Noise analysis of Direct Sampling Mixer (DSM) has been described in this paper. The output noise of the DSM is determined by the sum of continuous time noise and discrete time noise. The discrete time noise is calculated from the discrete time transfer function and Fourier transform of the sample/hold function. The input referred noise of the DSM is also derived and low noise design procedure is described. The simulation results of NF show good agreement between the theoretical calculations.
In this paper, CPM-OFDM systems which use CPM (Continuous Phase Modulation) as the first modulation scheme of OFDM (Orthogonal Frequency Division Multiplexing) are considered. As is the case for conventional OFDM systems, PAPR (Peak to Average Power Ratio) reduction is the most important task in CPM-OFDM systems. PAPR reduction by varying the initial phase of each sub-carrier with a fixed offset and a random offset are proposed. In the random offset method, the initial phase of each sub-carrier is not known at the receiver side, so we propose a demodulation algorithm using the phase continuity property of CPM and MLSD (Maximum Likelihood Sequence Detection). Simulation results show that the PAPR performance is improved if we use the random offset method. Also, we found that even though the initial phase is unknown at the receiver, the proposed algorithm can demodulate CPM-OFDM symbols as well as an algorithm where the initial phase is known.
This paper proposes a dynamic lightpath establishment scheme considering power consumption and four-wave mixing (FWM) in all-optical networks. In all-optical networks, an optical amplifier is used to amplify a group of optical signals of different wavelengths in a fiber without O/E/O conversion. Even if only one optical signal passes through an optical amplifier in a fiber, the optical amplifier operates. Thus, to efficiently use power of the optical amplifier, multiple optical signals in the fiber should be simultaneously amplified. FWM is one of the most important physical impairments to be resolved in all-optical networks because FWM decays the performance of all-optical networks. The FWM power in a fiber increases with the number of wavelengths used in the fiber. Therefore, in order to reduce the FWM power, it is preferred that optical signals are transmitted on different fibers. The proposed scheme provides an ingenious route, wavelength, fiber selection strategy considering the tradeoff between the power consumption and the FWM power. Furthermore, the proposed scheme avoids blocking of lightpath establishment due to depletion of wavelength resources. Through simulation experiments, we show that the proposed scheme efficiently reduces the blocking probability, the power consumption, and the FWM power in case of the number of fibers is fixed.
Estimation of communication zone for contactless electric-field intrabody communication (IBC) with a side electrode on the wall of a security gate is studied. The IBC with a side electrode has two transmission paths between a mobile device and the side electrode. By using a proposed method of measuring two capacitances corresponding to two paths, human position dependency of capacitances is obtained. Communication zone estimated from measured capacitances is consistent with the measured one.
In this paper, an Ethernet device using two ring buffers was implemented in order to achieve a parallel realization of a real-time communication and an IP communication. Using a conventional device driver, it is difficult to realize such a parallel realization. This is because the non real-time frames (IP frames) are processed using a NAPI mechanism, which introduces large delay and variation. Therefore, processing flows of the real-time frames (RT frames) must be separated from that of IP frames. A proposed mechanism was implemented by modifying the existing open source device driver to realize the flow separation mentioned above. By the modifications of the device driver, the RT frames and the IP frames can be distinguished and managed in the different ring buffers. RT frames are sent to a real-time frame ring buffer and they are processed immediately by using a hardware interrupt. IP frames are processed regularly by the conventional Linux network stack. By implementing them, the proposed device driver achieved 100µs or lower RTT (Round Trip Time) with a real-time communication in parallel with 500Mbit/s or wider bandwidth of IP traffic load. This paper shows the design, the implementation, and the evaluation of the priority processing device driver.
Improvement of the in-plane spatial resolution in cross-sectional imaging using terahertz waves was investigated. The effects of frequency filtering, which limits the frequency range of the terahertz waves, and unsharp mask processing, based on a two-dimensional convolution of the imaging result and a mask consisting of a linear combination of the original image and a Laplacian filter, were evaluated. The filtering methods were successful in improving the spatial resolution up to the sampling limit of 0.4 mm. The combination of frequency filtering and unsharp mask processing was found to be effective for improving the contrast in addition to the spatial resolution. Frequency filtering, unsharp mask processing, and their combination were applied to terahertz wave cross-sectional imaging of an IC card.
In order to study on event-related potential (ERP) in opinion tests of picture quality and food evaluation, the ERPs were measured at 14 electrode positions by the same evaluation method with the same picture, and the same subjects. The pictures of sushi were used. ERP waveform of opinion tests with stimulus-comparison and single-stimulus methods were compared. In result, the ERP waveform of picture quality test has one peak, and the waveform of food preference test has two peaks. The P300 amplitude in the cases of picture quality and food preference tests with stimulus-comparison method is different at Fz and F7. And there is no significant difference between P300 amplitudes of the cases with stimulus-comparison and single-stimulus methods in food preference test. These results indicate that a difference by evaluation method is small, and the content of the evaluation task such as picture quality or food preference is one of the causes.
Myelination is essential for rapid conduction of action potentials in central nervous system. The loss of myelin leads to impairment of motor and cognitive functions. Remyelination by transplantation of oligodendrocytes (OL) is a potent therapeutic strategy for the demyelinating diseases. However, little is known about how the conduction velocity increases after remyelination. Here, the aim of this study is to develop a culture device for evaluating the change in action potential conduction velocity along axon in co-culture of neurons and OL. We developed the culture device which composed of a culture chamber and a microelectrode array (MEA). The chamber has two neuron culture compartments and four OL culture compartments which are interconnected by four microchannels. Electrodes of the MEA were in alignment with the microchannels. Cortical neurons and OL were cultured separately with a co-culture chamber. OL maturation and axon outgrowth through the microchannels were confirmed by immunofluorescence imaging. After neural activities were recorded, spike sorting was performed to separate spikes into clusters of individual neurons. The propagations of action potentials along axon were detected from spike trains. Then, the conduction velocity increased with culture days. These results suggest that this device can be utilized for evaluating the change in action potential conduction velocity in myelination process.
We developed an experimental system to simultaneously characterize tonotopic activities of both the auditory cortex and thalamus of rats, each with a number of microelectrodes. The system consisted of a custom-designed surface electrode array and depth electrode array. The surface electrode array had 64 recording points in a 4.5 mm × 3 mm area. Between the recording points holes were made, through which the depth array was inserted. The depth array had 3 shanks, each of which was 6 mm long with an inter-shank distance of 500 µm. Each shank had 15 recording sites for the thalamus and 17 for the auditory cortex. To precisely insert the depth array perpendicularly to the cortical surface, a laser displacement meter was used. We measured tone-evoked local field potentials and multi-unit activities in the auditory cortex and thalamus of rats under anesthesia, and characterized tonotopic maps simultaneously in the auditory cortex and thalamus.
Living neuronal network in neural systems communicate through synaptic connections. For aiming artificial control of the synaptic transmission in neuronal network, we have applied conventional optical tweezers using a focused near-infrared (NIR) laser. The optical trapping of neural cell adhesion molecules (NCAMs) labeled with quantum-dots (Q-dots) at the plasma membrane of living neuronal cells was achieved at high laser power (>300 mW) in our previous study; therefore, the further reduction of laser power was required. Here, we propose and demonstrate resonant optical tweezers of Q-dots attached to NCAM in a neuron by simultaneous irradiation with non-resonance and resonance laser beams. The optical trapping dynamics of them was revealed by fluorescence correlation spectroscopy (FCS). The transit times of Q-dots attached to NCAM at the focal spot increased with the simultaneous irradiation of NIR laser and resonance laser. These results suggest that the particle motion of Q-dots attached to NCAM was constrained at the focus spot due to optical trapping force enhanced with resonance laser irradiation. Our method is applicable to selective manipulation of signaling molecules in living neurons.
We propose a technique called the Command Casting method to achieve high performance messaging technology for dual controller storage systems. A controller has a feature to cast commands to the other controller which has LU ownerships for the commands. We establish mathematical evaluation models for each proposed and conventional methods. We estimate each method's performance such as CPU overhead and message transmission time. Our findings show that the proposed method improves CPU overhead by a factor of between 1/5 and 1/10, and message transmission time by a factor of between 61% and 89% relative to the conventional methods. Our evaluation of the proposed method suggests that proposed method provides homogenous LU sharing access performance during actual operation regardless of LU ownership.
This paper describes a kind of portfolio selection problem under weather-risk that arises in development of DLC (Direct Load Control) execution plan, mainly for the coordinated power curtailment of office buildings' HVAC systems. Inspired by the Markowitz model of investment theory, we invented two-stage approximate means for scalable solution of the optimization problem. A functional relation between expected value of demand reduction and corresponding minimized risk, which is an analog of efficient frontier in investment theory, is plotted and analyzed its behavior along with selected portfolio's constraints. A numerical experiment is done to show the proposed method can improve reliability of HVAC demand reduction compared to non-optimized portfolios.
In floating offshore wind turbines, the platform motions induced by wind and wave conditions should be reduced to mitigate fatigue load on wind turbine components and decrease cost efficiency. In this paper, a pitch angle control of floating offshore wind turbines using H∞ control is investigated to reduce the platform motions. The performance of the H∞ controller is examined through a nonlinear simulation using a high-fidelity aeroelastic simulator “FAST. ” The simulation results show that the H∞ controller has a better performance compared with a widely-used gain scheduled PI controller.
M2M Systems, in which many sensors and devices are connected to the Internet and various services are provided, have been attracting attention in many fields. In M2M systems, the multi-service connectivity to allow multiple different applications to access a sensor or a device is required. We have proposed an M2M proxy communication method to realize multi-service connectivity at a lower cost. However, when applying the proposed method to a large-scale M2M system, load balancing of M2M proxy servers is one of the important issues. In this paper, we propose a load balancing method of M2M proxy servers using OpenFlow for network routing control. The proposed method realizes the multi-service connectivity in a large-scale M2M system by increasing M2M proxy servers without a load balancer. In this study, we implemented a prototype system to evaluate the functionality, performance and operability of the proposed method.
The system method of M2M data communication between M2M devices is important to build M2M systems. With the progress of technologies of sensor, wireless-communications, virtualization, and the large-scale data processing, it is able to build advanced M2M systems. In order to use M2M data effectively, it is necessary to connect efficiently the three parts of the M2M sensor, gateway, and the server. This paper proposes a communication method between M2M devices based on SIP (Session Initiation Protocol) which is used for the communication between these parts. We applied the proposed method to a prototype of a watching system for a person living in a remote house, and evaluated the effectiveness of the system.
The paper proposes a direct control parameter tuning method which employs the variance evaluation for the performance criterion to solve the disturbance attenuation problem for the CARMA(Controlled Auto-Regressive Moving Average) models. The proposed method tunes the control parameters so that the variance of the plant output approaches the minimum variance value, which can be estimated from the output prediction using the CARMA model. The method can avoid the disturbance reference model, which is indispensable for our earlier research. The efficiency of the proposed method is demonstrated from a numerical example.
In this study, the characteristics of a human operator in a human-machine control system on vertical plane task are analyzed. We already found that the compensatory characteristics of the human operator have the difference in task direction and his posture, and therefore suitable parameters of controlled object for maneuverability are also dependent on them. In this paper, validity of proposed method for adjusting the parameters considering task direction and operator's posture is confirmed by experiments.
Japanese electric power companies widely use the gas-in-oil based diagnostic criterion, which was developed in 1999, for determining the anomaly ranking of intermediate joint boxes of single-core cables during the maintenance of oil-filled cable joint boxes. However, it can determine neither the fault location nor aid in the diagnosis of terminal joint boxes. In addition, several joint boxes that are determined as normal using this criterion have recently been found to be anomalous in the overhaul. In this paper, we propose a new relatively accurate diagnostic criterion that covers both the intermediate and terminal joint boxes and aids in determining the anomaly ranking and fault location using the multiclass ν-linear support kernel machine (SKM), which we propose as an extension of the linear support vector machine (SVM). The proposed multiclass ν-linear SKM automatically scales data to maximize the performance of the linear SVM and obtains simpler linear evaluation functions. Furthermore, it is formulated as a linear programming problem, whereas general SKMs are formulated as semi-definite programming problems that are difficult to solve. The accuracy of our proposed linear criterion, which was estimated using 5 fold cross-validation, was approximately 75% which was almost comparable to 76% by the one-against-one non-linear RBF-support vector machine.
The discovery of associations between local facial features and image features is one of the current challenges in regard to facial expression recognition. To mitigate the negative effects caused by individual differences, this paper proposes an approach based upon human cognition which can recognize facial expression from six human cognitive regions. The proposed approach exploits descriptions of Local Binary Pattern (LBP) to extract the holistic facial area and establishes a pseudo 3D face model for segmenting the human face into six cognitive regions. Finally, we synthesize change trends and volume distribution of LBP of the six regions to recognize the expressions. Unlike many previous studies, this approach recognizes the expressions from regional features instead of holistic facial features. Further, the regional features are more robust than interesting point-based features because of idiosyncrasy of individuals. To validate our proposed approach, we conducted experiments on the Extended Cohn-Kanade (CK+) facial expression database. The results demonstrate that the proposed approach can effectively segment face into specific areas and recognize facial expressions.
We have seen great variability in the outcomes of activities to improve the capabilities of software development, and that such variability has been attributed primarily to the skills and experiences of promoters of individual support activities. In this paper, we propose an approach of software development support activity that enhance the probability of achieving expected result with reference to service approach and organization management paradigms.
The screening board using wall materials is effective to evaluate wireless system fundamental characteristics in the outdoor environment. In this letter, the electrical parameters of lath metal board are evaluated using a simple experimental value and ray-trace simulation results. Using evaluated parameters, the screening area using lath board can be calculated using ray-trace simulator.