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Original scientific paper The criteria of separation and dislocation of the layered roof in mining are put forward through the simplified mechanical model with weak inter-layers. Considering five different variables, namely the number of layers, the distance from the weak inter-layers to the mine opening, the thickness of the weak inter-layers, the lateral pressure coefficient and the spacing of the bedding planes, the distribution characteristics of the pressure-arch in the horizontal stratified rocks are analyzed during coal mining using FLAC3D. The results show that the newly appeared pressure-arch is composed of the original pressure-arch in each layer and the pressure-arch shape being affected by the weak layer in the surrounding rock of the mine opening. As the distance between the inter-layers and the coal seam increases, the effect on the pressure-arch is reduced gradually. The thinner inter-layers produce greater impact on the pressure-arch. The lateral pressure coefficient has a great influence on the pressure-arch and a stable pressure-arch could only be formed when the lateral pressure coefficient is in a suitable range. Keywords: numerical analysis; pressure-arch; stratified rock; weak inter-layers Analiza karakteristika raspodjele tlaka stropa u horizontalno slojevitim stijenama u uvjetima iskapanja ugljenaIzvorni znanstveni članak Predlažu se kriteriji za odvajanje i premještanje slojevitog nadsvođa u rudarstvu primjenom pojednostavljenog mehaničkog modela sa slabim međuslojevima. Uz razmatranje pet različitih varijabli, naime broja slojeva, razmaka od slabih među-slojeva do otvora rudnika, debljine slabih međuslojeva, lateralnog koeficijenta tlaka i međusobnog razmaka površina laminacije, analiziraju se karakteristike raspodjele tlaka stropa u horizontalno slojevitim stijenama tijekom iskapanja ugljena, primjenom FLAC3D. Rezultati pokazuju da se novonastali tlak stropa sastoji od originalnog tlaka stropa u svakom sloju te tlaka konture stropa prouzročenog slabim slojem u okruženju stijene okna rudnika. Kako se povećava razmak između međuslojeva i sloja (žile) ugljena, postepeno se smanjuje utjecaj na tlak stropa. Tanji međuslojevi imaju veći utjecaj na tlak stropa. Lateralni koeficijent tlaka ima veliki utjecaj na tlak stropa te se stabilni tlak stropa može stvoriti jedino kad je lateralni koeficijent tlaka odgovarajućeg raspona.

IntroductionCognitive impairment is the main clinical feature after traumatic brain injury (TBI) and is usually characterized by attention deficits, memory loss, and decreased executive function. Vagus nerve stimulation (VNS) has been reported to show potential improvement in the cognition level after traumatic brain injury in clinical and preclinical studies. However, this topic has not yet been systematically reviewed in published literature. In this study, we present a systematic review and meta-analysis of the effects of VNS on cognitive function in animal models of TBI and their underlying mechanisms.MethodsWe performed a literature search on PubMed, PsycINFO, Web of Science, Embase, Scopus, and Cochrane Library from inception to December 2021 to identify studies describing the effects of VNS on animal models of TBI.ResultsOverall, nine studies were identified in animal models (36 mice, 268 rats, and 27 rabbits). An analysis of these studies showed that VNS can improve the performance of TBI animals in behavioral tests (beam walk test: SMD: 4.95; 95% confidence interval [CI]: 3.66, 6.23; p < 0.00001) and locomotor placing tests (SMD: –2.39; 95% CI: –4.07, –0.71; p = 0.005), whereas it reduced brain edema (SMD: –1.58; 95% CI: –2.85, –0.31; p = 0. 01) and decrease TNF-α (SMD: –3.49; 95% CI: –5.78, –1.2; p = 0.003) and IL-1β (SMD: –2.84; 95% CI: –3.96, –1.71; p < 0.00001) expression level in the brain tissue. However, the checklist for SYRCLE showed a moderate risk of bias (quality score between 30% and 60%), mainly because of the lack of sample size calculation, random assignment, and blinded assessment.ConclusionThe present review showed that VNS can effectively promote cognitive impairment and neuropathology in animal models of TBI. We hope that the results of this systematic review can be applied to improve the methodological quality of animal experiments on TBI, which will provide more important and conclusive evidence on the clinical value of VNS. To further confirm these results, there is a need for high-quality TBI animal studies with sufficient sample size and a more comprehensive outcome evaluation.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021290797, identifier: CRD42021290797.

Original scientific paperIn order to provide a basis for the reinforcement design and construction safety of the double-arch tunnel, it is of theoretical and practical value to analyse the morphological characterization, the evolution process and the skewed effect of the pressure-arch in a double-arch tunnel. Based on the descriptions of the boundary parameters of the pressure-arch in a double-arch tunnel, taking the 80 m buried depth double-arch highway tunnel as the research object, the numerical calculation model of the double-arch tunnel was built by using FLAC3D, and then the morphological evolution of the pressure-arch induced by step-by-step excavation was analysed. The results showed that the pressure-arch of the double-arch tunnel displayed the skewed distribution characteristics which were gradually diminishing from the left tunnel to the right tunnel, the strain energy dissipation of the double-arch tunnel from the left tunnel to the right tunnel was from high to low, and the nonlinear response characteristics in different excavation sequences were sensitive to the changes of the stress state. The results provided a basis for the rock reinforcement design and safety construction of double-arch tunnel.Keywords: double-arch tunnel; numerical calculation; pressure-arch; skewed effect; strain energy Analiza razvoja značajki tlačnog svoda u tunelu s dvostrukim svodomIzvorni znanstveni članak Kako bi se osigurala osnova za pojačanje konstrukcije i sigurnost izgradnje tunela s dvostrukim svodom, od teorijske i praktične vrijednosti je analizirati morfološku karakterizaciju, proces razvoja i asimetrični učinak tlačnog svoda u tunelu s dvostrukim svodom. Na temelju opisa graničnih parametara tlačnog svoda u tunelu s dvostrukim svodom, kao istraživački objekt uzet je tunel autoceste s dvostrukim svodom iskopan na dubini od 80 m, te je izrađen numerički proračunski model tunela s dvostrukim svodom uporabom FLAC3D, a potom je analiziran morfološki razvoj tlačnog svoda induciran iskopom korak-po-korak. Rezultati su pokazali da tlačni svod tunela s dvostrukim svodom pokazuje karakteristike asimetrične distribucije koja se postupno smanjuje od lijevog tunela ka desnom tunelu, da rasipanje energije deformacije tunela s dvostrukim svodom od lijevog tunela ka desnom tunelu ide od visokog do niskog, te da su nelinearne odzivne karakteristike u različitim sekvencama iskopa osjetljive na promjene u stanju naprezanja. Rezultatima je omogućena osnova za konstrukcije pojačane kamenom i sigurnost u izgradnji tunela s dvostrukim svodom.Ključne riječi: asimetrični učinak; energija deformacije; numerički proračun; tlačni svod; tunel s dvostrukim svodom