Effect of Perforating an Intake Pipe on the Interior Noise of a Passenger Car

Zhu Yawei,Lu Chihua,Liu Zhien,Xie Liping,Li Xiaolong 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.4

The intake pipes designed by some experienced engineers have small holes. However, the role of these small holes is yet to be fully understood by most engineers. At present, the only research on this issue is also controversial. This work aims to reveal the effect of perforating an intake pipe on the interior noise and provide some suggestions to automotive engineers when applying this method. First, the effect of these small holes on the source strength of the intake nozzle and perforated region is theoretically analyzed. Thereafter, the noise transfer functions of the intake nozzle and perforated region to the target response point in the cab are measured on the basis of the reciprocity principle. Finally, the effect of perforating the intake pipe on the interior noise is studied by simulating the intake noise of the experimental car with an external sound source. Results show that perforating the intake pipe can increase the order noise component of the intake noise and reduce the mid-high frequency noise in the cab, thereby improving the powerful sound quality and reducing the feeling of noisy.

아프리카산 발톱개구리의 치아 발생과정에서 Bmp4 의 발현

홍지수,고병석,Yawei Cheng,YANG LIU,박병건,이영훈 대한구강해부학회 2019 대한구강해부학회지 Vol.40 No.1

Bmp4는 치아발생 과정에서 발현을 나타내고 치아형성 위치, 치아발생개시, 치아형태의 조절, 치아모양의 결정에 관여한다. 그러나 아프리카산 발톱개구리의 치아발생과정에서는 잘 알려져 있지 않다. 아프리카산 발톱개구리의 알을 수정하여 사육하여 26일째(stage 54)의 올챙이부터 변태 직후 어린 개구리의 위턱을 in situ hybridization 방법으로 실험하였다. Bmp4는 stage 54의 치배에서는 발현되지 않았고, stage 56부터 stage 62까지 중간엽과 치아유두, 바깥치아상피에서 발현되었다. 변태 직후 어린 개구리에 해당하는 stage 66에서, Bmp4 는 위턱뼈에 유착된 치아에서 발현되지 않았고, 계승치아의 중간엽과 바깥치아상피에서 발현되었다. 그러므로 Bmp4는 아프리카산 발톱개구리의 치아발생 과정에서 상아질 형성에 중요한 역할을 할 것으로 생각된다.

Exciton dynamics in cation-exchanged CdSe/PbSe nanorods: The role of defects

Lee, Sooho,Wang, Yimeng,Liu, Yawei,Lee, Dongkyu,Lee, Kangha,Lee, Doh C.,Lian, Tianquan Elsevier 2017 Chemical physics letters Vol.683 No.-

<P>Cation exchange occurs via defect initiated solid-state diffusion, a process that can lead to defect formations. The effect of such inherent defect formation on carrier dynamics of cation-exchanged heterostructures remains poorly understood. Herein, we report exciton dynamics in type II CdSe/PbSe heterostructure nanorods formed via cation exchange. The majority of electrons in CdSe domains decays in 5 ps due to ultrafast carrier trapping. The defect generated by cation exchange can be healed by annealing the as-synthesized CdSe/PbSe heterostructure nanorods. This study suggests a strategy for improving properties of heteronanostructures prepared by cation exchange for applications in photovoltaics and photocatalysis. (C) 2017 Elsevier B.V. All rights reserved.</P>

Efficient near ultraviolet organic light-emitting devices based on star-configured carbazole emitters

Jiarong Lian,Fangfang Niu,Yawei Liu,Pengju Zeng,Hanben Niu 한국물리학회 2011 Current Applied Physics Vol.11 No.3

Efficient near ultraviolet organic light-emitting devices with the maximum external quantum efficiency of 3.3% were fabricated using novel star-configurated carbazole derivatives (MTPC) as emitters. Beside the main peak wavelength at 408 nm, an obvious longer wavelength tail with peak emission at 493 nm was observed, which was certified because of the emission of exciplex between MTPC and TPBI exciton confiner. Our results clearly suggest that the star-configurated carbazole derivatives are potential to be served as high efficient near ultraviolet emitters and as hosts for visible color dopant.

Effects of vertebral number variations on carcass traits and genotyping of Vertnin candidate gene in Kazakh sheep

Zhang, Zhifeng,Sun, Yawei,Du, Wei,He, Sangang,Liu, Mingjun,Tian, Changyan Asian Australasian Association of Animal Productio 2017 Animal Bioscience Vol.30 No.9

Objective: The vertebral number is associated with body length and carcass traits, which represents an economically important trait in farm animals. The variation of vertebral number has been observed in a few mammalian species. However, the variation of vertebral number and quantitative trait loci in sheep breeds have not been well addressed. Methods: In our investigation, the information including gender, age, carcass weight, carcass length and the number of thoracic and lumbar vertebrae from 624 China Kazakh sheep was collected. The effect of vertebral number variation on carcass weight and carcass length was estimated by general linear model. Further, the polymorphic sites of Vertnin (VRTN) gene were identified by sequencing, and the association of the genotype and vertebral number variation was analyzed by the one-way analysis of variance model. Results: The variation of thoracolumbar vertebrae number in Kazakh sheep (18 to 20) was smaller than that in Texel sheep (17 to 21). The individuals with 19 thoracolumbar vertebrae (T13L6) were dominant in Kazakh sheep (79.2%). The association study showed that the numbers of thoracolumbar vertebrae were positively correlated with the carcass length and carcass weight, statistically significant with carcass length. To investigate the association of thoracolumbar vertebrae number with VRTN gene, we genotyped the VRTN gene. A total of 9 polymorphic sites were detected and only a single nucleotide polymorphism (SNP) (rs426367238) was suggested to associate with thoracic vertebral number statistically. Conclusion: The variation of thoracolumbar vertebrae number positively associated with the carcass length and carcass weight, especially with the carcass length. VRTN gene polymorphism of the SNP (rs426367238) with significant effect on thoracic vertebral number could be as a candidate marker to further evaluate its role in influence of thoracolumbar vertebral number.

Computer Simulation of Metal Surface Micro-Crack Inspection Using Pulsed Laser Thermography

Tang Qingju,Bu Chiwu,Liu Yuanlin,Yu Fengyun,Zhao Yawei 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.3

Surface micro cracks are easy to produce in the preparation and service process of metal material, which impacts on the safe operation of metal components. Pulsed laser spot excitation and infrared thermal imaging technology are combined to detect metal surface micro-cracks. The working principle of laser infrared thermal imaging detection technology was described. The three dimensional heat conduction model of pulsed laser excitation flux transfer in metal plate was established, and calculated using finite element method (FEM). The results showed that, thermal flow in the image is a “D” shape. There are temperature differences between the sound regions and defective regions, and the defects experiences the process of obscure, gradually clear, and gradually obscure. Pulsed infrared thermography sequence was processed by polynomial fitting method, and the coefficient images effectively improve the contrast between defective and non-defective areas, which is beneficial to the determination and of recognition micro cracks.

EpiLoc: Deep Camera Localization Under Epipolar Constraint

Luoyuan Xu,Tao Guan,Yawei Luo,Yuesong Wang,Zhuo Chen,WenKai Liu 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.6

Recent works have shown that the geometric constraint can be harnessed to boost the performance of CNN-based camera localization. However, the existing strategies are limited to imposing image-level constraint between pose pairs, which is weak and coarse-gained. In this paper, we introduce a pixel-level epipolar geometry constraint to vanilla localization framework without the ground-truth 3D information. Dubbed EpiLoc, our method establishes the geometric relationship between pixels in different images by utilizing the epipolar geometry thus forcing the network to regress more accurate poses. We also propose a variant called EpiSingle to cope with non-sequential training images, which can construct the epipolar geometry constraint based on a single image in a self-supervised manner. Extensive experiments on the public indoor 7Scenes and outdoor RobotCar datasets show that the proposed pixel-level constraint is valuable, and helps our EpiLoc achieve state-of-the-art results in the end-to-end camera localization task.

Microstructural Refinement and Performance Improvement of Cast n-Type Bi2Te2.79Se0.21 Ingot by Equal Channel Angular Extrusion

Xiaoming Hu,Xi’an Fan,Bo Feng,Dong Kong,Peihai Liu,Rusong Li,Yanglin Zhang,Guangqiang Li,Yawei Li 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

How to form a uniform fine-grained structure in n-type polycrystalline Bi2Te3based alloys to stabilize and improve thethermoelectric properties is the burning issue to be solved. In the present work, equal channel angular extrusion (ECAE)method was used to extrude the cast ingot directly at various temperatures to obtain the BiTeSe polycrystalline bulk alloyswith uniform microstructure. The initial lamellae coarse grains (hundreds microns to several millimeters) were efficiently anduniformly refined to a minimum of 4.07 μm at 703 K, which fully demonstrates the feasibility of grain refinement by ECAEfor cast n-type BiTeSe ingot. The average grain size of the extruded billets rapidly increased from 5.35 to 29.55 μm withthe increase of extrusion temperature from 703 to 823 K. Meanwhile, the behavior of abnormal grain growth became moreevident as the extrusion temperature increased because the growth rate increased more rapidly than the rate of nucleation. As the extrusion temperature increased, the Vickers hardness decreased gradually due to grain coarsening. BiTeSe alloysextruded at 703 K achieved the maximum Vickers hardness of 59.8 HV0.05,which was nearly three times higher than that ofthe initial cast ingot. All extruded BiTeSe billets possessed the much higher dimensionless figure of merit (ZT), comparedwith the initial cast ingot due to the simultaneously optimization of electrical and thermal transport performances caused byECAE process. Finally, the specimen extruded at 823 K achieved the maximum ZT of 0.685 at 383 K.

Controllable Production of Micro-nanoscale Metal-Organic Frameworks Coatings on Cotton Fabric for Sensing Cu2+

Xingfang Xiao,Lipei Ren,Shujun Wang,Qian Zhang,Yawei Zhang,Ruina Liu,Weilin Xu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.9

Luminescent lanthanide metal-organic frameworks (ln-MOFs) is a promising materials for sensing. However,seeking ideal method to scale up in mass production and can be uniform on flexible substrate is still a great challenge. In thisstudy, a novel and efficient process was employed for the fabrication of flexible and environmental copper ion-sensingmaterials using cotton fabric as a substrate. The micro-nanoscale Europium metal-organic frameworks (Eu-MOFs) wasprepared through adding blocking reagent, and then cotton fabric was coated with the Eu-MOFs by hot pressing. The resultsshow that controllable dense micro-nanoscale Eu-MOFs film was coated on the cotton fabric with different dipping and hotpressing times. The method is fast, simple, low-cost and suitable for production. The Eu-MOFs coated cotton fabric exhibitsgood photoluminescent properties. The selective sensing ability of Eu-MOFs coated fabric for Cu2+ over many other metalions (K+, Cd2+, Ca2+, Pb2+, Na+, Zn2+, Ni2+, Mg2+, Al3+ and Co2+) is verified by emission spectra, and by the fact that thefluorescence intensity of the fabric significantly decreased with an increase in the concentration of Cu2+ (10-6-10-1 mol/L). This method provides a new path for the controllable production of MOFs-coated functional textiles for differentapplications, such as anti-counterfeiting, UV-protection, superhydrophobic, and sensing materials in the textile industry.

Multivalency-Driven Formation of Te-Based Monolayer Materials: A Combined First-Principles and Experimental study

Zhu, Zhili,Cai, Xiaolin,Yi, Seho,Chen, Jinglei,Dai, Yawei,Niu, Chunyao,Guo, Zhengxiao,Xie, Maohai,Liu, Feng,Cho, Jun-Hyung,Jia, Yu,Zhang, Zhenyu American Physical Society 2017 Physical Review Letters Vol.119 No.10

<P>Contemporary science is witnessing a rapid expansion of the two-dimensional (2D) materials family, each member possessing intriguing emergent properties of fundamental and practical importance. Using the particle-swarm optimization method in combination with first-principles density functional theory calculations, here we predict a new category of 2D monolayers named tellurene, composed of the metalloid element Te, with stable 1T-MoS2-like (alpha-Te), and metastable tetragonal (beta-Te) and 2H-MoS2-like (gamma-Te) structures. The underlying formation mechanism is inherently rooted in the multivalent nature of Te, with the central-layer Te behaving more metal-like (e.g., Mo), and the two outer layers more semiconductorlike (e.g., S). We also show that the alpha-Te phase can be spontaneously obtained from the magic thicknesses divisible by three layers truncated along the [ 001] direction of the trigonal structure of bulk Te, and both the alpha- and alpha-Te phases possess electron and hole mobilities much higher than MoS2. Furthermore, we present preliminary but convincing experimental evidence for the layering behavior of Te on HOPG substrates, and predict the importance of multivalency in the layering behavior of Se. These findings effectively extend the realm of 2D materials to group-VI elements.</P>