Internal and external axial corner flows

The inviscid, internal, and external axial corner flows generated by two intersecting wedges traveling supersonically are obtained by use of a second-order shock-capturing, finite-difference approach. The governing equations are solved iteratively in conical coordinates to yield the complicated wave structure of the internal corner and the simple peripheral shock of the external corner. The numerical results for the internal flows compare favorably with existing experimental data

Spin Bose-Metal phase in a spin-1/2 model with ring exchange on a two-leg triangular strip

Recent experiments on triangular lattice organic Mott insulators have found evidence for a 2D spin liquid in proximity to the metal-insulator transition. A Gutzwiller wavefunction study of the triangular lattice Heisenberg model with appropriate four-spin ring exchanges has found that the projected spinon Fermi sea state has a low variational energy. This wavefunction, together with a slave particle gauge theory, suggests that such spin liquid possesses spin correlations that are singular along surfaces in momentum space ("Bose surfaces"). Signatures of this state, which we refer to as a "Spin Bose-Metal" (SBM), are expected to be manifest in quasi-1D ladder systems: The discrete transverse momenta cut through the 2D Bose surface leading to a distinct pattern of 1D gapless modes. Here we search for a quasi-1D descendant of the triangular lattice SBM state by exploring the Heisenberg plus ring model on a two-leg strip (zigzag chain). Using DMRG, variational wavefunctions, and a Bosonization analysis, we map out the full phase diagram. Without ring exchange the model is equivalent to the J_1 - J_2 Heisenberg chain, and we find the expected Bethe-chain and dimerized phases. Remarkably, moderate ring exchange reveals a new gapless phase over a large swath of the phase diagram. Spin and dimer correlations possess particular singular wavevectors and allow us to identify this phase as the hoped for quasi-1D descendant SBM state. We derive a low energy theory and find three gapless modes and one Luttinger parameter controlling all power laws. Potential instabilities out of the zigzag SBM give rise to other interesting phases such as a period-3 VBS or a period-4 Chirality order, which we discover in the DMRG; we also find an interesting SBM state with partial ferromagnetism.Comment: 30 pages, 23 figure

Balancing food waste and sustainability goals in online food delivery: Towards a comprehensive conceptual framework

Increasing food waste is a major threat to sustainability and food security. Recognizing the issue, the United Nations Sustainable Development Goal (SDG) 12 mandates reducing global food waste by 50 percent by 2030. This situation has also given impetus to academic research on consumer food waste in both household and out-of-home settings. However, food delivery apps (FDAs) remain under-researched from this perspective. This is a serious gap because operating under a business model that inherently facilitates food over-ordering, FDAs can be a major source of food waste. Understanding the demand-side factors that drive consumers to order more food than required to satiate their hunger can be useful in mitigating such wasteful indulgences. Noting this, we extend the seminal theory of planned behavior (TPB) to propose direct and intervening mechanisms that can better explicate why consumers indulge in a ‘shopping routine’ of ordering more food than required. We analyzed data from 487 FDA users to test the proposed hypotheses. Our results reveal the positive associations of (a) attitude and subjective norms with usage intentions and (b) trust, intentions, and leftover reuse routine with shopping routine. In addition, both proposed moderators—i.e., willingness to pay for eco-friendly packaging and number of years of FDA usage—do, in fact, moderate the associations of leftover reuse routine with both usage intentions and shopping routine. These findings can help marketers and policymakers devise appropriate strategies to promote pro-environmental green behaviors among FDA users without harming the commercial interests of the sector

A Quantum Theory of Cold Bosonic Atoms in Optical Lattices

Ultracold atoms in optical lattices undergo a quantum phase transition from a superfluid to a Mott insulator as the lattice potential depth is increased. We describe an approximate theory of interacting bosons in optical lattices which provides a qualitative description of both superfluid and insulator states. The theory is based on a change of variables in which the boson coherent state amplitude is replaced by an effective potential which promotes phase coherence between different number states on each lattice site. It is illustrated here by applying it to uniform and fully frustrated lattice cases, but is simple enough that it can easily be applied to spatially inhomogeneous lattice systems

Quality Flaws: Issues and Challenges in Software Development

A statement “Prevention is better than cure” for illnesses in medical sciences also applies to the software development life cycle in terms of software defects. A defect is a deviation from actual functionality of the application in terms of the correctness and completeness of the specification of the customer requirements. Defective software fails to meet its customer requirements leading to the development of applications with poor quality. Quality is a top priority in every enterprise these days. Organizations struggle in a treadmill race to deliver quality software to stay ahead with new technology, deal with accumulated development backlogs, handle customer issues as software teams work as hard as they can make their organizations stay alive and competitive in the market place. Software companies face an immense pressure to virtually release a bug-free product or a software package. The culture of an organization is a critical success factor in the efforts of process improvement. The paper aims at assessing quality as a function for monitoring and measuring the strength of development processes and any successful application development enterprise requires an unambiguous understanding of customer expectation and maximizing participation of customers in the development activities thereby ensuring that people involved in development activities do the right thing and do the thing right for delivering high quality software. Keywords: Software development, process improvement, software defect, bug-free product, software packag

On the Stability and Single-Particle Properties of Bosonized Fermi Liquids

We study the stability and single-particle properties of Fermi liquids in spatial dimensions greater than one via bosonization. For smooth non-singular Fermi liquid interactions we obtain Shankar's renormalization- group flows and reproduce well known results for quasi-particle lifetimes. We demonstrate by explicit calculation that spin-charge separation does not occur when the Fermi liquid interactions are regular. We also explore the relationship between quantized bosonic excitations and zero sound modes and present a concise derivation of both the spin and the charge collective mode equations. Finally we discuss some aspects of singular Fermi liquid interactions.Comment: 13 pages plus three postscript figures appended; RevTex 3.0; BUP-JBM-