Applying critical chain buffer management theory in location-based management

Guidelines for prioritizing buffers on location-based management (LBM) projects are established through the use of critical chain theory (CCT). Buffer management theory in LBM has gained little attention from the research community. CCT builds on the assumption that each task is, either consciously or unconsciously, given a certain time buffer with which to cope with unpredicted events, and that these buffers become a large part of the project lead time. However, CCT suggests that these buffers entail inherent waste within schedules and fail to protect both critical activities and projects. CCT assumes that time estimates become self-fulfilling prophecies, as practitioners tend to procrastinate, and the buffers are often wasted. In addition, excess time rarely benefits the project if activities do finish early, because succeeding activities are unlikely to begin before the planned date. Although the criticisms by CCT also apply to LBM projects, CCT is based on the critical path method, and the guidelines from CCT must be adapted to the criticality principle of LBM theory. Accordingly, the contribution to the body of knowledge of this article is guidelines of buffer placement and prioritization in LBM that are based on critical chain buffer management theory.     

适合硬件实现的解决色度上采样错误的算法实现

为了适应视频后处理芯片低成本的需求,提出一种每场仅需用两行缓存、适合硬件实现的解决色度上采样错误的算法。首先,检测出现色度上采样错误的地方;然后,对上采样错误的地方进行处理。具体表现为,检测出有上采样错误的地方,用帧处理方法来进行修复;否则用传统的场处理方法来处理。实验结果表明该算法在较少的资源下,仍然可以有效检测到出现CUE现象的像素点,较好地解决了该错误,并且便于硬件实现,可应用于低成本的数字视频后处理芯片中。     

Optical and photoelectrical properties of β-In2S3 thin films prepared by two-stage process

β-In₂S₃ films were grown on glass as well as on quartz substrates by rapid heating of metallic indium films in H₂S atmosphere. The effect of sulfurization temperature and time on the growth, structural, electrical and photoelectrical properties of β-In₂S₃ films has been investigated. Highly oriented single-phase β-In₂S₃ films were grown by the sulfurization technique. The morphology and composition of films have been characterized. The optical band gap of β-In₂S₃ is found to vary from 1.9 to 2.5 eV when the sulfurization temperature is varied from 300 to 600 °C or by increasing the sulfurization time. The electrical properties of the thin films have also been studied; they have n-type electrical conductivity. The photoelectrical properties of the β-In₂S₃ films are also found to depend on the sulfurizing temperature. A high photoresponse is obtained for films prepared at a sulfurizing temperature of 600 °C. β-In₂S₃ can be used as an alternative to toxic CdS as a window layer in photovoltaic technology.     

High-yield biohydrogen production from biodiesel manufacturing waste by Thermotoga neapolitana

Efficient conversion of glycerol waste from biodiesel manufacturing processes into biohydrogen by the hyperthermophilic eubacterium Thermotoga neapolitana DSM 4359 was investigated. Biohydrogen production by T. neapolitana was examined using the batch cultivation mode in culture medium containing pure glycerol or glycerol waste as the sole substrate. Pre-treated glycerol waste showed higher hydrogen (H₂) production than untreated waste. Nitrogen (N₂) sparging and pH control were successfully implemented to maintain the culture pH and to reduce H₂ partial pressure in the headspace for optimal growth rate and to enhance hydrogen production from the glycerol waste. It was found that hydrogen production increased from 1.24 ± 0.06 to 1.98 ± 0.1 mol-H₂ mol⁻¹ glycerol_consumed by optimising N₂ sparging and pH control. We observed that in medium containing 0.05 M HEPES, with three cycles of N₂ sparging, the H₂ yield increased to 2.73 ± 0.14 mol-H₂ mol⁻¹ glycerol_consumed, which was 2.22-fold higher than the non-N₂ sparged H₂ yield (1.23 ± 0.06 mol-H₂ mol⁻¹ glycerol_consumed).     

Evaluation of buffer zone effectiveness in mitigating the risks associated with agricultural runoff in Prince Edward Island

To minimize the risk posed by runoff from row crops, Prince Edward Island introduced buffer legislation in 2000. The legislation mandates 10-m and 20-m buffers, respectively, for moderate sloped (i.e. < 5%) and steep sloped (i.e. > 5%) agricultural fields that border streams. Since 2001, Environment Canada has been evaluating the effectiveness of various buffer widths on operational farms in reducing toxicity and contaminant concentrations in runoff. Sample collectors, placed in 44 fields at the field edge (0 m), 10 m and at distances out to 30 m, collected overland flow following rainfall-induced runoff events. Samples were collected within 24 hours of an event and analysed for seven pesticides (endosulfan, chlorothalonil, carbofuran, linuron, metribuzin, metalaxyl, mancozeb), water quality parameters and Daphnia magna toxicity. The 10-m buffer required for moderate sloped fields was effective at reducing contaminant concentrations but not always to less than lethal concentrations to Daphnia magna. Limited data beyond 10 m for fields of both slope types precluded making recommendations on a suitable buffer width for shallow sloped fields and evaluating the effectiveness of 20-m buffers for steep sloped fields. When paired data were combined and statistically tested for all fields, the studied pesticides underwent a 52-98% and 68-100% reduction in aqueous and particulate concentrations within 10 m and 30 m, respectively. In addition, by 10 m, soluble phosphorus, nitrate-nitrogen and total suspended solids were reduced by 34%, 38% and 64%, respectively. Results suggest buffer zones on operational farms are capable of achieving contaminant reductions comparable to those reported for controlled experiments. Inconsistent siting of sample collectors beyond 10 m limited the evaluation of the effects of field slope and buffer width on buffer effectiveness on working farms. Future studies on buffer efficiency on operational farms should focus on building the data set beyond 10 m and evaluating load reductions.     

Growth of CsLiB6O10 thin films on Si substrate by pulsed laser deposition using SiO2 and CaF2 as buffer layers

CsLiB₆O₁₀ (CLBO) thin films are grown on Si (100) and (111) substrates using lower index SiO₂ and CaF₂ as buffer layers by pulsed KrF (248 nm) excimer laser ablation of stoichiometric CLBO targets over a temperature range of 425 to 725°C. A CaF₂ buffer layer is grown on Si by laser ablation while SiO₂ is prepared by standard thermal oxidation. From extended x-ray analysis, it is determined that CaF₂ is growth with preferred orientation on Si (100) at temperatures lower than 525°C while on Si (111) substrate, CaF₂ is grown epitaxially over the temperature range; this agrees well with observed reflection high energy electron diffraction patterns. X-ray 2θ-scans indicate that crystalline CLBO are grown on SiO₂/Si and CaF₂/Si (100). Analysis of reflectance spectra from CLBO/SiO₂/Si yields the absorption edge at 182 nm. Surface roughness of the CaF₂ and CLBO/CaF₂/Si film are 19 and 15 nm, respectively. This relatively rough surface caused by the ablation of wide bandgap CaF₂ and CLBO limits the application of CLBO for waveguiding measurement.     

Spatio-temporal effects of multimedia objects storage and delivery for video-on-demand systems

As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration, or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance. Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small number of streams supported and the hardware trade-offs. It is imperative that current software developments account for the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval, while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective of guaranteeing the required data availability rates for continuous media display.     

硅基红外焦平面阵列技术的新进展(Ⅱ)

主要介绍以硅为衬底的ＰｂＳ、ＰｂＳｅ、ＰｂＴｅ、ＰｂＳｎＳｅ、ＨｇＣｄＴｅ、ＩｎＳｂ等红外探测器焦平面阵列的新进展。     

Burstiness and resource management in ATM networks

Networks based upon the asynchronous transfer mode (ATM) provide for high flexibility to cope with a wide range of applications, some of them producing highly sporadic traffic. Therefore, the problem of burstiness has become in the last few years a key issue for such networks. A basic question is how to dimension network buffers in the presence of bursty traffic? In this paper we investigate the concept of burstiness and its impact on resource management. In burstiness characterization encountered in the literature, special attention has been given to the squared coefficient of variation of inter-arrival time Cv² in a cell arrival process. In order to observe the impact of bursty traffic on a queue, we develop in the present paper a ‘bursty’ traffic model, namely the two-stage hyper-Bernoulli cell arrival process, HBP₂, for short. We numerically solve the HBP₂/D/1/K queue. We especially derive the rejection probability P_loss. Numerical results are then thoroughly studied and we discuss the relevance for burstiness characterization of Cv² and peak to mean rate ratio B. We draw attention to the concept of local overload, i.e. when the arrival rate is greater than the server rate. This seems to be the most relevant phenomenon in the impact of a bursty traffic on a queue. These results are finally applied to the problem of resource management in ATM networks.     

A two-moment approximation for a buffer design problem requiring a small rejection probability

A useful model for buffer capacity design in communication systems is the single server queueing model with restricted accessibility where arriving customers are admitted only if their waiting plus service times do not exceed some fixed amount. A two-moment approximation for the buffer capacity in order to achieve a specific rejection probability is proposed for the case of Poisson arrivals and general service requirements. This approximation is a weighted combination of exact results for the special cases of deterministic and exponential service requirements where the weights use only the coefficient of variation of the general service requirement. Numerical experiments show an excellent performance of the approximation.