Observed Differences In Performance Research Articles

Comparing large lecture mechanics curricula using the Force Concept Inventory: A five thousand student study

The performance of over 5000 students in introductory calculus-based mechanics courses at the Georgia Institute of Technology was assessed using the Force Concept Inventory (FCI). Results from two different curricula were compared: a traditional mechanics curriculum and the Matter & Interactions (M&I) curriculum. Both were taught with similar interactive pedagogy. Post-instruction FCI averages were significantly higher for the traditional curriculum than for the M&I curriculum; the differences between curricula persist after accounting for factors such as pre-instruction FCI scores, grade point averages, and SAT scores. FCI performance on categories of items organized by concepts was also compared; traditional averages were significantly higher in each concept. We examined differences in student preparation between the curricula and found that the relative fraction of homework and lecture topics devoted to FCI force and motion concepts correlated with the observed performance differences. Concept inventories, as instruments for evaluating curricular reforms, are generally limited to the particular choice of content and goals of the instrument. Moreover, concept inventories fail to measure what are perhaps the most interesting aspects of reform: the non-overlapping content and goals that are not present in courses without reform.

Planning with Specialized SAT Solvers

Logic, and declarative representation of knowledge in general, have long been a preferred framework for problem solving in AI. However, specific subareas of AI have been eager to abandon general-purpose knowledge representation in favor of methods that seem to address their computational core problems better. In planning, for example, state-space search has in the last several years been preferred to logic-based methods such as SAT. In our recent work, we have demonstrated that the observed performance differences between SAT and specialized state-space search methods largely go back to the difference between a blind (or at least planning-agnostic) and a planning-specific search method. If SAT search methods are given even simple heuristics which make the search goal-directed, the efficiency differences disappear.

Measuring competitive advantage with an asset-light valuation model

Defining competitive advantage as the ability of a firm to generate returns in excess of its synthetic normal returns; the present study develops an “asset-light” valuation model to capture intangible strategic resources, that do not appear on balance sheets and could explain abnormal returns. Three propositions are derived from the model: (1) firms emphasizing light assets over tangible assets, generate superior performance; (2) at a given level of synthetic normal returns, firms possessing more “light” assets have superior performance; and (3) to achieve a given book rate of return, firms with more light assets require fewer tangible assets as inputs. An empirical study of the global semiconductor industry significantly supports all three propositions. The results show that, the excess returns observed across an industry reflect heterogeneity in the “light assets” possessed by the firms, and provide an explanation for observed differences in performance. Key words: Competitive advantage, asset-light valuation, semiconductor industry.

Understanding Export Led Growth and Late Industrialisation to Explain the Differences in the Post Reform Performance of India and China

Both India and China began to reform in the early eighties, with the Indian reforms being very slow until 1991-92 after which they 'take-off' While there are many differences the crucial difference is that China adopted the same export led growth (ELG) policies of the successful East Asian economies - South Korea, Taiwan, Singapore, Hong Kong and Thailand, while Indian policies have been distinctly laissez-faire. Orthodoxy’s false understanding of ELG (the East Asian trade strategy), which was as far from laissez faire as can be imagined, is the root cause of the failure of other diversified economies in their pursuit of open door policies. Purposeful and massive under valuation of their currency was part of the East Asian strategy, which while making the ratio of exportables to importables close to their international prices, provided for simultaneous export growth and import substitution; something not possible in orthodoxy’s standard work horse -the 2x2x2 model of international trade. Simultaneous import substitution and export production is theoretically possible for economies with idle resources, with the introduction of third non-traded goods sector. ELG can therefore with compatible with little or no protectionism. This aspect of the East Asian trade (and development) strategy has been poorly understood even by the structuralists who otherwise (on the aspect of the state’s involvement) had demolished the liberal laissez-faire thesis. India's reforms have resulted in considerable discrimination against the manufacturing enterprises. Exports have grown far more slowly than was otherwise possible. The more equal distribution of income in China, and the differences in the macroeconomic policies explain most of the other observed performance differences between the two countries on aspects such as the inward flow of FDI, investment, savings, growth of particular industries. Some of he crucial dimensions of the macroeconomic policies consistent with ELG in the context of China are brought out. These are structural undervaluation of the currency, expansionary monetary policy and exchange rate targeting with only one way openness to the capital account, if at all. The character of FDI itself, which differs sharply between the two countries is related to the differences in the macro economic policies. The Chinese and the East Asian success extends the notion of 'late industrialisation' to one where external demand (along with domestic demand) is realised for the high speed expansion of manufacturing ELG. The supply side of the same strategy is build on exploiting ‘idle’ and underutilised labour which alone is capable of generating the vast gains from trade. Standard models gains from trade are incomparable small in relation. A significant part of the gains do accrue to the destination countries in the from of falling prices so that there are few political difficulties in the pursuit of ELG even by large countries like China. Thus ELG is more akin to a Lewisian process that employs previously underemployed labour for tradables goods production with rising (to high level) investment rates. India is more than ripe for ELG. It can ignore the lessons from the Chinese experience only at much cost to its growth. High growth in excess of 9% is possible with ELG since even with conservatism it is achieving 6%. This paper also argues that the mistaken pursuit of laissez-faire as being export led growth in India would only result in the further hollowing out of manufacturing.

Penalized maximum likelihood reconstruction for improved microcalcification detection in breast tomosynthesis.

We examined the application of an iterative penalized maximum likelihood (PML) reconstruction method for improved detectability of microcalcifications (MCs) in digital breast tomosynthesis (DBT). Localized receiver operating characteristic (LROC) psychophysical studies with human observers and 2-D image slices were conducted to evaluate the performance of this reconstruction method and to compare its performance against the commonly used Feldkamp FBP algorithm. DBT projections were generated using rigorous computer simulations that included accurate modeling of the noise and detector blur. Acquisition dose levels of 0.7, 1.0, and 1.5 mGy in a 5-cm-thick compressed breast were tested. The defined task was to localize and detect MC clusters consisting of seven MCs. The individual MC diameter was 150 μm. Compressed-breast phantoms derived from CT images of actual mastectomy specimens provided realistic background structures for the detection task. Four observers each read 98 test images for each combination of reconstruction method and acquisition dose. All observers performed better with the PML images than with the FBP images. With the acquisition dose of 0.7 mGy, the average areas under the LROC curve (A(L)) for the PML and FBP algorithms were 0.69 and 0.43, respectively. For the 1.0-mGy dose, the values of A(L) were 0.93 (PML) and 0.7 (FBP), while the 1.5-mGy dose resulted in areas of 1.0 and 0.9, respectively, for the PML and FBP algorithms. A 2-D analysis of variance applied to the individual observer areas showed statistically significant differences (at a significance level of 0.05) between the reconstruction strategies at all three dose levels. There were no significant differences in observer performance for any of the dose levels.

ON THE DESIGN OF OPTIMIZATION ALGORITHMS FOR PREDICTION OF MOLECULAR INTERACTIONS

This article presents a comprehensive study on the main characteristics of a novel optimization algorithm specifically designed for simulation of protein-ligand interactions. Though design of optimization algorithms has been a research issue extensively studied by computer scientists for decades, the emerging applications in bioinformatics such as simulation of protein-ligand interactions and protein folding introduce additional challenges due to (1) the high dimensionality nature of the problem and (2) the highly rugged landscape of the energy function. As a result, optimization algorithms that are not carefully designed to tackle these two challenges may fail to deliver satisfactory performance. This study has been motivated by the observation that the RAME (Rank-based Adaptive Mutation Evolutionary) optimization algorithm specifically designed for simulation of protein-ligand docking has consistently outperformed the conventional optimization algorithms by a significant degree. The experimental results reveal that the RAME algorithm is capable of delivering superior performance to several alternative versions of the genetic algorithm in handling highly-rugged functions in the high-dimensional vector space. This article also reports experiments conducted to analyze the causes of the observed performance difference. The experiences learned provide valuable clues for how the proposed algorithm can be effectively exploited to tackle other computational biology problems.

Comparison of dry laser printer versus paper printer in full-field digital mammography

Paper printers have been used to document radiological findings in some hospitals. It is critical to establish whether paper printers can achieve the same efficacy and quality as dry laser printers for full-field digital mammography (FFDM). To compare the image quality and detection rate of dry laser printers and paper printers for FFDM. Fifty-five cases (25 with single clustered microcalcifications and 30 controls) were selected by a radiologist not participating in the image review. All images were printed on film and paper by one experienced mammography technologist using the processing algorithm routinely used for our mammograms. Two radiologists evaluated hard copies from dry laser printers and paper printers for image quality and detectability of clustered microcalcifications. For the image quality comparisons, agreement between the reviewers was evaluated by means of kappa statistics. The significance of differences between both of the printers was determined using Wilcoxon's signed-rank test. The detection rate of two printing systems was evaluated using receiver operating characteristic (ROC) analysis. From 110 scores (55 patients, two readers) per printer system, the following quality results were achieved for dry laser printer images: 70 (63.6%) were rated as good and 40 (36.4%) as moderate. By contrast, for the paper printer images, 25 scores (22.7%) were rated as good and 85 (77.3%) as moderate. Therefore, the image quality of the dry laser printer was superior to that achieved by the paper printer (P=0.00). The average area-under-the-curve (Az) values for the dry laser printer and the paper printer were 0.991 and 0.805, respectively. The difference was 0.186. Results of ROC analysis showed significant difference in observer performance between the dry laser printer and paper printer (P=0.0015). The performance of dry laser printers is superior to that of paper printers. Paper printers should not be used in FFDM.

Application Performance on the Tri-Lab Linux Capacity Cluster - TLCC

In a recent acquisition by DOE/NNSA several large capacity computing clusters called TLCC have been installed at the DOE labs: SNL, LANL and LLNL. TLCC architecture with ccNUMA, multi-socket, multi-core nodes, and InfiniBand interconnect, is representative of the trend in HPC architectures. This paper examines application performance on TLCC contrasting them with Red Storm/Cray XT4. TLCC and Red Storm share similar AMD processors and memory DIMMs. Red Storm however has single socket nodes and custom interconnect. Micro-benchmarks and performance analysis tools help understand the causes for the observed performance differences. Control of processor and memory affinity on TLCC with the numactl utility is shown to result in significant performance gains and is essential to attenuate the detrimental impact of OS interference and cache-coherency overhead. While previous studies have investigated impact of affinity control mostly in the context of small SMP systems, the focus of this paper is on highly parallel MPI applications.

A comparison of photosynthesis-dependent stomatal models using twig cuvette field data for adult beech ( Fagus sylvatica L.)

Six photosynthesis-dependent stomatal models were tested and compared against twig cuvette gas exchange data for adult common beech ( Fagus sylvatica L.). The models differed in the use of (1) either leaf surface CO 2 concentration ( C s) or leaf intercellular CO 2 concentration ( C i), and of (2) either measured environmental humidity variables or a crudely calculated leaf water potential to simulate the effect of drought stress on stomatal conductance. The models applying C s performed slightly better than the models applying C i. The models based on environmental humidity variables performed distinctly better than the models applying a calculated leaf water potential. Several explanations for the observed performance differences between models applying C s or C i were brought forward and discussed.

Comparison of viewing angle and observer performances in different types of liquid-crystal display monitors

It is known that the performance of liquid-crystal display (LCD) monitors, such as the luminance and contrast ratio, is dependent on the viewing angle. Our purpose in this study was to compare the angular performance and the effect on observer performance of different types of LCD monitors. The luminance performance and contrast ratio as a function of viewing angle (-60 degrees to 60 degrees) in each direction for two types of LCD monitors, namely, a general-purpose LCD monitor and one especially designed for medical use, were measured in this study. Furthermore, the observer performance at various viewing angles in the horizontal direction for a medical-grade LCD monitor was investigated by eight observers based on a contrast-detail diagram. The two types of LCD monitors showed notable variations in luminance and contrast ratio as a function of the viewing angle. Acceptable viewing angles in terms of the contrast ratio were much smaller in each direction than those for nominal viewing angles in the specifications provided by the manufacturers, and those for the medical-grade LCD monitor in the horizontal and vertical directions were broader than those of the general-purpose LCD monitor. There was no significant difference in observer performance between 0 degrees and 40 degrees. On the other hand, our results showed a statistically significant difference in observer performance between 0 degrees and 60 degrees.

Performance of thin-film ferroelectric capacitors for EMC decoupling

This paper studied the effects of thin-film ferroelectrics as decoupling capacitors for electromagnetic compatibility applications. The impedance and insertion loss of PZT capacitors were measured and compared with the results from commercial off-the-shelf capacitors. An equivalent circuit model was extracted from the experimental results, and a considerable series resistance was found to exist in ferroelectric capacitors. This resistance gives rise to the observed performance difference around series resonance between ferroelectric PZT capacitors and normal capacitors. Measurements on paraelectric (Ba,Sr)TiO(3)-based integrated varactors do not show this significant resistance. Some analyses were made to investigate the mechanisms, and it was found that it can be due to the hysteresis in the ferroelectric thin films.

A critical band of phase alignment for discrimination but not recognition of human faces

We investigated the processes underlying the discrimination and recognition of human faces as a function of spatial phase alignment to assess whether face processing can be understood in terms of the amplitude spectrum alone. Specifically, we varied the amount of aligned Fourier phase in different regions of the face frequency spectrum and argue that the properties of the underlying neural processes are best understood in terms of the number of phase alignments as opposed to octave bandwidths. Additionally, we observed performance differences for face discrimination tasks compared to face recognition tasks. For face recognition, our results show that a narrower range of phase alignment is needed for face frequencies near 9 cpf when compared to 3 and 27 cpf, thereby supporting the notion of a critical frequency for face recognition. However, for face discrimination where participants were required to discriminate between an average face and different unique faces along a face morph continuum, performance depended on a fixed signal-to-noise ratio of phase alignment within a contiguous range of face frequencies (termed critical band of phase alignments), regardless of the central face frequency of that range within the face frequency spectrum when compared to non-phase randomized control thresholds.

SU‐GG‐I‐55: Comparison of Viewing Angle Performance and Observer Performance of Different Types of Liquid Crystal Displays

Purpose: Liquid crystal displays (LCDs) have a number of advantages over cathode ray tubes and conventional viewers based on film. However, it is nown that the performance of LCDs varies by viewing angle. The purpose of this study was to compare the angular performance and effects on observer performance in different types of LCDs, namely a general purpose LCD for personal computers and one especially designed for medical use. Method and Materials: Two types of LCDs were used in this study, an in‐plane switching (IPS) technology display especially designed for medical use and a general‐purpose twisted nematic (TN) technology display. We measured the luminance responses and contrast ratios for the two types of LCDs at different viewing angles (−60 degrees to 60 degrees). Furthermore, observer performance at various viewing angles in the horizontal direction for the medical display was also examined by eight observers based on contrast‐detail diagrams. Results: The two types of LCDs showed notable variations in luminance and contrast ratios as a function of the viewing angle. Results obtained in different directions (horizontal, vertical and diagonal directions) indicated different contrast ratios. Acceptable viewing angles in terms of the contrast ratio were much smaller in each direction than those for nominal viewing angles in the specifications provided by the manufacturers. Acceptable viewing angles of the medical‐grade display in the horizontal and vertical directions were broader than those of the general purpose display. There was no significant difference in observer performance between 0 and 40 degrees. On the other hand, our results showed a statistically significant difference in observer performance between 0 and 60 degrees. Conclusion: Contrast ratio and luminance response showed notable variations with different viewing angles and different types of LCD. More importantly, the detection of contrast‐detail materials of the LCD monitor was influenced by viewing angles.

Adaptive strategies for reading with a forced retinal location

Forcing normal-sighted participants to use a distinct parafoveal retinal location for reading, we studied which part of the visual field is best suited to take over functions of the fovea during early stages of macular degeneration (MD). A region to the right of fixation lead to best reading performance and most natural gaze behavior, whereas reading performance was severely impaired when a region to the left or below fixation had to be used. An analysis of the underlying oculomotor behavior revealed that practice effects were accompanied by a larger number of saccades in text direction and decreased fixation durations, whereas no adjustment of saccade amplitudes was observed. We provide an explanation for the observed performance differences at different retinal locations based on the interplay of attention and eye movements. Our findings have important implications for the development of training methods for MD patients targeted at reading, suggesting that it would be beneficial for MD patients to use a region to the right of their central scotoma.

Gender composition of teams: effects of competition

PurposeThe purpose of this article is to address and gain a more complete understanding of the effects on performance attributable to the gender composition of teams.Design/methodology/approachThe authors examined gender as a team composition variable that influences performance on a computer‐based task, and we investigated task framing (masculine/feminine) and competition (isolated/dyad) as explanatory factors in the gender composition‐performance relationship. Whereas previous research combines matched gender dyads in analyses, we distinguished male/male from female/female dyads to isolate the effects on performance and examine competition effects.FindingsDistinguishing between male/male and female/female dyads revealed only male/male dyads had superior performance. Task framing was not supported as an explanation for the observed performance differences, but competition was. Contrasting the gender effect in competitive conditions relative to isolated conditions revealed a gender difference in performance between competitive conditions only.Research limitations/implicationsGiven competition's clear role in the gender composition‐performance relationship, a more rigorous examination and manipulation of competition is needed beyond the comparison of isolated and dyadic conditions.Practical implicationsPrevious research suggests to organizations/practitioners that matching teams by gender will result in optimal performance. Based on our findings, such an implementation would be to the detriment of female teams in the organization, and associated legal issues could arise.Originality/valueThe authors found the superior performance of matched teams to be attributable to the matching of male/male teams and the associated competitive context, and not attributable to matched teams in general. The results should be considered as a caution for both the academic and applied domain alike.

Diamond Conditioner Wear Characterization for a Copper CMP Process

Conditioner wear, copper polish rates, pad temperature and coefficient of friction (COF) are measured for two novel Mitsubishi Materials Corporation designs during an extended wear and polishing test. Both designs are coated with a film to reduce substrate wear and chemical attack. Using optical interferometry, changes in the coating that result in gradual changes in diamond exposure are measured. Theories of the COF, conditioning, and polishing are applied to explain the observed performance differences between the designs.

Elucidating differences between carbon paper and carbon cloth in polymer electrolyte fuel cells

This paper seeks to develop a structure–performance relationship for gas diffusion layers (GDLs) of polymer electrolyte fuel cells (PEFCs), and hence to explain the performance differences between carbon paper (CP) and carbon cloth (CC). Three-dimensional simulations, based on a two-phase model with GDL structural information taken into account, are carried out to explore the fundamentals behind experimentally observed performance differences of the two carbon substrates, i.e. CC and CP, under low- and high-humidity operations. Validation against polarization data is made under both operating conditions, and the results indicate that the CC is the better choice as a GDL material at high-humidity operations due to its low tortuosity of the pore structure and its rough textural surface facilitating droplet detachment. However, under dry conditions, the CP shows better performance due to its more tortuous structure, which prevents the loss of product water to dry gas streams, thus increasing the membrane hydration level and reducing the ohmic loss. The present work is one step toward developing a science-based framework for selection of materials for next-generation, high-performance gas diffusion media.

Differences in Neuropsychological Performance Associated With Ethnicity in Children With HIV-1 Infection: Preliminary Findings

This study investigated the relationship between ethnicity (African American and European American) and neuropsychological performance in two specific neuropsychological domains (language and speed of information processing) in a group of HIV-1+ children. The Expressive One-Word Picture Vocabulary Test-Revised and the Rapid Color Naming subtest of the Comprehensive Test of Phonological Processing were administered to 5- to 7-year-old children (n = 22) as part of a comprehensive research or clinical protocol. African American children scored lower than European American children (p < .05) on both procedures. The observed performance difference emerged despite the fact that there were no group differences in age, immunologic clinical categories, intellect, level of maternal education, or CD4+ percentage and after using stringent exclusionary criteria, including history of enrollment in special education services and the presence of other chronic medical conditions. The implications of such findings are discussed within biological and demographic frameworks.

Performance evaluations of for‐profit and nonprofit U.S. hospitals since 1980

AbstractThis synthesis of studies examines whether the published literature shows an evidence‐based consensus on performance differences between private for‐profit and nonprofit hospitals in the United States since 1980. The author systematically and comprehensively surveyed peer‐reviewed publications to clarify this question. The author's second objective was to learn what proportion of all research assessing for‐profit and nonprofit health care providers is devoted to hospitals compared to all other providers. The third goal was to discover how any trends in observed performance differences among hospitals compare with trends among other provider types.Computerized bibliographic searches of all relevant databases yielded seventy‐five studies (ninety‐three assessments) that compared the performance of for‐profit and nonprofit hospitals on four performance criteria: access, quality, cost or efficiency, and amount of charity care. The author coded findings on performance in one of three ways: for‐profit superiority, nonprofit superiority, or inconclusive. Most studies (60 percent) reported that nonprofit hospitals have better relative performance than for‐profit hospitals, clear evidence of their organizational effectiveness. Thirty‐one percent were inconclusive, and 8 percent reported that for‐profits were better.

Articulation index predictions for hearing-impaired listeners with and without cochlear dead regions

Vickers, Moore, and Baer [J. Acoust. Soc. Am. 110, 1164–1175 (2001)] reported that hearing-impaired subjects with cochlear “dead regions” benefited from amplification of frequencies up to an octave above the estimated edge frequency of the dead region, but not beyond, whereas hearing-impaired subjects without dead regions did show benefit beyond this boundary. Dead regions are thought to have no functioning inner hair cells. Vickers et al. indicated that a clinical test for detecting dead regions would provide supplementary information that is important for hearing aid fitting. Furthermore, they suggested that the articulation index (AI) may overestimate the potential benefit of amplification for listeners with dead regions because the AI does not account for the presence of dead regions. To evaluate their claims, we conducted an AI analysis [H. Fletcher, Speech and Hearing in Communication (Van Nostrand, New York, 1953); H. Fletcher and R. H. Galt, J. Acoust. Soc. Am. 22, 89–151 (1950)]. Results show that the AI is generally accurate in predicting the consonant recognition test scores of Vickers et al.’s subjects irrespective of the presence/absence of dead regions. This suggests that audiogram differences account for the observed performance differences; it was not necessary to invoke dead regions to explain the speech test results. The results of the AI analysis are sufficiently accurate to call in to question whether a clinical test for dead regions would offer additional predictive information.