Journeys of the Modest Astronomers : Korean Astronomers’ Missions to Beijing in the Seventeenth and Eighteenth Centuries

Cet article s’intéresse aux astronomes de cour coréens qui se sont rendus à Pékin aux xviie et xviiie siècles. Conditionnés par la hiérarchie politique et épistémique entre les deux pays, les astronomes coréens allaient à Pékin pour y acquérir les secrets des calculs astronomiques détenus par le Bureau de l’astronomie des Qing. Ces voyages, riches en opportunités et en déceptions, devinrent un élément central dans la construction par les astronomes coréens de leur propre image. Ils se représentaient modestement comme les astronomes d’un « État marginal » qui ne pouvaient être compétents dans leur domaine sans effectuer des pèlerinages à la métropole impériale. Cette rhétorique de la modestie reflète la position conflictuelle des astronomes officiels coréens, qui ne pouvaient promouvoir leurs intérêts socio-culturels qu’en niant leur capacité à être compétents par eux-mêmes dans leur domaine.This article focuses on the Korean court astronomers who made the journeys to Beijing in the seventeenth and eighteenth centuries. Conditioned by the politico-epistemic hierarchy between the two countries, Korean astronomers traveled to Beijing with the task of acquiring the secrets of astronomical calculation possessed by the Qing Bureau of Astronomy. The author argues that in the course of these journeys that offered the Korean astronomers both frustrations and opportunities, traveling to the metropolitan center became crucially incorporated into their self-portrait. They presented themselves modestly as the astronomers of a “marginal state,” who could not expect to be competent in their specialty without making pilgrimages to the imperial metropolis. This rhetoric of modesty reflected the conflicted position of the Korean official astronomers, who could promote their sociocultural interests only by negating their ability to be competent in their specialty on their own.本文著重關注十七十八世紀訪問北京的朝鮮宮廷天文學者。由於兩國政治和知識形態的等級關係，前往北京的朝鮮天文學者負有獲取欽天監曆算秘密的使命。透過他們機遇和挫折並存的旅程，作者認為北京之旅是朝鮮天文學者自我形象構建的核心元素。他們謙虛自稱來自“邊鄙之邦”，若不到帝京朝覲，則無法勝任天文領域的專業職責。這套自謙的說辭反映了朝鮮宮廷天文學者矛盾的立場，他們必須通過否定自身的專業能力，才能取得最大的社會文化利益

Solution-processed near-infrared Cu(In,Ga)(S,Se)(2) photodetectors with enhanced chalcopyrite crystallization and bandgap grading structure via potassium incorporation

Although solution-processed Cu(In,Ga)(S,Se)(2) (CIGS) absorber layers can potentially enable the low-cost and large-area production of highly stable electronic devices, they have rarely been applied in photodetector applications. In this work, we present a near-infrared photodetector functioning at 980 nm based on solution-processed CIGS with a potassium-induced bandgap grading structure and chalcopyrite grain growth. The incorporation of potassium in the CIGS film promotes Se uptake in the bulk of the film during the chalcogenization process, resulting in a bandgap grading structure with a wide space charge region that allows improved light absorption in the near-infrared region and charge carrier separation. Also, increasing the Se penetration in the potassium-incorporated CIGS film leads to the enhancement of chalcopyrite crystalline grain growth, increasing charge carrier mobility. Under the reverse bias condition, associated with hole tunneling from the ZnO interlayer, the increasing carrier mobility of potassium-incorporated CIGS photodetector improved photosensitivity and particularly external quantum efficiency more than 100% at low light intensity. The responsivity and detectivity of the potassium-incorporated CIGS photodetector reach 1.87 A W-1 and 6.45 x 10(10) Jones, respectively, and the - 3 dB bandwidth of the device extends to 10.5 kHz under 980 nm near-infrared light

Joint and tandem source -channel coding with complexity and delay constraints.

Joint source-channel coding has been developed with the motivation that it can achieve better performance with less complexity and delay than tandem source-channel coding. However, little quantitative evidence for this claim has appeared in the literature. In this dissertation, we search for such evidence by quantitatively comparing representative systems of each type on the basis of distortion vs. complexity and distortion vs. delay when transmitting analog data samples across a binary symmetric channel. Channel-optimized transform coding is chosen as the system representative of joint source-channel coding, and transform coding with Reed-Solomon coding is chosen as the system representative of tandem source-channel coding. For each strategy, formulas for the mean-squared error, complexity and delay are found and used to minimize distortion subject to a complexity or a delay constraint, for data modeled as Gauss-Markov. The results of such optimizations suggest there are thresholds on complexity and delay such that when the available complexity or the permissible delay is above the threshold, tandem coding is better, and when below the threshold, channel-optimized transform coding is better. The investigation is expanded to unequal error protection in tandem source-channel coding. Providing different levels of error protection according to the importance of the transform coefficients, the performance of tandem source-channel coding is improved and the complexity threshold is reduced relative to that of an equal error protection system. Also, a fundamental problem in designing transform codes, rate allocation, is considered and an analytic expression for the optimal rate allocation is derived for noisy channels, based on high-resolution theory. The resulting asymptotically optimal rate allocation for noisy channels suggests that even more bits need to be allocated to the coefficients whose variances are greater than the geometric mean of such variances, compared to the optimal bit allocation for noiseless channels. On the other hand, even fewer bits are to be allocated to the coefficients whose variances are smaller than the geometric mean. The correspondence between experimental results and the asymptotic expression is observed to be good.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125922/2/3016905.pd

An Efficient Distributed SPARQL Query Processing Scheme Considering Communication Costs in Spark Environments

Various distributed processing schemes were studied to efficiently utilize a large scale of RDF graph in semantic web services. This paper proposes a new distributed SPARQL query processing scheme considering communication costs in Spark environments to reduce I/O costs during SPARQL query processing. We divide a SPARQL query into several subqueries using a WHERE clause to process a query of an RDF graph stored in a distributed environment. The proposed scheme reduces data communication costs by grouping the divided subqueries in related nodes through the index and processing them, and the grouped subqueries calculate the cost of all possible query execution paths to select an efficient query execution path. The efficient query execution path is selected through the algorithm considering the data parsing cost of all possible query execution paths, amount of data communication, and queue time per node. It is shown through various performance evaluations that the proposed scheme outperforms the existing schemes

A Performance Evaluation of Vertical Handoff Scheme between IEEE 802.16e and cdma2000 Networks

Abstract – Interworking technologies in heterogeneous network environments has become a hot issue these days. This interworking technology would provide optimized services to users and also benefit service operators by reducing network construction and maintenance costs. This paper proposes network architecture for fast handoff between IEEE 802.16e and cdma2000 networks. The smoothly-coupled integration (SCI) scheme proposed in this paper adopts the advantages of both loosely-coupled integration and tightly-coupled integration schemes. Also, the proposed scheme can be implemented with minimal modification of existing IEEE 802.16e and cdma2000 networks

The Amalgamation of the Object Detection and Semantic Segmentation for Steel Surface Defect Detection

Steel surface defect detection is challenging because it contains various atypical defects. Many studies have attempted to detect metal surface defects using deep learning and had success in applying deep learning. Despite many previous studies to solve the steel surface defect detection, it remains a difficult problem. To resolve the atypical defects problem, we introduce a hierarchical approach for the classification and detection of defects on the steel surface. The proposed approach has a hierarchical structure of the binary classifier at the first stage and the object detection and semantic segmentation algorithms at the second stage. It shows 98.6% accuracy in scratch and other types of defect classification and 77.12% mean average precision (mAP) in defect detection using the Northeastern University (NEU) surface defect detection dataset. A comparative analysis with the previous studies shows that the proposed approach achieves excellent results on the NEU dataset