Method Of Multiple Hypotheses Research Articles

Efficient Transceiving Search Scheme and Implementation Method for Collocated Distributed Coherent Aperture Radar via Grating Lobes Exploitation

Distributed coherent aperture radar (DCAR) can realize high-precision long-range detection because of its excellent angular resolution. However, it is accompanied by a low search efficiency problem caused by the narrow main lobe and the angular ambiguity problem stemming from the high grating lobes. By simultaneously utilizing multiple grating lobes, we propose an effective search method and pertinent unambiguous signal processing algorithms to address the issue of using collocated DCAR for unambiguous target search. We investigate the beam migration of a grating lobe-irradiated target at various frequencies in order to carry out the multi-frequency coherent integration of the suggested search method in DCAR. In order to address the issue of using multiple beam lobes to simultaneously detect multiple targets, we also take into account the scenario of multiple targets and introduce the multiple hypothesis method to solve the problem. The DCAR search efficiency can be improved by tens of times through grating lobes exploitation, which makes use of DCAR to make the searches feasible. We also improved the performance of multi-frequency DOA ambiguity solving compared to existing algorithms with the sliding window clustering scheme. The viability of using grating lobes for the DCAR target searching and detection is shown in simulations. The experiments confirm the performance enhancement of multi-frequency coherent integration for parameter estimation.

Climatic and anthropogenic drivers of a drying Himalayan river

Abstract. Streamflow regimes are rapidly changing in many regions of the world. Attribution of these changes to specific hydrological processes and their underlying climatic and anthropogenic drivers is essential to formulate an effective water policy. Traditional approaches to hydrologic attribution rely on the ability to infer hydrological processes through the development of catchment-scale hydrological models. However, such approaches are challenging to implement in practice due to limitations in using models to accurately associate changes in observed outcomes with corresponding drivers. Here we present an alternative approach that leverages the method of multiple hypotheses to attribute changes in streamflow in the Upper Jhelum watershed, an important tributary headwater region of the Indus basin, where a dramatic decline in streamflow since 2000 has yet to be adequately attributed to its corresponding drivers. We generate and empirically evaluate a series of alternative and complementary hypotheses concerning distinct components of the water balance. This process allows a holistic understanding of watershed-scale processes to be developed, even though the catchment-scale water balance remains open. Using remote sensing and secondary data, we explore changes in climate, surface water, and groundwater. The evidence reveals that climate, rather than land use, had a considerably stronger influence on reductions in streamflow, both through reduced precipitation and increased evapotranspiration. Baseflow analyses suggest different mechanisms affecting streamflow decline in upstream and downstream regions, respectively. These findings offer promising avenues for future research in the Upper Jhelum watershed, and an alternative approach to hydrological attribution in data-scarce regions.

Multiple hypothesis method for tracking move‐stop‐move target

This study presents a new approach to track the move-stop-move targets. In the presence of the radar Doppler blind area, a move-stop-move target may lead to track breakages, which has some adverse effects on estimating the number of targets in the surveillance area. The authors develop a mode switching-based multiple hypothesis tracking (MHT) method to solve this problem. In each association, MHT generates three types of hypotheses: moving and detected, moving and undetected and stopped. In the first two types of hypotheses, the target is in the mode of move and tracked with interacting multiple model (IMM)-extended Kalman filter (EKF) estimator, while in the third kind of hypotheses, the target is in the mode of stop and tracked by EKF with a stop model. The mode probabilities are calculated using the kinematic state statistics from the estimator and the Markov transfer probability of the target movement stage. The track discontinuity event in the classical log-likelihood ratio of MHT is modified as well. The results of simulation experiment show that the proposed MHT-based tracker outperforms the conventional MHT-based method when tracking move-stop-move target.

Multiple-model multiple hypothesis probability hypothesis density filter with blind zone

According to the problem of continuous tracking of multiple manoeuvring targets under the blind zone, a multiple-model probability hypothesis density (MM-PHD) filter based on the multiple hypothesis method is proposed. Under the blind zone, target state is estimated using the multiple model method. The hypothesis state is as the update state in the update step. Once the measurement is received, it will be updated using the MM filter. An improved pruning and merging algorithm is proposed to solve the problem of the number of hypothesis Gaussian components increasing continuously. Simulation results show that the novel algorithm is more effective in tracking multiple manoeuvring targets and improves performance of continuous target tracking.

Multiple-model multiple hypothesis probability hypothesis density filter with blind zone

According to the problem of continuous tracking of multiple manoeuvring targets under the blind zone, a multiple-model probability hypothesis density (MM-PHD) filter based on the multiple hypothesis method is proposed. Under the blind zone, target state is estimated using the multiple model method. The hypothesis state is as the update state in the update step. Once the measurement is received, it will be updated using the MM filter. An improved pruning and merging algorithm is proposed to solve the problem of the number of hypothesis Gaussian components increasing continuously. Simulation results show that the novel algorithm is more effective in tracking multiple manoeuvring targets and improves performance of continuous target tracking.

New Outlier Separability Test and Its Application in GNSS Positioning

With the increasing automation of measurement, adjustment, outlier detection and the consequential use of the results for real-time applications, reliable methods to detect and mitigate an outlier are required. However, it is frequently advised that the outlier test should not be used as a means to automatically reject an outlier. One of the reasons for this is that the outlier detection test at times can identify a wrong measurement. To address this issue, this paper proposes a new outlier separability test to confirm that the identified outlier, by the outlier test, can be confidently rejected as the outlier. In addition, the Minimally Separable Bias and the separability multiplying factor are also obtained for the proposed outlier separability test. With the initial comparisons between the proposed method with the reapplication of the global model test method and multiple hypothesis method, the advantages of the new outlier separability test are demonstrated.

Range ambiguity resolving of HPRF radar based on hybrid filter

In this paper, a novel method of range ambiguity resolving based on hybrid filter is proposed for high-pulse repetition frequency (HPRF) radars. By considering the discrete-valued pulse interval number (PIN) which is described as the radial range of the target divided by the maximum unambiguous range for a certain HPRF and its incremental variable as target states, the problem of range ambiguity resolving is converted to the hybrid state estimation problem. In the initial time steps, since the range measurement is ambiguous, the hybrid state initialization is achieved by utilizing multiple HPRFs based on Euclidean distance. Then, to avoid the choice of the thresholds, the hybrid model based on six-dimension state vector is made equivalent to several hybrid models based on five-dimension state vector according to the values that PIN incremental variable may take. The hybrid estimation is achieved by comparing 2-norm of the innovations obtained from several hybrid filters. Simulation results demonstrate that the proposed method can converge more rapidly than the existing multiple hypothesis method when only one HPRF has target measurement and overcome the mistake that multiple hypothesis method makes when PIN varies.

Making progress in forecasting

Twenty-five years ago, the International Institute of Forecasters was established “to bridge the gap between theory and practice”. Its primary vehicle was the Journal of Forecasting and is now the International Journal of Forecasting. The Institute emphasizes empirical comparisons of reasonable forecasting approaches. Such studies can be used to identify the best forecasting procedures to use under given conditions, a process we call evidence-based forecasting. Unfortunately, evidence-based forecasting meets resistance from academics and practitioners when the findings differ from currently accepted beliefs. As a consequence, although much progress has been made in developing improved forecasting methods, the diffusion of useful forecasting methods has been disappointing. To bridge the gap between theory and practice, we recommend a stronger emphasis on the method of multiple hypotheses and on invited replications of important research. It is then necessary to translate the findings into principles that are easy to understand and apply. The Internet and software provide important opportunities for making the latest findings available to researchers and practitioners. Because researchers and practitioners believe that their areas are unique, we should organise findings so that they are relevant to each area and make them easily available when people search for information about forecasting in their area. Finally, progress depends on our ability to overcome organizational barriers.

The Method of Multiple Hypotheses

The field of family studies would be enhanced by more systematic use of the method of multiple hypotheses. Multiple interpretations of family phenomena need to be considered routinely. Conceptual hypotheses should more frequently be designed to disconfirm theoretical expectations or to pit competing explanations against one another. Theories need to be bolder, particularly in the sense that they should aim to make counterintuitive and more precise predictions. This article elaborates such a view and relates it to philosophy of science (especially Popper and Kuhn), to current practice in family studies, to factors that inhibit attempts to disconfirm existing interpretations, and to implications for research and for theory development in family studies.

Advocacy and Objectivity in Science

Three strategies for scientific research in management are examined: advocacy, induction, and multiple hypotheses. Advocacy of a single dominant hypothesis is efficient, but biased. Induction is not biased, but it is inefficient The multiple hypotheses strategy seems to be both efficient and unbiased. Despite its apparent lack of objectivity, most management scientists use advocacy. For example, 2/3 of the papers published in a sampling of issues of Management Science (1955–1976) used advocacy. A review of the published empirical evidence indicates that advocacy reduces the objectivity of the scientists. No evidence was found to suggest that this lack of objectivity could be overcome by a “marketplace for ideas” (i.e., publication for peer review). It is recommended that the method of multiple hypotheses be used.

Econometric Forecasting and the Science Court

This paper examines the additional evidence produced by the seven scientists on each of the issues.The issues were: (1) Should econometricians use the method of multiple hypotheses rather than advocacy? (2) Do econometric provide the most accurate approach to short-range forecasting (Table 2 of versus Fact)? (3) Are complex econometric more accurate than simple econometric methods (Table 4 of versus Fact)? Comments Postprint version. Published in Journal of Business, Volume 51, Issue 4, October 1978, pages 595-600. Publisher URL: http://www.journals.uchicago.edu/ This journal article is available at ScholarlyCommons: http://repository.upenn.edu/marketing_papers/81 1 Published in the Journal of Business (1978), 51 (4), 595-600. Econometric Forecasting and the Science Court J. Scott Armstrong The Wharton School, University of Pennsylvania A man convinced against his will Is of the same opinion still. (Paraphrased from Samuel Butler, 1663) My paper, “Forecasting with Econometric Methods: Folklore versus Fact,” argued for the method of multiple hypotheses in econometrics. However, those who favor advocacy (e.g., Mitroff 1972) assert that ample opportunity exists for minority viewpoints to be aired. Furthermore, they feel that the marketplace for ideas will work efficiently. A recent proposal in Science (reviewed by Boffey 1976) called for a science court to improve the advocacy procedure (see also Callen 1976; Presidential Advisory Group 1976). Rather than wait for different viewpoints to appear in the literature, scientists would be called to act as advocates, much as in a court of law. Such a procedure should speed up the collection and examination of the evidence. The Journal of Business has, in effect, provided a science court to examine the issues discussed in “Folklore versus Fact.” Seven scientists were asked to participate in this endeavor. The Journal of Business assembled an impressive group of scientis ts, most of them well-known econometricians. These scientists also bring a variety of viewpoints with them. What should we expect of the science court? It should at least help to ensure that all relevant evidence on the issues has been presented. A second objective, though of lesser importance, is that it make recommendations on the basis of the evidence. The “Folklore versus Fact” paper obtained the relevant evidence by using the method of multiple hypotheses. I claimed that such an approach is efficient and relatively unbiased. What we have then, is a modest opportunity to contrast the method of multiple hypotheses with the most desirable form of the advocacy method – that is, with the science court. The next section of this paper examines the additional evidence produced by the seven scientists on each of the issues. The issues were: (1) “Should econometricians use the method of multiple hypotheses rather than advocacy?” (2) “Do econometric provide the most accurate approach to short-range forecasting” (Table 2 of “Folklore versus Fact”)? (3) “Are complex econometric more accurate than simple econometric methods” (Table 4 of “Folklore versus Fact”)? For simplicity, I refer to these issues as research strategies, short-range forecasting, and complex methods, respectively. Evidence Provided by the Seven Scientists If the advocacy method were superior to multiple hypotheses, it should generate substantially more evidence and the evidence should be more balanced. Did this happen? I examined each of the papers by the seven scientists (and 1 The editors of the Journal of Business made available to me a major work by Professor Victor Zarnowitz of the University of Chicago, An Analysis of Annual and Multiperiod Quarterly Forecasts of Aggregate Income, Output, and the Price Level,' which, though not directed at my versus Fact paper, nonetheless has implications for the issues discussed therein. 1 therefore refer to that paper as well. (The Zarnowitz paper appeared in the January 1979 issue of the Journal of Business.) 2 As in versus Fact, evidence was defined as published empirical evidence.

Forecasting with Econometric Methods: Folklore Versus Fact

Evidence from social psychology suggests that econometricians will avoid evidence that disconfirms their beliefs. Two beliefs of econometricians were examined: (1) Econometric methods provide more accurate short-term forecasts than do other methods; and (2) more complex econometric methods yield more accurate forecasts. A survey of 21 experts in econometrics found that 95% agreed with the first statement and 72% agreed with the second. A review of the published empirical evidence yielded little support for either of the two statements in the 41 studies. The method of multiple hypotheses was suggested as a research strategy that will lead to more effective use of disconfirming evidence. Although this strategy was suggested in 1890, it has only recently been used by econometricians.

Two self-test methods applied to an inertial system problem

The paper describes two self-test procedures applied to the problem of estimating the biases in accelerometers and gyroscopes on an inertial platform. The first technique is the weighted sum-squared residual (WSSR) test, with which accelerator bias jumps are easily isolated, but gyro bias jumps are difficult to isolate. The WSSR method does not take full advantage of the knowledge of system dynamics. The other technique is a multiple hypothesis method developed by Buxbaum and Haddad (1969). It has the advantage of directly providing jump isolation information, but suffers from computational problems. It might be possible to use the WSSR to detect state jumps and then switch to the BH system for jump isolation and estimate compensation.

What is Geologic Truth?

Geological identifications of minerals, fossils, stratigraphic succession, and the like may be analyzed in terms of operations and, if certain precautions are taken, the conclusions may be considered correct by definition. Historical implications are less easily tested for accuracy. For simple problems, however, such as the source direction for the San Onofre breccia of southern California, or the subaerial or subaqueous origin of the head of Monterey Submarine Canyon, the method of multiple hypotheses can be made exhaustive and apparently conclusive.