La Habra Research Articles

Examining spatial disparities in electric vehicle charging station placements using machine learning

• A framework for predicting equitable future EVCS placements is developed for Orange County, CA. • Santa Ana, Anaheim, Costa Mesa and La Habra experience the highest inequities in terms of EVCS placements. • Low-income areas with low car ownership and median age of population between 25-45 years, experience least EVCS access. • Random Forests achieve the highest predictive accuracy of 94.9% for EVCS density classes at 3 km resolution. • 11.04% of predicted EVCS placements lie within a high inequity zone. • 11.2% of the high inequity zones will require low to medium density of EVCS placements. Electric vehicles (EV) are an emerging mode of transportation that has the potential to reshape the transportation sector by significantly reducing carbon emissions thereby promoting a cleaner environment and pushing the boundaries of climate progress. Nevertheless, there remain significant hurdles to the widespread adoption of electric vehicles in the United States ranging from the high cost of EVs to the inequitable placement of EV charging stations (EVCS). A deeper understanding of the underlying complex interactions of social, economic, and demographic factors which may lead to such emerging disparities in EVCS placements is, therefore, necessary to mitigate accessibility issues and improve EV usage among people of all ages and abilities. In this study, we develop a machine learning framework to examine spatial disparities in EVCS placements by using a predictive approach. We first identify the essential socioeconomic factors that may contribute to spatial disparities in EVCS access. Second, using these factors along with ground truth data from existing EVCS placements we predict future ECVS density at multiple spatial scales using machine learning algorithms and compare their predictive accuracy to identify the most optimal spatial resolution for our predictions. Finally, we compare the most accurately predicted EVCS placement density with a spatial inequity indicator to quantify how equitably these placements would be for Orange County, California. Our method achieved the highest predictive accuracy (94.9%) of EVCS placement density at a spatial resolution of 3 km using Random Forests. Our results indicate that a total of 11.04% of predicted EVCS placements in Orange County will lie within a high spatial inequity zone – indicating populations with the lowest accessibility may require the greater investments in EVCS placements. 69.52% of the study area experience moderate accessibility issues and the remaining 19.11% face least accessibility issues w.r.t EV charging stations. Within least accessible areas, 7.8% of the area will require low density of predicted EVCS placements, 3.4% will require a medium density of predicted EVCS placements, and 0.55% will require high density of EVCS placements. The moderately accessible areas would require the highest placements of EVCS but mostly with low density placements covering 54.42% of the area. The findings from this study highlight a generalizable framework to quantify inequities in EVCS placements that will enable policymakers to identify underserved communities and facilitate targeted infrastructure investments for widespread EV usage and adoption for all. The findings from this study highlight a generalizable framework to quantify inequities in EVCS placements that will enable policymakers to identify underserved communities and facilitate targeted infrastructure investments for widespread EV usage and adoption for all.

0–5 Hz deterministic 3-D ground motion simulations for the 2014 La Habra, California, Earthquake

SUMMARYWe have simulated 0–5 Hz deterministic wave propagation for a suite of 17 models of the 2014 Mw 5.1 La Habra, CA, earthquake with the Southern California Earthquake Center Community Velocity Model Version S4.26-M01 using a finite-fault source. Strong motion data at 259 sites within a 148 km × 140 km area are used to validate our simulations. Our simulations quantify the effects of statistical distributions of small-scale crustal heterogeneities (SSHs), frequency-dependent attenuation Q(f), surface topography and near-surface low-velocity material (via a 1-D approximation) on the resulting ground motion synthetics. The shear wave quality factor QS(f) is parametrized as QS, 0 and QS, 0fγ for frequencies less than and higher than 1 Hz, respectively. We find the most favourable fit to data for models using ratios of QS, 0 to shear wave velocity VS of 0.075–1.0 and γ values less than 0.6, with the best-fitting amplitude drop-off for the higher frequencies obtained for γ values of 0.2–0.4. Models including topography and a realistic near-surface weathering layer tend to increase peak velocities at mountain peaks and ridges, with a corresponding decrease behind the peaks and ridges in the direction of wave propagation. We find a clear negative correlation between the effects on peak ground velocity amplification and duration lengthening, suggesting that topography redistributes seismic energy from the large-amplitude first arrivals to the adjacent coda waves. A weathering layer with realistic near-surface low velocities is found to enhance the amplification at mountain peaks and ridges, and may partly explain the underprediction of the effects of topography on ground motions found in models. Our models including topography tend to improve the fit to data, as compared to models with a flat free surface, while our distributions of SSHs with constraints from borehole data fail to significantly improve the fit. Accuracy of the velocity model, particularly the near-surface low velocities, as well as the source description, controls the resolution with which the anelastic attenuation can be determined. Our results demonstrate that it is feasible to use fully deterministic physics-based simulations to estimate ground motions for seismic hazard analysis up to 5 Hz. Here, the effects of, and trade-offs with, near-surface low-velocity material, topography, SSHs and Q(f) become increasingly important as frequencies increase towards 5 Hz, and should be included in the calculations. Future improvement in community velocity models, wider access to computational resources, more efficient numerical codes and guidance from this study are bound to further constrain the ground motion models, leading to more accurate seismic hazard analysis.

Calibration of the near-surface seismic structure in the SCEC community velocity model version 4

SUMMARYThe near-surface seismic structure (to a depth of about 1000 m), particularly the shear wave velocity (VS), can strongly affect the propagation of seismic waves and, therefore, must be accurately calibrated for ground motion simulations and seismic hazard assessment. The VS of the top (<300 m) crust is often well characterized from borehole studies, geotechnical measurements, and water and oil wells, while the velocities of the material deeper than about 1000 m are typically determined by tomography studies. However, in depth ranges lacking information on shallow lithological stratification, typically rock sites outside the sedimentary basins, the material parameters between these two regions are typically poorly characterized due to resolution limits of seismic tomography. When the alluded geological constraints are not available, models, such as the Southern California Earthquake Center (SCEC) Community Velocity Models (CVMs), default to regional tomographic estimates that do not resolve the uppermost VS values, and therefore deliver unrealistically high shallow VS estimates. The SCEC Unified Community Velocity Model (UCVM) software includes a method to incorporate the near-surface earth structure by applying a generic overlay based on measurements of time-averaged VS in top 30 m (VS30) to taper the upper part of the model to merge with tomography at a depth of 350 m, which can be applied to any of the velocity models accessible through UCVM. However, our 3-D simulations of the 2014 Mw 5.1 La Habra earthquake in the Los Angeles area using the CVM-S4.26.M01 model significantly underpredict low-frequency (<1 Hz) ground motions at sites where the material properties in the top 350 m are significantly modified by the generic overlay (‘taper’). On the other hand, extending the VS30-based taper of the shallow velocities down to a depth of about 1000 m improves the fit between our synthetics and seismic data at those sites, without compromising the fit at well-constrained sites. We explore various tapering depths, demonstrating increasing amplification as the tapering depth increases, and the model with 1000 m tapering depth yields overall favourable results. Effects of varying anelastic attenuation are small compared to effects of velocity tapering and do not significantly bias the estimated tapering depth. Although a uniform tapering depth is adopted in the models, we observe some spatial variabilities that may further improve our method.

Prophage Diversity of 'Candidatus Liberibacter asiaticus' Strains in California.

Huanglongbing (HLB) is a highly destructive citrus disease and is associated with a nonculturable bacterium, 'Candidatus Liberibacter asiaticus'. 'Ca. L. asiaticus' in the United States was first found in Florida in 2005 and is now endemic there. In California, 'Ca. L. asiaticus' was first detected in Hacienda Heights in Los Angeles County in 2012 and has now been detected in multiple urban locations in southern California. Knowledge of 'Ca. L. asiaticus' strain diversity in California is important for HLB management. In this study, genomic diversity among 10 'Ca. L. asiaticus' strains from six California locations were analyzed using a next-generation sequencing (NGS) (Illumina MiSeq and HiSeq) approach. Draft genome sequences of 'Ca. L. asiaticus' strains were assembled. Sequences of the 16S ribosomal RNA gene and nrdB confirmed 'Ca. L. asiaticus' identity. Prophages were detected in all 'Ca. L. asiaticus' strains. The California 'Ca. L. asiaticus' strains formed four prophage typing groups (PTGs): PTG1, with type 1 prophage only (strains from Anaheim, San Gabriel, and Riverside); PTG2, with type 2 prophage only (strains from Hacienda Heights); PTG1-3, with both type 1 and 3 prophages (a strain from Cerritos); and PTG1-2, with both type 1 and type 2 prophages (a strain from La Habra). Analyses of the terL sequence showed that all California 'Ca. L. asiaticus' strains were not introduced from Florida but likely from locations in Asia. Miniature inverted-repeat transposable elements were found in all 'Ca. L. asiaticus' strains, yet, a jumping-out event was detected in the 'Ca. L. asiaticus' strain from Cerritos. Altogether, this study demonstrated that the NGS approach focusing on prophage variation was sensitive and effective in revealing diversity of 'Ca. L. asiaticus' strains in California.

MEMORIAL TO ROBERT G. DOUGLAS (1937–2016)

Robert G. (Bob) Douglas, an internationally recognized micropaleontologist and marine geologist, passed away on January 26, 2016, after a long battle with cancer. During his career he pursued a diverse range of research interests, including the study of living foraminifera and modern environments, Cretaceous foraminiferal biostratigraphy, Cretaceous and modern paleoceanography and biogeography, and more. He published an extensive series of important and highly-cited articles, and he sat on a number of editorial boards and international scientific committees. Within every group that included Bob as a member, he was quickly recognized as a natural leader and a wise counselor. He was also a warm, thoughtful person with a great sense of humor and humility. A South Bay native, Bob’s interest in geology began during his childhood growing up in Palos Verdes, California. He and his brothers would hike around the Palos Verdes Peninsula, playing in the canyons, finding rocks, arrowheads and fossils, which sparked his curiosity, and ultimately lead him into a career in the Earth Sciences. He graduated from Redondo Union High School in 1955, and received his bachelor’s degree in Geology from the University of California at Santa Barbara in 1959. After graduating from UCSB, Bob worked as a geologist in Shell Oil’s Alaska Division before earning his PhD from the University of California at Los Angeles in 1966. At UCLA, Bob was part of the first group of graduate students working under the guidance of his PhD supervisor at UCLA, Helen N. Tappan. There Bob participated in seminars on micropaleontology and marine geology and in field trips to the coast that inspired his later work. Helen and her husband Alfred R. Loeblich Jr., who at the time was a chief scientist for oil exploration at Chevron Research Lab in La Habra, California, and …

Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake.

Tectonic motion across the Los Angeles region is distributed across an intricate network of strike‐slip and thrust faults that will be released in destructive earthquakes similar to or larger than the 1933 M6.4 Long Beach and 1994 M6.7 Northridge events. Here we show that Los Angeles regional thrust, strike‐slip, and oblique faults are connected and move concurrently with measurable surface deformation, even in moderate magnitude earthquakes, as part of a fault system that accommodates north‐south shortening and westerly tectonic escape of northern Los Angeles. The 28 March 2014 M5.1 La Habra earthquake occurred on a northeast striking, northwest dipping left‐lateral oblique thrust fault northeast of Los Angeles. We present crustal deformation observation spanning the earthquake showing that concurrent deformation occurred on several structures in the shallow crust. The seismic moment of the earthquake is 82% of the total geodetic moment released. Slip within the unconsolidated upper sedimentary layer may reflect shallow release of accumulated strain on still‐locked deeper structures. A future M6.1–6.3 earthquake would account for the accumulated strain. Such an event could occur on any one or several of these faults, which may not have been identified by geologic surface mapping.

Laboratory Colonization, Life History Observations, and Desiccation Tolerance of the Canyon Fly Fannia conspicua (Diptera: Fanniidae).

"Canyon flies" are flies within the Fannia benjamini Malloch species complex. These flies can be considerable pests to humans and animals due to their habit of feeding on animal body secretions such as tears, mucus, sweat, and blood. Adult "canyon flies" (Fannia conspicua Malloch) were collected from the coastal mountain community of La Habra Heights in Los Angeles County, CA, during late spring and early summer of 2011. Canyon flies were colonized in the laboratory and maintained for over two years. Larval growth, sex-specific adult emergence, and fecundity were evaluated quantitatively. At 25°C, male flies required a minimum of 22 d postoviposition to develop from egg to adult, with peak emergence occurring at 24-26 d; female flies required a minimum of 25 d postoviposition, with peak emergence occurring at 26-28 d. Female flies were capable of oviposition starting at 7 d postemergence, and produced a mean of 90.6±54.7 eggs over a 19-41-d life span. Canyon fly eggs were quite resistant to desiccation, with hatching rate of eggs reduced only after ≥12 wk of desiccation, and some successful hatching even when eggs were desiccated up to 28 wk. When immature flies were removed from their food source and subjected to continuous desiccation and starvation, flies at 3-d-old posthatching did not survive, and only 8% of flies at 5-d posthatching survived and completed development to the adult stage. Immature flies that were 7- or 11-d-old posthatching survived to adulthood in good numbers, having reached the mid to late L3 stage at the time of food removal. Exposure to desiccation in either the egg or larval stage had no effect on fecundity of surviving females. This extreme level of desiccation tolerance is likely an adaptation to increase survival in desert climates of the southwestern United States with long, hot summers and little precipitation, where Fannia conspicua are typically distributed.

The impact of satellite-adjusted NO<sub>x</sub> emissions on simulated NO<sub>x</sub> and O<sub>3</sub> discrepancies in the urban and outflow areas of the Pacific and Lower Middle US

Abstract. We analyze the simulation results from a CMAQ model and GOME-2 NO2 retrievals over the United States for August 2009 to estimate the model-simulated biases of NOx concentrations over six geological regions (Pacific Coast = PC, Rocky Mountains = RM, Lower Middle = LM, Upper Middle = UM, Southeast = SE, Northeast = NE). By comparing GOME-2 NO2 columns to corresponding CMAQ NO2 columns, we produced satellite-adjusted NOx emission ("GOME2009") and compared baseline emission ("BASE2009") CMAQ simulations with GOME2009 CMAQ runs. We found that the latter exhibited decreases of −5.6%, −12.3%, −21.3%, and −15.9 % over the PC, RM, LM, and SE regions, respectively, and increases of +2.3% and +10.0% over the UM and NE regions. In addition, we found that changes in NOx emissions generally mitigate discrepancies between the surface NOx concentrations of baseline CMAQ and those of AQS at EPA AQS stations (mean bias of +19.8% to −13.7% over PC, −13.8% to −36.7% over RM, +149.7% to −1.8% over LM, +22.5% to −7.8% over UM, +31.3% to −7.9% over SE, and +11.6% to +0.7% over NE). The relatively high simulated NOx biases from baseline CMAQ over LM (+149.7%) are likely the results of over-predictions of simulated NOx emissions, which could shed light on those from global/regional Chemical Transport Models. We also perform more detailed investigations on surface NOx and O3 concentrations in two urban and outflow areas, PC (e.g., Los Angeles, South Pasadena, Anaheim, La Habra and Riverside) and LM (e.g., Houston, Beaumont and Sulphur). From two case studies, we found that the GOME2009 emissions decreased surface NOx concentrations significantly in the urban areas of PC (up to 30 ppbv) and in those of LM (up to 10 ppbv) during the daytime and that simulated NOx concentrations from CMAQ with GOME2009 compare well to those of in-situ AQS observations. A significant reduction in NOx concentrations resulted in a comparable increase in surface O3 concentrations in the urban areas of PC (up to 30 ppbv) and the resulting simulated O3 concentrations compare well with in-situ surface O3 observations over South Pasadena, Anaheim, and Riverside. Over Houston, Beaumont, and Sulphur, large reductions in NOx emissions from CMAQ with GOME2009 coincides with large reduced concentrations of simulated NOx. These concentrations are similar to those of the EPA AQS NOx observations. However, the resulting simulated increase in surface O3 at the urban stations in Houston and Sulphur exacerbated preexisting high O3 over-predictions of the baseline CMAQ. This study implies that simulated low O3 biases in the urban areas of PC are likely caused by simulated high NOx biases, but high O3 biases in the urban areas of LM cannot be explained by simulated high NOx biases over the region. This study also suggests that both in-situ surface NOx and O3 observations should be used simultaneously to resolve issues pertaining to simulated high/low O3 bias and that remote-sensing data could be used as a constraint for bottom-up emissions. In addition, we also found that daytime O3 reductions over the outflow regions of LM following large reductions in NOx emissions in the urban areas are significantly larger than they are over outflow regions of PC. These findings provide policymakers in the two regions with information critical to establishing strategies for mitigating air pollution.

Adult <I>Fannia benjamini</I> Complex (Diptera: Muscidae) Activity in Southern California and Use of CO<SUB>2</SUB> as an Attractant

Diurnal activity of host-seeking "canyon flies" (Fannia benjamini complex) (Diptera: Muscidae) was determined on a warm, sunny day during their peak seasonal activity period (early July) in the coastal mountain community of La Habra Heights in Los Angeles County, California. High levels of activity persisted for several hours in the morning and evening, but peak abundance was within an hour after sunrise and an hour before sunset, when >600 flies (mainly Fannia conspicua Malloch) could be collected in 5 min from a person using a sweep net. Host-seeking activity was low during midday hours, when flies apparently were seeking shelter from the heat, and activity ceased after sunset. Potential bait materials, including some known to elicit a response by other host-seeking Diptera (water, rabbit feces, egg bait, milk bait, Limburger cheese, ethanol, and CO2) were tested for "canyon fly" response using CDC-type suction traps (without light). CO2 resulted in significantly higher capture of female "canyon flies" (up to approximately 2,000 flies per trap in a 6-h period) relative to traps baited with other materials or with no bait. Host-seeking activity in relation to distance from a putative developmental site was evaluated. The proportional capture of flies in CO2-baited suction traps was significantly explained by distance from a residential area planted with Aptenia cordifolia (L.) (Aizoaceae; red apple), a ground cover plant that is a developmental site for F. conspicua. Proportional trap capture rapidly decreased as distance from the residential area increased. Implications of these studies for "canyon fly" control are discussed.

Life History and Seasonal Abundance of Fannia benjamini Complex (Diptera: Muscidae) in Southern California

Abstract Seasonal abundance and life history of Fannia benjamini complex (Diptera: Muscidae) was studied in the coastal mountain community of La Habra Heights in Los Angeles County, California, with additional observations in drier, inland mountains in the Woodcrest area, Riverside County. The dominant species (>95% of fly collections) was Fannia conspicua Malloch, whereas Fannia benjamini Malloch also was present. Both species could be collected nearly year-round by netting adults (almost exclusively females) attracted to people, although F. benjamini was relatively more common in cooler weather (November-April). In La Habra Heights, adult activity peaked in June and July (both species), whereas peak activity in Woodcrest was late April through June for F. conspicua and February through April for F. benjamini. Field-collected adult females provided only water died within 2–4 d, whereas females provided with water plus a dry milk and sugar mixture survived up to 128–130 d in the laboratory. Males of F. conspicua (1–40 individuals) swarmed at heights of 0.5–4.0 m near Aptenia cordifolia (L.f.) Schwantes, an exotic, succulent, low-growing ground cover plant. Eggs of F. conspicua were deposited singly on older, decaying leaves of this plant, and adult F. conspicua emerged from Aptenia-covered areas in the field. In the laboratory, larvae of F. conspicua grazed on microbial surface films associated with Aptenia. Emergence of F. conspicua from field-collected soil-Aptenia mixtures (held in the laboratory) occurred from 1.5 to 5 mo after collection. Widespread Aptenia planting since the 1980s has probably resulted in F. conspicua becoming a severe human nuisance in some areas.

Life History and Seasonal Abundance of <I>Fannia benjamini</I> Complex (Diptera: Muscidae) in Southern California

Seasonal abundance and life history of Fannia benjamini complex (Diptera: Muscidae) was studied in the coastal mountain community ofLa Habra Heights in Los Angeles County, California, with additional observations in drier, inland mountains in the Woodcrest area, Riverside County. The dominant species (>95% of fly collections) was Fannia conspicua Malloch, whereas Fannia benjamini Malloch also was present. Both species could be collected nearly year-round by netting adults (almost exclusively females) attracted to people, although F. benjamini was relatively more common in cooler weather (November-April). In La Habra Heights, adult activity peaked in June and July (both species), whereas peak activity in Woodcrest was late April through June for F. conspicua and February through April for F. benjamini. Field-collected adult females provided only water died within 2-4 d, whereas females provided with water plus a dry milk and sugar mixture survived up to 128-130 d in the laboratory. Males of F. conspicua (1-40 individuals) swarmed at heights of 0.5-4.0 m near Aptenia cordifolia (L.f.) Schwantes, an exotic, succulent, low-growing ground cover plant. Eggs of F. conspicua were deposited singly on older, decaying leaves of this plant, and adult F. conspicua emerged from Aptenia-covered areas in the field. In the laboratory, larvae of F. conspicua grazed on microbial surface films associated with Aptenia. Emergence of F. conspicua from field-collected soil-Aptenia mixtures (held in the laboratory) occurred from 1.5 to 5 mo after collection. Widespread Aptenia planting since the 1980s has probably resulted in F. conspicua becoming a severe human nuisance in some areas.

Keeping Secrets Contributes To Another School Shooting

Keeping Secrets Contributes To Another School Shooting

Professional Stability…What You Can Do To Survive

Published in Oil & Gas Executive, Volume 1, Number 2, 1998, pages 34-39. Our industry is, and has been, in turbulent times. When we talk of turbulence, we generally are referring to the downside of the peak in industry employment that followed the collapse of oil prices (Fig. 1). During 1982-92, the upstream oil and gas sector lost more than 50%of the jobs that were created in the preceding 10 years. For me, however, it was equally turbulent on the front side of the peak. I was hired into Chevron's La Habra, California, laboratory in 1973, the first hire after nearly 4 years of a hiring freeze. The boom, related to the rise in oil prices, followed almost immediately. I worked in an exploratory research group that was looking for new ways to recover oil from old reservoirs. We had lots of wild ideas, and money for equipment and new laboratories was abundant. I then worked as a petroleum engineer in the Los Angeles basin doing million-dollar workovers to rejuvenate old wells. The rates of return were often more than 50%, and payout periods were less than 6 months. We had very clear guidance from senior corporate management: if we didn't spend our entire budget, they would find people who could. It was a time of double-digit pay raises - sometimes at 6-month intervals - and even "special" incentive payments. Oil was forecasted to be U.S. $50/bbl in a few years. Before 1982, turbulence was created by too few resources chasing too many opportunities. After 1982, turbulence was created by the opposite condition - too many resources chasing too few opportunities. This led to excessive costs, which meant jobs had to be eliminated. Fig. 2 illustrates how severely the oil price collapse affected jobs in a number of industries during the 10 years following the peak, with the most severe effects in the oil and gas industry. It is particularly instructive to look at employment in the Fortune 100 oil and gas companies during the last 25 years (Table 1). In 1973, 14 oil and gas companies were in the Fortune 100 and accounted for nearly 700,000 jobs. Of those companies, 11 were in the top 50.

Importance of patient education in disease management programmes

T he importance of patient education in disease management programmes was emphasised during the Second Annual Disease Management Congress [ Washington, D.C., US; September 1997 ]. Marian Ryan Henry, Regional Director of Health Education for MedPartners of La Habra, California, US, spoke of the need to identify both the processes for initiating patient education programmes and the tools and strategies to increase programme effectiveness.

Downhole seismic source

A prototype model of a downhole controlled seismic source has been built and field tested. This instrument is a swept‐frequency, penumatically powered seismic source that operates in the 10 to 100 Hz range. This particular version is a vertical‐dipole source and generates vertically polarized shear waves. The instrument is an improved version of a downhole monofrequency source first tested in the crust of Kilauea Lava Lake, Hawaii, in 1981. The present prototype source was field tested recently at the Chevron Oil Field Research facility in La Habra, California. Data from this test, combined with calculations for a full‐scale instrument, indicate that considerable amounts of energy can be coupled into the ground with this type of downhole source. Signals from these prototype sources are easily detectable at distances of 150 m or more. A larger version of the source is currently being designed and fabricated for use in 0.20 m diameter holes, and it will theoretically have a range 30 times greater than the current prototype model. This new seismic source has applications in scientific studies related to the Continental Scientific Drilling Program. The source also has applications in locating magma bodies for the Magma Energy Program and in evaluating oil reservoirs.

More views on the two‐career couple

The Education and Human Resources Committee sponsored a panel session on “The Two‐Career Couple” during the 1985 AGU Fall Meeting. Panelists were Gerard and Patricia Fryer (Hawaii Institute of Geophysics (HIG), Honolulu), Richard and Christina Scott (Acurex, Inc. and Earth Sciences Associates, Palo Alto), and Catherine Nigrini (private consultant, La Habra, Calif.). The panelists were asked to outline the stages in their personal and professional lives and to discuss the lessons they felt that they had learned and the advice that they wish others had given them. About 40 people attended the session; more than half of them were men, many of whom appeared to be mid‐career professionals.

To: “Tracing of rays through heterogenous media: An accurate and efficient procedure,” by R. T. Langan, L. Lerche, and R. T. Cutler, September 1985 GEOPHYSICS (v. 50, p. 1456–1465).

The company affiliations were reversed for two of the authors. The correct listings is as follows: R. T. Langan, Gulf Research and Development Co., Houston; currently Chevron Oil Field Research Co., P.O. Box 446, La Habra, CA 90631. I. Lerche, Gulf Research and Development Co., Houston; currently Dept. of Geology, University of South Carolina, Columbia, SC 29108.

A Review of: “Guide and Explanation for Remote Sensing Slide Sets.” By F. F. SABINS. (Remote Sensing Enterprises, PO Box 2893, La Habra, California 90681, U.S.A., 1981) Price $600.

(1983). A Review of: “Guide and Explanation for Remote Sensing Slide Sets.” By F. F. SABINS. (Remote Sensing Enterprises, PO Box 2893, La Habra, California 90681, U.S.A., 1981) Price $600. International Journal of Remote Sensing: Vol. 4, No. 2, pp. 481-482.

A model system for forecasting patronage on demand responsive transportation systems

Demand-responsive transportation (DRT) systems represent a broad class of public transportation options characterized by spatial and/or temporal flexibility in serving demand. These systems offer the potential to provide service in lower density areas. This paper presents a model system which provides DRT system designers with a behaviorally consistent and validated patronage forecasting procedure. The model system consists of three components: a work trip demand model; a non-work trip demand model; and a DRT service model. These components are applied in an equilibrium framework. The demand components of the system are disaggregate demand models. The work trip model forecasts modal split, while the non-work model forecasts trip frequency, time of day, mode and destination choice. The service model forecasts both wait time and ride time. The model was estimated on data from Rochester, New York, and validated against data from Davenport, Iowa and La Habra, California. Total daily trips by DRT appear to be forecast ±20–30%. A sketch planning model was also developed and validated against six other DRT sites with errors of a similar magnitude. The model system can analyze options such as varying the vehicle fleet or service area over the day, using differing vehicle sizes, alternate pricing policies, and improving vehicle speeds.

Grid-Orientation Effects and the Use of Orthogonal Curvilinear Coordinates in Reservoir Simulation

Robertson, G.E., Woo, P.T., Members SPE-AIME, Chevron Oil Field P.T., Members SPE-AIME, Chevron Oil Field Research Co., La Habra, Calif. Abstract Grid orientation effects in reservoir simulation recently have received considerable attention. Several authors have proposed methods to reduce or to eliminate these effects. However, the proposed methods require reprogramming of simulators based on standard techniques. The reprogramming effort can be considerable if the numerical model is highly complex, such as in steamflood simulation. An orthogonal curvilinear coordinate system that essentially eliminates the problem of grid orientation was investigated. With no reprogramming, this computing grid can be used readily in existing simulators. Such grids were used to study pattern steamfloods and pattern waterfloods. The results are compared in detail with those obtained by using conventional Cargesian grids. Grid orientation is shown to have a more pronounced effect on the saturation fronts than oil recovery, whether in a steamflood or a waterflood. It is concluded that orthogonal curvilinear grids can be used easily to estimate pattern flood performance without modification of the solution method. Introduction In a simulation study of unfavorable mobility displacement, the areal orientation of the grid system, with respect to the location of the injectors and producers, can affect the calculated results. This is referred to as the "grid-orientation" effect. Fig. 1 illustrates two Cartesian grid orientations for one-eighth of a repeated five-spot pattern. The "parallel" orientation has a direct-flow pattern. The "parallel" orientation has a direct-flow path along the grid lines between the injector and path along the grid lines between the injector and producer, whereas the path is indirect in the producer, whereas the path is indirect in the "diagonal" system. Using a repeated five-spot pattern, Todd et al., Holloway et al., and Yanosik and McCracken investigated grid-orientation effects in gas or waterfloods. Coats et al. reported grid-orientation effects in steamfloods. In all cases, the investigators found that grid orientation significantly affected the movement of saturation fronts and the breakthrough time. Oil recovery was affected to a lesser extent. The effect appears to increase as the mobility ratio becomes more unfavorable and as the transition zone across the saturation front shortens. Todd et al. presented the two-point mobility approximation to alleviate the grid-orientation effect. Holloway et al. introduced a transmissibility modification scheme to reduce this effect further. While these two schemes can be introduced readily into simulators using explicit relative permeability, it is difficult to implement the schemes in simulators using implicit or semi-implicit relative permeability. Yanosik and McCracken observed that the grid-orientation effect probably was caused by the lack of flow from a grid block to its diagonal neighbors and introduced a nine-point finite-difference formula to account for this flow. SPEJ p. 13