This paper presents an algorithmic approach to acquiring the influencing relationships among users by discovering implicit influencing group structure from smartphone usage. The method assumes that a time series of users' application downloads and activations can be represented by individual inter-personal influence factors. To achieve better predictive performance and also to avoid over-fitting, a latent feature model is employed. The method tries to extract the latent structures by monitoring cross validating predictive performances on approximated influence matrices with reduced ranks, which are generated based on an initial influence matrix obtained from a training set. The method adopts Nonnegative Matrix Factorization (NMF) to reduce the influence matrix dimension and thus to extract the latent features. To validate and demonstrate its ability, about 160 university students voluntarily participated in a mobile application usage monitoring experiment. An empirical study on real collected data reveals that the influencing structure consisted of six influencing groups with two types of mutual influence, i.e. intra-group influence and inter-group influence. The results also highlight the importance of sparseness control on NMF for discovering latent influencing groups. The obtained influencing structure provides better predictive performance than state-of-the-art collaborative filtering methods as well as conventional methods such as user-based collaborative filtering techniques and simple popularity.

This paper presents a novel CMOS readout circuit for satellite infrared time delay and integration (TDI) arrays. An integrate-while-read method is adopted, and a dead-pixel-elimination circuit for solving a critical problem of the TDI scheme is integrated within a chip. In addition, an adaptive charge capacity control method is proposed to improve the signal-to-noise ratio (SNR) for low-temperature targets. The readout circuit was fabricated with a 0.35-µm CMOS process for a 5004 mid-wavelength infrared (MWIR) HgCdTe detector array. Using the circuit, a 90% background-limited infrared photodetection (BLIP) is satisfied over a wide input range (∼200–330 K), and the SNR is improved by 11 dB for the target temperature of 200 K.

We propose a method for halftoning grayscale images by drawing weighted centroidal Voronoi tessellations (WCVTs) with black lines on white image planes. Based on the fact that CVT approaches a uniform hexagonal lattice asymptotically, we derive a relationship of darkness between input grayscale images and the corresponding halftone images. Then the derived relationship is used for adjusting the contrast of the halftone images. Experimental results show that the generated halftone images can reproduce the original tone in the input images faithfully.

We propose a novel method for measuring the matched total radiated power (TRP) and matched total radiated sensitivity (TRS) of small radio terminals, called over-the-air (OTA) measurement, using a spheroidal coupler (SC). To measure these parameters accurately in a multiple-reflection environment, such as in an SC, we developed two key techniques, i.e. displacement method and reflection compensation method, and verified their effectiveness by several simulations and fundamental experiments on a test transmitter. We also describe an absolute method for measuring antenna radiation efficiency using the displacement method. Furthermore, we describe TRP and TRS measurements for actual UMTS (Universal Mobile Telecommunications System) terminals, and verify that the proposed method achieves quick measurements with good accuracy. The SC provides a compact, low-cost OTA measurement system with high sensitivity and high speed.

Speaker change detection involves the identification of the time indices of an audio stream, where the identity of the speaker changes. This paper proposes novel measures for speaker change detection over the centroid model, which divides the feature space into non-overlapping clusters for effective speaker-change comparison. The centroid model is a computationally-efficient variant of the widely-used mixture-distribution based background models for speaker recognition. Experiments on both synthetic and real-world data were performed; the results show that the proposed approach yields promising results compared with the conventional statistical measures.

Ultra wideband (UWB) radar is considered a promising technology to complement existing camera-based surveillance systems because, unlike cameras, it provides excellent range resolution. Many of the UWB radar imaging algorithms are based on large-scale antenna arrays that are not necessarily practical because of their complexity and high cost. To resolve this issue, we previously developed a two-dimensional radar imaging algorithm that estimates unknown target shapes and motion using only three antennas. In this paper, we extend this method to obtain three-dimensional images by estimating three-dimensional motions from the outputs of five antennas. Numerical simulations confirm that the proposed method can estimate accurately the target shape under various conditions.

In this paper, we have proposed a new method of observing walking traces, which can observe people's indoor movement for life-logging. Particularly emphasized new techniques in this paper are methods to detect locations, where walking directions are changed, by analyzing azimuth orientations measured by an orientation sensor of an Android mobile device, and to decide walking traces by a map matching with a vector map. The experimental evaluation has shown that the proposed method can determine the correct paths of walking traces.

Phase synchronization is a crucial problem in Bistatic Synthetic Aperture Radar (BiSAR). As phase synchronization error and Doppler phase have nearly the same form, Doppler Centroid (DC) cannot be estimated with traditional method in BiSAR. A DC estimation method is proposed through phase-interferometry of Dual-channel direct signal. Through phase interferometry, phase synchronization error can be counteracted while Doppler phase is reserved and DC can be estimated from the reserved phase.

A readout circuit incorporating a pixel-level analog-to-digital converter (ADC) is studied for 2-dimensional microbolometer infrared focal plane arrays (IRFPAs). The integration time and signal-to-noise ratio (SNR) is improved using the current-mode bias and MSB skimming. The proposed pixel-level ADC is a two-step configuration, so its power consumption is very low. The readout circuit was designed using a 0.35 µm 2-poly 4-metal CMOS process for a 320240 microbolometer array with a pixel size of 35µm35µm. The noise equivalent temperature difference (NETD) was estimated to be 47 mK, with a power consumption of 390 nW for a pixel-level ADC.

In this paper, we present a new frequency identification technique using the recent methodology of compressive sensing and discrete prolate spheroidal sequences with optimal energy concentration. Using the bandpass form of discrete prolate spheroidal sequences as basis matrix in compressive sensing, compressive frequency sensing algorithm is presented. Simulation results are given to present the effectiveness of the proposed technique for application to detection of carrier-frequency type signal and recognition of wideband signal in communication.

A two-dimensional microarray of ten thousand (100100) hepatocyte hetero-spheroids, underlaid with non-parenchymal cells, was successfully constructed with a 100-µm spacing on micro-fabricated glass substrates that were coated with poly(ethylene glycol) (PEG). Co-cultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100-µm, functioning as a miniaturized liver to secrete albumin for at least 1 month. The most important feature of this study is that these substrates are defined to provide an unprecedented control of substrate properties for modulating cell behavior, employing both surface engineering and synthetic polymer chemistry. The spheroid array constructed here is highly useful as a platform of tissue and cell-based biosensors (TBB and CBB), detecting a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.

Device mismatch plays an important role in the design of accurate analog circuits. The common centroid structure is commonly employed to reduce device mismatches caused by symmetrical layouts and processing gradients. Among the candidate placements generated by the common centroid approach, however, whichever achieves better matching is generally difficult to be determined without performing the time-consuming yield evaluation process. In addition, this rule-based methodology makes it difficult to achieve acceptable matching between multiple capacitors and to handle an irregular layout area. Based on a spatial correlation model, this study proposed a design methodology for yield enhancement of analog circuits using switched-capacitor techniques. An efficient and effective placement generator is developed to derive a placement for a circuit to achieve the highest or near highest correlation coefficient and thus accomplishing a better yield performance. A simple yield analysis is also developed to evaluate the achieved yield performance of a derived placement. Results show that the proposed methodology derives a placement which achieves better yield performance than those generated by the common centroid approach.

On the use of a surveillance camera, there is a case where privacy protection should be considered. This paper proposes a new privacy protection method by automatically degrading the face region in surveillance images. The proposed method consists of ROI coding of JPEG2000 and a face detection method based on template matching. The experimental result shows that the face region can be detected and hidden correctly.

A new readout integrated circuit is developed for application in an amorphous silicon-based microbolometer array with a pixel pitch of 35 µm. The proposed circuit lowers the power dissipation for a pixel-level analog-to-digital converter (ADC), which uses a comparator and a counter for its data conversion. The infrared current of a microbolometer is proportional to the resistivity changes of the microbolometer. Thus, the required number of counter operations for the pixel ADC can be determined according to the microbolometer current variation. The counting number precisely determines how much infrared flux is absorbed. A 14 bit counter should normally be used for the pixel ADC for this kind of operation. However, when the proposed current skimming scheme is adopted, the total bits for the counter in the pixel ADC can be reduced to 12 bits. Due to the proposed mechanism, the required operational speed of the comparator can lower than that of a conventional circuit. Consequently, the overall power dissipation in the comparator and counter is less than that of a conventional structure. This low power approach is very suitable in the pixel-level ADCs of microbolometers.

JPEG2000 still image coding standard has a feature called Region of Interest (ROI) coding. This feature can encode a restricted region in an image prior to than its background (BG) region. In low bit rate compression, the code of the ROI region occupies the most of the bit stream in the whole image and it causes the serious deterioration of the image quality in the BG region. This paper proposes a new image quality control method between the ROI region and the BG one by the one time encoding process and it can achieve more detailed image quality control. The use of ROI masks in the encoder makes it possible. The standard decoder of JPEG2000 part1 can decode the encoded data in the proposed method.

Recently low-voltage and low-noise analog circuits with sub 100-nm CMOS devices are strongly demanded for implementing mobile digital multimedia and wireless systems. Reduction of supply voltage makes it difficult to attain a signal voltage swing, and device deviation causes large DC offset voltage and 1/f noise. This paper describes noise reduction technique for CMOS analog and RF circuits operated at a low supply voltage below 1 V. First, autozeroing and chopper stabilization techniques without floating analog switches are introduced. The amplifier test chip with a 0.18-µm CMOS was measured at a 0.6-V supply, and achieved 89-nV/ input referred noise (at 100 Hz). Secondly, in RF frequency range, to improve a phase noise of voltage controlled oscillator (VCO), two 1/f-noise reduction techniques are described. The ring VCO test chip achieves 1-GHz oscillation, -68 dBc/Hz at 100-kHz offset, 710-µW power dissipation at 1-V power supply.

In this paper, a coefficient-parameter embedding method into Motion-JPEG2000 (MJP2) is proposed for invertible deinterlacing with variable coefficients. Invertible deinterlacing, which the authors have developed before, can be used as a preprocess of frame-based motion picture codec, such as MJP2, for interlaced videos. When the conventional field-interleaving is used instead, comb-tooth artifacts appear around edges of moving objects. On the other hand, the invertible deinterlacing technique allows us to suppress the comb-tooth artifacts and also guaranties recovery of original pictures. As previous works, the authors have developed a variable coefficient scheme with a motion detector, which realizes adaptability to local characteristics of given pictures. However, when this deinterlacing technique is applied to a video codec, coefficient parameters have to be sent to receivers for original picture recovery. This paper proposes a parameter-embedding technique in MJP2 and constructs a standard stream which consists both of picture data and the parameters. The parameters are embedded into the LH1 component of wavelet transform domain through the ROI (region of interest) function of JPEG2000 without significant loss in the performance of comb-tooth suppression. Some experimental results show the feasibility of our proposed scheme.

An enhanced Ultra Wideband (UWB) signaling scheme that employs PSWF (Prolate Spheroidal Wave Functions)-based orthogonal chip pulses and ternary complementary code sets is proposed for Direct-Sequence (DS) UWB systems. Every information bit of each user is modulated and transmitted over a set of parallel sequences of PSWF-based orthogonal chip pulses and are further assigned to a ternary complementary code set with additional zero padding if necessary. Moreover, the ternary complementary code sets are generated to be mutually orthogonal and assigned to any pair of multiple users. Hence, the mitigation of multipath interference as well as multiple user interference (MUI) can be expected. Furthermore, the ternary code length can be greatly shortened by taking advantage of pulse and code orthogonality. Thus, the proposed transmission scheme is especially suitable for high data rate DS-UWB systems that offer very high flexibility.

For mobile visual communications, the development of more robust and efficient video traffic control and transmission techniques remains one of the most important issues. Foveated video originates from visual entropy reduction by removing undetectable high visual frequencies that occur at a distance from the fixation point. In this paper, compression gain is defined and measured to quantify the enhanced performance when the visual throughput of the regions of interest (ROI) is increased over a capacity-limited channel.

For point-to-point mobile visual communications, layered video has been utilized to adapt to time-varying channel capacity over noisy environments. From the perspective of the HVS (Human Visual System), it is necessary to minimize the loss of visual quality by specifically maintaining the throughput of visually important regions, objects and so on. Utilizing the prioritized bitstreams generated according to each layer, the throughput can be improved for given channel statistics. In this paper, we define the transmission gain and measure the improved performance when the throughput of ROI (Regions Of Interest) is increased relative to visually unimportant regions over a capacity limited mobile channel.