In this study, in order to determine the very early load transfer behavior in the bolted joint connection, experimental dynamic analysis of different laminated glass beams including two surface cracks is considered. F...In this study, in order to determine the very early load transfer behavior in the bolted joint connection, experimental dynamic analysis of different laminated glass beams including two surface cracks is considered. For this purpose, both three different plastic interlayers （i.e., three types of polyvinyl butyral--PVB） and three different glass-lamina thicknesses are taken into account. Effects of the plastic interlayer, thickness of the glass-lamina, number of surface cracks and their locations on the vibration characteristics/structural performances are examined experimentally. Vibration tests are performed to present free vibration characteristics of the laminated glass beams under clamped-free boundary conditions. Experimental dynamic analysis consists of six parts： （I） vibration analysis with no-crack and no-hole with a bolted joint; （I1） vibration analysis with a surface crack and no-hole with a bolted joint; （III） vibration analysis with two surface cracks and no-hole with a bolted joint; （IV） vibration analysis with no-crack and a hole with a bolted joint; （V） vibration analysis with a surface crack and a hole with a bolted joint; （VI） vibration analysis with two surface cracks and a hole with a bolted joint. For these experimental steps, an impact hammer with a force transducer is used to excite the uncracked or cracked composite beams through the selected points. After the excitation, the responses are obtained by an accelerometer. The vibration measurements are completed using a microprocessor-based data acquisition system and nCode GlyphWorks software. Results are given in tabular and graphical forms.展开更多
Difference systems of sets (DSSs) are combinatorial configurations which were introduced in 1971 by Levenstein for the construction of codes for synchronization. In this paper, we present two kinds of constructions of...Difference systems of sets (DSSs) are combinatorial configurations which were introduced in 1971 by Levenstein for the construction of codes for synchronization. In this paper, we present two kinds of constructions of difference systems of sets by using disjoint difference families and a special type of difference sets, respectively. As a consequence, new infinite classes of optimal DSSs are obtained.展开更多
To control the growth of space debris in the geostationary earth orbit （GEO）, a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug （i.e., active spacecraft）, tether, ne...To control the growth of space debris in the geostationary earth orbit （GEO）, a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug （i.e., active spacecraft）, tether, net, and target （i.e., GEO debris） constitute a rig- id-flexible coupled tethered combination system （TCS）, and subsequently the system is transported to the graveyard orbit by a thruster equipped on the tug. This paper attempts to study the dynamics of tether-tugging leorbiting after net capture. The net is equivalent to four flexible bridles, and the tug and target are viewed as rigid bodies. A sophisticated mathematical model is developed, taking into account the system orbital motion, relative motion of two spacecraft and spacecraft attitude motion. Given the complexity of the model, the numerical method is adopted to study the system dynamics characteristics. Particular attention is given to the investigation of the possible risks such as tether slack, spacecraft collision, tether rupture, tether-tug intertwist and destabilizing of the rug＇s attitude. The influence of the initial conditions and the magnitudes of the thrust are studied.展开更多
文摘In this study, in order to determine the very early load transfer behavior in the bolted joint connection, experimental dynamic analysis of different laminated glass beams including two surface cracks is considered. For this purpose, both three different plastic interlayers （i.e., three types of polyvinyl butyral--PVB） and three different glass-lamina thicknesses are taken into account. Effects of the plastic interlayer, thickness of the glass-lamina, number of surface cracks and their locations on the vibration characteristics/structural performances are examined experimentally. Vibration tests are performed to present free vibration characteristics of the laminated glass beams under clamped-free boundary conditions. Experimental dynamic analysis consists of six parts： （I） vibration analysis with no-crack and no-hole with a bolted joint; （I1） vibration analysis with a surface crack and no-hole with a bolted joint; （III） vibration analysis with two surface cracks and no-hole with a bolted joint; （IV） vibration analysis with no-crack and a hole with a bolted joint; （V） vibration analysis with a surface crack and a hole with a bolted joint; （VI） vibration analysis with two surface cracks and a hole with a bolted joint. For these experimental steps, an impact hammer with a force transducer is used to excite the uncracked or cracked composite beams through the selected points. After the excitation, the responses are obtained by an accelerometer. The vibration measurements are completed using a microprocessor-based data acquisition system and nCode GlyphWorks software. Results are given in tabular and graphical forms.
基金supported by National Natural Science Foundation of China (Grant Nos.10771051,10831002)
文摘Difference systems of sets (DSSs) are combinatorial configurations which were introduced in 1971 by Levenstein for the construction of codes for synchronization. In this paper, we present two kinds of constructions of difference systems of sets by using disjoint difference families and a special type of difference sets, respectively. As a consequence, new infinite classes of optimal DSSs are obtained.
基金supported by the National Natural Science Foundation of China(Grant No.11272345)
文摘To control the growth of space debris in the geostationary earth orbit （GEO）, a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug （i.e., active spacecraft）, tether, net, and target （i.e., GEO debris） constitute a rig- id-flexible coupled tethered combination system （TCS）, and subsequently the system is transported to the graveyard orbit by a thruster equipped on the tug. This paper attempts to study the dynamics of tether-tugging leorbiting after net capture. The net is equivalent to four flexible bridles, and the tug and target are viewed as rigid bodies. A sophisticated mathematical model is developed, taking into account the system orbital motion, relative motion of two spacecraft and spacecraft attitude motion. Given the complexity of the model, the numerical method is adopted to study the system dynamics characteristics. Particular attention is given to the investigation of the possible risks such as tether slack, spacecraft collision, tether rupture, tether-tug intertwist and destabilizing of the rug＇s attitude. The influence of the initial conditions and the magnitudes of the thrust are studied.
