List of Dissertation Abstract(Department of Information Environment)

NameSupervisor

Title

Abstract

ABE Toshiki

OZEKI Kenta

Colorings and dominating sets ofA coloring of a graph is the mapping from the vertex

graphs on surfaces

set to positive integer so that no two adjacentvertices receive the same colors and the chromatic
number is the minimum cardinality needed to color
the vertices of the graph.

In this thesis, we evaluate

chromatic numbers and analogical ones for planargraphs and near planar graphs and we solve ListColoring Conjecture partially, which is still an openproblem.

Moreover, we evaluate the domination

number of planar graphs by using a coloring method.

UEMURAToshiakiTOMII Takashi

An Energy Consumption Database In this research, we constructed an Electric Vehicle
of Electric Vehicle Utilizing(EV) energy consumption database using vehicle

Vehicle Driving Logs

driving logs. By collecting the sensor data of thevehicles currently drive by the users and estimating
the energy consumption of EVs, our system predicts
the "energy consumption in the future when users
change their car from Internal Combustion Vehiclesto EVs. In this paper, we showed practical examplesof the useful use of the data about EV’s energy
consumption obtained from the database todemonstrate problems specific to EVs can be solved
by using vehicle driving logs.

ENAMI Kengo

NEGAMI Seiya Re-embedding structures ofWe study topological graph theory and hence dealgraphs on surfaces and relatedwith embeddings of graphs on surfaces. Since atopics for graph coloringsgraph may not have only one embedding on anembeddable surface, the following two questions
attracted many topological graph theorists: (1) How
many (distinct) embeddings on a surface does agraph have? (2) What kind of structures generatethese embeddings of the graph? We often call such astructure the re-embedding structure and call thetopic about these questions re-embedding theory. We
hope that this thesis can contribute to developmentof re-embedding theory.

KANEI

MATSUMOTO

A Study on Analysis of Threats

I propose a framework that prevents threats ofFumihiro

Tsutomuthat Prevent Use and Distribution

fraudulent monetization caused by tampering ofof Secure Mobile Applications

Android apps. The proposed framework increases thecost of attacks by making automated tampering ofAndroid apps more difficult, while reducing thebenefits of attacks by performing ad fraud detectionthat is difficult to avoid. This makes attackerʼs
fraudulent monetization of app tampering inefficientand forces them to discontinue their attacks.

KOIDE Takashi

MATSUMOTO

A Study on Analyzing Cyber

This thesis focuses on cyber attacks against many

Tsutomu

Attacks through Active andand unspecified users or devices, which affect aPassive Observation

wider range of users. Current existing
countermeasures are effective against individualattacks, but reactive and limited to these attack
techniques. These countermeasures will not respondto changes in attack techniques and the evolution ofdevices in the future. In this thesis, we propose
methods for observing cyber attacks targeting many
and unspecified users and devices on the Internet bycombining passive and active observation. Correlation
analysis of the observation from two perspectives
allows us for a faster and more comprehensive
collection of cyber attacks in the wild.

KOBAYASHINAGAOA Study on Improving theAlthough machine learning techniques have received

Masayuki

Tomoharu

Interpretability of Image

considerable attention and demonstrated outstanding

Classification Models

performance, their uninterpretable nature is still
considered to be a major problem. This black-box
nature leaves only two questions: why and how did
they reach their decision? Therefore, it is importantto review work on machine learning interpretability. In
this study, we take a closer look at modelinterpretability and propose methods that canachieve reasonable performance while maintaining
high interpretability. To this end, we propose methods
for designing more interpretable training methods,
gaining an insight into how model works, and learning
more interpretable models.

HIGUCHIHARASHITAOn the boundary components ofIn algebraic geometry and number theory, p-divisible

Nobuhiro

Shushicentral streams and determining

groups are important research objects. For thetheir Newton polygons

universal family of p-divisible groups, its basescheme canonically has structures of a foliation andstratifications. In this research, we treat the mostimportant leaf of the foliation: central streams. The
central stream is determined by a line graph which iscalled a Newton polygon, and it is defined as thelocus the fibers over which are minimal p-divisiblegroups with the Newton polygon. In this paper, weclassify the boundary components of central streams
and determine their Newton polygons, which was anunresolved problem.

MAEZAWA
ShunichiOZEKI Kenta

Connected subgraphs with certain A Hamilton path is a path containing the all vertices
properties in dense graphsof a graph and a spanning tree is a tree containing
the all vertices of a graph. Degree conditions andforbidden subgraph conditions for a sufficientcondition of the existence of a Hamilton path havebeen studied. Graphs satisfying these conditions tend
to have many edges compared with the number ofvertices. Such graphs are called dense graphs. We
show degree conditions and forbidden subgraphconditions for the existence of spanning subgraphsthat are extended concepts of a Hamilton path, forexample, a spanning tree with bounded maximum
degree and a spanning tree with bounded total
number of branch vertices and leaves.