Results 1 - 10 of 20893
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[en] The paper examines the impact of daylight saving time (DST) on electricity consumption in Jordan. Two types of analysis were done: the first analysis examines the impact of DST on the lighting loads based on a survey study made for residential and commercial sectors. The second examines the impact of DST on the over all electricity generation through analyzing the daily load curves (DLCs) before and after the DST onset and removal in 2000 and 2007. The results show that the application of DST during the year 2000 saves the electricity used for illumination by -0.73% but it increases the overall generation at the onset and removal of DST by 0.5% and 1.4% due to increase in the heating and cooling loads. The analysis of DLCs during the year 2007 shows similar effects as in the year 2000 except during the early morning period at the DST onset where DST decreases the demand during this time. The analysis shows that DST decreases the electricity demand at DST onset by 0.2% and increases it at DST removal by 0.3%. A possible decrease in the electricity consumption may take place if the DST is implemented from April to end of August.
[en] The present paper proposes comparative study between Double Wish-Bone and Macpherson Suspension system. The objective is achieved by using ANSYS simulation package. Dynamic and static loads are applied on the suspension systems. Various analysis such as Structural analysis with static as well as dynamic loading, Modal analysis and Transient analysis are carried out in order to study deflection, stress, frequency and strain of both the suspension systems and a thorough comparative study is accomplished. (paper)
[en] In this paper, in order to suppress the mechanical resonance and anti- resonance in the DC brushless motor-based AC speed servo system with two-mass mechanical motion load, the load speed observer with load disturbance estimating function, which is suitable for the load speed feedback compensation, is proposed. The auto-tuning control implementation based on fuzzy reasoning with the observer- based load speed feedback compensation is compared with conventional PI compensation scheme. The experimental results prove considerable reduction in mechanical vibration and show improved response characteristics of mechanical motion load system. (author)
[en] To study the load time history variation in the frequency domain, both Fourier transformation and response spectra were considered. Normal approximation (Central Limit Theorem) is employed to derive statistics for various confidence levels. Correlation factors on responses from reduced case applications are presented for various confidence levels. It is concluded that normal approximation with response spectral approach is the better method for determining the correlation factor for a pre-established confidence level, and that sufficient reliability on the structural responses may be achieved when reduced case applications are considered. This paper discusses methods of establishing correlation factors required for the adjustment of structural responses to achieve in acceptable confidence level. (orig./HP)
[en] Highlights: • Operation guidelines for TABS by considering the building load characteristics were suggested. • Operation guidelines can be used by field technicians other than automatic control system. • Comfort criteria and surface condensation risk during TABS operation were considered in operation guidelines. • The building load characteristics were analyzed through the dynamic energy simulation. • Thermal output from TABS were estimated through the thermal simulation. - Abstract: Since the end of the 1990s, thermally activated building systems (TABSs) have emerged as an energy-efficient and economically viable means of heating and cooling buildings. Because the temperature of the water that these systems use is very close to room temperature, TABSs are one of the most energy- and exergy-efficient types of heating/cooling systems. However, because TABSs have a high thermal inertia and respond only slowly to control inputs, it is very difficult to maintain the room air temperature within a narrow control band. Control methods and operational strategies have been the main concerns of previous studies. There is a limit to the thermal output that a TABS can provide, owing to the possibility of surface condensation forming and possible thermal discomfort of the occupants. Thus, carefully considered operational strategies and use guidelines are necessary when applying such systems. This study focuses on the development of operational guidelines for TABSs according to the heating and cooling load characteristics of a specific campus building. The load characteristics of the building were analyzed, after which load zones were defined according to the heating and cooling characteristics. Simultaneously, the thermal output of a TABS for heating and cooling was calculated with a range of supply water temperatures. Operational guidelines are suggested, classified by load zone
[en] Highlights: • Difference between Charpy and toughness mainly geometrical, strain rate secondary. • Modified Weibull parameter calibration method proposed using Energy Scaling Model. • Energy Scaling Model then extended to cover both static and dynamic loading. • Weibull modulus shown to be broadly independent of strain rate. • Energy Scaling Model suitable for relating Charpy energy to fracture toughness. - Abstract: Accurate prediction of fracture toughness from Charpy energy is challenging due to the differences between fracture toughness tests and Charpy tests, such as geometry (deep sharp crack vs. shallow blunt V-notch) and loading rate (quasi-static vs. dynamic). This paper uses experimental and numerical approaches to investigate whether the Weibull stress can be used to scale Charpy energy to fracture toughness in the lower transition region. A Weibull-stress based energy scaling model is proposed which is shown to accurately predict cleavage fracture at quasi-static loading rates. An extension of the energy scaling approach to dynamic loading conditions indicates that the Weibull modulus is independent of strain rate, and that quasi-statically derived moduli can be used to predict fracture toughness from a dynamically tested Charpy specimen. The paper concludes that the proposed energy scaling approach, and its extension to dynamic loading conditions, provides a suitable basis for relating Charpy energy to fracture toughness in the lower transition region.
[en] During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 104 to 4 × 104 s−1. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of this cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading
[en] This paper introduces the concept of probabilistic design of nuclear power plant components and illustrates the methodology and usefulness of the concept with a simple example. It discusses the fundamental relationship between load and resistance factors associated with load combination formats that may be used for design. The simple example consists of a simply supported pipe subjected simultaneously to internal pressure, dead weight and a velocity transient. Associated with each of these loads is a coefficient or load factor whose value is governed by the dispersion of the loading magnitudes and the desired reliability level of the component. The task is to find the optimal set of load factors which results in a design having a specified target reliability. The load factors were derived using an ensemble of forty combinations of pipe length and diameter and were evaluated for target limit state probabilities ranging from 1.003 x 10-2 for the 10-2 target to 1.076 x 10-8 for the 10-8 target. The mean limit state probability for the ensemble of pipes designed in accordance with NB.3652 of the ASME Code was 2.571 x 10-3 with a coefficient of variation of 0.859. Designs executed with load factors to meet a target limit state probability of 10-3 had a coefficient of variation of only 0.107. This demonstrates that the use of probabilistically derived load factors can result in designs having both assured and more consistent levels a probability. (orig./HP)
[en] In this study, the critical load and buckling of the single pile foundation subjected to the vertical load are investigated. Considering the second-order moment of the soil-structure interaction, the refined model of the single pile foundation is derived. Then, the critical load and buckling phenomenon of the single pile foundation is examined. Moreover, the effects of the vertical load and the foundation parameters on the critical load and buckling of the single pile foundation are systematically investigated