Cyclic testing of steel column-tree moment connections with weakened beam splices

Traditionally, the beam splice assemblies of column-tree connections are designed according to the full-strength design principle. Actually, the beam splice is set up at a certain distance from the column face, thus the plastic moment capacity of the beam splice does not need to be greater than the plastic moment capacity of the beam. This paper experimentally presents the effects of the weakened beam splice on the seismic performance of column-tree steel moment connections. Cyclic tests of two column-tree connection specimens with weakened beam splices and one specimen following the full-strength design principle were conducted to verify their inelastic behavior and failure modes. The test results showed that the moment resisting capacity of the column-tree connection specimens with weakened beam splices did not obviously decrease. Also, their energy dissipation capacity was better than that of the specimen following the full-strength design principle.     

A discrete optimization process for the design of horizontal girders of rising sector gate using PIAnO

Many small dams have recently been constructed on several major rivers in the Republic of Korea to utilize these water resources and control water flows. One such water body is the Gangjeong reservoir in the Nakdong River; a rising sector gate was mounted on this reservoir. The finite element analysis (FEA) confirmed the empirical design of the gate to be safe with minor modifications. However, the positions of the horizontal girders are critical in the design of a gate, and it is must be determined by a trial-and-error process. To find the optimal solution for the positions and thicknesses of horizontal girders in a rising sector gate, this paper proposed a new procedure using the commercial optimization package, PIAnO, as well as Pro-Engineer, Hypermesh, and Abaqus. The optimal positions of the horizontal girders are selected from 9 predefined positions. A special technique was developed and applied to change the discrete position set, such as (1, 4, 8) to a continuous dimensionless variable. For this, a FORTRAN program was written to convert the dimensionless variable to a set of position numbers, and vice versa.     

Polychlorinated naphthalenes in air and snow in the Norwegian Arctic: a local source or an Eastern Arctic phenomenon?

PCNs were measured in air and snow during separate field campaigns at Ny-Alesund (April 2001) and Troms? (February/March 2003) in the Norwegian Arctic. Air concentrations ranged from 27 to 48 and 9 to 47 pg sigmaPCN m(-3) for Ny-Alesund (n=6) and Troms? (n=10), respectively. These concentrations (including the tri-chlorinated naphthalenes) greatly exceeded concentrations previously measured in the Canadian Arctic, but did fall within the upper range of concentrations observed over the eastern Arctic Ocean and regional seas. Local sources appear to be affecting concentrations observed at both sites, with the presence of several hexa-chlorinated naphthalenes at Troms? probably attributed to local/regional sources. Use of air mass back trajectories at Troms? revealed that background air concentrations in the Norwegian Arctic are likely to range between <9 and 20 pg sigmaPCN m(-3) and that contemporary concentrations derived close to potential sources (i.e. arctic towns) may equal or exceed those of PCBs. The mean concentration in surface snow was 350 and 240 pg sigmaPCN L(-1) (meltwater) (or 0.014 and 0.01 pg g(-1) (snow)) at Ny-Alesund and Troms?, respectively. The wide variation in concentrations observed between fresh snowfalls could be explained by different snow densities (as a surrogate of snow surface area), rather than attributed to varying air concentrations. A statistically significant inverse relationship was found between snow density and concentrations of tri- to penta-chlorinated homologues and compliments similar findings for the polychlorinated biphenyls (PCBs). This suggests that the vapour-sorbed quantity changes rapidly with snow ageing/compaction; with implications for the fate of these chemicals in the Arctic.     

Experimental study on the life prediction of servo motors through model-based system degradation assessment and accelerated degradation testing

The advent of smart factories has resulted in the frequent utilization of industrial robots within factories to increase production automation and efficiency. Due to the increase in the number of industrial robots, it has become more important to prevent any unexpected breakdowns of the factory. As a result, the lifespan prediction of machinery has become a crucial factor because such failures can be directly associated with factory productivity resulting in significant losses. Most of the failures occur within one of the core components of the robot arm, the servo motor, and thus we will focus on the analysis of the servo motor in this study. However, sensor attachment to such equipment is considered difficult due to the dynamic movement of the robot arm, meaning that internal instrumentation should be utilized during analysis. In addition, no definite measure to determine the degradation of the motor exists, and thus a new degradation index is proposed in this study. Therefore, in this study, the lifespan of the servo motor will be estimated through accelerated degradation testing methods based on a new system degradation assessment method, which estimates the fault of the system using observer-based residuals with encoder data obtained from internal instrumentation.     

A study on piezoelectric energy harvester using kinetic energy of ocean

Electricity generation through fossil fuels has caused environmental pollution. Accordingly, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels and solve this problem is in progress. These devices can consistently generate power. However, they have several drawbacks, such as high installation costs and limitations in possible set-up environments. Therefore, the piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. The piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Its advantages include a wider installation base and a lower technological cost. This study investigated a piezoelectric energy-harvesting device based on constant wave motion. This device can harvest power in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, percussion bar, triple layer piezoelectric bender, bearing and rudder. A multiphysical analysis coupled with the structure and piezoelectric elements was also conducted to estimate the device performance. The analysis accuracy was improved by applying the impact energy to the bender calculated based on the shape of the wave in the East Sea. The proposed device’s performance was finally confirmed by experiments.     

Three‐dimensional trajectory of electrospun polymer solution jet using digital holographic microscopy

The three‐dimensional trajectories of polymer solution jets during the electrospinning of polymer nanofibers were experimentally investigated. Test conditions included water solutions of polyethylene oxide (PEO) with concentrations typical of those producing beaded nanofibers, driving voltages ranging from 5 kV to 15 kV to generate a single polymer jet and injection pressures ranging from 0 kPa to 55 kPa. The present holographic imaging setup resolved the spatial growth of the bending instabilities, which is beneficial for validating numerical models. The results also showed the bead formation on the polymer fiber in‐flight. POLYM. ENG. SCI., 54:1765–1773, 2014. © 2013 Society of Plastics Engineers     

Advanced Chamfering Technology for Edge Strengthening

Damage‐free chamfering method for strengthening a glass edge was introduced and its effect on the edge property was discussed in detail. The chamfered surface was evaluated using an optical microscope, a confocal LSM, and a birefringence measurement system. The mechanical properties were characterized by measuring hardness, Young's modulus, and bending strength. The results revealed that the cut edge of 0.55t thin glass sheet containing median cracks and chips was exfoliated uniformly to a thickness of 200 μm, and a smooth edge surface was created (Ra = 0.03 μm). We also reported that the chamfered surface had a compressive stress enabling hardness and Young's modulus increase, and the edge strength improved from 117 to 199 MPa.     

Copper‐Catalyzed Aerobic Formation of Unstable Sulfinyl Radicals for the Synthesis of Sulfinates and Thiosulfonates

Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided.

     

Copper(I) Bromide‐Dimethyl Sulfide‐Catalyzed Direct Sulfanylation of 4‐Hydroxycoumarins and 4‐Hydroxyquinolinones with Arylsulfonylhydrazides and Selective Fluorescence Switch‐ On Sensing of Cadmium(II) Ion in Water

An efficient protocol for the direct sulfanylation of various 4‐hydroxycoumarins and 4‐hydroxyquinolinones in good yield with arylsulfonylhydrazides as sulfanylating agents was developed via copper(I) bromide⋅dimethyl sulfide‐catalyzed S–O, S–N bond cleavage and C–S cross‐coupling reactions. A highly selective fluorescence turning‐on sensing of cadmium(II) ions in water using the synthesized 3‐sulfanyl‐4‐hydroxycoumarin derivative was also investigated.