Characteristics of origin-destination pair traffic in Funet

In this paper we analyze measurements gathered from a 2.5~Gbps link in the Finnish university network (Funet) in 2004. The traffic is broken down into origin-destination (OD) pair components based on source and destination IP address. We study the traffic characteristics of these components, and identify four typical representative OD pairs. For these pairs we investigate the validity of a moving IID Gaussian model. We find that the statistical properties of these OD pairs differ significantly from each other, with only some of them close to Gaussian. The OD pairs are also found to have some cross-correlation between each other, contradicting an often made assumption about OD pair independence. Furthermore, the existence of a mean-variance relation between the OD pairs is studied. We find that there is a relation between mean and variance, but for some periods of time it is rather weak.     

Using results of eye movement signal analysis in the neural network recognition of otoneurological patients

We extracted a collection of eye movement signals employed for almost two decades in clinical otoneurological tests at a balance laboratory. During those years we designed and programmed signal analysis methods to analyse their features in detail and to compute medically important attributes. In the present study, using such attributes and their results computed we classified test cases into groups of healthy subjects and patients with multilayer perceptron neural networks. Classification succeeded in total accuracies from 60% to 90% depending on the type of eye movements, which were saccades, nystagmus, sinusoidal movements and vestibulo-ocular reflex stimulated in two different ways; these are the chief eye movement tests applied in otoneurology.     

Detection Efficiency of a Water-Based TSI Condensation Particle Counter 3785

In this article we present observations on the detection efficiency of a recently developed TSI 3785 Water Condensation Particle Counter (WCPC). The instrument relies on activation of sampled particles by water condensation. The supersaturation is generated by directing a saturated airflow into a “growth tube,” in which the mass transfer of water vapor is faster than heat transfer. This results in supersaturated conditions with respect to water vapor in the centerline of a “growth tube.” In this study, the cut-off diameter, that is, the size, where 50% of the sampled particles are successfully activated, varied from 4 to 14 nm for silver particles as a function of temperature difference between the saturator and the growth tube. The solubility of the sampled particles to water played an important role in the detection efficiency. Cut-off diameters for ammonium sulphate and sodium chloride particles were 5.1 and 3.6–3.8 nm, respectively at nominal operation conditions. Corresponding cut-off diameter for hydrophobic silver particles was 5.8 nm.     

Required Work in the M/M/1 Queue,with Application in IP Packet Processing

We consider the ordinary M/M/1 queue with the FIFO queueing discipline. It seems that the sum of service times of the customers in the system (or the required work, as we call it briefly) is a random variable that is not considered before. In this paper we derive the equilibrium distribution of this variable. The task is not quite trivial because of the dependencies between the elapsed service time and the number of customers in the system. Our motivation for this problem comes from the performance analysis of a dynamic memory allocation scheme of a packet buffer.     

Sub-/spl mu/s switching time in silicon-on-insulator Mach-Zehnder thermooptic switch

We have demonstrated both rise and fall times below 1 /spl mu/s with 10%-90% modulation in a silicon-on-insulator thermooptical Mach-Zehnder switch. The switch is based on 9-/spl mu/m-thick and 10-/spl mu/m-wide single-mode rib waveguides. Very fast switching was achieved by using a differential control method. The switch was driven with a digital signal processor accompanied by simple electronic circuitry.     

One-footed and externally disturbed two-footed postural control in patients with chronic low back pain and healthy control subjects. A controlled study with follow-up

STUDY DESIGN: A study of postural control during one-footed and externally disturbed two-footed stance among healthy control subjects and patients with chronic low back pain at the beginning of a functional back restoration program and 6 months later at follow-up examination. OBJECTIVES: To study postural control cross-sectionally among control subjects and patients with low back pain, and to evaluate the effects of functional restoration on the postural control parameters in a follow-up examination. SUMMARY OF BACKGROUND DATA: Deficits of motor skills and coordination have been reported in association with musculoskeletal disorders. It has been found that patients with chronic low back pain have impaired psychomotor control, but the impairment is reversible with successful low back rehabilitation. It is insufficiently known how functional activation and intensive physical training affect postural control. METHODS: Sixty-one healthy volunteers (32 men, 29 women) and altogether 99 patients with low back pain participated in the study. Sixty-eight patients (33 men, 35 women) had moderate and 31 (18 men, 13 women) had severe low back pain. Postural stability was measured with a force platform. In two-footed stance, vibration stimulation on calf and back muscles was used to disturb the balance. Center point of force-velocity (cm/sec), average position shift in anteroposterior direction (cm), and maximal position shift in lateral direction (cm) were used as the parameters. RESULTS: Reliability of all tests was acceptable. Center point of force-velocity was the most sensitive parameter and the one-footed measurement the most sensitivetest for evaluating postural stability. At the beginning, the patients with severe low back pain had poorer one-footed postural control compared with the control subjects (P = 0.0003). The subgroup of patients with moderate low back pain participated in the restoration program. The outcome of the restoration program was considered good if the disability because of low back pain (Oswestry index) decreased during the restoration program and poor if the disability increased or did not change. The one-footed postural stability remained primarily at the same level as the initial results in the control and good outcome groups, but became significantly poorer in the poor outcome group. The difference between poor outcome and control groups was statistically significant (P = 0.04). CONCLUSIONS: Impaired postural stability seems to be one factor in multidimensional symptomatology of patients with chronic low back trouble. Postural stability is easily disturbed in case of impairment in strength, coordination, or effective coupling of muscles in the lumbar and pelvic area. Patients with chronic low back pain seem to experience impairment in these functions, which should be taken into consideration when back rehabilitation programs are planned.     

Vestibulo-ocular reflex function as measured with the head autorotation test

The vestibulo-ocular reflex (VOR) of 125 healthy subjects was examined over the frequency range of 0.5-5 Hz with the head autorotation test (HART). During the HART the subjects fixated at a steady target while moving their heads horizontally from side to side with increasing frequencies according to auditory signals. The gain was determined as the ratio between the amplitude of the eye and head movements in five frequency bands between 0.5 and 5 Hz. The phase difference between the eye and head movements was determined in both degrees and milliseconds. The ability to reach high-frequency bands was evaluated. The mean gain was close to unity up 5 Hz, when it decreased to 0.91. The mean phase difference showed a lead of approximately 5 degrees at frequencies below 2 Hz, and at frequencies above 2 Hz there was no phase difference within the resolution of the test. The frequency band of 5 Hz was reached by 78% of the subjects, and that of 4 Hz was reached by 94% of the subjects. In summary, the HART is a new approach with which to study VOR function and determine accurately the VOR for healthy subjects. The normal upper frequency limit is 4 Hz in the HART.     

Intercomparison of Four Methods to Determine Size Distributions of Low-Concentration (∼ 100 cm−3), Ultrafine Aerosols (3 < D p < 10 nm) with Illustrative Data from the Arctic

Four different methods for measuring ultrafine particle size distributions in the 3–10-nm particle diameter range are compared and discussed. These methods all use an ultrafine condensation particle counter (TSI Inc. Model 3025 or its prototype) as the detector, but use different approaches to determine the size of the particles counted. Size classification was achieved using a Hauke Model VIE-06 differential mobility analyzer, a specially configured TSI Model 3040S diffusion battery, an ultrafine condensation particle counter with a variable condenser temperature, and an ultrafine condensation particle counter with a pulse height analyzer for signals produced by the optical detector. The response of these systems to ultrafine particles of known size and composition was studied during a workshop held in Lund, Sweden, during July 1991. After this workshop, measurements of ultrafine particles were made on the Swedish icebreaker Oden during the International Arctic Ocean Expedition 1991 (August 1, 1991 through October 7, 1991). In this article, the results of these laboratory and field measurements are discussed. The strengths and limitations of these measurement methods are emphasized.