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We propose an overloading control system with a novel method to estimate vehicle weight using the sensor data from a smartphone mounted on the vehicle. The conventional method based on fixed weigh stations has limited coverage, and is expensive to install and maintain. Our proposed system overcomes these limitations by using smartphones, which are portable and cheaper. A multiple linear regression model is created using vertical acceleration statistical features and loading status classification as explanatory variables to estimate the vehicle’s weight. A pilot experiment estimating a trolley’s weight was followed by an experiment estimating an actual vehicle’s weight to verify the feasibility of using our method. We achieved average error of 593 kg, which accounted for 5.89% of the true average vehicle’s weight.

Antibacterial silver with hydroxyapatite (Ag-HA) is a promising coating material for imparting antibacterial properties to implants. We previously reported that 3% (w/w) silver with HA (3% Ag-HA) has both antibacterial activity and osteoconductivity. In this study, we investigated the effects of Ag-HA on the in vitro osteoblast function and the in vivo anchorage strength and osteoconductivity of implants. Production of the osteoblast marker alkaline phosphatase, but not cytotoxicity, was observed in cells of the osteoblast cell line MC3T3-E1 cultured on the 3% Ag-HA-coated surface. These results were similar to those observed with silver-free HA coating. In contrast, a significant high level of cytotoxicity was observed when the cells were cultured on a 50% Ag-HA-coated surface. The anchorage strength of implants inserted into the femur of Sprague-Dawley (SD) rats was enhanced by coating the implants with 3% Ag-HA. On the 3% Ag-HA-coated surface, both metaphyseal and diaphyseal areas were largely covered with new bone and had adequate osteoconductivity. These results suggest that 3% Ag-HA, like conventional HA, promotes osteogenesis by supporting osteoblast viability and function and thereby contributes to sufficient anchorage strength of implants. Application of 3% Ag-HA, which combines the osteoconductivity of HA and the antibacterial activity of silver, to prosthetic joints will help prevent postoperative infections.

This paper describes a spot-controllable data-transfer method. The proposed method generates a beam-shaped spot using two commercial off-the-shelf speakers. In our method, a symbol consists of a pair of sinusoidal waves having different angular frequencies. The width and direction of a beam-shaped spot are controlled by the angular-frequency difference between the sinusoidal waves and the transmission-time difference between the two speakers. Multiple spots can be generated by transmitting multiple pairs of sinusoidal waves based on the principle of orthogonal frequency-division multiplexing. By over-lapping multiple beam-shaped spots, the locations and sizes of the areas enabled to receive data are controllable. Experiments using four speakers and computer simulation show that the proposed method can generate controllable spots. An analysis of the errors in a real indoor environment indicate that they are caused by multipath signals, radiation damping of transmitted signals, and the incident/output angle characteristics of the microphone and speakers.

For accurate indoor positioning, a heading estimation method that does not depend on smartphone orientation has been developed. While prior methods require the smartphone to be fixed in a certain orientation before processing, the proposed method works with the smartphone in any orientation. We utilize gyroscope data from three axes and use a low-pass filter to eliminate movement noise. Experimental results show that our method has an average error rate of just 3–5% in positioning distance for various smartphone orientations (held in the user's hand, belt pouch, side pants pocket, and back pants pocket). Using this method gives smartphone users a greater degree of freedom because they do not have to hold the device in a pre-defined orientation to obtain a reliable heading estimate.

This paper presents a rapid and accurate time-synchronization technique for acoustic localization. Two LED arrays for modulated illumination and an off-the-shelf camera are used. An equation that specifies the time difference between them accurately and precisely is proposed. Experiments in real environments show that the proposed technique using rectangular signals can achieve time synchronization to within 29.4 µs (5.94 µs standard deviation) and acoustic ranging to within 9.9 mm (2.01 mm standard deviation) for a measurement period of 0.1 s. Because of the smaller standard deviation in comparison with the error, it is indicated that there exist systematic errors to be removable. This technique will enable the implementation of an acoustic 3D localization system for mobile devices such as tablet PCs and smartphones based on time-of-arrival trilateration, which is more accurate than positioning taking a time-difference-of-arrival approach. Theoretical analyses for modulated illumination considering a camera exposure time clarify how an optimally modulated signal is designed for achieving rapid and accurate time synchronization.

For accurate indoor positioning, a moving activity recognition (AR) method has been developed that is based on a smartphone's sensor data. Prior methods can only recognize moving activities if the smartphone is held in a predefined place. We propose a method that works in various holding places to increase the usability. An SVM classifier is chosen because of its strength in utilizing features. New features are added such as percentiles of acceleration, air pressure, and acceleration magnitude. We have achieved 94.3% overall accuracy in various holding places: in users' hands, belt pouches, pant back pockets, and pant side pockets.

A novel method for separating trip periods from non-trip periods, called a "trip-separation method" hereafter, is proposed. Previous studies on such automatic "trip separation" use a fixed threshold to detect "stay periods" (i.e., periods in which a subject is staying put) and separate them from trip periods. However, this separation procedure does not always work well because the collected global positioning system (GPS)-positioning data can fluctuate according to the surrounding environment even when the subject stays within an area. The proposed method dynamically adjusts parameters for detecting stay periods according to the surrounding environment. The experimental evaluation on the method showed precision of 81%. This is a promising result implying that sensor-based travel-behavior surveys are possible by utilizing the proposed smartphone-based method.

To reduce the incidence of implant-associated infection, we previously developed a novel coating technology using hydroxyapatite (HA) containing silver (Ag). This study examinedin vivoacute and subacute toxicity associated with the Ag-HA coating in rat tibiae. Ten-week-old rats received implantation of HA-, 2% Ag-HA-, or 50% Ag-HA-coated titanium rods. Concentrations of silver in serum, brain, liver, kidneys, and spleen were measured in the acute phase (2–4 days after treatment) and subacute phase (4–12 weeks after treatment). Biochemical and histological examinations of those organs were also performed. Mean serum silver concentration peaked in the acute phase and then gradually decreased. Mean silver concentrations in all examined organs from the 2% Ag-HA coating groups showed no significant differences compared with the HA coating group. No significant differences in mean levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, creatinine, or blood urea nitrogen were seen between the three groups and controls. Histological examinations of all organs revealed no abnormal pathologic findings. No acute or subacute toxicity was seenin vivofor 2% Ag-HA coating or HA coating. Ag-HA coatings on implants may represent biologically safe antibacterial biomaterials and may be of value for reducing surgical-site infections related to implantation.

This paper deals with the classification problem of modes of transportation using the information obtained with mobile devices such as smartphones. We especially focus on distinction between cars and motorbikes, which have been a difficult problem due to their similarity. In order to solve this problem, we propose the classification method based on the model of vibration generation while vehicles are running. We conducted an experiment to evaluate the classification accuracy and obtained the accuracy of over 80%.

We describe an indoor localization technique for smart phones. Our new method, called the Frequency Division Multiplexing Phase Accordance Method (FDM-PAM), uses a beat called a sync pattern composed of a pair of sinusoidal waves with slightly different frequencies, which is similar to our original ultrasound ranging technique called the Phase Accordance Method (PAM). By generating multiple sync patterns with different central frequencies and transmitting them from different speakers, FDM-PAM conducts time-difference-of-arrival (TDOA) multilateration for localizing smart phones. In the current implementation of FDM-PAM, the 2D indoor position of a smart phone can be estimated. Three sync patterns are generated by using two out of six sinusoidal waves with frequencies ranging from 14.75 kHz to 17.25 kHz. The transmission of the sync pattern from the speakers lasts 4 ms. Through experiments, we have confirmed that FDM-PAM achieves accuracy of around 10 cm using only a short burst transmission, which indicates that the localization technique is sufficiently rapid and accurate.

Tracking people has become an important topic since it is needed to optimize human activities in commercial facilities, factories, and other business organizations. In buildings, where the Global Positioning System (GPS) lacks efficiency, there are mainly two positioning methods. One is called Fixed Indoor Positioning systems. The architecture is having fixed number of base stations which receives/sends the signals and calculates the coordinates of the target object. Another one is called Pedestrian Dead Reckoning (PDR). It happens when locating people who are carrying localization sensors while the building is not equipped with an indoor positioning system. The use of smart phones has rapidly spread in these days, so PDR using sensors of smart phones has been more realizable for versatile indoor tracking systems. PDR has a problem that the noise of sensors depending on sensitivity and surroundings reduces accuracy. To improve accuracy, particle filter is mostly used. Particle filter is sequential Monte Carlo methods based on point mass (or “particle”) representations of probability densities, which can be applied to any state-space model and which generalize the traditional Kalman filtering methods. However it costs computing resource, so it consumes battery heavily in smartphones. Heavy battery consumption reduces usability and it induces that the tracking application is not used. Therefore, we developed the improved particle filter method to reduce battery consumption. The method can change the number of particles and the error distribution of sensors adaptive to human moving modes. We evaluate the entire system on a smartphone by using the sensor data of an actual person walking in a commercial facility “THE RAILWAY MUSEUM” in Omiya, Japan. Our results show that we can reduce computing time for up to one-third keeping tracking accuracy. As a result, our method can be generally used to optimize human activities using smart phones.

A previously described automated thin-film deposition system based on rf-magnetron sputtering could deposit quite complex optical multilayer systems with good precision and with no one in attendance [ Sullivan Dobrowolski , Appl. Opt.32, 2351–2360 (1993)]. However, the deposition rate was slow, and the uniform area on the substrate was limited. We describe an ac-magnetron sputtering process in which the same deposition accuracy has been combined with significantly better film uniformity and a fivefold or sevenfold increase in the deposition rate. This makes the equipment of commercial interest. Experimental results are presented for several difficult coating problems.