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Cognitive load theory has been traditionally described as involving three separate and additive types of load. Germane load is considered as a learning-relevant load complementing extraneous and intrinsic load. This article argues...
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Cognitive load theory has been traditionally described as involving three separate and additive types of load. Germane load is considered as a learning-relevant load complementing extraneous and intrinsic load. This article argues that, in its traditional treatment, germane load is essentially indistinguishable from intrinsic load, and therefore this concept may be redundant. Contrary to extraneous and intrinsic load, germane cognitive load was added to the cognitive load framework based on theoretical considerations rather than on specific empirical results that could not be explained without this concept. The design of corresponding learning activities always required methods and techniques external to the theory. The article suggests that the dual intrinsic/extraneous framework is sufficient and non-redundant and makes boundaries of the theory transparent. The idea of germane load might have an independent role within this framework if (as recently suggested by John Sweller) it is redefined as referring to the actual working memory resources devoted to dealing with intrinsic rather than extraneous load.
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Precooling is a recognized technique for reducing cooling energy in buildings during peak hours by shifting load to off-peak hours. This technique is particularly effective in buildings with high thermal mass, because of their lar...
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Precooling is a recognized technique for reducing cooling energy in buildings during peak hours by shifting load to off-peak hours. This technique is particularly effective in buildings with high thermal mass, because of their large thermal energy storage capacity, and in commercial buildings due to their variable electricity pricing based on time-of-use rates. Precooling in residential buildings has been a matter of limited interest in the past because of their low thermal mass and typically uniform electricity pricing rate. While previous studies on precooling primarily focused on cost savings, an important aspect of precooling is the thermal load modulation, which could be very effective in managing peak demand in lightweight residential buildings integrated with thermal energy storage systems. In this study, we examine different precooling strategies to manage the heat gains in lightweight building walls integrated with phase-change materials. We create nine different precooling profiles by controlling the interior temperature, and then evaluate the influence of the precooling profiles on four key building energy performance parameters: total heat gain, peak heat gain, maximum heat gain during peak hours, and time at which peak occurs. To thoroughly understand the fundamental physics, we first consider hypothetical climates and obtain the optimal precooling strategy required to achieve maximum peak shedding and shifting while minimizing the total heat gains. We then extend the model to Baltimore, Maryland, and estimate the benefits of the optimized precooling strategy under real conditions. The optimal precooling strategy proposed in this study can shift the peak heat gain by up to 14 h, thereby reducing the heat gain during peak period by up to 95%, at the expense of 23% increase in the total heat gains.
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Barriers are purposely omitted from the structural analysis for bridge design or load rating. They are not considered as primary structural members because, after a forceful collision, they may sustain some structural damage and w...
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Barriers are purposely omitted from the structural analysis for bridge design or load rating. They are not considered as primary structural members because, after a forceful collision, they may sustain some structural damage and would no longer strengthen the bridge deck. However, when completely intact, these secondary structural members do affect the distribution of applied loads, which is of interest to permitting agencies, such as the Florida Department of Transportation (FDOT). For a prestressed concrete segmental box girder bridge, both design and load rating (for oversized load permits) are determined by longitudinal and transverse analyses without considering the influence of the barriers. For the transverse analysis, the maximum moment generated from the live load is traditionally calculated from Homberg charts. These influence surfaces are based on plate behavior and idealized support conditions and are generally conservative. This moment estimation and the lack of consideration for the barriers create a conservative transverse design and load rating for the bridge. In this study, finite-element bridge models show how much the barrier affects transverse live-load moments on a prestressed concrete segmental box girder bridge. Data obtained from these models were compared with measurements obtained from a FDOT load test and also with predictions made from Homberg influence surfaces, which are often used by engineers in design. The results show that a continuous barrier reduced transverse moments, a jointed barrier behaved more similarly to no barrier, and Homberg design moments were generally conservative. In addition, the joint in the barrier played a large role in transverse live-load effects. (C) 2016 American Society of Civil Engineers.
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The purpose of this study was to (a) assess the usefulness of volume load (VL), session rate of perceived exertion (SRPE), RPE load (RPEL), and a modified RPEL (RPEL-2) to estimate internal load from resistance exercise (RE) and (...
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The purpose of this study was to (a) assess the usefulness of volume load (VL), session rate of perceived exertion (SRPE), RPE load (RPEL), and a modified RPEL (RPEL-2) to estimate internal load from resistance exercise (RE) and (b) further assess the interactions between SRPE, VL, and RE intensity. Twelve healthy men (25 +/- 4 years) completed RE sessions at 55, 70, and 85 1 repetition maximum (1RM). Volume load, SRPE, RPEL, and RPEL-2 for each session were calculated, compared, and correlated with change values (Delta) for blood lactate and salivary cortisol. There were substantial increases in all measures of training load with progressive decreases in % 1RM. There were clear substantial increases in Delta lactate and Delta cortisol after RE at 55% 1RM when compared with 70 and 85%. Withinsubject correlations with Delta cortisol were small with SRPE (r = 0.25; 90% confidence limits; +/- 0.32), RPEL (r = 0.23; +/- 0.32), RPEL-2 (r = 0.19; +/- 0.32), and trivial for VL (r = 0.01; +/- 0.28). Correlations with Delta lactate were moderate with VL (r = 0.42; +/- 0.29) and RPEL-2 (r = 0.38; +/- 0.29), and small with SRPE (r = 0.25; +/- 0.32) and RPEL (r = 0.25; +/- 0.32). Correlation between SRPE and VL was large (r = 0.55; 60.25). Although Delta lactate and Delta cortisol did not follow the same trends as measures of workload, VL may be superior to estimate internal load from RE, particularly when measured through Delta lactate. When viewing training load globally, RPEL-2 may offer the greatest advantage. Finally, our results suggest that SRPE seems to be more closely related to VL than % 1RM.
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This paper describes the development of a unique rolling load simulator (ROLLS) for testing bridge superstructure with a footprint up to 4mx17 m, and its first application to test a full-scale 1220 mm x 900 mm x 16000 mm B900 pres...
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This paper describes the development of a unique rolling load simulator (ROLLS) for testing bridge superstructure with a footprint up to 4mx17 m, and its first application to test a full-scale 1220 mm x 900 mm x 16000 mm B900 prestressed concrete box girder. This facility at Queen's University in Kingston, Ontario, is the first of its kind in Canada. ROLLS can apply cyclic loading in a controlled laboratory environment, under realistic highway scale 'rolling wheel loads', in lieu of the conventional 'pulsating stationary loads'. It has two half-axles of a large tandem, each comprising a dual 1140 mm diameter air-inflated tires spaced at either 1.2 or 2.4 m. Each half-axle can apply up to 125 kN, representing the heaviest half-axle load of the CL-625 design truck of the Canadian Highway Bridge Design Code (CHBDC). The maximum travel range and speed are 14.9 m and 6 m/s, respectively. A case study involving analysis of a bridge with eight adjacent B900 box girders of 27.6 m span was carried out prior to experimentally testing one of the girders using ROLLS. Load distribution analyses were conducted using both (i) a finite element model of the full bridge under various CL-625 truck loading configurations and (ii) the CHBDC load distribution method, and both agreed well. Scaling analysis of the girder load share was then conducted to account for shortening it to 16 m to fit in the laboratory, resulting in two-115 kN ROLLS design loads, 1.2 m apart. Multiple passes were conducted at various loads of 40%-100% of the design load, at speeds of 1-5 m/s to examine the machine and girder behaviours. It was found that the applied load fluctuates by less than 10% of full capacity and a 0.13 s/cycle time lag occurs. The measured girder deflection and elastic strains were 11%-20% lower than predicted theoretically. With the two half-axles assembly spaced at 1.2 m, the apparatus has the ability to complete three million cycles in approximately 4.5 months if ran continuously at 5 m/s.
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Purpose: To compare the clinical outcome of single, partial and full fixed implant-supported prostheses immediately loaded (within 48 h), early loaded at 6 weeks and conventionally loaded at 3 months (delayed loading).
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In blast engineering, many designs begin with simplified hand procedures with the loading parameters determined based upon a reflective surface of infinite size. Individual structural members such as columns have finite widths and...
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In blast engineering, many designs begin with simplified hand procedures with the loading parameters determined based upon a reflective surface of infinite size. Individual structural members such as columns have finite widths and should be considered as finite surfaces for blast loading calculations. A study was performed to investigate the effect of finite flange width on blast loadings on structural components. The diffraction of a blast wave around the leading edges of the cross section and the propagation of rarefaction waves from the leading edges to the column centerline leads to a more rapid reduction in reflected pressure than that of an infinite surface: a process that is widely known as clearing. A series of analyses were performed using the computational fluid dynamics code Air3d. Peak reflected pressures are not changed by the "finiteness" of the section, although the reflected impulse can be substantially reduced by clearing. For a given charge mass, held constant for a range of stand-off distances, R, impulse is approximately proportional to 1/R when considering an infinite surface. If clearing is considered, the reflected impulse is still proportional to 1/R, but can be 50% lower than the value computed for an infinite surface, which has significant implications for blast resistant design of structural components.
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The combination of dead load and live load is very important in design of bridge superstructure as. in practice, it controls the strength limit states. The basic set of load factors for the Strength I limit state is 1.25 for dead ...
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The combination of dead load and live load is very important in design of bridge superstructure as. in practice, it controls the strength limit states. The basic set of load factors for the Strength I limit state is 1.25 for dead load and 1.75 for live load and dynamic load. For design cases when the dead load dominates, i.e. for Strength IV limit state, the dead load factor is 1.5. The acceptability criterion for load and resistance factors in the AASHTO LRFD Code is closeness to the target reliability index, which is assumed to be 3.5 for steel and concrete girder bridges. However, the reliability analysis performed for a full range of dead load to live load ratios indicates that when live load is about 10-20% of the total load, the reliability indices are about 3.0 which is lower than the target value of 3.5. This is an indication that the reliability level is insufficient and there is a need for increasing load factors. On the other hand, for dead load constituting about 100% of the total load (i.e. no live load), the reliability index is much higher than 3.5, which means that the load factor 1.5 can be reduced. Therefore, it is proposed to change the current Strength IV load factors to dead load of 1.4 and live load factor 1.4. The result is a more uniform reliability level for all combinations of dead load and live load. The results of reliability analysis are presented in graphs.
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This paper presents a methodology for specifying the winter and summer peak-load limits for substation transformers that carry a temperature-sensitive load, taking into account the random nature of load and ambient temperature as ...
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This paper presents a methodology for specifying the winter and summer peak-load limits for substation transformers that carry a temperature-sensitive load, taking into account the random nature of load and ambient temperature as well as their correlation. With this methodology, we can easily and accurately specify the peak-load limits for each substation transformer once the historical ambient temperature and load data are available. Also, we can collectively specify the peak-load limits for the transformer of each cooling type (OA, OA/FA, or OA/FA/FA) in a geographic region based on the mean and standard deviation of ambient temperatures in that region. Such peak-load limits are useful for power system planning.
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Long-term forecasts of the aggregate electric load profile are crucial for grid investment decisions and energy system planning. With current developments in energy efficiency of new and renovated buildings, and the coupling of he...
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Long-term forecasts of the aggregate electric load profile are crucial for grid investment decisions and energy system planning. With current developments in energy efficiency of new and renovated buildings, and the coupling of heating and electricity demand through heat pumps, the long-term load forecast cannot be based on its historic pattern anymore. This paper presents part of an on-going work aimed at improving forecasts of the electric load profile on a national level, based on a bottom-up approach. The proposed methodology allows to account for energy efficiency measures of buildings and introduction of heat pumps on the aggregated electric load profile. Based on monitored data from over 100 non-residential buildings from all over Norway, with hourly resolution, this paper presents panel data regression models for heat load and electric specific load separately. This distinction is crucial since it allows to consider future energy efficiency measures and substitution of heating technologies. The data set is divided into 7 building types, with two variants: regular and energy efficient. The load is dependent on hour of the day, outer temperature and type of day, such as weekday and weekend. The resulting parameter estimates characterize the energy signature for each building type and variant, normalized per floor area unit (m(2)). Hence, it is possible to generate load profiles for typical days, weeks and years, and make aggregated load forecasts for a given area, needing only outdoor temperature and floor areas as additional data inputs.
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