Hyukjae Jang

xShare: supporting impromptu sharing of mobile phones

Loaded with personal data, e.g. photos, contacts, and call history, mobile phones are truly personal devices. Yet it is often necessary or desirable to share our phones with others. This is especially true as mobile phones are integrating features conventionally provided by other dedicated devices, from MP3 players to games consoles. Unfortunately, when we lend our phones to others, we give away complete access because existing phones assume a single user and provide little protection for private data and applications. In this work, we present xShare, a protection solution to address this problem. xShare allows phone owners to rapidly specify what they want to share and place the phone into a restricted mode where only the data and applications intended for sharing can be accessed. We first present findings from two motivational user studies based on which we provide the design requirements of xShare. We then present the design of xShare based on file-level access control. We describe the implementation of xShare on Windows Mobile and report a comprehensive usability evaluation of the implementation, including mea-surements and user studies. The evaluation demonstrates that our xShare implementation has negligible overhead for interactive phone usage, is extremely favored by mobile users, and provides robust protection against attacks by experienced Windows Mobile users and developers.

Magneto-optical microscope magnetometer for simultaneous local probing of magnetic properties

The design of a magneto-optical microscope magnetometer (MOMM) for simultaneously probing local magnetic properties is described. The MOMM consists of an optical polarizing microscope capable of magneto-optical contrast that is used as a magnetometer by sweeping a magnetic field from an electromagnet. Due to full-field optical imaging, as opposed to single photodiode detection, the system is capable of simultaneous measurement of magnetic hysteresis loops and magnetization viscosity curves on 8000 individual local regions of 400×400 nm2 area in ferromagnetic materials. The most striking feature of the system is that it provides two-dimensional maps of the local magnetic properties including the coercivity, the switching time, and the activation magnetic moment from two-dimensional arrays of the hysteresis loops and the viscosity curves. We present the local magnetic properties and their correlations in Co/Pd multilayer films prepared by electron-beam evaporation.

Maintaining consistency under isolation relaxation of web services transactions

For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web services operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transactions, which can spoil data integrity and causes incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transactions. The mechanism effectively detects inconsistent states of transactions with a notion of a completion dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy integration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.

Running or gaming

We developed Exertainer, a sensor-enabled, interactive running entertainment system to support advanced exercise applications. We designed Exertainer to be used in urban environments where outdoor running is often not convenient or practical; as such, Exertainer and Exertainer running applications represent an attractive alternative to traditional treadmill running. Exertainer effectively creates a robust design space around treadmill running. Developers can leverage Exertainers components, an advanced treadmill called Interactive Treadmill, Sensor Bracelet and the PSD game platform, to design interactive and immersive running games and other advanced running applications. We also developed Swan Boat, a multiplayer team racing game making the treadmill running an exciting social activity, and conducted a user study.

A framework for ensuring consistency of Web Services Transactions

For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web service operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transactions, which can spoil data integrity and cause incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transactions. The mechanism effectively detects inconsistent states of transactions with a notion of an end-state dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy integration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.

Demo: ExerLink - enabling pervasive social exergames with heterogeneous exercise devices

We envision that diverse social exercising games, or exergames, will emerge, featuring much richer interactivity with immersive game play experiences. Further, the recent advances of mobile devices and wireless networking will make such social engagement more pervasive - people carry portable exergame devices (e.g., jump ropes) and interact with remote users anytime, anywhere. Towards this goal, we explore the potential of using heterogeneous exercise devices as game controllers for a multi-player social exergame; e.g., playing a boat paddling game with two remote exercisers (one with a jump rope, and the other with a treadmill). In this paper, we propose a novel platform called ExerLink that converts exercise intensity to game inputs and intelligently balances intensity/delay variations for fair game play experiences. We report the design considerations and guidelines obtained from the design and development processes of game controllers. We validate the efficacy of game controllers and demonstrate the feasibility of social exergames with heterogeneous exercise devices via extensive human subject studies.

Exploring inter-child behavioral relativity in a shared social environment: a field study in a kindergarten

A kindergarten is an interesting community of young children. The children continuously share their interactions and experiences, and grow along similar developmental stages. In this setting, studying relative differences among them can be an interesting approach to investigating how to help their individual and social development. In this study, we present our intuition on inter-child behavioral relativity and apply it to a real kindergarten environment. We conduct a close user study necessitating the monitoring of the childrens behavior. Then, utilizing wearable sensor technologies, we perform a field study to explore various interesting aspects of behavioral relativity in an automatic and quantitative fashion. We consulted the kindergarten teachers with our results obtained from our field study in order to validate the practical benefits in the kindergarten environment. We further discuss the potential, limitations, and opportunities of our approach.

Spin dynamics in Co/Pd multilayers by varying the number of repeats

The spin reversal of nanostructured Co/Pd multilayers by varying the number of repeats has been investigated quantitatively. The magnetization viscosity measurement and the direct observation of the time-dependent spin reversal patterns showed that their reversal behavior gradually changed from wall-motion dominant to nucleation dominant by increasing the number of repeats. Both the wall-motion speed V and the nucleation rate R of the samples were determined by a quantitative analysis of the time-dependent domain patterns. It was found that V was significantly decreased and R was increased by increasing the number of repeats, and the ratio of V/R was an important parameter of different spin reversal behavior.

DCF: an efficient data stream clustering framework for streaming applications

Streaming applications, such as environment monitoring and vehicle location tracking require handling high volumes of continuously arriving data and sudden fluctuations in these volumes while efficiently supporting multi-dimensional historical queries. The use of the traditional database management systems is inappropriate because they require excessive number of disk I/O in continuously updating massive data streams. In this paper, we propose DCF (Data Stream Clustering Framework), a novel framework that supports efficient data stream archiving for streaming applications. DCF can reduce a great amount of disk I/O in the storage system by grouping incoming data into clusters and storing them instead of raw data elements. In addition, even when there is a temporary fluctuation in the amount of incoming data, it can stably support storing all incoming raw data by controlling the cluster size. Our experimental results show that our approach significantly reduces the number of disk accesses in terms of both inserting and retrieving data.

Strain and magnetic anisotropy of epitaxial Ni/Cu(001) nanostructures

The magnetic anisotropy of isolated epitaxial Ni∕Cu(001) nanostructure on Si(001) has been studied together with structural characterization. The strain of the Ni nanostructure is released such that the perpendicular strain of nanostructure with tNi=10nm decreases to −0.48% from −1.17% of film with the same thickness. Because of this, strain becomes the main factor in determining magnetic anisotropy of Ni∕Cu nanostructure in the investigated Ni thickness range (tNi=4.5–10nm).