EXTRUSION AND ALKALI EXTRUSION OF CORN STOVER TO IMPROVE ENZYME SACCHARIFICATION

Biomass pretreatment constitutes an important part in the whole process of bioethanol production. The main goals of pretreatment include improving cellulose accessibility to enzyme, enhancing sugar yields from hemicellulose, achieving low capital and energy costs, as well as low sugar degradation and low chemical requirements. Extrusion, as a continuous and high throughput pretreatment method, requires much less chemical compared to traditional alkali pretreatment. In this research, twin-screw extrusion was evaluated for its effect with regard to promoting sugar yields from corn stover. Also, the underlying factors contributing to this improvement were examined. It was found that extrusion with no chemicals and post-pretreatment steps achieved significantly higher sugar yields than the untreated corn stover. It was shown that crystallinity indices were not different among the extruded and untreated samples. However, for pretreated samples, the specific surface areas estimated from the Langmuir adsorption model, were significantly different than the untreated corn stover. Extrusion using sodium hydroxide was shown to transform the structure of lignin. The sugar yields were greatly increased over the extrusion only and untreated corn stover. Crystallinity index and pore quantity were both examined. Crystallinity index was not significantly different from the untreated corn stover, however, pore quantities, measured by Congo red adsorption, were significantly amplified due to alkali combined extrusion. Advisor: Milford A. Hann

Autonomous navigation with constrained consistency for C-Ranger

Autonomous underwater vehicles (AUVs) have become the most widely used tools for undertaking complex exploration tasks in marine environments. Their synthetic ability to carry out localization autonomously and build an environmental map concurrently, in other words, simultaneous localization and mapping (SLAM), are considered to be pivotal requirements for AUVs to have truly autonomous navigation. However, the consistency problem of the SLAM system has been greatly ignored during the past decades. In this paper, a consistency constrained extended Kalman filter (EKF) SLAM algorithm, applying the idea of local consistency, is proposed and applied to the autonomous navigation of the C-Ranger AUV, which is developed as our experimental platform. The concept of local consistency (LC) is introduced after an explicit theoretical derivation of the EKF-SLAM system. Then, we present a locally consistency-constrained EKF-SLAM design, LC-EKF, in which the landmark estimates used for linearization are fixed at the beginning of each local time period, rather than evaluated at the latest landmark estimates. Finally, our proposed LC-EKF algorithm is experimentally verified, both in simulations and sea trials. The experimental results show that the LC-EKF performs well with regard to consistency, accuracy and computational efficiency

An analysis of wealth change of acquiring-firm shareholders in the recent technology mergers wave in U.S.

1 online resource (iv, 32 p.) : ill. (some col.)Includes abstract.Includes bibliographical references (p. 29-32).This paper examines the experience of acquiring-firm shareholders wealth during recent technology merger wave in U.S. from 2010 to 2014. The methodology in this paper uses 635 acquisitions from the high-tech industry over the period 2010 to 2014. The mean cumulative abnormal return and aggregate dollar return are used to measure the yearly wealth change of acquirer shareholders. The paper finds that large loss and gain deals lead to different results of acquiring-firm shareholders wealth change in the same year. In addition, the paper examines the impact of relative firm and deal characteristics on the results. The findings show that these characteristics contribute limitedly to abnormal returns associated with large loss and gain deals

Problems and Countermeasures of Rare Earth Industry in China

Rare earth elements are applied extensively in various industries, especially in the hi-tech and military fields. China has various and abundant deposits in rare earth resources. Since the end of the 20th century, China has been No.1 in both the production and exportation of rare earth products in the world. However, there are many rare earth problems in China, such as very low mining industry concentration, backward mining technology, disordered mining administration, low export price, difficult transformation of export policy, serious smuggling and decreasing storage. China’s comparative advantages in rare earth resources are gradually in decline and even in a danger of losing. As for rare earth elements China should integrate and standardize the disordered mining industry, extend the domestic supply chain, try to match the domestic industry policies with international trade policy, and improve the system of strategic storage

On Problems in Rare Earth Exports of China and Countermeasures

As a country with rich deposit domestically and huge amount of supplying internationally of rare earth, China has not received the matched benefits. The major problems faced by China in rare earth are low international price, difficult transition of export policy, rampant smuggling and decreasing export potential. To solve these problems, China must insist on the transformation of export policy in rare earth, try to match domestic policies with international ones, fully recognize the strategic status of rare earth, control the exporting, mining, utilizing and reserving of rare earth comprehensively, and attack rare earth smuggling more seriously. Key words: Rare earth; Export control; Smuggling; Strategic reserv

Quantum Interference of Stored Coherent Spin-wave Excitations in a Two-channel Memory

Quantum memories are essential elements in long-distance quantum networks and quantum computation. Significant advances have been achieved in demonstrating relative long-lived single-channel memory at single-photon level in cold atomic media. However, the qubit memory corresponding to store two-channel spin-wave excitations (SWEs) still faces challenges, including the limitations resulting from Larmor procession, fluctuating ambient magnetic field, and manipulation/measurement of the relative phase between the two channels. Here, we demonstrate a two-channel memory scheme in an ideal tripod atomic system, in which the total readout signal exhibits either constructive or destructive interference when the two-channel SWEs are retrieved by two reading beams with a controllable relative phase. Experimental result indicates quantum coherence between the stored SWEs. Based on such phase-sensitive storage/retrieval scheme, measurements of the relative phase between the two SWEs and Rabi oscillation, as well as elimination of the collapse and revival of the readout signal, are experimentally demonstrated