Existing large-scale systems suffer from various hardware/software failures, motivating the research of fault-tolerance techniques. Checkpoint-restart techniques are widely applied fault-tolerance approaches, especially in scientific computing systems. However, the overhead of checkpoint largely influences the overall system performance. Recently, the emerging byte-addressable, persistent memory technologies, such as phase change memory (PCM), make it possible to implement checkpointing in arbitrary data granularity. However, the impact of data granularity on the checkpointing cost has not been fully addressed. In this paper, we investigate how data granularity influences the performance of a checkpoint system. Further, we design and implement a high-performance checkpoint system named AG-ckpt. AG-ckpt is a hybrid-granularity incremental checkpointing scheme through: (1) low-cost modified-memory detection and (2) fine-grained memory duplication. Moreover, we also formulize the performance-granularity relationship of checkpointing systems through a mathematical model, and further obtain the optimum solutions. We conduct the experiments through several typical benchmarks to verify the performance gain of our design. Compared to conventional incremental checkpoint, our results show that AG-ckpt can reduce checkpoint data amount up to 50% and provide a speedup of 1.2x-1.3x on checkpoint efficiency.

The imaging of humans using radar is promising for surveillance systems. Although conventional radar systems detect the presence or position of intruders, it is difficult to acquire shape and motion details because the resolution is insufficient. This paper presents a high-resolution human imaging algorithm for an ultra-wideband (UWB) Doppler radar. The proposed algorithm estimates three-dimensional human images using interferometry and, using velocity information, rejects false images created by the interference of body parts. Experiments verify that our proposed algorithm achieves adequate pedestrian imaging. In addition, accurate shape and motion parameters are extracted from the estimated images.

Dynamic virtual network allocation is a promising traffic control model for cloud resident data center which offers virtual data centers for customers from the provider's substrate cloud. Unfortunately, dynamic virtual network allocation designed in the past was aimed to the Internet so it needs distributed control methods to scale with such a large network. The price for the scalability of the completely distributed control method at both virtual layer and substrate layer is the slow convergence of algorithm and the less stability of traffic. In this paper, we argue that the distributed controls in both virtual and substrate networks are not necessary for the cloud resident data center environment, because cloud resident data center uses centralized controller as the way to give network control features to customers. In fact, we can use the centralized algorithm in each virtual data center which is not very large network and the distributed algorithm is only needed in substrate network. Based on the specific properties of this model, we have used optimization theory to re-design the substrate algorithm for periodically re-adjusting virtual link capacity. Results from theoretical analysis, simulations, and experiments show that our algorithm has faster convergence time, simpler calculation and can make better use of the feedback information from virtual networks than the previous algorithm.

A new paradigm for building Virtual Controller Model (VCM) for traffic flow simulator is developed. It is based on flight plan data and is applied to Traffic Flow Management System (TFMS) in China. The problem of interest is focused on the sectors of airspace and how restrictions to aircraft movement are applied by air traffic controllers and demand overages or capacity shortfalls in sectors of airspace. To estimate and assess the balance between the traffic flow and the capacity of sector in future, we apply Virtual Controller model, which models by the sectors airspace system and its capacity constraints. Numerical results are presented and illustrated by applying them to air traffic data for a typical day in the Traffic Flow Management System. The results show that the predictive capabilities of the model are successfully validated by showing a comparison between real flow data and simulated sector flow, making this method appropriate for traffic flow management system.

A garbage collector relieves programmers from manual memory management and improves productivity and program reliability. However, there are many other finite system resources that programmers must manage by themselves, such as sockets and database connections. Growing resource leaks can lead to performance degradation and even program crashes. This paper presents the automatic resource collection approach called Resco (RESource COllector) to tolerate non-memory resource leaks. Resco prevents performance degradation and crashes due to resource leaks by two steps. First, it utilizes monitors to count resource consumption and request resource collections independently of memory usage when resource limits are about to be violated. Second, it responds to a resource collection request by safely releasing leaked resources. We implement Resco based on a Java Virtual Machine for Java programs. The performance evaluation against standard benchmarks shows that Resco has a very low overhead, around 1% or 3%. Experiments on resource leak bugs show that Resco successfully prevents most of these programs from crashing with little increase in execution time.

An important factor determining the performance of delay tolerant networks (DTNs) is packet delivery delay. In this paper, we study the block delivery delay of DTN with the epidemic routing scheme based on random linear network coding (RLNC). First, simulations show that the influence of relay buffer size on the delivery delay is not as strong in RLNC-based routing as it is in replica-based routing. With this observation,we can simplify the performance analysis by constraining the buffer of the relay node to just one size. Then we derive the cumulative distribution function (CDF) of block delivery delay with difference equations. Finally, we validate the correctness of our analytical results by simulations.

System-on-display panel design methodologies are proposed with the purpose of integrating DCT and IDCT on display panels for image codec and peripheral systems so as to reduce the bus data rate, memory size and power consumption. Unified constant geometry algorithms and architectures including recursive additions are proposed for DCT and IDCT butterfly computation, recursive additions and interconnections between stages. These schemes facilitate VLSI implementation and improve fault tolerance, suitable for low-yield SOP processing technologies through duplicate use of a PE as all the butterfly and recursive addition stages are composed and interconnected in a regular fashion. Efficient redundancy replacement methodologies optimizing the computation speed and the amount of hardware in various application areas are also described with testability and reliability issues. Finally, a performance analysis of speed, hardware and interconnection complexity is described with the proposed work's advantages.

A novel and compact electro-optic modulator implemented by a combination of a 12 multimode interference (MMI) coupler and an integrated Mach-Zehnder interferometer (MZI) modulator consisting of a microring and a phase modulator (PM) is presented and analyzed theoretically. It is shown that the proposed modulator offers both ultra-linearity and high output RF gain simultaneously, with no requirements for complicated and precise direct current (DC) control.

A novel design is proposed to implement highly parallel stream join operators on a field-programmable gate array (FPGA), by examining handshake join algorithm for hardware implementation. The proposed design is evaluated in terms of the hardware resource usage, the maximum clock frequency, and the performance. Experimental results indicate that the proposed implementation can handle considerably high input rates, especially at low match rates. Results of simulation conducted to optimize size of buffers included in join and merge units give a new intuition regarding static and adaptive buffer tuning in handshake join.

In this letter, for offloading traffic to Wireless Local Area Network (WLAN) with transport layer mobility where WLAN service is intermittently available, we propose a novel scheme to freeze and melt the timeout handling procedure of SCTP. Simulation results show that the proposed scheme significantly improves the performance in terms of file transfer completion time.

The large data-transfer time among different cores is a big problem in heterogeneous multi-core processors. This paper presents a method to accelerate the data transfers exploiting data-transfer-units together with complex memory allocation. We used block matching, which is very common in image processing, to evaluate our technique. The proposed method reduces the data-transfer time by more than 42% compared to the earlier works that use CPU-based data transfers. Moreover, the total processing time is only 15 ms for a VGA image with 1616 pixel blocks.

The Multiple-Input Multiple-Output (MIMO) Zero-Forcing (ZF) receiver requires accurate Channel State Information (CSI), which is impacted by channel estimation error, to perform properly. Moreover, interference occurs due to the change of channel coefficients between the channel estimation events in fading channels. Thus, in practice, both channel estimation error and interference greatly influence Bit Error Rate (BER) performance. In this letter, we derive an Signal-to-Interference-and-Noise Ratio (SINR) expression considering both channel estimation error and interference and develop approximate closed-form BER expressions of M-PSK and M-QAM for the MIMO ZF receiver in Nakagami-m fading channels. We then analyze the effects of channel estimation error, interference, and the numbers of transmit and receive antennas.

A novel type of millimeter/submillimeter wave sampler based on resonant tunneling diodes (RTDs) was proposed, and its operation was confirmed by circuit simulation. It consists of an RTD pulse generator and an RTD detector. Owing to the fuse-like nonlinear I-V curve, highly sensitive sampling can be obtained. We also found that the effects of non-ideality in the I-V curve of the RTD can be corrected by sweeping the DC bias for the RTD detector.

When the Akebono (EXOS-D) satellite passed through the plasmasphere, a series of lightning whistlers was observed by its analog wideband receiver (WBA). Recently, we developed an intelligent algorithm to detect lightning whistlers from WBA data. In this study, we analyzed two typical events representing the clear dispersion characteristics of lightning whistlers along the trajectory of Akebono. The event on March 20, 1991 was observed at latitudes ranging from 47.83 (47,83N) to -11.09 (11.09S) and altitudes between ∼2232 and ∼7537 km. The other event on July 12, 1989 was observed at latitudes from 34.94 (34.94N) and -41.89 (41.89S) and altitudes ∼1420–∼7911 km. These events show systematic trends; hence, we can easily determine whether the wave packets of lightning whistlers originated from lightning strikes in the northern or the southern hemispheres. Finally, we approximated the path lengths of these lightning whistlers from the source to the observation points along the Akebono trajectory. In the calculations, we assumed the dipole model as a geomagnetic field and two types of simple electron density profiles in which the electron density is inversely proportional to the cube of the geocentric distance. By scrutinizing the dipole model we propose some models of dispersion characteristic that proportional to the electron density. It was demonstrated that the dispersion D theoretically agrees with observed dispersion trend. While our current estimation is simple, it shows that the difference between our estimation and observation data is mainly due to the electron density profile. Furthermore, the dispersion analysis of lightning whistlers is a useful technique for reconstructing the electron density profile in the Earth's plasmasphere.

Existing forwarding strategies for delay tolerant networks aim at network throughput maximization. They provide forwarding opportunities to more reachable destinations. This results in the long end-to-end delay and low throughput of less reachable destinations. In this paper, we propose two forwarding strategies to improve the throughput of less reachable nodes with little throughput degradation of more reachable nodes. Evaluation results show that the proposed forwarding strategies can control the levels of fairness among the destinations while maintaining high throughput, compared with the legacy forwarding strategies.

In this paper, a single-channel adaptive noise canceller (SCANC) is proposed to enhance heart sounds during auscultation. Heart sounds provide important information about the condition of the heart, but other sounds interfere with heart sounds during auscultation. The adaptive noise canceller (ANC) is widely used to reduce noises from biomedical signals, but it is not suitable for enhancing auscultatory sounds acquired by a stethoscope. While the ANC needs two inputs, a stethoscope provides only one input. Other approaches, such as ECG gating and wavelet de-noising, are rather complex and difficult to implement as real-time systems. The proposed SCANC uses a single-channel input based on Heart Sound Inherency Indicator and reference generator. The architecture is simple, so it can be easily implemented in real-time systems. It was experimentally confirmed that the proposed SCANC is efficient for heart sound enhancement and is robust against the heart rate variations.

Polarization-maintaining photonic crystal fiber couplers (PM-PCFCs) were fabricated using a CO2 laser irradiation technique. We could control the states of air holes in the tapered region of couplers by adjusting the laser power density in the fusion and the elongation processes. It was demonstrated that the air hole remaining PM-PCFC exhibited polarization-splitting characteristics and that the air hole collapsed PM-PCFC had polarization insensitive coupling characteristics.

We propose an active learning framework for speech recognition that reduces the amount of data required for acoustic modeling. This framework consists of two steps. We first obtain a phone-error distribution using an acoustic model estimated from transcribed speech data. Then, from a text corpus we select a sentence whose phone-occurrence distribution is close to the phone-error distribution and collect its speech data. We repeat this process to increase the amount of transcribed speech data. We applied this framework to speaker adaptation and acoustic model training. Our evaluation results showed that it significantly reduced the amount of transcribed data while maintaining the same level of accuracy.

In this paper, we present a new fault-tolerant, large-scale star network scheme called Scalable Autonomous Fault-tolerant Ethernet (SAFE). The primary goal of a SAFE scheme is to provide network scalability and autonomous fault detection and recovery. SAFE divides a large-scale, mission-critical network, such as the naval combatant network, into several subnets by limiting the number of nodes in each subnet. This network can be easily configured as a star network in order to meet fault recovery time requirements. For SAFE, we developed a novel mechanism for inter-subnet fault detection and recovery; a conventional Ethernet-based heartbeat mechanism is used in each subnet. Theoretical and experimental performance analyses of SAFE in terms of fail-over time were conducted under various network failure scenarios. The results validate our scheme.

This paper proposes an easy-to-design, theory-consistent compact feeding circuit, with a single input and four outputs, being comprised of two hybrid circuits that are capable of switching a beam in three directions. The circuits that determine the phase differences between the antennas are present on the same single layer, and thus there is no effect of vias and the design agrees well with the underlying theory. In addition, the vertically and horizontally symmetrical circuit pattern contributes to a substantial reduction in design time. The circuit is designed for use in the ISM band and its properties are evaluated using an RF circuit simulator. A prototype is fabricated and evaluated. The results of the simulation and measurement agree well with the theoretical values. The dimensions of the feeding circuit are 75 (H)55 (W)3.0 (T) mm.