273 research outputs found
VR Mediated Teleoperation: Total workspace utilization using null-space projection control
No full textJoint limits and singularities limit the total and intuitive utilization of the robotic workspace in VR mediated teleoperation. This paper presents the development and validation of a novel null-space projection control method, used to adjust joint configurations of teleoperated robot arms containing joint limits and singularities. The novel null-space projection controller enables the operator to manually adjust invalid joint configurations. By doing so, we allow the operator to intuitively utilize the entire workspace of a teleoperated robot arm. A within-subject design experiment assessing operator task performance, acceptance and controller preference of 26 novel operators was executed. The participants were analyzed using the novel and the state-of-the-art end-effector controller for a trajectory following task. The novel controller significantly out-performed the end-effector controller in trajectory accuracy. Operators utilizing the novel controller use significantly less effort when operating the robot arm. The novel controller was also rated significantly more useful and satisfying than the end-effector controller, resulting in 81\% of the participants preferring the novel controller over the end-effector controller. Further development and future studies will explore the full capabilities of the novel controller, improve performance, user acceptance and explore additional applications.Mechanical Engineerin
Null subtraction imaging for small aperture phased array transducers
No full textIn medical ultrasound imaging phased array transducers are used for non-invasive imaging. For 3D intra-cardiac-echography technical borders are reached since blood vessel size limits the dimensions of the array. This dimensional limitation lowers lateral resolution. To solve part of the problem, non conventional ways of lateral resolution improvements are needed. For linear arrays R. Reeg [1] proposed null subtraction imaging (NSI), which resulted at best in 30 dB lower side lobes and a width reduction of up to 25 times for the main lobe. This is a non-linear image processing technique based on implementing multiple apodizations in post-processing. Three images are made from which one has a sharp drop to zero in the middle which can be exploited by subtracting it from the other images. This results in a improvement over a regular apodization scheme.To verify the technique for 2D phased array imaging, simulations are done using Field-II [2, 3] while taking array dimension into account. Measurements take place on an artificial phantom with evenly spaced line scatter targets. For the experiment a P4-l phased array transducer was used in combination with a Verasonics Vantage 256TMwhere a sub-aperture of 30 elements is used. The experiment is done on a CIRS 040GSE Phantom, where evenly spaced line scatter targets and lateral resolution targets are looked at. To form an image a simple delay-and-sum (DAS) algorithm was used. The effect of NSI on the speckle in an image is also measured, where for normal developed speckle a signal to noise ratio (SNR) of 1.91 is expected. Results for simulation were as expected with an average beamwidth reduction of 22.5 times and on average higher main lobe to side lobe ratio (MSR) of 33.4 dB for NSI imaging opposed to using a rectangular apodization. Experimentally an average beamwidth reduction of 5 times and an on average higher MSR of 20.5 dB are realised. The beamwidth reduction is lower then expected, this is due to rounding errors in the DAS algorithm, where data can only be delayed by integer elements. For the lateral scatter targets no extra targets can be distinguished when using NSI imaging opposed to rectangular apodization imaging, only the targets that where already visible show reduction in beamwidth and side lobe levels. When using NSI speckle SNR is reduced from 1.78 to on average 0.50 and seems to scale with energy present in the image. An hybrid image between the NSI image and rectangular apodization image is made to solve this. It results in reduced beamwidth, restored speckle SNR but the MSR is reduced. It can be concluded that the method works for phased array imaging under perfect conditions, the simulation. To get the full potential of the technique more research is needed towards the effects of improper sampling. Which in this case resulted in less then ideal ’sharp’ drops, lowering the reduction in beamwidth. Also the reduced speckle needs further research to understand it well. Once this is all achieved the next step to 3D imaging can be made
FOMC forecasts: is all the information in the central tendency?
No full textFederal Reserve policymakers began reporting their economic forecasts to Congress in 1979. These forecasts are important because they indicate what the Federal Open Market Committee members think will be the likely consequence of their policies. The Fed reports both the range (high and low) of the individual policymaker’s forecasts and a truncated central tendency. The central tendency range omits outliers from both the top and the bottom of the full range. The author finds, generally, that the forecasts derived from the full range are at least as good as those derived from the central tendency and, in a few cases, significantly better.Federal Open Market Committee ; Forecasting
The role of human volunteer studies to assess pesticide hazards from the evaluation of selected published studies
No full textThe question of the ethical and scientific acceptability of experimental studies involving human volunteers has been raised by recent debates, and has never found a clear answer. To the aim of reaching a better understanding of the advantages and the limits of these studies, the ICOH Scientific Committee on Rural Health has evaluated selected published papers to collect a better understanding of the real added value of these studies. To this aim, a PubMed search has been performed, and the papers to be evaluated have been selected based on type of study, compound addressed, and year of publication, for a total of 26 papers. For each paper the following items has been collected: author; year of publication; journal; peer review; aim of the study (absorption, distribution, metabolism and excretion –ADME); study of biological effects and/or toxicity; exposure; other, relation with pesticide authorization procedures, compound addressed, experimental design, number of groups and subjects, statistical power, approval of the ethical committee, and real need of the study to collect the requested information. Based on the evaluation carried out by our WG, it seems that most experimental studies in human volunteers, as published in the scientific literature, have not been explicitly performed to set reference values. Most of the recent studies deal with ADME rather than with toxicological effects. The problems with studies in human are the use of only one dose level and the usually relatively low number of subjects per group. For this reason, it seems that very seldom these studies are useful to set reference values, but sometime the results contribute in reducing the uncertainty of the assessments possibly help in defining a chemical-specific assessment factor. Another use of these studies might be the identification of the proper or most adequate indicators to be used in biological monitoring of exposure
[[alternative]]Study on the present operation of Curriculum Development Committee in junior high schools
No full text[[abstract]]The thesis of the paper is the ideas about the operational status quo of Committee of Curriculum Development in junior high schools by analyzing both native and foreign documents while coming up with the conclusion and some suggestions to be references for the educational reform policies is followed. By applying the quality and quantity considered research methods, such as document analysis, questionnaire survey, and interview, the conclusion goes as followed.
First, school members don’t have thorough cognitive understanding about Committee of Curriculum Development generally. Besides, their will to know the committee better is not well-emphasized.
Second, the operational status quo of the committee is established based on “Essentials of Nine Year Consistent Curriculum for Junior High and Elementary Schools.” The term of office of best-known members, the conveners of each learning fields, the directors and leaders of teaching affairs, and principals, is one year. Besides, members come into being mostly by recommendation; schedules of meetings are often held at common null curriculums or scheduled temporarily, so most meetings are not held regularly. However, the interaction between conveners and the committee is supposed to be close. Policies are usually carried out by mediation between teachers and each office. The teaching affair centers play a critical role in operation.
Third, the committee works better in distributing the number of learning classes for each learning fields and planning developmental in curriculum than evaluating teacher’s professional growth in curriculum development. Principals, administrative and committee members have more positive viewpoints toward its operation than teachers do. But members think the operation of the committee helps teachers more both in curriculum and teaching than non-committee members. Meanwhile, the committee also provides different international opportunities of learning fields.
Fourth, that teachers have no full understanding toward the committee, lack of proficiency of “curriculum development” and professional knowledge about other learning fields is the filter in operation. They are not able to provide any ideas about curriculum plans and teaching goals for other learning fields. There are also problems that parents and communities lack concern of it, teachers elected as the members are not well reward, the policies of government don’t go well with the need of school, and school members still suspect about the function of the committee. What’s worse, the insufficient communication and introduction about the committee makes the committee not well known by school members and the leaders hold negative attitude toward the operation of the committee.
The conclusion of the paper comes up with some ideas as the references for the board of related affairs. Education administrative institution should authorize flexibility for the human resources of school, give the members positive reward, reinforce the monitors and development of each school, and provide related support and resources to ensure the quality of the committee in operation. Schools have to make the organization of members to be multiple, promote the representatives of members and the professional level of members by life-long education, provide members and teachers with access of dialogue to reinforce the understanding to each other, establish one professional curriculum developmental research group to be responsible for the learning fields at school, and arrange meetings of the committee as part of the schedule, inducing this into school administration by systemizations. Teachers should shape the image of learning organization to promote the professional standard and accept the ideas of change to correspond with the trend of educational reform.
Signo y Pensamiento: Quests Related to the Mobility of Knowledge
No full textEste artículo fue solicitado al autor por el Comité Editorial,como un ejercicio de balance del proceso llevadoa cabo en la revista, tras su paso como editorThe author was asked to write this article by the Publishing Committee, an exercise of the carried out process in the journal, after his positioning as publisher
Self-explaining and Individual Differences in Multimedia Learning
No full textabstract: Multimodal presentations have been found to facilitate learning, however, may be a disadvantage for low spatial ability students if they require spatial visualization. This disadvantage stems from their limited capacity to spatially visualize and retain information from both text and diagrams for integration. Similarly, working memory capacity (WMC) likely plays a key role in a learner's ability to retain information presented to them via both modalities. The present study investigated whether or not the act of self-explaining helps resolve deficits in learning caused by individual differences in spatial ability, working memory capacity, and prior knowledge when learning with text, or text and diagrams. No interactions were found, but prior knowledge consistently predicted performance on like posttests. The author presents methodological and theoretical explanations as to the null results of the present study.Dissertation/ThesisM.S. Applied Psychology 201
Einstein Gravity and Beyond: Aspects of Higher-Curvature Gravity and Black Holes
No full textabstract: This thesis explores the different aspects of higher curvature gravity. The "membrane paradigm" of black holes in Einstein gravity is extended to black holes in f(R) gravity and it is shown that the higher curvature effects of f(R) gravity causes the membrane fluid to become non-Newtonian. Next a modification of the null energy condition in gravity is provided. The purpose of the null energy condition is to filter out ill-behaved theories containing ghosts. Conformal transformations, which are simple redefinitions of the spacetime, introduces serious violations of the null energy condition. This violation is shown to be spurious and a prescription for obtaining a modified null energy condition, based on the universality of the second law of thermodynamics, is provided. The thermodynamic properties of the black holes are further explored using merger of extremal black holes whose horizon entropy has topological contributions coming from the higher curvature Gauss-Bonnet term. The analysis refutes the prevalent belief in the literature that the second law of black hole thermodynamics is violated in the presence of the Gauss-Bonnet term in four dimensions. Subsequently a specific class of higher derivative scalar field theories called the galileons are obtained from a Kaluza-Klein reduction of Gauss-Bonnet gravity. Galileons are null energy condition violating theories which lead to violations of the second law of thermodynamics of black holes. These higher derivative scalar field theories which are non-minimally coupled to gravity required the development of a generalized method for obtaining the equations of motion. Utilizing this generalized method, it is shown that the inclusion of the Gauss-Bonnet term made the theory of gravity to become higher derivative, which makes it difficult to make any statements about the connection between the violation of the second law of thermodynamics and the galileon fields.Dissertation/ThesisDoctoral Dissertation Physics 201
Efficient Inference with Panel Data: On the pass-through of the Dutch 2001 and 2012 VAT increases to consumer prices
No full textThis thesis evaluates the pass-through of the 2001 and 2012 Dutch Value Added Tax (VAT) increases to customer prices using a difference-in-differences model. To this end, the first difference and feasible generalised least squares estimators are introduced. Contrary to the conventional pooled OLS estimator, these estimators always show significant causal effects for both VAT hikes. These also dramatically improve the accuracy of the estimates compared to earlier research on the incidence of VAT. For the 2012 tax increase, the null hypothesis of full pass through is even rejected. This result is a novelty in the econometric literature. Even in more general settings, the estimators used in this thesis prove far superior over conventional causal estimation techniques of difference-in-differences models.Applied Mathematic
Assessing Methods for Handling Missing Data Using an LSTM Deep Learning Model in Traffic Forecasting
No full textDue to the increasing popularity of various types of sensors in traffic management, it has become significantly easier to collect data on traffic flow. However, the integrity of these data sets is often compromised due to missing values resulting from sensor failures, communication errors, and other malfunctions. This study investigates the effect of missing data on the performance of Long Short-Term Memory (LSTM) models in traffic flow prediction and assesses strategies to handle these missing values. By actively removing values from a complete data set, three strategies to handle these missing values are evaluated: dropping null values, replacing them with zero, and linear interpolation. We show that LSTM models are surprisingly resilient to missing data, with little impact on prediction accuracy for up to 40% of missing data, irrespective of the strategy used. For higher proportions of missing data, dropping null values leads to significant performance degradation, while zero-filling and interpolation maintain predictive accuracy. This paper provides insights into the choice of missing data handling strategies in time-series prediction tasks, demonstrating the potential of LSTM models for traffic forecasting under less-than-ideal data conditionsCSE3000 Research ProjectComputer Science and Engineerin
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