1. |
- Abazajian, Kevork, et al.
(författare)
-
CMB-S4 : Forecasting Constraints on Primordial Gravitational Waves
- 2022
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 926:1
-
Tidskriftsartikel (refereegranskat)abstract
- CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5σ, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL.
|
|
2. |
- Adewumi, Oluwatosin, 1978-
(författare)
-
Word Vector Representations using Shallow Neural Networks
- 2021
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work highlights some important factors for consideration when developing word vector representations and data-driven conversational systems. The neural network methods for creating word embeddings have gained more prominence than their older, count-based counterparts.However, there are still challenges, such as prolonged training time and the need for more data, especially with deep neural networks. Shallow neural networks with lesser depth appear to have the advantage of less complexity, however, they also face challenges, such as sub-optimal combination of hyper-parameters which produce sub-optimal models. This work, therefore, investigates the following research questions: "How importantly do hyper-parameters influence word embeddings’ performance?" and "What factors are important for developing ethical and robust conversational systems?" In answering the questions, various experiments were conducted using different datasets in different studies. The first study investigates, empirically, various hyper-parameter combinations for creating word vectors and their impact on a few natural language processing (NLP) downstream tasks: named entity recognition (NER) and sentiment analysis (SA). The study shows that optimal performance of embeddings for downstream \acrshort{nlp} tasks depends on the task at hand.It also shows that certain combinations give strong performance across the tasks chosen for the study. Furthermore, it shows that reasonably smaller corpora are sufficient or even produce better models in some cases and take less time to train and load. This is important, especially now that environmental considerations play prominent role in ethical research. Subsequent studies build on the findings of the first and explore the hyper-parameter combinations for Swedish and English embeddings for the downstream NER task. The second study presents the new Swedish analogy test set for evaluation of Swedish embeddings. Furthermore, it shows that character n-grams are useful for Swedish, a morphologically rich language. The third study shows that broad coverage of topics in a corpus appears to be important to produce better embeddings and that noise may be helpful in certain instances, though they are generally harmful. Hence, relatively smaller corpus can show better performance than a larger one, as demonstrated in the work with the smaller Swedish Wikipedia corpus against the Swedish Gigaword. The argument is made, in the final study (in answering the second question) from the point of view of the philosophy of science, that the near-elimination of the presence of unwanted bias in training data and the use of foralike the peer-review, conferences, and journals to provide the necessary avenues for criticism and feedback are instrumental for the development of ethical and robust conversational systems.
|
|
3. |
- Aronsson, Fredrik, et al.
(författare)
-
Is cognitive impairment associated with reduced syntactic complexity in writing? Evidence from automated text analysis
- 2021
-
Ingår i: Aphasiology. - : ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD. - 0268-7038 .- 1464-5041. ; 35:7, s. 900-913
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Written language impairments are common in Alzheimers disease and reduced syntactic complexity in written discourse has been observed decades before the onset of dementia. The validity of average dependency distance (ADD), a measure of syntactic complexity, in cognitive decline needs to be studied further to evaluate its clinical relevance. Aims: The aim of the study was to determine whether ADD is associated with levels of cognitive impairment in memory clinic patients. Methods & procedures: We analyzed written texts collected in clinical practice from 114 participants with subjective cognitive impairment, mild cognitive impairment, and Alzheimers disease during routine assessment at a memory clinic. ADD was measured using automated analysis methods consisting of a syntactic parser and a part-of-speech tagger. Outcomes & results: Our results show a significant association between ADD and levels of cognitive impairment, using ordinal logistic regression models. Conclusion: These results suggest that ADD is clinically relevant with regard to levels of cognitive impairment and indicate a diagnostic potential for ADD in cognitive assessment.
|
|
4. |
|
|
5. |
- Debusmann, Ralph, et al.
(författare)
-
Dependency Grammar : Classification and Exploration
- 2010
-
Ingår i: Resource-Adaptive Cognitive Processes. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540894070 - 9783540894087 ; , s. 365-388
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Syntactic representations based on word-to-word dependencies have a long tradition in descriptive linguistics [29]. In recent years, they have also become increasingly used in computational tasks, such as information extraction [5], machine translation [43], and parsing [42]. Among the purported advantages of dependency over phrase structure representations are conciseness, intuitive appeal, and closeness to semantic representations such as predicate-argument structures. On the more practical side, dependency representations are attractive due to the increasing availability of large corpora of dependency analyses, such as the Prague Dependency Treebank [19].
|
|
6. |
|
|
7. |
- Dienes, Péter, et al.
(författare)
-
Statistical A-Star Dependency Parsing
- 2003
-
Ingår i: Proceedings of the Workshop on Prospects and Advances in the Syntax/Semantics Interface. ; , s. 85-89
-
Konferensbidrag (refereegranskat)abstract
- Extensible Dependency Grammar (XDG; Duchier and Debusmann (2001)) is a recently developed dependency grammar formalism that allows the characterization of linguistic structures along multiple dimensions of description. It can be implemented efficiently using constraint programming (CP; Koller and Niehren 2002). In the CP context, parsing is cast as a search problem: The states of the search are partial parse trees, successful end states are complete and valid parses. In this paper, we propose a probability model for XDG dependency trees and an A-Star search control regime for the XDG parsing algorithm that guarantees the best parse to be found first. Extending XDG with a statistical component has the benefit of bringing the formalism further into the grammatical mainstream; it also enables XDG to efficiently deal with large, corpus-induced grammars that come with a high degree of ambiguity.
|
|
8. |
- Doostmohammadi, Ehsan, 1993-, et al.
(författare)
-
On the Effects of Video Grounding on Language Models
- 2022
-
Ingår i: Proceedings of the First Workshop on Performance and Interpretability Evaluations of Multimodal, Multipurpose, Massive-Scale Models.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Transformer-based models trained on text and vision modalities try to improve the performance on multimodal downstream tasks or tackle the problem Transformer-based models trained on text and vision modalities try to improve the performance on multimodal downstream tasks or tackle the problem of lack of grounding, e.g., addressing issues like models’ insufficient commonsense knowledge. While it is more straightforward to evaluate the effects of such models on multimodal tasks, such as visual question answering or image captioning, it is not as well-understood how these tasks affect the model itself, and its internal linguistic representations. In this work, we experiment with language models grounded in videos and measure the models’ performance on predicting masked words chosen based on their imageability. The results show that the smaller model benefits from video grounding in predicting highly imageable words, while the results for the larger model seem harder to interpret.of lack of grounding, e.g., addressing issues like models’ insufficient commonsense knowledge. While it is more straightforward to evaluate the effects of such models on multimodal tasks, such as visual question answering or image captioning, it is not as well-understood how these tasks affect the model itself, and its internal linguistic representations. In this work, we experiment with language models grounded in videos and measure the models’ performance on predicting masked words chosen based on their imageability. The results show that the smaller model benefits from video grounding in predicting highly imageable words, while the results for the larger model seem harder to interpret.
|
|
9. |
- Doostmohammadi, Ehsan, 1993-, et al.
(författare)
-
Surface-Based Retrieval Reduces Perplexity of Retrieval-Augmented Language Models
- 2023
-
Ingår i: Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), pages 521–529, Toronto, Canada. - : Association for Computational Linguistics. ; 2, s. 521-529
-
Konferensbidrag (refereegranskat)abstract
- Augmenting language models with a retrieval mechanism has been shown to significantly improve their performance while keeping the number of parameters low. Retrieval-augmented models commonly rely on a semantic retrieval mechanism based on the similarity between dense representations of the query chunk and potential neighbors. In this paper, we study the state-of-the-art Retro model and observe that its performance gain is better explained by surface-level similarities, such as token overlap. Inspired by this, we replace the semantic retrieval in Retro with a surface-level method based on BM25, obtaining a significant reduction in perplexity. As full BM25 retrieval can be computationally costly for large datasets, we also apply it in a re-ranking scenario, gaining part of the perplexity reduction with minimal computational overhead.
|
|
10. |
- Dragisic, Zlatan, 1987-
(författare)
-
Completion of Ontologies and Ontology Networks
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The World Wide Web contains large amounts of data, and in most cases this data has no explicit structure. The lack of structure makes it difficult for automated agents to understand and use such data. A step towards a more structured World Wide Web is the Semantic Web, which aims at introducing semantics to data on the World Wide Web. One of the key technologies in this endeavour are ontologies, which provide a means for modeling a domain of interest and are used for search and integration of data.In recent years many ontologies have been developed. To be able to use multiple ontologies it is necessary to align them, i.e., find inter-ontology relationships. However, developing and aligning ontologies is not an easy task and it is often the case that ontologies and their alignments are incorrect and incomplete. This can be a problem for semantically-enabled applications. Incorrect and incomplete ontologies and alignments directly influence the quality of the results of such applications, as wrong results can be returned and correct results can be missed. This thesis focuses on the problem of completing ontologies and ontology networks.The contributions of the thesis are threefold. First, we address the issue of completing the is-a structure and alignment in ontologies and ontology networks. We have formalized the problem of completing the is-a structure in ontologies as an abductive reasoning problem and developed algorithms as well as systems for dealing with the problem. With respect to the completion of alignments, we have studied system performance in the Ontology Alignment Evaluation Initiative, a yearly evaluation campaign for ontology alignment systems. We have also addressed the scalability of ontology matching, which is one of the current challenges, by developing an approach for reducing the search space when generating the alignment.Second, high quality completion requires user involvement. As users' time and effort are a limited resource we address the issue of limiting and facilitating user interaction in the completion process. We have conducted a broad study of state-of-the-art ontology alignment systems and identified different issues related to the process. We have also conducted experiments to assess the impact of user errors in the completion process.While the completion of ontologies and ontology networks can be done at any point in the life-cycle of ontologies and ontology networks, some of the issues can be addressed already in the development phase. The third contribution of the thesis addresses this by introducing ontology completion and ontology alignment into an existing ontology development methodology.
|
|