Dissipative time-dependent quantum transport theory

published_or_final_versio

Rapid changes of precipitation pH in Qinghai Province, the northeastern Tibetan Plateau

Rainfall monitoring programs were conducted in two industrial cities of China's Qinghai Province, Xining and Germu, in some periods of the 1980s and 1990s. The results show that the natural precipitation in this area is originally alkaline. Compared with the late 1980s records, pH values declined significantly from approximately 8 in the 1980s to below 7 in mid-1990s. Such rapid and drastic changes were attributed to fast industrial development that released a large amount of pollutants. Subsequent tough control on pollutant emission partly restored pH values back to above 7 in the late 1990s. The pH and rainfall chemical analyses indicate that alkaline rain in this continental arid region is caused by airborne dusts which originate from local alkaline soils. With decrease of pH value, the total ionic concentration of rainwater is increased because acids were added to the rainwater. © 2002 Elsevier Science B.V. All rights reserved.postprin

Geochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belt

The Qilian Mountains in NW China comprise the North Qilian Orogenic Belt, Central Qilian Block, and South Qilian Orogenic Belt. The North Qilian Orogenic Belt consists of the Northern and Southern terranes separated by a volcanic rock belt. This belt is composed mainly of felsic and mafic volcanic rocks. Volcanic rocks in the Baiyin area of the eastern part of the belt include rhyolites, rhyodacite, andesitic basalts, and basalts. New zircon U-Pb isotopic data yield a crystallization age of ca. 445 Ma for the rhyolite, 30 m.yr. younger than the associated basalts. The mafic volcanic rocks are relatively enriched in Th, Sr, and light rare earth element with (La/Yb) N ratios ranging from 4.2 to 5.6 and LaN ranging from 40 to 49, and depleted in high field strength elements, with high Th/Nb ratios (0.9-1.3). These features together with their εNd(T) values (-1.4 to +3.1) are consistent with a subduction-related origin, most likely in a mature island arc or an arc built on thin continental crust in an active continental margin. The felsic volcanic rocks show a calc-alkaline affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies and relatively high Th/Nb ratios (0.8-1.6). They have significantly high εNd(T) values (+4.4 to +7.7) relative to the mafic volcanic rocks. Such radiogenic Nd isotopic compositions rule out a crustal origin and indicate the derivation from a depleted mantle source in a volcanic arc environment. Therefore, the geochemistry of the mafic and felsic volcanic rocks demonstrates an Ordovician volcanic arc above a northward subduction zone. The northward drifting of the Central Qilian Block eventually resulted in the amalgamation of the Northern and Southern terranes to form the North Qilian Orogenic Belt in the Early Paleozoic. © 2005 by The University of Chicago. All rights reserved.published_or_final_versio

High-resolution imaging of two bipolar proto-planetary nebulae

Sub-arcsecond resolution V and I images have been obtained for two proto-planetary nebulae. Both are found to show a definite bipolar morphology. A circumstellar disk is clearly seen in the V - I color image, suggesting that the bipolar lobes are due to starlight scattered into the polar openings. This indicates that bipolar morphologies develop early in the evolution of planetary nebulae, even before the onset of photoionization. © 1996. The American Astronomical Society. All rights reserved.published_or_final_versio

A variational approach for dissipative quantum transport in a wide parameter space

published_or_final_versio

Augmented reality in robot programming

Industrial robots have been traditionally programmed using teaching pendants, whereas offline programming methods are getting increasingly popular in recent years. Although the above two methods are widely-used in the industry, they both have certain disadvantages. For instance, the teaching pendant method requires a shutdown of the production line during the programming process, while offline programming method requires 3D CAD models of both the robot and the workpiece. In this paper, an augmented reality (AR) application which alleviates the aforementioned problems was proposed for robot programming purposes. The application is created using commercially available AR software, with the addition of our JavaScript code. The use of commercially available software allows an easier sharing and widespread adoption of the application

Reduction of motion artifact in pulse oximetry by smoothed pseudo Wigner-Ville distribution

BACKGROUND: The pulse oximeter, a medical device capable of measuring blood oxygen saturation (SpO2), has been shown to be a valuable device for monitoring patients in critical conditions. In order to incorporate the technique into a wearable device which can be used in ambulatory settings, the influence of motion artifacts on the estimated SpO2 must be reduced. This study investigates the use of the smoothed psuedo Wigner-Ville distribution (SPWVD) for the reduction of motion artifacts affecting pulse oximetry. METHODS: The SPWVD approach is compared with two techniques currently used in this field, i.e. the weighted moving average (WMA) and the fast Fourier transform (FFT) approaches. SpO2 and pulse rate were estimated from a photoplethysmographic (PPG) signal recorded when subject is in a resting position as well as in the act of performing four types of motions: horizontal and vertical movements of the hand, and bending and pressing motions of the finger. For each condition, 24 sets of PPG signals collected from 6 subjects, each of 30 seconds, were studied with reference to the PPG signal recorded simultaneously from the subject's other hand, which was stationary at all times. RESULTS AND DISCUSSION: The SPWVD approach shows significant improvement (p < 0.05), as compared to traditional approaches, when subjects bend their finger or press their finger against the sensor. In addition, the SPWVD approach also reduces the mean absolute pulse rate error significantly (p < 0.05) from 16.4 bpm and 11.2 bpm for the WMA and FFT approaches, respectively, to 5.62 bpm. CONCLUSION: The results suggested that the SPWVD approach could potentially be used to reduce motion artifact on wearable pulse oximeters

Analytical technology aided optimization and scale-up of impinging jet mixer for reactive crystallization process

Reactive crystallization is widely used in the manufacture of active pharmaceutical ingredients (APIs). Since APIs often have low solubility, traditional stirred tank reactors and the route of process operation and control using metastable zone width are not effective. The current work investigated the integration of an impinging jet mixer and a stirred tank crystallizer that can take advantage of both the reaction and crystallization characteristics, the focus being on design optimization and scale-up using process analytical techniques based on the Fourier transform Infrared spectroscopy and Focused Beam Reflectance Measurement, as well as X-ray diffraction and particle imaging Morphologi G3. The parameters for process operation and design of the impinging jet mixer were optimized. The research was carried out with reference to the manufacture of an antibiotic, sodium cefuroxime, firstly in a 1L reactor, then a 10L reactor. The crystals produced showed higher crystallinity, narrower size distribution, higher stability and purity

Seed Recipe Design for Batch Cooling Crystallization with Application to l-Glutamic Acid

In this paper, a seed recipe design is proposed for batch cooling crystallization to obtain the desired product attributes including product yield and product size distribution, based on simulation studies and experiments on β-l-glutamic acid (β-LGA) crystallization. The impact of seed recipe on product attributes is investigated based on the population balance model (PBM) simulations with respect to the size-dependent growth of crystals. It is found that the product yield is primarily affected by the seed loading ratio (SLR) and the batch time, but less affected by the mean size and variance of seeds. Smaller seeds could improve the product yield, and in contrast, larger seeds facilitate the growth into larger crystals but require a larger SLR to ensure the product yield. By introducing an objective function for optimization with the above PBM, a seed recipe design is given for obtaining the desired product attributes as above-mentioned. In addition, it is found that washing seeds by the solvent is necessary to ensure seed quality for quantitative seed recipe design and implementation, by comparing three different seed preparation methods. Simulation tests and experiments well demonstrate the effectiveness of the proposed seed recipe design for seeded batch cooling crystallization

Precipitation chemistry of Lhasa and other remote towns, Tibet

Precipitation event samples during 1987-1988 field expedition periods and 1997, 1998, 1999 and 2000 have been collected at Lhasa, Dingri, Dangxiong and Amdo, Tibet. The sampling and analysis were based on WMO recommendations for a background network with some modifications according to local conditions and environmental characteristics. The following precipitation constituents and related parameters were measured: pH, conductivity, CO2 partial pressure, total suspended particles, and the content of K+, Na+, Ca2+, Mg2+, Fe, Mn, NH4 +, Cl-, NO2 -, NO3 -, SO4 2-Br-, HCO3 - and HPO4 2-. Some atmospheric dust samples have also been collected. Over 300 precipitation events have been measured for pH and conductivity. Among these, 60 have been analysed for their chemical components. The results show that Lhasa's precipitation events were constantly alkaline with weighted averages of pH 8.36 in the 1987-1988 period, and 7.5 for 1997 to 1999. Only one event was weakly acidic during 1997-1999. Although CO2 partial pressure, a major producer of acidity in natural water on the Plateau, falls with increasing elevation, the lowest measured CO2 partial pressure can only raise pH value by 0.1 units in the sampling areas. Chemical analysis indicates that the major contributor to alkaline precipitation is the continental dust, which is rich in calcium. The analysis also shows that Tibet is still one of the cleanest areas in the world with little air pollution. However, the decline of pH from the 1980s to 1990s, which was reflected by an increase of NO3 - and SO4 2- in precipitation, alerts us to the urgency of environmental protection in this fragile paradise. © 2002 Elsevier Science Ltd. All rights reserved.postprin