Challenges in computer architecture evaluation

We focus on problems suited to the current evaluation infrastructure. The current limitation and trends in evaluation techniques are troublesome and could noticeably slow the rate of computer system innovation. New research has been recommended to help and make quantitative evaluations of computer systems manageable. We support research in the areas of simulation frameworks, benchmarking methodologies, analytic methods, and validation techniques.     

From sequential programs to concurrent threads

Chip multiprocessors are of increasing importance due to difficulties in achieving higher clock frequencies in uniprocessors, but their success depends on finding useful work for the processor cores. This paper addresses this challenge by presenting a simple compiler approach that extracts non-speculative thread-level parallelism from sequential codes. We present initial results from this technique targeting a validated dual-core processor model, achieving speedups ranging from 9-48% with an average of 25% for important benchmark loops over their single-threaded versions. We also identify important next steps found during our pursuit of higher degrees of automatic threading.     

Wide-band symmetrical analog multiplier IC for coherentoptical-fiber receivers operating up to 10 Gb/s

A versatile analog four-quadrant multiplier IC with large bandwidth (DC to 6 GHz and 10 Gb/s) and large dynamic range is presented. It was mainly developed for differential-phase-shift-keying (DPSK) phase demodulator and polarization diversity receivers in coherent optical-fiber transmission systems. The circuit consumes 450 mW and only needs a single power supply of -5 V. The circuit principle used allows exact symmetry with respect to both linear inputs, which reduced multiplication errors. In the intended application, especially, the time jitter and the offset voltage of the output pulse patterns are reduced to negligible values. The IC was realized in a 1.25-μm double-polysilicon bipolar technology     

Presence of pressure ulcer prevention methods used among patients considered at risk versus those considered not at risk

PURPOSE: This study examined pressure ulcer-prevention strategies available for patients considered at risk versus those considered not at risk. DESIGN: The study used a prospective, longitudinal design. SETTING AND SUBJECTS: Six hundred ninety-four patients from units of five acute care hospitals, a rehabilitation facility, and two nurses' home care caseloads participated in the investigation. INSTRUMENTS: Data-collection instruments included the Braden Scale for risk assessment, demographic information, and the Pressure Ulcer-Prevention Strategies tool, which assessed for the presence of 16 pressure ulcer-prevention strategies. METHODS: All patients admitted to a participating unit during a 2-month period were followed up until discharge. Depending on the site, patients were assessed for the presence of pressure ulcer-prevention strategies one to three times per week. RESULTS: Patients in the at-risk group versus those in the not-at-risk group were more likely (p < 0.01) to have the head of the bed in a low position, a pressure-reducing bed surface, pressure ulcer prevention charted, a positioning wedge, incontinence cleanser and ointment, heel protection, a prevention care plan, a trapeze, and a posted turning schedule. The at-risk group had significantly (p < 0.01) more prevention strategies present than did the not-at-risk group. However, the percentage of patients placed on a pressure ulcer-prevention program was low for both groups. CONCLUSIONS: Pressure ulcer prevention was evident for the at-risk group, but at a low rate. Institutions must continue to explore this critical area affecting patient outcomes.     

Semiconductor laser amplifier as optical switching gate

The properties of a semiconductor laser amplifier as optical switching gate are investigated. Particular attention is paid to gain, contrast ratio, and switching time of the device. These properties are studied experimentally and theoretically with respect to the injection current, optical input power, and cavity resonances. The experimental arrangements and the theoretical method are described. As an example of the various applications of semiconductor laser amplifier gates, packet switching experiments with self-routing, employing cascaded switching gates, are reported. In a theoretical analysis the restrictions that the properties of semiconductor laser amplifier gates impose on a larger switching system consisting of many such gates are investigated     

RELATIONS BETWEEN FAILURE BEHAVIOUR AND MICROSTRUCTURE IN TEMPERING STRUCTURE STEELS

用透射电镜研究了两种结构钢的断裂行为与显微组织的关系。结果表明,回火后准解理断口的出现和消失与Fe_3C的析出和聚集密切相关:经250℃回火时析出ε碳化物,呈现单一韧窝断口,回火温度超过350℃时,有Fe_3C析出,这时出现准解理断口,而于450℃回火后达最大比例。在550℃回火后,60Si2Mn钢因Fe_3C聚集,准解理断口消失,又变成单一韧窝断口,37SiMnCrNiMoV钢Fe_3C聚集的倾向小,经550℃回火后仍有少量准解理断口保留下来。观察试样上由负荷产生的残留显微裂纹发现,它们常沿孪晶马氏体的内孪晶界及板条马氏体的条界发展,因此认为这两种脆化了的界面是准解理的解理面,而Fe_3C沿这类界面析出并呈连续分布是导致界面脆化的原因。