Load Change Rate Research Articles

Rate of viral load change and adherence of HIV adult patients treated with Efavirenz or Nevirapine antiretroviral regimens at 24 and 48\u2009weeks in Yaound\xe9, Cameroon: a longitudinal cohort study

BackgroundHIV-load decrease and suppression over time is associated with consistent adherence to antiretroviral therapy (ART). Our study aimed to evaluate the difference in viral load and adherence of patients treated with a combination of either Tenofovir (TDF), Lamivudine (3TC) and Efavirenz (EFV) or TDF / Zidovudine (AZT), 3TC and Nevirapine (NVP) regimens at 24 and 48 weeks.MethodsA longitudinal study was conducted from May 2016 to June 2017 among 256 HIV infected adult patients who were enrolled at two approved treatment hospitals in Yaoundé, before the start of first-line ART. Whole blood samples were collected using standard operating procedures. HIV-loads were determined by a quantitative RealTime PCR assay. Adherence was evaluated by pharmacy refill data records. Statistical analyses were performed using the PRISM 5.0 software.ResultsOff the 256 HIV infected patients enrolled, 180 (70%) patients completed the study and 76 (30%) patients were lost to follow-up. The success rate in achieving viral load < 40 copies/ml was 1.8 times higher with the EFV regimen at 24 weeks and was 1.2 times higher in the NVP regimen at 48 weeks. At 48 weeks the treatment failure rate was 12.0 and 40.0% in patients on EFV and the NVP regimen, respectively. The rate of adherence varied in both ART based regimens with 84.0 to 74.0% for EFV and 65.5 to 62.5% for NVP, at 24 and 48 weeks respectively.ConclusionIn our study and setting, the rate of viral load decrease was higher in the NVP based regimen than with the EFV regimen. The adherence rate to ART was higher in the EFV regimen, compared to the NVP regimen. This adds to evidence that the EFV regimen is the preferred ART combination for non-nucleoside reverse transcriptase inhibitors (NNRTIs).

Design of load optimal control algorithm for smart grid based on demand response in different scenarios

Abstract The current game theory model method cannot accurately optimize the load control of smart grid, resulting in the problem of high load energy consumption when the smart grid is running. To address this problem, a load optimal control algorithm for smart grid based on demand response in different scenarios is proposed in this paper. The demand response of smart grid under different scenarios is described. Onthis basis, the load rate and actual load of smart grid are calculated by using the rated load of electrical appliances. The load classification of smart grid and the main factors affecting the load of smart grid are analyzed to complete the load distribution of smart grid. According to the evaluation function of smart grid, the number of load clusters is adjusted to calculate the load change rate. The trend of load curve of smart grid is analyzed to realize optimal load control of smart grid under different scenarios. The experimental results show that the proposed method has better control performance and higher accuracy through load control of smart grid.

Impact of HIV-1 CRF55_01B infection on CD4 counts and viral load in men who have sex with men naive to antiretroviral treatment

BackgroundCRF55_01B, a newly identified HIV-1 circulating recombinant form (CRF) with a backbone of CRF01_AE, originated from men who have sex with men (MSM) and can be traced back to 2005 in Shenzhen, China. Circulating primarily among MSM, it has now spread throughout most provinces of China with a prevalence ranging from 1·5% to 12·5%. However, its impact on the progression of disease has not been investigated. MethodsMSM with newly diagnosed HIV-1 (n=3418) were screened for HIV-1 genotypes from 2005 to 2015 in Shenzhen, China. Blood samples were collected for measurements of CD4 T-cell counts and viral load at the time of HIV diagnosis and initiation of combination antiretroviral therapy (cART). HIV-1 pol genes were sequenced and the subtype identified, and recent infection was defined as pol with less than 0·5% ambiguous nucleotides. Written informed consent was obtained from all of the participants. The protocol for recruitment was approved by the human subject committee of the Shenzhen Center for Disease Control and Prevention. Generalized linear regression models were applied to examine the relationship between viral subtype and the change rate of CD4 counts and viral load, with adjustments for confounding variables. FindingsOf the 2423 blood samples screened for genotypes, 1031 (42·3%) were CRF07_BC, 841 (34·7%) were CRF01_AE, 323 (13·3%) were CRF55_01B, 166 (6·9%) were subtype B, and 62 (2·6%) were other subtypes (eg, CRF_08BC, CRF59_01B, and C). CRF55_01B has replaced subtype B as the third most predominant strain in Shenzhen since 2012. Among the 1792 recent infections with the three main subtypes, those infected with CRF55_01B showed a significantly higher median viral load (5·4 [IQR 5·0, 5·9]) than CRF01_AE (5·3 [IQR 4·8, 5·7], P<0·01) and CRF07_BC (5·0 [IQR 4·5, 5·5], p<0·05) at the time of cART initiation. In terms of CD4 counts, CRF55_01B-infected (349·5 [IQR 250·2, 474·8]) MSM had a similar median to CRF01_AE-infected MSM (335·0 [IQR 237·0, 464·0], p=0·352), but a significantly lower median than CRF07_BC-infected (370·0, [IQR 278·0, 501·0], p<0·05) MSM at the time of diagnosis. Furthermore, CRF55_01B infection was associated with a significantly faster rate of increase of viral load than CRF07_BC infection (2·1 vs 0·7 log copies per ml per year, p<0·01). Furthermore, it showed a slower rate of decline of CD4 T-cell counts than CRF01_AE (13·6 vs 23·3 [cells per μL]1/2 per year, p<0·05) when the initial CD4 counts were between 200 and 350 cells per μL. InterpretationIt is well known that CRF01_AE leads to higher viral loads than CRF07_BC. However, our study revealed that CRF55_01B induced even higher viral loads than CRF01_AE, and thus the transmission risk of CRF55_01B may be higher than for CRF01_AE and CRF07_BC. Although CRF55_01B showed similar CD4 counts to CRF01_AE, the rate of decline of CD4 T-cell counts was slower, which may translate to a prolonged asymptomatic state. These findings help to explain the rapid increase in prevalence of CRF55_01B in China in recent years. Strengthened surveillance, tailored prevention plans and interventions, and in-depth research focusing on CRF55_01B are needed urgently to forestall a potential epidemic. FundingThis work was supported by the National Natural Science Foundation of China (81573211), the Shenzhen Municipal Technological Project (JCYJ20160331173336891) and the Shenzhen San-Ming Project of Medicine in Shenzhen (SZSM201811071).

MEA-based CO2 capture integrated with natural gas combined cycle or pulverized coal power plants: Operability and controllability through integrated design and control

Post-combustion solvent-based carbon capture is a promising technology that potentially can offset the greenhouse gas emissions from fossil-driven power generation systems. The challenge is that CO2 absorption (similar to other CCS technologies) imposes energetic penalties, and constrains the operational flexibility. In this paper, we build upon our recent contributions in the field (Sharifzadeh et al., 2016; Sharifzadeh and Shah, 2016), and study the dynamic response of such process to the electricity load changes in the power plant. The key research question is to investigate if the steady-state integrated process design and control framework applied in the previous studies, can also ensure controllability under a wide range of disturbances. The present study considers the mutual interactions between the power plant and capture process. Other features of interest include the implications of key design and operational decisions such as reboiler temperature, solvent circulation flow rate, solvent concentration and the rate of power load change or CO2 setpoint tracking for flexible process operation. The results suggest that the capture process exhibits a high degree of flexibility and the integrated design and control framework could be the key enabler for the commercialization of post-combustion solvent-based carbon capture.

Experimental study on the load response rate under the dynamic combined combustion of PC coal and CFB coal in a CFB boiler

The load response rate of the circulating fluidized bed (CFB) boiler is low for its great thermal inertia. In order to increase its load response rate, a new dynamic combined combustion technology featuring co-combustion of CFB coal and pulverized coal (PC) with high gross calorific value (GCV) is put forward. This combined combustion system was set up on a 240 t/h CFB boiler, and PC coal spraying positions, heating values, and heat ratios were evaluated for their effects on load response rate and combustion performance of the CFB boiler. When PC coal is fed from the secondary air pipes, the relative load change rates (RLCRs) exceed 2.0%/min and meet the requirement RLCR for power dispatching (1.5%/min), and the maximum RLCR is 3.69%/min. Moreover, the weighted average of carbon in residue decreases, and the original NOX emission of CFB boiler increases less than 40 mg/Nm3. Results indicate that the dynamic combined combustion of CFB coal and PC coal with higher GCV fed through secondary air pipes in CFB boiler is a feasible technology to increase its relative load response rate.

Analysis of Electric Load Characteristics of Commercial and Public Buildings Based on Big Data

This article is based on the power load data of several typical commercial and public buildings collected by electric power companies, analyzes its characteristics in terms of time dimension, load change rate, and temperature. The conclusions obtained indicate that, although the types of electricity load and user activity time used by commercial and public buildings are similar, their daily load characteristics are still quite different and need to be independently analyzed. The conclusions obtained provide some theoretical guidance for the future planning and operation of the electricity market.

Proposal of a Global Training Load Measure Predicting Match Performance in an Elite Team Sport.

Aim: The use of external and internal load is an important aspect of monitoring systems in team sport. The aim of this study was to validate a novel measure of training load by quantifying the training-performance relationship of elite Australian footballers.Methods: The primary training measure of each of 36 players was weekly load derived from a weighted combination of Global Positioning System (GPS) data and perceived wellness over a 24-week season. Smoothed loads representing an exponentially weighted rolling average were derived with decay time constants of 1.5, 2, 3, and 4 weeks. Differential loads representing rate of change in load were generated in similar fashion. Other derived measures of training included monotony, strain and acute:chronic ratio. Performance was a proprietary score derived from match performance indicators. Effects of a 1 SD within-player change below and above the mean of each training measure were quantified with a quadratic mixed model for each position (defenders, forwards, midfielders, and rucks). Effects were interpreted using standardization and magnitude-based inferences.Results: Performance was generally highest near the mean or ~1 SD below the mean of each training measure, and 1 SD increases in the following measures produced small impairments: weekly load (defenders, forwards, and midfielders); 1.5-week smoothed load (midfielders); 4-week differential load (defenders, forwards, and midfielders); and acute:chronic ratio (defenders and forwards). Effects of other measures in other positions were either trivial or unclear.Conclusion: The innovative combination of load was sensitive to performance in this elite Australian football cohort. Periods of high acute load and sustained increases in load impaired match performance. Positional differences should be taken into account for individual training prescription.

An improved coordinated control technology for coal-fired boiler-turbine plant based on flexible steam extraction system

Coordinated control system (CCS) used in thermal power unit can quickly coordinate energy balance between the plant boiler and steam turbine, and follow the load commands. The development of renewable energy, however, has increased the load change rate and amplitude requirements for thermal power units. This implies that the difficulties associated with ensuring plant parameters stable and rapid tracking of load commands has augmented as well. In order to improve the peaking rate and amplitude of thermal power units, based on energy and mass balance principles, a dynamic mathematical model of a thermal power unit including steam turbine regenerative systems is developed. The developed model is verified by comparing the results obtained from the model with the corresponding ones coming from field tests. Moreover, an improved coordinated control technology based on flexible steam extraction system is proposed, the flexible steam extraction system is achieved by installing throttle valve in the steam turbine extraction line. Finally, load command step and ramp up simulation tests are carried out under the improved CCS.

Design and evaluation of a fuzzy cloud controller

The management of cloud deployments is still largely the responsibility of system administrators. Introducing autonomy in cloud management would entail, amongst other things, the ability for automated cloud manager systems to scale up or down the number of deployed virtual machines, and/or deploy machines of different types to meet performance and other SLAs. However, the workload of cloud deployments can exhibit high variability over short time periods. This creates the necessity of introducing autonomic behaviour in the resource management function of the cloud deployment that makes decisions in real time so to optimise cost and/or performance. In this paper, we employ fuzzy logic to design a cloud controller whose scaling policies emulate the reasoning of human cloud operators, and take into account the current system load and the system load rate of change. The fuzzy controller's performance is compared and evaluated against Amazon's AWS auto-scaling policies. Results indicate the ability of the proposed fuzzy controller to adapt better to changing workloads by provisioning virtual machines appropriately to match the rate of system load change. Additionally, fuzzy rules are more intuitive than auto-scaling policies and thus easier to understand and modify by human users.

Design and evaluation of a fuzzy cloud controller

The management of cloud deployments is still largely the responsibility of system administrators. Introducing autonomy in cloud management would entail, amongst other things, the ability for automated cloud manager systems to scale up or down the number of deployed virtual machines, and/or deploy machines of different types to meet performance and other SLAs. However, the workload of cloud deployments can exhibit high variability over short time periods. This creates the necessity of introducing autonomic behaviour in the resource management function of the cloud deployment that makes decisions in real time so to optimise cost and/or performance. In this paper, we employ fuzzy logic to design a cloud controller whose scaling policies emulate the reasoning of human cloud operators, and take into account the current system load and the system load rate of change. The fuzzy controller's performance is compared and evaluated against Amazon's AWS auto-scaling policies. Results indicate the ability of the proposed fuzzy controller to adapt better to changing workloads by provisioning virtual machines appropriately to match the rate of system load change. Additionally, fuzzy rules are more intuitive than auto-scaling policies and thus easier to understand and modify by human users.

Development of a program for transient behavior simulation of heavy-duty gas turbines

In this study, a program for analyzing the transient behaviors of heavy-duty gas turbines was developed. Focus was given to simulating a practical load-following operation. A distinct feature of our work is that all of the gas turbine components are modularized to enhance the expandability of the program. We used object-oriented programing for this purpose. Mass and energy balances and performance maps for the compressor and turbine were used for the modeling, and a multivariable numerical solving technique was used to enhance the numerical stability. The fundamental thermodynamic modeling of the program was validated by comparison of the transient response of a simulated gas turbine with that of a commercial program. PID control was adopted for simultaneous control of the rotational shaft speed and turbine exhaust temperature by the modulations of the fuel flow and the opening of the compressor inlet guide vane at the same time. The influence of the magnitude of load change and ramp rate was investigated. Stable control of the gas turbine was possible, even for a very rapid change of load.

Study of synchronization characteristics of a multi-source driving transmission system under an impact load

Multi-source driving transmission systems, in which the gear assembly is driven by multiple induction motors, are extensively used in new energy, aerospace, marine engineering, and in other fields. The multi-source driving system faces an even-load distribution problem, i.e., torque or speed synchronization issues. In this study, the synchronization characteristics of a multi-source driving transmission system under an impact load at different load change rates are studied. An accurate electromechanical coupling dynamic model of the system considering the flexible shafts, support bearing and meshing gear pair is established by applying virtual equivalent shaft elements. By considering the time-varying meshing and the coupling effects of the dynamic electric motor and the speed, torque and stator current synchronization characteristics are investigated using this model. Computational results show that the influence of the load change rate on the speed synchronization characteristics of the system is minor, but has a significant influence on the torque and stator current synchronization characteristics. The stator current root mean square value (RMS) can be chosen as a feedback signal to monitor the synchronization characteristics of the system. The proposed research provides the theoretical basis for the formulation of the synchronization control strategy for multi-source driving transmission systems.

Failures during Load-Frequency Control Maneuvers in an Upgraded Hydropower Plant: Causes, Identification of Causes and Solution Proposals

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and to propose solutions that allow the power plant to continue providing secondary LFC in a safe and reliable manner. For this purpose, a simulation model has been developed and calibrated from data gathered during several on-site tests. Two different solutions are proposed in order to cope with the observed problem: using a state-dependent load change rate limiter or modifying the hydro turbine governor gains; the turbine governor remains the same as before the runner replacement. The proposed solutions are tested against a set of realistic secondary LFC signals by means of simulations and compared to each other as a function of the probability that the surge tank water level descends below a minimum safe level and the quality of the secondary LFC response. The results presented in the paper demonstrate the validity of the methodology proposed to determine the state-dependent ramp limit, as well as its effectiveness to prevent the surge tank drawdown and to provide clear insight into the trade-off between response quality and power plant safety.

STATCOM과 조상설비를 이용한 풍력단지가 연계된 전력계통의 전압제어

The wind power plant must be able to produce reactive power at the POI bus of a wind farm connected to power system to keep or control the voltage of POI bus. But, the reactive power capability of wind turbines may not be sufficient to control the voltage of POI bus due to the reactive power losses in connection lines between wind farm and POI bus. The solution of this problem is to install an external STATCOM. The proposed cooperative control method of STATCOM and conventional reactive power compensators such as Switched-shunt and tap changing transformer can control the voltage of POI bus more efficiently. The simulation results are shown that the voltage drop of POI Bus of Test System with the arbitrary load change rate to initial loads is improved more than 60% and the voltage of load bus is maintained more than 95% of rated voltage.

Dual-loop Control of Free Piston Engine Generator

The precise control of piston motion is the key to guaranteeing reliable free piston engine generator (FPEG) operation. This paper presents a dual-loop controller to manage piston motion in a free piston engine. In this paper, the piston motion dynamics are represented by a discrete-time model system which derived by energy balance while the airflow dynamics are represented by a mean value model. The outer-loop adjusts the fuel quantity and load change rate by a model predictive control (MPC) that tracks clearance height set-points. The desired cylinder airflow is calculated using the desired fuel amount from MPC assuming stoichiometric air-to-fuel ratio. A nonlinear inner loop controller is designed to regulate the throttle to meet the airflow demand. The design of the inner loop controller is based on the Triple Step method. In simulation, the proposed controller successfully tracks the target piston clearance height and satisfies the constraints during an instantaneous electrical load change while maintaining a stoichiometric air-fuel ratio.

Research of Paddle Wave-Maker Control System Based on Jonswap Spectrum

According to large energy consumption, overload and re-reflection problemr, the control algorithm of wave-maker has been improved based on Jonswap spectrum. The control algorithm is comprised of the offline calculation of the control waveform and the real-time governing of the wave paddle. Offline algorithm is implemented on a personal computer, whereas paddle control is realized on a programmable automation controller. The experiments results show that the speed is continuous and stable, change rate of load has been optimized obviously and achieves the purpose of energy saving.

Performance comparisons of intelligent load forecasting structures and its application to energy-saving load regulation

This study mainly focuses on the development of intelligent forecasting structures via a similar time method with historical load change rates for the hourly, daily and monthly load forecasting simultaneously based on the basic frameworks of fuzzy neural network (FNN) and particle swarm optimization (PSO). In the regulative aspect of network parameters, conventional back-propagation (BP) and PSO tuning algorithms are used, and varied learning rates are designed in the sense of discrete-time Lyapunov stability theory. The performance comparisons of different intelligent forecasting structures including neural network (NN) structure with BP tuning algorithm (NN-BP), FNN structure with BP tuning algorithm (FNN-BP), FNN structure with BP tuning algorithm and varied learning rates (FNN-BP-V), FNN structure with PSO tuning algorithm (FNN-PSO) and newly-designed adaptive PSO (APSO) structure are verified by numerical simulations. In order to verify the effectiveness of the superior APSO forecasting structure in practical energy-saving load regulation, the load forecasting during every 15 min is also given, and its result is used to manipulate the scheduled unloading control of a real case in Taiwan campus.

Collapse fragility assessment of steel roof framings with force limiting devices under transient wind loading

Steel structural frame is a popular structural form to cover large-span roof space and under high winds. Either part of the roof enclosure or the entire roof structure can be lifted off a building, particularly for low sloped roofs subject to wind-induced suction force. Collapse of roof could cause severe economic loss and poses safety risk to residents in the building. The buckling of members in a steel roof frame structure, which may lead to progressive collapse, may be dynamic in nature. This paper presents a fragility analysis of the collapse of steel roof frame structures under combined static and transient wind loading. Uncertainties associated with wind load change rate and member imperfections are taken into account in this study. A numerical example based on a Steel Joist Institute (SJI) K series joist was used to demonstrate the use of force limiting devices for collapse risk mitigation. For the presented fragility assessment of steel roof collapse, a Monte Carlo method combined with response surface approach was adopted, which greatly reduces the computation time and makes the Monte Carlo simulation feasible for probabilistic collapse analysis of steel roof frame structures.

Experimental and Analytical Study on the Operation Characteristics of the AHAT System

Operational flexibility, such as faster start-up time or faster load change rate, and higher thermal efficiency, have become more and more important for recent thermal power systems. The advanced humid air turbine (AHAT) system has been studied to improve operational flexibility and thermal efficiency of the gas turbine power generation system. Advanced humid air turbine is an original system which substitutes the water atomization cooling (WAC) system for the intercooler system of the HAT cycle. A 3 MW pilot plant, which is composed of a gas turbine, a humidification tower, a recuperator and a water recovery system, was built in 2006 to verify feasibility of the AHAT system.In this paper, ambient temperature effects, part-load characteristics and start-up characteristics of the AHAT system were studied both experimentally and analytically. Also, change in heat transfer characteristics of the recuperator of the 3 MW pilot plant was evaluated from Nov. 2006 to Feb. 2010. Ambient temperature effects and part-load characteristics of the 3 MW pilot plant were compared with heat and material balance calculation results. Then, these characteristics of the AHAT and the combined cycle (CC) systems were compared assuming they were composed of mid-sized industrial gas turbines.The measured cold start-up time of the 3 MW AHAT pilot plant was about 60 min, which was dominated by the heat capacities of the plant equipment. The gas turbine was operated a total of 34 times during this period (Nov. 2006 to Feb. 2010), but no interannual changes were observed in pressure drops, temperature effectiveness, and the overall heat transfer coefficient of the recuperator.

Nonlinear Multivariable Power Plant Coordinate Control by Constrained Predictive Scheme

A coordinated control strategy is often used to ensure a thermal power plant to have a higher rate of load change, but without violating the thermal constraints. Although model predictive control has been widely used for controlling power plant, handling input constraints is a major problem especially as these plants are nonlinear. Two alternative methods of exploiting the nonlinear predictive control are presented in this paper. One is the input-output feedback linearization technique based on a suitably chosen approximated linear model. The other is based on neuro-fuzzy networks to represent a nonlinear dynamic process using a set of local models. From the criteria based on the integral absolute errors and the relative optimization time for completing the simulation, it is shown that the performance of the coordinated control of a steam-boiler generation plant using these two nonlinear predictive methods are better than the conventional predictive method.