This paper summarizes several key issues of importance related to intercept of high-speed maneuvering targets under stratospheric altitude conditions, where it is unlikely that the interceptor will have a significant ...
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This paper summarizes several key issues of importance related to intercept of high-speed maneuvering targets under stratospheric altitude conditions, where it is unlikely that the interceptor will have a significant speed and/or maneuverability advantage. It explains why one cannot rely on traditional proportional navigation guidance and presents simulation results for a recently developed finite time method of guidance. A simplified version of finite time intercept guidance is derived, and a modification required to allow it to be practically implemented is described. Simulation results are presented to illustrate the advantages of the simplified version.
Purpose In this paper, an online convex optimization method for the exoatmospheric ascent trajectory of space interceptors is proposed. The purpose of this paper is to transform the original trajectory optimization pr...
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Purpose In this paper, an online convex optimization method for the exoatmospheric ascent trajectory of space interceptors is proposed. The purpose of this paper is to transform the original trajectory optimization problem into a sequence of convex optimization subproblems. Design/methodology/approach For convenience in calculating accuracy and efficiency, the complex nonlinear terminal orbital elements constraints are converted into several quadratic equality constraints, which can be better computed by a two-step correction method during the iteration. First, the nonconvex thrust magnitude constraint is convexified by the lossless convexification technique. Then, discretization and successive linearization are introduced to transform the original problem into a sequence of one convex optimization subproblem, considering different flight phases. Parameters of trust-region and penalty are also applied to improve the computation performance. To correct the deviation in real time, the iterative guidance method is applied before orbit injection. Findings Numerical experiments show that the algorithm proposed in this paper has good convergence and accuracy. The successive progress can converge in a few steps and 3-4 s of CPU time. Even under engine failure or mission change, the algorithm can yield satisfactory results. Practical implications The convex optimization method presented in this paper is expected to generate a reliable optimal trajectory rapidly in different situations and has great potential for onboard applications of space interceptors. Originality/value The originality of this paper lies in the proposed online trajectory optimization method and guidance algorithm of the space inceptors, especially for onboard applications in emergency situations.
ObjectivesWe aimed to develop a guidance on the use of pre-exposure prophylaxis (PrEP) for HIV tailored to the Belgian *** aspects of PrEP care were judged by an expert group of nine Belgian clinicians, seeking consen...
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ObjectivesWe aimed to develop a guidance on the use of pre-exposure prophylaxis (PrEP) for HIV tailored to the Belgian *** aspects of PrEP care were judged by an expert group of nine Belgian clinicians, seeking consensus for areas of *** should be considered in HIV negative patients at high risk of acquiring HIV. Currently, only oral tenofovir/emtricitabine is available in Belgium for PrEP, which can be used daily, or also event-driven in cisgender men and trans women who are not taking exogenous estradiol-based hormones. Personal counselling directed at medication adherence and sexual health should have a central role in PrEP care. At the initial assessment clinicians should give attention to symptoms of an acute HIV infection, the patients' immunization status and renal function. A regular follow-up must be set up to diagnose HIV seroconversion, treat sexually transmitted infections, and manage side effects of *** Belgian guidance on the use of PrEP provides a point of reference for standard PrEP care in Belgium and will be periodically updated.
It is necessary to foster teachers' ability to design and implement instructions that encourage students to construct evidence and engage in argumentative discourse. The argument of this paper is that the continuo...
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It is necessary to foster teachers' ability to design and implement instructions that encourage students to construct evidence and engage in argumentative discourse. The argument of this paper is that the continuous reflection and discussion as well as regular practice on instructional designs will promote pre-service science teachers' (PSSTs') competence to guide students in providing evidence. An in-depth analysis on PSSTs' instructional designs provided evidence for this argument. For this purpose, this study implemented an action research (AR) in which PSSTs' instructional designs were analyzed before and after the three-week reflection and discussion on instructions that they conducted in groups of three or four in a science education course. The author of this paper, who is also the instructor of the course, analyzed these instructional designs to identify PSSTs' level of guidance by using the rubric that she created with expert judgment. Two other researchers and the author coded each category in the rubric independently. She scored the PSSTs' level in each category from 1 to 3 and then calculated their total score for the design. She also made paired samples t-test on the scores of each category and in total scores to identify how the PSSTs' instructional design guides students to use evidence before and after the continuous reflection and discussion of their instructional designs. The results suggested that integrating continuous reflection and discussion into her teaching improved PSSTs' guidance in providing evidence. Concluding remarks will be made for the further implications of this study.
Previous research has shown that people prefer algorithmic to judgmental forecasts in the absence of outcome feedback but judgmental to algorithmic forecasts when feedback is provided. However, all this work has used ...
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Previous research has shown that people prefer algorithmic to judgmental forecasts in the absence of outcome feedback but judgmental to algorithmic forecasts when feedback is provided. However, all this work has used cue-based forecasting tasks. The opposite pattern of results has been reported for time series forecasting tasks. This reversal could have arisen because cue-based forecasting studies have used preference paradigms whereas the time series forecasting studies have employed advice-taking paradigms. In a first experiment, we show that when a preference paradigm is used in time series forecasting, the difference in the conclusions about the effects of feedback in the two types of forecasting disappears. In a second experiment, we show that provision of guidance showing accuracy of algorithmic and judgmental forecasts can eliminate effects of feedback. Two further experiments reveal how choices between algorithmic and judgmental forecasts are influenced by the way in which those forecasts are labeled. (c) 2024 Published by Elsevier B.V. on behalf of International Institute of Forecasters.
This article aims to investigate the contribution of career counseling and guidance based on Nusantara culture in the implementation of the independent curriculum. The scope of this writing is focused on the strategie...
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This article aims to investigate the contribution of career counseling and guidance based on Nusantara culture in the implementation of the independent curriculum. The scope of this writing is focused on the strategies and implementation of career counseling and guidance in high schools. The research method used a narrative review of career counseling and guidance based on Nusantara culture. The results of this study show that group counseling and classical guidance, as well as culturally infused individual and group counseling, can serve as basic services in the career field within the independent curriculum for high school students. These strategies can be further developed and explored according to the cultural context of each high school in their respective regions.
PurposeTo develop and evaluate an augmented reality instrument guidance system for MRI-guided needle placement procedures such as musculoskeletal biopsy and arthrography. Our system guides the physician to insert a ne...
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PurposeTo develop and evaluate an augmented reality instrument guidance system for MRI-guided needle placement procedures such as musculoskeletal biopsy and arthrography. Our system guides the physician to insert a needle toward a target while looking at the insertion site without requiring special *** system is comprised of a pair of stereo cameras, a projector, and a computational unit with a touch screen. All components are designed to be used within the MRI suite (Zone 4). Multi-modality fiducial markers called VisiMARKERs, detectable in both MRI and camera images, facilitate automatic registration after the initial scan. The navigation feedback is projected directly onto the intervention site allowing the interventionalist to keep their focus on the insertion site instead of a secondary monitor which is often not in front of *** evaluated the feasibility and accuracy of this system on custom-built shoulder phantoms. Two radiologists used the system to select targets and entry points on initial MRIs of these phantoms over three sessions. They performed 80 needle insertions following the projected guidance. The system targeting error was 1.09 mm, and the overall error was 2.29 *** demonstrated both feasibility and accuracy of this MRI navigation system. The system operated without any problems inside the MRI suite close to the MRI bore. The two radiologists were able to easily follow the guidance and place the needle close to the target without any intermediate imaging.
This letter proposes a three-dimensional nonlinear guidance strategy that guarantees the interception of stationary targets at the desired impact time while accounting for the onboard seeker's field-of-view constr...
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This letter proposes a three-dimensional nonlinear guidance strategy that guarantees the interception of stationary targets at the desired impact time while accounting for the onboard seeker's field-of-view constraints. The proposed approach for designing guidance law does not require a time-to-go estimation. It utilizes range-to-go, free from time-to-go approximations, allowing the interceptor to control the time of interception. guidance command, derived using prescribed constraint function and sliding mode control considering coupled and nonlinear engagement kinematics, continuously maintains the target within its field-of-view bound and achieves guidance objectives. The proposed guidance strategy performs effectively, even for large deviations from the collision course, where pitch and yaw channels may be strongly coupled. Finally, the proposed guidance scheme is shown to be superior to existing strategies through numerical simulations.
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