Due to the tremendous cooling costs, data center cooling efficiency improvement has been actively pursued for years. In addition to cooling efficiency, the reliability of the cooling system is also essential for guaranteed uptime. In traditional data center cooling system design with N+1 or higher redundancy, all the computer room air conditioning (CRAC) units are either constantly online or cycled according to a predefined schedule. Both cooling system configurations, however, have their respective drawbacks. Data centers are usually over provisioned when all CRAC units are online all the time, and hence the cooling efficiency is low. On the other hand, although cooling efficiency can be improved by cycling CRAC units and turning off the backups, it is difficult to schedule the cycling such that sufficient cooling provisioning is guaranteed and gross over provisioning is avoided. In this paper, we aim to maintain the data center cooling redundancy while achieving high cooling efficiency. Using model- based thermal zone mapping, we first partition data centers to achieve the desired level of cooling redundancy through zone overlap adjustment. We then design a distributed controller for each of the CRAC units to regulate the thermal status within its zone of influence. The distributed controllers coordinate with each other to achieve the desired data center thermal status using the least cooling power. When CRAC units or their associated controllers fail, racks in the affected thermal zones are still within the control "radius" of other decentralized cooling controllers through predefined thermal zone overlap, and hence their thermal status is properly managed by the active CRAC units and controllers. Using this failure resistant data center cooling control approach, both cooling efficiency and robustness are achieved simultaneously. A higher flexibility in cooling system maintenance is also expected, since the distributed control system can automatically adapt to the new cooling facility configuration incurred by maintenance.

关键词：数据中心；冷却；热区

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An electric current sensor based on Faraday rotation effect in optical fiber was developed for measuring aircraft lightning current. Compared to traditional sensors, the design has many advantages including the ability to measure total current and to conform to structure geometries. The sensor is also small, light weight, non-conducting, safe from interference, and free of hysteresis and saturation. Potential applications include characterization of lightning current waveforms, parameters and paths, and providing environmental data for aircraft certifications. In an optical fiber as the sensing medium, light polarization rotates when exposed to a magnetic field in the direction of light propagation. By forming closed fiber loops around a conductor and applying Ampere s law, measuring the total light rotation yields the enclosed current. A reflective polarimetric scheme is used, where polarization change is measured after the polarized light travels round-trip through the sensing fiber. The sensor system was evaluated measuring rocket-triggered lightning over the 2011 summer. Early results compared very well against a reference current shunt resistor, demonstrating the sensor's accuracy and feasibility in a lightning environment. While later comparisons show gradually increasing amplitude deviations for an undetermined cause, the overall waveforms still compared very well.

关键词：光机电；传感器；雷电流；测量

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Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage and empennage structures, control surfaces and coverings. However, the potential damage from the direct and indirect effects of lightning strikes is of increased concern to aircraft designers and operators. When a lightning strike occurs, the points of attachment and detachment on the aircraft surface must be found by visual inspection, and then assessed for damage by maintenance personnel to ensure continued safe flight operations. In this paper, a new method and system for aircraft in-situ damage detection and diagnosis are presented. The method and system are based on open circuit (SansEC) sensor technology developed at NASA Langley Research Center. SansEC (Sans Electric Connection) sensor technology is a new technical framework for designing, powering, and interrogating sensors to detect damage in composite materials. Damage in composite material is generally associated with a localized change in material permittivity and/or conductivity. These changes are sensed using SansEC. Unique electrical signatures are used for damage detection and diagnosis. NASA LaRC has both experimentally and theoretically demonstrated that SansEC sensors can be effectively used for in-situ composite damage detection.

关键词：光机电；传感器；开路谐振；复合材料检测

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The U.S. Department of Energy (DOE) and Lockheed Martin Space Systems Company (LMSSC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. This generator would use two highefficiency Advanced Stirling Convertors (ASCs), developed by Sunpower, Inc., and NASA Glenn Research Center. The ASCs convert thermal energy from a radioisotope heat source into electricity. As part of ground testing of these ASCs, different operating conditions are used to simulate expected mission conditions. These conditions require achieving a particular operating frequency, hot-end and cold-end temperatures, and specified electrical power output for a given heat input. It is difficult to measure heat input to Stirling convertors due to the complex geometries of the hot components, temperature limits of sensor materials, and invasive integration of sensors. A thin-film heat flux sensor was used to directly measure heat input to an ASC. The effort succeeded in designing and fabricating unique sensors, which were integrated into a Stirling convertor ground test and exposed to test temperatures exceeding 700 C in air for 10,000 hr. Sensor measurements were used to calculate thermal efficiency for ASC-E (Engineering Unit) No. 1 and No. 4. The post-disassembly condition of the sensors is also discussed.

关键词：光机电；传感器；斯特林转换器；性能测量

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Zero-calorie sweeteners are sugar substitutes which are used in food, beverage, and pharmaceutical products as additives to duplicate the effect of sugar. These calorie-free sweeteners help in leading a healthy life. Zero-calorie sweeteners can be both artificial and natural. The US FDA has approved the use of the following six artificial sweeteners: aspartame, sucralose, Ace-K, cyclamate, neotame, and saccharin. Besides these, there are other new sweeteners that are emerging in the market such as monk fruit and monatin. Demand for natural zero-calorie sweeteners is increasing rapidly in the market, especially for stevia-based sweeteners as they are considered to be more nutritive and safe to consume. Zero-calorie sweeteners deliver the same taste as other sugars and sweeteners without adding calories and are a healthy option for diabetics and obese people

关键词：零热量；甜味剂；添加剂

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Web-based services are used by many organizations to support their customers and employees. An important consideration in developing such services is ensuring the Quality of Service (QoS) that users experience is acceptable. Recent years have seen a shift toward deploying Web services on multi-core hardware. Leveraging the performance benefits of multi-core hardware is a non-trivial task. In particular, systematic Web server benchmarking techniques are needed so organizations can verify their ability to meet customer QoS objectives while effectively utilizing such hardware. However, our recent experiences suggest that the multi-core era imposes significant challenges to Web server benchmarking. In particular, due to limitations of current hardware monitoring tools, we found that a large number of experiments are needed to detect complex bottlenecks that can arise in a multi-core system due to contention for shared resources such as cache hierarchy, memory controllers and processor inter-connects. Furthermore, multiple load generator instances are needed to adequately stress multi-core hardware. This leads to practical challenges in validating and managing the test results. This paper describes the automation strategies we employed to overcome these challenges. We make our test harness available for other researchers and practitioners working on similar studies.

关键词：软件性能；性能测试；多核服务器

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With the introduction of cloud computing and Web 2.0, many applications are moving to the cloud environment. Version control systems have also taken a first step towards this direction. Nevertheless, existing systems are either client-server oriented or completely distributed, and they don't match exactly the nature of the cloud. In this paper we propose a new cloud version control system focusing on the requirements imposed by cloud computing, that we identified as: concurrent editing, history rewrite, accountability, scalability, security, and fault tolerance. Our plan is to tackle these issues in a systematic way, and we present in this paper an overview of the solutions organized in three separate layers: access API, logical structure, and physical storage.

关键词：软件开发；云计算；版本控制系统；修订；协作

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Processes to produce active-matrix backplanes on plastic substrates have been developed utilizing a- Si:H, multi-component oxide, and organic semiconductor technologies. The suitability of these technologies for future flat panel display applications is discussed. Of these material systems multi-component oxides exhibit highest field-effect mobilities (10cm2/Vs for zinc tin oxide demonstrated), followed by small molecule organic semiconductors (0.95 cm2/Vs), and a-Si:H (0.5 cm2/Vs). Yet despite higher mobilities, organic TFTs drive less current than a- Si:H because of the low device capacitances required to fabricate such devices. Backplanes made with a-Si:H appear to be the least risky technology, followed by multi-component oxide, and organic semiconductor technologies.

关键词：柔性电子产品；薄膜晶体管；柔性显示器；有机半导体；无定形硅；氧化锌

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We present a comparative study of HPES and HPMF deinking results of LEP printing using a variety of coated and uncoated substrates from different manufacturing locations. Our results identify three most important factors affecting the deinkability of LEP prints. We also show that all of the LEP digital prints are deinkable with the right understanding of the deinking science.

关键词：中性脱墨化学；碱性脱墨化学；LEP数码冲印

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Environmental conditions, cyclic loading, and aging contribute to structural wear and degradation, and thus potentially catastrophic events. The challenge of health monitoring technology is to determine incipient changes accurately and efficiently. This project addresses this challenge by developing health monitoring techniques that depend only on sensor measurements. Since actively controlled excitation is not needed, sensor-to-sensor identification (S2SID) provides an in-flight diagnostic tool that exploits ambient excitation to provide advance warning of significant changes. S2SID can subsequently be followed up by ground testing to localize and quantify structural changes. The conceptual foundation of S2SID is the notion of a pseudo-transfer function, where one sensor is viewed as the pseudo-input and another is viewed as the pseudo-output, is approach is less restrictive than transmissibility identification and operational modal analysis since no assumption is made about the locations of the sensors relative to the excitation.

关键词：光机电；传感器；飞机；结构监测

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