Specifying software features for composition: A tool-supported approach

Development of several computing and communication technologies is enabling the widespread availability of pervasive systems. In smart home applications, household appliances—such as security alarms, heating systems, doors and windows—are connected to home digital networks. These applications offer features that are typically developed by disparate vendors, and when composed together, these features are expected to work together harmoniously. Engineering these systems poses two main challenges. The first challenge is: how can developers of individual features specify the features in order to make them composable with other hitherto unknown features? The second challenge is: when composition of features does not produce the desired behaviour, what can be done to resolve this non-intrusively? This article argues that the two issues are intrinsically related, and proposes an approach that addresses the first challenge in a way that makes the second challenge manageable. In particular, we describe a way of writing feature specifications in which assumptions about the problem world are made explicit. These feature assumptions can then be evaluated at runtime in order to preserve the desired system behaviour to the extent possible. Our approach is illustrated with examples from smart home applications.     

随机创作：消费时代的草根影客文化

一部随身携带的拍照手机或卡片相机，再加上一点点天马行空的想法，属于草根阶层的影像文化便在无声无息中壮大了起来其实草根影客中没有几个来自于社会下层，他们手里的装备虽然算不上专业，但绝对扯不上简陋他们创造出来的影像在视觉识别特性上与“摄影家”有着明显的不同，可以是咬一口的苹果，也可以是回家路上偶遇的流浪猫。平凡人，关注平凡的事情，随机产生的想法加上随手拿起的影像工具，记录随机的生活。随机的创作．这就是属于我们的草根影客文化。     

Improvement of InGaN/GaN laser diodes by using a Si-doped In/sub 0.23/Ga/sub 0.77/N/GaN short-period superlattice tunneling contact layer

InGaN/GaN multiple-quantum-well laser diode (LD) structures, including an Si-doped n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN short-period superlattice (SPS) tunneling contact layer, are grown on c-face sapphire substrates by metalorganic vapor-phase epitaxy. The In/sub 0.23/Ga/sub 0.77/N/GaN(n/sup +/)-GaN(p) tunneling junction, which uses a low-resistivity n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN SPS instead of a high-resistivity p-type GaN as a top contact layer, allows the reverse-biased tunnel junction to form a "quasi-ohmic" contact. Experimental results indicate that LDs with n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN SPS contacting layers can achieve a lower threshold current and longer lasing duration under pulsed operation. Moreover, when the input pulse width is lengthened from 300 ns to 2 /spl mu/s, the lasing duration of the LD with Pt ohmic contact is three times longer than that of the LD with Ni/Au ohmic contacts. Therefore, we conclude that nitride-based LDs with an SPS reversed-tunneling contact layer may significantly reduce the contact resistance of an anode electrode and thereby increase the thermal stability of the device reliability.     

Nitrogen removal in a fluidized bed bioreactor by using mixed culture under oxygen-limited conditions.

Nitrogen removal involving nitrification and denitrification was investigated in a fluidized bed bioreactor by using mixed culture sludge under oxygen-limited conditions. Methane was used as a sole carbon source for denitrification. In this study, optimal nitrification and denitrification rates were examined by varying methane and oxygen gas dissolution flow rates, 90 ml/min, 400 ml/min and 650 ml/min, in each. Simultaneously nitrification and denitrification was achieved. The total nitrogen removal rate was 15-mg N/g VSS. d, 21-mg N/g VSS. d and 26.4-mg N/g VSS. d at gas dissolution flow rate 90 ml/min, 400 ml/min and 650 ml/min, respectively. No significant accumulation of nitrite was found in this experiment. Nitrogen removal rates depend on gas dissolution flow rates. DO concentration was at 0.5-2 mg/L.     

Effect of defects on the burst failure of butt fusion welded polyethylene pipes

With the increasing demand of Medium density polyethylene (MDPE) pipes for gas transmission, the safety concern related with welding defects is becoming a serious matter. In this paper, experimental burst tests and finite element analyses were employed to study butt fusion welded MDPE pipe joints with spherical and planar defects of various sizes. These defects were used to simulate lack of bonding during the welding. Test results showed that in all pipe test cases, the failure location originated from pipe substrates, even though the defect size was increased to 45% of the pipe’s wall thickness. The burst pressure could be estimated by the expression employed in the ASME BPVC, and in the burst pressure, the hoop stress was 20.28 MPa. Simulation results showed that the failure position was not only affected by the defect size, but also by the welding bead. It can be argued that a single welding defect whose maximum size is smaller than 15% of the thickness can be used without failure during short-term usage, even when there is no welding bead in the welded joint.     

Thermo‐ and pH‐ responsive copolymers: Poly(n‐Isopropylacrylamide‐co‐IAM) copolymers

Poly(N‐isopropylacrylamide) (NIPAAm) is well known as a smart material with good thermal sensitivity and favorable biocompatibility. A series of new smart hydrogels, NIPAAm copolymerized with IAM (itaconamic acid; 4‐amino‐2‐methylene‐4‐oxobutanoic acid), were synthesized through radical solution polymerization in this work. Poly(NIPAAm‐co‐IAM) can respond to the changes of temperature as well as pH value. Such a characteristic is due to the fact that IAM contains not only a hydrophilic acrylic acid moiety but also an acrylamide moiety to be thermal and pH sensitive. The experimental results show that the lower critical solution temperature (LCST) of the copolymer increases as the molar fraction of IAM increases. Moreover, based on the current experimental data, 3 wt % of Poly(NIPAAm‐co‐IAM) aqueous solution in this study exhibits a phase transition temperature (37.8°C) close to the human body temperature in the buffer solution of pH 7 possibly to be useful in drug delivery. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42367.     

A system of automatic control of motion speed of a city transport system electric train

An adaptive system of automatic control of the electric train motion speed permitting one to take into account the specific requirements imposed by the control object is proposed. Such requirements include limitation of the level of the index of the movement smoothness during the transient movement modes characterizing the degree of comfort for the passengers, as well as the possibility of implementing accelerations (delays) differing from nominal ones. The methods of automatic control and simulation modeling theory are used while solving the problem. The required control quality is provided by the fact that the input drive signal for the speed control circuit is smoothed by means of an operator, which is based on integration with saturation. The speed control circuit parameters are determined as a result of solving the task of the parametrical synthesis. The result of the work is an operation algorithm of the automatic control system (ACS) of the electric train speed, application of which provides limitation of the level of the movement smoothness index within the transient movement modes. As a result of solving the task of the parametrical synthesis the analytical dependences are also obtained connecting the ACS control law parameters with the train weight, use of which provides independence of the control quality on the train weight.     

GaN-Based LEDs With AZO:Y Upper Contact

We report the fabrication of GaN-based light-emitting diodes (LEDs) with ytterbium-doped alumina-zinc-oxide (AZO:Y) upper contact. It was found that AZO and AZO:Y are both highly transparent in the visible region with good thermal stability optically. However, it was found that AZO:Y is much more thermally stable electrically, as compared with AZO. Furthermore, it was found that the output power of GaN LEDs with AZO upper contact decreased significantly from 2.80 to 2.30 mW after 700°C annealing. With the same annealing condition, it was found that output power decreased only slightly from 2.77 to 2.69 mW for the LEDs with AZO:Y upper contact.     

金属橡胶弹性与多孔性结合的应用实例

根据金属橡胶构件的制造工艺过程及其母材性质分析了此在构件与起初橡胶材料相比的性能特点,介绍了金属橡胶胶构件在俄罗斯航天及民用领域的主要用途,通过轻转子液压静力轴承及测量管路介质扰动吸收器等实例阐述了金属橡胶弹性与多孔性相结合的独特应用。