Single-Threaded vs. Multithreaded: Where Should We Focus?

Today, with the increasing popularity of multicore processors, one approach to optimizing the processor's performance is to reduce the execution times of individual applications running on each core by designing and implementing more powerful cores. Another approach, which is the polar opposite of the first, optimizes the processor's performance by running a larger number of applications on a correspondingly larger number of cores, albeit simpler ones. The difference between these two approaches is that the former focuses on reducing the latency of individual applications or threads (it optimizes the processor's single-threaded performance), whereas the latter focuses on reducing the latency of the applications' threads taken as a group (it optimizes the processor's multithreaded performance). The panel, from the 2007 Workshop on Computer Architecture Research Directions, discusses the relevant issues.     

Intermittent Phenomena in Switched Systems With High Coupling Strengths

In this paper, one kind of intermittency generated by a discontinuous system is studied. Although this system, which is composed of two switched subsystems coupled with a high strength, is nonsmooth, the mechanism of this kind of intermittency can be analyzed with several explicit relations between the intermittency characteristics and the system control parameters. In particular, estimates of "steady-state" values of the system (in the laminar phases) and a critical value for this intermittency can be derived, which are helpful in relevant control systems design. Moreover, some power laws for the observed intermittency are obtained and discussed     

Pyrolysis of tertiarybutylphosphine at low pressure

The pyrolysis of tertiarybutylphosphine (TBP) has been studied in the low pressure conditions used for chemical beam epitaxy (CBE). The pyrolysis studies were carried out in low pressure reactors of two different configurations, one of which is a cracker cell designed for use in a CBE system. The reaction products were studied using a quadrupole mass spectrometer. The products observed are accounted for by a reaction mechanism involving homolysis of the parent TBP molecule to produce PH₂ and C₄H₉ radicals. These undergo subsequent reactions to form the stable products C₄H₈, PH₃ and H₂, with smaller amounts of P and P₂ being produced. The production of the sub-hydride PH₂ using this cracker cell design indicates that the use of partially cracked TBP may be a promising technique for reducing the amount of carbon incorporated into the growing epitaxial layer.     

Effective index drift from molecular hydrogen diffusion inhydrogen-loaded optical fibres and its effect on Bragg gratingfabrication

When hydrogen loading is used to enhance the photosensitivity of silica-based optical waveguides and fibres, the presence of molecular hydrogen dissolved in the glass matrix changes the effective index of propagation of guided optical modes by as much as 0.05%. Real-time monitoring of the reflectivity spectrum of Bragg gratings written in such conditions shows that the centre wavelength follows the changes in hydrogen concentration due to diffusion and reaction with glass defects     

The effect of residual stresses on brittle and ductile fracture initiation predicted by micromechanical models

The effect of a realistic residual stress field on the predicted initiation of brittle and ductile fracture in a pressure and axially loaded circumferentially cracked pipe is examined using finite element analysis, micromechanical models of fracture initiation, andJ-Q theory. The study confirms that residual stresses contribute to the driving force and reduce fracture loads early in the loading history. In addition, results show that the residual stresses severely alter theJ-value (i.e., fracture toughness) predicted for the onset of brittle fracture. The reason for this decrease is found to be the increase in constraint generated by the residual stress field. In contrast, the effect of residual stresses on the ductile fracture initiation toughness is shown to be negligible. kw]Key words kw]residual stress kw]fracture initiation kw]micromechanics     

High-risk sexual behavior at a midwestern university: a confirmatory survey

According to a 1991 study of sexual behavior based on a random sample of heterosexual undergraduates at a Midwestern university, 80% of the males and 73% of the females had experienced vaginal or anal intercourse. The average age at first vaginal intercourse was 17.2 years for both sexes. Seventeen percent of the sexually experienced males and 18% of the sexually experienced females had engaged in heterosexual anal intercourse; among these respondents, the average age at first anal intercourse was 20.3 for males and 19.1 for females. Although less than four years, on average, had elapsed since the respondents had first had vaginal intercourse, males reported an average of 8.0 lifetime vaginal-sex partners and females reported an average of 6.1. Overall, the findings from this random sample of students are similar to those from a 1988 convenience sample of the same college population.     

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.     

Outcome of patients with haemorrhagic shock: an indicator of performance in a trauma centre

The survival rate of patients admitted to the Royal Prince Alfred Hospital (RPAH) from the central Sydney area with a major injury has improved since regionalization of trauma services in early 1992. This improvement has been attributed to education, better hospital care and changing trauma epidemiology. This study was conducted to assess whether the outcome of patients admitted with haemorrhagic shock had improved. This is proposed as a more subtle indicator of hospital performance than overall survival rates. A prospective before and after study was carried out comparing outcome in the 18 months preceding 1 January 1992 with that in the subsequent 18 months. Entry criteria to the study included all primary retrievals from the central Sydney area to RPAH with injury severity scores (ISS) > 15. Outcomes were compared generally and in those who were in a state of haemorrhagic shock (systolic blood pressure < or = 90 mmHg) on arrival at the emergency department. Three hundred and eight patients were entered into the study. Stratification showed similar numbers, demographic features and mechanisms of injury in the two groups. Forty patients were in a state of haemorrhagic shock on admission. The overall mortality was reduced from 31% to 11% (P < 0.001) over the two phases of the study. The mortality from blood loss in the 40 shocked patients fell from 10/25 in the first period to 2/15 (P = 0.07) in the latter. These improved survival rates were felt to reflect the value of the educational and organizational initiatives introduced following designation of the hospital as a trauma centre.