Ideal Rectangle Research Articles

Experimental and numerical studies on friction energy-dissipating combination chord of staggered truss

Staggered truss framing systems have the problem of insufficient energy dissipation capacity in high intensity areas. To improve this situation, this paper proposes to replace the top chord of the staggered truss with a combination chord for frictional energy dissipation. Two groups and a total of four 1:2 scaled friction energy-dissipating combination top chord specimens were designed and fabricated, and hysteretic performance tests were carried out on them under low cycle reciprocating loads. It was investigated how high-strength bolt pre-tightening force and bolt layout affected the capacity of the combination chord to dissipate energy. The experimental results show that the hysteresis curve of the combination top chord for friction energy dissipation almost presents an ideal rectangle, and its energy-dissipating capacity is very strong. The combination top chord's capacity for friction energy dissipation increases with the increasing pre-tightening force of the high-strength bolt, but its stability for energy dissipation decreases. When the bolt layout is the staggered arrangement of single and double bolts, the initial energy dissipation and cumulative energy dissipation are weaker than that of the uniform arrangement of double bolts. Then, the friction energy-dissipating staggered truss with a sliding bottom chord was proposed to improve the load state of the diagonal web member in the staggered truss. The numerical simulation results show that the overall energy dissipation capacity and lateral bearing capacity of the staggered truss with the bottom chord sliding are 4.0% and 24.5% higher than those of the staggered truss with the top chord sliding.

Capacitive charge storage mechanism in sanmartinite to be determined by qualitative and quantitative electrochemical analysis

Pseudocapacitive behavior is one of the most concerned basic scientific issues in the electrochemical field. How to distinguish capacitive, pseudocapacitive and battery behavior accurately remains as a difficult problem. In addition, the capacitive charge storage mechanism of the non-Faraday process has been found in non-carbon-based materials in ways that challenge established theory. This is also the difficulty in defining the electrochemical behavior of newly discovered materials. Here, we report the pseudocapacitance behavior of sanmartinite (ZnWO4) for the first time. Under aqueous system conditions, the cyclic voltammetry curves of ZnWO4 present the ideal rectangle shape, and the galvanostatic charge/discharge curves exhibit the isosceles triangle shape. In addition, the calculated value of b is 0.88, which further indicates that the kinetic process is controlled by the surface capacitance.

A force-resisting rotary friction damper (RFD): Verification and comparison with traditional RFD

A force-resisting rotary friction damper (RFD) is proposed in this paper, which can be applied where there is a large rotational deformation. Its exclusive configuration lies in that multiple bolts are symmetrically arranged on concentric circles centered on the hinge pin to apply preload, resulting in: [i] an independent force-transfer capability decoupled with the moment to meet shear or axial forces-transfer demands and [ii] providing larger friction bending-moment with smaller compressive stresses on friction shim and lower maximum stress on the steel plate compared to the traditional RFD under the same preload and friction coefficient. A prototype of the proposed RFD was manufactured and tested twice without tightening the bolts again and replacing the friction shims by cyclic loading to investigate its mechanical property and recoverability. The test results showed that the moment–angle hysteretic curve of the proposed RFD was an ideal rectangle, indicating a reasonable mechanism. The variation of the friction bending-moment was within 4.00 % between the two-time tests, indicating that the proposed RFD has satisfactory recoverability and can uninterruptedly provide energy absorption during dense aftershocks. Then, a refined finite element model was established and calibrated by the test results. For the numerical prototype studied, the friction bending-moment of the proposed RFD was approximately 35 % larger than that of the traditional RFD while its maximum pressure on friction shim was about 40 % of the corresponding traditional RFD. The difference in the friction moment between the theoretical and numerical results was within 4.50 %. The concept of the force-resisting RFD was justified.

An Investigation into Accumulative Difference Mechanism in Time and Space for Material Removal in Micro-EDM Milling.

In micro-electrical discharge machining (micro-EDM) milling, the cross-section of the microgroove machine is frequently not an ideal rectangle. For instance, there are arc shapes on the bottom and corners, and the sidewall is not steep. The theoretical explanation for this phenomenon is still lacking. In addition to the tip discharge effect, the essential reason is that there is an accumulative difference in time and space during the shape change process of a tool electrode and the microstructure formation on a workpiece. The process parameters are critical influencing factors that determine this accumulative difference. Therefore, the accumulative difference mechanism in time and space is investigated in this paper, and then a theoretical model is developed to simulate the micro-EDM milling process with a straight-line single path. The simulation results for a cylindrical electrode at the two rotational speeds of 0 (nonrotating) and 300 rpm are compared, while the results for a cylindrical electrode and a square electrode at a rotation speed of 0 are also compared to verify that different process parameters generate accumulative differences in the time and space of material removal. Finally, micro-EDM milling experiments are carried out to verify the simulation model. The maximum mean relative deviation between the microgroove profiles of simulation results and those of experiments is 11.09%, and the profile shapes of simulations and experiments have a good consistency. A comparative experiment between a cylindrical electrode and a hollow electrode is also performed, which further verifies the mechanism revealed in the study. Furthermore, the cross-section profile of a microgroove can be effectively controlled by adjusting the process parameters when utilising these accumulative differences through fabricating a microgroove with a V-shaped cross-section by a square electrode and a microgroove with a semi-circular cross-section by a cylindrical electrode. This research provides theoretical guidance for solving the problems of the machining accuracy of detail features in micro-EDM milling, for instance, to machine a microgroove with an ideal rectangular cross-section.

Distortion compensation in continuous-time photonic time-stretched ADC based on redundancy detection.

In continuous-time photonic time-stretched analog-to-digital conversion (PTS-ADC), a wavelength-division multiplexer (WDM) is widely used to separate the overlapped stretched signal segments in both the wavelength and time domains. However, the spectrum shape of the WDM is not an ideal rectangle, and signal distortion occurs when we reconstruct the stretched signal by connecting the segments carried by the rising or falling edges of the spectrum. A signal distortion compensation scheme based on redundancy detection is proposed in this paper. Two WDMs with complementary spectrum division are employed; if we properly set the central wavelength of each channel of both WDMs, the signal segments that might be distorted by inter-channel mismatch can be redundantly detected and the distortion can be completely avoided. Moreover, by adjusting the dispersion amount of the first dispersive medium, the optical carrier obtained by connecting the stretched chirped pulses is partly overlapped, which guarantees the redundant modulation of signal segments that might be distorted by inter-pulse mismatch. Accordingly, the signal distortion induced by inter-pulse mismatch can be perfectly removed. In addition, the effective bandwidth of each chirped optical pulse is given. The maximum system stretch factor is also derived in this paper, and experiments based on the proposed signal distortion compensation scheme are carried out. The results obtained provide instructive guidelines for the design of a continuous-time PTS-ADC with the desired performance.

Analysis of Transient Pulse Electroosmotic Flow of Maxwell Fluid through a Circular Micro-Channel Using Laplace Transform Method

A semi-analytical solution is presented using method of Laplace transform for the transient pulse electroosmotic flow (EOF) of Maxwell fluid in a circular micro-channel. The driving mode of pulse EOF here is considered as an ideal rectangle pulse. The solution involves solving the linearized Poisson-Boltzmann (P-B) equation, together with the Cauchy momentum equation and the general Maxwell constitutive equation. The results show that the profiles of pulse EOF velocity vary rapidly and gradually stabilize as the increase of time within a half period. The velocity profiles at the center of the micro-channel increase significantly with relaxation time , especially for the smaller pulse width a. However, as the pulse width a increases, this change will be less obvious. At the same time, the different change frequency of velocity profiles will slow down, which means a long cycle time. Additionally, the time needed to attain the steady status becomes longer with the increase of relaxation time and pulse width a.

Tipografia não é invisível, é espelho

Ao observar uma página impressa é possível identificar a época em que esta foi produzida. Se o tipo, aquele retângulo ideal onde o corpo da letra, a linha de base, ascendentes, descendentes coexistem permanece inalterado, os elementos que compõem a página mostram uma considerável evolução. As mudanças observadas estão relacionadas a aspectos do contexto histórico, técnica e avanços tecnológicos que se interpõem entre o texto, o tipógrafo, o produto gráfico e o leitor. No amplo campo discursivo, onde os significados são negociados, o design torna visível práticas culturais compartilhados, permitindo que o objeto gráfico seja espelho de seu momento histórico. Dada sua relevância na história da tipografia o foco deste trabalho reside nas inovações ocorridas no livro impresso, mais do que impressos efêmeros.

Brillouin optical correlation analysis system using a simplified frequency-modulated time division method

A time-division Brillouin optical correlation domain analysis system was successfully achieved using simplified laser diode (LD) modulation and pump lightwave optimization. A complicated transfer function for a precise output waveform of a LD was required for the conventional system. However, a very simple modulation function gave a power output very close to a required ideal rectangle waveform without sacrificing optical output spectrum. An electrical input waveform applied into a gate in the pump lightwave path was also optimized for eliminating a probe lightwave included in a pump lightwave and for passing consecutive pump pulses alternatively. So the stimulated Brillouin scattering gain was attained without seriously distorting FM modulation, and the targeted spatial resolution was clearly accomplished. Additionally, using high speed response of a semiconductor optical amplifier (SOA), unlike an erbium-doped fiber amplifier (EDFA), the possibility was investigated that an SOA was going to replace an EDFA and a modulator used as a gate in the same time.

Design and Simulation of DC Speed Regulating System Based on Fuzzy Control

PID control is adopted in traditional DC speed regulating system. In start process the current super adjustment value is big. When adding load perturbation and voltage perturbation suddenly, its dynamic state function will be decended. Aimming at this problem, a kind of improved system was put forward. The speed modulator used fuzzy PID controller, according to e and ec, the parameters of the modulator can be modified on line. The current modulator adopted integral separable PID control method. The simulation results indicated that the improved system has better dynamic state function and anti- Rao function. Particularly the start current wave closes to the ideal rectangle wave more. So the responding speed of the system can be sped.

Anodic electrodeposition of redoxable film from manganese oxide nanosheet

Manganese oxide electrodeposited films were grown from the solutions containing manganese oxide nanosheet colloid. The nanosheet solutions were prepared by exfoliation of protonated layered manganese oxide by acid treatment of Na- or K-birnessite. The amount of deposit depends on the size of nanosheet, the concentration of added tetrabutylammonium salt and the current between electrodes. The thick film was deposited at low concentration of the salt; however, it was prone to peel off during deposition in the solution. The smooth and flat film can be prepared from the solution with tetrabutylammonium chloride concentration of 1.66 mmol/dm3. The grown films were examined for electrochemical properties by galvanostatic charge-discharge curves and cyclic voltammograms in the NaClO4 acetonitrile solution. The maximum capacitance estimated by the charge-discharge curves was around 224 F/g; however, the capacitance decrease logarithmically depending on the mass of deposit. The obtained cyclic voltammograms with ideal rectangle shape seemed to result from the electric double layer rather than redox reaction. Therefore, these voltammograms confirm that such capacitive behaviors are possibly controlled by ion-diffusion through the films.

Synthesis and Structure of Redox‐Active Heterotetranuclear Molecular Polygons by Self‐Assembly of Two Ferrocene‐Bridged Bis(pyridines) with Two Transition Metals

AbstractThe macrocyclic complexes [(η5‐C5H4C2‐4‐py)2Fe]2Ni2(NO3)4 (2), [(η5‐C5H4C2‐3‐py)2Fe]2Ag2(ClO4)2 (4), and [(η5‐C5H4C2‐3‐py)2Fe]2Pd2Cl4 (5) were obtained by reaction of [Ni(H2O)6](NO3)2, AgClO4, and PdCl2(COD) with the ligands (η5‐C5H4C2‐4‐py)2Fe (1) and (η5‐C5H4C2‐3‐py)2Fe (3), respectively, under high dilution conditions (Scheme 1). The molecular motifs of 2, 4, and 5 were studied by single‐crystal X‐ray structural investigations. Elemental analyses and 1H NMR and IR spectra were also used to confirm the structures. Compound 2 represents an unsymmetric paddlewheel, in which the centers of the four Cp rings define a nearly ideal rectangle with dimensions of 20.2 × 3.3 Å. In principle, macrocycles 4 and 5 can also be described as rectangles, however, due to the 3‐positioned nitrogen donors with deformed edges (17.4 × 3.3 Å for 4). In contrast to the offset packing of the molecules in 2, the macrocycles in the crystal of 4 are aligned, with trapped acetonitrile molecules in between. The intra‐ and intermolecular Ag−Ag distances are 3.50 and 3.79 Å, respectively. Cyclovoltammetric studies reveal chemically reversible ferrocene‐based redox reactions of 1−4. Although no electronic communication was observed between the two identical ferrocene units, a weak through‐bond electronic interaction between ferrocene and nickel, or silver, was established. In 2 a weak antiferromagnetic interaction between the nickel atoms was also found. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

NUMERICAL STUDY OF THE TURBULENT HEAT TRANSFER IN A MOTORIZED ENGINE UTILIZING A TWO-BOUNDARY METHOD-GRID GENERATION TECHNIQUE

An algorithm for a multidimensional numerical solution was developed to predict the turbulent flow field and heat flux in the cylinder of a reciprocating engine. The two-boundary method-grid generation technique associated with cubic interpolation was used to map the complex physical domain onto an ideal rectangle for every time step. Hence, the metrics of the coordinate transformation could be obtained by direct analytic differentiation, and the rapid solution time was another advantage. The heat and flow patterns in the cylinder were vividly visualized by means of the contour maps of velocity vectors and isotherms. The effects of piston crown shape on in-cytinder turbulent heat flux were investigated. Comparison was made of present heat flux results and earlier experimental and numerical results.