Using time and stochastic models for software reliability forecasting and analysis

Tämä työ luo katsauksen ajallisiin ja stokastisiin ohjelmien luotettavuus malleihin sekä tutkii muutamia malleja käytännössä. Työn teoriaosuus sisältää ohjelmien luotettavuuden kuvauksessa ja arvioinnissa käytetyt keskeiset määritelmät ja metriikan sekä varsinaiset mallien kuvaukset. Työssä esitellään kaksi ohjelmien luotettavuusryhmää. Ensimmäinen ryhmä ovat riskiin perustuvat mallit. Toinen ryhmä käsittää virheiden ”kylvöön” ja merkitsevyyteen perustuvat mallit. Työn empiirinen osa sisältää kokeiden kuvaukset ja tulokset. Kokeet suoritettiin käyttämällä kolmea ensimmäiseen ryhmään kuuluvaa mallia: Jelinski-Moranda mallia, ensimmäistä geometrista mallia sekä yksinkertaista eksponenttimallia. Kokeiden tarkoituksena oli tutkia, kuinka syötetyn datan distribuutio vaikuttaa mallien toimivuuteen sekä kuinka herkkiä mallit ovat syötetyn datan määrän muutoksille. Jelinski-Moranda malli osoittautui herkimmäksi distribuutiolle konvergaatio-ongelmien vuoksi, ensimmäinen geometrinen malli herkimmäksi datan määrän muutoksille.

Design for Customer Needs: Utilization of Quality Function Deployment in Product Development

Kansainvälisen kaupan kiristyessä yrityksien kyky täyttää asiakasketjunsa lailliset, sosiaaliset ja toiminnalliset asiakastarpeet tulee punnituksi. Globaalisuuden lisääntyessä asiakasketju voi sisältää toimintoja samanaikaisesti yli sadassa maassa. Jotta asiakasketjun tarpeet voidaan sisällyttää tuotteeseen tehokkaasti yhä useammat yritykset ovat siirtyneet käyttämään Quality Function Deployment nimistä projektijohto- ja laatutyökalua. Quality Function Deployment työkalu auttaa yritystä muuntamaan sisäisten ja ulkoisten asiakkaittensa tarpeet, tuotefunktioiksi ja tuotespesifikaatioiksi. Näin tehdessä voidaan uuden tuotteen kehitysaikaa ja hintaa alentaa merkittävästi suunnittelmalla tuote alunalkaen paremmin. QFD:tä on käytetty useissa yrityksissä Aasiassa, Pohjois-Amerikassa ja Euroopassa, sen kehittämisen jälkeen Japanissa 1960 luvulla. Tämä diplomityö antaa teoreettisen ja käytännön kuvauksen siitä miten QFD:tä kannatta käyttää ja mitä sen avulla voidaan saavuttaa vastaten kysymykseen "miten minä, ja yritykseni hyötyy jos käytän QFD:tä".

Cdk5 controls lymphatic vessel development and function by phosphorylation of Foxc2.

The lymphatic system maintains tissue fluid balance, and dysfunction of lymphatic vessels and valves causes human lymphedema syndromes. Yet, our knowledge of the molecular mechanisms underlying lymphatic vessel development is still limited. Here, we show that cyclin-dependent kinase 5 (Cdk5) is an essential regulator of lymphatic vessel development. Endothelial-specific Cdk5 knockdown causes congenital lymphatic dysfunction and lymphedema due to defective lymphatic vessel patterning and valve formation. We identify the transcription factor Foxc2 as a key substrate of Cdk5 in the lymphatic vasculature, mechanistically linking Cdk5 to lymphatic development and valve morphogenesis. Collectively, our findings show that Cdk5-Foxc2 interaction represents a critical regulator of lymphatic vessel development and the transcriptional network underlying lymphatic vascular remodeling.

Serum anticholinergic activity and postoperative cognitive dysfunction in elderly parients

BACKGROUND: Cerebral cholinergic transmission plays a key role in cognitive function, and anticholinergic drugs administered during the perioperative phase are a hypothetical cause of postoperative cognitive dysfunction (POCD). We hypothesized that a perioperative increase in serum anticholinergic activity (SAA) is associated with POCD in elderly patients. METHODS: Seventy-nine patients aged >65 years undergoing elective major surgery under stan- dardized general anesthesia (thiopental, sevoflurane, fentanyl, and atracurium) were investi- gated. Cognitive functions were assessed preoperatively and 7 days postoperatively using the extended version of the CERAD-Neuropsychological Assessment Battery. POCD was defined as a postoperative decline >1 z-score in at least 2 test variables. SAA was measured preop- eratively and 7 days postoperatively at the time of cognitive testing. Hodges-Lehmann median differences and their 95% confidence intervals were calculated for between-group comparisons. RESULTS: Of the patients who completed the study, 46% developed POCD. Patients with POCD were slightly older and less educated than patients without POCD. There were no relevant differences between patients with and without POCD regarding gender, demographically cor- rected baseline cognitive functions, and duration of anesthesia. There were no large differences between patients with and without POCD regarding SAA preoperatively (pmol/mL, median [inter- quartile range]/median difference [95% CI], P; 1.14 [0.72, 2.37] vs 1.13 [0.68, 1.68]/0.12 [−0.31, 0.57], P = 0.56), SAA 7 days postoperatively (1.32 [0.68, 2.59] vs 0.97 [0.65, 1.83]/0.25 [−0.26, 0.81], P = 0.37), or changes in SAA (0.08 [−0.50, 0.70] vs −0.02 [−0.53, 0.41]/0.1 [−0.31, 0.52], P = 0.62). There was no significant relationship between changes in SAA and changes in cognitive function (Spearman rank correlation coefficient preoperatively of 0.03 [95% CI, −0.21, 0.26] and postoperatively of −0.002 [95% CI, −0.24, 0.23]). CONCLUSIONS: In this panel of patients with low baseline SAA and clinically insignificant periopera- tive anticholinergic burden, although a relationship cannot be excluded in some patients, our analysis suggests that POCD is probably not a substantial consequence of anticholinergic medications admin- istered perioperatively but rather due to other mechanisms.

The contribution of real-time mirror reflections of motor actions on virtual body ownership in an immersive virtual environment

This paper reports an experiment that investigated people"s body ownership of an avatar that was observed in a virtual mirror. Twenty subjects were recruited in a within-groups study where 10 first experienced a virtual character that synchronously reflected their upper-body movements as seen in a virtual mirror, and then an asynchronous condition where the mirror avatar displayed prerecorded actions, unrelated to those of the participant. The other 10 subjects experienced the conditions in the opposite order. In both conditions the participant could carry out actions that led to elevation above ground level, as seen from their first person perspective and correspondingly in the mirror. A rotating virtual fan eventually descended to 2m above the ground. The hypothesis was that synchronous mirror reflection would result in higher subjective sense of ownership. A questionnaire analysis showed that the body ownership illusion was significantly greater for thesynchronous than asynchronous condition. Additionally participants in the synchronous condition avoided collision with the descending fan significantly more often than those in the asynchronous condition. The results of this experiment are put into context within similar experiments on multisensory correlation and body ownership within cognitive neuroscience.

Effect of radar rainfall time resolution on the predictive capability of a distributed hydrologic model

The performance of a hydrologic model depends on the rainfall input data, both spatially and temporally. As the spatial distribution of rainfall exerts a great influence on both runoff volumes and peak flows, the use of a distributed hydrologic model can improve the results in the case of convective rainfall in a basin where the storm area is smaller than the basin area. The aim of this study was to perform a sensitivity analysis of the rainfall time resolution on the results of a distributed hydrologic model in a flash-flood prone basin. Within such a catchment, floods are produced by heavy rainfall events with a large convective component. A second objective of the current paper is the proposal of a methodology that improves the radar rainfall estimation at a higher spatial and temporal resolution. Composite radar data from a network of three C-band radars with 6-min temporal and 2 × 2 km2 spatial resolution were used to feed the RIBS distributed hydrological model. A modification of the Window Probability Matching Method (gauge-adjustment method) was applied to four cases of heavy rainfall to improve the observed rainfall sub-estimation by computing new Z/R relationships for both convective and stratiform reflectivities. An advection correction technique based on the cross-correlation between two consecutive images was introduced to obtain several time resolutions from 1 min to 30 min. The RIBS hydrologic model was calibrated using a probabilistic approach based on a multiobjective methodology for each time resolution. A sensitivity analysis of rainfall time resolution was conducted to find the resolution that best represents the hydrological basin behaviour.

Serum 25-hydroxyvitamin D level and kidney function decline in a Swiss general adult population.

Molecular evidence suggests that levels of vitamin D are associated with kidney function loss. Still, population-based studies are limited and few have considered the potential confounding effect of baseline kidney function. This study evaluated the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline, and incidence of CKD and albuminuria. Baseline (2003-2006) and 5.5-year follow-up data from a Swiss adult general population were used to evaluate the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline (annual loss >3 ml/min per 1.73 m(2)), and incidence of CKD and albuminuria. Serum 25-hydroxyvitamin D was measured at baseline using liquid chromatography-tandem mass spectrometry. eGFR and albuminuria were collected at baseline and follow-up. Multivariate linear and logistic regression models were used considering potential confounding factors. Among the 4280 people included in the analysis, the mean±SD annual eGFR change was -0.57±1.78 ml/min per 1.73 m(2), and 287 (6.7%) participants presented rapid eGFR decline. Before adjustment for baseline eGFR, baseline 25-hydroxyvitamin D level was associated with both mean annual eGFR change and risk of rapid eGFR decline, independently of baseline albuminuria. Once adjusted for baseline eGFR, associations were no longer significant. For every 10 ng/ml higher baseline 25-hydroxyvitamin D, the adjusted mean annual eGFR change was -0.005 ml/min per 1.73 m(2) (95% confidence interval, -0.063 to 0.053; P=0.87) and the risk of rapid eGFR decline was null (odds ratio, 0.93; 95% confidence interval, 0.79 to 1.08; P=0.33). Baseline 25-hydroxyvitamin D level was not associated with incidence of CKD or albuminuria. The association of 25-hydroxyvitamin D with eGFR decline is confounded by baseline eGFR. Sufficient 25-hydroxyvitamin D levels do not seem to protect from eGFR decline independently from baseline eGFR.

Dysregulated ADAM10-Mediated Processing of APP during a Critical Time Window Leads to Synaptic Deficits in Fragile X Syndrome.

The Fragile X mental retardation protein (FMRP) regulates neuronal RNA metabolism, and its absence or mutations leads to the Fragile X syndrome (FXS). The β-amyloid precursor protein (APP) is involved in Alzheimer's disease, plays a role in synapse formation, and is upregulated in intellectual disabilities. Here, we show that during mouse synaptogenesis and in human FXS fibroblasts, a dual dysregulation of APP and the α-secretase ADAM10 leads to the production of an excess of soluble APPα (sAPPα). In FXS, sAPPα signals through the metabotropic receptor that, activating the MAP kinase pathway, leads to synaptic and behavioral deficits. Modulation of ADAM10 activity in FXS reduces sAPPα levels, restoring translational control, synaptic morphology, and behavioral plasticity. Thus, proper control of ADAM10-mediated APP processing during a specific developmental postnatal stage is crucial for healthy spine formation and function(s). Downregulation of ADAM10 activity at synapses may be an effective strategy for ameliorating FXS phenotypes.

Monotonic continuous-time random walks with drift and stochastic reset events

In this paper we consider a stochastic process that may experience random reset events which suddenly bring the system to the starting value and analyze the relevant statistical magnitudes. We focus our attention on monotonic continuous-time random walks with a constant drift: The process increases between the reset events, either by the effect of the random jumps, or by the action of the deterministic drift. As a result of all these combined factors interesting properties emerge, like the existence (for any drift strength) of a stationary transition probability density function, or the faculty of the model to reproduce power-law-like behavior. General formulas for two extreme statistics, the survival probability, and the mean exit time, are also derived. To corroborate in an independent way the results of the paper, Monte Carlo methods were used. These numerical estimations are in full agreement with the analytical predictions.

Beurling-Landau densities of weighted Fekete sets and correlation kernel estimates

Let $Q$ be a suitable real function on $C$. An $n$-Fekete set corresponding to $Q$ is a subset ${Z_{n1}},\dotsb, Z_{nn}}$ of $C$ which maximizes the expression $\Pi^n_i_{

Empirical study of correlated survival times for recurrent events with proportional hazards margins and the effect of correlation and censoring.

Background: In longitudinal studies where subjects experience recurrent incidents over a period of time, such as respiratory infections, fever or diarrhea, statistical methods are required to take into account the within-subject correlation. Methods: For repeated events data with censored failure, the independent increment (AG), marginal (WLW) and conditional (PWP) models are three multiple failure models that generalize Cox"s proportional hazard model. In this paper, we revise the efficiency, accuracy and robustness of all three models under simulated scenarios with varying degrees of within-subject correlation, censoring levels, maximum number of possible recurrences and sample size. We also study the methods performance on a real dataset from a cohort study with bronchial obstruction. Results: We find substantial differences between methods and there is not an optimal method. AG and PWP seem to be preferable to WLW for low correlation levels but the situation reverts for high correlations. Conclusions: All methods are stable in front of censoring, worsen with increasing recurrence levels and share a bias problem which, among other consequences, makes asymptotic normal confidence intervals not fully reliable, although they are well developed theoretically.

Dynamic range extension of SiPM detectors with the time-gated operation

The silicon photomultiplier (SiPM) is a novel detector technology that has undergone a fast development in the last few years, owing to its single-photon resolution and ultra-fast response time. However, the typical high dark count rates of the sensor may prevent the detection of low intensity radiation fluxes. In this article, the time-gated operation with short active periods in the nanosecond range is proposed as a solution to reduce the number of cells fired due to noise and thus increase the dynamic range. The technique is aimed at application fields that function under a trigger command, such as gated fluorescence lifetime imaging microscopy.

Sidelobe elimination for generalized synthetic discriminant functions by a two-filter correlation and subsequent postprocessing of the intensity distributions

One of the most important problems in optical pattern recognition by correlation is the appearance of sidelobes in the correlation plane, which causes false alarms. We present a method that eliminate sidelobes of up to a given height if certain conditions are satisfied. The method can be applied to any generalized synthetic discriminant function filter and is capable of rejecting lateral peaks that are even higher than the central correlation. Satisfactory results were obtained in both computer simulations and optical implementation.

State of Logistics and Operations Management in Finnish and Swedish Companies – Survey Research Findings

In this research we are examining what is the status of logistics and operations management in Finnish and Swedish companies. Empirical data is based on the web based questionnaire, which was completed in the end of 2007 and early 2008. Our examination consists of roughly 30 answers from largest manufacturing (highest representation in our sample), trade and logistics/distribution companies. Generally it could be argued that these companies operate in complex environment, where number of products, raw materials/components and suppliers is high. However, usually companies rely on small amount of suppliers per raw material/component (highest frequency is 2), and this was especially the case among Swedish companies, and among those companies, which favoured overseas sourcing. Sample consisted of companies which mostly are operating in an international environment, and are quite often multinationals. Our survey findings reveal that companies in general have taken logistics and information technology as part of their strategy process; utilization of performance measures as well as system implementations have followed the strategy decisions. In the transportation mode side we identify that road transports dominate all transport flow classes (inbound, internal and outbound), followed by sea and air. Surprisingly small amount of companies use railways, but in general we could argue that Swedish companies prefer this mode over Finnish counterparts. With respect of operations outsourcing, we found that more traditional areas of logistics outsourcing are driving factors in company's performance measurement priority. In contrary to previous research, our results indicate that the scope of outsourcing is not that wide in logistics/operations management area, and companies are not planning to outsource more in the near future. Some support is found for more international operations and increased outsourcing activity. From the increased time pressure of companies, we find evidence that local as well as overseas customers expect deliveries within days or weeks, but suppliers usually supply within weeks or months. So, basically this leads into considerable inventory holding. Interestingly local and overseas sourcing strategy does not have that great influence on lead time performance of these particular sourcing areas - local strategy is anyway considerably better in responding on market changes due to shorter supply lead times. In the end of our research work we have completed correlation analysis concerning items asked with Likert scale. Our analysis shows that seeing logistics more like a process rather than function, applying time based management, favouring partnerships and measuring logistics within different performance dimensions results on preferred features and performance found in logistics literature.

Time-Varying Benefits of International Diversification for Finnish Investor: Country-Specific Strategy Concentrating on Emerging Markets

The main objective of this study is to investigate whether the Finnish investors’ country-specific strategy concentrating on emerging markets provides diversification benefits. We also analyze whether the benefits of international diversification has been diminished after periods of high volatility caused by different market crisis. The objective is investigated with three methods: Correlation coefficients, rolling correlations added with OLS trend-lines and Box’s M statistic. All the empirical tests are analyzed and calculated with logarithmic returns of weekly time series data from Friday closing values between January 1995 and December 2007. The number of weekly observations is 678. The data type is total return indices of different countries. Data is collected from DataStream and provided by Datastream Financial. Countries investigated are Finland, Argentina, Brazil, Chile, China, India, Mexico, Poland, Russia, South Africa, South Korea, Thailand and Turkey. The current data is quoted both in U.S. Dollars and local currencies. The empirical results of this thesis show that the correlation coefficients are time-varying across Finland and 12 emerging market countries. Although the correlations have risen from 1995 to 2007, there can be found sub-periods where the correlation has declined from earlier period. The results also indicate that a Finnish investor constructing a portfolio of emerging market countries cannot rely on the correlation coefficients estimated from historical data because of the instability of correlation matrices.