Large Time Differences Research Articles

Visco-plasticity stress-based solid dynamics formulation and time-stepping algorithms for stiff case

In this paper, the visco-plastic behavior of solids is formulated based on the Hellinger–Reissner variational principle. The latter provides an optimal basis to obtain an increased accuracy of computed stress by using independent space-discretizations of both displacement and stress fields. The formulation is further adapted to solid dynamics and in particular to so-called stiff case that is characterized with a large difference in stiffness and/or evolution time between different deformation modes, which presents a great challenge when integrating the dynamic response. For this class of problem, we here propose the algorithmic modifications leading to energy conserving or decaying schemes that can either preserve the total energy or dissipate the energy of higher modes, and thus control the overall stability of numerical computations with large steps over long period of time. Several numerical examples are presented to illustrate a very satisfying performance of the proposed approach and algorithm.

Patenting Fast and Slow: Examiner and Applicant Use of Prior Art

Previous studies have shown that an applicant’s ability to obtain a patent is inexorably linked to the random assignment of a patent examiner. However, not all patent examiners are created equal. Some patent examiners allow patent applications quickly within just one or two Office Actions resulting in only a few months of substantive patent prosecution. In contrast, other patent examiners constantly reject patents applications, which can result in unnecessarily delaying prosecution and years of substantive patent prosecution. This study focuses on how different examiners use prior art rejections to prolong or compact prosecution. Prior art rejections are one of the most important hurdles to obtaining a patent. Specifically, the use of prior art rejections directly impacts the time and effort it takes to obtain a patent. Overcoming anticipation and obviousness rejections are usually the most important and difficult obstacles to overcome before obtaining a patent. This empirical study focuses on how different types of examiners (i.e., fast/high volume versus slow/low volume) use prior art rejections to either compact or delay prosecution. Since patent examination is dependent on both examiner and applicant behavior, this study also evaluates how applicants respond to these prior art rejections to also prolong or compress prosecution. Unlike many studies, this is the first paper that evaluates patent quality based on both individual examiner characteristics as well as applicant behavior at the patent prosecution level. In sum, high volume, average volume and low volume examiners issued a patent in approximately 1.64 years, 3.07 years, and 5.85 years respectively. Thus, high volume examiners issue patents almost twice as quickly as average volume examiners and more than three times as fast as low volume examiners. This large difference in time can represent a huge investment in both capital and time for the applicant as well as the PTO. Additionally, this study finds that low volume examiners reject applications based mainly on obviousness, issuing over four times as many obviousness rejections per office action compared to high volume examiners. Furthermore, low volume examiners issue five times as many 102(a)/(g)/(e) rejections and two times as many 102(b) rejections. And applicants most commonly make a “missing element” argument to traverse a slow examiner’s 102(a)/(g)/(e) rejection at three times the rate of a fast examiner. This type of traversal strategy relies on the examiner’s misunderstanding of either the art or the claimed invention. Similarly, applicants also use the “missing elements” argument to traverse a slow examiner’s 103 rejection at five times the rate of a fast examiner. Finally, applicants are also three times more likely to use a “teaching away” or “unexpected results” argument to traverse a slow examiner compared to a fast examiner. Both of these arguments can again rely on either the examiner’s misunderstanding of the prior art or a misunderstanding of the claimed invention. This study demonstrates that different types of examiners use different strategies to maximize their “counts.” Specifically, low volume examiners will generally reject applications creating lengthy prosecution histories while forcing the applicant to narrow claims, while showing a misunderstanding of either the prior art and/or the claimed invention. In contrast, high volume examiners will usually only make one rejection then allow the case, thus creating a small prosecution history with only small amendments to the claims.

Rural-urban differences in the association between individual, facility, and clinical characteristics and travel time for cancer treatment

BackgroundGreater travel time to cancer care has been identified as a potential barrier to care as well as associated with worse health outcomes. While rural cancer patients have been shown to travel farther for care, it is not known what patient, facility, and clinical characteristics may differentially be associated with greater roundtrip travel times for cancer patients by rurality of residence. Identifying these factors will help providers understand which patients may be most in need of resources to assist with travel.MethodsUsing 2010–2014 Pennsylvania Cancer Registry data, we examined the association between patient, facility, and clinical characteristics with roundtrip patient travel time using multivariate linear regression models. We then estimated separate models by rural residence based on the Rural-Urban Continuum Code (RUCC) of a patient’s county of residence at diagnosis to understand how the association of each factor with travel time may vary for patients separated into metro residents (RUCC 1–3); and two categories of non-metro residents (RUCC 4–6) and (RUCC 7–9).ResultsIn our sample (n = 197,498), we document large differences in mean roundtrip travel time—mean 41.5 min for RUCC 1–3 patients vs. 128.9 min for RUCC 7–9 patients. We show cervical/uterine and ovarian cancer patients travel significantly farther; as do patients traveling to higher volume and higher-ranked hospitals.ConclusionsTo better understand patient travel burden, providers need to understand that factors predicting longer travel time may vary by rurality of patient residence and cancer type.

Passenger Safety in the Warsaw Metro. Research Report

Aim: The article presents the results of research on the evacuation times of passengers of three different trains used by the Warsaw metro. In emergency situations on metro trains, fast and safe evacuation is crucial for saving passengers’ health and lives. Evacuation from the tunnels of the Warsaw metro can only take place properly on underground platforms. The key parameter determining passenger safety is required safe evacuation time. Project and methods: Four evacuation experiments were carried out. In the first experiment, people on the train left the train into the tunnel, walked towards the station and climbed the stairs to the platform level. The experiment ended when all people entered the platform level. In the second experiment, the passengers went to the end of the train. After a fixed sound signal, the persons moved along the train and went out onto the platform. The study ended when all the people entered the platform. Experiment 3 investigated the times when a certain number of people passed through one or more doors of the train. In experiment 4, the aim was to investigate the time of people walking along the platform and up the stairs to the mezzanine level. Results: The longest recorded average time of passage through the whole train is 133.5 s during longitudinal evacuation. The shortest recorded exit time is 9 seconds, evacuees were deployed throughout the car without restrictions. In the train of type 81, for technical reasons, no experiment was carried out consisting of moving along the entire train, and it should be noted that this train has separate, closed carriages and to walk through the whole train it would be necessary to open each door between the train. Conclusions: The data from experiments II and IV were combined and extrapolated taking into account the evacuation time for the maximum number of passengers who can occupy the trains, i.e. 1,500 people on the Inspiro train, 1,454 people on the Alstom train and 1,200 people on Type 81 train. The results of the experiment indicate that the longest passage time in very unfavourable conditions, when passengers have to pass the whole train and then exit the platform registered for type 81 train and is almost 433 seconds. For Inspiro and Alstom trains, the time is almost 25% shorter. Such a large difference in time is related to the way of connecting individual carriages – to move from car to car in type 81 train, it is necessary to open wo doors each time (from the abandoned car and the car to which you are passing), while this activity is not performed on Inspiro and Alstom trains.

Efficient multi-year economic energy planning in microgrids

With energy systems, the problem of economic planning is decisive in the design of a low carbon and resilient future grid. Although several tools to solve the problem already exist in literature and industry, most tools only consider a single “typical year” while providing investment decisions that last around a quarter of a century. In this paper, we introduce why such an approach is limited and derive two approaches to correct this. The first approach, the Forward-Looking model, assumes perfect knowledge and makes investment decisions based on the full planning horizon. The second novel approach, the Adaptive method, solves the optimization problem in single year iterations, making incremental investment decisions that are dependant on previous years, with only knowledge of the current year. Comparing the two approaches on a realistic microgrid, we find little difference in investment decisions (maximum 21% difference in total cost over 20 years), but large differences in optimization time (up to 12000% time difference). We close the paper by discussing implications of forecasting errors on the microgrid planning process, concluding that the Adaptive approach is a suitable choice.

Random cross-observation intensity consistency method for large-scale SAR images mosaics: An example of Gaofen-3 SAR images covering China

Large-scale microwave remote sensing research requires multiple synthetic aperture radar (SAR) image mosaics. However, owing to multiple factors, different SAR images frequently exhibit intensity differences. This leads to poor intensity continuity after mosaicking, making SAR image interpretation extremely difficult. The existing method assumes that SAR images have been subject to strict radiometric calibration and mainly focuses on intensity balancing to minimize the intensity difference between adjacent images. This method is not effective when the intensity difference between SAR images is large. In this paper, a novel random cross-observation intensity consistency (RCOIC) algorithm is proposed to eliminate the intensity differences for SAR image mosaics. The proposed algorithm is based on global intensity constraints. First, source images are downsampled. Then, the gain correction coefficients of each image in a study area are accurately estimated through random cross-observation. Further, multi-view local intensity correction of each image in the study area is performed using the overlapping areas of adjacent images, and a low-resolution intensity reference map covering the study area is generated. Finally, the intensities of high-resolution source images are corrected by constructing local independent linear models of images based on the low-resolution intensity reference map. Gaofen-3 satellite images with large ranges and large time differences, covering most of China's land area, were selected to test the effect of the newly developed algorithm. After processing, the overall visual effect was good after mosaicking, the intensity transitions at the edges of the images were smooth, the intensity distributions corresponded better to actual ground objects, and the statistical result of adjacent images overlapping regions was good. This validates the reliability of the algorithm.

Golden news? Analysis of summarizing coverage of the Olympic Winter Games 2018 on German TV

A maximum amount of media coverage is desirable for every sport to attract potential fans, new active members, and sponsors. The Olympic Games draw large audiences and are therefore a chance for niche sports to enter the big media stage. Large time differences between the hosting city and the audiences’ home countries sometimes limit the amount of live coverage viewers can consume – increasing the importance of summarizing coverage formats like bulletins and news shows. This study analyzes this type of coverage about the Olympic Games 2018 on German TV and tries to find predictors for variances in coverage time, with the help of news values theory. Results show that the success of national athletes is by far the strongest predictor, while simplicity, identification, and surprise play a lesser role and tradition and gender seem to make no significant difference in the amount of summarizing coverage a competition yields.

An objective comparison of common vacuum assisted resin infusion processes

This study executed an objective comparison between Resin Infusion methods currently used, providing a level comparison in identical circumstances. Six different resin infusion methods including VARTM, SCRIMP, CAPRI, DBVI, VAP, and PI were investigated to discern if the modifications made relevant to the standard VARTM process have a distinguishable effect, and how significant the effect was. Process parameters were found to vary significantly between methodologies, with large differences in infusion time, laminate pressure and relaxation, and resin usage. Fibre volume fractions were found to vary significantly both between methodologies and along the infusion length of some panels. Differences of up to 13% and 10% were found in short beam strength and compression strength between the infusion methods. There was found to be no significant difference in void content between methodologies once the best process parameters had been established, with the exception of PI which resulted in a significant increase.

Comparação entre o modelo de malha móvel e o modelo de fonte de quantidade de movimento para a simulação numérica do princípio de funcionamento de tanques misturadores

O presente trabalho tem o intuito de apresentar uma comparação entre dois modelos numéricos capazes de simular o princípio de funcionamento de tanques misturadores, os quais são utilizados em diversas indústrias químicas, entre elas, para a produção de biodiesel. O objetivo é realizar uma comparação entre os resultados obtidos com estes modelos e os resultados encontrados na literatura, a fim de mostrar a capacidade de predição dos modelos desenvolvidos e o esforço computacional de cada um deles. As simulações numéricas foram realizadas utilizando o software FLUENT, baseado no Método de Volumes Finitos (MVF). A comparação dos resultados entre o presente trabalho e dados encontrados na literatura, foi realizada a partir da previsão dos campos de velocidade monitorados no escoamento. Em geral, foi encontrado bom acordo entre os resultados do presente trabalho e resultados da literatura, com relação ao comportamento do escoamento, em determinados pontos que foram analisados no interior do tanque. Foi atestado também, uma grande diferença no tempo e esforço computacional entre os dois modelos numéricos.

Understanding node-link and matrix visualizations of networks: A large-scale online experiment

AbstractWe investigated human understanding of different network visualizations in a large-scale online experiment. Three types of network visualizations were examined: node-link and two different sorting variants of matrix representations on a representative social network of either 20 or 50 nodes. Understanding of the network was quantified using task time and accuracy metrics on questions that were derived from an established task taxonomy. The sample size in our experiment was more than an order of magnitude larger (N = 600) than in previous research, leading to high statistical power and thus more precise estimation of detailed effects. Specifically, high statistical power allowed us to consider modern interaction capabilities as part of the evaluated visualizations, and to evaluate overall learning rates as well as ambient (implicit) learning. Findings indicate that participant understanding was best for the node-link visualization, with higher accuracy and faster task times than the two matrix visualizations. Analysis of participant learning indicated a large initial difference in task time between the node-link and matrix visualizations, with matrix performance steadily approaching that of the node-link visualization over the course of the experiment. This research is reproducible as the web-based module and results have been made available at: https://osf.io/qct84/.

An Original Monomer Sampling from a Ready-Made Aβ42 NMR Fibril Suggests a Turn-β-Strand Synergetic Seeding Mechanism.

Aggregation of amyloid beta (Aβ) is a central step of Alzheimer's disease. Aβ42 monomers are building blocks in the formation of both "on pathway" intermediate structures and "off pathway" oligomers. How to sample an Aβ monomer becomes a problem however due to the instinct of Aβ high flexibility and diversity as well as aggregation propensity. Currently, (1) most samplings focus on either the ready-made helix-rich 1Z0Q/1IYT NMR structure, or the completely extended conformation, but (2) few on a ready-made Aβ NMR fibril (i. e., 2BEG). Here we compare the simulation results from sampling in scheme (1) with that in scheme (2), and find that the coil and β-sheet contents in the 1Z0Q-sampled system are comparable to the counterparts in the 2BEG-sampled system, but with a large difference in simulation time and dynamics character. 1Z0Q-sampled system not only takes several times longer than the 2BEG-sampled one, and only β1-seeding dynamics characteristic is observed probably due to far insufficient conformation transition in the limited simulation time. Two dynamics characteristics of Aβ42 folding observed experimentally, that either β1 region or β2 region aggregates first, reproduce in the present simulations for 2BEG-sampled system however, suggesting a preferential sampling in the future simulation. In addition, a turn-β-strand synergetic seeding mechanism of aggregation is first proposed based on the trajectory analyses on the four regions of Aβ42 chain.

The molecular evolution of C4 photosynthesis: opportunities for understanding and improving the world's most productive plants.

C4 photosynthesis is a convergent evolutionary trait that enhances photosynthetic efficiency in a variety of environmental conditions. It has evolved repeatedly following a fall in atmospheric CO2 concentration such that there is up to a 30 million year difference in the amount of time that natural selection has had to improve C4 function between the oldest and youngest C4 lineages. This large difference in time, coupled with the phylogenetic distance between lineages, has resulted in a large disparity in anatomy, physiology, and biochemistry between extant C4 species. This review summarizes the myriad of molecular sequence changes that have been linked to the evolution of C4 photosynthesis. These range from single nucleotide changes to duplication of entire genes, and provide a roadmap for how natural selection has adapted enzymes and pathways for enhanced C4 function. Finally, this review discusses how this molecular diversity can provide opportunities for understanding and improving photosynthesis for multiple important C4 food, feed, and bioenergy crops.

Predicting international students' clinical and academic grades using two language tests (IELTS and C-test): A correlational research study

Academic English tests are used to ascertain if international English as a Second Language nursing students have sufficient language skills to commence their nursing degrees, and later, if they have sufficient English for nursing registration. However, an academic English test may not be appropriate for clinical contexts. This study examines the relationship between two types of English test and the performance of forty-nine undergraduate international nursing students in both their first year of theory-centred academic topics and practice-centred clinical topics. An academic English test, called the International English Language Testing System (IELTS), and a general English proficiency/processing speed test using a variation of the cloze-test (C-test) format were administered at the commencement of the students' course of study. At the end of one year, grade percentages were collected. It was found that both the IELTS test and the C-test were significantly correlated to both types of topic, albeit with different patterns. The two English tests were also tested for similarities in the constructs they measured, with a significant overlap found. The implications are to rethink the way English tests are applied to entry in university degrees involving a clinical component and, by extension, to direct universities to rethink how nursing students are supported during their degree. The question is also raised about the practice of using academic English tests for professional nursing registration purposes. The benefits of the two testing approaches are also considered, particularly the large differences in monetary outlay and time found between the two tests, given their performance in explaining the variance in grade outcomes.

Effects of reverse seasonal submersion on the germination and persistence of soil seed banks in hydro‐fluctuation belts

AbstractThe construction of the Three Gorges Dam has resulted in the occurrence of reverse seasonal water‐level fluctuations. The species composition and quantity of riparian soil seed banks collected from four hydro‐fluctuation belts were assessed by simulating different submersion cycles to determine the effects of reverse seasonal water‐level fluctuations on the germination and persistence of soil seed banks in the Three Gorges Reservoir Region. Results showed the number of species that germinated from the soil seed bank decreased with submersion. The number of germinated seeds in soil seed banks after submersion for 7 months in Xingshan, Zigui, Wanzhou, and Zhongxian decreased by 60%, 53%, 57%, and 57%, respectively, relative to the control. The species diversity index and seed density of germinated seeds in soil seed banks also significantly decreased with prolongation of submersion time. Seed density decreased by 93%, 83%, 76%, and 72%, respectively, after 7 months of submersion. Species composition and dominance within the soil seed bank changed over time due to submersion. In general, reverse seasonal submersion negatively impacts the germination and persistence of soil seed banks. The response of soil seed bank germination and persistence to reverse seasonal submersion became the key factor determining the heterogeneity in the spatial distribution of the soil seed bank in hydro‐fluctuation belts due to the large differences in submersion time between areas at various elevations.

Spontaneous ignition behaviour of coal dust accumulations: A comparison of extrapolation methods from lab-scale to industrial-scale

Smouldering fires and explosions arising from self-ignition of coal dust deposits represent a serious hazard for human beings, environment and industry. It is essential for plant operators to know the conditions (temperature, duration and quantities) at which storage will be safe. In this work, self-ignition behaviour of three bituminous coal dusts in large scales are theoretically studied, based on the experimental data obtained via a standardized hot-basket apparatus. A comprehensive 2-D transient model is developed, using a 2nd-order reaction kinetics considering both coal and oxygen consumptions, to investigate self-ignition parameters of coal dust accumulations. The numerical model shows a less conservative prediction compared with the steady-state methods. The computed self-ignition temperature and ignition delay time show a satisfaction agreement with lab-scale experimental results. In addition, the influences of ambient temperature and moisture content are analysed. The result shows that the moisture content delays the ignition and a small variation of the ambient temperature nearby the critical condition will lead to a large difference in the ignition delay time.

Memory-Based Deception Detection: Extending the Cognitive Signature of Lying From Instructed to Self-Initiated Cheating.

From a cognitive perspective, lying can be regarded as a complex cognitive process requiring the interplay of several executive functions. Meta‐analytic research on 114 studies encompassing 3,307 participants (Suchotzki, Verschuere, Van Bockstaele, Ben‐Shakhar, & Crombez, 2017) suggests that computerized paradigms can reliably assess the cognitive burden of lying, with large reaction time differences between lying and truth telling. These studies, however, lack a key ingredient of real‐life deception, namely self‐initiated behavior. Research participants have typically been instructed to commit a mock crime and conceal critical information, whereas in real life, people freely choose whether or not to engage in antisocial behavior. In this study, participants (n = 433) engaged in a trivia quiz and were provided with a monetary incentive for high accuracy performance. Participants were randomly allocated to either a condition where they were instructed to cheat on the quiz (mimicking the typical laboratory set‐up) or to a condition in which they were provided with the opportunity to cheat, yet without explicit instructions to do so. Assessments of their response times in a subsequent Concealed Information Test (CIT) revealed that both instructed cheaters (n = 107) and self‐initiated cheaters (n = 142) showed the expected RT‐slowing for concealed information. The data indicate that the cognitive signature of lying is not restricted to explicitly instructed cheating, but it can also be observed for self‐initiated cheating. These findings are highly encouraging from an ecological validity perspective.

Both saccadic and manual responses in the amblyopic eye of strabismics are irreducibly delayed.

Abnormal early visual development can result in a constellation of neural and visual deficits collectively known as amblyopia. Among the many deficits, a common finding is that both saccadic and manual reaction times to targets presented to the amblyopic eye are substantially delayed when compared to the fellow eye or to normal eyes. Given the well-known deficits in contrast sensitivity in the amblyopic eye, a natural question is whether the prolonged reaction times are simply a consequence of reduced stimulus visibility. To address this question, in Experiment 1 we measure saccadic reaction times (RT) to perifoveal stimuli as a function of effective stimulus contrast (i.e., contrast scaled by the amblyopic eye's contrast threshold). We find that when sensory differences between the eyes are minimized, the asymptotic RTs of our anisometropic amblyopes were similar in the two eyes. However, our results suggest that some strabismic amblyopes have an irreducible delay at the asymptote. That is, even when the sensory differences of the stimulus were accounted for, these observers still had large interocular differences (on average, 77 ms) in saccadic reaction time. In Experiment 2, to assess the role of fixation on saccadic reaction time we compared reaction time with and without a foveal target (the “gap effect”). Our results suggest that, while removing the fixation target does indeed speed up reaction time in the amblyopic eye, the gap effect is similar in the two eyes. Therefore, the gap effect does not eliminate the irreducible delay in the amblyopic eye. Finally, in Experiment 3 we compared the interocular differences in saccadic and manual reaction times in the same observers. This allowed us to determine the relationship between the latencies in the two modalities. We found a strong correlation between the differences in saccadic and manual reaction times; however, the manual RT difference is about half that of saccadic RT, suggesting that there may be two separable effects on saccadic reaction time: (a) a central problem with directing actions to a target, related to disengagement of attention at the fovea, which results in delays in both saccadic and manual reaction times, and (b) a further delay in saccadic reaction times because of the motor refractory period from a previous saccade or microsaccade, made in an attempt to stabilize the amblyopic eye of strabismics.

Impact of clinical factors and UGT1A9 and CYP2B6 genotype on inter-individual differences in propofol pharmacokinetics.

Propofol is one of the most widely used fast-acting intravenously administered anesthetics. However, although large inter-individual differences in dose requirements and recovery time have been observed, there are few previous studies in which the association between several potential covariates, including genetic factors such as the UGT1A9 and CYP2B6 genotypes, and propofol pharmacokinetics was simultaneously examined. This study aimed to identify factors determining propofol pharmacokinetics. Eighty-three patients were enrolled, and their blood samples were collected 1, 5, 10, and 15min after administering a single intravenous bolus of propofol at a dose of 2.0ml/kg to measure propofol plasma concentration. Area under the time-plasma concentration curve from zero up to the last measurable time point (AUC15min) was determined from the concentration data. The inter-individual variability of the propofol pharmacokinetics was evaluated by investigating relationships between AUC15min and genotype of UGT1A9 and CYP2B6; clinical factors, such as age, sex, body mass index (BMI), and preoperative hematological examination; and hemodynamic variables measured by a pulse dye densitogram analyzer. The Spearman rank correlation coefficient and the Mann-Whitney U test were used for the statistical analysis of continuous and categorical values, respectively. Subsequently, clinical factors that had p values of<0.05 in the univariate analysis were examined in a multivariate analysis using multiple linear regression analysis. Age, BMI, indocyanine green disappearance ratio (K-ICG), hepatic blood flow (HBF), preoperative hemoglobin level, and sex were correlated with AUC15min (p<0.05) in univariate analysis. Multivariate analysis performed to adjust for age, BMI, K-ICG, HBF, preoperative hemoglobin level, and sex revealed only BMI as an independent factor associated with AUC15min. This study demonstrated that BMI influences propofol pharmacokinetics after its administration as a single intravenous injection, while UGT1A9 and CYP2B6 SNPs, other clinical factors, and hemodynamic variables do not. These results suggest that BMI is an independent factor associated with propofol pharmacokinetics in several potential covariates. University Hospital Medical Information Network (UMIN000022948).

Temperature variations in the southern Great Lakes during the last deglaciation: Comparison between pollen and GDGT proxies

Our understanding of deglacial climate history in the southern Great Lakes region of the United States is primarily based upon fossil pollen data, with few independent and multi-proxy climate reconstructions. Here we introduce a new, well-dated fossil pollen record from Stotzel-Leis, OH, and a new deglacial temperature record based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) at Silver Lake, OH. We compare these new data to previously published records and to a regional stack of pollen-based temperature reconstructions from Stotzel-Leis, Silver Lake, and three other well-dated sites. The new and previously published pollen records at Stotzel-Leis are similar, but our new age model brings vegetation events into closer alignment with known climatic events such as the Younger Dryas (YD). brGDGT-inferred temperatures correlate strongly with pollen-based regional temperature reconstructions, with the strongest correlation obtained for a global soil-based brGDGT calibration (r2 = 0.88), lending confidence to the deglacial reconstructions and the use of brGDGT and regional pollen stacks as paleotemperature proxies in eastern North America. However, individual pollen records show large differences in timing, rates, and amplitudes of inferred temperature change, indicating caution with paleoclimatic inferences based on single-site pollen records. From 16.0 to 10.0ka, both proxies indicate that regional temperatures rose by ∼10 °C, roughly double the ∼5 °C estimates for the Northern Hemisphere reported in prior syntheses. Change-point analysis of the pollen stack shows accelerated warming at 14.0 ± 1.2ka, cooling at 12.6 ± 0.4ka, and warming from 11.6 ± 0.5ka into the Holocene. The timing of Bølling-Allerød (B-A) warming and YD onset in our records lag by ∼300–500 years those reported in syntheses of temperature records from the northern mid-latitudes. This discrepancy is too large to be attributed to uncertainties in radiocarbon dating, and correlation between pollen and brGDGT temperature reconstructions rules out vegetation lags as a cause. However, the YD termination appears synchronous among the brGDGT record, regional pollen stack, and Northern Hemisphere stack. The cause of the larger and lagged temperature changes in the southern Great Lakes relative to Northern Hemisphere averages remains unclear, but may be due to the effects of continentality and ice sheet extent on regional climate evolution.

On the Performance of Tailored Base-Surge Policies: Theory and Application at Walmart.Com

Problem Definition: Many import items sold at Walmart.com have two suppliers: one is faster and has a random production capacity limit while the other is slower and has infinite capacity. The lead time difference of the two suppliers could be as large as 12 weeks. Walmart.com faces an important and challenging supply chain problem and must make routine inventory replenishment decisions. Academic/Practical Relevance: Dual-sourcing inventory models have been extensively studied in academia and dual-sourcing strategies have been widely implemented in practice. Recently, the so-called Tailored Base-Surge (TBS) policy has begun to receive more attention and demonstrated good performance in existing dual-sourcing models. TBS is intuitive and easy to manage: a constant-order is placed from the slow (regular) supplier every period and a base-stock policy is adapted from the fast (express) supplier. Methodology: This paper develops a new dual-sourcing inventory model incorporating large lead time difference as well as random capacity of the express supplier, and investigates the performance of TBS both theoretically and empirically by using Walmart’s data. Results: We prove that a TBS policy is asymptotically optimal as the regular lead time grows, extending the previous asymptotic optimality of TBS policies in the dual-sourcing system without random capacities. We complement the theory and compare TBS with three well-known heuristics in a “simulated” real-world setting through model calibration by using historical sales data from Walmart.com. Our results demonstrate that TBS outperforms others as for minimizing the long-run average inventory cost. In particular, the inventory cost would be reduced by at least 33% if adapting a TBS policy. Our results also suggest that at an aggregate level, TBS could reduce Weeks of Supply by 2.7 weeks while increasing Met Demand by 3.3% compared with the single-sourcing policy using only the import supplier. Managerial Implications: Our results show that if the proposed dual-sourcing model and algorithm are adapted, Walmart’s inventory system would be significantly improved especially for import items.