Seismic noise in South China Sea: High-quality time-frequency analysis from 0.01 to 125 Hz.

An efficient and precise time-frequency analysis method for real-time ocean bottom seismometer (RTOBS) data in the South China Sea (SCS) is presented. Overcoming the limitations of conventional methods, the method involves temporal segmentation, unique frequency octaves, and Fourier transforms to generate power spectral density (PSD) and probability density function profiles. The method demonstrates superior precision, computational efficiency, and full-bandwidth (0 to Nyquist) capability compared to traditional techniques, as validated through theoretical and empirical evaluations. Applied to SCS RTOBS data, it unveils temporal PSD variations, shedding light on underwater noise sources like earthquakes, offshore blasting, ship-induced disturbances, and tidal effects. Establishing background noise levels in the SCS supports noise source categorization and ocean environment monitoring. Furthermore, comparing onshore and offshore seismic stations advances interdisciplinary research, fostering a comprehensive understanding of acoustics and seismology in the region.

Tribological Performance and Enhancing Mechanism of 3D Printed PEEK Coated with In Situ ZIF-8 Nanomaterial.

Polyether ether ketone (PEEK) is esteemed as a high-performance engineering polymer renowned for its exceptional mechanical properties and thermal stability. Nonetheless, the majority of polymer-based lubricating materials fail to meet the contemporary industrial demands for motion components regarding high speed, heavy loading, temperature resistance, and precise control. Utilizing 3D printing technology to design and fabricate intricately structured components, developing high-performance polymer self-lubricating materials becomes imperative to fulfill the stringent operational requirements of motion mechanisms. This study introduces a novel approach employing 3D printing technology to produce PEEK with varying filling densities and conducting in situ synthesis of zeolitic imidazolate framework (ZIF-8) nanomaterials on its surface to enhance PEEK's frictional performance. The research discusses the synthetic methodology, characterization techniques, and tribological performance evaluation of in situ synthesized ZIF-8 nanomaterials on PEEK surfaces. The findings demonstrate a significant enhancement in frictional performance of the composite material under low-load conditions, achieving a minimum wear rate of 4.68 × 10-6 mm3/N·m compared to the non-grafted PEEK material's wear rate of 1.091 × 10-5 mm3/N·m, an approximately 1.3 times improvement. Detailed characterization and analysis of the worn surface of the steel ring unveil the lubrication mechanism of the ZIF-8 nanoparticles, thereby presenting new prospects for the diversified applications of PEEK.

Source depth estimation with feature matching using convolutional neural networks in shallow water.

A feature matching method based on the convolutional neural network (named FM-CNN), inspired from matched-field processing (MFP), is proposed to estimate source depth in shallow water. The FM-CNN, trained on the acoustic field replicas of a single source generated by an acoustic propagation model in a range-independent environment, is used to estimate single and multiple source depths in range-independent and mildly range-dependent environments. The performance of the FM-CNN is compared to the conventional MFP method. Sensitivity analysis for the two methods is performed to study the impact of different environmental mismatches (i.e., bottom parameters, water column sound speed profile, and topography) on depth estimation performance in the East China Sea environment. Simulation results demonstrate that the FM-CNN is more robust to the environmental mismatch in both single and multiple source depth estimation than the conventional MFP. The proposed FM-CNN is validated by real data collected from four tracks in the East China Sea experiment. Experimental results demonstrate that the FM-CNN is capable of reliably estimating single and multiple source depths in complex environments, while MFP has a large failure probability due to the presence of strong sidelobes and wide mainlobes.

Tribological Behavior of Cotton Fabric/Phenolic Resin Laminated Composites Reinforced with Two-Dimensional Materials.

In this study, cotton fabric-reinforced phenolic resin (CPF) composites were modified by adding four two-dimensional fillers: graphitic carbon nitride (g-C3N4), graphite (Gr), molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN). The tribological properties of these modified materials were investigated under dry friction and water lubrication conditions. The CPF/Gr composite exhibits significantly better tribological performance than the other three filler-modified CPF composites under dry friction, with a 24% reduction in friction coefficient and a 78% reduction in wear rate compared to the unmodified CPF composite. Under water lubrication conditions, all four fillers did not significantly alter the friction coefficient of the CPF composites. However, except for an excessive amount of Gr, the other three fillers can reduce the wear rate. Particularly in the case of 10% MoS2 content, the wear rate decreased by 56%. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed for the analysis of the morphology and composition of the transfer films. Additionally, molecular dynamics (MD) simulations were conducted to investigate the adsorption effects of CPF/Gr and CPF/MoS2 composites on the counterpart surface under both dry friction and water lubrication conditions. The difference in the adsorption capacity of CPF/Gr and CPF/MoS2 composites on the counterpart, as well as the resulting formation of transfer films, accounts for the variation in tribological behavior between CPF/Gr and CPF/MoS2 composites. By combining the lubrication properties of MoS2 and Gr under dry friction and water lubrication conditions and using them as co-fillers, we can achieve a synergistic lubrication effect.

The Study on the Morphology and Compression Properties of Microcellular TPU/Nanoclay Tissue Scaffolds for Potential Tissue Engineering Applications.

Thermoplastic polyurethane (TPU) materials have shown promise in tissue engineering applications due to their mechanical properties and biocompatibility. However, the addition of nanoclays to TPU can further enhance its properties. In this study, the effects of nanoclays on the microstructure, mechanical behavior, cytocompatibility, and proliferation of TPU/nanoclay (TPUNC) composite scaffolds were comprehensively investigated. The dispersion morphology of nanoclays within the TPU matrix was examined using transmission electron microscopy (TEM). It was found that the nanoclays exhibited a well-dispersed and intercalated structure, which contributed to the improved mechanical properties of the TPUNC scaffolds. Mechanical testing revealed that the addition of nanoclays significantly enhanced the compressive strength and elastic resilience of the TPUNC scaffolds. Cell viability and proliferation assays were conducted using MG63 cells cultured on the TPUNC scaffolds. The incorporation of nanoclays did not adversely affect cell viability, as evidenced by the comparable cell numbers between nanoclay-filled and unfilled TPU scaffolds. The presence of nanoclays within the TPUNC scaffolds did not disrupt cell adhesion or proliferation. The incorporation of nanoclays improved the dispersion morphology, enhanced mechanical performance, and maintained excellent biocompatibility. These findings suggest that TPUNC composites have great potential for tissue engineering applications, providing a versatile and promising scaffold material for regenerative medicine.

Pure-Phase, Large-Grained Wide-Band-Gap Perovskite Films for High-Efficiency, Four-Terminal Perovskite/Silicon Tandem Solar Cells.

High-quality, stable perovskite films with a wide band gap between 1.65 and 1.80 eV are highly suitable for efficient and cost-competitive silicon-based tandem solar cells. Herein, we demonstrate that the combined strategies of the Pb(SCN)2 additive and air annealing can enable the Cs0.22FA0.78Pb(I0.85Br0.15)3 films with a wide band gap of 1.65 eV and favored properties including pure composition, high crystallinity, micro-sized grains, and reduced defects. With these desired films, the average efficiencies of semitransparent perovskite solar cells (PSCs) are boosted from (18.13 ± 0.31) to (20.35 ± 0.28)%. Further, the semitransparent PSC is used to assemble the four-terminal perovskite/TOPCon tandem solar cell. Benefiting from its excellent performance and preferred optical properties, the obtained tandem solar cell yields a milestone efficiency of 30.32%.

The Study of Crystallization Behavior, Microcellular Structure and Thermal Properties of Glass-Fiber/Polycarbonate Composites.

Polycarbonate (PC) foam is a versatile material with excellent properties, but its low thermal stability limits its application in high-temperature environments. The aim of this study was to improve the thermal stability of PC foam by adding glass fibers (GF) and to investigate the effect of GF on PC crystallization behavior and PC foam cell morphology. This study was motivated by the need to improve the performance of PC foams in various industries, such as construction, automotive, and medical. To achieve this goal, PC/GF composites were prepared by extrusion, and PC/GF composite foams were produced using a batch foaming process with supercritical carbon dioxide (SC-CO2) as the blowing agent. The results showed that the addition of GF accelerated the SC-CO2-induced crystallization stability of PC and significantly increased the cell density to 4.6 cells/cm3. In addition, the thermal stability of PC/GF foam was improved, with a significant increase in the residual carbon rate at 700 °C and a lower weight loss rate than PC matrix. Overall, this study highlights the potential of GF as a PC foam reinforcement and its effect on thermal and structural properties, providing guidance for industrial production and applications.

Mitigation of lamp oven and cavity oven temperature-induced frequency variation in rubidium atomic clock.

The long-term frequency stability of the rubidium atomic clock is primarily affected by temperature variations in the lamp oven and the cavity oven, which cause changes in light intensity, which are then converted into frequency variations. Therefore, we propose using light intensity variations to actively improve the cavity oven and lamp oven temperature sensitivity of the rubidium atomic clock. This is accomplished through research into the theory of the rubidium atomic frequency standard, specifically the effect of light intensity, lamp oven temperature, and cavity oven temperature on the frequency deviation. In previous work, we discovered the relationship between the light intensity and frequency deviation by combining this with our engineering expertise. Furthermore, some related experiments show that the method is feasible with the lamp oven and cavity oven temperature sensitivity of the rubidium atomic clock greatly improved, providing an effective way to improve the rubidium atomic clock's long-term frequency stability.

Secure and noise-resistant underwater wireless optical communication based on spectrum spread and encrypted OFDM modulation.

In addition to requirements on increasing transmission distance and bitrate, the study of underwater wireless optical communication (UWOC) is also facing limitations and challenges, such as interference induced by background noise, demand of higher receiver sensitivity, and communication security issues. In this paper, we experimentally demonstrate a physical layer secure and noise-resistant UWOC system based on spectrum spread and encrypted orthogonal frequency division multiplexing (SSE-OFDM) modulation, transmission through a 14.2 m sediment circulating water tank. Firstly, experimental results show that the required optical power ratio of signal and noise light (OPR) for QPSK signal under BER threshold of 3.8×10-3 is around -5.77 dB for a spectrum spread factor (N) of 100, with a signal-to-noise ratio (SNR) improvement of 19.06 dB. Secondly, without the background noise interference, the receiver sensitivity is also improved from -50 dBm to -62.4 dBm by using the SSE-OFDM modulation, achieving a maximum attenuation length (AL) of 19.67. Thirdly, physical layer security of UWOC can also be realized, which suppresses the SNR of eavesdropper to -3.72 dB while improving SNR of the authorized receiver to 17.56 dB under the condition of no leakage of keys. Additionally, analytical expressions for SSE-OFDM based UWOC performance are also derived, which agree well with the experimental results. Based on the analytical expressions, the maximum secrecy capacity Cs for SSE-OFDM based UWOC system under eavesdropping can be obtained by optimizing the intentionally inserted artificial noise power ratio and the spectrum spread factor N.

Interfacial Dipole poly(2-ethyl-2-oxazoline) Modification Triggers Simultaneous Band Alignment and Passivation for Air-Stable Perovskite Solar Cells.

To promote the performance of perovskite solar cells (PSCs), its theoretical power conversion efficiency (PCE) and high stability, elaborative defect passivation, and interfacial engineering at the molecular level are required to regulate the optoelectric properties and charge transporting process at the perovskite/hole transport layer (HTL) interfaces. Herein, we introduce for the first time a multifunctional dipole polymer poly(2-ethyl-2-oxazoline) (PEOz) between the perovskite and Spiro-OMeTAD HTL in planar n-i-p PSCs, which advances the PSCs toward both high efficiency and excellent stability by stimulating three beneficial effects. First, the ether-oxygen unshared electron pairs in PEOz chemically react with unsaturated Pb2+ on the perovskite surfaces by forming a strong Pb-O bond, which effectively reduces the uncoordinated defects on the perovskite surfaces and enhances the absorption ability of the resulting PSCs. Second, the dipole induced by PEOz at the perovskite/HTL interface can decrease the HOMO and LUMO level of Spiro-OMeTAD and optimize the band alignment between these layers, thereby suppressing the interfacial recombination and accelerating the hole transport/extraction ability in the cell. Third, the hygroscopic PEOz thin film can protect perovskite film from water erosion by absorbing the water molecules before perovskite does. Finally, the PEOz-modified PSC exhibits an optimized PCE of 21.86%, with a high short-circuit current density (Jsc) of 24.88 mA/cm2, a fill factor (FF) of 0.79, and an open-circuit voltage (Voc) of 1.11 V. The unencapsulated devices also deliver excellent operation stability over 300 h in an ambient atmosphere with a humidity of 30~40% and more than 10 h under thermal stress.

Effects of expandable graphite on the flame-retardant and mechanical performances of rigid polyurethane foams.

Polyurethane foams (PUFs) are found everywhere in our daily life, but they suffer from poor fire resistance. In this study, expansible graphite (EG) as flame retardant was incorporated into PUFs to improve material fire resistance. With the presence of EGs in the PU matrix, bubble size in PUF became smaller as confirmed by the scanning electron microscopy. The mass density of PUFs is directly proportional to the content of EG additive. The compression strengths of EG0/PUF and EG30/PUF decrease from 0.51 MPa to 0.29 MPa. The Fourier transform infrared spectroscopy (FTIR) analysis of RPUFs showed that the addition of EGs did not change the functional group structures of RPUFs. Thermo-gravimetric analysis (TGA) testing results showed that the carbon residue weight of EG30/PUF is higher than other PU composite foams. The combination of TGA and FTIR indicated that the EG addition did not change the thermal decomposition products of EG0/PUF, but effectively inhibited its thermal decomposition rate. Cone calorimeter combustion tests indicated that the peak of the heat release rate of EG30/PUF significantly decreased to 100.5 kW m-2compared to 390.6 kW m-2for EG0/PUF. The ignition time of EG/PUF composites also increased from 2 s to 11 s with incorporation of 30 wt% EGs. The limiting oxygen index (LOI) and UL-94 standard tests show that the LOI of EG30/PUF can reach 55 vol%, and go through V-0 level. This study showed that adding EG into PU foams could significantly improve the thermal stability and flame retardancy properties of EG/PUF composites without significantly sacrificing material compression strength. The research results provide useful guidelines on industrial production and applications of PUFs.

A Hybrid Recommendation System for Marine Science Observation Data Based on Content and Literature Filtering.

With the development of ocean exploration technology and the rapid growth in the amount of marine science observation data, people are faced with a great challenge to identify valuable data from the massive ocean observation data. A recommendation system is an effective method to improve retrieval capabilities to help users obtain valuable data. The two most popular recommendation algorithms are collaborative filtering algorithms and content-based filtering algorithms, which may not work well for marine science observation data given the complexity of data attributes and lack of user information. In this study, an approach was proposed based on data similarity and data correlation. Data similarity was calculated by analyzing the subject, source, spatial, and temporal attributes to obtain the recommendation list. Then, data correlation was calculated based on the literature on marine science data and ranking of the recommendation list to obtain the re-rank recommendation list. The approach was tested by simulated datasets collected from multiple marine data sharing websites, and the result suggested that the proposed method exhibits better effectiveness.

Long non-coding RNA colon cancer-associated transcript-1 regulates tumor cell proliferation and invasion of non-small-cell lung cancer through suppressing miR-152.

AIM: Lung cancer serves as one of the most common cancers in the world, and approximately 50% of non-small-cell lung cancer (NSCLC) patients are found to be aged >70 when diagnosed. In this study, we aimed to explore the effect of long non-coding RNAs colon cancer-associated transcript-1 (CCAT1) in NSCLC. METHODS: A total of 72 clinical samples from older NSCLC patients were collected for analysis. The relative mRNA level of CCAT1 was detected through real-time polymerase chain reaction. Overall survival of NSCLC patients was detected through Kaplan-Meier survival analysis. MTT assays were used to detect cell proliferation. Cell invasion was determined by transwell assay. Protein levels were detected through western blot. RESULTS: CCAT1 expression levels significantly increased in NSCLC tumor tissues and were associated with poor overall survival of NSCLC patients. CCAT1 promotes cell proliferation, cell invasion and epithelial-mesenchymal transition of NSCLC cell lines. CCAT1 binds with miR-152, and the effect of si-CCAT1 in NSCLC cell proliferation, cell invasion and epithelial-mesenchymal transition was partially reversed by anti-miR-152. CONCLUSIONS: Long non-coding RNA CCAT1 regulates tumor cell proliferation and invasion in NSCLC through suppressing miR-152. Geriatr Gerontol Int 2020; ••: ••-••.

MicroRNA-205-5p Promotes Unstable Atherosclerotic Plaque Formation In Vivo.

PURPOSE: Atherosclerosis is a narrowing of the arteries caused by plaque buildup. MicroRNAs (miRNAs) have been proposed to participate in the pathogenesis of atherosclerosis. Here, we aimed to investigate miR-205-5p's role in promoting atherosclerotic progression. METHODS: Knock-in (KI) mice with human/murine miR-205-5p within the murine host gene for miR-205 (MIR205HG) were crossed with apolipoprotein E knockout (Apoe-/-) mice. This miR-205KI Apoe-/- murine model was employed to study the impact of miR-205-5p in Apoe-/- mice susceptible to atherosclerotic plaque formation. RESULTS: miR-205KI Apoe-/-mice developed larger, more unstable plaques relative to their Apoe-/- counterparts (0.45 vs. 0.26 mm2, P < 0.001). miR-205KI Apoe-/- mice exhibited lower serum levels of high-density lipoprotein cholesterol (HDL-C) (5.18 vs. 19.31 mg/dL, P < 0.001) and triglycerides (32.79 vs. 156.76 mg/dL, P < 0.001) with system-wide reversal of cholesterol transport. Macrophages derived from miR-205KI Apoe-/- mice exhibited ~ 20% lowered cholesterol efflux capability with enhanced pro-inflammatory gene expression through lipid raft formation. Bone marrow transplantation demonstrated that bone marrow (BM) donor cells with miR-205-5pKI simulated plaque formation independent of the recipients' miR-205-5p status. CONCLUSIONS: miR-205-5p encourages unstable atherogenesis in vivo. miR-205-5p also adversely influences lipid metabolism and promotes a pro-inflammatory macrophage phenotype. Our findings advocate miR-205-5p as a potential therapeutic target for combating unstable atherogenesis.

Synergistic antitumor effect of BRMS1 and sorafenib via inhibition of the PI3K/AKT/mTOR/ERK signaling pathway.

Liver cancer is the fifth most commonly occurring cancer in men and the ninth most commonly occurring cancer in women, worldwide, and is associated with a high mortality rate. Sorafenib is a new inhibitor of multiple kinases, that is regarded as standard treatment for liver cancer. Human breast carcinoma metastasis­suppressor 1 (BRMS1) is a tumor­suppressor gene, that reduces the metastatic ability of tumor cells without affecting their tumorigenicity. In the present study, a model of BRMS1 overexpression and BRMS1 knockdown was established in HepG2 cells. The results revealed that the proliferation of HepG2 cells was inhibited in response to sorafenib treatment using MTT assay. Furthermore, BRMS1 overexpression enhanced the effect of sorafenib. In addition, expression of inflammatory response­related genes was increased, while secretion of angiogenesis­related molecules was decreased, and apoptosis was also activated after sorafenib treatment using qPCR method, and it was further demonstrated that this effect was mediated by inhibition of the PI3K/AKT/mTOR/ERK signaling pathway using western blot analysis. In conclusion, overexpression of BRMS1 potentiated the effect of sorafenib via PI3K/AKT/mTOR/ERK signaling, while knockdown of BRMS1 expression attenuated this effect. These findings may present a novel therapeutic strategy for liver cancer.

[Experiment of bone morphogenetic protein 2 induced chondrogenic differentiation of human Achilles tendon-derived stem cells in vitro].

OBJECTIVE: To investigate the effects of bone morphogenetic protein 2 (BMP-2) on the chondrogenic differentiation of human Achilles tendon-derived stem cells (hATDSCs) in vitro. METHODS: Achilles tendon was harvested from a voluntary donor with acute Achilles tendon rupture. And nucleated cells were obtained by digesting with collagenase and were cultured to the 3rd passage. The flow cytometry was used to measure the immunophenotyping; and Oil red O staining, alizarin red staining, and Safranin O/fast green staining were used to identify the adipogenic differentiation, osteogenic differentiation, and chondrogenic differentiation, respectively. The hATDSCs pellet was cultured in complete culture medium with (experimental group) or without recombinant human BMP-2 (rhBMP-2) (control grup) for 3 weeks. Chondrogenic differentiation of hATDSCs was evaluated by HE staining, Safranin O/fast green staining, and immunohistochemical staining for collagen type II; and the mRNA expressions of SOX9, collagen type II, and Aggrecan were detected by real-time fluorescence quantitative PCR. RESULTS: Primary hATDSCs cultured in vitro showed clonal growth; after cell passage, homogeneous spindle fibroblast-like cells were seen. The cells were positive for CD44, CD90, and CD105, while negative for CD34, CD45, and CD146. The results were positive for Oil red O staining at 3 weeks after adipogenic differentiation, for alizarin red staining at 4 weeks after osteogenic differentiation, and for Safranin O/fast green staining at 3 weeks after chondrogenic differentiation. After hATDSCs were induced with rhBMP-2 for 3 weeks, pellets formed in the experimental group, and the size of pellets was significantly larger than that in the control group; the results of HE staining, Safranin O/fast green staining, and immunohistochemical staining for collagen type II were all positive. The results of real-time fluorescence quantitative PCR showed that the mRNA expressions of SOX9, collagen type II, and Aggrecan in the experimental group were significantly higher than those in the control group (P < 0.05). CONCLUSION: BMP-2 can promote proteoglycan deposition and induce chondrogenic differentiation of hATDSCs in vitro. The effect of BMP-2 on hATDSCs might provide a possible explanation for histopathological changes of tendinopathy.

Facile fabrication of superhydrophobic Cu(OH)2 nanorod and CuO nanosheet arrays on copper surface.

Cu(OH)2 nanorod and CuO nanosheet arrays have been successfully grown on the copper surfaces by a simple one-step solution-immersion process at ambient temperature and pressure. After the chemical modification with 1H, 1H, 2H, 2H-Perfluorodecyltriethoxysilane, the wettability of the copper substrate changed from superhydrophilic to superhydrophobic. Meanwhile, the sliding angle of the superhydrophobic surface is less than 5 degrees. It is confirmed that both the synergic effect of the surface morphology and the surface free energy contribute to this unique surface water repellence. Furthermore, the as-prepared surfaces were stable even after a long-term storage, and retained good superhydrophobicity for corrosive liquids. Such special superhydrophobic properties will greatly extend the applications of copper in many other important industrial fields.

Superhydrophobic and superoleophilic nanoparticle film: synthesis and reversible wettability switching behavior.

The present work describes a one-step facile spray deposition process for the fabrication of superhydrophobic and superoleophilic nanoparticle film. The film shows fast response wettability transition between superhydrophobicity and hydrophilicity. The reversible superhydrophobicity to hydrophilicity switching can be easily carried out by adjusting the temperature. The film also demonstrates oil uptake ability and can selectively adsorb oil floating on water surface. Furthermore, the film surface shows the antifouling performance for organic solvents, which can self-remove the organic solvents layer and recover its superhydrophobic behavior. The advantage of the present approach is that the damaged film can be easily repaired by spraying again.

Construction of a multiplex allele-specific PCR-based universal array (ASPUA) and its application to hearing loss screening.

We demonstrate a new method, using a universal array approach termed multiplex allele-specific PCR-based universal array (ASPUA), and applied it to the mutation detection of hereditary hearing loss. Mutations in many different genes may be the cause of hereditary hearing loss, a sensory defect disorder. Effective methods for genetic diagnosis are clearly needed to provide clinical management. Owing to the broad genetic basis of this condition, clinical assay of such a highly heterogeneous disorder is expensive and time consuming. In ASPUA, the allele discrimination reaction is carried out in solution by multiplex allele-specific PCR and a universal solid phase array with different tag probes is used to display the PCR result. The purpose of developing the ASPUA platform was to utilize the rapidity and simplicity of the amplification refractory mutation system (ARMS) with the detection power of microarray hybridization. This is the first report of the combination of these two technologies, which allow for the completion of allele-specific detection of 11 of the most frequent mutations causing hereditary hearing loss in under 5 hr. The ASPUA platform was validated by accurately analyzing 141 patient samples that had been previously genotyped for GJB2, GJB3, SLC26A4, and MTRNR1. In addition, we also developed a simplified assay by using streptavidin-coated magnetic beads instead of fluorescence for signal display that can be assessed through a conventional light microscope. We demonstrate that the ASPUA platform is rapid, cost-effective, and easily-used, and is especially appropriate for mutation detection in clinical genetic diagnostics.

[Improvement on simulation algorithm of excitation propagation in heart modeling].

It is important to simulate the excitation propagation process of cardiac bio-electricity in the research of ECG forward problem. Traditional methods describe them with wave simulation algorithm such as LFX simulation algorithm and vector propagation algorithm etc, these methods have some problems to certain extent, due to the presence of discreteness of space and time and asymmetry of the myocardium. This paper discussed the simulation algorithm in 2-dimension space under the circumstance of layered and non-layered structure of myocardium. By calculating the theoretic values of simulating time based on Huygen's principle, we found that there were errors in LFX algorithm and no errors in vector propagation algorithm under the circumstance of non-layered structure of the myocardium, no mater what myocardium is isotropic or anisotropic. However, there exist errors from both algorithms when the myocardium has the layered structure. An improved algorithm is proposed and the simulations have been performed to examine the efficacy of the new algorithm, and the errors are reduced obviously. By increasing the number of myocardial blocks in the model, we also analyzed its influence on the error of simulation algorithm.