Load Criteria Research Articles

PENGOLAHAN AIR LIMBAH DENGAN SISTEM REAKTOR BIOLOGIS PUTAR (ROTATING BIOLOGICAL CONTACTOR) DAN PARAMETER DISAIN

A rotating biological contactor (or RBC) is a type of fixed media filter which removes both organic matter and ammonia from water. It can be added to a packaged plant for more efficient ammonia removal, replacing the aerator in both location and function.The RBC consists of a series of rotating discs. These discs are coated with a biological slime like the slime on rocks in a healthy stream. This slime is rotated through the air and and then through the wastewater so that it picks up oxygen in the air and breaks down B.O.D. in the wastewater. Since the discs rotate through the air, there is no need to pump air into the wastewater. And since the slime stays on the discs, there is no need to recycle sludge. The present study describes basic consideration of rotating biological contactor (RBC) system for wastewater treatment. The design of an RBC system must include the following consideration sach as organics and surface loading criteria, staging of RBC units, peripheral velocity, temperature, effluent characteritics and secondary clarifier. The RBC system have some advantages : smaller basin, less upset, high loading rate, nitrification/de-nitrification, high tolerance, low OM Cost, durable constructions, odorless, no noise, and stable sludge characteristics. Kata Kunci : Reaktor bioloigis putar, air limbah, parameter disain.

An efficient, robust and automatic overlapping grid assembly approach for partitioned multi-block structured grids

An efficient, robust and fully automatic grid assembly method on multi-block cell-centered structured grids for massively parallel computation is proposed in this paper. Compared with the traditional serial algorithm, the new approach eliminates the complex irregular boundaries created during the grid partition and avoids the large load imbalance caused by the large variation of grid-block overlapping. The main task of the overlapping grid assembly is to categorize all grid points into field points, fringe points and hole points. As to the main processes of the overlapping grid assembly, for hole cutting, an improved hole map method is applied to accurately identify the hole points located on the wall boundary with less memory cost. For donor search which is the most complex process on account of the irregular distribution of the partitioned multi-block structured grids in a parallel computation environment, the Alternating Digital Tree (ADT) is utilized to find out the potential donor cells quickly for query points. Besides, to achieve better overlapping quality, the wall distance criterion is implemented for overlapping optimization. In addition, two load balance algorithms are designed to solve the imbalance problem of overlapping grid assembly. Two test cases are applied to test the new overlapping grid assembly algorithm and the results show that the new overlapping grid assembly algorithm can deal with large-scale simulation of vehicles. The comparison of total time and speed-up among three algorithms manifests that the initial load balance algorithm using query point number as load criterion is not reliable while the improved load balance algorithm achieves good speed-up and least runtime. Meanwhile, the maximum proportion the improved load balance algorithm takes in one physical unsteady step in wing-pylon-store separation test case is less than 6.1%.

A New Failure Load Criterion for Large-Diameter Under-Reamed Piles: Practical Perspective

Sustainable performance of heavy structures such as tanks, storage yards and tall buildings often rely on an efficient transfer of vertical and lateral loads to underlying ground. If the foundation soil does not have sufficient strength, the piles may be belled out (under-reamed) at the base, often termed as large-diameter belled piles (LDBPs). In reality the deformation and failure mechanism of LDBPs are significantly different and are influenced by the nature of foundation soil. However, in the absence of appropriate design guidelines, LDBPs are simply treated as conventional straight piles, often ignoring enlarged base. To access effects of enlarged base on load-deformation behavior, full-scale load tests are conducted on several LDBPs. A novel interpreted failure load criterion is proposed for LDBPs. The general applicability of this criterion is verified using the data from nine independent pile load tests retrieved from four different projects across China. Adopting the proposed method, provision of a much effective and economic design for LDBPs is feasible in comparison with the criteria currently prevalent in practice.

Critical plane and multiaxial criteria for in-phase and antiphase cyclic loading

Analytical solutions are obtained for determining of the critical plane orientation for a multiaxial stress state. This critical plane is the plane of initial development of fatigue damage under cyclic loading. The cases of in-phase and antiphase cyclic loading are considered for the classical fatigue range (low-cycle and high-cycle fatigue). Generalizations of the Findley fatigue criterion are proposed taking into account the orientation of critical plane for modes of very-high-cycle fatigue under in-phase and antiphase cyclic multiaxial loading. These generalizations are based on the similarity of the left and right branches of the bimodal fatigue curve. A procedure for determining the parameters of the generalized criterion is described according to the data of two uniaxial fatigue tests for tension-compression at various coefficients of the asymmetry of the cycle.

Proportionally and non-proportionally perturbed fatigue of stainless steel

Computational fluid dynamics and finite element based simulation of the cyclic thermal shock loading caused by turbulent mixing of water of different temperatures in the primary cooling system of a nuclear power plant, suggest a specific kind of non-proportional multi-axial fatigue loading exists on the inner surface cooling structures. Stress controlled experiments mimicking these loading conditions were designed and run on an axial-torsional fatigue testing system. The cyclic loading observed in the finite element simulations consists of the superposition of proportional loading and a second, non-proportionality inducing component, the latter with a substantially lower amplitude and running at a higher cycling frequency. The amplitude of the non-proportionality inducing loading component is of a magnitude so small that the fatigue loading criteria, typically used in engineering standards for nuclear power plant safety, do not recognize the difference with the reference loading without this component. However, first experimental results show that the endurance limit of stainless steel of grade 316L is reduced by this additional loading, which we name non-proportional fatigue noise. The fact that the endurance limit is unexpectedly lowered is a non-conservative safety issue that challenges the currently existing criteria used to estimate the fatigue damage for this type of loading.

Assessment of Replacement Bridge using Proof Load Test

This work begins with an overview of the condition assessment of old bridge and explained reasons for demolishing of the bridge. Briefly presented flexural analysis of two stage post-tensioned prestressed concrete girder, which will be replace the old (new bridge). Construction of I-girder and composite girder at first stage and second stage prestressing respectively is explained with figures. Assessment of the load-caring capacity of the one span of the replacement bridge with simple supports using proof load test is presented which is mandatory according to Indian standards. Weighted sand bags were used to load the bridge up to a predetermined service load with impact factor. Deflections of the I-girders of the bridge were measured at selected locations along and across the bridge span and compared with computed values. Linear response was observed during loading and unloading. Considering the load test results, theoretical estimation and criteria as stipulated in codes of practice, it can be inferred that prestressed concrete I-girder bridge span has adequate capacity to carry the loads and hence, deemed to have passed the test.

Effects of simultaneous compression and one-sided heat flux on the time to failure of carbon fiber-reinforced polymer composites

The time to failure of carbon fiber-reinforced polymer composites is investigated during simultaneous compression and one-sided thermal degradation from a constant heat flux. The purpose of this investigation is to determine the rate of thermal degradation and mechanical property loss from fire exposure by observing the time to failure during simultaneous compression loading. A custom compression test fixture is designed and validated for use under thermomechanical loading. Testing is conducted on CFRP samples of varying thicknesses and quasi-isotropic layups. Test conditions are adjusted for a range of heat fluxes and compressive loads. Test parameters are isolated to observe individual impacts on time to failure. In each case, decreasing exponential trends are observed. High heat fluxes and high compressive loads result in shorter failure times. Temperature profiles are created based on heat flux exposure time and the position through the material thickness in order to determine failure criteria for thermomechanical loading. An empirical model is created to extrapolate and predict failure times using a stretched exponential function, based on mechanical preload, heat flux, and material thickness.

Mathematical model of energy conversion mechanism in screw centrifugal pump based on load criteria of blade airfoil

PurposeTo analyze the work principle and capacity of energy conversion in each segment of profile lines, the energy transfer from impeller to transmission medium is separated into head coefficient and load coefficient to analyze the energy transfer process. The concepts of airfoil lift coefficient and drag coefficient are used; the third manifestation of the Euler equations is used as well.Design/methodology/approachThe numerical simulation of energy conversion mechanism based on load criteria of vane airfoil has been established in screw centrifugal pump to explain its energy conversion mechanism in an impeller. Upon this basis, the velocity and pressure along the entire blade are investigated through the numerical simulation of internal solid–liquid flow in the pump. The energy conversion process under load criteria in the blade airfoil has also been obtained.FindingsThe research suggests that the mathematical model of energy conversion mechanism based on the load criteria of the vane airfoil is reliable in the screw centrifugal pump. The screw centrifugal blade has twice or even several times the wrap angle than the ordinary centrifugal blade. It is a large wrap angle that forms the unique flow channel which lays the foundation for solid particles to pass smoothly and for soft energy conversion. At the same time, load distribution along the profile line on the long-screw centrifugal blade is an important factor affecting the energy conversion efficiency of the impeller.Originality/valueThe quantitative analysis method of energy in the screw centrifugal pump can help the pump designer improve certain features of the pump and shorten the research cycle.

The Study of Liquefaction Time Stages due to a Short Duration Shaking

During the 2006 Yogyakarta earthquake, liquefactions were massively found in Opak River, Yogyakarta, Indonesia. Learning from those events, an experimental study of liquefaction using shaking table was performed, especially to investigate the effect of short shaking duration to liquefaction potential. Several experimental tests were performed under varied accelerations (0.3g, 0.35g, and 0.4g) and vibration frequencies (1.4 Hz, 1.6 Hz, and 1.8 Hz), with a short shaking duration of 8 seconds. The liquefaction parameter used in this study was the excess pore water pressure ratio. The results revealed that liquefaction occurs in every loading criteria and the short shaking duration applied on each loading influences time stages of liquefaction, i.e. the liquefaction duration, the initial time of liquefaction, and the initial time of pore water pressure dissipation. In addition, the dynamic loads applied in a short duration influenced the maximum excess pore water pressure ratio.

Assessment of aortic valve calcium load by multidetector computed tomography. Anatomical validation, impact of scanner settings and incremental diagnostic value

ObjectivesTo validate aortic valve calcium (AVC) load measurements by multidetector row computed tomography (MDCT), to evaluate the impact of tube potential and slice thickness on AVC scores, to examine the accuracy of AVC load in distinguishing severe from nonsevere aortic stenosis (AS) and to investigate its effectiveness as an alternative diagnosis method when echocardiography remains inconclusive. MethodsWe prospectively studied 266 consecutive patients with moderate to severe AS who underwent MDCT to measure AVC load and a comprehensive echocardiographic examination to assess AS severity. AVC load was validated against valve weight in 57 patients undergoing aortic valve replacement. The dependence of AVC scores on tube potential and slice thickness was also tested, as well as the relationship between AVC load and echocardiographic criteria of AS severity. ResultsMDCT Agatston score correlated well with valve weight (r = 0.82, p < 0.001) and hemodynamic indices of AS severity (all p < 0.001). Ex-vivo Agatston scores decreased significantly with increasing tube potential and slice thickness (repeated measures ANOVA p < 0.001). Multivariate analysis identified mean gradient, the indexed effective orifice area, male gender and left ventricular outflow tract cross-sectional area as independent correlates of the in-vivo AVC load. ConclusionsMDCT-derived AVC load correlated well with valve weight and hemodynamic indices of AS severity. It also depends on tube potential and slice thickness, thus suggesting that these parameters should be standardized to optimize reproducibility and accuracy.

Measuring the Nursing Work Environment in Mainland China: Further Development of the Chinese Nursing Work Environment Scale.

For the stabilization of the nursing profession in mainland China, a valid and reliable nursing work environment instrument, grounded in China's context, should be developed to better provide rigorous evidence for policy makers. The purpose of the current research was to further develop a scale that could capture the characteristics of the nursing work environment in mainland China. A convenience sample of 542 nurses employed in a tertiary hospital of mainland China completed the 108-item Chinese Nursing Work Environment (C-NWE) Scale (1st ed.). Items that did not differentiate between respondents with the highest and lowest 27% of total scores and those that did not meet criteria for factor loadings were set aside. Exploratory factor analysis based on the maximum likelihood method was used to identify the structure of the scale. The chi-square test was used to evaluate model fit, and expert review was conducted to test content validity. Reliability was estimated using Cronbach's alpha coefficient. The revised C-NWE Scale, which consists of nine subscales and 47 items, is a simplified version of the C-NWE (1st ed.). Using exploratory maximum likelihood factor analysis, the normed chi-square fit index for a nine-factor solution was 1.97. The content validity index for the total scale was 0.93; Cronbach's alpha was .94. Initial evidence of the psychometric properties of C-NWE scores was presented. Further studies could be conducted in various settings to identify the C-NWE Scale's validity and reliability.

Beam Experiments on Acceptance Criteria for Bridge Load Tests

Loading protocols and acceptance criteria are available in the literature for load tests on buildings. For bridges, proof load tests are interesting when crucial information about the structure is missing, or when the uncertainties about the structural response are large. The acceptance criteria can then be applied to evaluate if further loading is acceptable, or could lead to permanent damage to the structure. To develop loading protocols and acceptance criteria for proof loading of reinforced concrete bridges, beam experiments were analyzed. In these experiments, different loading speeds, constant load level times, numbers of loading cycles, and required number of load levels were evaluated. The result of these experiments is the development of a standard loading protocol for the proof loading of reinforced concrete bridges. Based on these limited test results, recommendations for acceptance criteria are also proposed.

Differential Impact of Anastomotic Leak in Patients With Stage IV Colonic or Rectal Cancer: A Nationwide Cohort Study.

Anastomotic leak has a negative impact on the prognosis of patients who undergo colorectal cancer resection. However, data on anastomotic leak are limited for stage IV colorectal cancers. The purpose of this study was to investigate the impact of anastomotic leak on survival and the decision to administer chemotherapy and/or metastasectomy after elective surgery for stage IV colorectal cancer. This was a nationwide, retrospective cohort study. Data were obtained from the Danish Colorectal Cancer Group, the Danish Pathology Registry, and the National Patient Registry. Patients who were diagnosed with stage IV colorectal cancer between 2009 and 2013 and underwent elective resection of their primary tumors were included. The primary outcome was all-cause mortality depending on the occurrence of anastomotic leak. Secondary outcomes were the administration of and time to adjuvant chemotherapy, metastasectomy rate, and risk factors for leak. Of the 774 patients with stage IV colorectal cancer who were included, 71 (9.2%) developed anastomotic leaks. Anastomotic leak had a significant impact on the long-term survival of patients with colon cancer (p = 0.04) but not on those with rectal cancer (p = 0.91). Anastomotic leak was followed by the decreased administration of adjuvant chemotherapy in patients with colon cancer (p = 0.007) but not in patients with rectal cancer (p = 0.47). Finally, anastomotic leak had a detrimental impact on metastasectomy rates after colon cancer but not on resection rates of rectal cancer. Retrospective data on the selection criteria for primary tumor resection and metastatic tumor load were unavailable. The impact of anastomotic leak on patients differed between stage IV colon and rectal cancers. Survival and eligibility to receive chemotherapy and metastasectomy differed between patients with colon and rectal cancers. When planning for primary tumor resection, these factors should be considered.

A Hybrid CKF-NNPID Controller for MIMO Nonlinear Control System

This paper presents a detailed study to demonstrate the online tuning dynamic neural network PID controller to improve a joint angle position output performance of 4- joint robotic arm. The proposed controller uses a new updating weight rule model of the neural network architecture using multi-loop calculation of the fusion of the gradient algorithm with the cubature Kalman filter (CKF) which can optimize the internal predicted state of the updated weights to improve the proposed controller performances, called a Hybrid CKF-NNPID controller. To evaluate the proposed controller performances, the demonstration by the Matlab simulation program is used to implement the proposed controller that connects to the 4-joint robotic arm system. In the experimental result, it shows that the proposed controller is a superior control method comparing with the other prior controllers even though the system is under the loading criteria, the proposed controller still potentially tracks the error and gives the best performances.

Evaluation of limit load analysis for pressure vessels - Part II: Robust methods

Determining limit load for a pressure bearing structure using elastic-plastic finite element analysis was computationally very expensive. A series of robust methods using elastic modulus adjustment techniques (EMAP) to identify the limit load directly were proposed. The numerical implementation of the robust method had the potential to be an attractive alternative to elastic-plastic finite element analysis since it was simple, and required less computational effort and computer storage space. Another attractive feature was that the method provided a go/no go criterion for the limit load, whereas the results of an elastic-plastic analysis were often difficult to interpret near the limit load since it came from human sources. To explore the performance of the method further, it was applied to a number of configurations that include two-dimensional and threedimensional effects. In this study, limit load of cylinder with nozzle was determined by the robust methods.

Performance-based Design of Tall Building Envelopes using Competing Wind Load and Wind Flow Criteria

This paper investigates performance-based tall building design and the development of a combined architectural-urban design method focusing on the effects of wind loads on- and wind flows around tall buildings. The paper provides an overview of related buildings codes and city development design guidelines that define requirements for structural façade wind loading and urban ventilation. A review of performance-based design methods for the generation, analysis and optimization of buildings is also presented. Within this frame, an approach to performance-based tall building envelope design is proposed. The approach is aimed at addressing wind loading and wind impact requirements based on generative parametric modelling and performance analysis that integrates physical parameters at the architectural and urban scales and performance criteria can support filtering and optimization relative to prevailing wind conditions.

基于Workbench对核级蝶阀的抗震分析

本文介绍了抗震分析载荷组合和评价标准及方法，并通过workbench的ANSYS模块对核级蝶阀的抗震性能进行验证。通过抗震分析，本文不但验证了阀门的结构完整性，还使得在设计阶段就可验证和优化阀门的薄弱区域。这降低了企业成本，缩短了产品开发周期。 This paper introduces the load combination, criteria and methods of evaluation for seismic analysis, and verifies the seismic performance of the nuclear safety-Related butterfly valve by the ANSYS module of workbench. It has not only verified the structural integrity of the valve, but also verified and optimized the weak area of the valve at the design stage based on seismic analysis. It reduces the enterprise cost and shortens the product development cycle through the method of seismic analysis.

Elasto-plastic Damage Analysis Based on Strain-space Plasticity

Continuum Damage Mechanics (CDM) is an evolving area of Solid Mechanics. CDM has been found to have great potential. Most of the plastic damage models attempt to bring together the theories of plasticity and CDM. In this paper, the strain-space plasticity theory is implemented for elastic-plastic damage material model in the framework of non-linear finite element analysis. In the stress space plasticity models the yield surface, loading and unloading criteria, flow rule, and often hardening rules are defined in stress space. The research paper presents a set of systematic formulations for the theory of isotropic elasto-plastic ductile damage. Lemaitre's model is considered for the damage evolution growth. The plastic flow and damage flow are coupled within the potential function. In order to verify the formulations presented, numerical results are compared with the results available in literature.

Theoretical predictions of fracture and springback for high tensile strength steel sheets under stretch bending

Abstract For the last two decades, strong demands for the light weighted structures of automobiles have been increasing in all over the world. In order to satisfy the demands, the high strength steel sheets (hereafter HSSs) have been widely utilized in the various automobile related companies. However, for the companies, it is still one of the hard tasks to apply HSSs for the automobile parts with complex shapes, due to low ductility and large springback of the HSSs. In the present research, we assumed fracture limits in stretch bending are theoretically obtained with the assumption that fracture occurs when stretching force reaches its maximum value. The authors proposed an explicitly theoretical analysis method based on the maximum load criterion that can easily and rapidly allow us to predict the fracture and springback of HSSs by using two no dimensional parameters (limited wall stretch L/L0 (L: limit wall length of a sheet, L0: initial wall length) and bending radius t/R (t: sheet thickness, R: bending radius)). For the evaluations of this method, the comparisons between stretching bending experiments of HSSs and the corresponding theoretical calculations were conducted. From the comparisons, the calculated results by our proposed method have good agreements with the experimental observations.

Self-adaptive stress accelerated life testing scheme

The initial stress of step-up stress accelerated life tests is commonly too low which is not very efficient when used in accelerated life testing. Though the efficiency of step-down stress accelerated life tests has improved in general, researchers and engineers may have to deal with the failure mechanism changing due to the high starting stress. In this paper, we develop a new accelerated life test scheme, called self-adaptive stress accelerated life tests (SAS-ALT), with considerations of the relative stress loading criterion. We also develop algorithm steps for implementation of SAS-ALT. We formulate and discuss an optimization function of the proposed SAS-ALT that minimizes the variance of the system life time using the maximum-likelihood method, Fisher matrix, and accelerated model. Some factors of the SAS-ALT, such as stress and failure number, were chosen depending upon the optimum function. We also discuss an application of the computer numerical control system based on real failure data to illustrate step-by-step reliability accelerated life test design policy based on our proposed SAS-ALT scheme.