Deep Room Recognition Using Inaudible Echos

Recent years have seen the increasing need of location awareness by mobile applications. This paper presents a room-level indoor localization approach based on the measured room's echos in response to a two-millisecond single-tone inaudible chirp emitted by a smartphone's loudspeaker. Different from other acoustics-based room recognition systems that record full-spectrum audio for up to ten seconds, our approach records audio in a narrow inaudible band for 0.1 seconds only to preserve the user's privacy. However, the short-time and narrowband audio signal carries limited information about the room's characteristics, presenting challenges to accurate room recognition. This paper applies deep learning to effectively capture the subtle fingerprints in the rooms' acoustic responses. Our extensive experiments show that a two-layer convolutional neural network fed with the spectrogram of the inaudible echos achieve the best performance, compared with alternative designs using other raw data formats and deep models. Based on this result, we design a RoomRecognize cloud service and its mobile client library that enable the mobile application developers to readily implement the room recognition functionality without resorting to any existing infrastructures and add-on hardware. Extensive evaluation shows that RoomRecognize achieves 99.7%, 97.7%, 99%, and 89% accuracy in differentiating 22 and 50 residential/office rooms, 19 spots in a quiet museum, and 15 spots in a crowded museum, respectively. Compared with the state-of-the-art approaches based on support vector machine, RoomRecognize significantly improves the Pareto frontier of recognition accuracy versus robustness against interfering sounds (e.g., ambient music).Comment: 29 page

An Examination of Singular Third-Person Pronoun Usage Between Spoken and Written English by Chinese ESL Students

The objective of this project was to study the use of third-person singular pronouns in Chinese English as a second language (ESL) students’ spoken and written English. Specifically, this research studied the possible interpretations of Chinese students’ inability to use correct third-person pronouns with gender features (i.e. mixing “she” and “he”) while the speaker is speaking spontaneously. This study also examined the indistinguishability between masculine and feminine pronouns in spoken Mandarin Chinese and the effect of transference between the native language (Mandarin Chinese, L1), the target language (English, L2), and the lack of communicative English learning. This study reported the error rate of third-person pronoun usage in both spoken and written English of 48 ESL (English as a second language) Chinese students in a Midwest university in the U.S. By using the Suppliance in Obligatory Contexts (SOC) strategy, quantitative research procedures, and within-subject design, this study examined and analyzed the difference in third-person pronoun usage between spoken and written English by Chinese ESL students. The research discovered that the Chinese students had more third-person pronoun usage errors in spoken English than in written English, yet more research is needed to make a stronger case. The future implications for Mandarin Chinese ESL students are that they might benefit from high L2 input exposure and sufficient time to self-monitor when speaking in an L2 environment

Modeling and Investigation of Refrigeration System Performance with Two-Phase Fluid Injection in a Scroll Compressor

Vapor compression cycles are widely used in heating, refrigerating and air-conditioning. A slight performance improvement in the components of a vapor compression cycle, such as the compressor, can play a significant role in saving energy use. However, the complexity and cost of these improvements can block their application in the market. Modifying the conventional cycle configuration can offer a less complex and less costly alternative approach. Economizing is a common modification for improving the performance of the refrigeration cycle, resulting in decreasing the work required to compress the gas per unit mass. Traditionally, economizing requires multi-stage compressors, the cost of which has restrained the scope for practical implementation. Compressors with injection ports, which can be used to inject economized refrigerant during the compression process, introduce new possibilities for economization with less cost. This work focuses on computationally investigating a refrigeration system performance with two-phase fluid injection, developing a better understanding of the impact of injected refrigerant quality on refrigeration system performance as well as evaluating the potential COP improvement that injection provides based on refrigeration system performance provided by Copeland