Orthogonal Research Articles

Investigation of the WEDM Parameters’ Influence on the Recast Layer Thickness of Spark Plasma Sintered SiC-TiB2-TiC Ceramic

The influence of WEDM parameters (Spark gap voltage, Pulse-on time, Spark frequency, and Wire speed) on the recast layer thickness and surface roughness of Spark Plasma Sintered SiC-TiB2-TiC ceramic composite was investigated. For this, an orthogonal L9 Taguchi design was used, and grey relational analysis was carried out for multi-response WEDM parameter optimization in order to determine the minimum RLT and SR. It was noticed that for RLT, the Pulse-on time was observed as the most significant process parameter, followed by Spark gap voltage. On the other hand, Spark frequency and Wire speed had no significance for RLT. Moreover, Spark frequency was observed as the most significant process parameter, followed by Pulse-on time and Spark gap voltage, while Wire speed had a negligible effect on SR. It was found that at optimal process parameters (U = 48V; Ton = 1.0 µs; f = 10 kHz; q = 8 m/min), we obtained an RLT of 3.16 µm and an SR of Ra = 0.847 µm. The confirmation test showed a decrease in RLT and SR by 43.67% and 7.12%, respectively, in comparison to the initial machining conditions.

THE IMPLEMENTATION OF THE TAGUCHI METHOD WITH TRAPEZOIDAL FUZZY NUMBER IN THE TOFU PRODUCTION PROCESS

Indonesians consume more tofu every week, proving that it is one of the country's most well-liked and potential food ingredients. Therefore, several people benefit from this positive potential as a business opportunity and improve the quality of their products as part of a market competition strategy. This study uses the Taguchi method and fuzzy logic to optimize the multi-response characteristic tofu production process. These multi-responses include water and protein content, each of which has the characteristics of "nominal is best" and "larger is better". In this experiment, three independent variables were varied: soybean soaking time, soybean porridge boiling time, and tofu lump pressing time. The experimental design used is the orthogonal matrix L9. This study aims to determine the optimal combination of independent variables and determine the contribution of each varible to the multi-response of water content and protein content simultaneously. The findings indicated that soaking soybeans for 4 hours, boiling soybean porridge for 70 minutes, and pressing tofu lumps for 20 minutes are the ideal settings to produce optimal multi-response simultaneously. Additionally, the duration of soybeans soaking contributed 14,74%, the duration of boiling soybean porridge contributed 29,50%, and the duration of pressing lumps of tofu contributed 38,18% to the multi-response.

Efficient Intersystem Crossing and Long-lived Charge-Separated State Induced by Through-Space Intramolecular Charge Transfer in a Parallel Geometry Carbazole-Bodipy Dyad.

The design of efficient heavy atom-free triplet photosensitizers (PSs) based on through bond charge transfer (TBCT) features is a formidable challenge due to the criteria of orthogonal donor-acceptor geometry. Herein, we propose using parallel (face-to-face) conformation carbazole-bodipy donor-acceptor dyads (BCZ-1 and BCZ-2) featuring through space intramolecular charge transfer (TSCT) process as efficient triplet PS. Efficient intersystem crossing (ΦΔ =61 %) and long-lived triplet excited state (τT =186 μs) were observed in the TSCT dyad BCZ-1 compared to BCZ-3 (ΦΔ =0.4 %), the dyad involving TBCT, demonstrating the superiority of the TSCT approach over conventional donor-acceptor system. Moreover, the transient absorption study revealed that TSCT dyads have a faster charge separation and slower intersystem crossing process induced by charge recombination compared to TBCT dyad. A long-lived charge-separated state (CSS) was observed in the BCZ-1 (τCSS =24 ns). For the first time, the TSCT dyad was explored for the triplet-triplet annihilation upconversion, and a high upconversion quantum yield of 11 % was observed. Our results demonstrate a new avenue for designing efficient PSs and open up exciting opportunities for future research in this field.

Detection of molecular oxygen using nanosecond-laser-induced plasma.

Molecular oxygen (O2) concentration is measured by employing nanosecond laser-induced plasmas (ns-LIP) over a broad temperature spectrum ranging from 300 K to 1000 K, in the presence of an additional oxygen-containing molecule, CO2. Typically, emission spectra emanating from ns-LIP are devoid of molecular information, as the ns-LIP causes the dissociation of molecular species within the plasma. However, atomic oxygen absorption lines that momentarily appear at 777 nm in the broadband emission from the early-stage plasma are determined to be highly sensitive to the O2 mole fraction but negligibly affected by the CO2 mole fraction. The atomic O absorbing the plasma emission originates from the O2 adjacent to the plasma: robust UV radiation from the early-stage plasma selectively dissociates adjacent O2, exhibiting a relatively low photodissociation threshold, thus generating the specific meta-stable oxygen capable of absorbing photons at 777 nm. A theoretical model is introduced, explicating the formation of the meta-stable O atom from adjacent O2. To sustain the UV radiation from the plasma under high-temperature and low-density ambient conditions, a preceding breakdown is triggered by a split laser pulse (532 nm). This breakdown acts as a precursor, seeding electrons to intensify the inverse-Bremsstrahlung photon absorption of the subsequent laser pulse (1064 nm). Techniques such as proper orthogonal decomposition (POD) and support vector regression (SVR) are employed to precisely evaluate the O2 mole fraction (<1% uncertainty), by analyzing the short-lived (<10 ns) O2-indicator depicted in the early-stage plasma.

Stochastic-offset-enhanced restricted slice excitation and 180° refocusing designs with spatially non-linear ΔB0 shim array fields.

Developing a general framework with a novel stochastic offset strategy for the design of optimized RF pulses and time-varying spatially non-linear ΔB0 shim array fields for restricted slice excitation and refocusing with refined magnetization profiles within the intervals of the fixed voxels. Our framework uses the decomposition property of the Bloch equations to enable joint design of RF-pulses and shim array fields for restricted slice excitation and refocusing with auto-differentiation optimization. Bloch simulations are performed independently on orthogonal basis vectors, Mx, My, and Mz, which enables designs for arbitrary initial magnetizations. Requirements for refocusing pulse designs are derived from the extended phase graph formalism obviating time-consuming sub-voxel isochromatic simulations to model the effects of crusher gradients. To refine resultant slice-profiles because of voxelwise optimization functions, we propose an algorithm that stochastically offsets spatial points at which loss is computed during optimization. We first applied our proposed design framework to standard slice-selective excitation and refocusing pulses in the absence of non-linear ΔB0 shim array fields and compared them against pulses designed with Shinnar-Le Roux algorithm. Next, we demonstrated our technique in a simulated setup of fetal brain imaging in pregnancy for restricted-slice excitation and refocusing of the fetal brain. Our proposed framework for optimizing RF pulse and time-varying spatially non-linear ΔB0 shim array fields achieve high fidelity restricted-slice excitation and refocusing for fetal MRI, which could enable zoomed fast-spin-echo-MRI and other applications.

An orthogonal subspace method for source depth discrimination in shallow water using a horizontal line array

Source depth discrimination with a horizontal line array in a shallow water environment generally involves mode filtering. Since a limited horizontal aperture can make the observation matrix an ill-conditioned matrix, which affects the mode filtering, the application of the Schmidt Orthogonalization to the problem of source depth discrimination with a horizontal line array is investigated. It aims to construct orthogonal trapped and non-trapped component subspaces while preserving an almost complete mode space and reducing energy loss. An orthogonal subspace discriminator is proposed, and the corresponding decision metric relies on estimating the proportion of the trapped component. The performance of each method is predicted by receiver operating characteristic curves obtained by simulation, enabling one to compare the proposed method with the comparison methods. The impact of horizontal aperture, frequency, signal-to-noise ratio, and environmental mismatch on performance is numerically studied. The results show that the proposed method performs better than comparison methods at smaller apertures and is more robust against environmental mismatch at lower frequencies. Finally, the method is demonstrated on experimental data acquired with a bottom-mounted horizontal line array deployed in the South China Sea.

Multi-objective optimization of process parameters during friction stir welding of similar AA6061 using MOORA

This work is an attempt to select the optimum process parameters for friction stir welding of similar AA6061 aluminum alloy based on multiple criteria decision-making approach. The friction stir welding experiments have been conducted according to the orthogonal L9 array and the chosen input parameters are tool rotational speed, feed, and tilt angle. The responses measured are tensile strength, hardness, and % of elongation of welded joint. The multi-criteria decision-making technique namely multi-objective optimization based on the ratio analysis (MOORA) is used to find the optimum process parameters combination. The optimum conditions are tool rotational speed of 1120 rpm, feed of 30 mm/rev and tilt angle at 1 o.

Hypersphere guided embedding for masked face recognition

Hypersphere Guided Embedding for Masked Face Recognition has been proposed to address the problem encountered in the Masked Face Recognition task, which arises due to non-biological information from occlusions. While some existing algorithms prefer to digesting the existence of masks by probing and covering, others aim to integrate face recognition and masked face recognition tasks into a unified solution domain. In this paper, we propose a framework to enable existing methods to accommodate multiple data distributions by orthogonal subspaces. Specifically, We introduce constraints on multiple hypersphere manifolds via Multi-Center Loss and employ a Spatial Split Strategy to ensure the orthogonality of base vectors associated with different hypersphere manifolds, corresponding to distinct distribution. Our method is extensively evaluated on publicly available datasets on face recognition, mask face recognition and occlusion, demonstrating promising performance. Our code is available on an anonymous website: https://github.com/CaptainKai/HE_MFR.

Performance Comparison of Several Algorithms for Localization of Wideband Sources

In recent years, researchers have tried to estimate the direction-of-arrival (DOA) of wideband sources and several novel techniques have been proposed. In this paper, we compare six algorithms for calculating the DOA of broadband signals, namely coherent subspace signal method (CSSM), two-sided correlation transformation (TCT), incoherent multiple signal classification (IMUSIC), test of orthogonality of frequency subspaces (TOFS), test of orthogonality of projected subspaces (TOPS), and squared TOPS (S-TOPS). The comparison is made through computer simulations for different parameters, such as signal-to-noise ratio (SNR), in order to establish the efficiency and performance of the discussed methods in noisy environments. CSSM and TCT require initial values, but the remaining approaches do not need any preprocessing.

Orthogonal signed-distance coordinates and vector calculus near evolving curves and surfaces

We provide an elementary derivation of an orthogonal coordinate system for boundary layers around evolving smooth surfaces and curves based on the signed-distance function. We go beyond previous works on the signed-distance function and collate useful vector calculus identities for these coordinates. These results and provided code enable consistent accounting of geometric effects to arbitrary order for boundary layer asymptotics in a wide range of physical systems.

Data-Driven-Based Vector Space Decomposition Modeling of Multiphase Induction Machines

For contemporary variable-speed electric drives, the accuracy of the machine's mathematical model is critical for optimal control performance. Basically, phase variables of multiphase machines are preferably decomposed into multiple orthogonal subspaces based on vector space decomposition (VSD). In the available literature, identifying the correlation between states governed by the dynamic equations and the parameter estimate of different subspaces of multiphase IM remains scarce, especially under unbalanced conditions, where the effect of secondary subspaces sounds influential. Most available literature has relied on simple RL circuit representation to model these secondary subspaces. To this end, this paper presents an effective data-driven-based space harmonic model for n-phase IMs using sparsity-promoting techniques and machine learning with nonlinear dynamical systems to discover the IM governing equations. Moreover, the proposed approach is computationally efficient, and it precisely identifies both the electrical and mechanical dynamics of all subspaces of an IM using a single transient startup run. Additionally, the derived model can be reformulated into the standard canonical form of the induction machine model to easily extract the parameters of all subspaces based on online measurements. Eventually, the proposed modeling approach is experimentally validated using a 1.5 Hp asymmetrical six-phase induction machine.

Approximation of the ground and excited states of atoms and molecules with a single determinant by means of the exact many-particle Hamiltonian

In the present work, we search for the maximum of the functional | ⟨ Φ ′ | H ^ | Φ ⟩ | , where | Φ ′ ⟩ is a Slater Determinant (SlDet) and H ^ is the exact Hamiltonian of an atom or a molecule, starting from a SlDet | Φ ⟩ , with its spin orbitals calculated by the standard Hartree-Fock (HF) equation or other approximation or any determinant. The element | ⟨ Φ 1 | H ^ | Φ ⟩ | with | Φ 1 ⟩ the maximising | Φ ′ ⟩ gives a value greater or equal to | ⟨ Φ | H ^ | Φ ⟩ | . Next we calculate the corresponding maximum overlap | ⟨ Φ 2 | H ^ | Φ 1 ⟩ | and finally | ⟨ Φ n + 1 | H ^ | Φ n ⟩ | until | ⟨ Φ n + 1 | H ^ | Φ n ⟩ − ⟨ Φ n | H ^ | Φ n − 1 ⟩ | ≤ ε , where ε determines the desired numerical accuracy. We show that the sequence ⟨ Φ n + 1 | H ^ | Φ n ⟩ converges to an extremum ⟨ Φ | H ^ | Φ ⟩ . Having found the SlDet with the lowest energy we repeat the procedure in the orthogonal subspace for finding the first and the higher excited states. We applied this method in order to determine the energies of several configurations of H 3 , the Lithium atom, LiH and Be.

Much Stronger Chemiluminescence of 9-Mesityl-10-methylacridinium Ion than Lucigenin at Neutral Conditions for Co2+ Detection.

9-Mesityl-10-methylacridinium ion (Acr+-Mes) is a donor-acceptor molecule with a much longer lifetime and a higher energy electron transfer excited state than natural photosynthetic reaction centers. Unlike lucigenin with a coplanar geometry, Acr+-Mes has an orthogonal geometry. There is no π conjugation between Acr+ and Mes. Due to its special electron donor-acceptor structure, it does not rely on strong alkalinity to generate an electron transfer state like lucigenin, which makes it possible to achieve chemiluminescence (CL) under weakly alkaline or neutral conditions. In this study, we report Acr+-Mes CL for the first time. Acr+-Mes generates about 400 times stronger CL intensity than lucigenin under neutral conditions (pH = 7) using KHSO5 as the coreactant. Moreover, Co2+ can enhance Acr+-Mes/KHSO5 CL remarkably. Acr+-Mes/KHSO5 CL enables Co2+ detection with a linear range of 0.5-500 nM and a limit of detection of 28 pM (S/N = 3). This method was tested for the detection of Co2+ in lake water, and the standard recovery rate of 96.8-107% was achieved. This study provides a new way to develop efficient CL systems in neutral solutions.

Analisis Pengaruh Variasi Kecepatan Spindel Dan Feeding Terhadap Nilai Kekasaran Permukaan Proses Finishing Bubut CNC

In the industrial sector, technological progress has experienced very rapid development. So that the manufacturing industry is required to be able to produce quality products and a high level of accuracy with fast processing. One machine that can meet these demands is a CNC lathe, where a CNC lathe is a machine that is controlled using a computer system in its operation. In the machining process of CNC lathes, the level of surface roughness of the machining material is of great concern, because the lower the surface roughness value, the better the quality of the product. Therefore, the aim of this study was to obtain a low surface roughness value using a finishing cutting edge. The material used is AISI 1045 steel which is turned using a MORI SEIKI SL-25 CNC machine. The parameters used are spindle speed and feeding. The research method used was the Taguchi method with an orthogonal matrix L9(32) experimental design and 3 replications were carried out to reduce large deviations. The result of this research is to obtain a combination of parameters that produce minimum surface roughness values, namely spindle speed of 1804 rpm and feeding of 0.1 mm/put. And the parameter that has the greatest effect on the value of roughness is feeding with a difference of 16.029 and the one that has the least effect on the value of surface roughness is spindle speed with a difference of 1.384.

Graphs cannot be indexed in polynomial time for sub-quadratic time string matching, unless SETH fails

The string matching problem on a node-labeled graph G=(V,E) asks whether a given pattern string P equals the concatenation of node labels of some path in G. This is a basic primitive in various problems in bioinformatics, graph databases, or networks, and it was recently proven that solving it in time O(|E|1−ϵ|P|) or O(|E||P|1−ϵ) is hard under OVH, the Orthogonal Vectors Hypothesis, and thus under SETH, the Strong Exponential Time Hypothesis (Equi et al., 2019 [11]). We consider its indexed version, where the graph is indexed to support string queries. We show that, under OVH, no polynomial-time index of the graph performed in time O(|E|α) can support querying P in time O(|P|+|E|δ|P|β), with either δ<1 or β<1.We present our techniques as a general framework, introducing the notion of linear independent-components (lic) reduction, from which we derive our result. This allows us to also translate the quadratic conditional lower bound of Backurs and Indyk (2015) [48] for the problem of matching a query string inside a text, under edit distance, into an analogous tight quadratic lower bound for its indexed version. This improves the recent result of Cohen-Addad, Feuilloley and Starikovskaya (2019) [49], with a slightly different boundary condition. We also apply our technique to obtain the first quadratic indexing lower bounds for Fréchet distance and rooted unlabeled subtree-isomorphism queries.

Illegal Intelligent Reflecting Surface Based Active Channel Aging: When Jammer Can Attack Without Power and CSI

Illegal intelligent reflecting surfaces (I-IRSs), i.e., the illegal deployment and utilization of IRSs, impose serious harmful impacts on wireless networks. The existing I-IRS-based illegal jammer (IJ) requires channel state information (CSI) or extra power or both, and therefore, the I-IRS-based IJ seems to be difficult to implement in practical wireless networks. To raise concerns about significant potential threats posed by I-IRSs, we propose an alternative method to jam legitimate users (LUs) without relying on the CSI. By using an I-IRS to actively change wireless channels, the orthogonality of multi-user beamforming vectors and the co-user channels is destroyed, and significant inter-user interference is then caused, which is referred to as active channel aging. Such a fully-passive jammer (FPJ) can launch jamming attacks on multi-user multiple-input single-output (MU-MISO) systems via inter-user interference caused by active channel aging, where the IJ requires no additional transmit power and instantaneous CSI. The simulation results show the effectiveness of the proposed FPJ scheme. Moreover, we also investigate how the transmit power and the number of quantization phase shift bits influence the jamming performance.

Prediction of metal deformation due to line heating; an alternative method of mechanical bending, based on artificial neural network approach

Line heating is one of the alternative methods of forming metals and this kind of forming uses the heating torch as a source of heat input. During the process, many parameters are considered like the size of the substrate, thickness, cooling method, source power intensity, the travel speed of the power source, the sequence of heating, and so on. It is important to analyze the factors affecting the metal bending process to effectively predict the nature and final shape of a material. The present study addresses parametric research and a new prediction technique for the final shape of metal using the ANN (Artificial Neural Network) approach. The experimental data are validated using the numerical finite element method. The test setup with orthogonal arrangement L9 is used for the setup of the experimental investigation. ANN is used for model accuracy with less dependence on measured data. All steps are performed in MATLAB with different training schemes. The network takes into account three process parameters, such as metal thickness, movement speed, and the number of passes, and the multi-layered perceptron neural network is trained and tested on the data. The predictive output of the ANN model is compared to the experimental results of the final bending of a metal and shows a good fit of the predicted values of ANN to the measured data with higher values, 97% of the coefficient of determination.

Null Space Projection-Based Design of Multibeam for Joint Communication and Sensing Systems

This paper proposes a multibeam combining method for joint communication and sensing (JCAS) systems. A sensing beamforming (BF) vector is designed to have components only in the orthogonal subspace of the communication BF vector by using a null space projection. In addition, a sensing beam-centric coherence combining is adopted to align the phases of the communication beam and the sensing beam at the sensing beam direction. The proposed approach allows the communication channel to remain stable while scanning the region of interest with the combined beams. The sensing BF gain is also improved by making the sidelobe of the communication beam contribute to increasing the BF gain of the sensing beam. Simulation results are provided to verify the effectiveness of the proposed method.

Another Geometric Interpretation of Cramer’s Rule

Summary We develop a geometric interpretation of Cramer’s rule as a generalization of projection onto orthogonal basis vectors using the rows of the adjugate. This interpretation makes connections between elementary linear algebra concepts like the solution to linear equations, inner products, and projections. Such connections are useful for introducing broader concepts related to Hilbert spaces and geometric algebras like Grassman algebra. Such connections were essential for the author’s mathematical education as an engineer.

Using orthogonal vectors to improve the ensemble space of the ensemble Kalman filter and its effect on data assimilation and forecasting

Abstract. The space spanned by the background ensemble provides a basis for correcting forecast errors in the ensemble Kalman filter. However, the ensemble space may not fully capture the forecast errors due to the limited ensemble size and systematic model errors, which affect the assimilation performance. This study proposes a new algorithm to generate pseudomembers to properly expand the ensemble space during the analysis step. The pseudomembers adopt vectors orthogonal to the original ensemble and are included in the ensemble using the centered spherical simplex ensemble method. The new algorithm is investigated with a six-member ensemble Kalman filter implemented in the 40-variable Lorenz model. Our results suggest that the ensemble singular vector, the ensemble mean vector, and their orthogonal components can serve as effective pseudomembers for improving the analysis accuracy, especially when the background has large errors.