Shuo-Han Chen

Trace element concentration and arsenic speciation in the well water of a Taiwan area with endemic Blackfoot disease

Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological study has implicated high arsenic content in artesian well water in the endemic area, there is more to learn about the etiology of the disease. In this study, effort is paid on multielement determination and arsenic speciation in order to find out whether the trace element concentration pattern in well water in the Blackfoot disease endemic area is different from those of two control areas. Experimental results indicate that the concentrations of Fe, P, Na, and Ba in well water in the Blackfoot disease endemic area are found to be significantly higher than those of the controls, but they are still below the drinking water standard. The total arsenic in well water in the endemic area (671±149 ppb) is much higher than that of one normal control area of Hsin-Chu (<0.7 ppb), but is a similar level as that of other control areas of I-Lan (653±71 ppb) where no Blackfoot disease has ever been found. It was also found that the insoluble arsenic in the endemic area (21.9 ppb) is much higher than that in two control areas (≤1.8 ppb), and the concentration ratio between As(III) and As(V) species in the endemic area (2.6) is much lower than that in one of the control areas, where the total arsenic is also high (14.7). The possible connection of Blackfoot disease with trace elements, arsenic species, and possibly other as yet undefined environmental factors in the artesian well water, is discussed.

Mitigation of voltage sags by network reconfiguration of a utility power system

Among the high-tech industrial processes, the semiconductor fabrication plants (or fabs) are typical examples which are sensitive to voltage sags. Sags can interrupt fabs production. After a severe sag, the recovery of fab back to its normal production sometimes takes more than 10 minutes or even hours. It has been a common consensus that to prevent the production tools of fab from false tripping by sags requires the joint effort from the power utility, fabs, tool makers and the power facility designers. This paper focuses on sags mitigation by the network reconfiguration of a utility power system at Hsinchu Science Park (HSP). The presented can be also valuable to other power utilities, science parks and high-tech industries.

Enabling Write-Reduction Strategy for Journaling File Systems over Byte-addressable NVRAM

Non-volatile random-access memory (NVRAM) becomes a mainstream storage device in embedded systems due to its favorable features, such as small size, low power consumption, and short read/write latency. On NVRAM, a write operation consumes more energy and time than a read operation. However, current mobile/embedded file systems (e.g., EXT2/3 and EXT4) are very unfriendly for NVRAM devices. The reason is that a journaling mechanism writes the same data twice during data commitment and checkpoint. Such observations motivate this paper to design a two-phase write reduction journaling file system called wrJFS. In the first phase, wrJFS classified data into two categories: Metadata and user data. Metadata will be handled by partial byte-enabled journaling strategy, and user data will be processed in the second phase. In the second phase, user data will be compressed by hardware encoder so as to reduce the write size, and managed compressed-enabled journaling strategy to avoid the write amplification. The experimental results show that the proposed wrJFS can reduce the size of the write request by 89.7% on average, compared with the original EXT3.

Enabling sub-blocks erase management to boost the performance of 3D NAND flash memory

3D NAND has been proposed to provide a large capacity storage with low-cost consideration due to its high density memory architecture. However, 3D NAND needs to consume enormous time for garbage collection because of live-page copying overhead and long block erase time. To alleviate the impact of live-page copying on the performance of 3D NAND, a sub-block erase design has been designed. With sub-block erase design, this paper proposes a performance booster strategy to extremely boost the performance of garbage collection. As experimental results shows, the proposed strategy has a significant improvement on the average response time.

Developing a user-friendly sensor network simulator to imitate wireless charging vehicle behaviors

An emerging breakthrough in wireless charging technology is expected to solve the power constraint problem in wireless sensor networks (WSN). In various works, wireless chargers are being bundled with mobile vehicles to recharge sensor nodes. In these works, simulations of mobile vehicles are typically used in experiments because building a wireless sensor network test bed is very costly and many details of a wireless sensor network are neither standardized nor finalized. Accordingly, a simulator is extremely useful in testing new applications or protocols in wireless sensor networks. However, several well-known wireless sensor network simulators have no or limited support for wireless recharging. Researchers may want to construct their own simulating modules, but the highly complex design of current simulators is intimidating and stops researchers from testing their applications. This work develops a framework for simulating a WSN and focuses on the simulation of wireless power transfer and mobile vehicles. This simulator eliminates the need for researchers to build their own simulator or integrate complex wireless charging modules, allowing them simply to implement their algorithm. Moreover, the proposed simulator has been verified by implementing the work of Xie et al. [20].

Prolong Lifetime of Dynamic Sensor Network by an Intelligent Wireless Charging Vehicle

The lifetime of wireless sensor networks are constrained by its limited battery capacity. Therefore, the lifetime is widely regard as a bottleneck of technique of wireless sensor network. Recently, the emerging breakthrough in wireless power transfer technique is expected to eliminate the power constraint bottleneck. In this paper, we propose an intelligent wireless charging vehicle (IWCV) strategy to resolve above problem in a dynamic and scalable approach. The IWCV strategy includes an intelligent routing strategy to traverse the sensor network topology and charging their battery to prolong their lifetime. What makes IWCV different to previous studies is that IWCV can still work even if the topology changes by re-computing the traversing route and stop time for each node in a relative short amount of time, compared with the time needed to find the shortest Hamiltoaian cycle. With the scalable and dynamic feature of IWCV, one can change their sensor network topology without down time to reconfigure the wireless charging vehicle while still maintain low energy consumption during traveling and charging in dynamic network topologies.

Design a Hash-Based Control Mechanism in vSwitch for Software-Defined Networking Environment

Unlike a traditional network architecture, a software-defined networking architecture is divided into the control plane and the data plane. Network administrators use the centralized control plane to manage network authority and determine where network traffic is to be sent in the data plane. However, a centralized control structure causes a bottleneck with an overloading flow or under a DDoS attack. Under such conditions, the probability of network misconfiguration may increase rapidly and network performance may decline rapidly. This work paper proposes a hash-based mechanism that operates in the control plane to increase the reliability and scalability of the network. The hash function is utilized to assign incoming packets to queues in the control plane. The controller schedules the queues using a round-robin method to reduce the probability of failure in response to malicious attacks and to reduce transmission delay when network congestion occurs. The experimental results reveal that the proposed mechanism effectively distributes the workload and increases the reliability of the network under high-density data transmission.

Analysis and improvement of the 3-star algorithm for the STP-MSP problem in Wireless Sensor Networks

A Wireless Sensor Network (WSN) uses a larger number of low-power sensor nodes to gather environmental information which is then wirelessly forwarded to a base station. However, sensor nodes have very limited communication ranges. Thus, relay nodes are required to ensure reliable connectivity throughout the WSN. On the other hand, relay nodes are typically more sophisticated and expensive than sensor nodes. Therefore, deployment strategies should seek to minimize the number of required relay nodes, a problem referred to as the Steiner Tree Problem with Minimum Number of Steiner Points (SMT-MSP), which has been shown to be NP-hard. This paper analyzes and improves the 3-star approximation algorithm by reducing the time complexity from O(n3) to O(nlogn) with the identical performance ratio. Experiments are conducted to verify the correctness of the proposed algorithm.

Enhancing the Energy Efficiency of Journaling File System via Exploiting Multi-Write Modes on MLC NVRAM

Non-volatile random-access memory (NVRAM) is regarded as a great alternative storage medium owing to its attractive features, including low idle energy consumption, byte addressability, and short read/write latency. In addition, multi-level-cell (MLC) NVRAM has also been proposed to provide higher bit density. However, MLC NVRAM has lower energy efficiency and longer write latency when compared with single-level-cell (SLC) NVRAM. These drawbacks could lead to higher energy consumption of MLC NVRAM-based storage systems. The energy consumption is magnified by existing journaling file systems (JFS) on MLC NVRAM-based storage devices due to the JFSs fail-safe policy of writing the same data twice. Such observations motivate us to propose a multi-write-mode journaling file systems (mwJFS) to alleviate the drawbacks of MLC NVRAM and lower the energy consumption of MLC NVRAM-based JFS. The proposed mwJFS differentiates the data retention requirement of journaled data and applies different write modes to enhance the energy efficiency with better access performance. A series of experiments was conducted to demonstrate the capability of mwJFS on a MLC NVRAM-based storage system.

UnistorFS: A Union Storage File System Design for Resource Sharing between Memory and Storage on Persistent RAM-Based Systems

With the advanced technology in persistent random access memory (PRAM), PRAM such as three-dimen-sional XPoint memory and Phase Change Memory (PCM) is emerging as a promising candidate for the next-generation medium for both (main) memory and storage. Previous works mainly focus on how to overcome the possible endurance issues of PRAM while both main memory and storage own a partition on the same PRAM device. However, a holistic software-level system design should be proposed to fully exploit the benefit of PRAM. This article proposes a uni on stor age f ile s ystem (UnistorFS), which aims to jointly manage the PRAM resource for main memory and storage. The proposed UnistorFS realizes the concept of using the PRAM resource as memory and storage interchangeably to achieve resource sharing while main memory and storage coexist on the same PRAM device with no partition or logical boundary. This approach not only enables PRAM resource sharing but also eliminates unnecessary data movements between main memory and storage since they are already in the same address space and can be accessed directly. At the same time, the proposed UnistorFS ensures the persistence of file data and sanity of the file system after power recycling. A series of experiments was conducted on a modified Linux kernel. The results show that the proposed UnistorFS can eliminate unnecessary memory accesses and outperform other PRAM-based file systems for 0.2--8.7 times in terms of read/write performance.