The Maximum Setup Time and Setup Cost of Achieving Just-in-Time System

The primary topic of operation management has turned to setup cost reduction because of the success of Just-in-Time (JIT) system. Setup cost is treated as a policy variable that can be reduced. A few papers prove that setup cost reduction will increase the number of setups and approach to JIT. However, those papers do not discuss the maximum setup time allowed that will successfully achieve to JIT. The Wagner-Whitin (WW) algorithm is known to produce optimal lot size for T-period dynamic lot-sizing problems. This paper develops an extension of the WW algorithm to establish a recursive model and find the sufficient and necessary conditions of yielding JIT. Furthermore, the limited maximum setup time that will yield JIT system is discussed. The maximum setup time of achieving JIT can be easily computed and understood in practice. The formula and table of the setup time allowed are obtained to act as a goal of reducing setup time in JIT system

Entanglement and quantum phase transition in alternating XY spin chain with next-nearest neighbour interactions

By using the method of density-matrix renormalization-group to solve the different spin-spin correlation functions, the nearest-neighbouring entanglement(NNE) and next-nearest-neighbouring entanglement(NNNE) of one-dimensional alternating Heisenberg XY spin chain is investigated in the presence of alternating nearest neighbour interactions of exchange couplings, external magnetic fields and next-nearest neighbouring interactions. For dimerized ferromagnetic spin chain, NNNE appears only above the critical dimerized interaction, meanwhile, the dimerized interaction effects quantum phase transition point and improves NNNE to a large value. We also study the effect of ferromagnetic or antiferromagnetic next-nearest neighboring (NNN) interactions on the dynamics of NNE and NNNE. The ferromagnetic NNN interaction increases and shrinks NNE below and above critical frustrated interaction respectively, while the antiferromagnetic NNN interaction always decreases NNE. The antiferromagnetic NNN interaction results to a larger value of NNNE in comparison to the case when the NNN interaction is ferromagnetic.Comment: 13 pages, 4 figures,. accepted by Chinese Physics B 2008 11 (in press

A Sensitivity Analysis of the SPACSYS Model

A sensitivity analysis is critical for determining the relative importance of model parameters to their influence on the simulated outputs from a process-based model. In this study, a sensitivity analysis for the SPACSYS model, first published in Ecological Modelling (Wu, et al., 2007), was conducted with respect to changes in 61 input parameters and their influence on 27 output variables. Parameter sensitivity was conducted in a 'one at a time' manner and objectively assessed through a single statistical diagnostic (normalized root mean square deviation) which ranked parameters according to their influence of each output variable in turn. A winter wheat field experiment provided the case study data. Two sets of weather elements to represent different climatic conditions and four different soil types were specified, where results indicated little influence on these specifications for the identification of the most sensitive parameters. Soil conditions and management were found to affect the ranking of parameter sensitivities more strongly than weather conditions for the selected outputs. Parameters related to drainage were strongly influential for simulations of soil water dynamics, yield and biomass of wheat, runoff, and leaching from soil during individual and consecutive growing years. Wheat yield and biomass simulations were sensitive to the 'ammonium immobilised fraction' parameter that related to soil mineralization and immobilisation. Simulations of CO2 release from the soil and soil nutrient pool changes were most sensitive to external nutrient inputs and the process of denitrification, mineralization, and decomposition. This study provides important evidence of which SPACSYS parameters require the most care in their specification. Moving forward, this evidence can help direct efficient sampling and lab analyses for increased accuracy of such parameters. Results provide a useful reference for model users on which parameters are most influential for different simulation goals, which in turn provides better informed decision making for farmers and government policy alike

A New Recursive Dynamic Lot-Sizing Model with Multi-Level Discount

The optimal solution of dynamic lot-sizing problem with multi-level discount is solved by integer programming model in the past papers. However, a complex computation and a large computer memory are generated. Due to the complexity and the big computer memory, the heuristic approaches and the variable neighborhood algorithm are usually adopted in the large-scale multi-level lot-sizing problem. This paper develops a model with a recursive relation between the adjacent periods, and to obtain an optimal solution when multi-level discount is considered. Four types of the feasible policies in the Dynamic Lot-Sizing model with multi-level discount are classified to develop the recursive relations. A few properties, theorems and algorithms are developed to show the recursion between the adjacent periods. The number of addition items will significantly be reduced. The recursive algorithm can significantly decrease the computational entries, comparison entries and computer memory and improve the computation efficiency

Galilean invariance of lattice Boltzmann models

It is well-known that the original lattice Boltzmann (LB) equation deviates from the Navier-Stokes equations due to an unphysical velocity dependent viscosity. This unphysical dependency violates the Galilean invariance and limits the validation domain of the LB method to near incompressible flows. As previously shown, recovery of correct transport phenomena in kinetic equations depends on the higher hydrodynamic moments. In this Letter, we give specific criteria for recovery of various transport coefficients. The Galilean invariance of a general class of LB models is demonstrated via numerical experiments

Experiment on interaction of abutment, steel H-Pile and soil in integral abutment jointless bridges (IAJBs) under Low-cycle Pseudo-static displacement loads

Soil-abutment or soil-pile interactions under cyclic static loads have been widely studied in integral abutment jointless bridges (IAJBs). However, the IAJB has the combinational interaction of soil-abutment and soil-pile, and the soil-abutment-pile interaction is lack of comprehensively study. Therefore, a reciprocating low-cycle pseudo-static test was carried out under an cyclic horizontal displacement load (DL) to gain insight into the mechanical behavior of the soil-abutment-pile system. Test results indicate that the earth pressure of backfill behind abutment has the ratcheting effect, which induced a large earth pressure. The soil-abutment-pile system has a favorable energy dissipation capacity and seismic behavior with relatively large equivalent viscous damping. The accumulative horizontal deformation in pile will be occurred by the effect of abutment and unbalance soil pressure of backfill. The test shows that the maximum horizontal deformation of pile occurs in the pile depth of 1.0b~3.0b of pile body rather than at the pile head due to the accumulative deformation of pile, which is significantly different from those of previous test results of soil-pile interaction. The time-history curve for abutment is relatively symmetrical and its accumulative deformation is small. However, the time-history curve of pile is asymmetrical and its accumulative deformation is dramatically large. The traditional theory of deformation applies only to the calculation of noncumulative deformation of pile, and the influence of accumulative deformation should be considered in practical engineering. A significant difference of inclinations in the positive and negative directions increases when the displacement load is relatively large. The rotation of abutment when bridge expands is larger than that when bridge contracts due to earth pressure of backfill

Surgical Treatment of Benign Spinal Cord Tumors

Benign spinal cord tumors (SCTs) are uncommon neoplasms that can arise within or adjacent to the spinal cord. Depending on their anatomical location, benign SCTs can be categorized as intramedullary, intradural-extramedullary, and extradural. The three most common benign SCTs are meningioma, nerve sheath tumors, and ependymoma. Both meningioma and nerve sheath tumors develop in the intradural-extramedullary compartment, while ependymoma occurs in the intramedullary space. Spinal meningiomas derive from arachnoidal cells and most commonly occur within the thoracic segment of the spine. Nerve sheath tumors, including schwannomas and neurofibromas, are closely associated with spinal nerves. Half of the spinal cord ependymomas arise in the lumbosacral segment or the filum terminale. Surgical treatment of large or symptomatic benign SCTs concentrates on total or subtotal resection of the tumors, which should be cautiously individualized based on the tumor location and histopathology. A curable complete resection should be achieved if possible while preserving the nervous function of the spinal cord and minimizing potential complications. Thoracic spinal roots may be sacrificed to acquire a total resection, yet cervical and lumbar nerve roots should be preserved prudently. Due to the vulnerable and complex anatomic nature of the spinal cord, maximal resection of the tumors can be achieved with the aid of appropriate intraoperative neural monitoring and meanwhile preserve nervous function