Post Structure Research Articles

Use of Supporting Post Width to Increase the CMUT’s Resonant Frequency

A new method is proposed to increase the resonant frequency of a Capacitive Micromachined Ultrasonic Transducer (CMUT) device while keeping the radii unchanged for devices fabricated by sacrificial release (SR) method. The resonant frequency of a CMUT cell is determined by the properties of the membrane such as the Young’s modulus, membrane dimensions and effective membrane mass. Effective Young’s modulus is used to calculate the resonant frequency of CMUT fabricated by SR method. The supporting post structure will affect the boundary conditions at the edge of the CMUT membrane and in turn affect the deflection together with the effective Young’s modulus of the membrane. The perturbation method is used to derive the solution for the governing von Kármán equations. The results show that the thicker is the supporting post width, the higher is the resonant frequency. This method can also be used to simplify the mask design and CMUT fabrication process.

Variable Stiffness Design and Multiobjective Crashworthiness Optimization for Collision Post of Subway Cab Cars

This paper proposes a variable stiffness collision post (VSCP) structure based on a uniform stiffness collision post (USCP) structure and performs stiffness matching optimization for VSCPs. A collision post structure assembled in a subway front-end frame can maintain the living space and absorb a certain amount of the kinetic energy of an impact. The experiment was applied on USCP, and the finite element model was verified experimentally. To investigate the effects of the stiffness parameters of VSCP on the specific energy absorption response (SEA_VSCP) and the area of intrusion response (S_In), response surface models fitted from design of experiment were adopted with the finite element model. In addition, a multiobjective optimization design was realized by using the global response search method and a Pareto frontier sequence was generated, which was based on the developed response surface model. It was found that the optimal value of SEA_VSCP and S_In responses cannot be achieved at the same time. Finally, a grey relational analysis is propounded to attain a desirable balance between SEA_VSCP and S_In from the Pareto frontier sequence under constraints of the peak crash force of VSCP and energy absorption of the front-end of cab car. The optimization result shows that the crashworthiness of VSCP is better than that of USCP.

Uniform trichromacy in Alouatta caraya and Alouatta seniculus: behavioural and genetic colour vision evaluation

Primate colour vision depends on a matrix of photoreceptors, a neuronal post receptoral structure and a combination of genes that culminate in different sensitivity through the visual spectrum. Along with a common cone opsin gene for short wavelengths (sws1), Neotropical primates (Platyrrhini) have only one cone opsin gene for medium-long wavelengths (mws/lws) per X chromosome while Paleotropical primates (Catarrhini), including humans, have two active genes. Therefore, while female platyrrhines may be trichromats, males are always dichromats. The genus Alouatta is inferred to be an exception to this rule, as electrophysiological, behavioural and molecular analyses indicated a potential for male trichromacy in this genus. However, it is very important to ascertain by a combination of genetic and behavioural analyses whether this potential translates in terms of colour discrimination capability. We evaluated two howler monkeys (Alouatta spp.), one male A. caraya and one female A. seniculus, using a combination of genetic analysis of the opsin gene sequences and a behavioral colour discrimination test not previously used in this genus. Both individuals completed the behavioural test with performances typical of trichromatic colour vision and the genetic analysis of the sws1, mws, and lws opsin genes revealed three different opsin sequences in both subjects. These results are consistent with uniform trichromacy in both male and female, with presumed spectral sensitivity peaks similar to Catarrhini, at ~ 430 nm, 532 nm, and 563 nm for S-, M- and L-cones, respectively.

Structural and Economic Analysis of Meyal Oil Field in the Northern Potwar Deformed Zone, Upper Indus Basin, Pakistan

Potwar sub-basin is famous for its structural style, hydrocarbon exploration and production activities from Cambrian to Pliocene rocks. Foreland basin related subsurface structures, in the presence of source and seal rocks offer a variety of traps to host hydrocarbons. Meyal Oil field, situated in the NW Potwar sub-basin, is a hydrocarbon resource for the country. Subsurface structures of Meyal area were outlined by interpreting two strike and four dip lines in IHS Kingdom suite. Borehole data of MYL-10, MYL-12 and MYL-13 exploratory wells were incorporated to improve the subsurface understanding. A total five prominent reflectors of Permian, Triassic, Jurassic, Paleocene and Eocene rocks were marked on the seismic sections. The seismic interpretation shows a post Eocene pop-up structure flanked by a back thrust and a fore thrust. Moreover, the time structure maps for Meyal area display a doubly plunging and faulted anticline as a result of south directed compression. Four isochron maps show thickness variation in Permian to Eocene sediments in the study area. The results of interpretation show favorable structural trap for economic hydrocarbon exploration.

The Effect of Hybrid-Lattice Micro Post Arrays on Flow Field of Semi-Packed Gas Chromatography Column

In this paper, a hybrid-lattice array of micro post structure was proposed to deal with the velocity fluctuation in the channel of traditional semi-packed micro gas chromatography column. Its flow field was analyzed by using COMSOL software. According to the differences in the six types of microarray structures and the distribution of the flow velocity field of each structure, a triangular-quadrangular hybrid lattice array structure 1 is determined, which can most effectively improve the uniformity of the velocity field. The hybrid-lattice array microstructures proposed in this paper can effectively improve the velocity field distribution in the channel of semi-packed micro gas chromatography column. It provides a theoretical basis for the structural design of new micro gas chromatographic columns.

Dividend payout policies in the pre and post split share structure reform in China

This paper examines the motivation of dividend payout policies for Chinese listed firms before and after the Split Share Structure Reform in China from the corporate governance-related viewpoint. A...

Local mismatch and noise investigation for pre and post multilayer pHEMTs

The key objective of this study is to investigate the local mismatch of pre and post multilayer structure on the active devices. Five pre and post multilayer structure pHEMTs on the same wafer within the same cell between adjacent devices are considered. As the study of local mismatch ensures good yields and a way to gain insights about the technology various comparisons are made including the effects of multilayer structuring. The threshold voltage, built-in potential and the net doping concentration of the 2-DEG of the devices are extracted through capacitance-voltage data. The underlying electrical parameter of the transistors as well as the RF figure of merit has been analyzed. The microwave noise related parameters namely minimum noise figure, associate gain, noise resistance, magnitude of the optimum reflection are also discussed and investigated. Centre-to-edge mismatch results in minor variation in performance between devices. These studies would help within the advancement of solid, proficient and low cost generation of future compact structure in 3-D multilayer MMICs.

Crashworthiness design and experimental validation of a novel collision post structure for subway cab cars

This paper proposes a novel collision post structure designed to improve the crashworthiness of subway cab cars. The structure provides two innovative features: 1) a simpler connection between the post and the car roof, which gives a more reasonable load transfer path to reduce the stress concentration at the joint; and 2) a stiffness induction design that provides an ideal deformation model to protect the safe space of the cab cars. The novel collision post structure was evaluated with finite element analysis, and a prototype cab car was mechanically tested. The results demonstrate that the deformation response was stable and agreed well with the expected ideal mode. The maximum load was 874.17 kN and the responses remained well above the elastic design load of 334 kN as required by the design specification. In addition, there was no significant tearing failure during the whole test process. Therefore, the novel collision post structure proposed has met the requirements specified in new standard to improve the crashworthiness of subway cab cars. Finally, the energy absorption efficiency and light weight design highlights were also summarized and discussed.

Entry of Alphaherpesviruses

Alphaherpesviruses are enveloped viruses that enter cells by fusing the viral membrane with a host cell membrane, either within an endocytic vesicle or at the plasma membrane. This entry event is mediated by a set of essential entry glycoproteins, including glycoprotein D (gD), gHgL, and gB. gHgL and gB are conserved among herpesviruses, but gD is unique to the alphaherpesviruses and is not encoded by all alphaherpesviruses. gD is a receptor-binding protein, the heterodimer gHgL serves as a fusion regulator, and gB is a class III viral fusion protein. Sequential interactions among these glycoproteins are thought to trigger the virus to fuse at the right place and time. Structural studies of these glycoproteins from multiple alphaherpesviruses has enabled the design and interpretation of functional studies. The structures of gD in a receptor- bound and in an unliganded form reveal a conformational change in the C terminus of the gD ectodomain upon receptor binding that may serve as a signal for fusion. By mapping neutralizing antibodies to the gHgL structures and constructing interspecies chimeric forms of gHgL, interaction sites for both gD and gB on gHgL have been proposed. A comparison of the post fusion structure of gB and an alternative conformation of gB visualized using cryo- electron tomography suggests that gB undergoes substantial refolding to execute membrane fusion. Although these structures have provided excellent insights into the entry mechanism, many questions remain about how these viruses coordinate the interactions and conformational changes required for entry.

Advice Tie Reallocation Under Organizational Turmoil: A Longitudinal Intra-Firm Network Study

Drawing on both social network theory and social exchange theory, this study investigates how the hierarchical position of those constituting a firm’s discretionary advice network affects individual’s propensity to provide advice to others. Based on a unique field survey that captures the dynamics of organization downsizing, findings indicate that under enhanced organizational turmoil, new advice activity centers on advice provided to hierarchical equals, shifting away from a vertical orientation towards a horizontal advice orientation as organizational turmoil increases. Hierarchical popularity nor activity affects this relation, arguing for the direct effect of organization structure on advice giving activity within the firm. We discuss the implications of our findings on the literature of intra-organizational networks in the context of abrupt network disruption, contrasting pre and post network structure to a sudden downsizing event.

A Study of the Truncated Square Pyramid Geometry for Enhancement of Super-hydrophobicity

Super-hydrophobic surfaces are quite common in nature, inspiring people to continually explore its water-repellence property and applications to our lives. It has been generally agreed that the property of super-hydrophobicity is mainly contributed by the microscale or nanoscale (or even smaller) architecture on the surface. Besides, there is an energy barrier between the Cassie-Baxter wetting state and the Wenzel wetting state. An optimized square post micro structure with truncated square pyramid geometry is introduced in this work to increase the energy barrier, enhancing the robustness of super-hydrophobicity. Theoretical analysis is conducted based on the wetting transition energy curves. Numerical simulation based on a phase-field lattice Boltzmann method is carried out to verify the theoretical analysis. The numerical simulation agrees well with the theoretical analysis, showing the positive significance of the proposed micro structure. Furthermore, another novel micro structure of rough surface is presented, which combines the advantages of truncated pyramid geometry and noncommunicating roughness elements. Theoretical analysis shows that the novel micro structure of rough surface can effectively hinder the Cassie-Baxter state to Wenzel state transition, furtherly enhancing the robustness of the surface hydrophobicity.

Burnt daub talking: The formation of the LBK longhouse (a work hypothesis)

This paper has two starting points that will eventually converge in our argumentation. One focuses on the early 6th millennium cal BC Starčevo settlement at Alsónyék in the Sárköz region of south-western Hungary. While no houses with a post structure could be identified, the amount of the burnt daub found in pits totals more than two tons. Based on the weighing, the detailed description of the total amount of the recovered Early Neolithic burnt daub fragments and the 3D reconstruction of diagnostic pieces, details about early Neolithic architecture of the region can be explored. The second point concerns the earliest northward-oriented longhouses occurring in the western Carpathian Basin. While the north Balkan origin of the LBK has not been seriously challenged, the roots of the LBK longhouse have never been fully and precisely clarified. The already described formative LBK phase and its house types will be compared with newly found LBK settlement nuclei containing very early Vinča find material, and both will be compared to features of the late Starčevo house building tradition. Meanwhile, we also try to cast some light on the decisive, but nevertheless little known “Dark Age” of the 55th and 54th centuries cal BC.

The stone-base illusion

A popular method used to construct the post structure in traditional Korean buildings is simply placing a stone base on the ground in the natural form and a wooden post on top of the stone base. Interestingly, an illusory visual completion often occurs at the joint where the stone base and the post join. Thus, even though the wooden post stands on the top surface of the stone base, observers tend to perceive the post as embedded in the stone base. In Experiment 1, photographs of real stone bases and wooden posts were presented, and the results showed that the more uneven the stone base was, the more the post was judged as embedded in the stone base. In Experiment 2, 3D graphic models with a similar size and color were presented, and the results again showed that the unevenness of the stone base influenced the perceptual embedment of the post. The results are discussed in relation to several potential hypotheses, including figural goodness, edge similarity, and physical knowledge.

Additive Aerodynamic and Thermal Effects of a Central Guide Post and Baffle Installed in a Solar Updraft Tower

The solar updraft tower (SUT) is a renewable power generation system that uses natural air convection from the ground that is heated by solar radiation. Placing flow-guide structures within the collector of the SUT can enhance aerodynamic performance, and hence, increase the kinetic power. Here, we propose a central guide post (CGP) structure in the SUT that controls updraft flow. The effect of the CGP geometry on aerodynamic performance was investigated using computational fluid dynamics modeling (ANSYS Fluent 19.2) to show that a CGP can play a positive role by preventing stagnation of the airflow at the center of the collector, resulting in increased kinetic power output (up to ~2%). However, excessively long CGPs retarded airflow, resulting in a dramatic decrease in kinetic power output. We also investigated a system with both a CGP (to improve aerodynamic performance and minimize energy loss) and a heat-exchange baffle (to maximize thermal energy transfer). When installed with a proper distance between components, the CGP and baffle showed a combined effect of increasing the kinetic power output by up to 10%. We expect that our proposed method using the CGP and baffle system will contribute to the development of better future SUT technology.

Joint FDE and MLSD Algorithm for 56-Gbit/s Optical FTN-PAM4 System Using 10G-Class Optics

In this paper, we propose a joint frequency-domain equalizer (FDE) and maximum likelihood sequence detection (MLSD) algorithm to eliminate the serious inter-symbol interference for 56-Gbit/s optical faster-than-Nyquist 4-level pulse-amplitude modulation (FTN-PAM4) system using 10 G-class optics. The simplified FDE structure is first designed to replace the feed-forward equalization (FFE) and post filter structure in conventional joint FFE, post filter and MLSD algorithm. In the joint algorithms, the simplified FDE structure has approximately $13\%$ and $1\%$ computational complexity compared to FFE with least-mean-square (FFE-LMS) adaptive algorithm and FFE with recursive-least-squares (FFE-RLS) adaptive algorithm, respectively. Therefore, the proposed joint FDE and MLSD algorithm has much lower computational complexity than the conventional joint FFE, post filter and MLSD algorithm. Meanwhile, the experimental results show that the performance of joint FDE and MLSD algorithm is better than that of joint FFE-LMS, post filter and MLSD algorithm, and is similar with that of joint FFE-RLS, post filter and MLSD algorithm. In conclusion, the proposed joint FDE and MLSD algorithm has both low computational complexity and excellent performance for optical FTN-PAM4 systems, which shows its potential for applications in low-cost and low-power short-reach optical interconnects.

Experimental investigation and Finite Element (FE) analysis of the load-deformation response of PVC fencing structures

Polyvinyl Chloride (PVC) posts and rails are increasingly being used as components of fencing structures because of their good mechanical properties, which include long service life, good chemical resistance, ability to be processed into complex geometry and good aesthetics. However, there has been no experimental or Finite Element (FE) study on the load-deformation response of PVC fencing structures. In addition, currently, no stiffness or structural load-bearing design standards exist for these types of fencing structures. Therefore, this study describes an investigation of the load-deformation response of a two-bay PVC post and rail fencing structure. The fencing structure was loaded experimentally at the top of the centre post and mid-bay points of the top rail. The load-deflection responses recorded during the tests on the fencing structure are presented and shown to be both linear and repeatable (i.e. three load-unload tests were carried out and showed identical responses). Based on the transverse deflection at the maximum applied load, the transverse stiffness of the two-bay PVC fencing structure was calculated to be 12.7–14 N/mm. A comparison of the transverse stiffness of the PVC fence with a similar timber fence showed the timber fence was approximately 262% stiffer than the PVC fence. Furthermore, FE modelling using a commercial software (ANSYS) was carried out on the PVC fencing structure to supplement the experimental work, and good agreement between the FE analyses and experimental test results was demonstrated. Hence, this paper provides initial knowledge and understanding of the linear elastic load-transverse deflection response of PVC fencing structures, and constitutes useful structural design guidance for what may be regarded as the in-service or practical deformation limit. The results of this study also provide useful benchmarks for future composite materials and components for fencing and other structural applications.

Interest Rate Swap Market Complexity and Its Risk Management Implications

The primary objective of this paper is to study the post Dodd-Frank network structure of the interest rate swap market and propose a set of effective complexity measures to understand how the swap users respond to market risks. We use a unique swap dataset extracted from the swap data repositories (SDRs) to examine the network structure properties and market participants’ risk management behaviors. We find (a) the interest rate swap market follows a scale-free network where the power-law exponent is less than 2, which indicates that few of its important entities have a significant number of contracts within their subsidiaries (a.k.a. interaffiliated swap contracts); (b) swap rate volatility Granger-causes swap users to increase their risk sharing intensity at entity level, but market participants do not change their risk management strategies in general; (c) there is a significant contemporaneous correlation between the swap rate volatility and the underlying interest rate futures volatility. However, interest rate swap volatility does not cause the underlying interest rate futures volatility and vice versa. These findings provide the market regulators and swap users a better understanding of interest rate swap market participants’ risk management behaviors, and it also provides a method to monitor the swap market risk sharing dynamics.

Lifting Capability and Stress Analyses of the Crane System for a Large-Sized Tactical Wrecker

A large-sized tactical wrecker is a special-purpose vehicle that lifts and tows tactical vehicles and heavy loads. It consists of a crane, a post structure, outriggers and a suitable chassis truck, and during its initial design, the structural safety and tipping stability should be preemptively examined in terms of the layout of these components. This paper proposes computer-aided engineering (CAE) methods to evaluate the maximum lifting capacity of the wrecker and the structural safety of its crane during the initial design. The analytical model for the large-sized wrecker is constructed with 236 degrees of freedom by combining the crane system developed using the ADAMS macros with the dynamic model of large chassis truck with an axle suspension. The design parameters for the wrecker model that influence the tipping stability are selected, and then the maximum lifting loads with the corresponding changes are calculated. This parametric study shows that the characteristics of the boom and the layout of the outriggers greatly affect the maximum lifting capacity. Finite element (FE) analyses of the 1st stage boom and the 3rd stage boom show the stresses under the maximum overturning moment condition are within the allowable strength.

Dynamically Tunable Dry Adhesion via Subsurface Stiffness Modulation

AbstractTunable dry adhesion has a range of applications, including transfer printing, climbing robots, and gripping in automated manufacturing processes. Here, a novel concept to achieve dynamically tunable dry adhesion via modulation of the stiffness of subsurface mechanical elements is introduced and demonstrated. A composite post structure, consisting of an elastomer shell and a core with a stiffness that can be tuned via application of electrical voltage, is fabricated. In the nonactivated state, the core is stiff and the effective adhesion strength between the composite post and contact surface is high. Activation of the core via application of electrical voltage reduces the stiffness of the core, resulting in a change in the stress distribution and driving force for delamination at the interface and, thus a reduction in the effective adhesion strength. The adhesion of composite posts with a range of dimensions is characterized and activation of the core is shown to reduce the adhesion by as much as a factor of 6. The experimentally observed reduction in adhesion is primarily due to the change in stiffness of the core. However, the activation of the core also results in heating of the interface and this plays a secondary role in the adhesion change.

The Effect of a Vertical Electric Field on the Surface Flashover Characteristics of a Bushing Model

High-voltage bushings play a crucial role in energy conveyance. Their specialized electric structure makes the bushing more vulnerable to surface discharge. However, the influence of a vertical electric field on the surface flashover of bushing structures remains unclear. To investigate this mechanism, four simplified bushing samples were built and the influence of pollution, leakage length, and the electric field component vertical to the dielectric surface on flashover properties of the bushing samples were tested. It was found that the surface pollution level was the decisive factor that influenced flashover voltage. When the leakage length and form factor were the same, the pollution flashover of the bushing structure was lower than that of the post structure. It was also found that increasing the leakage length was not very effective in improving the flashover voltage of bushings when the equivalent salt deposit density (ESDD) was high. No obvious correlation was found between pollution flashover voltage and electric field stress. Furthermore, the uneven wetting flashover performance of the bushings was tested. Under this condition, the flashover voltage decreased with an increase of the electric field component vertical to the dielectric surface. In addition, the electric field distribution of the samples was calculated and the results were in accordance with the experimental results.