Shape Optimization of Free-form Shells Considering Strain Energy and Algebraic Invariants of Parametric Surface

p. 525-535A new approach is proposed for shape optimization of shell surfaces, where requirements on the aesthetic aspect and the constructability as well as the structural rationality are simultaneously considered in the problem formulation. The surface shape is modeled using B'ezier surface to reduce the number of variables, while the ability to generate moderately complex shape is maintained. To apply the new approach to shell structures that have various plan shapes, the surface shape which has a rectangle plan is modeled using a tensor product B'ezier surface, and the surface shape with an irregular plan is modeled using a triangular patch B'ezier surface. The strain energy is used to represent the mechanical performance, and the aesthetic aspects and smoothness of the surface are quantified by algebraic invariants of the surface. The developable surface that has high constructability is created by imposing appropriate algebraic invariants constraints. The e ectiveness of the present approach is confirmed through several numerical examples and the characteristics of the results are discussed.Fujita, S.; Ohsaki, M. (2009). Shape Optimization of Free-form Shells Considering Strain Energy and Algebraic Invariants of Parametric Surface. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/654

Worker flows and job flows: a quantitative investigation

Worker flows and job flows behave differently over the business cycle. The authors investigate the sources of the differences by studying quantitative properties of a multiple-worker version of the search/matching model that features endogenous job separation and intra-firm wage bargaining. Their calibration incorporates micro- and macro-level evidence on worker and job flows. The authors show that the dynamic stochastic equilibrium of the model replicates important cyclical features of worker flows and job flow simultaneously. In particular, the model correctly predicts that hires from unemployment move countercyclically while the job creation rate moves procyclically. The key to this result is to allow for a large hiring flow that does not go through unemployment but is part of job creation, for which procyclicality of the job finding rate dominates its cyclicality. The authors also show that the model generates large volatilities of unemployment and vacancies when a worker's outside option is at 83 percent of aggregate labor productivity.Employment ; Business cycles

Bosons after Symmetry Breaking in Quantum Field Theory

We present a unified description of the spontaneous symmetry breaking and its associated bosons in fermion field theory. There is no Goldstone boson in the fermion field theory models of Nambu-Jona-Lasinio, Thirring and QCD$_2$ after the chiral symmetry is spontaneously broken in the new vacuum. The defect of the Goldstone theorem is clarified, and the "massless boson" predicted by the theorem is virtual and corresponds to just a $free$ massless fermion and antifermion pair. Further, we discuss the exact spectrum of the Thirring model by the Bethe ansatz solutions, and the analytical expressions of all the physical observables enable us to understand the essence of the spontaneous symmetry breaking in depth. Also, we examine the boson spectrum in QCD$_2$, and show that bosons always have a finite mass for $SU(N_c)$ colors. The problem of the light cone prescription in QCD$_2$ is discussed, and it is shown that the trivial light cone vacuum is responsible for the wrong prediction of the boson mass.Comment: 56 pages,8 figure

A Scanning Electron Microscopy Study of Human Spleen: Relationship Between the Microcirculation and Functions

This paper reviews scanning electron microscope (SEM) observation of the circulatory system of the human spleen, based on our findings on freeze-cracked surfaces and vascular casts of the spleen. Central arteries ran straight in the white pulp without branching out follicular arteries and became penicillar arteries in the red pulp. Some penicillar arteries returned to the marginal zone. Some of their branches ended by opening there, whereas others passed through the marginal zone, entered the white pulp and became follicular arteries. Some of them took the shape of an arteriolar-capillary bundle . Most of the follicular capillaries ended opening into the marginal zone. The penicillar arteries usually ran straight or gently curved among the sinuses of the red pulp and opened into cordal spaces. Occasional arteries formed a labyrinthine structure of arterial channels which directly connected with thin sinuses. This study reveals that three different modes of arterial terminals are available in the human spleen: (1) arterial openings in the marginal zone which seem significant for presentation of antigens to the white pulp, (2) openings into the cords of Billroth which facilitate culling and pitting of blood cells, and (3) direct connections with sinuses (closed circulation) which account for the physiologically known quick blood flow through the spleen