Mathematical Analysis of Throughput Bounds in Random Access with Z<Emphasis Type="SmallCaps">ig</Emphasis>Z<Emphasis Type="SmallCaps">ag</Emphasis> Decoding

We investigate the throughput improvement that ZigZag decoding (Gollakota and Katabi 2008) can achieve in multi-user random access systems. ZigZag is a recently proposed 802.11 receiver design that allows successful reception of packets despite collision. Thus, the maximum achievable throughput of a wireless LAN can be significantly improved by using ZigZag decoding. We analyze the throughput bounds in four different idealized multi-access system models for the case when ZigZag decoding is used. We also provide results for the Aloha and CSMA models where exact closed form solutions are infeasible to calculate. Our analysis and simulation results show that ZigZag decoding can significantly improve the maximum throughput of the random access system.     

Risk Index Model for Minimizing Environmental Disputes in Construction

Although the number of environment-related disputes is increasing, no risk management approach exists to minimize such disputes at construction sites. The purpose of this study was to develop an environmental risk index model for general contractors to minimize third-party environmental disputes at construction sites. The analytic hierarchy process is used to weigh and calculate an environmental risk index. A case study demonstrated how to apply this model for risk evaluation, on-site monitoring, and environmental management, whereas a comparative analysis revealed that the model decreased the number of disputes to some degree at sites where it was used. This model makes it possible to minimize environmental disputes in the field effectively.     

Running a Profitable Construction Company: Revisited Break-Even Analysis

Many companies have a tendency to spread out their operations into branches and∕or separate corporations. The construction industry is a good example. With work being slow in some areas, it is sometimes more profitable to spread out the company into different areas in order to absorb more work and therefore create branches to the main office. When this is done, it is important to centralize these branches and analyze them as a whole to help the corporation. In this process, the break-even analysis can be used to help analyze the operations. Consideration for a corporation having one or more branches involved in several projects takes time and teamwork. The team that is organized to help in the decision-making process needs a plan to determine how the project will affect the company and other jobs that are already in progress. With one corporation having two or more branches, it can be difficult to figure out where the company as a whole needs to be in order to turn a profit. The team must consider what each branch is doing in volume and what their break-even points are. This comes down to an important point of this research, which is “where to break even” before the profit consideration is made. This research provides an exemplary application of the break-even analysis to an actual construction company with one or more branches.     

Numerical heat transfer analysis for the design of the engineering-scale electrowinning cell in pyroprocessing

A heat transfer analysis of the electrowinning cell was conducted to develop a basic tool for designing of the engineering-scale electrowinner. For calculating the heat transfer properties of argon gas and LiCl–KCl eutectic salt in the electrowinning cell, the ANSYS CFX commercial code was adapted. The simulation model was prepared, and the temperature profiles of the argon gas and the salt were compared with those in the lab-scale electrowinning cell. Using the simulation model, temperature distributions of the engineering-scale electrowinning cell were analyzed. When the heating zone length was 2.5 times longer than the height of the LiCl–KCl salt, the salt temperature was maintained at about 500 °C and its temperature gradient became less than 5 °C. The cooling zone length had an influence on both temperatures of the argon gas under the cell cover as well as the salt. When the cooling zone length was about 0.16–0.19 of the heating zone length, the temperature of the salt was maintained at 500 °C and the argon gas temperature under the cover decreased below 200 °C. The number of the heat shield plates and size mainly affected the temperature gradient of the salt and argon gas under the cover. More than 3 heat shield plates had to be placed in the cooling zone and their diameters should be extended over 410 mm that is over 0.95 of the cell diameter.     

Up-Regulation of Rhoa/Rho Kinase Pathway by Translationally Controlled Tumor Protein in Vascular Smooth Muscle Cells

Translationally controlled tumor protein (TCTP), a repressor for Na,K-ATPase has been implicated in the development of systemic hypertension, as proved by TCTP-over-expressing transgenic (TCTP-TG) mice. Aorta of TCTP-TG exhibited hypercontractile response compared to that of non-transgenic mice (NTG) suggesting dys-regulation of signaling pathways involved in the vascular contractility by TCTP. Because dys-regulation of RhoA/Rho kinase pathway is implicated in increased vascular contractility, we examined whether TCTP induces alterations in RhoA pathway in vascular smooth muscle cells (VSMCs). We found that TCTP over-expression by adenovirus infection up-regulated RhoA pathway including the expression of RhoA, and its downstream signalings, phosphorylation of myosin phosphatase target protein (MYPT-1), and myosin light chain (MLC). Conversely, lentiviral silencing of TCTP reduced the RhoA expression and Rho kinase signalings. Using immunohistochemical and Western blotting studies on aortas from TCTP-TG confirmed the elevated expression of RhoA and increase in p-MLC (phosphorylated MLC). In contrast, down-regulation of RhoA and p-MLC were found in aortas from heterozygous mice with deleted allele of TCTP (TCTP^+/−). We conclude that up-regulation of TCTP induces RhoA-mediated pathway, and that TCTP-induced RhoA plays a role in the regulation in vasculature. Modulation of TCTP may offer a therapeutic target for hypertension and in vascular contractility dysfunction.     

Plastic ELISA-on-a-chip based on sequential cross-flow chromatography

A plastic chip that can perform immunoassays using an enzyme as signal generator, i.e., ELISA-on-a-chip, was developed by incorporating an immunostrip into channels etched on the surfaces of the chip. To utilize an analytical concept of cross-flow chromatography, the chip consisted of two cross-flow channels in the horizontal and vertical directions. In the vertical channel, we placed a 2-mm-wide immunostrip for cardiac troponin I (cTnI), which was identical to a conventional rapid test kit except for the utilization of an enzyme, horseradish peroxidase (HRP), as tracer. An enzyme substrate supply channel and a horizontal flow absorption pad compartment were transversely arranged on each lateral side of the signal generation pad of the strip, respectively. Upon application of a sample containing cTnI, it migrated vertically through the membrane strip by capillary action, and antigen-antibody binding occurred. After 15 min, the horizontal flow was initiated by the addition of a chromogenic substrate solution for HRP into the supply channel and by partial superimposition of the horizontal flow absorption pad onto the signal generation pad. A color signal proportional to the analyte concentration was produced on this pad, measured after 5 min as optical densities using a digital camera-based detector, and quantified by integration of the densities under the peak after normalization. Its calibration curve indicated that the detection limit of the chip was approximately 0.1 ng/mL and its quantification limit was 0.25 ng/mL. In measuring blindly prepared samples, the chip performance correlated with that of a reference system, Beckman Coulter Access, within 2.5-fold discrepancy at the detection limit.     

A study of carbon-nanotube-based nanoelectromechanical resonators tuned by shear strain

This paper has investigated, using a classical molecular dynamics simulation method based on the Tersoff-Brenner potential, the resonance-frequency changes of single-walled carbon-nanotube resonators originating from the purely mechanical response of single-walled carbon nanotubes. The tension decreased with increasing rotation angle, so the resonance frequencies could be changed by controlling the rotation angles of the single-walled carbon nanotubes. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than 60°, the changes were marked. For nanotubes of similar length, the bandwidth for the (3, 3) single-walled carbon nanotube was higher than for the (5, 0) single-walled carbon nanotube. Because properties arising from the shear-strain-induced tension response can affect the electromechanical behavior of carbon nanotubes, the shear-strain-induced tension response should be given serious consideration in the application of embedded carbon nanotubes in nanoelectromechanical systems.     

Optical and Dielectric Properties of Chalcogenide Glasses at Terahertz Frequencies

Terahertz time‐domain spectroscopy has been used to study the optical and dielectric properties of three chalcogenide glasses: Ge₃₀As₈Ga₂Se₆₀, Ge₃₅Ga₅Se₆₀, and Ge₁₀As₂₀S₇₀. The absorption coefficients α(ν), complex refractive index n(ν), and complex dielectric constants ?(ν) were measured in a frequency range from 0.3 THz to 1.5 THz. The measured real refractive indices were fitted using a Sellmeier equation. The results show that the Sellmeier equation fits well with the data throughout the frequency range and imply that the phonon modes of glasses vary with the glass compositions. The theory of far‐infrared absorption in amorphous materials is used to analyze the results and to understand the differences in THz absorption among the sample glasses.     

In-situ observation of a dendrite growth in an aqueous condition and a uranium deposition into a liquid cadmium cathode in an electrowinning system

A zinc-gallium system was setup to observe the growth process of dendrites and to compare the performance of the stirrers which would prevent a dendrite formation. In a no-stirring condition, zinc was easily deposited on a liquid gallium cathode in the form of dendrites. It was difficult for a paddle stirrer to directly fracture the zinc dendrites to fine particles. However, a harrow stirrer was observed to fracture the dendrite to some extent at high speeds. Not only their rotation speed but also the length of their blades needed to be properly adjusted to enhance their performance. In the uranium-cadmium experiment, the diffusion coefficient of the uranium species was obtained by the cyclic voltammetry method, which is around 1 × 10⁻⁵ cm²/s. In a no-stirring condition, most of the uranium deposited at the current densities of 35, 100 and 200 mA/cm² did not sink into the liquid cadmium cathode.     

High-Throughput Growth of Wafer-Scale Monolayer Transition Metal Dichalcogenide via Vertical Ostwald Ripening

For practical device applications, monolayer transition metal dichalcogenide (TMD) films must meet key industry needs for batch processing, including the high-throughput, large-scale production of high-quality, spatially uniform materials, and reliable integration into devices. Here, high-throughput growth, completed in 12 min, of 6-inch wafer-scale monolayer MoS₂ and WS₂ is reported, which is directly compatible with scalable batch processing and device integration. Specifically, a pulsed metal–organic chemical vapor deposition process is developed, where periodic interruption of the precursor supply drives vertical Ostwald ripening, which prevents secondary nucleation despite high precursor concentrations. The as-grown TMD films show excellent spatial homogeneity and well-stitched grain boundaries, enabling facile transfer to various target substrates without degradation. Using these films, batch fabrication of high-performance field-effect transistor (FET) arrays in wafer-scale is demonstrated, and the FETs show remarkable uniformity. The high-throughput production and wafer-scale automatable transfer will facilitate the integration of TMDs into Si-complementary metal-oxide-semiconductor platforms.