High R-value Research Articles

Analysis of Fluctuating Friction Version in Sheet Metallic Designing

Conservative Coulomb method indicates steady constant of rub in thin metal panel making that appears or feels close to the real thing. It contributes to describing attainable future event too high shear pressure in making ahead in the position of high R-value steel (AHRS). The study is conducted by pretend the making and spring back of a specific panel to understand the characteristic of the stamping procedure. Corresponding of the describe probable future results with (i) physical force-dependent changeable rub method, (ii) perpetual rub method, and the conclusion of exploratory facts point out a significant upgrading of spring back forecast with the prospective method.

Thermal performance analysis of residential attics containing high performance aerogel-based radiant barriers

This paper is focused on a new, easy to install, extremely light weight, and high R-value radiant barrier that shows promise for attics and wall cavities in residential and light-commercial buildings in cooling-dominated and mixed climates. Roofs and attics are one of the major sources of thermal loads affecting energy performance of residential and commercial buildings in North America. Several novel prototype residential roofs and attics have been constructed in different North American climates. These technologies have demonstrated a significant reduction of the heat transfer penetrating the roof deck and the overall attic-generated thermal load compared to conventional insulation. One of these technologies is radiant barriers. This paper discusses the development, testing, and thermal performance of a novel radiant barrier containing aerogel insulation core. The newly developed aerogel-based radiant barrier is characterized at the system-scale in a controlled laboratory setting and deployed in a side-by-side field test with conventional insulation technology. The experimental data is used to validate numerical models created with the Fraunhofer Attic Thermal Model (FATM). The validated models were then used for thermal performance predictions of similar attic configurations located in 11 different climatic conditions worldwide.

Battery Technology as Applied to Thermal Insulation

The development of cost-effective, high performance thermal insulation (HPTI) is essential to improving the energy efficiency of buildings and appliances. An effective means of meeting this challenge involves the use of vacuum insulated panels (VIPs), which consist of an evacuated sealed enclosure that houses a porous solid core for structural integrity. As VIPs age, gases and moisture, permeate through the envelope and seals, making it necessary to use getters/desiccants to maintain their internal pressure and high R-values. The thermal performance of VIPs (R40/inch) greatly exceeds that of conventional materials, e.g. fiberglass, or foam used in the building industry (R5/inch). This very high R-value is the result of the low pressure within the panel. As pressure decreases from atmospheric conditions (1000 mbar), the R-value increases. For VIPs, pressures less than 1 mbar are desired initially to ensure that even with pressure creep due to leaks, the R-value will remain high during the life of the application. While potential energy savings are possible from HPTI, the current costs of VIPs are prohibitive and their performance can suffer from significant degradation over time. To ensure this technology is effective in building envelopes, extending their service life to several decades is desirable. The on demand getter (ODG) device proposed herein can greatly disrupt the building industry. The architecture of the ODG, (see Fig. 1), resembles that of a discharged thin film Li battery, which upon applying a negative current to the cathode produces metallic Li or Li alloys that react irreversibly with atmospheric molecular gases. The products of these reactions are solids that display no vapor pressure at ambient temperature. Additional ODG components include a microelectronics board and a battery which powers the device. As envisioned, the ODG incorporates a porous Ni cathode; a non-volatile , thin, Li+-conducting ceramic film, such as LiPON; and a Li-ion counter electrode. Preliminary measurements aimed at demonstrating the overall concept were performed using a Li-ion conducting polymer electrolyte and a Li film as the counter electrode. The assembled ODG was placed in vacuum and the voltage scanned to -0.7 V vs Li+|Li to deposit metallic Li (see insert, Fig. 2). The cell was then disconnected and its open circuit potential (OCP) recorded. As shown in Fig. 2 (black line), the OCP remained at 0.0 V for ca. 10 min., consistent with the presence of metallic Li on the cathode, and later increased to a higher value, as Li reacted with gases in the chamber. In similar experiments, the chamber was opened to air after Li deposition and the OCP was found to jump to a high value indicative of reactions of Li with atmospheric components (blue line, Fig. 2). The efficacy of the ODG is currently being characterized by measuring the thermal conductivity as a function of pressure and imposed degradation conditions. The ODG will be installed in VIPs along with other traditional getter systems, which will then be subjected to various laboratory and field exposures while monitoring their thermal performance either continuously or periodically over an extended service life and its efficacy compared with the present state of the art. Figure 1

Synthesis, Characterization of Guar-Containing Polyurethane Films and their Non-enzymatic Caffeic Acid Sensor Applications

ABSTRACTStable voltammetric sensors were fabricated by dropping the guar-containing polyurethane films on a platinum electrode for the non-enzymatic determination of caffeic acid. The voltammetric responses of PU-G-1% toward caffeic acid have a linear concentration range from 1 to 15 mM with a correlation coefficient of 0.9938. The detection limit of PU-G-1% electrode was approximately 0.25 mM. PU-G-1% sensor showed the good sensitivity, selectivity, high R-value, low detection limit, and high reproducibility toward caffeic acid. Therefore, it is claimed that the polyurethane film containing 1% guar can be used as an excellent selective membrane for caffeic acid detection in the presence of interferent molecules.

Diagnosis of Partial Retrograde Ejaculation in Non-Azoospermic Infertile Men with Low Semen Volume.

In non-azoospermic patients with low semen volume (LSV), looking for partial retrograde ejaculation (PRE) by searching sperm in the postejaculatory urine (PEU) is required. The use of a retro-ejaculatory index (R-ratio) was suggested to define PRE, but none of the studies indicated a specific threshold above which PRE must be considered. Our objective was to propose a threshold value for the R-ratio as indicative of PRE in patients with LSV selected to be devoid of any known causes or risk factors for retrograde ejaculation or LSV. Among our data base (2000–2009) including 632 patients with PEU, 245 male patients from infertile couples who had had a first semen analysis with LSV (< 2mL) and a second semen analysis associated with PEU, were selected on the previous criteria. A prospective control group was randomly constituted (2007–2008) of 162 first consulting male patients from infertile couples, with a normal semen volume (≥ 2mL) on a first semen analysis and who accepted to collect PEU with their usual second semen analysis, selected on the previous criteria. To define an R-ratio threshold indicative of PRE, we used a ROC curve analysis and a regression tree based on a classification and regression tree (CART) algorithm. Of the 245 LSV patients, 146 still presented low semen volume (< 2 mL) on the second semen analysis. From the use of the CART algorithm, two low (1.5% and 2.8%) and two high R-values (7.1% and 8.3%) were defined, according to the lower reference limit for semen volume of 2.0 mL (WHO 1999) or 1.5 mL (WHO 2010) respectively. As only one or no patient with normal semen volume was observed above the two high R-values, we suggest an R-value higher than the range of [7.1–8.3]% as indicative of PRE until confirmation by a prospective multicenter study.

Effect of Previous Grain Size on Recystallization Texture and the Formability of the Nb Ferritic Stainless Steel

The ferritic stainless steels are materials used in several segments due to the excellent combination of mechanical properties and corrosion resistance. The mechanical properties of these alloys are strongly dependent on the microstructural characteristics and crystallography texture. The aim of this experimental study is to investigate the roles of the grain size of the hot rolled sample on the development of the microstructure, texture and formability of ferritic stainless steel. The main elements of chemical composition of the steel under investigation were 16.0 %Cr, 0.021 %C, 0.024 %N and 0.35 %Nb. Coarse and fine grains samples were cold rolled up to 90% thickness reduction and annealed at 880°C with soaking time of the 24 s. The texture measurements were performed by Electron Backscattered Diffraction (EBSD) in the longitudinal section. The formability was evaluated by the R-value and planar anisotropy (Δr) in tensile tests. The final microstructure after annealed was more homogenous for smaller initial grain size sample. This condition was favorable to develop γ-fiber, with sharpness intensity in 111121 components. The highest R-value and smallest planar anisotropy was obtained for a {111}/{001} ratio around 5.37. On the other hand, coarser initial grain size sample had showed a heterogeneous microstructure and texture, performing badly in mechanical tests (anisotropy).

Crystal plasticity-based modeling for predicting anisotropic behaviour and formability of metallic materials

Metallic materials often exhibit anisotropic behaviour under complex load paths because of changes in microstructure, e.g., dislocations and crystallographic texture. In this study, we present the development of constitutive model based on dislocations, point defects and texture in order to predict anisotropic response under complex load paths. In detail, dislocation/solute atom interactions were considered to account for strain aging and static recovery. A hardening matrix based on the interaction of dislocations was built to represent the cross-hardening of different slip systems. Clear differentiation between forward and backward slip directions of dislocations was made to describe back stresses during path changes. In addition, we included dynamic recovery in order to better account for large plastic deformation. The model is validated against experimental data for AA5754-O with path changes, e.g., Figure 1 [1]Another effort is to include microstructure in forming predictions with a minimal increase in computational time. This effort enables comprehensive investigations of the influence of texture-induced anisotropy on formability [2]. Application of these improvements to predict forming limits of various BCC textures, such as γ, ρ, α, η and ϵ fibers and a random (R) texture. These simulations demonstrate that the crystallographic texture has significant (both positive and negative) effects on the forming limit diagrams (Figure 2). For example, the y fiber texture, that is often sought through thermo-mechanical processing due to high r-value, had the highest forming limit in the balanced biaxial strain path but the lowest forming limit under the plane strain path among textures under consideration.

Forming limit prediction using a self-consistent crystal plasticity framework: a case study for body-centered cubic materials

A rate-dependent self-consistent crystal plasticity model was incorporated with the Marciniak–Kuczyński model in order to study the effects of anisotropy on the forming limits of BCC materials. The computational speed of the model was improved by a factor of 24 when running the simulations for several strain paths in parallel. This speed-up enabled a comprehensive investigation of the forming limits of various BCC textures, such as , , , and fibers and a uniform (random) texture. These simulations demonstrate that the crystallographic texture has significant (both positive and negative) effects on the resulting forming limit diagrams. For example, the fiber texture, which is often sought through thermo-mechanical processing due to a high r-value, had the highest forming limit in the balanced biaxial strain path but the lowest forming limit under the plane strain path among the textures under consideration. A systematic investigation based on the results produced by the current model, referred to as ‘VPSC-FLD’, suggests that the r-value does not serve as a good measure of forming limit strain. However, model predictions show a degree of correlation between the r-value and the forming limit stress.

The effect of microstructure on damage and fracture in AZ31B and ZEK100 magnesium alloys

Room temperature fracture during tensile deformation has been studied in two commercial wrought magnesium alloys, namely AZ31B and ZEK100. As a consequence of differences in texture and grain size the deformation modes of these materials differ significantly. This leads to significant differences is the kind of damage that results prior to fracture as evidenced by a combination of traditional metallography and x-ray computed tomography (XCT). The AZ31B samples show little evidence of twinning, in part because of the fine grain size, until after the end of uniform elongation. Moreover, a high r-value, which increases as deformation proceeds, makes this material resistant to shear localization. Damage in this material forms by a combination of ductile dimple formation at second-phase particles and some twin-related microcracking. The ZEK100 samples exhibit extensive twinning and a low r-value (less than 1) meaning that the material is susceptible to shear localization. Although extension twins dominate once the material starts to neck contraction twins are also seen. These form the nucleation sites for an array of penny shaped cracks. In both materials the final fracture is triggered by a macroscopic shear localization that produces a slant fracture surface at 45° to the tensile axis. However, in AZ31B, void linkage produces a fracture surface that is quasi-ductile in appearance, while in ZEK100 the final fracture involves the linkage of the twin-induced microcracks and is quasi-brittle in nature.

A New Methodology for Quantifying the Impact of Direct and Diffuse Solar Radiation on Energy Savings in Commercial Office Spaces

In this paper, we describe a new methodology for quantifying how direct and diffuse solar radiation impact total energy consumption in a standard perimeter office room by optimizing the allowed daylight penetration for achieving overall energy reduction. Our methodology is different from standard studies that focus on modification of window glazing geometrical, optical and/or thermal parameters and their impact on energy consumption. In our study, we consistently use the same window glazing geometry, and modify the weather file by varying the direct and/or diffuse components of solar radiation. This combination emulates the effect of an advanced dynamic glazing on the incoming solar radiation and is independent of the technology used. Such a glazing would regulate the proportions of direct and diffuse solar radiation to achieve overall energy reduction. In other words, our approach does not try to qualify or evaluate a particular glazing technology, but rather to generate specifications for advanced dynamic glazings that can manage the incoming radiation and hence help drive the development of such advanced dynamic glazing technology.To achieve our goal, we use EnergyPlus to simulate a 6m×3m×3m (length×width×height) office space with a 40% WWR, at all four cardinal orientations. To eliminate any effects that could arise from heat transfer from adjacent rooms — e.g., through walls — we treat those surfaces as adiabatic. In addition, since the front façade wall is the host surface of the window and thus cannot be defined as adiabatic, we intentionally set the façade wall at very high R-value, thus minimizing any thermal impact from that surface too. As a result, the only element responsible for daylight and thermal impact in the office space is the glazing. We present the results by comparing the energy requirements under various solar radiation penetrations into the office, as they are managed by the glazing. We compare the results under non-dynamic and dynamic glazing operation and offer recommendations on the optimum glazing operation for achieving year around energy savings. By investigating the interplay between managed solar radiation, via the emulated advanced dynamic glazing, and energy consumption in the room, we identify and quantify opportunities for energy savings.

PROPOSED COOLING WALL SYSTEM: A LESSON FROM NATURE

The study commences with a comparative analysis between desert adapted cactus plants and traditional mud houses. Primary comparative results yielded three main similarities: 1) Effective utilization of self-shading surfaces; 2) Plant spikes that resemble the wooden poles projected around wind towers and building openings in mud structures; 3) Implementation of thick walls/plant body forms with high R-values. The ribbed facade and wooden poles will go through aerodynamic experiments to illustrate their roles as essential passive energy elements in traditional houses. Experiments on traditional mud houses has been previously carried out by many researchers while assuming the wind is facing the buildings; what is significant about this proposal is that wind directions will be tested with different angles (0 to 90 degrees) to find appropriate situations where wind generates enough turbulence that help directing the wind inside the building openings. The study requires two models for experimentation, one model related to the wooden pole, and the other focused on the ribbed elevation. Tests will then be carried out using wind tunnel equipment. The QU Aspire wind tunnel has a working section of 2.5 X 2.5 X 2.5 m and can simulate wind of up to 25 m/sec at the working section. Moreover, Computational Fluid Dynamics (CFD) software will be used to minimize the wind tunnel utilization time.

Chemical Composition, Nitrogen Fractions and Amino Acids Profile of Milk from Different Animal Species

Milk composition is an imperative aspect which influences the quality of dairy products. The objective of study was to compare the chemical composition, nitrogen fractions and amino acids profile of milk from buffalo, cow, sheep, goat, and camel. Sheep milk was found to be highest in fat (6.82%±0.04%), solid-not-fat (11.24%±0.02%), total solids (18.05%±0.05%), protein (5.15%±0.06%) and casein (3.87%±0.04%) contents followed by buffalo milk. Maximum whey proteins were observed in camel milk (0.80%±0.03%), buffalo (0.68%±0.02%) and sheep (0.66%±0.02%) milk. The non-protein-nitrogen contents varied from 0.33% to 0.62% among different milk species. The highest r-values were recorded for correlations between crude protein and casein in buffalo (r = 0.82), cow (r = 0.88), sheep (r = 0.86) and goat milk (r = 0.98). The caseins and whey proteins were also positively correlated with true proteins in all milk species. A favorable balance of branched-chain amino acids; leucine, isoleucine, and valine were found both in casein and whey proteins. Leucine content was highest in cow (108±2.3 mg/g), camel (96±2.2 mg/g) and buffalo (90±2.4 mg/g) milk caseins. Maximum concentrations of isoleucine, phenylalanine, and histidine were noticed in goat milk caseins. Glutamic acid and proline were dominant among non-essential amino acids. Conclusively, current exploration is important for milk processors to design nutritious and consistent quality end products.

In Situ Experimental Validation of therm Finite Element Analysis for a High R-Value Wall Using Vacuum Insulation Panels

This paper details the method used for a theoretical evaluation of Team Ontario's, U.S. Department of Energy Solar Decathlon 2013 entrant, high R-value wall using vacuum insulation panels (VIPs). The purpose is to determine a theoretical whole-wall thermal resistance to be used for energy modeling. Theoretical simulations are performed in therm, a two-dimensional finite element heat transfer modeling program, and an in situ experimental validation is conducted in Carleton University's Vacuum Insulation Test Facility located in Ottawa, Ontario, Canada. The theoretical model is refined based on the experimental study, and a whole-wall thermal resistance of Team Ontario's wall design is determined to be 9.4 m2·K/W (53 h·ft2·°F/Btu) at an exterior design temperature of −18 °C (0 °F).

Yogurt made from milk heated at different pH values

Milk for yogurt manufacture is subjected to high heat treatment to denature whey proteins. Low milk pH values (≤6.5) at heating result in most denatured whey proteins becoming associated with casein micelles, whereas high milk pH values (≥7.0) at heating result in the formation of mostly soluble (nonmicellar) denatured whey protein complexes. There are conflicting reports on the relative importance of soluble and casein-bound whey protein aggregates on the properties of acid gels. Prior studies investigating the effect of pH of milk at heating used model gels in which milk was acidified by glucono-δ-lactone; in this study, we prepared yogurt gels using commercial starter cultures. Model acid gels can have very different texture and physical properties from those made by fermentation with starter cultures. In this study, we investigated the effects of different pH values of milk at heating on the rheological, light backscatter, and microstructural properties of yogurt gels. Reconstituted skim milk was adjusted to pH values 6.2, 6.7, and 7.2 and heated at 85°C for 30 min. A portion of the heated milk samples was readjusted back to pH 6.7 after heating. Milks were inoculated with 3% (wt/wt) yogurt starter culture and incubated at 40°C until pH 4.6. Gel formation was monitored using dynamic oscillatory rheology, and parameters measured included the storage modulus (G′) and loss tangent (LT) values. Light-backscattering properties, such as the backscatter ratio (R) and the first derivative of light backscatter ratio (R′), were also monitored during fermentation. Fluorescence microscopy was used to observe gel microstructure. The G′ values at pH 4.6 were highest in gels made from milk heated at pH 6.7 and lowest in milk heated at pH 6.2, with or without pH adjustment after heating. The G′ values at pH 4.6 were lower in samples after adjustment back to pH 6.7 after heating. No maximum in the LT parameter was observed during gelation for yogurts made from milk heated at pH 6.2; a maximum in LT was observed at pH ~4.8 for samples heated at pH 6.7 or 7.2, with or without pH adjustment after heating. Higher R-values were observed with an increase in pH of heating, with or without pH adjustment after heating. The sample heated at pH 6.2 had only one major peak in its R′ profile during acidification, whereas samples heated at pH 6.7 and 7.2 had 2 large peaks. The lack of a maximum in LT parameter and the presence of a single peak in the R′ profile for the samples heated at pH 6.2 were likely due to the partial solubilization of insoluble calcium phosphate when milk was acidified to this lower pH value. No clear differences were observed in the microstructures of gels between the different treatments. This study indicates that heating milk at the natural pH (~6.7) created an optimum balance of casein-bound and soluble denatured whey proteins, which resulted in yogurt with the highest gel stiffness.

Deformation behavior of electro-deposited pure Fe and its texture evolution during cold-rolling and subsequent annealing

Electro-deposited pure Fe has a characteristic of having very sharp isotropic ND//<111> fiber texture with a needle-like shaped fine grain elongated to ND. This Fe exhibits a surprisingly high r-value of over 7; however, such a high r-value might not be rationalized only from texture. Careful slip analyses reveal that restricted slips take place in the specific {110} slip planes, which are perpendicular to the sheet surface. Since grain boundaries with columnar structure are also perpendicular to the sheet surface, the slip plane in a certain grain may easily connect to the slip plane in adjacent grains having within ±30 degree rotation relationship around the common axis of ND//<111>. The operation of such a slip system is considered to cause the width strain much larger than the thickness strain. Furthermore, the texture evolution during cold-rolling and subsequent annealing was investigated using electro-deposited pure Fe as a starting material. Regardless of the amount of cold-rolling reduction, 65% to 90%, {111}<112> cold-rolling texture developed. After recrystallization, {111}<112> texture remained when material is cold-rolled by 65%, while {111}<011> texture developed when materials are cold-rolled by 80% and 90%. From the investigation into the mechanism on the development of recrystallization texture, the oriented nucleation and selective growth theories are concluded to contribute to the evolution of annealing texture.

Technical note: A linear model for predicting δ13 Cprotein.

Development of a model for the prediction of δ(13) Cprotein from δ(13) Ccollagen and Δ(13) Cap-co . Model-generated values could, in turn, serve as "consumer" inputs for multisource mixture modeling of paleodiet. Linear regression analysis of previously published controlled diet data facilitated the development of a mathematical model for predicting δ(13) Cprotein (and an experimentally generated error term) from isotopic data routinely generated during the analysis of osseous remains (δ(13) Cco and Δ(13) Cap-co ). Regression analysis resulted in a two-term linear model (δ(13) Cprotein (%) = (0.78 × δ(13) Cco ) - (0.58× Δ(13) Cap-co ) - 4.7), possessing a high R-value of 0.93 (r(2) = 0.86, P < 0.01), and experimentally generated error terms of ±1.9% for any predicted individual value of δ(13) Cprotein . This model was tested using isotopic data from Formative Period individuals from northern Chile's Atacama Desert. The model presented here appears to hold significant potential for the prediction of the carbon isotope signature of dietary protein using only such data as is routinely generated in the course of stable isotope analysis of human osseous remains. These predicted values are ideal for use in multisource mixture modeling of dietary protein source contribution.

An albumin, collagen IV, and longitudinal diameter of spleen scoring system superior to APRI for assessing liver fibrosis in chronic hepatitis B patients

The aim of this study was to screen the non-invasive indexes correlated with liver fibrosis and establish a scoring system for the diagnosis of liver fibrosis in hepatitis B patients. Data of 34 non-invasive indexes were collected for 208 hepatitis B patients. Correlation analysis and stepwise discriminant analysis was used to screen out indexes useful for the diagnosis of liver fibrosis. Finally, a scoring system composed of indexes screened out by stepwise discriminant analysis was established for the assessment of liver fibrosis. Twenty-one indexes correlating with liver fibrosis were screened out by correlation analysis; hyaluronic acid had the highest r-value, 0.456. A scoring system including albumin, collagen IV, and the longitudinal diameter of the spleen was established. The areas under the receiver operating characteristic curves (AUC) for this scoring system and the aspartate aminotransferase to platelet ratio index (APRI) in differentiating S3-4 from S0-2 were 0.79 (95% confidence interval (CI) 0.72-0.85) and 0.27 (95% CI 0.18-0.35), respectively. With a cut-off value of <3, the presence of significant fibrosis (S3-4) could be excluded by this scoring system with a negative predictive value of 86.1% and sensitivity of 86.8%. With a cut-off of >6, the presence of S3-4 fibrosis could be correctly identified with a positive predictive value of 73.6% and specificity of 87.6%. Using this scoring system, 53.4% of patients could be classified correctly and avoid liver biopsy. The scoring system provides a simpler method to identify significant fibrosis (S3-4) in chronic hepatitis B patients.

한국 현생 화강암류의 Nd 동위원소 조성 특성과 성인적 의미

Nd isotopic compositions analyzed from the Phanerozoic granitoids of Korea are integrated and discussed. Variations in Nd isotopic compositions can be explained either by temporal trend or by regional differences. Among the three active periods, first two periods during the Permian-Triassic and Jurassic seem to show variations from rather high values at the beginning to lower values during the later stages. Such trends probably reflect melting of the subducting oceanic crust and producing magma with higher proportion of depleted mantle derived materials during the early stage of subduction process, and subsequent magmas with greater proportion of old continental crust with progress of subduction. However, the Cretaceous-Paleogene period of active magmatism displays higher values during the advanced stage of the igneous activities, which is opposite to the previous active periods. The other explanation is that such differences in reflect regional differences, based on the observations that such high- granitoids distribute in the northeastern Gyeongbuk Province and Gyeongsang Basin. If this is the case, the regions with highr values may have distinct crustal evolution histories, e.g. younger average age. The choice between the two hypothesis could be made through further studies.

Evaluation of the thermal and structural performance of potential energy efficient wall systems for mid-rise wood-frame buildings

Approximately 30% of energy use in Canada is consumed in buildings, specifically space heating, which can be reduced by constructing thermally-resistant building envelopes. This study evaluates potential innovative energy-efficient wall systems for mid-rise (four to six storeys) wood-frame buildings in terms of thermal and structural performances. Regarding the thermal resistance performance, four wall systems are developed, installed in a full-scale test house, and examined, along with a baseline wall system, using the field data collected. The selection of the wall systems is based on current practice, structural analysis, pre-fabricability, and energy-efficiency. Several sensors are installed on each wall system to measure temperature, heat flow, and relative humidity. In addition, structural tests are conducted to determine the compressive loading capacity of the tested wall systems for both concentric and eccentric loads, where full-scale panels are constructed and tested in laboratory. As a general finding, all the tested wall systems achieved ASHRAE's minimum assembly R-value recommendation of RSI 3.45, where the I-joist wall system had the highest R-value, while the conventional wall system had the highest load-bearing capacity. This paper recommends I-Joist wall systems for their higher energy efficiency suggesting more future research on efficient end connections to achieve consistent structural performance.

Mechanical properties of 7475 aluminum alloy sheets with fine subgrain structure by warm rolling

The effect of transition elements on grain refinement of 7475 aluminum alloy sheets produced by warm rolling was investigated. The alloy which contains zirconium instead of chromium showed ultra fine structures with stable subgrains after warm rolling at 350 °C, followed by solution heat treatment at 480 °C. The average subgrain diameter was approximately 3 μm. It became clear that zirconium in solution has the effect of stabilizing subgrains due to precipitation of fine Al3Zr compounds during warm rolling. On the other hand, chromium-bearing compounds precipitate before warm rolling and they grow up to relatively large size during warm rolling. The warm rolled sheets with fine subgrains have unique properties compared with conventional 7475 aluminum alloy sheets produced by cold rolling. The warm rolled sheets solution heat treated had subgrain structures through the thickness with a high proportion of low-angle boundary less than 15°. The strength of the warm rolled sheets in T6 condition was about 10% higher than that of conventional 7475 aluminum alloy sheets. As the most remarkable point in the warm rolled sheets, the high Lankford (r) value of 3.5 was measured in the orientation of 45° to rolling direction, with the average r-value of 2.2. The high r-value would be derived from well developed β-fiber textures, especially with the strong {011}«211» brass component. The warm rolled sheets also had high resistance to SCC. From Kikuchi lines analysis and TEM images, it was found that PFZs were hardly formed along the low-angle boundaries of the warm rolled sheets in T6 condition. This would be a factor to lead to the improvement of resistance to SCC because of reducing the difference in electrochemical property between the grain boundary area and the grain interior.