Explore the vast range of titles available.

Outdoor air conditioning systems (ACS) are used as autonomic systems as well as in combined outdoor and indoor ACS of the variable refrigerant flow (VRF) type, with variable speed compressors (VSC) as their advanced version. Methods for determining the optimal value of refrigeration capacity and providing the maximum rate of the summarized annual refrigeration energy generation increment, according to its needs at minimum compressor sizes and rational values, are applied to reveal the reserves for reducing the designed (installed) refrigeration capacity, thus enabling us to practically achieve maximum annual refrigeration energy generation as the primary criterion at the second stage of the general design methodology previously developed by the authors. The principle of sharing the total thermal load on the ACS between the ranges of changeable loads for outdoor air precooling, and a relatively stable load range for further processing air are used as its basis. According to this principle, the changeable thermal load range is chosen as the object for energy saving by recuperating the excessive refrigeration generated at lowered loading in order to compensate for the increased loads, thereby matching actual duties at a reduced designed refrigeration capacity. The method allows us to determine the corresponding level of regulated loads (LRL) of SRC and the load range of compressor operation to minimize sizes.

This paper focuses on the application of speed-regulated compressors (SRCs) to cover changeable heat loads with high efficiency in conventional air conditioning systems (ACS) as well as in the more advanced variable refrigerant flow (VRF)-type outdoor and indoor ACS. In reality, an SRC is an oversized compressor, although it can operate efficiently at part loads. The higher the level of regulated loads (LRL) of the SRC, the more the compressor is oversized. It is preferable to reduce the size of the SRC by covering the peak loads and recouping the excessive refrigeration energy reserved at decreased actual loads within the range of regulated loads. Therefore, the range of changeable loads is chosen as the object to be narrowed by using the reserved refrigeration capacity. Thus, the general fundamental approach of dividing the overall heat load range of the ACS into the ranges with changeable and unchangeable loads, as previously developed by the authors, is applied for the range of primary changeable loads. Due to this innovative step, the principle of two-stage outdoor air conditioning according to changeable and unchangeable loads, also proposed by the authors, has been extended over the range of primary changeable loads to reduce the level of refrigeration capacity regulation and SRC size. To realize this, part of the changeable load range is offset by the reserved refrigeration capacity, leading to a reduction in the changeable load range and the SRC size by approximately 20% for temperate climatic conditions.

All numerical and analytical methods dealing with the calculating deformation of rock mass require deformation modulus (D f ) which is measured by direct or estimated by indirect approaches. Direct methods such as plate loading, flat jack, and dilatometer test have been developed, but they are generally expensive, time-consuming, and sometimes questionable. Furthermore, D f data is often limited and insufficient to estimate its statistics or not being available at all in many rock engineering projects. The empirical approach, as a practical tool, seems attractive and an alternative approach for D f determination. This experimental study presents a new empirical correlation set for the D f estimation based on 73 dilatometer tests, 27 laboratory tests, and related rock quality designation (RQD) which belonged to several dam/hydro-power projects. The statistical method and regression approach were used to analyze the data to develop a new correlation set in which about 70% of the database gathered for D f equations development and the remaining data (30%) for its validation process. Data were used to developing of the new empirical equation set; generally belong to the fair to good quality rock masses. The input data for the D f estimation consist of laboratory elasticity modulus (E l ), RQD, and loading level factor ( B n ). The statistical analysis revealed that D f has a significant dependence on the loading level factor. Also, E l and in-situ elasticity modulus ( E f ) would have the best correlation if the laboratory specimen was achieved from the dilatometer test zone. The R-square ( R 2  = 0.91) and the mean absolute relative prediction error (MARPE about 20%) verified the new correlation set. Finally, the estimated total deformation modulus from this paper’s relation set compared with the deformation modulus achieved from two existing empirical equations, and the main cause of differences was discussed.

On the basis of energy approach, we propose computational models for the evaluation of the period of subcritical growth of small fatigue cracks in elastoplastic bodies under the action of force and physicochemical factors. The obtained results were compared with the available literature data.

On the basis of the energy approach, we develop a computational model for the evaluation of the period of subcritical growth of corrosion-fatigue short cracks in elastoplastic plates under the action of long-term cyclic loads and corrosive media in terms of the specific energy components. The results are compared with the available literature data.

A series of triaxial creep tests were carried out on intact and cracked Maokou limestone specimens under multi-level loading and unloading cycles. A new data processing algorithm is proposed to analyze the experimental data and divide the total strain into instantaneous and creep strains, with the instantaneous strain consisting of instantaneous elastic and plastic strains and the creep strain consisting of viscoelastic and visco-plastic strains. The results show that the viscoelastic strain converges to a certain value with time, but the visco-plastic strain keeps increasing with time, although both tend to increase with higher deviatoric stress. The ratio of the visco-plastic strain to the total creep strain also tends to increase when the deviatoric stress is higher. The steady-state creep strain rate increases with higher deviatoric stress or lower confining pressure, and the relation between the steady-state creep strain rate and the deviatoric stress can be well described by an exponential expression. The results also show that the preexisting cracks in the limestone have a great effect on its creep properties. At the same confining pressure and deviatoric stress, the cracked limestone shows larger instantaneous and creep strains (especially visco-plastic strains), longer duration of primary creep, and a higher steady-state creep strain rate than the intact limestone.

The structural damage of rail vehicle bogie frames is mostly caused by fatigue cumulative damage under the action of multi-level complex loads. Under complex loads, the sequence effect and coupling effect between loads have a significant impact on structural fatigue damage. Meanwhile, the performance degradation of components during service also affects the damage accumulation and the remaining life of the structure. Traditional linear cumulative damage models and the Manson-Halford model ignore the influences of load sequence effect, load interaction, and structural degradation on fatigue life, leading to inaccurate remaining life predictions. By introducing degradation parameters to modify the Manson-Halford model, an improved nonlinear cumulative damage model is proposed, and its accuracy is verified by combining standard specimen fatigue test data. Finally, the improved cumulative damage model was applied to engineering practice in engineering to predict and evaluate the fatigue life of bogie frames.

Fatigue damage failure is a process where the mechanical properties of different materials continuously degrade under the action of cyclic loads. The cumulative analysis of fatigue damage has a significant impact on the service structure of major equipment. This paper starts from the mechanism of fatigue damage evolution, comprehensively considers the influence of the order of high-low cycle load mixed cyclic loading on the fatigue life performance, and based on the Manson-Halford nonlinear fatigue damage accumulation theory and the mechanism of relative cumulative damage, a new nonlinear damage accumulation fatigue life model is established, and a fatigue damage accumulation influencing factor Dcr is introduced to improve the prediction accuracy of the model. The new model proposed in this paper is verified through multi-level fatigue load data. By comparing the prediction results with other models under the same experimental conditions, the fatigue life prediction error precision of the new model is the best in similar cases, generally with an error precision between 10% and 20%, which proves the effectiveness and accuracy of the nonlinear damage accumulation model proposed in this paper. At the same time, the improved method in this paper has better stability while ensuring prediction accuracy.

This study investigated the effect of sustained loading on the cumulative damage of a newly developed smart cement-based self-healing composite material (SMA-ECC). SMA-ECC is composed of engineered cementitious composite (ECC) and shape memory alloy (SMA) fibers. A uniaxial compressive test with five predefined loading levels (0%, 30%, 40%, 50%, and 60% of compressive strength) was conducted on SMA-ECC hollow-cylindrical specimens and ECC control hollow-cylindrical specimens. The cumulative damage was mainly determined by changes in the total water absorption of different groups of specimens during three different periods (not loaded, at a predefined loading level, and after unloading). A normalized water content index was proposed to couple the effects of self-healing, sustained loading, and cumulative damage. The test results indicate that the cumulative water absorption of SMA-ECC was 35% lower than that of ECC, which may indicate less irreparable damage. In addition, the self-healing ability of SMA-ECC specimens under different compression load levels was evaluated through normalized water content analysis. SMA-ECC exhibited a 100% repair rate at load levels of 30% and 40%. At a higher load level of 60%, the repair rate of SMA-ECC was 76%. These results collectively emphasize the significant impermeability and self-healing performance of SMA-ECC after unloading.

Emergency Department (ED) crowding is recognized as a national crisis. Load-leveling is the process of transferring patients between campuses in the same hospital system for admission to redistribute patient capacity. Our study evaluates the impact of this load-leveling on ED throughput from the transferred patient perspective and on ED operations to evaluate operational benefits and drawbacks. We performed a retrospective observational study on two EDs in a single health system. These EDs see more than 140,000 visits annually in the same city. Patients were categorized as transferred to the other campus or admitted to the same campus. Primary outcomes focused on the patients who were load-leveled, examining their boarding times and the effect of load-leveling on their inpatient length-of-stay. Secondary outcomes focused on ED throughput. A total of 42,046 admissions were included. Of these, 5520 (13.1 %) were load-leveled for admission, while the remaining 36,526 (86.9 %) were kept at the same campus. Load-leveled patients had shorter boarding times by 7.8 h (95 % CI −8.35, −7.31) but no significant difference in inpatient length-of-stay. Load-leveling also reduced door-to-room times and the risk of leaving without being seen, without significant changes in boarding time. Load-leveling decreases the boarding times and creates capacity for new patients to be seen. As boarding times continue to climb nationally, load-leveling can be a tool for hospital systems to improve patient throughput.