Users may face challenges while designing graphical user interfaces, due to a lack of relevant experience and guidance. This paper aims to investigate the issues users face during the design process, and how to resolve them. To this end, we conducted semi-structured interviews, based on which we built a GUI prototyping assistance tool called GUIComp. This tool can be connected to GUI design software as an extension, and it provides real-time, multi-faceted feedback on a user's current design. Additionally, we conducted two user studies, in which we asked participants to create mobile GUIs with or without GUIComp, and requested online workers to assess the created GUIs. The experimental results show that GUIComp facilitated iterative designs and the participants with GUIComp had better a user experience and produced more acceptable designs than those who did not use it.

We present Bendi, a shape-changing device for a tactile-visual phone conversation. Bendi enables users to deliver shape-changing movements (e.g., upward or downward bending, left or right tilting, and shrinking) from the user's joystick input to the other party's device in real time during phone conversations. We conducted a user study to observe how seven couples used it over three days in a coffeehouse. Our field trial of Bendi in a coffeehouse showed the private and natural uses, and integrated uses of tactile and visual expressions along with the uses of the vocabularies developed through Bendi. In addition, there were active uses even in negative and serious conversational context with its pleasant tactile feelings and movement representations. Lastly, we discuss issues for the future designs and real-world deployment of shape-changing mobile devices for daily use.

We present BreathingFrame, a breath signal sharing device that supports pairwise remote communication through delivering the physical inflating movement of the other party's breathing on the surface of a digital photo frame. The results of our observational study with eight couples showed that participants could associate the other party on the frame, feel sentimental connectedness and the breathing movement from the other party, and stimulate their curiosity in a positive way. We also found that it was effective for conveying affection and making users to do natural abdominal breathing through intentional breath signal delivery. Allowing the users to share breathing at a distance by applying unconscious but partially controllable breath signals on the digital picture frame which is used in everyday lives, BreathingFrame can deliver new forms of telepresence and support emotional communication.

We introduce Wrigglo, a shape-changing smart phone peripheral that allows pairs of users to share wriggling movements with one another. Attached to a smart phone, Wrigglo captures the sender's motions and activates the receiver's Wrigglo which repeats the motion simultaneously. The result of our in-lab use observation with twelve couples showed that Wrigglo supported emotional and functional roles of body gestures and postures, creating vocabularies related to the motion of specific body parts and, to some extent, reflected the connected user's presence through the device's movement. Through its peripheral anthropomorphization, Wrigglo can deliver new forms of telepresence by embodied posturing and gesturing in mobile communication.

We report the roles of touch during phone conversations by observing long-distance couples' one month use of POKE in their homes. POKE enables users to deliver touches through an inflatable surface on the front of the device that receives index finger pressure inputs on the back of another device, while allowing the callers to maintain a conventional phone-calling posture. After a month of use by three couples, we found unexpected roles of touch in that it supported the couples in developing and sharing their tactile vocabularies by applying POKE during various conversational situations. Moreover, the findings confirmed the roles that touch play in face-to-face communication. In particular, POKE was useful for expressing and understanding emotions, resolving conversations smoothly by replacing the words, feeling close to the partner at a distance, and concentrating on the phone conversations. We conclude by discussing the unused situations, privacy issues, and usable targets to improve POKE as a way of future tactile phone conversations.

In this paper we introduce CheekTouch, an affective audio-tactile communication technique that transmits multi-finger touch gestures applied on a sender's mobile phone to a receiver's cheek in real time during a call. We made a pair of CheekTouch prototypes each with a multi-touch screen and vibrotactile display to enable bidirectional touch delivery. We observed four romantic couples in their twenties using our prototype system in a lab setting over five consecutive days, and analyzed how CheekTouch affected their non-verbal and emotional communication. The results of the user study showed that CheekTouch could effectively support audio-tactile communication in various ways - persuading, conveying status, delivering information, emphasizing emotion/words, calling for attention, and being playful.

Several flash file systems have been developed based on the physical characteristics of NAND flash memory. However, previous flash file systems have performance overhead and scalability problems caused by metadata management in NAND flash memory. In this paper, we present a flash file system called PFFS2. PFFS2 stores all metadata into virtual metadata storage, which employs Phase-change RAM (PRAM). PRAM is a next-generation nonvolatile memory and will be good for dealing with word-level read/write of small-size data. Based on the virtual metadata storage, PFFS2 can manage metadata in a virtually fixed location and through byte-level in-place updates. Therefore, the performance of PFFS2 is 38 percent better than YAFFS2 for small file read/write while matching YAFFS2 performance for large file. Virtual metadata storage is particularly effective in decreasing the burden of computational and I/O overhead of garbage collection. In addition, PFFS2 maintains a 0.18 second mounting time and 284 KB memory usage in spite of increases in NAND flash memory size. We also propose a wear-leveling solution for PRAM in virtual metadata storage and greatly reduce the total write count of NAND flash memory. In addition, the life span of PFFS2 is longer than other flash file systems.

The Flash Translation Layer (FTL) in Solid-State Disks (SSDs) maps logical addresses to physical addresses for disk drive virtualization. In order to reduce garbage collection overhead, we propose full associative striped block-level mapping. In addition, an adaptive merge is proposed to avoid excessive data block reconstructions during garbage collection. With these mechanisms, the write latency is improved up to 78% in comparison with the previous multichannel hybrid FTLs in a sample PC trace. The performance improvements stem from 52% reduced garbage collection.

Memory contention among consolidated virtual machines (VMs) creates the need for a memory balancing operation. In an attempt to provide a prompt memory balancing mechanism, we found problems with the retardation of memory transfer by the reclamation delay. The scheduling of the VMs generates the delay, and a conflicts of two reclamation policies between the guest OS and the hypervisor deteriorates it. As a remedy to these problems, we propose HyperDealer, which selects the victim page by applying reference patterns, reclaims the pages with hypervisor-level paging, and transfers those pages with ballooning of the guest OS. Our scheme eliminates the involvement of the victim VM in memory balancing and extends the dwell time of reclaimed pages in the reclaimed state. Consequently, HyperDealer significantly reduces the time taken to transfer memory with a low overhead and enhances the value of additional memory for the recipient VM. The experimental results of our scheme show that the application performance in the recipient VM is 11% more time-efficient and has a penalty which is 50% less than previous approaches.

The advent of many core era breaks the performance wall but it causes severe energy consumption. NVRAM as a main memory can be a good solution to reduce energy consumption due to large size of DRAM. In this paper, we propose MN-MATE, a novel architecture and management techniques for resource allocation of a number of cores and large size of DRAM and NVRAM. In MN-MATE, a hyper visor partitions and allocates cores and memory for guest OSes dynamically. It is clear that optimized matching of heterogeneous cores, DRAM, and NVRAM enhances system performance. Selective locating of data in a main memory composed of DRAM and NVRAM significantly reduces energy consumptions. Preliminary results show that integration of dynamic resource partitioning and selective memory allocation scheme with MN-MATE reduces energy usage significantly and suppresses performance loss from NVRAM's characteristics.