Knowledge diffusion under patent with asymmetric firms

We show that if patent protection and trade secrecy generate asymmetric market structure, an innovator may prefer patent protection than trade secrecy even if the diffusion probability is higher under the former but it increases market concentration by preventing some imitators. So, whether an innovator prefers patent protection or trade secrecy depends on the trade-off between the diffusion probability and market concentration.

DEGRADATION OF YIELD STRENGTH OF LATERALLY LOADED WOOD-TO-ORIENTED STRANDBOARD CONNECTIONS AFTER EXPOSURE TO ELEVATED TEMPERATURES

Wood to sheathing connections is crucial to lateral force resisting system of the wood-frame structure. Engineers are often faced with the challenge of predicting strength of a partially damaged structure after it has been exposed to elevated temperature during a fire. Numerical simulations to predict the residual strength need thermal degradation data and models for the material as well as the connections. Therefore, it is important to categorize connection response when exposed to elevated temperatures for a sustained period of time. This study addresses this issue by developing models to predict lateral yield strength degradation of wood to Oriented Strandboard (OSB) connection after exposure to elevated temperature. A total of 394 Douglas-fir to OSB connections were tested laterally as a function of 8 different temperatures and 8 exposure times within each temperature regime. Yield strength of the connection decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. A regression-based statistical model was developed. Additionally, these results were fit to a 2-step simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model. The kinetics-based model was preferred over regression model as it fit the data better with one less parameter and predictions consistently matched the observed values for an independent data set

Export cartel and consumer welfare

The purpose of this paper is to show that export cartels are not necessarily harmful for consumers in the importing countries. Using the strategic trade policy model of Brander and Spencer (1985a), we show that, contrary to the harmful effect, product-market cooperation benefits consumers by affecting the trade policies. We further show that consumers in the importing countries are affected adversely if cooperation is among the governments of the exporting countries, instead of the exporting firms

Lateral Load-Carrying Connection Properties and Withdrawal Capacity of Hybrid Poplar

An experimental study is reported aimed at determining the yield load, withdrawal capacity, and validity of National Design Specification (NDS) yield models on connections between hybrid poplar and common sheathing materials using a dowel-type fastener. Plantation-grown hybrid poplar (Pacific Albus) was procured, and connections with two different thicknesses of oriented strandboard and plywood were constructed using a dowel-type fastener. The NDS does not list connection design values for low-density wood species. Therefore, it was important to validate the NDS yield model equations for applicability toward a low-density species such as hybrid poplar. The results quantify the lateral load-carrying and withdrawal capacities of hybrid poplar. Also, the prediction using NDS yield models consistently matched the observed yield loads and yield modes for all the sheathing types used in this study. The data suggest that the NDS yield model is an adequate tool for connection design even for low-density species, provided knowledge of dowel-bearing capacity of the hybrid poplar is known

Synthesis, characterization and in vitro biocompatibility study of strontium titanate ceramic: A potential biomaterial

Strontium (Sr), a mineral element present in trace in the human body, has significant effect on bone remodelling. Sr containing ceramics have huge potential to heal bone defects and improve osseointegration of implants. In this study, perovskite oxide – strontium titanate (SrTiO3) was synthesized and explored its potential for biomedical applications. The phase pure SrTiO3 powder was synthesized from solid state reaction of strontium carbonate (SrCO3) and titanium dioxide (TiO2) at 1200 °C for 2 h. The as synthesized SrTiO3 powder, pure hydroxyapatite (HAp) and SrTiO3-50 wt% HAp (SH50) premixed powders were sintered at different temperatures varies from 1100 to 1400 °C in air. The sintered samples were characterized using X-ray diffraction (XRD) for phases and scanning electron microscopy (SEM) for microstructure analysis. XRD results revealed no dissociation of HAp or reaction with SrTiO3 during sintering. The sintered samples were studied for mechanical properties, wettability, and biocompatibility. The relative density of the sintered SrTiO3 increases with increasing sintering temperature. The relative density of SrTiO3 was increased from 77% to 98% with increase in sintering temperature from 1250 to 1400 °C. The substantial improvement of hardness and compressive strength was observed for sintered SrTiO3 compared to HAp of similar porosity level. The hardness and compressive strength of SrTiO3 sintered at 1250 °C found ~6 and ~3.5 times higher than sintered HAp. In vitro dissolution study carried out in phosphate buffer solution at 37 °C, confirmed the release of Sr2+ ion from the bulk SrTiO3 sintered at 1250 °C. The in vitro cell materials interaction showed cytocompatibility of sintered SrTiO3 and SrTiO3-HAp composite. In summary, excellent biocompatibility of SrTiO3 with superior mechanical properties confirmed its potential as novel biomaterial for use in the repair of infected or aseptic bone defects

Quantifying environmental impacts of poplar biomass production in the U.S. Pacific Northwest

The life cycle impacts were determined for poplar-managed four ways in the Pacific Northwest of the United States. Two sites had 3-yr rotations and either no irrigation (Site 1) or irrigation with river water (Site 2). The other sites had 12-yr rotations and irrigation with wastewater from a treatment facility (Site 3) or irrigation with landfill leachate (Site 4). Primary data for land preparation, plantation management, harvesting, and land restoration at each site and the production of cuttings at an additional facility were collected. A cradle to gate life cycle assessment was conducted using SimaPro PhD v8 based on the primary data and secondary data from the US life cycle inventory and ecoinvent v3 database to create a life cycle inventory. Impact indicators were provided by TRACI model. Short rotations resulted in lower global warming impact per unit output (79.5 and 54.5 kg CO2 eq/t) and energy consumption (1381.8 and 877.4 MJ/t) than long rotations (93.1 and 81 kg CO2 eq/t and 1406.9 and 1343.5 MJ/t) mainly due to reduced diesel use. Higher planting densities resulted in greater water and electrical consumption attributed to cuttings. Pesticide and herbicide use strongly affected ozone depletion and eutrophication, whereas fuel consumption had strong effects on global warming impact, smog, and acidification. Increasing biomass yield reduced impacts. When the electricity was all from biomass, global warming and acidification decreased; however, ozone depletion, smog, and eutrophication increased. The results suggested that both, herbicide application during plantation management and diesel consumed during harvesting at these sites should be optimized to decrease the environmental impacts. 

Imaging of Structural Timber Based on in Situ Radar and Ultrasonic Wave Measurements: A Review of the State-Of-The-Art

With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR’s capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material’s complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced

Strain distribution in OSB and GWB in wood frame shear walls

The overall goal of this study was to gain an insight into the load sharing aspect between oriented strand board (OSB) and gypsum wall board (GWB) in shear wall assembly during racking load. More specifically the objectives of the study were to: (1) evaluate qualitatively the load sharing between OSB and GWB in a wood frame shear wall assembly, (2) analyze the failure progression of GWB and OSB, (3) study the strain profile around fastener on GWB and OSB sides of shear wall, and (4) study the effect of GWB on shear wall behavior. Monotonic tests were conducted on 2440 x 2440 mm walls with 38 x 89 mm Douglas-fir studs 610 mm on center. Two 1220x2440x11.1 mm OSB panels were installed and fastened vertically to the frame with Stanley Sheather plus ring shank nails 102 mm and 305 mm on center along panel edges and intermediate studs, respectively. Two 12.7 mm GWB panels were installed oriented vertically on the face opposite the OSB using standard dry wall screws on some walls. Anchorage to the walls was provided by two 12.7 mm A307 anchor bolts installed 305 mm inward on the sill plate from each end of the wall. In addition to these anchor bolts, walls included hold-downs installed at the end studs of the wall and were attached to the foundation with 15.9 mm Grade 5 anchor bolts making the walls fully anchored. The loading was monotonic and based on ASTM E564-00. Sixteen walls were tested in total, out of which 11 (Type A) were sheathed on both sides with OSB and GWB, while 5 walls were tested without GWB (Type B). Optical measurement equipment based on the principle of Digital Image Correlation (DIC) was used for data acquisition and analysis. DIC is a full-field, non-contact technique for measurement of displacements and strains. The set up consist of a pair of cameras arranged at an angle to take stereoscopic images of the specimen. The system returns full field 3D displacement and strain data measured over the visible specimen surfaces. The tests revealed that load is shared by both OSB and GWB initially in a shear wall assembly. GWB fails locally prior to OSB and load shifts to OSB as GWB starts to fail. Beyond this point, load continues to increase and walls finally fail in OSB. The tests also revealed that load path in wall type A and B is different. Failure in wall type A starts at the uplift corner in GWB and then moves to the uplift corner in OSB. Finally the walls fail at middle of top plate for GWB and OSB both. In wall type B the failure is initiated at the uplift corner in OSB followed by middle region at sill level and ends up at middle section of wall where two panels meet. The uplift corner fasteners are of prime importance in both types of wall and panels. Comparing the strain profiles created using DIC, strains only near fasteners are observed and no detectable strain is observed in the field of the panel. There is a steady built up of strain in wall type B from start to failure and there is no abrupt change in strain during entire loading indicating a ductile failure. Wall type B shows more ductile behavior than wall type A because of the lack of ability of GWB to deform at higher load in wall type A where as OSB in wall type B continues to deform at higher load. Also OSB panel in wall type B experiences higher strains than the OSB panel for wall type A for a given load. In wall type A, there is higher strain around the fasteners in GWB than in OSB in the initial part of loading. GWB is stiffer than OSB, it attracts load and in turn deformation is higher than OSB. But being brittle, GWB fails at around 60% of the ultimate wall capacity and load shifts to OSB. This is indicated by large change in strain in OSB. OSB continues to attract load but the strain in OSB increases at a faster rate till failure indicating a much less ductile behavior than that of wall type B. Contribution of GWB towards strength of the wall is marginal (0.8%) while an increase of 50% was observed in overall stiffness of the walls. Since GWB is stiffer than OSB, it contributes more to the overall stiffness of the wall. Ductility factor of the system increases by 20% and the ductility of the system increases by 13% while energy dissipated by the wall decreases when GWB is included in the shear wall assembly. GWB being brittle reduces the ability to deform before failing and hence a decrease in peak, failure and yield displacements is observed in magnitude of 18%, 13% and 27%, respectively Overall, these tests suggest that initially during loading of a wall the load is shared between OSB and GWB. However, the proportion of load sharing is not known. As GWB fails first the load shifts to the OSB panel which resists it till the failure of the wall. This aspect of load sharing between structural sheathing and gypsum wall board is not incorporated in current design practices. It is recommended that more tests especially with cyclic and dynamic loading be conducted to better understand and quantify the aspect of load sharing

Postpeak residual capacity of nailed connections of a shear wall

To quantify the postpeak residual capacity and to gain insights into the load transfer mechanism of a shear wall, nail connection tests were performed on salvaged connections after a monotonic shear wall test loaded up to peak load. Experimental results reveal that there is a loss of strength in most of the fasteners studied, indicating that almost all the fasteners contribute toward racking resistance of the wall. The maximum loss of strength was observed for the fastener in the uplift corner and for the fastener along the middle stud. Another area where fasteners exhibited a significant loss of strength was in plate connection located at the bottom plate. The performance of a shear wall can be enhanced by strengthening the two areas – uplift corner and bottom plate.This is the publisher’s final pdf. The published article is copyrighted by Walter de Gruyter GmbH and can be found at: http://www.degruyter.com/view/j/hfsg.Keywords: racking resistance, uplift corner, yield strength, national design specification, strength loss, nail connection test, bottom plate, wood-frame shear wall, load transfe

The effect of elevated temperature on mechanical behavior of structural wood and wood-based composites

Engineers, in practice, are often faced with the challenge of evaluating a fire-damaged structure and developing a rehabilitation and retrofit plan. In order to decide on a rehabilitation and retrofit plan, information on thermal degradation of building materials and connections are vital. A critical knowledge gap exists in terms of thermal degradation of materials and connections with respect to light-frame wood construction. Along with solid sawn lumber (SSL), various wood-based composites such as plywood, oriented strand board (OSB) and laminated veneer lumber (LVL) are also used in wood-frame construction. Characterization of the thermal degradation of strength of these structural materials will help assess the service life and strength of the damaged structure. This study addressed the thermal degradation of material strength and connection strength by conducting tests on wood, wood-based composites and connections after subjecting them to elevated temperatures, hence studying the post-fire residual strength in wood and wood composite construction. The properties evaluated in this study were bending strength (MOR), bending stiffness (MOE), lateral nail capacity, dowel bearing strength, fracture toughness and bond strength (IB) after exposing the materials to elevated temperature for various exposure times. In addition, the bending strength of OSB and plywood was studied in great detail as a function of additional temperatures and exposure times. A general trend of degrading bending properties, fracture toughness, dowel bearing strength of materials and yield strength of the connections of various configurations with high temperature and duration of exposure was observed and confirmed by statistical analysis. A statistical regression based model incorporating the effects of temperature, time of exposure and thier interaction and a model based on first-order kinetics were developed and evaluated for predicting the strength loss. The kinetics-based model was better than the regression-based approach. Using the kinetics analysis along with time-temperature superposition for OSB and plywood, a master curve was generated at a reference temperature of 150°C that can be used for residual strength estimates and failure time predictions. A reasonable prediction of connection design values was made using National Design Specifications (NDS) yield models for thermally degraded materials. Conventional tests for bond strength provided excessive scatter which renders any statistical comparison highly difficult. An alternative to IB and bond classification could be fracture testing using energy methods for wood bond strength evaluation. The various analytical models developed will help for characterizing the thermal degradation of material properties. Models specified in design codes were evaluated against the thermal degradation of materials. This knowledge of thermal degradation and the models will help engineers and architects in recommending categorical improvement, rehabilitation and retrofit of structures