, the authors conclude that a policy of regional minimum wages might result in a ten to twenty percent expansion in youth employment and achieving full employment for adult males might have an approximately equal effect.

Notes: Abstract The Federal Government's efforts to induce development of a coal-based synthetic fuel industry include direct subsidies, tax concessions, and assurances that it will purchase the industry's output, even if above the market price. In this note it is argued that these subsidies will enable this industry to secure a region's largest and lowest-cost coal deposits and that the costs imposed on other coal users will be substantial. Moreover, because the lowest-cost coal deposits will be committed to synthetic fuels production regardless of the industry's commercial viability, distortions in regional coal markets will develop. If economic efficiency requires that the price of the resource reflect its replacement value, then a State government is justified in imposing a tax on coal destined for subsidized synthetic fuel plants. Amounts of such a tax, based on the higher costs of coal that must be accepted by other users as the result of the subsidized synthetic fuel plants' preempting the largest and lowest-cost deposits, are estimated for the case of Illinois strippable coal.

Notes: Abstract This paper examines the rate of price inflation in twenty-two U.S. metropolitan areas over the 1961–1978 time period. A Phillips-Lipsey model containing specifications for unemployment, expected inflation, and imported inflation is evaluated for each region. The data are examined cross-sectionally as well as serially and little evidence is found to contradict the hypothesis that the rate of price inflation observed in U.S. metropolitan areas is the national rate. Local unemployment and expectations are generally insignificant explanators. A statistical problem associated with the use of the lagged dependent variable in a cross section regression is also discussed.

Notes: Abstract Earlier studies have attributed cyclical variations in regional manufacturing employment to differences in the regions’ industrial compositions and growth rates. Using OLS regressions, this paper demonstrates that the ownership characteristics of a region's manufacturers (branch plants versus unit concerns) and the location of the area with respect to national and regional markets were also factors that influenced the sensitivity of a region's manufacturing employment to fluctuations in aggregate demand. Areas with a relatively high concentration of multi-unit firms and geographically isolated regions experienced greater cyclical severity in manufacturing employment. This increased cyclical severity resulting from the tendency of multi-unit firms to: (1) consolidate production during periods of depressed demand through closing their high cost facilities, and (2) accommodate increased sales and reduce transportation costs during prosperity by opening branches outside the population centers.

Notes: Abstract The purpose of this paper is to examine the nature and significance of northern Mexico's rapidly-growingmaquiladora (assembly plant) industry, which has been promoted by policies in both the United States and Mexico. It is argued that this phenomenon is one aspect of the new international division of labor, which can be explained in terms of the related product cycle and spatial-industrial filtering concepts. The evidence suggests that despite problems, both countries have benefited on balance. In addition, the long-term implications of U.S.-Mexican interdependency are considered. The findings indicate that both countries need to adapt to changing international circumstances, but the potential gains from internal reforms are especially great for Mexico.

Notes: Abstract In determining metropolitan population size and changes therein, urban theorists traditionally have focused on the number of occupied dwelling units or households and have assumed that these households are equal in size. This paper argues that average household size is an indicator of how intensively the housing stock is utilized and that there is substantial variation in household size across SMSAs in the U.S. The experience of 150 SMSAs is examined for the time period 1960 to 1970. The study model attributes varying household size to differentials in birth and divorce rates, racial composition and age of housing. Ramifications of recent household size declines involve the internal spatial organization of metropolitan areas and the Census controversy with cities over alleged undercounts of urban populations.

Notes: Abstract This paper compares the output multipliers of the 1967 National input output model (367 industries) with the multipliers of the aggregated version (81 industries). The results show that, generally, the set of industries in the “full” model that were aggregated together for the “reduced” model, display a wide range of output multiplier values. Therefore, the output multiplier of an aggregated industry may not be truly representative of any of the industries that were joined together. Finally we show how information for a particular firm or disaggregated industry can be incorporated in an aggregated input-output model to obtain a close estimate of the actual output multiplier for that firm or industry.

Notes: Abstract A common dilemma in economic development planning is that the achievement of one objective often constrains the achievement of another, resulting in a range of options or tradeoffs among alternatives. This paper examines pairs of economic objectives for a multicounty planning region (e.g., maximize balance-of-trade surplus, maximize local employment) and derives tradeoff curves which might prove useful to planners. Several objectives examined might be considered as “capital-oriented” (e.g., maximize trade surplus). These objectives yield regional economic outcomes more similar to each other than to outcomes from “labor-oriented” objectives (e.g., maximize local employment). The range of the tradeoff curve is much greater for pairs of objectives between than within these two groups. The range and curvature of the tradeoff curves tend to increase as the level of the curve shifts outward due to a relaxation of the constraints for exports and incommuting labor. This suggests that conflicts may increase as regions become more open to trade and commuting; the need for compromise among differing local interests increases accordingly.

Notes: Résumé Nous nous proposons d'étudier l'influence de la vitesse de chargement sur les états limites de réversibilité de fissuration et de rupture d'un microbéton de calcite et d'un béton d'argile expansée. Nos expériences montrent que, pour les faibles contraintes appliquées, la fissuration et la valeur du degré de réversibilité ne sont pratiquement pas modifiées par la vitesse de montée en charge. Pour les charges élevées, la réversibilité du béton décroît avec la vitesse V d'autant plus que la valeur de la contrainte appliquée est grane. En statique, la contrainte de rupture qui diminue avec V semble tendre vers une limite.

Notes: Abstract The object of the paper is to determine the fracture toughness parameters K1C,G 1C and J1C for some aggregative materials. Values of the J-integral are calculated from load-displacement curves, following the procedure suggested by Begley and Landes for steel alloys. Some recurring experimental incoherences are explained applying Buckingham's Theorem for physical similitude and scale modeling to Fracture Mechanics. Thus a non-dimensional parameter can be defined (the test brittleness number), which governs the fracture-sensitivity phenomenon. The fracture parameters K1C and J1C are connected by a fictitious Young's modulus E*, which is lower than the real modulus E and represents the stiffness of the damaged material near the crack tip before the extension. When the specimen sizes are so small that the material becomes fracture insensitive, then E* appears higher than E.

Notes: Abstract The fatigue behaviour of concrete was a new aspect in the experimental program focused on the behaviour of concrete subjected to uniaxial impact tensile loading. The results obtained in repeated impact tensile loading tests (at stress rates of 2–6 N/mm2. ms) indicated that the impact fatigue was associated with progressive crack propagation resulting in accumulative damage of concrete. The upper stress limits varied between 1.7 and 0.6 times the static tensile splitting strength and specimen withstood 1 to 6,055 loading cycles respectively. The influence of water-cement ratio, cement content, specimen humidity, loading/casting direction and compressive strength upon the impact fatigue tensile strength of concrete was studied. The phenomena observed are discussed with the aid of fracture mechanics concepts.

Notes: Résumé Une étude expérimentale ayant pour but de vérifier le principe de superposition a été effectuée sur des éprowettes de béton soumises à des contraintes permanentes de compression. Une série d'éprouvettes a été chargée sous une contrainte σ à 7 jours, une autre sous la même contrainte à 28 jours et une troisième série d'éprouvettes chargée de 7 jours à 28 jours sous une contrainte σ, la contrainte étant ensuite doublée. L'étude des déformations après 1 700 jours de chargement sous trois contraintes (25, 50 et 75 bar), a été effectuée. L'interprétation des résultats prenant en compte les différentes sortes d'imprécisions expérimentales conduit à la vérification du principe de superposition de Boltzmann, bien qu'une différence de 10% existe entre la théorie et l'expérience.

Notes: Abstract This paper deals with three current functions of geotextiles: geotextile drains; geotextile filters; geotextile separators. The important properties of geotextiles in each function are discussed and permeability, filtration and strength criteria are proposed. Examples of design are presented for each function.

Notes: Abstract Various types of synthetic filter fabrics are available for geotechnical applications. Especially in the field of coastal engineering a lot of experiences are generally known. Unfortunately technical recommendations and testing regulations for specific implementations of geotextiles are not generally available and some actual examples of damage of coastal structures urgently require investigations on long-term resistance. A research program oriented towards the development of guidelines for testing geotextiles, the development of filtration rules and the clarification of long-term resistance of fabrics was carried out. This paper deals with testing procedures associated with the estimation of the opening size and the permeability to water of fabrics. Results of investigations on long-term resistance are described and filtration rules for selecting a fabric according to the special requirements of the application are given.