Virtualization of network I/O on modern operating systems

Network I/O of modern operating systems is incomplete. In this networkage, users and their applications are still unable to control theirown traffic, even on their local host. Network I/O is a sharedresource of a host machine, and traditionally, to address problemswith a shared resource, system research has virtualized the resource.Therefore, it is reasonable to ask if the virtualization can providesolutions to problems in network I/O of modern operating systems, inthe same way as the other components of computer systems, such asmemory and CPU. With the aim of establishing the virtualization ofnetwork I/O as a design principle of operating systems, thisdissertation first presents a virtualization model, hierarchicalvirtualization of network interface. Systematic evaluation illustratesthat the virtualization model possesses desirable properties forvirtualization of network I/O, namely flexible control granularity,resource protection, partitioning of resource consumption, properaccess control and generality as a control model. The implementedprototype exhibits practical performance with expected functionality,and allowed flexible and dynamic network control by users andapplications, unlike existing systems designed solely for systemadministrators. However, because the implementation was hardcoded inkernel source code, the prototype was not perfect in its functionalcoverage and flexibility. Accordingly, this dissertation investigatedhow to decouple OS kernels and packet processing code throughvirtualization, and studied three degrees of code virtualization,namely, limited virtualization, partial virtualization, and completevirtualization. In this process, a novel programming model waspresented, based on embedded Java technology, and the prototypeimplementation exhibited the following characteristics, which aredesirable for network code virtualization. First, users program inJava to carry out safe and simple programming for packetprocessing. Second, anyone, even untrusted applications, can performinjection of packet processing code in the kernel, due to isolation ofcode execution. Third, the prototype implementation empirically provedthat such a virtualization does not jeopardize system performance.These cases illustrate advantages of virtualization, and suggest thatthe hierarchical virtualization of network interfaces can be aneffective solution to problems in network I/O of modern operatingsystems, both in the control model and in implementation

Optimal Rendezvous L-Algorithms for Asynchronous Mobile Robots with External-Lights

We study the Rendezvous problem for two autonomous mobile robots in asynchronous settings with persistent memory called light. It is well known that Rendezvous is impossible in a basic model when robots have no lights, even if the system is semi-synchronous. On the other hand, Rendezvous is possible if robots have lights of various types with a constant number of colors. If robots can observe not only their own lights but also other robots\u27 lights, their lights are called full-light. If robots can only observe the state of other robots\u27 lights, the lights are called external-light. This paper focuses on robots with external-lights in asynchronous settings and a particular class of algorithms called L-algorithms, where an L-algorithm computes a destination based only on the current colors of observable lights. When considering L-algorithms, Rendezvous can be solved by robots with full-lights and three colors in general asynchronous settings (called ASYNC) and the number of colors is optimal under these assumptions. In contrast, there exist no L-algorithms in ASYNC with external-lights regardless of the number of colors. In this paper, extending the impossibility result, we show that there exist no L-algorithms in so-called LC-1-Bounded ASYNC with external-lights regardless of the number of colors, where LC-1-Bounded ASYNC is a proper subset of ASYNC and other robots can execute at most one Look operation between the Look operation of a robot and its subsequent Compute operation. We also show that LC-1-Bounded ASYNC is the minimal subclass in which no L-algorithms with external-lights exist. That is, Rendezvous can be solved by L-algorithms using external-lights with a finite number of colors in LC-0-Bounded ASYNC (equivalently LC-atomic ASYNC). Furthermore, we show that the algorithms are optimal in the number of colors they use

Phenomenology of NMSSM in TeV scale mirage mediation

We study the next-to-minimal supersymmetric standard model (NMSSM) with the TeV scale mirage mediation, which is known as a solution for the little hierarchy problem in supersymmetry. Our previous study showed that 125 GeV Higgs boson is realized with O(10) % fine-tuning for 1.5 TeV gluino (1 TeV stop) mass. The $\mu$ term could be as large as 500 GeV without sacrificing the fine-tuning thanks to a cancellation mechanism. The singlet-doublet mixing is suppressed by $\tan\beta$. In this paper, we further extend this analysis. We argue that approximate scale symmetries play a role behind the suppression of the singlet-doublet mixing. They reduce the mixing matrix to a simple form that is useful to understand the results of the numerical analysis. We perform a comprehensive analysis of the fine-tuning including the singlet sector by introducing a simple formula for the fine-tuning measure. This shows that the singlet mass of the least fine-tuning is favored by the LEP anomaly for moderate $\tan\beta$. We also discuss prospects for the precision measurements of the Higgs couplings at LHC and ILC and direct/indirect dark matter searches in the model.Comment: 47 pages, 46 figures, version accepted by JHE

Extracting Semantic Orientations of Words using Spin Model

We propose a method for extracting semantic orientations of words: desirable or undesirable. Regarding semantic orientations as spins of electrons, we use the mean field approximation to compute the approximate probability function of the system instead of the intractable actual probability function. We also propose a criterion for parameter selection on the basis of magnetization. Given only a small number of seed words, the proposed method extracts semantic orientations with high accuracy in the experiments on English lexicon. The result is comparable to the best value ever reported.

Alcohol Consumption or Excessive Use of Psychotropic Medication Prior to Suicidal Self-injury in Patients with Adjustment Disorder, Depression, and Schizophrenia: A Cross-sectional Study

The use of alcohol or drug(s) prior to self-injury is a possible inducing factor for suicidal self-injuries among patients with adjustment disorder. We analyzed the cases of 175 individuals who were admitted to the intensive care unit (ICU) of Tokyo Medical and Dental University Medical Hospital for suicidal self-injury to determine whether alcohol consumption or an excessive use of prescribed psychotropic medications prior to self-injury is more common in patients with adjustment disorder. During a 7-year period (July 2006 to June 2013) following their deliberate self-injuries, 971 patients were admitted to the ICU. Our study sample (n=175) was restricted to patients with adjustment disorder (n=48), major depressive disorder (n=90), or schizophrenia (n=37). The outcome variable was alcohol consumption or excessive use of medications prior to suicidal self-injury. A logistic regression analysis revealed that the patients with adjustment disorder more commonly showed alcohol consumption or excessive medication use prior to their suicidal self-injury compared to those with schizophrenia (odds ratio: 8.10; 95%CI: 2.97-24.60). To inhibit suicidal self-injury among patients with adjustment disorder, it is important to continue efforts to provide psychoeducation about alcohol use and to instruct the patients to take their prescribed medication(s) only as directed by their physician