Mean Downtime Research Articles

Prospective Study of 532-nm Picosecond Laser for the Treatment of Pigmented Lesions of the Face and Dorsal Hands.

Pigmented lesions from chronic UV photoaging are extremely common on the face and hands. To evaluate the safety and efficacy of a 532-nm picosecond laser for these types of pigmented lesions. This was a single-center, prospective, open-label clinical trial. Eligible subjects with pigmentation on the face and hands received 3 monthly treatments, with 1 month (1M) and 3 months (3M) follow-up. Change in investigator-graded overall facial and per lesion pigmentation and subject-graded satisfaction and pigmentation improvement was evaluated by a 5-point scale. Immediate skin response and adverse events (AEs) were evaluated post-treatment. The melanin index was measured using a mexameter. Randomized before and after photographs were graded by 3 blinded physicians for degree of pigmentation improvement. Twenty-five subjects (22F/3M) with Fitzpatrick skin types I-III were enrolled, with 23 subjects completing. Treatments used a 532 nm wavelength, 800 ps pulse duration, 4-6mm spot size, and 0.1 to 0.6J/cm2 fluence. Good-to-excellent clearance at 1M/3M was demonstrated in ≥95% of lesions (n = 116). Only mild treatment-related pain was reported, with transient post-treatment AEs (mean downtime of 2.1 ± 2.0 days) and no serious treatment-related AEs. Subject satisfaction (satisfied or very satisfied) was 95% at 1M and 91% at 3M. Treatment with a 532-nm picosecond laser is safe and highly effective for the treatment of the pigmented lesions of the face and dorsal hands.

Selection of Production Reliability Indicators for Project Simulation Model

Due to technological enhancements, traditional, qualitative decision-making methods are usually replaced by data-driven decision-making even in smaller companies. Process simulation is one of these solutions, which can help companies avoid costly failures as well as evaluate positive or negative effects. The reason for this paper is twofold: first, authors conducted a Quality Function Deployment analysis to find the most vital reliability indicators in the field of production scheduling. The importance was acquired from the meta-analysis of papers published in major journals. The authors found 3 indicators to be the most important: mean time between failure (MTBF), mean repair time and mean downtime. The second part of the research is for the implementation of these indicators to the stochastic environment: possible means of application are proposed, confirming the finding with a case study in which 100 products must be produced. The database created from the simulation is analyzed in terms of major production KPIs, such as production quantity, total process time and efficiency of the production. The results of the study show that calculating with reliability issues in production during the negotiation of a production deadline supports business excellence.

OPTIMUM UNIT COMMITMENT SOLUTION OF A POWER SYSTEM BASED ON SALP SWARM ALGORITHM

This paper presents an algorithm to solve the unit commitment problem in a power system. The proposed algorithm employs the Salp swarm algorithm technique to search the optimum unit schedule for a particular daily demand pattern and specific time horizon. Different constraints are taken into consideration, transition cost (start-up and shut down )cost, mean-up time, mean-down time, spinning reserve, and power balance. The proposed algorithm is applied to 10-units and 26-unit. The obtained results are compared with other methods. It reveals the robustness of the proposed algorithm in terms of minimizing overall running costs.

Port Equipment Downtime Prediction and Lifetime Data Analysis: Evidence from a Case Study

Prediction of downtime and lifetime data for gantry cranes in a container terminal is a crucial concern for port terminals due to the requirement for maintenance planning and capital expenditure. Correct estimation of lifetime behavior for gantry cranes is complex since multiple cranes are involved, each with different costs, capacities; installation, and retirement dates. This paper develops statistically-oriented predictions for the lifetimes of container terminals company fleet of gantry cranes. Data records on downtime for cranes were collected and analyzed using Weibull, normal, and Rayleigh distributions regarding a port in southwestern Nigeria. The downtime, probability density function, cumulative density function, reliability, and hazard rate were analyzed for three shape functions of Weibull, β=0.5, 1, and 3. The same was analyzed for Rayleigh and normal distribution functions. The mean downtime was 30.58 hrs. The highest PDF, CDF, R(t) for all β =0.5, 1, and 3, were 0.26, 0.78, .030 and 13.13, respectively. However, the least values for these parameters are 0.01, 0.71, 0.25, and 0.04, respectively. These values are means for thirty data points and concern the Weibull distribution function. For the Rayleigh distribution, the mean PDF, CDF, R(t) and h(t) are 0.002, 0.042, 0.958 and 0.002 while they are 0.002, 0.456, 0.542 and 35.755 for the normal distribution. This article provides new insights into the lifetime analysis of gantry cranes in a container terminal.

Predicting One's Turn With Both Body and Mind: Anticipatory Speech Postures During Dyadic Conversation.

In natural conversation, turns are handed off quickly, with the mean downtime commonly ranging from 7 to 423 ms. To achieve this, speakers plan their upcoming speech as their partner’s turn unfolds, holding the audible utterance in abeyance until socially appropriate. The role played by prediction is debated, with some researchers claiming that speakers predict upcoming speech opportunities, and others claiming that speakers wait for detection of turn-final cues. The dynamics of articulatory triggering may speak to this debate. It is often assumed that the prepared utterance is held in a response buffer and then initiated all at once. This assumption is consistent with standard phonetic models in which articulatory actions must follow tightly prescribed patterns of coordination. This assumption has recently been challenged by single-word production experiments in which participants partly positioned their articulators to anticipate upcoming utterances, long before starting the acoustic response. The present study considered whether similar anticipatory postures arise when speakers in conversation await their next opportunity to speak. We analyzed a pre-existing audiovisual database of dyads engaging in unstructured conversation. Video motion tracking was used to determine speakers’ lip areas over time. When utterance-initial syllables began with labial consonants or included rounded vowels, speakers produced distinctly smaller lip areas (compared to other utterances), prior to audible speech. This effect was moderated by the number of words in the upcoming utterance; postures arose up to 3,000 ms before acoustic onset for short utterances of 1–3 words. We discuss the implications for models of conversation and phonetic control.

Performance assessment analysis of UHF machines using Reliability, Availability, Maintainability and Safety (RAMS) analysis methods

XYZ Company is manufacturing engaged in the rubber industry located in the city of Bandung, because economic growth and demand from consumers are increasing, making companies demanded to meet the target orders promptly. One way to minimize losses and the possibilities that must be borne by the company is to increase Reliability, Availability, Maintainability of the production and the safety value. Data in the form of Mean Downtime, Mean Time to Failure, Mean Time to Repair is useful for system performance that works. MTTF data can be used to assess safety systems found in PT XYZ with the safety standards of IEC 61508 using Safety Integrity Level. From the results of processing RAMS data using Reliability Block Diagram modeling based on the analytical approach, for 120 hours, the system has a Reliability value (91.12%). The average value of system Maintainability at t = 2 hours is 100%. The Inherent Availability value is 99,981% and the Operational Availability value is 99,980%. Based on the world-class maintenance Key Performace Indicator, leading and lagging availability indicators have reached the indicator target standard. Safety Integrity Level values from calculations based on PFD and RRF values of each system are in SIL 1.

Reliability evaluation of stand-alone hybrid photovoltaic energy system for rural healthcare centre

This paper presents two methods for evaluation of reliability indices of stand-alone hybrid photovoltaic (PV) energy system. Markov model and frequency-duration (F-D) reliability techniques have been used for evaluation of reliability indices. Hybrid energy system is design and evaluated reliability indices for its configurations (Diesel only, PV/Battery and PV/Diesel/Battery). The system reliability is based on the system failure rate, interruption duration, unavailability, loss of load probability (LOLP), expected energy not supplied (EENS) mean downtime (MDT) indices, which are computed and compared different energy generation system configurations. This paper also presented hybrid energy system reliability analysis is based on monthly solar radiation and load demand data. It is observed that hybrid energy system failure rate, interruption duration, system unavailability, EENS, MDT and LOLP are least as compared to other configuration. The results show that hybrid PV/Battery/Diesel system is more efficient and reliable system as compared to other configurations. This research work will be useful for policymakers and system designers to determine optimal system in remote areas before installation.

Optimization and Reliability Evaluation of Hybrid Solar-Wind Energy Systems for Remote Areas

T his paper presents optimization and reliability analysis of renewable energy system for farm house electricity and irrigation load demand located at remote area. Optimum sizing of solar PV, wind turbine and battery energy system has been obtained to fully utilize the capacity of the system. The economic analysis have been carried out for different configuration of hybrid energy system in terms of net present cost (NPC), operating cost (OC), levelized cost of energy (LCOE). This paper proposes a recent evolutionary technique based on meta-heuristic optimization algorithm called grasshopper optimization algorithm (GOA), to be used for selecting optimal energy system configuration. Markov method has been employed for evaluating the reliability indices i.e. system failure rate, repair rate, availability, unavailability, mean up time (MUT), mean down time (MDT), loss of load probability (LOLP) and expected energy not supplied (EENS). Economic analysis, GOA and Markov method-based result shows that hybrid PV/wind/battery energy system is more reliable and cost effective system as compared to other configuration.Â

Reliability evaluation of power system incorporating wind farm for generation expansion planning based on ANLSA approach

AbstractReliability evaluation of power‐generating systems gives a mechanism to guarantee proper system operations in the face of different uncertainties including equipment failures. It is regularly not attainable to identify all possible failure states to figure the reliability indices because of the large number of system states engaged with system operations. Therefore, a hybrid optimization technique is required to analyse the reliability of the power system. This paper proposes a hybrid optimization technique to evaluate the reliability of a power system for the generation expansion planning incorporating wind energy source. The proposed hybrid methodology is the joined execution of both ant lion optimization algorithm (ALO) and lightning search algorithm (LSA), and it is named as ANLSA. ALO searching behavior is enhanced by LSA. Through the inherent convergence mechanisms, ANLSA search the meaningful system states. The most probable failure states contribute reliability indices of power generating system including mean down time (MDT), loss of load probability (LOLP), loss of load expectation (LOLE), loss of load frequency (LOLF), and expected demand not supplied (EDNS). Furthermore, ANLSA is utilized to assess the reliability of system under normal condition, integration of wind farm with capacity of 150 MW, and considering spinning reserve requirement (SRR). By then, the proposed work is actualized in MATLAB/Simulink platform and it is demonstrated on IEEE reliability test system (IEEE RTS‐79). Furthermore, the statistical analysis of proposed and existing techniques such as Monte Carlo simulation (MCS) and discrete convolution (DC) is considered. The comparison results demonstrate that proposed approach confirms its ability for evaluating the power system reliability.

Review in Maintenance Strategies for Haemodialysis Machine in Healthcare Facilities

Hemodialysis machines are critical medical equipment in healthcare facilities for renal replacement therapy in form of dialysis treatment on solving chronic kidney diseases in Sub Sahara Africa. It is a vital machine which acts as human kidney by incorporating electromechanical controlled extracorporeal blood paths that leverage pumps and semi permeable dialyzer membranes to filter the patient’s blood. The biggest challenge to the biomedical engineers in most African hospitals is to maintain the manufacturer’s safety and performance specification of the haemodialysis equipment. There is a need for effective maintenance strategy for haemodialysis medical equipment in order to maintain the manufacturer’s set specification to meet clinical expectations and hence improve its reliability. The overall goal of the research paper is therefore to analyze the influence of different maintenance strategies and subsequently improve on the reliability of hemodialysis equipment in healthcare institutions in Kenya. The research will prioritize hemodialysis machine as critical medical equipment and use comprehensive secondary data to review and analyze the strategic maintenance applied in health institutions to optimize the best and cost effective strategic maintenance for the hemodialysis medical equipment. The ant colony optimization (ACO) algorithms may be less expert reliant and avoid uncertainty and ambiguity to determine the best strategic maintenance management to manage hemodialysis medical equipment in the hospitals. The results will provide an opportunity to technical engineers to develop a predictive and intelligent management system in the hospitals to minimize or remove the Mean Downtime (MDT) and Mean time to repair (MTTR) for a failed hemodialysis machines and improve the reliability of the hemodialysis machine.

Dedicated path protection for optical networks based on function programmable nodes

Due to the constantly increasing volumes and tightening reliability requirements of network traffic, survivability is one of the key concerns in optical network design. Optical “white box” nodes based on the Architecture on Demand (AoD) paradigm allow for self-healing of nodal component failures due to their architectural flexibility and the ability to employ idle components for failure recovery. By incorporating node-level survivability with network-level protection from link failures, resiliency of optical networks can be significantly improved. To this end, we propose a survivable routing algorithm for AoD-based networks called Dedicated Path Protection with Enforced Fiber Switching (DPP-EFS), which combines self-healing at the node level with dedicated path protection at the network level. The algorithm aims at improving the self-healing capabilities of the nodes by increasing the percentage of fiber switching (FS). Namely, fiber-switched lightpaths require a minimal amount of processing within the node (i.e. only signal switching), while other aspects of processing (e.g. demultiplexing, bandwidth virtualization) and the related components (i.e. demultiplexers, splitters, wavelength selective switches) remain unused and may be used as redundancy. On the other hand, lightpaths that are not eligible for FS have to be re-routed to alternative, longer paths in order to allow for FS between certain ports within the node. Therefore, the proposed algorithm pursues an advantageous trade-off between the increase of the number of idle components which can be used as redundancy at the node level and the unwanted length increase of lightpaths re-routed to render components redundant. For particular cases when DPP-EFS is not able to reduce the mean down time (MDT) in the network merely by increasing the percentage of fiber switching, we propose an algorithm for Dedicated Path Protection with Fixed Shortest Path routing and added Redundancy (DPP-FSP-RED) which adds additional spare components at strategic nodes to ensure that all connections have at least one redundant node component along their path. Simulation results show a significant reduction in MDT with minimal extra capital expenses.

Summer doesn't mean downtime for campus safety leaders

The end of the academic year has concluded and hopefully everyone is starting to enjoy the summer and finding time for some much‐needed rest and relaxation.

한국 서남 해상 풍력발전단지 통신망 연구

With the increasing of the penetration rate of large-scale wind farms, a reliable, highly available and cost-effective communication network is needed. As the failure of a WF communication network will significantly impact the control and real-time monitoring of wind turbines, network reliability should be considered into the WF design process. This paper analyzes the network reliability of different WF configurations for the Southwest Offshore project that is located in Korea. The WF consists of 20 WTs with a total capacity of 60 MW. In this paper, the performance is compared according to a variety of indices such as network unavailability, mean downtime and network cost. To increase the network reliability, partial protection and full protection were investigated as strategies that can overcome the impact of a single point of failure. Furthermore, the reliability performances of different network architectures are analyzed, evaluated and compared.

Functional dependability of the display unit software of the BLOK system

Aim. The article is dedicated to the challenges of evaluating the functional dependability of the display unit software (SW) that is part of the BLOK vital integrated onboard system as attributed to program errors within a 24-hour target time. One of the key tasks is the calculation of the values of such SW functional dependability characteristics as accuracy, correctness, security, controllability, reliability, fault tolerance and availability, which are the primary indicators for evaluating the health of safety devices. With all this taken into account, it is to be evaluated whether the checking of the software of the display unit before each trip with a departure test is required. Method. The reference conditions do not contain statistical data of program executions over the course of its maintenance. There is also no information on the structural characteristics of the program (number of operators, operands, cycles, etc.) which prevents the use of statistical models of dependability, such as the Halstead metrics, IBM model or similar ones. That is why the Schumann model was chosen as the initial data definition apparatus. The method of evaluation of the display unit’s functional dependability is based on the findings of [1]. Results. At the first stage, the following initial data values were defined: initial number of defects in the program, program failure rate and probability of correct run. At the subsequent stage, the identified values were used to define such dependability parameters as probability of no-error as the result of program run within a given time, probability of no-failure of display unit as the result of program run within a given time and mean time to program failure. After the probability РSW (t) of no-error as the result of program run within a given time was calculated, such SW dependability attributes as accuracy, correctness, security and controllability were evaluated. After the probability of no-failure of the display unit РR (t) as the result of program run within a given time was calculated, an evaluation was given to such attributes as SW reliability and fault tolerance, while after the mean time to program failure TavSW was calculated, knowing the mean downtime due to elimination of the program error τpdt, the display unit availability for faultless execution of an information process at an arbitrary point in time Cfa was defined. The calculated partial functional availability coefficients for the display unit have shown that pre-trip checking of the unit and immediate elimination of errors, should such be identified, will enable a significant improvement of user performance of the onboard display unit (BIL) in terms of timely notification of the driver on the current operational situation to enable timely train control decision-making.

Valuation of performance-based contracts for capital equipment: A stochastic programming approach

ABSTRACTEvaluating performance-based contracts (PBCs) for capital equipment can be a challenge because it is difficult to map service-level improvements to operational availability. This article considers scenario-based stochastic programming models for the evaluation of PBC alternatives for capital equipment consisting of a single-component system. In particular, PBC alternatives are evaluated for robustness under uncertainty in mean time between failures and mean downtime. The models measure expected deviation of implied contract operational availability and realized operational availability, and robustness is measured by the extent of improvement in service quality under a budget constraint. Optimal contract service levels are also computed that can be compared to service levels offered in a contract alternative. Value at risk (VaR) and conditional value at risk (CVaR) values for contracts are generated to gain insight into the readiness risk of contracts.

Reliability analysis of GEM® Premier™ technology: a multicenter study

<p>This paper describes how specific blood gas analyzer characteristics can support the emerging clinical and organizational user’s needs while ensuring patient safety. A oneyear data set from two Italian hospitals was analyzed from 10 different blood gas analyzers. Performance measurements in terms of mean down time (MDT) were calculated to show how technical characteristics declared by the manufacturer compare to the analyzer availability in real clinical settings. Results show a high level of reliability for the analyzed technology, associated with very low MDT of each sensor integrated in the cartridge. Moreover, results show a high level of efficiency in cartridge usage. Such results are consistent with the specification of the GEM<sup>®</sup> Premier™ maintenance- free technology and are particularly relevant in the point-of-care testing setting.</p>

Abstract 240: Concomitant Use of Therapeutic Hypothermia with Mechanical Circulatory Support in Patients Post Cardiac Arrest in Cardiogenic Shock: A Single Center Experience

Background: The concurrent use of therapeutic hypothermia (TH) following cardiac arrest and mechanical circulatory support (MCS) for cardiogenic shock is becoming increasingly common. Little is known however, about the combined use of TH and MCS for patients after ROSC following a cardiac arrest who remain in cardiogenic shock. Therefore we describe the experience with concomitant use of TH and MCS from a large academic tertiary care center in Boston. Methods: Baseline characteristics and clinical outcomes at hospital discharge were reported for patients undergoing TH following cardiac arrest who also received MCS for cardiogenic shock. MCS included Intra-aortic balloon pump (IABP) two percutaneous ventricular assist devices (Impella, and TandemHeart), and extracorporeal membrane oxygenation (ECMO). Clinical outcomes included mortality as well as cerebral performance category (CPC) at hospital discharge. Results: There were a total of 14 patients who underwent concomitant TH and MCS following a cardiac arrest. Baseline characteristics and clinical outcomes are noted in the Figure. 9 patients underwent placement of IABP, 2 patients an Impella pump, 2 patients a TandemHeart, and 1 patient ECMO. All 14 cardiac arrests were due to cardiovascular etiologies; 9 of 14 had STEMI. 9 of 14 patients had an initial shockable rhythm. Mean age was 56 years (+/- 19), mean downtime was 35 minutes (+/- 24). All patients were vasopressor dependent. Bleeding events are noted in the table. 8 patients survived to hospital discharge, all with good neurologic outcome. These rates were comparable to the survival rates and neurologic outcomes among 82 patients who underwent TH post cardiac arrest (from cardiovascular etiologies) without concomitant MCS (Figure). Conclusion: Based on our experience from a large academic tertiary care center, concomitant use of TH and MCS is both safe and feasible with an encouraging rate of cardiac and neurologic recovery.

The Reliability Analysis of the Parallel Mechanical Leg (2UPS+UP) Based on a Repairable Markov Model

The reliability of the parallel mechanical leg (2ups+up) based on the repairable Markov model was studied. First the repairable Markov model was built up, and the matrix of the state transition rate was got. Then by solving the steady-state equation the steady state indexes such as the availability, the failure frequency, mean up-time, mean down-time, mean cycle time were obtained. Finally we gave the reliability and mean time to first failure by solving the differential equation group.

Discrimination of low- and high-demand modes of safety-instrumented systems based on probability of failure on demand adaptability

Probability of failure on demand is commonly used to measure the performance of safety-instrumented systems in the low (frequency) demand mode, while probability of failure per hour is taken as the measure in the high-demand mode. In current IEC 61508, once per year of the demand frequency is regarded as the borderline between two modes. However, few explanations can be found about why the borderline is here. This study focuses on the intermediate area of the two demand modes, examines the adaptability of probability of failure on demand with demand rates and then proposes a discrimination criteria of demand modes based on the analysis for the adaptability of probability of failure on demand with the Markov method. According to these criteria, in the high-demand mode where probability of failure on demand is not an effective measure, the equipment has higher probability to fall in hazard before a proof test when the safety-instrumented system is unavailable, and otherwise, the safety-instrumented system runs in the low-demand mode. The mean downtime of the safety-instrumented system before its failure is revealed in a proof test can help to locate the borderline, which is thus influenced by the configurations of safety-instrumented systems.

The Downtime Donor Heart: Analysis of Pre-Transplant Function and Current Utilization for Transplantation

Purpose Previous investigation reveals that donors resuscitated following cardiorespiratory arrest can be utilized for cardiac transplantation with satisfactory post-transplant survival within recipients of these organs. We analyzed this donor group to determine its contribution to transplantation and evaluate donor heart function after resuscitation. Methods and Materials We reviewed 225 consecutive donor organs offered to our institution for cardiac transplantation. Demographic and clinical data was obtained from UNOS. Functional data was obtained by analyzing donor echocardiograms. “Downtime” donor hearts (DD) were compared with organs from conventional donors without a period of arrest (CD). Results A history of resuscitation following circulatory arrest was present in 99 donors (44%). The mean downtime was 30 +/- 21 minutes. Organ utilization was 48% in the DD group vs. 45% for CD; p=NS. Donor age was significantly lower in the DD group (41+/-15 vs. 36+/-14;p=0.01), there was no difference in height or weight. Peak troponin I concentration (DD 2.3+/-4.3 vs. CD 1.1 +/-3.6 ng/ml; p=0.04) was elevated in the DD group. Left ventricular ejection fraction was significantly greater in the CD group. (DD 58.6+/-9% vs. CD 61.3+/-8.7%; p=0.02). The percentage of donor hearts with LV dysfunction (LVEF Conclusions Organs procured from donors resuscitated following cardiocirculatory arrest currently contribute a substantial proportion of organs for cardiac transplantation. Cardiac function in these donors is acceptable, albeit marginally impaired in comparison to those without a history of arrest. The potential for recovery and utilization of donor hearts in this setting may further support the prospect of clinical DCD cardiac transplantation.