Smart-1 Moon Impact Operations

This paper describes the operations to control the Moon impact of the 3-axis stabilized spacecraft SMART-1 in September 2006. SMART-1 was launched on 27/09/2003. It was the first ESA mission to use an Electric Propulsion (EP) engine as the main motor to spiral out of the Earth gravity field and reach a scientific moon orbit [1]. During September 2005 the last EP maneuvers were performed using the remaining Xenon, in order to compensate for the 3rd body perturbations of the Sun and Earth. These operations extended the mission for an additional year. Afterwards the EP performance became unpredictable and low, so that no meaningful operation for the moon impact could be done. To move the predicted impact point on the 16/8/2006 into visibility from Earth an alternative Delta-V strategy was designed. Due to their alignment, the attitude thrusters could not be used directly to generate the Delta-V, so this strategy was based on controlled angular momentum biasing. Firing along the velocity vector around apolune, the remaining Hydrazine left from the attitude control budget was used, to shift the impact to the required coordinates

Chen Shui-bian: on independence

Chen Shui-bian achieved an international reputation for his promotion of Taiwan independence. Whilst that reputation may have been well earned, the analyses on which this conclusion is based are frequently flawed in two ways. First, by using an undifferentiated notion of independence, they tend to conflate sovereignty with less threatening expressions of Taiwanese identity and pro-democracy discourse. Second, by failing to take into account the impact of immediate strategic context, analysts ignore a fundamental element of democratic political communication. In our empirical analysis of more than 2,000 of Chen’s speeches, we seek to avoid both flaws by unpacking the concept of independence and taking into account Chen’s strategic relationship with his primary audiences. Our findings challenge popular portrayals of Chen, but more importantly they have strong implications for policy makers and students of political rhetoric with regard to current and future ROC presidents

Excerpt: Why Taiwan Matters: Small Island, Global Powerhouse

Taipei 101, the blue-green glass tower that reigned for six years as the world’s tallest building, is everywhere in Taiwan. Its image appears on advertisements, magazine covers, brochures, guidebooks, and billboards; the soaring structure itself is visible from nearly everywhere in Taipei City. As ubiquitous as Shanghai’s Oriental Pearl TV tower—and considerably more graceful—Taipei 101 has become the iconic image of contemporary Taiwan

Developing Taiwan Studies Teaching Programme in Europe and the United States: the experience of SOAS University of London and University of Texas at Austin

Over the last two decades, there has been a rapid expansion in the number of Taiwan programmes at universities in America and Europe; however, few of these Taiwan programmes have attempted to develop teaching courses. Where Taiwan courses have been introduced, they have tended to be in isolation and not well integrated into existing academic programmes. Among the universities with Taiwan programmes, only two have attempted to create comprehensive teaching programmes through which students can graduate with a degree in Taiwan studies: SOAS University of London and the University of Texas at Austin. The purpose of this paper is to compare the experiences of these two institutions in developing such niche teaching programmes. It begins with a discussion of how these two programmes first emerged and then goes on to review their distinct development trajectories and key features. The paper offers an analysis of how these two programmes were able not only to survive but also to expand their offerings and thrive in an academic environment that should be hostile to such niche programmes. It concludes with a review of the remaining challenges facing these teaching programmes

Finding Performance Issues in Database Engines via Cardinality Estimation Testing

Database Management Systems (DBMSs) process a given query by creating an execution plan, which is subsequently executed, to compute the query's result. Deriving an efficient query plan is challenging, and both academia and industry have invested decades into researching query optimization. Despite this, DBMSs are prone to performance issues, where a DBMS produces an inefficient query plan that might lead to the slow execution of a query. Finding such issues is a longstanding problem and inherently difficult, because no ground truth information on an expected execution time exists. In this work, we propose Cardinality Estimation Restriction Testing (CERT), a novel technique that detects performance issues through the lens of cardinality estimation. Given a query on a database, CERT derives a more restrictive query (e.g., by replacing a LEFT JOIN with an INNER JOIN), whose estimated number of rows should not exceed the number of estimated rows for the original query. CERT tests cardinality estimators specifically, because they were shown to be the most important component for query optimization; thus, we expect that finding and fixing such issues might result in the highest performance gains. In addition, we found that some other kinds of query optimization issues are exposed by the unexpected cardinality estimation, which can also be detected by CERT. CERT is a black-box technique that does not require access to the source code; DBMSs expose query plans via the EXPLAIN statement. CERT eschews executing queries, which is costly and prone to performance fluctuations. We evaluated CERT on three widely used and mature DBMSs, MySQL, TiDB, and CockroachDB. CERT found 13 unique issues, of which 2 issues were fixed and 9 confirmed by the developers. We expect that this new angle on finding performance bugs will help DBMS developers in improving DMBSs' performance

Lessons of Defeat and Success: Taiwan’s 2012 Elections in Comparative Perspective

In early 2011, the Kuomintang (KMT, Guomindang) government appeared to be in danger of losing power in the upcoming presidential elections. The DPP had recovered sufficiently from its disastrous electoral performance in 2008 to pose a real challenge to Ma Ying-jeou (Ma Yingjiu) and had matched the KMT’s vote share in mid-term local elections. Ma also faced the challenge of an independent presidential candidate, James Soong (Song Chuyu), who had come a close second in 2000 and now threatened to divide the pro KMT vote. Nevertheless, the KMT was able to win reduced majorities in both the presidential and legislative elections in January 2012. This article seeks to explain how the KMT was able to hold on to power by comparing the campaign with earlier national-level elections. We are interested in identifying the degree to which the Democratic Progressive Party (DPP, Minjindang) learnt from its electoral setbacks in 2008 and whether the KMT employed a similar campaign strategy to the one that had been so effective in returning it to power in 2008. Our analysis relies of an examination of campaign propaganda and campaign strategies as well as participant observation and survey data from 2012 and earlier contests

Finding Cross-rule Optimization Bugs in Datalog Engines

Datalog is a popular and widely-used declarative logic programming language. Datalog engines apply many cross-rule optimizations; bugs in them can cause incorrect results. To detect such optimization bugs, we propose an automated testing approach called Incremental Rule Evaluation (IRE), which synergistically tackles the test oracle and test case generation problem. The core idea behind the test oracle is to compare the results of an optimized program and a program without cross-rule optimization; any difference indicates a bug in the Datalog engine. Our core insight is that, for an optimized, incrementally-generated Datalog program, we can evaluate all rules individually by constructing a reference program to disable the optimizations that are performed among multiple rules. Incrementally generating test cases not only allows us to apply the test oracle for every new rule generated-we also can ensure that every newly added rule generates a non-empty result with a given probability and eschew recomputing already-known facts. We implemented IRE as a tool named Deopt, and evaluated Deopt on four mature Datalog engines, namely Souffl\'e, CozoDB, $\mu$Z, and DDlog, and discovered a total of 30 bugs. Of these, 13 were logic bugs, while the remaining were crash and error bugs. Deopt can detect all bugs found by queryFuzz, a state-of-the-art approach. Out of the bugs identified by Deopt, queryFuzz might be unable to detect 5. Our incremental test case generation approach is efficient; for example, for test cases containing 60 rules, our incremental approach can produce 1.17$\times$ (for DDlog) to 31.02$\times$ (for Souffl\'e) as many valid test cases with non-empty results as the naive random method. We believe that the simplicity and the generality of the approach will lead to its wide adoption in practice.Comment: The ACM SIGPLAN Conference on Object Oriented Programming, Systems, Languages, and Applications (2024), Pasadena, California, United State