检索结果-内蒙古大学图书馆

Analytical model for melting in a semi-infinite PCM storage with an internal fin

HEAT AND MASS TRANSFER 2003年第2期39卷 167-176页

作者： Lamberg, P Sirén, K Helsinki Univ Technol HVAC Lab POB 4400 Helsinki 02015 Finland

The most PCMs with high energy storage density have an unacceptably low heat conductivity and hence internal heat transfer enhancement techniques such as fins or other metal structures are required in latent heat thermal storage (LHTS) applications. Previous work has concentrated on numerical and experimental examination in determining the influence of the fins in melting phase change material. This paper presents a simplified analytical model based on a quasi-linear, transient, thin-fin equation which predicts the solid-liquid interface location and temperature distribution of the fin in the melting process with a constant imposed end-wall temperature. The analytical results are compared to the numerical results and they show good agreement. Due to the assumptions made in the model, the speed of the solid-liquid interface during the melting process is slightly too slow.

关键词： Phase change materials Melting Thermal Conductivity ANALYSIS MODELS Fins MELT PROCESSING pulse code modulation Temperature distribution fins metal structure LIQUID SOLID INTERFACE

来源：评论

学校读者我要写书评

暂无评论

Growth rate of crystallization in disodium hydrogenphosphate dodecahydrate

引用

JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2002年第1期16卷 135-140页

作者： Hirano, S Saitoh, TS Nat Inst Adv Ind Sci & Technol Inst Atom Utilizat Tsukuba Ibaraki 3058569 Japan Tohoku Univ Sch Aeronaut & Space Engn Sendai Miyagi 9808579 Japan

The solidification process of disodium hydrogenphosphate dodecahydrate was investigated to develop long-term latent heat storage that uses supercooling. Supercooled thermal energy storage (Super-TES) stores thermal energy at temperatures lower than the melting point of the phase-change material (PCM), thus reducing the heat loss from the storage system. During nucleation and solidification, the temperature of PCM is not constant in Super-TES. The solidification process in Super-TES, therefore, influences the performance of the storage system because thermal properties of PCM, strongly depend on the temperature and phase of the material. The results show that the growth rate of the hydrate increased with increasing degree of supercooling and that this growth rate was slow compared with that of metals. When the degree of supercooling was less than about 10 K, the crystal of the hydrate grew like a single crystal, and the growth rate was approximately proportional to the third power of the degree of supercooling. Because the viscosity of the hydrate in the liquid, phase below the melting point increased drastically, when the degree of supercooling exceeded about 10 K, the crystal grew like a dendritic crystal, and the increase in the growth rate with increasing degree of supercooling, decreased.

关键词： Undercooling Heat loss disodium hydrogenphosphate Coagulation Cache Memory System melting point Growth rate Crystallization pulse code modulation supercooling degree Hydrates

来源：评论

学校读者我要写书评

暂无评论

Electronic warfare systems

引用

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2002年第3期50卷 633-644页

作者： Spezio, AE USN Res Lab Tactical Elect Warfare Div Elect Warfare Support Measures Branch Washington DC 20375 USA

Electronic warfare (EW) is an important capability that can advance desired military, diplomatic, and economic objectives or, conversely, impede undesired ones. In a military application, EW provides the means to counter, in all battle phases, hostile actions that involve the electromagnetic (EM) spectrum-from the beginning when enemy forces are mobilized for an attack, through to the final engagement. EW exploits the EM environment by sensing and analyzing an adversary's application of the spectrum and imposing appropriate countermeasures (CMs) to hostile spectrum use. EW sensors are one means by which the military gathers tactical intelligence from noncooperative forces. EW sensors, together with EW CMs, mitigate the effectiveness of an adversary's electrooptic/infrared, and radio frequency-controlled weapons. EW enhances the survivability of the host force through control and manipulation of the EM environment and denies or limits its use by an adversary. EM spectrum CMs to threat systems can be selectively applied on a time- and/or frequency-multiplexed basis so that host force use of the EM spectrum is uninhibited.

关键词： terms-circuit functions complex modulation cooperative sensors counter countermeasures countermeasures digital receiver technology electrooptic/infrared electromagnetic environment electromagnetic spectrum electronic attack electronic self-protection electronic support electronic surveillance electronic warfare filters high-gain antenna improved signal processing independent sensors isotropic antenna offboard countermeasures phased-array antennas pulse code modulation radar advancement response techniques sensor technology spectral selectivity subsystems sensors threat systems triangulation

来源：评论

学校读者我要写书评

暂无评论

A full-text retrieval approach to content-based audio identification 5

A full-text retrieval approach to content-based audio identi...

引用

5th IEEE Workshop on Multimedia Signal Processing (MMSP 2002)

作者： Ribbrock, A Kurth, F Univ Bonn D-53117 Bonn Germany

ISBN: (纸本)0780377133

We give an overview on a novel framework for content-based multimedia retrieval. In this paper we present an implementation for audio identification. This framework consists of an index-based search combining algebraic methods with classical full-text retrieval. In the main part of the paper we propose several feature extractors which may be used for indexing the PCM audio data. We give an overview on our test results containing performance data (e.g., query response times), memory requirements (e.g., index size), and robustness issues. The size of our index turns out to be only a 1/1000th to about 1/15000th of the original PCM material depending on the required granularity for identifying a piece of audio.

关键词： pulse code modulation

来源：评论

学校读者我要写书评

暂无评论

Packet loss concealment based on sinusoidal extrapolation

Packet loss concealment based on sinusoidal extrapolation

引用

IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： Lindblom, J Hedelin, P Chalmers Univ Technol Informat Theory Lab SE-41296 Gothenburg Sweden

ISBN: (纸本)0780374029

In this paper, a packet loss concealment scheme based on sinusoidal extrapolation is proposed. It is to be implemented at the receiver end of a packetized speech transmission system and conceals frame-erasures in a PCM waveform. The scheme operates on the source-filter components of the speech signal, which are obtained through Linear Prediction (LP) analysis. When one or more speech frames are missing, the LP residual and filter coefficients are extrapolated separately. The residual is extrapolated based on sinusoidal modeling of the last correct residual frame, whereas the latest filter is repeated and bandwidth expanded. The proposed scheme is compared to two benchmark systems by means of subjective testing. The benchmark systems are based on repetitions of the last pitch period;one operates on the source-filter components, the other directly on the speech signal. It is noted that the systems operating on the source-filter components are preferred by the listeners, and that the proposed system is clearly superior to both benchmark systems.

关键词： speech coding extrapolation pulse code modulation linear predictive coding filtering theory voice communication packet loss concealment sinusoidal extrapolation packetized speech transmission system frame-erasures concealment PCM waveform source-filter components linear prediction analysis filter coefficients LP residual subjective testing last pitch period repetitions source filter components packet voice communication

来源：评论

学校读者我要写书评

暂无评论

A 160 EVRC channel T1 and QoS

A 160 EVRC channel T1 and QoS

引用

Proceedings - 2001 International Conference on Third Generation Wireless and Beyond (Key Function of World Wireless Congress)

作者： Bowen, Wayne USPhoenix Ltd. 8 E. NW Hwy Arlington Heights IL 60005

A simple, naïve worst-case analysis of delay and jitter for air interface EVRC voice compression packets routed over a single transmission facility is discussed. Different worst-case characteristics occur if the incoming packets are not synchronized. If the EVRC packets arrive synchronously a minimal delay and jitter characteristics are possible using a packet router at the T1. The asynchronous case having a worst case delay and jitter of 2.5 ms, the STS-1 can carry 640 EVRC channels (32×20).

关键词： pulse code modulation

来源：评论

学校读者我要写书评

暂无评论

Differential PCM Representation of Acoustic Instruments and Wavetable Synthesis 28

Differential PCM Representation of Acoustic Instruments and ...

引用

28th International Computer Music Conference, ICMC 2002

作者： Trautmann, Steven Software Laboratory DCES Technology Center Texas Instruments United States

Sample based synthesis (including wavetable synthesis) of acoustic instruments usually relies on standard 16-bit pulse code modulation (PCM) for storage, playback and manipulations such as pitch-shift. However, storing the samples as differential pulse code modulation (DPCM) data has certain advantages. When shifting the pitch using linear interpolation, in most cases fewer operations are required when working with DPCM as opposed to PCM. Also the range of a DPCM signal is typically less than that of the equivalent PCM signal. This can improve coded representations of the signal. © 2002 International Computer Music Conference, ICMC Proceedings. All rights reserved.

关键词： pulse code modulation

来源：评论

学校读者我要写书评

暂无评论

The radical who shaped the future [Alec Reeves]

引用

IEE Review 2002年第3期48卷 31-36页

作者： D. Robertson Alec Reeves

2002 is the centenary of the birth of Alec Reeves. The author describes the achievements of a remarkable engineer and an uncommon man. Reeves devised the technology on which the information age depends. A committed pacifist, he developed a top secret bombing system that altered the course-and perhaps the outcome-of the Second World War. A prolific and practical inventor, he experimented with psychokinesis and acknowledged the possibility of the paranormal. In 1937 he formulated the principles of pulse-code modulation-laying the foundations for all of today's digital and multimedia technologies. During WWII he helped develop a technique using radio techniques for guiding bombers to their targets and when the bombs should be released. This system was known as Oboe. Following the war he worked on increasing the capacity and reliability of communication systems. His fascination with the human brain, its operation and capacity led him to study psychokinesis and telepathy.

关键词： brain Oboe system Other military topics paranormal psychokinesis Other general electrical engineering topics pulse-code modulation radio techniques modulation and coding methods Alec Reeves telepathy military systems radio applications pulse code modulation biographies bombing system inventor Radio links and equipment

来源：评论

学校读者我要写书评

暂无评论

On the heat removal characteristics and the analytical model of a thermal energy storage capsule using gelled Glauber's salt as the PCM

引用

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2001年第24期44卷 4693-4701页

作者： Saito, A Okawa, S Shintani, T Iwamoto, R Tokyo Inst Technol Grad Sch Sci & Engn Dept Engn Sci & Mech Meguro Ku Tokyo 1528552 Japan

An analytical and experimental investigation was performed on a heat removal process of the thermal energy storage (TES) capsule, using gelled Glauber's salt. Transient heat flux at the capsule wall was measured for various cooling conditions. In cases where the initial temperature was lower than the saturation temperature of the phase change material (PCM), numerical analyses were performed, approximating the process by a relaxation phenomenon where crystals grew around crystal nuclei. The results of the numerical solution agreed very well with the experimental results. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： Salts CAPSULES relaxation phenomenon cooling conditions heat storage heat removal pulse code modulation ANALYSIS MODELS crystal nucleus

来源：评论

学校读者我要写书评

暂无评论

Ab initio and DFT studies on the mechanism of ring-opening reactions of 4H-1-benzopyran-4-one with hydroxide ion

引用

JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 2001年第3期 422-426页

作者： Kóna, J Fabian, WMF Zahradník, P Karl Franzens Univ Graz Inst Chem A-8010 Graz Austria Comenius Univ Dept Organ Chem SK-84215 Bratislava Slovakia

The mechanism of the first steps of the degradation of 4H-1-benzopyran-4-one in alkaline media, i.e., nucleophilic addition of hydroxide ion at the C2 carbon of 4H-1-benzopyran-4-one followed by ring-opening, is investigated by ab initio [HF/6-31+G(d) and MP2/6-31+G(d)] and density functional theory [B3LYP/6-31+G(d)] methods. In addition, bulk solvent effects are estimated by the polarised continuum (overlapping spheres) model (PCM) and the polarizable conductor PCM model (CosmoPCM). Depending on the level of theory used three reaction coordinates are found: path A (1 --> TS1 -->2 --> TS2A --> 3A), path B (1 --> TS1 -->2 --> TS2B --> 3B) and path C (1 --> TS1 -->2 --> TS2A --> 3C). The ring-opening step passing through TS2B has a lower activation energy than the step proceeding through TS2A. These second barriers are higher compared with the barrier of the first step. Therefore fission of the gamma -pyrone ring (2 --> TS2B --> 3B) seems to be the rate-determining step in the gas phase. Contrary to these gas phase results, addition of hydroxide ion to C2 (reactants --> TS1 -->2) is the rate-determining step for the reaction in aqueous solution, in agreement with experimental results.

关键词： cycloaddition hydroxyl ion RING OPENING Byways gaseous phase rate determining step pulse code modulation discrete Fourier transform barriers

来源：评论

学校读者我要写书评

暂无评论

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

请选择保存的检索档案：

请选择收藏分类：

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

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

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：