Hypothetical Setting Research Articles

Fine grained software degradation models for optimal rejuvenation policies

In this paper, we address the problem of preventive maintenance of operational software systems, an approach recently proposed to counteract the phenomenon of software “aging”. We consider the so-called “software rejuvenation” technique [Software rejuvenation: analysis, module and applications, in: Proceedings of the 25th International Symposium on Fault-Tolerance Computing (FTCS-25), Pasadena, CA, USA, June 1995], which consists in periodically stopping the software system and then restarting it in a “robust” state after a proper maintenance, and we propose a methodology for the quantitative analysis of rejuvenation strategies. The methodology is based on a fine grained model that assumes that it is possible to identify the current degradation level of the system by monitoring an observable quantity, so that the rejuvenation strategy can be tuned on the measured degradation. Based on this methodology, we present two different strategies that allow to decide whether and when to rejuvenate, and we exploit the theory of renewal processes with reward to estimate the steady-state unavailability of the software system, which is used to define an optimality criterion that allows us to evaluate the proper rejuvenation intervals. The methodology and the rejuvenation strategies are demonstrated by applying them to a real-world case study, arising in the area of database maintenance for data archiving, and to a hypothetical setting used to assess the sensitivity of the technique to various degradation processes.

Unsaturated‐zone wedge beneath a large, natural lake

Lake Belle Taine (480 ha) in north central Minnesota receives on average 76,000 m3 d−1 of water from Little Sand Creek but has no outlet. Water seeps out of the lake, flows through glacial outwash, and discharges into three nearby lakes with stages 13–14 m lower than Belle Taine. Seepage‐meter data indicate water is seeping out of Belle Taine at velocities up to 263 cm d−1 . Hydraulic‐head measurements made in the lake bed indicate the sediments are unsaturated beneath a portion of the lake edge, and a wedge of unsaturated sediments extends beneath the lake bed as much as 20 m from the shoreline. At the shoreline the water table is as much as 6.7 m below the lake surface. Modeling results of a similar hypothetical setting indicate that the horizontal extent of an unsaturated zone beneath a lake depends on (1) the permeability contrast between the outwash and the lake bed, (2) anisotropy, (3) lake bed slope, and (4) thickness of the lower‐permeability lake bed sediments. Although rarely documented, unsaturated sediments beneath a lake may not be extremely uncommon. Similar, much smaller unsaturated‐zone areas also have been observed beneath two other lakes in Minnesota.

AN APPROACH TO REPRESENTING THE SPATIAL STRUCTURE OF THE INFORMATION SOCIETY

With recent advances in information and communications technologies (ICT), traditional conceptualizations and models of spatial interaction need updating. In a previous paper, this author developed an analytical framework that incorporated telecommunications capabilities as well as transportation modes and residential and work locations into a unified representation of the “geography of opportunities” (Shen, 1999). In this paper, the initial framework is extended by the inclusion in the formulation not only of employment opportunities, but also of other types of opportunities. Each type of opportunities is distributed among three components of geographic space: the physical space, the hybrid space, and the virtual space. The effects of ICT are captured by: (1) the saving of travel time for people who can partially substitute telecommunications for transportation as means to access opportunities in virtual and hybrid spaces and (2) the migration of opportunities from physical space to virtual and hybrid spaces. Individuals' position in the emerging spatial structure of the information society is measured in terms of accessibility to a wide range of economic and social opportunities. This new approach is shown to be an operational and promising analytical tool in a hypothetical setting. However, its refinement and application is currently constrained by the lack of systematically collected data on many aspects of the human geography. [Key words: telecommunications, human geography, spatial structure, spatial analysis.]

New Telecommunications and Residential Location Flexibility

Information and communications technologies are now used by a rapidly increasing number of people as means of spatial interaction. This has two major effects on transportation: (1) telecommunications partially substitute for travel to the workplace and to some other preexisting destinations; and (2) often indirectly, telecommunications stimulate new activities and generate extra travel. In this paper, I first develop an analytical framework for understanding changes in residential location flexibility that result from the direct travel substitution effect. I then apply this analytical tool to an exploration of the emerging urban spatial structure in the information age; alternative scenarios of telecommunications usage are simulated in a hypothetical metropolitan setting, and insightful results are obtained. The simulation is followed by a discussion of the role of urban planning in shaping the future pattern of residential growth. In an effort to stimulate further thinking and research, I point out in the conclusion that the analytical approach should be extended by taking into account the travel generation effect of telecommunications, and could be incorporated into land-use models.

Hypothetical surveys versus real commitments: further evidence

The contingent valuation method is frequently used to estimate willingness to pay for environmental services. However, numerous studies have raised serious questions about the validity and reliability of such estimates. The study reported here extends the analysis of hypothetical versus real commitments by considering the effects of alternative indicators of WTP in the hypothetical setting. While part of the results confirm the findings of previous studies–CV methods can result in an overestimate of actual mean WTP–evidence is also produced that a carefully designed CV instrument can produce an estimate of mean WTP that is much closer to actual mean WTP than previous studies would suggest.

ASSESSING THE VALIDITY OF A SOCIAL HISTORY INTERVENTION TO INDIVIDUATE NURSING HOME RESIDENTS

The purpose of the present study was to examine the efficacy of a social history intervention to individualize nursing home staff members' patient perceptions in order to generate more positive attitudes toward target patients, to foster more tolerant perceptions of those patients' problem behaviors, and to maximize staff members' perceived rewards of caregiving. Unlike previous studies that have demonstrated the effectiveness of such an intervention in a hypothetical setting (M. E. Pietrukowicz & M. M. Johnson, 1991), the goal of the current study was to assess the efficacy of this intervention among actual patient-staff dyads in a nursing home care unit. Findings showed that the use of the social history intervention did not produce the predicted changes in staff perceptions and attitudes among a representative sample of 42 staff members. Alternative explanations for the lack of significant findings among this sample of nursing home staff, such as employee burnout and attitudinal polarization, are presented, and suggestions for using this intervention successfully in other institutional settings are provided.

Assessing the Importance of Design Through Product Archaeology

This paper assesses the importance of design in determining product costs by measuring the variation in design performance among a set of competing design efforts. This assessment is completed for a set of functionally similar products in a single product category: automatic drip coffee makers. The approach of this study is to measure the manufacturing content—the attributes of the design that drive cost—through analysis of the physical products themselves, and to estimate how variation in manufacturing content relates to variation in cost in a hypothetical manufacturing setting. We call this approach product archaeology. For the domain of coffee makers, we find significant variation in manufacturing content. This variation in manufacturing content corresponds to a range of estimated manufacturing costs, for a hypothetical manufacturing system, of approximately 50 percent of the average manufacturing cost of the products. We also find that differences in capabilities among product development efforts are the most plausible explanation for the differences in manufacturing content.

Evaluation of Remote Altimeter Setting Penalty at Four North Georgia Airports

Although an airport may have an instrument approach procedure, the procedures' ceiling minimums may be artificially increased as a result of a lack of a local altimeter setting. If the pilot is not allowed to land at the intended airport because of the required use of a remote altimeter setting, the community is potentially denied economic benefit because of flight disruption. Altimeter settings based on automated weather observation systems at four northern Georgia airports recorded during a 6-month period in early 1995 are analyzed. Each airport was assigned a hypothetical remote altimeter setting source (one of the three other air-ports). A comparison was made between the altimeter settings at each destination airport and the hypothetical remote altimeter setting source airport for differences in altimeter settings. These altimeter setting differences were then compared with the associated ceiling penalty a pilot would be given when executing an instrument approach at an airport using a remote altimete...

Evaluation of Remote Altimeter Setting Penalty at Four North Georgia Airports

Although an airport may have an instrument approach procedure, the procedures' ceiling minimums may be artificially increased as a result of a lack of a local altimeter setting. If the pilot is not allowed to land at the intended airport because of the required use of a remote altimeter setting, the community is potentially denied economic benefit because of flight disruption. Altimeter settings based on automated weather observation systems at four northern Georgia airports recorded during a 6-month period in early 1995 are analyzed. Each airport was assigned a hypothetical remote altimeter setting source (one of the three other airports). A comparison was made between the altimeter settings at each destination airport and the hypothetical remote altimeter setting source airport for differences in altimeter settings. These altimeter setting differences were then compared with the associated ceiling penalty a pilot would be given when executing an instrument approach at an airport using a remote altimeter source. For the extreme differences found in the data, it was found that the existing remote altimeter setting source penalty protected an aircraft from possibly descending too low when using a remote altimeter setting source.

The role of gastric mast cells, enterochrornaffin-like cells and parietal cells in the regulation of acid secretion

The idea presented here is that, in gastric mucosa, two independent regulatory systems use the same transmitter: histamine molecules. The IgE/mast cell system is dispersed throughout the body, while the other regulates the gastric acid secretion. IgE molecules in gastric mucosa are attached to the mast cells. Mast cells release histamine molecules after the antigen has been recognized by IgE. These molecules normally act on vascular H1 receptors to promote extravasation and chemotaxy. Gastrin molecules are released from antral G cells to stimulate gastric acid secretion. Their influence on parietal cells is indirectly augmented by gastrin governed release of histamine molecules from enterochromaffin-like cells. These histamine molecules normally act on H2 receptors of parietal cells to promote gastric acid secretion. Chronic infection of gastric mucosa (i.e. with Helicobacter pylori), autoimmune disorders or repetitive mucosal exposure to the same antigen, can develop chronic inflammation of gastric mucosa. Gastric acid secretion is diminished with secondary hypergastrinemia and increased release of histamine from enterochromaffin-like cells in an attempt to stimulate the few remaining parietal cells. Hypothetically, increased concentrations of released histamine in gastric mucosa might activate the vascular H1 receptors with extravasation and aggravated inflammation. This can further decrease the number of active parietal cells, reduce gastric acid secretion and potentiate hypergastrinemia. In this hypothetical setting, H1 blockers might reduce the damage by abolishing the vascular reactions. The prolonged antigen load on gastric mucosa can promote production of specific IgE antibodies. Further exposures to the same antigen degranulate sensitized mucosal mast cells. Liberated histamine can produce extravasation through the vascular H1 receptor and, hypothetically, local hyperacidity through the parietal cell H2 receptors. The result would be hyperacidity and hypogastrinemia with possible ulcer disease. Some individuals are more predisposed to IgE production or have increased numbers of mast cells and that might explain why only some people develop ulcer disease after H. pylori infection.

Simulations of Flow in Crystalline Rock and Recharge from Overlying Glacial Deposits in a Hypothetical New England Setting

AbstractCross‐sectional, finite‐difference, steady‐state ground‐water‐flow models of a generalized New England landscape were constructed to examine the effects of hydraulic conductivity and topography on bulk‐fluid flow processes in fractured crystalline rock. The generalized landscape consists of a flat hilltop, a hillside that has a slope of 0.17 ft/ft, and a flat river valley. It includes three hydrogeologic units, stratified drift in the river valley, glacial till, and underlying crystalline rock.Distribution of recharge to and discharge from bedrock is affected by the presence of small topographic features, such as terraces on the hillside. Most of these terraces consist partly or entirely of sand, and they create localized areas of recharge to and discharge from bedrock. Maximum recharge to bedrock commonly occurs at downward inflections of the water table, and discharge occurs at upward inflections of the water table. These inflections of the water table are associated with inflections in topography because the shallow depth of water on hilltops and hillsides resemble the configuration of the land surface.Regional ground‐water flow in crystalline rock and distribution of bedrock recharge and discharge are also affected by heterogeneities in hydraulic conductivity of the bedrock. Vertical heterogeneity creates short, shallow flow paths in high‐relief terrain. Horizontal heterogeneity causes large variations in the size of bedrock recharge areas; in some cases the difference from homogeneous conditions is more than 50 percent.

Using Belief Functions to Represent Degrees of Belief

Belief functions are an alternative or supplement to probabilities for representing the degree to which we believe in various hypotheses, highlighting different aspects of subjects′ uses of evidence. In particular, belief functions have potential for situations in which the belief assessor is interested in judging the degree of support or justification that the evidence affords hypotheses, e.g., in legal situations. Noting that there is a lack of empirical evidence testing the theoretical claims in favor of using belief functions, we constructed an experiment to determine (a) if subjects could be trained in the meanings of belief-function responses; and, (b) once trained, how they use those belief functions in a hypothetical legal setting. We found that subjects could use belief functions, identified limits to belief functions′ descriptive representativeness, and discovered patterns in subjects′ uses of belief functions that inform our understanding of subjects′ uses of evidence.

Patients' willingness-to accept risk of medical treatments

Recent research has brought into question patients willingness to accept immediate treatment risk for the possibility of increased 5-year survival. This study was designed to assess whether patients are able to identify the probability of initial mortality they would be willing to accept in order to increase their chance of long-term survival. Cross-sectional structured interviews with continuity clinic patients. A university-based Department of Veterans Affairs Medical Center general medicine clinic. 128 consecutive patients (mean age = 65.4 years (s.d. = 11.27, range of ages = 30-83)), seen in the second half of 1992. In a hypothetical setting, patients were presented with a pair of curves representing expected survival over a 5-year period for I two alternative treatments. The disease and treatments were not identified. In one curve, there was a 10% peri treatment mortality rate and a 37% 5-year survival; in the second curve, there was a 0% peritreatment mortality rate and a 22% 5-year survival. Once patients selected the treatment they preferred based on the curve pair, they were asked whether they were willing to accept an initial risk higher than the one they had selected. Of the 128 patients, 26.6% (34/128) selected the treatment with a 0% mortality in the peritreatment period. For these 34 patients, their mean initial acceptable probability of death was 3.75% (s.d. = 2.32, range 0-9). Of the 94 study patients who selected the 5-year curve with 10% mortality in the peritreatment period, the mean initial risk they were willing to accept was 14.73% (s.d. = 9.12, range = 10-70). Older patients were less willing than younger patients to accept probabilities at higher than the given immediate peritreatment risks for both treatments (chi square = 4.330, d.f. = 1, P < 0.04). Patients are not as uncomfortable at taking immediate risks of death for a 5-year survival benefit. Patients report a willingness to accept risk of immediate death for 5-year survival benefits.

Comparison of response spectrum amplitudes from earthquakes with a lognormally and exponentially distributed return period

This paper addresses the significance, for engineering decisions, of replacing the Poissonian by one-step memory models in describing the occurrence of large periodic earthquakes on fault segments along the plate boundaries. A one-step memory model with a lognormally distributed return period was chosen for the analysis. The constraint imposed on both probabilistic models is that, for a given magnitude interval, the median of the lognormally distributed return period is equal to the expected value of the exponentially distributed return period of the Poissonian model. The hypothetical geologic setting chosen for the analysis is in southern California. It consists of a set of faults, one of which exhibits strongly periodic behavior for larger events (a hypothetical segment of the San Andreas fault about 350 km long, for example) whose occurrence is modeled by either of the two probabilistic models, and of other faults for which the earthquakes form a Poissonian sequence of events. PSV spectral amplitudes, PSL LN and PSV EX for the model with a lognormally and exponentially distributed return period, were evaluated for five probabilities of exceedance ( p = 0·01, 0·1, 0·5, 0·9 and 0·99) at a site on the fault and another site away from the fault. The significance of the difference between the PSV amplitudes calculated by the two models, is measured by the ratio of the two amplitudes (by factor f = PSV LN/PSV EX), and by their difference in terms of the overall uncertainty (by the factor f 1 = PSV LN −PSV EX/σ ∗ , where σ ∗ , is a measure of the standard deviation of the distribution of PSV LN). For a realistic geologic setting and plausible simple scenarios of earthquake occurrences, it is determined how the factors f and f 1 depend on the confidence level of the PSV estimate, the exposure time, Y, the time elapsed since the most recent significant event, t e, and on the uncertainty in the one-step memory model (measured by the parameter ζ, equal to the standard deviation of the distribution of the logarithm of the return period for the one-step memory model). The results show that the difference between the predicted PSV amplitudes by the two occurrence models is most significant for high confidence levels (1% or 10% probability of exceedance), during the exposure time following immediately after a larger earthquake on that fault (elapsed time since the most recent event on the segment of the San Andreas fault equal to zero), for the exposure time about 20–25% of the average return period of the events on the hypothetical segment of the San Andreas fault, and for a site on the hypothetical segment of the San Andreas fault. A factor of less than two and a difference within one standard deviation were considered to be of no significance for engineering practice. The results showed that, for a realistic value of the uncertainty of the one-step memory model ( ζ ≥ 0·2), and for a probability of exceedance of 0·1 or higher, even for a site on the fault, the difference between the predicted PSV amplitudes is not significant for engineering purposes. For a probability of exceedance of 0·01, for a site on the fault, the factor f is not much less than one half for the most conservative estimates of the Poissonian model, and barely or not more than two for the most nonconservative estimate. At the same time, the factor f 1 in absolute value can be well beyond one for the most conservative estimates, but, in general, not more than one for the most nonconservative estimates. For sites away from the fault and closer to the Los Angeles metropolitan area, the difference in the predicted spectra by the two occurrence models is insignificant in terms of the defined criterion.

A demand analysis for environmental goods

The value of goods that are routinely bought and sold in the market place has long been measured by social scientists. However, ordinary markets do not exist for “environmental goods” such as air quality and wilderness. Thus, their value estimation remains as a challenging task. The objective of this paper is to obtain an accurate estimate of the benefits of a change in the provision level of environmental goods, which can be used in a benefit-cost analysis. By balancing the costs of such environmental goods against their benefits, informed policy decisions can be made. The contingent valuation (survey) method along with the extended linear expenditure system (ELES) is employed to obtain the correct benefit measures for the good in the context of an appropriate hypothetical market setting.

A recursion model for cellular production/assembly systems

This article presents an efficient algorithm for applying the recursion modeling approach to describe the transient operation of cellular production/assembly systems that incorporate features such as finite buffers, job-shop routing, lot sequencing, and material handling. Tests evaluate the approximation method relative to number of machines at a station, capacity of input/output buffers, degree of balance among station processing times, and sequencing rule. Furthermore, the method is demonstrated in application to a hypothetical industrial setting that involves the assembly of electronic circuit cards in a facility composed of several cells. All tests indicate that the method gives accurate estimates of transient performance within reasonable runtime. In comparison with earlier recursion models, this research incorporates a number of new features (see list above), improves the accuracy of approximation, and facilitates implementation with a new, more efficient algorithm.

Antecedents of Crime and Suggested Punishment

Abstract The study assessed the effects of character, professional status, and intentions of a criminal on the magnitude of suggested punishment in a hypothetical experimental setting. The sample was composed of 120 male Indian undergraduates. The analysis yielded a significant main effect of intentions as well as interaction effects of Intentions × Character and of Intentions × Character × Status Factor. The results lend support to cognitive dissonance and attribution theories.

Interactive Information Management in Exploration: ABSTRACT

Conversational software provides a continuous dialog between the explorationist and the computer. Interactive procedures of this type create an environment in which storage, retrieval, manipulation, reporting, and mapping of information are integrated into one system. Automation of an exploration office provides increased speed, accuracy, and flexibility to the exploration effort. With present technology, noncomputer-orientated employees can easily access existing data files with computer programs, which produce a variety of information. From the creation of detailed base maps to interpretative geological mapping, interactive software has proven its usefulness. A rapid preliminary evaluation of an area will be performed using interactive information systems. A hypothetical geologic setting in Plaquemines Parish, Louisiana, serves as the setting for this reconnaissance study. All available information will be retrieved, manipulated, and displayed using conversational software. Base maps and reports created from existing well, seismic, velocity, and cartographic computer files comprise the initial information. Existing well marker depths and seismic times will aid in a more accurate interpretation of the geology. As the interpretation evolves, information is periodically updated and mapped to further develop the study. Computer-generated contour maps provide a rapid and reliable evaluation of the subsurface geology. End_of_Article - Last_Page 233------------

The measurement of patients' values in medicine.

The standard gamble, derived from decision theory, is considered a criterion method for obtaining patients' values for different health states. In this method, a rater's value for a health state is obtained by determining, in a hypothetical setting, his readiness to remain in that state or take a risky choice with different outcomes of known value. According to the expected utility criterion, a rater's utility or value for a particular state should not be influenced by changes in the gamble outcomes. The standard gamble was used to obtain 64 patients' judgments of a set of health states, first with the outcomes of perfect health or death, and subsequently with other health states as outcomes. The changes in gamble outcomes significantly influenced reported values for health states, indicating that the standard gamble is internally inconsistent. This observation poses a major limitation to its use as a value measurement method in medicine.

Two Major Island Arc-Trench Systems in the Northwest Pacific Ocean and the Philippine Basin - (I)

Geological researches of the Philippine Basin have been greatly advanced by works on the islands of frontal arc systems, by deep sea drillings, and by marine geophysical surveys. However, we cannot constract any concrete concept on the basin genesis. We can only suggest some speculative and qualitative indications arising from the synthesis of data, as follows.1 : Since the Middle Eocene or in places since the Oligocene or Early Miocene, the Philippine Basin has been almost entirely under sea, where thick beds of limestone and miscellaneous elastics often rich in fossils, together with volcanic ash, volcanic conglomerates and breccias, and volcanic rocks mostly basic in character were formed.2 : Synthesis of these data also suggests that the basin was subjected to wide spread crustal movements at least three times, namely the age ranging probably from the Late Cretaceous to the Early Eocene, the Mid-Tertiary and lastly the Pleistocene, and that the fundamental features of the submarine physiography as shown in the basin at present were formed most probably in an early stage of the Eocene.3 : It has been announced that the Daito Ridges area is constructed of continental crust (MIZUNO, 1975), extent of which, however, remained almost unexplained. In the writer's conception, areas extending widely from the Izu-Hakone crustal block in Central Honshu, Japan, so far as Izu Is. and adjacent areas of Yap Is., Palao Is., Halmahera Is. and Vogelkopf Penninsula of New Guinea are also constructed almost no doubt of continental crust. It may be rather possible that the basin is constructed entirely of continental crust, and further that the continental crust had been long remained in a state of continental land until it was covered by the Tertiary marine water.4 : The characteristic physiographic pattern shown by the NW-SE parallel arrangement of Daito Ridges, Shikoku Basin, Kinan Sea-mounts Area together with the Izu-Mariana insular arc-trench system is in fact note-worthy feature in the northern part of the Philippine Basin, the arrangement being nearly perpendicular in direction against the arcuate structure of the frontal insular arc-trench system of East Asia in the Angara Land. The characteristic feature may strongly suggests that the Philippine Basin belongs to a global structural unit, quite different from the Angara Land, and that the basin crust is most probably covered by the overthrusted plane of the East Asiatic frontal belt drifting away from the continental Angala Land.5 : In structure, the Philippine Basin extends southeasterly so far as New Zealand area as shown in Fig. 2, sarrounding Austrarian continent of the Gondwana Land, and constructing a frontal tectonic zone of the Gondwana. The tectonic zone is appropriately called the Austro-Philippine Tectonic Zone by the present writer, the tectonic zone being comparable in structural development with the Northwest Pacific Tectonic Zone (TATEIWA, 1976, 1979) of the Angara Land.6 : It is percieved that the Mariana trough has been extended at rates up to 10cm/yr. or more during the last 2-3 m. y. (KARIG, 1973). In general concept, however, these phenomena may be a matter of naturally expect in considering the genetic relationships between arcuate structure of insular arcs and inside marginal sea. Hypothetical setting of sea-floor spreading axis, specially fixed, for elucidation of the phenomena, seems to have no convincing basis.