Critical Pairs Research Articles

Deep Learning for Metro Short-Term Origin-Destination Passenger Flow Forecasting Considering Section Capacity Utilization Ratio

Origin-destination (OD) short-term passenger flow forecasting (OD STPFF) in urban rail transit (URT) is essential for developing timely network measures. The capacity utilization ratios of critical sections are key factors in developing these measures. The OD pairs passing through critical sections require a higher prediction accuracy than others; however, most studies have raised equal concerns on the prediction accuracy of each OD pair, namely, prediction at the network level. To address this problem, we raise heterogeneous time-variant concerns on OD pairs and employ an operation-oriented deep-learning architecture called the spatiotemporal convolutional neural network (STCNN) for realizing short-term OD passenger flow prediction. The architecture contains OD pair importance calculation, lagged spatiotemporal relationship construction, lagged spatiotemporal learning, real-time information learning, and sequential-temporal learning blocks. To this end, critical OD pairs are ascertained first, and the topological lagged spatiotemporal relationship among critical OD pairs are constructed and then normalized into grid-shaped data. The third block utilizes a convolutional neural network (CNN) to learn the grid-shaped lagged spatiotemporal feature and real-time information in parallel. A temporal convolutional neural network (TCN) is utilized for learning the sequential-temporal feature at last. Further, we design a time-varying weighted masked loss function to jointly reinforce the concerns on critical OD pairs during model training. Finally, we test the proposed STCNN and its components on a field dataset from Chengdu Metro. Although the proposed STCNN performs only slightly better at the network level than the other models, it outperforms state-of-the-art methods with significant superiority on critical OD pairs.

A Class-Imbalance Aware and Explainable Spatio-Temporal Graph Attention Network for Neonatal Seizure Detection.

Seizures are the most prevalent clinical indication of neurological disorders in neonates. In this study, a class-imbalance aware and explainable deep learning approach based on Convolutional Neural Networks (CNNs) and Graph Attention Networks (GATs) is proposed for the accurate automated detection of neonatal seizures. The proposed model integrates the temporal information of EEG signals with the spatial information on the EEG channels through the graph representation of the multi-channel EEG segments. One-dimensional CNNs are used to automatically develop a feature set that accurately represents the differences between seizure and nonseizure epochs in the time domain. By employing GAT, the attention mechanism is utilized to emphasize the critical channel pairs and information flow among brain regions. GAT coefficients were then used to empirically visualize the important regions during the seizure and nonseizure epochs, which can provide valuable insight into the location of seizures in the neonatal brain. Additionally, to tackle the severe class imbalance in the neonatal seizure dataset using under-sampling and focal loss techniques are used. Overall, the final Spatio-Temporal Graph Attention Network (ST-GAT) outperformed previous benchmarked methods with a mean AUC of 96.6% and Kappa of 0.88, demonstrating its high accuracy and potential for clinical applications.

Research on torsional stiffness of flexspline-flexible bearing contact pair in harmonic drive based on macro-micro scale modeling

The flexspline and flexible bearing constitute a critical contact pair in a harmonic drive system, and their torsional stiffness has a significant impact on the performance characteristics manifested by the harmonic drive. In this study, a micro scale three-dimensional fractal model was combined with a macro scale finite element simulation method to establish an equivalent torsional stiffness model for the flexspline-flexible bearing contact pair (FS-FB contact pair), which enables the theoretical prediction of the torsional stiffness of this contact pair. A torsional stiffness testing platform was constructed for a harmonic drive, and the consistency between the experimental results of the torsional stiffness curve and the theoretical predictions validates the effectiveness of the proposed model. The influences of torque, installation eccentricity, and deformation coefficient on the torsional stiffness of the FS-FB contact pair were also discussed. The results indicate that the torsional stiffness of the FS-FB contact pair increases nonlinearly with an increase in torque. On the other hand, the torsional stiffness of the FS-FB contact pair decreases with an increase in installation eccentricity, and increases before subsequently decreasing with an increase in deformation coefficient. Moreover, as torque increases, the impact of installation eccentricity and deformation coefficient on the torsional stiffness diminishes. This article provides a theoretical reference for the optimization design and performance enhancement of harmonic drives.

Extracting quantum-geometric effects from Ginzburg-Landau theory in a multiband Hubbard model

We first apply functional-integral approach to a multiband Hubbard model near the critical pairing temperature, and derive a generic effective action that is quartic in the fluctuations of the pairing order parameter. Then we consider time-reversal-symmetric systems with uniform (i.e., at both low-momentum and low-frequency) pairing fluctuations in a unit cell, and derive the corresponding time-dependent Ginzburg-Landau (TDGL) equation. In addition to the conventional intraband contribution that depends on the derivatives of the Bloch bands, we show that the kinetic coefficients of the TDGL equation have a geometric contribution that is controlled by both the quantum-metric tensor of the underlying Bloch states and their band-resolved quantum-metric tensors. Furthermore we show that thermodynamic properties such as London penetration depth, GL coherence length, GL parameter and upper critical magnetic field have an explicit dependence on quantum geometry.

Development, stability-Indicating assessment, and evaluation of influential method conditions using a full factorial design for the determination of Nintedanib Esylate related impurities.

The design of an appropriate analytical method for assessing the quality of pharmaceuticals requires a deep understanding of science, and risk evaluation approaches are appreciated. The current study discusses how a related substance method was developed for Nintedanib esylate. The best possible separation between the critical peak pairs was achieved using an X-Select CSH Phenyl Hexyl (150 × 4.6) mm, 3.5 μm column. A mixture of water, acetonitrile, and methanol in mobile phase-A (70:20:10) and mobile phase-B (20:70:10), with 0.1% trifluoroacetic acid and 0.05% formic acid in both eluents. The set flow rate, wavelength, and injection volumes were 1.0 mL/min, 285 nm, and 5 μL, respectively, with gradient elution. The method conditions were validated as per regulatory requirements and United States Pharmacopeia general chapter <1225>. The correlation coefficient for all impurities from the linearity experiment was found to be >0.999. The % relative standard deviation from the precision experiments ranged from 0.4 to 3.6. The mean % recovery from the accuracy study ranged from 92.5 to 106.5. Demonstrated the power of the stability-indicating method through degradation studies; the active drug component is more vulnerable to oxidation than other conditions. Final method conditions were further evaluated using a full-factorial design. The robust method conditions were identified using the graphical optimization from the design space. This article is protected by copyright. All rights reserved.

Trends and socioeconomic, demographic, and environmental factors associated with antimicrobial resistance: a longitudinal analysis in 39 hospitals in Chile 2008–2017

Antimicrobial resistance (AMR) is among the most critical global health threats of the 21st century. AMR is primarily driven by the use and misuse of antibiotics but can be affected by socioeconomic and environmental factors. Reliable and comparable estimates of AMR over time are essential to making public health decisions, defining research priorities, and evaluating interventions. However, estimates for developing regions are scant. We describe the evolution of AMR for critical priority antibiotic-bacterium pairs in Chile and examine their association with hospital and community-level characteristics using multivariate rate-adjusted regressions. Drawing on multiple data sources, we assembled a longitudinal national dataset to analyse AMR levels for critical priority antibiotic-bacterium combinations in 39 private and public hospitals (2008-2017) throughout the country and characterize the population at the municipality level. We first described trends of AMR in Chile. Second, we used multivariate regressions to examine the association of AMR with hospital characteristics and community-level socioeconomic, demographic, and environmental factors. Last, we estimated the expected distribution of AMR by region in Chile. Our results show that AMR for priority antibiotic-bacterium pairs steadily increased between 2008 and 2017 in Chile, driven primarily by Klebsiella pneumoniae resistant to third-generation cephalosporins and carbapenems, and vancomycin-resistant Enterococcus faecium. Higher hospital complexity, a proxy for antibiotic use, and poorer local community infrastructure were significantly associated with greater AMR. Consistent with research in other countries in the region, our results show a worrisome increase in clinically relevant AMR in Chile and suggest that hospital complexity and living conditions in the community may affect the emergence and spread of AMR. Our results highlight the importance of understanding AMR in hospitals and their interaction with the community and the environment to curtail this ongoing public health crisis. This research was supported by the Agencia Nacional de Investigación y Desarrollo (ANID), Fondo Nacional de Desarrollo Científico y Tecnológico FONDECYT, The Canadian Institute for Advanced Research (CIFAR), and Centro UC de Políticas Públicas, Pontificia Universidad Católica de Chile.

Failure Analysis and Intelligent Identification of Critical Friction Pairs of an Axial Piston Pump

Hydraulic axial piston pumps are the power source of fluid power systems and have important applications in many fields. They have a compact structure, high efficiency, large transmission power, and excellent flow variable performance. However, the crucial components of pumps easily suffer from different faults. It is therefore important to investigate a precise fault identification method to maintain reliability of the system. The use of deep models in feature learning, data mining, automatic identification, and classification has led to the development of novel fault diagnosis methods. In this research, typical faults and wears of the important friction pairs of piston pumps were analyzed. Different working conditions were considered by monitoring outlet pressure signals. To overcome the low efficiency and time-consuming nature of traditional manual parameter tuning, the Bayesian algorithm was introduced for adaptive optimization of an established deep learning model. The proposed method can explore potential fault feature information from the signals and adaptively identify the main fault types. The average diagnostic accuracy was found to reach up to 100%, indicating the ability of the method to detect typical faults of axial piston pumps with high precision.

Selection Strategy of F4-Style Algorithm to Solve MQ Problems Related to MPKC

Multivariate public-key cryptosystems are potential candidates for post-quantum cryptography. The security of multivariate public-key cryptosystems relies on the hardness of solving a system of multivariate quadratic polynomial equations. Faugère’s F4 algorithm is one of the solution techniques based on the theory of Gröbner bases and selects critical pairs to compose the Macaulay matrix. Reducing the matrix size is essential. Previous research has not fully examined how many critical pairs it takes to reduce to zero when echelonizing the Macaulay matrix in rows. Ito et al. (2021) proposed a new critical-pair selection strategy for solving multivariate quadratic problems associated with encryption schemes. Instead, this paper extends their selection strategy for solving the problems associated with digital signature schemes. Using the OpenF4 library, we compare the software performance between the integrated F4-style algorithm of the proposed methods and the original F4-style algorithm. Our experimental results demonstrate that the proposed methods can reduce the processing time of the F4-style algorithm by up to a factor of about seven under certain specific parameters. Moreover, we compute the minimum number of critical pairs to reduce to zero and propose their extrapolation outside our experimental scope for further research.

A new validated RP-HPLC-UV DAD method for assay of bisoprolol fumarate and related substances in tablets

The research focus of this work was development and validation of an efficient analytical method that can be used for separation and determination of related substances of bisoprolol in finished drug product using reversed-phase HPLC with UV-DAD. In a previous systematic study of various stationary phases and elution conditions it was found that several octadecylsilane phases can be successfully employed for separation of the critical pairs of bisoprolol and its related degradation products. Namely, method development led to conclusions that satisfactory resolution and peak shapes were obtained with gradient elution with water with 0.2% perchloric acid and acetonitrile and the reversed-phase columns: Hypersil 3 BDS C18 (100 x 4 mm, 3 m); Zorbax SB C18 (150 x 4.6 mm, 3.5 m); Acquity UPLC BEH C18 (50 x 2.1 mm, 1.7 m), and Xterra MS C18 (100 x 4.6 mm, 3.5 m). Since regular quality control includes the parameter related substances, which is of great importance for the overall quality of dosage forms, this study was oriented towards widening the available validated analytical methods for determination of this parameter. In this work, the results from the validation of the method for determination of related substances of bisoprolol using Zorbax SB C18 150 x 4.6 mm, 3.5 m, are presented. Validation parameters that were tested (linearity, accuracy, precision, selectivity) confirmed that the method is suitable for its intendance and it was used for characterization of the samples from a forced degradation study of bisoprolol tablets. Keywords: Bisoprolol, RP-HPLC-UV DAD, validation, related substances

Simplification of pharmacopoeial liquid chromatography methods for related substances of statins by hyphenated ultraviolet and charged aerosol detection

For a more comprehensive characterization of a drug substance and its impurities, multidetector approaches are a helpful tool in liquid chromatography. In particular, the relatively inexpensive hyphenation of the ultraviolet (UV) with the charged aerosol detector (CAD) extends the scope from UV-active to non- or weak chromophore analytes, respectively. In this study, the chromatographic methods of the test for related substances of simvastatin and lovastatin in the European Pharmacopoeia were adapted to UV-CAD and thus allowing a more sophisticated detection of the weak chromophore dihydro impurity besides the other UV-active impurities. The compendial gradient program for simvastatin had to be modified (lowered initial acetonitrile percentage and increased gradient slope) because an additional critical peak pair emerged with the Hypersil C18 BDS column used here. Therefore, a Plackett-Burman design with 11 factors (including 4 dummy factors) was chosen to evaluate robustness of the adapted method. The flow rate, initial acetonitrile percentage, and column temperature were identified as three critical parameters that had to be carefully observed. Finally, the validity of the method for simultaneous detection of dihydrosimvastatin with CAD and of lovastatin and simvastatin as examples of UV detection was verified according to ICH Q2 (R1). In the case of lovastatin, the direct comparison with the pharmacopoeial method reveal that a determination with CAD is the more sensitive method.

Isomer selectivity of one- and two-dimensional approaches of mixed-mode and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry for sugar phosphates of glycolysis and pentose phosphate pathways

In this study, the chromatographic behavior of mixed-mode and hydrophilic interaction liquid chromatography (HILIC) with the mixed-mode HILIC/strong anion-exchange (SAX) column HILICpak VT-50 2D and the two HILIC columns Atlantis Premier BEH Z-HILIC and Acquity Premier BEH Amide was assessed with regard to their separation capability of the metabolites from the glycolysis and pentose phosphate pathways. Chromatographic conditions were evaluated with the aim of achieving separation of the isomeric glycolytic phosphorylated carbohydrate metabolites free from isomeric interferences and thus allowing for selective targeted analysis by liquid chromatography with tandem mass spectrometry (MS/MS) using multiple reaction monitoring acquisition. The effects of pH values (8.0/9.0/10.0) of the ammonium bicarbonate buffer and gradient time were investigated during HILIC-MS/MS analysis, with the optimal conditions found at pH = 10.0. Separation of the pentose phosphate isomers (ribose 5- and 1-phosphate, xylulose 5-phosphate and ribulose 5-phosphate) was achieved on the mixed-mode HILIC/SAX (HILICpak VT-50 2D) column and HILIC BEH Amide column. Column performance was evaluated based on the direct comparison of chromatographic parameters, i.e. peak width at 50% and peak tailing factors of the individual metabolites. Parity plots were generated allowing a direct comparison between the normalized retention times and assessment of orthogonality of all 3 stationary phases evaluated. Separation of 7 biologically relevant hexose monophosphates metabolites turned out to be challenging by HILIC-MS/MS, with the BEH Amide providing the best individual results for such a separation. However, fructose 6-phosphate and glucose 1-phosphate co-eluted. Therefore, an on-line heart-cutting HILIC-Mixed Mode 2D-LC-QToF experiment was conducted, allowing the separation of this critical isomer pair. In this setup, the BEH Amide column in the 1D separated the majority of target metabolites, while a heart-cut of the peak from totally coeluted fructose 6-phosphate and glucose 1-phosphate was separated in the 2D with HILICpak VT50-2D column, thus allowing undisturbed determination of the glycolytic phosphorylated carbohydrate metabolites due to their chromatographic separation from hexose monophosphate metabolites. The assay specificity towards 7 common hexose monophosphates was characterized (glucose 1- and 6-phosphate, galactose 1- and 6-phosphate, fructose 6-phosphate, mannose 1- and 6-phosphate). The selectivity of some rare hexose monophosphates (allose 6-phosphate, tagatose 6-phosphate, sorbose 1-phosphate) was also tested.

Gradient Retention Factor Concept Applied to Method Development for Peptide Analysis by Means of RP-HPLC.

Using the van Deemter model, the efficiency of three stationary phase systems in the analysis of a mixture of synthetic peptides was evaluated: (i) monolithic, (ii) packed, and (iii) core-shell columns, and it was shown that the efficiency of the monolithic column is superior to the others, specifically using it, the lowest values of H min (0.03 and 0.1 mm) were obtained, and additionally its efficiency was not significantly affected by increasing the flow. Using the concept of the gradient retention factor (k*), a method for chromatographic separation of a peptide complex mixture was designed, implemented, and optimized and then transferred from a packed column to a monolithic one. The results showed that it was possible to separate all components of the mixture using both evaluated columns; moreover, the analysis time was reduced from 70 to 10 min, conserving the critical pair resolution (1.4), by the transfer method using the k* concept. The method developed was tested against a mixture of doping peptides, showing that this method is efficient for separating peptides of various natures. This investigation is very useful for the development of methods for the analysis of complex peptide mixtures since it provides a systematic approach that can be extrapolated to different types of columns and instrumentation.

Dielectric Relaxation of Ion-pairs, Micelles and Hydration in Aqueous Hexyltrimethylammonium Bromide Solutions

Through dielectric measurements of aqueous n-hexyltrimethylammonium bromide solutions, the structure and dynamics of ion-pairs, micelles, and water are investigated as functions of concentration and temperature. The frequency range of the study was ∼ 0.2 ≤ν/GHz ≤ 89, and the concentrations were changed from 0.0448 to 0.8476 mol.dm−3 at 298.15 K. The effects of temperature (278.15 ≤ T/K ≤ 338.15) on two selected solutions with concentrations above and below the critical micelle concentration were examined. A summation of three Debye processes fits the complex permittivity data of solutions with concentrations below the critical micelle concentration. To fit the spectra above the critical micelle concentration, a summation of five Debye processes is needed. Below the critical micelle concentration, solutes relax due to the tumbling motion of solvent-shared ion pairs. The two micelle relaxation processes that have been seen are the result of free and bound counter ions tangentially and radially diffusing around the charged micelles. Maxwell-Wagner relaxation is equivalent to the high frequency micelle relaxation process. Both the solvent and micelle dispersion provide acceptable volume fractions. Hexyltrimethylammonium behaves like higher n-alkyltrimethylammonium micelles in the context of micelle relaxation. Before critical micelle concentration, the cations, anions, and ion pairs strongly hydrate a total of ∼18 ± 4 non-rotational water molecules. Beyond the critical micelle concentration, there are an additional ∼ 5 ± 2 non-rotational water molecules in addition to ∼ 15 ± 3 slower-moving water molecules in the hydrophobic hydration shell.

Synergetic effects of surface textures with modified copper nanoparticles lubricant additives on the tribological properties of cylinder liner-piston ring

The cylinder liner-piston ring (CLPR) is one of the most critical frictional pair for energy conversion in diesel engines. In this study, two forms of surface texture were respectively prepared on the liner surface by laser processing, with the modified copper nanoparticles (CNP) applied as the lubricant additives. The reciprocating tribometer and accompanying tribological testing technologies were then used to explore the synergetic effects of surface textures and additives on the tribological properties of CLPR. The results show that the composite lubrication system exhibits good friction-reduction and wear-resistance as the appropriate texture was adopted. Additionally, the synergetic effects among the storage capability of textures and the self-repairing ability of CNP additives can explain the improvement mechanism of CLPR’s tribological properties.

AQbD based green UPLC method to determine mycophenolate mofetil impurities and Identification of degradation products by QToF LCMS

We report an ideal method for quantifying impurities in mycophenolate mofetil drug substances and their oral suspension preparations. We developed a systematic and eco-friendly analytical approach utilizing quality by design (QbD) and green chemistry principles. Initially, the critical method parameters (CMPs) were screened using a D-optimal design. The robust final method conditions were optimized using a systematic central composite design (CCD). Through graphical and numerical optimization, the protocol conditions were augmented. The pH of mobile phase buffer (25 mM KH2PO4) (MP-A), initial gradient composition (% MP-A), flow rate (mL min−1), and column oven temperatures (°C) are 4.05, 87, 0.4, and 30, respectively. The best possible separation between the critical pairs was achieved while using the Waters Acquity UPLC BEH C18 (100 × 2.1) mm, 1.7 µm analytical column. A mixture of water and acetonitrile in the ratio of 30:70 (v/v) was used as mobile phase-B for the gradient elution. The analytical method was validated in agreement with ICH and USP guidelines. The specificity results revealed that no peaks interfered with the impurities and MPM. The mean recovery of the impurities ranged between 96.2 and 102.7%, and the linearity results r > 0.999 across the range of LOQ – 150%. The precision results (%RSD) ranged between 0.8 and 4.5%. The degradation products formed during the base-induced degradation were identified as isomers of mycophenolic acid and sorbitol esters using Q-ToF LC–MS and their molecular and fragment ion peaks. The developed method eco-friendliness and greenness were assessed using analytical greenness (AGREE), green analytical procedure index (GAPI), and analytical eco score, and found it is green.

Coherence for Plactic Monoids via Rewriting Theory and Crystal Structures

Rewriting methods have been developed for the study of coherence for algebraic objects. This consists in starting with a convergent presentation and expliciting a family of generating confluences to obtain a coherent presentation – one with generators, generating relations, and generating relations between relations (syzygies). In this article we develop these ideas for a class of monoids which encode the representation theory of complex symmetrizable Kac-Moody algebras, called plactic monoids. The main tools for this are the crystal realization of plactic monoids due to Kashiwara, and a class of presentations compatible with a crystal structure, called crystal presentations. We show that the compatibility of the crystal structure with the presentation reduces many aspects of the study of plactic monoids via rewriting theory to computations with components of highest weight in the crystal. We thus obtain reduced versions of Newman’s Lemma and Critical Pair Lemma, which are results for verifying convergence of a presentation. Further we show that the family of generating confluences of a convergent crystal presentation is entirely determined by the components of highest weight, and show that this result applies to the plactic monoids of types An, Bn, Cn, Dn, and G2, via their convergent presentations due to Cain–Gray–Malheiro (Cain et al. J. Comb. Theory Ser. A. 162, 406–466, 6).

Identify miRNA-mRNA regulation pairs to explore potential pathogenesis of lung adenocarcinoma.

MicroRNA (miRNA) function via base-pairing with complementary sequences within mRNA molecules. This study aims to identify critical miRNA-mRNA regulation pairs contributing to lung adenocarcinoma (LUAD) pathogenesis. MiRNA and mRNA microarray and RNA-sequencing datasets were downloaded from gene expression omnibus (GEO) and the cancer genome atlas (TCGA) databases. Differential miRNAs (DE-miRNAs) and mRNAs (DE-mRNAs) were screened by the GEO2R tool and R packages. DAVID, DIANA, and Hiplot tools were used to perform gene enrichment analysis. The pairs of miRNA-mRNA were screened from the experimentally validated miRNA-target interactions databases (miRTarBase and TarBase). External validation was carried out in 30 pairs of LUAD tissues by quantitative reverse transcription and polymerase chain reaction (qRT-PCR). The diagnostic value of the miRNA-mRNA regulation pairs was evaluated by receiver operating characteristic curve (ROC) and decision curve analysis (DCA). Biological function assay was were also performed to confirm the function of miRNA-mRNA axis in LUAD progression. The study also performed the clinical, survival and tumor-associated phenotypic analysis of miRNA-mRNA pairs. A total of 7 miRNA and 13 mRNA expression datasets from GEO were analyzed, and 11 DE-miRNAs (5 down-regulated and 6 up-regulated in LUAD tissues) and 128 DE-mRNAs (30 up-regulated and 98 down-regulated in LUAD tissues) were identified. The pairs of miR-1-3p(down) and CENPF(up) and miR-126-5p(down) and UGT8(up) were verified in the external validation cohort (30 LUAD vs. 30 NC) using qRT-PCR. Areas under the ROC curve of the two miRNA-mRNA regulation pairs panel were 0.973 in TCGA-LUAD and 0.771 in the external validation. The DCA also showed that the miRNA-mRNA regulation pairs had an excellent diagnostic performance distinguishing LUAD from normal controls. The expression of the regulation pairs is different in different ages, TNM stages, and gender. The overexpression of miR-1-3p and miR-126-5p significantly inhibited the proliferation and migration of LUAD cells. Correlation analysis showed that CENPF correlated with prognosis and tumor immunity. The research identified potential miRNA-mRNA regulation pairs, providing a new idea for exploring the genesis and development of LUAD.

Pollution exacerbates interregional flows of virtual scarce water driven by energy demand in China

Existing studies on the virtual scarce water flows within the water-energy context focus on water quantity while largely ignoring water quality. This study improves the quantification method of scarce water uses by considering both blue water (representing water quantity) and grey water (indicating water quality). Based on a scarce-water extended multi-regional input–output model, we investigate the virtual scarce water flows driven by energy demand across 31 Chinese regions in 2012 and 2017. The results show that considering water quality provides new insights into the patterns of interregional flows of virtual scarce water driven by energy demand. The virtual integrated scarce water (VISW) flows, which consider both water quantity and quality, are 5 times the volume of virtual quantity-based scarce water (VQSW) flows. Moreover, certain regions (e.g., Hebei) are recognized as net VISW exporters, but are net importers in terms of VQSW. There are significant differences in the critical interregional pairs identified based on net VISW flows (e.g., Shandong–Zhejiang, and Shandong-Guangdong) and net VQSW flows (e.g., Heilongjiang-Guangdong, and Liaoning–Shaanxi). To reduce water scarcity based on the combined effect of both quantity and quality, the critical VISW interregional pairs should enhance cooperation through compensation payments and interregional technology transfer. This study highlights the importance of water quality in the assessment of virtual scarce water uses. Employing virtual scarce water as a policy tool to mitigate water scarcity might fail without the consideration of water quality.

Computing free non-commutative Gröbner bases over [formula omitted] with Singular:Letterplace

With this paper we present an extension of our recent ISSAC paper about computations of Gröbner(-Shirshov) bases over free associative algebras Z〈X〉. We present all the needed proofs in details, add a part on the direct treatment of the ring Z/mZ as well as new examples and applications to e.g. Iwahori-Hecke algebras. The extension of Gröbner bases concept from polynomial algebras over fields to polynomial rings over rings allows to tackle numerous applications, both of theoretical and of practical importance. Gröbner and Gröbner-Shirshov bases can be defined for various non-commutative and even non-associative algebraic structures. We study the case of associative rings and aim at free algebras over principal ideal rings. We concentrate on the case of commutative coefficient rings without zero divisors (i.e. a domain). Even working over Z allows one to do computations, which can be treated as universal for fields of arbitrary characteristic. By using the systematic approach, we revisit the theory and present the algorithms in the implementable form. We show drastic differences in the behaviour of Gröbner bases between free algebras and algebras, which are close to commutative. Even the process of the formation of critical pairs has to be reengineered, together with implementing the criteria for their quick discarding. We present an implementation of algorithms in the Singular subsystem called Letterplace, which internally uses Letterplace techniques (and Letterplace Gröbner bases), due to La Scala and Levandovskyy. Interesting examples and applications accompany our presentation.

Experimental and Numerical Investigations of Intermittence for Electronic Connectors Subjected to Mechanical Shocks

Abstract A phenomenon of intermittence is a critical issue for electronic joints of components installed in such as a mobile carrier. In this study, a finite element analysis of the DDR4 connector is utilized to assess the dynamic responses of terminal pairs embedded in the polymeric housing subjected to various mechanical shock conditions. Two approaches, respectively, based on the contact normal force and relative displacement between the contacting terminal and the associated gold finger, are proposed to investigate the presence of intermittence. The intermittence of the critical terminal pair under various shock conditions along the normal and longitudinal direction of the terminal is found to be strongly related to contact loss. Under the shock conditions along the transverse direction of the terminal, a threshold of the relative displacement between two reference points is set to effectively and accurately assess the occurrence of intermittence. The elastic/elastic-plastic multiscale rough surface (MSRS) model adopted to directly estimate the contact resistance history of the terminal pair is further attempted. The relatively low contact resistance of the terminal pair under the condition denoting pass can be observed. On the other hand, a sudden rise of the contact resistance of the terminal pair under the condition referring to fail is demonstrated based on the MSRS model although dramatic underestimations of the contact resistance are given when the contact normal force is rather low.