Analysis of Static Load Sharing in Star Gearing

In the current high-speed helicopter main reducer, coaxial reversal herringbone gear transmission system (CRHGTS) has the advantages of light weight, high stability and long service life. In order to study the static load sharing characteristics of coaxial reversal herringbone gear transmission system, considering the factors such as transmission chain stiffness, installation error and manufacturing error, the torque balance equation of the system is established, the deformation coordination condition of the system is deduced, and the influence of manufacturing and installation errors on the load sharing performance of the system under single and combined action of gears is analyzed. The result shows that when the gear has manufacturing error, the load sharing coefficient fluctuates periodically. When the manufacturing error acts on the reversal gear and the output gear at the same time, the load sharing performance will be reduced. When the gear has installation error, the load sharing coefficient of the system is linear. The increase of gear manufacturing error and installation error will lead to the increase of load sharing coefficient and reduce the load sharing performance of the system.

Many measurement systems suffers from different kind of errors. In this article we observe Ultra-Wide Band indoor navigation systems as one of the promising kind of indoor navigation system due to its features and rapidly extend market. We can distinguish two types of error: systematic and random. This article examines systematic type of measurement error. If systematic error has stationary nature it usually eliminates by calibration sensors. If it has non-stationary nature well-known approach to take it into account is so called “table method”. This method has many disadvantages such as discretization of dependency function, one-time measurement correction, not taken into account other possible measurements and so on. This article intend is to investigate new methods of systematic range bias correction specific to Ultra-Wide Band indoor navigation systems. As a good example we use Decawave Ultra-Wide Band modules. Comparison framework for such methods developed in MATLAB and presented, two methods proposed and compared with legacy.

A number of opportunistic content sharing services were developed that exploit device-to-device contacts for infrastructure-less operation. All of them depend, like geo-based ad-hoc routing protocols, on mobile devices knowing their respective positions to accurately perform data replication. In this paper, we explore the impact of different types of location errors on the performance of such a service. We use a GPS error distribution for mobiles derived from real-world measurements, consider different frequencies for GPS readings, and account for only subsets of mobile devices actively using GPS. We carry out extensive simulation studies using synthetic mobility models as well as real-world traces to assess the impact of different types of errors. We find that, overall, opportunistic content sharing is quite robust provided that a sufficient number of nodes support GPS and allow the others to have a rough estimate of where they are. Whether or not the GPS position is prone to errors affects some scenarios and is almost negligible in others.

Time-varying loads, manufacturing errors, and assembly errors are the main factors leading to the performance degradation of the planetary roller screw mechanism. This paper proposes a comprehensive analysis method for the performance degradation of the planetary roller screw mechanism caused by time-varying loads and manufacturing and assembly errors. Firstly, a simulation analysis model of the planetary roller screw mechanism was established and its effectiveness was verified. A quantitative analysis was conducted on the influence of manufacturing and assembly errors on the load distribution, revealing the load-bearing mechanism under the influence of errors. Secondly, loading experiments were conducted on the planetary roller screw mechanism, and the degradation of its load-bearing performance was divided into the normal degradation stage, the accelerated degradation stage, and the failure stage. The experimental results prove that the initial transmission accuracy has a significant impact on the degradation of the load-bearing performance, determining the occurrence of the node where the accelerated degradation stage appears in the load-bearing performance. Thirdly, the wear status of the threads and gears was examined, and the results showed that material peeling was the main factor causing the degradation of load-bearing performance.

How the detector resolution affects the clinical significance of SBRT pre-treatment quality assurance results

Physicians now enjoy a moment of tactical advantage in the evolution of the struggle for control over health care in the United States. The most effective way to capitalize on this-perhaps fleeting-position and to more permanently alter the balance of power in their favor is for physicians to establish strong and visionary leadership in health care quality improvement. Such an undertaking, if successful, could place the very essence of health care-defining, measuring, and improving its quality-in the hands of physicians. To succeed requires understanding the relationships between the different kinds of quality problems that plague our health care system, the various kinds of errors that lead to them, and how amenable these different kinds of errors may be to different interventions. The authors delineate a conceptual framework that describes these relationships, as well as their implications for conducting effective and durable quality improvement. The authors then illustrate how physicians could engage in this activity in three different settings: a four-or-five-physician primary care practice, a 50-physician multispecialty group, and a 450-bed community hospital. Finally, the authors submit that now is an opportune time for physicians and the organizations they direct or guide to take the leadership role in conducting health care quality improvement. Realizing the opportunity will require dedicating significant resources and changing traditional approaches to quality, but in so doing, physicians can regain much of the autonomy over the practice of medicine previously lost to government and managed care.

We describe a method of assessing the implications for human error on user interface design of safety-critical systems. In previous work we have proposed a taxonomy of influencing factors that contribute to error. In this article, components of the taxonomy are combined into a mathematical and causal model for error, represented as a Bayesian Belief Net (BBN). The BBN quantifies error influences arising from user knowledge, ability, and the task environ-ment, combined with factors describing the complexity of user action and user interface quality. The BBN model predicts probabilities of different types of errorslips and mistakes for each component action of a task involving user-system interaction. We propose an Impact Analysis Method that involves running test scenarios against this causal model of error in order to determine user interactions that are prone to different types of error. Applying the proposed method will enable the designer to determine the combinations of influencing factors and their interactions that are most likely to influence human error. Finally we show how such scenario-based causal analysis can be useful as a means of focusing on relevant guidelines for safe user interface design. The proposed method is demonstrated through a case study of an operator performing a task using the control system for a laser spectrophotometer.We describe a method of assessing the implications for human error on user interface design of safety-critical systems. In previous work we have proposed a taxonomy of influencing factors that contribute to error. In this article, components of the taxonomy are combined into a mathematical and causal model for error, represented as a Bayesian Belief Net (BBN). The BBN quantifies error influences arising from user knowledge, ability, and the task environ-ment, combined with factors describing the complexity of user action and user interface quality. The BBN model predicts probabilities of different types of errorslip for each component action of a task involving user-system interaction. We propose an Impact Analysis Method that involves running test scenarios against this causal model of error in order to determine user interactions that are prone to different types of error. Applying the proposed method will enable the designer to determine the combinations of influencing factors and their interactions that are most likely to influence human error. Finally we show how such scenario-based causal analysis can be useful as a means of focusing on relevant guidelines for safe user interface design. The proposed method is demonstrated through a case study of an operator performing a task using the control system for a laser spectrophotometer.

Fluoroscopy-based three-dimensional seed localization as a component of intraoperative dosimetry for prostate brachytherapy is an active area of research. A novel adaptive-grouping-based reconstruction approach is developed. This approach can recover overlapped seeds that are not detected from the fluoroscopic images. Two versions of the adaptive-grouping-based reconstruction approach are implemented and compared to an epipolar geometry-based seed reconstruction technique. Simulations based on nine patient datasets are used to validate the algorithms. A total of 2259 reconstructions is performed in which different types of error such as random noise in seed image locations and ambiguities in projection geometry are incorporated. Among those reconstructions, nine of the cases with overlapping seeds and the different types of error are performed. It is demonstrated that the adaptive-grouping-based reconstruction method is more accurate than the epipolar geometry method and allows faster reconstruction. At a random noise level of 0.6 mm, the mean distance error in reconstructed seed locations is approximately 1.0 mm for one of the relevant cases examined in detail. The best adaptive-grouping-based approach successfully recovered overlapped seeds in the majority of simulated cases (89%), with the remainder of cases generating one false positive seed. Phantom validation is also performed, and overlapped seeds are successfully recovered with all 92 seeds correctly localized and reconstructed. The mean distance error between segmented seed images and projected seeds is 0.5 mm in the phantom study.

The National Training Programme for laparoscopic colorectal surgery in England was implemented to ensure training was supervised, structured, safe and effective. Delegates were required to pass a competency assessment (sign-off) before undertaking independent practice. This study described the types of errors identified and associated these errors with competency to progress to independent laparoscopic colorectal practice. All sign-off submissions from the start of the process in January 2008 until July 2013 were included. Content analysis was used to categorise errors. Bayes factor (BF) was used to measure the impact of individual error on assessment outcome. A smaller BF indicates that an error has stronger associations with unsuccessful assessments. Bayesian network was employed to graphically represent the reasoning process whereby the chance of successful assessment diminished with the identification of each error. Quality of the error feedback was measured by the area under the ROC curve which linked the predictions from the Bayesian model to the expert verdict. Among 370 assessments analysed, 240 passed and 130 failed. On average, 2.5 different types of error were identified in each assessment. Cases that were more likely to fail had three or more different types of error (χ(2) = 72, p < 0.0001) and demonstrated poorer technical skills (CAT score <2.7, χ(2) = 164, p < 0.0001). Case complexity or right- versus left-sided resection did not have a significant impact. Errors associated with dissection (BF = 0.18), anastomosis (BF = 0.23) and oncological quality (BF = 0.19) were critical determinants of surgical competence, each reducing the odds of pass by at least fourfold. The area under the ROC curve was 0.84. Errors associated with dissection, anastomosis and oncological quality were critical determinants of surgical competency. The detailed error analysis reported in this study can guide the design of future surgical education and clinical training programmes.

Self-explanations (SE) are an effective method to promote learning because they can help students identify gaps and inconsistencies in their knowledge and revise their faulty mental models. Given this potential, it is beneficial for intelligent tutoring systems (ITS) to promote SEs and adaptively respond based on SE quality. We developed and evaluated classification models using combinations of SE content (e.g., inverse weighted word-overlap) and contextual cues (e.g., SE response time, topic being discussed). SEs were coded based on correctness and presence of different types of errors. We achieved some success at classifying SE quality using SE content and context. For correct vs. incorrect discrimination, context-based features were more effective, whereas content-based features were more effective when classifying different types of errors. Implications for automatic assessment of learner SEs by ITSs are discussed.

The relationship between errors and size in knowledge-based systems

PurposeThe study pursues two goals: first, as a replication study, the purpose of this paper is to test a model of learning from errors in the domain of insurance industry. Second, to increase insights in learning from errors, the authors focussed on different types of errors.Design/methodology/approachThe authors conducted a cross-sectional survey in the insurance industry (N=206). The authors used structural equation modelling and path modelling to analyse the data. To be able to analyse different types of errors, the authors used Critical Incident Technique and asked participants to describe error situations.FindingsFindings from the study are that the model of learning from errors could partly be replicated. The results indicate that a non-punitive orientation towards errors is an important factor to reduce the tendency of insurance agents to cover up errors when knowledge and rule-based errors happen. In situations of slips and lapses error strain has a negative influence on trust and non-punitive orientation which in turn both reduce the tendency to cover up errors.Research limitations/implicationsLimitation is the small sample size. By using Critical Incidents Technique, the authors were able to analyse authentic error situations. Implications of the results concern the importance of error-friendly climate in organisations.Originality/valueReplication studies are important to generalise results to different domains. To increase the insight in learning from errors, the authors analysed influencing factors with regard to different types of errors.

In this paper, we propose a framework to evaluate the impact on power system dynamic performance of different types of errors in the measurements utilized by the automatic generation control system. To address the random nature of these errors, stochastic system analysis methods are utilized to evaluate the statistics of system state variables. By examining the convergence properties of these statistics, errors that cause instability are identified. A reduced-order model, obtained by using singular perturbation arguments, is also formulated; this model enables us to provide analytical expressions for capturing the impact of the errors. The proposed method is illustrated and verified through several case studies with different types of errors on a simplified New England/New York system model.

Performance on the Bender Visual-Motor Gestalt test has been repeatedly shown to be sensitive to the effects of brain lesions. However, brain damaged and control populations typically overlap greatly in their error scores. A new Bender scoring system is presented with differential weighting for errors of greater or lesser severity, which permits a profile analysis of different types of error as well. Preliminary data from a validation study are included. There are several scoring systems for the Bender Visual-Motor Gestalt Test (Bender, 1938) including those developed by Hain (1964), Koppitz (1964) and Pascal and Suttell (1951) as well as that which was developed by Bender (1938). Each of these systems has been an attempt to objectify the differences in performance often seen between groups of people with different diagnoses. Developmental differences also have been shown on the Bender (Koppitz, 1964). Several studies have demonstrated that, based upon total error scores on the Bender, there are significant differences in performance between brain-damaged and other non brain-damaged groups (Hain, 1964; Kramer and Fenwick, 1966; Tymchuk, 1974). The rationale for the use of the Bender for individual classification derives from the fact that people with known brain lesions demonstrate disordered performances on tests such as the Bender including the Benton Visual Retention Test (Benton, 1963), the Graham-Kendall Memory for Designs Test (1960) and the Halstead-Wepman Aphasia Screening Test (1949). Scores on the Bender, however, cannot be used to classify subjects on an individual basis into the brain-damaged or non brain-damaged groups because of the great overlap in error scores (Cronbach, 1970). Despite this difficulty in individual classification, the Bender is a useful tool for research purposes in showing change in performance after training and has been used to predict learning disabilities (Silver, 1973) so that an objective method for scoring is needed. The author has developed a scoring system which goes beyond the other systems in that the errors are defined more finely with different weights given depending on the extent of the error. This system also has categories for the different types of errors which allows for a profile analysis of errors. The categories of errors include rotations, integration, distortion, size, perseveration and others (including collisions, incoordination, erasures, nonerasures or doubled or blackened lines). Each of the other scoring systems for the Bender include some or all of these types of errors, but do not offer scores for the individual types. As an example of the fineness of the error categories, for figure A, Rotation errors of the entire figure of 45, 90 and 180 degrees are given scores of 1, 2, or 3 respectively. For Integration errors when there is one-eighth inch or more overlap or separation for Figure A, this is scored 1 while super-imposition of the figures or where one figure is missing is scored 2. Various degrees of distortions are also scored 1, 2, or 3. This system also considers time scores for the individual errors as well as a total time score although in the present study time scores were unavailable. This system is an extension of several others including the Koppitz (1964) and is not meant to replace those systems. The purpose of the system is to be used where delineation of finer error categories may seem appropriate.

The performance of a gear set is strongly influenced by the manufacturing and assembly quality. Therefore, detailed analyses at the design stage, where the effects of expected assembly and manufacturing errors can be simulated, are crucial. At an early design stage, when contact conditions are addressed, the widely used finite element method (FEM) may still result in unwanted computing time. The paper presents an Express model developed to serve as a fast design tool offering fine simulation and a high precision level. The model establishes load sharing, fillet stresses and pressure distribution along the contacting surfaces of meshing helical gear teeth. The calculations combine the finite strip method with a pseudo-three-dimensional (3D) model of the tooth base solved with finite differences to calculate tooth bending deflexion and fillet stresses. The accuracy of the procedure is demonstrated through 3D FEM models. A contact cell discretization completes the model. This very fast and accurate approach gives the contact pressure distributions resulting from the roll-slide motion of mating teeth. An analysis of a helical gear set in two different assembly positions reveals the effects of edge contact, and exhibits the influence of tooth stiffness reduction near tooth corners.