A generalization of Alternating Sign Matrices

In alternating sign matrices the first and last nonzero entry in each row and column is specified to be +1. Such matrices always exist. We investigate a generalization by specifying independently the sign of the first and last nonzero entry in each row and column to be either a +1 or a -1. We determine necessary and sufficient conditions for such matrices to exist.Comment: 14 page

Presidential Instability in a Developing Country: Reassessing South Korean Politics from a State-Society Relations Perspective

This study attempts to explain why ALL of South Korean presidents, without exception and notwithstanding their individual major contributions to the process of Korea’s development, have fallen victim to disgraceful downfalls. For the analysis, I employ S.N. Sangmpam’s middle-range theory that establishes a causal link between society-rooted politics and political outcomes. Building on his analytical frameworks that non-Western countries are characterized by over-politicization in politics as a function of social context, I argue that patterned downfalls of all Korean presidents are an institutional outcome of over-politicization in Korean politics, which is itself a function of not fully entrenched capitalist society. In support of my thesis, I test three hypotheses. Hypotheses one and two posit Korea’s tenacious traditional and cultural traits as an internal modifier of capitalism and the nation’s dependent nature of its relationships with the United States and Japan as an external factor that prevented capitalist entrenchment in Korean society. The combined effect of these two variables is the alteration of capitalism in South Korea that defies the three cardinal rules of democracy, leading to over-politicized behaviors in presidential politics. As for the patterned downfalls of the presidents, I test the hypothesis empirically that as the nation’s most supreme political institution, the Korean presidency displayed the effects of over-politicization most saliently. The evidence reveals that both authoritarian (1948-1987) and democratic (1988-2009) presidents display diverse manifestations of over-politicized behaviors. However, there is also a striking difference between the two eras: Authoritarian presidents seem more influenced by the external causal variable mainly because of Korea’s heavy dependence on the United States and Japan in the formative years of the nation building. Democratic presidents are more challenged by internal causal variable, especially the characteristics of what I call familist collectivism, the dominant operating principle and code of conduct for most Koreans in the period of 1948-2009. Thus, unless the social causal variable is properly addressed, the problem may remain regardless of regime types

Towards Trouble-Free Networks for End Users

Network applications and Internet services fail all too frequently. However, end users cannot effectively identify the root cause using traditional troubleshooting techniques due to the limited capability to distinguish failures caused by local network elements from failures caused by elements located outside the local area network. To overcome these limitations, we propose a new approach, one that leverages collaboration of user machines to assist end users in diagnosing various failures related to Internet connectivity and poor network performance. First, we present DYSWIS ("Do You See What I See?"), an automatic network fault detection and diagnosis system for end users. DYSWIS identifies the root cause(s) of network faults using diagnostic rules that consider diverse information from multiple nodes. In addition, the DYSWIS rule system is specially designed to support crowdsourced and distributed probes. We also describe the architecture of DYSWIS and compare its performance with other tools. Finally, we demonstrate that the system successfully detects and diagnoses network failures which are difficult to diagnose using a single-user probe. Failures in lower layers of the protocol stack also have the potential to disrupt Internet access; for example, slow Internet connectivity is often caused by poor Wi-Fi performance. Channel contention and non-Wi-Fi interference are the primary reasons for this performance degradation. We investigate the characteristics of non-Wi-Fi interference that can severely degrade Wi-Fi performance and present WiSlow ("Why is my Wi-Fi slow?"), a software tool that diagnoses the root causes of poor Wi-Fi performance. WiSlow employs user-level network probes and leverages peer collaboration to identify the physical location of these causes. The software includes two principal methods: packet loss analysis and 802.11 ACK number analysis. When the issue is located near Wi-Fi devices, the accuracy of WiSlow exceeds 90%. Finally, we expand our collaborative approach to the Internet of Things (IoT) and propose a platform for network-troubleshooting on home devices. This platform takes advantage of built-in technology common to modern devices --- multiple communication interfaces. For example, when a home device has a problem with an interface it sends a probe request to other devices using an alternative interface. The system then exploits cooperation of both internal devices and remote machines. We show that this approach is useful in home networks by demonstrating an application that contains actual diagnostic algorithms

Current-Induced Resonant Motion of a Magnetic Vortex Core: Effect of Nonadiabatic Spin Torque

The current-induced resonant excitation of a magnetic vortex core is investigated by means of analytical and micromagnetic calculations. We find that the radius and the phase shift of the resonant motion are not correctly described by the analytical equations because of the dynamic distortion of a vortex core. In contrast, the initial tilting angle of a vortex core is free from the distortion and determined by the nonadiabaticity of the spin torque. It is insensitive to experimentally uncontrollable current-induced in-plane Oersted field. We propose that a time-resolved imaging of the very initial trajectory of a core is essential to experimentally estimate the nonadiabaticity.Comment: 4 pages, 4 figure

DYSWIS: Collaborative Network Fault Diagnosis - Of End-users, By End-users, For End-users

With increase in application complexity, the need for network faults diagnosis for end-users has increased. However, existing failure diagnosis techniques fail to assist the endusers in accessing the applications and services. We present DYSWIS, an automatic network fault detection and diagnosis system for end-users. The key idea is collaboration of end-users; a node requests multiple nodes to diagnose a network fault in real time to collect diverse information from different parts of the networks and infer the cause of failure. DYSWIS leverages DHT network to search the collaborating nodes with appropriate network properties required to diagnose a failure. The framework allows dynamic updating of rules and probes into a running system. Another key aspect is contribution of expert knowledge (rules and probes) by application developers, vendors and network administrators; thereby enabling crowdsourcing of diagnosis strategy for growing set of applications. We have implemented the framework and the software and tested them using our test bed and PlanetLab to show that several complex commonly occurring failures can be detected and diagnosed successfully using DYSWIS, while single-user probe with traditional tools fails to pinpoint the cause of such failures. We validate that our base modules and rules are sufficient to detect infrastructural failures causing majority of application failures

WiSlow: A WiFi Network Performance Troubleshooting Tool for End Users

The increasing number of 802.11 APs and wireless devices results in more contention, which causes unsatisfactory WiFi network performance. In addition, non-WiFi devices sharing the same spectrum with 802.11 networks such as microwave ovens, cordless phones, and baby monitors severely interfere with WiFi networks. Although the problem sources can be easily removed in many cases, it is difficult for end users to identify the root cause. We introduce WiSlow, a software tool that diagnoses the root causes of poor WiFi performance with user-level network probes and leverages peer collaboration to identify the location of the causes. We elaborate on two main methods: packet loss analysis and 802.11 ACK pattern analysis

Das südkoreanische (Aus-)Bildungssystem - Bestimmungsfaktoren und Trends

The present essay is about the evolution of the Korean education system and the effects it has on the Korean society. South Korea can look back on a history of rapid growth and industrialisation since the sixties of the last century. Among various factors that contributed to South Korea's unprecedented development, we can make out South Korea's school system that has gained worldwide reputation. What are the roots of its effectiveness? To what extent education in South Korea leads to the equal distribution of life chances? In how far it is more than just preparing people for the labour market? In order to answer these questions the authors look back further in the history of Korea and explain the relevance of certain cultural and religious ideas to Korea's social structure. Korean scholarship is deeply rooted in a centuries-old tradition of Korean Confucianism, but the modern educational system started to take shape due to cultural influences of Western powers and under colonial rule. In the decades after the Korean War, South Korean governments put much stress on an egalitarian development of human resources. With the introduction of market-oriented reforms at the end of the last century, however, education is becoming more and more a privilege of the wealthy and powerful classes of the Korean society.Der vorliegende Aufsatz behandelt die Entwicklung des koreanischen Bildungssystems und seine Auswirkungen auf die koreanische Gesellschaft. Südkorea blickt zurück auf eine Geschichte des schnellen Wachstums und der Industrialisierung seit den sechziger Jahren des vergangenen Jahrhunderts. Unter den verschiedenen Faktoren, die zu Südkoreas beispielloser Entwicklung beitragen, gehört Südkoreas Schulsystem, das weltweit Anerkennung findet. Worin liegt seine Wirksamkeit begründet? Inwieweit führt Ausbildung in Südkorea zu einer gleichmäßigen Verteilung von Lebenschancen? Ist Bildung in Korea mehr als nur eine Vorbereitung auf den Arbeitsmarkt? Um diese Fragen zu beantworten, gehen die Autoren weiter zurück in die koreanische Geschichte und erklären die Relevanz bestimmter kultureller und religiöser Ideen für die Herausbildung der südkoreanischen Sozialstruktur. Koreanische Gelehrsamkeit ist tief verwurzelt in einer Jahrhunderte alten Tradition des koreanischen Konfuzianismus. Aber das moderne Bildungssystem begann erst aufgrund kultureller Einflüsse der westlichen Mächte und unter japanischer Kolonialherrschaft Gestalt anzunehmen. In den Jahrzehnten nach dem Koreakrieg legten südkoreanische Regierungen viel Wert auf eine egalitäre Entwicklung der Humanressourcen. Mit der Einführung marktorientierter Reformen am Ende des letzten Jahrhunderts jedoch wird Bildung mehr und mehr Ausbildung und ein Privileg der wohlhabenden und mächtigen Klassen der koreanischen Gesellschaft