The commercial currency of construction framework agreements

A critique is presented of construction client–main contractor framework agreements. In the midst of an unpredictable and volatile construction environment, the commercial currency of collaborative working practice, and by extension framework agreements, is being put under increasing management scrutiny. Drawing on a literature review, the guiding principles of framework agreements are examined. A dramatic downturn in construction demand has created considerable surplus in supply. Under such conditions the buyer–supplier interdependencies become imbalanced and commercial relationships fraught. Reports by construction industry analysts demonstrate a number of private sector clients rejecting framework agreements in favour of traditional competitive procurement practices. Drawing upon a neoclassical lens, three guiding principles embedded within economic orthodoxy are employed to examine business-to-business tensions within construction framework agreements, namely, individualism, instrumentalism and equilibrium. This neoclassical interpretation of construction framework agreements reveals a potential relational management bias within mainstream rhetoric. Notably, providing a complementary account of framework agreements practice should not be construed as a rejection of collaborative working practices. An alternative account of framework agreements is presented that does not rely upon the mainstream behavioural model of contemporary contracting.     

Morality and Architecture

In the 1870s and 1880s, when the establishment of schools of architecture in the United States was in its infancy, one of the main methods of architectural education for builders, carpenters and others who wished to advance in the field was to study the many books on architecture being published after the Civil War. Even professional architects had frequent recourse to books (and also periodicals) for design ideas, theory and contemporary issues.     

Television as a Design Tool

Television is not only the most powerful medium of communication that our age has produced; it is also the most flexible. Yet its common role in education is that of a mere substitute, called in to mitigate the effects of the shortage of teachers or (to look at the matter historically) the excess of students. That it can be more than that is shown by two University of Nebraska faculty members, describing an experiment in the creative use of television as a tool in the development of that awareness of the characteristics of space which is among the architect's indispensable qualifications.     

Increased conversion efficiency in cadmium telluride photovoltaics by luminescent downshifting with quantum dot/poly(methyl methacrylate) films

Commercially available quantum dots have been encapsulated in a poly(methyl methacrylate) film and used as a luminescent downshifting layer on cadmium sulfide/cadmium telluride photovoltaic devices. Application of these films has resulted in a relative improvement to the short‐circuit current of over 4% by I–V measurement, with a significant increase in the contribution of short‐wavelength light resulting in 25% of the current available in this part of the spectrum being captured. The films have been shown to be highly scattering and the associated difficulties this provides to external quantum efficiency measurements have been discussed. A range of optical characterisation techniques, particularly laser beam induced current, have been used to probe the effect the films have on a cadmium sulfide/cadmium telluride device. An alternate methodology for performing external quantum efficiency measurements with the quantum dot films has been proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

Treatment of Critical Size Femoral Bone Defects with Biomimetic Hybrid Scaffolds of 3D Plotted Calcium Phosphate Cement and Mineralized Collagen Matrix

To treat critical-size bone defects, composite materials and tissue-engineered bone grafts play important roles in bone repair materials. The purpose of this study was to investigate the bone regenerative potential of hybrid scaffolds consisting of macroporous calcium phosphate cement (CPC) and microporous mineralized collagen matrix (MCM). Hybrid scaffolds were synthetized by 3D plotting CPC and then filling with MCM (MCM-CPC group) and implanted into a 5 mm critical size femoral defect in rats. Defects left empty (control group) as well as defects treated with scaffolds made of CPC only (CPC group) and MCM only (MCM group) served as controls. Eight weeks after surgery, micro-computed tomography scans and histological analysis were performed to analyze the newly formed bone, the degree of defect healing and the activity of osteoclasts. Mechanical stability was tested by 3-point-bending of the explanted femora. Compared with the other groups, more newly formed bone was found within MCM-CPC scaffolds. The new bone tissue had a clamp-like structure which was fully connected to the hybrid scaffolds and thereby enhanced the biomechanical strength. Together, the biomimetic hybrid MCM-CPC scaffolds enhanced bone defect healing by improved osseointegration and their differentiated degradation provides spatial effects in the process of critical-bone defect healing.     

太阳能发电面临的挑战与机遇

在所有可再生能源中,光伏太阳能只占一小部分,然而在早期采用它的国家中,如日本和德国,却对全球工业体系起到了促进作用,对未来能源需求产生了意义深远的影响。讨论了光伏模块的当前成本和计划中的成本以及为了拓宽光伏太阳能的应用,材料科学能够为降低此成本壁垒而作出贡献的途径。文章对当前统辖市场的相对成熟的单晶硅光伏电池和有可能降低光伏模块成本的薄膜光伏电池进行了比较,指出薄膜光伏电池的转换效率需要提高而且应该能够进行大规模生产。文中给出了当前碲化镉光伏电池材料研究的一些实例,并对它们应如何在将来进行改进提出了建议。     

Analysis of equiangular spiral antennas

In this work, equiangular spiral antennas are analyzed with the well-known method of moments in conjunction with triangular patch modeling. In particular, the analysis focuses on the validity of several generic guidelines hitherto available for designing such antennas. In our study, numerical results indicate that increasing the number of spiral arm turns broadens the radiation pattern (i.e., the axial ratio increases), but that tapering the outermost portion of the arms has little effect. Furthermore, as a spiral is wrapped tighter, the radiation pattern broadens and the gain increases. We also show that the useful frequency range of the spiral antenna depends not only on the spiral arm length and the inner radius near the spiral center, but also on the wrap tightness. Finally, numerically determined input impedance differed considerably from the 188-Ω impedance expected for these self-complementary type antennas. © 1996 John Wiley & Sons, Inc.