• Steel and Composite Structures
• /
• v.29 no.1
• /
• pp.1-22
• /
• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Steel and Composite Structures
• /
• v.29 no.5
• /
• pp.603-622
• /
• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• Membrane Journal
• /
• v.13 no.1
• /
• pp.37-46
• /
• 2003

The electrokinetic effect can be found in cases of the fluid flowing across the charged membrane micropores. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is taken into the equation of motion. The electrostatic potential profile is computed a priori by applying the finite difference scheme, and an analytical solution to the Navier-Stokes equation of motion for slit-like pore is obtained via the Green's function. An explicit analytical expression for the flow-induced streaming potential is derived as functions of relevant physicochemical parameters. The influences of the electric double layer, the surface potential of the wall, and the charge condition of the pore wall upon the velocity profile as well as the streaming potential are examined. With increasing of either the electric double layer thickness or the surface potential, the average fluid velocity is entirely reduced, while the streaming potential increases.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.6
• /
• pp.638-644
• /
• 2015

This paper describes the continuing effort to analysis and design on dynamic and electrical behavior of gamma-type free piston Stirling engine/generator with dual-opposed linear generator for domestic micro-CHP (Combined Heat and Power) system. The double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric sinusoidal displacement and are connected with moving magnet type linear generators for power generation. To operate Stirling engine/generator, combustion heat of natural gas is supplied to hot-end and heat is rejected from cold-end by cooling water. The temperature difference across the displacer induces the oscillating motion, and it can be explained with mass-spring vibration system. The purpose of this paper is to describe the design process of linear generator for the double acting free-piston Stirling engine.

• Restorative Dentistry and Endodontics
• /
• v.44 no.2
• /
• pp.18.1-18.9
• /
• 2019

Objective: This study evaluated the presence of residual root canal filling material after retreatment using micro-computed tomography (micro-CT). Materials and Methods: Extracted human teeth (single- and double-rooted, n = 21/each; C-shaped, n = 15) were prepared with ProFile and randomly assigned to three subgroups for obturation with gutta-percha and three different sealers (EndoSeal MTA, EndoSequence BC sealer, and AH Plus). After 10 days, the filling material was removed and the root canals were instrumented one size up from the previous master apical file size. The teeth were scanned using micro-CT before and after retreatment. The percentage of remaining filling material after retreatment was calculated at the coronal, middle, and apical thirds. Data were analyzed using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni post hoc correction. Results: The tested sealers showed no significant differences in the percentage of remaining filling material in single- and double-rooted teeth, although EndoSeal MTA showed the highest value in C-shaped roots (p < 0.05). The percentage of remaining filling material of AH Plus and EndoSeal MTA was significantly higher in C-shaped roots than in single- or double-roots (p < 0.05), while that of BC sealer was similar across all root types. EndoSeal MTA showed the highest values at the apical thirds of single- and double-roots (p < 0.05); otherwise, no significant differences were observed among the coronal, middle, and apical thirds. Conclusions: Within the limitations of this study, a large amount of EndoSeal MTA remained after retreatment, especially in C-shaped root canals.

• Asia pacific journal of information systems
• /
• v.30 no.3
• /
• pp.497-512
• /
• 2020

Anonymity is one of the key factors that influence communication and the work behaviours of people. It is even more evident in an online community where the role of anonymity can be akin to a double-edged sword: it can increase participation while at the same time having detrimental effects due to irresponsible and disruptive behaviour. Most studies on anonymous participation in groups or communities have reported this ambivalent view of anonymity: positive or negative. Furthermore, the effects of anonymous participation may be different in a dynamic sense because the task characteristics of participation can vary across time. In this study, we hypothesise that the effects of anonymity in online collaboration differ across the stages of collaboration. We analysed 2,978 featured articles on the English-language Wikipedia website and investigated the contributions of anonymous participants. While the contributions of anonymous participants were negative to collaboration efficiency as a whole, the negative effect of anonymous participants was stronger in the earlier stage than the later stage of collaboration. These findings indicate that the effect of anonymity has two sides in terms of collaboration efficiency in the same collaborative environment.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.44 no.1
• /
• pp.14-19
• /
• 2024

"Chamgreen" was a domestically developed rye (Secale cereal L.) cultivar in South Korea, known for its quick heading, cold resistance, and abundant yield of forage. The heading date of cv. 'Chamgreen' averaged April 17th, which was 4 days earlier than the standard cv. 'Gogu'. In the early harvesting stage, the plant height reached an average of 119 cm, 7 cm taller than the standard cv. 'Gogu', and the number of spikes per m² was 865, slightly less than cv. 'Gogu's 897. Resistance to cold and powdery mildow remained consistent across four regions nationwide over three years, with an average rating of 0, matching cv. 'Gogu'. Lodging resistance was also rated at 2, equivalent to cv. 'Gogu'. The dry matter yield of cv. 'Chamgreen' was 9.1 tons per hectare, 15% higher than cv. 'Gogu's 7.9 tons. Although the protein content in cv. 'Chamgreen' was 13.5%, 1.6% lower than cv. 'Gogu', the total digestible nutrients (TDN) content was 5.81 tons per hectare, 20% higher than cv. 'Gogu'. Due to its strong cold resistance, cv. 'Chamgreen' allows for winter cultivation through double cropping and rotation systems in various regions across the country.

• Journal of the Korean Chemical Society
• /
• v.38 no.6
• /
• pp.405-410
• /
• 1994

Molecular orbital calculations suggest that an interaction between the psoralen derivatives of excite state and the thymine of ground state is dicussed in terms of their differing abilities to molecular complex. PM3-CI-UHF indicates that photocycloadducts across the C3-C4 and C4'-C5' double bonds of the methylpsoralen and hydroxypsoralen with thymine C5-C6 double bonds were deduced to be formed by their preferable frontier orbital interactions. The electronic properties of psoralen derivatives in the ground and excited states correlate with this difference in structure-activity relationship.

• The KIPS Transactions:PartC
• /
• v.10C no.4
• /
• pp.519-524
• /
• 2003

During the period of co-existence of IPv4 and IPv6, Ipv6 over IPv4 tunneling technique is intended as a start-up transition mechanism. However, most of IPv4 firewalls do not support the IPv6 over IPv4 tunneling packet filtering. Finally, it is impossible that a user inside IPv4 firewall connects with an IPv6 host across IPv4 network. Without any additional hardware or changing the policy of IPv4 firewall, we solve this problem using proposed Double-encapsulation and applied-HTTP tunneling technique that are end-to-end solutions. This enables cheaper IPv6 migration solutions.

• Proceedings of the KIPE Conference
• /
• 2001.10a
• /
• pp.193-197
• /
• 2001

This paper presents a novel circuit topology of the double two-switch forward type high frequency transformer linked soft-switching PWM DC-DC power converter with tapped inductor filters that can operate under a condition of the low peak voltage stress across the power semiconductor devices and lowered peak current stress through the transformer for some high power applications. This circuit topology of an interleaved two-switch forward soft-switching power converter is proposed in the order to minimize an idle circulating current due to the tapped inductor filter without of any additional active auxiliary resonant-assisted snubber circuits, such as active resonant DC link snubbers and AC link snubbers, active resonant commutation leg link snubbers. The unique advantages of this power converter are less power circuit components and power semiconductor devices, constant frequency PWM scheme, cost effective configuration and wider soft-switching PWM operation range under PWM power regulations load variations. The practical effectiveness of the proposed soft-switching converter circuit topology is tested by simulations and is proved by experimental results received from the 500W-100kHz breadboard setup.