Time-domain CFD computation and analysis of acoustic attenuation performance of water-filled silencers

The multi-dimensional time-domain computational fluid dynamics(CFD) approach is extended to calculate the acoustic attenuation performance of water-filled piping silencers. Transmission loss predictions from the time-domain CFD approach and the frequency-domain finite element method(FEM) agree well with each other for the dual expansion chamber silencer, straight-through and cross-flow perforated tube silencers without flow. Then, the time-domain CFD approach is used to investigate the effect of flow on the acoustic attenuation characteristics of perforated tube silencers. The numerical predictions demonstrate that the mean flow increases the transmission loss, especially at higher frequencies, and shifts the transmission loss curve to lower frequencies.

Meta-silencer with designable timbre

Timbre,as one of the essential elements of sound,plays an important role in determining sound properties,whereas its manipulation has been remaining challenging for passive mechanical systems due to the intrinsic dispersion nature of resonances.Here,we present a meta-silencer supporting intensive mode density as well as highly tunable intrinsic loss and offering a fresh pathway for designable timbre in broadband.Strong global coupling is induced by intensive mode density and delicately modulated with the guidance of the theoretical model,which efficiently suppresses the resonance dispersion and provides desirable frequency-selective wave-manipulation capacity for timbre tuning.As proof-of-concept demonstrations for our design concepts,we propose three meta-silencers with the designing targets of high-efficiency broadband sound attenuation,efficiency-controlled sound attenuation and designable timbre,respectively.The proposed meta-silencers all operate in a broadband frequency range from 500 to 3200 Hz and feature deep-subwavelength sizes around 50 mm.Our work opens up a fundamental avenue to manipulate the timbre with passive resonances-controlled acoustic metamaterials and may inspire the development of novel multifunctional devices in noise-control engineering,impedance engineering,and architectural acoustics.

Host-Induced Gene Silencing of Effector AGLIP1 Enhanced Resistance of Rice to Rhizoctonia solani AG1-IA

Rice sheath blight, caused by Rhizoctonia solani AG1-IA, is a major disease in rice-growing areas worldwide. Effectors of phytopathogenic fungi play important roles during the infection process of fungal pathogens onto their host plants. However, the molecular mechanisms by which R. solani effectors regulate rice immunity are not well understood. Through prediction, 78 candidate effector molecules were identified. Using the tobacco rattle virus-host induced gene silencing(TRV-HIGS) system, 45 RNAi constructs of effector genes were infiltrated into Nicotiana benthamiana leaves. The results revealed that eight of these constructs resulted in a significant reduction in necrosis caused by infection with the AG1-IA strain GD-118. Additionally, stable rice transformants carrying the double-stranded RNA construct for one of the effector genes, AGLIP1, were generated to further verify the function of this gene. The suppression of the AGLIP1 gene increased the resistance of both N. benthamiana and rice against GD-118, and also affected the growth rate of GD-118, indicating that AGLIP1 is a key pathogenic factor. Small RNA sequencing showed that the HIGS vectors were processed into si RNAs within the plants and then translocated to the fungi, leading to the silencing of the target genes. As a result, AGLIP1 might be an excellent candidate for HIGS, thereby enhancing crop resistance against the pathogen and contributing to the control of R. solani infection.

Host-induced gene silencing of the Verticillium dahliae thiamine transporter protein gene(VdThit)confers resistance to Verticillium wilt in cotton

Verticillium wilt(VW),induced by the soil-borne fungus Verticillium dahliae(Vd),poses a substantial threat to a diverse array of plant species.Employing molecular breeding technology for the development of cotton varieties with heightened resistance to VW stands out as one of the most efficacious protective measures.In this study,we successfully generated two stable transgenic lines of cotton(Gossypium hirsutum L.),VdThitRNAi-1 and VdThit-RNAi-2,using host-induced gene silencing(HIGS)technology to introduce double-stranded RNA(dsRNA)targeting the thiamine transporter protein gene(VdThit).Southern blot analysis confirmed the presence of a single-copy insertion in each line.Microscopic examination showed marked reductions in the colonization and spread of Vd-mCherry in the roots of VdThit-RNAi cotton compared to wild type(WT).The corresponding disease index and fungal biomass of VdThit-RNAi-1/2 also exhibited significant reductions.Real-time quantitative PCR(qRT-PCR)analysis demonstrated a substantial inhibition of VdThit expression following prolonged inoculation of VdThit-RNAi cotton.Small RNA sequencing(sRNA-Seq)analysis revealed the generation of a substantial number of VdThit-specific siRNAs in the VdThit-RNAi transgenic lines.Additionally,the silencing of VdThit by the siVdThit produced by VdThit-RNAi-1/2 resulted in the elevated expression of multiple genes involved in the thiamine biosynthesis pathway in Vd.Under field conditions,VdThit-RNAi transgenic cotton exhibited significantly enhanced disease resistance and yield compared with WT.In summary,our findings underscore the efficacy of HIGS targeting VdThit in restraining the infection and spread of Vd in cotton,thereby potentially enabling the development of cotton breeding as a promising strategy for managing VW.

Writing the Silenced Female Body, Scrutinizing the Grand Narrative of Colonization and Decolonization: The Body in Zoë Wicomb’s David’s Story

David’s Story by Zoë Wicomb addresses the complexities of representing female suffering and the limitations of traditional historical narratives in capturing the experiences of marginalized bodies.It challenges the grand narratives of national history by emphasizing the indispensable role of women’s experiences.Through characters like Dulcie and Rachael,Wicomb portrays the female body as a site of resistance and resilience,highlighting the need for more nuanced and inclusive ways of documenting history.Underscoring the inexpressibility of trauma and the limitations of language and representation,the novel self-reflexively acknowledges its own aporia of completing the narrative,embodying the ongoing struggle to capture the full breadth of human experience.

Stress response silencing by an E3 ligase mutated in neurodegeneration

Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis,yet their prolonged activation induces apoptosis and disrupts organismal health1-3.How stress responses are turned off at the right time and place remains poorly understood.Here we report a ubiquitin-dependent mechanism that silences the cellular response to mitochondrial protein import stress.

CFD analysis of sound pressure in tank gun muzzle silencer

The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems such as exposure of location of troops. This high pressure impulsive sound, generated during the blast flow, was studied and attenuated. An axisymmetric computational domain was constructed by employing Spalart Allmaras turbulence model. Approximately 90% of pressure and 20 dB of sound level are reduced due to the use of the three baffle silencer at the muzzle end of the gun barrel, in comparison with the tank gun without silencer. Also, the sound pressure level at different points in the ambient region shows the same attenuation in results. This study will be helpful to understand the blast wave characteristics and also to get a good idea to design silencer for large caliber weapon system.

Trans-acting factors from the human fetal liver bindingto the human ε-globin gene silencer

The developmental stage-specific silencing of the human ε-globin gene during embryonic life is controlled, inpart, by the silencer (-392bp～-177bp) upstream of thisgene. In order to elucidate its role, the nuclear extractfrom the human fetal liver has been prepared and the interactions between trans-acting factors and this silencerelement have been examined. By using DNasel footprinting assay, a major protected region from -278bp to -235bpwithin this silencer element was identified. Furthermore,we found in gel mobility shift assay and Southwestern blotting assay that there were at least four trans-acting factors (MW ≈ 32, 28, 26 and 22kD) in the nuclear extractisolated from the human fetal liver, which could specifically bind to this region. Our results suggested that thesetrans-acting factors might play an important role in silencing the human embryonic ε-globin gene expression at thefetal stage through the interactions with this silencer.

Application of dual reciprocity boundary element method to predict acoustic attenuation characteristics of marine engine exhaust silencers

In marine engine exhaust silencing systems, the presence of exhaust gas flow influences the sound propagation inside the systems and the acoustic attenuation performance of silencers. In order to investigate the effects of three-dimensional gas flow and acoustic damping on the acoustic attenuation characteristics of marine engine exhaust silencers, a dual reciprocity boundary element method (DRBEM) was developed. The acoustic governing equation in three-dimensional potential flow was derived first, and then the DRBEM numerical procedure is given. Compared to the conventional boundary element method (CBEM), the DRBEM considers the second order terms of flow Mach number in the acoustic governing equation, so it is suitable for the cases with higher Mach number subsonic flow. For complex exhaust silencers, it is difficult to apply the single-domain boundary element method, so a substructure approach based on the dual reciprocity boundary element method is presented. The experiments for measuring transmission loss of silencers are conducted, and the experimental setup and measurements are explained. The transmission loss of a single expansion chamber silencer with extended inlet and outlet were predicted by DRBEM and compared with the measurements. The good agreements between predictions and measurements are observed, which demonstrated that the derived acoustic governing equation and the DRBEM numerical procedure in the present study are correct.

A Design Method of the Rotor Auxiliary Slot for the Water-filled Submersible Induction Motors

Aiming at the problem of electromagnetic vibration of the water-filled submersible induction motor(WSIM),a method of opening auxiliary slots on the rotor side is proposed to weaken the air-gap field harmonics caused by the rotor slot permeance harmonics.By analyzing the research status of electromagnetic vibration of the WSIM and the composition of the air-gap magnetic field of the motor,the idea that the auxiliary slots mainly affect the air-gap field harmonics by changing the air-gap permeance of the motor is put forward.The mathematical model of air-gap permeance of WSIM is established to simulate the influence of auxiliary slots on the air-gap permeance.Through the parametric analysis of the mathematical model,the change of auxiliary slot size is simulated.The air-gap permeance waveform is decomposed by the two-dimensional Fourier transform,and then the variation of the air-gap permeance harmonics with the size of the auxiliary slot is analyzed.Finally,the finite element simulation model of the WSIM with the auxiliary slots is established,and the waveform of the air-gap flux density of the motor is analyzed to verify the effectiveness of the mathematical model.Meanwhile,the results show that after opening the auxiliary slot,the radial electromagnetic force of the motor was reduced by 28.4%.

An Improved Water-filled Pulse Tube Method Using Time Domain Pulse Separation Method

Based on existing low-frequency water-filled impedance tube testing facilities, which is a part of the Low Frequency Facility of the Naval Undersea Warfare Center in Beijing, an improved water-filled pulse tube method is presented in this short paper. This proposed study is significantly different from the conventional pulse tube method because of the capability for a single plane damped sine pulse wave to generate in the water-filled pulse tube with a regular waveform and short duration time of about 1ms. During the generation process of the pulse, an inverse filter principle was adopted to compensate the transducer response. The effect of the characteristics of tube termination can be eliminated through the generation process of the pulse. Reflection coefficient from a water/air interface was measured to verify the proposed method. When compared with the expected theoretical values, a relatively good agreement can be obtained in the low frequency range of 500-2 000 Hz.

AN EXPERIMENTAL INVESTIGATION ON THE IMPACT PERFORATION FAILURE OF WATER-FILLED-PRESSURIZED PIPELINES

Some experimental data recorded from impact tests on empty and water-filled pressurized mild steel pipes are presented. The pipes were supported as a three-span continuous beam and impacted laterally by a rigid indenter at the mid-span of middle span. Three kinds of indenter nose shapes were used: blunt-nose, hemisphere-nose and 90?conical-nose. The internal pressure ranged up to 20 MPa. The perforation failure modes and corresponding critical impact energies were obtained under different test conditions. The time-history curves of the internal pressure and impact force were given. The experiments show that the media filled in the tube greatly decreased the ballistic limit energy.

An Exact Solution for Acoustic Simulation Based Transmission Loss Optimization of Double-Chamber Silencer

The optimization of the acoustic silencer volume is very important to develop it and to get high-performance,the importance of the silencer was appeared in industrial field to eliminate the noise of the duct by efficient and economical method.The main goal of this research is to optimize the transmission loss(TL)by analytical method of the Double-Chamber Silencer(DCS),the TL has been selected as the main parameter in silencer because it does not based on the source or the termination impedances.First we calculated the power transmission coefficient(PTC)and the TL of an acoustic silencer,then used the Lagrange method to optimize the silencer length.All calculation of silencer data is obtained by solving the governing equations in commercial software Matlab®.A several calculations for different silencer length at many frequency ranges were performed simultaneously.Finally,this research supports the efficient and rapid techniques for DCS optimal design under narrow space.The results show that the acoustic TL is maximized at the desired frequency.

Reducing Occupational Noise Propagated from Centrifugal Fan through Dissipative Silencers:A Field Study

Acoustic performance of dissipative silencer was evaluated to determine the effectiveness of perforated duct porosity and absorbent material density in reducing occupational noise exposure propagated from centrifugal fan.Design charts were applied to predict noise reduction and length of a dissipative silencer.Dissipative silencers with various punched duct porosity(14%,30%and 40%)and sound absorbent density(80 Kg/m^(3),120 Kg/m^(3),and 140 Kg/m^(3))were designed and fabricated.According to ISO9612 and ISO11820,noise level was measured before and after installing all nine test silencers at fixed workstations around the discharge side of a centrifugal fan in a manufacturing plant.On average,the noise level at the discharge side of a fan without silencer was measured to be 93.6 dBA,whereas it was significantly mitigated by 67.4 dBA to 70.1 dBA after installing all silencers.Dynamic insertion loss for a dissipative silencer with 100 cm length was predicted to be 27.9 dB,which was in agreement with experimental ones.Although,there was no significant differences between insertion loss of silencers,the one with 30%porosity and 120 Kg/m^(3)rock wool density had the highest insertion loss of 26.2 dBA.Dissipative silencers noticeably reduced centrifugal fan noise exposures.Increasing sound absorbent density and duct porosity up to a certain limit could probably be effective in noise reduction of dissipative silencers.

ASUS EN6600GT Silencer

这款采用nVidia GeForce 6600GT的产品最大的特点在于其100%的静音设计，由于采用了独特的热管散热系统，这款显卡上并未安装任何主动散热装置，它的主散热片被设置在显卡上方，并且可以向右侧旋转90°,

Being Human in a More-Than-Human World:Between a Silence Catalyst for(Re)Aestheticization and an Art Catalyst for Relationships

The contribution moves from highlighting how,in the context of Michel Serres’and posthumanism’s proposal of rethinking the human and the world in a perspective of inter-implication and universal co-belonging,silence(of the human word)assumes the function of a catalyst for the recognition/re-aestheticization of the human body in its sensory-aesthetic-cognitive-relational-hybrid dimensionality,and,with and for it,of the world in its agency(including artistic).Within the framework of this perspective,the investigation thus proposes a reading of art as a relation/catalyzer of relations,that is,as a(re)activation of positive relations of the human with and for a world that reveals itself to be increasingly hyper-complex,that is,more-than-human,in the continuity/inseparability of nature and culture.Taking Serresian ideas on artistic practices as non(only)human forms of expression and posthumanist“isomorphic”positions on non-human agency as tools,the research then highlights the“more-than-human”scope of art and the fact that artistic practices are responsive actions.So much so that,the human being emerges as co-agent and,of course,co-owner.

静音技术在颅脑磁共振成像中的初步应用

目的:探讨静音技术不同静音因子(QF)对颅脑MRI图像质量的影响。方法:招募50名志愿者[男23例,女27例,平均年龄(58.06±16.77)岁],以3.0 T MR扫描仪结合静音技术(QF分别为1、0.8、0.6、0.4、0.2)行颅脑矢状位T1液体抑制反转恢复(FLAIR)、T2WI、T2 FLAIR序列扫描,各序列受检者均为21例。扫描过程中记录各序列噪声最大值。在胼胝体、脑白质、小脑、脑桥划定感兴趣区测量信号值和噪声强度,计算信噪比(SNR)和对比度噪声比(CNR)。采用四分法对图像质量进行评分。采用Kappa检验评估两观察者主观评分的一致性。对各序列不同QF组间图像的SNR、CNR和主观评分差异采用单因素方差分析。结果:两观察者主观评分一致性良好(Kappa值=0.806~0.871)。T1 FLAIR序列胼胝体SNR、CNR、主观评分,T2 FLAIR序列胼胝体和小脑CNR,T2WI序列胼胝体CNR和主观评分,在不同QF时的差异有统计学意义(P<0.001)。两两比较结果:QF为0.4或0.2时,T1 FLAIR主观评分较QF为1.0时差异有统计学意义(P<0.05);QF为0.2时,T2 FLAIR胼胝体SNR、T2WI主观评分较QF为1.0时差异有统计学意义(P<0.05)。结论:基于静音技术的颅脑MR扫描时间随着QF的减小,噪声值逐渐降低,综合考虑噪声值与图像质量,临床推荐QF分别为0.6、0.4、0.2时行颅脑轴位T1 FLAIR、T2WI、T2 FLAIR序列扫描。

3所三级甲等综合医院护士组织沉默现况及其影响因素分析

目的了解3所三级甲等综合医院护士组织沉默现状,探讨其影响因素。方法采用便利抽样法,2023年4月—8月采用一般资料调查表、护士组织沉默问卷、医院磁性要素量表(the essential of magnetism scale,EMO)对西安市3所三级甲等综合医院的874临床护士进行调查,并采用多重线性回归分析其组织沉默的影响因素。结果共855名护士完成研究。护士组织沉默总分(56.33±8.55)分;医院磁性水平总分(107.63±12.85)分。护士组织沉默与医院磁性水平呈负相关(r=-0.318,P<0.010)。医院磁性水平、年龄、职称、护龄是护士组织沉默的影响因素(均P<0.001),共同解释其62.60%的变异。结论护士组织沉默与医院磁性水平处于中等偏低水平。护士年龄小、职称低、护龄短、医院磁性水平低,其组织沉默水平较高,护理管理者可通过提高医院磁性水平来减少护士的组织沉默。

带消声功能的潜艇换热器声学性能仿真

针对潜艇消声问题,提出一种带消声功能的换热器,开展环状橡胶气囊结构消声性能研究。建立仿真模型和进行传递损失计算,证明有囊式消声器的消声效果。利用控制变量法定量改变设计参数,分别研究气腔长度、穿孔直径和穿孔率对气囊消声效果的影响规律,为潜艇换热器的流动噪声控制提供有力支撑。

小麦镉胁迫响应基因TaMYB1的功能分析

【目的】MYB家族成员在植物生长发育、生物胁迫和非生物胁迫等方面发挥重要调控作用,然而,小麦MYB转录因子在重金属镉(Cd)胁迫中的生物学功能研究较少。挖掘小麦Cd胁迫应答相关基因,阐明其在Cd胁迫中的生物学功能,为耐/低Cd小麦品种的选育奠定基础。【方法】构建Cd胁迫小麦根系酵母cDNA文库,筛选获得Cd胁迫应答基因,利用荧光定量PCR技术检测Cd胁迫条件下小麦不同组织中Cd胁迫应答基因的相对表达量;利用病毒诱导的基因沉默对该基因进行功能验证,检测对照和沉默植株的Cd含量、叶绿素含量、丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化物酶(POD)活力等生理生化指标。此外,对Cd胁迫应答基因及其在小麦和其他物种中的同源基因进行生物信息学分析(系统进化关系、序列特征和表达谱)。【结果】Cd胁迫主要抑制小麦根系发育,在添加0.002 mol/L Cd的酵母培养基上筛选Cd胁迫小麦根系酵母cDNA文库获得18个耐Cd转化子,其中5个转化子编码TaMYB1蛋白,转化TaMYB1酵母菌株在高Cd培养基中生长良好,而对照则明显受到抑制。RT-qPCR结果表明,TaMYB1在小麦幼苗中响应Cd胁迫。与对照相比,TaMYB1沉默植株中TaMYB1表达量明显下降,且根系和叶片Cd含量显著低于对照植株,叶绿素含量、SOD、POD活性高于对照植株,MDA含量则低于对照植株。同时,生物信息学分析发现,TaMYB1属于1R-MYB家族成员,具有高度保守的MYB和CC结构域,其包含7个外显子和6个内含子,在拔节期中期的花序和成熟期的花序表达最高,在灌浆前期种子和灌浆中后期种子中表达量最低。【结论】TaMYB1在小麦响应Cd胁迫应答中发挥重要作用。