University of Houston

About: University of Houston is a education organization based out in Houston, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 23074 authors who have published 53903 publications receiving 1641968 citations.

Price variations in a stock market with many agents

Abstract: Large variations in stock prices happen with sufficient frequency to raise doubts about existing models, which all fail to account for non-Gaussian statistics. We construct simple models of a stock market, and argue that the large variations may be due to a crowd effect, where agents imitate each other's behavior. The variations over different time scales can be related to each other in a systematic way, similar to the Levy stable distribution proposed by Mandelbrot to describe real market indices. In the simplest least realistic case, exact results for the statistics of the variations are derived by mapping onto a model of diffusing and annihilating particles, which has been solved by quantum field theory methods. When the agents imitate each other and respond to recent market volatility, different scaling behavior is obtained. In this case, the statistics of price variations is consistent with empirical observations. The interplay between “rational” traders whose behavior is derived from fundamental analysis of the stock, including dividends, and “noise traders”, whose behavior is governed solely by studying the market dynamics and the behavior of other traders, is investigated. When the relative number of rational traders is small, “bubbles” often occur, where the market price moves outside the range justified by fundamental market analysis. When the number of rational traders is larger, the market price is generally locked within the price range they define.

Cobalt‐Catalyzed, Aminoquinoline‐Directed C(sp2)H Bond Alkenylation by Alkynes

Abstract: A method for cobalt-catalyzed, aminoquinoline- and picolinamide-directed C(sp2)H bond alkenylation by alkynes was developed. The method shows excellent functional-group tolerance and both internal and terminal alkynes are competent substrates for the coupling. The reaction employs a Co(OAc)2⋅4 H2O catalyst, Mn(OAc)2 co-catalyst, and oxygen (from air) as a terminal oxidant.

Dense Liquid Precursor for the Nucleation of Ordered Solid Phases from Solution

Abstract: A line of recent theories and simulations have suggested that the nucleation of protein crystals might, under certain conditions, proceed in two steps: the formation of a droplet of a dense liquid, metastable with respect to the crystalline state, followed by ordering within this droplet to produce a crystal. In this review, I discuss experimental tests of the applicability of this mechanism to the nucleation of ordered solid phases: crystals or linear, planar, branched, or otherwise ordered aggregates of proteins and small molecule materials from solution. The main arguments stem from recent results on the kinetics of homogeneous nucleation of crystals of the protein lysozyme. These results indicate that under a very broad range of conditions the nucleation of lysozyme crystals occurs via a modification of the theoretically postulated mechanismas a superposition of fluctuations along the order parameters density and structure. Depending on whether the system is above or below its liquid−liquid coexiste...

Reliability-Constrained Optimal Sizing of Energy Storage System in a Microgrid

Abstract: This paper presents a model for calculating the optimal size of an energy storage system (ESS) in a microgrid considering reliability criterion. A larger ESS requires higher investment costs while reduces the microgrid operating cost. The optimal ESS sizing problem is proposed which minimizes the investment cost of the ESS, as well as expected microgrid operating cost. Utilizing the ESS, generation shortage due to outage of conventional units and intermittency of renewable units is handled; hence microgrid reliability criterion is satisfied. A practical model for ESS is utilized. Mixed-integer programming (MIP) is utilized to formulate the problem. Illustrative examples show the efficiency of the proposed model.

Concrete structural health monitoring using embedded piezoceramic transducers

Abstract: Health monitoring of reinforced concrete bridges and other large-scale civil infrastructures has received considerable attention in recent years However, traditional inspection methods (x-ray, C-scan, etc) are expensive and sometimes ineffective for large-scale structures Piezoceramic transducers have emerged as new tools for the health monitoring of large-scale structures due to their advantages of active sensing, low cost, quick response, availability in different shapes, and simplicity for implementation In this research, piezoceramic transducers are used for damage detection of a 61 m long reinforced concrete bridge bent-cap Piezoceramic transducers are embedded in the concrete structure at pre-determined spatial locations prior to casting This research can be considered as a continuation of an earlier work, where four piezoceramic transducers were embedded in planar locations near one end of the bent-cap This research involves ten piezoceramic patches embedded at spatial locations in four different cross-sections To induce cracks in the bent-cap, the structure is subjected to loads from four hydraulic actuators with capacities of 80 and 100 ton In addition to the piezoceramic sensors, strain gages, LVDTs, and microscopes are used in the experiment to provide reference data During the experiment, one embedded piezoceramic patch is used as an actuator to generate high frequency waves, and the other piezoceramic patches are used as sensors to detect the propagating waves With the increasing number and severity of cracks, the magnitude of the sensor output decreases Wavelet packet analysis is used to analyze the recorded sensor signals A damage index is formed on the basis of the wavelet packet analysis The experimental results show that the proposed methods of using piezoceramic transducers along with the damage index based on wavelet packet analysis are effective in identifying the existence and severity of cracks inside the concrete structure The experimental results demonstrate that the proposed method has the ability to predict the failure of a concrete structure as verified by results from conventional microscopes (MSs) and LVDTs