International Expansion Decision for Construction Companies

There exist several reasons for construction firms to expand their business into international markets. But the complex international environment is affected by diverse factors and creates risks that are not well understood by companies that are active mostly in domestic markets. It is therefore essential for construction companies to follow a disciplined and well-informed strategy when deciding whether to enter international markets. Company strengths relative to conducting business in international markets, the threats and opportunities associated with overseas work, and the costs and benefits of undertaking construction projects in specific countries need to be considered in this decision. The interactions between the complex factors can be structured in a model that can help one to make a rational judgment. The International Expansion Decision Model developed in this study is based on the Analytic Hierarchy Process (AHP) improved by the addition of a Delphi survey. The main objective of this research study is to facilitate the entry decision into foreign markets and to highlight the importance of the factors involved in this decision. This study is of relevance to practitioners as it allows executives of construction companies to test if their company is ready for expansion into international markets in general and into a specific country in particular. It is also of relevance to researchers as it demonstrates the successful use of the combined Delphi and AHP methods.     

Modeling of a large electric power system for optimal control of dynamic stability

This paper describes a general state-variable form of mathematical modeling which may be used to control the dynamic stability of a larger power system optimally. Based on the linearization about the operating point of the system, a complete model for dynamic stability control is obtained by combining transmission network equations, full-order synchronous machine equations, the exciter and voltage regulator model, torque equations, and the governor-hydraulic model in a matrix form which includes supplementary excitation and governor control signals. The complete model may then be simplified as a low-order model by neglecting the governor effects, exciter time constant, and all but the field flux linkage variations of the machines in order to reduce computational requirements.     

An electrical circuit theoretical method for time‐ and frequency‐ domain solutions of the structural mechanics problems

Shrinking device dimensions in integrated circuit technology made integrated circuits with millions of components a reality. As a result of this advance, electrical circuit simulators that can handle very large number of components have emerged. These programs use new circuit simulation techniques and can find solutions accurately and quickly. In this paper, we apply these techniques to structural mechanics problems by adopting electrical circuit equivalents. We first apply finite element formulation to the mechanical problem. The obtained sets of equations are treated as if they are sets of equations of an equivalent electrical circuit which consists of linear circuit elements such as capacitors, inductors and controlled sources. The equivalent circuit is obtained in the form of a circuit netlist and solved using a general purpose electrical circuit simulator. Several examples showing the advantages of the circuit simulation techniques are demonstrated. Asymptotic waveform evaluation technique which is widely used for simulation of large electrical circuits is also studied for the same examples and the speed‐up advantage is shown. Copyright © 1999 John Wiley & Sons, Ltd.     

Controlled synthesis and characterizations of amphiphilic poly[(R,S)-3-hydroxybutyrate]-poly(ethylene glycol)-poly[(R,S)-3-hydroxybutyrate] triblock copolymers

Well-defined biodegradable amphiphilic triblock copolymers consisting of atactic poly[(R,S)-3-hydroxybutyrate] (PHB) and poly(ethylene glycol) (PEG) as the side hydrophobic block and middle hydrophilic block were synthesized via ring opening polymerization of (R,S)-β-butyrolactone from PEG macroinitiators and characterized using NMR, GPC, FT-IR, XRD, DSC and TG analyses. The controlled synthesis was made possible by the facile synthesis of pure PEG macroinitiators through a TEMPO-mediated oxidation. Constituting 40-70 wt% of the copolymer content, PHB blocks grown were amorphous while PEG formed crystalline phase when segment was sufficiently long. While hindering PEG crystallization, atactic PHB mixed well with amorphous PEG to give single T_g in all the copolymers. The copolymers exhibited two-step thermal degradation profile starting with PHB degradation from 210 to 300 °C, then PEG from 350 to 450 °C.     

Study of Metal and Ceramic Thermionic Vacuum arc Discharges

The thermionic vacuum arc （TVA） is a new type of plasma source, which generates a pure metal and ceramic vapour plasma containing ions with a directed energy. TVA discharges can be ignited in high vacuum conditions between a heated cathode （electron gun） and an anode （tungsten crucible） containing the material. The accelerated electron beam, incident on the anode, heats the crucible, together with its contents, to a high temperature. After establishing a steadystate density of the evaporating anode material atoms, and when the voltage applied is high enough, a bright discharge is ignited between the electrodes. We generated silver and Al2O3 TVA discharges in order to compare the metal and ceramic TVA discharges. The electrical and optical characteristics of silver and Al2O3 TVA discharges were analysed. The TVA is also a new technique for the deposition of thin films. The film condenses on the sample from the plasma state of the vapour phase of the anode material, generated by a TVA. We deposited silver and Al2O3 thin films onto an aluminium substrate layer-by-layer using their TVA discharges, and produced micro and/or nano-layer Ag-Al2O3 composite samples. The composite samples using scanning electron microscopy was also analysed.     

Nonlinear Optical Properties of Copolymers of Benzylaminofullerene with Methyl Methacrylate or Ethyl Methacrylate

Nonlinear optical properties of a C₆₀ derivative, benzylaminofullerene [C₆₀H_n(NHCH₂C₆H₅)_n] and its copolymers with methyl methacrylate or ethyl methacrylate were observed carefully by using the nanosecond laser pulses at 532 nm. These copolymers have been proved to be promising materials for optical limiting applications.     

Effects of nanosilica and steel fibers on the impact resistance of slag based self-compacting alkali-activated concrete

In this research, the effects of nanosilica and steel fibers on the impact resistance of ground granulated blast furnace slag based self-compacting alkali-activated concrete were investigated. Nanosilica volume fraction was kept constant at 2%. Two types of hooked-end steel fibers (Kemerix 30/40 and Dramix 60/80) and steel fiber volume contents (0.5% and 1%) were utilized to highlight the combined effects of nanosilica and steel fiber on the impact behavior. The fresh state and mechanical properties such as slump flow, L-box, V-funnel, compressive strength, modulus of elasticity, splitting tensile strength, and flexural strength were evaluated. The microstructure of the samples was examined using a scanning electron microscope. The impact resistance of the specimens was measured by a drop-weight test. Acceleration-time and force-time graphs were plotted and evaluated together with the crack photos of the specimens for the first and failure impactor drops. The incorporations of nanosilica and steel fiber improved splitting tensile strength, flexural strength, impact resistance, and energy absorption capacity, while they decreased compressive strength and modulus of elasticity. For the specimens without nanosilica and with 2% nanosilica, the impact energy improvements were five times and 12.5 times higher for 0.5% short fibrous, 20.5 times and 44.5 times higher for 1% short fibrous, 23.5 times and 31 times higher for 0.5% long fibrous, and 64 times and 144.5 times higher for 1% long fibrous specimens than the specimens without nanosilica and steel fiber, respectively. The long fibers were found more effective in mechanical strength and impact energy than short fibers, and the reinforcing efficiency of fibers enhanced with higher steel fiber volumes. The combined utilization of nanosilica and steel fibers have the potential to delay the crack formation and dissipate energy to the surrounding zones, and this potential increased with higher steel fiber lengths and volume ratios.     

Superlocal chemical reaction equilibrium in low temperature plasma

Low temperature plasmas (LTP) are a unique class of open-driven systems in which chemical reactions are unpredictable using established concepts. The terminal state of chemical reactions in LTP, termed the superlocal equilibrium state, is hypothesized to be defined by a proposed set of state variables. Using a LTP reactor wherein the state variables have been measured, it is shown that CO₂ spontaneously splits and the effluent speciation is independent of the influent speciation if the state variables are held constant and the residence time is long. CO₂ conversion at long residence times, which is expected to be nominally zero from equilibrium thermodynamics, can be as high as 70% in the LTP. The employed low pressure plasma reactor (P = 10 mbar) had a similar volume, productivity, and energy efficiency compared to an atmospheric pressure dielectric barrier discharge reactor, thanks to reaction rates that were three orders of magnitude faster.     

CDABC: chaotic discrete artificial bee colony algorithm for multi-level clustering in large-scale WSNs

The Journal of Supercomputing - Artificial bee colony or ABC is an interesting meta-heuristic algorithm designed to solve various continuous optimization problems. However, it cannot be directly...     

Isolation and characterization of verocytotoxin-producing Escherichia coli O157 from Turkish cattle

The objective of this study was to collect rectal swabs from the cattle in a slaughterhouse located in Hatay (Turkey) immediately after slaughter for the isolation and characterization of verotoxin-producing Escherichia coli O157 in each month during a 1-year period. The rectal swab samples were analyzed for the isolation of E. coli O157 through pre-enrichment, immunomagnetic separation and selective plating on CT-SMAC agar. E. coli O157 was isolated from 77 (13.6%) of the samples. The presence of E. coli O157 changed during a 1-year period, in that the occurrence of E. coli O157 was the highest in July and November and lowest in February. A total of 66 isolates out of 77 were serotype O157:H7 and 11 were serotype O157:NM. PCR analysis of E. coli O157 virulence genes revealed that all O157:H7/NM were positive for rbf(O157), 74 positive for EhlyA, 72 positive for eaeA, 62 positive for vtx2, and 3 positive for both vtx1 and vtx2. It was presented by cytotoxicity tests that many of E. coli O157 isolates showed high cytotoxicity on Vero cells. All of the isolates containing EhlyA showed enterohaemolysin production.