Weakly-supervised Visual Grounding of Phrases with Linguistic Structures

We propose a weakly-supervised approach that takes image-sentence pairs as input and learns to visually ground (i.e., localize) arbitrary linguistic phrases, in the form of spatial attention masks. Specifically, the model is trained with images and their associated image-level captions, without any explicit region-to-phrase correspondence annotations. To this end, we introduce an end-to-end model which learns visual groundings of phrases with two types of carefully designed loss functions. In addition to the standard discriminative loss, which enforces that attended image regions and phrases are consistently encoded, we propose a novel structural loss which makes use of the parse tree structures induced by the sentences. In particular, we ensure complementarity among the attention masks that correspond to sibling noun phrases, and compositionality of attention masks among the children and parent phrases, as defined by the sentence parse tree. We validate the effectiveness of our approach on the Microsoft COCO and Visual Genome datasets.Comment: CVPR 201

3D Imaging via Polarized Jet Fragmentation Functions and Quantum Simulation of the QCD Phase Diagram

Understanding the interactions between elementary particles and mapping out the internal structure of the hadrons are of fundamental importance in high energy nuclear and particle physics. This thesis concentrates on the strong interaction, described by Quantum Chromodynamics (QCD). We introduce a novel concept called "polarized jet fragmentation functions" and develop the associated theory framework known as QCD factorization which allows us to utilize jet substructure to probe spin dynamics of hadrons, especially nucleon's three-dimensional imaging. Furthermore, non-perturbative QCD studies, particularly of the QCD phase diagram, are important for understanding the properties of hadrons. The development of quantum computing and simulators can potentially improve the accuracy of finite-temperature simulations and allow researchers to explore extreme temperatures and densities in more detail. In this thesis, I present my work in two aspects of QCD studies: (1) investigating the nucleon structure using polarized jet fragmentation functions and (2) illustrating how to apply quantum computing techniques for studying phase diagram of a low energy QCD model. The first category investigates phenomena such as hadron production inside jets, spin asymmetries, etc., providing valuable insight into the behavior of quarks and gluons in hadrons. The second category provides potential applications of quantum computing in QCD and explores the non-perturbative nature of QCD.Comment: PhD Thesis submitted to University of California, Los Angele

The Impact of White Space on User Experience for Tablet Editions of Magazines

After declining for six years (Wang, 2016), printed magazines are facing the dilemma of a paperless era. As magazine publishing emerges into the digital world, it needs to achieve the degree of readers’ desire that is comparable to or surpassing print publications. Limited research has been done regarding white space in digital magazines. This thesis aimed to investigate how user experience is affected by white space in the layout of digital editions of food magazines designed for the Apple iPad. The study focused on the evaluation of white space as the factor influencing the quality of the user experience. White space was separated into macro and micro white space. The researcher defined and quantified levels of macro and micro white space and created samples of magazine pages with the corresponding white space levels. Subsequently, the researcher obtained subjective evaluations of three perspectives of user experience: satisfaction, ease of use, and usefulness. Analysis of Variance was employed to determine if any of these white space levels have significant effect on user experience. The study determined that macro, micro, and the interaction of macro and micro white space had a significant impact on all three perspectives of UX based on the questionnaire data. It was observed that the majority of 62 participants chose the 38% macro white space, and 135% micro white space was the best combination regarding all three aspects of the user experience. It was concluded that 135% micro white space had the most significant effect on legibility, and 120% micro white space had the most positive effect on readability. Upon conclusion of the study, the researcher believes there is no specific white space amount that would satisfy all of the people. However, within the scope of the present experiment, it could provide a useable manual to magazine publishers and designers

Multi-scale observational study of Sagittarius B2

The giant molecular cloud Sagittarius B2 (SgrB2) is the most massive (~ 10^7 Msun) region with ongoing high-mass star formation in the Galaxy. SgrB2 has a higher density (>10^5 cm^{-3}) and dust temperature (~50--70 K) compared to other star forming regions in the Galactic plane. Additionally, SgrB2 is located at a projected distance of only ~100 pc to the Galactic center. These features make SgrB2 an excellent case to study high-mass star formation in an extreme, high-pressure environment. Such an environment resembles nearby starburst galaxies. Understanding the structure of the SgrB2 molecular cloud complex is necessary to comprehend the most massive star forming region in our Galaxy, which at the same time provides an unique opportunity to study in detail the nearest counterpart of the extreme environments that dominate star formation in the Universe. At small scales (0.01--0.1 pc), dense cores appear spread throughout the whole region of SgrB2, embedded within a large scale (~20 pc) envelope with two main sites of high-mass star formation activity at the center of the cloud: SgrB2(M) and SgrB2(N). In order to characterize the properties of SgrB2 from small to large scales, I started an observational project covering spatial scales from 0.004 pc (1000 au) up to 20 pc (the size of the envelope of SgrB2). At small scales, I studied the physical properties of 308 dense cores distributed throughout the entire SgrB2 cloud. I combined mm wavelength data and cm wavelength data to characterize the properties of dense cores and their associated Hii regions. Among the 308 compact dust cores that are identified, 58 are found associated with Hii regions, and 49 are associated with outflows. The cores have a mean mH2 of 150--2500 Msun, by assuming various dust properties and gas temperatures. Most of the 58 Hii regions are ionized by B0 stars. At intermediate scales, I studied the SgrB2(DS) Hii region, which is located in the southern part of the envelope. Using VLA data from 4 to 12 GHz, I derived a spectral index between -1.2 and -0.4, suggesting that SgrB2(DS) is a mixture of thermal and non-thermal emission at radio wavelengths. The thermal free-free emission is likely tracing an Hii region ionized by an O7 star, while the non-thermal emission can be generated by relativistic electrons created through first-order Fermi acceleration. A model of the Sgr B2(DS) region was developed, which reveals that first-order Fermi acceleration can reproduce the observed flux density and spectral index. At the largest scales, I characterized the physical properties of all the Hii regions in the envelope as well as the kinematic structure of the envelope, using newly acquired VLA cm wavelength data and ALMA HC3N line data. The volume filling factor of ionized gas in the envelope of SgrB2 is ~0.03-0.01. The Hii regions in the envelope are more extended than those in SgrB2(M) and SgrB2(N), suggesting that the Hii regions in the envelope may be older than those in the central regions SgrB2(M) and SgrB2(N), and therefore, indicating that high-mass star formation might have started throughout the envelope before than in the central regions. The envelope is also filled with arcs and bubbles, which are traced by HC3N. In summary, this study reveals the properties of SgrB2 from the scale of dense dust cores to the large envelope. The dense cores show various evolutionary stages in terms of high-mass star formation activity. The envelope resembles a ``swiss cheese'' and hosts star forming activities that may have started before those in the central parts of SgrB2. Additionally, for the first time, a model reveals that synchrotron emission from Hii regions can be due to locally produced relativistic electrons accelerated by shocks with moderate velocities