• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.1
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• pp.71-76
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• 2022

Buffer cache bridges the performance gap between memory and storage, but its effectiveness is limited due to periodic flush, performed to prevent data loss in smartphones. This paper shows that selective flushing technique with small persistent memory can reduce the flushing overhead of smartphone buffer cache significantly. This is due to our I/O analysis of smartphone applications in that a certain hot data account for most of file writes, while a large proportion of file data incurs single-writes. The proposed selective flushing policy performs flushing to persistent memory for frequently updated data, and storage flushing is performed only for single-write data. This eliminates storage write traffic and also improves the space efficiency of persistent memory. Simulations with popular smartphone application I/O traces show that the proposed policy reduces write traffic to storage by 24.8% on average and up to 37.8%.

• Advances in Computational Design
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• v.4 no.1
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• pp.1-13
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• 2019

Recent generations of smartphones offer accelerometer sensors as a standard feature. While this has led to the development of a number of related applications (apps), there has been no study on their comparative or individual performance against a benchmark. This paper investigates the comparative performance of a number of smartphone accelerometer apps amongst themselves and to a calibrated benchmark accelerometer. A total of 12 apps were selected for testing out of 90 following an initial review. The selected apps were subjected to sinusoidal vibration testing of varying frequency and the response of each compared against the calibrated baseline accelerometer. The performance of apps was quantified using analysis of variance (ANOVA) and test of significance was carried out. The apps were then compared for a realistic dynamic scenario of measuring the acceleration response of a bridge due to the passage of a French Train $\grave{a}$ Grande Vitesse (TGV) in a laboratory environment.

• Journal of the Semiconductor & Display Technology
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• v.22 no.2
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• pp.112-119
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• 2023

In urban environments, signals of Global Positioning System (GPS) can be blocked and reflected by tall buildings, large vehicles, and complex components of road network. Therefore, the performance of the positioning system using the GPS module in urban areas can be degraded due to the loss of GPS signals necessary for the position estimation. To deal with this issue, various localization schemes using inertial measurement unit (IMU) sensors, such as gyroscope and accelerometer, and Bayesian filters, such as Kalman filter (KF) and particle filter (PF), have been designed to enhance the performance of the GPS-based positioning system. Among Bayesian filters, the PF has been widely used for the target tracking and vehicle navigation, since it can provide superior performance in estimating the state of a dynamic system under nonlinear/non-Gaussian circumstance. This paper presents a positioning system that uses the double-stacked particle filter (DSPF) as well as the accelerometer, gyroscope, and GPS receiver on the smartphone to provide higher pedestrian positioning accuracy in urban environments. The DSPF employs a nonparametric technique (Parzen-window) to create the multimodal target distribution that approximates the posterior distribution. Experimental results show that the DSPF-based positioning system can provide the significant improvement of the pedestrian position estimation in urban environments.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.149-160
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• 2014

Recently studies on application development and utilization using sensors and devices embedded in smartphones have flourished at home and abroad. This study aimed to analyze the accuracy of the images of smartphone to determine three-dimension position of close objects prior to the development of photogrammetric system applying smartphone and evaluate the feasibility to use. First of all, camera calibration was conducted on autofocus and infinite focus. Regarding camera calibration distortion model with balance system and unbalance system was used for the decision of lens distortion coefficient, the results of calibration on 16 types of projects showed that all cases were in RMS error by less than 1 mm from bundle adjustment. Also in terms of autofocus and infinite focus on S and S2 model, the pattern of distorted curve was almost the same, so it could be judged that change in distortion pattern according to focus mode is very little. The result comparison according to autofocus and infinite focus and the result comparison according to a software used for multi-image processing showed that all cases were in standard deviation less than ${\pm}3$ mm. It is judged that there is little result difference between focus mode and determination of three-dimension position by distortion model. Lastly the checkpoint performance by total station was fixed as most probable value and the checkpoint performance determined by each project was fixed as observed value to calculate statistics on residual of individual methods. The result showed that all projects had relatively large errors in the direction of Y, the direction of object distance compared to the direction of X and Z. Like above, in terms of accuracy for determination of three-dimension position for a close object, the feasibility to use smartphone camera would be enough.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.318-323
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• 2019

In this study, we examined the differences in age among the various functions required for everyday life through smartphone using environment. The subjects were composed of 30 young adults and 30 elderly people. We set up 12 tasks to evaluate the performance of smartphone functions. At the same time, a questionnaire about smartphone usage habits was made. The questionnaire consists of items related to user history and usage habits. ANOVA analysis was performed using Minitab version 14, and statistically significant differences were found in 10 tasks. The result of the actual values for each task showed that the elderly generally took more time to perform all the tasks than the younger ones. Especially, the tendency of the task which requires a lot of keystrokes was revealed. Especially, in the case of a task requiring a lot of keystrokes, the tendency was remarkable. Young adults have found that they use all functions uniformly overall, and the functions used by the elderly were biased toward some functions, such as dialing, text, kakao talk, and searching. These results suggest that young people use smartphones more frequently than elderly people, and as they become accustomed to using smartphones, the time required to perform functions may be shortened. We suggest that it is necessary to design in terms of hardware or software so that the elderly people can input easily and conveniently.

• Journal of Digital Convergence
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• v.12 no.1
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• pp.333-338
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• 2014

Zigbee is a wireless communication technology optimized for WSN (Wireless Sensor Network) environment. A WSN gateway is used for node control and data transmission. However, a fixed-type gateway can restrict the flexibility of the WSN environment. A smartphone-mounted high-performance processor and Android OS can be easily used in a mobile WSN gateway. In this paper, we proposed a mobile WSN gateway based on Android smartphones. In the proposed system, a Zigbee sensor module is connected with a smartphone via USB (Universal Serial Bus) port. We also implemented an Android application for the mobile WSN gateway.

• The KIPS Transactions:PartB
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• v.19B no.3
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• pp.177-182
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• 2012

We propose effective motion and observation models for the position of a WiFi-equipped smartphone user in large indoor environments. Three component motion models provide better proposal distribution of the pedestrian's motion. Our Gaussian interpolation-based observation model can generate likelihoods at locations for which no calibration data is available. These models being incorporated into the particle filter framework, our WiFi fingerprint-based localization algorithm can track the position of a smartphone user accurately in large indoor environments. Experiments carried with an Android smartphone in a multi-story building illustrate the performance of our WiFi localization algorithm.

• KIISE Transactions on Computing Practices
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• v.23 no.3
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• pp.148-155
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• 2017

In this paper, we develop a new system to estimate the step count for a smartphone user. The system analyzes data obtained from the accelerometer, magnetic sensor, and gyroscope of an android smartphone to extract pattern information of human steps. We conduct an experiment and evaluation to confirm that the proposed system successfully estimates the number of steps with 96% accuracy when hand-held and 95.5% accuracy when in-pocket. In addition, we found that detection errors were caused by human motions such as touching the screen, shaking the device up and down, sitting up and sitting down, and waving the phone around.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.1
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• pp.13-23
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• 2015

Recently, a few image-processing based mobile urine testers have actively been studied since the urine-analysis result can be available to the user in real time immediately after the test is done. However, the accuracy of test result can be severely degraded due to variable illumination environments and a variety of manners to capture the image with a camera embedded in the smartphone according to different users. This paper proposes the Check4Urine system, a novel smartphone-based portable urine-analysis tester and provides three techniques to improve such a performance degradation problem robust to various test environments and disturbances, which are the compensation algorithm to correct the varying illumination effect, an urine strip detection algorithm robust to edge loss of the object image, and the color decision algorithm based on the pre-processed reference table. Experimental results show that the proposed Check4Urine system increases the accuracy of urine-analysis by 20-50% at various test conditions, compared with the existing image-processing based mobile urine tester.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.1
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• pp.1-7
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• 2012

A Smartphone has an ability accessing Internet by URL stored in NFC(Near Field Communication) Tag for storing the information of items, blogs and web pages. Because the system works through the Internet with URL, however, it needs to pay some costs like communication fee and time. If we can store the web page on the tags, we can save the communication overhead. But they have too small memory to store it. In this paper, we introduce the Micro-Webpage technology which can be stored in NFC tag or QR(Quick Response) code. To make a Micro-Webpage, we remove control tags from the web page to leave a user original content. The removed control tags are stored in our smartphone application as a template. The user content is also compressed to a smaller one by an lossless compression algorithm. When a tag is read, the stored content is decompressed and, it is combined with the template to make the original web page. We have implemented a prototype of Micro-Webpage system on Android platform and confirmed that the prototype has reasonable performance improvements in saving memory and loading web page time.