Asim: a performance model framework

The longevity and usefulness of a microprocessor performance model has historically depended on the model writer's skills and discipline. However, at Compaq the models became extremely complex and unmanageable because designers lacked a structured way to develop them. To cope with these complexities, Compaq researchers began developing Asim in late 1998 to allow model writers to faithfully represent the detailed timing of complex modern machines and effectively manage the large software projects needed to model such machines. Asim addresses these needs by providing a modular and reusable framework for creating many models. The framework's modularity helps break down the performance-modeling problem into individual pieces that can be modeled separately, while its reusability allows using a software component repeatedly in different contexts     

Ultrafast operation of optically pumped resonant periodic gain GaAssurface emitting lasers

Generation and characterization of picosecond optical pulses from vertical-cavity resonant-periodic-gain GaAs-AlGaAs surface-emitting lasers optically pumped by picosecond dye-laser pulses is reported. The output pulseshape was obtained from the cross correlation of pump and signal pulses. Dependence of signal pulsewidth and pulse delay on pump power were investigated. The results are in good agreement with a single rate equation model of the pulse formation. A cavity lifetime of 8.3 ps, compared with a gain medium transit time of ~0.1 ps, is determined for this very high-Q structure     

A Survey of Test Techniques for MCM Substrates

This paper provides a survey of MCM substrate test techniques. Test techniques that are based on capacitance,resistance, electron beam, latent opens, time domain network analysis(TDNA) and RF resonator are discussed. In this paper, test techniquesare applied to interconnect testing.     

Multirate scheduling of VBR video traffic in ATM networks

One of the major attractions of asynchronous transfer mode (ATM) networks for transporting bursty video traffic is its ability to exploit the multiplexing gains of packet switching while providing quality of service guarantees. Unfortunately, most of the multiplexing mechanisms proposed in the literature fail to exploit the multiplexing gains of ATM. We propose a multirate service mechanism that allows a session to be served at different rates at different times. Applications generating bursty data, such as variable bit-rate (VBR) video, can take advantage of multirate service by requesting a high rate of service for brief periods of bursty arrivals and a much lower rate of service for all other times. Consequently, the applications can improve their delay performance without reserving a high bandwidth for the entire duration of the sessions. Furthermore, the scheduler can multiplex the peaks and the lulls in service rates of different sessions and improve the utilization of the system. Using MPEG video traces from a number of applications, we show that multirate servers outperform single-rate PGPS (packet-by-packet generalized processor sharing) servers and CBR (constant bit-rate) servers in terms of number of connections admitted, while providing the same level of service guarantees. We also investigate the performance of multirate service when service quality need not be guaranteed. We refer to this as predictive service. We propose a measurement-based admission control procedure for predictive service, and show that it helps increase the size of the admissible region even further     

Network security via reverse engineering of TCP code: vulnerabilityanalysis and proposed solutions

The Transmission Control Protocol/Internet Protocol (TCP/IP) suite is widely employed to interconnect computing facilities in today's network environments. However, there exist several security vulnerabilities in the TCP specification and additional weaknesses in a number of its implementations. These vulnerabilities may allow an intruder to “attack” TCP-based systems, enabling him/her to “hijack” a TCP connection or cause denial of service to legitimate users. The authors analyze the TCP code via a “reverse engineering” technique called “program slicing” to identify several of these vulnerabilities, especially those that are related to the TCP state-transition diagram. They discuss many of the flaws present in the TCP implementation of many widely used operating systems, such as SUNOS 4.1.3, SVR4, and ULTRIX 4.3. The corresponding TCP attack “signatures” (including the well-known 1994 Christmas Day Mitnick Attack) are described, and recommendations are provided to improve the security state of a TCP-based system (e.g., incorporation of a “timer escape route” from every TCP state). Also, it is anticipated that wide dissemination of this article's results may not only lead to vendor patches to TCP code to plug security holes, but also raise awareness of how program slicing may be used to analyze other networking software and how future designs of TCP and other software can be improved     

Enhanced photo luminescence from porous silicon on texturized surface

Porous silicon (PS) was formed on both polished and texturized single crystal silicon (100) by anodic etching. Photoluminescences (PL) from both of these silicon surfaces were measured and compared. A two-fold enhancement of PL from textured silicon surface was obtained. This enhancement could be ascribed to the geometry of the textured surface.     

Comparison of outcome of stroke patients--cerebral ischaemic versus cerebral haemorrhagic from the standpoint of a physiatrist

Thirty patients having hemiplegia arising out of stroke were considered for the study. There were 15 patients each of cerebral infarction and cerebral haemorrhage. The patients were evaluated initially and 6-8 weeks after the first visit for neuromuscular function and activity of daily living following the schedule of Feldman et al and Barthel index respectively. After determining neuromuscular function the patients were graded as 'not impaired', 'mild to moderately impaired' and 'moderate to severely impaired' taking into account of muscular function, spasticity and disabling contracture. In determining activity of daily living the patients were divided into 'A' to 'E' categories depending on the score (0 to 100) they obtained on assessment. The patients were put to standard physiotherapeutic measures in addition to standard medical therapy. At the end of the study it was found that haemorrhagic stroke patients showed better improvement both in neuromuscular function and activity of daily living.     

A New Node Architecture Employing Waveband-Selective Switching for Optical Burst-Switched Networks

We investigate a new node architecture based on waveband-selective switching in an optical burst-switching (OBS) network. Switching is performed at the granularity of a waveband, which aggregates multiple wavelength channels. A new data-transmission scheme is presented to incorporate waveband switching. Simulation results show that the proposed node architecture requires fewer components, costs less, and performs as well as traditional node designs.     

The effects of endothelin-A receptor blockade during the progression of pacing-induced congestive heart failure

OBJECTIVES: We sought to identify the effects of endothelin (ET) subtype-A (ET(A))) receptor blockade during the development of congestive heart failure (CHF) on left ventricle (LV) function and contractility. BACKGROUND: Congested heart failure causes increased plasma levels of ET and ET(A) receptor activation. METHODS: Yorkshire pigs were assigned to four groups: 1) CHF: 240 beats/min for 3 weeks; n=7; 2) CHF/ET(A)-High Dose: paced for 2 weeks then ET(A) receptor blockade (BMS 193884, 50 mg/kg, b.i.d.) for the last week of pacing; n=6; 3) CHF/ET(A)-Low Dose: pacing for 2 weeks then ET(A) receptor blockade (BMS 193884, 12.5 mg/kg, b.i.d.) for the last week, n=6; and 4) Control: n=8. RESULTS: Left ventricle fractional shortening decreased with CHF compared with control (12+/-1 vs. 39+/-1%, p < 0.05) and increased in the CHF/ET(A) High and Low Dose groups (23+/-3 and 25+/-1%, p < 0.05). The LV peak wall stress and wall force increased approximately twofold with CHF and remained increased with ET(A) receptor blockade. With CHF, systemic vascular resistance increased by 120%, was normalized in the CHF/ET(A) High Dose group, and fell by 43% from CHF values in the Low Dose group (p < 0.05). Plasma catecholamines increased fourfold in the CHF group and were reduced by 48% in both CHF/ET(A) blockade groups. The LV myocyte velocity of shortening was reduced with CHF (32+/-3 vs. 54+/-3 microm/s, p < 0.05), was higher in the CHF/ET(A) High Dose group (39+/-1 microm/s, p < 0.05), and was similar to CHF values in the Low Dose group. CONCLUSIONS: ET(A) receptor activation may contribute to the progression of LV dysfunction with CHF.