检索结果-南通市图书馆

Transmission loss simulation based on rectangular-pulse method and experimental evaluation of acoustic performance of perforated intake pipe

引用

Journal of Central South University 2017年第11期24卷 2605-2612页

作者： LI Heng HAO Zhi-yong ZHENG Xu LIU Lian-yun College of Energy Engineering Zhejiang UniversityHangzhou 310027China

Exact simulation of the acoustic performance is essential to the engineering application for a vehicle intake system. The rectangular-pulse method based on the computational fluid dynamics approach was employed for calculating the transmission loss. Firstly, the transmission loss of the single-cavity element was simulated without any airflow, and the effects of different structural parameters on the acoustic performance were investigated comprehensively. Secondly, the static transmission loss of the perforated intake pipe was obtained by the rectangular-pulse method, which is proved to be accurate enough compared with the result by finite element method. Thirdly, under the different conditions of the mean airflow and the operating temperature, the specific transmission loss was acquired respectively. In general, the peaks of the transmission loss are shifted to the lower frequency range because of the reverse airflow, but the amplitudes are irregularly changed. Besides, when the operating temperature increases, the peaks are shifted to the higher frequencies. Finally, with the designed perforated pipe installed to the intake system, the road tests were proceeded to evaluate the actual acoustic performance, and the result indicates that the intake sound pressure level is greatly attenuated. Typically in the range of 600–1500 Hz, the insertion loss of the intake noise at the decelerating moment is almost 20 d B(A), and the overall noise is reduced more than 14.2 d B(A). In conclusion, the perforated intake pipe has been proved excellent in improving the acoustic performance of intake system and could provide the guidance for the automotive engineering application.

关键词： perforated intake pipe rectangular-pulse method transmission loss mean flow temperature road test

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mitigating self-excited flame pulsating and thermoacoustic oscillations using perforated liners

引用

Science Bulletin 2019年第13期64卷 941-952页

作者： Dan Zhao Ephraim Gutmark Arne Reinecke Department of Mechanical Engineering College of EngineeringUniversity of CanterburyChristchurch 8140New Zealand Department of Aerospace Engineering and Engineering Mechanics University of CincinnatiCincinnatiOH 45221-0070USA School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore

Open-loop control of self-excited flame pulsating oscillations and thermo-acoustic instability is considered in this *** performance of the control strategy is numerically evaluated in a 2 D Rij ke-type combustor with a perfo rated pipe *** is found that approximately 38 dB sound pressure level(SPL)reduction can be achieved by actively tuning the cooling flow through the perforated ***,the vorticity-induced damping performance is contributing to the breaking up of flame-acoustics ***,the shedding of vortices is not uniformly distributed along the perforated *** apply the control strategy in practice and to validate the findings,experimental studies are performed on a customerdesigned Rij ke-type combustor with a perfo rated liner *** mimic practical engines,a cooling flow generated by a centrifugal pump is provided to pass through the perforated *** tuning the cooling flow rate is found to lead to the unstable combustor being successfully *** is red uced by approximately 35 dB at ω1/2π≈245 Hz,and harmonic thermoacoustic modes are completely *** study is conducted by suddenly re moving the perforated pipe *** combustion system is found to be associated with not only classical thermo-acoustic limit cycle oscillations with a dominant mode at 2.45 × 102 Hz,but also beating oscillations at 1.4 × 1 00 *** is revealed that increasing acoustic losses by implementing the perforated pipe is another critical mechanism contributing to attenuating flame pulsating *** present work opens up an applicable means to attenuate both selfexcited high-frequency thermoacoustic and low-frequency flame pulsating oscillations.

关键词： Flame beating Combustion instability Thermo-acoustic instability Thermal-diffusive instability perforated pipe Acoustic losses

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

perforated gastric ulcer causing mediastinal emphysema: A case report

引用

World Journal of Clinical Cases 2024年第4期12卷 859-864页

作者： Zhi-Cheng Dai Xun-Wu Gui Feng-He Yang Hao-Yuan Zhang Wen-Feng Zhang Department of General Surgery Mengcheng County First People's HospitalMengcheng 233500Anhui ProvinceChina Department of Medical Imaging Mengcheng County First People's HospitalMengcheng 233500Anhui ProvinceChina

BACKGROUND Mediastinal emphysema is a condition in which air enters the mediastinum between the connective tissue spaces within the pleura for a variety of *** can be spontaneous or secondary to chest trauma,esophageal perforation,medi-cally induced factors,*** common symptoms are chest pain,tightness in the chest,and respiratory *** mediastinal emphysema patients have mild symptoms,but severe mediastinal emphysema can cause respiratory and circulatory failure,resulting in serious *** SUMMARY A 75-year-old man,living alone,presented with sudden onset of severe epigastric pain with chest tightness after drinking *** to the remoteness of his residence and lack of neighbors,the patient was found by his nephew and brought to the hospital the next morning after the disease *** tomography(CT)showed free gas in the abdominal cavity,mediastinal emph-ysema,and subcutaneous *** gastrointestinal angiography showed that the esophageal mucosa was intact and the gastric antrum was ***,we chose to perform open gastric perforation repair on the patient under thoracic epidural anesthesia combined with intravenous *** operative incision of the muscle layer of the patient's abdominal wall was made,and a large amount of subperitoneal gas was *** a continued incision of the peritoneum revealed the presence of a perforation of approx-imately 0.5 cm in the gastric antrum,which we repaired after pathological ***,the patient received high-flow oxygen and cough *** CT was performed on the first and sixth postoperative days,and the mediastinal and subcutaneous gas was gradually *** After gastric perforation,a large amount of free gas in the abdominal cavity can reach the mediastinum through the loose connective tissue at the esophageal hiatus of the diaphragm,and upper gastrointestinal angiography can clarify the site of *** pat

关键词： Gastric ulcer perforated Mediastinal emphysema Case report

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Homogenization of Linear Parabolic Equations with a Certain Resonant Matching Between Rapid Spatial and Temporal Oscillations in Periodically perforated Domains

引用

Acta Mathematicae Applicatae Sinica 2019年第2期35卷 340-358页

作者： Tatiana LOBKOVA Department of Mathematics and Science Education Mid Sweden University

In this article, we study homogenization of a parabolic linear problem governed by a coefficient matrix with rapid spatial and temporal oscillations in periodically perforated domains with homogeneous Neumann data on the boundary of the holes. We prove results adapted to the problem for characterization of multiscale limits for gradients and very weak multiscale convergence.

关键词： Homogenization two-scale convergence multiscale convergence periodically perforated domains

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Epidemiology of perforated peptic ulcer:Age-and gender-adjusted analysis of incidence and mortality

引用

World Journal of Gastroenterology 2013年第3期19卷 347-354页

作者： Kenneth Thorsen Jon Arne Sreide Jan Terje Kvaly Tom Glomsaker Kjetil Sreide Department of Surgery Stavanger University HospitalN-4068 StavangerNorway Department of Surgical Science University of Bergen5020 BergenNorway Department of Mathematics and Natural Science University of Stavanger4036 StavangerNorway

AIM:To investigate the epidemiological trends in inci-dence and mortality of perforated peptic ulcer(PPU)in a well-defined Norwegian population. METHODS:A retrospective,population-based,single-center,consecutive cohort study of all patients diag-nosed with benign perforated peptic *** were both gastric and duodenal ulcer patients admitted to Stavanger University Hospital between January 2001 and December *** with a malignant neoplasia diagnosis,verified by histology after biopsy or resection,were *** were identified from the hospitals administrative electronic database using pertinent ICD-9 and ICD-10 codes(K25.1,K25.2,K25.5, K25.6,K26.1,K26.2,K26.5,K26.6).Additional searches using appropriate codes for relevant laparoscopic and open surgical procedures(e.g.,JDA 60,JDA 61,JDH 70 and JDH 71)were performed to enable a complete identification of all *** demographics,presentation patterns and clinical data were retrieved from hospital records and surgical *** and adjusted incidence and mortality rates were estimated by using national population demographics data. RESULTS:In the study period,a total of 172 patients with PPU were *** adjusted incidence rate for the overall 10-year period was 6.5 per 100 000 per year(95%CI:5.6-7.6)and the adjusted mortality rate for the overall 10-year period was 1.1 per 100 000 per year(95%CI:0.7-1.6).A non-significant decline in ad-justed incidence rate from 9.7 to 5.6 occurred during the *** standardized mortality ratio for the whole study period was 5.7(95%CI:3.9-8.2),while the total 30-d mortality was 16.3%.No difference in in-cidence or mortality was found between ***,for patients≥60 years,the incidence increased over 10-fold,and mortality more than 50-fold,compared to younger *** admission rates outside office hours were high with almost two out of three(63%) admissions seen at evening/night time shifts and/or during *** observed season

关键词： perforated peptic ulcer Epidemiology Incidence Mortality Seasonal variation

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Is a nasogastric tube necessary after transumbilical laparoscopic-assisted appendectomy in children with perforated appendicitis?

引用

World Journal of Pediatrics 2019年第6期15卷 615-619页

作者： Akinori Sekioka Koji Fukumoto Toshiaki Takahashi Hiromu Miyake Kengo Nakaya Akiyoshi Nomura Yutaka Yamada Naoto Urushihara Department of Pediatric Surgery Shizuoka Children's Hospital860 UrushiyamaAoi-kuShizuoka 420-8660Japan

Background This study assessed the necessity of postoperative nasogastric tube(NGT)use in acute pediatric cases of per-forated *** All cases of acute pediatric perforated appendicitis managed with transumbilical laparoscopic-assisted appendec-tomy at our hospital from 2011 to 2017 were retrospectively ***-two cases were selected and divided into two groups based on NGT *** There were no significant differences between the two groups in most parameters of patient demographics,or surgi-cal ***,the mean time to first oral intake and to regular diet was significantly shorter in no-NGT group(1 day vs 3 days,P<0.0001;and 4 days vs 7 days,P=0.003,respectively).Postoperative length of stay was significantly shorter in no-NGT group(7 days vs 9 days,P<0.0001).Conclusion Considering the results of our analysis,we believe that routine NGT placement is not always necessary in these situations.

关键词： Children perforated appendicitis Postoperative care

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Counteraction of perforated cecum lesions in rats: Effects of pentadecapeptide BPC 157,L-NAME and L-arginine

引用

World Journal of Gastroenterology 2018年第48期24卷 5462-5476页

作者： Domagoj Drmic Mariam Samara Tinka Vidovic Dominik Malekinusic Marko Antunovic Borna Vrdoljak Jelena Ruzman Marija Milkovic Perisa Katarina Horvat Pavlov Jerusha Jeyakumar Sven Seiwerth Predrag Sikiric Departments of Pharmacology and Pathology Medical Faculty University of Zagreb

AIM To study the counteraction of perforated cecum lesion using BPC 157 and nitric oxide(NO) system *** Alongside with the agents' application(after 1 min, medication(/kg, 10 ml/2 min bath/rat) includes: BPC 157(10 μg), L-NAME(5 mg), L-arginine(100mg) alone or combined, and saline baths(controls)) on the rat perforate cecum injury, we continuously assessed the gross reappearance of the vessels(USB microcamera) quickly propagating toward the defect at the cecum surface, defect contraction, bleeding attenuation, MDA-and NO-levels in cecum tissue at 15 min, and severity of cecum lesions and adhesions at 1 and 7 d. RESULTS Post-injury, during/after a saline bath, the number of vessels was significantly reduced, the defect was slightly narrowed, bleeding was significant and MDA-levels increased and NO-levels decreased. BPC 157 bath: the vessel presentation was markedly increased, the defect was noticeably narrowed, the bleeding time was shortened and MDA-and NO-levels remained normal. L-NAME: reduced vessel presentation but not more than the control, did not change defect and shortened bleeding. L-arginine: exhibited less vessel reduction, did not change the defect and prolonged bleeding. In combination, mutual counteraction occurred(L-NAME + L-arginine) or the presentation was similar to that of BPC 157 rats(BPC 157 + L-NAME; BPC 157 + L-arginine; BPC 157 + L-NAME + L-arginine), except the defect did not change. Thereby at day 1 and 7, saline, L-NAME, L-arginine and L-NAME + L-arginine failed(defect was still open and large adhesions present). CONCLUSION The therapeutic effect was achieved with BPC 157 alone or in combination with L-NAME and L-arginine as it was able to consolidate the stimulating and inhibiting effects of the NO-system towards more effective healing recruiting vessels.

关键词： BPC 157 perforated cecum L-arginine L-NAME vessels rats

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Transmission loss of a flexible micro-perforated muffler with a flexible back cavity for water-filled pipelines

引用

Chinese Journal of Acoustics 2021年第1期40卷 31-45页

作者： HOU Jiuxiao ZHU Haichao YUAN Suwei LIAO Jinlong National Key Laboratory on Ship Vibration&Noise Institute of Noise&VibrationNaval University of EngineeringWuhan 430033

To reduce low-frequency noise of the water-filled pipeline system,a compact flexible micro-perforated muffler with a flexible back cavity(FMPMFBC) is *** flexible pipe wall is made of a rubber-cord composite material.A numerical solution for the transmission loss is ***,the flexible micro-perforated panel(FMPP) is equivalent to a flexible porous material based on Biot-Allard porous-elastic ***,a periodic structural unit of the aramid fabric cloth is established with the two-scale method,and the equivalent stiffness matrix is ***,a multi-layer composite model for the flexible pipe wall is constructed according to the lamination *** with the internal sound field,the transmission loss of the FMPMFBC is *** a water-filled impedance tube,the transmission loss curves of the FMPMFBC prototypes are measured with the two source-location method,and compared with those of a flexible micro-perforated muffler with a rigid back cavity(FMPMRBC)and an expansion *** results are experimentally *** FMPMFBC is a hybrid muffler combining reflection with dissipation,capable of attenuating broadband lowfrequency *** transmission loss of prototype B2 in the frequency bands of [40 300] Hz and [40 1200] Hz is 36 dB and 30 dB,respectively,while the transmission loss of the same-sized expansion muffler in the corresponding frequency bands is 7 dB and 11 dB,respectively.

关键词： composite cavity perforated

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Sound absorption performance of gradiently slit-perforated double-porosity materials

引用

Chinese Journal of Acoustics 2021年第1期40卷 1-17页

作者： MA Xiaowen LIU Xuewei XIN Fengxian State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong UniversityXi’an 710049 MOE Key Laboratory for Multifunctional Materials and Structures Xi'an Jiaotong UniversityXi’an 710049

A gradiently slit-perforated double-porosity material is proposed by introducing macro-scale periodic gradient slit-perforations into traditional porous materials with *** material is one kind of multiscale material since it includes two scales of matrix micro-pore size and slit-perforation size.A theoretical model is developed for the sound absorption of the gradiently slit-perforated double-porosity *** the model,the material is divided into lots of thin layers and each layer is approximated to be straight slit-perforated *** equivalent density and dynamic compressibility of each thin layer are given by using the low or high permeability contrast double-porosity *** the sound pressure and particle velocity relations between adjacent thin layers are obtained by employing the transfer matrix ***,the surface acoustic impedance and the sound absorption of the gradiently slit-perforated porous material can be calculated.A finite element model is further established to validate the accuracy of the theoretical *** the considered frequency range of 100-3000 Hz,the simulation results agree well with theoretical *** influence of multiscale structural parameters on the sound absorption performance of the porous materials is analyzed theoretically and *** is proved that the multiscale structure design can significantly improve the sound absorption performance of porous *** to the slit-perforation gradient,the slit-perforation width plays a more significant influence on sound *** sound absorption enhancement mechanism of the multiscale structure design is revealed by the analysis of the sound pressure and energy dissipation distributions in the *** work provides a multiscale structural design method for improving the sound absorption performance of traditional porous materials at broadband frequency.

关键词： absorption gradient perforated

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The formula for acoustic length correction of perforated tube muffler

引用

Chinese Journal of Acoustics 2021年第4期40卷 553-565页

作者： WU Yong Chongqing Jinkang SERES NEV Design Institute Co.Ltd. Chongqing 401135

The formulas of acoustic length correction and resonance frequency of perforated tube muffler are *** is proved that in the case of uniform distribution,the acoustic length correction coefficient of the acoustic radiation from multiple holes to cavity is consistent with that from a single hole to *** the acoustic radiation from the holes to the main pipe,the effects of perforation porosity,circumferential uniform number and Helmholtz number on the acoustic length correction are studied according to the *** show that the theoretical formula of acoustic length correction coefficient is in good agreement with the simulation results when the diameter radio is less than 0.4.A practical fitting formula is obtained by using the properties of the theoretical formula and the simulation *** calculation accuracy of resonance frequency of perforated tube muffler at high frequency is improved.

关键词： correction perforated formula

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：