Causality in Quantiles and Dynamic Stock Return-Volume Relations

This paper investigates the causal relations between stock return and volume based on quantile regressions. We first define Granger non-causality in all quantiles and propose testing non-causality by a sup-Wald test. Such a test is consistent against any deviation from non-causality in distribution, as opposed to the existing tests that check only noncausality in certain moment. This test is readily extended to test non-causality in different quantile ranges, and the testing results enable us to identify the quantile range for which causality is relevant. In the empirical studies of 3 major stock market indices, we find that, while the conventional test suggests no causality in mean, there are strong evidences that lagged volume Granger causes return in all but some middle quantiles. In particular, the causal effects have opposite signs at lower and upper quantiles and are stronger at more extreme quantiles. These relations form (symmetric) V shapes across quantiles. They also show that the dispersion of the return distribution increases with volume so that volume has a positive effect on return volatility. It is also shown that the quantile causal effects of lagged return on volume are mainly negative.Granger non-causality in quantiles, quantile causal effect, quantile regression, return-volume relation, sup-Wald test

An Intelligent Auxiliary Vacuum Brake System

The purpose of this paper focuses on designing an intelligent, compact, reliable, and robust auxiliary vacuum brake system (VBS) with Kalman filter and self-diagnosis scheme. All of the circuit elements in the designed system are integrated into one programmable system-on-chip (PSoC) with entire computational algorithms implemented by software. In this system, three main goals are achieved: (a) Kalman filter and hysteresis controller algorithms are employed within PSoC chip by software to surpass the noises and disturbances from hostile surrounding in a vehicle. (b) Self-diagnosis scheme is employed to identify any breakdown element of the auxiliary vacuum brake system. (c) Power MOSFET is utilized to implement PWM pump control and compared with relay control. More accurate vacuum pressure control has been accomplished as well as power energy saving. In the end, a prototype has been built and tested to confirm all of the performances claimed above

Characterizing the function of transcription factor 15 (Tcf15) in pluripotent cells

Pluripotent embryonic stem (ES) cells are heterogeneous mixtures of naïve and lineage-primed states defined by distinct transcription factor expression profiles. However, the events that prime pluripotent cells for differentiation are not well understood. Id proteins, which are inhibitors of basic helix-loop-helix (bHLH) transcription factors, contribute to pluripotency by blocking differentiation. Using Yeast-Two-Hybrid screening, our lab identified Tcf15 as an Id-regulated transcription factor. In this study, I first examined the expression of Tcf15 during differentiation in vitro and during early development in vivo in the mouse. Tcf15 expression is higher in primed pluripotent embryonic stem (ES) cells than in naïve ES cells or epiblast stem cells (EpiSCs). In addition, Tcf15 is expressed heterogeneously in ES cells and is also detected in the inner cell mass (ICM) of E4.5 mouse embryos. Expression of Tcf15 was upregulated during early stages of differentiation and downregulated before cells committed to any specific lineage. Using Tcf15-Venus reporter cells, I found that expression of Tcf15 is specifically associated with a novel subpopulation of ES cells primed for somatic lineages. Gain of function and loss of function studies were then performed to perturb Tcf15 expression in ES cells in order to assess the function of Tcf15 in self-renewal and during differentiation. An inducible Id-resistant form of Tcf15 accelerates somatic lineage commitment by maturating naïve pluripotent ES cells transit toward primed epiblast and later on epiblastderived somatic lineages whilst suppressing differentiation towards extraembryonic endoderm. Preliminary loss of function studies also suggest that down-regulation of Tcf15 may promote a naïve state within pluripotent cells. I investigated the mechanism by which Tcf15 expression becomes associated with the epiblast-primed state by identifying the upstream regulators and downstream targets of Tcf15. Tcf15 expression is dependent on FGF signalling. Microarray analysis identified that Tcf15 downregulates the naïve pluripotency determinant Nanog and upregulates the epiblast determinant Otx2. Taken together, our results suggest that Tcf15 acts in opposition to the pluripotency network to prime pluripotent cells towards differentiation

Congestion Control for Machine-Type Communications in LTE-A Networks

Collecting data from a tremendous amount of Internet-of-Things (IoT) devices for next generation networks is a big challenge. A large number of devices may lead to severe congestion in Radio Access Network (RAN) and Core Network (CN). 3GPP has specified several mechanisms to handle the congestion caused by massive amounts of devices. However, detailed settings and strategies of them are not defined in the standards and are left for operators. In this paper, we propose two congestion control algorithms which efficiently reduce the congestion. Simulation results demonstrate that the proposed algorithms can achieve 20~40% improvement regarding accept ratio, overload degree and waiting time compared with those in LTE-A

Development and Illustration of a Risk-Based Framework for Use by the Colorado Department of Transportation for Built Facilities

This thesis develops a methodology for CDOT to use in the risk analysis of various types of facilities and provides illustrative examples for the use of the proposed framework. An overview of the current practices and applications to illustrate the context from which the proposed methodology has been developed is presented first. Next, the thesis introduces the proposed methodology for CDOT. In order to understand how the framework operates in practice, two illustrative examples are presented. The first example demonstrates the framework through the context of allocating resources for the operation and maintenance of a portfolio of signalized mast arms. Two risk assessment methods are introduced through the first example, and it is shown that mast arms could benefit from varied inspection frequencies based on current structural defects present. The second illustrative example uses the framework in the context of making design decisions with regard to seismic hazard in Colorado. A quantitative risk assessment method is introduced, and the illustration suggests that seismic hazard is not a controlling hazard in Colorado. Through the literature review and presented examples, CDOT is equipped with the resources and information necessary to implement a risk-based methodology in decision making across its organization