This paper reports an advanced millimeter-wave radar system to enable detection of vehicles and pedestrians in wide areas around the radar site such as an intersection. We focus on a pulse coding scheme using complementary codes to reduce range sidelobe for discriminating vehicles from pedestrians with high accuracy. In order to suppress sidelobe increase created by RF circuit imperfections, a π/2 shift pulse modulation method with a complementary code pair cycle is presented. Moreover, in order to improve the angular resolution, a high-resolution direction of arrival estimation involving Tx beam scanning is presented. Experiments on a prototype confirm its range sidelobe suppression exceeds 40dB and its angular resolution is 5° for two human's separation at the distance of about 10m in an anechoic chamber. In a trial intersection experiment, a pedestrian detection rate of 95% was achieved at the false alarm rate of 10% in the range from 5m to 40m. The results prove the system's feasibility for future automotive safety application.

To deal with failures as simply as possible, we propose a new foundation for the core (untyped) C++, which is based on a new logic called task logic or imperative logic. We then introduce a sequential-disjunctive statement of the form S : R. This statement has the following semantics: execute S and R sequentially. It is considered a success if at least one of S, R is a success. This statement is useful for dealing with inessential errors without explicitly catching them.

Multi-Walled CNT (MWCNT) are synthesized on a silicon wafer and sputter coated with a gold film. The planar surfaces are mounted on the tip of a piezo-electric actuator and mated with a gold coated hemispherical surface to form an electrical contact. These switching contacts are tested under conditions typical of MEMS relay applications; 4V, with a static contact force of 1mN, at a low current between 20-50mA. The failure of the switch is identified by the evolution of contact resistance which is monitored throughout the switching cycles. The results show that the contact resistance can be stable for up to 120 million switching cycles, which are 106 orders of higher than state-of-the-art pure gold contact. Bouncing behavior was also observed in each switching cycle. The failing mechanism was also studied in relation to the contact surface changes. It was observed that the contact surfaces undergo a transfer process over the switching life time, ultimately leading to switching failure the number of bounces is also related to the fine transfer failure mechanism.

Silver electrical contacts are separated at a constant speed and break arcs are generated in a DC300V-450V/10A resistive circuit. The transverse magnetic field formed by a permanent magnet is applied to the break arcs. Alumina pipes are placed around the contacts to restrict the motion of break arcs. The dependences of the arc lengthening time and arc length just before arc extinction L on the strength of the magnetic field and supply voltage are investigated. It was found that the arc lengthening time increases with increasing supply voltage E and tends to decrease when the magnetic flux density Bx is increased. The arc length just before arc extinction L increases with increasing E and decreasing Bx. It also increases linearly with increasing arc lengthening time tm when no reignitions occur.

In this letter, we propose a partial impedance-matching method using a two-strip resonator for noncontact Passive Intermodulation (PIM) measurements using a coaxial tube. It is shown that the strip closer to the inner tube of the coaxial tube is dominant in the observed PIM characteristics while both strips are excited equally. The ideal efficiency of power to each strip is 50%, which is a significant improvement in comparison with conventional methods.

The reliability of a connector depends on the contact force generated by the spring in the terminal of a connector. The springs are commonly formed by stamping from a strip of spring material. Therefore, the prediction of the force — displacement relation by the finite element (FE) method is very important for the design of terminals. For simulation, an accurate model of stress-strain (s-s) responses of the materials is required. When the materials are deformed in the forward and then the reverse directions, almost all spring materials show different s-s responses between the two directions, due to the Bauschinger effect. This phenomenon makes simulation difficult because the s-s response depends on the prior deformation of the material. Hence, the measurement of the s-s response is the elementary process, by cyclic tension and compression testing in which materials deform elastically and plastically. Then, the s-s responses should be described accurately by mathematical models for FE simulation. In this paper, the authors compare the experimental s-s responses of copper-based materials with conventional mathematical models and the Yoshida-Uemori model, which is a constitutive model having high capability of describing the elastic and plastic behavior of cyclic deformation. The calculated s-s responses only by Yoshida-Uemori model were in very good agreement with the corresponding experimental results. Therefore, the use of this model for FE simulation would be recommended for a more accurate prediction of force-displacement relation of the spring.

This paper proposes a coarse-fine Time-to-Digital Converter (TDC), based on a Ring-Tapped Delay Line (RTDL). The TDC achieves the picosecond's level timing resolution and microsecond's level dynamic range at low cost. The TDC is composed of two coarse time measurement blocks, a time residue generator, and a fine time measurement block. In the coarse blocks, RTDL is constructed by redesigning the conventional Tapped Delay Line (TDL) in a ring structure. A 12-bit counter is employed in one of the two coarse blocks to count the cycle times of the signal traveling in the RTDL. In this way, the input range is increased up to 20.3µs without use of an external reference clock. Besides, the setup time of soft-edged D-flip-flops (SDFFs) adopted in RTDL is set to zero. The adjustable time residue generator picks up the time residue of the coarse block and propagates the residue to the fine block. In the fine block, we use a Vernier Ring Oscillator (VRO) with MOS capacitors to achieve a scalable timing resolution of 11.8ps (1 LSB). Experimental results show that the measured characteristic curve has high-level linearity; the measured DNL and INL are within ± 0.6 LSB and ± 1.5 LSB, respectively. When stimulated by constant interval input, the standard deviation of the system is below 0.35 LSB. The dead time of the proposed TDC is less than 650ps. When operating at 5 MSPS at 3.3V power supply, the power consumption of the chip is 21.5mW. Owing to the use of RTDL and VRO structures, the chip core area is only 0.35mm × 0.28mm in a 0.35µm CMOS process.

Natural language (NL) requirements are usually human-centric and therefore error-prone and inaccurate. In order to improve the 3Cs of natural language requirements, namely Consistency, Correctness and Completeness, in this paper we propose a systematic pattern matching approach supporting both NL requirements modeling and inconsistency, incorrectness and incompleteness analysis among requirements. We first use business process modeling language to model NL requirements and then develop a formal language — Workflow Patterns-based Process Language (WPPL) — to formalize NL requirements. We leverage workflow patterns to perform two-level 3Cs checking on the formal representation based on a coherent set of checking rules. Our approach is illustrated through a real world financial service example — Global Equity Trading System (GETS).

This paper investigates potential to improve fault-detection coverage by means of on-chip redundancy. The international standard on functional safety, namely, IEC61508 Ed. 2.0 Part 2 Annex E.3 prescribes the upper bound of βIC (common cause failure (CCF) ratio to all failures) is 0.25 to satisfy frequency upper bound of dangerous failure in the safety function for SIL (Safety Integrated Level) 3. On the other hand, this paper argues that the βIC does not necessarily have to be less than 0.25 for SIL 3, and that the upper bound of βIC can be determined depending on failure rate λ and CCF detection coverage. In other words, the frequency upper bound of dangerous failure for SIL3 can also be satisfied with βIC higher than 0.25 if the failure rate λ is lower than 400[fit]. Moreover, the paper shows that on-chip redundancy has potential to satisfy SIL 4 requirement; the frequency upper bound of dangerous failure for SIL4 can be satisfied with feasible ranges of βIC, λ and CCF coverage which can be realized by redundant code.

A method to estimate sound source orientation in a reverberant room using a microphone array is proposed. We extend the conventional modeling of a room transfer function based on the image method in order to take into account the directivity of a sound source. With this extension, a transfer function between a sound source and a listener (or a microphone) is described by the superposition of transfer functions from each image source to the listener multiplied by the source directivity; thus, the sound source orientation can be estimated by analyzing how the image sources are distributed (power distribution of image sources) from observed signals. We applied eigenvalue analysis to the spatial correlation matrix of the microphone array observation to obtain the power distribution of image sources. Bsed on the assumption that the spatial correlation matrix for each set of source position and orientation is known a priori, the variation of the eigenspace can be modeled. By comparing the eigenspace of observed signals and that of pre-learned models, we estimated the sound source orientation. Through experiments using seven microphones, the sound source orientation was estimated with high accuracy by increasing the reverberation time of a room.

Finding DC operating points of nonlinear circuits is an important and difficult task. The Newton-Raphson method adopted in the SPICE-like simulators often fails to converge to a solution. To overcome this convergence problem, homotopy methods have been studied from various viewpoints. However, the previous studies are mainly focused on the bipolar transistor circuits. Also the efficiencies of the previous homotopy methods for MOS transistor circuits are not satisfactory. Therefore, finding a more efficient homotopy method for MOS transistor circuits becomes necessary and important. This paper proposes a Newton fixed-point homotopy method for MOS transistor circuits and proposes an embedding algorithm in the implementation as well. Moreover, the global convergence theorems of the proposed Newton fixed-point homotopy method for MOS transistor circuits are also proved. Numerical examples show that the efficiencies for finding DC operating points of MOS transistor circuits by the proposed MOS Newton fixed-point homotopy method with the two embedding types can be largely enhanced (can larger than 50%) comparing with the conventional MOS homotopy methods, especially for some large-scale MOS transistor circuits which can not be easily solved by the SPICE3 and HSPICE simulators.

To enhance the throughput while satisfying the quality of service (QoS) requirements of wireless local area networks (WLANs), this paper proposes a distributed coordination function-based (DCF-based) medium access control (MAC) protocol that realizes centralized radio resource management (RRM) for a basic service set. In the proposed protocol, an access point (AP) acts as a master to organize the associated stations and attempts to reserve the radio resource in a conventional DCF-manner. Once the radio resource is successfully reserved, the AP controls the access of each station by an orthogonal frequency division multiple access (OFDMA) scheme. Because the AP assigns radio resources to the stations through the opportunistic two-dimensional scheduling based on the QoS requirements and the channel condition of each station, the transmission opportunities can be granted to the appropriate stations. In order to reduce the signaling overhead caused by centralized RRM, the proposed protocol introduces a station-grouping scheme which groups the associated stations into clusters. Moreover, this paper proposes a heuristic resource allocation algorithm designed for the DCF-based MAC protocol. Numerical results confirm that the proposed protocol enhances the throughput of WLANs while satisfying the QoS requirements with high probability.

The influence of the splitter plates on the high-current arc roots formation in low voltage circuit breaker is investigated. One arc quenching chamber model is designed, where the shape of the splitter plates can be changed. The capacitor bank circuit is used to provide the test power supply, and the effective value of the prospective short circuit current is fixed to 10kA. High speed CCD camera is adopted to record the arc images during the arcing duration. Arc current and voltage are also measured to analyze the arc characteristics. In addition, a simplified 1-D thermal-electric model is developed to investigate the influence of the splitter plates on the distribution of the current density of the arc plasma with the assumption of local thermal equilibrium (LTE). It shows that the distance between the arc initial ignition location and the splitter plates is crucial to the arc root formation.

In this paper, for an odd prime p, new quaternary sequences of even period 2p with ideal autocorrelation property are constructed using the binary Legendre sequences of period p. For the new quaternary sequences, two properties which are considered as the major characteristics of pseudo-random sequences are derived. Firstly, the autocorrelation distribution of the proposed quaternary sequences is derived and it is shown that the autocorrelation values of the proposed quaternary sequences are optimal. For both p≡1 mod 4 and p≡3 mod 4, we can construct optimal quaternary sequences while only for p≡3 mod 4, the binary Legendre sequences can satisfy ideal autocorrelation property. Secondly, the linear complexity of the proposed quaternary sequences is also derived by counting non-zero coefficients of the discrete Fourier transform over the finite field Fq which is the splitting field of x2p-1. It is shown that the linear complexity of the quaternary sequences is larger than or equal to p or (3p+1)/2 for p≡1 mod 4 or p≡3 mod 4, respectively.

Orthogonal arrays have important applications in statistics and computer science, as well as in coding theory. In this letter, a new construction method of symmetric orthogonal arrays of strength t is proposed, which is a concatenation of two orthogonal partitions according to a latin square. As far as we know, this is a new construction of symmetric orthogonal arrays of strength t, where t is a given integer. Based on the different latin squares, we also study the enumeration problem of orthogonal partitions, and a lower bound on the count of orthogonal partitions is derived.

Spectrum sensing is one of the main functions in cognitive radio networks. To improve the sensing performance and increase spectrum efficiency, a number of cooperative spectrum sensing methods have been proposed. However, most of these methods focused on a single-channel environment. In this letter, we present a novel cooperative spectrum sensing method based on cooperator selection in a multi-channel cognitive radio network. Using reinforcement learning, a cognitive radio user can select reliable and robust cooperators, without any a priori knowledge. Using the proposed method, a cognitive radio user can achieve better sensing capability and overcome performance degradation problems due to malicious users or erratic user behavior. Numerical results show that the proposed method can achieve excellent performance.

Design equations for satisfying off-nominal operating conditions of the class E amplifier with a nonlinear shunt capacitance for a grading coefficient of 0.5 and the duty cycle D=0.5 are derived. By exploiting the off-nominal class E operation, various amplifier parameters such as input voltage, operating frequency, output power, and load resistance can be set as design specifications. As a result of the analysis in this paper, the following extension of the usability of the class E amplifier was achieved. With rising up the dc supply voltage, the shunt capacitance which achieves the off-nominal operation can be increased. This means that a transistor with higher output capacitance can be used for ZVS operation. This also means that maximum operating frequency which achieves ZVS can be increased. An example of a design procedure of the class E amplifier is given. The theoretical results were verified with an experiment.

This paper proposes T-CROM (Time-delayed Collaborative ROuting and MAC) protocol, that allows collaboration between network and MAC layers in order to extend the lifetime of MANETs in a resources-limited environment. T-CROM increases the probability of preventing energy-poor nodes from joining routes by using a time delay function that is inversely proportional to the residual battery capacity of intermediate nodes, making a delay in the route request (RREQ) packets transmission. The route along which the first-arrived RREQ packet traveled has the smallest time delay, and thus the destination node identifies the route with the maximum residual battery capacity. This protocol leads to a high probability of avoiding energy-poor nodes and promotes energy-rich nodes to join routes in the route establishment phase. In addition, T-CROM controls the congestion between neighbors and reduces the energy dissipation by providing an energy-efficient backoff time by considering both the residual battery capacity of the host itself and the total number of neighbor nodes. The energy-rich node with few neighbors has a short backoff time, and the energy-poor node with many neighbors gets assigned a large backoff time. Thus, T-CROM controls the channel access priority of each node in order to prohibit the energy-poor nodes from contending with the energy-rich nodes. T-CROM fairly distributes the energy consumption of each node, and thus extends the network lifetime collaboratively. Simulation results show that T-CROM reduces the number of total collisions, extends the network lifetime, decreases the energy consumption, and increases the packet delivery ratio, compared with AOMDV with IEEE 802.11 DCF and BLAM, a battery-aware energy efficient MAC protocol.

Break arcs are generated in a DC48V resistive circuit. The circuit current is varied from 1A to 6A. The contact resistance distribution on the anode surfaces eroded by break arcs is investigated. The following results are shown. When the current is 2A, 3A and 6A, the contact resistance at the center region of the anode surface is higher than that around the center region. The contact resistance around the center region decreases with the decrease of the circuit current. When the current is 1A, the contact resistance is very low at all positions on the contact surface. The lower contact resistance may be caused by the occurrence of the short arc that is extinguished in the metallic phase arc.

The contact surface of a loose connector has both contact resistance and low inductance, and the inductance depends on the distribution of the true contacts. The contact resistance and inductance were measured by time-domain reflectometry (TDR) for seven contact distribution models. The resistance was approximately constant, while the maximum inductance varied more than twofold depending on the distribution model.