An all adder systolic structure for fast computation of moments

Moment invariants play an important role in pattern recognition and computer vision. They have the nice properties of being invariant under translation, rotation and scaling. In this paper, we propose a new systolic array for computing ordinary moments from which moment invariants can be derived. The array exploits parallelism of the computation maximally and has an ideal time complexity ofO(n). Each computation step involves a single addition only and is thus far superior to most existing solutions that require multiplication. The systolic array can be directly implemented in VLSI and we also provide an estimate of the realizability of the array in a 0.8 micron BiCMOS technology. To achieve effective tradeoff between area and time requirement, we also propose a scalable array that allows us to fold the computation into a much smaller area. Our solution is suitable for both binary images and gray level images and is thus superior to an earlier work that has similar characteristics.     

Object boundary location by region and contour deformation

Many applications in image analysis need to distinguish an object from its surroundings. The `snake' method (Kass, 1987) is a well known method to solve such problems by locating the object boundary from an initial plan, but it has the limitation that the distance between the initial plan and the object boundary should be `very small'. The authors present a two-step method, which combines region and contour deformation, to locate the boundary of an object from a designated initial boundary plan. First, they propose a new deformable region model to represent an object, and use the model to locate the boundary of the object by region deformation. This step fills the gap between a fairly rough initial plan and the `snake' method. The resulting boundary is then used as the initial plan of a `snake' method to further refine the boundary. The results of the method are shown in simulated images and MRI images of brain tumour patients     

Energy performance of building envelopes in different climate zones in China

Energy performance of office building envelope designs in the five major climate zones – severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter – in China was investigated. A major city within each climate zone was selected. These were Harbin, Beijing, Shanghai, Kunming and Hong Kong. Generic building envelopes were developed based on data gathered from building surveys, local energy codes and the ASHRAE Standard. The overall thermal transfer value (OTTV) method and the heating degree-days technique were adopted in the analysis. Cooling and heating requirements due to heat gain/loss through the building envelopes were determined based on the respective OTTV parameters and building load coefficients. Different shape coefficients were also considered. For a typical floor, chiller load due to heat gain through the building envelope varied from 1.0 kW h/m² in Kunming to 23.5 kW h/m² in Beijing, and the heating load ranged from 2.7 kW h/m² in Hong Kong to 124.3 kW h/m² in Harbin.     

Effect of Oligothienyl Chain Length on Tuning the Solar Cell Performance in Fluorene‐Based Polyplatinynes

A series of solution‐processable and strongly visible‐light absorbing polyplatinynes containing oligothienyl–fluorene ring hybrids were synthesized and characterized. These rigid‐rod organometallic materials are soluble in polar organic solvents and show intense absorptions in the visible spectral region, rendering them excellent candidates for bulk heterojunction polymer solar cells. The photovoltaic behavior depends significantly on the number of thienyl rings along the polymer chain, and some of these polymer solar cells show high power conversion efficiencies (PCEs) of up to 2.9% and a peak external quantum efficiency to 83% under AM1.5 simulated solar illumination. The effect of oligothienyl chain length on improving the polymer solar cell efficiency and on their optical and charge transport properties is elucidated in detail. At the same blend ratio of 1:5, the light‐harvesting capability and PCE increase markedly with increasing number of thienyl rings. The power dependencies of the solar cell parameters (including the short‐circuit current density, open‐circuit voltage, fill‐factor, and PCE) were also examined. The present work opens up an attractive avenue to developing conjugated metallopolymers with broad and strong solar energy absorptions and tunable solar cell efficiency and supports the potential of metalated conjugated polymers for efficient power generation.     

Helical‐Like 3D Ultrathin Piezoelectric Element for Complicated Ultrasonic Field

The developments of personalized medicine, ultrasound imaging, and contactless “microscopic handle” techniques are pushing ultrasonic transducers toward features of high frequency, device miniaturization, and even novel function. However, the conventional ultrasonic transducer has severely limited the development of novel ideas for applications due to its ordinary ultrasonic field. Although transducer arrays and monolithic acoustic holograms are capable of producing the complicated ultrasonic field, it is still difficult to achieve high frequency, device miniaturization, and novel function simultaneously. Here, a simple but effective approach is introduced that aims at reconstructing the complicated and high‐frequency ultrasonic field via a compact single‐element ultrasonic transducer. The 3D ultrathin piezoelectric element with a complex configuration is demonstrated theoretically and experimentally to produce the desired complicated ultrasonic field. With helical‐like configuration, the single‐element ultrasonic transducer offers efficient noncontact trapping and manipulation of suspended microparticles and biological cells. Moreover, its strong trapping capability leads to the 3D stacking of microparticles, which is a novel and interesting phenomenon achieved by a single‐element ultrasonic transducer. This work brings the possibility of a complicated ultrasonic field for achieving novel high‐frequency ultrasound applications through the design of smart structure ultrathin piezoelectric materials.     

Protocol design for scalable and reliable group rekeying

We present the design and specification of a protocol for scalable and reliable group rekeying together with performance evaluation results. The protocol is based upon the use of key trees for secure groups and periodic batch rekeying. At the beginning of each rekey interval, the key server sends a rekey message to all users consisting of encrypted new keys (encryptions, in short) carried in a sequence of packets. We present a scheme for identifying keys, encryptions, and users, and a key assignment algorithm that ensures that the encryptions needed by a user are in the same packet. Our protocol provides reliable delivery of new keys to all users eventually. It also attempts to deliver new keys to all users with a high probability by the end of the rekey interval. For each rekey message, the protocol runs in two steps: a multicast step followed by a unicast step. Proactive forward error correction (FEC) multicast is used to reduce delivery latency. Our experiments show that a small FEC block size can be used to reduce encoding time at the server without increasing server bandwidth overhead. Early transition to unicast, after at most two multicast rounds, further reduces the worst-case delivery latency as well as user bandwidth requirement. The key server adaptively adjusts the proactivity factor based upon past feedback information; our experiments show that the number of NACKs after a multicast round can be effectively controlled around a target number. Throughout the protocol design, we strive to minimize processing and bandwidth requirements for both the key server and users.     

A Substitution‐Dependent Light‐Up Fluorescence Probe for Selectively Detecting Fe3+ Ions and Its Cell Imaging Application

Deliberate design of specific and sensitive molecular probes with distinctive physical/chemical properties for analyte sensing is of great significance. Herein, by taking advantage of the position‐dependent substituent effects, an aggregation‐induced emission featured iron (III) probe from ortho‐substituted pyridinyl‐functionalized tetraphenylethylene (TPE‐o‐Py) is synthesized. It displays high sensitivity and selectivity toward iron (III) detection. The recognition arises from the position isomer of ortho‐substitution, and the fact that TPE‐o‐Py has a low acid dissociation constant (pK _a) that is close to that of hydrolyzed Fe³⁺. Importantly, TPE‐o‐Py as a light‐up fluorescence probe could be employed for Fe³⁺ sensing in living cells with a pronounced red‐shift in fluorescence emission.     

Isometric data sequences and data-modulation schemes in fading channels

In multiplicative fading channels, joint channel estimation and data detection (CE/DD) schemes cannot differentiate among certain sequences of amplitude- and/or phase-modulated (AM/PM) symbols drawn from rotationally invariant signal constellations. This paper identifies these so-called isometric sequences as the main source of performance degradation, and introduces a unifying framework that effectively solves the problem by using asymmetric signal constellations (ASC) and a normalized innovations-based detector. The encompassing nature of the solution is clearly demonstrated by showing that seemingly unrelated previous results, such as training-based solutions, can be viewed as special cases of the modulation-based solution discussed here. A comprehensive analysis, supported by simulation studies, of the relationships among modulation schemes, isometry, and detection performance is provided. Results indicate that the proposed ASC solution offers excellent performance without incurring significant complexity or reducing the transmission rate. Furthermore, it is shown to be robust in various fading rates, and for different signal constellations.     

人脸识别研究进展

人脸识别技术在各种应用的推动下发展很快。而近几年中，为避免各种实际应用环境的限制，非约束环境下的人脸识别也得到了很大的发展。本文概述了人脸识别的一些主要方法，讨论了影响人脸识别的几个主要因素及其处理方法以及基于视频的人脸识别技术，最后指出了鲁棒的人脸识别技术的研究方向和发展前景。     

Transient Modeling and Analysis of Pulse-Width Modulated Z-Source Inverter

The newly proposed Z-Source inverter has been proven in the literature to exhibit both steady-state voltage buck and boost capabilities using a unique LC impedance network coupled between the power source and converter circuit. This paper now presents transient modeling and analysis of a voltage-type Z-source inverter. These aspects are found to be challenging and they need to be carefully investigated before attempting to design advanced control algorithms for controlling the Z-source inverter. Through detailed analysis, the paper identifies several phenomena on the dc and ac-sides of the inverter, which would result in the inverter having a non-minimum-phase transient response. The dc-side phenomenon is associated with the Z-source impedance network, which is shown through small-signal and signal-flow-graph analyses to be having a right-half-plane zero in its control-to-output transfer function. Also, the ac-side phenomenon is shown through space vector analysis to depend on the time intervals of inverter states used for reconstructing the desired inverter output voltage. Based on the ac vectorial analysis, a method for improving the inverter transient response is also presented. Last, simulation results obtained using a switching-functional model and experimental results obtained using a laboratory prototype are presented for validating the described theoretical concepts